DE60018005T2 - LUBRICANTS FOR STEAM COMPRESSION REFRIGERATOR WITH HYDROCARBON COOLANT - Google Patents

Description

technical area

The The invention relates to the composition of a working medium comprising a hydrocarbon coolant and a lubricant for a compressor cooling system, in which a hydrocarbon coolant that is not a cause for injury Ozone layer gives, and that a lower hydrocarbon with the Property includes, for global warming contribute much less than that of a halogen-containing Hydrocarbon refrigerant. Furthermore, the present invention relates to a cooling system that is compatible with the composition filled the working medium is.

background the invention

One Compressor cooling system is a compressor, a condenser, an expansion mechanism (such as an expansion valve), an evaporator and constructed further parts, and it is done by cooling Exploiting the property that when a high volatility refrigerant vaporizes, the coolant the environment evaporative heat withdraws. The compressor cooling system will be in a fridge, a freezer, air conditioning, a showcase, a Vending machines for beverages and ice creams and the like. In the case of air conditioning, of the vending machine and the like, the space heating or the heating and maintaining (a temperature) of the drinks or running the food, by utilizing the heat generated during condensation.

Usually were chlorofluorocarbons or chlorofluorocarbons (CFC or HCFC), such as trichlorofluoromethane (R11), dichlorodifluoromethane (R12) or chlorodifluoromethane (R22) used as a coolant.

JP-A-580 764 97 describes a cooler oil for use with a chlorofluorocarbon as a coolant.

US-A-4 983 313 describes an oil composition for one Chiller which is an alkylbenzene, a mineral oil based on paraffin and a naphthene-based mineral oil.

There however, causing such CFC and HCFC environmental problems to that that damage to the Ozone layer occurs, their manufacture and use has been international limited. Currently, they are made by non-chlorinated fluorocarbons (HFCs) substituted, such as difluoromethane (R32), tetrafluoroethane (R134 or R134a) or difluoroethane (R152 or R152a), each not Chlorine included. Although such fluorocarbons, although no damage cause the ozone layer to have a pronounced property to global warming contribute. As a result, there is concern that such refrigerants Issues involve a long - term view of worldwide environmental protection.

Out the fact that lower hydrocarbons with a lower Molecular weight of about 1 to 5 carbon atoms, ammonia or like no damage cause the ozone layer and a much lower ability own, to global warming contribute compared to the aforementioned fluorinated hydrocarbons of the chlorine type or non-chlorine type, therefore, are those as an environmentally friendly refrigerant known. Such compounds were usually not the leading ones Coolant, however, have the actual Results that they have been used by the old ones. According to the patent JP-A-10-130685 furthermore mineral oils naphthenic type or paraffin type, and synthetic oils such as for example, alkylbenzene oil, ether oil, ester oil or fluoro-oil as examples for lubricants for coolant serve, including the aforementioned Hydrocarbons. Of these lubricants are synthetic oils in general expensive. Therefore, one looks for mineral oils, the cheap and easy from the standpoint of practical use available are.

however There are also numerous problems with the combination of hydrocarbon refrigerants of low molecular weight (coolant of lower hydrocarbon) and mineral oil type lubricants. It is particularly desirable that lubricant for Cooling systems, the hydrocarbons as a coolant Use, excellent lubricity from the following have described reasons.

Low molecular weight hydrocarbons as the coolant and mineral oils as the coolant Lubricants have a (mutual) compatibility. However, if their density difference is large, it may be the case that it is difficult to mix them only by spontaneous diffusion. In a refrigeration system, it often happens that these substances are in a state where they can be difficult to mix with each other. For example, when charging a refrigerant into a compressor, a condition occurs that a relatively low-density refrigerant comes to rest on a high-density lubricant already filled. Further, this state also occurs when the refrigerant in the liquid state is returned to the compressor during a stop of the compressor, that is, in the case of so-called "flooding." If the compressor is started in such a state, the lubricant collects out of rotation due to centrifugal force, and the lubricant does not sufficiently reach a sliding portion such as the inner bearing requiring lubrication, as a result of which friction wear occurs on a sliding portion or sticking easily For this reason, a lubricant having excellent lubricating properties is required and desirably desired as a lubricant for a refrigerating system using a low molecular weight hydrocarbon refrigerant. In addition, a fluorinated hydrocarbon refrigerant of the chlorine type may be decomposed due to the presence in the molecule Keep chlorinated an extreme pressure effect. However, a hydrocarbon refrigerant itself has a low molecular weight, and therefore a lubricating property is not expected at all. This also supports the need to demand excellent lubricating properties for a lubricant for a refrigeration system using a hydrocarbon refrigerant.

Furthermore are lubricants for cooling systems a cooling cycle exposed in which constantly repeat high temperature and low temperature, even though these are generally used in a closed system become. For this reason, a lubricant with good stability and durability he wishes.

epiphany the invention

The The present invention has been made to the above-mentioned object to solve, and it is an object of the present invention to provide compositions for working media to provide lubricants for a refrigeration system, the Hydrocarbon refrigerants used with low molecular weight, wherein the lubricant an excellent compatibility with the hydrocarbon coolant, has excellent lubricating properties and stability.

The Inventors of the present invention conducted intensive research and discussions regarding the Mineral oil type lubricant through that a good compatibility with a hydrocarbon coolant own, and have found that the lubricants containing mineral oil include physical properties as a main component, and the composition is excellent compatibility with a hydrocarbon coolant owns, and re stability and lubricating properties in the presence of a hydrocarbon coolant is excellent, and have completed the present invention.

That is, the present invention is a composition of a working medium comprising a lubricant for a refrigeration system using a hydrocarbon refrigerant, the lubricant as a main ingredient being a mineral oil having a kinematic viscosity of 5-150 mm ² (cSt) at 40 ° C , a pour point of -25 ° C or less, a viscosity index of 50 or higher,% C _P and% C _A , measured by ndM ring analysis, of 50 or more, or 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 g I _2/100 g or less.

Further includes the composition of a working medium for compressor cooling systems at least one type of hydrocarbon coolant that is a hydrocarbon compound with 1-5 Carbon atoms. The present invention further relates a cooling system, which is filled with the composition of a working medium.

Furthermore are as mentioned above Lubricants are those lubricants which contain agents, the utmost Withstand pressure comprising phosphate, and / or antioxidant phenol or amine type.

The Lubricant comprising as a main ingredient, for example, a mineral oil, has excellent compatibility with the hydrocarbon coolant, has a high abrasion resistance with respect to the sliding parts of the compressor, and further shows excellent stability.

The best Type of execution the invention

The mineral oil used in the lubricant of the present invention has a kinematic viscosity of 3 - 150 mm ² / s at 40 ° C. If the kinematic viscosity is low, the sealing property and the lubricity in the compressor decrease, while when it becomes high, the pour point becomes too high or the energy efficiency lowers. It is preferably 5-100 mm ² / s.

Furthermore owns the mineral oil a pour point from -25 ° C or less. If the pour point is too is high, the fluidity decreases of the lubricant coming from the compressor together with a coolant is ejected in an expansion mechanism or an evaporator, and the lubricant settles on those parts of the cooling system with low temperature. This can lead to a decrease in effectiveness the heat transfer to lead, or wear due to friction or sticking of the bearing due cause the lack of lubricant in the compressor.

Further owns the mineral oil a viscosity index from 50 or more. In a cooling cycle The lubricant has a high temperature during ejection the compressor, and is then connected to an outlet of a Expansion mechanism exposed to a low temperature. Consequently The lubricant is in a relatively wide temperature range used. This is a lubricant with a high viscosity index, the in terms of a change the viscosity, which depends on the temperature, is small, that is, a mineral oil with a high viscosity index is desired. In general, a lubricant that has a large amount contains long-chain hydrocarbons, a high viscosity index, which leads to an increasing lubricating performance. The viscosity index of mineral oil is stronger preferably 80 or more.

In addition, the mineral oil has a% C _P and% C _A value, as measured by ndM ring analysis, of 50 or more, or 12 or less. The lubricity of the lubricant increases as the amount of chain hydrocarbons in the lubricant increases, in other words, when using a mineral oil with a greater% C _P value. Therefore, sufficient lubricity can be maintained even if the lubricant is diluted with low molecular weight hydrocarbon refrigerants, which have poor lubricating properties, and wear by friction or sticking of the bearing hardly occurs. The% C _P value is preferably 80 or more. In addition, the% C _A value greatly influences the viscosity index, and if it is large, the viscosity index decreases, which is not preferable. The% C _A value is preferably 10 or less. The% C _P and% C _A values can be determined by the ndM ring analytical method defined in ASTM D3238.

Furthermore influenced in the mineral oil contained nitrogen content and sulfur content the properties of the lubricant. If the nitrogen content exceeds 20 ppm by weight, the color stability deteriorates. Therefore, the nitrogen content is 20 ppm by weight or less. Furthermore, the sulfur content is 0.02-0.3% by weight, preferably 0.02-0.1 Wt .-%. If the sulfur content is large, take the corrosion properties too, and if it is small, its lubricity decreases. That's why it's important to keep the sulfur content in the above-mentioned range.

In addition, the iodine value is of the mineral oil used in the lubricant for refrigeration system of the present invention, 10 g I _2/100 g or less in order to ensure the stability against decomposition. If the iodine value of 10 g I _2/100 g exceeds, the stability deteriorates.

The Hydrocarbon refrigerant, used with the lubricant of the present invention, are hydrocarbon compounds of low molecular weight with 15 Carbon atoms. Specific examples of this include alkane compounds, such as methane, ethane, propane, n-butane, i-butane, n-pentane, i-pentane or neopentane, and cycloparaffin compounds, such as Example cyclopropane, cyclobutane or cyclopentane. Furthermore, derivatives the aforementioned Compounds also be used in which part of the carbon bonds a double bond is (olefins which are the compounds mentioned above correspond). As hydrocarbon coolant, such compounds may be used alone or used as a mixture by two or more compounds be mixed in a suitable manner.

The effect of the present invention is manifested by using the mineral oil having the above-mentioned physical properties in the compressor cooling system using a low molecular weight hydrocarbon coolant. That is, the above-mentioned mineral oil exhibits the above-mentioned good lubricating property and stability in the presence of the hydrocarbon fabric coolant, and also shows good compatibility, since the mineral oil has a molecular structure, which is very similar to that of the hydrocarbon coolant, compared with ester oils or ether oils. Further, the mineral oil is cheap compared to ester oils or ether oils, and hence it is very useful from a practical point of view.

The Lubricant of the composition of a working medium of the present The invention may optionally contain other ingredients if necessary. For example, you can conventional Base Oils for cooling systems, such as mineral oils, which differ from the ones mentioned above, in the present invention used mineral oils (for example mineral oils naphthenic type) or synthetic oils (for example, alkylbenzene oils, ether oils, ester oils or fluorinated oils), and conventional additions be added in a suitable manner. Examples of the additives include Phenol-type or amine-type antioxidants, for example 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-p-cresol, 4,4-methylene-bis (2,6-di-tert-butyl-p-cresol) or p, p'-di-octyldi-phenylamine, Stabilizers, such as phenyl glycidyl ether or alkyl glycidyl ether, Means, the utmost Withstand pressure, for example tricresyl phosphate or triphenyl phosphate, Greasing agents, such as glycerol monooleate, glycerol monooleyl ether or glycerol monolauryl ethers, metal inactivators, such as Benzotriazole, and defoamer, such as polydimethylsiloxane or polymethacrylic acrylate. Other than those mentioned above usual Additions, such as dispersants, means for improving the Viscosity index, Rust inhibitors, corrosion inhibitors or depressants of the pour point can optionally also be added. Such additives can with the lubricant the composition of a working medium of the present invention in an amount of generally about 10 wtppm to 10 wt% admixed become. In particular, when a phenol-type antioxidant or amine type in an amount of about 0.01 to 0.5 wt .-% added will, stability will and durability of the lubricant greatly improved. Further, phosphates, such as tricresyl phosphate or triphenyl phosphate, useful as a means, the utmost Withstand pressure, and their addition in a very small amount (For example, 0.05 - 1.0 % By weight) effectively improves the lubricating properties For example, the load when stuck (the camp) or the Frictional resistance.

Examples

The The present invention will be described in detail by the following is explained by reference to examples, however, the The invention is not limited to the specific examples.

Oils used for the evaluation

„<XX" bedeutet weniger als XX. Tabelle 2

„<XX" bedeutet weniger als XX.To evaluate the lubricant of the composition of a working medium for a refrigeration system of the present invention, the mineral oils 1-8 and hard-type alkylbenzenes (HAB) 1-2 of alkylbenzenes were prepared, their physical properties and compositions in Tables 1 and 2, respectively, and used in evaluation tests described below. Of these, mineral oils 1-3 and 6 correspond to a base oil of a lubricant of a working fluid composition of the present invention. Table 1

"<XX" means less than XX. Table 2

"<XX" means less than XX.

Test for evaluation performance

Base oils of mineral oils 1-4 and alkylbenzenes Hart Type (HAB) 1-2 were used as lubricants, isobutane (R600a) was used as a coolant used, and tests to evaluate the performance, such as Practical performance, lubricity (Falex seat load; Falex seizure load) and the compatibility with the coolant were executed.

„<XX" bedeutet weniger als XX.The test for evaluating the practical performance of the lubricant was carried out on the durability test by using a refrigerating cycle with a compressor for a refrigerator. That is, 200 g of each lubricant comprising the above-mentioned base oil and 15 g of R600a refrigerant was charged in the compressor, and the operation was carried out for 1000 hours, with the compressor pressure on the discharge side being maintained at 12 kgf / cm ² and the compressor surface temperature was 80 ° C. After completion of the durability test, the compressor was opened. The lubricant after the test, that is, the oil used, was sampled and the color and total acid value were measured. In addition, the compressor was disassembled and the extent of wear on the piston, cylinder, connecting rod and bearing were measured. Furthermore, the Falex interference fit and the compatibility with coolant (temperature, at which is separated into two layers) is also evaluated as a smear property. These measurement results are shown in Table 3. Table 3

"<XX" means less than XX.

Corresponding Table 3 showed the lubricants of the present invention (mineral oils 1-3) that the color was low as L1.0, and the total acid value was 0.01 mg KOH / g, opposite the value of new oil unchanged was, and that the extent of Wear due to friction of the parts (piston, cylinder, connecting rod and bearings) of the compressor was always 1.0 μm or less. In contrast to prove the mineral oil 4 and HAB 1-2 according to the comparative examples, values which are almost all were bigger than those of the preceding examples, and a deterioration of the Lubricant and wear due to friction of the compressor parts were observed.

Stability test (bomb test)

In Reference to the mineral oils Was 1-8 the stability test (Bomb test) carried out as follows. In terms of each of the mineral oils Were 1-8 100 g of mineral oil and 20 g isobutane (R600a coolant) filled in a 300 ml bomb. wires (1.6 mm diameter × 20 cm) of iron (Fe), copper (Cu) and aluminum (Al) as catalysts were about it inserted into the bomb. The bomb was sealed and "aged" for 30 days long at a temperature of 175 ° C was suspended. After aging, the mineral oils became 1-8 and catalysts taken from the bomb, and the color of the mineral oil after Decomposition, the extent of Mud formation and the change every catalyst surface were visually observed. The extent of discoloration of the catalyst was 4 grades of "big", "medium", "small" or "none". The extent of sludge formation was rated 4 degrees of "high", "medium", "low" or "none". The results are shown in Table 4.

Table 4

According to Table 4, the lubricants of the working fluid composition of the present invention (mineral oils 1-3 and 6) exhibited satisfactory stability in all respects, but those lubricants failing to satisfy any value or a plurality of values specified in this invention Viscosity index,% C _P value, nitrogen content, sulfur content (%) and the iodine value (mineral oils 4-5 and 7-8) showed that the color was poor as L2.0 or more, and that discoloration of the catalyst as well Precipitation of the sludge were observed.

rating the effect of adding an additive

Around To evaluate the effect of adding an additive was tricresyl phosphate (TCP) as a means, the utmost Pressure withstand and 2,6-di-tert-butyl-p-cresol (DBPC) as an antioxidant in circumstances which are shown in Table 5 to prepare the test oils 1-3. The same stability test (bomb test), as mentioned above, it was accomplished, and the Falex interference fit load was measured. The results are shown in Table 5.

Table 5

Various measurement test methods concerning the above-mentioned base oils, the oils used and the compressor parts were carried out according to the following methods. The color (ASTM) was determined by JIS K2580, the kinematic viscosity and the viscosity index were determined according to JIS K2283, the% C _P and% C _A values were determined according to the ndM ring analysis defined in ASTM D3238 Yield point was determined by JIS K2609, sulfur content was determined according to JIS K2269, total acid value was determined according to JIS K2501, nitrogen content was determined according to JIS K2541, Falex seizure load was determined according to ASTM D3233, and Compatibility with the coolant (temperature at which separation takes place in two layers) was determined in accordance with JIS K2211 (Appendix 3, provided that R600a is used instead of R12).

The Lubricant for the composition of a working medium for a refrigeration system of the present invention is a lubricant comprising a mineral oil as a main component, which are specific physical properties and composition possesses, so that it is excellent in the compatibility with hydrocarbon coolants and also excellent in stability and lubricant properties in the presence of hydrocarbon refrigerants. Therefore it is very useful as a lubricant for a cooling system using environmentally friendly hydrocarbon coolant.

Claims (3)

A working medium composition for use in a compressor refrigeration system, characterized in that it comprises at least one kind of hydrocarbon refrigerants comprising hydrocarbon compounds having 1-5 carbon atoms, and a lubricant comprising as a main component a mineral oil having a kinematic viscosity of 5-150 mm ² at 40 ° C, a pour point of -25 ° C or less, a viscosity index of 50 or higher,% C _P and% C _A after ndM ring analysis, defined in ASTM D3238, of 50 or more, or 12 or less, a nitrogen content of 20 ppm or less, a sulfur content of 0.02-0.3% and an iodine value of 10 gI ₂ / 100g or less comprising. The working fluid composition of claim 1, wherein the lubricant further comprises a high pressure medium containing a phosphate, and / or a phenol-type or amine-type antioxidant. A refrigeration system comprising a compressor, a condenser, a dryer, an expansion mechanism and an evaporator, the refrigeration system being filled with a working fluid composition comprising at least one type of hydrocarbon refrigerants comprising hydrocarbon compounds having 1-5 carbon atoms and a lubricant comprising a major ingredient is a mineral oil having a kinematic viscosity of 5-150 mm ² / s at 40 ° C, a pour point of -25 ° C or less, a viscosity index of 50 or higher,% C _P and% C _A after ndM ring analysis of 50 or more and 12 or less, a nitrogen content of 20 ppm or less, a sulfur content of 0.02-0.3% and an iodine value of 10 gI ₂ / 100g or less comprising.