United States Patent Office Patented Feb

3,168,542 United States Patent Office Patented Feb. 2, 1965

2 It is also often desired to separate mixtures of chloro 3,168,542 silanes having different organic substitutents attached to PROCESS FOR SEPARATENG MEXTURES OF silicon thereof into individual chlorosilane portions where

CHOROSLANES EEgyd H. Saaffer, Sayder, N.Y., assignor to Unioia Car in each portion contains specific chlorosilanes having the bide Corporation, a corporation of New York same organic substituents attached to silicon thereof. No Drawing. Fied May 15, 1957, Ser.3. No. 659,204 Illustratively, in the manufacture of vinyl silicone elas 23 Claims. (C. 260-44S.2) tomers the proportion of vinyl groups contained by the elastomer affects the properties of the elastomers. By This invention relates to chlorosilanes and in particular controlling the amount of vinyl siloxane groups com to a process for separating specific chlorosilanes from mix O bined in the elastomers, the properties of such elasto tures of different chlorosilanes. mers can be controlled substantially as desired. This It is often desirable to separate mixtures of chloro can be advantageously accomplished by regulating the silanes of different functionalities into chlorosilane por relative amounts of substantially pure vinyl chlorosilanes tions such that each portion contains only chlorosilanes and coreacting chlorosilanes. When low purity chloro of a specific functionality and is substantially uncontami 5 silanes are employed additional variables are encountered nated by chlorosilanes of other functionalities. Illus thus complicating an otherwise simple operation. Simi tratively, it has been found that dimethylpolysiloxane larly, substantially pure diphenyldichlorosilane, dimethyl gums that are suitable for conversion to silicone elastom dichlorosilane, methylphenyldichlorosilane, and the like ers cannot be prepared directly by the hydrolysis of di are highly desirable. - methyldichlorosilane prepared in the usual manner with 20 Various processes had been suggested heretofore for out further treatment. One explanation for the difficulty Separating mixtures of different chlorosilanes such as, encountered is that the starting dimethyldichlorosilane is mixtures of dimethyldichlorosilane and methyltrichloro rarely, if at all, obtained in a pure form. That is, it silane. These processes were not found to be entirely contains methyltrichlorosilane in an amount of 0.3 to Satisfactory for several reasons including incomplete sepa 0.5 mole percent or more based on the total moles of 25 rations, low yields and/or inability to separate low con methyltrichlorosilane and dimethyldichlorosilane even centrations of chlorosilanes from the mixtures. Known when careful purification procedures have been employed. physical methods, such as distillation, are often not well Thus, upon hydrolysis of the starting silane and dehy Suited for the separation of mixtures of different chloro dration of the resulting silanol, a pure difunctional silox silanes. By way of illustration, tetrachlorosilane and ane product is rarely obtained. Any trifunctional silane 30 trimethylchlorosilane form an azeotrope and hence can impurities present are converted to trifunctional silox not be separated from each other by simple distillation. ane groups, such as monomethylsiloxane groups, result As a further illustration, some chlorosilanes, such as ing in the cross-linking of the siloxane chains of the prod dimethyldichlorosilane and methyltrichlorosilane, boil at. ucts. Such cross-linking of the siloxane chains of the close to the same temperature and also are not readily products due to the presence of the trifunctional silane 35 separated from each other by simple distillation. prevents the production of the soft gums into which fillers In order to separate mixtures of chlorosilanes, it had can be milled. It has been found that amounts of com been proposed, heretofore, that a mixture containing two bined monomethylsiloxane groups of more than from or more chlorosilanes and a compound such as a tertiary about 0.01 part to about 0.02 part by weight per 100 amine, a diorganodiacyloxysilane or an alkali metal hy parts by weight of the monomethylsiloxane groups, di 40 droxide can be mixed and subjected to such conditions methylsiloxane groups and trimethylsiloxane groups that that one or more, but not all of the chlorosilanes react are combined in the siloxane products prevent the use with the amine, the diorganodiacyloxysilane or the hy of the product as as siloxane gum which can be subse droxide to form products that are appreciably higher qently converted to desirable silicone elastomers. boiling than the remaining unreacted . chlorosilane or Amounts of combined monomethylsiloxane groups equal 45 chlorosilanes. The remaining unreacted chlorosilane or to or less than these amounts were not found to prevent chlorosilanes can then be removed from the reaction the use of the product as a siloxane gum, which can be mixture by distillation. These latter-mentioned means subsequently converted to desirable elastomers. of separating mixtures of different chlorosilanes are not Similarly, by way of illustration, trimethylchlorosilane, entirely satisfactory because of incompiete separation, when produced by conventional means usually contains low yields and inability to remove small concentrations up to about 40 mole percent of chlorosilanes of higher of chlorosilanes from the mixtures. The method where functionality, e.g., tetrachlorosilane (i.e. silicon tetra in a tertiary amine is employed was not found to be chloride) and methyltrichlorosilane, based on the total generally applicable to separating all mixtures of chloro moles of trimethylchlorosilane and such higher func silanes but is limited to separating mixtures of inor tional chlorosilanes. Trimethylchlorosilane is utilized 55 ganic chlorosilanes. Diorganodiacyloxysilanes are not for furnishing end-blocking groups (i.e. chain-terminat readily available materials and hence the process for ing trimethylsiloxane groups) in the manufacture of sili separating mixtures of chlorosilanes using diorganodi cone oils that consist predominantly of combined di acyloxysilane entails the expenses of first synthesizing methylsiloxane units. The viscosity and tendency to gel said diorganodiacyloxysilanes. When an alkali metal of oils containing end-blocking groups furnished by tri 60 hydroxide is used in such separations, the materials ob methylchlorosilane decreases as the amounts of tri- and tained are higher boiling and are not found to be especial tetra-functional chlorosilanes in the trimethylchlorosilane ly useful because of their basic character and contami. so used are reduced. Hence, it is desirable to reduce the nation by salts. amount of tri- and tetra-functional chlorosilanes in tri It had been suggested also that zinc fluoride can be methylchlorosilane so that oils of low viscosity contain 65, added to a mixture of two chlorosilanes to selectively ing end-blocking groups furnished by trimethylchloro convert one of the chlorosilanes to the corresponding silane can be manufactured without gelation. fluorosilane. The fluorosilane so made could then be 3,168, 5 4. 3 separated from the unreacted chlorosilane by distillation. the reaction mixture leaving some of the combined nono However, the fluorosilane so separated is not a particu functional and trifunctional siloxane groups behind. larly useful material in view of the fact that when it is However, this method of producing the desired interme Subjected to hydrolysis reaction in the course of the pro diates is not adequate. By way of illustration, this meth duction of polysiloxane materials therefrom, hydrogen od produces cyclic dimethylsiloxanes that are still con fluoride is produced which is highly corrosive. taminated by materials containing combined trifunctional Still another process for separating mixtures of chlo siloxane groups. Furthermore, the high temperature rosilanes had been suggested and includes adding a phenol often employed causes decomposition and disproportion - to the mixture containing two or more chlorosilanes and ation reactions which lower the yield of the difunctional applying Such conditions that cause the chlorosilanes and O products and which produce undesired solid products that the phenol to react to form phenoxysilanes. The phen must be periodically removed from the reactor. In addi oxysilanes so made possess larger boiling point differ tion, under the conditions employed in this method, the ences than the starting chlorosilanes and hence can be equilibrium concentration of the difunctional interne separated by distillation. However, the relatively high diates is usually low and, when operated in a batchwise boiling points of these phenoxysilanes necessitate the use manner, this method inherently produces a low yield of of high temperature distillation or vacuum distiliation to the difunctional intermediates. effect a separation and regeneration of the separated This invention is based on the discovery that different phenoxysilanes to the corresponding chlorosilanes is re chlorosilanes hydrolyze at different rates and that mix quired. Hence this method of separating mixtures of tures of different chlorosilanes can be separated into chlorosilanes is often undesirable. 20 specific chlorosilane portions which are substantially free Another process for separating mixtures of methyl of other chlorosilanes by taking advantage of this dif chlorosilanes had been suggested and includes adding an ference in reactivity. In accordance with this invention, anhydrous salt of acetic acid to the mixture containing it has been found that the separation of chlorosilane mix two or more chlorosilanes and applying such conditions tures containing a first chlorosilane part and a second that cause the methylchlorosilanes and the salt to react 25 chlorosilane part, the first chlorosilane part being more to form methylsilylacetates. The methylsilylacetates pos readily hydrolyzable than the second chlorosilane part, SeSS larger differences in their boiling points than the can be accomplished by a process which comprises re starting methylchlorosilanes and hence can be separated acting the chlorosilane mixture with not less than 0.5 by distillation. However, the relatively high boiling mole of water per mole of the first chlorosilane part to points of these methylsilylacetates necessitate the use of form a mixture of a hydrolyzed chlorosilane part and an high temperature or vacuum distillation to effect a sepa unhydrolyzed chlorosilane part, and separating the un ration and hence this method of separating mixtures of hydrolyzed and hydrolyzed chlorosilane parts. Each chlorosilanes is often undesirable. chlorosilane part can contain a single specific chlorosilane In the case of purifying dimethyldichlorosilane, it was or several specific chlorosilanes all of which hydrolyze found that known processes for separating dimethyldi at rates above or below a certain value which distin chlorosilane from the methyltrichlorosilane did not ade guishes the first chlorosilane part from the second chlo quately purify the dimethyldichlorosilane so that it might rosilane part. For example, the specific chlorosilane or be readily used in the production of viscous oils and sili chlorosilanes of the first chlorosilane part hydrolyze at cone elastomers. a rate above a certain value whereas the specific chloro To overcome the difficulties encountered in the prepa 40 silane or chlorosilanes of the second chlorosilane part ration of the desired dimethylpolysiloxane gums it has hydrolyze at a rate below that value. When the second become general practice to prepare cyclic dimethylsilox chlorosilane part comprises more than cine specific chlo ane intermediates which can to some extent be separated rosilane, the process can be repeated to eliminate the from contaminating trifunctional impurities and which more hydrolyzable chlorosilanes of said mixture. The can be Subsequently equilibrated to produce a pure high process can be repeated as many times as desired or until molecular weight linear polysiloxane such as is used in 4. 5 a single specific chlorosilane has been obtained. the production of the desired siloxane oils and siloxane Our process is applicable to all mixtures of chloro gums. These intermediates may be produced by a hy silanes, wherein the chlorosilanes differ in rates of hy drolysis-dehydration procedure employing impure difunc drolysis. Among the many chlorosilane mixtures that tional dimethylsilanes under conditions that are carefully can be separated by this invention are mixtures of the controlled so as to cause a maximum yield of the desired 50 chlorosilanes represented by the formula: cyclic dimethylsiloxane product. The cyclic dimethylsi loxane intermediates are then distilled from the reaction ClSiX mixture leaving some of the combined monofunctional wherein X is a chlorine atom, a hydrogen atom or a and trifunctional siloxane groups behind. Once distilled, 5 5 monovalent hydrocarbyl group, particularly, an alkyl the difunctional intermediates can be further processed to group, an aryl group, an alkenyl group or an aralkyl siloxane oils and siloxane gums. However, this method group but is preferably a chlorine atom, a methyl group, of making Such difunctional intermediates has limitations an ethyl group, a vinyl group or a phenyl group. By illustrative of which are low yields of the difunctional the term "hydrocarbyl group, as used herein, is meant products and incomplete separation of compounds con 60 a monovalent group composed of carbon and hydrogen. taining combined trifunctional siloxane groups from the However, the hydrocarby groups represented by X in the difunctional siloxane product. formula can be substituted or unsubstituted and, if sub To accomplish the production of cyclic dimethylsilox stituted, the Substituents can be silyl groups (e.g. a tri ane intermediates that can be converted to the desired chlorosilyl group), cyano groups, halogen atoms, and the siloxane gums another process had been suggested. This 65 like. X can be the same or different throughout a pat Second process is similar to the above-mentioned hydroly ticular chlorosilane molecule. Illustrative of the chioro sis-dehydration procedure inasmuch as impure difunction silane represented by the formula are tetrachlorosilane, al dimethylsilanes are hydrolyzed and the silanols so the alkylchlorosilanes, the arylchlorosilanes, the aralkyl formed are dehydrated. The dehydrated material is treat chlorosilanes, the alkenyldichlorosilanes, the chlorohy ed further to produce a high molecular weight polysilox drogensilanes and the like. This invention is especially ane. The contaminated polysiloxane so formed is then applicable to the separation of mixtures of chlorosilanes heated in the presence of an alkaline catalyst at a ten that contain two or more members of the following perature of about 270° C. to cause depolymerization or classes of chlorosilanes: the methylchlorosilanes, the a rearrangement of the difunctional siloxane groups to ethylchiorosilanes, the pienychlorosilanes, the vinylchlo form cyclic dimethylsiloxanes which are distilled from rosilanes, the phenylmethylchlorosilanes, and the ethyl 3,168,542 S 6 phenylchlorosilanes, as well as to the separation of chlo and/or the siloxane (or the siloxane mixture) formed in . rosilane mixtures of one or more members of these classes our process. By way of illustration, a liquid organic and tetrachlorosilane. Illustrative of the mixtures of compound in which the unhydrolyzed chlorosilane part chlorosilanes that can be separated using the process of is soluble and in which the silanol and/or siloxane (or is this invention are mixtures of trimethylchlorosilane and mixtures thereof) are not soluble can be added to the tetrachlorosilane, mixtures of dimethyldichlorosilane and reaction mixture and the unhydrolyzed chlorosilane part methyltrichlorosilane, mixtures of phenylmethyldichloro can be separated from the reaction mixture by extraction. silane, phenyltrichlorosilane and diphenyldichlorosilane The preferred means of separating the unhydrolyzed chlo and like mixtures. Although our process will separate rosilane part from the reaction mixture is by heating the chlorosilane mixtures containing any percentages of spe 10. reaction mixture to a temperature sufficiently elevated to cific chlorosilanes, it is preferable to remove as much as volatilize the unhydrolyzed chlorosilane part thereby. possible of the more readily hydrolyzable chlorosilane leaving the silanol and/or siloxanes (or mixtures thereof) part by fractional distillation or other practical methods. as a residue. Heating the reaction mixture to volatilize so as to concentrate the less hydrolyzable chlorosilane the unhydrolyzed chlorosilane part can be conducted at part. This technique results in economies and higher high or low pressures and/or at or below the boiling yields of unhydrolyzed chlorosilanes. For- example, point of the reaction mixture. The process of this inven MeSiCl, containing 5 mole percent of MeSiCl3, and tion can be repeated as many times as desired using the MeSiC containing as much as 40 mole percent of more unhydrolyzed chlorosilane part obtained in each previous readily hydrolyzable impurities have been advantageously run so as to obtain a single chlorosilane which is sub purified using this process. - 20 stantially pure. Chlorosilanes, such as those represented by the formula, In order for our process to operate efficiently, the water were found to hydrolyze at different rates. By way of and chlorosilane mixture should be in intimate reactive illustration, it was found that methyltrichlorosilane is contact with one another. In other words, they should hydrolyzed faster than dimethyldichlorosilane, and tetra form a uniform reaction mixture or solution so as to chlorosilane is hydrolyzed faster than trimethylchloro react under homogeneous conditions. Most chlorosilanes silane. The following relative reaction rates at about are not miscible with water and in these instances a suit -20 C. were determined from a series of hydrolysis able common solvent is advantageously employed. Suit rate measurements: able common solvents are those with which both the Relative rates chlorosilane mixture and water are miscible and include Chlorosilane: of hydrolysis 30 dioxane, diethyl ether, tetrahydrofuran, diethylene glycol CH3SiCl3 ------0.59 diethers, and the like. When a common solvent is em C2H5SiCl3 ------1.00 ployed, the amount thereof is not critical as long as it is : CoH5SiCl3 ------2.10 sufficient to maintain a uniform reaction mixture and N-C(CH2)2SiCl3 ------120.00 it is not so great that dilution or low concentration im (CH3)2SiCl2 ------0.00006 practically retards the rate of hydrolysis. From about (C6H5 ) SiCl2 ------Slower than (CH ) 2SiCl2 5 parts to 500 parts by weight of common solvent per The hydrolysis rates of the chlorosilanes present in any 100 parts of the aggregate weight of water and chloro chlorosilane mixture to be separated by this invention can silane mixture have been found to be efficient. Excel be readily measured by known procedures. By way of lent results have been obtained in the experiments we illustration, the rates of hydrolysis of chlorosilanes can 40 have conducted by using from 20 parts to 200 parts by be measured conductometrically as well as by infrared weight of common solvent per 100 parts of the aggregate techniques in accordance with methods known in the art. weight of water and chlorosilane mixture. Higher or Not wishing to be bound by any theory or mechanics lower proportions of common solvent may be required of reaction, it, nevertheless, is believed that in our process depending upon the particular chlorosilane mixture and the more readily hydrolyzable chlorosilane part prefer the particular common solvent employed. More than entially hydrolyzes before any hydrolysis of the less readi one common solvent can be employed in our process. ly hydrolyzable chlorosilane part. In this reaction the Solvents which are miscible with only water or only the more readily hydrolyzable chlorosilane part is converted chlorosilane mixture may be employed, if the solutions into a silanol (or silanol mixture) which contains at least With such solvents are miscible. For example, solvents one silicon bonded hydroxyl group per molecule. The 50 for water but not for the chlorosilane mixture and solvents silanol (or silanol mixture) thus formed is not usually for the chlorosilane mixture but not for water are use stable and usually reacts further with a chlorosilane to ful as long as the particular water solution and the form a siloxane (or siloxane mixture) and hydrogen chlo particular chlorosilane solution formed thereby are mis ride which advantageously is rendered ineffective by re cible. In this connection, the term "solvent,” as used moval or other means to prevent undesirable side-reac herein, means a single solvent or a mixture of solvents tions which may be encouraged by its presence. Whether by the use of which in our process a homogeneous re the silanol is stable or undergoes reaction to form a silox action mixture containing said chlorosilane mixture and ane or not is immaterial for the purposes of this inven water is obtained. When the chlorosilane mixture and tion since both the silanol and siloxane differ in physical water are miscible, a common solvent is not required, properties from the unhydrolyzed chlorosilane part and 60 although one may be used, if desired. separation thereof can be easily acomplished by conven The proportion of water employed in this invention tional means, as by fractional distillation. Hence, for need not be narrowly critical. Theoretically, 0.5 mole of the purposes of simplification, the hydrolyzed chlorosilane water is sufficient to react with one mole of the more part can be considered as either a silanol, silanol mixture, readily hydrolyzable chlorosilane part whereas lesser siloxane and/or siloxane mixture. Hydrogen chloride amounts will result in unhydrolyzed chlorosilane parts can be rendered ineffective in encouraging undesirable which contain some of said more readily hydrolyzable side reactions by promoting its evolution from the reac chlorosilanes. Hence, at least 0.5 mole of water per tion mixture with sub-atmospheric pressures, by adding mole of the more readily hydrolyzable chlorosilane part a tertiary amine to combine with hydrogen chloride to (this being the stoichiometric amount of water) is re form an inert salt or by any other suitable means. It 70 quired for substantially complete separation of the two may not be desirable to employ a tertiary amine for such chlorosilane parts. Lesser amounts of water can be used, purposes if the amine is capable of reacting with any com of course, if complete separation is not desired. For ponent of the reaction mixture other than HCl. practical reasons, more than 5 moles of water per mole There are many ways of separating the unhydrolyzed of the more readily hydrolyzable chlorosilane part are chlorosilane part from the silanol (or silanol mixture) 5 not necessary. Although amounts greater than 5 moles 3,168, 543 7 per mole can be employed, if desired, no commenSurate temperature sufficiently elevated to cure it to produce advantage is seen to be obtained. In fact, such greater a silicone elastoner. water can be troublesome insofar as securing high yields Our process is also especially well suited to the puri of the less readily hydrolyzable chlorosilane part is con fication of triorganichlorosilanes that are containinated cerned. At water amounts above 5 moles per moie, care 5 with tetrachlorosilane. The triorganochlorosilanes puri should be devoted to reaction temperature and reaction fied by this invention were found to be useful in producing time since both influence the yield of the less readily end-blocker groups for silicone oils. By way of illustra hydrolyzable chlorosilane part as will be explained here tion, trimethylchlorosilane that has been purified by this inafter. We have found that water amounts of 1 mole invention may be used to produce end-blocker groups for to 3 moles of water per mote of the more readily hy 10 silicone cils by the following process. Purified trimethyl drolyzable chlorosilane part provide excellent separation, chlorosilane is hydrolyzed. The hydrolyzate so produced particularly, when said chlorosilane part contains chloro is condensed to form hexamethyldisiloxane. The hexa silanes of high hydrolysis rates. methyldisiloxane is mixed with a difunctional diorgano The temperature at which our process is conducted polysiloxane, such as a mixture of cyclic dimethylsiloxanes, is not narrowly critical. The lowest practical tempera and a basic catalyst, such as potassium dimethylsilanolate. ture is, of course, the freezing point of the water-chloro The Rixture so formed is heated to a temperature suffi silane reaction mixture or the temperature at which the ciently elevated to cause the hexamethyldisiloxane and rate of hydrolysis is so low as to be impractical. The the difunctional diorganopolysiloxane to undergo an equii highest practical temperature, of course, is that tempera ibration reaction to form a trimethylsiloxane end-blocked ture at which the relative rates of hydrolysis of the 20 silicone oil. specific chlorosilanes in the chlorosilane mixture become Tiis invention is useful in separating the mixtures of substantially indistinguishable. The relative rates of chiorosilanes produced by the disproportionation of or hydrolysis of chlorosilanes appear to be more widely ganochlorosilanes. separated at the lower temperatures, and at the higher The silanol, silanols, siloxane or siloxanes produced in temperatures the yield of unhydrolyzed chiorosilanes 2 5 this invention are also useful materials. By way of illus tends to decrease because of hydrolysis. Accordingly, tration, when a diorganopolysiloxane oil is produced in our process is advantageously carried out at temperatures this invention it can be converted to a gum which in turn below about 100° C. and above about -78° C. Super can be used to produce a silicone elastomer by the process atmospheric pressures may be employed in our process described above for converting diorganopolysiloxane oils at the high temperatures, if desired, to prevent the evolu 30 produced from dimethyldichlorosiiane to a silicone elas tion of gaseous water or chlorosiianes. We have found tonner. that when our process is conducted at temperatures in The following examples are presented. In certain ex the range of about -40° C. to -30° C. excellent results amples dealing with the purification of dimethyldichloro by way of high yields and short reaction times are ob silanes which are contaminated with methyltrichlorosilane, tained. the amounts of methyltrichlorosilane were reduced so low Reaction times also are not narrowly critical in the by our process that conventional analytical methods, e.g., practice of our process. The reaction time can be varied maSS Spectrophotometry, infrared analysis and quantita in accordance with needs and desires with respect to the tive analysis failed to provide dependable quantitative yield and purity (i.e., freedom from quantities of the lineasurements. it can be said that conventional analyti more readily hydrolyzable chlorosilane part) of the un 40 cal methods usually are not precise when the amounts of hydrolyzed chlorosilane part. At the lower reaction methyltrichlorosilane are below about 0.1 mole percent. temperatures longer reaction times are required than at As an indication of dimethyldichlorosilane purity in these the higher reaction temperatures in order to produce an examples, the purified dimethyldichlorosilane is converted unhydrolyzed chlorosilane part of a particular purity. into a gun, the hardness and solubility of which is meas When the amount of water employed in our process is 45 tired. It has been found that the hardness of this gun greater than that required to stoichiometrically react with is directly proportional and its solubility is inversely pro the more readily hydrolyzable chlorosilane part, longer portional to the concentration of methyltrichlorosilane in reaction times tend to reduce the yield of the unhydrolyzed the purified dimethyldichlorosilane from which said gum chlorosilane part because of hydrolysis. We have found Was made. By relating these values of hardness and solu that reaction times up to 20 hours can be used but prefer 50 bility to siniilar values obtained from gums made from reaction times not greater than 3 hours. dimethyldichlorosilanes containing known concentrations Our process is especially useful in the purification of of methyltrichlorosilanes, a good indication of purity can diorganodichlorosilanes that are contaminated by small be obtained. For example, a cyclic polydimethylsiloxane but troublesome amounts of mono-organotrichlorosilanes. Containing predominantly the tetramer was divided into Diorganodichlorosilanes containing as little as 0.3 mole 55 three portions. To the first portion 300 parts by weight percent of mono-organodichlorosilane are not readily of trifunctional polymethylsiloxane, (MeSiO4), per useful in manufacturing silicone elastomers. Diorgano million parts by weight of total siloxane were added. To dichlorosilanes so purified are free from such amounts the Second portion 100 parts by weight of trifunctional of the mono-organotrichlorosilane that prevent the ready polymethylsiloxane per million parts by weight of total conversion of said diorganodichlorosilanes to silicone 60 siloxane were added and nothing was added to the third gums which are satisfactory for use in the production portion. The resulting mixtures were polymerized in of silicone elastomers. By way of illustration, a di the usual nanner to form gums. The gun from the first methyldichlorosilane that has been purified by this in Portion did not dissolve even after 24 hours immersion vention can be convereted to a gum which in turn can in toluene. The gun from the second portion required be converted to a useful silicone elastomer by the fol 65 22 hours immersion in toluene while the gum from the lowing process. The purified dimethyldichlorosilane is third portion dissolved after 1% hours immersion in tolu hydrolyzed and the hydrolyzate so produced is condensed. ene. All portions were subjected to essentially the same The condensed hydrolyzate is usually a dimethylpolysi conditions, prior to, during and subsequent to polymeriza loxane oil that is then mixed with a catalytic amount tion. of a basic compound, Such as potassium dimethylsila 70 nolate. The mixture so formed is heated to a tempera Wherever given in these examples, mole percentages ture sufficiently elevated to produce a gum. This glim are based or the aggregate nimber of moles of chloro is mixed with a filler, such as finely divided silica, and silanes contained by a particular chlorosilane mixture. a curing catalyst, such as dibenzoyl peroxide, on a roll Room temperatures referred to in the examples are tem mill. The product of the Toll mill is then heated to a 75 peratures of about 25 C. Average molecular weights of 3,168,542 silicone oils were measured by determining the intrinsic cluding 72° C. was collected and analyzed. In this man viscosity of the silicone oil. ner, 249.3 grams of purified dimethyldichlorosilane con taining 0.07+0.04 mole percent methyltrichlorosilane as Example 1 determined by infrared analysis was obtained. This A mixture was formed containing 0.7925 mole (95 amount of dimethyldichlorosilane represented a recovery mole percent) of dimethyldichlorosilane and 0.0417 mole of about 97 weight percent. (5 mole percent) of methyltrichlorosilane. This mixture was dissolved in 25 milliters of dioxane. Ten milliliters Example 5 of a solution containing 2.24 grams (0.124 mole) of Water One hundred twelve and nine-tenths grams of a pre dissolved in dioxane were slowly added with stirring at O viously purified mixture that contained dimethyldichloro room temperature to the dioxane solution of the silanes. isilane (99.9 mole percent) and methyltrichlorosilane (0.1 A homogeneous solution formed. The solution was mole percent) as an impurity was dissolved in 53 cubic stirred for /2 hour. Hydrogen chloride formed and was centimeters of dioxane. A solution containing 0.01224 removed from the solution by subjecting the solution to gram of water dissolved in 8.7 cubic centimeters of dioxane sub-atmospheric pressure. After the removal of the hy 5 was added dropwise with stirring at room temperature to drogen chloride the solution was heated to 71 C. and a the silane solution. After the addition of the dioxane distillate was collected. Infrared analysis of the distil water Solution was complete, the resulting reaction mix late so obtained showed that it contained 0.48 mole per ture was stirred for 0.5 hour and hydrogen chloride cent of methyltrichlorosilane and 99.52 mole percent of formed. The hydrogen chloride was removed from the dimethyldichlorosilane by difference. 20 reaction mixture by subjecting the reaction mixture to a sub-atmospheric pressure. After the removal of the hy Example 2 drogen chloride the reaction mixture was heated to 72 Three hundred ninety-three and eight-tenths grams of C. and a distillate of purified dimethyldichlorosilane con a mixture that contained dimethyldichlorosilane (99.6i taining much less than 0.1 mole percent methyltrichloro mole percent) and methyltrichlorosilane (.39 mole per silane was collected. cent) as an impurity were dissolved in 600 cubic centi Example 6 meters of dioxane. A solution containing 0.66 gram of water dissolved in 30 cubic centimeters of dioxane was Another 393.8 grams sample of the mixture of di added to the silane solution over a period of 45 minutes methyldichlorosilane and methyitrichlorosilane used in with stirring at 25 C. Hydrogen chloride formed and 30 Example 2 was dissolved in 600 cubic centimeters of was removed by subjecting the reaction mixture to Sub dioxane and a solution containing 0.66 gram of water atmospheric pressure. After the removal of the hydrogen dissolved in 30 cubic centimeters of dioxane was slowly chloride, the reaction mixture was heated to 7 C. and added thereto. The addition was performed at from a distillate was collected. The fraction of the distillate -3°C. to 0° C. with continuous stirring. Hydrogen that was collected when the reaction mixture was heated chloride formed and was removed from the reaction mix up to 71° C. was analyzed on a mass spectrometer and ture by Subjecting the reaction mixture to subatmospheric was found to contain purified dimethyldichlorosilane with pressure. After the removal of the hydrogen chloride the about 0.06 to 0.07- 0.04 mole percent of methyltrichioro reaction mixture was heated to 71 C. and a distillate was silane. collected. The distillate was analyzed on a mass spec Example 3 40 trometer and was found to contain purified dimethyl dichlorosilane and about 0.04 to 0.05+0.04 mole percent One thousand, one hundred sixty-one grams of a mix of methyltrichlorosilane. ture that contained dimethyldichlorosilane (99.79 mole percent) and methyltrichlorosilane (0.21 mole percent) as Example 7 an impurity were dissolved in 1,700 cubic centimeters of 45 Three hundred ninety-three and eight-tenths grams of the dimethyl ether of ethylene glycol. The solution so a mixture that contained dimethyldichlorosilane (99.61 formed was cooled to -35° C. and a solution containing mole percent) and methyltrichlorosilane (0.39 mole per 2.13 grams of water dissolved in 100 cubic centimeters cent) as an impurity were dissolved in a solution that con of the dimethyl ether of ethylene glycol was slowly added tained 500 cubic centimeters of diethyl ether and 100 with stirring to the silane solution over a two-hour period. 50 cubic centimeters of dioxane. To the solution so formed The total amount of water in the solution was equal to Was added 0.66 gram of water dissolved in 30 cubic cen 3.3 moles of water per mole of methyltrichlorosilane. timeters of dioxane. The dioxane water solution was Hydrogen chloride formed during the addition and, after added dropwise over a period of 45 minutes at room tem the addition was complete, was removed from the reaction perature with stirring. Hydrogen chloride formed and mixture by subjecting the reaction mixture to sub-atmos 55 was separated from the reaction mixture by subjecting the pheric pressure. The residue remaining after the remov reaction mixture to sub-atmospheric pressure. After the ... al of the hydrogen chloride was heated to 71° C. and a hydrogen chloride had been removed the residue so pro distillate was collected. The distillate was analyzed on a duced was heated to 71. C. and a distillate was collected. mass spectrometer and was found to contain purified di The distillate was analyzed using infrared techniques and methyldichlorosilane with only 0.05+0.04 mole percent 60 was found to contain purified dimethyldichlorosilane with of methyltrichlorosilane. innuch less than 0.1 mole percent of methyltrichlorosilane. Example 4 Example 8 Two hundred and fifty-eight grams of a chlorosilane A sample of the purified dimethyldichlorosilane ob mixture containing 99.61 mole percent dimethyldichloro 65 tained as a distillate in Example 3 was dissolved in iso silane and 0.39 mole percent and methyltrichlorosilane propyl ether. The resulting solution was added drop were dissolved in 60 cubic centimeters of dioxane. To wise to a mixture containing ice and isopropyl ether. The the resulting solution there were added at room tempera addition was performed at a temperature of -5° C. and ture 25 cubic centimeters of an aqueous dioxane solution after the addition was complete the reaction mixture so containing 0.137 gram of water. A homogeneous solu 70 formed was stirred for one hour. An oil was obtained, tion formed. After the addition of aqueous dioxane, was separated from the reaction mixture and then was the solution was stirred for one hour and then stripped washed three times with separate portions of water. The under vacuum to remove hydrogen chloride that had oil was then mixed with sodium bicarbonate to remove formed. The residue after stripping was distilled through the residual chlorine. Sodium chloride formed and, a packed column and all material boiling up to and in 75 along with the excess sodium bicarbonate, was removed 3,168, $4.3 s from the- oil by washing with water. The oil was then a period of 10 minutes aid the railed raterials so formed dissolved in toluene. Isopropyl ether and Water Were were placed in a mold and cured at 35° C. for 10 minutes. removed from the resulting toluene Solution by distilla Elastomers were obtained from each gun. The properties tion. The toluene solution was then refixed in th& pres of the elastomers are correspondingly listed in the table ence of potassium carbonate. The potassium carbonate 5 below. The guins obtained from purified dinnethyldi was thereupon removed from the solution by filtration chlorosilanes were easily processed and for inned valuable and the toluene was distilled leaving a residue. The resi- elastoners. The gum made from unpurified dinnethyl due was an oil having the average molecular Weight listed dichlorosilane, however, was not easily processed and in the table below. for:lined a poorer elastoiner. Following the above procedure the dimethyldichloro- 10 silanes obtained as distiilates in Examples 5, 6 and 7 Were hydrolyzed to form oils of average molecular Weights listed in said table. Gum Elastomer Properties Forty-two and four-tenths grams of the oil produced Miniat fromExample the 3 digitlesiawere mixed with enough distillate potassium dimethyl-and, in " MeSiCl3rosio --- SS,trength E-ition, E.eter SENSE so that the resulting R contained 110 Source Solubility (psi) | Percent | Realing, St. Er p.p.m. of potassium (i.e., parts by weight of potassium (mm.f10 per million parts by weight of the oil). The oil-silanolate Sec.) mixturea was heated for two. hours a 50r s C. te. form a 20 Example 5. --- Soluble---- 420 259 38 O slightly more viscous oil. Sufficient potassiun dinnethyl- Exainple 7------do----- 652 300 38 O silanolate was added to this oil to provide an additional Ulipurified---- Insoluble-- 255 230 50 5 50 p.p.m. of potassium and the mixture was heated for 16 hours at 150° C. A more viscous oil formed. The oil was again heated for 16 hours at 150° C. to form a 25 gum that was completely soluble in dimethyl ether. Example 10 The oils obtained from the dimethyldichlorosilane Crude MeSiC obtained by distilling the reaction prod distillates produced in Examples 5, 6 and 7 were con- uct of methyl chloride and silicon was redistilled and 400 verted to gums using the procedure described for the con- grams of naterial boiling froin 54 C. to 60° C. was version of the dimethyldichlorosilane. distilate made in 80 collected. This cut was analyzed in the mass spectrometer Example 3. Gums having the following properties were and ratios of chlorosilanes found are entered in the first obtained. line of the table below. A solution of 245 grains of this chlorosiiane mixture in 696 graiias of dioxane was pre , EE Pol pared and cooled to 0°C. To this solution were added, ofSENSEE, Example Weight of silanolate Tirne Gm withof dioxane. stirring, 4.3The grams addition of water was ininade 100 cubicover acentimeters two-hour Oil (pl. of (Hours) period during which time the reaction mixture Was kept cool in an ice water bath. The number of moles of water 4. 498 5 48 Partly soluble in 40 used for the hydrolysis was 12 times half the icta inun dietyl ether. . . ber of moles cf MeSiCl3 and SiC in the 245 gram sample 5 423 260 34 C.E.E.Yilile l of chlorosilan. The mixture was distilled to recover the 6 438 275 82 Partly soluble in chlorosiianes. The results of this distilation are shown 7 39.5 275 ------cifisible in the table below. The process can be performed again in diethyl ether. on the purified trimethylchlorosilane to effect a further removal of the polyfunctional chiorosilanes.

Weight Molar Composition of Chiorosilane B. P. Weight Range, (Grams) Me3SiC MeSiC32 McSiHCl MeSiCl3 SiCl4

Orig. Dist, Sample------56-60 245 0, C69 0.284 0.209 0.05 Purified Mixture-Fraction

N: . . . . . ------a-- - - - 45-52 50 (1) 0.06 0.099 (1) 2------52-58 49 (I) 0.095 0.0343 (I) 8------58-60 23 1 0.023 O. O53 . 0.0597 (i) 4------60-85 4. 0.0297 0.020. 0.250 () Weighted Average------1 0.00345 0.034 0.052 0.00

1 Non detectable.

Example 9 What is claimed is: 1. A process for separating a chlorosilane mixture Three elastomers were prepared, respectively, from 00 containing a first chlorosilane part and a second chloro parts by weight of each of the guns prepared in Example silane part, the first chiorosilane part being more readily 8 from the dimethyidichlorosiianes of Examples 5 aid hydrolyzable than the second chlorosilane part, said proc 7 and a gum prepared from a dimethyldichlorosilane, un ess comprising bringing said chlorosilane mixture into purified by our process, and containing about 0.28-0.04 intimate reactive contact with not less than 0.5 mole of mole percent of methyitrichlorosilane, 40 parts by Weight water per mole of the first chlorosilane part, reacting said of a finely-divided silica filler and two parts by weight of chlorosilane mixture and water for a period of time less dibenzoyl peroxide. The ingredients for each elastoner than that required to completely hydrolyze all chloro were milled on a two-roii 6' x 12' laboratory mill at a silanes in said mixture thereby forming a hydrolyzed temperature of 25 C. The niiling was conditicted over 75 chlorosilane part and an unhydrolyzed chlorosilane part, 3,168,542 3. 4 and separating the unhydrolyzed and hydrolyzed chloro and separating the unhydrolyzed and hydrolyzed chloro silane parts. silane part. 2. A process for separating a chlorosilane mixture 8. A process for separating a chlorosilane mixture con containing a first chlorosilane part and a second chloro taining a first chlorosilane part and a second chlorosilane silane part, the first chlorosilane part being more readily part, the first chlorosilane part being more readily hy hydrolyzable than the second chlorosilane part, said proc drolyzable than the second chlorosilane part, said process ess comprising bringing said chlorosilane mixture into comprising dissolving in a solvent said chlorosilane mix intimate reactive contact with 0.5 to 5 moles of water per ture, and 0.5 to 5.0 moles of water per mole of the first mole of the first chlorosilane part, reacting said chloro chlorosilane part, reacting at -40°C. to -30°C. said silane mixture and water for a period of time less than O chlorosilane mixture and water for a period of time less that required to completely hydrolyze all chlorosilanes in than that required to completely hydrolyze all chloro said mixture thereby forming a hydrolyzed chlorosilane silanes in said mixture thereby forming a hydrolyzed part and an unhydrolyzed chlorosilane part, and separat chlorosilane part and an unhydrolyzed chlorosilane part, ing the unhydrolyzed and hydrolyzed chlorosilane part. and separating the unhydrolyzed and hydrolyzed chloro 3. A process for separating a chlorosilane mixture con 5 silane part. taining a first chlorosilane part and a second chlorosilane 9. A process for separating a chlorosilane mixture con part, the first chlorosilane part being more readily hy taining a first chorosilane, and a second chlorosilane, the drolyzable than the second chlorosilane part, said proc first chlorosilane being more readily hydrolyzable than ess comprising bringing said chlorosilane mixture into the Second chlorosilane, said process comprising dissolving intimate reactive contact with not less than 0.5 mole of 20 in a solvent said chlorosilane mixture and not less than water per mole of the first chlorosilane part, reacting at 0.5 mole of water per mole of the first chlorosilane, react -40 C. to -30° C. said chlorosilane mixture and water ing said chlorosilane mixture and water for a period of for a period of time less than that required to completely time less than the required to completely hydrolyze all hydrolyze all chlorosilanes in said mixture thereby form chlorosilanes in said mixture thereby forming a hydrolyzed ing a hydrolyzed chlorosilane part and an unhydrolyzed chlorosilane and an unhydrolyzed chlorosilane, and sepa chlorosilane part, and separating the unhydrolyzed and rating the unhydrolyzed and hydrolyzed chlorosilanes. hydrolyzed chlorosilane parts. 10. A process for separating a chlorosilane mixture 4. A process for separating a chlorosilane mixture con containing a first chlorosilane and a second chlorosilane, taining a first chlorosilane part and a second chlorosilane the first chlorosilane being more readily hydrolyzable part, the first chlorosilane part being more readily hy 30 than the second chlorosilane, said process comprising dis drolyzable than the second chlorosilane part, said proc Solving in a solvent said chlorosilane mixture and 0.5 to ess comprising bringing said chlorosilane mixture into 5.0 moles of water per mole of the first chlorosilane, intimate reactive contact with 0.5 to 5 moles of water per reacting said chlorosilane mixture and water for a period mole of the first chlorosilane part, reacting at -40° C. to of time less than that required to completely hydrolyze +30 C. said chlorosilane mixture and water for a period all chlorosilanes in said mixture thereby forming a hy of time less than that required to completely hydrolyze drolyzed chlorosilane and an unhydrolyzed chlorosilane, all chlorosilanes in said mixture thereby forming a hy and separating the unhydrolyzed and hydrolyzed chloro drolyzed chlorosilane part and an unhydrolyzed chloro silanes. silane part, and separating the unhydrolyzed and hy 11. A process for separating a chlorosilane mixture drolyzed chlorosilane part. 40 containing a first chlorosilane and a second chlorosilane, 5. A process for separating a chlorosilane mixture con the first chlorosilane being more readily hydrolyzable taining a first chlorosilane part and a second chlorosilane than the second chlorosilane, said process comprising dis part, the first chlorosilane part being more readily hy Solving in a solvent a chlorosilane mixture and not less drolyzable than the second chlorosilane part, said process than 0.5 mole of water per mole of the first chlorosilane, comprising dissolving in a solvent said chlorosilane mix reacting at -40° C. to +30 C, said chlorosilane mixture ture and not less than 0.5 mole of water per mole of the and Water for a period of time less than that required to first chlorosilane part, reacting said chlorosilane mixture completely hydrolyze all chlorosilanes in said mixture and Water for a period of time less than that required to thereby forming a hydrolyzed chlorosilane and an un completely hydrolyze all chlorosilanes in said mixture hydrolyzed chlorosilane, and separating the unhydrolyzed thereby forming a hydrolyzed chlorosilane part and an 50 and hydrolyzed chlorosilanes. unhydrolyzed chlorosilane part, and separating the un 12. A process for separating a chlorosilane mixture hydrolyzed and hydrolyzed chlorosilane part. containing a first chlorosilane and a second chlorosilane, 6. A process for separating a chlorosilane mixture the first chlorosilane being more readily hydrolyzable containing a first chlorosilane part and a second chloro than the Sceond chlorosilane, said process comprising silane part, the first chlorosilane part being more readily 55 dissolving in a solvent said chlorosilane mixture and 0.5 hydrolyzable than the second chlorosilane part, said proc to 5.0 moles of water per mole of the first chlorosilane, ess comprising dissolving in a solvent said chlorosilane reacting at -40 C. to +30 C, said chlorosilane mixture mixture and 0.5 to 5.0 moles of water per mole of the and water for a period of time less than that required first chlorosilane part, reacting said chlorosilane mixture to completely hydrolyze all chlorosilanes in said mixture and water for a period of time less than that required to 60 thereby forming a hydrolyzed chlorosilane and an unhy completely hydrolyze all chlorosilanes in said mixture drolyzed chlorosilane, and separating the unhydrolyzed thereby forming a hydrolyzed chlorosilane part and an and hydrolyzed chlorosilanes. unhydrolyzed chlorosilane part, and separating the un 13. A process for separating a chlorosilane mixture hydrolyzed and hydrolyzed chlorosilane part. containing a trichlorosilane and a dichlorosilane, the tri 7. A process for separating a chlorosilane mixture con 65 chlorosilane being more readily hydrolyzable than the di taining a first chlorosilane part and a second chlorosilane chlorosilane, said process comprising dissolving in a so part, the first chlorosilane part being more readily hy vent Said chlorosilane mixture and not less than 0.5 mole drolyzable than the second chlorosilane part, said process of water per mole of the trichlorosilane, reacting the comprising dissolving in a solvent said chlorosilane mix chlorosilane mixture and water for a period of time less ture and not less than 0.5 mole of water per mole of the 70 than that required to completely hydrolyze all chloro first chlorosilane part, reacting at -40° C. to -30° C. silanes in said mixture thereby forming hydrolyzed tri said chlorosilane mixture and water for a period of time chlorosilane and unhydrolyzed dichlorosilane, and sepa less than that required to completely hydrolyze all chloro rating said unhydrolyzed and hydrolyzed chlorosilanes. silanes in said mixture thereby, forming a hydrolyzed 14. A process for separating a chlorosilane mixture chlorosilane part and an unhydrolyzed chlorosilane part, containing a trichlorosilane and a dichlorosilane, the tri

. .3 ES chlorosilane being more readily hydrolyzable than the di 0.5 mole of water per mole of the polychlorosilane part chlorosilane, said process comprising dissolving in a Sol reacting the chlorosilane mixture and water for a period went said chlorosiane mixture and 0.5 to 5.0 moles of of time less than that required to completely hydrolyze water per mole of the trichlorosilane, reacting the chloro all chlorosilanes in said mixture thereby forming hy silane mixture and water for a period of time less than 5 drolyzed polychlorosilanes and unhydrolyzed trimethyl that required to completely hydrolyze all chlorosilates chlorosilane, and separating the unhydrolyzed and hy in said mixture thereby forming hydrolyzed trichloro drolyzed chlorosilanes. silane and unhydrolyzed dichlorosilane, and separating 21. The process for obtaining a diorganodichlorosilane said unhydrolyzed and hydrolyzed chlorosilanes. having the formula RR'SiCl2 of greater purity from mix 15. A process for separating a chlorosilane mixture O tures of the latter and an organotrichlorosilane having the containing a trichlorosilane and a dichlorosilane, the tri formula RSiCl3 in which the organotrichlorosilane com chlorosilane being more readily hydrolyzable than the di prises at most about 5.5 weight percent based on the chlorosilane, said process comprising dissciving in a sol total weight of the diorganodichlorosilane and the organo vent said chlorosilane mixture and 0.5 to 5.0 moles of trichlorosilane, where R and R are monovalent hydro water per mole of the trichlorosilane, reacting at -40° C. carbon radicals, which process comprises adding to the to --30 C, the chlorosilane mixttire and water for a aforesaid mixture of the diorganodichlorosilane and period of time less than that required to completely organotrichlorosilane a solution of water and an organic hydrolyze all chlorosilanes in said mixture thereby form ether solvent miscible with both the water and the afore ing hydrolyzed trichlorosilane and unhydrolyzed dichloro Said chlorosiaries, the amount of water being substan silane, and Separating said unhydrolyzed and hydrolyzed 20 tially less than that required to hydrolyze the diorganodi chlorosilanes. chlorosilane and being present in an amount equal to from 16. A procCSS for separating a chlorosiiane mixture 0.5 to 4 moles of water per moles of the organotrichloro containing a polychlorosilane part and a monochloro Silane and the amount of organic ether solvent being silane, the polychlorosilane part being more readily hy Within the range of from about 3 to 50 moles of the drolyzable than the nonochlorosilane, said process com organic ether Solvent per mole of water, and thereafter prising dissolving in a solvent said chlorosilane mixture recovering the diorganodichlorosilane of greater purity. and not less than 0.5 mole of water per moie of the poly 22. The process for obtaining purified trimethylchloro chlorosilane part, reacting the chlorosilane mixture and Silane from mixtures of the latter with a mixture of Water for a period of time less than that required to com methyltrichlorosilane and silicon tetrachloride wherein pletely hydrolyze all chlorosilanes in said inixture thereby 3. O the trimethylchlorosilane is present in larger amounts by forming hydrolyzed polychlorosilane and unhydrolyzed Weight than the other chlorosilanes, which process com monochlorosilane, and separating said unhydrolyzed and prises adding to the aforesaid mixture of trimethylchloro hydrolyzed chlorosilanes. Silane, methyltrichlorosilane and silicon tetrachloride a 7. A process for separating a chlorosiiane mixture Solution of water and an organic ether solvent miscible containing a polychlorosilane part and a monochloro 3 5 with both the water and the aforesaid chlorosilanes, the silane, the polychlorosilane part being more readily hy amount of Water in the organic ether solvent being sub drolyzable than the noncohorosilane, said process com stantially less than that required to hydrolyze completely prising dissolving in a solvent said chlorosiiane mixture the chlorosilanes containing more than one silicon-bonded and 0.5 to 5.0 moles of water per mole of the polychloro chlorine atom in its molecule, the moles of organic ether Silane part, reacting the chlorosilane mixture and water Solvent being greater than the moles of water present, and for a period of time less than that required to completely thereafter recovering trimethylchlorosilane of greater hydrolyze all chlorosilanes in said mixture thereby form purity. ing hydrolyzed polychlorosilane and unhydrolyzed mono 23. The process for obtaining purified trimethylchloro chlorosilane, and separating said unhydrolyzed and hy silane from mixtures of the latter with at least one chloro drolyzed chlorosilanes. silane Selected from the class consisting of methyltri i8. A process for separating a chlorosilane mixture chlorosiiane and silicon tetrachloride, wherein the tri containing a polychlorosilane part and a monochlorosii methylchlorosilane is present in larger amounts by weight ane, the polychlorosilane part being more readily hy thail the other other chlorosiiane, which process com drolyzable than the monochlorosilane, said process com prises adding to the aforesaid mixture of trimethylchloro prising dissolving in a solvent said chlorosilane mixture Silane and the other chlorosilane a solution of water and and 0.5 to 5.0 moles of water per mole of the polychloro an Organic ether solvent miscible with both the water and silane part, reacting at -40° C. to --30° C. the chloro tha aforesaid other chlorosiiane, the amount of water in silane mixture and water for a period of time less than the organic ether Solvent being substantially less than that that required to congletely hydrciyze all chlorosilanes in required to hydrolyze completely the other chlorosilane Said mixture thereby forming hydrolyzed polychloro 5 5 siane and unhydrolyzed monochlorosiiane, and separating containing more than one silicon-bonded chlorine atom said unhydrolyzed and hydrolyzed chlorosilanes. in its molecule, the moles of organic ether solvent being 19. A process for separating a chlorosilane mixture greater than the moles of water present, and thereafter containing methyltrichlorosilane and diraethyldichloro recovering trimethylchlorosilane of greater purity. silane, comprising dissolving in a solvent the chlorosiiane 60 mixture and not less than 0.5 mole of water per mole of Eeferences ( methyltrichlorosilane, reacting the chlorosilane mixture UNITED STATES PATENTS and Water for a period of time less than that required to 2,265,962 Bent et al. ------Dec. 9, 1941

completely hydrolyze all chlorosilanes in said mixture thereby forming hydrolyzed methyltrichlorosilane and un 2,486,162 Hyde ------Oct. 25, 1949 hydrolyzed dimethyldichlorosilane, and separating the un 2,519,926 Patnode et al. ------Aug. 22, 1950 hydrolyzed and hydrolyzed chlorosilanes. FOREIGN PATENTS 20. A process for Separating a chlorosilane mixture containing a polychlorosilane part of dimethyldichloro 824,050 Germany ------Dec. 10, 1951 silane, methyltrichlorosilane and tetrachlorosilane, and OTHER REFERENCES trimethylchlorosilane, said process comprising dissolving Alfrey et al.: “Jr. Polymer Science,” vol. 1 (1946), pp. in a solvent said chlorosilane mixture and not less than 102-120, pp. 103-105 only needed.