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Nov 26, 2020
Add materials 5, 6 and 7 into a clean and dry reaction flask with a stirring and reflux device, and gradually add a mixture of 1, 2, 3, 4 and 8 from the feeding port under stirring to maintain 20-40 The dripping is finished for about 1~1.5h between °C. Then the temperature was raised to 80C, and the ethanol produced in the reaction was evaporated. After most of the ethanol is evaporated, the temperature is raised to 120-130C, connected to a decompression system, the residual ethanol is removed under a vacuum state of 600mmHg (under 8kPa), and the temperature can be reduced by keeping it for 0.5~1h. The temperature is lowered to 60"C and the material is discharged. An organic silicon intermediate with an ethoxy content of 5.2% and a solid content of 54.21%.
Silicone polymers are based on Si-0 bonds and have good heat resistance. Ways to synthesize modified silicone resin
In many cases, organosilicon alcohols or organoalkoxysilanes are usually used to prepare organosilicon intermediates, and then the resin is modified by chemical or physical methods [2--3]. This study mainly used organoalkoxysilane to prepare organosilicon intermediates and chemically modify epoxy resin. Generally, among the monomers for preparing silicone resins, trifunctional monomers provide crosslinking points for resin curing, and difunctional monomers enhance its flexibility. The introduction of diphenyl difunctional monomers can increase the toughness and hardness of the paint film at high temperatures. However, due to the poor reactivity of diphenyl monomers, it is not easy to enter the resin structure completely, and low-molecular substances are also easy to volatilize. Therefore, the amount of diphenyl difunctional monomer should not be too much.
In the production of silicone resins, methyl phenyl monomers impart flexibility to the resin and will not reduce the hardness of the resin like dimethyl monomers, but the price is higher. Silicone resins with high methyl content have good flexibility, arc resistance, water repellency, and gloss retention; resins with high phenyl content have good thermal stability, oxidation resistance stability, and good compatibility with ordinary organic resins. . The R/Si and Ph/Me of the organosilicon intermediate have a greater impact on the polycondensation reactivity and the mechanical properties of the paint film. With the increase of R/Si, the elasticity of the paint film increases; with the increase of Ph/Me, the compatibility of silicone intermediates and organic resins increases, but the mechanical properties of the paint film decrease. The experiment uses dimethyldiethoxysilane, mono-methyltriethoxysilane, diphenyldiethoxysilane and monophenyltriethoxysilane as monomers for the synthesis of organosilicon intermediates, design m (R: m(Si+1.6+0.1, m(Ph: m(Me=1.4+0.1, in the obtained organosilicon
Some experts have proved that trace acids are powerful catalysts for the hydrolysis of alkoxysilanes [4]. The organosilicon intermediates used in this article are prepared by the partial hydrolysis of alkoxysilanes. When HCl is generated, HC1 is used to catalyze the hydrolysis of silane. Therefore, the amount of catalyst is expressed as a percentage of the chlorine content. The change in chlorine content corresponds to the change in H+ content. The Cl- content in this study is 0.2%~0.4%. The proton H+ catalyzed by qualified C1- content can catalyze ethoxyl hydrolysis to obtain silicon intermediates with qualified viscosity. When the Cl- content is less than 0.1%, the viscosity of the organosilicon intermediates is low, and excessive C1- content is unnecessary and not only causes The equipment is corroded and it will shorten the storage period of organosilicon intermediates.
Screening of epoxy resin
The relative molecular weight of epoxy resin has a direct effect on the copolymer [8]. In the case of a certain epoxy/silicone ratio, epoxy resins with large molecular weights have poor compatibility with silicone intermediates and low reactivity; small molecular weights will result in coatings that have mechanical properties and heat resistance. The performance is poor. Therefore, considering the hydroxyl value of the final product of epoxy-modified silicone resin and the properties of the paint film, such as normal mechanical properties and media resistance, E-20 epoxy resin with moderate hydroxyl content and relative molecular weight is selected. Prepare modified silicone resin with excellent comprehensive performance.