JP6979770B2 - Water-absorbent resin particles and their manufacturing method - Google Patents

Description

The present invention relates to water-absorbent resin particles and a method for producing the same. More specifically, the present invention relates to water-absorbent resin particles having no discoloration during storage, high stability over time, and high antibacterial properties, and a method for producing the same.

When the conventional water-absorbent resin is used for absorbent articles such as diapers and pet sheets, there is a problem that bacteria propagate with the passage of time after urination and a foul odor is generated. As a result, stress on the skin when wearing the absorbent article and discomfort to the wearer and the people around him are given. In order to prevent such a problem, a technique for imparting antibacterial properties to the water-absorbent resin is known. For example, Patent Documents 1 and 2 describe antibacterial hydrogel-forming and absorbing polymers in which the hydrogel-forming and absorbing polymer is coated with an antibacterial agent. Patent Document 3 describes an absorbent containing a compound having an antibacterial action against ammonia-producing bacteria. Patent Document 4 describes a curing step in which a superabsorbent and a solution having an antibacterial agent and a polyol are brought into contact with a surface cross-linking agent at the same time as or immediately after the super-absorbent is brought into contact with the surface cross-linking agent to complete the surface cross-linking. Described is a method of producing a superabsorbent having an antibacterial coating, which comprises a step of contacting prior to.

In the techniques described in Patent Documents 1 and 2, the hydrogel-forming absorbent polymer is dissolved in an organic solvent prior to coating with the antibacterial agent. If the selection of this organic solvent is not appropriate, there is a concern that an offensive odor peculiar to the organic solvent may occur, a problem may occur in the safety of the human body, and the safety against ignition or explosion may occur. In the technique described in Patent Document 3, depending on the method of addition, the absorbent material is colored by the amine compound derived from the antibacterial agent, and the antibacterial agent is non-uniformly adhered to the crosslinked polymer particles, so that the desired effect can be obtained. I can't get it. In the technique described in Patent Document 4, the antibacterial agent is altered due to the heat applied when the surface cross-linking agent is cured, and the absorbent is colored during storage.

Special Table No. 11-501362 Special Table 2000-513408 Gazette Japanese Unexamined Patent Publication No. 2000-79159 Japanese Patent Publication No. 2010-54004

An object of the present invention is to provide water-absorbent resin particles that exhibit sufficient absorption performance, do not discolor during storage, and do not generate odor over time after urination.

The present invention is a crosslinked polymer of a monomer composition containing a water-soluble vinyl monomer (a1) and / or a vinyl monomer (a2) which becomes a water-soluble vinyl monomer (a1) by hydrolysis, and a cross-linking agent (b). A), a reducing agent (B), and a quaternary ammonium salt (C) containing 0.01 to 2% by weight based on the weight of the crosslinked polymer (A), and containing 40 ° C. and 80% Rh conditions for 50 days. Water-absorbent resin particles having a yellowness (YI value) of 20 or less after an accelerated test (hereinafter, also simply referred to as a 50-day accelerated test in the present specification); and a method for producing the water-absorbent resin particles, which is crosslinked. This is a method for producing water-absorbent resin particles, which comprises a step of mixing the reducing agent (B) with the polymer (A) and then mixing the quaternary ammonium salt (C) after the mixing step.

The water-absorbent resin particles of the present invention and the water-absorbent resin particles obtained by the production method of the present invention prevent yellowing during storage and are excellent in yellowing resistance. It also has excellent antibacterial properties. Therefore, it stably exhibits excellent absorption performance (for example, liquid diffusivity, absorption rate, absorption amount, etc.) even under various usage conditions.

It is a figure which represented the cross-sectional view of the filtration cylinder tube for measuring the gel liquid passing rate schematically. It is a perspective view schematically showing a pressure shaft and a weight for measuring a gel liquid passing rate.

The water-absorbent resin particles of the present invention are a monomer composition containing a water-soluble vinyl monomer (a1) and / or a vinyl monomer (a2) that becomes a water-soluble vinyl monomer (a1) by hydrolysis, and a cross-linking agent (b). The quaternary ammonium salt (C) containing the crosslinked polymer (A) of the above, and 0.01 to 2% by weight with respect to the weight of the reducing agent (B) and the crosslinked polymer (A) (hereinafter, simply the ammonium salt (hereinafter, simply ammonium salt). Also referred to as C)).

The water-soluble vinyl monomer (a1) in the present invention is not particularly limited, and is a known monomer, for example, at least one water-soluble substituent disclosed in paragraphs 0007 to 0023 of Japanese Patent No. 36485553 and ethylenia-free. Vinyl monomers having a saturated group (for example, anionic vinyl monomers, nonionic vinyl monomers and cationic vinyl monomers), anionic vinyl monomers and nonionic vinyl monomers disclosed in paragraphs 0009 to 0024 of JP-A-2003-165883. Select from the group consisting of a sex vinyl monomer, a cationic vinyl monomer, and a carboxy group, a sulfo group, a phosphono group, a hydroxyl group, a carbamoyl group, an amino group, and an ammonio group disclosed in paragraphs 0041 to 0051 of JP-A-2005-75982. A vinyl monomer having at least one of these can be used.

A vinyl monomer (a2) that becomes a water-soluble vinyl monomer (a1) by hydrolysis [hereinafter, also referred to as a hydrolyzable vinyl monomer (a2). ] Is not particularly limited, and is a publicly known {for example, a vinyl monomer having at least one hydrolyzable substituent which becomes a water-soluble substituent by hydrolysis disclosed in paragraphs 0024 to 0025 of Japanese Patent No. 3648553, Japanese Patent Application Laid-Open No. At least one hydrolyzable substituent [1,3-oxo-2-oxapropylene (-CO-O-CO-) group, acyl group and cyano) disclosed in paragraphs 0052 to 0055 of JP-A-2005-75982. A vinyl monomer having a [group, etc.]} can be used. The water-soluble vinyl monomer is a concept well known to those skilled in the art, but when expressed using a quantity, it means, for example, a vinyl monomer that dissolves at least 100 g in 100 g of water at 25 ° C. Further, the hydrolytic property of the hydrolyzable vinyl monomer (a2) is a concept well known to those skilled in the art, but more specifically, for example, by the action of water and, if necessary, a catalyst (acid or base, etc.). It means the property of being hydrolyzed and becoming water-soluble. The hydrolyzable vinyl monomer (a2) may be hydrolyzed during or after the polymerization, or both of them, but it is preferable after the polymerization from the viewpoint of the absorption performance of the obtained water-absorbent resin particles.

Of these, the water-soluble vinyl monomer (a1) is preferable from the viewpoint of absorption performance, and the above-mentioned anionic vinyl monomer, carboxy (salt) group, sulfo (salt) group, amino group, and carbamoyl group are more preferable. Vinyl monomers having an ammonio group or a mono-, di- or tri-alkyl ammonio group, more preferably vinyl monomers having a carboxy (salt) group or carbamoyl group, particularly preferably (meth) acrylic acid (salt) and (Meta) acrylamide, particularly preferred is (meth) acrylic acid (salt), most preferred is acrylic acid (salt).

In addition, "carboxy (salt) group" means "carboxy group" or "carboxylate group", and "sulfo (salt) group" means "sulfo group" or "sulfonate group". Further, (meth) acrylic acid (salt) means acrylic acid, acrylate, methacrylic acid or methacrylamide, and (meth) acrylamide means acrylamide or methacrylamide. Examples of the salt include alkali metal (lithium, sodium, potassium, etc.) salt, alkaline earth metal (magnesium, calcium, etc.) salt, ammonium (NH ₄ ) salt, and the like. Of these salts, alkali metal salts and ammonium salts are preferable, and alkali metal salts are more preferable, and sodium salts are particularly preferable, from the viewpoint of absorption performance and the like.

When either the water-soluble vinyl monomer (a1) or the hydrolyzable vinyl monomer (a2) is used as a constituent unit, one of each may be used alone as a constituent unit, or two or more thereof may be used as a constituent unit, if necessary. good. The same applies to the case where the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2) are used as constituent units. When the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2) are used as constituent units, the molar ratio [(a1) / (a2)] of these is preferably 75/25 to 99/1. It is more preferably 85/15 to 95/5, particularly preferably 90/10 to 93/7, and most preferably 91/9 to 92/8. Within this range, the absorption performance is further improved.

As a constituent unit of the crosslinked polymer (A), in addition to the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2), another vinyl monomer (a3) copolymerizable with these shall be a constituent unit. Can be done. As the other vinyl monomer (a3), one type may be used alone, or two or more types may be used in combination.

The other copolymerizable vinyl monomer (a3) is not particularly limited, and is known (for example, the hydrophobic vinyl monomer disclosed in paragraphs 0028 to 0029 of Japanese Patent No. 36485553, JP-A-2003-165883). Hydrophobic vinyl monomers (such as the vinyl monomers disclosed in paragraph 0025 and paragraph 0058 of JP-A-2005-75982) can be used, and specifically, for example, the following vinyl monomers (i) to (iii) and the like can be used. Can be used.
(I) Aromatic ethylenic monomer having 8 to 30 carbon atoms Styrene such as styrene, α-methylstyrene, vinyltoluene and hydroxystyrene, halogen substituted styrene such as vinylnaphthalene and dichlorostyrene and the like.
(Ii) Alkenes (ethylene, propylene, butene, isobutylene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, etc.); and alkaziene (butadiene and isoprene, etc.) having 2 to 20 carbon atoms.
(Iii) Alicyclic ethylenic monomer having 5 to 15 carbon atoms Monoethylenically unsaturated monomer (pinene, limonene, indene, etc.); and polyethylene vinyl monomer [cyclopentadiene, bicyclopentadiene, ethylidene norbornene, etc.] and the like.

The content (mol%) of the other vinyl monomer (a3) unit is based on the total number of moles of the water-soluble vinyl monomer (a1) unit and the hydrolyzable vinyl monomer (a2) unit from the viewpoint of absorption performance and the like. The content is preferably 0 to 5, more preferably 0 to 3, particularly preferably 0 to 2, particularly preferably 0 to 1.5, and the content of other vinyl monomer (a3) units is high from the viewpoint of absorption performance and the like. Most preferably, it is 0 mol%.

The cross-linking agent (b) is not particularly limited and is known (for example, it reacts with a cross-linking agent having two or more ethylenically unsaturated groups and a water-soluble substituent disclosed in paragraphs 0031 to 0034 of Japanese Patent No. 3648553. JP-A-2003-165883, a cross-linking agent having at least one functional group to be obtained and having 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. 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 agent having two or more reactive substituents disclosed in paragraphs 0028 to 0031. , Crosslinkable vinyl monomers disclosed in paragraph 0059 of JP-A-2005-75982 and crosslinkable vinyl monomers disclosed in paragraphs 0015 to 0016 of JP-A-2005-59559) can be used. .. Of these, a cross-linking agent having two or more ethylenically unsaturated groups is preferable from the viewpoint of absorption performance and the like, and more preferable is a poly (triallyl cyanurate, triallyl isocyanurate and a polyol having 2 to 40 carbon atoms). Meta) Allyl ethers, particularly preferred are triallyl cyanurate, triallyl isocyanurate, tetraallyloxyetane, polyethylene glycol diallyl ether and pentaerythritol triallyl ether, most preferably pentaerythritol triallyl ether. The cross-linking agent (b) may be used alone or in combination of two or more.

The content (mol%) of the cross-linking agent (b) unit is (a1) when other vinyl monomers (a3) of the water-soluble vinyl monomer (a1) unit and the hydrolyzable vinyl monomer (a2) unit are also used. Based on the total number of moles of (a3), 0.001 to 5, more preferably 0.005 to 3, and particularly preferably 0.01 to 1. Within this range, the absorption performance is further improved.

Examples of the polymerization method of the crosslinked polymer (A) include known solution polymerization (adiabatic polymerization, thin film polymerization, spray polymerization, etc .; JP-A-55-133413, etc.) and known reverse phase suspension polymerization (Tokusho). 54-30710, JP-A-56-26909, JP-A-1-5808, etc.).

The crosslinked polymer (A) can be obtained by polymerizing a monomer composition containing a water-soluble vinyl monomer (a1) and / or a hydrolyzable vinyl monomer (a2) and a crosslinking agent (b) as essential constituents. However, the solution polymerization method is preferable as the polymerization method, and since it is not necessary to use an organic solvent and is advantageous in terms of production cost, the aqueous solution polymerization method is particularly preferable because it has a large amount of water retention and has a large water retention capacity. The aqueous adiabatic polymerization method is most preferable because a water-absorbent resin composition having a small amount of water-soluble components can be obtained and temperature control during polymerization is not required.

When performing 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, dimethyl sulfoxide, and two or more of these. Can be mentioned as a mixture of.
In the case of 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 an initiator is used for polymerization, conventionally known initiators for radical polymerization can be used. For example, azo compounds [azobisisobutyronitrile, azobiscyanovaleric acid and 2,2'-azobis (2-amidinopropane)) can be used. Hydrochloride, etc.], Inorganic peroxides (hydrogen peroxide, ammonium persulfate, potassium persulfate, sodium persulfate, etc.), organic peroxides [benzoyl peroxide, dit-butyl peroxide, cumene hydroperoxide, succinic acid, etc.] Acid peroxides and di (2-ethoxyethyl) peroxydicarbonates, etc.] and redox catalysts (alkali metal sulfites or persulfates, ammonium sulfites, reducing agents such as ammonium bicarbonate and ascorbic acid, and alkali metal persulfates. (Combined with an oxidizing agent such as salt, ammonium persulfate, hydrogen peroxide and organic peroxide) and the like. These catalysts may be used alone or in combination of two or more of them.
The amount (% by weight) of the radical polymerization initiator used is (a1) to (a3) when other vinyl monomers (a3) of the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2) are also used. Based on the total weight of the above, 0.0005-5 is preferable, and 0.001-2 is more preferable.

At the time of polymerization, a polymerization control agent typified by a chain transfer agent may be used in combination, and specific examples thereof include sodium hypophosphite, sodium phosphite, alkyl mercaptans, and alkyl halides. , Thiocarbonyl compounds and the like. These polymerization control agents may be used alone or in combination of two or more of them.
The amount (% by weight) of the polymerization control agent used is the same as that of the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2), and when other vinyl monomers (a3) are also used, (a1) to (a3). , 0.0005-5, more preferably 0.001-2, based on the total weight.

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

The polymerization start 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 a solvent (organic solvent, water, etc.) is used for the polymerization, it is preferable to distill off the solvent after the 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, and particularly preferably 0 to 5 based on the weight of the crosslinked polymer (A). Is 0 to 3, most preferably 0 to 1. Within this range, the absorption performance of the water-absorbent resin particles is further improved.

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

By the above-mentioned polymerization method, a water-containing gel in which the crosslinked polymer (A) contains water (that is, a crosslinked polymer (A) which is a water-containing gel; hereinafter, abbreviated as a water-containing gel) can be obtained. Further, the crosslinked polymer (A) can be obtained by drying the hydrogel.
When an acid group-containing monomer such as acrylic acid or methacrylic acid is used as the water-soluble vinyl monomer (a1), the water-containing gel may be neutralized with a base. The degree of neutralization of the acid group is preferably 50 to 80 mol%. When the degree of neutralization is less than 50 mol%, the adhesiveness of the obtained hydrogel polymer may be high, and the workability during production and use may be deteriorated. Further, the amount of water retention of the obtained water-absorbent resin particles may decrease. On the other hand, when the degree of neutralization exceeds 80%, the pH of the obtained resin becomes high, and there may be a concern about the safety of the obtained resin on the skin of the human body.
The neutralization may be performed at any stage after the polymerization of the crosslinked polymer (A) in the production of the water-absorbent resin particles, and for example, a method of neutralizing in the state of a hydrogel is preferable. Illustrated.
As the base to be neutralized, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and alkali metal carbonates such as sodium carbonate, sodium hydrogencarbonate and potassium carbonate can be usually used.

The hydrogel obtained by polymerization can be shredded as needed before drying. The size (longest diameter) of the gel after shredding is preferably 50 μm to 10 cm, more preferably 100 μm to 2 cm, and 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 shredded using a shredding device (for example, a Beck's mill, a rubber chopper, a pharma mill, a minced machine, an impact type crusher, a roll type crusher) or the like.

The content and moisture of the organic solvent are determined by an infrared moisture measuring instrument [JE400 manufactured by KETT Co., Ltd .: 120 ± 5 ° C., 30 minutes, atmospheric humidity 50 ± 10% RH before heating, lamp specification 100V, 40W. ] Is obtained from the weight loss of the measurement sample when heated.

As a method for distilling off the solvent (including water) of the hydrogel and drying it, a method of distilling off (drying) with hot air at a temperature of 80 to 230 ° C., a drum dryer heated to 100 to 230 ° C., or the like is used. Thin film drying method, (heating) vacuum drying method, freeze drying method, infrared drying method, decantation, filtration and the like can be applied.

After the hydrous gel is dried, it can be further pulverized. The crushing method is not particularly limited, and a crushing device (for example, a hammer type crusher, an impact type crusher, a roll type crusher, a shet airflow type crusher) or the like can be used. The particle size of the crushed crosslinked polymer can be adjusted by sieving or the like, if necessary.

The weight average particle size (μm) of the crosslinked polymer (A) when screened as necessary is preferably 100 to 800, more preferably 200 to 700, then preferably 250 to 600, and particularly preferably 300 to 500. Most preferably, it is 350 to 450. Within this range, the absorption performance is further improved.

The weight average particle size was determined by using a low-tap test sieve shaker and a standard sieve (JIS Z8801-1: 2006), Perry's Chemical Engineers Handbook 6th Edition (McGlow Hill Book Canvas, 1984). , Page 21). That is, the JIS standard sieves are combined in the order 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 the saucer from the top. Place about 50 g of the measurement particles in the uppermost sieve and shake with a low-tap test sieve shaker for 5 minutes. Weigh the measured particles on each sieve and saucer, and set the total to 100% by weight to obtain the weight fraction of the particles on each sieve. ), The vertical axis is the weight fraction], then draw a line connecting each point to obtain the particle size corresponding to the weight fraction of 50% by weight, and use this as the weight average particle diameter.

Further, when crushed, the smaller the content of the fine particles contained in the crushed crosslinked polymer (A), the better the absorption performance. Therefore, the total weight of the crosslinked polymer (A) is 106 μm or less (preferably 150 μm). The content (% by weight) of the fine particles (below) is preferably 3 or less, more preferably 1 or less. The content of the fine particles can be determined by using the graph created when determining the weight average particle diameter described above.

In the case of crushing, the shape of the crosslinked polymer (A) after crushing is not particularly limited, and examples thereof include amorphous crushed form, phosphorus fragment form, pearl form and rice granules. Of these, the amorphous crushed form is preferable from the viewpoint that it is easily entangled with the fibrous material for use in disposable diapers and the like and there is no concern that it will fall off from the fibrous material.

The crosslinked polymer (A) may contain some other components such as a residual solvent and a residual crosslinked component as long as the performance is not impaired.

The water-absorbent resin particles of the present invention preferably have a structure in which the surface of the crosslinked polymer (A) is crosslinked by the surface crosslinking agent (d). By cross-linking the surface of the crosslinked polymer (A), the gel strength of the water-absorbent resin particles can be improved, and the desirable water-retaining amount of the water-absorbent resin particles and the absorption amount under load can be satisfied. Examples of the surface cross-linking agent (d) include polyvalent glycidyl compounds, polyvalent amines, polyvalent aziridine compounds and polyhydric isocyanate compounds described in JP-A-59-189103, and JP-A-58-180233. And the polyhydric alcohol of JP-A-61-16903, the silane coupling agent described in JP-A-61-221305 and JP-A-61-252212, and described in JP-A-5-508425. Uses alkylene carbonates, polyvalent oxazoline compounds described in JP-A-11-240959, and surface cross-linking agents of JP-A-51-136588 and JP-A-61-257235 (polyvalent metals, etc.). can. Among these surface cross-linking agents, polyhydric glycidyl compounds, polyhydric alcohols and polyhydric amines are preferable, and polyhydric glycidyl compounds and polyhydric alcohols are more preferable, and polyhydric alcohols are particularly preferable, from the viewpoint of economic efficiency and absorption characteristics. Valuable glycidyl compounds, most preferably ethylene glycol diglycidyl ethers. One type of surface cross-linking agent may be used alone, or two or more types may be used in combination.

In the case of surface cross-linking, the amount (% by weight) of the surface cross-linking agent (d) used is not particularly limited because it can be variously changed depending on the type of the surface cross-linking agent, the conditions for cross-linking, the target performance, and the like. From the viewpoint of absorption characteristics and the like, 0.001 to 3 is preferable, and 0.005 to 2, particularly preferably 0.01 to 1.5, with respect to 100 parts by weight of the crosslinked polymer (A).

The surface cross-linking of the cross-linked polymer (A) can be carried out by mixing the cross-linked polymer (A) and the surface cross-linking agent (d) and heating as necessary. As a mixing method of the crosslinked polymer (A) and the surface crosslinking agent (d), a cylindrical mixer, a screw type mixer, a screw type extruder, a turbulizer, a Nauter type mixer, a double arm type kneader, and a flow Crosslinked polymer using a mixer such as a type mixer, V type mixer, minced mixer, ribbon type mixer, flow type mixer, air flow type mixer, rotary disk type mixer, conical blender and roll mixer ( A method of uniformly mixing the A) and the surface cross-linking agent (d) can be mentioned. At this time, the surface cross-linking agent (d) may be diluted with water and / or any solvent before use.

The temperature at which the crosslinked polymer (A) and the surface crosslinked 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 crosslinked agent (d), heat treatment is usually performed. The heating temperature is preferably 100 to 180 ° C., more preferably 110 to 175 ° C., and particularly preferably 120 to 170 ° C. from the viewpoint of fracture resistance of the resin particles. Indirect heating using steam is possible if the heating is 180 ° C or lower, which is advantageous in terms of equipment, and if the heating temperature is lower than 100 ° C, the absorption performance may deteriorate. The heating time can be appropriately set depending on the heating temperature, but is preferably 5 to 60 minutes, more preferably 10 to 40 minutes from the viewpoint of absorption performance. It is also possible to further surface-crosslink the water-absorbent resin obtained by surface-crosslinking with a surface-crosslinking agent of the same type or different from the surface-crosslinking agent used first.

After the surface of the crosslinked polymer (A) is crosslinked with the surface crosslinking agent (d), the particle size is adjusted by sieving if necessary. The average grain diameter of the obtained particles is preferably 100 to 600 μm, more preferably 200 to 500 μm. The content of the fine particles is preferably small, the content of the particles of 100 μm or less is preferably 3% by weight or less, and the content of the particles of 150 μm or less is more preferably 3% by weight or less.

Examples of the reducing agent (B) used in the present invention include an inorganic or organic reducing agent. For example, as the inorganic reducing agent, a phosphorus-based reducing agent, a sulfur-based reducing agent (particularly an oxygen-containing sulfur-based reducing agent), and a nitrite-based reducing agent are used. Reducing agents and metal-based reducing agents can be used. An amine-based reducing agent can also be used.

Phosphorus-based reducing agents that can be used in the present invention include hypophosphorous acid (salt) having an oxidation number of +1 and inorganic phosphorus-based reducing agents such as hypophosphorous acid (salt) and pyrophosphoric acid (salt) having an oxidation number of +3, and phosphinic acid. Examples thereof include organic phosphorus-based reducing agents such as (salt) and phosphite ester.

Sulfur-based reducing agents include sulfoxyphosphates with an oxidation number of +2, diantionic acid (salt) with an oxidation number of +3, sulfites with an oxidation number of +4, hydrogen sulfites, pyrosulfinic acid, and sulfamic acid. Examples thereof include sulfur-based reducing agents, formamidine sulfinic acid, sulfinic acid typified by 2-hydroxy-2-sulfinate acetate, and various thiols typified by cysteine. More specifically, as inorganic salts, sulfites such as sodium bisulfite, potassium sulfite, calcium sulfite, zinc sulfite, ammonium sulfite; hydrogen sulfites such as sodium bisulfite, potassium hydrogen sulfite, calcium hydrogen sulfite, ammonium hydrogen sulfite; Pyro sulfites such as sodium bisulfite, potassium pyrosulfite, ammonium pyrosulfite; nitiones such as sodium bisulfite, potassium bisulfite, ammonium bisulfite, calcium bisulfite, zinc bisulfite, etc. Acids; Trithionates such as potassium trithionate and sodium bisulfite; Tetrathionates such as potassium tetrathionate and sodium bisulfite; Thiosulfates such as sodium thiosulfate, potassium thiosulfite and ammonium thiosulfite Etc. are exemplified. As the sulfur-based reducing agent of the present invention, the sulfur-based reducing agent having an SO bond such as the sulfite is collectively referred to as an oxygen-containing sulfur-based reducing agent, as opposed to the thiol-based reducing agent having no SO bond. The system reducing agent may have a sulfur odor, and therefore, oxygen-containing sulfur-based reducing agent is preferably used in the present invention.

Examples of the nitrite-based reducing agent include nitrites such as sodium nitrite, potassium nitrite, calcium nitrite, and zinc nitrite.

Examples of the metal-based reducing agent include silver salts such as silver nitrate, ferrous salts such as ferrous chloride and ferrous sulfate; and ferrous salts such as ferrous chloride and ferrous sulfate.

Examples of the amine-based reducing agent include hydroxylamine or a salt (for example, hydroxylamine hydrochloride), ammonia, monoethanolamine, polyethyleneimine and the like.

Examples of the organic reducing agent include ascorbic acid, erythorbic acid, and reducing sugars (glucose, etc.). Here, the organic reducing agent refers to a reducing substance derived from an OH group or CHO.

The reducing substance may be a salt, and for example, all salts of ammonium, alkali metals, and alkaline earth metals are suitable. Aqueous solutions containing acid ions and at least one cation selected from sodium, potassium, ammonium, calcium, strontium, aluminum and magnesium, particularly alkali metal ions, are particularly preferred.

Among these reducing agents, a phosphorus-based reducing agent or a sulfur-based reducing agent, further an inorganic or organic oxygen-containing sulfur-based reducing agent, further an inorganic sulfur-based reducing agent, specifically, a sulfite or a sulfite, is preferable. Inorganic sulfur-based reducing agents selected from hydrogen salts, pyrosulfites, and dithionates, nitrites, and ascorbic acid are preferable, and sulfites such as sodium bisulfite and potassium bisulfite, sodium bisulfite, and hydrogen sulfite such as potassium hydrogen sulfite are preferable. Salt is more preferred.

The content of the reducing agent (B) is preferably 0.001 to 10% by weight, more preferably 0.01 to 5% by weight, based on the weight of the crosslinked polymer (A) from the viewpoint of yellowing resistance. It is particularly preferably 0.05 to 4% by weight, and most preferably 0.1 to 3% by weight.

The ammonium salt (C) is preferably an antibacterial activity, and more preferably a quaternary ammonium salt compound (C1) having at least one alkyl group having 8 to 30 carbon atoms. Examples of the alkyl group of (C1) include an octyl group, a decyl group, a lauryl group, a myristyl group, a cetyl group, an oleyl group, a stearyl group, a behenyl group and the like. Alkyl group When the number of carbon atoms is less than 8 or more than 30, the alkyl group does not exhibit sufficient antibacterial performance. The residue of the alkyl group having 8 to 30 carbon atoms in the quaternary ammonium salt compound (C1) is not particularly limited except for the alkyl group having 8 to 30 carbon atoms, but for example, an alkyl having 1 to 7 carbon atoms. Examples thereof include an oxyalkyl group such as a group and a 2-hydroxyethyl group, an aromatic aliphatic group such as a benzyl group, and an aromatic group such as a phenyl group. The number of quaternary ammonium groups in the molecule is not particularly limited, but is preferably one in the molecule.

Specific examples of such (C1) include compounds having the following quaternary ammonium group as a cation and the following organic acid or inorganic acid anion as a counter anion. It is preferably a quaternary ammonium salt compound having an anion of an organic acid as a counter anion.
Examples of the quaternary ammonium group include hexyltrimethylammonium, octyltrimethylammonium, decyltrimethylammonium, lauryltrimethylammonium, cetyltrimethylammonium, stearyltrimethylammonium, octyldimethylethylammonium, decyldimethylethylammonium, lauryldimethylethylammonium, and dihexyldimethylammonium. , Dioctyldimethylammonium, didecyldimethylammonium, didodecyldimethylammonium, dilauryldimethylammonium and other quaternary ammonium groups. Of these, preferred are quaternary ammonium groups having at least one alkyl group having 8 to 20 carbon atoms, and more preferably quaternary ammonium groups having at least one alkyl group having 8 to 12 carbon atoms. It is a group, and particularly preferably a quaternary ammonium group (dioctyldimethylammonium, didecyldimethylammonium, etc.) having two alkyl groups having 8 to 12 carbon atoms in the molecule.

Examples of the organic acid include carboxylic acid, sulfonic acid, organic phosphoric acid and the like.
Carboxylic acid: Saturated monocarboxylic acid (acetic acid, propionic acid, capric acid, lauric acid, myristic acid, stearic acid, behenic acid, etc.), unsaturated monocarboxylic acid (acrylic acid), which is a monocarboxylic acid having 1 to 30 carbon atoms. , Methacrylic acid, oleic acid, etc.), aliphatic oxycarboxylic acid (glycolic acid, lactic acid, gluconic acid, etc.), aliphatic polycarboxylic acid (succinic acid, succinic acid, adipic acid, azelaic acid, sebatic acid, maleic acid, fumar Acids, itaconic acid, etc.), aromatic carboxylic acids (phthalic acid, trimellitic acid, pyromellitic acid, etc.);
Sulfonic acid: aliphatic sulfonic acid having 1 to 30 carbon atoms (methane sulfonic acid, ethane sulfonic acid, raulul sulfonic acid, etc.), aromatic sulfonic acid (p-toluene sulfonic acid, naphthalin sulfonic acid, etc.), etc.;
Organic phosphoric acid: an aliphatic alkyl phosphoric acid having 1 to 30 carbon atoms, an aliphatic alkyl phosphinic acid having 1 to 30 carbon atoms, an aliphatic alkyl phosphonic acid having 1 to 30 carbon atoms, and the like.
Examples of the inorganic acid include hydrofluoric acid, hydrochloric acid, bromic acid, iodoic acid, sulfuric acid, nitric acid, phosphoric acid, carbonic acid, boric acid and the like. Of the inorganic acids, hydrochloric acid, sulfuric acid, phosphoric acid, carbonic acid and boric acid are preferable.
It is preferably an organic acid. Of the organic acids, carboxylic acids are preferable, and monocarboxylic acids, aliphatic oxycarboxylic acids, aliphatic polycarboxylic acids and amino (poly) carboxylic acids are more preferable, and gluconic acid and adipic acid are particularly preferable. Is. When the counter anion constituting the quaternary ammonium group-containing compound is an inorganic acid anion, the quaternary ammonium salt compound can be obtained by using an inorganic salt of an acid selected from a strong acid and carbonic acid, which will be described later, in combination with water-absorbent resin particles. Even if the constituent counter anion is an inorganic acid, it exhibits both excellent deodorizing and antibacterial functions.

(A) and (C) usually exist in a mixed form, but the water-absorbent resin particles of the present invention have the same effect even in a bonded form. When (A) and (C) are present in a bonded form, the quaternary ammonium salt compound (C1) in which (C) has at least one alkyl group having 8 to 30 carbon atoms is preferable. When (A) and (C) are present in the combined form, (C) is present in the form of a quaternary ammonium salt in (A), and the group represented by the following general formula (1) can be mentioned. ..

In the formula, X ^- is a covalently bonded anionic group to the polymer chain in the water-absorbent resin (A), and R _{1 to} R ₄ are groups in the above-mentioned quaternary ammonium salt compound, preferably at least 1. One is an alkyl group having 8 to 30 carbon atoms. The quaternary ammonium group of the residue ( _{including R 1 to} R ₄ ) corresponds to the quaternary ammonium group of (C).

That is, at least one of the acid groups covalently bonded to the polymer chain in (A) becomes a counter anion group X ^{− of the} quaternary ammonium cation to form a salt. X ^- is may be any anionic group covalently attached to the polymer chain is not particularly limited, a carboxyl anion group -COO ^-, a sulfonate anion group -SO 3 ^_-, sulfuric anionic group, a phosphoric acid anion group or the like Preferred are carboxyl anionic groups and sulfonic acid anionic groups, particularly carboxyl anionic groups. In (A), the content of the quaternary nitrogen atom is usually in the ^{range of 2 × 10 -4 to} 0.8% by mass, and at least a part of the acid group is present in the form of a quaternary ammonium salt. preferable. The remaining acid groups that are not in the form of quaternary ammonium salts are usually unneutralized acid groups and / or acid groups neutralized with alkali metal salts, ammonium salts or amine salts.

The combined form of (A) and (C) can be obtained by the reaction of the acid group of (A) with the quaternary ammonium carbonate of (C). In this reaction, the carbonate anion constituting (C) and at least one of the acid groups in (A) exchange anions, that is, the anion of (A) is a pair of the quaternary ammonium cation of (C). It proceeds by the reaction that becomes an anion, and the carbonic acid anion becomes carbonic acid gas by the reaction and is vaporized. Therefore, there is an advantage that a quaternary ammonium base-containing water-absorbent resin having high purity can be obtained without residual by-products. The above reaction does not necessarily mean that the reaction is 100%, and the unreacted (C) may remain in the (A) to some extent. However, since the quaternary ammonium carbonate has poor thermal stability, if unreacted quaternary ammonium carbonate remains, the color stability deteriorates, which is not preferable.

The ammonium salt (C) preferably contains an amine compound in an amount of 0.01 to 1% by weight based on the weight of the ammonium salt (C). From the viewpoint of yellowing resistance, it is not preferable that the amine compound exceeds 1% by weight, and reducing it to 0.01% by weight or less is not preferable from the viewpoint of economy.

In the water-absorbent resin particles of the present invention, the content of the ammonium salt (C) is 0.01 to 2% by weight, more preferably 0, based on the weight of the crosslinked polymer (A) from the viewpoint of antibacterial properties. It is 0.01 to 1% by weight. Within this range, the water-absorbent resin particles have good liquid permeability and antibacterial properties, which is more preferable.

In the water-absorbent resin particles of the present invention, the crosslinked polymer (A) may be further treated with a hydrophobic substance, and as a method for treating with a hydrophobic substance, the method described in Japanese Patent Application Laid-Open No. 2013-231199 is used. You can.

The method for producing water-absorbent resin particles of the present invention includes a step of mixing the reducing agent (B) with the crosslinked polymer (A) and a step of mixing the ammonium salt (C).
Examples of the mixing method for the reducing agent (B) include a cylindrical mixer, a screw type mixer, a screw type extruder, a turbulizer, a Nauter type mixer, a double-armed kneader, a fluid type mixer, and a V type mixer. Examples thereof include a method of uniformly mixing using a known mixing device such as a minced mixer, a ribbon type mixer, a flow type mixer, an air flow type mixer, a rotary disk type mixer, a conical blender and a roll mixer.

As the reducing agent (B), it is preferable to mix the reducing agent (B) with stirring of the crosslinked polymer (A). From the viewpoint of uniform mixing, it is more preferable to mix with the crosslinked polymer (A) which is a water-containing gel before the drying step. The reducing agent (B) to be added may be added at the same time as water and / or a solvent. When the reducing agent (B) is added at the same time as water and / or a solvent, a solution in which the reducing agent (B) is dissolved in water and / or a solvent or a dispersion in which the reducing agent (B) is dispersed in water and / or a solvent is prepared. It can be added, and it is preferable to add the solution from the viewpoint of workability and the like, and it is more preferable to add the solution dissolved in water. When adding a solution or dispersion, it is preferable to add by spraying or dropping.

When an aqueous solution in which the reducing agent (B) is dissolved in water is used, the content of the reducing agent (B) contained in the aqueous solution is the total weight of the aqueous solution from the viewpoint of whiteness at the time of finishing of the water-absorbent resin particles and yellowing resistance. It is preferably 5 to 70% by weight, more preferably 10 to 60% by weight.

The temperature at which the reducing agent (B) is mixed with the crosslinked polymer (A) is not particularly limited, but is preferably 10 to 150 ° C, more preferably 20 to 110 ° C.

The mixing time when the reducing agent (B) is mixed with the crosslinked polymer (A) is not particularly limited, but is preferably 1 hour or less, more preferably 30 minutes or less.

The water-absorbent resin particles of the present invention may be used after mixing the crosslinked polymer (A) and the reducing agent (B) and then sieving to adjust the particle size. The average grain diameter of the particles obtained by adjusting the particle size is preferably 100 to 600 μm, more preferably 200 to 500 μm. The content of the fine particles is preferably small, the content of the particles of 100 μm or less is preferably 3% by weight or less, and the content of the particles of 150 μm or less is more preferably 3% by weight or less.

The ammonium salt (C) is preferably mixed after the above-mentioned water-containing gel drying step is completed. If mixed before the drying step is completed, the ammonium salt (C) may be thermally decomposed, and the YI value after the 50-day accelerated test may be high.

The ammonium salt (C) may be added at the same time as water and / or a solvent. When the ammonium salt (C) is added at the same time as water and / or a solvent, the ammonium salt (C) can be added as a solution dissolved in water and / or a solvent, and is dissolved in water from the viewpoint of workability and the like. It is preferable to add the solution. When adding the solution, it is preferable to add it by spraying or dropping.

When an aqueous solution in which an ammonium salt (C) is dissolved in water is used, the content of the ammonium salt (C) contained in the aqueous solution is 0.1 to 70 with respect to the total weight of the aqueous solution from the viewpoint of antibacterial property and yellowing resistance. %% By weight is preferable, and more preferably 0.5 to 60% by weight.

The temperature at which the ammonium salt (C) is mixed is not particularly limited, but is preferably 10 to 150 ° C, more preferably 20 to 120 ° C.

The mixing time when mixing the ammonium salt (C) is not particularly limited, but is preferably 1 hour or less, and more preferably 30 minutes or less.

After mixing the ammonium salt (C), further heat treatment may be performed. The heating temperature is preferably 25 to 180 ° C., more preferably 30 to 175 ° C. from the viewpoint of breakage resistance of the resin particles. If the heating is 180 ° C or less, indirect heating using steam is possible, which is advantageous in terms of equipment. Further, when the heating is not performed, the water and the solvent used together will remain in the water-absorbent resin particles, which may affect the absorption performance.

The water-absorbent resin particles of the present invention may further contain a polyvalent metal salt (e). By containing the polyvalent metal salt (e), the blocking resistance and liquid permeability of the water-absorbent resin particles are improved. As the polyvalent metal salt (e), at least one metal selected from the group consisting of magnesium, calcium, zirconium, aluminum and titanium and the above-mentioned inorganic acid or organic acid mentioned in the description of the ammonium salt (C). Salt is mentioned.

Of these, from the viewpoint of availability and solubility, an inorganic acid salt of aluminum and an inorganic acid salt of titanium are preferable, and aluminum sulfate, aluminum chloride, potassium aluminum sulfate and sodium aluminum sulfate are particularly preferable. Is aluminum sulfate and sodium aluminum sulfate, most preferably sodium aluminum sulfate. One of these may be used alone, or two or more thereof may be used in combination.

The amount (parts by weight) of the polyvalent metal salt (e) used is preferably 0.05 to 5 and more preferably 0.1 to 5 parts by weight with respect to 100 parts by weight of the water-absorbent resin from the viewpoint of absorption performance and blocking resistance. 3, particularly preferably 0.2 to 2.

The polyvalent metal salt (e) may be mixed when the reducing agent (B) is mixed with the crosslinked polymer (A), or the reducing agent (B) and the crosslinked polymer (A) are mixed. It may be mixed later. From the viewpoint of the absorption performance of the water-absorbent resin particles under pressure, it is preferable to mix them at the same time as the surface cross-linking with the surface cross-linking agent (d).

The method for mixing the polyvalent metal salt (e) can be the same as that for the reducing agent (B), and the mixing temperature is also the same. The heat treatment may be performed after mixing the polyvalent metal salt (e), and the conditions thereof are the same as the heating conditions after mixing the reducing agent (B), and the preferable conditions are also the same. The water-absorbent resin particles containing the polyvalent metal salt (e) may be used by adjusting the particle size, and the adjustment method is the same as the particle size adjustment after the reducing agent (B) is added, and the adjusted particle size is also used. The same is true.

The water-absorbent resin particles may further contain water-insoluble inorganic particles (f). By including the water-insoluble inorganic particles (f), the surface of the particles contained in the water-absorbent resin particles is surface-treated with the water-insoluble inorganic particles (f), so that the blocking resistance and liquid permeability of the water-absorbent resin particles are improved. improves.

Examples of the water-insoluble inorganic particles (f) include colloidal silica, fumed silica, clay and talc, and colloidal silica and silica are preferable and further preferable from the viewpoint of availability, ease of handling, and absorption performance. Is colloidal silica. One kind of water-insoluble inorganic particles (f) may be used alone, or two or more kinds may be used in combination.

The amount (parts by weight) of the water-insoluble inorganic particles (f) used is preferably 0.01 to 5, more preferably 0.05 to 1, and particularly preferably 0.05 to 1 with respect to 100 parts by weight of the water-absorbent resin particles from the viewpoint of absorption performance. It is preferably 0.1 to 0.5.

When the water-insoluble inorganic particles (f) are contained, it is preferable to mix the water-absorbent resin particles and the water-insoluble inorganic particles (f), and the mixing can be performed in the same manner as the mixing of the ammonium salt (C). , The conditions are the same.

The water-absorbent resin particles after mixing the water-insoluble inorganic particles (f) may be used by adjusting the particle size, and the particle size adjustment can be performed in the same manner as the particle size adjustment performed after mixing the ammonium salt (C). The same applies to the particle size after adjusting the particle size.

If necessary, the water-absorbent resin particles may contain preservatives, fungicides, antioxidants, ultraviolet absorbers, colorants, fragrances, liquid-permeable improvers, organic fibrous substances and the like. When these additives are contained, the content (% by weight) of the additives is preferably 0.001 to 10, more preferably 0.01 to 5, particularly preferably 0.01 to 5, based on the weight of the crosslinked polymer (A). It is preferably 0.05 to 1, most preferably 0.1 to 0.5.

The water-absorbent resin particles of the present invention have a yellowness (YI value) (also simply referred to as a YI value in the present specification) of 20 or less after a 50-day accelerated test under the condition of 40 ° C. and 80% Rh. In this case, the 50-day accelerated test is the first (even if it may be performed multiple times) after the production of the water-absorbent resin particles. The degree of yellowness is also referred to as a YI value, and is calculated from the three stimulus values X, Y, and Z obtained by the color difference meter by a predetermined formula (see, for example, JIS K 7373 or ASTM E 313). The degree of yellowness is the degree to which the hue deviates from colorless or white in the yellow direction, and is usually a value of 0 or more. The higher the degree of yellowness, the more the yellow coloring is progressing. In the present invention, the yellowness (YI value) is suppressed to 20 or less even when the yellowing promotion test during storage, which is changed over time for 50 days under the condition of 40 ° C. and 80% Rh, is carried out. It is preferably 18 or less, and more preferably 16 or less. The YI value can be measured by the method described later.

The apparent density (g / ml) of the water-absorbent resin particles obtained by the production method of the present invention is preferably 0.50 to 0.80, more preferably 0.52 to 0.75, and particularly preferably 0.54 to 0.54. It is 0.70. Within this range, the anti-fog resistance of the absorbent article becomes even better. The apparent density of the water-absorbent resin particles is measured at 25 ° C. in accordance with JIS K7365: 1999.

The shape and particle size distribution of the water-absorbent resin particles of the present invention are not particularly limited. The shape may be any of granules, granules, granules, phosphorus flakes, lumps, pearls, fine powders and the like. The particle size distribution is also not particularly limited, and 90% by mass or more is a particle size distribution of 0.05 to 1 mm, and 90% by mass or more is preferably a particle size distribution of 0.1 to 0.9 mm.

The water-absorbent resin particles of the present invention show excellent effects in both deodorant and antibacterial properties. For example, regarding the deodorant property, since many subjects do not feel an unpleasant odor even after the accelerated test of the deodorant test, the water-absorbent resin particles of the present invention are caused by the generation of by-products and bacteria. Shows the effect of suppressing unpleasant odors. Regarding antibacterial properties, the number of viable strains measured by the mixed planar culture method after inoculating ammonia-producing bacteria at 37 ° C for 2 hours in the antibacterial test is 10,000 minutes of the initial number of viable strains (blank) inoculated. It is 1 or less, preferably 1 / 100,000.

By applying the water-absorbent resin particles of the present invention to various water-absorbent articles, an article that fully satisfies the three conditions of absorption performance, deodorant effect and antibacterial effect can be obtained. As a method of applying the water-absorbent resin particles to the absorbent article, the water-absorbent resin particles may form a water-absorbent layer held on the water-absorbent support made of the fibrous material (D), for example, ( 1) A method of scattering water-absorbent resin particles between layers of fibrous materials such as pulp and heat-sealing fibers arranged in layers, (2) Fibrous form of pulp and heat-sealing fibers. Examples thereof include a method of mixing an object and water-absorbent resin particles, and (3) a method of sandwiching water-absorbent resin particles together with a fibrous material with two or more sheets of water-absorbent paper or a non-woven fabric.

Examples of (D) include fibrous materials conventionally used for absorbent articles such as various fluff pulps and cotton-like pulps, as well as raw materials (conifers, broadleaf trees, etc.) and manufacturing methods [chemical pulps, semi-chemical pulps]. , Chemithermomechanical pulp (CTMP), etc.], bleaching method, etc. are not particularly limited. Further, as (D), synthetic fibers that do not swell in water can be used alone or in combination with the above-mentioned fluff pulp, cotton-like pulp, or the like, if necessary. Examples of synthetic fibers include polyolefin fibers (eg, polyethylene fibers, polypropylene fibers, polyester fibers (eg, polyethylene terephthalate fibers), polyolefin / polyester composite fibers, polyamide fibers, polyacrylonitrile fibers, and the like. The length and thickness of (D) are not particularly limited, and usually, the length is preferably in the range of 1 to 200 mm and the thickness is preferably in the range of 0.1 to 100 denier. The shape is also particularly fibrous. Examples thereof include, but are not limited to, a web shape, a thin cylindrical shape, a cut split yarn shape, a staple shape, and a filament shape.

Hereinafter, the present invention will be further described with reference to Examples and Comparative Examples, but the present invention is not limited thereto. Hereinafter, unless otherwise specified, parts indicate parts by weight and% indicates weight%. The amine compound content of the quaternary ammonium salt used, the amount of water retained in the physiological saline of the water-absorbent resin, the amount absorbed under load, the gel flow rate, the moisture absorption blocking rate, the YI value (yellowness), the odor and the antibacterial performance are It was measured by the following method.

<Amine compound content of quaternary ammonium salt>
The amine compound content (%) refers to the ratio of the quaternary ammonium salt to the pure content, and was determined by the following method.
Using a quaternary ammonium salt or solution (pure concentration C%) as a sample, weigh 2.0 ± 0.2 g (Sg), add 50 mL of 0.1 mol / L hydrochloric acid standard solution, and mix. Next, titration was performed with a 0.1 mol / L potassium hydroxide standard solution using a potentiometric titrator, and titration at the inflection point of the first stage (BmL) and titration at the inflection point of the second stage (AmL). ) And ask.
Amine compound (%) = {(AB) × f × (molecular weight of tertiary amine before quaternization)} / {S × C (%)}
In the formula, f: 0.1 mol / L potassium hydroxide standard solution titer.

<Measurement method of water retention>
Put 1.00 g of the measurement sample in a tea bag (length 20 cm, width 10 cm) made of a nylon net 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 soaking for 1 hour without stirring, the sample was pulled up and hung for 15 minutes to drain water. Then, each tea bag was placed in a centrifuge, dehydrated by centrifugation at 150 G for 90 seconds to remove excess physiological saline, the weight (h1) including the tea bag was measured, and the amount of water retained was determined from the following formula. The temperature of the physiological saline used and the measurement atmosphere was 25 ° C ± 2 ° C. (H2) is the weight of the tea bag measured by the same operation as above when there is no measurement sample.
Water retention (g / g) = (h1)-(h2)

<Measurement method of absorption under load>
250-500 μm using a 30-mesh sieve and a 60-mesh sieve in a cylindrical plastic tube (inner diameter: 25 mm, height: 34 mm) with a nylon mesh with a mesh opening of 63 μm (JIS Z8801-1: 2006) attached to the bottom surface. Weigh 0.16 g of the measurement sample sifted into a range, arrange the cylindrical plastic tube vertically on a nylon mesh so that the measurement sample has almost uniform thickness, and then put a weight (weight::) on this measurement sample. 300 g, outer diameter: 24.5 mm,) was placed. After weighing the entire weight (M1) of this cylindrical plastic tube, a cylindrical plastic containing a measurement sample and a weight is placed in a petri dish (diameter: 12 cm) containing 60 ml of physiological saline (salt concentration 0.9%). The tube was erected vertically and immersed with the nylon mesh side facing down, and allowed to stand for 60 minutes. After 60 minutes, the cylindrical plastic tube was pulled up from the petri dish, tilted diagonally, and the water adhering to the bottom was collected in one place and dropped as water droplets to remove excess water, and then the measurement sample and weight were contained. The weight (M2) of the entire cylindrical plastic tube was weighed, and the absorption amount under pressure was obtained from the following equation. The temperature of the physiological saline used and the measurement atmosphere was 25 ° C ± 2 ° C.
Absorption amount under load (g / g) = {(M2)-(M1)} /0.16

<Measurement method of gel flow rate>
The measurement was performed by the following operation using the instruments shown in FIGS. 1 and 2.
The swollen gel particles 2 were prepared by immersing 0.32 g of the measurement sample in 150 ml physiological saline 1 (salt concentration 0.9%) for 30 minutes. A vertically erect cylinder 3 {diameter (inner diameter) 25.4 mm, length 40 cm, and a scale line 4 and a scale line 5 are provided at a position 60 ml and a position 40 ml from the bottom, respectively. } In a filtration cylindrical tube having a wire mesh 6 (opening 106 μm, JIS Z8801-1: 2006) and an openable / closable cock 7 (inner diameter of the liquid passage portion 5 mm) at the bottom of the filter, with the cock 7 closed. After transferring the prepared swollen gel particles 2 together with physiological saline, a pressure shaft 9 (heavy) in which a circular wire mesh 8 (opening 150 μm, diameter 25 mm) is bonded perpendicularly to the wire mesh surface on the swollen gel particles 2. 22 g (22 g, 47 cm in length) was placed so that the wire net and the swollen gel particles were in contact with each other, and a weight 10 (88.5 g) was further placed on the pressure shaft 9 and allowed to stand for 1 minute. Subsequently, the cock 7 was opened, the time (T1; sec) 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 was measured, and the gel liquid passing speed (ml / min) was measured from the following equation. Asked. The temperature of the physiological saline used and the measurement atmosphere was 25 ° C ± 2 ° C. T2 is the time measured by the same operation as above when there is no measurement sample.
Gel passage rate (ml / min) = 20 ml x 60 / (T1-T2)

<Measurement method of moisture absorption blocking rate>
5 g of the measurement sample was uniformly placed in an aluminum dish having a diameter of 5 cm, and left in a constant temperature and humidity chamber at 30 ° C. and a relative humidity of 80% for 3 hours. The weight of the water-absorbent resin after being left to stand was measured, then lightly sieved with a wire mesh of 12 mesh, blocked by moisture absorption, and the mass of the water-absorbent resin that did not pass through 12 mesh was measured, and the moisture absorption blocking rate was determined by the following formula.
Moisture absorption blocking rate = (mass of water-absorbent resin remaining in the 12-mesh net after leaving / mass of water-absorbent resin after leaving) × 100

<Measurement method of YI value (yellowness)>
A digital colorimetric color difference meter (ND-1001DP type manufactured by Nippon Denshoku Kogyo Co., Ltd.) was used for the initial coloring of the water-absorbent resin particles (coloring immediately after production) and the ease of coloring in long-term storage or applied products. It was evaluated by measuring the YI value (yellowness) before and after the accelerated test. The higher the degree of yellowness, the more advanced the coloring. The procedure of the coloring promotion test (50-day promotion test) is as follows.
10 g of water-absorbent resin particles were placed in a glass petri dish having an inner diameter of 90 mm and leveled so that the surface became flat. This was stored in a constant temperature and humidity chamber at 40 ± 2 ° C. and 80 ± 2% Rh for 50 days. Then, the petri dish was taken out from the constant temperature and humidity chamber and returned to room temperature, and then the YI value (yellowness) after the accelerated test was measured.

<Odor test method>
The odor immediately after the production of the water-absorbent resin particles and after the accelerated test was evaluated by the following test method.
1 g of the aqueous liquid absorbent resin was placed in a 100 ml beaker, 20 g of a 0.9 wt% sodium chloride aqueous solution was added, and then the beaker was sealed with a film and left at 37 ° C. for 1 hour. Then, an odor sensory test was conducted by 10 adult subjects, and an average score was calculated based on the following scores.
0: No unpleasant odor 1: Slightly unpleasant odor 2: Unpleasant odor 3: Especially strong unpleasant odor The accelerated test was 50 ± 2 ° C, 80 ± 2% Rh in a constant temperature and humidity machine. The water-absorbent resin particles used for measuring the YI value (yellowness) after the coloring promotion test, which was stored for a day, were used as they were.

<Antibacterial test method>
3.45 g of sensitive bouillon medium and 150 ml of ion-exchanged water are placed in a 300 cc flask and dissolved, and then sterilized by autoclave. After 1.0 g of the test sample was added to the above medium and swollen with stirring, Escherichia coli was inoculated so that the ^{number of bacteria was 1 × 10 6 cells / ml.} This sample is shake-cultured at 37 ° C., sampled after 2 hours and 10 hours, and serially diluted with sterile saline as needed. The number of bacteria is measured by the miscible plane culture method. After putting 1 ml each of the sampled or diluted product in a sterile petri dish, pour 20 ml of agar medium, uniformly disperse and solidify on the petri dish, and incubate at 37 ° C. for 2 days. After culturing, the colonies are counted and multiplied by the dilution ratio to obtain the viable cell count. The viable cell count when inoculated with Escherichia coli alone without adding the test sample as a blank was 6.1 × 10 ⁸ cells / ml after 2 hours and 8.3 × 10 ⁹ cells / ml after 10 hours. Met. Antibacterial properties were tested for ammonia-producing bacteria as in the case of E. coli. In addition, as a blank, when only the ammonia-producing bacteria were inoculated without adding the test sample, the viable cell count was 8.6 × 10 ⁸ cells / ml after 2 hours and 9.7 × 10 ⁹ cells after 10 hours. It was / ml.

<Manufacturing example 1>
230 parts of a methanol solution of didecyldimethylammonium methyl carbonate (containing 69 parts of methanol; containing 69 parts of pure water; 0. 40 mol) was gradually added over 2 hours, and the generated carbon dioxide and methanol were distilled off to obtain an ammonium aqueous solution (1) containing 40% of didecyldimethylammonium gluconate (C1). When the amine content was measured, it was 0.1% with respect to the pure content of the ammonium salt.

<Manufacturing example 2>
124.6 parts (0.40 mol) of didecylmethylamine, 30.0 parts of ethanol and 114.8 parts of water were placed in an autoclave and replaced with nitrogen while keeping the temperature at 60 ° C. Then, 20.2 parts (0.40 mol) of methyl chloride is press-fitted over 1 hour, and the mixture is stirred and reacted at 60 to 70 ° C. for 3 hours to contain 50% didecyldimethylammonium hydrochloride (C2). An aqueous ammonium chloride solution (2) was prepared. The amine content was measured and found to be 1.0%.

<Manufacturing example 3>
0.5 part of didecylmethylamine was added to 99.5 parts of the ammonium aqueous solution (1) obtained in Production Example 1 to obtain an ammonium aqueous solution (3). The amine content was measured and found to be 1.3% of the pure ammonium content.

<Manufacturing example 4>
Water-soluble vinyl monomer (a1-1) {acrylic acid, manufactured by Mitsubishi Chemical Co., Ltd., purity 100%} 155 parts (2.15 mol parts), cross-linking agent (b1) {pentaerythritol triallyl ether, manufactured by Daiso Co., Ltd. } 0.6225 parts (0.0024 mol part) and 340.27 parts of deionized water were kept at 3 ° C. while stirring and mixing. After inflowing nitrogen into this mixture to reduce the amount of dissolved oxygen to 1 ppm or less, 0.62 parts of a 1% hydrogen peroxide solution and 1.1625 parts of a 2% ascorbic acid aqueous solution and 2% of 2,2'-azobis [ 2-325 parts of a 2-methyl-N- (2-hydroxyethyl) -propionamide] aqueous solution was added and mixed to initiate polymerization. After the temperature of the mixture reached 90 ° C., a water-containing gel (3-1) was obtained by polymerizing at 90 ± 2 ° C. for about 5 hours. Next, while 502.27 parts of this hydrogel (3-1) was shredded with a mincing machine (12VR-400K manufactured by ROYAL), 118.54 parts of a 48.5% sodium hydroxide aqueous solution was added and mixed. 18.68 parts of a 15% aqueous solution of sodium sulfite (B1) was added and kneaded once through a mincing machine to obtain a shredded gel (3-2). Further, the shredded gel (3-2) was dried at 140 ° C. for 75 minutes to obtain a dried product. The dried product was pulverized with a juicer mixer (OSTERIZER BLENDER manufactured by Oster), and then adjusted to a particle size of 150 to 710 μm using a sieve having a mesh size of 150 and 710 μm to obtain dried product particles. While stirring 100 parts of the dried body particles at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron: rotation speed 2000 rpm), a 2% water / methanol mixed solution of ethylene glycol diglycidyl ether (water / methanol weight ratio = 70/30). 4.5 parts of the above was added while spraying and mixed, and the mixture was allowed to stand at 150 ° C. for 30 minutes for surface cross-linking to obtain surface-crosslinked water-absorbent resin particles (S1). The weight average particle diameter of the water-absorbent resin particles (S1) was 400 μm, and the water retention amount was 38 g / g.

<Manufacturing example 5>
The same operation as in Production Example 4 was carried out except that the amount of the 15% aqueous solution of sodium sulfite (B1) added was changed from 18.68 parts to 8.30 parts to obtain surface-crosslinked water-absorbent resin particles (S2). .. The weight average particle size of the water-absorbent resin (S2) was 400 μm, and the water retention amount was 37 g / g.

<Manufacturing example 6>
The same operation as in Production Example 4 was carried out except that 18.68 parts of a 15% aqueous solution of sodium sulfite (B1) was not added to obtain surface-crosslinked water-absorbent resin particles (S3). The weight average particle size of the water-absorbent resin (S3) was 400 μm, and the water retention amount was 37 g / g.

<Example 1>
While stirring 100 parts of water-absorbent resin particles (S1) at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron: rotation speed 2000 rpm), spray spray 0.125 parts of ammonium aqueous solution (1) and 0.75 parts of 40% sodium alum. While adding and mixing, 0.2 part of fumed silica (Aerosil 200 manufactured by Aerosil Co., Ltd.) was added and uniformly mixed, and then heated at 80 ° C. for 30 minutes to obtain the water-absorbent resin particles (D1) of the present invention. rice field. Table 1 shows the performance measurement results of the water-absorbent resin particles (D1).

<Example 2>
The same operation as in Example 1 was carried out except that the amount of the ammonium ammonium aqueous solution (1) added was changed from 0.125 part to 2.5 part, to obtain the water-absorbent resin particles (D2) of the present invention. Table 1 shows the performance measurement results of the water-absorbent resin particles (D2).

<Example 3>
The same operation as in Example 1 was carried out except that the amount of the ammonium ammonium aqueous solution (1) added was changed from 0.125 part to 0.025 part, to obtain the water-absorbent resin particles (D3) of the present invention. Table 1 shows the performance measurement results of the water-absorbent resin particles (D3).

<Example 4>
The same operation as in Example 1 was carried out except that the amount of 40% sodium alum added was changed from 0.75 part to 3.0 part and no fumed silica was added, and the water-absorbent resin particles (D4) of the present invention were carried out. ) Was obtained. Table 1 shows the performance measurement results of the water-absorbent resin particles (D4).

<Example 5>
The same operation as in Example 1 was carried out except that 40% sodium alum was not added and the amount of fumed silica added was changed from 0.2 part to 0.4 part. D5) was obtained. Table 1 shows the performance measurement results of the water-absorbent resin particles (D5).

<Example 6>
The same operation as in Example 1 was carried out except that 0.125 part of the ammonium aqueous solution (1) was changed to 0.10 part of the ammonium aqueous solution (2) to obtain the water-absorbent resin particles (D6) of the present invention. Table 1 shows the performance measurement results of the water-absorbent resin particles (D6).

<Example 7>
The same operation as in Example 1 was performed except that 100 parts of the water-absorbent resin particles (S1) were changed to 100 parts of the water-absorbent resin particles (S2) to obtain the water-absorbent resin particles (D7) of the present invention. Table 1 shows the performance measurement results of the water-absorbent resin particles (D7).

<Example 8>
Except for changing 100 parts of the water-absorbent resin particles (S1) to 100 parts of the water-absorbent resin particles (S2) and further changing 0.125 parts of the ammonium aqueous solution (1) to 0.10 parts of the ammonium aqueous solution (2). The same operation as in Example 1 was carried out to obtain the water-absorbent resin particles (D8) of the present invention. Table 1 shows the performance measurement results of the water-absorbent resin particles (D8).

<Comparative Example 1>
The same operation as in Example 1 was carried out except that 0.125 part of the ammonium aqueous solution (1) was not added, to obtain water-absorbent resin particles (H1) for comparison. Table 1 shows the performance measurement results of the water-absorbent resin particles (H1).

<Comparative Example 2>
The same operation as in Example 1 was performed except that 100 parts of the water-absorbent resin particles (S1) were changed to 100 parts of the water-absorbent resin particles (S3) to obtain water-absorbent resin particles (H2) for comparison. Table 1 shows the performance measurement results of the water-absorbent resin particles (H2).

<Comparative Example 3>
The same operation as in Example 1 was carried out except that 0.125 part of the ammonium aqueous solution (1) was changed to 0.125 part of the ammonium aqueous solution (3) to obtain water-absorbent resin particles (H3) for comparison. Table 1 shows the performance measurement results of the water-absorbent resin particles (H3).

As can be seen from Table 1, the water-absorbent resin particles of the present invention have excellent antibacterial performance as compared with the water-absorbent resin of Comparative Example 1 containing no ammonium salt. Further, the water-absorbent resin particles of the present invention are YI as compared with the water-absorbent resin particles of Comparative Example 2 containing no reducing agent and the water-absorbent resin particles of Comparative Example 3 containing an ammonium salt having an amine content exceeding a specific range. The change over time of the value is greatly improved.

The water-absorbent resin particles of the present invention have excellent liquid permeability between swollen gels, and are characterized in that blocking, discoloration, and odor during storage do not occur. Since the above effects are obtained, the water-absorbent resin particles of the present invention can be used for absorbent articles having a large absorption amount and excellent reversion and surface dryness by being applied to various absorbent bodies, and can be used as disposable diapers (paper diapers). Suitable for sanitary products such as diapers for children and diapers for adults), napkins (sanitary napkins, etc.), paper towels, pads (pads for incontinence and surgical underpads, etc.) and pet sheets (pet urine absorption sheets). It is used and is especially suitable for disposable diapers.

1 Saline 2 Hydrous gel particles 3 Cylinder 4 Scale line 60 ml from the bottom 5 Scale line 40 ml from the bottom 6 Wire mesh 7 Cock 8 Circular wire mesh 9 Pressurized shaft 10 Weight

Claims (6)

A crosslinked polymer (A) of a monomer composition containing a water-soluble vinyl monomer (a1) and / or a vinyl monomer (a2) that becomes a water-soluble vinyl monomer (a1) by hydrolysis, and a cross-linking agent (b), reduction. After a 50-day accelerated test containing 0.01 to 2% by weight of the quaternary ammonium salt (C) with respect to the weight of the agent (B) and the crosslinked polymer (A) under the condition of 40 ° C. and 80% Rh. The water-absorbent resin particles are characterized by having a yellowness (YI value) of 20 or less, the reducing agent (B) is an inorganic sulfur-based reducing agent, and the quaternary ammonium salt (C) is a quaternary amine compound. Water-absorbent resin particles containing 0.01 to 1% by weight based on the weight of the ammonium salt (C), wherein the quaternary ammonium salt (C) has at least one alkyl group having 8 to 30 carbon atoms. Is a water-absorbent resin particle . A crosslinked polymer (A) of a monomer composition containing a water-soluble vinyl monomer (a1) and / or a vinyl monomer (a2) that becomes a water-soluble vinyl monomer (a1) by hydrolysis, and a cross-linking agent (b), reduction. After a 50-day accelerated test containing 0.01 to 2% by weight of the quaternary ammonium salt (C) with respect to the weight of the agent (B) and the crosslinked polymer (A) under the conditions of 40 ° C. and 80% Rh. The yellowness (YI value) is 20 or less, the reducing agent (B) is an inorganic sulfur-based reducing agent, and the quaternary ammonium salt (C) is an amine compound based on the weight of the quaternary ammonium salt (C). A method for producing water-absorbent resin particles containing 0.01 to 1% by weight, which comprises a step of mixing a reducing agent (B) with a crosslinked polymer (A), and after the mixing step, a quaternary ammonium salt. A method for producing water-absorbent resin particles, which comprises mixing (C), wherein the quaternary ammonium salt (C) has at least one alkyl group having 8 to 30 carbon atoms. .. The production method according to claim 2 , further comprising a step of drying the crosslinked polymer (A), which is a hydrogel-like product obtained by polymerizing the monomer composition with an aqueous solution. The production method according to claim 3 , wherein the quaternary ammonium salt (C) is mixed after the drying step. The production method according to claim 3 or 4 , wherein the reducing agent (B) is mixed with the crosslinked polymer (A) which is a hydrogel-like product before the drying step. An absorbent article containing the water-absorbent resin particles according to claim 1.

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