GB1097504A - Elastomeric polyurethanes - Google Patents

Abstract

An elastomeric polyurethane is the reaction product of a diisocyanate, a polyester diol of molecular weight 700-2000, and a mixture of at least two different glycols, in proportions such that the overall ration of isocyanate to hydroxyl groups is about 1:1, while the polyester/glycol ratio ranges from 2:1 to 1:3. The glycol contains between the hydroxy groups a divalent aliphatic group containing 2-10 C atoms, of which 2-6 may form a chain separating the hydroxy groups, and optionally such groups as -O-, <FORM:1097504/C3/1> alkyl, -arylene-, and -O-arylene-O-. Examples are ethylene and tri-, tetra-, penta- and hexamethylene, neopentylene, diethylene, dipropylene, dibutylene glycols, ethyl and methyl diethanolamines, methyl dipropanolamine, p-xylylene diol, p-phenylene diethylene glycol and hydroquinone di-(ethylene glycol) ether. No glycol should comprise less than 20% of a mixture of two glycols, or less than 10% of a mixture of more than two glycols. Many conventional aromatic and aliphatic diisocyanates are listed. Suitable polyester diols may be derived from adipic, succinic, suberic, azelaic, sebacic and terephthalic acids or anhydrides with C2- 10 normal alkylene glycols, or from e -caprolactone polymerized with a glycol or aminoalkanol initiator. Suitable catalysts are metal compounds (lists), phosphines and tertiary amines, in amounts of 0.1-2 weight per cent of the reactants. The preparation preferably proceeds as a one-shot process, but it is possible to form a prepolymer from the diisocyanate and the polyester diol. Conventional pigments, fillers, and colouring agents may be added. In Examples 1, 2, 4 and 5, mixtures of two of trimethylene glycol, tetramethylene glycol and neopentylene glycol are mixed with a poly-(e-caprolactone) diol or a poly-(9:1-ethylenepropylene) adipate diol, then with diphenylmethane diisocyanate. In Example 7 toluenediisocyanate is used, and in Example 8 a mixture of tetramethylene and hexamethylene glycols.