JPH115840A - Production of cross-linked polyaspartic acid-based resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject resin which is useful as an absorbent excellent in absorbability and applicable to paper diapers and agricultural/horticultural stuff by hydrolyzing the imide rings of cross-linked polysuccinimide in a specific condition so as to increase the hydrolytic rate. SOLUTION: This objective resin is obtained by controlling degree of swelling of the resin in the reaction system within 3 to 100 times regarding to the imide ring of cross-linked polysuccinimide according to any of the followings: by utilizing the polarity of an aqueous solution containing a water-miscible organic solvent (methanol, N,N-dimethyl formamide, etc.); by changing the osmotic pressure by properly determining a concentration or kind of an inorganic salt (hydrochloric acid, hydrobromic acid, etc.) and/or organic acid (organic phosphonic acid, organic sulfonic acid, etc.) in the solution thereof; or by changing an absorbability of the resin by varying a temperature of the solvent between 40 and 100 deg.C in addition to the above one.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a crosslinked polyaspartic acid-based resin having (bio) degradability and high water absorption.

[0002]

[Prior art]

[Technical background of water-absorbent resin] A water-absorbent resin is a resin that can absorb tens to thousands of times as much water as its own weight.
Sanitary articles such as disposable diapers, breast milk pads, disposable rags, dressing materials for wound protection, medical underpads, medical supplies such as cataplasms, pet sheets, portable toilets, gel fragrances, gel deodorants, and sweat-absorbing fibers , Household goods such as disposable body warmers, shampoos, gels for setting, toiletries such as moisturizers, water retention materials for agriculture and horticulture, life-extending agents for cut flowers, floral foam (fixing material for cut flowers), nursery for nursery, water Agricultural and horticultural products such as cultivation, vegetation sheet, seed tape, fluid sowing, dew condensation prevention agricultural sheet, freshness retaining material for food tray, food wrapping material such as drip absorbent sheet, cold insulator, fresh vegetable transportation Materials for transportation such as water-absorbent sheets, building materials for preventing dew condensation, sealing materials for civil engineering and construction, sludge preventing agents for shield method, concrete admixtures,
Materials for civil engineering and construction such as gaskets and packing, sealing materials for electronic devices such as optical fibers, waterproof materials for communication cables, materials for electric devices such as ink jet recording paper, coagulants for sludge, dehydration of gasoline and oils, and water removal. It is used in a wide range of fields such as water treatment agents such as agents, printing pastes, water-swellable toys, and artificial snow.

[0003] Further, by utilizing the sustained-release properties of the chemicals, it is expected to be used in applications such as sustained-release fertilizers, sustained-release pesticides, and sustained-release drugs. Further, it is expected to be used as a humidity control material utilizing its hydrophilicity and as an antistatic agent utilizing its charge retention.

[Prior art relating to water-absorbing resin] Examples of the water-absorbing resin used in such applications include, for example,
Crosslinked polyacrylic acid partially neutralized product (JP-A-55-8430)
No. 4, U.S. Pat. No. 4,625,001), a partially hydrolyzed starch-acrylonitrile copolymer (JP-A-46-439).
No. 95), a starch-acrylic acid graft copolymer (JP-A-51-125468), and a hydrolyzate of a vinyl acetate-acrylate copolymer (JP-A-52-14689).
No.), copolymerized crosslinked product of 2-acrylamido-2-methylpropanesulfonic acid and acrylic acid (European patent 00681)
No. 89), a crosslinked polymer of a cationic monomer (US Pat. No. 4,906,717), a hydrolyzate of a crosslinked isobutylene-maleic anhydride copolymer (US Pat. No. 4,389,513)
Etc. are known.

However, since these water-absorbent resins do not have decomposability, disposal after use is a problem.

At present, these water-absorbent resins are incinerated at the time of disposal and landfilled. However, in the incinerator method, damage to furnace materials due to heat generated during incineration is not considered. In addition, it is pointed out that it causes global warming and acid rain. In addition, the method of landfill processing has the problems that the volume of plastic is bulky, the ground does not stabilize because it does not rot, and there is a major problem that the place suitable for landfill has disappeared.

That is, these resins are poor in degradability and exist semipermanently in water and soil, which is a very serious problem in view of environmental conservation in waste treatment. For example, in the case of disposable resins represented by sanitary materials such as disposable diapers and sanitary articles, recycling the resin requires a great deal of cost, and the amount of incineration is large, so that the burden on the global environment is great. When a crosslinked polyacrylic acid resin is used as a water retention material for agriculture and horticulture, Ca2
It forms a complex with polyvalent ions such as +, forming an insoluble layer (Matsumoto et al., Polymer, 42
Vol., August issue, 1993). Although such layers are said to have low toxicity per se, they are not present in nature at all, and the effects on ecosystems of accumulation of these resins in soil for a long time are unknown. Need to be examined, and its use requires a careful attitude. Similarly, in the case of a nonionic resin, a complex is not formed, but the nondecomposable resin may accumulate in soil due to its nondegradability, and its effect on the natural world is doubtful.

Further, these polymerization resins use monomers that are highly toxic to human skin and the like, and many studies have been made to remove them from products after polymerization. Is difficult to remove. In particular, it is expected to be more difficult in production on an industrial scale.

[Technical background of water-absorbent resin having biodegradability] On the other hand, in recent years, biodegradable polymers have attracted attention as "earth-friendly materials", and it has been proposed to use this as a water-absorbent resin. ing.

Examples of the water-absorbing resin having biodegradability used in such applications include, for example, crosslinked polyethylene oxide (JP-A-6-157795), crosslinked polyvinyl alcohol, and crosslinked carboxymethyl cellulose (US Pat. No. 4650716), crosslinked alginic acid,
Crosslinked starch, crosslinked polyamino acid and the like are known.
Among these, crosslinked polyethylene oxide and crosslinked polyvinyl alcohol have low water absorption, and are not suitable especially when used as materials for products requiring high water absorption such as sanitary products, disposable diapers, disposable rags, and paper towels.

[0011] Further, since these compounds can be biodegraded only by special bacteria, biodegradation is slow or not decomposed under general conditions.
When the molecular weight is further increased, the decomposability extremely decreases.

Crosslinked saccharides such as crosslinked carboxymethylcellulose, crosslinked alginic acid, crosslinked starch and the like contain a large number of strong hydrogen bonds in their molecules, and therefore have strong interactions between molecules and between polymers. The molecular chains cannot be widely opened, and the water absorption capacity is not high.

[Technical background of polyamino acid-based water-absorbing resin] On the other hand, a resin obtained by crosslinking a polyamino acid is biodegradable and thus is friendly to the global environment. It has been shown that it is digested and absorbed, does not show antigenicity in the living body, and that the decomposition products have no toxicity.

As an example of description of such a resin, poly-γ
A method for producing a resin having a high water-absorbing ability by irradiating glutamic acid with γ-rays has been reported (Kunioka et al., Journal of Polymers, Vol. 50, No. 10, p. 755 (1993)). However, from an industrial point of view, the 60Co irradiation equipment used in this technology requires large-scale equipment to shut off radioactivity, and requires sufficient consideration for its management. Absent. Another problem is that polyglutamic acid as a starting material is expensive.

Further, a method of obtaining a hydrogel by crosslinking an acidic amino acid has been reported [Akamatsu et al., US Pat. No. 3,948,863 (corresponding to Japanese Patent Publication No. 52-41309), Iwatsuki et al., JP-A-5-279416. ]. Further, it has been reported that a crosslinked amino acid resin is used as a water-absorbing polymer (Sikes et al., JP-A-6-506244; US Pat. Nos. 5,247,068 and 5,284,936; Suzuki et al.
JP-A-7-309943, Harada et al., JP-A-8-598
No. 20).

However, in any of these reports, these resins are not practical because of insufficient water absorption and salt water absorption.

[Background of the technical idea of the present inventors] As described in JP-A-7-224163, the present inventors reacted polysuccinimide with a crosslinking agent to form A technique for producing a crosslinked polyaspartic acid-based resin having a high salt water absorption ability by hydrolysis is disclosed. The present inventors have also disclosed in Japanese Patent Application Laid-Open No. 9-16984.
As described in No. 0, after cross-linking the polysuccinimide, the remaining imide ring is hydrolyzed in a uniform mixed solvent of a water-miscible organic solvent and water, whereby the cross-linking with high salt water absorption ability is performed. A technique for producing a polyaspartic acid-based resin has been disclosed.

The crosslinked polyaspartic resin obtained by these techniques is very useful because it is earth-friendly and has a high water-absorbing ability. However, from an industrial point of view, there was room for further improvement. That is,
In these methods for producing a crosslinked polyaspartic acid-based resin, the concentration of the formed resin is as low as about 5% by weight, and there is room for improvement in volume efficiency. Further, according to the findings of the present inventors, when producing a crosslinked polyaspartic acid-based resin by hydrolyzing an imide ring of a crosslinked polysuccinimide, when a hydrolysis reaction is performed in water, the resin of the reaction system absorbs water. Swelling and gelling are remarkable, stirring of the reaction system becomes difficult, diffusion of the hydrolysis reagent becomes impossible, and sufficient reaction does not proceed,
As a result, there arises a problem that the water-absorbing ability of the resulting crosslinked polyaspartic acid-based resin does not increase. In addition, when a hydrolysis reaction is performed in an organic solvent or in a mixed solution of water and an organic solvent having a high composition ratio of the organic solvent, the resin of the reaction system tends to undergo a hydrolysis reaction only on the particle surface only. There was a problem that the reaction rate was remarkably slow, and as a result, the water-absorbing ability of the resulting crosslinked polyaspartic acid-based resin did not increase.

[0019]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned conventional problems and to improve the volumetric efficiency and increase the water absorption capacity in the hydrolysis of the imide ring of cross-linked polysuccinimide. An object of the present invention is to provide a method for easily producing a crosslinked polyaspartic acid-based resin having the same.

[0020]

The object of the present invention is to provide a method for producing a crosslinked polyaspartic acid resin by hydrolyzing an imide ring of a crosslinked polysuccinimide, wherein the hydrolysis reaction comprises the reaction of the resin in the reaction system. It can be achieved by a method for producing a crosslinked polyaspartic acid-based resin having a degree of swelling in the range of 3 to 100 times.

In the present invention, the degree of swelling is 3 to 1
If the reaction conditions at the time of hydrolysis such as the ratio of water and the water-miscible organic solvent, the salt concentration, and the temperature are appropriately determined so that the hydrolysis reaction is performed while maintaining the ratio within the range of 00 times, the gelation of the resin may occur. The degree of the most suitable, as a result, it is possible to increase the hydrolysis rate, as a result of a sufficient hydrolysis reaction, it is possible to improve the water absorption capacity of the resulting cross-linked polyaspartic resin, At the same time, stirring can be easily performed, the resin concentration in the reaction solution system can be increased, and the volume efficiency can be increased.

The crosslinked polyaspartic acid-based resin obtained according to the present invention is environmentally friendly by biodegradation after disposal, and is therefore used for disposable diapers, agricultural and horticultural applications, etc.
It is very useful as a superabsorbent resin having excellent water absorbing ability.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

[1] Structure of Cross-Linked Polyaspartic Acid Resin The polymer of the present invention can be roughly classified from its structure as follows:
It consists of a main chain basic skeleton part, a side chain part and a crosslinked part. Hereinafter, these will be described in three parts.

[1-1] Structure of Main Chain Basic Skeleton of Crosslinked Polyaspartic Acid Resin The repeating unit of the main chain basic skeleton of the crosslinked polyaspartic acid resin produced in the present invention is composed of an aspartic acid residue alone. Alternatively, a copolymer of aspartic acid and an amino acid other than aspartic acid may be used. In the present invention, the repeating unit composed of aspartic acid in the polymer is referred to as "polyaspartic acid residue" regardless of the type of bonding.

Specific examples of amino acids other than aspartic acid include, for example, 19 kinds of essential amino acids except aspartic acid, L-ornithine, a series of α-amino acids, and β-amino acids.
Amino acids and amino acids such as alanine, γ-aminobutyric acid, neutral amino acids, acidic amino acids, ω-esters of acidic amino acids, basic amino acids, N-substituted basic amino acids, aspartic acid-L-phenylalanine dimer (aspartame) Derivatives, aminosulfonic acids such as L-cysteic acid and the like can be mentioned. The α-amino acid may be an optically active form (L-form, D-form) or a racemic form.

When it is a copolymer, it may be a block copolymer or a random copolymer. Also, it may be a graft.

The number of repeating units comprising polyaspartic acid residues is not particularly limited, but is preferably 1 to 99.8% with respect to the total number of repeating units constituting the molecule.
10 to 99.8% is more preferable.

The repeating unit of the main chain basic skeleton of the crosslinked polyaspartic acid-based resin is composed of an aspartic acid residue alone or a copolymer with glutamic acid or lysine because of its high water absorbing ability. From the viewpoint of industrial production, it is particularly preferable that the repeating unit consists of an aspartic acid residue alone.

In the main chain basic skeleton of polyaspartic acid, the amide bond in the main chain may be an α bond or a β bond. That is, in the case of polyaspartic acid and its copolymer, when the amino group of aspartic acid or a copolymer unit and the carboxyl group at the α-position of aspartic acid are bonded, the α-bond is formed, and the β-position of aspartic acid is Is a β bond when bonded to a carboxyl group.
In the case of this polyaspartic acid, the α bond and the β bond usually exist in a mixed state. In the present invention, the binding mode is not particularly limited.

The side chain group and the crosslinking group of the polymer of the present invention are
Basically, it is a carboxylic acid derivative in which the carboxyl group of polyaspartic acid is substituted. The details will be described below. [1-2] Structure of Side Chain of Crosslinked Polyaspartic Acid Resin The side chain of the crosslinked polyaspartic acid resin has a structure in which the imide ring of the crosslinked polysuccinimide is opened by hydrolysis. Contains the generated carboxyl group. Further, the crosslinked polyaspartic acid-based resin may include a side chain having another substituent. Other substituents are not particularly limited, for example, a hydroxyl group, an amino group,
Pendant groups containing at least one mercapto group, carboxyl group, sulfonic acid group, phosphonic acid group, alkyl group, aryl group, aralkyl group and the like can be mentioned. Further, the pendant group may be an alkyl group, aralkyl group, or aryl group having no specific substituent. These pendant groups are connected to the polyaspartic acid residue by an amide bond, an ester bond, a thioester bond, or the like.

The carboxyl group formed by the hydrolysis may form a salt even in a free state. Specific examples of the ion forming a salt include, for example, sodium,
Ions such as potassium and lithium; alkali metal ions,
Ammonium; tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, tetrapentylammonium, tetrahexylammonium, ethyltrimethylammonium, trimethylpropylammonium, butyltrimethylammonium, pentyltrimethylammonium,
Ammonium ions such as hexyltrimethylammonium, cyclohexyltrimethylammonium, benzyltrimethylammonium, triethylpropylammonium, triethylbutylammonium, triethylpentylammonium, triethylhexylammonium, cyclohexyltriethylammonium, benzyltriethylammonium ion; trimethylamine, triethylamine, tripropylamine, tripropylamine Butylamine, tripentylamine, trihexylamine, triethanolamine, tripropanolamine, tributanolamine, tripentanolamine, trihexanolamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, dicycloamine Hexylamine, di-benzylamine, ethylmethylamine, methylpropylamine, butyl methylamine, methyl pentyl amine, methyl hexyl amine, methyl amine, ethylamine, propylamine, butylamine, pentylamine, hexylamine,
Examples thereof include amine ions such as octylamine, decylamine, dodecylamine, and hexadecylamine ions.

Of these, the higher the atomic weight or molecular weight of the ion, the higher the molecular weight per monomer unit and the smaller the water absorption per unit weight. Therefore, those having a lower molecular weight are preferred. When there is a possibility of touching human skin or the like, it is preferable that the skin or mucous membrane of an organism has low inflammatory properties. From these points,
It is preferable to use sodium, potassium, lithium, ammonium and triethanolamine, and it is particularly preferable to use sodium and potassium from the viewpoint of cost.

[1-3] Structure of Crosslinked Portion of Crosslinked Polyaspartic Acid Resin The molecular structure of the crosslinked portion in the crosslinked polyaspartic acid resin is not particularly limited. The crosslinked portion of the crosslinked polyaspartic acid-based resin can be understood as a “bonding portion” with the polymer main chain basic skeleton and a “connecting portion” bridging them. Hereinafter, these will be described.

[1-3-1] Bonding portion of crosslinked portion of crosslinked polyaspartic acid-based resin The bonding portion of crosslinked portion of crosslinked polyaspartic acid-based resin is not particularly limited. As a specific example, for example,
Examples of the structure include an amide bond, an ester bond, and a thioester bond. These may be used alone,
A plurality of structures may be mixed.

[1-3-2] Linking Portion of Crosslinked Portion of Crosslinked Polyaspartic Acid Resin The connecting portion of crosslinked portion of crosslinked polyaspartic acid resin is not particularly limited. Specific examples of the connecting portion are described below.

[0037]

Embedded image

[0038]

Embedded image

[0039]

Embedded image These linking moieties may be unsubstituted or substituted with a substituent. Examples of the substituent include an optionally branched alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, an aralkyl group, an optionally substituted phenyl group, and an optionally substituted A good naphthyl group, an optionally branched alkoxy group having 1 to 18 carbon atoms, an aralkyloxy group, a phenylthio group, an optionally branched alkylthio group having 1 to 18 carbon atoms, An alkylamino group which may be branched, a dialkylamino group wherein each alkyl group may have 1 to 18 carbon atoms and an optionally branched trialkyl wherein each alkyl group has 1 to 18 carbon atoms Ammonium group, hydroxyl group, amino group, mercapto group,
Examples include a carboxyl group, a sulfonic acid group, a phosphonic acid group and salts thereof, an alkoxycarbonyl group, an alkylcarbonyloxy group and the like.

For example, alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, cyclopropyl, cyclobutyl, Cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl such as cyclooctyl, benzyl, phenylethyl, phenylpropyl, aralkyl groups such as phenylbutyl, phenyl, tolyl, xylyl,
Chlorophenyl, phenyl group such as biphenyl, naphthyl, naphthyl group such as methylnaphthyl, methoxy, ethoxy, propoxy, butoxy, pentyloxy, hexyloxy, heptyloxy, octyloxy, decyloxy, undecyloxy, dodecyloxy, tridecyloxy, Alkoxy groups such as tetradecyloxy, pentadecyloxy, hexadecyloxy, heptyldecyloxy, octyldecyloxy, aralkyloxy groups such as phenoxy, benzyloxy, tolyloxy, methylthio, ethylthio, propylthio, butylthio, pentylthio, hexylthio, heptylthio, Octylthio, nonylthio, decylthio, undecylthio, dodecylthio, tridecylthio, tetradecylthio, pentadecylthio, hexadecylthio Alkylthio groups such as heptyldecylthio and octyldecylthio, phenylthio groups, aralkylthio groups such as benzylthio and tolylthio, methylamino, ethylamino, propylamino, butylamino, pentylamino, hexylamino, heptylamino, octylamino, nonylamino, Decylamino, undecylamino, dodecylamino, tridecylamino,
Alkylamino groups such as tetradecylamino, pentadecylamino, hexadecylamino, heptyldecylamino, octyldecylamino, dimethylamino, diethylamino, dipropylamino, dibutylamino, dipentylamino, dihexylamino, diheptylamino, dioctylamino, Dialkyl such as dinonylamino, didecylamino, diundecylamino, didodecylamino, ditridecylamino, ditetradecylamino, dipentadecylamino, dihexadecylamino, diheptyldecylamino, dioctyldecylamino, ethylmethylamino and methylpropylamino Amino group, trimethylammonium, triethylammonium, tripropylammonium, tributylammonium, tripentylammonium, trihexyl Ammonium, triheptyl ammonium, trioctyl ammonium, trinonyl ammonium, tridecyl ammonium, triundecyl ammonium, tridodecyl ammonium, tritetradecyl ammonium, tripentadecyl ammonium, trihexadecyl ammonium, triheptyl decyl ammonium, trioctyl decyl Ammonium, dimethylethylammonium, dimethylbenzylammonium, trialkylammonium groups such as methyldibenzylammonium, hydroxyl group, amino group, mercapto group, carboxyl group, or sulfonic acid group, or phosphonic acid group, and salts thereof, methyloxycarbonyl , Ethyloxycarbonyl, propyloxycarbonyl, butyloxycarbonyl, pentyloxycarbonyl, Sill oxycarbonyl, heptyloxycarbonyl, octyloxycarbonyl, nonyloxycarbonyl, decyloxycarbonyl, undecyl oxycarbonyl, dodecyloxycarbonyl, tridecyl oxycarbonyl, tetradecyloxy carbonyl, pentadecyloxy carbonyl,
Alkyloxycarbonyl groups such as hexadecyloxycarbonyl, heptadecyloxycarbonyl and octadecyloxycarbonyl, methylcarbonyloxy, ethylcarbonyloxy, propylcarbonyloxy, butylcarbonyloxy, pentylcarbonyloxy, hexylcarbonyloxy, heptylcarbonyloxy, octylcarbonyl Alkyl such as oxy, nonylcarbonyloxy, decylcarbonyloxy, undecylcarbonyloxy, dodecylcarbonyloxy, tridecylcarbonyloxy, tetradecylcarbonyloxy, pentadecylcarbonyloxy, hexadecylcarbonyloxy, heptadecylcarbonyloxy, and octadecylcarbonyloxy Examples thereof include a carbonyloxy group.

When one having a large molecular weight is selected from these, the molecular weight of the crosslinked portion becomes large, the molecular weight per repeating unit becomes relatively large, and the water absorption per unit weight becomes small. It is preferable to select In addition, it is generally preferable to select a simple production method. For example, unsubstituted or substituted (for example, methyl, ethyl, methoxy, methyloxycarbonyl and / or methylcarbonyloxy group; and / or hydroxyl group, amino group, mercapto group, carboxyl group, sulfonic acid group and / or Or a phosphonic acid group and / or a salt thereof).

Further, when the crosslinked polyaspartic acid-based resin is used for a water retention material, it is preferable that a polar group is present in the resin molecule. Therefore, the crosslinked portion contains an unsubstituted polar group. Or those substituted by a substituent containing a polar group (for example, a hydroxyl group, an amino group, a mercapto group, a carboxyl group, a sulfonic acid group, a phosphonic acid group and / or a salt thereof).

Here, the amount of the cross-linking portion is not particularly limited, but the number of the repeating units having the cross-linking portion is preferably 0.1 to 20% based on the total number of the repeating units of the whole polymer, and is preferably 0.5 to 20%. -10% is more preferable.

[2] Method for Producing Polysuccinimide The method for producing the polysuccinimide before crosslinking used in the present invention is not particularly limited. As a specific example, for example, Journal of American Chemical Society (J. Amer. Chem. Soc.)
80, 3361 to (1958).

The molecular weight of the polysuccinimide used is
Although not particularly limited, the higher the molecular weight, the higher the capacity as a water retention material. Generally, it is 30,000 or more, preferably 50,000 or more, more preferably 90,000 or more.

The polysuccinimide may have a linear structure or a branched structure.

[3] Method for Producing Cross-Linked Polysuccinimide The method for producing cross-linked polysuccinimide used in the practice of the present invention is not particularly limited, but a cross-linking agent is reacted with a solution of polysuccinimide dissolved in an organic solvent. Method.

A method of reacting a crosslinking agent with a solution of polysuccinimide dissolved in an organic solvent is described in, for example,
224163 and the like.
That is, a method in which a crosslinking agent is added to a solution in which polysuccinimide is dissolved in an organic solvent and reacted.

As the organic solvent used in the present invention, it is generally preferable to use a good solvent that can substantially dissolve the polysuccinimide used. Specific examples of the good solvent include, for example, N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, N, N′-dimethylimidazolidinone, dimethylsulfoxide, and sulfolane. Among these, the solubility of polysuccinimide is high,
N, N-dimethylformamide and N, N-dimethylacetamide are particularly preferred. These solvents alone,
Two or more kinds may be used as a mixture.

For the purpose of slowing down the crosslinking reaction, a poor solvent which does not dissolve or only slightly dissolves the polysuccinimide may be added. The poor solvent is not particularly limited, and is a solvent generally used for a chemical reaction, and any solvent having low solubility of polysuccinimide can be used.

Specific examples of the poor solvent include water, alcohols such as methanol, ethanol, propanol, isopropanol, butanol, pentanol, hexanol, heptanol, octanol, 2-methoxyethanol and 2-ethoxyethanol, ethylene glycol and diethylene glycol. , Triethylene glycol,
Propylene glycol, glycols such as dipropylene glycol, methyl glycosolve, glycosolves such as ethyl glycosolve, acetone, methyl ethyl ketone,
Ketones such as methyl isobutyl ketone, cyclic ethers such as tetrahydrofuran and dioxane, petroleum ether, pentane, hexane, heptane, octane, cyclohexane, benzene, toluene, ethylbenzene, xylene,
Decalin, diphenyl ether, anisole, cresol and the like. These solvents may be used alone or in combination of two or more.

The concentration of the polysuccinimide in the solution containing the polysuccinimide at the time when the crosslinking reaction proceeds is not particularly limited, but is generally 0.1 to 50% by weight.
Is particularly preferable, and 1 to 40% by weight is particularly preferable.

The crosslinking agent used in the present invention is not particularly limited as long as it is a polyfunctional compound which reacts with the imide ring of the polysuccinimide. For example, polyfunctional compounds such as polyamine and polythiol can be mentioned. Specific examples thereof include hydrazine, ethylenediamine, propylenediamine, 1,4-butanediamine, pentamethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, undecamethylenediamine, and dodecaamine. Methylenediamine, tetradecamethylenediamine, hexadecamethylenediamine, 1-amino-
Aliphatic polyamines such as 2,2-bis (aminomethyl) butane, tetraaminomethane, diethylenetriamine and triethylenetetramine, norbornenediamine, 1,4
-Alicyclic polyamines such as diaminocyclohexane, 1,3,5-triaminocyclohexane, isophoronediamine, aromatic polyamines such as phenylenediamine, tolylenediamine, xylylenediamine, basic amino acids or their esters, cystamine, etc. And polyamines such as compounds and derivatives thereof in which one or more molecules of a monoamino compound are bonded by one or more disulfide bonds, 1,2-ethanedithiol, 1,3-propanedithiol, 1,4-butanedithiol , 1,6-
Aliphatic polythiols such as hexanedithiol and pentaerythrithiol, alicyclic polythiols such as cyclohexanedithiol, aromatic polythiols such as xylylenedithiol, benzenedithiol, and toluenedithiol, trimethylolpropane tris (thioglycolate), trimethylolpropane Esters such as tris (3-mercaptopropionate) pentaerythritol tetrakis (thioglycolate) and pentaerythritol tetrakis (3-mercaptopropionate) polythiol. In addition, protein-constituting amino acids typified by lysine, cystine, and ornithine, and salts or esters thereof are also included.

Among these crosslinking agents, ethylenediamine, propylenediamine, 1,4-butanediamine, heptamethylenediamine, hexamethylenediamine, lysine, ornithine, which have low odor and high reactivity with the imide ring of polysuccinimide, Cystamine is preferred.

The amount of the crosslinking agent is not particularly limited, and may be appropriately determined depending on the degree of crosslinking determined by the functional number and the molecular weight of the crosslinking agent, and the type of use. Here, the degree of cross-linking is defined to indicate the distance between cross-links, the number of constituent monomer units, or the degree of the ratio of cross-linked portions to the polymer main chain.

In general, if the amount of the crosslinking agent is too large, the degree of crosslinking becomes too high, and the water absorption capacity of the resin when a crosslinked polyaspartic acid-based resin is formed is reduced. Conversely, if the amount of the cross-linking agent is too small, the degree of cross-linking becomes too low, and a resin which is water-soluble and does not exhibit water absorption, and is only partially cross-linked, is obtained. Therefore, the amount of the crosslinking agent may be appropriately determined so as to achieve an appropriate degree of crosslinking. In general, the amount of the crosslinking agent is preferably from 0.1 to 30%, more preferably from 1 to 20%, based on the total number of the monomer units of the polysuccinimide.
% Is preferred.

In the crosslinking reaction, a catalyst may be used if necessary. As the catalyst, a base catalyst is generally used.

Examples of the base catalyst include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide and lithium hydroxide, alkali metal carbonates such as sodium carbonate, potassium carbonate and lithium carbonate, sodium hydrogen carbonate and hydrogen carbonate. Inorganic base reagents such as alkali metal bicarbonates such as potassium, alkali metal acetates such as sodium acetate and potassium acetate, alkali metal salts such as sodium oxalate, and ammonia; trimethylamine, triethylamine, tripropylamine, tributylamine, tributylamine Pentylamine, trihexylamine, triethanolamine, tripropanolamine, tributanolamine, tripentanolamine, trihexanolamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentyne Amine, dihexyl amine, dicyclohexylamine, dibenzylamine, ethylmethylamine, methylpropylamine, butyl methylamine, methyl pentyl amine, methyl hexyl amine, methyl amine, ethylamine, propylamine, butylamine,
Organic base reagents such as amines such as pentylamine, hexylamine, octylamine, decylamine, dodecylamine, hexadecylamine, pyridine, picoline, quinoline and the like can be mentioned.

The reaction temperature in the crosslinking reaction is not particularly limited, and may be appropriately determined in consideration of the reactivity of the crosslinking agent and the dispersion state of the polysuccinimide. In general,
200 ° C is preferred, and 10-80 ° C is more preferred.

After the cross-linking reaction is completed, the organic solvent used for the cross-linking reaction may not be separated and the process may proceed to the next hydrolysis step as it is, or may be separated and taken out as a cross-linked polysuccinimide to proceed to the next hydrolysis step. You may proceed.

The separation of the crosslinked polysuccinimide and the organic solvent may be performed according to a generally used method. For example, filtration, decantation, centrifugation and the like can be adopted.

[4] Hydrolysis of the imide ring of the crosslinked polysuccinimide by adjusting the degree of swelling In the process for producing the crosslinked polyaspartic acid-based resin of the present invention, the imide ring of the crosslinked polysuccinimide is hydrolyzed. At this time, the degree of swelling of the resin in the reaction system is adjusted within a range of 3 to 100 times. By this adjustment, the hydrolysis is rapidly advanced, and the water absorbing ability of the resulting crosslinked polyaspartic acid-based resin can be improved. In the present invention, the degree of swelling indicates the degree (amount) in which a resin undergoing hydrolysis has absorbed water, an organic solvent, salts, oligomers and the like in a hydrolysis reaction system. At this time, the resin is in a state of swelling by absorbing water and an organic solvent. When the resin absorbs all the liquids in the system and swells, it is difficult to stir, but if there is an extra liquid not absorbed by the resin, stirring becomes possible. The actual reaction is that the resin swells,
Perform in the presence of extra liquid. In the range of the degree of swelling of the resin of the present invention, if the amount of excess liquid is large, stirring becomes easy. This extra liquid volume can be selected according to the capacity of the stirrer. For example, in the case of a stirrer that can realize high rotation or high torque, the number may be small, otherwise,
Increase excess liquid volume.

Further, it is possible to prevent the gel-like resin from further absorbing water and solidifying due to the progress of hydrolysis, and to prevent the gel-like resin from hardening due to solidification of the gel-like resin and aggregation of the precipitate. The concentration can be increased, and the volumetric efficiency can be increased. The degree of swelling is preferably adjusted within a range of 3 to 100 times, more preferably within a range of 5 to 20 times.

In the present invention, in the hydrolysis reaction of the imide ring, not all the reaction states have to be carried out within this range. You can go off. For example, a resin that is not sufficiently hydrolyzed at the beginning of the reaction has almost no swelling degree, and may be out of this range. In addition, the degree of swelling of the resin is not particularly specified in advance, and when a resin having an unknown degree of swelling is produced, the degree of swelling may be largely out of this range. The present invention is a method that can easily correct even when the degree of swelling of these resins is out of the range, and the present invention can rapidly perform the hydrolysis reaction of the imide ring of the crosslinked polysuccinimide, Moreover, it is a method excellent in workability. From that point, as the state during the hydrolysis reaction, it is also possible to temporarily use the method of the present invention during the hydrolysis reaction,
Temporarily using the method of the present invention in a step other than the hydrolysis step is also included in the present invention.

Specific methods for adjusting the degree of swelling within the range of 3 to 100 times include, for example, the following four methods.

[4-1] Method of performing hydrolysis reaction in an aqueous solution containing a water-miscible organic solvent [4-2] Method of performing hydrolysis reaction in an aqueous solution containing an inorganic salt and / or an organic salt [ 4-3] A method in which the hydrolysis reaction is performed in a solvent at 40 ° C. to 100 ° C. [4-4] At least two of these methods [4-1] to [4-3] are appropriately combined. Method These methods can be applied to the case where the side chain group described in [1-2] is introduced instead of hydrolyzing the imide ring with an alkali.

Hereinafter, the methods [4-1] to [4-4] will be described.

[4-1] Method in which the hydrolysis reaction is carried out in an aqueous solution containing a water-miscible organic solvent In this method, the ratio of water in the aqueous solution to the water-miscible organic solvent and other conditions (organic solvent Swelling degree of the gel resin in the reaction system is controlled.

The water-miscible organic solvent is not particularly limited as long as it is an organic solvent miscible with water. Specific examples thereof include methanol, ethanol, propanol, isopropanol, butanol, 2-methoxyethanol, and 2-methoxyethanol.
Alcohols such as ethoxyethanol, glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol and dipropylene glycol; ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; cyclic ethers such as tetrahydrofuran and dioxane; -Dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, N, N'-dimethylimidazolidinone,
Dimethyl sulfoxide, sulfolane and the like can be mentioned. Of these, methanol, ethanol, propanol, isopropanol, and butanol are preferred because the obtained resin is particularly easy to dry and the solvent hardly remains in the resin after drying.

The amounts of the water-miscible organic solvent and water, and the ratio of both, are particularly important in the hydrolysis. Their preferred values depend on the polarity of the water-miscible organic solvent and are determined by the polarity of the mixture of water and the water-miscible organic solvent. For example, when the ratio of both is 100% water, the water absorption of the crosslinked polyaspartic acid-based resin becomes maximum, and the water absorption decreases as the ratio of the organic solvent increases, and when the ratio exceeds a certain ratio, the resin absorbs almost no water. No longer.

Further, according to the findings of the present inventors, when a imide ring of a crosslinked polysuccinimide is hydrolyzed to produce a crosslinked polyaspartic acid-based resin, a hydrolysis reaction in water causes a reaction of the reaction system. The resin absorbs water and swells and gels significantly, making it difficult to stir the reaction system, preventing the hydrolysis reagent from diffusing and preventing a sufficient reaction from proceeding. As a result,
There is a problem that the resulting crosslinked polyaspartic acid-based resin does not have a high water-absorbing ability. Also, in an organic solvent or
When a hydrolysis reaction is performed in a mixture of water and an organic solvent having a high composition ratio of an organic solvent, the resin in the reaction system tends to undergo a hydrolysis reaction only on the particle surface, and the rate of the hydrolysis reaction is extremely slow. As a result, there arises a problem that the water-absorbing ability of the resulting crosslinked polyaspartic acid-based resin does not increase.

As described above, when a mixed solution of water and a water-miscible organic solvent is used, the degree of swelling of the resulting crosslinked polyaspartic acid-based resin is determined by the ratio between the two.
In this method, the degree of swelling of the resin in the reaction system in the hydrolysis reaction is adjusted to 3 by appropriately adjusting the ratio.
To within 100 times.

Here, the movement of the substance in the swollen gel is as follows.
Since it is slower than in solution, it takes an appropriate time (relaxation time) for the resin to absorb water or an organic solvent and reach equilibrium. That is, the degree of swelling of the resin changes immediately after the adjustment of the solution ratio and after a lapse of time from the adjustment. In other words, the degree of swelling of the resin changes over time. The present invention also includes resins that change with time, and those that temporarily go through the range of the swelling degree of the present invention.

Further, after the hydrolysis reaction of the imide ring of the crosslinked polysuccinimide starts in a mixture of water and a water-miscible organic solvent, if necessary, the reaction solution may be added in the course of the reaction. By adding water or a water-miscible organic solvent, the ratio of water to the water-miscible organic solvent in the reaction system can be appropriately changed.

For example, when the water absorption of the crosslinked polyaspartic acid-based resin to be produced is not limited to a specific value,
Initiate hydrolysis of the imide ring in water or a mixture of water and a water-miscible organic solvent with a high water ratio, and if the viscosity of the resin has increased due to gelation, the water-miscibility An organic solvent can be appropriately added to suppress the increase in viscosity. Also, for example, a water-miscible organic solvent, or a high ratio of a water-miscible organic solvent, to start a hydrolysis reaction of an imide ring in a mixture of water and a water-miscible organic solvent, and then suppress aggregation of a precipitate. For this purpose, water can be appropriately added to the reaction solution. That is, the method of the present invention is effective not only when the water absorption of the resin to be produced is predetermined but also when it is unknown.

The proportion of water in the mixture of water and the water-miscible organic solvent is preferably at least 5% by weight, particularly preferably in the range of 20 to 80% by weight. In addition, the separated crosslinked polysuccinimide may proceed to the next hydrolysis step in a state of a wet cake to which a solvent is attached, or may proceed to the next hydrolysis step in a state where the solvent is removed by drying.

[4-2] Method of Performing the Hydrolysis Reaction in an Aqueous Solution Containing Inorganic Salt and / or Organic Salt In this method, the hydrolysis reaction is performed in the presence of an inorganic salt and / or an organic salt. Then, the osmotic pressure in the reaction system is adjusted by appropriately determining the concentration and type of the inorganic salt and / or the organic salt, thereby controlling the degree of swelling of the gel resin.

The inorganic and organic salts used are not particularly limited, and general salts such as neutral salts, basic salts and acidic salts can be used over a wide range. When using a polyvalent metal salt,
Since this polyvalent metal salt ionically crosslinks the carboxyl group generated by hydrolysis of the imide ring, the degree of crosslinking of the resulting crosslinked polyaspartic acid-based resin increases, so it is better to lower the salt concentration appropriately. Good.

As the inorganic salt and the organic salt, a solution obtained by dissolving a salt in water may be added, or the salt may be formed by neutralization in water. When a salt is generated by the above crosslinking reaction, the salt can be used as it is.

The salts used include hydrochloric acid, hydrobromic acid,
Hydroiodic acid, hydrofluoric acid, sulfuric acid, sulfurous acid, disulfurous acid, amidosulfuric acid, thiosulfuric acid, nitric acid, nitrous acid, phosphoric acid, phosphorous acid, orthophosphoric acid, metaphosphoric acid, hypophosphoric acid, pyrophosphoric acid, phosphinic acid , Phosphonic acid, carbonic acid, percarbonic acid, boric acid, orthoboric acid, metaboric acid, chloric acid, perchloric acid, hypochlorous acid, bromic acid, perbronic acid, hypobromite, iodic acid,
Periodic acid, hypoiodic acid, silicic acid, orthosilicic acid, metasilicic acid, aluminate, telluric acid, isocyanic acid, thiocyanic acid, manganic acid, permanganic acid, chromic acid, dichromic acid, metaantimonic acid, metavanadic acid And inorganic salts of organic acids, such as molybdic acid, organic phosphonic acids, organic sulfonic acids, organic carboxylic acids, oxalic acids, and organic phenols.

Among these, hydrochloric acid, hydrobromic acid, and hydrogen iodide have low inflammatory properties to the skin and mucous membranes of living organisms, have no redox properties, are low in cost, and have high solubility in water. acid,
Hydrofluoric acid, sulfuric acid, sulfurous acid, nitric acid, nitrous acid, phosphoric acid,
Orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, phosphinic acid, phosphonic acid, carbonic acid, boric acid, orthoboric acid, metaboric acid, silicic acid, orthosilicic acid, metasilicic acid, oxalic acid,
Metal salts or organic base salts of organic phosphonic acids, organic sulfonic acids and organic carboxylic acids are preferred. In particular, metal salts or organic base salts of each acid such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, carbonic acid, boric acid, organic phosphonic acid, organic sulfonic acid, and organic carboxylic acid are preferable.

The metal constituting the metal salt includes lithium, sodium, potassium, beryllium, magnesium, aluminum, calcium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, Rubidium, strontium, yttrium, zirconium, niobium, molybdenum, ruthenium, rhodium, palladium, silver, cadmium, indium, tin, tellurium,
Cesium, barium, cerium, gold, mercury, thallium,
Lead and the like. Among them, lithium, sodium, and potassium, which have low inflammation on the skin and mucous membrane of an organism, are low in cost, and have high solubility in water, are preferable.

Further, as the organic salt, ammonium,
Tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, tetrapentylammonium, tetrahexylammonium, ethyltrimethylammonium, trimethylpropylammonium, butyltrimethylammonium, pentyltrimethylammonium, hexyltrimethylammonium, cyclohexyltrimethylammonium, benzyltrimethylammonium Ammonium salts such as triethylpropylammonium, triethylbutylammonium, triethylpentylammonium, triethylhexylammonium, cyclohexyltriethylammonium, benzyltriethylammonium, trimethylamine, triethylamine, tripropylamine, tributyamine , Tripentylamine,
Trihexylamine, triethanolamine, tripropanolamine, tributanolamine, tripentanolamine, trihexanolamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, dicyclohexylamine, dibenzylamine, Amines such as ethylmethylamine, methylpropylamine, butylmethylamine, methylpentylamine, methylhexylamine, methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, octylamine, decylamine, dodecylamine and hexadecylamine And the like.

Among these, tetramethylammonium is preferred in consideration of solubility in water, odor, safety, and cost.
Particularly preferred are ammonium salts such as tetraethylammonium, tetrapropylammonium, tetrabutylammonium, ethyltrimethylammonium, benzyltrimethylammonium and benzyltriethylammonium, and amine salts such as trimethylamine, triethylamine, tripropylamine, tributylamine and triethanolamine.

Further, examples of other specific salts include sodium chloride, potassium chloride, lithium chloride, ammonium chloride, calcium chloride, magnesium chloride, beryllium chloride, aluminum chloride, titanium tetrachloride, vanadium chloride, chromium chloride, and the like. Manganese chloride, iron chloride, cobalt chloride, nickel chloride, copper chloride, zinc chloride, strontium chloride, yttrium chloride, zirconium chloride, molybdenum chloride, ruthenium chloride, rhodium chloride, palladium chloride, silver chloride, cadmium chloride, tin chloride, tellurium chloride , Cesium chloride, barium chloride, cerium chloride, lead chloride, tetramethylammonium chloride, tetraethylammonium chloride, tetrabutylammonium chloride, chloride salts such as triethanolamine hydrochloride, sodium bromide Potassium bromide, lithium bromide, ammonium bromide, tetramethylammonium bromide, tetraethylammonium bromide, tetrabutylammonium bromide, triethanolamine hydrobromide, sodium iodide, potassium iodide, lithium iodide , Ammonium iodide, tetramethyl ammonium iodine, tetraethyl ammonium iodine,
Tetrabutylammonium iodine, triethanolamine hydroiodide, sodium sulfate, potassium sulfate, lithium sulfate, ammonium sulfate, tetramethylammonium sulfate, tetraethylammonium sulfate, tetrabutylammonium sulfate, triethanolamine・ Sulfate, sodium nitrate, potassium nitrate, lithium nitrate, ammonium nitrate, tetramethylammonium ・ Nitrate, tetraethylammonium ・ nitrate, tetrabutylammonium ・ nitrate, triethanolamine ・ nitrate, sodium phosphate, potassium phosphate, lithium phosphate, phosphorus Ammonium acid, sodium carbonate, potassium carbonate, lithium carbonate, ammonium carbonate, tetramethylammonium carbonate, tetraethylammonium carbonate, tetra Tylammonium carbonate, triethanolamine carbonate, sodium borate, potassium borate, lithium borate, ammonium borate, sodium benzenesulfonate, potassium benzenesulfonate, lithium benzenesulfonate, ammonium benzenesulfonate, tetra Methyl ammonium benzene sulfonate, tetraethyl ammonium benzene sulfonate, tetrabutyl ammonium benzene sulfonate, triethanolamine benzene sulfonate, sodium p-toluene sulfonate, potassium p-toluene sulfonate, p- Lithium toluenesulfonate, ammonium p-toluenesulfonate, tetramethylammonium / p-toluenesulfonate, tetraethylammonium / p-toluenesulfone Salt, tetrabutylammonium · p-toluenesulfonate, triethanolamine · p-toluenesulfonate, sodium benzoate, potassium benzoate, lithium benzoate,
Ammonium benzoate, tetramethylammonium benzoate, tetraethylammonium benzoate, tetrabutylammonium benzoate, triethanolamine benzoate, sodium oxalate, potassium oxalate, lithium oxalate, ammonium oxalate , Tetramethyl ammonium oxalate, tetraethyl ammonium oxalate, tetrabutyl ammonium
Oxalate, triethanolamine, oxalate, sodium acetate, potassium acetate, lithium acetate, ammonium acetate, tetramethylammonium acetate, tetraethylammonium acetate, tetrabutylammonium acetate, triethanolamine acetic acid Salt, sodium propionate, potassium propionate, lithium propionate, ammonium propionate, tetramethylammonium propionate, tetraethylammonium propionate, tetrabutylammonium propionate, triethanolamine propionate, etc. No.

Among these, sodium chloride, potassium chloride, lithium chloride, ammonium chloride, tetramethylammonium chloride, tetraethylammonium chloride
Chloride, tetrabutylammonium chloride, triethanolamine hydrochloride, sodium bromide, potassium bromide, lithium bromide, ammonium bromide, tetramethylammonium bromide, tetraethylammonium bromide, tetrabutylammonium bromide, triethanolamine・ Hydrobromide, sodium iodide, potassium iodide, ammonium iodide, tetramethylammonium iodine, tetraethylammonium iodide, tetrabutylammonium iodine, triethanolamine hydroiodide, sodium sulfate, sulfuric acid Potassium, ammonium sulfate, tetramethyl ammonium
Sulfate, tetraethylammonium / sulfate, tetrabutylammonium / sulfate, triethanolamine / sulfate, sodium nitrate, potassium nitrate, ammonium nitrate, tetramethylammonium / nitrate, tetraethylammonium / nitrate, tetrabutylammonium / nitrate, triethanolamine・ Nitrate, sodium phosphate, potassium phosphate, ammonium phosphate, sodium carbonate, potassium carbonate, lithium carbonate, ammonium carbonate, tetramethylammonium ・ carbonate, tetraethylammonium ・ carbonate, tetrabutylammonium ・ carbonate, triethanolamine・ Carbonates, sodium borate, potassium borate, ammonium borate, sodium benzenesulfonate, potassium benzenesulfonate, benzenesulfonate Monium, tetramethylammonium benzenesulfonate, tetraethylammonium benzenesulfonate, tetrabutylammonium benzenesulfonate, triethanolamine benzenesulfonate, sodium p-toluenesulfonate, potassium p-toluenesulfonate , Ammonium p-toluenesulfonate, tetramethylammonium.p
-Toluenesulfonate, tetraethylammonium
p-toluenesulfonate, tetrabutylammonium / p-toluenesulfonate, triethanolamine
p-toluenesulfonate, sodium benzoate, potassium benzoate, ammonium benzoate, tetramethylammonium benzoate, tetraethylammonium
Benzoate, tetrabutylammonium benzoate,
Triethanolamine / benzoate, sodium oxalate, potassium oxalate, ammonium oxalate, sodium acetate, potassium acetate, ammonium acetate, tetramethylammonium acetate, tetraethylammonium acetate, tetrabutylammonium acetate, tributylamine Preference is given to ethanolamine / acetate, sodium propionate, potassium propionate, etc., especially sodium chloride, potassium chloride, ammonium chloride, tetramethylammonium chloride, tetraethylammonium chloride, tetrabutylammonium chloride, triethanolamine hydrochloride , Sodium sulfate, potassium sulfate, ammonium sulfate, tetramethylammonium sulfate, tetraethylammonium sulfate, tetrabutylammonium sulfate Salt, triethanolamine sulfate, sodium phosphate, potassium phosphate, ammonium phosphate, sodium carbonate, potassium carbonate, ammonium carbonate, sodium borate, potassium borate, ammonium borate, sodium benzenesulfonate, benzenesulfonic acid Potassium, ammonium benzenesulfonate,
Tetramethylammonium benzenesulfonate, tetraethylammonium benzenesulfonate, tetrabutylammonium benzenesulfonate, triethanolamine benzenesulfonate, sodium p-toluenesulfonate, potassium p-toluenesulfonate, p -Ammonium toluenesulfonate, tetramethylammonium / p-toluenesulfonate, tetraethylammonium / p-toluenesulfonate, tetrabutylammonium / p-toluenesulfonate, triethanolamine / p-toluenesulfonate, benzoic acid Sodium oxalate, potassium benzoate, ammonium benzoate, sodium oxalate, potassium oxalate, ammonium oxalate, sodium acetate, potassium acetate, ammonium acetate, professional Sodium propionic acid, potassium propionate and the like are preferable.

Each of the salts listed above may be used alone or in combination of two or more. In some cases, inorganic salts and organic salts can be used in combination.

In this method, the salt may be added at the beginning of the reaction or may be added during the reaction as appropriate. By adding a salt, the degree of swelling of the generated gel can be controlled.

The concentration of the salt in the reaction solution is from 0.01 to
20% by weight is preferred, and 0.1-5% by weight is more preferred. If the concentration is appropriately increased, the effect of the salt is exhibited, and if the concentration is appropriately reduced, the salt can be prevented from being mixed into the resin.

In this method, an organic solvent may be mixed with an aqueous solution containing an inorganic salt and / or an organic salt. The organic solvent includes a water-miscible organic solvent and a water-immiscible organic solvent, both of which can be used.

Specific examples of the water-miscible organic solvent include those similar to the water-miscible organic solvents described in the description of the method [4-1]. On the other hand, specific examples of the water-immiscible organic solvent include petroleum ether, pentane, hexane, heptane, octane, cyclohexane, benzene,
Examples include toluene, ethylbenzene, xylene, decalin, diphenyl ether and the like. In particular, it is easy to dry the crosslinked polyaspartic acid-based resin obtained by the hydrolysis reaction, and it is difficult for the solvent to remain in the resin after drying, and the water-miscible organic solvents methanol, ethanol,
Propanol, isopropanol and butanol are preferred.

When a mixture of water and an organic solvent is used, the proportion of water in the mixture is preferably 5% by weight or more.
Particularly preferred is a range of from 80 to 80% by weight.

[4-3] Method of Performing Hydrolysis in Solvent at 40 ° C. to 100 ° C. This method utilizes the property that the crosslinked polyaspartic acid-based resin has a reduced water absorbing ability at high temperatures, and The degree of swelling of the gel resin in the reaction system is controlled by appropriately adjusting the temperature of the liquid.

In this method, the solvent used may be water or an aqueous solution in which an organic solvent is mixed. The organic solvent includes a water-miscible organic solvent and a water-immiscible organic solvent, both of which can be used. Specific examples of the water-miscible organic solvent and the water-immiscible organic solvent include the same organic solvents as those described in the description of the methods [4-1] and [4-2].

When a mixture of water and an organic solvent is used, the proportion of water in the mixture is likewise preferably at least 5% by weight, particularly preferably within the range of 20 to 80% by weight.

[4-4] Each method described above [4-
1] to [4-3], a method in which at least two of them are appropriately combined with each other. What is necessary is just to carry out in combination suitably considering the kind of resin desired, a manufacturing apparatus, reaction conditions, etc. When the degree of swelling is not adjusted at the temperature of the reaction system, that is, when the method [4-3] is not adopted, the temperature of the reaction system is generally 5 ° C to 100 ° C, preferably 10 ° C to 100 ° C. 60 ° C. is more preferred. By combining these methods, the degree of swelling of the resin can be more effectively controlled, the hydrolysis reaction can be performed efficiently, and a high-performance resin can be obtained.

[4-5] Amount of Water Used for Hydrolysis Reaction The hydrolysis reaction of the imide ring of the crosslinked polysuccinimide is as follows:
It is necessary to do in the presence of water. The amount of the water may be appropriately determined as desired. Generally, in each of the methods [4-1] to [4-4] described above, the amount of water is 1 to 1 of the cross-linked polyaspartic acid-based resin to be generated in order to increase the volumetric efficiency. It is preferably 50 times by weight, particularly preferably 1 to 20 times by weight. In the method [4-1], the amount of water may be determined in consideration of the ratio of water to the water-miscible organic solvent.

[4-6] Alkali Reagent Used in Hydrolysis Reaction The alkali reagent used for hydrolyzing the imide ring of the crosslinked polysuccinimide is not particularly limited, but an aqueous alkali solution is generally used. Can be

Examples of the alkaline aqueous solution include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide and lithium hydroxide, alkali metal carbonates such as sodium carbonate, potassium carbonate and lithium carbonate, sodium hydrogen carbonate, and the like.
Various aqueous solutions using an alkali metal bicarbonate such as potassium bicarbonate, an alkali metal acetate such as sodium acetate and potassium acetate, an alkali metal salt such as sodium oxalate, and aqueous ammonia. Of these, aqueous solutions of sodium hydroxide and potassium hydroxide, which are inexpensive, are preferred. These may be used alone or in combination of two or more.

When a side group other than the polyaspartic acid residue is partially introduced, an amine or thiol which can be a pendant group may be used.

[4-7] pH of Hydrolysis Reaction System The pH of the reaction solution at the time of the hydrolysis reaction varies depending on the concentration of a reagent such as alkaline water. If the pH is appropriately lowered, it is possible to prevent the resin molecules from being cut, and as a result, it is possible to prevent a decrease in water absorption capacity. If the pH is appropriately increased, the reaction rate can be increased, and the process becomes practical. This pH is
Generally, 7.5 to 13 is preferable, and 9 to 12 is more preferable.

[5] Post-Treatment of Cross-Linked Polyaspartic Resin The post-treatment of the cross-linked polyaspartic resin formed by subjecting the imide ring of the cross-linked polysuccinimide to an alkaline hydrolysis reaction is not particularly limited. For example, treatments such as neutralization, salt exchange, drying, purification, granulation, and surface cross-linking treatment may be performed as necessary. Hereinafter, the processes of neutralization, salt exchange, and drying will be particularly described.

[5-1] Neutralization treatment of cross-linked polyaspartic acid-based resin Neutralization treatment of cross-linked polyaspartic acid-based resin may be performed as necessary. However, the reaction solution containing the crosslinked polyaspartic acid-based resin after the hydrolysis reaction is usually alkaline. Therefore, it is preferable to neutralize by adding an acid or the like. By this neutralization treatment, a carboxyl group present in the molecule of the crosslinked polyaspartic acid-based resin can be converted into a salt. Although the degree of neutralization is not particularly limited, generally, the proportion of carboxyl groups forming a salt is 0 to 50% based on the total number of all aspartic acid residues in the molecule of the crosslinked polyaspartic acid-based resin. Preferably, 0 to 30
% Is more preferred.

The method of the neutralization treatment is not particularly limited, but a method of adjusting the pH by adding an acid after the hydrolysis reaction is generally used. Specific examples of this acid include mineral acids such as hydrochloric acid, hydrobromic acid, hydroiodic acid, sulfuric acid, sulfurous acid, nitric acid, nitrous acid, carbonic acid, and phosphoric acid, formic acid, acetic acid, propionic acid, oxalic acid, and benzoic acid. And sulfonic acids such as methanesulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid and toluenesulfonic acid, and phosphonic acids such as benzenephosphonic acid.

Of these, hydrochloric acid and sulfuric acid are preferred in view of cost and ease of removal, and hydrochloric acid is particularly preferred.

[5-2] Salt exchange treatment of cross-linked polyaspartic acid-based resin When the carboxyl group present in the molecule of the cross-linked polyaspartic acid-based resin is converted into a salt by neutralization, if necessary, the salt may be used. Can be exchanged for another type of salt.

Examples of reagents used for this salt exchange include, for example, alkali metal salts, ammonium salts, amine salts and the like. Specifically, sodium,
Alkali metal salts such as potassium and lithium salts, ammonium, tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, tetrapentylammonium, tetrahexylammonium, ethyltrimethylammonium, trimethylpropylammonium, butyltrimethylammonium, pentyltrimethylammonium , Hexyltrimethylammonium, cyclohexyltrimethylammonium, benzyltrimethylammonium, triethylpropylammonium, triethylbutylammonium, triethylpentylammonium, triethylhexylammonium, cyclohexyltriethylammonium, ammonium salts such as benzyltriethylammonium salt, trimethyi Amine, triethylamine, tripropylamine, tributylamine, tripentylamine, trihexylamine, triethanolamine, tripropanolamine, tributanolamine, tripentanolamine, trihexanolamine, dimethylamine, diethylamine, dipropylamine, dipropylamine Butylamine, dipentylamine, dihexylamine, dicyclohexylamine, dibenzylamine, ethylmethylamine, methylpropylamine, butylmethylamine, methylpentylamine, methylhexylamine, methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine And octylamine, decylamine, dodecylamine, and amine salts such as hexadecylamine salt.

Among these, the higher the molecular weight, the higher the molecular weight per monomer unit and the smaller the water absorption per unit weight. Therefore, the smaller the molecular weight, the better. When the obtained crosslinked polyaspartic acid-based resin has a possibility of touching human skin or the like, it is preferable that the skin irritation and the like be low. From these points, it is preferable to use a sodium, potassium, lithium, ammonium or triethanolamine salt, and it is particularly preferable to use a sodium or potassium salt in terms of cost.

[5-3] Drying Treatment of Crosslinked Polyaspartic Acid Resin The method of drying the crosslinked polyaspartic acid resin is not particularly limited. For example, known methods such as hot air drying, drying with specific steam, microwave drying, reduced pressure drying, drum dryer drying, and drying by azeotropic dehydration in a hydrophobic organic solvent can be used. The drying temperature is generally 20 to
200 ° C is preferable, and 50 to 120 ° C is more preferable.

The dried crosslinked polyaspartic acid-based resin may be further subjected to a purification treatment, a granulation treatment, a surface crosslinking treatment and the like.

[6] Shape of Crosslinked Polyaspartic Acid Resin Specific examples of the shape of the crosslinked polyaspartic acid resin include irregularly crushed, spherical, granular, granular, granulated, scaly, massive, Various shapes such as a pearl shape, a fine powder shape, a fiber shape, a bar shape, a film shape, and a sheet shape can be mentioned, and a preferable shape can be selected according to an application. Further, it may be a fibrous base material, a porous body, a foam, a granulated material, or the like.

[7] Particle size of crosslinked polyaspartic resin Resin particle size (average particle diameter)
Is not particularly limited, and a preferred particle size can be selected according to the application. For example, when used in a disposable diaper, it is desired that a high absorption rate and gel blocking do not occur. Therefore, the average particle size is preferably 100 to 1000 µm, more preferably 150 to 600 µm. Also, for example,
When used for kneading into a resin such as a water-stopping material, the average particle diameter is preferably 1 to 10 μm, and when used for a water retention material for agriculture and horticulture, in consideration of dispersibility with soil, 100 μm to
5 mm is preferred.

[8] Form of Use of Crosslinked Polyaspartic Acid Resin The form of use of the crosslinked polyaspartic acid resin is not particularly limited, and may be used alone or in combination with other materials. .

For example, when used in combination with another resin,
A method of kneading with a thermoplastic resin and molding by injection molding or the like, a method of mixing the constituent monomers of the constituent resin other than the above and a crosslinked polyaspartic acid-based resin and, if necessary, an initiator, and polymerizing with light or heat, Disperse the resin other than the above and the crosslinked polyaspartic acid-based resin in a solvent, cast,
After removing the solvent, mixing the prepolymer other than the above and the crosslinked polyaspartic acid-based resin, then cross-linking, mixing the other resin and the crosslinked polyaspartic acid-based resin,
There is a method of crosslinking and the like.

The molded product of the crosslinked polyaspartic resin is not particularly limited, and can be used as a solid, a sheet, a film, a fiber, a nonwoven fabric, a foam, a rubber and the like. Also, the molding method is not particularly limited.

On the other hand, the crosslinked polyaspartic resin is
It may be used alone or in a composite with other materials. The structure of the complex is not particularly limited, for example,
There are a method of sandwiching a pulp layer, a nonwoven fabric, or the like to form a sandwich structure, a method of forming a multilayer structure using a resin sheet or a film as a support, and a method of casting a resin sheet to form a two-layer structure. For example, if a crosslinked polyaspartic acid-based resin is formed into a sheet, a water-absorbing sheet (including a water-absorbing film) can be obtained.

The cross-linked polyaspartic acid-based resin is
If necessary, it may be used by mixing with one or more other water-absorbing resins. If necessary, an inorganic compound such as salt, colloidal silica, white carbon, ultrafine silica, titanium oxide powder, or an organic compound such as a chelating agent may be added. In addition, oxidizing agents, antioxidants, reducing agents,
An ultraviolet absorber, an antibacterial agent, a bactericide, a fungicide, a fertilizer, a fragrance, a deodorant, a pigment, and the like may be mixed.

The crosslinked polyaspartic acid resin can be used as a gel or as a solid. For example, when used as a water retention material for agricultural and horticultural use, a cut flower life-promoting agent, a gel fragrance, a gel deodorant, etc., it is used as a gel, and an absorbent for disposable diapers is used as a solid.

[9] Use of Crosslinked Polyaspartic Acid Resin The use of the crosslinked polyaspartic acid resin is not particularly limited, but it can be used for any of the applications in which conventional water-absorbing resins can be used.

For example, sanitary articles such as sanitary articles, disposable diapers, breast milk pads, disposable rags, dressings for protecting wounds, medical articles such as medical underpads, cataplasms,
Pet seats, portable toilets, gel air fresheners, gel deodorants, sweat-absorbing fibers, household items such as disposable warmers, toiletries such as shampoos, set gels, moisturizers, water retention materials for agriculture and horticulture, Agricultural and horticultural supplies, food trays, etc., for life extension of cut flowers, floral foam (fixed material for cut flowers), nursery beds, hydroponic vegetation sheets, seed tapes, fluid seeding media, dew condensation prevention agricultural sheets, etc. Food packaging materials such as freshness preservation materials, drip absorbent sheets, cold insulation materials,
Transportation materials such as water-absorbent sheets for transporting fresh vegetables, building materials for preventing dew condensation, sealing materials for civil engineering and construction, anti-sedimentation agents for shielding methods, concrete admixtures, civil engineering construction materials such as gaskets and packing, and electronic equipment Materials for electrical and electronic equipment, such as seal materials for optical fibers and optical fibers, waterproofing materials for communication cables, recording paper for ink-jet, coagulants for sludge, water treatment agents for dehydration of gasoline and oils, dewatering agents, and pastes for printing. , Water-swellable toys, artificial snow, sustained-release fertilizers, sustained-release pesticides,
Sustained-release drugs, humidity control materials, antistatic agents, and the like.

[0121]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the examples. In the following Examples and Comparative Examples, “parts” means “parts by weight”.

The water absorption in the examples was measured by the following tea bag method. In addition, the volumetric efficiency of the reaction in the hydrolysis of the imide ring of the crosslinked polysuccinimide was represented by% by weight of the produced resin with respect to the total weight of the solvent used and the crosslinked polysuccinimide resin.

(1) Tea bag method The amount of water absorption was measured for distilled water and physiological saline. That is, in the case of distilled water, about 0.05
Parts, in the case of physiological saline, about 0.1 part of a water-absorbent resin is placed in a non-woven tea bag (80 mm × 50 mm), immersed in an excess of the corresponding solution to swell the resin for 1 hour, The bag was pulled out and drained for 1 minute, and the weight of the tea bag containing the swollen resin was measured. The value obtained by subtracting the weight of the blank and the weight of the water-absorbent resin from the weight of the tea bag containing the swollen resin is divided by the weight of the water-absorbent resin, assuming that the same operation was performed using only the teabag as a blank. The amount of water absorption (g / g of resin) was used. The physiological saline is a 0.9% by weight aqueous sodium chloride solution.

Example 1 In a nitrogen stream, 5 parts of polysuccinimide having a weight average molecular weight of 96,000 was dissolved in 20 parts of N, N-dimethylformamide (DMF), and lysine methyl ester dihydrochloride. 8 parts and triethylamine 3.1
After stirring at room temperature for 5 hours, stirring was stopped and the reaction was carried out for 50 hours. 100 parts of methanol was added to the reaction product, and the mixture was stirred at room temperature for 2 hours to reprecipitate. The precipitate was collected by suction filtration and washed with methanol and then with water to obtain a crosslinked polysuccinimide wet cake.

This wet cake of crosslinked polysuccinimide was suspended in 15 parts of distilled water and 15 parts of methanol.
While maintaining the degree of swelling of the resin within the range of 3 to 100 times, 7.3 parts of a 24% by weight aqueous sodium hydroxide solution was added.
The suspension was dropped so that the pH of the suspension was in the range of 11 to 12. After the pH did not decrease, dilute hydrochloric acid was added until the pH of the reaction solution reached 7. The obtained mixture was discharged into 100 parts of methanol, and the resulting precipitate was dried and pulverized to obtain 7.6 parts of a crosslinked polyaspartic acid-based resin as a water-absorbing polymer.

The water absorption of the crosslinked polyaspartic resin was 480 times with distilled water and 61 times with physiological saline. The volumetric efficiency of the hydrolysis reaction was 20.2.
%Met.

Example 2 146 parts of a crosslinked polyaspartic resin was obtained in the same manner as in Example 1 except that the weight average molecular weight of the polysuccinimide was changed to 150,000. The water absorption of this crosslinked polyaspartic resin is
It was 550 times with distilled water and 63 times with physiological saline.

Example 3 A wet cake of crosslinked polysuccinimide obtained in the same manner as in Example 1 was suspended in 30 parts of a 2% by weight aqueous sodium chloride solution. While maintaining the degree of swelling of the resin within the range of 3 to 100 times, 24% by weight
8.6 parts of an aqueous sodium hydroxide solution was added dropwise so that the pH of the suspension was in the range of 11 to 12. After the pH did not decrease, dilute hydrochloric acid was added until the pH of the reaction solution reached 7. The obtained mixture was discharged into 100 parts of methanol, and the resulting precipitate was dried and pulverized to obtain 7.7 parts of a crosslinked polyaspartic acid-based resin as a water-absorbing polymer. The water absorption of the crosslinked polyaspartic acid resin was 460 times with distilled water and 60 times with physiological saline. Also,
The volumetric efficiency of the reaction in the hydrolysis was 20.4%.

Example 4 A wet cake of crosslinked polysuccinimide obtained in the same manner as in Example 1 was suspended in 25 parts of distilled water at 70 ° C. and 25 parts of isopropyl alcohol. While maintaining the degree of swelling of the resin in the range of 3 to 100 times, 7.6 parts of a 24% by weight aqueous sodium hydroxide solution was added dropwise so that the pH of the suspension was in the range of 9 to 10. After the pH did not decrease, dilute hydrochloric acid was added until the pH of the reaction solution reached 7. The resulting mixture is
The resulting precipitate was dried and pulverized to obtain 7.2 parts of a crosslinked polyaspartic acid-based resin as a water-absorbing polymer. The water absorption of the crosslinked polyaspartic acid resin was 460 times with distilled water and 60 times with physiological saline. The volumetric efficiency of the hydrolysis reaction is 1
2.6%.

Example 5 A wet cake of crosslinked polysuccinimide obtained in the same manner as in Example 1 was suspended in a mixture of 15 parts of a 2% by weight aqueous sodium chloride solution and 8 parts of methanol. While maintaining the degree of swelling of the resin in the range of 3 to 100 times, 8.6 parts of a 24% by weight aqueous sodium hydroxide solution was added dropwise so that the pH of the suspension was in the range of 11 to 12. After the pH did not decrease, dilute hydrochloric acid was added until the pH of the reaction solution reached 7. The obtained mixture was discharged into 100 parts of methanol, and the resulting precipitate was dried and pulverized to obtain 7.6 parts of a crosslinked polyaspartic acid-based resin as a water-absorbing polymer. The water absorption of the crosslinked polyaspartic acid resin was 480 times with distilled water and 61 times with physiological saline. Further, the volumetric efficiency of the reaction in the hydrolysis was 24.8%.

Example 6 A crosslinked polyaspartic acid-based compound was prepared in the same manner as in Example 1 except that 0.15 parts of hexamethylenediamine was used instead of lysine methyl ester dihydrochloride as a crosslinking agent. 7.0 parts of resin were obtained. The water absorption of the crosslinked polyaspartic resin was 380 times with distilled water and 59 times with physiological saline. Further, the volumetric efficiency of the reaction in the hydrolysis was 18.9%.

Example 7 Example 1 was repeated except that 8.2 parts of a 30% by weight aqueous solution of potassium hydroxide was used instead of a 24% by weight aqueous solution of sodium hydroxide as the alkaline water used for the hydrolysis reaction. Similarly, 7.9 parts of a crosslinked polyaspartic acid-based resin was obtained. The water absorption of the crosslinked polyaspartic resin was 450 times with distilled water and 58 times with physiological saline. Further, the volumetric efficiency of the reaction in the hydrolysis was 18.9%.

Comparative Example 1 A wet cake of crosslinked polysuccinimide obtained in the same manner as in Example 1 was distilled water 10
Suspended in 100 parts of an aqueous solution of 8% by weight of sodium hydroxide, so that the pH of the suspension is in the range of 10 to 11; The aqueous solution was continued to be added. After the pH did not decrease, dilute hydrochloric acid was added until the pH of the reaction solution reached 7. The obtained mixture was discharged into 3000 parts of acetone, and the resulting precipitate was dried and pulverized to obtain 7.7 parts of a crosslinked polyaspartic acid-based resin as a water-absorbing polymer. The water absorption of this crosslinked polyaspartic acid-based resin was 180 times with distilled water and 38 times with physiological saline, and the volumetric efficiency of the hydrolysis reaction was 0.8%.

Comparative Example 2 A wet cake of cross-linked polysuccinimide obtained in the same manner as in Example 1 was mixed with 30 parts of distilled water.
And 90 parts of acetone, and an 8% by weight aqueous sodium hydroxide solution was added dropwise so that the pH of the suspension was in the range of 10 to 11. Until the pH of the reaction solution did not decrease further. The 8% aqueous solution of caustic soda was continued to be added. p
After H was no longer reduced, dilute hydrochloric acid was added until the pH of the reaction solution reached 7. The obtained mixture was discharged into 3000 parts of acetone, dried and pulverized to obtain 7.1 parts of a crosslinked polyaspartic acid-based resin as a water-absorbing polymer. The water absorption of this crosslinked polyaspartic acid resin is 150
And that of physiological saline was 36 times, and the volumetric efficiency of the hydrolysis reaction was 5.6%.

[Comparison of Examples 1 to 7 with Comparative Examples 1 and 2] In Comparative Examples 1 and 2, the degree of swelling of the resin was 3 to 100.
Since the hydrolysis reaction was performed without keeping the ratio within the range, the obtained crosslinked polyaspartic acid-based resin had a low water absorption, and the volumetric efficiency of the hydrolysis reaction was very low.

In contrast, in each of Examples 1 to 7, the hydrolysis reaction was carried out while maintaining the swelling degree of the resin within the range of 3 to 100 times. An aspartic acid-based resin was obtained, and the volumetric efficiency of the hydrolysis reaction was high. As described above, by performing the hydrolysis reaction of the imide ring of the crosslinked polysuccinimide while maintaining the degree of swelling of the resin in the reaction system in the range of 3 to 100 times, an excellent effect in terms of water absorption and volume efficiency is obtained. Was obtained.

[0137]

As described above, according to the production method of the present invention, it is useful as a water absorbent used for disposable diapers, agricultural and horticultural uses, etc., and is biodegradable after use or disposal. In the hydrolysis step of the method for producing a crosslinked polyaspartic acid which is friendly to the global environment, its volumetric efficiency can be improved and a water-absorbing resin having high water-absorbing ability can be easily produced.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroaki Tamaya 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Chemicals, Inc.

Claims (8)

[Claims] 1. A method for producing a crosslinked polyaspartic acid resin by hydrolyzing an imide ring of a crosslinked polysuccinimide, wherein the degree of swelling of the resin in the reaction system is 3 to 10
A method for producing a crosslinked polyaspartic acid-based resin carried out within a range of 0 times. 2. The method for producing a crosslinked polyaspartic acid-based resin according to claim 1, wherein the hydrolysis reaction is performed in an aqueous solution containing a water-miscible organic solvent. 3. The method for producing a crosslinked polyaspartic resin according to claim 2, wherein the degree of swelling of the resin in the reaction system is controlled by the polarity of the aqueous solution containing the water-miscible organic solvent. 4. The method for producing a crosslinked polyaspartic acid-based resin according to claim 1, wherein the hydrolysis reaction is performed in an aqueous solution containing an inorganic salt and / or an organic salt. 5. The crosslinked polyaspartic acid according to claim 4, wherein the osmotic pressure of the resin in the reaction system is changed by an inorganic salt and / or an organic salt, thereby controlling the degree of swelling of the resin in the reaction system. Production method of resin. 6. The method for producing a crosslinked polyaspartic acid-based resin according to claim 1, wherein the hydrolysis reaction is performed in a solvent at 40 ° C. to 100 ° C. 7. The production of a crosslinked polyaspartic acid resin according to claim 6, wherein the water absorption capacity of the resin is changed by changing the solvent temperature, thereby controlling the degree of swelling of the resin in the reaction system. Method. 8. A crosslinked polyaspartic acid-based resin produced by the method according to claim 1.