GB1088534A - Process for the coating of substrates - Google Patents

Abstract

Coating compositions comprise a solution containing an aromatic polyisocyanate adduct and a compound or mixture of compounds each containing a plurality of aldimine and/or ketimine groups. The compositions are applied to the article to be coated and exposed to the action of moisture to hydrolyse the aldimine and/or ketimine groups and at the same time or thereafter subjecting the article to the action of heat. Polyisocyanate adducts are the interaction product of compounds containing a plurality of isocyanate groups with hydroxyl, more particularly aromatic hydroxyl, compounds such as phenols and its homologues. Numerous suitable adducts are listed. The polyaldimines or polyketimines used are those derived from diamines or polyamines and aldehydes or ketones and many suitable compounds are listed. In general, the amount of polyaldimine or polyketimine groups present should be such that about 0.05 to 1.0 aldimine or ketimine groups are present for every isocyanate adduct group.ALSO:A process for the production of films on articles comprises applying to the articles a solution containing an aromatic polyisocyanate adduct, a compound or mixture of compounds each containing a plurality of aldimine or ketimine groups, exposing the article to the action of moisture to provide water for the hydrolysis of the aldimine and/or ketimine groups and also at the same time or thereafter subjecting the article to the action of heat. Polyisocyanate adducts are the interaction products of compounds containing a plurality of isocyanate groups with hydroxyl compounds such as phenol and its homologues. The polyisocyanate may be aromatic di- or triisocyanates and also isocyanate ended pre-polymers. That is the further reaction products of phenol or its homologues with the reaction products of such aromatic isocyanates with compounds containing a plurality of hydroxyl groups in such proportions as to leave an excess of unreacted isocyanate groups. Examples of such prepolymers are the reaction product of excess of a polyisocyanate with a glycol, polyesteramide or polyether. Part of the polyaldimine or polyketimine may be replaced by a hydroxyl-ended polyether or an aliphatic polyol. The adduct may be dissolved in a solvent and the polyaldimine or polyketimine and the solution applied by brushing, dipping or spraying and the coating dried in moist air at up to 50 DEG C. The coated article is then cured by heating at up 200 DEG C or higher. The substrate may be rubber, paper, wood, leather, metals, glass, plastics such as polyvinyl chloride and textiles of artificial or synthetic fibres. Pigments, oil-soluble dyestuffs, plasticiser, light stabilisers, antioxidants and/or antistatic agents may be present.