CA1123172A - Amorphous silica, products thereof and methods of preparing the same - Google Patents
Amorphous silica, products thereof and methods of preparing the sameInfo
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- CA1123172A CA1123172A CA358,847A CA358847A CA1123172A CA 1123172 A CA1123172 A CA 1123172A CA 358847 A CA358847 A CA 358847A CA 1123172 A CA1123172 A CA 1123172A
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- particles
- amorphous silica
- shaped body
- opsil
- calcium
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Abstract
ABSTRACT OF THE DISCLOSURE
The present invention provides a shaped body of amorphous silica comprising secondary particles of amorphous silica compressed in at least one direction and interlocked with one another integrally into the body and voids interspersed therebetween, the secondary particle being composed of numer-ous primary particles of amorphous silica randomly three-dimensionally interlocked with one another, each of the primary particles having a crystalline appearance, at least two sur-faces in symmetric relation, a length of about 1 to about 500 µ and a thickness of about 50 .ANG. to about 1 µ, the length being at least about ten times the thickness. The silica particles are useful for the adsorption of gases and water, have high oil adsorbing capacity and provide light weight shaped bodies of high mechanical strength and acid resistance.
The present invention provides a shaped body of amorphous silica comprising secondary particles of amorphous silica compressed in at least one direction and interlocked with one another integrally into the body and voids interspersed therebetween, the secondary particle being composed of numer-ous primary particles of amorphous silica randomly three-dimensionally interlocked with one another, each of the primary particles having a crystalline appearance, at least two sur-faces in symmetric relation, a length of about 1 to about 500 µ and a thickness of about 50 .ANG. to about 1 µ, the length being at least about ten times the thickness. The silica particles are useful for the adsorption of gases and water, have high oil adsorbing capacity and provide light weight shaped bodies of high mechanical strength and acid resistance.
Description
31~
This invention relates to novel amorphous silicas having a crystalline appearance, products thereof and methods of preparing the silicas and their products.
This application is a divisional application of copending application No. 248,633 filed March 24, 1966.
Silica gel which is known as a representative example of amorphous silicas is mainly produced by neutralizing an aqueous solution of sodium silicate with an acid such as hydrochloric acid or sulfuric acid to form a recipitate, and washing and drying the precipitate. When desired, the silica gel obtained is heated at reduced pressure for activation.
Depending on the method of production, silica gel is obtained - in an indefinite or spherical shape. Furthermore when required, silica gel is shaped to tablets and the like using a binder.
Silica gel is used for example as a drying agent, adsorbent, dehydrant, deodorant, catalyst carrier, etc. because of its hygroscopicity and large specific surface area.
However, silica gel readily adsorbs water upon contact therewith and collapses. It is therefore impossible or difficult to use silica gel in a system in which it is directly exposed to water. Generally silica gel has a average pore diameter of 20 to 220 A. Silica gel with a relatively small average pore diameter usually has a great bulk density of about 0.7 g/cm3, whereas conversely one possessing a bulk density of about 0.2 g/cm3 j invariably has a large average pore diameter of about 180 to about 220 A in general. Accordingly, the silica gel with an average pore diameter of the order of 20 to 40 A suitable for use as an adsorbent for gases and .
r ;:131 Z3~L'~.;2 water has a great bulk density and an inherently limited adsorbing capacity per unit weight. Although the capacity to - adsorb oils increases with decreasing bulk density and increasing specific surface area, silica gel having a large specific surface area also has a high bulk density and therefore invariably possesses an insufficient or no oil adsorbing capacity.
Particles o~f silica gel in themselves are not shapable - without the use of a binder; in fact it is impossible to obtain a strong shaped body without using any binder. In addition, silica gel has not been used for the production of heat-resistant glass, refractory heat insulator, heat-resistant filter, etc.
The primary object of this invention is to provide a novel and useful amorphous silica, products thereof and methods of preparing the silica and its products.
Another object of this invention is to provide a novel amorphous silica which pos~esses various useful ~ properties and which are tnerefore usable in place of known silica gel and also applicable to uses for which the known - silica gel is unserviceable.
Another object of this invention is to provide a novel amorphous silica which has a high capacity to adsorb water but outstanding resistance to water and remains un-collapsible despite the adsorption of water and which is therefore usable in a system in which it is directly exposed to water.
3~7~
Another object of this invention is to provide a novel amorphous silica which has a small average pore diameter of about 20 to about 40 ~ and also a small bulk density although none of silica gels heretofore known do not possess both the characteristics and which is suitable for the adsorp-tion of gases and water.
Another object of this invention is to provide a novel amorphous silica having a small bulk density and a large specific surface area and accordingly a high oil adsorbing eapacity.
Another object of this invention is to provide an amorphous silica readily dispersible in water -to give an aqueous slurry from which a lightweight and strong shaped body can be obtained by shaping and drying without using any binder and also to provide the aqueous slurry.
Another object of this invention is to provide a light-weight shaped body of amorphous silica which has high mechanical strength and acid resistance and which is therefore usable as a heat insulator, filter medium, catalyst carriex, etc.
Another objeet of this invention is to provide a novel amorphous siliea suitable as a material for the product-; ion of heat-resistant glass.
Another objeet of this invention is to provide a novel amorphous silica which readily permits the passage :~ . . : , 31~2317%
of water, therefore can be drained easily and is uncollapsible when in contact with water, the amorphous silica thus being serviceable for various uses wherein these character-istics are advantageously utilized.
Another object of this invention is to provide methods of preparing the novel amorphous silicas having the foregoing excellent properties and products thereof.
Another object of this invention is to provide a novel composite material composed of the novel amorphous silica and extremely fine particles of calcium carbonate at-tached to the silica.
Another object of this invention is to provide a -method of preparing a novel composite material of amorphous silica and calcium carbonate which is useful as a filler and reinforcing agent and also to provide a method of preparing products from the composite material.
These and other features of this invention will become apparent from the following description.
Basically, the amorphous silicas of this invention are in the form of primary particles and characterized in that the particles having a crystalline appearance and has at least two surfaces in symmetric relation, a lenght of about 1 to about 500~ and a thickness oE about 50~l A to about 1~
the lenght being at least about 10 times the thickness. The amorphous silicas of this invention include, ' ~
,.. " ~
~23~ 7Z
in addition to those having the form of primary particles described above, those in the form of secondary particles and those in the form of a shaped body.
The term "Opsil" as used in the specification refers to the amorphous silica of this invention. Thus by the term "Opsil-I" is meant an amorphous silica of this invention having the form of primary particles, and by the term "Opsil-II" is meant an amorphous silica of this invention having the form of secondary particles.
Opsil-I of this invention is amorphous silica of high purity and therefore does not display and X-ray diffract-ion phenomenon and, when dehydrated by ignition and then chem-ically analyzed, is found to contain at least 98% by weight of SiO2. Observation under an electron microscope has revealed that the primary particle, the basic form of Opsils, has a crystalline appearance and at least two surfaces in symmetric relation, although it is amorphous.
The crystalline appearance, the most distinct feature of Opsils of this invention, is attributable to the fact that they are derived from silicate crystals by the conversion of the silicate crystals into amorphous silica which retains the original configuration of the crystals. Accordingly, the crystalline appearance and size of the particles of Opsil-I
are substantially in .. .
~Z31~:
conformity with the appearance and size of the silicate crystals from which they are derived, and Opsil-I particles have varying configurations and sizes in corresponding relation to the original crystals. For example, the lath-like crystals of wollastonite, xonotlite, foshagite or like calcium silicate are converted into the particles of Opsil-I having a lath-like configuration. The particles of Opsil-I have a plate-like con-figuration if they are derived from the plate-like crystals of tobermorite, gyrolite, ~-dicalcium silicate hydrate (~-C2SH) or like calcium silicate. The particles of Opsil-I derived from the foil-like crystals of calcium silicate such as CSHn have a foil-like configuration. The sizes of these lath-like, plate-like and foil-like Opsil~I particles range from about 1 to about 500~, preferably about 1 to about 300~, in length 15 and from about 50 A to about 1~, preferably about 100 ~ to about 1~ in thickness, the lenght being at least about 10 times, preferably about 10 to about 5,000 times the thickness.
The lath-like particles of Opsil~I derived from primary part-icles of xonotlite crystals have the configuration of the pri-20 mary particles and are about 1 to about 50~ in length, about 100 A to about 0.5~ in thickness and about 100 A to about 2~ in width, the length being about 10 to about 5,000 times the thick-ness. the plate-like particles of Opsil-I derived from primary '~" ' ~L231~2 particles of tobemorite crystals have the configuration oE
the primary particles and are about 1 to about 50~ in length about 100 ~ to about 0.5~ in thickness and about 0.2 to about 20u in width, the length being about 10 to about 5,000 times the thickness. The lath-like particles of Opsil-I derived from primary particles of wollastonite crystals have the con-figuration of the primary particles and are about 1 to about 500~ in length, about 100 A to about 1~ in thickness and about 100 A to about 5~ in width, the length being about 10 to about 5,000 times the thickness. The foil-like particles of Opsil-I
derived from primary particles of CSHn crystals have the con-figuration of the primary particles and are about 1 to about 20~ in length, about 50 ~ to about 500 ~ in thickness and about 100 A to about 20~ in width, the length being about 50 to about 5,000 times the thickness. The plate-like particles of Opsil-I derived from primary particles of gyrolite crystals have the configuration of the primary particles and are about 1 to about 50~ in length, about 100 ~ to about 0.5~ in thick-ness and about 1 to about 20~ in width, the length being about 20 10 to about 5,000 times the thickness. The plate-like particles of Opsil-I derived from primary particles of ~dicalcium silicate hydrate crystlas have the configuration of the primary part-icles and are about 1 to about 300~ in length, about ~3~i7~2 500 A to about 1~ in thickness and about 1 to about 50~ in width, the length being about 10 to about 5,000 times the thick-ness.
Table 1 gives the chemical composition of Opsil-I, which is subjected to ignition dehydration and thereafter to elementary analysis, and Table 2 shows the physical properties of Opsil-I in comparison with those of silica gel.
Table 1 Ig. loss 4-7 wt. %
SiO2 > 9~.0 wt. %
This invention relates to novel amorphous silicas having a crystalline appearance, products thereof and methods of preparing the silicas and their products.
This application is a divisional application of copending application No. 248,633 filed March 24, 1966.
Silica gel which is known as a representative example of amorphous silicas is mainly produced by neutralizing an aqueous solution of sodium silicate with an acid such as hydrochloric acid or sulfuric acid to form a recipitate, and washing and drying the precipitate. When desired, the silica gel obtained is heated at reduced pressure for activation.
Depending on the method of production, silica gel is obtained - in an indefinite or spherical shape. Furthermore when required, silica gel is shaped to tablets and the like using a binder.
Silica gel is used for example as a drying agent, adsorbent, dehydrant, deodorant, catalyst carrier, etc. because of its hygroscopicity and large specific surface area.
However, silica gel readily adsorbs water upon contact therewith and collapses. It is therefore impossible or difficult to use silica gel in a system in which it is directly exposed to water. Generally silica gel has a average pore diameter of 20 to 220 A. Silica gel with a relatively small average pore diameter usually has a great bulk density of about 0.7 g/cm3, whereas conversely one possessing a bulk density of about 0.2 g/cm3 j invariably has a large average pore diameter of about 180 to about 220 A in general. Accordingly, the silica gel with an average pore diameter of the order of 20 to 40 A suitable for use as an adsorbent for gases and .
r ;:131 Z3~L'~.;2 water has a great bulk density and an inherently limited adsorbing capacity per unit weight. Although the capacity to - adsorb oils increases with decreasing bulk density and increasing specific surface area, silica gel having a large specific surface area also has a high bulk density and therefore invariably possesses an insufficient or no oil adsorbing capacity.
Particles o~f silica gel in themselves are not shapable - without the use of a binder; in fact it is impossible to obtain a strong shaped body without using any binder. In addition, silica gel has not been used for the production of heat-resistant glass, refractory heat insulator, heat-resistant filter, etc.
The primary object of this invention is to provide a novel and useful amorphous silica, products thereof and methods of preparing the silica and its products.
Another object of this invention is to provide a novel amorphous silica which pos~esses various useful ~ properties and which are tnerefore usable in place of known silica gel and also applicable to uses for which the known - silica gel is unserviceable.
Another object of this invention is to provide a novel amorphous silica which has a high capacity to adsorb water but outstanding resistance to water and remains un-collapsible despite the adsorption of water and which is therefore usable in a system in which it is directly exposed to water.
3~7~
Another object of this invention is to provide a novel amorphous silica which has a small average pore diameter of about 20 to about 40 ~ and also a small bulk density although none of silica gels heretofore known do not possess both the characteristics and which is suitable for the adsorp-tion of gases and water.
Another object of this invention is to provide a novel amorphous silica having a small bulk density and a large specific surface area and accordingly a high oil adsorbing eapacity.
Another object of this invention is to provide an amorphous silica readily dispersible in water -to give an aqueous slurry from which a lightweight and strong shaped body can be obtained by shaping and drying without using any binder and also to provide the aqueous slurry.
Another object of this invention is to provide a light-weight shaped body of amorphous silica which has high mechanical strength and acid resistance and which is therefore usable as a heat insulator, filter medium, catalyst carriex, etc.
Another objeet of this invention is to provide a novel amorphous siliea suitable as a material for the product-; ion of heat-resistant glass.
Another objeet of this invention is to provide a novel amorphous silica which readily permits the passage :~ . . : , 31~2317%
of water, therefore can be drained easily and is uncollapsible when in contact with water, the amorphous silica thus being serviceable for various uses wherein these character-istics are advantageously utilized.
Another object of this invention is to provide methods of preparing the novel amorphous silicas having the foregoing excellent properties and products thereof.
Another object of this invention is to provide a novel composite material composed of the novel amorphous silica and extremely fine particles of calcium carbonate at-tached to the silica.
Another object of this invention is to provide a -method of preparing a novel composite material of amorphous silica and calcium carbonate which is useful as a filler and reinforcing agent and also to provide a method of preparing products from the composite material.
These and other features of this invention will become apparent from the following description.
Basically, the amorphous silicas of this invention are in the form of primary particles and characterized in that the particles having a crystalline appearance and has at least two surfaces in symmetric relation, a lenght of about 1 to about 500~ and a thickness oE about 50~l A to about 1~
the lenght being at least about 10 times the thickness. The amorphous silicas of this invention include, ' ~
,.. " ~
~23~ 7Z
in addition to those having the form of primary particles described above, those in the form of secondary particles and those in the form of a shaped body.
The term "Opsil" as used in the specification refers to the amorphous silica of this invention. Thus by the term "Opsil-I" is meant an amorphous silica of this invention having the form of primary particles, and by the term "Opsil-II" is meant an amorphous silica of this invention having the form of secondary particles.
Opsil-I of this invention is amorphous silica of high purity and therefore does not display and X-ray diffract-ion phenomenon and, when dehydrated by ignition and then chem-ically analyzed, is found to contain at least 98% by weight of SiO2. Observation under an electron microscope has revealed that the primary particle, the basic form of Opsils, has a crystalline appearance and at least two surfaces in symmetric relation, although it is amorphous.
The crystalline appearance, the most distinct feature of Opsils of this invention, is attributable to the fact that they are derived from silicate crystals by the conversion of the silicate crystals into amorphous silica which retains the original configuration of the crystals. Accordingly, the crystalline appearance and size of the particles of Opsil-I
are substantially in .. .
~Z31~:
conformity with the appearance and size of the silicate crystals from which they are derived, and Opsil-I particles have varying configurations and sizes in corresponding relation to the original crystals. For example, the lath-like crystals of wollastonite, xonotlite, foshagite or like calcium silicate are converted into the particles of Opsil-I having a lath-like configuration. The particles of Opsil-I have a plate-like con-figuration if they are derived from the plate-like crystals of tobermorite, gyrolite, ~-dicalcium silicate hydrate (~-C2SH) or like calcium silicate. The particles of Opsil-I derived from the foil-like crystals of calcium silicate such as CSHn have a foil-like configuration. The sizes of these lath-like, plate-like and foil-like Opsil~I particles range from about 1 to about 500~, preferably about 1 to about 300~, in length 15 and from about 50 A to about 1~, preferably about 100 ~ to about 1~ in thickness, the lenght being at least about 10 times, preferably about 10 to about 5,000 times the thickness.
The lath-like particles of Opsil~I derived from primary part-icles of xonotlite crystals have the configuration of the pri-20 mary particles and are about 1 to about 50~ in length, about 100 A to about 0.5~ in thickness and about 100 A to about 2~ in width, the length being about 10 to about 5,000 times the thick-ness. the plate-like particles of Opsil-I derived from primary '~" ' ~L231~2 particles of tobemorite crystals have the configuration oE
the primary particles and are about 1 to about 50~ in length about 100 ~ to about 0.5~ in thickness and about 0.2 to about 20u in width, the length being about 10 to about 5,000 times the thickness. The lath-like particles of Opsil-I derived from primary particles of wollastonite crystals have the con-figuration of the primary particles and are about 1 to about 500~ in length, about 100 A to about 1~ in thickness and about 100 A to about 5~ in width, the length being about 10 to about 5,000 times the thickness. The foil-like particles of Opsil-I
derived from primary particles of CSHn crystals have the con-figuration of the primary particles and are about 1 to about 20~ in length, about 50 ~ to about 500 ~ in thickness and about 100 A to about 20~ in width, the length being about 50 to about 5,000 times the thickness. The plate-like particles of Opsil-I derived from primary particles of gyrolite crystals have the configuration of the primary particles and are about 1 to about 50~ in length, about 100 ~ to about 0.5~ in thick-ness and about 1 to about 20~ in width, the length being about 20 10 to about 5,000 times the thickness. The plate-like particles of Opsil-I derived from primary particles of ~dicalcium silicate hydrate crystlas have the configuration of the primary part-icles and are about 1 to about 300~ in length, about ~3~i7~2 500 A to about 1~ in thickness and about 1 to about 50~ in width, the length being about 10 to about 5,000 times the thick-ness.
Table 1 gives the chemical composition of Opsil-I, which is subjected to ignition dehydration and thereafter to elementary analysis, and Table 2 shows the physical properties of Opsil-I in comparison with those of silica gel.
Table 1 Ig. loss 4-7 wt. %
SiO2 > 9~.0 wt. %
2 3 < 1.0 wt. %
Fe23 < 0.01 wt. %
CaO < 0.02 wt. %
.~
`: :
- ; . - , .
Table ?
Opsil-I Silica gel RD(l) ID(2) ~D(3 Bulk density (g/cm3)0.04-0.30 0.67-0.75 0.~5-0.40 0.12-0.17 True specifiC 1.9-2.2 2,2 2.2 2.2 graYity (g/cm3) surface area250-600 750-800 300-350 100-200 (m2/g) Pore volume0.1-0.5 0.37-0.40 0.9-1.1 1.4-2.0 Av. pore 0 20-40 22-26 120-160 180-220 diameter (A) Part~cle size 1-500 1,000 -5,000 1,000-5,000 1-5 (ccilOO g) 3 ~ygro(copicity 220 45 110 150 Water No Collapse Collapse resistance cha~ge Thermal (EndlC/tihltY 3 deg.) p~ 6-7 ~
, ~
Note: (1) RD stands for regular density.
(2) ID atands for intermediate density.
Fe23 < 0.01 wt. %
CaO < 0.02 wt. %
.~
`: :
- ; . - , .
Table ?
Opsil-I Silica gel RD(l) ID(2) ~D(3 Bulk density (g/cm3)0.04-0.30 0.67-0.75 0.~5-0.40 0.12-0.17 True specifiC 1.9-2.2 2,2 2.2 2.2 graYity (g/cm3) surface area250-600 750-800 300-350 100-200 (m2/g) Pore volume0.1-0.5 0.37-0.40 0.9-1.1 1.4-2.0 Av. pore 0 20-40 22-26 120-160 180-220 diameter (A) Part~cle size 1-500 1,000 -5,000 1,000-5,000 1-5 (ccilOO g) 3 ~ygro(copicity 220 45 110 150 Water No Collapse Collapse resistance cha~ge Thermal (EndlC/tihltY 3 deg.) p~ 6-7 ~
, ~
Note: (1) RD stands for regular density.
(2) ID atands for intermediate density.
(3) LD stands for low density.
(Literature: Encyclopedia of Cnemical ~echnology 18, (1969) p61-67) . . .. - -..~........... . . .
123~
The characteri5tic values in Table 2 are determined by the following methods.
Bulk density: A 10 g quantity of particles are placed in a cylinder 5 cm2 in cross sectional area and subjected - 5 to a load of 2~0 g by a 50 ~/cm2 capacity piston-- - - cylinder device. The volu~ne of the compressed mass is then measured. Bulk density is given by Bulk denslty = 10 (~)3 Volume (cm ) T~ue specific gravlty: l~easured by air comparison - pycnometer Model 930, Beckmann Co., vrith air replaced by He gas.
Average pore diameter: By BET nitrogen adsorption method.
Specific Surface area: Same as above.
Pore volume: Same as above.
~15 Particle size: Determined under optical and electron microscopes.
- Oil adsorption: Dioctyl phthalate (C6H4(COOC8H17)2) is ; \ added ~ropwise to 100 g of particles to cause the particles to adsorb the phthalate, and the amount of the phthalate is measured ~rhen the mass of the particels starts to become markedly viscous.
, Hygroscopicity: Particles are placed in a container at R.H. 100% and maintained at 25 C, allowing the particles to adsorb moisture until an equilibrium is established.
~ ',-; ' ., , 31~;;~3~1L7~
Hygroscopicity i~ expressed in terms of the weight by % of the moisture adsorbed based on the particles.
The values listed are obtained using Opsil-I having a bulk density of 0.1 g/cm3, and 5ilica gels with - 5 a bulk density o~ 0.7 g/cm3 for RD type, a bulk density - of 0.4 g~cm3 for ID type and a bulk density of 0.15 g/cm3 for LD type.
Table 2 shows that opsil-I has a small average pore diameter and a large specific surface area despite its small bulk density, does not collapse when immersed in water because of its good resistance to water and is highly . - oil-adsorbent, remarkably hygroscopic .~nd extremely low in thermal conductivity. Further, Opsil has an approximately neutral pH of 6 to 7 and high resistance to chemicals and will not be decomposed with hydrochloric - acid and like acid~, These properties are very advantageous - over the propertie5 of calcium silicate crystals from which they are derived; the crystals have a high pH of ; ~ 10 to 11~ are decomposable with an acid such as hydro-chloric acid and therefore find limited uses.
Moreover, Opsil-I i5 easily dispersible in water to form an aqueous ~lurry thereof and has a peculiar shapability - that the slurry gives, ~hen shaped and dried, a light ~eight shaped body composed of Opsil-I randomly three-dimensionally interlocked with one another integrally into ~2 `, . - . - . . . , . . . . ~
the body and having a high mechanical strength The aqueous slurry to be shaped may preferably have a water to solid ratio of 4 - 50 : 1 by weight. When desired, the slurry may in-corporate therein a fibrous reinforcing material such as as-bestos, glass fibers, rock wool, synthetic fibers, naturalfibers, pulp, carbon fibers, stainless steel fibers, alumina sol, colloidal silica sol, clay, cement, coloring agent, filler and various other additives. The shaped body is usable variously for example as a heat insulating material, filtration medium, catalyst carrier, etc.
Because of the unique particulate shape and proper-ties described above, Opsil-I is serviceable as a substitute for silica gel in uses for which silica gel is usually employed ànd is also serviceable in other uses to which silica gel is 15 not applicable. For example, Opsil-I is useful as a filler, .:
drying agent, adsorbent, deodorant, filter medium, heat-resist-ant filter, additive for adhesives, heat-resistant agent, delustering agent for paper making, emulsifier for cosmetics, abrasion-resistant agent, heat insulator, viscosity imparting agent, pigment, tooth powder, carrier for agricultural chem-icals, carrier for pharmaceuticals, catalyst, catalyst carrier, material for heat-resistant glass, absorbent for gas chroma-tography, excipient, anticaking agent, fixing agent for volatile :
`~
substances, molecular sieve, shaped body, etc.
Opsil-II is in the form of substantially globular secondary particles of the amorphous silica of this invention.
Each of the secondary particles is composed of numerous pri~
mary particles of amorphous silica randomly -three-dimensionally interlocked with one another and voids interspersed therebetween and has a diameter of about 10 to about 150~, preferably about 10 to about 80~, the primary particle having a crystalline appearance, at least two surfaces in symmetric relation, a length of about 1 to about 500~, preferably about 1 to about 300~, and a thickness of about 50 to about 1~, preferably about 100 to about 1~, the length being at least about 10 times, preferably about 10 to about 5,000 times, the thickness. Opsil-II usually has the porosity of at least about 75% preferably about 80 to about 98%.
Since Opsil-II is composed of Opsil-I described above, it has the foregoing properties of Opsil-I and finds the same uses as Opsil-I.
Moreover, Opsil-II is readily dispersible in water to form an aqueous slurry and has the peculiar shapability that the slurry gives a light-weight shaped body having high mechanical strength, when shaped and dried. Generally, the shaped body obtained from Opsil-II has higher mechanical strength than that obtained from Opsil-I having the same bulk density therewith. More specifically, when the aqueous slurry of ~ .-~ ~ :
~L~231'~
Opsil-II is subjected to pressure for shaping, the particles are compressed in the direction of pressure applied in the shaping step. Namely, the particles of Opsil-II in the present shaped body are compressed more or less in at least one direct-ion due to the pressure applied in the shaping step. The com-pressed particles are inter'ocked with one another and shaped to an integral body in this state when dried. The bulk density of the shaped body, which is controllable as desired by alter-ing the shaping pressure, can vary over a wide range. Prefer-ably, the bulk density is in the range of about 0.1 g/cm3 toabout 1.0 g/cm3. The shaped body is usable variously for example as a heat insulating material, filtration medium, catalyst carrier, etc.
Generally, the aqueous slurry of Opsil-II to be shaped may preferably have a water to solids ratio of 8 - 50 : 1 by weight. When desired, the aqueous slurry may incorporate therein a fibrous reinforcing material such as asbestos, glass fibers, rock wool, synthetic fibers, natural fibers, pulp, carbon fibers or stainless steel fibers, alumina sol, colloidal silica sol, clay, cement, coloring agent, filler and various other additives-. These additives afford useful properties to -~
the shaped body.
Table 3 gives the properties of Opsil-II.
:`.1 .. . .. . . .
~ ~ ~3~
Table 3 Bulk density (g/cm ) 0 03-0.5 Specific surface area (m2/g) 250-600 Specific surface areO (m /g) 200-550 after heating at 400 C
Porosity (%) Preferably at least 75 Oil adsorption (cc/100g) 500-1200 pH 6-7 Heat resistance Secondary paOrticles retain shape at 950 C
The properties listed above are determined by the same methods as in Table 2, wherein the porosity is given by Apparent specific gravity of Opsil - II
Porosity (%) = (1 - - ) X 100 True specific gravity of :.
Opsil - II
The heat resistance is determined with the unaided eyes.
This invention further provides novel shaped bodies of amorphous silica which include a shaped body composed of Opsil-I (hereinafter referred to as "Opsil-IS") and a shaped body composed of Opsil-II (hereinafter referred to as "Opsil-IIS"). Opsil-IS is a shaped body which is integrally formed from the particles of Opsil-I randomly three-dimensionally inter-locked with one another.
~ ~ 2~
J~IL
That is to say, Opsil-IS comprises primary particles oE amor-phous silica randomly three-dimensionally interlocked with one another integrally into the body and voids interspersed there-between, each of the primary particles having a crystalline appearance, at least two surfaces in symmetric relation, a length of about 1 to about 500~, preferably about 1 to about 300~, and a thickness of about 50 A to about 1~, preferably about 100 ~ to about 1~, the length being at leas-t about 10 times, preferably about 10 to about 5,000 times, the thickness.
The shaped body usually has a porosity of at least about 50~, preferably about 60 to about 95~.
Opsil-IIS is a shaped body in which the particles of Opsil-II are interlocked with one another into the integral body. Namely, Opsil-IIS comprises secondary particles of amorphous silica compressed in at least one direction and inter-locked with one another integrally into the body and voids interspersed therebetween, the secondary particle being composed of numerous primary particles of amorphous silica randomly three-dimensionally interlocked with one another, each of the primary particles having a crystalline ~ ~ 3 ~ ' appearanee, at least two surfaces in symmetrie relatlon, a length of about 1 to 500 ~ , prefelably about 1 to about 300~ ~ and a thickness of about 50 ~ to about 1~1 9 preferably about 100 R to about 1~ , the length being at least 10 times~ preferably about 10 to about ~,000 times~ the . thiekness. O~sil-IIS usuall~ h~s a porosit~ of at least _ . . .
about 50D~ ~referably ~b~ut 60~ t~ ~bout 97/~.
.....
- Both OpsiI-IS and Opsil-IIS have a large porosity, are lightweight and have high meehanical strength. More - speeifically~ they have a lo\~J bulk density of about 0.1 to about 0.4 g/cm3 and high bending strength of about 3 to 30 kg/em2. The bulk density ean be inereased. The - meehanical strength of the shaped body increases with - inereasing bulk density. ~or example, shaped bodies with -a bulk density of 0~4 g/cm3 to 1.0 g/cm~ possess high - . bending strength of 20 to 100 k~/cm3. The light~r~eight and mechanically strong eharacteristics of 5uch shaped bodies are attributable to the faet that the component ~ partieles of Opsil_I and/or Op5il-II are firmly ~oined to one another and have a large porosity. The porosity increases with decreasing bulk density.
These shaped bodies, i.e. Opsil-IS and Opsil-IIS7 may be eomposed of Opsil_I and Opsil~II or may further eontain an~ of varioù5 fibrous reinforcing materlals uch as glass fibers, ceramic fibers~ asbesto~, rock wool, 5ynthetie flbers (polyamide flber, polyvinylalehol fiber, ete.), 3~
natural fibers, pulp, stainless steel fibers, metal fibers - and carbon fibers, clay, cement, coloring agent, filler and like additives. The shaped bodies may incorporate .
therein iron reinforcing rods, wire nets, fabrics, etc Because of the properties described above9 Opsil-IS
and Opsil-IIS are useful as heat insulators, refractoriesS
filter media, catalyst carriers, etc.
- Opsils of~the present invention can be prepared - - - from various natural or synthetic silicate crystals having10- - the network or chain structurs of SiOI tetrahedrons~ The method for preparing Opsils of the invention is not limitative and optional methods are applicable, as far as the present opsils are obtained. According to one of the preferred - - methods~ Opsils are prepared from calcium silicate crystals by contactin~ the crystals with carbon dioxide gas in the presence of water to convert the calcium Silicate to ~ amorphous silica and extremely fine particles of calcium -- carbonate, treating the resulting product ~ith-an acid to decompose the calcium carbonate into carbon dioxide and ZO calcium salt and separating the amorphous silica from the calcium salt.
The most distinct feature of this method is that - calcium silicate can be converted to ~norphous silica - without entailing a substantial change in the configuration of the component crystals of calcium silicate. Consequantly, ".'''', ' .
' ' , ^
1~
r ~3i~7 the amorphous silica thus obtained, n~mely Opsil, substantially retains the original configuration of calcium silicate crystals and therefore possesses the foregoing variou5 useful properties as distinct from the properties of conventional amorphous silica.
The calcium silicate crystals usable a the starting crystals include crystals of wollastonite-type calcium silicates such as wollastonite, xonotlite, foshagite~ hillebrandite, rohsenhanite, etc , crystals of tobermorite-type calcium silicates such as tobermorite, crystals of gyrolite-type calcium silicates such as - gyrolite, truscottite, reyerite, etc., crystals of ~
dicalcium silicates hydrate such as calcio-condrodite, kilchoanite, afwillite, etc.~ cry~tals of a-dicalcium - 15 silicate hydrate~ tricalcium silicate hydrate, CSHn, CSH~ CSH(II)~ etc.
These crystals are used as a starting material ~ in the form of primary particle5, secondary particles or ~ A shaped body. Since Opsils as~u~e the original configuration of the crystals without any substantial ~- change, the forms of the starting crystals are retained in Opsils frea of any substantial change. Put in detail, primary particles of crystalline calcium silicate (having at least t~vo surfaces in symmetric relation, a length of about 1 to about ~00 ~ and a thicl~ness of about 50 A to ~0 7~
about 1~, the length being at least about 10 times the thickness) give Opsil-I in which the configuration of the crystalline particles remain intact. Secondary particles of crystalline calcium silicate, each composed of numerous primary particles of silicate randomly three-dimensionally interlocked together into a substantially globular form of abou-t 10 to about 150~ in diameter and voids interspersed therebetween, afford Opsil-II
substantially retaining the same form or structure. Secondary particles of crystalline calcium silicate having a porosity of about 50% or more are preferably used to obtain Opsil-II having a porosity of at least about 75% or more. In this case the secondary particles of crystalline calcium silicate having a porosity of at least about 60% are most preferable. Further Opsil-IS is obtained from a shaped body of calcium silicate crystals which is intergrally formed from primary particles of crystalline calcium silicate randomly three-dimensionally inter-locked with one another and has voids interspersed therebetween.
Opsil-IS having a porosity of about 50% or more can be prepared from a shaped body of calcium silicate crystals having a porosity of about 40% or more, preferably at least about 50%. Opsil-IS
can also be prepared from aqueous slurry o~ Opsil-I as disclosed berore. In this case Opsil-IS having various porosities can ; be obtained by varying pressures applied in shaping procedures.
Furthermore, Opsil-IIS is prepared from a shaped body of calcium silicate crystals wherein the above-mentioned globular secondary particles of crystalline calcium .
3~
silicate are integrally interlocl;eù wilh Ol!e another~ with voids interspersed therebetween.
The shaped body composed of the globular secondary particles of calcium silicate crystals and having a porosit~ of : 5 about 55/~ or more, , ., ~preferably at least about 60%, is used to obtain Opsil-IIS having a porosity of about 80% or more. Opsil-- IIS can also be prepared from Opsil-II by dewaterin~ and shaping the agueous slurr~ of O~sil~II with pressure and drying the shaped mass. In this case Opsil-IIS having a porosity of about 50~ or more is obtainable by varying the pressure for shaping.
The calcium silicate crystals in the versatile forms described and useful for the production of Opsils f this invention are known and can be prepared by known methods. For example, globular secondary particles of crystalline calcium silicate can be obtained by a method de~eloped by the present applicant and described in ; ~ Japanese Patent Publication No. 25771/1970. Accordin~
to this method, an aqueous slurry of globular secondary particles is prepared by dispersing a siliceous material and a lime materi~i in water, along with a desired rein-forcing material or like additivè, if desired, to obtain - a starting slurry and subiecting the slurry to hydrothermal ~ - 25 reaction ~Jith stirr~ng to effect crystallization. The - shaped body of calcium silicate crystals composed of the globular secondary particles is prepared by a further method described in the Japanese Patent Publication No. 25771/1970~
3~'72 ~l2 With this method, a reinforcin~ material or like additive is added, when desired, to the aqueous siurry of the globular secondary particles obtained as above, and the re~ulting slurry is shaped with de-llaterin~ and dried, ~Ihereby a shaped body of calcium silicate crystals i5 obtained in which the secondary particles are comp:ressed in at least one - direction and interlocked vJith one another into the integralbody The shaped body composed of numerous primary particles of crystalline calcium silicate randomly three dimensionally interlocked together for the production of Opsil-IS can be prepared by the method disclosed in Japanese Patent Publication No. 40~0/1955, Japanese Patent Publication Mo. 1953/1966, U.S.P. No. 2665996 and U.S.P. No. 2699097, namely by gelling a starting slurry containing a siliceous material and a lime material dispersed in water, placing the gel in a mold or shaping by dewatering, and subjecting the shaped mass to hydrothermal reaction for crystalli-zation and hardening. The primary particles of crystalline -~ calcium silicate can be readily prepared also by finely dividing the globular secondary particles or the shaped ~:
body of calcium silicate crystal Useful siliceous materials for the preparation -~
of the calcium silicate crystals are natural amorphou5 siliceous materials, siliceous sand~ synthetic siliceous materials~ diatomaceous earth, clay, slag, terra alba, ..
.. . - 23 -- ; :
fly ash, pearlite, white carbon, silicon dust and the like lhich predominantly comprises Si02. These can be used singly, or two ~r more of them are usable in admixture. E~amples of lime materials are quick lime, slaked lime, carbide residue, cement, etc. which predominantly comprises CaO. These materials are also usable singly, or two or more of them are usable in admixture. Generally, the materials may be used in a CaO to Si02 mole ratio approximately of 0.5-3.5:1.
When desired, the starting materials may be used conjointly with glass fibers, ceramics fibers, asbestos 9 rock wool, synthetic fibers, natural fibers, pulp, stainless steel fibers, carbon ~ibers or like ~ibrous reinIorcing material, and coloring agent or like additive which may be added to the materials~
The amount of water to be used, which is variable over a wide range, may generally be about ~,5 to about 30 times the 'Otal wel~ht of the solids. The reaction is "~ preferably conducted in an autoclave at a saturation temperature under particular water vapor pressure. The reaction temperature is usually higher than 100 C, preferably higher than 150 C, and the reaction pressure is the saturated vapor pressure corresponding to the temperature applied. The reaction is usually completed in about 0.5 to about 20 hours. The calcium silicate crystals are 3~'7~
obtained with varying degrees of crystallization depending on the CaO to SiO2 mole ratio, reaction pressure, temperature and time referred to above. The calcium silicate crystals include, for example, xonotlite, tobermorite, foshagite~
gyrolite, a-dicalcium silicate hydrate, CSHn and like crystals. The xonotlite crystals, when further baked at about l,000 C, can be converted to wollastonite crystals without resulting in any change in the shape of the crystal~
~Japanese Patent Publication No. 29493/1975).
According to this invention, the calcium silicate crystals in the form of primary particles, globular secondary particles and shaped bodies are contacted with carbon dioxide in the presence of water for forced carbonation.
The carbonat1on is effected by contacting the calcium - 15 silicate crystals ~ith the carbon dioxide in the presence of water. Preferably, the carbonation is effected, for example, by placing the calcium sllicate crystals of the - aforesaid form in à suitable closed container and introducing ~ carbon dioxide gas into the container at a high humidity or under wet atmosphere~ or by introducing carbon dioxide gas into ~Yater or carbonated water in which such calcium sillcate crystals have been immersed~ When the calcium silicate crystals are prepared in the form of an aqueous slurry of Secondary particlesl carbon dioxide gas may of course be introduced directly into the 91urry. Insofar ' c ~'~
3.~Lt7~
as carbon dioxide gas is introduced into the reaction system, the carbonation will proceed satisfactorily at room temperature under atmospheric pressure. However, it is preferable to effect the carbonation at increased pressure 'of up to 10 kg/cmZ gage, whereby the reaction can be ~ completed within a shorter time at an accelerated velocity.
The carbon dioxide is used in a stoichiometric a~ount or in excess. When the calcium silicate crystals are carbonated as immersed in water, the carbonation valocity 10- can be increased by stirring the reaction system. The preferable ratio of water to calcium silicate crystals ls in the range of 1-50 : 1, most preferably 1-25 to 1, by weight. The velocity of carbonation varies to some extent with the degree of crystallization of the calcium silicate used as the starting material. However, when carbonating xonotlite crystals the carbonation of which - proceeds at the lowest velocity, the reaction will be completed in about ~ to 10 hours by using water in an `-~ amount of about 2 to about 6 times the dry weight of the crystals. Further when the amount of water is 5 times as much, tha reaction will be completed usually in about one hour at reaction pressura of 2 kg/cm2 gauge, or in as short a period of time as about 30 minutes at reaction pressure of 3 kg/cm gauge.
Depending on the particular type of calcium ... ... .. .
~23~.72 silicate crystals used and the degree of crystallization there-of, the carbonation proceeds as represented by the following equations.
xCaO~ SiO2 mE~20 +, C02 ? CaC03 -~ SiO2 nH20 wherein x is a number of 0.5 to 3.5 In the step of carbonation calcium silicate crystals are converted into composite particles of amorphous silicate and ealcium earbonate without any substantial ehange of the con-figuration of calcium silicate crystals. The resulting caleium earbonate partieles are in the form of extremely fine particles having a partiele size of less than about 2~ and found to be attaehed to amorphous siliea particles through a chemical or physical action. For example, when the composite primary particles of amorphous silica and calcium carbonate resulting from the carbonation are dispersed in water to a concentration of 5 wt. %, stirred for 20 minutes and thereafter allowed to stand in an attempt to separate the particles into the two eomponents by settling utilizing the difference in specific gravity, they are in no way separable and found to be firmly joined together through a chemical or physical action.
Sinee the step of earbonation produces no ehange in the configuration of calcium silicate crystals, the primary partieles, secondary particles and shaped bodies of amorphous siliea-calcium carbonate composite materials can respeetively ;
be obtained by the earbonation from primary particles, seeondary particles and shaped bodies of ".' 3l7~
calcium silicate crystals without any change in conflgu-rations thereof.
The composite material of amorphous silica and calcium carbonate in the form of a primary particle comprises an amorphous silica particle and an extremely fine particle of calcium carbonate attached to the amorphous silica particle, the amorphous silica particle having a crystalline appearance, at least two surfaces in symmetric relation, a length of about 1 to about ~00~ and a thickness of 10- about ,0 A to about 1~ , the length being at least about 10 times the thickness. The composite meterial of amorphous silica and calcium carbonate in the form of a substantially globular secondary particle has a diameter of about 10 to about 150 ~ and is composed of numerous amorphous silica-cal.cium carbonate composite primary particles and voids intersper~ed therebetween, each of the constituent composite particles comprising an : amorphous silica particle in the` form of a primary `~ particle ~hd an extremely fine particle of calcium carbonate 20 attached to the amorphous silica particle, the amorphous silica particle having a crystalline appearance~ at least two surfaces in symmetric relation, a length of about 1 to about 500 ~ and a thickness of about 50 A to about 1~ ~ the length being at least about 10 times the thickness~
The composite materials of amorphous silica and calcium carbonate in the form of shaped body lnclude a ehaped .. ;'' ~3 ' 3~
body composed of numerous composite primary particles and one composed of numerous composite secondary particles.
The former shaped body comprises amorphous silica-calcium carbonate composite primary particles randomly three-dimensionally interlocked with one another integrally lnto the body;with void~ lnter~persed therebetween9 - each of t~e primary particles comprising an amorphous ~ilica p~rtilce in the form of a primary particle and ah extremely fine particle of calcium carbonate attached to the amorphous silica particle, the amorphous silica particle having a crystalline appearance, at least two surfaces in symmetric relation~ a length of about 1 to about 500~ and a thickness of about 50 A to about 1~ , the length being at least about 10 times the thickness.
The latter shaped body comprises numerous amorphous silica-calcium carbGnate composite secondary particles being compressed to at least one direction and inter-rocked with one another and ~oids intersper~ed therebetween~
~ each of the composite 6econdary particles - having originally a substantially glob~lar form of a diameter of about 10 to about 150 ~ and comprising an amorphous ~ilica particle in the form of a primary particle and extremely fine part~cle of ca~cium carbonate attached to the amorphous silica particle, the amorphous silica particle having a crystalline appearance, at least two ~;
surfaces in symmetric relation, a length of about 1 to about 500~ and a thickne~s of about 50 ~ to about 1 ~ ' ~3~7~:
the length being at least about 10 times the thickness.
The compos~te material6 composed of the amorphous silica and extremely fine particles of calcium carbonate chemically or physically attached thereto find versatile applications for which Opsils are useful, because of their characteristics attributable to the Opsil contained therein.
Further since the extremely fine particles of calcium carbonate are contained in the composite particles as attached to the Opsil, the compoSite particles are useful also as a filler. Moreover, the composite materials are useful as intermediate products for producing O~sil in various forms, According to this invention, the composite material of amorphous 8ilica and calcium carbonate resulting from carbonation is thereafter treated with an acid to remove the calcium carbonate from the amorphous silica The acids to be used for this purpose include those ha~ing no reactivity with silica but being capable o~ decompos1ng "~ calcium carbonate to produce carbon dioxide and a water-soluble salt. Examples thereof are hydrochloric acid, nitric acid~ acetic acid, perchloric acid or the like.
The acid treatment i6 carried out usually by immerSing the composite materlal in a solution of the acid, or by introducing an acid gas such as hydrochloric acid gas into water in which the composite particles are immersed ....
( 3~7 or dispersed~ The acid is used :Ln a stoichiometric amount or in excess. This treatment is preferably conducted at room temperatures, though elevated temperatures up to boiling points of the acid used are applicable. The reaction pressure is usually atmospheric~pressure, but incr~ased pressure is also applicable. Through the treatment, the calcium carbonate attached to the amorphous silica is decomposed with the acid to a water-soluble calcium salt, which is thereafter completely removed for example by washing with water, followed by drying, whereby primary particles, secondary particles or shaped body made up of amorphous silica are prepared. In the case of preparing shaped body, it can be treated with warm or hot water before drying, whereby linear shrinkage thereof due to drying can be lowered. The treatment can preferably be conducted by immersing the shaped body in hot water of higher than 60 C for 0.5 to 10 hours. When hot water of higher than 100 C is used, autoclave or the like closed vessel may be `~ employed. The step of removing calcium carbonate produces no change in the configuration of the primary particles of amorphous silica. Accordingly, composite globular secondary particles of the composite material give globular secondary particles of amorphous silica~ i.e. Opsil-II, retaining the original structure of the former, while shaped bodies of the composite material give shaped bodies . .
c ~~
~23~
of amorphous sil~ca, i.e. Opsil-IS and Opsll-IIS, similarly retaining the original structure thereof. Further, the composite materials of amorphous silica and calcium carbonate ln the form of primary particles and globular secondary particles have shapability similar to Opsil-I and Opsil-II.
More specifically~ the composite particles ~re easily dispersible in water and give shaped body having mechanical - strength~ when the~slurry is shaped and dried. Therefore, Opsil-IS and Opsil-IIS can be prepared by shaping and drying the aqueous slurry of the composite particles to prepare shaped body thereof and subjecting the shaped body to the acid treatment as above, followed by washing with ~ater and drying.
For a better understanding of this invention, Reference Examples and Examples of the invention are given belbw.
~he ~ccompanylng drawings show x-ray diffraction - patterns, electron micrographs~ scanning electron m~crographs ~ and a por~ 5ize distrlbution diagram of the substances prepared in Examples and Reference Examples.
Figs. l(A) to IC) show x-ray diffraction patterns of a starting material, i.e. xonotlite crystals, composite particles of amorphous silica and calcium carbonate prepared from the crystals by carbonation, and Opsil-I of this invention respecti~ely;
.
23~
! - Figs. 2 and 3 are electron micrographs at a magnification of 20,000X, in which Figs. (A) show calcium silicate crystals used as starting materials, Figs. (s) show composite materials of amoxphous silica and calcium carbonate prepared by carbonating the crystals, and Figs. (C) show the particles of Opsils-I obtained by treating the materials;
Figs. 4 are electron micrographs at a magnification of 5,000X in which Fig. (A) shows a-dicalcium silicate hydrate crystals used as a starting material, and Fig. (B) shows Opsil-I prepared from the crystals; ~
Figs. 5 and 6 are scanning electron micrographs, ~, in which Figs. (A) show globular secondary particles composed of calcium silicate crystals used as starting materials, - Figs. (B) show globular secondary particles composed of composite materials of amorphous silica and calcium carbonate prepared by carbonating the orystals, and Figs. (C) show Opsil-II of this invention;
Figs. 7 are scanning electron micrographs of - fractured surfaces of shapea bodies at a magnification of - 20 ~ 600X, in which^(A) shows a shaped body of globular secondary particles of calcium silicate crystals used as starting materials, (B) shows a shaped body of globular secondary part-icles of composite material of amorphous silica and calcium carbonate and (C) shows a shaped body of Opsil-IIS.
Fig. 8 is a scanning electron microgra~h at a magnification of 1,000X showing Opsil-IS of this invention;
and ... . .. .. ., . ......... . . . . ~
.
~3~l'7%
Fig. 9 is a pore size distribution diagram in which the pore size (A) is plotted as abscissa and the pore volume (cc/~.g x 103) as ordinate.
The x-ray diffraction patterns in Figs. 1 are pre-pared using an x-ray diffractometer, irradiating the sample with x-rays of wavelength of 1.5405 ~ emitted with a Cu target and measuring the diffraction angle and intensity. Three diffraction lines having the highest intensities are determined for the identification of the camples.
:~ .
:
' .
~3~'J72 Reference Example 1 Quick lime is used as a lime material and minus 350 mesh siliceous sand powder (Tyler scale) as a siliceous material.
The materials are dispersed in water in a CaO to SiO2 mole ratio of 0.98:1 to prepare a slurry having a water to solids ratio by weight of 12:1. The slurry is placed in an autoclave and sub~ected to hydrothermal reaction at a temperature of 191C and a saturated vapor pressure of 12 kg/cm2 with heating and stir-ring for 8 hours to obtain a slurry of xonotlite crystals.
The x-ray diffraction pattern of the xonotlite crystals in Fig. 1 ~A) shows diffraction peaks (23) at 12.7, 27.6 and 29.0 peculiar to xonotlite crystals. The analysis by ignition of the crystals reveals the following composition.
SiO2 48.88%
15 ~ 45.60 Al O3 0.26 Fe2O3 ~ 54 Ig. loss 4.51 Total 99.80 The slurry of xonotlite crystals is shown in the scanning electron micrograph of Fig. 5(A), which reveals that numerous lath-like xonotlite crystals are formed as randomly three-dimensionally interlocked with one another into many, substantially globular, secondary particles of xono-tlite ranging from about 10 to about 60~ in diameter and suspended ~L~2~
in water. The secondary particle has a porosity of about 95.6%.
Sub~equently, the slurry containing the globular secondary particle~ of xonotlite is dried at 150 C and then divided into prlmary particles Fig. 2(A) shows an electron micrograph of the primary particles. The micrograph indicates that the primary particles - have at least two surfaces in ~ymmëtric relation, a length of about 1 to about 20~ , a thickness of about 0.02 to about 0.1 and a width of about 0~02 to about 1.0~ , the length being at least about 10 times the thickness. The primary particle~ have a ~pecific surface area of about 50 m2/g.
The ~lurry of xonotlite crystals prepared above is placed in a mold, 40 mm x 120 mm x 150 mm, and dewatered and fihaped by a pres~ and dried to obtain a shaped body. Fig. 7(A) i8 a scanning electron micrograph showing a fractured surface of the shaped body of xonotlite. The micrograph indicate~
that globular secondary particles o~ xonotlite are compre~sed and formed as interlocked with one another; The shaped body has a bulk density of 0.2 gfcm3, bending ~trength of about
(Literature: Encyclopedia of Cnemical ~echnology 18, (1969) p61-67) . . .. - -..~........... . . .
123~
The characteri5tic values in Table 2 are determined by the following methods.
Bulk density: A 10 g quantity of particles are placed in a cylinder 5 cm2 in cross sectional area and subjected - 5 to a load of 2~0 g by a 50 ~/cm2 capacity piston-- - - cylinder device. The volu~ne of the compressed mass is then measured. Bulk density is given by Bulk denslty = 10 (~)3 Volume (cm ) T~ue specific gravlty: l~easured by air comparison - pycnometer Model 930, Beckmann Co., vrith air replaced by He gas.
Average pore diameter: By BET nitrogen adsorption method.
Specific Surface area: Same as above.
Pore volume: Same as above.
~15 Particle size: Determined under optical and electron microscopes.
- Oil adsorption: Dioctyl phthalate (C6H4(COOC8H17)2) is ; \ added ~ropwise to 100 g of particles to cause the particles to adsorb the phthalate, and the amount of the phthalate is measured ~rhen the mass of the particels starts to become markedly viscous.
, Hygroscopicity: Particles are placed in a container at R.H. 100% and maintained at 25 C, allowing the particles to adsorb moisture until an equilibrium is established.
~ ',-; ' ., , 31~;;~3~1L7~
Hygroscopicity i~ expressed in terms of the weight by % of the moisture adsorbed based on the particles.
The values listed are obtained using Opsil-I having a bulk density of 0.1 g/cm3, and 5ilica gels with - 5 a bulk density o~ 0.7 g/cm3 for RD type, a bulk density - of 0.4 g~cm3 for ID type and a bulk density of 0.15 g/cm3 for LD type.
Table 2 shows that opsil-I has a small average pore diameter and a large specific surface area despite its small bulk density, does not collapse when immersed in water because of its good resistance to water and is highly . - oil-adsorbent, remarkably hygroscopic .~nd extremely low in thermal conductivity. Further, Opsil has an approximately neutral pH of 6 to 7 and high resistance to chemicals and will not be decomposed with hydrochloric - acid and like acid~, These properties are very advantageous - over the propertie5 of calcium silicate crystals from which they are derived; the crystals have a high pH of ; ~ 10 to 11~ are decomposable with an acid such as hydro-chloric acid and therefore find limited uses.
Moreover, Opsil-I i5 easily dispersible in water to form an aqueous ~lurry thereof and has a peculiar shapability - that the slurry gives, ~hen shaped and dried, a light ~eight shaped body composed of Opsil-I randomly three-dimensionally interlocked with one another integrally into ~2 `, . - . - . . . , . . . . ~
the body and having a high mechanical strength The aqueous slurry to be shaped may preferably have a water to solid ratio of 4 - 50 : 1 by weight. When desired, the slurry may in-corporate therein a fibrous reinforcing material such as as-bestos, glass fibers, rock wool, synthetic fibers, naturalfibers, pulp, carbon fibers, stainless steel fibers, alumina sol, colloidal silica sol, clay, cement, coloring agent, filler and various other additives. The shaped body is usable variously for example as a heat insulating material, filtration medium, catalyst carrier, etc.
Because of the unique particulate shape and proper-ties described above, Opsil-I is serviceable as a substitute for silica gel in uses for which silica gel is usually employed ànd is also serviceable in other uses to which silica gel is 15 not applicable. For example, Opsil-I is useful as a filler, .:
drying agent, adsorbent, deodorant, filter medium, heat-resist-ant filter, additive for adhesives, heat-resistant agent, delustering agent for paper making, emulsifier for cosmetics, abrasion-resistant agent, heat insulator, viscosity imparting agent, pigment, tooth powder, carrier for agricultural chem-icals, carrier for pharmaceuticals, catalyst, catalyst carrier, material for heat-resistant glass, absorbent for gas chroma-tography, excipient, anticaking agent, fixing agent for volatile :
`~
substances, molecular sieve, shaped body, etc.
Opsil-II is in the form of substantially globular secondary particles of the amorphous silica of this invention.
Each of the secondary particles is composed of numerous pri~
mary particles of amorphous silica randomly -three-dimensionally interlocked with one another and voids interspersed therebetween and has a diameter of about 10 to about 150~, preferably about 10 to about 80~, the primary particle having a crystalline appearance, at least two surfaces in symmetric relation, a length of about 1 to about 500~, preferably about 1 to about 300~, and a thickness of about 50 to about 1~, preferably about 100 to about 1~, the length being at least about 10 times, preferably about 10 to about 5,000 times, the thickness. Opsil-II usually has the porosity of at least about 75% preferably about 80 to about 98%.
Since Opsil-II is composed of Opsil-I described above, it has the foregoing properties of Opsil-I and finds the same uses as Opsil-I.
Moreover, Opsil-II is readily dispersible in water to form an aqueous slurry and has the peculiar shapability that the slurry gives a light-weight shaped body having high mechanical strength, when shaped and dried. Generally, the shaped body obtained from Opsil-II has higher mechanical strength than that obtained from Opsil-I having the same bulk density therewith. More specifically, when the aqueous slurry of ~ .-~ ~ :
~L~231'~
Opsil-II is subjected to pressure for shaping, the particles are compressed in the direction of pressure applied in the shaping step. Namely, the particles of Opsil-II in the present shaped body are compressed more or less in at least one direct-ion due to the pressure applied in the shaping step. The com-pressed particles are inter'ocked with one another and shaped to an integral body in this state when dried. The bulk density of the shaped body, which is controllable as desired by alter-ing the shaping pressure, can vary over a wide range. Prefer-ably, the bulk density is in the range of about 0.1 g/cm3 toabout 1.0 g/cm3. The shaped body is usable variously for example as a heat insulating material, filtration medium, catalyst carrier, etc.
Generally, the aqueous slurry of Opsil-II to be shaped may preferably have a water to solids ratio of 8 - 50 : 1 by weight. When desired, the aqueous slurry may incorporate therein a fibrous reinforcing material such as asbestos, glass fibers, rock wool, synthetic fibers, natural fibers, pulp, carbon fibers or stainless steel fibers, alumina sol, colloidal silica sol, clay, cement, coloring agent, filler and various other additives-. These additives afford useful properties to -~
the shaped body.
Table 3 gives the properties of Opsil-II.
:`.1 .. . .. . . .
~ ~ ~3~
Table 3 Bulk density (g/cm ) 0 03-0.5 Specific surface area (m2/g) 250-600 Specific surface areO (m /g) 200-550 after heating at 400 C
Porosity (%) Preferably at least 75 Oil adsorption (cc/100g) 500-1200 pH 6-7 Heat resistance Secondary paOrticles retain shape at 950 C
The properties listed above are determined by the same methods as in Table 2, wherein the porosity is given by Apparent specific gravity of Opsil - II
Porosity (%) = (1 - - ) X 100 True specific gravity of :.
Opsil - II
The heat resistance is determined with the unaided eyes.
This invention further provides novel shaped bodies of amorphous silica which include a shaped body composed of Opsil-I (hereinafter referred to as "Opsil-IS") and a shaped body composed of Opsil-II (hereinafter referred to as "Opsil-IIS"). Opsil-IS is a shaped body which is integrally formed from the particles of Opsil-I randomly three-dimensionally inter-locked with one another.
~ ~ 2~
J~IL
That is to say, Opsil-IS comprises primary particles oE amor-phous silica randomly three-dimensionally interlocked with one another integrally into the body and voids interspersed there-between, each of the primary particles having a crystalline appearance, at least two surfaces in symmetric relation, a length of about 1 to about 500~, preferably about 1 to about 300~, and a thickness of about 50 A to about 1~, preferably about 100 ~ to about 1~, the length being at leas-t about 10 times, preferably about 10 to about 5,000 times, the thickness.
The shaped body usually has a porosity of at least about 50~, preferably about 60 to about 95~.
Opsil-IIS is a shaped body in which the particles of Opsil-II are interlocked with one another into the integral body. Namely, Opsil-IIS comprises secondary particles of amorphous silica compressed in at least one direction and inter-locked with one another integrally into the body and voids interspersed therebetween, the secondary particle being composed of numerous primary particles of amorphous silica randomly three-dimensionally interlocked with one another, each of the primary particles having a crystalline ~ ~ 3 ~ ' appearanee, at least two surfaces in symmetrie relatlon, a length of about 1 to 500 ~ , prefelably about 1 to about 300~ ~ and a thickness of about 50 ~ to about 1~1 9 preferably about 100 R to about 1~ , the length being at least 10 times~ preferably about 10 to about ~,000 times~ the . thiekness. O~sil-IIS usuall~ h~s a porosit~ of at least _ . . .
about 50D~ ~referably ~b~ut 60~ t~ ~bout 97/~.
.....
- Both OpsiI-IS and Opsil-IIS have a large porosity, are lightweight and have high meehanical strength. More - speeifically~ they have a lo\~J bulk density of about 0.1 to about 0.4 g/cm3 and high bending strength of about 3 to 30 kg/em2. The bulk density ean be inereased. The - meehanical strength of the shaped body increases with - inereasing bulk density. ~or example, shaped bodies with -a bulk density of 0~4 g/cm3 to 1.0 g/cm~ possess high - . bending strength of 20 to 100 k~/cm3. The light~r~eight and mechanically strong eharacteristics of 5uch shaped bodies are attributable to the faet that the component ~ partieles of Opsil_I and/or Op5il-II are firmly ~oined to one another and have a large porosity. The porosity increases with decreasing bulk density.
These shaped bodies, i.e. Opsil-IS and Opsil-IIS7 may be eomposed of Opsil_I and Opsil~II or may further eontain an~ of varioù5 fibrous reinforcing materlals uch as glass fibers, ceramic fibers~ asbesto~, rock wool, 5ynthetie flbers (polyamide flber, polyvinylalehol fiber, ete.), 3~
natural fibers, pulp, stainless steel fibers, metal fibers - and carbon fibers, clay, cement, coloring agent, filler and like additives. The shaped bodies may incorporate .
therein iron reinforcing rods, wire nets, fabrics, etc Because of the properties described above9 Opsil-IS
and Opsil-IIS are useful as heat insulators, refractoriesS
filter media, catalyst carriers, etc.
- Opsils of~the present invention can be prepared - - - from various natural or synthetic silicate crystals having10- - the network or chain structurs of SiOI tetrahedrons~ The method for preparing Opsils of the invention is not limitative and optional methods are applicable, as far as the present opsils are obtained. According to one of the preferred - - methods~ Opsils are prepared from calcium silicate crystals by contactin~ the crystals with carbon dioxide gas in the presence of water to convert the calcium Silicate to ~ amorphous silica and extremely fine particles of calcium -- carbonate, treating the resulting product ~ith-an acid to decompose the calcium carbonate into carbon dioxide and ZO calcium salt and separating the amorphous silica from the calcium salt.
The most distinct feature of this method is that - calcium silicate can be converted to ~norphous silica - without entailing a substantial change in the configuration of the component crystals of calcium silicate. Consequantly, ".'''', ' .
' ' , ^
1~
r ~3i~7 the amorphous silica thus obtained, n~mely Opsil, substantially retains the original configuration of calcium silicate crystals and therefore possesses the foregoing variou5 useful properties as distinct from the properties of conventional amorphous silica.
The calcium silicate crystals usable a the starting crystals include crystals of wollastonite-type calcium silicates such as wollastonite, xonotlite, foshagite~ hillebrandite, rohsenhanite, etc , crystals of tobermorite-type calcium silicates such as tobermorite, crystals of gyrolite-type calcium silicates such as - gyrolite, truscottite, reyerite, etc., crystals of ~
dicalcium silicates hydrate such as calcio-condrodite, kilchoanite, afwillite, etc.~ cry~tals of a-dicalcium - 15 silicate hydrate~ tricalcium silicate hydrate, CSHn, CSH~ CSH(II)~ etc.
These crystals are used as a starting material ~ in the form of primary particle5, secondary particles or ~ A shaped body. Since Opsils as~u~e the original configuration of the crystals without any substantial ~- change, the forms of the starting crystals are retained in Opsils frea of any substantial change. Put in detail, primary particles of crystalline calcium silicate (having at least t~vo surfaces in symmetric relation, a length of about 1 to about ~00 ~ and a thicl~ness of about 50 A to ~0 7~
about 1~, the length being at least about 10 times the thickness) give Opsil-I in which the configuration of the crystalline particles remain intact. Secondary particles of crystalline calcium silicate, each composed of numerous primary particles of silicate randomly three-dimensionally interlocked together into a substantially globular form of abou-t 10 to about 150~ in diameter and voids interspersed therebetween, afford Opsil-II
substantially retaining the same form or structure. Secondary particles of crystalline calcium silicate having a porosity of about 50% or more are preferably used to obtain Opsil-II having a porosity of at least about 75% or more. In this case the secondary particles of crystalline calcium silicate having a porosity of at least about 60% are most preferable. Further Opsil-IS is obtained from a shaped body of calcium silicate crystals which is intergrally formed from primary particles of crystalline calcium silicate randomly three-dimensionally inter-locked with one another and has voids interspersed therebetween.
Opsil-IS having a porosity of about 50% or more can be prepared from a shaped body of calcium silicate crystals having a porosity of about 40% or more, preferably at least about 50%. Opsil-IS
can also be prepared from aqueous slurry o~ Opsil-I as disclosed berore. In this case Opsil-IS having various porosities can ; be obtained by varying pressures applied in shaping procedures.
Furthermore, Opsil-IIS is prepared from a shaped body of calcium silicate crystals wherein the above-mentioned globular secondary particles of crystalline calcium .
3~
silicate are integrally interlocl;eù wilh Ol!e another~ with voids interspersed therebetween.
The shaped body composed of the globular secondary particles of calcium silicate crystals and having a porosit~ of : 5 about 55/~ or more, , ., ~preferably at least about 60%, is used to obtain Opsil-IIS having a porosity of about 80% or more. Opsil-- IIS can also be prepared from Opsil-II by dewaterin~ and shaping the agueous slurr~ of O~sil~II with pressure and drying the shaped mass. In this case Opsil-IIS having a porosity of about 50~ or more is obtainable by varying the pressure for shaping.
The calcium silicate crystals in the versatile forms described and useful for the production of Opsils f this invention are known and can be prepared by known methods. For example, globular secondary particles of crystalline calcium silicate can be obtained by a method de~eloped by the present applicant and described in ; ~ Japanese Patent Publication No. 25771/1970. Accordin~
to this method, an aqueous slurry of globular secondary particles is prepared by dispersing a siliceous material and a lime materi~i in water, along with a desired rein-forcing material or like additivè, if desired, to obtain - a starting slurry and subiecting the slurry to hydrothermal ~ - 25 reaction ~Jith stirr~ng to effect crystallization. The - shaped body of calcium silicate crystals composed of the globular secondary particles is prepared by a further method described in the Japanese Patent Publication No. 25771/1970~
3~'72 ~l2 With this method, a reinforcin~ material or like additive is added, when desired, to the aqueous siurry of the globular secondary particles obtained as above, and the re~ulting slurry is shaped with de-llaterin~ and dried, ~Ihereby a shaped body of calcium silicate crystals i5 obtained in which the secondary particles are comp:ressed in at least one - direction and interlocked vJith one another into the integralbody The shaped body composed of numerous primary particles of crystalline calcium silicate randomly three dimensionally interlocked together for the production of Opsil-IS can be prepared by the method disclosed in Japanese Patent Publication No. 40~0/1955, Japanese Patent Publication Mo. 1953/1966, U.S.P. No. 2665996 and U.S.P. No. 2699097, namely by gelling a starting slurry containing a siliceous material and a lime material dispersed in water, placing the gel in a mold or shaping by dewatering, and subjecting the shaped mass to hydrothermal reaction for crystalli-zation and hardening. The primary particles of crystalline -~ calcium silicate can be readily prepared also by finely dividing the globular secondary particles or the shaped ~:
body of calcium silicate crystal Useful siliceous materials for the preparation -~
of the calcium silicate crystals are natural amorphou5 siliceous materials, siliceous sand~ synthetic siliceous materials~ diatomaceous earth, clay, slag, terra alba, ..
.. . - 23 -- ; :
fly ash, pearlite, white carbon, silicon dust and the like lhich predominantly comprises Si02. These can be used singly, or two ~r more of them are usable in admixture. E~amples of lime materials are quick lime, slaked lime, carbide residue, cement, etc. which predominantly comprises CaO. These materials are also usable singly, or two or more of them are usable in admixture. Generally, the materials may be used in a CaO to Si02 mole ratio approximately of 0.5-3.5:1.
When desired, the starting materials may be used conjointly with glass fibers, ceramics fibers, asbestos 9 rock wool, synthetic fibers, natural fibers, pulp, stainless steel fibers, carbon ~ibers or like ~ibrous reinIorcing material, and coloring agent or like additive which may be added to the materials~
The amount of water to be used, which is variable over a wide range, may generally be about ~,5 to about 30 times the 'Otal wel~ht of the solids. The reaction is "~ preferably conducted in an autoclave at a saturation temperature under particular water vapor pressure. The reaction temperature is usually higher than 100 C, preferably higher than 150 C, and the reaction pressure is the saturated vapor pressure corresponding to the temperature applied. The reaction is usually completed in about 0.5 to about 20 hours. The calcium silicate crystals are 3~'7~
obtained with varying degrees of crystallization depending on the CaO to SiO2 mole ratio, reaction pressure, temperature and time referred to above. The calcium silicate crystals include, for example, xonotlite, tobermorite, foshagite~
gyrolite, a-dicalcium silicate hydrate, CSHn and like crystals. The xonotlite crystals, when further baked at about l,000 C, can be converted to wollastonite crystals without resulting in any change in the shape of the crystal~
~Japanese Patent Publication No. 29493/1975).
According to this invention, the calcium silicate crystals in the form of primary particles, globular secondary particles and shaped bodies are contacted with carbon dioxide in the presence of water for forced carbonation.
The carbonat1on is effected by contacting the calcium - 15 silicate crystals ~ith the carbon dioxide in the presence of water. Preferably, the carbonation is effected, for example, by placing the calcium sllicate crystals of the - aforesaid form in à suitable closed container and introducing ~ carbon dioxide gas into the container at a high humidity or under wet atmosphere~ or by introducing carbon dioxide gas into ~Yater or carbonated water in which such calcium sillcate crystals have been immersed~ When the calcium silicate crystals are prepared in the form of an aqueous slurry of Secondary particlesl carbon dioxide gas may of course be introduced directly into the 91urry. Insofar ' c ~'~
3.~Lt7~
as carbon dioxide gas is introduced into the reaction system, the carbonation will proceed satisfactorily at room temperature under atmospheric pressure. However, it is preferable to effect the carbonation at increased pressure 'of up to 10 kg/cmZ gage, whereby the reaction can be ~ completed within a shorter time at an accelerated velocity.
The carbon dioxide is used in a stoichiometric a~ount or in excess. When the calcium silicate crystals are carbonated as immersed in water, the carbonation valocity 10- can be increased by stirring the reaction system. The preferable ratio of water to calcium silicate crystals ls in the range of 1-50 : 1, most preferably 1-25 to 1, by weight. The velocity of carbonation varies to some extent with the degree of crystallization of the calcium silicate used as the starting material. However, when carbonating xonotlite crystals the carbonation of which - proceeds at the lowest velocity, the reaction will be completed in about ~ to 10 hours by using water in an `-~ amount of about 2 to about 6 times the dry weight of the crystals. Further when the amount of water is 5 times as much, tha reaction will be completed usually in about one hour at reaction pressura of 2 kg/cm2 gauge, or in as short a period of time as about 30 minutes at reaction pressure of 3 kg/cm gauge.
Depending on the particular type of calcium ... ... .. .
~23~.72 silicate crystals used and the degree of crystallization there-of, the carbonation proceeds as represented by the following equations.
xCaO~ SiO2 mE~20 +, C02 ? CaC03 -~ SiO2 nH20 wherein x is a number of 0.5 to 3.5 In the step of carbonation calcium silicate crystals are converted into composite particles of amorphous silicate and ealcium earbonate without any substantial ehange of the con-figuration of calcium silicate crystals. The resulting caleium earbonate partieles are in the form of extremely fine particles having a partiele size of less than about 2~ and found to be attaehed to amorphous siliea particles through a chemical or physical action. For example, when the composite primary particles of amorphous silica and calcium carbonate resulting from the carbonation are dispersed in water to a concentration of 5 wt. %, stirred for 20 minutes and thereafter allowed to stand in an attempt to separate the particles into the two eomponents by settling utilizing the difference in specific gravity, they are in no way separable and found to be firmly joined together through a chemical or physical action.
Sinee the step of earbonation produces no ehange in the configuration of calcium silicate crystals, the primary partieles, secondary particles and shaped bodies of amorphous siliea-calcium carbonate composite materials can respeetively ;
be obtained by the earbonation from primary particles, seeondary particles and shaped bodies of ".' 3l7~
calcium silicate crystals without any change in conflgu-rations thereof.
The composite material of amorphous silica and calcium carbonate in the form of a primary particle comprises an amorphous silica particle and an extremely fine particle of calcium carbonate attached to the amorphous silica particle, the amorphous silica particle having a crystalline appearance, at least two surfaces in symmetric relation, a length of about 1 to about ~00~ and a thickness of 10- about ,0 A to about 1~ , the length being at least about 10 times the thickness. The composite meterial of amorphous silica and calcium carbonate in the form of a substantially globular secondary particle has a diameter of about 10 to about 150 ~ and is composed of numerous amorphous silica-cal.cium carbonate composite primary particles and voids intersper~ed therebetween, each of the constituent composite particles comprising an : amorphous silica particle in the` form of a primary `~ particle ~hd an extremely fine particle of calcium carbonate 20 attached to the amorphous silica particle, the amorphous silica particle having a crystalline appearance~ at least two surfaces in symmetric relation, a length of about 1 to about 500 ~ and a thickness of about 50 A to about 1~ ~ the length being at least about 10 times the thickness~
The composite materials of amorphous silica and calcium carbonate in the form of shaped body lnclude a ehaped .. ;'' ~3 ' 3~
body composed of numerous composite primary particles and one composed of numerous composite secondary particles.
The former shaped body comprises amorphous silica-calcium carbonate composite primary particles randomly three-dimensionally interlocked with one another integrally lnto the body;with void~ lnter~persed therebetween9 - each of t~e primary particles comprising an amorphous ~ilica p~rtilce in the form of a primary particle and ah extremely fine particle of calcium carbonate attached to the amorphous silica particle, the amorphous silica particle having a crystalline appearance, at least two surfaces in symmetric relation~ a length of about 1 to about 500~ and a thickness of about 50 A to about 1~ , the length being at least about 10 times the thickness.
The latter shaped body comprises numerous amorphous silica-calcium carbGnate composite secondary particles being compressed to at least one direction and inter-rocked with one another and ~oids intersper~ed therebetween~
~ each of the composite 6econdary particles - having originally a substantially glob~lar form of a diameter of about 10 to about 150 ~ and comprising an amorphous ~ilica particle in the form of a primary particle and extremely fine part~cle of ca~cium carbonate attached to the amorphous silica particle, the amorphous silica particle having a crystalline appearance, at least two ~;
surfaces in symmetric relation, a length of about 1 to about 500~ and a thickne~s of about 50 ~ to about 1 ~ ' ~3~7~:
the length being at least about 10 times the thickness.
The compos~te material6 composed of the amorphous silica and extremely fine particles of calcium carbonate chemically or physically attached thereto find versatile applications for which Opsils are useful, because of their characteristics attributable to the Opsil contained therein.
Further since the extremely fine particles of calcium carbonate are contained in the composite particles as attached to the Opsil, the compoSite particles are useful also as a filler. Moreover, the composite materials are useful as intermediate products for producing O~sil in various forms, According to this invention, the composite material of amorphous 8ilica and calcium carbonate resulting from carbonation is thereafter treated with an acid to remove the calcium carbonate from the amorphous silica The acids to be used for this purpose include those ha~ing no reactivity with silica but being capable o~ decompos1ng "~ calcium carbonate to produce carbon dioxide and a water-soluble salt. Examples thereof are hydrochloric acid, nitric acid~ acetic acid, perchloric acid or the like.
The acid treatment i6 carried out usually by immerSing the composite materlal in a solution of the acid, or by introducing an acid gas such as hydrochloric acid gas into water in which the composite particles are immersed ....
( 3~7 or dispersed~ The acid is used :Ln a stoichiometric amount or in excess. This treatment is preferably conducted at room temperatures, though elevated temperatures up to boiling points of the acid used are applicable. The reaction pressure is usually atmospheric~pressure, but incr~ased pressure is also applicable. Through the treatment, the calcium carbonate attached to the amorphous silica is decomposed with the acid to a water-soluble calcium salt, which is thereafter completely removed for example by washing with water, followed by drying, whereby primary particles, secondary particles or shaped body made up of amorphous silica are prepared. In the case of preparing shaped body, it can be treated with warm or hot water before drying, whereby linear shrinkage thereof due to drying can be lowered. The treatment can preferably be conducted by immersing the shaped body in hot water of higher than 60 C for 0.5 to 10 hours. When hot water of higher than 100 C is used, autoclave or the like closed vessel may be `~ employed. The step of removing calcium carbonate produces no change in the configuration of the primary particles of amorphous silica. Accordingly, composite globular secondary particles of the composite material give globular secondary particles of amorphous silica~ i.e. Opsil-II, retaining the original structure of the former, while shaped bodies of the composite material give shaped bodies . .
c ~~
~23~
of amorphous sil~ca, i.e. Opsil-IS and Opsll-IIS, similarly retaining the original structure thereof. Further, the composite materials of amorphous silica and calcium carbonate ln the form of primary particles and globular secondary particles have shapability similar to Opsil-I and Opsil-II.
More specifically~ the composite particles ~re easily dispersible in water and give shaped body having mechanical - strength~ when the~slurry is shaped and dried. Therefore, Opsil-IS and Opsil-IIS can be prepared by shaping and drying the aqueous slurry of the composite particles to prepare shaped body thereof and subjecting the shaped body to the acid treatment as above, followed by washing with ~ater and drying.
For a better understanding of this invention, Reference Examples and Examples of the invention are given belbw.
~he ~ccompanylng drawings show x-ray diffraction - patterns, electron micrographs~ scanning electron m~crographs ~ and a por~ 5ize distrlbution diagram of the substances prepared in Examples and Reference Examples.
Figs. l(A) to IC) show x-ray diffraction patterns of a starting material, i.e. xonotlite crystals, composite particles of amorphous silica and calcium carbonate prepared from the crystals by carbonation, and Opsil-I of this invention respecti~ely;
.
23~
! - Figs. 2 and 3 are electron micrographs at a magnification of 20,000X, in which Figs. (A) show calcium silicate crystals used as starting materials, Figs. (s) show composite materials of amoxphous silica and calcium carbonate prepared by carbonating the crystals, and Figs. (C) show the particles of Opsils-I obtained by treating the materials;
Figs. 4 are electron micrographs at a magnification of 5,000X in which Fig. (A) shows a-dicalcium silicate hydrate crystals used as a starting material, and Fig. (B) shows Opsil-I prepared from the crystals; ~
Figs. 5 and 6 are scanning electron micrographs, ~, in which Figs. (A) show globular secondary particles composed of calcium silicate crystals used as starting materials, - Figs. (B) show globular secondary particles composed of composite materials of amorphous silica and calcium carbonate prepared by carbonating the orystals, and Figs. (C) show Opsil-II of this invention;
Figs. 7 are scanning electron micrographs of - fractured surfaces of shapea bodies at a magnification of - 20 ~ 600X, in which^(A) shows a shaped body of globular secondary particles of calcium silicate crystals used as starting materials, (B) shows a shaped body of globular secondary part-icles of composite material of amorphous silica and calcium carbonate and (C) shows a shaped body of Opsil-IIS.
Fig. 8 is a scanning electron microgra~h at a magnification of 1,000X showing Opsil-IS of this invention;
and ... . .. .. ., . ......... . . . . ~
.
~3~l'7%
Fig. 9 is a pore size distribution diagram in which the pore size (A) is plotted as abscissa and the pore volume (cc/~.g x 103) as ordinate.
The x-ray diffraction patterns in Figs. 1 are pre-pared using an x-ray diffractometer, irradiating the sample with x-rays of wavelength of 1.5405 ~ emitted with a Cu target and measuring the diffraction angle and intensity. Three diffraction lines having the highest intensities are determined for the identification of the camples.
:~ .
:
' .
~3~'J72 Reference Example 1 Quick lime is used as a lime material and minus 350 mesh siliceous sand powder (Tyler scale) as a siliceous material.
The materials are dispersed in water in a CaO to SiO2 mole ratio of 0.98:1 to prepare a slurry having a water to solids ratio by weight of 12:1. The slurry is placed in an autoclave and sub~ected to hydrothermal reaction at a temperature of 191C and a saturated vapor pressure of 12 kg/cm2 with heating and stir-ring for 8 hours to obtain a slurry of xonotlite crystals.
The x-ray diffraction pattern of the xonotlite crystals in Fig. 1 ~A) shows diffraction peaks (23) at 12.7, 27.6 and 29.0 peculiar to xonotlite crystals. The analysis by ignition of the crystals reveals the following composition.
SiO2 48.88%
15 ~ 45.60 Al O3 0.26 Fe2O3 ~ 54 Ig. loss 4.51 Total 99.80 The slurry of xonotlite crystals is shown in the scanning electron micrograph of Fig. 5(A), which reveals that numerous lath-like xonotlite crystals are formed as randomly three-dimensionally interlocked with one another into many, substantially globular, secondary particles of xono-tlite ranging from about 10 to about 60~ in diameter and suspended ~L~2~
in water. The secondary particle has a porosity of about 95.6%.
Sub~equently, the slurry containing the globular secondary particle~ of xonotlite is dried at 150 C and then divided into prlmary particles Fig. 2(A) shows an electron micrograph of the primary particles. The micrograph indicates that the primary particles - have at least two surfaces in ~ymmëtric relation, a length of about 1 to about 20~ , a thickness of about 0.02 to about 0.1 and a width of about 0~02 to about 1.0~ , the length being at least about 10 times the thickness. The primary particle~ have a ~pecific surface area of about 50 m2/g.
The ~lurry of xonotlite crystals prepared above is placed in a mold, 40 mm x 120 mm x 150 mm, and dewatered and fihaped by a pres~ and dried to obtain a shaped body. Fig. 7(A) i8 a scanning electron micrograph showing a fractured surface of the shaped body of xonotlite. The micrograph indicate~
that globular secondary particles o~ xonotlite are compre~sed and formed as interlocked with one another; The shaped body has a bulk density of 0.2 gfcm3, bending ~trength of about
4 kg/cm2 and a porosity of about 92.7%.
Reference Example 2 Minu6 325 mesh slaked lime (Tyler scale) i8 used a6 ~ lime material and minus 325 me~h siliceous sand powder (Tyler scale) as a ~illceous material. The materials are disper6ed ln water in a CaO to SiO2 mole ratio of 0.80:1 to prepare a 61urry having a water to solids ratio of ~3~2 12:1 by weight. The slurry ls placed in an autoclave and sub-jects to hydrothermal reaction at a temperature of 191 C and a saturated vapor pressure of 12 kg/cm2 with heating and stir-ring for 5 hours to obtain a slurry of tobermorite crystals.
The x-ray diffraction of the tobermorite crystals shows diffraction peaks (2~) at 7.8, 29.0 and 30.0 peculiar to tobermorite crystals. The analysis by ignition of the cry-stals reveals the following composition.
SiO2 48.38%
CaO 38.55 A12 3 0.31 ; 2 3 Ig. Loss 11.36 Total 99.05 The slurry of tobermorite crystals is shown in the scanning electron micrograph of Fig. 6(A), which reveals that numerous plate-like tobermorite crystals are formed as randomly three-dimensionally interlocked with one another into many, sub-stantially globular, secondary particles of tobermorite ranging from about 10 to about 60~ in diameter and suspended in water.
The secondary particle has a porosity of about 94.0%.
Subsequently, the slurry containing the globular sec-ondary particles of tobermorite is dried and then divided into primary particles.
Fig. 3(A) shows an electron micrograph of the primary , - f. C_ '~23~
particle~, The micrograph indicates that the primary particles have at lea~t two surfaces in symmetric relation, a length of about 1 t~ about 20~, a thickness of about 0.02 to about 0.1~ and a wi~th of about 0.2 to about 5.0~ , the length being at lea~t about 10 times the thickness. The primary particles have a specific surace area of about 61 m2/g.
. The slurry of tobermorite crystals prepared above is placed in a mold, 40 mm x 120 mm x 150 mm, and dewatered and shaped by a press and dried to obtain a shaped body~ The scanning electron micrograph showing a fractured surface of ~he shaped body of tobermorite resemble~ that of Fig. 7(A) and indicates that globular secondary particles of tobermorite are compressed ~nd.. formed as interlocked with one another.
The shaped body has a bulk density of 0.3 g/cm3, bending strength of about 12 kg/cm2 and a porosity of about 88.~/o.
Reference Example 3 ~ick li~e i8 used as a lime material and commercial white carbon having a particle size of less than 100 ~ and containing about 88 wt% of SiO2 (Ig. loss ~bout 12y~%) as a siliceou6 material. The materials are d~spersed in water in a CaO to SiO2 mole ratio of 1.35:1 to prepare a slu~ry having a water to solids ratio of 12:1 by weight. The slurry is placed in an autoclave and subjected to hydrothermal reaction at.a temperature of 191 C and a saturated vapor pressure of 14 kg/cm2 with heating and 6tirring for 3 hours to obtain a ~lurry of CSHn crystal~.
~3~
The x-ray diffraction of the CaSiH crystals shows diffraction peaks (23) at 29.4, 31.8 and 49.8 peculiar to CSHn crystals. The analysis by i~nition of the crystals reveals the following composition.
SiO238.19%
CaO47.78 Fe230.41 Ig. loss 13.04 Total 99.05 The slurry of CSH crystals is observed under a scanning electron microscope with a similar result to those shown in Figs. 5tA) and 6(A). It is found that numerous foil-like CSH crystals are formed as randomly three-dimensionally interlocked with one another into many, substantially globular, secondary particles of CSH ranging from about 10 to about 60~
in diameter and suspended in water. The secondary particle has a porosity of about 94.1%.
Subsequently, the slurry containing the globular secondary particles is dried and then divided into primary particles.
The electron micrograph of the primary particles indicates that the CSH crystals are in the form of primary particles having a length of about 1 to about 5~, a thickness of about 0.01 to about 0.02~ and a width of about 0.01 to about
Reference Example 2 Minu6 325 mesh slaked lime (Tyler scale) i8 used a6 ~ lime material and minus 325 me~h siliceous sand powder (Tyler scale) as a ~illceous material. The materials are disper6ed ln water in a CaO to SiO2 mole ratio of 0.80:1 to prepare a 61urry having a water to solids ratio of ~3~2 12:1 by weight. The slurry ls placed in an autoclave and sub-jects to hydrothermal reaction at a temperature of 191 C and a saturated vapor pressure of 12 kg/cm2 with heating and stir-ring for 5 hours to obtain a slurry of tobermorite crystals.
The x-ray diffraction of the tobermorite crystals shows diffraction peaks (2~) at 7.8, 29.0 and 30.0 peculiar to tobermorite crystals. The analysis by ignition of the cry-stals reveals the following composition.
SiO2 48.38%
CaO 38.55 A12 3 0.31 ; 2 3 Ig. Loss 11.36 Total 99.05 The slurry of tobermorite crystals is shown in the scanning electron micrograph of Fig. 6(A), which reveals that numerous plate-like tobermorite crystals are formed as randomly three-dimensionally interlocked with one another into many, sub-stantially globular, secondary particles of tobermorite ranging from about 10 to about 60~ in diameter and suspended in water.
The secondary particle has a porosity of about 94.0%.
Subsequently, the slurry containing the globular sec-ondary particles of tobermorite is dried and then divided into primary particles.
Fig. 3(A) shows an electron micrograph of the primary , - f. C_ '~23~
particle~, The micrograph indicates that the primary particles have at lea~t two surfaces in symmetric relation, a length of about 1 t~ about 20~, a thickness of about 0.02 to about 0.1~ and a wi~th of about 0.2 to about 5.0~ , the length being at lea~t about 10 times the thickness. The primary particles have a specific surace area of about 61 m2/g.
. The slurry of tobermorite crystals prepared above is placed in a mold, 40 mm x 120 mm x 150 mm, and dewatered and shaped by a press and dried to obtain a shaped body~ The scanning electron micrograph showing a fractured surface of ~he shaped body of tobermorite resemble~ that of Fig. 7(A) and indicates that globular secondary particles of tobermorite are compressed ~nd.. formed as interlocked with one another.
The shaped body has a bulk density of 0.3 g/cm3, bending strength of about 12 kg/cm2 and a porosity of about 88.~/o.
Reference Example 3 ~ick li~e i8 used as a lime material and commercial white carbon having a particle size of less than 100 ~ and containing about 88 wt% of SiO2 (Ig. loss ~bout 12y~%) as a siliceou6 material. The materials are d~spersed in water in a CaO to SiO2 mole ratio of 1.35:1 to prepare a slu~ry having a water to solids ratio of 12:1 by weight. The slurry is placed in an autoclave and subjected to hydrothermal reaction at.a temperature of 191 C and a saturated vapor pressure of 14 kg/cm2 with heating and 6tirring for 3 hours to obtain a ~lurry of CSHn crystal~.
~3~
The x-ray diffraction of the CaSiH crystals shows diffraction peaks (23) at 29.4, 31.8 and 49.8 peculiar to CSHn crystals. The analysis by i~nition of the crystals reveals the following composition.
SiO238.19%
CaO47.78 Fe230.41 Ig. loss 13.04 Total 99.05 The slurry of CSH crystals is observed under a scanning electron microscope with a similar result to those shown in Figs. 5tA) and 6(A). It is found that numerous foil-like CSH crystals are formed as randomly three-dimensionally interlocked with one another into many, substantially globular, secondary particles of CSH ranging from about 10 to about 60~
in diameter and suspended in water. The secondary particle has a porosity of about 94.1%.
Subsequently, the slurry containing the globular secondary particles is dried and then divided into primary particles.
The electron micrograph of the primary particles indicates that the CSH crystals are in the form of primary particles having a length of about 1 to about 5~, a thickness of about 0.01 to about 0.02~ and a width of about 0.01 to about
5~, the length being at least about 50 times the thickness. The primary particles have a specific surface area of about 150 m2/g.
'''`'!
The slurry of CSHn cry~tals prepared above is placed ln a mold, 40 mm x 120 mm x 150 mm , and dewatered and shaped by a press and dried to obtain a shaped body. The scanning electron micrograph showing a fractured surface of the shaped body of CSHn resembles that of Fig. 7(~) and indicates that globular secondary particles of C~Hn are compressed and formed as interlocked with one another. The shaped body has a bulk density of 0.3 g/c ~ , bending strength of about 8 kg/cm2 and a porosity of about 86.4%.
Reference Example 4 Quick lime is used as a lime material and commercial white carbon the same as in Reference Example 3 as a siliceous material. The materials are dispersed in water in a CaO to SiO2 mole rat~o of 0.57:1 to prepare a slurry having a water to 1~ solids ratio of 12:1 by weight. The slurry is placed in an autoclave and subjected to hydrothermal reaction at a temperature of 200 C and a saturated vapor pressure of 15 kg/cm2 with heating and stirring fGr 8 hours to obtain a slurry of gyrolite crystals.
The x-ray diffraction of the gyrolite crystals shows d~ffraction peaks at 4.0, 28.2 and 28.9 peculiar to gyrolite crystals. The analysis by ignition of the crystals reveals the follo~ing composition.
sio2 56.88%
CaO 30.75 Fe23 0.29 Ig. Loss 11.39 Total 99.70 The slurry of gyrolite crystals is observed under a scanning electron microscope with a similar result to those shown in Figs. 5(A) and 6(A). It is found that numerous plate-like gyrolite crystals are formed as randomly three-dimensionally interlocked with one another into many, subs-tantially globular, secondary particles of gyrolite ranging from about 10 to about 60~ in diameter and suspended in water. The secondary particle has a porosity of about 94.0~.
Subsequently, the slurry containing the globular secondary particles is dried and then divided into primary part-icles The electron micrograph of the primary particles in-dicates that the gyrolite crystals are in the form of primary particles having a length of about 1 to about 20~, a thickness 15 of about 0.02 to about 0.1~ and a width of about 0.2 to about 5~, the length being at least abou-t 10 times the thickness. The primary particles have a specific surface area of about 60 m /g.
The slurry of gyrolite crystals prepared above is placed in a mold, 40 mm x 120 mm x 150 mm, and dewatered and shaped by a press and dried to obtain a shaped body. The scan-ning electron micrograph showing a fractured surface of ,; , , .. ~
z the shaped body resembles that of Fig. 7(A) and indicates that secondary particles of gyrolite are compres~ed and formed as interlocked with one another,. The shaped body has a bulk density of 0.3 g/cm3, bending strength of about 8 kg/cm2 and a porosity of about 88~0%.
Reference Example 5 Quick lime is used as a lime material and minus 350 mesh siliceous ~and powder (Tyler scale) as a siliceous material. The materials are dispersed in Y~ater in a CaO to 10- SiO2 mole ratio of 2.0:1 to prepare a slurry having a water to ~-solids ratlo fo 4:1 by weight. The slurry is ~laced in an autoclave and subjected to hydrothermal reaction at a temperature of 191 C and a saturated vapor pressure of 12 kg~cm with heating for 5 hours to obtain a slurry of~ -dicalcum ~ilicate hydrate crystals.
The x-ray diffraction of the crystals ~hows diffraction peaks (20) at 16.6, 27.3 and 37.2 peculiar ~o~ -dicalcium ~ilicate h~drate crystals. The analysis by ignition of the cry~tals reveals.the following composition.
SiO2 30.81%
CaO 57.02 Fe203 0.50 Ig~ loss - 10.05 Total 99.05 ~2 .. , . , -~3~l72 The slurry of ~-dicalcium silicate hydrate crystal6 is dried to obtain a fine white powder. Fig. 4(A) shows an electron micrograph of the po~der at a magnification of 5~000X. The micrograph tndicates that the a-dicalcium silicate hydrate crystals are in the form of plate-like primary particles having a length o about 1 to about 300~ , a thickness of about 0~1 to about 1 ~ and a width of 1 to 30~ , the length being at least about 10 tirnes the thickness~
The crystals have a specific surface area of about 6 m2/g.
-Example 1 The primary particles of lath-like xonotlite crystals obtained in Reference Example 1 are used as a starting material. The particles are placed in a pressure-resistant container of the closed type along with water 5 times the weight of the particles. Carbon dioxide gas is forced into the container at room temperature, and the particles are carbonated for about 30 minutes while maintaining the internal pressure at 3 kg/cm2, whereby 10- composite particles of amorphous silica and calcium carbonate are obtained.
The analysis by ignition of the cornposite particles reveals the following composition.
~i2 36.04%
CaO 33.54 A123 0.18 Fe203 0.38 -~
Ig. loss 28.87 ~ Total 99.11 The x-ray diffraction of the particles shows the result given in Fig. l(B), which indicates that all the peaks peculiar to calcium silicate crystals seen in Fig. l(A) have disappeared and that only diffraction peaks (2~) indicative of calcium carbonate crystals have appeared at 23.0, 29.4 and 36ØThis evidences that the calcium ~ 7 ~
silicate has been converted to amorphous silica and calcium carbonate due to carbonation.
The co~posite particles are further observed under an electron microscope with the result given in Fig. 2(B). The microscopic observation reveals that the composlte particles comprise amorphous silica particles and extremely fine particles, up to about 2 ~ in size, of calcium carbonate attached to the amorphous silica -particles and that the particles of amorphous silica have at least two surfaces in symmetric relation, a length of about 1 to about 20~ , a thicknes, of about 0.02 to about and a width of about 0.02 to about 1.0~ , the length being at least about 10 times the thickness. The configuration of the amorphous silica particles is exactly the same as that of lath-like xonotlite crystals (Fig. 2(A)), Thi~
indicates that the amorphous silica particles retain the original lath-like configuration of xonotlite.
~he composite particles are dispersed in water "~ to a concentration of 5 wt. %~ and the dispersion is allowed to stand after stirring for 20 minute~ so as to separate the particles into the constituent silica and calcium carbonate by settling utilizlng the difference in specific gravity. However, the two components are found to be entirely lnseparable and proved to be firmly joined together chemically or physically.
3~
Subsequently, the composite particles of amorphous silica and calcium carbonate are immersed in a 6N HCl solution for one minute. With the evolution of carbon dioxide gas, the calcium carbonate in the primary particles is converted to carbon dioxide gas and calcium chloride. The acid-treated particles are then thoroughly washed with water to completely dissolve out the resulting calcium chloride. The particles are clried to obtain Opsil-I of this invention.
The Opsil-I thus prepared is subjected to ignition dehydration and thereafter to analy~is. The result is given below which indicates that the product i5 composed of silica of high purity, SiO2 99. 1%
CaO < 0.01 (Ig. loss - 5.0 ) The x-ray diffraction pattern of Opsil-I is ~ given in ~lg. l(C) which displays no peaks indicatlng the lath-like xonotlite crystals, the starting material, nor the peaks indicating the calcium carbonate contained in the composite particles resulting from the carbonation. ;
It ~s therefore confirmed that the Opsil_I is amorphous silica, The Opsil-I is shown in the electron micrograph ~31~2 of Fig. 2(C) which, exactly like Figs. 2(A) and 2(B)~
reve~ls that the Opsil-I has a crystalline appearance and at least two surfaces in symmetric relation. The particles of Opsil-I are about 1 to about 20 f~ in length~ about 0.02 to about 0.1 ~ in thickness and about 0.02 to about 1.0 ~ in width, the length being at least about 10 times the thickness and are ~n the form of primary particles. The appearance resembling lath-like crystals~remains-free of any change even when the particles are treated with acid.
10- The properties of the Opsil-I obtained above are as follows.
Bulk density 0.05 g/cm3 Specific surface area 335 m2/g Oil adsorption 800 cc/100 g pH 6.5 The reference numeral (1) in Fig. 9 shows the pore size distribution of the Opsil-I with the peak at 27 A.
Example 2 `~ The primary particles of plate-like tobermorite crystals obtained in Reference Example 2 are used as a starting material. The particels are placed ln a pressure-resistant container of the closed type along with water 5 times the weight of the particlesO Carbon dioxide gas is forced into the container at room temperature, and the particles are carbonated for about ~0 minutes while maintaining 3~
the internal pressure at 3 kg/cm2, whereby composite particles of amorphous silica and calcium carbonate are obtained The analysis by iginition of the composite particles reveals the iollowing compositic)n.
SiO2 39 77%
CaO 31.43 A123 0.24 Fe23 0.40 Ig. loss 27.42 - Total 99.26 The x-ray diffraction of the particles shows the same result as given in Fig. l(B), which indicates that all the peaks peculiar to tobermorite crystals, the starting material, have disappeared and that only diffraction peaks 15- (2~3) indicative of calcium carbonate crystals have appeared at 23.0-, 24~8, 27.0, 29.4, 32.8 and 36Ø This evidences that the calcium silicate has been converted to amorphous silica and calcium carbonate due to carbonation.
~he composite particles are further observed under an electron microscope with the result given in Fig. 3(B). The microscopic ob~ervation reveals that -the composite particles comprise amorphous silica particles and extremely fine particles, up to about 2 ~u in size~ of calcium carbonate attached to the amorphous silica particles and that the ~.......................... ..
.... ....
1~2~31 7~
particles of amorphous silica have at least two surfaces in symmetric relation, a length of about l to about 20~ , a thickness of about 0.02 to about 0.1 ~ and a ~idth of about 0.2 to about 5.0~ , the length being at least about lO
times the thickness. The configuration of the amorphous silica particles is exactly the same as that of plate-like tobermorite crystals (Fig. 3(A)) This indicates that the amorphous silica particles retain the original plate-like configuration of tobermoriteO
The composite particles are dispersed in water to a concentration of 5 wt. %, and the dispersion is allowed to stand after stirring for 20 minutes so as to separate the particles into the constituent silica and calcium carbonate by settling utilizing the difference in speci~ic gravity. However, the two components are found to be entirely inseparable and proved to be firmly joined together chemically or physically.
Subsequently, the composite particles of amorphous ~ silica and c~lcium carbonate are immersed in a 6N HCl ~olution for one minute. ~Jith the evolution of carbon dioxide gas, the calcium carbonate in the primary particles is converted to carbon dioxide gas and calcium chloride.
The acid_treated particles are then thoroughly washed with ; water to completely dissolve out the re;ulting calcium chloride. The particles are dried to obtain Opsil-I of .
, s, ~231~2 this invention.
The Opsil-I thus prepared is subjected to ignition dehydration and thereafter to analysis. The result is given below which indicates that the product is composed of silica of high purity.
SiO2 99.3%
A123 0.23 CaO ~ 0.01 (Ig . loss4.7 ) The x-ray diffraction pattern of Opsil-I is the same as in Fig. l(C) whieh displays no peaks indicating the plate-like tobermorite erystals, the starting material, nor the peaks indieating the caleium carbonate contained in the eomposite partieles resulting from the earbonation. The Opsil-I is a-15 morphous siliea. ;
The Opsil-I is shown in the electron microgragh of Fig. 3(C) which, exactly like Figs. 3(A) and 3(B), reveals that the Opsil-I has a erystalline appearance and at least two ~-surfaees in symmetrie relation. The partieles of Opsil-I are about 1 to 20~ in length, about 0.02 to about 0.1~ in thickness and about 0.2 to about 5.0~ in width, the length being at least about 10 times the thickness and are in the form of primary particles. The crystalline appearance remains free of ; any change even when the particles are treated with acid.
`
~. `
.~ ., .
- ~
,~ , . . -, : . :
~2~7;~:
The properties of the Op~ I obtained above are as follows.
Bulk density 0.04 g/cm3 Specific surface area 277 m2/g Oil adsorption 750 cc/100 g pH 6.7 The reference nurneral (2) in Fig. 9 shows the pore 5ize distribution of the Opsil-I ~ith the peak at 23 A.
Example 3 The primary particles of calcium silicate (CSXn) in the form of ~oil-like crystals obtained in Reference Example 3 are used as a starting material. The particles are placed in a pressure-resistant container of the closed type along with wat,er 5 times the weight of the particles.
Carbon dioxide gas ls forced into the container at room temperature, and the particles are carbonated for about 30 minutes while maintaining the internal pressure at 3 kg/cm2~ whereby composite particles of amorphous silica . and calci~m carbonate are obtained~
Thé analysis. by ignition of the composite particles reveals the following composition.
SiO2 ~9.98%
~e23 0.27 Ig. loss 31.28 Total 99.51 ~ :
:, , ' .
.
.
3~
The x-ray diffraction of the particles ~hows the same result as given in Fig~ l(B)~ hich indicateS that all the peaks peculiar to CSHn crystals, the starting rnaterial, have disappe~red and that only diffraction peaks (2~) indicative of calcium carbonate crystals have appeared at 23.0~ 24.8, 27.0, 29.4, 32.8 and 36.o. This evidences that the calcium silicate has been converted to amorphous silica and calcium~carbonate due to carbonation.
The composite particles are further observed under 10- an electron microscope with the result that the composite particles comprise amorphous silica particles and extremely fine particles, up to about 2f~ in size, of calcium ~-carbonate attached to the amorphous silica particles and that the particles of amorphous ~ilica have at least two surfaces in symmetric relation, a length of about 1 to about 5~L, a thickness of about 0.01 to about 0.02~ and a width of about 0.01 to about 5.0~ , the length ~eing at least about 50 times the thicknes~. The configuration of the amorphous silica particles is exactly the same as that of foil-like CSHn crystals. This indicates that the amorphous silica particles retain the original foil-like configuration of CSHn.
The composite particle~ are dispersed in water to a concentration of 5 wt. %, and the dispersion is allowed to stand after stirring for 20 minutes ,o a:, to separate - 52 _ - .
c ~23~ ~
the particles into the constituent silica and calcium carbonate by settlin~ utilizing the di~ference in specific grayity.
However, the two components are found to be entirely inseparable and proved to be fLrmly joined together chemi-cally or physically.
Subsequently, the compo~ite particles of amorphous silica and calcium carbonate are immersed in a 6N HCl solution-for one minute. With the evolution of carbon dioxide gas, the calcium carbonate in the primary particles 0 i5 converted to carbon dioxide gas and calcium chloride.
The acid-treated particles are then throughly ~iashed with water to completely dissolve out the resulting calcium chloride. The particles are dried to obtain Opsil_I of this invention.
The Opsil-I thus prepared is subjected to ignition dehydration and thereafter to analysis. The result is gi~en below which indicates that the product is composed of silica of high purity.
2 99 D 7%
A12~3 0.03 CaO < 0.01 (Ig. loss 5.1 ) The x-ray diffraction pattern of Opsil~ the same as in Fig. 1 (C) which display~ no peal{s indicating the foil-like CSHn crystal~ -the tarting material, nor the peak~ indicating the ~alcium carbonate contained in the composite particles resulting from the carbonation.
The Opsil-I is amorphous silica.
Observation of electron micrograph reveals that the Opsil-I has a crystalline appearance and at least two surfaces in symmetric relation. The particles of Opsil-I
are about 1 to ~bout 5 ~in length, about 0.01 to about 0.0 ~ in thickness and about 0.01 to about 5.0 ~'in width, the length being at least about 50 times the thickness and are in the ~;
form of primary particles. The crystalline appearance remains free of any change even when the particles are treated with acid.
The properties of the Opsil-I obtained above are as follows.
Bulk density 0.07 g/crn3 Specific surface area 461 m /g Oil adsorption 470 cc/100 g pH 6.5 ~he reference numeral (3) in Fig. 9 sho~Js the ; pore size di6tribution of the Opsil_I ~th the peak at O - o about 30 A and about 180 A.
Example 4 The primary particles of plate-like gyrolite ;~
crystals obtained in ~eference Example 4 are used as a starting materialr The particles are placed in a pressure-resistant container of the clo_ed type alon6 with water ~2~ 2 5 times the weight of the particles. Carbon dioxide gas is forced into the container at room temperature, and the particles are carbonated for about 30 minutes while maintain-ing the internal pressure at 3 kg/cm2, whereby composite particles of amorphous silica and calcium carbonate are obtained.
The analysis by ignition of the composite particles reveals the following composition.
SiO2 48~2~/o - CaO 26.07 Fe23 0.25 Ig. loss 24.33 - Total 99.20 The x-ray diffraction of the particles shows the same result as given in Fig, l~B), which indicates that all the peaks peculiar to calcium silicate crystals~ the starting material, have disappeared and that only diffraction peaks (2e) indicati~e of calcium carbonate crystals have ; 20 appeared at 23.0, 24.8, 27~0, 29.4, 32.8 and 36Ø
This evidences that the calcium silicate has been converted to amorphous silica and calcium carbonate due to carbonation. ~;
The composite particles are further observed under an e~ectron microscope with the result that the composite particles comprise amorphous ~iilica particles ~.
and extremely fine particles, up to about 2 ~ in size, of calcium carbonate attached to the amorphous silica particles and that the particles of amorphous silica have at least two surfaces in symmetric relation, a length of about 1 to about 20~ ~ a thickness of about 0.02 to about 0.1 ~ and a width of about 0.2 to about 5/~ the length being at least about 10 times the thickne-s. The configuration of the amorphous silica particles is exactly the same as that of plate-like gyrolite crystals. This indicates that the amorphous silica particles retaïn the original plate-like configuration of gyrolite.
The composite particles are dispersed in v~ater to a concentration of 5 wt. %, and the dispersion is allowed to stand after stirring for 20 minutes sa as to separate the particles into the constituent silica and calcium carbonate by settling utilizing the difference in specific gravity. However~ the two components are found to be entirely inseparable and proved to be firmly joined ~ together chemically or physically.
Subsequently9 the composite particles of amorphous silica and calcium carbonate are immersed in a 6N HCl solution for one minute. With the evolution of carbon dioxide gas, the calcium carbonate in the primary particles is converted to carbon dio.Yide ~as and calcium chloride.
Th~ acid_treated particles are then thoroughly washed ~ith
'''`'!
The slurry of CSHn cry~tals prepared above is placed ln a mold, 40 mm x 120 mm x 150 mm , and dewatered and shaped by a press and dried to obtain a shaped body. The scanning electron micrograph showing a fractured surface of the shaped body of CSHn resembles that of Fig. 7(~) and indicates that globular secondary particles of C~Hn are compressed and formed as interlocked with one another. The shaped body has a bulk density of 0.3 g/c ~ , bending strength of about 8 kg/cm2 and a porosity of about 86.4%.
Reference Example 4 Quick lime is used as a lime material and commercial white carbon the same as in Reference Example 3 as a siliceous material. The materials are dispersed in water in a CaO to SiO2 mole rat~o of 0.57:1 to prepare a slurry having a water to 1~ solids ratio of 12:1 by weight. The slurry is placed in an autoclave and subjected to hydrothermal reaction at a temperature of 200 C and a saturated vapor pressure of 15 kg/cm2 with heating and stirring fGr 8 hours to obtain a slurry of gyrolite crystals.
The x-ray diffraction of the gyrolite crystals shows d~ffraction peaks at 4.0, 28.2 and 28.9 peculiar to gyrolite crystals. The analysis by ignition of the crystals reveals the follo~ing composition.
sio2 56.88%
CaO 30.75 Fe23 0.29 Ig. Loss 11.39 Total 99.70 The slurry of gyrolite crystals is observed under a scanning electron microscope with a similar result to those shown in Figs. 5(A) and 6(A). It is found that numerous plate-like gyrolite crystals are formed as randomly three-dimensionally interlocked with one another into many, subs-tantially globular, secondary particles of gyrolite ranging from about 10 to about 60~ in diameter and suspended in water. The secondary particle has a porosity of about 94.0~.
Subsequently, the slurry containing the globular secondary particles is dried and then divided into primary part-icles The electron micrograph of the primary particles in-dicates that the gyrolite crystals are in the form of primary particles having a length of about 1 to about 20~, a thickness 15 of about 0.02 to about 0.1~ and a width of about 0.2 to about 5~, the length being at least abou-t 10 times the thickness. The primary particles have a specific surface area of about 60 m /g.
The slurry of gyrolite crystals prepared above is placed in a mold, 40 mm x 120 mm x 150 mm, and dewatered and shaped by a press and dried to obtain a shaped body. The scan-ning electron micrograph showing a fractured surface of ,; , , .. ~
z the shaped body resembles that of Fig. 7(A) and indicates that secondary particles of gyrolite are compres~ed and formed as interlocked with one another,. The shaped body has a bulk density of 0.3 g/cm3, bending strength of about 8 kg/cm2 and a porosity of about 88~0%.
Reference Example 5 Quick lime is used as a lime material and minus 350 mesh siliceous ~and powder (Tyler scale) as a siliceous material. The materials are dispersed in Y~ater in a CaO to 10- SiO2 mole ratio of 2.0:1 to prepare a slurry having a water to ~-solids ratlo fo 4:1 by weight. The slurry is ~laced in an autoclave and subjected to hydrothermal reaction at a temperature of 191 C and a saturated vapor pressure of 12 kg~cm with heating for 5 hours to obtain a slurry of~ -dicalcum ~ilicate hydrate crystals.
The x-ray diffraction of the crystals ~hows diffraction peaks (20) at 16.6, 27.3 and 37.2 peculiar ~o~ -dicalcium ~ilicate h~drate crystals. The analysis by ignition of the cry~tals reveals.the following composition.
SiO2 30.81%
CaO 57.02 Fe203 0.50 Ig~ loss - 10.05 Total 99.05 ~2 .. , . , -~3~l72 The slurry of ~-dicalcium silicate hydrate crystal6 is dried to obtain a fine white powder. Fig. 4(A) shows an electron micrograph of the po~der at a magnification of 5~000X. The micrograph tndicates that the a-dicalcium silicate hydrate crystals are in the form of plate-like primary particles having a length o about 1 to about 300~ , a thickness of about 0~1 to about 1 ~ and a width of 1 to 30~ , the length being at least about 10 tirnes the thickness~
The crystals have a specific surface area of about 6 m2/g.
-Example 1 The primary particles of lath-like xonotlite crystals obtained in Reference Example 1 are used as a starting material. The particles are placed in a pressure-resistant container of the closed type along with water 5 times the weight of the particles. Carbon dioxide gas is forced into the container at room temperature, and the particles are carbonated for about 30 minutes while maintaining the internal pressure at 3 kg/cm2, whereby 10- composite particles of amorphous silica and calcium carbonate are obtained.
The analysis by ignition of the cornposite particles reveals the following composition.
~i2 36.04%
CaO 33.54 A123 0.18 Fe203 0.38 -~
Ig. loss 28.87 ~ Total 99.11 The x-ray diffraction of the particles shows the result given in Fig. l(B), which indicates that all the peaks peculiar to calcium silicate crystals seen in Fig. l(A) have disappeared and that only diffraction peaks (2~) indicative of calcium carbonate crystals have appeared at 23.0, 29.4 and 36ØThis evidences that the calcium ~ 7 ~
silicate has been converted to amorphous silica and calcium carbonate due to carbonation.
The co~posite particles are further observed under an electron microscope with the result given in Fig. 2(B). The microscopic observation reveals that the composlte particles comprise amorphous silica particles and extremely fine particles, up to about 2 ~ in size, of calcium carbonate attached to the amorphous silica -particles and that the particles of amorphous silica have at least two surfaces in symmetric relation, a length of about 1 to about 20~ , a thicknes, of about 0.02 to about and a width of about 0.02 to about 1.0~ , the length being at least about 10 times the thickness. The configuration of the amorphous silica particles is exactly the same as that of lath-like xonotlite crystals (Fig. 2(A)), Thi~
indicates that the amorphous silica particles retain the original lath-like configuration of xonotlite.
~he composite particles are dispersed in water "~ to a concentration of 5 wt. %~ and the dispersion is allowed to stand after stirring for 20 minute~ so as to separate the particles into the constituent silica and calcium carbonate by settling utilizlng the difference in specific gravity. However, the two components are found to be entirely lnseparable and proved to be firmly joined together chemically or physically.
3~
Subsequently, the composite particles of amorphous silica and calcium carbonate are immersed in a 6N HCl solution for one minute. With the evolution of carbon dioxide gas, the calcium carbonate in the primary particles is converted to carbon dioxide gas and calcium chloride. The acid-treated particles are then thoroughly washed with water to completely dissolve out the resulting calcium chloride. The particles are clried to obtain Opsil-I of this invention.
The Opsil-I thus prepared is subjected to ignition dehydration and thereafter to analy~is. The result is given below which indicates that the product i5 composed of silica of high purity, SiO2 99. 1%
CaO < 0.01 (Ig. loss - 5.0 ) The x-ray diffraction pattern of Opsil-I is ~ given in ~lg. l(C) which displays no peaks indicatlng the lath-like xonotlite crystals, the starting material, nor the peaks indicating the calcium carbonate contained in the composite particles resulting from the carbonation. ;
It ~s therefore confirmed that the Opsil_I is amorphous silica, The Opsil-I is shown in the electron micrograph ~31~2 of Fig. 2(C) which, exactly like Figs. 2(A) and 2(B)~
reve~ls that the Opsil-I has a crystalline appearance and at least two surfaces in symmetric relation. The particles of Opsil-I are about 1 to about 20 f~ in length~ about 0.02 to about 0.1 ~ in thickness and about 0.02 to about 1.0 ~ in width, the length being at least about 10 times the thickness and are ~n the form of primary particles. The appearance resembling lath-like crystals~remains-free of any change even when the particles are treated with acid.
10- The properties of the Opsil-I obtained above are as follows.
Bulk density 0.05 g/cm3 Specific surface area 335 m2/g Oil adsorption 800 cc/100 g pH 6.5 The reference numeral (1) in Fig. 9 shows the pore size distribution of the Opsil-I with the peak at 27 A.
Example 2 `~ The primary particles of plate-like tobermorite crystals obtained in Reference Example 2 are used as a starting material. The particels are placed ln a pressure-resistant container of the closed type along with water 5 times the weight of the particlesO Carbon dioxide gas is forced into the container at room temperature, and the particles are carbonated for about ~0 minutes while maintaining 3~
the internal pressure at 3 kg/cm2, whereby composite particles of amorphous silica and calcium carbonate are obtained The analysis by iginition of the composite particles reveals the iollowing compositic)n.
SiO2 39 77%
CaO 31.43 A123 0.24 Fe23 0.40 Ig. loss 27.42 - Total 99.26 The x-ray diffraction of the particles shows the same result as given in Fig. l(B), which indicates that all the peaks peculiar to tobermorite crystals, the starting material, have disappeared and that only diffraction peaks 15- (2~3) indicative of calcium carbonate crystals have appeared at 23.0-, 24~8, 27.0, 29.4, 32.8 and 36Ø This evidences that the calcium silicate has been converted to amorphous silica and calcium carbonate due to carbonation.
~he composite particles are further observed under an electron microscope with the result given in Fig. 3(B). The microscopic ob~ervation reveals that -the composite particles comprise amorphous silica particles and extremely fine particles, up to about 2 ~u in size~ of calcium carbonate attached to the amorphous silica particles and that the ~.......................... ..
.... ....
1~2~31 7~
particles of amorphous silica have at least two surfaces in symmetric relation, a length of about l to about 20~ , a thickness of about 0.02 to about 0.1 ~ and a ~idth of about 0.2 to about 5.0~ , the length being at least about lO
times the thickness. The configuration of the amorphous silica particles is exactly the same as that of plate-like tobermorite crystals (Fig. 3(A)) This indicates that the amorphous silica particles retain the original plate-like configuration of tobermoriteO
The composite particles are dispersed in water to a concentration of 5 wt. %, and the dispersion is allowed to stand after stirring for 20 minutes so as to separate the particles into the constituent silica and calcium carbonate by settling utilizing the difference in speci~ic gravity. However, the two components are found to be entirely inseparable and proved to be firmly joined together chemically or physically.
Subsequently, the composite particles of amorphous ~ silica and c~lcium carbonate are immersed in a 6N HCl ~olution for one minute. ~Jith the evolution of carbon dioxide gas, the calcium carbonate in the primary particles is converted to carbon dioxide gas and calcium chloride.
The acid_treated particles are then thoroughly washed with ; water to completely dissolve out the re;ulting calcium chloride. The particles are dried to obtain Opsil-I of .
, s, ~231~2 this invention.
The Opsil-I thus prepared is subjected to ignition dehydration and thereafter to analysis. The result is given below which indicates that the product is composed of silica of high purity.
SiO2 99.3%
A123 0.23 CaO ~ 0.01 (Ig . loss4.7 ) The x-ray diffraction pattern of Opsil-I is the same as in Fig. l(C) whieh displays no peaks indicating the plate-like tobermorite erystals, the starting material, nor the peaks indieating the caleium carbonate contained in the eomposite partieles resulting from the earbonation. The Opsil-I is a-15 morphous siliea. ;
The Opsil-I is shown in the electron microgragh of Fig. 3(C) which, exactly like Figs. 3(A) and 3(B), reveals that the Opsil-I has a erystalline appearance and at least two ~-surfaees in symmetrie relation. The partieles of Opsil-I are about 1 to 20~ in length, about 0.02 to about 0.1~ in thickness and about 0.2 to about 5.0~ in width, the length being at least about 10 times the thickness and are in the form of primary particles. The crystalline appearance remains free of ; any change even when the particles are treated with acid.
`
~. `
.~ ., .
- ~
,~ , . . -, : . :
~2~7;~:
The properties of the Op~ I obtained above are as follows.
Bulk density 0.04 g/cm3 Specific surface area 277 m2/g Oil adsorption 750 cc/100 g pH 6.7 The reference nurneral (2) in Fig. 9 shows the pore 5ize distribution of the Opsil-I ~ith the peak at 23 A.
Example 3 The primary particles of calcium silicate (CSXn) in the form of ~oil-like crystals obtained in Reference Example 3 are used as a starting material. The particles are placed in a pressure-resistant container of the closed type along with wat,er 5 times the weight of the particles.
Carbon dioxide gas ls forced into the container at room temperature, and the particles are carbonated for about 30 minutes while maintaining the internal pressure at 3 kg/cm2~ whereby composite particles of amorphous silica . and calci~m carbonate are obtained~
Thé analysis. by ignition of the composite particles reveals the following composition.
SiO2 ~9.98%
~e23 0.27 Ig. loss 31.28 Total 99.51 ~ :
:, , ' .
.
.
3~
The x-ray diffraction of the particles ~hows the same result as given in Fig~ l(B)~ hich indicateS that all the peaks peculiar to CSHn crystals, the starting rnaterial, have disappe~red and that only diffraction peaks (2~) indicative of calcium carbonate crystals have appeared at 23.0~ 24.8, 27.0, 29.4, 32.8 and 36.o. This evidences that the calcium silicate has been converted to amorphous silica and calcium~carbonate due to carbonation.
The composite particles are further observed under 10- an electron microscope with the result that the composite particles comprise amorphous silica particles and extremely fine particles, up to about 2f~ in size, of calcium ~-carbonate attached to the amorphous silica particles and that the particles of amorphous ~ilica have at least two surfaces in symmetric relation, a length of about 1 to about 5~L, a thickness of about 0.01 to about 0.02~ and a width of about 0.01 to about 5.0~ , the length ~eing at least about 50 times the thicknes~. The configuration of the amorphous silica particles is exactly the same as that of foil-like CSHn crystals. This indicates that the amorphous silica particles retain the original foil-like configuration of CSHn.
The composite particle~ are dispersed in water to a concentration of 5 wt. %, and the dispersion is allowed to stand after stirring for 20 minutes ,o a:, to separate - 52 _ - .
c ~23~ ~
the particles into the constituent silica and calcium carbonate by settlin~ utilizing the di~ference in specific grayity.
However, the two components are found to be entirely inseparable and proved to be fLrmly joined together chemi-cally or physically.
Subsequently, the compo~ite particles of amorphous silica and calcium carbonate are immersed in a 6N HCl solution-for one minute. With the evolution of carbon dioxide gas, the calcium carbonate in the primary particles 0 i5 converted to carbon dioxide gas and calcium chloride.
The acid-treated particles are then throughly ~iashed with water to completely dissolve out the resulting calcium chloride. The particles are dried to obtain Opsil_I of this invention.
The Opsil-I thus prepared is subjected to ignition dehydration and thereafter to analysis. The result is gi~en below which indicates that the product is composed of silica of high purity.
2 99 D 7%
A12~3 0.03 CaO < 0.01 (Ig. loss 5.1 ) The x-ray diffraction pattern of Opsil~ the same as in Fig. 1 (C) which display~ no peal{s indicating the foil-like CSHn crystal~ -the tarting material, nor the peak~ indicating the ~alcium carbonate contained in the composite particles resulting from the carbonation.
The Opsil-I is amorphous silica.
Observation of electron micrograph reveals that the Opsil-I has a crystalline appearance and at least two surfaces in symmetric relation. The particles of Opsil-I
are about 1 to ~bout 5 ~in length, about 0.01 to about 0.0 ~ in thickness and about 0.01 to about 5.0 ~'in width, the length being at least about 50 times the thickness and are in the ~;
form of primary particles. The crystalline appearance remains free of any change even when the particles are treated with acid.
The properties of the Opsil-I obtained above are as follows.
Bulk density 0.07 g/crn3 Specific surface area 461 m /g Oil adsorption 470 cc/100 g pH 6.5 ~he reference numeral (3) in Fig. 9 sho~Js the ; pore size di6tribution of the Opsil_I ~th the peak at O - o about 30 A and about 180 A.
Example 4 The primary particles of plate-like gyrolite ;~
crystals obtained in ~eference Example 4 are used as a starting materialr The particles are placed in a pressure-resistant container of the clo_ed type alon6 with water ~2~ 2 5 times the weight of the particles. Carbon dioxide gas is forced into the container at room temperature, and the particles are carbonated for about 30 minutes while maintain-ing the internal pressure at 3 kg/cm2, whereby composite particles of amorphous silica and calcium carbonate are obtained.
The analysis by ignition of the composite particles reveals the following composition.
SiO2 48~2~/o - CaO 26.07 Fe23 0.25 Ig. loss 24.33 - Total 99.20 The x-ray diffraction of the particles shows the same result as given in Fig, l~B), which indicates that all the peaks peculiar to calcium silicate crystals~ the starting material, have disappeared and that only diffraction peaks (2e) indicati~e of calcium carbonate crystals have ; 20 appeared at 23.0, 24.8, 27~0, 29.4, 32.8 and 36Ø
This evidences that the calcium silicate has been converted to amorphous silica and calcium carbonate due to carbonation. ~;
The composite particles are further observed under an e~ectron microscope with the result that the composite particles comprise amorphous ~iilica particles ~.
and extremely fine particles, up to about 2 ~ in size, of calcium carbonate attached to the amorphous silica particles and that the particles of amorphous silica have at least two surfaces in symmetric relation, a length of about 1 to about 20~ ~ a thickness of about 0.02 to about 0.1 ~ and a width of about 0.2 to about 5/~ the length being at least about 10 times the thickne-s. The configuration of the amorphous silica particles is exactly the same as that of plate-like gyrolite crystals. This indicates that the amorphous silica particles retaïn the original plate-like configuration of gyrolite.
The composite particles are dispersed in v~ater to a concentration of 5 wt. %, and the dispersion is allowed to stand after stirring for 20 minutes sa as to separate the particles into the constituent silica and calcium carbonate by settling utilizing the difference in specific gravity. However~ the two components are found to be entirely inseparable and proved to be firmly joined ~ together chemically or physically.
Subsequently9 the composite particles of amorphous silica and calcium carbonate are immersed in a 6N HCl solution for one minute. With the evolution of carbon dioxide gas, the calcium carbonate in the primary particles is converted to carbon dio.Yide ~as and calcium chloride.
Th~ acid_treated particles are then thoroughly washed ~ith
- 6 water to completely dissolve out the r~sulting calcium chloride. The particles are dried to obtain Opsil-I of this invention.
The Opsil-I thus prepared is subjected to ignition dehydration and thereafter to analysis. The result is given below which indicates that the product is composed of silica of high purity.
SiO ; 99 4%
CaO C 0.01 (Ig. loss 5.8 ) The x-ray diffraction pattern of Opsil-I is the same as in Fig. l(C) which displays no peaks indicating the plate-like gyrolite crystals, the starting material, nor the peaks indicating the calcium carbonate contained in the composite particles resulting from the carbonation.
The Opsil-I is amorphous silica.
Ob~ervation of electron microgra~h reveals that the "~ opsil-I has a crystalline appearance and at least two surfaces in symmetric relation. The particles of Opsil-I are - about l to about 20 ~in length~ about 0.02 to about 0.1~ in ` thickness and about 0.2 to about 5/*~in width~ the length being at least about 10 times the thlckness and are in the form of primary particles. The crystalline appearance remains free of any change even when the particles are treated ~23~'7Z
, - with acld.
~ The properties of the Opsil-I obtained above are as follows.
Bulk density 0.06~ g/cm3 " 5 Specific surface area 285 m2/g '~ Oil adsorption 530 cc/100 g pH 6.3 : The reference numeral (4) in Fig. 9 sh~ws the pore size distribution of pore diameters of the Opsil-I
~th the peak at 28 R.
- Example 5 - The primary particles of plate-like a-dicalcium - silicate hydrate crystals obtained in Reference Example ; ~ 5 are used as a starting material. The particles are ; 15 placed in a pressure-resistant container of the closed type along ~ith water 5 times the weight of the particles~
;- Carbon dioxide gas is forced into the container at room , -- `temperature, and the particles are carbonated for about , 30 mlnutes while maintaining the internal pressure at - 20 - 3 kg/cm2, whereby composite particles of amorphous silica 'and calcium carbonate are obtained, ` ' ~ The analysi~ by ignition of the composite particles reveals the follo~ving composition.
., ' " ' '' ;.
. .
" ' ' ` ' ' . ~ .
~12 3 ~ 2 .:
SiO2 22.8~
: CaO 42.24 A1203 0.31 23 ~-33 ! 5 Ig. loss 31~.50 t ' . Total 100.24 - The x-ray diffraction of the particles shows the same result as given in Fig. l(B), which indicates that : ! - all the peaks peculiar to calcium silicate crystals~ the 10- . starting material, have disappeared and that only diffraction peaks (2e) indicative of calcium carbonate crystals have -.
. appeared at 23.0, 24.8, 27.0, 29.4, 32.8 and 36Ø
~- -` This evidences that the calcium silicate has been converted - to amorphous silica and calcium carbonate due to carbonation.
; 15 ;- - The composite particles are further observed . under an electron microscope with the result that the ~ . composite particles comprise amorphous silica particels .`;-` - and extremely ~ine particles, up to about 2~ in size~
t ~ of calcium carbonate attached to the amorphous silica particles and that the particles of amorphous silica have at least two 6urfaces in symmetric relation~ a length of . ` about 1 to about 300~ a thickness of about 0.1 to about and a width of about 1 to about 30~ ~ the length being at least about 10 times the thickness. The confi~uration of the . 25 amorphous sil-Lca particles is exactly the same at that of .
. . . .
~ . .
.. ..
.- . . . . - 59 - .
'7;2 plate-like ~-dicalcium silicate hydrate crystals (Fig.
4(A~). This indicates that the amorphous silica particles retain the original plate-like configuration of the crystals.
The composite particles are dispersed in water ` ~' 5 to a concentration of 5 u~to %, and the dispersion is allowed to stand after stirring for 20 minutes so as to separate the particles into the constituent silica and ~ calcium carbonate by settling utilizing the difference in - specific gravity. However, the two components are found 10- to be entirely inseparable and proved to be firmly joined together chemically or physically~
Subsequently, the composite particles of amorphous - silica and calcium carbonate are immersed in a 6N HCl - solution for one minute. With the evolution of carbon dioxide gas, the calcium carbonate in the primary particles ,; . -is converted to carbon dioxide gas and calcium chloride.
-- The acid-treated particles are then thoroughly washed ~ ~ .
; with water to completely dissolve out the resulting calcium .` t~: ~ ` - chloride. The particles are dried to obtain Opsil-I of ~-~!- 20 this invention~
The Opsil-I thus prepared is subjected to ignition dehydration and thereafter to analysis. The re~ult is given below which indicates that the product is composed of silica of high purity.
-.. ".' ` ' SiO2 99.6%
A123 0.12 CaO < 0.01 (Ig. loss 5.2 ) The x-ray diffraction pattern of Opsil-I is the same as in Fig. l(C) which displays ~o peaks indicating the plate-like ~-dicalcium silicate crystals, the starting material, nor the peaks indicating the calcium carbonate contained in the com-posite particles resulting from the carbonation. The Opsil-I is amorphous silica.
The Opsil-I is shown in the electron micrograph of Fig. 4(B) which reveals that the Opsil-I has a crystalline appearance and at least two surfaces in symmetric relation.
The particles of Opsil-I are about 1 to about 300~ in length, about 0.1 to about 1~ in thickness and about 1 to about 30~ in width, the length being at least about 10 times the thickness and are in the form of primary particles. The crystalline appearance remains free of any change even when the particles are treated with acid.
The properties of the Opsil-I obtained above are as follows.
Bulk density 0.15 g/cm3 Specific surface area 550 m2/g Oil adsorption 340 cc/100 g p~ 7.1 'i~VT 'i ~23~2 ~, The reference numeral (5) in Fig. 9 shows the pore size distribution of th~ ~psil-I with the peak at 24 ~.
, ':~
' ~ :
Exam~le 6 The slurry of xQnotlite crystgls obtained in Reference Example 1 is dewatered to a water to solids (xonotlite crystals) ratio by weight of 5 : 1 and is then placed in a closed container. Carbon dioxide gas is forced into the container to maintain an internal pressure of 3 kg/cm2, and the slurry is reacted for - about 30 minutes.' - - The reaction gives composite secondary particles io - of amorphous silica and calcium carbonate.
The analysis of the secondary particles reveals - that they have the same composition as the primary particles constituting them.
... , :
; , The x-ray diffraction of the particles further reveals the same result as given in Fig. l(B), indicating - ~ that the peaXs due to the calcium silicate crystals prior to the carbonation have 811 disappeared but showin~
; only the diffraction pesks ~2a) of calcium carbonate at 23.0, 2~.4 and 36Ø This evidences that the composite secondary particles are composed of amorphous silica and calcium carbonate. -- The composite secondary particles are ~urther observed under a scanning electron microscope at a magnification of 600X with the result given in Fi~. 5(B) which shows that the composite secondary particles are , , - 63 - ~
~23~7~
formed from numerous composite primary particles interlocked with one another substantially into globules ranging from about 10 to about 60 ~ in diameter. The electron microscope of the primary particles derived from the above secondary particles gives the same result as in Fig. 2(B).
This structure or form substantially conforms to that of secondàry particles of xonotlite used as the starting material and shown in Fig. 5(A). This IO indicates that the composite particles retain the original structure or nature of the secondary particles of xonotlite despite the carbonation.
The composite secondary particles are - - dispersed in water to a concentration of 5 wt.%, and ... .
the disper~ion is allowed to stand after stirring for 20 minutes. However, the particles are found inseparable by settling into their components, namely amorphous silica and calci~m carbonate.
~ Subsequently, the compoclite secondary particles are immersed iD a 6~ ~Cl solution for one minute.
Simultaneously with the immersion, carbon dioxide gas evolves due to the con~er~ion of the calcium carbonate in the primary particles to calcium chloride. The p~rticles are then thoroughly washed with water to completely dissolve out the resulting calcium chloride.
~he particles are dried to give Opsil-II of this ~.
~3~
invention.
~ he x-ray diffraction of the Opsil-II thus prepared exhibits the same result as in Fig. l(C), showiDg that the peaks due to cslciumsilicatecrystals and those due to calcium carbonate have all disappesred.
Thus the Opsil-II is found to be composed of amorphou~
silica.
The Opsil-II i5 observed under a scanning electron microscope at a magnification of 2,000X with the result given in Fig. 5(C), which indicates that the - particles of Opsil-II have substantially the same shape as the secondary particles of xonotlite and also as the composite secondary particles of amorphous silica and calcium - carbonate which retain the original structure of the former particles.
~ he Opsil-II prepared as gbove is readily dispersible in water to give a slurry which in itself is shapable. The Opsil-II has the following properties. ~-~ Bulk densit~ 0.04 g/cm3 Specific surrace area 400 m2/g Specific surface area 2 after heating at 400 C 350 m /g - Porosity 98 %
Heat re~istance No deformation at 95 ~
Oil adsorption 1,100 cc/100 g Chemical analysis:
SiO2 content 99.1 %
. . .
2~
Example 7 The slurry of tobermorite crystals obtained in - Reference Example 2 is dewatered to a water to ~olids (tobermorite crystals) ratio by weight of 5 : 1 and i8 then placed in a clo~ed container. Carbon dioxide ga~ i6 forced into the container to maintain an internal pressure of 3 kg/cm2, and the slurry is reacted for about 30 minutes.
The reaction gives composite secondary ~ particles of amorphous silica and calcium carbonate.
The analysis of the secondary particles reveals that they have the same composition as the - primary particles constituting them.
The x-ray diffraction of the particles further 15 , reveals that the peaks due to the calcium 3ilicate crystals prior to the carbonation have all disappeared but showing only the diffraction peaks (2~) of calcium c~rbonste at 23.0, 24.8, 27.0, 29.4s 32.8 and 36.0D.
This evideDces that the composite ~econdary particles are composed of amorphous silica and calcium carbonate.
~ he composite secondary particles are further observed under a scanning electron microscope at a magnificàtion of 600X with the result given in ~ig. 6(B), which sho~s that tbe composite secondary particles ar~
formed from numerous composite primary particles ~3~
interlocked with one another substantially into globules ranging from about 10 to~about 60 ~ in diameter.
The electron micro~cope of the primary particle~
derived from the above secondary particles gives the same result as in ~ig. 3(B).
This structure or form substantially conforms to that of secondary particles of tobermorite used as the starting material and shown in Fig. 6(A). This indicates that the composite particles retain the original ~ structure or nature of the secondary particles of xonotlite despite the carbonation.
The composite secondary particles are dispersed in water to a concentration of 5 wt.~, and the dispersion - : is allowed to stand after stirring for 20 minutes.
However, the particles are found inseparable by settling into their components, namely amorphous ~ilica snd calcium ~ carbonate.
- Subsequently, the composite secondary particles ~ are immersed in 8 6~ HCl solution for one minute.
Simultaneously with the immersion, carbon dioxide gas evolves due to the conversion of the calcium carbonate in the primary particles to calcium chloride. The particle~ are then thoroughly washed with water to completely dissolve out the resulting calciu~ chloride.
- 25 The particle~a are dried to give Opsil-II of this invention.
-- -- . .. . . .
The x-ray diffraction of the Opsil II thus prepared shows that the peaks due to calcium silicate crystals and those due to calcium carbonate have 811 disappeared. Thus the Opsil-II is found to be composed of amorphous silica.
-i The Opsil-II is observed under a scanning electron microscope at a magnification of 600X with ~ the result given in Fig. 6(C), which indicate~ that the particles of Opsil-II have substantially the same shape - ag the gecondary particles of tobermorite and also as the composite secondary particles of amrophous silica snd calcium carbonate which retain the original sbructure of the former particles.
- The Opsil-II prepared as above is re~dily - 15 dispersible in wster to give a slurry which in itself ~ i~ shapable. The Opsil-II has the following properties.
- ~ulk density 0.04 g/cm3 Specific surface area 430 m /g ` Specific surface area 2~ after heating at 400 C 380 m2/g Porosity 98 %
~eat resistance No deformation at Oil adsOrptiOn 980 cc/100 g Ch~mic~l analysis:
SiO2 content 99.3 %
. .
.- . ~ ,:
. . . i . , .
~l~23~7~
Example 8 The slurry of calcium silicate (CS~n) crystals obtained in RefereDce Example 3 is dewatered to a water to solids (CS~n crystals) ratio by weight of 5 : 1 and is then plsced in a closed container. Carbon dioxide gas i8 forced into the container to maintain an internal pressure of 3 kg/cm , and the slurr~ i~ reacted for about ;~
; 30 minutes.
The reaction gives composite secondary particles of amorphous silica and calcium carbonate.
The analysis of the secondary particles reveals that they have the same composition as the primary particles constituting them.
- The x-ray diffrac~ion of the particles further reveals that the peaks due to the calcium silicate c~ystals prior to the carbonation have all disappeared but showing onl~ the diffraction peaks t2~) of calcium - carbonate at 23.0, 24.8, 27.0, 29.4~ 32.8 and -; 36Ø This evidences that the composite secondar~
particles are composed of amorphous silica and calcium carbonate.
The composite secondary particles are further - observed under a scsnning electron microscope with the same res~lt as -those given in Figs. 5(B) and 6(B), showing that bhe composite secondar~ particles are formed from numerous composite primary particles interlocked with .
- 69 - ~
- . ~ ~ ,. .
~23~72 one another substantially into globules ranging from about 10 to about 60 ~ in diameter. The electron microscope of the primary particles derived from the above secondary particles gives the same result as obtained by that of composite primary particles prepared in Example 3.
This structure or form substantially conforms to that of secondary particles of CS~n used as the starting material. This indicates that the composite particles retain the original structure or nature of the secondary particles despite the carbonation.
The composite secondary particles are dispersed in water to a concentration of 5 Wt.D/o~ and the dispersion is allowed to stand after stirring for 20 minutes.
However, the particles are found inseparable by settling into their components, namely amorphous silica and calcium carbonate.
- Sub~equently, the composite secondary particles ; are immersed in a 6N HCl solution for one minute.
Simultaneousl~ with the immersion, carbon dioxide -gas evolves due to the conversion of the calcium carbonate in the primary particles to calcium chloride. The particleg are then thoroughl~ wsshed with water to completely dissolve out the resulting calcium chloride.
The particles are dried to give Opsil-II of this invention.
'2 The x-ra~ diffraction of the Opsil-II thus prepared shows that the peaks due to calcium silicate crystals and those due to calcium carbonate have all disappeared. Thus the Opsil-II is found to be composed of amorphous silica.
The Opsil-II is observed under 8 scanning electron microscope with the same result as those given in ~igs. 5(C) and'6(C), which indicates that the particles of Opsil-II have substantially the same shape ~`
as the secondary particles of CSHn and also as the composite secondary particles of amorphous silica and calcium carbonate which retain the original structure of the former particles.
The Opsil-II prepared as above is readily 15- dispersible in water to give a slurry which in itself is shapable. The Opsil-II has the following properties.
- Bulk density 0.08 g/cm3 Specific surface area , 550 m /g `~ Specific surface area after 2 heating at 400 C 480 m /g Porosity 96 %
Heat resistance No deformation at 950 C
Oil adsorption 750 cc/100 g Ch~mical an~ is:
SiO2 content 99.7 %
.. .. ... ..
~3~L7~
Example 9 The secondary particles of xonotlite crystals obtained in Refer~nce Exa~ple 1 are b~ked at 1,000 C for one hour into ~-wollastonite crystals, and the crystals are - 5 placed, in a water to solids (~-wollastonite crystals) ratio by weight of 5 : 1, in a closed container.
Carbon dioxide gas is forced into the container to maintain an internal pressure of 3 kg/cm2, and the slurry is reacted for about 30 minutes.
The reaction gives composite secondary particles - of amorphous silica and calcium carbonate.
The analysis of the secondary particles re~eals - the following composition.
- SiO2 36.00 %
CaO 33.58 %
A123 0.15 %
- 2 3 .35 %
- I~. loss 28.9~ %
- Total 99.0 %
The x-ray diffraction of the particles further reveals that the peaks due to the calcium silicate crystals prior to the carbonation have all disappeared b~t showing onl~ the diffraction peaks (20) of calcium carbonate at 23.0, 24.8, 27.0, 29.4, 32.8 and 36Ø
This evidences that the composite secondary particles ~ - 72 -.. . .
c ~23~7 are composed of amorphous silica and calcium carbonate.
The composite secondary particles are further observed under a scanning electron microscope with the same result as those given in Figs. 5~B) and 6(~), showing that the composite secondary particles are formed from numerous composite primary particles interlocked with one another substantially into globules rangin~ from about 10 to about`60~in diameter. By the electron micro~cope the primary particles derived from the above 0 - secondary particles are found to be formed of amorphous silica particles having the original configur~ation of the starting ~-wollastonite crystals and extremely fine psrticles of calcium carbonate attached thereto.
This structure or form substantiall~ conforms to that of secondary particles of ~-wollastonite used - a~ the starting material. This indicates that the composite ;;~
- particles retain the original structure or nsture of the secondary particles of ~-wollastonite dçqpite the carbonation.
' 20 The composite secondary particles are dispersed in water to a concentration of 5 wt.%, and the dispersion is allowed to stand after stirring for 20 minutes.
However, the particles are found inseparable by settling into their components, namely amorphous silica and calcium carbonate.
3~7;2 Subsequnetly, the composite secondary particles are immersed in a 6N HCl~solution for one minute.
Simultaneously with the immersion, carbon dioxide gas evolves due to the conversion of the calcium c~rbonate in the primary particles to calcium chloride. ~he particles are then thoroughly washed with water to completely dissolve out the resulting calcium chloride.
The particles are`dried to give Opsil-II of this invention.
10 - The x-ray diffraction of the Opsil-II thus prepared shows that the peaks due to calcium silicate crystals and those due to calcium carbonate have all disappeared. ~hus the Opsil-II is found to be composed - of amorphous silica.
The Opsil-II is observed under a scanning - electron mic~oscope with the same result as those given in Figs. 5(C) and 6(C), which indicates that the particles - of Opsil-II have substantially the same 6hape as the secondary particles of ~-wollastonite and also as the composite secondary particles of amorphous silica and calcium carbonate which retain the original structure of the former particles.
- ~he Opsil-II prepared aq above is readily dispersible in water to give a slurry which in itself is shapable.
....
The analysis reveal~ the Opsil-Il h~s revealed the following result which indicates that the product is composed of silica of high purity.
- SiO 99 A1203 0.25 %
CaO <0.01 %
(Ig. loss 5~0 %) The properties of the Opsil-II are as follows.
Bulk density 0.04 g/cm3 - Specific surface area 280 m2/g Specific surface area 2 sfter heating st 400 C 230 m /g Porosity 98 %
Heat resistance No deformation at ~il adsorption 780 cc/100-g Exam~le 10 .
The xonotlite shaped body (bulk density: 0~2 g/cm3) - obtained in Reference Example 1 i~ plac~d with water~ in a water solids ratio by weight of 2:1, in a closed container. Carbon dioxide gas i~ forced into the container to maintain an internal -pressure of 3 kg/cm2 for about 30 minutes for carbonation.
The reaction, followed by drying, gives a composite shaped body o~ amorphous ~ilica and calcium carbonate.
A fractured surface of the shaped body is observed under a scanning electron microscope with the result glven i~ Fig. 7(B), which shows that the shaped body has exactly the same structure as the starting materiaI, i.e. xonotlite -3~
~haped body (Fig. 7(A)). It is found that the ~haped body is formed from globular secondary particles which are compre~ed and interlocked with one another and firmly into an integral mas~, the composite body thus retaining the original structure of the starting material intact.
Furthermore, the primary particle~ forming the 6econdary particles are found to have the same ~orm as shown in Fig.
2(B) by electron microscopic observation and have the same diffraction peaks as shown in Fig~ l(B) according to x-ray diffraction. Thus the product is a compo~ite shaped body made up of needle-like particlefi of amorphou~ ~ilica and extremely fine particles of calcium carbonate attached thereto.
Subsequently, the composite shaped body is immersed in a 6N HCl solution for one minute. Simultaneously - with the immersion, carbon dioxide gas evolves and the calcium carbonate in the shaped body is converted to calcium chloride. The shaped body is then thoroughly washed with water to completely dissolve out the resulting calcium chloride and is thereafter dried to give Opsil-IIS of this invention.
X-ray diffraction confirms that the Opsil-IIS, like Opsil-I and Opsil-II, is amorphous.
Observation under a scanning electron micro6cope ~5 gives the result shown in Fig. 7(C), indicating that in ~tructure the Opsil-IIS substantially resembles the starting material~ namely xonotlite shaped body (Fig. 7(A))I and
The Opsil-I thus prepared is subjected to ignition dehydration and thereafter to analysis. The result is given below which indicates that the product is composed of silica of high purity.
SiO ; 99 4%
CaO C 0.01 (Ig. loss 5.8 ) The x-ray diffraction pattern of Opsil-I is the same as in Fig. l(C) which displays no peaks indicating the plate-like gyrolite crystals, the starting material, nor the peaks indicating the calcium carbonate contained in the composite particles resulting from the carbonation.
The Opsil-I is amorphous silica.
Ob~ervation of electron microgra~h reveals that the "~ opsil-I has a crystalline appearance and at least two surfaces in symmetric relation. The particles of Opsil-I are - about l to about 20 ~in length~ about 0.02 to about 0.1~ in ` thickness and about 0.2 to about 5/*~in width~ the length being at least about 10 times the thlckness and are in the form of primary particles. The crystalline appearance remains free of any change even when the particles are treated ~23~'7Z
, - with acld.
~ The properties of the Opsil-I obtained above are as follows.
Bulk density 0.06~ g/cm3 " 5 Specific surface area 285 m2/g '~ Oil adsorption 530 cc/100 g pH 6.3 : The reference numeral (4) in Fig. 9 sh~ws the pore size distribution of pore diameters of the Opsil-I
~th the peak at 28 R.
- Example 5 - The primary particles of plate-like a-dicalcium - silicate hydrate crystals obtained in Reference Example ; ~ 5 are used as a starting material. The particles are ; 15 placed in a pressure-resistant container of the closed type along ~ith water 5 times the weight of the particles~
;- Carbon dioxide gas is forced into the container at room , -- `temperature, and the particles are carbonated for about , 30 mlnutes while maintaining the internal pressure at - 20 - 3 kg/cm2, whereby composite particles of amorphous silica 'and calcium carbonate are obtained, ` ' ~ The analysi~ by ignition of the composite particles reveals the follo~ving composition.
., ' " ' '' ;.
. .
" ' ' ` ' ' . ~ .
~12 3 ~ 2 .:
SiO2 22.8~
: CaO 42.24 A1203 0.31 23 ~-33 ! 5 Ig. loss 31~.50 t ' . Total 100.24 - The x-ray diffraction of the particles shows the same result as given in Fig. l(B), which indicates that : ! - all the peaks peculiar to calcium silicate crystals~ the 10- . starting material, have disappeared and that only diffraction peaks (2e) indicative of calcium carbonate crystals have -.
. appeared at 23.0, 24.8, 27.0, 29.4, 32.8 and 36Ø
~- -` This evidences that the calcium silicate has been converted - to amorphous silica and calcium carbonate due to carbonation.
; 15 ;- - The composite particles are further observed . under an electron microscope with the result that the ~ . composite particles comprise amorphous silica particels .`;-` - and extremely ~ine particles, up to about 2~ in size~
t ~ of calcium carbonate attached to the amorphous silica particles and that the particles of amorphous silica have at least two 6urfaces in symmetric relation~ a length of . ` about 1 to about 300~ a thickness of about 0.1 to about and a width of about 1 to about 30~ ~ the length being at least about 10 times the thickness. The confi~uration of the . 25 amorphous sil-Lca particles is exactly the same at that of .
. . . .
~ . .
.. ..
.- . . . . - 59 - .
'7;2 plate-like ~-dicalcium silicate hydrate crystals (Fig.
4(A~). This indicates that the amorphous silica particles retain the original plate-like configuration of the crystals.
The composite particles are dispersed in water ` ~' 5 to a concentration of 5 u~to %, and the dispersion is allowed to stand after stirring for 20 minutes so as to separate the particles into the constituent silica and ~ calcium carbonate by settling utilizing the difference in - specific gravity. However, the two components are found 10- to be entirely inseparable and proved to be firmly joined together chemically or physically~
Subsequently, the composite particles of amorphous - silica and calcium carbonate are immersed in a 6N HCl - solution for one minute. With the evolution of carbon dioxide gas, the calcium carbonate in the primary particles ,; . -is converted to carbon dioxide gas and calcium chloride.
-- The acid-treated particles are then thoroughly washed ~ ~ .
; with water to completely dissolve out the resulting calcium .` t~: ~ ` - chloride. The particles are dried to obtain Opsil-I of ~-~!- 20 this invention~
The Opsil-I thus prepared is subjected to ignition dehydration and thereafter to analysis. The re~ult is given below which indicates that the product is composed of silica of high purity.
-.. ".' ` ' SiO2 99.6%
A123 0.12 CaO < 0.01 (Ig. loss 5.2 ) The x-ray diffraction pattern of Opsil-I is the same as in Fig. l(C) which displays ~o peaks indicating the plate-like ~-dicalcium silicate crystals, the starting material, nor the peaks indicating the calcium carbonate contained in the com-posite particles resulting from the carbonation. The Opsil-I is amorphous silica.
The Opsil-I is shown in the electron micrograph of Fig. 4(B) which reveals that the Opsil-I has a crystalline appearance and at least two surfaces in symmetric relation.
The particles of Opsil-I are about 1 to about 300~ in length, about 0.1 to about 1~ in thickness and about 1 to about 30~ in width, the length being at least about 10 times the thickness and are in the form of primary particles. The crystalline appearance remains free of any change even when the particles are treated with acid.
The properties of the Opsil-I obtained above are as follows.
Bulk density 0.15 g/cm3 Specific surface area 550 m2/g Oil adsorption 340 cc/100 g p~ 7.1 'i~VT 'i ~23~2 ~, The reference numeral (5) in Fig. 9 shows the pore size distribution of th~ ~psil-I with the peak at 24 ~.
, ':~
' ~ :
Exam~le 6 The slurry of xQnotlite crystgls obtained in Reference Example 1 is dewatered to a water to solids (xonotlite crystals) ratio by weight of 5 : 1 and is then placed in a closed container. Carbon dioxide gas is forced into the container to maintain an internal pressure of 3 kg/cm2, and the slurry is reacted for - about 30 minutes.' - - The reaction gives composite secondary particles io - of amorphous silica and calcium carbonate.
The analysis of the secondary particles reveals - that they have the same composition as the primary particles constituting them.
... , :
; , The x-ray diffraction of the particles further reveals the same result as given in Fig. l(B), indicating - ~ that the peaXs due to the calcium silicate crystals prior to the carbonation have 811 disappeared but showin~
; only the diffraction pesks ~2a) of calcium carbonate at 23.0, 2~.4 and 36Ø This evidences that the composite secondary particles are composed of amorphous silica and calcium carbonate. -- The composite secondary particles are ~urther observed under a scanning electron microscope at a magnification of 600X with the result given in Fi~. 5(B) which shows that the composite secondary particles are , , - 63 - ~
~23~7~
formed from numerous composite primary particles interlocked with one another substantially into globules ranging from about 10 to about 60 ~ in diameter. The electron microscope of the primary particles derived from the above secondary particles gives the same result as in Fig. 2(B).
This structure or form substantially conforms to that of secondàry particles of xonotlite used as the starting material and shown in Fig. 5(A). This IO indicates that the composite particles retain the original structure or nature of the secondary particles of xonotlite despite the carbonation.
The composite secondary particles are - - dispersed in water to a concentration of 5 wt.%, and ... .
the disper~ion is allowed to stand after stirring for 20 minutes. However, the particles are found inseparable by settling into their components, namely amorphous silica and calci~m carbonate.
~ Subsequently, the compoclite secondary particles are immersed iD a 6~ ~Cl solution for one minute.
Simultaneously with the immersion, carbon dioxide gas evolves due to the con~er~ion of the calcium carbonate in the primary particles to calcium chloride. The p~rticles are then thoroughly washed with water to completely dissolve out the resulting calcium chloride.
~he particles are dried to give Opsil-II of this ~.
~3~
invention.
~ he x-ray diffraction of the Opsil-II thus prepared exhibits the same result as in Fig. l(C), showiDg that the peaks due to cslciumsilicatecrystals and those due to calcium carbonate have all disappesred.
Thus the Opsil-II is found to be composed of amorphou~
silica.
The Opsil-II i5 observed under a scanning electron microscope at a magnification of 2,000X with the result given in Fig. 5(C), which indicates that the - particles of Opsil-II have substantially the same shape as the secondary particles of xonotlite and also as the composite secondary particles of amorphous silica and calcium - carbonate which retain the original structure of the former particles.
~ he Opsil-II prepared as gbove is readily dispersible in water to give a slurry which in itself is shapable. The Opsil-II has the following properties. ~-~ Bulk densit~ 0.04 g/cm3 Specific surrace area 400 m2/g Specific surface area 2 after heating at 400 C 350 m /g - Porosity 98 %
Heat re~istance No deformation at 95 ~
Oil adsorption 1,100 cc/100 g Chemical analysis:
SiO2 content 99.1 %
. . .
2~
Example 7 The slurry of tobermorite crystals obtained in - Reference Example 2 is dewatered to a water to ~olids (tobermorite crystals) ratio by weight of 5 : 1 and i8 then placed in a clo~ed container. Carbon dioxide ga~ i6 forced into the container to maintain an internal pressure of 3 kg/cm2, and the slurry is reacted for about 30 minutes.
The reaction gives composite secondary ~ particles of amorphous silica and calcium carbonate.
The analysis of the secondary particles reveals that they have the same composition as the - primary particles constituting them.
The x-ray diffraction of the particles further 15 , reveals that the peaks due to the calcium 3ilicate crystals prior to the carbonation have all disappeared but showing only the diffraction peaks (2~) of calcium c~rbonste at 23.0, 24.8, 27.0, 29.4s 32.8 and 36.0D.
This evideDces that the composite ~econdary particles are composed of amorphous silica and calcium carbonate.
~ he composite secondary particles are further observed under a scanning electron microscope at a magnificàtion of 600X with the result given in ~ig. 6(B), which sho~s that tbe composite secondary particles ar~
formed from numerous composite primary particles ~3~
interlocked with one another substantially into globules ranging from about 10 to~about 60 ~ in diameter.
The electron micro~cope of the primary particle~
derived from the above secondary particles gives the same result as in ~ig. 3(B).
This structure or form substantially conforms to that of secondary particles of tobermorite used as the starting material and shown in Fig. 6(A). This indicates that the composite particles retain the original ~ structure or nature of the secondary particles of xonotlite despite the carbonation.
The composite secondary particles are dispersed in water to a concentration of 5 wt.~, and the dispersion - : is allowed to stand after stirring for 20 minutes.
However, the particles are found inseparable by settling into their components, namely amorphous ~ilica snd calcium ~ carbonate.
- Subsequently, the composite secondary particles ~ are immersed in 8 6~ HCl solution for one minute.
Simultaneously with the immersion, carbon dioxide gas evolves due to the conversion of the calcium carbonate in the primary particles to calcium chloride. The particle~ are then thoroughly washed with water to completely dissolve out the resulting calciu~ chloride.
- 25 The particle~a are dried to give Opsil-II of this invention.
-- -- . .. . . .
The x-ray diffraction of the Opsil II thus prepared shows that the peaks due to calcium silicate crystals and those due to calcium carbonate have 811 disappeared. Thus the Opsil-II is found to be composed of amorphous silica.
-i The Opsil-II is observed under a scanning electron microscope at a magnification of 600X with ~ the result given in Fig. 6(C), which indicate~ that the particles of Opsil-II have substantially the same shape - ag the gecondary particles of tobermorite and also as the composite secondary particles of amrophous silica snd calcium carbonate which retain the original sbructure of the former particles.
- The Opsil-II prepared as above is re~dily - 15 dispersible in wster to give a slurry which in itself ~ i~ shapable. The Opsil-II has the following properties.
- ~ulk density 0.04 g/cm3 Specific surface area 430 m /g ` Specific surface area 2~ after heating at 400 C 380 m2/g Porosity 98 %
~eat resistance No deformation at Oil adsOrptiOn 980 cc/100 g Ch~mic~l analysis:
SiO2 content 99.3 %
. .
.- . ~ ,:
. . . i . , .
~l~23~7~
Example 8 The slurry of calcium silicate (CS~n) crystals obtained in RefereDce Example 3 is dewatered to a water to solids (CS~n crystals) ratio by weight of 5 : 1 and is then plsced in a closed container. Carbon dioxide gas i8 forced into the container to maintain an internal pressure of 3 kg/cm , and the slurr~ i~ reacted for about ;~
; 30 minutes.
The reaction gives composite secondary particles of amorphous silica and calcium carbonate.
The analysis of the secondary particles reveals that they have the same composition as the primary particles constituting them.
- The x-ray diffrac~ion of the particles further reveals that the peaks due to the calcium silicate c~ystals prior to the carbonation have all disappeared but showing onl~ the diffraction peaks t2~) of calcium - carbonate at 23.0, 24.8, 27.0, 29.4~ 32.8 and -; 36Ø This evidences that the composite secondar~
particles are composed of amorphous silica and calcium carbonate.
The composite secondary particles are further - observed under a scsnning electron microscope with the same res~lt as -those given in Figs. 5(B) and 6(B), showing that bhe composite secondar~ particles are formed from numerous composite primary particles interlocked with .
- 69 - ~
- . ~ ~ ,. .
~23~72 one another substantially into globules ranging from about 10 to about 60 ~ in diameter. The electron microscope of the primary particles derived from the above secondary particles gives the same result as obtained by that of composite primary particles prepared in Example 3.
This structure or form substantially conforms to that of secondary particles of CS~n used as the starting material. This indicates that the composite particles retain the original structure or nature of the secondary particles despite the carbonation.
The composite secondary particles are dispersed in water to a concentration of 5 Wt.D/o~ and the dispersion is allowed to stand after stirring for 20 minutes.
However, the particles are found inseparable by settling into their components, namely amorphous silica and calcium carbonate.
- Sub~equently, the composite secondary particles ; are immersed in a 6N HCl solution for one minute.
Simultaneousl~ with the immersion, carbon dioxide -gas evolves due to the conversion of the calcium carbonate in the primary particles to calcium chloride. The particleg are then thoroughl~ wsshed with water to completely dissolve out the resulting calcium chloride.
The particles are dried to give Opsil-II of this invention.
'2 The x-ra~ diffraction of the Opsil-II thus prepared shows that the peaks due to calcium silicate crystals and those due to calcium carbonate have all disappeared. Thus the Opsil-II is found to be composed of amorphous silica.
The Opsil-II is observed under 8 scanning electron microscope with the same result as those given in ~igs. 5(C) and'6(C), which indicates that the particles of Opsil-II have substantially the same shape ~`
as the secondary particles of CSHn and also as the composite secondary particles of amorphous silica and calcium carbonate which retain the original structure of the former particles.
The Opsil-II prepared as above is readily 15- dispersible in water to give a slurry which in itself is shapable. The Opsil-II has the following properties.
- Bulk density 0.08 g/cm3 Specific surface area , 550 m /g `~ Specific surface area after 2 heating at 400 C 480 m /g Porosity 96 %
Heat resistance No deformation at 950 C
Oil adsorption 750 cc/100 g Ch~mical an~ is:
SiO2 content 99.7 %
.. .. ... ..
~3~L7~
Example 9 The secondary particles of xonotlite crystals obtained in Refer~nce Exa~ple 1 are b~ked at 1,000 C for one hour into ~-wollastonite crystals, and the crystals are - 5 placed, in a water to solids (~-wollastonite crystals) ratio by weight of 5 : 1, in a closed container.
Carbon dioxide gas is forced into the container to maintain an internal pressure of 3 kg/cm2, and the slurry is reacted for about 30 minutes.
The reaction gives composite secondary particles - of amorphous silica and calcium carbonate.
The analysis of the secondary particles re~eals - the following composition.
- SiO2 36.00 %
CaO 33.58 %
A123 0.15 %
- 2 3 .35 %
- I~. loss 28.9~ %
- Total 99.0 %
The x-ray diffraction of the particles further reveals that the peaks due to the calcium silicate crystals prior to the carbonation have all disappeared b~t showing onl~ the diffraction peaks (20) of calcium carbonate at 23.0, 24.8, 27.0, 29.4, 32.8 and 36Ø
This evidences that the composite secondary particles ~ - 72 -.. . .
c ~23~7 are composed of amorphous silica and calcium carbonate.
The composite secondary particles are further observed under a scanning electron microscope with the same result as those given in Figs. 5~B) and 6(~), showing that the composite secondary particles are formed from numerous composite primary particles interlocked with one another substantially into globules rangin~ from about 10 to about`60~in diameter. By the electron micro~cope the primary particles derived from the above 0 - secondary particles are found to be formed of amorphous silica particles having the original configur~ation of the starting ~-wollastonite crystals and extremely fine psrticles of calcium carbonate attached thereto.
This structure or form substantiall~ conforms to that of secondary particles of ~-wollastonite used - a~ the starting material. This indicates that the composite ;;~
- particles retain the original structure or nsture of the secondary particles of ~-wollastonite dçqpite the carbonation.
' 20 The composite secondary particles are dispersed in water to a concentration of 5 wt.%, and the dispersion is allowed to stand after stirring for 20 minutes.
However, the particles are found inseparable by settling into their components, namely amorphous silica and calcium carbonate.
3~7;2 Subsequnetly, the composite secondary particles are immersed in a 6N HCl~solution for one minute.
Simultaneously with the immersion, carbon dioxide gas evolves due to the conversion of the calcium c~rbonate in the primary particles to calcium chloride. ~he particles are then thoroughly washed with water to completely dissolve out the resulting calcium chloride.
The particles are`dried to give Opsil-II of this invention.
10 - The x-ray diffraction of the Opsil-II thus prepared shows that the peaks due to calcium silicate crystals and those due to calcium carbonate have all disappeared. ~hus the Opsil-II is found to be composed - of amorphous silica.
The Opsil-II is observed under a scanning - electron mic~oscope with the same result as those given in Figs. 5(C) and 6(C), which indicates that the particles - of Opsil-II have substantially the same 6hape as the secondary particles of ~-wollastonite and also as the composite secondary particles of amorphous silica and calcium carbonate which retain the original structure of the former particles.
- ~he Opsil-II prepared aq above is readily dispersible in water to give a slurry which in itself is shapable.
....
The analysis reveal~ the Opsil-Il h~s revealed the following result which indicates that the product is composed of silica of high purity.
- SiO 99 A1203 0.25 %
CaO <0.01 %
(Ig. loss 5~0 %) The properties of the Opsil-II are as follows.
Bulk density 0.04 g/cm3 - Specific surface area 280 m2/g Specific surface area 2 sfter heating st 400 C 230 m /g Porosity 98 %
Heat resistance No deformation at ~il adsorption 780 cc/100-g Exam~le 10 .
The xonotlite shaped body (bulk density: 0~2 g/cm3) - obtained in Reference Example 1 i~ plac~d with water~ in a water solids ratio by weight of 2:1, in a closed container. Carbon dioxide gas i~ forced into the container to maintain an internal -pressure of 3 kg/cm2 for about 30 minutes for carbonation.
The reaction, followed by drying, gives a composite shaped body o~ amorphous ~ilica and calcium carbonate.
A fractured surface of the shaped body is observed under a scanning electron microscope with the result glven i~ Fig. 7(B), which shows that the shaped body has exactly the same structure as the starting materiaI, i.e. xonotlite -3~
~haped body (Fig. 7(A)). It is found that the ~haped body is formed from globular secondary particles which are compre~ed and interlocked with one another and firmly into an integral mas~, the composite body thus retaining the original structure of the starting material intact.
Furthermore, the primary particle~ forming the 6econdary particles are found to have the same ~orm as shown in Fig.
2(B) by electron microscopic observation and have the same diffraction peaks as shown in Fig~ l(B) according to x-ray diffraction. Thus the product is a compo~ite shaped body made up of needle-like particlefi of amorphou~ ~ilica and extremely fine particles of calcium carbonate attached thereto.
Subsequently, the composite shaped body is immersed in a 6N HCl solution for one minute. Simultaneously - with the immersion, carbon dioxide gas evolves and the calcium carbonate in the shaped body is converted to calcium chloride. The shaped body is then thoroughly washed with water to completely dissolve out the resulting calcium chloride and is thereafter dried to give Opsil-IIS of this invention.
X-ray diffraction confirms that the Opsil-IIS, like Opsil-I and Opsil-II, is amorphous.
Observation under a scanning electron micro6cope ~5 gives the result shown in Fig. 7(C), indicating that in ~tructure the Opsil-IIS substantially resembles the starting material~ namely xonotlite shaped body (Fig. 7(A))I and
- 7~ -~, the composite shaped body obtained by carbonating the material (Fig. 7(B)). The substantially globular particles of Opsil-II, ranging from about 10 to about 60 ~ in diameter, are compres~ed and interlocked with one another, forming the integral body of the Opsil-IIS.
The Opsil-IIS prepared as above has the following properties.
Bulk density 0.09 g/cm2 Specific surface area 288 m2/g 10- Compres6ion strength 6 kg/cm2 Porosity 95%
The Op6il-IIS prepared as above, when fired in an electric oven at 1000 C for 1 hour, gives a contraction:
- of about 12%, but no changes are observed in the compressedglobular form of Opsil-II constituting the ~haped body.
The properties of the fired product are as follows~
Bulk den~ity 0.085 g~m2 Compression Strength 10 kg/cm2 ~ Porofiity 95%
20- The fired product has a thermal expansion coefficient of 5.7 x 10 7~oc and exhibits substantially no expan~ion and contractio~ in repeated heating tests conducted at 950 C.
Further, Opsil-IIS having a bulk den~ity of 0.3 g/cm2 i~ prepared in th~ same manner as above except that a shaped b~dy of xonotlite crystals having a bulk density of 0.62g/c ~ , which i~ prepared in the 6ame manner as in Reference Example 1 with increased ~haping pressure, is employed a6 a starting material~ The Op~ IIS is cut along a plane vertical to .. . , .:
~ ~3~
the direction of the shaping pressure~ The scanning electron micrograph of the cut surface indicates that the Opsil-II constituting the shaped body has been compressed with the lath-like Opsil-I particles oriented in a direction vertical to the direction of the pressure applied. Thls structure is the same as that~of the st~r~ing xonotlite sha~ed body. The properties of Opsil-IIS are as follows:
Bulk density ~ 0 3 g/cm3 Specific surface area 290 m2/g Compression strength 15 kg/cm2 Porosity 85%
Example ll The tobermorite shaped body (bulk density: 0.3 ~cm3) obtained in Reference Example 2 is placed ~lith water, in a water to solids ratio by weight o 2:1, in a closed container.
Carbon dioxide gas is forced into the container to maintain an internal pressure of 3 kg/cm2 for about ~0 minutes for - carbonation.
\ The reaction, followed by drying, gives a composite shaped body of amorphous silica and calcium carbonate~
A fractured surface of the shaped body is observed under a scanning electron microscope with the same result as given in Fig. 7~B), which shows that the shaped body has exactly the same structure a~ the starting material, i.e. tobermorite shaped body. It is found that the shaped body is formed from globular secondary particles which are compressed and interlocked with one another and firmly into an integral mass, the composite body thus retaining the original structure of the starting material intact.
. _ . .
Furthermore, the primary particles forming the ~econdary partlcles are found to have the same form as shown in Fig.
3(B) by electron microscopic observation and have the same diffraction peaks peculiar to calciura carbonate according to x-ray diffraction. Thus the product is a composite ~haped body made up of plate-like particles of amorphous ~ilica and extremely ~ine particles of calcium carbonate attached thereto.
Subsequently, the composite shaped body i~ immersed in a 6N HCl solution for one minute. Simultaneously with the immer~ion, carbon dioxide gas evolves and the calcium carbonate in the shaped body is converted to calcium chloride.
- The shaped body is then thoroughly washed with water to completely dissolve out the resulting calcium chloride and is thereafter dried to give Opsil-IIS of thi~ invention~
X-ray diffraction confirms that the Op~il-IIS, like Opsll-I and Opsll-II, is amorphous.
Observation under a scanning electron mlcroscope gives the ~ame result a~ shown in Fig. 7(C), indicatlng that in structure the Opsil-IIS substantially resembles the ~tarting material, namely tobermorite ~haped body and the composite shaped body obtained by carbonating the material. The substantially globular particles of Opsil-II, ranging from about 10 to about 60 J~in diameter, are compressed and interlocked with one another forming the integral body of the Opsil-IIS.
~. .
- 79 - ~
f --~3~7~
The Opsil-IIS prepared as above has the following properties.
Bulk den~ity 0.13 g/cm2 - Specific surface area 277 m2/g Compression strength 4 kg/cm Porosity 93%
Example 12 The shaped body (bulk density: 0.3 g/cm3) of calcium silicate (CSHn) obtained in Reference Example 3 is placed with water in a water to solids ratio by weight of 2:1, in a closed container. Carbon dioxide gas is forced into the container to maintain an internal pressure of 3 kg/cm2 for about 30 minutes for carbonation.
The reaction, followed by drying, gives a composite shaped body of amorphous silica and calcium carbonateO
A ~ractured surface of the shaped body is observed under a scanning electron microscope with the same result as given in Fig. 7(B), which shows that the composite shaped body has exactly the same structure as the starting material, 20 ~ i.e. CSHn shaped body. It is found that the shaped body is formed form globular secondary particles which are compre~sed and interlocked with one another and firmly into an integral mass~ the composite body thus retaining the original structure of the starting material intact. Furthermore, the primary pa~ticles forming the secondary particles are found to have the same form as foil-like particle peculiar to CSHn by .23~7%
electron mlcroscopic observation and have the same diffraction peaks peculiar to calcium carbonate according to x-ray diffraction. Thus the product is a composite shaped body made up of foil-like particles of amophous silica and extremely fine particles of calcium carbonate attached theretoO
- Subsequently9 the composite shaped body is irnmersed in a 6N HCl solution for one minute~ Simultaneously with the immersion, car~bon dioxide gas evolves and the calcium carbonate in the shaped body is converted to calcium chloride.
10- The shaped body is then thoroughly washed with water to completely dissolve out the resulting calcium chIoride and is thereafter dried to give Opsil-IIS of this invention.
X-ray diffraction confirms that the Opsil-IIS, like Opsil-I and Opsil-II, is amorphous.
Observation under a scanning electron microscope gives the same result as shown in Fig. 7(C) 9 indicating that in structure the Opsil-IIS substantially resem~les the starting materlal, namely CSHn shaped body and the composite ~haped body obtalned by carbonating the material. The substantially globular particles of Opsil-II, ranging from about 10 to about 60y~ are compressed and interlocked with one another, forming the integ~al body of the Opsil-IIS.
The Opsil-IIS prepared as above has the following properties.
.,- .. , , . :,.
~3~72 Bulk den~ity 0.14 g/cm2 Specific surface area 461 m2/g Compre~ion ~trength 4 kg/cm Poro~ity 82%
7~
Example 13 The powder of Opsil-II (100 wt. parts) obtained in Example 6 and 2 wt. parts of glass fibers are dispersed in water to a water to solids ratio by weight of 10:1, to prepare a slurry. The slurry is placed in a mold, 40 mm x 120 mm x 150 mm, and then dewatered by a press. The shaped mass is removed from the mold and dried at 105 C for 24 hours to obtain a shaped body of this invention, i.e. Opsil-IIS, having the following properties.
10 Bulk density 0.11 g/cm3 Bending strength 6 kg/cm2 Compression strength 9 kg/cm2 Porosity 93%
Example 14 The Opsil-II obtained in Example 7 is shaped in the same manner as in Example 13 to prepare a shaped body of this invention, i.e. Opsil-IIS, having the following properties.
Bulk density 0.15 g/cm3 Bending strength 4.5 kg/cm 20 Compression strength 7 kg/cm2 Porosity 91%
Example 15 The Opsil-II obtained in Example 8 is shaped in the same manner as in Example 13 to prepare an Opsil-IIS of this invention having the following properties.
2~ 72 Bulk density 0.21 g/cm3 Bend1ng strengt~ 2.3 kg/em2 Compression strength 4 kg/cm Porosity 88 %
~xample 16 The eomposite secondary particles of amorphous silica and calcium carbonate obtained by the first step of EXample 6 are dispersed in water, to a water to solids ratio by weight of 10 : 1. The resulting slurry i~ placed in a mold, 40 mm x 120 mm x 150 mm, and dewatered and shaped by a press to prepare a composite shaped body of amorphous silica and ealeium earbonate. The shaped body has the same structure as the eomposite shaped body described in Example 10.
In the same manner as in Example 10, the shaped body is immersed in a 6N HCl solution for aeid treatment, then washed with water to eompletely dissolve out the ealeium ehloride formed and thereafter dried to obtain ;~ an Opsil-IIS of this invention.
The Opsil-IIS has substantially the same structùre and form as the Opsil-IIS obtained in EXample 10.
~he properties of the Opsil-IIS are as follows.
Bulk density 0.13 g/em~
Bending strength 5 kg/em Compression strength 10 kg/em2 Porosity 92 %
~l~L2~3172 Example 17 The Opsil-I obtained in Example 1 is dispersed in water in a water to solids ratio by weight of 5 : 1, The mixture is placed in a mold, dewatered and shaped by a prsss with varying shaping pressures, followed by drying. The physical properties of the shaped body (Opsil-IS) thus obtained are as follows.
Sample No.
Bulk density (g/cm3) 0.15 0.38 95 (kg7cm~) 4.2 18.0 43.2 ~ompression -, strength 7,3 23.5 61.0 (kg/cm2) - Porosity (/~) 92.5 61.0 52.5 Specific2/su)rface 340 338 330 .. : .:
Example 18 ~ he Opsil-l obtained in ~xample 2 iB dispersed in water in a water to solids ratio by weight of 5 : lo The mixture is placed in a mold, dewatered and shaped by a press with ~arying shaping pressures, followed by drying. ~he physical properties of the shaped body (Opsil-IS) thus obtained are as follows.
~ . . .
~3~7~
Sample No.
Bulk density (g/cm~) 0.1~ 0.50 Bending strength ~kg/cm ~ 4.0 25 Compression strength tkg/c~2) 5.2 ~5 ~orosity (/~) 93,5 75.0 Specific surface area 2 ~ 280 268 (m /g) - Example 19 Quick lime and siliceous sand powder in a CaO to SiO2 mole ratio of 0.98 : 1 are dispersed in water to prepare a slurry having a water to solids ratio by weight . 10 of 5 : 1. The slurry is swollen with stirring at 100 D C
for 5 hours, then press-molded and thereafter subjected in an autoclave to hydrothermal reaction at 15 kg/cm? at 200 C for 10 hours to obtain a shaped body with a bulk ~ density of 0.~5 g/cm3.
15~ The x-ra~ diffraction of the shaped body reveals the diffraction peaks (2e) peculiar to xonotlite crystals at 12.7, 27.6 and 29Ø Elementary analysis also confirms that the shaped body is composed of xonotlite crystals. When 8 fractured surface of the shaped body is obser~ed under an electron microscope, it is ascertained that the bod;y is formed from numerous needle-like xonotlite crystals randomly three-dimensionally interlocked with one - - .
- - ~
~23~7~
another to an integral mass.
In the same manner as in Examole 10, the shaped bod~ of xonotlite is placed, in a water to solids ratio by weight of 2 : 1, in a closed container. Carbon dioxide gas is froced into the container at an internal pressure of ~ kg~cm for about 30 minutes.
- The x-ray diffraction of the resulting shaped body shows exactly the same result as given in ~ig. l(B), revealing the diffraction peaks due to calcium carbonate.
Observation under an electron microscope further shows that the shaped body retains the original structure of xonotlite shaped body used as the starting material.
Thus the product is identified as a composite shaped body of amorphous silica and calcium carbonate which comprises amorphous silica having the original configuration of the xonotlite crystals and extremel~ fine particles of calcium carbonate attached thereto.
In the same manner as in Example 10, the "\ composite shaped body is immersed in a 6N HC1 solution for one minute, then thoroughl~ washed with water to completel~ dissolve out the resulting calcium chloride and thereafter dried, whereby an Opsil-IS of this invention is obtained.
The x-ra~ diffraction of the Opsil-IS shows the same result 8S given in Fig. l(C), indicating no diffraction peaks. The analysis of the product further .
..
3gL7;~
reveals that the SiO2 content is not lower than 99%, indicating that the Opsil-IS is composed of amorphous silica of high purity. The scanning electron micrograph of Fig. 8, showing a fractured surface Or the Opsil-IS
at a magnification of 1,000~, indicates that in structure the Opsil-IS is substantially indentical to the starting material,i.e. xonotlite shaped body, and to the composite shaped body of amorphous silica and calcium carbonate obtained-by carbonating the material. More specifically, the product is formed from the particles of amorphous silica (Opsil-I) which are randoml~ three-dimensionally interlocked with one another into an integral mass and which have at least two surfaces in symmetric relation, a length of about 1 to about 20 ~, a thickness f about 0.02 to about 0.1 ~ and a width of about 0.02 to about 1.0 ~, the length being at least about 10 times the thicknesQ.
The Opsil-IS has the following properties.
Bulk density 0.20 g/cm3 Specific surface area251 m2/g Compression strength5 kg/cm2 Poro 9i ty 9 %
~xample 20 Commercial autoclave light-weight cOhcrete containing about 80 wt.% Or tobermorite ana about 20 wt.%
of quartz and having a bulk density of 0.63 g/cm~ is ~, .
.
..... .... ...
23~
immersed in water ~or l hour and placed in a closed vessel.
The concrete is subjected to carbonation and acid treatment in the same manner as in Example lO, followed by drying, to obtain shaped body of the invention. X-ray diffraction shows only the diffraction peaks (20) of quartz at 26.7 and 20 8 D, This evidences that the tobermerite is converted to amorphous silica. The analysis shows the product contains SiO2 in a purity of not lower than 98 yO. The shaped body is cut along planes vertical and parallel to the direction of the shaping pressure. ~he scanning electron micrographs of the cut surfaces indicate that the shaped body is formed of numerous plate-like amorphous silica particles randomly three-dimensionally interlocked with one another and substantiall~ circular pores of a diameter of less than l mm. ~he properties of the shaped body are as follows.
Bulk density 0.30 g/cm3 Specific surface area 301 m2/g 20\ Compression strength 12 kg~cm2 Porosity 85 %
- 89 - ~
.
The Opsil-IIS prepared as above has the following properties.
Bulk density 0.09 g/cm2 Specific surface area 288 m2/g 10- Compres6ion strength 6 kg/cm2 Porosity 95%
The Op6il-IIS prepared as above, when fired in an electric oven at 1000 C for 1 hour, gives a contraction:
- of about 12%, but no changes are observed in the compressedglobular form of Opsil-II constituting the ~haped body.
The properties of the fired product are as follows~
Bulk den~ity 0.085 g~m2 Compression Strength 10 kg/cm2 ~ Porofiity 95%
20- The fired product has a thermal expansion coefficient of 5.7 x 10 7~oc and exhibits substantially no expan~ion and contractio~ in repeated heating tests conducted at 950 C.
Further, Opsil-IIS having a bulk den~ity of 0.3 g/cm2 i~ prepared in th~ same manner as above except that a shaped b~dy of xonotlite crystals having a bulk density of 0.62g/c ~ , which i~ prepared in the 6ame manner as in Reference Example 1 with increased ~haping pressure, is employed a6 a starting material~ The Op~ IIS is cut along a plane vertical to .. . , .:
~ ~3~
the direction of the shaping pressure~ The scanning electron micrograph of the cut surface indicates that the Opsil-II constituting the shaped body has been compressed with the lath-like Opsil-I particles oriented in a direction vertical to the direction of the pressure applied. Thls structure is the same as that~of the st~r~ing xonotlite sha~ed body. The properties of Opsil-IIS are as follows:
Bulk density ~ 0 3 g/cm3 Specific surface area 290 m2/g Compression strength 15 kg/cm2 Porosity 85%
Example ll The tobermorite shaped body (bulk density: 0.3 ~cm3) obtained in Reference Example 2 is placed ~lith water, in a water to solids ratio by weight o 2:1, in a closed container.
Carbon dioxide gas is forced into the container to maintain an internal pressure of 3 kg/cm2 for about ~0 minutes for - carbonation.
\ The reaction, followed by drying, gives a composite shaped body of amorphous silica and calcium carbonate~
A fractured surface of the shaped body is observed under a scanning electron microscope with the same result as given in Fig. 7~B), which shows that the shaped body has exactly the same structure a~ the starting material, i.e. tobermorite shaped body. It is found that the shaped body is formed from globular secondary particles which are compressed and interlocked with one another and firmly into an integral mass, the composite body thus retaining the original structure of the starting material intact.
. _ . .
Furthermore, the primary particles forming the ~econdary partlcles are found to have the same form as shown in Fig.
3(B) by electron microscopic observation and have the same diffraction peaks peculiar to calciura carbonate according to x-ray diffraction. Thus the product is a composite ~haped body made up of plate-like particles of amorphous ~ilica and extremely ~ine particles of calcium carbonate attached thereto.
Subsequently, the composite shaped body i~ immersed in a 6N HCl solution for one minute. Simultaneously with the immer~ion, carbon dioxide gas evolves and the calcium carbonate in the shaped body is converted to calcium chloride.
- The shaped body is then thoroughly washed with water to completely dissolve out the resulting calcium chloride and is thereafter dried to give Opsil-IIS of thi~ invention~
X-ray diffraction confirms that the Op~il-IIS, like Opsll-I and Opsll-II, is amorphous.
Observation under a scanning electron mlcroscope gives the ~ame result a~ shown in Fig. 7(C), indicatlng that in structure the Opsil-IIS substantially resembles the ~tarting material, namely tobermorite ~haped body and the composite shaped body obtained by carbonating the material. The substantially globular particles of Opsil-II, ranging from about 10 to about 60 J~in diameter, are compressed and interlocked with one another forming the integral body of the Opsil-IIS.
~. .
- 79 - ~
f --~3~7~
The Opsil-IIS prepared as above has the following properties.
Bulk den~ity 0.13 g/cm2 - Specific surface area 277 m2/g Compression strength 4 kg/cm Porosity 93%
Example 12 The shaped body (bulk density: 0.3 g/cm3) of calcium silicate (CSHn) obtained in Reference Example 3 is placed with water in a water to solids ratio by weight of 2:1, in a closed container. Carbon dioxide gas is forced into the container to maintain an internal pressure of 3 kg/cm2 for about 30 minutes for carbonation.
The reaction, followed by drying, gives a composite shaped body of amorphous silica and calcium carbonateO
A ~ractured surface of the shaped body is observed under a scanning electron microscope with the same result as given in Fig. 7(B), which shows that the composite shaped body has exactly the same structure as the starting material, 20 ~ i.e. CSHn shaped body. It is found that the shaped body is formed form globular secondary particles which are compre~sed and interlocked with one another and firmly into an integral mass~ the composite body thus retaining the original structure of the starting material intact. Furthermore, the primary pa~ticles forming the secondary particles are found to have the same form as foil-like particle peculiar to CSHn by .23~7%
electron mlcroscopic observation and have the same diffraction peaks peculiar to calcium carbonate according to x-ray diffraction. Thus the product is a composite shaped body made up of foil-like particles of amophous silica and extremely fine particles of calcium carbonate attached theretoO
- Subsequently9 the composite shaped body is irnmersed in a 6N HCl solution for one minute~ Simultaneously with the immersion, car~bon dioxide gas evolves and the calcium carbonate in the shaped body is converted to calcium chloride.
10- The shaped body is then thoroughly washed with water to completely dissolve out the resulting calcium chIoride and is thereafter dried to give Opsil-IIS of this invention.
X-ray diffraction confirms that the Opsil-IIS, like Opsil-I and Opsil-II, is amorphous.
Observation under a scanning electron microscope gives the same result as shown in Fig. 7(C) 9 indicating that in structure the Opsil-IIS substantially resem~les the starting materlal, namely CSHn shaped body and the composite ~haped body obtalned by carbonating the material. The substantially globular particles of Opsil-II, ranging from about 10 to about 60y~ are compressed and interlocked with one another, forming the integ~al body of the Opsil-IIS.
The Opsil-IIS prepared as above has the following properties.
.,- .. , , . :,.
~3~72 Bulk den~ity 0.14 g/cm2 Specific surface area 461 m2/g Compre~ion ~trength 4 kg/cm Poro~ity 82%
7~
Example 13 The powder of Opsil-II (100 wt. parts) obtained in Example 6 and 2 wt. parts of glass fibers are dispersed in water to a water to solids ratio by weight of 10:1, to prepare a slurry. The slurry is placed in a mold, 40 mm x 120 mm x 150 mm, and then dewatered by a press. The shaped mass is removed from the mold and dried at 105 C for 24 hours to obtain a shaped body of this invention, i.e. Opsil-IIS, having the following properties.
10 Bulk density 0.11 g/cm3 Bending strength 6 kg/cm2 Compression strength 9 kg/cm2 Porosity 93%
Example 14 The Opsil-II obtained in Example 7 is shaped in the same manner as in Example 13 to prepare a shaped body of this invention, i.e. Opsil-IIS, having the following properties.
Bulk density 0.15 g/cm3 Bending strength 4.5 kg/cm 20 Compression strength 7 kg/cm2 Porosity 91%
Example 15 The Opsil-II obtained in Example 8 is shaped in the same manner as in Example 13 to prepare an Opsil-IIS of this invention having the following properties.
2~ 72 Bulk density 0.21 g/cm3 Bend1ng strengt~ 2.3 kg/em2 Compression strength 4 kg/cm Porosity 88 %
~xample 16 The eomposite secondary particles of amorphous silica and calcium carbonate obtained by the first step of EXample 6 are dispersed in water, to a water to solids ratio by weight of 10 : 1. The resulting slurry i~ placed in a mold, 40 mm x 120 mm x 150 mm, and dewatered and shaped by a press to prepare a composite shaped body of amorphous silica and ealeium earbonate. The shaped body has the same structure as the eomposite shaped body described in Example 10.
In the same manner as in Example 10, the shaped body is immersed in a 6N HCl solution for aeid treatment, then washed with water to eompletely dissolve out the ealeium ehloride formed and thereafter dried to obtain ;~ an Opsil-IIS of this invention.
The Opsil-IIS has substantially the same structùre and form as the Opsil-IIS obtained in EXample 10.
~he properties of the Opsil-IIS are as follows.
Bulk density 0.13 g/em~
Bending strength 5 kg/em Compression strength 10 kg/em2 Porosity 92 %
~l~L2~3172 Example 17 The Opsil-I obtained in Example 1 is dispersed in water in a water to solids ratio by weight of 5 : 1, The mixture is placed in a mold, dewatered and shaped by a prsss with varying shaping pressures, followed by drying. The physical properties of the shaped body (Opsil-IS) thus obtained are as follows.
Sample No.
Bulk density (g/cm3) 0.15 0.38 95 (kg7cm~) 4.2 18.0 43.2 ~ompression -, strength 7,3 23.5 61.0 (kg/cm2) - Porosity (/~) 92.5 61.0 52.5 Specific2/su)rface 340 338 330 .. : .:
Example 18 ~ he Opsil-l obtained in ~xample 2 iB dispersed in water in a water to solids ratio by weight of 5 : lo The mixture is placed in a mold, dewatered and shaped by a press with ~arying shaping pressures, followed by drying. ~he physical properties of the shaped body (Opsil-IS) thus obtained are as follows.
~ . . .
~3~7~
Sample No.
Bulk density (g/cm~) 0.1~ 0.50 Bending strength ~kg/cm ~ 4.0 25 Compression strength tkg/c~2) 5.2 ~5 ~orosity (/~) 93,5 75.0 Specific surface area 2 ~ 280 268 (m /g) - Example 19 Quick lime and siliceous sand powder in a CaO to SiO2 mole ratio of 0.98 : 1 are dispersed in water to prepare a slurry having a water to solids ratio by weight . 10 of 5 : 1. The slurry is swollen with stirring at 100 D C
for 5 hours, then press-molded and thereafter subjected in an autoclave to hydrothermal reaction at 15 kg/cm? at 200 C for 10 hours to obtain a shaped body with a bulk ~ density of 0.~5 g/cm3.
15~ The x-ra~ diffraction of the shaped body reveals the diffraction peaks (2e) peculiar to xonotlite crystals at 12.7, 27.6 and 29Ø Elementary analysis also confirms that the shaped body is composed of xonotlite crystals. When 8 fractured surface of the shaped body is obser~ed under an electron microscope, it is ascertained that the bod;y is formed from numerous needle-like xonotlite crystals randomly three-dimensionally interlocked with one - - .
- - ~
~23~7~
another to an integral mass.
In the same manner as in Examole 10, the shaped bod~ of xonotlite is placed, in a water to solids ratio by weight of 2 : 1, in a closed container. Carbon dioxide gas is froced into the container at an internal pressure of ~ kg~cm for about 30 minutes.
- The x-ray diffraction of the resulting shaped body shows exactly the same result as given in ~ig. l(B), revealing the diffraction peaks due to calcium carbonate.
Observation under an electron microscope further shows that the shaped body retains the original structure of xonotlite shaped body used as the starting material.
Thus the product is identified as a composite shaped body of amorphous silica and calcium carbonate which comprises amorphous silica having the original configuration of the xonotlite crystals and extremel~ fine particles of calcium carbonate attached thereto.
In the same manner as in Example 10, the "\ composite shaped body is immersed in a 6N HC1 solution for one minute, then thoroughl~ washed with water to completel~ dissolve out the resulting calcium chloride and thereafter dried, whereby an Opsil-IS of this invention is obtained.
The x-ra~ diffraction of the Opsil-IS shows the same result 8S given in Fig. l(C), indicating no diffraction peaks. The analysis of the product further .
..
3gL7;~
reveals that the SiO2 content is not lower than 99%, indicating that the Opsil-IS is composed of amorphous silica of high purity. The scanning electron micrograph of Fig. 8, showing a fractured surface Or the Opsil-IS
at a magnification of 1,000~, indicates that in structure the Opsil-IS is substantially indentical to the starting material,i.e. xonotlite shaped body, and to the composite shaped body of amorphous silica and calcium carbonate obtained-by carbonating the material. More specifically, the product is formed from the particles of amorphous silica (Opsil-I) which are randoml~ three-dimensionally interlocked with one another into an integral mass and which have at least two surfaces in symmetric relation, a length of about 1 to about 20 ~, a thickness f about 0.02 to about 0.1 ~ and a width of about 0.02 to about 1.0 ~, the length being at least about 10 times the thicknesQ.
The Opsil-IS has the following properties.
Bulk density 0.20 g/cm3 Specific surface area251 m2/g Compression strength5 kg/cm2 Poro 9i ty 9 %
~xample 20 Commercial autoclave light-weight cOhcrete containing about 80 wt.% Or tobermorite ana about 20 wt.%
of quartz and having a bulk density of 0.63 g/cm~ is ~, .
.
..... .... ...
23~
immersed in water ~or l hour and placed in a closed vessel.
The concrete is subjected to carbonation and acid treatment in the same manner as in Example lO, followed by drying, to obtain shaped body of the invention. X-ray diffraction shows only the diffraction peaks (20) of quartz at 26.7 and 20 8 D, This evidences that the tobermerite is converted to amorphous silica. The analysis shows the product contains SiO2 in a purity of not lower than 98 yO. The shaped body is cut along planes vertical and parallel to the direction of the shaping pressure. ~he scanning electron micrographs of the cut surfaces indicate that the shaped body is formed of numerous plate-like amorphous silica particles randomly three-dimensionally interlocked with one another and substantiall~ circular pores of a diameter of less than l mm. ~he properties of the shaped body are as follows.
Bulk density 0.30 g/cm3 Specific surface area 301 m2/g 20\ Compression strength 12 kg~cm2 Porosity 85 %
- 89 - ~
.
Claims (11)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A shaped body of amorphous silica comprising secondary particles of amorphous silica compressed in at least one direction and interlocked with one another integrally into the body and voids interspersed therebetween, the secondary particle being composed of numerous primary particles of amor-phous silica randomly three-dimensionally interlocked with one another, each of the primary particles having a crystalline appearance, at least two surfaces in symmetric relation, a length of about 1 to about 500µ and a thickness of about 50 .ANG.
to about 1µ, the length being at least about ten times the thickness.
to about 1µ, the length being at least about ten times the thickness.
2. A shaped body as claimed in claim 1, which has a porosity of at least about 50%.
3. A shaped body as claimed in claim 1, wherein the primary particles are about 1 to about 300µ in length and about 100 .ANG. to about 1µ in thickness, the length being about 10 to about 5,000 times the thickness.
4. A shaped body as claimed in claim 1, which contains a fibrous reinforcing material.
5. A shaped body as claimed in claim 1, which contains clay.
6. A shaped body as claimed in claim 1, which contains cement.
7. A method of preparing a shaped body of amorphous silica having a crystalline appearance comprising the steps of contacting calcium silicate crystals with carbon dioxide in the presence of water to convert the calcium silicate into amorphous silica having the configuration of the calcium silicate crystals and extremely fine particles of calcium carbonate, contacting the resulting product with an acid to decompose the calcium carbonate to carbon dioxide and calcium salt, and separating the amorphous silica from the calcium salt, the calcium silicate crystals being in the form of a shaped body comprising numerous secondary particles of calcium silicate compressed in at least one direction and interlocked with one another integrally into the body, and voids interspersed therebetween, the secondary particle being composed of numerous primary particles of calcium silicate randomly three-dimensionally interlocked with one another, each of the primary particles hav-ing a length of about 1 to about 500 µ and a thickness of about 50 .ANG. to about 1 µ, the length being at least about 10 times the thickness, the amorphous silica being in the form of a shaped body retaining the form of the shaped body and of the secondary particle and the configuration of the constituent primary particle of calcium silicate.
8. A method as claimed in claim 7 wherein the amount of water is 1 to 50 times the weight of solids.
9. A method as claimed in claim 7 wherein the acid has no reactivity with silica and is capable of decomposing calcium carbonate into a water-soluble calcium salt and carbon dioxide.
10. A shaped body of amorphous silica and calcium car-bonate comprising numerous amorphous silica-calcium carbonate composite secondary particles being compressed to at least one direction and interlocked with one another and voids interspersed therebetween, each of the composite secondary particles comprising an amorphous silica particle in the form of a primary particle and extremely fine particle of calcium carbonate attached to the amorphous silica particle, the amorphous silica particle having a crystalline appearance, at least two surfaces in symmetric relation, a length of about 1 to about 500 µ and a thickness of about 50 .ANG. to about 1 µ, the length being at least about 10 times the thickness.
11. A method of preparing a shaped body of amorphous silica having a crystalline appearance and calcium carbonate comprising the steps of contacting calcium silicate crystals with carbon dioxide in the presence of water to con-vert the calcium silicate into amorphous silica having the con-figuration of the calcium silicate crystals and extremely fine particles of calcium carbonate attached to the amorphous silica particles, the calcium silicate crystals being in the form of a shaped body comprising numerous secondary particles of calcium silicate compressed in at least one direction and interlocked with one another integrally into the body, and voids interspersed therebetween each of the secondary particles being composed of numerous primary particles of calcium silicate randomly three-dimensionally interlocked with one another, each of the primary having a length of about 1 to about 500 µ and a thickness of about 50 .ANG. to about 1 µ, the length being at least about 10 times the thickness, the amorphous silica being in the form of a shaped body retaining the forms of the shaped body and of the secondary particle and the configuration of the constituent primary particle of calcium silicate, the amorphous silica having calcium carbon-ate attached thereto.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA358,847A CA1123172A (en) | 1975-03-25 | 1980-08-22 | Amorphous silica, products thereof and methods of preparing the same |
Applications Claiming Priority (8)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP50036298A JPS51125699A (en) | 1975-03-25 | 1975-03-25 | The production of moldable high purity and porous silica gel secondary particles |
| JP3630075A JPS528024A (en) | 1975-03-25 | 1975-03-25 | Manufacturing of porous silica gel plastics |
| JP36300 | 1975-03-25 | ||
| JP3629975A JPS528023A (en) | 1975-03-25 | 1975-03-25 | Method of manufacturing high purity porous silica gel mouldings |
| JP36298 | 1975-03-25 | ||
| JP36299 | 1975-03-25 | ||
| CA248,633A CA1097030A (en) | 1975-03-25 | 1976-03-24 | Amorphous silica, products thereof and methods of preparing the same |
| CA358,847A CA1123172A (en) | 1975-03-25 | 1980-08-22 | Amorphous silica, products thereof and methods of preparing the same |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1123172A true CA1123172A (en) | 1982-05-11 |
Family
ID=27508060
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA358,847A Expired CA1123172A (en) | 1975-03-25 | 1980-08-22 | Amorphous silica, products thereof and methods of preparing the same |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1123172A (en) |
-
1980
- 1980-08-22 CA CA358,847A patent/CA1123172A/en not_active Expired
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