Preparation of polymethylphenylsiloxanes, polydimethylphenylsiloxanes and varnishes based on them

Preparation of polymethylphenylsiloxanes, polydimethylphenylsiloxanes and varnishes based on them 

Polydimethylphenylsiloxanes are prepared by the hydrolytic cocondensation of di- and trifunctional organochlorosilanes and subsequent polycondensation of the obtained products. 

When di- and trifunctional organochlorosilanes cocondense in an acid medium, there are favourable conditions for the interaction (according to the scheme of intermolecular condensation) of structure I cyclic compounds, formed as a result of intermolecular dehydratation of alkyl- and aryltrihydroxysilanes, with linear products of the hydrolytic condensation of diorganodichlorosilanes. As a result, as the products polycondense further, we find structure II cyclolinear polymers  

Structure II polymers are relatively elastic when polymethylphenylsiloxanes are obtained by the hydrolytic cocondensation only of trifunctional monomers (e.g., methyl- and phenyltrichlorosilanes), there are polymers with low elasticity. Polydimethyl- and polymethylphenylsiloxanes can be modified with organic polymers (polyester, epoxy) or silicone substances, e.g. methyl(phenylaminomethyl)diethoxysilane. The modification of polydimethyl- and polymethylphenylsiloxanes improves some properties of these polymers and varnishes based on them in particular, it considerably increases adhesion and mechanical durability of varnish films. 

The production of polydimethyl- and polymethylphenylsiloxanes and varnishes based on them comprises two main stages hydrolytic cocondensation solvent distillation and filtering of varnish. 

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