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PATENT OFFICE 2,680,098 SILICON COMPOUNDS Ral B

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PATENT OFFICE 2,680,098 SILICON COMPOUNDS Ral B Patented June 1, 1954 2,680,098 UNITED STATES PATENT OFFICE 2,680,098 SILICON COMPOUNDS ral B. Johns, Jr., Dayton, Ohio, assignor to Mon santo Chemical Company, St. Louis, Mo., a cor poration of Delaware No Drawing. Application April 27, 1951, Serial No. 223,447 4 Claims. (C. 252-182) 1. 2 The present invention relates to methods of aration of the mixture of orthosilicate and poly preparing silicon compounds and deals more par silicates, the formation of the latter in yields ticularly with reaction products of silicon, Silica, which equal those of the orthosilicates, shows the and Sulfur. presence of an oxygen-containing compound of An object of the present invention is to prepare silicon and sulfur in the ignition product. from readily available, inexpensive starting ma While the prior art shows the production of terials, intermediates which may be employed to polysilicates by a variety of procedures, e.g., by give good yields of polysilicates. Another object esterification of polysilicic acids, by reaction of of the invention is the preparation of mixtures of SilicOn Oxychloride with alcohols or phenols, or Silicon disulfide and a compound containing Only as in the Italian Patent No. 436,808, to Lamberto the elements silicon, Sulfur and oxygen, which Malatesta, dated June 14, 1948, by the reaction mixtures may be employed for the preparation of of Silicon disulfide with aqueous alcohols, the valuable organic Silicon compounds. Still an prior methods have been of little commercial in other object of the invention is the preparation of terest because either the initial materials were mixtures of Orthosilicates and polysilicates from difficultly obtainable or because the yields of the inexpensive raw materials. polysilicates were too low for practical appli These and other objects of the invention which cation. The Silicon disulfide of the Malatesta, will be hereinafter disclosed are provided by the process is obtainable only at the expense of em following invention wherein there are prepared ploying Only elemental silicon as the silicon reaction products comprising silicon disulfide and 2) source. In the present process half of the silicon a compound containing only the elements silicon, present in the ester products is derived from oxygen and sulfur upon ignition of a mixture of Silica. That as cheap a source as silica can be Silicon, Sulfur and silica. My Copending appli utilized directly for the production of the hitherto cation Serial No. 223,446 filed April 27, 1951, difficultly obtainable organic silicates constitutes Which is assigned to the Sane assignee aS is the a major advancement in the art. present case describes and claims the process for In preparing the mixture of Silicon sulfide and reacting the present products With Organic hy the silicon-OXygen-Sulfur compound of the pres droxy compounds. ent invention, I mix Silicon With silica and Sul The product obtained by ignition of a mixture fur in a molar proportion which is advantageously of silicon, silica and sulfur consists essentially of 1:1:2, but which may deviate from that value in a mixture of silicon disulfide With a compound any Way depending upon the proportion of silicon which is probably silicon oxysulfide, but which disulfide and the silicon-oxygen-sulfur compound can be correctly described only in terms of the desired in the ignition product. Since the reac elements of which it is composed, i. e., as a Com tion is assumed to proceed substantially accord pound containing only Silicon, oxygen and Sulfur. ing to the scheme: X-ray analysis of the ignition product shows the absence of elemental silicon, and the presence of Si-SiO2-2S-----2SiOS a considerably diminished quantity of silica over that present in the original reaction mixture. stoichiometric proportions of the reactants are Such analysis shows the presence of Silicon disul 40 advantageously employed. The formation of sili fide. The presence of a compound containing the con disulfide from its elements is known to be a highly exothermic reaction; and While neither elements Silicon, oxygen and Sulfur can be as the identity of the present ignition products nor certained only by the nature of the products the responsible reaction mechanism are known which are formed upon reaction of the ignition it may be aSSunned that the extreme heat which is product with an organic hydroxy compound. 45 developed by the formation of Silicon disulfide Upon treating the ignition product with a hy permits the formation of a Silicon-oxygen-sulfur droxy compound there is obtained not only the compound which while probably silicon oxysul orthosilicate which could be expected by the re fide may be a cyclic thioether, or a polymer of action of silicon disulfide and the hydroxy com either the silicon oxysulfide or the cyclic com pound according to the scheme: 50 pound. SiS2-4ROH----- Si(OR) 4-2H2S In order to retain the exothermic reaction heat but also a series of polysilicates having the gen of the Silicon-Sulfur reaction, so that it can be eral formula: utilized for the Silica-Sulfur reaction, it is ad 55 vantageous to employ in the reaction mixture a Small quantity say, from 0.5% to 5.0% by weight Compounds having the above general formula, of the total weight of the Silicon, Silica and Sul can be formed only if a material supplying the fur, of an auxiliary heat-producing substance. necessary oxygen is present in the reaction mix The peroxides of barium, sodium or potassium ture. Since no water is present during the prep 60 are particularly suitable for this purpose, but 2,680,098 3. 4. other Solid heat-producing media, may be emi riety of commercial purposes, e.g., in the prepa ployed. ration of heat-resistant adhesives and binders, in Ignition of the mixture of silicon, Sulfur and the formulation of protective Coatings, for the silica, and, if desired, heat-producing agent, may Water proofing of textiles, as functional fiulids, be effected by Subjecting the mixture to a ten etc. Or, if desired, the orthosilicate may be perature of say, at least 2,000° C. and prefer Separated from the mixture by further fractiona ably of at least 2,500° C. to 3,500° C. Tempera tion to yield a residue consisting of only the tures of this magnitude may be readily attained polysilicates. While the orthosilicates may be by employing therite ignition; i. e., by using regarded as by-productS When the poly Silicates the heat which is liberated in the reaction of a O are the only desired materials, the orthosilicates mixture of aluminum and an oxide of a Weaker themselves are of considerable commercial im metal. The charge of Silicon, silica, and Sulfur portance and the present process provides an is contained in a highly heat-resistant vessel, inexpensive method for their production. In e.g., a fire-clay crucible. The thermite, say, a most instances, however, the mixtures of ortho mixture of aluminun and ferric oxide, is placed Silicates and polysilicates obtainable from the in the charge, and the mixture is ignited elec present process may be employed for functions trically and/or by a prinner Such as magnesium previously assumed to be Satisfactorily fulfilled ribbon. Heat evolved in the therinite reaction Only by the hitherto more difficultly available then effects ignition of the silicon-Silica-Sulfur poly Silicates, e.g., the present Orthosilicate-poly charge. The product of this ignition is generally Silicate mixtures are highly useful as heat trans a brownish, friable material which, as previously fer media, as additives to alkyd resins, for the Stated contains no eleinental silicon, only a very purpose of improving hardness and the drying Small quantity of silica, aid Silicon disulfide and rate thereof, etc. When the products are to be the silicon-oxyge-Sulfui compound. The pro used as liquid heat-responsive agents for therno portion of the last two compounds With respect 25 static devices, however, the polysilicates are pref to each other, when the composition of the ini erably employed in absence of Substantial quan tial reaction mixture observes Stoichiometric tities of the Orthosilicate. In this case the proportions, is generally in the Order of 1:1. OrthoSilicate is renoved by distillation. The This ignition product is empioyed directly, residue comprises a series of polysilicates of Without further treatinent Or isolation of con 30 varying degrees of polymerization, i. e., polysili Stituents, for the preparation of organic esters Cates having the general formula. of OrthoSilicic or polysilicic acids. The propor tion of orthosilicates to polysilicates which is ob SinCn-1 (OR)2n+2. tained depends upon the proportion of silicon disulfide to the Silicon-oxygen-sulfur conpound 35 in which n is greater than one and R is as herein which is present in the ignition product. defined. The individual inenbers of the Series Saturated Organic hydroxy compounds, gener are separable only with difficulty; however, since ally, may be ein ployed for the preparation of they resemble each other very much in proper the Silicates. Advantageously there may be en ties, resolution of the mixture into its constitu ployed saturated alcohols or phenols of from to ents is generally unnecessary. If desired, frac 18 carbon atoms, e. g., aliphatic alcohols such tionation of the polysilicate residue to give aS methanol, ethanol, isopropanol, n-butanol, fractions of polysilicates having a narrow range tert-n-butanol, n-hexanol, n-heptanol, 2-ethyl of molecular Weights and polymerization degrees hexanol, n-Octanol, lauryl alcohol, octadecyl al may be carried out. Cohol, etc., the aralkyl alcohols Such as benzyl The invention is illustrated but not limited by alcohol or 2-phenylethanol; and phenols such as 4. 5 the following examples.
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