Patent GB-808634-A (GB)
Title: Preparation of mixed glycerol ester compositions
IPC: C11C3/10
Filed: 1956-06-20
Abstract: Mixed glycerol esters (i.e. glycerides containing at least one lower acyl radical and at least one higher acyl radical) are prepared by a cyclic process comprising reacting together a triglyceride containing higher acyl radicals having at least 8 carbon atoms and a hydroxy radical-containing reactant which is either a mixture of glycerine with a triglyceride containing lower acyl radicals having from 2 to 6 carbon atoms or a glycerol partial ester composition comprising glycerine and a mixture of lower acylated glycerine, the reaction being effected in the presence of a basic transesterification catalyst, subjecting the resulting reaction mixture to a first vacuum distillation to separate therefrom the remaining portions of the hydroxyl radical-containing reactant as distillate, subjecting the residue to thin-film vacuum distillation to separate a distillate containing a substantial amount of a mixed glycerol ester (as above defined), combining the residue from the second distillation with the first distillate and with additional amounts of triglyceride containing higher acyl radicals and hydroxylradical-containing reactant, and repeating the sequential steps.  Suitable higher acylated triglycerides include trilaurin, tripalmitin, triolein, trilinolein and tristearin and such naturally occurring triglycerides as occur in lard, beef tallow, cottonseed oil, soyabean oil, peanut oil and coconut oil. Suitable lower acylated triglycerides include triacetin, tripropionin, tributyrin, triisobutyrin, trivalerin and tricaproin.  The lower acylated glycerol partial ester may be obtained by reacting glycerine and a lower acylated triglyceride in the presence of an interesterification catalyst, or by reacting glycerine and a lower acyl anhydride.  A typical premixture comprises monacetin, diacetin, triacetin and glycerine.  Suitable transesterification catalysts include alkali and alkaline earth metals, hydrides, glyceroxides, hydroxides and soaps, preferably in amounts from 0.001 to 1 per cent, particularly 0.005 to 0.1 per cent, by weight, based on the total weight of reactants.  Elevated temperatures of at least 180 DEG  C. may be used, preferably 230 DEG to 260 DEG  C.  The reaction time varies from 15 minutes to 6 hours. By utilizing thin-film high-vacuum distillation apparatus of the centrifugal type or falling film type it is possible to separate as first distillate only the unchanged glycerine and lower acylated glycerides and as second distillate a mixed glycerol ester having a higher acyl radical, a lower acyl radical and a hydroxyl radical, such mixed esters being called "lower acylated monoglycerides."  A typical mixed ester of this type may be obtained by reacting a 50 per cent acylated glycerine premixture with fully hydrogenated lard in a ratio of 4 to 1 for 1.5 hours at 250 DEG  C. in the presence of 0.8 per cent of calcium hydroxide.  The first distillate is removed at temperatures up to 135 DEG  C. at 15 microns.  The acylated monoglyceride is separated at temperatures up to 185 DEG  C. at 15 microns.  The residue from the second distillation may be distilled to separate a mixed glycerol ester, having a lower acyl radical and two higher acyl radicals (acylated diglyceride), at temperatures up to 220 DEG  C. at 15 microns.  These conditions may be varied somewhat in accordance with known vacuum distillation techniques. Alternatively the conditions may be arranged so that the first distillate contains unchanged hydroxyl radicalcontaining reactant and acylated monoglycerides while the second distillate contains acylated diglycerides, or the conditions may be so arranged that the second distillate contains both acylated monoglycerides and acylated diglycerides.  In the preparation of these compositions, the molar ratio of higher acyl radicals to the sum of lower acyl radicals and hydroxyl radicals in the reaction mixture may vary from 1/10 to 10/1 and the molar ratio of lower acyl radicals to hydroxyl radicals in the reaction mixture may vary from 1/10 to 10/1 .  A preponderance of a particular type of mixed glycerol ester may be obtained by varying these ratios.  The withdrawal of the reaction mixture from the reaction zone, the distillation steps, the recycle of first distillate and second distillation residue to the reaction zone and the addition of make-up materials to the reaction zone may all be effected continuously.  Preferably the make-up materials and second distillate comprise equal amounts of materials and have substantially equal proportions of higher acyl radicals, lower acyl radicals and hydroxyl radicals.ALSO:Mixed glycerol esters (i.e. glycerides containing at least one lower acyl radical and at least one higher acyl radical) are prepared by a cyclic process comprising reacting together a triglyceride containing higher acyl radicals having at least 8 carbon atoms and a hydroxyl radicalcontaining reactant which is either a mixture of glycerine with a triglyceride containing lower acyl radicals having from 2 to 6 carbon atoms or a glycerol partial ester composition comprising glycerine and a mixture of lower acylated glycerine, said reaction being effected in the presence of a basic transesterification catalyst, subjecting the resulting reaction mixture to a first vacuum distillation to separate therefrom the remaining portions of said hydroxyl radicalcontaining reactant as distillate, subjecting the residue to thin film vacuum distillation to separate a distillate containing a substantial amount of a mixed glycerol ester (as above defined) combining the residue from the second distillation with the first distillate and with additional amounts of said triglyceride containing higher acyl radicals and said hydroxylradical-containing reactant, and repeating said sequential steps.  Suitable higher acylated triglycerides include trilaurin, tripalmitin, triolein, trilinolein and tristearin and such naturally occurring triglycerides as occur in lard, beef tallow, cottonseed oil, soybean oil, peanut oil and coconut oil. Suitable lower acylated triglycerides include triacetin, tripropionin, tributyrin, triisobutyrin, trivalerin and tricaproin.  The lower acylated glycerol partial ester may be obtained by reacting glycerine and a lower acylated triglyceride in the presence of an interesterification catalyst, or, by reacting glycerine and a lower acyl anhydride.  A typical premixture comprises monacetin, diacetin, triacetin and glycerine.  Suitable transesterification catalysts include alkali and alkaline earth metals, hydrides, glyceroxides, hydroxides, and soaps, preferably in amounts from 0.001 to 1 per cent, particularly 0.005 to 0.1 per cent, by weight based on the total weight of reactants. Elevated temperatures of at least 180 DEG  C. may be used, preferably 230 DEG  to 260 DEG  C.  The reaction time varies from 15 minutes to 6 hours.  By utilizing thin film high-vacuum distillation apparatus of the centrifugal type or falling film type, it is possible to separate as first distillate only the unchanged glycerine and lower acylated glycerides and as second distillate a mixed glycerol ester having a higher acyl radical, a lower acyl radical and an hydroxyl radical, such mixed esters being called "lower acylated monoglycerides."  A typical mixed ester of this type may be obtained by reacting a 50 per cent acylated glycerine premixture with fully hydrogenated lard in a ratio of 4 to 1 for 1 1/2 hours at 250 DEG  C. in the presence of 0.8 per cent of calcium hydroxide.  The first distillate is removed at temperatures up to 135 DEG  C. at 15 microns.  The acylated monoglyceride is separated at temperatures up to 185 DEG  C. at 15 microns.  The residue from the second distillation may be distilled to separate a mixed glycerol ester, having a lower acyl radical and two higher acyl radicals (acylated diglyceride) at temperatures up to 220 DEG  C. at 15 microns.  These conditions may be varied somewhat in accordance with known vacuum distillation techniques.  Alternatively the condition may be arranged so that the first distillate contains unchanged hydroxyl radical-containing reactant and acylated monoglycerides while the second distillate contains acylated diglycerides, or the conditions may be so arranged that the second distillate contains both acylated monoglycerides and acylated diglycerides.  In the preparation of these compositions, the motor ratio of higher acyl radicals to the sum of lower acyl radicals and hydroxyl radicals in the reaction mixture may vary from 1/10 to 10/1 and the molar ratio of lower acyl radicals to hydroxyl radicals in the reaction mixture may vary from 1/10 to 10/1 .  A preponderance of a particular type of mixed glycerol ester may be obtained by varying these ratios.  The withdrawal of the reaction mixture from the reaction zone, the distillation steps, the recycle of first distillate and second distillation residue to the reaction zone and the addition of make-up materials to the reaction zone, may all be effected continuously. Preferably the make-up materials and second distillate comprise equal amounts of materials and have substantially equal proportions of higher acyl radicals, lower acyl radicals and hydroxyl radicals.