JPS5949926B2 - Production method of polyglutamic acid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing polyglutamic acid, and more particularly to a method for producing polyglutamic acid, and more specifically, a method for producing polyglutamic acid.
It will be abbreviated as A.

) in the presence of a primary amine. Polyglutamic acid or its sodium salt is a compound useful as a raw material for a textile treatment agent that does not cause skin damage. Conventionally, the method for synthesizing polyglutamic acid is as follows:
After converting glutamic acid into methyl or benzyl ester, N-carboxylic acid anhydrides of these esters are synthesized, and the acid anhydrides are further polymerized to obtain 30 poly-γ-methylglutamate or poly-γ-benzylglutamate. Synthesize.

Thereafter, in the case of poly-γ-methylglutamate, the side chain ester group is hydrolyzed and removed using sodium hydroxide to obtain polyglutamic acid. On the other hand, poly-γ
- In the case of benzyl glutamate, polyglutamic acid is obtained by debenzylation using hydrogen bromide or by catalytic reduction. In either case, these methods require a double operation of esterifying and protecting the carboxyl group at the γ-position of glutamic acid, and then removing it again, resulting in a large number of steps in an industrial sense, and traditional methods. As a result, the price also increased, creating an industrial disadvantage. On the other hand, regarding the method of directly synthesizing polyglutamic acid by polymerizing the N-carboxylic anhydride of glutamic acid obtained by directly phosgenating glutamic acid, H. N. Kovac et al. Although various studies have been conducted, it has been reported that unlike N-carboxylic anhydrides of other amino acids, most of the polyglutamic acid becomes pyroglutamic acid, and the desired polyglutamic acid could only be obtained in low yield.

[H, N. Kovaci et al., Journal of the American Chemical Society, vol. 85, 1839-184
4 (1963)] That is, GA-NCA was polymerized in pyridine or ether using pyridine or triethylamine as a polymerization initiator, but polyglutamic acid was obtained in a yield of only 20 to 27%. benzylamine in sodium bicarbonate solution as initiator,
Also, sodium methylate in dioxane (CH30Na
) as an initiator, the former was obtained in a yield of only 7%, and the latter was unable to obtain a water-insoluble polymer under acidic conditions.

As mentioned above, unlike the N-carboxylic acid anhydrides of other amino acids, GA-NCA is thought to either not undergo ring-opening polymerization to give polyglutamic acid in a good yield, or not to polymerize to give a polymer. was.

However, as a result of detailed research on the polymerization of GA-NCA, the present inventor found that when a tertiary amine such as triethylamine, a secondary amine such as diethylamine, or CH3ONa is used as a polymerization initiator,
H. N. The results were similar to those of Kovaci et al.'s experiment; almost no polyglutamic acid could be obtained, and only pyroglutamic acid or a gummy substance was obtained, but surprisingly,
The present invention was completed based on the discovery that polyglutamic acid can be obtained in high yield and with a high degree of polymerization when a primary amine is used as a polymerization catalyst.

Generally, when other amino acids NCA are polymerized, for example, when alanine NCA is polymerized to synthesize polyalanine, the degree of polymerization of the resulting polyalanine is the same as that of the alanine NCA used.
It depends on the ratio of the number of moles of the used initiator [I] to (the number of moles of the amino acid NCA) [A], that is, n2]/[Eq], and in general, the larger n, the higher the degree of polymerization. known to grow large. However, the inventor
As a result of a detailed study of the behavior of glutamic acid NCA toward primary amines, we surprisingly found that, contrary to the conventional concept, as the value of n, that is, the ratio of CA)/[I] was increased to 1 or more, the polymer It has been found that both the degree of polymerization and the polymer yield decrease.

The present invention has been completed based on these new findings. For example, when GA-NCA is polymerized in acetonitrile using n-butylamine as a polymerization initiator, [I]
The relationship between /[ and the polymerization rate is shown in Figure 1. Also] / [I]
The relationship between the polymerization degree and the polymerization degree is shown in Figure 2. As is clear from these figures, contrary to the conventional concept, as the initiator concentration increases, the polymerization rate and degree of polymerization also increase. These facts indicate that GA-NCA and n-butylamine first form a salt,
This is thought to be involved in polymerization, but this fact is a completely new finding. The present invention has been made based on this new knowledge.

Next, to explain the present invention in more detail, a specified primary amine is added to GA-NCA in an organic solvent kept at a specified temperature, and the mixture is stirred for a specified period of time to undergo ring-opening polymerization, resulting in the desired polyglutamic acid. It can be obtained in high yield.

As the polymerization solvent, solvents commonly used for polymerization of amino acids NCA are used.

For example, halogenated hydrocarbons such as methylene chloride, ethane dichloride, and chloroform, ethers such as ether and dioxane, and solvents such as acetonitrile, ethyl acetate, and N,N-dimethylformamide are used. In particular, when acetonitrile, ethyl acetate, etc. are used, polyglutamic acid will precipitate as the polymerization progresses.
Polyglutamic acid can be obtained by processing it directly. Particular preference is given to using acetonitrile.
It is known that GA-NCA is extremely unstable in water and immediately converts to pyroglutamic acid, so in order to obtain polyglutamic acid in a good yield, it is preferable to use these polymerization solvents after dehydration. . The polymerization temperature is preferably lower in consideration of the stability of glutamic acid NCA, but if it is too low, the polymerization rate will be slow, so polymerization is carried out at a temperature of 0°C to 50°C, preferably 10°C to 30°C. Types of amines that can be used include aliphatic amines such as methylamine, ethylamine, propylamine (including isomers), butylamine (including isomers), hexylamine (including isomers), and cyclohexylamine. Primary amines such as alicyclic amines and benzylamine are used, but these can be used alone or in combination.

Alternatively, after adding the primary amine in an equimolar ratio with GA-NCA, a tertiary amine such as triethylamine, or a secondary amine such as diethylamine may be added. The glutamic acid used in the present invention can be either optically active or inactive.

The polyglutamic acid obtained by the present invention can be easily converted into sodium polyglutamate by a conventional method.

Thus, inexpensive sodium polyglutamate that can be easily obtained industrially can be used as a fiber treatment agent. Hereinafter, aspects of the present invention will be explained with reference to Examples.

Example 1 50 g of an acetonitrile solution in which 500 mg of L-glutamic acid NCA was dissolved was placed in a 100 g O-angle flask equipped with a silica gel tube.

Add 50 ml of an acetonitrile solution containing 372 grams of n-butylamine, and heat in a constant temperature bath for 25. Polymerization was carried out at 0°C.

Polymerization is completely completed in about 5 hours, and the polymer begins to precipitate. Since the precipitated polymer is a salt with the initiator, it is washed with acetonitrile, dissolved in 50 Tnl of water, and adjusted to pH 3.0 with 3N hydrochloric acid. The precipitated polyglutamic acid was filtered out and dried under vacuum. 359 (polymer yield 95%) was obtained. The polymerization degree of this product was about 30. Example 2 Into a 300 WLI Erlenmeyer flask equipped with a silica gel tube, 1507 nl of ethyl acetate in which 5.09 L-glutamic acid NCA was dissolved was placed.

50 d of ethyl acetate in which 2.869 g of cyclohexylamine was dissolved was added, and polymerization was carried out at 25° C. in a constant temperature bath. After 15 hours, the precipitated polymer was collected, washed with ethyl acetate, dissolved in 200 d of water, and adjusted to pH 3.0-4.0 with 2N hydrochloric acid.
Adjust so that it becomes 0.

3. The precipitated polyglutamic acid was collected by filtration and dried under vacuum.
359 (yield 90%) was obtained. The degree of polymerization of this product is about 3
It was 2.

[Brief explanation of the drawing]

Figure 1 shows the polymerization of L-glutamic acid NCA in acetonitrile using n-butylamine as an initiator.
A) This is a graphical representation of the results of examining the conversion rate to polymer by changing the ratio of [A].

Claims (1)

[Claims] 1. A method for producing polyglutamic acid, which comprises polymerizing glutamic acid-N-carboxylic anhydride in the presence of a primary amine in an amount of 1 or more moles relative to glutamic acid-N-carboxylic anhydride.