CA1042458A - Branched-chain aliphatic ester oils - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Branched-chain aliphatic ester oils comprising full esters of branched-chain aliphatic polyols having from 2 to 6 hydroxyl groups with saturated, .alpha.-branched-chain, aliphatic monocarboxylic acids having from 14 to 22 carbon atoms, as well as their use alone, or as mixture components, as lubricants or hydraulic fluids.

Description

So-called eEIteI~ 0113 ha~1~fo~and ~n the la3t fow year~ a ~id~ flold of applicatlon aa v~ lubr~c~nt~.
Thu~, fo~ axa~ple, ~or th~ lubrication oP turbln~ ~ngln~ o~
~et-propelled airc~t, e~t~r~ o:e di~arbo~ylic acid~ and alcohol~ wlth ~ediu~ chain length~, ~uch a~, ~or ~x~pl~g dioQtyl ~bacate, or e~t~rs o~ Yarlous polyol~ with fatty ~cld~ ~lth a ~dillm chain l~ngth ~re us~d. Mor~ rec~ntly, such e~t~r oil~ h~e al~o b~en u~d to a~ incr~a~d extollt ~or other lubrl~atlon pr~bl~ her~ the lubrlcatlng requir~-10 rae~t~ ar~ high, a~ ~or oxa~pl~, a~ ~ixing co~po~n~s lx~ partlysynth~tlc englne oil~ spocial ~ult~bi llty o~ the ~ r oll~ ior the~e purpose~ i8 ba~ed on th~ ~cta that, co~pare~
with the u~u&l l~bricants bas~d Otl ~ r~l oil, they ha~ a ~ar ~or~ ~a~o~abl~ beha~rior o~ vloc~xity with t~Rp~r~ture ~nd that, co~pared ~th ~ub~tance~ o~ ~o~para~ co~iti~
th~ p~i~r po~nt i~ di3t~ctly low~r. ~h~ properties also rop~e~nt an e~sential ~quirom~E~ r~r th2 suita~lli~ o~
oil a~ th~ op~rating fluid in hy~rau~ y~t~m~, ~lnco it~
co~ity læ onl~r allow~d to al~3r to an ln~ ant ~:ct~nt 20 with co~s~ derable t~poratur~ riatlon~ ~d be~de~ i~ muJt al~o romaln cap~bl~ ~ u~ at lo~ t~mperature~.
It 1~ ~c~mmon kno~ledg~ t~ the techni¢ian th~ st~r oil~ Or h~gher visco~ity u6u~11y pro~e 1e~83 ~atiara~tory 1~ the~r b~havi~r in the oold, ~inc~ th~ lncr~a~ o~ the o~it~ 6~ne~rally acco~npani~s an l~¢r~as~ ~ th~ pour polnt.
For l~l~ri~atlon probl~ hich ab~olut~sly n~co~itate the u~ o~ mor~ highly ~i~o~ @~ter oils~ so-c~ d ~om~l~x ~ster~ ha~e beeli r~ently d~relop~d. The~e cont~ a~ ~t~r-li~icati~n c~mpone334t~ both diol~ or polyol~ a~d d~carboxylic 30 acl~ ln addition to o~onofunctloxlal s.lcohol~ or aela~, in .... . . . . . .

4S~
ord~r to b~ abl~ to pr~pare estere wi~ low ~eid ~nd hydroxyl numb~rs. The vl~cosltie~ o~ ~uch complex estere 119 at 100F at about 30 to 300 CSt ~nd at 210~ t 10 to 30 cSt.
me pQur point~ o~ ~U6h hi~hly Yi~3Cou8 co~plex est~ra do not gen~r~lly lie b~low -30C. ~her~ore, they are not ~ati~-~acto~r in this r~sp~ct i~or m~Lrur pUrpOBe~8 O~ U8e. ~ furthor ~eriou~ ai~advantage Or these ~omplox ~t~r~ 1~ that th~ir pr~paration cau~es llgroat dl~lcultios~ ~in~ dlarine th~
~teri~lcation o~ polyi~unctional acit~s with polyruncti~3nal 10 al~ohols, un~sire~ poly1neri~ation8 must b~ cont~mplate~l and controlled, 1~ poæsible. The acld rractil~na or rr~ctio~s o~
partlal ~ter~ rema$ning ln th~ compl~x ester a~tor the e~t~r-i~icatl~ reac1;ion can onl~ b~ remo~red ~rith d~ficulty reiinln~ or dlRt~ lon.
It ha~ al~o alr~ady be~l att~mpt~à to pr~par~ more h~ghly ~iscou~ e~tsr oil~ by ~stori~i¢ation ~ pol~unctional alcohol~ ~ith ~traight-chain monoc~rbo~ylic ~cid~. If, how-e~rer, the preparatioll oi~ c~ter~ wlth hlgh vi~cositia~ com-para~l~ with those pos~e$s~d by th~ eo~plex e~ter~ i3 d~red, 20 produ~t~ a~e obt~ined o~ ~hleh the p~ur poi~to ris~ to ~a~ue~
abo~ ~-G. Aa ~ay be ~e~n ~rom th~ ~oll~in~ Table I, ~co~lty o~ o~rer 3~ cSt at lOO~F ~ith a tri~3thylolpropax ester call b~ obta~ned wh~n an a~dition o~ i~akty ~id~ o~
~hairl len~ths ~r ~10 ls ma~e a~ the o~t~rl~lc~ti~ compon-~nt. I~7 ~o~ ~x~ampl~, laurl~ ~cid is u~d a~ ~t2ri~icatlo~
compon~nt, a tri~thylolprop~ est~r ~rith a ~ eo~lty o~ 36.4 cSt at 100F :L3 obtai~d, but w~th a pour p~in~ o~ *7"C. ~h~
corr0~porldll~g latlric aci~ ope~tyl~lyeol ~ster h~ alra~dy a pour pol~t ~ ~ C ~ith a ~i~co~ity of onl~r 16.2 ~St at 100 'F .

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T A B L ~ I

Pour Vl~cosity Point in c~t at V'i8~:0aity 13 ~ t o r in C lQ0-~ In~ox 3~
n C6-ac1d -60 12.1 113 n-C7-acid -60 14. 6 128 n-C8 acid -54, 18.~ 138 ~-Cg-dcl d -51 22.4 143 n-Cl~-acid -29 26.-~ 145 n-C12-acld + 7 36.4 143 ~, .
~5~ , ~-C~-acid -62 ~5 9S 116 :
n-Cg~aeid -27 9.18 113 n-C10-a~id -~7 11. 3 145 .~ .~

:
~ r~her, the prepar~t~on ~ e~ter oil~ ba~d on po~yols a~d brar~ched-chain fatty aci~ o~ ~dlum c}lalxl length ha~ already b~e~ attempted. Whe~ these rat1;y ~Lcld~ or m~:--20 ture~ o~ br~nched-~bain and ~tr~ight-chain ~atty aci~ o~
medlum chain le~gth are ueed, the pour point o~ the ~ster~
obtained ~ 8 irldee~ t~nctly lo~er, b~t thi.~ advantaea i8 o~fset by dl~advantages in the behavior o~ the vi~cosil;y ~lth temp~rature7 a~ products re~ult ~ith a lo~ ~i~co~lty ln~x, as liQay be ~oen ~ro~ l;h~ ~ollo~ing eoll~t;ed re~ults o~
Tabl~ II.

T ~ B ~ E

~_I
~ ~ ~08i~y ~i~co~i~y Pb~nt in cSt ~t 1~ cSt at ~i~C08~ ty E: 8 t e :r ln ac lOO-F 210-F Index ~?~
~-C8-ae~.d ~ ~ 19.0 4.09 138 i-C8-acld _ ~ 27.1 4~72 85 mix-C8-acid -62 19.1 3.92 115 ' ~
n-Cg-acid + 1 34.7 6.23 135 i-Cg-acid -34 129 . 211. 60 82 e~x-Cg-ac~ d 60 ~7,.3 7.07 116 .

An ob~ect of the present invention is the de~elop-~e~t of e~ter oils which, beside3 a very low pour point, ha~e ln comparison a h~gh visco~ity, and are at the same timé satis-factory in their viscosity temperature behavior.
~ nother ob~ect o~ the i~entlon i8 the development o~
a branched-chain aliphatic e~ter oil consisting e~entially o~
a ~ull e~ter o~ a branched-chain aliphatic polyol having from

2 to 6 primary hydroxyl ~roup3 ~elected from the group con~ist-- lng of alkanepolyols having ~rom 3 to 6 carbon atom~ and alkoxyalkanepolyols having ~rom 6 to 1~ carbon atoms with a-branched-chaln ~lkanoic acids ha~ing the f ormula Rl~
CH-COOH
. ~2 where~n Rl and R~ are al~yl ha~ing from 1 ko 19 carbon atom~
and the tokal number o~ carbon atoms in the acid is from 14 to ~2~
A f~rther ob~ck o~ the invention 1~ the development , ~ , ,; ~ . . . ~ .

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of lubricatlng ~nd hydraulic ~luid composition~ contalning from 20~ ~o lOOjt o~ at lea~t one of the above branch~d-chain ali-phatlc ester oils.
A yet ~urther ob~ct of the pre~ent in~ention i~ the improvement ln the method of facilitating the motion of on~
8011d over the 6ur~ace ~ another solid by l~nter~persing a thin film of a lubrican~ between the sur~ac2~ Or sald ~olid~ in frictional contact which consl~t~ of employing the abo~e branched-chaln aliphatic est~r oil~ aid lubricant~
The~e and other ob~ects o~ the in~ention will becomo more apparent a~ the description thereof proceeds.
It has no~ b~en found that e~ter oils con~i~ting of the full e~ters o~
a) branched, aliphatic polyols having 2 to 6 ~rlmary hy,d~oxyl groups, and b) qaturated, ~-br~nched-chain,a~iphatic monocarboxylic acids wi~h a total of 1~ to 22 carbon atoms in ~he molecule satisfy the necessary requirements of a, very low pour point 7 a high visco~ity and a ~atisfactory viscosity-temperature behavior 20 to an extent not pretriously attalned.
More particularly, th~ e~ter oil o~ the invention i8 a branched-chain aliphatic e~ter oil con~isting es~entlally of a ~ull ester G~ a branched-chain aliphatic polyol having from 2 to 6 primary hydroxyl group~ ~elected from the ~ro~p consisting of alkanepolyols having ~rom 3 to 6 carbon atom~ and alkoxy-alkanepolyols having ~rom 6 to 12 carbon atoms with a-branched-chain alkanoic acifls having ~he ~ormula 1~ CH-CO~H

wherein Rl and R2 are alkyl ha~lng from 1 to 19 carbon atom~ and 30 the total number o:E carbon atom~ the acid i~ ~rom 14 to 22.

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~ s th~ alcoholic component, all branched-chain aliphatic polyols having 2 to 6 primary hydroxyl groups form the basis of the ester oils according to the invention, such as the alkanepolyols having from 3 to 6 carbon atoms and the alkoxy~alkanepolyols having from 6 to 12 carbon atoms, a.s for example, neopentylglycol, trimethylo:Lpropane, pentaerythritol, or dipentaerythritol. The polyols neopentylglycol, trimethylol-propane and pentaerythritol are of particular importance.
Suitable acid components of the ester oils according to the invention are all saturated, a -branched-chain, aliphatic monocarboxylic acids with a total of 14 to 22 carbon atoms in the molecule. More particularly, these acids are ~-branched~
chain alkanoic acids having the formula l CH-COOH

wherein Rl and R2 are alkyl having from 1 to 19 carbon atoms and the total number of carbon atoms in the acid is from 14 to 22.
Such carboxylic acids are obtainable in various ways, as ~or example, by oxidation of the a-branched-chain alcohols with a corresponding number of carbon atoms obtained from shorter chain alcohols by the Guerbet process. Another source of such carbcxylic acids is provided by various a-branched alcohols from petxoleum chemistry, as well as the reaction products of conjugated diolefines, such as isoprene, pentadiene-1,3, butadiene-1,3, etc.
with methacrylic acid esters in the presence of an organometal complex of zero valent nickel and an electron donor according to German Patent ~DOS) No. 2,025,830 and the commonly-assigned U.S. Patent No. 3,855,255 issued December 17, 1974.

Of the ~-branched-chain carboxylic acids having a total of 14 to 22 carbon atoms in the molecule obtainable in the above-mentioned and other ways, special importance is . ~

attached ~o tho~e ~aturated, branched-chaln carboxylic acids ln whlch the chain branches ln the a-position to the carboxyl group and the two alkyls of the chain branche~ are ~traight-chained. The preparation of such ~atur~ted~ a-branched-chain carboxylic arid~ may be e~fected, for exampl~, by the Guerbet reaction on unbranched saturat~d alcohols of medium chain length to give alcohol~ o~ the deslred total number of carbon atom~, branched in the 2 position3 which are ~ubsequently oxidized to give a carboxyl group in place of the a~cohol group. Another m~thod, for example 3 iS the hydrogenation o~ the C20 carboxylic acid obtained by the reaction of lg3-butadiene with methyl meth-acrylate in the presence of an organometal complex o~ zero val~nt niekel ~nd an electron-donor and ~ubsequent saponiiication, acc~rding to the German Patent Speci~ication (DOS).~ 9j830.
The un~aturated e~ter i8 l~kewi~e described in U.S. P~tent No.

3,660,440. A nonadecanecarboxylic acid obtained ln thi~ ~ay ha~, for example, th~ structure [CH3(GH2)8]2-COOH-Other carboxylic acida branched in the a-po~ition to the carboxyl group can al~o be obtained by oxidation of branch~d-chain alcohols from petroleum chemistry, a6 ~or example, by theoxidation o~ an i~omeric mi~ture o~ bran~hed-chain C16 alcohols o~ the structure C8H17 ~
which can be prepared by aldol condensation o~ isooctylal~ehyde, ~hich itsel~ i obtainabl~ from i~oh~ptene, which i~ ~ormad during the cracking of petroloum. The two C6H13- and C~17-group~ o~ the c~rboxylic acids branched in the a-position ~o obtained are themselves also branched.
Particularly fa~orabl~ re~ult~ can be obtained with ~atu~ d, branched-chain, aliphatic monocarboxylic acid~ in whi~h the chain i~ branched in the a-position to the carboxyl :. . . . . ~
:: . . . . . . . .

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group, the branche~ are themsel~re~ ~traight-chain, and the total number o~ carbon ato;n3 in the molecule of which is 16. 0~ the Cl6-carboxylic acid~ branched in the ~-po~ition to the carboxyl group, isopalmitic acid obtained by oxidation o~ 2-hexyl-dccanol formed ~rom n-octanol in the ~uerbet ~ynthesi~ i8 0~ Yery 8pe-cial lmpor,~ance. The ester oil~ o'btained by u~e of this iso-palmitic acid ~how extremely favo~able properties w~th respect to behav~or in the cold and of it~ risco8ity behavior~.
The e~tera according to the invention consistine o~
10 branched, allphatic polyols having ~ to 6 primary hydroxyl groups and the ~aturated, a-branched-chain, aliphatic monocar-boxylic acid~ with a total o~ 14 to 22 carbon atoma~ can be pre-pared by the uæual esterificakion proce ~e8, æuch a~ by heating the reactant~ in the presence of an e~terification cataly~t, as ior example, tin or aluminum powder, or p-toluane~ul~onic acid : and other substances. In the preparation of the isopalmitic acid e~ter it ha~ pro~ed satisfactory to free the e~ter obtained ~rom ~cid residues by washing with a short-chain alcohol~ ~uch as methanol. Ob~ously the purification of the crude reaction mixture from exces~ acid can al~o be carried out by washing with cau~tic alk~li liquor~.
The e~ter oils according to the invention are out-standingly suitable both alone, and in admlxture with other products already known for this purpose, for use a~ lubricant~
and as hydraulic ~luid, on accoUnt o~ their extremely ~avor-able propertie with regard to visco~ity and behavlor in the cold. Such a ~avorable overall behavior cannot be obtainea with all previou31y known aæter oil~ obtaine~ble in such a simple manner. ~wing to their relativel~r high viscosity and their ~avorable viscosity behavior with temperature, the ester oils according to the invention can be used advantage-ously 9.180 in tbose ~ields which have previousl~ been barred to the complex esters. When used as a mixture component ln . .. . : .
~, . . . ~ . , :

Z~58 lubri~nt~ and hydraulic ~lulds, ~n~r d~lre~ mlx~ng proportions can be ~elected, which are det~rmined exclu~ ly by the ~raluea requ~ red wlth respect to working beh~.rior, pour point and vi~co~ity-temperature behavlor~ In general, howev~r3 the tots.l product does not contai2l a fract~o~ le~ than 20%. Both mi~eral oil~ and okher e~ter oll~ are ~uitabl~ as mi~cing com~
~onent~, depending on the purpo~e o~ use. Tha~e compo~itione ~ontain from 20g~ to 100~ of the e~ter oil~ o~ the lnvent~on.
The ~ollowing Exampl~ further de~crib@ th~ inventlon 10 without it being reatricke~ ther~to.
X A M P LE S
~ he iull ester~ o~ th~ inYentlon util~z~d ~or te~tiI~g for b~havior to cold and ~laco~ity-te~np~rature ~ehavior w~re preparea ~rom th~ polyol~ and branch~chain carboxyllc aclds a~ g~v~n below by the method outlined abo~ra o~ h~at~g a exc~ o~ about 1.2 mol o~ acid ~or each mol equiv~ t o~
hydroxyl group~ ~n the polyol in the ~resen~e o~ a p-tollleIl0-~ul~onic acid to a tempeæa~tLrs o~ about 125C ~hi~ r~mo~Jing the water pro~uced by the reactlo~ Tho e~ter~ ~7er~ r~cover~d 20 by w~hing the reaction mixture Yi~h metha~ol.
A 3 ~7aopell~yl~ ol B ~ Tri~ethylolprop~e C - P~rltaerythritol D - Isop~l~t~c acld, obt0,ix~d by oxidati~
t~e 2~h~3x~1-de~anol formed rroE~ octanol by 02cid~tion ~n the Gu~rbet ~nth~
E 5 No~ad~ca~ecarboxylle ~eid o~ the sts~llckure CH[3 ( CH2 ) ~-GI H- ( CH2 ) 8c~3 CO~E
The ~alu~s obtain~d during tha tests are ~ive~ in 30 the :~ollo~lng Table ITI.

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T A B L E I I I
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Pourvi8c09it;y Vt sco~ity Polnti~l ~St at in cSt at'Vi8Col~i1iy FU11 ~ster in C 100F 210~F Ind~x A ~ 2D - 60 28 . 03 5 .13 124 B + 3D -59 63.66 ~.86 125 C + 4D -54 88.15 11.92 136 A + :~ -5-~ 36.33 6. 29 135 , From th~ above ~ble III the extr~y favorabla 10 propertls~ ~or technlcal U813 O:e the e~E!!r oil8 according to the l~e~tion wl~h rof~rence to beha~lor to cold a~d of`
v~sco~ty te~perature b~ha~ r can ~ clearly not~d. In ~p~t~ of t}leir relatively h~ isco~iti~ and their favor~-able ~iscosi~y temperature beha~ior (vi3c08ity ind~x) ~ the pro~uct~ ha~e a~ extre~ly lo~ ~our po~ o* 7~11 b~low _30C .
The previous ~poci~ic embodlment~ ar~ illustrative o~ the praeti~s of the in~e~tl~ It 1~ t~ be und0~tood, ~o~er, that other e~cpedient~ wn to tho~e ~ d in the 20 art or disclo~ed herein may be employed without d~par~ng rrG~ the ~pirit c)~ the in~2n~ion or th~ ~cope o~ th~ appQn~ed claims ~

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Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A branched-chain aliphatic ester oil consisting es-sentially of a full ester of a branched-chain aliphatic polyol having only from 2 to 6 primary hydroxyl groups selected from the group consisting of alkanepolyols having from 3 to 6 carbon atoms and alkoxyalkanepolyols having from 6 to 12 carbon atoms with .alpha.-branched-chain alkanoic acids having the formula wherein R1 and R2 are straight-chained alkyl having from 1 to 19 carbon atoms and the total number of carbon atoms in the acid is from 14 to 22, said acids being selected from the group con-sisting of (1) acids derived from the oxidation of .alpha.-branched alcohols formed from normal alcohols by the Guerbet synthesis and (2) an acid of the formula

2. The ester oil of claim 1 wherein said .alpha.-branched alkanoic acid has 16 carbon atoms.

3. The ester oil of claim 2 wherein said .alpha.-branched C16-alkanoic acid is an isopalmitic acid obtained by oxidation of the 2-hexyl-decanol formed from n-octanol by the Guerbet synthesis.

4. The ester oil of claim 1 wherein said polyol is a branched-chain alkanepolyol having only 2 to 4 primary hydroxyl groups.

5. The ester oil of claim 4 wherein said alkanepolyol is neopentylglycol.

6. The ester oil of claim 4 wherein said alkanepolyol is trimethylolpropane.

7. The ester oil of claim 5 wherein said alkanepolyol is pentaerythritol.

8. Lubricating and hydraulic fluid compositions contain-ing from 20% to 100% by weight of at least one ester oil of claim 1.

9. In the process of facilitating the motion of one solid over the surf ace of another solid by providing a thin film of a lubricant between the surfaces of said solids in frictional contact, the improvement consisting essentially of utilizing at least one ester oil of claim 1 as said lubricant.

10. The ester oil of claim 1 being the triisopalmitic acid ester of trimethylolpropane, said isopalmitic acid being obtained by the oxidation of 2-hexyldecanol formed from n-octanol by the Guerbet synthesis.