Patent Description:
A compression-type refrigerating machine is a refrigeration system equipped with at least a compressor, a condenser, an expansion mechanism (such as an expansion valve), and an evaporator. Refrigerant and a refrigerating machine oil composition are mixed with each other and circulated within a sealed refrigeration system. Further, in the compression-type refrigerating machine, high and low temperature environments are created according to a compression ratio and phase change. Thus, a mixture of the refrigerant and the refrigerating machine oil composition is required to circulate in the refrigeration system without undesired phase separation even within a wide temperature range from low to high temperatures.

Conventionally, chlorofluorocarbon (CFC), hydrochlorofluorocarbon (HCFC), etc. have been mainly used as refrigerants for the refrigerating machine. However, CFC and HCFC are compounds comprising chlorine that causes environmental problems (destruction of the ozone layer). Thus, alternative refrigerants that do not contain chlorine such as hydrofluorocarbon (HFC) have been considered.

For example, <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoroethane, a <NUM>:<NUM> mixture of <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoroethane and pentafluoroethane, pentafluoroethane, and trifluoromethane (hereinafter, referred to as R134a, R410A, R125, and R23, respectively) as the hydrofluorocarbon (HFC) have attracted attention. For example, R134a has been used for the refrigerator system, and R410A has been used for an air conditioning system.

However, there was a concern that the HFC-based refrigerant may also have an adverse effect on global warming. Accordingly, as a so-called eco-friendly refrigerant that has a lower effect on ozone layer depletion and is more suitable for environmental protection, a refrigerant having a relatively low global warming potential (GWP) is attracting attention. The eco-friendly refrigerant includes, for example, difluoromethane (hereinafter, referred to as R32) as an HFC-based refrigerant; <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoro-<NUM>-propene(hereinafter, referred to as R1234yf) as an HFO-based refrigerant comprising olefin bonds; and a mixture of R32 and R1234yf at <NUM>: <NUM> and a mixture of R1234yf and R134a at <NUM>: <NUM> (hereinafter, referred to as R454B and R513A, respectively) as mixed refrigerant of HFC and HFO; and isobutane and propane (hereinafter referred to as R600a and R290, respectively) as a HC-based refrigerant composed of hydrocarbons.

<CIT> shows a refrigeration oil comprising polyol ester and a refrigeration lubricant composition comprising the refrigeration oil and R32. <CIT> shows a refrigerating machine oil comprising: an antioxidant, an anticorrosive agent, an antiwear agent, an antifoaming agent, with a balance of polyol ester. <CIT> shows a lubricant for use in air conditioner and refrigerator compressors, the lubricant comprising mixed esters of hindered polyols, most desirably di-pentaerythritol, usually mixed with some pentaerythritol, with a mixture of carboxylic acids including at least some of each of iso-pentanoic acid and iso-nonanoic acid.

Therefore, it is necessary to develop a base oil having excellent miscibility (compatibility) with various refrigerants, especially, refrigerants with high polarity, and at the same time, having high chemical resistance and abrasion resistance and excellent chemical stability when used in the refrigerating machine. Further, it is necessary to develop a refrigerating machine oil composition comprising the same.

A purpose of the present disclosure is to provide a base oil comprising a polyol ester having excellent miscibility with highly polar refrigerants, especially eco-friendly refrigerants with high polarity and low global warming potential (GWP), and having high abrasion resistance through relatively high viscosity.

Another purpose of the present disclosure is to provide a refrigerating machine oil composition that contains the base oil comprising polyol ester, and has excellent chemical stability.

Purposes of the present disclosure are not limited to the above-mentioned purpose. Other purposes and advantages of the present disclosure that are not mentioned may be understood based on following descriptions, and may be more clearly understood based on embodiments of the present disclosure. Further, it will be easily understood that the purposes and advantages of the present disclosure may be realized using means shown in the claims and combinations thereof.

One aspect of the present disclosure may provide a refrigerating machine oil composition comprising: a base oil comprising polyol ester, wherein the polyol ester is synthesized using: a polyhydric alcohol containing <NUM> or more hydroxyl groups; a first fatty acid as a linear fatty acid having <NUM> to <NUM> carbon atoms; a second fatty acid as a branched fatty acid having <NUM> to <NUM> carbon atoms; and a third fatty acid as a linear or branched fatty acid having <NUM> to <NUM> carbon atoms, wherein in synthesizing the polyol ester, a sum of a content of the first fatty acid and a content of the second fatty acid is in a range of <NUM> to <NUM> wt%, and a content of the third fatty acid is in a range of <NUM> to <NUM> wt%, based on <NUM> wt% of a total weight of the first fatty acid, the second fatty acid, and the third fatty acid, wherein the polyol ester has a kinematic viscosity at <NUM> (KV40) in a range of <NUM> to <NUM> cSt, wherein the refrigerating machine oil further comprises at least one additive selected from a group consisting of a corrosion inhibitor and an acid scavenger, whereby both a corrosion inhibitor and an acid scavenger are present, wherein the refrigerating machine oil composition has a kinematic viscosity at <NUM> (KV40) in a range of <NUM> to <NUM> cSt, wherein a total acid number (TAN) of the refrigerating machine oil composition is in a range of <NUM> to <NUM> mgKOH/g, wherein when a total weight of the refrigerating machine oil composition is <NUM> wt%, a content of the corrosion inhibitor is in a range of <NUM> to <NUM> wt%, and a content of the acid scavenger is in a range of <NUM> to <NUM> wt%, wherein the polyol ester has a floc point of -<NUM> or lower as measured according to following measurement method (<NUM>):.

In one embodiment, the refrigerant may include at least one selected from a group consisting of R32, R410A, R134a, R1234yf, R454B and R513A.

In one embodiment, when a total weight of the first fatty acid and the second fatty acid is <NUM> wt%, a content of the first fatty acid may be in a range of <NUM> to <NUM> wt%, and a content of the second fatty acid may be in a range of <NUM> to <NUM> wt%.

In one embodiment, the polyhydric alcohol may include dipentaerythritol.

In one embodiment, the corrosion inhibitor may include a benzotriazole-based compound.

In one embodiment, the acid scavenger may include a glycidyl ether-based compound.

In one embodiment, the refrigerating machine oil composition may further comprise at least one additive selected from a group consisting of an antioxidant and a wear resistance enhancer.

In one embodiment, the refrigerating machine oil composition may be used in at least one selected from a group consisting of an air conditioner, a refrigerator, and an air conditioner for a vehicle.

The base oil comprising the polyol ester according to the present disclosure may have an excellent miscibility with a refrigerant having polarity and having low global warming potential (GWP).

The base oil comprising the polyol ester according to the present disclosure may have a high viscosity.

The refrigerating machine oil composition containing the base oil comprising the polyol ester according to the present disclosure may have significantly improved chemical stability.

In addition to the above-described effects, the specific effects of the present disclosure will be described together while describing specific details for following the invention.

Advantages and features of the present disclosure, and a method of achieving the advantages and features will become apparent with reference to embodiments described later in detail together with the accompanying drawings. However, the present disclosure is not limited to embodiments as disclosed below, but may be implemented in various different forms. Thus, these embodiments are set forth only to make the present disclosure complete, and to completely inform the scope of the present disclosure to those of ordinary skill in the technical field to which the present disclosure belongs, and the present disclosure is only defined by the scope of the claims.

Further, descriptions and details of well-known steps and elements are omitted for simplicity of the description. Furthermore, in the following detailed description of the present disclosure, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be understood that the present disclosure may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail so as not to unnecessarily obscure aspects of the present disclosure.

The terminology used herein is directed to the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular constitutes "a" and "an" are intended to include the plural constitutes as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprise", "comprising", "include", and "including" when used in this specification, specify the presence of the stated features, integers, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, operations, elements, components, and/or portions thereof. Expression such as "at least one of" when preceding a list of elements may modify an entirety of list of elements and may not modify the individual elements of the list. In interpretation of numerical values, an error or tolerance therein may occur even when there is no explicit description thereof.

Hereinafter, the base oil comprising the polyol ester of the present disclosure and the refrigerating machine oil composition comprising the same will be described in detail.

A base oil for a refrigerating machine oil composition according to the present disclosure is characterized in that the base oil comprises a polyol ester, wherein the polyol ester may have excellent miscibility with refrigerant having high polarity and a low global warming potential (GWP) among variable refrigerants, and may have a high viscosity to increase wear resistance in the refrigerating machine.

Specifically, the polyol ester of the present disclosure has excellent miscibility with various polar refrigerants with a global warming potential of <NUM> to <NUM>,<NUM>. Especially, the polyol ester of the present disclosure has excellent miscibility with environment-friendly refrigerants with a global warming potential of <NUM> to <NUM>. For example, the refrigerant may include one or more HFC-based refrigerants selected from the group consisting of R134a, which is frequently used in refrigeration systems, R410A, which is frequently used in air conditioning technology systems, and R32, which is an eco-friendly refrigerant, however, refrigerants considered in the present disclosure is not necessarily limited hereto. For example, the polyol ester of the present disclosure may be used with the HC-based refrigerant and/or the HFO-based refrigerant, in addition to the HFC-based refrigerant.

Specific examples of refrigerants that may be applied in addition to the above listed refrigerants may include R1234yf (HFO-based refrigerant), R454B (mixture of HFC-based refrigerant and HFO-based refrigerant), R513A (mixture of HFC-based refrigerant and HFO-based refrigerant), and the like, however, it is not necessarily limited hereto.

The polyol ester preferably has a floc point of -<NUM> or lower as measured according to a following measurement method (<NUM>). The lower the value of the floc point, the better the miscibility with a target refrigerant.

[Measuring method (<NUM>)] The floc point is measured according to ASHRAE STANDARD <NUM>, based on a content of <NUM> vol% of the refrigerant based on a total of <NUM> vol% of the polyol ester and the refrigerant.

The polyol ester is required to have the excellent miscibility, and at the same time, have high viscosity required for wear resistance of a compressor of the refrigerating machine. Thus, the polyol ester according to the present disclosure is required to have a kinematic viscosity at <NUM> (KV40) of <NUM> to <NUM> cSt.

Based on a result of intensive research in order to achieve the above technical requirements, the present inventors have derived the polyol ester synthesized using polyhydric alcohol comprising <NUM> or more hydroxyl groups; a first fatty acid, which is a linear fatty acid having <NUM> to <NUM> carbon atoms; a second fatty acid, which is a branched fatty acid having <NUM> to <NUM> carbon atoms; and a third fatty acid, which is a linear or branched fatty acid having <NUM> to <NUM> carbon atoms, and the synthesized polyol ester is used as the base oil for the refrigerating machine oil composition.

The polyol ester (POE) is generally prepared by synthesizing a polyhydric alcohol (polyol) and a fatty acid. In this regard, the present disclosure has a purpose to provide the POE which has excellent miscibility with refrigerant having relatively high polarity. Therefore, in order to increase the miscibility with the polar refrigerant, the polyol ester is also required to have a high polarity, and at the same time, is also required to be synthesized with a high viscosity to ensure lubricity and.

Therefore, in accordance with the present disclosure, in order to increase the polarity of the polyol ester as synthesized, preferably, the polyhydric alcohol may comprise five or more hydroxyl groups (-OH), for example, five to ten hydroxyl groups. For example, di-pentaerythritol (di-PE), tri-pentaerythritol (tri-PE), and the like may be used.

Further, in accordance with the present disclosure, the polyol ester is synthesized by mixing three types of fatty acids with each other: the first fatty acid, which is a linear fatty acid having <NUM> to <NUM> carbon atoms; the second fatty acid, which is a branched fatty acid having <NUM> to <NUM> carbon atoms; and the third fatty acid, which is a linear or branched fatty acid having <NUM> to <NUM> carbon atoms.

The fatty acid having <NUM> to <NUM> carbon atoms such as the first fatty acid and the second fatty acid may be a fatty acid having a relatively smaller number of carbon atoms and may contribute to increasing the polarity of the polyol ester to ensure miscibility with the polar refrigerant. The fatty acids having <NUM> to <NUM> carbon atoms such as the third fatty acid may contribute to ensuring lubricity and high viscosity.

Further, irrespective of the number of carbon atoms (chain length) of the fatty acid, the branched fatty acid may increase the polarity of polyol ester and protect the polyhydric alcohol to increase chemical and hydrolytic stability, compared to the linear fatty acid. However, the branched fatty acid has disadvantages of high cost and high coefficient of friction. Thus, it is preferable to mix the branched fatty acid and the linear fatty acid with each other.

In order to synthesize the polyol ester that the present disclosure requires due to the characteristics of the fatty acids as described above, when a total weight of the first fatty acid, the second fatty acid and the third fatty acid is <NUM> wt%, a content of a combination of the first fatty acid and the second fatty acid is in a range of <NUM> to <NUM> wt%, and a content of the third fatty acid is in a range of <NUM> to <NUM> wt% which is lower than or equal to the content of the combination of the first fatty acid and the second fatty acid.

More specifically, when the total weight of the first fatty acid and the second fatty acid is <NUM> wt%, a content of the first fatty acid may be in a range of <NUM> to <NUM> wt%, and a content of the second fatty acid may be in a range of <NUM> to <NUM> wt%. Accordingly, all of the properties required in the present disclosure, such as the polarity, high viscosity, lubricity, abrasion resistance and chemical stability, may be achieved. As described above, the content of the first fatty acid is lower than or equal to that of the second fatty acid, and the content may be adjusted according to the specific type of the fatty acid.

The refrigerating machine oil composition of the present disclosure is prepared by mixing an additive with the base oil containing the polyol ester. For example, the additive may further include at least one selected from the group consisting of a corrosion inhibitor and an acid scavenger, and may further include an additive such as a wear resistance enhancer, or an antioxidant, etc..

The refrigerating machine oil composition according to the present disclosure has a kinematic viscosity at <NUM> (KV40) of <NUM> to <NUM> cSt, and has a total acid number (TAN) of <NUM> to <NUM> mgKOH/g. In this regard, the total acid number refers to a total acid value, and means an acid value measured according to ASTM D664<IMG>Standard Test Method for Acid Number of Petroleum Products by Potentiometric Titration<IMG>.

When the additive is mixed with the base oil containing the polyol ester, the viscosity of the prepared refrigerating machine oil composition may be somewhat lowered. However, the present disclosure aims to prepare the refrigerating machine oil composition having high viscosity and sufficient lubricity, at the same time. From this point of view, the kinematic viscosity at <NUM> (KV40) of the base oil containing the polyol ester according to the present disclosure is in a range of <NUM> to <NUM> cSt.

In the refrigerating machine oil composition of the present disclosure, the corrosion inhibitor plays a role in preventing degradation of the refrigerating machine oil and corrosion of the expansion valve. However, when the corrosion inhibitor is added in an excessive amount, there may be a problem in that an initial total acid number (TAN) of the refrigerating machine oil composition becomes excessively high. From this point of view, when the total weight of the refrigerating machine oil composition is 100wt%, a content of the corrosion inhibitor is in a range of <NUM> to <NUM>. 10wt%, and more preferably, in a range of <NUM> to <NUM>.

In the refrigerating machine oil composition of the present disclosure, the acid scavenger may trap acids resulting from decomposition of the refrigerant such as hydrofluoric acid, thereby increasing operational stability of the refrigerating machine. When the acid scavenger is added in an excessive amount, the total acid number (TAN) of the refrigerating machine oil composition may increase after aging the refrigerating machine oil composition. Thus, when the total weight of the refrigerating machine oil is 100wt%, a content of the acid scavenger is in a range of <NUM> to <NUM>. 00wt%, and more preferably, in a range of <NUM>. 00wt% to <NUM>.

Those commonly used in the art may be used as the corrosion inhibitor. For example, a thiazole-based compound, a triazole-based compound, or a thiadiazole-based compound may be used as the corrosion inhibitor. For example, the triazole-based compound may include a benzotriazole-based compound containing a benzotriazole group in which the compound contains <NUM> to <NUM> carbon atoms, preferably, <NUM> to <NUM> carbon atoms, excluding the carbon atoms in the benzotriazole group. The present disclosure is not necessarily limited thereto. Specific examples of the compound may include N,N-bis(alkyl)-AR-methyl-<NUM>-benzotriazole-<NUM>-methanamine (CAS No. <NUM>-<NUM>-<NUM>) or the like.

The acid scavenger may be used generally used in the art. For example, an epoxy-based compound, a carbodiimide compound, a glycidyl ether-based compound, a terpene-based compound, and the like may be used as the acid scavenger. For example, the acid scavenger may include a glycidyl ether-based compound, specifically, triglycidyl ether, diglycidyl ether, glycidyl ether, lauryl glycidyl ether, or the like. However, the kinds of the acid scavenger used in the present disclosure is not necessarily limited hereto.

The refrigerating machine oil composition according to the present disclosure may satisfy a following condition (A):
<MAT>.

The (TAN)i means a TAN value measured immediately after the preparation of the refrigerating machine oil composition, and the (TAN)f means a TAN value measured after aging of the refrigerating machine oil composition according to ASHRAE STANDARD <NUM>.

The refrigerating machine oil composition may further contain one or more additives such as the antioxidant and the wear resistance enhancer in addition to the corrosion inhibitor and the acid scavenger. However, the present disclosure is not necessarily limited thereto as long as the purpose of the present disclosure may be achieved.

The refrigerating machine oil composition according to the present disclosure may be applied to a typical refrigerating machine in which the above-described refrigerant is used. A ratio of a content of the refrigerant and a content of the composition may be adjusted according to a type and an operating condition of the refrigerating machine.

According to one embodiment, the refrigerating machine oil composition according to the present disclosure may be preferably used, for example, in an air conditioner, a refrigerator, or an air conditioner of an enclosed car. Further, the refrigerating machine oil composition according to the present disclosure may be preferably used for a dehumidifier, a hot water heater, a freezer, a refrigeration and freezing warehouse, a vending machine, a showcase, a cooling device of a chemical plant, and the like. Further, the refrigerating machine oil composition according to the present disclosure may also be preferably used in a cooling device having a centrifugal compressor.

Hereinafter, the present disclosure will be described in more detail based on Examples and Experimental Examples. However, the following Examples and Experimental Examples are merely examples of the present disclosure, and the present disclosure is not limited to the following Examples and Experimental Example.

Polyol ester of each of Present Example <NUM> and Comparative Examples <NUM> to <NUM> was synthesized using polyhydric alcohol and fatty acids according to Table <NUM> below.

The KV40 kinematic viscosity of the synthesized polyol ester was measured. The synthesized polyol ester and the refrigerant were mixed with each other in a volume ratio of <NUM>: <NUM> to prepare a mixture. Then, the floc point of the mixture was measured according to ASHRAE STANDARD <NUM>. The measurement results are shown in a following Table <NUM>.

Further, the polyol ester according to Present Example <NUM> was mixed with each of various refrigerants listed in Table <NUM> below, and then the floc point of each mixture was measured. It was determined that the excellent miscibility with the refrigerant as required in the present disclosure was satisfied when the floc point was -<NUM> or lower. It was interpreted that the lower the floc point value, the higher the miscibility with the refrigerant.

A refrigerating machine oil composition was prepared by mixing a corrosion inhibitor and an acid scavenger with the polyol ester as prepared in Present Example <NUM> as described above. Specifically, the refrigerating machine oil composition of each of Present Examples A to B and Comparative Examples A to C was prepared by mixing different types and contents of the corrosion inhibitor and the acid scavenger as described in Table <NUM> below with the polyol ester as prepared in Present Example <NUM> as described above.

The initial KV40 and initial TAN values of the prepared refrigerating machine oil compositions (New Oil) were measured. Next, the KV40 and TAN values of the refrigerating machine oil compositions after aging (aged oil) were measured according to ASHRAE STANDARD <NUM> under the condition of an environment-friendly R32 refrigerant environment. Change in the TAN value before and after the aging was calculated and shown in Table <NUM> below.

In Table <NUM> below, a semi-finished product was prepared by mixing the polyol ester prepared in Present Example <NUM> with the antioxidant and the wear resistance enhancer at the same weight ratio. In Table <NUM> below, the corrosion inhibitor was N,N-bis(<NUM>-ethylhexyl)-AR-methyl-<NUM>-benzotriazole-<NUM>-methanamine. 'acid scavenger <NUM>' was lauryl glycidyl ether, 'acid scavenger <NUM>' was butyl glycidyl ether, and 'acid scavenger <NUM>' was trimethylolpropane triglycidyl ether.

Claim 1:
A refrigerating machine oil composition comprising:
a base oil comprising polyol ester,
wherein the polyol ester is synthesized using:
a polyhydric alcohol containing <NUM> or more hydroxyl groups;
a first fatty acid as a linear fatty acid having <NUM> to <NUM> carbon atoms;
a second fatty acid as a branched fatty acid having <NUM> to <NUM> carbon atoms; and
a third fatty acid as a linear or branched fatty acid having <NUM> to <NUM> carbon atoms,
wherein in synthesizing the polyol ester, a sum of a content of the first fatty acid and a content of the second fatty acid is in a range of <NUM> to <NUM> wt%, and a content of the third fatty acid is in a range of <NUM> to <NUM> wt%, based on <NUM> wt% of a total weight of the first fatty acid, the second fatty acid, and the third fatty acid,
wherein the polyol ester has a kinematic viscosity at <NUM> (KV40) in a range of <NUM> to <NUM> cSt,
wherein the refrigerating machine oil further comprises at least one additive selected from a group consisting of a corrosion inhibitor and an acid scavenger, whereby both a corrosion inhibitor and an acid scavenger are present,
wherein the refrigerating machine oil composition has a kinematic viscosity at <NUM> (KV40) in a range of <NUM> to <NUM> cSt,
wherein a total acid number (TAN) of the refrigerating machine oil composition is in a range of <NUM> to <NUM> mgKOH/g,
wherein when a total weight of the refrigerating machine oil composition is <NUM> wt%, a content of the corrosion inhibitor is in a range of <NUM> to <NUM> wt%, and a content of the acid scavenger is in a range of <NUM> to <NUM> wt%,
wherein the polyol ester has a floc point of -<NUM> or lower as measured according to following measurement method (<NUM>):
[Measuring method (<NUM>)] The floc point is measured according to ASHRAE STANDARD <NUM>, based on a content of <NUM> vol% of a refrigerant used with the polyol ester and having a global warming potential (GWP) of <NUM> to <NUM>,<NUM>, based on a total of <NUM> vol% of the polyol ester and the refrigerant,
wherein the refrigerating machine oil composition satisfies a following condition (A): <MAT>
where (TAN)i means a TAN value measured immediately after preparation of the refrigerating machine oil composition, and (TAN)f means a TAN value measured after aging of the refrigerating machine oil composition according to ASHRAE STANDARD <NUM>.