JPH07196790A - Production of polyamino acids - Google Patents

Abstract

PURPOSE:To obtain a polyamino acid having a given molecular weight in a shortened reaction time in excellent reproducibility in high yield and simply without requiring a strict control of reaction temperature. CONSTITUTION:This method for producing a polyamino acid comprises subjecting an amino acid containing >=50mol% of an acidic amino acid and an amino acid containing a modified amino acid prepared by modifying the carboxyl group of the amino acid into carboxy ammonium salt and/or amide group as raw materials to polycondensation under heating.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing polyamino acids such as polyamino acids or salts thereof, copolyamino acids or salts thereof, and more specifically, a simple production method for controlling the molecular weight of polyamino acids produced. It is about. Polyamino acids, especially water-soluble polyamino acids, are useful as dispersants, scale inhibitors, detergent builders, and the like.

[0002]

2. Description of the Related Art It is known that an amino acid or its derivative is heated and polycondensed as a method for producing polyamino acids. In particular, it is known that aspartic acid or glutamic acid is thermally polymerized and alkali-hydrolyzed to obtain a water-soluble polymer.

It is considered that such a water-soluble polyamino acid is used as a dispersant for inorganic fine particles or organic fine particles, a scale inhibitor with sparingly soluble salts, and a builder for detergents. However, in order to exhibit sufficient performance in each of such applications, different optimum molecular weights exist, and therefore a production method capable of strictly controlling the molecular weight is required, and generally a weight average molecular weight of 10,000 is required. The following relatively low molecular weight polymers are desired.

The following techniques are conventionally known as methods for controlling the molecular weight. Kokufuta et al.
In polycondensation of L-aspartic acid, it is disclosed that polyaspartic acid having different molecular weights can be obtained by changing the temperature (Bull. Chem. Soc. J.
apan vol. 51, 1555 (1978)). However, in this method, it is necessary to lower the polycondensation temperature in order to obtain a low molecular weight product, and as a result, there are problems that the yield of the polymer is low and the reaction time is long.

On the other hand, Koskan states that by varying the polycondensation temperature and time of L-aspartic acid under specific conditions, a relatively low molecular weight polymer can be synthesized in good yield regardless of conversion (WO92 / 14753). ). However, even in this method, the temperature must be strictly controlled, and in order to produce polymers having different molecular weights, optimum conditions must be set for each polymer, and the operation becomes complicated. Thus, until now, in producing water-soluble polyamino acids, a simple and strict control of the molecular weight has not been found.

[0006]

The present invention has been made to solve the above problems, and is a water-soluble polyamino acid having a desired molecular weight suitable for use as a dispersant, scale inhibitor, builder, etc. , A relatively low molecular weight water-soluble polyamino acid, without the need for strict control of the reaction temperature,
It is an object of the present invention to provide a method for producing a high yield, which has a short reaction time, is simple, has good reproducibility.

[0007]

Means for Solving the Problems As a result of intensive studies on the method for producing polyamino acids by heating amino acids and polycondensing, the present inventors have found that 50 mol% of acidic amino acids are contained.
A polycondensation reaction by heating and polycondensing an amino acid containing the above-containing amino acid and a modified amino acid obtained by modifying the carboxyl group of the amino acid with a carboxyammonium salt and / or an amide group The present invention has been completed by finding that polyamino acids having a desired molecular weight can be easily obtained without changing the temperature and time of the step and requiring strict temperature control.

In the present invention, the amino acids used as raw materials include amino acids containing 50 mol% or more of acidic amino acids, and modified amino acids obtained by modifying the carboxyl groups of the amino acids with carboxyammonium salts and / or amide groups. And are essential.

The above-mentioned acidic amino acid means an amino acid which exhibits acidity when dissolved in water, and examples thereof include aspartic acid and glutamic acid, and any one compound or a mixture thereof can be used. Amino acids that may be contained in addition to the acidic amino acids include glycine, alanine,
Examples include neutral amino acids such as β-alanine and valine, and amino acids such as basic amino acids such as lysine and arginine.A compound of any one of neutral or basic amino acids, a mixture of the same kind of amino acids or different kinds of amino acids. Mixtures can be used.

However, in the present invention, it is an essential requirement that the amino acids used as the raw material contain at least 50 mol% of acidic amino acid. When the content of the acidic amino acid is less than 50 mol%, the water solubility of the obtained polymer is poor,
There arises a problem that satisfactory performance cannot be obtained as a dispersant, a scale inhibitor and a builder. In particular, it is preferable that all of the above amino acids are acidic amino acids because of high reactivity and water solubility. Further, as the above-mentioned acidic amino acids, those containing aspartic acid are preferable in terms of high reactivity, and therefore, all of the starting amino acids are most preferably aspartic acid.

The optically active amino acids among the above-mentioned amino acids used as raw materials may be any of D-form, L-form and DL-form.

As the modified amino acids used as the raw material, compounds obtained by modifying the carboxyl group of the amino acid with a carboxyammonium salt and / or an amide group are used. The amino acid ammonium salt obtained by modifying the amino acid carboxyl group into a carboxyammonium salt may be an ammonium salt of any amino acid, more preferably an aspartic acid ammonium salt or a glutamic acid ammonium salt, and even more preferably an aspartic acid monoammonium salt. However, it is more preferable because the conversion rate of the raw material amino acids is high. As the amino acid amide obtained by modifying the carboxyl group of an amino acid into an amide group, amides of any amino acid may be used, but asparagine, glutamine, and isoasparagine are more preferable in that the conversion rate of the raw material amino acids is high. .

The optically active amino acids among the modified amino acids may be any of D-form, L-form and DL-form.

These amino acid ammonium salts and amino acid amides can be obtained by known methods, and the production method is not particularly limited.

The amino acids used as raw materials include amino acids containing 50 mol% or more of the acidic amino acid and the modified amino acids obtained by modifying the carboxyl group of the amino acid with a carboxyammonium salt and / or an amide group. , And the proportion of both is not particularly limited, but the proportion of all carboxyammonium bases and / or amide groups in the starting amino acids is such that all carboxy groups and carboxyammonium bases of the amino acids are And / or the total amount with the amide group is preferably 1% or more and 50 mol% or less, more preferably 3 mol% or more and 40 mol% or less.
If it is less than this range, the molecular weight hardly changes and a polymer having a molecular weight of 10,000 or less cannot be obtained. On the other hand, when the amount is more than this range, even if the amount of ammonium salt or amide is further increased, the effect of lowering the molecular weight is poor, and the amount of by-products such as ammonia is increased, resulting in work and equipment problems. The problem arises with the difficulty of. In the raw material amino acids, the amount of amino acid and the amount of modified amino acid are
By setting it within the above range, it is possible to easily control the molecular weight of the produced polyamino acids. That is, the larger the amount of amino acid ammonium salt and / or amino acid amide in the raw material amino acids, the smaller the molecular weight of the polyamino acids obtained under the same reaction conditions, and the smaller the amount of the compound, the same reaction conditions. Even if it exists, polyamino acids having a large molecular weight can be obtained.

As a method for incorporating a desired amount of amino acid ammonium salt and / or amino acid amide into the amino acid as the amino acid used as the reaction raw material, (1) amino acid and amino acid ammonium salt and / or amino acid amide are finely divided, respectively. As a method of mixing, (2) Once,
A method of preparing an aqueous dispersion of an amino acid, adding a predetermined amount of ammonia thereto, synthesizing a predetermined amount of a modified amino acid, and directly using it as a mixed aqueous solution of an amino acid and a modified amino acid in a reaction, (3) the mixed aqueous solution The water is removed to prepare a solid mixture of amino acids and modified amino acids, and the like. In particular, the method (2) is preferable because it has good operability and is advantageous in terms of the process. Further, at this time, an aqueous dispersion of amino acids as a raw material is prepared, and a predetermined amount of ammonia is added to the dispersion, so that the proportion of carboxyammonium base and / or amide group in the amino acid is all in the amino acid. The amount of 1 mol% or more and 50 mol% or less, based on the total of the carboxyl group and the carboxyammonium base and / or the amide group, is modified to the carboxyammonium base and / or the amide group,
It is particularly preferable to use a mixed aqueous solution of an amino acid and a modified amino acid and then use it in the polycondensation reaction because the yield is high, the operability is good, and the process is advantageous.

In the present invention, the polycondensation temperature is preferably 160 ° C. or higher, more preferably 200 ° C. to 300 ° C., in order to increase the conversion rate of amino acids and enhance productivity. The time required for polycondensation varies depending on the temperature, but is preferably about 30 minutes to 24 hours. Further, the reaction can be carried out in a solid phase without using a solvent, or can be carried out by dispersing it in a solvent having a high boiling point such as tetralin. Although the pressure of the reaction system is not particularly limited, it is preferably carried out under normal pressure or reduced pressure, and under nitrogen atmosphere in order to suppress coloring and decomposition due to oxidation.

The polyamino acids obtained by polycondensation are insoluble in water because some or most of the aspartic acid units in the produced polymer have the structure of succinic anhydride, but water-soluble polyamino acids. When the polyamino acids obtained by polycondensation are hydrolyzed by alkali hydrolysis of the structure of the succinimide anhydride to obtain a polyamino acid alkali salt, it is necessary to render the polyamino acids water-soluble.

At this time, the method of alkali hydrolysis is not particularly limited, and known methods can be used. For example, the method of dissolving the basic compound after dissolving in a solvent such as dimethylformamide, the obtained polymer with water is used. And the basic compound is added until the basic compound is completely dissolved into an aqueous solution, and the latter is preferable because the latter can be performed more easily.

The hydrolysis temperature is also not particularly limited,
It is preferable to carry out at a temperature of 10 to 100 ° C. 100 ° C
If it exceeds, the amide bond may be broken and a polymer having a desired molecular weight may not be obtained. Examples of the basic compound used for alkaline hydrolysis include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide and calcium hydroxide, alkaline earth metal hydroxides and sodium carbonate. Examples thereof include alkali metal carbonates, ammonia or organic amines such as ethanolamine, diethanolamine and triethanolamine.

As described above, by using the method of the present invention, polyamino acids having a desired molecular weight suitable for each application can be obtained arbitrarily and in good yield. In particular, the water-soluble polyamino acids having a weight average molecular weight of 10,000 or less obtained by the method of the present invention are suitable for dispersants, scale inhibitors, detergent builders and the like.

[0022]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. In addition, "part" in the examples represents "part by weight", and the molecular weight of the water-soluble polyamino acids and the residual amino acid amount were quantified according to the following methods.

<Molecular weight> The molecular weight was measured by gel permeation chromatography (GPC). The column used is an aqueous one, and the eluent is 0.1M-NaH ₂
And adjustment) to pH7.0 with PO ₄ /0.2M-NaCl(NaOH, was measured polyacrylic acid as a standard goods.

<Residual Amino Acid Content> The residual amino acid content was measured by ion exchange resin column chromatography. The eluent was a 0.1 wt% phosphoric acid aqueous solution.

Example 1 13.3 parts of DL-aspartic acid was dispersed in 30 parts of water, and 0.272 parts of 25% by weight ammonia water was added thereto, and 2 mol% of the carboxyl group of DL-aspartic acid as a raw material was added. Was neutralized by modifying it with a carboxyammonium salt. Then, the water was distilled off under reduced pressure, and the whole amount of the obtained powder was charged into a flask, which was then stored under a nitrogen stream at 25
Polycondensation was performed by heating for 60 minutes in an oil pass of 0 ° C. The obtained powder was dispersed in 30 parts of ion-exchanged water, and a 48 wt% sodium hydroxide aqueous solution was added thereto until the polymer was completely hydrolyzed and dissolved. The pH of the obtained polymer aqueous solution was 9.0. The weight average molecular weight of the obtained sodium polyaspartate was 9000,
The conversion rate of aspartic acid calculated from the amount of residual amino acids was 99.1%.

Example 22 0.27% by weight aqueous ammonia 0.27
The same as Example 1 except that 1.36 parts of 25 wt% ammonia water was used instead of 2 parts, and 10 mol% of the carboxyl groups of the raw material DL-aspartic acid was modified to a carboxyammonium salt for neutralization. The operation was performed. The weight average molecular weight of the obtained sodium polyaspartate was 7
It was 300, and the conversion rate of aspartic acid calculated from the amount of residual amino acids was 98.3%.

Example 32 0.27 25% by weight aqueous ammonia
The same as Example 1 except that 5.44 parts of 25 wt% ammonia water was used instead of 2 parts, and 40 mol% of the carboxyl groups of the starting material DL-aspartic acid was modified to a carboxyammonium salt and neutralized. The operation was performed. The obtained sodium polyaspartate also has a weight average molecular weight of 4
It was 100, and the conversion rate of aspartic acid calculated from the residual amino acid amount was 98%.

Example 4 The same operation as in Example 2 was carried out except that L-aspartic acid was used instead of DL-aspartic acid. The obtained sodium polyaspartate also had a weight average molecular weight of 7,200, and the conversion rate of aspartic acid calculated from the amount of residual amino acids was 99.2%.

Example 5 7.98 parts of L-aspartic acid and 6.0 parts of L-asparagine monohydrate were mixed in a powder state, and raw material amino acids composed of L-aspartic acid and L-asparagine monohydrate. The same operation as in Example 1 was carried out except that DL-aspartic acid was used instead of DL-aspartic acid in which the proportion of the amide group was 20 mol% based on the total of the carboxyl group and the amide group. The weight average molecular weight of the obtained sodium polyaspartate was 5200, and the conversion rate of L-aspartic acid and L-asparagine monohydrate calculated from the amount of residual amino acids was 98.8% in terms of L-aspartic acid. there were.

Example 6 DL-Aspartic acid 11.97
Parts and 0.75 parts of glycine are dispersed in 30 parts of water, 1.29 parts of 25% by weight ammonia water is added thereto, and 10 mol% of carboxyl groups in raw material amino acids consisting of DL-aspartic acid and glycine are added. Was neutralized by modifying it with a carboxyammonium salt. After this, the same operation as in Example 1 was performed. The obtained Kobori amino acid sodium also had a weight average molecular weight of 7,000, and the conversion rate of the raw material amino acid calculated from the amount of residual amino acid was 99.2%.

Example 7 7.98 parts of DL-aspartic acid and 5.88 parts of glutamic acid were dispersed in 30 parts of water, and 2.72 parts of 25% by weight aqueous ammonia was added thereto to prepare DL-
20 mol% of the carboxyl groups in the starting amino acids consisting of aspartic acid and glycine were modified with carboxyammonium salts for neutralization. After this, the same operation as in Example 1 was performed. The obtained copolyamino acid sodium also had a weight average molecular weight of 5,200, and the conversion rate of the raw material amino acid calculated from the amount of residual amino acid was 99.9%.

Example 8 The same operation as in Example 3 was carried out except that the polycondensation temperature was 210 ° C. and the polycondensation time was 16 hours. The weight average molecular weight of the obtained sodium polyaspartate was 3,900, and the conversion rate of aspartic acid calculated from the amount of residual amino acids was 95.8%.

Example 9 Example 1 was repeated except that L-asparagine monohydrate was used in place of DL-aspartic acid, and the proportion of amide groups was 50 mol% based on the total of carboxyl groups and amide groups. The same operation was performed. The obtained sodium polyaspartate also has a weight average molecular weight of 3
It was 700, and the conversion rate of asparagine calculated from the amount of residual amino acids was 98.7%.

Example 10 25% by Weight Ammonia Water 0.2
Instead of 72 parts, 8.16 parts of 25% by weight aqueous ammonia was used, and 60% of the carboxyl group of DL-aspartic acid was used.
The same operation as in Example 1 was performed, except that the mol% was modified to a carboxyammonium salt and neutralized. A large amount of ammonia was generated during the reaction. The weight average molecular weight of the obtained sodium polyaspartate was 4000, and the conversion rate of aspartic acid calculated from the amount of residual amino acids was 97.1%.
Met.

Comparative Example 1 Thermal polymerization was carried out in the same manner as in Example 1 except that DL-aspartic acid powder which had not been neutralized with ammonia was used as the raw material amino acid. The weight average molecular weight of the obtained sodium aspartate was 11
The conversion rate of aspartic acid calculated from the amount of residual amino acids was 99.4%.

Comparative Example 2 The same operation as in Comparative Example 1 except that DL-aspartic acid powder which had not been neutralized with ammonia was used as the raw material amino acid and heat polycondensation was carried out in a bath at 180 ° C. for 4 hours. I went. The weight average molecular weight of the obtained polyaspartic acid was 4,200, but the conversion rate of aspartic acid calculated from the amount of residual amino acids was 30.
%Met.

Comparative Example 3 The same as Comparative Example 1 except that DL-aspartic acid powder which had not been neutralized with ammonia was used as the raw material amino acid and heat polycondensation was carried out in a bath at 180 ° C. for 12 hours. The operation was performed. The weight average molecular weight of the obtained sodium polyaspartate was 5,500, but the conversion rate of aspartic acid calculated from the amount of residual amino acids was 55%.

[0038]

EFFECTS OF THE INVENTION The production method of the present invention has the effect that the desired polyamino acid having a relatively low molecular weight can be easily and inexpensively obtained without changing the temperature and time of the polycondensation reaction. In particular, the present invention is effective in producing relatively low molecular weight water-soluble polyamino acids having a weight average molecular weight of 10,000 or less. Therefore, the polyamino acids obtained in the present invention exhibit optimum effects for dispersants, scale inhibitors, detergent builders and the like.

Claims (2)

[Claims] 1. A method for producing a polyamino acid by heating and polycondensing an amino acid, wherein the starting amino acid is an amino acid containing 50 mol% or more of an acidic amino acid, and a carboxyl group of the amino acid is carboxy. A method for producing a polyamino acid, comprising a modified amino acid obtained by modifying an ammonium salt and / or an amide group. 2. The raw material amino acid is such that the proportion of carboxyammonium base and / or amide group in the amino acid is the sum of all carboxy groups and carboxyammonium base and / or amide group in the amino acid. In the range of 1 mol% to 50 mol%, the method for producing polyamino acids according to claim 1.