Method for producing alpha, omega-dihydroxy polydimethyl siloxane

A technology of dimethyl cyclosiloxane and octamethyl cyclotetrasiloxane, which is applied in the field of alpha production, can solve the problems of wide molecular weight distribution, inconsistent degree of polymer degradation, easy blockage of steam pipes, etc., so as to shorten the reaction time. time, improve production efficiency and save production costs

Active Publication Date: 2008-07-02
ZHONGHAO CHENGUANG RES INST OF CHEMICALINDUSTRY CO LTD
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  • Summary
  • Abstract
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  • Claims
  • Application Information

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

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0023] Production method of room temperature vulcanized silicone rubber-107 (RTV-107)

[0024] 300kg D 4 Add to a 500L vertical reactor, start stirring, dehydrate at 170°C for 1 hour, add 0.09kg of tetramethylammonium hydroxide at 110°C, evacuate and catalyze polymerization at -0.03Mpa for 20min, until the viscosity of the polymer reaches 530,000Mpa·s , close the vacuum valve of the reactor, spray 300g of liquid water on the surface of the polymer within 8s after being atomized by the atomizer to degrade it, continue to stir for 5min, then rapidly heat up to 170°C and evacuate to 0.090Mpa for 2h, Stop stirring to obtain 267kg RTV-107 (α, ω-dihydroxypolydimethylsiloxane).

[0025] The theoretical yield of the product RTV-107 in this example is 90%, and the actual yield is 89%.

Embodiment 2

[0027] Production method of room temperature vulcanized silicone rubber-107 (RTV-107)

[0028] 300kg D 4 Add to a 500L vertical reactor, start stirring, dehydrate at 170°C for 1h, add 0.11kg of tetramethylammonium hydroxide at 110°C, evacuate and catalyze polymerization at -0.04Mpa for 15min, when the viscosity of the polymer reaches 500,000Mpa·s , close the vacuum valve of the reaction kettle, spray 300g of liquid water on the surface of the polymer within 10s after being atomized by the atomizer to degrade it, continue stirring for 3min, then rapidly raise the temperature to 170°C and evacuate to 0.093Mpa, and maintain it for 2h. Stop stirring to obtain 265 kg of RTV-107 (α, ω-dihydroxy polydimethylsiloxane), the theoretical yield is 90%, and the actual yield is 88%.

Embodiment 3

[0030] Except for degradation and continued stirring for 30 minutes, other conditions were the same as in Example 2, and about 268 kg of RTV-107 was obtained, with a yield of 89%, which was almost the same as the yield of 88% after stirring for 3 minutes.

[0031] Considering factors such as yield and energy consumption comprehensively, it is more economical to continue stirring for 3 minutes.

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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...

Claims

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Application Information

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IPC IPC(8): C08G77/16C08G77/06
Inventor 李志超蒲文伦刘媛
Owner ZHONGHAO CHENGUANG RES INST OF CHEMICALINDUSTRY CO LTD
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