Refrigerating machine oil

Abstract: The present invention provides an oil for a refrigerating machine using a hydrogen-containing halogenated hydrocarbon as a refrigerant, the oil comprising a fluorine-containing polyether.

Description: Field of the Invention The present invention relates to a refrigerating machine oil. The refrigerating machines referred to herein include heat pumps. Background of the Invention Heretofore known as refrigerating machine oils are mineral oils such as paraffin oils, naphthene oils and the like, and synthetic oils such as alkylbenzene oils, ester oils and the like. These oils are used chiefly for refrigerating machines using trichlorofluoromethane (R-11), dichlorodifluoromethane (R-12) or the like as the refrigerant. In recent years, however, it has been suggested that chlorine-containing fully halogenated hydrocarbons such as R-11 or R-12 released into the atmosphere would deplete the stratospheric ozone layer, thereby inflicting a serious adverse influence on the ecosystem including humans on the earth. Consequently a world-wide agreement, "The Montreal Protocol" signed in September 1987, calls for the restriction of consumption and production of the major ozone-depleting flons such as R-11 and R-12. Use of CH₂FCF₃ (R-134a) or like hydrogen-containing fluorinated hydrocarbons has been proposed as a substitute for R-11 or R-12. The proposed hydrocarbons are unlikely to deplete the ozone layer but very low in compatibility with conventional refrigerator oils. Because of this defect, the hydrogen-containing fluorinated hydrocarbon used as a refrigerant in a refrigerator together with a conventional refrigerator oil significantly reduces the refrigerating capacity and coefficient of performance. Summary of the Invention According to the present invention, there is provided a machine oil used in a refrigerating machine employing a hydrogen-containing halogenated hydrocarbon as a refrigerant, the oil comprising a fluorine-containing polyether having repeated structural units represented by the formula (I) wherein ℓ, m and n are all an integer of at least zero, the polyether being capable of satisfying the relationship represented by 2≦ ℓ + m + n ≦ 200 Means for Solution of Problems We conducted extensive research to overcome the foregoing prior art problems and found that when a specific fluorine-containing oil is used in a refrigerating machine using a hydrogen-containing halogenated hydrocarbon as a refrigerant, the machine is operated without reducing the refrigerating capacity and the coefficient of performance as compared with conventional refrigerators employing R-12 (refrigerant) and a known mineral-type refrigerator oil in combination. The machine oil of the invention, used in a refrigerating machine, employing halogenated hydrocarbon as a refrigerant, comprises a fluorine-containing polyether having repeated structural units represented by the formula (I) wherein ℓ, m and n are all an integer of at least zero, the polyether being capable of satisfying the relationship represented by 2≦ ℓ + m + n ≦ 200 Such fluorine-containing polyethers are excellent in compatibility with hydrogen-containing halogenated hydrocarbons as a refrigerant over a wide temperature range. These polyethers used as a refrigerating machine oil enable the refrigerating machine to operate for an extended period of time due to their excellent resistance to abrasion. With a high volume resistivity and a low dielectric constant, the polyethers can exhibit a high electrical insulating characteristic and are useful for preventing leak of electricity. Among the fluorine-containing polyethers having the repeated units of the formula (I), preferred are those containing groups as substituents at one or both of terminals selected from the group -CH₂OH, group and group -CF₂CF₃. Among the fluorine-containing polyethers having the repeated units of the formula (I), those capable of satisfying the relationship expressed by are excellent in abrasion resistance, hence more desirable. The refrigerating machine oil of the present invention may be used in combination with a conventional refrigerating machine oil which would not adversely affect the properties of the oil of the invention. Use of such conventional oil can reduce the costs and facilitates wetting of the machine element. The oil of the invention as mixed with the conventional oil at a suitable ratio can be emulsified unexpectedly despite the incompatibility of the two oils with each other and can form a highly stable uniform layer over a wide temperature range. Such mixture used with the refrigerant specified in the invention can function as contemplated with the refrigerator oil. Examples of conventional oils for use herein are mineral oils (paraffin oils, naphthene oils, etc.), oils of alkyl benzene, polybutene, α-olefin oligomer, polyalkylene glycol, diester, polyol ester, ester sulfate, ester silicate, silicone, polyphenyl ether or the like. There is no specific limitation on the hydrogen-containing halogenated hydrocarbons usable as a refrigerant in this invention. Such hydrocarbons include hydrogen-containing fluorinated hydrocarbons, hydrogen-containing chlorinated fluorinated hydrocarbons, etc. These hydrocarbons are usable singly or at least two of them can be used in mixture. The hydrogen-containing fluorinated hydrocarbons (hereinafter referred to as "HFC") are not specifically limited. The abbreviation HFC used herein refers to chlorine-free hydrogen-containing fluorinated hydrocarbons. Examples of such hydrocarbons are: CHF₃ (HFC 23), CH₂F₂ (HFC 32), CH₃F (HFC 41), CHF₂CF₃ (HFC 125), CHF₂CHF₂ (HFC 134), CF₃CH₂F (HFC 134a), CHF₂CH₂F (HFC 143), CF₃CH₃ (HFC 143a), CH₂FCH₂F (HFC 152), CHF₂CH₃ (HFC 152a), CH₂FCH₃ (HFC 161), CHF₂CF₂CF₃ (HFC 227ca), CH₂FCF₂CF₃ (HFC 236cb), CH₃CF₂CF₃ (HFC 245cb), CH₃CF₂CHF₂ (HFC 254cb), CH₃CH₂CF₃ (HFC 236fb), etc. Among them, preferable are HFC 125, HFC 134a , HFC 143a, HFC 152a and the like. HFC's are usable singly or at least two of them can be used in mixture. The hydrogen-containing chlorinated fluorinated hydrocarbons (hereinafter referred to as "HCFC") usable with the oil of the invention are not specifically limited. Examples of such hydrocarbons are CHClF₂ (HCFC 22), CHCl₂CF₃ (HCFC 123), CHClFCClF₂ (HCFC 123a), CHF₂CCl₂F (HCFC 123b), CHClFCF₃ (HCFC 124), CHF₂CClF₂ (HCFC 124a), CHClFCHF₂ (HCFC 133), CH₂ClCF₃ (HCFC 133a), CClF₂CH₂F (HCFC 133b), CHCl₂CH₂F (HCFC 141a), CCl₂FCH₃ (HCFC 141b), CHF₂CH₂Cl (HCFC 142), CHClFCH₂F (HCFC 142a), CClF₂CH₃ (HCFC 142b), CHClFCF₂CF₃ (HCFC 226ca), CH₂ClCF₂CF₃ (HCFC 235cb), CH₃CF₂CClF₂ (HCFC 244cc), CH₃CHClCF₃ (HCFC 253db), CH₃CH₂CClF₂ (HCFC 262fc), etc. Among them, desirable are HCFC 22, HCFC 123, HCFC 141b, HCFC 142b, HCFC 235cb, etc. HCFC's are usable singly or at least two of them can be used in mixture. The mixing ratio of HFC and HCFC is not specifically limited. Usually selected is a mixing ratio at which the refrigerator can exhibit the highest refrigerating capacity. Advantages of the Invention The refrigerating machine oils of the invention are outstanding in compatibility with the hydrogen-containing halogenated hydrocarbon over a wide temperature range and suitable for use in a refrigerating machine using a hydrogen-containing halogenated hydrocarbon as a refrigerant. The refrigerator charged with a combination of a hydrogen-containing halogenated hydrocarbon (refrigerant) and the refrigerator oil of the invention can exhibit a refrigerating capacity and a coefficient of performance as high as or higher than conventional techniques employing a combination of R-12 (refrigerant) and a mineral-type refrigerator oil. The refrigerator oils of the invention have an excellent resistance to abrasion and thus render the refrigerator serviceable for an extended life time. Example The present invention will be described below in more detail with reference to the following Examples and Comparison Examples. Examples 1 to 10 and Comparison Examples 1 to 3 A refrigerating machine was operated for 2,856 hours under the conditions as shown below in Table 1 using the refrigerants and the refrigerating machine oils as indicated below in Table 2. Table 2 also shows the refrigerating capacity (kcal/hr), ratio of refrigerating capacity, and coefficient of performance (COP). Cond. No. Inlet of Evaporator Inlet of Condenser Amount (ℓ/min) Temperature (°C) Amount (ℓ/min) Temperature (°C) (1) 15.2 12.1 5.6 30.0 (2) 20.2 11.7 7.8 30.1 (Note) The amount and temperature in Table 1 are those of water. The temperature at the outlet of the evaporator is 8°C. The temperature at the outlet of the condenser is 6°C. In Examples 2 and 7, the ratio of the two refrigerants in the HFC 134a/HFC 143a mixture was 90/10 (% by weight). In Examples 3 and 8, the ratio of the two refrigerants in the HFC 134a/HCFC 124 mixture was 90/10 (% by weight). Symbols A to D in Tables 2 to 7 represent the following refrigerating machine oils. Among them, A to C designate the refrigerating machine oils of the invention, and D, a conventional refrigerator oil for comparison. (wherein ℓ=15, m=14, n=1), fluorination percentage 74%. (wherein ℓ=15, m=14, n=1), fluorination percentage 74%. (wherein ℓ=17, m=5, n=0), fluorination percentage 88%. D: Refrigerating machine oil: Naphthene type mineral oil (trade name "Suniso 4GS", product of Nihon Sun Petroleum Co., Ltd.) Table 2 shows that the combination of the refrigerant (hydrogen-containing halogenated hydrocarbon) and the refrigerator oil (the fluorine-containing oil of the formula (I)) according to the invention produces a refrigerating effect as high as or higher than the combination of the conventional refrigerant (R-11 or -12) and the conventional refrigerator oil (mineral oil or synthetic oil). Example 11 A refrigerating machine was operated for 2,856 hours under the conditions (1) in Table 1 employing the refrigerant mixture and the refrigerator oil indicated below in Table 3. Table 3 also shows the refrigerating capacity (kcal/hr), refrigerating capacity ratio, coefficient of performance (COP), and coefficient of performance ratio. The former to latter ratio of two refrigerants in the refrigerant mixture are 90/10 (% by weight). Examples 12 to 15 and Comparison Examples 4 A 0.3 to 0.5 g quantity of the refrigerating machine oil and 1.2 to 2.0 g of the refrigerant as shown in Table 2 were charged into and sealed in a pressure-proof glass tube under a vacuum at an oil/refrigerant weight ratio of 1 : 4. The contents of the tube were cooled or heated and the temperature range over which the oil and the refrigerant remained compatible with each other was determined by visual inspection. Table 4 shows the results. Ex. Refrigerant Refrigerator oil Temp. range for compatibility low temp. range high temp. range 12 HFC 134a A -30 100↑ 13 HFC 125 A -60↓ 65↑ 14 HFC 134a B -20 to 22 95 to 98 15 HFC 125 B -60↓ 65↑ Comp. Ex. 4 HFC 134a D Incompatible Note: The mark "↑" shows that the oil and refrigerant remained compatible with each other until the critical temperature of the refrigerant was reached. The mark "↓" shows that the oil and the refrigerant remained compatible with each other until the pour point of the oil was reached. Table 4 reveals that the refrigerating machine oils of the invention are excellent in compatibility with hydrogen-containing halogenated hydrocarbons as a refrigerant over a wide temperature range. Examples 16 and 17 and Comparison Example 5 The volume resistivity value (Ωcm) and the specific dielectric constant of the refrigerating machine oil of the invention were measured according to JIS C2101-1982. Table 5 below shows the results. Example Refrigerator oil Volume resistivity (Ωcm) Dielectric constant 16 A 3.50 X 10¹² 3.31 17 B 1.00 X 10¹³ 1.72 Comp.Ex. 5 PAG 9.0 X 10¹⁰ 5.06 Note: PAG stands for polyalkylene glycol Table 5 shows that the refrigerating machine oils of the invention have a high volume resistivity and a low dielectric constant, and are excellent in electrical insulating property and useful for preventing leak of electricity. Examples 18 and 19 and Comparison Examples 6 and 7 The refrigerating machine oils of the invention were subjected to Falex test according to ASTM D-3233 to determine the critical load value for seizing (Lbs). Table 6 shows the results. Ex. Refrigerator oil Critical load value for seizing (Lbs) 18 A 3000 or more 19 B 2900 Comp.Ex. 6 D 500 7 PAG 900-1000 Table 6 indicates that the refrigerating machine oils of the invention have a high lubricity. Example 20 and Comparison Examples 8 and 9 The abrasion loss was determined by conducting Falex test according to ASTM D-3233-73. Stated more specifically, HFC134a was blown in under a load of 600 Lbs, and the weight loss of the block and pin caused during a 10-minute period was determined. Table 7 below shows the results. Ex. Refrigerator oil Weight loss (mg) Block Pin 20 C 1.0 3.3 Comp.Ex. 8 D (pin broke in 30 sec.) 9 PAG 2.6 10.0 Table 7 indicates that because of their high abrasion resistance, the refrigerating machine oils of the invention used for a refrigerating machine improve the durability of the machine.

Claims: A machine oil used in a refrigerating machine employing a hydrogen-containing halogenated hydrocarbon as a refrigerant, the oil comprising a fluorine-containing polyether having repeated structural units represented by the formula(I) ―(CF₂CF₂CF₂O) ℓ ―(CHFCF₂CF₂O) m ―(CH₂CF₂CF₂O) n ― (I) wherein ℓ, m and n are all an integer of at least zero, the polyether being capable of satisfying the relationship represented by 2≦ ℓ + m + n ≦ 200 A refrigerating machine oil according to claim 1 wherein the fluorine-containing polyether having the repeated units of the formula (I) contains group as a substituent at one or both of terminals selected from the group -CH₂OH, group and group -CF₂CF₃. A refrigerating machine oil according to claim 1 wherein the fluorine-containing polyether having the repeated units of the formula (I) is capable of satisfying the relationship expressed by A refrigerating machine oil according to claim 1 wherein the hydrogen-containing halogenated hydrocarbon is at least one hydrocarbon selected from hydrogen-containing fluorinated hydrocarbons, and hydrogen-containing chlorinated fluorinated hydrocarbons.

Inventors: FUJIWARA KATSUKI, HISHIDA SATOSHI, NOGUCHI MASAHIRO, OMURE YUKIO, TSUCHIYA TATSUMI, YAMAMOTO IKUO, FUJIWARA, KATSUKI, HISHIDA, SATOSHI, NOGUCHI, MASAHIRO, OMURE, YUKIO, TSUCHIYA, TATSUMI, YAMAMOTO, IKUO
Applicants: DAIKIN IND LTD, DAIKIN INDUSTRIES, LIMITED
Application year: 1990
Main classification: C09K5
IPC codes: C09K5, C10N40, C10M107, C10M171, C10M105