US3213025A - Polyaryl ether thickened to a grease with an aryloxy benzoate - Google Patents

Description

United States Patent 3,213,025 POLYARYL ETHER THICKENED TO A GREASE WITH AN ARYLOXY BENZOATE John F. Hedenburg, Cheswick, Pa., assignor to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware No Drawing. Filed Mar. 15, 1962, Ser. No. 180,035 3 Claims. (Cl. 252-42) This invention relates to an improved lubricating composition and more particularly to a polyaryl ether lubricant suitable for high temperature lubrication.

The trend in design of modern aircraft has accentuated the need for greases which will lubricate anti-friction bearings operating at high rotational speeds and high temperatures. While considerable progress has been made in recent years in producing improved aircraft greases some difiiculty has been encountered in producing a grease which will effectively lubricate bearings operating at high rotational speeds and high temperatures for prolonged periods of time.

I have discovered that a lubricating composition having improved lubricating characteristics for an extended period of time when used to lubricate bearings operating at an elevated temperature under high rotational speeds can be obtained by incorporating an alkali metal salt of an aryloxy benzoic acid in a polyaryl ether in an amount suflicient to produce a composition having the consistency of a grease. Thus, the improved lubricating composition of my invention comprises a dispersion in a polyaryl ether of a sufficient amount to thicken the polyaryl ether to a grease consistency of an alkali metal salt of an aryloxy benzoic acid.

The thickening agents employed in the composition of the invention are the alkali metal salts of aryloxy benzoic acids, which are exemplified as follows: sodium o-phenoxy-benzoate; sodium m-phenoxybenzoate; sodium p-phenoxybenzoate; sodium o-naphthoxybenzoate; sodium mnaphthoxybenzoate; sodium p-naphthoxybenzoate; potassium d-phenoxybenzoate; potassium p-napthoxybenzoate; lithium o-phenoxybenzoate; lithium p-napthoxybenzoate; etc.

The alkali metal salts of the aryloxy benzoic acids can be prepared by treating an aryloxy benzoic acid with an aqueous alkali solution. For example, sodium o-phenoxybenzoate can be prepared by reacting aqueous sodium hydroxide and o-phenoxybenzoic acid in equimolar proportions at room temperature. Neither the compounds per se nor their method of preparation constitutes any portion of the invention. The amount of the alkali metal salt of an aryloxy benzoic acid which I use is an amount sufficient to thicken the lubricating oil to a grease consistency. In general, this amount comprises about to about 50 percent by weight of the total composition. In most in stances, a composition having the consistency of a grease can be prepared when the alkali metal salt of the aryloxy benzoic acid comprises about to about percent by weight of the total composition.

The polyaryl ether in which the alkali metal salt of the aryloxy benzoic acid is incorporated is preferably a polyphenyl ether. Exemplary of the polyphenyl ethers are bisphenoxyphenyl ether, bis (phenoxyphenoxy)phenyl ether and bis(phenoxyphenoxy)benzene. The ethers can be used either in the form of a substantially pure individual isomers or in the form of mixtures of isomers such as mixed ortho, meta and para isomers of bis(phenoxyphenoxy)benzene. Exemplary of exceedingly good individual isomers are m-bis(m-phenoxyphenoxy)benzene and bis-m(m-phenoxyphenoxy)phenyl ether.

If desired, a blend of polyaryl ethers having different viscosities may be employed as the lubricant base instead of a single polyaryl ether by means of which a base 3,213,025 Patented Oct. 19, 1965 lubricant having a particular viscosity may be secured. Therefore, depending upon the particular use for which the ultimate composition is designed, the lubricant base may be a bis(phenoxyphenoxy)benzene, a bis(phenoxyphenoxy)phenyl ether or a mixture thereof. The polyaryl ether content of the composition prepared according to this invention comprises about 50 to about percent by weight of the total composition.

In compounding the compositions of the present invention, various mixing and blending procedures may be used. In a preferred embodiment of the invention, the polyaryl ether and the alkali metal salt of the aryloxy benzoic acid together with conventional lubricant additives, if desired, are mixed together at room temperature for a period of 10 to 30 minutes to form a slurry. During this initial mixing period some thickening is evidenced. Some lumps may be formed. The slurry thus formed is then subjected, to a conventional milling operation in a ball mill, a colloid mill, homogenizer or similar device used in compounding greases to give the desired degree of dispersion. In the illustrative composition of this invention, the slurry was passed twice, by means of a pump, through a Premier Colloid Mill set at a stator-rotor clearanee of 0.002 inch. Maximum thickening occurred on the second pass through the mill.

The lubricating composition of this invention can contain conventional lubricant additives, if desired, to improve other specific properties of the lubricant without departing from the scope of the invention. Thus, the lubricating composition can contain a filler, a corrosion and rust inhibitor, an extreme pressure agent, an antioxidant, a metal deactivator, a dye and the like. Whether or not such additives are employed and the amounts thereof depend to a large extent upon the severity of the conditions to which the composition is subjected and upon the stability of the lubricating base in the first instance. Since the polyaryl ethers, for example, are in general more stable than mineral oils, they require the addition of very little, if any, oxidation inhibitor. When such conventional additives are used they are generally added in amounts between about 0.01 and 5 percent by weight based on the Weight of the total composition.

In order to illustrate the lubricating characteristics of a grease composition of the invention at 20,000 revolutions per minute and at a temperature of 400 F., Pope spindles were used in a test procedure similar to that outlined by the Coordinating Research Council Tentative Draft (July 1954) Research Technique for the Determination of Performance Characteristics of Lubricating Grease in Antifriction Bearings at Elevated Temperatures, CRC Designation L-35. According to this procedure, 3 grams of the grease to be tested are placed in a bearing assembly containing an eight-ball SAE No. 204 ball bearing. In general, bearings fabricated from high speed tool steel and ball retainers fabricated from silver-plated berylliumcopper (MRC 204S17) are used as both test and outboard bearings. The bearing assembly which is mounted on a horizontal spindle is subjected to a radial load of 5 pounds. The portion of the spindle upon which the test bearing assembly is located is encased in a thermostatically controlled oven. By this means the temperature of the bearing can be maintained at a desired elevated temperature which in the test reported hereinafter was 400 F. The spindle is driven by a constant belt-tension motor drive assembly, capable of giving spindle speeds of 20,000 revolutions per minute. The test continues until the lubricant fails. The lubricant is considered to have failed when any one of the following conditions occurs: (1) spindle input power increases to a value approximately 300 percent above the steady state condition at the test temperature; (2) an increase in temperature at the test bearing of 20 F. over the test temperature; or (3) the 3 test bearing locks or the drive belt slips at the start or during the test.

The polyaryl ether used in preparing the lubricating composition summarized in Table I was mixed isomers of bis(phenoxyphenoxy)benzene having as typical characteristics a viscosity at 100 F. of 1691 SUS, a viscosity at 210 F. of 71 SUS and a pour point of +40 F.

The sodium o-phenoxybenzoate was prepared by new tralizing (pH of 7) at room temperature, 100 g. of ophenoxybenzoic acid dissolved in a minimu of 95 percent ethanol with a 50 percent aqueous solution of sodium hydroxide. Water and additional ethanol were added just to dissolve the precipitate. The solution was then added With stirring to three liters of acetone from which the product precipitated. The product was then Washed twice with acetone and dried. The dried product, sodium o phenoxybenzoate, melted at 345 C. (653 F.).

In preparing the lubricating composition, the polyaryl ether and the alkali metal of o-phenoxybenzoic acid were mixed at room temperature for a period of 10 to 30 minutes. The slurry thus formed was passed twice through a Premier Colloid Mill set at a stator-rotor clearance of 0.002 inch. The thickened lubricating composition thus prepared had the following approximate make-up and The long performance life of the composition of the invention at a high rotational speed and a high temperature is self evident from the above data.

Other lubricating compositions within the scope of the invention are illustrated in Table II. The polyaryl ethers shown in Table II have the following typical characteristics.

Viscosit SUS:

At iii) F 1, 567 1,691 3, 565 At 210 F 70 71 118 Pour Point, F +35 +40 +70 (1) m-Bis(m-phenoxyphenoxy)benzene.

(2) Bis(phenoxypheuoxy)benzene (mixed isomers),

(3) Bis-111(m-phenoxyphenoxy)phenyl ether,

4 Table II Composition, percent By Weight B C Polyaryl Ether:

m-Bis(rn-phenoxyphenoxy)benzene". Bis(phenoxyphe110xy)benzene (mixed isomers) Bis-m(m-phenoxyphenoxy)phenyl ether Thiekener:

Soium o-uaphthoxybenzoate Potassium p-naphthoxybenzoate Lithium p-phenoxybenzoate While my invention has been described with reference to various specific examples and embodiments, it will be understood that the invention is not limited to such examples and embodiments and may be variously practiced within the scope of the claims hereinafter made.

I claim:

1. A lubricating composition capable of functioning in bearings rotating at speeds up to about 20,000 r.p.m. at temperatures up to about 400 F. consisting essentially of 5 a dispersion in a major amount of a polyphenyl ether of a References Cited by the Examiner UNITED STATES PATENTS 2,623,854 12/52 Morway et al 25241 2,690,429 9/54 Morway et a1 25242 3,012,966 12/61 Copes et a1. 447 3,113,849 12/63 McCoy 447 OTHER REFERENCES Synthetic Lubricants, by Gunderson et al., Reinhold Pub. Corp., New York, 1962, page 460.

DANIEL E. WYMAN, Primary Examiner.

JULIUS GREENWALD, Examiner.

Claims (1)

1. A LUBRICATING COMPOSITION CAPABLE OF FUNCTIONING IN BEARINGS ROTATING AT SPEEDS UP TO ABOUT 20,000 R.P.M. AT TEMPERATURES UP TO ABOUT 400*F. CONSISTING ESSENTIALLY OF A DISPERSION IN A MAJOR AMOUNT OF A POLYPHENYL ETHER OF A SUFFICIENT AMOUNT TO THICKEN THE POLYPHENYL ETHER TO A GREASE CONSISTENCY OF SODIUM O-PHENOXYBENZOATE.