Title of Invention

"REFRIGERATION LUBRICANT COMPOSITION"

Abstract

The present invention provides a refrigeration lubricant composition comprises an ester obtained by reacting a mixed alcohol and a mixed saturated straight-chain carboxylic acid, wherein the mixed alcohol consists of 10 to 50 mol% of neopentyl glycol, 50 to 89 mol% of pentaerythritol, and 0.03 to 3 mol% of dipentaerythritol, the mixed saturated straight-chain carboxylic acid consists of 70 to 95 mol% of pentanoic acid and heptanoic acid, and 5 to 30 mol% of caprylic acid in a specific ratio, and the composition has a kinematic viscosity at 40°C of 6 to 28 mm2/s.

Full Text

SPECIFICATION Refrigeration lubricant composition BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigeration lubricant composition and more specifically to a refrigeration lubricant composition that is used for a chlorine-free hydrofluorocarbon refrigerant, a refrigerant working fluid containing the lubricant composition, and a refrigerating apparatus including the refrigerant working fluid. 2. Description of the Related Art Refrigerants containing chlorofluorocarbon have been used for refrigerators, air conditioning equipment, and the like. However, in recent years, due to problems such as depletion of the ozone layer, the replacement of chlorofluorocarbon refrigerants with chlorine-free hydrofluorocarbon refrigerants such as those containing 1,1,1,2-tetrafluoroethane (R-134a), pentafluoroethane (R-125), difluoroethane (R-32), and mixtures thereof has been promoted. Consequently, a variety of refrigeration lubricant compositions (hereinafter referred to as "refrigeration oils") containing a polyol ester, which has good compatibility with chlorine-free hydrofluorocarbons, as a base oil have been proposed. In addition to the above-mentioned compatibility with chlorine-free hydrofluorocarbon refrigerants, a variety of properties such as thermal stability, hydrolytic stability, low-temperature fluidity, and electrical insulating properties are required for the refrigeration oils in order to ensure the stability of the above- 1A mentioned refrigerators, air conditioning equipment, and the like. Among these, in view of hydrolytic stability and compatibility with chlorine-free hydrofluorocarbon refrigerants, hindered esters obtained by a carboxylic acid having a side chain and pentaerythritol and having excellent thermal resistance have been put to practical use. For example, Japanese Laid-Open Patent Publication No. 10-8084 discloses refrigeration oils containing an ester obtained from pentaerythritol and a mixed fatty acid of 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid as a main component and that such refrigeration oils have good stability at high temperatures. Japanese Laid-Open Patent Publication No. 5-209171 describes that esters obtained from neopentyl glycol and branched carboxylic acid have excellent compatibility with hydrofluorocarbon, thermal stability and the like. Furthermore, Japanese Laid-Open Patent Publication No. 11-228984 describes refrigeration oils comprising straight-chain fatty acid has an excellent lubricity. On the other hand, in line with increasing awareness of environmental issues of recent years, refrigerators, air conditioning equipment, and the like are required to have energy-saving properties. In the refrigeration oils, decreasing the viscosity thereof is the most efficient way to make a contribution to the energy-saving properties, and thus there is an attempt to decrease the viscosity of the refrigeration oils. In order to decrease the viscosity of the refrigeration oils, it is effective to use esters comprising a dihydric alcohol such as neopentyl glycol, which has a lower viscosity than pentaerythritol esters and excellent hydrolytic stability, thermal stability, viscosity, and other properties. However, these esters have low viscosity so that the lubricity may be insufficient. As a method for improving lubricity, there is a method of using an ester of straight-chain fatty acid as in Laid-Open Patent Publication No. 11-228984. However, ester made by this straight-chain fatty acid has crystallinity so that it is known that the long-term stability at low temperatures is reduced. Thus, there is a demand for a refrigeration lubricant having excellent 2 low-temperature stability, low viscosity, and lubricity. SUMMARY OF THE INVENTION It is an object of the present invention to provide a refrigeration lubricant composition having low viscosity and good lubricity and also having excellent long-term stability in a low temperature region, and, in particular, a refrigeration lubricant composition employing a chlorine-free hydrofluorocarbon refrigerant. It is another object of the present invention to provide a refrigerant working fluid containing the refrigeration lubricant composition and a refrigerant compression type refrigerating apparatus containing the refrigerant working fluid. The inventors of the present invention conducted in-depth research on the lubricity and the low-temperature stability of lubricant compositions having low viscosity for use in refrigerators employing a chlorine-free hydrofluorocarbon refrigerant, and conducted molecular design by combining a variety of polyhydric alcohols and carboxylic acids. As a result, the inventors found that the above-described object can be attained by an ester obtained by reacting a mixed alcohol and a mixed saturated straight-chain carboxylic acid so as to a certain quantitative relation between them, wherein the mixed alcohol consists of neopentyl glycol, pentaerythritol, and dipentaerythritol in a specific ratio, and the mixed saturated straight-chain carboxylic acid consists of pentanoic acid (saturated straight-chain carboxylic acid having 5 carbon atoms), heptanoic acid (saturated straight-chain carboxylic acid having 7 carbon atoms), and caprylic acid (saturated straight-chain carboxylic acid having 8 carbon atoms) in a specific ratio, and thus the present invention was achieved. The refrigeration lubricant composition of the present invention comprises an ester obtained from a mixed alcohol and a mixed saturated straight-chain carboxylic acid, wherein the mixed alcohol consists of 10 to 50 mol% of neopentyl glycol, 50 to 89 mol% of pentaerythritol, and 0.03 to 3 mol% of dipentaerythritol, wherein the mixed saturated straight-chain carboxylic acid 3 consists of 70 to 95 mol% of pentanoic acid and heptanoic acid, and 5 to 30 mol% of caprylic acid, wherein the ester is obtained by a reaction in which the following relation is satisfied: , and the composition has a kinematic viscosity at 40°C of 6 to 28 mm2/s. The refrigerant working fluid of the present invention consists of the refrigeration lubricant composition and a chlorine-free hydrofluorocarbon refrigerant. The refrigerant compression type refrigerating apparatus of the present invention comprises a compressor, a condenser, an expansion mechanism, an evaporator, and the above mentioned refrigerant working fluid. The refrigeration lubricant composition of the present invention has low viscosity, good lubricity, and excellent long-term low-temperature stability. Furthermore, the composition also has excellent compatibility with chlorine-free hydrofluorocarbon refrigerants, thermal resistance, and electrical insulating properties, which are required for a refrigeration lubricant composition. Therefore, the composition of the present invention is useful as a lubricant for use in refrigerators employing a chlorine-free hydrofluorocarbon refrigerant, in particular, a chlorine-free hydrofluorocarbon refrigerant containing at least one of 1,1,1,2-tetrafluoroethane and difluoromethane. The composition of the present invention is also used as a refrigerant working fluid mixed with a chlorine-free hydrofluorocarbon refrigerant. Furthermore, the composition of the present invention contributes also to improved fuel efficiency of a variety of types of refrigerating apparatuses. DESCRIPTION OF THE PREFERRED EMBODIMENT Hereinafter, an ester contained in the composition of the present 4 invention, a refrigeration lubricant composition containing the ester, a refrigerant working fluid containing the composition, and a refrigerant compression type refrigerating apparatus employing the refrigerant working fluid will be described. (I) Ester The ester contained in the refrigeration lubricant composition of the present invention is a mixed ester obtained from three kinds of alcohols (mixed alcohol) and three kinds of saturated straight-chain carboxylic acid (mixed saturated straight-chain carboxylic acid). More specifically, this ester is obtained by reacting a mixed alcohol and a mixed saturated straight-chain carboxylic acid, wherein the mixed alcohol consists of 10 to 50 mol% of neopentyl glycol, 50 to 89 mol% of pentaerythritol, and 0.03 to 3 mol% of dipentaerythritol, the mixed saturated straight-chain carboxylic acid consists of 70 to 95 mol% of pentanoic acid and heptanoic acid, and 5 to 30 mol% of caprylic acid, and wherein the ester is obtained by a reaction in which the following relation is satisfied: The inventors of the present invention found that when reacting the mixed alcohol and the mixed saturated straight-chain carboxylic acid, among these components, the quantitative relation between neopentyl glycol in the mixed alcohol and pentanoic acid and caprylic acid in the mixed saturated straight-chain carboxylic acid contributes the long-term low-temperature stability and lubricity of the obtained low viscosity ester. That is to say, the inventors found that an ester having low viscosity, good lubricity, and excellent long-term low-temperature stability can be obtained by conducting the molecular design such that the above-described relation is satisfied. 5 A mixed alcohol that serves as a raw material of the ester consists of neopentyl glycol, pentaerythritol, and dipentaerythritol, as described above. In the present invention, pentaerythritol is used for the purpose of obtaining an ester having excellent electrical insulating properties, neopentyl glycol is used for the purpose of achieving low viscosity, and dipentaerythritol is used for the purpose of long-term low-temperature stability. The content of neopentyl glycol in the mixed alcohol is 10 to 50 mol%, preferably 12 to 48 mol% and more preferably 15 to 46 mol%. When the content of the neopentyl glycol is less than 10 mol%, the long-term low-temperature stability of the obtained ester becomes insufficient, so that the desired viscosity may not be obtained. When the content is more than 50 mol%, the lubricity of the obtained ester is insufficient, and the electrical insulating properties become also insufficient. The content of pentaerythritol in the mixed alcohol is 50 to 89 mol%, preferably 52 to 85 mol% and more preferably 54 to 80 mol%. When the content of pentaerythritol is less than 50 mol%, the lubricity of the obtained ester becomes insufficient, and the electrical insulating properties become also insufficient. When the content is more than 89 mol%, the long-term low-temperature stability of the obtained ester becomes insufficient. The content of dipentaerythritol in the mixed alcohol is 0.03 to 3 mol%, preferably 0.04 to 2.8 mol% and more preferably 0.05 to 2.5 mol%. When the content of dipentaerythritol is less than 0.03 mol%, the low-temperature stability of the obtained ester becomes insufficient. When the content is more than 3 mol%, the compatibility with hydrofluorocarbon of the obtained ester is deteriorated and furthermore the desired viscosity may not be obtained. The mixed saturated straight-chain carboxylic acid (mixed saturated straight-chain monocarboxylic acid) consists of pentanoic acid, heptanoic acid, and caprylic acid. In the present invention, straight-chain fatty acid, in particular, caprylic acid (saturated straight-chain carboxylic acid having 8 carbon 6 atoms), which has good lubricity, is used for an essential component in order to obtain high lubricity. In order to improve the low-temperature stability when caprylic acid is used, a straight-chain acid having an odd number carbon atoms, that is, pentanoic acid (saturated straight-chain carboxylic acid having 5 carbon atoms), and heptanoic acid (saturated straight-chain carboxylic acid having 7 carbon atoms) are used. Although these acids have poorer lubricity than caprylic acid, these acids have a relatively good lubricity and also good low-temperature stability. Using such a mixed saturated straight-chain carboxylic acid, an ester having a desired viscosity and excellent lubricity can be obtained. The total content of pentanoic acid and heptanoic acid in the mixed saturated straight-chain carboxylic acid is 70 to 95 mol%, preferably 72 to 93 mol% and more preferably 74 to 91 mol%. When the total content of pentanoic acid and heptanoic acid is less than 70 mol%, the long-term low-temperature stability of the obtained ester becomes insufficient, and when the total content is more than 95 mol%, the lubricity of the obtained ester becomes insufficient. In order to obtain the ester contained in the composition of the present invention, the mixed alcohol and the mixed saturated straight-chain carboxylic acid are reacted such that the following relation is satisfied: When the value of this expression of relations is in the range from 5 to 25, an ester having excellent lubricity and long-term low-temperature stability. The reaction in producing the ester is performed by conventional esterification reaction or transesterification. It is preferable that the ratio between the above-described mixed alcohol and mixed fatty acid is determined as appropriate such that the resultant mixed ester has a hydroxyl value of 5.0 mgKOH/g or less and an acid value of 0.05 mgKOH/g or less. 7 There is no particular limitation regarding the method for producing an ester used in the present invention, as long as the performance is not impaired. The ester described above can be obtained in the following manner, for example. First, a mixed saturated straight-chain carboxylic acid is mixed with a mixed alcohol such that the carboxyl group in the mixed saturated straight-chain carboxylic acid is 1.0 to 1.5 equivalents, preferably 1.05 to 1.3 equivalents in view of production efficiency and economic efficiency, with respect to one equivalent of hydroxyl group in the mixed alcohol, and then a catalyst is added thereto, if necessary. This mixture is reacted for 3 to 15 hours at 220 to 260°C under a nitrogen, and at the point when the hydroxyl value becomes 2.0 mgKOH/g or less, excess carboxylic acid is removed under a reduced pressure. Then, after neutralization with an alkali, operations such as adsorption treatment using activated clay, acid clay, and a synthesized adsorbent and steaming are performed either alone or in combination. (II) Refrigeration Lubricant Composition The refrigeration lubricant composition of the present invention contains the above-described ester preferably in 80 wt% or more, more preferably 90 wt% or more based on the total weight of the composition, and in addition to that, may contain other esters, an additive or the like, as long as the performance of the present invention is not impaired. Examples of other esters include esters containing neopentyl glycol having 5 to 10 carbon atoms and a monocarboxylic acid having 5 to 10 carbon atoms. The refrigeration lubricant composition of the present invention may contain known additives, for example, a phenolic antioxidant, a metal deactivator such as benzotriazole, thiadiazole, and dithiocarbamate, an acid scavenger such as epoxy compounds and carbodiimides, and a phosphorous extreme pressure agent as appropriate, depending on the purpose. The additive is contained in any ratio. 8 The refrigeration lubricant composition of the present invention has the kinematic viscosity at 40°C of 6 to 28 mm2/s. In view of excellent lubricity and compatibility with chlorine-free hydrofluorocarbon refrigerants and good startability of refrigerating machines and energy-saving properties by using the lubricant composition, the kinematic viscosity at 40°C is preferably 7 to 20 mm2/s, and more preferably 8 to 18 mm2/s. There is no particular limitation regarding the acid value of the refrigeration lubricant composition of the present invention. The acid value is preferably 0.05 mgKOH/g or less, more preferably 0.03 mgKOH/g or less, and even more preferably 0.01 mgKOH/g or less. A refrigeration lubricant composition having an acid value of more than 0.05 mgKOH/g is likely to corrode metals and may have poor hydrolytic stability. There is no particular limitation regarding the hydroxyl value of the refrigeration lubricant composition of the present invention. The hydroxyl value is preferably 5.0 mgKOH/g or less, more preferably 3.0 mgKOH/g or less, even more preferably 2.0 mgKOH/g or less, and most preferably 1.0 mgKOH/g or less. When the hydroxyl value is more than 5.0 mgKOH/g, in the equipment in which the composition is employed, the sealing material that is made of an organic material may be adversely affected. Also, additives that are further contained may be adversely affected. (III) Refrigerant Working Fluid The refrigerant working fluid of the present invention consists of the above-described refrigeration lubricant composition and a chlorine-free hydrofluorocarbon refrigerant. There is no particular limitation regarding the amount of the refrigeration lubricant composition and the chlorine-free hydrofluorocarbon refrigerant, but the weight ratio of the refrigeration lubricant composition and the chlorine-free hydrofluorocarbon refrigerant is preferably from 10:90 to 90:10. When a weight ratio of the chlorine-free 9 hydrofluorocarbon refrigerant is higher than the above-mentioned range, viscosity of the resultant refrigerant working fluid is reduced, and may cause poor lubrication. If it is lower than the above-described range, then when the resultant refrigerant working fluid is used for refrigerating apparatuses, refrigerating efficiency of the refrigerating apparatuses may deteriorate. Examples of the chlorine-free hydrofluorocarbon refrigerant include 1,1,1,2-tetrafluoroethane (R-134a), pentafluoroethane (R-125), difluoroethane (R-32), trifluoroethane (R-23), 1,1,2,2-tetrafluoroethane (R-134), 1,1,1-trifluoroethane (R-143a), and 1,1-difluoroethane (R-152a). These refrigerants may be used either alone or as a mixed refrigerant in combination of two or more thereof. The above-mentioned mixed refrigerants are commercially available, and, for example, R-407C (R-134a/R-125/R-32 = 52/25/23 wt%), R-410A (R-125/R-32 = 50/50 wt%), R-404A (R-125/R-143a/R-134a = 44/52/4 wt%), R-407E (R-134a/R-125/R-32 = 60/15/25 wt%), and R-410B (R-32/R-125 = 45/55 wt%) are used. Among these, mixed refrigerants containing at least one of R-134a and R-32 are particularly preferable. (IV) Refrigerant Compression Type Refrigerating Apparatus The refrigeration lubricant composition of the present invention or the refrigerant working fluid comprising the composition of the present invention can be used in a refrigerant compression type refrigerating apparatus having at least a compressor, a condenser, an expansion mechanism and an evaporator, and if necessary, a drier. Examples of such a refrigerating apparatus include low temperature apparatuses such as refrigerators or industrial refrigerators, air conditioning equipment such as room air conditioners and packaged air conditioners, and automotive air conditioners such as hybrid cars and electric cars. Examples 10 Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited to these examples. The methods for testing esters produced in the examples and the comparative examples of the present invention will be described below: The kinematic viscosity is measured with a Cannon-Fenske viscometer at 40°C and 100°C according to JIS K-2283, and the viscosity index is calculated from the resultant values. The acid value is measured according to JIS C-2101. The hydroxyl value is measured according to JIS K-0070. The color number (APHA) is measured according to JOCS 2.2.1.4-1996. The volume resistivity (TW.m) at 25°C is measured according to JIS C-2101. The pour point is measured according to JIS K-2269. First, 400 g of a sample (ester), moisture content of which was adjusted to 100 ppm or less, is placed in a square can made of steel and allowed to stand for 1000 hours in a low temperature storage apparatus at -30°C, and then checked visually to determine whether or not crystals are precipitated. First, 0.6 g of a sample (ester) and 2.4 g of refrigerant R-134a or R-407C were enclosed in a thick PYREX (registered trademark) tube (entire length of 300 mm, outer diameter of 10 mm, and inner diameter of 6 mm) that is preliminary cooled in dry ice-ethanol, and warmed or cooled at a rate of l°C/min. Then the two-phase separation temperature at a low temperature was measured visually within a temperature range from -30°C to 20°C. First, 10 g of a sample (ester), moisture content of which was adjusted to 200 ppm or less, 5 g of hydrofluorocarbon R-410A, and one each of iron, copper, and aluminum metal pieces having a diameter of 1.6 mm and a 11 length of 50 mm are put in a glass tube. Then, the glass tube is sealed, and is heated at 175°C for 14 days, and then the acid value and the color number (APHA) of the fluorocarbon-containing sample from which the metal pieces were removed are measured. The Falex friction test was performed according to ASTM D-2670 while blowing R-134a into a sample (ester) at a rate of 150 mL/min in the following manner. First, the temperature of the sample (ester) is set at 100°C, and a trial operation under a load of 150 pounds is carried out for one minute, followed by an operation under a load of 300 pound for 1 hour. After the operation, the wear amount of the pin is measured. Example 1.1: Preparation of Ester First, the mixed alcohol and the mixed carboxylic acid shown in Table 1 were placed in a one-liter four-necked flask provided with a thermometer, a nitrogen inlet tube, a stirrer and a cooling tube such that the ratio of the hydroxyl group in the mixed alcohol to the carboxyl group in the mixed carboxylic acid is 1:1.1 in the equivalent ratio, and then reacted under a nitrogen at 220°C at an atmospheric pressure while water generated by the reaction was removed by distillation. During the reaction, the hydroxyl value of the reaction mixture was monitored, and the reaction was stopped at the point when the hydroxyl value became lower than 2.0 mgKOH/g. Then, stripping was performed under a reduced pressure of 1 to 5 kPa to remove unreacted carboxylic acid for one hour. The resultant reaction mixture was neutralized with an aqueous solution of potassium hydroxide. Washing of the resultant ester with water was repeated five times so that the pH of the discharged water became neutral. Then, the resultant ester layer was dehydrated at 100°C under a reduced pressure of 1 kPa, and acid clay and a silica-alumina adsorbent were added thereto for an adsorption treatment such that each amount of them becomes 1.0 wt% of the theoretical production amount of an ester. The adsorption treatment temperature, pressure, 12 and adsorption treatment time were 100°C, 1 kPa, and 3 hours, respectively. Thereafter, the mixture was filtrated using a one-micron filter, and thus an ester (which is referred to as "ester A") was obtained. Table 1 shows the composition of the obtained ester A. Examples 1.2 to 1.6 Esters (i.e., esters B to F) were obtained in the same manner as in Example 1 except that the mixed alcohols and the mixed carboxylic acids shown in Table 1 were used. Table 1 shows the compositions of the obtained esters B toF. Comparative Examples 1.1 to 1.8 Esters (i.e., esters G to N) were obtained in the same manner as in Example 1 except that the mixed alcohols and the mixed carboxylic acids shown in Table 1 were used. Table 1 shows the compositions of the obtained esters G toN. 13 14 The esters A to N shown in Table 1 were obtained. Among these, the esters G to N of Comparative Examples 1.1 to 1.8 do not satisfy the requirements of the esters used in the present invention. That is, the esters G and H of Comparative Examples 1.1 and 1.2 do not have appropriate quantitative relation (values of the expression of relations) of pentanoic acid, heptanoic acid and neopentyl glycol. The ester I of Comparative Example 1.3 does not contain pentanoic acid and heptanoic acid. The ester J of Comparative Example 1.4 does not contain dipentaerythritol. The ester K of Comparative Example 1.5 has a low content of neopentyl glycol and a high content of pentaerythritol. For the esters L and N of Comparative Examples 1.6 and 1.8, the total amount of pentanoic acid and heptanoic acid and the content of caprylic acid are outside the ranges of the present invention, and the values of the expression of relations are not appropriate. The ester M of Comparative Example 1.7 has a high content of dipentaerythritol. Example 2.1 The ester A obtained in Example 1.1 was used as a lubricant (lubricant 1). Regarding the lubricant 1, the kinematic viscosity at 40°C and 100°C, viscosity index, color number, acid value, hydroxyl value, volume resistivity, pour point, and two-phase separation temperature (low temperature) were measured according to the above described methods. Furthermore, the long-term low-temperature test, sealed tube test, and Falex friction test were performed, according to the above-described methods. Table 2 shows the results. Examples 2.2 to 2.6 The esters B to F obtained in Examples 1.2 to 1.6 were used as lubricants (i.e., lubricants 2 to 6). Regarding each lubricant, measurement and tests were performed in the same manner as Example 2.1. Table 2 also shows the results. 15 Comparative Examples 2.1 to 2.8 The esters G to N obtained in Comparative Examples 1.1 to 1.8 were used as lubricants (i.e., lubricants 7 to 14). Regarding each lubricant, measurement and tests were performed in the same manner as Example 2.1. Table 2 also shows the results. 16 Table 2 17 As is apparent from the results in Table 2, the lubricants (lubricants 1 to 6) of the examples have a kinematic viscosity of 6 to 28 mm2/s at 40°C, which is a desired viscosity, and excellent lubricity, which is indicated by the kinematic viscosity and the Falex friction test, and also have excellent stability with no precipitation occurring even in the long-term low-temperature test. Furthermore, these lubricants 1 to 6 have a low pour point, excellent compatibility with hydrofluorocarbon refrigerants, which is indicated by the two-phase separation temperature, and less susceptibility to deterioration due to thermal oxidation, which is indicated by the results of the sealed tube test, and satisfy other performance requirements required for a refrigeration lubricant. Therefore, it is evident that they are excellent refrigeration lubricants, in particular a refrigeration lubricant for chlorine-free hydrofluorocarbon refrigerants. In contrast, as for the lubricants of the comparative examples (lubricants 7 to 14), the esters contained therein do not satisfy the ranges of the present invention, so that either the lubricity or long-term low-temperature stability was insufficient. That is, for the lubricants of Comparative Examples 2.1 and 2.4 to 2.6 (lubricants 7 and 10 to 12), precipitation occurs in the long-term low-temperature test, and the stability is insufficient. For the lubricants of Comparative Examples 2.2, 2.3 and 2.8 (lubricants 8, 9 and 14), pins were significantly worn in the Falex friction test and the lubricity is insufficient. The lubricant 13 of Comparative Example 2.7 has a high two-phase separation temperature and particularly poor compatibility with hydrofluorocarbon refrigerants, although it has good long-term low-temperature stability and lubricity. The refrigeration lubricant composition of the present invention has low viscosity, good lubricity, and excellent long-term low-temperature stability. This composition also has excellent compatibility with chlorine-free hydrofluorocarbon refrigerants, thermal resistance and electrical insulating properties, which are necessary as a refrigeration lubricant composition. Therefore, the composition 18 of the present invention is useful as a lubricant for refrigerators employing a chlorine-free hydrofluorocarbon refrigerant, in particular a chlorine-free hydrofluorocarbon refrigerant containing at least one of 1,1,1,2-tetrafluoroethane and difiuoromethane or as a refrigerant working fluid mixed with a chlorine-free hydrofluorocarbon refrigerant, and contributes to fuel efficiency of various refrigerating apparatuses. Specifically, the refrigeration lubricant composition of the present invention and the refrigerant working fluid containing the lubricant composition and a chlorine-free hydrofluorocarbon refrigerant can be used for low-temperature apparatus such as refrigerators and industrial refrigerators, air conditioning equipment such as room air conditioners and packaged air conditioners, and automotive air conditioners such as hybrid cars and electric cars. The invention may be embodied in other forms without departing from the spirit or essential characteristics thereof. The embodiments disclosed in this application are to be considered in all respects as illustrative and not limiting. The scope of the invention is indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein. 19 What we claim is : 1. A refrigeration lubricant composition comprising an ester obtained from a mixed alcohol and a mixed saturated straight-chain carboxylic acid, wherein the mixed alcohol consists of 10 to 50 mol% of neopentyl glycol, 50 to 89 mol% of pentaerythritol, and 0.03 to 3 mol% of dipentaerythritol, the mixed saturated straight-chain carboxylic acid consists of 70 to 95 mol% of pentanoic acid and heptanoic acid, and 5 to 30 mol% of caprylic acid, wherein the ester is obtained by a reaction in which the following relation is satisfied: , and the composition has a kinematic viscosity at 40°C of 6 to 28 mmf/s. 2. A refrigerant working fluid consisting of the refrigeration lubricant composition of claim 1 and a chlorine-free hydrofluorocarbon refrigerant. 3. A refrigerant compression type refrigerating apparatus comprising a compressor, a condenser, an expansion mechanism, an evaporator, and the refrigerant working fluid of claim 2. Dated this 24th day of May 2006. 20

Documents:

00494-kol-2006 form-3-1.1.pdf

00494-kol-2006-abstract.pdf

00494-kol-2006-claims.pdf

00494-kol-2006-correspondence other.pdf

00494-kol-2006-correspondence others-1.1.pdf

00494-kol-2006-description complete.pdf

00494-kol-2006-form 1.pdf

00494-kol-2006-form 2.pdf

00494-kol-2006-form 3.pdf

00494-kol-2006-form 5.pdf

00494-kol-2006-general power of auth0rity.pdf

00494-kol-2006-priority document.pdf

494-KOL-2006-(05-10-2012)-ABSTRACT.pdf

494-KOL-2006-(05-10-2012)-AMANDED CLAIMS.pdf

494-KOL-2006-(05-10-2012)-AMANDED PAGES OF SPECIFICATION.pdf

494-KOL-2006-(05-10-2012)-ANNEXURE TO FORM 3.pdf

494-KOL-2006-(05-10-2012)-CORRESPONDENCE.pdf

494-KOL-2006-(05-10-2012)-DESCRIPTION (COMPLETE).pdf

494-KOL-2006-(05-10-2012)-FORM-1.pdf

494-KOL-2006-(05-10-2012)-FORM-2.pdf

494-KOL-2006-(05-10-2012)-OTHERS.pdf

494-kol-2006-form 18.pdf