1. Synthesis of methyl silicone resin from methyl chlorosilane

Using methylchlorosilane as the main raw material to synthesize methyl silicone resin, due to the different structure and composition of silicone resin (crosslinking degree of silicone resin, namely [CH3]/[Si] value), different synthesis process conditions are required.

When synthesizing low R/Si ([CH3]/[Si] ≈ 1.0) methyl silicone resin, the hydrolysis and condensation reaction speed of the main raw material monomer methyl trichlorosilane is quite fast, and the reaction temperature must be strictly controlled not to exceed 0 °C, The reaction also needs to be carried out in a complex solvent, and the shelf life of the reaction product at room temperature is only a few days. Such products have little practical value.

Using methylchlorosilane to synthesize methylsilicone resin with larger R/Si, although the hydrolysis condensation reaction of methyltrichlorosilane and dimethyldichlorosilane mixture is slightly slower than the hydrolysis condensation reaction of methyltrichlorosilane alone, However, the hydrolysis and condensation reaction rates of methyltrichlorosilane and dimethyldichlorosilane are too different. Often because methyltrichlorosilane is hydrolyzed and condensed in advance, the ratio of the obtained mixed hydrolyzate and the raw material monomers does not match. , and the methyltrichlorosilane is often hydrolyzed and condensed in advance to form a partial cross-linked gel, and the final methyl silicone resin has poor comprehensive properties.


2. Synthesis of methyl silicone resin from methyl alkoxy silane

The hydrolysis and condensation reaction speed of methyl alkoxy silane can be controlled by changing the reaction conditions. Starting from methyl alkoxy silane, methyl silicone resins with different cross-linking degrees can be synthesized.

Commercial methyl silicone resins with a moderate degree of crosslinking ([CH3]/[Si] ≈ 1.2 to 1.5) are mostly prepared by hydrolysis and condensation of methyl alkoxy silane: methyl triethoxy refined by removing acid Silane and dimethyldiethoxysilane monomers are mixed with water, add a trace amount of hydrochloric acid or an appropriate amount of strong acid type cation exchange resin (macroporous strong acid type ion exchange resin has better catalytic effect), activated clay (dry after acidification treatment) Use it as a catalyst, heat it, and carry out a hydrolysis reaction. When the end point is reached, add an appropriate amount of hexamethyldisilazane to neutralize the catalyst hydrochloric acid, or filter out the ion exchange resin or activated clay used as a catalyst to terminate the condensation reaction. The resulting product is an alcoholic solution of methyl silicone resin.