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United States Patent [191 [11] Patent Number: 5,070,175 Tsumura Et Al

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United States Patent [191 [11] Patent Number: 5,070,175 Tsumura Et Al United States Patent [191 [11] Patent Number: 5,070,175 Tsumura et al. [45] Date of Patent: Dec. 3, 1991 [54] METHOD FOR THE PREPARATION OF AN Primary Examiner-Morton Foelak ORGANOPOLYSILOXANE CONTAINING Attorney, Agent, or Firm-Millen, White & Zelano TETRAFUNCI'IONAL SILOXANE UNITS [57] ABSTRACT [75] Inventors: Hiroshi Tsumura; Kiyoyuki Mutoh, An ef?cient and economically advantageous method is both of Gunma; Kazushi Satoh, proposed for the preparation of an organopolysiloxane Tokyo; Ken-ichi Isobe, Gunma, all of comprising tetrafunctional siloxane units, i.e. Q units, Japan and, typically, monofunctional siloxy units, i.e. M units, [73] Assignee: Shin-Etsu Chemical Co., Ltd., Tokyo, and useful as a reinforcing agent in silicone rubbers. The Japan method comprises the steps of: mixing the reactants for providing the Q and M units, such as ethyl orthosilicate [21] Appl. No.;. 706,148 and trimethyl methoxy silane, in a desired molar ratio; [22] Filed: May 28, 1991 and heating the mixture at a temperature higher by at least 10° C. than the boiling point of the mixture under [30] Foreign Application Priority Data normal pressure in a closed vessel in the presence of May 29, 1990 [JP] Japan ............ .Q .................. .. 2-l39ll9 water and a catalyst such as a sulfonic acid group-con taining compound. In addition to the greatly shortened [51] Int. 01.5 ............................................ .. C08G 77/06 reaction time and remarkably decreased contents of [52] U.S. c1. ...................................... .. 528/12; 528/10; residual alkoxy groups and gelled matter in the product, 528/21; 528/23; 528/34; 528/36 the method is advantageous also in respect of the ab [58] Field of Search ..................... .. 528/10, 12, 21, 23, sence of the problems caused by the disposal of the 528/34, 36 waste water as well as the corrosiveness of hydrogen [56] References Cited chloride unavoidably produced in the conventional prior art methods. U.S. PATENT DOCUMENTS 4,184,995 l/l980 Noble ................................ .. 524/398 7 Claims, No Drawings 5,070,175 1 2 have disadvantages that measures for the disposal of METHOD FOR THE PREPARATION OF AN waste water and against the adverse effects of toxic and ORGANOPOLYSILOXANE CONTAINING corrosive hydrochloric acid must be undertaken like TETRAFUNCI'IONAL SILOXANE UNITS wise as in the above described method since a large amount of hydrochloric acid must be added to the reac BACKGROUND OF THE INVENTION tion mixture in addition to the hydrochloric acid pro The present invention relates to a method for the duced by the reaction or the alcohol admixed in the preparation of an organopolysiloxane or, more particu reaction mixture. larly, to a method for the preparation of an organopoly At any rate, these known methods are each industri siloxane having tetrafunctional siloxane units and con ally disadvantageous because a large volume of acid taining little amount of residual alkoxy groups so as to containing waste water must be safely disposed and the be useful as a reinforcing agent of silicone rubbers. productivity is low with a relatively low yield of the Among various types of organopolysiloxanes, those organopolysiloxane product per unit reaction volume as soluble in organic solvents and consisting of monofunc a consequence of the use of a large volume of organic tional organosiloxy units represented by the general solvents as a hydrolysis aid. When an organopolysilox unit formula R3SiOQ,5, in which R is a hydrogen atom ane containing a large amount of the Q units or, in par or a monovalent hydrocarbon group, referred to as the ticular, having the molar ratio of the M units to the Q M units hereinbelow, and tetrafunctional siloxane units units not exceeding 2 is desired, it is a rather difficult of the formula SiOg, referred to as the Q units hereinbe matter to adequately control the reaction so as to obtain low, are widely used in the art of silicone products, for an organopolysiloxane having the molar ratio of the example, as a reinforcing agent of silicone rubbers. Such units and molecular weight distribution exactly con an organopolysiloxane consisting of the M units and Q trolled as desired. Furthermore, difficulties are encoun units is prepared, for example, by the method disclosed tered in the preparation of an organopolysiloxane hav in US Pat. Nos. 2,676,182 and 2,814,601, in which a ing a controlled amount of the silanol groups or alkoxy water-soluble basic silicate such as sodium orthosilicate groups with good reproducibility. is converted into a silicic acid oligomer by the addition As a measure to dissolve the above described disad of hydrochloric acid or sulfuric acid followed by the vantages, accordingly, a method is proposed in Japa~ reaction with a trialkyl chlorosilane. nese Patent Kokai No. 63-256628, in which an organosi This method, however, has several problems as an industrial process because, since the silicic acid oligo lane or an organosiloxane is reacted with an alkyl sili cate or a partial hydrolysis product thereof in the pres mer is relatively unstable, difficulties are encountered in the control of the molecular weight distribution in the ence of a sulfonic acid group-containing compound organopolysiloxane product so that the molar ratio of and/or phosphonitrile chloride as a catalyst. This the M units and the Q units in the organopolysiloxane method has advantages that control of the molar ratio product cannot be always consistent with the target of the M units to the Q units is relatively easy and no molar ratio. In addition, since the waste water coming hydrochloric acid is produced as a by-product of the from the process necessarily contains a large amount of reaction. This method, however, is not free from the the waste acid used for the neutralization of the starting disadvantages that, since the reaction is conducted basic silicate as well as the hydrochloric acid produced under atmospheric pressure, residual amount of the as a byproduct in the reaction of the trialkyl chlorosi 40 alkoxy groups must be removed by the addition of an lane and also a large amount of an alcohol admixed with excess amount of water taking a long reaction time the reaction mixture with an object of stabilization of during which gelled materials are sometimes formed in the reaction mixture, a large cost is required for the the reaction mixture resulting in very poor ?ltrability of disposal of the waste water in order not to cause the the mixture with a greatly decreased productivity. problem of environmental pollution. When the waste 45 When such a measure is not undertaken to leave a large water contains hydrochloric acid in a substantial con amount of the residual alkoxy groups in the product, the centration, in particular, the hydrogen chloride gas applicability of such an organopolysiloxane product as a emitted therefrom is very harmful against human health reinforcing agent of silicone rubbers would be low be with a strong irritating odor and strong corrosion is cause no sufficient reinforcing effect can be obtained unavoidable on the apparatuses and pipe lines as well as therewith and the mechanical strengths of the silicone other auxiliary instruments in the manufacturing plant rubber compounded with such an organopolysiloxane so that they must be constructed by using highly corro would be subject to gradual degradation in the lapse of sion-resistant but very expensive materials in addition to time. the disadvantage of large man power and very high cost required for the maintenance of the plant. 55 SUMMARY OF THE INVENTION Alternatively, the organopolysiloxane of this type The present invention accordingly has an object to can be prepared by the method taught in U.S. Pat. No. provide a novel and efficient method for the prepara 2,857,356, in which an alkyl silicate and a trialkyl chlo tion of an organopolysiloxane comprising the Q units rosilane are subjected to cohydrolysis in the presence of without the problems and disadvantages in the above hydrochloric acid, or by the method taught in Japanese described prior art methods. Patent Kokai No. 61-195129, in which an alkyl silicate Thus, the method of the present invention for the or a partial hydrolysis product thereof is added drop preparation of an organopolysiloxane containing the wise to a trialkyl chlorosilane in the presence of hydro tetrafunctional siloxane units comprises the steps of: chloric acid. As compared with the ?rst described (a) mixing an alkyl silicate or a partial hydrolysis prod method, these methods have an advantage because the 65 uct thereof as a first reactant with an organosilane molar ratio of the M units and the Q units or the molec compound represented by the general formula ular weight distribution in the organopolysiloxane product can be controlled relatively easily while they 5,070,175 3 4 ganosiloxane units each represented by the general unit in which R is a hydrogen atom or an unsubstituted or formula RbSiO(4_b,/2, in which R has the same meaning substituted monovalent hydrocarbon group, X is an ' as de?ned above for the organosilane compound and alkoxy group or a hydroxyl group and the subscript a the subscript b is l, 2 or 3. Two kinds or more of differ is l, 2 or 3, or an oligomeric organosiloxane com ent organosiloxane units can be contained in a molecule pound consisting of the siloxane units represented by of the organosiloxane compound. Examples of suitable the general unit formula oligomeric organosiloxane compounds include hex amethyl disiloxane, 1,1,3,3-tetramethyl-1,3-divinyl disi Rb5i0(4~b)/2. (II) loxane, l,l,3,3-tetramethyl disiloxane, octamethyl cy 10 in which R has the same meaning as de?ned above clotetrasiloxane, l,3,5,7-tetramethyl- l ,3,5,7-tetravinyl and the subscript b is l, 2 or 3, as a second reactant to cyclotetrasiloxane and the like though not particularly form a mixture; and limitative thereto.
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