WO2022254874A1

WO2022254874A1 - Water-absorbent resin composition, absorber and absorbent article employing same, and method for manufacturing water-absorbent resin composition

Info

Publication number: WO2022254874A1
Application number: PCT/JP2022/011302
Authority: WO
Inventors: 英二森田; 駿佑鈴木; 一充鈴木
Original assignee: Ｓｄｐグローバル株式会社
Priority date: 2021-06-04
Filing date: 2022-03-14
Publication date: 2022-12-08
Also published as: JPWO2022254874A1

Abstract

The present invention provides a water-absorbent resin composition that contains a cross-linked polymer (A) that has, as constituent units: at least one type of monomer (A1) selected from the group consisting of a water-soluble unsaturated monocarboxylic acid (a1), salts thereof, and so forth; at least one type of monomer (A2) selected from the group consisting of a water-soluble unsaturated dicarboxylic acid (a3), salts thereof, and so forth; and a cross-linking agent (b), wherein a surface of the cross-linked polymer (A) has a structure that is cross-linked by means of a surface cross-linking agent (d), and the 14C/C of at least one of the monomer (A1) and the monomer (A2) is 1.2×10-12 to 1.0×10-16. According to the present invention, it is possible to provide a water-absorbent resin composition: with which, while employing a plant-origin raw material that is useful in terms of environmental conservation from the viewpoint of carbon neutrality, it is not necessary to remove impurities contained in said raw material in the manufacturing processes; and that achieves absorption performance that is equivalent to 《MK1》a polyacrylic acid-based absorbent resin composition《/MK1》 in which a monomer serving as the principal component has a single composition.

Description

Water-absorbent resin composition, absorbent body and absorbent article using the same, and method for producing water-absorbent resin composition

The present invention relates to a water absorbent resin composition, absorbent bodies and absorbent articles using the same, and a method for producing a water absorbent resin composition.

A water-absorbing resin composition is a resin that can absorb water several tens to thousands times its own weight. For example, a polyacrylic acid-based absorbent resin composition is known. These water-absorbing resin compositions are widely used in disposable sanitary products due to their high water-absorbing properties. However, it has been pointed out that conventional water-absorbing resin compositions are problematic from the viewpoint of environmental load in the disposal method of sanitary goods containing them, and that the method of disposal in an incinerator causes global warming. there is Under such circumstances, there is a strong demand for a water-absorbing resin composition using a plant-derived raw material from the viewpoint of carbon neutrality and the like.

Examples of water absorbent resin compositions using plant-derived raw materials include carboxymethylcellulose crosslinked products (Patent Document 1), alginic acid crosslinked products, starch crosslinked products (Patent Document 2), polyamino acid crosslinked products (Patent Documents 3 to 7), Galactomannan-metal ion crosslinked products (Patent Documents 8 to 10) and the like are known. However, when comparing the water absorbent resin composition using these plant-derived raw materials with the polyacrylic acid-based water absorbent resin composition, the absorbent resin composition using the plant-derived raw material has poor productivity. However, it has not been put to practical use due to problems such as low absorption performance.

In addition, as an example of a polyacrylic acid-based water absorbent resin composition, for example, there is an example in which mercerized cellulose is dissolved or dispersed in an aqueous acrylic acid solution derived from petrification during polymerization, and this is polymerized (Patent Document 11). However, in the example described in Patent Literature 11, a mercerization treatment using a strong base substance such as sodium hydroxide is essential in advance, which is not a preferable form from the viewpoint of safety and productivity efficiency.

Furthermore, water absorbent resin compositions obtained by copolymerizing acrylic acid and methylenesuccinic acid are also known (Patent Documents 12 and 13). However, the water-absorbent resin compositions described in Patent Documents 12 and 13 do not have sufficient water absorbency under load and cannot withstand practical use. Another way of thinking is to improve the biomass ratio by changing acrylic acid from petrified acrylic acid to plant-derived acrylic acid. However, plant-derived acrylic acid contains impurities such as, for example, propionic acid, 3-hydroxypropionic acid, hydroxypropionic acid derivatives, formic acid, acetic acid, lactic acid, lactic acid derivatives, acetaldehyde, acrolein, furfural, or mixtures thereof. If these impurities are included, the plant-derived acrylic acid is made into a water-absorbing resin composition after chemical treatment such as polymerization, and sanitary products such as disposable diapers and napkins are the cause of reduced absorption performance and odor generation. This is not preferable for users because it leads to Therefore, for example, when producing plant-derived acrylic acid, the amount of impurities contained in acrylic acid is reduced by distillation or recrystallization, or when drying is performed in the gel state after polymerization of acrylic acid. (Patent Documents 14 and 15). However, in these methods, there is a concern that the polymer may deteriorate even in a gel state due to equipment for recovering volatilized impurities and heating, and as a result, it may lead to a decrease in water absorption performance as a water absorbent resin composition. Therefore, it is not a preferable method from the viewpoint of productivity.

Patent Documents 16 and 17 also report that traceability is possible by specifying the stable carbon isotope ratio δ ¹³ C. In these patent documents, there are examples in which the ratio of acrylic acid derived from petrification and acrylic acid derived from plants and cross-linking conditions are variously studied.

However, since it is assumed that the plant-derived acrylic acid obtained by the methods described in Patent Documents 16 and 17 also contains many impurities, the same problems as those exemplified above can be said.

Japanese Patent Application Laid-Open No. 2004-010634 JP-A-55-15634 JP-A-7-224163 JP-A-7-309943 JP-A-8-59820 JP-A-8-504219 JP-A-9-169840 JP-A-8-59891 Japanese Patent Publication No. 3-66321 JP-A-56-97450 JP 2009-185216 A Chinese Patent Application Publication No. 103183764 U.S. Patent Application Publication No. 9109059 Japanese Patent Application No. 2010-549538 Japanese Patent Application No. 2009-525070 Japanese Patent Application No. 2012-512867 Japanese Patent Application No. 2012-512868

The object of the present invention is to use a plant-derived raw material that is useful for environmental conservation from the carbon-neutral viewpoint, does not require removal of impurities contained in the raw material during the manufacturing process, and has a main component monomer A water-absorbent resin composition having absorption performance comparable to that of a single-component polyacrylic acid-based absorbent resin composition, an absorbent body and absorbent articles using the same, and a method for producing a water-absorbent resin composition. to provide.

The present invention
one or more monomers (A1) selected from the group consisting of water-soluble unsaturated monocarboxylic acids (a1) and salts thereof, and monomers (a2) that become the water-soluble unsaturated monocarboxylic acids (a1) by hydrolysis; , one or more monomers (A2) selected from the group consisting of a water-soluble unsaturated dicarboxylic acid (a3) and a salt thereof, and a monomer (a4) that becomes the water-soluble unsaturated dicarboxylic acid (a3) by hydrolysis; A water-absorbing resin composition containing a cross-linked polymer (A) having a cross-linking agent (b) as a structural unit, and having a structure in which the surface of the cross-linked polymer (A) is cross-linked by the surface cross-linking agent (d). and
At least one of the monomer (A1) and the monomer (A2) has ^{a 14} C/C measured by a carbon radiocarbon dating method of 1.2×10 ⁻¹² to 1.0×10 ⁻¹⁶ . ,
A water-absorbing resin having a water retention capacity (g/g) of 0.9 wt% saline of 10 to 60 and an absorption capacity (g/g) of 0.9 wt% saline under load of 12 to 25. composition.

According to the present invention, while using a plant-derived raw material that is useful for environmental conservation from the carbon-neutral viewpoint, it does not require removal of impurities contained in the raw material during the manufacturing process, and the main component monomer is A water-absorbent resin composition having absorption performance comparable to that of a single-component polyacrylic acid-based absorbent resin composition, an absorbent body and absorbent articles using the same, and a method for producing a water-absorbent resin composition. can provide.

The figure which represented typically the cross section of the filtration cylindrical tube for measuring the liquid permeability of a water-absorbent-resin composition. FIG. 3 is a perspective view schematically showing a pressurizing shaft and a weight for measuring the liquid permeability of the water absorbent resin composition.

<Water absorbent resin composition>
The water absorbent resin composition of the present embodiment is
one or more monomers (A1) selected from the group consisting of water-soluble unsaturated monocarboxylic acids (a1) and salts thereof, and monomers (a2) that become the water-soluble unsaturated monocarboxylic acids (a1) by hydrolysis; , one or more monomers (A2) selected from the group consisting of a water-soluble unsaturated dicarboxylic acid (a3) and a salt thereof, and a monomer (a4) that becomes the water-soluble unsaturated dicarboxylic acid (a3) by hydrolysis; A water-absorbing resin composition containing a cross-linked polymer (A) having a cross-linking agent (b) as a structural unit, and having a structure in which the surface of the cross-linked polymer (A) is cross-linked by the surface cross-linking agent (d). and
At least one of the monomer (A1) and the monomer (A2) has ^{a 14} C/C measured by a carbon radiocarbon dating method of 1.2×10 ⁻¹² to 1.0×10 ⁻¹⁶ . ,
The water retention capacity (g/g) of 0.9% by weight saline is 10-60, and the absorption under load (g/g) of 0.9% by weight saline is 12-25.

The water absorbent resin composition uses plant-derived raw materials that are useful for environmental conservation from the viewpoint of carbon neutrality, does not require removal of impurities contained in the raw materials during the manufacturing process, and It has the same level of absorption performance as a polyacrylic acid-based absorbent resin composition having a single monomer composition.

[Crosslinked polymer (A)]
[Monomer (A1)]
(Water-soluble unsaturated monocarboxylic acid (a1) and its salt)
The water-soluble unsaturated monocarboxylic acid (a1) can be used without particular limitation as long as it is a water-soluble unsaturated monocarboxylic acid. The water-soluble unsaturated monocarboxylic acid (a1) is preferably at least one selected from the group consisting of acrylic acid, methacrylic acid, and crotonic acid, from the viewpoint of water absorption performance when crosslinked and ease of availability. , acrylic acid, and methacrylic acid are more preferred.

Examples of the salt of the water-soluble unsaturated monocarboxylic acid (a1) include alkali metal (lithium, sodium, potassium, etc.) salts, alkaline earth metal (magnesium, calcium, etc.) salts and ammonium (NH ₄ ) salts. . Among these salts, alkali metal salts and ammonium salts are preferable, alkali metal salts are more preferable, and sodium salts are particularly preferable, from the viewpoint of absorption performance and the like.

(monomer (a2))
The monomer (a2) that becomes the water-soluble unsaturated monocarboxylic acid (a1) by hydrolysis can be used together with or instead of the water-soluble unsaturated monocarboxylic acid (a1). The monomer (a2) is not particularly limited, and a monomer having one hydrolyzable substituent that becomes a carboxy group by hydrolysis can be exemplified. Examples of the hydrolyzable substituent include acid anhydride-containing groups (1,3-oxo-1-oxapropylene group, -COO-CO-), ester bond-containing groups (alkyloxycarbonyl, vinyloxycarbonyl, allyl oxycarbonyl or propenyloxycarbonyl, —COOR), cyano group and the like. R is an alkyl group having 1 to 3 carbon atoms (methyl, ethyl and propyl), vinyl, allyl and propenyl.

In this specification, "water-soluble" means that at least 100 g dissolves in 100 g of water at 25°C. Further, the hydrolyzability of the monomer (a2) means the property of being hydrolyzed by the action of water and, if necessary, a catalyst (acid, base, etc.) to become water-soluble. The hydrolysis of the monomer (a2) may be carried out during polymerization, after polymerization, or both of them, but from the viewpoint of the absorption performance of the resulting water-absorbent resin composition, it is preferably carried out after polymerization.

[Monomer (A2)]
(Water-soluble unsaturated dicarboxylic acid (a3) and salts thereof)
The water-soluble unsaturated dicarboxylic acid (a3) can be used without particular limitation as long as it is a water-soluble unsaturated dicarboxylic acid. The water-soluble unsaturated dicarboxylic acid (a3) consists of maleic acid, fumaric acid, methylenesuccinic acid, and citraconic acid from the viewpoint of reactivity with the water-soluble unsaturated monocarboxylic acid (a1) and availability. One or more selected from the group is preferable, and methylenesuccinic acid is more preferable.

Examples of the salt of the water-soluble unsaturated dicarboxylic acid (a3) include alkali metal (lithium, sodium, potassium, etc.) salts, alkaline earth metal (magnesium, calcium, etc.) salts and ammonium (NH ₄ ) salts. Among these salts, alkali metal salts and ammonium salts are preferable, alkali metal salts are more preferable, and sodium salts are particularly preferable, from the viewpoint of absorption performance and the like.

(Monomer (a4))
The monomer (a4) that becomes the water-soluble unsaturated dicarboxylic acid (a3) by hydrolysis can be used together with or instead of the water-soluble unsaturated dicarboxylic acid (a3). The monomer (a4) is not particularly limited, and examples thereof include monomers having at least one hydrolyzable substituent.

The hydrolysis of the monomer (a4) may be performed during polymerization, after polymerization, or both of them, but from the viewpoint of the absorption performance of the resulting water-absorbent resin composition, it is preferably performed after polymerization.

At least one of the monomer (A1) and the monomer (A2) has ^{a 14} C/C measured by carbon radiocarbon dating of 1.2×10 ⁻¹² to 1.0×10 ⁻¹⁶ , preferably is 1.5×10 ⁻¹² to 1.2×10 ⁻¹⁴ . The radiocarbon age of carbon is specifically measured by the method described in Examples.

In the radiocarbon dating method of carbon, the carbon that existed as carbon dioxide in the atmosphere is incorporated into plants, and radiocarbon, which is carbon present in plant-derived raw materials synthesized using the plants as raw materials (i.e., Carbon 14) is measured. Since almost no carbon-14 atoms remain in fossil raw materials such as petroleum, the concentration of carbon-14 in the target sample is measured, and the content of carbon-14 in the atmosphere (107 pMC (percent modern carbon)) By calculating back using as an index, the ratio of biomass-derived carbon in the carbon contained in the sample can be obtained.

It is also possible to identify the origin of the raw material by measuring the stable carbon isotope ratio (δ ¹³ C). The stable carbon isotope ratio (δ ¹³ C) refers to three types of isotopes of carbon atoms that exist in nature (abundance ratio ¹² C: ¹³ C: ¹⁴ C = 98.9: 1.11: 1.2 x 10 ⁻¹² units; %), the ratio of ¹³ C to ¹² C, and the stable carbon isotope ratio is expressed as a deviation from a standard substance and refers to a value (δ value) defined by the following formula.
δ ¹³ C (‰) = [(δ ¹³ C/δ ¹² C) _sample / ( ¹³ C/ ¹² C) _PDB −1.0] × 1000

Here, [( ¹³ C/ ¹² C) _sample ] represents the stable isotope ratio of the measurement sample, and [( ¹³ C/ ¹² C) _PDB ] represents the stable isotope ratio of the standard substance. PDB is an abbreviation for "Pee Dee Belemnite" and means a fossil of a pilaster made of calcium carbonate (as a reference material, a fossil of a pilaster excavated from the PeeDee Formation in South Carolina), and has ^{a 13} C/ ¹² C ratio. used as a standard body for In addition, the "stable carbon isotope ratio (δ ¹³ C)" is measured by accelerator mass spectrometry (AMS method; Accelerator Mass Spectrometry). Since standard substances are scarce, a working standard with a known stable isotope ratio to the standard substance can also be used.

At least one of the monomer (A1) and the monomer (A2) preferably has a stable carbon isotope ratio (δ ¹³ C) of −60‰ to −5‰ from the viewpoint of environmental conservation, more preferably -50‰ to -10‰.

The ratio of the substance amount of the monomer (A1) to the substance amount of the monomer (A2) in the crosslinked polymer (A) (substance amount of the monomer (A1)/substance amount of the monomer (A2)) is the load From the standpoints of improving water absorption performance under conditions and protecting the environment, it is preferably from 99/1 to 1/99, more preferably from 99/1 to 10/90, still more preferably from 90/10 to 10/90.

In addition to the monomer (A1) and the monomer (A2), other vinyl monomers (A3) copolymerizable therewith can be used as structural units of the crosslinked polymer (A). One of the vinyl monomers (A3) may be used alone, or two or more of them may be used in combination.

The vinyl monomer (A3) is not particularly limited, and is known (for example, hydrophobic vinyl monomers disclosed in paragraphs 0028 to 0029 of Japanese Patent No. 3648553; 2005-75982, paragraph 0058) can be used, and specifically, vinyl monomers (i) to (iii) below can be used.
(i) Aromatic ethylenic monomer having 8 to 30 carbon atoms Styrene such as styrene, α-methylstyrene, vinyltoluene and hydroxystyrene, vinylnaphthalene, and halogen-substituted styrene such as dichlorostyrene.
(ii) Aliphatic ethylenic monomers having 2 to 20 carbon atoms Alkenes (ethylene, propylene, butene, isobutylene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, etc.); and alkadienes (butadiene, isoprene, etc.).
(iii) C5-C15 alicyclic ethylenic monomers monoethylenically unsaturated monomers (pinene, limonene, indene, etc.); and polyethylene vinyl monomers [cyclopentadiene, bicyclopentadiene, ethylidenenorbornene, etc.], and the like.

The content (mol%) of the vinyl monomer (A3) unit is preferably 0 to 5, based on the total number of moles of the monomer (A1) unit and the monomer (A2) unit, from the viewpoint of absorption performance and the like. It is more preferably 0 to 3, particularly preferably 0 to 2, and most preferably 0 to 1.5. From the viewpoint of absorption performance and the like, the content of the vinyl monomer (A3) unit is preferably 0 mol%. Most preferred.

[Crosslinking agent (b)]
The cross-linking agent (b) is not particularly limited and is known (for example, a cross-linking agent having two or more ethylenically unsaturated groups disclosed in paragraphs 0031 to 0034 of Japanese Patent No. 3648553, a water-soluble substituent and a A cross-linking agent having at least one functional group capable of reacting with at least one ethylenically unsaturated group and a cross-linking agent having at least two functional groups capable of reacting with a water-soluble substituent, JP-A-2003-165883 A cross-linking agent having two or more ethylenically unsaturated groups, a cross-linking agent having an ethylenically unsaturated group and a reactive functional group, and a cross-linking having two or more reactive substituents disclosed in paragraphs 0028 to 0031 of the publication crosslinkable vinyl monomers disclosed in paragraph 0059 of JP-A-2005-75982 and crosslinkable vinyl monomers disclosed in paragraphs 0015-0016 of JP-A-2005-95759). can.

The cross-linking agent (b) is preferably a cross-linking agent having two or more ethylenically unsaturated groups, and from the viewpoint of reactivity with monomers and water absorption properties, polyvalent (meta) having two or more ethylenically unsaturated groups More preferably one or more selected from the group consisting of allyl compounds and acrylamide compounds, poly (meth) allyl ethers of polyhydric alcohols such as alkylene glycol, trimethylolpropane, glycerin, pentaerythritol and sorbitol, tetraallyloxyethane and tri One or more selected from the group consisting of polyvalent (meth)allyl compounds such as allyl isocyanurate and compounds represented by the following general formula (1) are more preferred. The said crosslinking agent (b) may be used individually by 1 type, or may use 2 or more types together. From the viewpoint of reactivity and balance between water retention capacity and absorption capacity under load, it is more preferable to use poly(meth)allyl ether of polyhydric alcohol and a compound represented by the following general formula (1) in combination.

[In general formula (1), R ¹ and R ² are each independently a hydrogen atom or a methyl group. X ¹ is an n-valent organic group having an aliphatic group having 2 or more carbon atoms and optionally containing a nitrogen atom, an oxygen atom, or a sulfur atom, and the aliphatic group may be linear or branched. may have. n is an integer from 2 to 6; ]

In general formula (1), R ¹ and R ² are each independently a hydrogen atom or a methyl group. R ¹ and R ² are preferably hydrogen atoms from the viewpoint of good polymerization reactivity.

X ¹ is an n-valent organic group having an aliphatic group having 2 or more carbon atoms and optionally containing a nitrogen atom, an oxygen atom or a sulfur atom. The aliphatic group may be linear or branched.

The number of carbon atoms in the aliphatic group is 2 or more, preferably 30 or less, more preferably 15 or less, from the viewpoint of absorption performance and the like.

In the organic group, from the viewpoint of absorption performance, etc., the aliphatic group is from —O— and —NX ² — (wherein X ² is a hydrogen atom, an alkyl group, or a (meth)acryloyl group). It is preferable to connect via at least one selected divalent linking group. The linking group is preferably one or more selected from —O— and —NX ² — (where X ² is a (meth)acryloyl group) from the viewpoint of absorption performance and the like. The number of linking groups is preferably 1 to 4, more preferably 1 to 3, from the viewpoint of absorption performance and the like.

In the general formula (1), n is an integer of 2 to 6, and preferably an integer of 2 to 4 from the viewpoint of absorption performance and the like.

When n is 2 in the general formula (1), X ¹ is preferably an organic group represented by the following general formula (b1) or the following general formula (b2) from the viewpoint of absorption performance and the like.

[In general formula (b1), R ³ is an alkylene group having 1 to 6 carbon atoms, R ⁴ is a hydrogen atom or a methyl group, x is an integer of 2 to 4, and r is an integer of 1 to 6 and R ⁵ is a single bond or an alkylene group having 1 to 6 carbon atoms. ]

[R ⁶ is an alkylene group having 1 to 3 carbon atoms, y is an integer of 2 to 4, s is an integer of 1 to 6, and R ⁷ is a single bond or an alkylene group having 1 to 3 carbon atoms. be. ]

In general formula (b1), R ³ is an alkylene group having 1 to 6 carbon atoms, preferably an alkylene group having 1 to 3 carbon atoms, and more preferably an ethylene group, from the viewpoint of availability of raw materials.

In the general formula (b1), R ⁴ is a hydrogen atom or a methyl group, preferably a hydrogen atom, from the viewpoint of good polymerization reactivity.

In the general formula (b1), x is an integer of 2 to 4, preferably 2 or 3, more preferably 2, from the viewpoint of availability of raw materials.

In the general formula (b1), r is an integer of 1 to 6, preferably 1 or 2, from the viewpoint of availability of raw materials.

In general formula (b1), R ⁵ is a single bond or an alkylene group having 1 to 6 carbon atoms, preferably a single bond, from the viewpoint of availability of raw materials.

In general formula (b2), R ⁶ is an alkylene group having 1 to 3 carbon atoms, preferably an alkylene group having 2 or 3 carbon atoms, and more preferably a propylene group, from the viewpoint of availability of raw materials.

In the general formula (b2), y is an integer of 2 to 4, preferably 2, from the viewpoint of raw material availability.

In the general formula (b2), s is an integer of 1 to 6, preferably 2 to 5, more preferably 3 or 4, from the viewpoint of availability of raw materials.

In general formula (b2), R ⁷ is a single bond or an alkylene group having 1 to 3 carbon atoms, preferably a methylene group, from the viewpoint of availability of raw materials.

In the general formula (1), when X ¹ is an organic group represented by the general formula (b1), a specific example of the cross-linking agent (b) is represented by the following general formula (b1-1) Cross-linking agents (b1-1), cross-linking agents (b1-2) represented by the following general formula (b1-2), and the like.

In the general formula (1), when X ¹ is an organic group represented by the general formula (b2), a specific example of the cross-linking agent (b) is represented by the following general formula (b2-1). A cross-linking agent (b2-1), a cross-linking agent (b2-2) represented by the following general formula (b2-2), a cross-linking agent (b2-3) represented by the following general formula (b2-3), and the following general A cross-linking agent (b2-4) represented by the formula (b2-4), a cross-linking agent (b2-5) represented by the following general formula (b2-5), and a cross-linking agent represented by the following general formula (b2-6) (b2-6) and the like.

When n is 4 in the general formula (1), X ¹ is preferably an organic group represented by the following general formula (b3) from the viewpoint of absorption performance and the like.

In the general formula (b3), R ⁸ is a single bond or an alkylene group having 1 to 3 carbon atoms, preferably an alkylene group having 1 or 2 carbon atoms, more preferably a methylene group, from the viewpoint of availability of raw materials. preferable.

In the general formula (b3), z is an integer of 2 to 4, preferably 2 or 3, more preferably 2, from the viewpoint of raw material availability.

In the general formula (b3), t is an integer of 1 to 6, preferably an integer of 1 to 4, more preferably 1, from the viewpoint of availability of raw materials.

In the general formula (b3), R ⁹ is a single bond or an alkylene group having 1 to 3 carbon atoms, preferably an alkylene group having 1 or 2 carbon atoms, more preferably a methylene group, from the viewpoint of availability of raw materials. preferable.

In the general formula (1), when X ¹ is an organic group represented by the general formula (b3), a specific example of the cross-linking agent (b) is represented by the following general formula (b3-1). Examples thereof include a cross-linking agent (b3-1) and a cross-linking agent (b3-2) represented by the following general formula (b3-2).

Examples of commercially available products of the cross-linking agent (b) include FOM-03006, FOM-03007, FOM-03008, and FOM-03009 (all manufactured by FUJIFILM Corporation).

The content (mol%) of the cross-linking agent (b) in the cross-linked polymer (A) is, from the viewpoint of absorption performance, etc., the total number of moles of the monomer (A1) units and the monomer (A2) units, other When the vinyl monomer (A3) is used, it is preferably 0.001 to 5, more preferably 0.005 to 3, particularly preferably 0.005 to 1, based on the total number of moles of (A1) to (A3). is.

The water retention capacity of 0.9% by weight physiological saline of the crosslinked polymer (A) is preferably 20 g/g or more, more preferably 25 g/g or more.

The water absorbent resin composition has a structure in which the surface of the crosslinked polymer (A) is crosslinked by the surface crosslinking agent (d). When the monomer (A1) and the monomer (A2) are copolymerized, the dicarboxylic acid moiety derived from the monomer (A2) is more ordered than the monocarboxylic acid homopolymer derived from the monomer (A1). It can be assumed that the copolymer is likely to have a low molecular weight and the gel elasticity of the crosslinked polymer is low. By cross-linking the surface of the crosslinked polymer (A), the gel strength of the water-absorbing resin composition can be improved, and the water-absorbing resin composition satisfies the desired water retention capacity and absorption capacity under load. can be done. The surface cross-linking agent (d) can be inorganic or organic. As the surface cross-linking agent (d), known (polyvalent glycidyl compounds, polyvalent amines, polyvalent aziridine compounds and polyvalent isocyanate compounds described in JP-A-59-189103, etc., JP-A-58-180233 And the polyhydric alcohol of JP-A-61-16903, the silane coupling agent described in JP-A-61-211305 and JP-A-61-252212, the JP-A-5-508425 described Organic surface cross-linking agents such as alkylene carbonates and polyvalent oxazoline compounds described in JP-A-11-240959 can be used. Among these surface cross-linking agents, one or more selected from the group consisting of polyhydric glycidyl compounds, polyhydric alcohols and polyhydric amines is preferable from the viewpoint of economic efficiency and absorption characteristics. More preferably, one or more selected from the group consisting of, more preferably polyhydric glycidyl compounds, and still more preferably ethylene glycol diglycidyl ether. The surface cross-linking agent (d) may be used alone or in combination of two or more.

The water-absorbing resin composition may contain some other components such as residual solvent and residual cross-linking components within a range that does not impair its performance.

In addition, since the crosslinked polymer (A) contains an organic solvent that can be used in the surface cross-linking step of the method for producing a water-absorbent resin composition described later, the crosslinked polymer (A) is broken. It also has the advantage of contributing to prevention and stability against aging. This is because the diol or triol site in the solvent forms an ester site, i.e., a double bond, formed by the dicarboxylic acid site derived from the monomer (A2) in the crosslinked polymer (A) and the surface cross-linking agent (d). We speculate that the coordination to the oxygen site in the carbon-oxygen group increases the stability against nucleophilic attack.

The content of the organic solvent in the water absorbent resin composition is preferably 0.1% by weight or more from the viewpoint of preventing breakage of the crosslinked polymer (A) and improving stability against changes over time. And from the viewpoint of handleability, it is preferably 3.0% by weight or less. The content of the organic solvent in the water absorbent resin composition can be measured by the method described below.

In the water-absorbent resin composition, the other component is preferably selected from the group consisting of iodine, tellurium, antimony, and bismuth, from the viewpoint of improving gel strength, absorption under load, and gel flow rate at the time of water absorption. It contains at least one type of typical element. When the water-absorbent resin composition contains the typical element, the content of the typical element in the water-absorbent resin composition is adjusted from the viewpoint of improving the gel strength, the absorption amount under load, and the gel liquid permeation rate at the time of water absorption. , preferably 0.0005 to 0.1% by weight, more preferably 0.001 to 0.05% by weight. The water-absorbing resin composition containing the main group element is prepared by adding a monomer composition containing the monomer (A1) and the monomer (A2) and the cross-linking agent (b) in the presence of the organic main group element compound described later. It can be obtained by polymerizing and drying the resulting hydrous gel.

Other examples of the other ingredients include preservatives, antifungal agents, antibacterial agents, antioxidants, ultraviolet absorbers, antioxidants, colorants, fragrances, deodorants, liquid permeability improvers, and inorganic substances. Examples include powders and organic fibrous materials. The amount is usually 5% by weight or less based on the weight of the water absorbent resin composition.

Although the shape of the water-absorbing resin composition is not particularly limited, it is preferably particulate from the viewpoint of improving absorption performance. The particulate water absorbent resin composition (hereinafter also referred to as water absorbent resin particles) has a weight average particle diameter (μm) of 250-600, preferably 300-500, more preferably 340-460. When the weight-average particle size is less than 250 µm, the liquid permeability deteriorates, and when it exceeds 600 µm, the absorption speed deteriorates.

In addition, the weight average particle size was measured using a low-tap test sieve shaker and a standard sieve (JISZ8801-1:2006), Perry's Chemical Engineers Handbook 6th Edition (McGraw-Hill Book Company, 1984, page 21). That is, JIS standard sieves of 1000 μm, 850 μm, 710 μm, 500 μm, 425 μm, 355 μm, 250 μm, 150 μm, 125 μm, 75 μm and 45 μm and a saucer are combined in this order from the top. About 50 g of the particles to be measured are placed in the top sieve and shaken for 5 minutes with a Rotap test sieve shaker. The weight of the particles to be measured on each sieve and the tray is weighed, the total is 100% by weight, and the weight fraction of the particles on each sieve is obtained. ) and the weight fraction on the vertical axis], draw a line connecting the points, determine the particle diameter corresponding to a weight fraction of 50% by weight, and take this as the weight average particle diameter.

Since the smaller the content of the fine powder contained in the water absorbent resin particles, the better the liquid permeability, the weight ratio (weight %) is 3 or less, preferably 1 or less. The weight ratio of the water-absorbing resin particles having a particle size of less than 150 μm can be determined using the graph created when determining the weight average particle size.

The shape of the water-absorbent resin particles is not particularly limited, and examples thereof include irregular crushed shapes, scale-like shapes, pearl-like shapes, and grain-like shapes. Of these, irregularly crushed forms are preferred from the viewpoints of good entanglement with fibrous materials for use in paper diapers and the like, and no fear of falling off from fibrous materials.

<Method for producing water absorbent resin composition>
The method for producing the water absorbent resin composition of the present embodiment is a method for producing the water absorbent resin composition,
A polymerization step of obtaining a hydrous gel containing the crosslinked polymer (A);
A drying step of drying the hydrous gel;
and a surface cross-linking step of cross-linking the surface of the cross-linked polymer (A) after the drying step with a surface cross-linking agent (d).

[Polymerization process]
The polymerization step is a step of obtaining a hydrous gel containing the crosslinked polymer (A) by polymerizing a monomer composition containing the monomer (A1), the monomer (A2), and the crosslinking agent (b). . Examples of the method for polymerizing the monomer composition include known solution polymerization and known reversed-phase suspension polymerization.

Of the methods for polymerizing the monomer composition, preferred is the solution polymerization method, which does not require the use of an organic solvent and is advantageous in terms of production cost, and from the viewpoint of water absorption performance under load. The aqueous solution polymerization method is particularly preferable, and the aqueous solution adiabatic polymerization method is the most preferable in that a water-absorbent resin composition having a large water retention capacity and a small amount of water-soluble components can be obtained, and temperature control during polymerization is unnecessary. preferable.

When the monomer composition is polymerized by aqueous solution polymerization, a mixed solvent containing water and an organic solvent can be used, and the organic solvent includes methanol, ethanol, acetone, methyl ethyl ketone, N,N-dimethylformamide, Dimethylsulfoxide and mixtures of two or more thereof are included. When the monomer composition is polymerized by aqueous solution polymerization, the amount (% by weight) of the organic solvent used is preferably 40 or less, more preferably 30 or less based on the weight of water.

When a catalyst is used for polymerization, conventionally known radical polymerization catalysts can be used, for example, azo compounds [azobisisobutyronitrile, azobiscyanovaleric acid and 2,2′-azobis(2-amidinopropane) hydrochloride etc.], inorganic peroxides (hydrogen peroxide, ammonium persulfate, potassium persulfate and sodium persulfate, etc.), organic peroxides [benzoyl peroxide, di-t-butyl peroxide, cumene hydroperoxide, persuccinic acid oxide and di(2-ethoxyethyl) peroxydicarbonate, etc.] and redox catalysts (alkali metal sulfites or bisulfites, ammonium sulfite, ammonium bisulfite and reducing agents such as ascorbic acid and alkali metal persulfates, A combination with an oxidizing agent such as ammonium persulfate, hydrogen peroxide and organic peroxide). These catalysts may be used alone, or two or more of them may be used in combination.

The amount (% by weight) of the radical polymerization catalyst used is 0 based on the total weight of the monomers (A1) and (A2), and (A1) to (A3) when another vinyl monomer (A3) is used. 0.0005 to 5 is preferred, and 0.001 to 2 is more preferred.

At the time of polymerization, a polymerization control agent such as a chain transfer agent may be used in combination as necessary. Specific examples thereof include sodium hypophosphite, sodium phosphite, alkyl mercaptan, alkyl halide, thiocarbonyl compound etc. These polymerization control agents may be used alone, or two or more of them may be used in combination.

The amount (% by weight) of the polymerization control agent used is 0, based on the total weight of the monomers (A1) and (A2), and (A1) to (A3) when another vinyl monomer (A3) is used. 0.0005 to 5 is preferred, and 0.001 to 2 is more preferred.

The crosslinked polymer (A) is a monomer composition containing the monomers (A1) and (A2) and the crosslinking agent (b), and By polymerizing in the presence of at least one organic main group element compound selected from the group consisting of compounds, gel strength, absorption under load and gel permeation rate upon water absorption can be improved.

The organic iodine compound, the organic tellurium compound, the organic antimony compound, and the organic bismuth compound are not limited as long as they are organic main group element compounds that act as dormant species for radical polymerization, and are described as dormant species in WO2011/016166. Organic iodine compounds, organic tellurium compounds described in WO2004/014848, organic antimony compounds described in WO2006/001496, organic bismuth compounds described in WO2006/062255, and the like can be used. Among them, from the viewpoint of reactivity, an organic main group element compound represented by the following general formula (2) is preferable. These organic main group element compounds may be used alone or in combination of two or more.

In the general formula (2), R ¹⁰ and R ¹¹ are each independently a hydrogen atom, a saturated hydrocarbon group having 1 to 7 carbon atoms, or at least one non-addition polymerizable double bond or at least one non-addition polymerizable triple is a monovalent group having 1 to 7 carbon atoms and having a bond, and R ¹² is an m-valent saturated hydrocarbon group having 1 to 6 carbon atoms or at least one non-addition polymerizable double bond or at least one non- an m-valent group having 2 to 12 carbon atoms and an addition-polymerizable triple bond, provided that at least one of R ¹⁰ to R ¹² in one molecule is the corresponding non-addition-polymerizable divalent a group having a double bond or at least one non-addition polymerizable triple bond, m is an integer of 1 to 3, and when m is 1, R ¹⁰ and R ¹¹ may be bonded to each other; ³ is a monovalent organic main group element group containing tellurium, antimony or bismuth or an iodine group. In the present specification, non-addition polymerizable double bond (hereinafter also simply referred to as non-polymerizable double bond) and non-addition polymerizable triple bond (hereinafter simply referred to as non-polymerizable triple bond) means an unsaturated bond Of these, the bonds excluding addition-polymerizable unsaturated bonds (addition-polymerizable carbon-carbon double bonds and addition-polymerizable carbon-carbon triple bonds, respectively), non-addition-polymerizable double bonds and non-addition-polymerizable As the triple bond, the carbon-oxygen double bond contained in the carbonyl group, the carbon-nitrogen triple bond contained in the nitrile group, the carbon-carbon double bond that constitutes the aromatic hydrocarbon, and the oxygen that constitutes the heteroaromatic compound -Nitrogen double bonds and carbon-nitrogen double bonds, among others, carbon-oxygen double bonds contained in carbonyl groups, carbon-nitrogen triple bonds contained in nitrile groups and carbons constituting aromatic hydrocarbons - Carbon double bonds are preferred.

When R ¹⁰ and R ¹¹ are saturated hydrocarbon groups having 1 to 7 carbon atoms, the saturated hydrocarbon groups having 1 to 7 carbon atoms include linear saturated hydrocarbon groups having 1 to 7 carbon atoms (methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group and n-hexyl group) and branched saturated hydrocarbon groups having 1 to 7 carbon atoms (i-propyl group, isobutyl group, s-butyl group, t -butyl group, isopentyl group, neopentyl group, t-pentyl group, 1-methylbutyl group, isohexyl group, s-hexyl group, t-hexyl group, neohexyl group, heptyl group, etc.). Among them, straight-chain saturated hydrocarbon groups having 1 to 5 carbon atoms are preferable, and straight-chain saturated hydrocarbon groups having 1 to 3 carbon atoms are more preferable from the viewpoint of solubility and polymerizability.

When R ¹⁰ and R ¹¹ are C 1-7 monovalent groups having at least one non-polymerizable double bond or at least one non-polymerizable triple bond, preferred groups are carboxy (salt) groups. (carbon number 1, carbon-oxygen double bond), phenyl group (carbon number 6, non-polymerizable carbon-carbon double bond), cyano group (carbon number 1, carbon-nitrogen triple bond), cyanomethyl group (carbon number 2, carbon-nitrogen triple bond), cyanoethyl group (3 carbon atoms, carbon-nitrogen triple bond), cyanopropyl group (4 carbon atoms, carbon-nitrogen triple bond), cyanobutyl group (5 carbon atoms, carbon-nitrogen triple bond ), cyanopentyl group (6 carbon atoms, carbon-nitrogen triple bond), cyanohexyl group (7 carbon atoms, carbon-nitrogen triple bond), carboxymethyl group (2 carbon atoms, carbon-oxygen double bond), carboxyethyl group (3 carbon atoms, carbon-oxygen double bond), carboxypropyl group (4 carbon atoms, carbon-oxygen double bond), carboxybutyl group (5 carbon atoms, carbon-oxygen double bond), carboxypentyl group ( 6 carbon atoms, carbon-oxygen double bond), carboxyhexyl group (7 carbon atoms, carbon-oxygen double bond), benzyl group (7 carbon atoms, non-polymerizable carbon-carbon double bond), methoxycarbonyl group ( 2 carbon atoms, carbon-oxygen double bond), ethoxycarbonyl group (3 carbon atoms, carbon-oxygen double bond), propyloxycarbonyl group (4 carbon atoms, carbon-oxygen double bond), butyloxycarbonyl group ( 5 carbon atoms, carbon-oxygen double bond), pentyloxycarbonyl group (6 carbon atoms, carbon-oxygen double bond), hexyloxycarbonyl group (7 carbon atoms, carbon-oxygen double bond), hydroxyethoxycarbonyl group (C3, carbon-oxygen double bond), hydroxypropyloxycarbonyl group (4 carbons, carbon-oxygen double bond), hydroxybutyloxycarbonyl group (5 carbons, carbon-oxygen double bond), hydroxy Examples include a pentyloxycarbonyl group (6 carbon atoms, carbon-oxygen double bond) and a hydroxyhexyloxycarbonyl group (7 carbon atoms, carbon-oxygen double bond), and more preferably a carboxy (salt) group, cyano group, carboxymethyl group, and carboxyethyl group. Examples of salts include alkali metal (lithium, sodium, potassium, etc.) salts, alkaline earth metal (magnesium, calcium, etc.) salts, ammonium (NH ₄ ) salts, and the like. Among these salts, alkali metal salts and ammonium salts are preferable, alkali metal salts are more preferable, and sodium salts are particularly preferable, from the viewpoint of absorption performance and the like.

R ¹² is an m-valent saturated hydrocarbon group having 1 to 7 carbon atoms or an m-valent group having 2 to 12 carbon atoms and having at least one non-polymerizable double bond or at least one non-polymerizable triple bond; , m is an integer from 1 to 3.

Among the m-valent saturated hydrocarbon groups having 1 to 7 carbon atoms represented by R ¹² , the monovalent saturated hydrocarbon group having 1 to 7 carbon atoms is a linear saturated hydrocarbon group having 1 to 7 carbon atoms. (methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, heptyl group, etc.) and branched saturated hydrocarbon groups having 1 to 7 carbon atoms (i-propyl group, isobutyl group, etc.) group, s-butyl group, t-butyl group, isopentyl group, neopentyl group, t-pentyl group, 1-methylbutyl group, isohexyl group, s-hexyl group, t-hexyl group, neohexyl group, isoheptyl group, etc.). be done. Among the m-valent saturated hydrocarbon groups having 1 to 7 carbon atoms represented by R ¹² , the divalent saturated hydrocarbon group having 1 to 7 carbon atoms is a linear saturated divalent hydrocarbon group having 1 to 7 carbon atoms. Hydrocarbon groups (methylene group, ethylene group, propylene group, butylene group, pentene group, hexene group, heptene group, etc.) and divalent branched saturated hydrocarbon groups having 1 to 7 carbon atoms (isopropylene group, isobutylene group, s -butylene group, t-butylene group, isopentylene group, neopentylene group, t-pentylene group, 1-methylbutylene group, isohexylene group, s-hexylene group, t-hexylene group, neohexylene group, isoheptylene group, etc.). Among the m-valent saturated hydrocarbon groups having 1 to 7 carbon atoms represented by R ¹² , trivalent saturated hydrocarbon groups having 1 to 7 carbon atoms include a methine group and the like. Of the m-valent saturated hydrocarbon groups having 1 to 7 carbon atoms represented by R ¹² , methyl group, methylene group and methine group are preferred, and methyl group and methylene group are more preferred.

Among m-valent groups in which R ¹² has 2 to 12 carbon atoms and at least one non-polymerizable double bond or at least one non-polymerizable triple bond, the monovalent groups include R ¹⁰ and R ¹¹ Examples include the same groups as the exemplified groups, and preferred ones are also the same. When R ¹² is a divalent group having 2 to 12 carbon atoms and having at least one non-polymerizable double bond or at least one non-polymerizable triple bond, preferred groups include a benzenediyl group (6 carbon atoms , non-polymerizable carbon-carbon double bond), 1-methoxycarbonyl-carbonyloxyethyleneoxycarbonyl group (6 carbon atoms, oxygen-oxygen double bond) and carbonyloxyethylenecarbonyl group (4 carbon atoms, oxygen-oxygen two double bond) and the like. When R ¹² is a trivalent group having 2 to 12 carbon atoms having at least one non-polymerizable double bond or at least one non-polymerizable triple bond, it is preferably a benzenetriyl group (having 6, non-polymerizable carbon-carbon double bond) and 2-carbonyloxy-carbonyloxypropylenecarbonyl group (5 carbon atoms, oxygen-oxygen double bond).

When m is 1, R ¹⁰ and R ¹¹ may be bonded to each other, and preferred groups having a ring structure formed by bonding R ¹⁰ and R ¹¹ are γ-butyrolactonyl and A fluorenyl group and the like can be mentioned. The group in which R ¹⁰ and R ¹¹ are bonded together to form a ring structure includes the carbon atom to which R ¹⁰ and R ¹¹ are bonded in the ring structure.

^X3 is a monovalent organic main group element group containing tellurium, antimony or bismuth or an iodine group, preferably methyltheranyl, dimethylstivanyl, dimethylbismutanyl and iodine. Among them, a methylteranyl group and an iodo group are more preferred, and an iodo group is most preferred.

Examples of the organic main element compound represented by the general formula (2) include 2-iodopropionitrile, 2-methyl-2-iodopropionitrile, α-iodobenzyl cyanide, 2-iodopropionamide, ethyl -2-methyl-2-iodo-propionate, methyl 2-methyl-iodopropionate, 2-methyl-propyl iodopropionate, butyl 2-methyl-iodopropionate, 2-methyl-pentyl iodopropionate, 2-methyl - hydroxyethyl iodopropionate, 2-methyl-2-iodo-propionic acid (salt), 2-iodopropionic acid (salt), 2-iodoacetic acid (salt), methyl 2-iodoacetate, ethyl 2-iodoacetate, Ethyl 2-iodopentanoate, Methyl 2-iodopentanoate, 2-iodopentanoic acid (salt), 2-iodohexanoic acid (salt), 2-iodoheptanoic acid (salt), diethyl 2,5-diiodoadipate , 2,5-diiodoadipate (salt), dimethyl 2,6-diiodo-heptanedioate, 2,6-diiodo-heptanedioic acid (salt), α-iodo-γ-butyrolactone, 2-iodoacetophenone, Benzyl iodide, 2-iodo-2-phenylacetic acid (salt), methyl 2-iodo-2-phenylacetate, ethyl 2-iodo-2-phenylacetate, 1,4-bis(1'-iodoethyl)benzene, ethylene Glycol bis(2-methyl-2-iodopropionate), tris(2-methyl-iodopropionate) glycerol, 1,3,5-tris(1′-iodoethylbenzene), ethylene glycol bis(2-iodo-2 phenyl acetate), etc. Among them, 2-methyl-2-iodopropionitrile, ethyl-2-methyl-2-iodo-propionate, 2-methyl-2-iodo-propionic acid (salt ), 2-iodoacetic acid (salt), methyl 2-iodoacetate, diethyl 2,5-diiodoadipate, 2,5-diiodoadipate, ethylene glycol bis(2-methyl-2-iodo-propinate), Ethylene glycol bis(2-iodo-2phenylacetate) can be mentioned.

The amount of the organic main group element compound used is preferably 0.0005 to 0.1% by weight, more preferably 0.005 to 0.05% by weight.

When suspension polymerization or reverse-phase suspension polymerization is used as the polymerization method, polymerization may be carried out in the presence of a conventionally known dispersant or surfactant, if necessary. In the case of the reversed-phase suspension polymerization method, the polymerization can be carried out using conventionally known hydrocarbon solvents such as xylene, normal hexane and normal heptane.

The polymerization initiation temperature can be appropriately adjusted depending on the type of catalyst used, but is preferably 0 to 100°C, more preferably 2 to 80°C.

When using a solvent (organic solvent, water, etc.) for polymerization, it is preferable to distill off the solvent after polymerization. When the solvent contains an organic solvent, the content (% by weight) of the organic solvent after distillation is preferably 0 to 10, more preferably 0 to 5, particularly preferably 0 to 5, based on the weight of the crosslinked polymer (A). is 0-3, most preferably 0-1. Within this range, the absorption performance of the water absorbent resin composition is further improved.

When the solvent contains water, the water content (% by weight) after distillation is preferably 0 to 20, more preferably 1 to 10, particularly preferably 2 to 9, based on the weight of the crosslinked polymer (A). Most preferably 3-8. Within this range, the absorption performance is further improved.

A water-containing gel-like substance (hereinafter also referred to as a water-containing gel) in which the crosslinked polymer (A) contains water can be obtained by the polymerization method described above.

The hydrous gel may be neutralized with a base. The degree of neutralization of acid groups is preferably 50 to 80 mol %. If the degree of neutralization is less than 50 mol %, the resulting hydrous gel polymer will have high adhesiveness, and workability during production and use may deteriorate. Furthermore, the water-retaining capacity of the obtained water-absorbent resin composition may decrease. On the other hand, if the degree of neutralization exceeds 80%, the resulting resin will have a high pH and may be unsafe for human skin.

The neutralization may be performed at any stage after the polymerization of the crosslinked polymer (A) in the production of the water-absorbent resin composition. exemplified as

As the neutralizing base, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and alkali metal carbonates such as sodium carbonate, sodium hydrogencarbonate and potassium carbonate can usually be used.

The content and water content of the organic solvent were measured using an infrared moisture meter [JE400 manufactured by KETT Co., Ltd., etc.: 120 ± 5 ° C., 30 minutes, atmospheric humidity before heating 50 ± 10% RH, lamp specifications 100 V, 40 W ] is obtained from the weight loss of the measurement sample when heated by

[Shredding process]
The method for producing the water-absorbing resin composition of the present embodiment may have a shredding step of shredding the hydrous gel, if necessary. The size (maximum diameter) of the gel after shredding is preferably 50 μm to 10 cm, more preferably 100 μm to 2 cm, particularly preferably 1 mm to 1 cm. Within this range, the drying property in the drying step is further improved.

Shredding can be performed by a known method, and can be performed using a shredding device (eg, Vex mill, rubber chopper, farmer mill, mincing machine, impact pulverizer, and roll pulverizer).

[Drying process]
The method for producing a water-absorbent resin composition of the present embodiment has a drying step of drying the water-containing gel and distilling off the solvent (including water) in the water-containing gel to obtain the crosslinked polymer (A).

In the drying step, the method of distilling off the solvent in the hydrous gel includes a method of distilling (drying) with hot air at a temperature of 80 to 230 ° C., and a thin film drying method using a drum dryer or the like heated to 100 to 230 ° C. , (heating) vacuum drying method, freeze drying method, infrared drying method, decantation, filtration, and the like can be applied.

[Pulverization process]
The method for producing a water absorbent resin composition of the present embodiment includes a pulverizing step of pulverizing the crosslinked polymer (A) obtained in the drying step to obtain the crosslinked polymer (A) in the form of particles. may

In the pulverization step, the method for pulverizing the crosslinked polymer (A) is not particularly limited, and a pulverizing device (e.g., hammer pulverizer, impact pulverizer, roll pulverizer, and jet stream pulverizer). etc. can be used. The pulverized crosslinked polymer (A) can be adjusted in particle size by sieving or the like, if necessary.

[Surface cross-linking step]
The method for producing a water absorbent resin composition of the present embodiment has a surface cross-linking step of cross-linking the surface of the cross-linked polymer (A) obtained in the drying step with the surface cross-linking agent (d).

The amount (% by weight) of the surface cross-linking agent (d) used is not particularly limited because it can be varied depending on the type of the surface cross-linking agent, cross-linking conditions, target performance, etc., but is not particularly limited from the viewpoint of absorption characteristics and the like. Therefore, it is preferably 0.001 to 3, more preferably 0.005 to 2, and particularly preferably 0.01 to 1.5, based on the weight of the crosslinked polymer (A).

The surface cross-linking of the cross-linked polymer (A) can be performed by mixing the cross-linked polymer (A) and the surface cross-linking agent (d) and heating. Examples of the method for mixing the crosslinked polymer (A) and the surface cross-linking agent (d) include a cylindrical mixer, a screw mixer, a screw extruder, a turbulizer, a Nauta mixer, a twin-arm kneader, a fluid A crosslinked polymer ( A method of uniformly mixing A) and the surface cross-linking agent (d) can be mentioned.

When mixing the crosslinked polymer (A) and the surface cross-linking agent (d), from the viewpoint of uniformly mixing the crosslinked polymer (A) and the surface cross-linking agent (d), the surface cross-linking agent (d) is preferably used after being diluted with water and/or any solvent.

The solvent used when mixing the crosslinked polymer (A) and the surface cross-linking agent (d) refers to a liquid substance that does not chemically react during surface cross-linking. Examples of the solvent include organic solvents such as propylene glycol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol and glycerin. The solvent may be used alone or in combination of two or more. The solvent is preferably an organic solvent having a boiling point of 100° C. or higher, more preferably diethylene glycol, from the viewpoint of improving the reactivity of the surface cross-linking agent (d) and absorption performance. By using a solvent having a boiling point of 100° C. or higher, volatilization is suppressed when the crosslinked polymer (A) and the surface cross-linking agent (d) are reacted under heating, uniformity of cross-linking is improved, and absorption performance is improved. quality can be more stable. In addition, by using a carbon-neutral raw material for the solvent, the carbon-neutrality of the water-absorbing resin composition itself can be improved.

By using a polar solvent as a solvent when mixing the crosslinked polymer (A) and the surface cross-linking agent (d), the monomer (A1) and/or the monomer ( When the carboxyl group derived from A2) reacts with the surface cross-linking agent (d), it is assumed that the polar solvent temporarily coordinates with the surface cross-linking agent (d), thereby promoting the reaction. In particular, a polar solvent having a diol, triol, or the like in the structure of the polar solvent is coordinated to the unneutralized carboxy group site of the monomer (A2) to donate electrons, thereby easily releasing protons from the carboxy group. This proton coordinates with a reactive group such as a glycidyl group in the surface cross-linking agent (d) to promote the reaction. As a result, it can be inferred that uniform surface cross-linking can be achieved, and excellent absorption performance can be achieved even with a cross-linked copolymer having a dicarboxylic acid, which is inferior in gel strength to an acrylic acid homopolymer.

When a solvent is used in combination with water when the crosslinked polymer (A) is surface-crosslinked with the surface-crosslinking agent (d), the amount of the solvent used can be appropriately adjusted depending on the type of solvent. From the viewpoint of performance, it is preferably 0.1 to 10% by weight based on the crosslinked polymer (A) before surface crosslinking. Also, the ratio of solvent to water can be arbitrarily adjusted, but is preferably 1 to 70% by weight, more preferably 2 to 60% by weight. By setting the amount of the solvent used to be at least the above lower limit, the surface cross-linking agent (d) can be uniformly added to the crosslinked polymer (A), and the balance between the water retention amount and the absorption amount under load is further improved. .

The temperature at which the crosslinked polymer (A) and the surface cross-linking agent (d) are mixed is not particularly limited, but is preferably 10 to 150°C, more preferably 20 to 100°C, and particularly preferably 25 to 80°C. .

After mixing the crosslinked polymer (A) and the surface cross-linking agent (d), heat treatment is usually performed. The heating temperature is preferably 100 to 180°C, more preferably 110 to 175°C, particularly preferably 120 to 170°C, from the viewpoint of breaking resistance of the water absorbent resin. Heating at 180° C. or less enables indirect heating using steam, which is advantageous in terms of facilities. Heating temperatures below 100° C. may result in poor absorption performance. The heating time can be appropriately set depending on the heating temperature, but from the viewpoint of absorption performance, it is preferably 5 to 60 minutes, more preferably 10 to 40 minutes. It is also possible to further surface-crosslink the water-absorbing resin obtained by surface-crosslinking using a surface-crosslinking agent that is the same as or different from the surface-crosslinking agent used first.

After cross-linking the surface of the cross-linked polymer (A) with the surface cross-linking agent (d), the particle size is adjusted by sieving if necessary. The average particle size of the obtained particles is preferably 100-600 μm, more preferably 200-500 μm. The content of fine particles is preferably as small as possible, the content of particles of 100 μm or less is preferably 3% by weight or less, and the content of particles of 150 μm or less is more preferably 3% by weight or less.

In the method for producing the water absorbent resin composition of the present embodiment, the plant-derived raw material may be added after the polymerization step. The method of adding the plant-derived raw material is not particularly limited, and includes a method of kneading with the hydrous gel, a method of shredding the hydrous gel by adding the plant-derived raw material in the shredding step, and a water-absorbing resin obtained in the drying step. and a method of kneading a plant-derived raw material, and a method of mixing a cross-linked polymer (A), a surface cross-linking agent (d), and a plant-derived raw material in the surface cross-linking step. From the viewpoint of absorption performance and productivity, it is preferable to add the water-containing gel particles obtained in the shredding step and/or the gel shredding step during the drying step.

Plant-derived raw materials include the water-soluble unsaturated dicarboxylic acid (a3) and salts thereof, as well as oils and fats, proteins, fibers, extracts, sugars, and the like. Among these, fats and oils, fibers, and sugars are preferred from the viewpoint of water absorption performance, and fibers and sugars are more preferred, and the stable carbon isotope ratio (δ ¹³ C) is from −60‰ to −5‰, And if the ¹⁴ C/C measured by the carbon radiocarbon dating method satisfies 1.2×10 ⁻¹² to 1.0×10 ⁻¹⁶ , part or all of it is chemically modified or a mixture thereof.

Fats and oils include soybean oil, coconut oil, palm oil, palm kernel oil, corn oil, olive oil, safflower oil, safflower oil, cottonseed oil, rapeseed oil, castor oil, sesame oil, and the like.

Fibers include vegetable fibers, and vegetable fibers include kenaf, jute hemp, manila hemp, sisal hemp, ganpi, kozo, banana, pineapple, coconut palm, corn, sugar cane, bagasse, palm, papyrus, reed, Coniferous trees such as esparto, surviving grass, barley, rice, bamboo, cedar and cypress, broad-leaved trees, and fibers of various plants such as cotton.

Sugars include fructose, glucose, lactose, maltose, galactose, sucrose, starch, cellulose, and cellulose derivatives.

Methods for kneading the hydrous gel or water-absorbent resin composition and the plant-derived raw material include cylindrical mixers, screw mixers, screw extruders, turbulizers, Nauta mixers, double-arm kneaders, Mix uniformly using a mixing device such as a fluidized mixer, a V-shaped mixer, a mincing mixer, a ribbon mixer, a fluidized mixer, an airflow mixer, a rotating disk mixer, a conical blender, and a roll mixer. method.

Furthermore, at any stage, water, preservatives, antifungal agents, antibacterial agents, antioxidants, ultraviolet absorbers, antioxidants, coloring agents, fragrances, deodorants, liquid permeability improvers, inorganic powders and An organic fibrous material or the like can be added, and the amount thereof is usually 5% by weight or less based on the weight of the water absorbent resin composition. Moreover, if necessary, it may have a foamed structure, and may be granulated or molded.

The content of the crosslinked polymer (A) in the water absorbent resin composition is preferably 50 to 99.5% by weight, more preferably 60 to 99% by weight. When the content of the crosslinked polymer is 50% or more, it is possible to obtain a water absorbent resin composition having sufficient water retention capacity.

The water retention capacity (g/g) of 0.9% by weight physiological saline of the water absorbent resin composition is 10-60. The water retention capacity (g/g) of the water absorbent resin composition can be measured by the method described later, and is preferably 15 or more, more preferably 18 or more, and particularly preferably 20 or more from the viewpoint of absorption capacity. . From the viewpoint of stickiness, the upper limit is preferably 55 or less, more preferably 50 or less, and particularly preferably 45 or less. The amount of water retention can be appropriately adjusted by the amount (% by weight) of the cross-linking agent (b) and the surface cross-linking agent (d) used.

The gel permeation rate (ml/min) of the water-absorbing resin composition can be measured by the method described later, and is preferably 3 to 300, more preferably 5 to 200, from the viewpoint of diaper absorption rate. Particularly preferably, it is 10-180. It is empirically known that the gel permeation rate conflicts with the water retention capacity, and there are cases where a high water retention capacity is required and there are cases where a high gel permeation rate is required depending on the configuration of the diaper.

The absorption amount (g/g) of 0.9% by weight of physiological saline under load of the water-absorbing resin composition can be measured by the method described later, and from the viewpoint of the absorption amount of diapers under load, it is preferably 12 to 25, more preferably 15 to 25, particularly preferably 18 to 23. It is empirically known that the absorbency under load conflicts with the water retention capacity, and there are cases where a high water retention capacity is required and cases where a high gel permeation rate is required depending on the configuration of the diaper.

<Absorber>
An absorbent body can be obtained using the water absorbent resin composition. As the absorbent, the water absorbent resin composition may be used alone, or may be used together with other materials to form an absorbent. Such other materials include fibrous materials and the like. The structure and manufacturing method of the absorbent when used with fibrous materials are the same as those of known ones (Japanese Patent Laid-Open Nos. 2003-225565, 2006-131767 and 2005-097569). be.

Cellulose fibers, organic synthetic fibers, and mixtures of cellulosic fibers and organic synthetic fibers are preferable as the fibrous material.

Examples of cellulosic fibers include natural fibers such as fluff pulp, and cellulosic chemical fibers such as bicose rayon, acetate and cupra. The raw material (softwood, hardwood, etc.), manufacturing method (chemical pulp, semi-chemical pulp, mechanical pulp, CTMP, etc.), bleaching method, and the like of this cellulose-based natural fiber are not particularly limited.

Examples of organic synthetic fibers include polypropylene fibers, polyethylene fibers, polyamide fibers, polyacrylonitrile fibers, polyester fibers, polyvinyl alcohol fibers, polyurethane fibers, and heat-fusible composite fibers (the above fibers having different melting points). (sheath-and-core type, eccentric type, side-by-side type, etc.), fibers obtained by blending at least two of the above fibers, and fibers obtained by modifying the surface layer of the above fibers.

Among these fibrous materials, cellulosic natural fibers, polypropylene fibers, polyethylene fibers, polyester fibers, heat-fusible conjugate fibers and mixed fibers thereof are preferred, and more preferred are fluff pulp, heat-fusible conjugate fibers and mixed fibers thereof in that they are excellent in shape retention after water absorption by the water absorbing agent.

The length and thickness of the above-mentioned fibrous material are not particularly limited, and if the length is in the range of 1 to 200 mm and the thickness is in the range of 0.1 to 100 denier, it can be suitably used. The shape is not particularly limited as long as it is fibrous, and examples include a thin cylindrical shape, a split yarn shape, a staple shape, a filament shape, a web shape, and the like.

When the water absorbent resin particles are used as an absorber together with fibrous materials, the weight ratio of the water absorbent resin particles and fibers (weight of water absorbent resin particles/weight of fibrous materials) is 40/60 to 90/10. It is preferably 70/30 to 80/20, more preferably 70/30 to 80/20.

<Absorbent article>
An absorbent article can be obtained using the water absorbent resin composition. Specifically, the absorber described above is used. Absorbent products include not only sanitary products such as paper diapers and sanitary napkins, but also anti-condensation agents, water retention agents for agriculture and gardening, soil solidification agents, disaster sandbags, waste blood solidification agents, disposable body warmers, refrigerants, and alkaline batteries. It can be used for various purposes such as absorption of various aqueous liquids, retention agent use, and gelling agent use in various industrial fields such as cosmetics, pet sheets, and cat litter. The manufacturing method of the absorbent article and the like are the same as those known (described in JP-A-2003-225565, JP-A-2006-131767, JP-A-2005-097569, etc.).

EXAMPLES The present invention will be further described with reference to Examples and Comparative Examples below, but the present invention is not limited to these. Hereinafter, unless otherwise specified, parts indicate parts by weight and % indicates % by weight. The water retention capacity of the water-absorbing resin against physiological saline, absorption under load, liquid permeability, and radiocarbon dating ( ¹⁴ C/C) were measured by the following methods.

<Method for measuring water retention>
Put 1.00 g of the measurement sample in a tea bag (20 cm long, 10 cm wide) made of nylon mesh with an opening of 63 μm (JIS Z8801-1: 2006), and put it in 1,000 ml of physiological saline (salt concentration 0.9%). After being immersed for 1 hour without stirring, it was taken out and hung for 15 minutes to drain. After that, the whole tea bag was placed in a centrifuge and dehydrated by centrifugation at 150 G for 90 seconds to remove excess physiological saline. The physiological saline used and the temperature of the measurement atmosphere were 25°C ± 2°C.
Water retention amount (g/g) = (h1) - (h2)
In addition, (h2) is the weight of the tea bag measured by the same operation as above without the measurement sample.

<Method for measuring absorption under load>
In a cylindrical plastic tube (inner diameter: 25 mm, height: 34 mm) with a mesh opening of 63 μm (JIS Z8801-1: 2006) attached to the bottom, 250 to 500 μm using a 30 mesh sieve and a 60 mesh sieve. Weigh 0.16 g of the measurement sample sieved to the range, vertical the cylindrical plastic tube, arrange the measurement sample on the nylon mesh so that the thickness is almost uniform, and put a weight (weight: 306.2 g, outer diameter: 24.5 mm,) was placed. After measuring the weight (M1) of the entire cylindrical plastic tube, a cylindrical plastic tube containing a measurement sample and a weight in a petri dish (diameter: 12 cm) containing 60 ml of physiological saline (salt concentration 0.9%) The tube was placed vertically, immersed with the nylon mesh side down, and allowed to stand for 60 minutes. After 60 minutes, the cylindrical plastic tube was pulled up from the petri dish, tilted to collect the water adhering to the bottom in one place, and dripped down to remove excess water. The weight (M2) of the entire cylindrical plastic tube was weighed, and the absorption under load was obtained from the following formula. The physiological saline used and the temperature of the measurement atmosphere were 25°C ± 2°C.
Absorption under load (g/g) = {(M2) - (M1)}/0.16

<Method for measuring liquid permeability>
It was measured by the following operation using the instrument shown in FIGS.
Swollen gel particles 2 were prepared by immersing 0.32 g of the measurement sample in 150 ml of physiological saline 1 (salt concentration: 0.9%) for 30 minutes. A vertical cylinder 3 (diameter (inner diameter) 25.4 mm, length 40 cm) has scale lines 4 and 5 at positions 60 ml and 40 ml from the bottom, respectively. } at the bottom of the filtration cylindrical tube having a wire mesh 6 (opening 106 μm, JIS Z8801-1: 2006) and a freely openable and closable cock 7 (inner diameter of the liquid passing part 5 mm), with the cock 7 closed, After transferring the prepared swollen gel particles 2 together with a physiological saline solution, a circular wire mesh 8 (opening 150 μm, diameter 25 mm) was placed on the swollen gel particles 2, and a pressurizing shaft 9 (heavy weight) was attached perpendicularly to the surface of the wire mesh. 22 g in length and 47 cm in length) was placed so that the wire mesh and the swollen gel particles were in contact with each other, and a weight 10 (88.5 g) was placed on the pressure shaft 9 and allowed to stand for 1 minute. Subsequently, open the cock 7, measure the time (T1; seconds) required for the liquid level in the filtration cylindrical tube to change from the 60 ml scale line 4 to the 40 ml scale line 5, and use the following formula to obtain the gel flow rate (ml / min). was obtained to evaluate the liquid permeability.
Gel permeation rate (ml / min) = 20ml × 60 / (T1-T2)
The physiological saline used and the temperature of the measurement atmosphere were set at 25° C.±2° C., and T2 is the time measured by the same operation as above without the measurement sample.

<Method for measuring residual solvent>
5.0 g of the water-absorbent resin composition was taken, sufficiently cooled with liquid nitrogen, and pulverized with a freezer pulverizer (manufactured by Japan Analytical Industry Co., Ltd., model number: JFL-300). 2.000 g of the pulverized water absorbent resin composition was put into a 50 ml screw tube, 20 ml of 80% aqueous methanol solution and a stirrer were put thereinto, and then the tube was covered. After stirring at 400 rpm for 1.5 hours under airtight conditions, the mixture was allowed to stand for 10 minutes. Next, 5 ml of the supernatant of the screw tube was recovered, filtered through a membrane filter (sample pretreatment filter, GL chromatodisc, pore size: 0.2 μm, manufactured by GL Sciences Inc.), and the filtrate was injected into the gas chromatograph with a syringe. , was measured. By comparing this measured value with the calibration curve, the amount of organic solvent in the water absorbent resin composition was determined.
[Measurement condition]
(1) Apparatus: Gas Chromatograph Nexis GC-2030, manufactured by Shimadzu Corporation (2) Column: "ZB-WAX 30 m × 0.25 mmφ × 0.25 µm"
(3) Eluent: methanol/water = 80/20 (volume ratio)
(4) Injection conditions: carrier gas: nitrogen, column flow rate: 1.47 ml/min, column temperature: 80°C
(5) Calibration curve: 0.600 g of an organic solvent to be measured was placed in a 20 ml volumetric flask, and diluted with a 60% methanol aqueous solution to prepare a sample to give a 3% by weight solution.
Then, using the 3% weight solution, 0.3%, 0.2% and 0.1% by weight concentration calibration curves were prepared.

<Radiocarbon dating method ( ¹⁴ C/C)>
By measuring the concentration of carbon-14 in the sample and calculating backward using the content of carbon-14 in the atmosphere (107 pMC (percent modern carbon)) as an index, the ratio of carbon-14 in the carbon contained in the sample is obtained. rice field. The sample (water-absorbent resin) is converted to CO ₂ from the constituent carbon, or the obtained CO ₂ is further converted to graphite (C), and then subjected to an accelerator mass spectrometer (AMS) and subjected to a standard substance (for example, US NIST Shu The content of carbon-14 relative to the acid) was determined by comparative measurement, and evaluated according to the following criteria.
〔criterion〕
○: ¹⁴ C/C is 1.2×10 ^-12 to 1.0×10 ^-16
×: ¹⁴ C/C is less than 1.0×10 ⁻¹⁶

<Example 1>
Acrylic acid (a1-1) (manufactured by Mitsubishi Chemical) 279 parts, methylene succinic acid (manufactured by Fuso Chemical Industry) 31 parts, internal cross-linking agent (b-1) N, N'-{(2-acrylamide-2-[( 3-acrylamidopropoxy)methyl]propane-1,3-diyl)bis(propane-1,3-diyl)}diacrylamide (manufactured by Wako Pure Chemical Industries, product name FOM-03006) 0.3 parts and 680 parts of deionized water was kept at 3°C while stirring and mixing. After flowing nitrogen into this mixture to make the dissolved oxygen content 1 ppm or less, 4.6 parts of a 2% 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide] aqueous solution, 1.2 parts of 1% aqueous hydrogen peroxide solution, 2.3 parts of 2% aqueous ascorbic acid solution and 1.6 parts of 0.03% iron sulfate heptahydrate aqueous solution were added and mixed to initiate polymerization. After the temperature of the mixture reached 80° C., polymerization was carried out at 80±2° C. for about 12 hours to obtain a hydrous gel.

Next, while chopping 500 parts of this hydrous gel with a mincing machine (12VR-400K manufactured by ROYAL), 129 parts of a 48.5% sodium hydroxide aqueous solution is added and mixed and neutralized, resulting in a neutralized gel (neutralized degree: 72%). Further, the neutralized water-containing gel was dried for 50 minutes in a ventilated dryer {150° C., wind speed 2 m/sec} to obtain a dry product. The dried product was pulverized with a juicer mixer (Osterizer Blender manufactured by Oster), sieved, and adjusted to a particle size range of 710 to 150 μm in opening to obtain a crosslinked polymer (A-1).

Then, 100 parts of the obtained crosslinked polymer (A-1) was stirred at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron: number of rotations: 2000 rpm), and ethylene glycol diglycidyl ether as an organic surface cross-linking agent (d) was added to 0. 0.8 parts of propylene glycol, and 1.5 parts of water are added and mixed uniformly, followed by heating at 140° C. for 40 minutes to obtain the water absorbent resin particles of the present invention (P- 1) was obtained.

<Example 2>
In Example 1, 279 parts of acrylic acid (a1-1) and 31 parts of methylene succinic acid (manufactured by Fuso Chemical Industry) were replaced with 248 parts of acrylic acid (a1-1) (manufactured by Mitsubishi Chemical) and methylene succinic acid (manufactured by Fuso Chemical Industry ) to obtain water-absorbing resin particles (P-2) of the present invention in the same manner as in Example 1, except that the content was changed to 62 parts.

<Example 3>
In Example 1, 279 parts of acrylic acid (a1-1) and 31 parts of methylenesuccinic acid were added to 124 parts of acrylic acid (a1-1) and 186 parts of methylenesuccinic acid, and 129 parts of a 48.5% aqueous sodium hydroxide solution was added to 133 parts. Water-absorbent resin particles (P-3) of the present invention were obtained in the same manner as in Example 1, except that the content was changed.

<Example 4>
In Example 1, 279 parts of acrylic acid (a1-1) and 31 parts of methylenesuccinic acid were changed to 31 parts of acrylic acid (a1-1) and 279 parts of methylenesuccinic acid, and the temperature of the mixture was adjusted to 80 ° C. Water-absorbing resin particles (P-4) of the present invention were obtained in the same manner as in Example 1 except that heat treatment was performed and 129 parts of the 48.5% aqueous sodium hydroxide solution was changed to 140 parts.

<Example 5>
In Example 1, the internal cross-linking agent (b-1) N,N'-{(2-acrylamido-2-[(3-acrylamidopropoxy)methyl]propane-1,3-diyl)bis(propane-1,3 - diyl)} diacrylamide (manufactured by Wako Pure Chemical Industries, product name: FOM-03006) 0.3 parts of internal cross-linking agent (b-1) N,N',N''-triacryloyldiethylenetriamine (manufactured by Wako Pure Chemical Industries, product name) Water-absorbent resin particles (P-5) of the present invention were obtained in the same manner except that the name FOM-03007) was changed to 0.3 parts.

<Example 6>
In Example 1, the internal cross-linking agent (b-1) N,N'-{(2-acrylamido-2-[(3-acrylamidopropoxy)methyl]propane-1,3-diyl)bis(propane-1,3- Diyl)} diacrylamide (manufactured by Wako Pure Chemical Industries, Ltd., product name: FOM-03006) is added to 0.3 parts of an internal cross-linking agent (b-1) N,N'-diacryloyl-4,7,10-trioxa-1,13- Water-absorbent resin particles (P-6) of the present invention were obtained in the same manner except that tridecanediamine (manufactured by Wako Pure Chemical Industries, Ltd., product name: FOM-03008) was changed to 0.3 parts.

<Example 7>
In Example 1, the internal cross-linking agent (b-1) N,N'-{(2-acrylamido-2-[(3-acrylamidopropoxy)methyl]propane-1,3-diyl)bis(propane-1,3- diyl)} diacrylamide (manufactured by Wako Pure Chemical Industries, product name: FOM-03006) 0.3 parts of internal cross-linking agent (b-2) N,N',N'',N'''-tetraacryloylethylenetetramine (sum Kojunyaku Co., Ltd., product name FOM-03009) was changed to 0.3 parts to obtain water-absorbing resin particles (P-7) of the present invention.

<Example 8>
In Example 1, the internal cross-linking agent (b-1) N,N'-{(2-acrylamido-2-[(3-acrylamidopropoxy)methyl]propane-1,3-diyl)bis(propane-1,3- diyl)} diacrylamide (manufactured by Wako Pure Chemical Industries, product name: FOM-03006) was changed to 0.7 parts of the internal cross-linking agent (b-2) triallylpentaerythritol (manufactured by TCI) in the same manner. Inventive water absorbent resin particles (P-8) were obtained.

<Production Example 1>
In paragraphs 0041 to 0043 of JP-A-2018-52955, plant-derived acrylic acid was obtained by performing the same operation except that petrified ethylene oxide was changed to plant-derived ethylene oxide. Plant-derived ethylene oxide can be obtained, for example, by converting ethanol obtained by fermentation or the like into ethylene with an enzyme and then oxidizing the ethanol.

<Example 9>
In Example 1, 310 parts of acrylic acid (a1-1) (Mitsubishi Chemical) was changed to acrylic acid (a1-2) of Production Example 1. ).

<Example 10>
In Example 1, the internal cross-linking agent (b-1) N,N'-{(2-acrylamido-2-[(3-acrylamidopropoxy)methyl]propane-1,3-diyl)bis(propane-1,3 -diyl)} diacrylamide (manufactured by Wako Pure Chemical Industries, Ltd., product name: FOM-03006) was changed to 0.74 parts of polyethylene glycol diacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) in the same manner as the water absorbent of the present invention. Resin particles (P-10) were obtained.

<Example 11>
Acrylic acid (a1-1) (manufactured by Mitsubishi Chemical) 279 parts, methylene succinic acid (manufactured by Fuso Chemical Industry) 31 parts, internal cross-linking agent (b-1) N, N'-{(2-acrylamide-2-[( 3-acrylamidopropoxy)methyl]propane-1,3-diyl)bis(propane-1,3-diyl)}diacrylamide (manufactured by Wako Pure Chemical Industries, product name FOM-03006) 0.3 parts and 680 parts of deionized water was kept at 3°C while stirring and mixing. After flowing nitrogen into this mixture to make the dissolved oxygen content 1 ppm or less, 4.6 parts of a 2% 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide] aqueous solution, 1.2 parts of 1% aqueous hydrogen peroxide solution, 2.3 parts of 2% aqueous ascorbic acid solution and 1.6 parts of 0.03% iron sulfate heptahydrate aqueous solution were added and mixed to initiate polymerization. After the temperature of the mixture reached 80° C., polymerization was carried out at 80±2° C. for about 12 hours to obtain a hydrous gel.

Next, 258 parts of a 48.5% sodium hydroxide aqueous solution is added while shredding this hydrous gel with a mincing machine (12VR-400K manufactured by ROYAL), and further corn-derived starch (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.). 31 parts were mixed and neutralized to obtain a neutralized gel (degree of neutralization: 72%). Further, the neutralized water-containing gel was dried for 50 minutes in a ventilated dryer {150° C., wind speed 2 m/sec} to obtain a dry product. The dried product was pulverized with a juicer mixer (Osterizer Blender manufactured by Oster), sieved, and adjusted to a particle size range of 710 to 150 μm in opening to obtain a crosslinked polymer (A-2).

Then, 100 parts of the obtained crosslinked polymer (A-2) was stirred at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron: 2000 rpm), and ethylene glycol diglycidyl ether as the organic surface cross-linking agent (d) was added to 0. 0.8 parts of propylene glycol, and 0.1 parts of water are added and mixed uniformly, followed by heating at 140° C. for 40 minutes to obtain the water absorbent resin particles of the present invention (P- 11) was obtained.

<Example 12>
In Example 1, 0.08 parts ethylene glycol diglycidyl ether, 0.8 parts propylene glycol, and 1.5 parts water were mixed with 0.15 parts ethylene glycol diglycidyl ether, 1.5 parts propylene glycol, and 1.5 parts water. Water absorbent resin particles (P-12) of the present invention were obtained in the same manner except that the amount was changed to 5 parts.

<Example 13>
Water absorbent resin particles (P-13) of the present invention were obtained in the same manner as in Example 1, except that 0.1 part of propylene glycol was not used.

<Comparative Example 1>
310 parts of acrylic acid (a1-1) (manufactured by Mitsubishi Chemical), 1.0 part of triallyl pentaerythritol (manufactured by TCI) as a cross-linking agent (b-2), and 679 parts of deionized water are stirred and mixed at 3°C. kept to After flowing nitrogen into this mixture to make the dissolved oxygen content 1 ppm or less, 4.6 parts of a 2% 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide] aqueous solution, 1.2 parts of 1% aqueous hydrogen peroxide solution, 2.3 parts of 2% aqueous ascorbic acid solution and 1.6 parts of 0.03% iron sulfate heptahydrate aqueous solution were added and mixed to initiate polymerization. After the temperature of the mixture reached 90° C., polymerization was carried out at 90±2° C. for about 12 hours to obtain a hydrous gel.

Next, while shredding this hydrous gel with a mincing machine (12VR-400K manufactured by ROYAL), 261 parts of a 48.5% aqueous sodium hydroxide solution is added and mixed and neutralized, resulting in a neutralized gel (degree of neutralization: 72%) was obtained. Further, the neutralized water-containing gel was dried for 50 minutes in a ventilated dryer {150° C., wind speed 2 m/sec} to obtain a dry product. The dried product was pulverized with a juicer mixer (Osterizer Blender manufactured by Oster), sieved, and adjusted to a particle size range of 710 to 150 μm in opening to obtain a crosslinked polymer (A-3).

Then, 100 parts of the obtained crosslinked polymer (A-3) was stirred at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron: 2000 rpm), and ethylene glycol diglycidyl ether as the organic surface cross-linking agent (d) was added to 0. .08 parts, 0.8 parts of propylene glycol, and 1.5 parts of water were added to a mixed solution, mixed uniformly, and then heated at 140° C. for 40 minutes to obtain water absorbent resin particles for comparison (R- 1) was obtained.

<Comparative Example 2>
Under a nitrogen atmosphere, 90.0 parts of methylene succinic acid, 247 parts of 48.5% aqueous sodium hydroxide solution, 120 parts of acrylic acid, and 572 parts of deionized water are stirred and mixed in a two-necked 1000 ml flask, and further N, N- 1.5 parts of methylenebisacrylamide, 2.1 parts of ethylene glycol and 4 parts of 4,4'-azobis(4-cyanopentanoic acid) were added and heated in a silicon water bath at 80°C for 5 hours. Then, the temperature was raised to 145° C., and the hydrous gel was taken out from the flask after 2 hours. After washing with water, it was transferred to a SUS vat and dried for 48 hours in a smooth wind dryer set at 85°C. Next, after pulverizing this dried body with a juicer mixer (Osterizer Blender manufactured by Oster), it is sieved and adjusted to a particle size range of 710 to 150 μm in opening, and water absorbent resin particles for comparison (R-2 ).

Table 1 shows the evaluation results.

Claims

one or more monomers (A1) selected from the group consisting of water-soluble unsaturated monocarboxylic acids (a1) and salts thereof, and monomers (a2) that become the water-soluble unsaturated monocarboxylic acids (a1) by hydrolysis; , one or more monomers (A2) selected from the group consisting of a water-soluble unsaturated dicarboxylic acid (a3) and a salt thereof, and a monomer (a4) that becomes the water-soluble unsaturated dicarboxylic acid (a3) by hydrolysis; A water-absorbing resin composition containing a cross-linked polymer (A) having a cross-linking agent (b) as a structural unit, and having a structure in which the surface of the cross-linked polymer (A) is cross-linked by the surface cross-linking agent (d). and
At least one of the monomer (A1) and the monomer (A2) has a 14 C/C measured by a carbon radiocarbon dating method of 1.2×10 −12 to 1.0×10 −16 . ,
A water-absorbing resin having a water retention capacity (g/g) of 0.9 wt% saline of 10 to 60 and an absorption capacity (g/g) of 0.9 wt% saline under load of 12 to 25. Composition.
The ratio of the substance amount of the monomer (A1) to the substance amount of the monomer (A2) in the crosslinked polymer (A) (substance amount of the monomer (A1)/substance amount of the monomer (A2)) is 99. /1 to 10/90, the water absorbent resin composition according to claim 1.
The water absorbent resin composition according to claim 1 or 2, wherein the water-soluble unsaturated dicarboxylic acid (a3) is one or more selected from the group consisting of maleic acid, fumaric acid, methylenesuccinic acid and citraconic acid.
The cross-linking agent (b) is one or more selected from the group consisting of polyvalent (meth)allyl compounds having two or more ethylenically unsaturated groups and acrylamide compounds, according to any one of claims 1 to 3. The water absorbent resin composition described.
The water absorbent resin composition according to any one of claims 1 to 4, wherein the content of the organic solvent in the water absorbent resin composition is 0.1 to 3.0% by weight.
The water absorbent resin composition according to any one of claims 1 to 5, wherein the water absorbent resin composition is particulate.
An absorbent body containing the water absorbent resin composition according to any one of claims 1 to 6.
An absorbent article comprising the absorbent body according to claim 7.
A method for producing a water absorbent resin composition according to any one of claims 1 to 6,
A polymerization step of obtaining a hydrous gel containing the crosslinked polymer (A);
A drying step of drying the hydrous gel;
and a surface cross-linking step of cross-linking the surface of the cross-linked polymer (A) after the drying step with the surface cross-linking agent (d).
The method for producing a water absorbent resin composition according to claim 9, comprising a gel shredding step of shredding the hydrous gel obtained in the polymerization step to obtain hydrous gel particles.
In the gel shredding step, a plant-derived raw material having a 14 C/C measured by carbon radiocarbon dating of 1.2×10 −12 to 1.0×10 −16 is added to the hydrous gel. 11. The method for producing a water absorbent resin composition according to claim 10.
In the drying step, a plant-derived raw material having a 14 C/C measured by a carbon radiocarbon dating method of 1.2×10 −12 to 1.0×10 −16 is added to the hydrous gel. Item 10. A method for producing a water absorbent resin composition according to Item 10 or 11.