US2528373A

US2528373A - Alkenyl succinic acid grease

Info

Publication number: US2528373A
Application number: US72094A
Authority: US
Inventors: Edwin C Knowles; George W Eckert; Oney P Puryear
Original assignee: Texaco Inc
Current assignee: Texaco Inc
Priority date: 1949-01-21
Filing date: 1949-01-21
Publication date: 1950-10-31
Anticipated expiration: 1967-10-31

Description

. Patented Oct. 31, 1950 UNITED sures PATENT. OFFICE;

l latza,srs'" Edwin C. Knowles and George W. Eokrrt, Glenham, and Oney P. Puryear, Fishkill, N. Y., llsignors to The Texas Company, New York, N. Y., a corporation of Delaware 1 No Drawing. Application January Serial No. 72,094 v 1 1'! Claims.

This invention relates to a lubricating grease and particularly to a gel-like lubricant prepared from a soap of an alkyl or an alkenyl substituted aliphatic dicarboxylic acid.

One of the principal objects of the invention is to provide a gel-like lubricating grease utilizing as part or all of the soap component a soap of an aliphatic dicarboxylic acid having a long allgyl or alkenyl side chain substituted for a hydrogen atom on one of the carbon atoms oi the dicarboxylic acid chain.

Another object of the invention is to provide a dicarboxylic acid soap grease of this character having advantageously modified properties by the use of a mixture of the dicarboxylic acid with a soap-forming monocarboxylic acid for the saponiiication step.

Other objects and advantages of the invention will be apparent from the following description and the accompanying claims.

The use of a metal salt of an alkyl or alkenyl substituted aliphatic dicarboxylic acid as an additive in small proportions in a liquid lubricating oil, such as a motor oil, in order to improve the'ring sticking and lacquer forming tendencies oi the motor oil has been heretofore proposed. The present invention is distinguished by the use of particular metal soaps of the said dicarboxylic acids in sufficiently large proportion, and by a particular method of preparation involving high temperature heating to reach a gelation stage, to produce as a final product a gel-like lubricating grease; and also by the use of a mixture of the said dicarboxylic acid with a soap-forming monocarboxylic acid for the saponiflcation step.

In accordance with the present invention, a suitable alkyl or alkenyl substituted aliphatic dicarboxylic acid having the carboxyl groups in a plane symmetrical configuration (on the same side of the carbon chain) and wherein the alkyl or alkenyl substituent group contains at least 8 carbon atoms and up to 25 carbon atoms or more to provide an oil solubilizing hydrocarbon group. is selected as part or all of the soap-forming acid; Examples of suitable acids for purposes of the present invention are the alkyl and alkenyl substituted fumaric, succinic, maleic, citraconic glutaric and adipic acids. The alkyl or alkenyi substituent group, which generally contains about 8-16 carbon atoms and preferably 10 to 12 carbon atoms, is substituted for a hydrogen atom attached to one of the carbon atoms of the dicarboxylic acid chain. This is accomplished in known manner such as condensing an anhydride 0! the dicarboxyiic acid with a high molecular weight olefin of the carbon atom content desired in theside chain. such as a propylene or butylene polymer or a selected fraction of polymer gasoline of the desired boiling range. The presence of the alkyl or alkenyl side chain of the stated carbon atomcontent on the dicarboxylic acid appears essential since experiments with high molecular weight dicarboxylic acids containing a similar number of carbon atoms in the acid chain but without an alkyl or' alkenyl substituent group as specified, such as sebacic acid and dimerized linoleic acid. proved unsuitable in forming soaps compatible with the mineral lubricating oil or other liquid oleaginous lubricating base, and they exhibited no gelation effect when heated in the oil in substantial proportions at temperatures up to 580 F.

As representative of the dicarboxylic acids empioyed in accordance with the present invention and constituting the preferred acid from 'the standpoints of economic availability and improved results. the following description is directed to the use of a. so-called alkenyl succinic acid. However, it should be understood that the invention is not restricted to this particular dicarboxylic acid since the other alkyl or alkenyl substituted aliphatic dicarboxylic acids mentioned can be employed in similar manner. The alkenyl succinic acid is obtained by condensing an olefin of the desired molecular weight with maleic acid anhydride to obtain the alkenyl succinic acid anhydride, and this may be followed by hydrolysis to produce the aikenyl succinic acid. The product produced in this manner may actually exist as an alkenyl succinic acid or an alkyl maleic acid (depending on whether the double bond remains in the hydrocarbon side chain or in the dicarboxylic acid chain). or a mixture thereof. In order to simplify the description of these condensation products and the acids produced thereby, reference will be made throughout the specification and claims to an alkenyl succlnic acid or anhydride; but it is to be understood that this includes the alkyl maleic acid as well as the alkenyl succinic acid or mixtures thereof, or the corresponding anhydrides, as may be produced by this condensation reaction of an olefin with malelc acid anhydride with or without subsequent hydrolysis. It is not necessary to convert the anhydride to the corresponding dicarboxylic acid before forming the soap since the anhydride will also saponify with the metal oxide or hydroxide in the presence of the water used in the saponiflcatlon step to form the soap.

By way of example. a Clo-C12 alkenyl succinio acid anhydride was prepared by the condensation or maieic acid anhydride and a Clo-Cm fraction of propylene polymer by heating with agitation for hours at a temperature of about 350- 390 F. under gentle reflux. The reaction product was then allowed to cool and fractionated under diminished pressure to remove unreacted polymer and low boiling reaction products. The resulting alkenyl succinic acid anhydride was employed directly to produce certain of the soaps hereinafter described. On the other hand, the alkenyl succinic acid anhydride can be heated at about 200 F. in the presence of an equal vol-- ume or water to aifect hydrolysis to the alkenyl succinic acid and until the excess water has evaporated. Products containing a Cs-Cm alkyl side chain and a Cit-Cid alkyl side chain were prepared in a similar manner except that a different fraction of the propylene polymer of the specified carbon atom content was employed in each case.

Metal soaps of the resulting alkenyl succinic acid anhydride or the alkenyl succinic acid were then prepared by heating the former with a metal oxide or hydroxide in the presence oi water and a portion or all or the mineral lubricating oil or other liquid oleaginous vehicle at a temperature of about rib-240 F. for a period of about 1-2 hours. Following this saponification period, the product was dehydrated by heating at a higher temperature up to about 300-320 F. for a further period of about -1 hour. The resulting dehydrated saponii'led product then had to be heated to a still higher temperature, with any further oil addition to obtain the desired consistency and with continual stirring, to reach a gelation temperature inexcess of 450 F. and generally about 500 F., this additional heating and stirring usually requiring about l-2 hours. The product was then allowed to cool to room temperature. Products were prepared containing 20% soap each of the following metal soaps of the Clo-C12 alkenyl succinic acid in a naphthene base lubricating oil having a S. U. S. viscosity at 100 F. of 307 with the results shown in Table I below.

Table I Type of Metal soap Characteristic of Product Sodium Soap insoluble-separate oil and soap phases. Potassium Do. Lithium Do. Calcium. Liquid-not uniform. Barium---.

Soap) inso1uble-separate oil and soap phases.

Strontium. Magnesium- Dry amber gel-like rease. Beryllium. Rubbery elastic dar amber gel grease. Lead Soap insoluble-separate oil and soap phases. Tin (staunous) Do. Zine Do. Titanium (ous).. Do. Titanium (ic)-.-- No reaction to form soap. Aiuminum-- Transparent tacky amber gel grease.

' 10% soap.

in 20% concentration formed a liquid non-uniform product; while the titanic oxide did not react with the alkenyl succinlc acid anhydride.

The type and viscosity of the mineral lubricating oil employed in the grease also affects its properties. This is illustrated in the followin Table II which sets forth the characteristics of magnesium Clo-Cu alkenyl succinlc acid (referred to as ABA) greases prepared from dif ferent types of paraflln base and naphthene base lubricating oils and mixtures thereof.

Table II Luau Lubflmun B Pics ,1 Character iisgc of Prod- Paraflln base lubrlcat oil in Gel-like.

SUB Vls. at F. 0H0 see. P n bass lubrimtlng oil 20 Do.

SAE 10 motor oil Vls at 100" F of 108.

:1 base lubricating oil a) Do. SAE 2) motor oil Via at100 F. 0(830. it, m ti fmii' stii 'E""lfin2 mo 0 an ge Vls. at 100" F. of p Resid n bass lubrlcata) Viscous liquid-no gellng ollmematie lie. at 210 ation. F. oi cs. Na hthene base lubricating oil 15 Hard; gel-like.

B 8 Via. at 02$; set i 3 so I 11 base u as o 2 ii t stringy ge BUB Vis. at 100 F. of 00 sec. P n base lubricating oil 15 Soft sandy gel.

SAE 2) motor oil e. Mixture of 2.9% nap thene base 10 Tacky translucent gel.

oil of BUS oi 307 with 07.1 n of parafin base oil oi SA 5!) grade.

As shown in the foregoing table. the lighter and medium grades of paraflin base and naphthene base lubricating oils of the distillate type all provide excellent grease structure. However, the distillate lubricating oils of heavier grade generally having an SUS viscosity at 100 F. in excess of about 800 and the residual lubricating oils result in products which are either viscous liquids or are too soft with non-homogeneous texture. Moreover, the naphthene base lubricating oils of comparable viscosity require less soap content than the paraflln base lubricating oils to produce greases of the same consistency or penetration. The grease listed in the last item of the table was prepared by saponifying the acid in the presence of the naphthene base oil, and following dehydration the paraflln base oil was added to bring the product to the desired consistency and soap content. In general, the soap content varies from somewhat in excess of 5% to less than 50% on the weight of the grease composition, depending on the type of lubricating oil as well as the type of soap employed, to produce gel-like greases meeting the specifications for the various grades of grease.

In addition to th distillate mineral lubricating oils mentioned, the various types of synthetic liquid oleaginous lubricating bases having comparable viscosities can also be employed as part or all of the lubricating base with these particular soaps. Among the types of synthetic liquid oleaginous lubricating bases which can be employed are the oil soluble high boiling high molecular weight aliphatic ethers, aromatic esters, aliphatic monoand dicarboxylic esters. phosphorus acid esters and halogenated aromatic compounds which possess lubricating properties and also have small change in viscosity for a given change in temperature. of the various synthetic oleaginous compounds specified, those tailing within the category of aliphatic disarasaaara bonlic acid esters, and particularly the branched chain aliphatic esters, such as di-2-ethylhexyl sebacate. are preferred. In the following description and claims. the expression "liquid oleaginous lubricating base is employed to designate both the mineral lubricating oils and the synthetic lubricating bases specified.

Typical properties oi the magnesium. beryllium, and aluminum base greases prepared as outlined above from alkenyl succinic acid or alkenyl succinic anhydride are set forth in the following Table III, wherein the acid component of the soap consisted of the Clo-C12 alkenyl succinic acid.

Table III PenetrigigiFAfl'lM Drop a Boa Per T ype of Oil pin Pt. r. Um

worked Worked M 0'7 Naphthene BUB at over 500 305 too soft 8 100 F. 01307. Mg 10" do over 500 220 32) Mg -.do over 500 133 273 Mg 154 Paraflin SAE over 500 252 341 Be 20'? Nsglnthene HUS at over 500 1 F. of 307. Be 8.3%. do 300 359 334 Al Il% over 500 Al 11.4% over 500 too soft 369 The foregoing table shows that the greases of the present invention have exceptional charactelistics including melting or dropping points above 500 F., even in the lighter grades employing the lower soap contents. Moreover, these greases are obtained with excellent yields which further makes this type of dicarboxylic acid grease attractive. It will be noted that the reases discussed above consisted of the dinerboxylic acid soap as the entire soap content. While these are satisfactory for certain uses, it is to be understood that the foregoing data has been listed primarily to illustrate the properties of the dicarboxylic acid soap grease. and that other types of soap will frequently be included, as well as various other additives, to improve the properties thereof for specialized uses. Thus the magnesium, beryllium and aluminum soaps oi the dlcarboxylic acids enumerated above can be employed in conjunction with the ordinary soaps in various proportions to produce mixed base, as well as mixed acid type, greases. Among the soaps which can be added to the greases of the present invention may be mentioned the sodium, calcium, barium, lithium, strontium, zinc and lead soaps of the ordinary saturated and unsaturated soap-forming fatty acids and fats including the hydrogenated fats and fatty acids, such as hydrogenated fish oil acids. Also, soaps of soap-forming hydroxy fatty acids and their glycerides, such as hydrogenated castor oil, naphthenic acids and sulionic acids can be employed. Ordinarily, to obtain the desirable properties of the dicarboxylic acid grease including extremely high melting or dropping point, the magnesium, beryllium, or aluminum soap of these dicarboxylic acids is employed in about an equal or major proportion with respect to the conventional soap used. except where the conventional soap also possesses similar properties.

As an example of a suitable mixed base grease of this character. which has been prepared with an extreme pressure additive to meet specialized service for ball bearing lubrication. the following is mentioned:

6 Table IV Composition oi grease: Per Cent By Weight Mg. CID-C12 ABA soap 10 Lead soap oi menhaden (fish oil) acids 10 The Timken test referred to above employs the well known Timken machin used for testing extreme pressure lubricants, except for replacement of the usual liquid lubricant reservoir, gravity flow line to feed the liquid over the test specimens, and the scavenging pump which removes the used lubricant from the sump and returns it to the reservoir, with a special air pressure grease feed system. The latter involves a grease reservoir cylinder fitted with a. piston and cap. Air pressure between 20 and 50 p. s. i. is applied to the top of the piston to force grease from the bottom of the reservoir to the test pieces. The new of grease is maintained between 0.1 and 0.2 pound per minute by a regulating valve in the feed line. The conditions of the test are the same as for liquid lubricants except that the grease is not heated. The weights indicated in the foregoing table are those which are applied to the lever arm which forces the test block against the hardened steel cup mounted on the end of the horizontal spindle rotated at 800 R. P. M. in conventional manner. This test is thus a measure of the load carrying capacity or the grease.

The Torque Breakdown Machine test is designed to evaluate the lubricating properties of greases used for the lubrication of anti-friction bearings. Two standard 3.9370 inch Timken tapered roller bearings packed with about 25 g. each of the grease under test, and a. standard Federal Precision Ball Bearing No. 1211 packed with about 32 g. of the grease are employed, the packed bearings being weighed before test. In the test of each bearing, the bearing is assembled on a motor driven shaft supported by pillow blocks within a bearing housing mounted within an insulated chamber with a system of levers connected to register any movement of the bearing housing in grams on a platform scale, whereby both the starting torque and the running torque can be measured. The insulated chamber is equipped with a copper coil tubing for the circulation of a cooling or heating medium, and also with an insulated cover equipped with an electric heater and a motor driven fan, whereby the temperature of the chamber and bearing under test can be accurately controlled. The test of the Timken bearings at F. is made at 900 R. P. M., and the test of the Federal bearing at 80 F. is made at 1750 R. P. M., each for a period of two hours. The instant the motor driving the test bearing is started, the first torque reading is recorded as the starting torque. Then running torque and temperature readings Oi the bearing are recorded at one minute intervals for the first 30 minutes, and at minute intervals for the remaining 1% hours, while the temperature within the chamber is adjusted to maintain the temperature within 2 of 80 F. At the end of the run, the bearing is removed from the housing and weighed, whereby the weight of the grease remaining on the bearing can be computed. The weight of the grease on the housing is also determined; and grease leakage (grease escaping from both the bearing and housing) is determined by actual weight measurement or by difference. A visual inspection is made of the grease remaining on the bearing to ascertain whether any structure or texture change has taken place; and the penetration of a sample of the grease taken from the bearing after test is compared with the original penetration of the grease. A second test procedure is conducted on the same machine in this manner, except that in this case the temperature of the chamber and of the bearing is raised gradually from an initial 80'' F. to a temperature of 250 F. at the end of an hour. The test is then run at 250 F. for an additional two hours before terminating the test. Similar readings are made, as previously described. The results thus obtained are compared with those secured in the same tests on a standard. premium ball and roller bearing grease of known excellent performance; and overall inbricating performance of the test grease is generally reported on the basis of this comparison as excellent, good, fair or poor.

The foregoing data showthat this mixed base grease containing the sulfurized sperm oil EP additive provided improved extreme pressure properties and afforded fair to excellent lubrication of ball and roller bearings under the rigorous conditions of the torque breakdown test. These results, in conjunction with the high dropping point and excellent yield of the magnesium ASA type product, are indicative of the advantageous results of the present invention.

In the preparation of the mixed base greases described above, the magnesium ASA soap and the lead menhadenate were separately formed and mixed in the lubricating oil by blending at high temperatures with agitation. Thus the magnesium ASA soap was formed by saponiflcation of the alkenyl succinic acid anhydride in 1 the customary manner, the product dehydrated, and then further heated with addition of oil to the gelation temperature of about 500 F. The lead menhadenate and sulfurized sperm oil were then added with stirring as the product cooled from about 500 to 440 F. It will be understood properties of the dicarboxylic acid soap greases can also be desirably modified, particularly from the standpoint of improving lubricating properties and storage stability, by saponifyin a mixture of the alkyl or alkenyl substituted aliphatic dicarboxylic acid with a soap-forming mono-carboxylic acid. Various types of soapforming saturated and unsaturated fatty acids, hydroxy fatty acids, sulfonic acids, naphthenic acids, acids from the oxidation of paraflin wax, etc., have been found effective for this purpose. In addition to desirably modifying the properties of the grease, the manufacturing procedure is also aided in some cases since the gelation tem-- perature has been found to be lowered. These mixed acid type greases are prepared utilizing a major proportion of the dicarboxylic acid with a minor proportion of the mono-carboxylic acid generally in a ratio of about 2:1, although ratios from above approximately 1:1 up to 9:1 have been employed with good results. Increasing the proportion of the mono-basic acid in the mixture utilized for saponification up to and over an equal proportio with the dicarboxylic acid, results in a very substantial lowering of the dropping point from that of the dicarboxylic acid grease itself, and consequently the desirable properties of the latter are not effectively retained.

The procedure for manufacture of these mixed acid greases is essentially the same as previously described for the dicarboxylic acid greases. Thus the mixture of the dicarboxylic acid with the selected mono-carboxylic acid in the desired proportions is saponiiled by heating with an oxide or hydroxide of magnesium, beryllium or aluminum in the presence of water and a portion of the mineral lubricating oil or other liquid oleasinous lubricating base. In place of the dicarboxyiic acid, the corresponding anhydride thereof can be employed. Saponlfication takes place at a temperature of about -220" F., the saponifled product is then heated to about 280-320" F. for dehydration. and the resulting dehydrated material is then further heated with the necessary oil addition and stirring to a geiation temperature of about 450-500 F., followed by cooling and drawing at a temperature of about 340l00 F.

As examples of these mixed acid greases, the following Table V sets forth the gelation temperature during manufacture and the properties of certain Mg base greases prepared from a 2:1 mixture by weight of Clo-Cr.- alkenyl succinic acid anhydride with the specified mono-basic acid, the soap content of the grease in each case being approximately 10% by weight.

Table V giriuli d to D I xgg i GLubricgtior; 0 emrop mg reasc [Ba Mono'Basc Add per iture, PL, F. down Test, Unworked Worked RT-m Hellenic Acid 460 449 201) 308 Good. Stearic Acid. 450 -1l0 218 207 Excellent. Myristic Acid 490 374 362 Soil, Do. Bnodotw Acids (hydrogenated fish oil acids). 460 iii 241 346 Do. l2-H ydroxystearic Acid 470 458 28! Fair. Suiionic Acid 500 349 270 332 Do. Naphthcnic Ac 495 420 170 205 Poor. Oleic Acid. 500 382 312 37G Fair. Wax Acids i. 490 350 366 Soft Excellent.

that other types of additives, such as oxidation inhibitors, dyes and the like, can also be added during the cooling and stirring stage and prior to drawing of the grease.

The foregoing Grease Breakdown Test is used to determine the lubricating properties of ball bearing greases at various temperatures. The machine employed consisting essentially of a stand- In accordance with the present invention, the 75 am motor-driven rotating ball bearing (20 mm.

bore x 4'7 mm. diameter x 14 mm. width) mounted vertically and enclosed in an oil Jacket containing an electric immersion coil with adjustable rheostat for temperature control. The upper face of the bearing is not covered, so that observations of performance during operation can be made. The bearing is charged with 5 grams of the grease. With the system at atmospheric temperature, rotation of the packed test bearing is started at 3450 R. P. M. and allowed to proceed for 3 minutes, during which time observations are taken of the general nature of the lubrication provided, 1. e., whether or not the grease folds over the bearing, channels, slings away from the bearing, tends to ball up," etc. Then heat is applied to the bearing as it continues to rotate at the same speed so as to gradually raise the temperature of the bearing until the grease fails to lubricate (the breakdown point) or until a temperature of 300 F. is reached in about 40 minutes from the start of the test. Beginning at a bearing temperature of 100 R, observations of performance are recorded for every 25 F. temperature rise or for any significant development such as texture change, expansion in volume, air entrainment, channeling, leakage, melting and consequent thinning, separation, discoloration, vaporization, etc. After completing the run, the bearing is removed and cooled; and grease remaining on the bearing is examined for texture and consistency change, discoloration, etc. and compared with the original grease. The results obtained are compared with those secured in the same test on a standard premium ball and roller bearing grease of known excellent performance; and the performance of the test grease is rated on a comparative basis as excellent, good, fair or poor.

From the foregoing table it will be noted that behenic acid, stearic acid, hydrogenated fish oil acids and IZ-hydroxystearic acid produced a substantial lowering of the gelation temperature, while at the same time maintaining the dropping point of the resultant grease above 400 F. The stearic. myristic, hydrogenated fish oil acids and the acids from the oxidation of paraffin wax provided greases of excellent lubricating properties as determined by the rigorous Grease Breakdown Test, with all the listed greases withstanding a temperature as high as 300 F. in this test. While monocarboxylic acids proved satisfactory in admixture with the dicarboxylic acids for preparation of these greases, the use of fats, such as tallow and hydrogenated castor oil, proved unsatisfactory in that liquid or viscous to unsuitably stiff grainy products were obtained.

The effect of varying the dicarboxylic acid to mono-carboxylic acid ratio in the preparation of these mixed acid greases is illustrated in the following Table VI for a magnesium Cid-Cu ASAzMg stearate grease prepared with a paraffin base lubricating oil of SAE 20 grade, the soap content being in each case.

In the foregoing table, it will be seen that an increase in the ratio oi the magnesium ASA to the magnesium stearate within the limits of 1:1 to 3:1 produced a substantial increase in dropping point of the grease, while the desirable lowering of the gelation temperature to 450 F. was maintained. The best lubricating qualities were obtained with the 2:1 ratio, as very strikingly shown by the Grease Breakdown Test. The presence of the mono-carboxylic acid in all cases improved the storage stability of the grease.

The efiect of total soap content in the 2:1 Mg Clo-Cu A8A:Mg stearate grease was found to be in line with the general behavior of soap/oil systerns as illustrated in the following Table VII.

Table VII Penetration, ASTM, 71 F.

Total Soap,

Drop Per Cent Egg Unworked Worked The effect of the alkyl side chain length of the ASA in the system, 10% soap of 2:1 Mg ASAzMg stearate/paraiiln base oil of BAE 20 grade, was investigated by using alkenyl succinic acid with alkyl side chains of Ca-Cm, Clo-C12 and Cir-Cu, respectively. The following results with respect to gelation temperature and properties of the resulting products were obtained.

Table VIII Required Tempera ture ior Gelation, F.

Drop, PenetraiglgAS'li/l,

Chain ping Point, F.

Length Appearance Unworked Worked Fluid. Uniform, gellike 011-"... 106 m0 GEiny, but- Table IX Penetration ABTM, Gelatlon 77 F. Tempera- Alkyl Group tum, F.

Drop ing Pt., F.

Unworked Worked over 500 over 500 over 600 The type and viscosity of mineral lubricating oil used has a similar effect in the mixed acid greases as described above in connection with the straight dicarboxylic acid greases. This is illustrated in the following Table X for the y tem 1 2:]. Mg. Cir-1: ASAzMg. stearate/oil.

areas-rs Table I M m Penetng onfi ASTM,

8 um T Drop ing ype Oil F. Pt" P Appearance Unworked Worked Poraiiin base oil BAE l0 450 300 170 202 Gel-like Poraflin base oil SAE 20 450 410 218 297 Do. Parafl'in base oil SAE 40 400 Viscous liquid. N aphthenc base oil HUS Via. at I00 F. 01300 455 428 174 245 Gel-like. Paraflin 1 base residuum BUS Via. at 210' I. ol100- 400 Gel-like fluid.

1 Soap.

The following details of preparation of a su- Table XI perlor type of ball and roller bearing grease Dropping i t 409 containing an oxidation inhibitor are set forth as 20 p t t s-nm 7 p I a preferred example of the present invention. Unwm-ked Five pounds of water, 24 pounds of a paraflin base worked 397 lubricating oil of SAE 20 grade. 1658 grams of Soap, Mg, (determmed) 1 5 Cio-Cn alkenyl succinic acid anhydride, a slurry of 518 grams of magnesium hydroxide in 10 pounds of water, and 881 grams of triple pressed stearic acid were charged to a grease kettle in the order listed, and heating and stirring was started. The temperature was raised to 200 F. in about 1 hour and then was maintained at about 200-219 F. with continued stirring and boiling for about 6 hours, at which time saponification was completed and the product had thickened. The temperature was then raised to about 300 F. with continued stirring in about 2 hours and maintained slightly above 300 F. for another hour, when the kettle was shut down overnight. The product at this time was a soft amber-colored liquid and dehydration was substantially complete. The next morning heating and stirring or the kettle were resumed with the temperature being rather rapidly raised to about 460 F. over a period of 2 /2 hours, and then being held at a gelation temperature of 450-476 F. while an additional 30 pounds or the parailln base oil were gradually added during a period of about 2 hours. The heat was then cut and the product slowly cooled down to 200 F. with continued stirring over about 4 hours, when the mix assumed a smooth glossy dark brown gel-like appearance. A sample removed for control purposes at this time had an unworked ASTM penetration at 78 F. of 309 and a worked penetration of 327. The product was allowed to continue to cool with stirring to about 90 F. when 30 pounds of the uninhibited grease were drawn. To the remaining batch of grease in the kettle a blend of 70 grams of diphenylamine in one pound of the paraflln base lubricating oil were added. Stirring of the mix was continued at about 90 F. for an hour, when the final inhibited grease was drawn as an amber gel-like tacky product, which became soft on slight rubbing. The calculated composition of this grease was:

Per cent by weight Mg. Clo-C12 ASA soap 6.4 Mg. Stearate soap 3.2 Parafiin base lubricating oil SAE grade 89.9 Diphenylamine 0.5

Tests on the inhibited grease prepared as outlined above were obtained as listed in the BP- pended Table XI.

Lubrication (torque breakdown and grease breakdown machine tests):

Small ball bearing, -300" F Excellent Large ball bearing, 80 F Excellent Large ball bearing, 80-250 F Excellent Roller bearing, 80' F Good Roller bearing, 80-250 F Fair Shear resistance, Dynamic shear, 8 hr.

Miniature penetration, original Miniature penetration, after test 86 Low temperature torque:

Minus 40 F., sec/rev 66 Minus 50 F., sec/rev 108 Water resistance test loss, per cent 20 Norma-Hoifmann oxidation:

Hours at 210 F Pressure drop, lb 5 Oil separation, 50 hr. 210 F.:

Separation, per cent 0.5

Evaporation, per cent 0.25

1 Basis of weight of total fatty acid.

The Dynamic Shear Resistance test of the foregoing table is a measure of the resistance of the grease to texture change when worked under high shearing stress, the test being carried out as described in U. 8. Patent No. 2,450,219, Ashburn and Puryear, in column 5, lines 6-19. A small change in miniature penetration of the sample after test in comparison with the original is indicative of excellent texture stability under high shearing stress. The miniature penetration test is described in Ind. Eng. Chem. analytical edition, vol. 11, page 108, February 15, 1939.

The Low Temperature Torque test of the loregoing table is essentially a measure of the resistance oi the grease to congealing and oi its ability to afford proper lubrication under extremely low temperature conditions, such as are encountered in aircraft at very high altitudes. The apparatus employed for the test consists essentially of a vertically mounted hollow spindle with a No. 204K Conrad type 8-ball bearing mounted on the bottom, and a drum on which is wrapped a coiled line for applying torque mounted on the top. The bearing packed with a 60% capacity charge of the grease to be tested is clamped at the inner race to the spindle, while the outer race is clamped immovably to a stationary cup within which the bearing is inserted. The assembly is inserted with the lower bearing end in a low temperature bath containing lsopropyl alcohol,

and the desired temperature of the bath and bearing is attained by droppin dry ice in the bath. The drum and drum extension carried at the upper end of the hollow spindle and protruding from the bath are held in vertical position by a tapered roller hearing. The line coiled around the drum extends over a pulley to a container into which the desired weights are added to apply the torque load to the hollow spindle to thereby cause rotation of the spindle and inner race of the bearing with respect to the fixed outer race. A time of not less than two hours is utilized to cool the bearing to the test temperature, and an additional soaking period at the test temperature is permitted such that the test is not run until three hours from the start of cooling. The bearing is rotated one revolution in each direction during the cooling and soaking periods. When the desired bearing temperature and soaking period are attained, a 2000 g.-cm. torque load is applied in both clockwise and counterclockwise directions, and the number of seconds for one rotation in each direction is observed and the readings averaged.

The Water Resistance test of the foregoing table is that described in Army-Navy Aeronautical Specification AN-G-25, Low Temperature Aircraft Lubricating Grease, item F-4f, October 9, 1947. This measures the resistance of the grease against being washed out of the bearing in the presence of water. Briefly, the test involves th 204 ball bearing mentioned above packed with 4 grams of the grease and clamped in a tight fitting housing which allows the inner race to rotate. The latter is mounted on a horizontal shaft and rotated at 600 R. P. M. while a fine stream 01' distilled water is directed against the end plate of the bearing housing just above the outer opening of the bearing housing. This operation is continued for one hour, when the loss in weight of the dried bearing is than re orted as grease loss: and this loss in weight divided by the weight of the grease used in packing the hearing is reported as the loss.

The Norma-Hoffmann Oxidation test is a measure of the resistance to oxidation of lubricating greases when stored under static conditions for long periods of time, as when coated in thin films on anti-friction bearings, motor parts, etc. In this test five four gram samples of the grease are put in flat sample dishes and placed in a stain ess steel bomb sealed with a lead gasket in an atmosphere of oxygen under an initial pressure oi 110 pounds per square inch at a temper ture of 210 F. The pressure drop in pounds within the bomb is then recorded at 100 hours as shown in the table. or at different times up to 500 hours or until a pressure drop of 55 pounds per square inch occurs.

The Oil Separation test is described in Armr- Navy Aeronautical Specification AN-G-fia. Low Temperature Lubricating Grease, page 5, March 6, 1943. This is a measure of the resistance of the grease to oil bleeding and eva oration. In this test 10 grams of the grease are p aced in a weighed 60 mesh screen cone supported from the rim of a weighed 100 milliliter beaker so that the pointed bottom of the screen cone containing the grease issubstantially above the bottom of th beaker. This assembly is then placed in a gra t convection oven maintained at 210 F. for a p r od of 50 hours. At the end of that period. the assembly is removed, cooled in a desiccator, and the beaker and cone weighed together and the beaker weighed separately. The final weight of the beaker minus the initial weight of the beaker divided by the initial weight of the grease sample times 100 is reported as bleeding. The initial weight of the beaker plus cone and grease minus the final weight of the beaker plus cone and grease divided by the initial weight of the grease sample times 100 is reported as evaporation.

The foregoing Table XI shows that this grease has excellent characteristics in regard to lubrication, low temperature torque. shear resistance, resistance to oil separation and water resistance. Comparison of this grease with a premium type of ball and roller bearing grease now on the market showed the former to be comparable or superior for this specialized type of service.

Other greases prepared in accordance with the detailed procedure outlined above but employing different oxidation inhibitors showed that the present type of grease has excellent response to oxidation inhibitors, as illustrated by the follow- It is postulated that the ASA soap grease has a chain-like structure, as illustrated below for the straight magnesium ASA grease.

where n represents a number satisfying the chain length of the polymer. Rather high chain length is believed responsible for the comparatively hard gel-like appearance, high melting point and good yield of the magnesium ASA greases. It is further postulated that the incorporation of the mono-carboxylic acid in the mixture being saponifled effects a reduction in the average chain minal group and preventing further lengthening of the chain, as illustrated below:

where n is a number indicating the chain length of the magnesium ASA polymer. Molecular weight determinations by the Staudinger viscosity method on lutidine solutions of the 2:1 Mg Clo-C12 ASA:Mg stearate soap gave values of approximately 2100 and 1600 respectively. Similar molecular weight determinations by this method on 2% and 1% solutions of the soap in a paraflin base lubricating oil of SAE 20 grade gave values of 1860 and 1295 respectively. The theoretical molecular weight of the 2:1 (weight ratio) magnesium ASA:M stearate (equivalent to a 4:1 mol ratio) soap is 1770. assuming a polymer with 4 mols of ASA and 2 mols oi stearic acid per molecule. From these determinations, it is believed that the value of n in the above formula for the compound dicarboxylic-monocarboxylic acid soap may vary between about i and 4 including fractional increments therebetween.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A lubricating grease comprising an oleaginous liquid lubricating base as the predominant constituent, and in excess of but below 50% by weight based on the grease oi a soap 01' a hydrocarbon substituted aliphatic dicarboxylic acid having the carboxyl groups in a plane symmetrical configuration and wherein the hydrocarbon substituent is selected from the group consisting of alkyl and alkenyl and contains at least eight carbon atoms, said soap being formed from a polyvalent metal selected from the group consisting of magnesium, aluminum and beryllium. said soap being in suiiicient proportion with the mixture of soap and lubricating base heat treated at a gelation temperature to thicken said lubricating base to a gel-like consistency.

2. A lubricating grease according to claim 1, wherein the aliphatic substituted dicarboxyiic acid is an alkenyl succinic acid.

3. A lubricating grease according to claim 2, wherein the soap is magnesium CID-C12 alkenyl succinate.

4. A lubricating grease comprising an oleaginous liquid lubricatin base as the predominant constituent, and in excess oi. 5% but less than 50% by weight based on the grease oi a soap of a polyvalent metal selected from the group consisting of magnesium, aluminum, and beryllimn. said soap being formed from a mixture of a major proportion of a hydrocarbon substituted aliphatic dicarboxylic acid having the carboxyl groups in a plane symmetrical configuration and wherein the hydrocarbon substituent is selected from the group consisting of alkyl and aikenyl and contains at least eight carbon atoms, and a minor proportion of a soap-forming mono-carboxylic acid, said soap being in suillcient proportion with the mixture of soap and lubricating base heat treated at a gelation temperature to thicken said lubricating base to a gel-like consistency.

5. A lubricatin grease according to claim 4, wherein the substituted aliphatic dicarboxylic acid is an alkenyl succinic acid.

6. A lubricating grease according to claim 5, wherein the soap is magnesium alkenyl succinatemagnesium stearate.

7. A lubricating grease comprising a mineral lubricating oil as the major constituent. in excess of 5% but less than 50% by weight based on the grease of soap consisting of a major proportion of magnesium Cm-Cn alkenyl succinate and a minor proportion of magnesium stearate suflicient with heat treatment at a gelation temperature to thicken said lubricating oil to a gel-like consistency, and a small amount of an oxidation inhibitor.

8. A lubricating grease according to claim 7, wherein the soap is about a 2:1 mixture by weight 01' the magnesium Clo-C12 alkenyl succinate and the magnesium stearate respectively, and the oxidation inhibitor is selected from the group consisting of a diphenylamine, phenyl-alpha-naphthylamine, 4-methyl 2.6-ditertiary butyl phenol, and tetra-methyl diamino diphenyl methane.

9. A lubricating grease comprising an oleaginous liquid lubricating base as the predominant constituent, and in excess of 5% and less than 50% by weight based on the grease oi a magnesium polymer soap oi the formula where ADA represents a hydrocarbon substituted aliphatic dicarboxylic acid residue having the carboxyl groups in a plane symmetrical configuration and wherein the hydrocarbon substituent is selected troin the group consisting of alkyl and alkenyl and contains at least eight carbon atoms, R represents the hydrocarbon portion or terminal soap-forming mono-carboxylic acid residues, and n is a number indicating the cha n length oi the magnesium dicarboxylate portion of the soap polymer which may vary between 1 and 4 including fractional increments therebetween, said soap being in sufficient proportion with the mixture of soap and lubricating base heat treated at a gelation temperature to thicken said lubricating base to a gel-like consistency.

10. A lubricating grease according to claim 9, wherein ADA is Cid-Cu alkenyl succinate, and

is a stearic acid residue.

11. A lubricating grease according to claim 10, wherein the soap polymer has a molecular weight approximating a chain length of about four ADA groups.

12. The method of preparing a lubricating grease which comprises saponifying a hydrocarbon substituted aliphatic dicarboxylic acid or anhydride thereof having the carboxyl groups in a plane symmetrical configuration, and wherein the hydrocarbon substituent is selected from the group consisting of alkyl and alkenyl and substituent group contains at least eight carbon atoms, with an oxide or hydroxide oi a polyvalent metal selected from the group consisting of magnesium, aluminum and beryllium, dehydrating the resultin saponlflcation product, then heating the dehydrated saponifled product in the presence of a predominant proportion 01' a liquid oleaginous lubricating base to a gelation temperature above about 450" F.. and drawing the product to obtain a gel-like grease containing in excess of 5% and less than 50% by weight of said soap based on the grease.

13. The method according to claim 12, wherein the dicarboxylic acid is an alkenyl succinic acid.

14. The method or preparing a lubricating grease which comprises saponii'ying a mixture consisting of a major proportion of a hydrocarbon substituted aliphatic dicarboxylic acid or anhydride thereof having the carboxyl groups in a plane symmetrical configuration, and wherein the hydrocarbon substitutent is selected from the group consisting of alkyl and alkenyl and contains at least eight carbon atoms. and a minor proportion of a soap-forming mono-carboxylic acid, with an oxide or hydroxide of a polyvalent metal selected from the group consisting of magnesium, aluminum and beryllium, dehydrating the resulting saponifieation product, then heating the dehydrated saponifled product in the presence of a predominant proportion of a liquid oleaginous lubricating base to a gelation temperature above about 450 F., and drawing the product to obtain a gel-like grease containing in excess of 5% and less than 50% by weight of said soap based on the grease.

15. The method according to claim 14, wherein the dicarboxylic acid is an alkenyl succinic acid, and the mono-carboxylic acid is stearic acid.

16. A lubricating grease comprising an oleaginous liquid lubricating base as the predominant constituent, and in excess of 5% but less than 50% by weight based on the grease of a mixed base soap, said soap consisting of a major proportion of a. polyvalent metal soap of a hydrocarbon substituted aliphatic dicarboxylic acid having the carboxyl groups in a plane 5ymmetri cal configuration and wherein the hydrocarbon substituent is selected from the group consisting of alkyl and alkenyl radicals containing at least eieht carbon atoms, with the polyvalent metal selected from the group consisting of magnesium, aluminum and beryllium, and a minor proportion of metal soap of a soap-forming mono-carboxylie acid, said mixed base soap beimz in sufficient proportion with the mixture of soap and lubricating base heat treated at a relation temperature to thicken said lubricating grease to a gel-like consistency.

17. The method of preparing a lubricating crease which comprises heating a mixture of a distillate mineral lubricating oil containing in excess of 56; but less than 50% by weight of a polyvalent metal soap of a hydrocarbon substituted aliphatic dicarboxylic acid having the earboxyl groups in a plane symmetrical configuration wherein the polyvalent metal is selected from the group consisting of magnesium, aluminum and beryllium, and wherein the said hydroearbon substituent is selected from the group consisting of alkyl and alkenyl containing at least eight carbon atoms, to a gelation temperature in excess of 450 F., and allowing the product to cool to obtain a gel-like grease.

EDWIN C. KNOWLES. GEORGE W. ECKERT. ONEY P. PURYEAR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,292,308 Watkins Aug. 4, 1942 2,349,817 Farrlngton et a1. May 30, 1944 2,363,516 Farrington et al. Nov. 28, 1944 2,402,825 Lovell et al. June 25, 1946 2,417,281 Wasson et al. Mar. 11, 1947 2,436,347 Zimmer et a1 Feb. 17, 1948 2,448,567 Zisman et a1 Sept. 7, 1948 2,458,425 Rocchini Jan. 4, 1949

Claims

1. A LUBRICATING GREASE COMPRISING AN OLEAGINOUS LIQUID LUBRICATING BASE AS THE PREDOMINANT CONSTITUENT, AND IN EXCESS OF 5% BUT BELOW 50% BY WEIGHT BASED ON THE GREASE OF A SOAP OF A HYDROCARBON SUBSTITUTED ALIPHATIC DICARBOXYLIC ACID HAVING THE CARBOXYL GROUPS IN A PLANE SYMMETRICAL CONFIGURATION AND WHEREIN THE HYDROCARBON SUBSTITUENT IS SELECTED FROM THE GROUP CONSISTING OF ALKYL AND ALKENYL AND CONTAINS AT LEAST EIGHT CARBON ATOMS, SAID SOAP BEING FORMED FROM A POLYVALENT METAL SELECTED FROM THE GROUP CONSISTING OF MAGNESIUM, ALUMINUM AND BEYLLIUM, SAID SOAP BEING IN SUFFLCIENT PROPORTION WITH THE MIXTURE OF SOAP AND LUBRICATING BASE HEAT TREATED AT A GELATION TEMPERATURE TO THICKEN SAID LUBRICATING BASE TO A GEL-LIKE CONSISTENCY.