Thermosetting Ethylenically Unsaturated Ester Resin Compositions

1,197,810. Modified epoxy resins. DOW CHEMICAL CO. 7 Nov., 1967 [7 Nov., 1966 (2); 29 Dec., 1966], No. 59646/68. Headings C3B and C3P. A thermosetting resin composition comprises a blend of: (A) at least 30% by wt. of an ethylenically unsaturated resin prepared by first reacting an ethylenically unsaturated monocarboxylic acid, e.g. (meth)acrylic acid or cinnamic acid, with a polyepoxide, e.g. a diglycidyl ether of bisphenol A or an epoxy novolac resin. A dicarboxylic acid anhydride is then reacted with the secondary hydroxyl groups to provide pendant half-ester groups; from 0À8 to 1À2 equivalents of epoxide are used per equivalent of monocarboxylic acid and from 0À1 to 1À2 moles of dicarboxylic acid anhydride, e.g. of maleic or phthalic acid per equivalent epoxide. (B) Up to 70% by weight of a polymerizable monomer containing a >C = CH 2 group, e.g. a vinyl aromatic monomer such as styrene, a hydroxyalkyl ester of (meth)acrylic acid or of crotonic acid, alkyl esters of these acids or acrylic or methacrylic acid. Rapidly thickening compositions may be obtained by mixing: (A) a thermosetting composition as set out above; (B) an oxide or hydroxide of a metal of Group II of the Periodic Table, e.g. MgO, in an amount sufficient to provide at least 0À75 equivalents per -COOH equivalent; and (C) a catalytic amount of water, i.e. at least 0À25 equivalents per -COOH equivalent. Water may be provided as water of adsorption by adding clay or other inert fillers. Reinforcing fillers, e.g. glass fibres, may also be present. The composition may contain a catalyst for free radical polymerization, e.g. an organic peroxide.