AU661756B2

AU661756B2 - Lubricant for refrigerating machine employing refrigerant comprising tetrafluoroethane

Info

Publication number: AU661756B2
Application number: AU32080/93A
Authority: AU
Inventors: Tadashi Katafuchi; Akira Nakamura
Original assignee: Idemitsu Kosan Co Ltd
Current assignee: Idemitsu Kosan Co Ltd
Priority date: 1992-02-18
Filing date: 1993-01-28
Publication date: 1995-08-03
Anticipated expiration: 2013-01-28
Also published as: KR930018013A; JPH05295385A; DE69310230D1; DE69310230T2; TW235306B; EP0556662B1; SG84474A1; KR0139611B1; AU3208093A; EP0556662A1

Description

-LII- __1711-

AUSTRALIA

Patents Act COMPLETE SPECIFICATION

(ORIGINAL)

661A 6 Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority Related Art: o Name of Applicant: e 0 t r o 1 r I.r o ~t Idemitsu Kosan Co., Ltd.

Actual Inventor(s): Tadashi Katafuchi Akira Nakamura Ir I

I

r I i ri r r ~c c r r rr r Address for Service: PHILLIPS ORMONDE FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne 3000 AUSTRALIA Invention Title: LUBRICANT FOR REFRIGERATING MACHINE EMPLOYING COMPRISING TETRAFLUOROETHANE

REFRIGERANT

Our Ref 317003 POF Code: 93170/47107 The following statement is a full description of this invention, including the best method of performing it known to applicant(s): -1- 6006 i 1 -1a- LUBRICANT FOR REFRIGERATING MACHINE EMPLOYING REFRIGERANT COMPRISING TETRAFLUOROETHANE BACKGROUND OF THE INVENTION 1. Field of the invention.

The present invention relates to a lubricant composition for refrigerating machines said composition including a refrigerant comprising tetrafluorethane and a lubricant. More particularly, it relates to lubricant compositions for refrigerating machines including a substitute fluorohydrocarbon (hereinafter sometimes referred to as "flon compound") such as 1,1,1,2- tetrafluorethane (R-134a). As such, the lubricant composition is excellent in the performance such as wear resistance, electrical insulating properties, hydrolytic stability, nonhygroscopicity and the like and S further has excellent returnability of the lubricant in the refrigerating cycle (characteristics that the lubricant is inclined to return to a compressor after it is circulated in the refrigerating cycle).

2. Description of the Related Arts Conventionally, in the compression-type refrigerating cycle comprising a compressor, a condenser, an expansion valve and an evaporator, a flon compound including a fluorinated hydrocarbon such as dichloridifluoromethane (R-12) and chlorodifluoromethane (R-22) has been used as the refrigerant. Many kinds of lubricants compatible with them have been produced industrially available for use.

However, there have been misgivings that these flon compounds widely used as the refrigerant are liable to cause A l rfiX i depletion of the ozone layer and environmental pollution after they are released into the open air. In an effort to prevent environmental pollution, fluorohydrocarbons (or chlorofluorohydrocarbons), for ex, ,le 1,1,1,2-tetrafluoroethane (R-134a) and the like have been developed as a possible replacement in recent years. Until now there have been introduced into market many so-called substitute flon compounds with minimized danger of environmental pollution and capable of satisfying said required properties, for example 1,1,2,2tetrafluoroethane (R-134) and the like, as well as R-134a.

These new substitute flon refrigerants are different from conventional flon refrigerants in characteristics. Thus, glycol compounds, ester compounds and the like have been proposed as the lubricant for use in combination with them Patent No.

4,755,316, P. L. 339359l1, NO. 20089511991, M5. 08/19, o. 20 77 a N, DP .h199,n and these patents are intended to dissolve substitute flon refrigerants and lubricants completely so as to provide good returnability of the lubricants.

In an attempt to circulate all over a refrigerating cycle a refrigerant and a lubricant in their completely dissolved state as envisaged by these patents, however, said lubricant must be selected from only a very limited number of compounds acceptable to the chemical properties of substitute flon refrigerants such as R-134a. Accordingly, the selected lubricant is forced to sacrifice certain aspects of the important performance required as the lubricant.

I

4 #0 0 2

I

In fact, polyalkylene glycol compounds and ester compounds thereof, both known as compatible with R-134a, have been found to have insufficient wear resistance, along with faulty electrical insulating properties. It has also been found that the polyalkylene glycol compounds are highly hygroscopic while the ester compounds thereof are unstable hydrolytically. Thus the demand for a solution in these problems has been raised in relevant industrial segments.

The present invention has been completed on the basis of a concept quite contrary to ordinary common knowledge as set forth above, in an effort to find the solution in the problems.

As the result, it has been found that all these aspects of the 00 0 performance can be unified by using a substance excellent in wear resistance, insulation resistance and the like as the lubricant, compounding therewith a fluidity improver to improve the fluidity of the lubricant in the presence of a refrigerant (R134a and the like) and thus providing excellent returnability of the lubricant in a compression-type refrigerating cycle. It has thus been made possible that a lubricant combined even with a new refrigerant has all the required performance including excellent wear resistance, electrical insulating properties, 0° hydrolytic stability and the like and further ensuring excellent returnability of the lubricant. The present invention has been accomplished based on this finding.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a lubricant for refrigerating machines empl.oyiJg a refrigerant 3 i k .lc. -4comprising tetrafluoroethane; and a lubricant which is excellent in the performance such as wear resistance, electrical insulating properties, hydrolytic stability, nonhydrogroscopicity and especially has excellent returnability of the lubricant. The lubricant can be used in combination with the substitute flon refrigerant in a compression-type refrigerant cycle without a hitch, Another object of the present invention is to provide a lubricant composition for refrigerating machines including a refrigerant comprising tetrafluorethane; and a lubricant; which is especially effective when used in automobile or household air conditioners, refrigerators and the like, having high industrial usefulness.

The present invention provides a lubricant composition for compression type refrigerating machines including a refrigerant selected form the group 1,1,1,2tetrafluorethane or 1,1,2,2-tetrafluorethane; and a lubricant comprising 60 to by weight of a synthetic oil composed of a poly-a-olefin or a mixture of a poly-a-olefin and an alkylbenzene and 10 to 40% by weight of a fluidity improver composed of to 4 a at least one member selected from an ester compound and a triglyceride.

S0 The lubricant composition of the present invention can be suitably used in various refrigerating machines and ordinarily in a compression-type refrigerating cycle comprising a compressor, a condenser, an expansion valve and an evaporator.

DESCRIPTION OF PREFERRED EMBODIMENTS As set forth above, the lubricant of the present invention includes components and as the essential f a. i mu 4 i- components, and the synthetic oil constituting the component is a poly-a-olefin or a mixture of a poly-a -olefin and an alkylbenzene.

Various poly-a -olefins can be used and ordinarily are each a polymer of a -olefin having 8 to 14 carbon atoms and a kinematic viscosity of 10 to 350cSt at 40°C. Preferred among them is a polymer of 1-dodecene, a polymer of 1-decene or a polymer of 1-octene, each having a kinematic viscosity of 10 to 350cSt at 40°C. A lubricant containing a synthetic oil comprising such a poly-a-olefin has a lower viscosity at low temperatures to provide better returnability of the lubricant.

Various alkylbenzenes can be used as well and ordinarily are each an alkylbenzene having a kinematic viscosity of 5 to 500cSt, preferably 10 to 350cSt at 40°C. Either soft or hard alkylbenzene can be used provided that it meets the abovementioned condition.

The alkylbenzene is not used singly but in the form of its mixture with said poly-a-olefin as the synthetic oil as the component of the present invention. The mixing ratio of the poly-a -olefin and the alkylb zene is appropriately selected according to circumstances and anot particularly limited.

Preferably the mixture has a poly-'l"efin content of 5% or more by weight, more preferably 50% or e by weight of the mixture. When the mixture of the poly-a-olefin and the alkylbenzene is used as the synthetic oil as the component the mixing stability between the poly-a -olefin and the fluidity improver as the component is improved.

5 i Ir I 1 On the other hand, the fluidity improver acts to improve the fluidity of a hydrocarbonic compound at low temperatures (those of evaporator) in the presence of a small amount of a substitute flon refrigerant such as R-134a, so as to provide better returnability of the lubricant in a refrigerating cycle.

The kinematic viscosity of the fluidity improver is not particularly limited but ordinarily is 2 to 100cSt, preferably 3 to 50cSt at Typical examples of the fluidity improver include an ester compound, particularly an ester compound having at least 2 ester bonds. A variety of these ester compounds can be used and an appropriate ester compound may be selected from them according to the intended use. Preferred among them is a reaction product as set forth in any of to below: A reaction product of CD a polybasic carboxylic acid or its derivative, (2 a po.yhydric alcohol or its derivative and a monobasic fatty acid or its derivative.

(II) A reaction product of (D a polybasic carboxylic acid or its derivative, a polyhydric alcohol or its derivative ind a monohydrio aliphatic alcohol or its derivative.

(III) A reaction product of D a po'yhydric alcohol or its I erivative and 3 a monobasic fatty acid or its derivative .eferably an equivalent reaction product).

(IV) A reaction product of a monohydric aliphatic alcohol or its derivative and CD a polybasic carboxylic acid or its derivative.

A reaction product of a polybasic carboxylic acid -6ri\ I-1 I- r- or its derivative and 0 a polyhydric alcohol or its derivative.

Various polybasic carboxylic acids D can be used herein, and their preferred examples include an aliphatic saturated dicarboxylic acid having 2 to 12 carbon atoms (oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanoic-2 acid and the like), an aliphatic unsaturated dicarboxylic acid having 4 to 14 carbon atoms (maleic acid, fumaric acid, alkenylsuccinic acid and the like) and an aromatic dicarboxylic acid having 8 carbon atoms (phthalic acid, isophthalic acid, terephthalic acid and the like), a dicarboxylic acid such as epoxide of epoxyhexahydrophthalic acid and a tribasic or higher carboxylic acid such as citric acid, o trimellitic acid and pyromellitic acid. Examples of their derivative include monoester, diester, metal salt, anhydride, acid chloride and the like of these polybasic carboxylic acids.

Examples of the polyhydric alcohol 2 include glycols i (ethylene glycol; diethylene glycol; triethylene glycol; tetraethylene glycol; polyethylene glycol; propylene glycol; dipropylene glycol; polypropylene glycol; 1,2-butylene glycol; o;o 1,3-butylene glycol; 1,4-butylene glycol; 2,3-butylene glycol; polybutylene glycol; 2-methyl-2,4-pentanediol; 2-ethyl-1,3hexanediol and the like), glycerin, hindered alcohol (neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol and the like), sorbitol and sorbitan. Examples of their I derivative include acid chloride, metal salt and the like.

i7 7 i; I I; I__ Furthermore, various monobasic fatty acids (including primary, secondary and tertiary compounds) can be used herein, and a monobasic fatty acid containing an alkyl group having 1 to 20 carbon atoms, particularly a branched alkyl group having 3 to 18 carbon atoms, and more particularly a branched alkyl group having 4 to 12 carbon atoms is preferable because of their marked effect on improving the fluidity of the lubricant.

Their specific examples include acetic acid; propionic acid; iso-propionic acid; butyric acid; iso-butyric acid; pivalic acid; n-val.ric acid; iso-valeric acid; caproic acid; 2ethylbutyric acid; n-caproic acid; 2-methylcaproic acid; nheptylic acid; n-octanoic acid; 2-ethylhexanoic acid; 3,5,5trimethylhexanoic acid; nonanoic acid; tert-nonanoic acid, dodecanoic acid; lauric acid and the like). Examples of their derivatives include ester, metal salt, acid chloride, anhydride and the like.

Various monohydric aliphatic alcohols or their derivatives can be used herein, and a monohydric aliphatic alcohol or its derivative containing an alkyl group having 1 to 20 carbon atoms, particularly a branched alkyl group having 3 to 18 carbon atoms and more particularly a branched alkyl group having 4 to 12 carbon atoms is preferable because of their marked effect on improving the fluidity of the lubricant. Their specific examples include methyl alcohol, ethyl alcohol, n-propyl alcohol, iso-propyl alcohol, n-butyl alcohol, iso-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, n-amyl alcohol, iso-amyl alcohol, tert-amyl alcohol, diethyl carbinol, n-hexyl alcohol, 8 i ii compounds as enumerated in Z and above. For this reaction product (II) every detail of its structure has not necessarily been brought to light. Ordinarily, however, the reactior product (II) has a structure wherein 2 hydroxyl groups of the polyhydric alcohol Z each react to be bonded with a carboxyl group of the polybasic carboxylic acid (D and further the remaining carboxyl group of this polybasic carboxylic acid (D reacts to be bonded with a hydroxyl group of the monohydric aliphatic alcohol 0. Meanwhile, the rest of carboxyl groups of the polybasic carboxylic acid 0 and the rest of hydroxyl groups of the polyhydric alcohol may remain as the carboxyl group and hydroxyl grrmip respectively, as they are or react with other functional groups.

These synthetic oils and fluidity improvers are mixed at a ratio by weight of 40 to 95%, desirably 5 to particularly desirably 55 to 90%, most desirably 60 to 90% of to 5 to 60%, desirably 10 to 50%, particularly desirably 10 I to 45%, most desirably 10 to 40%, respectively of i The fluidity of the lubricant is undesirably not improved when less than 5% by weight of the fluidity improver is used, resulting in insufficient returnability of the lubricant. When o" OJ more than 60% by weight of the fluidity improver is used, wear j resistance is undesirably lowered, accompanied by the degradation of the fundamental performance required of refrigerating machine lubricant including decrease in insulation resistance, worsening of hydrolytic stability, increase in hygroscopicity and the like.

L

As set forth above, the lubricant of the present invention comprises the synthetic oil and the fluidity improver and the essential component, but various additives can be incorporated therein as the need arises. Examples of the additive include and anti-wear additive such as phosphoric acid ester and phosphorus acid ester, an antioxidant, a chorine scavenger, a metal deactivator, defoaming agent, a detergentdispersant, a viscosity index improver, a rust preventive, a corrosion inhibitor and the like.

As set forth above, the lubricant composition for refrigerating machines including a refrigeirant comprising tetrafluorethane, as claimed herein, and a lubricant that is excellent in the performance such as wear resistance, electrical insulating properties, hydrolytic stability, norhygroscopicity and the like and especially has excellent returnability of the lubricant. The lubricant composition can be used in a compressiontype refrigerating cycle without a hitch.

Thus, the lubricant composition of the present invention is especially effective when used in automobile or household air conditioner, refrigerator and the like, having high industrial usefulness.

The present invention will now be described in greater detail below with reference to non-limitative examples and comparative examples.

Examples 1 to 8 and Comparative Examples 1 to 3 j The synthetic oils and the fluidity improvers were mixed as shown in Table 1 to prepare the lubricants for use in the following tests. The results thereof are given in Table 2.

0> *O 0 0 0 0 0 0 0 01 4 0 -11- 1 i. 1 Table 1 Mixing Composition Synthetic Oil Fluidity Improver Compound Wt% Compound Wt% Example 1 Poly- a -olefinI* 1 80 Ester Example 2 Poly- a -olefinI* 1 60 Ester A*'4 Example 3 Poly- a -olefinI*l 70 Ester B* 5 Example 14 Poly- a -olefinT*l 70 Triglyceride* 6 Example 5 Poly- a -olefinII* 2 60 Ester A*'4 Example 6 Poly- a -olefinI* 1 50 Ester A*'4 Alkylbenzene* 3 Example 7 Poly- a -olefinI*l 140 Ester A*'4 Alkylbenzene* 3 Example 8 Poly- a -olefinI*1 50 Ester B*5 Alkylbenzene* 3 Comparative Alkylbenzene* 3 80 Ester B* 5 Example 1 Comparative Poly- a -olefinI*' 30 Ester A*'4 Example 2 Comparative Poly- a -olefinI*' 10 Ester B*5 Example 3 Alkylbenzene 3 Oatt o 4 04#4 'at' 00 ~t 00 04 4.

400 0 04 0 4 40 04 a 12

I-

Table 2 Performance Fluidity at low temperatures Wear resistance (relative value) Example 1 20 0 Example 2 20 0 Example 3 18 0 Example 4 16 0 Example 5 22 0 Example 6 30 0 Example 7 25 0 Example 8 40 0 Comparative 100 0 Example 1 Comparative 20 x Example 2 Comparative 20 x Example 3 *t 4 4, 4% *4 U a 4 40 (r 4 -13ib Table 2 (continued) Performance Insulation resistivity Hydrolysis Hygroscopicity Q0 cm Example 1 6.8 x 1014 0 0 Example 2 8.2 x 1013 A 0 Example 3 2.2 x 10' O 0 Example 4 8.8 x 1013 0 0 Example 5 8.0 x 1013 A 0 Example 6 3.2 x 1014 O O Example 7 7.2 x 1013 0 0 Example 8 1.2 x 1013 0 0 Comparative 3.0 x 1014 0 0 Example 1 Comparative 1.5 x 1013 x A Example 2 Comparative 1.2 x 1013 x A Example 3 All the lubricants used were mixed with 0.5% by weight of an antiwear additive (phosphoric acid ester). The notes in the tables will be supplemented below: A polymer of 1-decene (a kinematic viscosity of 32cSt at A polymer of 1-decene (a kinematic viscosity of 46cSt at Soft alkylbenzene (a kinematic viscosity of 38cSt at An ester of C 7 fatty acid and pentaerythritol (a kinematic viscosity of 30cSt at An ester of C 7 fatty acid and trimethylolpropane (a kinematic viscosity of 14cSt at 40 0

C).

2-ethylhexyltriglyceride (a kinematic viscosity of 16cSt at -14o 0 4 04 .4 4 L r ii #4 4 *1 I 44 4 The lubricants were evaluated by determining each aspect of their performance thereof in accordance with the following test method: Evaluation of the performance Fluidity of the lubricants at low temperatures A lubricant mixed with 10% of R-134a was collected into a pressure glass tube having a diameter of 8mm, a steel ball of 3/16in in diameter was introduced therein and the pressure glass tube was sealed.

After the pressure glass tube was retained at -45 0

C,

the steel ball was caused to fall to determine the time (second) required until the steel ball reached a point to 5cm above the bottom of the tube. The result thereof is given in terms of a relative value.

Wear resistance The wear resistance was tested under the following conditions by using a Falex friction testing machine.

R-134a was blown at a rate of 5 liter/hr, and a test piece was subjected to wear for 60 minutes under a load of 3001bs and at 1,000rpm. The test pieces such as block and pin were made of a standard material in accordance with ASTM D-3233.

Standard of evaluation (amount of wear) 0: Less than A: 6.0mg or more to 15mg or less x More than Electrical insulating properties 1 5 i

Claims

1. A lubricant composition for a compression-type refrigerating machine said composition including a refrigerant selected from the group consisting of 1,1,1,2- tetraflorethane or 1.1.2.2-tetraflorethane; and a lubricant comprising 60 to 90% by weight of a synthetic oil composed of a poly-a-olefin or a mixture of a poly-a-olefin and an alkylbenzene wherein said poly-a-olefin is a polymer of an a-olefin having 8 to 14 carbon atoms and has a kinematic viscosity of 10 to 350cSt at 40°C and 10 to 40 by weight of a fluidity improver composed of at least one member selected form an ester compound and a triglyceride.

2. The lubricant composition according to claim 1, wherein said polymer a-olefin is a polymer of 1-dodecene, 1-decene or 1-octene, each having a kinematic viscosity of to 350cSt at 400C.

3. The lubricant composition according to any one of the preceding claims, wherein said alkylbenzene is selected from a soft alkylbenzene or a hard alkylbenzene, each having a kinematic viscosity of 10 to 350cSt at 400C. a

4. The lubricant composition according to any one of the preceding claims, wherein said mixture of the poly-a-olefin and the alkylbenezene has a poly-a-olefin content of or more by weight of the mixture. o

5. The lubricant composition according to any one of the preceding claims, wherein the fluidity improver has a kinematic viscosity of 3 to 50cSt at 40 0 C.

6. The lubricant composition according to any one of the preceding claims, wherein said ester compoUnd has 2 or more ester bonds.

7. The lubricant composition according to claim 6, wherein said ester compound is selected from: a reaction product of 1 a polybasic carboxylic aid or a derivative thereof, 2 a polyhydric alcohol or a derivative thereof and 3 a monobasic fatty acid or a derivative thereof, (ii) a reaction product of 1 a polybasic carboxylic acid or a derivative thereof and 4 a monohydric aliphatic alcohol or a derivative thereof, (iii) a reaction product of 2 a polyhydric alcohol or a derivative thereof and 3 a monobasic fatty acid or a derivative thereof, -17- i -I- 1L (iv) a reaction product of 4 a monohydric aliphatic or a derivative thereof and 1 a polybasic carboxlic acid or derivative thereof and 2 a polyhydric alcohol or a derivative thereof.

8. A lubricant composition according to claim 1 substantially as hereinbefore described with reference to any one of Examples 1 to 8.

9. A refrigerating system which comprises a compressor, and a lubricant composition as defined by any one of claims 1 to 9. DATED: 18 May, 1995 PHILLIPS ORMODNE FITZPATRICK Attorneys for: IDEMITSU KOSAN CO., LTD. t i t tI 0 I 0 it t a 0 o o* S 2 a -18- ABSTRACT There has been disclosed herein a lubricant for refrigerating machines employing as a refrigerant 1,1,1,2- tetrafluoroethane or 1,1,2,2-tetrafluoroethane which comprises as an essential component a base oil comprising 40 to by weight of a synthetic oil formed of a poly-a -olefin or a mixture of a poly-a-olefin and an alkylbenzene and 5 to by weight of a fluidity improver formed of both or either of an ester compound and a triglyceride. The lubricant is used along with a substitute flon refrigerant, and is excellent in the performance such as wear resistance, electrical insulating properties, hydrolytic stability, nonhygroscopicity, etc. and also in returnability of the lubricant. Thus, the lubricant is especially effective when used in automobile or household air conditioner, refrigerator, etc. having high industrial usefulnes 4 i 4 T