Fatty acid salt production
CROSS-REFERENCE TO RELATED APPLICATION 
     The subject matter of the present patent application is related to that disclosed in patent application Ser. No. 761,234, filed Sep. 17, 1991 now U.S. Pat. No. 5,191,097. 
     BACKGROUND OF THE INVENTION 
     Conventional cattle feeds such as corn and alfalfa often fail to provide sufficient energy for cattle, especially lactating dairy cattle during periods of heavy milk production. Feed containing a high proportion of corn also has a tendency to depress the milk fat content of the milk produced by such cattle. Fat is an excellent energy source, and it is known that if the proportion of fat in cattle food is increased, lactating dairy cattle produce high milk yields without draining their reserves of body fat and without diminishing the proportion of milk fat in the milk produced. 
     However, it has been found that if the proportion of fat in the diet of cattle exceeds about 2% of the total feed solids, the feed has toxic effects upon the microorganisms in the rumen of the cattle. It appears that fat reduces the growth rate or even kills certain microorganisms which digest fiber in the cow&#39;s rumen, thereby lowering fiber digestibility. This deleterious effect on the cow&#39;s rumen is particularly true of unsaturated fats. Although the decreased fiber digestion in the rumen is partially compensated by greater fiber digestion in the lower parts of the alimentary canal, such later fiber digestion produces a blend of different fatty acids than that which is produced by the digestion in the rumen, and the different blend of fatty acids is less suited to the cow&#39;s metabolism. 
     There has been a continuing need for new dietary supplements for animal feed which can be fed to ruminant animals without interfering with the rumen microorganisms. 
     U.S. Pat. Nos. 4,642,317; 4,826,694; 4,853,233; and 4,909,138 describe the incorporation of insoluble fatty acid salts in ruminant feed as a means of increasing the fat content of the feed without deleteriously affecting the ruminant digestion cycle. A feed additive such as fatty acid calcium salt functions as a rumen bypass product, and is subsequently metabolized in the abomasum or small intestine of the ruminant. 
     Accordingly, it is an object of this invention to provide a fatty acid salt composition which can function as a rumen bypass animal feed supplement, and permit a beneficial increase in the dietary fat content of the feed. 
     It is another object of this invention to provide an improved process for production of a fatty acid alkaline earth metal salt, utilizing a combination of basic compounds as a salt-forming reactant. 
     Other objects and advantages of the present invention shall become apparent from the accompanying description and examples. 
     DESCRIPTION OF THE INVENTION 
     One or more objects of the present invention are accomplished by the provision of a process for the preparation of a fatty acid salt product which comprises (1) forming an admixture of reactive ingredients comprising (a) at least one C 14  -C 22  fatty acid, (b) between about 0.8-1.2 equivalents of basic alkaline earth metal compound per equivalent of C 14  -C 22  fatty acid, (c) a quantity of basic alkali metal compound which provides an alkaline earth metal:alkali metal atomic ratio between about 2:1 and 20:1, and (d) between about 10-50 weight percent of an aqueous medium, based on the weight of fatty acid; and (2) recovering the salt product after completion of the exothermic salt-forming reaction. 
     In another embodiment this invention provides a fatty acid salt product in friable solid form which comprises (a) at least one C 14  -C 22  fatty acid salt of an alkaline earth metal; and (b) a basic alkali metal compound; wherein the atomic ratio of alkaline earth metal:alkali metal is between about 2:1 and 20:1. 
     The C 14  -C 22  fatty acid component of the salt-forming reaction medium consists of one or more saturated or unsaturated carboxylic acids such as those derived from beef and mutton tallow, lard, cottonseed oil, palm oil, and the like. 
     Palm fatty acid distillate is a commercial product produced by distilling the fatty acids present in natural palm oil. A distillate product typically has the following weight percent content: 
     
         ______________________________________                                    
Free fatty acids                                                          
                60-90                                                     
Water           &lt;1                                                        
Triglycerides   10-40                                                     
Unsaponifiables &lt;3                                                        
______________________________________                                    
 
    
     The iodine value is less than 54 and the melting point is about 45° C. The content of peroxides is below 10 milliequivalents of oxygen per kilogram. The fatty acids in the free fatty acids and the triglycerides consist of the following weight percent: 
     
         ______________________________________                                    
       Palmitic acid                                                      
                38-50                                                     
       Oleic acid                                                         
                35-40                                                     
       Linoleic acid                                                      
                 5-10                                                     
       Stearic acid                                                       
                3-6                                                       
       Lauric acid                                                        
                1-3                                                       
______________________________________                                    
 
    
     Beef tallow acids are available commercially as a byproduct obtained by alkaline extraction of waste beef fat and subsequent acidification, and normally contain the following weight percent of fatty constituents: 
     
         ______________________________________                                    
Free fatty acids                                                          
                60-90                                                     
Triglycerides   10-40                                                     
Water           &lt;1                                                        
Unsaponifiables &lt;3                                                        
______________________________________                                    
 
    
     The iodine value is less than 50 and the melting point is 40°-45° C. The content of peroxides is less than 10 milliequivalents of oxygen per kilogram. The fatty acids in the free fatty acids and in the triglycerides have the following weight percent content: 
     
         ______________________________________                                    
       Palmitic acid                                                      
                22-28                                                     
       Oleic acid                                                         
                38-44                                                     
       Linoleic acid                                                      
                3-6                                                       
       Stearic acid                                                       
                18-24                                                     
______________________________________                                    
 
    
     Because C 14  -C 22  fatty acids and glycerides are susceptible to atmospheric oxidation, it is advantageous to incorporate an oil-soluble antioxidant, and a chelating agent to bind any ferric, copper, zinc or other metal capable of catalyzing atmospheric oxidation. Suitable quantities for inclusion in the fatty acid bulk are about 0.03-0.08% of antioxidant, and about 0.05-0.3% of chelating agent, based on the weight of fatty acid. 
     Illustrative of preferred additives are butylated hydroxytoluene antioxidant and citric acid chelating agent. The chelating agent is added in an edible solvent such as propylene glycol to facilitate blending into the fatty acid. 
     The alkaline earth metal ingredient of the process is at least one member selected from the group consisting of basic calcium and magnesium compounds, such as oxides, carbonates, phosphates, hydroxides, and the like. The alkaline earth metal component preferably has a particle size which passes a 150 μ mesh screen. 
     The alkali metal ingredient is at least one member selected from the group consisting of basic sodium and potassium and lithium oxides, carbonates, bicarbonates, phosphates, hydroxides, and the like. 
     The invention process can be conducted in a batch reactor or as a continuous operation. The fatty acid, alkaline earth metal compound, alkali metal compound and aqueous medium can be admixed simultaneously, or the fatty acid and alkaline earth metal compound can be blended first and then combined with the alkali metal compound and aqueous medium. Alternatively, the alkaline earth metal and alkali earth metal compounds can be premixed, or the alkali metal compound can be pre-dissolved in the aqueous medium before the admixing of process ingredients. 
     In one method the fatty acid is heated to 80°-110° C., and then mixed with the alkaline earth metal compound. After the alkali metal compound and aqueous medium are added to the mixture, there is a short induction period which is followed by an exothermic salt-forming reaction. 
     The amount of aqueous medium employed is sufficient to support the salt-forming reaction, and preferably is vaporized as steam during the exothermic reaction period to yield a friable fatty acid salt product which in granule form is suitable for use as an animal feed supplement. 
     The use of a combination of alkaline earth metal and alkali metal compounds as the salt-forming reagent imparts several important advantages to the invention process. 
     As described in U.S. Pat. No. 4,826,694, the production of a fatty acid calcium or magnesium salt typically involves the use of about 20-80 percent excess of expensive calcium or magnesium basic reagent over the calculated stoichiometric quantity to insure an acceptable degree of fatty acid salt formation. In contradistinction, the basic alkaline earth metal compound in the present invention process is employed in a quantity between about 0.8-1.2 equivalents per equivalent of fatty acid, rather than a large stoichiometric excess. 
     Another important advantage of the invention process is in the efficiency of insoluble fatty acid alkaline earth metal salt formation. It appears that the alkali metal compound present in the aqueous reaction medium interacts readily with the fatty acid component to form an intermediate fatty acid alkali metal salt. Subsequently the fatty acid alkali metal salt interacts with the hydrated alkaline earth metal compound to produce the insoluble fatty acid alkaline earth metal salt product. If the alkali metal content is in an atomic ratio between about 1:5 and 1:2 of alkali metal:alkaline earth metal, the kinetically favorable alkali metal salt intermediate reaction converts essentially all of the fatty acid from free acid to alkali metal salt. Without the presence of the basic alkali metal ions, the kinetically less favorable reaction of alkaline earth metal ions with fatty acid tends to be incomplete and some residual unreacted fatty acid remains under the processing conditions. The presence of alkali metal ions facilitates the conversion of fatty acid via the alkali metal salt intermediate to its alkaline earth metal salt derivative. 
     The following Examples are further illustrative of the present invention. The components and specific ingredients are presented as being typical, and various modifications can be derived in view of the foregoing disclosure within the scope of the invention. 
    
    
     EXAMPLE I 
     This Example illustrates the continuous production of fatty acid calcium salt in accordance with the present invention. 
     The fatty acid component is a palm fatty acid distillate of the following composition: 
     
         ______________________________________                                    
       Lauric acid                                                        
                2.3%                                                      
       Palmitic acid                                                      
                49.9%                                                     
       Stearic acid                                                       
                5.4%                                                      
       Oleic acid                                                         
                35.0%                                                     
       Linoleic acid                                                      
                7.4%                                                      
______________________________________                                    
 
    
     The alkali metal component is introduced as an aqueous potassium carbonate solution. The concentration of the aqueous potassium carbonate solution is calculated to provide the required volume of water to the reaction medium, and provide potassium ions to satisfy a calcium:potassium atomic ratio of about 5:1. 
     The process is operated continuously with equipment which is essentially the same as described and illustrated with reference to FIG. 1 of U.S. Pat. No. 4,826,694 by W. McAskie. 
     Calcium oxide from a hopper and hot palm oil distillate (96° C.) from a supply line are mixed in predetermined proportions in a mixing pump. The aqueous potassium carbonate solution is added to the reactant admixture via a supply line. 
     The hydrated mixture is passe through a mixing pump and the resultant semi-liquid reaction medium at about 100° C. is discharged as a spread layer onto a continuously moving conveyor belt. Steam and carbon dioxide evolve from the conveyor transported reaction mass. 
     At the end of the conveyor belt solid lumps of reaction product fall through a sizing machine onto a second conveyor belt. In this conveying zone the salt-forming reaction and evolution of water proceed to completion. The essentially dry fatty acid calcium salt product is passed through a sifter, and collected in bags suitable for transportation and storage. 
     The residence time on the first conveyor is about 30 minutes, and the overall production time from reactant mixing to collection of the dry granulated product is about 2.5 hours. 
     The final product has a total fatty acid calcium salt content of 85 weight percent, a water content of about 3-5 weight percent, and an ash content of about 15 weight percent. 
     The invention fatty acid calcium salt product can be incorporated as a dietary supplement in cattle feed such as hay silage or corn silage, in a calculated quantity which will provide each animal about 100 grams per day of fatty acid salt. 
     EXAMPLE II 
     This Example illustrates the production of fatty acid calcium salt in a batch reaction medium in accordance with the present invention. 
     A batch reaction is conducted for the preparation of palm oil distillate calcium salt. The palm oil distillate is the same as described in Example I. 
     Calcium oxide (18.2 g, 0.325 M) and palm oil distillate (170 g, 0.65 M) are added to a 10% by weight solution of sodium carbonate (35 g) with stirring, and the admixture then is allowed to stand. 
     After a short induction period, an exothermic reaction commences and steam and carbon dioxide evolve from the semi-liquid reaction mass. The time period to solid formation is about 6 minutes.