JPH11147953A - Polyaspartic acid having excellent hue and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyaspartic acid having a specified or lower yellowness index (YI value) and therefore having an excellent hue. SOLUTION: The YI value should be 1.23 or below. To obtain such a polyaspartic acid, it is desirable to perform deceleration with active carbon before and/or after the hydrolysis of polysuccinimide. It is desirable that the treatment with active carbon is applied to an aqueous polyaspartic acid solution obtained after the hydrolysis of polysuccinimide. In this case, it can be performed by, for example, a technique including passing an aqueous polyaspartic acid solution into a tower packed with active carbon or a technique including adding active carbon to an aqueous polyaspartic solution and agitating the mixture. In the production of polysuccinimide, it is the most suitable that it is carried out by using aspartic acid as a monomer in the presence of a catalyst in an atmosphere of an inert gas. The catalyst used is, for example, an acid catalyst. The inert gas is particularly desirably argon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polyaspartic acid having an excellent color tone and a method for producing the same. For more information,
The present invention relates to a method for producing a polyaspartic acid and a polysuccinimide having a YI value of 1.25 or less by subjecting them to an activated carbon treatment before or after hydrolysis. Polyaspartic acid and its derivatives have recently attracted attention as biodegradable polymers, and have been used as detergent builders, medical materials,
Use for various uses such as cosmetic base materials has been proposed.

[0002]

2. Description of the Related Art As a method for producing polyaspartic acid, there is known a method in which L-aspartic acid is polycondensed to produce polysuccinimide as an intermediate, and then the imide ring in the polyimide chain is hydrolyzed. ing. The polycondensation method by this method is simple, but requires treatment at a high temperature, so that the obtained polyaspartic acid is colored and needs to be decolorized depending on the use. Examples of the decolorizing method include a method of performing a polycondensation reaction in the absence or presence of a catalyst and adding hydrogen peroxide to the obtained polysuccinimide (U.S. Pat. No. 5,521,257);
A method of adding a decolorizing agent (hypochlorous acid, chlorine, peroxide) after hydrolyzing polysuccinimide (WO9403)
No. 526) and a method of adding a sulfite to a product obtained by hydrolyzing polysuccinimide obtained by performing a polycondensation reaction at a low temperature (Japanese Patent Application Laid-Open No. 8-208848).
Etc. are known.

[0003]

However, in these methods, decolorization cannot be said to be sufficient, so that the use of polyaspartic acid has been limited. An object of the present invention is to provide polyaspartic acid having an excellent color tone and a method for producing the same.

[0004]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have found that a polyaspartic acid having an excellent color tone can be obtained by treating an aqueous solution of polyaspartate with activated carbon. As a result, the present invention has been completed. . That is, the gist of the present invention is as follows. 1. a polyaspartic acid having a YI value of 1.25 or less; A method for producing polyaspartic acid by hydrolyzing polysuccinimide, comprising a step of performing a treatment with activated carbon before and / or after hydrolysis of polysuccinimide. Hereinafter, the present invention will be described in detail.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The polyaspartic acid of the present invention refers to those having a YI value of 1.25 or less, and there is no particular limitation on the production method as long as this value is satisfied. When polyaspartic acid is produced by hydrolysis of polysuccinimide, in order to satisfy this criterion, it is preferable to subject the polysuccinimide to hydrolysis and / or an activated carbon treatment after the hydrolysis.

(Polysuccinimide) When polysuccinimide is hydrolyzed to produce polyaspartic acid,
The raw material polysuccinimide is not particularly limited,
Those manufactured using various known monomers can be used, and copolymers can also be used. In the case of a copolymer, 50 mol% of succinimide units are contained in the polymer.
Those containing above are preferred. As the molecular weight of polysuccinimide, the weight average molecular weight is 300 to 300000
Is preferable, and 500 to 200,000 is more preferable.

The polysuccinimide is disclosed, for example, in Japanese Patent Publication No. 48-20638, US Pat. No. 5,057,5.
No. 97, U.S. Pat. No. 5,142,062, U.S. Pat. No. 5,219,986,
JP-A-248075, JP-A-7-126379, JP-A-7-216084, JP-A-8-176
It can be manufactured according to the method described in JP-A-297-297. The outline is as follows. Examples of the monomer include a reaction product of maleic acid and ammonia, maleamic acid and / or aspartic acid, and aspartic acid is preferable. In this case, aspartic acid is D
It may be a body, an L body, or a mixture thereof.

Although the use of a catalyst is not required, the use of a catalyst is preferred because a product with less coloring can be obtained. As the catalyst to be used, for example, an acid catalyst, an inorganic acid such as sulfuric acid, sulfuric anhydride, phosphoric acid, polyphosphoric acid, metaphosphoric acid, condensed phosphoric acid, phosphoric anhydride, p-toluenesulfonic acid, trichloroacetic acid, trifluoroacetic acid And organic acids such as trifluoromethanesulfonic acid. Other examples include phosphoric acid monoester, phosphoric acid diester, phosphoric acid triester, phosphite monoester, phosphite diester, phosphite triester and the like, preferably phosphoric acid, polyphosphoric acid, metaphosphoric acid , Condensed phosphoric acid, phosphoric anhydride, phosphoric acid monoester, phosphite diester, and phosphite triester.

A suitable amount of the acid catalyst is usually 0.1 to 30 parts by weight, preferably 0.5 to 25 parts by weight, based on 100 parts by weight of the polymer raw material. When the amount of the catalyst is less than 0.1 part by weight, the effect of improving the speed of the polycondensation reaction is small. On the other hand, if the amount exceeds 30 parts by weight, the reaction product is in a solidified state at the time of polymerization, and a large burden is imposed on the stirring, which is not preferable. The reaction conditions are not particularly limited, but the reaction temperature is usually 100
To 400 ° C, preferably 150 to 350 ° C. If the polycondensation temperature is lower than 100 ° C., the reaction hardly proceeds, and if it exceeds 400 ° C., decomposition products may be generated, which is not preferable.

The atmosphere during the polymerization is not particularly limited, but it is preferable to conduct the polymerization in an atmosphere of an inert gas because coloring is reduced. Examples of the inert gas include nitrogen, argon and the like, and argon is particularly preferable. Among the methods for producing polysuccinimide, the most preferable one is a method in which aspartic acid is used as a monomer, a catalyst is used, and an inert gas atmosphere is used.

(Hydrolysis) Polyaspartic acid is obtained by hydrolyzing polysuccinimide,
The hydrolysis can be performed according to a conventional method. A typical example is the Journal of American Chemical Society (J. Am. Chem. Soc.)
80, 3361 (1958), Journal of Organic Chemistry (J. Org. Chem.) 2
6,1084 (1961); U.S. Patent No. 5,221,7
No. 33, U.S. Pat. No. 5,288,783, and JP-A-60-203636. In a preferred embodiment, 50 to 1000 parts by weight of water is added to 100 parts by weight of the reaction product, and an alkali metal hydroxide is added in an amount of 1 to 3 moles per mole of the imide ring, The reaction is performed at 0 to 50 ° C for 10 minutes to 8 hours. As a result, most of the imide ring is opened.

The hydrolysis product thus obtained is an alkali salt of aspartic acid. When an acid acts on the alkali metal salt type polyaspartic acid, free polyaspartic acid can be obtained. By adjusting the amount of the acid used, the ratio between the free form and the salt form of the carboxylic acid group of polyaspartic acid can be arbitrarily adjusted. The molecular weight of polyaspartic acid is not particularly limited. Preferably, the weight average molecular weight is from 300 to 300,000, more preferably from 500 to 200,000.

When polyaspartic acid is produced by hydrolysis of polysuccinimide, in order to obtain a polyaspartic acid having a YI value of 1.25 or less, decolorization treatment with activated carbon is performed before and / or after hydrolysis of polysuccinimide. It is preferable to apply. Here, “before hydrolysis and / or after hydrolysis” means before hydrolysis, after hydrolysis,
In addition to both before and after the hydrolysis, the time point during the hydrolysis is also included. And in these aspects,
This activated carbon treatment is preferably performed on an aqueous solution of polyaspartic acid obtained after hydrolysis of polysuccinimide.

In this case, the decolorizing treatment can be carried out by passing an aqueous solution of polyaspartic acid through a column filled with activated carbon, or adding activated carbon to the aqueous solution of polyaspartic acid and stirring. In the case of the latter method, 1 to 200 parts by weight, preferably 5 to 50 parts by weight of activated carbon is added to 100 parts by weight of polyaspartic acid, and this aqueous solution may be stirred at room temperature to 100 ° C. for 30 minutes to 3 hours. .

The activated carbon has a surface area of 100 to 150.
Those having 0 m ² / g are preferred. The structure (DBP absorption amount) is 50 to 300 ml / 100 g-C
Those in the range of B are preferred. The pH is 2.5 to 1
A range of 1.0 is preferred. The particle size is 0.04 mm
It is preferable that the particle size is not less than the above. In the case of performing a decolorization treatment before the hydrolysis of polysuccinimide, the polysuccinimide may be dissolved in a solvent such as DMF, and the solution may be treated according to the above method.

[0016]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples unless it exceeds the gist thereof. The method for measuring the molecular weight and hue of polyaspartic acid is as follows.

1) Measurement of weight average molecular weight of polyaspartic acid "TSKgel""G6000PWX" manufactured by Tosoh Corporation
L "+" TSKgel "," G3000PWXL "column, and a value in terms of polyethylene glycol obtained by gel permeation chromatography (differential refractometer) using a 0.4 M aqueous solution of sodium nitrate as an eluent.

2) Measurement of color difference Using a color difference meter (SM Color Computer-SM-5-CH) manufactured by Suga Test Machine Co., Ltd., add distilled water to a 5 mm cell, perform standard adjustment, and then sample in the cell. (60% by weight aqueous solution of polyaspartic acid), and measured by permeation. Yellowness index (Yellowness Index)
x: YI value) was calculated.

Comparative Example 1 L-aspartic acid (5.0 kg) under an argon atmosphere
And 85% phosphoric acid (500 g) were mixed with a super mixer (manufactured by Kawata Corporation) for 5 minutes to disperse the catalyst. The polycondensation reaction was carried out as follows using a KRC kneader (50φ × 661.5 L, L / D 13.2) manufactured by Kurimoto Iron Works, Ltd. The mixture of aspartic acid and phosphoric acid obtained above was supplied at a heating medium of 260 ° C., a screw rotation speed of 30 rpm, and a discharge rate of 1 kg / h (average residence time of 16 minutes) to supply polycondensation. The reaction was performed to obtain a brown powder (polysuccinimide). The resulting product was washed with water to remove phosphoric acid as a catalyst. 3
93 wt% sodium hydroxide (1
1.05 g) and water (140 g) were added to dissolve sodium hydroxide. After cooling the beaker with ice water,
The brown solid (28.8 g) obtained above was added little by little, and then stirred at room temperature for 1 hour to obtain an aqueous solution of polyaspartate. Table 1 shows the YI value of this polyaspartic acid.

Example 1 Method for producing polyaspartic acid Activated carbon was added to the aqueous solution of polyaspartic acid obtained in Comparative Example 1 at the ratio shown in Table 1, stirred for 3 hours, and filtered. Table 1 shows the YI value of this polyaspartic acid.

Comparative Example 2 To the aqueous solution of polyaspartic acid obtained in Comparative Example 1, 73.14 g of water containing 3.12 g of a 30% by weight hydrogen peroxide solution was added. Thereafter, the mixture was stirred for 24 hours. Table 1 shows the YI value of this polyaspartic acid.

[0022]

According to the present invention, colored polyaspartic acid can be easily decolorized. And the obtained polyaspartic acid with excellent color tone is a detergent builder,
It is expected to be used for various uses such as medical materials and cosmetic base materials.

[0023]

[Table 1]

Claims (5)

[Claims] 1. A polyaspartic acid having a YI value of 1.25 or less. 2. A method for producing polyaspartic acid by hydrolyzing polysuccinimide, wherein the polyaspartic acid is treated with activated carbon before and / or after hydrolysis of polysuccinimide. 3. The method according to claim 2, wherein the polysuccinimide is treated with activated carbon. 4. The method of claim 2, wherein the aspartic acid obtained by hydrolyzing the polysuccinimide is treated with activated carbon.
The production method described in 1. 5. The method according to claim 4, wherein polysuccinimide produced in an atmosphere of an inert gas is used.