Addition type liquid fluorinated silicone rubber base rubber and preparation method thereof

Abstract

The invention relates to addition type liquid fluorinated silicone rubber base rubber and a preparation method thereof. The base rubber has following structural general formula of Vi(Me)2SiO-Si(Me)2O-[Si(Rf)(Me)O]m-Si(Me)2Vi, wherein Me represents CH3-, Vi represents CH2=CH-, Rf represents CF3CH2CH2-, and m represents an integer of 18-2000. According to the preparation method, 1-vinyl-3-hydroxy-1,1,3,3-tetramethyldisiloxane is taken as an end-capping agent, and two dimethyl siloxane chains are linked with vinyl, so that the screening effect of trifluoropropyl groups on vinyl at terminals of molecular chains is reduced, the steric-hinerance effect is reduced, the crosslinking activity of vinyl is guaranteed, and the oil resistance of the fluorinated silicone rubber is not damaged.

Description

technical field [0001] The invention relates to the field of rubber preparation, in particular to an addition-type liquid fluorosilicone rubber base rubber and a preparation method thereof. Background technique [0002] Addition-type liquid fluorosilicone rubber has excellent electrical insulation properties, aging resistance, good elasticity, rapid and convenient molding, no by-products in the reaction, and a wide range of operating temperatures. It can be used for packaging or infusion of electronic components and electrical equipment. In particular, it has excellent oil resistance, low volume swelling rate, can produce gaskets, sealing rings, etc. that are in direct contact with fuel, without secondary vulcanization, and has a low compression set rate, which is very suitable for the production of oil resistance for automobiles, etc. part. [0003] The vulcanization of addition-type liquid fluorosilicone rubber is based on the vinyl group in the molecular chain of the bas...

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Problems solved by technology

[0004] The structure of fluorosilicone rubber base rubber prepared in the industry is usually: Vi(Me) 2 SiO-[Si(Me) 2 O] n -[Si(Rf)(Me)O] m -[Si(Vi)(Me)O] q -Si(Me) 2 Vi, where Me represents CH 3 -, Vi stands for CH 2 =CH-, Rf represents CF 3 CH 2 CH 2 -, when more dimethylsiloxane chains or methyl vinylsiloxane chains are introduced into the molecular chain of the base rubber, it will damage the oil resistance of fluorosilicone rubber; when the molecular chain of the base rubber does not contain dimethyl silicon Oxygen chains and methyl vinyl siloxane chains (n=0, q=0), due to the larger spatial structure of the trifluoropropyl group, will cause a shielding effect on the Si-Vi directly connected to the end of the molecular chain, The steric hindrance effect will seriously affect the cross-linking activity of the vinyl group, resulting in incomplete vulcanization and affecting the mechanical properties of the product

[0005] A fluorosilicone copolymer base rubber is prepared in the Chinese patent document CN101250266A; however, the copolymer base rubber has poor oil resistance and cannot be used in harsh oil and gas environments

However, this process is not easy to control the molecular weight. When the molecular weight of the base rubber is small, it is necessary to add an excessive amount of lithium vinyl silicon alkoxide to catalyze the reaction and end-capping, and the corresponding amount of dimethyl vinyl chlorosilane must also be increased, resulting in There is a large amount of lithium chloride salt, which causes the product to be cloudy and affects the vulcanization performance

[0008] In addition, the basic rubber molecular chains in Chinese patent documents such as CN102225997B, CN103725199B, and CN103642046B are directly connected to the Si-Vi at the end of the chain with trifluoropropylmethylsiloxane chains, causing steric hindrance to the terminal vinyl group. Affects the crosslinking activity of vinyl

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