Esters as lubricants for a haloalkane refrigerant.

摘要

An oily lubricant for mixing with the refrigerant 1,1,1,2-tetrafluoroethane (R134a) is an ester of viscosity 2-30 mm<2>/s at 100 DEG C. Suitable classes of esters are (1) polyesters of a polyol and straight or branched chain carboxylic acid (CA), (2) diesters of neopentyl glycol and a C6-9 CA, (3) complex esters of partial esters of an aliphatic polyhydric alcohol with C3-C9 fatty acids and aliphatic or aromatic di CA, (4) C16-22 diallyl esters of aliphatic di- CA, (5) C18-26 diethyl esters of aromatic di-CA, and (6) diesters of an addition product of an alkylene oxide to a monohydric alcohol by an aliphatic di-CA. The viscosity is adjusted by using mixture of esters or by adding a polymer; suitable viscosity for a refrigerator is 2-9 mm <2>/s and for a car air conditioner it is 7-30 mm<2>/s. The ester should be purified to have a low acid number of 0.1-0.5 mg KOH (g), to prevent metal corrosion, whilst keeping high insulating property, and it is purified so as to be stable and to have no more than 500 ppm of moisture. An anti-wear agent of the sulfur type is preferably added in amount of 0.01-5 w/t%, and other additives can be an anti-oxidant and corrosion inhibitors. The lubricant has excellent compatibility with R134a, low hygroscopicity, high thermal stability and lubricating property.