Compositions – Vaporization – or expansion – refrigeration or heat or energy... – With lubricants – or warning – stabilizing or anti-corrosion...
Reexamination Certificate
1997-10-02
2001-02-06
Skane, Christine (Department: 1751)
Compositions
Vaporization, or expansion, refrigeration or heat or energy...
With lubricants, or warning, stabilizing or anti-corrosion...
C062S084000, C252S067000, C508S485000
Reexamination Certificate
active
06183662
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to lubricant base stocks, which can also serve as complete lubricants in some cases; compounded lubricants, which include at least one additive for such purposes as improving high pressure and/or wear resistance, corrosion inhibition, and the like along with the lubricant base stocks which contribute the primary lubricity to the compounded lubricants; refrigerant working fluids including lubricants according to the invention along with primary heat transfer fluids, and methods for using these materials. The lubricants and lubricant base stocks are generally suitable for use with most or all halocarbon refrigerants and are particularly suitable for use with substantially chlorine-free, fluoro-group-containing organic refrigerating heat transfer fluids such as pentafluoroethane, 1,1-difluoroethane, 1,1,1-trifluroethane, and tetrafluoroethanes, most particularly 1,1,1,2-tetrafluoroethane. The lubricants and base stocks, in combination with these heat transfer fluids, are particularly suitable for lubricating compressors that operate at least part of the time at temperatures substantially higher than those at which humans can be comfortable; such compressors are generally used, for example, in vehicle air conditioning.
2. Statement of Related Art
Chlorine-free heat transfer fluids are desirable for use in refrigerant systems, because their escape into the atmosphere causes less damage to the environment than the currently most commonly used chlorofluorocarbon heat transfer fluids such as trichlorofluoromethane and dichlorodifluoromethane. The widespread commercial use of chlorine-free refrigerant heat transfer fluids has been hindered, however, by the lack of commercially adequate lubricants. This is particularly true for one of the most desirable working fluids, 1,1,1,2-tetrafluoroethane, commonly known in the art as “Refrigerant 134a” or simply “R134a”. Other fluoro-substituted ethanes are also desirable working fluids.
Before the change to substantially chlorine-free halocarbon refrigerants that was legally mandated during the last few years as a result of concern about the effect on chlorine containing emissions in harming the earth's ozone layer, it was conventional to use mineral oil lubricants for compressors of this type. Because of the design of many vehicle air conditioners, it has been found to be impossible to flush the former chlorine containing refrigerant heat transfer fluids and their associated mineral oil lubricants from the air conditioning equipment in these vehicles thoroughly. Instead, only drainage of the former fluids from the air conditioning equipment is possible, and such drainage can easily result in as much as 25% of the formerly used mineral oil lubricant remaining behind in the equipment when it is retrofitted with a chlorine free heat transfer fluid and lubricants suitable for use with such heat transfer fluids.
Esters of hindered polyols, which are defined for this purpose as organic molecules containing at least five carbon atoms, at least 2 —OH groups, and no hydrogen atoms on any carbon atom directly attached to a carbon atom bearing an —OH group, have already been recognized in the art as high quality lubricant base-stocks for almost any type of refrigeration machinery employing a fluorocarbon refrigerant, particularly one free from chlorine. However, room for improvement in the art still exists.
DESCRIPTION OF THE INVENTION
Except in the claims and the operating examples, or where otherwise expressly indicated, all numerical quantities in this description indicating amounts of material or conditions of reaction and/or use are to be understood as modified by the term “about” in defining the broadest scope of the invention. Practice of the invention within the boundaries corresponding to the numerical quantities stated is usually preferable, however. Also, unless explicitly stated to the contrary, the description of more than one chemical compound or class of compounds as suitable or preferred for the a particular purpose in connection with the invention shall be understood as implying that mixtures of any two or more of the entities so described individually as suitable or preferred are equally as suitable or preferred as the individual entities.
OBJECT OF THE INVENTION
A major object of this invention is to provide lubricants that avoid phase separations when used with chlorine-free halocarbon refrigerants over a wide temperature range and that have good lubricity, resistance to hydrolysis and other chemical reactions leading to degradation in use, and viscosities in the range needed for most normal vehicle air conditioners; more specifically, esters according to this invention should have a viscosity of not more than 220, or with increasing preference in the order given, not more than 200, 173, 157, 145, 134, 123, 115, or 110, centistokes at 40° C. Independently, esters according to this invention should have a viscosity of at least 45, or with increasing preference in the order given, at least 51, 64, 76, 85, or 90, centistokes at 40° C. Another object of one major embodiment of the invention is to provide lubricants which, in addition to the other qualities described above, can be mixed with at least 25% of its own mass of mineral oils, whether paraffinic or naphthenic oils or mixtures of both, such as those that might be left behind in drained vehicle air conditioning equipment as described above. Still another objective of the most preferred embodiments of this invention is to provide ester lubricants with good resistance to hydrolysis in use.
SUMMARY OF THE INVENTION
It has now been found that selected polyol esters provide high quality lubrication for this kind of service. Specifically effective are esters or mixtures of esters made by reacting (i) a mixture of alcohol molecules selected from the group consisting of 2,2-dimethyl-1,3-propanediol (also known as “neopentyl glycol” and often abbreviated hereinafter as “NPG”); 2,2-dimethylol-1-butanol (also known as “trimethylolpropane” and often abbreviated hereinafter as “TMP”); di-trimethylolpropane (often abbreviated hereinafter as “DTMP”), a molecule with four hydroxyl groups and one ether linkage, formally derived from two molecules of TMP by removing one hydroxyl group from one of the TMP molecules and one hydrogen atom from a hydroxyl group of the other TMP molecule to form water and join the two remainders of the original TMP molecules with an ether bond; 2,2-dimethylol-1,3-propanediol (also known as “pentaerythritol” and often abbreviated hereinafter as “PE”); di-pentaerythritol (often abbreviated hereinafter as “DPE”), a molecule with six hydroxyl groups and one ether bond, formally derived from two PE molecules by the same elimination of the elements of water as described above for DTMP; tripentaerythritol (often abbreviated hereinafter as “TPE”), a molecule with eight hydroxyl groups and two ether bonds, formally derived from three PE molecules by an analogous elimination of the elements of two molecules of water as described above (for elimination of a single water molecule) for DTMP and DPE; and tri-trimethylolpropane (hereinafter often abbreviated as “TTMP”), a molecule with five hydroxyl groups and two ether bonds, formally derived from three TMP molecules by the same elimination of the elements of two molecules of water as described above for TPE, with (ii) a mixture of acid molecules selected from the group consisting of all the straight and branched chain monobasic and dibasic carboxylic acids with from four to twelve carbon atoms each, with the alcohol moieties and acyl groups in the mixture of esters selected subject to the constraints that (a) a total of at least 3%, or, with increasing preference in the order given, at least 7, 10, 14, 16, 19, 21, 23, 25, or 27%, of the acyl groups in the mixture are 2-methylbutanoyl or 3-methylbutanoyl groups, which are jointly abbreviated hereinafter as “acyl groups from [or of] i-C
5
acid”; (b) the ratio of the % of acyl groups in the mixt
Child John S.
Drach John E.
Henkel Corporation
Skane Christine
LandOfFree
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