Patented Oct. 9, 1945 2,386,337

UNITED STATES PATENT OFFICE 2,386,337 PROCESS FOR MAKENG IFNELY DIW DED SLCA Paul S. Moyer, deceased, late of Lake Forest, Ill., by Elizabeth F. Moyer, administratrix, Lake Forest, . No Drawing. Application October 25, 1941, Seria No. 46,582 10 Claims. (C. 23-182) The present invention relates to an improved in which, however, the sodium is still united with process for the manufacture of extremely finely the silicic acid component. The suspension is divided silica from Such materials as the alkali then neutralized until it is faintly acid. This silicates, and the product thus made. Primarily may be accomplished by any suitable acid-react the process involves the conversion of an aqueous ing material, or organic or mineral acid, but pref alkali silicate solution into particles of free silicic erably is accomplished by passing carbon dioxide acid, or silica, by the expedient of admixing the gas into and through the mixture. The bubbling Solution with a considerable volume of a Water of the carbon dioxide gas also serves as a means miscible organic liquid such as a ketone, alcohol, of agitating the mixture. The acid-reacting sub or the like, which has the effect of throwing the 10 stance used will unite with the sodium component silicate out of solution in the form of fine par of the silicate, forming the corresponding sodium ticles of the alkali silicate. salt. In the case of carbon dioxide, it will obvi The resulting suspension of particles is then ously be sodium carbonate; and, as sufficient car neutralized with an acid-reacting material So as bon dioxide is used to produce a faintly acid re to produce the free silicic acid, or silica, while at 5 action, most of the sodium carbonate will have the same time forming a Solution of the Sodium been changed over into bicarbonate. The result. salt of the particular acid-reacting material em ing suspension of free silica, then probably in the ployed. The silica thus produced is then filtered form of silicic acid, is filtered or otherwise treated off, washed substantially free from water-soluble to recover therefrom the free silicic acid particles, material, and then dried. The dry product may, 20 which are then washed, preferably by means of if desired, be lightly ground in order to re-sepa a mixture of methanol and water, having about rate it into its constituent particulate form in the same relative proportions of alcohol and Case there has been any formation of aggregates water as have been present in the mixture of the of particles into lumps. silicate solution and the alcohol. The reason for The material produced is characterized by being this is to avoid, if possible, re-solution of silicic in such finely divided form that the particles in acid or silica during the washing operation. The most cases are not much larger than 1.0 or 1.5 resulting filter cake, if filtration has been used microns and in any event very much smaller than as a separating means, is then dried and may be could be obtained by the grinding of ordinary lightly ground or separated back into its original Silica, rock, or sand. Moreover, the particles are particles. Substantially globular and free from sharp edges The filtrate as well as the wash-liquor are com and are hence desirable if the product is to be bined, thus producing an aqueous solution of, in used as a filler in paints or enamels, for example this case, Sodium carbonate and bicarbonate and as a base for application to metallic plates to alcohol. This solution is then fractionally dis Which lithographing or printing is to be applied. tilled to recover from it the therein contained As a more particular example of the method methanol, which of course may be re-used im of carrying out the present invention, for example, mediately in the further carrying out of the a solution of sodium silicate may be prepared, process-that is to say, for the treatment of fur containing approximately 10% of sodium silicate, 40 ther batches of silicate solution. The residue in which may be any of the commercially available the still, containing the sodium carbonate and forms of this commodity, but most advanta bicarbonate, is then evaporated to dryness, thus geously is in the form of water-glass. recovering the sodium salts. They either may be A Solution of sodium silicate containing about Sold or, quite advantageously, may be mixed with 10% of total solids-such as may, for instance. be 45 an appropriate amount of silica, as for example produced by diluting 190 grams of a 38% solution a high silica Sand, and heated therewith to gentle of sodium silicate with 800 c.c. of hot water, so fusion, thereby producing a new supply of sodium adjusted that the mixture will have a tempera silicate. As a result of the reaction between the ture of about 30° F.-may be poured into a mix Sodium carbonate and bicarbonate with the silica, ture of 800 c.c. of methyl alcohol (methanol) and 50 carbon dioxide will be liberated and thus may be 100 c. c. of water. The alcohol solution should employed for the further carrying out of the be rapidly stirred as the sodium silicate solution process. This gas may be stored to form a supply is introduced, the result being the separation of which may be passed into a subsequently made very finely divided globular particles of sodium new Suspension of Sodium silicate particles in a Silicate. This forms a sort of creamy suspension 55 mixture of methanol and water. 2 2,386,887 It will be seen that by this expedient a com ing the mixture, separating the thus formed free plete cyclic process will eventuate in which, silica from the liquid, and drying the same. starting with sodium carbonate and sand, ex 3. Process of preparing very finely divided tremely finely divided silica can be produced. silica which comprises mixing an aqueous solu The only ingredient thus used up will be the tion of an alkali silicate with a water-miscible sand or other source of silica, while the alcohol organic liquid non-reactive therewith, passing and the sodium salt, i.e., the carbonate, are con carbon dioxide gas into the resulting mixture tinually regenerated in the process. until it has been substantially neutralized, sep If instead of carbon dioxide, hydrochloric acid, arating the thus formed free silica from the liq for example, is employed, this will, of course, O uid, and drying the same. form sodium chloride, which will be in the residue 4. Process of preparing very finely divided of the distillation of the alcohol. This sodium silica which comprises mixing an aqueous solu-. chloride can also be melted with Sand, forming tion of sodium silicate with a Water-miscible al sodium silicate, while liberating hydrochloric cohol, neutralizing the mixture with an acid-re acid, which may then be re-used in the process. s acting substance, separating the thus formed free However, the process is not limited to a cyclic silica from the liquid, and drying the same. operation, and therefore other acids or acid 5. Process of preparing very finely divided reacting Substances may be employed for the silica which comprises pouring an aqueous solu purpose of removing the Sodium component of tion of sodium silicate into methanol to pre the finely divided precipitated silica. 20 cipitate finely divided sodium silicate particles, While the proceSS has been described in con adding sufficient acid-reacting material to the nection with sodium silicate and methanol, it suspension to abstract the sodium from the pre will be obvious to any experienced chemist that it cipitate and to convert it into silicic acid, sepa can be practiced, with substantially the same re rating the latter from the liquid in which it is Sults, by starting Out with potassium silicate. 25 suspended, washing the same substantially free Furthermore, the methanol employed for pre from soluble material, and drying the silica par- . cipitating the alkali silicate solution may be re ticles thus obtained. placed by equivalent materials, such as other al 6. The process of claim 5, in which the acid cohols of the aliphatic series such as ethyl alcohol reacting, substance is carbonic acid. (ethanol), propyl or isopropyl alcohol, or some 30 other water-Soluble or water-miscible organic 7. Cyclic process of producing very finely liquid such as acetone, ethyl-methyl ketone, and divided silica which comprises dissolving sodium the like. However, methanol is probably the silicate in water to form a solution, pouring the least expensive and most easily procurable of latter into a substantial volume of a water these materials, and hence is the preferred sub 35 miscible organic liquid non-reactive therewith to stance for the carrying out of the present inven precipitate said silicate in finely divided form, tion. passing carbon dioxide into the suspension to The product, in addition to the uses already form free silica and sodium carbonate, separat given for it, also forms an excellent filler or pig ing the silica from the liquid in which it is sus ment which may be used in paper coating Com pended, washing and drying it, collecting the fill positions and the like. trate and wash-liquor, distilling the organic liq Obvious modifications of the process herein uid therefrom for re-use, recovering the sodium disclosed, such as those which will occur to any carbonate from the residual liquid and heating skilled chemist, are to be construed as within the same with silica to form sodium silicate and the scope of the present invention, for which 45 carbon dioxide, dissolving the former to form a is claimed: sodium silicate solution, pouring the latter into 1. Process of preparing very finely divided the recovered organic liquid and passing the silica which comprises mixing an aqueous Solu carbon dioxide into the suspension. tion of an alkali silicate with a water-miscible 8. The process of claim 7, in which the organic organic liquid non-reactive therewith, thereby 50 liquid is an alcohol. precipitating said silicate in finely divided form, 9. The process of claim 7, in which the organic and acidulating the suspension to form free liquid is a ketone. silica, separating the latter from the liquid, and 10. The process of claim 7, in which the or drying the Same. ganic liquid is methanol. 2. Process of preparing very finely divided 55 silica, which comprises mixing an aqueous Solu 2ABETH F. MOYER, tion of an alkali silicate with a water-Iniscible Administratric of the Estate of Paul S. Mower, organic liquid non-reactive therewith, acidulat Deceased.