US2682506A - Cellulose base lubricating grease - Google Patents

Description

Patented June 29, 1954 CELLULOSE BASE LUBRICATING GREASE Aurelio F. Sirianni and Ira E. Puddington, t-

tawa, Ontario, Canada, assignors to National Research Council, Ottawa, Ontario, Canada, a

body corporate No Drawing. Application October 17, 1951, Serial No. 251,818

9 Claims. 1

The present invention relates to cellulose base lubricating grease, that is, lubricating grease wherein cellulose, or cellulose derivatives, are employed as the thickening or gel forming material which forms the grease structure.

The present application is a continuation-inpart of our copending applications, Serial No. 66,130 and Serial No. 66,133, filed December 18, 1948, now Patents No. 2,583,603 and 2,583,606, issued January 29, 1952.

In the above-mentioned applications, lubricating greases and processes for their preparation are described where the normal solvent or liquid component which is present in a gel or related material, such as water, is replaced first with a mutual solvent for oil and water and finally the mutual solvent is replaced, directly or indirectly, by a lubricating oil. Greases of this type have some very desirable properties. They appear to have certain advantages over soap thickened greases of conventional type, some of them being especially suited for high temperature service. However, as also pointed out in the aforesaid applications, these greases commonly have the disadvantage that water tends to replace the oil upon contact, causing the composition to break down when moisture gains access to the lubricant.

During the course of experiments relating to the present invention it has been found that the oil thickeners useful for grease making must have certain physical properties. Conventional colloidal suspensions of grease forming particles, such as the soaps of prior art lubricating greases, usually must have a high ratio of length to breadth if they are to be useful. In other words, the soap fibres which form in a lubricating grease for giving it structural stability are relatively long, slender and essentially fibrous in character.

Various materials other than soaps have been found in the prior art to have gel forming characteristics, with lubricating oil. In general, however, the shape of the particles, as well as their size, has an important bearing upon the character and stability of the lubricating grease. It appears that the solid phase of a lubricating grease should not only be fibrous, and its particles relatively long and slender, but it should also possess a strong affinity for oil so that it will attract and hold the lubricating oil to its surfaces to give the grease structural stability. Patent No. 2,583,603, mentioned above, points out how various materials much unlike conventional soaps, such as wood pul and other cellulose sub- 2 stances may be divided into micro-particles sufficiently fine that a good grease structure may be established when they are placed in oil.

It is therefore an object of the present invention to prepare stable lubricating greases from, cellulose and cellulose type materials while at the same time avoiding the objectionable instability of such greases in the presence of moisture. According to the present invention, the addition of certain resins and/or metal soaps to the cellulose materials tends to render them relatively water repellant. Such treatment of the cellulose material is an important feature of the present invention.

When the normal water content of cellulose is replaced by acetone, for example, and the acetone ultimately replaced by mixing with a lubricating oil such as mineral base oil, and then flashing off the acetone, the cellulose retains its original colloidal or gel like structure unless and until it comes in contact with moisture. The lubricant is relatively useless in the presence of moisture, however, without additional treatment. By treating the cellulose, while in the presence of oil, with surface active agents which are hydrophobic in nature, the greases are very substantially improved. Various materials which reduce substantially the preferential adsorption of water on cellulose and which are sufficiently oleophilic to be wetted by oil may be employed to accomplish the desired result. The oil soluble water insoluble resins and soaps are preferred.

A particularly suitable surface active agent is the resinous reaction 'product of substantially equimolar proportions of maleic anhydride and glyceryl monoricinoleate. Other resins of similar type may be used.

A further feature of the present invention involves the treatment of the cellulose itself to give it the desired physical properties for preparation of lubricating greases. Cellulose of appropriate type may be readily obtained by treating viscose with dilute mineral acids such, as sulfuric acid or phosphoric acid. The sulfuric acid treatment is normally preferred. By carrying out the acid precipitation in the presence of sodium sulfate cellulose is produced of sufliciently fine fibrous structure that it sets up a stable grease structure with lubricating oils. On the other hand if the cellulose is precipitated without treatment with sodium sulfate the fibrous structure of the precipitated cellulose is somewhat coarser and less satisfactory.

Although the resinous reaction product of maleic anhydride and glyceryl monoricinoleate is a 3 preferred surface active agent, to render the grease water repellant and physically stable, other types of surface active agents may be used. In particular, the relatively oil soluble and water insoluble long chain fatty acid soaps of certain metals may be used to treat the cellulose before oil is incorporated therein. In general, these metal soaps which make'good grease thickening agents but which are substantially insoluble in water, such as aluminum, calcium, barium, or lithium stearate and related materials are useful. It is preferred that they be used in proportions of about 3 to 60% by weight based on the weight of solvent exchanged cellulose treated therewith,

or about one-tenth of these quantities based onthe total grease. It is preferred, however, to use at least some resin of the type mentioned above, using soap along with the resin where the' 's'o'ap can otherwise be tolerated. Thus a composition containing about 4 to 10% by weight of cellulose, based on the solvent-free material, about 4 to 8% of the maleic anhydride glyceryl monoricinoleate resin, jtb6 of soap, andthe remainder of lubricating'oil, preferably but not necessarily of mmeral'base, makes a good-"grease"composition. Cellulosewhich has not been treated with soap atall can be'used." s

hen soap treated cellulose is to be used, the soap is preferably'formedon the cellulose as the latter is 'precipitated."" either case, upon precipitatioma 'slurry of, viscose is formed which maybe treated next with a'inild alkaline solution to condition "it for further processing. Thereafterthe slurry is' filtered' and theprecipitated cellulose is washed substantiallyfree from water soluble mamas; It is next solvent exchanged with-a soluble mutual solvent for oil andwaterl 'siich as acetone-"Other mutual sol- Vents, such as an-appropriate alcohol or ether, especially propyl and butyl alcohols, and pyridine, may be-used in lieuof acetone, some of these being pointed outin Patent No. 2,583,603 pre -reuse mentioned. The solvent selected should vaporiz'eat a temperature well below that of the inineral base oil or other lubricating oil "used. "The mutual solvent may, in "turn, be

replaced directly bylubricatingoiI or 'it' may first be replacedby an intermediate solvent such aspetroleum ether" or the likeand the'1atter'replaced bythe lubricating oil. Inthis wayjthe watcher-the cellulose-water system may be re-- moved without; shrinkage of the cellulose. cellulose solvent system thus obtained may be termed a solvent-exchangedcellulose; Greases made-directly from this type'ofcellulose, i. e. by

solvent-exchange, result when oil isadded to" the'solveht 'exchanged cellulose and the solvent is flashed ofi, They immediately begin-to disintegrate," however, in the "presence of water. The cellulose component absorbs or adsorbswa te'r'in preference'to 011* and the product is useless, especially-where the grease is to'come in contactwith free water or with appreciable quantities of moisture in'any form.

The greases of this invention may be substantially improved'in'water resistance by adding modified resinous condensation products of polyh ydric'alc'o'hol and p'olyba'sicacid; These may be waterproofing agents of the maleate-glycer'yl ester type, previously mentioned.- The manner inwhich thisis done is an important aspect of this invention. "While, aspreviously mentioned;

the preferred waterproofing agent isthe reaction product of maleic anhydride and glycer'yl monoricinoleate insubstantially equi-mo'lar proportions, related alkyd resins such as those obtained by reacting tetrachlorophthalic anhydride with glycerylmonostearate or by reacting succinic acid with glyceryl monostearate may be used, though somewhat less satisfactory. Related monoesters of glycerol, such as the mono-oleate or monoricihole'ate'i'may bu'sed. l 7

In order "to test water repellancy of various grease samples an apparatus was devised consisting of an elongated grease worker of 50 cc. capacity fitted with a single orifice of diametrl For this test about 10 grams of the grease and 40 cc. of water are placed in the worker and forced back andl'fo'rth through the orifice. This testordiharily-iscarried out for 50 cycles, passing the greaseand water 100 times through the orifice. Greases which do not liquefy or disintegrate durin'g-such tests are considered to be satisfactorily water repellant. Some of the products ran considerably more than 50 cycles which is considered very superior performance. A typical experiment for obtaining a cellulose in sufficiently finely-dividedform from viscose consisted in dilutirigfifib' grains of viscose with-I500 cc. ofwater containmg 20 gramsfof sodium sulfate. The cellulose w s; then precipitated from the solution withthecal' culated amount'of sulfuridacidj dilutedwith water 'to"a"volur'ne of 500" cc. This pro'duct was washed free of water-soluble salts and solvent exchanged with acetone and the acetone "re placed with oil to make a grease m the manner described above. Somc' samples-were tes ted withoutaddition of waterproofing or surfaceac tive' agents. In others" the" maleic anhydride glyceryl monoricinoleate" resin was added shown in the examples below. In" each case-fth'e" oil-cellulose system was" homogenized 1 to make a grease structure." l

' Example} 6.75% by weight of cellulose based on the weight of the final grease'was' 'solveritexchanged' firstwith acetone'theh with lubricating oil er 30Q' viscosity Sz'S. U. at F. The 'oil hada vis-" cosity' index of 95. 93.25% by weight of'oil with the cellulose made agrease of good'yield value uponhomogenization. The product," however} disintegrated without shearing-in the prese'h'ceof water.

Example II 5.5% by weight of solvent exchanged cellulose, based on the weight of th'efinal grease composition, prepared'as described above, was combined with 5185 of the resin'derived by reacting to completion substantially edui molar proportions of 'maleic"anhydride and glycerol monoricirloleate. "I'othis was added 83.65% ofthe same mineral oil as in Example II" The resulting grease product had'a good consistency and passed the water "resistance'test of SOs't'rokes of'the plunger in the grease worker test apparatus described wow,

' Example III 50 strokes of'the mngerer the test apparatus? I suggested above, the useof a soap in com bin'a-tion with the resinhas' been'" f un to be" 500 grams of viscose were added to 1500 cc. of water containing 20 grams of sodium sulfate and 8.2 grams of sodium stearate. In order to kee the viscosity low the mixture was heated moderately to a temperature of 50 to 60v C. The cellulose and an aluminum stearate were coprecipitated from the solution by adding 500 cc.

of an aqueous solution containing the calculated amount of concentrated sulfuric acid and aluminum sulfate. The aluminum sulfate obviously reacts by double decomposition with the sodium stearate to precipitate the aluminum soap. However, since the viscose is normally sufiiciently alkaline, stearic acid may be used if desired in lieu of sodium stearate, e. g. as an emulsion in the first water solution mentioned above.

After precipitation, the slurry of cellulose and soap in water was treated with to cc. of 3 normal ammonium hydroxide. This raised the pH value of the slurry to about 8. The slurry was then filtered, washed free from soluble salts and solvent exchanged with acetone. and the acetone flashed off by heating above its boiling point.

Greases made in the manner just described were found to be somewhat water repellant without the addition of resin. However, they disintegrated after shearing in the presence of water at 70 C., and a few strokes in the grease worker described above.

Example V Example VI A grease was prepared as in Example V except that the cellulose contained 10% of its own weight of aluminum mono-stearate. The cellulose and aluminum soap constituted 7.9% by weight, with waterproofing resin 5.4%, and mineral oil of 90 viscosity index and 500 S. S. U. viscosity at 300 F., constituted 86.7%. This product had a good yield value and passed the water resistance test of 150 cycles. It was an excellent grease.

Example VII A cellulose prepared as in Example IV but containing 3% of its own weight of aluminum monostearate coprecipitated therewith was used in proportions of 8.69% by weight, based on the final grease. 5.21% by Weight of resin and 86.1%

Oil was added 6 of the same oil as in Example VI were blended together. After flashing off the solvent and homogenizing the product in a colloid mill this grease had a good yield value. It passed the water resistance test of 55 cycles of the plunger but emulsified after 60 cycles. This appears to' indicate that it is desirable to have a minimum of at least 3% of the soap in the cellulose and preferably a little more.

Example VIII 8% by weight, based on the final grease composition, of soap coated cellulose, (coprecipitated with 60% of its own weight of aluminum monostearate) was prepared as in Example IV. The

cellulose was combined with 6% by weight of the resin of Example II and 86% by Weight of mineral lubricating oil of viscosity index and 300 S. S. U. viscosity at F. After heating to C. to flash off the solvent, which was used to displace water from the cellulose, the product was passed twice through a colloid mill. The resulting grease was found to possess a very good yield value. It had a very firm consistency, considering the amount of thickener employed. This product also passed the water resistance test of cycles of the plunger.

Instead of the particular maleic anhydridefatty acid resin described above, other resins, particularly the commercially available alkyd resins 1. A lubricating grease composition compris ing a lubricating oil thickened to a grease consistency with solvent-exchanged cellulose precipitated from viscose and containing 3 to 60% by weight, based on the cellulose, of a water insoluble metal soap as a waterproofing agent, said grease containing 2 to 10% by weight, based on the weight of the total composition, of a waterproofing alkyd resin of the glyceryl partial ester dibasic acid type.

2. A lubricating grease composition comprising a major proportion of mineral base lubricating oil, 2 to 10% by weight, based on the total grease composition, of solvent exchanged cellulose of gel type precipitated from viscose containing 3 to 60% of its own weight of an aluminum monostearate as a hydrophobic agent, and 2 to'10% by weight, based on the total composition of a maleic anhydride-glyceryl monoricinoleate ester resin as a waterproofing agent.

3. Composition according to claim 2 where the amount of resin is between 5 and 8%.

4. Composition according to claim 2 wherein the amount of cellulose is between 5 and 8% of the weight of the total composition.

5. The process of preparing a lubricating grease which comprises coprecipitating a cellulose of gel type from viscose with a metal soap capable of rendering the cellulose relatively hydrophobic, adding lubricating oil by solvent exchange to replace the normal water content of the cellulose, incorporating 2 to 10% by weight, based on the total grease composition, of a waterproof- 77,-, c e i an s mc cni in te m. a sta e: sytiucfium W t s h ch com ae e n a water. slurry: of viscose "containing mine? 'quan titles, of sodium sulfate and water sol'uhleCiz to C20 fatty. acid radical, cobrecipitatingl the celh'ilose and the fatty acid, ragical iromfs'aie' solunanny addition of an" aqgeagsseiiipi of a mineral acid and a mansmtm relat'iy low molecular weight, treating the coprecipitate'd slurry with a small-amount'of alkaline material, lter ashi ree fmm watcn solublematerials, exchanging, the water, content of the filtered; cellulose with a. mutual solvent for water and oil, replacingthe mutualtsolvent with lubricating oil, 'adding2 toil-02 27 by weight, based:

on the.total compositionof awatei'pi oofing resin, and homogenizing to form a stable lubricating. grease.

of; amea p n i 1% h m a y c d. either C12 to Q2 range said. soap beingselecte 1911 the group consisting of the soap of aluminum, ar m a1 m s h droph biq agent.

q s o d ng]: to c aim; herei he resin; is a malei nh d de; x er l mono: ricinoleate reaction product.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,260,625 Kistler Oct. 28 1941 2,573,650 Peterson Oct, 30, 1951' 2,583,605 Sirianni et a1 Jan. 29, 1952

Claims (1)

1. A LUBRICATING GREASE COMPOSITION COMPRISING A LUBRICATING OIL THICKENED TO A GREASE CONSISTENCY WITH SOLVENT-EXCHANGED CELLULOSE PRECIPITATED FROM VISCOSE AND CONTAINING 3 TO 60% BY WIEIGHT, BASED ON THE CELLULOSE, OF A WATER INSOLUBLE METAL SOAP AS A WATERPROOFING AGENT, SAID GREASE CONTAINING 2 TO 10% BY WEIGHT, BASED ON THE WEIGTH OF THE TOTAL COMPOSITION, OF A WATERPROOFING ALKYD RESIN OF THE GLYCERYL PARTIAL ESTER DIBASIC ACID TYPE.