CA1285116C - Silica with a high oil absorption capability and a controlled primary structure and process for the production thereof - Google Patents
Silica with a high oil absorption capability and a controlled primary structure and process for the production thereofInfo
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- CA1285116C CA1285116C CA000486487A CA486487A CA1285116C CA 1285116 C CA1285116 C CA 1285116C CA 000486487 A CA000486487 A CA 000486487A CA 486487 A CA486487 A CA 486487A CA 1285116 C CA1285116 C CA 1285116C
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- silica
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/113—Silicon oxides; Hydrates thereof
- C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/113—Silicon oxides; Hydrates thereof
- C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
- C01B33/18—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof
- C01B33/187—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by acidic treatment of silicates
- C01B33/193—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by acidic treatment of silicates of aqueous solutions of silicates
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/01—Particle morphology depicted by an image
- C01P2004/04—Particle morphology depicted by an image obtained by TEM, STEM, STM or AFM
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/50—Agglomerated particles
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- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/64—Nanometer sized, i.e. from 1-100 nanometer
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/11—Powder tap density
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/12—Surface area
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/14—Pore volume
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/19—Oil-absorption capacity, e.g. DBP values
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/90—Other properties not specified above
Abstract
Abstract of the Disclosure The present invention relates to precipitation silicas with a mean projected area of aggregates which is higher than 15,000 nm2. It also concerns a novel process for the production thereof with constant-volume addition of reactants, reaction with an electrolyte and consolidation of the resulting product by the addition of a solution of silicate and an acidifying agent. The silicas have high oil absorption capability and an elevated primary structure so that they are eminently suitable for many purposes, such as thickening agents and strengthening fillers.
Description
~511~
- ~ - 655~1-296 SILICA WITH A HIG~ O~L ABSORPTION CAPA~ILITY AND ~ CONTROLLED
PRIMARY STRUCTURE AND PROCESS FOR THE PRODUCTION THEREOF
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The present invention concerns a silica with a high oil absorption capability and an elevated primary structure.
The invention also concerns a process which permits in particular the production -thereoE.
It is known that generally the precipitation of silica corresponds to a complex group of phenomena which involves a number oE chemical actions and in particular polycondensation and a flocculation phenomenon, those two ac-tions readily competing with each other.
Moreover, it is known that the expression precipitated silica covers a product which is of variable morphology, taking account simply of -the ultimate particles or elementary balls (*) such as may be considered under an electron microscope (according to R.K. ILER - The Chemistry of Silica - ~ohn WILE~ & Sons - 1979, page 465).
The above-mentioned balls may vary in size. They may result in different states of association in the form of aggre-gates (as defined by Ralph K. ILER, page 477) and groups of weakerbonds, which results in a high degree of diversity of morphologies of amorphous types. The aggregates may be characterised in parti-cular by their size, their form factor and their sur~ace area.
There is therefore not one silica but an infinity of silicas, the behaviour of which cannot be foreseen, especially as surface chemistry is another important characteristic.
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- ~ - 655~1-296 SILICA WITH A HIG~ O~L ABSORPTION CAPA~ILITY AND ~ CONTROLLED
PRIMARY STRUCTURE AND PROCESS FOR THE PRODUCTION THEREOF
. . . ~
The present invention concerns a silica with a high oil absorption capability and an elevated primary structure.
The invention also concerns a process which permits in particular the production -thereoE.
It is known that generally the precipitation of silica corresponds to a complex group of phenomena which involves a number oE chemical actions and in particular polycondensation and a flocculation phenomenon, those two ac-tions readily competing with each other.
Moreover, it is known that the expression precipitated silica covers a product which is of variable morphology, taking account simply of -the ultimate particles or elementary balls (*) such as may be considered under an electron microscope (according to R.K. ILER - The Chemistry of Silica - ~ohn WILE~ & Sons - 1979, page 465).
The above-mentioned balls may vary in size. They may result in different states of association in the form of aggre-gates (as defined by Ralph K. ILER, page 477) and groups of weakerbonds, which results in a high degree of diversity of morphologies of amorphous types. The aggregates may be characterised in parti-cular by their size, their form factor and their sur~ace area.
There is therefore not one silica but an infinity of silicas, the behaviour of which cannot be foreseen, especially as surface chemistry is another important characteristic.
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- 2 - 6551~-296 When produciny such silicaq, it is possible to involve a large number of parameters, such as the levels of concentration of various reactants, the pH-value, the time, the temperature, etc...
Now, attempts have long been made to isolate the various chemical actions involved. I'hus, as early as 1951, in US No.
2 731 326, there is the teaching of Eirst forming a sol by the addition of a solution of sulphuric- acid to a solution of sili-cate, then heating the sol in order to increase the size of the particles to 5 to 7 nm.
That is then followed by sim~lltaneou~ addition oE an acid solution and a solution of silicate, at a constant pH-value, ~o as to provide for precipitation and to deposit the remainder of the silica on the precipitate (ILER page 558).
Along the same line, US Nos. 3 954 944 and 4 127 541 provide for the simultaneous addition of sulphuric acid and a solution of silicate to an aqueous heel, with the production of a sol, maturing of the sol, flocculation of the sol with the intro-duction of an alkaline electrolyte, maturing of the flocculation product, and the further addition of acid alone or acid and sili-cate.
It will be seen that the mode of operation is complex,in particular in regard to the properties of the products describ-ed, which are still difficult to evaluate.
Thus, generally, in spite of substantial efforts which have been made over a long period of time, it has not been possi-ble hitherto for anyone to propose a process which makes it .
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- 2a - 65511-296 possible to isolate the chemical actions and to control them sufficiently to control in particular the primary structure of the silicas.
Now, we have now found a process wherein an aqueou~
solution of an alkaline silicate is reacted with an acidifying agent by forming a sediment or bottoms containing an aqueous ~ub-stance, by simultaneous addition of the acidifying agent and the si].icate solution, and which is characterised in that it compri~es the following steps:
a) addition of the reactants at constant volume and continuously .
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Now, attempts have long been made to isolate the various chemical actions involved. I'hus, as early as 1951, in US No.
2 731 326, there is the teaching of Eirst forming a sol by the addition of a solution of sulphuric- acid to a solution of sili-cate, then heating the sol in order to increase the size of the particles to 5 to 7 nm.
That is then followed by sim~lltaneou~ addition oE an acid solution and a solution of silicate, at a constant pH-value, ~o as to provide for precipitation and to deposit the remainder of the silica on the precipitate (ILER page 558).
Along the same line, US Nos. 3 954 944 and 4 127 541 provide for the simultaneous addition of sulphuric acid and a solution of silicate to an aqueous heel, with the production of a sol, maturing of the sol, flocculation of the sol with the intro-duction of an alkaline electrolyte, maturing of the flocculation product, and the further addition of acid alone or acid and sili-cate.
It will be seen that the mode of operation is complex,in particular in regard to the properties of the products describ-ed, which are still difficult to evaluate.
Thus, generally, in spite of substantial efforts which have been made over a long period of time, it has not been possi-ble hitherto for anyone to propose a process which makes it .
, , :
~L~8~;11~;
- 2a - 65511-296 possible to isolate the chemical actions and to control them sufficiently to control in particular the primary structure of the silicas.
Now, we have now found a process wherein an aqueou~
solution of an alkaline silicate is reacted with an acidifying agent by forming a sediment or bottoms containing an aqueous ~ub-stance, by simultaneous addition of the acidifying agent and the si].icate solution, and which is characterised in that it compri~es the following steps:
a) addition of the reactants at constant volume and continuously .
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-3 65511~
drawincJ off the reclcltion medium 50 as to ohtain in the constant volume a spherica:L co:lloicl whieh is monodisperse in respect of diameter and in the medium drawn off a colloid of silica ~,7hieh is polydisperse in respeet of diameter, b) reaetion of at least a part of the product ohtained ~ith an eleetrolyte, and e) eonsolidation of the procluet from step b) by the addit:Lon o e a solution of .silicate and an acidifyincJ agent.
Thus, aeeording to one aspeet, the presen~ invention provide.s a process for the pror1uctlon of preeipltated Yllica compri~inq:
(a) provicling a colloid of silica by (i) forming a reactlon medium hy simultaneously adding an aeidifying agent and an alkaline silicate solution to a ~ reaction vessel;
(ii) reaeting said acidifying agent and said alkaline ; .
silieate solution; and (iii) maintaining a constant volume of said reaction medium hy drawing off said reaction medium while adding additional acidifying agent and alkaline silieake solution in a eonstant volume to the reaction medium, wherein said alkaline silieate is added to sald reaction medium to provide a silica eoncentration that avoids aq~lomeration of eolloidal partieles;
~: (b) reaeting at least a portion of the eolloicl obtainecl in -~ step (a) with an eleetrolyte, said eolloicl having a mean diameter ; of between about 10 and 100 nm and a polydisperity faetor of from : about 1 to 4; and , .~,--}"
' 1~85116 ~-3a- 65511 29(j (c) consolidatincl the suhstance ohtained in ~tep (h) hy adding a solution of silicate and an acidifyin~l agent to obtain said precipita~ed sill.ca with a CTAB specifi.c surface area from about 20-120 m2/g.
According to another aspect~ the pre.sent inventior provides precipitation silica cha:racteri.sed in that it has:
- a CTAB surface area of between 20 and 120 m /g -- a DBP oil absorption capabillty of between ~50 and 500 ml/100 g of silica, - a mean projected area o:E the aggreCJates of greater than 8,000 nm2, ancl - a high inter~aggreyate volume which is higher than 1 cm3/g and a homogenous inter-aggregate pore population.
The term colloids will be used to denote sols which consist of fine particles, in accordance with the definition given by Ralph K. ILER - The Chemistry of Silica - John WIIIEY ~ Sons -1979, page 415.
Polydispersity is ascertained in known manner (see MYSELS - Introduction to Colloid Chemistry - Interscience Publisher New York).
It will be appreciated that the characteristics of the colloids depend on a certain number of parameters.
Advantageously, they are obtained by using a sillcate with an SiO2/Na20 weight ratio of between 2 and 4.
The concentration of silica in the colloid must be such as to avoid the agglomeration of the colloidal particles.
The temperature is advantageously between 50 and 100C.
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1~8~ 6 -.3b- 65511-2~6 An :Lmportant ~actor is the residence time in the constant volume.
It is observed that the diameter of the coLloid~ depends on the resldence time.
Another important facto~ the duration of the reaction.
It i~ observed in particvular that a stable situation ls established at the end of a certai.n per:iod of time, a~ter the commenc~ement of khe operation of clrawing of~ the reacti.on med:Lum.
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l~as~6 - ~ - 65511-296 When the stable state is reached, there is no longer any difference between the two types of col].oids, and a polydisperse colloid is obtained, on a continuous way.
In particular, in step a~, it is possible to obtain monodisperse colloids with a spheri.cal form factor and a mean diameter of between 10 and 100 nm, and with a polydispersity factor of between 1 and 1.2 in the constant volume, and poly~
disperse colloids which also are of. a mean diameter of Erom 10 to 100 nm, oE spherical Eorm, but with a polydispersity index which 0 i6 advantageo~lsly between 1.2 and 4 in the substance drawn oEf.
It is also possible to obtain much higher bal:L sizes which tend to undergo sedimenta-tion and which may reach sizes ranging up to 300 nm.
It is thereore possible to act on the colloid over a wide range of effects and for example to mix different fractions for the same residence time or colloids obtained with different residence times.
Therefore, step b) is carried out on one or other or one and the other of the fractions produced ~rom the constant volume and/or the material which i5 drawn of, before or from the obten-tion of the stable state.
The electrolyte used is of any type and in particular comprises a metal salt such as of an alkali or alkaline earth metal.
It will be appreciated however that it would not be a ' ~ , ' :
1 2~51~L6 departure Erom the scope of the presen-t invention to use a differ-ent metal salt such as a rare earth or otherwise.
Step b) is advantageously performed at a pH-value of between 6 and 10, with a silica concentration of between 20 and 100 g/l and at a temperature of from 20 to 100C.
Step c) is advantageously carried out by the simultane--ous addition of the solution of siLicate and the acidi~ying agent, at a constant pH-value of from 6 to 10, and at a temperature of from 50 to 100C.
The ~uspension produce~ at the end of step c) is filter-ed, washed and dried.
An advantageous method of drying compriqes carrying out a process in accordance with FR-A- 2 257 326 which provides form-ing a symmetrical axial spinning flow configuration with a hot gas having a large momentum, and introducing the suspension to be dried along the axis of symmetry of rotation of said ~low configu-ration in the region of said flow configuration which is a rela-tive depression, the momentum of said symmetrical axial spinning flow configuration, with respect to the axial flow of the suspen-sion, being sufficient to cause the axial flow to be broken down,dispersed, taken over and dried.
The process according to the invention therefore pro-vides access to a large number of silicas according to the more or less polydisperse character of the colloid of step a) and accord-ing to the mean diameter thereof.
The process according to the invention makes it possible :
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' in par-ticular to provlde novel silicas. For a given value in respect of specific surface area, such novel silicas have high values in regard to oil absorption and the mean projected area of the aggreyate.
Thus, the invention covers silicas with a mean diameter in respect of number of the elementary balls of from 10 to 100 nm and with a mean projected area in respect of number o~ the aggre-gate expressed in nm2, o~ higher tllan 8000, preferably higher than lS000 and advantageously between 20000 and 100000.
In particular, the invention relates to silcas having a hiyh inter-aggregate pore volume (higher than 1 cm3/g), with a homogenous inter-aggregate pore population.
The specific surface areas and the oil absorption vaLues may vary widely for the same types of silica, but it is possible in particular to produce silicas with a CTAB specific surface area of between ~0 and 120 m2/g, with an oil absorption value of be-tween 250 and 500 ml/100 g, and a projected area in respect of the aggregates of greater than 8,000 and preEerably 15,000 nm2.
Finally, on the same silicas, it is possible to observe apparent densities of between 0.05 and 0.25.
It will be appreciated that the present invention is not limited to the silicas which have just been described and it is possible in particular to obtain silicas having larger elementary balls .
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65511-2~6 According to the invention The CTAB surface area is the external surface area as evaluated by absorption of cetyl trimethyl ammonium bromide with a pH-value of 9 using the method disclosed by JAY, JANSEN and C.
KRAUS in "Rubber Chemistry and Technoloyy" 44 (1971), pages 1287-1296.
Specific volume Vo i5 det:ermined in the -following fashion:
- using a die with an in!3ide diameter of 25 mm and a height of 80 mm, 3 g of silica is added, then placed thereabove i6 a piston to which a given weight is added so as to apply a pressure of 4 105 Pa to the silica. The specific volume of the silica is then measured, being the volume "Vo" expressed in cm3/g (initial volume).
Oil absorption is evaluated using the method described in the French standard NF.T 30-022 (March 1953), using dibutyl p'hthalate as the oil, on 5 g of silica.
The pH-value is measured in accordance with the standard DIN 53200, the tapped apparent density corresponds to the standard ~20 NF.A 95-112, and apparent density is also indicated as measured without compacting.
Polydispersity of the elementary particles is the ratio of the mean diameter by weight (dw) to the mean diameter by number (dn). The mean diameters are calculated as stated by Joseph T.
BAILEY et aI (Average Quantities in Colloid Science - Journal of ' Chemical Education - Vol. 39, No. 4, April 1962 - pages 196-200).
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- 8 - 655Ll-296 The mean area of -the aygregate was determined in accor-dance with the standard ASTM D 3849-~0, adapted to the specific character of silica by disagglomerating the silica by crushing a paste formed by 100 mg of dry silica powder for 0.5 ml of glycerin and then diluting that paste in 300 ml of water, with a pH-value of 3.
The operations of determining the inter-aqggregate pore volume and determining the populat:ion of pores corresponding to that volume are carried out by means of a mercury porosimeter (porosimeter used: pore si~er 9300 from COULTRONICS). The mercury is caused to penetrate into the pores o the degassed sample, thereby establishing a porosity curve repr~senting the variation in the volume of the pores in dependence on the pressure or the radius of the pores. The porosity curve i8 esta~lished using the method disclosed by N.M. WINSLOW and J.J. SHAPIRO in ~ ASTM BULLETIN, page 39, February 1959.
Piling up the aggregates gives rise to an inter-aggregate porosity, the filling of which with the mercur~ will be revealed by the appearance of a step on the porosity curve. The height of the step makes it possible to arrive at the inter-aggregate pore volume. The inclination of the step reflects the dispersion or scatter in the population of the pores. The derived curve has a peak configuration, the degree of fineness of which is in direct proportion to increasing homogeneity in regard to the ~ : population of the inter-aggregate pores~
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~28~i~16 - 9 - 65511-2g6 It will be appreciated that the silicas according to the invention may be used for any purpo~e such as a strengt'hening fiLler or a thickening agent.
However, the present invention will be more readily appreciated by reference to t'he fo:Llowing examples which are given purely by way o-f illustration.
In all the examples, the drying operation is carried out by means of an apparatus producing a symmetrical axial spinning flow con-figuration, in accordance with FR-A 2 257 326, with a gas at a temperature of 500C at t'he intake and 150C at the outlet.
Figures 1, 2 and 3 are photographs of aggregates.
Figures 4 and 5 show the curves in respect of mercury absorption which represents the evolution of cumulated volume V in respect with the diameter of pores D and their derivatives dV/dD
for carbon blacks N 326 and N 347.
Figure 6 illustrates the similar absorption curves for a silica according to the invention. The curves in solid lines correspond to the adsor'bed volume in cm3/g while the curves in broken lines correspond to those derived from the former.
The first reaction stage consists of the preparation of a monodisperse silica SQl with a mean diameter by numbex of 62 nm.
'~Por that purpose, use is made of a reactor with a volume of 20 litres, provided with a double jacket heating system and a system for agitation by means of a turbine-type agitator. The ;reactor comprises a system for continuous evacuation of a reaction ' :
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liquid as soon as the volume o~ liquid reaches a fixed value. An array of meteriny pumps provide for the feed of the reactants.
8 litres of distilled water is introduced into the reactor and the temperature is raised to 90C. The turbine agitator is operated (speed of rotation 400 rpm), and the following are simultaneously in-trocluced :
- a dilute a~ueous sodium silicate solution (ratio by weight : SiO2/Na2O = 3.25 ; [SiO2] = 40 g/l), at a rate of 67 ml per minute, and ~ an aqueous solution of sulphuric acid ([H2SO41= 17 g/l) at a rate of 67 ml per minute.
The acid is introduced at a point which is clearly separate from the point at which the silicate solution is introduced. After the two reactants have been simultaneously introduced for a period of 10 minutes, the drawing-off operation is started so as to maintain a substantially constant volume in the reactor (that is to say, 9.3 litres); in that way, a spherical silica colloid is formed and increased in size in the reactor.
Thus, the following are present at any time:
- a spherical silica colloid which is monodisperse in respect of size of diameter present in the reactor (colloid A) and - a spherical silica colloid which is polydisperse in respect of size of mean diameter by num~er which is less than that of the colloid A (colloid B).
The caracteristlcs of colloid A are as follows:
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~ 28~6 - 11 - 65511-29~
_ Tlme LSiO2~g/1 Mean diameter By number dnBy weight dw nm nm _ .
1 hour 16 17.5 18.3 2 hours 16.2 22.2 22.6 3 hours 20.8 30 31.4 4 hours 21.6 ~8.3 39.3 5 hours 23.6 50 51.6 6 hours 23.5 62.1 62.9 Second reac_ion stage Seven litres of the colloid in the reactor (dn = 62.1 nm) are used to gain the silica. The seven litres is maintained at a temperature of 90C and is agitated at 400 rpm, and sulphuric acid (~H2S04~ = 34 g/l) is added thereto at a rate of 22.6 ml/min, over a period o-f 5 minutes. Then, over a period of 2 minutes, 2.6 litres of aqueous solution o ~a2S04 containing 350 g per litre of ~a2S04 is introduced. The resulting mixture is left to age for a period of 10 minutes.
Third reaction stage Introduced into the resulting mixture is an aqueous solution of sodium silicate (ratio by weight: SiO2/Na20 = 3.25;
~sio2J = 75 g/l), at a rate of 25.1 ml per minute, for a period of 90 minutes.
~ Two minutes a-fter the operation of introducing the silicate is begun, an aqueous solution of sulphuric acid (~H2S0 = 34 g/l) is simultaneously introduced, at a rate of 22.6 ml per ~,.~ ,, , - 12 - 65511-2g6 mlnute, for 88 minutes. Throughout the pe:riod for which the acid and -the silicate are introduced at the same time, the pH-value is maintained at 8.0 ~ 0.2 (measured at 90C) and the temperature is held at 90C.
The procedure -through stages 2 and 3 may be diagrammatically represen-ted in the following ~rashion:
Time minutes 0 5 7 17 19 107 130 A~ueous r I ~ I
silicate ~ 25.1 ml/minl Dilute l l I l l I
H2S04 l22.6 ~ t I l l I
l l I 1 26 ml/mim L
Na2SOas solution Temperature The silica suspension obtained at the end of the reaction has a pH value of 3.5. It is filtered, then washed and dried.
The characteristics of the dried silica are as follows:
- CTAB speci~ic surface a~ea 23 ~2/g - BET specl~ic sur~ace area 30 m2/g - pH-value with 5% in water 6.9 : - . Vo 3 . 64 cm3 /g - DBP oil absorption 300 ml/100 g of silica :~ - Apparent density 0.19 g/cm3 : - Tapped apparent density 0.23 g/cm3 : ~ :
~'~8511~;
In -the silica aggregates, the spherical elementary particle is clearly defined and monodisperse as shown in Figure 1.
The mean projected area of the aggregates is 87,000 nm2.
A silica having the followiny characteristics is prepar~
ed, at the conclusion of a 3-stage reaction:
~ CTAB specific surface area 8g m2/g - BET specific surface area 109 m2/y - Vo ~.9 cm3/g - DBY oi:L absorption 492 ml/100 g oE silica ~ Apparent density 0.072 g/am3 - Tapped apparent density 0.085 g/cm3 - pH-value 7.2 The mean projected area by number of the aggregates is 12,000 nm2. The spherical elementary particles which are to be found in the aggregates have a mean diameter by number of 27 nm and a polydispersity index of 1.16.
First reaction stage ;: 20 The first stage comprises preparing a polydisperse ~ spherical silica colloid, with diameters ranging between 15 and 50 : nanometres, with a~mean diameter by number of 26 nanometres~
This colloid is prepared as described in the first re-:~ action stage of Example l, but with the following alterations in the reaction conditions:
the reactlon is carried out at 78C ~~ 1C, instead of 90C, and ::
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gl~8513L6 - the drawiny-off operation is commenced as from the 25th minute af-ter the beginning of the operation of simultane-ously adding aqueous sulphuric acid and aqueous sodium silicate so that the liquid volume in the reactor is main-tained constant at 11.3 litres.
The reaction liquid which is drawn off between 2 hours 30 minutes and 5 hours 30 minutes :is collected. Examination by a transmission-type electron microscope and examina-tion by lic~ht diffusion show that it is a spherical silica colloid in polydis-perse condition with diameters ranging between 15 and 55 nano~metres.
The silica concentration is 18 g o SiO2 per litre.
Second reaction stage Taking a 20 litre reactor as described in Example l, a portion (~ litres) of the reaction liquid collected by being drawn off between 2 hours 30 minutes and 5 hours 30 minutes is introdu-ced thereinto. The colloid is raised to 90C in a 20 litre reactor. An aqueous solution of Na2SO4 is then added so as to give an aqueous suspension of silica containing 0.37 mole per litre of Na2SO4. The mixture is allowed to age, in an agitated condition, for a period of lO minutes.
Third reaction stage : Introduced into the resulting suspension which is main-tained in an agitated condition at 90C, over a period of 60 minutes and simultaneously, are aqueous sodium silicate (~sio2] =
40 g/l; ratio by weight SiO2/Na2O - 3.25) at a mean flow rate of 128S1~6 40 ml/minute, and dilute aqueous sulphuric acid ([H2SO~] = 17 g/l, at a mean rate of 40 ml per minute.
At the end of -the reaction, the pH-value of -the slurry is adjusted to 3.5 with dilute sulphuric acid. After filtration, washing and drying, the silica whose characteristics are set out below is obtained.
A silica having the following characteristics ls obtain-ed at -the conclusion of a 3-~stage process:
- CTAB surface area 103 m2/g - BET surface area 120 m2/g T.E.M. inveskigation reveals that the primary structure comprises aggregates of clearly defined elementary balls with a mean diameter by number of 27 nm and a polydispersity index of 1.04.
- DPB oil absorption 460 ml/100 g - Vo 4.71 cm3/g - p~-value 5.2 - Apparent density 0.070 g/cm3 - Tapped apparent density 0.084 g/cm3 A colloid is formed and grown as indicated in Example 1 in respect of colloid A. The operation of drawing off reaction medium is begun 3 minutes after the commencement of the operation of simultaneously introducing the two reactants. After two and a half hours, the reactor (20 litres) contains a colloid (8 litres) of silica with a mean diameter dn of 25 nm ([SiO2] = 20 g/l).
'~ : '. "
.
~28S~
Introduced into ttl~ colloid at 90C is sodium sulphate so as to give an aqueous mixture of 0.37 mole per litre of Na2S04. The mixture is then allowed to mellow, with agitation, for a period of 65 minutes. Acid and silicate which are diluted, in accordance with the preceding Example, are then added to the resulting mix-ture by simultaneous addition over 60 minutes. The silica whose characteristics are se-t out above is o'b-tained in t'hat way.
A colloid is formed and grown as set forth in Example 1 in respect oE colloid A. T'he drawiny-off operation is started 3 minutes after the commencement of the reactant feed. After two and a half hours, the reactor (volume of 20 li-tre.s) contains a colloid of silica with a mean diameter by number of 27 nm ([SiO2]
= 20 gl~l). Taking that silica suspension (8 litres) which is held at 90C, 3 litres of aqueous solution containing 1070 g of Na2S04 is then added over 3 minutes. The mixture is then mellowed for a period o-f 10 minutes, with agitation, then followed by the simultaneous addition (for a period of 60 minutes) of sulphuric acid in dilute form and sodium silicate in dilute farm with -the reactants and under the conditions specified in Example 2. The characteristics of t'he silica powder obtained after filtration, washing and drying are as follows:
- BET surface area 111 m2/g - CTAB surface area 107 m2/g ; - Specific volume under 4 105 Pa 4.8 cm3/g - DBP oil absorption 465 ml/100 g of silica ~: :
~Z~ 6 ~ pH-value 6.5 - Apparent density 0.058 g/cm3 - Tapped apparent density 0.067 g/cm3 T.E.M. investigation and image analysis reveal that the silica has aygregates whose characteristics fall between a low structure carbon black N 326 and a high structure carbon black N 347.
_ , _ Mean diameter (by number) of Mean projected area PRODUCTthe elementary (by number) of the balls aggregates in nm2 __ .. ...... ___ N 326 26 nm 18 000 N 347 25 nm 26 000 ; Silica 27 nm 22 000 .
:
A spherical colloidal silica suspension (mean diameter dn = 24 nm) containing 36 g/l of silica is prepared. That colloid is formed in 2 hours 30 minutes as described in Example 1 (first reaction stage) but using reactants which are twice as concentrated and operating at 80C. Na2S04 is then added so as to give a salt concen-tration of 0.37 mole per litre of suspension, after aging for;65 minutes, acid and aqueous sodium silicate are simultaneously added, with a pH-value of 9, at 60C.
:
: ' , : ~ . ~,, : . .
~85~6 ~ 65511-296 At the end of reaction dilute sulfuric acid is added in order to lower the pH of the slurry at 3.5.
The characteristics of the silica obtained after filtra-tion, washing and drying are as follows :
- CTAB specific surface area 90m2/g - BET specific surface area 120 m2/g - Vo 4.52 cm3/g - DBP oil absorption 420 ml/100 g of silica - Apparent density 0.083 g/cm3 - Tapped apparent clensity 0.098 g/cm3 - pH-value 6.1 Transmission-type electron microscope investigation reveals tha-t the primary structure is formed by aggregates of clearly defined elementary balls of silica, with a mean projected area by number of the aggregates of 12,000 nm2. The inter-aggre-gate pore volume which is ascertained by porosity with respect to mercury is 1.1 cm3/g.
:
~ First reaction stage :
The first reaction stage comprises the formation of a spherical silica colloid with a histogram in respect of diameters which extends between 12 and 60 nm, with a mean diameter by number (dn) of 31 nm, a mean diameter by weight (dw) of 44 nm and a poly-dispersity index (dn/dw) of 1.40.
Operation is as in the first reackion stage of Example 1, but the interest is in the collold which is drawn off. Thus .
~: :
.
' 85~6 the whole of the sol which is drawn off in 2 hours and 15 minutes from the commencement of the drawing-off operation is combined, thus giving 20 litres of colloidal. suspension: fraction I. The whole oE the colloid which i5 drawn oEf between 2 hours 15 minutes and 4 hours 30 minutes is then combined: fraction II. 9.15 litres of fraction I and 0.85 li-tre of fraction II are then mixed, thus giving 10 litreæ of colloidal silica suspension which is found to have the foregoing charact:eristics by investigation by means of a transmission-type electron microscope.
Second reaction stage ~he 10 litres of colloid are raised to 90C in a 20 litre reactor. Sulphuric acid (~H2SO4~ = 34 gl) is then added over a period of 6 minutes 30 seconds to the above-mentioned sus~
pension which is maintained at 90C and agi-tated 400 rpm), so as to adjust the pH-value from 9 to 8. 1.76 litre of aqueous solu-tion of Na2SO4 containing 350 g of Na2S04 per litre is then intro-duced over a period of one minute. The resulting mixture is then left to age for 10 minutes 30 seconds, with ayitation.
~hird rsaction stage An aqueous solution of sodium silicate (ratio by weight:
SiO2/Na2O = 3.25; [SiO2] = 75 g/l) is introduced at a rate of 27.5 ml/min, for a period o~ 100 minutes.
2 minutes 30 seconds after the silicate introduction operation begins, an aqueous solution of sulphuric acid ([H2SO4] =
34 g/l) is simultaneously introduced at a rate of 30.1 ml/min for 97 minutes 30 seconds. Throughout the period for which the acid , . . j, ~L~85~6 ~ 20 - 6551l-2g6 ana the aqueous silicate are introduced at the same time, the pH-value is rnaintained at 8 ~ 0.1 and the temperature is held at 90C. Af-ter the silicate feed is stopped, the introduction of acid is continued for 12 minutes so as to give a pEI value of 3.5.
The procedure through stages 2 and 3 may be diagrammatically represented in the following manner:
0 6'30" 7'30" 1~ 20'30" :Ll8' 130' TIME
27.5 ml/min SILICATE L~
ACID 30.1 ml/min l I I _ I
Na2SOa 350 g11 1.76.L
pH-value 9 8 7i6 7i6 8-1 8i0 7,9 3 5l The silica suspension ob-tained at the end of -the precipitation step is fil-tered, washed and dried.
The characteristics of the dried silica are as follows:
- CTAB surface area 47 m2/g - BET surface area 58 m2/g - pH-value 6.6 - Vo 4.2 cm3/g - DBP oil absorption 378 ml/100 g of silica - Apparent density 0.11 g/cm3 - Tapped apparent density 0.135 g/cm3 . ~, .
~:85~6 - 21 - 65511~29~
Characterization by means of an electron microscope quantified by imaye analysis of the aggregates gives the following characteristics:
- mean diameter by number (dn) of the elementary balls present in the aggregates: 36 nm, - mean diameter by weight (dw) of the elementary balls:
50 nm, polydispersity index dw/dn = 1.4, and - mean projected area by number of the aggregates: 15,000 nm2.
The appearance of the agyregates is as shown in Figure 2.
A silica colloid is formed and grown, as set forth in Example 1, in respect of colloid A.
The drawing-off operation is begun 2 minutes after the commencement of -the feed of the two reactants, the reactant feed being such as to maintain a pH-value of 9 + 0.1 at 90C0 Ater 2 hours 30 minutes, the reactor (20 litres) contains a colloid (volume = 8 litres) of silica with a mean diameter by number of 28 ~:: 20 nm.
Two litres of the colloidal suspension is then drawn off. 2.25 litres of an aqueous solution containing 551.3 g of Na2SO4 is then added to the colloidal suspension remaining in the reactor. This introduction is effected with agitation over a period of 2 minutes. The resulting suspension is then maintained : in an agitated condition for further period of 10 minutes, .
351~6 - 22 ~ 6~511-296 followed by the simultaneous addition (peri.od of 75 minutes) of dilute sulphuric acld ([H2SO4] = 17 g/l) and dilute sodium sili-cate ([SiO2] = 40 g/l).
The sodium silicate flow rate is maintainecl between 36 and 38 ml per minute. The dilute sulphuric acid flow rate is automatically controlled so as to give a pH-value of 9 ~ 0.1 in the medium, at 90C. After washing, filtration and drying, the resulting silica powder is of the iollowing charaateristic~:
- CTAB sur:~ace area 85 m2/g - BET surEace area 80 m2/g - Vo 4.95 cm3/y - DBP oil absorption 406 ml/100 g of silica - Apparent density 0.098 g/cm3 - Tapped apparent density 0.117 g/cm3 - pH-value 5.2 - dn 32 nm - dw 34 nm - mean projected area by number of the aggregates 14,000 nm2 The inter-aggregate pore volume as determined by porosi-ty with respect to mercury is 1.1 cm3/g.
First reaction staye : This Example uses a 20 litre reactor provided with a double jacke-t heating system and a system for agitation by means of a turbine device. The reactor comprises a system for .
' S~6 - 23 - 65511-2g~
continuously removing a reaction liquid as soon as the volume of ].iquid reaches a -fixed value. An array of metering pumps provides for the reactants feed.
8 litres of water is introduced in-to the reactor and the tem~erature is raised to 90C. The turbine agitator is operated (speed of rotation of 400 rpm) to agitate the mixture, and the following are simultaneously introcluced into the liquid:
- an aqueous solution of sc~dium silicate in dilut~ form (ratio by weight: SiO2/Na20 = 3.25, ~rsio2] = 20 g/1) at a rate of 120 ml per min~lte, and ~ C2 at a rate which is automat:ically controlled at a value of the order of ~ g/hour so that -the pH-value is maintained at 9.1 ~ 0.1 at 90C.
The C02 feed is at a separa-te point from the silica-te solution feed.
About 2 minutes after the beginning of the simultaneous feed of the two reactants, the drawing-off operation is started so as to maintain a constant volume in the reactor. A spherical silica colloid is thus caused to form and grow in diame-ter in the reactor. After 2 hours 30 minutes, the feed of reactants into the reactor is stopped. The silica colloid present in the reactor has a mean diameter by number of 28 nm and a mean diameter by weight of 29 nm.
Second reaction s e Taking the colloidal suspension obtained at the end of the first reaction stage, being maintained at 90C, 2 litres of ~ ''' ' ' ' ~8~
- 2~ - 65511~296 aqueous solution (at 80~) contalning 90 g of Na2C03 and 286 g of ~aH003 are introduced over a period of 3 minutes. The suspension -then undergoes aging for 9 minutes at 90C, with agitation.
Third reactlo_ stage l'he following are introduced simultaneously into the aqueous suspension:
- aqueous sodium silicate (ratio by weight: SiO2/Na20 =
3~25/ [SiO2~ a 20 g/l), at a rate of 87 ml/minute, and - undiluted C02 at a rate which is automaticaLly control-led so as to give a pH-value Oe 8.7 ~ 0.1 (flow rate =
0.67 g/min).
The simultaneous introduction operation lasts Eor 60 minutes.
The silica suspension obtained at the close of the third reaction stage is filtered, washed and dried. The charactsristics of the dried silica are as follows:
- CTAB surface area 85 m2/g - BET surface area 101 m2/g - pH-value 7. 5 - DBP oil absorption 386 ml/100 g of silica - Vo 5.1 cm3/g - Apparent density 0.071 g/cm3 - Tapped apparent density 0.083 g/cm3.
Electron microscope investigation of the aggregates reveals that they comprise balls of silica with a mean diame-ter by number of 29 nm.
'f~
, .. . ....
~t~ 6 - 25 - 655~ 29 EXAMPL,~ 9 A sph~ricaJ. coLloid of silica which is monodisperse in respect of diameter is formed and grown, as set forth in ~xample 1, for colloid A, but with the following modification: the drawing-off operation is started 2 minutes after the commencement of the simultaneous introduction of dilute sulphuric acid and aqueous sodium silicate, that operation being carried out in ~uc~
a way that the pH-value is held at 9 ~ 0.2 at 90C. After 2 hours 30 minute.s, the reactor contains a monodisperse spherical colloid (volume = 8 lltres) Oe .si.lica. The pH-value is lowered to with 300 mol of dilute El2S04. 3 litres of an a~ueous solution containing 1050 g of Na2S04 is then introduced into the above-mentioned colloidal suspension which is maintained with agitation at 90C. The opera-tion of introducing the 3 litres of aqueous solution is carried out over a period of 2 minutes and the result-ing mixture is maintained with agitation (turbine agitator opera-ting at 110 rpm) at a pH-value of 8 at 90C, over a period of 10 minutes.
Dilute sulphuric acid ([H2SO4~ = 17.1 g/l) and dilute sodium silicate (ratio by weight SiO2/~a2O = 3.325, SiO2 = 40 g/l) are simultaneously added (over a period of 65 minutes).
The sodium silicate rate is maintained at 37 ml per minute. The dilute sulphuric acid rate is automatically control-- led so that the pH-value in the reaction medium is maintained at 8 :~ + 0.1 at 90C.
The resulting silica slurry is then adjusted to a ~
: ' lZ~5~16 - 26 ~ 65511-296 pH-value of 3.5 by the addition of dilute ~;ulphuric acid. After filtration, washing and drying, the silica powder produced has the following characteristics:
- CTAB surface area 110 m2/g - B~T surface area 110 m2/g - Vo 4.5 cm3/g - DBP oil absorption 400 ml/100 g of si:Lica - Apparen-t density 0.054 g/cln3 - Tapped apparent density 0.068 g/cm3 - p~-value 6.9.
In the case of a drying operation carried out in a dry-ing oven (15 hours at 150C), a silica is obtained which has a lower level oE oil absorption: 220 ml of DBP for 100 g of silica.
Observation by means of a -transmission-type electron microscope shows that the silica aggregates comprise elementary particles of spherical silica which are welded together and which are clearly defined, with a mean diameter of 25 nm. The poly-dispersity index is 1.04. The appearance of the aggreyates is shown in Figure 3.
Image analysis shows that the aggreyates have a mean projected area of 27,000 nm2.
Figures 4, 5 and 6 show the porosity curves obtained with a mercury porosimeter in respect of carbon blacks N 326 and N 347, and in respect of the silicas prepared. The carbon blacks are characterized by a highly homogenous inter-aggregate pore ~,,`'' Sll~
- 26a - 65511-296 population, which is revealecl by a very narrow peak on the deriva-tive of the curve (broken line curve). That characteristic is also to be perfectly found on the curve relating to the silica prepared in accordance with the invention. The silica has an inter-aggregate pore volume which is higher than that o carbon black N 347, while preservlny substantially the same pore distri-bution.
The inter~aggregate pore volumes are as follows:
Product Pore volume_cm3 ~
~, . . = . = _ 10 Silica according to the invention 1.5 N 326 0.7 A precipitation silica is prepared by three successive operations which are carried out in the following manner:
- the first stage is the formation o~ a monodisperse spherical silica colloid as indicated in Example 7, - the second stage involves introducing into the colloidal solution present in the reactor, 291 g of NaCl in solu-tion in 1 litre of water. That operation lasts for 2 minutes~. The reaction mixture is then maintained at 90C with agitation for 10 minutes, - the third stage involves introducing into the reaction medium and simultaneously, over a period of 90 minutes, aqueous sodium silicate (ratio by weight SiO2/~a2O =
.
.
, ~2!3~1~L6 - 26~ - 65511-29~
3.25; ~SiO2~ = ~0 yl) at a rate of 4~ ml per minute, and dilute sulphur:ic acid (LH2SO~] = 17 g/l) at a rate of 42.3 ml per minute, 50 controlled -that the p~-value of the silica suspension is 8.g + 0.2 at gOC. The resul-ting silica slurry is then adjuYted to a pII-value of 3.5 by the addition of dilute sulp~luric acid. Ater filtration, washing and drying, the characteristics of the silica obtained are as follows:
- CTAB specific surface area 60 m2/g - BET specific surface area 60 m2/y - pH-value 6.1 - DBP oil absorption 380 ml for 100 g of silica - Apparent density 0.106 g/cm3 Tapped apparent density 0.133 g/cm3 The mean projected area by number of the aggregates is 27,000 nm2.
The spherical elementary particles present in the aggre-gates have a mean dia~eter by number of 33 nm and a polydispersity index of 1.05.
E~AMPLE ll A precipitation silica is prepared by three successive reaction stages. The procedure followed is as described in Example 7, with the following differences:
- the spherical silica colloidal solution being formed at the end of the first stage, 3 litres of that solution is drawn off. 657 g of ~a2S0~ in so1ution in 1.87 litres of water is introduced into the colloidal solution remaining in the ~ -: .~
- 26c - 65511-296 reactor. The operation of introducing the Na2SO~ solution lasts for 2 minutes. The resulting suspension is maintained at 90C with agi-tation for a -further period of 10 minutes.
That is then followed by the simultaneous addition (for a period of 90 minutes) of aqueous sodium silicate ([Sio2] -40 g/l, ratio by weight- SiO2/Na2C) = 3.25) at a rate of 52.5 ml, with the rate being so controlled t:hat the pH-value of t'he reaction suspension is maintained ~t 8.9 + 0.1.
The resulting silica slurry is adjusted to a pH-value of 3.5 by t'he addition of dilute sulphuric acid.
After filtration, washiny with water and drying by atomisation, the characteristics of the silica collected are as follows:
- Cl'AB surface area 45 m2/g - BET surface area 50 m2/g - DBP oil absorption 310 ml for 100 g of silica - pH-value 6.3 - Vo 4.34 cm3/g - Apparent density 0.17 g/cm3 - Tapped apparent density 0.20 g/cm3.
The mean projected area by number of the aggregates is 29,000 nm2.
The spherical particles present in the aggregates have a mean diameter by number of 40 nm and a polydispersity index of 1.04.
: ,~
~ : :
.
' :
- 26d - 65511-296 First reaction stage Use is made of a reactor with a volume of 1 litre, pro-vided with a heating sys-tem and a turbine-type agitator. Metering pumps provide for the Eeed of -the reactants in two separated places. The reactor comprises a system for continuous evacuation of the reaction liquid in order to maintain the volume of the reaction product at a fixed value of 0.8 litre.
0.8 litre of water is introduced into the reactor and the temperature is raised to 75C. The turbine agitator is opera-ted (speed of rotation 1000 rpm) and the following are simultane-ously introduced:
- an aqueous sodium silicate solution (ratio by weight SiO2/Na20 = 3.25; Csio2] = 50 g/l, at a ra-te of 22 ml per minute, and - an aqueous solution of sulfuric acid ( CH2SO4] = 22.8 g) at a rate of 22 ml per minute.
After about 4 hours of reaction, a stable operating state is attained. The concentration of silica in the reactor and the characteristics :,~
- .
.
85~16 of colloid obtained do no more vary with the time as indicated by examination by a transmission--type electron microscope and examination by light diffusion of the obtained product, which are made by taking the substance at regular time between the 4th and the 100th hours.
S The silica colloid obtained consists in ~pherical particles showing diameter so%es situated in a range of 10 to S0 nm, at every time, with a mean diameter by number (dn) of 19 nm, a~nd a mean diameter by weight (dw) of 33 nm.
The sol of colloid drawn-off and accumulated between the 4th and the 100th hours is used in the second reaction stage.
For the second a~d third reaction stages the reaction temperature is a-t 90C and the turbine agitation is operated at a speed of rotation of 110 rpm.
Sec~ a ~ ,t.=~
3 litres of an aqueous solution containing 450 g of NaS04 are introduced in the reactor of 20 1 described in Example 1. The temperature is raised at 90C.
8 litres of the coiloid obtained in stage one are introduced in the reactor under agitation (110 rpm), preheated at the temperature of 90C
and brought to a pH of 8 by adding dilute sulfuric acid (350 ml of an aqueous solution containing 100 g of H2S04 are introduced in 10 minutes).
The colloid is added in the aqueous solution of H2S04 over a period of 9 minutes. The resulting mixture is left to age for a period of 3 minutes under agitation (110 rpm).
Third reaction stage :
Introduced into the resulting mixture, maintained under agitation at 90C, are simultaneousl~ introduced over a period of 70 minutes :
- an aqueous solution of sodium silicate containing 110 g of SiO2 per litre of a weight ratio SiO2/Na20 equal to 3.25, this 30 solution is fed at a rate of 25 ml per minute.
- an aqueous solution of sulfuric acid containing 100 g per litre of H2S04, this solutlon is fed at a rate of 13.5 ml per minute.
.
' : : ' , : ' ' 3S~6 After thls period of 70 rninutes of simultaneous adding of the t~,~o reactants (silicate + acid) the feeding of silicate is stop~ed. The introduction of dilute sulfuric acid is maintained over a period of 8 minutes at a rate of 25 ml per minute.
The silica slurry obtained at the end of the reaction has a pH-value of 3.5.
It is filtered, then washed and dried.
The characteristics of the dried powdered silica are as follows :
- BET specific surface area 96m /y - CTAB specific surface area 95m /g - pH-value with 5 % in water 6.6 - DBP oil absorption 260 ml/lOOg of silica - Tapped apparent densi-ty 0.17 g/cm3 Exarnination by a transmisssion-type electron microscope shows that aggregates of silica constituted by elementary spherical particles showing a mean diameter in number of 26 nm and polydispersity index of 2 the inter-aggregate pore volume is of 1.15 cm3/g.
Carbon dioxide is added as acid reactant.
First reaction stage This first stage comprises p~eparing a polydisperse colloid of silica on a continuous way in the same manner as in Example 12 but by using CO as acid reactant instead of H2S04.
The colloid is prepared as described in the first reaction stage of Example 1, but with the following alterations in the reaction conditions :
- the reaction is carried out a 72C, - the following are simultaneously introduced :
an aqueous sodium silicate solution (ratio by weight ~ 30 SiO2 / Na20 = 3.25 ; [SiO2~ = 25 g/l, at a rate of 67 ml ; per minute, and ; . pure C02 in the gaseous state at a rate of 1.53 g per minute.
' , : ' ' ' ' ' ' ' ' lZ~3S116 The product of reaction drawn o~f continuously between the 40 minutes and -the 6 hours is accumula-ted.
This reaction product consists in a colloid o~ polydisperse silica : the spherical particles of silica have a mean diameter by number of 19 nm and a mean diameter by weight o~ 37 nm.
Second reaction stage Taking a 20 litres reactions as described in Example 1, 3 litres of an aqueous solution containing 117 g of NazCO3 and 277 g of NaHco3 are introduced there into.
m e solution is raised to a temperature of 90C.
8 litres of the colloid obtained in stage 1 prealably heated to 90C and adjusted to a pH oE 8,4 by introduction of 36 g of C02 ln 30 minutes are added to this solution maintained under agitation.
The introduction of this colloid solution on the aqueous solution of Na2C03 ~ NaHC03 is carried out in 9 minutes. The mixture is allowed to age, in an agitated conditi.on, for a period of 3 minutes.
Third reaction stage _ Introduced into the resulting suspension which is maintained in an agitated condition at 90C, over a period of 70 minutes and simultaneouslY :
- an aqueous solution of sodium silicate (~SiO2]) = 75 g/l, ratio by weight SiO2 / Na20 = 3.25 at a mean flow rate of 36 ml per minute ;
- pure C02 in aqueous state at a rate of 1.2 g per minute.
At the end of reaction the resulting slurry of silica is filtrated.
The re.sulting filter cake is washed with 4 litres of water. After spin drying the resulting product is diluted in 3 litres of water.
The resulting slurry is raised to 60C.
The pH-value of the slurry is adjusted to 4 with dilute sulfuric acid.
The resulting suspension is filtrated, washed and dried.
A silica having the following characteristics i9 obtained :
- BET surface area 130 m2/g - CTAB surface area 82 m 2/g - pH-value 6.3 - DBP oil absorption 300 ml/lO0 g - Tapped apparent density 0.128 g/cm3 .. . .
, 51~6 T.E.M. lnvestlgation reveals that the prirnary structure comprises aggregates of spherical particles wlth a mea~ diameter by number of 25 nm and a polydispersity index of 1.8.
Mean projected area (by number) of the ~ggrega-tes in nm2 = 30 COO.
Inter-aggregate pore volurne = 1.10 crn /g.
.
,
drawincJ off the reclcltion medium 50 as to ohtain in the constant volume a spherica:L co:lloicl whieh is monodisperse in respect of diameter and in the medium drawn off a colloid of silica ~,7hieh is polydisperse in respeet of diameter, b) reaetion of at least a part of the product ohtained ~ith an eleetrolyte, and e) eonsolidation of the procluet from step b) by the addit:Lon o e a solution of .silicate and an acidifyincJ agent.
Thus, aeeording to one aspeet, the presen~ invention provide.s a process for the pror1uctlon of preeipltated Yllica compri~inq:
(a) provicling a colloid of silica by (i) forming a reactlon medium hy simultaneously adding an aeidifying agent and an alkaline silicate solution to a ~ reaction vessel;
(ii) reaeting said acidifying agent and said alkaline ; .
silieate solution; and (iii) maintaining a constant volume of said reaction medium hy drawing off said reaction medium while adding additional acidifying agent and alkaline silieake solution in a eonstant volume to the reaction medium, wherein said alkaline silieate is added to sald reaction medium to provide a silica eoncentration that avoids aq~lomeration of eolloidal partieles;
~: (b) reaeting at least a portion of the eolloicl obtainecl in -~ step (a) with an eleetrolyte, said eolloicl having a mean diameter ; of between about 10 and 100 nm and a polydisperity faetor of from : about 1 to 4; and , .~,--}"
' 1~85116 ~-3a- 65511 29(j (c) consolidatincl the suhstance ohtained in ~tep (h) hy adding a solution of silicate and an acidifyin~l agent to obtain said precipita~ed sill.ca with a CTAB specifi.c surface area from about 20-120 m2/g.
According to another aspect~ the pre.sent inventior provides precipitation silica cha:racteri.sed in that it has:
- a CTAB surface area of between 20 and 120 m /g -- a DBP oil absorption capabillty of between ~50 and 500 ml/100 g of silica, - a mean projected area o:E the aggreCJates of greater than 8,000 nm2, ancl - a high inter~aggreyate volume which is higher than 1 cm3/g and a homogenous inter-aggregate pore population.
The term colloids will be used to denote sols which consist of fine particles, in accordance with the definition given by Ralph K. ILER - The Chemistry of Silica - John WIIIEY ~ Sons -1979, page 415.
Polydispersity is ascertained in known manner (see MYSELS - Introduction to Colloid Chemistry - Interscience Publisher New York).
It will be appreciated that the characteristics of the colloids depend on a certain number of parameters.
Advantageously, they are obtained by using a sillcate with an SiO2/Na20 weight ratio of between 2 and 4.
The concentration of silica in the colloid must be such as to avoid the agglomeration of the colloidal particles.
The temperature is advantageously between 50 and 100C.
.
. :. ' ,,:
:. . ' ' ' ~
1~8~ 6 -.3b- 65511-2~6 An :Lmportant ~actor is the residence time in the constant volume.
It is observed that the diameter of the coLloid~ depends on the resldence time.
Another important facto~ the duration of the reaction.
It i~ observed in particvular that a stable situation ls established at the end of a certai.n per:iod of time, a~ter the commenc~ement of khe operation of clrawing of~ the reacti.on med:Lum.
2~
, ~:
;: -, '' ' .
.
l~as~6 - ~ - 65511-296 When the stable state is reached, there is no longer any difference between the two types of col].oids, and a polydisperse colloid is obtained, on a continuous way.
In particular, in step a~, it is possible to obtain monodisperse colloids with a spheri.cal form factor and a mean diameter of between 10 and 100 nm, and with a polydispersity factor of between 1 and 1.2 in the constant volume, and poly~
disperse colloids which also are of. a mean diameter of Erom 10 to 100 nm, oE spherical Eorm, but with a polydispersity index which 0 i6 advantageo~lsly between 1.2 and 4 in the substance drawn oEf.
It is also possible to obtain much higher bal:L sizes which tend to undergo sedimenta-tion and which may reach sizes ranging up to 300 nm.
It is thereore possible to act on the colloid over a wide range of effects and for example to mix different fractions for the same residence time or colloids obtained with different residence times.
Therefore, step b) is carried out on one or other or one and the other of the fractions produced ~rom the constant volume and/or the material which i5 drawn of, before or from the obten-tion of the stable state.
The electrolyte used is of any type and in particular comprises a metal salt such as of an alkali or alkaline earth metal.
It will be appreciated however that it would not be a ' ~ , ' :
1 2~51~L6 departure Erom the scope of the presen-t invention to use a differ-ent metal salt such as a rare earth or otherwise.
Step b) is advantageously performed at a pH-value of between 6 and 10, with a silica concentration of between 20 and 100 g/l and at a temperature of from 20 to 100C.
Step c) is advantageously carried out by the simultane--ous addition of the solution of siLicate and the acidi~ying agent, at a constant pH-value of from 6 to 10, and at a temperature of from 50 to 100C.
The ~uspension produce~ at the end of step c) is filter-ed, washed and dried.
An advantageous method of drying compriqes carrying out a process in accordance with FR-A- 2 257 326 which provides form-ing a symmetrical axial spinning flow configuration with a hot gas having a large momentum, and introducing the suspension to be dried along the axis of symmetry of rotation of said ~low configu-ration in the region of said flow configuration which is a rela-tive depression, the momentum of said symmetrical axial spinning flow configuration, with respect to the axial flow of the suspen-sion, being sufficient to cause the axial flow to be broken down,dispersed, taken over and dried.
The process according to the invention therefore pro-vides access to a large number of silicas according to the more or less polydisperse character of the colloid of step a) and accord-ing to the mean diameter thereof.
The process according to the invention makes it possible :
:
~.
' in par-ticular to provlde novel silicas. For a given value in respect of specific surface area, such novel silicas have high values in regard to oil absorption and the mean projected area of the aggreyate.
Thus, the invention covers silicas with a mean diameter in respect of number of the elementary balls of from 10 to 100 nm and with a mean projected area in respect of number o~ the aggre-gate expressed in nm2, o~ higher tllan 8000, preferably higher than lS000 and advantageously between 20000 and 100000.
In particular, the invention relates to silcas having a hiyh inter-aggregate pore volume (higher than 1 cm3/g), with a homogenous inter-aggregate pore population.
The specific surface areas and the oil absorption vaLues may vary widely for the same types of silica, but it is possible in particular to produce silicas with a CTAB specific surface area of between ~0 and 120 m2/g, with an oil absorption value of be-tween 250 and 500 ml/100 g, and a projected area in respect of the aggregates of greater than 8,000 and preEerably 15,000 nm2.
Finally, on the same silicas, it is possible to observe apparent densities of between 0.05 and 0.25.
It will be appreciated that the present invention is not limited to the silicas which have just been described and it is possible in particular to obtain silicas having larger elementary balls .
.~1 .
: ' .
65511-2~6 According to the invention The CTAB surface area is the external surface area as evaluated by absorption of cetyl trimethyl ammonium bromide with a pH-value of 9 using the method disclosed by JAY, JANSEN and C.
KRAUS in "Rubber Chemistry and Technoloyy" 44 (1971), pages 1287-1296.
Specific volume Vo i5 det:ermined in the -following fashion:
- using a die with an in!3ide diameter of 25 mm and a height of 80 mm, 3 g of silica is added, then placed thereabove i6 a piston to which a given weight is added so as to apply a pressure of 4 105 Pa to the silica. The specific volume of the silica is then measured, being the volume "Vo" expressed in cm3/g (initial volume).
Oil absorption is evaluated using the method described in the French standard NF.T 30-022 (March 1953), using dibutyl p'hthalate as the oil, on 5 g of silica.
The pH-value is measured in accordance with the standard DIN 53200, the tapped apparent density corresponds to the standard ~20 NF.A 95-112, and apparent density is also indicated as measured without compacting.
Polydispersity of the elementary particles is the ratio of the mean diameter by weight (dw) to the mean diameter by number (dn). The mean diameters are calculated as stated by Joseph T.
BAILEY et aI (Average Quantities in Colloid Science - Journal of ' Chemical Education - Vol. 39, No. 4, April 1962 - pages 196-200).
''~ :
' . , , '.
~z~s~
- 8 - 655Ll-296 The mean area of -the aygregate was determined in accor-dance with the standard ASTM D 3849-~0, adapted to the specific character of silica by disagglomerating the silica by crushing a paste formed by 100 mg of dry silica powder for 0.5 ml of glycerin and then diluting that paste in 300 ml of water, with a pH-value of 3.
The operations of determining the inter-aqggregate pore volume and determining the populat:ion of pores corresponding to that volume are carried out by means of a mercury porosimeter (porosimeter used: pore si~er 9300 from COULTRONICS). The mercury is caused to penetrate into the pores o the degassed sample, thereby establishing a porosity curve repr~senting the variation in the volume of the pores in dependence on the pressure or the radius of the pores. The porosity curve i8 esta~lished using the method disclosed by N.M. WINSLOW and J.J. SHAPIRO in ~ ASTM BULLETIN, page 39, February 1959.
Piling up the aggregates gives rise to an inter-aggregate porosity, the filling of which with the mercur~ will be revealed by the appearance of a step on the porosity curve. The height of the step makes it possible to arrive at the inter-aggregate pore volume. The inclination of the step reflects the dispersion or scatter in the population of the pores. The derived curve has a peak configuration, the degree of fineness of which is in direct proportion to increasing homogeneity in regard to the ~ : population of the inter-aggregate pores~
,~ . .
.
~28~i~16 - 9 - 65511-2g6 It will be appreciated that the silicas according to the invention may be used for any purpo~e such as a strengt'hening fiLler or a thickening agent.
However, the present invention will be more readily appreciated by reference to t'he fo:Llowing examples which are given purely by way o-f illustration.
In all the examples, the drying operation is carried out by means of an apparatus producing a symmetrical axial spinning flow con-figuration, in accordance with FR-A 2 257 326, with a gas at a temperature of 500C at t'he intake and 150C at the outlet.
Figures 1, 2 and 3 are photographs of aggregates.
Figures 4 and 5 show the curves in respect of mercury absorption which represents the evolution of cumulated volume V in respect with the diameter of pores D and their derivatives dV/dD
for carbon blacks N 326 and N 347.
Figure 6 illustrates the similar absorption curves for a silica according to the invention. The curves in solid lines correspond to the adsor'bed volume in cm3/g while the curves in broken lines correspond to those derived from the former.
The first reaction stage consists of the preparation of a monodisperse silica SQl with a mean diameter by numbex of 62 nm.
'~Por that purpose, use is made of a reactor with a volume of 20 litres, provided with a double jacket heating system and a system for agitation by means of a turbine-type agitator. The ;reactor comprises a system for continuous evacuation of a reaction ' :
; .
liquid as soon as the volume o~ liquid reaches a fixed value. An array of meteriny pumps provide for the feed of the reactants.
8 litres of distilled water is introduced into the reactor and the temperature is raised to 90C. The turbine agitator is operated (speed of rotation 400 rpm), and the following are simultaneously in-trocluced :
- a dilute a~ueous sodium silicate solution (ratio by weight : SiO2/Na2O = 3.25 ; [SiO2] = 40 g/l), at a rate of 67 ml per minute, and ~ an aqueous solution of sulphuric acid ([H2SO41= 17 g/l) at a rate of 67 ml per minute.
The acid is introduced at a point which is clearly separate from the point at which the silicate solution is introduced. After the two reactants have been simultaneously introduced for a period of 10 minutes, the drawing-off operation is started so as to maintain a substantially constant volume in the reactor (that is to say, 9.3 litres); in that way, a spherical silica colloid is formed and increased in size in the reactor.
Thus, the following are present at any time:
- a spherical silica colloid which is monodisperse in respect of size of diameter present in the reactor (colloid A) and - a spherical silica colloid which is polydisperse in respect of size of mean diameter by num~er which is less than that of the colloid A (colloid B).
The caracteristlcs of colloid A are as follows:
.
~ .
.
~ 28~6 - 11 - 65511-29~
_ Tlme LSiO2~g/1 Mean diameter By number dnBy weight dw nm nm _ .
1 hour 16 17.5 18.3 2 hours 16.2 22.2 22.6 3 hours 20.8 30 31.4 4 hours 21.6 ~8.3 39.3 5 hours 23.6 50 51.6 6 hours 23.5 62.1 62.9 Second reac_ion stage Seven litres of the colloid in the reactor (dn = 62.1 nm) are used to gain the silica. The seven litres is maintained at a temperature of 90C and is agitated at 400 rpm, and sulphuric acid (~H2S04~ = 34 g/l) is added thereto at a rate of 22.6 ml/min, over a period o-f 5 minutes. Then, over a period of 2 minutes, 2.6 litres of aqueous solution o ~a2S04 containing 350 g per litre of ~a2S04 is introduced. The resulting mixture is left to age for a period of 10 minutes.
Third reaction stage Introduced into the resulting mixture is an aqueous solution of sodium silicate (ratio by weight: SiO2/Na20 = 3.25;
~sio2J = 75 g/l), at a rate of 25.1 ml per minute, for a period of 90 minutes.
~ Two minutes a-fter the operation of introducing the silicate is begun, an aqueous solution of sulphuric acid (~H2S0 = 34 g/l) is simultaneously introduced, at a rate of 22.6 ml per ~,.~ ,, , - 12 - 65511-2g6 mlnute, for 88 minutes. Throughout the pe:riod for which the acid and -the silicate are introduced at the same time, the pH-value is maintained at 8.0 ~ 0.2 (measured at 90C) and the temperature is held at 90C.
The procedure -through stages 2 and 3 may be diagrammatically represen-ted in the following ~rashion:
Time minutes 0 5 7 17 19 107 130 A~ueous r I ~ I
silicate ~ 25.1 ml/minl Dilute l l I l l I
H2S04 l22.6 ~ t I l l I
l l I 1 26 ml/mim L
Na2SOas solution Temperature The silica suspension obtained at the end of the reaction has a pH value of 3.5. It is filtered, then washed and dried.
The characteristics of the dried silica are as follows:
- CTAB speci~ic surface a~ea 23 ~2/g - BET specl~ic sur~ace area 30 m2/g - pH-value with 5% in water 6.9 : - . Vo 3 . 64 cm3 /g - DBP oil absorption 300 ml/100 g of silica :~ - Apparent density 0.19 g/cm3 : - Tapped apparent density 0.23 g/cm3 : ~ :
~'~8511~;
In -the silica aggregates, the spherical elementary particle is clearly defined and monodisperse as shown in Figure 1.
The mean projected area of the aggregates is 87,000 nm2.
A silica having the followiny characteristics is prepar~
ed, at the conclusion of a 3-stage reaction:
~ CTAB specific surface area 8g m2/g - BET specific surface area 109 m2/y - Vo ~.9 cm3/g - DBY oi:L absorption 492 ml/100 g oE silica ~ Apparent density 0.072 g/am3 - Tapped apparent density 0.085 g/cm3 - pH-value 7.2 The mean projected area by number of the aggregates is 12,000 nm2. The spherical elementary particles which are to be found in the aggregates have a mean diameter by number of 27 nm and a polydispersity index of 1.16.
First reaction stage ;: 20 The first stage comprises preparing a polydisperse ~ spherical silica colloid, with diameters ranging between 15 and 50 : nanometres, with a~mean diameter by number of 26 nanometres~
This colloid is prepared as described in the first re-:~ action stage of Example l, but with the following alterations in the reaction conditions:
the reactlon is carried out at 78C ~~ 1C, instead of 90C, and ::
~J
, ,, .
, ;: .
'' : :
gl~8513L6 - the drawiny-off operation is commenced as from the 25th minute af-ter the beginning of the operation of simultane-ously adding aqueous sulphuric acid and aqueous sodium silicate so that the liquid volume in the reactor is main-tained constant at 11.3 litres.
The reaction liquid which is drawn off between 2 hours 30 minutes and 5 hours 30 minutes :is collected. Examination by a transmission-type electron microscope and examina-tion by lic~ht diffusion show that it is a spherical silica colloid in polydis-perse condition with diameters ranging between 15 and 55 nano~metres.
The silica concentration is 18 g o SiO2 per litre.
Second reaction stage Taking a 20 litre reactor as described in Example l, a portion (~ litres) of the reaction liquid collected by being drawn off between 2 hours 30 minutes and 5 hours 30 minutes is introdu-ced thereinto. The colloid is raised to 90C in a 20 litre reactor. An aqueous solution of Na2SO4 is then added so as to give an aqueous suspension of silica containing 0.37 mole per litre of Na2SO4. The mixture is allowed to age, in an agitated condition, for a period of lO minutes.
Third reaction stage : Introduced into the resulting suspension which is main-tained in an agitated condition at 90C, over a period of 60 minutes and simultaneously, are aqueous sodium silicate (~sio2] =
40 g/l; ratio by weight SiO2/Na2O - 3.25) at a mean flow rate of 128S1~6 40 ml/minute, and dilute aqueous sulphuric acid ([H2SO~] = 17 g/l, at a mean rate of 40 ml per minute.
At the end of -the reaction, the pH-value of -the slurry is adjusted to 3.5 with dilute sulphuric acid. After filtration, washing and drying, the silica whose characteristics are set out below is obtained.
A silica having the following characteristics ls obtain-ed at -the conclusion of a 3-~stage process:
- CTAB surface area 103 m2/g - BET surface area 120 m2/g T.E.M. inveskigation reveals that the primary structure comprises aggregates of clearly defined elementary balls with a mean diameter by number of 27 nm and a polydispersity index of 1.04.
- DPB oil absorption 460 ml/100 g - Vo 4.71 cm3/g - p~-value 5.2 - Apparent density 0.070 g/cm3 - Tapped apparent density 0.084 g/cm3 A colloid is formed and grown as indicated in Example 1 in respect of colloid A. The operation of drawing off reaction medium is begun 3 minutes after the commencement of the operation of simultaneously introducing the two reactants. After two and a half hours, the reactor (20 litres) contains a colloid (8 litres) of silica with a mean diameter dn of 25 nm ([SiO2] = 20 g/l).
'~ : '. "
.
~28S~
Introduced into ttl~ colloid at 90C is sodium sulphate so as to give an aqueous mixture of 0.37 mole per litre of Na2S04. The mixture is then allowed to mellow, with agitation, for a period of 65 minutes. Acid and silicate which are diluted, in accordance with the preceding Example, are then added to the resulting mix-ture by simultaneous addition over 60 minutes. The silica whose characteristics are se-t out above is o'b-tained in t'hat way.
A colloid is formed and grown as set forth in Example 1 in respect oE colloid A. T'he drawiny-off operation is started 3 minutes after the commencement of the reactant feed. After two and a half hours, the reactor (volume of 20 li-tre.s) contains a colloid of silica with a mean diameter by number of 27 nm ([SiO2]
= 20 gl~l). Taking that silica suspension (8 litres) which is held at 90C, 3 litres of aqueous solution containing 1070 g of Na2S04 is then added over 3 minutes. The mixture is then mellowed for a period o-f 10 minutes, with agitation, then followed by the simultaneous addition (for a period of 60 minutes) of sulphuric acid in dilute form and sodium silicate in dilute farm with -the reactants and under the conditions specified in Example 2. The characteristics of t'he silica powder obtained after filtration, washing and drying are as follows:
- BET surface area 111 m2/g - CTAB surface area 107 m2/g ; - Specific volume under 4 105 Pa 4.8 cm3/g - DBP oil absorption 465 ml/100 g of silica ~: :
~Z~ 6 ~ pH-value 6.5 - Apparent density 0.058 g/cm3 - Tapped apparent density 0.067 g/cm3 T.E.M. investigation and image analysis reveal that the silica has aygregates whose characteristics fall between a low structure carbon black N 326 and a high structure carbon black N 347.
_ , _ Mean diameter (by number) of Mean projected area PRODUCTthe elementary (by number) of the balls aggregates in nm2 __ .. ...... ___ N 326 26 nm 18 000 N 347 25 nm 26 000 ; Silica 27 nm 22 000 .
:
A spherical colloidal silica suspension (mean diameter dn = 24 nm) containing 36 g/l of silica is prepared. That colloid is formed in 2 hours 30 minutes as described in Example 1 (first reaction stage) but using reactants which are twice as concentrated and operating at 80C. Na2S04 is then added so as to give a salt concen-tration of 0.37 mole per litre of suspension, after aging for;65 minutes, acid and aqueous sodium silicate are simultaneously added, with a pH-value of 9, at 60C.
:
: ' , : ~ . ~,, : . .
~85~6 ~ 65511-296 At the end of reaction dilute sulfuric acid is added in order to lower the pH of the slurry at 3.5.
The characteristics of the silica obtained after filtra-tion, washing and drying are as follows :
- CTAB specific surface area 90m2/g - BET specific surface area 120 m2/g - Vo 4.52 cm3/g - DBP oil absorption 420 ml/100 g of silica - Apparent density 0.083 g/cm3 - Tapped apparent clensity 0.098 g/cm3 - pH-value 6.1 Transmission-type electron microscope investigation reveals tha-t the primary structure is formed by aggregates of clearly defined elementary balls of silica, with a mean projected area by number of the aggregates of 12,000 nm2. The inter-aggre-gate pore volume which is ascertained by porosity with respect to mercury is 1.1 cm3/g.
:
~ First reaction stage :
The first reaction stage comprises the formation of a spherical silica colloid with a histogram in respect of diameters which extends between 12 and 60 nm, with a mean diameter by number (dn) of 31 nm, a mean diameter by weight (dw) of 44 nm and a poly-dispersity index (dn/dw) of 1.40.
Operation is as in the first reackion stage of Example 1, but the interest is in the collold which is drawn off. Thus .
~: :
.
' 85~6 the whole of the sol which is drawn off in 2 hours and 15 minutes from the commencement of the drawing-off operation is combined, thus giving 20 litres of colloidal. suspension: fraction I. The whole oE the colloid which i5 drawn oEf between 2 hours 15 minutes and 4 hours 30 minutes is then combined: fraction II. 9.15 litres of fraction I and 0.85 li-tre of fraction II are then mixed, thus giving 10 litreæ of colloidal silica suspension which is found to have the foregoing charact:eristics by investigation by means of a transmission-type electron microscope.
Second reaction stage ~he 10 litres of colloid are raised to 90C in a 20 litre reactor. Sulphuric acid (~H2SO4~ = 34 gl) is then added over a period of 6 minutes 30 seconds to the above-mentioned sus~
pension which is maintained at 90C and agi-tated 400 rpm), so as to adjust the pH-value from 9 to 8. 1.76 litre of aqueous solu-tion of Na2SO4 containing 350 g of Na2S04 per litre is then intro-duced over a period of one minute. The resulting mixture is then left to age for 10 minutes 30 seconds, with ayitation.
~hird rsaction stage An aqueous solution of sodium silicate (ratio by weight:
SiO2/Na2O = 3.25; [SiO2] = 75 g/l) is introduced at a rate of 27.5 ml/min, for a period o~ 100 minutes.
2 minutes 30 seconds after the silicate introduction operation begins, an aqueous solution of sulphuric acid ([H2SO4] =
34 g/l) is simultaneously introduced at a rate of 30.1 ml/min for 97 minutes 30 seconds. Throughout the period for which the acid , . . j, ~L~85~6 ~ 20 - 6551l-2g6 ana the aqueous silicate are introduced at the same time, the pH-value is rnaintained at 8 ~ 0.1 and the temperature is held at 90C. Af-ter the silicate feed is stopped, the introduction of acid is continued for 12 minutes so as to give a pEI value of 3.5.
The procedure through stages 2 and 3 may be diagrammatically represented in the following manner:
0 6'30" 7'30" 1~ 20'30" :Ll8' 130' TIME
27.5 ml/min SILICATE L~
ACID 30.1 ml/min l I I _ I
Na2SOa 350 g11 1.76.L
pH-value 9 8 7i6 7i6 8-1 8i0 7,9 3 5l The silica suspension ob-tained at the end of -the precipitation step is fil-tered, washed and dried.
The characteristics of the dried silica are as follows:
- CTAB surface area 47 m2/g - BET surface area 58 m2/g - pH-value 6.6 - Vo 4.2 cm3/g - DBP oil absorption 378 ml/100 g of silica - Apparent density 0.11 g/cm3 - Tapped apparent density 0.135 g/cm3 . ~, .
~:85~6 - 21 - 65511~29~
Characterization by means of an electron microscope quantified by imaye analysis of the aggregates gives the following characteristics:
- mean diameter by number (dn) of the elementary balls present in the aggregates: 36 nm, - mean diameter by weight (dw) of the elementary balls:
50 nm, polydispersity index dw/dn = 1.4, and - mean projected area by number of the aggregates: 15,000 nm2.
The appearance of the agyregates is as shown in Figure 2.
A silica colloid is formed and grown, as set forth in Example 1, in respect of colloid A.
The drawing-off operation is begun 2 minutes after the commencement of -the feed of the two reactants, the reactant feed being such as to maintain a pH-value of 9 + 0.1 at 90C0 Ater 2 hours 30 minutes, the reactor (20 litres) contains a colloid (volume = 8 litres) of silica with a mean diameter by number of 28 ~:: 20 nm.
Two litres of the colloidal suspension is then drawn off. 2.25 litres of an aqueous solution containing 551.3 g of Na2SO4 is then added to the colloidal suspension remaining in the reactor. This introduction is effected with agitation over a period of 2 minutes. The resulting suspension is then maintained : in an agitated condition for further period of 10 minutes, .
351~6 - 22 ~ 6~511-296 followed by the simultaneous addition (peri.od of 75 minutes) of dilute sulphuric acld ([H2SO4] = 17 g/l) and dilute sodium sili-cate ([SiO2] = 40 g/l).
The sodium silicate flow rate is maintainecl between 36 and 38 ml per minute. The dilute sulphuric acid flow rate is automatically controlled so as to give a pH-value of 9 ~ 0.1 in the medium, at 90C. After washing, filtration and drying, the resulting silica powder is of the iollowing charaateristic~:
- CTAB sur:~ace area 85 m2/g - BET surEace area 80 m2/g - Vo 4.95 cm3/y - DBP oil absorption 406 ml/100 g of silica - Apparent density 0.098 g/cm3 - Tapped apparent density 0.117 g/cm3 - pH-value 5.2 - dn 32 nm - dw 34 nm - mean projected area by number of the aggregates 14,000 nm2 The inter-aggregate pore volume as determined by porosi-ty with respect to mercury is 1.1 cm3/g.
First reaction staye : This Example uses a 20 litre reactor provided with a double jacke-t heating system and a system for agitation by means of a turbine device. The reactor comprises a system for .
' S~6 - 23 - 65511-2g~
continuously removing a reaction liquid as soon as the volume of ].iquid reaches a -fixed value. An array of metering pumps provides for the reactants feed.
8 litres of water is introduced in-to the reactor and the tem~erature is raised to 90C. The turbine agitator is operated (speed of rotation of 400 rpm) to agitate the mixture, and the following are simultaneously introcluced into the liquid:
- an aqueous solution of sc~dium silicate in dilut~ form (ratio by weight: SiO2/Na20 = 3.25, ~rsio2] = 20 g/1) at a rate of 120 ml per min~lte, and ~ C2 at a rate which is automat:ically controlled at a value of the order of ~ g/hour so that -the pH-value is maintained at 9.1 ~ 0.1 at 90C.
The C02 feed is at a separa-te point from the silica-te solution feed.
About 2 minutes after the beginning of the simultaneous feed of the two reactants, the drawing-off operation is started so as to maintain a constant volume in the reactor. A spherical silica colloid is thus caused to form and grow in diame-ter in the reactor. After 2 hours 30 minutes, the feed of reactants into the reactor is stopped. The silica colloid present in the reactor has a mean diameter by number of 28 nm and a mean diameter by weight of 29 nm.
Second reaction s e Taking the colloidal suspension obtained at the end of the first reaction stage, being maintained at 90C, 2 litres of ~ ''' ' ' ' ~8~
- 2~ - 65511~296 aqueous solution (at 80~) contalning 90 g of Na2C03 and 286 g of ~aH003 are introduced over a period of 3 minutes. The suspension -then undergoes aging for 9 minutes at 90C, with agitation.
Third reactlo_ stage l'he following are introduced simultaneously into the aqueous suspension:
- aqueous sodium silicate (ratio by weight: SiO2/Na20 =
3~25/ [SiO2~ a 20 g/l), at a rate of 87 ml/minute, and - undiluted C02 at a rate which is automaticaLly control-led so as to give a pH-value Oe 8.7 ~ 0.1 (flow rate =
0.67 g/min).
The simultaneous introduction operation lasts Eor 60 minutes.
The silica suspension obtained at the close of the third reaction stage is filtered, washed and dried. The charactsristics of the dried silica are as follows:
- CTAB surface area 85 m2/g - BET surface area 101 m2/g - pH-value 7. 5 - DBP oil absorption 386 ml/100 g of silica - Vo 5.1 cm3/g - Apparent density 0.071 g/cm3 - Tapped apparent density 0.083 g/cm3.
Electron microscope investigation of the aggregates reveals that they comprise balls of silica with a mean diame-ter by number of 29 nm.
'f~
, .. . ....
~t~ 6 - 25 - 655~ 29 EXAMPL,~ 9 A sph~ricaJ. coLloid of silica which is monodisperse in respect of diameter is formed and grown, as set forth in ~xample 1, for colloid A, but with the following modification: the drawing-off operation is started 2 minutes after the commencement of the simultaneous introduction of dilute sulphuric acid and aqueous sodium silicate, that operation being carried out in ~uc~
a way that the pH-value is held at 9 ~ 0.2 at 90C. After 2 hours 30 minute.s, the reactor contains a monodisperse spherical colloid (volume = 8 lltres) Oe .si.lica. The pH-value is lowered to with 300 mol of dilute El2S04. 3 litres of an a~ueous solution containing 1050 g of Na2S04 is then introduced into the above-mentioned colloidal suspension which is maintained with agitation at 90C. The opera-tion of introducing the 3 litres of aqueous solution is carried out over a period of 2 minutes and the result-ing mixture is maintained with agitation (turbine agitator opera-ting at 110 rpm) at a pH-value of 8 at 90C, over a period of 10 minutes.
Dilute sulphuric acid ([H2SO4~ = 17.1 g/l) and dilute sodium silicate (ratio by weight SiO2/~a2O = 3.325, SiO2 = 40 g/l) are simultaneously added (over a period of 65 minutes).
The sodium silicate rate is maintained at 37 ml per minute. The dilute sulphuric acid rate is automatically control-- led so that the pH-value in the reaction medium is maintained at 8 :~ + 0.1 at 90C.
The resulting silica slurry is then adjusted to a ~
: ' lZ~5~16 - 26 ~ 65511-296 pH-value of 3.5 by the addition of dilute ~;ulphuric acid. After filtration, washing and drying, the silica powder produced has the following characteristics:
- CTAB surface area 110 m2/g - B~T surface area 110 m2/g - Vo 4.5 cm3/g - DBP oil absorption 400 ml/100 g of si:Lica - Apparen-t density 0.054 g/cln3 - Tapped apparent density 0.068 g/cm3 - p~-value 6.9.
In the case of a drying operation carried out in a dry-ing oven (15 hours at 150C), a silica is obtained which has a lower level oE oil absorption: 220 ml of DBP for 100 g of silica.
Observation by means of a -transmission-type electron microscope shows that the silica aggregates comprise elementary particles of spherical silica which are welded together and which are clearly defined, with a mean diameter of 25 nm. The poly-dispersity index is 1.04. The appearance of the aggreyates is shown in Figure 3.
Image analysis shows that the aggreyates have a mean projected area of 27,000 nm2.
Figures 4, 5 and 6 show the porosity curves obtained with a mercury porosimeter in respect of carbon blacks N 326 and N 347, and in respect of the silicas prepared. The carbon blacks are characterized by a highly homogenous inter-aggregate pore ~,,`'' Sll~
- 26a - 65511-296 population, which is revealecl by a very narrow peak on the deriva-tive of the curve (broken line curve). That characteristic is also to be perfectly found on the curve relating to the silica prepared in accordance with the invention. The silica has an inter-aggregate pore volume which is higher than that o carbon black N 347, while preservlny substantially the same pore distri-bution.
The inter~aggregate pore volumes are as follows:
Product Pore volume_cm3 ~
~, . . = . = _ 10 Silica according to the invention 1.5 N 326 0.7 A precipitation silica is prepared by three successive operations which are carried out in the following manner:
- the first stage is the formation o~ a monodisperse spherical silica colloid as indicated in Example 7, - the second stage involves introducing into the colloidal solution present in the reactor, 291 g of NaCl in solu-tion in 1 litre of water. That operation lasts for 2 minutes~. The reaction mixture is then maintained at 90C with agitation for 10 minutes, - the third stage involves introducing into the reaction medium and simultaneously, over a period of 90 minutes, aqueous sodium silicate (ratio by weight SiO2/~a2O =
.
.
, ~2!3~1~L6 - 26~ - 65511-29~
3.25; ~SiO2~ = ~0 yl) at a rate of 4~ ml per minute, and dilute sulphur:ic acid (LH2SO~] = 17 g/l) at a rate of 42.3 ml per minute, 50 controlled -that the p~-value of the silica suspension is 8.g + 0.2 at gOC. The resul-ting silica slurry is then adjuYted to a pII-value of 3.5 by the addition of dilute sulp~luric acid. Ater filtration, washing and drying, the characteristics of the silica obtained are as follows:
- CTAB specific surface area 60 m2/g - BET specific surface area 60 m2/y - pH-value 6.1 - DBP oil absorption 380 ml for 100 g of silica - Apparent density 0.106 g/cm3 Tapped apparent density 0.133 g/cm3 The mean projected area by number of the aggregates is 27,000 nm2.
The spherical elementary particles present in the aggre-gates have a mean dia~eter by number of 33 nm and a polydispersity index of 1.05.
E~AMPLE ll A precipitation silica is prepared by three successive reaction stages. The procedure followed is as described in Example 7, with the following differences:
- the spherical silica colloidal solution being formed at the end of the first stage, 3 litres of that solution is drawn off. 657 g of ~a2S0~ in so1ution in 1.87 litres of water is introduced into the colloidal solution remaining in the ~ -: .~
- 26c - 65511-296 reactor. The operation of introducing the Na2SO~ solution lasts for 2 minutes. The resulting suspension is maintained at 90C with agi-tation for a -further period of 10 minutes.
That is then followed by the simultaneous addition (for a period of 90 minutes) of aqueous sodium silicate ([Sio2] -40 g/l, ratio by weight- SiO2/Na2C) = 3.25) at a rate of 52.5 ml, with the rate being so controlled t:hat the pH-value of t'he reaction suspension is maintained ~t 8.9 + 0.1.
The resulting silica slurry is adjusted to a pH-value of 3.5 by t'he addition of dilute sulphuric acid.
After filtration, washiny with water and drying by atomisation, the characteristics of the silica collected are as follows:
- Cl'AB surface area 45 m2/g - BET surface area 50 m2/g - DBP oil absorption 310 ml for 100 g of silica - pH-value 6.3 - Vo 4.34 cm3/g - Apparent density 0.17 g/cm3 - Tapped apparent density 0.20 g/cm3.
The mean projected area by number of the aggregates is 29,000 nm2.
The spherical particles present in the aggregates have a mean diameter by number of 40 nm and a polydispersity index of 1.04.
: ,~
~ : :
.
' :
- 26d - 65511-296 First reaction stage Use is made of a reactor with a volume of 1 litre, pro-vided with a heating sys-tem and a turbine-type agitator. Metering pumps provide for the Eeed of -the reactants in two separated places. The reactor comprises a system for continuous evacuation of the reaction liquid in order to maintain the volume of the reaction product at a fixed value of 0.8 litre.
0.8 litre of water is introduced into the reactor and the temperature is raised to 75C. The turbine agitator is opera-ted (speed of rotation 1000 rpm) and the following are simultane-ously introduced:
- an aqueous sodium silicate solution (ratio by weight SiO2/Na20 = 3.25; Csio2] = 50 g/l, at a ra-te of 22 ml per minute, and - an aqueous solution of sulfuric acid ( CH2SO4] = 22.8 g) at a rate of 22 ml per minute.
After about 4 hours of reaction, a stable operating state is attained. The concentration of silica in the reactor and the characteristics :,~
- .
.
85~16 of colloid obtained do no more vary with the time as indicated by examination by a transmission--type electron microscope and examination by light diffusion of the obtained product, which are made by taking the substance at regular time between the 4th and the 100th hours.
S The silica colloid obtained consists in ~pherical particles showing diameter so%es situated in a range of 10 to S0 nm, at every time, with a mean diameter by number (dn) of 19 nm, a~nd a mean diameter by weight (dw) of 33 nm.
The sol of colloid drawn-off and accumulated between the 4th and the 100th hours is used in the second reaction stage.
For the second a~d third reaction stages the reaction temperature is a-t 90C and the turbine agitation is operated at a speed of rotation of 110 rpm.
Sec~ a ~ ,t.=~
3 litres of an aqueous solution containing 450 g of NaS04 are introduced in the reactor of 20 1 described in Example 1. The temperature is raised at 90C.
8 litres of the coiloid obtained in stage one are introduced in the reactor under agitation (110 rpm), preheated at the temperature of 90C
and brought to a pH of 8 by adding dilute sulfuric acid (350 ml of an aqueous solution containing 100 g of H2S04 are introduced in 10 minutes).
The colloid is added in the aqueous solution of H2S04 over a period of 9 minutes. The resulting mixture is left to age for a period of 3 minutes under agitation (110 rpm).
Third reaction stage :
Introduced into the resulting mixture, maintained under agitation at 90C, are simultaneousl~ introduced over a period of 70 minutes :
- an aqueous solution of sodium silicate containing 110 g of SiO2 per litre of a weight ratio SiO2/Na20 equal to 3.25, this 30 solution is fed at a rate of 25 ml per minute.
- an aqueous solution of sulfuric acid containing 100 g per litre of H2S04, this solutlon is fed at a rate of 13.5 ml per minute.
.
' : : ' , : ' ' 3S~6 After thls period of 70 rninutes of simultaneous adding of the t~,~o reactants (silicate + acid) the feeding of silicate is stop~ed. The introduction of dilute sulfuric acid is maintained over a period of 8 minutes at a rate of 25 ml per minute.
The silica slurry obtained at the end of the reaction has a pH-value of 3.5.
It is filtered, then washed and dried.
The characteristics of the dried powdered silica are as follows :
- BET specific surface area 96m /y - CTAB specific surface area 95m /g - pH-value with 5 % in water 6.6 - DBP oil absorption 260 ml/lOOg of silica - Tapped apparent densi-ty 0.17 g/cm3 Exarnination by a transmisssion-type electron microscope shows that aggregates of silica constituted by elementary spherical particles showing a mean diameter in number of 26 nm and polydispersity index of 2 the inter-aggregate pore volume is of 1.15 cm3/g.
Carbon dioxide is added as acid reactant.
First reaction stage This first stage comprises p~eparing a polydisperse colloid of silica on a continuous way in the same manner as in Example 12 but by using CO as acid reactant instead of H2S04.
The colloid is prepared as described in the first reaction stage of Example 1, but with the following alterations in the reaction conditions :
- the reaction is carried out a 72C, - the following are simultaneously introduced :
an aqueous sodium silicate solution (ratio by weight ~ 30 SiO2 / Na20 = 3.25 ; [SiO2~ = 25 g/l, at a rate of 67 ml ; per minute, and ; . pure C02 in the gaseous state at a rate of 1.53 g per minute.
' , : ' ' ' ' ' ' ' ' lZ~3S116 The product of reaction drawn o~f continuously between the 40 minutes and -the 6 hours is accumula-ted.
This reaction product consists in a colloid o~ polydisperse silica : the spherical particles of silica have a mean diameter by number of 19 nm and a mean diameter by weight o~ 37 nm.
Second reaction stage Taking a 20 litres reactions as described in Example 1, 3 litres of an aqueous solution containing 117 g of NazCO3 and 277 g of NaHco3 are introduced there into.
m e solution is raised to a temperature of 90C.
8 litres of the colloid obtained in stage 1 prealably heated to 90C and adjusted to a pH oE 8,4 by introduction of 36 g of C02 ln 30 minutes are added to this solution maintained under agitation.
The introduction of this colloid solution on the aqueous solution of Na2C03 ~ NaHC03 is carried out in 9 minutes. The mixture is allowed to age, in an agitated conditi.on, for a period of 3 minutes.
Third reaction stage _ Introduced into the resulting suspension which is maintained in an agitated condition at 90C, over a period of 70 minutes and simultaneouslY :
- an aqueous solution of sodium silicate (~SiO2]) = 75 g/l, ratio by weight SiO2 / Na20 = 3.25 at a mean flow rate of 36 ml per minute ;
- pure C02 in aqueous state at a rate of 1.2 g per minute.
At the end of reaction the resulting slurry of silica is filtrated.
The re.sulting filter cake is washed with 4 litres of water. After spin drying the resulting product is diluted in 3 litres of water.
The resulting slurry is raised to 60C.
The pH-value of the slurry is adjusted to 4 with dilute sulfuric acid.
The resulting suspension is filtrated, washed and dried.
A silica having the following characteristics i9 obtained :
- BET surface area 130 m2/g - CTAB surface area 82 m 2/g - pH-value 6.3 - DBP oil absorption 300 ml/lO0 g - Tapped apparent density 0.128 g/cm3 .. . .
, 51~6 T.E.M. lnvestlgation reveals that the prirnary structure comprises aggregates of spherical particles wlth a mea~ diameter by number of 25 nm and a polydispersity index of 1.8.
Mean projected area (by number) of the ~ggrega-tes in nm2 = 30 COO.
Inter-aggregate pore volurne = 1.10 crn /g.
.
,
Claims (10)
1. A process for the production of precipitated silica comprising:
(a) providing a colloid of silica by (i) forming a reaction medium by simultaneously adding an acidifying agent and an alkaline silicate solution to a reaction vessel;
(ii) reacting said acidifying agent and said alkaline silicate solution; and (iii) maintaining a constant volume of said reaction medium by drawing off said reaction medium while adding additional acidifying agent and alkaline silicate solution in a constant volume to the reaction medium, wherein said alkaline silicate is added to said reaction medium to provide a silica concentration that avoids agglomeration of colloidal particles;
(b) reacting at least a portion of the colloid obtained in step (a) with an electrolyte, said colloid having a mean diameter of between about 10 and 100 nm and a polydispersity factor of from about 1 to 4; and (c) consolidating the substance obtained in step (b) by adding a solution of silicate and an acidifying agent to obtain said precipitated silica with a CTAB specific surface area from about 20-120 m2/g.
(a) providing a colloid of silica by (i) forming a reaction medium by simultaneously adding an acidifying agent and an alkaline silicate solution to a reaction vessel;
(ii) reacting said acidifying agent and said alkaline silicate solution; and (iii) maintaining a constant volume of said reaction medium by drawing off said reaction medium while adding additional acidifying agent and alkaline silicate solution in a constant volume to the reaction medium, wherein said alkaline silicate is added to said reaction medium to provide a silica concentration that avoids agglomeration of colloidal particles;
(b) reacting at least a portion of the colloid obtained in step (a) with an electrolyte, said colloid having a mean diameter of between about 10 and 100 nm and a polydispersity factor of from about 1 to 4; and (c) consolidating the substance obtained in step (b) by adding a solution of silicate and an acidifying agent to obtain said precipitated silica with a CTAB specific surface area from about 20-120 m2/g.
2. A process according to claim 1 wherein the colloid in step (b) corresponds to one or more fractions of colloid coming from the constant volume.
3. A process according to claim 1 wherein the colloid in step (b) corresponds to one or more fractions of the colloid coming from the drawn-off substance.
4. A process according to claim 1, 2 or 3 wherein the colloid in step (b) corresponds to a mixture of fractions of colloids coming from the constant volume and from the drawn-off substance.
5. A process according to claim 1, 2 or 3 wherein the colloid in step (b) is obtained before the stable state is reached.
6. A process according to claim 1, 2 or 3 wherein the colloid use in step (b) is obtained after the stable state has been reached.
7. A process according to claim 1, 2 or 3 characterised in that coagulation in step (b) is produced by an electrolyte of the group comprising salts of alkali and alkaline earth metals.
8. A process according to claim 1, 2 or 3 further comprising a drying operation (d) effected after consolidation by forming a symmetrical axial spinning flow configuration with a hot gas, with a large momentum, and introducing a silica formed in step (c) along the axis of symmetry of rotation of said flow configuration such that the silica of step (c) is broken up, dispersed and dried.
9. Precipitation silica characterised in that is has;
- a CTAB surface area of between 20 and 120 m2/g - a DBP oil absorption capability of between 250 and 500 - ml/100 g of silica, - a mean projected area of the aggregates of greater than - 8,000 nm2, and - a high inter-aggregate volume which is higher than - 1 cm3/g and a homogenous inter-aggregate pore population.
- a CTAB surface area of between 20 and 120 m2/g - a DBP oil absorption capability of between 250 and 500 - ml/100 g of silica, - a mean projected area of the aggregates of greater than - 8,000 nm2, and - a high inter-aggregate volume which is higher than - 1 cm3/g and a homogenous inter-aggregate pore population.
10. A precipitation silica according to claim 9 characterised in that it has a mean projected area of the aggregates of greater than 15,000 nm2.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR84.11004 | 1984-07-11 | ||
| FR8411004A FR2567505B1 (en) | 1984-07-11 | 1984-07-11 | HIGH-OIL SILICA WITH CONTROLLED PRIMARY STRUCTURE AND PROCESS FOR OBTAINING SAME |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1285116C true CA1285116C (en) | 1991-06-25 |
Family
ID=9306012
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000486487A Expired - Fee Related CA1285116C (en) | 1984-07-11 | 1985-07-09 | Silica with a high oil absorption capability and a controlled primary structure and process for the production thereof |
Country Status (8)
| Country | Link |
|---|---|
| US (3) | US4708859A (en) |
| EP (1) | EP0170579B1 (en) |
| JP (1) | JPS61117113A (en) |
| KR (1) | KR910009573B1 (en) |
| AT (1) | ATE40669T1 (en) |
| CA (1) | CA1285116C (en) |
| DE (1) | DE3568155D1 (en) |
| FR (1) | FR2567505B1 (en) |
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|---|---|---|---|---|
| FR2589871B1 (en) * | 1985-09-13 | 1987-12-11 | Rhone Poulenc Chim Base | REINFORCING FILLER FOR SILICA-BASED ELASTOMER |
| GB8713263D0 (en) * | 1987-06-05 | 1987-07-08 | Unilever Plc | Spheroidal silica |
| US5614177A (en) * | 1987-11-04 | 1997-03-25 | Rhone-Poulenc Chimie | Dentifrice-compatible silica particulates |
| US5286478A (en) * | 1987-11-04 | 1994-02-15 | Rhone-Poulenc Chimie | Dentifrice-compatible silica particulates |
| FR2631620B1 (en) * | 1988-05-19 | 1990-07-27 | Rhone Poulenc Chimie | NOVEL PRECIPITATED ABSORBENT SILICA AND COMPOSITION BASED ON SAILOR |
| FR2632185B1 (en) * | 1988-06-01 | 1992-05-22 | Rhone Poulenc Chimie | SILICA FOR TOOTHPASTE COMPOSITIONS COMPATIBLE IN PARTICULAR WITH ZINC |
| FR2649089B1 (en) * | 1989-07-03 | 1991-12-13 | Rhone Poulenc Chimie | CONTROLLED POROSITY SILICA AND PROCESS FOR OBTAINING SAME |
| US5225177A (en) * | 1990-01-19 | 1993-07-06 | J. M. Huber Corporation | Dentifrice abrasives and compositions |
| US5094829A (en) * | 1990-06-21 | 1992-03-10 | Ppg Industries, Inc. | Reinforced precipitated silica |
| FR2678259B1 (en) * | 1991-06-26 | 1993-11-05 | Rhone Poulenc Chimie | NOVEL PRECIPITATED SILICA IN THE FORM OF GRANULES OR POWDERS, METHODS OF SYNTHESIS AND USE FOR REINFORCING ELASTOMERS. |
| US6001322A (en) | 1993-09-29 | 1999-12-14 | Rhone-Poulenc Chimie | Precipitated silicas |
| US6169135B1 (en) | 1993-09-29 | 2001-01-02 | Rhone Poulenc Chimie | Precipitated silica |
| FR2710630B1 (en) * | 1993-09-29 | 1995-12-29 | Rhone Poulenc Chimie | New precipitated silicas, their preparation process and their use for reinforcing elastomers. |
| DE69432248T2 (en) * | 1993-09-29 | 2004-08-19 | Rhodia Chimie | PRECIPITATION SILICA |
| WO1995017458A1 (en) * | 1993-12-20 | 1995-06-29 | Ppg Industries, Inc. | Tire tread composition comprising highly reinforcing silica |
| WO1995017459A1 (en) * | 1993-12-20 | 1995-06-29 | Ppg Industries, Inc. | Tire tread composition comprising highly reinforcing silica |
| FR2714369B1 (en) * | 1993-12-29 | 1996-01-26 | Rhone Poulenc Chimie | Abrasive silicas for toothpaste compositions. |
| JP2908253B2 (en) * | 1994-09-26 | 1999-06-21 | 日本化学工業株式会社 | Hydrated silica and its production method |
| US5846506A (en) * | 1994-10-07 | 1998-12-08 | Degussa Aktiengesellschaft | Precipitated silicas |
| US5571494A (en) * | 1995-01-20 | 1996-11-05 | J. M. Huber Corporation | Temperature-activated polysilicic acids |
| IL117915A (en) * | 1995-04-19 | 2001-05-20 | Ppg Ind Ohio Inc | Amorphous precipitated silica having large liquid carrying capacity |
| US5911963A (en) * | 1995-05-12 | 1999-06-15 | Ppg Industries Ohio, Inc. | Amorphous precipitated silica having a low proportion of small pores |
| DE19527278A1 (en) * | 1995-07-26 | 1997-01-30 | Degussa | Precipitated silica |
| US5804293A (en) * | 1995-12-08 | 1998-09-08 | Ppg Industries, Inc. | Coating composition for recording paper |
| DE69705121T2 (en) * | 1996-05-31 | 2001-09-27 | Ppg Ind Ohio Inc | AMORPHE FALLING SILICO |
| CN1094898C (en) * | 1996-05-31 | 2002-11-27 | Ppg工业俄亥俄公司 | Amorphous precipitated silica |
| FR2750692B1 (en) * | 1996-07-05 | 1998-10-16 | Rhone Poulenc Chimie | NOVEL ABRASIVE SILICA FOR USE IN TOOTHPASTS, METHOD FOR PREPARING SAME AND TOOTHPASTE COMPOSITIONS CONTAINING THE SAME |
| FR2762611B1 (en) * | 1997-04-29 | 1999-06-11 | Atochem Elf Sa | MODIFIED POROUS SILICA, MANUFACTURING METHOD THEREOF AND USE THEREOF IN PAINTS AND AS A PIGMENT AND DYE VECTOR |
| US5891949A (en) * | 1997-05-02 | 1999-04-06 | J.M. Huber Corporation | Natural rubber compound |
| US5929156A (en) * | 1997-05-02 | 1999-07-27 | J.M. Huber Corporation | Silica product for use in elastomers |
| FR2763581B1 (en) * | 1997-05-26 | 1999-07-23 | Rhodia Chimie Sa | PRECIPITATED SILICA FOR USE AS A REINFORCING FILLER FOR ELASTOMERS |
| US6607648B1 (en) * | 1998-11-10 | 2003-08-19 | Integrity Technologies Llc | Method and apparatus for generating aqueous silica network particles |
| US6573032B1 (en) | 1999-04-22 | 2003-06-03 | J. M. Huber Corporation | Very high structure, highly absorptive hybrid silica and method for making same |
| ATE271977T1 (en) * | 1999-05-31 | 2004-08-15 | Pirelli | VEHICLE TIRES WITH LOW ROLLING RESISTANCE |
| US6624233B2 (en) | 1999-05-31 | 2003-09-23 | Pirelli Pneumatici S.P.A. | Low rolling resistance tire for vehicles |
| CA2292819A1 (en) * | 1999-12-22 | 2001-06-22 | Bayer Inc. | Process for the production of a precipitated silica slurry with a controlled aggregate particle size distribution |
| EP1324947A2 (en) * | 2000-10-13 | 2003-07-09 | University of Cincinnati | Methods for synthesizing precipitated silica and use thereof |
| EP1284277B1 (en) * | 2001-08-08 | 2004-10-20 | Degussa Aktiengesellschaft | Silica-coated metal oxide particles |
| US20030096900A1 (en) * | 2001-11-16 | 2003-05-22 | Holden Brian David | Organic plant derived precipitated silica aggregates, elastomers reinforced therewith and articles such as tires with component thereof |
| FR2833937B1 (en) * | 2001-12-26 | 2004-11-12 | Rhodia Chimie Sa | SILICA WITH LOW WATER RESUME |
| CA2475296A1 (en) * | 2002-02-07 | 2003-08-14 | Kvg Technologies, Inc. | Lead acid battery with gelled electrolyte formed by filtration action of absorbent separators, electrolyte therefor, and absorbent separators therefor |
| JP2005053728A (en) * | 2003-08-01 | 2005-03-03 | Dsl Japan Co Ltd | Amorphous silica particle having high oil absorption and high structural performance |
| AU2008246949B2 (en) * | 2007-05-03 | 2012-11-01 | Council Of Scientific & Industrial Research | A process for the preparation of finely divided precipitated silica |
| FR2928363B1 (en) * | 2008-03-10 | 2012-08-31 | Rhodia Operations | NOVEL PROCESS FOR THE PREPARATION OF PRECIPITED SILICES, PRECIPITED SILITIES WITH SPECIAL MORPHOLOGY, GRANULOMETRY AND POROSITY AND THEIR USES, IN PARTICULAR FOR THE STRENGTHENING OF POLYMERS |
| US8790608B2 (en) * | 2008-09-12 | 2014-07-29 | Nalco Company | Siliceous materials having tunable porosity and surface morphology and methods of synthesizing same |
| CN102164853B (en) * | 2008-09-26 | 2014-12-31 | 扶桑化学工业株式会社 | Colloidal silica containing silica secondary particles having bent structure and/or branched structure, and method for producing same |
| US8609068B2 (en) | 2010-02-24 | 2013-12-17 | J.M. Huber Corporation | Continuous silica production process and silica product prepared from same |
| JP5495880B2 (en) * | 2010-03-25 | 2014-05-21 | 扶桑化学工業株式会社 | Method for adjusting secondary particle size of colloidal silica |
| EP2592140A4 (en) * | 2010-06-09 | 2014-08-13 | Jgc Corp | Support for protein immobilization, immobilized protein and method for producing same |
| US9028605B2 (en) | 2011-02-25 | 2015-05-12 | J.M. Huber Corporation | Coating compositions comprising spheroid silica or silicate |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2466842A (en) * | 1945-11-15 | 1949-04-12 | Davison Chemical Corp | Method for making silica hydrosol |
| US2577485A (en) * | 1950-09-08 | 1951-12-04 | Du Pont | Process of making stable silica sols and resulting composition |
| GB710015A (en) * | 1950-12-02 | 1954-06-02 | Degussa | An improved process for the production of finely divided silica |
| CH341802A (en) * | 1955-02-03 | 1959-10-31 | Basf Ag | Process for the continuous production of silicic acid-containing hydrogels |
| US2956957A (en) * | 1956-04-02 | 1960-10-18 | Grace W R & Co | Method for producing clear, homogeneous silica hydrosols |
| GB1044019A (en) * | 1963-10-17 | 1966-09-28 | Permutit Co Ltd | Improvements relating to the production of silica sol |
| DE1299617B (en) * | 1965-01-13 | 1969-07-24 | Degussa | Process for the manufacture of finely divided precipitated silica |
| US3337299A (en) * | 1965-05-24 | 1967-08-22 | Jr Oliver W Burke | Silica pigments and process for producing same |
| US4001379A (en) * | 1968-04-27 | 1977-01-04 | Deutsche Gold- Und Silber-Scheideanstalt Vormals Roessler | Process of making superfine amorphous high structural silicic acid |
| US3954944A (en) * | 1973-03-08 | 1976-05-04 | Joseph Crosfield & Sons, Ltd. | Fine silicas |
| US4191742A (en) * | 1974-05-22 | 1980-03-04 | J. M. Huber Corporation | Amorphous precipitated siliceous pigments and methods for their production |
| US4144321A (en) * | 1974-10-31 | 1979-03-13 | J. M. Huber Corporation | Amorphous precipitated siliceous pigments and methods for their production |
| US4127641A (en) * | 1975-12-10 | 1978-11-28 | Joseph Crosfield And Sons Limited | Process for the preparation of precipitated silicas having morphology similar to pyrogenic silicas |
| FR2353486A1 (en) * | 1976-06-04 | 1977-12-30 | Rhone Poulenc Ind | NEW AMORPHIC SYNTHETIC SILICA, PROCESS FOR OBTAINING AND APPLYING THE SAID SILICA IN VULCANISATES |
| FR2444700A1 (en) * | 1978-12-20 | 1980-07-18 | Rhone Poulenc Ind | NOVEL NON-ABRASIVE SCURING AGENT AND LAUNDRY COMPOSITION CONTAINING THE SAME |
| US4243428A (en) * | 1979-01-24 | 1981-01-06 | Donnet Jean Baptise | Processes for the manufacturing of precipitated silica |
| US4356107A (en) * | 1979-11-26 | 1982-10-26 | Nalco Chemical Company | Process for preparing silica sols |
| JPS59163306A (en) * | 1983-03-08 | 1984-09-14 | Taki Chem Co Ltd | Silica as tooth paste base and its preparation |
| FR2562534B1 (en) * | 1984-04-06 | 1986-06-27 | Rhone Poulenc Chim Base | NOVEL PRECIPITATED SILICA WITH IMPROVED MORPHOLOGICAL CHARACTERS, PROCESS FOR OBTAINING THE SAME AND APPLICATION THEREOF, IN PARTICULAR AS FILLER |
-
1984
- 1984-07-11 FR FR8411004A patent/FR2567505B1/en not_active Expired
-
1985
- 1985-07-08 DE DE8585401379T patent/DE3568155D1/en not_active Expired
- 1985-07-08 EP EP85401379A patent/EP0170579B1/en not_active Expired
- 1985-07-08 AT AT85401379T patent/ATE40669T1/en not_active IP Right Cessation
- 1985-07-09 CA CA000486487A patent/CA1285116C/en not_active Expired - Fee Related
- 1985-07-10 JP JP60152150A patent/JPS61117113A/en active Granted
- 1985-07-11 KR KR1019850004952A patent/KR910009573B1/en not_active IP Right Cessation
-
1986
- 1986-06-24 US US06/879,492 patent/US4708859A/en not_active Expired - Lifetime
-
1987
- 1987-01-16 US US07/005,012 patent/US4842838A/en not_active Expired - Lifetime
- 1987-08-05 US US07/081,980 patent/US4874594A/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| US4874594A (en) | 1989-10-17 |
| US4842838A (en) | 1989-06-27 |
| ATE40669T1 (en) | 1989-02-15 |
| KR860001008A (en) | 1986-02-22 |
| JPS61117113A (en) | 1986-06-04 |
| FR2567505A1 (en) | 1986-01-17 |
| FR2567505B1 (en) | 1986-11-21 |
| KR910009573B1 (en) | 1991-11-21 |
| DE3568155D1 (en) | 1989-03-16 |
| JPH0130764B2 (en) | 1989-06-21 |
| US4708859A (en) | 1987-11-24 |
| EP0170579A1 (en) | 1986-02-05 |
| EP0170579B1 (en) | 1989-02-08 |
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