CA1207314A

CA1207314A - Grease composition

Info

Publication number: CA1207314A
Application number: CA000430821A
Authority: CA
Inventors: Jeffrey E. Stemke
Original assignee: Chevron Research and Technology Co
Current assignee: Chevron USA Inc
Priority date: 1982-06-30
Filing date: 1983-06-21
Publication date: 1986-07-08
Also published as: GB2122216B; FR2529566A1; JPH0447720B2; IT8321833A0; DE3322822C2; SE459182B; GB8317470D0; NL8302220A; GB2122216A; DE3322822A1; IT1163614B; SE8303695D0; SE8303695L; JPS5918798A; FR2529566B1

Abstract

ABSTRACT OF THE DISCLOSURE
Disclosed is a polyurea-thickened grease containing a polymeric material which improves the low shear stability of the grease.

Description

1207310~

REASE COMPOSITION

05 BACKGROUND OF THE IN~ENTION
The requirement that grease compositions provide adequate lubrication at high temperature for extended periods of time has become increasingly important. For this reason, grease compositions containing a variety of 1~ organic thickening agents, such as those containing multi-ple ~riedo or urea functional groups, have been developed~
For exa~ple, V.S. Patent Nos. 3,242,210, 3,243,372, and 3,401,027 disclose polyurea grease thickeners obtained by reacting a three-component reactant mixture comprising a monoaminer a diamine and a diisocyanste, or a monoisocyan-ate, a diisocyanate and a diamine. As a general rule, the reaction product is comprised of a mixture of urea-containing species of varying chaln length and urea con-tent. However, by careful control of reaction variables

2~ 5~ch as, e.g., the relative quantities of reactants employed, the reaction temperature and the rate and order of reactant mixing, a product may nor~ally be obtained which predominates in one polyurea species. The polyurea reaction is preferably carried out in situ in the grease carrier~ and the reaction product may be utilized directly as a grease thickener.
While greases thickened with polyurea thickeners are in many respects superior to older lubricants in severe service application, especially with regard to

3~ maintenance of grease consistency at high temperature~, such greases suffer several disadvantages which limit their usefulness under practical service conditions. For examp~e~ while polyurea thickened greases show excellent retentic)n of n~echanical proper'cies at high temperature ~70~C or above) and high shear, they tend to soften considerably when subjected to low shear. In fack, the tendency to soften under low shear can be so great that the grease can, when subject to mechanical working under these condi~ions, undergo a change in penetration grade~
~0 ~07314 ~1 -2-e.g., from a 210. 2 NLGI penetration grade ~o a No. 1 NLGI
penetration grade. This change in penetration grade under low shear is particularly troublesome since it may occur under practical use conditions when the grease is trans-ferred from the original shipping container OE i5 other-wise stirred or handled. Consequently, normal handling of the grease in making it available to the ultimate consumer lQ may chan~e its consistency to such extent that it i5 no longer the desired penetration grade for the intended-application. While it is true that the change in consis-tency is reversible in that the softened grease can be subjected to high shear to return the grease to its original consistency, this rever~al often requires that the softened grease be shipped be~ck to the formulator for reprocessing.
DESCRIPTION OF THE PRIOR ART
Disclosed in U.S. Patent Nos. 4,104,177 and

4,111,822 are polyurea-thickened greases containing certain acylated alkylene polyamines of the formula:

Y~ ,X
Z~ A-N)n-A

wherein A is alkylene of 2 to 4 carbon atoms and n is an integer of from O to 3; X is H or Z; Y is selected from H, alkyl containing 12 to 22 carbon atoms; and Z is an acyl group. These additives are disclosed as providing 3 i~proved ambient temperature mechanical stability and improved rust protection in polyurea-thickened greases.
As is readily apparent to those skilled in the art, the above polyamine is not a polymer because of its low mole-cular weight and limited number of monomeric units (5).

. .
A grease compositis: n comprising a ma~or amount of a lubricating oil base vehicle, a polyurea gellant in an amount sufficient to thicken the base vehicle to a grease consistency, a~d a minor amount of a polymer having a pKa value greater than 5Ø

~Zg~ 4 ~1 --3--DETAILED DESCRIPTION OF THE INVENTION
The grease composition of the present invention 05 comprises the combination of at least three components.
(1~ a lubricating oil base vehicle, (2) a polyurea gellant, and (3) a polymer. Other additives can also be present but only the above three are absolutely essential.
The lubricating oil base vehicle and the poly-urea gellant are well known in the art. Any lubricatingoil base vehicle commonly used in greases can be used.
Generally, the base vehicle will comprise 50 to 99 weight percent of the final grease composition. The base vehicles are most con~only petroleum oils or synthetic base oils~
The polyurea gellant component for use in the present combination is also well known in the grease art and may be prepared by conventional means. For example, U.S. Patent No. 3,242,210 describes the preparation of polyurea-thickened greases suitable for use in the combi-nation of the present invention, and its disclosure is incorporated herein by reference. The polyurea is ~sed in an amoun~ sufficient to thicken the base vehicle to grease consistency. When used as a gellant, the polyureas are normally present in an amount of at le~st about 0.5 weight percent and more usually from abou~ 1 ~o 25 or more ~eigh~
percent.
The third essential component in the grease of the present invention is a polymer (different than the 3~ polyurea gellant) having a pRa value greater than 5Ø
As used in the present invention, the term ~polymer~ refers to a macromolecule composed of an indefi-nite number of monomers as distinguished from an ~oligomer~ which is a molecule consisting of only a few monomer units, for example, dimer, trimer~ tetramer, etc.
For purposes of clarity in the present invention, the term ~oligomerH is defined herein as molecules containing less than 6 monomer units and apolymer" as those containing 6 or more monomer unitsO Generally, the p~lymers useful in the present invention will have molecular weights greater ~2~7314 01 -4_ than 1000 and preferably will be high molecular weight polymers having molecular weights from 2,000 to 5,000,000 05 or more and most preferably in the range of 5,000 to 100,000.
Addition of the polymer to the polyurea grease composition significantly improves the low shear stability of the composition. Why the polymers improve the low shear stability of polyurea-thickened greases is not com-pletely understoodO However, it is believed that hydrogen-bonding interactions between the polyurea mole-cules or ibers and the polymer may account for the improvement in the low shear sta~ility. Thu~, it is pre-ferred to use polymers which are capable of hydrogen-bonding interac~ions with the polyurea molecules. Gener-ally, these polymers will have a pKa value greater than

5.0 and preferably greater than 7Ø "pKa" refers to ~he negative logarithm of the acid dissociation constant which 20 i5 well known in the art. Such polymers will be charac-terized by the presence of hydrogen-bond donor groups and/
or hydrogen-bond acceptor groups. The most common of such p~lymers will generally contain oxygen, and/or nitrogen.
Representative cla~ses of polymers for use in the present invention include the polyesters, polyamides, polyurethans, polyoxides; polysul~ides, and polyamines.
Representative polvesters ~include:
poly(ethylene terephthalate), poly(ethylene 4,4'-dibenzoate), poly(ethylene p-phenylenediacetate~, poly-(ethylene 4,4-isopropylidene-dibenzoate), poly(e~hylene 4~4'-sulfonyldibenzoate)~ and polyvinylacetate.
Representative polyamides include: polyglycine, poly(B-alanine) or poly(3-aminopropionic acid)~
poly(4-aminobutyric acid), poly~5-aminovaleric acid), poly(6 aminocaproic acid), poly(7-aminoenanthic acid~, poly(8 aminocaprylic acid~, poly(9-aminopelargonic acid)~
poly(10-aminocapric acid)~ poly(ll-aminoundecanoic acid), and poly(l2-aminolauric acid).
Representative polyurethans include-~0 poly(trimethylene ~thylene urethan).

;)7;~1~

01 ~5~

Representative polyoxides include:polyformaldehyde, polyacetaldehyde, poly~ethylene oxide), 05 poly(propylene oxide), and poly(trimethylene oxide~.
Representative polysulfides include: poly-(ethylene trimethylene sulfide), and polyethylenesulfide.
Representative polyamines include: poly-(ethylene trimethylene amine), and polyvinylamine.
Other representative polymers for use in the present invention include polyvinyl alcohol, ethylene/vinyl acetate copolymers, polyvinyl pyrollidone, and polyacrylamide. Particularly preferred are the ethylene/vinyl acetate copolymers.
A minor but effective amount of the poly~er is used to improve the low shear stability of the polyurea-thickened ~rease. Generallyr from 0.l to 20 weight percent or more of the final grease composition will comprise polymer and preferably l to l0 weight percent and most preferably 2 to 6 weight percent.
In order to demonstrate the invention more fully, reference is made to the following examples.
EXAMPLES
Exam~_es 1-4 Polyurea Grease Containing Polyvin,yl Pyrollidone A mixture of 85.76 grams (0.32 mole~ of oleylamine (Armeen O), and 750.0 grams of oil were heated and stirred in a 3-liter stainless beaker to 75C.
9.6 grams (0.16 mole) of ethylene diamine were then added and then a mixture of 55c68 grams (0.32 mole) toluene diisocyanate in ~50 grams oil. The reaction mixture wa~
then maintained at 75C for 30 minutes. 7.67 grams of NaNO~ di~solved in a minimum of water were then added and the temperature of the reaction mixture was increased.
At 120C, 75 grams of polyvinyl pyrollidone and 3.1 grams of an aromatic amine antioxidant were added and the heat increased to 150C~ The reaction mixture was then held at 150C for 30 minutes and then cooled to l00~C. 4.43 grams of a ~econd conventional antioxidant were added and the mixture stir~ed at l00~C for 15 ~inutes and allowed to ~`j ~2~73~
01 -6~

cool to 70C. 78.22 grams of conventional rust inhibitors were added and additional oil to bring the total oil added oS to 1200 grams. The cooled grease was milled 3 ~imes through a 3-roll mill. The oil used was a conventional mineral oil (Chevron Neutral Oil 115).
The low shear stability of the grease was tested by measuring the percent softening using the ASTM
Worked Penetra~ion after 60 strokes ~ASTM D-1403) and after 100,000 strokes lASTM D-217~. The greases were also tested using the Shell Roll Test (ASTM D-1831). The improvement in low shear stability is demonstrated by a lower percent softening. The results are shown in Table I. Also shown in Table I are the results of using other polymeric additives with the polyurea-thickened grease base described above, referred to as base grease ~A" in Table I.
E~amples 5-12 2~ Polyurea Greases Made From Syntheti~ on Base A mixture of 1500 grams oleylamine (Adogen 172) and 10,750 grams of Mobil MCP-151 Synthetic Base Oil was heated and stirred to 75~C. When the mixture reached 75C, 168 grams of ethylene diamine were added. Uhen the temperature leveled off at 75C, 836 grams of toluene diisocyanate in 3,750 grams of Mobil MCP-151 were added.
An additional 500 grams of Mobil MCP-151 were then added and the mixture was stirred and kept at 75C for 1/2 hour.
1,425 grams of this mixture alone or with 75 grams of a polymer listed in Table I were later heated to 150C while stirring and held there for 30 minutes and then cooled to room temperature. The composition ~as milled through a 3-roll mill 3 times. The test results of the grease along with the various polymeric addi~ives are shown in Table I.
The base grease prepared above is re~erred to as base grease ~B" in Table I.
Example 13 Prio A polyurea grease containing an acylated alkylene amine, ~pecifically additive A (Table I~ in * Trademark 3~4 01 _7_ U.S. Patent No. 4~104,177, was prepared. The additive was prepared according to the procedure specified in the 05 patent from the reaction of Duomeen T and oleic acid at 190C. The additive was tested for low shear stability at a concentration of 5 weight percent in the same polyurea-containing base grease as used in Examples 5-12. The results are ~hown in Table I.

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3~4 As will be appreciated by those skilled in the art, the results of Table I demonstrate the effectiveness 05 of the polymers of the present invention in improving the low shear stability of polyurea-containing greases.
Examples 9 and 10 demonstrate that a polymer having a pKa value less than 5.0 was ineffective in improving the low shear stability of the grease.
Example 13 further indicates that the polymers of the present invention are superior to the acylated alkylene amine of U.S~ Patent No. 4,104i177 in improving low shear stability of the grease.

2~

Claims

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

1. A grease composition comprising a major amount of a lubricating oil base vehicle, a polyurea gellant in an amount sufficient to thicken the base vehicle to a grease consistency, and a minor amount of a polymer having a pKa value greater than 5Ø

2. The grease composition of Claim 1 wherein said grease contains 0.1 to 20 weight percent of said polymer.

3. The grease composition of Claim 2 wherein said polymer has a molecular weight greater than 1,000.

4. The grease composition of Claim 3 wherein said polymer has a molecular weight in the range 2,000 to 5,000,000 and a pKa value greater than 7Ø

5. The grease composition of Claim 4 wherein said polymer is an oxygen-containing polymer.

6. The grease composition of Claim 4 wherein said polymer is selected from the group of polyesters, polyamides, polyurethans, polyamines, or polyoxides.

7. The grease composition of Claim 4 wherein said polymer is selected from polyacrylamide, polyvinyl alcohol, ethylene-vinylacetate copolymers, or polyvinyl pyrollidone.

8. The grease composition of Claim 3, 4 or 5 wherein said grease contains 1 to 10 weight percent of said polymer.