JPS61130389A - Refrigerator oil composition - Google Patents

Abstract

PURPOSE:To provide the titled compsn. which has a high viscosity index and excellent flon refrigerant solubility, by dissolving a polymethacrylate in an alkylbenzene. CONSTITUTION:A polymethacrylate is dissolved in a base composed of a soft and/or hard alkylbenzene to obtain a base oil having a viscosity index of 180 or above and a critical solution temp. with monochlorodifluromethane of 30 deg.C or above. Not more than 3.0wt% phosphorus extreme-pressure additive such as tricresyl phosphate and not more than 3.0wt% silicone anti-foaming agent such as dimethyl-polysiloxane are blended with the base oil.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a refrigeration compressor using Freon as a refrigerant, particularly to a rotary refrigeration compressor.

Generally, chlorofluorocarbon gas is used as a refrigerant in refrigerators, and its solubility with hydrocarbon-based refrigerating machine oil can be said to be large, although there may be some differences depending on its structure. Compared to a reciprocating type such as a rotary refrigeration compressor, if the compression pressure of the fluorocarbon refrigerant is high, the amount of fluorocarbon gas dissolved in the refrigeration oil also increases. As the amount of fluorocarbon refrigerant dissolved in oil increases, the original viscosity of the refrigerating machine oil decreases. The decrease in oil viscosity during operation of the refrigeration compressor has an adverse effect on the sealing performance, that is, it causes a leakage phenomenon of the fluorocarbon refrigerant, reducing the refrigeration efficiency.

Hydrocarbon composition oils used as refrigerating machine oils tend to have lower viscosity as the temperature rises.

Viscosity index values are generally used to express the tendency of viscosity changes. The highest viscosity index value of natural mineral oil is about 100, and that of alkylbenzene is 60 or less even in soft form. At high temperatures during operation of the refrigeration compressor, the refrigeration oil only needs to have a sufficient viscosity so as not to impair the sealing performance. When the machine is started up, a load is applied, reducing the overall refrigeration efficiency.

Furthermore, if the refrigerating machine oil has a high viscosity, its mutual solubility with the fluorocarbon refrigerant will decrease, causing a two-layer separation phenomenon in the system, clogging the gear pillar, and accumulating in the piping, which will adversely affect the operation of the refrigerating compressor. Since refrigerating machine oil with low intrinsic viscosity cannot be used, we considered adding a viscosity index improver to solve this problem.

As viscosity index improvers, polymethacrylate,
Examples include polyimbutylene, olefin copolymers, and polyalkylstyrenes. When looking at the molecular structure of other viscosity index improvers other than polymethacrylate, their effectiveness depends on the size of the molecular weight, and the addition of large amounts carries the risk of causing cavillary leeching. . Further, even when these low molecular weight compounds were added, results were observed that the effect was weak.

The present inventor considered that polymethacrylate not only has an effect of improving the viscosity index but also has an ester structure that shows good results in mutual solubility with fluorocarbon refrigerants.

There are two types of polymethacrylate: dispersed type and non-dispersed type, and the general formula is expressed by the following formula.

Non-dispersed Dispersed R2 = H or CH3 X = polar group R and R1 of alkyl methacrylate are ci"" c
The polarity of the dispersed polymethacrylate is mainly N compounds such as amines and amides, and there are also polyalkylene glycol esters and the like.

Examples will be specifically described below.

Examples (1) Alkylbenzene (VCl2) paste oil Nipolymethacrylate was added with varying molecular weights and amounts, and the viscosity and viscosity index were measured.

Practical Example (2) A polyα-olefin was added to an alkylbenzene base oil, and the viscosity and viscosity index were measured.

Actual example (3) Oil made by adding polymethacrylate to alkylbenzene■
The mutual solubility with Freon-22 was measured.

The results of the real rights case are shown in the table and figure below.

Table fi! ! Results of Example (1) Measurement of polymethacrylate weight half-uniform molecular weight: GPC method Dynamic viscosity measurement JIS K 2283 Dynamic viscosity test method for petroleum products Viscosity index: JIS K 2283 Petroleum product viscosity index calculation method table ■ Example (2) ) Result of kinematic viscosity measurement: JIS K 2283 Viscosity index: JIS K 2283 Figure 1 Results of practical example (3) The effect of improving the viscosity index of the sample oil wt tipolymethacrylate in R-22 is due to the increase in its molecular weight. , no large difference in viscosity index was observed even with slight differences in the amount added.

Regarding the critical dissolution temperature with monochlorodifluoromethane, no problem-problematic increase was observed at the amount added in this practical example.

Based on these results, the present inventors have found that adding a small amount of polymethacrylate to 4-alkylbenzene greatly improves the viscosity index and does not adversely affect the solubility with fluorocarbon refrigerants, and has completed the present invention.

The refrigerating machine oil composition of the present invention may contain a lubricating oil additive, lf
There is no hindrance to further adding oxidation stabilizers, metal deactivators, rust preventives, etc. to l.

Claims (1)

[Claims] 1. The base oil in which polymethacrylate is dissolved based on soft, hard, or a mixture of alkylbenzene has a viscosity index of 180 or more and a critical dissolution temperature with monochlorodifluoromethane of 30°C or less. A refrigerating machine oil composition characterized by: 2. The refrigerating machine oil composition according to claim 1, which contains a phosphorus extreme pressure agent such as tricresyl phosphate and a silicone antifoaming agent such as dimethylpolysiloxane in an amount of 3.0% by weight or less, respectively.