US2372052A - Lubricants - Google Patents

Description

March 20, 1945. A. BEWER ETAL, 2,372,052.

LUBRICANTS `rrfiledpocf.'7,'1942 Patented Mar. 20, 1945A UNITED STATES PATENT OFFICE LUBRICAN TS Alan Beerbower, Westeld, and John C. Zimmer,

Union, N. J., assignors to Standard Oil Development Company, a corporation of Delaware Application october 7,1942, serial No. 461,114 s claims. (ci. 25e- 35) This invention relates to an improved process and apparatus for manufacturing lubricating greases, especially aluminum soap greases. The invention is particularly adapted for continuous manufacture of such greases.

Many different attempts have been made to develop satisfactory continuous pro-cesses for manufacturing lubricating greases, but few of these methods have met with the desired degree of success, particularly due to difculties which characterize the manufacture of certain types of greases, especially aluminum grease, and in certain Irespects soda, barium and lithium greases. )ne object of the present invention is to overcome thesevarious difficulties of the prior art and to provide a process for the continuous l' manufacture of aluminum soap grease, as well as soda soap grease and even other soap greases, if desired, in' simple and relatively fool-proof equipmentl which in operation results in a high quality homogeneous uniform and reproducible product at relatively low oost.

Broadly, the invention comprises mixing a soap and a lubricating oil at a temperature consider.- ably below the maximum grease-cooking temperature to: form a lump-free slurry, diluting f said slurry with additional oil to give the pro-- portions of soap and oil desired in the finished grease, mixingl said materials to make a substan' tially homogeneous mixture, then passing the mixture through a heating zone ofl relatively large heating surface per volume, in order to get complete solution of the soap in oil with oncethrough operation, and cooling the resultant grease stock atleast to a grease structurefforming temperature. The invention may be exemplified by mixing a dry aluminum stearato powder with oil in a suflicient amount tomaken thick slurry, this mixingbeing preferably done' in a roller or pug mill which breaks up lumps eiliclently, although it may be done with an agitaytor in a barrel, then adding more oil, .still withoutany substantial heating of the mass, mixing these materials thoroughly and passing them through a pipe coil heater Ato bring the mixture up to a suitable grease-cooking temperature, suchv as 250-350 F. for an aluminum soap grease, or higher for other soaps such as soda or lithium or barium, then passing the materials to a surge tank from which accumulated vapors may vbe discharged,land nally cooling the mixture in a suitable manner to permit the formation of the desired grease structure. Usually in the past with aluminum soap grease this cooling has been generally effected by pouring the grease stock into a. large number of relatively small shallow pans and allowing them to cool for a day or two, then returning to the kettle working the product to a uniform consistency and then packaging.

The preferred method is .to passI the grease stock through a helical blade (or screw conveyor) chiller, preferably one cooling down to the transl` tion temperature of the grease, and'allowing it to remain there for the required transition period of a A hour to six hours or so, or slowly cooling the grease even on down past the transition temperature and allowing the grease to go through its finalA transition stages in a storage kettle or shipping containers. This procedure does not require hoor-space for -storage and use of pans, eliminates labor, shortens manufacturing time and produces greases of uniform and satisfactory consistency from lot to lot, since the 'cooling operation can be more closely controlled. Pan operation, where cooling is not controlled, frequently yields non-uniform products from pan to pan.

Instead of using aluminum stearate, other aluminum soaps may be used such as aluminum naphthenate or aluminum soaps of other carboxylic acids having 10, or preferably l5, carbon atoms or more, such as aluminum soaps of synthetic fatty `acids derived from the oxidation of paraffin wax, or mixtures of these various soaps,

, or change the rubbery liquid to solid gel transition temperature range attendant upon Vthe use of aluminum stearate.

Theroil to be used vboth in making the original slurry and in subsequently diluting the slurry to the desired n-al proportion of oil in the finished grease may be any of the conventionally used lubricating base stocks, su'ch -as various light,

medium or heavy lubricating oil distillates or residual fractions which m-ay Ahave been subjected to any of the conventional'rening treatmentsv such as clay-treatng, acidtreating, solvent extraction, etc., and 'may be derived from various crude oils such as parailinic, naphthenic, or mixed f base crudes. In addition, other suitable iluld lubricants, fuels or liquids-'may be compounded with soap to yield pastes, solid fuels, etc.

The proportions in whichA the soap and oil should be. mixed in order to make the slurry in the firststep according to this invention, should be-about to 35% by weight of soap and 65 to 85% of oil, depending largely upon the viscosity and other characteristics of the oil used as well as the type of soap used.

Although the soap, aluminum, lithium soda, or other metal soap, which is preferably in the form of a dry powder, may be mixed with the oil in this rst step without the use of any heat whatsoever, it is possible if desired to use oil which has been warmed slightly, e. g., up to 100 or 150 F., or so, to facilitate the mixing.

As suggested above, the slurry mixer should preferably be an eiilcient lump-breaking mixer, such as the usual roller mill, inwhich the periphery of a roller having a horizontal axis and a peripheral edge of substantial Width, rolls in contact with the upper side of a disc roller rotating on a vertical axis, so that lumps in the material being mixed arecrushed between the rollers. Other types of slurry mixers may be used such as a small grease kettle with rotating paddle blades, a bread-dough ty'pe of mixer or a parallelroll paint mill. An effective type is; also available in which two interlocking' rotorsknead the mass together. L

Of the various types of slurry mixers described above, the Lancaster roller mill is preferred. This is described briey as follows: 'Ihe mixer tank rotates about one axis and the mixer blades about another eccentric to the first. The blades consist of both plows" to lift the mass and mullers to force it against the tank bottom.

The mixer in which the slurry is subsequently mixed or diluted with more oil, which for the sake of clarity may be referred to as the blending mixer, is preferably one which is suitable for continuous operation, such as the orifice mixer. Other types of blending mixers may be used, however, such as gear or rotor pumps, in which controlled amounts of the slurry and oil are fed in together and ,rapidly mixed and discharged in a continuous operation, the amount of recycling of the material through the gear being controlled at will. A centrifugal pump or a rotary mixer of the colloid mill type or the Lancaster disperser type may also be used.

The heater through which the blend of slurry and oil is then passed should preferably be a. pipe coil heater having suillcient inside pipe diameter to give the desired capacity, and of sufficient pipe length to give the required heating in a once-through operation. The surface of the pipe coil heater should be at least 4 square inches per cubic inch of volume and the temperature of the grease at the outlet should be between the` approximate limits of 200 and 500 F., depending upon the ty-pe of grease being produced, for instance about 250 to 350 F. for aluminum, magnesium or barium soap, preferably about 280 to 300 F., and on the other hand about 350 to 500 F. for sodium or lithium soap grease, and about 200to 250 F. for calcium, lead or zinc soap grease. Other types of heaters suitable for continuous operation are those contain-- ing a rotating scraper toinsure good heat transfer, or a tubebank variety.

On the other hand, for batch operation an ordinary kettle without wall Scrapers is suitable eitherfor use with high pressure steam or heated by' direct ring.

Although the surge tank mentionedabove is notnecessary in all cases, it is a desirable accessory in the equipment in order to provide for venting of accumulating gases and vapors, and also in order to even out any irregularities in the volume of flow of the materials in the Various parts of the equipment before or after the surge tank.

If it is desired to cool the grease, this is preferably done in -a screw conveyor type of cooler. such as the Carbondale scraped Chiller. If desired, of course, other types of coolers can be used such as a tubular heat exchanger or a jacketed kettle or drum with cooling water circulating through a jacket.

A standing or storage kettle may also be used, if desired, either to permit the fresh grease product toremain quiescent for a required period during which it changes from a thick solution of oil in soap and acquires the desired grease structure, or this kettle may be used merely as a temporary storage vessel.

For the production of aluminum soap greases it is desirable to use both the chiller and the standing kettle so that the hot grease may be quickly cooled down to the grease structureforming temperature, then permitted to remain in a quiescent condition at that temperature until the desired grease structure has been acquired. If desired, two er more of these standing kettles may be used in order to provide for uninterrupted or continuous manufacture. It is also possible to discharge the grease from the chiller directly into shipping containers such as barrels, kegs or cans.

If desired, the whole equipment may be maintained and operated under a pressure slightly above atmospheric in order to prevent evaporation of water during the manufacture of a lime soap grease.

'Ihe invention will be better understood from a consideration of the accompanying drawing which shows a schematic lay-out of the equip ment used in applying this invention to the manuiacture of aluminum or lithium soap grease.

Referring to the drawing, aluminum soap I. preferably in the form of a dry powder, is fed along with oil from a supply tank (not shown) through line 2 into the roller mill 3 where the soap and oil are mixed together in the form of a thick slurry and then passed by line 4 into the slurry tank 5 through slurry-metering pump 6 into line 'l where it meets oil `being fed from ,line 2 through line 8 and oil-metering pump 9,

and the mixture of slurry and oil passes from line 1 into orifice mixer I0 through line II into pipe coil heater I2 where the mixture is heated to the required grease blending temperature, and thence passes by line I3 into surge tank I4 and is then pumped by pump I5 through line I6 into the Carbondale Chiller I1, into the standing kettle I8 where it is permitted to remain quiescent until the desired Agrease structure has been acquired, and finally through filter I9 and discharged into suitable containers (not shown) for shipping or storage. Suitable lines 20, 2I, and

1 22 may be used for by-passing thesurge tank I3,

A mend of 33% aluminum stearate and 67% c:l

'10 vS. S. U, at 210 F. lubricating oil was mixed byhandinabeaker. Thiswas fedthroughs ture to form a slurry,

Example 2 A suspension of 8% aluminum stearate in 70 S. S. U. at 210 F. lubricating oil was prepared by first mixing a concentrate of 331/3% and diluting this in a kettle. VThis mixture was fed through a coil of 20 feet length and l" I. D., immersed in a bath offused sodium and potassium nitrates at 400 F. vThe feed rate was approximately l lb, per minute and the exit temperature was 325 F. This melted grease was then held in a surge tank holding 15 lbs. for the transit time of approximately 15 minutes, allowing air which had been trapped in the suspension to escape. This melted, de-aerated grease was then pumped through a cooler coil immersed in running water at 125 F. The exit temperature was 150 F. and the grease was stored in containers at this temperature until set. A satisfactory cup grease was produced. Lithium, calcium, barium, lead, zinc, soda orother soap may be similarly employed to make the respective types of grease, or soaps such as soda, lithium, barium, lime, freshly prepared in a kettle or other equipment'by direct saponication of fats or fatty acid'with the respective alkalis may be fed directly into the mixing equipment for blending with oil cooling and the formation of greases.

This invention is not intended to be limited to the specic examples which have been given merely for the sake of illustration, but only by the appended claims in which it is intended to claim all novelty inherent in the invention as well as all modifications coming within the scope and spirit of the invention.

We claim:

- 1.l Process for manufacturing grease which comprises mixing a soap and oil at a temperature substantially below the grease-cooking temperadiluting` said slurry with additional oil to' give the proportions of soap and oil desired in the inished grease, mixing to make uously .passing said fresh grease stock through 'l a surge tank to insure complete and homogeneous solution of the soap in the oil-and the release of formed or entrained gases and vapors, then passing the soap oil solution through a cooling zone to form the grease structure.

4. Continuous process for the manufacture of an aluminum soap lubricating grease which comprises continuously mixing a dry aluminum soap powder and a mineral lubricating oil base stock at'a temperature of below about 150 F. to form a thick, smooth relatively homogeneous slurry with about to 35% by weight of aluminum soap and about 65 to 85% by weight of mineral oil mixing` in controlled grease-forming proportions said slurry with additional quantities of mineral oil, continuously heating the resultant blend of slurry and oil to a temperature of about 250 to 350 F. in a heating zone of sufficiently large heating surface per volume -to get complete solution of the soap in oil with once-through operation, continuously passing the resultant fresh stock through a surge tank to insure complete and homogeneous dispersion of the soap in the oil and release of formed vapors, quickly and continuously cooling the resultant mixture to a grease structure-forming temperature of about ture, and continuously removing nished alumi- 100 to 150 F., and continuously passing said cooled mixture into one of a plurality of transition zones where said grease stock remains quiescent until it acquires the desired gelled strucnum soap grease from at leastone of said transition zones.

5. Process according to claim 4 in which the slurry is formed 'from-said soap powder and oil base stock by passing through a roller mill, metering pumps are used for continuously feeding slurry and oil together into an orifice mixer, the

heating is aifected in pipe coil heater of at least 4 square inches of heated area per cubic inch of volume, and the hot grease stock is pumped through a helicalscraped cooler.A i

a substantially homogeneous mixture, passing said mixture to a heating zone of relatively large heating surface per volume in order to heat it to at` least a grease-cooking temperature and get complete lsolution of the soap in oil with oncethrough operation, and cooling the resultant grease stock at least to a grease structure-forming temperature.

2. Process according to claim 1 in which the heating zone is a' pipe coil heater.

l.and about 65 to 85% 6; Continuous process for the manufacture of a lithium soap lubricating grease which comprises continuously mixing a, dry lithium-fatty acid soap powder and a mineral lubricating oil base stock at a temperature of below about 150 F. to form a thick, smooth homogeneous slurry with about l5 to 35% by weight of lithium soap byA weight of mineral oil, mixing in controlled said slurry with additional quantities of mineral oil, continuously heating the resultant blendof slurry and oil to 'a temperature of about 250 vto 500 F. in a heating zone of sufficiently large heating surface per volume to get complete solution of the soap in oil with once-through operation, continuously passing the resultant fresh stock through a surge tank to insure complete and homogeneous dispersion of the soap in the oil and release of formed vapors, quickly and continuously cooling the resultant mixture to a grease structure-forming temperature of about to 150 I F., and continuously passing said cooled mixture into one of a plurality of transition zones where said grease stock remains quiescent until it acquires the desired gelled structure, soap grease zones. 4

7. Apparatus for the manufacture oflubricating grease, whichcomprises a mixer adapted to break up lumps sufficiently and to make'a thick homogeneousslurry, a slurry supply tank, an-

from at least one of said transition grease-forming proportions and continuously removing finished lithium other mixer, and a heater, together with means for feeding a dry soap powder and a mineral oil into the rst slurry mixer, means for passing the resultant slurry into the slurry supply tank, means for withdrawing the slurry from said slurry supply tank into the second mixer, means for feeding a mineral oil also into said second mixer, means for passing the mixture produced in said second mixer into the heater, means for withdrawing hoi'l grease stock from said heater.`

8. Apparatus according to claim 7 in which the.

slurry mixer is a roller mill and the second mixer is an orice mixer, metering pumps are used as the means for feeding slurry and oil into the

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