GB723467A - Improved cellular phenolic resin - Google Patents

Abstract

Low density resin foams of uniform texture are made by adding an aliphatic ether, having a boiling point not in excess of 150 DEG C., in an amount of 0.5 to 10 per cent by weight of the resin and an acid selected from hydrochloric, sulphuric, nitric, and water-soluble aromatic sulphonic acids, to a heat-hardenable liquid A-stage monohydric phenol-formaldehyde condensate containing less than 10 per cent by weight of water. The ether may be mixed with the condensate before the acid is added, or preferably the acid and ether are mixed together and then added to the condensate. Ageing of the acid-ether mixture at room temperature for 24 to 28 hours results in a firm uniform foamed structure. Phosphoric acid may be added in an amount equal to the specified acids which are used in amounts of 1 to 2 per cent by weight of the neutral mixture of the resin and ether. Ethers specified are dimethyl, diethyl, diisopropyl, n-butyl, methyl-tertiary butyl, isopropyl-tertiary butyl, methyl-isopropyl and methyl-ethyl ethers. The liquid condensates specified are the alkaline catalysed reaction products of 1.3 to 1.6 mols. of formaldehyde with 1 mol. of a monohydric phenol, e.g. phenol, m-cresol, m-xylenol or a mixture of phenol and o-cresol. Catalysts specified are sodium, potassium, barium and ammonium hydroxides, magnesium oxide, diethylamine and ethylene diamine. In examples, liquid condensates made from phenol and formalin in the presence of (1) barium hydroxide, and (2) caustic soda, are foamed by rapidly mixing with polyethylene ether of sorbitan monopalmitate, hydrochloric acid, sodium bicarbonate and diethyl ether. Other foams are made by using other ethers, a different acid, other esters or by omitting the bicarbonate. U.S.A. Specification 2,446,429 is referred to.