Defoamers, lubricating oil compositions containing defoamers, and machinery using lubricating oil compositions.

Abstract

This invention provides an antifoaming agent that exhibits excellent defoaming properties even under high-temperature conditions. The antifoaming agent of this invention contains a polymer in which at least a polymeric monomer (1) and a polymeric monomer (2) are polymeric components, wherein the polymeric monomer (1) is a compound represented by the following general formula (1-1), and the polymeric monomer (2) has two or more vinyl unsaturated groups. (In general formula (1-1), R is independently an alkyl group with 1 to 3 carbon atoms, R' is independently an alkyl group with 1 to 3 carbon atoms, L1 is a divalent organogroup or a single bond, n is an integer in the range of 1 to 3, P is a polymerizable group represented by general formula (P-1), general formula (P-2), or general formula (P-3), and in general formula (P-1), general formula (P-2), and general formula (P-3), R11 is a hydrogen atom or a methyl group, R12 is a hydrogen atom or an organogroup, R13 is a hydrogen atom or a methyl group, and * is a bond bonded to L1)