US3807702A

US3807702A - An improved apparatus for encapsulating a finely divided clay within an organic polymeric material

Info

Publication number: US3807702A
Application number: US00155173A
Authority: US
Inventors: T Grillo; W Morris
Original assignee: JM Huber Corp
Current assignee: JM Huber Corp
Priority date: 1971-06-21
Filing date: 1971-06-21
Publication date: 1974-04-30
Anticipated expiration: 1991-04-30

Abstract

An improved apparatus for encapsulating a finely divided clay within an organic polymeric material comprises a pin mixer having a container inclined to the horizontal, and a rotatable shaft therein carrying pins defining a helix of decreasing pitch from the upper inlet end to the lower discharge end of the mixer.

Description

[451 Apr. 30, 1974 United States Patent [191 Grillo et a1.

1.7x ww /5 MWN 3 m mmmA mmmw ww amA as; w "O f Pe .finm FACE men mw w 0062 M O F 1,147,185 4/1969 Great 259/7 224,397 4/1962 415/72 [75] Inventors: Thomas A. Grillo; Walter Eugene Morris, both of Macon, Ga.

Assignee: J. M. Huber Corporation, Locust Primary Examinerl-larvey C. Homsby Assistant ExaminerAlan I. Cantor Attorney, Agent, or Firm-Harold H. Flanders; Donald S. Lilly [22] Filed: June 21, 1971 Appl. No.: 155,173

[57] ABSTRACT An improved apparatus for encapsulating a finely divided clay within an organic polymeric material com- [52] US. 259/ 7, 259/DIG. 13 [51] B01f 7/04, BOlf 7/08 Int. Cl.

[58] Field of Search............. 259/7, 22, 42, 65, 106, 259/191, 194, DIG. 13, D16. 24; 416/176, 200

prises a pin mixer having a container inclined to the horizontal and a rotatable shaft therein carrying pins 5 References Cited defining a helix of decreasing pitch from the upper UNITED STATES PATENTS inlet end to the lower discharge end of the mixer.

259/7 1 Claim, 1 Drawing Figure AN IMPROVED APPARATUS FOR ENCAPSULATING A FINELY DIVIDED CLAY WITHIN AN ORGANIC POLYMERIC MATERIAL BACKGROUND OF THE INVENTION This invention relates generally to an improved apparatus for encapsulating a finely divided clay within an organic polymeric material in the production of record materials, of the type having a sensitized surface which reacts to a colorless ink applied thereto by displaying distinctive colors in the image-configurated areas where said ink is present.

Within recent years a highly successful recording system has come into use based upon a multiple coloring principle in which an oily ink having two types of chromogenic reactants, normally colorless, is used upon an ink-receiving sheet sensitized with materials which react respectively with the two chromogenic substances to yield distinctive coloration. In one version of such system the said ink-receiving sheet is sensitized with substantially insoluble acid-like materials of high surface activity, such as attapulgite and zeolite, the chromogenic reactants being such substances as Crystal Violet Lactone and Benzoyl Leuco Methylene Blue. Such a system is disclosed, for example, in U. S. Pat. No. 2,712,507 to Barrett K. Green, pertaining to the well-known NCR paper (the quoted phrase being a trademark ofthe National Cash Register Company), wherein the said ink is applied from an oversheet by pressure release from microscopic capsules. In recording systems of this type the coloration of Crystal Violet Lactone is effected by an electron donor-acceptor solid-surface reaction with the acid clay like mineral and the coloration of the Benzoyl Leuco Methylene Blue is brought about by hydrolysis followed by an oxidation reduction reaction.

Because of the considerable time differential present with respect to completion of the two coloration reactions for the Crystal Violet Lactone and the Benzoyl Leuco Methylene Blue, an hiatus is often found to exist in the continuity of existence of the recorded marks produced by the previously described system. As such problem has been demonstrated to largely result from the fact that the two coloration reactions occur entirely via solid-surface reaction, improved record members have been developed wherein the coloration reactions are not dependent upon absorption on a solid surfaceactive material. Such an improved system is set forth, for example, in U. S. Pat. No. 3,455,721, wherein a record member is disclosed carrying in recording areas two types of microfine particles: the first an oil soluble acid-reactant organic polymeric material; the second, a colorless acid-type of mineral such as kaolin clay. When the previously described oily ink is applied to such a member, the polymeric particles enter the oil solution and promptly bring about the electron donoracceptor reaction which effects coloration in Crystal Violet Lactone. At the same time contact of the oily ink with the acid type mineral initiates the oxidation reduction reaction which in time colorates the Benzoyl Leuco Methylene Blue dye. Because coloration of the Crystal Violet Lactone occurs in solution, the colored material is capable of entering the support sheet, and this coupled with the absence of particle contamination such as occurs where surface active particles are used,

assures much greater persistence in coloration of the said dye.

Additional disclosures relative to the state of the art in which the present invention occurred may be found in U. S. Pat. Nos. 2,173,346; 2,463,501; 2,674,587; 3,516,845; 3,525,630; 3,535,412; British Pat. Nos. 1,212,731; 1,215,618; and Canadian Pat. Nos. 852,785 and 864,009.

The concept of using both an oil soluble polymer material and an acid-type mineral in the manner as set forth above, is less than satisfactory in the important respect that utilization of discrete particles of the one and of the other materials necessarily introduces undesirable discontinuitives into the recording surface, with a consequent loss of resolution and uniformity in the marking qualities of such surface. In particular it will be evident that even with the most uniform distribution of discrete particles, one particle type being uniformly dispensed among the other, coloration will occur whether in the case of Crystal Violet Lactone or of Benzoyl Leuco Methylene Blue at points spaced by the intervening alternate type particles. Such a result is compounded by the fact that idea] uniform distribution of one group of particle types among the other is, of course, not achieved in practice.

SUMMARY OF THE INVENTION In accordance with the foregoing, it may be regarded as an object of the present invention to provide an improved apparatus for encapsulating a finely divided clay within an organic polymeric material for use in a record member for receiving an oily colorless ink containing chromogenic materials that react to colorate respectively with an oil soluble acid-reactant organic polymer material and with a colorless acid-type of mineral, wherein said polymeric and mineral materials are present at the surface of said record member'in a form yielding exceptional resolution and uniformity of recording.

It is further an object of the invention to provide an improved apparatus for encapsulating a finely-divided clay within an organic polymeric material to produce a clay-polymeric material composition which enables the result set forth in the proceeding paragraph.

Now in accordance with the present invention, the foregoing objects, and others as will become apparent in the cause of the ensuing specification, are achieved by coating the base sheet of paper or other fibroin material with a composition wherein the acid-type mineral, such as kaolin clay, is present as a microfine dispersion of particles, individual of said particles being encapsulated within the said polymeric material, thereby producing a recording member the sensitized surface of which presents to the oily ink applied thereto an essentially unbroken polymeric layer in which individual mineral particles are effectively embedded.

The said coating composition is produced by a process wherein the heated mineral, preferably kaolin clay, is combined with a heated liquid polymer, preferably dispersed in a solvent, and the combined mix subjected to high shear mixing and compaction.

A coating composition having the desired properties is produced in the herein-described process by employing an improved apparatus for encapsulating a finely divided clay within an organic polymeric material. This apparatus includes:

an inclined cylindrical chamber having an upper end and lower end and a pair of end plates secured thereto;

a stand securing the cylindrical chamber whereby the upper end thereof is elevated with respect to the lower end; an inlet adjacent the upper end plate for introducing a mixture of clay and an organic polymeric material and a solvent therefore into the upper end of the chamber;

a journaled mixer shaft passing through the end plates concentrically with the walls defining the cylindrical chamber, the shaft having an array of rounded pins protruding therefrom and defining a helix extending about the shaft from one end to the other;

means to rotate the shaft to intimately blend the admixture of the clay and organic polymeric material and to advance the same through the chamber;

means for compacting the admixture during its passage through the chamber and prior to the discharge thereof, including the arrangement of the rounded pins defining the helix such that the helix decreases in pitch from the elevated or upper end of the shaft toward the opposite or lower shaft end;

and a discharge means adjacent the lower end plate for removing the encapsulated clay from the lower end of the chamber.

Thereafter the admixtures may be desolventized, preferably in the presence of continuing shearing forces, and milled. The resulting composition may then be coated upon base sheet by standard methods to yield the desired recording member.

BRIEF DESCRIPTION OF THE DRAWING In the drawing appended hereto the FIGURE is a partially broken-away view of the pin mixer apparatus of the present invention utilized in connection with the process set forth herein.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In accordance with one preferred process for preparing the composition described herein, the acid-type mineral intended for use in the composition is initially fed to a conventional heater station.

The preferred material for such acid-type mineral is a white kaolin clay such as, for example, the clay of this type available from the J. M. Huber Corporation of Huber, Georgia under the designation special Hydratex."

Such clays as are preferred as starting materials are generally paper coating grade clays derived from water fractionated Georgia kaolins having a TAPPI Brightness (in percentage reflectance) of at least 85 and approximately 80 percent of their particle size distribution finer than 2 microns with less than 6 percent of their particles coarser than microns. Such clays generally have a Brookfield viscosity measured in a 70 percent clay slip with a No. 1 spindle at 20 revolutions per minute at 25 C. of 100 200 cps. Typical properties of such clays are an average equivalent spherical particle diameter of 0.8 microns, a specific gravity of 2.60, an oil absorption of approximately 30 gms/100 gms., a pH of on the order of 4.5 5.0 measured with 100 gms of clay/250 ml. water, a refractive index on the order of 1.5 1.6 and a BET surface area on the order of 10 11 m /g.

Clays of this type are ideal for use in the present application in that in addition to possessing the necessary acid properties, their plate-like particle form, whiteness, and their ready availability lend them unparalleled paper coating advantages. Other types of particulate, colorless, water and oil-insoluble acid-type clays and other minerals such as some of the bentonites, can also be used in the invention, although these latter materials do not possess as favorable rheological characteristics as do the kaolin clays.

When the kaolin clays are thus utilized, they will representatively be heated below 140 C., preferably to the temperature range of to C. Thereafter, the heated clay is passed to a mixing chamber where it is combined in the presence of high intensity shearing with a suitable polymerized resin and a diluting solvent for the resin.

The solvent may be added with the resin or may be added to the mixing chamber following addition of the resin or may in some cases as discussed hereinafter be omitted.

The polymerized resin materials utilized with the present invention may be any of the substances of this type set forth in U. S. Pat. No. 3,455,721, previously alluded to. Thus among the oil-soluble organic polymeric materials suitable for use in this invention together with appropriate ink solvents to be used therewith, certain phenol-aldehyde and phenol-acetylene polymers, maleic acid-rosin resins, partially or wholly hydrolyzed styrene-maleic anhydride copolymers, ethylene-maleic anhydride copolymers, carboxy polymethylene, and wholly or partially hydrolyzed vinyl methyl ether-maleic anhydride copolymers are specified as typical of the reactive acidic polymeric materials.

Of the phenol-aldehyde resin group, examples of typically suitable resins include:

Bakelite phenolic coating materials manufactured by Union Carbide, meeting Federal Specification No. 'I"T--R27l and Military Specification No. MIL--- R-15184A, which are non-heat-reactive, 100 percent paraphenylphenol, oil soluble resins having a softening point range of 225 F. and a specific gravity at 25 C. of 1.20 1.23.

A p-phenylphenol resin prepared from a monomer having a general structural formula,

a molecular weight of 170.2, a freezing point of l66.5 C., a boiling point at 760 mm. Hg of 321 C., and a specific gravity at 25 C. of 1.275.

A p-sec-butylphenol resin prepared from a monomer having a general structural formula,

CHzra H- C ali s CHa- CH:

a molecular weight of 150.2, a boiling range at 760 mm. Hg of 237 239.7 C. and a specific gravity at 25 C. of 1.037.

Bisphenol A resins prepared from a monomer having a general structural formula,

a molecular weight of 228.3, a boiling point at 4 mm.

Hg of 220 C. and a specific gravity at 25 C. of 1.195; and other known resins of the type described herein.

Of preferable use in the invention are the paraphenylphenol-aldehyde polymerization products. At least a dimer structure having CH OH end bonds for a terminable structure is desirable.

It is believed that a'desirable molecular weight distribution may include 5 percent monomer, 15-20 trimer percent dimer, approximately 20 percent timer and the remaining portions of high molecular weights.

The admixture of polymerized resin and diluting solvent which may for example comprise xylene or the like may itself be heated on the order of to 125 C. prior to addition to mixing chamber. Temperatures 45 in mixing chamber are maintained in the range of to 130 C. and the mix of polymeric material, solvent, ahd kaolin clay is therein subjected to a high intensity, high shear mixing and compaction action, following which the mix is transferred to a desolventizing chamber. The latter may simply comprise a heat room wherein temperatures are maintained of the order of F. to fully evaporate the solvent. During such desolventization the mix is preferably subjected to a shearing action as by mixer blades or the like. Subsequently the mix is transferred to a milling station which may preferably include bead grinding of the material, after which the product emerges in a form suitable for coating upon paper webs or other fibrous base sheets by standard techniques known in the paper coating art.

The desired high intensity, high shear mixing action described in connection with the mixing chamber is preferably brought about by the apparatus shown in the partially sectioned, partially broken-away view of the thereof. A power shaft 22 is joumaled by bearing

blocks

24 and 26 and passes into container 12' where it widens to form a mixer shaft 28. Container 12 together with the other components of the apparatus set forth are mounted upon a support stand 30, which is seen to so support container 12 that a natural gravity flow is provided through the apparatus from inlet 18 to outlet 20. Because of the flow direction specified and the compaction action which will be set forth below it is necessary to seal the shaft 28 22 at its lower end, and it will be seen that a packing gland 32 is provided for such purposes.

Mixer shaft 28 is seen to be provided with a helically formed array of rounded pins 34. Such pins 34 serve as the primary means achieving mixing and breaking up of agglomerates in apparatus 10. Typically, apparatus 10 will be operated at rotational speeds of the order of 100 to 1,000 RPM, and will act both as amixer and as a mill to break up the agglomerates. It will be observed that the pitch of the helix formed by pins 34 which is suggested by the dotted line 36 in the FIGURE decreases from the upper end of mixer shaft 28 toward the lower end thereof. In consequence of this decreasing pitch arrangement and of the gravitationally directed flow toward the shaft end with decreasing pitch, compaction and increased inner-particulate shear ensue as the mix passes through apparatus 10. Both of these phenomena are believed to be significant in accomplishing clay encapsulation. In particular when mixes are thus processed in accordance with the scheme set forth it is found that they do indeed result in coating compositions wherein the kaolin clay is thoroughly encapsulated in the polymeric materials as previously described, and when such mixes are thereafter utilized in preparing coated recording members for use in record systems of the NCR" type previously referred to, that a new and superior member is enabled having resolution and marking qualities of a greatly improved nature. In essence such result stems from the fact that when the composition produced byuse of the present invention is coated upon its support base, an essentially continuous surface of polymeric material is presented to the reactive oily ink subsequently applied hereto, with the individual kaolin clay particles being entirely encapsulated and embedded in the polymeric material, and thus below the immediately accessible record surface. I

Evidence of the fact that the above described process and apparatus actually results in the clay being encapsulated in the resin is found in the discovery that when produced in accord with the present invention the resin is not separable from the clay by mechanical means, froth flotation or the like as were the resin-clays of the prior art.

A resin coating of less than 10 percent, preferably on the order of 7.5%, has been found operative while prior art systems generally required in excess of 15 percent resin in operative coatings. N

This reduction in resin content is significant in the economics of the system and provides clear evidence of the synergism produced by the present invention as compared with prior art physical blends.

FIGURE. A pin mixer is shown therein generally com- 65 prising a cylindrical container 12 provided with upper and lower end plates 14 and 16, a feed inlet 18 at the upper end thereof, and a feed outlet 20 at the lower end The apparatus of the present invention may be employed to particular advantage as follows:

A polymerization reaction producing, for example, a para-phenyl phenol/formaldehyde resin is carried out in the absence of clay.

The resin polymerization product is made down with a solvent such as xylene. The solvent helps to extend the resin and allows for more uniform coverage of the clay in subsequent steps. A preheated kaolin clay is added along with the resin solvent makedown to a steam heated pin auger where the hot clay particles are coated with resin in a liquid form. The heated clay helps keep the resin fluid throughout the treating operation and in later steps aids in desolventizing the modified clay. The process may be carried out utilizing unheated clay if the solvent level is increased accordingly. Sufficiently heated clay may be employed as to reduce or eliminate the need for additional heating in the mixing steps.

Typically, the auger may be fed at the rate of 3 tons of clay per hour with the resin-solvent flow regulated to coat the clay with approximately 7.5 percent resin based on the clay.

The modified clay discharged from the auger may be somewhat agglomerated and is thus passed into and through a pin mixer to reduce the average agglomerate size and to make the modification more uniform.

The output of the pin mixer is then passed to desolventizer which is a jacketed, steam heated, double screw auger conveyor designed to remove volatiles. The solvent is vented to solvent recovery apparatus.

The desolventized, modified clay may then preferably be cooled to prevent degradation of the resin encapsulation.

Subsequently the modified clay is passed to impact mill to reduce the particle and agglomerate size of the modified clay.

The milled product is then made down in water in slurry makedown tanks.

Following slurry makedown the slurry is passed to a bead grinding mill which breaks down any resincemen-ted clay particles and brings the particle size of the modified clay back in line with the starting clay.

Excessive bead grinding has a deleterious effect on the coating properties of the modified clay, since excess grinding removes the encapsulating resin from the clay and produces a mere physical mixture of the resin and clay similar to the prior art compositions.

Following bead grinding at the modified clay is passed to a flocculation tank and then through filters to raise the solids content. The filter cake may then be prepared for shipment or passed to storage tanks.

in summary, a coating composition having the desired properties is produced in the herein-described process by employing an improved apparatus for encapsulating a finely divided clay within an organic polymeric material. This apparatus includes:

a stand securing the cylindrical chamber whereby the upper end thereof is elevated with respect to the lower end;

an inlet adjacent the upper end plate for introducing a mixture of clay and an organic polymeric material and a solvent therefore into the upper end of the chamber;

While the present invention has been particularly described in terms of specific embodiments thereof, it will be understood in view of the present disclosure, that numerous variations are now enabled to those skilled in the art, which variations in propriety, are yet within the true scope of the instant teaching. Accordingly the present invention should be broadly construed and limited only by the scope and spirit of the claim now appended hereto. 1

What is claimed is:

1. An improved apparatus for encapsulating a finely divided clay within an organic polymeric material, said apparatus comprising: an inclined cylindrical chamber having an upper end and lower end and a pair of end plates secured thereto; stand means securing said cylindrical chamber whereby the upper end thereof is elevated with respect to the lower end, means comprising an inlet adjacent said upper end plate for introducing a mixture of clay and an organic polymeric material and a solvent therefor into the upper end of said chamher; a journaled mixer shaft passing through said end plates concentrically with the walls defining said cylindrical chamber, said shaft having an array of rounded pins protruding therefrom and defining a helix extending about said shaft from one end to the other; means to rotate said shaft to intimately blend said admixture of the clay and organic polymeric material and to advance same through said chamber; means for compacting said admixture during its passage through said chamber and prior to the discharge thereof, said means including the arrangement of the rounded pins defining said helix such that the helix decreases in pitch from the elevated or upper end of said shaft toward the opposite or lower shaft end, and discharge means for removing the encapsulated clay from the lower end of said chamber, said discharge means being adjacent said lower end plate.

Claims

1. An improved apparatus for encapsulating a finely divided clay within an organic polymeric material, said apparatus comprising: an inclined cylindrical chamber having an upper end and lower end and a pair of end plates secured thereto; stand means securing said cylindrical chamber whereby the upper end thereof is elevated with respect to the lower end, means comprising an inlet adjacent said upper end plate for introducing a mixture of clay and an organic polymeric material and a solvent therefor into the upper end of said chamber; a journaled mixer shaft passing through said end plates concentrically with the walls defining said cylindrical chamber, said shaft having an array of rounded pins protruding therefrom and defining a helix extending about said shaft from one end to the other; means to rotate said shaft to intimately blend said admixture of the clay and organic polymeric material and to advance same through said chamber; means for compacting said admixture during its passage through said chamber and prior to the discharge thereof, said means including the arrangement of the rounded pins defining said helix such that the helix decreases in pitch from the elevated or upper end of said shaft toward the opposite or lower shaft end, and discharge means for removing the encapsulated clay from the lower end of said chamber, said discharge means being adjacent said lower end plate.