Preparation method of hydroxyl-terminated polymethylphenyl siloxane with controllable viscosity

Abstract

The invention provides a preparation method of hydroxyl-terminated polymethylphenyl siloxane with controllable viscosity, which comprises the following steps: A) mixing methylphenylcyclosiloxane and methylcyclosiloxane, and dehydrating under vacuum conditions to obtain a dehydrated material; B) adding a double-hydroxy-terminated siloxane end-capping agent and a basic catalyst into the dehydrated material, heating to 90-110 DEG C, reacting for 3-6 hours, continuously heating to 120-160 DEG C, and introducing nitrogen to break the medium, with the dosage of the double-hydroxyl-terminated siloxane end-capping reagent calculated according to a formula (1) and accounting for 0.05%-5% of the total weight of the ring body; and C) removing low-boiling-point substances in the reaction product obtained in the step B) under a vacuum condition to obtain the viscosity-controllable hydroxyl-terminated polymethylphenyl siloxane with the structure shown in the formula I. The preparation method solvesthe problem of poor compatibility between the end-capping agent and the raw material, and finally, realizes the controllable viscosity of a methylphenyl 108 adhesive.

Description

technical field [0001] The invention belongs to the technical field of rubber preparation, and in particular relates to a preparation method of a viscosity-controllable hydroxyl-terminated polymethylphenylsiloxane. Background technique [0002] Methyl phenyl 108 glue is a kind of polymer in which some dimethylsiloxane links in 107 glue (α,ω-dihydroxy polydimethylsiloxane) are replaced by methylphenylsiloxane links. It is a commonly used base for room temperature vulcanized silicone rubber. Compared with the traditional 107 glue, due to the introduction of methylphenylsiloxane, this kind of product has more excellent properties, such as lower low temperature resistance, higher high temperature resistance, better heat resistance Oxidation performance, high refractive performance and better radiation resistance will play an irreplaceable role in aerospace, military nuclear power, electronic packaging, cryogenic equipment and other fields. [0003] At present, the commonly use...

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Problems solved by technology

[0004] 1) Using methylphenyl ring body and dimethyl ring body, under the action of basic catalyst (such as tetramethylammonium hydroxide alkali gel), first polymerize, then add water to degrade to a suitable viscosity, and finally under high temperature and high vacuum The main problem of removing volatile low molecules under conditions is: due to the low boiling point and saturated vapor pressure of water, the water actually participating in the reaction cannot be accurately controlled, which in turn leads to uncontrollable viscosity of the product and wide molecular weight distribution;

[0005] 2) The use of methylphenyl hydrolyzate and dimethyl hydrolyzate to polymerize under the action of an acid catalyst has the following main problems: high requirements for equipment, especially the use of acid as a catalyst; in addition, the neutralization of acid catalysts produces more Too much salt will also lead to problems such as poor product transparency, difficulty in filtering salt, and uncontrollable viscosity.

[0006] 3) It is prepared by the hydrolysis equilibrium method of dimethyldichlorosilane and methylphenyldichlorosilane. Although the cost is relatively low, there are still many problems, mainly: 1) There will be a large amount of acidic waste water, which requires high equipment ;2) Uncontrollable viscosity, etc.

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