Method for production of mixed polymers containing silicon
View Patent ↗Polymer dispersions of polymers derived from silicone macromers and ethylenically unsaturated monomers are capable of incorporating large amounts of chemically bonded macromer, when the silicone macromer and part of the unsaturated monomer are polymerized in aqueous medium as an initial charge with an oil soluble initiator, and the remaining monomers are fed in and polymerized using a water soluble initiator. The dispersions may be dried to form water redispersible polymer powders.
1. A process for preparing an aqueous dispersion of silicone-containing copolymers of an ethylenically unsaturated organic monomer and a silicone macromer, or a water-redispersible polymer powder prepared therefrom, comprising: initially charging at least one silicone macromer and a portion of ethylenically unsaturated organic monomer(s); initiating polymerization with an oil-soluble free radical polymerization initiator having a solubility in water of <1% by weight; and subsequently adding the remainder of the ethylenically unsaturated organic monomer(s) and a water-soluble initiator having a solubility in water of >10% by weight to form an aqueous polymer dispersion, and optionally drying an aqueous polymer dispersion thereby obtained to form a redispersible polymer powder.
2. The process of claim 1 , wherein the initial charge is polymerized to a conversion of from 10 to 100%, the remaining monomers are then metered in and polymerized by means of a water-soluble initiator which is likewise fed in.
3. The process of claim 1 , wherein the ethylenically unsaturated organic monomer comprises one or more monomers selected from the group consisting of vinyl esters of unbranched or branched alkylcarboxylic acids having from 1 to 15 carbon atoms, (meth)acrylic esters of alcohols having from 1 to 15 carbon atoms, vinylaromatics, olefins, dienes and vinyl halides.
4. The process of claim 1 , wherein one or more linear, branched, or cyclic silicones having at least 10 siloxane repeating units and having at least one free-radically polymerizable functional group are used as silicone macromers.
5. The process of claim 1 , wherein one or more silicones of the formula R 1 a R 3-a SiO(SiR 2 O) n SiR 3-a R 1 a , where radicals R are identical or different monovalent, substituted or unsubstituted alkyl radicals or alkoxy radicals having from 1 to 18 carbon atoms, R 1 is a polymerizable group, a is 0 or 1 and n=10 to 1000, are used as silicone macromers.
6. The process of claim 3 , wherein vinyl acetate or a mixture of vinyl acetate and ethylene is copolymerized with at least one silicone macromer selected from the group consisting of α,ω-divinylpolydimethylsiloxane, α,ω-di(3-acryloxypropyl)polydimethylsiloxane and α,ω-di(3-methacryloxypropyl)polydimethylsiloxane.
7. The process of claim 1 , wherein one or more precrosslinking or postcrosslinking auxiliary comonomers are used.