Method for producing N-substituted aspartic acid

Abstract

To provide a method for producing high-purity N-substituted aspartic acid from which impurities such as long-chain aliphatic amines have been sufficiently removed. [Solution] A method for producing N-substituted aspartic acid (1), comprising: (A) an acid decomposition step in which crude N-substituted aspartate obtained by an addition reaction of maleate and / or fumarate with a long-chain aliphatic amine is acid-decomposed in an aqueous solution with an inorganic acid having an acid dissociation constant smaller than that of N-substituted aspartic acid at a temperature range of 40 to 100°C to precipitate N-substituted aspartic acid; (B) a separation step to separate the precipitated N-substituted aspartic acid; and (C) a washing step to wash the N-substituted aspartic acid after the separation step with water and a lower alcohol. JPEG2026115080000014.jpg42159

Description

[Technical Field]

[0001] This invention relates to a method for producing N-substituted aspartic acid. [Background technology]

[0002] N-substituted aspartic acid, when neutralized with any base to form an N-substituted aspartate salt, becomes an amino acid-based amphoteric surfactant. By selecting the lipophilic group chain length, the neutralization rate of the carboxyl group, and the neutralizing base, it exhibits excellent surface activity and is known to be useful as a raw material for detergents, dispersants, emulsifiers, and other products.

[0003] Conventionally, an addition reaction between a long-chain aliphatic amine and maleic acid has been known as a method for producing N-substituted aspartic acid (Patent Document 1). When N-substituted aspartic acid is produced by this method, the reaction rate is very low, less than 30%, and it is known that many impurities, such as unreacted long-chain aliphatic amines, remain. Long-chain aliphatic amines are known to be skin irritants, and when N-substituted aspartic acid obtained by the above method is used as a raw material for surfactants, the remaining long-chain aliphatic amines may cause skin irritation. Therefore, there has been a need for a method of producing N-substituted aspartic acid that reduces impurities such as long-chain aliphatic amines. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2000-136172 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The present invention aims to provide a method for producing high-purity N-substituted aspartic acid from which impurities such as long-chain aliphatic amines have been sufficiently removed. [Means for solving the problem]

[0006] In order to solve the above problems, the present inventors have considered various methods and conducted intensive studies. As a result, a crude N-substituted aspartate is acid-decomposed with a specific inorganic acid under specific temperature conditions in an aqueous solution to precipitate N-substituted aspartic acid, including an acid decomposition step (A), a separation step (B) of separating the precipitated N-substituted aspartic acid, and a washing step (C) of washing the N-substituted aspartic acid after the separation step with water and a lower alcohol. It has been found that high-purity N-substituted aspartic acid can be obtained by the production method, and the present invention has been completed.

[0007] That is, the present invention provides a method for producing the following high-purity N-substituted aspartic acid.

[0008] [Item 1] General formula (1) [Chemical formula] [In the formula, R 1 represents a linear or branched alkyl or alkenyl group having 8 to 22 carbon atoms, and R 2 represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms which may be substituted with a hydroxyl group.] A method for producing N-substituted aspartic acid represented by General formula (2) [Chemical formula] [In the formula, the wavy line indicates that the isomer configuration of the double bond may be either the cis form or the trans form. M 1 and M 2 are the same or different and represent a hydrogen atom, a lithium ion, a sodium ion, a potassium ion, a magnesium ion, an ammonium ion or an organic ammonium ion, and either one of M 1 , M 2 represents a lithium ion, a sodium ion, a potassium ion, a magnesium ion, an ammonium ion or an organic ammonium ion.] The maleate and / or fumarate represented by General formula (3)

Chemical formula

Chemical formula

[0009] [Item 2] R of the N-substituted aspartic acid represented by general formula (1) 1 is a linear or branched alkyl group or alkenyl group having 8 to 18 carbon atoms, The method for producing N-substituted aspartic acid according to [Item 1].

[0010] [Item 3] R of the N-substituted aspartic acid represented by general formula (1) 2 is a hydrogen atom, The method for producing N-substituted aspartic acid according to [Item 1] or [Item 2].

[0011] [Section 4] A method for producing N-substituted aspartic acid according to any one of [Item 1] to [Item 3], wherein the crude N-substituted aspartate contains 0.8 to 3.0% by mass of a long-chain aliphatic amine.

[0012] [Section 5] M of N-substituted aspartate represented by general formula (4) 1 However, it is a sodium ion or a potassium ion, and M 2 However, it is a hydrogen atom, or M 1 However, it is a hydrogen atom, and M 2 A method for producing N-substituted aspartic acid according to any of [Item 1] to [Item 4], wherein the ion is a sodium ion or a potassium ion.

[0013] [Section 6] (A) A method for producing N-substituted aspartic acid according to item 1, wherein in the acid decomposition step, the inorganic acid is one or more inorganic acids selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid.

[0014] [Section 7] (A) A method for producing N-substituted aspartic acid according to item [1] or [6], wherein the inorganic acid in the acid decomposition step is sulfuric acid.

[0015] [Section 8] (A) A method for producing N-substituted aspartic acid according to any one of [Item 1], [Item 6], or [Item 7], wherein the temperature range in the acid decomposition step is 60 to 80°C.

[0016] [Section 9] (C) A method for producing N-substituted aspartic acid as described in [Item 1], wherein the washing step involves washing with water followed by washing with a lower alcohol.

[0017] [Section 10] (C) A method for producing N-substituted aspartic acid according to [Item 1] or [Item 9], wherein in the washing step, the lower alcohol is a linear or branched alcohol having 1 to 4 carbon atoms.

[0018] [Item 11] (C) In the washing step, the lower alcohol is methanol, and the method for producing N-substituted aspartic acid according to [Item 1] or [Item 9].

[0019] [Item 12] Furthermore, (D) a drying step of drying the N-substituted aspartic acid obtained after the washing step The method for producing N-substituted aspartic acid according to [Item 1], comprising

[0020] [Item 13] (D) In the drying step, the pressure is 10 kPa or less and the temperature range is 60 to 90 °C, and the method for producing N-substituted aspartic acid according to [Item 12]. [Advantages of the Invention]

[0021] By the production method of the present invention, it has become possible to produce high-purity N-substituted aspartic acid with a small residual amount of long-chain aliphatic amine and which can be used as a raw material for amino acid-based amphoteric surfactants. [Embodiments for Carrying Out the Invention]

[0022] The method for producing high-purity N-substituted aspartic acid of the present invention will be described in detail.

[0023] <N-Substituted Aspartic Acid> The N-substituted aspartic acid according to the present invention is General formula (1) [Chemical formula] [In the formula, R 1 represents a linear or branched alkyl group or alkenyl group having 8 to 22 carbon atoms, and R 2 represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms which may be substituted with a hydroxyl group.] is represented by. As R 1 , a linear or branched alkyl group or alkenyl group having 8 to 18 carbon atoms is preferable.

[0024] R 1 Examples of such groups include octyl group, 2-ethylhexyl group, decyl group, lauryl group, myristyl group, palmityl group, stearyl group, isostearyl group, oleyl group, behenyl group, coconut oil alkyl group, palm kernel oil alkyl group, palm oil alkyl group, and beef tallow alkyl group. Among these, lauryl group, myristyl group, palmityl group, and oleyl group are preferred.

[0025] Also, R 2 Examples of these groups include hydrogen atoms, methyl groups, ethyl groups, propyl groups, hydroxymethyl groups, hydroxyethyl groups, and hydroxypropyl groups. Among these, hydrogen atoms are preferred.

[0026] The maleate and / or fumarate according to the present invention are General formula (2) [ka] [In the formula, the wavy line indicates that the isomer configuration of the double bond can be either cis or trans. M 1 and M 2 M represents the same or different hydrogen atom, lithium ion, sodium ion, potassium ion, ammonium ion, or organic ammonium ion. 1 M 2 One of these represents a lithium ion, sodium ion, potassium ion, magnesium ion, ammonium ion, or organic ammonium ion. It is represented as follows.

[0027] M 1 M 2 Examples include hydrogen atoms, lithium ions, sodium ions, potassium ions, magnesium ions, ammonium ions, monoethanolammonium ions, diethanolammonium ions, triethanolammonium ions, isopropanolammonium ions, alkylammonium ions having 1 to 4 carbon atoms, and ammonium ions of basic amino acids. However, M1 , M 2 shall not be a hydrogen atom at the same time. Among these, it is preferable that one of M 1 , M 2 is a hydrogen atom. In particular, it is preferable that M 1 is a sodium ion or a potassium ion, and M 2 is a hydrogen atom, or M 1 is a hydrogen atom, and M 2 is a sodium ion or a potassium ion.

[0028] The long-chain aliphatic amine according to the present invention is represented by the general formula (3) [Chemical formula] [In the formula, R 1 and R 2 are the same as those in the general formula (1).] and is represented by

[0029] <N-substituted aspartate> The N-substituted aspartate according to the present invention is represented by the general formula (4) [Chemical formula] [In the formula, R 1 and R 2 are the same as those in the general formula (1), and M 1 and M 2 are the same as those in the general formula (2).] and is represented by

[0030] The N-substituted aspartate represented by the general formula (4) is obtained in the state of a crude N-substituted aspartate in a reaction mixture obtained by an addition reaction of a maleate and / or fumarate represented by the general formula (2) and a long-chain aliphatic amine represented by the general formula (3). For the addition reaction, a known method can be used. For example, the method described in JP-A-2000-136172 can also be used.

[0031] In this specification, crude N-substituted aspartate refers to the solid content obtained by removing evaporative components such as the reaction solvent from the reaction mixture obtained by the above addition reaction.

[0032] The N-substituted aspartate content in the crude N-substituted aspartate obtained by the above method is typically around 94-98% by mass, and the amine content of the long-chain aliphatic amine is approximately 0.8-3.0% by mass. In this specification, the N-substituted aspartate content and amine content are values ​​measured by the methods described in the examples below.

[0033] (A) Acid decomposition process The acid decomposition step is a process of obtaining N-substituted aspartic acid by reacting an N-substituted aspartate in an aqueous solution with a specific inorganic acid under specific temperature conditions. It also includes a step aimed at precipitating the N-substituted aspartic acid crystals from the aqueous solution. In this specification, acid decomposition refers to the process of obtaining N-substituted aspartic acid from an N-substituted aspartate by reacting it with an inorganic acid.

[0034] As the raw materials for the above acid decomposition step, a reaction mixture obtained by the addition reaction of maleate and / or fumarate with a long-chain aliphatic amine may be used, or a crude N-substituted aspartate obtained by removing evaporated components from the reaction mixture may be used.

[0035] The acid decomposition step is carried out in an aqueous solution by dissolving the reaction mixture or crude N-substituted aspartate in water. It is acceptable for a small amount of water-soluble organic solvent to be present in the aqueous solution, as long as it does not interfere with the effects of the invention. The concentration of crude N-substituted aspartate in the aqueous solution is preferably 10 to 30% by mass, more preferably 20 to 30% by mass, and particularly preferably 25 to 30% by mass. If the concentration of crude N-substituted aspartate exceeds 30% by mass, the efficiency of impurity removal in the subsequent washing step tends to decrease, while diluting to a concentration below 10% by mass does not yield an effect commensurate with the amount of water used.

[0036] The inorganic acid used in the acid decomposition process can be added all at once or in stages, but from an industrial safety standpoint, it is preferable to add it in stages due to the heat generated during acid decomposition. The time required for addition is not particularly limited, but 15 to 60 minutes is preferred.

[0037] The acid decomposition step is preferably carried out under stirring. The temperature of the acid decomposition step is 40 to 100°C, preferably 60 to 90°C, and particularly preferably 60 to 80°C. If the temperature is below 40°C, the precipitated N-substituted aspartic acid crystals become finer, and the impurity content in the crystals after the washing step tends to increase. On the other hand, if the temperature exceeds 100°C, the resulting N-substituted aspartic acid tends to have undesirable characteristics in terms of color and odor.

[0038] The inorganic acid used in the acid decomposition process is an inorganic acid whose acid dissociation constant (pKa1) is smaller than that of N-substituted aspartic acid. Specifically, sulfuric acid (pKa1=-3.29, pKa2=1.98), hydrochloric acid (pKa1=-5.9), nitric acid (pKa1=-1.43), and phosphoric acid (pKa1=1.83) are preferred, with sulfuric acid being particularly preferred among these. The above inorganic acids may also be used in mixtures. Note that the acid dissociation constant (pKa1) refers to the negative common logarithm of the acid dissociation constant (Ka1). The acid dissociation constant (pKa1) of N-substituted aspartic acid is estimated to be pKa1=2.19.

[0039] The amount of inorganic acid used in the acid decomposition step is preferably 1.0 to 1.5 molar equivalents, more preferably 1.0 to 1.2 molar equivalents, and particularly preferably 1.0 to 1.1 molar equivalents, relative to the amount of cations contained in the crude N-substituted aspartate. Using more than 1.5 molar equivalents of inorganic acid does not yield an effect commensurate with the amount used, while using less than 1.0 molar equivalent results in insufficient acid decomposition, and tends to reduce the yield of N-substituted aspartic acid. Furthermore, if the inorganic acid is divalent or higher and its acid dissociation constant (pKa2) is smaller than the acid dissociation constant (pKa1) of N-substituted aspartic acid, the amount of inorganic acid is preferably 0.5 to 0.75 molar equivalents, more preferably 0.5 to 0.6 molar equivalents, and particularly preferably 0.5 to 0.55 molar equivalents, relative to the amount of cations contained in the crude N-substituted aspartate. Note that the acid dissociation constant (pKa2) refers to the negative common logarithm of the acid dissociation constant (Ka2).

[0040] It is preferable to adjust the pH of the aqueous solution at the end of the acid decomposition step to a range of 1.5 to 3.5 using the inorganic acid described above, and particularly preferable to adjust it to a range of 1.8 to 2.5. If the pH is less than 1.5, it is difficult to obtain an effect commensurate with the amount of inorganic acid used, while if the pH exceeds 3.5, the acid decomposition becomes insufficient, and the yield of N-substituted aspartic acid tends to decrease.

[0041] While there are no particular limitations on the duration of the acid decomposition process, it is generally recommended to wait 10 minutes to 5 hours after the completion of inorganic acid addition.

[0042] From a safety standpoint, the acid decomposition process is more preferably carried out under an inert gas atmosphere, such as argon, helium, nitrogen, or carbon dioxide.

[0043] (B) Separation process The separation step involves separating the N-substituted aspartic acid crystals that precipitated during the acid decomposition step.

[0044] Separation methods include, for example, filtration and centrifugation. Filtration can be performed at atmospheric pressure, reduced pressure, or pressurized pressure.

[0045] (C) Cleaning process The washing step involves washing the N-substituted aspartic acid crystals obtained in the separation step using water and a lower alcohol. Water and the lower alcohol may be used separately or mixed together. Washing methods include, for example, adding water to the separated crystals to form a suspension again, performing the separation step, then adding the lower alcohol to the separated crystals again to form a suspension, and performing the separation step once more, or a rinsing method in which water and then lower alcohol are passed through the crystals in a filter, but are not particularly limited.

[0046] In terms of the cleaning order, it is preferable to wash with water first, followed by washing with a lower alcohol, from the viewpoint of the efficiency of removing impurities.

[0047] For the water used, ion-exchanged water, distilled water, pure water, purified water, etc., can be used.

[0048] Examples of lower alcohols include linear or branched lower alcohols having 1 to 4 carbon atoms, more specifically methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, etc. Among these, methanol is preferred.

[0049] The amount of water used in the washing process is preferably 0.5 to 10 times the mass of the crude N-substituted aspartate, and from an economic standpoint, 0.5 to 3 times the mass is particularly preferable. If the amount of water is less than 0.5 times the mass, the desired washing effect is difficult to obtain, while if more than 10 times the mass is used, the washing effect will not be commensurate with the amount used. The entire amount of water can be used at once, or it can be divided and used in multiple steps.

[0050] Furthermore, the amount of lower alcohol used in the washing process is preferably 0.5 to 10 times the mass of the crude N-substituted aspartate, and from an economic standpoint, 0.5 to 3 times the mass is particularly preferable. The entire amount of lower alcohol can be used at once, or it can be used in multiple portions.

[0051] In the manufacturing method of the present invention, in addition to (A) acid decomposition step, (B) separation step, and (C) washing step, a (D) drying step may also be performed.

[0052] (D) Drying process The drying process involves drying the N-substituted aspartic acid containing water and / or a lower alcohol obtained in the washing process to obtain dried crystals of N-substituted aspartic acid. Drying methods include, but are not limited to, drying the crystals while stirring them in a stirring-type dryer or drying the crystals while they are standing in a shelf-type dryer.

[0053] The pressure during the drying process is not particularly limited, but is preferably 10 kPa or less, and especially preferably 3 kPa or less. If it exceeds 10 kPa, it is difficult to obtain the desired drying effect.

[0054] The temperature of the drying process is not particularly limited, but 60 to 90°C is preferred. Below 60°C, the desired drying effect is difficult to obtain, while above 90°C, the resulting N-substituted aspartic acid tends to have an undesirable odor.

[0055] The manufacturing method of the present invention yields high-purity N-substituted aspartic acid. The purity of the N-substituted aspartic acid is preferably 99.5% or higher, more preferably 99.6% or higher, and particularly preferably 99.7% or higher. In this specification, the purity of the N-substituted aspartic acid is the value measured by the method described in the examples below.

[0056] The amine residue of the long-chain aliphatic amine in N-substituted aspartic acid is preferably 0.30% by mass or less, more preferably 0.20% by mass or less, and particularly preferably 0.15% by mass or less. In this specification, the amine residue of N-substituted aspartic acid is the value measured by the method described in the examples below.

[0057] The content of cations derived from crude N-substituted aspartate in N-substituted aspartic acid is preferably 100 ppm or less, more preferably 50 ppm or less, and even more preferably 30 ppm or less. In the present specification, the content of cations derived from crude N-substituted aspartate is the value measured by the method described in the examples below.

[0058] The content of sulfur, chlorine, phosphorus, etc. derived from the inorganic acid used in the (A) acid decomposition step in N-substituted aspartic acid is preferably 300 ppm or less, more preferably 200 ppm or less, and even more preferably 100 ppm or less. In the present specification, the sulfur content, chlorine content, and phosphorus content of N-substituted aspartic acid are the values measured by the method described in the examples below.

[0059] By the production method of the present invention, high-purity N-substituted aspartic acid can be industrially produced, and the N-substituted aspartic acid can be used as a raw material for amino acid-based amphoteric surfactants.

Examples

[0060] Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. Commercially available products or reagents were used for compounds not specifically mentioned.

[0061] The various measurement methods and evaluation methods are as follows.

[0062] <Purity (%) of N-substituted aspartic acid> The purity (%) of N-substituted aspartic acid obtained in each example and comparative example was determined by HPLC analysis (RI detector), and the detected area% was taken as the purity (%). (HPLC analysis conditions) System controller: CBM-20A manufactured by Shimadzu Corporation Liquid delivery unit: LC-20AT manufactured by Shimadzu Corporation Column oven: CTO-20A manufactured by Shimadzu Corporation Column: STR-ODS-II manufactured by Showa Chemical Industry Co., Ltd. (octadecylsilylated silica gel, particle size 5 μm, inner diameter 6 mm, length 15 cm) Degassing unit: DGU-20A3 manufactured by Shimadzu Corporation Autosampler: SIL-20A manufactured by Shimadzu Corporation RI detector: RID-20A manufactured by Shimadzu Corporation Mobile phase: A solution prepared by dissolving 55.8 g of sodium perchlorate in 900 mL of ion-exchanged water, adding 900 mL of isopropanol and homogenizing, and then adding 62.5% by mass sulfuric acid to adjust the pH to 2.5 Flow rate: 1.0 mL per minute Analytical sample: A solution prepared by dissolving 1.0 g of N-substituted aspartic acid in a mixed solution of the mobile phase and 62.5% by mass sulfuric acid (mixing ratio is by volume, mobile phase:sulfuric acid = 26:1) to make 100 mL Sample injection volume: 20 μL

[0063] <Crude N-substituted aspartate> The crude N-substituted aspartate was obtained by subjecting a reaction mixture obtained by an addition reaction of maleate and / or fumarate with a long-chain aliphatic amine to distill off evaporation components such as the reaction solvent under reduced pressure using a rotary evaporator under the conditions of 70 °C and 3 kPa.

[0064] <Content (%) of N-substituted aspartate> The content (%) of N-substituted aspartate in the crude N-substituted aspartate obtained in each production example was calculated by HPLC analysis. The HPLC analysis conditions were the same as those for the purity (%) of N-substituted aspartic acid. Under the HPLC analysis conditions, since N-substituted aspartate is detected as N-substituted aspartic acid, first, the content (g) was determined as N-substituted aspartic acid by the HPLC internal standard method. From this content, the content (g) of N-substituted aspartate was calculated, and the content (%) of N-substituted aspartate was calculated from the following formula (A). Content (%) of N-substituted aspartate = Content (g) of N-substituted aspartate × 100 / Crude N-substituted aspartate (g) (A)

[0065] <Amine content (mass%)> The amine content (mass%) of the long-chain fatty acid amines in the crude N-substituted aspartates obtained in each production example was calculated using the following formula (B) after determining the amine content by the GC internal standard method. Amine content (mass%) = Amine content (g) × 100 / Crude N-substituted aspartate (g) (B) (GC analysis conditions) Measurement device: Shimadzu GC-2010 Column: Agilent J&W capillary column CAM (0.25 mm I.D. × 30 m, df = 0.25 μm) Injection method: Split method (30:1) Injection temperature: 220℃ Detection method: FID Detector temperature: 220℃ Column temperature: 100°C (held for 5 minutes) → 20°C / min → 220°C (held for 5 minutes)

[0066] <Amine residue (mass %)> The amine residue (mass%) of the long-chain fatty acid amine in the N-substituted aspartic acid obtained in each example and comparative example was calculated using the following formula (C) after determining the amine content by the GC internal standard method. Amine residue (mass%) = Amine content (g) × 100 / N-substituted aspartic acid (g) (C) The GC analysis conditions were carried out using the same method as for the amine content (mass%).

[0067] <Chlorine and sulfur content (ppm)> The chlorine and sulfur content in the N-substituted aspartic acid obtained in each example and comparative example was measured using ICS-1500, SPU-300, and ASRS-UL II 4-mm from Nippon Dionex Co., Ltd. by thermally decomposing the N-substituted aspartic acid obtained in each example and comparative example using AQF-100, WS-100, and GA-100 from Mitsubishi Chemical Corporation, dissolving the generated gas in a measurement solution, and measuring the content using ICS-1500, SPU-300, and ASRS-UL II 4-mm from Nippon Dionex Co., Ltd.

[0068] <Phosphorus and potassium content (ppm)> The phosphorus and potassium content in the N-substituted aspartic acid obtained in each example and comparative example was measured by oxidative decomposition of the N-substituted aspartic acid obtained in each example and comparative example with nitric acid, and then using a PerkinElmer Optima2000DV high-frequency plasma emission spectrometer.

[0069] [Manufacturing Example 1] Using a 500 ml four-necked flask equipped with a stirrer, reflux condenser, and stirring device, 24.5 g (250 mmol) of maleic anhydride and 12 g of deionized water were added and stirred. While stirring, 28.9 g (250 mmol) of 48.5% potassium hydroxide aqueous solution was added, followed by 30.5 g of n-butanol and 41.7 g (225 mmol) of laurylamine. The mixture was stirred at 99°C for 18 hours to allow the amine to be added, yielding reaction mixture A. The N-lauryl aspartate content in reaction mixture A was 92.3% by mass, and the amine content was 1.6% by mass relative to the crude N-lauryl aspartate.

[0070] [Manufacturing Example 2] Reaction mixture B was obtained in the same manner as in Production Example 1, except that laurylamine was replaced with myristylamine. The N-myristyl aspartate content in reaction mixture B was 93.2% by mass and the amine content was 1.4% by mass relative to the crude N-myristyl aspartate.

[0071] [Example 1] (A) Acid decomposition process 137.6 g of reaction mixture A obtained in Production Example 1 was added to 200 g of deionized water and stirred at 70°C to obtain an aqueous solution. Then, 20.5 g (130 mmol, 0.52 molar equivalents relative to potassium ions) of 62.5% by mass sulfuric acid (pKa1=-3.29, pKa2=1.98) was added over 30 minutes while stirring, and the mixture was stirred at 70°C for 2 hours to precipitate a white solid. The pH of the suspension was 2.1.

[0072] (B) Separation process The suspension obtained from the acid hydrolysis process was filtered under reduced pressure using a Kiriyama funnel. Kiriyama funnel filter paper No. 5C was used as the filter paper.

[0073] (C) Cleaning process The white solid on the Kiriyama funnel was washed by passing 150g of water through it twice, and then washed again by passing 150g of methanol through it twice.

[0074] (D) Drying process The white solid was removed from the Kiriyama funnel and dried at 1.3 kPa and 70°C for 6 hours, yielding 62.6 g of N-lauryl aspartic acid with a purity of 99.9%. Other impurities are shown in Table 1.

[0075] [Example 2] (A) Acid decomposition process 3.9 g of reaction mixture B14 obtained in Production Example 2 was added to 220 g of deionized water and stirred at 70°C to obtain an aqueous solution. Then, 20.5 g (130 mmol, 0.52 molar equivalents relative to potassium ions) of 62.5% by mass sulfuric acid (pKa1=-3.29, pKa2=1.98) was added over 30 minutes while stirring, and the mixture was stirred at 70°C for 2 hours to precipitate a white solid. The pH of the suspension was 2.2.

[0076] (B) Separation, (C) Washing, and (D) Drying steps were carried out in the same manner as in Example 1 to obtain N-myristyl aspartic acid with a yield of 68.2 g and a purity of 99.8%. Other impurities are shown in Table 1.

[0077] [Example 3] (A) Acid decomposition process 37.6 g of reaction mixture A obtained in Production Example 1 was added to 200 g of deionized water and stirred at 70°C to obtain an aqueous solution. Then, 25.6 g (260 mmol, 1.04 molar equivalent relative to potassium ions) of 37% by mass hydrochloric acid (pKa1=-5.9) was added over 30 minutes while stirring, and the mixture was stirred at 70°C for 2 hours to precipitate a white solid. The pH of the suspension was 2.2.

[0078] (B) Separation, (C) Washing, and (D) Drying steps were carried out in the same manner as in Example 1 to obtain N-lauryl aspartic acid with a yield of 61.5 g and a purity of 99.8%. Other impurities are shown in Table 1.

[0079] [Example 4] (A) Acid decomposition process 137.6 g of reaction mixture A obtained in Production Example 1 was added to 200 g of deionized water and stirred at 70°C to obtain an aqueous solution. Then, 30.1 g (260 mmol, 1.04 molar equivalent relative to potassium ions) of 85% by mass phosphoric acid (pKa1=1.83) was added over 30 minutes while stirring, and the mixture was stirred at 70°C for 2 hours to precipitate a white solid. The pH of the suspension was 3.3.

[0080] (B) Separation, (C) Washing, and (D) Drying steps were carried out in the same manner as in Example 1 to obtain N-lauryl aspartic acid with a yield of 60.0 g and a purity of 99.8%. Other impurities are shown in Table 1.

[0081] [Comparative Example 1] When reaction mixture A obtained in Production Example 1 was used, and the (A) acid decomposition step of Example 1 was carried out with acetic acid (pKa1=4.76) instead of sulfuric acid, N-lauryl aspartate was not acid-decomposed.

[0082] [Comparative Example 2] (A) The procedure was the same as in Example 1, except that the temperature of the acid decomposition step was changed from 70°C to 30°C. After drying, N-lauryl aspartic acid was obtained in a yield of 52.7 g with a purity of 98.6%. Other impurities are shown in Table 1.

[0083] [Comparative Example 3] (C) The procedure was the same as in Example 1, except that the washing step was omitted. After drying, 65.7 g of N-lauryl aspartic acid with a purity of 95.2% was obtained. Other impurities are shown in Table 1.

[0084] [Comparative Example 4] (C) The procedure was the same as in Example 1, except that methanol washing was not performed in the washing step. After drying, N-lauryl aspartic acid was obtained with a yield of 64.0 g and a purity of 97.7%. Other impurities are shown in Table 1.

[0085] [Table 1] [Industrial applicability]

[0086] The manufacturing method of the present invention can be suitably used as an industrial method for producing high-purity N-substituted aspartic acid.

[0087] The high-purity N-substituted aspartic acid obtained by the manufacturing method of the present invention is an amino acid-based amphoteric surfactant that exhibits excellent surface activity by selecting the chain length of the lipophilic group, the neutralization rate of the carboxyl group, and the neutralizing base.

Claims

1. General formula (1) 【Chemistry 1】 [In the formula, R １ R represents a linear or branched alkyl or alkenyl group having 8 to 22 carbon atoms. ２ This represents an alkyl group having 1 to 3 carbon atoms, which may be substituted with a hydrogen atom or a hydroxyl group. A method for producing N-substituted aspartic acid represented by, General formula (2) 【Chemistry 2】 [In the formula, the wavy line indicates that the isomer configuration of the double bond can be either cis or trans. M １ and M ２ M represents the same or different hydrogen atom, lithium ion, sodium ion, potassium ion, magnesium ion, ammonium ion, or organic ammonium ion. １ M ２ One of these represents a lithium ion, sodium ion, potassium ion, magnesium ion, ammonium ion, or organic ammonium ion. Maleates and / or fumarates represented by, General formula (3) 【Transformation 3】 [In the formula, R １ and R ２ This is the same as in general formula (1). Obtained by addition reaction with long-chain aliphatic amines represented by, General formula (4) 【Chemistry 4】 [wherein, R １ and R ２ are the same as those in General Formula (1), and M １ and M ２ are the same as those in General Formula (2).] A crude N-substituted aspartate containing the N-substituted aspartate represented by [formula] is prepared in an aqueous solution. (A) In the temperature range of 40 to 100°C, the acid dissociation constant (pKa) １ ) Acid decomposition step in which N-substituted aspartate is acid-decomposed by an inorganic acid smaller than N-substituted aspartic acid, and N-substituted aspartic acid is precipitated. (B) Separation step to separate the precipitated N-substituted aspartic acid, (C) Washing step in which the N-substituted aspartic acid after the separation step is washed with water and lower alcohol. A method for producing N-substituted aspartic acid, comprising the following:

2. (A) The method for producing N-substituted aspartic acid according to claim 1, wherein in the acid decomposition step, the inorganic acid is one or more inorganic acids selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid.

3. (A) A method for producing N-substituted aspartic acid according to claim 1 or 2, wherein the inorganic acid in the acid decomposition step is sulfuric acid.

4. (C) The method for producing N-substituted aspartic acid according to claim 1, wherein the washing step involves washing with water followed by washing with a lower alcohol.

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