KR0131016B1 - Refrigeration lubricants - Google Patents

Abstract

Containing one or more straight chain or branched monovalent fatty acids having a specific carbon number with neopentyl glycol or a polyvalent alcohol of the following formula or an ester obtained by further esterifying at least one polybasic acid having a specific carbon number as a main component Lubricants for Fluorocarbon coolants:

This lubricant is fully compatible with the hydrofluorocarbon coolant used as a replacement refrigerant for conventional chlorine containing compounds.

Description

Cooling lubricant

Accordingly, an object of the present invention is to provide a cooling lubricant which has excellent compatibility with a novel coolant such as HFC-134a in a wide temperature range, and has high electrical insulation and low hygroscopicity.

At present, some of the commercially available esters are used in systems using refrigerants R-12, R-22 and the like, but they can not be used with HFC-134a, which is a novel refrigerant, or their commercial range is very narrow. In this connection, the present inventors have found that, in view of the fact that the ester has a high electrical insulating property, a low hygroscopicity, a good lubricity and a high stability as compared with the PAG, the molecular design of the ester exhibiting a wide range of compatibility with HFC- And it has been found that only esters having a remarkably limited structure can be used in the HFC-134a refrigeration system. As a result, the present invention has been completed.

The present invention relates to a lubricant for use with a coolant and more particularly to a lubricant which contains no chlorine, such as hydrofluorocarbons (HFC), preferably HFC-134a (1,1,1,2-tetrafluoroethane) Lt; RTI ID = 0.0 > lubricant < / RTI >

R-22 (monochlorodifluoroethane) as R-11 (trichloromonofluoromethane), R-12 (dichlorofluoromethane) and hydrochlorofluorocarbon (HCFC) as chlorofluorocarbons Chloromethane) and the like have been used as coolants for refrigerators, air conditioners, refrigerators and the like. In connection with the recent problem of ozone depletion, new chlorine-free coolants such as HFC-134a and the like have been proposed as coolants that do not destroy the ozone layer that can displace R-12.

As a cooling lubricant, many inorganic systems and synthetic oils are known. However, these oils are not compatible with HFC - 134a because they are not very compatible. Therefore, it is important now to take measures against this problem. Furthermore, lubricants, electrical insulation properties, energy saving properties, anti-abrasion resistance, hermeticity, thermal stability and sludge formation prevention are mentioned as performance requirements for lubricating coolants, and these factors are therefore required to be considered in the development of the above measures.

In addition, polyether-based synthetic lubricants as synthetic oils are known in the art and are described in Journal of the Oil Chemistry, Vol. 29, No. 9, pp 336-343 (1980) and Journal of the Petroleum Technology, vol. 8, Ho, 6, pp 562-566 (1985). Further, Japanese Unexamined Patent Publication No. 61-281199 to No. formula _{R1 [O- (R 2 O)} mR 3] , and the mixture, such as polyglycol, alkylbenzene represented by n is described, Japanese Patent Laid-Open No. 57-63395 discloses an oil obtained by mixing a polyether such as a high molecular weight polyoxypropylene monobutyl ether with an epoxycycloalkyl compound. Japanese Patent Application Laid-Open No. 59-117590 discloses an oil obtained by mixing a polyether compound and a paraffin- A high viscosity blended oil of naphthenic mineral oil is described.

However, the above-mentioned conventional synthetic lubricants can not be a cooling lubricant using HFC-134a as a lubricant from the viewpoint of mixing and the like.

United States Patent No. 4755316 discloses a polyoxyalkylene glycol (hereinafter abbreviated as PAG) having a hydroxyl group (-OH) at both ends as a cooling lubricant using HFC-134a. In addition, PAG dissolves in HFC-134a over a wide temperature range, as compared to conventional PAG containing a hydroxyl group and an alkyl group as an end group, thereby improving the recirculation of the lubricant into the compressor in the cooling system, Is prevented.

In addition, the temperature range compatible with HFC-134a is stated to be -40 ° C to + 50 ° C.

On the other hand, HFC-134a is an alternative refrigerant for R-12 and is expected to be mainly used in automobile air conditioners and refrigeration. In the case of a refrigerator, it is required to have good compatibility between the lubricant and the coolant, and furthermore, the lubricant itself needs to have electrical insulation because the motor is almost always present in the cooling system. However, conventional compounds investigated as lubricants for HFC-134a refrigerants, including PAG, as disclosed in U.S. Pat. No. 4,755,316, have significantly poor electrical insulation and high hygroscopicity as compared to conventional cooling mineral oils.

According to a first aspect of the present invention there is provided a hydrofluorocarbon coolant such as HFC-134a, which contains an ester comprising neopentyl glycol as the main component and at least one straight chain or branched chain monohydric fatty acid having 3 to 18 carbon atoms and 4 to 18 carbon atoms Is provided.

According to a second aspect of the present invention, there is provided a curable resin composition comprising at least one of pentaerythritol, dipentaerythritol and tripentaerythritol represented by the following general formula (1) as a main component and at least one side chain 1 having 2 to 18 carbon atoms, There is provided a lubricant for a hydrofluorocarbon coolant, such as HFC-134a, containing an ester of a fatty acid.

(Wherein n is 1, 2 or 3)

According to a third aspect of the present invention, there is provided a polyhydric alcohol represented by the following general formula (2) as a main component, at least one straight chain or branched chain monovalent fatty acid having 2 to 18 carbon atoms and 4 to 18 carbon atoms, and at least 25 mol% There is provided a lubricant for a hydrofluorocarbon coolant such as HFC-134a containing an ester of one polyhydroxy acid having 4 to 36 carbon atoms.

(Wherein R is an alkyl group having 3 or less carbon atoms)

In a preferred embodiment of the present invention, the hydrofluorocarbon refrigerant is 1,1,1,2-tetrafluoroethane (HFC-134a).

The cooling lubricant for the coolant HFC-134a etc. according to the first invention is an ester obtained by esterification of neopentyl glycol with at least one straight-chain or branched-chain monovalent fatty acid having 3 to 18 carbon atoms and 4 to 18 carbon atoms as a main component .

In the first invention, the number of carbon atoms of the monovalent fatty acid is limited to 3 to 18 because if the number of carbon atoms is less than 3, the viscosity becomes too low. On the other hand, if the number of carbon atoms is more than 18, the resulting ester becomes enriched or miscible with the coolant HFC- It is very poor.

Examples of the monovalent fatty acids include propionic acid, isopropionic acid, butanoic acid, isobutanoic acid, pentanoic acid, isopentanoic acid, hexanoic acid, heptanoic acid, isoheptanoic acid, octanoic acid, 2-ethylhexanoic acid, - trimethylhexanoic acid, decanoic acid, undecanoic acid, lauric acid, myristic acid, palmitic acid, palmitooleic acid, stearic acid, isostearic acid, oleic acid and the like.

In the first aspect of the invention, one or more of these monovalent fatty acids are appropriately mixed with neopentyl glycol to be esterified to obtain an ester which satisfies desired properties required for various cooling apparatuses.

In order to obtain sufficiently satisfactory compatibility with the coolant HFC-134a and the like, it is preferable to use a mixed acid of a side chain monovalent fatty acid or a linear monovalent fatty acid and a side chain monovalent fatty acid.

It is preferable to use a mixture of a linear fatty acid having 3 to 11 carbon atoms, preferably 5 to 10 carbon atoms, more preferably 7 carbon atoms, and a branched chain fatty acid having 4 to 14 carbon atoms, preferably 7 to 9 carbon atoms as the monovalent fatty acid. In this case, the amount of the side chain monovalent fatty acid to be used is preferably at least 50 mol% based on the total amount of monovalent fatty acids used.

According to the present invention, one or more polyhydric acids having 4 to 36 carbon atoms can be esterified with neopentyl glycol in an amount of 80 mol% or less based on the total amount of fatty acids, in order to provide an appropriate viscosity to the produced ester. Considering higher compatibility and physical properties with the coolant HFC-134a and the like of the produced ester, a polyhydric acid having 4 to 10 carbon atoms is preferable among the polyhydric acids. Specific examples of the polyvalent acid include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, maleic acid and trimellitic acid. In addition, a polyvalent acid having 3 or less carbon atoms is difficult to obtain at actual cost as a special product, and is poor in stability of the ester after shredding. On the other hand, when the number of carbon atoms exceeds 36, the compatibility of the resulting ester with HFC-134a and the like is significantly lowered. In the present invention, the addition amount of the polyvalent acid is limited to 80 mol% or less based on the total amount of the fatty acid, because if it exceeds 80 mol%, gelation may occur and it is difficult to obtain desired physical properties.

The ester compound according to the first aspect of the present invention can be obtained by esterification reaction through dehydration reaction between the specific polyhydric alcohol and a specific fatty acid as described above or by a general esterification reaction originating from a derivative of a fatty acid such as phosphoric acid anhydride or acid chloride have.

Since the esters according to the invention can be obtained by this process, the residual acid value and the hydroxy value are not particularly critical. However, when the acid value is more than 3, the acid value is preferably 3 or less, since an unfavorable phenomenon that the metal soap is formed and precipitated by the reaction with the metal used in the cooler can occur.

Incidentally, when the hydroxyl value exceeds 50, the hydroxy value is preferably 50 or less, because an unfavorable phenomenon that the resulting ester becomes enriched may occur.

The lubricant for refrigerant HFC-134a according to the second invention is at least one member selected from the group consisting of pentaerythritol, dipentaerythritol and tripentaerythritol represented by the above formula (1), at least one of which is a linear or branched As a main component, an ester obtained by esterification with a branched chain monovalent fatty acid having 4 to 18 carbon atoms.

In the pentaerythritol condensate, the polymerization degree can be determined according to the viscosity required for the resulting synthesized ester. In the second aspect of the present invention, the number of carbon atoms of the monovalent fatty acid is limited to 2 to 18 because if the value exceeds 18, the resultant ester becomes enriched or miscibility with the refrigerant HFC-134a or the like becomes very poor .

Examples of monovalent fatty acids include acetic acid, propionic acid, isopropionic acid, butanoic acid, isobutanoic acid, pentanoic acid, isopentanoic acid, hexanoic acid, heptanoic acid, isoheptanoic acid, octanoic acid, 2-ethylhexanoic acid, , 5,5-trimethylhexanoic acid, decanoic acid, undecanoic acid, lauric acid, myristic acid, palmitic acid, palmitooleic acid, stearic acid, isostearic acid, oleic acid, linoleic acid and linolenic acid have.

In the second invention, at least the heavenly pentaerythritol or condensate thereof of these monovalent fatty acids is appropriately mixed and esterified to obtain an ester which satisfies the desired physical properties required for various kinds of coolants.

In order to obtain compatibility with sufficiently satisfactory coolant HFC-134a and the like, it is preferable to use a mixed acid of a side chain monovalent fatty acid or a monovalent monovalent bicyclic acid and a side chain monovalent fatty acid.

As the monovalent fatty acid, it is preferable to use a mixture of a straight-chain fatty acid having 3 to 11 carbon atoms, preferably 5 to 10, more preferably 7 or less, and a branched chain fatty acid having 4 to 14 carbon atoms, preferably 7 to 9 carbon atoms . In this case, the use amount of the branched chain monovalent fatty acid is preferably 50 mol% or more per total amount of the monovalent fatty acid.

On the other hand, in order to impart a suitable viscosity to the resulting ester, at least one polybasic acid having 4 to 36 carbon atoms is mixed with at least one of pentaerythritol, dipentaerythritol, and tripentaerythritol and not more than 80 mol% ≪ / RTI > In this case, the same polybasic acid as that described in the first invention is used in the same manner as in the first invention.

The ester compound according to the second invention can be obtained by the same method as in the first invention.

In the ester according to the second invention, the acid value and the hydroxy value are not more than 3 and not more than 50, respectively, as in the first invention.

The refrigerant HFC-134a according to the third invention and the lubricant for other purposes are obtained by esterifying the polyhydric alcohol represented by the above formula (2) with at least one straight chain or branched chain monovalent fatty acid having 2 to 18 carbon atoms or a branched chain monovalent fatty acid having 4 to 14 carbon atoms It contains ester as a main component.

When the number of carbon atoms of R in the formula (2) is 4 or more, miscibility with the produced ester and HFC-134a or the like is significantly lowered. As the polyhydric alcohol, trimethylolethane, trimethylolpropane, trimethylolbutane and the like can be mentioned.

In the third invention, when the number of carbon atoms of the monovalent fatty acid is larger than 18, miscibility with the resulting synthesized ester is poor with HFC-134a and the like.

Particularly, a straight chain or branched chain monovalent fatty acid having 3 to 10 carbon atoms or a branched chain monovalent fatty acid having 4 to 10 carbon atoms is preferable. As the monovalent fatty acid, the same compounds as described in the second invention can be mentioned.

On the other hand, at least one polybasic acid having 4 to 36 carbon atoms can be esterified together in an amount of 25 mol% or less based on the total amount of the fatty acids in order to give an appropriate degree of ester to the produced ester.

In a polybasic acid, a polybasic acid having 3 or less carbon atoms is an unusual product, which is difficult to obtain cheaply and is poor in the stability of the ester after synthesis.

On the other hand, when the elasticity number exceeds 36, miscibility with the produced ester and HFC-134a or the like is significantly lowered. Therefore, the number of carbon atoms of the polybasic acid is preferably from 4 to 36, and more preferably from 4 to 10, in view of ensuring compatibility with HFC-134a in a wide range. As the polybasic acid, adipic acid, agelacic acid, and sebacic acid can be used. Preferably, the monovalent fatty acid is 2-ethylhexanoic acid and the multipartic acid is adipic acid.

In addition, in the present invention, the amount of the polybasic acid added is limited to 25 mol% or less based on the total fatty acids, because if the amount exceeds 25 mol%, gelation may be induced and it is difficult to obtain desirable physical properties.

The ester compound according to the third invention can be obtained in the same manner as in the first and second inventions. In either case, it is preferable that the ester does not contain a carboxyl group.

Since the ester according to the present invention exhibits excellent mixing with the coolant HFC-134a and the like as a lubricant for use in a cooler using HFC-134a as a coolant widely from a low temperature to a high temperature, the lubricity and thermal stability of the cool lubricant are considerably high Can be improved. In addition, they are high electrical insulation and low wettability as compared to PAGs previously tested as cooling lubricants for HFC-134a. Therefore, the cooling lubricant using the ester according to the present invention as a main component can solve the problems of compatibility with HFC-134a and wettability, which can not be solved in the prior art, and furthermore, the HFC- It is possible to enhance the electrical insulation which is a problem in use.

In addition, additives commonly used in lubricants such as antioxidants, anti-wear agents, epoxy compounds and the like can be appropriately added to the cooling lubricant according to the present invention.

The following examples are intended to illustrate but not limit the invention.

Examples 1 to 8 and Comparative Examples 1 to 5

Performance as a cooling lubricant using HFC-134a as a coolant was evaluated for the eight esters A-1 to A-8 shown in Table 1 below (all of these esters are not commercially available but prepared according to the first invention). For comparison, the above-mentioned PAG (B-1 to B-3, Asahi Denka Kasei) and the esters (D-1 to C-2, Nippon Oil & Perform the same evaluation as the bars.

Lubricity, conformability, thermal stability, electrical insulation and hygroscopicity as the performance of the cooling lubricant for compressors shown in Tables 1 and 2 were evaluated under the following conditions.

Lubricity

Measure the inactivated loading (Palex-rood transport capacity) of HFC-134a according to ASTM D-3233-73 under controlled pressure.

compatibility

0.6 g of a test lubricant and 2 and 4 g of a coolant (HFC-134a) are sealed in a glass tube, followed by cooling and heating at 1 캜 / min.

Thermal stability

After 1 g of the test lubricant, 1 g of coolant (HFC-134a or R-12) and catalyst (wire of iron, copper or aluminum) were sealed in a glass tube, the mixture was heated to 175 ° C and after 10 days the color of the lubricant It is determined according to ASTM, color number according to ANSI / ASHRAE 97-1983.

Electrical insulation

It is measured according to JIS C-2101 by a dielectric constant of 80 캜.

Hygroscopic

A 100 ml beaker is filled with 60 g of the test lubricant and left for 3 hours at a temperature of 25 캜 and a humidity of 70 캜, and then the moisture concentration is measured.

The evaluation results are shown in Table 3 below.

Note) The amount of starting material is expressed in mole%.

1) polyoxypropylene glycol monoalkyl ether

2) polyoxypropylene glycol monoalkyl ether

3) Polyoxyethylene propylene glycol monoalkyl ether

4) Monoester of 2-ethylhexanol and palmitic acid

*: 50 ° C or less

**: above 80 ℃

As can be seen from Table 3, when the ester according to the present invention is compared with the conventional PTA (B-1 to B-3), the electric insulation expressed by a dielectric constant is 100,000 times or more, and no two phase separation occurs at a high temperature. In addition, the stop load amount is high and the hygroscopicity is low. Thermal stability is the same for HFC-134a, but fairly good for R-12 systems. This is very useful in practice because it is inevitable to mix HFC-134a and R-12 in the step of replacing the coolant with RFC to HFC-134a.

On the other hand, when the ester according to the present invention is compared with the commercially useful esters (C-1 to C-2), the two phase separation temperatures are significantly different and conventional esters are insoluble in HFC-134a. In this respect, the molecules designed according to the invention have a great advantage.

As can be seen from the above, the ester according to the present invention has excellent performance as a lubricant as compared with the comparative example.

Examples 9 to 17

The performance as a cooling lubricant using HFC-134a as a coolant was measured for the nine esters A-9 to A-17 shown in Table 4 below (these esters, although not commercially available, were prepared according to the second invention) .

The same measurements as in Example 1 were carried out to obtain the results shown in Table 5 below.

Note)% mol is the amount for the whole acid.

As shown in Table 5, when the ester according to the present invention is compared with the conventional PGA (B-1 to B-3) shown in Table 2 and Table 3, the electric insulating property expressed by the dielectric constant is 100,000 times or more, 2-phase separation does not occur at the interface. Moreover, the load of the stopping load is excellent and the water absorption is low. The thermal stability is the same for the HFC-134a system, but very good for the R-12 system. This fact is very advantageous in practice because HFC-134a and R12 are inevitably mixed at the stage of replacing the coolant with R-12 to HFC-134a.

On the other hand, when the ester according to the present invention is compared with the commercially available ester (C-15 I C-2) shown in Table 2 and Table 3, it can be seen that the two-phase separation temperature is very different and the usual ester is insoluble in HFC- to be. At this point, the molecularized esters according to the invention have great advantages.

As seen from the above, the ester according to the present invention is excellent in performance as a lubricant as compared with the comparative example.

HFC-134a is referred to as a possible alternative to R-12 and is used in automotive air conditioners, coolers, and the like. In particular, in the case of automobile air conditioners, since the compressor operates in summer, compatibility between oil and coolant becomes important at high temperatures.

If a two-phase separation between oil and coolant occurs in the compressor during operation, refrigerant with a larger specific gravity remains in the lower portion of the compressor, resulting in compressor shutdown.

In the case of a freezer, a short circuit is a problem because the compressor is included in the compressor. In this connection, the ester of the present invention has a dielectric constant of 100,000 times or more higher than that of a conventional PAG and is excellent in electrical insulation, so that it can be considered as a cooling lubricant for a cooler.

Specifically, since the lubricant having a dynamic viscosity of 10 to 50 cSt at 40 占 폚 is used as a lubricant for cooling requiring a two-phase separation temperature of -40 占 폚 or less, the esters A-10, A-11 and A- Especially suitable for that. On the other hand, since the lubricant having a dynamic viscosity of 80 to 150 cSt at 40 占 폚 is used as a lubricant for automobile air conditioners requiring a two-phase separation temperature of -20 占 폚 or lower, the ester A-9, A-13, A- A-16 and A-17 are particularly suitable.

Examples 18 to 35

The performance as a cooling lubricant using HFC-134a as a coolant is evaluated for the eight esters A-18 to A-25 (all of these esters are not commercially available but are prepared according to the third invention) shown in Table 6 below . The results shown in Table 7 below were obtained in the same evaluation as in Example 1.

Note) Values in parentheses are in mole% per total fatty acids.

As shown in Table 7, when the ester according to the present invention is compared with the conventional PAG (B-1 to B-3) shown in Table 2 and Table 3, the electric insulating property expressed by the dielectric constant is 100,000 times or more, The two-phase branching of the two- Moreover, the load of the stopping load is excellent and the water absorption is low. The thermal stability is the same for the HFC-134a system, but very good for the R-12 system.

Recently, HFC-134a, which does not actually cause ozone depletion, is used instead of R-12, which is widely used as a coolant, in order to cope with destruction of ozone layer through chlorofluorobarbon and hydrochlorofluorocarbon which are the biggest problems in the world , The compatibility with the ordinary cooler lubricant is poor, which hinders the development of an alternative system. However, since the coolant lubricant according to the present invention has high compatibility with HFC-134a as a coolant and has high electrical insulation and excellent in all performances, even when HFC-134a is used as a coolant instead of ordinary R-12 and R-22 The conventional system can be used.

Claims (12)

(1) Neopentyl glycol and (2) at least one linear monovalent fatty acid having 3 to 18 carbon atoms, a branched monovalent fatty acid having 4 to 14 carbon atoms or a mixed acid thereof and having an acid value of 3 mg KOH / g or less, a hydroxyl value of 50 mg KOH / g or less, and an electric insulating property of 1 x 10 < ¹² > OMEGA .cm or more as a main component. The lubricant for a chlorofluorocarbon (HFC) The lubricant according to claim 1, wherein the hydrofluorocarbon coolant is 1,1,1,2-tetrafluoroethane. (1) Neopentyl glycol and (2) at least one linear monovalent fatty acid having 3 to 18 carbon atoms, a branched monovalent fatty acid having 4 to 14 carbon atoms, (3) at least one polybasic acid having 4 to 36 carbon atoms, wherein the acid polybasic acid is 80 mol% or less of the total fatty acids, and having an acid value of 3 mg KOH / g or less, a hydroxyl value of 50 mg KOH / g or less, A lubricant for a chlorine-free hydrofluorocarbon (HFC) coolant containing an ester as a main component in an insulating property of 1 x 10 < ¹² > 4. The lubricant according to claim 3, wherein the hydrofluorocarbon coolant is 1,1,1,2-tetrafluoroethane. (1) Neopentyl glycol and (2) at least one branched chain monovalent fatty acid having 4 to 18 carbon atoms Containing hydrofluoric acid having an acid value of not more than 3 mg KOG / g, a hydroxyl value of not more than 50 mg KOH / g, and an electric insulating property of not less than 1 x 10 & Lubricants for carbon (HFC) coolants. The lubricant according to claim 5, wherein the hydrofluorocarbon coolant is 1,1,1,2-tetrafluoroethane. (1) at least one polyhydric alcohol represented by the formula:

(Wherein R is an alkyl group having 3 or less carbon atoms) (2) at least one linear monovalent fatty acid having 2 to 18 carbon atoms, a branched monovalent fatty acid having 4 to 14 carbon atoms, or a mixed acid thereof and (3) at least one polybasic acid having 4 to 36 carbon atoms 25% by mole or less) and having an acid value of 3 mg KOH / g or less, a hydroxyl value of 50 mg KOH / g or less, and an electrical insulating property of 1 x 10 ¹² ? ≪ / RTI > is a lubricant for hydrofluorocarbon (HFC) coolants that do not contain a lubricant. 8. The method of claim 7, (1) at least one polyhydric alcohol represented by the formula:

(Wherein R is an alkyl group having 3 or less carbon atoms) (2) 2-ethylhexanoic acid and (3) adipic acid (the adipic acid is 25 mol% or less of the total fatty acids) And having an acid value of 3 mg KOH / g or less and a hydroxyl value of 50 mg KOH / g or less and an electrical insulating property of 1 x 10 < ¹² > OMEGA .cm or more as a main component, the chlorine-free hydrofluoro Lubricants for Locavon (HPC) coolant. The lubricant according to claim 7 or 8, wherein the hydrofluorocarbon coolant is 1,1,1,2-tetrafluoroethane. The lubricating oil composition according to claim 1, wherein the mixed acid comprises at least 50 mol% of branched chain monovalent fatty acids 4. The lubricant according to claim 3, wherein the mixed acid comprises at least 50 mol% of branched chain monovalent fatty acids. The lubricant according to claim 7, characterized in that said mixed acid comprises at least 50 mol% of branched chain monovalent fatty acids.