JP2000281782A - Production of crosslinked polysuccinimide and production of crosslnked polyaspartic acid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a crosslinked polymer excellent in absorbency and biodegradability by heating a compound selected from among aspartic acid, etc., in the presence of a catalyt, pulverizing the resultant solid polysuccinimide, adding, to the resultant power, a crosslinker having functional groups reactive with the functional groups of the polysuccinimide and heating the mixture to cause simultaneously the mol.-wt.-increasing reaction and crosslinking. SOLUTION: At least one compound selected from among aspartic acid, glutamic acid, maleamic acid, maleimide and a reaction product of maleic anhydride with NH3 is heated in the presence of a catalyst to give solid polysuccinimide, which is pulverized and mixed with a crosslinker, preferably a polyamine compound, having functional groups reactive with the functional gropus of the polysuccinimide. The resultant mixture is heated to cause simultaneously the mol.-wt.-increasing reaction and crosslinking. Thus produced crosslinked polysuccinimide is hydrolyzed to give crosslinked polyaspartic acid which has such a water absorbency that the absorption of physiological salt solution is 10 g/g or higher.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a crosslinked product of polysuccinimide and a crosslinked product of polyaspartic acid having high water absorption performance and biodegradability. The crosslinked polyaspartic acid product of the present invention can be used as a water-absorbing resin such as disposable sanitary wares and household products, water-stopping materials, soil improvement materials, dew condensation inhibitors, and water retention agents for agricultural and horticultural use.

[0002]

2. Description of the Related Art Water-absorbent resins are used in a wide variety of fields such as sanitary articles such as diapers and sanitary articles, medical fields, civil engineering and construction fields, food fields, industrial fields, soil modifiers, agriculture and horticultural fields. Utilization is required in the field.

[0003] The first property desired for a water-absorbent resin in such a field is a high water absorption ratio. It has been empirically known that the high water absorption capacity of a water-absorbent resin is related to the molecular weight, ionic strength, and cross-link density of the polymer. And starch acrylic acid copolymers. In recent years, with increasing awareness of environmental issues, there has been an increase in demand for biodegradability of water-absorbent resins, and therefore, a water-absorbent resin having a biodegradability that replaces the above-mentioned conventional polymers has been demanded. .

As high molecular compounds having both water absorption and biodegradability, natural resins such as polysaccharides and polyamino acid resins are known. Among the natural resins such as polysaccharides, those having high absorbency include hyaluronic acid,
And polysaccharides produced by microorganisms belonging to the family Alcaligenes are known (JP-A-4-200389). However, although these polysaccharides have a sufficient function as a water-absorbing resin, it is difficult to obtain them inexpensively and in large quantities by current production methods.

[0005] Further, as a water-absorbing resin made of cellulose and starch, which are inexpensive polysaccharides, a water-absorbing resin obtained by mixing a polysaccharide with an amino acid and drying by heating is known (Japanese Patent Laid-open No. Hei 8-8). 89796). However, these water absorbent resins have a problem that their water absorbing ability is insufficient.

As the polyamino acid-based resin, there are known water-absorbing resins obtained by hydrolyzing a partially crosslinked product of polyaspartic acid with a polyamine (JP-A-7-309943 and JP-A-9-169840). I have.
In this method, a high molecular weight polysuccinimide is once prepared and then reacted with a polyamine to carry out crosslinking, thereby obtaining a crosslinked polyaspartic acid having water absorption performance.

Various methods for producing this high molecular weight polysuccinimide have been proposed.

For example, Japanese Patent Publication No. 48-20638 discloses a method for obtaining a high molecular weight polysuccinimide by performing a reaction in the form of a thin film using a rotary evaporator using 85% phosphoric acid as a catalyst. JP-A-10-72524 discloses a method for producing a high-molecular-weight polysuccinimide which reacts in an organic solvent in a suspended or bulk state in the presence of a protonic acid as a catalyst. Further, in US Pat. No. 5,142,062, after aspartic acid is heated and condensed under reduced pressure using phosphoric acid or the like as a catalyst,
It is stated that this is ground and further polymerized to obtain a high molecular weight polysuccinimide. However, since any of these methods for producing a water-absorbent resin discloses a method using polysuccinimide as a raw material, first, a high-molecular-weight polysuccinimide is prepared, and then the cross-linking of the polysuccinimide is performed. Need to be carried out, and the polymerization step and the cross-linking step of the polysuccinimide are separated. Therefore, there is a problem that the number of steps is increased and all the steps are complicated.

[0009]

DISCLOSURE OF THE INVENTION The present invention provides a method for producing a crosslinked polysuccinimide capable of simultaneously performing a high molecular weight reaction and a crosslinking reaction, and particularly a polysuccinimide excellent in water absorption performance and biodegradability. An object of the present invention is to provide a method for producing a crosslinked aspartic acid.

[0010]

Means for Solving the Problems Accordingly, the present inventors have:
In view of the existence of various disadvantages in the prior art as described above, as a result of intensive studies, after adjusting a low molecular weight polysuccinimide solid, a crosslinking agent is added to this solid, and heated. The present invention has been completed by finding that it is possible to easily increase the molecular weight and simultaneously carry out crosslinking without going through a complicated process.

That is, [I] The present invention provides (I) at least one selected from the group consisting of aspartic acid, glutamic acid, maleamic acid, maleimide, and a reaction product of maleic anhydride and ammonia in the presence of a catalyst. A first step of heating to obtain a polysuccinimide solid, and (II) a cross-linking agent having a functional group capable of reacting with a functional group in the polysuccinimide by granulating the polysuccinimide solid. And a second step of further heating, which provides a method for producing a crosslinked polysuccinimide, wherein a cross-linking reaction is carried out simultaneously with the high molecular weight reaction in the second step, [II] The present invention also relates to (I) a catalyst selected from the group consisting of aspartic acid, glutamic acid, maleamic acid, maleimide, and a reaction product of maleic anhydride and ammonia. A first step of heating to obtain a polysuccinimide in the presence of a medium, and (II) crosslinking the polysuccinimide solid into fine particles and having a functional group capable of reacting with a functional group in the polysuccinimide. After the addition of the agent, the mixture is further heated to increase the molecular weight of the polysuccinimide to obtain a crosslinked polysuccinimide, and (III) a second step of hydrolyzing the crosslinked polysuccinimide. [III] The present invention provides a method for producing a crosslinked polyaspartic acid comprising three steps, wherein the crosslinked polyaspartic acid has a water-absorbing function. The present invention also provides a method for producing a crosslinked aspartic acid, and [IV] the present invention further provides a crosslinked polyaspartic acid according to the above [II] or [III], wherein the water absorption capacity of physiological saline is 10 g / g or more. Provide a manufacturing method for [V] The present invention provides the method for producing a crosslinked polysuccinimide according to claim 1, wherein the crosslinking agent having a functional group capable of reacting with a functional group in the polysuccinimide is a polyamine compound. [VI] The present invention relates to the above-mentioned [II] to [I], wherein the crosslinking agent having a functional group capable of reacting with the functional group in the polysuccinimide is a polyamine compound.
V]. A method for producing the crosslinked polyaspartic acid according to any one of [1] to [5].

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a crosslinked polysuccinimide is obtained by (I) a first step of heating a monomer together with a catalyst to obtain a solid polysuccinimide, and (II) the polysuccinimide. The solid is finely divided, and a crosslinking agent having a functional group capable of reacting with a functional group in the polysuccinimide is added,
It is manufactured through a second step of further heating.

First, the first step of the present invention will be described.

In the first step, a relatively low molecular weight polysuccinimide is obtained by heating the monomer together with the catalyst. The molecular weight of this polysuccinimide is 20,000 to 100,000 in terms of weight average molecular weight. Such a low molecular weight polysuccinimide can be obtained by heating a monomer in the presence of a catalyst.

The monomer used in the present invention is one or more selected from the group consisting of aspartic acid, maleamic acid, maleimide, and a reaction product of maleic anhydride and ammonia.

Aspartic acid may be in D-form, L-form or a mixture thereof. Further, a metal salt of aspartic acid may be used. The alkali metal forming a salt with aspartic acid is not particularly limited, but lithium, sodium or potassium is preferable. When a reaction product of maleic anhydride and ammonia is used as a monomer, ammonia may be any of ammonia gas, an aqueous ammonium solution, and an ammonium salt.

Although the reaction proceeds without a catalyst, it is preferable to use a catalyst. The use of a catalyst is expected to lower the reaction temperature and shorten the reaction time. The type of the catalyst is appropriately selected depending on the monomer used. When aspartic acid is used as a monomer, phosphoric acid, sulfuric acid,
Protonic acids such as p-toluenesulfonic acid, trifluoromethanesulfonic acid, and the like, metals of Groups II, III, IV, and V of the periodic table;
Or salts thereof, and specifically, for example, metals such as zinc powder, tin powder, aluminum and magnesium, or metal oxides such as zinc oxide, tin oxide, magnesium oxide and titanium oxide, or tin chloride and magnesium chloride Metal chlorides such as zinc carbonate, magnesium carbonate, etc., organic carboxylate salts such as tin octoate, tin acetate, zinc acetate, sulfates such as zinc sulfate and aluminum sulfate, trifluoromethanesulfonic acid zinc,
Organic sulfonates such as tin methanesulfonate and zinc p-toluenesulfonate are exemplified. Other examples include metal organic oxides of the above metals such as dibutylitin oxide, metal alkoxides of the above metals such as titanium isopropoxide, and ion exchange resins such as Dowex and Amberlite. Of these, protonic acids such as phosphoric acid, sulfuric acid, p-toluenesulfonic acid, and trifluoromethanesulfonic acid are preferred, and phosphoric acid is more preferred, in that washing after the reaction is easy and availability is easy.

When maleimide is used as a monomer, it is preferable to use a basic catalyst. Examples of the basic catalyst include alkali metals such as potassium, sodium, and lithium; and phenol salts of these metals, imide salts such as alcoholate, maleimide, and phthalimide; butyllithium, phenyllithium, triethylamine, tributylamine, diisopropylamine, and tetraethylamine. Second, third, such as ammonium hydroxide, trimethylcetyl ammonium hydroxide,
Preferred are quaternary amine compounds and other strong alkalis such as sodium hydroxide, potassium hydroxide, lithium hydroxide and magnesium hydroxide. Catalysts can be appropriately selected and used for other monomers.

The reaction may be carried out in a solventless system or using a solvent. When a solvent is used, the handling of the reaction itself is facilitated, and the monomer and the catalyst are sufficiently mixed, so that the reaction can be efficiently performed. When not used, agitation becomes a problem, but the cost can be reduced. The organic solvent is not particularly limited, and a conventionally known organic solvent can be used.It is desirable that the organic solvent has a high boiling point, and examples of such an organic solvent include mesitylene, naphthalene, tetralin, diethylbenzene, pentylbenzene, and the like. Aromatic hydrocarbons such as dodecylbenzene, dichlorobenzene, aromatic halogenated hydrocarbons such as trichlorobenzene, phenetole, butyl phenyl ether, diphenyl ether,
4,4′-dimethyldiphenyl ether, 3,3′-dimethyldiphenylether, 3-methyldiphenylether, 4,4′-dibromodiphenylether, 4,4
Examples include aromatic ethers such as' -dichlorodiphenyl ether, 4-methoxydiphenyl ether, 4-methyl-4'-methoxydiphenyl ether, dibenzofuran, xanthene, and dimethoxybenzene, and aromatic nitro compounds such as nitrobenzene. These can be used alone, but a mixed solvent with at least one aprotic organic solvent selected from dimethylformamide, dimethylacetamide, N-methylpyrrolidone, N, N'-dimethylimidazolinone, dimethylsulfoxide and sulfolane Is preferred from the viewpoint of increasing the dispersibility of the obtained succinimide. The mixing ratio of at least one selected from aromatic hydrocarbons, aromatic hydrogen halides, aromatic ethers, and aromatic nitro compounds with the aprotic organic solvent is such that the proportion of the aprotic organic solvent in all the solvents is It is preferably from 1 to 99% by weight, more preferably from 5 to 95% by weight. Although the amount of the solvent used is not particularly limited, it is usually 1 to 5000 parts by weight, preferably 3 to 2000 parts by weight per 100 parts by weight of aspartic acid, maleamic acid, maleimide or maleic anhydride and ammonia.
It is the ratio of parts by weight. When the reaction is carried out in a solvent, the reaction solution is filtered and dried, or the solvent is distilled off under reduced pressure and dried to obtain a polysuccinimide solid. When the reaction is carried out without a solvent, the reaction solution can be used as it is in the second step.

The reaction temperature is not particularly limited, but if the reaction temperature is low, the reaction does not proceed, and if it is high, a thermal decomposition reaction is likely to occur. Specifically, the temperature is preferably −30 ° C. to 300 ° C., more preferably in the range of room temperature to 240 ° C., and still more preferably in the range of 50 ° C. to 200 ° C.

The reaction may be carried out in the air, but is preferably carried out in an inert gas atmosphere, since double reaction can be suppressed. The pressure during the reaction is not particularly limited, but is preferably reduced pressure or normal pressure, and more preferably reduced pressure. Specifically, 10P
a to 1.013 × 10 ⁵ Pa.

The reaction time is from 1 minute to 100 hours, preferably from 1 minute to 50 hours, more preferably from 1 minute to 20 hours.

Next, the second step of the present invention will be described.

In the second step of the present invention, the polysuccinimide solid obtained in the first step is finely divided, and a crosslinking agent having a functional group capable of reacting with a functional group in the polysuccinimide is added. Then, high molecular weight and crosslinking are simultaneously performed.

The method for pulverizing the polysuccinimide solid is not particularly limited as long as it can be pulverized to a desired particle size. In other words, any method may be used as long as the center of the particle diameter is in the range of 0.2 to 20 mm. As a mechanical device for refining solids,
Specific examples include a compression crusher such as a roll crusher, a ring roll and a ring hole mill; an impact mill such as a hammer mill and a pin mill; and a rolling mill such as a rod mill and a ball mill. In the case where particles in the range of 0.2 to 20 mm are obtained in advance by polymerization using a solvent, it is not necessary to use these fine-granulating devices.

The crosslinking agent used in the present invention is not particularly limited as long as it has a functional group capable of reacting with the functional group in the polysuccinimide. Examples of the crosslinking agent include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, glycerin, polyglycerin, propylene glycol, diethanolamine, triethanolamine, polyoxypropylene, oxyethyleneoxypropylene block copolymer, Polyhydric alcohols such as pentaerythrol and sorbitol; linear aliphatic polyamines such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, hexamethylenediamine, polyetherpolyamine, mensendiamine, isophoronediamine; Bis (4-aminocyclohexyl) methane 3,9-bis (3-aminopropyl)-
Cycloaliphatic polyamines such as 2,4,8,10-tetraoxane pyro [5,5] undecane, aromatic polyamines such as m-xylenediamine and p-xylenediamine, and dimer acids and aliphatic polyamines Polyamines and polyamines such as basic amino acids such as lysine. Of these, polyamines are preferred because the crosslinking reaction proceeds at lower temperatures. The amount of these polyamines to be used is 0.005 to 20% by weight, preferably 0.1 to 100% by weight, based on 100 parts by weight of the polysuccinimide after pulverization.
005-5% by weight, more preferably 0.01-1% by weight
It is. When the amount is less than 0.005% by weight, no cross-linking effect is exhibited, and when the amount exceeds 20% by weight, the effect corresponding to the amount of the cross-linking agent cannot be obtained, and conversely, when the water absorption capacity becomes extremely small. There is.

When the cross-linking agent and the polysuccinimide fine particles are mixed, the cross-linking agent is sprayed or dropped on the fine particles as they are, or a solution in which the cross-linking agent is dissolved in water and a low boiling organic solvent is used as a solid. It is common to spray or drop on the pulverized material. The organic solvent for dissolving the crosslinking agent is not particularly limited, but an aprotic organic solvent is preferable. Such solvents include, for example, dimethylformamide, dimethylacetamide, N-methylpyrrolidone,
N, N'-dimethylimidazolinone, dimethylsulfoxide, sulfolane and the like can be mentioned. The amount of the organic solvent used is preferably such that the concentration of the crosslinking agent is 0.1 to 50% by weight. If it exceeds 50% by weight, the mixture of the finely divided product and the crosslinking agent solution may be non-uniform. On the other hand, if the amount is less than 0.1% by weight, the amount of the solvent to be used increases, and the effect corresponding to the amount used cannot be obtained, which only raises the cost and is not industrially preferable.

The conditions such as the reaction temperature and pressure in the second step are not particularly limited. The same conditions as in the first step can be used as they are.

Next, the third step of the present invention will be described.

The third step of the present invention is a step of obtaining a crosslinked polyaspartic acid by hydrolyzing the crosslinked polysuccinimide obtained in the second step.

In the hydrolysis reaction, an aqueous alkali solution is added dropwise to the crosslinked polysuccinimide solid, or this solid is added to an aqueous alkali solution at 0 to 100 ° C., preferably 2 to 100 ° C.
The reaction is carried out at 0 to 50 ° C for 0.5 to 24 hours.

Alkali metallization for use in alkaline aqueous solutions
Compounds and / or alkaline earth metal compounds
Is preferably a hydroxide or a carbonate. These compounds
Specific examples of LiOH, NaOH, KOH, Mg
(OH)_{Two ,}Ca (OH)_{Two ,}Li _TwoCO_Three, Na_TwoCO_Three, K
_TwoCO_Three, MgCO_{Three ,}CaCO_ThreeAnd the like. Arca
The aqueous solution is sodium hydroxide or potassium hydroxide
It is common to use a 0.1 to 40% by weight aqueous solution of
You. The amount of the alkali compound to be added is based on 1 imide ring group.
It is preferable to use 0.2 to 2.0 mol.

After completion of the hydrolysis reaction, the reaction product is poured into a large amount of methanol, ethanol, acetone, or the like, and isolated by precipitation of the polymer composition, or by evaporating ion-exchanged water to dryness. Obtain the desired product.

The crosslinked polyaspartic acid prepared by a synthesis reaction according to the present invention is excellent in both water absorption performance and biodegradability.

The water absorption performance is determined by the method of testing the water absorption of a superabsorbent resin specified in Japanese Industrial Standards (JIS K-722).
It can be measured by a test of the amount of water absorption by the tea bag method according to 3). When evaluated by the tea bag method, the resin composition according to the present invention has a water absorption performance of 20 times or more with respect to ion-exchanged water and 5 times or more with respect to physiological saline (0.9% by weight physiological saline). Furthermore, since the crosslinked polyaspartic acid according to the present invention has biodegradability that can be decomposed by bacteria and microorganisms in the soil, it is degraded only by burying in the soil. For this reason, disposal is simple and excellent in safety, and does not cause environmental health problems such as environmental pollution. Therefore, it can be applied to all uses of conventionally known water-absorbing resins. For example, hygiene fields such as sanitary articles such as diapers and sanitary articles, medical fields such as wrapping agents, civil engineering and construction fields such as waste mud gelling agents, food fields, industrial fields, soil modifiers, and water retention It can be used in various fields such as agriculture and horticulture as an agent.

[0036]

The present invention will be described more specifically with reference to the following examples. In addition, various properties of the resin of the present invention were measured by the following methods. Water absorption capacity: In the examples, the water absorption capacity of the resin is based on Japanese Industrial Standards, JIS
It carried out based on the water absorption test method of the superabsorbent resin described in K-7223. That is, 0.20 dry resin
g (1.00 g for 0.9% sodium chloride) in a tea bag (20
(0 mm × 100 mm) and immersed in 1000 ml of ion-exchanged water or 0.9% sodium chloride aqueous solution to swell the resin for a certain period of time. Then, the tea bag was pulled up, drained for 10 minutes, and weighed. . The measurement was performed using the weight obtained when the same operation was performed using only the tea bag as a blank. The water absorption capacity W (g / g) was determined by immersing a tea bag containing the sample, a tea bag containing the sample for a predetermined time, removing the mass b (g) after draining, and removing the tea bag containing no sample for a predetermined time. Average value of mass after immersion and draining c
From (g), it was calculated according to the following equation.

[0037]

(Equation 1)

(B) Biodegradation rate: The biodegradability test was performed using the modified M
Performed according to the ITI test. That is, 200m of basal culture
To l, a polymer composition as a test substance was added to 100 ppm, and activated sludge was added to 30 ppm. Thereafter, the basal culture was maintained at 25 ° C. in a dark place and cultured with shaking for 28 days. During the above period, the amount of oxygen consumed by the activated sludge was measured periodically to obtain a biochemical oxygen demand (BOD) curve.
The biodegradation rate (%) is calculated from the biochemical oxygen demand A (mg) of the test substance (resin) obtained from the BOD curve and the BO
From the blank obtained from the D curve, that is, the oxygen demand B (mg) of the basal culture solution and the total oxygen demand (TOD) C (mg) required for complete oxidation of the test substance,

[0039]

(Equation 2)

Calculated according to:

[Reference Example 1] 100 g of L-aspartic acid and 50 g of 85% phosphoric acid were charged into a 2 L eggplant flask.
Using an evaporator, the reaction was carried out at 200 ° C. in an oil bath at a reduced pressure for 4 hours.

[Reference Example 2] Product 25 obtained in Reference Example 1
g were washed several times with water and methanol. As a result of measuring the obtained polysuccinimide by GPC, the weight average molecular weight was 75,000.

Example 1 10 g of the polysuccinimide obtained in Reference Example 1 was pulverized using a ring ball mill to obtain a powder having a particle size of about 0.01 to 2 mm. The obtained powder was thinly collected on a vat, and 1 g of hexamethylenediamine was added to DM.
5 g of a crosslinking agent solution dissolved in 50 g of F was sprayed by spraying. After spraying, the mixture was transferred to a 1-L eggplant-shaped flask, and reacted for 4 hours under reduced pressure at an oil bath temperature of 200 ° C. using an evaporator. The obtained reaction product was pulverized again, suspended in 500 ml of ion-exchanged water, and a 2N aqueous NaOH solution was added dropwise thereto to adjust the pH.
Was adjusted to 9 to 11 to hydrolyze the remaining imide ring. The obtained reaction suspension was discharged into methanol, filtered and dried to obtain 8.5 g of a product. Table 1 shows the water absorption capacity and biodegradability of the obtained resin.

Example 2 8.2 g of a product was obtained in the same manner as in Example 1 except that the amount of hexamethylenediamine was changed to 0.1 g. Table 1 shows the water absorption capacity and biodegradability of the obtained resin.

Comparative Example 1 10 g of the polysuccinimide obtained in Reference Example 2 was dissolved in 60 g of DMF. A solution prepared by dissolving 0.1 g of hexamethylenediamine in 8 g of DMF was added and stirred at room temperature for 1 hour. 6. Methanol was added to this solution to cause reprecipitation, filtration and drying, followed by polysuccinimide crosslinked product.
3 g were obtained. 500 ml of the obtained polysuccinimide
, And the remaining imide ring was hydrolyzed while adjusting the pH to 9 to 11 by dropping a 2N aqueous solution of NaOH. The obtained reaction suspension was discharged into methanol, filtered and dried to obtain 6.5 g of a product. Table 1 shows the water absorption capacity and biodegradability of the obtained resin.

REFERENCE EXAMPLE 3 100 g of maleimide and 100 mg of hydroquinone were placed in a 2 L eggplant flask, and 1.0 g of sodium hydroxide was added. Reaction temperature 100 ° C
For 10 hours under reduced pressure.

Reference Example 4 Product 25 obtained in Reference Example 3
g were washed several times with water and methanol. As a result of measuring the obtained polysuccinimide by GPC, the weight average molecular weight was 20,000.

Example 3 Product 10 obtained in Reference Example 3
g is ground using a ring ball mill to a particle size of about 0.01 to
2 mm powder was obtained. The obtained powder was thinly gathered on a vat, and 5 g of a crosslinking agent solution obtained by dissolving 1 g of hexamethylene diamine in 50 g of DMF was sprayed. After spraying, the mixture was transferred to a 1-L eggplant-shaped flask, and reacted for 4 hours under reduced pressure at an oil bath temperature of 200 ° C. using an evaporator. The obtained reaction product was pulverized again, suspended in 500 ml of ion-exchanged water, and 2N NaOH aqueous solution was added dropwise to adjust the pH to 9 to 11.
The remaining imide ring was hydrolyzed while adjusting the pH. The obtained reaction suspension was discharged into methanol, filtered and dried to obtain 7.2 g of a product. Water absorption capacity of the obtained resin,
Table 1 shows the biodegradation rates.

Comparative Example 2 10 g of the polysuccinimide obtained in Reference Example 4 was dissolved in 60 g of DMF. A solution prepared by dissolving 0.1 g of hexamethylenediamine in 8 g of DMF was added and stirred at room temperature for 1 hour. 5. Methanol is added to this solution to cause reprecipitation, filtration and drying, followed by cross-linked polysuccinimide.
9 g were obtained. 500 ml of the obtained polysuccinimide
, And the remaining imide ring was hydrolyzed while adjusting the pH to 9 to 11 by dropping a 2N aqueous solution of NaOH. The obtained reaction suspension was discharged into methanol, filtered and dried to obtain 6.2 g of a product. Table 1 shows the water absorption capacity and biodegradability of the obtained resin.

[0050]

[Table 1]

[0051]

According to the method of the present invention, a polysuccinimide solid having a relatively low molecular weight is once obtained, and a crosslinking agent is added to the solid to simultaneously increase the molecular weight and crosslink.
This has the effect of being greatly simplified without going through complicated steps. Moreover, the crosslinked polyaspartic acid obtained by the method of the present invention is excellent in water absorption performance and biodegradability.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shigeki Ideguchi 4-17 Jonanmachi, Izumiotsu-shi, Osaka (72) Inventor Yaya Kato 3-3-4-610, Kamotanidai, Sakai-shi, Osaka F-term (reference) 4F070 AA54 AA55 AB01 AB09 AC12 AC46 AE08 AE30 BA05 BB08 GA06 GA08 GA10 GB09 GC01 4J001 DA01 DB01 DB09 DD07 EA36 EE42A EE43B EE53A FA03 FB01 GA12 GE01 GE11 JA01 JB17 JB50 JC01 4J043 PA02 PA15 QB05 QB01 TA05 QB05 QB05 XB01 XB13 XB27 YA25 YA30 YB02 YB08 YB12 YB32 YB50 ZA03 ZA04 ZB04 ZB60

Claims (6)

[Claims] (I) aspartic acid, glutamic acid,
A first step of heating at least one selected from the group consisting of maleamic acid, maleimide, and a reaction product of maleic anhydride and ammonia in the presence of a catalyst to obtain a solid polysuccinimide; (II) The polysuccinimide solid is finely divided, a crosslinking agent having a functional group capable of reacting with a functional group in the polysuccinimide is added, and a second heating step is performed.
A method for producing a crosslinked polysuccinimide, wherein a crosslinking reaction is carried out simultaneously with the high molecular weight reaction in the second step. (I) aspartic acid, glutamic acid,
A first step of heating one kind selected from the group consisting of maleamic acid, maleimide, and a reaction product of maleic anhydride and ammonia in the presence of a catalyst to obtain a polysuccinimide; (II) the polysuccinic acid After the imide solid is finely divided and a crosslinking agent having a functional group capable of reacting with a functional group in the polysuccinimide is added, the mixture is further heated to increase the molecular weight of the polysuccinimide, thereby obtaining a polysuccinimide. A method for producing a crosslinked polyaspartic acid, comprising: a second step of obtaining a crosslinked acidimide, and (III) a third step of hydrolyzing the crosslinked polysuccinimide. 3. The method for producing a crosslinked polyaspartic acid according to claim 2, wherein the crosslinked polyaspartic acid has a water absorbing function. 4. The method for producing a crosslinked polyaspartic acid according to claim 2, wherein the absorption capacity of physiological saline is 10 g / g or more. 5. The method for producing a cross-linked polysuccinimide according to claim 1, wherein the cross-linking agent having a functional group capable of reacting with a functional group in the polysuccinimide is a polyamine compound. 6. The method for producing a crosslinked polyaspartic acid according to claim 2, wherein the crosslinker having a functional group capable of reacting with a functional group in the polysuccinimide is a polyamine compound.