WO2022091975A1 - Method for dehydration treatment of water-absorbent resin particles - Google Patents

Method for dehydration treatment of water-absorbent resin particles Download PDF

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Publication number
WO2022091975A1
WO2022091975A1 PCT/JP2021/039108 JP2021039108W WO2022091975A1 WO 2022091975 A1 WO2022091975 A1 WO 2022091975A1 JP 2021039108 W JP2021039108 W JP 2021039108W WO 2022091975 A1 WO2022091975 A1 WO 2022091975A1
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Prior art keywords
water
absorbent resin
resin particles
dehydration treatment
acid
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PCT/JP2021/039108
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French (fr)
Japanese (ja)
Inventor
英二 森田
真平 長谷川
一充 鈴木
範朋 栗田
孝義 小西
健司 板東
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三洋化成工業株式会社
ユニ・チャーム株式会社
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Priority to JP2022559094A priority Critical patent/JPWO2022091975A1/ja
Publication of WO2022091975A1 publication Critical patent/WO2022091975A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/30—Processes for preparing, regenerating, or reactivating
    • B01J20/34—Regenerating or reactivating
    • 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
    • C08J11/00—Recovery or working-up of waste materials
    • C08J11/04—Recovery or working-up of waste materials of polymers
    • C08J11/06—Recovery or working-up of waste materials of polymers without chemical reactions
    • 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
    • C08J3/12—Powdering or granulating
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/62—Plastics recycling; Rubber recycling

Definitions

  • the present invention relates to a method for dehydrating water-absorbent resin particles.
  • Patent Document 1 proposes a method of decomposing, solubilizing and removing water-absorbent resin particles in used sanitary products by immersing the used sanitary products in acidic ozone water having a pH of 3 or less. ing.
  • Patent Document 2 immerses used hygiene products in an acidic aqueous solution to dehydrate the swollen gel-like water-absorbent resin particles in the used hygiene products, thereby shrinking and separating the water-absorbent resin particles.
  • Patent Document 3 the swollen gel-like water-absorbent resin particles are immersed in a polyvalent metal salt to form crosslinks between the polymer chains of the water-absorbent resin particles with polyvalent metal ions, thereby forming a highly water-absorbent resin.
  • Patent Document 1 uses acidic ozone water having a pH of 3 or less, it cannot be said that the processing apparatus becomes complicated and the problem is not always sufficiently solved from the viewpoint of safety. The problem was that it took time to complete the disassembly of SAP. Further, in the method of Patent Document 2, the water-absorbent resin particles can be shrunk and separated easily by dehydrating the water absorbed by the water-absorbent resin particles, but the dehydration is not sufficient, so that the subsequent steps are performed. Therefore, it is necessary to dry the water-absorbent resin particles containing a large amount of water, which complicates the process.
  • Patent Document 3 makes it easy to separate by dehydrating the water absorbed by the water-absorbent resin particles as in Patent Document 2, and also makes it easy to dry in the subsequent steps by sufficiently dehydrating.
  • the water-absorbent resin particles obtained as a polymer crosslinked with polyvalent metal ions had poor water absorption and did not have sufficient performance for reuse as SAP.
  • the present invention provides a dehydration treatment method capable of sufficiently dehydrating the water absorbed by the water-absorbent resin particles, facilitating the drying of the water-absorbent resin particles in the subsequent steps, and facilitating the reuse thereof.
  • the purpose is to do.
  • the present invention is a method for dehydrating water absorbed by water-absorbent resin particles containing a crosslinked polymer (A) containing (meth) acrylic acid (salt) and a crosslinking agent (b) as essential constituent units.
  • Method (1) A method including a step of mixing the water-absorbent resin particles absorbing water with a water-soluble inorganic acid (c1), and then a step of further mixing with a water-soluble monovalent metal compound (c2).
  • Method (2) A method including a step of mixing the water-absorbent resin particles absorbing water with a water-soluble monovalent metal compound (c2), and then a step of further mixing with a water-soluble inorganic acid (c1).
  • And method (3) any of a method including a step of mixing the water-absorbent resin particles absorbing water with a water-soluble inorganic acid (c1) and a water-soluble monovalent metal compound (c2). It is a dehydration treatment method using the method.
  • the dehydration treatment method of the present invention is excellent in dehydrating the water absorbed by the water-absorbent resin particles, and the water-absorbent resin particles can be easily dried in the subsequent steps. In addition, the water-absorbent resin particles can be easily reused.
  • the water-absorbent resin particles in the dehydration treatment method of the present invention contain a crosslinked polymer (A) containing (meth) acrylic acid (salt) and a crosslinking agent (b) as essential constituent units.
  • (meth) acrylic acid (salt) means acrylic acid, methacrylic acid, acrylate or methacrylic acid. Therefore, the carboxylic acid moiety of (meth) acrylic acid may be, for example, a salt neutralized with sodium ions.
  • the salt includes an alkali metal (lithium, sodium, potassium, etc.) salt, an alkaline earth metal (magnesium, calcium, etc.) salt, an 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 characteristics and the like.
  • the cross-linking agent (b) (also referred to as an internal cross-linking agent (b)) is not particularly limited, and is known (for example, Japanese Patent No. 36485553, Japanese Patent Application Laid-Open No. 2003-165883, Japanese Patent Application Laid-Open No. 2005-75982 and JP-A-2005-75982).
  • a cross-linking agent or the like described in 2005-95759 (Ab. 2005) can be used.
  • These cross-linking agents may be used alone or in combination of two or more.
  • a cross-linking agent having two or more ethylenically unsaturated groups and more preferably a poly (meth) allyl ether of a polyhydric alcohol having 2 to 40 carbon atoms and 2 carbon atoms.
  • the content (mol%) of the cross-linking agent (b) unit is preferably 0.001 to 5, more preferably 0.005 to 3, and particularly preferably 0.01, based on the (meth) acrylic acid (salt). ⁇ 1. Within this range, the absorption performance is further improved.
  • the crosslinked polymer (A) is surface-crosslinked with the surface cross-linking agent (d) from the viewpoint of suppressing coalescence gel blocking between gel particles and controlling the required absorption characteristics (balance between the amount of water retained and the amount of absorption under load).
  • the surface cross-linking agent (d) the polyvalent glycidyl described in JP-A-59-189103 and the like, JP-A-58-180233 and JP-A-61-16903 are preferably used.
  • the alkylene carbonate described in JP-A-508425, the polyvalent oxazoline compound described in JP-A-11-240959, and the polyvalent metal described in JP-A-51-136588 and JP-A-61-257235, etc. Can be mentioned.
  • These surface cross-linking agents may be used alone or in combination of two or more.
  • cyclic carbonates, oxozaridone ring compounds, polyhydric glycidyl compounds, polyhydric alcohols and polyhydric amines are preferable, and polyhydric glycidyl compounds and polyhydric alcohols are more preferable, from the viewpoint of material cost economy and absorption characteristics.
  • the most preferred are ethylene glycol diglycidyl ether and 1,4-butanediol.
  • the amount (% by weight) of the surface cross-linking agent (d) used is the cross-linking weight from the viewpoint of suppressing coalescence gel blocking between gel particles and controlling the required absorption characteristics (balance between water retention amount and absorption amount under load). Based on the weight of the coalesced (A), it is preferably 0.01 to 0.10, more preferably 0.03 to 0.08, and particularly preferably 0.05 to 0.06. If it is less than 0.01, the effect of suppressing gel blocking is small, and if it is more than 0.10, the absorption characteristics are deteriorated.
  • Examples of the polymerization method of the crosslinked polymer (A) include known solution polymerization (adiabatic polymerization, thin film polymerization, spray polymerization, etc .; JP-A No. 55-133413, etc.) and known reverse phase suspension polymerization (Tokusho). 54-30710, JP-A-56-26909, JP-A No. 1-5808, etc.). Further, a method of polymerizing by two-step polymerization can also be used.
  • the degree of water swelling of the water-absorbent resin particles in the dehydration treatment method of the present invention is preferably 10 from the viewpoint of the dehydration rate (easiness of penetration of the water-soluble inorganic acid (c1) and the water-soluble monovalent metal compound (c2)). It is about 50 times, more preferably 20 to 45 times, and most preferably 30 to 40 times.
  • the water in this case may or may not contain a water-soluble electrolyte or a non-electrolyte.
  • the degree of water swelling of water-absorbent resin particles is adjusted during manufacturing before use (drying, water addition), urine volume during use (frequency of replacement of sanitary products), and moisture content after use (storage, washing with water). ) Etc. can be adjusted.
  • the weight of the water-absorbent resin particles after drying is, for example, heated at 150 ° C. for 30 minutes using a heated dry moisture meter (manufactured by A & D), and the weight change for 1 minute is within ⁇ 10%. It can be measured by treating the value after treatment as a constant weight value and using it as the weight of the water-absorbent resin particles after drying.
  • Method (1) A method including a step of mixing the water-absorbent resin particles absorbing water and a water-soluble inorganic acid (c1), and then a step of further mixing with a water-soluble monovalent metal compound (c2);
  • Method (2) A method including a step of mixing the water-absorbing resin particles absorbing water and the water-soluble monovalent metal compound (c2), and then a step of further mixing with the water-soluble inorganic acid (c1);
  • Method (3) A method comprising a step of mixing water-absorbent resin particles absorbing water with a water-soluble inorganic acid (c1) and a water-soluble monovalent metal compound (c2).
  • the methods (1) and (3) are preferable from the viewpoint of dehydration, and the method (1) is more preferable.
  • the water-soluble inorganic acid (c1) is not particularly limited as long as it is known, but for example, sulfuric acid, sulfamic acid, hydrochloric acid, nitrate, phosphoric acid, metaphosphoric acid, pyrophosphate, tripolyphosphoric acid and hexametaphosphoric acid. And so on.
  • these water-soluble inorganic acids (c1) those having an acid dissociation constant (pKa) of 2 or less are preferable from the viewpoint of dehydration.
  • the pKa of the water-soluble inorganic acid is pKa in water at 25 ° C.
  • “Chemical Handbook (Revised 5th Edition) Basic Edition II” (edited by The Chemical Society of Japan), pp.
  • water-soluble inorganic acid having an acid dissociation constant (pKa) of 2 or less examples include hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid and the like. One of these may be used alone or two or more thereof may be used in combination.
  • hydrochloric acid, sulfuric acid and phosphoric acid are preferable, and sulfuric acid and phosphoric acid are more preferable, from the viewpoint of material cost economy and safety. From the viewpoint of load on the treatment equipment (corrosiveness), phosphoric acid is most preferable.
  • the water-soluble inorganic acid (c1) suppresses the spread due to charge repulsion between the polymer chains during water absorption by changing the acrylic acid cation salt forming site of the polymer of the water-absorbent resin particles to acrylic acid, resulting in dehydration.
  • the pH of the step of mixing the water-soluble inorganic acid (c1) is preferably 0.0 to 5.0 from the viewpoint of dehydration, and more preferably from the viewpoint of load on the processing equipment (corrosiveness). It is 2.0 to 4.0. From this viewpoint, the pH of the 0.01% by weight aqueous solution (25 ° C.) of the water-soluble inorganic acid (c1) is preferably 2.0 to 4.0.
  • the pH can be measured using, for example, HORIBA, Ltd. (desktop pH meter F-71S) at a temperature of 25 ° C ⁇ 1 and the room temperature at the time of measurement is 25 ° C. ⁇ 2 and humidity can be 50% RH ⁇ 3.
  • the content (% by weight) of the water-soluble inorganic acid (c1) varies depending on the type of acid, but the pH of the step of mixing the water-soluble inorganic acid (c1) is preferably in the above range. be. That is, the addition amount is appropriately adjusted so that the pH of the step is within the above range.
  • the water-soluble inorganic acid (c1) may be diluted with water at the time of mixing with the water-absorbing resin particles and / or the water-soluble monovalent metal compound (c2) that has absorbed water, or may be used. It may be used without dilution. From the viewpoint of workability, it is preferable to dilute with water before use.
  • water for dilution ion-exchanged water, tap water, industrial water, water containing an electrolyte such as seawater, and other water-soluble organic solvents are 50/50 by weight of water / organic solvent.
  • the mixed water containing ⁇ 99/1 may be used.
  • the water-soluble monovalent metal compound (c2) is an element having a valence of 1 in the periodic table, which is dissolved in water or reacts with water to become an ion, or is charged with a polymer of water-absorbent resin particles.
  • a polymer of water-absorbent resin particles There are no particular restrictions as long as it is a sum.
  • water-soluble monovalent metal compound (c2) examples include monovalent metal compounds containing alkali metals such as sodium, potassium and cesium, and among them, chlorine-based monovalent metal compounds (c21) containing chlorine and chlorine. Examples thereof include a non-chlorine monovalent compound (c22) which is not contained.
  • the monovalent metal compound may be a non-hydrate or a hydrate such as a monohydrate, a dihydrate, a trihydrate, or a tetrahydrate.
  • These water-soluble monovalent metal compounds (c2) may be used alone or in combination of two or more.
  • the "water-soluble monovalent metal compound” refers to a monovalent metal compound having a solubility in 100 ml of water at 20 ° C. of 0.1 g / 100 ml or more, preferably 10 g / 100 ml or more.
  • the chlorine-based monovalent metal compound (c21) is a monovalent metal compound containing a chlorine atom, and is, for example, chloride-based [sodium chloride, potassium chloride, cesium chloride, etc.], hypochlorite-based [hypochlorite].
  • chloride-based sodium, potassium hypochlorite, and cesium hypochlorite, etc.]
  • chloric acid-based sodium chlorite, potassium chlorate, and cesium chlorate, etc.
  • perchloric acid-based sodium perchlorite, perchloric acid, etc.] Potassium, cesium perchlorate, etc.].
  • the non-chlorine monovalent metal compound (c22) is a chlorine-free monovalent metal compound, and is, for example, an oxide-based [sodium oxide, etc.], a peroxide-based [sodium peroxide, lithium peroxide, etc.], and the like.
  • Hydroxide-based [sodium hydroxide, potassium hydroxide, cesium hydroxide, etc.], fluoride-based [sodium fluoride, potassium fluoride, and cesium fluoride, etc.], bromide-based [sodium bromide, potassium bromide, etc.] And cesium bromide, etc.], iodide-based [sodium iodide, potassium iodide, cesium iodide, etc.], hydrides [sodium hydride, potassium hydride, cesium hydride, etc.], carbide-based [sodium carbide, etc.
  • the water-soluble monovalent metal compound (c2) is preferably a non-chlorine monovalent metal compound (c22) from the viewpoint of reducing the load on equipment and the environmental load, and is more preferably from the viewpoint of material cost economy.
  • the content (% by weight) of the water-soluble monovalent metal compound (c2) is preferably 10 to 80 from the viewpoint of dehydration, based on the weight of the mixture including (c2) in the step of mixing (c2). It is% by weight, more preferably 20 to 70% by weight, and most preferably 40 to 60% by weight. If it is too small, dehydration is not sufficient, and if it is too large, the salt remaining in the water-absorbent resin particles after the dehydration treatment significantly deteriorates the absorption characteristics.
  • the water-soluble monovalent metal compound (c2) may be diluted with water at the time of mixing with the water-absorbing resin particles and / or the water-soluble inorganic acid (c1) that has absorbed water, or may be used. It may be used without dilution. From the viewpoint of workability, it is preferable to use it without diluting it with water.
  • water for dilution ion-exchanged water, tap water, industrial water, water containing an electrolyte such as seawater, and other water-soluble organic solvents are 50/50 by weight of water / organic solvent.
  • the mixed water containing ⁇ 99/1 may be used.
  • the water-soluble inorganic acid (c1) and the water-soluble monovalent metal compound (c2) may be mixed in advance.
  • the dehydration treatment method of the present invention is suitably performed for sanitary products containing a water-absorbent resin containing a cross-linking polymer (A) containing (meth) acrylic acid (salt) and a cross-linking agent (b) as essential constituent units. Can be done.
  • the dehydration treatment method of the present invention may be carried out as it is for sanitary goods, or the dehydration treatment method of the present invention may be carried out for crushed sanitary goods. From the viewpoint of dehydration efficiency, it is preferable to carry out the dehydration treatment method of the present invention on crushed sanitary goods. Further, the water-absorbent resin particles absorbing water can be taken out from the sanitary goods and dehydrated by applying the present invention.
  • a method of crushing hygiene products there is a method of crushing hygiene products using a crushing device.
  • the crushing device include a juicer mixer, a hammer type crusher, an impact type crusher, a roll type crusher, a shet airflow type crusher, and the like.
  • the water-absorbent resin particles are usually present in the liquid and may be in any state of immersion, stirring or standing, but are stirred in the liquid from the viewpoint of contact frequency and dehydration.
  • the state of being dehydrated is preferable.
  • the temperature of the water-absorbent resin particles when dehydrating the water-absorbent resin particles is not particularly limited as long as the temperature is such that the water-absorbent resin particles can be dispersed, but from the viewpoint of the ease of the treatment process, the temperature of the water-absorbent resin particles is not particularly limited.
  • the temperature is 5 to 100 ° C, more preferably 10 to 40 ° C from the viewpoint of dehydration.
  • the temperature is high, the polymer chains of the water-absorbent resin are dissociated and charge repulsion is likely to occur, and the water absorption becomes high, so that the dehydration property deteriorates.
  • the time of the dehydration treatment method of the present invention is not particularly limited as long as it is the time for the water-absorbent resin particles to be dehydrated, but is preferably 5 minutes to 20 hours, and more preferably 10 to 30 minutes.
  • the dehydration treatment method of the present invention may further include at least one of a filtration step, a pressure dehydration step and a centrifugal dehydration step in addition to the steps described in the above-mentioned methods (1) to (3).
  • the filtration step include a step of separating the slurry into water-absorbent resin particles and a filtrate by using a filter medium such as a filter cloth, a filter paper, and a nylon mesh.
  • a known method can be applied, and examples thereof include a method using a filter press.
  • the centrifugal dehydration step a known method can be applied, and examples thereof include a method using a rotary centrifugal dehydrator. Of these, from the viewpoint of dehydration, it is preferable to further include a centrifugal dehydration step.
  • additives may be included.
  • the additive include a viscosity modifier, a flocculant, a dispersant, an emulsifier, an antifoaming agent, a pigment, a dye, a colorant, an antistatic agent, an antibacterial agent, a bactericidal agent, and a rust preventive agent.
  • the water-absorbent resin particles are dried after the steps described in the above-mentioned methods (1) to (3). It is preferable to carry out the process. Drying can be performed by a known method.
  • a regeneration step for reuse can be performed, and in that case, either the dehydration treatment step of the present invention or the above-mentioned drying step can be performed. It may be done after the process of.
  • the regeneration step include a step of neutralizing the water-absorbent resin particles obtained in the dehydration treatment step of the present invention or the drying step after the dehydration treatment with a basic compound.
  • the basic compound is not particularly limited as long as it is a compound capable of neutralizing acrylic acid in the water-absorbent resin particles, and examples thereof include sodium hydroxide.
  • a method of neutralization treatment a known method for neutralizing gel-like particles can be applied.
  • a method of immersing water-absorbent resin particles in an aqueous solution of a basic compound and an aqueous solution containing a basic compound are used as a water-absorbent resin.
  • Examples thereof include a method of spraying particles.
  • the solid content of the recovered water-absorbent resin can be recycled and used as a compost raw material, a soil modifier, a solid fuel, water-absorbent resin particles for pet sheets, and water-absorbent resin particles for sanitary goods.
  • soil modifiers are soil modifiers, solid fuels, water-absorbent resin particles for pet sheets and water-absorbent resin particles for sanitary goods, and more preferably water-absorbent resin for pet sheets.
  • Particles and water-absorbent resin particles for sanitary goods most preferably water-absorbent resin particles for sanitary goods.
  • the mixture was polymerized at 90 ⁇ 2 ° C. for about 5 hours to obtain a hydrogel (1) composed of the crosslinked polymer (A-1).
  • a hydrogel (1) composed of the crosslinked polymer (A-1).
  • 502.27 parts of this hydrogel (1) was shredded with a minced machine, 128.42 parts of a 48.5% sodium hydroxide aqueous solution was added and mixed to obtain hydrogel particles.
  • the hydrogel particles were dried with an aeration type band dryer ⁇ 150 ° C., wind speed 2 m / sec ⁇ to obtain a dried product.
  • the dried product was pulverized with a juicer mixer and then adjusted to a particle size range of 710 to 150 ⁇ m, whereby the dried product particles (1) were obtained.
  • the dried body particles (2) were obtained by adjusting the particle size range with a sieve.
  • An aqueous solution of a surface cross-linking agent consisting of 0.5 part by weight of propylene glycol, 0.3 part by weight of 1,4-butanediol (d-3) and 1.0 part by weight of pure water was added to 100 parts by weight of the dried body particles (2).
  • the mixture was uniformly mixed and heat-treated at 210 ° C. for 40 minutes to obtain water-absorbent resin particles (P-2).
  • the weight average particle size of (P-2) was 450 ⁇ m.
  • a reflux condenser As a reflux condenser, a dropping funnel, a nitrogen gas introduction pipe, and a stirrer, a round-bottomed cylindrical separable flask having an inner diameter of 100 mm equipped with a stirring blade having four inclined paddle blades having a blade diameter of 50 mm in two stages was prepared. Take 500 mL of n-heptane in this flask, 0.92 parts of HLB3 sucrose stearic acid ester (Ryoto Sugar Ester S-370, manufactured by Mitsubishi Chemical Foods Co., Ltd.), maleic anhydride-modified ethylene-propylene copolymer (Mitsui Chemicals).
  • High wax 1105A manufactured by the same company was added, the temperature was raised to 80 ° C. to dissolve the surfactant, and then the temperature was cooled to 50 ° C.
  • 92 parts of an 80.5% by weight acrylic acid aqueous solution was placed in a 500 mL triangular flask, and 154.3 parts of a 20.0% by mass sodium hydroxide aqueous solution was added dropwise while cooling from the outside in 75 mol%. After summing, the mixture was completely dissolved by stirring at room temperature. 0.11 g of ammonium persulfate and 0.0092 parts of N, N'-methylenebisacrylamide (b-3) were added and dissolved to prepare a first-stage monomer aqueous solution.
  • the number of revolutions of the stirrer was 450 rpm, the aqueous monomer solution was added to the separable flask, the system was held at 35 ° C. for 30 minutes while replacing the inside with nitrogen, and then immersed in a water bath at 70 ° C. to ascend. By warming and polymerizing, a slurry of the crosslinked polymer (A-3') after the polymerization of the first stage was obtained. On the other hand, 110.4 parts of an 80.5 mass% acrylic acid aqueous solution was placed in another 500 mL triangular flask, and 149.9 parts of a 24.7 mass% sodium hydroxide aqueous solution was dropped while cooling from the outside to 75.
  • Example 4 In Production Example 1, the same operation as in Example 1 was carried out except that the surface cross-linking agents (d-1) and (d-2) were not used, and the cross-linked polymer (A-4) and the water-absorbent resin particles were carried out. (P-4) was obtained. (P-4) The weight average particle size was 450 ⁇ m.
  • Example 1 By immersing 20 parts by weight of the water-absorbent resin particles (P-1) obtained in Production Example 1 in ion-exchanged water so that the water swelling degree of the water-absorbent resin particles is 40 times, the water-absorbent resin particles can be obtained. The degree of water swelling was adjusted. Then, 800 parts by weight of the obtained swollen water-absorbent resin particles were carried out in the following order. That is, a 1 wt% aqueous solution of sulfuric acid (c1-1) as a water-soluble inorganic acid (c1) was stirred and mixed with the swollen water-absorbent resin particles at 25 ° C. for 15 minutes at 25 ° C.
  • Example 2 ⁇ Examples 2 to 6, 8 to 11, 13>
  • Example 1 except that (A-1), (c1-1), (c22-1), the degree of water swelling of the water-absorbent resin particles and the method order were changed based on Tables 1 and 2.
  • the pH, dehydration, easiness of drying and easiness of reuse of the water-soluble inorganic acid aqueous solution were evaluated according to the following evaluation methods (1) to (4).
  • the evaluation results are shown in Tables 1 and 2.
  • the pKa of the aqueous solution of a water-soluble inorganic acid is also shown.
  • the method (1), method (2), and method (3) in the order of the methods were carried out according to the following procedures.
  • Method (1) The swollen water-absorbent resin particles are mixed with a water-soluble inorganic acid (c1), filtered through a nylon mesh, and the solid obtained by filtration is combined with the water-soluble monovalent metal compound (c2). Mix and filter again using nylon mesh to obtain solids.
  • Method (2) The swollen water-absorbent resin particles are mixed with the water-soluble monovalent metal compound (c2), filtered through a nylon mesh, and the solid obtained by filtration is combined with the water-soluble inorganic acid (c1). Mix and filter again using nylon mesh to obtain solids.
  • Method (3) A sequence in which swollen water-absorbent resin particles are simultaneously mixed with a water-soluble inorganic acid (c1) and a water-soluble monovalent metal compound (c2) and then filtered through a nylon mesh to obtain a solid substance.
  • Example 7 By immersing 20 parts by weight of the water-absorbent resin particles (P-1) obtained in Production Example 1 in ion-exchanged water so that the water swelling degree of the water-absorbent resin particles is 40 times, the water-absorbent resin particles can be obtained. The degree of water swelling was adjusted. Then, 800 parts by weight of the obtained swollen water-absorbent resin particles were carried out in the following order. That is, after carrying out the method (3) in which the swollen water-absorbent resin particles are simultaneously mixed with a 1% by weight aqueous solution of phosphoric acid (c1-2) and sodium phosphate (C22-2), sodium sulfate is further added. It was mixed with (C22-1) and filtered again using a nylon mesh to obtain a solid substance. The evaluation results are shown in Table 1.
  • Example 12 In Example 1, in the adjustment of the water swelling degree of the water-absorbent resin particles, the water swelling degree was 40 times and the ion-exchanged water was replaced with 30 times and physiological saline, respectively, in the same manner as in Example 1 and evaluated. Was done. The evaluation results are shown in Table 2.
  • Solid content concentration (%) (after dehydration treatment) Dry weight of water-absorbent resin particles after dehydration treatment (B) (g) / Weight of swollen water-absorbent resin particles after dehydration treatment (A) (g) ⁇ 100%
  • the dry weights (B) and (g) of the water-absorbent resin particles after the dehydration treatment are such that the sample (the total amount of the water-absorbent resin particles after the dehydration treatment) is placed on a metal bat made of SUS (length 30 cm ⁇ width 20 cm ⁇ height). It can be obtained by placing it in a safety oven [SPHH-201 manufactured by Espec Co., Ltd.] and drying it at 150 ° C. for 120 minutes. When drying on the sample on a metal vat made of SUS, the samples were spread evenly so as not to overlap each other.
  • ⁇ The dried water-absorbent resin particles are touched with a finger and peeled off from the bat, and the agglomerates are crushed by being pinched by the fingers.
  • ⁇ Some of the dried water-absorbent resin particles are touched by a finger and peeled off from the bat, and the agglomerates are not broken by being pinched by the fingers.
  • X The dried water-absorbent resin particles are so attached to the bat that some of them cannot be peeled off from the bat by touching with a finger.
  • a tea bag (length 20 cm, width 10 cm) made of a nylon net having an opening of 63 ⁇ m (JIS Z8801-1: 2006) with 5 g open. ), Suspended with a tea bag in 200 ml of a 10% sodium hydroxide aqueous solution stirred with a magnetic stirrer, soaked at 25 ⁇ 5 ° C. for 1 hour, and then stirred with a magnetic stirrer. The tea bag was hung in 200 ml of water (salt concentration 0.9%), soaked and washed at 25 ° C. ⁇ 2 ° C.
  • the dehydration treatment method of the present invention shown in Examples 1 to 13 is easier to dehydrate and dry than the dehydration treatment methods shown in Comparative Examples 1 to 4. It can be seen that the ease of reuse is good. That is, it can be said that the moisture absorbed by the water-absorbent resin particles can be sufficiently dehydrated, and that the water-absorbent resin particles are easy to dry and reuse in the subsequent steps.
  • the dehydration treatment method of the present invention includes paper diapers (children's disposable diapers, adult disposable diapers, etc.), napkins (physiological napkins, etc.), paper towels, pads (pads for incontinence, surgical underpads, etc.) and pet sheets (pet urine). Not only for water-absorbent resin particles in the field of sanitary materials such as (absorbent sheet), but also for water-stopping materials for communication cables in the electric and electronic fields, for soil water-retaining agents and seedling raising sheets in the fields of agriculture and gardening, and for wound protection in the medical field. Water-absorbent resin particles discharged for dressing agents and waste blood coagulants, for cold insulation materials and dew condensation prevention sheets in the distribution / transportation field, and for gel fragrances and disposable body warmers in other fields. Can be suitably used for reuse of.

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Abstract

Provided is a method for dehydration treatment that is capable of adequately dehydrating moisture absorbed by water-absorbent resin particles, that facilitates drying of water-absorbent resin particles in a subsequent step, and that facilitates reuse of the water-absorbent resin particles. The present invention is a method for dehydration treatment of moisture absorbed by water-absorbent resin particles containing a crosslinked polymer (A) having as essential structural units a (meth)acryl(ate) and a crosslinking agent (b), wherein the method for dehydration treatment uses any of a method (1) including a step for mixing the water-absorbent resin particles which are absorbing moisture with a water-soluble inorganic acid (c1) and a subsequent step for further mixing with a water-soluble monovalent metal compound (c2), a method (2) including a step for mixing the water-absorbent resin particles which are absorbing moisture with (c2) and a subsequent step for further mixing with (c1), and a method (3) including a step for mixing the water-absorbent resin particles which are absorbing moisture with (c1) and (c2).

Description

吸水性樹脂粒子の脱水処理方法Dehydration treatment method of water-absorbent resin particles
　本発明は、吸水性樹脂粒子の脱水処理方法に関する。 The present invention relates to a method for dehydrating water-absorbent resin particles.
　日本では少子高齢化が急速に進展し、紙おむつなどの衛生用品の使用量が増加するにつれ、環境面や衛生面、更には介護者の負担増加等の観点から、使用後の衛生用品のごみ処理問題が深刻な問題となりつつある。使用後の衛生用品のごみ処理に関し、紙おむつは焼却処理されているが、紙おむつ中の水分の割合は約８割近くであるため、大きな燃焼エネルギーが必要となる。このため焼却炉に大きな負荷がかかり、焼却炉の寿命を短くする原因に繋がる。また、焼却処理は大気汚染や地球の温暖化に繋がり、環境に負荷をかける要因にもなるため、改善が強く望まれている。 In Japan, the declining birthrate and aging population are rapidly advancing, and as the amount of hygiene products such as disposable diapers increases, waste disposal of hygiene products after use is considered from the viewpoint of environment, hygiene, and the burden on caregivers. The problem is becoming a serious problem. Regarding the waste disposal of sanitary goods after use, disposable diapers are incinerated, but the proportion of water in the disposable diapers is close to 80%, so a large amount of combustion energy is required. For this reason, a large load is applied to the incinerator, which leads to shortening the life of the incinerator. Incineration also leads to air pollution and global warming, and is a factor that puts a burden on the environment, so improvement is strongly desired.
　上記課題に対し、使用済み衛生用品から部材を回収し、再利用するための検討が進められている。衛生用品はパルプ繊維と吸水性樹脂粒子（ＳＡＰともいう）から構成される吸収体を含み、部材として再利用するためにはパルプ繊維と吸水性樹脂粒子を分離する必要がある。しかし、使用済み衛生用品の吸収体中の吸水性樹脂粒子は水を吸収して膨潤したゲル状態となるため、そのままでは分離が難しい。そこで、特許文献１は、使用済み衛生用品をｐＨが３以下の酸性のオゾン水に浸漬することにより、使用済み衛生用品中の吸水性樹脂粒子を分解し可溶化して除去する方法を提案している。特許文献２は、使用済み衛生用品を、酸性の水溶液に浸漬することで、使用済み衛生用品中の膨潤したゲル状の吸水性樹脂粒子を脱水することで、吸水性樹脂粒子を収縮させ、分離を容易とする方法を提案している。また、特許文献３は、膨潤したゲル状の吸水性樹脂粒子を、多価金属塩に浸漬することで、吸水性樹脂粒子のポリマー鎖間を多価金属イオンで架橋形成し、高吸水性樹脂粒子を不活化させることで、脱水する方法を提案している。 For the above issues, studies are underway to collect and reuse parts from used hygiene products. The sanitary goods include an absorber composed of pulp fibers and water-absorbent resin particles (also referred to as SAP), and it is necessary to separate the pulp fibers and the water-absorbent resin particles in order to reuse them as members. However, since the water-absorbent resin particles in the absorber of the used hygiene product absorb water and become a swelled gel state, it is difficult to separate them as they are. Therefore, Patent Document 1 proposes a method of decomposing, solubilizing and removing water-absorbent resin particles in used sanitary products by immersing the used sanitary products in acidic ozone water having a pH of 3 or less. ing. Patent Document 2 immerses used hygiene products in an acidic aqueous solution to dehydrate the swollen gel-like water-absorbent resin particles in the used hygiene products, thereby shrinking and separating the water-absorbent resin particles. We are proposing a method to facilitate. Further, in Patent Document 3, the swollen gel-like water-absorbent resin particles are immersed in a polyvalent metal salt to form crosslinks between the polymer chains of the water-absorbent resin particles with polyvalent metal ions, thereby forming a highly water-absorbent resin. We are proposing a method of dehydration by inactivating particles.
特開２０１４－２１７８３５号公報Japanese Unexamined Patent Publication No. 2014-217835 特開２０１９－００７１２３号公報Japanese Unexamined Patent Publication No. 2019-007123 特開２０１９－０８５３４３号公報Japanese Unexamined Patent Publication No. 2019-085343
　しかし、特許文献１の方法は、ｐＨが３以下の酸性のオゾン水を使用するため、処理装置が複雑になることや、安全面の観点から必ずしも十分に課題を解決するとは言い難く、また、ＳＡＰの分解完了までに時間がかかることが問題であった。また、特許文献２の手法は、吸水性樹脂粒子に吸収されている水分を脱水することで、吸水性樹脂粒子を収縮させ、分離を容易にできるが、脱水が十分ではないため、その後の工程で、水分を多く含む吸水性樹脂粒子の乾燥をする必要があり、工程が煩雑となってしまう。さらに特許文献３は、特許文献２同様に吸水性樹脂粒子に吸収されている水分を脱水することで、分離を容易にでき、かつ十分に脱水することで、その後の工程での乾燥も容易となるが、多価金属イオンで架橋されたポリマーとなって得られた吸水性樹脂粒子は吸水性に乏しく、ＳＡＰとして再利用するには十分な性能ではなかった。 However, since the method of Patent Document 1 uses acidic ozone water having a pH of 3 or less, it cannot be said that the processing apparatus becomes complicated and the problem is not always sufficiently solved from the viewpoint of safety. The problem was that it took time to complete the disassembly of SAP. Further, in the method of Patent Document 2, the water-absorbent resin particles can be shrunk and separated easily by dehydrating the water absorbed by the water-absorbent resin particles, but the dehydration is not sufficient, so that the subsequent steps are performed. Therefore, it is necessary to dry the water-absorbent resin particles containing a large amount of water, which complicates the process. Further, Patent Document 3 makes it easy to separate by dehydrating the water absorbed by the water-absorbent resin particles as in Patent Document 2, and also makes it easy to dry in the subsequent steps by sufficiently dehydrating. However, the water-absorbent resin particles obtained as a polymer crosslinked with polyvalent metal ions had poor water absorption and did not have sufficient performance for reuse as SAP.
　従って、本発明は、吸水性樹脂粒子に吸収されている水分を十分に脱水でき、その後の工程において吸水性樹脂粒子の乾燥が容易となり、かつ、その再利用も容易となる脱水処理方法を提供することを目的とする。 Therefore, the present invention provides a dehydration treatment method capable of sufficiently dehydrating the water absorbed by the water-absorbent resin particles, facilitating the drying of the water-absorbent resin particles in the subsequent steps, and facilitating the reuse thereof. The purpose is to do.
　本発明は、（メタ）アクリル酸（塩）及び架橋剤（ｂ）を必須構成単位とする架橋重合体（Ａ）を含有する吸水性樹脂粒子に吸収されている水分の脱水処理方法であって、
　方法（１）：水分を吸収している前記吸水性樹脂粒子と水溶性無機酸（ｃ１）とを混合する工程及びその後、さらに水溶性一価金属化合物（ｃ２）と混合する工程を含む方法、
　方法（２）：水分を吸収している前記吸水性樹脂粒子と水溶性一価金属化合物（ｃ２）とを混合する工程及びその後、さらに水溶性無機酸（ｃ１）と混合する工程を含む方法、ならびに
　方法（３）：水分を吸収している前記吸水性樹脂粒子と水溶性無機酸（ｃ１）および水溶性一価金属化合物（ｃ２）とを混合する工程を含む方法、のうちのいずれかの方法を用いる脱水処理方法である。 The present invention is a method for dehydrating water absorbed by water-absorbent resin particles containing a crosslinked polymer (A) containing (meth) acrylic acid (salt) and a crosslinking agent (b) as essential constituent units. ,
Method (1): A method including a step of mixing the water-absorbent resin particles absorbing water with a water-soluble inorganic acid (c1), and then a step of further mixing with a water-soluble monovalent metal compound (c2).
Method (2): A method including a step of mixing the water-absorbent resin particles absorbing water with a water-soluble monovalent metal compound (c2), and then a step of further mixing with a water-soluble inorganic acid (c1). And method (3): any of a method including a step of mixing the water-absorbent resin particles absorbing water with a water-soluble inorganic acid (c1) and a water-soluble monovalent metal compound (c2). It is a dehydration treatment method using the method.
　本発明の脱水処理方法は、吸水性樹脂粒子に吸収されている水分を脱水するのに優れ、その後の工程において、吸水性樹脂粒子の乾燥が容易となる。また、吸水性樹脂粒子の再利用が容易である。 The dehydration treatment method of the present invention is excellent in dehydrating the water absorbed by the water-absorbent resin particles, and the water-absorbent resin particles can be easily dried in the subsequent steps. In addition, the water-absorbent resin particles can be easily reused.
　本発明の脱水処理方法における吸水性樹脂粒子は、（メタ）アクリル酸（塩）及び架橋剤（ｂ）を必須構成単位とする架橋重合体（Ａ）を含有する。
　ここで、「（メタ）アクリル酸（塩）」は、アクリル酸、メタクリル酸、アクリル酸塩又はメタクリル酸塩を意味する。従って、（メタ）アクリル酸のカルボン酸部位が、例えば、ナトリウムイオンで中和された塩でも良い。また、塩としては、アルカリ金属（リチウム、ナトリウム及びカリウム等）塩、アルカリ土類金属（マグネシウム及びカルシウム等）塩又はアンモニウム（ＮＨ４）塩等が含まれる。これらの塩のうち、吸収特性の観点等から、アルカリ金属塩及びアンモニウム塩が好ましく、さらに好ましくはアルカリ金属塩、特に好ましくはナトリウム塩である The water-absorbent resin particles in the dehydration treatment method of the present invention contain a crosslinked polymer (A) containing (meth) acrylic acid (salt) and a crosslinking agent (b) as essential constituent units.
Here, "(meth) acrylic acid (salt)" means acrylic acid, methacrylic acid, acrylate or methacrylic acid. Therefore, the carboxylic acid moiety of (meth) acrylic acid may be, for example, a salt neutralized with sodium ions. The salt includes an alkali metal (lithium, sodium, potassium, etc.) salt, an alkaline earth metal (magnesium, calcium, etc.) salt, an 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 characteristics and the like.
　架橋剤（ｂ）（内部架橋剤（ｂ）ともいう）は、特に限定はなく、公知（例えば、特許第３６４８５５３号公報、特開２００３－１６５８８３号公報、特開２００５－７５９８２号公報及び特開２００５－９５７５９号公報）の架橋剤等が使用できる。これらの架橋剤は単独で使用してもよく、２種以上を併用してもよい。
　これらのうち、吸水性能の観点から、好ましくはエチレン性不飽和基を２個以上有する架橋剤であり、更に好ましくは炭素数２～４０の多価アルコールのポリ（メタ）アリルエーテル、炭素数２～４０の多価アルコールの（メタ）アクリレート、炭素数２～４０の多価アルコールの（メタ）アクリルアミドであり、最も好ましくはペンタエリスリトールトリアリルエーテル、ポリエチレングリコールジアクリレート（エチレンオキシドの平均付加モル数９）、メチレンビスアクリルアミドである。 The cross-linking agent (b) (also referred to as an internal cross-linking agent (b)) is not particularly limited, and is known (for example, Japanese Patent No. 36485553, Japanese Patent Application Laid-Open No. 2003-165883, Japanese Patent Application Laid-Open No. 2005-75982 and JP-A-2005-75982). A cross-linking agent or the like described in 2005-95759 (Ab. 2005) can be used. These cross-linking agents may be used alone or in combination of two or more.
Of these, from the viewpoint of water absorption performance, it is preferably a cross-linking agent having two or more ethylenically unsaturated groups, and more preferably a poly (meth) allyl ether of a polyhydric alcohol having 2 to 40 carbon atoms and 2 carbon atoms. 40 to 40 polyhydric alcohol (meth) acrylates, 2 to 40 polyhydric alcohols (meth) acrylamides, most preferably pentaerythritol triallyl ethers, polyethylene glycol diacrylates (average number of moles of ethylene oxide added 9). ), Methylenebisacrylamide.
　架橋剤（ｂ）単位の含有量（モル％）は、（メタ）アクリル酸（塩)に基づいて、０．００１～５が好ましく、更に好ましくは０．００５～３、特に好ましくは０．０１～１である。この範囲であると、吸収性能が更に良好となる。 The content (mol%) of the cross-linking agent (b) unit is preferably 0.001 to 5, more preferably 0.005 to 3, and particularly preferably 0.01, based on the (meth) acrylic acid (salt). ~ 1. Within this range, the absorption performance is further improved.
　架橋重合体（Ａ）は、ゲル粒子同士の合着ゲルブロッキングの抑制および必要な吸収特性（保水量と荷重下吸収量のバランス）の制御の観点から、表面架橋剤（ｄ）により表面架橋されたものであることが好ましく、表面架橋剤（ｄ）としては、特開昭５９－１８９１０３号公報等に記載の多価グリシジル、特開昭５８－１８０２３３号公報及び特開昭６１－１６９０３号公報等に記載の多価アルコール、多価アミン、多価アジリジン及び多価イソシアネート、特開昭６１－２１１３０５号公報及び特開昭６１－２５２２１２号公報等に記載のシランカップリング剤、特表平５－５０８４２５号公報に記載のアルキレンカーボネート、特開平１１－２４０９５９号公報に記載の多価オキサゾリン化合物並びに特開昭５１－１３６５８８号公報及び特開昭６１－２５７２３５号公報等に記載の多価金属等が挙げられる。これらの表面架橋剤は単独で使用してもよく、２種以上を併用してもよい。
　これらのうち、材料費用経済性及び吸収特性の観点から、好ましくは環状カーボネート、オキソザリドン環化合物、多価グリシジル化合物、多価アルコール及び多価アミンであり、更に好ましくは多価グリシジル化合物及び多価アルコールであり、最も好ましくはエチレングリコールジグリシジルエーテル及び１，４－ブタンジオールである。 The crosslinked polymer (A) is surface-crosslinked with the surface cross-linking agent (d) from the viewpoint of suppressing coalescence gel blocking between gel particles and controlling the required absorption characteristics (balance between the amount of water retained and the amount of absorption under load). As the surface cross-linking agent (d), the polyvalent glycidyl described in JP-A-59-189103 and the like, JP-A-58-180233 and JP-A-61-16903 are preferably used. , And the like, polyhydric alcohols, polyhydric amines, polyvalent aziridines and polyvalent isocyanates, silane coupling agents described in JP-A-61-21305 and JP-A-61-252212, etc. The alkylene carbonate described in JP-A-508425, the polyvalent oxazoline compound described in JP-A-11-240959, and the polyvalent metal described in JP-A-51-136588 and JP-A-61-257235, etc. Can be mentioned. These surface cross-linking agents may be used alone or in combination of two or more.
Of these, cyclic carbonates, oxozaridone ring compounds, polyhydric glycidyl compounds, polyhydric alcohols and polyhydric amines are preferable, and polyhydric glycidyl compounds and polyhydric alcohols are more preferable, from the viewpoint of material cost economy and absorption characteristics. The most preferred are ethylene glycol diglycidyl ether and 1,4-butanediol.
　表面架橋剤（ｄ）の使用量（重量％）は、ゲル粒子同士の合着ゲルブロッキングの抑制および必要な吸収特性（保水量と荷重下吸収量のバランス）の制御等の観点から、架橋重合体（Ａ）の重量に基づいて、０．０１～０．１０が好ましく、更に好ましくは０．０３～０．０８、特に好ましくは０．０５～０．０６である。０．０１より少ないと、ゲルブロッキングの抑制効果が小さく、０．１０より多いと、吸収特性が悪くなる。 The amount (% by weight) of the surface cross-linking agent (d) used is the cross-linking weight from the viewpoint of suppressing coalescence gel blocking between gel particles and controlling the required absorption characteristics (balance between water retention amount and absorption amount under load). Based on the weight of the coalesced (A), it is preferably 0.01 to 0.10, more preferably 0.03 to 0.08, and particularly preferably 0.05 to 0.06. If it is less than 0.01, the effect of suppressing gel blocking is small, and if it is more than 0.10, the absorption characteristics are deteriorated.
　架橋重合体（Ａ）の重合方法としては、公知の溶液重合（断熱重合、薄膜重合及び噴霧重合法等；特開昭５５－１３３４１３号公報等）や、公知の逆相懸濁重合（特公昭５４－３０７１０号公報、特開昭５６－２６９０９号公報及び特開平１－５８０８号公報等）が挙げられる。また、２段階重合により重合する方法も使用できる。 Examples of the polymerization method of the crosslinked polymer (A) include known solution polymerization (adiabatic polymerization, thin film polymerization, spray polymerization, etc .; JP-A No. 55-133413, etc.) and known reverse phase suspension polymerization (Tokusho). 54-30710, JP-A-56-26909, JP-A No. 1-5808, etc.). Further, a method of polymerizing by two-step polymerization can also be used.
　本発明の脱水処理方法における吸水性樹脂粒子の水膨潤度は、脱水速度（水溶性無機酸（ｃ１）及び水溶性一価金属化合物（ｃ２）の浸透し易さ）の観点から、好ましくは１０～５０倍であり、更に好ましくは２０～４５倍であり、最も好ましくは３０～４０倍である。なお、この場合の水には、水溶性の電解質や非電解質を含んでもいてもいなくてもどちらでも良い。吸水性樹脂粒子の水膨潤度は、使用前の製造時の水分量調整（乾燥、水添加）、使用中の尿量（衛生用品の取り替え頻度）や使用後の水分量調整（保管、水洗浄）等により調整することができる。 The degree of water swelling of the water-absorbent resin particles in the dehydration treatment method of the present invention is preferably 10 from the viewpoint of the dehydration rate (easiness of penetration of the water-soluble inorganic acid (c1) and the water-soluble monovalent metal compound (c2)). It is about 50 times, more preferably 20 to 45 times, and most preferably 30 to 40 times. The water in this case may or may not contain a water-soluble electrolyte or a non-electrolyte. The degree of water swelling of water-absorbent resin particles is adjusted during manufacturing before use (drying, water addition), urine volume during use (frequency of replacement of sanitary products), and moisture content after use (storage, washing with water). ) Etc. can be adjusted.
＜吸水性樹脂粒子の水膨潤度の測定方法＞
　なお、水膨潤度は以下の測定で算出することができる。すなわち、
　水膨潤度（倍）＝膨潤した吸水性樹脂粒子の重量（ｇ）／乾燥後の吸水性樹脂粒子の重量（ｇ）
　乾燥後の吸水性樹脂粒子の重量は、例えば、加熱式乾燥水分計（エー・アンド・ディー社製）を用いて１５０℃で３０分間加熱し、１分間の重量変化が±１０％以内になった後の値を恒量値として扱い、乾燥後の吸水性樹脂粒子の重量とすることで、測定することができる。 <Measurement method of water swelling degree of water-absorbent resin particles>
The degree of water swelling can be calculated by the following measurement. That is,
Water swelling degree (double) = weight of swollen water-absorbent resin particles (g) / weight of dried water-absorbent resin particles (g)
The weight of the water-absorbent resin particles after drying is, for example, heated at 150 ° C. for 30 minutes using a heated dry moisture meter (manufactured by A & D), and the weight change for 1 minute is within ± 10%. It can be measured by treating the value after treatment as a constant weight value and using it as the weight of the water-absorbent resin particles after drying.
　本発明の吸水性樹脂粒子に吸収されている水分の脱水処理方法は、以下（１）～（３）のいずれかの方法を用いる。
　方法（１）：水分を吸収している吸水性樹脂粒子と水溶性無機酸（ｃ１）とを混合する工程及びその後、さらに水溶性一価金属化合物（ｃ２）と混合する工程を含む方法；
　方法（２）：水分を吸収している吸水性樹脂粒子と水溶性一価金属化合物（ｃ２）とを混合する工程及びその後、さらに水溶性無機酸（ｃ１）と混合する工程を含む方法；
　方法（３）：水分を吸収している吸水性樹脂粒子と水溶性無機酸（ｃ１）および水溶性一価金属化合物（ｃ２）とを混合する工程を含む方法。 As the method for dehydrating the water absorbed by the water-absorbent resin particles of the present invention, any of the following methods (1) to (3) is used.
Method (1): A method including a step of mixing the water-absorbent resin particles absorbing water and a water-soluble inorganic acid (c1), and then a step of further mixing with a water-soluble monovalent metal compound (c2);
Method (2): A method including a step of mixing the water-absorbing resin particles absorbing water and the water-soluble monovalent metal compound (c2), and then a step of further mixing with the water-soluble inorganic acid (c1);
Method (3): A method comprising a step of mixing water-absorbent resin particles absorbing water with a water-soluble inorganic acid (c1) and a water-soluble monovalent metal compound (c2).
　前述（１）～（３）の方法のうち、脱水の観点より好ましくは方法（１）と（３）であり、更に好ましくは方法（１）である。 Of the above-mentioned methods (1) to (3), the methods (1) and (3) are preferable from the viewpoint of dehydration, and the method (1) is more preferable.
　水溶性無機酸（ｃ１）は、公知のものであれば、特に限定されるものではないが、例えば、硫酸、スルファミン酸、塩酸、硝酸、リン酸、メタリン酸、ピロリン酸、トリポリリン酸及びヘキサメタリン酸等が挙げられる。これら水溶性無機酸（ｃ１）のうち、脱水の観点より、好ましいものは酸解離定数（ｐＫａ）が２以下である水溶性無機酸である。
　なお、水溶性無機酸のｐＫａは、２５℃水中におけるｐＫａであり、例えば「化学便覧（改訂５版）基礎編ＩＩ」（日本化学会編）３３２～３４２頁（１９９３年５月発行）等の書籍に記載されている値を用いることができる。
　酸解離定数（ｐＫａ）が２以下である水溶性無機酸としては、塩酸、硝酸、硫酸及びりん酸等が挙げられる。これらのうち１種を単独で用いても２種以上を併用してもよい。酸解離定数（ｐＫａ）が２以下である水溶性無機酸のうち、材料費用経済性及び安全性の観点から、好ましくは塩酸、硫酸及びりん酸であり、更に好ましくは硫酸及びりん酸であり、処理設備への負荷（腐食性）の観点より、最も好ましくはりん酸である。水溶性無機酸（ｃ１）は、吸水性樹脂粒子のポリマーのアクリル酸カチオン塩形成部位をアクリル酸にすることで、吸水時のポリマー鎖間の電荷反発による拡がりが抑制され、結果として脱水性を発現する。 The water-soluble inorganic acid (c1) is not particularly limited as long as it is known, but for example, sulfuric acid, sulfamic acid, hydrochloric acid, nitrate, phosphoric acid, metaphosphoric acid, pyrophosphate, tripolyphosphoric acid and hexametaphosphoric acid. And so on. Among these water-soluble inorganic acids (c1), those having an acid dissociation constant (pKa) of 2 or less are preferable from the viewpoint of dehydration.
The pKa of the water-soluble inorganic acid is pKa in water at 25 ° C. For example, "Chemical Handbook (Revised 5th Edition) Basic Edition II" (edited by The Chemical Society of Japan), pp. 332-342 (issued in May 1993). The values described in the book can be used.
Examples of the water-soluble inorganic acid having an acid dissociation constant (pKa) of 2 or less include hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid and the like. One of these may be used alone or two or more thereof may be used in combination. Of the water-soluble inorganic acids having an acid dissociation constant (pKa) of 2 or less, hydrochloric acid, sulfuric acid and phosphoric acid are preferable, and sulfuric acid and phosphoric acid are more preferable, from the viewpoint of material cost economy and safety. From the viewpoint of load on the treatment equipment (corrosiveness), phosphoric acid is most preferable. The water-soluble inorganic acid (c1) suppresses the spread due to charge repulsion between the polymer chains during water absorption by changing the acrylic acid cation salt forming site of the polymer of the water-absorbent resin particles to acrylic acid, resulting in dehydration. Express.
　水溶性無機酸（ｃ１）を混合する工程のｐＨとしては、脱水性の観点より、好ましくは０．０～５．０であり、処理設備への負荷（腐食性）の観点より、より好ましくは２．０～４．０である。この観点から、前記水溶性無機酸（ｃ１）の０．０１重量％水溶液（２５℃）のｐＨが２．０～４．０であることが好ましい。
　なお、ｐＨの測定方法は、例えば、株式会社　堀場製作所製（卓上型ｐＨメータ　Ｆ－７１Ｓ）を用いて測定液の温度は２５℃±１で測定することができ、測定時の室温は２５℃±２、湿度は５０％ＲＨ±３とすることができる。 The pH of the step of mixing the water-soluble inorganic acid (c1) is preferably 0.0 to 5.0 from the viewpoint of dehydration, and more preferably from the viewpoint of load on the processing equipment (corrosiveness). It is 2.0 to 4.0. From this viewpoint, the pH of the 0.01% by weight aqueous solution (25 ° C.) of the water-soluble inorganic acid (c1) is preferably 2.0 to 4.0.
The pH can be measured using, for example, HORIBA, Ltd. (desktop pH meter F-71S) at a temperature of 25 ° C ± 1 and the room temperature at the time of measurement is 25 ° C. ± 2 and humidity can be 50% RH ± 3.
　水溶性無機酸（ｃ１）の含有量（重量％）は、酸の種類によって異なるが、水溶性無機酸（ｃ１）を混合する工程のｐＨが、上述の範囲となる量が好ましい含有量範囲である。すなわち、工程のｐＨが上述の範囲となるように、適宜、添加量を調節して添加する。 The content (% by weight) of the water-soluble inorganic acid (c1) varies depending on the type of acid, but the pH of the step of mixing the water-soluble inorganic acid (c1) is preferably in the above range. be. That is, the addition amount is appropriately adjusted so that the pH of the step is within the above range.
　水溶性無機酸（ｃ１）は、水分を吸収している吸水性樹脂粒子及び／又は水溶性一価金属化合物（ｃ２）と混合時または事前に、水で希釈を行い使用してもよいし、希釈を行わずに使用してもよい。作業性の観点から、水で希釈を行い使用することが好ましい。なお、希釈用の水としては、イオン交換水、水道水、工業用水、海水のような電解質を含んだ水、その他、水に可溶な有機溶剤が水／有機溶剤を重量比で５０／５０～９９／１含んだ混合水でも構わない。 The water-soluble inorganic acid (c1) may be diluted with water at the time of mixing with the water-absorbing resin particles and / or the water-soluble monovalent metal compound (c2) that has absorbed water, or may be used. It may be used without dilution. From the viewpoint of workability, it is preferable to dilute with water before use. As the water for dilution, ion-exchanged water, tap water, industrial water, water containing an electrolyte such as seawater, and other water-soluble organic solvents are 50/50 by weight of water / organic solvent. The mixed water containing ~ 99/1 may be used.
　水溶性一価金属化合物（ｃ２）は、周期表において１の価数を有する元素であって、水へ溶解又は水と反応して、イオンになるものまたは吸水性樹脂粒子のポリマーの荷電を中和するものであれば、特に制限されない。吸水性樹脂粒子内部と周囲の水とのイオン濃度の差を低下することで浸透圧差も低下し、吸水性樹脂粒子のポリマーの荷電を中和することでポリマー鎖間の電荷反発による拡がりが抑制され、いずれも結果として吸水性樹脂粒子内部からの脱水を生じさせることができる。 The water-soluble monovalent metal compound (c2) is an element having a valence of 1 in the periodic table, which is dissolved in water or reacts with water to become an ion, or is charged with a polymer of water-absorbent resin particles. There are no particular restrictions as long as it is a sum. By reducing the difference in ion concentration between the inside of the water-absorbent resin particles and the surrounding water, the difference in osmotic pressure is also reduced, and by neutralizing the charge of the polymer of the water-absorbent resin particles, the spread due to charge repulsion between the polymer chains is suppressed. As a result, dehydration from the inside of the water-absorbent resin particles can occur.
　水溶性一価金属化合物（ｃ２）は、例えば、ナトリウム、カリウム、セシウム等のアルカリ金属を含む一価金属化合物が挙げられ、なかでも、塩素を含む塩素系一価金属化合物（ｃ２１）及び塩素を含まない非塩素系一価化合物（ｃ２２）が挙げられる。なお、一価金属化合物は、非水和物であっても、一水和物、二水和物、三水和物、四水和物のような水和物であってもよい。これらの水溶性一価金属化合物（ｃ２）は単独で使用してもよく、２種以上を併用してもよい。
　なお、本発明において「水溶性一価金属化合物」とは、２０℃の水１００ｍｌに対する溶解度が０．１ｇ／１００ｍｌ以上であり、好ましくは１０ｇ／１００ｍｌ以上である一価金属化合物を示す。 Examples of the water-soluble monovalent metal compound (c2) include monovalent metal compounds containing alkali metals such as sodium, potassium and cesium, and among them, chlorine-based monovalent metal compounds (c21) containing chlorine and chlorine. Examples thereof include a non-chlorine monovalent compound (c22) which is not contained. The monovalent metal compound may be a non-hydrate or a hydrate such as a monohydrate, a dihydrate, a trihydrate, or a tetrahydrate. These water-soluble monovalent metal compounds (c2) may be used alone or in combination of two or more.
In the present invention, the "water-soluble monovalent metal compound" refers to a monovalent metal compound having a solubility in 100 ml of water at 20 ° C. of 0.1 g / 100 ml or more, preferably 10 g / 100 ml or more.
　塩素系一価金属化合物（ｃ２１）は、塩素原子を含む一価金属化合物であり、例えば、塩化物系［塩化ナトリウム、塩化カリウム、および塩化セシウム等］、次亜塩素酸系［次亜塩素酸ナトリウム、次亜塩素酸カリウム、および次亜塩素酸セシウム等］、塩素酸系［塩素酸ナトリウム、塩素酸カリウム、および塩素酸セシウム等］、および過塩素酸系［過塩素酸ナトリウム、過塩素酸カリウム、および過塩素酸セシウム等］が挙げられる。 The chlorine-based monovalent metal compound (c21) is a monovalent metal compound containing a chlorine atom, and is, for example, chloride-based [sodium chloride, potassium chloride, cesium chloride, etc.], hypochlorite-based [hypochlorite]. Sodium, potassium hypochlorite, and cesium hypochlorite, etc.], chloric acid-based [sodium chlorite, potassium chlorate, and cesium chlorate, etc.], and perchloric acid-based [sodium perchlorite, perchloric acid, etc.] Potassium, cesium perchlorate, etc.].
　非塩素系一価金属化合物（ｃ２２）は、塩素を含まない一価金属化合物であり、例えば、酸化物系［酸化ナトリウム等］、過酸化物系［過酸化ナトリウム、および過酸化リチウム等］、水酸化物系［水酸化ナトリウム、水酸化カリウム、および水酸化セシウム等］、フッ化物系［フッ化ナトリウム、フッ化カリウム、およびフッ化セシウム等］、臭化物系［臭化ナトリウム、臭化カリウム、および臭化セシウム等］、ヨウ化物系［ヨウ化ナトリウム、ヨウ化カリウム、およびヨウ化セシウム等］、水素化物［水素化ナトリウム、水素化カリウム、および水素化セシウム等］、炭化物系［炭化ナトリウム、炭化カリウム、および炭化セシウム等］、リン化物系［リン化ナトリウム、リン化カリウム、およびリン化セシウム等］、炭酸化物［炭酸ナトリウム、炭酸カリウム、および炭酸セシウム等］、硝酸化物系［硝酸ナトリウム、硝酸カリウム、および硝酸セシウム等］、亜硫酸化物系［亜硫酸ナトリウム、亜硫酸カリウム、および亜硫酸セシウム等］、硫酸化物系［硫酸ナトリウム、硫酸カリウム、および硫酸セシウム等］、硫酸エステル化物系［ラウリル硫酸ナトリウム等］、スルホン酸化物系［メタンスルホン酸ナトリウム、ドデシルベンゼンスルホン酸ナトリウム、メタンスルホン酸カリウム、およびメタンスルホン酸セシウム等］、ケイ酸化物系［ケイ酸ナトリウム、ケイ酸カリウム、およびケイ酸セシウム等］、りん酸化物系［りん酸ナトリウム、りん酸カリウム、およびりん酸セシウム等］、ピロリン酸化物系［ピロリン酸ナトリウム、ピロリン酸カリウム、およびピロリン酸セシウム等］、臭素酸化物系［臭素酸ナトリウム、臭素酸カリウム、および臭素酸セシウム等］、ヨウ素酸化物系［ヨウ素酸ナトリウム、ヨウ素酸カリウム、およびヨウ素酸セシウム等］、クロム酸化物系［クロム酸ナトリウム、クロム酸カリウム、およびクロム酸セシウム等］、酢酸化物系［酢酸ナトリウム、酢酸カリウム、および酢酸セシウム等］、グルコン酸［グルコン酸ナトリウム、グルコン酸カリウム、およびグルコン酸セシウム等］、安息香酸化物系［安息香酸ナトリウム、安息香酸カリウム、および安息香酸セシウム等］、および炭素数３以上の脂肪族カルボン酸化物系［プロピオン酸ナトリウム、ステアリン酸ナトリウム、ステアリン酸カリウム、およびステアリン酸セシウム等］が挙げられる。 The non-chlorine monovalent metal compound (c22) is a chlorine-free monovalent metal compound, and is, for example, an oxide-based [sodium oxide, etc.], a peroxide-based [sodium peroxide, lithium peroxide, etc.], and the like. Hydroxide-based [sodium hydroxide, potassium hydroxide, cesium hydroxide, etc.], fluoride-based [sodium fluoride, potassium fluoride, and cesium fluoride, etc.], bromide-based [sodium bromide, potassium bromide, etc.] And cesium bromide, etc.], iodide-based [sodium iodide, potassium iodide, cesium iodide, etc.], hydrides [sodium hydride, potassium hydride, cesium hydride, etc.], carbide-based [sodium carbide, etc. Potassium carbide, cesium carbide, etc.], Phosphorus-based [sodium phosphate, potassium phosphate, and cesium phosphate, etc.], carbon oxides [sodium carbonate, potassium carbonate, cesium carbonate, etc.], glass oxide-based [sodium nitrate, etc.] Potassium nitrate, cesium nitrate, etc.], sulfite-based [sodium sulfite, potassium sulfite, and cesium sulfite, etc.], sulfated-based [sodium sulfate, potassium sulfate, cesium sulfate, etc.], sulfate esterified-based [sodium lauryl sulfate, etc.] , Sulfonide-based [sodium methanesulfonate, sodium dodecylbenzenesulfonate, potassium methanesulfonate, cesium methanesulfonate, etc.], silicate-based [sodium silicate, potassium silicate, cesium silicate, etc.], Phosphorus oxides [sodium phosphate, potassium phosphate, cesium phosphate, etc.], Pyrophosphate oxides [sodium pyrophosphate, potassium pyrophosphate, cesium pyrophosphate, etc.], bromine oxides [sodium bromine, bromine, etc.] Potassium acid and cesium bromide, etc.], Iode oxides [sodium iodate, potassium iodate, cesium iodate, etc.], Chromide oxides [sodium chromate, potassium chromate, cesium chromate, etc.], Acetate-based [sodium acetate, potassium acetate, cesium acetate, etc.], gluconic acid [sodium gluconate, potassium gluconate, cesium gluconate, etc.], benzoic oxide-based [sodium benzoate, potassium benzoate, and benzoic acid, etc.] Cesium, etc.] and aliphatic carboxylic oxides having 3 or more carbon atoms [sodium propionate, sodium stearate, potassium stearate, cesium stearate, etc.] can be mentioned.
　水溶性一価金属化合物（ｃ２）は、設備への負荷、環境負荷の低減の観点から、好ましくは非塩素系一価金属化合物（ｃ２２）であり、材料費用経済性の観点より、更に好ましくは硫酸ナトリウム及び／又はりん酸ナトリウム、設備への負荷（腐食性）低減の観点より、最も好ましくはりん酸ナトリウムである。 The water-soluble monovalent metal compound (c2) is preferably a non-chlorine monovalent metal compound (c22) from the viewpoint of reducing the load on equipment and the environmental load, and is more preferably from the viewpoint of material cost economy. Sodium sulfate and / or sodium phosphate, most preferably sodium phosphate, from the viewpoint of reducing the load (corrosiveness) on the equipment.
　水溶性一価金属化合物（ｃ２）の含有量（重量％）は、（ｃ２）を混合する工程中の（ｃ２）を含めた混合物の重量に基づいて、脱水の観点から、好ましくは１０～８０重量％であり、更に好ましくは２０～７０重量％であり、最も好ましくは４０～６０重量％である。少なすぎると脱水が十分ではなく、多すぎると、脱水処理後の吸水性樹脂粒子に残存する塩が、吸収特性を著しく悪化させる。 The content (% by weight) of the water-soluble monovalent metal compound (c2) is preferably 10 to 80 from the viewpoint of dehydration, based on the weight of the mixture including (c2) in the step of mixing (c2). It is% by weight, more preferably 20 to 70% by weight, and most preferably 40 to 60% by weight. If it is too small, dehydration is not sufficient, and if it is too large, the salt remaining in the water-absorbent resin particles after the dehydration treatment significantly deteriorates the absorption characteristics.
　水溶性一価金属化合物（ｃ２）は、水分を吸収している吸水性樹脂粒子及び／又は水溶性無機酸（ｃ１）と混合時または事前に、水で希釈を行い使用してもよいし、希釈を行わずに使用してもよい。作業性の観点から、水で希釈を行わず使用することが好ましい。
　なお、希釈用の水としては、イオン交換水、水道水、工業用水、海水のような電解質を含んだ水、その他、水に可溶な有機溶剤が水／有機溶剤を重量比で５０／５０～９９／１含んだ混合水でも構わない。 The water-soluble monovalent metal compound (c2) may be diluted with water at the time of mixing with the water-absorbing resin particles and / or the water-soluble inorganic acid (c1) that has absorbed water, or may be used. It may be used without dilution. From the viewpoint of workability, it is preferable to use it without diluting it with water.
As the water for dilution, ion-exchanged water, tap water, industrial water, water containing an electrolyte such as seawater, and other water-soluble organic solvents are 50/50 by weight of water / organic solvent. The mixed water containing ~ 99/1 may be used.
　方法（３）において、水溶性無機酸（ｃ１）と水溶性一価金属化合物（ｃ２）とは、事前に混合しておいてもよい。 In the method (3), the water-soluble inorganic acid (c1) and the water-soluble monovalent metal compound (c2) may be mixed in advance.
　本発明の脱水処理方法は、（メタ）アクリル酸（塩）及び架橋剤（ｂ）を必須構成単位とする架橋重合体（Ａ）を含有する吸水性樹脂を含む衛生用品に対して好適に行うことが出来る。本発明の脱水処理方法においては、衛生用品に対してそのまま本発明の脱水処理方法を実施しても良いし、粉砕された衛生用品に対して本発明の脱水処理方法を実施してもよいが、脱水効率の観点から、粉砕された衛生用品に対して本発明の脱水処理方法を実施することが好ましい。また、衛生用品から水分を吸収している吸水性樹脂粒子を取り出し、本発明を適用して、脱水することが出来る。 The dehydration treatment method of the present invention is suitably performed for sanitary products containing a water-absorbent resin containing a cross-linking polymer (A) containing (meth) acrylic acid (salt) and a cross-linking agent (b) as essential constituent units. Can be done. In the dehydration treatment method of the present invention, the dehydration treatment method of the present invention may be carried out as it is for sanitary goods, or the dehydration treatment method of the present invention may be carried out for crushed sanitary goods. From the viewpoint of dehydration efficiency, it is preferable to carry out the dehydration treatment method of the present invention on crushed sanitary goods. Further, the water-absorbent resin particles absorbing water can be taken out from the sanitary goods and dehydrated by applying the present invention.
　衛生用品を粉砕する方法としては、衛生用品を、粉砕装置を用いて粉砕する方法が挙げられる。粉砕装置としては、例えば、ジューサーミキサー、ハンマー式粉砕機、衝撃式粉砕機、ロール式粉砕機及びシェット気流式粉砕機等が挙げられる。 As a method of crushing hygiene products, there is a method of crushing hygiene products using a crushing device. Examples of the crushing device include a juicer mixer, a hammer type crusher, an impact type crusher, a roll type crusher, a shet airflow type crusher, and the like.
　本発明の脱水処理方法において、吸水性樹脂粒子は、通常、液中に存在し、浸漬、撹拌、静置いずれの状態であってもよいが、接触頻度と脱水の観点から、液中に撹拌されている状態が好ましい。 In the dehydration treatment method of the present invention, the water-absorbent resin particles are usually present in the liquid and may be in any state of immersion, stirring or standing, but are stirred in the liquid from the viewpoint of contact frequency and dehydration. The state of being dehydrated is preferable.
　本発明の脱水処理方法において、吸水性樹脂粒子を脱水する時の吸水性樹脂粒子の温度は、吸水性樹脂粒子が分散できる温度であれば特に限定されないが、処理プロセスの容易さの観点から、５～１００℃であり、脱水の観点から、より好ましくは１０～４０℃である。温度が高いと、吸水性樹脂のポリマー鎖間が解離して電荷反発しやすくなり、吸水性が高くなるため、脱水性が悪化する。 In the dehydration treatment method of the present invention, the temperature of the water-absorbent resin particles when dehydrating the water-absorbent resin particles is not particularly limited as long as the temperature is such that the water-absorbent resin particles can be dispersed, but from the viewpoint of the ease of the treatment process, the temperature of the water-absorbent resin particles is not particularly limited. The temperature is 5 to 100 ° C, more preferably 10 to 40 ° C from the viewpoint of dehydration. When the temperature is high, the polymer chains of the water-absorbent resin are dissociated and charge repulsion is likely to occur, and the water absorption becomes high, so that the dehydration property deteriorates.
　本発明の脱水処理方法の時間は、吸水性樹脂粒子が脱水する時間であれば特に限定されないが、好ましくは５分～２０時間であり、更に好ましくは１０～３０分である。 The time of the dehydration treatment method of the present invention is not particularly limited as long as it is the time for the water-absorbent resin particles to be dehydrated, but is preferably 5 minutes to 20 hours, and more preferably 10 to 30 minutes.
　本発明の脱水処理方法は、前述の方法（１）～方法（３）に記載の工程の他に、ろ過工程、加圧脱水工程及び遠心脱水工程のうち少なくとも一つをさらに含んでもよい。
　ろ過工程としては、ろ布、ろ紙、ナイロンメッシュなどのろ材によって、スラリーを吸水性樹脂粒子とろ液に分離する工程が挙げられる。
　加圧脱水工程としては、公知の方法が適用でき、例えば、フィルタープレスを使用する方法が挙げられる。
　遠心脱水工程としては、公知の方法が適用でき、例えば、回転式遠心脱水機を使用する方法が挙げられる
　これらのうち、脱水性の観点より、さらに遠心脱水工程を含むことが好ましい。 The dehydration treatment method of the present invention may further include at least one of a filtration step, a pressure dehydration step and a centrifugal dehydration step in addition to the steps described in the above-mentioned methods (1) to (3).
Examples of the filtration step include a step of separating the slurry into water-absorbent resin particles and a filtrate by using a filter medium such as a filter cloth, a filter paper, and a nylon mesh.
As the pressure dehydration step, a known method can be applied, and examples thereof include a method using a filter press.
As the centrifugal dehydration step, a known method can be applied, and examples thereof include a method using a rotary centrifugal dehydrator. Of these, from the viewpoint of dehydration, it is preferable to further include a centrifugal dehydration step.
　前述の方法（１）～方法（３）に記載の工程の際、水溶性無機酸（ｃ１）及び水溶性一価金属化合物（ｃ２）の他に、本発明の脱水処理方法を阻害しない範囲で、他の添加剤を含んでいてもよい。添加剤としては、粘度調整剤、凝集剤、分散剤、乳化剤、消泡剤、顔料、染料、着色剤、帯電防止剤、抗菌剤、殺菌剤、および防錆剤を挙げることができる。 In the steps described in the above-mentioned methods (1) to (3), in addition to the water-soluble inorganic acid (c1) and the water-soluble monovalent metal compound (c2), as long as the dehydration treatment method of the present invention is not impaired. , Other additives may be included. Examples of the additive include a viscosity modifier, a flocculant, a dispersant, an emulsifier, an antifoaming agent, a pigment, a dye, a colorant, an antistatic agent, an antibacterial agent, a bactericidal agent, and a rust preventive agent.
　本発明の脱水処理方法に対する後工程として、吸水性樹脂粒子の再利用を容易にするため、前述の方法（１）～方法（３）に記載の工程の後に、吸水性樹脂粒子を乾燥させる乾燥工程を行うことが好ましい。乾燥は公知の方法で行うことが出来る。 As a post-step to the dehydration treatment method of the present invention, in order to facilitate the reuse of the water-absorbent resin particles, the water-absorbent resin particles are dried after the steps described in the above-mentioned methods (1) to (3). It is preferable to carry out the process. Drying can be performed by a known method.
　また、本発明の脱水処理方法に対する後工程として、再利用に向けた再生化工程（中和処理等）を行うことができ、その場合は、本発明の脱水処理工程又は上述の乾燥工程のどちらの工程の後に行っても良い。再生化工程とは、例えば、本発明の脱水処理工程又は脱水処理後の乾燥工程で得られた吸水性樹脂粒子を塩基性化合物で中和処理する工程等が挙げられる。塩基性化合物としては、吸水性樹脂粒子中のアクリル酸を中和できる化合物であれば、特に限定はされず、例えば、水酸化ナトリウムが挙げられる。中和処理の方法としては、ゲル状粒子を中和処理する公知の方法が適用でき、例えば、吸水性樹脂粒子を塩基性化合物の水溶液に浸漬する方法及び塩基性化合物を含む水溶液を吸水性樹脂粒子に噴霧する方法等が挙げられる。
　再生化工程を経ることで、吸水性に優れた吸水性樹脂粒子にすることができ、衛生材料用途向け吸水性樹脂粒子などとして、リサイクルすることができる。 Further, as a post-step to the dehydration treatment method of the present invention, a regeneration step (neutralization treatment or the like) for reuse can be performed, and in that case, either the dehydration treatment step of the present invention or the above-mentioned drying step can be performed. It may be done after the process of. Examples of the regeneration step include a step of neutralizing the water-absorbent resin particles obtained in the dehydration treatment step of the present invention or the drying step after the dehydration treatment with a basic compound. The basic compound is not particularly limited as long as it is a compound capable of neutralizing acrylic acid in the water-absorbent resin particles, and examples thereof include sodium hydroxide. As a method of neutralization treatment, a known method for neutralizing gel-like particles can be applied. For example, a method of immersing water-absorbent resin particles in an aqueous solution of a basic compound and an aqueous solution containing a basic compound are used as a water-absorbent resin. Examples thereof include a method of spraying particles.
By going through the regeneration process, it is possible to obtain water-absorbent resin particles having excellent water absorption, and it can be recycled as water-absorbent resin particles for sanitary material applications.
　回収した吸水性樹脂の固形分は、リサイクル利用が可能であり、堆肥原料、土壌改質剤、固形燃料、ペットシート用吸水性樹脂粒子および衛生用品用吸水性樹脂粒子として使用することができ、リサイクル性および環境負荷低減の観点から、好ましい用途としては、土壌改質剤、固形燃料、ペットシート用吸水性樹脂粒子および衛生用品用吸水性樹脂粒子であり、更に好ましくはペットシート用吸水性樹脂粒子および衛生用品用吸水性樹脂粒子、最も好ましくは、衛生用品用吸水性樹脂粒子である。 The solid content of the recovered water-absorbent resin can be recycled and used as a compost raw material, a soil modifier, a solid fuel, water-absorbent resin particles for pet sheets, and water-absorbent resin particles for sanitary goods. From the viewpoint of recyclability and reduction of environmental load, preferred applications are soil modifiers, solid fuels, water-absorbent resin particles for pet sheets and water-absorbent resin particles for sanitary goods, and more preferably water-absorbent resin for pet sheets. Particles and water-absorbent resin particles for sanitary goods, most preferably water-absorbent resin particles for sanitary goods.
　以下、実施例及び比較例により本発明をさらに説明するが、本発明はこれらに限定されるものではない。なお、特に定めない限り、部は重量部、％は重量％を示す。 Hereinafter, the present invention will be further described with reference to Examples and Comparative Examples, but the present invention is not limited thereto. Unless otherwise specified, parts indicate parts by weight and% indicates weight%.
＜製造例１＞
　アクリル酸１５７部、内部架橋剤（ｂ）としてペンタエリスリトールトリアリルエーテル（ｂ－１）０．６３０５部及び脱イオン水３４４．６５部を攪拌・混合しながら３℃に保った。この混合物中に窒素を流入して溶存酸素量を１ｐｐｍ以下とした後、１％過酸化水素水溶液０．６３部、２％アスコルビン酸水溶液１．１７７４部及び２％の２，２’－アゾビス［２－メチル－Ｎ－（２－ヒドロキシエチル）－プロピオンアミド］水溶液２．３５５部を添加・混合して重合を開始させた。混合物の温度が９０℃に達した後、９０±２℃で約５時間重合することにより架橋重合体（Ａ－１）からなる含水ゲル（１）を得た。次にこの含水ゲル（１）５０２．２７部をミンチ機で細断しながら４８．５％水酸化ナトリウム水溶液１２８．４２部を添加して混合し、含水ゲル粒子を得た。更に含水ゲル粒子を通気型バンド乾燥機｛１５０℃、風速２ｍ／秒｝で乾燥し、乾燥体を得た。乾燥体をジューサーミキサーにて粉砕した後、目開き７１０～１５０μｍの粒子径範囲に調整することにより、乾燥体粒子（１）を得た。この乾燥体粒子（１）１００部を高速攪拌しながら表面架橋剤（ｄ）としての硫酸ナトリウムアルミニウムミョウバン１２水和物（ｄ－１）を０．５部、エチレングリコールジグリシジルエーテル（ｄ－２）の２％水／メタノール混合溶液（水／メタノールの重量比＝７０／３０）の５．００部をスプレー噴霧しながら加えて混合し、１５０℃で３０分間静置して表面架橋して、吸水性樹脂粒子（Ｐ－１）を得た。（Ｐ－１）の重量平均粒子径は、４００μｍであった。 <Manufacturing example 1>
157 parts of acrylic acid, 0.6305 parts of pentaerythritol triallyl ether (b-1) as an internal cross-linking agent (b), and 344.65 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, 0.63 parts of a 1% hydrogen peroxide solution and 1.1774 parts of a 2% ascorbic acid solution and 2% of 2,2'-azobis [ 2-355 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., the mixture was polymerized at 90 ± 2 ° C. for about 5 hours to obtain a hydrogel (1) composed of the crosslinked polymer (A-1). Next, while 502.27 parts of this hydrogel (1) was shredded with a minced machine, 128.42 parts of a 48.5% sodium hydroxide aqueous solution was added and mixed to obtain hydrogel particles. Further, the hydrogel particles were dried with an aeration type band dryer {150 ° C., wind speed 2 m / sec} to obtain a dried product. The dried product was pulverized with a juicer mixer and then adjusted to a particle size range of 710 to 150 μm, whereby the dried product particles (1) were obtained. While stirring 100 parts of the dried body particles (1) at high speed, 0.5 part of sodium aluminum sulfate dodecahydrate (d-1) as a surface cross-linking agent (d) and ethylene glycol diglycidyl ether (d-2). ), Add 5.00 parts of a 2% water / methanol mixed solution (water / methanol weight ratio = 70/30) while spraying, mix, and allow to stand at 150 ° C. for 30 minutes for surface cross-linking. Water-absorbent resin particles (P-1) were obtained. The weight average particle size of (P-1) was 400 μm.
＜製造例２＞
　内容積１０Ｌのシグマ型羽根を２本有する双腕型のジャケット付きステンレス製ニーダーに蓋を付けて形成した反応器に、アクリル酸４２５．２部、３７重量％のアクリル酸ナトリウム水溶液４４９９．５部、純水５３８．５部、ポリエチレングリコールジアクリレート（分子量５２３）４．９３部（ｂ－２）及びジエチレントリアミン５酢酸３ナトリウム０．２１部を投入して反応液とした後、窒素ガス雰囲気下で２０分間脱気した。
　その後、１０重量％の過硫酸ナトリウム水溶液２８．３部及び０．１重量％のＬ－アスコルビン酸水溶液２３．６部をそれぞれ別個に、上記反応液を攪拌しながら添加し、約２５秒後に重合が開始した。架橋重合体（Ａ－２）からなる含水ゲル（２）を解砕しながら２５～９５℃で重合し、重合開始から３０分経過後に含水ゲル（２）を反応器から取り出し、細粒化された含水ゲル（２）を得た。
　上記細粒化された含水ゲル（２）を、目開き３００μｍ（５０メッシュ）の金網上に広げ、１７０℃で６５分間熱風乾燥をした後、ロールミルで粉砕し、更に目開きが８５０μｍのＪＩＳ標準篩で粒子径範囲を調整することにより、乾燥体粒子（２）を得た。
　乾燥体粒子（２）１００重量部に、プロピレングリコール０．５重量部、１，４－ブタンジオール（ｄ－３）０．３重量部及び純水１．０重量部からなる表面架橋剤水溶液を均一に混合し、２１０℃で４０分間加熱処理を行うことで吸水性樹脂粒子（Ｐ－２）を得た。（Ｐ－２）の重量平均粒子径は、４５０μｍであった。 <Manufacturing example 2>
425.2 parts of acrylic acid and 4499.5 parts of 37 wt% sodium acrylate aqueous solution were added to a reactor formed by attaching a lid to a double-armed jacketed stainless steel kneader having two sigma-shaped blades with an internal volume of 10 L. , 538.5 parts of pure water, 4.93 parts (molecular weight 523) of polyethylene glycol diacrylate (molecular weight 523) and 0.21 part of diethylenetriamine 5 acetate 3 sodium were added to prepare a reaction solution, and then under a nitrogen gas atmosphere. Degassed for 20 minutes.
Then, 28.3 parts of a 10 wt% sodium persulfate aqueous solution and 23.6 parts of a 0.1 wt% L-ascorbic acid aqueous solution were added separately with stirring, and the reaction solution was polymerized after about 25 seconds. Has started. The hydrogel (2) made of the crosslinked polymer (A-2) is polymerized at 25 to 95 ° C. while being crushed, and 30 minutes after the start of the polymerization, the hydrogel (2) is taken out from the reactor and granulated. A hydrogel (2) was obtained.
The finely divided hydrogel (2) is spread on a wire mesh having a mesh size of 300 μm (50 mesh), dried with hot air at 170 ° C. for 65 minutes, pulverized with a roll mill, and further has a JIS standard with a mesh size of 850 μm. The dried body particles (2) were obtained by adjusting the particle size range with a sieve.
An aqueous solution of a surface cross-linking agent consisting of 0.5 part by weight of propylene glycol, 0.3 part by weight of 1,4-butanediol (d-3) and 1.0 part by weight of pure water was added to 100 parts by weight of the dried body particles (2). The mixture was uniformly mixed and heat-treated at 210 ° C. for 40 minutes to obtain water-absorbent resin particles (P-2). The weight average particle size of (P-2) was 450 μm.
＜製造例３＞
　還流冷却器、滴下ロート、窒素ガス導入管、攪拌機として、翼径５０ｍｍの４枚傾斜パドル翼を２段で有する攪拌翼を備えた内径１００ｍｍの丸底円筒型セパラブルフラスコを準備した。このフラスコにｎ－ヘプタン５００ｍＬをとり、ＨＬＢ３のショ糖ステアリン酸エステル（三菱化学フーズ社製、リョートーシュガーエステルＳ－３７０）０．９２部、無水マレイン酸変性エチレン・プロピレン共重合体（三井化学社製、ハイワックス１１０５Ａ）０．９２ｇを添加し、８０℃まで昇温して界面活性剤を溶解したのち、５０℃まで冷却した。
　一方、５００ｍＬの三角フラスコに８０．５重量％のアクリル酸水溶液９２部をとり、外部より冷却しつつ、２０．０質量％の水酸化ナトリウム水溶液１５４．３部を滴下して７５モル％の中和を行ったのち、室温にて撹拌して完全に溶解させた。過硫酸アンモニウム０．１１ｇ、Ｎ，Ｎ’－メチレンビスアクリルアミド（ｂ－３）０．００９２部を加えて溶解し、第１段目の単量体水溶液を調製した。
　攪拌機の回転数を４５０ｒｐｍとして、前記単量体水溶液を前記セパラブルフラスコに添加して、系内を窒素で置換しながら、３５℃で３０分間保持した後、７０℃の水浴に浸漬して昇温し、重合を行なうことにより、第１段目の重合後の架橋重合体（Ａ－３’）のスラリーを得た。
　一方、別の５００ｍＬの三角フラスコに８０．５質量％のアクリル酸水溶液１１０．４部をとり、外部より冷却しつつ、２４．７質量％の水酸化ナトリウム水溶液１４９．９部を滴下して７５モル％の中和を行なったのち、２，２’－アゾビス（２－アミジノプロパン）二塩酸塩０．１３部、Ｎ，Ｎ’－メチレンビスアクリルアミド（ｂ－３）０．０３３１部を加えて溶解して、第２段目の単量体水溶液を調製した。
　前記架橋重合体（Ａ－３’）のスラリーの撹拌回転数を１０００ｒｐｍに変更した後、２３℃に冷却し、前記第２段目の単量体水溶液を系内に添加し、窒素で置換しながら３０分間保持したのち、再度、フラスコを７０℃の水浴に浸漬して昇温し、重合を行なうことにより、第２段目の架橋重合体（Ａ－３）のスラリーを得た。
　次いで、１２０℃の油浴を使用して昇温し、水とｎ－ヘプタンを共沸することにより、ｎ－ヘプタンを還流しながら、２５６．１部の水を系外へ抜き出した後、エチレングリコールジグリシジルエーテルの２質量％水溶液８．１０部を添加し、８０℃で２時間保持した後、ｎ－へプタンを蒸発させて乾燥することによって、球状の１次粒子が凝集した２次粒子の形態を有する吸水性樹脂粒子（Ｐ－３）２１３．８部を得た。（Ｐ－３）の重量平均粒子径は、４５０μｍであった。 <Manufacturing example 3>
As a reflux condenser, a dropping funnel, a nitrogen gas introduction pipe, and a stirrer, a round-bottomed cylindrical separable flask having an inner diameter of 100 mm equipped with a stirring blade having four inclined paddle blades having a blade diameter of 50 mm in two stages was prepared. Take 500 mL of n-heptane in this flask, 0.92 parts of HLB3 sucrose stearic acid ester (Ryoto Sugar Ester S-370, manufactured by Mitsubishi Chemical Foods Co., Ltd.), maleic anhydride-modified ethylene-propylene copolymer (Mitsui Chemicals). High wax 1105A) manufactured by the same company was added, the temperature was raised to 80 ° C. to dissolve the surfactant, and then the temperature was cooled to 50 ° C.
On the other hand, 92 parts of an 80.5% by weight acrylic acid aqueous solution was placed in a 500 mL triangular flask, and 154.3 parts of a 20.0% by mass sodium hydroxide aqueous solution was added dropwise while cooling from the outside in 75 mol%. After summing, the mixture was completely dissolved by stirring at room temperature. 0.11 g of ammonium persulfate and 0.0092 parts of N, N'-methylenebisacrylamide (b-3) were added and dissolved to prepare a first-stage monomer aqueous solution.
The number of revolutions of the stirrer was 450 rpm, the aqueous monomer solution was added to the separable flask, the system was held at 35 ° C. for 30 minutes while replacing the inside with nitrogen, and then immersed in a water bath at 70 ° C. to ascend. By warming and polymerizing, a slurry of the crosslinked polymer (A-3') after the polymerization of the first stage was obtained.
On the other hand, 110.4 parts of an 80.5 mass% acrylic acid aqueous solution was placed in another 500 mL triangular flask, and 149.9 parts of a 24.7 mass% sodium hydroxide aqueous solution was dropped while cooling from the outside to 75. After neutralizing in mol%, 0.13 part of 2,2'-azobis (2-amidinopropane) dihydrochloride and 0.0331 part of N, N'-methylenebisacrylamide (b-3) were added. It was dissolved to prepare a second-stage monomer aqueous solution.
After changing the stirring rotation speed of the slurry of the crosslinked polymer (A-3') to 1000 rpm, the mixture was cooled to 23 ° C., the second-stage monomer aqueous solution was added into the system, and the mixture was replaced with nitrogen. After holding the flask for 30 minutes, the flask was again immersed in a water bath at 70 ° C. to raise the temperature, and polymerization was carried out to obtain a slurry of the crosslinked polymer (A-3) in the second stage.
Then, the temperature was raised using an oil bath at 120 ° C., and 256.1 parts of water was extracted from the system while refluxing n-heptane by co-boiling water and n-heptane, and then ethylene. Secondary particles in which spherical primary particles are aggregated by adding 8.10 parts of a 2% by mass aqueous solution of glycol diglycidyl ether, holding at 80 ° C. for 2 hours, and then evaporating and drying n-heptane. 213.8 parts of water-absorbent resin particles (P-3) having the above morphology were obtained. The weight average particle size of (P-3) was 450 μm.
＜製造例４＞
　製造例１において、表面架橋剤（ｄ－１）、（ｄ－２）を使用しなかった以外は、実施例１と同様の操作を行い、架橋重合体（Ａ－４）、吸水性樹脂粒子（Ｐ－４）を得た。（Ｐ－４）重量平均粒子径は、４５０μｍであった。 <Manufacturing example 4>
In Production Example 1, the same operation as in Example 1 was carried out except that the surface cross-linking agents (d-1) and (d-2) were not used, and the cross-linked polymer (A-4) and the water-absorbent resin particles were carried out. (P-4) was obtained. (P-4) The weight average particle size was 450 μm.
＜実施例１＞
　製造例１で得られた吸水性樹脂粒子（Ｐ－１）２０重量部について、吸水性樹脂粒子の水膨潤度が４０倍となるよう、イオン交換水に浸漬させることで、吸水性樹脂粒子の水膨潤度の調整を行った。
　その後、得られた膨潤した吸水性樹脂粒子８００重量部について、以下の順序で実施を行った。すなわち、水溶性無機酸（ｃ１）として硫酸（ｃ１－１）の１重量％水溶液を、膨潤した吸水性樹脂粒子に、ｐＨが０．５となるよう２５℃で１５分間撹拌混合した後、目開き６３μｍ（ＪＩＳ　Ｚ８８０１－１：２００６）のナイロンメッシュでろ過し、さらに、ろ過して得られた固形物を、水溶性一価金属化合物（ｃ２）として硫酸ナトリウム（ｃ２２－１）２０重量部と２５℃で１５分間撹拌混合、再びナイロンメッシュを用いてろ過を行う順序で、固形物を得た。 <Example 1>
By immersing 20 parts by weight of the water-absorbent resin particles (P-1) obtained in Production Example 1 in ion-exchanged water so that the water swelling degree of the water-absorbent resin particles is 40 times, the water-absorbent resin particles can be obtained. The degree of water swelling was adjusted.
Then, 800 parts by weight of the obtained swollen water-absorbent resin particles were carried out in the following order. That is, a 1 wt% aqueous solution of sulfuric acid (c1-1) as a water-soluble inorganic acid (c1) was stirred and mixed with the swollen water-absorbent resin particles at 25 ° C. for 15 minutes at 25 ° C. Filtration is performed with a nylon mesh having an opening of 63 μm (JIS Z8801-1: 2006), and the solid obtained by further filtering is used as a water-soluble monovalent metal compound (c2) with 20 parts by weight of sodium sulfate (c22-1). A solid substance was obtained in the order of stirring and mixing at 25 ° C. for 15 minutes and filtering again using a nylon mesh.
＜実施例２～６、８～１１、１３＞
　実施例１において、（Ａ－１）、（ｃ１－１）、（ｃ２２－１）、吸水性樹脂粒子の水膨潤度および方法順序を表１、表２に基づいて替えたこと以外は実施例１と同様にし、下記評価方法（１）～（４）に従って、水溶性無機酸水溶液のｐＨ、脱水、乾燥の容易さ及び再利用の容易さの評価を行った。評価結果を表１、表２に示す。また、水溶性無機酸水溶液のｐＫａも示した。
　なお、方法順序の方法（１）、方法（２）、方法（３）については、それぞれ以下の手順で実施した。すなわち、
　方法（１）：膨潤した吸水性樹脂粒子を水溶性無機酸（ｃ１）と混合した後、ナイロンメッシュでろ過し、ろ過して得られた固形物を、水溶性一価金属化合物（ｃ２）と混合、再びナイロンメッシュを用いてろ過を行い、固形物を得る順序。
　方法（２）：膨潤した吸水性樹脂粒子を水溶性一価金属化合物（ｃ２）と混合した後、ナイロンメッシュでろ過し、ろ過して得られた固形物を、水溶性無機酸（ｃ１）と混合、再びナイロンメッシュを用いてろ過を行い、固形物を得る順序。
　方法（３）：膨潤した吸水性樹脂粒子を水溶性無機酸（ｃ１）と水溶性一価金属化合物（ｃ２）とを同時に混合した後、ナイロンメッシュでろ過し、固形物を得る順序。 <Examples 2 to 6, 8 to 11, 13>
In Example 1, except that (A-1), (c1-1), (c22-1), the degree of water swelling of the water-absorbent resin particles and the method order were changed based on Tables 1 and 2. In the same manner as in 1, the pH, dehydration, easiness of drying and easiness of reuse of the water-soluble inorganic acid aqueous solution were evaluated according to the following evaluation methods (1) to (4). The evaluation results are shown in Tables 1 and 2. The pKa of the aqueous solution of a water-soluble inorganic acid is also shown.
The method (1), method (2), and method (3) in the order of the methods were carried out according to the following procedures. That is,
Method (1): The swollen water-absorbent resin particles are mixed with a water-soluble inorganic acid (c1), filtered through a nylon mesh, and the solid obtained by filtration is combined with the water-soluble monovalent metal compound (c2). Mix and filter again using nylon mesh to obtain solids.
Method (2): The swollen water-absorbent resin particles are mixed with the water-soluble monovalent metal compound (c2), filtered through a nylon mesh, and the solid obtained by filtration is combined with the water-soluble inorganic acid (c1). Mix and filter again using nylon mesh to obtain solids.
Method (3): A sequence in which swollen water-absorbent resin particles are simultaneously mixed with a water-soluble inorganic acid (c1) and a water-soluble monovalent metal compound (c2) and then filtered through a nylon mesh to obtain a solid substance.
＜実施例７＞
　製造例１で得られた吸水性樹脂粒子（Ｐ－１）２０重量部について、吸水性樹脂粒子の水膨潤度が４０倍となるよう、イオン交換水に浸漬させることで、吸水性樹脂粒子の水膨潤度の調整を行った。
　その後、得られた膨潤した吸水性樹脂粒子８００重量部について、以下の順序で実施を行った。すなわち、膨潤した吸水性樹脂粒子をりん酸（ｃ１－２）の１重量％水溶液とりん酸ナトリウム（Ｃ２２－２）を用いて、同時に混合する方法（３）を実施した後、さらに、硫酸ナトリウム（Ｃ２２－１）と混合、再びナイロンメッシュを用いてろ過を行い、固形物を得た。評価結果を表１に示す。 <Example 7>
By immersing 20 parts by weight of the water-absorbent resin particles (P-1) obtained in Production Example 1 in ion-exchanged water so that the water swelling degree of the water-absorbent resin particles is 40 times, the water-absorbent resin particles can be obtained. The degree of water swelling was adjusted.
Then, 800 parts by weight of the obtained swollen water-absorbent resin particles were carried out in the following order. That is, after carrying out the method (3) in which the swollen water-absorbent resin particles are simultaneously mixed with a 1% by weight aqueous solution of phosphoric acid (c1-2) and sodium phosphate (C22-2), sodium sulfate is further added. It was mixed with (C22-1) and filtered again using a nylon mesh to obtain a solid substance. The evaluation results are shown in Table 1.
＜実施例１２＞
　実施例１において、吸水性樹脂粒子の水膨潤度の調整において、水膨潤度が４０倍およびイオン交換水を、それぞれ３０倍および生理食塩水に替えたこと以外は実施例１と同様にし、評価を行った。評価結果を表２に示す。 <Example 12>
In Example 1, in the adjustment of the water swelling degree of the water-absorbent resin particles, the water swelling degree was 40 times and the ion-exchanged water was replaced with 30 times and physiological saline, respectively, in the same manner as in Example 1 and evaluated. Was done. The evaluation results are shown in Table 2.
＜比較例１＞
製造例１で得られた吸水性樹脂粒子（Ｐ－１）２０重量部について、吸水性樹脂粒子の水膨潤度が４０倍となるよう、イオン交換水に浸漬させることで、吸水性樹脂粒子の水膨潤度の調整を行った。
　その後、得られた膨潤した吸水性樹脂粒子８００重量部について、以下の順序で実施を行った。すなわち、水溶性無機酸（ｃ１）として硫酸（ｃ１－１）の１重量％水溶液３，０００重量部を膨潤した吸水性樹脂粒子８００重量部に添加し、２５℃で１５分間撹拌混合した後、目開き６３μｍ（ＪＩＳ　Ｚ８８０１－１：２００６）のナイロンメッシュでろ過し、さらに、ろ過して得られた固形物をナイロンメッシュにてろ過を行う順序で、固形物を得た。 <Comparative Example 1>
By immersing 20 parts by weight of the water-absorbent resin particles (P-1) obtained in Production Example 1 in ion-exchanged water so that the water swelling degree of the water-absorbent resin particles is 40 times, the water-absorbent resin particles can be obtained. The degree of water swelling was adjusted.
Then, 800 parts by weight of the obtained swollen water-absorbent resin particles were carried out in the following order. That is, 3,000 parts by weight of a 1 wt% aqueous solution of sulfuric acid (c1-1) as a water-soluble inorganic acid (c1) was added to 800 parts by weight of swollen water-absorbent resin particles, and the mixture was stirred and mixed at 25 ° C. for 15 minutes, and then mixed. A solid substance was obtained by filtering with a nylon mesh having an opening of 63 μm (JIS Z8801-1: 2006), and further filtering the solid substance obtained by filtration with a nylon mesh.
＜比較例２＞
製造例１で得られた吸水性樹脂粒子（Ｐ－１）２０重量部について、吸水性樹脂粒子の水膨潤度が４０倍となるよう、イオン交換水に浸漬させることで、吸水性樹脂粒子の水膨潤度の調整を行った。
　その後、得られた膨潤した吸水性樹脂粒子８００重量部について、以下の順序で実施を行った。すなわち、水溶性一価金属化合物（ｃ２）として塩化ナトリウム（ｃ２１－１）２０重量部を膨潤した吸水性樹脂粒子８００重量部に添加し、２５℃で１５分間撹拌混合した後、目開き６３μｍ（ＪＩＳ　Ｚ８８０１－１：２００６）のナイロンメッシュでろ過し、さらに、ろ過して得られた固形物をナイロンメッシュにてろ過を行う順序で、固形物を得た。 <Comparative Example 2>
By immersing 20 parts by weight of the water-absorbent resin particles (P-1) obtained in Production Example 1 in ion-exchanged water so that the water swelling degree of the water-absorbent resin particles is 40 times, the water-absorbent resin particles can be obtained. The degree of water swelling was adjusted.
Then, 800 parts by weight of the obtained swollen water-absorbent resin particles were carried out in the following order. That is, 20 parts by weight of sodium chloride (c21-1) as a water-soluble monovalent metal compound (c2) was added to 800 parts by weight of swollen water-absorbent resin particles, and the mixture was stirred and mixed at 25 ° C. for 15 minutes, and then the opening was 63 μm (. A solid substance was obtained by filtering with a nylon mesh of JIS Z8801-1: 2006) and further filtering the solid substance obtained by filtration with a nylon mesh.
＜比較例３＞
製造例１で得られた吸水性樹脂粒子（Ｐ－１）２０重量部について、吸水性樹脂粒子の水膨潤度が４０倍となるよう、イオン交換水に浸漬させることで、吸水性樹脂粒子の水膨潤度の調整を行った。
　その後、得られた膨潤した吸水性樹脂粒子８００重量部について、以下の順序で実施を行った。すなわち、水溶性一価金属化合物（ｃ２）として塩化ナトリウム（ｃ２１－１）１５０重量部を膨潤した吸水性樹脂粒子８００重量部に添加し、２５℃で１５分間撹拌混合した後、目開き６３μｍ（ＪＩＳ　Ｚ８８０１－１：２００６）のナイロンメッシュでろ過し、さらに、ろ過して得られた固形物をナイロンメッシュにてろ過を行う順序で、固形物を得た。 <Comparative Example 3>
By immersing 20 parts by weight of the water-absorbent resin particles (P-1) obtained in Production Example 1 in ion-exchanged water so that the water swelling degree of the water-absorbent resin particles is 40 times, the water-absorbent resin particles can be obtained. The degree of water swelling was adjusted.
Then, 800 parts by weight of the obtained swollen water-absorbent resin particles were carried out in the following order. That is, 150 parts by weight of sodium chloride (c21-1) as a water-soluble monovalent metal compound (c2) was added to 800 parts by weight of swollen water-absorbent resin particles, and the mixture was stirred and mixed at 25 ° C. for 15 minutes, and then the opening was 63 μm (. A solid substance was obtained by filtering with a nylon mesh of JIS Z8801-1: 2006) and further filtering the solid substance obtained by filtration with a nylon mesh.
＜比較例４＞
製造例１で得られた吸水性樹脂粒子（Ｐ－１）２０重量部について、吸水性樹脂粒子の水膨潤度が４０倍となるよう、イオン交換水に浸漬させることで、吸水性樹脂粒子の水膨潤度の調整を行った。
　その後、得られた膨潤した吸水性樹脂粒子８００重量部について、以下の順序で実施を行った。すなわち、多価金属化合物（ｒｃ２）として塩化カルシウム（ｒｃ２－１）８０重量部を膨潤した吸水性樹脂粒子８００重量部に添加し、２５℃で１５分間撹拌混合した後、目開き６３μｍ（ＪＩＳ　Ｚ８８０１－１：２００６）のナイロンメッシュでろ過し、さらに、ろ過して得られた固形物をナイロンメッシュにてろ過を行う順序で、固形物を得た。 <Comparative Example 4>
By immersing 20 parts by weight of the water-absorbent resin particles (P-1) obtained in Production Example 1 in ion-exchanged water so that the water swelling degree of the water-absorbent resin particles is 40 times, the water-absorbent resin particles can be obtained. The degree of water swelling was adjusted.
Then, 800 parts by weight of the obtained swollen water-absorbent resin particles were carried out in the following order. That is, 80 parts by weight of calcium chloride (rc2-1) as a polyvalent metal compound (rc2) was added to 800 parts by weight of swollen water-absorbent resin particles, and after stirring and mixing at 25 ° C. for 15 minutes, the opening was 63 μm (JIS Z8801). -The solid matter was obtained by filtering with the nylon mesh of (1: 2006) and further filtering the solid matter obtained by the filtration with the nylon mesh.
＜比較例１～４＞
　実施例と同様にし、水溶性無機酸水溶液のｐＨ（比較例１）、脱水、乾燥の容易さ及び再利用の容易さの評価を行った。評価結果を表３に示す。また、水溶性無機酸水溶液のｐＫａも示した（比較例１）。 <Comparative Examples 1 to 4>
In the same manner as in Examples, the pH of the aqueous solution of the water-soluble inorganic acid (Comparative Example 1), the ease of dehydration and drying, and the ease of reuse were evaluated. The evaluation results are shown in Table 3. Moreover, the pKa of the water-soluble inorganic acid aqueous solution was also shown (Comparative Example 1).
［評価方法］
（１）水溶性無機酸水溶液のｐＨ測定方法
水溶性無機酸（ｃ１）をイオン交換水で希釈して、０．０１重量％水溶性無機酸（ｃ１）水溶液を作製した。０．０１重量％水溶性無機酸（ｃ１）水溶液を２５℃に調整し、ｐＨメーター（株式会社　堀場製作所製Ｆ－７１Ｓ）を用いて測定した。
（２）脱水
　膨潤した吸水性樹脂粒子の脱水処理後の重量（Ａ）、脱水処理後の吸水性樹脂粒子の乾燥重量（Ｂ）をそれぞれ測定し、以下の（脱水処理後の）固形分濃度の算出式で、脱水を評価した。すなわち、（脱水処理後の）固形分濃度（％）が高いほど、脱水に優れる。なお、膨潤した吸水性樹脂粒子とは、製造例１～３で得られた吸水性樹脂粒子２０重量部それぞれに対して、イオン交換水７８０重量部に浸漬させ、イオン交換水全量を吸水させた試料のことである。
（脱水処理後の）固形分濃度（％）＝脱水処理後の吸水性樹脂粒子の乾燥重量（Ｂ）（ｇ）／膨潤した吸水性樹脂粒子の脱水処理後の重量（Ａ）（ｇ）×１００％
　なお、脱水処理後の吸水性樹脂粒子の乾燥重量（Ｂ）（ｇ）は、試料（脱水処理後の吸水性樹脂粒子の全量）をＳＵＳ製の金属バット上（縦３０ｃｍ×横２０ｃｍ×高さ５ｃｍ）に置き、セーフティオーブン［エスペック社製ＳＰＨＨ－２０１］１５０℃１２０分間で乾燥することで得ることができる。ＳＵＳ製の金属バット上に試料上で乾燥させる際は、試料同士が重ならないように均一的に広げて行った。 [Evaluation methods]
(1) Method for Measuring pH of Water-Soluble Inorganic Acid Aqueous Solution A water-soluble inorganic acid (c1) was diluted with ion-exchanged water to prepare a 0.01 wt% water-soluble inorganic acid (c1) aqueous solution. An aqueous 0.01 wt% water-soluble inorganic acid (c1) solution was adjusted to 25 ° C. and measured using a pH meter (F-71S manufactured by Horiba, Ltd.).
(2) Dehydration The weight (A) of the swollen water-absorbent resin particles after dehydration treatment and the dry weight (B) of the water-absorbent resin particles after dehydration treatment are measured, and the following solid content concentration (after dehydration treatment) is measured. Dehydration was evaluated by the formula of. That is, the higher the solid content concentration (%) (after dehydration treatment), the better the dehydration. The swollen water-absorbent resin particles were obtained by immersing 20 parts by weight of the water-absorbent resin particles obtained in Production Examples 1 to 3 in 780 parts by weight of ion-exchanged water to absorb the entire amount of ion-exchanged water. It is a sample.
Solid content concentration (%) (after dehydration treatment) = Dry weight of water-absorbent resin particles after dehydration treatment (B) (g) / Weight of swollen water-absorbent resin particles after dehydration treatment (A) (g) × 100%
The dry weights (B) and (g) of the water-absorbent resin particles after the dehydration treatment are such that the sample (the total amount of the water-absorbent resin particles after the dehydration treatment) is placed on a metal bat made of SUS (length 30 cm × width 20 cm × height). It can be obtained by placing it in a safety oven [SPHH-201 manufactured by Espec Co., Ltd.] and drying it at 150 ° C. for 120 minutes. When drying on the sample on a metal vat made of SUS, the samples were spread evenly so as not to overlap each other.
（３）乾燥の容易さ
　（２）の評価で得られたＳＵＳ製のバット上の乾燥後の吸水性樹脂粒子について、室温１時間で静置した後、バットへの付着程度と凝集程度を確認し、脱水処理後の吸水性樹脂粒子の乾燥の容易さを以下の基準で評価した。すなわち、付着が少なく、凝集が少ないほど、乾燥が容易な脱水処理方法として優れる。
＜評価基準＞
◎：乾燥後の吸水性樹脂粒子が、指で触らずとも凝集塊がない。
〇：乾燥後の吸水性樹脂粒子が、指で触ってバットから剥がれ、かつ指で挟んで凝集塊が砕ける。
△：乾燥後の吸水性樹脂粒子が、指で触ってバットから剥がれ、かつ指で挟んで凝集塊が砕けないものがある。
×：乾燥後の吸水性樹脂粒子が、指で触ってバットから剥がれないものがあるほどバットに付着している。 (3) Ease of drying The dried water-absorbent resin particles on the SUS vat obtained in the evaluation of (2) were allowed to stand at room temperature for 1 hour, and then the degree of adhesion to the vat and the degree of aggregation were confirmed. Then, the ease of drying the water-absorbent resin particles after the dehydration treatment was evaluated according to the following criteria. That is, the less the adhesion and the less the agglomeration, the better the dehydration treatment method for easy drying.
<Evaluation criteria>
⊚: The dried water-absorbent resin particles do not have agglomerates even if they are not touched with a finger.
〇: The dried water-absorbent resin particles are touched with a finger and peeled off from the bat, and the agglomerates are crushed by being pinched by the fingers.
Δ: Some of the dried water-absorbent resin particles are touched by a finger and peeled off from the bat, and the agglomerates are not broken by being pinched by the fingers.
X: The dried water-absorbent resin particles are so attached to the bat that some of them cannot be peeled off from the bat by touching with a finger.
（４）再利用の容易さ
　（２）の評価で得られた吸水性樹脂粒子について、５ｇを目開き６３μｍ（ＪＩＳ　Ｚ８８０１－１：２００６）のナイロン網で作製したティーバッグ（縦２０ｃｍ、横１０ｃｍ）に入れて、マグネティックスターラーで撹拌している１０％の水酸化ナトリウム水溶液２００ｍｌ中に、ティーバッグごと吊るして、２５±５℃で１時間浸漬させ、その後、マグネティックスターラーで撹拌している生理食塩水（食塩濃度０．９％）２００ｍｌ中に、ティーバッグごと吊るして、２５℃±２℃で１５分浸漬洗浄し、生理食塩水での浸漬洗浄を３回繰り返し行った。
　その後、引き続きティーバッグごと、生理食塩水１，０００ｍｌ中に無撹拌下、１時間浸漬した後引き上げて、１５分間吊るして水切りした。その後、ティーバッグごと、遠心分離器にいれ、１５０Ｇで９０秒間遠心脱水して余剰の生理食塩水を取り除き、ティーバッグを含めた重量（ｈ１）を測定し次式から保水量を求めた。なお、使用した生理食塩水及び測定雰囲気の温度は２５℃±２℃とした。（ｈ２）は、測定試料の無い場合について上記と同様の操作により計測したティーバッグの重量である。
保水量（ｇ／ｇ）＝［（ｈ１）－（ｈ２）］／５
　上述の方法で、生理食塩水に対する保水量を確認し、以下の基準で再利用の容易さを評価した。すなわち、保水量が高いほど、再利用が容易な脱水処理方法として優れる。
＜評価基準＞
◎： ３０≦保水量
〇： ２０≦保水量＜３０
△： １０≦保水量＜２０
×： ０≦保水量＜１０ (4) Ease of reuse Regarding the water-absorbent resin particles obtained in the evaluation of (2), a tea bag (length 20 cm, width 10 cm) made of a nylon net having an opening of 63 μm (JIS Z8801-1: 2006) with 5 g open. ), Suspended with a tea bag in 200 ml of a 10% sodium hydroxide aqueous solution stirred with a magnetic stirrer, soaked at 25 ± 5 ° C. for 1 hour, and then stirred with a magnetic stirrer. The tea bag was hung in 200 ml of water (salt concentration 0.9%), soaked and washed at 25 ° C. ± 2 ° C. for 15 minutes, and soaked and washed with physiological saline was repeated 3 times.
Then, the whole tea bag was continuously immersed in 1,000 ml of physiological saline without stirring for 1 hour, then pulled up, hung for 15 minutes and drained. Then, each tea bag was placed in a centrifuge and 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 amount of water retained by 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)] / 5
The amount of water retained in the saline solution was confirmed by the above method, and the ease of reuse was evaluated according to the following criteria. That is, the higher the amount of water retained, the better the dehydration treatment method, which is easy to reuse.
<Evaluation criteria>
⊚: 30 ≤ water retention 〇: 20 ≤ water retention <30
Δ: 10 ≦ water retention amount <20
×: 0 ≦ water retention amount <10
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
　表１、表２に示す結果から明らかなように、実施例１～１３に示す本発明の脱水処理方法は、比較例１～４に示す脱水処理方法と比べて、脱水、乾燥の容易さ及び再利用の容易さが良好であることが分かる。すなわち、吸水性樹脂粒子に吸収されている水分を十分に脱水でき、かつ、その後工程において、吸水性樹脂粒子の乾燥の容易さと再利用の容易さに優れると言える。 As is clear from the results shown in Tables 1 and 2, the dehydration treatment method of the present invention shown in Examples 1 to 13 is easier to dehydrate and dry than the dehydration treatment methods shown in Comparative Examples 1 to 4. It can be seen that the ease of reuse is good. That is, it can be said that the moisture absorbed by the water-absorbent resin particles can be sufficiently dehydrated, and that the water-absorbent resin particles are easy to dry and reuse in the subsequent steps.
　本発明の脱水処理方法は、紙おむつ（子供用紙おむつ及び大人用紙おむつ等）、ナプキン（生理用ナプキン等）、紙タオル、パッド（失禁者用パッド及び手術用アンダーパッド等）及びペットシート（ペット尿吸収シート）等といった衛生材料分野の吸水性樹脂粒子のみならず、電気・電子分野の通信ケーブル用止水材向け、農業・園芸分野の土壌保水剤や育苗用シート向け、医療分野の創傷保護用ドレッシング剤や廃血凝固化剤向け、流通・搬送分野の保冷材や結露防止シート向け、その他分野のゲル芳香剤や使い捨てカイロ向けの吸水性樹脂粒子に対しても、排出される吸水性樹脂粒子の再利用に向けて、好適に利用できる。

  The dehydration treatment method of the present invention includes paper diapers (children's disposable diapers, adult disposable diapers, etc.), napkins (physiological napkins, etc.), paper towels, pads (pads for incontinence, surgical underpads, etc.) and pet sheets (pet urine). Not only for water-absorbent resin particles in the field of sanitary materials such as (absorbent sheet), but also for water-stopping materials for communication cables in the electric and electronic fields, for soil water-retaining agents and seedling raising sheets in the fields of agriculture and gardening, and for wound protection in the medical field. Water-absorbent resin particles discharged for dressing agents and waste blood coagulants, for cold insulation materials and dew condensation prevention sheets in the distribution / transportation field, and for gel fragrances and disposable body warmers in other fields. Can be suitably used for reuse of.

Claims (8)

  1. 　（メタ）アクリル酸（塩）及び架橋剤（ｂ）を必須構成単位とする架橋重合体（Ａ）を含有する吸水性樹脂粒子に吸収されている水分の脱水処理方法であって、
    　方法（１）：水分を吸収している前記吸水性樹脂粒子と水溶性無機酸（ｃ１）とを混合する工程及びその後、さらに水溶性一価金属化合物（ｃ２）と混合する工程を含む方法、
    　方法（２）：水分を吸収している前記吸水性樹脂粒子と水溶性一価金属化合物（ｃ２）とを混合する工程及びその後、さらに水溶性無機酸（ｃ１）と混合する工程を含む方法、ならびに
    　方法（３）：水分を吸収している前記吸水性樹脂粒子と水溶性無機酸（ｃ１）および水溶性一価金属化合物（ｃ２）とを混合する工程を含む方法、のうちのいずれかの方法を用いる脱水処理方法。     (Meta) A method for dehydrating water absorbed by water-absorbent resin particles containing a crosslinked polymer (A) containing acrylic acid (salt) and a crosslinking agent (b) as essential constituent units.
    Method (1): A method including a step of mixing the water-absorbent resin particles absorbing water with a water-soluble inorganic acid (c1), and then a step of further mixing with a water-soluble monovalent metal compound (c2).
    Method (2): A method including a step of mixing the water-absorbent resin particles absorbing water with a water-soluble monovalent metal compound (c2), and then a step of further mixing with a water-soluble inorganic acid (c1). And method (3): any of a method including a step of mixing the water-absorbent resin particles absorbing water with a water-soluble inorganic acid (c1) and a water-soluble monovalent metal compound (c2). Dehydration treatment method using the method.
  2. 　前記吸水性樹脂粒子が表面架橋剤（ｄ）を使用して表面架橋されたものである請求項１記載の脱水処理方法。 The dehydration treatment method according to claim 1, wherein the water-absorbent resin particles are surface-crosslinked using the surface cross-linking agent (d).
  3. 　前記吸水性樹脂粒子の水膨潤度が、１０～５０倍である請求項１又は２に記載の脱水処理方法。 The dehydration treatment method according to claim 1 or 2, wherein the water swelling degree of the water-absorbent resin particles is 10 to 50 times.
  4. 　前記方法（１）を用いる請求項１～３のいずれか記載の脱水処理方法。 The dehydration treatment method according to any one of claims 1 to 3, which uses the method (1).
  5. 　前記水溶性無機酸（ｃ１）の酸解離定数（ｐＫａ）が２以下である請求項１～４のいずれか記載の脱水処理方法。 The dehydration treatment method according to any one of claims 1 to 4, wherein the acid dissociation constant (pKa) of the water-soluble inorganic acid (c1) is 2 or less.
  6. 　前記水溶性無機酸（ｃ１）が、硫酸及び／又はりん酸である請求項１～５のいずれか記載の脱水処理方法。 The dehydration treatment method according to any one of claims 1 to 5, wherein the water-soluble inorganic acid (c1) is sulfuric acid and / or phosphoric acid.
  7. 　前記水溶性一価金属化合物（ｃ２）が、硫酸ナトリウム及び／又はりん酸ナトリウムである請求項１～６のいずれか記載の脱水処理方法。 The dehydration treatment method according to any one of claims 1 to 6, wherein the water-soluble monovalent metal compound (c2) is sodium sulfate and / or sodium phosphate.
  8. 　前記水溶性無機酸（ｃ１）の０．０１重量％水溶液（２５℃）のｐＨが２．０～４．０である請求項１～７のいずれか記載の脱水処理方法。

          The dehydration treatment method according to any one of claims 1 to 7, wherein the pH of the 0.01% by weight aqueous solution (25 ° C.) of the water-soluble inorganic acid (c1) is 2.0 to 4.0.
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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH06502454A (en) * 1991-06-17 1994-03-17 ノワスト・テクノロジーズ・インコーポレーテツド Processing of absorbent sanitary paper products
JP2003326161A (en) * 2002-03-06 2003-11-18 Nippon Shokubai Co Ltd Regeneration method for water absorbing resin, and water absorbent
JP2013198862A (en) * 2012-03-23 2013-10-03 Hokkaido Univ Method for regenerating used highly water-absorbent polymer
JP2019084470A (en) * 2017-11-01 2019-06-06 ユニ・チャーム株式会社 Method of and system for recovering pulp fiber and highly water-absorbing polymer from used absorbent article
JP2019108639A (en) * 2017-12-20 2019-07-04 ユニ・チャーム株式会社 Method for manufacturing recycle pulp fiber
JP2019135046A (en) * 2018-02-05 2019-08-15 ユニ・チャーム株式会社 Method for regenerating highly absorbent polymer, method for producing highly absorbent recycled polymer, and use of alkali metal supply source

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH06502454A (en) * 1991-06-17 1994-03-17 ノワスト・テクノロジーズ・インコーポレーテツド Processing of absorbent sanitary paper products
JP2003326161A (en) * 2002-03-06 2003-11-18 Nippon Shokubai Co Ltd Regeneration method for water absorbing resin, and water absorbent
JP2013198862A (en) * 2012-03-23 2013-10-03 Hokkaido Univ Method for regenerating used highly water-absorbent polymer
JP2019084470A (en) * 2017-11-01 2019-06-06 ユニ・チャーム株式会社 Method of and system for recovering pulp fiber and highly water-absorbing polymer from used absorbent article
JP2019108639A (en) * 2017-12-20 2019-07-04 ユニ・チャーム株式会社 Method for manufacturing recycle pulp fiber
JP2019135046A (en) * 2018-02-05 2019-08-15 ユニ・チャーム株式会社 Method for regenerating highly absorbent polymer, method for producing highly absorbent recycled polymer, and use of alkali metal supply source

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