Method for producing alpha, omega-dihydroxy polydimethyl siloxane

Abstract

The invention relates to a method for preparing Alpha and Omega-dihydroxy dimethylsiloxane and is characterized in that: copolymerization occurs between octamethylcy clotetrasiloxane or dimethyl cyclosiloxane and an alkaline catalyst; when the polymerization reaches to a certain degree, atomized water is sprayed on the surface of high viscosity high polymer to lead to degradation reaction, and after low-boiling-point compound separation process is carried out for 2 to 3 hours, the Alpha and Omega-dihydroxy dimethylsiloxane is obtained. The degradation method is characterized by being capable of leading molecular weight of the prepared Alpha and Omega-dihydroxy dimethylsiloxane to be distributed uniformly and high yield, etc.

Description

technical field [0001] The present invention relates to a method for producing rubber, in particular, to a method for producing α,ω-dihydroxypolydimethylsiloxane. Background technique [0002] α, ω-Dihydroxypolydimethylsiloxane is mainly used in the production of condensation-type silicone rubber, and its molecular weight and molecular weight distribution will directly affect the performance of the condensation-type silicone rubber produced. When using octamethylcyclotetrasiloxane (D 4 ) or dimethylcyclosiloxane (DMC) in the process of producing α, ω-dihydroxy polydimethylsiloxane, the degradation process plays a decisive role in the molecular weight size and distribution. [0003] Traditional degradation process for producing α, ω-dihydroxypolydimethylsiloxane: D 4 Or copolymerize DMC with a basic catalyst such as KOH; after the degree of polymerization of the polymer reaches a certain level, stop the stirring of the reactor, quickly add a sufficient amount of liquid wate...

AI Technical Summary

Problems solved by technology

[0004] This degradation process uses a one-time addition of sufficient liquid water. Since the water cannot be fully and evenly distributed in the polymer being polymerized, the degree of degradation of the polymer is inconsistent, resulting in the obtained α, ω-dihydroxy polydimethyl The molecular weight distribution of siloxane is wide; and the yield is only 80% to 83% after removing low boilers at 170°C with a vacuum of 0.098Mpa

[0005] In view of the disadvantages of the above process, there is a technology in China that heats the degraded water into steam and then directly passes it into the polymer being polymerized to degrade it. However, this method needs to extend the steam pipe into the high-viscosity polymer. It is easy to block; and the amount of steam is not easy to measure, resulting in the production of α, ω-dihydroxypolydimethylsiloxane difficult to control the molecular weight and distribution, and the product quality is unstable