DE68927916T3 - Use a lubricant for compressors that use a chlorine-free fluorocarbon refrigerant - Google Patents

Description

The The invention relates to the use of lubricants for compressors using a hydrofluorocarbon coolant that does not contain chlorine, such as Hydrofluorocarbons (HFC), preferably HFC-134a, (1,1,1,2-tetrafluoroethane).

So far were compounds containing fluorine and chlorine as the element of the compound such as R-11 (trichloromonofluoromethane), R-12 (dichlorodifluoromethane) as chlorofluorocarbon (CFC), R-22 (monochlorodifluoromethane) as Chlorofluorocarbon (HCFC) used as a coolant for refrigerators, air conditioners and refrigerators.

JP-A-56131548 discloses neopentyl polyol esters useful as freon resistant lubricant oils are suitable.

JP-A-59164393 discloses a refrigeration machine oil which as a base oil contains a complex ester, made of a polyvalent alcohol, C16-C18 unsaturated fatty acid and C4-C10 dicarboxylic acid synthesized were. The complex ester has a high lubricity and chemical stability and has a balanced compatibility with Freon.

The Freons disclosed in the above references are polyhalogenated Hydrocarbons containing fluorine and chlorine.

in the Regard to the youngest Problems with destruction the ozone layer, new coolants, which do not contain chlorine, such as HFC-134a, suggested as a possible replacement for R-12, no destruction the ozone layer leads.

When coolant Many mineral series and synthetic oils are known. It became, however proves that these oils a very bad compatibility with HFC-134a and thus can not be used. It It is therefore important, at present, to take countermeasures against this problem hold true. Furthermore, the lubricity, the electrical insulating properties, the energy-saving properties, the anti-abrasion resistance, the sealability, the thermal resistance, the avoidance of sludge formation etc. as properties mentioned that for a coolant are required, so you can use them in the preparation of the above Countermeasures for required.

Coincidentally, synthetic polyether series lubricants have hitherto been known as a synthetic oil, of which Journal of the Oil Chemistry, Vol. 29, No. 9, pp. 336-343 (1980) and Journal of the Petroleum Technology, Vol. 6, pp. 562-566 (1985). Further, Japanese Patent Laid-Open No. 61-281199 discloses a mixture of polyglycol represented by the general formula R ₁ [O- (R ₂ O) m R ₃ ] _n , an alkylbenzene and the like, and Japanese Laid-Open Patent No. 57- 63395 describes an oil obtained by blending a polyether such as high molecular weight polyoxypropylene monobutyl ether with an epoxycycloalkyl compound, and Japanese Laid-Open Patent No. 59-117590 discloses a high viscosity oil blend of a polyether compound and a paraffin or naphthan mineral oil.

however can the ones mentioned above conventional synthetic lubricant not in a cooling lubricant using HFC-134a as a refrigerant, e.g. regarding the compatibility be used.

in the U.S. Patent No. 4,755,316 reports that polyoxyalkylene glycol (abbreviated below as PAG) with hydroxyl groups at both ends a coolant when using HFC-134a. It is further described that PAG in HFC-134a within a wide temperature range in comparison to the usual PAG, which holds hydroxyl groups and alkyl groups at its ends, is soluble, whereby the return of the lubricant in the compressor in the cooling system is improved and seizing when starting the compressor is prevented at a high temperature. Furthermore, the temperature range, compatible with HFC-134a, as described between -40 ° C and + 50 ° C.

on the other hand HFC-134a is a replacement coolant for R-12 and you expect mainly its application e.g. in air conditioners or refrigerators.

With a refrigerator, it is necessary to have good compatibility between lubricant and Coolant is present, and further, the lubricant itself must have an electrical insulating property, since the engine is present substantially in the cooling system. However, conventional compounds tested as lubricants for HFC-134a refrigerant, including PAG, as disclosed in U.S. Patent No. 4,755,316, exhibit remarkably poor electrical insulating property as compared to conventional coolant mineral oil, and exhibit high hygroscopicity.

It It is an object of the invention to provide a cooling lubricant which has excellent compatibility with new coolants, such as. HFC-134a, within a wide temperature range, one has high electrical insulating property, and a low hygroscopicity for compressors that a fluorocarbon refrigerant use that does not contain chlorine, Has.

to Time becomes a part of commercial available Esters in systems using refrigerants such as R-12 and R-22, however, it is incompatible with HFC-134a as a new coolant, or it shows a very close compatible area. In this In connection with this, the inventors sought that the ester high electrical insulation properties, low hygroscopicity, good Has lubricant property and high stability compared to PAG, and have different investigations with regard to the molecular Structure of the Ester Showing a Wide Compatibility Range with HFC-134a undertaken, and found that only esters with a significantly restricted structure in a HFC-134a cooling system can be used on which the invention is based.

The The invention relates to the use of a lubricant for compressors using a fluorocarbon refrigerant containing no chlorine as the major component (s) of ester obtainable by reacting (a) at least one polyvalent alcohol selected from pentaerythritol, dipentaerythritol and tripentaerythritol with (b) a mixture of at least one of straight-chain monovalent fatty acids with a carbon number from 3-11 and with at least one of branched-chain monovalent fatty acids a carbon number of 4-14, wherein the amount of branched-chain monovalent fatty acid is not less than 50 mol% per used total of monovalent fatty acid is, with the proviso that the lubricant is not in a liquid composition, as the main component (more than 50 wt .-%) a fluorine-containing Hydrocarbon refrigerants and as a minor ingredient (less than 50% by weight) the lubricant contains is used.

Further The invention relates to the use of a lubricant for compressors using a fluorocarbon refrigerant containing no chlorine as the major component (s) of ester obtainable by reacting (a) at least one polyvalent alcohol selected from pentaerythritol, dipentaerythritol and tripentaerythritol with (b) a mixture of at least one of straight-chain monovalent fatty acids with a carbon number from 3-11 and at least one of branched-chain monovalent fatty acids having a carbon number of 4-14, wherein the amount of branched chain monovalent fatty acid is not less than 50 mol% per total monovalent fatty acid used, and (c) at least one polybasic acid having a carbon number of 4-10, wherein the amount of the polybasic acid is not more than 80 mol% per total fatty acid is, with the proviso that the lubricant is not in a liquid composition, as the main component (more than 50 wt .-%) a fluorine-containing Hydrocarbon refrigerants and as a minor ingredient (less than 50% by weight) the lubricant contains is used.

The The invention also relates to the use of a lubricant for compressors using a fluorocarbon refrigerant containing no chlorine as the major component (s) of ester obtainable by reacting (a) at least one polyvalent alcohol selected from pentaerythritol and Dipentaerythritol with (b) at least one branched-chain monovalent fatty acid with a carbon number of 4 to 18, with the proviso that

• (I) the lubricant no polyether polyol in an amount of 5 to 95 wt .-% according to the general formula Z - [(CH ₂ CH (R ₁ ) -O-) _n - (CH ₂ -CH (CH ₃ ) -O-) _m -R ₂ ] _p wherein Z is the radical of a compound having 1 to 8 active hydrogens, R is hydrogen, ethyl or mixtures thereof n is 0 or a positive number, m is a positive number, n + m is a number having a value corresponding to Polyether polyol an average molecular weight in Be R ₂ is hydrogen or an alkyl group having 1 to 6 carbon atoms, p is an integer having a value corresponding to the number of active hydrogens of Z, and
• (ii) the lubricant is not in a liquid composition, the as the main ingredient (more than 50% by weight), a fluorine-containing hydrocarbon refrigerant and as a minor ingredient (less than 50% by weight) the lubricant contains is used.

(worin n gleich 1, 2 oder 3 ist).Pentaerythritol, dipentaerythritol and tripentaerythritol are represented by the following formula (I):

(where n is 1, 2 or 3).

In a preferred inventive embodiment For example, the fluorocarbon refrigerant is 1,1,1,2-tetrafluoroethane (HFC-134a).

In the pentaerythritol condensate, the degree of polymerization according to the viscosity, for the obtained synthesized ester is required.

When monovalent fatty acid can be mentioned become propionic acid, Butyric acid, isobutyric, Pentanoic, isopentanoic, hexanoic, heptanoic, isoheptanoic, octanoic 2-ethylhexanoic acid, nonanoic, 3,5,5-trimethylhexanoic acid, decanoic acid and Undecanoic.

At least one of branched-chain monovalent fatty acids having a carbon number from 4-18 or a mixture of at least one straight-chain monovalent fatty acid having a carbon number of 3-11 and at least one of branched chain monovalent fatty acids with a carbon number of 4-14 are mixed thoroughly and with pentaerythritol or its condensate to obtain a Esters esterifies the one for different refrigeration units required and desired physical properties is sufficient.

Around a sufficient and sufficient compatibility with the coolant HFC-134a and similar To achieve this, a mixture of a straight-chain fatty acid with a carbon number of 3-11, preferably 5-10, and a branched chain fatty acid having a carbon number of 4-14, preferably 7-9, as monovalent fatty acid be used.

In In this case, the amount of branched-chain fatty acid used is not less than 50 mol% per used total amount of monovalent fatty acid.

on the other hand can, in order to give the resulting ester a sufficient viscosity, at least one polybasic acid having a carbon number of 4-10 with at least one of pentaerythritol, Dipentaerythritol and tripentaerythritol in an amount of not more than 80 mol% of the total fatty acid is esterified. In this Case, the following polybasic acids are used: succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, maleic acid and Trimellitic acid.

The inventively used ester compounds by esterification reaction a dehydration reaction between the specified polyvalent Alcohol and the specified fatty acid as mentioned above, or a general esterification reaction over an acid anhydride, an acid chloride or similar as a derivative of the fatty acid to be obtained.

In according to the invention used esters is the acid number preferably not more than 3 mg KOH / g and the hydroxyl value preferably not more than 50 mg KOH / g.

The esters used according to the invention show good compatibility with the coolant HFC-134a and the like over a wide range from a low temperature to a high temperature as a lubricant for use in a refrigeration unit using HFC-134 as a refrigerant, whereby the lubricity and thermal resistance of the cooling lubricant can be remarkably improved. Further, they have a high electrical insulating property and a small hygroscopicity as compared with PAG, which is conventionally tested as a cooling lubricant for HFC-134a. Therefore, the cooling lubricants used containing the esters used as the main component of the present invention can solve the problems of compatibility with HFC-134a and hygroscopicity, which have not been solved in the rest, and the electrical insulating property which results in a Problem will be further improved when HFC-134a is used in a compressor for a refrigeration unit.

Further can Additives, usually be used in the lubricant, such as e.g. antioxidant agents, Anti-abrasive and epoxy compounds, suitably the cooling lubricant as used according to the invention, be added.

EXAMPLES 1 to 6

The Properties of a cooling lubricant using HFC-134a as a refrigerant were used in terms of on six esters A-1 to A-6 in the following Table 1, examined (all esters were not commercially available, but were prepared according to the invention). For comparison, the same rating as mentioned above was used in Regard to commercial PAG performed (B-1 - B-3, manufactured by Asahi Denka Co., Ltd.) and esters (C-1 - C-2 by Nippon Oil and Fats Co., Ltd.) as a cooling lubricant in the following Table 2 is shown.

The Lubricating property, compatibility, thermal stability, electrical Insulation property and hygroscopicity as properties of cooling lubricants for the Compressor, as shown in Tables 1 and 2, were among the measured under the following conditions.

Lubricating property:

Seize load (Falex loading capacity) measured according to ASTM D-3233-73 under a blown HFC-134a atmosphere.

Compatibility:

After this 0.6 g of test lubricant and 2.4 g of coolant (HFC-134a) were sealed in a glass tube, Cooling took place at 1 ° C / min and heating, Meanwhile the temperature which caused a separation into two phases, was measured.

Thermal stability:

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

Electrical insulation properties:

These was judged by the dielectric constant at 80 ° C according to JIS C-2101.

hygroscopicity:

In A 100 ml flask was charged with 60 g of test lubricant at a temperature of 25 ° C and a humidity of 70% was allowed to stand for 3 hours, and then the water concentration was measured.

The Evaluation results are shown in the following Table 3.

As is apparent from Table 3, comparing the inventive esters with conventional PGA (B-1-B-3) as used for comparison in Tables 2 and 3, the electrical insulating property represented by the dielectric constant is 100,000 times larger, and there is no separation into two Phases at a high temperature. Furthermore, the seizure load is excellent and the hygroscopicity is low. The thermal stability corresponds to the HFC-134a system, but is excellent in the R-12 system. This is very advantageous in practical use since the mixing of HFC-134a and R-12 is not avoided when the refrigerant is changed from R-12 to HFC-134a.

If on the other hand, according to the invention used esters with commercially available available Esters (C-1 - C-2), as shown in Tables 2 and 3 for comparison, the temperature of the separation into the two phases is extremely different, and the conventional esters are insoluble in HFC-134a. At At this point, the esters used according to the invention with special molecular design a big advantage.

As From the above, have the used according to the invention Ester compares pretty good properties as a lubricant to those who are used for comparison.

HFC-134a was considered possible Replacement for Mentioned R-12 and is e.g. For Autoklimaanlagen and cooling units used. Especially in car air conditioners, the compressor is in the summer time operated so that the compatibility between oil and coolant at high temperatures becomes important. If a two-phase separation between oil and coolant in the compressor during When driving occurs, the coolant remains with the larger specific Density in the lower part of the compressor back, causing the occurrence of seizure of the compressor leads.

at a cooling unit the engine is built into the compressor so that electricity leaks become a problem. In this context, the inventively used Ester a dielectric constant, the 100,000 times higher or more than that of conventional PAG, and they have excellent electric Insulating properties, so you can say that they are a cooling lubricant for a Represent refrigeration unit.

In this case, lubricants with a dynamic viscosity of 10 - 50 mm ² / s (cSt) at 40 ° C are used as lubricants for refrigeration units requiring a two-phase separation temperature not higher than -40 ° C, so that ester A- 2 is particularly suitable for this. On the other hand, lubricants having a dynamic viscosity of 80-150 mm ² / s (cSt) at 40 ° C are used as lubricants for automobile air conditioners requiring a two-phase separation temperature of not higher than -20 ° C, so that the esters A-1 , A-3, A-4 and A-6 are particularly suitable for this.

In recently, Time is HFC-134a, which causes virtually no destruction of the ozone layer, instead of R-12, which is widely used as a coolant used, used to destroy the ozone layer Chlorofluorocarbon and chlorofluorocarbon, what the biggest Problem on a global scale, but a bad one compatibility with usual cooling lubricants which is a hindrance to the development of a replacement system represents. However, the cooling lubricants, the invention used, sufficient compatibility with HFC-134a as a coolant and a high electrical insulating property, and are also in their rest Properties outstanding, so that they have the effect of that Conventional systems can be used as they are, though HFC-134a instead of conventional R-12 and R-22 as a coolant is used.

Claims (16)

Use of a lubricant for compressors using a fluorocarbon coolant, that does not contain chlorine, comprising as main component (s) an ester obtainable by Reacting (a) at least one polyvalent alcohol selected from Pentaerythritol, dipentaerythritol and tripentaerythritol with (b) a mixture of at least one of straight-chain monovalent fatty acids with a carbon number of 3 - 11 with at least one of Branched-chain monovalent fatty acid with a carbon number from 4 - 14, wherein the amount of branched-chain monovalent fatty acid is not less than 50 mol% per used total amount of monovalent fatty acid, with the proviso that the lubricant is not in a liquid composition, as the main component (more than 50 wt .-%) a fluorine-containing Hydrocarbon refrigerants and as a minor ingredient (less than 50% by weight) the lubricant contains is used. Use of a lubricant according to claim 1, wherein the straight-chain monovalent fatty acid is selected from propanoic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid and undecanoic acid, and the branched-chain monovalent fatty acid is selected from isobutane acid, isopentanoic acid, isoheptanoic acid, 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid. Use of a lubricant according to claim 1, wherein the branched-chain monovalent fatty acid is one having a carbon number from 7 - 9 is. Use of a lubricant according to any one of claims 1 to 3, wherein the ester is a total acid number of not more than 3 mgKOH / g and a hydroxyl value of not more than 50 mgKOH / g. Use of a lubricant according to any one of claims 1 to 4, wherein the fluorocarbon coolant 1,1,1,2-tetrafluoroethane. Using a lubricant for compressors using a fluorocarbon coolant, that does not contain chlorine, comprising as main component (s) an ester obtainable by Reacting (a) at least one polyvalent alcohol selected from Pentaerythritol, dipentaerythritol and tripentaerythritol with (b) a mixture of at least one of straight-chain monovalent fatty acids with a carbon number of 3 - 11 with at least one of Branched-chain monovalent fatty acid with a carbon number from 4 - 14, wherein the amount of branched-chain monovalent fatty acid is not less than 50 mol% per used total of monovalent Fatty acid, and (c) at least one polybasic acid having a carbon number from 4 - 10, wherein the amount of the polybasic acid is not more than 80 mol% per total fatty acid is, with the proviso that the lubricant is not in a liquid composition, as the main component (more than 50 wt .-%) a fluorine-containing Hydrocarbon refrigerants and as a minor ingredient (less than 50% by weight) the lubricant contains is used. Use of a lubricant according to claim 6, wherein the straight-chain monovalent fatty acid is selected from propionic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid and undecanoic, and the branched-chain monovalent fatty acid is selected from isobutyric acid, isopentanoic acid, isoheptanoic acid, 2-ethylhexanoic acid and 3,5,5-. Use of a lubricant according to claim 6, wherein the polybasic acid selected is from succinic acid, glutaric, adipic acid, pimelic, suberic, azelaic acid and sebacic acid. Use of a lubricant according to one of claims 6 to 8, wherein the ester is a total acid number of not more than 3 mgKOH / g and a hydroxyl value of not more than 50 mgKOH / g. Use of a lubricant according to one of claims 6 to 9, wherein the fluorocarbon coolant 1,1,1,2-tetrafluoroethane. Use of a lubricant for compressors using a fluorohydrocarbon refrigerant containing no chlorine, comprising as an essential component an ester obtainable by reacting (a) at least one polyvalent alcohol selected from pentaerythritol and dipentaerythritol with (b) at least one branched chain Monovalent fatty acid having a carbon number of 4 to 18, with the proviso that (i) the lubricant no polyether polyol in an amount of 5 to 95 wt .-% according to the general formula Z - [(CH ₂ CH (R ₁ ) -O-) _n - (CH ₂ -CH (CH ₃ ) -O-) _m -R ₂ ] _p wherein Z is the radical of a compound having 1 to 8 active hydrogens, R is hydrogen, ethyl or mixtures thereof n is 0 or a positive number, m is a positive number, n + m is a number having a value corresponding to R ₂ is hydrogen or an alkyl group having 1 to 6 carbon atoms, p is an integer having a value corresponding to the number of active hydrogens of Z, and (ii ) the lubricant is not used in a liquid composition containing as the main ingredient (more than 50% by weight) a fluorine-containing hydrocarbon refrigerant and as a minor ingredient (less than 50% by weight) the lubricant. Use of a lubricant according to claim 11, wherein polyvalent alcohol is pentaerythritol. Use of a lubricant according to claim 11 or 12, wherein the branched-chain monovalent fatty acid is selected from isobutyric acid, isopentanoic, isoheptanoic, 2-ethylhexanoic and 3,5,5-trimethylhexanoic acid. Use of a lubricant according to claim 11 or 12, wherein the branched-chain monovalent fatty acid is a with a carbon number of 7-9. Use of a lubricant according to claim 14, wherein the branched-chain monovalent fatty acid is selected from isoheptanoic acid, 2-ethylhexanoic acid and 3,5,5-. Use of a lubricant according to any one of claims 11 to 15 wherein the fluorohydrocarbon refrigerant is 1,1,1,2-tetrafluoroethane.