PCT
`
`WORLD INTELLECTUAL PROPERTY ORGANIZATION
`International Bureau
`
`
`
`
`
`‘ INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)
`(51) International Patent Classification 5 :
`(11) International Publication Number:
`WO 93/24597
`C10M 105/34, 105/38, 105/42
`(43) International Publication Date:
`9 December1993 (09.12.93)
`
`
`a PCT/US93/04887|(74) Agent: WISDOM,Norvell, E.; Henkel Corporation, 140(21) International Application Number:
`Germantown Pike, Suite 150, Plymouth Meeting, PA
`19462 (US).
`
`iyi
`;
`
`(22) International Filing Date:
`
`27 May 1993 (27.05.93)
`
`(30) Priority data:
`3 June 1992 (03.06.92)
`PCT/US92/04438
`(34) Countries for which the regional
`or international application
`wasfiled:
`08/027,628
`
`10 March 1993 (10.03.93)
`
`wo
`
`(81) Designated States: CA, JP, KR, European patent (AT, BE,
`CH, DE, DK, ES, FR, GB, GR, IE, IT, LU, MC, NL,
`PT, SE).
`
`CA et al.
`US|
`
`Published
`With international search report.
`
`
` (54) Title: POLYOL ESTER LUBRICANTS FOR HERMETICALLY SEALED REFRIGERATING COMPRESSORS
`
`140
`(71) Applicant: HENKEL CORPORATION [US/US];
`Germantown Pike, Suite 150, Plymouth Meeting, PA
`19462 (US).
`
`; 4347 Mount Alverno
`(72) Inventors: SCHNUR,Nicholas, E.
`Road, Cincinnati, OH 45238 (US). ZEHLER,Eugene, R.
`; 7449 Cinnamon Woods Drive, West Chester, OH 45069
`(US).
`
`(57) Abstract
`
`A high quality lubricant for hermetically sealed domestic air conditioner and refrigerator compressors, especially those us-
`ing chlorine free hydrofluorocarbon refrigerant working fluids, is provided by mixed esters of hindered polyols, most desirably
`pentaerythritol, with a mixture of carboxylic acids including at least some isopentanoic acid along with either or both of iso-nona-
`noic acid and dibasic acids such as adipic.
`
`
`
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`FOR THE PURPOSES OF INFORMATION ONLY
`
`Codes used to identify States party to the PCTon the front pages of pamphlets publishing international
`applications under the PCT.
`
`Viet Nam
`
`France
`Gabon
`United Kingdom
`Guinca
`Greece
`Hungary
`ireland
`Italy
`Japan
`Democratic People’s Republic
`of Korea
`Republic of Korea
`Kazakhstan
`Licehtenstein
`Sri Lanka
`Luxembourg
`Monaco
`Madagasear
`Mali
`Mongolia
`
`Austria
`Australia
`Barbados
`Belgium
`Burkina Faso
`Bulgaria
`Benin
`Brazii
`Canada
`Central African Republic
`Congo
`Switzerland
`Céte d'lvoire
`Cameroon
`Cacchoslovakia
`Czech Republic
`Germany
`Denmark
`Spain
`Finland
`
`Mauritania
`Malawi
`Netherlands
`Norway
`New Zealand
`Poland
`Portugal
`Romania
`Russian Federation
`Sudan
`Sweden
`Slovak Republic
`Senegal
`Soviet Union
`Chad
`Togo
`Ukraine
`United States of America
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`PCT/US93/04887
`
`POLYOL ESTER LUBRICANTS FOR HERMETICALLY SEALED
`REFRIGERATING COMPRESSORS
`
`CROSS~REFERENCE TO RELATED APPLICATION
`
`This application is a continuation-in-part of copend-
`ing International Application No. PCT/US92/04438 designat-
`ing the United States and filed June 3, 1992,
`the entire
`disclosure of which, except to the extent contrary to any
`explicit statement herein,
`is hereby incorporated herein
`by reference.
`BACKGROUND OF THE INVENTION
`
`Field of the Invention
`
`10
`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 resistance,
`corrosion inhibition, and the like along with the lubri-
`cant base stocks which contribute the primary lubricity to
`the compounded lubricants; refrigerant working fluids in-
`cluding lubricants according to the invention along with
`primary heat transfer fluids, and methods for using these
`materials.
`The lubricants and lubricant base stocks are
`
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`
`generally suitable for use with most or all halocarbon
`refrigerants and are particularly suitable for use with
`substantially chlorine-free,
`fluoro-group-containing or-
`ganic refrigerating heat
`transfer fluids such as penta-
`fluoroethane,
`1,1-difluoroethane,
`1,1,1-trifluroethane,
`and tetrafluoroethanes, most particularly 1,1,1,2-tetra-
`fluoroethane.
`The lubricants and base stocks,
`in combina-
`tion with these heat
`transfer
`fluids, are particularly
`suitable for hermetically sealed compressors for domestic
`air conditioners and refrigerators, where long lubricant
`service lifetimes are important because of the difficulty
`and expense of supplying additional
`lubricant after the
`initial assembly of the compressor.
`Statement of Related Art
`
`
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`.
`
`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 dichlor-
`odifluoromethane.
`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, com-
`monly known in the art as "Refrigerant 134a" or simply
`"R134a". Other fluoro-substituted ethanes are also desir-
`
`able 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 bear-
`ing 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 re-
`frigerant, particularly one free from chlorine.
`The fol-
`lowing 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:
`US 4,851,
`144; UK 2 216 541; US 5,021,179; US 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 O 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 quant-
`ities 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
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`the boundaries corresponding to the exact quantities stat-
`
`:
`ed is usually preferable, however.
`More specifically, esters according to this invention
`should have a viscosity of not more than 44, or with in-
`creasing preference in the order given, not more than 42,
`40, 38.5, 37.2, 36.6, 36.2, 35.7, or 35.2, centistokes at
`40° C.
`Independently, esters according to this invention
`should have a viscosity of at least 22.5, or with increas-
`ing preference in the order given, at
`least 23.9, 25.0,
`25.9, 26.7, 27.4, 28.0, 28.5, 29.0, 29.4, or 29.8, centi-
`
`stokes 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 se-
`lected from the group consisting of 2,2-dimethylol-1-buta-
`nol (also known as "trimethylolpropane" and often abbrevi-
`ated 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");
`and di-pentaerythritol
`(often abbreviated here-
`inafter 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, with (ii) a mixture of acid molecules se-
`lected 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’
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`.
`
`least 7, 10, 14, 16, or 19 %, of the acyl groups in the
`mixture 2-methylbutanoyl] or 3-methylbutanoyl groups, which
`are jointly abbreviated hereinafter as “acyl groups from
`i-C, acid";
`(b)
`the ratio of the % of acyl groups in the
`mixture that contain 8 or more carbon atoms and are un-
`
`branched 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 pref-
`erably 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
`in-
`creasingly more preferably, not greater than 67 or 49; and
`
`(ad) 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
`
`a
`(d)(1)
`more than two carboxyl groups each; and either
`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 trimethylhex-
`anoic acids, most preferably from 3,5,5-trimethylhexanoic
`acid; and not more than 7.5, or, with increasing prefer-
`ence 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
`from dibasic acids; or
`(d)(2) at
`least 2.0, or with in-
`creasing preference in the order given, at least 2.8, 3.6,
`4.1, or 4.9, %, but not more than 13 %, preferably not
`more than 10 %, or still more preferably not more than 7.0
`%, of the acyl groups in the ester mixture are from dibas-
`ic acid molecules; and a total of at least 82, or with in-
`creasing preference in the order given, at
`least 85, 89,
`93, 96, or 99 % of the monobasic acyl groups in the acid
`mixture have either five or six, or more preferably exact-
`ly five, carbon atoms each.
`In all these percentages,
`acyl groups are counted as a single group,
`irrespective of
`the number of valences they have.
`For example, each mole-
`cule of adipic acid yields a single, dibasic, acyl group
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`when completely esterified.
`
`the types of esters described
`for all
`(Of course,
`herein as part of the invention, it is possible to obtain
`the same esters or mixture of esters by reacting acid de-
`rivatives 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 es-
`ters defined herein by reaction with acids can be equally
`well obtained by reaction of alcohols with the correspond-
`ing acid derivatives, or even by other reactions.
`The
`only critical feature is the mixture of acyl groups and
`alcohol moieties in the final mixture of esters formed.)
`Preferably, with increasing preference in the order
`given, at least 60, 75, 85, 90, 95, or 98 % of the hydrox-
`yl groups in the mixture of alcohols reacted to make es-
`ters according to this invention are moieties of PE mole-
`
`in the mixtures reacted to make the
`Independently,
`cules.
`esters according to this invention, with increasing pref-
`erence in the order given, at least 60, 75, 85, 90, 95, or
`98 % of the monobasic acid molecules in the acid mixture
`consist of molecules having no more than ten carbon atoms
`each and, with increasing preference in the order given,
`at least 60, 75, 85, 90, 95, or 98 % of the dibasic acid
`molecules in the acid mixture consist of molecules having
`no more than ten carbon atoms each, or more preferably
`from five to seven carbon atoms each. Most preferably,
`with increasing preference in the order given, at
`least
`60, 75, 85, 90, 95, or 98 % of the monobasic acid mole-
`cules in the acid mixture consist of molecules having ei-
`ther five or nine carbon atoms each.
`
`These preferences for the acyl groups and alcohol
`moieties in esters according to this invention are based
`on empirically determined generalizations.
`In order to
`achieve the desired middle range of viscosity, correspond-
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`‘
`
`ing approximately to ISO grades 22 - 46, it is advantage-
`ous to have a substantial fraction of alcohols with at
`least four hydroxyl groups. Among the commercially avail-
`able hindered alcohols that satisfy this criterion, PE is
`less expensive than DTMP and is free from the ether link-
`age in DTMP, which increases the hygroscopicity of
`the
`esters formed and thereby may promote undesirable corro-
`sion of the metal surfaces lubricated. Alcohols with more
`than four hydroxyl groups produce esters with higher than
`optimum viscosities, but
`some such esters can be toler-
`ated, and mixtures including them may be cheaper.
`Commer-
`cial grade PE often contains a substantial amount of DPE,
`and costs at
`least a little less than more purified PE.
`When cost factors are not severely constraining,
`removing
`most or all of the DPE from a predominantly PE mixture of
`alcohols used to make the esters is preferable,
`in order
`to minimize the chance of insolubility of part of the es-
`
`ter mixture at low temperatures.
`In order to obtain esters with adequate viscosity, a
`considerable fraction of the acid molecules reacted need
`to have eight or more carbon atoms or be dibasic. Dibasic
`acids are less desirable.
`They must be used,
`if at all,
`in rather small amounts in order to avoid excessive vis-
`cosity, because of the capability of forming very high mo-
`lecular weight and very viscous oligomers or polymers by
`reaction between alcohol and acid molecules that both have
`at least two functional groups.
`In practice, it has been
`found that the amount of dibasic acid that can be effect-
`ively used in the acid mixture reacted to make esters ac-
`cording to this invention is substantially less than the
`amount that would be sufficient to provide at
`least one
`dibasic acid group to link each two alcohol molecules in
`the alcohol mixture also reacted.
`Therefore, when such
`
`amounts of dibasic acid are used,
`some of the alcohol mol-
`ecules will be joined together in the esters formed and
`some will not;
`the esters with two or more alcohol moie-
`ties will be much more viscous and normally less readily
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`soluble in the fluorocarbon refrigerant fluids than the
`other esters in the mixture,
`those with only one alcohol
`moiety,
`thereby increasing the risk of undesirable phase
`
`separation in the course of use of the esters. However,
`limited amounts of dibasic acid may nevertheless be used,
`
`as already noted above.
`When substantially only monobasic acids are used to
`make the esters, as already noted,
`in order to obtain ade-
`quate viscosity in the mixture, a substantial fraction of
`the acid molecules must have at least eight carbon atons.
`With acids of such length, solubility in the fluorocarbon
`refrigerant fluids is less than for esters with shorter
`acids, and this reduced solubility is particularly marked
`for straight chain acids,
`so that a substantial fraction
`of the longer acids normally needs to be branched; alter-
`natively,
`it has been found that
`these longer straight
`chain acids can be "balanced" for solubility with an equal
`or not too much less than equal fraction of branched acids
`with five or six carbon atoms. When the number of carbon
`atoms per molecule is nine or more, not even branching is
`sufficient
`to produce adequate solubility by itself,
`so
`that an upper limit on the fraction of such acids is in-
`dependently required.
`In general, a minimum amount of the
`particularly advantageous i-c, acid is specified to aid in
`solubilizing the parts of the esters in the mixture that
`contain dibasic acids or those with eight or more carbon
`atoms.
`
`For both performance and economic reasons,
`
`it has
`
`been found that five and nine carbon monobasic acids are
`
`the most preferred constituents, and they are very effec-
`tive in balancing each other to achieve a mix of viscosity
`and solubility characteristics that is better suited than
`others to most applications.
`Trimethylhexanoic acids,
`with their three methyl branches, produce the most soluble
`esters among the readily available nine carbon acids.
`(In
`
`general, methyl branches are the most effective in promot-
`ing solubility without
`increasing viscosity excessively,
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`in other
`the larger number of carbon atoms
`because of
`branching groups.)
`Branches on the carbon alpha to the
`carboxyl
`increase the difficulty of esterification and do
`not appear to be any more effective in increasing solubil-
`ity than more remotely located branches. The most econon-
`ical commercially available mixture of branched nine car-
`bon acids, which contains from 88 - 95 mole % of 3,5,5-
`trimethylhexanoic acid with all but at most 1 mole % of
`the remainder being other branched Cg monobasic acids,
`appears at least as effective as any other and is there-
`fore preferred for economic reasons as the source of Cy
`monobasic acids.
`
`It is to be understood that only the desired alcohols
`and acids are explicitly specified, but some amount of the
`sort of
`impurities normally present
`in commercial or in-
`dustrial grade products can be tolerated in most cases.
`For example, commercial pentaerythritol normally contains
`only about 85 - 90 mole % of pure pentaerythritol, along
`with 10 - 15 mole % of di-pentaerythritol, and commercial
`pentaerythritol is satisfactory for use in making lubri-
`cant esters according to this invention in many cases.
`In
`general, however, it is preferred, with increasing pref-
`erence in the order given,
`that not more than 25, 21, 17,
`12, 8, 5, 3, 2, 1, 0.5, or 0.2 % of either the hydroxyl
`groups in the alcohol mixtures specified herein or of the
`carboxyl groups
`in the acid mixtures specified herein
`
`should be part of any molecules other than those explicit-
`ly specified for each type of lubricant base stock.
`Per-
`centages of specific chemical molecules or moieties speci-
`fied herein, such as the percentages of carboxyl and hy-
`droxyl groups stated in the preceding sentence, are to be
`understood as number percentages, which will be mathemat-
`ically identical
`to percentages by chemical equivalents,
`with Avogadro’s number of each specified chemical moiety
`regarded as a single chemical equivalent.
`The above descriptions for each of the acid and al-
`cohol mixtures reacted to produce lubricant esters accord-
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`ing to this invention refers only to the mixture of acids
`or alcohols that actually reacts to form esters and does
`not necessarily imply that the mixtures of acids or alco-
`hols contacted with each other for the purpose of reaction
`will have the same composition as the mixture that actu-
`ally reacts.
`In fact, it has been found that reaction be-
`tween the alcohol(s)
`and the acid(s) used proceeds more
`effectively if the quantity of acid charged to the reac-
`tion mixture initially is enough to provide an excess of
`10 - 25 % of equivalents of acid over the equivalents of
`alcohol reacted with the acid.
`(An equivalent of acid is
`defined for
`the purposes of
`this specification as the
`amount containing one gram equivalent weight of carboxyl
`groups, while an equivalent of alcohol is the amount con-
`taining one gram equivalent weight of hydroxyl groups.)
`The composition of the mixture of acids that actually re-
`acted can be determined by analysis of the product ester
`mixture for its acyl group content.
`In making most or all of the esters and mixtures of
`esters preferred according to this invention,
`the acid(s)
`reacted will be lower boiling than the alcohol(s) reacted
`and the product ester(s). When this condition obtains, it
`is preferred to remove the bulk of any excess acid remain-
`ing at the end of the esterification reaction by distilla- .
`tion, most preferably at a low pressure such as 1
`-
`5
`torr.
`
`the product is often
`After such vacuum distillation,
`ready for use as a lubricant or lubricant base stock ac-
`cording to this invention.
`If further refinement of the
`product is desired,
`the content of free acid in the prod-
`uct after the first vacuum distillation may be further
`reduced by treatment with epoxy esters as taught in U. S.
`Patent 3,485,754 or by neutralization with any suitable
`alkaline material such as lime, alkali metal hydroxide, or
`alkali metal carbonates.
`If treatment with epoxy esters
`
`is used, excess epoxy ester may be removed by a second
`distillation under very low pressure, while the products
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`of reaction between the epoxy ester and residual acid may
`be left behind in the product without harm.
`If neutrali-
`zation with alkali is used as the refinement method, sub-
`sequent washing with water, to remove any unreacted excess
`alkali and the small amount of soap formed from the excess
`fatty acid neutralized by the alkali,
`is strongly pre-
`ferred before using the product as a lubricant and/or base
`stock according to this invention.
`Under
`some conditions of use,
`the ester(s)
`as de-
`scribed herein will
`function satisfactorily as complete
`
`for a
`is generally preferable, however,
`It
`lubricants.
`complete lubricant
`to contain other materials generally
`denoted in the art as additives, such as oxidation resist-
`ance and thermal stability improvers, corrosion inhibi-
`tors, metal deactivators,
`lubricity additives, viscosity
`index improvers, pour and/or floc point depressants, de-
`tergents,
`dispersants,
`antifoaming
`agents,
`anti-wear
`agents,
`and extreme pressure resistant additives.
`Many
`additives are multifunctional.
`For example, certain ad-
`ditives may impart both anti-wear and extreme pressure
`resistance properties, or function both as a metal de-
`activator and a corrosion inhibitor.
`Cumulatively, all
`additives preferably do not exceed 8 % by weight, or more
`preferably do not exceed 5 % by weight, of the total con-
`pounded lubricant formulation.
`An effective amount of the foregoing additive types
`
`is generally in the range from 0.01 to 5 % for the anti-
`oxidant component, 0.01 to 5 % for the corrosion inhibitor
`component,
`from 0.001 to 0.5 % for the metal deactivator
`component,
`from 0.5 to 5 % for the lubricity additives,
`from 0.01 to 2 % for each of the viscosity index improvers
`
`%
`from 0.1 to 5
`and pour and/or floc point depressants,
`for each of the detergents and dispersants,
`from 0.001 to
`0.1 % for anti-foam agents, and from 0.1 - 2 % for each of
`the anti-wear and extreme pressure resistance components.
`All these percentages are by weight and are based on the
`total lubricant composition.
`It is to be understood that
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`more or less than the stated amounts of additives may be
`more suitable to particular circumstances,
`and that
`a
`single molecular type or a mixture of types may be used
`for each type of additive component. Also,
`the examples
`listed below are intended to be merely illustrative and
`not limiting, except as described in the appended claims.
`Examples of suitable oxidation resistance and thermal
`stability improvers are diphenyl-, dinaphthyl-, and phen-
`ylnaphthyl-amines,
`in which the phenyl and naphthyl groups
`can be substituted, e.g., N,N’-diphenyl phenylenediamine,
`p-octyldiphenylamine, p,p-dioctyldiphenylamine, N-phenyl-
`i-naphthyl amine, N-phenyl-2-naphthyl amine, N-(p-dodec-
`yl)phenyl-2-naphthyl amine, di-1-naphthylamine, and di-2-
`naphthylamine;
`phenothazines
`such as N-alkylphenothia-
`zines;
`imino(bisbenzyl); and hindered phenols such as 6-
`(t-butyl) phenol, 2,6-di-(t-butyl) phenol, 4-methyl-2,6-
`di-(t-butyl)
`phenol,
`4,4’-methylenebis(-2,6-di-{t-butyl}
`phenol), and the like.
`Examples of suitable cuprous metal deactivators are
`imidazole, benzamidazole, 2-mercaptobenzthiazole, 2,5-di-
`mercaptothiadiazole,
`salicylidine-propylenediamine, pyr-
`azole, benzotriazole, tolutriazole, 2-methylbenzamidazole,
`3,5-dimethyl pyrazole,
`and methylene bis-benzotriazole.
`Benzotriazole derivatives are preferred. Other examples
`of more general metal deactivators and/or corrosion inhib-
`itors include organic acids and their esters, metal salts,
`and anhydrides, e.g., N-oleyl-sarcosine, sorbitan monoole-
`ate,
`lead naphthenate, dodecenyl-succinic acid and its par-
`tial esters and amides,
`and 4-nonylphenoxy acetic acid;
`primary, secondary, and tertiary aliphatic and cycloali-
`phatic amines and amine salts of organic and inorganic ac-
`ids, e.g., Oil-soluble alkylammonium carboxylates; hetero-
`cyclic nitrogen containing compounds, e.g.,
`thiadiazoles,
`substituted imidazolines, and oxazolines; quinolines, qui-
`nones, and anthraquinones; propyl gallate; barium dinonyl
`naphthalene sulfonate; ester and amide derivatives of al-
`kenyl succinic anhydrides or acids, dithiocarbamates, di-
`
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`thiophosphates; amine salts of alkyl acid phosphates and
`their derivatives.
`,
`Examples of suitable lubricity additives include long
`chain derivatives of fatty acids and natural oils, such as
`esters, amines, amides,
`imidazolines, and borates.
`in-
`Examples of suitable viscosity index improvers
`clude polymethacrylates, copolymers of vinyl pyrrolidone
`and methacrylates, polybutenes, and styrene-acrylate co-
`
`polymers.
`Examples of suitable pour point and/or floc point de-
`pressants include polymethacrylates such as methacrylate-
`ethylene-vinyl acetate terpolymers; alkylated naphthalene
`derivatives; and products of Friedel-Crafts catalyzed con-
`densation of urea with naphthalene or phenols.
`Examples of suitable detergents and/or dispersants in-
`clude polybutenylsuccinic acid amides; polybutenyl phos-
`phonic acid derivatives; long chain alkyl substituted aro-
`matic sulfonic acids and their salts; and metal salts of
`alkyl sulfides, of alkyl phenols, and of condensation prod-
`ucts of alkyl phenols and aldehydes.
`Examples of suitable anti-foam agents include sili-
`cone polymers and some acrylates.
`Examples of suitable anti~wear and extreme pressure
`resistance agents include sulfurized fatty acids and fatty
`acid esters,
`such as sulfurized octyl tallate; sulfurized
`terpenes; sulfurized olefins; organopolysulfides; organo
`phosphorus derivatives including amine phosphates, alkyl
`acid phosphates,
`dialkyl phosphates,
`aminedithiophos-
`phates,
`trialkyl and triaryl phosphorothionates, trialkyl
`and triaryl phosphines, and dialkylphosphites, e.g., amine
`salts of phosphoric acid monohexyl ester, amine salts of
`dinonylnaphthalene sulfonate,
`triphenyl phosphate,
`tri-
`naphthyl phosphate, diphenyl cresyl and dicresyl phenyl
`phosphates, naphthyl diphenyl phosphate,
`triphenylphos-
`phorothionate; dithiocarbamates,
`such as an antimony di-
`alkyl dithiocarbamate; chlorinated and/or fluorinated hy-
`drocarbons, and xanthates.
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`it is believed
`some conditions of operation,
`Under
`that the presence in lubricants of the types of polyether
`polyols that have been prominent constituents of most pri-
`or art lubricant base stocks taught as useful with fluoro-
`carbon refrigerant working fluids are less than optimally
`stable and/or
`inadequately compatible with some of
`the
`most useful lubricant additives.’ Thus,
`in one embodiment
`of this invention, it is preferred that the lubricant base
`stocks and lubricants be substantially free of such poly-
`ether polyols.
`By "substantially free", it is meant that
`the compositions contain no more
`than about
`10
`%
`by
`weight, preferably no more than about 2.6 % by weight, and
`more preferably no more than about 1.2 % by weight of the
`materials noted.
`invention is a
`One major embodiment of the present
`refrigerant working fluid comprising both a suitable heat
`transfer fluid such as a fluorocarbon and a lubricant ac-
`cording to this invention.
`Preferably,
`the refrigerant
`working fluid and the lubricant should have chemical char-
`acteristics and be present
`in such a proportion to each
`other that
`the working fluid remains homogeneous,
`i.e.,
`free from visually detectable phase separations or turbid-
`ity, over
`the entire range of working temperatures to
`which the working fluid is exposed during operation of a
`refrigeration system in which the working fluid is used.
`This working range may vary from ~-60° C to as much as
`+175° C.° It is often adequate if the working fluid re-
`mains single phase up to +30° C, although it is increas-
`ingly more preferable if the single phase behavior
`is
`maintained up to 40, 56, 71, 88, or 100 ° Cc.
`Similarly,
`it is often adequate if the working fluid compositions
`remains a single phase when chilled to 0° C, although it
`is increasingly more preferable if the single phase behav-
`ior persists to -10,
`-20,
`-30,
`-40, or -55 °
`Cc.
`Single
`phase mixtures with chlorine free hydrofluorocarbon re-
`frigerant working fluids are usually obtained with the
`suitable and preferred types of esters described above.
`
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`Inasmuch as it is often difficult to predict exactly
`how much lubricant will be mixed with the heat transfer
`fluid to form a working fluid, it is most preferable if
`the lubricant composition forms
`a single phase in all
`proportions with the heat transfer fluid over the temper-
`ature ranges noted above. This however,
`is a very strin-
`gent requirement, and it is often sufficient if there is
`single phase behavior over
`the entire temperature range
`for a working fluid mixture containing up to 1 % by weight
`of
`lubricant according to this invention.
`Single phase
`behavior over a temperature range for mixtures containing
`up to 2, 4, 10, and 15 % by weight of lubricant is suc-
`cessively more preferable.
`In some cases, single phase behavior is not required.
`The term "miscible" is used in the refrigeration lubrica-
`
`tion art and hereinafter, except when part of the phrase
`
`"miscible in all proportions", when two phases are formed
`but are readily capable of being mixed into a uniform dis-
`persion that remains stable as long as it is at least mod-
`erately agitated mechanically.
`Some refrigeration (and
`other) compressors are designed to operate satisfactorily
`with such miscible mixtures of refrigerant working fluid
`and lubricant.
`In contrast, mixtures that lead to coagu-
`lation or significant
`thickening and form two or more
`phases are unacceptable commercially and are designated
`herein as "immiscible". Any such mixture described below
`is a comparative example and not an embodiment of
`the
`present invention.
`Another major embodiment of the invention is the use
`of a lubricant according to the invention, either as total
`lubricant or lubricant base stock,
`in a process of operat-
`ing refrigerating machinery in such a manner that the lub-
`ricant is in contact with the refrigerant working fluid.
`The practice of the invention may be further under-
`stood and appreciated by consideration of
`the following
`examples and comparative examples.
`General Ester Synthesis Procedure
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