WO2020115988A1 - Particules de résine absorbant l'eau et leur procédé de production - Google Patents

Particules de résine absorbant l'eau et leur procédé de production Download PDF

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WO2020115988A1
WO2020115988A1 PCT/JP2019/036663 JP2019036663W WO2020115988A1 WO 2020115988 A1 WO2020115988 A1 WO 2020115988A1 JP 2019036663 W JP2019036663 W JP 2019036663W WO 2020115988 A1 WO2020115988 A1 WO 2020115988A1
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Prior art keywords
water
resin particles
absorbent resin
minutes
weight
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PCT/JP2019/036663
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English (en)
Japanese (ja)
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泰知 松山
佑介 松原
宮島　徹
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Ｓｄｐグローバル株式会社
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Priority to CN201980079691.XA priority Critical patent/CN113166439B/zh
Priority to JP2020559740A priority patent/JP7453918B2/ja
Publication of WO2020115988A1 publication Critical patent/WO2020115988A1/fr

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F13/00—Bandages or dressings; Absorbent pads
    • A61F13/15—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F13/00—Bandages or dressings; Absorbent pads
    • A61F13/15—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators
    • A61F13/53—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F8/00—Chemical modification by after-treatment
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J3/00—Processes of treating or compounding macromolecular substances
    • C08J3/24—Crosslinking, e.g. vulcanising, of macromolecules

Definitions

  • the present invention relates to water absorbent resin particles and a method for producing the same.
  • hydrophilic fibers such as pulp and a water absorbent resin mainly containing acrylic acid (salt) is widely used as an absorber.
  • a water absorbent resin mainly containing acrylic acid (salt) is widely used as an absorber.
  • Consumers in recent years tend to demand more comfort, and the demand is shifting to those with higher dryness and thinner, which is accompanied by higher dryness and the amount of hydrophilic fiber used. Reduction has come to be desired. Therefore, the water-absorbent resin itself has been required to play the role of high initial absorption rate and liquid diffusibility that the hydrophilic fiber has been playing so far.
  • acrylic acid/acrylic acid salt aqueous solution is suspended in an alicyclic or aliphatic hydrocarbon solvent in the presence of a surfactant of HLB 8 to 12, and acrylic acid/acrylic acid salt is polymerized by reverse phase suspension polymerization.
  • a method reverse phase suspension polymerization method for producing pearl-like water-absorbent resin particles having a large surface area.
  • Patent Document 1 a method (Patent Document 1) is known that has an excellent water absorption rate and suppresses the generation of volatile component odor after water absorption, but the odor cannot be completely suppressed.
  • Patent Document 2 a method of increasing the drying speed of the water absorbent resin to reduce the apparent density (Patent Document 2) or a method of internally foaming in the drying process of the water absorbent resin to reduce the apparent density (Patent Document) 3) is known. Further, a method of granulating water-absorbent resin particles (Patent Document 4) is also known.
  • Patent Document 4 a method of granulating water-absorbent resin particles
  • Patent Document 5 a method of improving the absorption rate by reducing the particle size of the water absorbent resin particles in the sieving step (Patent Document 5) is also known, but when the particle size of the water absorbent resin is reduced, the moisture absorption resistance decreases, Similar to the above, there is a problem that causes particle clogging in the diaper manufacturing process.
  • An object of the present invention is to generate no odor due to volatile components after absorbing water, to quickly dry liquid from the nonwoven fabric and to have excellent dryness, and to prevent problems such as fogging and the like.
  • the object of the present invention is to exhibit an initial high absorption rate, that is, an initial high water retention capacity, and a water-absorbent resin particle with little liquid return, an absorbent body and an absorbent article containing the same. Is to provide.
  • the water-absorbent resin particle of the present invention comprises 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) as an essential constituent unit. It is a water-absorbent resin particle containing a polymer (A), the particle shape of which is irregular and crushed, and which satisfies the following (i) and (ii). (I) 0.9 wt% physiological saline solution has a water retention capacity after 30 minutes of 30 to 50 g/g per unit weight. (Ii) Capillary absorption amount (CAP) after 5 minutes defined by the following formula (1) is 6 g/g or more.
  • CAP Capillary absorption amount
  • the present invention also relates to 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 an internal crosslinking agent (b) as essential constituent units.
  • the water-absorbent resin particles of the present invention and the water-absorbent resin particles obtained by the production method of the present invention do not generate odor due to volatile components after absorbing water, and exhibit high capillary absorption ability at the initial stage. Therefore, the absorbent article to which the water-absorbent resin particles of the present invention are applied has a fast initial liquid draining from the nonwoven fabric, is excellent in dryness, and is free from problems such as fogging. Further, according to a preferred embodiment of the present invention, the water-absorbent resin particles of the present invention and the water-absorbent resin particles obtained by the production method of the present invention have high water retention capacity and liquid permeability at the initial stage of water absorption.
  • the absorbent article to which the water-absorbent resin particles of the present invention are applied has less liquid return and liquid leakage when urinating, and there is no problem such as rash. Furthermore, the shape of the water-absorbent resin particles is irregularly crushed to form irregularities on the surface, and by forming irregularities for a certain controlled proportion of particles, a high average particle diameter and capillary absorption capacity can be obtained. It is possible to achieve both compatibility, and it is possible to stably manufacture absorbent articles (paper diapers, sanitary napkins, etc.) even under high humidity.
  • FIG. 3 is a perspective view schematically showing a pressurizing shaft and a weight for measuring a gel passage rate.
  • the water-soluble vinyl monomer (a1) in the present invention is not particularly limited, and known monomers such as at least one water-soluble substituent and an ethylenic vinyl group disclosed in paragraphs 0007 to 0023 of Japanese Patent No. 3648553 are used.
  • Vinyl monomers having a saturated group for example, anionic vinyl monomers, nonionic vinyl monomers and cationic vinyl monomers), anionic vinyl monomers and nonionic compounds disclosed in paragraphs 0009 to 0024 of JP-A-2003-165883.
  • Vinyl monomer and cationic vinyl monomer and selected from the group consisting of carboxy group, sulfo group, phosphono group, hydroxyl group, carbamoyl group, amino group and ammonio group disclosed in paragraphs 0041 to 0051 of JP-A-2005-75982.
  • Vinyl monomers having at least one of
  • the vinyl monomer (a2) (hereinafter, also referred to as a hydrolyzable vinyl monomer (a2)) that becomes a water-soluble vinyl monomer (a2) by hydrolysis is not particularly limited and is publicly known (for example, 0024 to 0025 of Japanese Patent No. 3648553).
  • a vinyl monomer having a decomposable substituent (a vinyl monomer having a 1,3-oxo-2-oxapropylene (—CO—O—CO—) group, an acyl group, a cyano group, etc.) can be used.
  • the water-soluble vinyl monomer means a vinyl monomer having a property of dissolving at least 100 g in 100 g of water at 25°C.
  • the term "hydrolyzable" means a property of being hydrolyzed by being hydrolyzed by the action of water at 50°C and, if necessary, a catalyst (acid or base etc.). Hydrolysis of the hydrolyzable vinyl monomer may be carried out during the polymerization, after the polymerization, or both of them, but the polymerization is preferable from the viewpoint of the molecular weight of the water-absorbent resin particles to be obtained.
  • the water-soluble vinyl monomer (a1) is preferable from the viewpoint of absorption characteristics.
  • the water-soluble vinyl monomer (a1) is preferably an anionic vinyl monomer, more preferably a carboxy (salt) group, a sulfo (salt) group, an amino group, a carbamoyl group, an ammonio group or a mono-, di- or tri-alkyl group. It is a vinyl monomer having an ammonio group.
  • a vinyl monomer having a carboxy (salt) group or a carbamoyl group further preferably (meth)acrylic acid (salt) and (meth)acrylamide, particularly preferably (meth)acrylic acid (salt), Most preferably, it is acrylic acid (salt).
  • a “carboxy (salt) group” means a “carboxy group” or a “carboxylate group”
  • a “sulfo (salt) group” means a “sulfo group” or a “sulfonate group”.
  • (meth)acrylic acid (salt) means acrylic acid, acrylic acid salt, methacrylic acid or methacrylic acid salt
  • (meth)acrylamide means acrylamide or methacrylamide.
  • the salt include alkali metal (lithium, sodium and potassium etc.) salts, alkaline earth metal (magnesium and 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 characteristics.
  • each may be a constitutional unit independently, or if necessary, two or more types may be constitutional units.
  • the molar ratio (a1/a2) of these is preferably 75/25 to 99/1, and more preferably 85/15 to 95/5, particularly preferably 90/10 to 93/7, most preferably 91/9 to 92/8. Within this range, the absorption performance is further improved.
  • 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. 3648553, JP-A-2003-165883, JP Hydrophobic vinyl monomers such as vinyl monomers disclosed in paragraph 0058 of Japanese Unexamined Patent Publication No. 2005-75982 can be used, and the following vinyl monomers (i) to (iii) can be used.
  • (I) Aromatic ethylenic monomer having 8 to 30 carbon atoms Styrene such as styrene, ⁇ -methylstyrene, vinyltoluene and hydroxystyrene, and halogen-substituted styrene such as vinylnaphthalene and dichlorostyrene.
  • Styrene such as styrene, ⁇ -methylstyrene, vinyltoluene and hydroxystyrene
  • halogen-substituted styrene such as vinylnaphthalene and dichlorostyrene.
  • the content (mol%) of the other vinyl monomer (a3) unit is the same as that of the water-soluble vinyl monomer (a1) unit and the hydrolyzable vinyl monomer (a2) unit. It is preferably 0.01 to 5, more preferably 0.05 to 3, still more preferably 0.08 to 2, and particularly preferably 0.1 to 1.5, based on the number of moles. Despite the above, it is most preferable that the content of the other vinyl monomer (a3) unit is 0 mol% from the viewpoint of absorption characteristics.
  • the internal cross-linking agent (b) (hereinafter, also simply referred to as the cross-linking agent (b)) is not particularly limited and is publicly known (for example, the ethylenically unsaturated group disclosed in paragraphs 0031 to 0034 of Japanese Patent No. 3648553 is 2). At least one cross-linking agent, a cross-linking agent having at least one functional group capable of reacting with a water-soluble substituent and having at least one ethylenically unsaturated group, and a functional group capable of reacting with a water-soluble substituent.
  • a cross-linking agent of cross-linkable vinyl monomer can be used.
  • a crosslinking agent having two or more ethylenically unsaturated groups is preferable from the viewpoint of absorption performance and the like, and more preferable are poly(poly(aryl)(triallyl cyanurate, triallyl isocyanurate, and polyol having 2 to 10 carbon atoms).
  • (Meth)allyl ether particularly preferred are triallyl cyanurate, triallyl isocyanurate, tetraallyloxyethane and pentaerythritol triallyl ether, most preferred is pentaerythritol triallyl ether.
  • the crosslinking agent (b) one type may be used alone, or two or more types may be used in combination.
  • the content (mol %) of the crosslinking agent (b) unit is from (a1) to (a1) when the other vinyl monomer (a3) of the water-soluble vinyl monomer (a1) unit and the hydrolyzable vinyl monomer (a2) unit is used. Based on the total number of moles of (a3), it is preferably 0.001 to 5, more preferably 0.005 to 3, and particularly preferably 0.01 to 1. Within this range, the absorption performance will be further improved.
  • Examples of the method for producing the crosslinked polymer (A) include known solution polymerization (adiabatic polymerization, thin film polymerization, spray polymerization, etc.; JP-A-55-133413, etc.), known suspension polymerization method, reverse phase suspension method, etc. If necessary, a water-containing gel polymer (consisting of a cross-linked polymer and water) obtained by turbid polymerization (Japanese Patent Publication No. 54-30710, Japanese Patent Publication No. 56-26909, Japanese Patent Publication No. 1-5808, etc.). It can be obtained by heating and drying and pulverizing.
  • the crosslinked polymer (A) may be a single type or a mixture of two or more types.
  • the solution polymerization method is preferable, and since it is advantageous in terms of production cost that it is not necessary to use an organic solvent or the like, particularly preferable is the aqueous solution polymerization method, which has a large water retention amount and is water-soluble.
  • the aqueous solution adiabatic polymerization method is most preferable because a water-absorbent resin having a small amount of components can be obtained and temperature control during polymerization is unnecessary.
  • a mixed solvent containing water and an organic solvent can be used, and as the organic solvent, methanol, ethanol, acetone, methyl ethyl ketone, N,N-dimethylformamide, dimethylsulfoxide and two or more of them can be used.
  • the amount of organic solvent used (% by weight) is preferably 40 or less, and more preferably 30 or less, based on the weight of water.
  • radical polymerization catalysts When a catalyst is used for the polymerization, conventionally known radical polymerization catalysts can be used, and examples thereof include azo compounds [azobisisobutyronitrile, azobiscyanovaleric acid and 2,2′-azobis(2-amidinopropane) hydrochloride.
  • inorganic peroxides hydrogen peroxide, ammonium persulfate, potassium persulfate and sodium persulfate, etc.
  • organic peroxides benzoyl peroxide, di-t-butyl peroxide, cumene hydroperoxide, succinic acid peroxide] Oxide and di(2-ethoxyethyl)peroxydicarbonate, etc.
  • redox catalysts alkali metal sulfites or bisulfites, ammonium sulfite, ammonium bisulfite, ascorbic acid and other reducing agents and alkali metal persulfates, (Combined with an oxidizing agent such as ammonium persulfate, hydrogen peroxide and organic peroxide).
  • the amount (% by weight) of the radical polymerization catalyst used is the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2), or (a1) to (a3) when other vinyl monomer (a3) is used.
  • the total weight is preferably 0.0005 to 5, and more preferably 0.001 to 2.
  • the polymerization method is a suspension polymerization method or a reverse phase suspension polymerization method
  • the polymerization may be carried out in the presence of a conventionally known dispersant or surfactant, if necessary.
  • the reverse phase suspension polymerization method the polymerization can be carried out using a conventionally known hydrocarbon solvent 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 5 to 80°C.
  • the solvent organic solvent, water, etc.
  • the content (% by weight) of the organic solvent after distillation is preferably 0 to 10 based on the weight of the crosslinked polymer (A), more preferably 0 to 5, and particularly preferably Is 0 to 3, most preferably 0-1. Within this range, the absorbent performance of the water absorbent resin particles will be further improved.
  • 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 3-8. Within this range, the absorption performance will be further improved.
  • the content and water content of the organic solvent are infrared moisture meter [JE400 manufactured by KETT Co., Ltd.: 120 ⁇ 5° C., 30 minutes, atmospheric humidity before heating 50 ⁇ 10% RH, lamp specification 100V, 40W. ] It is calculated from the weight loss of the measurement sample when heated.
  • the crosslinked polymer (A) can be obtained by drying the hydrogel polymer obtained by polymerization after shredding.
  • the size (longest diameter) of the gel after chopping is preferably 50 ⁇ m to 10 cm, more preferably 100 ⁇ m to 2 cm, and particularly preferably 1 mm to 1 cm. Within this range, the drying property in the drying step becomes even better.
  • the stress applied to the hydrogel during the shredding step can be relaxed and the shape inside the gel can be maintained.
  • the shape of the inside of the water-absorbent resin particles it is possible to prevent the mechanical strength of the water-absorbent resin particles from decreasing, and the water-absorbent resin particles have good absorption performance.
  • the water-absorbent resin particles of the present invention does not have trouble such as clogging in the diaper manufacturing process, good initial Since the water retention ability can be exhibited, the amount of liquid returned when used as an absorber is small and there is no fear of rash.
  • the method of subdividing is not particularly limited, and may be subdivided by, for example, scissors, and a frozen water-containing gel is pulverized (for example, a hammer pulverizer, an impact pulverizer, a roll pulverizer and a shet airflow pulverizer). ).
  • a frozen water-containing gel is pulverized (for example, a hammer pulverizer, an impact pulverizer, a roll pulverizer and a shet airflow pulverizer).
  • the size (longest diameter) of the gel after subdivision is preferably 50 ⁇ m to 10 cm, more preferably 100 ⁇ m to 2 cm, and particularly preferably 500 ⁇ m to 1 cm.
  • the structure inside the hydrogel can be maintained in the subsequent shredding step, so that irregularities are formed on the surface of the water-absorbent resin particles while maintaining the shape of the inside of the water-absorbent resin particles, resulting in absorption of the water-absorbent resin particles. The performance becomes even better. If necessary, an alkali can be mixed with the gel after the subdivision to neutralize it.
  • the alkali known ⁇ Patent No. 3205168 etc. ⁇ can be used.
  • lithium hydroxide, sodium hydroxide and potassium hydroxide are preferable, sodium hydroxide and potassium hydroxide are more preferable, and sodium hydroxide is particularly preferable, from the viewpoint of water absorption performance.
  • the neutralization rate is preferably 50 to 100%, more preferably 60 to 80%.
  • the shredding can be performed by a known method, and can be shredded using a shredding device (for example, Beck's mill, rubber chopper, pharma mill, mincing machine, impact crusher and roll crusher).
  • a shredding device for example, Beck's mill, rubber chopper, pharma mill, mincing machine, impact crusher and roll crusher.
  • the temperature of the hydrogel at the time of shredding is preferably 40 to 120°C, more preferably 60 to 100°C, and the shredding number is preferably 1 to 4 times, more preferably 2 to 3 times.
  • a method for distilling off the solvent (including water) in the hydrogel As a method for distilling off the solvent (including water) in the hydrogel, a method for distilling off (drying) with hot air at a temperature of 80 to 230° C., a thin film drying method by a drum dryer heated to 100 to 230° C. , (Heating) vacuum drying method, freeze drying method, infrared ray drying method, decantation, filtration, and the like can be applied.
  • the crushing method is not particularly limited, and a crushing device (for example, a hammer crusher, an impact crusher, a roll crusher, and a shett airflow crusher) 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 diameter ( ⁇ m) of the crosslinked polymer (A), which is screened as necessary, is preferably 100 to 800, more preferably 200 to 700, next preferably 250 to 600, particularly preferably 300 to 500, and most preferably It is preferably 350 to 450. Within this range, the absorption performance will be further improved.
  • the weight average particle size is determined by using a low tap test sieve shaker and a standard sieve (JIS Z8801-1:2006), Perry's Chemical Engineers Handbook 6th Edition (MacGlow Hill Book Company, 1984). , Page 21). That is, the JIS standard sieve is combined from the top in the order of 1000 ⁇ m, 850 ⁇ m, 710 ⁇ m, 500 ⁇ m, 425 ⁇ m, 355 ⁇ m, 250 ⁇ m, 150 ⁇ m, 125 ⁇ m, 75 ⁇ m and 45 ⁇ m, and a saucer. About 50 g of the measurement particles are put into the uppermost sieve and shaken for 5 minutes with a low tap test sieve shaker.
  • the weight of the measured particles on each sieve and the pan is weighed, and the total is 100% by weight to obtain the weight fraction of the particles on each sieve.
  • This value is used as a logarithmic probability paper [the horizontal axis is the sieve opening (particle size ), and the vertical axis is the weight fraction], and a line connecting the points is drawn to obtain the particle diameter corresponding to the weight fraction of 50% by weight, which is taken as the weight average particle diameter.
  • the content of fine particles contained in the crosslinked polymer (A) the better the absorption performance. Therefore, the content of fine particles of 106 ⁇ m or less (preferably 150 ⁇ m or less) in the total weight of the crosslinked polymer (A).
  • the ratio (% by weight) is preferably 3 or less, more preferably 1 or less.
  • the content of the fine particles can be determined using the graph created when determining the weight average particle size.
  • Examples of the shape of the crosslinked polymer (A) include irregular crushed shapes, flaky shapes, pearl shapes, and rice granules, but they have good entanglement with the fibrous materials in applications such as disposable diapers, and From the viewpoint that there is no fear of falling off, an irregular crushed shape is preferable.
  • a hydrocarbon dispersion medium is used in the reverse phase suspension polymerization for producing pearl-shaped water-absorbent resin particles, which causes odor, which is not preferable.
  • the crosslinked polymer (A) or the polymer gel may be treated with a hydrophobic substance, if necessary, by the method described in JP2013-231199A or the like.
  • the surface of the crosslinked polymer (A) is preferably crosslinked.
  • the gel strength can be further improved, and the desired water retention amount and absorption amount under load can be satisfied in actual use.
  • a conventionally known method for example, a method of mixing a cross-linked polymer (A), a surface cross-linking agent (c), a mixed solution of water and a solvent, and reacting with heating is used.
  • a method of mixing include a method of spraying the mixed solution onto the crosslinked polymer (A), or a method of dipping the crosslinked polymer (A) into the mixed solution, and preferably, the crosslinked polymer (A) is added to the crosslinked polymer (A). This is a method of spraying and mixing the above mixed solution.
  • Examples of the surface cross-linking agent (c) include polyglycidyl compounds such as ethylene glycol diglycidyl ether, glycerol diglycidyl ether and polyglycerol polyglycidyl ether, polyhydric alcohols such as glycerin and ethylene glycol, ethylene carbonate, polyamines and polyhydric alcohols. A metal compound etc. are mentioned. Of these, polyglycidyl compounds are preferable because they can be crosslinked at a relatively low temperature. These surface cross-linking agents may be used alone or in combination of two or more.
  • the amount of the surface crosslinking agent (c) used is preferably 0.001 to 5% by weight, more preferably 0.005 to 2% by weight, based on the weight of the crosslinked polymer (A) before crosslinking.
  • the amount of the surface cross-linking agent (c) used is less than 0.001% by weight, the degree of surface cross-linking is insufficient, and the effect of improving the absorption amount under load may be insufficient, which is not preferable.
  • the amount of the surface cross-linking agent (c) used exceeds 5% by weight, the degree of cross-linking on the surface becomes excessive and the water retention amount may decrease, which is not preferable.
  • the amount of water used for surface crosslinking is preferably 0.5 to 10% by weight, more preferably 1 to 7% by weight, based on the weight of the crosslinked polymer (A) before crosslinking. If the amount of water used is less than 0.5% by weight, the degree of penetration of the surface-crosslinking agent (c) into the water-absorbent resin particles becomes insufficient, and the effect of improving the amount of absorption under load may be poor. Not preferable. On the other hand, when the amount of water used exceeds 10% by weight, the penetration of the surface cross-linking agent (c) into the interior becomes excessive, and although the absorption amount under load is improved, the water retention amount may decrease. Not preferable.
  • the solvent used in combination with water at the time of surface cross-linking conventionally known solvents can be used, and the degree of penetration of the surface cross-linking agent (c) into the water-absorbent resin particles and the reactivity of the surface cross-linking agent (c).
  • a hydrophilic organic solvent such as methanol, diethylene glycol or propylene glycol, which is soluble in water, is preferable.
  • the solvent may be used alone or in combination of two or more kinds.
  • the amount of the solvent used can be appropriately adjusted depending on the type of the solvent, but it is preferably 1 to 10% by weight based on the weight of the water absorbent resin before surface crosslinking.
  • the ratio of the solvent to water can be adjusted arbitrarily, but it is preferably 20 to 80% by weight, more preferably 30 to 70% by weight.
  • the reaction temperature is preferably 100 to 230°C, more preferably 120 to 180°C.
  • the reaction time can be appropriately adjusted depending on the reaction temperature, but is preferably 3 to 60 minutes, more preferably 10 to 45 minutes.
  • the surface-crosslinking of the particulate water-absorbent resin can be further surface-crosslinked by using the same or different surface-crosslinking agent as the surface-crosslinking agent initially used.
  • the weight average particle size of the particles obtained after the particle size adjustment is preferably 100 to 600 ⁇ m, more preferably 200 to 500 ⁇ m.
  • the content of fine particles is preferably small, the content of particles of 100 ⁇ m or less is preferably 3% by weight or less, and the content of particles of 150 ⁇ m or less is more preferably 3% by weight or less.
  • the water-absorbent resin particles of the present invention may further contain water-insoluble inorganic particles (d). Therefore, the production method of the present invention described below may further include a step of mixing with the water-insoluble inorganic particles (d). From the viewpoint of absorption characteristics, it is preferable to have a step of mixing the water-insoluble inorganic particles (d) after the shredding step.
  • the surface of the particles contained in the water-absorbent resin particles is surface-treated with the water-insoluble inorganic particles (d), thereby improving the capillary absorption of the water-absorbent resin particles. Blocking resistance and liquid permeability are also improved.
  • water-insoluble inorganic particles (d) examples include colloidal silica, fumed silica, clay, and talc. From the viewpoint of easy availability, easy handling, and absorption performance, colloidal silica and fumed silica are preferable. Preferred is colloidal silica.
  • the water-insoluble inorganic particles (d) may be used alone or in combination of two or more.
  • the amount (% by weight) of the water-insoluble inorganic particles (d) is preferably as small as possible from the viewpoint of cost, but is preferably 0.01 to 1 based on the weight of the crosslinked polymer, and more preferably 0 from the viewpoint of absorption performance. 0.05 to 1, particularly preferably 0.1 to 1. Within this range, the performance balance between the capillary absorption amount and the liquid passage with respect to the water retention amount for 60 minutes becomes good, and the anti-fogging property of the absorbent article becomes even better.
  • the water-absorbent resin particles of the present invention may further contain a polyvalent metal salt (e). Therefore, in the production method of the present invention described below, a step of further mixing with the polyvalent metal salt (e) is performed. May be included. By containing the polyvalent metal salt (e), blocking resistance and liquid permeability of the water absorbent resin particles are improved.
  • the polyvalent metal salt (e) include salts of 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.
  • an inorganic acid salt of aluminum and an inorganic acid salt of titanium are preferable from the viewpoint of easy availability and solubility, and more preferable are aluminum sulfate, aluminum chloride, potassium aluminum sulfate and sulfuric acid.
  • Aluminum aluminum particularly preferred are aluminum sulfate and sodium aluminum sulfate, and most preferred is sodium aluminum sulfate. These may be used alone or in combination of two or more.
  • the amount (% by weight) of the polyvalent metal salt (e) used is preferably 0.01 to 5, and more preferably 0.05 to 4 based on the weight of the crosslinked polymer from the viewpoint of absorption performance and blocking resistance. , Particularly preferably 0.1 to 3.
  • the timing of mixing with the polyvalent metal salt (e) is not particularly limited, but it is preferable to mix the water-containing gel polymer after drying to obtain a crosslinked polymer from the viewpoint of absorption performance and blocking resistance. preferable.
  • the water-absorbent resin particles of the present invention may contain other additives (for example, known antiseptics, antifungal agents, antibacterial agents, antioxidants, ultraviolet rays, etc. (Japanese Patent Laid-Open Nos. 2003-225565 and 2006-131767). Absorbents, colorants, fragrances, deodorants, organic fibrous substances, etc. ⁇ can also be included.
  • the content (% by weight) of the additive is preferably 0.001 to 10 based on the weight of the crosslinked polymer (A), more preferably 0.01 to 5, and especially It is preferably 0.05 to 1, and most preferably 0.1 to 0.5.
  • the shape of the water-absorbent resin particles of the present invention is an irregular crushed shape from the viewpoint of forming irregularities on the surface of the water-absorbent resin particles, high capillary absorption, and excellent drainage from the nonwoven fabric. In addition, if it is in an irregular crushed state, it has good entanglement with the fibrous material for use in a disposable diaper, etc., and there is no fear of falling off from the fibrous material.
  • the water-absorbent resin particles of the present invention have a water retention capacity of 0.9 wt% physiological saline for 60 minutes of 30 to 50 g/g.
  • the water retention capacity for 60 minutes can be measured by the method described below, and is preferably 33 to 49 g/g, more preferably 36 to 48 g/g, and further preferably 39 to 47 g/g from the viewpoint of suppressing leakage of the absorbent article. Is particularly preferable. If it is less than 30 g/g, leakage tends to occur during repeated use. Moreover, when it exceeds 50 g/g, blocking becomes easy. Further, it is preferable that the 5-minute water retention capacity of 0.9 wt% physiological saline is 23 to 49 g/g.
  • the water retention capacity for 5 minutes can be measured by the method described below, and is more preferably 25 to 48 g/g, particularly preferably 28 to 47 g/g, and most preferably from the viewpoint of suppressing the liquid return amount of the absorbent article. Is 30 to 47 g/g. When it is less than 23 g/g, the amount of liquid returned from the absorbent article increases, which is not preferable. Further, if it exceeds 49 g/g, the permeation rate into the absorber becomes slow, and leakage is likely to occur, which is not preferable.
  • the water retention amount can be appropriately adjusted by the type and amount of the crosslinking agent (b) and the surface crosslinking agent (c). For example, when it is necessary to increase the water retention amount, it can be realized by reducing the amounts of the crosslinking agent (b) and the surface crosslinking agent (c) used.
  • the physiological saline absorption amount after 5 minutes (also referred to as DW 5 minutes absorption amount) of the water-absorbent resin particles of the present invention measured by the Demand Wetability method (hereinafter, also referred to as DW method) is 40 g/g or more.
  • DW method can be performed by the method described below.
  • the water-absorbent resin particles of the present invention have a capillary absorption after 5 minutes (CAP) defined by the following formula (1) of 6 g/g or more.
  • CAP capillary absorption after 5 minutes
  • the amount of absorbed capillaries after 5 minutes is high, the liquid from the surface non-woven fabric used in the absorbent article will be good, and the surface dryness of the absorbent body will be excellent. From the viewpoint of surface dryness, it is preferably 8 g/g or more, more preferably 10 g/g or more.
  • the capillary absorption amount is less than 6 g/g, as can be seen from the formula (1), the absorption amount after 5 minutes of DW is low and the absorption amount after 5 minutes of constant DW is lower than the water retention amount after a certain 5 minutes. Water retention after 5 minutes may be high relative to the amount.
  • the former case is not preferable from the viewpoint of surface dryness, because the water-absorbent resin particles are poorly drained from the nonwoven fabric.
  • the swelling speed of the water-absorbent resin particles is high, the liquid permeability between the particles is deteriorated, and the liquid easily accumulates in the liquid-introducing part of the absorber, which is not preferable from the viewpoint of surface dryness.
  • the surface dryness is not obtained from the viewpoint of the liquid drainage property and liquid permeability from the nonwoven fabric. It was found that the dryness is excellent by satisfying the back capillary absorption amount.
  • the water-absorbent resin particles of the present invention include particles having a particle deficiency (CONV) of 1% or less defined by the following formula (2) among particles sieving in a range of 300 to 600 ⁇ m using a JIS standard sieve.
  • the volume ratio is preferably 50% or less.
  • the volume ratio of the particles having a particle deficiency of 8% or more is preferably 5% or less.
  • CONV(%) ⁇ B/(A+B) ⁇ 100 (2)
  • CONV represents the degree of particle deficiency
  • A represents the projected area of the target particles obtained by the image analysis method
  • B represents the envelope connecting the convex portions of the target particles obtained by the image analysis method.
  • the degree of particle deficiency is 0% or more and less than 100%, and the closer to 0%, the more uneven the particles are and the smoother the surface is.
  • a method for obtaining the degree of particle defect will be described with reference to FIG.
  • the projected area (A) of the target particle is obtained from the “particle projected area” in FIG.
  • the projection area (A+B) surrounded by the envelope connecting the convex portions of the particle projection area is obtained as an area including the A area which is the projection area (A) of the target particle and the B area which is the defective area. Be done.
  • the area of the B part is obtained from these values.
  • the volume ratio of the particles having a particle deficiency of 1% or less is 50% or less, the proportion of particles having a smooth surface is small. Since the water-absorbent resin particles have sufficient irregularities, they exhibit good capillary absorption ability, and when made into an absorbent article, the initial drainage from the nonwoven fabric is good, the surface dryness is excellent, and the anti-fogging property is good. The property is good. On the other hand, as the degree of particle deficiency increases, the unevenness of the particles increases and the absorption rate increases, but the fragility of the water-absorbent resin particles increases and the fine powder increases in the diaper manufacturing process.
  • the volume ratio of particles having a particle deficiency of 8% or more to all particles is preferably 5% or less from the viewpoint of breakability. This can prevent the mechanical strength of the water-absorbent resin particles from being reduced.
  • the water-absorbent resin particles of the present invention preferably have a 5-minute water retention index of 70 or more defined by the following formula (3).
  • 5 minute water retention index (5 minute water retention of 0.9% by weight saline)/(60 minute water retention of 0.9% by weight saline) ⁇ 100 (3)
  • the 5-minute water retention index defined by equation (3) is an index showing the water retention capacity in the initial stage of absorption, and the larger the value, the more the water retention capacity close to the 60-minute water retention capacity can be reached after 5 minutes. It was found that this 5-minute water retention index is useful as an index showing the liquid return property that cannot be adjusted from the absolute value of the water retention amount, and that a liquid return suppression is extremely good by showing a numerical value of 70 or more. .. From the viewpoint of suppressing the liquid return of the absorbent article, it is 70 or more, preferably 75 or more, particularly preferably 80 or more. When it is less than 70, the liquid return of the absorbent article increases.
  • the 5-minute water retention index can be adjusted, for example, by controlling the shape of the surface of the water absorbent resin particles.
  • the finely divided hydrous gel may be shredded and dried, and in order to lower the 5-minute water retention index, the finely divided hydrous gel may be dried without shredding. .. It is also possible to control by mixing and adjusting water-absorbent resin particles having different surface shapes.
  • the apparent density (g/ml) of the water absorbent resin particles of the present invention is preferably 0.5 to 0.7, more preferably 0.52 to 0.69, and particularly preferably 0.54 to 0.68. .. Within this range, the anti-fogging property of the absorbent article will be further improved.
  • the apparent density of the water-absorbent resin particles is measured at 25° C. according to JIS K7365:1999.
  • the water absorbent resin particles of the present invention preferably have an absorption amount under load of 10 to 27 g/g.
  • the absorption under load can be measured by the method described below, and from the viewpoint of absorption characteristics, 13 to 27 is more preferable, 16 to 27 is still more preferable, and 19 to 27 is particularly preferable.
  • the gel permeation rate (ml/min) of the water absorbent resin particles of the present invention is preferably 5 to 250.
  • the gel passage rate can be measured by the method described later, and is more preferably 10 to 230, particularly preferably 30 to 210 from the viewpoint of absorption characteristics.
  • the moisture absorption blocking rate (%) of the water absorbent resin particles of the present invention is preferably 20 or less.
  • the moisture absorption blocking rate can be measured by the method described below, and is preferably 15 or less, more preferably 10 or less, and particularly preferably 5 or less, from the viewpoint of suppressing particle clogging in the diaper manufacturing process.
  • the whitening speed of the water absorbent resin particles of the present invention is preferably 100 seconds or less.
  • the whitening rate can be measured by the method described below, and is preferably 95 seconds or less, more preferably 90 seconds or less from the viewpoint of surface dryness. It is possible to reduce the whitening rate by reducing the particle size, but due to the smaller particle size, the moisture absorption resistance deteriorates, which may cause clogging of resin particles in the diaper manufacturing process. .. Further, by the reverse phase suspension polymerization, when reducing the whitening rate by producing water-absorbent resin particles that are aggregates of a small primary particle size, the hydrocarbon dispersion medium used during production is a volatile component inside the particles. There is a problem that it remains and produces an odor after absorbing water.
  • the whitening rate is satisfied by setting the CAP to 6 g/g or more, the particle shape is made into an irregular crushed state, and it is desirable that the degree of particle deficiency is within a specific range so that the resin in the manufacturing process is It is possible to exhibit good surface dryness when used as an absorber without causing particle clogging and generation of odor of volatile components after absorption.
  • the liquid return amount of the absorbent body produced using the water absorbent resin particles of the present invention is preferably 15 g or less.
  • the method for producing the absorber and the measurement of the liquid return amount can be carried out by the method described later, and the liquid return amount is more preferably 14 g or less, and further preferably 13 g or less from the viewpoint of anti-fogging property.
  • reverse phase suspension polymerization may be used to produce water-absorbent resin particles that are agglomerates of small primary particles, but the hydrocarbon dispersion medium used during production remains inside the particles as a volatile component, causing odor after water absorption. There is a problem that occurs.
  • the particle shape is made into an irregular crushed shape having a degree of particle deficiency within a specific range, and the water retention index of 5 minutes is set to 70 or more to suppress the above-mentioned liquid return amount when used as an absorbent body, and to prevent fogging.
  • the property is good, and there is no problem that an odor is generated after absorbing water.
  • the water-absorbent resin particle of the present invention comprises a water-soluble vinyl monomer (a1) and/or a vinyl monomer (a2) which becomes a water-soluble vinyl monomer (a1) by hydrolysis and an internal cross-linking agent (b) as essential constituent units.
  • the production method of the present invention by subdividing before the shredding step, it is possible to maintain the shape of the inside of the water-absorbent resin particles, it is possible to prevent the mechanical strength of the water-absorbent resin particles from decreasing, the water-absorbent resin produced The particle absorption performance is improved.
  • the absorber of the present invention contains the water absorbent resin particles of the present invention.
  • the water absorbent resin particles may be used alone, or may be used together with other materials to form the absorber. Examples of other materials include fibrous materials.
  • the structure and manufacturing method of the absorber when used together with the fibrous material are the same as known ones (JP 2003-225565 A, JP 2006-131767 A, JP 2005-097569 A, etc.). is there.
  • Preferred as the fibrous material are cellulosic fibers, organic synthetic fibers, and a mixture of cellulosic fibers and organic synthetic fibers.
  • cellulosic fibers examples include natural fibers such as fluff pulp, and cellulosic chemical fibers such as viscose rayon, acetate and cupra.
  • natural fibers such as fluff pulp
  • cellulosic chemical fibers such as viscose rayon, acetate and cupra.
  • raw material softwood, hardwood, etc.
  • manufacturing method chemical pulp, semi-chemical pulp, mechanical pulp, CTMP, etc.
  • bleaching method of this cellulosic natural fiber There are no particular limitations on the raw material (softwood, hardwood, etc.), manufacturing method (chemical pulp, semi-chemical pulp, mechanical pulp, CTMP, etc.), and bleaching method of this cellulosic natural fiber.
  • organic synthetic fibers examples include polypropylene fibers, polyethylene fibers, polyamide fibers, polyacrylonitrile fibers, polyester fibers, polyvinyl alcohol fibers, polyurethane fibers and heat-fusible composite fibers (the above-mentioned fibers having different melting points).
  • cellulose-based natural fibers cellulose-based natural fibers, polypropylene-based fibers, polyethylene-based fibers, polyester-based fibers, heat-fusible composite fibers and mixed fibers thereof are preferable, and more preferable are obtained.
  • the fluff pulp, the heat-fusible composite fiber, and the mixed fiber thereof are excellent in the shape retention of the water absorbent body after absorbing water.
  • the length and thickness of the fibrous material are not particularly limited, and the length of 1 to 200 mm and the thickness of 0.1 to 100 denier can be suitably used.
  • the shape is not particularly limited as long as it is fibrous, and examples thereof include a thin cylinder shape, a split yarn shape, a staple shape, a filament shape, and a web shape.
  • the weight ratio of the water-absorbent resin particles and the fibers is preferably 40/60 to 90/10, and more preferably Is 70/30 to 80/20.
  • the absorbent article of the present invention uses the above absorber.
  • the absorbent article is applicable not only to hygiene products such as disposable diapers and sanitary napkins, but also to various applications such as various aqueous liquid absorbents and holding agents, gelling agents, etc. described below. ..
  • the method of manufacturing the absorbent article and the like are the same as known methods (those described in JP 2003-225565 A, JP 2006-131767 A, JP 2005-097569 A, etc.).
  • part means “part by weight” and “%” means “% by weight”.
  • the water-absorbent resin is measured according to the DW method described in paragraphs 0117 to 0121 of JP-A-2014-005472 using water-absorbent resin particles and physiological saline, and the water-absorbent resin after 5 minutes has elapsed from the start of measurement.
  • the amount of absorption (g) per 1 g of particles was determined.
  • the tea bag was pulled up, put in a centrifuge together with the tea bag, centrifugally dehydrated at 150 G for 90 seconds to remove excess physiological saline, and the weight (h1) including the tea bag was measured to determine the water retention amount from the following formula.
  • the temperature of the physiological saline used and the measurement atmosphere was 25°C ⁇ 2°C.
  • Water retention (g/g) (h1)-(h2) (H2) is the weight of the tea bag measured by the same operation as above in the case where there is no measurement sample.
  • CAP capillary absorption amount
  • the particle deficiency of the water-absorbent resin particles was measured using a Camsizer (registered trademark) image analysis system (manufactured by Retsch Technology GmbH). From the sample feeder on the upper part of the device, 5.00 g of the measurement sample sieved in the range of 300 to 600 ⁇ m using a standard sieve (JIS Z8801-1:2006) was allowed to fall freely little by little, and the falling measurement sample was continuously measured with a CCD camera. I took it. The particle deficiency of the measurement sample was derived by analyzing the captured image.
  • the measurement for all particles was performed in the same manner as above except that no screening was performed.
  • ⁇ Measurement method of absorption under load Measurement in a cylindrical plastic tube (inner diameter: 25 mm, height: 34 mm) having a nylon net with an opening of 63 ⁇ m (JIS Z8801-1:2006) attached to the bottom surface and sieving in the range of 250 to 500 ⁇ m using a standard sieve. 0.16 g of the sample was weighed, and the cylindrical plastic tube was placed vertically to prepare a measurement sample on the nylon net so that the measurement sample had a substantially uniform thickness. Then, a weight (weight: 210.6 g, external weight) was placed on the measurement sample. Diameter: 24.5 mm,) was mounted.
  • Nonwoven fabric (basis weight 20 g/m 2 , Eltas Guard manufactured by Asahi Kasei Co., Ltd.) cut into 10 cm ⁇ 30 cm is placed on a back sheet (polyethylene film UB-1 manufactured by Tama Poly) cut into 12 cm ⁇ 35 cm, and water-absorbent resin particles 6 g was evenly spread by hand, and a non-woven fabric (basis weight 20 g/m 2 , Eltas Guard manufactured by Asahi Kasei Co., Ltd.) cut into 10 cm ⁇ 30 cm was placed on the outermost surface to prepare an absorber.
  • Nonwoven fabric (basis weight 20 g/m 2 , Eltas Guard manufactured by Asahi Kasei Co., Ltd.) cut into 10 cm ⁇ 30 cm is placed on a back sheet (polyethylene film UB-1 manufactured by Tama Poly) cut into 12 cm ⁇ 35 cm, and water-absorbent resin particles 6 g was evenly spread by hand, and a non-woven fabric (basis weight 20 g/m 2 , Eltas Guard manufactured by Asahi Kasei Co., Ltd.) cut into 10 cm ⁇ 30 cm was placed on the outermost surface to prepare an absorber.
  • ⁇ Odor sensory test> The unpleasant odor during swelling of the water absorbent resin particles was evaluated by the following method. 20.0 g of physiological saline was added to a glass container with a lid (mayonnaise bottle) having an inner volume of 140 mL, and a rotor having a length of 3 cm was put therein and stirred. 2.0 g of water-absorbent resin particles were added to the above glass container and sealed. The presence or absence of an unpleasant odor in the glass container was judged by five analysts, and the number of people judged to be present was taken as the evaluation result.
  • Example 1 131 parts of acrylic acid (a1) ⁇ manufactured by Mitsubishi Chemical Corporation, purity 100% ⁇ , internal cross-linking agent (b-1) ⁇ pentaerythritol triallyl ether, manufactured by Daiso Corporation ⁇ 0.44 parts and 362 parts of deionized water was kept at 3° C. with stirring and mixing. Nitrogen was flowed into this mixture to adjust the dissolved oxygen content to 1 ppm or less, and then 0.5 part of 1% hydrogen peroxide solution, 1 part of 2% ascorbic acid solution and 2% of 2,2'-azobisamidinopropane. Polymerization was initiated by adding and mixing 0.1 part of an aqueous dihydrochloride solution. After the temperature of the mixture reached 80°C, a hydrogel was obtained by polymerizing at 80 ⁇ 2°C for about 5 hours.
  • this hydrogel was subdivided into about 1 mm square pieces with scissors, and 162 parts of a 45% sodium hydroxide aqueous solution was added. Further, after being minced 4 times with a mincing machine with a perforated plate diameter of 16 mm (12VR-400K manufactured by ROYAL) at a gel temperature of 80° C., it was dried with a ventilation type dryer ⁇ 150° C., wind speed 2 m/sec ⁇ to obtain a dried body. .. The dried product is crushed with a juicer mixer (OSTERIZER BLENDER manufactured by Oster), sieved, and adjusted to have a particle size range of 710 to 150 ⁇ m (400 ⁇ m as a weight average particle size) to contain crosslinked polymer particles. Resin particles were obtained.
  • a juicer mixer OSTERIZER BLENDER manufactured by Oster
  • Example 2 Water-absorbent resin particles (P-2) were obtained in the same manner as in Example 1 except that 0.12 parts by weight of ethylene glycol diglycidyl ether as a surface crosslinking agent was used.
  • Example 3 Water absorption in the same manner as in Example 1 except that Klebosol 30cal25 (colloidal silica manufactured by Merck & Co., solid content 30%, particle size 25 nm) as the water-insoluble inorganic particles (d) was 0.5 part by weight. Resin particles (P-3) were obtained.
  • Example 4 Water absorption in the same manner as in Example 2 except that Klebosol 30cal25 (colloidal silica manufactured by Merck & Co., solid content 30%, particle size 25 nm) as the water-insoluble inorganic particles (d) was 0.5 part by weight. Resin particles (P-4) were obtained.
  • Klebosol 30cal25 colloidal silica manufactured by Merck & Co., solid content 30%, particle size 25 nm
  • Resin particles (P-4) were obtained.
  • this water-containing gel is subdivided into about 1 mm square with scissors, and after being minced 4 times at a gel temperature of 80°C with a mincing machine (12VR-400K manufactured by ROYAL) having a plate diameter of 16 mm, an aeration dryer ⁇ 150°C, It was dried at a wind speed of 2 m/sec ⁇ to obtain a dried body.
  • the dried product is crushed with a juicer mixer (OSTERIZER BLENDER manufactured by Oster), sieved, and adjusted to have a particle size range of 710 to 150 ⁇ m (400 ⁇ m as a weight average particle size) to contain crosslinked polymer particles. Resin particles were obtained.
  • Water-absorbent resin particles (P-6) were obtained in the same manner as in Example 5, except that 0.12 parts by weight of ethylene glycol diglycidyl ether as a surface crosslinking agent was used.
  • Example 7 Water absorption in the same manner as in Example 5 except that Klebosol 30cal25 (colloidal silica manufactured by Merck & Co., solid content 30%, particle size 25 nm) as the water-insoluble inorganic particles (d) was 0.5 part by weight. Resin particles (P-7) were obtained.
  • Example 8 Water absorption in the same manner as in Example 6 except that Klebosol 30cal25 (colloidal silica manufactured by Merck & Co., solid content 30%, particle size 25 nm) as the water-insoluble inorganic particles (d) was 0.5 part by weight. Resin particles (P-8) were obtained.
  • Example 9 The neutralized water-containing gel was dried with an aeration dryer ⁇ 150°C, wind speed 2 m/sec ⁇ without being shredded with a mincing machine (ROYAL 12VR-400K) to obtain a dried body.
  • the dried product is crushed with a juicer mixer (OSTERIZER BLENDER manufactured by Oster), sieved, and adjusted to a particle size range of 710 to 150 ⁇ m (200 ⁇ m as a weight average particle size) to contain crosslinked polymer particles.
  • Water-absorbent resin particles (P-9) were obtained in the same manner as in Example 1 except that resin particles were obtained.
  • Example 10 Water-absorbent resin particles (P-10) were obtained in the same manner as in Example 9 except that 0.12 parts by weight of ethylene glycol diglycidyl ether as a surface crosslinking agent was used.
  • Comparative water absorbent resin particles (R-1) were obtained in the same manner as in Example 1 except that 0.01 part by weight of ethylene glycol diglycidyl ether as a surface crosslinking agent was used.
  • Comparative Example 4 A hydrogel subdivided into about 1 mm square was dried by a ventilation dryer ⁇ 150°C, wind speed 2 m/sec ⁇ without being shredded by a mincing machine (ROYAL 12VR-400K), and dried. Comparative water absorbing resin particles (R-4) were obtained in the same manner as in Example 5 except that the above was obtained.
  • Comparative Example 5 A hydrogel subdivided into about 1 mm square was dried with an aeration dryer (150°C, wind speed 2 m/sec) without being shredded with a mincing machine (ROYAL 12VR-400K), and dried. Comparative water absorbing resin particles (R-5) were obtained in the same manner as in Example 6 except that the above was obtained.
  • the monomer aqueous solution composition was introduced through a supply section of a polymerization vessel consisting of a conveyor belt that continuously moves, it was irradiated with ultraviolet rays by a UV irradiation device (irradiation amount: 2 mW/cm 2 ) and UV polymerization was performed for 2 minutes.
  • a UV irradiation device irradiation amount: 2 mW/cm 2
  • UV polymerization was performed for 2 minutes.
  • the hydrogel polymer was transferred to a cutting machine and then cut into 0.2 cm. At this time, the water content of the cut hydrogel polymer was 50% by weight.
  • the hydrogel polymer was dried with a hot air dryer at a temperature of 160° C. for 30 minutes to obtain a dried product.
  • the dried product is crushed with a juicer mixer (OSTERIZER BLENDER manufactured by Oster), sieved, and adjusted to have a particle size range of 710 to 150 ⁇ m (400 ⁇ m as a weight average particle size) to contain crosslinked polymer particles. Resin particles were obtained.
  • n-heptane a hydrocarbon dispersion medium
  • sorbitan monolaurate NONION LP-20R; HLB8.6, manufactured by NOF CORPORATION
  • the total amount of the above aqueous solution was added to the above round bottom flask while stirring with the number of revolutions of the stirrer being 700 rpm. After purging the system with nitrogen for 30 minutes, the round-bottomed flask was immersed in a water bath at 70° C. to raise the temperature of the system, and the polymerization reaction was carried out for 1 hour to obtain a hydrogel polymer.
  • the temperature inside the system was raised using an oil bath at 120° C., and water and n-heptane were azeotropically distilled, and 111.7 g of water was extracted from the system while refluxing the n-heptane ( Primary drying step).
  • 4.14 g (0.00048 mol) of a 2% by mass aqueous solution of ethylene glycol diglycidyl ether as a post-crosslinking agent was added to the round bottom flask to obtain a mixture containing the post-crosslinking agent.
  • the water content in the round bottom flask was 40.9 g, and the water content of the hydrogel polymer after primary drying (during post-crosslinking) was 45% by mass.
  • the water-absorbent resin particles of the present invention have a water retention amount within a certain range and a high initial capillary absorption amount, as compared with the water-absorbent resin particles of Comparative Examples 1 to 6. It can be seen that the absorbent article using the water-absorbent resin particles of the present invention has a dramatically increased whitening rate and excellent dryness.
  • the water-absorbent resin particles of the present invention by the irregular crushed shape having irregularities formed on the surface of the water-absorbent resin particles, can be compatible with a high average particle size and capillary absorption capacity, in the moisture absorption blocking property. It turns out that it is excellent and can be manufactured stably. Further, the water-absorbent resin particles of the present invention can suppress odor as compared with Comparative Example 7 by not using the hydrocarbon dispersion medium in the manufacturing process.
  • Example 1a In the same manner as in Example 1, resin particles containing crosslinked polymer particles were obtained. Next, while stirring 100 parts of the obtained resin particles at high speed (high-speed stirring turbulator made by Hosokawa Micron: rotation speed 2000 rpm), sodium aluminum alum dodecahydrate 12 hydrate as the polyvalent metal salt (e) was added thereto. After adding 0.6 parts by weight, 0.08 parts by weight of ethylene glycol diglycidyl ether as a surface cross-linking agent and 3.3 parts by weight of a 45% propylene glycol aqueous solution as a solvent, and uniformly mixing them. Then, the mixture was allowed to stand at 130° C. for 60 minutes for drying to obtain water-absorbent resin particles (P-1a) of the present invention.
  • high-speed stirring turbulator made by Hosokawa Micron: rotation speed 2000 rpm sodium aluminum alum dodecahydrate 12 hydrate as the polyvalent metal salt (e) was added thereto. After adding 0.6 parts by weight, 0.08
  • Example 2a Water-absorbent resin particles (P-2a) were obtained in the same manner as in Example 1a, except that 0.12 parts by weight of ethylene glycol diglycidyl ether as a surface crosslinking agent was used.
  • Example 3a A water-absorbent resin was obtained in the same manner as in Example 1a except that the neutralized hydrous gel was shredded twice at a gel temperature of 80°C with a mincing machine (12VR-400K manufactured by ROYAL) with a 16 mm plate diameter. Particles (P-3a) were obtained.
  • Example 4a A water-absorbent resin was prepared in the same manner as in Example 2a except that the neutralized hydrogel was shredded twice at a gel temperature of 80°C with a mincing machine (12VR-400K manufactured by ROYAL) having a plate diameter of 16 mm. Particles (P-4a) were obtained.
  • Example 5a In the same manner as in Example 5, resin particles containing crosslinked polymer particles were obtained. Next, while stirring 100 parts of the obtained resin particles at high speed (high-speed stirring turbulator made by Hosokawa Micron: rotation speed 2000 rpm), sodium aluminum alum dodecahydrate 12 hydrate as the polyvalent metal salt (e) was added thereto. After adding 0.6 parts by weight, 0.08 parts by weight of ethylene glycol diglycidyl ether as a surface cross-linking agent and 3.3 parts by weight of a 45% propylene glycol aqueous solution as a solvent, and uniformly mixing them. After drying at 130° C. for 60 minutes, the water-absorbent resin particles (P-5a) of the present invention were obtained. ..
  • Example 6a Water-absorbent resin particles (P-6a) were obtained in the same manner as in Example 5a except that 0.12 parts by weight of ethylene glycol diglycidyl ether as a surface crosslinking agent was used.
  • Example 7a In the same manner as in Example 5a except that the water-containing gel subdivided into about 1 mm square was shredded twice at a gel temperature of 80° C. with a mincing machine (12VR-400K manufactured by ROYAL) having a plate diameter of 16 mm. Water-absorbent resin particles (P-7a) were obtained.
  • Example 8a Water-absorbent resin particles (P-8a) were obtained in the same manner as in Example 7a except that 0.12 parts by weight of ethylene glycol diglycidyl ether as a surface crosslinking agent was used.
  • Example 9a The neutralized water-containing gel was dried with an aeration dryer ⁇ 150°C, wind speed 2 m/sec ⁇ without shredding with a mincing machine (12VR-400K manufactured by ROYAL) to obtain a dried body.
  • the dried product is crushed with a juicer mixer (OSTERIZER BLENDER manufactured by Oster), sieved, and adjusted to a particle size range of 710 to 150 ⁇ m (200 ⁇ m as a weight average particle size) to contain crosslinked polymer particles.
  • Water-absorbent resin particles (P-9a) were obtained in the same manner as in Example 1a except that resin particles were obtained.
  • Example 10a Water-absorbent resin particles (P-10a) were obtained in the same manner as in Example 9a, except that 0.12 parts by weight of ethylene glycol diglycidyl ether as a surface crosslinking agent was used.
  • Comparative Example 4a A hydrogel subdivided into about 1 mm square was dried with an aeration dryer ⁇ 150°C, wind speed 2 m/sec ⁇ without being shredded with a mincing machine (ROYAL 12VR-400K), and dried. Comparative water absorbing resin particles (R-4a) were obtained in the same manner as in Example 5a except that the above was obtained.
  • Comparative example 5a A hydrogel subdivided into about 1 mm square was dried with an aeration dryer ⁇ 150°C, wind speed 2 m/sec ⁇ without being shredded with a mincing machine (ROYAL 12VR-400K), and dried. Comparative water absorbent resin particles (R-5a) were obtained in the same manner as in Example 6a except that the above was obtained.
  • the water-absorbent resin particles of the present invention have a water-retaining amount in a certain range and a water-retaining index of 70 or more as compared with the water-absorbent resin particles of Comparative Examples 1a to 6a. It can be seen that the amount of liquid returned has decreased dramatically. In Examples 9a and 10a, the water retention index can be increased by 5 minutes by reducing the weight average particle diameter, and the liquid return amount is small, but it is easy to block due to moisture absorption.
  • the ratio of the particle deficiency of 1% or less is as small as 50% or less of the sieved particles, and the volume ratio of the particles having the particle deficiency of 8% or more to the sieved particles is 5% or less, preferably Furthermore, since the volume ratio of particles having a particle deficiency of 8% or more to all particles is 5% or less, mechanical strength is not reduced. Furthermore, since there is no large difference in the apparent density and the average particle size, it can be seen that the 5-minute water retention index greatly contributes to the liquid return amount of the absorber. As compared with Comparative Example 7a, it can be seen that the odor can be suppressed by not using the hydrocarbon dispersion medium in the manufacturing process.
  • the water-absorbent resin particles of the present invention can be applied to an absorbent body containing the water-absorbent resin particles and a fibrous material, and an absorbent article comprising the absorbent body ⁇ paper diaper, sanitary napkin and medical blood retaining agent. It is useful for agents.
  • pet urine absorbent, urine gelling agent for mobile toilets, freshness keeping agent for fruits and vegetables, drip absorbent for meat and seafood, cooler, disposable body warmer, gelling agent for batteries, water retaining agent for plants and soil, dew condensation It can also be used in various applications such as preventive agents, waterstop agents, packing agents and artificial snow.

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  • Health & Medical Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Veterinary Medicine (AREA)
  • Epidemiology (AREA)
  • Heart & Thoracic Surgery (AREA)
  • Vascular Medicine (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Animal Behavior & Ethology (AREA)
  • General Health & Medical Sciences (AREA)
  • Public Health (AREA)
  • Engineering & Computer Science (AREA)
  • Biomedical Technology (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Absorbent Articles And Supports Therefor (AREA)
  • Processes Of Treating Macromolecular Substances (AREA)
  • Solid-Sorbent Or Filter-Aiding Compositions (AREA)

Abstract

L'invention concerne : des particules de résine absorbant l'eau qui, après avoir absorbé de l'eau, n'émettent pas d'odeur liée à un composant volatil et qui extraient rapidement le liquide du tissu non tissé au début pour atteindre d'excellentes propriétés de séchage et ne sont à l'origine d'aucun problème de type érythème, etc. ; et un absorbant et un article absorbant comprenant ou incluant chacun ces particules de résine absorbant l'eau. Les particules de résine absorbant l'eau de la présente invention comportent un polymère réticulé (A) comprenant des motifs constitutifs essentiels issus d'un monomère vinylique hydrosoluble (a1) et/ou d'un monomère vinylique hydrolysable (a2) et d'un agent de réticulation (b), les particules présentant des formes indéterminées résultant du broyage et étant conformes aux propositions (i) et (ii) suivantes. (I) La rétention d'eau après 60 minutes en termes de solution saline physiologique à 0,9 % en poids par unité de poids varie de 30 à 50 g/g. (Ii) L'absorption capillaire (CAP) après 5 minutes, comme définie par l'équation suivante (1), est égale ou supérieure à 6 g/g. CAP (g/g) = (poids sec après 5 minutes d'absorption ) - (rétention d'eau après 5 minutes)
PCT/JP2019/036663 2018-12-04 2019-09-19 Particules de résine absorbant l'eau et leur procédé de production WO2020115988A1 (fr)

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