DE868975C - Process for the production of siloxane resins by hydrolysis and condensation of silane mixtures - Google Patents

Description

Process for the production of siloxane resins by hydrolysis and condensation of silane mixtures The invention relates to a further advantageous embodiment the method according to patent 853 35I.

According to this older process, a mixture of silanes is common Formulas C H3 Si ---, C, H6 Si --- and C, H5 C H3 Si =, where the remaining Valences are saturated by halogen or alkoxy groups, hydrolyzed to siloxane resins and condensed, with io to 40 mol percent methylsilanes in the starting mixture, at least g, but less than 25 mole percent phenylsilanes and q.o to 70 mole percent Methylphenylsilanes are included.

It has been found that modifying this procedure is too valuable Siloxane resins can come, which can be used in all the cases in which previously known siloxane resins were used.

Siloxane resins are hydrophobic and have a high dielectric constant. These properties in conjunction with their compared to other organic Compounds with high resistance to decomposition when heated require usability this Group of resins for various purposes. While these properties are common to all siloxane resins, they differ the other properties of these resins are quite considerable, depending on the siloxane polymer constituents present and their proportions. For certain "uses are often special Properties desired.

Resins containing methyl or phenylsiloxane units with different degrees of substitution are known. They are often not enough for technical use suitable. Also the production of a resin by coupling methyl and phenyl Grignard reagents with silicon tetrachloride and hydrolysis of the coupling product is already known. The silicon compounds to be hydrolyzed contained in the coupling product unsubstituted silicon tetrachloride as well as the two monoorgano-, comprise the three diorgano and the four triorgano silicon compounds. This Resin is also unsuitable for technical use.

For many purposes it is now desirable that during the polymerization of siloxane resins @, the thickening of the resin in the last stage of thickening proceeds only slowly, since the risk of polymerization is too rapid insoluble gels are formed, their technical use in many Cases is impossible.

It has now been found that the rate of polymerization in the last stages of thickening with methyl, phenyl and methylphenylsiloxane copolymers depends on the percentage of these groups in the siloxane copolymer.

The invention now aims to provide improved ones Siloxane resins, the solutions of which dry in the air to form solids and their production can be reproduced at any time in the thickened state. The invention also aims the creation of siloxane resins of such a nature that the physical properties of the partially polymerized resins are largely predetermined during manufacture can, the siloxane resins monomethylsiloxane copolymer groups in such Composition that the resins contain technically without significant losses of monomethylsilicon derivatives can be produced.

In the siloxanes according to the invention, practically all structural groups consist mainly of the following units: CH @ Si01, "C, H, SiOi, s, CH, C, H, SiO, the methylsiloxane groups 15 to qo mol percent, the phenylsiloxane groups between 25 and 55 mol percent and the methylphenylsiloxane groups make up between 30 and 50 mol percent. The silicon atoms of the various siloxane groups are connected to one another via oxygen atoms, with oxygen and silicon atoms alternating with one another. Although most of the oxygen atoms in the groups are bonded to silicon atoms, some of the oxygen atoms form active Sites for further polymerization and is present in the form of residual hydroxyl, alkoxy, and the like. When the siloxanes are made from halides they may also contain traces of halogens. A small amount of these elements are present in all siloxanes until the Polymerization is completely finished.

In a preferred embodiment of the invention, the siloxanes largely partially condensed, but not polymerized to such an extent that they are insoluble in benzene are. _ The siloxanes according to the invention can by hydrolyzing a mixture easily hydrolyzable organosilane derivatives are obtained. The one to be hydrolyzed Mixture contains monomethylsilane, monophenylsilane and methylphenylsilane derivatives, in which the residual valences of the silicon atoms with hydrolyzable groups, such as Ethoxy groups and chlorine, are concatenated. Be for industrial manufacture the chlorine derivatives are preferred because they are cheapest to use.

In addition to monomethylsilane, monophenylsilane, the mixture to be hydrolyzed and methylphenylsilane derivatives practically no other hydrolyzable silicon compounds contain. The remaining valences of the silicon of these derivatives can with the known, easily hydrolyzable radicals or elements, such as alkoxy, aroxy, amino radicals and halogens, be saturated. The organosilicon derivatives can be according to any one of known methods can be obtained, e.g. B. by using methyl and phenyl Grignard reagents simultaneously couples with silicon in the form of tetrachlorosilane or ethyl orthosilicate. Purification of the crude reaction mixture produces the three desired silane derivatives obtained in commercially pure form, i.e. practically free from the others in the reaction product contained hydrolyzable silicon compounds, such as silicon tetrachloride or Ethyl orthosilicate. One can also separate the methyl and phenyl Grignard reagents react with silicon tetrachloride, then after cleaning monomethyl- and monophenyltrichlorosilane to win. The methylphenyldichlorosilane can be obtained by a phenyl group into the methyltrichlorosilane using a phenyl Grignard reagent, or a methyl group into the phenyltrichlorosilane using a methyl Grignard reagent introduces.

The hydrolysis can be carried out by reacting the organosilanes with water. The temperature should be low enough so that the pressure applied Methylsilane derivative does not evaporate too quickly. If the hydrolysis is too slow, it can be accelerated by adding a catalyst. Appropriately contains the reaction mixture an organic solvent, such as toluene, to the resulting Take up hydrolysis product. Even if it is from an economic point of view it is advisable to hydrolyze the silanes as a mixture, but can still be used Achieve results also by hydrolyzing the individual silanes separately and mixes the hydrolysis products with one another in the required ratio, before extensive polymerization of the individual substances has taken place.

If the silanes to be hydrolyzed are or contain chlorosilanes, this is how the Hydrolysis of hydrogen chloride. This can be in the aqueous phase remain wholly or partially in solution, depending on the Temperature, pressure and the amount of water present. For the manufacture of resins from organochlorosilanes are compositions of over 40 mole percent monomethylsiloxane undesirable, since otherwise gels will be formed from the monomethyl constituents during hydrolysis. These are undesirable and also cause emulsions to form during the later washing out of the hydrogen chloride.

If the silanes contain alkoxy groups, the hydrolysis produces alcohol, which can also remain in the aqueous phase. When using alkoxysilanes, it is even expedient to add an alcohol to the hydrolyzing agent as a solvent for the silanes. The aqueous layer may be separated or remain after the polymerization in the mixture also until after the hydrolysis of the formed 01.

Partial polymerization generally already occurs in the course of the hydrolysis of the hydrolysis product. This partially polymerized material can thickened by further partial condensation or polymerization, which takes place on heating and thus obtain the desired viscosity, which shortens the curing time. If the content of methylphenylsiloxane groups is higher, the temperatures are generally higher or longer treatment times are required to bring about the same degree of thickening, than with a lower proportion. The solvent can be used as the viscosity rises let themselves evaporate. But it can also be the solvent before thickening by heating under vacuum so that the solvent evaporates before the temperature is high enough to cause a substantial increase in viscosity bring about.

During thickening, polymerization or condensation takes place with the escape of water. With the quantitative ratios according to the invention, the viscosity increases only very gradually over the entire course of thickening, that is to say also during the last polymerization stages before the mass forms an insoluble gel. Example i A resin containing equal mole percent methyl, phenyl and methylphenylsiloxane groups is prepared as follows A mixture of the following composition: k @ Mo1- percent CH, SiC13 ................... 4.7 33.3 Co H, SiC13 ................... 6.7 33.3 C "H" CH, SiC12 ....... ...... 5.9 33.3 is gradually added to a mixture of 25.4 liters of toluene and 3791 of water at about 25-30 ° over the course of 3 hours. Then this mixture is shaken for 15 minutes and left to stand for 15 minutes. The aqueous phase is then poured off and the toluene solution of the resin is washed 7 times with water. During the first two washes, the wash water is heated to 70 °. 100 cc of concentrated ammonium hydroxide to 26.5 liters of water are added to the fifth wash water. The oil layer is concentrated by distilling off the toluene at a temperature of 115 °. The resin is then thickened by heating to 13o to 15o ° for 13 hours. Example z A resin containing 45 mole percent phenylmethylsiloxane groups, 25 mole percent phenylsiloxane groups, and 30 mole percent methylsiloxane groups is prepared as follows: A mixture of the following composition Molar percent CH3S'C13 ................... 55 30 C6 H5 Si C13. . . . . . . . . . . . . . . . . . . 65 25 CH3C, H5S'C12 ............... 195 45 is added to a mixture of 36o kg of toluene and 45o kg of water so slowly that the maximum temperature does not rise above 25 °. The aqueous layer containing hydrogen chloride is then separated from the toluene solution and this is washed with water until it is essentially acid-free. The solvent is then removed under a vacuum of 25 to 45 mm of mercury. This distillation under vacuum to remove the solvent is carried out before the siloxane has noticeably thickened. The remaining siloxane is then thickened by heating to 150 to 170 ° without a solvent and held at this temperature until the viscosity of a 5% by weight toluene solution of the resin is about 60 to 100 cSt.

Claims (3)

PATENT CLAIMS: i. Further development of the process for the production of siloxane resins by hydrolysis and condensation of silane mixtures according to -Patent 853 351, characterized in that a mixture of silanes of the general formulas C H3 Si -, C3 H5 Si ---, C, H5 C H3 Si = , in which the remaining valences are saturated by halogen or alkoxy groups, is used, the mixture containing 15 to 40 mol percent methylsilanes, 25 to 55 mol percent phenylsilanes and 3o to 5o mol percent methylphenylsilanes. 2. The method according to claim i, characterized characterized in that the hydrolysis is carried out with water. 3. Procedure according to Claim i and 2, characterized in that a further condensation or polymerization which is separated from the water layer as oil by hydrolysis and partial condensation Siloxanes are made into viscous siloxane resins by heating.