| 摘要 |
Phenol resin foams are obtained by mixing a silicone oil which has surface active properties into the resin in solution in water and introducing a foaming agent into the mixture. The silicone oil may be of the silicone glycol copolymer type. The foaming agent may be an aliphatic hydrocarbon or halohydrocarbon, e.g. "Freon" (Registered Trade Mark), petroleum ether, pentane. Setting of the resin and evaporation of the foaming agent are achieved by heating the mixture or by using a hardening agent which is a mineral or organic acid, for example HCl, H3PO4, H2SO4, toluene sulphonic acid and metanitrobenzene sulphonic acid. The resins used are those obtained by condensation by basic catalysis of phenol with formaldehyde or trioxan. The phenol and formaldehyde may be copolymerized with urea, melamine or polyvinyl alcohol. A polymerization catalyst, e.g. urea, ammonium chloride, methylene diamine and a mineral charge, e.g. talcum, mica, kieselguhr, asbestos, sawdust, small glass balls, ground glass fibre and lamp-black may be used. The process may be carried out batchwise or continuously. In the latter case the resin, oxyalkylene, silicone oil and foaming agent are in one receiver and the hardener and mineral charge in another. The constituents are stirred in a mixing chamber by a screw and the cream obtained poured into a mould or on to a moving band. |
