US3453211A - Grease composition containing ethylene-vinyl acetate copolymer - Google Patents

Description

United States Patent O 3,453,211 GREASE COMPOSITION CONTAINING ETHYL- ENE-VINYL ACETATE COPOLYMER Rodger W. Phillips, Glen Mills, Pa., assignor to Sun Oil fompany, Philadelphia, Pa., a corporation of New ersey No Drawing. Filed Nov. 7, 1967, Ser. No. 681,117 Int. Cl. C10m 5/10 U.S. U. 25237 11 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION Greases that resist water wash off have been highly desirable in the automotive accessory field, for example, as lubricants on door latching mechanisms. As a result many attempts have been made to improve the adhesion and cohesion of greases.

Recently a successful water wash off resistant grease was shown in US. Patent No. 3,290,244 to Arthur T. Polishuk and Herbert L. Johnson. The successful greases employ weight percent oil soluble atactic polypropylene or 0.3-5 weight percent oil-soluble atactic ethylenepropylene copolymer. Both of these polymers are the byproducts of polymerizations directed to the production of the valuble and useful isotactic polymers. Because of recent technological and economical advances the supply of low cost atactic materials is dwindling. It has become necessary to develop new greases with water wash off resistant properties and to that end the present invention is directed.

SUMMARY OF THE INVENTION DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS The greases of the invention contain a major proportion of a mineral lubricating oil. The proportions and percentages in relation to the components of the grease in this specification are by weight of the total grease composition. The oil can be any oil prepared by conventional petroleum refining techniques such as solvent eX- traction, sulfuric acid treatment, clay treatment and the like, provided that the oil employed has a sufliciently high aromatic hydrocarbon content. The aromatic content of the oil should be at least 40 percent by volume and more 7 preferably should be in excess of 60 percent by volume. There is very little improvement in the water wash off 3,453,211 Patented July 1, 1969 properties of greases made from oils containing less than 40 volume percent to which ethylene-vinyl acetate has been added. This is attributable to the lack of solubility of ethylene-vinyl acetate in oils having less than 40 volume percent aromatic, which results in an inhomogenous grease. Normally the lubricating oil used in the grease composition will have a viscosity in the range of 35-180 S. U.S. at 210 F.

The grease compositions of the invention also contain a thickener. The amount of thickener used is a minor proportion but should be sufiicient to thicken the lubricating oil used to grease consistency. Normally the amount of thickener used will be 5-40 percent. Any conventional thickener can be employed such as the fatty acid metallic soaps, inorganic thickeners such as colloidal silica and bentonite clay, etc. Since greases containing a fatty acid metallic soap as thickener have superior properties for many applications, they are preferred. The metal component of the soap can be any of the known soap-forming metals such as sodium, potassium, lithium, barium, aluminum, strontium, calcium, magnesium, etc. although preferably the metal is sodium, lithium, calcium, aluminum, or barium. The fatty acid component of the soap can be derived from any fatty acid containing 10-25 carbon atoms, can be saturated or unsaturated, and can contain hydroxy substituents. As the term fatty acid is used herein it includes only those fatty acids having 10- 25 carbon atoms. Examples of suitable fatty acid metallic soaps containing metal and fatty acid components as described include sodium stearate, lithium stearate, lithium oleate, calcium ricinoleate, calcium oleate, aluminum palmitate, etc.

Although the suitable soaps described above are characterized in that all acid anions of the soap molecule are derived from fatty acids, the term fatty acid metallic soap also includes, for the present purpose, the fatty acid complex metallic soaps well known in the art. These soaps, which have also been referred to in the art as complex soaps, complex soap-salts, etc., contain a polyvalent soap forming metal as the cation of the soap molecule while the anions of the soap molecule are derived from both fatty acids and relatively low molecular weight organic acids. The relatively low molecular weight organic acid anion present will depend mainly upon the polyvalent metal present. Where the polyvalent metal is aluminum the anion is preferably the anion of an aromatic monocarboxylic acid containing 7-12 carbon atoms. Preferably the anion is that of benzoic acid. Where the polyvalent metal is an alkaline earth metal such as calcium, or barium the anion is preferably derived from aliphatic monoand polycarboxylic acids containing 2-7 carbon atoms. Preferably the anion is that of acetic acid. The fatty acids and polyvalent metals suitable for use in forming fatty acid complex metallic soaps are as previously described. Preferably the polyvalent metal is calcium, aluminum, or barium. Examples of fatty acid complex metallic soaps having metal and acid components as described above are aluminum benzoate stearate, aluminum palmitate toluate, calcium stearate acetate, barium oleate propionate, barium linolenate acetate, etc.

The complex soaps can be prepared by methods well known in the art. Thus aluminum benzoate stearate is precipitated from an aqueous solution of sodium stearate and sodium benzoate by the addition thereto of aluminum sulfate. The ratio of benzoate anions to stearate anions in the resulting soaps is determined by the ratio of sodium benzoate to sodium stearate in the aqueous solution. For grease purposes the ratio of benzoate anions to stearate anions in the soap is usually in the range of 0.2:1 to 5:1.

0 It is also well known to prepare the complex soap in situ in the oil component of the grease composition. Thus a mixture of acetic acid and stearic acid is admixed with oil after which hydrated lime is added to the admixture and allowed to react with the mixed acids to form the complex soap.

Of the fatty acid metallic soaps suitable for the present purpose the fatty acid complex metallic soaps are preferred because they generally result in greases having substantially higher dropping points than can be obtained in greases prepared from the non-complex soaps such as sodium stearate, calcium stearate, aluminum stearate, etc.

The preparation of ethylene-vinyl acetate copolymer is known in the art. Preparations are shown in United States Patent No. 2,200,429 to Pe-rrin et al. and Canadian Patent No. 657,977 to Strauss dated Jan. 29, 1963. Generally, the preparation involves copolymerizing a mixture of ethylene and vinyl acetate by means of a free-radicalproducing catalyst, such as oxygen or an organic peroxide at a pressure of 100 to 200 atmospheres and a temperature in the range of 150 C. to 250 C. and recovering the product. The proportion of vinyl acetate in the copolymer is unimportant for the grease compositions of this invention. Generally suitable copolymers will have 15 to 65 weight percent vinyl acetate, preferably 17 to 42 weight percent.

From 0.5 to weight percent of the ethylene-vinyl acetate copolymer can be added to the greases. Less than 0.5 weight percent of the copolymer provides no improvement in the water wash off properties. Generally no more than 2 weight percent of the copolymer will be employed in a usual grease composition. For example, a grease containing 4 percent aluminum complex grease produced a rubbery product when 3 weight percent of the copolymer was added. However, by lowering the soap content it is possible to load more of the copolymer into the grease. This approach results in gradual transition of the composition from a grease to a sticky oil which lacks the stiifness and other requisite properties of a grease. It should be pointed out that a grease containing a reduced amount of soap and up to 10 weight percent ethylene-vinyl acetate oifers no greater wash off protection than an ordinary grease containing 2 weight percent ethylenevinyl acetate.

The ethylene-vinyl acetate component of the grease can be incorporated into the grease during the preparation thereof or subsequently thereto. For example, most greases are prepared by adding the thickener to the lubricating oil at a temperature of about 200 F., stirring until uniform, heating so about 350-500 F., and cooling to room temperature. Grease consistency is generally reached at some point in the cooling cycle. Where additives such as oxidation inhibitors are to be included in the grease composition they are usually milled into the grease at about 200 F. in the cooling cycle. The specific techniques employed vary depending mainly upon the actual thickeners used and are well known in the art. The copolymer can be added to the oil at about the same time the soap or other thickener is added to the oil, or, alternatively, can be milled into the grease at some point, preferably about 300 F., in the cooling cycle. In either case the polymer dissolves in the oil to produce a grease having improved adhesive-cohesive properties. In order to improve the rate of dissolution of the polymer in the oil, it has generally been found preferable to add the polymer to the oil at or about the time the thickener is added, i.e., after addition of the thickener and prior to heating to the elevated temperature.

The following examples illustrate the invention more specifically. The water spray resistance test used to evaluate the greases in the examples is the test (PETM #1015) presently used by General Motors Corp, Ternstedt Division, in order to determine the suitability of the grease as an auto body hardware grease. Auto body hardware greases are used on automobile door latches, door hinges, window mechanisms, etc. In such an application it is desirable that the grease not wash off when contacted by water. The test utilizes a chrome plated steel panels 2" by 6" by M Two parallel lines on the panel divide it into three adjacent rectangular areas, the center area being 2" by 4", the two outer areas being 1'' by 2". The test panel is Weighed to the nearest 0.001 of a gram. The 2" x 4" area is covered by a layer of the grease to be tested, thick, any grease outside of this area is removed from the panel. The panel is weighed to the nearest 0.001 of a gram and is then mounted 12" away from a nozzle attached to a water line. The nozzle used is identified as Full Jet /z 66-25 and is manufactured by Spraying Systems, Inc., Chicago, Ill. Water at F. and at a nozzle pressure of 20 p.s.i.g. is sprayed onto the panel for a period of 5 minutes, after which the water is shut off and the panel is dried at F. for 1 hour. Next any grease on the two 1 by 2" outer areas is scraped off and the panel is again weighed to the nearest 0.001 of a gram. The percent grease lost on panel is calculated by:

X 100: percent grease lost on panel A=weight of clean dry test panel B=weight of initially greased test panel C=weight of spray exposed greased test panel Example 1 2 weight percent of ethylene-vinyl acetate having a melt index of 45-65 and containing 39-42 weight percent vinyl acetate sold under the trade name Elvax 40 by Du Pont Chemical Company was added to a mineral oil containing about 46 percent aromatics having a viscosity at 100 F. of about 500 SUS and API gravity at 60 F. of about 20. This material was too fluid, i.e., merely a viscous oil. It was not a grease and could not be evaluated in conventional grease testing equipment.

Example 2 The same materials were employed as in Example 1 but 20 weight percent of the copolymer was added to the oil. The composition still was not sufficiently stiif to test as a grease. An additional 20 weight percent of the copolymer produced a solid rubbery, sticky material that could hardly be pulled apart and which could not be classified as a grease.

The grease compositions employed were prepared in the following manner:

The soap components were added to one half of the total volume of oil to be employed at room temperature. The mixture was then heated to 240 F. and held at this temperature and stirred for about 20 minutes to complete the saponification. After the saponification the ethylene-vinyl acetate copolymer, if any, is added. The balance of the oil is added and the mixture is stirred until uniform. The mixture is then heated to a temperature of 400 F., held there for 5-10 minutes and is then cooled to 200 F. where grease consistency has been reached. At this point any functional additives, i.e., antioxidant etc. are blended in. The grease is milled at 150 F. in a Gaulin Homogenizer at a pressure of 1000 p.s.i.g. and is then allowed to cool to room temperature.

Example 3.-Lithium soap grease without copolymer Component: Wt. percent Petroleum oil 81.50 12 hydroxy stearic acid 4.25 12 hydroxy glycerides 4.25 Lead naphthenate 2.00 Sulfurized sperm oil 8.00 Lithium hydroxide, lb./ lb. of fat 0.15

The petroleum oil is a blend of 53.00 parts by weight of an oil containing 45.5 volume percent aromatics and having a viscosity at 100 F. of 300-320 SUS, API gravity at 60 F. of 19-22, and open cup flash point of 350 F. and 28.50 parts by weight of an oil containing 50.0 volume percent aromatics and having a viscosity at 210 F.

of 130-140 SUS, API gravity at 60 F. of 17-14, and open cup flash point of 490 F. The grease has a water wash off of 44.0 percent.

Example 4.Lithium soap grease with copolymer The same grease composition as in Example 3 was prepared with 2 weight percent ethylene-vinyl acetate copolymer, having melt index of 5-7 and containing 27-29 weight percent vinyl acetate, based on the total weight of the grease. Water wash oif was 7.7 percent.

Example 5 .Aluminum complex soap grease Without copolymer Component: Wt. percent Petroleum oil 84.35 Stearic acid 2.62 Benzoic acid 1.38 Kolate 65 1 6.15 Penyl-Bmaphthyl amine 0.50 Zinc oxide 5.00 Diisopropoxy palmitate cyclic aluminum oxide trimercan be prepared according to 11.8. Patent 2,979,497 to Rinse. The petroleum oil is a blend of 56.00 parts by weight of an oil containing 46.0 volume percent aromatics and having a viscosity at 100 F. of 500-530 SUS, API gravity at 60 F. of 18-21, and open cup flash point of 370 F. and 28-35 parts by weight of an oil containing 50.0 volume percent aromatics and having a viscosity at 210 F. of 130-140 SUS, API gravity at 60 F. of 17-19 and open cup flash point of 490 F. The water wash off was 12.0 percent.

Example 6.-Alu-minum complex grease with copolymer TABLE Soap type Lithium Aluminum complex Example 3 4 5 We ht percent ethylene-vinyl acetate Water wash off, percent- Penetration, 60 strokes. Penetration, 10,000 strokes Dropping point, F Shell roll stability, percent change in pen. (150 F., 100

hrs., r.p.m., 150 gr.) ASTM D-1263 (6 hrs., 220 F.,

90 gr.) wheelbearing, percent change in pen Sun wheelbearing, percent change in pen. (6 hrs., 260 F.

130 gr.) (ASTM D-1263 modified as indicated) 1 Elvax 260-Du Pent.

It can readily be seen that compositions according to the present invention offer substantial and unexpected improvement in their adhesion and cohesion properties over the comparable grease compositions without the ethylene-vinyl acetate copolymer.

The invention claimed is:

1. A grease composition comprising a major proportion of a mineral lubricating oil containing at least 40 percent by volume of aromatic hydrocarbons and a minor proportion of a thickening agent and an amount in the range of 0.5 to 10 weight percent of ethylene-viny1 acetate copolymer.

2. A grease composition according to claim 1 wherein the ethylene-vinyl acetate contains from 15 to weight percent vinyl acetate.

3. A grease composition according to claim 2 wherein the ethylene-vinyl acetate contains from 17 to 42 weight percent vinyl acetate.

4. A grease composition according to claim 3 wherein the thickening agent is a fatty acid metallic soap.

5. A grease composition according to claim 1 wherein the ethylene-vinyl acetate copolymer is present in an amount in the range of 0.5 to 2 weight percent.

6. A grease composition according to claim 3 wherein the ethylene-vinyl acetate copolymer is present in an amount in the range of 0.5 to 2' weight percent.

7. A grease composition according to claim 4 wherein the fatty acid metallic soap is a complex soap.

8. A grease composition according to claim 7 wherein the complex soap is complex aluminum soap.

9. A grease composition according to claim 8 wherein the ethylene-vinyl acetate copolymer is present in an amount in the range of 0.5 to 2 weight percent.

10. A grease composition according to claim 4 wherein the fatty acid metallic soap is a lithium soap.

11. A grease composition according to claim 10whe1'ein the ethylene-vinyl acetate copolymer is present in an amount in the range of 0.5 to 2 weight percent.

References Cited UNITED STATES PATENTS 2,499,723 3/ 1950 Coifman et al 25256 3,010,899 11/1961 Boyer 252-56 3,014,867 12/1961 Fronczak 25241 3,103,493 9/1963 Groszek et al 25241 3,173,965 3/1965 Pappas et a1 25259 3,250,714 5/1966 Ilnyckyj et a1. 25256 3,290,244 12/ 1966 Polishuk et al 25259 DANIEL E. WYMAN, Primary Examiner. I. VAUGHN, Assistant Examiner.

US. Cl. X.R. 25242, 5 6