GB591767A - Improvements in prevention of foaming of hydrocarbon oils - Google Patents

Abstract

Foaming of hydrocarbon oils, particularly mineral oils and lubricants containing them, is inhibited by forming in the oils a fine dispersion of a small amount of a substantially oil-insoluble liquid "organo-silicon oxide" condensation compound which has a very low interfacial tension toward oils. Suitable compounds may be prepared from organic substituted silane diols, e.g., dimethyl silane diol, whose general formula is probably: <FORM:0591767/III/1> or from organic substituted orthosilicates, e.g., tetramethyl orthosilicate, whose general formula is probably: <FORM:0591767/III/2> where R is an alkyl, aryl, aralkyl, alkaryl or hetero-cyclic radicle, and n may be zero or higher. The former compounds may be prepared according to Specifications 542,655, 549,081, 561,136 and 561,226, [all in Group IV], and the latter according to U.S.A. Specification 2,317,891. Preferred compounds are where R is a methyl, ethyl or short chain alkyl group as these are more oil-insoluble. The effectiveness of these compounds for inhibiting foaming increases with Mol. Wt. and B. Pt. In use, 5-100 parts per million of such a compound is finely dispersed in the oil by a colloid mill, gear pump or other means so that the size of the dispersed oil-insoluble particles is not greater than 2m : or a similar concentrate containing 100-2000 parts per million may be made for later addition to the bulk of the oil, this latter concentrate being also suitable for direct addition to an oil which is already foaming. Alternatively the compound may be added directly to the oil if a gear pump is present in the oil circuit. Such dispersions are stable during storage and have a long life in service, and have no deleterious effects on the normal properties of the oil, and are stated to resist emulsification of the oil with water. An example is given of a dispersion of 10 parts per million of a condensation product of dimethylsilane diol of Mol. Wt. approx. 2,000 in a highly refined SAE Grade 50 paraffinic oil, which completely inhibited foaming under the conditions of a test described in the Specification. These compounds are stated to have an interfacial tension toward oils that is too low to be conveniently measured on a standard DuNoüy tensiometer. The Specification as open to inspection under Sect. 91 states that similar compounds in which the silicon is replaced by titanium, germanium, zirconium, tin, lead or boron may be used. This subject-matter does not appear in the Specification as accepted.