Preparation method of alkoxy-terminated linear polydimethylsiloxane

Abstract

The invention provides a preparation method of linear polydimethylsiloxane with an end capped by an alkoxy group. The raw materials for preparing the polydimethylsiloxane by the method are low in price and easy to obtain, the production process is simple, the operation is easy, the reaction temperature is mild, no special requirement on equipment exists, the alkoxy end capping rate is greater than 99%, no side reaction exists, the viscosity range of the product is controllable, the thickening and crosslinking phenomena do not exist after the polydimethylsiloxane is mixed with phthalic ester, and industrialization is easy to realize.

Description

technical field [0001] The invention belongs to the field of organosilicon materials, in particular to a preparation method of alkoxy-terminated linear polydimethylsiloxane. Background technique [0002] The low-molecular-weight alcohol released during the vulcanization of dealcoholized room temperature vulcanized silicone rubber is low-toxic and environmentally friendly, has no irritating odor, and is non-corrosive to metals. It can be widely used in electronic appliances and construction industries. As a green and environmentally friendly sealant, it has great Good development prospects. At present, the dealcoholized silicone rubber sealants on the domestic market mainly use α, ω-dihydroxy-terminated polydimethylsiloxane as the base rubber, alkoxysilane as the crosslinking agent, organic titanium as the catalyst, and fillers. In the preparation process, the viscosity of the system rises sharply or even gels, which is usually called "viscosity peak"; at the same time, duri...

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Problems solved by technology

[0004] Chinese patent CN103936995A mentions that the reaction product of secondary amine and weak acid can be used as a catalyst to prepare alkoxy-terminated linear polysiloxane, but the catalyst needs to be self-made, which increases the reaction process; CN103382251A mentions the use of tetramethylammonium hydroxide or Alkali gum is used as a catalyst to prepare alkoxy-terminated polysiloxane. There will be mono-alkoxy-terminated by-products in this reaction. The catalyst needs to be decomposed at high temperature, releasing an unfriendly smell, and the requirements for equipment are relatively high. High; CN104558612A mentions to use organic amine salt as catalyst to prepare alkoxy-terminated polysiloxane, although this method can improve the capping efficiency of alkoxy group, it is reported that its alkoxy group capping rate can only reach 95% at the highest ; CN104927058A mentions the use of granular cation exchange resins as catalysts to prepare alkoxy-terminated polysiloxanes, and this patent reports that this reaction is only applicable to the preparation of low-viscosity alkoxy-terminated polysiloxanes; CN106674524A utilizes at least Three alkoxy silsesquioxanes are used as end-capping agents, which can improve the stability and heat resistance of the final alkoxy-terminated polydimethylsiloxane, but because silsesquioxane has a large cage The structure makes the reaction between silanoxy and silanol relatively difficult. Compared with ordinary alkoxysilane, at the same reaction temperature, it is necessary to prolong the reaction time or increase the reaction temperature, and the price of silsesquioxane is much higher. Far higher than the price of ordinary alkoxysilane; CN106905530A discloses a preparation method of alkoxy-terminated polysiloxane, the preparation method is complex, and the catalyst 4-vinylbenzo-18- The crown ether-6 complex has a high boiling point and is difficult to remove, and the price is relatively expensive

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