| 摘要 |
Stable aqueous emulsions of polymers or copolymers of vinyl esters are produced by means of emulsion polymerization in an aqueous medium having a neutral or weakly acid pH and containing an anionic emulsifying agent, and in the presence of a compound of a metal selected from the metals of Group IIA of the Periodic System and aluminium, a molar equivalent of the metal being present for each mol. of the anionic emulsifying agent. The metal compounds may be magnesium chloride, calcium chloride or aluminium sulphate and the anionic emulsifying agent may normally be available as their sodium salts or as an aluminium or Group IIA metal salt of long chain alkyl sulphonic acids, alkyl aryl sulphonic acids where the alkyl chain has 12-18 carbon atoms, long chain alkyl sulphuric acids or sulphates, and the dialkylesters of sulphosuccinic acid, such as the dihexyl, diamyl and dioctyl esters. Polymerization may be effected in the presence of a catalyst such as hydrogen peroxide, or an organic hydroxy peroxide or a persulphate, optionally with the addition of a reducing agent or tartaric acid or cobalt acetate. The vinyl ester which may be the acetate or propionate may be copolymerized with vinyl laurate, vinyl stearate, vinyl capronate or acrylic acid esters, dibutyl maleate or esters of fumaric acid. As protective colloids there may be added polyvinyl alcohol and its water soluble derivatives, gum arabic, gum tragacanth, gelatine and water soluble cellulose derivatives such as hydroxyethyl cellulose, and in addition long chain alkyl, aryl, or alkyl/aryl ethers of polyethylene glycols containing 5-30-C2H4O units in the chain may also be included. |
