CA1134120A - Calcium silicate and process for producing same - Google Patents

Abstract

Abstract of the disclosure Globular secondary particles of wollastonite group calcium silicate crystals represented by the formula ?CaO?mSiO2?nH2O
wherein 1 ? ? ? 6, 1 ? m ? 6 and 0 ? n ? 1, characterized in that the particles comprise hollow globular secondary particles of the wollastonite group calcium silicate crystals, the globular secondary particles having an average spontaneous sedimentation height of at least 800 ml, an outside diameter of 5 to 110 µm, an average apparent density of 0.04 to 0.09 g/cm3 and an average shell density defined by the equation Y = 0.0033X + B
wherein Y is the average shell density, X is the average diameter of the particles, B is a constant, 15 µm ? X
? 40 µm and 0 ? B ? 0.115.

Description

CALCIUM SILICATE AND PROCESS FOR PRODUCING SAME

This invention relates to calcium silicate and a process for producing the same, and more particularly to secondary particles of calcium silicate crystals, aqueous slurries of calcium silicate crystals containing such secondary particles as dispersed in water, calcium silicate shaped bodies composed of such secondary particles and processes for producing these secondary particles, slurries and shaped bodies.
It is well known that calcium silicate shaped bodies have the features of being light and strong and having outstanding resistance to fire and good heat insulating properties. These characteristics appear attributable largely to the structure of the bodies and the method of production thereof.
We have already conducted extensive research on calcium silicate shaped bodies and processes for producing the same. In the course of the research, we found that calcium silicate crystals, when agglomerated into globular secondary particles of unique structure, afford shaped bodies having a low bulk density and high mechanical strength. Based on this novel finding, we accomplished an invention which has already been patented (U.S.P. No.3,679,446).

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The globular secondary particles of calcium silicate disclosed in the patent are substantially globular, are composed of needlelike crysta~s of calcium silicate interlocked with one another three-dimensionally, range from 10 to 150 ~m in outside diameter and have needlelike to platelike calcium silicate crystals partly pro~ecting from the surface in the form of whiskers. The secondary particles give calcium silicate shaped bodies having a low bulk density and high mechanical strength.
It is also well known that the heat insulating properties of calcium silicate shaped bodies improve with a decrease in the bulk density of the body. Thus efforts have been focused on the development of shaped bodies having a minimized density and nevertheless possessing useful strength.
An object of this invention is to provide calcium silicate shaped bodies having useful strength and a greatly reduced weight (i.e. a low bulk density).
Another object of this invention is to provide a process for producing exceedingly light shaped bodies of calcium silicate having useful strength.
Another object of the invention is to provide globular secondary particles of calcium silicate capable of affording calcium silicate shaped bodies having .
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useful strength and yet possesslng a greatly reduced weight.
Another object of the invention is to provide aqueous slurries of globular secondary part`icles of calcium silicate which can be used directly for the production of such shaped bodies of calcium silicate.
These objects and other features of the invention will become apparent from the following descrip-tion.
Stated more specifically, the present invention provides globular secondary particles of calcium silicate characterized in that the particles are hollow globular secondary particles of wollaston~ite group calcium silicate crystals represented by the formula QCaO mSiO2-nH2O
wherein 1 ~ Q < 6, 1 < m < 6 and 0 _ n < 1, the globular secondary particles having an average spontaneous sedimen-tation helght of at least 800 ml, an outside diameter of 5 to 110 ~m an average apparent density of 0.04 to 0.09 g/cm3 and an average shell density defined by the equation Y = 0.0033X + B
wherein Y is the average shell density, X is the average diameter of the particles, B is a constant, 15 ~m c X
< 40 ~m and 0 ~ B < 0.115.
Put in greater detail, the secondary particles f calcium silicate crystals of this invention have the ;
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following characteristics.
(1) -The calcium silicate crystals are wollastonite group crystals represented by the following formula as determined by a thermobalance and chemical analysis.
QCaO mSiO2 nH2O
wherein 1 < ~ < 6, 1 < m < 6 and 0 < n < 1. Typical of the wollastonite group calcium silicate crystals represented - by the above formula are ~-wollastonite (5aO~SiO2), xonotlite (5CaO~5SiO2-H2O or 6CaO~6SiO2~H2O) and foshagite (4CaO 3SiO2~H2O). For use in this invention, xonotlite may contain a small amount of quasi-crystalline xonotlite which differs from xonotlite in crystallinity.
Quasi-crystalline xonotlite grows into crystals of xonotlite and contains varying amounts of crystal water.
Of the wollastonite group crystals exemplified above, wollastonite and xonotlite have the most preferred properties. Xonotlite as defined by the foregoing formula has good properties if Q and m are each at least

2 and n is not larger than 1.
Insofar as the secondary particles of this invention comprise calcium silicate crystals of wollastonite group as the main component (usually in a proportion of at least 50% by weight?, the particles may contain other calclum silicate crystals, such as tobermorite group calcium silicate crystals.

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(2) The secondary particles of this invention have an average spontaneous sedimentation height of at least 800 ml, preferably at least 850 ml.
The average spontaneous sedimetation height is measured by the following method and~shows the settling - properties of the secondary particles when the particles are dispersed in water and then allowed to stand.
Secondary particles of calcium silicate crystals are dispersed in water to a concentration of 1% by weight to prepare an aqueous slurry of crystals.
A 1000-ml portion of the slurry is placed into a 1000-ml measuring cylinder having an inside diameter of 6.5 cm, and the cylinder is shaken up and down 5 times with its open end closed with a cover. The slurry is then allowed to stand for 30 minutes with the cover removed, and the volume of the resulting sediment of the secondary particles is measured. The same procedure is repeated 5 times.
The average spontaneous sedimentation height is the average of the five measurements in ml. An average spontaneous sedimentation height of 800 ml, for example, means that the cylinder contains a 200-ml upper layer of water only and a 800 ml of a suspension of the secondary particles in water in its lower portion.

(3) The secondary particles of this invention are composed of needlelike calcium silicate crystals which - ~.
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^ 113~120 are three-dimensionally interlocked with one another and each in the form of a hollow globe having an outside diameter of 5 to 110 ~m. For example, Fig; l which is an optical micrograph at a magnification of 200X showing secondary particles of Example 1 of the invention reveals that the particles are in the range of 5 to 110 ~m in outside diameter and that most of the particles are in the range of 10 to 50 ~m. Further from the photograph of Fig. 2 taken by a scanning electron microscope at a magnification of 600X and showing secondary particles - of Example 1 of the invention, it is seen that the secondary particles are formed of numerous calcium silicate crystals which are three-dimensionally inter-locked with one another and have a hollow interior.
Figs. 3 and 4 are scanning electron micrographs at magnifications of 600X and 2000X, respectively, showing a slice of about 1.5 ~m in thickness of a shaped body obtained by subjecting the aqueous slurry of secondary particles of Example 1 of the invention to spontaneous sedimentation to form a mass and drying the resulting mass. The slice was prepared by cutting off a portion of the shaped body, fixing the portion with a mixture of methyl methacrylate, ethyl methacrylate and n-butyl methacrylate resins and slicing the fixed portion with a super microtome. Figs. 3 and 4 indicate that the ' ~

~13~1~0 secondary particles are in the form of hollow globes made up of three-dimensionally interlocked crystals of calcium silicate.

(4) The secondary particles of the invention have an average apparent density of 0.04 to 0.09 g/cm3 as determined by the following method.
Secondary particles of the invention are dis-persed in water to prepare a slurry of calcium silicate crystals One part by weight of a nonionic surfactant ("FC-430," trademark for a surfactant consisting mainly of fluorocarbon and manufactured by Sumitomo 3M Co., Ltd., effective component 100%)-is uniformly admixed with the slurry per 100 parts by weight of the slurry.
A 200 g quantity of the mixture is then placed into a mold 16 cm in length, 4 cm in width and 4 cm in depth, and allowed to stand for 24 hours for spontaneous sedimentation with the mold placed in a dryer at 50C.
The mass as contained in the mold is further dried in the dryer at 110C to obtain a shaped body. A piece, about 2 mm in length, about 2 mm in width and about 1 mm in thickness, is cut out from the shaped body, then fixed with a mixture of methyl methacrylate, ethyl methacrylate and n-butyl methacrylate resins and thereafter sliced successively by a super microtome in a thickness of about 1.5 um such that a secondary ;, , .

113~1~0 particle is contained in a series of slices from one end to the other end of the particle. The slices are photographed under a scanning electron mic`roscope at a magnification of 2000X. The photographs are cut into the particle portions and space portions which are weighed on a chemical balance respectively. Since the weight ratio thus determined is approximately constant for any other like series of slices, the weight ratio of the secondary particle portions can be regarded as the volume ratio of the secondary particles in the shaped body. Accordingly the average apparent density can be calculated from the following e~quation.
Average apparent densitY (g/m ) Volume ratio of particles in which: Volume ratio of particles _ Weight of particle portions Weight of particle portions + Weight of space portions

(5) The secondary particles of the invention have a shell about 0.1 to about 7.0 ~m in thickness, and have a density of 0.02 to 0.06 g/cm when made into a shaped body by spontaneous sedimentation. The particles have an average shell density Y defined by the equation Y = 0.0033X + B
wherein X is the average diameter of the particles in the range of 15 ~m < X < 40 ~m, and B is a constant in the range of 0 < B < 0.115. Fig. 7 shows the dis--.. , I

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tribution of average shell densities in the hatched area.
Fig. 7 also shows the distribution of average apparent densities of secondary particles in the boxed area.
The shell thickness, the density of the spontaneous sedimentation shaped body and the average shell density are measured by the following methods.
Shell thickness (~m):
The same surfactant as used above is uniformly admixed with an aqueous slurry of secondary particles of the invention in an amount of 1 part by weight per 100 parts by weight of the slurry. A 200 g quantity of the mixture is poured into the same mold as used above and allowed to stand for 24 hours for spontaneous sedimentation with the mold placed in a dryer at 50C.
The mass is further dried, as contained in the mold, within the dryer at 110C to obtain a shaped body.
A piece, about 2 mm in length, about 2 mm in width and - about 1 mm in thickness, is cut out from the shaped body, then fixed with a mixture of methyl methacrylate, ethyl methacrylate and n-butyl methacrylate resins and thereafter sliced by a super microtome in a thickness of about 1.5 ~m. The slices are photographed under a scanning electron microscope at magnifications of 600X
and 2000X to measure the minimum and maximum thicknesses of the secondary particles. The miminum and maximus thus ::

--~ 1134~20 measured provide the range of thicknesses of the shells.
Density of the spontaneous sedimentation shaped body (g/cm3):
The same surfactant as used above is uniformly admixed with an aqueous slurry (concentration: z% by we,ght) of secondary particles of the invention in an amount of 1 part by weight per 100 parts by weight of the slurry. A 200 g quantity of the mixture is poured into the same mold as above and allowed to stand for 24 hours for spontaneous sedimentation in a dryer at 50C. The mass as contained in the mold is further dried in the dryer at 110C. The volume (V) of the resulting shaped body is measured. The density of the shaped body thus formed by spontaneous sedimentation is calculated from the following equation.

Density (g/cm3) = ~
V (cm ) in which the weight (W g) of the shaped body is given by 200 x 100 x 1OO (g).
Average shell density (g/cm3):
Calculated from the following equation.

Average shell densitY (g/c ) Average volume of shell of one particle The average volume of the shell of one particle is given by 3~ [(r)3 - (r-d)3] wherein r is the average ~ .
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113~120 radius of the secondary particles, and d is the average thickness of the shell.
The average weight of one partic~e (g) is given by ~average apparent density (g/cm3)] x [volume of one particle having average dlameter (cm3)].
The average diameter of the particles is deter-mined by plotting the outside diameters of the secondary particles vs. relative frequency to obtain a cumulative curve of the outside diameters and reading the outside diameter at a cumulative weight percent of 50%.
In addition to the characteristics described above, the secondary particles.of this invention are further characterized by burrs provided by calcium silicate crystals projecting from the surface of the particle. Fig. 5 is an electron micrograph showing secondary particles of Example 1 of the invention given later, at a magnification of 6000X.
As already stated, the secondary particles of the invention are in the form of hol-low globes com-posed of a large number of calcium silicate crystalsof the wollastonite group which are interlocked with one another three-dimensionally. The particles have a very large average spontaneous sedimentation height of at least 800 ml. The large spontaneous sedimentation height indicates that the globular secondary particles .. . .
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per se are extremely light and have very low settling properties in water. This is one of distinct features of the secondary particles of the invention. The secondary particles of the invention further include those having an average apparent density of 0.05 g/cm3 which is lower than that of almost any other like particles heretofore available. Accordingly such secondary particles afford super-light calcium silicate shaped bodies having a density of about 0.05 g/cm3.
Despite the low density, the shaped bodies have bending ~;
strength of at least 0.5 kg/cm and therefore satisfactory useful strength because they are ~composed of hollow globular secondary particles.
Most of the secondary particles of the invention, usually at least about 80% thereof, are about lO to about 50 ~m in outside diameter.
The secondary particles of the invention can be produced, for example, by dispersing fine siliceous particles up to 0.5 ~m in average diameter in water to prepare a slurry, admixing the slurry with milk of lime having a sedimentation volume of at least 5 ml to obtain a starting slurry containing water in an amount of at least 30 times the weight of the solids of the starting slurry, subjecting the starting slurry to hydrothermal reaction with application of pressure and heat and with ....
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li3~20 continuous or temporarily interrupted stirring to prepare an active slurry of calcium silicate crystals, and drying the active slurry. This process will be desrcribed below in greater detail.
According to this invention, fine siliceous particles up to 0.5 ~m in average diameter are used in the form of an aqueous slurry as a siliceous material.
The term "average diameter of particles" as used in this invention means the diameter of specific surface area as measured by the BET method and calculated from the following equation.
Specific surface area diameter (dsp) = pKsw in which p is the specific gravity of siliceous material, Sw is specific surface area (as measured by the BET method) and K is a shape factor (6, assuming that the particle is spherical).
Typical of useful fine particle siliceous materials is so-called silicon dust resulting from the production of silicon metal, ferrosilicon and compounds thereof as a by-product in large quantities. Silicon dust is usually 0.05 to 0.5 ~m in average diameter, contains amorphous silica as the main component and has an SiO2 content of at least 80% by weight and a bulk density of up to about 0.2 g/cm3. Silicon dust, unlike natural siliceous material, is an artificial product and , . ... . .. . . . . .
., : .. " . ,, . , -, ~13~120 is therefore commercially available easily at a low cost with a considerably uniform composition and is very useful as a siliceous material Typically s1 icon dust has the following chemical composition.
SiO280 - 99 by weight Fe23 0 - 6 CaO 0 - 4 ~gO 0 - 3 - Miscellaneous0 - 5 Another example of suitable siliceous materials is fine particle reinforcing silica up to 0.5 ~m in average dia-meter and heretofore used, for instance, as a filler for rubbers. Other siliceous materials, up to 0.5 ~m in average diameter, are also useful in this invention, such as fine crystalline particles of quartzite, quartz, sandstone quartzite, cemented quartzite~ recrystallized quartzite, composite quartzite, silica sand, silica stone, etc. and opalic silica stone. Provided that the siliceous materials have an average particle diameter in the above-specified range, the materials may contain relatively coarse particles. For use as the f`ine particle siliceous material, silicon dust, for example, can be used conjointly with a small amount of relatively large usual siliceous - particles.

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li34:1~0 - According to the invention it is critical to use such fine siliceous particles in the form of an aqueous slurry as a siliceous material. Whè'n the slurry of fine siliceous particles is used in combination with 5 the specific lime material to be described later and made into a starting slurry having water to solids ratio by weight of 30:1 or greater, the starting slurry gives super-light globular secondary particles of calcium silicate and eventually super-light shaped bodies of calcium silicate as contemplated, when further subjected to hydrothermal reaction with stirring.
The aqueous slurry can~be prepared, for example, by adding fine siliceous particles to an amount of water at least equal to the amount of the particles by weight and thoroughly dispersing the particles in the water with use of a mechanical stirring device such as a homogenizer. With this invention the slurry is advan-tageously usable in which 70% by weight of the particles are up to 2 ~m in diameter (hereinafter referred to as "particles at cumulative weight percent of 70% are up to 2 ~ml') To obtain the desired slurry, fine siliceous particles are dispersed in varying amounts of water by various dispersing methods to prepare slurries each 1000 ml in quantity and containing 50 g of solids, and the distribution of particle sizes in each of the slurries , :. , -~ ' '' ,, ' ~ .

il3 is measured according to the method of JIS A 1204-1970 to identify the slurry having the specified particle sizes. Particles of various materials inclùding siliceous materials are generally more likely to agglomerate into larger particles in water with a decrease in particle size although the degree of agglomeration varies with the kind and properties of the particles. For this reason, fine siliceous particles up to 0.5 ~m, when merely placed into water, usually will not provide a uniform slurry but agglomerate in the water, with the result that the particles at cumulative weight percent of 70%
become larger in diameter. Slurries containing particles of low dispersibility will present difficulty in the production of contemplated shaped bodies, whereas such difficulty is avoidable for the production of the desired product with use of a slurry in which fine siliceous particles have been dispersed in water by high-speed or forced stirring as with a homomixer so that the particles at cumulative weight percent of 70% are up to 2 ~m in diameter. If the stirring conditions such as speed of stirring for effecting the dispersionare stricter, the particle diameter can be decreased in a shorter period of time in achieving the cumulative-weight percent of 70%. A dispersant such as sodium metaphosphate is usable for dispersing the particles.

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~i3~ 0 According to the invention, it is also critical to use the above-specified siliceous material in com-bination with milk of lime having a sedimentation volume of at least 5 ml.
The sedimentation volume of milk of lime referred to in this specification is a value obtained by preparing 50 ml of milk of lime having a water to solids ratio by weight of 120:1, allowing the milk to stand for 20 minutes in a cylindrical container 1.3 cm in diameter and at least 50 cm in capacity and measuring the volume (ml) of the resulting sediment of the particles of the lime. Thus a sedimentation volume of 10 ml means that the volume of such sediment is 10 ml, with 40 ml of a supFrnatant above the sediment in the container.
Accordingly the value of the sedimentation volume is indicative of the degree of fineness of the lime particles in the water; the value, if large, indicates that the lime particles are very fine and are dispersed in the water w1th stability and are less prone to sedimentation.
With this invention, various milks of lime are usable effectively if having a sedimentation volume of at least 5 ml. The sedimentation volume of the milk of lime is dependent on the limestone used as the raw material, calclnation temperature and time, the amount of water and temperature used for slaking, stirring or grinding .: :

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conditions involved in slaking, etc. It is dependent especially largely on the temperature and stirring or grinding conditions employed for slaking. ~ilks of lime having a sedimentation volume of at least 5 ml can be prepared when such conditions are used in ingenious combination. In the technique for producing shaped bodies of calcium silicate, no investigation has been made on the effect of sedimentation volume of milk of lime used as a lime material on the properties of the shaped body obtained, nor has it been attempted to use as a lime material a special milk of lime having such high dispersibility as to have a sedimentation volume of at least 5 ml. While the lime material for the production of shaped bodies of the type described may be prepared in the form of a milk of lime, the milk of lime is usually lower than 5 ml in sedimentation volume.
The milk of lime having a sedimentation volume of at least 5 ml to be used in this invention is prepared typically by treating water and lime, for example in a water to solids ratio by weight of 5:1, preferably at a temperature of at least 60C in a homomixer for high-speed or forced stirring, or in a wet grinder for grinding, and dispersing the mixture in water. The speed and intensity of stirring as by the homomixer can be usually reduced when the stirring is conducted at a higher temperature or for a prolonged period of time.

,. ' ~ ' ~ , , 3~ 0 Various stirrers with or without a ba~le plate are usable for this purpose. Similarly various grinders are effectively usable. Various lime materials are useful for the preparation of the milk of lime. Typical example is quick lime. Although slaked lime, carbide slag, etc. are usuable, milk of lime having a large sedimentation volume can be prepared most easily from quick lime.
The mole ratio of the specific siliceous material to the lime material, when altered, produces a difference in the type of calcium silicate crystals afforded by hydrothermal reaction. Lower mole ratios yield tobermorite, while higher mole ratios lead to formation of dicalcium silicate hydrate, etc. The mole ratios suitable for the formation of xonotlite crystals are usually in the range of about o.8 to about 1.2, especially in the range of about 0.92 to about lØ
For practicing the present invention, a starting slurry is prepared first by mixing a slurry of fine siliceous particles and milk of lime so that the two materials are in the desired mole ratio within the foregoing range. The starting slurry must contain water in an amount of at least 30 times the weight of the total solids in the starting slurry. If the water contained in the slurry of siliceous material and milk : " ' of lime used is insufficient to afford the specified proportion of water, the amount of water ~s adjusted with addition of water. The amount of watër is prèferably about 35 to about 80 times, more preferably about 40 to 70 times, the total weight of the solids in the starting slurry. The super-light secondary particles of calcium silicate and, accordingly, light calcium silicate shaped bodies contemplated by the inven-tion can be produced only when water is used in a quantity much largerthan the quantities heretofore used for the production of shaped bodies of this type.
With this invention, the starting slurry thus prepared is subjected to hydrothermal reaction with application of pressure and heat and with continuous or temporarily interrupted stirring. The starting slurry can be stirred by any of various methods insofar as the solids in the slurry can be held dispersed uniformly in the aqueous medium. The slurry can be stirred, for example, with a mechanical device, air or liquld or by vibration. The reaction conditions such as pressure, stirring speed, etc. are suitably deter-mined in accordance with the type of the reactor, stirring device and reaction product, etc. The preferred pressure is usually about 8 to 50 kg/cm2, while the preferred temperature is about 175 to about 264C.

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~13~120 The reaction can be completed within a shorter period of time with an increase in the pressure.
The hydrothermal reaction stated above gives a slurry of xonotlite and/or foshagite crystals con-taining numerous globular secondary particles of theinvention as dispersed in water. The secondary particles can be obtained by drying the slurry without impairing the shape of the particles. Globular secondary particles of wollastonite crystals can be obtained according to this invention when the above secondary particles are baked at a temperature of at least 800C so as not to impair the shape of the particles.
For the production of the globular secondary particles of the invention, inorganic fibers such as asbestos, rock wool and glass fibers can be incorporated into the starting slurry. When such inorganic fibers are incorporated into the starting slurry, the calcium silicate crystals formed by the hydrothermal reaction are very likely to form globular secondary particles on the fibrous material, with the result that the globular secondary particles are partly joined with the fibers.
,Such slurry gives shaped bodies of higher mechanical strength than a slurry of calcium silicate crystals to which inorganic fibers are added, i.e. after it has ~134120 been prepared from a starting slurry.
The globular secondary particles of this invention can be dispersed or suspended in ~water with ease to form a slurry with their structure retained free of deterioration. The slurry can be made into a shaped body merely when it is shaped to the desired form and dried. The amount of water to be used for the preparation of slurry, which is widely variable, is usually about 15 to about 100 times, preferably about 20 to about 80 times, the weight of the solids.
The aqueous slurry of globular secondary particles of the invention, when shaped and then dried, affords a super-light shaped body. Due to the presence of water in the hollow portions of the globular secondary particles forming the slurry, the particles will not be easily broken down even when subjected to the shaping pressure, while the globular secondary particles are rigidly joined with one another by the engagement between the numerous burrs projecting from their surfaces.
During drying, the water is removed from the hollow portions. As a result, the shaped body obtained is very light and has sufficient useful strength.
The slurry can be shaped by various methods, for example, by injection molding, with use of a press for dewatering and shaping, or with use of a sheet making , .
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~134120 machine. It is also possible to sub~ect the slurry to spontaneous sedimentation and dry the resulting mass to a shaped body. Use of increased pressure ~or dewatering the slurry during shaping gives a shaped body of increased density and enhanced strength. The shaped mass may slightly shrink during drying, in which case it is preferable to incorporate a surfactant or reinforcing `-material into the slurry in an amount capable of effectively preventing the shrinkage. In this case when a surfactant is incorporated into a starting slurry, the shrinkage may be effectively prevented. The amount is widely variable in accordance with the conditions under which the slurry is prepared, the materials of the slurry, shaping method, etc. Useful surfactants include nonionic, cationic and anionic surfactants, such as those of quaternary ammonium type, fluorine type, higher alcohol type, straight-chain alkylbenzene type, alkyl sulfate type, polyoxyethylene alkyl phenol type, sorbitan-fatty acid ester type, etc. These surfactants can be used in admixture. Commercial products containing such surfactants are also usable. The surfactants are used in an amount, calculated as solids, of 0.01 to 5%
by weight, preferably 0.02 to 2% by weight, based on the weight of the slurry or starting slurry. Examples of useful reinforcing materials are inorganic fibers 113~1ZO

such as asbestos~ rock wool, glass fiber, ceramics fiber, carbon fiber and metal fiber; natural fibers such as pulp, cotton, wood fiber, hemp, etc.; and synthetic fibers such as rayon and fibers of polyacrylonitrile, polypropylene, polyamide and polyester. These fibers are usable singly, or at least two of them are usable in combination. Examples of other useful reinforcing materials are cements such as portland cement and alumina cement, clay, gypsum, binders of phosphoric acid and water glass type, organic binders, etc. ~ wide variety of such reinforcing materials are usable depend-ing on the properties desired of the shaped body and contemplated use. They are usable in a suitably deter-mined amount. For example, it is suitable to use inorganic or organic fibers in an amount of usually u~
to 50% by weight, preferably 5 to 20% by weight, clays in an amount of 3 to 50% by weight, preferably 5 to ~0%
by weight, and cements in an amount of about 0.5 to about 40% by weight, all based on the weight of the solîds in the slurry.
The shaped mass, when dried, gives a very light calcium silicate shaped body which has never been hereto-fore available. The shaped body has a density of about 0.04 g/cm3 and has useful strength.
This invention will be described below in , :. ,.

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~3~20 greater detail with reference to examples, in which the parts and percentages are all by weight.
Fig. 1 is a photograph o~ globular secondary particles of this invention taken under an optical microscope at a magnification of 200X;
- Fig. 2 is a scanning electron micrograph showing the same particles at a magnification of 600X;
Figs.3 and 4 are scanning electron micrographs at magnifications of 600X and 2000X, respectively of about 1.5 ~m thick slice prepared by subjecting secondary particles of the invention to spontaneous sedimentation to obtain a shaped body, cutting out a piece from the body and slicing the piece after fixing the piece with a resin mixture;
Fig. 5 is an electron micrograph showing secondary particles of the invention at a magnification of 6000X;
Fig. 6 is an electron micrograph at a magnifi-cation of 80QoX showing xonotlite crystals forming secondary particles of the invention; and Fig. 7 is a graph showing average shell densities and bulk densities of globular secondary particles of the invention.

Example 1 Quick lime (19.94 parts, containing 95.02% of CaO) is slaked in 478.6 parts of hot water a`t 95C, and the mixture is stirred in a homomixer at a high speed for 7 minutes to prepare milk of lime having a sedimenta-tion volume of 18.7 ml. Subsequently an aqueous sus-pension (concentration 4.76%) of ferrosilicon dust (containing 92.0% of SiO2) 0.24 ~m in average particle diameter is stirred in a homomixer at a high speed for 5 minutes to disperse the dust particles and obtain an aqueous slurry 1.2 ~m in particle diameter at cumulative weight percent of 70%. The milk of lime is admixed with a portion of the aqueous slurry of the ferrosilicon dust (22.06 parts, calculated as solids), and the mixture is stirred with addition of water to obtain a starting slurry having a water to solids ratio by weight of 50:1.
The starting slurry is subjected to hydrothermal reaction at saturated water vapor pressure of 12 kg/cm at a tem-perature of 191C for 8 hours in an autoclave having an inside diameter of 15 cm, with a stirrer driven at 112 r.p.m. to obtain a slurry of crystals. The slurry is dried at 110C for 24 hours and thereafter sub~ected to x-ray diffractiometry,which reveals that the crystals are xonotlite crystals.
The slurry is dried on slide glass and then :
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: ~ , ,. ' ~ ' photographed under an optical microscope at a magnifica-tion of 200X. The photograph reveals globular secondary particles 28 ~m in average outside diameter as shown in Fig. 1. An observation of the dry slurry by the reflection method reveals that the particles have distinct contours and substantially transparent interior.
One part of a nonionic surfactant ("FC-430,"
trade mark for a surfactant consisting mainly of fluoro-carbon and manufactured by Sumitomo 3M Co., Ltd., effective component 100%) is admixed with the slurry of crystals per 100 parts of the slurry. A 200 g quantity of the mixture is then placed into a mold 16 cm in length, 4 cm in width and 4 cm in depth, and allowed to stand for 24 hours for spontaneous sedimentation with the mold placed in a dryer at 50C. The mass as contained in the mold is further dried in the dryer at 110C to obtain a shaped body. A piece is cut out from the shaped body, then fixed with a mixture of methyl methacrylate, ethyl methacrylate and n-butyl methacrylate resins and there-after sliced by a super microtome~ The slice is photo-graphed under a scanning electron microscope at magnifi-cationS of 600X and 2000X. Figs. 3 and 4 presenting the photographs reveal that the particles have a shell thickness o~ 0.1 to 7 ~m, an average shell thickness of 2.25 ~m and substantially hollow interior. An electron ' ' ' ~
. ~ .
:

micrograph of the secondary particles taken at a magnifi-cation of 6000X reveals that the shells have numerous burrs on the surface due to the presence of xonotlite crystals as seen in Fig.s. Fig. 2 is a scanning electron micrograph of the secondary particles at 600X which shows that the particles have a hollow globular shell composed of a large number of xonotlite crystals inter-locked with one another three-dimensionally. The xonotlite crystals (primary particles) forming the secondary particle are needlelike crystals l to 20 ~m in length and about 0.05 to about l.0 ~m in width as seen in Fig. 6 which is an electron micrograph at 8000X.
These crystals, when baked at 1000C for 3 hours, are converted to ~-wollastonite crystals.
Table l below shows properties of the secondary particles.
Table 1 Properties Measurements Average particle diameter (~m) 28 Range of outside diameters of 80% lO - 50 of the particles (~m) Average apparent density ~g/cm3) 0.053 Average weight of particles (g) 6.og x lO lO
Thlckness of shell (~m) 0.1 - 7 Average shell thickness (~m)2.25 Average shell density (g/cm3)0.130 I

~13~1ZO

The same surfactant as used above is admixed with the slurry of xonotlite crystals obtained as above, in an amount of 1 part per 100 parts of the ~lurry.
A 200 g quantity of the slurry is then poured into a mold, 16 cm in length, 4 cm in width and 4 cm in depth, and allowed to stand for 24 hours for spontaneous sedimenta-tion with the mold placed in a dryer at 5OC. The mass as contained in the mold is further dried in the dryer at 110C to obtain a shaped body having a density of 0.031 g/cm3. The slurry of crystals has an average spontaneous sedimentation height of 950 ml.
Specimens of shaped bodies are prepared from portions of the slurry prepared as above (each 88 parts, calculated as solids) by adding 5 parts of glass fiber, 4 parts of pulp and 3 parts of cement to the slurry (specimen I), or by adding 5 parts of glass fiber, 4 parts of pulp, 3 parts of cement and 20 parts of a mix~ure of a nonionic surfactant and an anionic surfactant (trade mark "Guranatupu NF-50," product of Sanyo Kasei Kogyo Co., Ltd., containing 20% solids) to the slurry (specimen I~), thoroughly mixing the ingredients, shaping the mixture by a press and drying the shaped mass at 120C for 20 hours. Other specimens are produced in the same manner as above except that the surfactants used are 6.7 parts of an anionic surfactant (product of ,,. :1 .. I
.
:: .

113~120 Tokyo Kaseikogyo Co., Ltd., containing sodium dodecyl-benzene sulfonate and having a solids content of 60%) for specimen III, 4 parts of a nonionic sur~actant (product of Tokyo Kaseikogyo Co., Ltd., containing polyoxyethylene sorbitan monooleate, effective component 100%) for specimen IV, and 4 parts of cationic surfactant (product of Tokyo Kaseikogyo Co., Ltd., containing dimethylbenzylphenylammonium chloride, solids content 100%) for specimen V. Table 2 shows properties of the specimens.

Table 2 ~~~---____~pecimen No.
Properties ~ I II - III IV V
Density (g/cm3) 0.056 0.051 0.051 0.053 0.053 Bending strength 1.79 1.45 1.42 1.56 1.59 ( kg/cm2 ) Specific strength 570.8 557.5 545.9 555.4 566.0 Linear shrinkage 2. 73 0.53 0.57 o . 49 0.63 on drying (%) The properties listed above are measured by the following methods.

Bending strength: According to JIS A 9510.

Specific Strength Given by Bending strengt~
(Density) The specimens exhibit the properties shown in Table 3 when baked at 850c for 3 hours.

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~1 3~ZO

Table 3 ~ Specimen No.
Properti~ ~ I II III IV V
Density (g/cm3) 0.053 0.049 0.049 0.~50 0.050 Bending strength 1. 24 1.03 1. oo 1.05 l . lo (k /cm2) Specific strength 441.4 429.0 416.5 420.0 440.0 Linear shrinkage 0. 51 0.47 o .48 0.43 0.49 after heating (%) Residual specific 77.3 77.0 76.3 75.6 77.7 strength The residual specific strength is calculated from the following equation.

Residual specific strength=Specifi~ strenggth before baking x 100 Example 2 Quick lime (16.65 parts, containing 95.0% of CaO) is slaked in 499. 5 parts of hot water at 95C, and the mixture is stirred in a homomixer at a high speed for 30 minutes to prepare milk of lime having a sedimenta-20` tion volume of 43.9 ml. Subsequently an aqueous sus-pension (concentration 7.69%) of ferrosilicon dust tcon-taining 92.0% of SiO2) 0.24 ~m in average particle diameter is stirred in a homomixer at a high speed for 5 minutes to disperse the dust particles and obtain an aqueous slurry 1. 2 ~m in particle diameter at cumulative weight percent of 70%. The milk of lime is admixed with a portion of the aqueous slurry of the ferrosilicon dust 113~i20 (18.35 parts, calculated as solids), and the mixture is stirred with addition of water to obtain a starting slurry having a water to solids ratio by weight of 60:1.
The starting slurry is subjected to hydrothermal reaction at saturated water vapor pressure of 12 kg/cm at a temperature of 191C for 8 hours in the same autoclave as used in Example l, with a stirrer driven at 112 r.p.m. to obtain a slurry of crystals. The slurry - is dried at 110C for 24 hours and thereafter subjected to x-ray diffractiometry, which reveals that the crystals are xonotlite crystals. When observed under an optical microscope in the same manner as in Example l, the slurry is found to contain globular secondary particles having an average outside diameter of 35 ~m. An observation of the slurry by the reflection method reveals that the particles have distinct contours and sub-stantially transparent interior. In the same manner as in Example l, a shaped body is prepared from the slurry of crystals by spontaneous sedimentation. A portion of the body is fixed with a mixture of methyl methacrylate, ethyl methacrylate and n-butyl methacrylate resins and thereafter sliced with a super microtome. An observation of the slice under a scanning electron microscope reveals that the particles have a shell thickness of 0.1 to

6 ~m, an average shell thickness of 2.51 ~m and substan-. . ~ . . .
. :

-~3~120 tially hollow interior. An electron microscopic observation of the particles indicates that the shells have numerous burrs on the surface due to the presence of xonotlite crystals. A further observation of the secondary particle under a scanning electron microscope indicates that the particle has a hollow globular shell composed of a large number of xonotlite crystals interlocked with one another three-dimensionally.
When observed under an electron microscope, the xonotlite crystals (primary crystals) forming the secondary particle are found to be needlelike crystals l to 20 ~m in length and about 0.05 to l.O ~m in width. These crystals, when baked at 1000C for 3 hours, give ~-wollastonite crystals.
Table 4 below shows properties of the secondary particles.
Table 4 Properties Measurements .
Average particle diameter (~m) 35 Range of outside diameters of 80% 20 - 50 of the particles (~m) Average apparent density (g/cm3) 0.045 Average weight of particles (g)1.009 x lO 9 Thickness of shell (~m) 0.1 - 6 Average shell thickness (~m) 2.51 Average shell density (g/cm3) 0.121 ~' ~

:. .: , , . ............................... '' :'' ':
.~ :

1134~20 .

In the same manner as in Example 1, the slurry of xonotlite crystals is made into a shaped body by spontaneous sedimentation. The body had a density of 0.027 g/cm3. The slurry of crystals has an average spontaneous sedimentation height of 970 ml.
A specimen of shaped body is prepared from a ~ -portion of the slurry prepared as above (88 parts, calculated as solids) by thoroughly admixing 5 parts of asbestos, 3 parts of glass fiber and 3 parts of cement with the slurry, press-shaping the mixture and drying the shaped mass at 120C for 20 hours (specimen I).
Specimen II is prepared in the same manner as above except that 27.1 parts of the same mixture of nonionic and ' anionic sur~actants as used in Example 1 is incorporated 15 into the slurry. Table 5 shows properties of the specimens.

Table 5 ~~~~~~-----~æ cimen No.
Propert'ie's'''' Density (g/cm3) 0.054 0.052 20 Bending strength (kg/cm2) 1.33 1.28 Specific strength 456.1 473.4 Linear shrinkage on drying (%) o.66 0.42 The specimens, when baked at 850C for 3 hours, have the properties listed in Table 6 below.

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ii3~120 Table 6 ~ e~cimen No.
Properties ' '- - - I II
Density (g/cm3) 0.0~1 o.o49 Bending strength (kg/cm ) 0.870 0.774 Specific strength 334.5 322. 4 Linear shrinkage after heating (%) O. 71 0. 53 Residual specific strength 73.3 68.1 Example 3 Quick lime (20.23 parts, containing 95.0% of CaO) is s,laked in 485.5 parts of hot water at 85c, and the mixture is stirred in a homomixer at a high speed for 5 minutes to prepare milk of,lime having a sedimenta-tion volume of 13.0 ml. Subsequently an aqueous suspen-sion (concentration 5.45%) of finely divided silicastone particles comprising crystalline silica and amorphous silica (containing 97.0% of SiO2) 0.093 ~m in average particle diameter is stirred in a homomixer at a high speed for 30 minutes to disperse the silica particles and obtain an aqueous slurry o.36 ~m in particle diameter at cumulative weight percent of 70%. The milk of lime is admixed with a portion of the aqueous slurry of the finely divided silica stone particles (21.77 parts, calculated as solids), and the mixture is stirred with addition of water to obtain a starting slurry having a water to solids ratio by weight of 50: 1. The starting 113~20 slurry is subjected to hydrothermal reaction at saturated water vapor pressure of 12 kg/cm2 at a temperature cf 191C for 8 hours in the same autoclave as used in Example 1, with a stirrer driven at 112 r.p.m. to obtain a slurry of crystals. The slurry is dried at 110C for 24 hours and thereafter subjected to x-ray diffractiometry, which reveals that the crystals are a mixture of large amount of xonotlite crystals and small amount of tobermorite crystals. When observed under an optical microscope in the same manner as in Example 1, the slurry is found to contain globular secondary particles having an average outside diameter of 18 ~m. An observation of the slurry by the reflection method reveals that the particles have distinct contours and substantially transparent interior.
In the same manner as in Example 1, a shaped body is prepared from the slurry of crystals by spontaneous sedimentation. A portion of the body is fixed with a mixture of methyl methacrylate, ethyl methacrylate and n-butyl methacrylate resins and thereafter sliced with a super microtome. An observation of the slice under a scanning electron microscope reveals that the particles have a shell thickness of 0.5 to 1.7 ~m, an average shell thickness of 1.47 ~m and substantially hollow interior. An electron microscopic observation of the particles indicates that the shells have numerous burrs ,, . , :. ; , ~

.

:: ... , . . :

1134~20 on the surface due to the presence of xonotlite crystals.
A further observation of the secondary particle under a scanning electron microscope indicates thatithe particle has a hollow globular shell composed of a large number of xonotlite crystals interlocked with one another three-dimensionally. When the particles are observed under an electron microscope, the xonotlite crystals (primary crystals) forming the secondary particle are found to be needlelike crystals 1 to 20 ~m in length and about 0.05 to 1.0 ~m in width and also the tobermorite crystals are found to be platelike crystals. These crystals, when baked at 1000C for 3 hours~ give ~-wollastonite crystals.
Table 7 below shows properties of the secondary particles.
Table 7 Properties Measurements Average particle diameter (~m) 18 ` Range of outside diameters of 80% 10 - 28 of the particles (~m) Average apparent density (g/cm3) 0.053 Average weight of particles (g)1.62 x 10 10 Thickness of shell (~m) 0.5 - 1.7 Average shell thickness (~m) 1.47 Average shell density (g/cm3) 0.128 .

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.
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.

113~120 In the same manner as in Example 1, the slurry of xonotlite crystals is made into a shaped body by spontaneous sedimentation. ~he body had a density of 0.032 g/cm . The slurry of crystals has an average spontaneous sedimentation height of 965 ml.
'A specimen of shaped body is prepared from a portion of the slurry prepared as above (90 parts, calculated as solids) by thoroughly admixing 5 parts of asbestos, 3 parts of glass fiber and 3 parts of cement with the slurry, press-shaping the mixture and~drying the shaped mass at 120C for 20 hours (specimen I).
Specimen II is prepared in the same manner as above except that 22.9 parts of the same mixture of nonionic and anionic surfactants as used in Example 1 is incor-porated into the slurry. Table 8 shows properties of thespecimens.

Table 8 ~ ecimen No.
'Pr'ope'rtie's' - - _ '' ' I II
Density (g/cm3) 0.054 Q.053 Bending strength (kg/cm ) 1.40 1.33 Specific strength 480.1 473.5 Linear shrinkage on drying (%) 0.33 0.27 The specimens, when baked at 1000C for 3 hours, have the properties listed in Table 9 below.

.
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~134120 Table 9 ~ pecimen No.
Properties Density (g/cm3) 0.051t 0.050 Bending strength (kg/cm ) 1.03 0.873 Specific strength 396.o 349.2 Linear shrinkage after heating (%) 0.67 0.~1 Residual specific strength 82.5 73.7 Example 4 Quick lime (19.99 parts, containing 95.0% of CaO) is slaked in 240 parts of hot water at 95C, and the mixture is stirred in a homomixer at a high speed for 6.5 minutes to prepared milk of lime having a sedimentation volume o~ 17.8 ml. Subsequently an aqueous suspension (concentration 4.76~) of ferrosilicon dust (containing 92.0% of SiO2) 0.24 ~m in average particle diameter is stirred in a homomixer at a high speed for 5 minutes to disperse the dust particles and obtain an aqueous slurry 1.2 ~m in particle diameter at cumula.tive weight percent of 70%. The milk of lime and 0.42 parts of asbestos of amosite type (S~ 65) are admixed with ~ portion of the aqueous slurry of the ferrosilicon dust (22.01 parts, calculated as solids), and the mixture is stirred with addition of water to.obtain a starting slurry having a water to solids ratio by weight of 50:1.
The starting slurry is subjected to hydrothermal reaction I - , ~ ,., ~ ~-..

il34120 at saturated water vapor pressure of 12 kg/cm at a temperature of 191C for 8 hours in the same autoclave as used in Example 1, with a stirrer driven at 112 r.p.m.
to obtain a slurry of crystals. Th~ slurry is dried at 110C for 24 hours and thereafter subjected to x-ray diffractiometry, which reveals that the crystals are xonotlite crystals. When observed under an optical microscope in the same manner as in Example 1, the slurry is found to contain globular secondary particles having an average outside diameter o~ 32 ~m and partly ~oined with asbestos fibers. An observation of the slurry by the reflection method~reveals that the particles have distinct contours and substantially transparent interior. In the same manner as in Example 1, a shaped body is prepared from the slurry of crystals by spontaneous sedimentation. A portion of the body is fixed with a mixture of methyl methacrylate, ethyl methacrylate and n-butyl methacrylate resins and thereafter sliced with a super microtome. An observation of the slice under a scannin~electron microscope reveals that the particles have a shell thickness of 0.1 to 7 ~m, an average shell thickness of 2.30~m and substantially hollow interior.
An electron microscopic observation of the particles indicates that the shells have numerous burrs on the surface due to the presence of xonotlite crystals.

. . :

. ., : -. . . - . , .-.... . .

A further observation of the secondary particle under a scanning electron microscope indicates that the particle has a hollow globular shell composed of a large number of xonotlite crystals interlocked with one another - 5 three-dimensionally. When observed under an electron microscope, the xonotlite crystals (primary crystals) forming the secondary particle are found to be needlelike crystals 1 to 20 ~m in length and about 0.05 to 1.0 ~m in width. These crystals, when baked at 1000C for 3 hours, give ~-wollastonite crystals.
Table 10 below shows properties of the secondary particles.
Table 10 Properties Measurements Average particle diameter (~m) 32 Range of outside diameters of 80% 10 - 50 of the particles (~m) Average apparent density (g/cm3) o.o48 Average weight of particles (g)8.23 x 10 Thickness of shell (~m) 0.1 - 7 Average shell thickness (~m) 2.30 Average shell density (g/cm3) 0.129 In the same manner as in Example 1, the slurry of xonotlite crystals is made into a shaped body by spontaneous sedimentation. The body had a density of 0.029 g/cm3. The slurry of crystals has an average .

1~34120 .

spontaneous sedimentation height of 954 ml.
A specimen of shaped body is prepared from a portion of the slurry prepared as above (88'parts, calculated as solids) by thoroughly admixing 4 parts of pulp, 5 parts of glass fiber and 3 parts of cement with the slurry, press-shaping the mixture and drying the shaped mass at 120C for 20 hours (specimen I).
Specimen II is prepared in the same manner as above except that 20 parts of the same mixture of nonionic and-anionic surfactants as used in Example 1 is incor-porated into the slurry. Table 11 shows properties of the specimens.

Table 11 - _ Specimen No.
'Properties Density (g/cm3) 0.0550.053 ~
Bending strength (kg/cm2) 1.82 1.65 ' Specific strength 601.6587.4 Linear shrinkage on drying (%) 2.24 0.33 The specimens, when baked at 850C for 3 hours, 20 have the properties listed in Table 12 below.

Table 12 ~ _L~gglpen No.
''Pro'perti'es' ' ~~ -'- ' ' I II
Density (g/cm3) o.o530 050 Bending strength (kg/cm2) 1.27 1.09 Specific strength 452.1436.0 Linear shrinkage after heating (%) 0.62 0.45 ~esidual spec1fic streneth 75.1 74.2 !
.: . , , .: ' ' :

.

113~120 Ex mple 5 Quick lime (19.99 parts, containing 95.0% of CaO) is slaked in 240 parts of hot water at 95C, and the mixture is stirred ~in a homomixer at a high speed for 5 minutes to prepare milk of lime having a sedimenta-tion volume of 15.3 ml. Subsequently an aqueous sus-pension (concentration 4.76%) of ferrosilicon dust (containing 92.0% of SiO2) 0.24 ~m in average particle diameter is stirred in a homomixer at a high speed for 10 minutes to disperse the dust particles and obtain an aqueous slurry 1.0 ~m in particle diameter at cumulative weight percent of 70%. The mil~ of lime is admixed with a portion of the aqueous slurry of the ferrosilicon dust (22.01 parts, calculated as solids), and the mixture is stirred with addition of water to obtain a starting slurry having a water to solids ratio by weight of 50:1. The starting slurry is subjected to hydrothermal reaction at saturated water vapor pressur,e of 12 kg~cm2 at a temperature of 191C for 8 hours in the same auto-clave as used in Example 1, with a stirrer driven at112 r.p.m. to obtain a slurry of crystals. The slurry is dried at 110C for 24 hours and thereafter sub~ected to x-ray diffractiometry, which reveals that the crystals are xonotlite crystals. When observed under an optical microscope in the same manner as in Example 1, the ,, , , .

, ,, : , ,, - , .. , - . ~. .
.,,, . . : .. -.: ~ ' , ~, , : . . . .. .

1~3~1ZO
_ 44 -slurry is found to contain globular secondary particles having an average outside diameter of 31 ~m. An observation of the slurry by the reflection method reveals that the particles have distinct contours and sub-stantially transparent interior. In the same manner asin Example l, a shaped body is prepared from the slurry of crystals by spontaneous sedimentation. A portion of the body is fixed with a mixture of methyl methacrylate, ethyl methacrylate and n-butyl methacrylate resins and thereafter sliced with a super microtome. An observa-tion of the slice under a scanning electron microscope reveals that the particles have a shell thickness of - 0.1 to 7 ~m, an average shell thickness of 2.25 ~m and substantially hollow interior. An electron microscopic-observation of the particles indicates that the shellshave numerous burrs on the surface due to the presence of xonotlite crystals. A further observation of the secondary particle under a scanning electron microscope indicates that the particle has a hollow globular shell composed of a large number of xonotlite crystals inter-locked with one another three-dimensionally. When observed under an electron microscope, the xonotlite crystals (primary crystals) forming the secondary particle are found to be needlelike crystals 1 to 20 ~m in length and about 0.05 to 1.0 ~m in width. These . .
.. . .
, .
...

crystals, when baked at 1000C for 3 hours, give ~-wollastonite crystals.
Table 13 below shows properties of the secondary particles.
Table 13 Properties Measurements Average particle diameter (~m) 31 Range of outside diameters of 80% 10 - 50 of the particles (~m) Average apparent density (g/cm3) 0.073 Average weight of particles (g)1.14 x 10 9 Thickness of shell (~m) 0.1 - 7 Average shell thickness (~m) 2.25 Average shell density (g/cm3) 0.194 In the same manner as in Example 1, the slurry of xonotlite crystals is made into a shaped body by spontaneous sedimentation. The body had a density of 0.043 g/cm3. The slurry of crystals has an average spontaneous sedimentation height of 917 ml.
Specimens of shaped body are prepared from portions of the slurry prepared as above (each 88 parts, calculated as solids) by thoroughly admixing 4 parts of pulp, 5 parts of glass fiber and 3 parts of cement with each of the portions, press-shaping the mixture and drying the shaped mass as 120C for 20 hours (specimens I and II). Specimens III and IV are prepared in the same .~

;' ' ' . . . . , .,:.:
, . . : . " : . .:.
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li3~120 manner as above except that 20 parts of the same mixture of nonionic and anionic surfactants as used in Example 1 is incorporated into the slurry. Table 14 shows pro-perties of the specimens.

Table 14 ~~~~----__~L_imen No.
Properties ~ I II III IV
.. . .
Density (g/cm3) 0.056 0.080 0.050 0.075 Bending strength (kg/cm2)1.39 4.03 1.06 3.24 Specific strength 443.2 629.7 424.0 576.0 Linear shrinkage on drying (%)2.41 0.33 0.48 0 The specimens, when baked at 850C for 3 hours, have the properties listed in Table 15 below.

Table 15 ~--- ~ SPecimen No.
Properties- ~ I II III IV

Density (g/cm3) 0.053 o.o78 0.048 0.072 Bending strength (kg/cm2)0.93 2.91 o.78 2.21 Specific strength 331.1 478.3 338.5 426.3 Linear shrinkage after heating0.57 0.24 0.45 0.31 ( % ) 1.
20- Residual specific strength 74.7 76.0 79.8 74.0 Example 6 Quick lime (19.99 parts, containing 95.0% of CaO) is slaked in 240 parts of hot water at 90C, and the mixture is stirred in a homomixer at a high speed for 7 minutes to prepare milk of lime having a sedimentation volume of 20.0 ml. Subsequently an aqueous suspension .. .. . . . .
. . ; . , :
.
., . i .

- : :

.- . . .
. , ~ . . ~ :. , ~134~20 - 47 ~

(concentration 4.76%) of ferrosilicon dust (containing 92.0% of SiO2) 0.24 ~m in average particle diameter is stirred in a homomixer at a high speed for 10 minutes to disperse the dust particles and obtain an aqueous slurry 1.0 ~m in particle diameter at cumulative weight percent of 70%. The milk of lime and 14 parts of the same mixture of nonionic and anionic surfactants as used in Example 1 are admixed with a portion of the aqueous slurry of the ferrosilicon dust (22.01 parts, calculated as solids), and the mixture is stirred with addition of water to obtain a starting slurry having a water to solids ratio by weight of 50:1~ The starting slurry is subjected to hydrothermal reaction at saturated water vapor pressure of 12 kg/cm2 at a temperature of 191C
for 8 hours in the same autoclave as used in Example 1, with a stirrer driven at 112 r.p.m. to obtain a slurry of crystals. The slurry is dried at 110C for 24 hours and thereafter subjected to x-ray diffractiometry, which reveals that the crystals are xonotlite crystals.
When observed under an optical microscope in the same manner as in Example 1, the slurry is found to contain globular secondary particles having an average outside diameter of 28 ~m. An observation of the slurry by the re~lection method reveals that the particles have distinct contours and substantially transparent interior.

"
. .

. ;, :
:, . , ,., :

113~120 ~18 In the same manner as in Example 1, a shaped body is prepared from the slurry of crystals by spontaneous sedimentation. A portion of the body is fixed with a mixture of methyl methacrylate, ethyl methacrylate and n-butyl methacrylate resins and thereafter sliced with a super microtome. An observation of the slice under a scannin~ electron microscope reveals that the particles have a shell thickness of 0.1 to 6 ~m, an average shell thickness of 2.28 ~m and substantially hollow interior.
An electron microscopic observation of the particles indicates that the shells have numerous burrs on the surface due to the presence of xonotlite crystals.
A ~urther observation of the secondary particle under a scanning electron microscope indicates that the particle has a hollow globular shell composed of a large number of xonotlite crystals interlocked with one another ;~
three-dimensionally. When observed under an electron microscope, the xonotlite crystals (primary crystals) forming the secondary particle are found to be needle-like crystals 1 to 20 ~m in length and about 0.05 to 1.0 ~m in w1dth. These crystals, when baked at 1000C for 3 hburs, give B-wollastonite crystals.
Table 16 below shows properties of the secondary particles.

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.
.

~134120 _ 49 _ Table 16 '' ''''Pr'op'erties ' '''' '' ''' ' Measurements Average particle diameter (~m) 28 Range of outside diameters of 80% 10 - 50 of the particles (~m) Average apparent density (g/cm3) 0.051 Average weight of particles (g) 5.86 x 10 10 Thickness of shell (~m) 0.1 - 6 Average shell thickness (~m) 2.28 Average shell density (g/cm3) 0.123 In the same manner as in Example 1, the slurry of xonotlite crystals is made into a shaped body by spontaneous sedimentation. The body had'a density of - 0.030 g/cm3. The slurry of crystals has an average spontaneous sedimentation height of 943 ml. -Specimens of shaped body are prepared from portions of the slurry prepared as above teach 88 parts, calculated as solids) by throughly admixing 4 parts of pulp, 5 parts of glass fiber and 3 parts of cement with ~' each portion, press-shaping the mixture and drying the shaped mass at 120C for 20 hours (specimens I and II).
Table 17 shows properties of the specimens.

:, ,- ~ ' '~" ' .. .

Table 17 _ S~ecimen No.
Properties ' .. _ I II
Density (g/cm3) 0.050 0.053 Bending strength (kg/cm2) 1.38 1.44 Specific strength 552.0 512.6 Linear shrinkage on drying (%) 0.37 0.41 The specimens, when baked at 850c for 3 hours, have the properties listed in Table 18 below.
Table 18 - _ S~imen No.
'Prope'rties - ---______ I II
Density (g/cm3) o.o48 o.o5o Bending strength (kg/cm2) ~ 0.915 1.00 Specific strength 397.1 400.0 Linear shrinkage after heating (%) 0.56 0.61 ;
15 Residual specific strength 71.9 78,o Comparisbn Exampl'e' 1 ~uick lime (51.38 parts, containing 95.0% of CaO) is slaked in 616.6 parts of hot water at 95C, and the mixture is stirred in a homomixer at a high speed 20 for 10 minutes to prepare milk of lime having a sedimenta-tion volume of 25.5 ml. Subsequently 53.62 parts of finely divided silica stone (containing 97.5% of SiO2) 3.7 ~m in average particle diameter.and composed of crystalline silica is added to the milk of lime, and 25 the mixture is stirred with addition of water to obtain ~, .
:
.
, .. .. , ~ ., ~, .
: : . ,:
~: :

; ' ; ':i`' ~ , 113~1ZO

a starting slurry having a water to solids ratio by weight of 20:1. The starting slurry is subjected to hydrothermal reaction at saturated water vapor pressure of 12 kg/cm at a temperature of 191C for 8 hours in the same autoclave as used in Example 1, with a stirrer driven at 174 r.p.m. to obtain a slurry of crystals.
The slurry is dried at 110C for 24 hours and thereafte subjected to x-ray diffractiometry, which reveals that the crystals are a mixture of large amount of xonotlite crystals and small amount of tobermorite crystals. When observed under an optical microscope in the same manner as in Example 1, the slurry is found to contain globular secondary particles having an average outside diameter of 40 ~m. An observation o~ the slurry by the reflection method reveals that the particles have distinct contours and substantially transparent interior. In the same manner as in Example 1, a shaped body is prepared from the slurry of crystals by spontaneous sedimentation. A portion of the body is fixed with a mixture of methyl methacrylate, ethyl methacrylate a~d n-butyl methacrylate resins and thereafter sliced with a super microtome. An observation of the slice under a scanning electron microscope reveals that the particles have a shell thickness of 0.5 to 6 ~m, an average shell thickness of 2.60 ~m and substantially hollow interior.

113~120 An electron microscopic observation of the particles indicates that the shells have numerous burrs on the surface due to t~le presence of xonotlite crystals.
A further observation of the secondary particle under a scanning electron microscope indicates that the particle has a hollow globular shell composed of a large number of xonotlite crystals interlocked ~ith one another --three-dimensionally When the particles are observed under an electron microscope, the xonotlite crystals (primary crystals) forming the secondary particle are found to be needlelike crystals 1 to 20 ~m in length and about 0.05to l.0 ~m in width and also the tobermorite crystals are found to be platelike crystals. These crystals, when baked at 1000C for 3 hours, give ~-wollastonite crystals.
Table l9 below shows properties of the secondary particles.
Table 19 Properties Measurements Average particle diameter (~m)40 ~ange of outside diameters of 80% 20 - 50 of the particles (~m) Average apparent density (g/cm3) 0.10 Average weight of particles (g) 3.35 x lO 9 ~hickness of shell (~m) 0.5 - 6 Average shell thickness (~m) 2.60 Average shell density (g/cm3)0.293 , -- 1~34120 In the same manner as in Example 1, the slurry of xonotlite crystals is made into a shaped body by spontaneous sedimentation. The body had a density of 0.069 g/cm3. The slurry of crystals has an average spontaneous sedimentation height of 605 ml.
Specimens of shaped body are prepared from portions of the slurry prepared as above (each 88 parts, calculated as solids) by thoroughly admixing 4 parts Or pulp, 5 parts of glass fiber and 3 parts of cement with each portion, press-shaping the mixture and drying ,the shaped mass at 120C for 20 hours (specimens I and II).
Table 20 shows properties of the specimens.

Table 20 ecimen No.
' Properties Density (g/cm3) 0.076 o.o80 Bending strength (kg/cm ) 1.82 2.35 Specific strength 315.1 367.2 Linear shrinkage on drying (%) 0.61 0.33 .

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Claims (26)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Globular secondary particles of wollastonite group calcium silicate crystals represented by the formula ?CaO?mSiO2?nH2O
wherein 1 ? ? ? 6, 1 ? m ? 6 and 0 ? n ? 1, characterized in that the particles comprise hollow globular secondary particles of the wollastonite group calcium silicate crystals, the globular secondary particles having an average spontaneous sedimentation height of at least 800 ml, an outside diameter of 5 to 110 µm, an average apparent density of 0.04 to 0.09 g/cm3 and an average shell density defined by the equation Y = 0.0033X + B
wherein Y is the average shell density, X is the average diameter of the particles, B is a constant, 15 µm ? X
? 40 µm and 0 ? B ? 0.115.

2. Globular secondary particles of calcium silicate as defined in claim 1 further comprising tobermorite group crystals admixed with the wollastonite group calcium silicate crystals in an amount of up to 100 parts by weight per 100 parts by weight of the wollastonite group calcium silicate crystals.

3. Globular secondary particles of calcium silicate as defined in claim 1 wherein the average spontaneous sedimentation height is at least 850 ml.

4. Globular secondary particles of calcium silicate as defined in claim 1 wherein the globular secondary particles of calcium silicate are about 0.1 to about 7.0 µm in the thickness of shell.

5. A slurry of calcium silicate crystals comprising the globular secondary particles of calcium silicate as defined in claim 1 and dispersed in water.

6. A slurry of calcium silicate crystals as defined in claim 5 which contains the water in an amount of at least 15 times the weight of the solids in the slurry.

7. A slurry of calcium silicate crystals as defined in claim 5 wherein at least about 80% of the globular secondary particles are 10 to 50 µm in outside diameter.

8. A slurry of calcium silicate crystals as defined in claim 5 further comprising a reinforcing material.

9. A slurry of calcium silicate crystals as defined in claim 8 wherein the reinforcing material is a fibrous material.

10. A slurry of calcium silicate crystals as defined in claim 9 wherein the fibrous reinforcing material is in the form of inorganic fibers at least partly joined with the globular secondary particles of calcium silicate.

11. A slurry of calcium silicate crystals as defined in claim 5 further comprising a surfactant.

12. A shaped body of wollastonite group calcium silicate crystals represented by the formula ?CaO?mSiO2?nH2O
wherein 1 ? ? ? 6, 1 ? m ? 6, 0 ? n ? 1, characterized in that the shaped body comprises hollow globular secondary particles of crystals of wollastonite group calcium silicate, the globular secondary particles being joined with one another and having, before shaping, an average spontaneous sedimentation height of at least 800 ml, an outside diameter of 5 to 110 µm an average apparent density of 0.04 to 0.09 g/cm3 and an average shell density defined by the equation Y = 0.0033X + B
wherein Y is the average shell density, X is the average diameter of the particles, B is a constant, 15 µm ? X
? 40 µm and 0 ? B ? 0.115.

13. A shaped body as defined in claim 12 further comprising a reinforcing material uniformly incorporated therein.

14. A shaped body as defined in claim 13 wherein the reinforcing material is a fibrous material.

15. A shaped body as defined in claim 12 further comprising a surfactant uniformly incorporated therein.

16. A process for producing the globular secondary particles of calcium silicate as defined in claim 1 characterized by the steps of subjecting a starting slurry to hydrothermal reaction with application of pressure and heat and with continuous or temporarily interrupted stirring to prepare an active slurry of calcium silicate crystals, and drying the active slurry, the starting slurry being a mixture of a slurry of fine siliceous particles up to 0.5 µm in average diameter and dispersed in water and milk of lime having a sedimentation volume of at least 5 ml, the starting slurry containing water in an amount at least 30 times the weight of the solids of the starting slurry.

17. A process as defined in claim 16 wherein the fine siliceous particles are silicon dust and/or fine particle reinforcing silica.

18. A process as defined in claim 16 wherein the slurry of fine siliceous particles has the particles so dispersed in water that the particles thereof having cumulative weight percent of at least 70% are up to 2 µm in diameter.

19. A process as defined in claim 16 wherein the milk of lime has a sedimentation volume of at least 8 ml.

20. A process for producing the active slurry of calcium silicate crystals as defined in claim 5 characterized by subjecting a starting slurry to hydro-thermal reaction with application of pressure and heat and with continuous or temporarily interrupted stirring, the starting slurry being a mixture of a slurry of fine siliceous particles up to 0.5 µm in average diameter and dispersed in water and milk of lime having a sedimentation volume of at least 5 ml, the starting slurry containing water in an amount at least 30 times the weight of the solids of the starting slurry.

21. A process as defined in claim 20 wherein the starting slurry further incorporates an inorganic reinforcing material.

22. A process as defined in claim 20 wherein the starting slurry further incorporates a surfactant.

23. A process for producing a shaped body of calcium silicate characterized by shaping the slurry of calcium silicate crystals as defined in claim 5 and drying the shaped mass.

24. A process as defined in claim 23 wherein the slurry incorporates a surfactant.

25. A process as defined in claim 23 wherein the slurry incorporates a reinforcing material.

26. A process as defined in claim 23 wherein the shaped body is baked to convert the xonotlite forming the shaped body to .beta.-wollastonite.