SETT ATT FRAMSTELLA FENOLHARTSSKUMPLASTER MED MINSKAD BENEGENHET TILL KRYMPNING OCH SPRICKBILDNING

1362393 Phenolic resin foams DYNAMIT NOBEL AG 24 Nov 1971 [28 Nov 1970] 54685/71 Headings C3C and C3R A process for the preparation of a phenolic resin foam comprises foaming and hardening a liquid resol resin having a solid resin content of 60-85% by weight, the resin having incorporated therein, before foaming, 2-30% by weight, based on the weight of the resin, of a hydrocarbon oil which, at room temperature, is liquid at all pressures within the range of 1-11 atmospheres and which has a flash point (accordding to DIN 51 584) of above 150‹ C. The hydrocarbon oil may consist of paraffinic hydrocarbons, aromatic hydrocarbons, naphthenic hydrocarbons, or mixtures thereof with olefinically unsaturated hydrocarbons. Preferred hydrocarbon oils are mineral oils and extracts. The resin may also contain boric acid, in an amount 5-30% by weight, as a fire-proofing agent. The foaming may be-carried out by using solid compounds, e.g. alkali metal carbonates and bicarbonates which liberate inert gases under the reaction conditions or liquid blowing agents e.g. n-pentane, chlorofluoromethanes or petroleum fractions. The phenolic resin foam produced by such a process has a density of 20- 200 kg./m.3 and a shrinkage capacity of 0À1- 2À8% and little or no tendency to form cracks when exposed, in the form of panels measuring 250mm. x 130 mm. x 30 mm., for 30 minutes to a temperature of 450‹ C. in a muffle furnace. Conventional hardening agents may be added to the liquid resol. A surfactant, e.g. ethoxylated castor oil, which also acts as a cell regulator may also be present. In the examples the resol resins are prepared by reacting phenol and formaldehyde in aqueous sodium hydroxide. The foams may be made in open box moulds or continuously by foaming the mixture between the belts of a double belt press.