GB648639A - Improvements in the production of moulded rubber articles - Google Patents

Abstract

Esters of hydroxy-carboxylic acids containing an uninterrupted chain of at least 18 carbon atoms, in which an hydroxyl group is esterified with a monocarboxylic acid and a carboxylic group is esterified with a saturated aliphatic alcohol, in particular esters conforming to the formula R[OOC.CnHm(OOC.R1)p]q where n is at least 17, p is 1 or 2 and m+p=(2n - 1) or (2n+1), R is a saturated straight-chain aliphatic hydrocarbon radical of valence q, and R1 is an alkyl radical, are used as mould lubricants for rubber goods (see Group V). Preferably R contains 2 or 3 and R1 1 to 3 carbon atoms. Examples are glycerides of acetylated aliphatic hydroxy-carboxylic acids containing a double bond but the ester may be an ester of ethylene glycol and the hydroxy group of the hydroxy-carboxylic acid may be esterified with the propionic or benzoic acid radical. The esters may be obtained from the corresponding long-chain unsaturated acids by first esterifying an alcohol of formula R(OH)q with an hydroxycarboxylic acid and then esterifying the hydroxy group of the long-chain acid, e.g. with the acid chloride of the appropriate carboxylic acid. Alternatively an ester of a long-chain unsaturated acid may be heated with a peracid to give the corresponding epoxide and organic acid. The organic acid thus liberated reacts on continued heating with the epoxide giving the half-ester which can then be further esterified. The reaction may be interrupted after the first stage, however, and the epoxide hydrolysed to the corresponding dihydroxy compound and the hydroxy groups esterified. Olein (glyceride of oleic acid) may thus be converted to the acetylated glyceride of dihydroxystearic acid (the essential constituent of grape seed oil). Acetylated castor oil (acetylated glyceride of ricinoleic acid) is also specifically referred to.ALSO:Moulds for moulding articles from rubber compositions are lubricated with an ester of an hydroxy-carboxylic acid containing an uninterrupted chain of at least 18 carbon atoms, in which an hydroxyl group is esterified with a monocarboxylic acid and a carboxylic acid group is esterified with a saturated aliphatic alcohol. The preferred lubricants, e.g. acetylated grape-seed or castor oil, fall within the general formula R[OOC.CnHm(OOC.R1p)]q, where n is at least 17, m+p=2n or 2n/sB1, R is a saturated straight-chain aliphatic hydrocarbon radicle of valence q and R1 is an alkyl radical, R preferably containing 2 to 3 carbon atoms and R1 1 to 3 carbon atoms. The glycerides of acetylated aliphatic hydroxycarboxylic acids containing a double bond are stated to be suitable but the alcohol may be ethylene glycol and R1 may be the propionic or benzoic acid radicals. The lubricant may be applied to a warm mould by spraying as a 1 per cent solution in naphtha or ethyl alcohol, the solvent is allowed to evaporate and the rubber composition moulded in the usual manner. Where corrosion of the mould is not likely to be great a 2-3 per cent dispersion in water may be used.