KR20050053502A - Refrigerating machine oil for hydrocarbon coolant - Google Patents

Abstract

An object of the present invention is to provide a refrigeration oil for a hydrocarbon refrigerant that can suppress foaming, prevent the occurrence of cavitation of the compressor, and reduce operation noise.

The above object of the present invention is a refrigeration oil for hydrocarbon refrigerants comprising 1 to 20 ppm of polyether-modified silicone oil and / or silicone oil having an average molecular weight of 80,000 or more in base oil mainly composed of mineral oil, preferably As said mineral oil, it is achieved by using propane and / or isobutane as a hydrocarbon refrigerant which% CA by ndM ring analysis is 15 or less, nitrogen content is 50 ppm or less, and sulfur content is 2,000 ppm or less.

Description

REFRIGERATING MACHINE OIL FOR HYDROCARBON COOLANT}

The present invention is concerned with freezing lubricants using hydrocarbon refrigerants, in particular propane or isobutane, which have no fear of destroying the ozone layer and which have a global warming capacity even lower than halogen-containing hydrocarbon refrigerants.

The refrigerator is generally composed of a compressor, a condenser, an expansion mechanism (e.g., an expansion valve), an evaporator, etc., and performs cooling by using the property of taking away the heat of evaporation when the highly volatile refrigerant evaporates, and the refrigerator, freezer, air conditioning ( It is used in vending machines, showcases, soft drinks and vending machines such as ice cream. In air-conditioning, vending machines, etc., it is also used for heating using heat generated at the time of condensation, or heating and maintaining a beverage or food.

Conventionally, fluorinated hydrocarbons (CFC or HCFC) containing chlorine such as trichlorofluoromethane (R11), dichlorodifluoromethane (R12), and chlorodifluoromethane (R22) have been used as the refrigerant. However, since these CFCs and HCFCs cause environmental problems that destroy the ozone layer, their production and use are regulated internationally and currently do not contain chlorine, such as difluoromethane (R32), tetrafluoro. Non-chlorine fluorinated hydrocarbons (HFC) such as ethane (R134 or R134a), difluoroethane (R152 or R152a), and so-called replacement prones have been converted.

In recent years, in a refrigerator using such a replacement prone as a refrigerant, operation noise becomes a problem, and in order to reduce the operation noise, it has been attempted to control the bubble of lubricating oil in the compressor. For example, synthetic oil-based lubricating oils, such as ester oils, are generally difficult to foam, and thus silicone oil (Japanese Patent Application Laid-open No. Hei 10-88173) is used as a foaming agent. It is proposed to add a fluoride of an organic fluorine compound or a siloxane compound (Japanese Patent Laid-Open No. 10-46174) to the oil and furthermore, a base foaming agent.

However, these alternative prolons do not destroy the ozone layer, but they are not good for protecting the global environment in the long term because of their high global warming capacity. On the other hand, low molecular weight hydrocarbons and ammonia of 1 to 5 carbon atoms do not destroy the ozone layer. In addition, since the global warming ability is also very low compared to the chlorine-based or non-chlorine-based fluorinated hydrocarbons, it has been attracting attention as an environmentally friendly refrigerant. These refrigerants have not been mainstream in the past, but have been used for a long time, and lubricants such as naphthenic or paraffinic mineral oil, alkylbenzene oil, ether oil, ester oil, fluorine oil and the like have been proposed and used. Generally, since synthetic oil is expensive, mineral oil which is cheap and easy to obtain is used abundantly.

By the way, although the low molecular weight hydrocarbon as a refrigerant and the mineral oil as a lubricant have high compatibility, there is a problem that foaming occurs and the operation sound of the compressor increases, and in severe cases, it causes a cavitation. In addition, it has been found that silicone oil, which has been generally used in the past, is dissolved in a hydrocarbon refrigerant and does not function as an antifoaming agent.

SUMMARY 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 refrigeration oil for hydrocarbon refrigerant which can suppress the generation of bubbles, prevent the occurrence of cavitation of the compressor, and reduce operation noise. .

MEANS TO SOLVE THE PROBLEM As a result of earnestly searching and examining the foaming characteristic of the mineral oil type lubricant under a hydrocarbon refrigerant, the present inventors discovered that a specific silicone oil exerts antifoaming property without being influenced by a hydrocarbon refrigerant, and came to complete this invention.

The present invention relates to a refrigeration oil for hydrocarbon refrigerants comprising 1-20 ppm of a polyether-modified silicone oil and / or a silicone oil having an average molecular weight of 80,000 or more, to a base oil mainly containing mineral oil. Preferably, as the mineral oil, ndM It is related with using propane and / or isobutane as a hydrocarbon refrigerant using what% CA by a ring analysis is 15 or less, nitrogen content is 50 ppm or less, and sulfur content is 2,000 ppm or less.

The refrigeration oil of the present invention uses mineral oil as a main component, that is, at least 50% by mass or more of the base oil, but in addition to the mineral oil, well-known lubricating base oil for refrigerators such as synthetic oils such as alkylbenzene oil, ether oil, ester oil, fluorine oil, etc. You can mix. The mixing ratio of synthetic oils other than mineral oil is less than 50 mass%, preferably 30 mass% or less, particularly preferably 10 mass% or less based on the base oil.

As said mineral oil, it is preferable to use the mineral oil which has the characteristics of% CA of 15 or less, nitrogen content of 50 ppm or less, and sulfur content of 2,000 ppm or less by n-d-M ring analysis. The% CA value greatly affects the viscosity index, and when it is large, the viscosity index is lowered, and mineral oil having a% CA of 15 or more is not preferable as a refrigerator oil. In addition, mineral oil having a% CP of 50 or more has a high lubricity, and can maintain sufficient lubricity even when diluted with a hydrocarbon refrigerant having a low lubricity, and wear and sticking of the bearing are not easily generated. It is preferable to use. These% CA and% CP can be obtained by n-d-M ring analysis according to ASTM D3238.

In addition, nitrogen content and sulfur content contained in mineral oil may adversely affect the characteristic of lubricating oil. If the nitrogen content exceeds 50 ppm by weight, the stability tends to be deteriorated, and the nitrogen content is preferably 50 ppm by weight or less. In addition, since sulfur content has corrosiveness, it is preferable to set it as 2,000 ppm or less, and also, if too small, on the contrary, since lubricity falls, it is preferable to exist 100 ppm or more.

These mineral oils are solvent deasphalting, solvent extraction, hydrocracking, hydrodewaxing, solvent dewaxing, hydrorefining, sulfuric acid washing, and one or two or more kinds of refining for lubricating oil distillates obtained by atmospheric distillation and vacuum distillation of crude oil. It can obtain by combining suitably.

As for the refrigeration oil of this invention, it is preferable that kinematic viscosity in 40 degreeC is 3-150 mm <2> / s, especially 5-100 mm <2> / s, and it is more preferable that a pour point is -25 degrees C or less. If the pour point is higher than -25 ° C, the lubricant discharged with the refrigerant from the compressor is deteriorated in fluidity by an expansion mechanism or an evaporator, and stays at a low temperature part of the refrigeration plant to reduce the heat transfer efficiency or the bearing due to the lack of lubricant in the compressor. It may cause wear, sticking, or the like, which is not preferable. Furthermore, it is preferable that the viscosity index is 50 or more, especially 80 or more. In the refrigeration cycle, the lubricant becomes hot at the discharge of the compressor and is exposed to low temperatures at the outlet of the expansion mechanism and used in a relatively wide temperature range. Therefore, there is a need for a lubricant having a high viscosity index with low viscosity change due to temperature, that is, a mineral oil having a high viscosity index. Generally, lubricants containing a lot of long chain hydrocarbons have a high viscosity index and tend to have high lubricating performance.

As the hydrocarbon refrigerant used in the present invention, a hydrocarbon compound having a low molecular weight of 1 to 5 carbon atoms, specifically, alkane compounds such as methane, ethane, propane, n-butane, isobutane, n-pentane, isopentane and neopentane And cycloparaffin compounds such as cyclopropane, cyclobutane, cyclopentane, and the like, and derivatives of the compounds (olefins corresponding to the above compounds) in which some carbon bonds are double bonds can also be used. As the hydrocarbon refrigerant, these compounds may be used alone or in combination of two or more kinds as appropriate. Of these, propane or isobutane are particularly preferred.

The present invention is to add a polyether-modified silicone oil and / or a silicone oil having an average molecular weight of 80,000 or more to the base oil mainly containing mineral oil as described above. Since polyether modified silicone oil is what modified | denatured by introducing a polyether group into the side chain, the terminal, or both of polysiloxane as shown in following General formula (1), either can be used in this invention.

Wherein A ₁ , A ₂ , and A ₃ are-(C ₂ H ₄ O) a (C ₃ H ₆ 0) bR ₂ or -R ₁ (C ₂ H ₄ O) a (C ₃ H ₆ 0) It is a polyether group or methyl group represented by bR <_2> , At least _{1 of} A <_1> , A <_2> , A <_3> is a polyether group, Moreover, m and n are integers of 0-1000 and m + n is 10 or more. In the polyether group, a represents an integer of 0 to 100, b represents an integer of 1 to 100, R ₁ represents a hydrocarbon group of ₁ to 8 carbon atoms, and R2 represents a hydrocarbon group of 1 to 8 carbon atoms or hydrogen.

On the other hand, about silicone oils other than polyether modified silicone oil, if an average molecular weight is 80,000 or more, it will melt | dissolve in a hydrocarbon refrigerant and cannot perform a defoaming function. Preferably, the average molecular weight is 100,000 or more, particularly preferably 500,000 or more. Moreover, since dispersion in base oil is easy, this average molecular weight is preferably 1,000,000 or less. Moreover, as a polyorganosiloxane of this kind of silicone oil, although a substituent may have any of an alkyl group, a cycloalkyl group, and an aromatic group, polydimethylsiloxane is especially preferable.

1-20 ppm of these silicone oils are added with respect to base oil. The addition of 1 ppm or less does not sufficiently exert the defoaming effect. If the amount exceeds 20 ppm, cloudiness may occur in the refrigerator oil, which may adversely affect the expansion mechanism of the refrigerator. It is preferable that the addition amount is 5-15 ppm.

You may mix | blend another additive with the refrigerator oil of this invention suitably as needed. As this additive, 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-p-cresol, 4,4-methylene-bis- (2,6-di-tert-butyl-p-cresol ), phenolic or amine antioxidants such as p, p'-di-octyl-di-phenylamine, stabilizers such as phenylglycidyl ether and alkylglycidyl ether, tricredyl phosphate and triphenyl phosphate Oily agents such as extreme pressure agents, glycerin monooleate, glycerin monooleyl ether, glycerin monolauryl ether, metal deactivators such as benzotriazole, polydimethylsiloxane, polymethacryl acrylate, and the like. Antifoaming agents, antifoaming agents and the like.

In addition, additives, such as a well-known clean dispersing agent, a viscosity index improver, a rust preventive agent, a corrosion inhibitor, a pour point depressant, can also be mix | blended as needed. These additives are usually blended so as to contain about 10 wt% to 10 wt% of the lubricant of the present invention. In particular, by adding about 0.01 to 0.5% by weight of an phenol or amine antioxidant, the stability and durability of the lubricant are greatly improved. In addition, phosphate esters such as tricredil phosphate and triphenyl phosphate are useful as extreme pressure agents, and effectively improve lubrication characteristics such as pressing load and abrasion resistance with a small amount of addition (for example, 0.05 to 1.0% by weight).

Example 1

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these specific examples.

As the base oil, paraffinic mineral oil VG10 (base oil A) and naphthenic mineral oil VG46 (base oil B) having the properties shown in Table 1 were used.

Base oil A Base oil B Kinematic viscosity (mm ² / s) 40 ℃ 100 ℃ 10.32.62 55.16.00 Viscosity index 80 14 Sulfur (ppm) 585 100 Nitrogen content (ppm) 0 12 Pour point (℃) -30 -35 n-d-M ring analysis% CA% CN% CP 93655 114247

The properties of commercially available polyether modified silicone oils and non-modified silicone oils (both manufactured by Shin-Etsu Chemical Co., Ltd.) used in this example are shown in Table 2 below. In addition, only KF96H-3 and KF96H-1 in Table 2 are used as an antifoamer conventionally.

type Polyether modification Undenatured product name KF352 KF615A KF96H100 only KF96H50 only KF96H3 only KF96H1 only Viscosity 25 ° C (mm ² / s) 1600 1000 1,000,000 500,000 30,000 10,000 Average molecular weight - - 150,000 100,000 70,000 55,000

To the base oil, as shown in Table 3, silicone oil was added to provide a foaming test.

Base oil Silicone oil Addition amount (ppm) Example 1 A KF352 5 Example 2 A KF352 10 Example 3 A KF352 15 Example 4 A KF615A 10 Example 5 A KF96H-100 only 10 Example 6 A KF96H-50 only 20 Example 7 A KF96H-50 only / KF352 5/5 Example 8 B KF352 10 Example 9 B KF615A 5 Example 10 B KF96H-10 only 5 Example 11 B KF96H-30 only 10 Comparative Example 1 A KF96H-3 only 5 Comparative Example 2 A KF96H-3 only 10 Comparative Example 3 A KF96H-3 only 20 Comparative Example 4 A KF96H-1 only 20 Comparative Example 5 B KF96H-3 only 15 Comparative Example 6 B KF96H-1 only 15

Foam generation test

20 g of sample oil and 20 g of n-hexane, which are similar in properties to the hydrocarbon refrigerant and liquid, were added to a glass bottle (capacity 110 ml) having an inner diameter of 34 mm, and stirred for 10 minutes. Next, a tube made of a metal having an inner diameter of 1 mm was set at a position of 5 mm from the bottom of the bottle, and nitrogen gas was flowed at 60 ml / min, and after 1 minute, after 5 minutes, a foam state on the oil surface at the time of stop Was observed. The results are shown in Table 4.

Foaming (ml) 1 minute later 5 minutes later At stop Example 1 0 0 0 Example 2 0 0 0 Example 3 0 0 0 Example 4 0 0 0 Example 5 0 0 0 Example 6 0 0 0 Example 7 0 0 0 Example 8 0 0 0 Example 9 0 0 0 Example 10 0 0 0 Example 11 5 or less 5 or less 0 Comparative Example 1 20 30 10 Comparative Example 2 20 20 10 Comparative Example 3 20 20 0 Comparative Example 4 30 30 20 Comparative Example 5 10 20 0 Comparative Example 6 30 30 20

As a result, addition of the polyether modified silicone oil and the silicone oil of 80,000 or more of average molecular weight can confirm that foaming is suppressed even if a hydrocarbon melt | dissolves.

Example 2

Next, 220 ml of the disclosed oil of Table 3 was put into a refrigerator compressor (with a visible window for observing the state of the foam), and 30 g of isobutane was used as the refrigerant, and the discharge pressure was 5 to The operation was performed under the conditions of 6 kg / cm 2 · G and suction pressure of 0 kg / cm 2 · G, and the state of foam immediately after the start of operation and 5 minutes later was observed. The results are shown in Table 5.

Foam condition in the compressor Immediately after starting 5 minutes after driving Example 1 a very small amount None Example 2 a very small amount None Example 3 a very small amount None Example 4 a very small amount None Example 5 a very small amount None Example 6 a very small amount None Example 7 a very small amount None Example 8 a very small amount None Example 9 a very small amount None Example 10 a very small amount None Example 11 a very small amount None Comparative Example 1 Medium Medium Comparative Example 2 Medium Medium Comparative Example 3 Medium Medium Comparative Example 4 block Medium Comparative Example 5 Medium Medium Comparative Example 6 block Medium

In Table 5, the bulk is the whole of the holding window, the medium is 50 to 80% of the holding window, the trace amount is 10% or less of the holding window, respectively, indicating that the bubbles. As is clear from this result, the addition of polyether-modified silicone oil and silicone oil having an average molecular weight of 80,000 or more indicates that foaming is suppressed even in practical use.

In the refrigerator oil of the present invention, since polyether-modified silicone oil and / or silicone oil having a high average molecular weight are added to the base oil mainly containing mineral oil, foaming can be suppressed and the occurrence of cavitation of the compressor can be prevented. It is very useful as a lubricant for a refrigerator using a hydrocarbon refrigerant which can reduce driving noise and is environmentally friendly.

The refrigeration oil for hydrocarbon refrigerants of the present invention has a remarkable effect that the generation of bubbles in the refrigerator is suppressed, the cavitation of the compressor does not occur, and the operation sound of the refrigerator can be reduced.

Claims (3)

A refrigeration oil for hydrocarbon refrigerant, wherein polyether-modified silicone oil and / or 1-20 ppm of silicone oil having an average molecular weight of 80,000 or more are added to the base oil mainly containing mineral oil. The refrigeration oil for a hydrocarbon refrigerant according to claim 1, wherein the mineral oil has a% CA of 15 or less, a nitrogen content of 50 ppm or less, and a sulfur content of 2,000 ppm or less by n-d-M ring analysis. The refrigerant oil for a hydrocarbon refrigerant according to claim 1 or 2, wherein the hydrocarbon refrigerant is propane and / or isobutane.