US 2664429 A
Description (OCR text may contain errors)
Dec.'29, 1953 c. G. GQEBEL 2,664,429
METHOD FOR MANUFACTURING POLYMERIZED FATTY ACIDS Fild Aug. 15, 1949' EJECTOR 17 22 FLASH VENT TILL 5 (couosusm STEAM 20 "T DR'ER. r
MONOMER V 16 p e STORAGE P A r U w a AUTOCLAVE FURNACE INVENTOR. WZW
M g ,7 Am#a- Patented Dec. 29, 1953 UNITED stares areas METHOD FOR MANUFACTURING POLY- MERIZED FATTY ACIDS Charles G. 'Goebel, cincinnati ohio, assignonto Emery Industries, llnc cincinnati, Ohio, a corporation of ()hio Application August 15, 1949,:Serial No. 119,348
3 Claims. (01. 260-407) This invention relates to a method for effect- I ing the continuous polymerization of the polyunsaturated components of a mixture of fatty acids, and to their separation from the monounsaturated and saturated components thereof.
The general method of accom lishing this result involves the dimerization of the polyunsaturated components thereby increasing their boiling points, which facilitates subsequent separation of the respective components, as .by distillation.
The inventions disclosed and claimed in my ing the polyunsaturated components of the red.
oil and then separating them from the monounsaturated components. Application Ser. No. 681,765 discloses a method of manufacturing dimers by polymerizing the polyunsaturated components of fatty acids, such as linseed oil or soybean oil fatty acids, from which saturated and monounsaturated acids may then be removed if necessary or desirable. The present application is a continuation-in-part of each of these earlier applications.
' Each of these methods is characterized by the utilization of a relatively small amount of water maintained in solution in the fatty acids by application of pressure during a polymerization heat treatment of intensity which would otherwise be destructive to the carboxyl radicals of the fatty acids.
The chief problem in utilizing the methods of either of these inventions is to carry them out on a commercial scale without concomitant equipment of rodigious pro ortions and co t. The heating of large bodies of fatty acids to high temperatures with the use of ouantities of water which establish corresponding high pressures, and the holdin'r of the acids at such temperatures and pressures over prolonged periods of time, pose a problem of providing practical equipment which will be of reasonable proportions as to size and cost in relation to throughput.
Expensive corrosion resistant alloys are requiredfor the fabrication of pressure Vessels.
which permit the employment of temperatures and pressures of the order involved without ruinous corrosion and forbidding safety hazards, But
' vessels fabricated from such alloys of a size ade- .of substantially 1-5% water by weight.
quate to provide throughput which can be characterized in tons per day, rather than pounds per day, are enormously expensive, particularly if their utilization is limited to batch processing as distinguished from continuous processing.
It is the object of this invention to provide apparatus for continuously polymerizing the polyunsaturated components of a mixture of fatty acids and separating them as dimer acids from the less unsaturated components without prohibitive equipment costs. It is also the objective to provide a practical commercial process for effecting this dimerization and separation which permits a throughput which is high in relation to the amount of equipment and to the cost of equipment utilized in the operation.
This invention involves establishing a continuous flow of a stream of mixed fatty acids from a stock storage tank to individual storage tanks in which the separated components are received at I the end of the process. The apparatus comprises means for pumping under the pressure requisite at each stage of the operation and means for heating and cooling the stream at predetermined points in the cycle.
The fatty acids which are adapted to be used as raw materials, or starting materials, in this process are mixed fatty acids which contain polyunsaturated components and less unsaturated components such as the fatty acids of linseed, soybean, cottonseed, corn and fish oils. The fatty acids of all of these oils provide substantial yields of polymerized acids. On the other hand, red oil (commercial oleic acid) or the fatty acids of tallow, lard oil or the like may be processed, although in such case, the primary purpose would probably be the enhancement of the value of the fatty acids themselves, rather than the production of the polymerized acids which would be recovered as lay-products. For convenience in describing this invention, all of the fatty acids which contain polyunsaturated components and less unsaturated components will be termed the fatty acids of drying and semi-drying oils to distinguish them from fatty acids such as commercial stearic which is substantially devoid of polyunsaturants.
The stream of mixed fatty acids is first conditioned for polymerization by the introduction It is the function of the Water which is injected into the fatty acids to protect them against deterioration 01" decarboxylation which they otherwise would suffer under the temperatures employed in the operation. The amount of water, percent- 3 agewise, is not precisely critical and, of course, willwary in accordance with the permissible pressures for which the equipment is designed, the greater the percentage of water the greater the resultant pressure and vice versa. The apparatus components of the system, including the pumps, are adapted to operate at pressures which, at polymerizing temperatures, will pre vent vaporization of the water, so that the water remains in the fatty acids and aiiords its full protective efiect.
Quantities of water substantially greater than 5% have not been found to be desirable since they do not confer additional protective benefits and they do increase the operating pressures which are required to hold them in liquid condition or in solution in the fatty acids. On the other hand, substantially less than 1% by: weight of water based on the weight of the fatty acids may be insufiicient to accomplish the desired inhibitory result. Best, operation is obtained by selecting a percentage of water within approximately the range indicated and then, adjusting the water content of the fatty acids being treated to maintain the water content selected.
Preferably the fatty acids are dried under vacuum to such degree that their moisture content is of no significance from the point of view of the generation of steam pressure within the system, and then the predetermined amount of water is added. The maintenance or" the predetermined content of water in the flowing stream insures the required stability of opera tional conditions and the continuation of the chosen relationships of temperature, pressure and duration of treatment. for each quota of the stream. If the. stream of fatty acids were not first dehydrated it might vary in moisture content. and this would unbalance. the operating conditions. Moisture contents above the expected might even endanger the equipment itself as a result of development of excessive pressure.
The Watered stream of fatty acids is next heated under pressure to effect polymerization after which the pressure is released to flash distill the monomers from the polymers. Considerations pertinent to the relationship. of the preferred method and. themost economical apparatus are several and interrelated. Although. polymerization commences slowly somewhere in the neighborhood of 250 0., with most fatty acids, the rate of polymerization substantially doubles with each to C. temperature rise. It follows that at substantially 400 C. the time required for polymerization is but a fraction of that necessary at 250 C. Thus the size of the equipment required to hold the body of fatty acids being polymerized for the time requisite decreases in inverse ratio to the temperature utilized.
Since equipment suitable for holding the hot corrosive acids under high pressure must necessarily be stainless steel or the equivalent, and relatively thick walled, it is desirable, to. mini:- mize its size. and hence its overall cost in order to reduce the fixed cost component of each unit.
of throughput. But, on the other hand, it is futile to attempt to reduce the fixed cost component by the use of high temperatures if the saving is nullified by the, added operating cost in.- herently involved in the utilization of the higher temperatures.
I solve this problem by heating the stream of fatty acids to a polymerizing temperature above that which is. requisite later to. flash distill the.
stream, but chill it after polymerization to distillation temperature by heat exchange with the infeed, whereby the high temperature and concomitant economical equipment are had at no operating cost greater than that represented by the radiation losses, which may be minimized by appropriate utilization of insulation.
Instead of utilizing the heat not required for distillation to preheat the infeed, it may be utilized to generate the steam required for other steps of the process, such as stripping steam or the operation of vacuum ejector-s or even the high temperature steam for a counter-current fatty acid splitting tower. By this device, the stream or. fatty acids is polymerized at optimum temperature and flash distilled at a lower, but also optimum, temperature. By this method, I avoid flash distillation temperatures which might tend to distill over the polymer with the monomer or which might tend to be destructive to the acid radicals after the release of pressure, which permits the moisture content to volatilize.
While processing of the stock through the polymerizer and dash still preferably proceed as sequential steps to which the continuous stream of stock is subjected, the polymerized component may also be recycled through the polymerizer, if desired, whereby the material passing through the polymerizing zone more than once becomesv more highly polymerized than would otherwise be the case.
The apparatus of this invention is illustrated diagrammatically in the accompanying flow sheet according to which the material to be processed is drawn from feed tank I by pump 2 which forcesit through heat exchangers 3 and 4 and drier 5. In heat exchanger heat is withdrawn from the dimerized acids which constitute the still residue, and in heat exchanger heat. iswithdrawn from the monomer acidvapors resulting from distillation. Drier 5 is utilized for the. purpose of insuring a standard moisture content for the stream of, material to be treated.
The material is fed from drier 5 to pump 5 which forces it under high pressure through the apparatus in which the polymerization is accomplished. A pump 1, preferably a metering pump, forces a small but measured stream of water into the material discharged from pump 6 to provide a. Water content of substantially l to 5%. After this the material enters heat exchanger .l in which it withdraws heat from the material which has been polymerized, but has not yet been distilled.
The material being processed then passes from the heat exchanger through a furnace iii in which it is heated to. a temperature approximating but not equalling, the maximum temperature to be utilized in the process. From furnace It the fatty acids pass into autoclave H which is provided with baiiies (not shown) which maintain the stream like character of the flow. The dimerization is completed in the autoclave and, since this is, an. exothermic reaction, the temperature of the fatty acids tends to rise above the temperature to which they were. elevated in furnace Iii. From autoclave H the fatty acids may be conducted by line ba .1 to heat exchanger 9 Where they are cooled by the incoming feed directed to furnace id. Preferably the amount of heat removed is sufiicient to reduce the temperature of the fatty acids to just that amount necessary for subsequent flash distillation. In order to control the temperature of the fatty acids. to be subjected to the. flash distillation, heat transfer device 9 may be bypassed by line I2, so that the amount of fatty acids subjected to the cooling action can be proportioned, in relation to the/fatty acids fed directly to the flash still, by control valves It and I5. Thisarrangement provides flexibility adapting the equipment for the utilization of various fatty acid stocks and various polymerization temperatures.
From autoclave H and'exchanger 9, the fatty acids are delivered through pressure control valve it which maintains pressure in the system between it and pump 5. This pressure must'at all times be suff cient to hold the moisture present in solution or in the liquid state (Whichever it is) to protect the carboxylic radicals of the fatty acid from the decomposition temperature tends to induce.
After passing throu h pressure control valve which the high it, the fatty acids are fed into fla h still if. The
monomer acids, that is, the unpolvmerized fatty acids, volatilize or vaporize rapidly, i. e., they flash. In other words, they vaporize to be ultimately recovered as condensate and the hi her boiling point polymer or dimer acids are withdrawn as still residue. The flash still I! is operated under a vacuum and steam is introduced into its lower portion by means of line I 8 to strip unpolymerized fattv acids from the still residue. This residue is withdrawn from the bottom of the still and conducted to heat exchange device 3 where it is cooled by the fatty acid infeed, after which it is conducted to storage container I9.
The distillate is conducted from the hash still I! to the heat exchanger 4 where it supplies heat to theincoming feed of fatty acids. The dis tillate then passes to condenser'zu from which it is'delivered to stora e tank 2| The condenser is provided with cooling water b lines 22 and 23 which are utilized to maintain the condenser at the desired operating temperature. An ejector or evacuator 24 is connected with condenser 2H and is utilized to draw a vacuum on the condenser and the flash still. In accordance with accepted distillation practices, it is desirable to maintain as reat a vacuum as possible in the flash still within the limits of economical size of the evacuator or eductor. Under less favorable vacuum conditions it may be necessary to increase the temperature of the stock in the flash still in order to effect volatilization of some of the less volatile monomeric materials, but, in this respect, it should. be remembered that the protective water is no longer present in the stock and it is desirable therefore to hold the temperature as low as possible in order to avoid deterioration or decarboxylation of the products during dist llation.
The exact temperature and time conditions employed for effecting the polymerization may be governed by the nature of the infeed stock, and of course, the specifications of the equipment which is available. In general the time during which the fatty acids are subjected to the polymerizing temperature will be governed by the nature of the fatty acid stock and the degree of polymerization which is desired, as well as by the actual polymerizing temperature. Thus, the polymerizing operation may be completed to the extent desired in as little as approximately 20 minutes, or the processing may be continued for as long as two hours or more. Since the polymerization is conducted in a ba ed autoclave or elongated conduit, the time for polymerization may be controlled conveniently by adjustment of the rate of flow of material through the system.
By way of illustration, but not by way of limitation, polymerization may proceed, for example, at a temperature of approximately 385 C. under a pressure of 600 lbs. per square inch for a period of from 20 to 60 minutes. There is also considerable latitude in the exact conditions under which flash distillation is conducted. For example, with a polymerizing temperature of 350 to 400 C., the dimer-monomer mixture may be cooled to within the range of 260 to 360 C. before flash distilling. Preferably, but not necessarily, flash distillation may occur under an absolute pressure of substantially 10 millimeters of mercury, and. monomer vapors ar stripped later from the residue by introducing saturated steam at approximately (3., in the proportion of substantially 1 1b. of steam to each 10 to 25} lbs. of residue,
While polymerization temperatures in excess of 400 C. have not been mentioned specifically, itis to'be understood that temperatures up to those'destructive to the fatty acids themselves may be employed provided the water content of the fatty acids is increased proportionately to provide proper protection against decarboxylation. However, 375 to 400 C. would appear to constitute the operational range which is optimum at present in view of the limitations of presently available materials.
Obviously, precise operating conditions must bedetermined in relation to the nature of the fatty acid stock beina treated and the end products desired. For instance, the temperature proper for flash distillation necessarily varies with-the ratio of monomer to polymer after completion of polymerization. The greater the proportion of monomer the greater must be the total available heat necessary to distill it,
The disclosure has been made primarily in relation to the processing of fatty acids such as those obtained from soybean or cottonseed oil, i. e., acids in which the prevailing chain length is 18 carbon atoms. For acids of greater chain length distillation temperatures should be properly adjusted. Likewise, if the process be practiced to remove very small percentages of polyunsaturants from the acids so that the monomers are present in predominant proportions, then each distillation temperature must be individually calculated. Since polymerization is an exothermic reaction, the increase in temperature due to it must be taken into account in all calculations.
While it might be desirable in some cases to conform the specifications of a given polymerization plant to the requirements of the processing of a specific fatty acid stock, the apparatus of this invention has the virtue of flexibility, that is, a sin' le piece of equipment may be used to process many types of raw material by appropriate selection of operatin conditions. While waterin the fatty acids may be accomplished at any time prior to their subjection to high heat, even before introducinq them into the equipment, it is believed to be preferable to provide in the equipment for the dehydration of the fatty acids under atmospheric or subatmospheric pressure, followed by watering. It is also preferable to provide the equipment with variable speed pumps and to have the pressure control valve adjustable. These arrangements, together with temperature control of the furnace and the adjustable by-pass of the heat exchanger J which is located between the autoclave and the flash still, provide a flexibility which permits one piece or equipment to handle many types of raw material.
In any case, the size of the polymerization closure may be calculated to provide the lowest equipment cost for each unit of throughput which available construction materials permit,
without regard to operating costs. This is made possible by the utilization of polymerization temperatures above those requisite for flash distillation and the reuse of the excess heat, whereby utilization of the low cost equipment entails no increased operating cost, save for radiation losses.
Having described my invention, I claim:
1. The method of removing polyunsaturated components as dimer acids from a mixture of fatty containing polyunsaturated fatty acids, said process comprising establishing a flowing s ream of said mixed fatty acids, adding to said flowing stream substantially from one to five per cent water, heating said flowing stream to a temperature or" from substantially 350 to 400 C., while maintaining a pressure sufficient to retain said Water in solution in the fatty acids to inhibit decarboxylation of said fatty acids, holding said stream of fatty acids at said polymerizing temperature for a period of substantially twenty minutes to an hour, cooling said stream of fatty acids to substantially 260 to 360 0., releasing the pressure on said stream of fatty acids and flash distilling the unpolymerized components as distillate and recovering the polymerized components as a residue.
2. The method or heat treating a mixture of fatty acids containing polyunsaturants which comprises establishing a flowing stream of said fatty acids, adding water to said stream in amount sufficient to inhibit decarboxylation thereof during heating, and subjecting the fatty acids in said stream to a temperature of substantially 350 to 400 C., under a pressure of 300 6 to GOO-lbs. per square inch pressure, for a period of time suiiicient to effect polymerization of polyunsaturated components in said stream, and then cooling the stream and flash distilling unpolymerized components from it.
3. The method of heat treating' a mixture of fatty acids containing polyunsaturants which comprises establishing a flowing stream of said fatty acids, adding water to said stream in amount sufficient to inhibit decarboxylation thereof during heating, and subjecting the fatty acids in said stream to a temperature of sub stantially 350 to 400 C., under a pressure of 300 to 600 lbs. per. square inch pressure for a period of time sufiicient to effect polymerization. of polyunsaturated components in said stream, and then cooling the stream and flash distilling unpolymerized components from it, at an absolute pressure not substantially exceeding 10 millimeters of mercury.
CHARLES G. GOEBEL.
References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 414,936 Burcy Nov. 12, 1889 1,474,772 Foster 1; Nov. 20, 1923 1,594,024 Soule July 27, 1926 1,828,691 Stransky et a1. Oct. 26, 1931 1,856,021 Bentel Apr. 26, 1932 2,006,186 Stines June 25, 1935 2,109,347 Beekhuis Feb. 22, 1935 2,054,096 Potts et a1. Sept. 15, 1936 2,086,808 Kallam July 13, 1937 2,152,665 Rosenthal Apr. 4, 1939 2,224,984 Potts et a1 Dec. 17, 1940 2,260,111 Caldwell Oct. 21, 1941 2,310,986 Murphy Feb. 16, 1943 2,435,745 Ittner Feb. 10, 1948 2,482,761 Goebel Sept. 27, 1949 2,489,713 Leaders Nov, 29, 1949 2,495,071 Mills Jan. 17, 1950