GB2222823A - A process for producing high purity silica - Google Patents
A process for producing high purity silica Download PDFInfo
- Publication number
- GB2222823A GB2222823A GB8821722A GB8821722A GB2222823A GB 2222823 A GB2222823 A GB 2222823A GB 8821722 A GB8821722 A GB 8821722A GB 8821722 A GB8821722 A GB 8821722A GB 2222823 A GB2222823 A GB 2222823A
- Authority
- GB
- United Kingdom
- Prior art keywords
- silica
- aqueous solution
- mineral acid
- high purity
- acid solution
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/113—Silicon oxides; Hydrates thereof
- C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
- C01B33/18—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof
- C01B33/187—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by acidic treatment of silicates
- C01B33/193—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by acidic treatment of silicates of aqueous solutions of silicates
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/02—Amorphous compounds
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/50—Agglomerated particles
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/12—Surface area
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/19—Oil-absorption capacity, e.g. DBP values
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
- C01P2006/82—Compositional purity water content
Description
. r r 2)28,.'-2- c- j 1 A PROCESS FOR PRODUCING HIGH PURITY SILICA
This invention relates to a process for producing high purity silica from alkali silicate aqueous solution. More particularly, it relates to a process for producing high purity silica from cheap water glass for industrial use, which commonly contains more than 2000 ppm of impurities in total, by effectively removing metals, such as Al, Fe, and Ti, alkali metals, such as Na, or radioactive elements, such as U. Prior Art
Recently, the demand for silica used as functional, optical, or electronic materials has been increasing so rapidly that it is becoming more and more difficult to use natural silica as it is, in view of the purity, shape, or property it is required to have for its individual use. Especially, for use in plastic fillers for IC sealants, such low radioactive, high purity silica is required that artificial silica is produced by various processes in order to meet the increasing demand.
In the meantime, when high purity silica is desired, there have so far been employed such processes as follows. (1) Most general process so far used: chemical treatment melting and pulverization process of high purity natural silica or quartz cx2ntamu-ng less radioactive elements, such as U or Th (2) Process of causing deliberately purified silicon tetrachloride to react with oxygen in the oxy-hydrogen flame 1 or process of hydrolyzing and then sintering silicate alkoxides, such as tetraethylsilicate. (3) Process of treating an alkali silicate aqueous solution with an ion-exchange resin and then removing impurities before collecting silica (4) Process of rinsing silica, produced from the reaction of an alkali silicate aqueous solution and a mineral acid solution which contains a chelating agent.and hydrogen peroxide, with a mineral acid solution which contains a chelating agent and hydrogen peroxide (Japanese patent application laid-open publication sho 62-12608) These processes are all designed to produce high purity silica. Despite that, silica produced by the process (1) contains about 30 ppm of Al, 2 ppm of Fe, 3 ppm of Ti, 3 ppm of Na, 1 ppm of K, and 1-10 ppb of U; hence, it does not fit at all for plastic fillers for IC sealants used in an integrated circuit of 256 kilobits and above.
On the contrary, silica produced by the process (2) is certainly of very high purity since puritied raw material is used. But the material itself is so expensive that in fact the silica cannot be put to general use, except for some limited special'purposes.
In the case of the process (3), the SiO 2 content in alkali silicate aqueous solution has to be reduced to less than 10 percent by weight in advance of purification; thus, the production efficiency becomes very low, in terms of the apparatus to be used therefor. Moreover, because the silica- 1L.1 111 o& 1 precipitating operation is complex and the refreshing process of ion- exchange resin has trouble in itself, this process has problems in productivity.
According to the process (4), JIS-standardized No. 3 alkali silicate aqueous solution, which contains as high as 28.5 percent by weight of SiO 21 is used; however, it has to be added to a mineral acid solution slowly in order to precipitate silica. What is more, thesilica precipitate has to be kept standing at 80 C for as long as 2 hours for ageing, because this is indispensable for silica dissolving in the mineral acid solution to fully precipitate. Furthermore, after filtered out, silica has to be rinsed in acid at 90 OC for as long as 3 hours to remove impurities.
As apparent from the above, as long as conventional processes are employed, there are always problems whatsoever. Generally speaking, when it comes to a high purity product, mostly there have been proposed many production processes for that product in relation to the purity of its material. However, as far as the production process of silica is concerned, there is no such disclosure that it can be said that conventic; nal problems have not been fully solved yet. Summary of the Invention
Under the circumstances, the present Inventors made intensive studies to eliminate conventional problems in the production process of silica and finally accomplished this invention by finding a process for producting high purity silica very simply from a cheap alkali silicate aqueous solu1 tion for industrial use. That is, according to this invention, an alkali silicate aqueous solution available on the market as water glass, of which the SiO 2 /Na 2 0 molar ratio is in the range 1-4, can be used as material as it is. Moreover, silica can be precipitated by directly adding the material to a mineral acid solution, such as hydrochloric acid, nitric acid, and sulfuric acid, wherein the mineral acid solution can be used singly or in combination'with one another.
Incidentally, a great feature of this invention is in rapidly forming silica precipitate while dissolving impurities in the mineral acid solution, by previously adjusting the viscosity of the alkali silicate aqueous solution in such a way that silica may not disperse and dissolve in the mineral acid. In order that this invention may be more clearly understood, reference will now be made to the production process of silica according to this invention, which essentially comprises the following two sub-processes. (1) Viscosity adjustment of an alkali silicate aqueous solution Generally, the neutralization reaction of an alkali silicate aqueous solution and a mineral acid solution gives rise to silica precipitate. When the acidity of the mineral acid solution is strong, silica does not almost precipitate because it dissolves in the solution. This phenomenon is remarkable, especially when the SiO 2 content in the alkali aqueous solution is less than about 10 percent by weight.
1A However, the dissolution of silica in the mineral acid solution becomes slow with the increase of the viscosity or the increase of SiO 2 content in the alkali silicate aqueous solution.
An alkali silicate aqueous solution available on the market commonly contains about 30 percent by weight of S'02 and has a viscosity of about 5 poise. if the alkali silicate aqueous solution is put in a mineral acid solution as it is, almost all of it dissolve in the solution. However, the present inventor has come up with the fact that those having a viscosity of 10 poise and above liberate alkali metal and impurities, and allow only silica to precipitate in a mineral acid solution, almost in a moment from a few seconds to a few minutes after both mixed, whereas those having a viscosity of 10000 poise and above liberate alkali metal in a mineral acid solution but cause other metal impurities to mingle with silica precipitate. For this reason, he has decided to use an alkali silicate aqueous solution whose viscosity has been adjusted in such a way as to promote the neutralization reaction and liberate impurities. Accordingly, the viscosity of an alkali silicate aqueous solution is desirable to be in the range 10-10000 poise, and particularly more desirable to be in the range 10-3000 poise.
In order to increase its viscosity, an alkali silicate aqueous solution is made polymerize or allowed to contain an organic polymer according to this invention. As for the polymerization, the partial polymerization process by means - 6 of acid substance, the dehydration-condensation process, or the polyvalent metal addition process can be employed, for example. But# in view of the production of high purity silica, it is disadvantageous to add a substance that lgter makes impurity@ whichever the substancemay be orgaic or inorganic. Moreover. the simpler the process is the more advantageous it is.for commercialization. Thus, the dehydrationcondensation process is considered the best of all in this case. In the meantime, the viscosity of an alkali silicate aqueous solution characteristically increases with the removal of a few percent of water therefrom; therefore, evaporation by either heating, evacuating, or microwave heating may be applied to the dehydration-condensation process. (2) Production of high purity silica An alkali silicate aqueous solution whose viscosity has been appropriately adjusted in accordance with the above is added to a mineral acid solution whose normal is adjusted to 1 or more in order that out of the silicate solution, alkali metal and other metal impurities may dissolve in the mineral acid solution and silica may precipitate through gelation reactionb The rate of adding an alkali silicate. aqueous solution to a mineral acid solution is not entirely limited; that is, the former can be mixed in the latter in a short period of time, from a few seconds to a few minutes, for example. If, however, an alkali silicate aqueous solution is used as it is, without.previously adjusting its viscosity, almost all silicate dissolve in a mineral acid solu- tion, with the result that the production yield of silica becomes extremely low. Thus, if silica is desired to precipitate with no adjusting the viscosity of an alkali silicate aqueous solution, heating and ageing the solution mixture for a long time become necessary. Also, silica precipitate thus produced contains so much water that the content of impurities involved in the silica with water inevitably increases as much. As a result, the silica has to be rinsed with acid more thoroughly in the next process in order to remove such impurities. Considering these unnecessary operations to be made later, it will become apparent what an important role the viscosity adjustment plays in this invention.
Among mineral acids to be used in association with an alkali silicate aqueous solution are hydrochloric acid, nitric acid, sulfuric acid, and the like; they can be used singly or in combination with one oanother. In addition to these, spent mineral acid solution after the next acidrinsing process can also be recycled in the same way as a fresh mineral acid solution. Nonetheless, aconsidering the reactor material to withstand.the acid action or the'cost thereof, it is desirable to use sulfuric acid or nitric acid.
It is certainly effective to add a chelating agents such as EDTA, commonly used for the chemical analysis, to stabilize metal impurities in the mineral acid solution, or add hydrogen peroxide, commonly used for Ti chemical analysis, to fully remove Ti in the mineral acid, but they have 1 not so much importance in this invention. In terms of reaction kinetics, the higher the reaction temperature, the more effectively the silica production can be carried out, as a matter of course. According to this invention, however, there is particularly no need of restricting the reaction temperature.
After having been filtered out, silica precipitate is simply'rinsed with water, filtered out, and then transferred to the next acid-rinsing process, where the silica precipitate is rinsed in acid solution with stirring, wherein the word acid is meant to specify inorganic acids, such as hydrochloric acid, nitric acid, and sulfuric acid, and organic acids, such as formic acid. Nonetheless, virtually, it is desirable to use sulfuric acid or nitirc acid in the acidrinsing process. And, the acid concentration is preferable to be not less than 0.5 normal, while the rinsing temperature and duration are not so significant factors.
High purity silica, as it contains water, is produced after the acidrinsing process, which is followed by filtration, simple water-rinsing and filtration. The acid-rinsing process may be carried out more than once, if necessary. The silica is dried,-and then sintered at 1100 OC in such a way as to fully remove water, before collected as product. Example 1 In order to remove water, 3330g of JIS-standardized No.3 water glass available on the market, which contains 29.5 percent by weight of SiO 2 and 9.8 percent by weight ii of Na 2 0, is heated at 100 C for about 3 hours; as a result, it weighs 3100 g. The SiO 2 content in the water glass is 32 percent by weight; the solution viscosity of the water 9 glass is about 100 poise at 30 C.
The water glass solution is added to 10 1 of 21.7 % (by weight) nitiric acid aqueous solution containing 50 9 of 35 % (by weight) hydrogen peroxide, extending over about 1 minute. Then, there appears silica precipitate.
After filtered out, the silica precipitate is rinsed twice withabout 10 1 of pure water and then filtered out. It is put in 5 1 of 32.5 % (by weight) nitric acid aqueous solution containing 1.5 g of EDTA, and 30 g of 35 % (by weight) hydrogen peroxide, heated at 70 OC for 1 hour with stirring, and filtered out. It is further rinsed twice with about 5 1 of pure water, dried, and sintered at 1100 C for 2 hours. As a result, it gives 9509 of high purity silica. Impurities contained in the silica are shown in Table 1, together with those in the raw water glass. Example 2 Raw water glass, the viscosity of which is adjusted in the same way as in Example I is added to 7 1 of 16.3 (by weight) sulfuric acid aqueous solution containing 50 g of 35 S (by weight) hydrogen peroxide, extending over 1 minute. The solution mixture is stirred at 50 C for 20 minutes. Then, there appears silica precipitate.
After filtered out, the silica precipitate is rinsed twice with about 10 1 of pure water and then filtered out.
1 4 - 10 It is put in 3 1 of 24.5 % (by weight) sulfuric acid aqueous solution containing 1.5 g of EDTA and 30 g of 35 % (by weight) hydrogen peroxidey stirred at 70 C for 1 hour# and filtered out. It is further rinsed twice with about 5 1 of pure watert dried, and sintered at 1100 C for 2 hours. As a result, it gives Q609 of high purity silica.
Impurities cofitained in the silica are shown in Table 1. Comparative Example 1 Without previously adjusting the viscosity of the water glass, silica is produced in the same way as in Example 1. As a result,700 g of silica is obtained. Impurities contained in the silica are shown in Table 1.
As apparent from the above, according to this invention, it is possible to economically produce high purity silica with less than 5 ppm of total impurities from cheap water glass available on the market in a short period of time by means of very simple operations. Additionally, silica thus produced is so pure that it can be used in various industrial fields, such as optics, electronics# and chemical reactionsneeding high functional catalysers, as well as served as a material for the production of cheap and high purity quartz glass. Like thist considering the fact that naturali high purity silica has been running short these days, the significance of this invention enabling us to supply plentiful high purity silica is very great.
i a Comparative Example 2 3330g of water glass available is added to sulfuric acid aqueous solution ( H 2 so 4 contents 16.3 weight %) containing 1.5g of EDTA and 50g of 35% ( by Weight) hydrogen peroxide without previously adjusting the viscosity of the waterglass. Then there appears silica precipitate after aging at about 80 OC for 2 hours.
After filtered out,the silica precipitate is rinsed twice with about 10 1 of pure water and then filtered out. It is put in 3 1 of 24.5% (by weight) sulfuric acid aqueous solution containing 1.5g of EDTA and 30g of 35% (by weight) hydrolgen peroxide, stirred at 70 C for 1 hour, and filtered out. It is further rinsed twice with about 5 1 of pure water, dried, and sintered at 1100 C for 2 hours. As a result, it gives 8OOg of purity silica.
Impurities contained in the silica are shown in Table 1.
Table 1
Impurities in Raw Water in Produced Silica Glass Ex. 1 Ex. 2 Comp.Ex. 1 Comp.Ex.2 A1 (ppm) 1100 1.1 1.6 3.0 4.0 Fe 130 o.2 0.3 3.0 2.0 Ti 160 0.5 0.3 2.0 1.0 K 1 100 <0.1 <0.1 0.4 0.4 Na 'I <1.0 (1.0 6.3 9.0 Ca 100 <0.1 (0.1 0.7 0.8 Mg 100 <0.1 0.1 0.1 0.1 U (ppb) 102 C0.1 (0.1 0.7 0.5 Th +. 220 (0.1 (0.1 0.9 0.8 Sio 2 Yield (%) - 95 96 70 80 The quantity of impurities in raw water glass is calculated, given that S'02 is 100 percent by weight, except Na 2 0.
1 1 4 k, t
Claims (6)
1. A process for producing high purity silica having a total impurity amount of 5 ppm or less, which comprises adding an alkali silicate aqueous solution having a viscosity of 1 to 100 Pas (10 to 10 4 poise) directly to a mineral acid solution to dissolve impurities in said mineral acid solution and form a silica precipitate, and rinsing said silica precipitate with an acid solution.
2. A process according to claim 1 wherein the alkali silicate aqueous solution has a viscosity of 1 to 300 Pas (10 to 3000 poise).
3. A process according to claim 1, 2 or 3 wherein the mineral acid is at least one of hydrochloric acid, nitric acid and sulfuric acid.
4. A process according to claim 1, 2 or 3 wherein the silica precipitate is rinsed with an at least 0.5N acid solution.
5. A process according to any one of the preceding 1 claims wherein a mineral acid solution is used to rinse the silica precipitate.
6. A process according to claim 1 substantially as described with reference to Example 1 or 2.
1 Published 1990 at The Patent OMce. State House.803.? t High Ho3burn. London WMR4TP.Purthorcoples maybe ob-nedfromThapstantOMes. Sales Branch. StM&ry Cray, OrpinjWn.K=z'4R5 3RD- Printed by MuIUpI@z:tecbn1(iU9sItd. StMLry Cray. Kent. Com 1.87 9
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP12578587A JPS63291808A (en) | 1987-05-25 | 1987-05-25 | Production of high-purity silica |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8821722D0 GB8821722D0 (en) | 1988-10-19 |
| GB2222823A true GB2222823A (en) | 1990-03-21 |
| GB2222823B GB2222823B (en) | 1992-04-08 |
Family
ID=14918798
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8821722A Expired GB2222823B (en) | 1987-05-25 | 1988-09-16 | A process for producing high purity silica |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS63291808A (en) |
| DE (1) | DE3830777A1 (en) |
| FR (1) | FR2636938B1 (en) |
| GB (1) | GB2222823B (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0409167A2 (en) * | 1989-07-18 | 1991-01-23 | Nkk Corporation | High purity silica and method for producing high purity silica |
| WO2006125927A1 (en) * | 2005-05-27 | 2006-11-30 | Rhodia Chimie | Method of preparing precipitated silica, precipitated silica thus obtained and use thereof, for example as a filler in silicon matrices |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6375735B1 (en) * | 1996-05-06 | 2002-04-23 | Agritec, Inc. | Precipitated silicas, silica gels with and free of deposited carbon from caustic biomass ash solutions and processes |
| US7922989B2 (en) | 2006-03-15 | 2011-04-12 | Amendola Steven C | Method for making silicon for solar cells and other applications |
| DE102011004532A1 (en) * | 2011-02-22 | 2012-08-23 | Evonik Degussa Gmbh | High purity silica granules for quartz glass applications |
| JP5689038B2 (en) * | 2011-07-27 | 2015-03-25 | 太平洋セメント株式会社 | Method for producing high purity silica |
| DE102015113360A1 (en) * | 2015-08-13 | 2017-02-16 | Osram Opto Semiconductors Gmbh | Method for producing a conversion element |
| CN111039298B (en) * | 2020-01-13 | 2023-10-24 | 福建省三明正元化工有限公司 | Preparation method of high-dispersion silicon dioxide |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB215011A (en) * | 1923-04-26 | 1925-05-14 | Elektro Osmose Ag | Improved manufacture of amorphous silicic acid |
| GB561750A (en) * | 1942-11-27 | 1944-06-02 | Cole E K Ltd | Improvements in the manufacture of precipitated silica |
| GB719918A (en) * | 1951-12-11 | 1954-12-08 | Wyandotte Chemicals Corp | Production of pigment grade silica |
| GB745822A (en) * | 1951-10-09 | 1956-03-07 | Columbia Southern Chem Corp | Improvements in or relating to a method and process for preparing finely divided pigmentary silica |
| GB800694A (en) * | 1954-11-05 | 1958-09-03 | Columbia Southern Chem Corp | Improvements in or relating to silicas |
| GB1501905A (en) * | 1974-05-22 | 1978-02-22 | Huber Corp J M | Amorphous precipitated siliceous pigments and methods for their production |
| EP0206353A2 (en) * | 1985-06-27 | 1986-12-30 | Nitto Chemical Industry Co., Ltd. | Process for manufacturing high purity silica |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6025325B2 (en) * | 1977-06-17 | 1985-06-18 | 石川島播磨重工業株式会社 | Cylindrical object storage device |
| JPS6117416A (en) * | 1984-07-03 | 1986-01-25 | Nippon Chem Ind Co Ltd:The | High-purity silica and its preparation |
| JPS6212608A (en) * | 1985-07-11 | 1987-01-21 | Nippon Chem Ind Co Ltd:The | Silica of high purity and production thereof |
-
1987
- 1987-05-25 JP JP12578587A patent/JPS63291808A/en active Pending
-
1988
- 1988-09-09 DE DE19883830777 patent/DE3830777A1/en not_active Withdrawn
- 1988-09-16 GB GB8821722A patent/GB2222823B/en not_active Expired
- 1988-09-26 FR FR8812520A patent/FR2636938B1/en not_active Expired - Lifetime
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB215011A (en) * | 1923-04-26 | 1925-05-14 | Elektro Osmose Ag | Improved manufacture of amorphous silicic acid |
| GB561750A (en) * | 1942-11-27 | 1944-06-02 | Cole E K Ltd | Improvements in the manufacture of precipitated silica |
| GB745822A (en) * | 1951-10-09 | 1956-03-07 | Columbia Southern Chem Corp | Improvements in or relating to a method and process for preparing finely divided pigmentary silica |
| GB719918A (en) * | 1951-12-11 | 1954-12-08 | Wyandotte Chemicals Corp | Production of pigment grade silica |
| GB800694A (en) * | 1954-11-05 | 1958-09-03 | Columbia Southern Chem Corp | Improvements in or relating to silicas |
| GB1501905A (en) * | 1974-05-22 | 1978-02-22 | Huber Corp J M | Amorphous precipitated siliceous pigments and methods for their production |
| EP0206353A2 (en) * | 1985-06-27 | 1986-12-30 | Nitto Chemical Industry Co., Ltd. | Process for manufacturing high purity silica |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0409167A2 (en) * | 1989-07-18 | 1991-01-23 | Nkk Corporation | High purity silica and method for producing high purity silica |
| EP0409167A3 (en) * | 1989-07-18 | 1991-06-26 | Nkk Corporation | High purity silica and method for producing high purity silica |
| WO2006125927A1 (en) * | 2005-05-27 | 2006-11-30 | Rhodia Chimie | Method of preparing precipitated silica, precipitated silica thus obtained and use thereof, for example as a filler in silicon matrices |
| FR2886285A1 (en) * | 2005-05-27 | 2006-12-01 | Rhodia Chimie Sa | PROCESS FOR THE PREPARATION OF PRECIPITATED SILICA, PRECIPITATED SILICA AND USES, IN PARTICULAR AS CHARGING IN SILICONE MATRICES |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2222823B (en) | 1992-04-08 |
| FR2636938B1 (en) | 1992-03-06 |
| JPS63291808A (en) | 1988-11-29 |
| FR2636938A1 (en) | 1990-03-30 |
| GB8821722D0 (en) | 1988-10-19 |
| DE3830777A1 (en) | 1990-03-15 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19940916 |