WO2000060031A1

WO2000060031A1 - Lubricant for vapor compression refrigerator using hydrocarbon coolant

Info

Publication number: WO2000060031A1
Application number: PCT/JP2000/001675
Authority: WO
Inventors: Takashi Kaimai; Hitoshi Takahashi
Original assignee: Japan Energy Corporation
Priority date: 1999-04-02
Filing date: 2000-03-17
Publication date: 2000-10-12
Also published as: KR100648186B1; JP3933872B2; DE60018005D1; EP1092760A1; ES2233339T3; DE60018005T2; EP1092760A4; KR20010052428A; CN1297472A; EP1092760B1; CN1183236C

Abstract

A lubricant for a vapor compression refrigerator using a lower hydrocarbon coolant which comprises, as a main component, a mineral oil having a kinetic viscosity at 40 °C of 3 to 150 mm2/s, a pour point of -25 °C or lower, a viscosity index of 50 or more, a % C¿P? and a % CA as determined by the n-d-M ring analysis of 50 or more and 12 or less respectively, a nitrogen content of 20 ppm or less, a sulfur content of 0.02 to 0.3 %, and an iodine value of 10g I2/100g or less; a hydraulic fluid composition for a vapor compression refrigerator comprising the lubricant and a lower hydrocarbon coolant; and a refrigeration unit employing the hydraulic fluid composition. The lubricant has excellent compatibility with a hydrocarbon coolant and is excellent in stability and lubricity, and hence is markedly useful as a lubricant for a refrigerator using a lower hydrocarbon coolant which is in no danger of ozone layer destruction or global warming.

Description

Description Lubricants for compression refrigerators using hydrocarbon refrigerants

The present invention is directed to a compression refrigeration system using a hydrocarbon refrigerant made of a lower hydrocarbon, which has no risk of destruction of the ozone layer and has a much lower global warming ability and a much lower halogen-containing hydrocarbon refrigerant. Related to lubricants. The present invention also relates to a working fluid composition comprising the hydrocarbon refrigerant and the lubricant, and a refrigeration device filled with the working fluid composition. Background of the Invention

A compression refrigerator is composed of a compressor, a condenser, an expansion mechanism (for example, an expansion valve), an evaporator, etc., and uses the property of taking off the heat of evaporation from the surroundings when a highly volatile refrigerant evaporates. It is used in refrigerators, freezers, air conditioners, showcases, and vending machines for soft drinks and ice cream. Air-conditioning and vending machines are also used for heating using heat generated during condensation and for heating and holding beverages and foods.

Conventionally, as the refrigerant, a fluorinated hydrocarbon (CFC or HCFC) containing chlorine such as trichlorofluoromethane (R11), dichlorodifluoromethane (R12), and chlorodifluoromethane (R22) has been used. However, since these CFCs and HCFCs cause environmental problems that deplete the ozone layer, their production and use are regulated internationally and are now chlorine-free, for example, difluoromethan (R32 ), Tetrafluoroethane (R134 or R134a), difluorethane (R152 or R152a), and other non-chlorofluorocarbons (HFCs). However, although these HFCs do not destroy the ozone layer, there is concern that they have problems from a long-term perspective of global environmental protection due to their high global warming potential.

Therefore, low-molecular-weight, low-molecular-weight hydrocarbons having about 1 to 5 carbon atoms do not destroy the ozone layer, and have the global warming ability of the above-mentioned chlorinated or non-chlorinated fluorocarbons. Because it is very low compared to elemental, it is attracting attention as an environmentally friendly refrigerant. These compounds have been used for a long time, although they have not been the mainstream as refrigerants. Further, as lubricants of the above-mentioned refrigerants composed of hydrocarbons, for example, according to Japanese Patent Application Laid-Open No. 10-130658, naphthenic or paraffinic mineral oils, alkylbenzene oils, ether oils, ester oils Synthetic oils such as fluorine oil have been proposed. Among these lubricants, synthetic oils are generally expensive, so that inexpensive and readily available mineral oils are expected from a practical viewpoint.

However, there are various problems also in the combination of a low molecular weight hydrocarbon refrigerant (lower hydrocarbon refrigerant) and a mineral oil-based lubricant. In particular, refrigerator lubricants using hydrocarbon refrigerants are desired to have excellent lubricating properties themselves for the reasons described below.

Low-molecular-weight hydrocarbons as refrigerants and mineral oils as lubricants are compatible, but due to the large difference in specific gravity, they may be difficult to mix by natural diffusion alone. Frequently, refrigerators are placed in such a state that they are difficult to mix. For example, when a compressor is filled with refrigerant, low-density refrigerant is stacked on top of the high-density lubricant that has been charged earlier. Such a state also occurs at the time of so-called stagnation in which the refrigerant returns to the compressor in a liquid state while the compressor is stopped. When the compressor is started in such a state, the lubricant collects on the outside of the rotation due to centrifugal force, and the lubricant does not sufficiently spread to the sliding parts such as internal bearings that require lubrication. There is a problem that abrasion occurs and seizure easily occurs. For this reason, lubricants for refrigerators using low-molecular-weight hydrocarbon refrigerants are desired to have excellent lubricating properties. Also, unlike a chlorinated fluorinated hydrocarbon refrigerant, which can be expected to have an extreme pressure effect due to chlorine in the molecule, the hydrocarbon refrigerant itself has a small molecular weight, so lubricating performance cannot be expected at all. This has also promoted the demand for excellent lubrication properties for lubricants for refrigerators using hydrocarbon refrigerants.

In addition, although lubricants for refrigerators are generally used in closed systems, they are always exposed to a refrigeration cycle that repeats high and low temperatures, so that they do not easily deteriorate and have good stability. It has been demanded. Disclosure of the invention

The present invention has been made to solve the above problems, and an object of the present invention is to provide a lubricant for a refrigerator using a low molecular weight hydrocarbon refrigerant, which has excellent compatibility with the refrigerant, and It is to provide a lubricant excellent in lubricity and stability.

The present inventor has been diligently searching for and studying a mineral oil-based lubricant that is compatible with a hydrocarbon refrigerant, and has found that a lubricant mainly composed of a mineral oil having a specific physical property and component composition is a hydrocarbon coolant. Have been found to be excellent in compatibility and excellent in stability and lubricity in the presence of a hydrocarbon refrigerant, and have completed the present invention.

That is, the present invention has a kinematic viscosity at 40 ° C. of 5 to 15 OmmVs (c St), a pour point of 125 ° C. or less, a viscosity index of 50 or more, and n-d-M ring analysis. to 5% C _P 5 0 or more and% Rei_4 1 2 or less, the nitrogen content of 2 O ppm or less, sulfur content to zero. 0 2 to 0.3% and an iodine value of 1 0 gl at ₂ 100 g or less It is a lubricant for compression refrigerating machines that uses a hydrocarbon refrigerant containing a certain mineral oil as a main component.

Further, the present invention is a working fluid composition for use in a compression refrigerator comprising at least one hydrocarbon refrigerant comprising a hydrocarbon compound having 1 to 5 carbon atoms and the lubricant. This is a refrigeration apparatus filled with the working fluid composition.

Further, it is preferable that the lubricant further contains an extreme pressure agent composed of a phosphate ester and / or a phenol-based or amine-based antioxidant.

Such a lubricant containing a mineral oil as a main component has excellent compatibility with a hydrocarbon refrigerant, has high abrasion resistance to a sliding member of a compressor, and exhibits excellent stability. BEST MODE FOR CARRYING OUT THE INVENTION

The mineral oil used in the present invention has a kinematic viscosity at 40 ° C of 3 to 15 OmraVs. If the kinematic viscosity is low, the sealing and lubricating properties of the compressor will be low. It is preferably 5 to 100 thighs 2 / s.

Mineral oil has a pour point below 125 ° C. If the pour point is high, the lubricant discharged together with the coolant from the compressor will have a reduced fluidity due to the expansion mechanism or evaporator, and will stay in the low-temperature part of the refrigeration facility, causing a decrease in heat transfer efficiency or compression. Due to lack of lubricant in the machine This may cause bearing wear and seizure.

Mineral oil has a viscosity index of 50 or more. In the refrigeration cycle, the lubricant becomes hot at the compressor discharge and is exposed to a low temperature at the outlet of the expansion mechanism, and is used in a relatively wide temperature range. Therefore, a lubricant having a high viscosity index, which causes little change in viscosity with temperature, that is, a mineral oil having a high viscosity index is desired. Generally, a lubricant containing a large amount of long-chain hydrocarbons has a high viscosity index and a high lubrication performance. The viscosity index of the mineral oil is more preferably 80 or more.

Furthermore, mineral oils, n-d-M ring analysis to 5% C _P 5 0 or more and. /. C _A is 1 2 or less. Lubricants, as is rich chain hydrocarbon, in other words,% since higher lubricity value of C _P is used a large mineral oil is higher, diluted by a hydrocarbon refrigerant lubricity poor low molecular weight Even so, sufficient lubricity can be maintained, and bearing wear and seizure are less likely to occur. % C _P 8 0 or more is more preferable. Moreover,% C value of _A greatly affects the viscosity index, which is not preferable because the larger the viscosity index is low. % C _A is 1 0 or less is more preferable. In addition,% 〇1> and% じ can be determined by n-d-M ring analysis specified in ASTM D3238. In addition, nitrogen and sulfur content in mineral oil affect the properties of lubricating oil. If the nitrogen content exceeds 20 ppm by weight, hue stability deteriorates, so the content should be 20 ppm by weight or less. Further, the sulfur content is set to be 0.02 to 0.3% by weight, preferably 0.02 to 0.1%. If the sulfur content is high, the corrosiveness increases, and if the sulfur content is low, the lubricity decreases. Therefore, it is important to contain the sulfur content in the above range. '

Further, iodine value of the mineral oil used in the refrigerator lubricants of this invention is less _{1 0 g I 2/1 0} 0 g in order to ensure the stability against deterioration. Stability is deteriorated when the iodine value exceeds _{1 0 g I 2/1 0} 0 g.

The hydrocarbon refrigerant used in the present invention is a low molecular weight hydrocarbon compound having 1 to 5 carbon atoms. Specific examples include alkane compounds such as methane, ethane, propane, n-butane, i-butane, n-pentane, i-pentane, and neopentane, and cycloparaffin compounds such as cyclopropane, cyclobutane, and cyclopentane. . Furthermore, a derivative of the above compound in which some of the carbon bonds are double bonds (olefins corresponding to the above compounds) can also be used. Also, these compounds as hydrocarbon refrigerants Can be used alone or in an appropriate combination of two or more.

The effect of the present invention is exerted by using a mineral oil having the above-mentioned properties in combination with a compression refrigerator using a low molecular weight hydrocarbon refrigerant. That is, the mineral oil exhibits the above-described good lubricity and stability in the presence of the hydrocarbon refrigerant, and the mineral oil has a molecular structure much higher than that of the ester oil or ether oil in the hydrocarbon compound refrigerant. Because of similarity, it shows good compatibility. Further, the mineral oil is inexpensive as compared with the ester oil / ether oil, so that it is very useful in practical terms.

The lubricant of the present invention may contain other components as necessary. For example, well-known lubricant bases for refrigerators such as mineral oils other than the above-mentioned mineral oils used in the present invention (for example, naphthenic mineral oils), synthetic oils such as alkylbenzene oil, ether oil, ester oil, and fluorine oil. Oil and well-known additives may be appropriately blended. Examples of the additives include 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-p-cresol, and 4,4-methylene-bis (2,6-di-butyl). Tertiary butyl-p-cresol), p, p '-phenolic / amine-based or antioxidants such as dioctyl-di-phenyl / reamine, phenyldaricidyl ether, alkyl glycidyl ether Stabilizers, extreme pressure agents such as tricresyl phosphate and trifenyl phosphate, oily agents such as dali serine monooleate, glycerin monooleyl ether, glycerin monolauryl ether, and metal inactive agents such as benzotriazole Agents, defoaming agents such as polydimethylsiloxane and polymethacrylate, or antifoaming agents. In addition, additives such as well-known detergents / dispersants, viscosity index improvers, anti-corrosion agents, corrosion inhibitors, pour point depressants and the like can be added as necessary. These additives are usually blended so that the lubricant of the present invention contains about 10% by weight to about 10% by weight. In particular, the phenol-based or amine-based antioxidant has a weight ratio of 0.01 to 0.5 / ⁰ . By adding a certain amount, the stability and durability of the lubricant are greatly improved. Phosphate esters such as tricresyl phosphate and triphenyl phosphate are useful as extreme pressure agents and can be used with a small amount (for example, 0.05 to 1.0 weight./.) Of seizure load and abrasion resistance. Effectively improve the lubrication characteristics.

Example

Hereinafter, the present invention will be described in more detail with reference to Examples. Not limited to physical illustrations.

Oil used for evaluation

In order to evaluate the refrigerator lubricant of the present invention, mineral oils 1 to 8 and hard alkylbenzenes (HAB) 1 to 2 having physical properties and compositions shown in Tables 1 and 2, respectively, were prepared. Used for evaluation test. In addition, among these, the mineral oils 1 to 3 and 6 correspond to the base oil of the lubricant of the present invention.

Γ <ΧΧ ”indicates less than XX.

Table 2

“く XX” indicates less than XX.

Performance evaluation test

Using mineral oils 1-4 and HAB 1-2 as base oils and i-butane (R600a) as a refrigerant, it provides practical performance, lubricity (Falex baking load) and compatibility with refrigerants. A performance evaluation test was performed.

The performance evaluation test of the practical performance of the lubricant was carried out by a durability test using a refrigeration cycle using a refrigerator compressor. That was charged with lubricant made of the base oil 200 g and R600 a refrigerant 15 g compressor, the compressor discharge pressure 12 kg f Zcm ^2, for 1000 hours keeping the compressor surface temperature of 80 ° C Operation was carried out. After the endurance test, open the compressor, collect the lubricant after the test, so-called oil, measure the color and total acid value, disassemble the compressor and wear the pistons, cylinders, connecting rods and bearings. The amount was measured.

In addition, we evaluated Falex baking load and compatibility with refrigerant (two-layer separation temperature) as lubricity. Table 3 shows the measurement results.

Table 3

Mineral oil HAB

1 2 3 4 1 2 colors (ASTM) L1.5 L1.5 L1.5 L2.0 L1.5 L1.5 Oil used Total acid value

Properties mgKOH / g 0.01 0.01 0.01 0.04 0.03 0.03 1.0 <1.0 <1.0 2.1 2.5 2.9 Compressor

Sintering "(iron) 1.0 1.0 1.0 <1.0 1.0 1.0

Conlot,

1.0 1.0 1.0 1.0 4.2 4.9 5.6 (Aluminum alloy)

(μπι)

Bearing (iron) <1.0g 1.0g 1.0 1.2 1.7 2.6

Fale baking load

440 430 400 300 280 250 (Lbf)

Two-layer separation temperature ° C

<-40 <-40 <-40 c-40 c-40 <-40 (refrigerant R600a)

“く XX” indicates less than XX.

According to Table 3, the lubricants (mineral oils 1 to 3) of the present invention have low color of all L1.0 and total acid value of 0.0 lmgKOH / g, which is different from that of the new oil. In addition, the wear of the compressor components (Biston, cylinder, connecting rod, and bearings) was all less than 1.0 μm. On the other hand, in mineral oil 4 and HAB 1-2 corresponding to the comparative example, most of these values are larger than those in the example, and deterioration of the lubricant and wear of the compressor member are observed.

Stability test (cylinder test)

A stability test (bomb test) was conducted on mineral oils 1 to 8 as follows. For each of mineral oils 1 to 8, put 100 g of mineral oil and 20 g of isobutane (R600a refrigerant) in a 30-Oml cylinder, and wire iron (Fe), copper (Cu), and aluminum (A1) as a catalyst. (1.6 mm × 20 cm), sealed, and kept at 175 ° C. for 30 days. After cooling, the mineral oils 1 to 8 and the catalyst were taken out of the cylinder, and the color of the deteriorated mineral oil, the degree of sludge precipitation, and changes in the surface of each catalyst were visually observed. The amount of discoloration of the catalyst is evaluated in four levels of "large", "medium", "small" and "none", and the degree of sludge deposition is four levels of "high", "medium", "small" and "none" Was evaluated. The results are shown in Table 4.

Table 4

mineral oil

1 2 3 4 5 6 7 8 colors (ASTM) L1.5 L1.5 L1.5 L2.0 L4.5 L1.5 L3.0 L3.0 F e None None None Small Medium None Small Small Catalytic

Cu None None None Small Medium None Medium Small Discoloration

A 1 None None None None None None None None Sludge deposition None None None None Many None None Small

According to Table 4, the lubricants of the present invention (mineral oils 1-3 and 6) showed satisfactory stability for all items, but the viscosity index,% _CP , nitrogen content, sulfur content% and iodine value Lubricants (mineral oils 4 to 5 and 7 to 8) that did not satisfy one or more of the specified values for L had poor colors of L 2.0 or more, and discoloration of the catalyst and precipitation of sludge were also observed. Evaluation of additive effect

In addition, to evaluate the effect of the additive, tricresyl phosphate (TCP) as an extreme pressure agent and 2,6-di-tert-butylbutyl p-cresol (DBPC) as an antioxidant were added to mineral oil 1. Test oils 1 to 3 were prepared by adding at the ratio shown in 5, and the same stability test (bomb test) as above was conducted, and the Falex seizure load was measured. Table 5 shows the results. Table 5

Use mineral oil 1 as base oil

Various measurement test methods for the above base oil, used oil and compressor members were performed according to the following methods. The color was determined according to the ASTM color test method of JISK 2580, and the kinematic viscosity and viscosity index were determined according to JISK 2283. / oC _P and. /. C _A is n-d- M ring analysis specified in ASTM D 3238, pour point is JISK 2269, total acid value is JISK 2 50.1, Nitrogen content to JISK2609, Sulfur content to JISK2541, Fale X baking load to ASTM D3233, and compatibility with refrigerant (Two-layer separation temperature ) Is J

The values were determined in accordance with ISK2 211 (Annex 3, where R12 was read as R600a).

Since the lubricant for refrigerators of the present invention is a lubricant mainly composed of mineral oil having specific physical properties and component compositions, it has excellent compatibility with hydrocarbon refrigerants and is stable in the presence of hydrocarbon refrigerants. Excellent in lubricity and lubrication. Therefore, it is very useful as a lubricant for refrigerators that use hydrocarbon refrigerants that are friendly to the global environment.

Claims

The scope of the claims

1. In the lubricant for compression type refrigerator that uses a hydrocarbon refrigerant, 40 ° kinematic viscosity at C is 3-150 thigh ² / s, pour point - 25 ° C or less, a viscosity index of 50 or more, n one d _M ring analysis shows that% C _P is 50 or more and% C _A force is 12 or less, nitrogen is 20 ppm or less, sulfur is 0.02 to 0.3%, and iodine value is 10 gI ₂ Zl00 g or less. A lubricant characterized by containing a certain mineral oil as a main component.

2. The lubricant according to claim 1, further comprising an extreme pressure agent comprising a phosphate ester and / or a phenol-based or amine-based antioxidant.

3. At least one hydrocarbon refrigerant consisting of a hydrocarbon compound having 1 to 5 carbon atoms, a kinematic viscosity at 40 ° C of 5 to 15 OmmVs, a pour point of 125 ° C or less, a viscosity index of 50 or more and n — D—% C _P by M ring analysis is more than 50. ). ; ^ 12 or less, the nitrogen content is 20 ppm or less, and lubricant sulfur content .02 to 0.3% and ® © iodine value is predominant mineral oil is less than 10 g I _2/100 g A working fluid composition for use in a compression refrigerator, comprising:

4. In a refrigeration system consisting of a compressor, a condenser, a dryer, an expansion mechanism and an evaporator, at least one hydrocarbon refrigerant composed of a hydrocarbon compound having 1 to 5 carbon atoms and 40 ° kinematic viscosity of 5 to 15 Omm s in C, and one 25 ° C below the pour point, 5% C _P to 50 or more viscosity index and n-d-M ring analysis of 50 or more and. /. Operation consisting of a lubricant mainly composed of mineral oil with a C _A of 12 or less, a nitrogen content of 20 ppm or less, a sulfur content of 0.02 to 0.3% and an iodine value of 10 gl ₂ 100 g or less. A refrigeration apparatus characterized by being filled with a fluid composition.