US3047499A - Grease compositions - Google Patents

Description

United States Patent entries Patented July 31, 1962 tire The present invention relates to a method for producing improved grease compositions and to the compositions produced thereby. More particularly, the present invention relates to a method of improving the leach resistance of soap'filled grease compositions by imparting improved water repellency to the soap with certain organopolysiloxane compositions, and to the improved grease compositions produced thereby.

Oil based greases that are thickened with soap materials such as alkali s-tearates in the range of about 5 to 50% by weight soap based on the weight of the grease are widely used because soap thickened greases have good structural characteristics. A problem that often arises with the use of soap thickened grease compositions is that the soap has a tendency to be leached out of the grease due to excessive exposure to moisture when the grease is being used, resulting in a breakdown of the grease structure and reduced lubricating performance.

Of these soap-filled grease-s available to date two of the most used are greases thickened with sodium salts or lithium salts of fatty acids. Patent 2,731,417, King et 211.,

suggests that the leach resistance of sodium salt-thickened greases can be improved by treating the soap with an alkali metal siliconate prior to incorporation of the soap into the grease formulation. While this procedure is satisfactory for the sodium soap greases, the leach resistant greases are still unsatisfactory for many applications because the sodium soap, even in its treated form, is not satisfactory for high temperature lubricating applications, e.g., applications in which temperatures in the order of 250 C. are encountered.

This high temperature deficiency in sodium soap greases is, of course, known in the art, and for this reason lithium soap thickened greases are now used in many applications where high temperature service is required. While these lithium soap greases are satisfactory in high temperature service under dry conditions, it is found that the lithium soap thickened greases have even less leach resistance than sodium soap thickened greases. When an attempt is made to treat lithium soaps with alkali methyl siliconate such as sodium methyl siliconate or lithium methyl siliconate, the leach resistance of greases prepared from these siliconate treated metals is improved to some extent However, the leach resistance is still substantially below that required for operation of the greases at elevated temperatures in moist environments.

It has now been discovered that the leach resistance of conventional soap thickened, oil base grease compositions can be markedly improved by thickening the base oil with a fatty acid soap that has been modified by the process of the present invention. This process comprises treating the fatty acid soap under grease-making conditions with a curable mixture of ingredients comprising a curable organopolysiloxane containing carboxyalkylsiloxy units and an effective amount of a curing catalyst in the form of a polyvalent metal-containing material.

While I do not wish to be bound by the theory, it is believed that a curing of the curable organopolysiloxane takes place in and about the fibers of the soap thickener to form modified fibers. This curing is believed to be a cross-linking between the carboxyalkyl radicals on the curable organopolysiloxane which is induced by the polyvalent metal which is present in the system.

In accordance with the present invention there is provided a process for making an improved grease composition containing a major proportion of a base oil, comprising mixing together under grease-making conditions said base oil and a mixture of ingredients comprising a soap and from 1% to 15% by weight, based on the weight of said soap, of a carboxyalkylorganopolysiloxane having the formula:

l (HO 0 0 omnzmnsio and from 0.01 to 5%, based on the weight of said base oil, of :a polyvalent metal selected from the class of tin, zinc and lead in the form of a polyvalent metal-containing material, where m is an integer equal to from 1 to 5, inclusive, a is equal to 0.001 to 1.0, b is equal to 1.001 to 2, and the sum of a and b is equal to 1.001 to 2.5, and R is a member selected from the class of monovalent hydrocarbon radicals, halogenated monovalent hydrocarbon radicals, and a mixture of radicals consistingof at least one of the aforementioned members and up to 20 mol percent of cyanoalkyl radicals.

The carboxyalkylorganopolysiloxanes of Formula 1 can be made by the procedure illustrated in French Patent 1,158,808. Other procedures are shownin Patent 2,900,363, Bluestein, which describes the preparation of carboxyalkylpolysiloxanes by hydrolyzing the corresponding cyanoalkylchlorosilanes or mixtures of cyanoalkylchlorosilanes and alkylchlorosilanes. The cyanoalkylchlorosilanes can be synthesized by methods shown in French Patent 1,118,500 and Us. Patent 2,913,742, Prober.

The carboxyalkylorganopolysiloxanes of Formula 1, preferably contain the following carboxyalkylsiloxy units:

HOOC-CH2CHPS1O 2 intercondensed with one or more of the following siloxy units (4) R SiO )z (6) )a 1 2 where c is a whole number equal to from 0 to 2, inclusive, R is as defined in Formula 1 and R is a member selected from the class consisting of monovalent hydrocarbon radicals, and halogenated monovalent hydrocarbon radicals. The carboxyalkylsiloxy unit represented by Formula 3 preferably is present in the carboxyalkylorganopolysiloxane of Formula 1 in the range of 1 to 10 mol percent based on the total number of siloxy units contained in said carboxyalkylorganopolysiloxane.

Included within the radicals represented by R of Formula 1 are more particularly aromatic and chloro aromatic, such as phenyl, ohlorophenyl, tolyl, diphenyl, naphthyl, etc.; aliphatic and ohloroaliphatic such as alkyl, cycloalkyl, chloroalkyl, alkenyl and alkynyl, particularly methyl, ethyl, propyl, butyl, cyclohexyl, chloroethyl, vinyl, allyl, etc. R can be all the same radicalor R can be a mixture of any two or more of said radicals. In addition, R can be a mixture of two or more of the aforementioned radicals and up to 20 mol percent of cyanoalkyl radicals, such as cyanoethyl, cyanopropyl, cyanobutyl, and cyanopentyl. Where R is a cyanoalkyl radical, R can be all the same cyanoalkyl radical or a mixture of cyanoalkyl radicals. R is preferably' methyl, phenyl, chlorophenyl, and where R is a cyanoalkyl radical, R is is preferably ,B-cyanoethyl.

The polyvalent metal-containing materials which are used as curing catalysts are any materials containing either tin, zinc or lead, and preferably tin, which can be blended with the base oil, soap thickener and carboxyalkylorganopolysiloxane without detrimentally affecting the lubricating properties of the resulting grease while it is being employed under standard operating conditions, such as temperatures up to 250 C. or higher. Included within the scope of the present invention are Zinc, tin and lead salts of branched or straight chain saturated and unsaturated fatty acids from 8 to 20 carbon atoms and also the corresponding metal oxides and carbonates of said metals. Specific examples of these salts are tin octoate, tin oleate, tin laurate, tin stearate, tin carbonate, tin oxide, etc., zinc octoate, zinc palmitate, zinc oxide, zinc carbonate and lead oxide, lead carbonate, etc.

Further examples of tin or Zinc materials employed as curing catalysts in the practice of the present invention are organometallics of tin or zinc with monomeric or polymeric organic materials with active replaceable hydrogens. In addition, copolymers of said polyvalent metals with organosiloxy units such as organopolysiloxane-tin compounds having SiCSn and SiO--Sn linkages are also operable. Many of these copolymers are shown in Patents 2,937,994, Holdstock, and 2,937,- 995, Holdstock et al.

The base oils that can be blended with soaps to produce the improved grease compositions of the present invention include mineral oils between about 150 to 200,000 S.S.U. viscosity, and having a viscosity index between about 40 and 100. In addition, the grease compositions of the present invention can also be made with organo polysiloxane oils corresponding to the formula:

( (R)dSiO larly described as triorganosilyl chain-stopped linear or branched-chain organopolysiloxanes where the organo radicals correspond to R" in Formula 7.

In addition, tin containing copolymers discussed above as a curing catalyst and having the SiC-Sn or Si-O-Sn linkage can also serve as a base oil, serving both as the base oil and as the curing catalyst.

The preferred soaps employed in the practice of the present invention as thickeners for the base oils are any alkali metal salts of fatty acids that are either branched chain, or straight chain, and saturated or unsaturated and which have 8 carbon atoms to 20 carbon atoms. A few examples are the lithium, sodium, and potassium salts of caprylic, pelargonic, capric, undecylic, lauric, myristic,

palmitic, stearic, octanoic, 2-ethylhexanoic, oleic acid, as

well as other carboxylic acids derived from tallow, halogenated fish oils and castor oil. In addition to the metallic soaps, antioxidants such as diphenylarnine, and inorganic filler materials such as natural clays, carbon black, silica and various metal oxides can also be added to the improved grease compositions of the present invention.

In the practice of the present invention, the soap thickener for the base oil is merely mixed with the carjboxyalkylorganopolysiloxane and the polyvalent metalcontaining material. Depending upon the compatibility of the ingredients of the mixture, the mixture is blended either in the presence or in the absence of the base oil by conventional means such as by employing a grease mill.

Except as noted earlier, the proportions of the various ingredient in the grease composition can be varied almost without limit. However, it is preferred that the base oil comprise a major portion of the grease composition, e.g.,

from 50 to percent by weight, based on the weight of the grease composition. Preferably the soap comprises from 5 to 45% by weight, based on the weight of the grease composition.

The order in which the ingredients are blended to produce the improved grease compositions of the present invention is not critical. It has been found expedient, however, in order to insure that the resulting grease composition has the maximum obtainable leach resistance, to avoid directly blending at grease making temperatures the curing catalyst with the carboxyalkylorganopolysiloxane without having at least one of the aforementioned ingredients substantially dispersed throughout the soap. Direct mixing of the curing catalyst and carboxyalkylorganopolysiloxane at curing temperatures in the absence of the soap is to be particularly avoided, since the opportunity for the polysiloxane to cure through and about the fibers of the soap is substantially reduced. Curing of the carboxyalkylorganopolysiloxane in the presence of the curing catalyst takes place at temperatures in the range of 80 C. to 250 C., which temperature range is within the range of standard greasemaking conditions. Preferably, the ingredients are blended at temperatures of about C. to C. to provide for curing of the grease composition during the blending operation.

In order that those skilled in the art will be better able to practice the present invention, the following examples are given by way of illustration and not by way of limitation.

Example 1 Over a ten minute period 94 parts of B-cyanoethyltrichlorosilane was added with stirring to 225 parts of contrated aqueous HCl. To the clear solution that was obtained there was added sufiicient NaOH to bring the pH up to 5. The reaction product was recovered with ethanol. A resinous product was obtained which consisted essentially of recurring HOOCCH CH SiO units. This product was free of cyanoalkyl radicals as determined by infrared analysis.

There was equilibrated with 20 parts of the resin prepared above, 290 parts of octamethylcyclotetrasiloxane and 20 parts of hexamethyldisiloxane in the presence of three parts of 87 percent concentrated sulphuric acid. The resulting product was stripped of its volatiles and a curable polysiloxane fluid was obtained which contained about 5 mol percent of fi-carboxyethylsiloxy units,

HO OCCH CH SiO 89 mol percent dimethylsiloxane units and 6 mol percent trimethylsiloxane units.

A carboxyethyl grease within the scope of the present invention was prepared by mixing together in a grease mill 29 parts of lithium ethylhexanoate, 4.8 parts of the above curable polysiloxane fluid and 65 parts of a fluid tetrachlorophenyl organopolysiloxane having a viscosity of about 40 centistokes at 25 C. and consisting of about 4 mol percent of tetrachlorophenyl siloxane units, 88 mol percent of dimethyl siloxane units and 8 mol percent of trimethyl siloxane units. There are added to the resulting mixture 0.1 part of tin oleate containing about 16% by weight of tin, and 0.34 part of a diphenylamine antioxidant was also added. After these ingredients had been thoroughly blended together, the blend was heated to a temperature of 150 C. for 60 minutes.

A methylsiliconate grease was prepared by initially blending together 50 parts of lithium 2-ethylhexanoate in the form of an aqueous saturated solution with 2.5 parts of lithium methylsiliconate. The blend was placed in an oven at 80 C. and the excess Water was evaporated. The dried product was slurried in the presence of 150 parts by weight of the fluid tetrachlorophenyl organopolysiloxane mentioned above and 1.2 parts of a diphenylamine antioxidant.

The leach resistance of both the carboxyethyl grease" and the methylsiliconate grease were measured in accordance with procedure described in Federal specification VVI.791D, amendment 1, June 20, 1950, method 325.2, entitled Water Resistance (if-Lubricating Greases. In this procedure the greases were exposed to the washing action of distilled Water for one hour while in a rotating ball bearing assembly. Theweight percent of grease washed away during the hour is a measure of leach resistance, lower weight loss indicating better leach resistance.

Table I shows the results of these tests and tests run on a control comprising a mixture of 30 parts of lithium 2-ethylhexan0ate and 70 parts of the aforementioned fluid tetrachlorophenyl organopolysiloxane.

TABLE I Grease Percent weight loss Carboxyethyl 11.8 Methylsiliconate 53 Control 94-98 Example 2 A carboxyethyl grease is prepared having the same proportions by Weight of ingredients as in Example 1, except that the procedure in blending the ingredients is changed. The tin oleate and the curable polysiloxane fluid are blended under grease-making conditions in the absence of the lithium Z-ethylhexanoate and the fluid tetrachlorophenyl organopolysiloxane. The resulting grease composition is found to have substantially reduced leach resistance as compared to the carboxyethyl grease of Example 1.

Example 3 The procedure of Example 1 is repeated except that parts of tin oleate is added to the grease forming mixture instead of the 0.1 part of Example 1. The resulting mixture is blended under grease-making conditions and the grease that is formed is found to have water repellency superior to that of the methyl siliconate grease of Example 1.

Example 4 A mixture of two parts of 'y-cyanopropyltrichlorosilane, three parts of dimethyldichlorosilane and one part of trimethylchlorosilane was hydrolyzed by adding it slowly with stirring to an excess of ice water. A mixture of one part of the resulting hydrolyzate and 0.16 part of octamethylcyclotetrasiloxane was equilibrated and further treated in accordance with the Bluestein method as shown in Patent 2,900,363. The final product was silicone fluid containing mol percent of HOOC-CH CH -CH -SiO units, 5 mol percent of CNCI-l CIl -CH SiO units and a balance of 53 mol percent dimethylsiloxy units and 22 mol percent of trimethylsiloxy units, based on infrared analysis and method of preparation.

A Tinsil grease formulation was prepared by blending 28.1 parts of lithium octoate, 4.3 parts of the above silicone fluid, 64 parts of the tetrachlorophenylorganopolysiloxane fluid described above, 3.3 parts of silicontin copolymer described in Example '1 of Patent 2,937,- 994, Holdstock, and 0.4 part of a diphenylamine antioxidant.

Another grease was prepared by blending 25 parts of lithium octoate, 69.6 parts of the tetrachlorophenylpolysiloxane fluid, 0.4 part of tin octoate as a mineral spirits solution containing 28% by weight of tin, and 0.5 part of a diphenylamine antioxidant.

Table II shows the leach resistance of these two grease compositions as compared to the methylsiliconate grease described in Example 1.

TABLE [I Grease: Percent weight loss Tinsil 30.6 Carboxypropyl 4.2 Methylsiliconate 53 The above examples clearly show that the leach resistance of the grease compositions of the present invention are substantially better than the prior art greases.

While the foregoing examples have of necessity described only a few of the very many grease compositions within the scope of the present invention, it should be understood that the present invention is directed to a much broader class of grease compositions that can be produced in accordance with the practice of the present invention by the use of a suitable carboxyalkylpolysiloxane shown in Formula 1 with the other grease forming ingredients included and illustrated in the foregoing description.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A. grease composition comprising (A) a major proportion of a base oil selected from the class consisting of an organopolysiloxane oil and a mineral oil and (B) a minor proportion of thickener consisting essentially of an alkali metal soap of a fatty acid having its fibers modified at a temperature in the range of between C. to 250 C. with a mixture of ingredients consisting of (1) from 0.01 to 5 percent, based on the weight of (A) of a polyvalent metal material selected from the class consisting of tin copolymers having the characteristic linkage Si-CSn, tin copolymers having the characteristic linkage, Si-OSn, tin salts of fatty acids having from 8 to 20 carbon atoms, tin carbonate, tin oxide, zinc salts of fatty acids having from 8 to 20 carbon atoms, zinc carbonate, zinc oxide, lead salts of fatty acids having from 8 to 20 carbon atoms, lead carbonate, and lead oxide, and (2) from 1 to 15 percent, based on the weight of said alkali metal soap of a fatty acid of a carboxyalkylpolysiloxane having the formula (HOOOC H2mn(S iO where m is an integer equal to from 1 to 5, inclusive, a is equal to from 0.001 to 1.0, b is equal to from 1.001 to 2, and the sum of a and b is equal to from 1.001 to 2.5, and R is a member selected from the class consisting of monovalent hydrocarbon radicals, halogenated monovalent hydrocarbon radicals, and a mixture of radicals consisting of at least one of the aforementioned members and up to 20 mole percent of cyanoalkyl radicals.

2. A grease composition comprising (A) a major proportion of a base oil selected from the class consisting of an organopolysiloxane oil and mineral oil and (B) a minor proportion of the product or" reaction at a temperature between 80 C. to 250 C. of (1) a fatty acid soap of an alkali metal, (2) from 0.01 to 5 percent, based on the weight of (A) of a polyvalent metal material selected from the class consisting of tin copolymers having the characteristic linkage Si-C-Sn, tin copolymers having the characteristic linkage Si-O-Sn, tin salts of fatty acids having from 8 to 20 carbon atoms, tin carbonate, tin oxide, zinc salts of fatty acids having from 8 to 20 carbon atoms, Zinc carbonate, zinc oxide, lead salts of fatty acids having from 8 to 20 carbon atoms, lead carbonate, and lead oxide, and (3) from 1 to 15 percent based on the weight of said fatty acid soap of a carboxyalkylpolysiloxane having the formula (HO O O CmHZm) S10 where m is an integer equal to from 1 to 5, inclusive, a is equal to from 0.001 to 1.0, b is equal to from 1.001 to 2, and the sum of a and b is equal to from 1.001 to 2.5, and R is a member selected from the class consisting of monovalent hydrocarbon radicals, halogenated monovalent hydrocarbon radicals, and a mixture of radicals consisting of at least one of the aforementioned members and up to 20 mole percent of cyanoalkyl radicals.

133A process for making a grease composition comprising blending together at a temperature between 80 C. to 250 C., from 50 to 95 percent by Weight, based on the weight of said grease composition of'an oil component (A) and from 50 to 5 percent, based on the weight of said grease composition of a thickener (B), where (A) is a base oil selected from the class consisting of a mineral oil and an organopolysiloxane oil and (B) is a mixture of ingredients comprising (-1) a fatty acid soap of an alkali metal, (2) from 1 percent to 15 percent by 'we'ight, based on the weight of said fatty acid soap of a carboxyalkylorganopolysiloxane having the formula IDb (HO O C CmHQLn) {10 and (3) from 0.01 to 5 percent based on the weight of (A) of a polyvalent metal material selected from the class consisting of tin copolymers having the characteristic linkage Si-CSn, tin copolymers having the characteristic linkage Si-OSn, tin salts of fatty acids having from 8 to 20 carbon atoms, tin carbonate, tin oxide, zinc salts of fatty acids having from 8 to 20 carbon atoms,

zinc oxide, Zinc carbonate, lead salts of fatty acids having from 8 to 20 carbon atoms, lead oxide, and lead carbonate, where m is an integer equal to from 1 to 5,

inclusive, a is equal to from 0.001 to 1.0, b is equal to from 1.001 to 2, and the sum of a and b is equal to from where R" is a member selected from the class of monovalent hydrocarbon radicals, halogenated monovalent hydrocarbon radicals, and cyanoalkyl radicals, and d has a value from 2.01 to 2.5.

References (Jilted in the file of this patent UNITED STATES PATENTS 2,446,177 Hain Aug. 3, 1948 2,705,700 Iler Apr. 5, 1955 2,721,856 Sommer Oct. 25, 1955 2,833,802 Merker May 6, 1958 2,891,980 Gilbert et a1 June 23, 1959 2,907,783 Kerschner et a1 Oct. 6, 1959 2,957,899

Black etal. Oct. 25, 1960

Claims (1)

1. A GREASE COMPOSITION COMPRISING (A) A MAJOR PROPORTION OF A BASE OIL SELECTED FROM THE CLASS CONSISTING OF AN ORGANOPOLUYSILOXANE OIL AND A MINERAL OIL AND (B) A MINOR PROPORTION OF THICKNER CONSISTING ESSENTIALLY OF AN ALKALI METAL SOAP OF A FATTY ACID HAVING ITS FIBERS MODIFIED AT A TEMPERATURE IN THE RANGE OF BETWEEN 80* C. TO 250* C. WITH A MIXTURE OF INGREDIENTS CONSISTING OF (1) FROM 0.01 TO 5 PERCENT, BASED ON THE WEIGHT OF (A) OF A POLYVALENT METAL MATERIAL SELECTED FROM THE CLASS CONSISTING OF TIN COPOLYMERS HAVING THE CHARACTERISTIC LINKAGE SI-C-SN, TIN COPOLYMERS HAVING THE CHARACTERISTIC LINKAGE, SI-O-SN, TIN SALTS OF FATTY ACIDS HAVING FROM 8 TO 20 CARBON ATOMS, TIN CARBONATE, TIN OXIDE, ZINC SALTS OF FATTY ACIDS HAVIANG FROM 8 TO 20 CARBON ATOMS, ZINC CARBONATE, ZINC OXIDE, LEAD SALTS OF FATTY ACIDS HAVING FROM 8 TO 20 CARBON ATOMS, LEAD CARBONATE, AND LEAD OXIDE, AND (2) FROM 1 TO 15 PERCENT, BASED ON THE WEIGHT OF SAID ALKALI METAL SOAP OF A FATTY ACID OF A CARBOXYALKYLPOLYSILOXANE HAVING THE FORMULA