Patent Application: US-57765995-A

Abstract:
this invention relates to synthetic based turbo oils , preferably polyol ester - based turbo oils which exhibit exceptional load - carrying capacity by use of a synergistic combination of sulfur - based and phosphorous - based load additives . the s - containing additive of the present invention is thiophene carboxylic acid derivatives , preferably tca per se or thiophene c 1 - c 4 alkanoic acid and the p - containing additive is one or more amine phosphate . the turbo oil composition consisting of the dual p / s additives of the present invention achieves an excellent load - carrying capacity , which is better than or equivalent to that obtained when each additive was used alone at a higher treat rate than the total p / s additive combination treat rate , and this lower concentration requirement of the p and s additive allows the turbo oil composition to meet or exceed us navy mil - l - 23699 requirements including oxidation and corrosion stability and si seal compatibility .

Description:
a turbo oil having unexpectedly superior load - carrying capacity comprises a major portion of a synthetic base oil selected from diesters and polyol ester base oil , preferably polyol ester base oil , and minor portion of a load additive package comprising a mixture of one or more amine phosphate and thiophene carboxylic acid ( tca ), its derivatives and mixtures thereof . the diester , which can be used in the high load - carrying lube composition of the present invention is formed by esterification of linear or branched c 6 to c 15 aliphatic alcohols with one of such dibasic acids as sebacic , adipic , azelaic acids . examples of diester are di - 2 - ethyhexyl sebacate , di - octyl adipate . the preferred synthetic base stock which is synthetic polyol ester base oil is formed by the esterification of aliphatic polyols with carboxylic acids . the aliphatic polyols contain from 4 to 15 carbon atoms and have from 2 to 8 esterifiable hydroxyl groups . examples of polyols are trimethylolpropane , pentaerythritol , dipentaerythritol , neopentyl glycol , tripentaerythritol and mixtures thereof . the carboxylic acid reactants used to produce the synthetic polyol ester base oil are selected from aliphatic monocarboxylic acids or a mixture of aliphatic monocarboxylic acids and aliphatic dicarboxylic acids . the carboxylic acids contain from 4 to 12 carbon atoms and includes the straight and branched chain aliphatic acids , and mixtures of monocarboxylic acids may be used . the preferred polyol ester base oil is one prepared from technical pentaerythritol and a mixture of c 4 - c 12 carboxylic acids . technical pentaerythritol is a mixture which includes about 85 to 92 % monopentaerythritol and 8 to 15 % dipentaerythritol . a typical commercial technical pentaerythritol contains about 88 % monopentaerythritol having the structural formula ## str1 ## and about 12 % of dipentaerythritol having the structural formula ## str2 ## the technical pentaerythritol may also contain some tri and tetra pentaerythritol that is normally formed as by - products during the manufacture of technical pentaerythritol . the preparation of esters from alcohols and carboxylic acids can be accomplished using conventional methods and techniques known and familiar to those skilled in the art . in general , technical pentaerythritol is heated with the desired carboxylic acid mixture optionally in the presence of a catalyst . generally , a slight excess of acid is employed to force the reaction to completion . water is removed during the reaction and any excess acid is then stripped from the reaction mixture . the esters of technical pentaerythritol may be used without further purification or may be further purified using conventional techniques such as distillation . for the purposes of this specification and the following claims , the term &# 34 ; technical pentaerythritol ester &# 34 ; is understood as meaning the polyol ester base oil prepared from technical pentaerythritol and a mixture of c 4 - c 12 carboxylic acids . as previously stated , to the synthetic oil base stock is added a minor portion of an additive comprising a mixture of one or more amine phosphate ( s ) and tca , its derivatives , and mixtures thereof . the amine phosphate used includes commmercially available monobasic hydrocarbyl amine salts of mixed mono - and di - acid phosphates and specialty amine salt of the diacid phosphate . the mono - and di - acid phosphate amines have the structural formula : ## str3 ## where r and r 1 are the same or different and are c 1 to c 12 linear or branched chain alkyl r 1 and r 2 are h or c 1 to c 12 linear or branched chain alkyl r 3 is c 4 to c 12 linear or branched chain alkyl , or aryl - r 4 or r 4 - aryl where r 4 is h or c 1 - c 12 alkyl , and aryl is c 6 . the preferred amine phosphates are those wherein r and r 1 are c 1 - c 6 alkyl , and r 1 and r 2 are h or c 1 - c 4 , and r 3 is aryl - r 4 where r 4 is linear chain c 4 - c 12 alkyl or r 3 is linear or branched chain c 8 - c 12 alkyl . the molar ratio of the monoacid to diacid phosphate amine in the commmercial amine phosphates of the present invention ranges from 1 : 3 to 3 : 1 . mixed mono -/ di - acid phosphate and just diacid phosphate can be used , with the latter being the preferred . the amine phosphates are used in an amount by weight in the range 50 to 300 ppm ( based on base stock ), preferably 75 to 250 ppm , most preferably 100 to 200 ppm amine phospate . materials of this type are available commercially from a number of sources including r . t . vanderbilt ( vanlube series ) and ciba geigy . tca and its derivatives , the sulfur containing additive used in this invention is described by the structural formula : ## str4 ## where r 5 is cooh or c 1 - c 12 linear alkanoic acid ( hereafter collectively referred to as tca derivatives ). the preferred tca derivatives are wherein r is cooh or c 1 - c 4 linear alkanoic acid . the tca derivative is used in an amount by weight in the range 100 to 1000 ppm ( based on polyol ester base stock ), preferably 150 to 800 ppm , most preferably 250 to 500 ppm . the amine phosphate and the tca derivative are used in the weight ratio of 1 : 1 to 1 : 10 , preferably 1 : 1 . 5 to 1 : 5 , most preferably 1 : 2 to 1 : 3 amine phosphate : tca derivative . the synthetic oil based , preferably polyol ester - based high load - carrying oil may also contain one or more of the following classes of additives : antioxidants , antifoamants , antiwear agents , corrosion inhibitors , hydrolytic stabilizers , metal deactivator , detergents . total amount of such other additives can be in the range 0 . 5 to 15 wt %, preferably 2 to 10 wt %, most preferably 3 to 8 wt %. antioxidants which can be used include aryl amines , e . g ., phenyl - naphthylamines and dialkyl diphenyl amines and mixtures thereof , hindered phenols , phenothiazines , and their derivatives . the antioxidants are typically used in an amount in the range 1 to 5 %. antiwear additives include hydrocarbyl phosphate esters , particularly trihydrocarbyl phosphate esters in which the hydrocarbyl radical is an aryl or alkaryl radical or mixture thereof . particular antiwear additives include tricresyl phosphate , t - butyl phenyl phosphates , trixylenyl phosphate , and mixtures thereof . the antiwear additives are typically used in an mount in the range 0 . 5 to 4 wt %, preferably 1 to 3 wt %. corrosion inhibitors include , but are not limited to , various triazols , e . g ., tolyl triazol , 1 , 2 , 4 - benzene triazol , 1 , 2 , 3 - benzene triazol , carboxy benzotriazole , alkylated benzotriazol and organic diacids , e . g ., sebacic acid . the corrosion inhibitors can be used in an amount in the range 0 . 02 to 0 . 5 wt %, preferably 0 . 05 % to 0 . 25 wt %. lubricating oil additives are described generally in &# 34 ; lubricants and related products &# 34 ; by dieter klamann , verlag chemie , deerfield , fla ., 1984 , and also in &# 34 ; lubricant additives &# 34 ; by c . v . smalheer and r . kennedy smith , 1967 , pages 1 - 11 , the disclosures of which are incorporated herein by reference . the turbo oils of the present invention exhibit excellent load - carrying capacity as demonstrated by the severe fzg gear test , while meeting or exceeding the oxidation and corrosion stability ( ocs ) and si seal compatibility requirements set out by the united states navy in mil - l - 23699 specification . the polyol ester - based turbo oils to which have been added a synergistic mixture of the amine phosphate and the tca derivative produce a significant improvement in antiscuffing protection of heavily loaded gears over that of the same formulations in the absence of the amine phosphate and the tca derivative , and furthermore , attain the load - carrying capability better than or equivalent to that achieved with one of these two additives used alone at the higher treat rate than the total p / s additive combination treat rate . the present invention is further described by reference to the following non - limiting examples . in the following examples , a series of fully formulated aviation turbo oils were used to illustrate the performance benefits of using a mixture of the amine phosphate and tca derivative in the load - carrying , ocs and si seal tests . a polyol ester base stock prepared by reacting technical pentaerythritol with a mixture c 5 to c 10 acids was employed along with a standard additive package containing from 1 . 7 - 2 . 5 % by weight aryl amine antioxidants , 0 . 5 - 2 % tri - aryl phosphates , and 0 . 1 % benzo or alkyl - benzotriazole . to this was added various load - carrying additive package which consisted of the following : 1 ) amine phosphate alone : vanlube 692 , a mixed mono -/ di - acid phosphate amine , sold commercially by r . t . vanderbilt 2 ) tca derivative alone : thiophene carboxylic acid ( tca ) or thiophene acetic acid ( taa ), both commercially available from numerous chemical suppliers such as sigma , aldrich , etc . 3 ) combination ( present invention ): the combination of the two materials described in ( 1 ) and ( 2 ). the load - carrying capacity of these oils was evaluated in the severe fzg gear test . the fzg gear test is an industry standard test to measure the ability of an oil to prevent scuffing of a set of moving gears as the load applied to the gears is increased . the &# 34 ; severe &# 34 ; fzg test mentioned here is distinguished from the fzg test standardized in din 51 354 for gear oils in that the test oil is heated to a higher temperature ( 140 versus 90 ° c . ), and the maximum pitch line velocity of the gear is also higher ( 16 . 6 versus 8 . 3 m / s ). the fzg performance is reported in terms of failure load stage ( fls ), which is defined by a lowest load stage at which the sum of widths of all damaged areas exceeds one tooth width of the gear . table 1 lists hertz load and total work transmitted by the test gears at different load stages . table 1______________________________________load stage hertz load ( n / mm . sup . 2 ) total work ( kwh ) ______________________________________1 146 0 . 192 295 0 . 973 474 2 . 964 621 6 . 435 773 11 . 86 927 19 . 57 1080 29 . 98 1232 43 . 59 1386 60 . 810 1538 82 . 0______________________________________ the ocs [ fed - std - 791 ; method 5308 @ 400 ° f .] and si seal [ fed - std - 791 ; method 3433 ] tests used here to evaluate the turbo oils were run under the standard conditions as required by the navy mil - l - 23699 specification . the results from the severe fzg , si seal and ocs tests are shown in tables 2 , 3 and 4 , respectively . the wt % concentrations ( based on the polyol ester base stock ) of the amine phosphate and tca or taa , either used alone or in combination are also specified in the tables . table 2 demonstrates that the combination of the amine phosphate and the tca or taa exhibits an excellent load - carrying capacity , which is better than or comparable to that attributed to each additive used alone at a significantly higher treat rate than that of the p / s additive combination . tables 3 and 4 show that the turbo oil fomulation containing the synergistic p / s load additive combination also meets or exceeds the mil - l - 23699 ocs and si seal specifications whereas 0 . 1 % vl 692 - containing formulation fails the si seal test and yields only the equivalent fzg performance to that of the present invention . table 2______________________________________load additives severe fzg fls______________________________________none 40 . 02 wt % vanlube 692 ( vl 692 ) 5 . 3 ( average of 6 runs ) 0 . 05 wt % taa 50 . 10 wt % tca 60 . 10 wt % vl 692 7 - 80 . 03 wt % taa + 0 . 02 % vl 692 70 . 05 wt % tca + 0 . 02 % vl 692 7 - 8______________________________________ table 3__________________________________________________________________________mil - 23699 - ocs test @ 400 ° f . % vis δ tan sludge δ cu δ agload additives change ( mg koh / g oil ) ( mg / 100 cc ) ( mg / cm . sup . 2 ) ( mg / cm . sup . 2 ) __________________________________________________________________________none 14 . 45 0 . 83 0 . 7 - 0 . 07 - 0 . 020 . 05 % taa + 0 . 02 % vl 692 9 . 44 0 . 18 0 . 4 - 0 . 05 - 0 . 02limits - 5 - 25 3 50 ± 0 . 4 ± 0 . 2__________________________________________________________________________ table 4______________________________________si seal compatibilityload additives δ swell % tensile strength loss______________________________________none 13 . 1 10 . 30 . 1 % vl 692 3 . 9 84 . 40 . 02 % vl 692 7 . 8 28 . 70 . 05 taa + 0 . 02 % 7 . 9 24 . 6vl 692spec 5 - 25 & lt ; 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