Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Heterocyclic ring compound; a heterocyclic ring is one...
Reexamination Certificate
2001-01-17
2003-04-15
McAvoy, Ellen M. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Heterocyclic ring compound; a heterocyclic ring is one...
C508S251000, C508S485000, C508S556000, C508S579000, C508S583000, C252S067000, C252S068000, C062S502000
Reexamination Certificate
active
06548457
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a lubricant for a compression type refrigeration system using ammonia refrigerant that does not have the possibility of ozone layer depletion and global warming. Further, the present invention relates to a working fluid composition comprising the ammonia refrigerant and the lubricant, and a refrigeration system which is filled with the working fluid composition.
2. Description of the Related Art
A compression type refrigeration system is composed of a compressor, a condenser, an expansion mechanism (such as an expansion valve or a capillary tube), an evaporator and so forth, and conducts cooling by utilizing a property of a refrigerant with high volatility which takes latent heat from its surroundings during evaporation. The compression type refrigeration system is used in a refrigerator, a freezer, an air conditioner, a showcase, a vending machine of soft drinks or ice creams, and the like. In air conditioner, vending machine or the like, the system is also used as a heater to warm the air, or drinks and foods by utilizing heat generated by condensing.
As the refrigerant, (hydro) fluorocarbons containing chlorine (CFC or HCFC) have conventionally been used. Recently, CFC or HCFC is being replaced by hydrofluorocarbons (HFC) not containing chlorine. However, CFC and HCFC break an ozone layer, and HFC has a high global warming ability. In view of earth environment protection, refrigerants that do not adversely-affect environment are desired as alternates of those hydrofluorocarbons. As a result, refrigerants such as low molecular weight hydrocarbons or ammonia, which do not break an ozone layer and have much smaller global warming ability than the above hydrofluorocarbons, become reevaluated as environment-friendly refrigerants. In particular, ammonia has high coefficient of performance.
Mineral oils or alkylbenzenes have been used as a base oil for a lubricant for a refrigeration system using an ammonia refrigerant. Recently, polyether compounds having compatibility with ammonia are proposed (for example, European Patent No. 490810A, European Patent No. 585934A, German Patent No. 4404804A and International Patent WO 95/12594A). By using a polyether compound having a compatibility with ammonia, there is the advantage that it is not necessary to provide a lubricant circulation facilities that separate and recover a lubricant at a discharge side of a refrigerating compressor, and return the recovered lubricant to the compressor.
However, ammonia as a refrigerant is a compound having high activity, it reacts with a base oil or additives of a lubricant for a refrigeration system, or deteriorated materials thereof to form separation substances (reaction products). As a result, there is fear of plugging of an expansion valve or capillary, abrasion of a sliding member, and further promoting deterioration of the lubricant. Further, ammonia has high corrosion property to a metal, particularly under the presence of water, and by using it with a polyether compound having high hygroscopicity, corrosion and deterioration of a metal, such as rust, are promoted. Further, because ammonia refrigerant requires high pressure operation compared with flon type refrigerant, refrigerant and lubricant are exposed to severer conditions such as high temperature and high pressure, and sliding conditions also become hard. As a result, there are the possibilities of increase of formation of separation substances, promotion of deterioration of lubricant (base oil and additives), and increase of friction and abrasion. Lubricants that have high lubricating properties including stability even under the severe condition using ammonia refrigerant are desired.
Regarding polyether compounds, derivatives of polyether compounds in which its terminal hydroxyl group is substituted with alkyl group or acyl group to improve stability and hygroscopicity (hereinafter referred to “polyether compounds” including derivatives) are proposed. However, the step producing the derivatives is added, and it brings the disadvantage such that good compatibility with ammonia lowers. Thus, the degree of improvement in stability and hygroscopicity are not sufficiently satisfied, and there is a limit to resolve by a base oil only. Therefore, it is required to select and use an appropriate additive in the combination of ammonia and a base oil. However, in many cases, additives have higher activity than base oil, more easily react with ammonia, and may promote deterioration and formation of separation substance.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a lubricant having excellent compatibility with ammonia and having excellent performances of good stability and lubricating properties for practical use, as a lubricant for a refrigeration system using ammonia refrigerant.
The present invention has solved the above-mentioned various problems and achieved the the expected results. That is, the present invention provides a lubricant for a compression type refrigeration system using ammonia as a refrigerant, and the lubricant comprises (A) at least one kind of polyether compounds, and (B) at least one kind of aromatic amine compounds or phenothiazine compounds, and the lubricant preferably further comprises (C) at least one kind of alcohol compounds selected from the group consisting of oleyl alcohol, polyhydricalcohol partial ester and polyhydricalcohol partial ether, and/or (D) at least one kind of benzotriazole compounds selected from benzotriazole and its derivatives.
The present invention further provides a working fluid composition for a compression type refrigeration system, comprising the lubricant and ammonia refrigerant.
The present invention further provides a refrigeration system which is filled with the working fluid composition.
BEST MODES FOR CARRY OUT THE INVENTION
The polyether compounds (A) used in the present invention are used as a base oil that is the main component of a lubricant. Though they include various compounds, the polyether compounds may be used by appropriately selecting according to the purpose of use or the like. The preferable compounds include polyether compounds represented by the following formula (1):
X[—O—(AO)
n
-R]m (1)
where X shows a hydrocarbon group in the form of excluding hydroxyl group from monool or polyol, A shows an alkylene group having 2-4 carbon atoms, R shows hydrogen or an alkyl group having 1-10 carbon atoms, m is a valence number of X, and n is a positive integer of 2 or more.
In the above formula (1), if X is a hydrocarbon group in the form of being derived from monool, X is preferably a straight-chain or branched-chain, saturated or unsaturated hydrocarbon group having 1-20 carbon atoms, and further preferably an alkyl group having 1-8 carbon atoms. Specific examples of the preferred monool include methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol and octanol. If X is in the form of being derived from polyol, X is preferably a hydrocarbon group in the form of removing all hydroxyl groups from divalent to hexavalent polyol having 2-15 carbon atoms. Specific examples of the polyol include ethylene glycol, propylene glycol, glycerol, trimethylol ethane, trimethylol propane, trimethylol butane, pentaerythritol, sorbitan, sorbitol, and the like. Condensation type polyols such as diglycerol or dipentaerythritol may be used.
If the valence number m of X becomes large, the molecular weight of the polyether compound increases and its viscosity is too high, so that there is the tendency that compatibility with ammonia lowers. Therefore, the valence number m of X is preferably 1, 2 or 3. Of those, the valence number m of 1, that is, a hydrocarbon group in the form of being derived from monool, is particularly preferable as X. Even in such a hydrocarbon group, if the number of carbon atoms increases, viscosity becomes too high, compatibility lowers. Therefore, the carbon number of X is preferably 1-8 as mentioned above, more preferably 1-4. Th
Kaimai Takashi
Takahashi Hitoshi
Hollander Law Firm, P.L.C.
Japan Energy Corporation
McAvoy Ellen M.
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