GB802531A - Synthetic rubber-like materials - Google Patents

Abstract

A process for the manufacture of synthetic rubber-like materials by heating together (a) an organic polyisocyanate or an isocyanate adduct which on heating decomposes to form an organic polyisocyanate and optionally also a substance which will react with a polyisocyanate to form a thermolabile adduct and (b) the polymer obtained by heating together an organic diisocyanate and a substantially linear polyester or polyesteramide prepared by condensation of one or more dicarboxylic acids and one or more bifunctional hydroxyl or amino compounds and having as terminal groups predominantly hydroxyl groups is characterised in that there is incorporated in the mix formaldehyde or a polymer thereof, in amount itself not sufficient to achieve a complete cure. The proportion of diisocyanate used in the preparation of the polyester or polyesteramide/diisocyanate reaction product (referred to as "raw rubber") is preferably such that the product attains on heating a maximum Williams Plasticity Number in the range 200 to 550. In the curing of the raw rubber adducts of polyisocyanates with, for example, acetoacetic esters, phenols, tertiary alcohols or secondary amines can be used. Preferred are adducts (containing no free isocyanate group) with phenols such as phenol itself, p-tert.-butylphenol, o- or p-nitrophenol or 2:4-dichlorophenol. Other suitable phenols are those substituted by alkyl, cycloalkyl, aralkyl, aryl, alkoxy, halogen, nitro, cyano, carbalkoxy, acyl or alkylsulphonyl radicals. The substances forming thermolabile adducts with diisocyanates may be those referred to in Specification 785,882. Suitable amounts of formaldehyde are from 0.2 to 4.0 parts per 100 parts of polymer. An acidic or basic catalyst can be used in the curing stage. The formaldehyde may be incorporated together with the other curing agents or in a preliminary step. In an example: (1) a "raw rubber" of Williams Plasticity Number 540 prepared by reacting a polyethylene adipate with 1.1 mols. of naphthylene-1:5-diisocyanate is milled with paraformaldehyde and naphthylene-1:5-diisocyanate and the mixture is moulded under heat and pressure. In further, generally similar, examples: (2) the "raw rubber" is a glycol-succinic acid/adipic acid reaction product; (3) phenol is included in the moulding mixture; (4) and (5) in the moulding stage there are used adducts (containing no free isocyanate group) of phenol and diphenylene4:41-diisocyanate, and of phenol and naphthylene-1:5-diisocyanate, respectively. In comparison experiments the paraformaldehyde or diisocyanate are omitted. Specifications 580,524 and 767,578 are referred to.ALSO:Masked diisocyanates, for use in the preparation of polyurethanes, are prepared by reacting a phenol, which may contain alkyl, cycloalkyl, aralkyl, aryl, alkoxy, halogen, nitro, cyano, carbalkoxy, acyl or alkylsulphonyl substituents (e.g. p-tert.-butyl phenol, o- and p-nitrophenol or 2:4-dichlorophenol) with the appropriate diisocyanate. In this manner there are prepared the bis adducts of phenol with diphenylene - 4:41 - diisocyanate and naphthalene-1:5-diisocyanate, respectively, in the presence of dimethylcyclohexylamine as catalyst. Specifications 580,524, 767,578 and 785,882 are referred to.