Enzymatic process for preparing intermediates useful as precursors to ester quaternary ammonium compounds

Abstract

The present invention provides a method for preparing a triethanolamine / fatty acid ester composition of a modified ratio by treating a conventional triethanolamine fatty acid ester composition with a hydrolase. Also provided is a novel mixture of monoesters, diesters and triesters of triethanolamine and fatty acids that can be used to prepare cationic surfactants useful in fabric softening applications. On the one hand, the method increases the triester portion without significantly affecting the amount of monoesters and unesterified species, which in turn increases flexibility in the formulation of the corresponding fabric softening composition.

Description

Technical Field

[0001] The present invention relates to the field of fabric softeners. In particular, it relates to an enzymatic process for preparing intermediates useful in the preparation of cationic surfactants. Background Art

[0002] Ester quaternary ammonium compounds ("quats") based on triethanolamine are widely used as fabric softening agents in rinse-cycle fabric softeners. These materials are usually prepared from triethanolamine and fatty acids or fatty acid methyl esters, using insufficient amounts of fatty acids compared to the available number of hydroxyl groups. The use of such insufficient but defined amounts of fatty acids enables processable ester quat mixtures to be obtained, since these water-insoluble materials are usually formulated as water-based emulsions. Thus, the acid-catalyzed esterification results in a statistical distribution of esters (monoesters, diesters and triesters) as well as some unreacted triethanolamine, which can be easily formulated after quaternization. However, insufficient amounts of fatty acids limit the fat content of the product and can thereby result in low fabric softening efficiency in the balance of competing properties of dispersibility in water and performance as a fabric softening agent. The use of higher amounts of fatty acids results in high levels of triesters, but also in correspondingly low levels of triethanolamine and monoesters, which makes emulsion formation of the corresponding quaternary ammonium compounds problematic without the aid of additional processing aids.

[0003] A method of varying the ester ratio (and thereby the ester quat ratio) to increase the amount of triester while maintaining triethanolamine and monoester levels would be advantageous. Summary of the invention

[0004] The invention is as set forth in the claims. In one embodiment, the invention provides a method for preparing a triethanolamine / fatty acid ester composition of a modified ratio by treating a conventional triethanolamine fatty acid ester composition with a hydrolase. The conventional triethanolamine ester composition is a mixture of triethanolamine and an ester of formula (II), (III) and (I):

[0005]

[0006] wherein each R is independently selected from linear and branched, saturated and unsaturated C 11 -C 23Hydrocarbyl groups. The molar ratios of these four components are generally determined by the stoichiometry of the reaction in which the mixture is formed, but are limited by the statistical properties of the products derived from non-selective acid catalysts. In conventional methods and resulting mixtures, the stoichiometry is generally 1.5 to 2 equivalents of fatty acid / triethanolamine. As described herein, the present invention provides a novel enzymatic method to prepare a novel triethanolamine / fatty acid ester mixture, which is more highly desired for use in the preparation of fabric softeners. In particular, increasing the triester content of conventionally derived ester quaternary ammonium compounds results in a reduction in monoesters and unesterified materials, which results in ester quaternary ammonium compounds being difficult to formulate (see, e.g., U.S. Pat. No. 9,388,367) and requiring processing aids to provide adequate dispersion. Therefore, it is generally accepted that high triester ester quaternary ammonium compounds generally perform poorly. However, methods for increasing the triester portion without significantly affecting the amount of monoesters and unesterified species are of interest, thereby adding greater flexibility in the formulation of corresponding fabric softening compositions. DETAILED DESCRIPTION

[0007] In one embodiment, the present invention provides a method for increasing the molar proportion of the triester of formula (I) in a mixture,

[0008]

[0009] The mixture comprises (i) triethanolamine and (ii) a fatty acid ester having the formula (II), (III) and (I):

[0010]

[0011] wherein each R is independently selected from linear and branched, saturated and unsaturated C 11 -C 23 The method comprises contacting the mixture with a hydrolase. In another embodiment, the method results in increasing the molar ratio of triesters of formula (I) while reducing the molar ratio of fatty acid esters of formula (II) and / or (III).

[0012] In certain embodiments, treating such a triethanolamine / fatty acid ester mixture with an enzyme results in a change in the ester ratio, wherein the combined amounts of triethanolamine and monoester are relatively unchanged (changed by 3 mole % or less), but the diester is reduced by at least 4 mole %, and the triester is increased by at least 4 mole %. Thus, in another embodiment, the present invention provides a method of increasing the molar ratio of triester of formula (I) in the mixture, while the molar ratio of the combination of triethanolamine and fatty acid ester of formula (II) is neither reduced nor increased by more than 3 mole %, while the fatty acid ester of formula (III) is reduced by at least 4 mole % (but not more than 15 mole %), and the fatty acid ester of formula (I) is increased by at least 4 mole % (but not more than 15 mole %),

[0013]

[0014] The mixture comprises (i) triethanolamine and (ii) a fatty acid ester having the formula (II), (III) and (I):

[0015]

[0016] wherein each R is independently selected from linear and branched, saturated and unsaturated C 11 -C 23 Hydrocarbyl groups,

[0017] The method comprises contacting the mixture with a hydrolase.

[0018] The resulting mixture is a novel result of the enzymatic equilibrium reaction of the triethanolamine / fatty acid ester mixture; this mixture is particularly desirable in the case where the relative proportion of the more desirable triesters is increased without substantially affecting the monoesters (and unesterified materials). Thus, the method provides a novel mixture of triethanolamine / fatty acid esters, the triester concentration of the mixture being increased, and in other embodiments, the diester concentration is also reduced. Therefore, in another embodiment, the present invention provides a mixture comprising:

[0019] a. triethanolamine in a ratio of about 5 to about 15 mol% based on the sum of a, b, c and d;

[0020] b. Fatty acid monoester of formula (II)

[0021]

[0022] The ratio thereof is about 22 to about 30 mol% based on the sum of a, b, c and d;

[0023] c. Fatty acid diester of formula (III)

[0024]

[0025] The proportion thereof is about 38 to about 45 mol % based on the sum of the combinations a, b, c and d, and

[0026] d. Fatty acid triesters of formula (I)

[0027]

[0028] The proportion thereof is from about 17 to about 31 mole % based on the sum of the combination a, b, c and d, wherein the total mole % of a, b, c and d is equal to 100%;

[0029] wherein each R is independently selected from linear and branched, saturated and unsaturated C11 -C 23 Hydrocarbyl group.

[0030] In this embodiment, the mixture may also be characterized as having an average degree of substitution (DS) of the hydroxyl groups of triethanolamine and the esters of formula (II), (III), and (I) of about 1.5 to about 1.9.

[0031] In a further embodiment, the present invention provides a mixture comprising:

[0032] a. triethanolamine in a ratio of about 7 to about 15 mol% based on the sum of a, b, c and d;

[0033] b. Fatty acid monoester of formula (II)

[0034]

[0035] The ratio thereof is about 23 to about 30 mol% based on the sum of a, b, c and d;

[0036] c. Fatty acid diester of formula (III)

[0037]

[0038] The ratio thereof is about 38 to about 45 mol% based on the sum of the combinations a, b, c and d; and

[0039] d. Fatty acid triesters of formula (I)

[0040]

[0041] The proportion thereof is from about 17 to about 27 mole % based on the sum of the combination a, b, c and d, wherein the total mole % of a, b, c and d equals 100%;

[0042] wherein each R is independently selected from linear and branched, saturated and unsaturated C 11 -C 23 Hydrocarbyl group.

[0043] In this embodiment, the mixture may also be characterized as having an average degree of substitution (DS) of the hydroxyl groups of triethanolamine and the esters of formula (II), (III), and (I) of about 1.5 to about 1.75.

[0044] The novel mixtures mentioned above can then be converted into various subsequent materials as is known in the literature for triethanolamine esters. Of particular interest is the alkylation of the nitrogen to provide a cationic surfactant. Such alkylation can be carried out with dialkyl sulfates such as dimethyl sulfate or diethyl sulfate, benzyl halides such as benzyl chloride and many other substances known in the art. The most widespread use of cationic surfactants derived from triethanolamine esters is as hair care agents and particularly as laundry fabric softeners for rinse cycles.

[0045] Examples of the compounds represented by formula (I), (II) and (III) include those wherein

[0046]

[0047] The moiety (hereinafter "RCO") is lauroyl, myristoyl, palmitoyl, stearoyl, oleoyl, linoleoyl or a mixture thereof, or a C 2-hydroxy-1-hydroxy-1-ol derived from an animal fat, vegetable oil, nut oil or seed oil. 12 To C 24 In one embodiment, the compounds of formula (I), (II) and (III) wherein RCO is a mixture are derived from fatty acids derived from one or more of palm oil, tallow and partially hydrogenated tallow.

[0048] As used herein, the term "hydrocarbyl" refers to a monovalent hydrocarbon group. The term includes groups such as alkyl, alkenyl, and alkynyl. The hydrocarbyl group R can be substituted or unsubstituted; branched or straight chain; and saturated, monounsaturated, or polyunsaturated. The hydrocarbyl group R can also be a substituted or unsubstituted C3-C8 cycloalkyl group.

[0049] In one embodiment, R is selected from substituted or unsubstituted, branched or linear saturated C5-C 19 Alkyl; substituted or unsubstituted, branched or linear C5-C 17 Alkenyl; substituted or unsubstituted, branched or straight-chain C5-C 17 diene group; and a substituted or unsubstituted C3-C8 cycloalkyl group.

[0050] The hydrocarbon group of R may be substituted by 1 to 5 substituents selected from the group consisting of C1-C6 alkoxy, C1-C6 carboxyl, C1-C 15 Aminocarbonyl, C1-C 15 acylamino, cyano, C2-C6 alkoxycarbonyl, C2-C6 alkanoyloxy, hydroxyl, aryl, heteroaryl, thioether, C2-C 10 Dialkylamino, C3-C 15 Trialkylammonium, chloride and bromine.

[0051] As used herein, the terms "C1-C6 alkoxy", "C2-C6 alkoxycarbonyl" and "C2-C6 alkanoyloxy" are used to represent the radicals corresponding to the structure -OR 2 、 -CO2R 2 and-OCOR 2 A group in which R 2 is a substituted or unsubstituted C1-C6 alkyl group.

[0052] As used herein, the term "C1-C 15 Aminocarbonyl" and "C1-C 15 "Acylamino" is used to represent the structure corresponding to -NHCOR 3 and-CONHR 3 The group whose R 3 is substituted or unsubstituted C1-C 15 Alkyl group.

[0053] As used herein, "degree of substitution" or "DS" refers to the total average degree of hydroxyl moieties of a mixture of triethanolamine and esters of formula (II), (III) and (I) present as ester groups (as fatty acid esters). For example, a maximum DS is 3.0, as it represents a fully esterified triethanolamine substrate, while a DS of 2 represents an average esterification of two of the three hydroxyl groups on the triethanolamine substrate; similarly, when converted to the corresponding quaternary ammonium compound ("quat"), the DS will correspond to the average esterification on the triethanolamine substrate that remains intact during the alkylation reaction to form the quat.

[0054] Conventional methods are used to prepare the above-mentioned starting mixture. The mixture is prepared by esterification of triethanolamine with a selected (but usually insufficiently substituted, i.e., less than three molar equivalents of fatty acid are usually used in the reaction to form an ester) amount of fatty acid to provide a mixture of unreacted triethanolamine, monoester (II), diester (III) and triester (I). The reaction can be carried out at high temperatures without a catalyst (i.e., autocatalysis) or using a strong acid catalyst as known in the art. Typically, high temperatures (up to about 200° C.) are used accompanied by removal of water by distillation to provide a shorter reaction time. A variety of strong acid catalysts have been shown in the art (e.g., U.S. Patent No. 6,004,913, incorporated herein by reference). Perhaps the most effective catalyst is hypophosphorous acid because it catalyzes at low levels and also minimizes color formation. The strong acid catalyst can be retained in the product mixture, or, if desired, can be removed by alkaline treatment before enzymatic equilibrium. Minimal residual fatty acids are such a result-usually less than an acid value of 5.

[0055] The ratios of products obtained from such esterification are generally statistical mixtures, depending on the ratio of fatty acid to triethanolamine. The variation of product composition relative to the ratio of starting materials is known in the literature and for convenience the results at different DS levels are presented in Table 1.

[0056] Table 1: Triethanolamine ester compositions via acid catalyzed esterification

[0057]

[0058] In one aspect, the process of the invention comprises enzymatic equilibration of the product mixture from the first step of the process (conventional acid-catalyzed esterification).

[0059] In certain embodiments, the enzymatic equilibration process of the present invention may be performed at a temperature of about -100°C to about +100°C, about 20-90°C, or about 50-80°C.

[0060] In one embodiment, the enzymatic equilibration process is carried out in the absence of a significant amount of solvent. If a solvent is used, the solvent can be selected from a cyclic or non-cyclic ether solvent, such as diethyl ether, diisopropyl ether, tert-butyl methyl ether or tetrahydrofuran; an aromatic hydrocarbon, such as benzene, toluene or xylene; an aliphatic or alicyclic saturated or unsaturated hydrocarbon, such as hexane, heptane, cyclohexane or limonene; a halogenated hydrocarbon, such as dichloromethane, dichloroethane, dibromoethane, tetrachloroethylene or chlorobenzene; a polar aprotic solvent, such as acetonitrile, dimethylformamide or dimethyl sulfoxide; or a mixture thereof.

[0061] The enzymatic balancing process uses a hydrolase (e.g., a protease, a lipase, or an esterase); in one embodiment, the enzyme is a lipase. Examples of these lipases include, but are not limited to, Lipase PS (from Pseudomonas Pseudomonas sp ), Lipase PS-C (from Pseudomonas immobilized on ceramic), Lipase PS-D (from Pseudomonas immobilized on diatomaceous earth), Lipoprime 50T, Lipozyme TL IM, Novozym® 435 (from Candida antarctica immobilized on acrylic resin Candida antarctica ) lipase), Candida antarctica lipase B immobilized on acrylic resin, or Candida antarctica lipase B immobilized on a porous fluoropolymer support, as described in U.S. Pat. No. 8,889,373. Immobilized enzymes, such as Lipase PS-C, Lipase PS-D, Novozym® 435, Candida antarctica lipase B immobilized on acrylic resin, or Candida antarctica lipase B immobilized on a porous fluoropolymer support, enable simple removal of the product from the insoluble loaded enzyme, and allow the enzyme to be easily reused.

[0062] There are no particular pressure requirements for the enzymatic equilibration process, as no byproducts are removed during this step of the process. The reaction pressure is typically about atmospheric pressure, but subatmospheric or superatmospheric pressures may also be used.

[0063] The enzymatic equilibration process provides significant compositional changes compared to the product ratios obtained by conventional acid-catalyzed esterification. Examples of such compositional changes are shown in Table 2.

[0064] Table 2: Composition comparison between conventional mixtures and mixtures obtained by the present invention for DS 1.6

[0065]

[0066] In certain embodiments, the method of the present invention provides a reduction of at least 4% of the diester amount and an increase of at least 5% of the triester amount, and in some cases the change is greater. The upper limit of the change of both diesters and triesters is 11 mole % in one embodiment, and 15 mole % in another embodiment.

[0067] As is known in the literature for triethanolamine esters, the product of the second step of the method can be converted into various subsequent materials. Of particular interest is the alkylation of nitrogen to provide a cationic surfactant. This alkylation can be carried out with dialkyl sulfates such as dimethyl sulfate or diethyl sulfate, benzyl halides such as benzyl chloride, and many other substances known in the art. The most widespread use of cationic surfactants derived from triethanolamine esters is as a hair care agent and particularly as a laundry fabric softener for the rinse process. See, for example, U.S. Patent Nos. 9,476,012, 5,180,508, 9,338,367 and US 2016 / 0010029, which are incorporated herein by reference.

[0068] Therefore, in another embodiment, the present invention provides a mixture comprising:

[0069] a. Compounds of the formula

[0070]

[0071] The proportion thereof is about 5 to 15 mol% based on the sum of a, b, c and d;

[0072] b. Compounds of the formula

[0073]

[0074] The ratio thereof is about 22 to about 30 mol% based on the sum of a, b, c and d;

[0075] c. Compounds of the formula

[0076]

[0077] The ratio thereof is about 38 to about 45 mol% based on the sum of the combinations a, b, c and d; and

[0078] d. Compounds of the formula

[0079]

[0080] The proportion thereof is from about 17 to about 23 mole % based on the sum of the combination a, b, c and d, wherein the total mole % of a, b, c and d is equal to 100%;

[0081] wherein each R is independently selected from linear and branched, saturated and unsaturated C 11 -C 23 A hydrocarbon group; wherein R' is a C1-C6 alkyl group or a benzyl group, and X - Selected from C1-C6 monoalkyl sulfate and halide anions.

[0082] In this embodiment, the mixture may also be characterized as having a mixture average DS of about 1.5 to about 1.9. In another embodiment, the mixture has a DS of about 1.5 to about 1.75; a. is present in a proportion of about 7 to about 15%, b. is present in a proportion of about 23 to about 30%, c. is present in a proportion of about 38 to about 45%, and d. is present in a proportion of about 17 to about 27%, based on the total moles of a., b., c., and d. combined, the sum equaling 100%.

[0083] Experimental Section

[0084] Example 1: Enzymatic esterification of triethanolamine with tallow fatty acid (1.6 equiv.) without removal of the acid catalyst Promotes balance

[0085] Step 1: Conventional acid-catalyzed esterification

[0086] Triethanolamine (15 g; 0.101 mol) was added to tallow fatty acid (Twin Rivers Technology; TRT-11) (43.9 g; 0.176 mol; 1.6 eq.). 50% aqueous hypophosphorous acid (0.22 mL; 0.27 g; 0.002 eq.) was added and the mixture was heated to 140°C with stirring, accompanied by a nitrogen purge in the headspace to remove the generated water. After 12 hours, the reaction was complete and cooled to 70°C.

[0087] Step 2: Balancing with Novozym® 435

[0088] Novozym® 435 (1.40 g) was added to the above mixture at 70°C. The mixture was stirred at 70°C for 12 hours under nitrogen protection, and the enzyme was removed by filtration. The composition of the ester after step 1 and step 2 is shown below.

[0089] Table 3

[0090]

[0091] Example 2: Enzymatic esterification of triethanolamine with tallow fatty acid (1.5 equivalents) without removal of the acid catalyst Promotes balance

[0092] This example used the same procedure as Example 1 using triethanolamine (15 g; 0.101 mol), tallow fatty acid (Twin Rivers Technology; TRT-11) (41.2 g; 0.151 mol; 1.5 eq.), 50% hypophosphorous acid (0.22 mL; 0.27 g; 0.002 eq.) and Novozym® 435 (1.35 g). The results are shown in Table 4 below.

[0093] Table 4

[0094]

[0095] Example 3: Ester of triethanolamine with tallow fatty acid (1.75 equivalents) without removal of the acid catalyst Enzymatic balance

[0096] This example used the same procedure as Example 1 using triethanolamine (15 g; 0.101 mol), tallow fatty acid (Twin Rivers Technology; TRT-11) (48.0 g; 0.176 mol; 1.75 equivalents), 50% hypophosphorous acid (0.22 mL; 0.27 g; 0.002 equivalents) and Novozym® 435 (1.50 g). The results are shown in Table 5 below.

[0097] Table 5

[0098]

[0099] Example 4: Enzymatic esterification of triethanolamine with tallow fatty acid (1.9 equiv.) without removal of the acid catalyst Promotes balance

[0100] This example used the same procedure as Example 1 using triethanolamine (15 g; 0.101 mol), tallow fatty acid (Twin Rivers Technology; TRT-11) (52.2 g; 0.191 mol; 1.9 equivalents), 50% hypophosphorous acid (0.22 mL; 0.27 g; 0.002 equivalents) and Novozym® 435 (1.59 g). The results are shown in Table 6 below.

[0101] Table 6

[0102]

[0103] Example 5: Ester of triethanolamine and tallow fatty acid (1.75 equivalents) without removal of the acid catalyst Enzymatic balance

[0104] Step 1: Conventional acid-catalyzed esterification

[0105] Triethanolamine (15 g; 0.101 mol) was added to tallow fatty acid (Twin Rivers Technology; TRT-11) (48.0 g; 0.176 mol; 1.75 equiv). 50% aqueous hypophosphorous acid (0.22 mL; 0.27 g; 0.002 equiv) was added and the mixture was heated to 140°C with stirring, accompanied by a nitrogen purge in the headspace to remove the generated water. After 12 hours, the reaction was complete and cooled to 70°C.

[0106] Step 2: Equilibration using lipase from Candida antarctica B immobilized on acrylic resin

[0107] An immobilized enzyme catalyst (1.50 g) prepared by treating lipase from Candida antarctica B (Novozymes Lipozyme® CalB-L) with an acrylic resin (Lanxess Lewitat® VP OC1600) was added to the above mixture at 70°C. The mixture was stirred at 70°C for 6 hours under nitrogen protection, and the enzyme was removed by filtration. The composition of the ester after step 1 and step 2 is shown below.

[0108] Table 7

[0109]

[0110] Example 6: Ester of triethanolamine and tallow fatty acid (1.75 equivalents) without removal of the acid catalyst Enzymatic balance

[0111] Step 1: Conventional acid-catalyzed esterification

[0112] Triethanolamine (15 g; 0.101 mol) was added to tallow fatty acid (Twin Rivers Technology; TRT-11) (48.0 g; 0.176 mol; 1.75 equiv). 50% aqueous hypophosphorous acid (0.22 mL; 0.27 g; 0.002 equiv) was added and the mixture was heated to 140°C with stirring, accompanied by a nitrogen purge in the headspace to remove the generated water. After 12 hours, the reaction was complete and cooled to 70°C.

[0113] Step 2: Equilibration using lipase from Candida antarctica B immobilized on fluoropolymer

[0114] To the above mixture was added small pieces of fluoropolymer sheets (270 cm 2 ) on Candida antarctica lipase B (Novozymes Lipozyme® CalB-L). The mixture was stirred at 70°C for 6 hours under nitrogen protection, and the enzyme was removed by filtration. The composition of the ester after step 1 and step 2 is shown below.

[0115] Table 8

[0116]

[0117] Example 7: Preparation of triethanolamine and tallow fatty acid (1.75 equivalents) without acid catalyst Enzymatic Equilibration of Esters

[0118] Step 1: Conventional non-catalyzed esterification

[0119] Triethanolamine (324.7 g; 2.18 mol) was added to tallow fatty acid (Twin Rivers Technology; TRT-11) (1039.7 g; 3.81 mol; 1.75 equiv.) The mixture was heated to 140°C with stirring, with a nitrogen purge in the headspace to remove the generated water, until the reaction was complete (indicated by an acid value of <5).

[0120] Step 2: Equilibration using lipase from Candida antarctica B immobilized on acrylic resin

[0121] A portion (59.9 g) of the above triethanolamine fatty acid ester was treated with 1.50 g of Candida antarctica B lipase (Novozymes Lipozyme® CalB-L) immobilized on acrylic resin (Purolite Lifetech™ ECR1030M) at 70°C. The mixture was stirred at 70°C for 3 hours under nitrogen. The composition of the ester after step 1 and step 2 is shown below.

[0122] Table 9

[0123]

[0124] Example 8: Enzymatic esterification of triethanolamine with tallow fatty acid (1.75 equiv.) with removal of the acid catalyst Promotes balance

[0125] Step 1: Conventional acid-catalyzed esterification using a basic resin to remove the acid

[0126] Triethanolamine (324.7 g; 2.18 mol) was added to tallow fatty acid (Twin Rivers Technology; TRT-11) (1039.7 g; 3.81 mol; 1.75 equiv). The mixture was heated to 140°C with stirring, with a nitrogen purge in the headspace to remove the generated water. After 12 hours, the reaction was complete and cooled to 70°C and treated with dry Amberlyst A-21 weakly basic ion exchange resin (2.40 g). The mixture was stirred for 15 minutes, and the Amberlyst resin was removed by filtration.

[0127] Step 2: Equilibration using lipase from Candida antarctica B immobilized on acrylic resin

[0128] The triethanolamine fatty acid ester mixture prepared above was treated with 1.50 g of Candida antarctica B lipase (Novozymes Lipozyme® CalB-L) immobilized on acrylic resin (Purolite Lifetech™ ECR1030M) at 70°C. The mixture was stirred at 70°C for 6 hours under nitrogen protection. The composition of the ester after step 1 and step 2 is shown below.

[0129] Table 10

[0130]

[0131] Example 9: Enzymatic Equilibration of the Ester of Triethanolamine and Oleic Acid (1.75 Equivalents) without Removal of the Acid Catalyst Balance

[0132] Step 1: Conventional acid-catalyzed esterification

[0133] Triethanolamine (20 g; 0.134 mol) was added to oleic acid (66.3 g; 0.235 mol; 1.75 eq.). 50% aqueous hypophosphorous acid (0.29 mL; 0.35 g; 0.002 eq.) was added and the mixture was heated to 140°C with stirring, accompanied by a nitrogen purge in the headspace to remove the generated water. After 12 hours, the reaction was complete and cooled to 70°C.

[0134] Step 2: Balancing with Novozym® 435

[0135] Novozym® 435 (2.05 g) was added to the above mixture at 70°C. The mixture was stirred at 70°C for 8 hours under nitrogen protection, and the enzyme was removed by filtration. The composition of the ester after step 1 and step 2 is shown below.

[0136] Table 11

[0137]

[0138] Example 10: Enzymatic esterification of triethanolamine with palmitic acid (1.75 equiv.) without removal of the acid catalyst balance

[0139] Step 1: Conventional acid-catalyzed esterification

[0140] Triethanolamine (15 g; 0.101 mol) was added to palmitic acid (45.1 g; 0.176 mol; 1.75 eq.). 50% aqueous hypophosphorous acid (0.22 mL; 0.27 g; 0.002 eq.) was added and the mixture was heated to 140°C with stirring, accompanied by a nitrogen purge in the headspace to remove the generated water. After 12 hours, the reaction was complete and cooled to 70°C.

[0141] Step 2: Balancing with Novozym® 435

[0142] Novozym® 435 (1.42 g) was added to the above mixture at 70°C. The mixture was stirred at 70°C for 6 hours under nitrogen protection, and the enzyme was removed by filtration. The composition of the ester after step 1 and step 2 is shown below.

[0143] Table 12

[0144]

[0145] Table 13

[0146] This table illustrates the relative compositions of two embodiments of the novel mixture of the present invention.

[0147]

[0148] Example 11: Synthesis of N-methyl (triethanolamine) from the enzyme-equilibrated ester of triethanolamine and animal fatty acids (1.5 equivalents) TEA esters) methyl sulfate

[0149] To a 300 ml three-necked flask equipped with a thermocouple, overhead stirrer, and addition funnel was added the ester prepared as in Example 2 (120 g, 0.2148 mol), followed by 16.28 g of isopropanol. The resulting mixture was stirred at a controlled rate and heated to 50°C using a heating mantle. Dimethyl sulfate (26.55 g, 0.2105 mol) was added dropwise to the TEA ester mixture at a rate such that the internal temperature did not exceed 60°C. After the addition was complete, the mixture was maintained at 60°C for 7.5 hours, at which time the mixture was stirred for 10 minutes. 1 H NMR analysis showed that all dimethyl sulfate had been consumed. Free amine titration showed that 98% of the TEA ester had been quaternized. The final product contained 90% N-methyl (triethanolammonium tallow fatty acid ester) methyl sulfate (TEA ester quaternary ammonium compound) and 10% IPA.

[0150] The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

Claims

1. A method for increasing the molar ratio of triesters of formula (I) in a mixture The mixture comprises (i) triethanolamine and (ii) a fatty acid ester having the formula (II), (III) and (I): wherein each R is independently selected from linear and branched, saturated and unsaturated C 11 -C 23 A hydrocarbon group, the method comprising carrying out an acid-catalyzed esterification process to obtain the above mixture of unreacted triethanolamine, a monoester of formula (II), a diester of formula (III) and a triester of formula (I), and then contacting the mixture with a hydrolase, wherein the hydrolase is a lipase from Candida antarctica immobilized on an acrylic resin, an Candida antarctica lipase B immobilized on an acrylic resin and / or an Candida antarctica lipase B immobilized on a porous fluoropolymer.

2. The method according to claim 1, wherein each R is independently selected from linear and branched, saturated and unsaturated C 13 -C 17 Hydrocarbyl group.

3. The method according to claim 1, wherein R in the -C(O)-R moiety is selected from lauroyl, myristoyl, palmitoyl, stearoyl, oleoyl, linoleoyl or a mixture thereof.

4. The method of claim 1, wherein RC(O)- is C derived from an oil selected from the group consisting of animal fat, nut oil and seed oil. 12 To C 24 Mixture of acyl groups.

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