Polytrimethylhydrosilysilicone’s application in silicone defoamers

Ordinary silicone defoamers are generally emulsified by high-temperature treatment of methyl silicone oil and hydrophobic white carbon black. White carbon black quickly dissolves into sodium silicate in a strong alkali and high temperature environment, while the needle tip under the white carbon black punctures the foam. The methyl silicone oil without the needle tip will inevitably lead to a decrease in the ability to defoam and suppress foaming. On the other hand, the linear molecules of methyl silicone oil gradually break in a strong alkali and high temperature environment to generate small molecules without defoaming ability. At present, there are many reports on the emulsification of silicone defoaming actives. However, emulsification is only to disperse the defoaming actives in water, which itself has little effect on the defoaming and suppressing performance. The defoaming actives are the determining factors of the defoaming and suppressing performance of the defoamer.

Silicone defoamers that are resistant to high temperature and strong alkali are mainly synthesized by adding high-viscosity hydroxyl silicone oil and MQ silicone resin to synthesize a highly branched network polymer, thereby improving the high temperature and strong alkali resistance of the defoamer.

a. The M/Q ratio of MQ silicone resin has a great influence on the defoaming performance of the defoamer. Silicone resin with M/Q=0.68 can well enhance the defoaming performance. The remaining Si-OH groups of MQ silicone resin and the residual Si-OH on hydroxy silicone oil and partially hydrophobic white carbon black can undergo complex chain breaking, condensation and cross-linking reactions under strong base catalysis to generate a polymer with a branched spatial network structure. The structure and molecular weight of MQ silicone resin are determined by the M/Q ratio. The smaller the value, the more complex its spatial network structure, and the more conducive to improving the anti-foaming performance of the defoamer. However, if the M/Q ratio is too small, it is difficult to dissolve in methyl silicone oil and cannot be used.

b. When the mass fraction of MQ silicone resin is greater than 10%, there is no obvious difference in the anti-foaming performance of the defoamer. Excessive use does not improve the anti-foaming performance. Too little does not contribute much to the anti-foaming performance, because the cross-linking degree of the formed polymer is too small, which affects the anti-foaming performance of the defoamer. Considering the cost factor, 5-10% is appropriate.

SF-201 series polytrimethylhydrosilysilicone (cas no.: 68988-56-7) with different M:Q value also widely used in products: Barrier cream, Mould release agents, High temperature resistant adhesive tape, Automobile paint sealant, Vehicle coating, Shoe Polish, etc.

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Item

CAS No./Countertype

Chemical Name

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68988-56-7

Polytrimethylhydrosilysilicone

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919-30-2

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SF-T689

546-68-9

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