JP2000290371A - Production of water-absorbent resin - Google Patents

Abstract

(57) [Abstract] [Problem] It has water absorption properties that can be used as a water absorbent resin such as disposable sanitary ware products and household goods, water stoppage agents, soil improvement materials, dew condensation preventive agents, agricultural and horticultural water retention agents, In addition, a biodegradable resin is provided at low cost without going through complicated steps. SOLUTION: A resin having two or more functional groups obtained by hydrolyzing a reaction product of a polysuccinimide and a polysaccharide is converted into a crosslinking agent having a functional group capable of reacting with a functional group of the resin. And producing a water-absorbent resin by crosslinking the vicinity of the surface of the resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a water-absorbing resin in which the vicinity of the surface of a resin is crosslinked.

More specifically, the present invention relates to a method for producing a water-absorbent resin having a water-absorbing function and biodegradability and usable as a molded article having water-absorbing and water-retaining properties. It can be used as a water stopping agent, a soil conditioner, a condensation inhibitor, a water retention agent for agricultural and horticultural use, a sludge solidifying agent, and the like.

[0003]

2. Description of the Related Art As a resin having water absorption performance,
Polyacrylate partially crosslinked product, starch acrylic acid copolymer hydrolyzate, polyethylene oxide partially crosslinked product,
Vinyl alcohol-acrylic acid copolymers and the like are known. However, although the material has excellent water absorbing ability, the material cannot be easily decomposed into low molecules, which is a problem when considering environmental conservation after disposal. Further, the partially crosslinked product of polyethylene oxide has a small water absorbing ability itself.

As resin compositions having both water absorption and biodegradability, natural resins such as polysaccharides and polyamino acid resins are known.

As natural resins such as polysaccharides, it is known that hyaluronic acid and polysaccharides produced by microorganisms belonging to the family Alcaligenes have high water absorption (Japanese Patent Application Laid-Open No. 4-200389).

[0006] As an inexpensive polysaccharide-based water-absorbing resin using cellulose or starch as a raw material, a water-absorbing resin obtained by crosslinking a polysaccharide with an amino acid is known (JP-A-8-89796). Gazette). As the polyamino acid-based resin, a water-absorbing resin obtained by hydrolyzing a partially crosslinked product of polyaspartic acid with a polyamine (Japanese Patent Application Laid-Open No.
309943, JP-A-9-169840), a water-absorbing resin in which the polyamine compound is an amino acid such as lysine, ornithine, cystine, and cystamine (JP-A-7-224163), and a crosslinking agent such as ethylene glycol glycidyl ether. A water-absorbing resin which is a diepoxy compound (Polym. Mater. Sci. Eng., 79, 232, 1998) is known. Further, polyaspartic acid (Japanese Unexamined Patent Publication No. 9-2
02825), polyglutamic acid (JP-A-6-3)
No. 22358), polylysine (JP-A-8-1759)
No. 01) and a method of irradiating a mixed solution of polyglutamic acid and polylysine (J. Appl. Polym. Sci., 58, 807, 1995) with γ-radiation to obtain a crosslinked polyamino acid.

The water-absorbing resin is used for sanitary articles such as diapers and sanitary articles, medical fields, civil engineering and construction fields, food fields, industrial fields, soil modifying agents,
It is required to be used in various fields such as horticulture. The properties desired of the water-absorbent resin for such use include high water absorption ratio, salt resistance, low water-soluble content, high water absorption rate, high gel strength, and the like, in order to improve these properties. In addition, there is known a method of further cross-linking the vicinity of the surface of a water-absorbent resin in a partially crosslinked polyacrylate or a hydrolyzate of a starch acrylic acid copolymer. As a method for improving the water absorbing property by surface-crosslinking a water-absorbent resin having biodegradability, a method of slightly crosslinking the surface of a water-absorbent resin obtained by crosslinking a polysaccharide with amino acids is known. (JP-A-8-196901).

However, natural resins such as polysaccharides and water-absorbing resins such as polyamino acid-based resins are required to have properties such as water absorption capacity, salt resistance, and the like.
At present, cross-linking near the surface has hardly been improved in order to improve the water absorption rate, and even those whose surface cross-linking has been studied cannot provide sufficient water absorption properties.

[0009]

SUMMARY OF THE INVENTION The present invention provides a method for producing a resin having water absorption and water retention properties such as high water absorption capacity, salt resistance, low water soluble content, high water absorption rate, and high gel strength. The purpose is to provide.

[0010]

Means for Solving the Problems Accordingly, the present inventors have:
In view of the above-described various disadvantages in the prior art, as a result of intensive studies, by cross-linking the vicinity of the surface of the water-absorbent resin, among various water-absorbing properties, among others, the water-absorbing rate is excellent, and high The present invention has been completed by finding a production method capable of obtaining a resin composition having excellent biodegradability at low cost without going through complicated steps. That is, [I] the present invention provides a resin having two or more functional groups obtained by hydrolyzing a reaction product of a polysuccinimide and a polysaccharide with a functional group capable of reacting with a functional group of the resin. The present invention provides a method for producing a water-absorbent resin, which comprises contacting and reacting with a crosslinking agent having a group to crosslink the vicinity of the surface of the resin. The present invention provides a method for producing a water-absorbent resin, which comprises irradiating a resin obtained by hydrolyzing a reaction product with a saccharide with radiation to crosslink the vicinity of the surface of the resin. The invention [II] above wherein the crosslinking agent is 0.005 to 20 parts by weight with respect to 100 parts by weight of the resin.
[IV] The present invention provides a method for preparing a water-absorbent resin according to the present invention, wherein the water-absorbent resin has a physiological saline absorption capacity of 10 g / g.
An object of the present invention is to provide the production method according to any one of the above [I] to [III].

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The polysuccinimides used in the present invention include polyaspartic acid and anhydrides of copolymers and derivatives thereof. Of these, polysuccinimide is particularly desirable in terms of simplicity of the production method, water absorption performance, and price. The weight average molecular weight of the polysuccinimides is preferably 3000 or more,
More preferably, it is 5000 or more. As polysuccinimides in the present invention, polyaspartic acid,
In addition, those obtained by partially cross-linking anhydrides of copolymers and derivatives thereof in advance can also be used. In this case, a partially crosslinked product of polysuccinimide is particularly preferred in terms of reactivity.

The method for producing the above-mentioned polysuccinimides is not particularly limited.

Taking polysuccinimide as an example, (a)
A method for producing D / L-aspartic acid by heat dehydration-condensation, (b) a method for producing D / L-aspartic acid by heat dehydration-condensation in the presence of a catalyst such as phosphoric acid, and (c) a suitable solvent. In which D / L-aspartic acid is heated and dehydrated and condensed in the presence of a catalyst such as phosphoric acid, (d) maleimide, fumaric acid, malic acid and the like are reacted with ammonia to produce maleimide, maleamide, (E) Maleimide anhydride, fumaric acid, malic acid, etc. are reacted with ammonia by heating to produce maleimide, maleamide, or ammonium maleate, and a catalyst such as phosphoric acid is present. Below, it can be obtained by a manufacturing method or the like. The following formula is shown in the case where aspartic acid is used as a raw material for these reactions.

[0014]

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In the present invention, the method for producing the partially crosslinked polysuccinimide is not particularly limited. Taking a partially crosslinked product of polysuccinimide as an example, it can be obtained by partially crosslinking polysuccinimide with a polyamine. In this case, specific examples of the polyamine include, for example, hydrazine, ethylenediamine, hexamethylenediamine, diethylenetriamine, aliphatic polyamines such as triethylenetetramine, norbornenediamine, alicyclic polyamines such as isophoronediamine,
Phenylenediamine, tolylenediamine, aromatic polyamines such as xylylenediamine, lysine, amino acids having an amino group in the side chain represented by ornithine and derivatives thereof, cystine, cystamine and the like, monoamino Compounds bonded by disulfide bonds, derivatives thereof, and amino groups having a side chain of 2
And peptides having a molecular weight of 100 or more. Examples of the polysaccharide used in the present invention include, but are not particularly limited to, polysaccharides, polysaccharide derivatives, salts thereof, and partially cross-linked polysaccharides. As the polysaccharide, specifically, for example, starch, methyl starch, ethyl starch, methyl ethyl starch, cellulose, methyl cellulose, ethyl cellulose, methyl ethyl cellulose, hemicellulose,
Agar, carrageenan, alginic acid, pectic acid, guar gum, tamarind gum, locust bean gum, xanthan gum, konjac mannan, dextran, xanthan gum, pullulan, gellan gum, chitin, chitosan, water-soluble chitin, chitooligosaccharide, chondroitin sulfate, heparin, gelled starch , Amylose, gum arabic, sodium alginate, curdlan, hyaluronic acid, glycogen, peptidoglycan, mulein, and the like. Examples of the polysaccharide derivatives include carboxyalkylated or hydroxyalkylated compounds of the above polysaccharides. Specific examples of the polysaccharide derivatives include carboxyalkyl starch, carboxyalkyl cellulose, hydroxyalkyl starch, hydroxyalkyl cellulose, starch glycolic acid, agar derivatives, carrageenan derivatives and the like. Among these polysaccharides, carboxyalkyl starch, carboxyalkyl cellulose, and salts thereof are preferable in that they have highly reactive functional groups. In addition, as said salts,
Alkali metal salts such as sodium and potassium salts are preferred. The method for crosslinking the partially crosslinked polysaccharide is not particularly limited, and examples thereof include self-crosslinking by heat and a method using a crosslinking agent. In the method of crosslinking a carboxylated product, an epoxy crosslinking agent, a polyamine crosslinking agent, an oxazoline crosslinking agent, an aziridine crosslinking agent, and a carbodiimide crosslinking agent are exemplified, but those using an amino acid or a salt thereof as a crosslinking agent are obtained. However, it is preferable because of high biodegradability. As amino acids, specifically, for example, lysine, glycine, alanine, valine,
Leucine, isoleucine, phenylalanine, proline, serine, threonine, tyrosine, cystine, methionine, tryptophan, arginine, histidine, aspartic acid, glutamic acid and the like. These polysaccharides may be used alone or as a mixture of two or more. In the present invention, a step of reacting the polysuccinimides and the polysaccharide is required. At this time, the method of mixing the two is not particularly limited, and for example, 1) a method of mixing both with a solid 2)
A method of mixing both in a solution state or a suspension state, 3)
Various methods can be adopted, such as a method in which one of them is in a solution state or a suspension state, and the other is added and mixed. Among these mixing methods, a method 2) of mixing both in a solution state or a suspension state is preferable because a uniform mixture is easily obtained.

In the above mixing method, a solvent is used if necessary. As a solvent to be used, it is necessary to easily dissolve or suspend polysuccinimides and polysaccharides, and it is most preferable to use water. The concentration of the aqueous suspension or aqueous solution of the polysuccinimides and the polysaccharide is preferably in the range of 0.1% by weight to 50% by weight. If the liquid concentration is less than 0.1% by weight, heating must be carried out for a long time to remove water, so that the production efficiency decreases. On the other hand, when the liquid concentration exceeds 50% by weight, the viscosity of the liquid concentration increases, and it becomes difficult to uniformly mix the polysuccinimides and the polysaccharide.
Not preferred. Examples of the method of reacting polysuccinimides and polysaccharides include a method of reacting functional groups in a mixture with each other by heat, a method of using a compound capable of reacting with each functional group in the mixture, and an electron beam such as γ-ray. And the like.

Taking the case where an imide ring group is present in a polysuccinimide and a carboxyl group is present in a polysaccharide as an example, a heating temperature of 70.degree. C. to 200.degree. C is preferably within the range,
More preferably, it is in the range of 110 ° C to 180 ° C. If the heating temperature during the reaction does not reach 70 ° C., the above reaction hardly proceeds, which is not preferable. On the other hand, when the heating temperature exceeds 200 ° C., it is not preferable because coloring occurs. The heating time is not particularly limited, and may be appropriately set according to the types and combinations of the polysuccinimides, the polysaccharides, and the solvent, the heating temperature, the desired properties of the resin composition, and the like. Specifically, for example, when the heating temperature is 120 ° C., the heating time may be 1 minute to 5 hours. When there is no specific functional group having reactivity between the two, the bonding between the two can be achieved by using a compound capable of reacting with each functional group. At this time, as the compound that can be used, any compound having a reactive group capable of reacting with a polysuccinimide and a functional group in the polysaccharide in one molecule can be used without any particular limitation. Examples of such a crosslinking agent include an epoxy compound, a polyamine compound, an oxazoline compound, an aziridine compound, and a carbodiimide compound. Furthermore, a silane coupling agent having an epoxy group, an amino group, a carboxyl group, a hydroxyl group, or the like, or a titanium coupling agent thereof can also be used. These may be used alone or in combination of two or more. The amount of the crosslinking agent used can be arbitrarily determined based on the amount of each functional group. The ratio of the polysaccharide to the polysuccinimide is 0.1 to 1000 parts by weight, preferably 1.0 to 300% by weight, based on 100 parts by weight of the polysuccinimide. When the amount is less than 0.1% by weight, the water-absorbing effect of the water-absorbent resin of the present invention does not appear. Even when the amount exceeds 1000% by weight, the water-absorbing effect corresponding to the amount of the polysaccharide used is not obtained. The water absorption capacity may be significantly reduced.

Reaction products between polysuccinimides and polysaccharides
The hydrolysis reaction of the product is carried out by dropping an aqueous alkali solution,
The reaction product was added to an aqueous alkali solution,
The reaction is preferably carried out at 20 to 50 ° C for 0.5 to 24 hours.
It is done by doing. Alkaline aqueous solution is alkali gold
Uses genus compounds and / or alkaline earth metal compounds
Is done. Alkali metal compounds, alkaline earth metal compounds
Hydroxide or carbonate is preferred in terms of reactivity
For example, LiOH, NaOH, KOH, Mg
(OH)_{Two ,}Ca (OH)_{Two ,}Li_TwoCO_Three, Na_TwoCO_Three, K
_TwoCO_Three, MgCO _{Three ,}CaCO_ThreeIs mentioned. alkali
The aqueous solution is sodium hydroxide or potassium hydroxide
Generally, a 0.1 to 40% by weight aqueous solution is used.
The amount of alkali compound to be added is much higher than that of polysuccinimides.
When hydrolyzing saccharide reactants,
0.2 to 2.0 mol per imide ring group 1
Is preferred.

After the completion of the hydrolysis reaction, the reaction product is poured into a large amount of methanol, ethanol, acetone, or the like, and isolated by precipitation of the resin, or ion-exchanged water is evaporated to dryness to obtain the desired product. Get things.

When polysuccinimides or polysaccharides have an acid group such as a carboxyl group, the amount of alkali added may be increased to adjust the pH of the hydrolysis product.

The crosslinking agent used in the present invention has a plurality of reactive groups capable of reacting with a functional group in a product obtained by hydrolyzing a reaction product of a polysuccinimide and a polysaccharide. Any crosslinking agent can be used without particular limitation. Such crosslinking agents include, for example, epoxy crosslinking agents, polyamine crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, carbodiimide crosslinking agents, polyhydric alcohols,
And isocyanate crosslinking agents.

Of these, epoxy crosslinking agents include:
Examples thereof include ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, glycerin-1,3 diglycidyl ether, polyethylene glycol diglycidyl ether, and bisphenol A-epichlorohydrin type epoxy resin.

Examples of the polyamine crosslinking agent include chain aliphatic polyamines such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, hexamethylenediamine, polyetherpolyamine, mensendiamine, isophoronediamine, (4-aminocyclohexyl) methane 3,9-bis (3-aminopropyl)-
Cycloaliphatic polyamines such as 2,4,8,10-tetraoxane pyro [5,5] undecane, aromatic polyamines such as m-xylenediamine and p-xylenediamine, and dimer acids and aliphatic polyamines Examples include polyamides and basic amino acids such as lysine.

Examples of the oxazoline crosslinking agent include 2,2′-bis (2-oxazoline), 2,2′-bis (3-methyl-2-oxazoline), and 1,4-bis (2
-(4-methyl-5-phenyloxazoline)) benzene, 2,2 ′-(1,4-phenylene) -bis (2-oxazoline), 2,2 ′-(1,3-phenylene) -bis (2 -Oxazoline).

As the aziridine crosslinking agent, for example,
2-bishydroxymethylbutanol-tris [3- (1
-Aziridinyl) propionate], diphenylmethane-
Bis-4,4-N, N′-ethyleneurea, hexamethylene-bis-ω, ω-N, N′-ethyleneurea, tetramethylene-bis-N, N′-ethyleneurea, triphenylmethane-4, 4 ′, 4 ″ -tetramethylene-bis-N, N′-ethyleneurea, p-phenylenebisethyleneurea, m-toluylene-bis-N, N′-ethyleneurea, carbonylbisaziridine and methyl derivatives thereof, -(1-aziridinyl) ethyl-methacrylate and copolymers thereof.

Examples of the carbodiimide compound include dicyclohexylcarbodiimide, diphenylcarbodiimide, di- (diisopropyl) phenylcarbodiimide and the like, and a so-called isocyanate group-containing carbodiimide compound (A) represented by the following general formula:

[0027]

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(Wherein, R ₅ in the formula represents an aromatic or aliphatic divalent linking group) or a compound derived from the compound (A) and containing no isocyanate group. General formula

[0029]

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(However, R ₅ in the formula represents an aromatic or aliphatic divalent linking group, and R ₆ represents an alkyl group, an aralkyl group or an oxyalkylene group.)
And a carbodiimide compound such as a carbodiimide compound containing no hydrophilic group or containing a hydrophilic group (B).

Examples of polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, glycerin, polyglycerin, propylene glycol, diethanolamine, triethanolamine, polyoxypropylene and oxyethyleneoxypropylene block. Copolymers, pentaerythrol and sorbitol.

Examples of the isocyanate crosslinking agent include tolylene diisocyanate (TDI), phenylene diisocyanate (PPDI), diphenylmethane diisocyanate (MDI), hydrogenated MDI, polymeric MDI, tolidine diisocyanate (TODI), hexamethylene diisocyanate (HDI), Isophorone diisocyanate (IPDI), xylylene diisocyanate (XDI), lysine diisocyanate (LD
I), tetramethylene xylene diisocyanate (TM
XDI), triphenylmethane triisocyanate, tris (isocyanatophenyl) thiophosphate,
Undecane triisocyanate, lysine ester triisocyanate, 1,8-diisocyanate-4-isocyanatomethyloctane, bicycloheptane triisocyanate, and urethane-modified, allophanate-modified, buret-modified, isocyanurate-modified, carbodiimide-modified products thereof , Blocked isocyanates, mixtures thereof, and the like.

Also, polyvalent metal salts such as aluminum chloride, magnesium chloride, calcium chloride, aluminum sulfate and magnesium sulfate can be used as a crosslinking agent.

Further, a silane coupling agent having an epoxy group, an amino group, a carboxyl group, a hydroxyl group or the like, or a titanium coupling agent thereof can also be used as a crosslinking agent. These may be used alone or in combination of two or more.

The amount of the crosslinking agent used is from 0.005 to 20% by weight, preferably from 0.005 to 20% by weight, based on the resin obtained by hydrolyzing the reaction product of the polysuccinimides and the polysaccharide. 10% by weight, more preferably 0.01 to 5
% By weight. If the amount is less than 0.005% by weight, no surface treatment effect is exhibited, and even if the amount exceeds 20% by weight, the effect corresponding to the amount of the cross-linking agent cannot be obtained, and the water absorption capacity may be significantly reduced. is there. When the crosslinking agent is mixed with the hydrolysis product, it is more preferable to use a treatment liquid containing water and a hydrophilic organic solvent in order to enhance the treatment effect. The amount of water that constitutes the processing liquid is 0.1 to the hydrolysis product.
1 to 10% by weight. When this amount is less than 0.1% by weight, it is difficult to appropriately penetrate the cross-linking agent into the vicinity of the surface of the hydrolysis product, and the surface cross-linked layer is not formed appropriately. On the other hand, if it exceeds 10% by weight, it may permeate excessively and the water absorption capacity may be significantly reduced. The hydrophilic organic solvent constituting the treatment liquid is not particularly limited as long as it dissolves the crosslinking agent and does not affect the performance of the water absorbent resin. Such organic solvents include, for example, methyl alcohol, ethyl alcohol, n-propyl alcohol,
iso-propyl alcohol, n-butyl alcohol,
lower alcohols such as iso-butyl alcohol and t-butyl alcohol; ketones such as acetone and methyl ethyl ketone; ethers such as dioxane and tetrahydrofuran; amides such as N, N-dimethylformamide;
Sulfoxides such as dimethyl sulfoxide and the like can be mentioned. The amount of the hydrophilic organic solvent used is preferably 0 to 10% by weight based on the hydrolysis product. 1
Even if the amount exceeds 0% by weight, an effect commensurate with the amount used is not obtained, and only the cost is increased, which is not industrially preferable. As a method of mixing the hydrolysis product and the crosslinking agent, it is common to spray or drop the treatment solution on the hydrolysis product. The reaction is achieved by heating these mixtures. The heating temperature ranges from 80C to 200C.

In the present invention, a resin obtained by hydrolyzing a reaction product of a polysuccinimide and a polysaccharide may be dissolved or suspended in water and then irradiated with radiation for crosslinking. As radiation, α rays, β rays, γ
Examples include a beam, an electron beam, a neutron beam, an X-ray, and a valence electron beam, and preferably a γ-ray is used. The γ-ray absorption amount is preferably from 1 to 500 KGy, and crosslinking proceeds usually at room temperature under normal pressure. It is more preferable to use an inert gas such as nitrogen or argon.

The resin according to the present invention is excellent in both water absorption and biodegradability. The water absorption performance is determined by the water absorption test method (JIS K) of the highly water-absorbent resin specified in Japanese Industrial Standards.
-7223) can be measured by a test of the amount of water absorption by the tea bag method. When evaluated by the teabag method,
The resin according to the present invention is at least 50 times the amount of ion exchange water,
It has a water absorption capacity 10 times or more that of physiological saline (0.9% by weight physiological saline). Further, the resin according to the present invention has biodegradability that can be decomposed by bacteria and microorganisms in the soil, and is decomposed only by burying in the soil. For this reason, disposal is simple and excellent in safety, and does not cause environmental health problems such as environmental pollution. Therefore, the resin can be applied to all uses of conventionally known water-absorbing resins. For example, hygiene fields such as sanitary articles such as diapers and sanitary products, medical fields for use in buffering agents, civil engineering and construction fields such as waste mud gelling agents, food fields, industrial fields, soil modifying agents, and water retention It can be used in various fields such as agriculture and horticulture as an agent.

[0038]

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

[0039]

(Equation 1)

(B) Water absorption rate: artificial urine (1.9% by weight of urea, 0.8% by weight of sodium chloride, 0.1% by weight of calcium chloride)
1% by weight, containing 0.1% by weight of magnesium sulfate) 20m
1.0 g of the resin was added to 1 l, and the time until the resin absorbed all the artificial urine and the fluidity of the swollen gel was lost was defined as the water absorption rate. (C) Biodegradation rate: The biodegradability test was performed according to a modified MITI test. That is, a resin as a test substance was added to 200 ml of the basic culture solution so as to be 100 ppm, and activated sludge was added to be 30 ppm. Thereafter, the basal culture was maintained at 25 ° C. in a dark place and cultured with shaking for 28 days. During the above period, the amount of oxygen consumed by the activated sludge was measured periodically to obtain a biochemical oxygen demand (BOD) curve. The biodegradation rate (%) can be calculated from the biochemical oxygen demand A (mg) of the test substance (resin) obtained from the BOD curve and the blank obtained from the BOD curve, that is, the oxygen demand B (basic culture solution) ( mg)
And the total oxygen demand (TOD) C (mg) required for complete oxidation of the test substance,

[0041]

(Equation 2)

Calculated according to the following:

Reference Example 1 A 1 L metal separable flask was charged with 100 g of L-aspartic acid and 50 g of phosphoric acid, and reacted at a bath temperature of 180 ° C. and a reduced pressure of 600 Pa for 3.5 hours with stirring. After the reaction is completed, D
400 ml of MF was added to uniformly dissolve the reaction product. The resulting solution was dropped into 1.5 L of ion-exchanged water to reprecipitate the formed resin, and then the slurry was pulverized by a mixer and filtered under reduced pressure. After filtration, washing was performed until the pH of the ion-exchanged water became neutral, and the obtained cake was dried with hot air at 150 ° C. for 24 hours to obtain a white powdered polysuccinimide 7
2.5 g were obtained. As a result of measuring the obtained resin by GPC, the weight average molecular weight was 125,000.

Reference Example 2 In the same manner as in Reference Example 1, 100 g of L-aspartic acid was reacted at a bath temperature of 260 ° C. under a nitrogen atmosphere with stirring for 6 hours. After the completion of the reaction, 68.3 g of a white powdery polysuccinimide was obtained by the same operation as in Reference Example 1. As a result of measuring the obtained resin by GPC, the weight average molecular weight was 9,000.

Reference Example 3 98 g of granular maleic anhydride,
70 g of a 25% aqueous ammonia solution was placed in a 1 L metal separable flask, and the reaction temperature was 85 ° C. and the degree of vacuum was 600 Pa.
And reacted for 3 hours with stirring. Next, 65 g of 85% phosphoric acid was added, the reaction temperature was 180 ° C., and the degree of pressure reduction was 600 Pa.
And reacted for 5 hours while stirring. By the same operation as in Reference Example 1, 88.7 g of white powdery polysuccinimide was obtained.
I got As a result of measuring the obtained resin by GPC, the weight average molecular weight was 6,000.

Example 1 10 g of the polysuccinimide obtained in Reference Example 1 was dissolved in 50 g of ion-exchanged water, and a solution prepared by dissolving 4 g of carboxymethylcellulose in 96 g of ion-exchanged water was added. The mixture obtained after the addition was heated at 120 ° C. for 70 minutes using a dryer to obtain 12.9 g of a dried product. This dried product was added to a solution prepared by dissolving 4.2 g of sodium hydroxide in 100 g of ion-exchanged water, and stirred at room temperature for 3 hours to hydrolyze to obtain a viscous liquid. This viscous liquid was dried with hot air to obtain 12.2 g of a white powdery resin having a water content of 2.2%. Next, 0.1 g of ethylene glycol diglycidyl ether was dissolved in a mixed solution of 1 g of water and 0.5 g of methanol to prepare a crosslinking agent solution. A white powdery resin was thinly spread on the vat, and the crosslinking agent solution was sprayed by spraying. This mixture was placed in a hot-air dryer adjusted to 180 ° C. for 60 minutes to obtain 12.8 g of the resin of the present invention. Water absorption ratio, water absorption speed,
Table 1 shows the biodegradation rates.

Example 2 10 g of the polysuccinimide obtained in Reference Example 1 was suspended in 50 g of ion-exchanged water, and a suspension of 4 g of carboxymethyl cellulose in 96 g of ion-exchanged water was added. A cross-linking agent solution obtained by dissolving 0.5 g of ethylene glycol diglycidyl ether in a mixed solution of 2 g of water and 1 g of methanol is added to the mixture obtained after the addition, and heated at 120 ° C. for 70 minutes using a drier to obtain a dried product. 13.2 g were obtained. 100 g of this dried product
Was added to a solution prepared by dissolving 4.2 g of sodium hydroxide in ion-exchanged water, and the mixture was stirred at room temperature for 3 hours and hydrolyzed to obtain a viscous liquid. 600 ml of methanol is added to this liquid,
The resulting precipitate was filtered under reduced pressure, washed with methanol, and washed with methanol.
Dry under reduced pressure at 0 ° C. for 12 hours to obtain a resin 11.4 as a white powder.
g was obtained. Next, 0.1 g of ethylene glycol diglycidyl ether was dissolved in a mixed solution of 1 g of water and 0.5 g of methanol to prepare a crosslinking agent solution. The resin in the form of a white powder was thinly spread on the vat, and the above-mentioned crosslinking agent solution was sprayed by spraying. This mixture was placed in a hot-air dryer adjusted to 180 ° C. for 60 minutes to obtain 12.8 g of the resin of the present invention. Table 1 shows the water absorption capacity, water absorption rate, and biodegradation rate of the resin.

Example 3 10 g of the polysuccinimide obtained in Reference Example 1 was dissolved in 50 g of ion-exchanged water, and a solution prepared by dissolving 4 g of carboxymethyl cellulose in 96 g of ion-exchanged water was added. A cross-linking agent solution obtained by dissolving 0.5 g of ethylene glycol diglycidyl ether in a mixed solution of 2 g of water and 1 g of methanol is added to the mixture obtained after the addition, and heated at 120 ° C. for 70 minutes using a drier to obtain a dried product. 13.2 g were obtained. 100 g of this dried product
Was added to a solution prepared by dissolving 4.2 g of sodium hydroxide in ion-exchanged water, and the mixture was stirred at room temperature for 3 hours and hydrolyzed to obtain a viscous liquid. This viscous liquid is dried with hot air to obtain a water content of 2.
12.2 g of a 2% white powdery resin was obtained. Next, 0.1 g of dicyclohexylcarbodiimide was dissolved in a mixed solution of 1 g of water and 0.5 g of methanol to prepare a crosslinking agent solution. A white powdery resin was thinly spread on the vat, and the crosslinking agent solution was sprayed by spraying. This mixture was placed in a hot-air dryer adjusted to 180 ° C. for 60 minutes to obtain 12.8 g of the resin of the present invention. Water absorption ratio, water absorption speed,
Table 1 shows the biodegradation rates.

Example 4 12.8 g of a resin was obtained in the same manner as in Example 1 except that lysine was used in place of ethylene glycol diglycidyl ether used in Example 1. Table 1 shows the water absorption capacity, water absorption rate, and biodegradation rate of the obtained resin.

Example 5 12.6 g of a resin in the form of a white powder was obtained in the same manner as in Example 1, except that the polysuccinimide obtained in Reference Example 2 was used. Table 1 shows the water absorption capacity and biodegradability of the obtained resin.

Example 6 In the same manner as in Example 1, except that the polysuccinimide obtained in Reference Example 3 was used, 12.2 g of a white powdery resin was obtained. Table 1 shows the water absorption capacity and biodegradability of the obtained resin.

Comparative Example 1 10 g of the polysuccinimide obtained in Reference Example 1 was dissolved in 50 g of ion-exchanged water, and a solution prepared by dissolving 4 g of carboxymethyl cellulose in 96 g of ion-exchanged water was added. The mixture obtained after the addition was heated at 120 ° C. for 70 minutes using a dryer to obtain 12.9 g of a dried product. This dried product was added to a solution in which 1.6 g of sodium hydroxide was dissolved in 100 g of ion-exchanged water, and stirred at room temperature for 3 hours to hydrolyze to obtain a viscous liquid. This viscous liquid was put into a hot-air drier adjusted to 180 ° C. for 60 minutes to obtain 13.2 g of a white powdery resin. Table 1 shows the water absorption capacity and biodegradability of the obtained resin.

Comparative Example 2 10 g of the polysuccinimide obtained in Reference Example 1 was added to a solution prepared by dissolving 4.2 g of sodium hydroxide in 100 g of ion-exchanged water, followed by stirring at room temperature for 3 hours for hydrolysis. To obtain a viscous liquid. This viscous liquid is dried with hot air to obtain a white powdery resin having a water content of 3.8%.
2 g were obtained. Next, 0.1 g of ethylene glycol diglycidyl ether was dissolved in a mixed solution of 1 g of water and 0.5 g of methanol to prepare a crosslinking agent solution. The resin in the form of a white powder was thinly spread on the vat, and the above-mentioned crosslinking agent solution was sprayed by spraying. This mixture was placed in a hot-air dryer adjusted to 180 ° C. for 60 minutes to obtain 9.8 g of the resin of the present invention. Table 1 shows the water absorption capacity, water absorption rate, and biodegradation rate of the resin.
It described in.

[0054]

[Table 1]

[0055]

[0056]

According to the present invention, a resin obtained by hydrolyzing a reaction product of a polysuccinimide and a polysaccharide is crosslinked in the vicinity of the surface of the resin, thereby being excellent in water absorption, salt resistance, and water absorption speed.
In addition, there is an effect that a resin having high biodegradability can be obtained. Since the above resin has biodegradability that can be decomposed by bacteria and microorganisms in the soil, it is decomposed only by burying in the soil. For this reason, disposal is simple and excellent in safety, and does not cause environmental health problems such as environmental pollution. Therefore, it can be used in various fields such as sanitary fields such as sanitary articles such as diapers and sanitary articles, medical fields, civil engineering and construction fields, food fields, industrial fields, and agricultural and horticultural fields.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shigeki Ideguchi 4-17 Jonanmachi, Izumiotsu-shi, Osaka (72) Inventor Toshige Tanaka 4-17 Jonanmachi, Izumiotsu-shi, Osaka F-term (reference) 4F070 AA56 AB13 AB17 AC18 AC20 AC35 AC36 AC38 AC45 AC46 AC52 AC64 AC65 AC66 AC87 AC90 AE08 HA01 HA03 HA04 HA05 HB01 4J001 DA01 DB01 DB09 DB10 EA36 EE09D EE25B EE38B EE42B EE43B EE55B EE57B EE64B FA03 FB01 Y04J04B04 YB22 YB32 YB33 YB34 YB35 YB40 YB44 ZA04 ZB60

Claims (4)

[Claims] 1. A resin having two or more functional groups obtained by hydrolyzing a reaction product of a polysuccinimide and a polysaccharide is crosslinked with a functional group capable of reacting with a functional group of the resin. A method for producing a water-absorbent resin, which comprises contacting and reacting with an agent to crosslink the vicinity of the surface of the resin. 2. A method for producing a water-absorbent resin, which comprises irradiating a resin obtained by hydrolyzing a reaction product of a polysuccinimide and a polysaccharide with radiation to crosslink the vicinity of the surface of the resin. . 3. The crosslinking agent is added to 100 parts by weight of the resin.
The method according to claim 1, wherein the amount is 0.005 to 20 parts by weight. 4. The production method according to claim 1, wherein the water-absorbent resin has an absorption capacity of physiological saline of 10 g / g or more.