CA2124497A1 - Polymer enhanced grease compositions - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A grease composition having improved water resistance, adhesion and low temperature pumpability properties which comprises:

(a) from 50 to 98 wt%, based on grease, of a lubricating oil;

(b) from 1 to 30 wt%, based on grease, of a thickener; and (c) from 0.5 to 2.0 wt%, based on grease of polymer selected from the group consisting of (1) a block copolymer of the structure A-B where A is a polymer block comprising at least about 75 percent by weight of condensed styrene units, no more than 25 percent of the aromatic unsaturation in said block being reduced by hydrogenation and B is hydrogenated polymer block comprising, prior to hydrogenation, at least 75 percent by weight of condensed isoprene units, at least 95 percent of the olefinic unsaturation in said block being reduced by hydrogenation, and (2) a hydrogenated star-shaped polymer having a poly(divinylbenzene) nucleus and at least seven hydrogenated poly-isoprene arms linked to said nucleus;

wherein the grease has an apparent viscosity of less than about 3500 poise at 20 sec-1.

Description

2 1 2 l~ ~ 9 ~

B~CKGROUND OF THE INVENTION

1. Field of The Invention Thiq invention relate~ to a grease compo~ition having im-proved adhesion and water resistance.

2. Descri~tion of The Related Art Many greases are ~ubjected to operating conditions wherein the grease is exposed to an aqueou~ environment. Aqueou~ environment~
are detrimental to greass performance because of problem~ such aq leaching of water soluble componentq and reduced adhesion. The uqe of polymers to impart desirable properties to greaaes is well-known. For e~ample, a pre~entation by G. D. Husqey at the October, 1986 NLGI
meeting in San Diego, California, discuq~ed the alteration of grease characteristic~ uqing new generation polymerq. ~owever, many polymerq mu~t be incorporated at relatively high concentrations in order to impact tha deqired propertieq. This Gan lead to other problemq quch a~ poor pumpability, e~pecially at low temperatures.

It would be deairable to have a polymer addit~ve to greaqes which has good water resiqtance and adhesion prope~ties at low concen-tration~ while at the same time producing a grea~e with good pump-ability.

SI~MARY OF T}lE INVENTI(:)N

Thi~ invention relates to a grease compo~ition having im-proved water resistance,; adhe~`ion and low temperature pumpability properties which comprises~

(a) from 50 to 90 wt%, baqed on greasc of a lubricating oil;

(b) from 1 to 30 wt%, based on grease of a thickener; and - 212~g~

(c) from O.5 to 2.0 wt%, based on grea~e of polymer selected from the group con~isting of (1) a block copolymer of the structure A-B where A i~ a polymer block comprising at lea~t about 75 percent by weight of condensed styrene unit~, no more than 25 percent of the aromatic unsaturation in said block b~ing reduced by hydrogenation and B is hydrogenated polymer block comprising, prior to hydrogenation, at least 75 percent by weight of condensed isoprene units, at least 95 percent of the olefinic unsaturation in ~aid block being reduced by hydrogenation, and (2) a hydrogenated ~tar-shaped polymer having a poly(divinylbenzene) nucleus and at least aeven hydrogenated poly-isoprene arm~ linked to said nucleus;

wherein the grea~e has an apparent viscosity of less than about 3500 poi~e at 20 sec~~

DETAILED DESCRIPTION OF THE INVENTION

A wide variety of lubricating oil~ can be employed in prepar-~ng the grease compositions of the present invention. Accordingly, tha lubricating oil base can be any of the conventionally u~ed mineral oils, synthetic hydrocarbon oils or synthetic ester oll~, depending upon the particular grease being prepared. In general theae lubricat-ing oils will ha~e a viscosity in the range of about 5 to ahout 10,000 cSt at 40C, although typical applications will require an oil having a vlsco~ity ranging fro~ about 10 to about 1,000 aSt at 40C. Nineral lubricating oil base stocks used in preparing the greases can be any conventionally refined ba~e stocks derived from paraffinic, naphthenic and mixed ba~e crudes. Synthetic lubricating oil8 that can be used include esters of glycols such as a C13 oxo acid diester of tetra-ethylene glycol, or complex e3ters ~uch as one formed from 1 mole of sebacic acid and 2 moles of tetraethylene glycol and 2 moles of 2-ethylhexanoic acid. Other synthetic oils that c3n be used include ~ynthetic hydrocarbon~ ~uch a~ polyalphaolefin~; alkyl benzenes, e.g.
alkylate bottom~ from the alkylation of benzene with tetrapropylene, or the copolymers of ethylene and propylene; silicon oil~, e.g. ethyl phenyl poly~iloxane~, methyl polysiloxanes, etc.; polyglycol oil~, e.g. tho~e obtained by condensing butyl alcohol with propylene oxide;

21~9~ ~
~ 3 --carbonate esters, e.g. the product of reacting c8 oxo alcohol with ethyl carbonate to form a half e~ter followed by reaction of the latter with tetraethylene glycol, etc. Other ~uitable ~ynthetic oils include the polyphenyl e~ter3, e~g. those having from about 3 to 7 ether linkages and about 4 to A phenyl groups. The amount of lubri-cating oil in the grea~e can also vary broadly, but, typically, will range from about 50 to about 98 wt%, preferably from about 75 to about 95 wt%, of the grea~e.
' The grease composition will also contain a thickener dis-persed in the lubricating oil to form a base grea~e. ~owever, the particular thickener employed i~ not critical and can vary broadly provided it i~ essentially water insoluble. For example, the thicken-er may be ba~ed on aluminum, barium, calcium, lithium soap~, or their complexe~. Soap thickeners may be derived from a wide range of animal Oilfl, vegetable oils, and grea~es as well as the fatty acid3 derived therefrom. ~he~e materials are well known in the art and are de-~cribed in, for example, C. J. Boner, Manufacture and Application of Lubricating Grea~e~, Chapter 4, Robert E. Krieger Publishing Company, Inc., New York ~1971). Carbon black, ~ilica, and clays may be used as well a~ dye~, polyurea~, and other organic thickener~. Pyrrolidone ba~ed thickener~ can al~o be u~ed. Preferred thickener~ are ba~ed on lithium soap, calcium soap, their complexes, or mixtures thereof.
Particularly preferred is a lithium or lithium complex thickener that incorporates an hydroxy fatty acid havlng from 12 to 24 (preferably from 16 to 20) carbon atom~. A preferred hydroxy fatty acid i~ an hydroxy ~tearic acid ~e.g., a 9-hydroxy or a 10-hydroxy 3tearic acid) of which 12 hydroxy ~tearic acid is most preferred (See U.S. Pat. No.

3,929,651, the di~clo~ure of which i~ incorporated herein by refer-ence). The amount of thickener in the lubricating composition will typically range from about 1 to about 30 wt%. For most purposes, between about 5 to about 20 wt%, preferably between about 10 to about 15 wt%, of the thickener will be present in the composition. The grease preferably ha~ a hardnesc between an NLGI rating of O to 2, pr-f-rably b-tween 1 and 2 a~ ~ea~urod by ~Sf~ D217.

2 ~ l g 7 The grease composition z180 contains hydrogenated ~tyrene-isoprene block copolymers or hydrogenated polyisoprene ~tar-shaped polymer~. In the styrene/isoprene block copolymer of the ctructure A-B, the polymer A block is a polymerized ~tyrene having an average molecular weight between about 10,000 and about 55,000, preferably about 25,000 and about 50,000. Polyi~oprene i8 th~ conjuga~ed diene employed in preparing the precursor block B. Preferably the poly-isoprene block ~hould have at least about 80%, preferably 88%, 1,4-~tructure which may be Ci9 or trans and an average molecular weight b~tween about 35,000 and 80,000. The weight ratio of block A to block B iB bstween about 0.45:1 and 0.8:1, preferably 0.5:1 to 0.7:1. The average molecular weight of the styrene/isoprene block copolymer# is between about 80,000 to about 120,000.

The block copolymer3 are commercially available from Shell Chemical Company a~ Sh~llvisO 40 and ShellviE~ 50. Such copolymers are prepared according to the methods de~cribed in V.S. Patent 3,772,196, which i~ incorporated herein by reference. The block copolymers are prepared using lithium-ba3ed initiators, preferably lithium alkyls such a~ lithium butyla or lithium amyls. Polymeriza-tion iB uBually conducted in ~olution in an inert solveDt ~uch a~
cyclohexane or alkane~ such a~ butanes or pentan2s and mixtures of the same. The first monomer to be polymerized (which may be either ~tyr~ne or i~oprene) i~ injected into th~ ~y~tem and contacted with the polymerization initiator which ia added in an amount calculated to provide the predetermined average molecular weight. Subsequent to obtaining tha de~ired molecular weight and depletion of the monomer, the ~econd monomer i~ then injected into the living polymer ~ystem and block polymerization occurs, resulting in the formulation of the living block copolymer poly~styrene)-polyisoprene which is then killed, eOg., by ~he addition of methanol.

Thi~ precursor is then subjerted to selactive hydrogenation to form the block copolymer~. Preferably hydrogenation i8 conducted in the same solvent in which the polymer wa~ prepared, utilizing a cataly~t comprising the reaction product of aluminum alkyl and a :

2 ~ 2 4 ~

nLckel or cobalt carboxylate or alkoxide. A favored catalyst i~ the -~
reaction product formed from triethyl aluminum and nickel octoate.

The temperatureq and pre~sures employed in the hydrogenation step are adjusted such as to cause essentially complete hydrogenation of the polyisoprene block with es~entially no effective hydrogenation of the monoalkenyl arene polymer block.

The polymer may be isolated from its solvent after its -::-~
hydrogenation and dispersed in lubricating oil. Thi~ may be effected, for example, by adding a lubricating oil to the solution of hydro-genated polymer and thereafter evaporating the relatively volatile solvent.

The hydrogenated star polymer has a poly(divinylbenzene coupling agent) nucleus and hydrogenated polyi~oprene arms linked to the nucleus. The average molecular weights of each arm are from about 15,000 to about 100,000, and the average molecular weight of the star polymar is between about 250,000 and 1,25t),000, preferably 350,000 to 1,000,000. :: :
' .:
The star polymers ar~ commercially available fxom Shell .
. Chemical Company as Shellvi~O 200 and Shellvis~ 250. These polymers ~ are prepared u~ing the methods deffcribed ln U.S. Patent 4,116,917, ~ which is incorporated herein by reference, and are generally produced ; by the proces~ compr1sing the following reaction stepa~

~ (a) polymerizing isoprene in the presence of an ionic ~:~
.: ~ .
initiator to form a living polymer, !
~: (b) reacting the living polymer with a poly(divinylbenzene ~: ~ coupling agent) to form a star-shaped polymer, and :

(c) hydrogenating the star-shaped polymer to form a hydro~
genated atar-shaped poly~er.

2 ~ 2~97 The living polymer0 produced from i00prene in reaction step ~a) are the precursori3 of the hydrogenated polymer chain~ which extend outwardly from the poly(divinylbenzene coupling agent) nucleus.

As is ~ell known, living polymer~ may be prepared by anionic solution polymerization o~ conjugated diene~ and, optionally, mono-alkenyl arene compounds in the pre~ence of an alkali metal or an alkali-metal hydrocarbon, e.g. ~odium naphthalene, as anionic initia-tor. The preferred initiator i~ lithium or a monolithium hydrocarbon.
Suitable lithium hydrocarbon~ include un4aturated compounds such as allyl lithium, methallyl lithium; aromatic compounds such as phenyl-lithium, the tolyllithiums, the xylyll~thiums and the naphthyllithiums and in particular the alkyl lithium~ such as methyllithium, ethyl~
lithium, propyll~thium, butyllithium, amyllithium, he~yllithium, 2-ethylhexyllithium and n-hexadecyllithium. Secondary-butyllithium is the preferred initiator. The initiators may be added to the poly-merization mixture in two or more ~tagea optionally together with additional monomer. The living polymers are olefinically unsaturated.
The concentration of the initiator u~ed to prepare the living polymer may al80 vary between wide limit~ and is determined by the de~ired molecular weight of the living polymer.

The ~olvents in which the living polymers are formed are inert liquid ~olvent~ ~uch ia~ hydrocarbon~ e.g. aliphatic hydrocar- ;~
bons, ~uch a~ pentane, hexane, heptane, octane, 2-ethylhexane, nonane, decane, cyclohexane, methylcyclohexane or aromatic hydrocarbon4 e.g.
b~nzene, toluene, ethylbenzen~, the xylenes, diethylbenzene~, propyl~
bsnzenes. Cyclohexane i~ preferred. Mixture~ of hydrocarbons e.g. ;~
lubricating oils may al80 be u~ed. ~ ;~

The temperature at which the polymerization is carried out may vary betwPen wide limit~ such a~ from -50C to 150C, preferably from about 200 to about 800C. The reaction is 0uitably carried out in an inert atmosphere ~uch a4 nitrogen and may be carried out under pres~ure e.g. a pre0sure of from about 0.5 to about 10 bars. ~-;`, ";' ~'~

',`'~

2~2~

The living polymer~ produced in reaction step ~a) are then react0d, in reaction step ~b), with a polydivinylbenzene coupling agent. Polyalkenyl coupling agents, such a~ polydivinyl benzene, capable of forming ~tar-shaped polymers are known. See generally, Fetters et al., U.S. Patent No. 3,985,830. They are usually compound~
having at least two non-conjugated alkenyl groupa. Such groups are usually attached to the same or different electron-withdrawing group~
e.g. an aromatic nucleus. Such compound~ have the property that at least two of the alkenyl groups are capable of independent reaction with diffexent living polymer~ and in this respect are different from conventional conjugated diene polymerizable monomers such as buta-diene, i~oprene, etc.

The polyvinylbenzene coupling agent should be added to the living polymer after the polymerization of i~oprene i8 gubgtantially complete, i.e. the agent ahould only be added after sub~tantially all of the i~oprene monomer has been converted to living polymers.

The amount of polydivinylbenzene coupling agsnt added may vary between wide limita, but preferably at lea~t 0.5 mole is used per mole of un~aturated living polymer. Amounts of from 1 to 15 moles, preferably from 1.5 to 5 mole~ are preferred. The amount, which may be added in two or more stages, i~ u~ually ~uch 30 a~ to convert at laast 80 or 85% of the living polymer~ into star-shaped polymer~

The reaction steps tb~ may be carried out in the ~ame solvent as for reaction step (a~. A list of ~uitable sol~ents is given above.
The reaction step ~b) temperature may also vary between wide limLts e.g. from 0 to 150C., preferably from 20C to 120C. The reaotion may al~o take place in an inért atmo~phere e.g. nitrogen and under presaure e.g. a pre~ure of from 0.5 to 10 bars.
.~
The ~tar ~haped polymera prepared ln reactibn step (b) are characteri~ed by having a dens0 center or nucleus of cross-linked poly(polydivinylbenzene soupling agent) and a number of arma of substantially linear polyiuoprene extending outwardly there~rom. The 212 ~ ~ 9 ~

number of arm~ may vary c~nsiderably, but is typically between 4 and 25, prefer~bly from about 7 to about 15.

Such qtar-~haped polymers, which are ~till "living", may then be deactivated or ~killed", in known manner, by the addition of a compound which reacts with the aarbanionic end group. As example~ of auitable deactivators may be mentioned, compound~ with one or more active hydrogen atoms ~uch as water, alcohol~ ~e.g. methanol, ethanol, i~opropanol, 2-ethylhexanol) or carboxylic acids ~e.g. acetic acid), compound~ with one active halogen atom, e.g. a chlorine atom (e.g.
ben~yl chloride, chloromethane), compound# with one e~ter group and carbon dioxide. If not deactivated in thi~ way, the living star-~haped polymers will be killed by the hydrogenation atep ~c).

In ~tep ~c~, the star-shaped polymers are hydrogenated by any suitable technique. Suitably at least 50~, preferably at least 70%, more preferably at least 90%, most preferably at lea~t 95% of the original olefinic un~aturation i~ hydrogenated. Preferably leas than 10~, more preferably less than 5% o ~uoh aromatic unsaturation is hydrogenated. The hydrogenation can ba carried out in any desire way.
A hydrogenation cataly~t may be used e O g ~ a copper or molybdenum compound. Compounds containing noble metala or noble-metal compounds can be u~ed a~ hydrogenation catalysts~ Preference is given to catalyst containing a non-noble metal or a compound thereof of Group VlII of the Periodic Table, i.e. iron, cobalt and in particular, nikel. As example~ may be mentioned, Raney nic~el and nickel on kie~elguhr. Special preference ia giv~n to hydrogenation catalyqts which are obtained by causing metal hydrocarbyl compounds to react with organi~ compound~ of any one of the group VIII metals iron, cobalt or nickel, the lat~er compounds containing at least one organic compound which i~ attached to the metal atom by meana of an oxygen atom. Preference i8 gi~en to hydrogenation cataly~ts obtained by cau~ing an aluminum trialkyl (e.g. aluminum triethyl (Al~Et)3~ or aluminum trii~obutyl) to react with a nickel ~alt of an organic acid le.g. nickel dii~opropyl salicylate, nickel naphthenate, nickel 2-ethyl hexanoate, nickel di-tert-butyl benzoate, nickel ~alts of 3aturated monocarboxylic acid3 obtained by reaction of olefins having 2~ 2~97 g from 4 to 20 carbon atoms in the molecule wlth carbon monoxide and water in the preqence of acid catalysts~ or with nickel enolate~ or phenolate3 (e.g. nickel acetonylacetonate, the nickel ~alt of butyl-acetophenone).

The hydrogenation of the qtar-shaped polymer iq very suitable conducted in solution in a solvent which i~ inert during the hydro-genation reaction. Saturated hydrocarbonq and mixtures of ~aturated hydrocarbona are very quitable and it i~ of advantage to carry out the hydrogenation in the ~ame ~olvent in which the polymerization haq been ~ ~
ePfected. ~ -The hydrogenation star-~haped polymer i~ then re~overed in ~olid form from the ~olvent in which it i~ hydrogenated by an con-venient technique ~uch as by evaporation of the solvent.
:~ , While the addition of polymer~ to grea~e~ to alter tha grea~epropertie~ i8 known, the precise impact of a given polymer on a given grea~e cannot be predlcted. The effectiv6ane 0 or laak thereof of any polymer for modifying any particular gre21~e property is dependent on the type of grea~e and thickener. Even for a given polymer, there may b0 trade-off~ with regard to impact on clifferent properties of the grease. Applicants have di~covered that t:he water re~i~tance adhesion and pumpability properties of a grease can be improved by adding a hydrogenated polyi~oprehe radial polymer or hydrogenated 0tyrene-isoprene block copolymer at low concentrations of from 0.5 to 2.0 wt%, based on grea0E. While higher amount~ of polymer may marginally improve water re~istance, ~uch higher amount~ negatively impact pumpability, e~pecially at the low temperature~ common in many grea~e application~. For this rea~on, it i~ important that at the minimum di~pensing temperature of the polymer-frPe grea~e, i.e., that tempera- -ture at which the grea~e reache~ an ASTM D1092 ~i~cosity of about 2000 to 3000 poi~e at 20 sec~l, the vis osity of the same grea~e containing polymer be 1~8B than 3500 poi~e at 20 ~ec~l, preferably be ~rom 2000 to 3000 poise at 20 ~ec~l a~ measured by AST~ D1092. This allow~ -improvement of the grea~e without imparting a reduction in dispen~ing propertieq which ia noticeable to the u~er.

21~97 The grease composition may al30 contain ~mall amounts of supplemental additives which include, but are not limited to, anti-corro~ive agenta, extreme pressure antiwear agents, pour point deprea-sants, tackiness agents, oxidation inhibitors, dyes, and the like, which are incorporated for specific purposes. The total amount of these additiveq will typically range from about 2 to about 5 wt~ based on total weight of the grçase composition. In addition, ~olid lubri-cants ~uch as molybdenum di~ulfide and graphite may be preaent in the composition -- typically from about 1 to about 5 wtg, preferably from about 1.5 to about 3 wt% for molybdenum disulfide and from about 3 to about 15 wt%, preferably from about 6 to about 12 wt~ for graphite.

The grea~e compo~ition of thi~ invention $8 usually prepared in situ by chemically reacting or mechanically disper3ing thickener components in the lubricating oil for from about 1 to about 8 hours or more (preferably from about 3 to about 6 hours) follow~d by heating at elevated temperature ~e.g., from about 140C to about 225C, depending upon the particular thickener used) until the mixture thlckens. In 00me cases ~e.g. a ~imple lithium grea~e), a preformed thickener can be used. The mixture is then coolsd to ambient temperature (typically about 60C) during which time the ethylene copolymer and other addi~
tives are added. The polymer and the ot:her additivel can be added together or separately in any order.

The components of the grease composition can be mixed, blended, or milled in any number of ways which can readily be ~elected by one ~killed in the art. Suitable mean~ include external mixera, roll mills, internal mixtures, Banbury mixers, screw extruder~
augers, colloid mills, homogenizer~, and the like.

The grease compo~ition of thi~ invention may be ~uitably employed in e~sentially any application requiring good water re~is-tance. Example~ of such application~ include wheel bearing, auto~
motive chassi~, fifth wheel~, paper machine, wet-end bearings, open pit and underground mining equlpment, construction equipment and the like.

212~9~
,~

Thi~ invention will be ~urther understood by reference to the ~ ~-following example~ which include a pre~erred ambodiment of the inven~
tion.
: :~

:
This example i~ a screening test for water shedding and adhesion properties of variou~ polymer~ in a lithium grea~e.
: ., A ~erie~ of lithium 12-hydroxystearate grea~es wa~ prepared -~
with ~i) a conventional mineral oil ba~e~tock (180 cSt at 40C), a 5 wt% treat of a multipurpo~e grease aclditive containing EP/antiwear and anticorro~ion additive~ and (iii~ polymer adclitive~ ~elscted ~rom Table 1. The~e were evaluated using a modified Roll ~tabillty te~t ~ -~
(apparatus described in AS~ D1831) in which 100 gram~ o~ grea3e and 100 gram~ oP water are mixed in the roll apparatus for 1 hour; at the ;~
end of the test th~ amount of water ab~orbQd by grea~e, the change in penetration ~mea~ured by ASTM D1401), and the adhe~ion of the grea~a to the roller were are evaluated. The low temperature Apparent - -~
Visco~ity of each grea~e was also mea~urecl u~Lng the ASTM D1092 te~t, --for which re~ult~ are given at a temperature of -20C and a ~hear rate ~-~
of 20 reciprocal ceaondc. The~e re~ult~ alre 2hown in Table 2.
.
,.: : ::-Polvmer De~crietlon A ~ 2500 Melt Index Ethylenevinylacetate copolymer B 200 Melt Index MaleLc Acid modified Ethylenevinylacetate copolymer ~ -C 50 Melt Index PoIyethylene D Polyi~obutylene (Molecular Weight 1500) Hydrogenated Styrene-Butadiene Copolymer F Di~per~ant Ethylene-Propylene Block Copolymer G Hydrogenated Polyi~oprene Radial Polymer H Hydrogenated Styrene-I30prene Block Copolymer ~ , f'i''; ~

212~97 ~ ; i ~ .
1~,, oooooo I ~ 1n UO)U7 o ~ ~
I . o O ~ N ~ U~
~: l ,~

C O
~J al ~ o ','".,:.,,' ~
E, N N N t' ~I ~ ~ ~

JJ ,~ ~
" al n~ O O C ~

0 E~ "
..
C ~
J O ~ f`l ~ m o u~
O E I` g~ O

O ~
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: . " ' ',- :

æl o : , ~
I Z

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2 1 2 !~ ~L 9 7 The results in Table 2 ~how that Polymers A, D, and G provid-ed that bPst water shedding ability (water absorbed) in the Roll Stability te~t. of the3e, D and G had the least effect on penetra-tion, with G showing far better adhesion to the roller after the termination of the test.

This example i~ a further ~creening test of various polymers ~et forth in Table 1 in a lithium complex grease.

A serie~ of lithium complex grea~es were prepared from lithium 12-hydroxystearic acid and azelaic acid according to the method~ of ~.S. 3,791,973. These greaae~ were prepared using (i) a conventional mineral oil baaestock (100 cSt at 40C), (ii) a 5 wt~
treat of a multipurpoae grease additive containing EP/antiwear and anticorro~ion additive~ and (iii) polymer additives 0elected from Table 1. In addltion to the Roll Stability and Apparent Vi~co~ity te~ts used in Example 1, the greases were evaluated ln the ASTM D4049 Water Spray-Off test. The reaults are given in Table 3.

, :, ~ '::

1: -', ;;

Z~2~

., ;:

- 14 ~

c~c~loooooo .~, ~ m m ~ to ~ g g u~
1 t~ .,.1 o m o o o u ~- O~ N t~l ~1 ~ 31 In 1~ ~ 0 n ~

C O ',':~.'~ '''''' Q) ~ ~ o 0 c: J- E
E
~" c) a~
_~ ~ .

o al ~ Gl a _I m O ~ _l O
o a) o ~ al o 0 ~ ~ x x ~ X r,~

: ~ X ~ m a ~ O E
: ~ 3: ~

~. . - .
~; ; 0~ ,,', ~ , o ~ 0 0 - ~
~ ~ ~ 0 0 a~ ~n - - :: ~::., :: ~ o ~ ~: : : ~ `

~ ~ o 4~

, .. . :

~ 2~97 - 15 - - ~
~ . ' ~ he result~ ~how that Polymers E, F, G and H were superior in water ~hedding ability. Of the~e, polymer~ E, G, and H ~howed superi-or adhesion after the modified Roll Stability te~t. Polymer H gave the overall best reaults when Water Spray-Off and Apparent Visco~ity are further taken into con~ideration.

In this example a lithium complex grease of the type de-scribed in Example 2, but incorporating a 220 cSt conventional mineral oil ba~estock, wa~ prepared. The effect of different concentrations of Polymer H on performance in the Water Spray-Off te~t, and the Apparent Vi~cosity test, were evaluated as shown in Table 4.
. ~
TABLE 4 ~ ~ -Apparent Water Visco~itv Polymer SoapPenetration Spray- Poi~e @ -10C
Polymer h7t%Wt~ mm/10 off, Wt~ and 20 ~-1 None 0.012.7273 73.4 2,400 H1.012.5 30631.3 H1.512.5 30524.~ 3,000 2.012.7 29921.0 3,500 ~2.512.3 3109.0 4,500 H3.012.3 2954.2 4,000 Thi~ Table illustrate~ that the de~ree of Water Spray-Off . .
resi~tance is dependant upon concentration of Polymer ~, but that the effact of incremental addition is dimini~h0d a~ concentration of polymer approache~ 2.0 wt~ based on grea~e. This occurs in concert with an increa~e in Apparent Vi~cosity which adver~ely impacts the pumpability of the grease.

~XAMP~ 4 In this example, a lithlum complex grease of the type de~
scribed in ~xample 2, and incorporating different concentrations of Polymer G, was evaluated in the modifi~d Roll Stability test, and the results are giv~n in Table 5.

2 ~ 9 7 ,"
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C ., ni --~
~o Q'c~I oIIgo . ni ~ .. ~ O ~ I i o ~ m ~ N N "~
:.
~ 3o c S ~ ~
~ c ~c . I O '-1 ~
~, ~ I O Q~ fJI
;~ ~ I ~ ~X,~ X,~ ~X,~

.,1 . L~ ~ c r~

C~
f!'~ C

" ,-.~ .. .

2~2~C~97 ~ ~

- 17 ~

Thi~ Table illustrates that the ability of grea e treated with Polymer G to shed water increases as concentrations are increased to 1.9 wt%, but that little incremental benefit re~ult~ fro~ further addition of polymer.
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Claims (6)

1. A grease composition having improved water resistance, adhesion and low temperature pumpability properties which comprises:

(a) from 50 to 98 wt%, based on grease, of a lubricating oil;

(b) from 1 to 30 wt%, based on grease, of a thickener; and (c) from 0.5 to 2.0 wt%, based on grease of polymer selected from the group consisting of (1) a block copolymer of the structure A-B where A is a polymer block comprising at least about 75 percent by weight of condensed styrene units, no more than 25 percent of the aromatic unsaturation in said block being reduced by hydrogenation and B is hydrogenated polymer block comprising, prior to hydrogenation, at least 75 percent by weight of condensed isoprene units, at least 95 percent of the olefinic unsaturation in said block being reduced by hydrogenation, and (2) a hydrogenated star-shaped polymer having a poly(divinylbenzene) nucleus and at least seven hydrogenated poly-isoprene arms linked to said nucleus;

wherein the grease has an apparent viscosity of less than about 3500 poise at 20 sec-1.

2. The grease composition of claim 1 wherein the apparent viscosity is from about 2000 to 3000 poise at 20 sec-1.

3. The grease composition of claim 1 wherein the thickener is a lithium or lithium complex thickener which incorporates a C12 to C24 hydroxy fatty acid.

4. The grease composition of claim 1 wherein the block copolymer has an average molecular weight between about 10,000 and 55,000.

5. The grease composition of claim 1 wherein the star polymer has an average molecular weight from about 250,000 to 1,250,000.

6. The grease composition of claim 1 additionally containing from about 1 to 5 wt%, based on grease, of a molybdenum disulfide or graphite.