Patent GB-1517673-A (GB)
Title: Process for the production of thermoformable polyisocyanurate foams
IPC: C08G18/80
Filed: 1977-02-22
Abstract: 1517673 Thermoformable polyisocyanurate foams BAYER AG 22 Feb 1977 [24 Feb 1976] 7340/77 Heading C3R A process for the production of a thermoformable rigid polyisocyanurate foam comprises reacting in the presence of at least one isocyanate trimerization catalyst and at least one blowing agent, an excess of polyisocyanate reactant which is a polymethylene polyphenyl polyisocyanate which contains at least 80% wt. of diisocyanatodiphenylmethane with an OH group-containing reactant which comprises: (a) at least one polyoxy-alkylene polyether containing at least one OH group and having an OH number of from 28 to 112 in which at least 20% wt. of the alkylene oxide component consists of ethylene oxide units, and (b) at least one dihydric alcohol having a molecular weight of from 62 to 200, the polyether (a) being used in an amount of from 0À015 to 0À04 equivalents of OH per equivalent of NCO, and the dihydric alcohol (b) being used in an amount of from 0À2 to 0À4 equivalents of OH per equivalent of NCO. The polyisocyanate component may be pure diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanates prepared by phosgenating polyphenyl polymethylene polyamines or chemically modified diisocyanato-diphenylmethanes. The polyisocyanate preferably contains from 5-60% wt. of 2,4<1>-diisocyanatodiphenylmethane. In polyether component (a) preferably at least 10% wt. of the OH groups are primary OH groups. Part of the polyether component (a) may be replaced by compounds ofM.Wt. 800 to 10,000 containing NCO-reactive hydrogen atoms, e.g. polyesters, polyamines, polythiols, polycarboxylic acids, polyacetals, polycarbonates and OH-containing polybutadienes. The dihydric alcohol (b) may be a C2-C8 alkane diol, 1,4-bis-hydroxymethylcyclohexane, di-, tri-, tetra- or poly-ethylene, - propylene or -butylene glycols. The blowing agent may be water and/or a volatile inert organic substance. Suitable trimerization catalysts include quaternary ammonium hydroxides, alkali metal hydroxides, alkali metal alkoxides, alkali metal salts of carboxylic acids, lead octoate and certain tertiary amines, e.g. N-(2- dimethyl-aminoethyl)-N<1>-methyl piperazine and tris - (3 - dimethylaminopropyl) - hexahydrotriazine. The above catalysts may be used together with conventional urethane catalysts. Conventional additives such as foam stabilizers, cell regulators and stabilizers may be added. The process is preferably carried out by the oneshot procedure and it may be carried out continuously or discontinuously. The cell diameter of the foam is generally from 0À3 to 2À5 mm. Thermoforming of the foam may be carried out by bending, pressing or stamping and the heating may be carried out in hot air ovens, microwave or infra-red heating channels or contact hot plates. The thermoforming temperature is generally from 150 to 210 C. The thermoforming may be carried out continuously or discontinuously and the foam may be profiled. In a typical example a rigid polyisocyanurate foam is prepared by vigorously mixing a component (A) comprising an ethylene oxide/propylene oxide/trimethylolpropane polyether of OH number 56, ethane-1,2-diol, water, tris - (dimethylaminopropyl) -hexahydrotriazine, potassium acetate, permethylated diethylenetriamine, a polyether polysiloxane stabilizer and a phenylmethyl polysiloxane cell regulator, with a component (B) comprising monofluorotrichloromethane and diisocyanatodiphenylmethane consisting of 90% wt. of 4,4<1>-isomers and 10% wt. of 2,41-isomers modified with 14% wt. of tripropylene glycol.