GB1564557A - Crease compositions - Google Patents

Description

(54) IMPROVED GREASE COMPOSITIONS (71) We, SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V., a company organised under the laws of the The Netherlands, of 30 Carel van Bylandtlaan, The Hague, The Netherlands, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: 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 organic thickening agents, such as those containing multiple ureido or urea functional groups, have been developed. For example, U.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 monoamine, a diamine and a di-isocyanate, or a mono-isocyanate, a di-isocyanate and a diamine. As a general rule, the reaction product is comprised of a mixture of urea-containing species of varying chain length and urea content. However, by careful control of reaction variables, such as, e.g., the relative quantities of reactants employed, the reaction temperature and the rate and order of reactant mixing, a product may normally be obtained which predominates in one polyurea species.

The polyurea reaction is preferably carried out in situ in the grease carr:er, 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 maintenance of grease consistency at high temperatures, such greases suffer several disadvantages which limit their usefulness under practical service conditions. For example, while polyur'a thickened greases show excellent retention of mechanical properties at high temperature (70"C or above) and high or low shear, they tend to soften considerably when subjected to low shear at ordinary temperature ranges (20-30 C). In fact, the tendency to soften at ordinary temperature under low shear can be so great that the grease can, when subject to mechanical working under these conditions, undergo a change in penetration grade, e.g. from a No. 2 NLGI penetration grade to a No. 1 NLGI penetration grade. This change in penetration grade at ordinary temperature under low shear is particularly troublesome since it may occur under practical use conditions when the grease is transferred from the original shipping container or is otherwise stirred or handled. Consequently, normal handling of the grease in making it available to the ultimate consumer may change its consistency to such extent that it is no longer of the desired penetration grade for the intended application. While it is true that the change in consistency is reversible, in that the softened grease can be subjected to high shear at high temperatures (conditions used in the original grease preparation) to return the grease to its original consistency, this reversal often requires that the softened grease be shipped back to the manufacturer for reprocessing.

Additionally, neat polyurea thickened greases demonstrate poor ability to inhibit rust formation, especially where lubricant service is required in corrosive environments. While additives have been proposed to overcome this problem. many conventional rust inhibitors adversely effect other desirable grease properties. For example, some additives cause the grease to soften, or function only as rust inhibitors (U.S. Patent No. 3,868,329), thereby necessitating the use of other additives for a fully formulated grease package.

Accordingly, a need has existed for the development of a polyurea grease containing a multi-purpose additive which enhances the mechanical and chemical properties of the grease.

The invention satisfies that need, and provides improved polyurea grease compositions containing a multi-functional additive effective in enhancing certain mechanical and chemical properties of the grease composition.

More particularly, the invention relates to polyurea thickened grease compositions having both improved ordinary temperature mechanical stability and enhanced resistance against rust formation.

Therefore, this invention relates to a grease composition, comprising a major amount of a lubricating base oil, a polyurea gellant in an amount sufficient to thicken the base oil to a grease consistency and a minor amount of an acylated alkylene polyamine or mixture of acylated alkylene polyamines, having the formula:

wherein A is alkylene of 2 to 4 carbon atoms and n is an integer from 0 to 3, Xis H or Z, Y is selected from H, alkyl containing 12 to 22 carbon atoms, and Z, and Z is an acyl group selected from alkanoyl containing 2 to 22 carbon atoms, hydroxyalkanoyl containing 2 to 22 carbon atoms, alkenoyl containing 2 to 22 carbon atoms, hydroxyalkenoyl containing 2 to 22 carbon atoms, hexahydrobenzoyl, cycloalkylalkanoyl containing 5 to 28 carbon atoms, and a group having the formula:

wherein R is alkyl containing 2 to 22 carbon atoms, or RCO is oleolyl and R' is hydrogen or alkyl containing 1 to 3 carbon atoms.

Preferred acylated polyamines are those wherein Z is selected from alkanoyl containing 6 to 22 carbon atoms, hydroxyalkanoyl containing 6 to 22 carbon atoms, alkenoyl containing 6 to 22 carbon atoms, hydroxyalkenoyl containing 6 to 22 carbon atoms, hexahydrobenzoyl, and cycloalkylalkanoyl containing 6 to 23 carbon atoms.

The compositions of the invention exhibit several advantages. As indicated, they provide improved ordinary temperature mechanical stability and improved rust protection. Additionally, the acylated polyamine additives increase the efficiency of the polyurea grease thickener so that less thickener is required to thicken the lubricating base oil to give penetration grade. The increase in grease yield based on the quantity of polyurea thickener employed has the secondary advantage of improving the low-temperature properties of the grease because of the reduction in gellant content and concomitant increase in oil content.

Other advantages accrue in that the multipurpose acylated polyamine additives of the compositions of the invention appear to act as bridging solvents in the polyurea thickened grease formulations, thereby reducing the opacity of the finished grease formulation. Again, the compositions are easily prepared. Where the acylated polyamine additive is added to the other components during preparation of the polyurea grease at a point prior to the conventional high-pressure homogenization of the grease, the acylated polyamine appears to act as a highly effective dispersant, allowing production of a smooth grease without going through the costly homogenization step. Finally, the grease compositions of the invention are completely ashless.

The acylated alkylene polyamines employed as multifunctional additives in the polyurea thickened grease compositions of the invention, broadly speaking, are oil-soluble amides which contain at least two acyl groups per molecule. More particularly, suitable acylated alkylene polyamines may be derived from an alkylene polyamine of the formula:

wherein A is alkylene of 2 to 4 carbon atoms, Y is H or alkyl containing 2 to 22 carbon atoms and n is an integer from 0 to 3. Preferred alkylene amines suitable for preparing the polyamides employed in the present invention are alkylene amines, wherein the alkylene unit, A, comprises 2 to 3 carbon atoms, and the number of alkylene amine units, n, is an integer from 1-3. The additives may be produced by reaction with an organic carboxylic acid which produces the acyl group, Z, as indicated, and preferably with those alkanoic acids containing 6 to 22 carbon atoms, hydroxyalkanoic acids containing 6 to 22 carbon atoms, hydroxyalkenoic acids containing 6 to 22 carbon atoms, hexahydrobenzoic acid, cycloalkylalkanoic acids containing 6 to 23 carbon atoms, an acid having the formula:

and mixtures thereof. The multifunctional additive may be present as a single derivative of the reaction between an amine and an acid, a derivative of the reaction of an amine and more than one acid, a derivative of a mixture of amines and an acid, or a derivative of the reaction between mixed amines and mixed acids, all of the types described.

Preferred amines include ethylene diamine, propylene diamine, tallow propylene diamine, diethylene triamine, and triethylene tetramine. Particularly preferred acids include caproic acid, lauric acid, 2-ethylhexanoic acid, oleic acid, tall oil fatty acid, stearic acid, linoleic acid, 2-methylpentanoic acid, ricinoleic acid, naphthenic acid, cyclopentylacetic acid, oleoylsarcosine, lauroylsarcosine, cocoylsarcosine, and stearoylsarcosine.

The acylated polyamine additives of the present invention may be prepared by mixing one or more of the above-described alkylene amines together with one or more of the acids at atmospheric pressure or greater, while simultaneously applying heat to the mixture. Generally, temperatures from 75"C to 1900C are satisfactory, with a temperature from 85"C to 95"C being preferred. The reactants are supplied generally in ratios of amine to acid from 1 to 2, to 1 to 6, preferably in ratios from 1 to 2, to 1 to 4. Heating is continued until the reaction is essentially complete, as evidenced by cessation of water evolution from the reaction mixture.

Suitable amides prepared by acylating an alkylene amine and polyamine with a hydrocarbyl carboxylic acid include those prepared using tall oil fatty acid and oleic acid. Particularly preferred amides are diokoyl tallow-1,3-propylenediamine, and dinaphthenoyl-1,3propylenediamine.

The polyurea grease component suitable for use in combination with the multipurpose additive of the present invention 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 combination of the present invention, and its disclosure is incorporated herein by reference.

In order to ensure uniform corrosion-inhibiting effectiveness and uniform hardening effect, the acylated alkylene polyamines are preferably combined with the polyurea grease after the polyurea forming reaction between the monoamine, isocyanate or di-isocyanate, and diamine is complete. Addition at such a time avoids side reactions of the isocyanates in the reaction mixture with the amine functions of the additives. The additives may be incorporated at any time after the grease is thickened. For example, the additive may be supplied immediately after the polyurea reaction to permit use of a single mixing vessel, or the additive may also be added to previously prepared base greases. These base greases may include other additives, e.g. extreme pressure additives, such as sulphurized fatty acids, and chlorinated paraffin waxes; anti-oxidant additives, such as phenyl-alpha-naphthylamine and diisooctyldiphenylamine; copper anti-corrosion additives, such as 3-amino-1,2,4-triazole; and pour point depressants, such as methacrylate polymers.

The effective amount or necessary concentration of the acylated polyamide additives in the polyurea grease will depend to some extent upon which of the multi-purpose properties, e.g. rust inhibition, low temperature, low shear stabilization clarity improvement or gellant efficiency, is desired most in a given application. For general use, the acylated polyamines may be employed in concentrations from 0.5 per cent to 10 per cent, by weight, based on the final weight of the grease, with from 2 per cent to 10 per cent by weight being preferred.

In order to demonstrate the invention more fully, reference is made to the following Examples.

EXAMPLE I A polyurea thickened base grease was prepared from the following components: Base Polyurea grease formula Components Per cent Toluene diisocyanate 4.10 Tallow amine 7.06 Ethylene diamine 0.85 500 HVI oil blend 86.99 Di-iso-octyl diphenylamine 0.50 Phenyl-alpha-naphthylamine 0.50 The above components were combined in the manner described in U.S. Patent No.

3,242,210 and, except where indicated, the gel formation reaction was allowed to go to completion before the inclusion of the acylated polyamine additive. The alkylene amines and carboxylic acids of the class described were combined in separate containers and heated at about 190"C until water no longer evolved from the given reaction mixture. The particular acylated alkylene amine was then added to the gelled grease, and the mixture was stirred and heated at about 88"C until the additive was uniformly incorporated. The corrosion resistances of the acylated polyamine containing greases were then tested using the modified ASTM D1743 corrosion test, described as Test B in U.S. Patent No.3,660,288. For this test, results are indicated by a rating, ranging from 1 to 3, reported for the compositions' effect with three bearings. A grade of 1 indicates no corrosion, while a rating of 2 indicates incipient corrosion with no more than three spots of size just sufficient to be visible to the naked eye. A bearing with larger or more than three spots is rated 3. In this test, in all instances, the polyamide additive comprises 4 per cent by weight of the grease tested. Results of the test are shown in Table I.

TABLE I Additive - amineloarboxylic acid Molar ASTM proportion corrosion A. Tallow propylene diamineloleic 1:2 1,1,1 acid B. Tallow propylene diamine! naphthenicacid 1:2 1,1,1 C. Tallow propylene diamine! ricinoleicacid 1:2 1,1,1 D. Triethylene tetramine/oleic acid 1:6 1,1,3 E. Triethylene tetramine/ricin oleic 1:6 1,1,1 acid F. Tally propylene diamine/oleic 1:2 1,1,1 acid 1 G. Tallow propylene diamine/oleic 1:2 1,1,1 acid2) H. Triethylene tetramine/oleoylsarcosine 1:6 1,1,1 1. Base grease - no polyamide - fail 1) Amide added before tetra-urea reaction complete 2) Amide added after tetra-urea reaction complete. as will be appreciated by those skilled in the art, the results in Table I demonstrate the effectiveness of the acylated polyamines of the present invention as rust inhibitors. Experiments F and G demonstrate that the rust inhibition properties are not effected by the time of addition of the additives relative to the time of gel formation.

EXAMPLE II Polyurea thickened greases of the formulation of Example I were tested for penetration to demonstrate the effect the present acylated polyamines have upon grease gellant efficiency.

The ASTM Unworked Penetration (Po) and the ASTM Worked Penetration (P60) after 60 strokes in the ASTM worker, were determined at 25"C.

TABLE II Additive Tetra- Po P60 urea gellant % by weight 2A Base grease 12 291 297 2B Additive A - 4% by wt 12 246 268 2C AdditiveA-4%bywt (1) 10 300 345 2D Additive A - 4% by wt (2) 9.5 232 255 1) Polyamide added before grease structure formed 2) Polyamide added after grease structure formed.

Experiments 2A and 2B clearly demonstrate that less gellant is necessary to attain a given penetration with the acylated polyamine compositions of the invention. Experiments 2C and 2D demonstrate that in order to attain the greatest gellant efficiency, the polyamides should be added after grease formation is complete. The grease compositions containing the additives and less gellant were visibly clearer, and lacked the cloudiness of the base grease.

EXAMPLE III This example demonstrates the improved stability of the compositions of the invention with regard to consistency when exposed to ordinary temperature low shear. In this example, 960 grams of polyurea grease with the same formulation as shown in Example I were placed in a mixer and stirred at 25"C (44 r.p.m.). Forty grams of polyamide were added with stirring, and heating of the grease mixture to 85"C. The grease composition was then removed, cooled to 25"C and the ASTM worked and unworked penetrations were taken. The procedure was then repeated without the addition of the additive of the invention. Both grease compositions were then stirred for 45 minutes at ordinary temperature. This stirring technique is designed to simulate grease handling and transfer conditions which expose the grease to low rates of shear. The penetration results before and after exposure to low shear are shown in Table III.

TABLE III 3A 3B 3C Base grease, per cent by weight 100 96 96 Additive A, per cent by weight none 4 Additive H, per cent by weight none - 4 Original penetration of base grease, 306/306 306/306 306/306 Po/P60 Penetration after stirring at ordinary temp. 365/323 for 45 minutes, Po/P60 Penetration after stirring/heating 297/279 220/252 179/216 to85 C Po/P60 45 Minutes of stirring at ordinary 350/313 273/273 234/243 temperature, Po/P60 Heat has partially improved the penetration of the base grease, but additional shear results in softening to the next NLGI grade (350/313). The additive, however, reduced the softening to where it remained in the No. 2 NLGI grade (e.g., 273/273). The close correspondence and the Po and P60 indicate the stabilizing effect of the additive. The unworked/worked penetration of 306/306 was a result of the original grease softening in handling from its original 265/295 No. 2 grade. This grease had been sheared in a high shear device when originally made.

EXAMPLE IV This example illustrates the improved gellant efficiency of the compositions of the invention. This characteristic is desirable, in that either less gellant will be required for a given formulation, or greases may be formulated to a given NLGI specification without requiring the use of high shear devices.

In this example, a polyurea grease of the composition used in Example I was made by a continuous method. It was not sheared, but was processed through a mixing tube. This base grease shall be designated grease A. Other portions were treated, as indicated in Table IV, with results also recorded in the Table.

TABLE IV Po P60 4A Base grease A 268 304 4B Base grease A, heated to 930C for 265 302 one-half hour 4C Base grease A, sheared at 5000 psi 265 281 4D Base grease A, sheared twice at 5000 psi 249 271 4E Base grease A + 4 percent by weight 215 255 additive A, heated to 930C and then cooled to ordinary temperature (not sheared) Experiment 4E shows that the grease yield expressed in penetration has been improved by incorporating an additive, without the use of high-shear devices.

EXAMPLE V This example demonstrates further the low temperature shear stability of the compositions of the invention. The acylated alkylene polyamines as shown in Table V, were added to the polyurea grease of Example I. The mixture was then stirred and heated to 880C until uniform incorporation of the acylated polyamines into the grease was obtained. The unworked and worked penetrations were taken. Then the samples were subjected to low temperature, low shear by slow stirring at ordinary temperature for 45 minutes, as above. The term "shear", as employed herein, is that condition occurring during the agitation of the samples in the mixing vessel resulting from applied forces which causes two contiguous elements of the compositions to slide relative to each other in a direction parallel to their plane of contact. In this example, "low shear" means that the approximate relative velocity used was 70 cm/sec. The following results were observed. Rust resistance was also determined.

TABLE V Experiment 5A 5B 5C 5D Additive - dinaphthenoyl- dioleoyl- additive trimethylene ethyl- A diamine ene diamine Amount of additive, per cent by weight none 4 4 4 Penetration after mixing in additive, 313/306 257/275 203/264 189/383 Po/P60 45 Minutes of slow stirring at ambient 364/325 310/306 338/331 276/282 temperature, Po/P60 Modified ASTM D1743 corrosion fail 1,1,1 1,1,1 1,1,1 The stability of the compositions of the invention when subjected to ordinary temperature low shear is demonstrated by only slight variation in unworked/worked penetrations.

Claims (3)

WHAT WE CLAIM IS:

1. A grease composition comprising a major amount of a lubricating base oil, a polyurea gellant in an amount sufficient to thicken the base oil to a grease consistency and a minor amount of an acylated alkylene polyamine or mixture of acylated alkylene polyamines, having the formula:

wherein A is alkylene of 2 to 4 carbon atoms and n is an integer from 0 to 3, X is H or Z, Y is selected from H, alkyl containing 12 to 22 carbon atoms, and Z, and Z is an acyl group selected from alkanoyl containing 2 to 22 carbon atoms, hydroxyalkanoyl containing 2 to 22 carbon atoms, alkenoyl containing 2 to 22 carbon atoms, hydroxyalkenoyl containing 2 to 22 carbon atoms, hexahydrobenzoyl, cycloalkylalkanoyl containing 5 to 28 carbon atoms, and a group having the formula:

wherein R is alkyl containing 2 to 22 carbon atoms, or RCO is oleolyl and R' is hydrogen or alkyl containing 1 to 3 carbon atoms.

2. The grease composition of claim 1, wherein Z is alkanoyl containing 6 to 22 carbon atoms, hydroxyalkanoyl containing 6 to 22 carbon atoms, or hexahydrobenzoyl.

3. A grease composition according to claim 1, substantially as hereinbefore described with special reference to the Examples.