WO2019221154A1 - 吸水性樹脂粒子の製造方法 - Google Patents
吸水性樹脂粒子の製造方法 Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J3/00—Processes of treating or compounding macromolecular substances
- C08J3/24—Crosslinking, e.g. vulcanising, of macromolecules
- C08J3/245—Differential crosslinking of one polymer with one crosslinking type, e.g. surface crosslinking
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
- A61F13/00—Bandages or dressings; Absorbent pads
- A61F13/15—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators
- A61F13/53—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium
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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
- B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
- B01J20/26—Synthetic macromolecular compounds
- B01J20/265—Synthetic macromolecular compounds modified or post-treated polymers
- B01J20/267—Cross-linked polymers
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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
- B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
- B01J20/28002—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their physical properties
- B01J20/28004—Sorbent size or size distribution, e.g. particle size
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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
- B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
- B01J20/28014—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their form
- B01J20/28016—Particle form
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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
- B01J20/3021—Milling, crushing or grinding
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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
- B01J20/3078—Thermal treatment, e.g. calcining or pyrolizing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
- B29B13/00—Conditioning or physical treatment of the material to be shaped
- B29B13/06—Conditioning or physical treatment of the material to be shaped by drying
- B29B13/065—Conditioning or physical treatment of the material to be shaped by drying of powder or pellets
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F20/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride, ester, amide, imide or nitrile thereof
- C08F20/02—Monocarboxylic acids having less than ten carbon atoms, Derivatives thereof
- C08F20/04—Acids, Metal salts or ammonium salts thereof
- C08F20/06—Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
- C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
- C08F220/04—Acids; Metal salts or ammonium salts thereof
- C08F220/06—Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof
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- 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
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/0037—Rotary furnaces with vertical axis; Furnaces with rotating floor
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/0068—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for particular articles not mentioned below
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B11/00—Machines or apparatus for drying solid materials or objects with movement which is non-progressive
- F26B11/12—Machines or apparatus for drying solid materials or objects with movement which is non-progressive in stationary drums or other mainly-closed receptacles with moving stirring devices
- F26B11/16—Machines or apparatus for drying solid materials or objects with movement which is non-progressive in stationary drums or other mainly-closed receptacles with moving stirring devices the stirring device moving in a vertical or steeply-inclined plane
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B17/00—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement
- F26B17/30—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement with movement performed by rotary or oscillating containers; with movement performed by rotary floors
- F26B17/32—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement with movement performed by rotary or oscillating containers; with movement performed by rotary floors the movement being in a horizontal or slightly inclined plane
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B3/00—Drying solid materials or objects by processes involving the application of heat
- F26B3/18—Drying solid materials or objects by processes involving the application of heat by conduction, i.e. the heat is conveyed from the heat source, e.g. gas flame, to the materials or objects to be dried by direct contact
- F26B3/22—Drying solid materials or objects by processes involving the application of heat by conduction, i.e. the heat is conveyed from the heat source, e.g. gas flame, to the materials or objects to be dried by direct contact the heat source and the materials or objects to be dried being in relative motion, e.g. of vibration
- F26B3/24—Drying solid materials or objects by processes involving the application of heat by conduction, i.e. the heat is conveyed from the heat source, e.g. gas flame, to the materials or objects to be dried by direct contact the heat source and the materials or objects to be dried being in relative motion, e.g. of vibration the movement being rotation
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
- A61F13/00—Bandages or dressings; Absorbent pads
- A61F13/15—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators
- A61F13/53—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium
- A61F2013/530481—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium having superabsorbent materials, i.e. highly absorbent polymer gel materials
- A61F2013/530569—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium having superabsorbent materials, i.e. highly absorbent polymer gel materials characterized by the particle size
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
- A61F13/00—Bandages or dressings; Absorbent pads
- A61F13/15—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators
- A61F13/53—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium
- A61F2013/530481—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium having superabsorbent materials, i.e. highly absorbent polymer gel materials
- A61F2013/530583—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium having superabsorbent materials, i.e. highly absorbent polymer gel materials characterized by the form
- A61F2013/530591—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium having superabsorbent materials, i.e. highly absorbent polymer gel materials characterized by the form in granules or particles
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- 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
- C08J2333/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers
- C08J2333/02—Homopolymers or copolymers of acids; Metal or ammonium salts thereof
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- 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
- C08J2451/00—Characterised by the use of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Derivatives of such polymers
- C08J2451/08—Characterised by the use of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Derivatives of such polymers grafted on to macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
Definitions
- the present invention relates to a method for producing water-absorbing resin particles. Specifically, the present invention relates to a method for producing water-absorbing resin particles including a surface crosslinking step.
- Water-absorbing resin (SAP / Super Absorbent Polymer) is a water-swellable, water-insoluble polymer gelling agent, absorbent articles such as paper diapers and sanitary napkins, water retaining agents for agriculture and horticulture, and industrial waterstops. It is widely used in various fields such as drugs.
- the water-absorbent resin uses many monomers and hydrophilic polymers as raw materials. From the viewpoint of water absorption performance, polyacrylic acid (and acrylic acid and / or its salt as a monomer) is used. Salt) water-absorbing resins are most industrially produced.
- the water-absorbing resin is required to have various functions (higher physical properties) as the paper diaper, which is the main application, has improved performance. Specifically, in addition to the basic physical properties, water absorption capacity without pressure and water absorption capacity under pressure, gel strength, water-soluble content, water content, water absorption speed, liquid permeability, particle size distribution, urine resistance, antibacterial properties Various properties such as damage resistance, powder flowability, deodorization, color resistance, low dust, and low residual monomer are required for the water-absorbing resin. In particular, in the use of sanitary goods such as paper diapers, further improvement in the water absorption speed is desired as the product becomes thinner.
- Such a water-absorbing resin can have various shapes such as a sheet shape, a fiber shape, and a film shape, but in general, it is often in a powder shape or a particle shape. It is known that the water-absorbing performance, handleability, and feeling of use vary depending on the particle diameter, particle size distribution, and the like of a powdered or particulate water-absorbing resin. Therefore, a powdered or particulate water-absorbing resin in which the particle size and particle size distribution are appropriately controlled is demanded.
- a water-absorbent resin with a low content of fine powder fine particles having a particle diameter of less than 100 ⁇ m to less than 150 ⁇ m, particularly fine particles of less than 150 ⁇ m
- the water absorbent resin particles are generally subjected to surface crosslinking treatment.
- Examples of the main production method of the powdery or particulate water-absorbing resin include an aqueous solution polymerization method and a reverse phase suspension polymerization method.
- a polymerization step for polymerizing a water-soluble ethylenically unsaturated monomer in an aqueous solution in order to finally obtain a particulate water-absorbing resin polymerization Gel pulverization (fine-graining) step for pulverizing the hydrogel crosslinked polymer obtained in step 1, drying step for drying the pulverized gel, pulverization step for pulverizing the dried product, classification step for adjusting the pulverized product to an appropriate particle size range
- a water-soluble ethylenically unsaturated monomer aqueous solution is dispersed in a hydrophobic organic solvent to carry out a polymerization reaction in a suspended particle state, so that a gel grinding step during or after polymerization Is generally unnecessary, but the subsequent manufacturing process includes substantially the same steps as aqueous solution polymerization.
- the amount of fine powder generated in the conventional manufacturing process reaches around 10% by mass to several tens of mass% (for example, 20-30% by mass) of the entire production amount.
- fine powder is generated not only by the polymerization step and the pulverization step, but also by process damage such as a surface crosslinking step, a sizing step, and a transport step after the drying step.
- process damage such as a surface crosslinking step, a sizing step, and a transport step after the drying step.
- the generation of fine powder due to the surface cross-linking step or subsequent process damage is accompanied by the destruction of the surface cross-linking structure, which may lead to a decrease in physical properties of the water-absorbent resin.
- the generated fine powder is removed in the classification process or the sizing process, but its disposal is disadvantageous in terms of cost. Therefore, the fine powder is collected before the classification process, particularly before the drying process, and further, the polymerization process and the gel grinding process. Recycled to the drying process. However, it is difficult to handle fine powder because it tends to aggregate. In addition, the addition of the fine powder recycling process further complicates or enlarges the manufacturing process (equipment) of the water absorbent resin. Moreover, in order to increase the load of the polymerization process which recycles a fine powder, and a drying process, the increase in the amount of fine powder collection may be accompanied by the fall of productivity and the performance of the water absorbing resin obtained.
- Patent Document 1 A method using a stirring and drying apparatus provided with a crushing means (Patent Document 1) and a specific structure in order to reduce the processing time in the surface cross-linking step and suppress the generation of fine powder due to mechanical damage from the stirring plate A method using a device (Patent Document 2) has been proposed.
- Patent Document 3 a method for heat-treating water-absorbing polymer particles using a fluidized bed dryer has been proposed (Patent Document 3).
- an object of the present invention is to provide an industrial production method for water-absorbing resin particles that generates a small amount of fine powder in the production process, suppresses a decrease in physical properties due to the fine powder, and generates a small amount of colored foreign matter.
- Another object of the present invention is to provide a heating device and a surface crosslinking method used in the surface crosslinking step.
- the present inventors have conducted heat treatment on a mixture of a particulate dry polymer having a predetermined moisture content and a surface cross-linking agent using a heating device having a specific structure.
- the present invention has been completed by finding that the mechanical and thermal damage is reduced and the amount of fines generated and the amount of colored foreign matter is reduced. Furthermore, the present inventors have found that the effect of the present invention becomes more remarkable in the scale-up production of water-absorbent resin particles.
- the present invention is a surface cross-linking step in which a mixture of a particulate dry polymer having a water content of 15% by mass or less obtained with an acid group-containing unsaturated monomer as a main component and a surface cross-linking agent is heated.
- a method for producing water-absorbent resin particles using a heating device comprising a container and a plurality of heating tubes that are positioned inside the rotating container, extend in the axial direction thereof, and rotate together with the rotating container. .
- the present invention is a heating apparatus for heat-treating a mixture of a particulate dry polymer having a water content of 15% by mass or less obtained mainly from an acid group-containing unsaturated monomer, and a surface crosslinking agent
- the heating device includes a rotating container, a plurality of heating tubes that are positioned inside the rotating container, extend in the axial direction of the rotating container, and rotate together with the rotating container, and gas is introduced into the rotating container. It is a heating device provided with a means for discharging.
- the present invention uses the above-described heating device to heat a mixture of a particulate dry polymer having a water content of 15% by mass or less obtained mainly from an acid group-containing unsaturated monomer and a surface cross-linking agent.
- This is a surface cross-linking method to be processed, and is a surface cross-linking method in which the temperature of the inner surface of the rotating container is set to 100 ° C. or higher.
- the production method of the present invention by using a heating device having a specific structure in the surface cross-linking step, particularly in the heating step of heat-treating the mixture of the particulate dry polymer and the surface cross-linking agent, the machine to the water-absorbent resin particles Damage is reduced and generation of fine powder is suppressed.
- the load in the sizing process is small, and the deterioration of physical properties due to the destruction of the surface crosslinking is suppressed.
- the residence time of the water-absorbent resin particles inside the heating device is not excessively prolonged, so the amount of fine powder generated is reduced.
- the heating device of this specific structure since the discharge time of the water-absorbent resin particles after the end of operation is appropriate, the generation of colored foreign matters due to excessive heating is suppressed, and the production efficiency is improved.
- FIG. 1 is a partially cutaway side view showing an example of a heating device (rotary heating device with a heating tube) used in the manufacturing method according to the present invention.
- FIG. 2 is an enlarged cross-sectional view showing a part of the heating apparatus of FIG.
- FIG. 3 is a cross-sectional view taken along line III-III of the heating apparatus of FIG.
- FIG. 4 is a cross-sectional view for explaining a heating device (rotary heating device with double heating tubes) used in the manufacturing method according to the present invention.
- FIG. 5 is an example of a shield (opening ratio 20%) having an opening used in a drying apparatus (rotary heating apparatus with a heating tube) used in the manufacturing method according to the present invention.
- FIG. 1 is a partially cutaway side view showing an example of a heating device (rotary heating device with a heating tube) used in the manufacturing method according to the present invention.
- FIG. 2 is an enlarged cross-sectional view showing a part of the heating apparatus of FIG.
- FIG. 3 is a cross
- FIG. 6 is an example of shielding (opening ratio 50%) having an opening used in a drying apparatus (rotary heating apparatus with a heating tube) used in the manufacturing method according to the present invention.
- FIG. 7 is a flowchart for explaining a typical method for producing a water absorbent resin.
- FIG. 8 is a partially cutaway side view showing an example of a drying device (stir dryer) used in a conventional manufacturing method.
- Water absorbent resin refers to a water-swellable, water-insoluble polymer gelling agent and satisfies the following physical properties. That is, the CRC (centrifuge retention capacity) defined by ERT441.2-02 as water swellability is 5 g / g or more, and Ext (water-soluble) defined by ERT470.2-02 as water-insoluble The polymer gelling agent whose (min) is 50 mass% or less.
- the water-absorbent resin can be designed according to its use and purpose, and is not particularly limited, but is preferably a hydrophilic cross-linked polymer obtained by cross-linking an unsaturated monomer containing a carboxyl group. Moreover, it is not limited to the form whose whole quantity is a crosslinked polymer, As long as each said physical property (CRC, Ext) satisfy
- water-absorbent resin when referred to as “water-absorbent resin”, it may be surface-crosslinked (also known as post-crosslinking, secondary crosslinking) or may not be surface-crosslinked.
- water-absorbing resin particles particularly when referred to as “water-absorbing resin particles” or “water-absorbing agent”, the water-absorbing resin in which the predetermined surface cross-linking treatment is completed and / or the water-absorbing resin in which the predetermined surface treatment is completed and the particle size is adjusted. Means.
- poly (meth) acrylic acid (salt) refers to poly (meth) acrylic acid and / or a salt thereof, and (meth) acrylic acid and / or a salt thereof (hereinafter referred to as “(meta) ) (Also referred to as “acrylic acid (salt)”) as a repeating unit, and a cross-linked polymer containing a graft component as an optional component.
- main component is preferably such that the amount (content) of (meth) acrylic acid (salt) used is 50% with respect to the whole monomer (all monomers excluding the crosslinking agent) used in the polymerization. It means that it is from mol% to 100 mol%, more preferably from 70 mol% to 100 mol%, still more preferably from 90 mol% to 100 mol%, particularly preferably substantially 100 mol%.
- the poly (meth) acrylic acid (salt) may be unneutralized, but is preferably a partially or completely neutralized poly (meth) acrylate, more preferably a monovalent salt, More preferred are alkali metal salts or ammonium salts, even more preferred are alkali metal salts, and particularly preferred are sodium salts.
- EDANA is an abbreviation for European Disposables and Non-Womens Associations.
- ERT is an abbreviation for EDANA Recommended Test Methods and is a European standard that defines a method for evaluating water-absorbing resins.
- the measurement method described in the original ERT is measured in accordance with it.
- the measurement is carried out using the methods and conditions described in the examples.
- CRC is an abbreviation for Centrifugation Retention Capacity (centrifuge retention capacity) and means the water absorption capacity of the water absorbent resin under no pressure (sometimes referred to as “water absorption capacity”). Specifically, 0.2 g of the water-absorbing resin was put in a non-woven bag, and then immersed in a large excess of 0.9 mass% sodium chloride aqueous solution for 30 minutes for free swelling, and then centrifuged (250G ) Is the water absorption capacity (unit: g / g) after draining for 3 minutes. In addition, about water-containing gel after superposition
- Ext is an abbreviation for Extractables and means the water-soluble content of the water-absorbent resin (the amount of water-soluble polymer in the water-absorbent resin). Specifically, 1.0 g of water-absorbing resin is added to 200 ml of a 0.9% by mass sodium chloride aqueous solution, stirred for 16 hours at 500 rpm, and then the amount of substance dissolved in the aqueous solution (unit: mass%). . PH titration is used to measure the water-soluble content. In addition, about the water-containing gel after superposition
- “Moisture Content” (ERT430.2-02) “Moisture Content” means the moisture content defined by the loss on drying of the water-absorbent resin. Specifically, it refers to a value (unit: mass%) calculated from loss on drying when 4.0 g of water-absorbing resin is dried at 105 ° C. for 3 hours.
- the dried water-absorbent resin is defined by 1.0 g of a water-absorbent resin at 180 ° C. and a loss on drying for 3 hours, and the hydrogel before drying is 2.0 g of hydrous gel at 180 ° C. , Defined as 24-hour loss on drying.
- PSD is an abbreviation for Particle Size Distribution, and means a particle size distribution of a water-absorbent resin measured by sieving.
- the mass average particle diameter (D50) and the logarithmic standard deviation ( ⁇ ) of the particle size distribution are measured by the same method as described in US Pat. No. 7,638,570.
- the particle size distribution (PSD) of the particulate hydrous gel is defined by wet sieving by the method described below.
- the particle size ( ⁇ m) in terms of solid content of the particulate hydrogel is defined by the calculation method described later from the particle size ( ⁇ m) of the particulate hydrogel and the solid content rate (mass%).
- AAP is an abbreviation for Absorption against Pressure, and means the water absorption capacity of a water absorbent resin under pressure. Specifically, 0.9 g of the water-absorbing resin was swollen with a large excess of 0.9 mass% sodium chloride aqueous solution for 1 hour under a load of 2.06 kPa (21 g / cm 2 , 0.3 psi). It refers to the subsequent water absorption ratio (unit: g / g). In the present specification, it is defined as a value measured by changing the load condition to 4.83 kPa (about 49 g / cm 2 , corresponding to about 0.7 psi).
- “Residual Monomers” (ERT410.2-02) “Residual Monomers” means the ratio (unit: ppm) of the mass of the monomer (monomer) remaining in the water absorbent resin (hereinafter referred to as “residual monomer”) to the mass of the water absorbent resin. Specifically, 1.0 g of a water-absorbing resin is added to 200 ml of a 0.9% by mass sodium chloride aqueous solution, and the amount of monomer eluted after stirring for 1 hour is measured using high performance liquid chromatography. The residual monomer of the water-containing gel is a ratio (unit) of the residual monomer mass obtained by measuring by the method described later after the polymerization stopping operation such as forced cooling if necessary, to the resin solid content of the water-containing gel. ; Mass%).
- X to Y indicating a range means “X or more and Y or less”.
- t (ton) which is a unit of mass, means “Metric ton”
- ppm means “mass ppm” or “weight ppm”.
- mass and weight means “mass part” and “part by weight”, “mass%” and “wt%” are treated as synonyms.
- ⁇ acid (salt) means “ ⁇ acid and / or salt thereof”
- (meth) acryl means “acryl and / or methacryl”.
- the method for producing water-absorbent resin particles according to the present invention comprises a mixture of a particulate dry polymer obtained by using an acid group-containing unsaturated monomer as a main component and a surface cross-linking agent.
- a surface cross-linking step of heat-treating Preferably, the surface crosslinking step includes a surface crosslinking agent addition step and a heat treatment step.
- the production method comprises a polymerization step, a gel grinding step (simultaneously or separately from the polymerization), a drying step, a cooling step (after drying and / or after surface crosslinking), and a (after drying and / or surface).
- the surface cross-linking step in the present invention means a step performed separately from the drying step after the drying step.
- This step is a step of preparing an aqueous solution containing an acid group-containing unsaturated monomer as a main component (hereinafter referred to as “monomer aqueous solution”).
- monomer aqueous solution an aqueous solution containing an acid group-containing unsaturated monomer as a main component
- the slurry liquid of a monomer can also be used in the range by which the water absorption performance of the water-absorbing resin obtained does not fall, in this section, monomer aqueous solution is demonstrated for convenience.
- the “main component” means that the amount (content) of the acid group-containing unsaturated monomer is based on the whole monomer (excluding the internal cross-linking agent) used for the polymerization reaction of the water absorbent resin. Usually, it is 50 mol% or more, preferably 70 mol% or more, more preferably 90 mol% or more (the upper limit is 100 mol%).
- (Acid group-containing unsaturated monomer) Although the acid group prescribed
- the monomer other than the acid group-containing unsaturated monomer may be a compound that can be polymerized to become a water-absorbing resin.
- amide group-containing unsaturated monomers such as (meth) acrylamide, N-ethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide; N, N-dimethylaminoethyl (meth) acrylate, N, N
- An amino group-containing unsaturated monomer such as dimethylaminopropyl (meth) acrylate and N, N-dimethylaminopropyl (meth) acrylamide; a mercapto group-containing unsaturated monomer; a phenolic hydroxyl group-containing unsaturated monomer;
- lactam group-containing unsaturated monomers such as N-vinylpyrrolidone.
- the monomer used for the polymerization preferably contains a small amount of a polymerization inhibitor in view of the stability of the polymerization.
- a preferred polymerization inhibitor is p-methoxyphenol.
- the amount of the polymerization inhibitor contained in the monomer (particularly acrylic acid and its salt) is usually from 1 ppm to 250 ppm, preferably from 10 ppm to 160 ppm, more preferably from 20 ppm to 80 ppm.
- the salt of the acid group-containing unsaturated monomer is preferably a salt with a monovalent cation, more preferably at least one selected from alkali metal salts, ammonium salts and amine salts, An alkali metal salt is more preferable, at least one selected from a sodium salt, a lithium salt and a potassium salt is still more preferable, and a sodium salt is particularly preferable.
- the neutralizing agent used for neutralizing the acid group-containing unsaturated monomer is not particularly limited, but includes inorganic salts such as sodium hydroxide, potassium hydroxide, sodium carbonate, ammonium carbonate, and amino groups. Or a basic substance such as an amine-based organic compound having an imino group is appropriately selected and used. Two or more basic substances may be used in combination as a neutralizing agent.
- the monomer in this invention is the concept containing a neutralization salt unless there is particular notice.
- the number of moles of the neutralized salt relative to the total number of moles of the acid group-containing unsaturated monomer and the neutralized salt is preferably 40 mol% or more, More preferably, it is 40 mol% to 80 mol%, still more preferably 45 mol% to 78 mol%, and particularly preferably 50 mol% to 75 mol%.
- a method for adjusting the neutralization rate a method of mixing an acid group-containing unsaturated monomer and a neutralized salt thereof; a method of adding a known neutralizing agent to an acid group-containing unsaturated monomer; A method using a partially neutralized salt of an acid group-containing unsaturated monomer adjusted to a predetermined neutralization rate (that is, a mixture of an acid group-containing unsaturated monomer and a neutralized salt thereof); . Moreover, you may combine these methods.
- the adjustment of the neutralization rate may be performed before the polymerization reaction of the acid group-containing unsaturated monomer is started, may be performed in the polymerization reaction of the acid group-containing unsaturated monomer, or may contain an acid group. You may carry out with respect to the hydrogel crosslinked polymer obtained after completion
- an internal cross-linking agent In the method for producing water absorbent resin particles, an internal cross-linking agent is preferably used.
- the internal cross-linking agent adjusts the water absorption performance of the resulting water-absorbent resin, the gel strength during water absorption, and the like.
- the internal cross-linking agent only needs to have a total of two or more unsaturated bonds or reactive functional groups in one molecule.
- Poly propylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, glycerin (meth) acrylate, glycerin acrylate methacrylate, ethylene oxide modified trimethylolpropane tri (meth) acrylate, pentaerythritol hexa (meth) acrylate, tri
- Examples include allyl cyanurate, triallyl isocyanurate, and triallyl phosphate.
- an internal cross-linking agent having a plurality of reactive functional groups (which can react with a monomer functional group (eg, carboxy group)) in the molecule, triallylamine, polyallyloxyalkane, (poly) ethylene glycol diglycidyl ether, Glycerol diglycidyl ether, ethylene glycol, polyethylene glycol, propylene glycol, glycerin, 1,4-butanediol, pentaerythritol, ethylenediamine, ethylene carbonate, propylene carbonate, polyethyleneimine, etc.
- Cyclic carbonate is a cross-linking agent that further generates a functional group OH by reaction with a carboxyl group).
- glycidyl (meth) acrylate etc. are mentioned as an internal crosslinking agent which has a polymerizable unsaturated group and a reactive functional group in a molecule
- a compound having a plurality of polymerization unsaturated groups in the molecule is preferable, and a compound having a (poly) alkylene structural unit in the molecule is more preferable. More preferred is a compound having a polyethylene glycol structural unit, and particularly preferred is an acrylate compound having a polyethylene glycol structural unit.
- Water-containing gels obtained using these internal cross-linking agents have a low water absorption ratio at the beginning of drying and have low adhesiveness. When the water-containing gel having low adhesiveness is dried by stirring, it is preferable because fusion and aggregation during drying can be reduced. Furthermore, the water-containing gel obtained using these internal cross-linking agents has an effect that the water absorption capacity is easily improved by drying.
- the amount of the internal cross-linking agent used is appropriately set according to the type of monomer and internal cross-linking agent. From the viewpoint of gel strength of the resulting water-absorbent resin, the amount is preferably 0.001 mol% or more, more preferably 0.005 mol% or more, still more preferably 0.01 mol% or more based on the monomer. Moreover, from a viewpoint of the water absorption performance improvement of a water absorbing resin, Preferably it is 5 mol% or less, More preferably, it is 2 mol% or less. In the polymerization conditions in which the monomer self-crosslinking reaction is effective, the internal crosslinking agent may not be used.
- chain transfer agents such as thiols, thiolic acids, secondary alcohols, amines and hypophosphites
- foaming agents such as carbonates, bicarbonates, azo compounds, and bubbles
- ethylenediamine Chelating agents such as tetra (methylenephosphinic acid) and its metal salt, ethylenediaminetetraacetic acid and its metal salt, diethylenetriaminepentaacetic acid and its metal salt
- polyacrylic acid (salt) and cross-linked products thereof (for example, recycled water-absorbing resin) Fine powder starch, cellulose, starch-cellulose derivatives, and hydrophilic polymers such as polyvinyl alcohol.
- Other substances may be used alone or in combination of two or more.
- the amount of other substances used is not particularly limited, but for fine powder to be recycled, it is 30% by mass or less based on the monomer, and other than the fine powder, the total concentration of other substances is preferably 10% for the monomer. It is not more than mass%, more preferably 0.001 mass% to 5 mass%, particularly preferably 0.01 mass% to 1 mass%.
- the monomer concentration may be referred to as “monomer concentration”.
- the polymerization initiator used in the present invention is not particularly limited since it is appropriately selected depending on the polymerization form and the like.
- a thermal decomposition polymerization initiator, a photodecomposition polymerization initiator, or a combination thereof, or a polymerization start is used.
- a redox polymerization initiator combined with a reducing agent that accelerates the decomposition of the agent is used.
- one or more of the polymerization initiators disclosed in US Pat. No. 7,265,190 are used.
- a peroxide or an azo compound is preferably used, more preferably a peroxide, and still more preferably a persulfate.
- the amount of the polymerization initiator used is preferably 0.001 mol% to 1 mol%, more preferably 0.001 mol% to 0.5 mol%, based on the monomer.
- the amount of the reducing agent used in combination with the oxidizing agent is preferably 0.0001 mol% to 0.02 mol% with respect to the monomer.
- the dissolved oxygen is preferably reduced to 5 ppm or less, more preferably 3 ppm or less, and particularly preferably 1 ppm or less.
- bubbles can be dispersed in the monomer aqueous solution.
- foam polymerization is performed in the polymerization reaction.
- This step is a step of polymerizing the aqueous monomer solution to obtain a hydrated gel-like crosslinked polymer (sometimes referred to as “hydrated gel” in the present specification).
- the polymerization form is not particularly limited. From the viewpoint of water absorption performance, ease of polymerization control, etc., preferably droplet polymerization in the gas phase, aqueous solution polymerization, reverse phase suspension polymerization (here, droplet polymerization in a hydrophobic organic solvent is also an example of reverse phase suspension) More preferably aqueous solution polymerization, reverse phase suspension polymerization, and still more preferably aqueous solution polymerization.
- continuous aqueous solution polymerization is particularly preferable, and examples thereof include continuous belt polymerization and continuous kneader polymerization.
- “high temperature initiation polymerization” and “high concentration polymerization” can be mentioned.
- “High temperature initiation polymerization” means that the temperature of the monomer aqueous solution is preferably 30 ° C. or higher, more preferably 35 ° C. or higher, further preferably 40 ° C. or higher, particularly preferably 50 ° C. or higher (the upper limit is the boiling point).
- the “high concentration polymerization” means that the monomer concentration is preferably 30% by mass or more, more preferably 35% by mass or more, still more preferably 40% by mass or more, and particularly preferably 45% by mass or more.
- the upper limit is a saturation concentration.
- the polymerization in the droplet polymerization in the gas phase, can be performed in an air atmosphere, but from the viewpoint of the color tone of the obtained water-absorbing resin, the polymerization is performed in an inert gas atmosphere such as nitrogen or argon. Is preferred. In this case, for example, it is preferable to control the oxygen concentration in the gas phase to 1% by volume or less.
- the polymerization rate of the water-containing gel-like crosslinked polymer obtained in the polymerization step is the suppression of aggregation during drying of the particulate water-containing gel-like crosslinked polymer obtained in the next gel grinding step, and the residual monomer reduction in the resulting water-absorbent resin. From this viewpoint, it is preferably 90% by mass or more, more preferably 95% by mass or more, still more preferably 98% by mass or more, and particularly preferably 99% by mass or more.
- the polymerization reaction proceeds during the drying, and the gel particle having a small particle size is changed to a large particle. Since gel particles having a diameter are regenerated, problems such as a decrease in the water absorption rate of the resulting water-absorbent resin and an increase in the particle size of the dried product occur.
- the CRC (centrifuge retention capacity) of the hydrogel crosslinked polymer obtained in the polymerization step is preferably 5 g / g to 80 g / g, more preferably 10 g / g to 50 g / g, more preferably in terms of solid content. Is 15 g / g to 45 g / g, particularly preferably 20 g / g to 40 g / g. Further, the water-soluble content of the hydrogel crosslinked polymer obtained in the polymerization step is preferably 1% by mass to 20% by mass, more preferably 2% by mass to 15% by mass, and further preferably 3% by mass to 10% by mass. %. If the CRC and / or water-soluble content exceeds the above range, the crushed water-containing gel particles exhibit adhesiveness, and the fluidity of the particulate water-containing gel decreases.
- Gel pulverization step This step is a step of pulverizing and pulverizing the hydrogel crosslinked polymer obtained in the polymerization step simultaneously with and / or after polymerization.
- a kneader This is a step of obtaining a particulate hydrogel crosslinked polymer (hereinafter referred to as “particulate hydrogel”) by pulverizing with a screw extruder such as a meat chopper, a cutter mill or the like.
- the particle diameter of the particulate water-containing gel is adjusted to a preferable range described later so that the water-absorbent resin particles having the target shape and performance can be obtained in high yield.
- this process may be performed twice or more. Further, when a particulate hydrogel having a target particle size is obtained in the polymerization step, such as reverse phase suspension polymerization or gas phase polymerization, this step may not be performed.
- a chopping step of cutting or coarsely crushing the hydrogel crosslinked polymer into a size that can be charged into a gel pulverization apparatus may be performed before the gel pulverization step after the polymerization step.
- the shredding step is preferably performed when the polymerization step is belt polymerization and a sheet-like or block-like hydrous gel is obtained.
- the means for cutting or crushing the hydrogel in the shredding step is not particularly limited, and a roller cutter, a guillotine cutter, a shredder cutter, or the like is used.
- the size to be shredded is not particularly limited as long as it can be put into a gel crusher described later, but the maximum diameter of the hydrous gel after shredding is preferably 1 mm to 3 m, more preferably 5 mm to 2.5 m. It is particularly preferably 1 cm to 2 m. In addition, when the objective of this invention is achieved, it is not necessary to implement a shredding process.
- the type of the gel crusher is not particularly limited as long as a particulate hydrogel having a predetermined particle size can be obtained without impairing the water absorption performance.
- examples thereof include a gel crusher equipped with a plurality of rotary stirring blades, such as a batch type or continuous double arm type kneader, a single screw extruder, a twin screw extruder, and a meat chopper.
- Solid content of hydrous gel As for the solid content rate (henceforth, gel solid content rate) of the water-containing gel provided to a gel grinding
- a gel fluidizing agent may be added before and / or during the gel crushing step. Thereby, the particulate water-containing gel containing a gel fluidizing agent is obtained.
- the gel fluidizing agent By adding the gel fluidizing agent, adhesion or adhesion between the water-containing gel particles is suppressed in the drying step described later, and the effect of improving the water absorption rate of the resulting water-absorbent resin is obtained.
- pulverization process after drying mentioned later is reduced, and the effect that the generation amount of fine powder reduces is also acquired.
- the particle diameter of the obtained particulate dry polymer approaches the product particle diameter, and thus the above-described effect becomes remarkable.
- each particle of the obtained particulate hydrous gel contains the gel fluidizing agent uniformly, addition during the gel pulverization step is preferable.
- the gel pulverization step is not required, such as when reverse phase suspension polymerization is performed in the polymerization step, it is preferable to add a gel fluidizing agent to the particulate hydrous gel at least before the drying step.
- the addition amount of the gel fluidizing agent is appropriately set according to the moisture content of the hydrous gel or particulate hydrous gel and the type of the gel fluidizing agent.
- the addition amount is preferably 0.001% to 0.5% by mass, more preferably 0.01% to 0.3% by mass, and still more preferably 0.02% by mass, based on the solid content of the hydrogel. % To 0.2% by mass.
- gel fluidizing agent examples include anionic, cationic, nonionic and amphoteric surfactants, low molecular or high molecular surfactants, and polymeric lubricants.
- sucrose fatty acid ester Specifically, (1) sucrose fatty acid ester, polyglycerin fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene glycerin fatty acid ester, sorbitol fatty acid Esters, polyoxyethylene sorbitol fatty acid esters, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene castor oil, polyoxyethylene hydrogenated castor oil, alkylallyl formaldehyde condensed polyoxyethylene ether, polyoxyethylene polyoxypropylene Block copolymer, polyoxyethylene polyoxypropyl alkyl ether, polyethylene glycol fatty acid ester, alkyl gluco Nonionic surfactants such as N, alkyl gluconamides, polyoxyethylene fatty acid amides, polyoxyethylene alkyl amines, polyoxyethylene alkyl ether phosphates, and polyoxyethylene alkyl
- anionic surfactants such as mono-alkali metal alkylacetates, and (4) cationic surfactants such as long-chain alkyldimethylaminoethyl quaternary salts. Of these, two or more may be used in combination.
- Polymer lubricant In the production method according to the present invention, a polymer lubricant exemplified below can be added to the monomer aqueous solution and the water-containing gel as long as the object of the present invention is achieved.
- polymer lubricant examples include maleic anhydride modified polyethylene, maleic anhydride modified polypropylene, maleic anhydride modified ethylene / propylene copolymer, maleic anhydride modified ethylene / propylene / diene terpolymer (EPDM).
- Maleic anhydride modified polybutadiene maleic anhydride / ethylene copolymer, maleic anhydride / propylene copolymer, maleic anhydride / ethylene / propylene copolymer, maleic anhydride / butadiene copolymer, polyethylene, polypropylene, Polyalkylene such as ethylene / propylene copolymer, oxidized polyethylene, oxidized polypropylene, oxidized ethylene / propylene copolymer, ethylene / acrylic acid copolymer, ethyl cellulose, ethyl hydroxyethyl cellulose, polyethylene glycol Alkylene oxide, and the like.
- These molecular weights are preferably selected in the range of preferably 2 to 2 million, more preferably 4 to 1 million. Of these, two or more may be used in combination.
- these polymer lubricants and the above surfactants may be used in combination as a gel fluidizing agent.
- the surfactant and the polymeric lubricant are used in combination, the total addition amount is appropriately set according to the polymerization form, the composition of the monomer aqueous solution, and the moisture content of the hydrogel.
- the concentration relative to the monomer component is set, and when added to the hydrogel, the solid content is set, and when added to both, the total is set.
- the total addition amount of the surfactant and the polymeric lubricant is preferably 1.0% by mass or less, more preferably 0.5% by mass or less, preferably 0.05% by mass or more, and particularly preferably 0.1% by mass. It is at least mass%.
- the kind and addition amount of the gel fluidizing agent are appropriately adjusted in consideration of the fluidity of the particulate hydrous gel in the gel grinding step and the drying step.
- a gel fluidizing agent of a kind and amount that does not excessively reduce the surface tension of the water absorbent resin of the final product is preferable in view of the amount of return of the water absorbent resin obtained in an absorbent article (diaper) in actual use.
- the surface tension of the water absorbent resin (the surface tension of the dispersion of the water absorbent resin in physiological saline) is preferably 55 mN / m or more, more preferably 60 mN / m or more, and even more preferably 65 mN / m or more.
- the type and amount of gel fluidizing agent are selected. This surface tension is measured by the method described in WO2015 / 129917.
- the water-containing gel can be pulverized in the gel pulverization step, and the polymerization rate can be advanced to adjust the polymerization rate.
- the degree of progress of the polymerization reaction is appropriately adjusted by the heating and residence time in the gel pulverizer, the residual amount of the polymerization initiator in the hydrous gel after polymerization, the post-addition amount of any polymerization initiator, and the like.
- the polymerization rate of the particulate hydrogel obtained after gel pulverization is preferably 90% by mass or more, more preferably 95% by mass or more, and still more preferably 98 to 99.99% by mass in terms of solid content. Ideally, it is 100%.
- the particulate hydrogel having a polymerization rate in the above range In the particulate hydrogel having a polymerization rate in the above range, aggregation and adhesion during drying are avoided. Adjustment of the polymerization rate of the particulate hydrogel is particularly effective in the case of stirring and drying.
- the polymerization rate of particulate water-containing gel is prescribed
- the water content of the particulate water-containing gel (hereinafter, gel water content) is determined by the measurement method described in the following examples. From the viewpoint of fluidity of the particulate hydrogel in the drying step described later, the gel moisture content is preferably 25% by mass or more, more preferably 30% by mass or more, further preferably 35% by mass or more, and particularly preferably 40% by mass or more. 43% by mass or more is extremely preferable. Excessive high-concentration polymerization may decrease the properties of the water-absorbent resin, and from the viewpoint of drying efficiency and absorption performance, the gel moisture content is preferably 75% by mass or less, more preferably 60% by mass or less, and 55% by mass. The following are particularly preferred:
- the mass average particle diameter d1 of the particulate hydrogel crosslinked polymer before drying is preferably 3000 ⁇ m or less in terms of solid content. More preferably, it is 2000 ⁇ m or less, more preferably 50 ⁇ m to 1000 ⁇ m, and still more preferably 100 ⁇ m to 800 ⁇ m.
- the average particle diameter d1 of the particulate hydrogel in terms of solid content is calculated from the mass average particle diameter (D50) of the particulate hydrogel by the method described in the following examples.
- the CRC (centrifuge retention capacity) of the particulate hydrogel before drying is preferably 5 g / g to 80 g / g, more preferably 10 g / g to 50 g / g in terms of solid content (specified by the measurement method described later). g, more preferably 15 g / g to 45 g / g, particularly preferably 20 g / g to 40 g / g.
- the water-soluble content (Ext) of the particulate hydrogel before drying is preferably 1% by mass to 15% by mass, more preferably 2% by mass to 10% in terms of solid content (specified by the measurement method described later). % By mass, more preferably 3% by mass to 5% by mass.
- Drying step This step is a step of drying a particulate hydrous gel (preferably containing a gel fluidizing agent) to a desired moisture content to obtain a dry polymer, preferably a particulate dry polymer. is there.
- the particulate hydrous gel used for this process is not limited to what is obtained through a gel grinding
- the dry polymer obtained at this process may also contain the granulated material (henceforth granular dry granulated material) formed when several particle
- the temperature T2 of the particulate hydrogel subjected to the drying step is preferably 50 ° C or higher, more preferably 60 ° C or higher, further preferably 70 ° C or higher, particularly preferably 80 ° C. As mentioned above, it is most preferably controlled to 90 ° C. or higher. Further, from the viewpoint of coloring of the material to be dried and suppression of performance degradation, the temperature T2 is preferably 130 ° C. or lower, more preferably 110 ° C. or lower, and further preferably 105 ° C. or lower.
- the drying method in the drying step of the present invention is not particularly limited, and stationary drying, stirring drying, fluidized bed drying and the like are appropriately used. Also, various drying methods such as heat drying, hot air drying, vacuum drying, infrared drying, microwave drying, drum dryer drying, azeotropic dehydration drying with hydrophobic organic solvents, and high humidity drying using high temperature steam are adopted. Can be done. From the viewpoint of drying efficiency, heat drying or hot air drying is preferable, and stirring-type heat drying in which an object to be dried is dried while moving is more preferable.
- Drying device It does not specifically limit as a drying apparatus used at a drying process, 1 type, or 2 or more types, such as a heat-transfer conduction type dryer, a radiant heat transfer type dryer, a hot-air heat transfer type dryer, and a dielectric heating type dryer Is appropriately selected. It may be a batch type or a continuous type. Further, a direct heating method or an indirect heating method may be used. Examples thereof include heat transfer type dryers such as a ventilation band type, a ventilation circuit type, a ventilation vertical type, a parallel flow band type, a ventilation tunnel type, a ventilation stirring type, a ventilation rotation type, a fluidized bed type, and an air flow type.
- a heat transfer type dryer such as a ventilation band type, a ventilation circuit type, a ventilation vertical type, a parallel flow band type, a ventilation tunnel type, a ventilation stirring type, a ventilation rotation type, a fluidized bed type, and an air flow type.
- the water-soluble content (Ext) of the dried polymer obtained in the drying step is preferably larger than the water-soluble content of the particulate hydrous gel before drying.
- the water-soluble content of the dried polymer obtained after drying is preferably + 0.5% by mass or more, more preferably +1 to 20% by mass, and more preferably +2 to 10% by mass in terms of solid content.
- the crosslink density of the hydrogel (particularly the type and amount of the internal crosslinker) and the heat drying conditions are adjusted so as to increase within the range.
- the water-soluble content of the obtained dry polymer is preferably 50% by mass or less, more preferably 25% by mass or less, still more preferably 20% by mass or less, and particularly preferably 15% by mass or less.
- Pulverization step, classification step In this step, the dry polymer obtained in the drying step is pulverized (pulverization step), adjusted to a predetermined particle size (classification step), and water-absorbing resin powder It is the process of obtaining.
- the powdery water absorbent resin before surface cross-linking is referred to as “water absorbent resin powder” for convenience.
- Examples of the equipment used in the pulverization process of the present invention include a high-speed rotary pulverizer such as a roll mill, a hammer mill, a screw mill, and a pin mill, a vibration mill, a knuckle type pulverizer, and a cylindrical mixer. These devices may be used in combination as necessary.
- a high-speed rotary pulverizer such as a roll mill, a hammer mill, a screw mill, and a pin mill, a vibration mill, a knuckle type pulverizer, and a cylindrical mixer. These devices may be used in combination as necessary.
- the particle size adjustment method in the classification step of the present invention is not particularly limited, and examples thereof include sieve classification using JIS standard sieve (JIS Z8801-1 (2002)), airflow classification, and the like.
- the particle size adjustment of the water-absorbing resin is not limited to the pulverization step and the classification step, but a polymerization step (particularly, reverse phase suspension polymerization or spray droplet polymerization), other steps (for example, granulation step, fine powder recovery) Step).
- the weight average particle diameter (D50) of the water absorbent resin powder obtained in this step is preferably 200 to 600 ⁇ m, more preferably 200 to 500 ⁇ m, still more preferably 250 to 500 ⁇ m, and particularly preferably 350 to 450 ⁇ m.
- the proportion of particles having a particle diameter of less than 150 ⁇ m is preferably 10% by mass or less, more preferably 5% by mass or less, and still more preferably 1% by mass or less.
- the ratio of particles having a particle diameter of 850 ⁇ m or more is preferably 5% by mass or less, more preferably 3% by mass or less, and still more preferably 1% by mass or less.
- the logarithmic standard deviation ( ⁇ ) of the particle size distribution is preferably 0.20 to 0.50, more preferably 0.25 to 0.40, and still more preferably 0.27 to 0.35. These particle sizes are measured using a standard sieve according to the methods described in US Pat. No. 7,638,570 and EDANA ERT420.2-02.
- the preferred particle size described above applies not only to the water-absorbing resin after surface crosslinking (hereinafter, sometimes referred to as “water-absorbing resin particles” for convenience) but also to the water-absorbing resin as the final product. Therefore, in the water-absorbent resin particles, the surface cross-linking step is preferably performed so as to maintain the particle size in the above range, and it is more preferable that the particle size is adjusted by providing a particle size adjusting step after the surface cross-linking step.
- the surface cross-linking step is a step performed separately from the drying step described above, and the functional group (particularly carboxyl group) of the water-absorbent resin is added to the dry polymer. It includes a surface cross-linking agent addition step for adding a surface cross-linking agent that reacts, and a heat treatment step for subjecting the dry polymer containing the surface cross-linking agent to a cross-linking reaction by heating.
- This step is a step of providing a portion having a higher cross-linking density on the surface layer of the water-absorbent resin powder obtained through the steps described above (portion of several tens of ⁇ m from the surface of the water-absorbent resin powder).
- surface-crosslinked water-absorbing resin (water-absorbing resin particles) is obtained by radical cross-linking reaction, surface polymerization reaction, cross-linking reaction with a surface cross-linking agent, etc. on the surface of the water-absorbing resin powder.
- This step is a step of adding a surface cross-linking agent to the particulate dry polymer.
- the surface cross-linking agent is added to the particulate dry polymer after drying or the particulate dry polymer whose particle size has been adjusted after drying.
- the moisture content of the particulate dry polymer subjected to the surface crosslinking agent addition step is 15% by mass or less.
- the moisture content of the particulate dry polymer is preferably 10% by mass or less, more preferably 7% by mass or less, and particularly preferably 5% by mass or less.
- the water content is preferably more than 1% by mass.
- the moisture content of a particulate dry polymer is calculated
- the particulate dry polymer subjected to the surface cross-linking agent addition step is preferably warmed or kept warm.
- the temperature T3 of the particulate dry polymer is preferably 30 to 120 ° C, more preferably 35 to 80 ° C, and further preferably 40 to 70 ° C.
- the temperature T3 of the particulate dry polymer subjected to this step is less than 30 ° C.
- the surface crosslinking treatment is insufficient or non-uniform due to precipitation of the added surface crosslinking agent or moisture absorption of the particulate dry polymer. There is a case.
- this temperature T3 exceeds 100 degreeC, there exists a possibility that a surface crosslinking agent may precipitate because the water or solvent in a surface crosslinking agent solution volatilizes.
- the temperature T4 of the mixture of the particulate dry polymer obtained through this step and the surface cross-linking agent is preferably 30 to 100 ° C., more preferably 30 to 90 ° C., and further preferably 30 to 80 ° C.
- the added surface cross-linking agent reacts effectively in the heat treatment step described later, and appropriate fluidity is maintained inside the heating apparatus.
- the temperatures T3 and T4 are measured with a contact thermometer in the same manner as the temperature T2 of the particulate hydrogel described above.
- a surface cross-linking agent capable of reacting with a plurality of functional groups (preferably a plurality of carboxyl groups) of the water-absorbent resin, preferably a covalent bond or an ionic bond, and further a surface cross-linker capable of covalent bonding is used.
- Alkylene carbonate compounds such as epichlorohydrin, epibromohydrin, ⁇ -methylepichlorohydrin and their polyvalent amine adducts; oxetane compounds; ⁇ -glycidoxypropyltrimethoxysilane, ⁇ -amino Silane coupling agents such as propyltriethoxysilane; hydroxides such as zinc, calcium, magnesium, aluminum, iron and zirconium; polyvalent metal compounds such as chloride, sulfate, nitrate or carbonate; . Of these, two or more may be used in combination.
- the surface cross-linking agents one or more selected from polyvalent metal ions, epoxy compounds, oxazoline compounds, and alkylene carbonate compounds are preferable.
- the amount of the surface cross-linking agent added is preferably 15% by mass or less, more preferably 10% by mass or less, and still more preferably 2% by mass or less with respect to the solid content of the particulate dry polymer.
- the lower limit is preferably 0.001% by mass.
- the form of addition of the surface cross-linking agent may be as it is, but from the viewpoint of ease of addition, it is preferable to add it as a solution dissolved in water or an organic solvent.
- concentration of the surface crosslinking agent solution is preferably 1 to 80% by mass, more preferably 5 to 60% by mass, still more preferably 10 to 40% by mass, and particularly preferably 15 to 30% by mass.
- the surface crosslinking agent solution contains water.
- the amount of water is preferably 0.5 to 20% by mass, more preferably 0.5 to 10% by mass, based on the solid content of the particulate dry polymer.
- concentration of the aqueous solution can be adjusted according to the water content of the particulate dry polymer at the time of contact with the surface crosslinking agent, which is preferable.
- the surface crosslinking agent does not become a solution due to its low solubility in water, it is preferable to add a hydrophilic solvent such as alcohol as appropriate to obtain a uniform solution.
- a hydrophilic solvent such as alcohol
- the amount of the hydrophilic organic solvent is preferably 0 to 10% by mass, more preferably 0 to 5% by mass, based on the solid content of the particulate dry polymer. It is.
- hydrophilic organic solvent examples include primary alcohols having preferably 1 to 4 carbon atoms, more preferably 2 to 3 carbon atoms, and lower ketones having 4 or less carbon atoms.
- lower alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol and t-butyl alcohol; ketones such as acetone; dioxane, tetrahydrofuran, methoxy (poly ) Ethers such as ethylene glycol; sulfoxides such as dimethyl sulfoxide; and polyhydric alcohols such as polyoxypropylene and oxyethylene-oxypropylene block copolymers.
- the surface crosslinking agent solution may further contain water-insoluble fine particles, a surfactant, an organic acid or a salt thereof, an inorganic acid or a salt thereof, and an inorganic base.
- the temperature of the surface crosslinking agent solution added to the particulate dry polymer is appropriately determined depending on the solubility of the surface crosslinking agent used or its viscosity.
- the temperature of the surface crosslinking agent solution is preferably ⁇ 10 to 100 ° C., more preferably 5 to 70 ° C., still more preferably 10 to 65 ° C., and particularly preferably 25 to 50 ° C.
- the temperature of the surface cross-linking agent solution exceeds 100 ° C., the surface cross-linking agent is hydrolyzed before mixing with the particulate dry polymer, or the miscibility with the particulate dry polymer decreases due to volatilization of water or an organic solvent. There is a case.
- precipitation of the surface crosslinking agent or solidification of the surface crosslinking agent solution may occur.
- the method for adding the surface crosslinking agent to the particulate dry polymer is not particularly limited.
- (1) the particulate dry polymer is immersed in a hydrophilic organic solvent, and the surface crosslinking agent is adsorbed to the particulate dry polymer.
- a mixing device used in the surface cross-linking agent addition step
- a cylindrical mixer for example, a cylindrical mixer, a double wall conical mixer, a V-shaped mixer, a ribbon mixer, a screw mixer , Fluid type furnace, rotary disk mixer, airflow type mixer, double arm type kneader, internal mixer, pulverizing type kneader, rotary mixer, screw type extruder, turbulizer, pro shear mixer, and the like.
- a cylindrical mixer for example, a cylindrical mixer, a double wall conical mixer, a V-shaped mixer, a ribbon mixer, a screw mixer , Fluid type furnace, rotary disk mixer, airflow type mixer, double arm type kneader, internal mixer, pulverizing type kneader, rotary mixer, screw type extruder, turbulizer, pro shear mixer, and the like.
- an apparatus capable of continuous mixing is preferable.
- a surface crosslinking agent addition process you may add a surface crosslinking agent
- the surface cross-linking agent may be added once or multiple times. In the case of adding two or more times, it is preferred that the particulate dry polymer in contact with at least the first one-time surface cross-linking agent has the above-mentioned moisture content and temperature. More preferably.
- the same addition apparatus may be used for each addition process, and a different apparatus may be used.
- Heat treatment step This step is a step of obtaining a surface-crosslinked particulate dry polymer by heat-treating the mixture of the particulate dry polymer and the surface cross-linking agent.
- the surface-crosslinked particulate dry polymer is obtained by heating the mixture of the particulate dry polymer and the surface crosslinking agent to 100 ° C. or higher.
- the heating temperature is appropriately selected depending on the type of surface crosslinking agent to be added, but from the viewpoint of heat treatment efficiency, it is preferably 100 ° C. to 250 ° C., more preferably 120 ° C. to 230 ° C., and even more preferably 150 ° C. ° C to 210 ° C.
- the time for heat-treating the particulate dry polymer containing the surface cross-linking agent at the surface cross-linking temperature is appropriately determined according to the moisture content of the particulate dry polymer, the type of the surface cross-linking agent, the operating conditions of the heating apparatus described later, and the like. Is set.
- the water-absorbing resin particles obtained may be heated until the water content becomes 10% by mass or less, and the time is in the range of 10 minutes to 120 minutes, preferably 30 minutes to 90 minutes. .
- Heating device In the production method according to the present invention, in the surface cross-linking step performed separately from the drying step, the mixture of the particulate dry polymer and the surface cross-linking agent is heat-treated using a heating device having a specific structure.
- the heating device includes a rotating container that contains therein a mixture of the particulate dry polymer and the surface cross-linking agent and rotates, and is positioned inside the rotating container and extends in the axial direction thereof. And a plurality of heating tubes that rotate together with the rotating container.
- the heating device having this configuration may be referred to as a “rotary heating device” or a “rotating heating device with a heating tube”.
- this rotary heating apparatus the contents flow in the container mainly due to the rotation of the rotating container and the action of a plurality of heating tubes rotating together with the rotating container, so that mechanical and thermal damage to the particulate dry polymer is caused. Less is. Thereby, generation
- the heat transfer area inside the heating device can be increased by increasing the number of heating tubes as compared with a conventionally used paddle dryer.
- the large heat transfer area enables heat treatment in a short time and also reduces the residence time inside the apparatus, further reducing thermal damage.
- the rotary heating device may further include other heating means or heat retaining means.
- other heating means or heat retaining means from the viewpoint of heat treatment efficiency and thermal damage reduction, direct heat transfer by convective heat transfer and / or a heating surface of a heating device heated by a heating medium (particles containing a surface cross-linking agent) Indirect heat transfer by heat conduction from the contact surface with the dried polymer and the heat source portion) is preferred.
- More preferable heating means or heat retaining means is a ventilation heating type for direct heat transfer and an outer wall heating type for indirect heat transfer.
- this heating device is provided with heating means or heat retaining means on the outer peripheral surface of the rotating container.
- the particulate dry polymer and the surface cross-linking agent accommodated therein are stirred and uniformly mixed by the rotation of the rotating container, and the mixture is contacted with a plurality of heating tubes or heated tubes. It is heated by heat conduction from.
- the inner surface of the rotating container is also heated by radiant heat of a plurality of heating tubes, etc., but if necessary, the particulate dry polymer mixed with the surface crosslinking agent is heated by a heating means or a heat retaining means located on the outer peripheral surface of the rotating container. Further heating.
- this heating device may be provided with other flow means for flowing the contents.
- other flow means include a scraping plate and a stirring blade installed on the inner surface of the rotating container.
- this heating device has a function of introducing gas into the device (preferably means for introducing and discharging gas).
- means for introducing and discharging gas include a gas inlet and outlet.
- the number and location of the gas inlets and outlets are not limited, but are preferably installed on the inlet side and outlet side of the particulate dry polymer to the heating device, and if necessary, equipped with a gas introduction mechanism and a gas discharge mechanism. May be. Although it does not specifically limit as this gas, For example, air, nitrogen, water vapor
- the gas acts as a carrier gas and promotes the crosslinking reaction by discharging water vapor generated during the heat treatment to the outside of the apparatus.
- the gas when a heated gas is used, the gas also acts as a heat medium, and quickly raises the particulate dry polymer containing the surface cross-linking agent to the surface cross-linking temperature described above.
- nitrogen, water vapor, a mixed gas of these and air, or the like is used.
- a mixed gas containing water vapor hereinafter also referred to as a high-humidity mixed gas
- the inside of the apparatus is in a low oxygen state, and oxidation and deterioration during heat treatment are suppressed. As a result, the performance improvement and low coloring of the water absorbent resin can be achieved.
- the amount of the gas introduced is usually 0.01 to 3 Nm 3 / kg in terms of solid content with respect to the processing amount (kg / hr) per unit time of the dry polymer, but is preferably 0 0.1 to 2 Nm 3 / kg, more preferably 0.1 to 1 Nm 3 / kg, still more preferably 0.3 to 0.5 Nm 3 / kg.
- the atmospheric dew point inside the heating device may be adjusted by introducing the gas into the heating device from one or more locations. It is preferable to appropriately adjust the atmospheric dew point in accordance with the moisture content of the particulate dry polymer containing the surface cross-linking agent charged into the heating apparatus.
- the atmospheric dew point is measured at the time of exhaust from the heating device, and is preferably 60 ° C. or higher, more preferably 65 ° C. or higher, and further preferably 70 ° C. or higher. Although an upper limit is not specifically limited, Preferably it is 100 degrees C or less.
- the moving direction of the gas in this heating device may be a cocurrent flow or a countercurrent flow with respect to the moving direction of the particulate dry polymer containing the surface cross-linking agent accommodated in the rotating container. You may have done.
- the rotary heating device can also have a function of making the inside of the device pressurized, normal pressure, or reduced pressure.
- a pressurized state for example, it is adjusted by increasing the amount of carrier gas introduced into the heating device.
- the degree of pressurization with respect to atmospheric pressure is a slight pressurization of more than 0 to 0.01 kPa.
- it adjusts by changing the suction
- the degree of decompression with respect to atmospheric pressure is preferably slightly above 0 to 5 kPa, more preferably above 0 to 2 kPa, and even more preferably from 0.01 to 0.5 kPa.
- the degree of reduced pressure within the above range, water vapor generated during the heat treatment can be efficiently removed without excessively depriving the amount of heat inside the heating apparatus, so that the processing time is shortened. Moreover, aggregation and agglomeration of the water absorbent resin particles in the heat treatment step are reduced.
- “the degree of pressurization with respect to atmospheric pressure” and “the degree of depressurization with respect to atmospheric pressure” mean a differential pressure from the atmospheric pressure, and are expressed as an absolute value of the difference from the atmospheric pressure. For example, when the atmospheric pressure is the standard atmospheric pressure (101.3 kPa) and the degree of pressure reduction with respect to the atmospheric pressure is 10 kPa, the actual atmospheric pressure is 91.3 kPa.
- the surface crosslinking temperature described above is also adjusted by the temperature of the heat medium used in the heating device.
- the above-mentioned gas hot air
- this gas directly acts as a heat transfer heat medium.
- the temperature of the heating medium gas is preferably 100 ° C. or higher, more preferably 120 ° C. or higher, still more preferably 150 ° C. or higher.
- the aforementioned heated gas hot air
- this gas is indirectly transferred to heat. It acts as a heating medium.
- the temperature of the heating medium (gas) is preferably 100 ° C. or higher, more preferably 120 ° C. or higher, still more preferably 150 ° C. or higher, and particularly preferably 180 ° C. or higher.
- the heating medium temperature is less than 100 ° C., the progress of the cross-linking reaction of the surface treatment becomes slow.
- a liquid heat medium such as oil may be used as a heat medium other than gas, but water vapor is preferable.
- the temperature of the heated gas (hot air) introduced into the plurality of heating pipes may be the same or different from the viewpoint of heating efficiency. Usually, it is the same. If they are different, they are defined by their average temperature.
- the range is 0.001 to 1, more preferably 0.005 to 0.5, still more preferably 0.01 to 0.3, and particularly preferably 0.02 to 0.2.
- the Froude number Fr is the ratio of the centrifugal acceleration ⁇ 2 * r acting on the contents stirred in the rotating container to the gravitational acceleration g.
- ⁇ is the angular velocity [rad / sec] of the rotating body
- r is the representative radius [m] of the rotating body.
- the rotation speed of the rotating container is appropriately set depending on the apparatus size and the processing amount per unit time, but is preferably 1 rpm to 250 rpm, more preferably 1 rpm to 100 rpm, and further preferably 2 rpm to 50 rpm.
- the maximum peripheral speed is not particularly limited, but is preferably 0.05 m / s to 10 m / s, more preferably 0.1 m / s to 8 m / s, and still more preferably 0.15 m / s to 5 m / s. is there.
- filling rate of the rotary-type heating apparatus (the ratio of the fill volume of contained object to the effective volume of the rotating vessel (m 3) (m 3) ) is appropriately selected from the viewpoint of heat treatment efficiency, preferably 5%
- the range is from -95%, more preferably from 6% to 50%, and still more preferably from 10% to 40%.
- a heating device having a large heat transfer area with respect to the internal volume is preferable.
- the heat transfer area with respect to the internal volume is defined as the ratio of the heat transfer area (m 2 ) to the effective volume (m 3 ) of the rotating container (heat transfer area / effective volume). The larger this ratio, the higher the heat transfer efficiency and the faster the rate of temperature rise of the contents. As a result, the heat treatment time is shortened, so that thermal and mechanical damage is reduced and productivity is improved.
- This ratio is appropriately set depending on the specification, form, and shape of the contents of the heating device, but is preferably 10 m ⁇ 1 or more, more preferably 12 m ⁇ 1 , and even more preferably 15 m ⁇ 1 or more.
- the effective volume is the internal volume of the rotating container in which the contents are accommodated, and the heat transfer area means the area of the heating surface that can add heat to the contents accommodated in the rotating container. Specifically, the sum of the area of the outer peripheral surface of the plurality of heating tubes and the area of the inner peripheral surface of the rotating container when the outer surface of the rotating container is heated is the heat transfer area.
- FIGS. 1 and 2 show an example of a rotary heating device 100 with a heating tube.
- FIGS. 1 and 2 show an example of a rotary heating device 100 with a heating tube.
- the heating device 100 has a main part 4, a charging part 6, and a taking-out part 8.
- the main part 4 includes a rotating container 10, a plurality of heating pipes 12, a first gear 14, a second gear 16 and a packing 18.
- the rotating container 10 is generally cylindrical.
- the horizontal direction in FIG. 1 is the axial direction of the rotating container 10.
- a plurality of barriers 11 are provided on the inner wall of the rotating container 10 at intervals in the axial direction. Each barrier 11 extends along the inner peripheral surface of the rotating container 10.
- a plurality of heating tubes 12 are accommodated in the rotating container 10. Each heating tube 12 extends in the axial direction of the rotating container 10 and penetrates both ends of the rotating container 10. The plurality of heating tubes 12 are not in contact with the inner peripheral surface of the rotating container 10 in the axial direction.
- FIG. 2 shows only a part of the heating tubes 12 for convenience of explanation.
- the first gear 14 is fixed to the outer peripheral surface of the rotating container 10.
- the second gear 16 is in mesh with the first gear 14. In FIG. 2, the first gear 14 and the second gear 16 are not shown for convenience of explanation.
- the packing 18 is located between the rotary container 10 and the charging unit 6.
- the charging unit 6 has a main cylinder 20 and a hopper 22. As shown in FIG. 2, the main cylinder 20 is open inside the rotating container 10. The inside of the main cylinder 20 is referred to as an inner space 28.
- the hopper 22 has a shape in which the inner dimension gradually decreases from top to bottom. The lower end of the hopper 22 is fixed to the main cylinder 20. Although not shown, the hopper 22 communicates with the inner space 28.
- the take-out unit 8 has a take-out port 40, a steam inlet 44, and a drain 46.
- the steam inlet 44 communicates with the plurality of heating pipes 12.
- the drain 46 is also in communication with the plurality of heating tubes 12.
- FIG. 3 is a cross-sectional view taken along line III-III of the heating apparatus 100 of FIG.
- the heating device 100 of this embodiment has 18 heating tubes 12. These heating tubes 12 are arranged on a concentric circle with the rotation axis of the rotating container 10 as a center at an interval.
- the inner diameter (radius) of the rotating container 10 is R and the axial length L is L
- the inner area of the rotating container 10 is 2 ⁇ rL.
- the outer diameter (radius) of the heating tube 12 is r and the axial length is 1, the total area of the outer peripheral surfaces of the 18 heating tubes 12 is 36 ⁇ rl.
- the outer diameter r of the heating tube 12 is sufficiently smaller than the inner diameter R of the rotating vessel 10, and the axial length l of the heating tube 12 and the axial length L of the rotating vessel 10 are usually approximate. Therefore, the heat transfer area of the 18 heating tubes 12 is larger than the inner area of the rotating container 10. In the heating apparatus 100, the 18 heating tubes 12 have a heat transfer surface wider than the inner area of the rotating container 10, thereby enabling efficient heat treatment.
- steam is introduced from the steam inlet 44 toward the heating pipe 12. This steam increases the temperature in the rotating container 10. A part of the steam is cooled by heat exchange. The cooled steam becomes water and is discharged from the drain 46. The temperature inside the rotary container 10 is controlled by continuously introducing steam from the steam inlet 44 so as to supplement the steam discharged as water.
- Gas is introduced into the rotating container 10.
- the gas fills the rotating container 10.
- Excess gas is discharged from the rotating container 10.
- the second gear 16 is rotated by driving means (not shown) (for example, a motor).
- the first gear 14 is rotated by the rotation of the second gear 16, and the rotating container 10 is further rotated.
- a plurality of heating tubes 12 also rotate together with the rotating container 10. Since the rotary container 10 is cut off by the packing 18, the charging unit 6 does not rotate even if the rotary container 10 rotates. Similarly, even if the rotating container 10 rotates, the take-out unit 8 does not rotate.
- a particulate dry polymer containing a surface cross-linking agent is charged into the hopper 22.
- the particulate dry polymer containing the surface cross-linking agent proceeds through the inner space 28 in the direction indicated by the arrow A in FIG.
- the particulate dry polymer containing the surface cross-linking agent is introduced into the rotating container 10.
- the particulate dry polymer containing the surface cross-linking agent is stirred and mixed by the rotation of the rotating container 10 and the action of the plurality of heating tubes 12 rotating together with the rotating container 10.
- the particulate dry polymer containing the surface cross-linking agent is heated by heat exchange with the steam passing through the heating tube 12 and the gas introduced into the rotary container 10, and the temperature is raised to the surface cross-linking temperature.
- the crosslinking reaction proceeds, and the particulate dry polymer containing the surface crosslinking agent is adjusted to a predetermined moisture content.
- the heating device 100 is inclined in the axial direction from one end to the other end.
- a downward inclination is provided from the input unit 6 toward the extraction unit 8. Due to this inclination and rotation of the rotating container 10, the particulate dry polymer containing the surface cross-linking agent is heated in the rotating container 10 in the right direction of FIG. 1, that is, from the charging unit 6 to the extracting unit 8. And gradually proceed with stirring.
- the barrier 11 exists in the traveling direction of the particulate dry polymer containing the surface cross-linking agent 48.
- This barrier 11 in the rotating container 10, mixing of particulate dry polymers having different surface cross-linked states and moisture contents is avoided, and the piston flow property is improved. Thereby, surface cross-linking is achieved substantially uniformly, and a high-quality particulate dry polymer adjusted to a predetermined moisture content is obtained.
- This surface-crosslinked particulate dry polymer is taken out from the take-out port 40.
- the plurality of heating tubes 12 are not in contact with the inner peripheral surface of the rotating container 10 in the axial direction. As shown in FIG. 3, the plurality of heating tubes 12 are viewed from the center (rotary axis) of the rotating container 10 and in the vicinity of the inner peripheral surface of the rotating container 10 (preferably 50 to 99% of the radius of the rotating container 10, preferably Is installed at a position 60 to 95% outside). The plurality of heating tubes 12 are in efficient contact with the particulate dry polymer containing the surface cross-linking agent.
- the particulate dry polymer containing the surface cross-linking agent is stirred by the rotation of the heating tube 12 synchronized with the rotation of the rotating vessel 10 in addition to the rotation of the rotating vessel 10, and at the same time is heated by indirect heat transfer from the heating tube 12. As a result, the crosslinking reaction proceeds.
- the rotating container 10 may have other heating mechanisms, but mainly the radiant heat from the heating tube 12, the heat transfer from the particulate dry polymer, or the gas when the heated gas is introduced.
- the inner surface of the container 10 is heated
- a heating medium (preferably 100 ° C. or higher) having the above-described temperature is preferably introduced into the plurality of heating tubes 12.
- the inner surface of 10 is also heated to a predetermined temperature by radiant heat from the heating tube 12 and optionally heated gas.
- the inner surface temperature of the rotating vessel 10 is preferably 100 ° C. or higher, more preferably 120 ° C. or higher, still more preferably 150 ° C. or higher, and particularly preferably 180 ° C. or higher.
- the upper limit of the temperature of the inner surface of the rotating container 10 is usually the temperature of the heating tube 12.
- the temperature of the inner surface of the rotating container 10 is measured by, for example, one or more thermometers installed in the heating device 100 for measuring the material temperature.
- the inner surface of the rotating container 10 is heated to the above-described temperature mainly by radiant heat from the heating tube 12.
- the temperature of this gas is preferably 100 ° C. or higher, more preferably 120 ° C. or higher.
- the temperature of the inner surface of the rotating container 10 is preferably higher than + 10 ° C., more preferably + 20 ° C. or higher, particularly preferably + 30 ° C. or higher.
- the temperature of the inner surface of the rotating container 10 is heated to the above temperature range (preferably 100 ° C. or more) before the particulate dry polymer containing the surface cross-linking agent is charged into the rotating container 10. Is preferred. Thereby, the adhesion of the particulate dry polymer containing the surface cross-linking agent to the inner surface of the rotating container 10 and the heating tube 12 is reduced, and the decrease in the processing efficiency accompanying the adhesion to the heating tube 12 is also avoided, which is preferable. That is, in the surface cross-linking method according to the present invention, it is preferable that the inner surface of the rotating container 10 is heated to the predetermined temperature or higher before the particulate dry polymer containing the surface cross-linking agent is charged.
- the number, arrangement and shape of the barriers 11 are not particularly limited, and include a surface cross-linking agent provided to the heating device 100.
- a surface cross-linking agent provided to the heating device 100.
- a donut-shaped barrier 11 can be used, but is not particularly limited.
- the number of the opening part of the barrier 11 should just be 1 or more, and when it has several opening part, the size may be the same and may differ. One or more openings may be provided for discharging to the outside. A preferable aperture ratio will be described later.
- the barrier 11 may be installed perpendicular to the cross section of the rotating container 10 or may be inclined.
- the barrier 11a in FIG. 5 and the barrier 11b in FIG. 6 are donut-shaped partition plates that are installed so as to be orthogonal to the axial direction of the cylindrical rotating container 10 and have an open substantially central portion.
- the opening ratio of the barrier 11 (the opening ratio of the barrier 11 with respect to the cross-sectional area perpendicular to the axial direction of the rotating container 10) is appropriately determined, but is usually 1 to 90%, preferably 2 to 50%, more preferably 5 to 45%, still more preferably 10 to 40%.
- the aperture ratio is larger than the above range, the effect of the barrier 11 is low, and when the aperture ratio is small, there is a possibility of causing a discharge failure.
- the aperture ratio of the barrier 11a in FIG. 5 is 20%
- the aperture ratio of the barrier 11b in FIG. 6 is 50%.
- the number (n) of the barriers 11 is at least 1, preferably 2 or more, particularly preferably 3 or more.
- the upper limit of the number of the barriers 11 depends on the size of the heating device 100, it is preferably 20 or less, more preferably 10 or less.
- the arrangement of the heating tube 12 provided in the heating device 100 is not particularly limited, and is appropriately set according to the manufacturing amount or the like.
- the plurality of heating tubes 12 may be arranged on the circumference centered on the rotation axis of the rotating container 10 at intervals, and as shown in FIG. 4, the rotating container 12 They may be arranged at intervals on two or more (multiple) concentric circles centered on 10 rotation axes. Further, the plurality of heating tubes 12 may be arranged radially spaced from the rotation axis of the rotating container 10 toward the radially outer side.
- the number is selected according to the purpose, but preferably double to 10 times, more preferably double to 8 times, more preferably double. Installed in five layers. By arranging in multiple, it has a wider heat transfer surface, and more efficient heat treatment becomes possible.
- the number of heating tubes 12 included in the heating device 100 and the radius (diameter) thereof are not particularly limited.
- the number of heating tubes 12 is appropriately determined depending on the size and processing amount of the heating device 100, but is preferably 5 or more, more preferably 10 or more, still more preferably 15 or more, and even more. Preferably it is 20 or more, particularly preferably 100 or more.
- the upper limit of the number of the heating tubes 12 is not particularly limited, for example, 2000 or less, and further 1000 or less are appropriately selected.
- a large number of heating tubes 12 are preferable because the area of the heating surface that comes into contact with the material by indirect heating increases.
- the heating apparatus 100 further includes a heating unit or a heat retaining unit, more preferably a heating unit, on the outer peripheral surface of the rotating container 10.
- a heating unit or a heat retaining unit for example, a part or the whole of the outer peripheral surface of the rotating container 10 (preferably 50% or more, more preferably 80% or more, particularly preferably the entire outer surface of the rotating container 10) is made of a heat insulating material. The method of coating is mentioned.
- examples of the heating means include an electric tres, a steam tres, a jacket heated with a heat medium, and the like.
- the heating means include an electric tres, a steam tres, a jacket heated with a heat medium, and the like.
- the heating means or the heat retaining means provided on the outer surface of the rotating container 10 is effective for controlling the temperature of the inner surface of the rotating container 10.
- additives may be added to the particulate dry polymer containing the surface crosslinking agent in the heating device 100.
- examples of other additives include the gel fluidizing agent and polymer lubricant described above.
- the amount of treatment per unit time in terms of solid content of the water-absorbent resin is obtained by using the heating device 100 having the basic configuration shown in FIG. (Kg / hr) is 7 kg / hr or more, preferably 50 Kg / hr or more, more preferably 100 Kg / hr or more, and particularly preferably 500 Kg / hr.
- the continuous treatment time is preferably 12 hours or longer, more preferably 24 hours or longer, particularly 240 hours or longer and 1200 hours or longer.
- a rotary dryer with a steam pipe there is a rotary dryer with a steam pipe.
- a steam tube dryer manufactured by Kurimoto Engineering Co., Ltd.
- a steam tube dryer manufactured by Ube Industries Co., Ltd.
- a steam tube dryer manufactured by Tsukishima Kikai Co., Ltd.
- a steam tube dryer manufactured by Mitsui Engineering & Shipbuilding Co., Ltd.
- a steam tube dryer manufactured by Mitsui Engineering & Shipbuilding Co., Ltd.
- the number of rotary heating devices that can be used in the heat treatment step may be only one or may be two or more.
- a plurality of rotary heating apparatuses having different specifications may be used in combination.
- an additional heat treatment is then performed using another heating device that is not classified as a rotary heating device. It is also possible to do this. In this case, the kind and number of heating devices used for the additional heat treatment are not limited.
- Examples include a dryer and a rotary kiln.
- solid air manufactured by Hosokawa Micron Corporation
- CD dryer manufactured by Kurimoto Steel Factory
- paddle dryer manufactured by Nara Machinery Co., Ltd.
- rotary kiln manufactured by Kurimoto Steel Factory
- rotary dryer Okawara Seisakusho Co., Ltd.
- Cooling step Preferably, after the drying step and / or the heat treatment step, and before the sizing step described later, the dried polymer or the surface-dried particulate dry polymer is forcibly cooled to obtain a desired It has a cooling process to adjust the temperature.
- the surface cross-linking step is performed separately from the drying step, the surface cross-linking treatment is appropriately performed in the rotating container 10 and adjusted to a desired moisture content or solid content.
- This cooling step is carried out before the dried particulate polymer is subjected to the sizing step.
- this cooling step is carried out before the dried polymer whose water content or solid content has been adjusted in the drying step is subjected to the granulation step prior to the surface crosslinking step.
- the temperature t ° C. of the dry polymer and / or surface-crosslinked particulate dry polymer is preferably (t ⁇ 20) ° C. or less, more preferably (t ⁇ 30) ° C. or less, further preferably (t ⁇ 40) Forced cooling to below °C.
- the temperature t of the dry polymer and / or the surface-crosslinked particulate dry polymer is 150 ° C. to 250 ° C.
- it is preferably 50 ° C. to 130 ° C., more preferably 60 ° C. before being subjected to the granulation step.
- the method for cooling the dry polymer or the surface-dried particulate dry polymer is not particularly limited.
- a continuous cooler having an aeration heat transfer type or conduction heat transfer type cooling means is used. It may be cooled in a stationary state or may be cooled in a stirring state.
- a material stirring type cooler is preferable, and a continuous material stirring type cooler is more preferable.
- a fluidized bed cooler that is direct heat transfer can be used. Cool air cooling in a continuous belt type cooler may be used.
- a stirring device having a rotating shaft can be used for stirring and cooling.
- a mixer having a function of allowing an air current to aerate and cool an object to be cooled is widely used as a cooler.
- the direction of the airflow is not particularly limited, and may be up and down or left and right.
- Specific examples of such a cooler include a mixer (horizontal cylindrical, inclined cylindrical, V-shaped, double-conical, regular cubic, S-shaped, continuous V, whose rotating shaft is horizontal and the container itself rotates.
- a mixer with a horizontal rotation axis and a fixed container may be used by ventilating an airflow.
- a container-fixed type cooler that includes a rotary stirring blade for stirring the water-absorbent resin powder that is an object to be cooled and is ventilated with an air flow is used.
- These coolers may be a continuous type or a batch type, but are preferably a continuous type.
- This step is a step of adjusting the particle size of the dried polymer and / or the surface-dried particulate dried polymer.
- the particulate dry polymer that has undergone the surface cross-linking step is subjected to this sizing step, whereby water-absorbing resin particles whose particle diameter or particle size distribution is more positively controlled are obtained.
- the surface-crosslinked particulate dry polymer obtained in the production method according to the present invention reduces the adhesion and aggregation between particles in the surface crosslinking step, and therefore, the load in this step is small, and excessive pulverization and disintegration are avoided. There is an advantage that the amount of fine powder generated by crushing is small. In addition, this process can also be implemented in multiple times.
- Fine powder recycling process means a process of supplying the fine powder removed in the classification process as it is or after granulating the fine powder to any process.
- the fine powder or the fine powder granulated product is a step of throwing it into a step before the drying step and reusing it.
- the step before the drying step include a monomer solution before polymerization adjusted in the polymerization step, a hydrogel during polymerization, a pulverization step of the hydrogel after polymerization, and a drying step of the granular hydrogel.
- the fine powder may be added as it is, or the fine powder may be swelled or granulated with water and then added.
- water In addition to fine powder, water, a crosslinking agent, a binder other than water (eg, water-soluble polymer, thermoplastic resin), a polymerization initiator, a reducing agent, a chelating agent, an anti-coloring agent, and the like may be added.
- a crosslinking agent eg, water-soluble polymer, thermoplastic resin
- a polymerization initiator e.g., water-soluble polymer, thermoplastic resin
- a reducing agent e.g., a reducing agent
- a chelating agent e.g., sodium metabisulfite, sodium metabisulfite, sodium metabisulfite, sodium metabisulfite, sodium metabisulfite, sodium metabisulfite, sodium metabisulfite, sodium metabisulfite, sodium metabisulfite, sodium metabisulfite, sodium metabisulfite, sodium metabisulfite, sodium metabisulfite, sodium metabisulfite, sodium metabisulfite
- the amount of coarse particles in the obtained surface-crosslinked particulate dry polymer is small, the mechanical load in the sizing process is reduced, and the amount of fine powder is also reduced. Therefore, labor can be saved in the fine powder removing process and the fine powder collecting process.
- recovery and recycling of the removed fine powder may lead to a decrease in the performance of the water-absorbing agent (for example, a reduction in water absorption ratio or regeneration of fine powder during the process). Since the amount of fine powder is reduced, the performance deterioration accompanying fine powder collection and recycling is also reduced, and the performance of the resulting water-absorbing agent is improved.
- a preferable fine powder recovery amount is appropriately set depending on the target particle size.
- the amount of fine powder tends to increase as a result, but preferably the amount of fine powder is less than 30% by mass of the total production amount, more preferably 20% by mass or less, Preferably it is 15 mass% or less, Most preferably, it is 10 mass% or less.
- the production method according to the present invention includes, as necessary, a pulverization step, a rewetting step, a granulation step, a transport step, a storage step, a packing step, and a storage step. Etc. may be further included.
- the inorganic fine particles include mineral products such as talc, kaolin, fullerite, hydrotalcite, bentonite, activated clay, barite, natural asphalt, strontium ore, ilmenite, pearlite; aluminum sulfate 14-18
- Aluminum salts such as hydrate (or its anhydride), potassium aluminum sulfate 12 hydrate, sodium aluminum sulfate 12 hydrate, ammonium aluminum sulfate 12 hydrate, aluminum chloride, polyaluminum chloride, aluminum oxide; and other various compounds such as calcium phosphate Valent metal salt, polyvalent metal oxide and polyvalent metal hydroxide; hydrophilic amorphous silicas; silicon oxide / aluminum oxide / magnesium oxide complex, silicon oxide / aluminum oxide complex, silicon oxide / magnesium oxide complex Etc. oxidation Complexes like; and the like. Of these, two or more may be used in combination.
- the water-absorbent resin particles are used in absorbent articles, particularly paper diapers.
- the physical properties listed in the following (3-1) to (3-6) at least one, preferably two or more, more preferably three or more, more preferably all the physical properties are within the desired range. It is desirable to be controlled by When all of the following physical properties do not satisfy the following range, the effect of the present invention is not sufficiently obtained, and particularly in a so-called high-concentration paper diaper where a large amount of water-absorbing agent is used per paper diaper. There is a possibility that performance may not be demonstrated.
- CRC centrifuge retention capacity
- the CRC (centrifuge retention capacity) of the water absorbent resin particles (water absorbing agent) of the present invention is usually 5 g / g or more, preferably 15 g / g or more, more preferably 25 g / g or more.
- the upper limit is not particularly limited, and higher CRC is preferable, but from the viewpoint of balance with other physical properties, it is preferably 70 g / g or less, more preferably 50 g / g or less, and still more preferably 40 g / g or less. .
- CRC When the CRC is less than 5 g / g, the amount of absorption is small and it is not suitable as an absorbent body for absorbent articles such as paper diapers. In addition, when the CRC exceeds 70 g / g, the rate of absorbing body fluids such as urine and blood decreases, so that it is not suitable for use in a high water absorption rate type paper diaper.
- CRC can be controlled by changing the type and amount of the internal cross-linking agent and surface cross-linking agent.
- Water-soluble component (Ext) Ext is usually 1 to 40% by mass, preferably 2 to 35% by mass, more preferably 3 to 30% by mass, still more preferably 4 to 25% by mass, and particularly preferably 5 to 20% by mass.
- Ext When Ext exceeds the above range, the gel strength is weak, and there is a possibility that the water absorption agent is inferior in absorption capacity under load and liquid permeability. If Ext is below the above range, CRC may be too low. In either case, since rewetting increases, it is not suitable as an absorbent body for absorbent articles such as paper diapers. Ext can be controlled by changing the type and amount of the internal cross-linking agent.
- the water content of the water-absorbent resin particles is preferably more than 0% by mass and 20% by mass or less, more preferably 1 to 15% by mass, and still more preferably 2 to 13% by mass. Particularly preferred is 2 to 10% by mass.
- a water-absorbing agent having excellent powder characteristics for example, fluidity, transportability, damage resistance, etc.
- the mass average particle size (D50) of the water-absorbent resin particles (water-absorbing agent) is as described above, preferably 200 ⁇ m or more, more preferably 200 to 600 ⁇ m, still more preferably 250 to 550 ⁇ m, particularly preferably. Is 300 to 500 ⁇ m.
- the proportion of particles having a particle diameter of less than 150 ⁇ m is preferably 10% by mass or less, more preferably 8% by mass or less, and further preferably 6% by mass or less.
- the ratio of particles having a particle size of more than 850 ⁇ m is preferably 5% by mass or less, more preferably 3% by mass or less, and further preferably 1% by mass or less.
- This water-absorbing agent contains particles having a particle size of 150 to 850 ⁇ m, preferably 90% by mass or more, more preferably 95% by mass or more, still more preferably 97% by mass or more, and particularly preferably 99% by mass or more. Ideally, it is 100% by mass.
- the logarithmic standard deviation ( ⁇ ) of the particle size distribution is preferably 0.20 to 0.50, more preferably 0.25 to 0.40, and still more preferably 0.27 to 0.35.
- AAP Water absorption capacity under pressure
- the AAP (water absorption capacity under pressure) of the water absorbent resin particles (water absorbing agent) is preferably 15 g / g or more, more preferably 20 g / g or more, still more preferably 23 g / g or more, particularly preferably 24 g / g or more, most preferably Preferably it is 25 g / g or more.
- the upper limit is not particularly limited, but is preferably 30 g / g or less.
- the amount of liquid returned when pressure is applied to the absorbent body may increase. Not suitable as an absorber.
- AAP can be controlled by adjusting the particle size or changing the surface cross-linking agent.
- Vortex water absorption speed
- the Vortex (water absorption rate) of the water absorbent resin particles (water absorbing agent) is preferably 60 seconds or less, more preferably 50 seconds or less, still more preferably 40 seconds or less, particularly preferably 30 seconds or less, and most preferably 25 seconds or less. is there. Although it does not specifically limit about a lower limit, Preferably it is 5 second or more, More preferably, it is 10 second or more.
- Vortex When the Vortex is within the above range, a predetermined amount of liquid can be absorbed in a short time.
- the user feels less time to feel the skin wet, making it less likely to cause discomfort and reducing the amount of leakage.
- water-absorbing resin particles water-absorbing agent
- the use of water-absorbing resin particles (water-absorbing agent) is not particularly limited, but is preferably used as an absorbent for absorbent articles such as paper diapers, sanitary napkins, incontinence pads, etc. Is mentioned. In particular, it can be used as an absorbent for high-density paper diapers. Furthermore, since the water-absorbing agent is excellent in water absorption time and the particle size distribution is controlled, a remarkable effect can be expected when used in the upper layer portion of the absorber.
- an absorbent material such as pulp fiber can be used together with the water absorbing agent.
- the content (core concentration) of the water-absorbing agent in the absorber is preferably 30% by mass to 100% by mass, more preferably 40% by mass to 100% by mass, and still more preferably 50% by mass to 100% by mass. Even more preferably, it is 60% by mass to 100% by mass, particularly preferably 70% by mass to 100% by mass, and most preferably 75% by mass to 95% by mass.
- the absorbent article can be kept in a clean white state. Furthermore, since the absorbent body is excellent in diffusibility of body fluids such as urine and blood, the amount of absorption can be improved by efficient liquid distribution.
- the “water-absorbing resin” described below means a dry polymer that has undergone a drying step, a surface-dried particulate dry polymer, or a particulate dry polymer that has been subjected to particle size adjustment after surface cross-linking.
- a 200V or 100V power source at 60 Hz was used for electrical equipment (including equipment for measuring physical properties of water-absorbing resin) used in the experimental examples unless otherwise noted.
- the physical properties of the water-absorbent resin and hydrogel described below were measured under conditions of room temperature (20 ° C. to 25 ° C.) and relative humidity of 50% RH ⁇ 10% unless otherwise noted.
- liter may be expressed as “l” or “L”
- mass% or “weight%” may be expressed as “wt%”.
- D Non Detected
- msi is the mass (unit; g) of the hydrogel before measurement
- mb is the free swollen mass after dehydration (nonwoven fabric only) (unit; g)
- mwi is free.
- ⁇ is the solid content ratio (unit: mass%) of the hydrogel before measurement.
- VHCl. s is the amount of HCl (unit: ml) required to bring the filtrate containing the dissolved polymer from pH 10 to pH 2.7
- VHCl. b is the amount of HCl (unit: ml) necessary to bring Blank (0.9 mass% sodium chloride aqueous solution) from pH 10 to pH 2.7
- CHCl is the concentration of HCl solution (unit: mol / l)
- Mw acrylic Average molecular weight of monomer units in acid (salt) polymer (unit: g / mol)
- Fdi1 is the dilution of the filtrate containing the dissolved polymer
- ms is the weight of the hydrogel before measurement (unit: g)
- ⁇ is the measurement It is the solid content rate (unit; mass%) of the previous hydrogel.
- (C) Water content and solid content of water-absorbing resin The water content of the water-absorbing resin was measured according to the EDANA method (ERT430.2-02). In the present invention, the measurement was performed by changing the sample amount to 1.0 g and the drying temperature to 180 ° C. The solid content (mass%) was determined by subtracting the moisture content (mass%) from 100 mass%.
- M means the mass (g) of the hydrogel and ⁇ means the solid content (mass%) of the hydrogel.
- C means the polymerization rate (mass%) of the hydrogel.
- solid content ratio (alpha) of a hydrogel is measured according to the following (f).
- (F) Water content and solid content of water-containing gel The water content of the water-containing gel was measured according to the EDANA method (ERT430.2-02). In the measurement, the mass of the sample was changed to 2.0 g, the drying temperature was changed to 180 ° C., and the drying time was changed to 24 hours. Specifically, after putting 2.0 g of the hydrogel into an aluminum cup having a bottom diameter of 50 mm, the total mass W1 (g) of the sample (hydrogel and aluminum cup) was accurately weighed. Next, the sample was allowed to stand in an oven set at an atmospheric temperature of 180 ° C. After 24 hours, the sample was taken out from the oven, and the total mass W2 (g) was accurately weighed. When the mass of the hydrogel subjected to this measurement was M (g), the water content (100- ⁇ ) (mass%) of the hydrogel was determined according to the following (Formula 5). ⁇ is the solid content (mass%) of the hydrogel.
- a 20% sodium chloride aqueous solution hereinafter referred to as “polyester” containing 20 g of a particulate hydrogel (solid content ⁇ mass%) at a temperature of 20 to 25 ° C. containing 0.08 mass% sodium polyoxyethylene lauryl sulfate (surfactant).
- the dispersion was added to 1000 g of an aqueous sodium oxyethylene lauryl sulfate solution) and stirred for 16 hours at 300 rpm using a stirrer chip having a length of 50 mm and a diameter of 7 mm.
- the container used was a polypropylene cylindrical container (height 21 cm, diameter 8 cm, internal volume about 1.14 L).
- the water pouring operation was repeated four times so that the water pouring range (50 cm 2) spread over the entire sieve, and the hydrogel was classified.
- the hydrated gel on the classified first stage sieve was drained for about 2 minutes and weighed.
- the second and subsequent sieves were classified in the same manner, and the water-containing gel remaining on each sieve after draining was weighed. The sieve was appropriately changed depending on the gel particle size.
- the ratio (mass%) was calculated from the following (formula 6) from the mass of the hydrous gel remaining on each sieve.
- the sieve opening after draining was calculated according to the following (formula 7), and the particle size distribution of the hydrogel was plotted on a logarithmic probability paper.
- the particle diameter corresponding to 50% by mass on the integrated sieve on the plot was set as the mass average particle diameter (D50) of the hydrogel.
- the logarithmic standard deviation ( ⁇ ) was obtained from the following (formula 8).
- a smaller value of ⁇ means that the particle size distribution is narrower.
- Vortex (water absorption time) of the water absorbent resin Vortex (water absorption time) of the water absorbent resin was measured according to the following procedure. First, after adding 0.02 part by weight of edible blue No. 1 (brilliant blue), which is a food additive, to 1000 parts by weight of physiological saline (0.9% by weight sodium chloride aqueous solution) prepared in advance, the liquid temperature is adjusted. Adjusted to 30 ° C.
- edible blue No. 1 brilliant blue
- the monomer aqueous solution adjusted to 38 ° C. was continuously supplied by a metering pump, and then 150.6 parts by mass of a 48% by mass sodium hydroxide aqueous solution was continuously mixed by line mixing. At this time, the temperature of the aqueous monomer solution increased to 87 ° C. due to heat of neutralization.
- the strip-shaped water-containing gel (1b) obtained in a screw extruder was charged and gel pulverization was performed.
- a meat chopper having an outer diameter of a screw shaft of 86 mm and a perforated plate having a diameter of 100 mm, a hole diameter of 8.0 mm, and a thickness of 10 mm is used at the same time as the hydrogel (1b).
- Gel pulverization (first gel pulverization) was performed while supplying water and water vapor.
- the pulverized gel obtained by the first gel pulverization was further gel pulverized (second gel pulverization) while supplying water and water vapor while changing to a porous plate having a pore diameter of 4.7 mm.
- the obtained particulate hydrous gel (1c) has a solid content of 44% by mass (moisture content is 56% by mass), an average particle size d1 in terms of solid content of 130 ⁇ m, and a ratio of particles having a particle size of less than 150 ⁇ m of about 53%. It was mass%.
- the particulate hydrogel (1c) had a polymerization rate of 98.6%, CRC of 36 g / g, and water-soluble content of 6%.
- the obtained particulate hydrogel (1c) was dried at 190 ° C. for 30 minutes using a hot air dryer to obtain a dried product.
- the dried product was pulverized using a roll mill (manufactured by Inoguchi Giken Co., Ltd.), and further classified with 850 ⁇ m and 150 ⁇ m JIS standard sieves to obtain a particulate dry polymer (A1).
- the particle size distribution of the particulate dry polymer (A1) is 3% by mass of the particles that pass through the 850 ⁇ m sieve and do not pass through the 600 ⁇ m sieve, and the ratio of the particles that pass through the 600 ⁇ m sieve and does not pass through the 500 ⁇ m sieve.
- the particulate dry polymer (A1) had a CRC of 46.6 g / g and a moisture content of 4% by mass.
- the obtained particulate hydrogel (1d) has a solid content of 49% by mass (moisture content of 51% by mass), an average particle size d1 in terms of solid content of 2000 ⁇ m, and a ratio of particles having a particle size of less than 150 ⁇ m of about 4%. It was 9 mass%.
- the particulate hydrogel (1d) had a polymerization rate of 98.6%, CRC of 34 g / g, and water-soluble content of 4%.
- the obtained particulate hydrogel (1d) was dried at 190 ° C. for 30 minutes using a hot air dryer to obtain a dried product.
- the dried product was pulverized using a roll mill (manufactured by Inoguchi Giken Co., Ltd.), and further classified with 850 ⁇ m and 150 ⁇ m JIS standard sieves to obtain a particulate dry polymer (A2).
- the particle size distribution of the particulate dry polymer (A2) is such that the proportion of particles that pass through the 850 ⁇ m sieve and does not pass through the 600 ⁇ m sieve is 4% by mass, and the proportion of particles that pass through the 600 ⁇ m sieve and does not pass through the 500 ⁇ m sieve.
- the proportion of the particles that pass through the 12 mass%, 500 ⁇ m sieve but does not pass through the 300 ⁇ m sieve is 49 mass%
- the percentage of the particles that pass through the 300 ⁇ m sieve and does not pass through the 150 ⁇ m sieve passes through the 33 mass%, 150 ⁇ m sieve.
- the ratio of the particles that did not pass through the 45 ⁇ m sieve was 2% by mass
- the mass average particle diameter (D50) was 346 ⁇ m
- ⁇ was 0.384.
- the particulate dry polymer (A2) had a CRC of 49.6 g / g and a moisture content of 4% by mass.
- Example 1 0.025 parts by mass of ethylene glycol diglycidyl ether, 0.3 parts by mass of ethylene carbonate, 0.5 parts by mass of propylene glycol with respect to 100 parts by mass of the 60 ° C. particulate dry polymer (A1) obtained in Production Example 1
- the surface cross-linking agent solution consisting of 2.0 parts by mass and deionized water was spray-mixed with a continuous high-speed agitation dryer (Turbulizer manufactured by Hosokawa Micron Corporation) to obtain a humidified product (B1).
- the obtained humidified product (B1) was heat-treated using a rotary heating device with a heating tube.
- This dryer has ten heating tubes extending in the direction of the rotation axis and two barriers (a donut-shaped partition plate having one circular opening at the center, an opening ratio of 8%).
- a cylindrical rotating container (with an internal volume of 100 L) is provided.
- this dryer has a donut-shaped partition plate (also referred to as discharge weir) having a single circular opening (opening ratio: 8%) at the center at the outlet.
- water vapor with a gauge pressure of 1.8 MPa (temperature: 210 ° C.) is introduced into each heating tube of the rotary heating device, the inner surface of the rotary vessel is preheated to over 180 ° C., and the outer wall of the rotary vessel is further tressed. And fully heated.
- the humidified product (B1) was supplied into the dryer at 40 kg / hr, and the rotating container was rotated so that the fluid number was Fr0.07, and the heat treatment was continuously performed.
- the average residence time of the humidified product (B1) was 30 minutes.
- the supply amount and the exhaust amount of the carrier gas were adjusted so that the pressure difference with respect to the outside air inside the rotating container was ⁇ 20 Pa and the exhaust dew point was 80 ° C.
- the water-absorbent resin discharged from the dryer was forcibly cooled to 80 ° C. or lower with cold air to obtain water-absorbent resin particles (C1).
- the obtained water-absorbent resin particles (C1) were visually observed, no contamination with colored foreign matters was observed.
- the physical properties of the water absorbent resin particles (C1) are shown in Table 1 below.
- Example 2 A water-absorbing resin was obtained in the same manner as in Example 1 except that the surface crosslinking agent solution was changed to 0.4 parts by mass of 1,4-butanediol, 0.6 parts by mass of propylene glycol and 3.0 parts by mass of deionized water. Particles (C2) were obtained. When the obtained water-absorbent resin particles (C2) were visually observed, no contamination with colored foreign matters was observed. The physical properties of the water absorbent resin particles (C2) are shown in Table 1 below.
- Example 3 The surface cross-linking agent solution was changed to 0.025 parts by mass of ethylene glycol diglycidyl ether, 1.0 part by mass of propylene glycol, and 3.0 parts by mass of deionized water, and water vapor introduced into each heating tube of the rotary heating apparatus was changed.
- Water-absorbing resin particles (C3) were obtained in the same manner as in Example 1 except that the inner surface of the rotating container was previously heated to over 100 ° C. with a gauge pressure of 0.1 MPa (temperature of 120 ° C.). When the obtained water-absorbent resin particles (C3) were visually observed, no contamination with colored foreign matters was observed.
- the physical properties of the water absorbent resin particles (C3) are shown in Table 1 below.
- Example 4 30 g of the water-absorbent resin particles (C1) obtained in Example 1 were combined with hydrotalcite (Mg 6 Al 2 (OH) 16 CO 3 .4H 2 O, volume average particle size 0.5 ⁇ m) and a mayonnaise bottle with a capacity of 225 mL. And mixed by vibrating for 3 minutes using a paint shaker (manufactured by Toyo Seiki Co., Ltd.) to obtain water-absorbing resin particles (C4). Hydrotalcite was added in an amount of 0.3 parts by mass with respect to 100 parts by mass of the water-absorbent resin particles (C1). When the obtained water-absorbent resin particles (C4) were visually observed, no contamination with colored foreign matters was observed.
- Table 1 The physical properties of the water absorbent resin particles (C4) are shown in Table 1 below.
- Example 5 Water-absorbing resin particles (C5) were obtained in the same manner as in Example 4 except that the hydrotalcite was changed to silica (product name “Aerosil 200CF” manufactured by Nippon Aerosil Co., Ltd.). When the obtained water-absorbent resin particles (C5) were visually observed, no contamination with colored foreign matters was observed. The physical properties of the water absorbent resin particles (C5) are shown in Table 1 below.
- Example 6 Water-absorbing resin particles (C6) were obtained in the same manner as in Example 1 except that the particulate dry polymer (A1) was changed to the particulate dry polymer (A2) obtained in Production Example 2. When the obtained water-absorbing resin particles (C6) were visually observed, no contamination with colored foreign matters was observed. The physical properties of the water absorbent resin particles (C6) are shown in Table 1 below.
- Example 7 Except for changing the particulate dry polymer (A1) to the particulate dry polymer (A2) obtained in Production Example 2, the humidified product (B2) and the water absorbent resin particles (C7) were obtained in the same manner as in Example 2. ) When the obtained water-absorbent resin particles (C7) were visually observed, no contamination with colored foreign matters was observed.
- the physical properties of the water absorbent resin particles (C7) are shown in Table 1 below.
- Example 8 Water-absorbing resin particles (C8) were obtained in the same manner as in Example 3 except that the particulate dry polymer (A1) was changed to the particulate dry polymer (A2) obtained in Production Example 2. When the obtained water-absorbent resin particles (C8) were observed with the naked eye, no contamination with colored foreign matters was observed.
- the physical properties of the water absorbent resin particles (C8) are shown in Table 1 below.
- Example 1 The humidified product (B1) obtained in Example 1 was used by using a conductive heat transfer type grooved stirring dryer (product name “Paddle Dryer NPD-1.6W type” manufactured by Nara Opportunity Manufacturing Co., Ltd.) shown in FIG. Heat-treated.
- the dryer 200 includes a stirring shaft 202, a stirring blade (paddle) 204, and a drum 206.
- the dryer 200 had a paddle diameter of 160 mm ⁇ , a heat transfer area of 2.5 m 2 , and an effective volume of 0.065 m 3 .
- a heated heat transfer oil (trade name “Perrel Therm 400” manufactured by Matsumura Oil Co., Ltd.) is introduced into the inner wall of the dryer 200, the stirrer 204, and the rotating shaft 202.
- the surface temperature was adjusted to 210 ° C.
- water-absorbent resin particles (C6) were obtained by forcibly cooling to 80 ° C. or lower with cold air. When the obtained water-absorbent resin particles (C6) were observed with the naked eye, slight contamination with colored foreign matter was observed.
- the physical properties of the water absorbent resin particles (C6) are shown in Table 1 below.
- the 150-micrometer sieve passage rate and average particle diameter in an Example and a comparative example were classified and measured by the JIS standard sieve of 850 micrometers, 600 micrometers, 500 micrometers, 300 micrometers, and 150 micrometers of openings.
- fine powder is generated because mechanical and thermal damage to the water-absorbent resin particles is reduced by using a heating device having a specific structure in the surface cross-linking step, particularly in the heating step.
- a heating device having a specific structure in the surface cross-linking step, particularly in the heating step.
- the water-absorbent resin particles obtained by the present invention are suitable for use as an absorbent material for sanitary goods such as paper diapers.
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Abstract
Description
〔1-1〕「吸水性樹脂」
本発明における「吸水性樹脂」とは、水膨潤性水不溶性の高分子ゲル化剤を指し、下記の物性を満たすものをいう。即ち、水膨潤性としてERT441.2-02で規定されるCRC(遠心分離機保持容量)が5g/g以上であり、かつ、水不溶性としてERT470.2-02で規定されるExt(水可溶分)が50質量%以下である高分子ゲル化剤を指す。
本発明における「ポリ(メタ)アクリル酸(塩)」とは、ポリ(メタ)アクリル酸及び/又はその塩を指し、主成分として(メタ)アクリル酸及び/又はその塩(以下、「(メタ)アクリル酸(塩)」とも称する)を繰り返し単位として含み、任意成分としてグラフト成分を含む架橋重合体を意味する。
「EDANA」は、European Disposables and Nonwovens Associationsの略称である。また、「ERT」は、EDANA Recommended Test Methodsの略称であり、吸水性樹脂の評価方法を規定した欧州標準である。本発明では、特に断りのない限り、ERT原本(2002年改定)に記載されている測定法に関しては、それに準拠して測定する。ERT原本(2002年改定)に記載のない評価方法に関しては、実施例に記載された方法及び条件で測定する。
「CRC」は、Centrifuge Retention Capacity(遠心分離機保持容量)の略称であり、吸水性樹脂の無加圧下での吸水倍率(「吸水倍率」と称する場合もある)を意味する。具体的には、吸水性樹脂0.2gを不織布製の袋に入れた後、大過剰の0.9質量%塩化ナトリウム水溶液中に30分間浸漬して自由膨潤させ、その後、遠心分離機(250G)で3分間、水切りした後の吸水倍率(単位;g/g)のことをいう。なお、重合後及び/又はゲル粉砕後の含水ゲルについては、含水ゲル0.4gを使用し、測定時間を24時間に変更し、且つ固形分補正してCRCを求める。
「Ext」は、Extractablesの略称であり、吸水性樹脂の水可溶分(吸水性樹脂中の水可溶分ポリマー量)を意味する。具体的には、吸水性樹脂1.0gを0.9質量%塩化ナトリウム水溶液200mlに添加し、500rpmで16時間攪拌した後、水溶液に溶解した物質の量(単位;質量%)のことをいう。水可溶分の測定には、pH滴定が用いられる。なお、重合後及び/又はゲル粉砕後の含水ゲルについては、含水ゲル2.0gを使用して測定し、固形分当たりの水可溶分の質量%として算出する。
「Moisture Content」は、吸水性樹脂の乾燥減量で規定される含水率を意味する。具体的には、吸水性樹脂4.0gを105℃で3時間乾燥した際の乾燥減量から算出した値(単位;質量%)のことをいう。なお、本発明において、乾燥後の吸水性樹脂については、吸水性樹脂1.0gの180℃、3時間の乾燥減量で規定され、乾燥前の含水ゲルについては、含水ゲル2.0gの180℃、24時間の乾燥減量で規定される。
「PSD」は、Particle Size Distributionの略称であり、篩分級により測定される吸水性樹脂の粒度分布を意味する。なお、質量平均粒子径(D50)及び粒度分布の対数標準偏差(σζ)は、米国特許第7638570号に記載された方法と同様の方法で測定される。なお、本発明において粒子状含水ゲルの粒度分布(PSD)は後述の方法で湿式に篩分級することで規定される。さらに、粒子状含水ゲルの固形分換算の粒子径(μm)は、粒子状含水ゲルの粒子径(μm)とその固形分率(質量%)から後述の計算方法で規定される。
「AAP」は、Absorption Against Pressureの略称であり、吸水性樹脂の加圧下における吸水倍率を意味する。具体的には、吸水性樹脂0.9gを大過剰の0.9質量%塩化ナトリウム水溶液に対して、1時間、2.06kPa(21g/cm2、0.3psi)の荷重下で膨潤させた後の吸水倍率(単位;g/g)のことをいう。本願明細書では荷重条件を4.83kPa(約49g/cm2、約0.7psiに相当)に変更して測定した値として定義される。
「Residual Monomers」は、吸水性樹脂中に残存する単量体(モノマー)質量(以下、「残存モノマー」と称する)の、吸水性樹脂の質量に対する割合(単位;ppm)を意味する。具体的には、吸水性樹脂1.0gを0.9質量%塩化ナトリウム水溶液200mlに添加し、1時間攪拌した後に溶出したモノマー量を、高速液体クロマトグラフィーを用いて測定する。尚、含水ゲルの残存モノマーは、必要により強制冷却等の重合停止操作を行った後、後述する方法にて測定して得られる残存モノマー質量の、含水ゲルの樹脂固形分の質量に対する割合(単位;質量%)とする。
本明細書において、範囲を示す「X~Y」は「X以上、Y以下」を意味する。また、特に注釈のない限り、質量の単位である「t(トン)」は「Metric ton(メトリック トン)」を意味し、「ppm」は「質量ppm」又は「重量ppm」を意味する。更に、「質量」と「重量」、「質量部」と「重量部」、「質量%」と「重量%」はそれぞれ同義語として扱う。また、「~酸(塩)」は「~酸及び/又はその塩」、「(メタ)アクリル」は「アクリル及び/又はメタクリル」をそれぞれ意味する。
本発明に係る吸水性樹脂粒子の製造方法は、酸基含有不飽和単量体を主成分として得られる粒子状乾燥重合体と、表面架橋剤との混合物を加熱処理する表面架橋工程を有している。好ましくは、この表面架橋工程は、表面架橋剤添加工程と、熱処理工程とを有している。好ましくは、この製造方法は、重合工程、(重合と同時又は別途の)ゲル粉砕工程、乾燥工程、(乾燥後の及び/又は表面架橋後の)冷却工程、並びに(乾燥後の及び/又は表面架橋後の)整粒工程をさらに含んでいる。その他には、単量体水溶液の調製工程、各種添加剤の添加工程、微粉除去工程及び微粉リサイクル工程を含んでもよい。さらに、目的に応じて各種の公知の工程を含むことができる。なお、本発明における表面架橋工程は、乾燥工程後に、この乾燥工程とは別途に行う工程を意味する。
本工程は、酸基含有不飽和単量体を主成分として含む水溶液(以下、「単量体水溶液」と称する)を調製する工程である。なお、得られる吸水性樹脂の吸水性能が低下しない範囲で、単量体のスラリー液を使用することもできるが、本項では便宜上、単量体水溶液について説明を行う。
本発明に規定する酸基は、特に限定されないが、カルボキシル基、スルホン基、リン酸基等が例示される。この酸基含有不飽和単量体の例としては、(メタ)アクリル酸、(無水)マレイン酸、イタコン酸、ケイ皮酸、ビニルスルホン酸、アリルトルエンスルホン酸、ビニルトルエンスルホン酸、スチレンスルホン酸、2-(メタ)アクリルアミド-2-メチルプロパンスルホン酸、2-(メタ)アクリロイルエタンスルホン酸、2-(メタ)アクリロイルプロパンスルホン酸、2-ヒドロキシエチル(メタ)アクリロイルフォスフェート等が挙げられる。吸水性能の観点から、好ましくは(メタ)アクリル酸、(無水)マレイン酸、イタコン酸、ケイ皮酸であり、より好ましくは(メタ)アクリル酸である。
酸基含有不飽和単量体以外の単量体としては、重合して吸水性樹脂となり得る化合物であればよい。例えば、(メタ)アクリルアミド、N-エチル(メタ)アクリルアミド、N,N-ジメチル(メタ)アクリルアミド等のアミド基含有不飽和単量体;N,N-ジメチルアミノエチル(メタ)アクリレート、N,N-ジメチルアミノプロピル(メタ)アクリレート、N,N-ジメチルアミノプロピル(メタ)アクリルアミド等のアミノ基含有不飽和単量体;メルカプト基含有不飽和単量体;フェノール性水酸基含有不飽和単量体;N-ビニルピロリドン等のラクタム基含有不飽和単量体等が挙げられる。
重合に使用される単量体は、重合の安定性から、好ましくは少量の重合禁止剤を含む。好ましい重合禁止剤はp-メトキシフェノールである。単量体(特にアクリル酸及びその塩)中に含まれる重合禁止剤の量は、通常1ppm~250ppm、好ましくは10ppm~160ppm、より好ましくは20ppm~80ppmである。
本発明において、酸基含有不飽和単量体に含まれる酸基の一部又は全部が中和された中和塩を用いることができる。この場合、酸基含有不飽和単量体の塩としては一価のカチオンとの塩であることが好ましく、アルカリ金属塩、アンモニウム塩及びアミン塩から選ばれる少なくとも1種であることがより好ましく、アルカリ金属塩であることが更に好ましく、ナトリウム塩、リチウム塩及びカリウム塩から選ばれる少なくとも1種であることがより更に好ましく、ナトリウム塩が特に好ましい。
上記酸基含有不飽和単量体を中和するために使用される中和剤としては、特に限定されないが、水酸化ナトリウム、水酸化カリウム、炭酸ナトリウム、炭酸アンモニウム等の無機塩や、アミノ基やイミノ基を有するアミン系有機化合物等の塩基性物質が適宜選択されて用いられる。中和剤として、2種以上の塩基性物質が併用されてもよい。なお、本発明における単量体は、特に断りのない限り、中和塩を含む概念である。
吸水性能の観点から、酸基含有不飽和単量体とその中和塩の合計モル数に対する中和塩のモル数(以下、「中和率」と称する)は、好ましくは40モル%以上、より好ましくは40モル%~80モル%、更に好ましくは45モル%~78モル%、特に好ましくは50モル%~75モル%である。
吸水性樹脂粒子の製造方法において、好ましくは内部架橋剤が用いられる。該内部架橋剤によって、得られる吸水性樹脂の吸水性能や吸水時のゲル強度等が調整される。
本発明に係る製造方法において、本発明の目的が達成される範囲内で、以下に例示する物質(以下、「その他の物質」と称する)を単量体水溶液に添加することもできる。
本工程において、単量体水溶液中の単量体濃度(=総単量体量/(総単量体量+総重合溶媒量(通常は水)))は、吸水性樹脂の物性及び生産性の観点から、好ましくは10質量%~90質量%、より好ましくは20質量%~80質量%、更に好ましくは30質量%~70質量%、特に好ましくは40質量%~60質量%である。以下、単量体濃度を「モノマー濃度」と称する場合がある。
本発明で使用される重合開始剤は、重合形態等によって適宜選択されるため、特に限定されないが、例えば、熱分解型重合開始剤、光分解型重合開始剤、若しくはこれらの併用、又は重合開始剤の分解を促進する還元剤を併用したレドックス系重合開始剤等が挙げられる。具体的には、米国特許第7265190号に開示された重合開始剤のうち、1種又は2種以上が用いられる。なお、重合開始剤の取扱性や吸水性樹脂の物性の観点から、好ましくは過酸化物又はアゾ化合物、より好ましくは過酸化物、更に好ましくは過硫酸塩が使用される。
なお、重合前の単量体水溶液中の溶存酸素を、昇温又は不活性ガスとの置換により低減させることも好ましい。例えば、溶存酸素は、好ましくは5ppm以下、より好ましくは3ppm以下、特に好ましくは1ppm以下に低減される。
本工程は、前記単量体水溶液を重合して、含水ゲル状架橋重合体(本願明細書においては「含水ゲル」と称する場合がある)を得る工程である。
重合形態としては、特に限定されない。吸水性能や重合制御の容易性等の観点から、好ましくは気相中の液滴重合、水溶液重合、逆相懸濁重合(ここで疎水性有機溶媒中の液滴重合も逆相懸濁の一例に含む)、より好ましくは水溶液重合、逆相懸濁重合、更に好ましくは水溶液重合が挙げられる。中でも、連続水溶液重合が特に好ましく、その例として、連続ベルト重合、連続ニーダー重合とが挙げられる。連続水溶液重合を採用することで、吸水性樹脂の生産効率が向上する。
重合工程で得られる含水ゲル状架橋重合体の重合率は、次のゲル粉砕工程で得られる粒子状含水ゲル状架橋重合体の乾燥中の凝集抑制や、得られる吸水性樹脂中の残存モノマー低減の観点から、好ましくは90質量%以上、より好ましくは95質量%以上、更に好ましくは98質量%以上、特に好ましくは99質量%以上である。重合工程後に、重合率の低い含水ゲルを粉砕して、多量の未反応モノマーを含む状態で乾燥工程を行った場合、乾燥中に重合反応が進行して、粒子径の小さいゲル粒子から大粒子径のゲル粒子が再生されるため、得られる吸水性樹脂の吸水速度の低下、乾燥物の粒子径の増大等の問題が発生する。
重合工程で得られる含水ゲル状架橋重合体のCRC(遠心分離機保持容量)は、固形分換算で、好ましくは5g/g~80g/g、より好ましくは10g/g~50g/g、さらに好ましくは15g/g~45g/g、特に好ましくは20g/g~40g/gである。また、重合工程で得られる含水ゲル状架橋重合体の水可溶分は、好ましくは1質量%~20質量%、より好ましくは2質量%~15質量%、さらに好ましくは3質量%~10質量%である。CRC及び/又は水可溶分が上記範囲を上回る場合には、粉砕された含水ゲル粒子に粘着性が発現して、粒子状含水ゲルの流動性が低下する。
本工程は、上記重合工程で得られた含水ゲル状架橋重合体を、重合と同時及び/又は重合後に粉砕して細粒化する工程であり、例えば、ニーダー、ミートチョッパー等のスクリュー押出し機、カッターミル等の装置により粉砕して、粒子状含水ゲル状架橋重合体(以下、「粒子状含水ゲル」)を得る工程である。目的とする形状及び性能の吸水性樹脂粒子が高収率で得られるように、粒子状含水ゲルの粒子径が、後述する好ましい範囲に調整される。なお、所定の粒子径の粒子状含水ゲルを得るために、本工程を2回以上実施してもよい。また、逆相懸濁重合又は気相重合のように、重合工程で目的とする粒度の粒子状含水ゲルが得られる場合には、本工程を実施しなくてもよい。
本発明の製造方法において、吸水性能を損なうことなく、所定の粒度の粒子状含水ゲルが得られる限り、ゲル粉砕装置の種類は特に限定されない。例えばバッチ式又は連続式の双腕型ニーダー等、複数の回転撹拌翼を備えたゲル粉砕機、1軸押出機、2軸押出機、ミートチョッパー等が挙げられる。
ゲル粉砕工程に供される含水ゲルの固形分率(以下、ゲル固形分率)は、25質量%以上が好ましい。ゲル粉砕後の含水ゲル粒子同士の凝集抑制、粉砕に要するエネルギー、乾燥効率及び吸収性能の観点から、ゲル固形分率は25質量%~75質量%がより好ましく、30質量%~70質量%がさらに好ましく、35質量%~65質量%がよりさらに好ましく、40質量%~60質量%が特に好ましい。
本発明に係る製造方法において、ゲル粉砕工程前及び/又はゲル粉砕工程中に、ゲル流動化剤を添加してもよい。これにより、ゲル流動化剤を含む粒子状含水ゲルが得られる。ゲル流動化剤の添加により、後述する乾燥工程において、含水ゲル粒子同士の付着又は接着が抑制され、得られる吸水性樹脂の吸水速度が向上するという効果が得られる。また、後述する乾燥後の粉砕工程における負荷が低減され、微粉発生量が減少するという効果も得られる。さらに、乾燥工程において攪拌乾燥を行う場合には、得られる粒子状乾燥重合体の粒子径が製品粒子径に近づくため、上記効果が顕著になる。得られる粒子状含水ゲルの各粒子が均一にゲル流動化剤を含むとの観点から、ゲル粉砕工程中の添加が好ましい。なお、重合工程で逆相懸濁重合を行う場合等、ゲル粉砕工程を要しない場合にも、少なくとも乾燥工程前に、粒子状含水ゲルにゲル流動化剤を添加することが好ましい。
具体的には、ゲル流動化剤に用いられる界面活性剤として、(1)ショ糖脂肪酸エステル、ポリグリセリン脂肪酸エステル、ソルビタン脂肪酸エステル、ポリオキシエチレンソルビタン脂肪酸エステル、ポリオキシエチレングリセリン脂肪酸エステル、ソルビトール脂肪酸エステル、ポリオキシエチレンソルビトール脂肪酸エステル、ポリオキシエチレンアルキルエーテル、ポリオキシエチレンアルキルフェニルエーテル、ポリオキシエチレンヒマシ油、ポリオキシエチレン硬化ヒマシ油、アルキルアリルホルムアルデヒド縮合ポリオキシエチレンエーテル、ポリオキシエチレンポリオキシプロピレンブロックコポリマー、ポリオキシエチレンポリオキシプロピルアルキルエーテル、ポリエチレングリコール脂肪酸エステル、アルキルグルコシド、N-アルキルグルコンアミド、ポリオキシエチレン脂肪酸アミド、ポリオキシエチレンアルキルアミン、ポリオキシエチレンアルキルエーテルのリン酸エステル、及びポリオキシエチレンアルキルアリルエーテルのリン酸エステルなどのノニオン性界面活性剤、(2)カプリルジメチルアミノ酢酸ベタイン、ラウリルジメチルアミノ酢酸ベタイン、ミリスチルジメチルアミノ酢酸ベタイン、ステアリルジメチルアミノ酢酸ベタイン等のアルキルジメチルアミノ酢酸ベタイン;ラウリン酸アミドプロピルベタイン、ヤシ油脂肪酸アミドプロピルベタイン、パーム核油脂肪酸アミドプロピルベタイン等のアルキルアミドプロピルベタイン、ラウリルヒドロキシスルホベタイン等のアルキルヒドロキシスルホベタイン、2-アルキル-N-カルボキシメチル-N-ヒドロキシエチルイミダゾリニウムベタイン等のアルキルカルボキシメチルヒドロキシエチルイミダゾリニウムベタインなどの両性界面活性剤、(3)ラウリルアミノジ酢酸モノナトリウム、ラウリルアミノジ酢酸カリウム、ミリスチルアミノジ酢酸ナトリウム等のアルキルアミノジ酢酸モノアルカリ金属などのアニオン性界面活性剤、(4)長鎖アルキルジメチルアミノエチル4級塩などのカチオン性界面活性剤等が挙げられる。これらのうち、2種以上を併用してもよい。
本発明に係る製造方法において、本発明の目的が達成される範囲内で、以下に例示する高分子滑剤を、上記単量体水溶液や含水ゲルに添加することができる。
ゲル流動化剤の種類と添加量とは、ゲル粉砕工程及び乾燥工程における粒子状含水ゲルの流動性等を考慮して適宜調整される。得られる吸水性樹脂の吸収性物品(おむつ)での実使用における戻り量等から、最終製品の吸水性樹脂の表面張力が過度に低下しない種類や量のゲル流動化剤が好ましい。例えば、吸水性樹脂の表面張力(生理食塩水中の吸水性樹脂の分散液の表面張力)が、好ましくは55mN/m以上、より好ましくは60mN/m以上、更に好ましくは65mN/m以上となるように、ゲル流動化剤の種類及び量が選択される。この表面張力はWO2015/129917に記載の方法で測定される。
本発明に係る製造方法において、ゲル粉砕工程で含水ゲルを粉砕するとともに、重合反応を進行させて重合率を調整することも可能である。重合反応の進行の程度は、ゲル粉砕装置における加熱及び滞留時間、重合後の含水ゲル中の重合開始剤の残存量、任意の重合開始剤の後添加量等で適宜調整される。ゲル粉砕後に得られる粒子状含水ゲルの重合率は、固形分換算で、好ましくは、90質量%以上であり、より好ましくは95質量%以上であり、更に好ましくは、98~99.99質量%であり、理想的には、100%である。重合率が上記範囲の粒子状含水ゲルでは、乾燥時の凝集及び付着が回避される。粒子状含水ゲルの重合率の調整は、攪拌乾燥の場合に特に有効である。なお、粒子状含水ゲルの重合率は、ゲル粉砕前の含水ゲルの重合率と同様に、後述する物性測定方法で規定される。
粒子状含水ゲルの含水率(以下、ゲル含水率)は、下記実施例に記載した測定方法によって求められる。後述する乾燥工程における粒子状含水ゲルの流動性の観点から、ゲル含水率は25質量%以上が好ましく、30質量%以上がより好ましく、35質量%以上がさらに好ましく、40質量%以上が特に好ましく、43質量%以上が極めて好ましい。過度の高濃度重合は吸水性樹脂の物性を低下させる可能性があり、乾燥効率及び吸収性能の観点から、ゲル含水率は75質量%以下が好ましく、60質量%以下がより好ましく、55質量%以下が特に好ましい。
得られる吸水性樹脂の吸水速度及び粒子径、並びに粉砕時の微粉発生抑制の観点から、乾燥前の粒子状含水ゲル架橋重合体の質量平均粒子径d1は、固形分換算で、好ましくは3000μm以下、より好ましくは2000μm以下、さらに好ましくは50μm~1000μm、よりさらに好ましくは100μm~800μmである。なお、固形分換算の粒子状含水ゲルの平均粒子径d1は、下記実施例に記載の方法により、粒子状含水ゲルの質量平均粒子径(D50)から算出される。
乾燥前の粒子状含水ゲルのCRC(遠心分離機保持容量)は、固形分換算(後述する測定方法で規定)で、好ましくは5g/g~80g/g、より好ましくは10g/g~50g/g、更に好ましくは15g/g~45g/g、特に好ましくは20g/g~40g/gである。また、乾燥前の粒子状含水ゲルの水可溶分(Ext)は、固形分換算(後述する測定方法で規定)で、好ましくは1質量%~15質量%、より好ましくは2質量%~10質量%、さらに好ましくは3質量%~5質量%である。
本工程は、粒子状含水ゲル(好ましくはゲル流動化剤を含む)を所望の含水率にまで乾燥させて乾燥重合体、好ましくは粒子状乾燥重合体を得る工程である。なお、本工程に供される粒子状含水ゲルは、ゲル粉砕工程を経て得られるものに限定されず、例えば逆相懸濁重合により得られてもよい。また、本工程で得られる乾燥重合体が、複数の粒子が物理的又は化学的に付着することで形成された造粒物(以下、粒状乾燥造粒物)を含んでもよい。
含水ゲル粒子の凝集抑制の観点から、乾燥工程に供される粒子状含水ゲルの温度T2を、好ましくは50℃以上、より好ましくは60℃以上、さらに好ましくは70℃以上、特に好ましくは80℃以上、最も好ましくは90℃以上に制御する。また、被乾燥物の着色や性能低下抑制の観点から、この温度T2は好ましくは130℃以下、より好ましくは110℃以下、さらに好ましくは105℃以下である。
乾燥工程で使用される乾燥装置としては、特に限定されず、伝熱伝導型乾燥機、輻射伝熱型乾燥機、熱風伝熱型乾燥機、誘電加熱型乾燥機等の1種又は2種以上が適宜選択される。バッチ式でもよく、連続式でもよい。また、直接加熱式でもよく、間接加熱式でもよい。例えば、通気バンド式、通気回路式、通気縦型式、平行流バンド式、通気トンネル式、通気攪拌式、通気回転式、流動層式、気流式等の伝熱型乾燥機が挙げられる。静置状態で乾燥させるバンド式等の場合、大きな塊状の乾燥物が得られるため、これを粉砕して粒子状の製品に加工する際に多量の微粉が発生することがある。一方、乾燥機中で被乾燥物を流動させる流動手段(例えば、乾燥機に備えた撹拌翼や乾燥機自体の回転)と、1又は2以上の加熱手段を備えた攪拌乾燥機を用いれば、粒子状の乾燥物(以下、粒状乾燥重合体と称する場合がある)が得られるため好ましく、連続式の攪拌乾燥機がより好ましい。好ましい攪拌乾燥方法は、PCT/JP/2017/041371号及びPCT/JP2017/041372号に記載され、係る攪拌乾燥の記載は本発明の記載として適用できる。
乾燥工程で得られる乾燥重合体の水可溶分(Ext)は、好ましくは、乾燥前の粒子状含水ゲルの水可溶分より大きい。乾燥後に得られる乾燥重合体の水可溶分は、固形分換算、好ましくは+0.5質量%以上増加、より好ましくは+1~20質量%の範囲で増加、さらに好ましくは+2~10質量%の範囲で増加するように、含水ゲルの架橋密度(特に内部架橋剤の種類や量)や加熱乾燥条件などが調整される。
本工程は、上記乾燥工程で得られた乾燥重合体を粉砕(粉砕工程)し、所定の範囲の粒度に調整(分級工程)して、吸水性樹脂粉末を得る工程である。ここで、表面架橋する前の、粉末状の吸水性樹脂を、便宜上、「吸水性樹脂粉末」と称する。
本発明に係る製造方法において、表面架橋工程は、前述の乾燥工程とは別途行われる工程であり、乾燥重合体に吸水性樹脂の官能基(特にカルボキシル基)と反応する表面架橋剤を添加する表面架橋剤添加工程と、この表面架橋剤を含む乾燥重合体を加熱処理して架橋反応させる熱処理工程とを含む。本工程は、前述した工程を経て得られる吸水性樹脂粉末の表面層(吸水性樹脂粉末の表面から数10μmの部分)に、さらに架橋密度の高い部分を設ける工程であり、表面架橋剤添加工程及び熱処理工程と、任意になされる冷却工程とから構成される。この表面架橋工程において、吸水性樹脂粉末表面でのラジカル架橋反応、表面重合反応、表面架橋剤との架橋反応等により、表面架橋された吸水性樹脂(吸水性樹脂粒子)が得られる。
本工程は、粒子状乾燥重合体に、表面架橋剤を添加する工程である。表面架橋剤は、乾燥後の粒子状乾燥重合体又は乾燥後に粒度調整された粒子状乾燥重合体に対して添加される。
本発明に係る製造方法において、表面架橋剤添加工程に供される粒子状乾燥重合体の含水率は15質量%以下である。得られる吸水性樹脂粒子の吸水性能の観点から、粒子状乾燥重合体の含水率は、好ましくは10質量%以下、より好ましくは7質量%以下、特に好ましくは5質量%以下である。過度の凝集又は付着防止の観点から、この含水率は、1質量%を超えることが好ましい。尚、粒子状乾燥重合体の含水率は、下記実施例に記載した測定方法により求められる。
表面架橋剤添加工程に供される粒子状乾燥重合体は、加温又は保温されていることが好ましい。粒子状乾燥重合体の温度T3は、好ましくは30~120℃、より好ましくは35~80℃、さらに好ましくは40~70℃である。本工程に供される粒子状乾燥重合体の温度T3が30℃未満の場合、添加された表面架橋剤の析出や粒子状乾燥重合体の吸湿等により、表面架橋処理が不十分又は不均一になる場合がある。また、この温度T3が100℃を超える場合、表面架橋剤溶液中の水又は溶媒が揮発することで、表面架橋剤が析出する恐れがある。
上記表面架橋剤として、吸水性樹脂の複数の官能基(好ましくは複数のカルボキシル基)と反応しうる表面架橋剤、好ましくは共有結合またはイオン結合、さらには共有結合しうる表面架橋剤が使用される。具体的には、エチレングリコール、ジエチレングリコール、プロピレングリコール、トリエチレングリコール、テトラエチレングリコール、ポリエチレングリコール、1,3-プロパンジオール、ジプロピレングリコール、2,2,4-トリメチル-1,3-ペンタンジオール、ポリプロピレングリコール、グリセリン、ポリグリセリン、2-ブテン-1,4-ジオール、1,3-ブタンジオール、1,4-ブタンジオール、1,5-ペンタンジオール、1,6-ヘキサンジオール、1,2-シクロヘキサンジメタノール、1,2-シクロヘキサノール、トリメチロールプロパン、ジエタノールアミン、トリエタノールアミン、ポリオキシプロピレン、オキシエチレン-オキシプロピレンブロック共重合体、ペンタエリスリトール、ソルビトール等の多価アルコール化合物;エチレングリコールジグリシジルエーテル、ポリエチレングリコールジグリシジルエーテル、グリセロールポリグリシジルエーテル、ジグリセロールポリグリシジルエーテル、ポリグリセロールポリグリシジルエーテル、プロピレングリコールジグリシジルエーテル、ポリプロピレングリコールポリグリシジルエーテル、グリシドール、ソルビトールポリグリシジルエーテル、ペンタエリスリトールポリグリシジルエーテル、トリメチロールプロパンポリグリシジルエーテル、ネオペンチルグリコールジグリシジルエーテル、1,6-ヘキサンジオールジグリシジルエーテル等のエポキシ化合物;エチレンジアミン、ジエチレントリアミン、トリエチレンテトラミン、テトラエチレンペンタミン、ペンタエチレンヘキサミン、ポリエチレンイミン等の多価アミン化合物及びこれらの無機塩又は有機塩;2,4-トリレンジイソシアネート、ヘキサメチレンジイソシアネート等の多価イソシアネート化合物;ポリアジリジン等のアジリジン化合物;1,2-エチレンビスオキサゾリン、ビスオキサゾリン、ポリオキサゾリン等の多価オキサゾリン化合物;尿素、チオ尿素、グアニジン、ジシアンジアミド、2-オキサゾリジノン等の炭酸誘導体;1,3-ジオキソラン-2-オン、4-メチル-1,3-ジオキソラン-2-オン、4,5-ジメチル-1,3-ジオキソラン-2-オン、4,4-ジメチル-1,3-ジオキソラン-2-オン、4-エチル-1,3-ジオキソラン-2-オン、4-ヒドロキシメチル-1,3-ジオキソラン-2-オン、1,3-ジオキサン-2-オン、4-メチル-1,3-ジオキサン-2-オン、4,6-ジメチル-1,3-ジオキサン-2-オン、1,3-ジオキソパン-2-オン等のアルキレンカーボネート化合物;エピクロロヒドリン、エピブロムヒドリン、α-メチルエピクロロヒドリン等のハロエポキシ化合物及びこれらの多価アミン付加物;オキセタン化合物;γ-グリシドキシプロピルトリメトキシシラン、γ-アミノブロピルトリエトキシシラン等のシランカップリング剤;亜鉛、カルシウム、マグネシウム、アルミニウム、鉄、ジルコニウム等の水酸化物、塩化物、硫酸塩、硝酸塩又は炭酸塩等の多価金属化合物;等が挙げられる。これらのうち、2種以上を併用してもよい。上記表面架橋剤の中でも、多価金属イオン、エポキシ系化合物、オキサゾリン系化合物、アルキレンカーボネート化合物から選択された1又は2以上が好ましい。
上記表面架橋剤の添加量は、粒子状乾燥重合体の固形分に対して好ましくは15質量%以下、より好ましくは10質量%以下、更に好ましくは2質量%以下である。また、下限値としては好ましくは0.001質量%である。
粒子状乾燥重合体に表面架橋剤を添加する方法は、特に限定されず、例えば、(1)粒子状乾燥重合体を親水性有機溶媒に浸漬し、表面架橋剤を粒子状乾燥重合体に吸着させる方法、(2)粒子状乾燥重合体に、直接表面架橋剤溶液を噴霧もしくは滴下して混合する方法等が挙げられる。所定量の表面架橋剤を吸水性樹脂に均一に添加する観点から、(2)の方法が好ましい。同様の観点から、表面架橋剤溶液の添加中、粒子状乾燥重合体を撹拌することが好ましく、表面架橋剤溶液を噴霧添加することがより好ましい。
乾燥工程後に別途行う表面架橋工程において、表面架橋剤を添加する回数は、1回でも複数回でもよい。2回以上添加する場合には、少なくとも最初の1回の表面架橋剤と接触する粒子状乾燥重合体が、前述した含水率及び温度を有することが好ましく、全ての接触において上記含水率及び温度を有することがより好ましい。また、各添加処理に、同じ添加装置を用いてもよく、異なる装置を用いてもよい。
本工程は、粒子状乾燥重合体と表面架橋剤との混合物を加熱処理して、表面架橋された粒子状乾燥重合体を得る工程である。
本工程において、粒子状乾燥重合体と表面架橋剤との混合物を100℃以上に加熱することにより、表面架橋された粒子状乾燥重合体が得られる。加熱温度(表面架橋温度)は、添加する表面架橋剤の種類により適宜選択されるが、熱処理効率の観点から、好ましくは100℃~250℃、より好ましくは120℃~230℃、さらに好ましくは150℃~210℃である。
表面架橋剤を含む粒子状乾燥重合体を、上記表面架橋温度で加熱処理する時間は、粒子状乾燥重合体の含水率、表面架橋剤の種類、後述する加熱装置の運転条件等に応じて適宜設定される。一応の目安としては、得られる吸水性樹脂粒子の含水率が10質量%以下になるまで加熱すればよく、時間としては10分間~120分間の範囲であり、好ましくは30分間~90分間である。
本発明に係る製造方法では、乾燥工程とは別途実施する表面架橋工程において、特定の構造を有する加熱装置を用いて、粒子状乾燥重合体と表面架橋剤との混合物を加熱処理することを特徴とする。この加熱装置は、その内部に粒子状乾燥重合体と表面架橋剤との混合物を収容して回転する回転容器と、この回転容器の内部に位置して、その軸方向に延在し、かつこの回転容器とともに回転する複数の加熱管とを備えている。本願明細書において、この構成を有する加熱装置を、「回転型加熱装置」又は「加熱管付き回転型加熱装置」と称する場合がある。
本発明の効果が阻害されない限り、加熱装置100において、表面架橋剤を含む粒子状乾燥重合体に、他の添加剤を添加してもよい。他の添加剤として、例えば前述したゲル流動化剤及び高分子滑剤が挙げられる。
本発明に係る製造方法では、表面架橋工程の熱処理工程に、図1-2に示される基本構成を備えた加熱装置100を用いることにより、吸水性樹脂の固形分換算による単位時間当たりの処理量(kg/hr)が7kg/hr以上、好ましくは50Kg/hr以上、より好ましくは100Kg/hr以上、特に好ましくは500Kg/hrの連続処理が可能となる。連続処理時間は好ましくは12時間以上、さらには24時間以上、特に240時間以上、1200時間以上である。
好ましくは、前述の乾燥工程及び/又は熱処理工程後、後述する整粒工程前に、乾燥重合体又は表面架橋された粒子状乾燥重合体を強制冷却して、所望の温度に調整する冷却工程を有している。例えば、前述の加熱装置100において、乾燥工程とは別途に、表面架橋工程が実施される場合、回転容器10において、表面架橋処理が適正になされ、かつ所望の含水率又は固形分率に調整された粒子状乾燥重合体が、整粒工程に供される前に、この冷却工程が実施される。また、乾燥工程において所望の含水率又は固形分率調整された乾燥重合体が、表面架橋工程に先だって整粒工程に供される前に、この冷却工程が実施される。
冷却工程において、乾燥重合体又は表面架橋された粒子状乾燥重合体を冷却する方法は、特に限定されない。好ましくは、通気伝熱式又は伝導伝熱式の冷却手段を有する連続冷却機が用いられる。静置状態で冷却してもよく、攪拌状態で冷却してもよい。材料撹拌型冷却機が好ましく、連続式の材料撹拌型冷却機がより好ましい。例えば、直接伝熱である流動層冷却機が挙げられる。連続ベルト式冷却機における冷風冷却でもよい。
本工程は、乾燥重合体及び/又は表面架橋された粒子状乾燥重合体の粒度を調整する工程である。表面架橋工程を経た粒子状乾燥重合体が、この整粒工程に供されることにより、粒子径又は粒度分布がより積極的に制御された吸水性樹脂粒子が得られる。特に、本発明に係る製造方法において得られる表面架橋された粒子状乾燥重合体は、表面架橋工程における粒子同士の付着及び凝集が軽減されるため、本工程における負荷が小さく、過度の粉砕や解砕による微粉の発生量が少ないという利点が得られる。尚、本工程は、複数回実施することも可能である。
「微粉リサイクル工程」とは、分級工程で除去された微粉をそのまま、又は微粉を造粒した後に何れかの工程に供給する工程を意味する。好ましくは、微粉又は微粉造粒物を、乾燥工程以前の工程に投入して再利用する工程である。乾燥工程以前の工程としては、重合工程で調整した重合前の単量体溶液、重合途中の含水ゲル、重合後の含水ゲルの粉砕工程、粒状含水ゲルの乾燥工程等が挙げられる。これらの工程に、微粉をそのまま添加してもよく、微粉を水で膨潤ゲル化ないし造粒してから添加してもよい。また、微粉とともに、水、架橋剤、水以外のバインダー(例;水溶性ポリマー、熱可塑性樹脂)、重合開始剤、還元剤、キレート剤、着色防止剤などを添加してもよい。例えば、水を添加する場合、微粉に対して1質量%~1000質量%、その他の化合物を添加する場合は、微粉に対して0.01質量%~10質量%の量で使用されることが好ましい。
本発明に係る製造方法は、上述した各工程以外に、必要に応じて、粉砕工程、再湿潤工程、造粒工程、輸送工程、貯蔵工程、梱包工程、保管工程等を更に含んでもよい。
本発明の効果が阻害されない限り、上記任意に使用されるゲル流動化剤や高分子滑剤以外にも、その他添加剤として、無機微粒子、粉塵防止剤、乾燥した吸水性樹脂(微粉)、通液性向上剤等を更に加えることが可能である。
本発明に係る製造方法で得られる吸水性樹脂粒子(吸水剤)については、該吸水性樹脂粒子を吸収性物品、特に紙オムツに使用する場合に、下記の(3-1)~(3-6)に掲げた物性のうち、少なくとも1つ以上、好ましくは2つ以上、より好ましくは3つ以上、更に好ましくは全ての物性が、所望する範囲に制御されることが望まれる。以下の全ての物性が下記の範囲を満たさない場合、本発明の効果が十分に得られず、特に、紙オムツ一枚当たりの吸水剤の使用量が多い、所謂、高濃度紙オムツにおいて十分な性能を発揮しないおそれがある。
本発明の吸水性樹脂粒子(吸水剤)のCRC(遠心分離機保持容量)は、通常5g/g以上であり、好ましくは15g/g以上、より好ましくは25g/g以上である。上限値については特に限定されず、より高いCRCが好ましいが、他の物性とのバランスの観点から、好ましくは70g/g以下、より好ましくは50g/g以下、更に好ましくは40g/g以下である。
Extは、通常1~40質量%であり、好ましくは2~35質量%、より好ましくは3~30質量%、さらに好ましくは4~25質量%、特に好ましくは5~20質量%である。
吸水性樹脂粒子(吸水剤)の含水率は、好ましくは0質量%を超えて20質量%以下、より好ましくは1~15質量%、更に好ましくは2~13質量%、特に好ましくは2~10質量%である。この含水率を上記範囲内とすることで、粉体特性(例えば、流動性、搬送性、耐ダメージ性等)に優れた吸水剤が得られる。
吸水性樹脂粒子(吸水剤)の質量平均粒子径(D50)は前述した通りであり、好ましくは200μm以上、より好ましくは200~600μm、さらに好ましくは250~550μm、特に好ましくは300~500μmである。また、粒子径150μm未満の粒子の割合は、好ましくは10質量%以下、より好ましくは8質量%以下、さらに好ましくは6質量%以下である。また、粒径850μm超の粒子の割合は、好ましくは5質量%以下、より好ましくは3質量%以下、さらに好ましくは1質量%以下である。この吸水剤は、粒子径150~850μmの粒子を、好ましくは90質量%以上、より好ましくは95質量%以上、さらに好ましくは97質量%以上、特に好ましくは99質量%以上含む。理想的には100質量%である。粒度分布の対数標準偏差(σζ)は、好ましくは0.20~0.50、より好ましくは0.25~0.40、更に好ましくは0.27~0.35である。
吸水性樹脂粒子(吸水剤)のAAP(加圧下吸水倍率)は、好ましくは15g/g以上、より好ましくは20g/g以上、更に好ましくは23g/g以上、特に好ましくは24g/g以上、最も好ましくは25g/g以上である。上限値については特に限定されないが、好ましくは30g/g以下である。
吸水性樹脂粒子(吸水剤)のVortex(吸水速度)は、好ましくは60秒以下、より好ましくは50秒以下、更に好ましくは40秒以下、特に好ましくは30秒以下、最も好ましくは25秒以下である。下限値については特に限定されないが、好ましくは5秒以上、より好ましくは10秒以上である。
吸水性樹脂粒子(吸水剤)の用途は、特に限定されないが、好ましくは紙オムツ、生理用ナプキン、失禁パッド等の吸収性物品の吸収体用途が挙げられる。特に、高濃度紙オムツの吸収体として使用することができる。更に、吸水剤は、吸水時間に優れ、かつ粒度分布が制御されているので、上記吸収体の上層部に使用する場合に、顕著な効果が期待できる。
(a)吸水性樹脂及び含水ゲルのCRC(遠心分離機保持容量)
吸水性樹脂のCRC(遠心分離機保持容量)を、EDANA法(ERT441.2-02)に準拠して測定した。また、含水ゲルのCRC(遠心分離機保持容量)は、試料の質量を含水ゲルとして0.4gに、自由膨潤時間を24時間に、それぞれ変更した以外はEDANA法(ERT441.2-02)と同様の操作を行った。更に、別途含水ゲルの固形分率αを下記(f)に従って測定し、下記(式1)に従って含水ゲルのCRCを算出した。
吸水性樹脂のExt(水可溶分)は、EDANA法(ERT470.2-02)に準拠して測定した。また、含水ゲルのExt(水可溶分)は、試料の質量を含水ゲルとして2.0gに変更した以外はEDANA法(ERT470.2-02)と同様の操作を行った。更に、別途含水ゲルの固形分率αを下記(f)に従って測定し、下記(式2)に従って含水ゲルのExtを算出した。
吸水性樹脂の含水率を、EDANA法(ERT430.2-02)に準拠して測定した。なお、本発明においては、試料量を1.0g、乾燥温度を180℃にそれぞれ変更して測定した。固形分率(質量%)は、100質量%から含水率(質量%)を引くことで求めた。
吸水性樹脂の粒度(粒度分布、質量平均粒子径(D50)及び粒度分布の対数標準偏差(σζ))を、米国特許第7638570号のカラム27及び28に記載された方法に準拠して測定した。
イオン交換水1000gに含水ゲル1.00gを投入し、300rpmで2時間攪拌した後に、ろ過することにより、不溶分を除去した。上記操作で得られたろ液中に抽出された単量体の量を、液体クロマトグラフを用いて測定した。得られたデータについて、下記(式3)にしたがってゲル固形分補正を行い、含水ゲルの重合率C(質量%)を求め、下記(式4)にしたがって、含水ゲルの残存モノマー量R(質量%)を求めた。
R(質量%)=100-C ・・・ (式4)
含水ゲルの含水率を、EDANA法(ERT430.2-02)に準拠して測定した。なお、測定に際し、試料の質量を2.0gに、乾燥温度を180℃に、乾燥時間を24時間にそれぞれ変更した。具体的には、底面の直径が50mmのアルミカップに含水ゲル2.0gを投入した後、試料(含水ゲル及びアルミカップ)の総質量W1(g)を正確に秤量した。次に、上記試料を、雰囲気温度180℃に設定されたオーブン内に静置した。24時間経過後、該試料を上記オーブンから取り出し、総質量W2(g)を正確に秤量した。本測定に供された含水ゲルの質量をM(g)としたときに、下記(式5)にしたがって、含水ゲルの含水率(100-α)(質量%)を求めた。なお、αは含水ゲルの固形分率(質量%)である。
粒子状含水ゲルの粒度(質量平均粒子径(D50)及び粒度分布の対数標準偏差(σζ))以下の方法で測定した。
X;分級、水切り後に各篩上に残留した含水ゲルの質量%(%)
w;分級、水切り後に各篩上に残留した含水ゲルのそれぞれの質量(g)
W;分級、水切り後に各篩上に残留した含水ゲルの総質量(g)
R(α);固形分率α(質量%)の含水ゲルに換算したときの篩の目開き(mm)
r;20質量%塩化ナトリウム水溶液中で膨潤した含水ゲル状架橋重合体(含水ゲル粒子)が分級された篩の目開き(mm)である。
上記(f)含水ゲルの固形分率(α)及び(g)粒子状含水ゲルの質量平均粒子径(D50)から、下記(式9)に従って、固形分換算の質量平均粒子径(含水ゲル粒子の乾燥後の質量平均粒子径)d1を求めた。
SolidD50=GelD50×(α/100)1/3 ・・・ (式9)
尚、ここで、(式9)中、
GelD50:含水ゲル粒子の質量平均粒子径(μm)
α:含水ゲル粒子の固形分率(質量%)
SolidD50:含水ゲル粒子の乾燥物に換算した質量平均粒子径(μm)
である。
吸水性樹脂のVortex(吸水時間)は、以下の手順にしたがって測定した。先ず、予め調整された生理食塩水(0.9質量%塩化ナトリウム水溶液)1000質量部に、食品添加物である食用青色1号(ブリリアントブルー)0.02質量部を添加した後、液温を30℃に調整した。
吸水性樹脂のAAP(加圧下吸水倍率)を、EDANA法(ERT442.2-02)に準拠して測定した。なお、測定に当たり、荷重条件を4.83kPa(0.7psi)に変更した。
アクリル酸300質量部、48質量%水酸化ナトリウム水溶液100質量部、ポリエチレングリコールジアクリレート(平均n数9)0.61質量部、0.1質量%ジエチレントリアミン5酢酸3ナトリウム水溶液16.4質量部、脱イオン水273.2質量部からなる単量体水溶液を作成した。
製造例1と同様の操作をおこなって、短冊状の含水ゲル(1b)を得た。次に、スクリュー押出機に含水ゲル(1b)を投入して、ゲル粉砕をおこなった。該スクリュー押出機としては、スクリュー軸の外径が86mmであり、先端部に直径100mm、孔径9.5mm、厚さ10mmの多孔板が備えられたミートチョッパーを使用し、含水ゲル(1b)と同時に水及び水蒸気を供給しながらゲル粉砕(第1ゲル粉砕)をおこなった。得られた粒子状含水ゲル(1d)は、固形分率が49質量%(含水率が51質量%)、固形分換算の平均粒子径d1が2000μm、粒子径150μm未満の粒子の割合が約4.9質量%であった。また粒子状含水ゲル(1d)の重合率は98.6%、CRCは34g/g、水可溶分は4%であった。
製造例1で得られた60℃の粒子状乾燥重合体(A1)100質量部に対して、エチレングリコールジグリシジルエーテル0.025質量部、エチレンカーボネート0.3質量部、プロピレングリコール0.5質量部及び脱イオン水2.0質量部からなる表面架橋剤溶液を、連続式高速撹拌乾燥機(ホソカワミクロン社製タービュライザー)にて噴霧混合して、加湿物(B1)を得た。
表面架橋剤溶液を、1,4-ブタンジオール0.4質量部、プロピレングリコール0.6質量部及び脱イオン水3.0質量部に変更した以外は実施例1と同様にして、吸水性樹脂粒子(C2)を得た。得られた吸水性樹脂粒子(C2)を目視にて観察したところ、着色異物の混入は見られなかった。この吸水性樹脂粒子(C2)の物性を下表1に示す。
表面架橋剤溶液を、エチレングリコールジグリシジルエーテル0.025質量部、プロピレングリコール1.0質量部及び脱イオン水3.0質量部に変更し、回転型加熱装置の各加熱管に導入する水蒸気をゲージ圧0.1MPa(温度120℃)として、回転容器の内表面を予め100℃超に加熱した以外は、実施例1と同様にして、吸水性樹脂粒子(C3)を得た。得られた吸水性樹脂粒子(C3)を目視にて観察したところ、着色異物の混入は見られなかった。この吸水性樹脂粒子(C3)の物性を下表1に示す。
実施例1で得た吸水性樹脂粒子(C1)30gを、ハイドロタルサイト(Mg6Al2(OH)16CO3・4H2O、体積平均粒子径0.5μm)とともに、容量225mLのマヨネーズ瓶に投入し、ペイントシェーカー(東洋精機製)を用いて3分間振動させることにより混合し、吸水性樹脂粒子(C4)を得た。ハイドロタルサイトは、100質量部の吸水性樹脂粒子(C1)に対して0.3質量部添加した。得られた吸水性樹脂粒子(C4)を目視にて観察したところ、着色異物の混入は見られなかった。この吸水性樹脂粒子(C4)の物性を下表1に示す。
ハイドロタルサイトをシリカ(日本アエロジル株式会社製の製品名「アエロジル200CF」)に変更した以外は、実施例4と同様にして、吸水性樹脂粒子(C5)を得た。得られた吸水性樹脂粒子(C5)を目視にて観察したところ、着色異物の混入は見られなかった。この吸水性樹脂粒子(C5)の物性を下表1に示す。
粒子状乾燥重合体(A1)を製造例2で得られた粒子状乾燥重合体(A2)に変更した以外は、実施例1と同様にして、吸水性樹脂粒子(C6)を得た。得られた吸水性樹脂粒子(C6)を目視にて観察したところ、着色異物の混入は見られなかった。この吸水性樹脂粒子(C6)の物性を下表1に示す。
粒子状乾燥重合体(A1)を製造例2で得られた粒子状乾燥重合体(A2)に変更した以外は、実施例2と同様にして、加湿物(B2)及び吸水性樹脂粒子(C7)を得た。得られた吸水性樹脂粒子(C7)を目視にて観察したところ、着色異物の混入は見られなかった。この吸水性樹脂粒子(C7)の物性を下表1に示す。
粒子状乾燥重合体(A1)を製造例2で得られた粒子状乾燥重合体(A2)に変更した以外は、実施例3と同様にして、吸水性樹脂粒子(C8)を得た。得られた吸水性樹脂粒子(C8)を目視にて観察したところ、着色異物の混入は見られなかった。この吸水性樹脂粒子(C8)の物性を下表1に示す。
実施例1で得られた加湿物(B1)を、図8に示される伝導伝熱式溝型撹拌乾燥機(奈良機会製作所製の製品名「パドルドライヤーNPD-1.6W型」)を用いて加熱処理した。図示される通り、この乾燥機200は、撹拌軸202、攪拌翼(パドル)204及びドラム206を備えている。この乾燥機200は、パドル径160mmφ、伝熱面積2.5m2、有効容積0.065m3であった。
表面架橋剤溶液を、エチレングリコールジグリシジルエーテル0.025質量部、プロピレングリコール1.0質量部及び脱イオン水3.0質量部に変更し、伝導伝熱式溝型撹拌乾燥機200の内壁、撹拌盤204及び回転軸202の表面温度を120℃に変更した以外は、比較例1と同様にして、吸水性樹脂粒子(C7)を得た。得られた吸水性樹脂粒子(C7)を目視にて観察したところ、わずかに着色異物の混入が見られた。この吸水性樹脂粒子(C7)の物性を下表1に示す。
加湿物(B1)を実施例7で得られた加湿物(B2)に変更した以外は、比較例1と同様にして、吸水性樹脂粒子(C11)を得た。得られた吸水性樹脂粒子(C11)を目視にて観察したところ、わずかに着色異物の混入が見られた。この吸水性樹脂粒子(C11)の物性を下表1に示す。
表面架橋剤溶液を、エチレングリコールジグリシジルエーテル0.025質量部、プロピレングリコール1.0質量部及び脱イオン水3.0質量部に変更し、伝導伝熱式溝型撹拌乾燥機200の内壁、撹拌盤204及び回転軸202の表面温度を120℃に変更した以外は、比較例3と同様にして、吸水性樹脂粒子(C12)を得た。得られた吸水性樹脂粒子(C12)を目視にて観察したところ、わずかに着色異物の混入が見られた。この吸水性樹脂粒子(C12)の物性を下表1に示す。
(1)実施例1~3及び6~8と比較例1~4との対比から、加熱管付き回転型加熱装置を用いて、含水率15質量部以下の粒子状乾燥重合体(A1)及び粒子状乾燥重合体(A2)を表面架橋することにより、微粉量が少なく、かつ着色異物の混入がない、吸水性能に優れた吸水剤が得られることがわかる。
(2)実施例4及び5の結果から、表面架橋された含水率15質量%以下の吸水性樹脂粒子(C1)の表面処理においても、加熱管付き回転型加熱装置の使用により、所定の吸水性能を低下することなく、微粉の抑制及び着色異物の低減という効果が得られることがわかる。
4・・・主部
6・・・投入部
8・・・取り出し部
10・・・回転容器
11、11a、11b・・・障壁
12・・・加熱管
14・・・第一歯車
16・・・第二歯車
18・・・パッキン
20・・・主筒
22・・・ホッパー
28・・・インナースペース
40・・・取り出し口
44・・・スチーム入口
46・・・ドレーン
200・・・攪拌乾燥機
202・・・攪拌軸
204・・・攪拌翼
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Claims (21)
- 酸基含有不飽和単量体を主成分として得られる粒子状乾燥重合体と、表面架橋剤との混合物を加熱処理する表面架橋工程を含んでおり、
上記粒子状乾燥重合体の含水率が15質量%以下であり、
上記表面架橋工程において、回転容器と、この回転容器の内部に位置して、その軸方向に延在し、かつこの回転容器とともに回転する複数の加熱管を備えた加熱装置を使用する吸水性樹脂粒子の製造方法。 - 上記加熱管に100℃以上の熱媒を供給する請求項1に記載の製造方法。
- 上記回転容器の内表面の温度が100℃以上である請求項1又は2に記載の製造方法。
- 上記粒子状乾燥重合体と表面架橋剤との混合物が投入される前に、上記回転容器の内表面の温度を100℃以上とする請求項1から3のいずれかに記載の製造方法
- 上記回転容器内にガスを導入し、上記回転容器の内表面の温度が、当該ガスの温度より高い請求項1から4のいずれかに記載の製造方法。
- 上記回転容器内に導入するガスの温度が100℃以上である請求項5に記載の乾燥方法。
- 上記表面架橋工程で表面架橋された粒子状乾燥重合体を冷却する冷却工程をさらに有する請求項1から6のいずれかに記載の製造方法。
- 上記表面架橋剤と混合される粒子状乾燥重合体の温度が、30~120℃である請求項1から7のいずれかに記載の製造方法。
- 上記表面架橋剤と混合される粒子状乾燥重合体の平均粒子径が200~1000μm以下である請求項1から8のいずれかに記載の製造方法。
- 上記加熱装置のフルード数Frが0.001~1である請求項1から9のいずれかに記載の製造方法。
- 上記粒子状乾燥重合体が、ポリ(メタ)アクリル酸(塩)を主成分とする架橋体である請求項1から10のいずれかに記載の製造方法。
- 酸基含有不飽和単量体を主成分として得られる含水率15質量%以下の粒子状乾燥重合体と、表面架橋剤との混合物を加熱処理する加熱装置であって、
上記加熱装置が、回転容器と、この回転容器の内部に位置して、その軸方向に延在し、かつこの回転容器とともに回転する複数の加熱管と、この回転容器の内部にガスを導入及び排出する手段を備えている加熱装置。 - 上記加熱管の数が5本以上であり、これらの加熱管が、軸方向において、上記回転容器の内表面と接触していない請求項12に記載の加熱装置。
- 上記回転容器の外周面に、加熱手段又は保温手段を有している請求項12又は13に記載の加熱装置。
- 上記回転容器が、その一端から他端に向かって傾斜している請求項12から14のいずれかに記載の加熱装置。
- 上記回転容器の内部に、少なくとも1つの障壁が設けられている請求項12から15のいずれかに記載の加熱装置。
- 上記障壁の開口率が1~90%である請求項16に記載の加熱装置。
- 上記加熱管の外周面の表面積と上記回転容器の内周面の面積との和である伝熱面積の、この回転容器の有効容積に対する比(伝熱面積/有効容積)が、10m-1以上である請求項12から17のいずれかに記載の加熱装置。
- 上記複数の加熱管が、上記回転容器の回転軸から径方向外側に向かって、放射状に間隔を空けて配置されている請求項12から18のいずれかに記載の加熱装置。
- 上記複数の加熱管が、上記回転容器の回転軸を中心とする2以上の同心円上に、間隔を空けて配置されている請求項12から18のいずれかに記載の加熱装置。
- 請求項12から20のいずれかに記載の加熱装置を用いて、酸基含有不飽和単量体を主成分として得られる粒子状乾燥重合体と、表面架橋剤との混合物を加熱処理する表面架橋方法であって、
上記加熱装置に投入する粒子状乾燥重合体の含水率が15質量%以下であり、
上記回転容器内に熱媒としてガスを導入し、この回転容器の内表面の温度を100℃以上とする表面架橋方法。
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Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2022024787A1 (ja) * | 2020-07-28 | 2022-02-03 | 住友精化株式会社 | 吸水性樹脂粒子の製造方法 |
WO2022035407A1 (en) * | 2020-08-13 | 2022-02-17 | Kahramanmaraş Sütçü İmam Üni̇versi̇tesi̇ | Solar-powered hybrid vacuum dryer |
WO2022071503A1 (ja) * | 2020-10-02 | 2022-04-07 | 住友精化株式会社 | 架橋重合体粒子を製造する方法 |
WO2022075258A1 (ja) * | 2020-10-07 | 2022-04-14 | 住友精化株式会社 | 吸水性樹脂粒子を製造する方法 |
EP3981827A4 (en) * | 2019-10-07 | 2022-08-10 | LG Chem, Ltd. | METHOD FOR PRODUCING A SUPERABSORBENT POLYMER |
WO2022181771A1 (ja) | 2021-02-26 | 2022-09-01 | 株式会社日本触媒 | 粒子状吸水剤、該吸水剤を含む吸収体及び該吸収体を用いた吸収性物品 |
JP2023508211A (ja) * | 2020-10-16 | 2023-03-01 | エルジー・ケム・リミテッド | 高吸水性樹脂の製造方法 |
WO2024009541A1 (ja) * | 2022-07-07 | 2024-01-11 | Sdpグローバル株式会社 | 吸水性樹脂組成物の製造方法 |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN113432408B (zh) * | 2021-08-25 | 2021-11-05 | 山东蓝湾新材料有限公司 | 一种聚丙烯酰胺干燥用分段加热热烘炉 |
WO2024126174A1 (de) * | 2022-12-14 | 2024-06-20 | Basf Se | Verfahren zur herstellung von superabsorbern |
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Citations (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5918864B2 (ja) | 1976-11-22 | 1984-05-01 | 日本電気株式会社 | 半導体ウエハ−検査装置 |
JPS6314076A (ja) * | 1986-07-01 | 1988-01-21 | 三井造船株式会社 | 回転式乾燥機の運転方法 |
JP2004352941A (ja) | 2003-05-30 | 2004-12-16 | Nippon Shokubai Co Ltd | 吸水性樹脂の製造法 |
US7265190B2 (en) | 2002-11-07 | 2007-09-04 | Nippon Shokubai Co., Ltd. | Process and apparatus for production of water-absorbent resin |
JP2008038128A (ja) | 2005-12-22 | 2008-02-21 | Nippon Shokubai Co Ltd | 吸水性樹脂の表面架橋方法および吸水性樹脂の製造方法 |
US7638570B2 (en) | 2003-02-10 | 2009-12-29 | Nippon Shokubai Co., Ltd. | Water-absorbing agent |
JP2012012482A (ja) * | 2010-06-30 | 2012-01-19 | Nippon Shokubai Co Ltd | ポリアクリル酸アンモニウム塩系吸水性樹脂およびその製造方法 |
WO2014181859A1 (ja) * | 2013-05-10 | 2014-11-13 | 株式会社日本触媒 | ポリアクリル酸(塩)系吸水性樹脂の製造方法 |
WO2015129917A1 (ja) | 2014-02-28 | 2015-09-03 | 株式会社日本触媒 | ポリ(メタ)アクリル酸(塩)系粒子状吸水剤及び製造方法 |
JP2015200499A (ja) * | 2014-03-31 | 2015-11-12 | 月島機械株式会社 | 被処理物の乾燥方法、横型回転式乾燥機 |
WO2017221911A1 (ja) * | 2016-06-20 | 2017-12-28 | 株式会社日本触媒 | 吸水剤の製造方法 |
WO2018092863A1 (ja) * | 2016-11-16 | 2018-05-24 | 株式会社日本触媒 | 吸水性樹脂粉末の製造方法、並びに粒子状含水ゲルの乾燥装置及び乾燥方法 |
Family Cites Families (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3819323A (en) | 1972-03-17 | 1974-06-25 | Midland Ross Corp | Minimum scale reheating furnace and means relating thereto |
US4412813A (en) * | 1982-02-02 | 1983-11-01 | Alco Standard Corporation | Rotary hearth furnace and method of loading and unloading the furnace |
JPS5918864U (ja) | 1982-07-28 | 1984-02-04 | ダイワ精工株式会社 | 魚釣用スピニングリ−ル |
US4763880A (en) | 1987-04-03 | 1988-08-16 | Holcroft/Loftus Inc. | Rotary hearth multi-chamber, multi-purpose furnace system |
TWI377222B (en) | 2005-12-22 | 2012-11-21 | Nippon Catalytic Chem Ind | Method for surface crosslinking water-absorbing resin and method for manufacturing water-absorbing resin |
US9567414B2 (en) * | 2011-01-28 | 2017-02-14 | Nippon Shokubai Co., Ltd. | Method for producing polyacrylic acid (salt)-based water absorbent resin powder |
EP2620466B1 (en) | 2012-01-27 | 2014-09-10 | Evonik Degussa GmbH | Heat-treatment of water-absorbing polymeric particles in a fluidized bed |
-
2019
- 2019-05-15 WO PCT/JP2019/019225 patent/WO2019221154A1/ja unknown
- 2019-05-15 KR KR1020207036272A patent/KR102629476B1/ko active IP Right Grant
- 2019-05-15 US US17/055,249 patent/US12030997B2/en active Active
- 2019-05-15 JP JP2020519878A patent/JP7174756B2/ja active Active
- 2019-05-15 EP EP19803632.9A patent/EP3795616A4/en active Pending
- 2019-05-15 CN CN201980032381.2A patent/CN112135864B/zh active Active
Patent Citations (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5918864B2 (ja) | 1976-11-22 | 1984-05-01 | 日本電気株式会社 | 半導体ウエハ−検査装置 |
JPS6314076A (ja) * | 1986-07-01 | 1988-01-21 | 三井造船株式会社 | 回転式乾燥機の運転方法 |
US7265190B2 (en) | 2002-11-07 | 2007-09-04 | Nippon Shokubai Co., Ltd. | Process and apparatus for production of water-absorbent resin |
US7638570B2 (en) | 2003-02-10 | 2009-12-29 | Nippon Shokubai Co., Ltd. | Water-absorbing agent |
JP2004352941A (ja) | 2003-05-30 | 2004-12-16 | Nippon Shokubai Co Ltd | 吸水性樹脂の製造法 |
JP2008038128A (ja) | 2005-12-22 | 2008-02-21 | Nippon Shokubai Co Ltd | 吸水性樹脂の表面架橋方法および吸水性樹脂の製造方法 |
JP2012012482A (ja) * | 2010-06-30 | 2012-01-19 | Nippon Shokubai Co Ltd | ポリアクリル酸アンモニウム塩系吸水性樹脂およびその製造方法 |
WO2014181859A1 (ja) * | 2013-05-10 | 2014-11-13 | 株式会社日本触媒 | ポリアクリル酸(塩)系吸水性樹脂の製造方法 |
WO2015129917A1 (ja) | 2014-02-28 | 2015-09-03 | 株式会社日本触媒 | ポリ(メタ)アクリル酸(塩)系粒子状吸水剤及び製造方法 |
JP2015200499A (ja) * | 2014-03-31 | 2015-11-12 | 月島機械株式会社 | 被処理物の乾燥方法、横型回転式乾燥機 |
WO2017221911A1 (ja) * | 2016-06-20 | 2017-12-28 | 株式会社日本触媒 | 吸水剤の製造方法 |
WO2018092863A1 (ja) * | 2016-11-16 | 2018-05-24 | 株式会社日本触媒 | 吸水性樹脂粉末の製造方法、並びに粒子状含水ゲルの乾燥装置及び乾燥方法 |
Non-Patent Citations (1)
Title |
---|
See also references of EP3795616A4 |
Cited By (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP3981827A4 (en) * | 2019-10-07 | 2022-08-10 | LG Chem, Ltd. | METHOD FOR PRODUCING A SUPERABSORBENT POLYMER |
WO2022024787A1 (ja) * | 2020-07-28 | 2022-02-03 | 住友精化株式会社 | 吸水性樹脂粒子の製造方法 |
WO2022035407A1 (en) * | 2020-08-13 | 2022-02-17 | Kahramanmaraş Sütçü İmam Üni̇versi̇tesi̇ | Solar-powered hybrid vacuum dryer |
WO2022071503A1 (ja) * | 2020-10-02 | 2022-04-07 | 住友精化株式会社 | 架橋重合体粒子を製造する方法 |
WO2022075258A1 (ja) * | 2020-10-07 | 2022-04-14 | 住友精化株式会社 | 吸水性樹脂粒子を製造する方法 |
JP2023508211A (ja) * | 2020-10-16 | 2023-03-01 | エルジー・ケム・リミテッド | 高吸水性樹脂の製造方法 |
JP7436119B2 (ja) | 2020-10-16 | 2024-02-21 | エルジー・ケム・リミテッド | 高吸水性樹脂の製造方法 |
WO2022181771A1 (ja) | 2021-02-26 | 2022-09-01 | 株式会社日本触媒 | 粒子状吸水剤、該吸水剤を含む吸収体及び該吸収体を用いた吸収性物品 |
WO2024009541A1 (ja) * | 2022-07-07 | 2024-01-11 | Sdpグローバル株式会社 | 吸水性樹脂組成物の製造方法 |
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