JPH0657010A - High absorptive polymer - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] The initial absorption rate is high when contacted with a large amount of aqueous liquid such as body fluids (mainly urine) excreted from the human body, and there is no decrease in absorption capacity after swelling. To provide a high-absorbent polymer capable of sufficiently exhibiting the absorbency possessed by the absorbent polymer. In an absorbent polymer composed of water-insoluble hydrophilic cross-linked polymer particles having a carboxyl group or a carboxylate group, the cross-linked polymer particles are provided with the following absorption capacity by increasing the cross-linking density on the surface of the particles. It is characterized by i) The equilibrium swelling absorption amount of physiological saline is 40 g / g (polymer) or more. ii) 0.3 g of the polymer is swollen with physiological saline for 10 seconds and the absorption amount is 3 ml or more.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention, when used as a superabsorbent polymer, more specifically, as an absorbent material for absorbent articles such as disposable diapers, has a high initial absorption rate for a large amount of aqueous liquid such as body fluid, and has an initial stage of initial absorption. The present invention relates to a high-absorbent polymer that does not exhibit a decrease in absorbency after absorption and can sufficiently exhibit the absorbency possessed by the absorbable polymer.

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
Paper, pulp, sponge, etc. have been used as water-absorbing or water-retaining materials in the fields of sanitary materials (sanitary napkins, disposable diapers, etc.) and in the field of agriculture and forestry, but these materials have low water-absorption capacity, and The water absorbed by these materials easily squeezes out a significant portion of it under pressure. Therefore, as a water-absorbing material replacing the above-mentioned materials, in recent years, starch-acrylonitrile graft polymer hydrolyzate, polyacrylic acid sodium cross-linked product, modified cellulose ether and methyl acrylate / vinyl acetate copolymer hydrolyzate, etc. An absorbent polymer was proposed,
Further, their improved products have also been proposed.

As a conventional method for obtaining an absorptive polymer, a method in which a water-soluble polymer is slightly crosslinked to make it water-insoluble is the mainstream. As the crosslinking method, the following method has been proposed. ing. 1) Perform self-crosslinking by optimizing manufacturing conditions. 2) Crosslinking is carried out by adding a crosslinking agent during or after the polymerization. Although some of the water-absorbent polymers obtained by the above-mentioned method show excellent performance, they do not satisfy all the performances required for the absorbent polymer. That is, the required performance for the water-absorbent polymer, 1) water absorption amount, 2) water absorption rate,
3) Gel strength can be mentioned, and it is generally accepted that there is the following relationship between these performances, but conventional water-absorbing polymers have a structure that maintains the balance of the following relationships. , Each performance was manufactured as a structure with some sacrifice.

Various inventions have been proposed for the purpose of improving the above-mentioned performance requirements for water-absorbent polymers, and various publications disclose them. That is, JP-A-56-161413 and JP-A-60-1205 disclose the invention for the purpose of improving the absorption capacity (improving the water absorption amount). The ability to absorb water (improve water absorption rate)
As a disclosure of the invention aimed at,
18690, Japanese Examined Patent Publication No. 3-74241, Japanese Patent Laid-Open No. 61-9730, and the like, and further discloses an invention for improving the particle strength after swelling (improving gel strength). There are JP-A-60-185550 and the like, and as the disclosure of the invention relating to the improvement of the water-absorbing polymer, in addition to the above, there is JP-A-61-62463.
Japanese Patent Publication No. 63-28639, Japanese Patent Publication No. 3-4
There are Japanese Patent No. 0623 and Japanese Patent Publication No. 3-742141.

However, in all of the above-mentioned conventional means for improving the absorbability of the absorbent polymer, the absorbent polymer is in contact with the aqueous liquid and absorbs the aqueous liquid from the initial state to the swelling equilibrium state. It is only improving the absorption capacity and improves the function of the absorbent polymer when it is actually used for hygiene products such as disposable diapers and sanitary napkins, in particular, it absorbs the aqueous liquid again after the initial absorption of the aqueous liquid. In this case, no consideration is given to the improvement of absorption capacity.

When a hygiene article provided with an absorbent polymer is used, the absorbent polymer usually completely absorbs the aqueous liquid when it comes into contact with the aqueous liquid, and the absorbent polymer is still absorbed in the aqueous liquid. It has the function of stopping the absorption and then reabsorbing the newly contacted aqueous liquid, but in such an actual usage mode, it is difficult to sufficiently exhibit the absorbing ability of each of the absorbent polymers, and therefore, it is excellent. Even in diapers and sanitary napkins that use absorbent polymers with high absorbency (absorbent polymers whose absorbency values are measured by equipment etc.), they actually exhibit excellent action and effect regarding absorbency. It's hard to say.

As described above, the main reason why the absorbability of the absorbent polymer is not sufficiently exerted is the inhibition of absorption of the liquid caused by the interaction of the absorbent polymers swollen by absorbing the aqueous liquid such as body fluid. The phenomenon (gel blocking) is mentioned. It is recognized that this gel blocking occurs more significantly in proportion to the magnitude of the initial absorption rate of the absorbent polymer.

That is, the absorbent polymer absorbs the aqueous liquid when it comes into contact with the aqueous liquid such as body fluid. The higher the initial absorption rate, the faster the swelling in a limited narrow area in contact with the aqueous liquid in a short time. However, it softens, and a large amount of aqueous liquid exists in a limited narrow area. As a result, the absorbent polymers come into contact with each other by swelling and softening, or the polymers come into close contact with each other due to their rearrangement and the like, so that the voids between the swollen polymers become smaller and the voids as passages for body fluids. The part is closed, a liquid layer is formed there, and so-called gel blocking is exhibited. Therefore, in the absorbent polymer that once absorbed the aqueous liquid, the gel blocking acts as a barrier, so that the absorbent polymer that has come into contact with the aqueous liquid again absorbs even if the absorption amount does not reach the saturated state. Will not contribute to.

The main causes of gel blocking are generally 1) reduction of voids between particles and 2) generation of viscosity (tackiness) on the outer wall of the particles in the swollen state of the absorbent polymer. Conceivable. Also,
For the above reason, the larger the initial absorption rate of the absorbent polymer, the more likely gel blocking occurs in proportion to the size thereof. Therefore, even if the absorbent polymer having an improved initial absorption rate is used in the absorbent article, it does not always lead to the leakage suppressing effect of the absorbent article.

As an absorbent material for absorbent articles, it is necessary to explain that an absorbent polymer having a low initial absorption rate has various problems in comparison with an absorbent polymer having a high initial absorption rate. It is well known. Further, in order to improve the absorbency of the absorbent article, the amount of the absorbent polymer has been increased. However, in such a structure, the distance between the particles of the absorbent polymer becomes small, and therefore the absorbent polymer is reduced. Is in a state where gel blocking is likely to occur.

Therefore, the main object of the present invention is to have a high initial absorption rate when in contact with a large amount of aqueous liquid such as body fluid (mainly urine) excreted from the human body, and further, to absorb gel blocking after the initial absorption. It is an object of the present invention to provide a superabsorbent polymer that does not cause a function inhibition phenomenon, does not decrease in absorbency after swelling, and can sufficiently exhibit the absorbency possessed by the absorbable polymer.

[0012]

As a result of various investigations, the present inventors have increased the crosslink density on the surface of an absorbent polymer composed of conventional water-insoluble hydrophilic crosslinked polymer particles such as alkali metal acrylate. It has been found that the polymer exhibits an extremely excellent absorption capacity as compared with the conventional absorbent polymer and can achieve the above object (first finding). Further, as a result of further studies, the inventors of the present invention have found that a polymer having a specific structure exerts an extremely excellent absorption capacity as compared with a conventional absorbent polymer and can achieve the above object. (Second finding). That is, the present inventors have found that a polymer having an increased crosslink density on the surface of the absorbent polymer can achieve the above object, and that a polymer having a specific structure can also achieve the above object. I found out.

The present invention (first invention) is based on the above first finding, and achieves the above object by providing the following superabsorbent polymer.
Note that, hereinafter, the first invention means the following invention.

In the absorbent polymer comprising water-insoluble hydrophilic cross-linked polymer particles having a carboxyl group or a carboxylate group, the cross-linked polymer particles are increased by increasing the cross-link density on the surface of the water-insoluble hydrophilic cross-linked polymer particles. A superabsorbent polymer characterized by having the following i) to iii) absorbency. i) The equilibrium swelling absorption amount of physiological saline is 40 g / g (polymer) or more. ii) 0.3 g of the polymer is swollen with physiological saline for 10 seconds and the absorption amount is 3 ml or more. iii) After packing 0.05 g of a polymer into a cylinder (inner diameter: 10 mmφ) having a cross-sectional area of 0.785 cm ² together with physiological saline, swelling the polymer with the physiological saline, reaching the equilibrium swelling absorption amount and allowing the swollen polymer to settle The passing time of 5 ml of physiological saline solution is 40 seconds or less.

The present invention (the second invention) is based on the above first finding, and achieves the above object by providing the following superabsorbent polymer. In the following description, the second invention refers to the following invention.

In an absorbent polymer comprising water-insoluble hydrophilic cross-linked polymer particles having a carboxyl group or a carboxylate group, the cross-linked polymer particles are increased by increasing the cross-link density on the surface of the water-insoluble hydrophilic cross-linked polymer particles. A superabsorbent polymer characterized by having the following i) to iii) absorbency. i) The equilibrium swelling absorption amount of physiological saline is 40 g / g (polymer) or more. ii) 0.3 g of the polymer is swollen with physiological saline for 30 seconds and the absorption amount is 6 ml or more. iii) 0.5 g of the polymer was filled into a cylinder (inner diameter 25.6 mmφ) having a cross-sectional area of 5.15 cm ² together with physiological saline, and the polymer was swollen by the physiological saline to reach the equilibrium swelling absorption amount and the swollen polymer was precipitated. After that, the passage time of 50 ml of physiological saline is 150 seconds or less.

Further, the present invention (third invention) is based on the above-mentioned second finding and provides the following superabsorbent polymer as an invention achieving the above object.
In addition, hereinafter, when the third invention is referred to, the following invention is referred to.

A superabsorbent polymer composed of aggregates having water-insoluble hydrophilic crosslinked polymer particles having a carboxyl group or a carboxylate group as constituent particles, and having a structure having the following requirements (a) to (d): A superabsorbent polymer characterized by being. (A) The constituent particles are aggregated in a state in which there is a void portion between them that substantially communicates with the outside of the aggregate. (B) The total amount of voids is 0.2 cc / g (polymer)
That is all. (C) The aggregated product has a non-spherical shape with an irregularity P of 1.2 or more. (D) The average particle size d ₅₀ (particle size at an integrated particle size of 50%) of the aggregate is 100 to 500 μm.

The superabsorbent polymers of the first and second inventions will be described below together with their manufacturing methods. The term "superabsorbent polymer" means only the superabsorbent polymer of the present invention (first invention, second invention and third invention) in order to distinguish it from the conventional "absorbent polymer". . Further, in the present invention, “absorption amount” and “water absorption amount”, and “absorption rate” and “water absorption rate” are synonyms.

The "absorbent polymer composed of water-insoluble hydrophilic cross-linked polymer particles having a carboxyl group or a carboxylate group" in the present invention is described in JP-B-3-74241 and JP-B-54-30710. Means a conventional absorbent polymer obtained by the method of, etc., as long as it is composed of water-insoluble hydrophilic crosslinked polymer particles having a carboxyl group or a carboxylate group, the production method and the like are not particularly limited. Preferred examples of the water-insoluble hydrophilic crosslinked polymer having a carboxyl group (or a carboxylate group) include those obtained by polymerizing a carboxyl group-containing water-soluble ethylenically unsaturated monomer.

As the carboxyl group-containing water-soluble ethylenically unsaturated monomer, polyacrylic acid (and its salt),
And polymethacrylic acid (and salts thereof) and the like can be exemplified as preferable ones, and acrylic acid or methacrylic acid can be combined with maleic acid, itaconic acid, acrylamide,
2-acrylamido-2-methylpropanesulfonic acid,
Those obtained by appropriately copolymerizing monomers such as 2- (meth) acryloylethanesulfonic acid and 2-hydroxyethyl (meth) acrylate may also be used.

The superabsorbent polymers of the first and second inventions are water-insoluble hydrophilic crosslinked polymer particles (hereinafter referred to as "crosslinked polymer particles") having the above-mentioned carboxyl group or carboxylate group. Is the one in which the cross-linking density of the surface of the absorbent polymer composed of these particles) is increased to such an extent that the superabsorbent polymer exhibits the absorbing ability of the above i) to iii). The term "absorptive polymer" means an absorptive polymer mainly composed of the above crosslinked polymer particles.

The superabsorbent polymers of the first and second inventions are:
Since it has the above-mentioned i) absorption ability, it can absorb and retain a large amount of aqueous liquid, and because it has the above-mentioned ii) absorption ability, it can quickly absorb the aqueous liquid at the time of initial absorption. )) (Because it does not cause gel blocking), even after absorbing and holding the aqueous liquid once, the equilibrium swelling and absorption amount of the aqueous liquid again held by the polymer does not decrease. Can absorb and hold up to.

In order to achieve the intended purpose, the superabsorbent polymers of the first and second inventions have a soluble portion of the polymer in physiological saline of 5% by weight or less (relative to the polymer). Is preferred.

Incidentally, the above i) to ii in the first and second inventions.
The measurement of the absorption capacity of i) is specifically as follows.
The measurement method of The amount of the soluble portion of the polymer was calculated by the following measuring method. [Measurement Method of Equilibrium Swelling Absorption of Super Absorbent Polymer] About 1 g of a polymer is dispersed in a large excess of physiological saline (0.9% saline), and the water absorption amount of the polymer is in an equilibrium swelling state. After swelling to normal, physiological saline is filtered through a wire mesh of 80 mesh, the weight (W) of the obtained swollen polymer is measured, and this value is divided by the weight W ₀ of the polymer before water absorption, That is, the value of W / W ₀ was taken as the absorption amount (g / g) of the above i).

[Measurement Method of Absorption Amount Representing Absorption Rate of Superabsorbent Polymer] FIG. 1 which is generally known as an apparatus for carrying out the DW method.
1, the polymer spray table 2 (70 mmφ, No. 2 filter paper with the liquid surface of the physiological saline W set to the same water level was placed on the glass filter No. 1 as shown in FIG. Polymer P on top of the
g, and the absorption amount at the time of spraying the polymer is set to 0,
The absorption amount after 10 seconds and after 30 seconds (this absorption amount is measured by a burette scale indicating the amount of decrease in the water level of the physiological saline W) is measured, and the measured value is the absorption amount of ii) above. m
l).

-(1) [Measurement method of physiological saline solution passage time (factor showing evaluation of gel blocking property)] The absorption property of iii) in the first invention was measured by this measurement method. This measurement method is suitable for a polymer having a very high liquid passage rate. The device 10 shown in FIG. 2 [inner diameter
A burette consisting of a glass cylindrical tube with a length of 10.0 mm and a length of about 300 mm (cylindrical part) was filled with 0.05 g of a polymer, and the polymer was equilibrated and swelled with an excess of physiological saline, and the liquid level was 20 ml. , The swollen polymer P was settled sufficiently as shown in the drawing, and the cock was opened. The physiological saline W showed the two rating lines L shown in the figure.
The time for passing between (the liquid surface with a liquid volume of 15 ml) and M (the liquid surface with a liquid volume of 10 ml) (the liquid volume of 5 ml) was measured, and this measured value was defined as the liquid passage time (second) in iii) above. .

-(2) [Measurement method of physiological saline solution passage time (factor showing evaluation of gel blocking property)] The absorption property of iii) in the second invention was measured by this measurement method. This measurement method is suitable for a polymer having a high liquid passage rate. Although the scale is larger than that of the device 10 shown in FIG. 2, 0.5 g of the polymer is added to a device similar to the device 10 shown in FIG. 2 (a glass cylindrical filter with a cock having an inner diameter of 25.6 mm and a length of about 500 mm (cylindrical portion)). Filling,
The polymer was equilibrated and swelled using an excess of saline, and the cock was adjusted to the liquid level of 200 ml, and the cock was opened after confirming that the swollen polymer P had fully settled as shown in FIG. The time during which the physiological saline W passes between the two marked lines L (liquid level of 150 ml of liquid volume) and M (liquid level of 100 ml of liquid volume) (50 ml of liquid volume) shown in FIG. 2 is measured,
This measured value was defined as the liquid passage time (second) in iii) above.

[Measurement Method of Soluble Part Content of Super Absorbent Polymer] 1 g of the superabsorbent polymer was precisely weighed in a 300 ml beaker, 150 ml of physiological saline was added, and the mixture was occasionally stirred for about 15 hours and left at room temperature for about 15 hours. To swell. After that, about 30 ml (Aml) of swollen polymer was taken, and Marusan ultracentrifuge (Sakuma Seisakusho, 50s-2 type, angle type rotor 1)
s) at 40,000 rpm (105,400G) 25
After treating at ℃ for 2 hours, collect the above solution, filter,
Dilute the filtrate to 100 ml. 50 ml to 100 ml
Then, add 10 ml of 0.005N methylglycol chitosan solution to the Erlenmeyer flask, adjust the pH to about 11 with aqueous ammonia, and add toluidine blue solution to it.
Add ~ 3 drops. Excess methyl glycol chitosan should be adjusted to 0.
Titrate the N-polyvinyl potassium sulfate solution until the color changes from blue to magenta. Separately, a blank test was conducted by the same method, and the calculated value by the following formula [Equation 1] was used as the soluble part polymer amount (%).

[0030]

[Equation 1]

The superabsorbent polymers of the first and second inventions are:
The crosslinked polymer particles have an increased crosslink density on the surface of the crosslinked polymer particles so as to have the absorbency of i) to iii), and the production method is not limited, but for example, the production method described below. Can be manufactured by.

The water-insoluble hydrophilic crosslinked polymer particles having a carboxyl group or a carboxylate group used in the method for producing the superabsorbent polymer of the first and second inventions are described in JP-B-3-74241 and JP-A-3-74241. Japanese Patent Office Sho 5
The absorbent polymer obtained by the method described in JP-A No. 4-30710 or the like, that is, a conventional water-absorbing polymer belonging to the cross-linked polymer particles, for example, a polymer obtained by polymerizing a carboxyl group-containing water-soluble ethylenically unsaturated monomer Can be used. Incidentally, these polymers can also be used without taking them out of the reaction system after production.

The above-mentioned conventional absorbent polymer can be used as it is as the above-mentioned crosslinked polymer particles, but it is preferable to use an absorbent polymer having a particle diameter of 100 to 500 μm.

The dispersion medium in which the crosslinked polymer particles are dispersed in the production of the superabsorbent polymer of the first and second inventions is a dispersion medium used in obtaining the above-mentioned conventional absorbent polymer, that is, a hydrocarbon. Or halogen aromatic hydrocarbon, specifically, aromatic hydrocarbon such as benzene, ethylbenzene, toluene, xylene, alicyclic hydrocarbon such as cyclohexane, methylcyclohexane, cyclooctane, decalin, hexane, pentane, heptane, octane. Aliphatic hydrocarbons such as chlorobenzene, bromobenzene, halogenated hydrocarbons such as dichlorobenzene, and the like, toluene, xylene, cyclohexane, methylcyclohexane, hexane, heptane, chlorobenzene,
Chlorobenzene is preferred.

Examples of the protective colloid used when the superabsorbent polymers of the first and second inventions are produced by utilizing the reverse phase suspension polymerization method include, for example, sorbitan fatty acid ester, polyglycerin fatty acid ester, and sorbitan fatty acid ester. Sugar fatty acid ester, sorbitol fatty acid ester, polyoxyethylene alkyl ether, nonionic surfactant such as polyoxyethylene alkylphenyl ether, or cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate phthalate, ethyl cellulose, benzyl cellulose, Examples of the polymer protective colloid include ethyl hydroxyethyl cellulose, polyethylene oxide, maleic anhydride polyethylene, and maleic anhydride polybutadiene.

Examples of the cross-linking agent used for producing the superabsorbent polymers of the first and second inventions include polyglycidyl ethers such as ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin triglycidyl ether, and the like. Haloepoxy compounds such as epichlorohydrin and α-methylchlorohydrin, polyaldehydes such as glutaraldehyde and glyoxal, glycerin, pentaerythritol, polyols such as ethylene glycol and polyamines such as ethylenediamine, but trifunctional or higher functional compounds can be mentioned. A crosslinking agent having a functional group is particularly preferable.

As specific embodiments of the production method for obtaining the superabsorbent polymers of the first and second inventions, for example, the following embodiments can be mentioned. 1. The crosslinked polymer particles are dispersed in a mixed solvent of the dispersion medium and water (mixing ratio; water / solvent = 50 to 5/50 to 95) and heated, and the crosslinker is added thereto. A method of further increasing the crosslink density on the surface of the crosslinked polymer particles by further contacting the crosslinker with the crosslinked polymer particles. 2. A hydrophilic monomer aqueous solution containing a carboxyl group (or a carboxylate group) containing a water-soluble initiator was dispersed and suspended in a non-aqueous solvent in the presence of a protective colloid to polymerize to obtain the crosslinked polymer particles. After that, the water content in the solution of the crosslinked polymer particles is controlled to 10 to 40% by weight, and then a crosslinking agent is added and further reacted with the crosslinking agent to further crosslink the surface.

The amount of the cross-linking agent used in carrying out the method of the present invention is 1,00 with respect to the cross-linked polymer particles.
0 ppm to 10,000 ppm is preferable, and by adjusting the amount used within this range, the crosslinked polymer particles can be made suitable for obtaining a superabsorbent polymer having an intended crosslinking density.

Next, the superabsorbent polymer of the third invention will be described. The superabsorbent polymer of the third invention is composed of an aggregated product containing the crosslinked polymer particles as constituent particles, and has a structure having the above (a) to (d). The constituent particles constituting the superabsorbent polymer of the third invention may be composed of substantially the same components as the cross-linked polymer particles constituting the superabsorbent polymer of the first invention described above, but the composition particles of the second invention are high. The constituent particles of the absorbent polymer are different from the crosslinked polymer particles in terms of structure (physical structure).

In the superabsorbent polymer of the third invention,
As in the case of (a) above, the constituent particles are aggregated in a state in which they have voids that are substantially in communication with the outside of the aggregate, and the superabsorbent polymer is Upon contact with the aqueous liquid, the aqueous liquid is easily absorbed in the superabsorbent polymer through the voids.

In addition, in the superabsorbent polymer of the third invention, the total amount of the voids is 0.
2 cc / g or more, preferably 0.3 cc / g or more,
If it is less than 0.2 cc / g, the function of the liquid as a temporary stock decreases, and it becomes difficult to obtain a sufficient initial absorption rate. Considering the gel strength of the polymer particles after swelling, if the total amount of voids is too large, the gel strength will decrease and the swollen polymer will collapse due to a small pressure, so the total amount of voids is 1.0 cc / It is preferably g or less. In addition, the total amount of the voids is the mercury porosimeter (Shimadzu Corporation,
Autopore 9220) was used for the measurement. This measurement method uses the principle that the pressure is inversely proportional to the minimum pore size into which mercury can penetrate due to the property of mercury that does not wet the substance, and that the mercury penetration amount is equal to the pore volume. .

Further, the superabsorbent polymer of the third invention has a non-spherical shape with an irregularity P of 1.2 or more as described in (c) above, and since it has such a non-spherical shape, it swells. After that, it is possible to prevent rearrangement of particles and reduction of voids due to adhesion. If the degree of irregularity P is less than 1.2, the deformation value of the surface irregularities of the swollen particles becomes insufficient, and the voids between the swollen particles cannot be maintained, causing gel blocking. The irregularity P expresses the roughness of the superabsorbent polymer particles and is defined by the following [Equation 2]. In addition, the actual area (S) and the peripheral length (l) of the projected particles when calculating the irregularity P are obtained by observing the superabsorbent polymer particles as projected particles with a Japanese Avionics IV image processor EXCEL. ,It was measured.

[0043]

[Equation 2]

[0044]

[Equation 3]

Further, in the superabsorbent polymer of the third invention, as in the above (d), the value d ₅₀ of the particle diameter of 50% of the integrated particle diameter as the average particle diameter is 100 μm or more, preferably d ₅₀ is 1.
When it is 50 μm or more and d ₅₀ is 500 μm or less, and the amount of fine powder is large, voids are reduced due to rearrangement after swelling, so gel blocking is likely to occur. When applied, it tends to cause discomfort after swelling of the polymer.

The superabsorbent polymer of the third invention is not limited to the production method thereof, but can be produced by the above-described production method of the superabsorbent polymer of the first and second inventions. The explanations of the "water-insoluble hydrophilic crosslinked polymer particles having a carboxyl group or a carboxylate group" and the "carboxyl group-containing water-soluble ethylenically unsaturated monomer" in the first and second inventions are applied to the third invention. .

[0047]

When the superabsorbent polymer of the first and second inventions comes into contact with a large amount of aqueous liquid (mainly urine) such as body fluid, it absorbs the aqueous liquid and swells like conventional absorbent polymers.
Further, according to the superabsorbent polymer of the first invention, since the crosslink density of the surface is increased, it is difficult for the voids between the polymers to be closed during swelling, and after swelling,
The tackiness (stickiness) of the surface of the swollen polymer is suppressed, the swollen polymers are less likely to cause blocking, and even if some of the swollen polymers that are in contact with each other adhere to each other, a void is formed between the swollen polymers. It is considered that the remaining particles adhere to each other, the voids serve as passages for the aqueous liquid, and the swelling polymer does not hinder the diffusion of the aqueous liquid throughout the superabsorbent polymer. Moreover, since the cross-linked structure of the surface of each superabsorbent polymer is a structure that facilitates the suction of the aqueous liquid in contact with the surface into the superabsorbent polymer, the absorption rate is considered to be high. To be Therefore, it is presumed that the superabsorbent polymers of the first and second inventions exhibit the above-mentioned i) to iii) absorbability.

Further, since the superabsorbent polymer of the third invention comprises an aggregated product having the structure having the above (a) to (d), the superabsorbent polymer of the third invention also has the above (a). ) To (d) produce substantially the same actions as the above actions of the superabsorbent polymers of the first and second inventions, and
~ Iii) It is presumed that it exerts the absorption ability.

[0049]

【Example】

Example 1 In a 500 ml four-necked round bottom flask equipped with a stirrer, a reflux condenser, a dropping funnel and a nitrogen gas introduction tube, 230 ml of cyclohexane and sorbitan monostearate (span 60).
1.4 g was charged and these were stirred to make a uniform solution. Separately, in an Erlenmeyer flask, add acrylic acid monomer 30
g was neutralized with 13.4 g of caustic soda dissolved in 39 g of water. The monomer concentration in this acrylic acid monomer aqueous solution was 45% (water content 55%). Next, 0.1 g of potassium persulfate was added to and dissolved in this aqueous monomer solution. This monomer aqueous solution was dropped into the above-described four-necked round bottom flask charged with cyclohexane and the like under a nitrogen atmosphere, and then this was heated to 70 to 75 ° C. to initiate polymerization.

Next, the amount of water in the polymer suspended in cyclohexane was controlled to 35%, 27% and 20% by azeotropic dehydration (cyclohexane was refluxed). Then, an aqueous solution prepared by dissolving 0.03 g of ethylene glycol diglycidyl ether in 1 ml of water was added at 73 ° C., and the mixture was kept at this temperature for 2 hours and then cyclohexane was removed to obtain a polymer at 80 to 100 ° C.
And dried under reduced pressure to obtain superabsorbent polymers A, B and C (inventive products) shown in Table 1 below.

Example 2 The superabsorbent polymers A, B and C obtained in Example 1 above.
40 g of each was again charged into a 500 ml four-neck round bottom flask together with 230 ml of cyclohexane, water was added, and the water content of each was controlled to 35%, 27% and 20%, and each was heated to 75 ° C. Let After reaching a certain temperature, ethylene glycol diglycidyl ether (2500 ppm relative to the polymer) was added to each. Then, this was kept at 75 ° C. for 3 hours, cyclohexane was removed, and the obtained polymers were each added to 8
It was dried under reduced pressure at 0 to 100 ° C, and each of the following [Table 1].
The superabsorbent polymers D, E and F (invention products) described in 1. were obtained.

Example 3 In Example 1 above, except that after the polymerization, the crosslinking agent (ethylene glycol diglycidyl ether) was added to the aqueous monomer solution in advance instead of being added after the water content control after polymerization. A superabsorbent polymer G (invention product) shown in the following [Table 1] was obtained in the same manner as when the superabsorbent polymer A was obtained.

Example 4 72.1 g of acrylic acid was diluted with 18.0 g of water, neutralized with 98.9 g of a 30 wt% sodium hydroxide aqueous solution while cooling, and then 2.8 wt% of 2,2'-azobis. An aqueous monomer / initiator solution was prepared by adding 10.7 g of an aqueous solution of (2-amidinopropane) dihydrochloride to obtain a uniform solution.
Separately, 283 ml of cyclohexane was placed in a 500 ml flask equipped with a reflux condenser, a dropping funnel, a stir bar, and a nitrogen introducing pipe, and polyoxyethylene dodecyl ether sulfuric acid ester sodium salt [average ethylene oxide addition mole number =
2.2 g of a 25 wt% aqueous solution of 2] was added and stirred (300 rp
m) -Dispersed, the flask was replaced with nitrogen, and then the temperature was raised to 75 ° C. To this, add the above-mentioned monomer / initiator aqueous solution to 30
Dropping over a period of 1 minute, and after the dropping is completed, at 75 ° C for 1.5 hours,
Further, the mixture was stirred and polymerized at 80 ° C. for 4 hours.

After the completion of the polymerization, the products were separated and dried under reduced pressure to obtain 88.4 g of acrylic acid (sodium) polymer. The obtained polymer is a distorted granular particle having an average particle diameter of 400 μm measured by a sieving method,
The bulk density was 0.41 g / ml. The particle surface of the polymer had a structure in which irregular particles of several to 20 μm were fused to each other, and the surface irregularities were extremely remarkable. The equilibrium swelling water absorption, the water absorption representing the water absorption rate, the passage time of the physiological saline solution, and the like were measured for the obtained polymer (Product Q of the invention). The results are shown in [Table 1] below.

Example 5 72.1 g of acrylic acid was diluted with 32.0 g of water, neutralized with 98.9 g of a 30 wt% sodium hydroxide aqueous solution while cooling, and then 2.8 wt% potassium persulfate aqueous solution. 7
g to make a homogenous solution to make an aqueous monomer / initiator solution. Separately, add cyclohexane 2 to a 500 ml flask equipped with a reflux condenser, a dropping funnel, a stir bar, and a nitrogen introducing tube.
Taking 83 ml, 1.5 g of a 25 wt% aqueous solution of polyoxyethylene dodecyl ether sulfuric acid sodium salt [average ethylene oxide addition mole number = 3] was added and stirred (3
(00 rpm) -Disperse, and after replacing the flask with nitrogen, 75
The temperature was raised to ° C. Add 3 parts of the above monomer / initiator solution.
It was dripped over 0 minutes. At this time, at the same time, 0.058 g of ethylene glycol diglycidyl ether) as an epoxy-based bifunctional crosslinking agent was gradually dropped using a syringe. After completion of dropping, at 75 ° C for 1.5 hours, then at 80 ° C
The mixture was stirred and polymerized for 4 hours.

After the completion of the polymerization, the product was separated and dried under reduced pressure to obtain 88.4 g of acrylic acid (sodium) polymer. The obtained polymer is a distorted granular particle having an average particle diameter of 400 μm measured by a sieving method,
The bulk density was 0.41 g / ml. The particle surface of the polymer had a structure in which irregular particles of several to 20 μm were fused to each other, and the surface irregularities were extremely remarkable. With respect to the obtained polymer (Product R of the present invention), the equilibrium swelling water absorption amount, the water absorption amount indicating the water absorption rate, the liquid transit time of physiological saline, and the like were measured. The results are shown in [Table 1] below.

Example 6 72.1 g of acrylic acid was diluted with 18.0 g of water, neutralized with 98.9 g of 30 wt% sodium hydroxide aqueous solution while cooling, and then 5.6 g of 5.2 wt% potassium persulfate. In addition, a homogeneous solution was prepared to prepare an aqueous monomer / initiator solution. Separately, 283 ml of cyclohexane was placed in a 500 ml flask equipped with a reflux condenser, a dropping funnel, a stir bar, and a nitrogen introducing pipe, and dodecyl glucoside (sugar condensation degree: 1.25)
8 g was added, and the mixture was stirred (300 rpm) and dispersed, the flask was purged with nitrogen, and then the temperature was raised to 75 ° C. The above-mentioned monomer / initiator aqueous solution was added dropwise thereto over 30 minutes, and after completion of the addition, the mixture was stirred and polymerized at 75 ° C. for 1.5 hours and further at 80 ° C. for 4 hours.

After the polymerization was completed, the products were separated and dried under reduced pressure to obtain 88.4 g of acrylic acid (sodium) polymer. The obtained polymer has an average particle diameter of 65.
Granular particles with a distorted shape of 0 μm and a bulk density of 0.3
It was 0 g / ml. The surface of the polymer particles has a number of
It had a structure in which amorphous particles of 20 μm were fused to each other, and the surface irregularities were extremely remarkable. Equilibrium swelling water absorption, water absorption representing the water absorption rate, passage time of physiological saline solution, and the like were measured for the obtained polymer (Product S of the present invention). The results are shown below [Table 1]
Shown in.

Example 7 72.1 g of acrylic acid was diluted with 18.0 g of water, neutralized with 98.9 g of a 30 wt% aqueous sodium hydroxide solution while cooling, and then 10.7 g of 2.8 wt% potassium persulfate. Was added to make a homogeneous solution, and an aqueous monomer / initiator solution was prepared.
Separately, 283 ml of cyclohexane was placed in a 500 ml flask equipped with a reflux condenser, a dropping funnel, a stir bar, and a nitrogen introducing tube, and trimethylstearyl ammonium chloride (0.1 ml) was added.
55 g was added and stirred (300 rpm) and dispersed, and the flask was purged with nitrogen, and then heated to 75 ° C. The above-mentioned monomer / initiator aqueous solution was added dropwise thereto over 30 minutes, and after completion of the addition, the mixture was stirred and polymerized at 75 ° C. for 1.5 hours and further at 80 ° C. for 4 hours.

After the completion of the polymerization, the product was separated and dried under reduced pressure to obtain 88.4 g of acrylic acid (sodium) polymer. The obtained polymer has a particle size of 100 to 1
The granular particles had a distorted shape of 500 μm (average particle diameter: 800 μm) and had a bulk density of 0.54 g / ml. The surface of the polymer particles had a structure in which irregular particles of several to 20 μm were fused to each other, and the surface irregularities were extremely remarkable. Equilibrium swelling water absorption, water absorption representing the water absorption rate, passage time of physiological saline solution, etc. were measured for the obtained polymer (Product T of the present invention). The results are shown in [Table 1] below.

Comparative Example 1 In the above-mentioned Example 1, the solution in the above-mentioned four-necked round bottom flask charged with cyclohexane and the like was heated to 70 to 75 ° C., and the monomer aqueous solution was added thereto under a nitrogen atmosphere at 1.5. After dropping polymerization for a long time and then maintaining the temperature at 70 to 75 ° C. for 0.5 hour to terminate the polymerization, the same procedure as in the case of obtaining the superabsorbent polymers A to C in Example 1 described above was performed. The absorbent polymer H described in [Table 2] below,
I and J (comparative products) were obtained.

Comparative Example 2 In the above Comparative Example 1, except that 1.94 g of ethyl cellulose N-200 was used as the dispersion medium instead of the span 60, the above absorbent polymers H to I were used.
The absorbent polymers K, L and M (comparative products) shown in the following [Table 2] were obtained in the same manner as in the case of obtaining the above.

Comparative Example 3 Commercially available three types of crosslinked polyacrylic acid soda (trade names: Aronzap RSII, Aquakeep 10SH-P, and Aqualic CAW-4) were respectively used as the absorbent polymer N,
O and P (comparative products) were used. See [Table 2] below.

[0064]

[Table 1]

[0065]

[Table 2]

INDUSTRIAL APPLICABILITY The superabsorbent polymer of the present invention has a high initial absorption rate when contacted with a large amount of an aqueous liquid such as body fluid (mainly urine) excreted from the human body, and further, gel blocking etc. after the initial absorption. The phenomenon of inhibition of absorption capacity does not occur, the absorption capacity does not decrease after swelling, and the absorption capacity of the absorbent polymer can be sufficiently exhibited.

[Brief description of drawings]

FIG. 1 is a diagram showing a method of measuring an absorption amount showing an absorption rate of a superabsorbent polymer together with an outline of the apparatus.

FIG. 2 is a diagram showing a method for measuring the passage time of a physiological saline solution (a factor indicating the evaluation of gel blocking property) together with the outline of the apparatus.

[Explanation of symbols]

 W Physiological saline solution P Polymer I Absorption amount measuring device showing absorption rate of polymer 10 Measuring device for physiological saline solution passage time

Claims (8)

[Claims] 1. An absorbent polymer comprising water-insoluble hydrophilic cross-linked polymer particles having a carboxyl group or a carboxylate group, wherein the cross-linking weight is increased by increasing the cross-link density on the surface of the water-insoluble hydrophilic cross-linked polymer particles. The following i) ~ iii) in the coalesced particles
A high-absorbent polymer, which is provided with the above-mentioned absorbency. i) The equilibrium swelling absorption amount of physiological saline is 40 g / g (polymer) or more. ii) 0.3 g of the polymer is swollen with physiological saline for 10 seconds and the absorption amount is 3 ml or more. iii) After packing 0.05 g of a polymer into a cylinder (inner diameter: 10 mmφ) having a cross-sectional area of 0.785 cm ² together with physiological saline, swelling the polymer with the physiological saline, reaching the equilibrium swelling absorption amount and allowing the swollen polymer to settle The passage time of 5 cc of physiological saline solution is 40 seconds or less. 2. The superabsorbent polymer according to claim 1, wherein the liquid passage time in iii) above is 20 seconds or less. 3. An absorbent polymer comprising water-insoluble hydrophilic cross-linked polymer particles having a carboxyl group or a carboxylate group, wherein the cross-linking weight is increased by increasing the cross-link density on the surface of the water-insoluble hydrophilic cross-linked polymer particles. The following i) ~ iii) in the coalesced particles
A high-absorbent polymer, which is provided with the above-mentioned absorbency. i) The equilibrium swelling absorption amount of physiological saline is 40 g / g (polymer) or more. ii) 0.3 g of the polymer is swollen with physiological saline for 30 seconds and the absorption amount is 6 ml or more. iii) 0.5 g of the polymer was filled into a cylinder (inner diameter 25.6 mmφ) having a cross-sectional area of 5.15 cm ² together with physiological saline, and the polymer was swollen by the physiological saline to reach the equilibrium swelling absorption amount and the swollen polymer was precipitated. After that, the passage time of 50 ml of physiological saline is 150 seconds or less. 4. The absorption amount in ii) of claim 3 is 9
The superabsorbent polymer according to claim 3, wherein the superabsorbent polymer is at least ml. 5. The superabsorbent polymer according to claim 3, wherein the liquid passage time in the above iii) of claim 3 is 75 seconds or less. 6. The superabsorbent polymer according to any one of claims 1 to 5, wherein the amount of the soluble portion of the polymer in physiological saline is 5% by weight or less (relative to the polymer). 7. A superabsorbent polymer comprising an aggregate comprising water-insoluble hydrophilic crosslinked polymer particles having a carboxyl group or a carboxylate group, which has the following requirements (a) to (d). A superabsorbent polymer characterized by comprising a structure. (A) The constituent particles are aggregated in a state in which there is a void portion between them that substantially communicates with the outside of the aggregate. (B) The total amount of voids is 0.2 cc / g (polymer)
That is all. (C) The aggregated product has a non-spherical shape with an irregularity P of 1.2 or more. (D) The average particle size d ₅₀ (particle size at an integrated particle size of 50%) of the aggregate is 100 to 500 μm. 8. The superabsorbent polymer according to claim 7, wherein the soluble amount of the polymer in physiological saline is 5% by weight or less (relative to the polymer).