JP2021038146A - Method for producing n-acylamine - Google Patents

Abstract

To provide a method for producing easily N-acylamine that resists coloring without using other components (such as catalysts) in addition to raw materials.SOLUTION: An method for producing N-acylamino acid includes a process in which, while irradiating an amino acid with microwaves, the amino acid is brought into contact with a fatty acid having a smaller amount of substance than that of the amino acid, to acylate the amino acid.SELECTED DRAWING: None

Description

The present invention relates to a method for producing N-acylamines.

N-acylamines such as N-acyl-N-methyltaurine salt are widely used as raw materials for various cleaning agents for body washing such as shampoo and cosmetics.
Various methods are known as methods for producing N-acylamines. For example, a method for producing N-acylamino acid by a dehydration reaction between an amino acid and a fatty acid, and a method for producing an alkali metal salt of N-methyltaurine and a fatty acid. A method for producing an N-acyl-N-methyltaurine salt by a reaction is known (Patent Documents 1 and 2 and the like). However, problems such as coloration of the product have been recognized in these methods.

As a solution to this problem, a method of carrying out the dehydration reaction in the presence of a catalyst (Patent Document 3), a method of carrying out the dehydration reaction under predetermined conditions while blowing nitrogen gas, and the like have been proposed. ing.

However, when N-acylamines are used as raw materials for cosmetics or cleaning agents for body cleaning (shampoo, etc.), it is desirable that no components such as catalysts remain, and N-acylamines do not require complicated operations. It is desirable to be able to produce acylamines.

UK Pat. No. 133,782 U.S. Pat. No. 2,880,219 JP-A-2002-234868 Japanese Unexamined Patent Publication No. 2005-8603

In view of the above-mentioned problems in the prior art, an object of the present invention is to provide a method for producing N-acylamines in which coloration is suppressed by a simple operation without using components other than raw materials such as a catalyst. To do.

As a result of diligent research, the present inventors have found that the above problems can be solved by selectively and uniformly activating desired components by microwaves, and have completed the present invention.
The present invention relates to the following [1] to [3].

[1]
Of N-acylamino acids, which comprises a step of acylating the amino acids by contacting the amino acids with a fatty acid having a substance amount smaller than the substance amount of the amino acids while irradiating the amino acids with microwaves. Production method.

[2]
The step is a step of acylating the amino acids by irradiating a mixture containing the amino acids and the fatty acid and having a substance amount of the amino acids larger than the substance amount of the fatty acid with microwaves. [1] Method for producing N-acylamino acids.

[3]
The method for producing N-acylamino acids according to the above [1] or [2], wherein the amino acids are amino acids, a taurine compound represented by the following formula (1), or a salt thereof.

[In the formula, R ¹ is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.
R ² is a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms.
R ³ is a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms. ]

According to the production method of the present invention, N-acylamines whose coloring is easily suppressed can be produced without using components other than raw materials such as a catalyst, and therefore without requiring post-treatment such as removal of residual components and decolorization. can do.

FIG. 1 shows the microwave absorption characteristics (dielectric loss rate ε ″ -frequency curve) of an aqueous solution of sodium N-methyltaurine. FIG. 2 shows the microwave absorption characteristics (dielectric loss rate ε ″ -frequency curve) of lauric acid. FIG. 3 shows the microwave absorption characteristics of water (dielectric loss rate ε ″ -frequency curve). FIG. 4 shows the microwave absorption characteristics (dielectric loss rate ε ″ -frequency curve) of the N-lauroyl-N-methyltaurine sodium aqueous solution. FIG. 5 shows the color tone quantification results of N-lauroyl-N-methyltaurine sodium synthesized in Example 1 and Comparative Example 1.

Hereinafter, the present invention will be described in more detail.
The method for producing N-acylamino acids according to the present invention is to contact the amino acids with a fatty acid having a substance amount smaller than the substance amount of the amino acids while irradiating the amino acids with microwaves. It is characterized by including a step of acylating.

As an aspect of the step, for example,
(Aspect 1): A step of acylating the amino acids by irradiating a mixture containing the amino acids and the fatty acid and having a substance amount of the amino acids larger than the substance amount of the fatty acid with a microwave. 2): A step of acylating the amino acids by adding the fatty acid in a substance amount smaller than the substance amount of the amino acids to the amino acids while irradiating the amino acids with microwaves.

Hereinafter, the production method of the present invention will be described with a focus on the first aspect.
(Amino acids)
Examples of the amino acids include amino acids, amino acid derivatives, and salts thereof.

The amino acid is a compound having one or more amino groups and one or more carboxyl groups in one molecule, preferably one amino group and one carboxyl group.

The amino group contained in the amino group is NH ₂ , NHR or NRR'(R represents an alkyl group having 1 to 6 carbon atoms, preferably a methyl group, and R'is an alkyl group having 1 to 6 carbon atoms. , Preferably representing a methyl group), and at least one amino group is an amino group represented by _{NH 2 or NHR.}

Examples of the amino acid include glycine, alanine, β-alanine, aminobutyric acid, aminovaleric acid, N-methylglycine, N-methylalanine, and N-methyl-β-alanine.

The amino acid derivative is a compound in which one or more carboxyl groups of the amino acid are replaced with a group selected from the group consisting of _{a sulfo group (SO 3} H) and a phosphate group (H ₂ PO _4). ..

Examples of the amino acid derivative include a taurine compound represented by the following formula (1).

[In the formula, R ¹ is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, preferably a methyl group.
R ² is a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms (preferably 1 to 8, more preferably 1 to 4), and is preferably a hydrogen atom.
R ³ is a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms (preferably 1 to 8, more preferably 1 to 4), and is preferably a hydrogen atom. ]

The taurine compound represented by the above formula (1) is preferably N-methyl taurine.

Examples of the salt of the amino acid or the amino acid derivative include alkali metal salts such as sodium salt and potassium salt, alkaline earth metal salts such as calcium salt and magnesium salt, and ammonium salts, and alkali metal salts are preferable. Sodium salts are more preferred.

Examples of the amino acids include N-methyltaurine sodium, N-methylalanine, and N-methylglycine, and more preferably N-methyltaurine sodium.

FIG. 1 shows a dielectric loss rate ε ″ -frequency curve of an aqueous solution of sodium N-methyltaurine, which is one of the amino acids, measured at an example described later at 50 ° C. at frequencies in the measurement range shown in FIG. , N-Methyltaurine sodium has a large dielectric loss rate ε ”and high microwave absorption ability.

Amino acid molecules form zwitterions because they have a carboxyl group and an amino group. Generally, microwave energy is converted into heat by any of conduction loss, dielectric loss, and magnetic loss, depending on the molecule to be absorbed. Therefore, many of the amino acids that are conductors have a very high ability to absorb microwaves. Therefore, amino acids and their salts have a greater dielectric loss rate ε ”than fatty acids.

(fatty acid)
The number of carbon atoms of the fatty acid is usually 6 to 22, preferably 8 to 20, and more preferably 10 to 18.

The fatty acid may be either a saturated fatty acid or an unsaturated fatty acid, and may be linear or have a branched chain.
The fatty acid may be a single type of fatty acid or a mixture of a plurality of types of fatty acids. The mixture of fatty acids may be naturally obtained or artificially formulated. Examples of the mixture include coconut oil fatty acids (ie, a mixture of a plurality of fatty acids obtained by hydrolysis of coconut oil).

Specific examples of the fatty acid include caproic acid, capric acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid and the like, among which lauric acid, myristic acid, palmitic acid and oleic acid. Is preferable, and lauric acid is more preferable.
As the fatty acid, lauric acid and coconut oil fatty acid are preferable.

FIG. 2 shows a dielectric loss rate ε ”− frequency curve of lauric acid, which is one of the fatty acids, measured in Examples described later at 50 ° C. At frequencies in the measurement range shown in FIG. 2, lauric acid is dielectric. The loss rate ε ”is small and the microwave absorption capacity is extremely low.

It is known that the polarity of molecules affects the dielectric properties. The polarity of the fatty acid molecule largely depends on the portion of COOH in the molecule, and even if the carbon chain length changes, the polarity does not change, and therefore the dielectric loss rate does not change. Regarding this point, for example, Dielectric properties of some edible and medicinal oils at microwave frequency / Thomas Mathew, AD Vyas, Deepti Tripathi / Canadian Journal of Pure and Applied Sciences, Vol. 3, No. 3, pp. 953-957, It can also be confirmed from the fact that in 2009, it was shown that the dielectric constants and dielectric loss rates of various fats and oils (triglycerides) were almost unchanged even when the constituent fatty acids were changed.
As described above, the microwave absorption capacity of the fatty acid is extremely small.

(blend)
In the production method of the present invention, the amino acids are brought into contact with the fatty acids in a substance amount smaller than the substance amount of the amino acids while irradiating the amino acids with microwaves. For example, a mixture containing the amino acids and the fatty acids and having a substance amount of the amino acids larger than the substance amount of the fatty acids is irradiated with microwaves.

The ratio of the amino acids and the fatty acids is, for example, more than 1 and 10 or less: 1, preferably more than 1 and 5 or less: 1, more preferably more than 1.0 in molar ratio (amino acids: fatty acids). 1.1 or less: 1.0.

In the production of N-acylamines according to the present invention, the ratio of the amount of substance of the fatty acid to the amino acids does not affect the coloring of the N-acylamines. That is, even if the amount of substance of the fatty acid is equal to or greater than the amount of substance of the amino acids, the N-acylamines produced by acylating the amino acids do not have a coloring problem. However, if the amount of substance of fatty acid is equal to or greater than the amount of substance of amino acids, unreacted fatty acid remains in N-acylamines. Since N-acylamines are water-insoluble in water-based toiletries such as shampoos and oil-in-water cosmetics such as cleansing emulsions, they are formulated. Immediately after, or with the passage of time after formulation, it precipitates as crystals, which not only deteriorates the appearance of the final formulation, but also greatly affects the product quality such as emulsification destruction. That is, when the amount of substance of the fatty acid is equal to or greater than the amount of substance of the amino acids, the step of removing the remaining fatty acid is indispensable. Distillation removal by high temperature and high vacuum is widely used for removing fatty acids, but it also includes the possibility of coloring and decomposition of N-acylamines due to heating during the operation.

On the other hand, when the amount of substance of the fatty acid is smaller than the amount of substance of the amino acids (that is, the amount of substance of the amino acids is larger than the amount of substance of the fatty acid), according to the production method of the present invention, N-acylamine. It is possible to suppress the coloring of such substances and avoid the residual unreacted fatty acids described above. That is, in using N-acylamines in products such as cosmetics, a step of removing residual fatty acids becomes unnecessary. Unreacted amino acids remain in the N-acylamines produced by the method of the present invention, but since these amino acids are water-soluble, the N-acylamines can be used in the above-mentioned products such as toiletries and cosmetics. It is not always necessary to remove the remaining amino acids when using the amino acids. Therefore, by producing N-acylamines by the method of the present invention, products such as cosmetics using N-acylamines can be produced with a small number of steps without providing steps such as decolorization and fatty acid removal. Can be done.

The mixture is prepared by mixing the amino acids and the fatty acids in the above proportions.
According to the production method of the present invention, N-acylamino acids having suppressed coloring can be produced without adding a component such as a catalyst to the mixture. Normally, no components other than the amino acids and the fatty acids, which are raw materials, such as a catalyst, are added to the mixture.

(Acylation process)
Conventionally, as a method for producing N-acylamino acids, N-Amino acids include a step of activating and acylating a mixture containing the amino acids and the fatty acid (hereinafter, also referred to as "acyllation step"). A method for producing acyl amino acids is known. The production method of the present invention includes, for example, amino acids and fatty acids by bringing the amino acids into contact with the fatty acids while irradiating the amino acids with microwaves, and the amount of substance of the amino acids is the fatty acid. It is characterized in that it is carried out by irradiating a mixture larger than the amount of substance of the above with microwaves.

The frequency of the irradiated microwave may be, for example, a frequency in the range of 300 MHz to 20 GHz, or may be 434 MHz, 915 MHz, 2.45 GHz, 5.8 GHz, 10 GHz, or 24 GHz.

The temperature at which the acylation step is carried out (hereinafter, also referred to as “reaction temperature”) is determined by, for example, measuring the temperature of the reaction system and adjusting the output of microwaves based on the measured temperature. Can be controlled.

Here, the reaction temperature is the temperature of the mixture as a whole. As described above, since amino acids and fatty acids actually have significantly different microwave absorption abilities, their activation states are different and their temperatures are different for each component. However, since it is difficult to measure the temperature of each component, the temperature of the mixture as a whole is controlled.

The reaction temperature is appropriately set according to the types of amino acids and fatty acids within the range below the decomposition temperature of N-acylamino acids. For example, a practical reaction rate is ensured and N-acylamino acids are colored. From the viewpoint of suppressing the temperature, it is, for example, 200 to 250 ° C, preferably 210 to 230 ° C. The reaction temperature may be measured invasively by thermoelectric pair or the like, or may be measured non-invasively by infrared rays or the like.

As a method for raising the temperature of the mixture containing amino acids and fatty acids to the reaction temperature, preferably, the fatty acids are melted by an arbitrary method, the amino acids and the melted fatty acids are mixed, and a microwave is applied to the obtained mixture. A method of irradiating can be mentioned.

The time during which the acylation step is carried out, that is, the time from when the temperature of the reaction system rises to a desired reaction temperature until the end of microwave irradiation is appropriately set, for example, 0.1 to 3 It's time.

The amino acids may be provided as an aqueous solution or as a dry powder, preferably as a dry powder or in a form in which water is sufficiently removed.
The atmosphere in which the acylation step is carried out is preferably an inert gas (for example, helium gas, nitrogen gas, argon gas) atmosphere from the viewpoint of suppressing coloring of N-acylamino acids, and is preferably a nitrogen gas atmosphere. Is. The inert gas may be fed into the headspace of the reactor in which the acylation step is performed, or may be fed directly into the mixture.

In the acylation step, the mixture is preferably stirred.
The N-acylamines produced in the acylation step may be further purified by a conventionally known method or the like.

The reason why the N-acylamines whose coloring is suppressed by the production method of the present invention can be presumed as follows.
As described above, the amino acids, which are one of the raw materials used in the production method of the present invention, have a large dielectric loss rate, and the fatty acid, which is another raw material, has a small dielectric loss rate. On the other hand, the activation temperature of amino acids is higher than that of fatty acids.

In the production method of the present invention, the raw material is preferably supplied to the reaction system in a form in which water is appropriately removed. The stirring efficiency of the mixture containing water is poor.
When the reaction intermediate via the powder or high viscosity state is heated by the conventional heating method, the components located near the heating source such as the heater, the internal heat medium coil, and the steam jacket are locally heated. An easy situation will arise. In heating by the conventional method of powder or high-viscosity liquid, the contact time between these substances and the heat transfer surface becomes relatively long. Therefore, there arises a problem that a part or all of the reaction intermediate is altered and colored.

However, according to microwave irradiation, it is possible to heat the inside of the reactor without depending on the contact with the heat transfer surface as seen in the conventional heating method. This is because microwaves can directly transfer energy to a microwave-absorbing component (molecule) and heat the component as a result of the vibration of the molecule. Therefore, also in the present invention, the microwave-absorbing amino acids can obtain energy regardless of their position in the reactor, and as a result, selectively (that is, among the raw material amino acids and fatty acids). Amino acids are selected) and uniform heating is achieved. Therefore, when microwave irradiation is used, the active agitation that is usually seen in heating may be unnecessary.

In the acylation reaction in the present invention, the microwave-absorbing components are amino acids and N-acylamino acids. Coloring can be suppressed by achieving uniform and internal heating of these components by microwave irradiation.

(Use of N-acylamines, etc.)
According to the production method of the present invention, N-acylamines in which coloration is suppressed can be produced. Since the production method of the present invention can produce N-acylamines without adding components other than amino acids and fatty acids as raw materials, for example, a catalyst, etc., it does not contain unfavorable residual components and is mostly colored. No N-acylamines can be produced in a simple process. When a large amount of N-acylamines produced in this manner is blended in toiletry products such as cosmetics and shampoos, they are excellent in processability from the viewpoint of reducing coloration of the preparations in their final product forms. In addition, when it is added to quasi-drugs, it is particularly useful because there is no concern about the effects of residual components on the body.

Hereinafter, the present invention will be described in more detail with reference to Examples and the like, but the present invention is not limited to the Examples.

[Microwave absorption characteristics of raw materials, etc.]
(Measurement of complex permittivity of sodium salts of amino acids)
Sodium N-methyltaurine was dissolved in water to a concentration of 20% by mass. The obtained aqueous solution was measured for the complex permittivity under the condition of a frequency of 0.2 GHz to 20 GHz with a probe for measuring the complex permittivity of liquid. The measurement results (dielectric loss rate ε ″ -frequency curve) are shown in FIG. 1. The microwave absorption by N-methyltaurine sodium was found to be extremely high at frequencies in the measurement range. Also, the dielectric loss of blank water was found to be extremely high. The rate ε ”− frequency curve is shown in FIG.

(Measurement of complex permittivity of fatty acids)
Lauric acid was heated to 50 ° C. and melted, and the complex permittivity under the condition of 0.2 GHz to 20 GHz was measured with a probe for measuring the complex permittivity of liquid. The measurement results (dielectric loss rate ε ″ -frequency curve) are shown in FIG. 2. It was found that the microwave absorption by lauric acid was extremely low at the frequencies in the measurement range.

(Measurement of complex permittivity of sodium N-acyl-N-methyltaurine)
Sodium N-lauroyl-N-methyltaurine was dissolved in water to a concentration of 20% by mass. The obtained aqueous solution was measured for complex permittivity under the conditions of 0.2 GHz to 20 GHz with a probe for measuring liquid complex permittivity. The measurement result (dielectric loss rate ε ″ -frequency curve) is shown in FIG. 4. It was found that the microwave absorption by N-lauroyl-N-methyltaurine sodium was extremely high at the frequency in the measurement range.

[Example 1]
(Synthesis of N-lauroyl-N-methyltaurine sodium by microwave heating)
22.3 g of N-methyltaurine sodium powder and 25.0 g of lauric acid melted by heating to 60 ° C. were added to a 100 mL glass three-necked flask. A reflux tube is connected to the flask, and while supplying dry nitrogen gas into the flask, the contents of the flask are subjected to a frequency of 2.45 GHz using a microwave reactor (μReactorEX, manufactured by Shikoku Measurement Industry Co., Ltd.). The contents were heated by irradiating with microwaves. Stirring was started when the internal temperature of the flask reached 230 ° C., the internal temperature was maintained at 230 ° C. for 60 minutes, and then microwave irradiation was stopped. The internal temperature was maintained at 230 ° C. by measuring with a thermocouple and controlling the microwave output according to the measured temperature.

A part of the obtained reaction product (mixture containing the target product) was recovered and dissolved in water to a concentration of 10% by mass, and the content of the target product (N-lauroyl-N-methyltaurine sodium) was obtained. Was quantified. The quantification was performed by high performance liquid chromatography (manufactured by Shimadzu Corporation) equipped with an evaporation light scattering detector and a UV detector. The content was 72.3% by mass.

A part of the obtained reaction product (mixture containing the target product) was recovered, dissolved in water to a concentration of 10% by mass, and the color tone of the aqueous solution was quantified based on the L * a * b color system. .. The quantification was performed by an ultraviolet-visible spectrophotometer (V-750, manufactured by JASCO Corporation). The results are shown in FIG.

[Comparative Example 1]
(Synthesis of N-lauroyl-N-methyltaurine sodium by heat transfer)
22.3 g of sodium N-methyltaurine and 25.0 g of lauric acid melted by heating to 60 ° C. were added to a 100 mL glass three-necked flask. A reflux tube was connected to the flask, and while supplying dry nitrogen gas into the flask, the flask was heated with an aluminum block heater until the internal temperature of the flask reached 230 ° C. Stirring was started when the internal temperature of the flask reached 230 ° C., the internal temperature was maintained at 230 ° C. for 60 minutes, and then heating was stopped. The internal temperature was maintained at 230 ° C. by measuring with a thermocouple and controlling the output of the heater according to the measured temperature.

A part of the obtained reaction product (mixture containing the target product) was recovered and dissolved in water to a concentration of 10% by mass, and the content of the target product (N-lauroyl-N-methyltaurine sodium) was obtained. Was quantified in the same manner as in Example 1. The content was 77.5% by mass.

A part of the obtained reaction product (mixture containing the target product) was recovered, dissolved in water to a concentration of 10% by mass, and based on the L * a * b color system as in Example 1. The color tone of the aqueous solution was quantified. The results are shown in FIG.

In Example 1 in which heating was performed by microwave irradiation, the L * -a * plane, in the color tone quantification of the produced N-lauroyl-N-methyltaurine sodium, was compared with that in Comparative Example 1 in which heating was performed by a heater. It was found that the value of the brightness L * was high on all the L * -b * surfaces and the coloring was suppressed.

Claims (3)

Of N-acylamino acids, which comprises a step of acylating the amino acids by contacting the amino acids with a fatty acid having a substance amount smaller than the substance amount of the amino acids while irradiating the amino acids with microwaves. Production method. The step is a step of acylating the amino acids by irradiating a mixture containing the amino acids and the fatty acids and having a substance amount of the amino acids larger than the substance amount of the fatty acids with microwaves. The method for producing N-acylamino acids according to 1. The method for producing N-acylamino acids according to claim 1 or 2, wherein the amino acids are amino acids, a taurine compound represented by the following formula (1), or a salt thereof.
[In the formula, R ¹ is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.
R ² is a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms.
R ³ is a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms. ]