Preparation method and application of hexamethyldisiloxane

Background and overview

Hexamethyldisiloxane is a colorless transparent liquid. Insoluble in water, soluble in various organic solvents. Deliquescence, flammable, in case of high heat, open flame, strong oxidant, there is a danger of burning. It is used in the preparation of personal protection and cosmetic products, medical defoamers and lubricants, mold release agents in the food industry, damping fluids and brake fluids for transportation equipment and instruments, cold and heat carriers, coatings, rubber and plastic additives, etc.

Preparation

A 250ml three-necked flask was equipped with an addition funnel, a nitrogen conduit and a reflux condenser, and the nitrogen purge was turned on, and 17.4g of anion exchange resin (201×4 (711) strongly basic styrene type I anion exchange resin) and purified water 26ml ( 1.4mol) into the three-necked flask, start stirring, heat up to 45 ° C, add 43.4 g (400 mmol) of trimethylchlorosilane, add trimethylchlorosilane and be warming up to 75 °C and stir for 2.5 hours, distilled at atmospheric pressure, collect 99 -100°C fraction, dried over anhydrous sodium sulfate, and filtered to obtain 30.5 g of hexamethylsiloxane with a purity of 99.5% and a yield of 93.8%.

Use

Hexamethyldisiloxane plays an important role in the production of silicone as the primary raw material for the production of downstream products of silicone, such as the preparation of personal protection and cosmetic products, medical defoamer and lubricants, mold release agents in the food industry, transportation Damping fluids and brake fluids for equipment and instruments, heat and cold carriers, coatings, rubber and plastic additives, etc.

Hexamethyldisiloxane is not only used as a raw material for the production of downstream silicone products, but is now more directly used in the cleaning industry. As a representative of cyclic and linear volatile methyl siloxanes (VMSs), hexamethyldisiloxane is environmentally friendly and does not destroy the ozone layer like fluorocarbon cleaning agents. In the United States, volatile methyl siloxane fluids are exempt from volatile organic compound (VOC) regulations and can be used as a substitute for regulated solvents, making formulations more beneficial to human health and the environment. Can be used as an alternative to cleaning agents for precision equipment used in the electronics, defense and aerospace industries. For this reason, the silicone giant Dow Corning has specially designed a cleaning agent based on hexamethyldisiloxane, which is suitable for cleaning aviation navigation system components, medical instruments and electronic components. Its low surface tension allows it to be quickly coated. And effectively remove the pollution of seals, is also an excellent carrier for oils, lubricants, coatings and silicone polymers, suitable for carrier applications requiring high purity.

High-end applications of hexamethyldisiloxane also put forward higher requirements for its quality. The silyl hydroxyl group in hexamethyldisiloxane (represented by trimethylsilanol) has strong acidity, and due to its existence, it is impossible to synthesize siloxane molecules with the expected structure; chloride ions can enhance the corrosion effect and thus greatly The most obvious effect is the chloride ion in the acid cleaning agent. For example, in the pressure vessel made of austenitic stainless steel, if there is a chloride solution, stress corrosion will occur, even if it is a trace amount of chloride ion. , stress corrosion may also occur. Both the downstream processing of silicone and the high-end cleaning industry require hexamethyldisiloxane products with low silanol content and low chlorine content.

In addition, hexamethyldisilazane is widely used in pharmaceutical industry, gas chromatographic analysis, bonding aid for photoresist in semiconductor industry, additives in rubber industry, and surface treatment agent for diatomite, silica, etc. , is also one of the silylation reagents. It can be seen that hexamethyldisilazane has important industrial application value and good application prospects.

References

【1】CN106279234,2017, A