TETRAFLUOROETHANE COMPOSITION FOR A REGRIGERATOR

Abstract: A tetrafluoroethane composition for a refrigerator, which comprises a tetrafluoroethane and at least one polyether selected from the group consisting of: (I), (II) and (III), wherein R<1> is an alkylene group, each of R<2>, R<3>, R<4>, R<5>, R<6>, R<7> and R<8> which may be the same or different is a hydrogen atom, and alkyl group, an aralkyl group, an aryl group, an acyl group, a glycidyl group, -SO2R<9>, alpha , beta or -Y<1>-(OR<1>)p-OR<12>, wherein R<1> is as defined above, each of R<9>, R<10> R<11> and R<12> is an alkyl group, an aralkyl group or an aryl, and Y<1> is a residue of a dicarboxylic compound having at least 3 carbon atoms, provided that at least one of R<2> and R<3> and at least one of R<4> and R<5> are not hydrogen atoms, and when R<2> is a hydrogen atom, an alkyl group for R<3> has 1 or 2 carbon atoms, and when R<3> is a hydrogen atom, an alkyl group for R<2> has 1 or 2 carbon atoms, l, m, n and p which may be the same or different are integers which bring the kinematic viscosity of the compounds of the formulas (I) to (III) to a level of from 5 to 300 cSt at 40 DEG C, X<1> is a residue obtained by removing hydroxyl groups from a dihydroxy compound or a dicarboxylic compound, and X<2> is a residue obtained by removing hydroxyl groups from a trihydroxy compound or a tricarboxylic compound.

Description: DESCRIPTION TITLE OF THE INVENTION TETRAFLUOROETHANE COMPOSITION FOR A REFRIGERATOR TECHNICAL FIELD The present invention relates to a composition for a refrigerator comprising a tetrafluoroethane and a polyether which is compatible at any optional ratio with a tetrafluoroethane, preferably 1,1,1,2-tetrafluoroethane (R-134a), as a cooling medium at a temperature of from -20°C or lower to +40°C or higher and which has a low hygroscopic property. R-12 (dichlorodifluoromethane) is used as an excellent cooling- medium in a refrigerating cycle of e.g refrigerators or car air conditioners. However, R-12 is likely to destroy the ozone layer in the stratosphere and adversely affect the living bodies. Therefore, a study for a substitute material is being made. As a substitute for R-12, R-134a is considered to be most prospective. However, a naphthene mineral oil and a paraffin mineral oil which are refrigerator oils commonly used for R-12, are incompatible with R-134a. Therefore, such a naphthene mineral oil or paraffin mineral oil can not be used as a refrigerator oil for R-134a. Polyether oils having the structures as identified in Table 1 are known as substances relatively well compatible with R-134a. The polyether oil (a) is disclosed, for example, in Dupont Research Disclosure (17483, Oct., 1978). The polyether.oil (b) is disclosed, for example, in US Patent 4,755,316. However, the polyether oils as identified in Table 1 had the following problems. (1) Compatibility with R-134a is not adequate. In order to provide a lubricating property as the most important role of the freezer oil, it is essential that the oil is compatible with R-134a and capable of being circulated in the system together with R-134a. With respect to the freezer oils -(a) and (b), the upper critical solution temperatures (see the footnote of Table 1) are as shown in Table 1 in the case where the kinematic viscosity at 40°C is 100 cSt. The compatibility can hardly be regarded as adequate. (2) Hygroscopicity is high. The freezer oils (a) and (b) are highly hygroscopic and apt to absorb moisture. Inclusion of moisture brings about adverse affects such as a deterioration of insulation resistance and an increase of corrosiveness to metal. Table 1: Conventional polyether oils and their upper critical solution temperatures (*) Upper critical temperature: The oil and R-134a are mixed in a weight ratio of 15:85 and sealed. The temperature is gradually raised, and the temperature at which turbidity or phase separation has started, is taken as the upper critical solution temperature. The better the compatibility, the higher the upper critical solution temperature. To solve the above problems, the present inventors have presumed that the hygroscopicity of the polyether oils is attributable to the terminal hydroxyl groups. Therefore, by using polyethers having from 1 to 3 terminal hydroxyl groups, all or a part of the terminal hydroxyl groups of such polyethers have been acylated or alkylated, and evaluation of such acylated or alkylated compounds for usefulness as freezer oils for R-134a has been conducted. As a result, it has been found that not only the hygroscopicity but also the compatibility with R-134a and the viscosity indexes have been improved. The present invention has been accomplished on the basis of this discovery. The present invention provides a tetrafluoroethane composition for a refrigerator, which comprises a tetrafluoroethane and at least one polyether selected from the group consisting of: R 2 -0-(R 1 0)- £ -R 3 (1) wherein R 1 is an alkylene group, each of R 2 , R 3 , R 4 , R 5 , R 6 , R 7 and R 8 which may be the same or different is a hydrogen atom, an alkyl group, an aralkyl group, an aryl group, an acyl group, a glycidyl group, -S0 2 R 9 , -CNHR 10 , 0 -COR 11 or -Y 1 —OR 1 -)-r-OR 12 wherein R 1 is as defined above, o each of R 9 , R 10 , R 11 and R 12 is an alkyl group, an aralkyl group or an aryl group, and Y 1 is a residue of a dicarboxylic compound having at least 3 carbon atoms, provided that at least one of R 2 and R 3 and at least one of R 4 and R 5 are not hydrogen atoms, and when R 2 is a hydrogen atom, an alkyl group for R 3 has 1 or 2 carbon atoms, and when R 3 is a hydrogen atom, an alkyl group for R 2 has 1 or 2 carbon atoms, « , m, n and p which may be the same or different are integers which bring the kinematic viscosity of the compounds of the formulas (1) to (3) to a level of from 5 to 300 cSt at 40°C, X 1 is a residue obtained by removing hydroxyl groups from a . dihydroxy compound or a dicarboxylic compound, and X 2 is a residue obtained by removing hydroxyl groups from a trihydroxy compound or a tricarboxylic compound. Now, the present invention will be described in detail with reference to the preferred embodiments. In the above definitions, the alkyl group includes, for example, a methyl group, an ethyl group, a propyl group, a butyl group, a 2-ethylhexyl group and a nonyl group. The aralkyl group includes, for example, a benzyl group, a phenylethyl group and a methylbenzyl group. The aryl group includes, for example, a phenyl group and a tolyl group. All or a part of hydrogen atoms of these hydrocarbon groups may be substituted by halogen atoms such as fluorine atoms or chlorine atoms. Further, the alkyl group may be a hydroxyalkyl group such as a hydroxymethyl group, a hydroxyethyl group or a hydroxybutyl group. The acyl group may be an acyl group of the formula -C-A, wherein A is the above-mentioned alkyl, aralkyl or 0 aryl group. The above-mentioned alkyl, aralkyl or aryl group may be employed also for R 9 , R 10 , R 11 and R 12 in the above- mentioned radicals of the formulas -SO-,R 9 , -CNHR 10 , I - 0 -COR 11 or -Y 1 ---OR^- r-OR 12 . I! p o Y 1 is a residue obtained by removing both hydroxyl groups from a dicarboxylic compound having at least 3 carbon atoms. The dicarboxylic compound includes, for example, aliphatic dicarboxylic acids such as malonic acid, succinic acid, glutaric_acid, adipic acid, sebacic acid, suberic acid, methyl succinic acid, methyl adipic acid, maleic acid, fumaric acid and itaconic acid; aromatic dicarboxylic acids such as phthalic acid, diphenyl dicarboxylic acid and diphenyl methane - 1 - dicarboxylic acid; hydrogenated products of the above aromatic dicarboxylic acids, such as alicyclic dicarboxylic acids; and dicarboxylic acids prepared by introducing carboxyl groups to both terminals of polyalkylene glycols having a molecular weight of from 50 to 1,000. X 1 in the formula (2) is preferably a residue obtained by removing hydroxyl groups from a dihydroxy compound, such as an ethylene glycol residue or a propylene glycol residue, or a residue obtained by removing hydroxyl groups from the same dicarboxylic compound as mentioned above for the definition of Y 1 . X 2 in the formula (3) is preferably a residue obtained by removing hydroxy-1 groups from a trihydroxy compound, such as a glycerol. residue or a trimethylol propane residue, or a residue obtained by removing hydroxyl groups from a tricarboxylic compound such as trimellitic acid or trimesic acid. R 1 in the formulas (1) to (3) and in the radical of the formula -Y 1 —{OR^-^-z-OR 12 is an alkylene group such as an ethylene group, a propylene group, a butylene group or a tetramethylene group. These alkylene groups may be present alone or in combination in the form of a random or block state. In the case of the combination, the main component is preferably a propylene group. R 1 in the formulas (2) and (3) may be the same or different. For the preparation of the compounds of the formulas (1), (2) and (3), the corresponding initiators are OH OH R 2 -OH, X 1 and X 2 -OH, respectively, and the numbers of \ \ OH OH active hydrogen groups thereof are 1, 2 and 3 , respectively. If it is attempted to obtain a compound having a kinematic viscosity within a range of from 12 cSt (40°C) to 200 cSt (40°C) which is common to freezer oils for car air conditioners or refrigerators, by using an initiator having 4 or more active hydrogen groups, the numbers for £ , m and n, i.e. the addition molar numbers of alkylene oxides, tend to be too small, whereby the lubricating property will be low, such being undesirable. The compounds of -the formulas ( ^ 1) to (3) are desired to have a kinematic viscosity of from 5 to 300 cSt (40°C), preferably from 12 to 200 cSt (40°C), so that they provide adequate functions as freezer oils such as the functions for preventing friction, abrasion and seizing of sliding portions of e.g. compressors. Accordingly, it is desirable that the molecular weights of the compounds of the formulas (1) to (3) or the values for £ , m and n and the value for p in the formula are selected so as to bring the kinematic viscosity within the above-mentioned range. The values for £ , m, n and p are from about 3 to 60, preferably from 6 to 30, and they may be the same or different. The weight ratio of the compounds of the formulas (1) to (3) to R-134a is usually from 1/99 to 99/1, preferably from 5/95 to 60/40. R-134a may contain a small amount of 1,1,2,2-tetrafluoroethane (R-134). The compounds of the formulas (1) to (3) may be used alone or in combination as their mixtures. The composition of the present invention is particularly effective when applied to a refrigerating cycle intended for freezing, for refrigerating and for air conditioning. However, it is also useful for other various heat recovery technologies such as a Rankine cycle. The composition of the present invention has excellent heat stability and requires no stabilizer under a usual application condition. However, if an improvement of the heat stability for use under a severe condition is desired, a small amount of a stabilizer including a phosphite compound such as dimethyl phosphite, diisopropyl phosphite or diphenyl phosphite, a phosphine sulfide compound such as triphenoxy phosphine sulfide or trimethyl phosphine sulfide, and other glycidyl ethers, may be added. Further, the compounds of the formulas (1) to (3) of the present invention may be used in combination with conventional oils such as a naphthene mineral oil, a paraffin mineral oil, an alkylbenzene synthetic oil, a poly-α-olefin synthetic oil, a fluorine type lubricating oil such as a perfluoropolyether oil or a fluorine-containing silicone oil, or polyether oils other than the polyether oils of the present invention. Further, various additives including a phenol type or amine type antioxidant, a sulfur or phosphorus type high pressure additive, a silicone type anti-foaming agent or a metal inactivating agent such as benzotriazole, may be added to the composition of the present invention. It is believed that in the present invention, the hydrophilicity is lowered by the modification such as acylation or alkylation of the terminal hydroxyl groups and the hygroscopicity oil is thereby lowered. The mechanism for the compatibility of the oils of the present invention with tetrafluoroethane as a cooling ' medium, is not clearly understood. However, a certain interaction between tetrafluoroethane and the carbonyl group of the ester bond or the like, is related thereto. Now, the present invention will be described in further detail with reference to Examples. However, it should be understood that the present invention is by no means restricted by such specific Examples. EXAMPLES 1-1 TO 1-5 AND COMPARATIVE EXAMPLES 1-1 TO 1-5 The structures of the oils used in Examples 1-1 ' "to 1- 5 and Comparative Examples 1-1 to 1-5 and the test results for their compatibility with R-134a, hygroscopicity and kinematic viscosities at 40°C, are shown in Table 2. Method for testing hygroscopicity: Into a Petri dish having a diameter of 150 mm, 15 g of an oil having a water content of not higher than 0.03% - is introduced. The Petri dish is left open in a constant humidity and temperature room at a temperature of 20°C under a humidity of 50%. The weight increase is calculated by the following equation in which Y is the weight (g) of the oil upon expiration of 30 hours. Y - 15 Weight increase = x 100 ( % ) 15 Table 2 EXAMPLES 2-1 TO 2-7 AND COMPARATIVE EXAMPLE 2-1 Compounds (1) as identified in Tables 3 and 4 were tested for the solubility in R-134a and the stability. A compound (1) and R-134a were sealed in a glass ampoule at a weight ratio of 30/70, and the solubility of the compound (1) in R-134a was determined by a visual observation of whether or not phase separation was observed. The results are shown in Table 1 together with the results of the Comparative Example. Table 3 Compound (1): O * Naphthene oil, manufactured by Nippon Su-n Petroleum Corporation, ** (cSt, at 40°C) A compound (1) and R-134a were sealed in a SUS316 pressure container in a weight ratio of 50/50 together with SS41 and Cu as representative metals and left to stand for 14 days at a high temperature of 175°C in a constant temperature tank. After the test, deterioration of the compound (1), R-134a and the metals was determined in comparison with the deterioration of the conventional combination of R-12 and Sniso 4GS. The results are shown in Table 4. * Naphthene oil, manufactured by Nippon Sun Petroleum Corporation, ** (cSt, at 40°C) EXAMPLES 3-1 TO 3-9 AND COMPARATIVE EXAMPLE 3-1 Compounds (2) as identified in Tables 5 and 6 were tested for the solubility in R-134a and the stability. A compound (2) and R-134a were sealed in a glass ampoule in a weight ratio of 30/70, and the solubility of the compound (2) in R-134a was determined by a visual observation of whether or not phase separation was observed. The results are shown in Table 5 together with the Comparative Example. Table 5 Compound (2): R 2 -0-(R 1 0)^-C-NHR 1 ° 0 * Naphthene oil, manufactured by Nippon Sun Petroleum Corporation. ** (cSt, at 40°C) A compound (2) and R-134a were sealed in a SUS316 pressure container in a weight ratio of 50/50 together with SS41 and Cu as representative metals and left to stand for 14 days at a high temperature of 175°C in a constant temperature tank. After the test, deterioration of the compound (2), R-134a and the metals was ascertained in comparison with the deterioration of a conventional combination of R-12 and Sniso 4GS. The results are shown in Table 6. * Naphthene oil, manufactured by Nippon Sun Petroleum Corporation. ** (cSt, at 40°C) EXAMPLES 4-1 TO 4-7 AND COMPARATIVE EXAMPLE 4-1 Compounds (3) as identified in Tables 7 and 8 were tested for the solubility in R-134a and the stability. A compound (3) and R-134a were sealed in a glass ampoule in a weight ratio of 30/70, and the solubility of the compound (3) in R-134a was determined by a visual observation of whether or not phase separation was observed. The results are shown in Table 7 together with the Comparative Example. Table 7 Compound (3): R 2 -0-(R 1 0) £ -R 3 * Naphthene oil, manufactured by Nippon Sun Petroleum Corporation. ** (cSt, at 40°C) A compound (3) and R-134a were sealed in a SUS316 pressure container in a weight ratio of 50/50 together with SS41 and Cu as representative metals and left to stand for 14 days at a high temperature of 175°C in a constant temperature tank. After the test, deterioration of the compound (3), R-134a and the metals was ascertained in comparison with the deterioration of a conventional combination of R-12 and Sniso 4GS. The results are shown in Table 8. * Naphthene oil, manufactured by Nippon Sun Petroleum Corporation. ** (cSt, at 40°C) EXAMPLES 5-1 TO 5-6 AND COMPARATIVE EXAMPLES 5-1 TO 5-2 The structures of the oils used in Examples 5-1 to 5- 6 and Comparative Examples 5-1 to 5-2 and the test results for their compatibility with R-134a, hygroscopicity and kinematic viscosities at 40°C, are shown in Table 9. Table 9 EXAMPLES 6-1 TO 6-5 AND COMPARATIVE EXAMPLES 6-1 TO 6-5 The structures of the oils used in Examples 6-1 to 6- 5 and Comparative Examples 6-1 to 6-5 and the test results for their compatibility with R-134a, hygroscopicity and kinematic viscosities at 40°C, are shown in Table 10. Table 10 Table 10 (continued) EXAMPLES 7-1 TO 7-5 AND COMPARATIVE EXAMPLES 7-1 TO 7-3 The structures of the oils used in Examples 7-1 to 1- 5 and Comparative Examples 7-1 to 7-3 and the test results for their compatibility with R-134a, hygroscopicity and kinematic viscosities at 40°C, are shown in Table 11. Table 11 EXAMPLES 8-1 TO 8-5 AND COMPARATIVE EXAMPLES 8-1 TO 8-4 The structures of the oils used in Examples 8-1 to 8- 5 and Comparative Examples 8-1 to 8-5 and the test results for their compatibility with R-134a, hygroscopicity and kinematic viscosities at 40°C, are shown in Table 12. Table 12 EXAMPLES 9-1 TO 9-6 AND COMPARATIVE EXAMPLES 9-1 TO 9-6 The structures of the oils used in Examples 9-1 to 9- 6 and Comparative Examples 9-1 to 9-6 and the test results for their compatibility with R-134a, hygroscopicity, viscosity indices and kinematic viscosities at 40°C, are shown in Table 13. Table 13 Viscosity index: The viscosity index is a value representing the temperature dependency of the viscosity of a lubricating oil. The larger the value, the smaller the change of the viscosit .due to the temperature, and accordingly the better the lubricating properties. Compatibility with R-134a; An oil and R-134a are mixed in a weight ratio of 15:85 and sealed. The temperature is maintained at 25°C, and the solubility is visually observed. EXAMPLES 10-1 TO 10-5 AND COMPARATIVE EXAMPLES 10-1 TO 10-6 The structures of the oils used in Examples 10-1 to 10-5 and Comparative Examples 10-1 to 10-6 and the test results for their compatibility with R-134a, hygroscopicity and kinematic viscosities at 40°C, are shown in Table 14. Table 14 Table 14 (continued) EXAMPLES 11-1 TO 11-5 AND COMPARATIVE EXAMPLES 11-1 TO 11-2 The structures of the oils used in Examples 11-1 to 11-5 and Comparative Examples 11-1 to 11-2 and the test results for their compatibility with R-134a, hygroscopicity and kinematic viscosities at 40°C, are shown in Table 15. Table 15 The compositions of the present invention provide good compatibility of tetrafluoroethane and polyether oils, and they are capable of adequately providing functions such as the prevention of the friction, 'abrasion and seizing of sliding portions of e.g. compressors. Further, their hygroscopicity is low, and inclusion of moisture can be minimized, whereby a decrease of insulation resistance can be prevented, and the progress of corrosion of a metal such as a copper pipe by the moisture can be prevented.

Claims: CLAIMS 1. A tetrafluoroethane composition for a refrigerator, which comprises a tetrafluoroethane and at least one polyether selected from the group consisting of: wherein R 1 is an alkylene group, each of R 2 , R 3 , R 4 , R 5 , R 6 , R 7 and R 8 which may be the same or different is a hydrogen atom, an alkyl group, ' an aralkyl group, an aryl group, an acyl group, a glycidyl group, -S0 2 R 9 , -CNHR 10 , 0 -COR 11 or -Y 1 —fOR 1 - j *-OR 12 wherein R 1 is as defined above, 0 each of R 9 , R 10 r R 11 and R 12 is an alkyl group, an aralkyl group or an aryl group, and Y 1 is a residue of a dicarboxylic compound having at least 3 carbon atoms, provided that at least one of R 2 and R 3 and at least one of R 4 and R 5 are not hydrogen atoms, and when R 2 is a hydrogen atom, an alkyl group for R 3 has 1 or 2 carbon atoms, and when R 3 is a hydrogen atom, an alkyl group for R 2 has 1 or 2 carbon atoms, £ , m, n and p which may be the same or different are integers which bring the kinematic viscosity of the compounds of the formulas (1) to (3) to a level of from 5 to 300 cSt at 40°C, X 1 is a residue obtained by removing hydroxyl groups from a dihydroxy.compound or a dicarboxylic compound, and X 2 is a residue obtained by removing hydroxyl groups from a trihydroxy compound or a tricarboxylic compound. 2. The composition according to Claim 1, wherein the tetrafluoroethane is 1,1,1,2-tetrafluoroethane. 3. The composition according to Claim 1, wherein the weight ratio of the polyether to the tetrafluoroethane is from 1/99 to 99/1. 4. The composition according to Claim 1, which further contains at least one member, selected from the group consisting of a naphthene mineral oil, a paraffin mineral oil, an alkylbenzene synthetic oil, a poly-α-olefin synthetic oil and a fluorine-containing silicone oil. 5. The composition according to Claim 1, which further contains at least one stabilizer selected from the group consisting of a phosphite compound, a phosphine sulfide compound and a glycidyl ether compound. 6. The composition according to Claim 1, wherein R 1 in the formulas (1) to (3) is ah " ethylene group, a propylene group or a mixture of an ethylene group and a propylene group. 7. The composition according to Claim 1, wherein R 2 in the formula (1) is an alkyl group. 8. The composition according to Claim 1, wherein X 1 in the formula (2) is a propylene glycol residue. 9. The composition according to Claim 1, wherein X 2 in the formula (3) is a trimethylol propane residue. 10. The composition according to Claim 1, wherein R 2 , R 3 , R 4 , R 5 , R 6 , R 7 and R 8 in the formulas (1) to (3) are the same or different acyl groups.

Inventors: FUKUDA HIROKI, FUKUSHIMA MASATO, OHTSUKA YOSHIHIRO, TANABE KIYOSHI, WATANABE NAHOHIRO, FUKUDA, HIROKI, FUKUSHIMA, MASATO, OHTSUKA, YOSHIHIRO, TANABE, KIYOSHI, WATANABE, NAHOHIRO
Applicants: ASAHI GLASS CO LTD, ASAHI GLASS COMPANY LTD.
Application year: 1989
Main classification: C07C43
IPC codes: C09K5, C10M171