Intermittent Synthesis of Methylphenyl Silicone Resin
Apr 6, 2023
Among organic silicone resins, methyl silicone resin has the lowest carbon content and high heat resistance. The steric hindrance of methyl groups connected to silicon atoms is the smallest, and the resin has high cross-linking degree, high hardness, and low thermoplastic properties. It is a good waterproof and moisture-proof surface coating and adhesive. However, pure methyl silicone resin has poor compatibility with organic compounds, pigments, etc., low thermal elasticity, and limited application range. Methylphenyl silicone resin can be seen as introducing phenyl siloxane chains into the main chain of methyl silicone resin. The introduction of phenyl siloxane chains can improve the thermal elasticity of products, compatibility with organic resins and pigments, and adhesion to various substrates. Its mechanical properties, glossiness, and compatibility with inorganic fillers are also significantly better than those of methyl silicone resin. It has the characteristics of both methyl silicone resin and phenyl silicone resin. It has been widely used as high-temperature insulation paint, high-temperature coating, high-temperature adhesive, high-temperature molding sealing material, ablation material, etc.
Organic silicone resin synthesis
(1)Hydrolyze the monomer dimethyl dichlorosilane 52 5kg, 39.9kg of diphenyldichlorosilane, 79.4kg of diphenyltrichlorosilane, and 175.5kg of solvent xylene were added to the mixed solvent, stirred, and thoroughly mixed for 30 minutes. The mixture was then pressed into the mixed monomer drip tank using carbon dioxide or nitrogen gas. Add 87kg of solvent xylene and 870kg of tap water to the hydrolysis solvent, stir for 15 minutes, control the temperature at 30-35 ° C, and start adding the mixed monomer dropwise. Afterwards, the hydrolysis temperature is controlled at 35-40 ° C, and the dropwise time is 5-5.5 hours. After the dropwise addition is completed, continue stirring for 30 minutes, and then let it stand for layering for 30 minutes. Remove the lower layer of acidic water, and draw the upper layer of silicone alcohol into the washed material. Add about 600kg of tap water for water washing. Stir for about 10 seconds, let stand and layer for 30 minutes, and remove the lower layer of water washing solution. After 6 consecutive washes, stop washing until the pH value of the washing solution is 7 '. Wash the water to neutral and filter the silicone alcohol once using a high-speed centrifuge.
(2) Concentrate by adding silicone alcohol to the concentration stick, stirring, heating with steam, vacuuming, and decompressing to remove some solvents. Measure the solid content. The solid content of concentrated silicone alcohol should be controlled between 55% and 65%. Cooling and discharging.
(3) The condensation reaction involves adding 100kg of concentrated silicone alcohol to a condensation vessel heated with an oil jacket, stirring, adding 0.03kg of catalyst zinc octanoate (mixed into a paste with less pulled xylene), opening a vacuum pump, vacuuming, heating, steaming out the remaining solvent, and then heating it to 165-175 ° C for condensation. Sampling and measuring the gelation time is carried out at any time. When the gelation time reaches 1-2 minutes and the temperature reaches 200 ° C, it is used as the end point of condensation. Mixing is continued and heating is stopped, Cool down, stop vacuuming, add the solvent xylene already prepared in the high-level tank (dilute the resin to about 60%), and while it is hot, put a small amount of resin back into the solvent at the bottom discharge port to prevent blockage. Stir o 5 hours, discharge the material, measure the solid content, adjust the solid content to 55%~56%, filter twice, pack in barrels, and inspect.
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