JPH11158267A - Production of crosslinked polysuccinimide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a crosslinked polysuccinimide as a precursor for a crosslinked polyaspartic acid resin having both high water absorptivity and (bio)degradability in excellent productivity and operability by dissolving a polysuccinimide in a good solvent, adding a crosslinking agent to the solution to introduce pendant groups into the polymer, adding a dispersant to the solution to form a mixture in the state of a dispersion, and subjecting the suspension to a crosslinking reaction in the presence of a base. SOLUTION: The polysuccinimide used is the one having a weight-average molecular weight of 10,000 or above. The good solvent used is, for example, N,N-dimethylformamide. The crosslinking agent used is, for example a polyamine having at least one carboxyl group in the molecule (e.g. lysine or ornithine). Its amount of use is desirably 0.1-30 mol.% based on the monomer units of the main chain of the polysuccinimide. The dispersant used is exemplified by a poor solvent, for example, water or methanol. Its amount of use is 0.5-10 times as large as the weight of the good solvent used. The base used is NaOH or the like. The crosslinking temperature is -10 to 200 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a crosslinked polysuccinimide. The method for producing a crosslinked polysuccinimide according to the present invention is particularly useful in that a water-absorbing resin or the like having degradability and / or biodegradability can be provided. More specifically, it is excellent in degradability and / or biodegradability,
Further, the present invention is useful in that a crosslinked polysuccinimide useful as a precursor of a crosslinked polyaspartic acid-based resin having a high water absorption ability can be provided with excellent productivity.

[0002]

2. Description of the Related Art [Technical background of water-absorbent resin] A water-absorbent resin is a resin that can absorb water of several tens to several thousand times its own weight, and is used for sanitary products, disposable diapers, breast milk pads, disposable rags and the like. Supplies, dressings for wound protection, medical supplies such as medical underpads, cataplasms, pet seats, portable toilets, gel fragrances, gel deodorants, sweat-absorbent fibers, disposable warmers and other household items, shampoos, Gels for setting, toiletries such as moisturizers, water retention materials for agriculture and horticulture, life extension materials for cut flowers, floral foam (fixed material for cut flowers), nurseries for raising seedlings, hydroponics, vegetation sheets, seed tapes, fluids Agricultural and horticultural products such as agricultural sheets for preventing sowing and dew condensation, freshness-retaining materials for food trays, food packaging materials such as drip-absorbent sheets, cooling materials, and transport materials such as water-absorbent sheets for transporting fresh vegetables Building materials for preventing dew condensation, sealing materials for civil engineering and construction, anti-sludge agents for shielding methods, concrete admixtures, civil engineering and building materials such as gaskets and packing, sealing materials for electronic devices such as optical fibers, and waterproof materials for communication cables Used in a wide range of fields, including electrical equipment-related materials such as inkjet recording paper, sludge coagulants, gasoline, dehydration of oils, water treatment agents such as water removers, printing pastes, water-swellable toys, and artificial snow. ing. In addition, it is expected to be used for sustained-release fertilizers, sustained-release pesticides, sustained-release drugs, and the like by utilizing the sustained-release properties of the chemicals. Further, it is expected to be used as a humidity control material utilizing its hydrophilicity, and as an antistatic agent utilizing its charge retention.

[0003] Specific examples of the water-absorbing resin used in such applications include, for example, a partially neutralized cross-linked polyacrylic acid (JP-A-55-84304, US Patent No. 4,62).
5,001), a partially hydrolyzed starch-acrylonitrile copolymer (JP-A-46-43995), a starch-acrylic acid graft copolymer (JP-A-51-125468).
No.), hydrolyzate of vinyl acetate-acrylic acid ester copolymer (JP-A-52-14689), copolymerized cross-linked product of 2-acrylamido-2-methylpropanesulfonic acid and acrylic acid (European Patent 0068189) A crosslinked product of a cationic monomer (US Pat. No. 4,906,717);
Crosslinked isobutylene-maleic anhydride copolymer (US Pat. No. 4,389,513) can be mentioned. However, since the water-absorbing resin compositions produced by these prior arts do not have decomposability, waste disposal after use becomes a serious problem.

[0004] In Japan, the disposal of the water-absorbent resin is currently mainly performed by incineration and landfill. For example, disposal of disposable sanitary materials (paper diapers, sanitary articles, etc.) after use, and packaging materials that are no longer needed after unpacking are used. As a problem of incineration, not only is the heat generated during incineration of water-absorbent resin waste not only damaged the incinerator furnace material, but also the carbon dioxide gas, sulfur-containing compounds, and nitrogen-containing compounds that are generated due to global warming. It has been pointed out that it causes acid rain and inhibits an increase in the incineration temperature in the furnace, thereby causing the generation of dioxin. This has a large impact on the global environment.
In addition, as a problem of landfill treatment, these water-absorbent resin wastes are bulky and hard to decay, so not only the ground of the landfill is not stable, but also it becomes difficult to secure land suitable for landfill. And biohazard (eg, pathogens of diseases that become extremely difficult to treat once infected (HIV, MRSA, O-157, hepatitis B / C virus, Ebola hemorrhagic fever, Creutzfeldt-Jakob disease and madness). Disposable sanitary materials (paper diapers, diapers, etc.) that absorb feces, body fluids, blood, etc.
It has been pointed out that there is a danger that sanitary products and the like will be buried without sterilization. In addition, enormous costs are required to recover, recycle, and recycle resin from used disposable sanitary materials (paper diapers, sanitary products, etc.). As described above, the water-absorbent resin composition produced by the above prior art does not have degradability or biodegradability, and exists semipermanently in water and soil, so when considering waste treatment and environmental conservation. There are serious problems inherent.

It has been reported that when a crosslinked polyacrylic acid resin is used as a water retention material for agriculture and horticulture, it forms a complex with polyvalent ions such as Ca ions in soil to form an insoluble layer (Matsumoto et al.). , Polymer, Vol. 42, August,
1993). However, although such layers are said to be less toxic in and of themselves, they do not naturally exist in nature, and the accumulation of such resins in soil has no impact on ecosystems. It is unknown and may need to be scrutinized. Similarly, in the case of nonionic raw resin, no complex is formed, but it is not degradable and may accumulate in the soil. The effect on the ecosystem is still unknown, and it is necessary to thoroughly examine the resin. In addition, since these resins use monomers that are toxic to living organisms as raw materials, unreacted monomers and oligomers remain in the polymerization products. Therefore, depending on the use of the resin product, it is necessary to remove unreacted monomers and oligomers from the resin product. However, this purification operation requires high cost and is extremely difficult in some cases.

[Technical Background of Biodegradable Water-Absorbent Resin] In recent years, biodegradable polymers have attracted attention as "earth-friendly materials". In particular, a polymer having both biodegradability and water absorbency has attracted attention as a trump card to solve the above-mentioned problems relating to the waste of the water absorbent resin, but has not always met expectations as described below.
Specific examples include, for example, polyethylene oxide crosslinked product (Japanese Patent Application Laid-Open No. 6-157795), polyvinyl alcohol crosslinked product, carboxymethylcellulose crosslinked product (US Pat. No. 4,650,716), alginic acid crosslinked product, starch crosslinked product, polyamino acid Crosslinked bodies and the like can be mentioned. However, crosslinked polyethylene oxide and crosslinked polyvinyl alcohol have low water absorbing ability. In addition, crosslinked saccharides such as crosslinked carboxymethylcellulose, crosslinked alginic acid, and crosslinked starch have many strong hydrogen bonds in their molecules, and therefore have strong interactions between molecules and between polymers, and therefore have a wide molecular chain. Unable to open, low water absorption capacity. Since these polymers have low water absorption, there is a problem that they are not particularly suitable as materials for products requiring high water absorption (for example, freshness preserving materials for fresh foods, disposable diapers, sanitary products, disposable rags, paper towels, etc.). is there. In many of these polymers, the microorganisms that biodegrade the polymer are limited to special strains. Therefore, the growth environment (temperature, pH, anaerobic / aerobic, light (Intensity, wavelength of light, etc.), the rate of biodegradation is very slow, and if the molecular weight of the polymer is large, the rate of biodegradation is further reduced.

The resin obtained by cross-linking a polyamino acid is biodegradable and thus is friendly to the global environment. Even when absorbed in a living body, it is digested and absorbed by enzymes, and shows no antigenicity in a living body. The product has also been shown to have low or no toxicity and is a human-friendly material. As a specific example, for example, a method of irradiating poly-γ-glutamic acid with γ-rays to produce a resin having a high water-absorbing ability (Kunioka et al .; Polymer Journal, Vol. 50, No. 10, No. 75)
5 to (1993)). However,
From an industrial point of view, the ⁶⁰ Co irradiation equipment used in this technology is not realistic because a large-scale equipment is required to shield the radiation and sufficient care must be taken for its management. Another problem is that polyglutamic acid as a starting material is expensive. As another example of the water-absorbing resin obtained by cross-linking a polyamino acid, a method of cross-linking an acidic amino acid to obtain a hydrogel (Akamatsu
U.S. Pat. No. 3,948,863, JP-B-52-4
No. 1309, Iwatsuki et al., JP-A-5-279416), a method of using a crosslinked amino acid resin as a water absorbent resin (Sikes)
No. 6-506244, U.S. Pat. No. 5,24
7,068 and 5,284,936, Suzuki et al., JP-A-7-309943, and the like. However, these water-absorbing resins are not always sufficient in water-absorbing ability and are not practical.

The present inventors have already disclosed in JP-A-7-2241.
No. 63, a polysuccinimide is reacted with a cross-linking agent, the reaction is terminated before the reaction solution is gelled to obtain a cross-linked polysuccinimide, and the remaining imide ring is hydrolyzed to absorb salt water. A technique for producing a crosslinked polyaspartic acid-based water-absorbent resin having a high water content was disclosed. Also,
The present inventors have disclosed in Japanese Patent Application Laid-Open No. 9-169840 that after partially cross-linking a polysuccinimide, an alkaline aqueous solution is added to the reaction solution without isolating the cross-linked polysuccinimide, and the remaining imide ring is removed. A technique for producing a crosslinked polyaspartic acid-based water-absorbing resin having a high saltwater-absorbing ability by hydrolyzing the resin has been disclosed. These inventions disclosed by the present inventors are extremely significant in terms of novelty, inventive step, and industrial applicability.

However, Japanese Patent Application Laid-Open No. 7-224163 describes
In the method disclosed in JP-A-9-169840, crosslinking does not proceed sufficiently unless the steps are sufficiently controlled,
In some cases, a water-absorbing resin having high water-absorbing ability was not obtained. In addition, if the process is not sufficiently controlled, the whole reaction solution may be solidified during the crosslinking reaction and stirring may be difficult. Although the crosslinked polyaspartic acid-based water-absorbing resin is very useful as described above, there is room for improvement in controlling the production process of the crosslinked polysuccinimide as an intermediate.

[0010]

SUMMARY OF THE INVENTION In the present invention, in view of the above-mentioned problems of the prior art, an excellent technical idea of the invention disclosed by the present inventors has been developed. (Bio) degradable water-absorbing resin with water absorbing ability,
In particular, it is an object of the present invention to provide a method for producing a crosslinked polysuccinimide useful as a precursor of a crosslinked polyaspartic acid-based water-absorbing resin or the like with high productivity and simple operability.

[0011]

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, added a crosslinking agent to polysuccinimide and introduced it as a pendant group, and then charged a dispersing agent. A crosslinked polysuccinimide useful as a precursor of a crosslinked polyaspartic acid-based water-absorbing resin having high water absorbing ability can be produced with high productivity by bringing the reaction system into a dispersed state and then performing a crosslinking reaction by adding a base. And completed the present invention. That is, the present invention is characterized in that after reacting a polysuccinimide and a crosslinking agent and introducing them as a pendant group, a dispersant is charged to bring the reaction system into a dispersed state, and then a base is added to carry out a crosslinking reaction. To produce a crosslinked polysuccinimide.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The method for producing polysuccinimide used in the present invention is not particularly limited. Specific examples of the method for producing polysuccinimide include, for example, the Journal of American Chemical Society (J. Amer. Ch.).
em. Soc. 80), 3361- (1958)
Can be exemplified. That is, aspartic acid is converted from 150 ° C. to 200 ° C. in the presence of phosphoric acid.
It can be produced by heating to ℃ and dehydration by condensation.

[0013] The molecular weight (weight average molecular weight) of the polysuccinimide used in the present invention is not particularly limited, but generally, a higher one is preferable because the ability as a water retaining material is higher. Although depending on the cross-linking agent to be selected, a resin having a high water-absorbing ability is obtained by using polysuccinimide having a high weight average molecular weight, and a resin having a weight average molecular weight of 10,000 or more is usually used.

The polysuccinimide used in the present invention may have a linear structure or a branched structure. Further, it may partially contain an amide bond. Further, the main chain basic skeleton may contain a bond with an amino acid derivative other than aspartic acid (that is, it may be a copolymer). Examples of amino acid derivatives other than aspartic acid include, for example, aliphatic acids such as glycine, alanine, valine, leucine, isoleucine, serine, threonine, asparagine, glutamine, glutamic acid, lysine, ornithine, cysteine, cystine, methionine, proline, hydroxyproline, and arginine. Aromatic α-amino acids such as α-amino acids, tyrosine, phenylalanine, tryptophan, histidine, etc., those in which the side chain functional groups of these α-amino acids are substituted, aminocarboxylic acids such as β-alanine, γ-aminobutyric acid, and glycyl- Examples include dipeptides (dimers) such as glycine and aspartyl-phenylalanine, and tripeptides (trimers) such as glutathione. These amino acid derivatives may be optically active forms (L-form, D-form) or racemic forms. In addition, these bonds may be present randomly (random copolymer) or may be present blockwise (block copolymer).

The good solvent used in the present invention means an organic solvent capable of substantially completely dissolving the polysuccinimide. Specific examples include N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2
Amide-based organic solvents such as -pyrrolidone, 1,3-dimethyl-2-imidazolidinone, and 1,3-diethyl-2-imidazolidinone; and sulfur-containing organic solvents such as dimethyl sulfoxide and sulfolane. These solvents may be used alone or in combination of two or more. The amount of the good solvent used is not particularly limited, and varies depending on the type of the solvent, but is usually 2 to 100 times the weight of the polysuccinimide.
Weight times are used.

The dispersant used in the present invention is not particularly limited, but it is preferable to use a poor solvent for polysuccinimide. The poor solvent used in the present invention,
Includes organic solvents and water that cannot substantially completely dissolve the polysuccinimide. Specific examples include water, alcohols such as methanol, ethanol, propanol, isopropanol, butanol, pentanol, hexanol, octanol, 2-methoxyethanol and 2-ethoxyethanol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol and the like. Glycols and ethers thereof, ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone, ethers such as diethyl ether, methyl ter-butyl ether and diphenyl ether, cyclic ethers such as tetrahydrofuran and dioxane, petroleum ether, pentane and hexane , Heptane, octane,
Hydrocarbons such as cyclohexane, benzene, toluene, ethylbenzene, xylene, mesitylene, cumene, cymene, decalin, dichloromethane, 1,2-dichloroethane, dibromoethane, chloroform, monochlorobenzene, bromobenzene, o-dichlorobenzene, p-dichlorobenzene And anisole, cresol and the like. These may be used alone or as a mixture of two or more. The use amount of these poor solvents is not particularly limited, but is usually 0.5 times by weight or more based on the good solvent used to dissolve the polysuccinimide.
10 weight times are used. If the amount of the poor solvent is too small, the polysuccinimide may not be in a dispersed state and may gel during the crosslinking reaction.

The crosslinking agent used in the present invention is not particularly limited, but is preferably a polyfunctional compound having at least one carboxyl group in the molecule and capable of reacting with an imide ring. Specific examples include, for example, (polyamino) polycarboxylic acids. More specific examples include protein-constituting amino acids such as lysine, cystine, ornithine, Nδ- (2-amino-2-carboxyethyl) ornithine, Nδ- (2-amino-2-carboxyethyl) lysine, o- ( 2-amino-3-hydroxypropyl) homoserine, kynurenine, α, β-diaminosuccinic acid, α, ε-diaminopimelic acid, 2,6-diamino-7-hydroxyazelaic acid, isolidine, 3,5
-Diaminohexanoic acid, α, γ-diaminobutyric acid, gencolic acid, cystathionine, cystine disulfoxide,
Amino acids other than protein constituent amino acids such as α, ε-diamino-β-hydroxypimelic acid, hypusine, γ-hydroxyornithine, α-hydroxylysine, lanthionine, lysinonorleucine, rhizobitoxin, and roseanine. In addition, these amino acids include mineral salts such as hydrochloride, sulfate and hydrobromide, organic acid salts such as p-toluenesulfonic acid salt and methanesulfonic acid salt, and alkyl carboxylate such as methyl ester and ethyl ester. Alkali metal carboxylate such as ester, sodium salt and potassium salt, and organic amine salt of carboxylic acid such as triethanolamine salt and triethylamine salt may be used. Among these, amino acids such as lysine, cystine and ornithine and derivatives thereof such as esters and salts are preferred. When these are used, the resulting water-absorbent resin is safe for a living body and environment even after decomposition and / or biodegradation, and is particularly preferable. These may be used alone or as a mixture of two or more.

In the crosslinking agent of the present invention, in the case of amino acids such as lysine and ornithine, one of the two amino groups is hydrogen-bonded to a carboxyl group, and is formally a monofunctional amine. These do not function as cross-linking agents, but can be introduced as pendant groups into the polymer by reacting with polysuccinimide. When a base is added to the polysuccinimide in which a pendant group has been introduced, the carboxylic acid that has formed a hydrogen bond with another amino group is neutralized, and the amino group becomes free and reacts with the imide ring. The crosslinking reaction proceeds. Therefore, in the present invention, the above amino acids are added to a solution of polysuccinimide in such a manner that only one amino group in the molecule is free. For example, when a diaminomonocarboxylic acid such as lysine is used, it is left as it is, and when a diaminomonocarboxylic acid / mineral acid salt such as lysine / monohydrochloride is used, only a mineral acid is neutralized to form one amino group. Becomes free and is introduced as a pendant group to polysuccinimide. Also, for example, when using diaminodicarboxylic acids such as cystine,
Since there are two inner salts in the molecule, if one base is added to form a carboxylate, only one amino group is free and introduced as a pendant group to polysuccinimide. it can. Furthermore, for example, when using ornithine methyl ester or the like, a cross-linking reaction occurs as it is, which is not preferable. Therefore, the monohydrochloride is used in the reaction with one amino group blocked.

In the present invention, the "pendant group"
A compound having a functional group capable of reacting with the imide ring of the polysuccinimide means that the imide ring is opened and the compound is in a "hanging" state with respect to the polysuccinimide main chain.

That is, in the present invention, a crosslinking agent is introduced as a pendant group. The reaction system is dispersed to prevent the reaction system from gelling even when the crosslinking reaction proceeds. A base is added to activate the cross-linking agent introduced as a pendant group to start a cross-linking reaction. The cross-linking reaction is performed in three steps.

The amount of the crosslinking agent used in the present invention is not particularly limited, and can be appropriately selected depending on the desired degree of crosslinking. Here, the degree of crosslinking means the ratio of the crosslinked portion to the polymer main chain. The type of the crosslinking agent (the number of functional groups, the length between functional groups), the molecular weight of the polysuccinimide, and the intended use vary depending on the intended use. As a result, for example, the water-absorbing ability of a water-absorbent resin decreases. On the other hand, if the amount of the cross-linking agent is too small, the degree of cross-linking becomes low. Therefore, in the present invention, the amount of the cross-linking agent used substantially in the cross-linking reaction is usually adjusted to be about 0.1 to 30 mol% based on the monomer unit of the polysuccinimide main chain. You.

In the present invention, a solution in which a crosslinking agent is dissolved as it is or in a suitable organic solvent or water is added to a solution in which polysuccinimide is dissolved in a good solvent. Here, the suitable organic solvent is not particularly limited as long as it can substantially completely dissolve the crosslinking agent, but is preferably a good solvent of polysuccinimide. When water or a poor solvent of polysuccinimide is used, it is preferable to use a minimum amount such that the reaction system does not become dispersed when added. Usually, an amount of 1/30 to 1/5 of the good solvent used to dissolve the polysuccinimide is used.

In the present invention, the base used to activate the crosslinking agent introduced as a pendant group is not particularly limited as long as it can dissociate the hydrogen bond between the amino group and the carboxyl group. , Potassium hydroxide, alkali metal hydroxides such as lithium hydroxide, sodium acetate, alkali metal acetates such as potassium acetate, trimethylamine, triethylamine, tripropylamine, tributylamine, tripentylamine,
Examples include tertiary amines such as trihexylamine, triethanolamine, tripropanolamine, tributanolamine, tripentanolamine, trihexanolamine, N-methylmorpholine, pyridine, quinoline, and picoline.

In the present invention, the amount of the base used to activate the cross-linking agent introduced as a pendant group is substantially equivalent to the carboxyl group in the cross-linking agent introduced as a pendant group. However, it is possible to adjust the degree of crosslinking by adjusting the amount used. That is, when a base having a smaller amount than the carboxyl group of the cross-linking agent introduced as a pendant group is applied, the degree of cross-linking becomes lower than the degree of cross-linking calculated from the amount of the used cross-linking agent, and a part of the cross-linking agent remains unchanged It will act as a pendant group. That is, the above-mentioned preferable amount of the cross-linking agent used in a narrow sense means the amount of the base used for activating the cross-linking agent.

In the present invention, the reaction temperature of the reaction for introducing a crosslinking agent as a pendant group and the reaction temperature of the reaction for crosslinking by adding a base are not particularly limited. Although it depends on the reactivity of the crosslinking agent, the presence or absence of a catalyst, the molecular weight of polysuccinimide, etc., it is usually carried out at -10 ° C to 200 ° C,
C is preferred.

The cross-linked polysuccinimide obtained by the cross-linking reaction may be used as a resin as it is, or may be hydrolyzed on the remaining imide ring to obtain a “cross-linked polyaspartic resin”. Further, a “polysuccinimide derivative” may be introduced by introducing a pendant group.

The obtained crosslinked polysuccinimide may proceed to the pendant group introduction reaction and / or hydrolysis step of the next step as it is in the reaction solution, or the solvent may be separated by a solid-liquid separation operation to give the crosslinked polysuccinimide. Take out as
You may use it. As a solid-liquid separation operation of the crosslinked polysuccinimide and the solvent, a method generally used in chemistry can be used. For example, filtration, decantation, centrifugation and the like can be mentioned. The obtained crosslinked polysuccinimide may be used in the next step as it is as a wet cake to which the solvent has adhered, or may be used in the next step after drying to remove the solvent.

The method for drying the crosslinked polysuccinimide according to the present invention is not particularly limited. For example, hot air drying, drying with specific steam, microwave drying, reduced pressure drying, drum dryer drying, Nauter dryer drying, micron dryer drying And the like. Further, a drying temperature of generally 20 to 200 ° C. is adopted.

The crosslinked polysuccinimide after drying may be further subjected to purification treatment, pulverization treatment, granulation treatment, surface treatment and the like. The particle size of the crosslinked polysuccinimide is not particularly limited. However, if the particle size is too large, the reaction rate becomes slow when the next pendant group introduction reaction and / or hydrolysis reaction of the remaining imide ring is performed.
m is preferred.

When the crosslinked polysuccinimide itself is used, the form of use is not particularly limited, and it may be used alone or in combination with other materials as an additive such as a resin. For example, a method of kneading with a thermoplastic resin and molding by injection molding or the like, a method of mixing a monomer of a constituent resin with a crosslinked polysuccinimide and, if necessary, an initiator and then polymerizing the mixture with light or heat, and a method of mixing the resin with a crosslinked polysuccinic acid Examples thereof include a method of dispersing the imide in a solvent and casting to remove the solvent, a method of mixing and mixing the prepolymer and the crosslinked polysuccinimide, and a method of mixing and mixing the polymer and the crosslinked polysuccinimide. It is not particularly limited as a molded product, solids, sheets, films, fibers,
It can be used as non-woven fabric, foam, rubber and the like. Further, it may be used alone as a composite with another material. For example,
There are a method of forming a sandwich structure between pulp and nonwoven fabric, a method of forming a resin sheet or film into a multilayer structure as a poem itself, and a method of casting a resin sheet to form a two-layer structure.

[0031]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to the examples.
The crosslinked polysuccinimide according to the present invention hydrolyzes the remaining imide ring into a `` crosslinked polyaspartic resin '',
Alternatively, a pendant group was introduced to derive a “crosslinked polysuccinimide derivative”, and its water absorption performance was evaluated. In this example, the water absorption of the crosslinked polyaspartic acid-based resin and the crosslinked polymer was measured by the following tea bag method.

[Tea Bag Method] Preparation of Tea Bag A non-woven tea bag (80 mm × 50 mm) is filled with a dry water-absorbent resin whose dry weight (Wd) is weighed in advance. The sample prepared by immersion and the tea bag (blank) not filled with the water-absorbent resin were immersed in a large excess of distilled water or physiological saline maintained at 25 ° C. for 1 hour. In addition, the physiological saline (0.9 wt% sodium chloride aqueous solution) was prepared with distilled water and sodium chloride. Weighing After completion of the immersion, the sample swollen by the immersion and the blank were lifted and drained for 1 minute, and the sample weight after immersion (Ww) and the blank weight after immersion (Wb) were weighed, respectively. Evaluation of water absorption The water absorption (distilled water or physiological saline [g] / dry resin [1 g]) was evaluated by the following equation [Equation 1].

[0033]

[Equation 1] [Water absorption amount] = (Ww−Wd−Wb) / Wd

As an index for comparing the water absorption rate, the water absorption (W1
0) was measured, and the ratio to the water absorption (W60) one hour later was calculated. In addition, in consideration of the variation of the water absorption rate due to the particle size of the resin, 100 to 500 μm is sieved.
Only the resin with a particle size of m was used for the measurement.

Example 1 2.78 g (0.015 mol) of lysine monohydrochloride (hereinafter Lys.HCl) was dissolved in 1.5 g of distilled water.
2.44 g of 24.5 wt% NaOH aqueous solution (0.015
mol) was added for neutralization. The solution was treated with a polysuccinimide having a weight average molecular weight of 96,000 (hereinafter referred to as PSI) 9.71.
g (0.10 mol) in a solution of 38.8 g of N, N-dimethylformamide (DMF) for 0.5 h
The mixture was dropped and charged for 1 hr. Then 3
The reaction system was dispersed by charging 8.8 g of methanol, and aged at 25 ° C. for 3 hours. Then, 24.5wt%
1.63 g (0.01 mol) of an aqueous NaOH solution was added dropwise, and a crosslinking reaction was performed at 25 ° C. for 20 hours. The resulting reaction mass was filtered and washed to obtain a wet crosslinked polysuccinimide. The wet body was suspended in 83.1 g of water and 116.5 g of methanol, and a 24.5 wt% NaOH aqueous solution was added dropwise, and hydrolysis was performed at 25 to 35 ° C. and pH = 9 to 11.5. . The consumption of 24.5 wt% NaOH is 13.
8 g (0.085 mol), 3 hours until the reaction is completed
Cost. Hydrochloric acid is added to the hydrolyzed mass to obtain a pH of 7 to
It was adjusted to 7.5 and the resulting precipitate was removed by decantation. 20 g of water was added to the obtained precipitate to form a slurry, and the slurry was discharged into 200 g of methanol for reprecipitation. The resulting precipitate was filtered, washed and dried to obtain 10.5 g of a crosslinked polyaspartic resin. The water absorption of the obtained water-absorbent resin is 1090 times that of distilled water,
It was 96 times that of physiological saline. Also, W10 / W
60 × 100 = 60.2%.

Example 2 2.78 g (0.015 mol) of Lys.HCl was dissolved in 1.5 g of distilled water, and 2.44 g (0.015 mol) of a 24.5 wt% NaOH aqueous solution was added for neutralization. The solution was treated with PSI 9.7 having a weight average molecular weight of 96,000.
A solution prepared by dissolving 1 g (0.10 mol) in 38.8 g of DMF was charged dropwise over 0.5 hr, and reacted for 1 hr. Thereafter, 38.8 g of methanol was charged to bring the reaction system into a dispersed state, and the mixture was aged at 25 ° C. for 3 hours. Then 2
2.44 g of a 4.5 wt% NaOH aqueous solution (0.015 m
ol) was added dropwise, and a crosslinking reaction was carried out at 25 ° C. for 20 hours. The resulting reaction mass was filtered and washed to obtain a wet crosslinked polysuccinimide. The wet body was mixed with 83.1 g of water and 1
Suspended in 16.5 g of methanol, 13.5 g (0.
083 mol) of a 24.5 wt% NaOH aqueous solution for 3 hours.
r, and charged dropwise at 25 to 35 ° C., pH = 9 to 11.
The mixture was hydrolyzed at 5 and ripened for 1 hour. Hydrochloric acid was added to the hydrolyzed mass to adjust the pH to 7 to 7.5, and the resulting precipitate was taken out by decantation. 20 g of water was added to the obtained precipitate to form a slurry, and the slurry was discharged into 200 g of methanol for reprecipitation. The obtained precipitate was filtered, washed and dried to obtain 12.3 g of a crosslinked polyaspartic acid-based resin. The water absorption of the obtained water absorbent resin was 690 times that of distilled water and 75 times that of physiological saline.
It was twice. W10 / W60 × 100 = 75.9
%Met.

Example 3 3.70 g (0.020 mol) of Lys · HCl was dissolved in 1.5 g of distilled water, and 3.27 g (0.020 mol) of a 24.5 wt% NaOH aqueous solution was added for neutralization. The solution was treated with PSI 9.7 having a weight average molecular weight of 96,000.
A solution prepared by dissolving 1 g (0.10 mol) in 38.8 g of DMF was charged dropwise over 0.5 hr, and reacted for 1 hr. Thereafter, 38.8 g of methanol was charged to bring the reaction system into a dispersed state, and the mixture was aged at 25 ° C. for 3 hours. Then 2
1.63 g of a 4.5 wt% NaOH aqueous solution (0.010 m
ol) was added dropwise, and a crosslinking reaction was carried out at 25 ° C. for 20 hours. The resulting reaction mass was filtered and washed to obtain a wet crosslinked polysuccinimide. The wet body was mixed with 83.1 g of water and 1
Suspended in 16.5 g of methanol, 13.5 g (0.
083 mol) of a 24.5 wt% NaOH aqueous solution for 3 hours.
r, and charged dropwise at 25 to 35 ° C., pH = 9 to 11.
The mixture was hydrolyzed at 5 and ripened for 1 hour. Hydrochloric acid was added to the hydrolyzed mass to adjust the pH to 7 to 7.5, and the resulting precipitate was taken out by decantation. 20 g of water was added to the obtained precipitate to form a slurry, and the slurry was discharged into 200 g of methanol for reprecipitation. The obtained precipitate was filtered, washed and dried to obtain 12.3 g of a crosslinked polyaspartic acid-based resin. The water absorption of the obtained water-absorbent resin was 600 times that of distilled water and 83 times that of physiological saline.
It was twice. W10 / W60 × 100 = 61.9
%Met.

Example 4 4.63 g (0.025 mol) of Lys.HCl was dissolved in 1.5 g of distilled water, and 4.08 g (0.025 mol) of a 24.5 wt% NaOH aqueous solution was added for neutralization. The solution was treated with PSI 9.7 having a weight average molecular weight of 96,000.
A solution prepared by dissolving 1 g (0.10 mol) in 38.8 g of DMF was charged dropwise over 0.5 hr, and reacted for 1 hr. Thereafter, 38.8 g of methanol was charged to bring the reaction system into a dispersed state, and the mixture was aged at 25 ° C. for 3 hours. Then 2
1.63 g of a 4.5 wt% NaOH aqueous solution (0.010 m
ol) was added dropwise, and a crosslinking reaction was carried out at 25 ° C. for 20 hours. The resulting reaction mass was filtered and washed to obtain a wet crosslinked polysuccinimide. The wet body was mixed with 83.1 g of water and 1
Suspended in 16.5 g of methanol, 13.5 g (0.
083 mol) of a 24.5 wt% NaOH aqueous solution for 3 hours.
r, and charged dropwise at 25 to 35 ° C., pH = 9 to 11.
The mixture was hydrolyzed at 5 and ripened for 1 hour. Hydrochloric acid was added to the hydrolyzed mass to adjust the pH to 7 to 7.5, and the resulting precipitate was taken out by decantation. 20 g of water was added to the obtained precipitate to form a slurry, and the slurry was discharged into 200 g of methanol for reprecipitation. The obtained precipitate was filtered, washed and dried to obtain 14.8 g of a crosslinked polyaspartic acid-based resin. The water absorption of the obtained water-absorbent resin was 450 times that of distilled water and 48 times that of physiological saline.
It was twice. W10 / W60 × 100 = 62.7
%Met.

Example 5 The same operation as in Example 1 was performed to obtain a wet product of crosslinked polysuccinimide. The obtained wet body was suspended in 120 g of methanol, and 7.73 g (0.1 mol) of glycine and 4.
A glycine aqueous solution in which 2 g of NaOH was dissolved in 30 g of water was dropped and reacted at 25 ° C. for 24 hours. Then 9
The precipitate was filtered, washed and dried to obtain 18.1 g of a crosslinked polysuccinimide derivative having glycine introduced as a pendant group. The water absorption of the obtained water-absorbent resin is 7 with respect to distilled water.
It was 20 times, and 79 times that of physiological saline. Also, W
10 / W60 × 100 = 75.5%.

Comparative Example 1 2.78 g (0.015 mol) of Lys.HCl was dissolved in 1.5 g of distilled water, and 4.08 g (0.025 mol) of a 24.5 wt% NaOH aqueous solution was added for neutralization. The solution was added for 0.5 hr to a solution of 9.71 g (0.1 mol) of PSI dissolved in 38.8 g of DMF.
The mixture was dropped and charged. During the charging, the viscosity significantly increased, and after the charging, the whole reaction solution gelled and became unable to stir. Thereafter, the mixture was aged at 25 ° C./30 hr without stirring. An attempt was made to loosen the gel by adding 100 g of methanol to the obtained gel, but it was difficult to stir, so it took about 20 hours to loosen the entire gel. The resulting precipitate was filtered and washed to obtain a wet crosslinked polysuccinimide. The obtained wet body was suspended in 90 g of water and 120 g of methanol, and a 24.5 wt% NaOH aqueous solution 13.1 was used.
g was added dropwise at 25 to 35 ° C and pH = 9 to 11 to perform hydrolysis. The reaction was slow due to the large particle size of the precipitate, and the hydrolysis required about 6 hours. Thereafter, 9% hydrochloric acid was added to adjust the pH to 7.5, and the resulting precipitate was taken out by decantation, and 20 g of water was added to form a slurry. The obtained slurry was discharged into 200 g of methanol and reprecipitated, filtered, washed and dried to obtain 8.8 g of a crosslinked polyaspartic resin. The water absorption of the obtained water-absorbent resin was 400 times that of distilled water and 53 times that of physiological saline. Also, W10 / W60 × 100
= 60.7%.

Comparative Example 2 3.50 g (0.015 mol) of lysine methyl ester dihydrochloride was suspended in 100 g of DMF and neutralized with an equal amount of triethylamine. The solution was mixed with 9.71 g (0.10 mol) of PSI having a weight average molecular weight of 96,000
The solution dissolved in 8.8 g of DMF is charged dropwise,
Stirred for 1 hr. Then, 3.03g (0.030mo
l) Triethylamine was added to carry out a crosslinking reaction at 25 ° C. for 40 hours. The reaction solution was discharged into 300 g of ethanol, reprecipitated, filtered and washed to obtain a wet crosslinked polysuccinimide. The obtained wet body was suspended in 2000 g of water, and 2
A 4.5 wt% NaOH aqueous solution is added dropwise, and pH = 9 to
The hydrolysis was performed while adjusting to 11. The obtained reaction liquid (fluid gel) was discharged into 5000 ml of ethanol, reprecipitated, filtered, washed and dried to obtain 12.8 g of a crosslinked polyaspartic resin. The water absorption of the obtained water-absorbent resin is 110 times that of distilled water and 30 times that of physiological saline.
It was twice. W10 / W60 × 100 = 61.2
%Met.

[Comparison / Consideration of Example and Comparative Example] Comparative Example 1
In the crosslinked polyaspartic acid-based resin derived by hydrolysis, a sufficiently high water absorption was obtained,
The operability at the time of producing a crosslinked polysuccinimide was poor, for example, the entire crosslinking reaction solution was gelled, and the productivity was reduced. In Comparative Example 2, an attempt was made to produce a crosslinked polysuccinimide with high productivity, and as a result, the water absorption of the crosslinked polyaspartic acid-based resin induced by hydrolysis was reduced. In contrast, in Examples 1-5, in each case,
Cross-linked polyaspartic acid resin with high water absorption,
It could be manufactured with high productivity.

[0043]

According to the production method of the present invention, a crosslinked polysuccinimide useful as a precursor of a crosslinked polyaspartic acid-based resin having both high water absorption capacity and (bio) degradability can be obtained with high productivity and excellent operation. It can be manufactured by the nature.

Claims (6)

[Claims] 1. A method in which a crosslinking agent is added to a solution in which polysuccinimide is dissolved in a good solvent and introduced as a pendant group, a dispersant is charged to bring the reaction system into a dispersed state, and then a base is added. A method for producing a crosslinked polysuccinimide, which comprises advancing a crosslinking reaction. 2. The cross-linking agent is a polyamine having at least one carboxyl group in its molecule.
A method for producing the crosslinked polysuccinimide according to the above. 3. The method for producing a crosslinked polysuccinimide according to claim 1, wherein the dispersant is a poor solvent for the polysuccinimide. 4. The method according to claim 1, wherein the good solvent is N, N-dimethylformamide,
The at least one selected from the group consisting of N, N-dimethylacetamide, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, dimethylsulfoxide, and sulfolane. A method for producing a crosslinked polysuccinimide. 5. The method according to claim 1, wherein the crosslinking agent is at least one selected from the group consisting of lysine, ornithine and cystine.
5. The method for producing a crosslinked polysuccinimide according to any one of items 1 to 4. 6. A crosslinked polysuccinimide produced by the production method according to claim 1.