抄録
We developed polyether modified silicones as a nonionic w/o type emulsifier for dimethylpolisiloxane. However, the silicone emulsion prepared with the polyether silicone gave an unpleasant odor after a few days, making it difficult to apply to cosmetics. We found that the smell is caused by a very smal amount of propionaldehyde and that the mechanism forming the propionaldehyde is as follows.
In the process of producing polyether modified silicone, the terminal allyl group of polyether which is used as a starting material is partially isomerized to iso-propenyl group in the presence of the platinum catalyst. Isopropenyl group does not react with the hydrogen siloxane and remains as an impurity in the polyether modified silicone produced by the main reaction. Then, it is gradually hydrolyzed to produce produce propionaldehyde and polyethyleneglycol with the passage of time. And the hydrolysis of the isopropenyl group is accelerated by acid.
We developed refined and cosmetically applicable silicones by treating polyether modified silicones containing the iso-propenyl impurities with a dilute hydrochloric acid to give rise to propionaldehyde, followed by elimination of it.
