JP6801929B2 - Selection method of refrigerating machine oil, composition for refrigerating machine, refrigerating machine and refrigerating machine oil - Google Patents

Description

The present invention relates to a method for selecting a refrigerator oil, a composition for a refrigerator, a refrigerator, and a refrigerator oil.

Generally, a refrigerator is composed of at least a compressor, a condenser, an expansion mechanism (expansion valve, etc.), an evaporator, a dryer, etc., and a mixed liquid of a refrigerant and a lubricating oil (refrigerator oil) is a sealed system. It has a structure that circulates inside.
Chlorofluorocarbons and other chlorine-containing compounds have been widely used as refrigerants for refrigerators, but since there is a risk of environmental pollution such as depleting the ozone layer, chlorine-free hydrofluorocarbons (HFCs) and hydrofluorocarbons (HFCs) are used. It is being replaced by natural refrigerants such as carbon dioxide.

As the refrigerating machine oil for chlorine-containing chlorofluorocarbon refrigerants, synthetic hydrocarbon oils such as mineral oil and alkylbenzene have been used. However, since these oils have low compatibility with CFC substitute refrigerants, it has become difficult to fully exhibit their performance as refrigerating machine oils.
For this reason, polyvinyl ethers, polyoxyalkylene glycols, polyol esters and the like are widely used as refrigerating machine oils in recent years (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2012-97638

In recent years, as the equipment has become more compact, the amount of refrigerating machine oil used in the equipment has been decreasing, and the conditions for using refrigerating machine oil have become harsher. ing. For example, due to frictional heat in the sliding part of the compressor, the refrigerating machine oil locally exposed to high temperature conditions is thermally decomposed, and the generated decomposition product corrodes the metal member or adversely affects the resin material. there is a possibility. For this reason, refrigerating machine oil is required to have higher stability than ever before.

Refrigerating machine oils containing compounds selected from polyvinyl ethers, polyoxyalkylene glycols, and polyol esters may have insufficient thermal and oxidative stability. However, Patent Document 1 does not examine the problem at all.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a refrigerating machine oil having excellent thermal stability and oxidative stability.

As a result of diligent studies, the present inventor has found a relationship between the colors of polyvinyl ethers, polyoxyalkylene glycols, and polyol esters at the time of synthesis and thermal stability and oxidative stability, and has completed the present invention. It was.

The present invention provides the following (1) to (4).
(1) A refrigerating machine oil containing at least one compound selected from the group consisting of polyvinyl ethers, polyoxyalkylene glycols, and polyol esters, and having a Hazen color number of 0 to 10 according to ASTM D1209-05.
(2) A composition for a refrigerator containing the refrigerating machine oil and the refrigerant of the above (1).
(3) A refrigerator containing the refrigerator oil according to (1) above or the composition for a refrigerator according to (2) above.
(4) The number of Hazen colors according to ASTM D1209-05 of refrigerating machine oil containing at least one compound selected from the group consisting of polyvinyl ethers, polyoxyalkylene glycols, and polyol esters was measured, and the number of Hazen colors was measured. A method for selecting a refrigerating machine oil, which selects a refrigerating machine oil satisfying the conditions of 0 to 10.

According to the present invention, it is possible to provide a refrigerator oil, a composition for a refrigerator and a refrigerator having excellent thermal stability and oxidative stability. Further, according to the present invention, a refrigerating machine oil having excellent thermal stability and oxidative stability can be easily selected.

Hereinafter, embodiments of the present invention will be described.
<Refrigerator oil>
The refrigerating machine oil of the present embodiment contains at least one compound selected from the group consisting of polyvinyl ethers, polyoxyalkylene glycols, and polyol esters, and has a Hazen color number of 0 to 10 according to ASTM D1209-05. Refrigerating machine oil.

An oil containing a compound selected from polyvinyl ethers, polyoxyalkylene glycols, and polyol esters (hereinafter, may be referred to as "oil X") has insufficient thermal stability and oxidative stability. There is. Conventionally, the cause of insufficient thermal stability and oxidative stability of oil X has not been sufficiently investigated.
As a result of diligent studies by the present inventor, among the oils X, an oil having a Hazen color number (APHA color) of 0 to 10 conforming to ASTM D1209-05 can improve thermal stability and oxidation stability. I found. Specifically, among oil X, oil having a Hazen color number of 0 to 10 can suppress deterioration of the oil in a high temperature environment, and therefore, an increase in the acid value of the oil, discoloration of the oil, and a metal Corrosion and the like can be suppressed. On the other hand, among the oils X, the oil having more than 10 Hazen colors cannot improve the thermal stability and the oxidative stability.
The reason why an oil having a Hazen color number exceeding 10 among oil X cannot improve thermal stability and oxidation stability is "a by-product in the process of synthesizing polyvinyl ethers, polyoxyalkylene glycols, and polyol esters. Is produced, coloring occurs due to by-products. "," Coloring is derived from unsaturated groups, carboxyl groups, ketone groups, aldehyde groups, alcohol groups, etc. contained in the by-products, and these groups It is considered that unpaired electron pairs resonate and color due to the presence of a plurality of esters in the molecule. "," By-products are easily altered by heat, etc., so if the oil contains by-products, it will be secondary. It is considered that the alteration of the product causes an increase in the acid value of the oil, discoloration of the oil, corrosion of the metal, and the like. " In other words, the Hazen color number of oil X is 0 to 10, which means that the proportion of by-products in the oil is small, and the low proportion of by-products is the thermal stability and oxidation stability of the oil. It is thought that it contributes to sex.
The proportion of by-products in oil having a Hazen color number of 0 to 10 is estimated to be less than 1% by mass.

The Hazen color number of the oil X is preferably 0 from the viewpoint of thermal stability and oxidative stability. The number of Hazen colors of 0 includes a case where the number is equal to or less than the detection limit by the measurement method based on ASTM D1209-05.

[Polyvinyl ethers (PVE)]
Polyvinyl ethers (PVE) are polymers having a structural unit derived from vinyl ether, and specific examples thereof include compounds having a structural unit represented by the following general formula (A-1). One type or two or more types of PVE can be used.

R ^1a , R ^2a and R ^3a in the general formula (A-1) independently represent a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, and they may be the same or different from each other. Here, as the hydrocarbon group, specifically, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, various pentyl groups, and various hexyl groups. Alkyl groups such as groups, various heptyl groups, various octyl groups; cycloalkyl groups such as cyclopentyl group, cyclohexyl group, various methylcyclohexyl groups, various ethylcyclohexyl groups, various dimethylcyclohexyl groups; phenyl group, various methylphenyl groups, various ethyls Aryl groups such as a phenyl group and various dimethylphenyl groups; arylalkyl groups such as a benzyl group, various phenylethyl groups and various methylbenzyl groups are mentioned, but an alkyl group is preferable.
Further, R ^1a , R ^2a and R ^3a are more preferably hydrogen atoms or alkyl groups having 3 or less carbon atoms, and most preferably all are hydrogen atoms.

R ^4a represents a divalent hydrocarbon group having 2 to 10 carbon atoms, and here, as the divalent hydrocarbon group having 2 to 10 carbon atoms, specifically, an ethylene group, a phenylethylene group, 1, 2-propylene group, 2-phenyl-1,2-propylene group, 1,3-propylene group, various butylene groups, various pentylene groups, various hexylene groups, various heptylene groups, various octylene groups, various nonylene groups, various decylene groups. Divalent aliphatic hydrocarbon groups such as: Alicyclic hydrocarbon groups having two bonding sites to alicyclic hydrocarbons such as cyclohexane, methylcyclohexane, ethylcyclohexane, dimethylcyclohexane, propylcyclohexane; various phenylene groups, Divalent aromatic hydrocarbon groups such as various methylphenylene groups, various ethylphenylene groups, various dimethylphenylene groups and various naphthylene; monovalent in the alkyl group portion and aromatic portion of alkyl aromatic hydrocarbons such as toluene and ethylbenzene, respectively. Alkyl aromatic hydrocarbon group having a bond site of; There is an alkyl aromatic hydrocarbon group having a bond site in the alkyl group portion of a polyalkyl aromatic hydrocarbon such as xylene and diethylbenzene. Of these, an aliphatic hydrocarbon group having 2 to 4 carbon atoms is more preferable. Further, the plurality of R ^4a O may be the same or different. Further, r in the general formula (A-1) indicates the number of repetitions, and the average value thereof is preferably 0 to 10, more preferably 0 to 5, and even more preferably 0 to 2.

Further, R ^5a in the general formula (A-1) represents a hydrocarbon group having 1 to 10 carbon atoms, and the hydrocarbon group is specifically a methyl group, an ethyl group, an n-propyl group or an isopropyl group. , N-butyl group, isobutyl group, sec-butyl group, tert-butyl group, various pentyl groups, various hexyl groups, various heptyl groups, various octyl groups, various nonyl groups, various decyl groups and other alkyl groups; cyclopentyl groups, Cycloalkyl groups such as cyclohexyl group, various methylcyclohexyl groups, various ethylcyclohexyl groups, various propylcyclohexyl groups, various dimethylcyclohexyl groups; phenyl group, various methylphenyl groups, various ethylphenyl groups, various dimethylphenyl groups, various propylphenyl groups , Various trimethylphenyl groups, various butylphenyl groups, various naphthyl groups and other aryl groups; benzyl groups, various phenylethyl groups, various methylbenzyl groups, various phenylpropyl groups, various phenylbutyl groups and other arylalkyl groups.
Among these, a hydrocarbon group having 1 to 8 carbon atoms is preferable, an alkyl group having 1 to 6 carbon atoms is more preferable, and an alkyl group having 1 to 3 carbon atoms is further preferable. The alkyl group may be linear, branched or cyclic.

Among the compounds having a structural unit represented by the general formula (A-1), R ^1a , R ^2a and R ^3a are all hydrogen atoms, r is 0, and R ^5a is an ethyl group or a methyl group. Those containing a certain structural unit are preferable. More specifically, it is preferable that R ^1a , R ^2a and R ^3a all contain a hydrogen atom, r is 0, and R ^5a contains an ethyl group or a methyl group in an amount of 50% by mass or more. Those containing 80% by mass or more are more preferable, and those containing 80% by mass or more are further preferable.

The PVE has a structural unit represented by the general formula (A-1), and the number of repetitions thereof may be appropriately selected according to the target kinematic viscosity. Further, PVE is obtained by homopolymerization of one kind of vinyl ether-based monomer represented by the following general formula (A-2) or copolymerization of two or more kinds of vinyl ether-based monomers represented by the following general formula (A-2). Can be synthesized.
In addition, when synthesized by a usual method, the number of Hazen colors of the obtained PVE exceeds 10. Therefore, it is preferable to carry out the hydrogenation reaction until the number of Hazen colors becomes 10 or less after the completion of the normal synthesis reaction. It is considered that the hydrogenation reaction hydrogenates unsaturated groups, carboxyl groups, ketone groups, aldehyde groups, alcohol groups and the like in the by-products, thereby enhancing thermal stability and oxidative stability.
The conditions of the hydrogenation reaction differ depending on the number of Hazen colors after the completion of the normal synthesis reaction, and therefore cannot be unconditionally stated. The condition is preferably 50 to 200 ° C.). In the hydrogenation reaction, as catalysts, metal catalysts such as nickel-based catalysts, platinum-based catalysts, palladium-based catalysts, and ruthenium-based catalysts, catalysts in which these metal catalysts are supported on alumina, diatomaceous earth, etc., laney-type catalysts, etc. It is preferable to use. The hydrogenation reaction of PAG and POE, which will be described later, has the same conditions.

(In the formula, R ^1a , R ^2a , R ^3a , R ^4a and R ^5a and r are the same as described above.)

As the vinyl ether-based monomer, there are various types corresponding to the compound having a structural unit represented by the general formula (A-1), and examples thereof include vinyl methyl ether, vinyl ethyl ether, vinyl-n-propyl ether, and the like. Vinyl isopropyl ether, vinyl-n-butyl ether, vinyl isobutyl ether, vinyl-sec-butyl ether, vinyl-tert-butyl ether, vinyl-n-pentyl ether, vinyl-n-hexyl ether, vinyl-2-methoxyethyl ether, vinyl- 2-ethoxyethyl ether, vinyl-2-methoxy-1-methylethyl ether, vinyl-2-methoxy-propyl ether, vinyl-3,6-dioxaheptyl ether, vinyl-3,6,9-trioxadecyl ether , Vinyl-1,4-dimethyl-3,6-dioxaheptyl ether, vinyl-1,4,7-trimethyl-3,6,9-trioxadecyl ether, vinyl-2,6-dioxa-4-heptyl Ether, vinyl-2,6,9-trioxa-4-decyl ether, 1-methoxypropene, 1-ethoxypropene, 1-n-propoxypropene, 1-isopropoxypropene, 1-n-butoxypropene, 1-iso Butoxypropene, 1-sec-butoxypropene, 1-tert-butoxypropene, 2-methoxypropene, 2-ethoxypropene, 2-n-propoxypropene, 2-isopropoxypropene, 2-n-butoxypropene, 2-iso Butoxypropene, 2-sec-butoxypropene, 2-tert-butoxypropene, 1-methoxy-1-butene, 1-ethoxy-1-butene, 1-n-propoxy-1-butene, 1-isopropoxy-1- Butene, 1-n-butoxy-1-butene, 1-isobutoxy-1-butene, 1-sec-butoxy-1-butene, 1-tert-butoxy-1-butene, 2-methoxy-1-butene, 2- Ethoxy-1-butene, 2-n-propoxy-1-butene, 2-isopropoxy-1-butene, 2-n-butoxy-1-butene, 2-isobutoxy-1-butene, 2-sec-butoxy-1 -Buten, 2-tert-butoxy-1-butene, 2-methoxy-2-butene, 2-ethoxy-2-butene, 2-n-propoxy-2-butene, 2-isopropoxy-2-butene, 2- n-butoxy-2-butene, 2-isobutoxy-2-butene, 2-sec-butoki Examples thereof include si-2-butene and 2-tert-butoxy-2-butene. These vinyl ether-based monomers can be produced by a known method.

PVE may be a copolymer having a structural unit other than the structural unit derived from vinyl ether. Examples of such a copolymer include those having a structure of a structural unit (A) derived from vinyl ether and a structural unit (B) derived from poly (oxy) alkylene glycol or a monoether thereof.
The poly (oxy) alkylene glycol refers to both a polyalkylene glycol and a polyoxyalkylene glycol.

[Polyoxyalkylene glycols (PAG)]
Examples of the polyoxyalkylene glycols (PAG) include compounds represented by the following general formula (B-1). One type or two or more types of PAG can be used.

R ^1b [-(OR ^2b ) _m- OR ^3b ] _n (B-1)
(In the formula, R ^1b is a hydrogen atom, a hydrocarbon group having 1 to 10 carbon atoms, an acyl group having 2 to 10 carbon atoms, a hydrocarbon group having 2 to 6 bonding portions, or a hydrocarbon group having 1 to 10 carbon atoms or 1 carbon atom. 10 to 10 oxygen-containing hydrocarbon groups, R ^2b is an alkylene group having 2 to 4 carbon atoms, R ^3b is a hydrogen atom, a hydrocarbon group having 1 to 10 carbon atoms, an acyl group having 2 to 10 carbon atoms, or 1 to 1 carbon atoms. 10 oxygen-containing hydrocarbon groups, n is an integer of 1 to 6, and m is a number in which the average value of m × n is 6 to 80.)

In the general formula (B-1), the hydrocarbon groups having 1 to 10 carbon atoms in each of R ^1b and R ^3b may be linear, branched, or cyclic. The hydrocarbon group is preferably an alkyl group, and specific examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, various butyl groups, various pentyl groups, various hexyl groups, various heptyl groups, and various octyl groups. Examples thereof include various nonyl groups, various decyl groups, cyclopentyl groups, cyclohexyl groups and the like. By setting the number of carbon atoms of the hydrocarbon group to 10 or less, the compatibility with the refrigerant becomes good. From such a viewpoint, the number of carbon atoms of the hydrocarbon group is more preferably 1 to 4, still more preferably 1 to 2, and even more preferably 1.
Further, the hydrocarbon group portion of the acyl group having 2 to 10 carbon atoms in each of R ^1b and R ^3b may be linear, branched or cyclic. The hydrocarbon group portion of the acyl group is preferably an alkyl group, and specific examples thereof include those having 1 to 9 carbon atoms among the alkyl groups that can be selected as R ^1b and R ^3b described above. When the number of carbon atoms of the acyl group is 10 or less, the compatibility with the refrigerant is improved. The preferred acyl group has 2 to 4 carbon atoms.
When both R ^1b and R ^3b are hydrocarbon groups or acyl groups, R ^1b and R ^3b may be the same or different from each other.

When R ^1b is a hydrocarbon group having 2 to 6 binding sites and having 1 to 10 carbon atoms, the hydrocarbon group may be chain-like or cyclic. As the hydrocarbon group having two bonding sites, an aliphatic hydrocarbon group is preferable, and for example, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, a decylene group and a cyclopenti. Examples thereof include a len group and a cyclohexylene group. Examples of other hydrocarbon groups include residues obtained by removing hydroxyl groups from bisphenols such as biphenol, bisphenol F, and bisphenol A. Further, as the hydrocarbon group having 3 to 6 binding sites, an aliphatic hydrocarbon group is preferable, for example, trimethylolpropane, glycerin, pentaerythritol, sorbitol, 1,2,3-trihydroxycyclohexane, 1,3. Residues obtained by removing hydroxyl groups from polyhydric alcohols such as 5-trihydroxycyclohexane can be mentioned.
When the number of carbon atoms of this aliphatic hydrocarbon group is 10 or less, the compatibility with the refrigerant is improved. The preferred number of carbon atoms of this aliphatic hydrocarbon group is 2 to 6.

Further, as the oxygen-containing hydrocarbon group having 1 to 10 carbon atoms in each of R ^1b and R ^3b , a chain-like aliphatic group having an ether bond, a cyclic aliphatic group (for example, a tetrahydrofurfuryl group) or the like can be used. Can be mentioned.

At least one of R ^1b and R ^3b is preferably an alkyl group, more preferably an alkyl group having 1 to 4 carbon atoms, further preferably an alkyl group having 1 to 2 carbon atoms, and carbon. It is even more preferably an alkyl group of number 1. Further, it is preferable that both R ^1b and R ^3b satisfy the above conditions.

R ^2b in the general formula (B-1) is an alkylene group having 2 to 4 carbon atoms, and examples of the repeating unit oxyalkylene group include an oxyethylene group, an oxypropylene group, and an oxybutylene group. The oxyalkylene group in one molecule may be the same or may contain two or more kinds of oxyalkylene groups, but those containing at least an oxypropylene unit in one molecule are preferable, and the oxyalkylene unit contains More preferably 50 mol% or more of oxypropylene units, and more preferably 70 mol% or more of oxypropylene units.

N in the general formula (B-1) is an integer of 1 to 6, and is determined according to the number of binding sites of R ^1b . For example, if R ^1b is an alkyl group or an acyl group, n is 1, and if R ^1b is an aliphatic hydrocarbon group having 2, 3, 4, 5 and 6 binding sites, n is 2, 3 respectively. , 4, 5 and 6.
Further, m is a number in which the average value of m × n is 6 to 80. When the average value is 80 or less, the compatibility with the refrigerant becomes good. However, it is preferable that the average value of m × n is appropriately set so that the viscosity of the base oil is in a desired range.

Further, n is preferably an integer of 1 to 3, more preferably 1. When n is 1, it is preferable that either one of R ^1b and R ^3b is an alkyl group, and it is more preferable that both are alkyl groups. Similarly, when n is 2 or more, it is preferable that any one of a plurality of R ^3b in one molecule is an alkyl group, and it is more preferable that all of them are alkyl groups.
When n is 2 or more, a plurality of R ^{3b in} one molecule may be the same or different.

The compound represented by the general formula (B-1) may have a hydroxyl group at the terminal. When the terminal has a hydroxyl group, the ratio of the terminal hydroxyl group to all the terminal groups is preferably 50% or less.

PAG can be synthesized, for example, by addition-polymerizing an alkylene oxide such as ethylene oxide or propylene oxide to alcohols and etherifying the terminal hydroxyl group.
In addition, when synthesized by a usual method, the number of Hazen colors of the obtained PAG exceeds 10. Therefore, it is preferable to carry out the hydrogenation reaction until the number of Hazen colors becomes 10 or less after the completion of the normal synthesis reaction. It is considered that the hydrogenation reaction hydrogenates unsaturated groups, carboxyl groups, ketone groups, aldehyde groups, alcohol groups and the like in the by-products, thereby enhancing thermal stability and oxidative stability.

<Polyprester esters (POE)>
As the polyol esters (POE), esters of a polyol having about 3 to 20 diols or hydroxyl groups and a fatty acid having about 1 to 24 carbon atoms are preferably used. One type or two or more types of POE can be used.
In addition, in this embodiment, the term "ester" simply means a complete ester.

Examples of the diol include ethylene glycol, 1,3-propanediol, propylene glycol, 1,4-butanediol, 1,2-butanediol, 2-methyl-1,3-propanediol, and 1,5-pentanediol. Neopentyl glycol, 1,6-hexanediol, 2-ethyl-2-methyl-1,3-propanediol, 1,7-heptanediol, 2-methyl-2-propyl-1,3-propanediol, 2, Examples thereof include 2-diethyl-1,3-propanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, and 1,12-dodecanediol.

Examples of the polyol include trimethylolethane, trimethylolpropane, trimethylolbutane, trimethylolpropane), trimethylolpropane, pentaerythritol, dipentaerythritol, tripentaerythritol, glycerin, and polyglycerin (2 to 20 mer of glycerin). ), 1,3,5-pentantriol, sorbitol, sorbitan, sorbitol glycerin condensate, polyhydric alcohols such as adonitol, arabitol, xylitol, mannitol, xylose, arabinose, ribose, lambnorse, glucose, fructose, galactose, mannose, sorbose , Cerobiose, maltose, isomaltose, trehalose, sucrose, raffinose, gentianose, merenjitose and other saccharides, as well as partial etherified products thereof, methylglucoside (sugar glycoside) and the like.

The carbon number of the diol and the polyol is not particularly limited, but the carbon number is preferably 3 to 15, more preferably 4 to 12, and even more preferably 5 to 10.
Among these diols and polyols, neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, trimethylolpropane, trimethylolpropane, pentaerythritol, dipentaerythritol and tripentaerythritol (hereinafter, "polyvalent alcohol group A"). ”) Is preferable.

The fatty acid is not particularly limited, but a fatty acid having 1 to 24 carbon atoms is usually used. Among the fatty acids having 1 to 24 carbon atoms, those having 3 or more carbon atoms are preferable, those having 4 or more carbon atoms are more preferable, and those having 5 or more carbon atoms are even more preferable, from the viewpoint of lubricity. Further, from the viewpoint of compatibility with the refrigerant, those having 18 or less carbon atoms are preferable, those having 12 or less carbon atoms are more preferable, and those having 9 or less carbon atoms are even more preferable.
Further, it may be either a linear fatty acid or a branched fatty acid, and a linear fatty acid is preferable from the viewpoint of lubricity, and a branched fatty acid is preferable from the viewpoint of hydrolysis stability. Further, it may be either a saturated fatty acid or an unsaturated fatty acid.

Examples of fatty acids include isobutyric acid, pentanoic acid, hexanoic acid, heptanic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid and octadecanoic acid. , Nonadecanic acid, icosanoic acid, oleic acid and other linear or branched ones, or so-called neoacids having a quaternary α-carbon atom.
Among these fatty acids, isovalic acid, valeric acid (n-pentanoic acid), caproic acid (n-hexanoic acid), enanthic acid (n-heptanic acid), caprylic acid (n-octanoic acid), pelargonic acid (n-). Nonanoic acid), caprylic acid (n-decanoic acid), oleic acid (cis-9-octadecenoic acid), isoponic acid (3-methylbutanoic acid), 2-methylbutanoic acid, 2-ethylbutanoic acid, 2-methylpentanoic acid, 2 -Ethylpentanoic acid, 2-methylhexanoic acid, 2-ethylhexanoic acid, and 3,5,5-trimethylhexanoic acid (hereinafter, may be referred to as "fatty acid group A") are preferable.

As the POE, an ester of at least one selected from the polyhydric alcohol group A and at least one selected from the fatty acid group A is preferable.

POE can be synthesized by an esterification reaction between a diol or a polyol and a fatty acid.
When synthesized by a usual method, the number of Hazen colors of the obtained POE exceeds 10. Therefore, it is preferable to carry out the hydrogenation reaction until the number of Hazen colors becomes 10 or less after the completion of the normal synthesis reaction. It is considered that the hydrogenation reaction hydrogenates unsaturated groups, carboxyl groups, ketone groups, aldehyde groups, alcohol groups and the like in the by-products, thereby enhancing thermal stability and oxidative stability.

The PVE, PAG, and POE preferably have a polystyrene-equivalent weight average molecular weight (Mw) of less than 5000, more preferably 200 to 3000, and even more preferably 250 to 2000.

The refrigerating machine oil in the present embodiment preferably contains at least one compound selected from the group consisting of PVE, PAG, and POE as a main component. Here, the term "containing as the main component" means that the compound is contained in the refrigerating machine oil in a proportion of 50% by mass or more.
The content of the compound in the refrigerating machine oil is more preferably 70% by mass or more, further preferably 90% by mass or more, further preferably 95% by mass or more, and 97% by mass or more. Is particularly preferable.
When the refrigerating machine oil contains at least one compound selected from the group consisting of PVE, PAG, and POE as a main component, the compound constituting the main component is a single type of PVE, PAG, and POE. Is preferable. For example, it is preferable that the main component is composed only of a compound selected from PVE. Alternatively, it is preferable that the main component is composed only of a compound selected from PAG. Alternatively, it is preferable that the main component is composed only of the compound selected from POE.
The refrigerating machine oil contains synthetic oils other than PVE, PAG, and POE (for example, partial esters in which all the hydroxyl groups of the polyol remain without esterification) and mineral oils as long as the effects of the present invention are not impaired. May be good.

[Physical properties of refrigerating machine oil]
The kinematic viscosity of the refrigerating machine oil at 40 ° C. is preferably 3 to 200 mm ² / s, more preferably 3 to 150 mm ² / s, from the viewpoint of suppressing poor lubrication and balancing power loss.
The kinematic viscosity of the refrigerating machine oil at 100 ° C. is preferably 1 to 40 mm ² / s, more preferably 1 to 25 mm ² / s, from the viewpoint of suppressing poor lubrication and balancing power loss.
The viscosity index of the refrigerating machine oil is preferably 50 or more, and more preferably 60 or more.

From the viewpoint of stability, the acid value of the refrigerating machine oil is preferably 0.05 mgKOH / g or less, more preferably 0.03 mgKOH / g or less, and further preferably 0.01 mgKOH / g or less. .. The acid value can be measured according to the "indicator titration method" of JIS K2501: 2003.

From the viewpoint of stability, the hydroxyl value of the refrigerating machine oil is preferably 10 mgKOH / g or less, more preferably 5 mgKOH / g or less, and further preferably 3 mgKOH / g or less. The hydroxyl value can be measured according to the "neutralization titration method" of JIS K0070: 1992.

The volume resistivity of the refrigerating machine oil is preferably 2.0 × 10 ⁸ Ω · m or more, more preferably 5.0 × 10 ⁸ Ω · m or more, and 1.0 × 10 ⁹ Ω · m or more. The above is more preferable. When the volume resistivity is 2.0 × 10 ⁸ Ω · m or more, the refrigerator insulation is enhanced oil was driving source as such as an electric car air conditioner is be an electric, 1 mA or more to be a practical problem Leakage current is less likely to occur.

The water content of the refrigerating machine oil is preferably less than 1000 ppm, more preferably 300 ppm or less, and even more preferably 150 ppm or less. By lowering the water content, hydrolysis of the refrigerating machine oil is less likely to occur, the stability of the refrigerating machine oil is improved, and good lubrication performance can be provided for a long period of time.

<Composition for refrigerator>
The composition for a refrigerator of the present embodiment contains the above-mentioned refrigerating machine oil of the present embodiment and a refrigerant.

[Refrigerant]
Examples of the refrigerant include a fluorinated hydrocarbon refrigerant, a fluorinated ether compound refrigerant, a fluorinated alcohol compound refrigerant, a fluorinated ketone compound refrigerant, and a natural refrigerant. The refrigerant may be one type, but two or more types may be mixed and used.

Examples of the fluorinated hydrocarbon refrigerant include saturated fluorinated hydrocarbon refrigerants and unsaturated fluorinated hydrocarbon refrigerants.
Examples of the saturated fluorinated hydrocarbon refrigerant include difluoromethane (R32), fluoroethane (R161), 1,1,1,2,2-pentafluoroethane (R125), and 1,1,1,2-tetrafluoroethane (1,1,1,2-tetrafluoroethane). R134a), 1,1,2,2-tetrafluoroethane (R134), 1,1,1-trifluoroethane (R143a), 1,1,2-trifluoroethane (R143), 1,1-difluoroethane (R134a) R152a) and the like.

Examples of the unsaturated fluorinated hydrocarbon refrigerant include 1,1,2-trifluoroethane (R1123), 1,2,3,3,3-pentafluoropropene (R1225ye), 2,3,3,3-. Tetrafluoropropene (R1234yf), 1,3,3,3-tetrafluoropropene (R1234ze), 1,2,3,3-tetrafluoropropene (R1234yz), (Z) -1,1,1,4,4 , 4-Hexafluoro-2-butene (trans-R1336mzz) and the like.

Examples of the fluoroether compound include hexafluorodimethyl ether, pentafluorodimethyl ether, bis (difluoromethyl) ether, fluoromethyltrifluoromethyl ether, trifluoromethylmethyl ether, difluoromethoxypentafluoroethane, and 1-trifluoromethoxy-1. , 2,2,2-tetrafluoroethane, perfluorooxetane, perfluoro-1,3-dioxolane, various isomers of pentafluorooxetane, various isomers of tetrafluorooxetane, and the like.

Examples of the fluoroalcohol compound include monofluoromethyl alcohol, difluoromethyl alcohol, trifluoromethyl alcohol, various isomers of difluoroethyl alcohol, various isomers of trifluoroethyl alcohol, various isomers of tetrafluoroethyl alcohol, and penta. Examples thereof include various isomers of fluoroethyl alcohol and difluoropropyl alcohol, various isomers of trifluoropropyl alcohol, fluorinated propylene glycol such as hexafluoropropylene glycol, and fluorinated trimethylene glycol corresponding to the fluorinated propylene glycol. ..

Examples of the fluoride ketone compound include hexafluorodimethyl ketone, pentafluorodimethyl ketone, bis (difluoromethyl) ketone, fluoromethyltrifluoromethyl ketone, trifluoromethyl methyl ketone, perfluoromethyl ethyl ketone, and trifluoromethyl-1,1,. Examples thereof include 2,2-tetrafluoroethyl ketone.

Examples of the natural refrigerant include carbon dioxide (carbon dioxide), hydrocarbons such as propane, n-butane, isobutane, 2-methylbutane, n-pentane, cyclopentane isobutane, and normal butane, and ammonia.

Among the above-mentioned refrigerants, at least one selected from the group consisting of difluoromethane (R32) and 2,3,3,3-tetrafluoropropene (R1234yf) is preferable from the viewpoint of stability of refrigerating machine oil.

The content ratio of the refrigerating machine oil to the refrigerant (refrigerant machine oil / refrigerant) is preferably 1/99 to 99/1, more preferably 5/95 to 60/40 in terms of mass ratio.

[Additive]
The refrigerating machine oil and the composition for the refrigerating machine may contain at least one selected from additives consisting of antioxidants, extreme pressure agents, acid scavengers, oxygen scavengers and copper inactivating agents. .. The content of each additive is usually 0.01 to 5% by mass, preferably 0.05 to 3% by mass, based on the total amount of the refrigerator oil and the total amount of the composition for the refrigerator.

Antioxidants include 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, and 2,2'-methylenebis (4-methyl-6-tert). Examples thereof include phenolic antioxidants such as −butylphenol) and amine-based antioxidants such as phenyl-α-naphthylamine and N, N'-di-phenyl-p-phenylenediamine.
Examples of extreme pressure agents include phosphorus-based extreme pressure agents such as phosphoric acid esters, acidic phosphoric acid esters, phosphite esters, acidic phosphite esters and amine salts thereof, and sulfur-based extreme pressure agents such as sulfide oils and fats, sulfide fatty acids, and sulfide esters. Examples include extreme pressure agents and fatty acid metal salts having 3 to 60 carbon atoms.
Examples of the acid trapping agent include epoxy compounds such as phenylglycidyl ether, alkylglycidyl ether, alkylene glycol glycidyl ether, glycidyl ester, cyclohexene oxide, α-olefin oxide, and epoxidized soybean oil.
Oxygen trapping agents include 4,4'-thiobis (3-methyl-6-t-butylphenol), diphenyl sulfide, dioctyl diphenyl sulfide, dialkyl diphenylene sulfide, benzothiophene, dibenzothiophene, phenothiazine, benzothiapyran, thiapyran, thiantorene, Examples thereof include sulfur-containing aromatic compounds such as dibenzothiapyran and diphenylenedisulfide, aliphatic unsaturated compounds such as various olefins, diene and triene, and terpenes having a double bond.
Examples of the copper inactivating agent include N- [N, N'-dialkyl (alkyl group having 3 to 12 carbon atoms) aminomethyl] triazole and the like.

[Physical properties of composition for refrigerator]
The preferred ranges of kinematic viscosity, viscosity index, acid value, hydroxyl value, volume resistivity and water content of the chiller composition are the same as those of the chiller oil described above.

<Refrigerator>
The refrigerator of the present embodiment contains the above-mentioned refrigerating machine oil of the present embodiment or the above-mentioned composition for the refrigerator of the present embodiment.

The refrigerator of the present embodiment is preferably a compression type refrigerator. Further, the compression type refrigerator compressor has a refrigerating cycle including a condenser, an expansion mechanism (expansion valve, etc.) and an evaporator, or a refrigerator equipped with a compressor, a condenser, an expansion mechanism, a dryer and an evaporator. Those having a cycle are more preferable.
The freezer oil or the composition for a refrigerator is used, for example, to lubricate a sliding portion provided in a compressor or the like.
The sliding portion is not particularly limited, but it is preferable that any of the sliding portions contains a metal such as iron, and it is preferable that the sliding portion slides between metals.

The refrigerator can be used, for example, in an air conditioner, a gas heat pump (GHP), an air conditioner, a refrigerator, a vending machine, a refrigeration system such as a showcase, a hot water supply system, a heating system, and the like.

<How to select refrigerating machine oil>
The method for selecting a refrigerator of the present embodiment is a Hazen color conforming to ASTM D1209-05 of a refrigerator oil containing at least one compound selected from the group consisting of polyvinyl ethers, polyoxyalkylene glycols, and polyol esters. The number is measured, and the refrigerating machine oil having a Hazen color number satisfying the conditions of 0 to 10 is selected.

Conventionally, the cause of insufficient thermal stability and oxidative stability of an oil (oil X) containing a compound selected from polyvinyl ethers, polyoxyalkylene glycols, and polyol esters has not been sufficiently investigated. .. For this reason, it was essential to carry out a reliability test for oil X before shipping.
According to the refrigerating machine oil selection method of the present embodiment, oil X having excellent thermal stability and oxidation stability can be selected by a simple method of measuring the number of Hazen colors in accordance with ASTM D1209-05, and the reliability is high. It is not necessary to carry out the test, and the work efficiency can be greatly improved.
The determination condition for the number of Hazen colors is preferably 0 to 10, and more preferably 0. The number of Hazen colors of 0 includes a case where the number is equal to or less than the detection limit by the measurement method based on ASTM D1209-05.

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

1. 1. Measurement The following measurements were performed on the refrigerating machine oil and the refrigerating machine composition of Examples and Comparative Examples. The results are shown in Tables 2-5.
1-1. Measurement of Hazen Colors The Hazen colors of the refrigerating machine oils of Examples and Comparative Examples were calculated according to ASTM D1209-05. The results are shown in Table 2.
1-2.40 ° C. kinematic viscosity, 100 ° C. kinematic viscosity, viscosity index The 40 ° C. kinematic viscosity, 100 ° C. kinematic viscosity and viscosity index of the refrigerating machine oils of Examples and Comparative Examples were measured according to JIS K2283: 2000. The results are shown in Table 2.

1-3. Weight average molecular weight (Mw)
Using gel permeation chromatography (GPC), the weight average molecular weight (Mw) of the refrigerating machine oils of Examples and Comparative Examples was measured. For GPC, two TSKgel SuperMultipore HZ-M manufactured by Tosoh Corporation were used as columns, and measurement was performed using tetrahydrofuran as an eluent and a refractive index detector as a detector to determine the weight average molecular weight (Mw) using polystyrene as a standard sample. It was. The results are shown in Table 2.
1-4. Acid Value The acid value of the refrigerating machine oils of Examples and Comparative Examples was measured in accordance with the "Indicator Titration Method" of JIS K2501: 2003. The results are shown in Table 2. The acid value of stability tests 1 to 3 described later was also measured by the indicator titration method.

2. 2. Synthesis of refrigerating machine oil 2-1. Synthesis of POEs 1 to 20 The alcohols shown in Table 1-1 are mixed by putting them in a flask so that the carboxyl groups of the carboxylic acids shown in Table 1-1 are 1.2 equivalents with respect to 1 equivalent of the hydroxyl groups. The composition A was obtained by heating at 230 ° C. under normal pressure under a nitrogen atmosphere and reacting for 15 hours to esterify. Unreacted carboxylic acid was removed from composition A, activated clay was added to carry out adsorption treatment, activated clay was removed with a filter, and the acid value was adjusted to 0.03 or less to obtain POE 11 to 20.
Further, POE 11 to 20 were subjected to a hydrogenation reaction (reaction temperature 100 ° C., hydrogen pressure 3.5 MPa, catalyst: nickel diatomaceous earth) until the Hazen color number reached the value shown in Table 2 to obtain POE 1-10.

2-2. Synthesis of PAGs 1 to 4 100 parts of methanol was placed in an airtight container and replaced with nitrogen gas, and the alkylene oxide shown in Table 1-2 was press-fitted together with 5 parts of potassium hydroxide, and the weight average shown in Table 2 was obtained at 110 to 140 ° C. Polymerization was carried out until the molecular weight was reached to obtain polyalkylene glycol monomethyl ether. 1.05 mol of sodium methoxide was added to 1 mol of polyalkylene glycol monomethyl ether, and demethanolization was performed at 130 ° C. in nitrogen gas under a pressure of 2.7 kPa. After reacting for 4 hours, 0.54 mol of methylene dichloride was press-fitted into 1 mol of polyalkylene glycol monomethyl ether over 3 hours, further aged for 2 hours, and stirred at 120 to 140 ° C. to compose the composition. I got B. Composition B was filtered together with 0.2 part of Radiolite as a filtration aid to prepare an acid value of 0.03 or less to obtain PAGs 3 to 4.
Further, PAGs 3 to 4 were subjected to a hydrogenation reaction (reaction temperature: 140 ° C., hydrogen pressure 3.5 MPa, catalyst: nickel diatomaceous earth) until the Hazen color number reached the value shown in Table 1 to obtain PAGs 1 and 2. ..

2-3. Synthesis of PVE1-6 106 g of toluene, 24.3 g of ethanol, and 0.2 g of boron trifluoride diethyl ether complex were added to a 1 L flask made of glass equipped with a stirrer. Further, 400 g of the vinyl ether-based monomer shown in Table 1-3 was added to the separately prepared Erlenmeyer flask.
Then, the stirrer was operated, and the pump was temporarily stopped when 46 g of the vinyl ether-based monomer in the Erlenmeyer flask was supplied by the pump into the stirred system of the 1 L flask at 5 mL / min.
After confirming that the temperature in the system of the 1L flask had risen, the pump was restarted, and the remaining vinyl ether-based monomer was supplied into the stirred system of the 1L flask over 4 hours, and after the supply was completed. Continued stirring for another 5 minutes to obtain composition C. During the supply of the vinyl ether-based monomer, the inside of the system was constantly stirred, and the temperature inside the system was controlled to 25 ° C. using a water bath.
Activated clay is added to composition C for adsorption treatment, activated clay is removed with a filter, and unreacted vinyl ether-based monomers and solvents are further removed to prepare an acid value of 0.03 or less, and PVE4 to I got 6.
Further, PVE4 to 6 were subjected to a hydrogenation reaction (reaction temperature 140 ° C., hydrogen pressure 3.5 MPa, catalyst: nickel diatomaceous earth) until the Hazen color number reached the value shown in Table 2 to obtain PVE1 to 3.

The following stability tests were performed using the refrigerating machine oil synthesized in 2-1 to 2-3.

[Examples 1-1-1-15], [Comparative Examples 1-1-1-15]
<Stability test 1 (shield tube test 1)>
In a glass tube, 4 mL of refrigerating machine oil in Table 3, 1 g of refrigerant (R32), additives (1 part by mass of tricresyl phosphate with respect to 100 parts by mass of refrigerating machine oil, 0.5 parts by mass of 2,6-di- It was filled with t-butyl paracresol (1 part by mass of 2-ethylhexyl glycidyl ether) and a metal catalyst (iron, copper, aluminum), sealed, and held at an air pressure of 6.7 kPa and a temperature of 175 ° C. for 10 days. Then, the acid value of the composition for the refrigerator in the glass tube was measured, and the appearance of the oil and the appearance of the iron catalyst were visually evaluated. The water content of the composition for the refrigerator in the glass tube was adjusted to 50 ppm or less. The results are shown in Table 3.

[Examples 2-1 to 2-6], [Comparative Examples 2-1 to 2-6]
<Stability test 2 (shield tube test 2)>
Change the refrigerating machine oil to that in Table 4, change the refrigerant to a 1: 1 mixture (mass ratio) of R32 and R1234yf, and add 1.5 parts of 2-ethylhexyl glycidyl ether to 100 parts by mass of refrigerating machine oil. The acid value, oil appearance, and iron catalyst appearance of the composition for the refrigerator were evaluated in the same manner as in Stability Test 1 except that the parts were changed to parts by mass. The results are shown in Table 4.

[Examples 3-1 to 3-6], [Comparative Examples 3-1 to 3-6]
<Stability test 3 (shield tube test 3)>
Same as stability test 1 except that the refrigerating machine oil was changed to that in Table 5, the refrigerant was changed to R1234yf, and the amount of 2-ethylhexyl glycidyl ether added was changed to 3 parts by mass with respect to 100 parts by mass of the refrigerating machine oil. The acid value, oil appearance, and iron catalyst appearance of the composition for the refrigerator were evaluated. The results are shown in Table 5.

From the results in Tables 1 to 3, it is a refrigerating machine oil containing at least one compound selected from the group consisting of polyvinyl ethers, polyoxyalkylene glycols, and polyol esters, and has a Hazen color conforming to ASTM D1209-05. Refrigerating machine oils having a number of 0 to 10 can suppress deterioration of the oil in a high temperature environment, and therefore can suppress an increase in the acid value of the oil, discoloration of the oil, corrosion of metal, and the like. It can be confirmed that it is excellent in thermal stability and oxidation stability.

Claims (18)

Comprises at least one compound selected from polyvinyl ethers, which are hydrogenation treatment, Ri Hazen color number 0 der conforming to ASTM D1209-05, an acid value is not more than 0.05 mg KOH / g, not Refrigerating machine oil used with refrigerants containing saturated fluorinated hydrocarbon refrigerants . Comprises at least one compound selected from polyvinyl ethers, which are hydrogenation treatment, Ri Hazen color number 0 der conforming to ASTM D1209-05, an acid value is not more than 0.05 mg KOH / g, unsaturation fluoride Refrigerating machine oil used with refrigerants containing hydrocarbon refrigerants . Comprising at least one compound selected from the hydrogenation treatment polyol esters, Hazen color number conforming to ASTM D1209-05 is Ri 0 der, it is used together with the refrigerant containing an unsaturated fluorinated hydrocarbon refrigerant that, the refrigerating machine oil. The refrigerating machine oil according to any one of claims 1 to 3, wherein the compound is contained in the refrigerating machine oil in an amount of 50% by mass or more. The refrigerating machine oil according to any one of claims 1 to 3, which comprises only the compound. The refrigerating machine oil according to claim 1 or 2, wherein the polyvinyl ethers are compounds having a structural unit represented by the following general formula (A-1).

[R ^1a , R ^2a and R ^3a in the general formula (A-1) each independently represent a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, and they may be the same or different from each other. .. R ^4a represents a divalent hydrocarbon group having 2 to 10 carbon atoms. R ^5a represents a hydrocarbon group having 1 to 10 carbon atoms. r indicates the number of repetitions. ] The refrigerating machine oil according to claim 1, 2 or 6, wherein the polyvinyl ethers are at least one selected from polymethyl vinyl ethers, polyethyl vinyl ethers, and polyethyl polybutyl vinyl ethers. The polyol esters include at least one selected from neopentyl glycol, trimethylolpropane, pentaerythritol and dipentaerythritol, 2-methylbutanoic acid, 2-methylpentanoic acid, 3,5,5-trimethylhexanoic acid, 2 The refrigerating machine oil according to claim 3, which is an ester with at least one selected from -ethylhexanoic acid and n-pentanoic acid. The refrigerating machine oil according to any one of claims 1 to 8, wherein the kinematic viscosity at 40 ° C. is 3 to 200 mm ² / s. The refrigerating machine oil according to claim 3 or 8 , which has an acid value of 0.05 mgKOH / g or less. A composition for a refrigerator containing the refrigerating machine oil according to any one of claims 1 to 10 and a refrigerant containing an unsaturated fluorinated hydrocarbon refrigerant . The composition for a refrigerator according to claim 11 , wherein the refrigerant is only 2,3,3,3-tetrafluoropropene. The composition for a refrigerator according to claim 11 , wherein the refrigerant is a mixed refrigerant of difluoromethane and 2,3,3,3-tetrafluoropropene. The refrigerator according to any one of claims 11 to 13 , further comprising at least one selected from an additive consisting of an antioxidant, an extreme pressure agent, an acid scavenger, an oxygen scavenger and a copper inactivating agent. Composition for. A refrigerator containing the refrigerator oil according to any one of claims 1 to 10 or the composition for a refrigerator according to any one of claims 11 to 14 . The number of Hazen colors and the acid value of the refrigerating machine oil containing at least one compound selected from the hydrogenated polyvinyl ethers were measured according to ASTM D1209-05, and the number of Hazen colors was 0 to 10 , and the acid value. A method for selecting a refrigerating machine oil to be used together with a refrigerant containing an unsaturated fluorinated hydrocarbon refrigerant, in which a refrigerating machine oil satisfying the condition of 0.05 mgKOH / g or less is selected. The Hazen color number and acid value of the refrigerating machine oil containing at least one compound selected from the hydrogenated polyvinyl ethers were measured according to ASTM D1209-05, and the Hazen color number was 0 and the acid value was 0. A method for selecting a refrigerating machine oil to be used together with a refrigerant containing an unsaturated fluorinated hydrocarbon refrigerant, which selects a refrigerating machine oil satisfying the condition of .05 mgKOH / g or less . The number of Hazen colors of refrigerating machine oil containing at least one compound selected from hydrogenated polyol esters is measured according to ASTM D1209-05, and refrigerating machine oils having Hazen color numbers satisfying the conditions of 0 to 10 are used. A method for selecting refrigerating machine oil to be used together with a refrigerant containing an unsaturated fluorinated hydrocarbon refrigerant .