JP4098263B2 - Lubricating oil composition for refrigerator and lubricating method using the composition - Google Patents

Description

    The present invention relates to a lubricating oil composition for a refrigerator and a lubricating method, and more particularly, to a lubricating oil composition for a refrigerator using a refrigerant mainly composed of a hydrocarbon having 1 to 8 carbon atoms and the composition. Related to the lubrication method.

  In general, in a compression refrigeration cycle of a refrigerator, for example, a compression refrigerator comprising a compressor, a condenser, an expansion valve, and an evaporator, a structure in which a mixed liquid of refrigerant and lubricating oil circulates in the sealed system. It has become. In such compression refrigerators, dichlorodifluoromethane (R-12), chlorodifluoromethane (R-22) and the like are conventionally used as refrigerants, and various mineral oils and synthetic oils are used as lubricating oils. I came. However, since chlorofluorocarbons such as R-12 and R-22 may cause environmental pollution such as destruction of the ozone layer existing in the stratosphere, recently, regulations on their use are becoming stricter worldwide. is there. Therefore, hydrogen-containing chlorofluorocarbon compounds such as hydrofluorocarbon and hydrochlorofluorocarbon have attracted attention as new refrigerants. This hydrogen-containing chlorofluorocarbon compound, particularly hydrofluorocarbons represented by 1,1,1,2-tetrafluoroethane (R-134a), has no risk of destroying the ozone layer, but has a long life in the atmosphere. In recent years, various hydrocarbons, in particular hydrocarbons having 1 to 8 carbon atoms, are being studied as natural refrigerants free from such problems because of concern over the impact on global warming. However, when such hydrocarbons are used as refrigerants for compression refrigerators, the use of conventional lubricating oils results in poor lubricity, insufficient wear resistance, and insufficient stability. As a result, long-term stable use becomes impossible. This tendency is particularly strong when a capillary tube is used as an expansion valve.

  The present invention has been made from the above viewpoint, and in a compression refrigeration cycle using a refrigerant mainly composed of hydrocarbons, lubrication can be performed efficiently, and as a result, wear resistance and stability can be improved. It is an object of the present invention to provide a lubricating oil composition for a refrigerator that can improve the refrigerating efficiency and a lubricating method using the composition.

As a result of extensive research, the present inventors have found that the object of the present invention can be effectively achieved by using a hydrocarbon compound having a specific property as a lubricating base oil. It has been completed. That is, the present invention includes (1) (A) a refrigerant mainly composed of a hydrocarbon having 1 to 8 carbon atoms, and (B) a non-aromatic unsaturation degree of 10% or less and a dynamic behavior at 100 ° C. A lubricating oil composition for a refrigerator, comprising a base oil composed of at least one hydrocarbon compound selected from alkylbenzene, alkylnaphthalene and poly-α-olefin having a viscosity of 5 mm ² / s or more, and (2) (A) a refrigerant mainly composed of a hydrocarbon having 1 to 8 carbon atoms, and (B) a non-aromatic unsaturation degree of 10% or less and a kinematic viscosity at 100 ° C. of 5 mm ² / s. It is characterized by using a lubricating oil composition for a refrigerator containing a base oil comprising at least one hydrocarbon compound selected from alkylbenzene, alkylnaphthalene and poly-α-olefin as described above. The present invention provides a lubrication method for a compression type refrigerator.

  According to the present invention, in a compression refrigeration cycle using a refrigerant whose main component is a hydrocarbon having 1 to 8 carbon atoms, lubrication can be efficiently performed, and as a result, wear resistance and stability are improved. It is possible to provide a lubricating oil composition for a refrigerator that can improve the refrigerating efficiency and a lubricating method using the composition.

Hereinafter, embodiments of the present invention will be described. The lubricating oil composition for a refrigerator according to the first invention of the present application is (A) a refrigerant mainly composed of a hydrocarbon having 1 to 8 carbon atoms, and (B) a non-aromatic unsaturation degree of 10% or less. And a base oil composed of a hydrocarbon compound having a kinematic viscosity at 100 ° C. of 5 mm ² / s or more.

The carbon number of the hydrocarbon which is the main component of the component (A) (refrigerant) used in the present invention is 1 to 8, preferably 1 to 5, and more preferably 3 to 5. When the number of carbon atoms is 9 or more, the boiling point becomes too high, which is not preferable as a refrigerant. Examples of the hydrocarbon used in the present invention include methane, ethane, ethylene, propane, cyclopropane, propylene, n-butane, i-butane, n-pentane, i-pentane and the like. The hydrocarbon may be one kind or two or more kinds. It is also possible to use only hydrocarbon, which can also be used a mixture hydrofluorocarbons such as R-134a, ether, and refrigerant such as CO _2.

In the present invention, a hydrocarbon compound having a non-aromatic unsaturation of 10% or less is used as the base oil of component (B). The degree of non-aromatic unsaturation means the amount of unsaturation excluding the aromatic component, and can be expressed by the following formula, and each value used for calculation can be measured by NMR method.
Unsaturation (%) = (Number of unsaturated bonds excluding aromatic groups in the molecule / total number of carbon-carbon bonds in the molecule) × 100
In the present invention, this value needs to be 10% or less. If it exceeds 10%, it causes sludge and clogged capillaries. From this point, in the present invention, the degree of unsaturation is preferably 5% or less, more preferably 1% or less, and particularly preferably 0.1% or less.

In the present invention, the base oil of component (B) has a kinematic viscosity at 100 ° C. of 5 mm ² / s or more. When the kinematic viscosity is less than 5 mm ² / s, the sealing performance and the lubricating performance are deteriorated, which is not preferable. From such a viewpoint, the viscosity range is preferably 10 mm ² / s or more, and more preferably ²⁰ to 500 mm ² / s.
Various components can be used as the component (B) used in the present invention. Preferably, highly refined mineral oil, alkylbenzene, alkylnaphthalene or poly-α-olefin is selected from the above-mentioned non-aromatic unsaturation degree and Used in the kinematic viscosity range.

  Specific examples of such highly refined mineral oils include, for example, distillates obtained by atmospheric distillation of paraffinic crude oil, intermediate crude oil or naphthenic crude oil, or by distillation of atmospheric residue oil under reduced pressure. Examples thereof include refined oil obtained by refining oil according to a conventional method, deep dewaxed oil obtained by further deep dewaxing after refining, and hydrotreated oil obtained by hydrotreating. . There are no particular limitations on the purification method at that time, and various methods can be used.

  Usually, (a) hydrogenation treatment, (b) dewaxing treatment (solvent dewaxing or hydrodewaxing), (c) solvent extraction treatment, (d) alkali distillation or sulfuric acid washing treatment, (e) clay treatment alone Or in combination in an appropriate order. It is also effective to repeat the same process in multiple stages. For example, a method in which the distillate is hydrotreated or hydrotreated, and then subjected to alkali distillation or sulfuric acid washing treatment, a method in which the distillate is hydrotreated and then dewaxed, and the distillate is treated with a solvent. After the extraction treatment, a method of hydrotreating, a method of subjecting the distillate to a two-stage or three-stage hydrotreating, or a subsequent alkali distillation or sulfuric acid washing treatment, and further after the treatment as described above There is a method of dewaxing again to make a deep dewaxed oil. Among the above methods, as the highly refined mineral oil used in the present invention, mineral oil obtained by deep dewaxing is preferable from the viewpoints of low temperature fluidity and no wax precipitation at low temperatures. This deep dewaxing process is performed by a solvent dewaxing process under severe conditions, a contact dewaxing process using a zeolite catalyst, or the like.

In addition, as the alkylbenzene used as the base oil in the present invention, any alkylbenzene conventionally used in refrigerating machine oil and the like can be used, but those having higher viscosity are preferably used in the present invention.
There are various types of such high-viscosity alkyl benzenes. Alkyl benzenes (monoalkyl benzene, dialkyl benzene, Trialkylbenzene), preferably having a total carbon number of 20 or more and having 2 or more alkyl groups (such as dialkylbenzene) is preferably used from the viewpoint of thermal stability. The high-viscosity alkylbenzene may be a single type or a mixture of two or more types as long as the kinematic viscosity falls within the above range.

  Furthermore, as the alkyl naphthalene used as the base oil, one in which two or three alkyl groups are bonded to the naphthalene ring is preferably used. In particular, such an alkylnaphthalene is more preferably one having a total carbon number of 20 or more from the viewpoint of thermal stability. In the present invention, these alkyl naphthalenes may be used alone or in combination.

  In addition, various poly-α-olefins used as the base oil in the present invention can be used, but usually they are α-olefin polymers having 8 to 18 carbon atoms. Among them, preferred is a 1-dodecene, 1-decene or 1-octene polymer in terms of thermal stability, sealing properties, lubricity and the like. In the present invention, as the poly-α-olefin, the hydrotreated product is particularly preferably used from the viewpoint of thermal stability. These poly-α-olefins may be used alone or in combination.

  In the present invention, among the above base oils, highly refined mineral oil can be preferably used from the viewpoint that the degree of unsaturation can be controlled by the price and the degree of refinement. In this invention, about the usage-amount of the hydrocarbon refrigerant of said (A) component, and the base oil of (B) component, it is the range of 99/1-10/90 by the weight ratio of (A) component / (B) component. Preferably there is. When the amount of the component (A) is less than the above range, the refrigerating capacity may be lowered, and when it is more than the above range, the lubricating performance may be lowered, which is not preferable. From such a viewpoint, the weight ratio of the component (A) / (B) is more preferably in the range of 95/5 to 30/70.

  The lubricating oil composition for refrigerating machines of the present invention includes various known additives as necessary, such as phosphate esters such as tricresyl phosphate (TCP) and phosphite esters such as trisnonylphenyl phosphite. Pressure agent; Phenolic and amine antioxidants; Stabilizers such as phenylglycidyl ether, cyclohexene oxide and epoxidized soybean oil; Copper deactivators such as benzotriazole and its derivatives; Silicone oil and fluorinated silicone oil An antifoaming agent or the like can be appropriately blended. Furthermore, load bearing additives, chlorine scavengers, detergent dispersants, viscosity index improvers, oiliness agents, rust inhibitors, corrosion inhibitors, pour point depressants, and the like can be added as desired. These additives are usually contained in the composition of the present invention in an amount of 0.5 to 10% by weight.

The lubricating oil composition of the present invention can be used in various refrigerators. In particular, the present invention can be applied to a compression refrigeration cycle of a compression type refrigerator, and can be preferably applied to a normal compression refrigeration cycle including a compressor-condenser-expansion valve-evaporator as shown in FIG. That is, the second invention of the present application is (A) a refrigerant mainly composed of a hydrocarbon having 1 to 8 carbon atoms, and (B) a non-aromatic unsaturation degree of 10% or less and a dynamic behavior at 100 ° C. A method for lubricating a compression type refrigerator, comprising using a lubricating oil composition for a refrigerator containing a base oil composed of a hydrocarbon compound having a viscosity of 5 mm ² / s or more.
As the lubricating oil having such characteristics, the above-mentioned highly refined mineral oil, alkylbenzene, alkylnaphthalene or poly-α-olefin is preferably mentioned.

EXAMPLES Next, although an Example demonstrates this invention further more concretely, this invention is not limited at all by these examples.
Examples 1 to 7 and Comparative Examples 1 and 2
Each of the base oils having the properties shown in Table 1 was subjected to an actual machine test and evaluated by the following method. The results are shown in Table 1.

(1) Method of compression refrigeration cycle In the compression refrigeration cycle of a normal "compressor-condenser-expansion valve-evaporator" (see FIG. 1), an expansion valve of the capillary tube type was used.
(2) Actual machine test For the above-mentioned refrigerator with an output of 100 W, as a refrigerant, a refrigeration test was conducted for one year under the following conditions at a ratio of 70% by weight of a propane-isobutane mixture at a molar ratio of 1: 1 and 30% by weight of lubricating oil. Carried out.
(Operating status) Inhalation temperature: 0 ° C
Discharge temperature: 100 ° C
Condenser outlet temperature: 10 ° C
(Evaluation method) When an abnormality occurred in the driving state, the operation was stopped, and each part was observed to investigate the cause.

* 1: Base oil obtained by deep dewaxing and hydrogenation of paraffinic mineral oil * 2: Base oil obtained by deep dewaxing and hydrogenation of paraffinic mineral oil * 3: Base obtained by deep dewaxing and hydrogenation of paraffinic mineral oil Oil * 4: Base oil obtained by solvent refining of paraffinic mineral oil * 5: Base oil treated with hydrogenated alkyl benzene and clay treated * 6: Base oil treated with hydrogenated alkyl naphthalenes and clay treated * 7: 1-decene polymerization * 8: Base oil obtained by deep dewaxing and hydrotreating paraffinic mineral oil * 9: Base oil obtained by solvent purification of naphthenic mineral oil

  The present invention provides a lubricating oil composition for a refrigerator that is effectively applied in a compression refrigeration cycle using a refrigerant mainly composed of a hydrocarbon having 1 to 8 carbon atoms, and a lubricating method using the composition. To do.

It is a flowchart of the compression-type refrigeration cycle of "compressor-condenser-expansion valve-evaporator".

Explanation of symbols

1: Compressor 2: Condenser 3: Expansion valve 4: Evaporator

Claims (2)

(A) a refrigerant mainly composed of a hydrocarbon having 1 to 8 carbon atoms, and (B) a non-aromatic unsaturation degree of 1 % or less and a kinematic viscosity at 100 ° C. of 5 mm ² / s or more. Lupo Li -α- olefin down or Ranaru base oil, refrigeration lubricant composition characterized in that it contains. (A) a refrigerant mainly composed of a hydrocarbon having 1 to 8 carbon atoms, and (B) a non-aromatic unsaturation degree of 1 % or less and a kinematic viscosity at 100 ° C. of 5 mm ² / s or more. Lupo Li -α- olefin down or Ranaru base oil, lubrication of compression type refrigerator which comprises using a lubricating oil composition for refrigerator containing.

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