JPH07157671A - Water-absorptive resin composition - Google Patents

Abstract

PURPOSE:To obtain an odorless substantially white water-absorptive resin composition excellent in resistance to urine, deodorizing effect and photodegradability after disposal by composing it of a specified compound and a water-absorptive resin. CONSTITUTION:This resin composition is composed of desirably 100 pts.wt. water-absorptive resin (e.g. a resin obtained from a partially neutralized (75%) sodium acrylate and trimethylol-propane acrylate) and desirably 0.001-10 pts.wt. at least one compound selected from maleimides (e.g. maleimide).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a water absorbent resin composition. More specifically, the present invention relates to a water absorbent resin composition having excellent urine resistance, deodorizing effect and photodegradability after use.

[0002]

2. Description of the Related Art In recent years, a water-absorbent resin has been developed as a polymer that absorbs a large amount of water and gels. Widely used in the fields, medical field, housing field, etc.

Therefore, many water-absorbent resins have been developed up to now, for example, crosslinked polyacrylic acid partially neutralized products (US Pat. Nos. 4,654,039 and 4,286082).
No.), a hydrolyzate of a starch-acrylonitrile graft polymer (US Pat. No. 3,618,815), a starch-acrylic acid graft polymer (US Pat. No. 4,076,663), a saponified product of a vinyl acetate-acrylic acid ester copolymer (US Pat. No. 4,124,748). No.), an isobutylene-maleic anhydride copolymer (US Pat. No. 4,389,513), and an acrylonitrile copolymer hydrolyzate (US Pat. No. 3935099).
No.), a hydrolyzate of an acrylamide polymer or copolymer (US Pat. No. 3,959,569), a cross-linked copolymer of 2-acrylamido-2-methylpropanesulfonic acid and acrylic acid (European patent No. 068189), carboxymethyl cellulose salt. Crosslinked product (US Pat. No. 4,650,716,
No. 4,689,408), crosslinked polymers of cationic monomers, and crosslinked polymers of 2-sulfoethyl methacrylate are known.

However, although it is a water-absorbent resin which shows a high water-absorption capacity with respect to pure water and physiological saline for a long time, the water-absorbent resin swollen with urine deteriorates and collapses with time. Since the main use of the water-absorbent resin is as a urine absorbent article such as paper diapers, simple toilet bowls, incontinence pads, cat wastes, etc., the water-absorbent resin is currently used. There is a strong demand for improved urine resistance. As a means for preventing such urine deterioration and improving the durability of the water absorbent resin, a highly cross-linked water absorbent resin may be obtained by increasing the amount of the crosslinking agent at the time of polymerization, but the water absorption ratio is significantly reduced and it is costly. Is disadvantageous to

Therefore, a method for imparting urine resistance by adding a specific additive to the water-absorbent resin has been proposed. For example, a method of adding an oxygen-containing reducing inorganic salt (Japanese Patent Laid-Open No. 63-11).
8375, US Patent 4972019, US Patent 48
No. 63989), a method of adding an antioxidant (Japanese Patent Laid-Open No. Sho 6-62).
3-127754), a method of adding an oxidizing agent (JP-A-63-153060), a method of adding a sulfur-containing reducing agent (JP-A-63-272349), and a method of adding a water-soluble phosphorus compound ( JP-A-64-33158) and the like are known. Further, a method for imparting urine resistance by using a specific compound at the time of polymerization is also proposed, for example, a method of polymerizing in the presence of a specific amount of a chain transfer agent and a specific amount of a cross-linking agent (JP-A-2-255804, JP-A-3-179008
No., European Patent No. 0372981) and a method of polymerizing in the presence of a water-soluble phosphoric acid compound (JP-A-5-97929).
Is also known. However, it was difficult to say that any of the methods for improving urine resistance is still perfect in its effect and convenience.

In addition to the urine resistance improving method, many means for improving the light resistance and heat resistance of the water absorbent resin have been proposed. For example, the light resistance by adding a specific additive to the water absorbent resin or As a method of imparting heat resistance, for example, a method of adding carbon black or activated carbon (Japanese Patent Laid-Open No. 59-38).
No. 271), a method of adding a radical chain inhibitor and a metal chelating agent (JP-A 1-210463), a method of adding a reducing substance (JP-A 1-223161), and a method of adding an ultraviolet absorber (special Kaihei 2-64163
No.), a method of adding fine titanium oxide powder (JP-A-2-1)
35263), and a method of adding an ultraviolet absorber such as benzophenone (JP-A-63-165457 and JP-A-6-165457).
3-165458), a method of adding 2-mercaptothiazole (JP-A-5-311023), a method of adding ammonia or pyrrolidine (JP-A-3-2273).
No.), a method of adding ethylenediaminetetraacetic acid, benzophenone, ethanolamine, etc. (JP-A-58-1)
7157), a method of adding an organic phosphoric acid compound (JP-A-5-86251), and the like. Further, as a method for imparting light resistance and heat resistance by using a specific compound at the time of polymerization, for example, a method of performing polymerization in the presence of a benzophenone-based ultraviolet absorber (Japanese Patent Laid-Open No. 63-165402).
No.), a method of copolymerizing with an acrylic acid ester containing a hindered amine (JP-A-4-103067), and a method of copolymerizing a nonionic monomer (JP-A-2-79911).
No.), a method of neutralizing 96 mol% or more of the acid groups of the polymer (JP-A-1-285119), and the like. However, even if the light resistance and heat resistance are improved by these methods, there is a problem of cost and coloring of the water absorbent resin, and the effect of improving urine resistance is not observed or insufficient. .

In addition to the durability such as the urine resistance of the water-absorbent resin described above, the water-absorbent resin is used in the field of sanitary ware, vomiting treatment,
Since it is often used for waste disposal, fragrance, etc., its deodorizing effect is currently required.

For this reason, various additives such as deodorants have been proposed as a method for imparting deodorant ability to water-absorbent resins.
Various adsorbents such as activated carbon (JP-A-56-31425,
JP-A-57-563425, JP-A-59-1628
32), carboxyvinyl polymer (JP-A-57-1)
No. 42255), and plants of theaceae family (JP-A-60-1588).
61), stabilized chlorine dioxide (JP-A-62-14108).
9), tea making (JP-A-2-41155), oxides of specific metals (JP-A-1-5546, JP-A-1-5547).
No.), perfume (Japanese Patent Laid-Open No. 61-73664) and the like are known. However, these additives are generally expensive, and when they themselves are black or green, they usually have a bad appearance when mixed with a white water-absorbing resin, and they have volatile and peculiar aroma and odor. Moreover, the deodorizing effect is insufficient, and it is the present situation that almost no effect is observed in improving the urine resistance to the water absorbent resin.

In addition to the problems of improving the urine resistance and imparting deodorant effect of such a water-absorbent resin, the water-absorbent resin usually used in the disposable field such as disposable diapers for the past several years has been used with an increase in the amount used. The problem of the later disposal of the water-absorbent resin and the difficulty of decomposing the water-absorbent resin that requires a crosslinked structure after the disposal have come to be taken up.

Therefore, many methods of decomposing the water absorbent resin after disposal have been proposed, for example, irradiation with ultraviolet rays (JP-A-1-231983) and addition of an oxidizing agent (JP-A-1-28).
4507), addition of L-ascorbic acid and the like (JP-A-5-247221, JP-A-5-247307) and the like. However, if such an additive is added in advance, the urine resistance may decrease, so it is necessary to add the additive separately at the time of disposal, and
Decomposition by ultraviolet irradiation requires not only sunlight but also a special ultraviolet irradiation device and long-time irradiation, and it is difficult to say that they are all sufficient decomposition methods.

[0011]

The present invention has been made in view of the above situation. Therefore, the object of the present invention is to provide a water-absorbent resin with urine resistance and a deodorant effect by an inexpensive and simple method,
It is to impart photodegradability after use.

[0012]

MEANS TO SOLVE THE PROBLEMS As a result of intensive studies to solve the above problems, the present inventors have found that a water-absorbent resin composition comprising at least one compound selected from maleimides and a water-absorbent resin is odorless. In addition to being substantially white and inexpensive,
The inventors have found that they exhibit excellent properties in terms of urine resistance, deodorizing effect, and photodegradability after use, and have completed the present invention.

That is, the present invention relates to a water absorbent resin composition comprising at least one compound selected from maleimides and a water absorbent resin.

The present invention will be described in more detail below.

The water-absorbent resin used in the present invention is a known water-absorbent resin which absorbs a large amount of water in water and swells to form a hydrogel. For example, a polyacrylate cross-linked product, starch-acrylonitrile graft Polymer hydrolyzate, starch-acrylic acid (salt) graft polymer, vinyl acetate-acrylic acid ester copolymer saponification product, 2-acrylamido-2-methylpropanesulfonic acid (salt) polymer, polyacrylamide cross-linking Examples thereof include a hydrolyzate of the body and a neutralized product of isobutylene maleic anhydride copolymer.

Among these water-absorbent resins, the ones in which the water-absorbent resin composition of the present invention is more effective are acrylic acid (salt), β-acryloyloxypropionic acid (salt), methacrylic acid (salt), 2 -(Meth) acryloylethanesulfonic acid (salt), 2- (meth) acrylamido-2-methylpropanesulfonic acid (salt), methoxypolyethylene glycol (meth) acrylate, N, N-
Dimethylaminoethyl (meth) acrylate and its quaternary salts, water-absorbent resin polymerized with an unsaturated monomer such as acrylamide as a main component is exemplified, and more preferably,
It is a water-absorbent resin whose main component is acrylic acid. Incidentally, these water absorbent resins may be a copolymer with a hydrophobic unsaturated monomer such as butadiene, isobutene, ethylene, propylene, stearyl (meth) acrylate,
It may be a graft polymer.

When the water-absorbent resin has an acid group such as a carboxyl group, the acid group is preferably 30-100.
Mol% neutralization, more preferably 40 to 95 mol% neutralization, and even more preferably 50 to 80 mol% neutralization. Examples of the basic substance used before or after the polymerization for neutralization include carbonic acid (hydrogen) salts, alkali metal hydroxides, ammonia, organic amines and the like.

There are no particular restrictions on the cross-linking method for forming the water-absorbent resin, but it is preferable to carry out polymerization by adding a predetermined amount of the internal cross-linking agent in advance. Examples of the internal crosslinking agent used include N, N′-methylenebisacrylamide, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, Trimethylolpropane di (meth) acrylate,
Polyethylene glycol di (β-acryloyloxypropionate), poly (meth) allyloxy alkane, glycerin acrylate methacrylate, (poly) ethylene glycol diglycidyl ether, (poly) ethylene glycol, glycerin, pentaerythritol, ethylenediamine, polyethyleneimine, etc. One or two
One or more species are exemplified, but a polymerizable internal crosslinking agent is more preferable. The amount used is preferably 0.005 to 5 mol% and more preferably 0.01 to 1 mol% with respect to the monomer.

The polymerization of the above-mentioned monomer in the present invention can be carried out by bulk polymerization or precipitation polymerization, but it is usually preferable to use the solution of water or an aqueous liquid as the monomer. The concentration of the monomer is not particularly limited to exceed the saturation concentration, but it is usually 20
It is preferably in the range of wt% to saturated concentration. In addition,
At the time of polymerization, various hydrophilic polymers such as starch, cellulose, polyvinyl alcohol, polyethylene glycol, and cross-linked polyacrylates, and water-soluble chain transfer agents such as hypophosphorous acid (salt) may be added.

The method of polymerizing the above-mentioned monomers is not particularly limited, but polymerization with a radical polymerization initiator is preferred.
Examples of the radical polymerization method used include known polymerization methods such as aqueous solution polymerization, reverse phase suspension polymerization, reverse phase emulsion polymerization, precipitation polymerization, bulk polymerization and the like. Turbid polymerization is particularly preferred. Further, a fibrous base material or an inorganic substance may be allowed to coexist at the time of polymerization to form a water-absorbent composite.

The radical polymerization initiator used is
Known polymerization initiators such as sodium persulfate, t-butyl hydroperoxide, hydrogen peroxide, 2,2′-azobis (2-amidinopropane) dihydrochloride are used,
Further, there is no limitation on the combined use of these initiators and a reducing agent such as a sulfurous acid (hydrogen) salt or L-ascorbic acid, or the combined use of ultraviolet rays. The amount of these initiators and reducing agents used is usually 0.001 to 2 mol% based on the monomers.

Further, the gelled polymer after polymerization is dried if necessary depending on the use and the solid content after polymerization. As the drying method, for example, known drying methods such as hot air drying, infrared drying, microwave drying, drum dryer drying, azeotropic dehydration in a hydrophobic organic solvent are used without limitation, but usually, these methods are used. , Solid content of 60% or more,
Furthermore, it is preferable to dry to 90% or more.

Further, the particle size may be adjusted by further pulverizing or granulating after polymerization or drying. For example, when a powdery water absorbent resin is intended, the average particle size is 10 to 2000 μm.
m, more preferably 100 to 1000 μm, most preferably 300 to 600 μm, and the particle size distribution is preferably narrow.

The present invention is achieved by using the above water-absorbent resin as a composition with at least one compound selected from maleimides.

The maleimides used to obtain the composition of the present invention include maleimide, N-methylmaleimide, N-ethylmaleimide, N-n-propylmaleimide, N-isopropylmaleimide and N-cyclohexylmaleimide. Examples include one kind or two or more kinds of various white alkyl-substituted maleimides such as, and pale yellow N-phenylmaleimide, and the combination thereof is not limited. In addition, methyl group, phenyl group, chloro group, methylol group, at the 2-position and 3-position of these maleimides and N-phenyl group,
It may be various maleimides in which a substituent such as an amino group or an aminoalkyl group is introduced. Among these various maleimides, one or more selected from the group consisting of maleimide, N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide and N-isopropylmaleimide are selected from the viewpoint of the effect of the present invention. Maleimide is preferred and most preferred.

The method of obtaining the composition of the present invention is not particularly limited. For example, a method of dry mixing maleimides with a water-absorbent resin, or a method of dry mixing maleimides and then water, a binder, a crosslinking agent, etc. Method, a method of mixing a solution or dispersion of maleimides by means of spraying, impregnation, coating, etc., and then drying if necessary, a method of mechanically kneading maleimides with a meat chopper or a kneader, maleimides Examples of the method include a method in which the above is supported on a fiber base material or an inorganic base material and then mixed. In these methods, the water-absorbent resin to which the maleimides are added may be a swollen gel, may be in a dried state, or may be in a dispersed state in an inert solvent such as cyclohexane. Furthermore, the mixed state of the maleimides and the water absorbent resin is
It may be evenly mixed inside the particles of the water absorbent resin,
It may be mixed in the vicinity of the particle surface or may be mixed in a non-contact state with each other via another base material. Further, when the maleimides are mixed with the water absorbent resin, an inert inorganic powder such as silicon dioxide or bentonite, a natural or synthetic fibrous substance, or a water absorbent resin in which various surfactants are allowed to coexist, Maleimides may be mixed.

In the present invention, the mixing ratio of the water-absorbent resin and the maleimides is appropriately determined depending on the durability of the water-absorbent resin used, its use, usage time and the like. Normally, the maleimides are used per 100 parts by weight of the water-absorbent resin. 0.0005-
The amount is 50 parts by weight, preferably 0.001 to 10 parts by weight, and more preferably 0.01 to 5 parts by weight. When the proportion of maleimides is less than 0.0005 parts by weight, the resulting water-absorbent resin composition has low durability, deodorizing ability and photodegradability after use, and also has a deodorizing ability in a relatively short time. Urine resistance may disappear. Further, when the proportion of maleimides exceeds 50 parts by weight, long-term durability, deodorizing ability and excellent photodegradability are exhibited, but when the resulting water-absorbent resin composition becomes uneconomical, or maleimide It may become pale yellow depending on the type of species.

Further, the surface of the water-absorbent resin before addition of the maleimides or the water-absorbent resin composition with the obtained maleimides is further cross-linked in the vicinity of the surface thereof or sulfurous acid (hydrogen) is added.
A reducing agent such as salt, an inert inorganic substance, a surfactant and the like may be added. A known method can be used without limitation as a method for crosslinking the vicinity of the surface of the water absorbent resin, but it is usually carried out by adding a surface crosslinking agent of a polyhydric alcohol or a polyvalent glycidyl to the vicinity of the surface of the particle.

Regarding maleimides, a method for deodorizing mercaptans by directly using an aqueous solution of maleimides or a water / alcohol solution (Japanese Patent Laid-Open Nos. 48-8934 and 4-4).
No. 8-72339) or a technique for reducing unpolymerized monomer in a sheet-like water-absorbing complex by copolymerizing phenylmaleimides with a monomer in the presence of a fiber base material (Japanese Patent Application Laid-Open No. HEI-1 (1999)).
No. 121308) is also known. However, such a technique does not disclose any water-absorbent resin composition of a water-absorbent resin and maleimides, and moreover, such a composition has a marked deodorizing effect as compared with maleimides alone, No suggestion of imparting urine resistance or photodegradability.

[0030]

The water-absorbent resin composition of the present invention comprising a water-absorbent resin and maleimides has (1) excellent urine resistance, (2) excellent deodorant effect, and (3) excellent. Shows photodegradability after disposal, (4) Odorless that is simple and inexpensive to obtain
It is a substantially white water-absorbent resin composition. The water-absorbent resin composition of the present invention is suitably used for various urine absorbing articles such as disposable diapers, portable toilets, pet sheets, cat sand, and other various industrial fields such as aromatic agents. It can also be suitably used in the fields of agriculture and horticulture.

[0031]

EXAMPLES The present invention will be described below with reference to examples.
The scope of the invention is not limited to only these examples. The physical properties described in the examples are values measured by the following test methods.

(1) Water absorption ratio 0.2 g of a water-absorbent resin is used as a non-woven tea bag type bag (4
(0 * 150 mm) and then immersed in a 0.9 wt% sodium chloride aqueous solution. After 30 minutes, the tea bag type bag was pulled up and drained for a certain period of time, then the weight of the tea bag type bag was measured, and the water absorption capacity was calculated by the following formula.

[0033]

[Equation 1]

(2) Water-soluble content 0.5 g of the water-absorbent resin corrected by solid content is stirred in 1 L of ion-exchanged water to swell and disperse. After stirring for 16 hours, the swollen gel was filtered with a filter paper, and the solid content of the filtrate was measured to determine the water-soluble content in the water-absorbent resin for 16 hours.

(3) Urine resistance Using human urine uniformly sampled from 10 healthy adult males, 2 g of water-absorbent resin in a 100 ml glass bottle with a lid.
Was swelled 25 times and left in an atmosphere of a temperature of 37 ° C. and a relative humidity of 90% for a predetermined time. While visually observing the appearance of the swollen gel after 16 hours, the water-soluble content of the swollen gel was measured for 1 hour by the method of (2) at the same time, and the water-absorbent content was determined by the amount of water-soluble content. The urine deterioration of the resin was quantified.

(4) Deodorizing effect With respect to the swelling gel with human urine used in (3), the odor was tested by the sense of smell of 10 adult males and ranked into 5 levels.

(5) Photodegradability After 1 g of water-absorbent resin was swollen 100 times with ion-exchanged water and sealed in a glass bottle, the glass bottle was opened in Himeji City from October 28, 1993 to November 1, 1993. Left unattended.
After standing for 4 days, the appearance of the swollen gel in the glass bottle is visually observed, and at the same time, the water-soluble content of the swollen gel for 1 hour is measured by the method (2), and the water-soluble content of the water-absorbent resin is dissolved. The photodegradability of the water-absorbent resin was quantified by the size. (Note that all the water-absorbent resins tested this time showed a swelling ratio of 200 times or more in ion-exchanged water.) (Production Example 1)
Water solubility by dissolving 3.4 g of trimethylolpropane acrylate as an internal cross-linking agent (0.05 mol% of monomer) in 5500 g of an aqueous solution of partially neutralized sodium acrylate with a neutralization ratio of 75 mol% and a concentration of 37% Adjust unsaturated monomer (1) and use 2 sigma-type blades with an internal volume of 10 L.
Nitrogen substitution was carried out in a reactor equipped with a lid on a jacketed stainless steel double-armed kneader. Then, while stirring the kneader blade, 0.15 mol% of ammonium persulfate and 0.03 mol% of sodium bisulfite were added as polymerization initiators, polymerization was carried out for 60 minutes, and the obtained fragmented hydrogel polymer was obtained. Was dried with hot air at 150 ° C. for 60 minutes, and the dried product was further pulverized with a vibration mill to be classified into particles having a particle diameter of 75 μm to 850 μm to obtain a white water-absorbent resin (1). The water absorbing resin (1) had a water absorption capacity of 46 times and a water-soluble content of 10%.

Production Example 2 In Production Example 1, the water-soluble unsaturated monomer (2) was prepared by adjusting the amount of the internal cross-linking agent used to 6.8 g (0.1 mol% with respect to the monomer). Thereafter, polymerization and the like were performed in the same manner as in Production Example 1 to obtain a highly crosslinked white water-absorbent resin (2). The water absorbing resin (2) had a water absorption capacity of 39 times and a water-soluble content of 6%.

Example 1 A mixture of 1 g of maleimide and 10 g of water was added to 100 g of the water absorbent resin (1) obtained in Production Example 1, followed by drying at 100 ° C.
A white, odorless water-absorbent resin composition (1) containing 1% of maleimide was obtained. Regarding the obtained water absorbing composition (1),
Table 1 shows the results of evaluation of the various physical properties (2) to (5).

(Examples 2 and 3) By changing the amounts of maleimide used in Example 1 to 0.1 g and 5 g, respectively, a white and odorless water-absorbent resin composition containing 0.1% and 5% of maleimide ( 2) and (3) were obtained. Table 1 shows the results of the similar evaluation of these physical properties.

Example 4 To 100 g of the water absorbent resin (2) obtained in Production Example 2, 0.02 g of maleimide and 1 part of water were added.
A white, odorless water-absorbent resin composition (4) containing 0.02% of maleimide was obtained by dry-mixing 5 g of white natural pulp having g absorbed therein. Table 1 shows the results of the similar evaluation of these physical properties.

Example 5 To 100 g of the water absorbent resin (1) obtained in Production Example 1, 5 g of N-methylmaleimide powder was added.
By dry-mixing, a white, odorless water-absorbent resin composition (5) containing 5% of N-methylmaleimide was obtained. Table 1 shows the results of the similar evaluation of these physical properties.

Comparative Example 1 In Example 1, 100 g of the water absorbent resin (1) was simply added with 10 g of water, and then 100
A comparative water absorbent resin composition (1) was obtained by drying at 0 ° C. Table 1 shows the results of the similar evaluation of these physical properties.

Comparative Example 2 A comparative water absorbent resin composition (2) was obtained in the same manner as in Example 4, except that maleimides were not used. Table 1 shows the results of the similar evaluation of these physical properties.

Comparative Example 3 As a blank test of the deodorizing effect of maleimide, instead of Example 1 in which 50 g of human urine was swollen with 2 g of water-absorbent resin composition (1) containing 1% of maleimide, 50 g of human urine was directly added. A maleimide alone was added to 20 mg of maleimide to conduct a deodorizing test using maleimide alone. The results are shown in Table 1.

[0046]

[Table 1]

Claims (4)

[Claims] 1. At least one selected from maleimides
A water absorbent resin composition comprising one compound and a water absorbent resin. 2. The water absorbent resin composition according to claim 1, wherein the maleimides are maleimides. 3. The water absorbent resin composition according to claim 1, wherein the total amount of the maleimides is 0.001 to 10 parts by weight with respect to 100 parts by weight of the water absorbent resin. 4. At least one selected from maleimides
A water absorbent resin composition for solidifying excrement and urine, which comprises two compounds and a water absorbent resin.