Synthesis of silicone resins
According to its refractive index, it can be divided into two categories: low refractive index (1.4) and high refractive index (1.5). The refractive index of 1.4 is mainly methyl silicone materials, while the refractive index of 1.53 is mainly phenyl silicone materials.
Because the greater the refractive index of organic silicon materials, the higher the light efficiency, so we should try to improve the refractive index of organic silicon materials.
Silicone resin is usually made of organosilane, hydrolyzed and condensed in the presence of a solvent.
The raw material for synthesis is usually chlorosilane or alkoxy silane.
The specific process is as follows: first, the silane is hydrolyzed to silicol under certain conditions; second, the silicol itself is polycondensation reaction; third, the silicone resin is obtained by neutralizing with water washing and removing small molecules by concentration.
For example, Xu Xiaoqiu et al. first hydrolyzed methyl phenyl diethoxysilane, and then pyrolyzed into methyl phenyl ring body, and then synthesized colorless and transparent phenyl vinyl silicone oil with a refractive index of more than 1.5 through anion ring-opening polymerization.
Wu Tao et al. used the method of anionic ring-opening polymerization to prepare vinyl terminated methylphenyl silicone oil from the cyclic methylphenyl siloxane containing dimethylsiloxy chain and the vinyl double head under the action of alkaline catalyst.
Wu Chuan et al used acid catalysis, octamethylcyclotetrasiloxane (D4), or 1, 3, 5, 7-tetramethylcyclotetrasiloxane (D4H) and methylphenyl mixed ring polymerization in toluene solvent to prepare crosslinking agent organosilicone containing hydrogen silicone oil.
The molar ratio of pH to Si ranges from 0.30 to 0.60, the mass fraction of active hydrogen ranges from 0 to 0.5%, the refractive index ranges from 1.39 to 1.51(25℃), and the dynamic viscosity ranges from 100 to 550 MPa ·s.
Wang Xiaolu et al. synthesized phenyl vinyl transparent silicone resin by solvent-free method.
Transparent silicone resin with high refractive index and fluidity at room temperature was synthesized by hydrolysis and condensation reaction using vinyl trimethoxy silane, hydroxy-terminated polydimethylsiloxane, diphenyl dimethoxy silane and phenyl trimethoxy silane as raw materials and hydrochloric acid solution as catalyst.
In order to reduce the surface tension of LED packaging adhesive and make it easy to vacuum defoaming, Yang Xiongfa et al. prepared transparent vinyl silicone oil containing methyl trifluoropropyl siloxy chain and methyl phenyl siloxy chain.
Huang, etc with methyl vinyl chlorosilane phenyl chlorosilane, methyl chlorosilane, phenyl chlorosilane as raw material, using methyl head agent and vinyl head sealing side, the synthesis of phenyl vinyl silicone resin, and then use the aperture for 0. 45 microns of the membrane filter for filtering, which can effectively remove residual hydrochloride granules, improve product transparency, colorless transparent vinyl phenyl silicone resin.