JPH11147954A - Production of polyaspartic acid excellent in color tone - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain polyaspartic acid excellent in color tone by polycondensing aspartic acid in the presence of an acid catalyst in an inert gas atmosphere and subjecting the resultant polysuccinimide to decoloration before and/or after the hydrolysis thereof. SOLUTION: Argon is esp. pref. as the inert gas. Pref., in hydrolyzing polysuccinimide, a decolorizer is added to the hydrolysis system to carry out the decoloration simultaneously with the hydrolysis. Active carbon and hydrogen peroxide are each pref. as the decolorant. Pref., the decoloration is carried out by using 5-200 pts.wt. decolorizer based on 100 pts.wt. polysuccinimide or polyaspartic acid. When hydrogen peroxide is used, its pref. concn. is 1-30 wt.%. When the decoloration is conducted during the hydrolysis of polysuccinimide, a certain amt. of hydrogen peroxide is added to an aq. soln. contg. polysuccinimide dispersed therein, adding thereto an aq. soln. of an alkali metal hydroxide, and subjecting the mixture to reaction at 0-50 deg.C for 10 min to 8 hr.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing polyaspartic acid having excellent color tone. More specifically, the present invention relates to a method for producing polyaspartic acid by subjecting polysuccinimide obtained by subjecting aspartic acid to a polycondensation reaction in the presence of an inert gas to hydrolysis and decolorization. Polyaspartic acid and its derivatives have recently attracted attention as polymers having excellent biodegradability, and have been proposed for use in various applications such as detergent builders, medical materials, and cosmetic base materials.

[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 polysuccinimide main chain is hydrolyzed. Have been. Although the polycondensation method by this method is simple, it is easy to produce a colored product due to high temperature, and it is not easy to remove the coloring. Conventionally, as a method for decolorizing polyaspartic acid, a polycondensation reaction is carried out in the absence or presence of a catalyst, and hydrogen peroxide is added to the obtained polysuccinimide (US Pat. No. 5,521,257). ) Or a method of adding a decolorizing agent (hypochlorous acid, chlorine, peroxide) after hydrolyzing polysuccinimide (WO
No. 9403526) 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 Laid-Open No. 8-208848).
And the like have been proposed.

[0003]

However, the products treated by these methods are not sufficiently decolorized, so that there is room for improvement especially in the above-mentioned applications. An object of the present invention is to provide a method for producing polyaspartic acid having an excellent color tone.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have hydrolyzed polysuccinimide obtained by subjecting aspartic acid to a polycondensation reaction in the presence of an inert gas. It has been found that polyaspartic acid with little coloring can be obtained by decolorizing treatment, and the present invention has been completed. That is, the gist of the present invention is to provide a method for producing polyaspartic acid by hydrolyzing polysuccinimide, wherein the polysuccinimide obtained by polycondensing aspartic acid with an acid catalyst in the presence of an inert gas is subjected to hydrolysis. A method for producing polyaspartic acid, wherein a decolorization treatment is performed before decomposition and / or after hydrolysis. Hereinafter, the present invention will be described in detail.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (1) Production of Polysuccinimide (Monomer) The monomer used for production of polysuccinimide includes a product obtained by reacting maleic acid and ammonia, maleamic acid or aspartic acid. These may be used alone or as a mixture. Of these, aspartic acid alone is preferred. The product obtained by reacting maleic acid and ammonia refers to a product obtained by reacting maleic acid and ammonia by a conventional method, for example, German Patent No.
No. 72, U.S. Pat. No. 4,839,461, and U.S. Pat. No. 5,286,810. Specifically, it is mainly a monoammonium maleate salt, and may further contain products such as maleic acid, a diammonium maleate salt, ammonia, fumaric acid, aspartic acid, asparagine, iminodisuccinic acid, and maleamic acid. .

[0006] The maleic acid used in the above reaction includes its anhydride, partial and full esters. Ammonia is used as a gas or a solution. When used as a solution, a method of dissolving in water to make an ammonium hydroxide aqueous solution, a method of dissolving in an alcohol such as methanol or ethanol, or a method of dissolving in another appropriate organic solvent are used. As the monomer, preferably, aspartic acid,
Aspartic acid may be in D-form, L-form or a mixture thereof. Further, other than aspartic acid, other copolymerizable monomers can be used within a range not exceeding 50%. The copolymerizable monomer is not particularly limited, for example,
Amino acids such as aspartate, glutamic acid and salts thereof, alanine, leucine and lysine; hydroxycarboxylic acids such as glycolic acid, lactic acid and 3-hydroxybutyric acid;
-Other compounds having one or more functional groups capable of reacting with an amino group or a carboxylic acid group such as hydroxyethanol, maleic acid and aniline.

(Catalyst) In the polycondensation reaction of aspartic acid or the like, a catalyst may not be used, but it is preferable to use an acid catalyst as a catalyst. Specific examples thereof include inorganic acids 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 trifluoromethanesulfonic acid. And the like. 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, phosphoric acid diester, phosphoric acid triester, phosphite monoester, phosphite diester, phosphite triester and the like.

[0008] A suitable amount of these acid catalysts 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.

(Reaction conditions) The conditions of the polycondensation reaction of aspartic acid and the like in the present invention are not particularly limited except that the reaction is carried out in the presence of an inert gas. In general, the monomer and the catalyst are mixed in a wet or dry manner and then polycondensed. Incidentally, polycondensation (bulk polymerization) in the absence of a solvent,
Since no solvent is used, the production cost is low, but there is a drawback that a high molecular weight product cannot be obtained as compared with the solvent method. However, when the reaction method of the present invention in the presence of an inert gas is applied, it is possible to increase the molecular weight of polysuccinimide.

The pressure during the reaction is not particularly limited and may be normal pressure, reduced pressure, or increased pressure.
１1 MPa. The inert gas that can be used in the present invention is not particularly limited as long as it is a gas having no activity with respect to the polycondensation reaction. For example, nitrogen and argon are preferably used, and argon is particularly preferable.

The volume of the inert gas is at least 50%, preferably at least 80%, of the total gas volume of the reactor. Further, it is preferable to carry out the reaction in an inert gas stream in order to remove the condensed water generated by the reaction. The flow rate of the inert gas is preferably 1 ml / min or more, preferably 10 ml / min or more. Hereinafter, polycondensation (bulk polymerization) in the absence of a reaction solvent will be described in detail as a typical example.

(Mixing Method) In the bulk polymerization, the dispersion state of the catalyst is not limited, but it is preferable to sufficiently mix the powdered monomer and the catalyst before performing the polycondensation reaction.
If polycondensation is started in an insufficiently mixed state, problems such as partial melting and solidification, a decrease in molecular weight, and an increase in reaction time may occur. Examples of the mixing method include a wet mixing method using a catalyst and a solvent as a diluent, and a dry mixing method using equipment. The mixing temperature is not particularly limited as long as the polycondensation to polysuccinimide does not occur at 150 ° C. or lower, but is preferably a temperature from normal temperature to 120 ° C., and the mixing time is 0.01 to 600 minutes, preferably 0.0
The mixing is performed for 1 to 300 minutes, more preferably 0.01 to 50 minutes.

In the case of the wet mixing method, a solvent and a catalyst are mixed, and then each mixture is mixed with a powdered monomer. At this time, there is no particular limitation on the solvent that can be used, but it is preferable that the solvent has a boiling point of 150 ° C. or lower and is uniformly mixed with the catalyst to be used for distillation after the mixing is completed. Specifically, hexane, aliphatic and alicyclic hydrocarbons such as cyclohexane,
Examples include aromatic hydrocarbons such as benzene and toluene, esters such as ethyl acetate and butyl acetate, ketones such as acetone and methyl ethyl ketone, alcohols such as methanol, ethanol and propanol, and water. Water is particularly preferred in that it is by-produced in the subsequent reaction and does not require a complicated recovery step. The solvent is usually used in an amount of 0.1 to 30 parts by weight, preferably 0.5 to 2 parts by weight, per 100 parts by weight of the monomer.
Used in the range of 5 parts by weight. When the amount 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 it exceeds 30 parts by weight, it takes a long time for the distillation, which is not preferable.

In the case of the dry mixing method, the catalyst is added to the monomers, and then mixed using a mixing device. The method for adding the catalyst is not particularly limited, and may be added all at once or in small amounts. Mixing devices that can be used include:
General mixers, blenders, kneaders, and the like are preferable. Specific examples of large-size stirring-kneading equipment include a single-screw or twin-screw extruder or a high-viscosity reactor, an SV-mixer, and a conical dryer (Shinko Pantech). , M
Examples include Z-processor (Okawara Seisakusho), paddle dryer (Nara Machinery), SC-processor and pressure kneader (Kurimoto Iron Works).

(Polycondensation reaction) In the polycondensation reaction in the method of the present invention, the above mixture is charged into a reactor, and 100 to 4
Under heating at 00 ° C, preferably 150-350 ° C, more preferably 200-240 ° C, the average residence time is 0.01
The reaction is carried out in a solid phase with stirring or kneading for a period of from 240 to 240 minutes, preferably from 0.01 to 180 minutes, more preferably from 10 to 100 minutes. If the reaction time is less than 100 ° C. and the average residence time is less than 10 minutes, the reaction may not be completed. Further, when the reaction is carried out at a reaction temperature exceeding 400 ° C. and an average residence time exceeding 240 minutes, there is a possibility that a decomposed product is formed, the reaction efficiency is reduced, and coloring is performed.

The reactor which satisfies the above conditions may be either a batch type or a continuous type. In the case of the batch type, a usual reactor, a Prosure mixer (Taikai Kiko Co., Ltd.), Pol
yphase System (Littleford
Day Co., Ltd.), an SV-mixer, an MZ-processor, and a batch kneader. In the continuous type, single- and twin-screw kneaders, paddle dryers, LCRs (Lurgi
Corporation), SC processor, KRC kneader (Kurimoto Iron Works), Vivolac (Sumitomo Heavy Industries), N-SCR (Mitsubishi Heavy Industries) and the like.

(2) Hydrolysis of polysuccinimide The hydrolysis of the polysuccinimide thus obtained can be carried out in accordance with a conventional method.
Journal of American Chemical Society (J. Am. Chem. Soc.) 80, 3361
(1958), Journal of Organic Chemistry (J. Org. Chem.) 26, 1084.
(1961), U.S. Pat. No. 5,221,733, U.S. Pat. No. 5,288,783,
What is necessary is just to carry out according to 0-203636 gazette. In a preferred embodiment, 5 parts by weight per 100 parts by weight of the above reaction product is used.
0 to 1000 parts by weight of water is added, and an alkali metal hydroxide is further added in an amount of 1 to 3 moles per mole of the imide ring, and the mixture is reacted 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 metal salt of polyaspartic acid, and the polyaspartic acid according to the present invention includes this. When an acid acts on this 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 the polyaspartic acid is not particularly limited, but is preferably 500 to 300,000, more preferably 1,000 to 2,000 in weight average molecular weight.
00.

(3) Decolorization treatment The decolorization treatment in the present invention is performed before and / or after hydrolysis of polysuccinimide. Here, “before hydrolysis and / or after hydrolysis” includes before hydrolysis, after hydrolysis, both before and after hydrolysis, and also includes the point during hydrolysis. Among these embodiments, it is convenient and preferable in terms of operation to add a decolorizing agent to the system and to perform a decolorization treatment simultaneously with hydrolysis when hydrolyzing polysuccinimide.

In the bleaching treatment, it is preferable to use a bleaching agent. The decolorizing agent is not particularly limited,
Specific examples include, for example, hydrogen peroxide, percarbonate, hypochlorite, chlorine, ozone, chlorperacid, borohydride, dicarboxylic peroxide, persulfate, perborate, activated carbon, etc. Is mentioned. Among them, activated carbon and hydrogen peroxide are preferred.
In the decolorizing treatment of polyaspartic acid, it is preferable to use 5 to 200 parts by weight of the above-described decolorizing agent based on 100 parts by weight of polysuccinimide or polyaspartic acid. When using hydrogen peroxide, the concentration of hydrogen peroxide is 1 to 30% by weight.
Is preferred.

In the case of performing a decolorization treatment during the hydrolysis of polysuccinimide, a predetermined amount of aqueous hydrogen peroxide is added to an aqueous solution of polysuccinimide suspended in water, and then an aqueous solution of an alkali metal hydroxide is added thereto. 0 to 50 ° C, 1
By allowing the reaction to proceed for 0 minutes to 8 hours, the hydrolysis reaction and the decolorization treatment are performed simultaneously. In the case of performing a decolorizing treatment after the hydrolysis, a treatment may be performed by adding a decoloring agent such as hydrogen peroxide to an aqueous solution of polyaspartic acid. Also,
In the case of performing a decolorization treatment before hydrolysis, polysuccinimide may be dissolved in a solvent such as DMF, and a decolorizing agent such as hydrogen peroxide may be added to the solution for treatment.

[0022]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the scope of the invention. The methods for measuring the molecular weight and color difference are as follows.

<Measurement of weight average molecular weight of polyaspartic acid>"TSKgel""G6000" manufactured by Tosoh Corporation
"PWXL" + "TSKgel""G3000PWXL"
It is a value in terms of polyethylene glycol obtained by gel permeation chromatography (differential refractometer) using a column and a 0.4 M aqueous solution of sodium nitrate as an eluent.

<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. * (A 60% by weight aqueous solution of polyaspartic acid) was added, and measurement was performed by transmission.
lowness Index: YI value) was calculated.

Example 1 Under an argon atmosphere, L-aspartic acid (25.0 g)
And 85% phosphoric acid (2.5 g) were mixed in an Oster blender (Phoenix) for 5 minutes to disperse the catalyst. This mixture was cooled to 2 with a cooler, thermometer and stirrer.
It was charged in a 00 ml separable flask. Under an argon atmosphere, the mantle heater was set at 235 ° C. and 4.5
The polymerization reaction was performed while keeping the time. The water generated during this time was distilled out of the system.

After the completion of the reaction, the reaction product is filtered off and the product is
g for 4 times, and further washed with 100 g of methanol.
The product was dried under reduced pressure at 80 ° C. for 24 hours to obtain 17.9 g of yellowish white powder. This product is referred to as resin A. In a 50 cc beaker equipped with a stirrer, 2.0 g of the polysuccinimide (resin A) obtained above and 3.3 ml of 3% by weight hydrogen peroxide were charged. Under ice cooling, 50% by weight
1.5 g of aqueous sodium hydroxide solution was added little by little, and then stirred at room temperature for 1 hour to hydrolyze. The results of the color difference are shown in Table 1.

Example 2 Under a nitrogen atmosphere, L-aspartic acid (25.0 g) and 8
5% phosphoric acid (2.5 g) was mixed with an Oster blender (Phoenix) for 5 minutes to disperse the catalyst. The mixture was cooled to 200 m with a cooler, thermometer and stirrer.
1 separable flask. Under a nitrogen atmosphere, the mantle heater was set at 235 ° C., and the polymerization reaction was carried out for 4.5 hours. The water generated during this time was distilled out of the system.

After completion of the reaction, the reaction mixture was filtered off, and the product was purified with 100% pure water.
g for 4 times, and further washed with 100 g of methanol.
The product was dried under reduced pressure at 80 ° C. for 24 hours to obtain 17.9 g of yellowish white powder. This product is referred to as resin B. In a 50 cc beaker equipped with a stirrer, 2.0 g of the polysuccinimide (resin B) obtained above and 3.3 ml of 3% by weight hydrogen peroxide were charged. Under ice cooling, 50% by weight
1.5 g of aqueous sodium hydroxide solution was added little by little, and then stirred at room temperature for 1 hour to hydrolyze. The results of the color difference are shown in Table 1.

Comparative Example 1 Under an air atmosphere, L-aspartic acid (25.0 g) and 8
5% phosphoric acid (2.5 g) was mixed with an Oster blender (Phoenix) for 5 minutes to disperse the catalyst. The mixture was cooled to 200 m with a cooler, thermometer and stirrer.
1 separable flask. Under an air atmosphere, the temperature of the mantle heater was set to 235 ° C., and the polymerization reaction was carried out for 4.5 hours. The water generated during this time was distilled out of the system.

After the completion of the reaction, the reaction mixture was filtered off, and the product was treated with 100 parts of pure water.
g for 4 times, and further washed with 100 g of methanol.
The product was dried under reduced pressure at 80 ° C. for 24 hours to obtain 17.9 g of yellowish white powder. This product is referred to as resin C. In a 50 cc beaker equipped with a stirrer, 2.0 g of the polysuccinimide (resin C) obtained above and 3.3 ml of a 3% by weight hydrogen peroxide solution were charged. Under ice cooling, 50% by weight
1.5 g of aqueous sodium hydroxide solution was added little by little, and then stirred at room temperature for 1 hour to hydrolyze. The results of the color difference are shown in Table 1.

Comparative Example 2 25 g of L-aspartic acid was charged into a 200 ml separable flask equipped with a cooler, a thermometer and a stirrer, a mantle heater was set at 235 ° C., and a polymerization reaction was carried out under a nitrogen atmosphere. When the internal temperature reached 200 ° C., water began to evaporate, and the mixture was stirred at the same temperature for 7 hours to obtain 21.25 g of polysuccinimide. This product is referred to as resin D.
In a 50 cc beaker equipped with a stirrer, 2.0 g of the polysuccinimide (resin D) obtained above and 3.3 ml of 3% by weight of hydrogen peroxide were charged. Under ice cooling, 1.5 g of an aqueous sodium hydroxide solution was added little by little, and the mixture was stirred at room temperature for 1 hour to hydrolyze. The results of the color difference are shown in Table 1.

[0032]

[Table 1]

[0033]

According to the present invention, polyaspartic acid having an excellent color tone can be easily produced.

Claims (3)

[Claims] 1. A method for producing polyaspartic acid by hydrolyzing polysuccinimide, wherein the polysuccinimide obtained by polycondensation of aspartic acid with an acid catalyst in the presence of an inert gas is used before the hydrolysis and A method for producing polyaspartic acid, comprising performing a decolorization treatment after hydrolysis. 2. The method according to claim 1, wherein the inert gas is argon. 3. The method according to claim 1, wherein hydrogen peroxide is used as the decolorizing agent.