EP3476924A1

EP3476924A1 - Grease for refrigerating machine oil

Info

Publication number: EP3476924A1
Application number: EP18202619.5A
Authority: EP
Inventors: Norihisa Horaguchi
Original assignee: Mitsubishi Heavy Industries Thermal Systems Ltd
Current assignee: Mitsubishi Heavy Industries Thermal Systems Ltd
Priority date: 2017-10-27
Filing date: 2018-10-25
Publication date: 2019-05-01
Anticipated expiration: 2038-10-25
Also published as: JP2019081817A; JP7044514B2; EP3476924B1

Abstract

Provided is a grease for a refrigerating machine oil which is difficult to be compatible with a refrigerant and hardly flows into the refrigerant. The grease for a refrigerating machine oil includes a hydrocarbon oil, a resin having a melting point of 270°C or lower, and in which an unworked penetration is 100 to 340 at 25°C.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a grease for a refrigerating machine oil.

Description of Related Art

In a refrigeration cycle, a refrigerant circulates while repeatedly changing from a liquid to a gas and from a gas to a liquid. A compressor for compressing the refrigerant is disposed in a circulation line through which the refrigerant circulates.
The refrigerating machine oil for lubricating is contained in the compressor. For example, Patent Document 1 discloses a refrigerating compressor using at least one of an ester oil, an ether oil, and a carbonate oil as a refrigerating machine oil.
The refrigerating machine oil is easily dissolved in a refrigerant. The refrigerant in which the refrigerating machine oil is dissolved is discharged from the compressor and circulates in the refrigerating cycle. At this time, a part of the refrigerating machine oil dissolved in the refrigerant precipitates and adheres to a pipe wall, a heat exchanger, or the like in the refrigeration cycle, so as to form an oil film. As a result, the thermal conductivity is decreased and the heat exchange capability is decreased in some cases.
Here, in recent years, the refrigerating machine oil which is hardly soluble in a refrigerant has been used.

Citation List

Patent Literature

[PTL1] Japanese Unexamined Patent Application, First Publication No. 9-303278

SUMMARY OF THE INVENTION

However, even if the refrigerating machine oil that is hardly soluble in the refrigerant is used, the refrigerating machine oil may flow along with the flow of the refrigerant and may be discharged from the compressor together with the refrigerant. As a result, the refrigerating machine oil adheres to the pipe wall, the heat exchanger, or the like in the refrigeration cycle so as to form an oil film, and thereby the heat exchange capacity is deteriorated.
If an oil separator is provided on the discharge port side of the compressor and the refrigerant discharged from the compressor is separated from the refrigerating machine oil, the formation of the oil film on the pipe wall, the heat exchanger, or the like can be suppressed, but it causes a large refrigerating cycle.
For this reason, the refrigerating machine oil is required to be hardly soluble in the refrigerant and hardly flow into the refrigerant.
The present invention provides a grease for a refrigerating machine oil which is hardly soluble in a refrigerant and hardly flows into the refrigerant.

Solution to Problem

A grease for a refrigerating machine oil according to an aspect of the present invention includes a hydrocarbon oil and a resin having a melting point of 270°C or lower, in which an unworked penetration is 100 to 340 at 25°C.
According to the above configuration, a hydrocarbon oil which is a base oil and a resin having a melting point of 270°C or lower which is a thickener, in which an unworked penetration is 100 to 340 at 25°C, are included. For this reason, the grease for a refrigerating machine oil of this embodiment is hardly compatible with a refrigerant, and hardly flows into the refrigerant. Therefore, it is difficult for the refrigerating machine oil to be discharged from the compressor, and it is possible to prevent the refrigerating machine oil from adhering to a pipe wall, a heat exchanger, or the like in a refrigeration cycle so as to form an oil film. As a result, it is possible to maintain favorable thermal conductivity and to suppress the deterioration of the heat exchange capacity.
In addition, since the grease for a refrigerating machine oil of this embodiment is not easily discharged from the compressor, there is no need to provide an oil separator in the refrigerating cycle. Therefore, it is possible to suppress an increase in the size of the refrigeration cycle and an increase in the number of parts.
In addition, the compressor using the grease for a refrigerating machine oil of this embodiment is like an oil-less compressor since the grease for a refrigerating machine oil is hardly discharged.
Also, it is preferable for the kinematic viscosity of the hydrocarbon oil to be 20,000 mm²/s or more at 40°C and the content of the resin to be 4% to 10% by mass.
According to the above configuration, when a hydrocarbon oil having a kinematic viscosity of 20,000 mm²/s or higher at 40°C is used, the content of the resin having a melting point of 270°C or lower with respect to the total mass of the grease for the refrigerating machine oil is set to 4% to 10 mass %, and thereby it hardly flows with the refrigerant while maintaining an appropriate viscosity as a refrigerating machine oil.
Also, it is preferable for the kinematic viscosity of the hydrocarbon oil to be less than 20,000 mm²/s at 40°C and the content of the resin to be 5% to 15% by mass.
According to the above configuration, when a hydrocarbon oil having a kinematic viscosity of lower than 20,000 mm²/s at 40°C is used, the content of the resin having a melting point of 270°C or lower with respect to the total mass of the grease for the refrigerating machine oil is set to 5% to 15 mass %, and thereby it hardly flows with the refrigerant while maintaining an appropriate viscosity as a refrigerating machine oil.
The grease for a refrigerating machine oil of the invention is hardly soluble in a refrigerant and hardly flows into the refrigerant.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, an embodiment of a grease for a refrigerating machine oil according to the present invention will be described in detail.
The grease for a refrigerating machine oil of this embodiment includes a hydrocarbon oil and a resin having a melting point of 270°C or lower (hereinafter, also referred to as "resin (A)").

The hydrocarbon oil serves as a base oil and assumes a liquid state at 25°C.
When the grease for a refrigerating machine oil contains the hydrocarbon oil, the refrigerating machine oil becomes less soluble in refrigerant. In addition, since a viscous oil film is formed on a sliding surface and a stress acting on the sliding surface can be alleviated, the grease for a refrigerating machine oil is excellent in lubricity.
The hydrocarbon oil may be chain (acyclic) or cyclic. An aliphatic hydrocarbon oil is preferable, and a chain hydrocarbon oil is more preferable in view of the fact that it is difficult to be compatible with the refrigerant and hardly flows into the refrigerant.
As the chain type hydrocarbon oil, an olefin-based polymer can be exemplified. Examples of the olefin-based polymer include a homopolymer or a copolymer of olefin having 4 to 10 carbon atoms. Examples of the olefin include 1-butene, 2-butene, isobutylene, isoprene, 4-methyl-1-pentene, 1,5-hexadiene, and 1,9-decadiene.
As the chain type hydrocarbon oil, a polymer having a unit represented by General Formula (1) (hereinafter, also referred to as "polymer (a)") is preferable.

-(CH₂-C(CH₃)₂)-... (1)
As the polymer (a), a copolymer of isobutylene homopolymer (that is, polyisobutylene), a monomer copolymerizable with isobutylene (hereinafter, also referred to as "monomer (x)") and isobutylene can be used. That is, the polymer (a) may further have a unit derived from the monomer (x).
Examples of the monomer (x) include ones other than isobutylene among the olefins exemplified as described above. Among them, 1-butene, 2-butene, and isoprene are preferable.
The cyclic hydrocarbon oil is preferably a polymer having a cyclic structure and having a unit represented by General Formula (1) (hereinafter, also referred to as "polymer (b)").
Examples of the polymer (b) include a copolymer of isobutylene and a monomer copolymerizable with isobutylene and having a cyclic structure (hereinafter, also referred to as "monomer (y)"), and a copolymer of the monomer (y), the monomer (x), and isobutylene. That is, the polymer (a) may further have a unit derived from the monomer (y) and a unit derived from the monomer (x).
Examples of the monomer (y) include divinyl benzene, styrene, 2-methyl styrene, 3-methyl styrene, 4-methyl styrene, α-methyl styrene, β-methyl styrene, 3,5-dimethyl styrene, and 2,4-dimethyl styrene.
These hydrocarbon oils may be used alone or two or more kinds thereof may be used in combination.
The kinematic viscosity of the hydrocarbon oil is preferably 100 to 50,000 mm²/s at 40°C, is more preferably 1000 to 30,000 mm²/s at 40°C, and is still more preferably 1,500 to 25,000 mm²/s at 40°C. When the kinematic viscosity of the hydrocarbon oil is 100 mm²/s or higher, abrasion resistance of the grease for a refrigerating machine oil can be favorably maintained. When the kinematic viscosity of the hydrocarbon oil is 50,000 mm²/s or lower, an excessive rise in the stickiness (viscosity) of the grease for a refrigerating machine oil can be suppressed, and the function as a lubricating oil of the compressor can be sufficiently exhibited.
The kinematic viscosity of the hydrocarbon oil is measured at a measurement temperature of 40°C based on JIS K 2283.
A number average molecular weight of the hydrocarbon oil is preferably 200 to 5,000, is more preferably 300 to 4,000, and is still more preferably 500 to 3,000.
The number average molecular weight of the hydrocarbon oil is measured according to a vapor pressure osmotic pressure method (VPO method).
The content of the hydrocarbon oil with respect to the total mass of the grease for a refrigerating machine oil is preferably 90% to 96% by mass, and is more preferably 93% to 96% by mass in a case where the kinematic viscosity is 20,000 mm²/s or higher at 40°C, is preferably 85% to 95% by mass, and is more preferably 90% to 95% by mass in a case where the kinematic viscosity is lower than 20,000 mm²/s at 40°C.
When the content of the hydrocarbon oil is within the above range, appropriate viscosity can be exhibited. Particularly, when the content of the hydrocarbon oil is equal to or more than the above lower limit value, the grease for a refrigerating machine oil is not excessively hardened, and can sufficiently exhibit a function as a lubricant of the compressor. In addition, the grease for a refrigerating machine oil can maintained excellent slidability. When the content of the hydrocarbon oil is equal to or lower than the above upper limit value, the grease for a refrigerating machine oil is not excessively flexible, and does not easily flow with the refrigerant.

A resin (A) serves as a thickener.
When the grease for a refrigerating machine oil contains the resin (A), the refrigerating machine oil is difficult to be compatible with the refrigerant due to the interaction with the hydrocarbon oil and hardly flows into the refrigerant. In addition, a moderate viscosity can be imparted to the grease for a refrigerating machine oil.
A melting point of the resin (A) is 270°C or lower, is preferably 200°C or lower, is more preferably 150°C or lower, and is still more preferably 120°C or lower. The grease for a refrigerating machine oil is normally manufactured by melting the resin (A) after mixing the resin oil (A) with the hydrocarbon oil, or mixing the resin oil (A) with the hydrocarbon oil after melting the resin (A). When the melting point of the resin (A) is 270°C or lower, the hydrocarbon oil hardly deteriorates when the resin (A) is melted. The lower limit of the melting point of the resin (A) is not particularly limited, but it is usually about 100°C.
Examples of the resin (A) include a polyethylene resin, a polypropylene resin, a polycarbonate resin, a polyethylene terephthalate resin, a polybutylene terephthalate resin, and a polyvinylidene fluoride resin. Among them, a polyethylene resin and a polypropylene resin are preferable in view of their excellent affinity with hydrocarbon oil and low oil separation degree.
These resins (A) may be used alone or two or more kinds thereof may be used in combination.
In a case where the kinematic viscosity of the hydrocarbon oil is 20,000 mm²/s or higher at 40°C, the content of the resin (A) with respect to the total content of the grease for a refrigerating machine oil is preferably 4% to 10% by mass, and is more preferably 4% to 7% by mass.
In a case where the kinematic viscosity of the hydrocarbon oil is lower than 20,000 mm²/s at 40°C, the content of the resin (A) with respect to the total content of the grease for a refrigerating machine oil is preferably 5% to 15% by mass, and is more preferably 5% to 10% by mass.
When the content of the resin (A) is within the above range, appropriate viscosity can be exhibited in the grease. Particularly, when the content of the resin (A) is equal to or greater than the above lower limit value, the grease for a refrigerating machine oil is not excessively flexible, and does not easily flow with the refrigerant. When the content of the resin (A) is equal to or lower than the above upper limit value, the grease for a refrigerating machine oil is not excessively hardened, and can sufficiently exhibit a function as a lubricant of the compressor. In addition, the grease for a refrigerating machine oil can maintained excellent slidability.

The grease for a refrigerating machine oil of the present invention may be formed of the hydrocarbon oil and the resin (A), or may contain components (optional components) other than the hydrocarbon oil and the resin (A).
As optional components, various additives such as a lubricant, an antioxidant, an acid scavenger, and a metal deactivator can be mentioned.
Examples of the lubricant include a phosphate ester compound such as mono-m or p-toluyl-diphenyl phosphate, di-m or p-toluyl-monophenyl phosphate, tri-m or p-toluyl phosphate (tricresyl phosphate (TCP)), mono-m or p-toluyl-dixylenyl phosphate, di-m or p-toluyl-monoxylenyl phosphate, mono-m or p-toluyl-dixylenyl phosphate, di-m or p-toluyl-monoxylenyl phosphate, tris(m or p-tert-butyl phenyl)-phosphate, bis-(m or p-tert-butylphenyl)-mono-phenyl phosphate, mono-(m or p-tert-butylphenyl)-diphenyl phosphate, triphenyl phosphate (TPP)), trixylenyl phosphate, monophenyl-dixylenyl phosphate, diphenyl-monoxylenyl phosphate, monobutyl thiophate, dibutyl thiophate or tributyl thiophate (these are abbreviated as "mono/di/tributyl thiophate", the same applies hereinafter), mono/di/trihexyl thiophosphate, mono/di/trioctyl thiophosphate, mono/di/tri (2-ethylhexyl) thiophosphate, mono/di/trinonyl thiophosphate, mono/di/tridecyl thiophosphate, mono/di/trilauryl thiophosphate, mono/di/trimyristyl thiophosphate, mono/di/tripalmityl thiophosphate, mono/di/tristearyl thiophosphate, and mono/di/trioleyl thiophosphate.
These lubricants may be used alone or two or more kinds thereof may be used in combination.
Examples of the antioxidant include phenolic antioxidants such as 2,6-di-tert-butyl hydroxytoluene (BHT), 4,4'-methylenebis (2,6-di-tert-butyl hydroxytoluene), 2,2'-methylenebis (4-methyl-6-tert-butyl phenol), 3,5-di-tert-butyl-4-hydroxy phenyl propionic acid 2-ethyl hexyl ester, 3-tert-butyl-4-hydroxy-5-methylphenyl propionic acid 2-ethyl hexyl ester, 3,5-di-tert-butyl-4-hydroxyphenyl propionic acid tridecyl ester, 3-tert-butyl-4-hydroxy-5-methyl phenyl propionic acid tridecyl ester, 3,5-di-tert-butyl-4-hydroxyphenyl propionic acid stearyl ester, 3-tert-butyl-4-hydroxy-5-methylphenyl propionic acid stearyl ester, bis(3,5-di-tert-butyl-4-hydroxyphenylpropionic acid)-triglycol ester, bis(3-tert-butyl-4-hydroxy-5-methyl phenyl propionic acid)-triglycol ester, and 2,5-tert-amyl hydroquinone.
These antioxidants may be used alone or two or more kinds thereof may be used in combination.
Examples of the acid scavenger include a glycidyl ester compound or a glycidyl ether compound (hereinafter, these are collectively referred to as "epoxy-based acid scavengers") such as butyl glycidyl ether, butyric acid glycidyl ester, hexyl glycidyl ether, hexanoic acid glycidyl ester, 2-ethyl hexyl glycidyl ether, 2-ethyl hexanoic acid glycidyl ester, neopentyl glycidyl ether, pivalic acid glycidyl ester, decyl glycidyl ether, decanoic acid glycidyl ester, stearyl glycidyl ether, stearic acid glycidyl ester, oleyl glycidyl ether, oleic acid glycidyl ester, phenyl glycidyl ether, benzoic acid glycidyl ester, toluyl glycidyl ether, xylenyl glycidyl ether, tert-butyl phenyl glycidyl ether, phthalic acid glycidyl ester, and oxacyclohexyl methyl oxacyclohexyl carboxylic acid ester.
These acid scavengers may be used alone or two or more kinds thereof may be used in combination.
Examples of the metal deactivator include a benzotriazole-based compound such as 1 H-benzotriazole, 4-methyl benzotriazole, 5-methyl benzotriazole, benzotriazole-1-methylamine,4-methyl benzotriazole-1-methylamine, 5-methyl benzotriazole-1-methylamine, N-methyl benzotriazole-1-methylamine, N-ethyl benzotriazole-1-methylamine, N,N-dimethyl benzotriazole-1-methylamine, N,N-diethyl benzotriazole-1-methylamine, N,N-dipropyl benzotriazole-1-methylamine, N,N-dibutyl benzotriazole-1-methylamine, N,N-dihexyl benzotriazole-1-methylamine, N,N-dioctyl benzotriazole-1-methylamine, N, N-bis(2-ethyl hexyl)-benzotriazole-1-methylamine, N,N-dimethyl-4-benzotriazole-1-methylamine, N,N-dimethyl-5-benzotriazole-1-methylamine, N,N-diethyl-4-benzotriazole-1-methylamine, N,N-diethyl-5-benzotriazole-1-methy lamine, N,N-dipropyl-4-benzotriazole-1-methylamine, N,N-dipropyl-5-benzotriazole-1-methylamine, N,N-dibutyl-4-benzotriazole-1-methylamine, N,N-dibutyl-5-benzotriazole-l-methylamine, N,N-dihexyl-4-benzotriazole-1-methylamine, N,N-dihexyl-5-benzotriazole-1-methylamine, N,N-bis (2-ethylhexyl)-4-methyl benzotriazole-1-methylamine, N,N-bis(2-ethyl hexyl)-5-methyl benzotriazole-1-methylamine, N,N-dioleyl-4-methyl benzotriazole-1-methylamine, N,N-dioleyl-5-methyl benzotriazole-1-methylamine, N,N-distearyl-4-methyl benzotriazole-1-methylamine, and N,N-distearyl-5-methyl benzotriazole-1-methylamine; derivatives thereof; and mixtures thereof.
These metal deactivators may be used alone or two or more kinds thereof may be used in combination.
The content of the optional components for the total mass of the grease for a refrigerating machine oil is preferably 10% by mass or less, and is more preferably 7% by mass or less. When the content of the optional components is 10% by mass or less, it hardly precipitates from the grease for a refrigerating machine oil.

The unworked penetration of the grease for a refrigerating machine oil at 25°C is 100 to 340. When the unworked penetration of the grease for a refrigerating machine oil is 100 or higher, the grease for a refrigerating machine oil is not excessively hardened, and can sufficiently exhibit a function as a lubricant of the compressor. In addition, the grease for a refrigerating machine oil can maintained excellent slidability. When the unworked penetration of the grease for a refrigerating machine oil is 340 or lower, the grease for a refrigerating machine oil is not excessively flexible, and does not easily flow with the refrigerant. The unworked penetration of the grease for a refrigerating machine oil is preferably 150 or higher, is more preferably 200 or higher, and is further preferably 250 or higher.
The unworked penetration of the grease for a refrigerating machine oil can be adjusted by the physical properties (particularly, the kinematic viscosity) of the hydrocarbon oil, or the content of the resin (A). Specifically, as the kinematic viscosity of the hydrocarbon oil becomes higher, the unworked penetration tends to be lower. In addition, as the content of the resin (A) is increased, the unworked penetration tends to be lower.
The unworked penetration of the grease for a refrigerating machine oil is measured at a measurement temperature of 25°C based on JIS K 2220.

The grease for a refrigerating machine oil can be manufactured, for example, as follows.
First, the hydrocarbon oil, the resin (A), and optionally optional components are mixed. Next, the mixture is heated to a temperature not lower than the melting point of the resin (A) so as to melt the resin (A) in the mixture, thereby obtaining a grease for a refrigerating machine oil.
The optional components may be added to the mixture after melting the resin (A). Alternatively, the resin (A) may be melted in advance, and the molten resin (A), the hydrocarbon oil, and if necessary, the optional components may be mixed.
A temperature at which the resin (A) is melted is not particularly limited as long as it is not lower than the melting point of the resin (A), but from the viewpoint of suppressing deterioration of the hydrocarbon oil, the upper limit is preferably the melting point of the resin (A) + 10°C.

According to the grease for a refrigerating machine oil of this embodiment described above, the grease for a refrigerating machine oil contains the hydrocarbon oil and the resin (A), in which the unworked penetration is 100 to 340 at 25°C, and thus is hardly soluble in the refrigerant and hardly flows into the refrigerant. Therefore, it is difficult for the grease for a refrigerating machine oil of this embodiment to be discharged from the compressor, and it is possible to prevent the grease for a refrigerating machine oil from adhering to a pipe wall, a heat exchanger, or the like in a refrigeration cycle so as to form an oil film. As a result, it is possible to maintain the thermal conductivity favorably and to suppress the deterioration of the heat exchange capacity.
In addition, since the grease for a refrigerating machine oil of this embodiment is not easily discharged from the compressor, there is no need to provide an oil separator in the refrigerating cycle. Therefore, it is possible to suppress an increase in the size of the refrigeration cycle and an increase in the number of parts.
In addition, the compressor using the grease for a refrigerating machine oil of this embodiment is like an oil-less compressor since the grease for a refrigerating machine oil is hardly discharged.
Further, in a case where the kinematic viscosity of the hydrocarbon oil is 20,000 mm²/s or higher at 40°C, when the content of the resin (A) is 4% to 10% by mass, it hardly flows with the refrigerant while maintaining an appropriate viscosity as a refrigerating machine oil.
Further, in a case where the kinematic viscosity of the hydrocarbon oil is lower than 20,000 mm²/s at 40°C, when the content of the resin (A) is 5% to 15% by mass, it hardly flows with the refrigerant while maintaining an appropriate viscosity as a refrigerating machine oil.

The grease for a refrigerating machine oil of the present invention is suitable for a refrigerating machine oil of the compressor.

[Examples]

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

"Measurement and evaluation"

The unworked penetration of the grease for a refrigerating machine oil was measured at a measurement temperature of 25°C based on JIS K 2220.

The viscosity of the grease for a refrigerating machine oil is measured at measurement temperature 25°C by using a B-type viscosity based on JIS Z 8803.

The incompatibility of the grease for a refrigerating machine oil is measured as follows based on JIS K 2211.
The grease for a refrigerating machine oil was applied in a lump to the inside of a container by using a hyperglass cylinder (a pressure-resistant container provided with an observation window). The part to which it was applied was one side of the container and the part without the observation window.
Subsequently, the hydrofluorocarbon was charged as a refrigerant into the container to half the height of the container, and then the container was hermetically closed.
After shaking the container for one minute, it was visually confirmed from the observation window whether or not the lump of the grease for a refrigerating machine oil was dissolved in the refrigerant, and incompatibility was evaluated according to the following evaluation criteria. A represents "success".
A: The lump of the grease for a refrigerating machine oil is not dissolved in the refrigerant.
C: The lump of the grease for a refrigerating machine oil is dissolved in the refrigerant.

In the same manner as that in the evaluation of incompatibility, the grease for a refrigerating machine oil was applied in a lump to the container, and the container was sealed after charging the refrigerant.
After shaking the container for one minute, when the container was held and rotated by hand to flow the refrigerant, it was visually confirmed from the observation window whether or not the lump of the grease for a refrigerating machine oil flowed together with the refrigerant so as to evaluate a difficulty in the flow (non-flowability) of the grease for a refrigerating machine oil based on the following evaluation criteria. Also, the softness of the grease for a refrigerating machine oil was checked by touching it with a finger. A represents "success".
A: The lump of the grease for a refrigerating machine oil does not flow together with the refrigerant, and the grease for a refrigerating machine oil has appropriate softness.
C1: The lump of the grease for a refrigerating machine oil flows together with the refrigerant.
C2: Although the lump of the grease for a refrigerating machine oil does not flow together with the refrigerant, the grease for a refrigerating machine oil is hardened and has a waxy shape.

The grease for a refrigerating machine oil was applied in a lump to a glass plate, and the slidability was evaluated by the feeling the applied grease for a refrigerating machine oil with a finger while rubbing it based on the following evaluation criteria. A represents "success", and B is determined as having no practical problem.

A: No resistance is felt.
B: Slight resistance is felt.
C: Resistance is felt.

Based on the results of the evaluation of the incompatibility, the evaluation of the flow difficulty, and the evaluation of the slidability, evaluation was performed based on the following evaluation criteria. A represents "success", and B is determined as having no practical problem.

A: All evaluations are A.
B: The evaluation of the incompatibility and the evaluation of the flow difficulty are "A" and the evaluation of the slidability is "B".
C: In each evaluation, there are one or more C's.

"Example 1"

As a hydrocarbon oil, a polymer (a1) having a unit represented by the General Formula (1) (trade name "NOF POLYBUTENE EMAWET (registered trademark) 30N" prepared by NOF CORPORATION, kinematic viscosity (40°C) of 24,000 mm²/s, and number average molecular weight (Mn) of 1,350) was used.
A bead-like polyethylene resin (PE) (melting point: 92°C to 127°C, specific gravity: 0.88 to 0.97) having a long diameter of about 2 mm was used as the resin (A).
According to the blend composition indicated in Table 1, after mixing the hydrocarbon oil and the resin (A), the obtained mixture was heated to 130°C so as to melt the resin (A) in the mixture, thereby obtaining a grease for a refrigerating machine oil.
Regarding the obtained grease for a refrigerating machine oil, the unworked penetration and the viscosity were measured so as to evaluate the incompatibility, the flow difficulty (non-flowability), and the slidability. The results are indicated in Table 1.

"Examples 2 to 7"

The grease for a refrigerating machine oil was manufactured in the same manner as that used in Example 1 for various measurements and evaluations except that the composition was changed so as to have the composition indicated in Table 1, and various measurements and evaluations were performed. The results are indicated in Table 1.

"Examples 8 to 10"

The grease for a refrigerating machine oil was manufactured in the same manner as that used in Example 1 for various measurements and evaluations except that the composition was changed so as to have the composition indicated in Table 2 by using the polymer (a1) having a unit represented by the General Formula (1) (trade name "NOF POLYBUTENE EMAWET (registered trademark) 3N" prepared by NOF CORPORATION, kinematic viscosity (40°C) of 21,000 mm²/s, and number average molecular weight of 720) as the hydrocarbon oil. The results are indicated in Table 2.

"Comparative Examples 1 to 3"

The grease for a refrigerating machine oil was manufactured in the same manner as that used in Example 1 for various measurements and evaluations except that the composition was changed so as to have the composition indicated in Table 3, and various measurements and evaluations were carried out. The results are indicated in Table 3.

"Comparative Example 4"

As a hydrocarbon oil, a polymer (a2) having a unit represented by the General Formula (1) (trade name "NOF POLYBUTENE EMAWET (registered trademark) 3N" prepared by NOF CORPORATION, kinematic viscosity (40°C) of 2,100 mm2/s, and number average molecular weight of 720) was used.
Silica (a particle diameter of 5 to 50 nm and a specific gravity of 2.2) was used instead of the resin (A).
In accordance with the blend composition indicated in Table 3, the hydrocarbon oil and silica were mixed so as to obtain the grease for a refrigerating machine oil. The obtained grease for a refrigerating machine oil was heated and defoamed at 130°C for 60 minutes or longer.
The immiscibility consistency and the viscosity of the grease for a refrigerating machine oil before and after heating and defoaming were measured. The results are indicated in Table 3. Note that, in Table 3, the unworked penetration and the viscosity of the grease for a refrigerating machine oil before heating and defoaming are indicated in an upper row of a column of the unworked penetration and the viscosity, and the unworked penetration and the viscosity of the grease for a refrigerating machine oil after heating and defoaming are indicated in a lower row.
In addition, after heating and defoaming the grease for a refrigerating machine oil, the unworked penetration and the viscosity were measured so as to evaluate the incompatibility, the flow difficulty (non-flowability), and the slidability. The results are indicated in Table 3.
As is apparent from the results of Tables 1 and 2, the grease for a refrigerating machine oil obtained in each example was difficult to be compatible with a refrigerant and hardly flowed into the refrigerant. It was also excellent in slidability.
On the other hand, as is apparent from the results in Table 3, the grease for a refrigerating machine oil obtained in Comparative Examples 1 and 2 in which the unworked penetration degree was more than 340 was apt to flow into the refrigerant.
The grease for a refrigerating machine oil obtained in Comparative Example 3, which had an unworked penetration of less than 100, did not flow with the refrigerant, but had a waxy shape, and was unsuitable as a refrigerating machine oil.
The grease a for a refrigerating machine oil obtained in Comparative Example 4 in which silica was used instead of the resin (A) was apt to flow into the refrigerant.
In the case of Comparative Examples 1, 2, and 4, since it was easy for the grease for a refrigerating machine oil to flow into the refrigerant, it was determined that the evaluation for the slidability was unnecessary and thus it was not performed.

[Industrial Applicability]

According to the present invention, it is possible to provide a grease for a refrigerating machine oil which is difficult to be compatible with a refrigerant and hardly flows into the refrigerant.

Claims

A grease for a refrigerating machine oil, comprising:
a hydrocarbon oil; and

a resin having a melting point of 270°C or lower,

wherein an unworked penetration is 100 to 340 at 25°C.
The grease for a refrigerating machine oil according to Claim 1,
wherein a kinematic viscosity of the hydrocarbon oil is 20,000 mm²/s or more at 40°C and a content of the resin is 4% to 10% by mass.
The grease for a refrigerating machine oil according to Claim 1,
wherein a kinematic viscosity of the hydrocarbon oil is less than 20,000 mm²/s at 40°C and a content of the resin is 5% to 15% by mass.