JPH0322439B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a refrigerating machine oil composition that has excellent thermal stability in the coexistence of a fluorocarbon refrigerant and extremely good resistance to oil film breaking load in bearings. In order to save power in refrigerant compressors used in room air conditioners, refrigerators, etc., in recent years efforts have been made to reduce the power loss by taking into account the viscous resistance of refrigerating machine oil. Progress is being made to reduce the viscosity of refrigeration oil used in However, if the viscosity of the refrigerating machine oil is reduced too much, the oil film will break at the bearing, and the original function of the refrigerating machine oil, which is to prevent direct contact between the shaft and the bearing, may be impaired. As a means to prevent such inconveniences, it is effective to add tricresyl phosphatate (hereinafter abbreviated as TCP), an extreme pressure additive, to ordinary lubricating oils.
According to studies conducted by the present inventors, when using a lubricating oil with additives as a refrigerating machine oil, the thermal decomposition reaction with CFC refrigerant at high temperatures is accelerated compared to additive-free oil, and the refrigerant compressor is damaged under harsh conditions. It has been confirmed that when the compressor is operated, carbide precipitation occurs around the discharge valve, which may impede normal operation of the compressor. The purpose of the present invention is to improve the oil film rupture resistance between a shaft and a bearing by the effect of its addition without impairing thermal stability resistance in the coexistence of a fluorocarbon refrigerant, and to create a new system that enables the use of lower viscosity oil. An object of the present invention is to provide a refrigerating machine oil composition. That is, the present inventors have been searching for a new extreme pressure additive that can improve oil film rupture resistance without impairing thermal stability in the coexistence of fluorocarbon refrigerants, and as a result, have decided to add fluorine oil to the base oil. It has thus been discovered that the desired refrigerating machine oil composition can be obtained. The refrigeration oil composition of the present invention uses mineral oil, alkylbenzene, or a mixture of mineral oil and alkylbenzene as a base oil, and adds fluorine oil equivalent to 0.1 to 5.0 weight percent of the base oil. As the fluorine oil to be added, a trifluorochloroethylene low polymer with an average molecular weight in the range of 600 to 900 was effective. Base oils with kinematic viscosity in the range of 15 centistokes to 80 centistokes at 40°C have been commonly used as refrigeration oils for refrigerant compressors, but in the new refrigeration oil composition containing the fluorine oil of the present invention, The viscosity range of the base oil could be expanded from 3 centistokes to 80 centistokes at 40°C depending on the load of the refrigerant compressor used. Conventional antifoaming agents, antioxidants, and the like can be appropriately added to the above-mentioned new refrigerating machine oil composition as necessary. Next, examples of the present invention will be shown and explained. Examples Table 1 shows the types and viscosity of base oils, types and amounts of additives, oil film breaking load, and refrigerant stability for 20 types of new refrigeration oil compositions of the present invention and 9 types of comparative examples of conventional products. The results of measurements regarding gender are shown. The oil film breaking load and refrigerant resistance stability shown in Table 1 were investigated by the following method. (1) Oil film breaking load A pair of upper and lower test pieces consisting of a cylindrical test piece and a flat plate test piece are immersed in test oil, and a constant test load is applied to the upper cylindrical test piece while the lower flat plate test piece is fixed. A friction test was conducted by rotating at high speed, and the test load was gradually increased to determine the load at which metal contact suddenly increased as the oil film rupture load. As the test pieces, carbon steel was used for the cylindrical test piece and cast iron was used for the flat plate test piece, as they were representative of the shaft/bearing combination of a refrigerant compressor. Furthermore, the sliding speed of the test piece was kept constant at 0.2 m/s, assuming a low speed range in which oil film breakage is likely to occur. (2) Refrigerant resistance stability In a pressure-resistant glass test tube with an inner diameter of 6 mm and a wall thickness of 3 mm.
0.5 ml of sample oil was collected, a steel piece (φ3.2 x 25 mm) was placed as a catalyst, this was cooled with dry ice, 0.5 ml of fluorocarbon refrigerant R-12 was collected, and it was melt-sealed. The material was heated at 175°C for 960 hours. After heating, the color of the oil/refrigerant mixture solution in the glass test tube was compared with a predetermined standard color to evaluate the progress of the chemical reaction between the oil/refrigerant. What is this standard color?
The larger the number, the more progressed the reaction between the oil and the refrigerant, and the more carbides, which are problematic reaction products, are precipitated. According to the experience of the present inventors, if the color of the oil/refrigerant mixture solution after this test is below standard No. 6, problems due to carbide precipitation will not occur under the actual operating conditions of the refrigerant compressor. . As is clear from Table 1 showing the test results under the above test conditions, the refrigerating machine oil composition of this example was
Fluorine oil added to base oil (molecular weight 600~molecular weight
900), oil film rupture resistance and refrigerant resistance stability better than the comparative example can be obtained with an addition amount of 0.1% by weight, and the oil film rupture resistance performance is improved by adding 0.5% by weight when using fluorine oil with a molecular weight of 900. It was also found that in the case of fluorine oil with a molecular weight of 600, a saturated state began to be reached at an addition amount of 1.0% by weight. In this one,
Considering that the test time was within a limited range, the amount of fluorine oil added at which oil film rupture resistance begins to reach saturation was set at 5.0% by weight, and the amount of fluorine oil added was adjusted to 0.1% by weight depending on the application. It may be determined as appropriate to a value in the range of 5.0% to 5.0% by weight. As is clear from the above results, the refrigerating machine oil composition of the present invention not only has extremely good oil film rupture resistance, but also has excellent refrigerant resistance stability at high temperatures. extremely useful.

【table】

[Table] ** Weight percentage

Claims (1)

[Scope of Claims] 1 Mineral oil, alkylbenzene, or a mixed oil of mineral oil and alkylbenzene is used as a base oil, and to this base oil, fluorine oil is added in an amount equivalent to 0.1 weight percent to 5.0 weight percent, A refrigeration oil composition characterized in that a base oil having a kinematic viscosity of 3 to 80 centistokes at 40°C is used as the base oil, and a trifluorochloroethylene low polymer having an average molecular weight of 600 to 900 is used as the fluorine oil. .