JPH0358396B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to thermally stabilized fluorinated hydrocarbon compounds (hereinafter referred to as fluorocarbons). CFCs have low toxicity, are chemically inert, and have better thermodynamic properties than other media, so they are used in many types as heating and cooling media, working fluids, and heat exchange media. It has been known. For example, difluorochloromethane (Freon 22) is used as a compression or absorption refrigerant.
Trichlorofluoromethane (Freon 11) is used as the working fluid. CFCs are chemically stable compounds, but if they coexist with metal materials in various parts of equipment, lubricating oil, or moisture, and at high temperatures of 100°C or higher, they tend to decompose, leading to corrosion of metals and contamination of lubricating oil. is known to cause
At the generator outlet of a compression refrigerator using Freon 22, the discharge gas temperature can reach 150°C or higher, so lubricating oils and Freon with high thermal stability are desired. Also, in heating and cooling systems using absorption refrigerators or absorption heat pumps, the generator temperature may exceed 100%.
Temperatures reaching ~200°C are common. Freon as an absorption medium needs to be well dissolved in the absorption solvent (absorbent), but the more thermally stable the absorbent, the worse the solubility; Thermal stability tends to be poor in the coexistence of fluorocarbons and metals, so it is desired to search for a thermal stabilizer for fluorocarbons. Furthermore, CFCs, which are used as working fluids when converting thermal energy into mechanical energy by the Rankine cycle, tend to have poor thermal stability as the Rankine cycle efficiency increases, so it is desirable to search for thermal stabilizers. It is rare. As described above, thermal stabilization of fluorocarbons is important in order to increase device efficiency, and this can also prevent corrosion of device materials and contamination of lubricating oil and the like. Based on this recognition, the present inventors conducted a search for a thermal stabilizer for fluorocarbons, and were able to discover a stabilizer that had an extremely high stabilizing effect compared to conventionally known stabilizers. did it. That is, the present invention relates to a fluorocarbon composition for a working fluid or a heat transfer medium, which is made of a thermally stabilized fluorocarbon containing a phosphine sulfide compound represented by the following general formula (). [R ₁ , R ₂ , R ₃ are the same or different alkyl groups,
Indicates an alkoxy group, or a phenyl group or phenoxy group which may have an alkyl substituent. ] CFCs are inherently chemically stable and have excellent electrical insulation properties, but at high temperatures of 100°C or higher, they tend to decompose due to the influence of coexisting substances, resulting in HCl
Produces corrosive compounds such as and HF. Such impurities not only corrode device metal materials, but also lead to a decrease in insulation resistance, and their formation must be prevented. Coexisting substances that affect the decomposition of fluorocarbons include various metals used in equipment materials,
Lubricating oil, water, alcohol, absorbent, etc. are known, and it is not uncommon for these to coexist at the same time, influencing each other and making it easier to decompose. The stabilizer of the present invention can suppress the influence of these coexisting substances and prevent the decomposition of fluorocarbons even at high temperatures. The stabilizer in the present invention has the general formula ()
It is a compound having a P=S group represented by
Examples of the alkyl group or alkoxy group represented by R in the formula include trimethyl, tripropyl, tributyl, triisobutyl, diethyl(proboxymethyl)phosphine sulfide, and the like. In the formula, examples of R being a phenyl group or a phenoxy group include triphenyl, triphenoxy, or (phenoxyphenyl) diphenylphosphine sulfide, and examples of R having these alkyl groups and phenyl groups at the same time include methyldiphenyl, Examples include methylphenylpropyl or diethylphenylphosphine sulfide. In addition, R may be a phenyl group or phenoxy group having an alkyl substituent, or R may be a halogen such as fluorine, bromine, chlorine, or sulfur, or an alkyl group or phenyl group substituted with these. . A suitable example is

【formula】

[Formula] etc. can be mentioned. The amount of these phosphine sulfide stabilizers added is at least 100 parts of fluorocarbons.
It is sufficient as long as it is 0.01 part or more, and even if 10 parts or more is added, there is no significant difference in the stabilizing effect. Preferably, about 0.02 parts to 5 parts may be added. The fluorocarbon composition stabilized according to the present invention may be used in combination with other stabilizers such as phosphite compounds, thiophosphite compounds, and other known stabilizers. The fluorocarbons stabilized by the stabilizer of the present invention are not limited in any way, but suitable examples include fluorocarbons for working fluids and heat transfer media that are exposed to high temperatures of 80° C. or higher. For example, trichlorofluoromethane, dichlorodifluoromethane, bromotrifluoromethane, dichlorofluoromethane, chlorodifluoromethane, 1,1,2-trichloro-1,2,2-trifluoroethane, dichlorotetrafluoroethane, chloropentafluoroethane, These include dichlorohexafluoropropane, octafluorocyclobutane, etc., or an azeotrope of dichlorodifluoromethane and difluoroethane, or an azeotrope of chlorodifluoromethane and chloropentafluoroethane. Coexisting lubricating oils include naphthenic and paraffinic mineral oil-based lubricating oils, linear or branched alkylbenzenes,
Synthetic lubricating oils such as ester oils and polyglycol oils, to which phenol-based or amine-based antioxidants, sulfur-based or phosphorus-based oiliness improvers, and dehydrochlorination agents such as epoxides are added as necessary. It is. On the other hand, alloys such as steel, copper, aluminum, or brass are used for the metal materials of various parts of the device, and the stabilizer of the present invention can stabilize fluorocarbons even in the coexistence of these various metals. . Examples of the present invention will be described in more detail below, but the present invention is not limited by such explanations. The material was sealed in a pressure-resistant cylinder at 150°C for 7 days, and the acid content (chloride ion concentration) based on the decomposition of fluorocarbons was then measured to evaluate the stabilizing effects of various stabilizers in the coexistence of oil and metal. The results are shown in Table 1.

【table】

[Table] All stabilizer addition amounts are based on 100 parts of Freon.
It is 0.3 parts.

Claims (1)

[Scope of Claims] 1. A fluorocarbon composition for a working fluid or a heat transfer medium comprising a thermally stabilized fluorocarbon containing a phosphine sulfide compound represented by the following general formula. [R ₁ , R ₂ and R ₃ represent the same or different alkyl group, alkoxy group, or phenyl group or phenoxy group which may have an alkyl substituent. 2. The composition according to claim 1, wherein the amount of the phosphine sulfide compound added is selected from the range of 0.02 to 5 parts per 100 parts of chlorofluorocarbons.