GB1030746A - Aldehyde polymerisation process - Google Patents

Abstract

A polymeric aldehyde is prepared by polymerizing at least one aldehyde in the presence of a polymerization initiator at a temperature below that at which the initiator would also act as a catalyst for the degradation of the polymer so formed and the initiator is thereafter rendered ineffective as a catalyst for such degradation, the initiator being the product of reacting together equimolar amounts of a N,N-dihydrocarbon substituted amide and a hydride or hydrocarbon derivative of an element of Groups Ia, IIa, IIIa and IVa (other than carbon or silicon) of the Periodic Table according to Mendel<\>aeeff. The polymerization may be effected in the presence of acid contamination provided the amount of acid present does not substantially exceed 3 moles per mole of initiator. After the polymerization and before allowing the product to warm up, the initiator is either extracted with a suitable selective solvent or a weak acid is added, if sufficient is not already present, to render it ineffective as a degradation catalyst on raising the temperature to that at which degradation of the polymer would normally occur. Aldehydes specified are formaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, n-valeraldehyde, iso-valeraldehyde, n-caproaldehyde, cyclohexaldehyde, 2-ethyl hexaldehyde, benzaldehyde and phenyl acetaldehyde. The polymerization may be effected in organic solvents that are liquid at the temperature of the polymerization and a number of these are specified. In the examples, the monomers used are acetaldehyde and n-butyraldehyde in the presence of acetic acid and butyric acid respectively, the catalysts being the reaction products of aluminium triethyl with either dimethyl formamide or tetramethyl urea, the solvents toluene alone or mixed with methyl cyclohexane. The polymerization is effected at -78 DEG C., and is terminated by adding n-butanol and acetone before allowing the mixture to warm up to room temperature. Thermal instability of the polymers may be reduced by reacting the polymer with compounds to replace its terminal hydroxyl groups with more stable groups such as carboxylate, by etherification or by the heat treatment described in Specification 980,516. The polymers may be formed into shaped articles such as films, sheets, fibres and filaments. Conventional composition additives may be incorporatedALSO:Catalysts, used for the low temperature polymerization of aldehydes (see Division C3), are made by reacting equimolar amounts of a N, N-dihydrocarbon substituted amide and a hydride or hydrocarbon derivative of an element of groups IA, IIA, IIIA and IVA (other than carbon or silicon) of the periodic table according to Mendel<\>aeeff. In the examples either dimethyl formamide or a toluene solution of tetramethyl urea are added to a solution of aluminium triethyl in a mixture of cyclohexane and toluene.