Esterification catalyst and method for producing ester

Abstract

To provide an esterification catalyst that allows a low-temperature esterification reaction between a carboxylic acid and an alcohol and enables production of an ester exhibiting superior odor and color suitable for cosmetic use.SOLUTION: An esterification catalyst comprising a silyl triflate A represented by formula (1) and an aromatic amine B represented by formula (2), the molar ratio of the silyl triflate A to the aromatic amine B being 80:20 to 20:80.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an esterification catalyst and a method for producing an ester. [Background technology]

[0002] Esters are compounds obtained by the dehydration condensation reaction between carboxylic acids and alcohols, and examples include monoesters, diesters, triesters, tetraesters, etc. Among these, polyol esters having a neopentyl skeleton (hereinafter referred to as neopentyl polyol esters) are widely used in the cosmetics industry as oily bases because they have excellent adhesion and spreadability to skin and hair, as well as a suitable feel and emollient effect.

[0003] Since neopentyl polyols have poor reactivity, the esterification reaction is carried out at high temperatures. For example, Patent Document 1 describes a method for producing tetrapentaerythritol 2-ethylhexanoate by dehydration condensation reaction of 2-ethylhexanoic acid and pentaerythritol at 240°C in the absence of a catalyst.

[0004] In recent years, there has been a demand for energy conservation in the production of chemical products, and studies have been conducted to use metals such as titanium, tin, and antimony as catalysts in order to lower the reaction temperature in the production of esters. For example, Patent Document 2 describes a method for producing pentaerythritol tetra-2-ethylhexanoate using titanium isopropoxide as a catalyst under reaction conditions of 220°C. Furthermore, Patent Document 3 describes a method for producing pentaerythrityl tetraisononanoate using methanesulfonic acid as a catalyst under reaction conditions of 230°C. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-227255 [Patent Document 2] Japanese Patent Application Publication No. 2018-2973 [Patent Document 3] International Publication No. 2010 / 146616 Summary of the Invention [Problem to be solved by the invention]

[0006] The production method described in Patent Document 1 involves a reaction at a high temperature of 200°C or higher, which can lead to thermal degradation of the ester, resulting in odor and coloration. When such odorous and colored esters are used in cosmetics, the odor can be unpleasant for consumers, limiting the amount of esters that can be incorporated into cosmetics and making it difficult to improve the feel when used. In terms of coloring, there is a strong demand for cosmetics with excellent appearance in terms of luxury, cleanliness, and aesthetic effects, so esters with a low hue are desired.

[0007] Furthermore, even when the catalysts described in Patent Documents 2 and 3 are used, the reaction temperature is not sufficiently reduced, and when the produced ester is used in cosmetics, there is room for improvement in terms of odor and color.

[0008] Therefore, the methods described in the above-mentioned documents require a reaction at a high temperature, and when the produced ester is to be used in cosmetics, there is room for improvement in terms of odor and color.

[0009] As described above, an object of the present invention is to provide an esterification catalyst that enables the esterification reaction between a carboxylic acid and an alcohol to proceed at a low temperature and that produces an ester that is excellent in odor and color and that can be used in cosmetics. [Means for solving the problem]

[0010] As a result of intensive research into solving the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by carrying out a reaction using a catalyst in which the compounds represented by formula (1) and formula (2) are combined in a specific molar ratio.

[0011] That is, the present invention provides: Formula (1): [ka] (In formula (1), R 1 may be the same or different and are hydrocarbon groups having 1 to 18 carbon atoms, and n is 1 to 3. Formula (2): [ka] (In formula (2), R 2 represents a hydrogen atom or a hydrocarbon group having 1 to 18 carbon atoms, and R 3 , and R 4 represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms. 3 , and R 4 may be the same or different.) The present invention relates to an esterification catalyst in which the molar ratio of silyl triflate A to aromatic amine B is 80:20 to 20:80.

[0012] The present invention also relates to a method for producing an ester, which comprises a step of reacting a carboxylic acid with an alcohol using the esterification catalyst. [Effects of the Invention]

[0013] According to the present invention, the esterification reaction between a carboxylic acid and an alcohol can be carried out at a low temperature, and a high-quality ester having an excellent odor and color that can be used in cosmetics can be obtained. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the esterification catalyst of the present invention will be described in detail. In this specification, a numerical range defined using the symbol "to" includes the numerical values ​​at both ends (upper and lower limits) of the symbol "to." For example, "1 to 10" means 1 or more and 10 or less.

[0015] [Esterification catalyst] The esterification catalyst contains silyl triflate A represented by the following formula (1) and aromatic amine B represented by formula (2), and the molar ratio of silyl triflate A to aromatic amine B (silyl triflate A:aromatic amine B) is 80:20 to 20:80.

[0016] <Silyl Triflate A> Silyl triflate A is represented by the following formula (1). [ka] (In formula (1), R 1 may be the same or different and are hydrocarbon groups having 1 to 18 carbon atoms, and n is 1 to 3.

[0017] R 1 Examples of R include linear saturated hydrocarbon groups such as methyl, ethyl, propyl, butyl, hexyl, heptyl, octyl, decyl, lauryl, myristyl, palmityl, and stearyl groups, and branched saturated hydrocarbon groups such as isopropyl, 2-methylpropyl, t-butyl, 1,1,2-trimethylpropyl, 1,1-dimethylbutyl, 3,3-dimethylbutyl, and 1,1,2,2-tetramethylpropyl groups. 1 is preferably a linear or branched saturated hydrocarbon group having 1 to 8 carbon atoms, and more preferably a branched saturated hydrocarbon group having 3 to 5 carbon atoms.

[0018] n represents the number of trifluoromethanesulfonic acid groups, and is 1 to 3. n is preferably 2 or less, and more preferably 2.

[0019] The method for producing silyl triflate A represented by the above formula (1) is not particularly limited, but examples thereof include a method of reacting trifluoromethanesulfonic acid with a halogenated alkylsilane such as chlorotrimethylsilane or a dihalogenated alkylsilane such as dichloroisopropylsilane at, for example, 0 to 100°C.

[0020] The silyl triflate A may be used alone or in combination of two or more kinds.

[0021] <Aromatic amine B> The aromatic amine B is represented by the following formula (2). [ka] (In formula (2), R 2 represents a hydrogen atom or a hydrocarbon group having 1 to 18 carbon atoms, and R 3 , and R 4 represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms. 3 , and R 4 may be the same or different.)

[0022] R 2 Examples of R include a hydrogen atom, a linear saturated hydrocarbon group such as a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, a heptyl group, an octyl group, a decyl group, a lauryl group, a myristyl group, a palmityl group, or a stearyl group, and a branched saturated hydrocarbon group such as an isopropyl group, an isobutyl group, a t-butyl group, an isopentyl group, or a 2-ethylhexyl group. 2 is preferably a linear or branched saturated hydrocarbon group having 1 to 8 carbon atoms, and more preferably a linear or branched saturated hydrocarbon group having 2 to 6 carbon atoms.

[0023] R 3 , and R 4 Examples of R include a hydrogen atom, a linear saturated hydrocarbon group such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, a lauryl group, a myristyl group, a palmityl group, a stearyl group, or an arachidyl group, and a branched saturated hydrocarbon group such as an isopropyl group, an isobutyl group, a t-butyl group, an isopentyl group, an isohexyl group, a 2-ethylhexyl group, or a 1,1,3,3,5,5-hexamethylhexyl group. 3 , and R 4is preferably a hydrogen atom or a linear or branched saturated hydrocarbon group having 1 to 10 carbon atoms, more preferably a hydrogen atom or a linear or branched saturated hydrocarbon group having 1 to 6 carbon atoms, and even more preferably hydrogen.

[0024] The aromatic amine B may be used alone or in combination of two or more kinds.

[0025] In the esterification catalyst of the present invention, the molar ratio of the silyl triflate A to the aromatic amine B (silyl triflate A:aromatic amine B) is 80:20 to 20:80. If the content of silyl triflate A in the esterification catalyst is less than 20 mol% or exceeds 80 mol%, the color will deteriorate. Also, if the content of aromatic amine B exceeds 80 mol% or less than 20 mol%, the color will deteriorate. Also, if the content of aromatic amine B exceeds 80 mol%, the odor will become unpleasant. The molar ratio of silyl triflate A to aromatic amine B (silyl triflate A:aromatic amine B) is preferably 70:30 to 30:70, more preferably 60:40 to 40:60.

[0026] The amount of the esterification catalyst used in producing the ester of the present invention may be appropriately determined depending on the reaction system (such as the types of carboxylic acid and alcohol). For example, it is preferable to add the catalyst so that the amount of silyl triflate A in the esterification catalyst is 0.001 mol % to 10 mol % relative to the molar amount of hydroxyl groups in the alcohol or the molar amount of carbonyl groups in the carboxylic acid, whichever is smaller.

[0027] The reaction temperature and reaction time during the production of an ester according to the present invention vary depending on the amount of esterification catalyst added, the reaction temperature, etc., but the reaction temperature is generally 200°C or lower, preferably 180°C or lower.

[0028] Examples of carboxylic acids used in producing the ester of the present invention include linear carboxylic acids having 1 to 22 carbon atoms, such as acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, pentadecylic acid, palmitic acid, stearic acid, arachidic acid, and behenic acid. Other examples include branched carboxylic acids having 4 to 18 carbon atoms, such as 2-methylpropionic acid (isobutyric acid), 3-methylbutanoic acid (isovaleric acid), 2-methylpentanoic acid, 2-ethylhexanoic acid (octylic acid), 3,5,5-trimethylhexanoic acid (isononanoic acid), 2,2-dimethyloctanoic acid (neodecanoic acid), 2-hexyldecanoic acid (isopalmitic acid), and isostearic acid. These may be used alone or in combination of two or more. From the viewpoint of reactivity, branched carboxylic acids are preferred, as they allow the effects of the present invention to be more effectively achieved.

[0029] The alcohol used in producing the ester of the present invention is not particularly limited and can be appropriately selected depending on the purpose. For example, neopentyl polyols include 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2,2-diethyl-1,3-propanediol, 2-propyl-2-methyl-1,3-propanediol, 2-propyl-2-ethyl-1,3-propanediol, 2,2-dipropyl-1,3-propanediol, 2-butyl-2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-butyl-2-propyl-1,3-propanediol, 2,2-dibutyl-1,3-propanediol, trimethylolethane, trimethylolpropane, pentaerythritol, ditrimethylolpropane, dipentaerythritol, tripentaerythritol, and tetrapentaerythritol. These may be used alone or in combination of two or more.

[0030] The esterification catalyst of the present invention is capable of carrying out the esterification reaction between carboxylic acids and alcohols at low temperatures and can produce esters with excellent odor and color, making it particularly suitable as a catalyst for esterifying neopentyl polyols for use in cosmetics, foods, and lubricants. [Example]

[0031] EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0032] <Preparation of esterification catalyst> Using silyl triflate A in Table 1 and aromatic amine B in Table 2, esterification catalysts 1 to 10 in Table 3 were prepared according to the following formulation examples 1 to 10.

[0033] [Table 1]

[0034] [Table 2]

[0035] (Composition Example 1, Esterification Catalyst 1) A 20 mL vial equipped with a stirrer tip was charged with 1.58 g (3.82 mmol) of diisopropylsilyl bis(trifluoromethanesulfonate) (A-1, manufactured by Merck) and 0.86 g (3.82 mmol) of N-butyldiphenylamine (B-1, manufactured by Cymit Quimica SL), and the mixture was stirred at 50°C for 2 minutes to prepare esterification catalyst 1.

[0036] (Composition Example 2, Esterification Catalyst 2) Esterification catalyst 2 was prepared in the same manner as in Blending Example 1, except that 1.58 g (3.82 mmol) of diisopropylsilyl bis(trifluoromethanesulfonate) (A-1) and 0.46 g (2.06 mol) of N-butyldiphenylamine (B-1) were added.

[0037] (Composition Example 3, Esterification Catalyst 3) Esterification catalyst 3 was prepared in the same manner as in Blending Example 1, except that 0.70 g (3.82 mmol) of N-methyldiphenylamine (Tokyo Chemical Industry Co., Ltd., B-2) was used instead of N-butyldiphenylamine.

[0038] (Composition Example 4, Esterification Catalyst 4) Esterification catalyst 4 was prepared in the same manner as in Blending Example 1, except that 0.65 g (3.82 mmol) of diphenylamine (Tokyo Chemical Industry Co., Ltd., B-3) was used instead of N-butyldiphenylamine.

[0039] (Composition Example 5, Esterification Catalyst 5) Esterification catalyst 5 was prepared in the same manner as in Blending Example 1, except that 0.75 g (3.82 mmol) of 4,4'-dimethyldiphenylamine (Tokyo Chemical Industry Co., Ltd., B-4) was used instead of N-butyldiphenylamine and the mixture was stirred at 85°C for 2 minutes.

[0040] (Composition Example 6, Esterification Catalyst 6) Esterification catalyst 6 was prepared in the same manner as in Blending Example 1, except that 1.17 g (3.82 mmol) of triisopropylsilyl trifluoromethanesulfonate (Tokyo Chemical Industry Co., Ltd., A-2) was used instead of diisopropylsilyl bis(trifluoromethanesulfonate).

[0041] (Composition Example 7, Esterification Catalyst 7) Esterification catalyst 7 was prepared in the same manner as in Blending Example 1, except that 0.85 g (3.82 mmol) of trimethylsilyl trifluoromethanesulfonate (Tokyo Chemical Industry Co., Ltd., A-3) was used instead of diisopropylsilyl bis(trifluoromethanesulfonate).

[0042] (Comparative Blend Example 1, Esterification Catalyst 8) Esterification catalyst 8 was prepared in the same manner as in Blending Example 1, except that 1.58 g (3.82 mmol) of diisopropylsilyl bis(trifluoromethanesulfonate) (A-1) and 7.75 g (34.4 mmol) of N-butyldiphenylamine (B-1) were added.

[0043] (Comparative Blend Example 2, Esterification Catalyst 9) Esterification catalyst 9 was prepared in the same manner as in Blending Example 1, except that 2.84 g (6.88 mmol) of diisopropylsilyl bis(trifluoromethanesulfonate) (A-1) and 0.17 g (0.76 mmol) of N-butyldiphenylamine (B-1) were added.

[0044] (Comparative Blend Example 3, Esterification Catalyst 10) An esterification catalyst 10 was prepared in the same manner as in Formulation Example 1, except that 1.35 g (3.82 mmol) of tri-n-octylamine was used instead of N-butyldiphenylamine.

[0045] [Table 3]

[0046] <Production of esters> Example 1: Production of pentaerythritol tetra-2-ethylhexanoate using esterification catalyst 1 A 1000 mL four-neck flask equipped with a thermometer, nitrogen inlet tube, stirrer, Dimroth condenser, and a 30 mL oil-water separator was charged with 130.0 g (0.96 mol, hydroxyl molar amount: 3.8 mol) of pentaerythritol (Perstorp, Penta mono) and 578.1 g (4.0 mol, carbonyl molar amount: 4.0 mol) of 2-ethylhexanoic acid (KH Neochem, octylic acid) (carboxylic acid / hydroxyl molar amount: 1.05 equivalent ratio). 2.44 g of the esterification catalyst 1 prepared in Blend Example 1 was then charged. While removing the reaction water accumulating in the oil-water separator, the reaction solution was heated to 160°C. The acid value of the reaction solution was measured every hour, and the reaction was continued until the rate of decrease in acid value per hour reached 0.5 mg KOH / g or less. The reactor was then cooled to 85°C, and 1.5 equivalents of sodium hydroxide, calculated from the acid value, were diluted with ion-exchanged water to prepare a 10% by weight aqueous solution. This solution was then added to the reaction solution and stirred for 30 minutes. After stopping the stirring, the mixture was allowed to stand for 30 minutes, and the separated aqueous layer was removed. Next, ion-exchanged water in an amount equivalent to 20% by weight of the reaction solution was added, stirred at 85°C for 10 minutes, allowed to stand for 15 minutes, and the separated aqueous layer was removed. This procedure was repeated five times. The mixture was then dehydrated by stirring at 85°C and 30 Torr for 1 hour. Finally, activated clay in an amount equivalent to 2% by weight of the reaction solution was added, and the mixture was stirred at 80°C and 30 Torr for 1 hour. The adsorbent was then removed by filtration, yielding pentaerythritol tetra-2-ethylhexanoate.

[0047] (Example 2, Production of Pentaerythritol Tetra-2-ethylhexanoate Using Esterification Catalyst 2) The same procedure as in Example 1 was carried out except that 2.04 g of the esterification catalyst 2 prepared in Blending Example 2 was charged, thereby obtaining pentaerythritol tetra-2-ethylhexanoate.

[0048] (Example 3, Production of Pentaerythritol Tetra-2-ethylhexanoate Using Esterification Catalyst 3) The same procedure as in Example 1 was carried out except that 2.28 g of the esterification catalyst prepared in Blending Example 3 was charged, thereby obtaining pentaerythritol tetra-2-ethylhexanoate.

[0049] (Example 4, Production of Pentaerythritol Tetra-2-ethylhexanoate Using Esterification Catalyst 4) The same procedure as in Example 1 was carried out except that 2.23 g of the esterification catalyst 4 prepared in Blending Example 4 was charged, thereby obtaining pentaerythritol tetra-2-ethylhexanoate.

[0050] (Example 5, Production of Pentaerythritol Tetra-2-ethylhexanoate Using Esterification Catalyst 5) The same procedure as in Example 1 was carried out except that 2.33 g of the esterification catalyst prepared in Blending Example 5 was charged, thereby obtaining pentaerythritol tetra-2-ethylhexanoate.

[0051] Example 6: Production of pentaerythritol tetra-2-ethylhexanoate using esterification catalyst 6 The same procedure as in Example 1 was carried out except that 2.03 g of the esterification catalyst 6 prepared in Blending Example 6 was charged, thereby obtaining pentaerythritol tetra-2-ethylhexanoate.

[0052] Example 7: Production of pentaerythritol tetra-2-ethylhexanoate using esterification catalyst 7 The same procedure as in Example 1 was carried out except that 1.71 g of the esterification catalyst prepared in Blending Example 7 was charged, thereby obtaining pentaerythritol tetra-2-ethylhexanoate.

[0053] Example 8: Production of Dipentaerythryl Hexaisononanoate Using Esterification Catalyst 1 A 1000 mL four-neck flask equipped with a thermometer, a nitrogen inlet tube, a stirrer, a Dimroth condenser, and a 30 mL oil-water separator was charged with 587.9 g of 3,5,5-trimethylhexanoic acid (KH Neochem Corporation, isononanoic acid) and 150.0 g of dipentaerythritol (Perstorp, dipentaerythritol) (carboxylic acid / alcohol equivalent ratio = 1.05). The same procedure as in Example 1 was then carried out, except that 2.26 g of the esterification catalyst 1 prepared in Blend Example 1 was added, to obtain dipentaerythryl hexaisononanoate.

[0054] Example 9: Production of neopentyl glycol dicaprate using esterification catalyst 1 A 1000 mL four-neck flask equipped with a thermometer, a nitrogen inlet tube, a stirrer, a Dimroth condenser, and a 30 mL oil-water separator was charged with 513.5 g of capric acid (NOF Corporation, NAA (registered trademark)-102) and 194.7 g of neopentyl glycol (Mitsubishi Gas Chemical Company, Inc., NPG) (carboxylic acid / alcohol equivalent ratio = 1.05). The same procedure as in Example 1 was then carried out, except that 2.23 g of the esterification catalyst 1 prepared in Blend Example 1 was added, to obtain neopentyl glycol dicaprate.

[0055] (Comparative Example 1, Production of Pentaerythritol Tetra-2-ethylhexanoate Using Diisopropylsilyl Bis(trifluoromethanesulfonate) (A-1)) The same procedure as in Example 1 was carried out except that N-butyldiphenylamine was not added, to obtain pentaerythritol tetra-2-ethylhexanoate.

[0056] (Comparative Example 2) The same procedure as in Example 1 was carried out except that 2.93 g of the esterification catalyst 8 prepared in Comparative Formulation Example 1 was charged, thereby obtaining pentaerythritol tetra-2-ethylhexanoate.

[0057] (Comparative Example 3) The same procedure as in Example 1 was carried out except that 3.01 g of the esterification catalyst 9 prepared in Comparative Formulation Example 2 was charged, thereby obtaining pentaerythritol tetra-2-ethylhexanoate.

[0058] Comparative Example 4 The same procedure as in Example 1 was carried out except that 2.93 g of the esterification catalyst 10 prepared in Comparative Formulation Example 3 was charged, thereby obtaining pentaerythritol tetra-2-ethylhexanoate.

[0059] The resulting esters were subjected to the following evaluation tests, and the evaluation results are shown in Table 4.

[0060] (Method for evaluating odor intensity) The odor intensity of the esters was evaluated by a sensory evaluation by five panelists. The evaluation was carried out by heating the esters to 30°C immediately after production according to the following criteria, and the total scores of the five panelists are shown in Table 4. A total score of 7 or less was indicated as ⊚, 8 to 10 was indicated as ◯, and 11 or more was indicated as ×. 3: I feel strongly 2: Slightly felt 1: No feeling at all

[0061] (Evaluation method for coloring degree) The hue (APHA) of the ester was measured and evaluated according to JIS K 0071-1. In Table 4, a lower hue (APHA) indicates a better hue. Less than 50 was marked with ⊚, 50 to less than 150 with ◯, and 150 or more with ×.

[0062] [Table 4]

[0063] As is clear from the results shown in Table 4, when Examples 1 and 2 using esterification catalysts 1 and 2 according to the present invention are compared with Comparative Example 2 using esterification catalyst 8, it is found that esters with excellent odor and color can be obtained when the molar ratio of silyl triflate A to aromatic amine B (silyl triflate A:aromatic amine B) is 80:20 to 20:80.

[0064] As is clear from Examples 1 and 3 to 7, which used esterification catalysts 1 and 3 to 7, a catalyst comprising silyl triflate A and aromatic amine B can produce esters with excellent odor and color.

[0065] Comparative Example 1 shows the results when the molar ratio of silyl triflate A to aromatic amine B (silyl triflate A:aromatic amine B) was 100:0, and it can be seen that the color deteriorates when the molar ratio of silyl triflate A exceeds 80 mol%. Comparative Example 2 shows the results when the molar ratio of silyl triflate A to aromatic amine B (silyl triflate A:aromatic amine B) was 10:90, and it can be seen that the odor and color deteriorate when the molar ratio of aromatic amine B exceeds 80%. Comparative Example 3 shows the results when the molar ratio of silyl triflate A to aromatic amine B (silyl triflate A:aromatic amine B) was 90:10, and it can be seen that the color deteriorates when the molar ratio of silyl triflate A exceeds 80%. Comparative Example 4 shows the results when silyl triflate A and an aliphatic amine compound were used, and the odor and color deteriorate, indicating that a catalyst of silyl triflate A and aromatic amine B is effective.

Claims

1. Formula (1): 【Chemistry 1】 (In formula (1), R １ may be the same or different and are hydrocarbon groups having 1 to 18 carbon atoms, and n is 1 to 3. Formula (2): 【Chemistry 2】 (In formula (2), R ２ represents a hydrogen atom or a hydrocarbon group having 1 to 18 carbon atoms, and R ３ , and R ４ represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms. ３ , and R ４ may be the same or different; An esterification catalyst comprising a silyl triflate A and an aromatic amine B in a molar ratio of 80:20 to 20:

80.

2. A method for producing an ester, comprising a step of reacting a carboxylic acid with an alcohol using the esterification catalyst according to claim 1.

Images