Dimethicone preparation method

Abstract

The invention provides a dimethicone preparation method. The method comprises the following steps: pretreating hydroxyl terminated polydimethyl siloxane; evenly mixing the pretreated hydroxyl terminated polydimethyl siloxane with trimethyl chlorosilane and stirring, compressing and reacting for 1 to 8 h under 50 to 100 DEG C; releasing pressure and removing trimethyl chlorosilane and hydrogen chloride to obtain dimethicone. The raw materials of the dimethicone preparation method disclosed by the invention are easy to obtain, the preparation method is simple, the preparation conditions are moderate and easy to achieve, no additive such as a catalyst is added into, no impurity of metal ions, non-volatile acid and the like is introduced into, and the purity of a target product is high; furthermore, aftertreatment is simple, no wastewater or waste salt is generated, and environmental friendliness are achieved; in addition, reaction is complete, trimethyl silane termination is utilized, theyield of the target product is higher, the hydroxyl content is low, and no other miscellaneous element is introduced into.

Description

technical field [0001] The invention relates to a preparation method of high-purity dimethyl silicone oil, which belongs to the technical field of chemical industry. Background technique [0002] Dimethicone oil, also known as methyl silicone oil and polydimethylsiloxane, is a colorless, transparent, viscous liquid, tasteless, odorless, and non-toxic. It has excellent hydrophobicity, moisture resistance, good light transmission, and chemical Stability, widely used in insulation, heat-resistant, moisture-proof fillers, high-efficiency defoamers, release agents, lubricants and surface treatment agents. At present, the preparation methods of simethicone oil are mainly as follows: [0003] 1. Prepare simethicone oil by acid method; generally use dimethylcyclosiloxane and hexamethyldisiloxane as raw materials to prepare through equilibrium reaction. The catalysts used are mainly sulfuric acid and solid acid; the preparation of silicone oil using sulfuric acid as a catalyst requ...

AI Technical Summary

Problems solved by technology

Both steps of this method use acid, which also has the problem of relatively large waste acid production in waste water, which is not environmentally friendly, and post-treatment such as washing with water is relatively complicated, and the overall preparation steps are cumbersome. A certain non-volatile acid is difficult to remove, thereby contaminating the product and reducing the purity; and, after a long period of use, there will be a large amount of invalid solid acid, which is difficult to handle

In addition, there is a dehydroxylation step in the method, and hexamethyldisilazane is added to introduce heteroelement nitrogen into the silicone oil, which makes the obtained silicone oil prone to yellowing. At the same time, the price of the raw material hexamethyldisilazane is relatively high, which is not conducive to cost reduction.

[0007] 3. Alkali method is used to prepare silicone oil, generally using temporary catalyst tetramethylammonium hydroxide or potassium hydroxide; tetramethylammonium hydroxide is used as catalyst to produce trimethylamine during the decomposition process, which has a fishy smell and is not conducive to environmental protection, and Still there is a certain amount of metal ions in tetramethylammonium hydroxide (the traditional method for preparing tetramethylammonium hydroxide has defects such as high content of impurity ions); using potassium hydroxide as a catalyst metal ion content will be higher, reducing the target product the purity of

[0008] For example, the Chinese patent document CN102643427A discloses a method for catalyzing the production of high-purity simethicone oil with anhydrous strong base catalyst, using hexamethyldisiloxane of low molar mass as the head-sealing agent, and using anhydrous tetramethylhydroxide The ammonium methanol concentrated solution is used as a catalyst to catalyze the ring-opening of dimethylcyclosiloxane with low molar mass. The simethicone oil prepared by this invention has high purity, but it also has the above-mentioned problems, that is, tetramethylcyclosiloxane Ammonium hydroxide will decompose to produce trimethylamine in the later stage of the reaction, which has a fishy smell and is not conducive to environmental protection, and there is still a certain amount of metal ions in tetramethylammonium hydroxide, which will pollute the target product and reduce the purity; and the overall preparation steps are cumbersome, and the use of Tetramethylammonium hydroxide methanol solution will inevitably produce a small amount of methoxy-terminated silicone oil

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