US2506906A - Stabilized lubricating grease compositions - Google Patents

Description

Patented May 9, 1950 A FUNITED; .srArEs 506,906 STABILIZED LUBRICA'HNG GREASE COMPOSITIONS Herschel a. Smith, Walllngford, and Troy L. Can- Lanadowne, Pa., assignors to Gull Oil Corporation, Pittsburgh, Pa., a corporation of Pennsylvania No Drawing. Application May 19, 1948, Serial No. 94,252

Claims. (01. 252-424) 1 This invention relates to stabilized lubricatin grease compositions, and more particularly to grease compositions having increased stability against oil separation and structural breakdown at high and low temperatures, and improved resistance; to oxidation.

This application is a continuation-in-part of our prior copending application Serial No. 44,578, filed August 16, 1948.

In general, when greases are employed under operating conditions for extended periods of time, they have a tendency to become oxidized, resulting in the formation of gummy substances which prevent satisfactory lubricating action. When this occurs, it necessitates complete change of the lubricating grease which has become fouled due to oxidative deterioration. Accordingly, it is highly desirable to increase the resistance oi greases to such deterioration.

Another serious problem encountered in the use of grease compositions is that of bleeding. The tendency of a mineral lubricating oil base to separate or bleed from a grease composition in which the oil has been compounded is well known in the art. Excessive bleeding will tend to result in a complete breakdown of the grease involved, to the detriment of any mechanism lubricated thereby.

Still another serious problem is encountered when greases are employed at either relatively high or relatively low temperatures, which tend to promote structural breakdown of grease compositions.

Accordingly, it is an object of this invention to provide improved lubricating grease compositions characterized by their resistance to oxidation.

A further object of this invention is the provision of improved lubricating grease compositions having increased stability against oil separation and structural breakdown at relatively high and low temperatures.

These and other objects are accomplished by the present invention wherein we provide improved grease comoositions comprising a mineral lubricating oil thickened to the consistency of a grease by a soap, and relatively small stabilizing amounts of substantially neutral condensation products of formaldehyde and higher fatty mono-carboxylic acid esters of a mono-alkylated phenol, the higher fatty 'acid being a saturated or mono-oleflnic fatty acid having at least 8 carbon atoms, and the alkyl substituent o mono-alkylated phenol having from 4 to 12 carbon atoms.

Such Eesters, which are added to grease compositions in accordance with our invention, are

described and claimed in our copendin applica= tion hereinabove identified. As showntherein. the condensation products are prepared by first esterifying a mono-alkylated phenol with a higher fatty mono carboxylic saturated or mono-oleflnic acid containing at least 8 carbon atoms. In general, the esteriflcation reaction is conducted at a temperature not in excess of 220 F., employing conventional esterification catalysts and techniques. The esterified monoalkylated phenol is then condensed with formaldehyde at a'moderately elevated temperature of about 210 F., the mol ratio of alkylated phenol ester to formaldehyde varying from 1:1 to 1:2.

As stated, the alkyl substituent of the monoalkylated phenols employed in preparing the addition agents for use in accordance with our invention have from 4 to 12 carbon atoms. It is preferred to prepare these alkylated phenols by alkylation of phenol with an olefin having from 4 to 12 carbon atoms in the presence of a concentrated sulfuric acid catalyst. Thus, representative olefins or olefin-containing materials which are employed for the alkylation of phenol are butene-l, isobutylene, the amylenes, refinery gas, diisobutylene and triisobutylene. The use of diisobutylene is preferred since the alkylated phenol obtained is primarily para-(alpha, alpha, gamma, gamma) tetramethylbutyl phenol, which is particularly useful in preparing grease additives. However, the n-alkyl phenols having 4 to 12 carbon atoms in the alkyl substituent, preparing by alkylating phenol with an n-alkyl halide in the presence of a Friedel-Crafts catalyst, such as aluminum chloride, can also be employed. Accordingly, any mono-alkylated phenol having from 4 to 12 carbon atoms in the alkyl substituent is useful. Among these alkylated phenols are n-butyl phenol, sec-butyl phenol, tert-butyl phenol, n-amyl phenol, sec-amyl phenol, tert-amyl phenol, n-hexyl phenol, noctyl phenol, (alpha, alpha, gamma, gamma) tetramethylbutyl phenol, triisobutyl phenol, and mixtures thereof.

' The use of alkylated phenols having an alkyl substituent of less than 4 carbon atoms is not satisfactory because the resulting esterified condensation products prepared from such phenols are not sufficiently soluble in mineral lubricating oils and mineral oil lubricant compositions to serve the functions of an efficient additive. Sim larly, if the alkyl substituent of the alkylated phenol exceeds 12 carbon atoms, the resulting esterified condensation products tend to be unstable and to become insoluble in mineral oils.

As statedabove, suitable fatty mono-carboxylic acids which are esterified with the alkylated phenol before condensation with formaldehyde are the saturated and the mono-olefinic fatty acids having at least 8 carbon atoms. A preferred group of fatty acids are the fatty acids of from 8 to 32 carbon atoms. The saturated fatty acids include caprylic, pelargonic, capric, undecylic, lauric, myristic, palmitic, stearic,

arachidic, behenic, carnaubic, cerotic, melissic and psyllaic acids. The mono-oleflnic fatty acids include nonylenic, decylenlc, undecylenic, oleic, ricinoleic, erucic and brassidic acids. Mixtures of fatty acids having at least 8 carbon atoms, as obtained from the saponiflcation of fats and fatty oils for example, may also be employed. Naphthenic acids and Hydrofol acids (hydrogenated fish oil fatty acids) are also suitable saturated fatty acids. The fatty acids are generally employed in substantially equimolar amounts with the mono-alkylated phenols. Conventional esteriflcation catalysts, such as sulfuric acid and p-toluene sulfonic acid, can be employed for the esterification.

when the fatty acid has less than 8 carbon atoms, the condensation products of formaldehyde and the fatty acid esters of the monoalkylated phenols tend to become hard and brittle and of poor solubility in mineral oils. These effects increase as the length of the fatty acid chain decreases. Accordingly. the fatty acid must have at least 8 carbon atoms.

In the condensation of the esterified monoalkylated phenol with formaldehyde to yie1d the additives of this invention, the condensation takes place at a mildly elevated temperature of about 210 F. by refluxing the reactants until all of the formaldehyde is consumed. Either acid or alkaline condensing agents may be employed. The condensation product of the monoalkylated phenol ester and formaldehyde is then dehydrated in the usual manner.

The following example illustrates the preparation of the additives which are employed in accordance with our invention.

Example I Into a suitable reaction vessel equipped with a stirrer and means for heating and cooling, there were charged 112 pounds (1 pound mol) of octylene (commercial diisobutylene) and 94 pounds (1 pound mol) of phenol. Agitation was begun and 10 pounds of 96% sulfuric acid were gradually added. The temperature of the reac tion was so controlled that it did not exceed 220 1". The resulting product was primarily para- (alpha, alpha, gamma, gamma) tetramethylbutyl phenol.

One pound mol of the octyl phenol prepared as described hereinabove and still containing the sulfuric acid catalyst, and 1 pound mol of lauric acid were charged into a suitable closed reaction vessel equipped with a stirrer, a reflux condenser and means for heating and cooling. Agitation was begun and the charge heated while controlling the temperature so that it did not exceed 220 1''. Upon completion of the esterification reaction, 1 pound mol of formaldehyde (in a 37% by weight aqueous solution) was added and the 4 for two hours. The charge was then transferred to an open reaction vessel and the temperature increased to 500 F. to complete the reaction and dehydrate the product. The resulting dehydrated product had the following properties:

Penetration, ASTM D5-25:

77 F., 100 grams, 5 sec Penetration, ASTM D217-44T:

77 F., 150 grams, 5 sec., unworked 43 Neutralization No. 12.2

We have found that the above described condensation products may be compounded with a wide variety of greases to impart advantageous properties thereto. Such greases may be described as mineral lubricating oils thickened to the consistency of a grease by suitable soaps. These greases themselves are well known in the art and may be manufactured by conventional methods. For example, the mineral lubricating oil bases include parafl'inic, naphthenic and mixed base mineral lubricating oils, representative examples of which are shown in the following table. As known in the art, the soaps used in thickening the mineral oil base to a grease are fatty acid soaps derived from fatty materials such as tallow, lard, cottonseed oil, stearic acid, soy bean fatty acids and various other fats and fatty acids. The metal of the soap can be an alkali metal, an alkaline earth metal, and various other metals such as lead, zinc, chromium, tin, aluminum, iron, cobalt, nickel, cadmium, mercury, etc.

As will be understood by those skilled in the art.

the soap and mineral oil base will be selected in accordance with the specific properties of the grease it is desired to manufacture.

In accordance with our invention, small proportions of the herein-described condensation products in a grease will substantially stabilize the grease against bleeding and structural breakdown at high and low temperatures, and will improve the resistance of the grease to oxidation. The amount of condensation product used is sufllcient to retard separation of oil from the grease or inhibit oxidation of the grease, the same amount of condensation product conferring both effects, and in general, small amounts, from 0.1 to 5 per cent by weight on the grease, will suifice. The condensation product may be dispersed in an already formed grease by simple mixing, or it may be introduced during the manufacture of the grease, for example by dissolving it in the mineral lubricating oil base used in the manufacture of the grease.

As has been stated, the grease compositions of the present invention may be compounded from a variety of lubricating oil base stocks. The table below is illustrative of mineral lubricating oils which may advantageously be used as a base for the greases referred to; it sets forth the inmixture refluxed at a temperature of 205-210 F. spection data of such oils.

Table Base on Stock. s00 /2 200 MC 500 1000 5 Inspection Nmmd 'lzir as P32- i il Tex/Z Tags on on on on on Gravity, arr... 20.2 22.9 21.0 25.4 21.4 21.5 Viscosity SUV:

100- i- 210 304 102. 2 2,001 510 1,000 40.4 41.0 38.8 03.0 21 10 02 91 an 415 305 505 335 415 415 405 410 050 440 as our -r +15 -15 +10 +5 l0 +s 2.0 4.15 1.15 4.10 an 4.10 Carbon Residue Per Cent.. 0.02 0.00 0. 01 1.10 0.00 0.21 so rio.. 0.02 0.02 0.00 0.05 aoa 0.00

Example II Into a closed pressu yp steam heated kettle, equipped with double motion stirring paddles, were charged 15.65 parts by weight of Hydrofol acids, 1.2 parts by weight of a condensation prodnot prepared in accordance with Example I, 2.05 parts by weight of hydrated lime in a slurry of 4 parts water, and 17 parts by weight of mineral lubricating oils having the following character-- lstics and blended in the following proportions:

Parts Texas 011 (500 SUV/100 F.) 74.5 Mid-Continent Bright Stock (150 SUV/210 F.) 6.5

The kettle was closed. saturated steam applied to the heating jacket and the stirring mechanism started. After two hours an internal temperature of 290 F. and a pressure of 39 p. s. i. were attained. The supply of steam to the steam heating jacket was then cut oil and the internal pressure of the kettle was reduced to atmospheric pressure by bleeding steam therefrom for a period of /4 hour. Thereafter, the kettle was opened to the atmosphere and the temperature of the contents was gradually raised to 240 F. over a /z hour period and further gradually raised to 275 F. over another /2 hour period while adding 13 parts by weight of the blended oil. Steam to the heating jacket was again cut oil and 0.94

part by weight of stearic acid was introduced to 3 the mixture. Following this, 51 parts by weight of the blended oil were added over a period of V hour while cooling to 250 F. at which time p 0.025 part by weight of water was added. The contents of the kettle were then cooled to 175 F. in the course of hour. Hydrated lime in the amount of 0.21 part by weight was then sprinkled slowly into the kettle over A hour period. The 0.015 part by weight of water was added and the kettle closed and stirred under 20 inches of vacuum for 2 hours while maintaining an internal temperature of 175 F. to 180 F. Grease was then drawn out of the kettle through a 60 mesh screen.

The grease thus prepared had the following make-up and properties as compared to an otherwise identical grease not containing the condensation product.

Unim- Improved proved ruse Grease Make-up, percent by Wt.:

500/25 Texas Oil (500 SUV/100 F.) 75.6 74.5 150 MC Bright Stock (150 SUV/210 F.) 6. 6 6. 5 Calcium Soap 01' Hydroiol Acids- 16. 7 16.7 Calcium Soap oi Stcaric Acid 1.0 1.0 Excess Alkali calculated as Ca (0H),. 0. 1 0. l Ester of Example 1 1.2 Water by Distillation trace trace Inspection:

Dropping Point, F.

AS'IM D560-42 267 268 Flow Point, F.

Navy Dept. Spec. l4-G-ld 274 272 Penetration. AS'IM D21744T 77 F., 1m (3., 5 See:

Unworked 164 166 Worked 270 270 Free Alkalinity as CaO, percent trace trace Oil Separation, 175 F., 7 days, percent- AAR M-914-42 8. 0 nil Freezing Point, F.

AAR M-914-42 Oxidation Test, 176 F., Hrs 18 500+ Pressure Drop, Lbs 20 3 1g lb./sq. in. pressure, and then allowing the oxygen This composition was found to be extremely stable against oil separation or structural breakdown at temperatures up to approximately 200' I". As shown, the grease is further characterized by its high resistance to oxidation.

Further grease compositions compounded in a manner similar to that set forth in Example II and embodying the type of esters prepared as in Example I are illustrated by the following examples:

Example III Unim- Improved proved Grease Grease Make-up, percent by Wt:

500/25 Texas Oil (500 SUV/ F.).- 75. 7 74. 4 MC Bright Stock (150 SUV/210 F.) o. a I as Calcium Soap oi Hydrotol Acids 13. 2 l3. 2 Sodium Soap oi Hydroioi Acids. l. 8 1J Calcium Soap oi Oieic Acid 2. 7 2. 7 Ester of Example I using Oloic Acid instead of Lauric Acid 1. 4 Inspection:

Dropping Point, F.

AS'IM D566-42. 225 22! Flow Point, F.

Navy Dept. Spec. 14-Gld 254 256. Penetration, AS'IM D21744T- 77 F., 150 (3., 5 Sec;

Unworked. 168 168 Workcd 289 289 Free Acidity as Oleic Acid, percent 1.0 0. 0 Oil Separation, F., peroent- AAR M9l4-42 15. 0 nil Freezing Point, F.--

AAR M-914-42 50 Mineral Oil Content: percent by Wt 82. 3 80. 9 Oxidation Test, 176 Hrs 70 500+ Pressure Drop, Lbs 20 8 Example IV Unim- Improved proved- Grease Grease Make-up, percent by Wt:

500/25 Texas Oil (500 SUV/100 F.) 76. 3 74. 9 15%MO Bright Stock (150 SUV/2m 6 6 6 6 Calcium Soap of Stearic Acid" 14.3 14.3 Sodium Soap of Oleic Acid 1.9 l. 0 Calcium Soap of Oieic Acid 0. 9 0. 9 Excess Alkali calculated as CA(OH)1 trace 0. 03

Ester of Example I using Naphthenic Acids instead of Lauric Acid Q l. 5 Inspection:

Dropping Point, F.- ASTM 13566-42 232 234 Penetration, ASTM D217-44T- 7 F., 150 G., 5 Sec.:

219 217 or o 320 315 Free Acidity as Oleic Acid, percent--- 0. 01 0. 02 Mineral Oil Content percent by Wt 82. 9 g 81. 4 Oxidation Test, 176 F., Hrs 50 500+ Pressure Drop, Lbs 20 2 grams of the grease to be tested equally into five stainless steel sample trays, and placing the trays into a pressure bomb equipped with a valve and pressure gauge and adjusted to a volume of 173 cc.:2 cc. The bomb is then closed and flushed five times by filling it with oxygen to about 100 to escape. The bomb is then filled with oxygen to 105 lb./sq. in. pressure and immersed in an oil bath held at 176 F.:0.5 F. After two hours, oxygen is released from the bomb so as to adjust the pressure to exactly 110 lb./sq. in. The pressure is read and recorded every two hours until the pressure drops 20 lb./sq. in., or for 500 hours if the pressure does not drop as much as 20 lb./sq. in. in that length of time. The oxidation stability of the grease is reported as the number of hours required for the pressure in the bomb to drop 20 lbs., unless this does not occur in 500 hours. In the latter event, the result is reported as 500+.

The grease compositions of our invention may include additional modifying agents, as will be apparent to those skilled in the art, provided they contain the condensation products disclosed herein. Resort may be had to such modifications and variations as fallwithin the spirit of the invention and the scope of the appended claims.

' We claim:

1. A grease composition comprising a mineral lubricating oil thickened to a grease by a soap, and a small amount of a substantially neutral condensation product oi formaldehyde and a higher fatty mono-carboxylic acid ester of a mono-alkylated phenol, the higher fatty acid being selected from the class consisting of saturated and mono-oleilnic fatty acids having at least 8 carbon atoms and the alkyl substituent of the alkylated phenol having from 4 to 12 carbon atoms, said condensation product being present in an amount sufficient to retard oxidation of the grease.

2. The composition of claim 1, wherein the higher fatty acid is a saturated fatty acid.

3. The composition of claim 1, wherein the higher fatty acid is a mono-oleflnic fatty acid.

4. A grease composition comprising a mineral lubricating oil thickened to a grease by a soap, and a small amount of a substantially neutral condensation product of formaldehyde and a higher fatty mono-carboxylic acid ester of a mono-alkylated phenol, the higher fatty acid being selected from the class consisting of saturated and morio-oleflnic fatty acids having from 8 to 32 carbon atoms and the alkyl substituent of the alkylated pienol having from 4 to 12 carbon atoms; the molar ratio of alkylated phenol ester to formaldehyde in the condensation product varying from 1:1 to 1:2, said condensation product being present in an amount sufllcient to retard oxidation of the grease.

5. The composition of claim 4, wherein the said condensation product is present in an amount of from 0.1 to 5 per cent by weight on the grease.

6. A grease composition comprising a mineral lubricating oil thickened to a grease by a soap, and a small amount of a substantiall neutral condensation product of formaldehyde and a higher fatty mono-carboxylic acid ester of a mono-alkylated phenol, the higher fatty acid being selected from the class consisting of saturated and mono-oleflnic fatty acids having from 8 to 32 carbon atoms, and the alkylated phenol being (alpha, alpha, gamma, gamma) tetramethylbutyl phenol, said condensation product being present in an amount suflicient to retard oxidation of the grease.

7. A grease composition comprising a mineral lubricating oil thickened to a grease by a, soap, and a small amount of a substantially neutral condensation product of formaldehyde and the lauric acid ester of (alpha, alpha, gamma, gamma) tetramethylbutyl phenol, said condensation product being present in an amount sufficient to retard oxidation of the grease.

8. A grease composition comprising a mineral lubricating oil thickened to a grease by a soap, and a small amount of a substantially neutral condensation product of formaldehyde and the oleic acid ester of (alpha, alpha, gamma, gamma) tetramethylbutyl phenol, said condensation product being present in an amount suflicient to re- REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 4 Name 7 Date Roehner et al Nov. 8, 19

Number

Claims (1)

1. A GREASE COMPOSITION COMPRISING A MINERAL LUBRICATING OIL THICKENED TO A GREASE BY A SOAP, AND A SMALL AMOUNT OF A SUBSTANTIALLY NEUTRAL CONDENSATION PRODUCT OF FORMALDEHYDE AND A HIGHER FATTY MONO-CARBOXYLIC ACID ESTER OF A MONO-ALKYLATED PHENOL, THE HIGHER FATTY ACID BEING SELECTED FROM THE CLASS CONSISTING OF SATURATED AND MONO-OLEFINIC ACIDS HAVING AT LEAST 8 CARBON ATOMS AND THE ALKYL SUBSTITUENT OF THE ALKYLATED PHENOL HAVING FROM 4 TO 12 CARBON ATOMS, SAID CONDENSATION PRODUCT BEING PRESENT IN AN AMOUNT SUFFICIENT TO RETARD OXIDATION OF THE GREASE.