US2374913A - Preparation of lubricating greases and apparatus therefor - Google Patents

Description

y 1, 1945- A. BEERBOWER ETAL 2,374,913

PREPARATION OF LUBRICATING GREASES AND APPARATUS THEREFOR Filed Aug. 15,1941

V2Tl CAL Mix/N6 CHAMB R KETTLE MA TION eon) ZONE.

HEATER Patented May UNITED STATES PATENT OF-FICE PREPARATION OF LUBRICATING GREASES AND APPARATUS THEREFOR Alan Beerbower, Kenilworth, and John C. Zim-' mer, Union, N. J., assignors to Standard 011 Development Company, a corporation of Delaware Application August 15, 1941, Serial No. 406,988

7 1'0 Claims.

This invention relates to novel methods for and to novel apparatus therefor; and more par ticularly it relates to a novel and improved process and apparatus for continuously making producing lubricating greases and soap stocks or V concentrates for the manufacture of greases admixed with a small amount of water as a slurry, although the water may be fed in separately, if desired) and the mineral oil through line 8, although, if desired, the soap concentrate may be prepared without the use of any mineral oil. The mixing zone may be of any a lubricating grease soap concentrate which can then be compounded with the required proportion of mineral oil, with the result that a completely continuous process for making lubricating greases from start to finish is made possible by an improved process which attains high quality products at relatively much lower cost than processes used heretofore.

The invention has been found particularly applicable to the manufacture of calcium-soap greases and will first be described as such. For producing calcium soap concentrate which is to be used for making lime base greases, a saponifiable material, such as the usual animal fat, is

mixed with the saponifying agent, preferably hydrated lime, with or without a small amount of water and/or a, small amount of a mineral oil, and this mixture, preferably in the form of a semi-fluid paste, is passed continuously in a relatively small stream through a heating zonewhere the temperature of the mixture is raised at least to saponification temperature, then the mixture is'maintained at a. temperature at least as high as the saponification temperature until saponification is substantially complete and there is thus continuously produced a calcium soap concentrate suitable for grease making which may then either be passed to a storage zone or preferably, immediately compounded either continuously or by batch operation with the required proportion of mineral oil to produce a lime-soap lubricating grease of uniform and high quality.

, The invention will be better understood by referring tothe accompanying schematic draw-'- ing showing a complete grease-making apparatus consisting essentially of a mixing chamber I, a heater 2, a reaction-completingzone 3, to-

gether with alternate batch or continuous equipment 4 or 5, respectively, for blending the soap concentrate discharging from the reaction-completing zone 3 with the required amount of mineral oil of desired grade (A, B, C, D,- or E, etc.) from suitable supply sources not shown. In carrying out the invention, the mixing zone I is preferably charged continuously by feeding the fat or other suitable saponifiable material through line 8, the hydrated lime or other saponifying agent through line I (either dry or v suitable type, such as the vertical cylindrical mixing chamber I, equipped with an agitator as illustrated in the drawing, or it may be in various other form not shown, such as a screw conveyor or even a simple or baffled pipe in which'the variousmaterials become mixed by turbulent flow through the pipe.

Also if desired, this mixing may be accomplished in a semi-continuous manner by using two or more batch mixing tanks operated alternately or in series so that .while one is being continuously fed into the heater 2, one or more others may be used for mixing new batches; in this manner a continuous supply of cold saponi fication mixture may be made available for continuous feeding into the heater 2. The mixture to be. saponified, e. g., hydrated lime and fat, preferably also containing a small amount of water and of mineral oil,,is then forced through line 9 by pump l0 into heater 2, illustrated in the drawing as consisting of a steam-heated coil of pipe. Obviously, the number of tubes or length of pipe used in such a coil heater may be varied according to the speed of flow desired and the degree of heat available, as a single straight tube may be sufficient if a high enough steam pressure is used and a small enough tube diameter or slow enough fiow through the tube is used. As an example -of designing this feature of the invention, it may be mentioned that an overall heat transfer coefficient of 35 B. t. u.

per hour per square foot per degree Fahrenheit may be obtained. This means, specifically, that a steam gauge pressure of about 100 pounds per I square inch would be sufficient to heat a. saponification mixture from a room temperature of about F. up to about 320 F. when pumped If desired, the temperature maintained in the heater 2, may be so controlled in relation to the size and length of .tubing therein as to effect a complete saponification before issuing from the heater per se, if desired, or alternatively, as shown in the drawing, the saponification mixture may be merely rapidly heated in heater 2 as, for instance, in a period of less than minutes, to a temperature at least as high as the saponification temperature, namely, to a minimum of 250 F. and preferably to 300 or 400 F. or even higher, in some cases even as high as 550 F., and then immediately passed through line I l to a consummation zone or a reaction-completing zone 3 which may or may not be heated, but if not heated, is insulated or so designed to maintain a sufficient amount of the heat in the saponification mixture to effect the completion of the saponification reaction. In the drawing, this reactioncompleting zone 3 is illustrated as being a tank of substantial volume into which the heated saponiflcation mixture is charged at the top and discharged continuously at the bottom. Obviously other shapes and types of equipment may be used as a reaction-completing zone. For instance, this result may be accomplished by using a long tube or coil of pipe, either heated slightly or insulated to prevent cooling, and designed of sufllcient length that when the soap stock is discharged therefrom,v the saponification reaction will have been substantially completed, i. e., at least to the extent of 95%, and preferably to at least 98%. In the above .hypothetical example, the reaction-completing chamber should be of about 60 gallons working capacity. The reactioncompleting zone may be provided, if desired, or necessary, with suitable baflles to prevent channelling of the soap stock while passing therethrough. The reaction-completing zone 3 is preferably provided with a safety valve l3 to provide for release of vapors in case dangerously or undesirably high pressures are developed in this soap-stock manufacturing equipment, though no vapors should be removed in ordinary operation with lime soap greases. Normally, in the production of a calcium soap stock for lubricating grease manufacture, it is desirable to operate the whole system under a superatmospheric pressure of, for instance, to 250 pounds per square inch, in order to facilitate hydrolysis of glycsure-controlled valves so as to maintain the entire system including the heater, reaction-completing zone and blending unit under the desired erides and to retain in the soap concentrate a sufficient proportion of water to assist in forming the proper grease structure when the soap concentrate is finally compounded with the main body of mineral oil.

When the finished soap concentrate issues continuously'from the reaction-completing zone 3, it may either be passed directly to storage through line I, or passed throughline l5 into one of the two alternative grease-blending units 4 and 5, 4 being shown in the drawing as a batch-operated mixing tank equipped with an agitator and provided with a soap-concentrate inlet and a mineral oil inlet at the top and a discharge outlet ii at the bottom. The blending unit 5 is shown in the drawing as composed of two gear pumps or. other suitable metering devices l1, one for the soap stock and the other for the mineral oil fed from suitable sources A, B, C, D, or

E, and a high-speed mixer It, as claimed in copendingappllcation Serial Number 342,081, filed June 24, 1940, now Patent Number 2,318,668, granted May 11, 1943, preferably of the Lancaster mixer type for final discharge through outlet l9. Outlets l6 and, shouldbe provided with prosoperating pressure. Obviously the mineral oil from source A, B, C, D, or E may be preheated, if desired, in order to obtain the proper temperature in'the blended grease for facilitating homogeneous dispersion of the soap within the oil and production of the proper grease structure.

As indicated in the drawing, the mixer I may be provided with a line 20 for temporarily recycling the cold saponification mixture through the mixer I, at least long enough to insure that a substantially homogeneous mixture will be fed into the heater 2. The equipment is provided with suitable valves, such asindicated in the drawing. for controlling the flow or stoppage of the saponification mixture, as required for normal operation as described, with proper means for discharging and cleaning the various parts of the apparatus when necessary.

The saponifiable material to be used may be any of the fats, fatty oils, fatty acids, etc., commonly used for making lubricating grease. Speciflc examples of such materials include beef stearin, mutton tallow, hog fat, lard oil, cottonseed oil, soya bean oil, oleic, stearic or tallow fatty acids, or degras. Of these various types of saponiflable material hog fat, lard oil and the various fatty acids are preferred, especially for making lime soap greases.

As the saponifying agent, lime is preferred and this may be used either in the form of calcium hydroxide or calcium oxide, although the former is preferred. Other alkaline earth metal bases of periodic Group II-A may be used, such as gelatinous magnesium hydroxide and corresponding strontium and barium hydroxides or oxides. Although the invention is particularly applicable to the preparation of alkaline earth metal soap greases, other saponifylng agents may be used, such as caustic soda, caustic potash, caustic lithium, gelatinous aluminum hydroxide, or mixtures of two saponifying agents such as lime and soda, lime and potash, soda and barium, lime and barium, etc., in which the metal outside Group II-A is less than 10% of the base.

The saponification of fats to make a grease concentrate by long cooking continuously has already been suggested as in U. S. Patent No. 2,084,974. This invention, however, is different in that complete and eflicient mixing is effected before heating and therefore the time of reaction is much shorter, namely from to 1 3 hours and also differs in other important features. I

As indicated earlier, it is desirable with certain types of greases, particularly the lime greases, to have a small amount of water-present in order to obtain the best grease structure and the optimum yield, expressed in volume-of grease produced for any particular soap content. For lime soap greases, it is preferable to have a water content between the approximate limits of 0.5 and 5.0% in the finished grease composition, or approximately 0.10% of'water' for each per cent of lime soap present. If the saponiflable material used is a glyceride or a mixture of giycerides, some glycerine is formed as a by-product of the saponification reaction, and whatever water is desired in the finished grease must be added. On the other hand, if fatty acids are used as the saponifiable material, then some water is formed as by-product during the saponification, and in oil having a viscosity of 40 seconds Saybolt (Univ.) at 210 F. of 225 and 300 worked peneof mineral oil, usually less than 30% of the,

weight of saponifiable material, and preferably about 10-20% of the weight of saponifiable mate rial.

The mineral oil for this purpose may be panying drawing which are given merely for illusof any particular type, as to whether it is parafllnic, naphthenic, or mixed base oil, or of the particular boiling range and viscosity range intended to be used in the finished grease composition, or, since only a relatively smallamount of the oil is used in making the concentrated soap stock, a medium type of mineral lubricating oil may be used for this purpose, e. g., one having a Saybolt viscosity between the approximate limits of 40 seconds and 60 seconds at 210 F., this soap concentrate then being blended with a much larger proportion of a mineral oil of the desired characteristics for making the finished lubricating grease. The oil used in the soap concentrate should be of as light a color as any oil be used in blending.

For the sake of illustratiomthe Jfollowing example is given.

The materials listed herebelow were mixed at ordinaryroom temperature (the quantities being expressed in per cent by weight) and formed'a semi-fluid paete: I

Material Per cent Commercial hog fat T5 Hydrated lime (chemical'grade) l0. 5 er 7. 5 Mineral oil of 40 S. S. U. paraflin at 210 F 7.0

The above mixture must be used *within 24 hours, because if it stands longer, it sets practically solid. These materials were mixed in a .mixer such as illustratedat I in the accompanying drawing, and the resultant slurry was pumped through the heater 2, whereby it was raised to a temperature of about 320 F. in about minutes, and then it was admitted at the top of the reaction-completing chamber}, its course through the latter taking at least an hour, after nor anystirring mechanism. One analysis during this continuous grease soap concentrate manufacture indicated that the saponification was 98.7% complete, and this compares very favorably with the 95-98% ordinarily obtained in batch operations. 7

The soap concentrate produced in this test was, when cooled, a hard, brittle material of approximately 10 penetration by the A; S. T. M. grease penetration-test. It had a melting point of 210 F. If melted under pressure it becomes a viscous fluid, thinning as the temperature is raised. At 300 F. it flows quite freely.

Several different greases were blended from the above concentrate, including two containing tration, and one withoil having a viscosity of 70 seconds Saybolt'at 210 F., of 300 worked penetration.

.\ It is not intended that this invention be limited Ito" the speciflcexamples recited, nor to the particular types of equipment shown in the accomtration, but only by the appended claims in which it is intended to claim all novelty inherent in the invention.

We claim:

1. The process of preparing a lubricating grease soap concentrate which comprises mixing in a mixing zone of relatively large capacity a saponifiable material, a saponifying agent in substantial amounts to completely saponify the saponiiiable material and a small amountof mineral oil, at a temperature lower than saponification reaction temperature but sufliciently high to maintain the mixture in a semiiluid or iiuid state and ,to permit thorough mechanical mixing, continuously heating the resulting mixture in a small stream in a heating zone of relatively small capacity compared to thatof the mixing zone to a temperature at least ashigh as saponiflcation reaction temperature, maintaining said mixture 'at a temperature at least as high as reaction temperature until the saponiflcation reaction is substantially complete, and continuously withdrawing the finished lubricating grease soap stock.

2. Process according to claim 1 in which an alkaline earth saponifying agent is used and the saponiiication mixture is heated in a confined stream for a period of less than 10 minutes.

3. Process according to claim 1 in which animal fat and hydrated lime are used, the saponification mixture is heated to about 300 F. to 450 F. in a pipe coilheater in less than about 10 minutes, and the saponiilcation mixture is then kept at reacting temperature for at least one quarter hour.

4. The process of preparing a lubricating grease soap stock which comprises mixing at room temperature the i'ollowing amounts of materials, expressed in percent by weight:

Material Per cent evaporization of water while hot, and continu- 'ously withdrawing from the reaction-completing zone a finished lubricating grease soap stock.

5. The process of-preparing a lubricating grease soap stock which comprises continuously mixing in a mixing zone of relatively large capacity a saponifiable material, a saponii'ying agent and a small amount of mineral oil, at a temperature lower than saponification reaction temperature but sufliclently high to maintain the mixture in a semitluid or fluid state and to permit thorough mechanical mixing, continuously withdrawing a portion or said mixture from said mixing zone,

continuously heating said mixture in a small stream in a heating zone of relatively small ca- Y pacity to a temperature at least as high as saponification reaction temperature, maintaining said mixture at a temperature at least as high as action temperature until the saponification reaction is substantially complete, and continuously withdrawing the finishedlubricating grease soap stock. 6. The process of preparing a lubricating grease resulting soap concentrate with a major proportion of mineral oil to make a finished lubricating grease.

'7. The process of preparing a lubricating grease which comprises continuously mixing a saponlfiable material, a saponifying agent and a small amount of mineral oil at a temperature lower than saponification reaction temperature but suiflciently high to maintain the mixture in a semifluld or fluid state and to permit thorough mechanical mixing, continuously heating said mixture in a small stream to a temperature at least as high as saponification reaction temperature, maintaining said mixture at a temperature at least as high as reaction temperature until the s'aponification reaction is substantially complete, continuously withdrawing a finished-lubricating grease soap concentrate, and continuously compounding the resulting soapconcentrate with a major proportion of mineral oil to make a flnished lubricating grease,

8. A continuous process for making a calcium soap lubricating grease which comprises continuously mixing at about room temperature the following proportions of materials by weight:

continuously heating the resulting mixture to about 300-400 F. in a steam-heated pipe coil in a short time of less than about 10 minutes, continuously passing the heated mixture through a reaction-completing zone where the temperature of said mixture is kept at least as high as saponification temperature until the saponification is substantially complete, and continuously blending the resultant calcium soap stock with additional mineral lubricating oil, said materials being kept under a sufficient superatmospheric pres- Sure while hot to prevent undue vaporization of water.

9. The process of preparing a mineral lubricating oil grease which comprises mixing a saponiflable material and a saponification agent at a temperature lower than saponiflcation reaction temperature but sufl'lciently high to maintain the mixture in a semifluid or fluid state and to permit thorough mechanical mixing, continuously heating said mixture in a small stream to a temperature at least as high as saponification reaction temperature, maintaining said mixture at a temperature at least as high as reaction temperature -until the saponification is substantially complete, continuously withdrawing a soap stock, and compounding said resulting soap stock with a mineral lubricating oil to make a lubricating grease.

10. A continuous process for making a lubricating grease soap stock which consists essentially in continuously feeding into a mixing zone of relatively large capacity a saponifiable material, a saponifying agent in sufilcient amount to substantially completely saponify said saponifiable material, and a small amount of mineral oil, cont nuously mixing said materials in said mixing zone, with a mechanically operated agitator at a temperature lower than saponification reaction temperature but suificiently high to maintain the mixture in a semifluid or fluid state and to permit thorough mechanical mixing, continuously withdrawinga portion of said mixture from said mixing zone and continuously heating it in a once-through operation in a small stream in a heating zone of relatively small capacity to a temperature at least as high as saponification reaction temperature and maintaining said mixture at a temperature at least as high as saponification temperature until saponification is substantially complete.

ALAN BEERBOWER. JOHN C. zlMMER.

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