GB990634A - Stabilisation of polyisocyanates - Google Patents

Abstract

Polyisocyanates are stabilized by incorporating therein a zinc salt of an acid selected from the group of thio acids consisting of thio- and dithiophosphoric acids of the formula <FORM:0990634/C2/1> thiophosphinic and dithiophosphinic acids of the formula <FORM:0990634/C2/2> and thio- and dithio-carbamic acids of the formula <FORM:0990634/C2/3> wherein X represents sulphur or oxygen and wherein (a) R and R1 represent hydrocarbon radicals which may be the same or different and may be unsubstituted or substituted (e.g. by methoxy groups) or (b) R and R1 together form an alkylene group, optionally containing a hetero atom (e.g. oxygen or sulphur), which together with the remainder of the thio acid molecule will form a ring structure containing 4 to 8 atoms in the ring, or (c) R represents an hydrocarbon radical and R1 represents a group of the formula (-A-T)nR, wherein A represents a bifunctional alkylene or arylene radical or an alkylene radical interrupted by hetero atoms (e.g. oxygen or sulphur), T is the residue of the thio acid concerned after removal of the groups R and R1, and n is a positive integer. The stabilizer is preferably employed in quantities ranging from 0.002% to 5% by weight of the polyisocyanate. Specified polyisocyanates include hexamethylene, phenylene, tolylene, diphenylmethane, chlorophenylene, naphthylene, 3 - methyldiphenylmethane, diphenylether and dichlohexylmethane diisocyanates; 4,41 - diisocyanato - 3,31 - dimethyl - diphenyl; 2,4,6-triisocyanatotoluene, 2,4,41 - triisocyanatodiphenyl ether; reaction products of an excess of a diisocyanate with polyhydric alcohols such as trimethylolpropane; uretedione and isocyanurate polymers of tolylene diisocyanates and polyisocyanate compositions obtained by phosgenation of the mixed polyamine reaction products of formaldehyde and a mixture of aromatic amines such as aniline and ortho-toluidine. The polyisocyanates may be subsequently converted to polyurethanes. Specifications 990,631 and 990,632 are referred to.