WO2015072536A1 - ポリアクリル酸(塩)系吸水性樹脂の製造方法 - Google Patents
ポリアクリル酸(塩)系吸水性樹脂の製造方法 Download PDFInfo
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- WO2015072536A1 WO2015072536A1 PCT/JP2014/080156 JP2014080156W WO2015072536A1 WO 2015072536 A1 WO2015072536 A1 WO 2015072536A1 JP 2014080156 W JP2014080156 W JP 2014080156W WO 2015072536 A1 WO2015072536 A1 WO 2015072536A1
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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
- B01J20/261—Synthetic macromolecular compounds obtained by reactions only involving carbon to carbon unsaturated bonds
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
- A61L15/00—Chemical aspects of, or use of materials for, bandages, dressings or absorbent pads
- A61L15/16—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons
- A61L15/22—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons containing macromolecular materials
- A61L15/24—Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds; Derivatives thereof
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
- A61L15/00—Chemical aspects of, or use of materials for, bandages, dressings or absorbent pads
- A61L15/16—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons
- A61L15/42—Use of materials characterised by their function or physical properties
- A61L15/60—Liquid-swellable gel-forming materials, e.g. super-absorbents
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/1418—Recovery of products
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/1487—Removing organic compounds
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/1493—Selection of liquid materials for use as absorbents
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/38—Removing components of undefined structure
- B01D53/44—Organic components
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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
- B01J20/3085—Chemical treatments not covered by groups B01J20/3007 - B01J20/3078
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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
- C08F2/00—Processes of polymerisation
- C08F2/04—Polymerisation in solution
- C08F2/10—Aqueous solvent
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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
- C08F6/00—Post-polymerisation treatments
- C08F6/001—Removal of residual monomers by physical means
- C08F6/003—Removal of residual monomers by physical means from polymer solutions, suspensions, dispersions or emulsions without recovery of the polymer therefrom
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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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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2252/00—Absorbents, i.e. solvents and liquid materials for gas absorption
- B01D2252/10—Inorganic absorbents
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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
Definitions
- the present invention relates to a method for producing a polyacrylic acid (salt) water-absorbing resin. More specifically, the polyacrylic acid further includes a step (gas absorption step) of absorbing gas discharged from the production step of the polyacrylic acid (salt) -based water absorbent resin including a polymerization step, a drying step, a surface cross-linking step, and the like.
- the present invention relates to a method for producing a (salt) water-absorbing resin.
- Water-absorbing resin (SAP / Super Absorbent Polymer) is a water-swellable, water-insoluble polymer gelling agent, such as sanitary products such as paper diapers and sanitary napkins, agricultural and horticultural water retention agents, industrial water-stopping agents, etc. , Mainly used in disposable applications.
- sanitary products such as paper diapers and sanitary napkins, agricultural and horticultural water retention agents, industrial water-stopping agents, etc.
- Such a water-absorbing resin uses many monomers and hydrophilic polymer compounds as raw materials. Among them, polyacrylic acid (salt) water-absorbing resins using acrylic acid and / or a salt thereof are most frequently used industrially because of their high water absorption performance.
- Non-Patent Document 1 Such a water-absorbing resin is produced as a particulate product through polymerization, drying, pulverization, classification, surface crosslinking, etc.
- Non-Patent Document 1 polymerization, drying, heat treatment (surface crosslinking)
- the exhaust gas contains raw materials for the water-absorbing resin (monomers, crosslinking agents, water, organic solvents, etc.), and these substances need to be collected.
- any stage of a process for producing waste water generated from acrylic acid and polyacrylic acid production processes (Patent Document 1), a water-absorbing resin, and a raw monomer aqueous solution thereof.
- Patent Documents 2 to 4 For scrubbing the exhaust gas removed from the reactor with a basic aqueous solution (Patent Documents 2 to 4), and for recycling water and monomer vapor generated in the polymerization process to the monomer aqueous solution and the polymerization process (Patent Document) 5 to 11) are disclosed.
- the liquid property of the exhaust gas absorption liquid is preferably adjusted to alkaline, but if the alkalinity is excessively increased, There was a problem that the amount of water-insoluble polyvalent metal salt produced by the reaction with polyvalent metal ions rapidly increased, and the absorption tower was easily clogged. When clogging occurs in the exhaust gas absorption tower, cleaning or the like is necessary, and production must be temporarily stopped. Therefore, since it takes time to adjust the polymerization temperature and the surface treatment temperature immediately after re-operation, there arises a problem that the physical properties of the water-absorbent resin immediately after re-operation are not stable.
- Patent Documents 1 to 4 disclose a technique for absorbing exhaust gas with a basic aqueous solution, but there is no technique for eliminating clogging in the exhaust gas absorption tower. It was not revealed.
- the present invention has been made in view of the above problems, and an object of the present invention is to provide a stable and continuous method for producing a water-absorbent resin by suppressing clogging in an exhaust gas absorption tower. Furthermore, it is providing the manufacturing method of the stable and continuous water absorbing resin including the efficient and continuous gas absorption process of the gas discharged
- the inventors have conducted intensive studies. As a result, in order to suppress clogging in the exhaust gas absorption tower, the pH of the exhaust gas absorption liquid is adjusted to a specific range, and the exhaust gas absorption liquid is adjusted. It has been found that it is necessary to reduce the amount of polyvalent metal ions and electrolyte contained below a certain value.
- the present invention uses a gas discharged from the production process of a polyacrylic acid (salt) water-absorbing resin, having a pH of 7 to 11 and a polyvalent metal.
- a method for producing a polyacrylic acid (salt) -based water-absorbing resin further comprising a step of absorbing water with an ion content of 100 ppm or less.
- the present invention uses a gas discharged from the production process of a polyacrylic acid (salt) water-absorbing resin, with an electric conductivity at 25 ° C. of 500 ( ⁇ S / cm) or less of water and an alkali compound are mixed to be absorbed in water having a pH adjusted to 7 to 11, and a method for producing a polyacrylic acid (salt) -based water absorbent resin is further provided.
- the exhaust gas absorption process for absorbing the exhaust gas discharged from the water absorbent resin manufacturing process is continuously operated, the generation of water-insoluble salts that cause clogging in the exhaust gas absorption tower is suppressed. It becomes possible to do. As a result, the exhaust gas absorption treatment can be continued for a long time. In particular, the exhaust gas absorption treatment performance and treatment efficiency can be improved, the occurrence frequency of clogging is very low, and the running cost can be reduced without interrupting the production of the water absorbent resin.
- FIG. 1 is a schematic diagram showing an embodiment of the present invention.
- Water absorbent resin refers to a water-swellable, water-insoluble polymer gelling agent and satisfies the following physical properties. That is, as “water swellability”, the CRC specified by ERT441.2-02 is 5 g / g or more, and as “water-insoluble”, Ext specified by ERT470.2-02 is 50% by weight or less. It refers to a polymer gelling agent that satisfies the above.
- the water-absorbing resin can be designed as appropriate according to its use and is not particularly limited, but is preferably a hydrophilic cross-linked polymer obtained by cross-linking an unsaturated monomer having a carboxyl group. Moreover, the whole amount (100 weight%) is not limited to the form which is a polymer, The water absorbing resin composition containing the additive etc. may be sufficient in the range which satisfies the said physical property (CRC, Ext).
- the water-absorbent resin in the present invention is not limited to the final product, but is an intermediate in the manufacturing process of the water-absorbent resin (for example, a water-containing gel-like crosslinked polymer after polymerization, a dried polymer after drying, a water absorption before surface crosslinking).
- a water-containing gel-like crosslinked polymer after polymerization for example, a water-containing gel-like crosslinked polymer after polymerization, a dried polymer after drying, a water absorption before surface crosslinking.
- water-absorbent resin examples of the shape of the water absorbent resin include a sheet shape, a fiber shape, a film shape, a particle shape, and a gel shape.
- a particulate water absorbent resin is preferable.
- polyacrylic acid (salt) refers to polyacrylic acid and / or a salt thereof, and acrylic acid and / or a salt thereof (hereinafter referred to as “acrylic acid (salt)”) as a main component.
- acrylic acid (salt) acrylic acid and / or a salt thereof
- the “main component” means that the amount (content) of acrylic acid (salt) used is usually 50 to 100 mol%, preferably 50% to 100% by mole, preferably based on the total amount of monomers (excluding the internal crosslinking agent) used in the polymerization. 70 to 100 mol%, more preferably 90 to 100 mol%, still more preferably substantially 100 mol%.
- the polyacrylic acid salt essentially contains a water-soluble salt, preferably a monovalent salt, more preferably an alkali metal salt or an ammonium salt.
- EDANA European Disposables and Nonwovens Associations
- ERT is an abbreviation for a method of measuring water-absorbent resin of the European standard (almost the world standard) (EDANA Recommended Test Methods). .
- the physical properties of the water-absorbent resin are measured according to the original ERT (revised in 2002 / known literature).
- CRC is an abbreviation for Centrifugal 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 a water-absorbing resin was put in a nonwoven fabric, and then freely swollen by immersion in a large excess of 0.9 wt% sodium chloride aqueous solution for 30 minutes, and then drained with a centrifuge (250 G). It means the water absorption ratio (unit; g / g) after
- Extractables which means the water-soluble component (water-soluble component amount) of the water-absorbent resin. Specifically, for 1.0 g of water-absorbing resin, a value obtained by measuring the amount of dissolved polymer after stirring for 16 hours at 500 rpm with respect to 200 ml of 0.9 wt% aqueous sodium chloride solution (unit: wt%) ).
- AAP is an abbreviation for Absorption against Pressure, which means the water absorption capacity of a water absorbent resin under pressure. Specifically, 0.9 g of the water-absorbing resin was swollen under a load of 0.3 psi (2.06 kPa, 21 g / cm 2 ) for 1 hour against a large excess of 0.9 wt% sodium chloride aqueous solution. It refers to the subsequent water absorption ratio (unit: g / g). In some cases, the load condition is changed to 0.7 psi (4.83 kPa, 49 g / cm 2 ).
- Liquid permeability “Liquid permeability” of the water-absorbent resin refers to the fluidity of the liquid passing between the particles of the swollen gel under load or no load.
- SFC Seline Flow Conductivity / Saline flow conductivity
- GBP Gel Bed Permeability / gel bed permeability
- SFC Seline Flow Inducibility
- GFP gel bed permeability
- Water absorption speed The “water absorption rate” of the water absorbent resin refers to the speed at which a certain amount of aqueous liquid is absorbed, and “FSR” and “Vortex” (unit: seconds) are typical measurement methods. is there. In addition, the water absorption speed in this invention was evaluated by FSR. “FSR” is an abbreviation for Free Swell Rate. Specific measurement methods will be described in the examples described later.
- X to Y indicating a range means “X or more and Y or less”.
- t (ton) as a unit of weight means “Metric ton”
- ppm means “weight ppm” or “mass ppm”.
- weight and “mass”, “parts by weight” and “parts by mass”, “% by weight” and “% by mass” are treated as synonyms.
- ⁇ acid (salt) means “ ⁇ acid and / or salt thereof”
- (meth) acryl means “acryl and / or methacryl”.
- liter may be described as “l” or “L”
- wt% may be described as “wt%”.
- D Non Detected
- the gas discharged from the polyacrylic acid (salt) water absorbent resin production process has a pH of 7 to 11 and a polyacrylic acid (salt) water-absorbing resin production method, further comprising a step of absorbing the polyvalent metal ion in water of 100 ppm or less.
- the manufacturing process of the polyacrylic acid (salt) water-absorbing resin common to the first and second inventions of the present invention will be described, and the exhaust gas absorption process will be described in the next section [3]. .
- This step is a step of preparing and preparing an aqueous solution containing acrylic acid (salt) as a main component (hereinafter referred to as “monomer aqueous solution”).
- a monomer slurry liquid can be used as long as the water absorption performance is not deteriorated. However, in this section, the monomer aqueous solution will be described for convenience.
- this step includes a neutralization step (neutralization reaction) as shown below. Therefore, a part of acrylic acid may be volatilized by the heat of neutralization generated by the neutralization reaction, and the generated gas is supplied to the exhaust gas absorption process as necessary.
- neutralization reaction neutralization reaction
- acrylic acid is used as a monomer from the viewpoint of the effects of the invention.
- the acrylic acid may be a known one, and the polymerization inhibitor preferably contains phenols, more preferably methoxyphenols. Further, the concentration of the polymerization inhibitor is preferably 1 to 200 ppm, more preferably 10 to 160 ppm, from the viewpoint of the polymerizability of acrylic acid and the color tone of the water absorbent resin.
- a water-absorbing resin can also be produced by using a monomer other than acrylic acid (salt) (hereinafter referred to as “other monomer”) in combination with acrylic acid (salt).
- other monomer a monomer other than acrylic acid (salt)
- water-soluble or hydrophobic unsaturated monomer is mentioned. Specific examples include monomers (excluding acrylic acid) disclosed in paragraph [0035] of US Patent Application Publication No. 2005/215734.
- the water-absorbing resin obtained by the production method according to the present invention includes those having the above water-soluble or hydrophobic unsaturated monomer as a copolymerization component.
- the “basic composition” means a composition containing a basic compound, such as a commercially available sodium hydroxide aqueous solution.
- the basic compound examples include alkali metal carbonates and hydrogen carbonates, alkali metal hydroxides, ammonia, and organic amines.
- alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide are preferable, and sodium hydroxide is particularly preferable.
- the water-absorbing resin of the present invention is polyacrylic acid (salt) obtained by crosslinking polymerization of acrylic acid (salt). Therefore, in order to obtain the polyacrylic acid (salt), it is preferable to have a step of neutralizing acrylic acid with the basic composition (neutralization step).
- neutralization process in addition to neutralization of the monomer acrylic acid, neutralization of the hydrogel crosslinked polymer obtained by crosslinking polymerization of acrylic acid (hereinafter referred to as “post-neutralization”). ) Is also included. These neutralizations may be continuous or batch, but continuous is preferred from the viewpoint of production efficiency. Moreover, these neutralization can also be used together.
- the acrylate obtained in the neutralization step is a substantially monovalent salt.
- a very small amount of 5 mol% or less may be used as a polyvalent metal salt.
- the neutralization rate in the present invention is preferably 10 to 90 mol%, more preferably 40 to 85 mol%, still more preferably 50 to 80 mol%, particularly preferably 60 to 90 mol% based on the acid group of the monomer. 75 mol%.
- the neutralization rate is less than 10 mol%, water absorption magnification may fall remarkably.
- the said neutralization rate exceeds 90 mol%, a water absorbing resin with a high water absorption capacity under pressure may not be obtained.
- the neutralization rate is the same even in the case of post-neutralization.
- the said neutralization rate is applied also about the neutralization rate of the water absorbing resin as a final product.
- Internal crosslinking agent examples include compounds having two or more substituents capable of reacting with acrylic acid, and specific examples include compounds disclosed in column 14 of US Pat. No. 6,241,928. . Of these, one or more compounds are used.
- a compound having two or more polymerizable unsaturated groups is preferable, more preferably a compound having thermal decomposability at about the drying temperature described below, and more preferably ( And compounds having two or more polymerizable unsaturated groups having a poly) alkylene glycol structural unit.
- the polymerizable unsaturated group is preferably an allyl group or a (meth) acrylate group, more preferably a (meth) acrylate group.
- the alkylene glycol structural unit is preferably polyethylene glycol, and the n number is preferably 1 to 100, more preferably 6 to 50. The above “average n number” means the average number of methylene chain polymerizations in the polyethylene glycol chain.
- the amount of the internal crosslinking agent used is preferably 0.005 to 2 mol%, more preferably 0.01 to 1 mol%, and still more preferably 0.05 to 0.5 mol%, based on the monomer. is there. By setting the amount to be used within the above range, a desired water absorbent resin can be obtained.
- a method in which a predetermined amount of an internal cross-linking agent is previously added to the monomer aqueous solution and a cross-linking reaction is performed simultaneously with the polymerization is preferably applied.
- an internal crosslinking agent was added during or after polymerization, a method of post-crosslinking, a method of radical crosslinking using a radical polymerization initiator, active energy rays such as electron beams and ultraviolet rays were used.
- a method of radiation crosslinking or the like can also be employed.
- said method can also be used together.
- the water-soluble resin or water-absorbing resin is preferably 50% by weight or less, more preferably 20% by weight or less, still more preferably 10% by weight or less, and particularly preferably 5% by weight or less (the lower limit is 0% by weight).
- a foaming agent such as carbonates, azo compounds and bubbles, surfactants, chelating agents, chain transfer agents and the like are preferably 5% by weight or less, more preferably 1% by weight or less, still more preferably 0.8%. Or 5% by weight or less (the lower limit is 0% by weight).
- a graft polymer or a water-absorbent resin composition for example, starch-acrylic acid polymer, PVA-acrylic acid polymer, etc.
- Combined and water-absorbing resin compositions are also within the category of the polyacrylic acid (salt) -based water-absorbing resin of the present invention.
- the concentration of the monomer component in the aqueous monomer solution is not particularly limited, but is preferably 10 to 80% by weight, more preferably 20 to 75% by weight, from the viewpoint of physical properties of the water absorbent resin. More preferably, it is 30 to 70% by weight.
- the below-mentioned range is applied preferably.
- the “concentration of the monomer component” is a value calculated from the following formula (1).
- the monomer aqueous solution includes a graft component, a water absorbent resin, and a reverse phase suspension polymerization. Hydrophobic solvents are not included.
- This step is a step of polymerizing the monomer aqueous solution obtained in the monomer aqueous solution preparation step to obtain a hydrated gel-like crosslinked polymer (hereinafter referred to as “hydrated gel”). It is.
- hydrated gel a hydrated gel-like crosslinked polymer
- a part of acrylic acid may be volatilized by the generated heat of polymerization, and the generated gas is supplied to the exhaust gas absorption step as necessary.
- Polymerization initiator examples include a thermally decomposable polymerization initiator, a photodegradable polymerization initiator, or a redox polymerization initiator used in combination with a reducing agent that promotes the decomposition of these polymerization initiators. Specific examples include compounds disclosed in column 5 of US Pat. No. 7,265,190. Of these, one or more compounds are used.
- a peroxide or an azo compound more preferably a peroxide, and still more preferably a persulfate is used.
- the amount of the polymerization initiator used is preferably 0.001 to 1 mol%, more preferably 0.001 to 0.5 mol%, based on the monomer.
- the amount of the reducing agent used is preferably 0.0001 to 0.02 mol% with respect to the monomer.
- the polymerization reaction can also be carried out by irradiating active energy rays such as electron beams and ultraviolet rays. Moreover, these can also be used together.
- the polymerization form applied to the present invention is not particularly limited, but is preferably spray polymerization, droplet polymerization, aqueous solution polymerization, reverse phase suspension polymerization from the viewpoint of water absorption performance of the water absorbent resin and ease of polymerization control. More preferably, aqueous solution polymerization, reverse phase suspension polymerization, still more preferably aqueous solution polymerization, and particularly preferably continuous aqueous solution polymerization.
- continuous aqueous solution polymerization examples include continuous belt polymerization and continuous kneader polymerization.
- continuous belt polymerization U.S. Pat. Nos. 4,893,999 and 6,241,928, U.S. Patent Application Publication No. 2005/215734, etc.
- continuous kneader polymerization disclosed in U.S. Pat. Nos. 6,987,151 and 6,710,141, respectively.
- the contents applied are applied to the present invention.
- the production efficiency of the water-absorbent resin is improved.
- polymerization process is efficiently supplied to a gas absorption tower, it is preferable.
- preferred embodiments of the continuous aqueous solution polymerization include high temperature initiation polymerization and high concentration polymerization.
- the “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, still more preferably 40 ° C. or higher, particularly preferably 50 ° C. or higher (the upper limit is that of the monomer aqueous solution).
- “high concentration polymerization” means that the concentration of the monomer component is preferably 30% by weight or more, more preferably 35% by weight or more, and still more preferably 40% by weight. % Or more, particularly preferably 45% by weight or more (upper limit is 80% by weight), and then the polymerization is started.
- the solid concentration can also be increased during the polymerization.
- the increase in the solid content concentration is defined by the following formula (2) as “solid content increase degree”.
- the degree of increase in the solid content is preferably 1% by weight or more, more preferably 2% by weight or more.
- the “solid content concentration of the monomer aqueous solution” is a value defined by the following formula (3).
- the “component weight in the polymerization system” refers to the total weight of the monomer aqueous solution, graft component, water-absorbing resin and other solid components (for example, water-insoluble fine particles).
- the hydrophobic solvent used in suspension polymerization or the like is not included. That is, the “solid content concentration of the monomer aqueous solution” refers to the concentration of the component that is solidified by polymerization.
- the polymerization is preferably performed in an inert gas atmosphere such as nitrogen or argon, and the oxygen concentration is controlled in an atmosphere of 1% by volume or less. Is more preferable.
- the dissolved oxygen in the monomer or the monomer aqueous solution is sufficiently substituted with an inert gas (for example, the dissolved oxygen concentration is less than 1 (mg / l)).
- it can also be set as foaming polymerization which superpose
- the polymerization rate of the hydrogel obtained after polymerization is preferably 90 mol% or more, more preferably 95 mol% or more, still more preferably 98 mol% or more, and particularly preferably 99 mol% or more.
- the upper limit is preferably 99.99 mol% or less, more preferably 99.9 mol% or less, still more preferably 99.8 mol% or less.
- the polymerization rate is less than 90 mol%, there are many residual monomers in the water-absorbent resin, while when the polymerization rate exceeds 99.99 mol%, it takes more polymerization time than necessary, and the productivity decreases. It is not preferable. Furthermore, depending on the case, the physical properties (relationship between water absorption and soluble content) of the water-absorbent resin after drying are lowered.
- the present invention it is not necessary to advance the polymerization excessively, and it is possible to reduce the residual monomer in the drying step described below, particularly in the hot air drying step, and as a result, productivity can be improved. Furthermore, clogging in the gas absorption tower, which is a problem when absorbing the gas discharged from the drying process, is reduced, which is preferable.
- the gel pulverization form applied to the present invention is not particularly limited, and examples thereof include a method disclosed in International Publication No. 2011/126079.
- the weight average particle diameter (D50) of the particulate hydrogel obtained by such gel pulverization is preferably 4000 ⁇ m or less, more preferably 2000 ⁇ m or less.
- the surface area is increased, so that the residual monomer (particularly acrylic acid) is likely to volatilize, and the residual monomer can be reduced.
- pulverization process is efficiently supplied to a gas absorption tower, it is preferable.
- This step is a step of obtaining a dry polymer by drying the particulate hydrogel obtained in the polymerization step and / or the gel grinding step to a desired solid content concentration.
- a part of acrylic acid may volatilize with the heat at the time of drying, and the gas generated in that case is supplied to an exhaust gas absorption process as needed.
- fine particles fine gel, fine particles after drying contained in the particulate hydrous gel may be scattered by hot air. At this time, the scattered fine particles preferably have a particle size of 2 mm or less, more preferably 0.5 mm. The following is supplied to the exhaust gas absorption step together with the exhaust gas.
- the drying form applied to the present invention is not particularly limited, but is heat drying, hot air drying, vacuum drying, fluidized bed drying, infrared drying, microwave drying, drum dryer drying, azeotropic dehydration with a hydrophobic organic solvent.
- Various drying methods such as drying and high-humidity drying using high-temperature steam can be applied.
- hot air drying is preferable as a drying form suitable for the present invention, and band drying in which hot air drying is performed on a ventilation belt is particularly preferable.
- the hot air temperature (drying temperature) is preferably 100 to 300 ° C., more preferably 120 to 220 ° C., and still more preferably 160 to 200 ° C.
- the wind speed of the hot air is preferably 3.0 (m / s) or less, more preferably 0.5 to 2.0 (m / s) or less.
- the drying time is appropriately determined, but is preferably 1 minute to 10 hours, more preferably 5 minutes to 3 hours, and still more preferably 10 minutes to 1 hour.
- the water content can be controlled to a desired range, and further, the deterioration of the color tone and water absorption performance of the obtained water absorbent resin can be suppressed. Can do.
- the solid content concentration of the dry polymer obtained in this step is preferably 80% by weight or more, more preferably 85 to 99% by weight, still more preferably 90 to 98% by weight, and particularly preferably 92 to 97% by weight.
- concentration is calculated
- the hot air drying is excellent in drying efficiency and physical properties of the water-absorbing resin, it has a problem that the monomer and the water-absorbing resin are easily mixed in the hot air. Therefore, it is important to collect monomers and water-absorbing resins in the exhaust gas from the environmental aspect. Therefore, by applying the present invention, continuous production can be performed without interrupting production of the water absorbent resin.
- Pulverization step classification step
- the dried polymer obtained in the above drying step is pulverized (pulverization step), adjusted to a predetermined particle size (classification step), and the water-absorbent resin powder (surface
- classification step is a step of obtaining a particulate water-absorbing resin before crosslinking, for convenience, as “water-absorbing resin powder”.
- the equipment used in the pulverization step of the present invention is not particularly limited, and examples thereof 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 are used together 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 a JIS standard sieve (JIS Z8801-1 (2000)), airflow classification, and the like.
- the particle size of the water-absorbing resin is not limited to the pulverization step and the classification step, and is appropriately determined in the polymerization step (especially reverse phase suspension polymerization, spray polymerization, droplet polymerization) and other steps (for example, granulation step). Can be adjusted.
- the weight average particle size (D50) is preferably 200 to 600 ⁇ m, more preferably 200 to 550 ⁇ m, still more preferably 250 to 500 ⁇ m, and particularly preferably 350 to 450 ⁇ m.
- the proportion of particles having a particle size of less than 150 ⁇ m is preferably 10% by weight or less, more preferably 5% by weight or less, still more preferably 1% by weight or less (the lower limit is 0% by weight), and the particle size is 850 ⁇ m or more.
- the proportion of the particles is preferably 5% by weight or less, more preferably 3% by weight or less, still more preferably 1% by weight or less (the lower limit is 0% by weight).
- the logarithmic standard deviation ( ⁇ ) of the particle size distribution is preferably 0.20 to 0.50, more preferably 0.25 to 0.45, and still more preferably 0.30 to 0.40.
- the above particle size applies not only to the water-absorbing resin after surface cross-linking (hereinafter referred to as “water-absorbing resin particles” for convenience) but also to the water-absorbing resin as a final product. Therefore, it is desired that the surface is crosslinked so as to maintain the particle size in the above range.
- This step is a step of providing a portion having a high cross-linking density in the surface layer of the water-absorbent resin powder obtained through the above-described steps (portion of several tens of micrometers from the surface of the water-absorbent resin powder) , A mixing step, a heat treatment step and, if necessary, a cooling step.
- surface-crosslinked water-absorbing resin (water-absorbing resin particles) is obtained by radical polymerization or surface polymerization on the surface of the water-absorbing resin powder, a cross-linking reaction with a surface cross-linking agent, or the like.
- acrylic acid and a part of the surface cross-linking agent may be volatilized by reaction heat during the heat treatment, and the generated gas is supplied to the exhaust gas absorption step as necessary.
- fine powder contained in the water-absorbent resin powder is scattered by hot air. At that time, the scattered fine particles are supplied to the exhaust gas absorption step together with the exhaust gas.
- the surface cross-linking agent used in the present invention is preferably various organic or inorganic surface cross-linking agents, more preferably a covalent bond by reacting with a carboxyl group from the viewpoint of water absorption performance of the water-absorbent resin and handling of the surface cross-linking agent.
- An organic surface cross-linking agent that forms Specifically, surface cross-linking agents disclosed in columns 9 to 10 of US Pat. No. 7,183,456 can be mentioned. Of these, one or more surface cross-linking agents are used.
- a hydrophilic organic solvent can also be used as needed.
- the amount of the surface cross-linking agent used is preferably 0.01 to 10 parts by weight, more preferably 0.01 to 5 parts by weight per 100 parts by weight of the water-absorbent resin powder. Part.
- the surface crosslinking agent is preferably added as an aqueous solution.
- the amount of water used is preferably 0.1 to 20 parts by weight, more preferably 0, relative to 100 parts by weight of the water absorbent resin powder. .5 to 10 parts by weight.
- the amount used when using a hydrophilic organic solvent as required is preferably 10 parts by weight or less, more preferably 5 parts by weight or less, with respect to 100 parts by weight of the water-absorbent resin powder.
- This mixing step is a step of obtaining a mixture by mixing the water absorbent resin powder and the surface cross-linking agent.
- the method for adding and mixing the surface cross-linking agent is not particularly limited, but after preparing the surface cross-linking agent and water as a solvent, a hydrophilic organic solvent, or a mixture thereof in advance, the water-absorbent resin powder is sprayed. Or it is preferable to add and mix by dripping, and it is more preferable to add and mix by spraying.
- the equipment used for the mixing is not particularly limited, but preferably a high-speed stirring type mixer, more preferably a high-speed stirring type continuous mixer.
- This heat treatment step is a step of obtaining water absorbent resin particles by heat-treating the mixture of the water absorbent resin powder and the surface cross-linking agent.
- the equipment used for the heat treatment is not particularly limited, but preferably includes a paddle dryer.
- the temperature during the heat treatment is preferably 80 to 250 ° C, more preferably 100 to 220 ° C.
- the heating time is preferably 1 minute to 2 hours. Note that the combination of the temperature during the heat treatment and the heating time is preferably 0.1 to 1.5 hours at 180 ° C., 0.1 to 1 hour at 200 ° C., and the like.
- This cooling process is an arbitrary process installed as necessary after the heat treatment process.
- the equipment used in the cooling process is not particularly limited, but equipment having the same specifications as the equipment used in the heat treatment process is preferable, and a paddle dryer is more preferable. It is because it can be used as a cooler by using a refrigerant instead of the heat medium.
- Rehumidification step comprises adding, as additives, the water-absorbent resin particles obtained in the surface cross-linking step, as polyvalent metal salt compounds, polycationic polymers, chelating agents, inorganic reducing agents and ⁇ -hydroxy In this step, at least one compound selected from the group consisting of carboxylic acid compounds is added. In the rehumidification step, acrylic acid and some of the additives may be volatilized, and the gas generated at that time is supplied to the exhaust gas absorption step as necessary.
- the above-mentioned additive is preferably added as an aqueous solution or slurry, and the water-absorbing resin is again swollen with water, so this step is referred to as a “rehumidification step”.
- heating or drying is performed as necessary to control the water content of the resulting water-absorbent resin to preferably 1 to 10% by weight, more preferably 2 to 9% by weight.
- the above additives may be added and mixed simultaneously with the above-described surface cross-linking agent, or may be added separately from the surface cross-linking agent in the surface cross-linking step.
- a polyvalent metal salt compound and / or cationic polymer it is preferable to add a polyvalent metal salt compound and / or a cationic polymer from the viewpoint of the water absorption performance of the resulting water absorbent resin.
- the water absorption rate (for example, FSR) and liquid permeability (for example, SFC) of the water absorbent resin can be improved, and the fluidity at the time of moisture absorption can also be improved.
- a chelating agent in this invention, it is preferable to add a chelating agent from a viewpoint of the physical property of the water-absorbing resin obtained. By adding the compound, deterioration or deterioration of the color tone of the water-absorbent resin can be suppressed or prevented.
- Inorganic reducing agent In this invention, it is preferable to add an inorganic reducing agent from a viewpoint of the physical property of the water absorbent resin obtained. By adding the compound, it is possible to suppress or prevent the color tone deterioration and deterioration of the water-absorbent resin, and further reduce the residual monomer.
- ⁇ -hydroxycarboxylic acid compound In the present invention, it is preferable to add an ⁇ -hydroxycarboxylic acid compound from the viewpoint of the physical properties of the resulting water-absorbent resin. By adding the compound, deterioration of the color tone of the water-absorbent resin can be suppressed or prevented.
- ⁇ -hydroxycarboxylic acid compound refers to a carboxylic acid having a hydroxyl group in the molecule or a salt thereof, and is a compound having a hydroxyl group at the ⁇ -position.
- additives include surfactants, oxidizing agents, organic reducing agents, water-insoluble inorganic fine particles, organic powders such as metal soaps, deodorants, antibacterial agents, compounds having phosphorus atoms, pulp and thermoplastic fibers. Can be mentioned.
- a surfactant disclosed in International Publication No. 2005/077500 is preferably applied as the surfactant.
- the surfactant may be added to the aqueous monomer solution as described in (2-1) above, or may be added to the water-absorbent resin after surface crosslinking.
- the amount of the additive used is not particularly limited as long as it is appropriately set depending on the application, but is preferably 5% by weight or less, more preferably 3% by weight or less, and further preferably 1% by weight or less (the lower limit is 0% by weight). %).
- the particle size adjusting step includes a fine powder removing step after the surface cross-linking step, and a pulverizing step and a classification step that are performed when the water-absorbing resin aggregates and exceeds a desired size.
- the fine powder reuse step includes a step of adding the fine powder as it is or making it into a large hydrogel in the granulation step and adding it to any of the production steps of the water absorbent resin.
- This step is a step in which a water-absorbing resin as a final product manufactured through at least a part of the above-described steps is filled into a filling container such as a container bag or a paper bag.
- the water-absorbent resin filled in the filling container is shipped after undergoing a predetermined inspection.
- the filling unit may be appropriately set according to the shipment form, and is preferably 100 g to 100 ton, more preferably 10 kg to 10 ton.
- Exhaust gas absorption step This step is a process in which the gas discharged from the polyacrylic acid (salt) water-absorbing resin manufacturing process (hereinafter referred to as “exhaust gas”) is an aqueous liquid such as water (hereinafter referred to as “absorption”). (Referred to as “liquid”).
- absorption water having a pH of 7 to 11 and a polyvalent metal ion content of 100 ppm or less is used in the first invention, and the electric conductivity at 25 ° C. is 500 ( ⁇ S / second) in the second invention. cm) or less water and an alkali compound are used to adjust the pH to 7 to 11, respectively.
- the first invention absorbs the gas discharged from the production process of the polyacrylic acid (salt) water-absorbing resin in water having a pH of 7 to 11 and a polyvalent metal ion content of 100 ppm or less.
- a method for producing a polyacrylic acid (salt) water-absorbing resin further comprising
- 2nd invention mixes the water discharged
- a method for producing a polyacrylic acid (salt) -based water-absorbing resin is further provided, which further comprises a step of absorbing in water having a pH adjusted to 7 to 11.
- the exhaust gas is discharged from the steps (2-1) to (2-11) and the like, but is not particularly limited as long as it is discharged from the polyacrylic acid (salt) water-absorbing resin manufacturing step.
- exhaust gas refers to a gas discharged from the production process of a polyacrylic acid (salt) -based water absorbent resin as described above.
- the exhaust gas is a gas discharged from the production process of the polyacrylic acid (salt) water-absorbing resin, preferably an exhaust gas mainly composed of a discharge from the polymerization process, the drying process, and the surface crosslinking process, more preferably Exhaust gas mainly composed of components discharged from the polymerization step and drying step, more preferably exhaust gas mainly composed of components discharged from the drying step.
- the said "main component” means that the ratio for the whole volume of exhaust gas becomes like this. Preferably it is 50 volume% or more, More preferably, it is 70 volume% or more, More preferably, it is 90 volume% or more.
- the drying step is preferably hot air drying, more preferably hot air drying at a temperature of 100 to 300 ° C. and a wind speed of 3 (m / s) or less.
- a fluidized bed dryer a rotary stirring dryer, an aeration band dryer, a more preferably an aeration band dryer, and still more preferably an aeration band dryer.
- the exhaust gas is absorbed in the absorption liquid in an exhaust gas absorption tower, and then recovered in a manufacturing process of a polyacrylic acid (salt) water-absorbing resin, or is subjected to disposal processing such as combustion processing or biological processing. .
- the exhaust gas is absorbed into the absorption liquid by gas-liquid contact between the absorption liquid (for example, an aqueous sodium hydroxide solution) and the exhaust gas in the exhaust gas absorption tower.
- the absorption liquid for example, an aqueous sodium hydroxide solution
- the contents organic matter, particularly acrylic acid
- the absorbent is collected or discarded in the manufacturing process of the water absorbent resin.
- the organic matter is preferably 90% by weight or more, more preferably 95% by weight or more, still more preferably 99% by weight or more, particularly preferably 99.9% by weight or more based on the total amount of organic matter in the exhaust gas. Removed.
- the temperature of the gas discharged from the production process is preferably 30 to 150 ° C., more preferably 50 to 130 ° C., still more preferably 80 to 120 ° C. when introduced into the exhaust gas absorption tower. is there.
- the organic substance (especially acrylic acid) in exhaust gas may precipitate and apparatus troubles, such as obstruction
- produce in order to make the temperature of exhaust gas less than 30 degreeC, it is necessary to forcibly cool, and since energy cost starts excessively, it is unpreferable.
- a heat exchanger in order to control the temperature of the exhaust gas within the above temperature range, it is desirable to use a heat exchanger if necessary. For example, when the exhaust gas temperature is high, it is desirable to cool the exhaust gas and recover heat. When the temperature of the exhaust gas is low, it is desirable to heat the exhaust gas with a heat exchanger. In addition to the heat exchanger, various known temperature adjusting means such as a heater and a cooler can be used.
- the specific cooling output of the heat exchanger is preferably more than 0 and not more than 10 (W / cm 2 ), more preferably 0.012 to 5 (W / cm 2 ), still more preferably 0.1 to 2 ( W / cm 2 ).
- W / cm 2 The specific cooling output exceeds 10 (W / cm 2 ), it is not preferable because it is not only disadvantageous in terms of energy but also may be precipitated due to overcooling.
- the gas discharged from the production process of the water-absorbent resin includes, in addition to the inert gas, air, and water vapor used in the production process, raw materials of the water-absorbent resin (for example, monomers, crosslinking agents) , Water, organic solvents, additives, etc.).
- raw materials of the water-absorbent resin for example, monomers, crosslinking agents
- Water organic solvents, additives, etc.
- fine particles fine gel, fine particles after drying generated from the drying step and fine powder of the water-absorbing resin generated from the surface cross-linking step may be included.
- the liquid that absorbs the gas discharged from the production process of the polyacrylic acid (salt) water-absorbing resin has a pH of 7 to 11 and a polyvalent metal ion content.
- the content of the polyvalent metal ions is preferably 50 ppm or less, preferably 20 ppm or less, 10 ppm or less, 5 ppm or less, 1 ppm or less, or 0.5 ppm or less in order, and most preferably 0.1 ppm or less.
- the lower limit is 0 ppm, but may be about 0.01 ppm.
- the polyvalent metal ion is not particularly limited, but is preferably a metal ion belonging to Group 2 of the periodic table, more preferably a magnesium ion or a calcium ion, and still more preferably a calcium ion. Since polyvalent metal salts (particularly carbonates and hydroxides) containing these polyvalent metal ions have low solubility in water, it is particularly necessary to suppress the content.
- the content of the polyvalent metal ion refers to the amount of the polyvalent metal cation excluding the counter anion. Specifically, in the case of calcium hydroxide, the amount of Ca 2+ is the amount of polyvalent metal cation.
- the water having a polyvalent metal ion content of 100 ppm or less is not particularly limited.
- produce in a manufacturing process are mentioned.
- the water absorbent resin containing the polyvalent metal salt is mixed into the exhaust gas, resulting in the polyvalent metal in the absorbing liquid.
- the ion content may exceed 100 ppm. Therefore, it is possible to monitor the content of polyvalent metal ions in the absorption liquid as needed, and use water with less polyvalent metal ions as necessary so that the content of polyvalent metal ions is 100 ppm or less. preferable.
- water having an electric conductivity at 25 ° C. of 500 ( ⁇ S / cm) or less is used as a liquid that absorbs the gas discharged from the production process of the polyacrylic acid (salt) -based water absorbent resin. And water whose pH is adjusted to 7 to 11 by mixing the alkali compound with alkali.
- the electrical conductivity ( ⁇ S / cm) at 25 ° C. is preferably 100 or less, preferably 50 or less, 30 or less, 20 or less, or 10 or less in order, and most preferably 5 or less.
- the lower limit is 0.0546 to 0.0549 of theoretical pure water, but is preferably about 0.1, more preferably about 0.5, and still more preferably about 0.8 from the viewpoint of water purification cost.
- the water used in the present invention is preferably an aqueous solution of an alkali compound, more preferably from the viewpoint of the absorption efficiency of organic matter (particularly acrylic acid) contained in the exhaust gas.
- an aqueous solution of an alkali metal hydroxide, carbonate or bicarbonate more preferably an aqueous solution of sodium hydroxide, sodium carbonate or sodium bicarbonate.
- water having a polyvalent metal ion content of preferably 100 ppm or less, more preferably 50 ppm or less, and even more preferably 10 ppm or less is used as water for dissolving the alkali compound. .
- the liquidity of the aqueous solution is preferably adjusted to be alkaline in order to efficiently and surely absorb organic substances (particularly residual monomers) in the exhaust gas.
- the liquidity of the absorbing solution is preferably adjusted to pH 7 to 11, more preferably pH 9 to 11.
- the pH value is a value measured at a liquid temperature of 25 ° C.
- the alkalinity By controlling to be the alkalinity, it is possible to suppress the excessive production of water-insoluble polyvalent metal salt due to the reaction between the alkali compound and the polyvalent metal ion contained in the absorption liquid, It is preferable because the amount of the alkali compound used can be suppressed and it is economical.
- the pH value may vary to some extent during the operation of the exhaust gas absorption tower, and the fluctuation range is preferably controlled to be ⁇ 2, more preferably ⁇ 1.
- Examples of the control method include a method of monitoring the pH of the absorbing solution during operation of the exhaust gas absorption tower and adding water, acid or alkali as appropriate to adjust the pH within the above range.
- a scale inhibitor or a chelating agent may be added to the absorbing solution.
- the scale inhibitor is not particularly limited.
- lignin derivatives such as lignin sulfonic acid soda, water-soluble poly (meth) acrylic acid soda, or inorganic polyphosphates, phosphonates, organic phosphates, etc.
- the chelating agent is not particularly limited, and examples thereof include chelating agents, aminocarboxylic acids, aminophosphoric acids, and polyphosphoric acids described in [2] chelating agents in International Publication No. 2011/040530. It is done.
- the amount of the scale inhibitor or chelating agent used is preferably 0.01 to 500 ppm with respect to the absorbing solution.
- the temperature of the absorbing liquid to be contacted with the exhaust gas is not particularly limited, but from the viewpoint of absorption efficiency, it is preferably 30 to 100 ° C, more preferably 40 to 95 ° C, still more preferably 50 to 90 ° C, particularly preferably. Is 60-90 ° C.
- the temperature of the absorption liquid exceeds 100 ° C., the exhaust gas absorption efficiency is lowered, which is not preferable.
- the temperature is lower than 30 ° C., it is disadvantageous in terms of energy, and further, the solubility of the polyvalent metal salt dissolved in the absorbing solution is lowered and precipitation may occur.
- the temperature of the absorption liquid refers to the temperature immediately before the absorption liquid is sprayed on the packed bed which is the gas-liquid contact means of the exhaust gas absorption tower, and can be appropriately adjusted by temperature adjustment means such as a heat exchanger or a heater. .
- the pressure in the absorption tower may be any of normal pressure, pressurization, and reduced pressure, but is preferably slightly reduced pressure, for example, a pressure in the range of ⁇ 10 to ⁇ 1 mbar. Will be implemented.
- the ratio between the amount of exhaust gas and the amount of absorbing liquid is adjusted as appropriate according to the composition of the exhaust gas, but the amount of absorbing liquid per exhaust gas 1000 (Nm 3 / min) (100 ° C. conversion) is preferably 0.8. It is 01 to 100 (m 3 / min), more preferably 0.05 to 50 (m 3 / min), and still more preferably 0.1 to 10 (m 3 / min).
- This invention also provides the manufacturing apparatus suitable for the manufacturing method of the polyacrylic acid (salt) type water absorbing resin mentioned above. That is, the water absorption which removes organic substance from this exhaust gas by making gas-liquid contact the exhaust gas discharged
- a gas-liquid contact means for bringing the exhaust gas into contact with the absorption liquid, a spray means for supplying the absorption liquid to the gas-liquid contact means from above the gas-liquid contact means, and the exhaust gas Exhaust gas supply means for supplying gas from the lower part of the gas-liquid contact means, and a circulation path for transferring the absorbing liquid staying in the lower part of the gas-liquid contact means to the spray means, wherein the gas-liquid contact means comprises the gas-liquid contact
- the exhaust gas supplied from the lower part of the means is installed so as to pass through the gas-liquid contact means in a longitudinal state, and the spray
- the exhaust gas absorption device used as the water absorbent resin production device according to the present invention is not particularly limited as long as it has the gas-liquid contact means, the spray means, the exhaust gas supply means, and the circulation path.
- various wet exhaust gas absorption towers such as spray tower, plate tower, bubble tower, wet wall tower, wet shelf tower, fluidized bed scrubber, cyclone scrubber, venturi scrubber, jet scrubber, and cross flow contact device.
- a packed tower is preferable from the viewpoint of gas-liquid contact efficiency.
- the gas-liquid contact means includes a packed bed incorporating various fillers from the viewpoint of improving the contact efficiency between the exhaust gas and the absorbing liquid.
- the material and shape of the filler are not particularly limited, and examples of the material include fillers made of metal, ceramic, resin, and the like.
- Examples of the shape include a shape having a large space ratio and a small pressure loss, a shape having a large number of contact points, and a shape capable of uniformly distributing the absorbing liquid in the packed bed.
- the gas-liquid contact area of absorption liquid and waste gas increases by employ
- the spraying means is not particularly limited as long as it is an apparatus that can spray the absorbing liquid uniformly on the gas-liquid contact means, and examples thereof include a shower nozzle and a spray nozzle.
- FIG. 1 is a schematic apparatus diagram showing an embodiment of the present invention, in which a gas discharged from a production process of a polyacrylic acid (salt) water-absorbing resin and an absorbing solution for neutralizing organic substances in the exhaust gas Is a device for producing a water-absorbing resin that removes organic substances from the exhaust gas, and uses a spray tower as an exhaust gas absorption tower.
- the present invention is not limited to this embodiment, and can be appropriately selected within a range that does not impair the effects of the present invention.
- a packed bed 13 which is a gas-liquid contact means for bringing the exhaust gas and the absorption liquid into gas-liquid contact is provided.
- Gas (exhaust gas) discharged from the production process of the polyacrylic acid (salt) water-absorbing resin of the present invention is supplied to the bottom of the wet exhaust gas absorption tower 1 (below the packed bed) via the exhaust gas supply line 2. Is done.
- an absorbent that neutralizes organic substances present in the exhaust gas is prepared in the absorbent supply tank 8.
- the absorption liquid is prepared by adding a certain amount of water and an aqueous alkali compound solution to the absorption liquid supply tank 8 from the water supply line 14 and the alkaline compound aqueous solution supply line 15 respectively.
- the bottom of the exhaust gas absorption tower 1 is filled. Thereafter, the absorption liquid passes through the circulation line 7 and the absorption liquid line 5 using the circulation pump 4 from the upper part of the wet exhaust gas absorption tower 1 (above the packed bed 13) toward the packed bed 13 from the shower nozzle 6. Sprayed downward.
- the exhaust gas supplied to the wet exhaust gas absorption tower 1 rises in the tower and makes gas-liquid contact (countercurrent contact) with the sprayed absorption liquid as it passes through the packed bed 13 in a longitudinal state. At that time, impurities in the exhaust gas are taken into the absorption liquid and removed from the exhaust gas. A certain amount of the absorbent after the gas-liquid contact is retained at the bottom of the absorption tower 1.
- the absorption liquid is forcibly circulated and used by the circulation pump 4 through the circulation line 7 and the absorption liquid line 5 and through a spray nozzle disposed on the upper part of the packed bed.
- the absorption efficiency gradually decreases due to circulation, but when the absorption efficiency falls below a certain absorption efficiency, the valve 10 is operated to extract a certain amount of absorption liquid from the absorption liquid extraction line.
- the extracted absorption liquid is collected in an arbitrary manufacturing process of the water-absorbent resin, or is subjected to a disposal process such as a combustion process or a biological process.
- the decrease in the absorption liquid due to the operation is compensated for the shortage by using the absorption liquid supply pump 9 from the absorption liquid supply tank 8.
- This operation may be a batch type or a continuous type. In order to maintain the above range by monitoring the pH of the absorbent and the content of polyvalent metal ions as needed, remove the used absorbent or supply new absorbent to make contact with the exhaust gas. You may adjust pH and polyvalent metal ion content.
- the method for producing a polyacrylic acid (salt) water-absorbing resin according to the present invention is suitable for long-term continuous operation on a large scale, and the production amount is preferably 1 (t / hr) or more per line, more preferably Is preferably 2 (t / hr) or more, and is preferably used for industrial scale production for continuous operation for 10 days or more, more preferably for 1 month or more, and even more preferably for 3 months or more. It is.
- continuous operation refers to substantially continuous operation including switching of product numbers, and even if it is temporarily stopped, it falls within the category of continuous operation.
- polyacrylic acid (salt) water-absorbing resin obtained by the production method according to the present invention preferably satisfies the following physical properties.
- the CRC water absorption capacity without pressure
- the CRC water absorption capacity without pressure
- AAP water absorption capacity under pressure
- the SFC saline flow conductivity
- the SFC is preferably 1 ( ⁇ 10 ⁇ 7 ⁇ cm 3 ⁇ s ⁇ g ⁇ 1 ) or more, more preferably 10 ( ⁇ 10 ⁇ 7 ⁇ cm 3 ⁇ s ⁇ g ⁇ ). 1 ) or more
- the FSR water absorption rate
- the FSR water absorption rate
- water-absorbent resin When used in sanitary goods, particularly paper diapers, at least one or more of the physical properties described above, preferably two or more including AAP (water absorption under pressure), more preferably AAP (water absorption under pressure). 3) or more, more preferably all four physical properties, including
- the polyacrylic acid (salt) -based water-absorbing resin obtained by the production method according to the present invention can be used as an absorbent article for absorbent articles, particularly sanitary articles such as paper diapers, sanitary napkins, and incontinence pads. preferable. At that time, it is combined with hydrophilic fibers and formed into a sheet or the like. In addition, when hydrophilic fiber is not used, an absorptive article is obtained by immobilizing the water-absorbent resin on paper, nonwoven fabric, or the like.
- the electrical device including the physical property measurement of a water absorbing resin
- a manufacture example used by a manufacture example, an Example, and a comparative example used the power supply of 200V or 100V.
- the physical properties of the water-absorbent resin of the present invention were measured under conditions of room temperature (20 to 25 ° C.) and relative humidity of 50% RH unless otherwise specified.
- AAP water absorption magnification under pressure
- the AAP water absorption capacity under pressure of the water-absorbent resin of the present invention was measured according to the EDANA method (ERT442.2-02).
- the load condition was changed to 4.83 kPa (0.7 psi).
- Weight average particle diameter (D50) of the water-absorbent resin of the present invention was measured in accordance with the measurement method disclosed in US Patent Application Publication No. 2006/204755.
- FSR Water absorption rate
- the FSR (water absorption rate) of the water-absorbent resin of the present invention was measured according to the measurement method disclosed in International Publication No. 2009/016055.
- the monomer aqueous solution (1) an aqueous solution of partial sodium salt of acrylic acid having a neutralization rate of 73 mol% and a monomer concentration of 38% by weight was prepared. At that time, polyethylene glycol diacrylate (average n number; 9) was added as an internal cross-linking agent so as to be 0.09 mol% with respect to the number of moles of all monomers.
- the monomer aqueous solution (1) was continuously supplied (liquid fed) to the polymerization apparatus using a metering pump. At that time, nitrogen gas was continuously blown from the middle of the liquid feeding pipe so that the concentration of dissolved oxygen in the monomer aqueous solution (1) was 0.5 ppm or less.
- sodium persulfate and L-ascorbic acid were continuously mixed (line mixing) using separate supply pipes. The addition amounts of sodium persulfate and L-ascorbic acid were 0.12 g and 0.005 g, respectively, per 1 mol of the monomer.
- the above polymerization apparatus is a flat steel belt polymerization apparatus having weirs at both ends, and using the polymerization apparatus, standing aqueous solution polymerization was continuously performed.
- the liquid supplied to the polymerization apparatus had a thickness of about 30 mm on a flat steel belt, and the polymerization time for the polymerization was 30 minutes. By this operation, a band-shaped hydrogel crosslinked polymer (hydrogel) (1) was obtained.
- the strip-like hydrogel (1) is cut at equal intervals in the vertical direction with respect to the traveling direction of the flat steel belt, and then continuously supplied to a meat chopper having a pore diameter of 7 mm to obtain weight average particles.
- the gel was crushed into particles having a diameter (D50) of about 2 mm. By the operation, a particulate hydrous gel (1) was obtained.
- the particulate hydrogel (1) was loaded on the perforated plate of the ventilation band type continuous dryer so as to have a thickness of 50 mm, and hot air at a temperature of 185 ° C. was applied at a wind speed of 1.6 (m / s). And aerated for 30 minutes to dry. By this operation, a block-shaped dry polymer (1) was obtained at the outlet of the dryer.
- the whole amount of the pulverized polymer (1) is continuously supplied to a classification device (a sieving device composed of a total of two metal sieving meshes having a mesh opening of 710 ⁇ m / 150 ⁇ m in order from the top), Classified.
- the temperature of the pulverized polymer (1) supplied to the classifier was about 60 ° C., and the frame on which the classifier was installed was grounded (static elimination) with a ground resistance value of 5 ⁇ . By this operation, an irregularly shaped water-absorbing resin powder (1) was obtained.
- the physical properties of the water absorbent resin powder (1) obtained by the above series of operations were as follows. That is, solid content: 97% by weight, weight average particle diameter (D50): 375 ⁇ m, logarithmic standard deviation of particle size distribution ( ⁇ ); 0.38, absorption capacity without load (CRC); 33.9 (g / g) Met.
- the water absorbent resin powder (1) was continuously supplied to a high-speed mixer (turbulator / 1000 rpm) at 2000 (kg / hr). In that case, the said surface treating agent solution (1) was sprayed using the spray, and was mixed uniformly.
- the paddle dryer having the same specifications as the paddle dryer used in the heat treatment step is used to forcibly cool the surface-treated water absorbent resin powder (1) until the temperature reaches 60 ° C. (Cooling step).
- weight average particle diameter (D50): 387 ⁇ m
- CRC water absorption capacity without pressure
- AAP water absorption capacity under pressure
- SFC physiological saline Flow inductivity
- FSR water absorption rate
- Ext water soluble content
- FIG. 1 shows a gas (hereinafter referred to as “exhaust gas”) discharged from a ventilation band type continuous dryer (drying step) in the production process of the polyacrylic acid (salt) -based water absorbent resin of Production Example 1 above. It collected using the wet-type exhaust gas absorption tower 1 shown.
- the exhaust gas contained 200 ppm by volume of gaseous acrylic acid, and the temperature of the exhaust gas was 160 ° C.
- the exhaust gas is cooled and recovered by a heat exchanger having a specific cooling output of 1.4 (W / cm 2 ), and then absorbed through the exhaust gas supply line 2 at a flow rate of 1000 (Nm 3 / min). Feeded to column 1.
- the temperature of the exhaust gas after the heat recovery was 100 ° C.
- the exhaust gas absorbing solution ion-exchanged water having a calcium ion content of 0.2 ppm (electric conductivity at 25 ° C. is 1.1 ( ⁇ S / cm)), 48% by weight sodium hydroxide aqueous solution, A 1.0 ⁇ 10 ⁇ 3 (mol / l) aqueous sodium hydroxide solution (pH 10) prepared by mixing was used.
- the absorption liquid was stored in the absorption liquid supply tank 8. Moreover, in the long-term continuous operation, since the absorption liquid in the wet exhaust gas absorption tower 1 gradually decreases, it was appropriately supplemented. Further, since the amount held in the absorption liquid supply tank 8 also decreased, replenishment was performed as appropriate.
- the pH of the absorption liquid and the content of polyvalent metal ions in the wet exhaust gas absorption tower 1 are monitored to maintain the pH of the absorption liquid at 9 to 11 and the content of polyvalent metal ions at 100 ppm or less.
- the absorption liquid was appropriately extracted from the absorption liquid extraction line 11 and the absorption liquid was appropriately added from the absorption liquid supply tank 8.
- the pH of the absorbent in the absorbent supply tank 8 was adjusted by controlling the supply amount from the water supply line 14 and the alkaline compound aqueous solution supply line 15 as necessary.
- the absorption liquid As an operation in the wet exhaust gas absorption tower 1, first, 3 m 3 of the absorption liquid was supplied to the bottom of the wet exhaust gas absorption tower 1 using the absorption liquid supply pump 9. Next, the absorption liquid was sprayed downward from the shower nozzle 6 using the circulation pump 4 through the circulation line 7 and the absorption liquid line 5 at a flow rate of 1.4 (m 3 / min). In addition, the temperature of the said absorption liquid was adjusted using the heat exchanger 16 so that the temperature just before spraying from the shower nozzle 6 might be 50 degreeC.
- the exhaust gas was supplied from the exhaust gas supply line 2 to make a countercurrent contact with the absorbing solution.
- the temperature of the absorbent after absorbing the exhaust gas was 64 ° C.
- the gas-liquid contact was performed more efficiently by the packed bed 13 installed in the wet exhaust gas absorption tower 1.
- the liquid that absorbed the exhaust gas was circulated through the circulation line 7 and the absorption liquid line 5 using the circulation pump 4.
- the liquid was sprayed from the shower nozzle 6 after adjusting using a heat exchanger so that the temperature immediately before spraying from the shower nozzle 6 was 50 ° C.
- the exhaust gas that was not absorbed by the absorbing solution was discharged out of the system from the exhaust gas discharge line 3 at the top of the tower via the mist separator 12.
- 99.92% by weight of the total amount of organic matter contained in the exhaust gas before being supplied to the absorption tower was removed.
- a steam ejector is installed at the tip of the exhaust gas discharge line 3, and the internal pressure of the wet exhaust gas absorption tower 1 is slightly reduced (atmospheric pressure -5 mbar).
- the shower nozzle 6 of the wet exhaust gas absorption tower 1 was inspected, and no adhesion of water-insoluble metal salt was observed, and there was no clogging.
- Example 1 As an exhaust gas absorbing solution, ion-exchanged water having a calcium ion content of 300 ppm (electric conductivity at 25 ° C. is 1550 ( ⁇ S / cm)) and a 48 wt% aqueous sodium hydroxide solution are used. The same operation as in Example 1 was performed except that the mixture was changed to a 0.1 (mol / l) aqueous sodium hydroxide solution (pH 13) prepared by mixing.
- Example 2 In Example 1 above, as an exhaust gas absorbing solution, ion-exchanged water having a calcium ion content of 300 ppm (electric conductivity at 25 ° C. is 1550 ( ⁇ S / cm)) and a 48 wt% aqueous sodium hydroxide solution are used. The same operation as in Example 1 was performed except that the mixture was changed to a 1.0 ⁇ 10 ⁇ 3 (mol / l) aqueous sodium hydroxide solution (pH 10) prepared by mixing.
- Example 3 As an exhaust gas absorbing liquid, ion-exchanged water having a calcium ion content of 0.2 ppm (electric conductivity at 25 ° C. is 1.1 ( ⁇ S / cm)) and 48% by weight of hydroxide The same operation as in Example 1 was performed except that the aqueous solution was changed to a 0.1 (mol / l) aqueous sodium hydroxide solution (pH 13) prepared by mixing with an aqueous sodium solution.
- Example 1 water having a pH of 7 to 11 and a polyvalent metal ion content of 100 ppm or less (electric conductivity at 25 ° C. of 500 ( ⁇ S / cm) or less) is absorbed in exhaust gas.
- a polyvalent metal ion content of 100 ppm or less electrical conductivity at 25 ° C. of 500 ( ⁇ S / cm) or less
- clogging at the spray nozzle of the shower nozzle 6 does not occur, and adhesion of a water-insoluble polyvalent metal salt can be suppressed.
- the method for producing a polyacrylic acid (salt) water-absorbent resin according to the present invention can be applied to the production of water-absorbent resins, particularly to mass production.
- the polyacrylic acid (salt) water-absorbing resin obtained by the present invention is suitable for use as an absorbent material for sanitary goods such as paper diapers.
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、以下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が5g/g以上、かつ、「水不溶性」として、ERT470.2-02で規定されるExtが50重量%以下の物性を満たす高分子ゲル化剤を指す。
本発明における「ポリアクリル酸(塩)」とは、ポリアクリル酸及び/又はその塩を指し、主成分として、アクリル酸及び/又はその塩(以下、「アクリル酸(塩)」と称する)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重合体を指す。
「EDANA」は、欧州不織布工業会(European Disposables and Nonwovens Associations)の略称であり、「ERT」は、欧州標準(ほぼ世界標準)の吸水性樹脂の測定法(EDANA Recommended Test Methods)の略称である。本発明では、特に断りのない限り、ERT原本(2002年改定/公知文献)に準拠して、吸水性樹脂の物性を測定する。
「CRC」は、遠心分離保持容量(Centrifuge Retention Capacity)の略称であり、吸水性樹脂の無加圧下吸水倍率(「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を不織布に入れた後、大過剰の0.9重量%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)で水切りした後の吸水倍率(単位;g/g)のことをいう。
「Ext」は、Extractablesの略称であり、吸水性樹脂の水可溶分(水可溶成分量)を意味する。具体的には、吸水性樹脂1.0gについて、0.9重量%塩化ナトリウム水溶液200mlに対して、500rpmで16時間攪拌した後の溶解したポリマー量をpH滴定で測定した値(単位;重量%)のことをいう。
「AAP」は、Absorption Against Pressureの略称であり、吸水性樹脂の加圧下吸水倍率を意味する。具体的には、吸水性樹脂0.9gについて、大過剰の0.9重量%塩化ナトリウム水溶液に対して、1時間、0.3psi(2.06kPa、21g/cm2)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。なお、荷重条件を0.7psi(4.83kPa、49g/cm2)に変更して測定する場合もある。
吸水性樹脂の「通液性」とは、荷重下または無荷重下での膨潤ゲルの粒子間を通過する液の流れ性のことをいい、代表的な測定方法として、SFC(Saline Flow Conductivity/生理食塩水流れ誘導性)や、GBP(Gel Bed Permeability/ゲル床透過性)がある。
吸水性樹脂の「吸水速度」とは、ある一定量の水性液を吸収する際の速さのことをいい、代表的な測定方法として、「FSR」や、「Vortex」(単位:秒)がある。なお、本発明における吸水速度は、FSRで評価した。また、「FSR」とは、Free Swell Rateの略称である。具体的な測定方法については、後述の実施例において説明する。
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、重量の単位である「t(トン)」は「Metric ton(メトリック トン)」を意味し、「ppm」は「重量ppm」又は「質量ppm」を意味する。更に、「重量」と「質量」、「重量部」と「質量部」、「重量%」と「質量%」は同義語として扱う。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(第1の発明)は、ポリアクリル酸(塩)系吸水性樹脂の製造工程から排出されるガスを、pHが7~11で、かつ多価金属イオンの含有量が100ppm以下の水に吸収させる工程を更に含む、ポリアクリル酸(塩)系吸水性樹脂の製造方法を提供する。なお、本項では本発明の第1の発明及び第2の発明に共通するポリアクリル酸(塩)系吸水性樹脂の製造工程について説明し、排ガスの吸収工程については次項〔3〕で説明する。
本工程は、アクリル酸(塩)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、準備する工程である。なお、吸水性能が低下しない限り、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する。
本発明では、発明の効果の観点から単量体としてアクリル酸が用いられる。当該アクリル酸としては公知のものでよく、重合禁止剤として好ましくはフェノール類、より好ましくはメトキシフェノール類が含まれていればよい。また、重合禁止剤の濃度として、アクリル酸の重合性や吸水性樹脂の色調の観点から、好ましくは1~200ppm、より好ましくは10~160ppmであればよい。
本発明においては、アクリル酸(塩)以外の単量体(以下、「他の単量体」と称する)を、アクリル酸(塩)と併用して吸水性樹脂を製造することもできる。当該他の単量体としては、特に限定されないが、水溶性又は疎水性の不飽和単量体が挙げられる。具体的には、米国特許出願公開第2005/215734号の段落〔0035〕に開示された単量体(但し、アクリル酸は除く)が挙げられる。
本発明において、「塩基性組成物」とは塩基性化合物を含有する組成物を意味し、例えば、市販の水酸化ナトリウム水溶液等が該当する。
上記中和工程として本発明では、単量体のアクリル酸に対する中和の他に、アクリル酸を架橋重合させて得られる含水ゲル状架橋重合体に対する中和(以下、「後中和」と称する)も含まれる。これらの中和は、連続式でもバッチ式でもよいが、生産効率等の観点から連続式が好ましい。また、これらの中和を併用することもできる。
本発明で使用される内部架橋剤として、アクリル酸と反応しうる置換基を2個以上有する化合物が挙げられ、具体的には、米国特許第6241928号のカラム14に開示された化合物が挙げられる。これらのうち、1種又は2種以上の化合物が用いられる。
本発明において、吸水性樹脂の吸水性能等の諸物性を向上させることを目的として、下記の物質を単量体水溶液を調製する際に、添加することもできる。
本発明において、単量体水溶液中の単量体成分の濃度としては、特に限定されないが、吸水性樹脂の物性の観点から、好ましくは10~80重量%、より好ましくは20~75重量%、更に好ましくは30~70重量%である。なお、後述する高濃度重合を採用する場合には、後述の範囲が好ましく適用される。
本工程は、上記単量体水溶液の調製工程で得られる単量体水溶液を重合させて、含水ゲル状架橋重合体(以下、「含水ゲル」と称する)を得る工程である。なお、当該重合工程では、発生する重合熱によってアクリル酸の一部が揮発する可能性があり、その際、発生するガスは必要に応じて排ガス吸収工程に供給される。
本発明で使用される重合開始剤として、熱分解性重合開始剤、光分解性重合開始剤又はこれらの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、具体的には、米国特許第7265190号のカラム5に開示された化合物が挙げられる。これらのうち、1種又は2種以上の化合物が用いられる。
本発明に適用される重合形態としては、特に限定されないが、吸水性樹脂の吸水性能や重合制御の容易性等の観点から、好ましくは噴霧重合、液滴重合、水溶液重合、逆相懸濁重合、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、特に好ましくは連続水溶液重合が挙げられる。
本工程は、上記重合工程で得られる含水ゲルをニーダー、ミートチョッパー又はカッターミル等のゲル粉砕機でゲル粉砕し、粒子状の含水ゲル(以下、「粒子状含水ゲル」と称する)を得る工程である。なお、上記重合工程がニーダー重合の場合、重合工程とゲル粉砕工程が同時に実施されていることになる。
本工程は、上記重合工程及び/又はゲル粉砕工程で得られる粒子状含水ゲルを所望の固形分濃度まで乾燥させて乾燥重合体を得る工程である。なお、当該乾燥工程では、乾燥時の熱によってアクリル酸の一部が揮発する可能性があり、その際、発生するガスは必要に応じて排ガス吸収工程に供給される。また、粒子状含水ゲルに含まれる微粒子(微細ゲル、乾燥後の微粒子)が熱風によって飛散する可能性もあり、その際、飛散した微粒子は粒径が好ましくは2mm以下、より好ましくは0.5mm以下であり、当該排ガスと共に排ガス吸収工程に供給される。
本工程は、上記乾燥工程で得られる乾燥重合体を粉砕(粉砕工程)し、所定範囲の粒度に調製(分級工程)して、吸水性樹脂粉末(表面架橋前の、粒子状の吸水性樹脂を便宜上「吸水性樹脂粉末」と称する)を得る工程である。
本工程は、上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)に架橋密度の高い部分を設ける工程であり、混合工程、加熱処理工程及び必要により冷却工程から構成される。
本発明で使用される表面架橋剤として、好ましくは種々の有機又は無機の表面架橋剤、より好ましくは吸水性樹脂の吸水性能や表面架橋剤の取扱性の観点からカルボキシル基と反応して共有結合を形成する有機表面架橋剤が挙げられる。具体的には、米国特許第7183456号のカラム9~10に開示された表面架橋剤が挙げられる。これらのうち、1種又は2種以上の表面架橋剤が用いられる。また、必要に応じて、親水性有機溶媒を使用することもできる。
本混合工程は、吸水性樹脂粉末と上記表面架橋剤とを混合して混合物を得る工程である。当該表面架橋剤の添加、混合方法については、特に限定されないが、表面架橋剤及び溶媒としての水、親水性有機溶媒、又はこれらの混合物を予め用意した後、吸水性樹脂粉末に対して、噴霧又は滴下して添加し混合することが好ましく、噴霧して添加し混合することがより好ましい。
本加熱処理工程は、上記吸水性樹脂粉末と表面架橋剤との混合物を加熱処理して、吸水性樹脂粒子を得る工程である。
本冷却工程は、上記加熱処理工程の後に必要に応じて設置される任意の工程である。
本工程は、上記表面架橋工程で得られる吸水性樹脂粒子に、添加剤として、多価金属塩化合物、ポリカチオン性ポリマー、キレート剤、無機還元剤及びα-ヒドロキシカルボン酸化合物からなる群から選ばれる少なくとも1種の化合物を添加する工程である。なお、当該再加湿工程では、アクリル酸や添加剤の一部が揮発する可能性があり、その際、発生するガスは必要に応じて排ガス吸収工程に供給される。
本発明において、得られる吸水性樹脂の吸水性能の観点から、多価金属塩化合物及び/又はカチオン性ポリマーを添加することが好ましい。これらの化合物を添加することによって、吸水性樹脂の吸水速度(例えば、FSR)や通液性(例えば、SFC)を向上させることができ、更に吸湿時の流動性も向上させることができる。
本発明において、得られる吸水性樹脂の物性の観点から、キレート剤を添加することが好ましい。当該化合物を添加することによって、吸水性樹脂の色調悪化や劣化を抑制又は防止することができる。
本発明において、得られる吸水性樹脂の物性の観点から、無機還元剤を添加することが好ましい。当該化合物を添加することによって、吸水性樹脂の色調悪化や劣化を抑制又は防止、更には残存モノマーを低減させることができる。
本発明において、得られる吸水性樹脂の物性の観点から、α-ヒドロキシカルボン酸化合物を添加することが好ましい。当該化合物を添加することによって、吸水性樹脂の色調悪化を抑制又は防止することができる。
本工程は、上述した添加剤以外の添加剤を添加する工程であり、吸水性樹脂に対して種々の機能を付与するために設置される任意の工程である。かような添加剤として、界面活性剤、酸化剤、有機還元剤、水不溶性無機微粒子、金属石鹸等の有機粉末、消臭剤、抗菌剤、リン原子を有する化合物、パルプや熱可塑性繊維等が挙げられる。
上述した工程以外に、造粒工程、整粒工程、微粉除去工程、微粉の再利用工程等を必要に応じて設けることができる。
上述した各工程の間は、スクリューフィーダー、バケットコンベア、フライトコンベア、ベルトコンベアや空気輸送等の各種搬送機で連結され、必要に応じて、各工程の間で中間貯蔵される。吸水性樹脂の製造工程全体として、基本的に各工程が連結されおり、好ましくは密閉系で製造及び充填がなされる。
本工程は、上述した工程の少なくとも一部を経て製造される最終製品としての吸水性樹脂が、コンテナバッグやペーパーバッグ等の充填容器に充填される工程である。当該充填容器に充填された吸水性樹脂は、所定の検査を受けた後に出荷される。
本工程は、上記ポリアクリル酸(塩)系吸水性樹脂の製造工程から排出されるガス(以下、「排ガス」と称する)を水等の水性液(以下、「吸収液」と称する)に吸収させる工程である。当該吸収液として、第1の発明では、pHが7~11で、かつ多価金属イオンの含有量が100ppm以下の水を、第2の発明では、25℃における電気伝導率が500(μS/cm)以下の水と、アルカリ化合物とを混合してpHを7~11に調整した水をそれぞれ使用する。
本発明において、「排ガス」とは、上述したようにポリアクリル酸(塩)系吸水性樹脂の製造工程から排出されるガスのことをいう。
本発明において、上記排ガスは、排ガス吸収塔で上記吸収液に吸収させた後に、ポリアクリル酸(塩)系吸水性樹脂の製造工程に回収、又は燃焼処理若しくは生物処理等の廃棄処理がなされる。
本発明において、上記製造工程から排出されるガスの温度としては、排ガス吸収塔に導入される時点で、好ましくは30~150℃、より好ましくは50~130℃、更に好ましくは80~120℃である。上記温度が30℃未満の場合、排ガス中の有機物(特にアクリル酸)が析出し、配管等での閉塞等の装置トラブルが発生する虞がある。また、排ガスの温度を30℃未満とするには強制冷却する必要があり、エネルギーコストが余分に掛かるため、好ましくない。一方、上記温度が150℃を超える場合、排ガスと吸収液が接触した際、当該吸収液の一部が蒸発してしまい、吸収効率が低下するため、好ましくない。また、上記蒸発によって失われた吸収液を補うため、余分な水が必要となり、コスト増の観点から好ましくない。
本発明において、上記吸水性樹脂の製造工程から排出されるガスには、当該製造工程で使用される不活性ガスや空気、水蒸気の他、吸水性樹脂の原材料(例えば、単量体、架橋剤、水、有機溶媒、添加剤等)等が含まれる。また、乾燥工程から発生した微粒子(微細ゲル、乾燥後の微粒子)や表面架橋工程から発生した吸水性樹脂の微粉が含まれる場合がある。
本発明(第1の発明)では、ポリアクリル酸(塩)系吸水性樹脂の製造工程から排出されるガスを吸収する液として、pHが7~11で、かつ多価金属イオンの含有量が100ppm以下の水を使用する。当該多価金属イオンの含有量は、好ましくは50ppm以下であり、以下順に、20ppm以下、10ppm以下、5ppm以下、1ppm以下、0.5ppm以下が好ましく、最も好ましくは0.1ppm以下である。下限値としては0ppmであるが、0.01ppm程度であってもよい。上記多価金属イオンの含有量が100ppmを超える場合、吸収液との反応により水不溶性の多価金属塩が多量に生成し、排ガス吸収塔内の吸収液噴霧ノズルや気液接触用充填層等に付着し、目詰まり等の装置トラブルが発生するため、好ましくない。
本発明において、排ガスと接触させる吸収液の温度としては特に限定されないが、吸収効率の観点から、好ましくは30~100℃、より好ましくは40~95℃、更に好ましくは50~90℃、特に好ましくは60~90℃である。上記吸収液の温度が100℃を超える場合、排ガスの吸収効率が低下するため、好ましくない。一方、30℃未満の場合は、エネルギー的に不利であり、更に吸収液中に溶解している多価金属塩の溶解度が低下し、析出が発生する虞があるため、好ましくない。該吸収液の温度は、吸収液を排ガス吸収塔の気液接触手段である充填層に噴霧する直前での温度を指し、熱交換器や加熱器などの温度調整手段によって適宜調整することができる。
本発明は、上述したポリアクリル酸(塩)系吸水性樹脂の製造方法に適した製造装置をも提供する。即ち、ポリアクリル酸(塩)系吸水性樹脂の製造工程から排出される排ガスと、該排ガス中の有機物を中和する吸収液とを気液接触させて、該排ガスから有機物を除去処理する吸水性樹脂の製造装置であって、前記排ガスと前記吸収液とを気液接触させる気液接触手段、前記気液接触手段上部から前記気液接触手段に前記吸収液を供給する噴霧手段、前記排ガスを前記気液接触手段下部から供給する排ガス供給手段、前記気液接触手段下部に滞留する前記吸収液を前記噴霧手段に移送する循環経路を有し、前記気液接触手段は、前記気液接触手段下部から供給された前記排ガスが前記気液接触手段内を縦断状態で通過するように設置し、前記噴霧手段は前記吸収液を前記気液接触手段に向けて下向きに設置し、前記循環経路は、前記吸収液を強制的に循環させる手段を有する、吸水性樹脂の製造装置を提供する。
本発明に係るポリアクリル酸(塩)系吸水性樹脂の製造方法は、大スケールでの長期連続稼働に適しており、生産量として1ラインあたり、好ましくは1(t/hr)以上、より好ましくは2(t/hr)以上がよく、また、稼働日数として好ましくは10日間以上、より好ましくは1ヶ月間以上、更に好ましくは3ヶ月以上の連続稼働を目的とする工業的規模の生産に好適である。なお、本発明では、「連続稼働」は品番の切り替えを含め、実質的な連続稼働を指し、一時的に停止する場合も連続稼働の範疇に入るものとする。
本発明に係る製造方法で得られるポリアクリル酸(塩)系吸水性樹脂は、以下の物性を満たすものが好ましい。
(a)CRC(無加圧下吸水倍率)
本発明の吸水性樹脂のCRC(無加圧下吸水倍率)は、EDANA法(ERT441.2-02)に準拠して測定した。
本発明の吸水性樹脂のAAP(加圧下吸水倍率)は、EDANA法(ERT442.2-02)に準拠して測定した。なお、荷重条件を4.83kPa(0.7psi)に変更した。
本発明の吸水性樹脂のSFC(生理食塩水流れ誘導性)は、米国特許第5669894号に開示された測定方法に準拠して測定した。
本発明の吸水性樹脂の重量平均粒子径(D50)は、米国特許出願公開第2006/204755号に開示された測定方法に準拠して測定した。
本発明の吸水性樹脂のFSR(吸水速度)は、国際公開第2009/016055号に開示された測定方法に準拠して測定した。
本発明の吸水性樹脂のExt(水可溶分)は、EDANA法(ERT470.2-02)に準拠して測定した。
ポリアクリル酸(塩)系吸水性樹脂の連続製造装置として、重合工程、ゲル粉砕工程、乾燥工程、粉砕工程、分級工程、表面架橋工程(表面架橋剤の混合工程、加熱処理工程、冷却工程)及び整粒工程を含む製造装置を用意した。当該製造装置は、上記各工程がこの順序で構成されており、各工程間は輸送工程によって連結されていた。当該連続製造装置を用いて、2000(kg/hr)で吸水性樹脂を連続的に製造した。
次に、上記単量体水溶液(1)を、定量ポンプを用いて連続的に重合装置に供給(送液)した。その際、送液配管の途中から窒素ガスを連続的に吹き込み、単量体水溶液(1)中の溶存酸素の濃度を0.5ppm以下とした。続いて、重合開始剤として、過硫酸ナトリウム及びL-アスコルビン酸を別々の供給配管を用いて、連続的に混合(ラインミキシング)した。過硫酸ナトリウム及びL-アスコルビン酸の添加量は、単量体1モルに対して、それぞれ0.12g、0.005gであった。
次に、上記帯状の含水ゲル(1)を、上記平面スチールベルトの進行方向に対して、垂直方向に等間隔に切断した後、孔径7mmのミートチョッパーに連続的に供給して、重量平均粒子径(D50)約2mmの粒子状にゲル粉砕した。当該操作によって、粒子状の含水ゲル(1)を得た。
続いて、粒子状の含水ゲル(1)を、通気バンド型連続乾燥機の多孔板上に、厚みが50mmとなるように積載し、温度185℃の熱風を風速1.6(m/s)で30分間通気して乾燥した。当該操作によって、乾燥機出口において、ブロック状の乾燥重合体(1)を得た。
続いて、ブロック状の乾燥重合体(1)全量を、3段ロールミル(ロールギャップ;上から順に1.0mm/0.65mm/0.42mm)に連続的に供給して、粉砕した。なお、当該粉砕装置(3段ロールミル)に供給された乾燥重合体(1)の温度は約60℃であり、粉砕工程での減圧度を0.29kPaに調整した。当該操作によって、粉砕重合体(1)を得た。
続いて、粉砕重合体(1)全量を、分級装置(目開きが上から順に、710μm/150μmである合計2枚の金属篩網から構成される篩い分け装置)に連続的に供給して、分級した。なお、当該分級装置に供給される粉砕重合体(1)の温度は約60℃であり、当該分級装置が据え付けられている架台は、接地抵抗値が5Ωの接地(除電)がなされていた。当該操作により、不定形破砕状の吸水性樹脂粉末(1)を得た。
次に、上記吸水性樹脂粉末(1)100重量部に対して、エチレンカーボネート0.35重量部、プロピレングリコール0.58重量部、ポリオキシエチレン(20)ソルビタンモノステアレート(花王株式会社製)0.001重量部及び脱イオン水2.3重量部からなる表面処理剤溶液(1)を用意した。
上記吸水性樹脂粉末(1)を高速混合機(タービュライザー/1000rpm)に、連続的に2000(kg/hr)で供給した。その際、上記表面処理剤溶液(1)を、スプレーを用いて噴霧し、均一に混合した。
その後、当該混合物をパドルドライヤーに移送し、200℃で40分間加熱処理を行った。
上記加熱処理後、当該加熱処理工程で使用したパドルドライヤーと同一仕様のパドルドライヤーを用いて、表面処理された吸水性樹脂粉末(1)の温度が60℃となるまで、強制的に冷却を行った(冷却工程)。
その後、目開き710μmのJIS標準篩を有する篩い分け装置を用いて、表面処理された吸水性樹脂粉末(1)の全量が通過するまで解砕を行った。なお、左記の「解砕」とは、表面処理時に凝集した吸水性樹脂粉末(1)について、目開き710μmの篩網を通過するまで解す操作のことをいう。以上の操作により、製品としての吸水性樹脂(A)を得た。得られた吸水性樹脂(A)の物性は以下の通りであった。即ち、重量平均粒子径(D50);387μm、無加圧下吸水倍率(CRC);30.1(g/g)、加圧下吸水倍率(AAP);24.6(g/g)、生理食塩水流れ誘導性(SFC);50(×10-7・cm3・s・g-1)、吸水速度(FSR);0.25(g/g/s)、水可溶分(Ext);9.3重量%であった。
上記製造例1のポリアクリル酸(塩)系吸水性樹脂の製造工程において、通気バンド型連続乾燥機(乾燥工程)から排出されるガス(以下、「排ガス」と称する。)を、図1に示した湿式排ガス吸収塔1を用いて捕集した。なお、当該排ガス中には気体のアクリル酸が200容積ppm含有しており、排ガスの温度は160℃であった。
上記実施例1において、排ガスの吸収液として、カルシウムイオンの含有量が300ppmのイオン交換水(25℃での電気伝導率は1550(μS/cm))と48重量%の水酸化ナトリウム水溶液とを混合して調製した、0.1(mol/l)の水酸化ナトリウム水溶液(pH13)に変更した以外は、実施例1と同様の操作を行った。
上記実施例1において、排ガスの吸収液として、カルシウムイオンの含有量が300ppmのイオン交換水(25℃での電気伝導率は1550(μS/cm))と48重量%の水酸化ナトリウム水溶液とを混合して調製した、1.0×10-3(mol/l)の水酸化ナトリウム水溶液(pH10)に変更した以外は、実施例1と同様の操作を行った。
上記実施例1において、排ガスの吸収液として、カルシウムイオンの含有量が0.2ppmのイオン交換水(25℃での電気伝導率は1.1(μS/cm))と48重量%の水酸化ナトリウム水溶液とを混合して調製した、0.1(mol/l)の水酸化ナトリウム水溶液(pH13)に変更した以外は、実施例1と同様の操作を行った。
上記のとおり、比較例1のように強アルカリ性(pH=13)で、かつ多価金属イオンの含有量が100ppmを超える水を排ガスの吸収液として使用した場合、シャワーノズル6の噴霧口において急速に水不溶性の多価金属塩が大量に付着し、詰まりが発生する。
2:排ガス供給ライン
3:排ガス排出ライン
4:循環ポンプ
5:吸収液ライン
6:シャワーノズル
7:循環ライン
8:吸収液供給タンク
9:吸収液供給ポンプ
10:バルブ
11:吸収液抜出ライン
12:ミストセパレーター
13:充填層
14:水供給ライン
15:アルカリ化合物水溶液供給ライン
16:熱交換器
Claims (22)
- ポリアクリル酸(塩)系吸水性樹脂の製造工程から排出されるガスを、pHが7~11で、かつ多価金属イオンの含有量が100ppm以下の水に吸収させる工程を更に含む、ポリアクリル酸(塩)系吸水性樹脂の製造方法。
- 上記多価金属イオンの含有量が10ppm以下である、請求項1に記載の製造方法。
- 上記多価金属イオンの含有量が1ppm以下である、請求項1又は2に記載の製造方法。
- 上記多価金属イオンが、周期表第2族元素のイオンである、請求項1~3の何れか1項に記載の製造方法。
- ポリアクリル酸(塩)系吸水性樹脂の製造工程から排出されるガスを、25℃における電気伝導率が500(μS/cm)以下の水とアルカリ化合物とを混合してpHを7~11に調整した水に吸収させる工程を更に含む、ポリアクリル酸(塩)系吸水性樹脂の製造方法。
- 上記水の温度が30~100℃である、請求項1~5の何れか1項に記載の製造方法。
- 上記アルカリ化合物が、アルカリ金属の水酸化物、炭酸塩又は炭酸水素塩から選ばれる少なくとも1種以上の化合物である、請求項5に記載の製造方法。
- 上記製造工程から排出されるガスの温度が、排ガス吸収塔に導入される時点で30~150℃である、請求項1~7の何れか1項に記載の製造方法。
- 上記製造工程から排出されるガス中に単量体が含まれる、請求項1~8の何れか1項に記載の製造方法。
- 上記製造工程から排出されるガスが微減圧で上記水に吸収される、請求項1~9の何れか1項に記載の製造方法。
- 上記製造工程から排出されるガスを熱交換器で冷却して熱回収される、請求項1~10の何れか1項に記載の製造方法。
- 上記熱交換器の比冷却出力が10(W/cm2)以下である、請求項11に記載の製造方法。
- 上記水吸収工程から排出される吸収液をポリアクリル酸(塩)系吸水性樹脂の製造工程にリサイクルする、請求項1~12の何れか1項に記載の製造方法。
- 上記水吸収工程から排出される吸収液を燃焼処理する、請求項1~12の何れか1項に記載の製造方法。
- 上記水吸収工程から排出される吸収液を生物処理する、請求項1~12の何れか1項に記載の製造方法。
- 上記ポリアクリル酸(塩)系吸水性樹脂の生産量が1ラインあたり1(t/hr)以上であり、かつ、10日間以上の連続生産である、請求項1~15の何れか1項に記載の製造方法。
- 上記ポリアクリル酸(塩)系吸水性樹脂の製造工程において、多価金属を使用する、請求項1~16の何れか1項に記載の製造方法。
- 上記ポリアクリル酸(塩)系吸水性樹脂の製造工程に、アクリル酸(塩)系単量体水溶液の重合工程、含水ゲル状架橋重合体の乾燥工程、及び吸水性樹脂粉末の表面架橋工程が含まれる、請求項1~17の何れか1項に記載の製造方法。
- 上記含水ゲル状架橋重合体の重量平均粒子径(D50)が2000μm以下である、請求項18に記載の製造方法。
- 上記乾燥工程が乾燥温度100~300℃で、風速3(m/s)以下の熱風乾燥である、請求項18又は19に記載の製造方法。
- 上記製造工程から排出されるガスが上記乾燥工程から排出されるものである、請求項18~20の何れか1項に記載の製造方法。
- ポリアクリル酸(塩)系吸水性樹脂の製造工程から排出される排ガスと、該排ガス中の有機物を中和する吸収液とを気液接触させて、該排ガスから有機物を除去処理する吸水性樹脂の製造装置であって、
上記排ガスと上記吸収液とを気液接触させる気液接触手段、
上記気液接触手段上部から上記気液接触手段に上記吸収液を供給する噴霧手段、
上記排ガスを上記気液接触手段下部から供給する排ガス供給手段、
上記気液接触手段下部に滞留する上記吸収液を上記噴霧手段に移送する循環経路を有し、
上記気液接触手段は、上記気液接触手段下部から供給された上記排ガスが上記気液接触手段内を縦断状態で通過するように設置し、
上記噴霧手段は上記吸収液を上記気液接触手段に向けて下向きに設置し、
上記循環経路は、上記吸収液を強制的に循環させる手段を有する吸水性樹脂の製造装置。
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US10285866B2 (en) | 2015-01-16 | 2019-05-14 | Lg Chem, Ltd. | Super absorbent polymer |
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CN107847905A (zh) * | 2015-07-01 | 2018-03-27 | 株式会社日本触媒 | 颗粒状吸水剂 |
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 |
WO2018092864A1 (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及びその製造装置 |
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US11766659B2 (en) | 2016-11-16 | 2023-09-26 | Nippon Shokubai Co., Ltd. | Method for producing water-absorbent resin powder, and drying device and drying method for particulate hydrous gel |
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US20160279602A1 (en) | 2016-09-29 |
EP3069782A4 (en) | 2017-07-26 |
EP3069782A1 (en) | 2016-09-21 |
US9682362B2 (en) | 2017-06-20 |
CN105722581B (zh) | 2018-07-17 |
CN105722581A (zh) | 2016-06-29 |
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JP2017006808A (ja) | 2017-01-12 |
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