US2937993A - High melting point synthetic base grease containing an alkali metal salt of a dicarboxylic acid - Google Patents

Description

United States atent HIGH MELTIN G POINT SYNTHETIC BASE GREASE CONTAINING AN ALKALI METAL SALT OF A DICARBOXYLIC ACID Warren C. Pattenden, Courtright, Ontario, Lorne W. Sproule, Sarnia, Ontario, and James H. Norton, Corunna, Ontario, Canada, assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Filed Sept. 23, 1957, Ser. No. 685,395

Claims. (Cl. 252-41) This invention relates to greases and grease thickeners and to methods for their preparation. In particular, it relates to grease compositions comprising a major proportron of a lubricating oil and a thickening amount of a thickener comprising a salt of a dicarboxylic acid and to methods for preparing the grease compositions.

This application is a continuation-in-part of US. application Serial No. 605,726, filed August 23, 1956, and now issued as US. Patent No. 2,898,296.

Salts of dicarboxylic acids are known to have high melting points but are usually so indispersible in mineral oil that they have found little use in grease manufacture. It has now been discovered that grease thickeners having high dropping points can be prepared by the direct reaction of a metal base with either a dibasic acid ester or with a mixture of an aliphatic dicarboxylic acid and a monohydric aliphatic alcohol. It has also been discovered that excellent grease thickeners can be prepared in a lubricating oil menstruum from a'mixture of an aliphatic monocarboxylic acid salt and a metal salt of a dicarboxylic acid, the latter salt being obtained by saponification of the diester of the dicarboxylic acid. The latter thickeners maybe prepared by neutralizing a mixture of an aliphatic monocarboxylic acid and a synthetic ester of a dicarboxylic acid with a metal base in either a mineral oil or synthetic oil menstruum. Greases prepared with any of the above grease thickeners are homogeneous in appearance and have exceptionally high dropping points.

The synthetic diesters useful in this invention are those formed by the reaction of an aliphatic dicarboxylic acid and a monohydric aliphatic alcohol. These diesters have the general formula:

ROOC--(CH -COOR wherein R and R are alkyl radicals of either straightchain or branched-chain aliphatic saturated monohydric alcohols containing about 1 to 22, advantageously 1 to carbon atoms per molecule, and x is a number from 0 to 20, advantageously 4 to 8. The diester molecule will contain a total of about 4 to 64, advantageously 6 to 28 carbon atoms. Also included are diesters prepared from Oxo alcohols, which are an isomeric mixture of highly branched-chain primary alcohols prepared by the 0x0 process, which is well known in the art.

The aliphatic monocarboxylic acids useful in carrying out the invention are those acids'which have about 6 to 30, advantageously 10 to 18 carbon atoms per molecule. These aliphatic monocarboxylic acids may be saturated or unsaturated, straight or branched-chain, and may be hydroxy substituted.

The monohydric aliphatic alcohols used in the mixtures which contain an aliphatic dicarboxylic acid are either 2,937,993 Patented May 24, 1960 straight-chained or branched-chained aliphatic saturated monohydric alcohols containing about 1 to 22 and preferably 1 to 10 carbon atoms per molecule.

The aliphatic dicarboxylic acids used in accordance with this invention have the following formula:

HOOD-(CH -COOH wherein x is a number from 0 to 20, advantageously from 4 to 8.

Metal bases of any of the metals commonly used in making grease thickeners may be used to neutralize the mixture of an aliphatic monocarboxylic acid and a synthetic ester. Generally used are the alkali metal and alkaline earth metal hydroxides or oxides. These may be used in the form of a hydrate or in water solution.

The metal bases contemplated'for use with mixtures not containing an aliphatic monocarboxylic acid are the alkali metal bases lithium hydroxide and sodium hydroxide used in the form of a hydrate or in an aqueous solution. It was found that it was not possible to substitute calcium hydroxide for the alkali metal bases in the process not employing an aliphatic monocarboxylic acid.

The menstruum for preparing the thickeners may be a mineral oil, a synthetic oil, or a synthetic diester oil of the 'type used to form the thickener. When the menstruum is a synthetic diester oil, only a portion of the synthetic diester is converted into the thickener, depending upon the amount of metal base which is used. After the grease thickener is formed by the reaction with a metal base, additional mineral oil, or-additional synthetic ester oil, or even additional amounts of anyof the other known synthetic oils may be added to form the final grease composition.

,The grease cooking temperature is generally determined by the bo-iling point of the alcohol which is added to the mixture or formed by the saponification of the diester, depending on which variation of the process is used. The presence of too much alcohol in the final grease reduces the yield and dropping point appreciably. It is therefore desirable to cook the grease sufficiently to remove the alcohol which 'is added or which is formed during the process. Generally used are temperatures of about 300 to 500 R, preferably 300 to 400 F. Lower temperatures can be used if the alcohol is removed under reduced pressure. The mixture is thenheated for a period of time suflicient to complete the neutralization of the acids, form the thickener, and to evaporate the alcohol. This period of time will generally be about 5 to 120 minutes, usually 10 to 30 minutes.

Additional lubricating oil and additives may be added to form the final grease product. The grease may then be homogenized through a Manton-Gaulin homogenizer or a similar type of homogenizer, and packaged.

The grease compositions of the invention consist of -a major proportion, 60 to 95 wt. percent, preferably to 93 wt. percent, of a lubricating oil and a thickening amount, about 5 to 40 wt. percent, preferably 7 to 25 wt. percent of the grease thickener. The grease thickener containing an aliphatic monocarboxylic acid comprises about 20 to wt. percent, preferably 30 to 70 wt. percent of the aliphatic monocarboxylic acid salt and about 80 to 20 wt. percent, preferably 70 to 30 wt. percent of the dicarboxylic acid salt.

The invention will be better understood by the following illustrations which include the preferred embodiments of the invention.

and a'V.T.C. of 0.83.

A grease was prepared by mixing 15 grams of di-(2- ethyl hexanol) sebacate with 81.7 grams of a silicone lubricating oil having a viscosity at 100 F. of 475 cst. 3.3 grams of LiOHH O were added and the mixture was then heated to a temperature of about 400 F. and maintained at this temperature for about 15 minutes. The 2-ethyl hexanol which formed during the reaction was driven off almost as rapidly as it formed. The grease was then cooled and inspected.

EXAMPLES II TO IV Additional greases were prepared in the manner described in Example I using the ingredients as noted in Table I. The composition of the greases of Examples I a through IV and their characteristics are likewise shown in Table I.

Table I Example Number. I II III IV 30. 33 33 L'O 6. 6 NaO'FI 10 Dow Corning Fluid 710 l 81. 7 57 57 Mineral Oil 1 64. 0 Inspections:

AS'IM micropenetration, mm./

10 at 8O 74 48 400+ Dropping Point, F 500+ 680+ 580+ 1 Dow Corning Fluid 710 is a silicone fluid having a viscosity at 100' F. of 475 est. and a V.T.O. of 0.83.

9 A solvent treated and dewaxed Canadian distillate having a viscosity at 100 F. of 550 S.U.S., and a V.I. of 90.

The following greases are examples of the process using an aliphatic dicarboxylic acid and a monohydric aliphatic alcohol as starting materials in place of the above dicsters. These greases can be prepared by slowly adding an aqueous solution of the alkali to the acid and alcohol dissolved in lubricating oil or the dicarboxylic acid can be dissolved and/ or dispersed in a suitable volatile solvent such as 2-ethyl hexanol or water, and this solution then added to an aqueous alkali, alcohol, lubricating oil mixture.

EXAMPLE V A grease was prepared by mixing 20 grams of adipic acid and 36 grams of 2-ethyl hexanol with 100 grams of a silicone lubricating oil having a viscosity at 100 F. of 100 cst. and a V.T.C. of 0.78. 11 grams of LiOH.H O dissolved in water were added and the mixture was then heated to a temperature of about 400 F. and maintained at this temperature for about 15 minutes in order to complete the reaction and drive off the water and alcohol. The grease was then cooled and inspected.

EXAMPLES VI TO VIII Additional greases were prepared in the manner described in Example V using the ingredients as noted in the following Table II. The compositions of the greases of Examples V through VIII and their characteristics are shown in the following table.

4 Table II Example Number VII VIII Composition in grams:

dipie acid Sebacic acid Z-ethylhexanol- LIOH.H2O Dow Corning Fluid 550 1 Mineral Oil 2 Inspections:

ASIM micropenetration mmJlU. ASTM dropping point 1 Dow Corning Fluid 550 is methyl phenyl polysiloxane fluid having a flash point 01675 F. and a viscosity oi 10D est. at F.

7% mineral oil having a viscosity of 300 5.8.U. at 100 F. and a v.1.

In order to show that the salt of a dibasic acid and the soap of an aliphatic carboxylic acid does not form the same type of thickener as the saponified mixture of an aliphatic carboxylic acid and diester or alcohol-dicarboxylic acid mixtures, the following experiment was made.

EXAMPLE IX A grease was prepared by heating 10 wt. percent stearic acid, 4.8 wt. percent sebacic acid, 3.6 wt. percent LiQH.H- O (suificient LiOH.H O to neutralize both acids) and mineral oil, to 300 F. This grease had a dropping point of 360 F. and contained most, if not all, of the lithium sebacate as coarse visible particles. Attempts to disperse or redisperse the salt of the dicarboxylic acid, once it had separated into the grainy state, have been unsuccessful, even when the grease was heated to 500 F. Since the dropping point of lithium stearate grease is about 370 F., it is apparent that little or no lithium sebacate has been codispersed with the soap.

EXAMPLE X A grease of the invention was prepared by mixing 10 grams of stearic acid and 10 grams of di-2-ethyl hexyl sebacate (equivalent to 4.8 grams of sebacic acid) with 80 grams of a mineral lubricating oil having a viscosity at 100 F. of 300 S.U.S. and V1. of 70. 3.6 grams of LiOHH O were added and the mixture was then heated to a temperature of'about 400 F., and maintained at this temperature for about 15 minutes. The 2-ethylhexanol which formed during the reaction was driven cit almost as rapidly as it'formed. The grease was then cooled and inspected.

EXAMPLES XI TO XV Additional greases of the invention were prepared in the manner described in Example X using the ingredients as noted in Table HI. The compositions of the greases of Examples X through XV, and their characteristics, are also shown in Table HI.

EXAMPLE XVI A grease of the invention was prepared by mixing 13.7 parts by weight of stearic acid and 19.4 parts of diethyl adipate (equivalent to 14.0 parts of adipic acid) with 58.2 parts of Diol 50 at a temperature of 200 F. in a Manton-Gaulin homogenizer. The mixture was circulated through the homogenizer and a water slurry containing 8.7 parts of calcium hydroxide was added. The resultant mixture was then circulated for 6 hours at temperature of 200 F. and a pressure of 2,000 lbs. Thereafter, the grease was removed and transferred to a grease kettle where it was dehydrated at a temperature of 400 F. The grease was, then cooled and inspected.

Table III Example Number IX X XI XII XIII XIV XV XVI Composition in grams:

Btearic Acid 10. 10.0 10.0 10.0 10.0 10.0 10.0 13. 7

Sebaeic Acid..." 4. 8

Di-2-ethyl hexyl sebacate 10.0 10.0 10.0 10.0

Di-2-ethyl hexyl adipatel0. 0 10.0

Diethyl adipate 19 4 LiOH.HaO 3. 6 3. 6 3. 9 4. 0 4.0 4.0

a(0 s 8, 7 Mineral Oil (Viscosity at 100 F.

300 SUS; V.I. 70) 80.0 80.0 51.0 80.0 20.0

Di-2-ethyl hexyl adipate (as oil). 60. 0

Dow Corning Silicone Fluid 500 76. 0

Diol 50 58. 2 Inspections:

ASTM penetration, 77 F 320 250 220 270 AS'IM wkd. penetration, 77 F" 350 265 265 310 340 300 250 273 ASTM Dropping Point, F 360 500 500 485 479 500+ 640+ 450+ pp arance (0 0) (0 0) (0 (0 1 Ucon LB-1800X is a water-insoluble poiyalkylene glycol type of lubricating fluid which is predominantly polypropylene glycol, and has a viscosity at 100 F.

of 1800 SU 1 Dow Corning Silicone Fluid 550 is a phenyl methyl polysiloxane having a flash point oi As seen from Table III, the greases of the invention (X through XVI) had very high dropping points of from above 450 F. to above 540 F. and formed homogeneous products. However, the grease formed by the neutralization of the stearic acid and sebacic acid (IX) had a dropping point of only 360 F. and contained many undispersed particles.

Various other additives may be added to the grease composition of the invention, such as oxidation inhibitors, dyes, metal deactivators, corrosion inhibitors, deodorants, and so forth, as understood by those skilled in the art.

What is claimed is:

1. A process for preparing a lubricating grease composition comprising a major proportion of a lubricating oil and about to 40 wt. percent of an alkali metal salt of a dicarboxylic acid which comprises heating a mixture of an alkali metal base, lubricating oil, an aliphatic dicarboxylic acid containing from 2 to 22 carbon atoms per molecule and a monohydric aliphatic alcohol having from 1 to 22 carbon atoms per molecule, said heating taking place at a temperature in the range of 300 to 500 F. for a time sufficiently to form said metal salt and to evaporate said alcohol.

2. A process according to claim 1 wherein said lubricating grease composition comprises about 60 to 95 wt. percent of said lubricating oil and about 40 to 5 wt. percent of said thickener.

3. A process for preparing a lubricating grease composition having to wt. percent of a lubricating oil and 40 to 5 wt. percent of an alkali metal salt of a dicarboxylic acid which comprises heating to a temperature in the range of 300 to 500 F. for a time in the range of S to minutes, a mixture of (1) an alkali metal base, (2) a lubricating oil, and (3) a mixture of a C to C aliphatic dicarboxylic acid and a C to C monohydric aliphatic alcohol, said heating being sufiicient to form said metal salt and to remove substantially all of said alcohol.

4. A process according to claim 3 wherein said alkali metal base is used in an aqueous solution.

5. A process according to claim 3 wherein said metal base is taken from the group consisting of lithium hydroxide and sodium hydroxide.

References Cited in the file of this patent UNITED STATES PATENTS 2,363,514 Farrington et a1. Nov. 28, 1944 2,528,373 Knowles et al. Oct. 31, 1950 2,583,607 Sirianni et a1 Jan. 29, 1952 2,699,428 Lux et al Jamil, 1955 2,710,838 Morway et al. June 14, 1955 2,801,220 Smith July 30, 1957

Claims (1)

1. A PROCESS FOR PREPARING A LUBRICATING GREASE COMPOSITION COMPRISING A MAJOR PROPORTION OF A LUBRICATING OIL AND ABOUT 5 TO 40 WT. PERCENT OF AN ALKALI METAL SALT OF A DICARBOXYLIC ACID WHICH COMPRISES HEATING A MIXTURE OF AN ALKALI METAL BASE, LUBRICATING OIL, AN ALIPHATIC DICARBOXYLIC ACID CONTAINING FROM 2 TO 22 CARBON ATOMS PER MOLECULE AND A MONOHYDRIC ALIPHATIC ALCOHOL HAVING FROM 1 TO 22 CARBON ATOMS PER MOLECULE, SAID HEATING TAKING PLACE AT A TEMPERATURE IN THE RANGE OF 300* TO 500* F. FOR A TIME SUFFICIENTLY TO FORM SAID METAL SALT AND TO EVAPORATE SAID ALCOHOL.