GB986814A - Method for forming resin foams - Google Patents

Abstract

A process of forming a resin foam comprises introducing into a zone of agitation liquid polymerizable resin-forming ingredients comprising a >CH = CH2 monomer and a polyester of a glycol or dihydric alcohol and of an alpha-beta ethylenically unsaturated dicarboxylic acid, a curing agent for the ingredients, and a blowing agent soluble in the ingredients, said blowing agent being adapted to be absorbed in the mixture at relatively high pressures and at relatively low temperatures, but being adapted at lower pressures and higher temperatures to produce foaming, the introduction of the ingredients into the zone of agitation being at a temperature and under a pressure sufficient to maintain the blowing agent in solution without appreciable bubble formation, ejecting the mixture from the zone of agitation into a zone at the pressure of foaming and allowing the material to foam and cure, the material being ejected through a pressure reduction zone have a sufficiently low ratio of depth to diameter that the formation of bubbles in the mixture is substantially inhibited until the mixture has essentially escaped from the pressure reduction zone into the zone of lower pressure. The blowing agent may be a chlorofluorocarbon. The reaction may also generate a gas, such as carbon dioxide, which under the conditions in the zone of agitation is also absorbed in the resin-forming components. In the example the unsaturated polyester is prepared by reacting isophthalic acid, triethylene glycol and maleic anhydride. For storage it is mixed with a gelation inhibitor, e.g. hydroquinone, 3-isopropyl-catechol or tertiary butyl catechol, or a quaternary ammonium salt, e.g. trimethyl benzyl chloride or diisobutylphenoxyethoxy ethyl dimethyl benzyl ammonium chloride, or copper naphthenate. Mixed with polystyrene it gives an interpolymerizable mixture. To it may be added emulsifiers or flameretardants such as chlorinated wax. Foam stability is improved by adding an organic acid, e.g. fumaric or maleic. Such a mixture is passed to a suitable mixing apparatus (see Division B1) having a shearing effect in which it is mixed under pressure with a mixture of CC12F2, CC13F and methyl ethyl ketone peroxide (or benzoyl peroxide or cumene hydroperoxide) (to which carbon dioxide may be added) dissolved in dimethylphthalate, added at a lower level in the mixing chamber. Foaming and the gelling and setting of the resin take place after the discharge from a suitably proportioned orifice, and may be accelerated by heating, e.g. at 100 DEG to 250 DEG F.