Patent GB-1537007-A (GB)
Title: Crosslinked polymers based on cyanic acid esters
IPC: C08G73/06
Filed: 1977-05-04
Abstract: 1537007 Polymers based on cyanic acid esters BAYER AG 4 May 1977 [8 May 1976] 18643/77 Heading C3R In one aspect the invention is for a process for the production of a crosslinked polymer based on a cyanic acid ester which comprises reacting in a first stage at a temperature of from 30 to 250 C. a polyol containing hydroxyl groups attached to aliphatic carbon atoms and a polyfunctional aromatic cyanic acid ester to form a partially crosslinked prepolymer which contains one or more hydroxyl groups, iminocarboxylic acid ester groups, triazine rings, and optionally, one or more free cyanate groups, and which is soluble in organic solvents, and in a second reaction stage, hardening the prepolymer by heating to a temperature of from 100 to 350 C. and/or by reaction with a polyisocyanate and, optionally, a compound containing NCO- reactive groups. When the hardening reaction is carried out in the absence of a polyisocyanate, polytriazines containing polyols as internal plasticizers are formed, and when the hardening is carried out using polyisocyanates, the crosslinked polymer obtained contains triazine rings, tri-substituted bis-oxymethylene urea groups and urethane groups. In another aspect the invention is for a partially crosslinked prepolymer formed from a polyol containing hydroxyl groups attached to aliphatic carbon atoms and a polyfunctional aromatic cyanic acid ester, the prepolymer being soluble in organic solvents and stable in storage at room temperature and containing one or more hydroxyl groups, triazine rings, iminocarboxylic acid ester groups, and optionally, one or more free cyanate groups. The cyanic acid esters preferably have the Formula Ar(OCN) n  where Ar is an aromatic radical optionally interrupted by one or more bridge members and n is 2 to 5. The polyol generally contains 2 to 8 hydroxyl groups and may be of low M.Wt., e.g. mono-, di-, tri- or polyalkylene glycols having a M.Wt. of up to 400, glycerol, trimethylolpropane, castor oil, certain ester diols, diol urethanes and diol ureas, or of high M.Wt., e.g. M.Wt. from 400 to 10,000, such as polyesters, polyethers, polythio ethers, polyacetals, polycarbonates, polyamides or polyesteramides. Preferred polyols are polyesters, polyethers or polyurethanes containing 2 or 3 hydroxyl groups. The reaction stages may be carried out in the presence of a solvent and a catalyst and, in the case of the production of a crosslinked polyurethane, a blowing agent. Other conventional additives may be present. The polyisocyanate may be aliphatic, cycloaliphatic, araliphatic, aromatic or heterocyclic. Suitable NCO-reactive compounds are the above polyols and aliphatic or aromatic diamines. The foams are preferably produced in moulds. In typical examples a prepolymer prepared by reacting a polypropylene glycol and bis-2,2-(4-cyanatophenyl)- propane at 120 C. is either (1) hardened by heating at 160 C. to form a composite material of two inseparable layers; or (2) reacted with 4,4<SP>1</SP>- diisocyanato-diphenylmethane to form an NCO- prepolymer which is reacted with 1,4-butane diol. In another example a polyurethane foam having a compact outer skin and a cellular core is prepared by reacting a polypropylene glycol with bis - 2,2 - (4 - cyanatophenyl) - propane in the presence of dibutyltin dilaurate, followed by reaction with a trifunctional polypropylene oxide, ethylene glycol, trimethyol-propane and crude diphenylmethane diisocyanate in a mould in the presence of monofluorotrichloromethane and dibutyltin dilaurate.