Patent GB-1526022-A (GB)
Title: Manufacture and use of crosslinkable thermoplastic polyurethanes
IPC: C08G18/83
Filed: 1976-01-16
Abstract: 1526022 Thermoplastic polyurethanes BASF AG 16 Jan 1976 [18 Jan 1975] 01728/76 Heading C3R A crosslinkable thermoplastic polyurethane which has a molecular weight greater than 1000 contains at least two urethane groups, at least two urea groups, at least two hydroxyl groups in side positions, at least two tertiary amino groups, and as end groups, secondary amino groups and/or epoxide or isocyanate groups is prepared by two methods the first one comprising reacting in a first stage a polyhydroxy compound (a) with a diisocyanate, (b) using more than 0À5 molecule of diisocyanate per OH group of (a), and in a second stage reacting the resulting polyisocyanate with a diamine (C1) which has a primary and a secondary amino group using more than 0À5 molecule of diamine per NCO group of the polyisocyanate, and in a third stage reacting the resulting polyamine with a diepoxide, (d) using from 0À5 to 2 epoxide groups per secondary amino group of the polyamine. The product contains secondary amino and/or epoxide end groups. In the second method a polyamine, prepared by reacting an amine (C2) carrying one primary amino group with a diepoxide compound (d) using one amino group per epoxide group, is reacted with the polyisocyanate prepared as in stage (a) of the first method, using 0À5 to 2 NCO groups per secondary amino group. In the end product the urea groups contain a tertiary nitrogen atom, and the end groups are secondary amino groups and/or isocyanate groups. The polyurethanes may be chain-lengthened by reaction with diepoxides, diisocyanates or diamines. Some or all of the OH groups in side positions on the polyurethane may be reacted with a partially blocked diisocyanate, e.g. toluene diisocyanate, isophorone diisocyanate or 4,4<SP>1</SP>-diisocyanatophenyl-cyclohexylmethane partially blocked with a dialkyl malonate, caprolactam or a phenol; the polyurethanes wherein only some of the OH groups have been reacted can be used as self-crosslinking heat curable one component coating compositions. Alternatively the polyurethane may be mixed with completely blocked di- or poly-isocyanates to produce heat-curable one component coating compositions. The polyurethane may also be crosslinked with a polyfunctional organic compound, e.g. a polyepoxide, a melamine or urea resin, but preferably a di- or poly-isocyanate, e.g. a trimethylolpropane/toluene diisocyanate adduct, a biuret polyisocyanate from hexamethylenediisocyanate or an isocyanato-polyisocyanate from toluene diisocyanate; and used as 2-component coating compositions. The compositions are applied as solutions in organic solvents. Suitable polyhydroxy compounds (a) are low M.Wt. polyols, e.g. alkane diols, unsaturated diols, ether and ester-diols, and trimethylolpropane, triethanolamine and pentaerythritol; high M.Wt. polyols (M.Wt. 600-5000), e.g. OH-containing saturated or unsaturated polyesters, polyethers, polyacetals, polycarbonates and polyacrylates; or mixtures of low and high M.Wt. polyols. The diisocyanate (b) may be aromatic, aliphatic, cycloaliphatic or heterocyclic, preferably p-phenylene diisocyanate, diphenyl-methane-4,4<SP>1</SP>-diisocyanate, naphthalene-1,5-diisocyanate, toluene diisocyanate, hexamethylenediisocyanate, isophorone diisocy anate and trimethylhexamethylenediisocyanate. The diamines (C1) are preferably N-methyl- or N- butyl-propylene-1,3-diamine or any amine of the formula where R<SP>3</SP> is an alkylene, aromatic or cycloaliphatic radical of up to 10 carbon atoms and R<SP>4</SP> is an aromatic, cycloaliphatic or aliphatic radical of up to 20 carbon atoms. The monoamines (C2) may be aromatic, aliphatic or cycloaliphatic. The epoxide is preferably a bisphenol A-epichlorohydrin condensate. In Examples 1, 2 and 4 polyurethanes are prepared by first reacting polytetrahydrofuran (M.Wt. 2000), neopentyl glycol and isophorone diisocyanate in the presence of dibutyltindilaurate and ethylglycol acetate and reacting the resulting polyisocyanate first with methylaminopropylamine and then with the reaction product of bisphenol A and epichlorohydrin. The product is optionally reacted with an addition product of caprolactam and isophoronediisocyanate. In Example 3 a polyurethane is prepared by reacting a polyisocyanate prepared from butanediol adipate (M. Wt. 1000), neopentyl glycol and diphenylmethane diisocyanate, with a polyamine prepared from butylamine and the reaction product of bisphenol A and epichlorohydrin. The product from Example 4 alone or from Examples 1 and 2 mixed either with a biuretisocyanate of the formula optionally blocked with diethylmalonate, or with a isophorone diisocyanate blocked with diethyl malonate are coated on to iron sheets and cured either at room temperature or by heating.