| 摘要 |
Bead polymers are prepared by polymerising ethylenically unsaturated monomers at below 50 DEG C in the presence of water, a dispersing agent (a) and a catalyst system comprising dicyclopentadienyl iron, an oil-soluble organic peroxide oxidizing agent (b) and a water-soluble reducing agent (c). Specified ingredients are (a) polyvinyl alcohol, gelatin, pectin, methylcellulose, alginates, starch and bentonite; (b) benzoyl, lauroyl, di-t-butyl, acetyl, tolyl, acetyl-benzoyl and o-chlorobenzoyl peroxides, and (c) sodium and zinc formaldehyde sulphoxylates, chlorobenzene-and p-toluene-sulphinic acids, and sodium p-toluenesulphinate, bisulphite and thiosulphate. Dicyclopentadienyl iron and the peroxide (b) are preferably utilized as solutions in the monomer. Vinyl acetate is the preferred monomer, but other specified monomers are acrylonitrile, ethyl acrylate, methyl methacrylate as well as acrylic and methacrylic acids; vinyl chloride and vinylidene chloride; vinyl stearate; styrene. Copolymerisatio of e.g. vinyl acetate with either dibutyl maleate or crotonic acid, is also mentioned. Polyvinyl acetate beads prepared according to the invention may be hydrolysed to polyvinyl alcohol by use of e.g. methanolic NaOH. The polymerization reaction may be stopped with hydroquinone. U.S.A. Specification 2,680,756 is referred to.ALSO:A catalyst system, used in suspension polymerization to give bead polymers, comprises dicyclopentadienyl iron, an oil-soluble organic peroxide oxidising agent and a water-soluble reducing agent. Specified catalyst components are:- sodium and zinc formaldehyde sulphoxylates, chlorobenzene- and R-toluenesulphuric acids, and sodium p-toluenesulphinate, bisulphite and thiosulphate; benzoyl, lauroyl, di-t-butyl, acetyl, tolyl, acetyl-benzoyl and o-Cl-benzoyl peroxides. For polymerization, a dispersing agent such as polyvinyl alcohol, gelatin, pectin, methylcellulose, alginates, starch and bentonite, is also present. It is preferred to add both the dicyclopentadienyl iron and the peroxide as solutions in monomer, specifically vinyl acetate. U.S.A. Specification 2,680,756 is referred to.
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