Compositions – Vaporization – or expansion – refrigeration or heat or energy... – With lubricants – or warning – stabilizing or anti-corrosion...
Reexamination Certificate
1999-04-09
2001-07-31
Johnson, Jerry D. (Department: 1764)
Compositions
Vaporization, or expansion, refrigeration or heat or energy...
With lubricants, or warning, stabilizing or anti-corrosion...
C508S485000, C508S492000, C508S494000
Reexamination Certificate
active
06267906
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 chlorof luorocarbon heat transfer fluids such as trichlorof luoromethane 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.
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 basestocks for almost any type of refrigeration machinery employing a fluorocarbon refrigerant, particularly one free from chlorine. The following patents and published patent applications also teach many general classes and specific examples of polyol esters useful as-refrigerant lubricants with chlorine-free fluoro group containing heat transfer fluids: U.S. Pat. No. 4,851,144; UK 2 216 541; U.S. Pat. No. 5,021,179; U.S. Pat. No. 5,096,606; WO 90/12849 (Lubrizol); EP 0 406 479 (Kyodo Oil); EP 0 430 657 (Asahi Denka KK); EP 0 435 253 (Nippon Oil); EP 0 445 610 and 0 445 611 (Hoechst AG); EP 0449 406; EP 0 458 584 (Unichema Chemie BV); and EP 0 485 979 (Hitachi).
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 exact quantities stated is usually preferable, however.
More specifically, esters according to this invention should have a viscosity of not more than 157, or with increasing preference in the order given, not more than 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.
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-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; tri-pentaerythritol (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 tritrimethylolpropane (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, or 19%, 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 mixture that contain 8 or more carbon atoms and are unbranched to the % of acyl groups in the mixture that are both branched and contain not more than six, preferably not more than five, carbon atoms is not greater than 1.56, more preferably not greater than 1.21, or still more preferably not greater than 1.00; (c) the % of acyl groups in the ester mixture that contain at least nine carbon atoms, whether branched or not, is not greater than 81, or increasingly more preferably, not greater than 67 or 49; and (d) not more than 2, more preferably not more than 1, or still more preferably not more than 0.4, % of the acyl groups in the ester mixture are from acid molecules with more than two carboxyl groups each; and (e) a total of at least 20, or, with increasing preference in the order given, at least 29, 35, or 41% of the acyl groups in the mixture are from one of the trimethylhexanoic acids, most preferably from 3,5,5-trimethylhexanoic acid; and not more than 7.5, or, with increasing preference in the order given, not more than 6.0, 4.5, 3.0, 1.7, 0.9, or 0.4% of the acyl groups in the acid mixture are dibasic. In all these percentages, acyl groups are counted as a single group, irrespective of the number of valences they have. For example, each molecule of adipic acid yields a single, dibasic, acyl group when completely esterified.
(Of course, for all the types of esters described herein as part of the invention, it is possible to obtain the same esters or mixture of esters by reacting acid derivatives such as acid anhydrides, acyl chlorides, and esters of the acids with lower molecular weight alcohols than those desired in the ester products according to this invention, instead of reacting the acids themselves. The acids are generally preferred for economy and are normally specified herein, but it is to be understood that the esters defined herein by reaction with acids can be equally well obtained by reaction
Schnur Nicholas E.
Zehler Eugene R.
Child, Jr. John S.
Drach John E.
Henkel Corporation
Johnson Jerry D.
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