Ⅰ. Background and overview of hydroxy silicone oil

Hydroxy silicone oil is a linear polydimethylsiloxane whose terminal group is hydroxyl. Hydroxy silicone oils are reactive by virtue of hydroxyl groups. Higher viscosity hydroxy silicone oil, commonly known as 107 glue, is the main raw material for the preparation of condensed silicone rubber. It has been widely used in sealants, potting glue, etc., and can also be used in polyester, polycarbonate, polyurethane, epoxy resin, etc. The modification of organic polymers endows the properties of polysiloxane to the corresponding organic polymers. It can be used as a hair conditioner to make the hair bright, moist and fluffy; it can be used as a coating and pigment additive to defoam, improving leveling, anti-skinning, anti-pollution and other functions.

The low-viscosity hydroxy silicone oil in hydroxy silicone oil can be used as a structure control agent in the processing of silicone rubber. For example, in the process of processing silicone rubber, the rubber compound mixed with silicone rubber raw rubber and high-reinforcement hydrophilic silica will gradually harden during storage, reduce plasticity, and gradually lose re-milling and molding processing and other process performance.

In addition, low-molecular-weight hydroxy silicone oil emulsion is also widely used in fiber fabric finishing, and can also be used as an additive for plastic products and an excellent treatment agent for silanization of fillers. With the continuous expansion of market demand for products such as mixing silicone rubber and plastic products in China, and its application prospects will be broader.

Ⅱ. The preparation method of hydroxy silicone oil

At present, there are three methods for the preparation of hydroxy silicone oil:

1. Chlorosilane hydrolysis

Since a large amount of hydrogen chloride is generated during the hydrolysis of chlorosilane, it is difficult to control the speed of hydrolysis and polycondensation, and it is difficult to obtain hydroxy silicone oil with a very low molecular weight. In order to maintain hydrolysis under neutral conditions, a large amount of HCL absorbent must be added, so the process is complicated and difficult to synthesize low molecular weight hydroxy silicone oil.

2. Hydrolysis of alkoxysilane

Generally, the hydrolysis reaction uses a base as a catalyst or does not use a catalyst. For example, U.S. Patent US2415389 uses an alkoxysilane with the general formula (RO)nSiR', uses a small amount of base as a catalyst, and adds less water for hydrolysis. This method is used to obtain hydroxy silicone oil has a higher molecular weight.

3. Cyclic siloxane ring-opening polymerization

Cyclic siloxanes available in this method include D3, D4, etc., and their ring-opening catalysts generally use strong acids such as sulfuric acid, acid clay or strongly acidic cation exchange resins.

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