Research and development of dimethyldiethoxysilane

The general solution silicone resin is mainly used as the basic polymer of heat-resistant coating, weather resistant coating and high-temperature electrical insulation material.

1.2 technical evolution of silicone resin

Among all kinds of silicone polymers, silicone resin is a kind of silicone product synthesized and applied early. Compared with the high-speed development of silicone rubber pattern renovation technology, the technology improvement of silicone resin is relatively slow, and the major technological breakthroughs are few. Since about 20 years ago, due to the technical progress of aromatic heterocyclic heat-resistant polymers, some of them were originally used in the field of silicone resin. However, the solvent toxicity and harsh curing conditions of aromatic heterocyclic heat-resistant polymers limited their application. In recent years, people began to pay more attention to the research and development of silicone resin. Silicone resin has a wide temperature range and aging resistance. The performance and hydrophobic moisture-proof performance are good and other outstanding advantages, there are signs that the silicone resin may have a larger development space in the future.

2. General silicone resin

2.1 production process of general silicone resin

Different kinds of silicones have different raw materials and synthetic routes. In this paper, the production process of several kinds of silicone resins is simply introduced.

2.1.1 methyl silicone

2.2.1.1 synthesis of methylsilicone resin from methylchlorosilane

Methylsilicones are synthesized with methylchlorosilane as the main raw material. Due to the different structure and composition of silicones (the crosslinking degree of silicones, i.e., [CH3] / [Si] value), different synthesis conditions are needed.

When low R / Si ([CH3] / [Si] ≈ 1.0) methyl silicone resin is synthesized, the hydrolysis and condensation reaction speed of the main raw material monomers methyltrichlorosilane is quite fast, and the reaction temperature must be strictly controlled within 0 ℃, and the reaction should be carried out in a compound solvent, and the storage period of the reaction product at room temperature is only a few days. This kind of product has little practical value.

In the synthesis of R / Si methylsilicone resin, methyltrichlorosilane and dimethyldichlorosilane are used. Although the hydrolytic condensation reaction of the mixture of methyltrichlorosilane and dimethyldichlorosilane is slightly slower than that of methyltrichlorosilane alone, the hydrolytic condensation reaction speed of methyltrichlorosilane and dimethyldichlorosilane is too different, which is often caused by the hydrolytic condensation of methyltrichlorosilane in advance. The hydrolysate is not consistent with the ratio of the two monomers, and methyl chlorosilane is often hydrolyzed to form a local crosslinking gel, resulting in poor comprehensive properties of the methyl silicone resin obtained from the hydrolysis of the three monomer.

2.2.1.2 synthesis of methylsilicone from methylalkoxysilane

The reaction rate of hydrolysis condensation of methylalkoxysilane can be controlled by changing reaction conditions. Starting from methylalkoxysilane, methylsilicone resin with different crosslinking degrees can be synthesized.

The commercial methylsilicones with moderate degree of crosslinking ([CH3] / [Si] ≈ 1.2-1.5) are mostly prepared by hydrolysis and condensation of methylalkoxysilane. The monomers of methyltriethoxysilane and dimethyldiethoxysilane refined by deacidification are mixed with water, added with trace hydrochloric acid or appropriate amount of strong acid cation exchange resin (the catalysis effect of macroporous strong acid ion exchange resin is better), and live. Sexual clay (dried after acidification) is used as catalyst, heated and hydrolyzed. When the end point is reached, add proper amount of hexamethyldisilazane to neutralize the catalyst hydrochloric acid, or filter the ion exchange resin or active clay used as catalyst to terminate the condensation reaction. The product obtained is an alcohol solution of methylsilicone resin.

2.2.2 methyl phenyl silicone

The main raw materials for industrial production of methylphenyl silicone resin are methyltrichlorosilane, dimethyldichlorosilane, Phenyltrichlorosilane and Diphenyldichlorosilane. Some or all of the above monomers are added with solvent toluene or xylene, mixed in proper proportion, dropped into water under agitation, temperature controlled for hydrolysis reaction, and HCl (hydrochloric acid aqueous solution), the by-product of reaction, is removed by water washing. The hydrolyzed silicone solution is obtained, and then part of the solvent is evaporated to form the concentrated silicone alcohol, and then the silicone resin is prepared by cold condensation or heat condensation reaction, and the finished silicone resin is obtained through filtration and packaging.

2.2.3 general purpose methyl phenyl vinyl silicone resin and its related components

The production process of methyl phenyl vinyl silicone resin is similar to that of methyl phenyl silicone resin, except that in addition to methyl chlorosilane and phenyl chlorosilane monomers, a proper amount of methyl vinyl dichlorosilane and other vinyl containing silicone monomers are added into the hydrolysis raw materials. The mixed monomers were hydrolyzed, washed and concentrated to obtain concentrated hydrolyzed silanol, adding metal organic acid salt catalyst, decompressing heat to predefined viscosity, or controlling the condensation reaction end point according to gelation time, and preparing methyl phenyl vinyl silicone resin.

Methylphenyl hydropolysiloxane, which is used as the component of crosslinker in addition reaction of methylphenyl vinyl silicone resin, is usually a ring or linear polymer with small degree of polymerization. They are produced by hydrolysis and cyclization of methylhydrodichlorosilane, or by CO hydrolysis and condensation of methylhydrodichlorosilane, Phenyltrichlorosilane and trimethylchlorosilane.

2.2.4 modified silicone

The production of blending modified silicone resin with organic resin is usually in toluene or xylene solution of methylphenyl silicone resin, adding alkyd resin, phenolic resin, acrylic resin and other organic resins, fully mixing evenly to get the finished product.

The copolymerized modified silicone resin is prepared by a series of chemical reactions. The organic resins that can be copolymerized with silicone include polyester, epoxy, phenolic, melamine formaldehyde, polyacrylate, etc. A variety of synthetic routes can be used to prepare copolymerized silicone resin, but the more practical industrial production method is copolymerization of silicone alcohol and organic resin. That is, hydrolysis of methyl chlorosilane and phenyl chlorosilane monomers together to obtain hydrolyzed silicon alcohol solution or concentrated solution, and then adding pre synthesized organic resin prepolymer to the catalyst, then mixing co heat evaporation solvent, adding zinc, zinc naphthenate and other catalysts, and cocondensation reaction at 150-170 degree temperature, until the reaction material reaches proper viscosity or predetermined gelation time, cooling, Adding solvent to dissolve and filter to obtain the finished product of copolymerized silicone resin.