US2946751A - Continuous grease manufacture using coated free-flowing alkali metal saponifying agent - Google Patents

Description

July 26, 1960 A. BEERBowER Erm. 2,946,751

CONTINUOUS GREASE: MANUFAOTURU USING COATED FREE-FLOWING ALKALI METAL SAPONIFYING AGENT Filed March 26. 1956 nited States Patent CONTINUOUS GREASE MANUFACTURE USING" COATED FREE-FLOWING ALKALI METAL. SA- PONIFYING AGENT Filed Mar. 2'6, 1956, Ser. No. 573,677-

5 Claims. (Cl. 252-40).

This invention relates toa new and improved method for the manufacture oft metal base oil slurries.k More particularly, the invention relates' toa processv for continuously makingv alkali metal,l oil slurries useful in the preparation of lubricating greasecompositions and lubril eatingA grease soap'concentrates.

In the prior art therehave been many attempts to devise effective Ycontinuous methods for the manufacture of lubricating grease compositions. Therehave also been several' attempts to directly utilize the` essential ingredients Such as the saponifying agent, the saponiable material and the base oil. In U.S. Patent No. 1,912,001 to Lauer an aqueous solution of the saponifying agent was first prepared and then` meteredlin by a pump to the 'greasemaking process. The Lauer process is restricted to the u'se ofsogiiumV hydroxide as noother grease-forming alkali metal base is sufliciently water soluble to avoid theinclusion of ver-y large amounts of water into4 the grease-making system. In order to obtain a solutionv of lithium hydroxide, for example, about nine parts of water are required for each part of lithium hydroxide. Thus, a heavy dehydration load is imposed on theV subsequent grease-making steps. Another method proposed for the direct. utilization of the saponifying agentv involved the feedingof dry,.powdered' metal base by means of a vibrator.y meter. This latter method: is, however, limited to free-flowing powders, such as lime. Alkali metal bases, on. the other. hand, are not free-flowing. powders, since they are hygroscopic in nature andreadily absorb mois.- ture: from the atmosphere. 'Consequently alkali` metal bases becomeKV adhesive andwcoalescive and? will' notA flow freely when utilized, for example,l after storageror in a vibratory: meter feed system. Y

.In accordance with theV present invention, a method has been found whereby alkali metal saponifying. agents can be utilized directly in continuous grease manufacture without using` it to preform the soap thickener or in the form of an aqueous solution.. Broadly, the invention comprises rendering alkali metal bases non-hygroscopic and free-flowing by coating thenr with a dry hydrophobic powder which will be acceptable in the finished grease composition. The coated alkali metal bases may then be used directly in a continuous grease manufacturing opera'- tion. Though this method is particularly adapted for continuous grease manufacture, it may also be employed v in semi-continuous or batch processes. A

rIhe alkali metals contemplated' in this invention include sodium and lithium. These alkali metals may be employed in the form of hydroxides, oxides, and carice 0.02 times thediameter and as lowv as 0.001 times the diameter. The sizevvillV range from 30 millimicrons'- to mesh, preferablyl about l micronto 200 mesh.

In the preferred embodiment of the invention, lithium hydroxide is the alkali metal base and hydrated lime; i.e. calcium hydroxide, is the dry, powdery coating material. Generally, about 50 to 99V wt. percent, preferably about 60 to: 75 wt..percent, of the. alkalimetal base will be: employed in conjunction with about 1 to 50 wt. percent, preferably about 25 `to 40 wt. percent, of the hydrophobie coating material. The amount will depend on the particle sizeY ratio in. that enough coating material must be used to provide a more or less' continuous coating;

The. oil used both in making the saponifying agent slurry and in formulating the finished greasel composition may be any of the mineral, vegetable, animal or synthetic lubricating oils known to the art'. In general, these lubricating oils should have a viscosity of about 50 to 2000 S.U.S. at 100 F. and-about 35 to 200 S.U.S. at 210 F., an ASTM pourv point of about +20 to -75 F., a flash point of about 350" to 650 F., and a viscosity index of about 0 to 165. Conventionally refined mineral lubrieating oil derived from parainic, naphthenic or mixed base crudes are preferred. The saponifying agent-oil slurry of thefinvention will contain about 40 to 70 Wt. percent, preferably aboutY 45 to 50 wt. percent, of the lubricating oil baseistock. The proportion of'lubricating l oil in ther finished grease composition 'will ordinarily be about 75 to 95 wt. percent, preferably about 80 to 90 wt. percent.

The synthetic lubricating oils' useful in the invention include esters'of monobasic acids (eg. an ester ofCs Oxo alcoholl with C8 Oxo acid, an ester of C13 Oxo alcohol with octanoic acid', etc), esters of dibasic acids (e.g. di- Z-ethyl' hexyl sebacate, di-nonyl adipate, `etc.), esters of' glycols (eg. C13 Oxo acid diester of tetraethylene glycol, etc.), complex esters (eg. the complex ester formed by reacting one mole of tetraethylene glycol with two moles of sebacic acid and two moles of Z-ethyl-hexanol, a complex ester formed by reacting one mole of tetraethylene glycol, one mole of C8 Oxo alcohol, one mole of adipic acid, and one mole of C8 Oxo acid, etc.), esters ofY phosphoric acid (eg. the ester formed by contacting three moles of the mono-methyl ether of ethylene glycol with one mole of. phosphorous oxychloride, et'c.), halocarbon oils (c g. the polymer of chlorotrilluroethylene containing twelve. recurring units of chlorotriiluoroethyl.- ene), alkyl silicates (eg. methyl polysiloxanes, ethyl polysiloxanes, methyl-phenyl polysiloxanes, etc.), suliite esters (e.g. ester formed by reacting one mole of sulfur oxychloride with two moles of the methyl ether of ethyl.- ene glycol, etc.), carbonates (eg. the carbonate formed by reacting'Ca Oxo alcohol with ethyl carbonate to form a half ester andreacting this half ester with tetraethylene glycol), mercaptals (egg.l the mercaptal formed by reacting Z-ethyly hexyl mei-captan with formaldehyde), formals (eg. the formal formed by reacting C13 Oxo alcohol 'with formaldehyde), polyglycol type synthetic oilsv (eg. the compounds formed by condensing butyl alcoholwith fourteen units of propylener oxide, etc.), or kmixtures ofthe above in any proportions. l The slurry may also, if desired, be madev with any volatile non-solvent for'the alkali and coating which may be removed during subsequent steps. Ketones, alcohols, ethers, etc. may be employed for this purpose.

The saponiable material'. useful in preparing the soap th-ickeners of the invention may beV any of the naturally occurring or synthetic fats or fatty acids. Examples of these materials include aliphatic saturatedor unsaturated fatty acids having Iodine Numbers within the range of 0 to and having about 12 to 30, preferably about 14 to 22, carbon atoms per molecule, such as laun'c, myristic,

Patented July 26,. 196.0-

palmitic, stearie, 12-hydroxy stearic, 9,10-dihydroxy stearic, behemic, myristoleic, palmitoleic, oleic, linoleic, cottonseed oil fatty acids, .palm oil fatty acids, hydrogenated fishY oil fatty acids, lignoceric, riciuoleic, erucic acids and their mixtures and/ or their glycerides such as lard, beef, rapeseed, palm, menhaden, herring, castor oils, etc. Ordinarily, about 5 to 20 wt. percent, preferably about 8 to l2 wt. percent, of saponifiable fats or fatty acids will be employed in preparing the nished lubricating grease compositions.

In general, the saponifying agent or metal base slurry of the invention is prepared by flrst mixing the alkali metal base with the desired proportion of the hydrophobic coating material, e.g. hydrated lime. Any of the known powder mixers may be employed to blend the alkali metal base and the dry coating powder. The powder may, for example, be added intermittently as in a Patterson-Kelly Dry Blender. Alternatively, the dry ingredients may be dumped more or less continuously into a mixing trough fitted with an agitator such as ribbon mixer. VA continuous tube or ball mill may also be employed. Any of the mixing devices used must have a sufficient volume to average the composition of the mixed powders after charging the separate ingredients. The product may be used immediately or stored for as much as a year without deterioration.

The coated alkali metal base is then fed to a vibratory feed meter or a similar type device so that the ow of material can be controlled within about i1/2% of the desired rate. The coated alkali metal base is fed to a slurry mixer, which may be open top and relatively small but which is adapted for continuous operation. A metered stream of the oil dispersant is charged to the 'slurry mixer at the same time, and a slurry of the alkali metal base and the oil is formed by continuous stirring. The resulting slurry may then be either stored or fed to the subsequent grease-making steps by means of a synchronized metering pump or a flow controller. In some instances the slurry may tend to settle in the lines due to the presence of lumps of the alkali metal base. This may be readily prevented by adding a small portion of fatty acid material to the oil stream or directly to the slurry mixer -in order to form a sufficient amount of soap which will suspend the alkali metal base in the oil. Ordinarily, only about 0.5 to 5 wt. percent, preferably about 0.5 to 1.0 wt. percent, based on the alkali metal oil slurry, of the fatty acid material need be employed. However, a preferred alternative to this method of stabilizing the suspension of the alkali metal base in the oil involves recycling about 3 to l5 Wt. percent, preferably about 5 to 10 wt. percent, based on the slurry, of the finished grease composition to the slurry mixer.

As previously noted, the alkali metal base-oil slurry prepared in accordance with this invention may be utilized in the preparation of any lubricating grease composition v wherein alkali metal bases may be employed as the saponifying agent. it is important, of course, that the hydrophobic coating material be acceptable in the final grease composition. In the preferred embodiment the alkali metal base is lithium hydroxide and the dry coating powder is calcium hydroxide. The resulting alkali metal base oil slurry can be utilized in the preparation of lithium-calcium soap thickened greases, having a mol ratio of lithium soap to calcium soap within the range of about 2:1 to 8:1. These particular grease compositions are disclosed in detail in U.S, Patent Nos. 2,641,577 and 2,646,401.

Other grease compositions wherein the alkali metal base-oil slurry of the invention may be utilized include the mixed base and complex soap-salt thickened lubricating grease compositions described in chapters 15 and 16, respectively, of Boners Manufacture and Application of Lubricating Greases (Reinhold Publishing Corp., New York, 1954).

In order to more clearly set forth the invention, reference is now made to the accompanying drawing, which 4 is a flow diagram illustrating a method of preparing the metal base oil slurries and the finished grease compositions of this invention. It is to be understood, however, that modification as to equipment, its arrangement, the type of materials and their proportions can be resorted to without departing from the concept of this invention.

Referring now -to the drawing, ribbon mixer 1 is supplied with a hygroscopic alkali metal base powder via line 9 and a dry, hydrophobic powder via line 10 in a continuous manner. The powders are thoroughly mixed together in ribbon mixer 1, and the resulting mixture passed via line 11, vibratory feed meter Z and line 12 into slurry mixer 3i. Simultaneously, an oil dispersant is charged to slurry mixer 3 via line 14 from oil reservoir 5, and the resulting mixture thoroughly agitated to produce a metal base oil slurry. The slurry is continuously removed from slurry mixer 3 via line 15 and slurry pump 16 either to storage via line 25 or to grease cooker 4. If the metal base oil slurry is passed to grease cooker 4, the desired proportion of lubricating oil is simultaneously pumped into grease cooker 4 from o-il reservoir 5 via line 17. Fatty acid material is also charged to grease cooker 4 from the fatty acid tank 6 via line 18. Sufficient heat is supplied to cooker 4 to heat the resulting mixture to a grease-making temperature within the range of about 22.5 to 350 F., preferably about 300 to 325 F., though the temperature required will depend upon the various grease-making ingredients employed. If desired, the Water liberated by the reaction in cooker 4 can be vaporized and vented via line 26.

After saponication of the fatty material has been completed in cooker 4, the resulting grease mixture is withdrawn via line 211 and passed to cooler 7, which may be any one of the conventional coolers employed in the grease manufacture art. In general, the grease Will be cooled to a temperature `within the range of about to F. If desired, the cooled grease may then be homogenized at high rates of shear Within the range of about 50,000 to 500,000 reciprocal seconds in such milling orA homogenizing devices as a Morehouse mill, Charlotte mill, ink mill, Manton-Gaulin homogenizer, etc. Where it is desirable, conventional lubricating grease additives may be added to the grease prior to homogenization via line 24. Examples of such additives include oxidation inhibitors, corrosion and rust inhibitors, extreme pressure agents, metal deactivators and the like.

As previously discussed, should the metal base-oil slurry tend to settle in the lines, this can be prevented by charging a small amount of the fatty acid material directly to slurry mixer 3 from fatty acid tank 6 via line 19 or to oil stream 14 via lines 19 and 20. However, the preferred method of stabilizing the metal base in the oil involves supplying a small portion of the finished grease composition from the homogenizer via lines 23 and 13.

The following examples are presented to illustrate the preparation of a metal base-oil slurry and a finished grease composition manufactured according to the process of this invention.

Example I A metal base-oil slurry was prepared from the following ingredients:

The slurry was prepared by mixing the lithium hydroxide monohydrate and the hydrated lime in a Patterson Kelly Blender for about 15 minutes. The resulting mixed powder was then metered on an Omega Machine Feeder to Temperature, F.: Y Viscosity, poises Example II The alkaline slurry of Example I was metered by a. screw type pump at 6.9 lb./min., 200 F. and l0O'p.s.i.g.

while fatty acid was metered by a gear pump at 15.3 1b./min., 180 F. and 100 p.s.i.g. The streams joined in a Lancaster Disperse-r driven at 3500 r.p. m. The soap mixture, then at 260 F., was led through a scraped surface heater, leaving at 296 F. Oil at a rate of 77.8 lb./min., 135 F. and 100 p.s.i. was metered in by a gear pump and mixed with the soap in a second disperser. The resulting grease at 235 F. was passed through a pressure reducing valve and dehydrated in a Cornell Homogenizer at 21" vaccum cooled to 135 F. and milled in a Charlotte Colloid Mill at .015" clearance. It had a Worked penetrationk of 270, passed the A.S.T.M. Wheel Bearing Test, and was smooth and unctious in texture.

It Will be further understood that the invention is not necessarily limited to the specific materials and operating conditions of the foregoing examples. These `materials and conditions may be varied within the limits indicated in the general portions of the specification.

What is claimed is:

1. In a process for preparing a lubricating grease comline earth metal base powder suiiicient in amount to coat said alkali metal base.

2. A continuous process for preparing a lubricating grease composition which comprises forming an intimate mixture consisting essentially of dry finely divided lithium hydroxide and dry finely divided calcium hydroxide in a separate mixing `zone to obtain non-hygroscopic lithium hydroxide coated with said calcium hydroxide, feeding said coated lithium hydroxide to a second mixing zone, charging a dispersing proportion of a lubricating oil to said second mixing zone to obtain a metal base oil slurry, then admixing-said Yslurry with additionallubricating oil and av grease-thickening proportion of a high molecular weight carboxylic acid having from about 12 to 30 carbon position comprising feeding an alkali metal base to a mixing zone, simultaneously feeding a lubricating oil dispersant to said mixing zone to obtain an alkali metal base oil slurry, mixing said slurry with additional lubricating oil dispersant and a grease-thickening proportion of a sapom'fiable material, heating the resulting mixture to a grease-forming temperature, dehydrating and then cooling to obtain said lubricating grease composition, the improvement which comprises maintaining said alkali metal base free-flowing by thoroughly mixing it with a dry, alkaatoms per molecule, heating the resulting mixture to a grease-forming temperature, dehydrating and then cooling to obtain said lubricating grease composition.

3. The process of claim 2 wherein a small proportion of said high molecular weight carboxylic acid is charged to said second mixing zone.

4. The process of claim 2 wherein asmall proportion of said nished lubricating grease composition is charged to said second mixing zone.

5. The process of claim 2 wherein the finished lubricating grease composition contains a mol ratio of lithium to calcium soap within the range of about 2:1 to 8: 1.

References Cited in the file of this patent UNITED STATES -PATENTS 143,430 Wyle Oct. 7, 1873 318,044 Semper May 19, 1885 1,342,148 Armstrong June 1, 1920 1,601,898 Wiley et al. Oct. 5, 1926 1,872,026 Carey Aug. 16, 1932 2,031,972 Moser Feb. 25, 1936 2,207,737 Vissert Hooft et al. July 16, 1940 2,296,689 Soderberg Sept. 22, 1942 2,383,906 Zimmer et al Aug. 28, 1945 2,470,214 Egan May 17, 1949 V2,488,485 Winternitz Nov. 15, 1949 2,514,331 Morway July 4, 1950 2,589,108 Mark Mar. 11, 1952 2,625,508v Stross Jan. 13, 1953 2,629,652 Schechter et al Feb. 24, 1953 2,641,577 OHalloran June 9, 1953 2,684,947 Kramer July 27, 1954

Claims (1)

1. IN A PROCESS FOR PREPARING A LUBRICATING GREASE COMPOSITION COMPRISING FEEDING AN ALKALI METAL BASE TO A MIXING ZONE, SIMULTANEOUSLY FEEDING A LUBRICATING OIL DISPERSANT TO SAID MIXING ZONE TO OBTAIN AN ALKALI METAL BASE OIL SLURRY, MIXING SAID SLURRY WITH ADDITIONAL LUBRICATING OIL DISPERSANT AND A GREASE-THICKENING PROPORTION OF A SAPONIFIABLE MATERIAL, HEATING THE RESULTING MIXTURE TO A GREASE-FORMING TEMPERATURE, DEHYDRATING AN THE COOLING THE OBTAIN SAID LUBRICATING GREASE COMPOSITION, THE IMPROVEMENT WHICH COMPRISES MAINTAINING SAID ALKALI METAL BASE FREE-FLOWING BY THOROUGHLY MIXING IT WITH A DRY, ALKALINE EARTH METAL BASE POWDER SUFFICIENT IN AMOUNT TO COAT SAID ALKALI METAL BASE.

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