WO2020067310A1 - Method for producing water-absorbing resin - Google Patents

Method for producing water-absorbing resin Download PDF

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Publication number
WO2020067310A1
WO2020067310A1 PCT/JP2019/037908 JP2019037908W WO2020067310A1 WO 2020067310 A1 WO2020067310 A1 WO 2020067310A1 JP 2019037908 W JP2019037908 W JP 2019037908W WO 2020067310 A1 WO2020067310 A1 WO 2020067310A1
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water
organic solvent
monomer
absorbent resin
polymerization
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PCT/JP2019/037908
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French (fr)
Japanese (ja)
Inventor
井村　元洋
井上　雅史
舞 佐藤
耕士 本田
峻一 田島
知幸 荒毛
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株式会社日本触媒
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Priority to JP2020549365A priority Critical patent/JP7174769B2/en
Publication of WO2020067310A1 publication Critical patent/WO2020067310A1/en

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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
    • C08F2/001—Multistage polymerisation processes characterised by a change in reactor conditions without deactivating the intermediate polymer
    • 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
    • C08F2/01—Processes of polymerisation characterised by special features of the polymerisation apparatus used
    • 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
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J3/00—Processes of treating or compounding macromolecular substances
    • C08J3/12—Powdering or granulating
    • 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
    • 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
    • C08F2500/00—Characteristics or properties of obtained polyolefins; Use thereof
    • C08F2500/24—Polymer with special particle form or size
    • 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
    • C08F2810/00—Chemical modification of a polymer
    • C08F2810/20—Chemical modification of a polymer leading to a crosslinking, either explicitly or inherently

Definitions

  • the present invention relates to a method for producing a water absorbent resin.
  • a water-absorbing resin as a constituent material has been widely used as a water-absorbing agent.
  • Many monomers and hydrophilic polymers are used as raw materials for the water-absorbing resin.
  • polyacrylic acid using acrylic acid and / or a salt thereof as a monomer is used.
  • (Salt) -based water-absorbing resins are produced most industrially.
  • the reverse phase suspension polymerization method is a method in which a monomer aqueous solution is suspended in an organic solvent to perform polymerization. For example, there is a method in which polymerization is started after a monomer is dispersed in an organic solvent in the form of droplets by mechanical stirring (JP-A-61-192703). In such a method, it is necessary to add a large amount of a dispersing aid when dispersing the solution containing the monomer in the organic solvent. As a result, a part of the dispersing agent remains in the water-absorbent resin obtained by the polymerization reaction, and the surface tension is reduced, and the physical properties of the water-absorbent resin are sometimes reduced.
  • WO 2016/1822082 discloses a method for dispersing an aqueous monomer solution in an organic solvent using a spray nozzle for the purpose of reducing the amount of a dispersing aid added. Specifically, in WO 2016/1822082, a monomer aqueous solution and an organic solvent are guided to the tip of a spray nozzle without making contact with the monomer aqueous solution, and immediately before or immediately after being discharged from the spray nozzle, The monomer aqueous solution is brought into contact with the organic solvent to disperse the monomer aqueous solution in the organic solvent.
  • an object of the present invention is to provide a method for producing a water-absorbent resin, in which a monomer can be dispersed with a small flow rate of a dispersion medium and the particle size of the water-absorbent resin is constant over a long period of time.
  • a water-soluble ethylenically unsaturated monomer solution and an organic solvent are separately and continuously supplied to a flow path that forms a shear field by a pair of walls having opposing surfaces that oppose each other with a gap therebetween.
  • FIG. 4 is a cross-sectional view of a two-fluid spray nozzle used in Comparative Example 1. It is a schematic diagram which shows the measuring device of DRC5min. It is the schematic which shows some manufacturing processes of the water absorbent resin which concerns on other embodiment of this invention.
  • water absorbent resin refers to a water-swelling component (CRC) defined by ERT441.2-02 of 5 g / g or more, and a water-soluble component defined by ERT470.2-02 ( Ext) refers to a polymer gelling agent having an Ext) of 70% by weight or less.
  • the “water-absorbing resin” is not limited to an embodiment in which the total amount (100% by weight) is only the water-absorbing resin. On the contrary, if the above-mentioned CRC and Ext are satisfied, a water-absorbing resin composition containing an additive or the like may be used. Further, in this specification, the term "water-absorbent resin” is a concept that also includes intermediates in the process of producing the water-absorbent resin. For example, a hydrogel polymer after polymerization, a dried polymer after drying, a water-absorbing resin powder before surface cross-linking, and the like may also be referred to as “water-absorbing resin”.
  • water-absorbent resin in addition to the water-absorbent resin itself, the water-absorbent resin composition and the intermediate may be collectively referred to as “water-absorbent resin”.
  • ppm means “weight ppm”.
  • —acid (salt) means “—acid and / or salt thereof”.
  • (Meth) acryl means “acryl and / or methacryl”.
  • volume ⁇ ⁇ ⁇ ⁇ ⁇
  • L the unit of volume “liter” may be described as “l” or “L”.
  • the method for producing a water-absorbent resin of the present invention is characterized in that a water-soluble ethylenically unsaturated monomer is formed in a flow path that forms a shear field by a pair of walls having opposing surfaces opposing each other with a gap therebetween moving relatively.
  • a body solution (hereinafter, also simply referred to as a monomer solution) and an organic solvent are separately and continuously supplied to prepare droplets containing a water-soluble ethylenically unsaturated monomer solution, and the water-soluble ethylenically unsaturated
  • a monomer solution a body solution
  • an organic solvent a solvent for removing water-soluble ethylenically unsaturated
  • the pair of walls move relatively to each other due to the relative movement of the walls. Shear force is applied. This shear force enables fine dispersion of the water-soluble ethylenically unsaturated monomer in the organic solvent.
  • the shearing force is generated by the relative movement of the moving wall, a large amount of the organic solvent is not required as compared with the two-fluid spray method.
  • the water-soluble ethylenically unsaturated monomer can be dispersed in the organic solvent with a small amount of the dispersion medium, and the particle size of the water-absorbing resin is kept constant for a long time.
  • FIG. 1 is a schematic view showing a part of a process for producing a water absorbent resin according to one embodiment of the present invention.
  • a plurality of valves for adjusting the flow rate and the pressure are provided in the piping system, but these valves are not shown in FIG.
  • the manufacturing process of the water-absorbent resin includes a mixing device 10, a dispersion device 12, a reaction device 14, a separation device 16, a liquid sending pump 18, a heat exchanger 20, a drying device 22, and these devices. Are connected to each other.
  • a pipe 37 for discharging the dried polymer is connected to the drying device 22.
  • the structure of the dispersion device 12 will be described later in detail.
  • the reaction device 14 is composed of, for example, a vertical reaction tower.
  • the water-soluble ethylenically unsaturated monomer supplied to the reactor 14 is polymerized to obtain a hydrogel polymer (hereinafter, also referred to as a “hydrogel” or a “gel polymer”).
  • the separation device 16 is composed of, for example, a screw press or a continuous centrifugal separator, and extracts a hydrogel and performs solid-liquid separation.
  • the drying device 22 includes, for example, a paddle dryer, a fluidized bed dryer, a rotary dryer, and a steam tube dryer, and agitates and dries the hydrogel.
  • the pipe 35 branches off from a pipe 34 extending from the heat exchanger 20 to the reaction device 14 and is connected to the dispersion device 12.
  • a pipe 41 for supplying the monomer solution and a pipe 42 for supplying the polymerization initiator are connected to the mixing device 10.
  • a pipe 43 for supplying a dispersion aid is connected to a pipe 33 from the liquid sending pump 18 to the heat exchanger 20.
  • a pipe 44 for supplying a drying aid is connected to a pipe 36 extending from the separation device 16 to the drying device 22.
  • the method for producing the water-absorbent resin includes an optional mixing step; a dispersion step; a polymerization step, and optionally includes a drying step after the polymerization step.
  • the organic solvent is filled in the dispersion device 12, the reaction device 14, the separation device 16, the heat exchanger 20, and the pipes 32, 33, 34, 35 connecting these devices.
  • the liquid pump 18 is operated to circulate the organic solvent.
  • Part of the organic solvent is also supplied to the dispersion device 12 via the pipe 35.
  • the dispersion aid is supplied to the organic solvent flowing through the pipe 33 via the pipe 43.
  • the organic solvent in each device and pipe is heated to a predetermined temperature in the heat exchanger 20.
  • a separately prepared water-soluble ethylenically unsaturated monomer solution and a polymerization initiator are continuously supplied to and mixed with the mixing device 10 via pipes 41 and 42, respectively, to produce a monomer composition.
  • the mixing device 10 is not particularly limited, and examples thereof include a line mixer.
  • the monomer composition is continuously supplied to the dispersion device 12 via the pipe 31.
  • the monomer composition and the organic solvent are separately and continuously supplied to the dispersion device 12.
  • the monomer composition is dispersed in the form of droplets in the organic solvent by the dispersion device 12 (dispersion step).
  • the water-soluble ethylenically unsaturated monomer is continuously dispersed in the organic solvent.
  • a polymerization method in which a polymerization reaction is started in a state where droplets containing a monomer solution are dispersed or suspended in a liquid phase (continuous phase) composed of an organic solvent to obtain a hydrogel is described as a liquid phase liquid. This is referred to as drop (suspension) polymerization.
  • the water-containing gel obtained by the liquid phase droplet polymerization is continuously discharged from the reaction device 14 together with the organic solvent, and is continuously supplied to the separation device 16.
  • the hydrogel and the organic solvent are continuously separated (separation step).
  • the separated hydrogel is continuously supplied to the next step (drying device 22) via the pipe 36 (drying step).
  • the separated organic solvent passes through the heat exchanger 20 via the pipes 32 and 33 and is continuously re-supplied to the reaction apparatus 14 via the pipe 34. Part of the organic solvent is also supplied again to the dispersion device 12 via the pipe 35.
  • the drying device 22 the water contained in the hydrogel and the organic solvent that cannot be separated in the separation device 16 are removed to obtain a particulate dried polymer.
  • the particulate dry polymer is discharged from the pipe 37 and supplied to the next step (such as a cooling device).
  • the organic solvent removed by the drying device 22 is supplied again to the reaction device 14.
  • continuous polymerization continuous production method
  • the monomer solution or the monomer composition containing the monomer solution is continuously sent to an organic solvent in a reaction apparatus, polymerized, and a hydrogel formed by a polymerization reaction.
  • the organic solvent is continuously discharged from the reactor. Therefore, the present embodiment is a liquid phase droplet continuous polymerization. In this case, since each step and each operation between the steps can be performed continuously, troubles such as blockage due to stop and restart of each device can be avoided.
  • continuous polymerization is a form in which a monomer solution or a monomer composition containing a monomer solution is continuously supplied to a reaction device from a dispersion device, and thus dispersion and polymerization are performed in one device. It is clearly distinguished from the form in which it is performed (batch operation).
  • the operation time is preferably 1 hour or more, more preferably 3 hours or more, and usually 1 year or less.
  • This step is an optional step, and is a step of obtaining a monomer composition by mixing a water-soluble ethylenically unsaturated monomer solution and a polymerization initiator.
  • the method of preparing the monomer composition by mixing the monomer solution and the polymerization initiator is not particularly limited.
  • a monomer solution and a solution containing the polymerization initiator ( Hereinafter, referred to as “polymerization initiator solution”), a method of simultaneously supplying the mixture to the mixing device from separate pipes and mixing them, and (2) supplying the prepared monomer solution to the mixing device.
  • a method of supplying a polymerization initiator to the mixing device and mixing the polymerization initiator and the like can be given.
  • the polymerization initiator may be in the form of a polymerization initiator solution in which the polymerization initiator is dissolved (dispersed) in a solvent.
  • the solvent of the polymerization initiator solution is not particularly limited, but water is preferable.
  • the concentration of the polymerization initiator solution at this time is not particularly limited as long as it is within a range in which the polymerization initiator can be dissolved in a solvent, but is preferably from 0.1% by weight to a saturated concentration or less, preferably from 1% by weight to 1% by weight. 30% by weight is more preferred.
  • the mixing device is not particularly limited, and examples thereof include a line mixer and a tank. From the viewpoint of storage stability and safety of the polymerization initiator, the mixing method (1) using a line mixer as the mixing device is preferable.
  • Water-soluble ethylenically unsaturated monomer solution refers to a solution containing a water-soluble ethylenically unsaturated monomer.
  • the solvent for the monomer solution is preferably water, a water-soluble organic solvent (eg, alcohol) and a mixture thereof, and more preferably water or a mixture of water and a water-soluble organic solvent, and more preferably water. Is even more preferred.
  • the content of the water-soluble organic solvent eg, alcohol is preferably 30% by weight or less, more preferably 5% by weight or less.
  • water-soluble ethylenically unsaturated monomer examples include (meth) acrylic acid, (anhydride) maleic acid, itaconic acid, cinnamic acid, vinyl sulfonic acid, allyl toluene sulfonic acid, vinyl toluene sulfonic acid, and styrene sulfonic acid.
  • a polymerization inhibitor may be added to the water-soluble ethylenically unsaturated monomer as needed.
  • the polymerization inhibitor for example, a known polymerization inhibitor such as p-methoxyphenol, phenothiazine, and Vitamin-E can be used. When p-methoxyphenol is used, oxygen is used in combination if necessary.
  • the amount of the polymerization inhibitor to be used is preferably 0.1 ppm to 1000 ppm, more preferably 5 ppm to 500 ppm, based on the amount of the water-soluble ethylenically unsaturated monomer.
  • the salt of the acid group-containing unsaturated monomer is preferably a salt with a monovalent cation, more preferably at least one selected from alkali metal salts, ammonium salts and amine salts, It is more preferably an alkali metal salt, even more preferably at least one selected from a sodium salt, a lithium salt and a potassium salt, and particularly preferably a sodium salt.
  • the water-soluble ethylenically unsaturated monomer is preferably an acid group-containing unsaturated monomer and / or a salt thereof, and more preferably (meth) ) Acrylic acid (salt), (anhydride) maleic acid (salt), itaconic acid (salt), cinnamic acid (salt), more preferably (meth) acrylic acid (salt), particularly preferably acrylic acid (salt) ).
  • the number of moles of the neutralized salt relative to the total number of moles of the acid group-containing unsaturated monomer and the neutralized salt thereof (hereinafter, referred to as "neutralization ratio") is preferably 40 mol% or more, More preferably, it is from 40 mol% to 95 mol%, further preferably from 50 mol% to 90 mol%, still more preferably from 55 mol% to 85 mol%, particularly preferably from 60 mol% to 80 mol%.
  • a method of adjusting the neutralization rate a method of mixing an acid group-containing unsaturated monomer and a neutralized salt thereof; a method of adding a known neutralizing agent to the acid group-containing unsaturated monomer; A method using a partially neutralized salt of an acid group-containing unsaturated monomer adjusted to a predetermined neutralization ratio (that is, a mixture of an acid group-containing unsaturated monomer and a neutralized salt thereof) is exemplified. Further, these methods may be combined.
  • the neutralizing agent used for neutralizing the acid group-containing unsaturated monomer is not particularly limited, but includes inorganic salts such as sodium hydroxide, potassium hydroxide, sodium carbonate, and ammonium carbonate, and amino groups. And a basic substance such as an amine organic compound having an imino group is appropriately selected and used. As the neutralizing agent, two or more basic substances may be used in combination.
  • the addition of the neutralizing agent may be performed before the polymerization reaction of the acid group-containing unsaturated monomer is started, may be performed during the polymerization reaction of the acid group-containing unsaturated monomer, or may be added. It may be carried out on a hydrogel obtained after the completion of the polymerization reaction of the unsaturated monomer. Further, any one of the stages before the start of the polymerization reaction, during the polymerization reaction or after the end of the polymerization reaction may be selected and the neutralizing agent may be added, or the neutralization ratio may be adjusted in a plurality of stages.
  • any one of the monomers exemplified above may be used alone, or two or more arbitrary monomers may be appropriately mixed and used. Further, other monomers can be mixed as long as the object of the present invention is achieved.
  • the ratio of (meth) acrylic acid (salt) to the entire monomer used for polymerization is usually 50 mol% or more, preferably 70 mol% or more, from the viewpoint of the water absorbing performance of the obtained water-absorbing resin. It is more preferably at least 80 mol%, further preferably at least 90 mol% (the upper limit is 100 mol%).
  • the concentration of the water-soluble ethylenically unsaturated monomer in the monomer solution is not particularly limited as long as the water-soluble ethylenically unsaturated monomer can be dissolved in the solvent. To less than the saturation concentration, more preferably from 20% by weight to the saturation concentration, still more preferably from 25 to 80% by weight, and particularly preferably from 30 to 70% by weight.
  • an internal crosslinking agent can be used, if necessary. That is, the monomer solution may further contain an internal crosslinking agent.
  • the internal crosslinking agent include conventionally known internal crosslinking agents having two or more polymerizable unsaturated groups or two or more reactive groups in one molecule.
  • Examples of the internal crosslinking agent include N, N′-methylenebis (meth) acrylamide, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, Trimethylolpropane di (meth) acrylate, glycerin tri (meth) acrylate, glycerin acrylate methacrylate, ethylene oxide modified trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, tri Allyl cyanurate, triallyl isocyanurate, triallyl phosphate, triallylamine, poly (meth) allyloxyalkane, (poly) ethylene glycol di Risidyl ether, glycerol diglycidyl ether
  • the internal cross-linking agent in view of the water absorbing properties of the obtained water-absorbing resin.
  • the amount of the internal cross-linking agent may be appropriately determined depending on the desired physical properties of the water-absorbing resin. Usually, the amount of the internal crosslinking agent is 0.0001 to 5 mol%, more preferably 0.001 to 3 mol%, based on the monomer. And still more preferably 0.005 to 1.5 mol%.
  • chain transfer agents such as thiols, thiolic acids, secondary alcohols, amines, and hypophosphites
  • blowing agents such as carbonates, bicarbonates, azo compounds, and bubbles
  • ethylenediamine Chelating agents such as metal salts of tetraacetic acid and metal salts of diethylenetriaminepentaacetic acid
  • thickeners such as polyacrylic acid (salt) and cross-linked products thereof, starch, cellulose, starch-cellulose derivatives, and polyvinyl alcohol.
  • Other substances may be used alone or in combination of two or more.
  • the use amount of the other substance is not particularly limited, but the total concentration of the other substance is preferably 10% by weight or less, more preferably 1% by weight or less, more preferably 1% by weight based on the monomer. Is 0.1% by weight or less.
  • the viscosity of the monomer solution (Brookfield viscometer / 20 ° C., 6 rpm) is preferably 10 mPa ⁇ s to 500,000 mPa ⁇ s, more preferably 20 mPa ⁇ s.
  • the thickener may be added in a range of from 300 mPa ⁇ s to 300,000 mPa ⁇ s, and more preferably from 50 mPa ⁇ s to 100000 mPa ⁇ s.
  • a thermal decomposition type polymerization initiator As the polymerization initiator, a thermal decomposition type polymerization initiator is preferably used.
  • the thermal decomposition type polymerization initiator refers to a compound which is decomposed by heat to generate radicals. From the viewpoint of the storage stability of the thermal decomposition type polymerization initiator and the production efficiency of the water-absorbing resin, a 10-hour half-life temperature (hereinafter, referred to as a temperature). , "T10”) is preferably 0 ° C. to 120 ° C., more preferably 30 ° C. to 100 ° C., and even more preferably 50 ° C. to 80 ° C., is preferably used as a polymerization initiator.
  • thermal decomposition type polymerization initiator having T10 in the above range include persulfates such as sodium persulfate, potassium persulfate and ammonium persulfate; 2,2′-azobis (2-methylpropionamidine) dihydrochloride , 2,2'-azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride, 2,2'-azobis (2-methylpro Azo compounds such as pionitrile); peroxides such as hydrogen peroxide, t-butyl peroxide and methyl ethyl ketone peroxide; Two or more of these may be used in combination.
  • persulfates such as sodium persulfate, potassium persulfate and ammonium persulfate
  • 2,2′-azobis (2-methylpropionamidine) dihydrochloride 2,2'-azobis (2-amidinopropane) dihydroch
  • the polymerization initiator is preferably a persulfate, more preferably sodium persulfate, potassium persulfate, ammonium persulfate, and still more preferably.
  • Sodium persulfate is used.
  • the amount of the thermal decomposition type polymerization initiator used is appropriately set according to the type of the monomer and the polymerization initiator, and is not particularly limited. However, from the viewpoint of production efficiency, preferably 0 to the monomer. 0.001 g / mol or more, more preferably 0.005 g / mol or more, and still more preferably 0.01 g / mol or more. In addition, from the viewpoint of improving the water absorbing performance of the water absorbent resin, the amount is preferably 2 g / mol or less, more preferably 1 g / mol or less.
  • a combination of a thermal decomposition type polymerization initiator and a photodecomposition type polymerization initiator is also a preferred embodiment.
  • the photolytic polymerization initiator include a benzoin derivative, a benzyl derivative, an acetophenone derivative (eg, 1-hydroxycyclohexyl phenyl ketone), a benzophenone derivative, and the like.
  • the amount of the photodecomposition type polymerization initiator is not particularly limited, but is preferably 0.001 g / mol or more, more preferably 0.005 g / mol or more, more preferably 0.005 g / mol or more, based on the production efficiency. Is 0.01 g / mol or more.
  • the amount is preferably 2 g / mol or less, more preferably 1 g / mol or less.
  • the ratio of the thermal decomposition type polymerization initiator to the total polymerization initiator is preferably 60 mol% or more, more preferably 80 mol% or more. is there.
  • a redox-based polymerization initiator may be used in combination with the above-mentioned thermal decomposition-type polymerization initiator and a reducing agent.
  • the thermal decomposition type polymerization initiator functions as an oxidizing agent.
  • the reducing agent used is not particularly limited, but includes, for example, (bis) sulfites such as sodium sulfite and sodium bisulfite; reducing metal salts such as ferrous salt; L-ascorbic acid (salt); amines; Is mentioned.
  • the polymerization may be performed by irradiating an active energy ray such as a radiation, an electron beam, or an ultraviolet ray.
  • an active energy ray such as a radiation, an electron beam, or an ultraviolet ray.
  • polymerization may be carried out using these active energy rays and a polymerization initiator in combination.
  • the concentration of the water-soluble ethylenically unsaturated monomer in the monomer composition is selected according to the type of the water-soluble ethylenically unsaturated monomer and the organic solvent selected,
  • the lower limit is preferably at least 10% by weight, more preferably at least 20% by weight, even more preferably at least 30% by weight, and the upper limit is preferably at most 100% by weight. , More preferably 90% by weight or less, further preferably 80% by weight or less, and still more preferably 70% by weight or less.
  • the concentration of the water-soluble ethylenically unsaturated monomer in the monomer composition is preferably from 10% by weight to 90% by weight, more preferably from 20% by weight to 80% by weight. %, More preferably 30% to 70% by weight.
  • additives such as an internal cross-linking agent, a surfactant, a density adjuster, a thickener and the like can be added to the monomer composition.
  • the type and amount of the additive can be appropriately selected depending on the combination of the monomer and the organic solvent used.
  • a water-soluble ethylenically unsaturated monomer solution (or monomer composition) and an organic solvent are separately and continuously supplied to a flow path to disperse the water-soluble ethylenically unsaturated monomer in the organic solvent.
  • This is a step of producing a droplet including the liquid.
  • to supply the water-soluble ethylenically unsaturated monomer solution (or monomer composition) and the organic solvent “separately” to the channel means that the water-soluble ethylenically unsaturated monomer solution (or simply Water-soluble ethylenically unsaturated monomer solution (or monomer composition) and the organic solvent are not separately supplied to the flow path "separately”. And supply them separately.
  • a pair of walls having opposing surfaces opposing each other with a gap can relatively move to form a flow path that forms a shear field, and circulates a flow path that forms a shear field.
  • the method can realize a method of continuously supplying a water-soluble ethylenically unsaturated monomer solution in an organic solvent.
  • the “flow path” allows a fluid (a fluid in which a water-soluble ethylenically unsaturated monomer solution is supplied in an organic solvent) to flow through a gap between opposing surfaces of a pair of walls.
  • the shape is not particularly limited as long as it is a form.
  • the flow path can be formed in a bent shape by the concavo-convex opposing surfaces opposing each other.
  • the flow path can be formed in a bent shape by making one of the opposing surfaces a peripheral surface shape and the other opposing surface an uneven surface.
  • the flow path can be formed in a linear shape by the flat opposing surfaces opposing each other.
  • the flow path can be formed in a cylindrical shape by opposing peripheral surfaces that oppose each other.
  • the specific shape of the “wall” can have various shapes such as a planar shape, a blade shape, a disk shape, a hollow cylindrical shape, or a solid cylindrical shape, depending on the shape of the flow path.
  • the “movement of the pair of walls relatively” is not particularly limited as long as a flow path that forms a shear field can be formed.
  • one wall can be configured as a fixed wall and the other wall can be configured as a movable wall.
  • both the pair of walls can be configured as movable walls so that a difference occurs in the moving speed.
  • the water-soluble ethylenically unsaturated monomer in the organic solvent be supplied into a relatively narrow channel from the viewpoint of miniaturization of the monomer droplet in the organic solvent.
  • the dimension of the gap is preferably 5 mm or less, and more preferably 2 mm or less.
  • the size of the gap is preferably 0.1 mm or more, and more preferably 0.5 mm or more.
  • the relative movement speed of the gap and the pair of walls is designed to suppress the generation of the Taylor vortex.
  • the illustrated dispersion devices 12A to 12G are constituted by high-speed rotary shear type stirrers.
  • a monomer composition will be described, but a water-soluble ethylenically unsaturated monomer solution may be used instead.
  • the monomer composition and the organic solvent are separately and continuously supplied, and the monomer composition is dispersed in the organic solvent in the form of droplets.
  • FIG. 2 is a cross-sectional view illustrating a dispersion apparatus 12A according to an example.
  • the dispersing device 12A is a rotary mixer type high-speed rotary shear type stirrer.
  • the dispersion device 12A includes a flow path 54A formed by a pair of walls 50A and 52A having opposing surfaces 51A and 53A facing each other with a gap therebetween, and a driving unit 60A that relatively moves the pair of walls 50A and 52A. ,have. By relatively moving the pair of walls 50A and 52A by the driving unit 60A, a flow path 54A that forms a shear field is formed.
  • the dispersion device 12A further has a first supply system 55A that continuously supplies the monomer composition to the flow path 54A, and a second supply system 56A that continuously supplies the organic solvent to the flow path 54A. ing.
  • the pair of walls 50A and 52A have a cylindrical shape.
  • One wall 50A is formed of a non-rotating outer cylinder having a center hole.
  • the other wall 52A is formed from a solid inner cylinder rotatably disposed in the center hole of the outer cylinder.
  • the drive unit 60A is composed of, for example, a motor and is connected to the inner cylinder. By operating the driving unit 60A, the inner cylinder is rotationally driven.
  • one wall 50A forms a fixed wall
  • the other wall 52A forms a movable wall.
  • the inner peripheral surface of the outer cylinder and the outer peripheral surface of the inner cylinder form opposing surfaces 51A and 53A that oppose each other.
  • the facing surfaces 51A and 53A facing each other have an uneven shape.
  • the convex portion of the opposing surface 51A enters the concave portion of the opposing surface 53A, and the convex portion of the opposing surface 53A enters the concave portion of the opposing surface 51A.
  • the channel 54A has a bent shape.
  • the gap between the opposing surfaces 51A and 53A is formed in such a size that a desired shear field is generated in the flow path 54A.
  • the bottom of the wall 52A is tapered downward.
  • a communication path 58A is formed between the bottom of the wall 52A and the bottom of the wall 50A to communicate the flow path 54A and the liquid discharge pipe 57A.
  • the gap of the communication path 58A is larger than the gap of the flow path 54A.
  • the liquid discharge pipe 57A is connected to the upper end of the reaction device 14.
  • the inner diameter of the liquid discharge pipe 57A and the inner diameter of the reactor 14 are formed to have substantially the same dimensions. This is for smoothing the flow of the fluid from the dispersing device 12A to the reaction device 14 so that no stagnation occurs. Since no stagnation occurs in the dispersing device 12A, it is possible to prevent the monomer composition from polymerizing and becoming a hydrogel. When the gel-like material is generated in the dispersing device 12A, the particle diameter of the generated droplet is difficult to be constant.
  • the pipe 31 is connected to the first supply system 55A.
  • the monomer composition produced in the mixing device 10 is continuously supplied to the flow path 54A via the pipe 31 and the first supply system 55A.
  • the pipe 35 is connected to the second supply system 56A.
  • a part of the organic solvent circulated by the operation of the liquid feed pump 18 is continuously supplied to the flow path 54A via the pipe 35 and the second supply system 56A.
  • the drive unit 60A is operated to rotationally drive the wall 52A.
  • the opposing surface 53A of the wall 52A moves with respect to the opposing surface 51A of the opposing wall 50A. While rotating the wall 52A, the monomer composition is continuously supplied to the flow path 54A through the pipe 31 and the first supply system 55A.
  • the organic solvent and the monomer composition are mixed in the channel 54A in a state where the pair of walls 50A and 52A having the opposing surfaces 51A and 53A opposing each other are relatively moved by the driving unit 60A. It is supplied separately and continuously.
  • a strong shearing force acts on the organic solvent flowing into the flow path 54A due to a speed difference between the facing surface 53A of the rotor-side wall 52A and the facing surface 51A of the stator-side wall 50A.
  • the monomer composition is directly injected into the flow path 54A where a shear force is applied, and is quickly dispersed in an organic solvent in the form of droplets. Further, the droplet-shaped monomer composition is miniaturized.
  • FIG. 3 is a cross-sectional view illustrating a dispersion apparatus 12B according to another example.
  • the dispersing device 12B is a turbo mixer type high-speed rotary shear type stirrer.
  • One wall 50B is formed of a non-rotating casing.
  • the other wall 52B is formed of a blade-shaped vortex fan that is rotatably arranged in the casing.
  • the driving unit 60B is connected to the vortex fan. By operating the driving unit 60B, the vortex fan is rotationally driven.
  • one wall 50B constitutes a fixed wall
  • the other wall 52B constitutes a movable wall.
  • the inner peripheral surface of the casing and the outer peripheral surface of the vortex fan form opposing surfaces 51B and 53B that oppose each other.
  • the facing surface 51B has a peripheral shape.
  • the facing surface 53B has an uneven shape.
  • the blade of the opposing surface 53B faces the opposing surface 51B.
  • the channel 54B has a bent shape.
  • a part of the organic solvent circulated by the operation of the liquid feed pump 18 is continuously supplied to the flow path 54B via the pipe 35 and the second supply system 56B.
  • the drive unit 60B is operated to rotationally drive the wall 52B.
  • the opposing surface 53B of the wall 52B moves with respect to the opposing surface 51B of the opposing wall 50B. While rotating the wall 52B, the monomer composition is continuously supplied to the flow path 54B through the pipe 31 and the first supply system 55B.
  • the organic solvent and the monomer composition are placed in the channel 54B in a state where the pair of walls 50B and 52B having the opposing surfaces 51B and 53B opposing each other are relatively moved by the driving unit 60B. It is supplied separately and continuously.
  • a strong shearing force acts on the organic solvent flowing into the flow path 54B due to a speed difference between the facing surface 53B of the rotor-side wall 52B and the facing surface 51B of the stator-side wall 50B.
  • the monomer composition is directly injected into the flow path 54B where a shear force is applied, and is quickly dispersed in the organic solvent in the form of droplets. Further, the droplet-shaped monomer composition is miniaturized.
  • FIG. 4 is a sectional view showing a dispersion apparatus 12C according to still another example.
  • the dispersing device 12C is a disk-type high-speed rotary shearing stirrer.
  • One wall 50C is formed from a non-rotating casing.
  • the other wall 52C is formed of a disk-shaped circular plate rotatably disposed in the casing.
  • the driving unit 60C is connected to the circular plate.
  • the circular plate is rotationally driven by operating the driving unit 60C.
  • one wall 50C forms a fixed wall
  • the other wall 52C forms a movable wall.
  • the inner peripheral surface of the casing and the outer peripheral surface of the circular plate form opposing surfaces 51C and 53C that oppose each other. Both the opposing surfaces 51C and 53C have a peripheral shape.
  • the channel 54C has a cylindrical shape.
  • a part of the organic solvent circulated by the operation of the liquid feed pump 18 is continuously supplied to the flow path 54C via the pipe 35 and the second supply system 56C.
  • the drive unit 60C is operated to rotationally drive the wall 52C.
  • the opposing surface 53C of the wall 52C moves with respect to the opposing surface 51C of the opposing wall 50C. While rotating the wall 52C, the monomer composition is continuously supplied to the flow path 54C through the pipe 31 and the first supply system 55C.
  • the organic solvent and the monomer composition are separately and continuously connected to the channel 54C in which the pair of walls 50C and 52C having the opposing surfaces 51C and 53C opposing each other are relatively moved by the driving unit 60C. Supplied. A strong shearing force acts on the organic solvent flowing into the flow path 54C due to a speed difference between the facing surface 53C of the rotor-side wall 52C and the facing surface 51C of the stator-side wall 50C.
  • the monomer composition is directly injected into the channel 54C where a shear force is acting, and is quickly dispersed in an organic solvent in a droplet form. Further, the droplet-shaped monomer composition is miniaturized.
  • FIG. 5 is a cross-sectional view illustrating a dispersion apparatus 12D according to still another example.
  • the dispersion device 12D is a disk-type high-speed rotary shearing stirrer.
  • One wall 50D is formed of a non-rotating casing.
  • the other wall 52D is formed of a frustum-shaped plate that is rotatably arranged in the casing.
  • the driving unit 60D is connected to the plate. By driving the driving unit 60D, the plate is rotationally driven.
  • one wall 50D constitutes a fixed wall
  • the other wall 52D constitutes a movable wall.
  • the inner peripheral surface of the casing and the outer peripheral surface of the plate form opposing surfaces 51D and 53D that oppose each other. Both the opposing surfaces 51D and 53D have a peripheral shape.
  • the channel 54D has a cylindrical shape.
  • a part of the organic solvent circulated by the operation of the liquid feed pump 18 is continuously supplied to the flow path 54D via the pipe 35 and the second supply system 56D.
  • the driving unit 60D Activate the driving unit 60D to rotationally drive the wall 52D.
  • the opposing surface 53D of the wall 52D moves with respect to the opposing surface 51D of the opposing wall 50D.
  • the monomer composition is continuously supplied to the flow path 54D through the pipe 31 and the first supply system 55D.
  • the organic solvent and the monomer composition are mixed in the flow path 54D in a state where the pair of walls 50D and 52D having the opposing surfaces 51D and 53D opposing each other are relatively moved by the driving unit 60D. It is supplied separately and continuously. A strong shearing force acts on the organic solvent flowing into the flow path 54D due to a speed difference between the facing surface 53D of the rotor-side wall 52D and the facing surface 51D of the stator-side wall 50D.
  • the monomer composition is directly injected into the channel 54D where a shear force is acting, and is quickly dispersed in an organic solvent in the form of droplets. Further, the droplet-shaped monomer composition is miniaturized.
  • FIG. 6 is a sectional view showing a dispersion apparatus 12E according to still another example.
  • the dispersion device 12E is a disk-type high-speed rotary shearing stirrer.
  • One wall 50E is formed of a disk-shaped circular plate that is rotatably arranged in the casing.
  • the other wall 52E is formed of a disk-shaped circular plate rotatably disposed in the casing.
  • the driving units 60E1 and 60E2 are connected to the respective circular plates. By operating the driving units 60E1 and 60E2, the respective circular plates are rotationally driven.
  • the one wall 50E and the other wall 52E together constitute a movable wall.
  • the lower surface of one wall 50E in the drawing is formed as a flat surface
  • the upper surface of the other wall 52E in the drawing is formed as a flat surface.
  • the lower surface of one wall 50E and the upper surface of the other wall 52E form opposing surfaces 51E and 53E which oppose each other. Both the opposing surfaces 51E and 53E have a circular flat shape.
  • the flow path 54E has a linear shape.
  • a first supply system 55E for continuously supplying the monomer composition to the flow path 54E by a passage formed between the rotation shafts, and a second supply system for continuously supplying the organic solvent to the flow path 54E. 56E are formed.
  • the drive units 60E1 and 60E2 rotationally drive the respective circular plates so that the rotational speeds of the respective circular plates are different.
  • the driving units 60E1 and 60E2 can rotate the respective circular plates in opposite directions. Further, the drive units 60E1 and 60E2 can rotate the respective circular plates in the same direction with a speed difference.
  • a part of the organic solvent circulated by the operation of the liquid feed pump 18 is continuously supplied to the flow path 54E through the pipe 35 and the second supply system 56E.
  • the drive units 60E1 and 60E2 are operated to rotationally drive the walls 50E and 52E.
  • the opposing surface 53E of the wall 52E moves relatively to the opposing surface 51E of the opposing wall 50E. While rotating the walls 50E and 52E, the monomer composition is continuously supplied to the flow path 54E through the pipe 31 and the first supply system 55E.
  • the organic solvent and the monomer composition are supplied to the flow path 54E in which the pair of walls 50E and 52E having the opposing surfaces 51E and 53E opposing each other are relatively moved by the driving units 60E1 and 60E2. , Are separately and continuously supplied.
  • a strong shearing force acts on the organic solvent that has flowed into the flow path 54E due to the speed difference between the opposing surface 51E of the wall 50E and the opposing surface 53E of the wall 52E, both of which are on the rotor side.
  • the monomer composition is directly injected into the flow path 54E where a shear force is acting, and is quickly dispersed in the form of droplets in the organic solvent. Further, the droplet-shaped monomer composition is miniaturized.
  • FIG. 7 is a cross-sectional view illustrating a dispersion apparatus 12F according to still another example.
  • the dispersion device 12F is a double-cylindrical high-speed rotary shearing stirrer.
  • the pair of walls 50F and 52F have a cylindrical shape.
  • One wall 50F is formed from a non-rotating outer cylinder having a center hole.
  • the other wall 52F is formed of a solid inner cylinder rotatably disposed in the center hole of the outer cylinder.
  • the driving unit 60F is connected to the inner cylinder. By operating the driving unit 60F, the inner cylinder is rotationally driven.
  • one wall 50F constitutes a fixed wall
  • the other wall 52F constitutes a movable wall.
  • the inner peripheral surface of the outer cylinder and the outer peripheral surface of the inner cylinder form opposing surfaces 51F and 53F that oppose each other. Both the opposing surfaces 51F and 53F have a peripheral shape.
  • the flow path 54F has a cylindrical shape.
  • the bottom of the wall 52F is tapered downward.
  • a communication path 58F is formed between the bottom of the wall 52F and the bottom of the wall 50F to communicate the flow path 54F and the liquid discharge pipe 57F.
  • a part of the organic solvent circulated by the operation of the liquid feed pump 18 is continuously supplied to the flow path 54F via the pipe 35 and the second supply system 56F.
  • the drive unit 60F is operated to rotationally drive the wall 52F.
  • the opposing surface 53F of the wall 52F moves with respect to the opposing surface 51F of the opposing wall 50F. While rotating the wall 52F, the monomer composition is continuously supplied to the flow path 54F through the pipe 31 and the first supply system 55F.
  • the organic solvent and the monomer composition are mixed in the flow path 54F in which the pair of walls 50F and 52F having the opposing surfaces 51F and 53F opposing each other are relatively moved by the driving unit 60F. It is supplied separately and continuously.
  • a strong shearing force acts on the organic solvent flowing into the flow path 54F due to a speed difference between the facing surface 53F of the rotor-side wall 52F and the facing surface 51F of the stator-side wall 50F.
  • the monomer composition is directly injected into the flow path 54F where a shear force is applied, and is quickly dispersed in an organic solvent in the form of droplets. Further, the droplet-shaped monomer composition is miniaturized.
  • FIG. 8 is a cross-sectional view illustrating a dispersion apparatus 12G according to still another example.
  • the dispersing device 12G is a double-cylindrical high-speed rotary shearing stirrer, like the dispersing device 12F.
  • the dispersing device 12G is different from the dispersing device 12F in that the bottom of the wall 52G is formed to be flat.
  • the bottom surface of the wall 50G is open.
  • the bottom opening 59G of the wall 50G functions as a liquid discharge pipe.
  • the liquid discharged from the flow path 54G falls as it is and is charged into the reaction device 14. Since the wall 52G has a cylindrical shape and the inner diameter of the center hole of the wall 52G is substantially equal to the inner diameter of the reaction device 14, the flow of the fluid from the dispersion device 12G to the reaction device 14 is reduced. Smoothness makes it difficult for the monomer composition to stay in the dispersion device.
  • the 12G dispersing apparatus since the stagnation does not easily occur in the apparatus, it is possible to further suppress the monomer composition from being polymerized and becoming a hydrated gel, and the particle diameter of the generated droplets Tends to be constant.
  • the other structure and operation of the dispersing device 12G are the same as those of the dispersing device 12F, and thus description thereof is omitted.
  • the outer cylinder is not limited to a configuration in which the outer cylinder is non-rotating and the inner cylinder is rotatable.
  • the inner cylinder may be non-rotating and the outer cylinder may be rotatable (the inner cylinder forms a fixed wall, and the outer cylinder forms a moving wall).
  • each of the outer cylinder and the inner cylinder may rotate in the opposite direction (a form in which the outer cylinder and the inner cylinder together form a moving wall).
  • the outer cylinder and the inner cylinder may be configured to rotate in the same direction with a speed difference (a form in which the outer cylinder and the inner cylinder together form a moving wall).
  • the rotation speed of the wall 52G is not particularly limited.
  • the rotation speed of the wall 52G may be derived in consideration of the structure, scale, and the like of the dispersing device so as to have the following preferable shear rate.
  • the rotation speed of the wall 52G is, for example, 100 to 10,000 rpm, 500 to 9,000 rpm, and 1,000 to 8,000 rpm.
  • Shear rate in flow channel The shear rate in the flow path of the dispersing device is preferably 1,000 [1 / s] or more.
  • the shear rate is 1,000 [1 / s] or more, the shear rate is sufficient to disperse the monomers in the flow path in the organic solvent. Become smaller. As the primary particle diameter decreases, the specific surface area of the water-absorbing resin increases, leading to an improvement in the water absorption rate. Further, when the shear rate is 1,000 [1 / s] or more, it is possible to shorten the time for generating droplets. Furthermore, when the shear rate is 1,000 [1 / s] or more, the amount of the surfactant used during dispersion can be reduced.
  • the shear rate in the flow path of the dispersion device is preferably 1,000 [1 / s] or more, more preferably 2,000 [1 / s] or more, and 3,000 [1 / s]. 1 / s] or more, more preferably 3,500 [1 / s] or more.
  • the shear rate is preferably 40,000 [1 / s] or less, more preferably 20,000 [1 / s] or less, and It is more preferably at most 000 [1 / s], particularly preferably at most 6,000 [1 / s].
  • the shear rate in the flow path of the dispersing device is preferably from 1,000 to 40,000 [1 / s], more preferably from 2,000 to 20,000 [1 / s], and 3,000. Even more preferably, it is from 10,000 to 1 / s, and particularly preferably from 3,500 to 6,000 [1 / s].
  • the shear rate in the flow channel of the dispersing device is preferably 1,000 to 40,000 [1 / s], and 2,000 to 20,000 [1 / S], more preferably 3,000 to 10,000 [1 / s], and particularly preferably 3,500 to 6,000 [1 / s].
  • the shear rate is determined by the rotor rotation speed and the flow path width (clearance, for example, the outer cylinder radius and the inner cylinder radius in the case of a double cylinder type dispersion device).
  • the shear rate is calculated as follows.
  • Shearing speed [1 / s] moving speed [m / s] / gap (clearance) [m] of a relatively moving wall (rotor, rotor) in the dispersion device
  • the moving speed is the maximum moving speed in the liquid contact part when one of the walls is a fixed wall.
  • the moving speed is the moving speed at the point where the difference between the moving speeds is maximum. In the case where both of the pair of walls rotate, a difference in the moving speed occurs.
  • the maximum shear rate is defined as the shear rate in the present specification.
  • Average residence time of the water-soluble ethylenically unsaturated monomer solution in the flow channel (hereinafter, also simply referred to as average residence time)"
  • the organic solvent and the monomer solution (or the monomer composition) are rapidly mixed and discharged to the reaction device. Therefore, the residence time of the monomer solution (or the monomer composition) in the dispersing device is reduced. This suppresses the monomer composition from being polymerized into a gel in the dispersing apparatus, and can suppress clogging in the dispersing machine due to the gel.
  • the average residence time is calculated by the following formula.
  • Average residence time [s] dispersion part volume [ml] / ⁇ (flow rate of water-soluble ethylenically unsaturated monomer solution (or monomer composition) [ml / min] + flow rate of organic solvent [ml / min] ]) / 60 ⁇
  • the dispersion portion volume (effective outer cylinder volume ⁇ effective rotation portion volume).
  • the dispersion portion is a region where a shearing force is applied in a state where two fluids (an organic solvent and a monomer solution (or a monomer composition)) intersect. For example, in FIG.
  • the tapered shape region (L in FIG. 7) is the dispersion portion, and the volume of the dispersion portion is defined as the dispersion portion volume.
  • a region (H in FIG. 8) from the midpoint in the height direction of the first supply system 55F to which the monomer composition is supplied to the bottom of the wall 52F is a dispersion portion,
  • the volume of the dispersing part is defined as the dispersing part volume.
  • the average residence time is preferably 0.1 to 5 seconds.
  • the average residence time is more preferably 0.3 to 3 seconds, and further preferably 0.5 to 1.5 seconds. In the case where the dispersion and the polymerization are performed in one apparatus (batch operation), the average residence time usually exceeds 60 seconds.
  • the average residence time can be controlled by the shape of the dispersing device (rotor size, gap, addition position of the monomer solution, shape of the outlet following the reactor, etc.) and the amount of dispersion medium.
  • the preferable volume average particle diameter of the droplet containing the water-soluble ethylenically unsaturated monomer is 2000 ⁇ m or less from the viewpoint of the stability of the dispersed or suspended state and the heat transfer efficiency of the organic solvent. Preferably it is 1000 ⁇ m or less, more preferably 800 ⁇ m or less. In addition, from the viewpoint of production efficiency, it is preferably 10 ⁇ m or more, more preferably 20 ⁇ m or more, and further preferably 30 ⁇ m or more.
  • the “volume average particle diameter” of the droplet is determined by “particle diameter analysis-laser diffraction / scattering method” specified in JIS Z 8825: 2013 and “particle diameter measurement result” specified in JIS Z 8819-2: 2001.
  • Expression-Part 2 Calculation of average particle diameter or average particle diameter and moment from particle diameter distribution "or a method of calculating the dispersion state by image analysis of a photograph of a photographed image. I can do it.
  • the ratio of the monomer composition flow rate [ml / min] flowing into the dispersion apparatus to the organic solvent flow rate [ml / min] flowing into the dispersion apparatus is preferably 0.01 or more, more preferably 0.02 or more, further preferably 0.04 or more, and more preferably more than 0.04. More preferably, it is particularly preferably 0.08 or more. In the present embodiment, since a monomer is dispersed by applying a shearing force by a shear field, a large amount of an organic solvent is not required.
  • the upper limit of the monomer composition flow rate [ml / min] / organic solvent flow rate [ml / min] is not particularly limited, but is preferably 1.00 or less, more preferably 0.40 or less, and .20 or less is more preferable.
  • Organic solvent Preferred organic solvents include at least one organic solvent selected from the group consisting of aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, and halogenated hydrocarbons. Specific examples include aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane and n-octane; alicyclic hydrocarbons such as cyclohexane, methylcyclohexane, cyclooctane and decalin; benzene, toluene, xylene and the like.
  • Aromatic hydrocarbons include, for example, halogenated hydrocarbons such as chlorobenzene, bromobenzene, carbon tetrachloride, and 1,2-dichloroethane.
  • halogenated hydrocarbons such as chlorobenzene, bromobenzene, carbon tetrachloride, and 1,2-dichloroethane.
  • n-hexane, n-heptane, and cyclohexane are preferable from the viewpoint of availability and quality stability. It is also possible to use a mixture of two or more solvents.
  • the temperature of the organic solvent supplied into the dispersion device is controlled so as to be Td described later.
  • the boiling point of the organic solvent is preferably 70 ° C. or higher, more preferably 80 to 95 ° C.
  • a stable dispersion state can be achieved without adding a dispersing aid or with a very small amount of a dispersing aid.
  • a dispersion aid such as a surfactant and a polymer additive may be added to the organic solvent forming the continuous phase.
  • the type of the dispersing aid is appropriately selected depending on the combination of the organic solvent and the monomer used. Examples of the dispersing aid that can be used include the following surfactants and polymer additives.
  • sucrose fatty acid ester specifically, sucrose fatty acid ester, polyglycerin fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene glycerin fatty acid ester, sorbitol fatty acid ester, polyoxyethylene sorbitol fatty acid ester, Polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene castor oil, polyoxyethylene hydrogenated castor oil, alkyl allyl formaldehyde condensed polyoxyethylene ether, polyoxyethylene polyoxypropylene block copolymer, polyoxyethylene polyoxypropyl Alkyl ether, polyethylene glycol fatty acid ester, alkyl glucoside, N-alkyl glucoside Amides, polyoxyethylene fatty acid amides, polyoxyethylene alkyl amines, phosphoric esters of polyoxyethylene alkyl ethers, and phosphoric esters of polyoxyethylene alky
  • R 1 and R 2 are each independently hydrogen, methyl or ethyl, and n represents an integer of 3 to 20.
  • maleic anhydride-modified polyethylene maleic anhydride-modified polypropylene, maleic anhydride-modified ethylene-propylene copolymer, maleic anhydride-modified ethylene-propylene-diene terpolymer (EPDM), maleic anhydride-modified polybutadiene, maleic anhydride / ethylene copolymer, maleic anhydride / propylene copolymer, maleic anhydride / ethylene / propylene copolymer, maleic anhydride / butadiene copolymer, polyethylene, polypropylene Ethylene-propylene copolymer, oxidized polyethylene, oxidized polypropylene, oxidized ethylene-propylene copolymer, ethylene-acrylic acid copolymer, ethyl cellulose, ethyl hydroxyethyl cellulose, and the like.
  • maleic anhydride-modified polyethylene maleic anhydride-modified polypropylene, maleic anhydride-modified ethylene-propylene copolymer, maleic anhydride-ethylene copolymer, maleic anhydride -Propylene copolymer, maleic anhydride-ethylene-propylene copolymer, polyethylene, polypropylene, ethylene-propylene copolymer, oxidized polyethylene, oxidized polypropylene, and oxidized ethylene-propylene copolymer are preferred. Two or more of these may be used in combination. Further, these polymer additives may be used in combination with the above surfactant.
  • a polymer additive it is preferable to use a polymer additive, and it is more preferable to use a maleic anhydride-modified ethylene / propylene copolymer.
  • a polymer additive alone without using a surfactant it is preferable to use a polymer additive alone without using a surfactant.
  • the dispersion of the liquid droplets is improved even when the polymer additive is added alone.
  • the amount of the dispersing aid used is appropriately set according to the polymerization form, the type of the monomer composition and the type of the organic solvent. Specifically, the concentration of the dispersing aid in the organic solvent in the continuous phase is preferably 0.0001 to 2% by weight, more preferably 0.0005 to 1% by weight.
  • This step is a step of obtaining a hydrogel by polymerizing the water-soluble ethylenically unsaturated monomer supplied to the reaction device in the above-mentioned dispersion step.
  • the shape of the reactor in which the polymerization reaction is performed is not particularly limited, but in the case of a continuous production method, preferably, the monomer (composition) is mixed with an organic solvent that is a continuous phase formed in the reactor.
  • a reaction device for example, a reaction device in which a tubular reaction tube is arranged in a vertical type, a horizontal type, or a spiral type is used.
  • One preferred embodiment of the present invention polymerizes a water-soluble ethylenically unsaturated monomer in a tubular reaction tube.
  • the ratio (L / D) of the inner diameter D (mm) to the length L (mm) of the reaction tube is preferably 2 to 100,000, more preferably 3 to 50,000. And more preferably 4 to 20,000.
  • the reactor may be provided with a temperature adjusting means so that the continuous phase inside the reactor can be heated or cooled from the outside as necessary.
  • the temperature of the continuous phase in the reactor is maintained within a predetermined range by the temperature adjusting means.
  • the temperature adjusting means is not particularly limited, but includes, for example, installation of a jacket in the reactor, installation of a heater, installation of a heat insulating material or heat insulating material, supply of hot air or cold air, and the like.
  • a fluororesin is preferably used, and more preferably, one in which the inner wall surface of the reaction apparatus is subjected to surface processing such as fluororesin processing is used.
  • Polymerization temperature In the production method according to the present invention, the temperature of the organic solvent forming the continuous phase in the reactor (hereinafter, referred to as “Td”) is defined as the polymerization temperature.
  • the temperature of the monomer composition quickly rises due to heat transfer from the continuous phase.
  • the polymerization initiator contained in the droplet is a thermal decomposition type polymerization initiator
  • the thermal decomposition type polymerization initiator is decomposed with the above-mentioned temperature rise to generate radicals.
  • the polymerization reaction is started by the generated radical, and a gel polymer is formed with the progress of the polymerization reaction.
  • the formed gel polymer moves inside the reactor by the circulating continuous phase and is discharged from the reactor together with the organic solvent forming the continuous phase.
  • the Td is preferably 70 ° C. or higher, more preferably 75 ° C. or higher, and still more preferably 80 ° C. or higher, from the viewpoint of the polymerization rate.
  • the upper limit of Td is not particularly limited, but is appropriately selected from the viewpoint of safety within a range not exceeding the boiling point of the organic solvent constituting the continuous phase.
  • the Td is preferably the same as or higher than T10 of the thermal decomposition type polymerization initiator used.
  • the upper limit of the difference ⁇ T2 is preferably 50 ° C. or less from the viewpoint of energy efficiency.
  • the temperature of the continuous phase fluctuates as the monomer composition is supplied to the reactor.
  • a temperature change is large in a region where the monomer composition is supplied. Therefore, preferably, the organic solvent heated by the heat exchanger is re-supplied to this region so that a desired Td is obtained in the region, or the reaction is carried out by a temperature adjusting means such as a jacket installed in the reactor. Heat the continuous phase in the apparatus. Thereby, the temperature change of the continuous phase contributing to the initiation and progress of the polymerization reaction can be suppressed, and Td can be controlled more precisely.
  • the “polymerization time” refers to the time when the monomer composition is charged into a reaction apparatus in the case of a continuous production method, and a gel state obtained by a polymerization reaction.
  • the droplets of one monomer composition Means the time required from the start point to the end point.
  • the time from the start of the supply of the monomer composition to the reactor to the first discharge of the gel polymer from the reactor is the polymerization time.
  • the polymerization time corresponds to the residence time of the droplet in the reactor.
  • the polymerization time is controlled depending on the type of the monomer and the polymerization initiator, etc., but from the viewpoint of production efficiency, preferably 60 minutes or less, more preferably 30 minutes or less, further more preferably 20 minutes or less, particularly preferably 20 minutes or less. It is preferably controlled to 10 minutes or less, most preferably 5 minutes or less.
  • the lower limit of the polymerization time is not particularly limited, the viewpoint of the heat transfer efficiency from the continuous phase when the droplets of the monomer composition supplied into the reactor are heated to the polymerization temperature. Therefore, it is preferably controlled to 30 seconds or more. Controlling the polymerization time within the above range is preferable because the size of the reactor can be reduced.
  • the space velocity (LHSV) in the reactor where the polymerization reaction is performed refers to a monomer solution in the polymerization device.
  • LHSV space velocity
  • it is an index indicating the passing speed of the monomer composition (hydrogel) and the organic solvent, and is an index which is a guide when controlling the polymerization time.
  • the lower limit of space velocity in the polymerization system is preferably from 2 hr -1 or more, more preferably 3 hr -1 or more, 4hr -1 or more is more preferable.
  • the upper limit of space velocity in the polymerization system is preferably 10 hr -1 or less, 9Hr -1 or less More preferably, it is even more preferably 8 hr -1 or less.
  • the space velocity in the polymerization system is 2 ⁇ 10 hr -1, preferably 3 ⁇ 9hr -1.
  • the space velocity (LHSV) (unit: hr ⁇ 1 ) in the polymerization apparatus is determined by the volume flow rate Qm (unit: m 3 / hr) of the monomer solution or the monomer composition (hydrogel) supplied to the polymerization apparatus. It is a value obtained by dividing the total volume flow rate Qs (unit: m 3 / hr) of the organic solvent and the dispersing aid by the volume V (unit: m 3 ) of the polymerization apparatus, and can be calculated by the following equation.
  • the volume of the polymerization apparatus refers to the volume of the reaction field in which the polymerization reaction of the monomer is performed.
  • the inlet of the monomer solution or the monomer composition (injection) Part) to the discharge part of the gel polymer in the case of a vertical tubular reaction tube, the inlet of the monomer solution or the monomer composition (injection) Part) to the discharge part of the gel polymer.
  • This step is a step of separating the gel polymer discharged from the reaction device and the organic solvent in the polymerization step to obtain a gel polymer (hydrogel).
  • the type and structure of the separation device are not particularly limited.
  • a known method such as filtration, sedimentation, centrifugal separation, or squeezing can be used.
  • Shape of gel polymer '' In the present invention, the shape of the obtained gel polymer is spherical.
  • the particle size of the gel polymer (hereinafter referred to as “gel particle size”) is appropriately adjusted according to the use of the obtained water-absorbent resin.
  • the “spherical shape” is a concept including a shape other than a true spherical shape (for example, a substantially spherical shape), and the ratio of the average major axis to the average minor axis (also referred to as “sphericity”) is preferably 1.0. Means particles that are ⁇ 3.0. The average major axis and average minor axis of the particles are measured based on an image taken with a microscope.
  • the gel polymer may be formed as an aggregate of a fine spherical gel, or may be obtained as a mixture of a fine spherical gel and an aggregate of the spherical gel.
  • the particle size of each spherical gel constituting the aggregate is referred to as a primary particle size.
  • the average primary particle diameter is not particularly limited, but is preferably 1 to 2000 ⁇ m, more preferably 5 to 1000 ⁇ m, further preferably 10 to 800 ⁇ m, and particularly preferably 10 to 800 ⁇ m, from the viewpoint of suppressing generation of fine powder in the drying step. Is 10 to 200 ⁇ m.
  • the average primary particle diameter of the gel polymer (hydrogel) is a value measured by the method described in the following Examples.
  • Solid concentration of gel polymer The solid content of the gel polymer to be subjected to the drying step described below is not particularly limited, but from the viewpoint of drying cost, is preferably 20% by weight or more, more preferably 30% by weight or more, and further preferably 40% by weight. The content is particularly preferably 45% by weight or more.
  • the upper limit of the solid content of the gel polymer is not particularly limited, but is preferably 90% by weight or less, more preferably 80% by weight or less, further preferably 70% by weight or less, and particularly preferably 60% by weight or less. .
  • the method for producing a water-absorbent resin according to the present invention may further include a drying step, a pulverizing step, a classification step, a surface cross-linking step, a sizing step, a fine powder removing step, a granulating step, A recycling step may be included. In addition, it may further include a transportation step, a storage step, a packing step, a storage step, and the like.
  • a preferred embodiment of the present invention further comprises drying the hydrogel polymer obtained by the polymerization to obtain a water-absorbent resin powder, and subjecting the water-absorbent resin powder to a surface crosslinking with a surface crosslinking agent, Having. By such an operation, the physical properties of the obtained water-absorbent resin can be improved.
  • This step is a step of drying the gel polymer separated in the separation step to a desired solid content to obtain a particulate dry polymer.
  • the gel polymer may be crushed or granulated to adjust to a desired particle size or particle size distribution and then subjected to a drying step.
  • drying the gel polymer for example, drying by conduction heat transfer, drying by convection heat transfer (for example, hot air), drying by reduced pressure, drying using infrared rays, and microwaves are used. Drying, drying by azeotropic dehydration with a hydrophobic organic solvent, and superheated steam drying using high-temperature steam (for example, superheated steam) are exemplified.
  • a stirring-type conduction heat transfer drying that has high drying efficiency and facilitates recovery of a liquid component such as an organic solvent is preferable, and a continuous stirring-type drying apparatus using an indirect heating method is more preferable. used.
  • the shape of the gel polymer formed by the production method according to the present invention is spherical.
  • the dried polymer composed of spherical particles is obtained by drying the spherical gel polymer with the above-mentioned stirring type drying device.
  • the dry polymer composed of spherical particles obtained in the present drying step can be used as it is as a water-absorbing resin for various uses.
  • the spherical dried polymer obtained in the drying step can be subjected to a surface cross-linking step described later.
  • the dried polymer that is subjected to the surface cross-linking step described below is referred to as “water-absorbent resin powder” for convenience.
  • the drying temperature and the drying time are appropriately adjusted using the solid content as an index according to the use of the obtained water-absorbent resin.
  • the solid content is preferably 85% by weight or more, more preferably 90% to 98% by weight, from the viewpoint of water absorbing performance.
  • the solid content of the water-absorbent resin is a value calculated based on the loss on drying when the sample (water-absorbent resin) is dried at 180 ° C. for 3 hours.
  • the particulate dried polymer obtained in the drying step is subjected to a pulverizing step and a classifying step, if necessary, to obtain a water-absorbent resin having a controlled particle diameter or particle size distribution.
  • 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, a cylindrical mixer and the like are appropriately selected and used.
  • classification step for example, sieving classification using a JIS standard sieve (JIS Z8801-1 (2000)) or air flow classification is appropriately selected and used.
  • the particulate dry polymer obtained through the drying step is subjected to a surface cross-linking step as necessary.
  • This surface cross-linking step is a step of providing a portion having a high cross-linking density on the surface layer of the water-absorbent resin powder (a portion several tens of ⁇ m from the surface of the water-absorbent resin powder).
  • a known surface crosslinking technique is appropriately applied.
  • the “grain sizing step” means a step in which the water-absorbent resin powder loosely aggregated through the surface cross-linking step is disintegrated to adjust the particle diameter.
  • the sizing step includes a fine powder removing step, a gel crushing step, and a classifying step after the surface crosslinking step.
  • the “fine powder recycling step” refers to a step of supplying the fine powder generated in each of the above steps to any step as it is or after granulating the fine powder.
  • the use of the water-absorbent resin of the present invention is not particularly limited, but is preferably a water-blocking material, a paint, an adhesive, an anti-blocking agent, a light diffusing agent, a matting agent, a decorative plate additive, and an artificial marble additive. And resin additives such as toner additives.
  • the use as the water-absorbent resin is not particularly limited, but preferably includes absorbent uses for absorbent articles such as disposable diapers, sanitary napkins, incontinence pads, and the like. In particular, it can be used as an absorber for a high-concentration paper diaper that has had problems with odor, coloring, and the like derived from the raw materials. Furthermore, since this water-absorbent resin has excellent water absorption time and a controlled particle size distribution, a remarkable effect can be expected when used in the upper layer of the absorber.
  • an absorbent material such as pulp fiber can be used together with the water absorbent resin.
  • the content (core concentration) of the water-absorbent resin in the absorber is preferably 30% by weight to 100% by weight, more preferably 40% by weight to 100% by weight, and further preferably 50% by weight to 100% by weight. %, Even more preferably from 60% to 100% by weight, particularly preferably from 70% to 100% by weight, most preferably from 75% to 95% by weight.
  • the absorbent article can be kept in a clean white state. Furthermore, since the absorber has excellent diffusibility for bodily fluids such as urine and blood, an efficient liquid distribution can be expected to improve the absorption amount.
  • the polymerization is carried out by so-called reverse phase suspension polymerization.
  • the water-absorbing resin obtained in this way usually becomes spherical polymer particles.
  • the term “spherical” includes shapes other than a true sphere.
  • the term “spherical” means particles having a ratio of the average major axis to the average minor axis (also referred to as sphericity) of preferably 1.0 to 3.0.
  • the average major axis and average minor axis of the particles are measured based on an image observed with a microscope.
  • the “spherical polymer particles” are not limited to existing as single particles, and may form aggregates of spherical polymer particles.
  • the spherical polymer particles in the present invention are designed by selecting a polymerizable monomer according to the use and purpose.
  • a polymerizable monomer typically used is (meth) acrylic acid and / or a salt thereof.
  • the particle shape is spherical, particularly a spherical aggregate, the water absorption rate of the water-absorbing resin tends to be higher than that of the irregular shape.
  • CRC Centrifuge Retention Capacity
  • water absorption capacity means the water absorption capacity of the water-absorbent resin under no pressure (sometimes referred to as “water absorption capacity”).
  • CRC centrifuge holding capacity
  • EDANA is an abbreviation for European, Disposables, and Nonwovens Associations.
  • ERT is an abbreviation of EDANA Recommended Test Methods and is a European standard that defines a method for measuring a water-absorbent resin. In the present invention, unless otherwise specified, physical properties of the water-absorbent resin are measured based on the original ERT (revised in 2002).
  • the water absorbing resin preferably has a CRC (centrifuge holding capacity) of 15 g / g or more, more preferably 25 g / g or more.
  • the upper limit is not particularly limited, and a higher CRC is preferred, but from the viewpoint of balance with other physical properties, it is preferably 70 g / g or less, more preferably 50 g / g or less, and further more preferably 40 g / g or less.
  • the CRC When the CRC is less than 5 g / g, the amount of absorption is small and it is not suitable as an absorbent for absorbent articles such as disposable diapers. On the other hand, if the CRC exceeds 70 g / g, the rate of absorbing body fluids such as urine and blood decreases, so that it is not suitable for use in paper diapers with a high water absorption rate.
  • the CRC can be controlled by changing the type and amount of an internal crosslinking agent, a surface crosslinking agent, and the like.
  • DRC5min is an abbreviation for “Dunk Retention Capacity” (immersion holding capacity), and “DRC5min” means a 5-minute immersion holding capacity (water absorption capacity under no pressure in 5 minutes).
  • Dunk Retention Capacity immersion holding capacity
  • DRC5min means a 5-minute immersion holding capacity (water absorption capacity under no pressure in 5 minutes).
  • the lower limit of the DRC of the water absorbent resin is preferably 46 g / g or more, more preferably 47 g / g or more, still more preferably 50 g / g or more, and particularly preferably. Is 52 g / g or more.
  • the upper limit of DRC of the water absorbent resin is not particularly limited, but is usually 70 g / g or less.
  • the DRC of 5 min can be controlled by the water absorption ratio, the average primary particle size of the hydrogel, the polymerization rate, the particle size, and the like.
  • the residual monomer amount means the amount of the monomer (monomer) remaining in the water absorbent resin.
  • the monomer remaining in the water absorbent resin is referred to as “residual monomer”.
  • the residual monomer amount was measured according to the EDANA method (ERT440.2-02). Specifically, it refers to the amount (unit: ppm) of a monomer dissolved in an aqueous solution after adding 1.0 g of a water-absorbent resin to 200 ml of a 0.9% by weight aqueous solution of sodium chloride and stirring for 1 hour at 500 rpm. High-performance liquid chromatography (HPLC) is used to measure the amount of residual monomer.
  • the amount of residual monomers contained in the water-absorbing resin is preferably 1000 ppm or less, more preferably 400 ppm or less, and still more preferably 300 ppm or less, from the viewpoint of safety.
  • the lower limit is preferably as low as possible, and is not particularly limited, but is preferably 0 ppm, and more preferably about 10 ppm.
  • the amount of the residual monomer can be controlled by the temperature of the organic solvent supplied into the dispersion device, LHSV, or the like. As the polymerization time is appropriately secured and the polymerization rate is higher, the amount of the residual monomer is reduced.
  • One embodiment is a water-absorbent resin obtained by the above production method, wherein the DRC is 5 min or more and the residual monomer is 400 ppm or less.
  • Average primary particle size of hydrogel The hydrogel was photographed with an optical microscope (KH-3000, manufactured by Hilox Corporation), and the major diameter of the primary particles was measured from the obtained image. The measurement was performed on 50 primary particles, and the average value was defined as the average primary particle size of the hydrogel.
  • the average primary particle diameter of the hydrogel was calculated as follows.
  • DRC5min According to the method described in International Publication No. 2017/170605, the DRC of the water-absorbent resin (1) was measured for 5 minutes (immersion holding capacity 5 minutes value).
  • a 400 mesh stainless steel wire mesh 201 (mesh size: 38 ⁇ m) was fused to the bottom of a plastic support cylinder 200 having an inner diameter of 60 mm, and the room temperature (20 to 25 ° C.) ) And a humidity of 50% RH, the water-absorbent resin (1) 202 @ 1.000 ⁇ 0.005 g was evenly sprayed on the wire net 201, and the weight Wa (g) of the set of measuring devices was measured.
  • a glass filter 204 having a diameter of 120 mm (manufactured by Mutual Life Science Glass Co., Ltd., pore diameter: 100 to 120 ⁇ m) is placed inside a circular or square petri dish 203 having a bottom area of 400 cm 2 , and 0.90 wt% saline. 206 (23 ⁇ 0.5 ° C.) at the same level as the upper surface of the glass filter (the liquid is slightly floating on the outer periphery of the glass filter due to surface tension, or about 50% of the surface of the glass filter is covered with the liquid) State).
  • One sheet of filter paper 205 having a diameter of 110 mm (ADVANTEC Toyo Co., Ltd., product name: JIS P 3801, No. 2, thickness 0.26 mm, diameter of retained particles 5 ⁇ m) was placed thereon, and the entire surface of the filter paper was wetted.
  • the above set of measuring devices was placed on the wet filter paper to absorb the liquid (the liquid temperature was strictly controlled at 23 ⁇ 0.5 ° C. even during the measurement). After exactly 5 minutes (300 seconds), the set of measuring devices was lifted and its weight Wb (g) was measured. Then, DRC 5 min (g / g) was calculated from Wa and Wb according to the following equation.
  • Example 1 After producing the hydrogel (1) according to the production process shown in FIG. 1, the obtained hydrogel (1) was dried and further subjected to surface cross-linking to produce a spherical water-absorbing resin (1).
  • n-heptane (density: 0.68 g / ml) was charged as an organic solvent into the dispersion device 12, the reaction device 14, the separation device 16, and the piping connecting these components.
  • the liquid pump 18 was operated to start circulation of the organic solvent at a flow rate of 300 ml / min.
  • the heat exchanger 20 was operated to heat the circulating organic solvent such that the set temperature was 90 ° C.
  • sucrose fatty acid ester (trade name: DK Ester F-50 / Daiichi Kogyo Seiyaku Co., Ltd.) was added to n-heptane as a dispersing aid.
  • the monomer composition (1) had a monomer concentration of 43% by weight and a neutralization ratio of 73 mol%.
  • polyethylene glycol diacrylate as an internal cross-linking agent is 0.023 mol% based on the monomer
  • diethylene triamine pentaacetic acid / 3 sodium as a chelating agent is 200 ppm based on the monomer
  • persulfuric acid as a polymerization initiator is used.
  • Sodium (T10 @ 70 ° C.) was 0.1 g / mol based on the monomer.
  • a dispersing device 12G of a double-cylindrical high-speed rotary shearing stirrer shown in FIG. 8 was used as the dispersing device.
  • the inner diameter of the casing (the inner diameter of the outer cylinder 50G) is 25 mm
  • the outer diameter of the rotor (the outer diameter of the inner cylinder 52G) is 22 mm
  • the effective rotor length (from the monomer aqueous solution inlet 55G to the outlet) is 65 mm.
  • a vertically arranged tube made of PFA (perfluoroalkoxy alkane) inner diameter: 25 mm, total length: 10 m
  • the rotor (inner cylinder 52G) is rotated at a rotation speed of 4,800 rpm (shear rate 3686 [1 / s]), and then the monomer composition (1) is supplied at a flow rate of 40 ml / min (47.2 g). / Min), the liquid was sent to the pipe 31 of the dispersion device 12G.
  • the supplied monomer composition (1) was dispersed in the form of fine droplets in the organic solvent by a dispersing device (average residence time of the monomer composition (1) 1.27 s).
  • the droplet composed of the monomer composition (1) changed into a fine spherical gel as the polymerization reaction proceeded while falling in the reactor filled with the organic solvent as the continuous phase. These small spherical gels adhered to each other as they fell to form aggregates. In the vicinity of the outlet of the reaction apparatus, a hydrogel (1) having a diameter of about 1 cm and consisting of fine spherical gel aggregates was confirmed.
  • the space velocity (LHSV) in the reactor 14 was 4.2 hr -1 .
  • the hydrogel (1) and the organic solvent discharged from the reaction device 14 were continuously supplied to the separation device 16 as they were.
  • the hydrogel (1) and the organic solvent were separated.
  • the organic solvent separated by the separation device was temperature-controlled by the heat exchanger 20 so that the set temperature became 90 ° C., and then supplied to the reaction device 14 again.
  • the hydrogel (1) obtained by the above operation had a shape in which minute spherical hydrogel was adhered and aggregated. Further, the water-containing gel (1) was sampled every 20 minutes from 100 minutes after the start of the operation to the end of the operation (5 hours), and the average primary particle diameter was measured to be 50 to 60 ⁇ m.
  • the water-absorbent resin powder (1) containing the surface cross-linking agent is introduced into a heat treatment machine whose atmosphere temperature is adjusted to 195 ° C. ⁇ 2 ° C., and is subjected to heat treatment for 30 minutes, until the powder temperature becomes 60 ° C. Forced cooling. By this operation, water-absorbent resin particles (1) were obtained.
  • the water-absorbent resin particles (1) were passed through a JIS standard sieve having openings of 850 ⁇ m to regulate the particle size, thereby obtaining a water-absorbent resin (1) as a product.
  • the shape of the water-absorbent resin (1) was a tufted aggregate of spheres.
  • Table 1 shows the physical properties measured for the obtained hydrogel (1) and water-absorbent resin (1).
  • Example 2 A water-containing gel (2) was obtained in the same manner as in Example 1, except that the rotor rotation speed was changed to 3600 rpm (shear speed 2765 [1 / s]). The hydrogel (2) obtained by the above operation was sampled every 20 minutes from 100 minutes after the start of the operation to the end of the operation (5 hours), and the average primary particle diameter was measured to be 80 to 90 ⁇ m.
  • Example 3 In Example 1, the rotor rotation speed was set to 7200 rpm (shear rate 5529 [1 / s]), and the dispersing aid to be added to n-heptane was maleic anhydride-modified polyethylene (acid value: 60 mg KOH / g) 0.005% by weight. Except that the addition was changed, the same operation as in Example 1 was performed to obtain a hydrogel (3). The water-containing gel (3) obtained by the above operation was sampled every 20 minutes from 100 minutes after the start of the operation to the end of the operation (5 hours), and the average primary particle diameter was measured to be 50 to 60 ⁇ m.
  • Example 1 is the same as Example 1 except that the amount of the dispersion medium was changed to 500 ml / min and the rotor length was shortened (the axial length of the inner cylinder 52G of the dispersion device 12G was shorter by 2.5 cm from the bottom).
  • the hydrogel (4) obtained by the above operation was sampled every 20 minutes from 100 minutes after the start of the operation to the end of the operation (5 hours), and the average primary particle diameter was measured to be 60 to 80 ⁇ m.
  • the dispersing device is the same as the dispersing device 12F shown in FIGS. 8 to 7 (gap (clearance) 3.0 mm, casing inner diameter (inner diameter of outer cylinder 50F) 76 mm, rotor outer diameter (outer diameter of inner cylinder 52F)). 70 mm, the effective rotor length (35 mm from the monomer aqueous solution inlet 55F to the outlet), the dispersion medium amount to 500 ml / min, and the rotor rotation speed changed to 4500 rpm (shear speed 5498 [1 / s]). Except that, the same operation as in Example 1 was performed to obtain a hydrogel (5). The hydrogel (5) obtained by the above operation was sampled every 20 minutes from 100 minutes after the start of the operation to the end of the operation (5 hours), and the average primary particle diameter was measured to be 60 to 80 ⁇ m.
  • Example 6 In Example 1, the dispersion device was changed from the shape of FIG. 8 to the shape of the dispersion device 12E of FIG. 6, and the circular plate 52E was rotated at 3600 rpm (shear speed 9425 [1 / s], gap (clearance) 1.0 mm). Was performed in the same manner as in Example 1 to obtain a hydrogel (6).
  • the water-containing gel (6) obtained by the above operation was sampled every 20 minutes from 100 minutes after the start of the operation to the end of the operation (5 hours), and the average primary particle diameter was measured to be 70 to 100 ⁇ m.
  • Example 1 In Example 1, the same operation as in Example 1 was performed except that the dispersing step was performed using a two-fluid spray nozzle (dispersing apparatus 200) shown in FIG. 9 instead of the high-speed rotary shear type stirrer. A hydrogel (1) and a comparative water-absorbent resin (1) were obtained.
  • a PTFE two-fluid spray nozzle (external mixing type, spray nozzle inner diameter: 1.0 mm, type: SETOJet, air consumption classification 075, injection amount 10, manufactured by Ikeuchi Co., Ltd.) was used as a dispersing device.
  • the two-fluid spray has a first supply pipe 201 for continuously supplying the monomer composition and a second supply pipe 202 for continuously supplying the organic solvent.
  • the monomer composition is spray-dispersed from the first nozzle 203 and the organic solvent is sprayed and dispersed from the second nozzle 204, and are continuously discharged to the reactor.
  • the position of the two-fluid spray was adjusted so that the tip of the two-fluid spray nozzle was immersed in the organic solvent contained in the polymerization apparatus. Further, the flow rate of the circulating mixture of the organic solvent and the dispersing aid was changed to 1000 ml / min, and the path of the circulated mixture of the organic solvent and the dispersing aid was passed through a dispersion device (two-fluid spray nozzle). It was branched into a path to be charged into the polymerization apparatus and a path to be directly charged into the polymerization apparatus.
  • the flow rate of the organic solvent supplied to the reaction device via the dispersing device was 800 ml / min, and the flow rate of the organic solvent directly supplied to the reaction device was 200 ml / min.
  • the monomer composition (1) prepared in the mixing step was immediately sent to the first supply pipe 201 of the two-fluid spray. Thereafter, the monomer composition (1) was introduced into the organic solvent filling the polymerization apparatus at a flow rate of 40 mL / min (47.2 g / min) using the two-fluid spray.
  • the monomer composition (1) charged by the two-fluid spray was dispersed in the organic solvent in the form of fine droplets.
  • the space velocity (LHSV) in the reactor 14 was 12.7 hr -1 .
  • the comparative hydrogel (1) obtained by the above operation has a shape in which minute spherical hydrogel is adhered and agglomerated, and is sampled every 20 minutes from 100 minutes after the start of operation to the end of operation (5 hours). However, when the average primary particle diameter was measured, the average primary particle diameter was extremely varied from 30 to 80 ⁇ m.
  • Table 1 shows various physical properties of the obtained comparative hydrogel (1) and comparative water-absorbent resin (1).
  • Example 7 After producing the hydrogel (7) according to the production process shown in FIG. 11, the obtained hydrogel (7) was dried and further subjected to surface crosslinking to produce a spherical water-absorbing resin (7).
  • An ultraviolet irradiation device 23 is provided in the upper half of the reaction device 14.
  • n-heptane (density: 0.68 g / ml) was charged as an organic solvent into the dispersion device 12, the reaction device 14, the separation device 16, and the piping connecting these components.
  • the liquid feed pump 18 was operated, and circulation of the organic solvent was started at a flow rate of 200 ml / min. Further, the heat exchanger 20 was operated to heat the circulating organic solvent such that the set temperature was 70 ° C.
  • sucrose fatty acid ester (trade name: DK ester F-50 / Daiichi Kogyo Seiyaku Co., Ltd.) was added to n-heptane as a dispersing aid.
  • the monomer composition (7) had a monomer concentration of 45% by weight and a neutralization ratio of 70 mol%.
  • polyethylene glycol diacrylate as an internal cross-linking agent was 0.020 mol% based on the monomer
  • diethylene triamine pentaacetic acid / 3 sodium as a chelating agent was 200 ppm based on the monomer
  • 1 ppm as a photopolymerization initiator was 200 ppm based on the monomer.
  • a dispersing device 12G of a double-cylindrical high-speed rotary shearing stirrer shown in FIG. 8 was used as the dispersing device.
  • the inner diameter of the casing (the inner diameter of the outer cylinder 50G) is 25 mm
  • the outer diameter of the rotor (the outer diameter of the inner cylinder 52G) is 22 mm
  • the effective rotor length (from the monomer aqueous solution inlet 55G to the outlet) is 65 mm.
  • a vertically arranged tube made of PFA (perfluoroalkoxy alkane) inner diameter: 25 mm, total length: 10 m
  • the rotor (inner cylinder 52G) is rotated at a rotation speed of 4,800 rpm (shear rate 3686 [1 / s]), and then the monomer composition (7) is supplied at a flow rate of 40 ml / min (47.2 g). / Min), the liquid was sent to the pipe 31 of the dispersion device 12G.
  • the supplied monomer composition (7) was dispersed in the form of fine droplets in the organic solvent by a dispersing device (average residence time of the monomer composition (7) 1.80 s).
  • Droplets composed of the monomer composition (7) fall in a reactor filled with the organic solvent as the continuous phase, and polymerization is started by an ultraviolet irradiation device installed on the upper portion of the reactor, As the polymerization reaction progressed, it changed to a minute spherical gel. These small spherical gels adhered to each other as they fell to form aggregates. Then, in the vicinity of the outlet of the reactor, a hydrogel (7) having a diameter of about 1 to 3 cm and comprising an aggregate of fine spherical gel was confirmed.
  • the space velocity (LHSV) in the reactor 14 was 2.9 hr -1 .
  • the hydrogel (7) and the organic solvent discharged from the reaction device 14 were continuously supplied to the separation device 16 as they were.
  • the hydrogel (7) and the organic solvent were separated.
  • the organic solvent separated by the separation device was temperature-controlled by the heat exchanger 20 so that the set temperature was 70 ° C., and then supplied to the reaction device 14 again.
  • the hydrogel (7) obtained by the above operation had a shape in which minute spherical hydrogel was adhered and aggregated.
  • the water-containing gel (7) was sampled every 20 minutes from 100 minutes after the start of the operation to the end of the operation (5 hours), and the average primary particle diameter was measured to be 70 to 80 ⁇ m.
  • Example 8 A series of the following steps 2 to 5 is operated according to the manufacturing process shown in FIG. 1 to prepare a hydrogel (8), and then the obtained hydrogel (8) is dried to remove the water-absorbent resin (8). Manufactured. The specific operation time was set to 10 hours after the start of the supply of the monomer composition to the dispersion device in the following step 2.
  • n-heptane (density: 0.68 g / ml) as an organic solvent was charged into the dispersion device 12, the polymerization device 14, the separation device 16 and the piping connecting these.
  • the liquid pump 18 was operated to start circulation of the organic solvent at a flow rate of 300 ml / min.
  • the whole amount of the organic solvent was charged into the polymerization apparatus 14 via the dispersion apparatus 12.
  • the heat exchanger 20 was operated to heat the organic solvent so that the temperature of the circulating organic solvent became 90 ° C.
  • a maleic anhydride-modified polyethylene (acid value: 60 mg KOH / g) was separately mixed with n-heptane as a dispersing aid and dissolved by heating to 90 ° C. to obtain a 0.030 wt% dispersing aid solution. (8) was prepared. Subsequently, the dispersion aid solution (8) obtained by the above operation was added to the n-heptane flowing through the pipe 33 via the pipe 43 at a flow rate of 50 ml / min for 30 minutes. The ratio of the content of the maleic anhydride-modified polyethylene to the total amount of the organic solvent before the start of the polymerization was 0.005% by weight.
  • the monomer composition (8) had a monomer concentration of 43% by weight and a neutralization ratio of 75 mol%.
  • polyethylene glycol diacrylate as an internal cross-linking agent is 0.010 mol% based on the monomer
  • diethylene triamine pentaacetic acid / 3 sodium as a chelating agent is 200 ppm based on the monomer
  • persulfate as a polymerization initiator is used.
  • Sodium (T10 @ 70 ° C.) was 0.1 g / mol based on the monomer.
  • a double-cylindrical high-speed rotary shearing stirrer (dispersing device 12G) shown in FIG. 8 was used.
  • the inner diameter of the casing (the inner diameter of the outer cylinder 50G) is 25 mm
  • the outer diameter of the rotor (the outer diameter of the inner cylinder 52G) is 22 mm
  • the effective rotor length (from the monomer aqueous solution inlet 55G to the outlet) is 65 mm.
  • a vertically arranged tube made of PFA (perfluoroalkoxyalkane) (inner diameter: 25 mm, total length: 10 m) was used.
  • Droplets composed of the monomer composition (8) fall into a polymerization apparatus filled with an organic solvent as the continuous phase, and form fine spherical hydrogels (8) as the polymerization reaction proceeds. changed. These small spherical gels adhered to each other as they fell to form aggregates. In the vicinity of the outlet of the polymerization apparatus, a hydrogel (8) having a diameter of about 1 cm and comprising an aggregate of fine spherical gel was confirmed.
  • the space velocity (LHSV) in the polymerization apparatus 14 was 4.2 hr -1 .
  • the hydrogel (8) and the organic solvent discharged from the polymerization device 14 were continuously supplied to the separation device 16 as they were.
  • the hydrogel (8) was separated from the organic solvent.
  • the organic solvent separated by the separation device is supplied to the heat exchanger 20 via the pipe 32, the liquid sending pump 18 and the pipe 33, and heat exchange is performed so that the set temperature (organic solvent temperature) becomes 90 ° C.
  • the mixture was supplied to the dispersion apparatus 12 and the polymerization apparatus 14 via a pipe 35 while maintaining the temperature at 70 ° C. or higher.
  • the dispersion aid solution (8) as a replenishing dispersion aid was added to the continuous phase containing the organic solvent flowing through the pipe 33 at a flow rate of 5 ml / min via the pipe 43 in a single amount to the dispersion device. Feeding was started continuously 10 minutes after the start of the liquid feeding of the body composition. That is, the flow rate of the dispersing aid [ml / min] / the flow rate of the continuous phase [ml / min] was 0.017.
  • the addition amount of the dispersing aid maleic anhydride-modified polyethylene
  • the hydrogel (8) obtained by the above operation had a shape in which minute spherical hydrogel was adhered and aggregated. Further, the water-containing gel (8) was sampled every 20 minutes from 100 minutes after the start of the operation to the end of the operation (10 hours), and the average primary particle diameter was measured to be 60 to 70 ⁇ m.
  • the hydrogel (8) discharged from the separation device 16 was continuously supplied to the indirect heating type stirring and drying device as it was, and a previously prepared aqueous solution of betayl lauryl dimethylaminoacetate (concentration: 3.1% by weight) was charged. The amount of the aqueous solution of betayl lauryldimethylaminoacetate based on the hydrogel (8) was 0.5% by weight. Subsequently, the heating medium temperature of the drying device was adjusted to 180 ° C., and the water-containing gel (8) was continuously dried while being mixed with betaine lauryl dimethylaminoacetate, to thereby obtain a particulate dry polymer (8).
  • the obtained dried polymer (8) was continuously supplied to a sieving device having a metal sieve mesh (JIS standard sieve) having openings of 850 ⁇ m and 150 ⁇ m to be classified, thereby obtaining a water-absorbent resin powder (8).
  • a metal sieve mesh JIS standard sieve
  • Step 1 above. ⁇ 5. was operated for 10 hours, and the mixture was mixed except for 1 hour immediately after the start of the polymerization, in which the discharge amount was not stable, and the sample after the termination of the polymerization, to obtain a water-absorbent resin powder (8).
  • the water absorbent resins of Examples 1 to 3, 7 and 8 had small fluctuations in the average primary particle diameter of the obtained water absorbent resin. Furthermore, the water-absorbent resins of Examples 1, 3, and 8 had a small average primary particle diameter and a very high DRC of 5 min.

Abstract

[Problem] To provide a method for producing a water-absorbing resin, wherein a monomer can be dispersed in a small amount of a dispersion medium, and the particle size of the water-absorbing resin is constant during the production over a long period of time. [Solution] A method for producing a water-absorbing resin, said method including: supplying, separately and continuously, a water-soluble ethylenically unsaturated monomer solution and an organic solvent to a flow channel in which a pair of walls having opposing surfaces that face each other with a gap therebetween are relatively moved so as to form a shear field; producing droplets containing the water-soluble ethylenically unsaturated monomer solution; and polymerizing said water-soluble ethylenically unsaturated monomer.

Description

吸水性樹脂の製造方法Method for producing water absorbent resin
　本発明は、吸水性樹脂の製造方法に関する。 The present invention relates to a method for producing a water absorbent resin.
　近年、紙オムツ、生理用ナプキン、失禁パット等の衛生材料には、体液吸収の観点から、その構成材としての吸水性樹脂が、吸水剤として幅広く利用されている。上記吸水性樹脂には、その原料として多くの単量体や親水性高分子が使用されているが、吸水性能の観点から、アクリル酸及び／又はその塩を単量体として用いたポリアクリル酸（塩）系吸水性樹脂が、工業的に最も多く生産されている。 In recent years, for sanitary materials such as disposable diapers, sanitary napkins, incontinence pads, etc., from the viewpoint of body fluid absorption, a water-absorbing resin as a constituent material has been widely used as a water-absorbing agent. Many monomers and hydrophilic polymers are used as raw materials for the water-absorbing resin. From the viewpoint of water absorption performance, polyacrylic acid using acrylic acid and / or a salt thereof as a monomer is used. (Salt) -based water-absorbing resins are produced most industrially.
　吸水性樹脂の一般的製造方法としては、水溶液重合法と、逆相懸濁重合法とに大別される。逆相懸濁重合法によれば、パール状（球状）の吸水性樹脂が得られる。逆相懸濁重合法は、有機溶媒中に単量体水溶液を懸濁させ、重合を行う方式である。例えば、有機溶媒中に単量体を機械的攪拌により液滴状に分散させた後に重合を開始する方法がある（特開昭６１－１９２７０３号公報等）。このような方法では、単量体を含む溶液を有機溶媒中に分散させる際に多量の分散助剤の添加が必要であった。その結果、分散助剤の一部が重合反応で得られる吸水性樹脂中に残存して表面張力が低下することになり、吸水性樹脂の物性が低下することがあった。 一般 General methods for producing water-absorbent resins are broadly classified into aqueous polymerization methods and reversed-phase suspension polymerization methods. According to the reverse phase suspension polymerization method, a pearl-like (spherical) water-absorbing resin can be obtained. The reverse phase suspension polymerization method is a method in which a monomer aqueous solution is suspended in an organic solvent to perform polymerization. For example, there is a method in which polymerization is started after a monomer is dispersed in an organic solvent in the form of droplets by mechanical stirring (JP-A-61-192703). In such a method, it is necessary to add a large amount of a dispersing aid when dispersing the solution containing the monomer in the organic solvent. As a result, a part of the dispersing agent remains in the water-absorbent resin obtained by the polymerization reaction, and the surface tension is reduced, and the physical properties of the water-absorbent resin are sometimes reduced.
　これに対し、国際公開第２０１６／１８２０８２号では、分散助剤の添加量の低減を目的として、スプレーノズルを用いて単量体水溶液を有機溶媒中に分散させる方法が開示されている。具体的には、国際公開第２０１６／１８２０８２号では、単量体水溶液と、有機溶媒とを、接触させることなくスプレーノズルの先端にまで誘導し、スプレーノズルから排出される直前または直後に、単量体水溶液と有機溶媒とを接触させて、単量体水溶液を有機溶媒に分散させている。 On the other hand, WO 2016/1822082 discloses a method for dispersing an aqueous monomer solution in an organic solvent using a spray nozzle for the purpose of reducing the amount of a dispersing aid added. Specifically, in WO 2016/1822082, a monomer aqueous solution and an organic solvent are guided to the tip of a spray nozzle without making contact with the monomer aqueous solution, and immediately before or immediately after being discharged from the spray nozzle, The monomer aqueous solution is brought into contact with the organic solvent to disperse the monomer aqueous solution in the organic solvent.
　しかしながら、国際公開第２０１６／１８２０８２号に記載の方法による分散の後、単量体を重合して吸水性樹脂を製造すると、長時間の運転により、吸水性樹脂の粒子径が変動するという問題があった。また、国際公開第２０１６／１８２０８２号に記載の方法では、流体を吹き込むことで粒径を制御しているため、多量の分散媒を要する。 However, when the water-absorbing resin is produced by polymerizing the monomer after the dispersion according to the method described in WO 2016/1822082, there is a problem that the particle size of the water-absorbing resin fluctuates due to long-term operation. there were. Further, in the method described in WO 2016/182082, since a particle diameter is controlled by blowing a fluid, a large amount of a dispersion medium is required.
　そこで本発明は、少ない分散媒流量で単量体を分散できるとともに、長時間の製造にわたって吸水性樹脂の粒子径が一定である、吸水性樹脂の製造方法を提供することを目的とする。 Accordingly, an object of the present invention is to provide a method for producing a water-absorbent resin, in which a monomer can be dispersed with a small flow rate of a dispersion medium and the particle size of the water-absorbent resin is constant over a long period of time.
　間隙を隔てて互いに対向する対向面を有する一対の壁が相対的に移動することによってせん断場を形成する流路に、水溶性エチレン性不飽和単量体溶液、有機溶媒を別々に連続的に供給し、前記水溶性エチレン性不飽和単量体溶液を含む液滴を作製し、当該水溶性エチレン性不飽和単量体を重合することを有する、吸水性樹脂の製造方法によって、上記課題を解決する。 A water-soluble ethylenically unsaturated monomer solution and an organic solvent are separately and continuously supplied to a flow path that forms a shear field by a pair of walls having opposing surfaces that oppose each other with a gap therebetween. Supplying, producing a droplet containing the water-soluble ethylenically unsaturated monomer solution, and polymerizing the water-soluble ethylenically unsaturated monomer, the method for producing a water-absorbent resin, the above-described problem is solved. Solve.
本発明の一実施形態に係る吸水性樹脂の製造プロセスの一部を示す概略図である。It is a schematic diagram showing a part of manufacturing process of water absorbent resin concerning one embodiment of the present invention. 分散装置の一例を示す断面図である。It is sectional drawing which shows an example of a dispersion apparatus. 分散装置の他の例を示す断面図である。It is sectional drawing which shows the other example of a dispersion apparatus. 分散装置のさらに他の例を示す断面図である。It is sectional drawing which shows another example of a dispersing apparatus. 分散装置のさらに他の例を示す断面図である。It is sectional drawing which shows another example of a dispersing apparatus. 分散装置のさらに他の例を示す断面図である。It is sectional drawing which shows another example of a dispersing apparatus. 分散装置のさらに他の例を示す断面図である。It is sectional drawing which shows another example of a dispersing apparatus. 分散装置のさらに他の例を示す断面図である。It is sectional drawing which shows another example of a dispersing apparatus. 比較例１で用いた２流体スプレーノズルの断面図である。FIG. 4 is a cross-sectional view of a two-fluid spray nozzle used in Comparative Example 1. ＤＲＣ５ｍｉｎの測定装置を示す模式図である。It is a schematic diagram which shows the measuring device of DRC5min. 本発明の他の実施形態に係る吸水性樹脂の製造プロセスの一部を示す概略図である。It is the schematic which shows some manufacturing processes of the water absorbent resin which concerns on other embodiment of this invention.
　以下、本発明を最良の形態を示しながら説明する。本明細書の全体にわたり、単数形の表現は、特に言及しない限り、その複数形の概念をも含むことが理解されるべきである。従って、単数形の冠詞（例えば、英語の場合は「ａ」、「ａｎ」、「ｔｈｅ」等）は、特に言及しない限り、その複数形の概念をも含むことが理解されるべきである。また、本明細書において使用される用語は、特に言及しない限り、当該分野で通常用いられる意味で用いられることが理解されるべきである。したがって、他に定義されない限り、本明細書中で使用される全ての専門用語及び科学技術用語は、本発明の属する分野の当業者によって一般的に理解されるのと同じ意味を有する。矛盾する場合、本明細書（定義を含めて）が優先する。本発明は、下記の実施形態に限定されるものではなく、特許請求の範囲内で種々改変することができる。 Hereinafter, the present invention will be described with reference to the best mode. It should be understood that throughout this specification, the use of the singular includes the plural concept unless specifically stated otherwise. Thus, it is to be understood that singular articles (eg, "a", "an", "the", etc. in English) also include the plural concept unless specifically stated otherwise. It should also be understood that the terms used in this specification are used in a meaning commonly used in the art unless otherwise specified. Thus, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including definitions, will control. The present invention is not limited to the following embodiments, but can be variously modified within the scope of the claims.
　〔１．用語の定義〕
　［１－１．吸水性樹脂］
　本明細書において「吸水性樹脂」とは、ＥＲＴ４４１．２－０２により規定される水膨潤性（ＣＲＣ）が５ｇ／ｇ以上であり、およびＥＲＴ４７０．２－０２により規定される水可溶成分（Ｅｘｔ）が７０重量％以下である高分子ゲル化剤をいう。 [1. Definition of terms〕
[1-1. Water absorbent resin]
As used herein, the term “water-absorbent resin” refers to a water-swelling component (CRC) defined by ERT441.2-02 of 5 g / g or more, and a water-soluble component defined by ERT470.2-02 ( Ext) refers to a polymer gelling agent having an Ext) of 70% by weight or less.
　本明細書において「吸水性樹脂」とは、全量（１００重量％）が当該吸水性樹脂のみである態様に限定されない。そうではなく、上述のＣＲＣおよびＥｘｔを満足するならば、添加剤などを含んでいる吸水性樹脂組成物であってもよい。また、本明細書において「吸水性樹脂」とは、吸水性樹脂の製造工程における中間体をも包含する概念である。例えば、重合後の含水ゲル状重合体、乾燥後の乾燥重合体、表面架橋前の吸水性樹脂粉末なども、「吸水性樹脂」と表記する場合がある。 に お い て In the present specification, the “water-absorbing resin” is not limited to an embodiment in which the total amount (100% by weight) is only the water-absorbing resin. On the contrary, if the above-mentioned CRC and Ext are satisfied, a water-absorbing resin composition containing an additive or the like may be used. Further, in this specification, the term "water-absorbent resin" is a concept that also includes intermediates in the process of producing the water-absorbent resin. For example, a hydrogel polymer after polymerization, a dried polymer after drying, a water-absorbing resin powder before surface cross-linking, and the like may also be referred to as “water-absorbing resin”.
　このように、本明細書においては、吸水性樹脂そのものに加えて、吸水性樹脂組成物および中間体をも総称して「吸水性樹脂」と表記する場合がある。 Thus, in this specification, in addition to the water-absorbent resin itself, the water-absorbent resin composition and the intermediate may be collectively referred to as “water-absorbent resin”.
　［１－２．その他］
　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。 [1-2. Others]
In the present specification, “X to Y” indicating a range means “X or more and Y or less”.
　本明細書において、「ｐｐｍ」は、「重量ｐｐｍ」を意味する。 に お い て In this specification, “ppm” means “weight ppm”.
　本明細書において、「～酸（塩）」は「～酸および／またはその塩」を意味する。「（メタ）アクリル」は「アクリルおよび／またはメタクリル」を意味する。 書 In the present specification, “—acid (salt)” means “—acid and / or salt thereof”. “(Meth) acryl” means “acryl and / or methacryl”.
　本明細書においては、体積の単位「リットル」を「ｌ」または「Ｌ」と表記する場合がある。 に お い て In this specification, the unit of volume “liter” may be described as “l” or “L”.
　本明細書においては、単に「平均」という場合、算術平均を意味する。
〔２．吸水性樹脂の製造方法〕
　本発明の吸水性樹脂の製造方法は、間隙を隔てて互いに対向する対向面を有する一対の壁が相対的に移動することによってせん断場を形成する流路に、水溶性エチレン性不飽和単量体溶液（以下、単に単量体溶液とも称する）、有機溶媒を別々に連続的に供給し、水溶性エチレン性不飽和単量体溶液を含む液滴を作製し、当該水溶性エチレン性不飽和単量体を重合することを有する、吸水性樹脂の製造方法である。 In this specification, the term “average” simply means an arithmetic average.
[2. Production method of water absorbent resin)
The method for producing a water-absorbent resin of the present invention is characterized in that a water-soluble ethylenically unsaturated monomer is formed in a flow path that forms a shear field by a pair of walls having opposing surfaces opposing each other with a gap therebetween moving relatively. A body solution (hereinafter, also simply referred to as a monomer solution) and an organic solvent are separately and continuously supplied to prepare droplets containing a water-soluble ethylenically unsaturated monomer solution, and the water-soluble ethylenically unsaturated This is a method for producing a water-absorbing resin, comprising polymerizing a monomer.
　一対の壁が形成する流路内に存在している有機溶媒中に供給された水溶性エチレン性不飽和単量体に対して、一対の壁が相対的に移動することによって流路内に強いせん断力がかかる。このせん断力によって、水溶性エチレン性不飽和単量体の有機溶媒中への微細分散が可能となる。 With respect to the water-soluble ethylenically unsaturated monomer supplied in the organic solvent present in the flow path formed by the pair of walls, the pair of walls move relatively to each other due to the relative movement of the walls. Shear force is applied. This shear force enables fine dispersion of the water-soluble ethylenically unsaturated monomer in the organic solvent.
　また、国際公開第２０１６／１８２０８２号に記載のように、二流体スプレー法による水溶性エチレン性不飽和単量体の分散の場合、その後の重合により製造されたゲル状の吸水性樹脂がスプレー先端に付着することでスプレーから吐出される流体によるせん断力が弱くなり、粒子径が経時的に増加していく（後述の比較例１）。これに対し、本発明の製造方法によれば、流路内で水溶性エチレン性不飽和単量体の分散が行われるため、ゲル状の吸水性樹脂と、水溶性エチレン性不飽和単量体とが、接触しにくい。ゆえに、長時間の製造にわたって、得られる吸水性樹脂の粒子径が安定する。 In the case of dispersing a water-soluble ethylenically unsaturated monomer by a two-fluid spray method as described in WO 2016/1822082, a gel-like water-absorbing resin produced by subsequent polymerization is sprayed at the spray tip. As a result, the shearing force of the fluid discharged from the spray becomes weaker, and the particle size increases with time (Comparative Example 1 described later). On the other hand, according to the production method of the present invention, the water-soluble ethylenically unsaturated monomer is dispersed in the channel, so that the gel-like water-absorbing resin and the water-soluble ethylenically unsaturated monomer are dispersed. But difficult to contact. Therefore, the particle size of the obtained water-absorbent resin is stable over a long production time.
　さらに、本発明では、移動壁が相対的に移動することでせん断力を生じさせているため、２流体スプレー法と比較して多量の有機溶媒を要しない。 Further, in the present invention, since the shearing force is generated by the relative movement of the moving wall, a large amount of the organic solvent is not required as compared with the two-fluid spray method.
　ゆえに、本発明によれば、少ない分散媒量で水溶性エチレン性不飽和単量体を有機溶媒中に分散できるとともに、吸水性樹脂の粒子径が長時間にわたって一定となる。 Therefore, according to the present invention, the water-soluble ethylenically unsaturated monomer can be dispersed in the organic solvent with a small amount of the dispersion medium, and the particle size of the water-absorbing resin is kept constant for a long time.
　以下、添付した図面を参照しながら、本実施形態を説明する。なお、図面の説明において同一の要素には同一の符号を付し、重複する説明を省略する。また、図面の寸法比率は、説明の都合上誇張されており、実際の比率とは異なる場合がある。 Hereinafter, the present embodiment will be described with reference to the accompanying drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description. In addition, the dimensional ratios in the drawings are exaggerated for convenience of description, and may be different from the actual ratios.
　図１は、本発明の一実施形態に係る吸水性樹脂の製造プロセスの一部を示す概略図である。なお、配管系には流量や圧力を調整するための複数のバルブが設けられているが、図１においてはこれらバルブの図示は省略する。 FIG. 1 is a schematic view showing a part of a process for producing a water absorbent resin according to one embodiment of the present invention. A plurality of valves for adjusting the flow rate and the pressure are provided in the piping system, but these valves are not shown in FIG.
　図１に示すように、吸水性樹脂の製造プロセスには、混合装置１０、分散装置１２、反応装置１４、分離装置１６、送液ポンプ１８、熱交換器２０、乾燥装置２２、及びこれらの装置を接続する配管３１～３６が含まれている。乾燥装置２２には、乾燥後の重合体を排出する配管３７が接続されている。分散装置１２の構造については後に詳述する。反応装置１４は、例えば縦型反応塔から構成されている。反応装置１４に供給された水溶性エチレン性不飽和単量体を重合して、含水ゲル状重合体（以下、「含水ゲル」、「ゲル状重合体」とも称する）を得る。分離装置１６は、例えばスクリュープレス機や、連続遠心分離機から構成され、含水ゲルを抜き出し、固液分離を行う。乾燥装置２２は、例えばパドルドライヤ、流動層乾燥機、ロータリードライヤ、スチームチューブドライヤから構成され、含水ゲルを撹拌乾燥する。配管３５は、熱交換器２０から反応装置１４に至る配管３４から分岐し、分散装置１２に接続されている。 As shown in FIG. 1, the manufacturing process of the water-absorbent resin includes a mixing device 10, a dispersion device 12, a reaction device 14, a separation device 16, a liquid sending pump 18, a heat exchanger 20, a drying device 22, and these devices. Are connected to each other. A pipe 37 for discharging the dried polymer is connected to the drying device 22. The structure of the dispersion device 12 will be described later in detail. The reaction device 14 is composed of, for example, a vertical reaction tower. The water-soluble ethylenically unsaturated monomer supplied to the reactor 14 is polymerized to obtain a hydrogel polymer (hereinafter, also referred to as a “hydrogel” or a “gel polymer”). The separation device 16 is composed of, for example, a screw press or a continuous centrifugal separator, and extracts a hydrogel and performs solid-liquid separation. The drying device 22 includes, for example, a paddle dryer, a fluidized bed dryer, a rotary dryer, and a steam tube dryer, and agitates and dries the hydrogel. The pipe 35 branches off from a pipe 34 extending from the heat exchanger 20 to the reaction device 14 and is connected to the dispersion device 12.
　混合装置１０には、単量体溶液を供給する配管４１、および重合開始剤を供給する配管４２が接続されている。送液ポンプ１８から熱交換器２０に至る配管３３には、分散助剤を供給する配管４３が接続されている。分離装置１６から乾燥装置２２に至る配管３６には、乾燥助剤を供給する配管４４が接続されている。 配 管 A pipe 41 for supplying the monomer solution and a pipe 42 for supplying the polymerization initiator are connected to the mixing device 10. A pipe 43 for supplying a dispersion aid is connected to a pipe 33 from the liquid sending pump 18 to the heat exchanger 20. A pipe 44 for supplying a drying aid is connected to a pipe 36 extending from the separation device 16 to the drying device 22.
　吸水性樹脂の製造方法の一例を、図１にしたがって説明する。吸水性樹脂の製造方法としては、任意の混合工程；分散工程；重合工程を含み、重合工程の後に、任意に乾燥工程などを含む。 (1) An example of a method for producing a water absorbent resin will be described with reference to FIG. The method for producing the water-absorbent resin includes an optional mixing step; a dispersion step; a polymerization step, and optionally includes a drying step after the polymerization step.
　先ず、分散装置１２、反応装置１４、分離装置１６、熱交換器２０、及びこれらの装置を接続する配管３２、３３、３４、３５の内部に有機溶媒を満たす。次に、送液ポンプ１８を稼働させ、有機溶媒を循環させる。有機溶媒の一部は、配管３５を介して分散装置１２にも供給される。分散助剤を、配管４３を介して配管３３を流れる有機溶媒に供給する。各装置及び配管中の有機溶媒は、熱交換器２０において所定温度に加熱される。 {First, the organic solvent is filled in the dispersion device 12, the reaction device 14, the separation device 16, the heat exchanger 20, and the pipes 32, 33, 34, 35 connecting these devices. Next, the liquid pump 18 is operated to circulate the organic solvent. Part of the organic solvent is also supplied to the dispersion device 12 via the pipe 35. The dispersion aid is supplied to the organic solvent flowing through the pipe 33 via the pipe 43. The organic solvent in each device and pipe is heated to a predetermined temperature in the heat exchanger 20.
　次に、別途用意した水溶性エチレン性不飽和単量体溶液および重合開始剤を、それぞれ配管４１、４２を介して、混合装置１０に連続供給して混合し、単量体組成物を作製する（混合工程）。混合装置１０としては、特に限定されないが、例えばラインミキサー等が挙げられる。 Next, a separately prepared water-soluble ethylenically unsaturated monomer solution and a polymerization initiator are continuously supplied to and mixed with the mixing device 10 via pipes 41 and 42, respectively, to produce a monomer composition. (Mixing step). The mixing device 10 is not particularly limited, and examples thereof include a line mixer.
　その後、該単量体組成物を、配管３１を介して分散装置１２に連続供給する。分散装置１２には、単量体組成物および有機溶媒が別々に連続的に供給される。単量体組成物は、分散装置１２によって有機溶媒中に液滴状に分散される（分散工程）。このように本実施形態では、有機溶媒に水溶性エチレン性不飽和単量体を連続分散させる。 Thereafter, the monomer composition is continuously supplied to the dispersion device 12 via the pipe 31. The monomer composition and the organic solvent are separately and continuously supplied to the dispersion device 12. The monomer composition is dispersed in the form of droplets in the organic solvent by the dispersion device 12 (dispersion step). As described above, in the present embodiment, the water-soluble ethylenically unsaturated monomer is continuously dispersed in the organic solvent.
　液滴状に分散した水溶性エチレン性不飽和単量体は、反応装置１４の有機溶媒中に連続的に投入され、反応装置１４において重合反応が開始される（重合工程）。反応装置１４では、循環する有機溶媒の移動によって、単量体組成物からなる液滴が移動する。この液滴は、移動しながら、重合反応によって、含水ゲルに変化する。この液滴及び含水ゲルの移動方向は、該有機溶媒の移動方向と同じ（並流）である。本発明において、有機溶媒からなる液相（連続相）に、単量体溶液を含む液滴が分散又は懸濁した状態で、重合反応を開始して含水ゲルを得る重合方法を、液相液滴（懸濁）重合と称する。 (4) The water-soluble ethylenically unsaturated monomer dispersed in the form of droplets is continuously charged into the organic solvent of the reaction device 14, and the polymerization reaction is started in the reaction device 14 (polymerization step). In the reaction device 14, droplets composed of the monomer composition move due to the movement of the circulating organic solvent. These droplets change into hydrogels by a polymerization reaction while moving. The moving direction of the droplet and the hydrogel is the same (cocurrent) as the moving direction of the organic solvent. In the present invention, a polymerization method in which a polymerization reaction is started in a state where droplets containing a monomer solution are dispersed or suspended in a liquid phase (continuous phase) composed of an organic solvent to obtain a hydrogel is described as a liquid phase liquid. This is referred to as drop (suspension) polymerization.
　続いて、上記液相液滴重合によって得られた含水ゲルは、有機溶媒と共に反応装置１４から連続的に排出され、分離装置１６に連続供給される。分離装置１６において、含水ゲルと有機溶媒とが連続的に分離される（分離工程）。分離された含水ゲルは、配管３６を介して次の工程（乾燥装置２２）へ連続的に供給される（乾燥工程）。分離された有機溶媒は配管３２、３３を介して熱交換器２０を経由し、さらに配管３４を介して反応装置１４に連続的に再供給される。有機溶媒の一部は、配管３５を介して分散装置１２にも再供給される。 Subsequently, the water-containing gel obtained by the liquid phase droplet polymerization is continuously discharged from the reaction device 14 together with the organic solvent, and is continuously supplied to the separation device 16. In the separation device 16, the hydrogel and the organic solvent are continuously separated (separation step). The separated hydrogel is continuously supplied to the next step (drying device 22) via the pipe 36 (drying step). The separated organic solvent passes through the heat exchanger 20 via the pipes 32 and 33 and is continuously re-supplied to the reaction apparatus 14 via the pipe 34. Part of the organic solvent is also supplied again to the dispersion device 12 via the pipe 35.
　乾燥装置２２において、含水ゲルに含まれる水分と、分離装置１６において分離しきれなかった有機溶媒とが除去され、粒子状の乾燥重合体とされる。粒子状の乾燥重合体は、配管３７から排出され、次の工程（冷却装置など）に供給される。図示されないが、乾燥装置２２により除去された有機溶媒は、反応装置１４に再供給される。 (4) In the drying device 22, the water contained in the hydrogel and the organic solvent that cannot be separated in the separation device 16 are removed to obtain a particulate dried polymer. The particulate dry polymer is discharged from the pipe 37 and supplied to the next step (such as a cooling device). Although not shown, the organic solvent removed by the drying device 22 is supplied again to the reaction device 14.
　以上説明した実施形態では、連続重合（連続式製造方法）が採用されている。連続式製造方法とは、単量体溶液または単量体溶液を含む単量体組成物を連続的に反応装置中の有機溶媒に送液し、重合させ、重合反応により形成される含水ゲルと有機溶媒とを連続的に反応装置から排出する方法である。したがって、本実施形態は液相液滴連続重合である。この場合、各工程及び工程間におけるそれぞれの操作を連続的に実施できるため、各装置の停止及び再稼働に伴う閉塞等のトラブルを回避することができる。なお、連続重合は、分散装置から連続的に単量体溶液または単量体溶液を含む単量体組成物が反応装置へと供給される形態であるため、分散と重合とが一の装置で行われる形態（回分操作）とは明確に区別される。 で は In the embodiment described above, continuous polymerization (continuous production method) is employed. With the continuous production method, the monomer solution or the monomer composition containing the monomer solution is continuously sent to an organic solvent in a reaction apparatus, polymerized, and a hydrogel formed by a polymerization reaction. In this method, the organic solvent is continuously discharged from the reactor. Therefore, the present embodiment is a liquid phase droplet continuous polymerization. In this case, since each step and each operation between the steps can be performed continuously, troubles such as blockage due to stop and restart of each device can be avoided. In addition, continuous polymerization is a form in which a monomer solution or a monomer composition containing a monomer solution is continuously supplied to a reaction device from a dispersion device, and thus dispersion and polymerization are performed in one device. It is clearly distinguished from the form in which it is performed (batch operation).
　また、連続的に操作を行う場合、その運転時間としては、１時間以上であることが好ましく、３時間以上であることがより好ましく、また、通常１年以下である。 場合 In addition, when the operation is performed continuously, the operation time is preferably 1 hour or more, more preferably 3 hours or more, and usually 1 year or less.
　以下、各工程について説明する。 Hereinafter, each step will be described.
　［２－１：混合工程］
　本工程は任意の工程であり、水溶性エチレン性不飽和単量体溶液および重合開始剤を混合して単量体組成物を得る工程である。 [2-1: Mixing step]
This step is an optional step, and is a step of obtaining a monomer composition by mixing a water-soluble ethylenically unsaturated monomer solution and a polymerization initiator.
　本工程において、単量体溶液と重合開始剤とを混合して単量体組成物を作製する方法は特に限定されないが、例えば、（１）単量体溶液、及び重合開始剤を含む溶液（以下、「重合開始剤溶液」と称する）を予め用意しておき、それぞれ別の配管から同時に混合装置に供給して混合する方法、（２）予め用意した単量体溶液を混合装置に供給した後に、重合開始剤を該混合装置に供給して混合する方法等が挙げられる。 In this step, the method of preparing the monomer composition by mixing the monomer solution and the polymerization initiator is not particularly limited. For example, (1) a monomer solution and a solution containing the polymerization initiator ( Hereinafter, referred to as “polymerization initiator solution”), a method of simultaneously supplying the mixture to the mixing device from separate pipes and mixing them, and (2) supplying the prepared monomer solution to the mixing device. Later, a method of supplying a polymerization initiator to the mixing device and mixing the polymerization initiator and the like can be given.
　重合開始剤は、溶媒に重合開始剤を溶解（分散）させた重合開始剤溶液の形態であってもよい。重合開始剤溶液の溶媒としては、特に限定されるものではないが、水が好ましい。この際の重合開始剤溶液の濃度としては、重合開始剤が溶媒に溶解できる範囲内であれば特に限定されるものではないが、０．１重量％～飽和濃度以下が好ましく、１重量％～３０重量％がより好ましい。 The polymerization initiator may be in the form of a polymerization initiator solution in which the polymerization initiator is dissolved (dispersed) in a solvent. The solvent of the polymerization initiator solution is not particularly limited, but water is preferable. The concentration of the polymerization initiator solution at this time is not particularly limited as long as it is within a range in which the polymerization initiator can be dissolved in a solvent, but is preferably from 0.1% by weight to a saturated concentration or less, preferably from 1% by weight to 1% by weight. 30% by weight is more preferred.
　また、混合装置としては、特に限定されないが、例えば、ラインミキサーやタンク等が挙げられる。重合開始剤の貯蔵安定性や安全性の観点から、混合装置としてラインミキサーを用いた上記（１）の混合方法が好ましい。 混合 Also, the mixing device is not particularly limited, and examples thereof include a line mixer and a tank. From the viewpoint of storage stability and safety of the polymerization initiator, the mixing method (1) using a line mixer as the mixing device is preferable.
　以下、本工程で用いられる材料について説明する。 材料 Hereinafter, the materials used in this step will be described.
　「水溶性エチレン性不飽和単量体溶液」
　水溶性エチレン性不飽和単量体溶液は、水溶性エチレン性不飽和単量体を含む溶液を指す。 "Water-soluble ethylenically unsaturated monomer solution"
The water-soluble ethylenically unsaturated monomer solution refers to a solution containing a water-soluble ethylenically unsaturated monomer.
　単量体溶液の溶媒としては水、水溶性有機溶媒（例えば、アルコール等）およびこれらの混合物であることが好ましく、水または水および水溶性有機溶媒の混合物であることがより好ましく、水であることがさらにより好ましい。水および水溶性有機溶媒の混合物である場合、水溶性有機溶剤（例えば、アルコール等）は３０重量％以下であることが好ましく、５重量％以下であることがより好ましい。 The solvent for the monomer solution is preferably water, a water-soluble organic solvent (eg, alcohol) and a mixture thereof, and more preferably water or a mixture of water and a water-soluble organic solvent, and more preferably water. Is even more preferred. In the case of a mixture of water and a water-soluble organic solvent, the content of the water-soluble organic solvent (eg, alcohol) is preferably 30% by weight or less, more preferably 5% by weight or less.
　水溶性エチレン性不飽和単量体の例としては、（メタ）アクリル酸、（無水）マレイン酸、イタコン酸、ケイ皮酸、ビニルスルホン酸、アリルトルエンスルホン酸、ビニルトルエンスルホン酸、スチレンスルホン酸、２－（メタ）アクリルアミド－２－メチルプロパンスルホン酸、２－（メタ）アクリロイルエタンスルホン酸、２－（メタ）アクリロイルプロパンスルホン酸、２－ヒドロキシエチル（メタ）アクリレート、２－ヒドロキシプロピル（メタ）アクリレート、２－ヒドロキシエチル（メタ）アクリロイルフォスフェート、メトキシポリエチレングリコール（メタ）アクリレート、ポリエチレングリコールモノ（メタ）アクリレート等の酸基含有不飽和単量体；（メタ）アクリルアミド、Ｎ－エチル（メタ）アクリルアミド、Ｎ，Ｎ－ジメチル（メタ）アクリルアミド、Ｎ－ｎ－プロピル（メタ）アクリルアミド、Ｎ－イソプロピル（メタ）アクリルアミド、ビニルピリジン、Ｎ－ビニルピロリドン、Ｎ－アクリロイルピペリジン、Ｎ－アクリロイルピロリジン、Ｎ－ビニルアセトアミド等のアミド基含有不飽和単量体；Ｎ，Ｎ－ジメチルアミノエチル（メタ）アクリレート、Ｎ，Ｎ－ジメチルアミノプロピル（メタ）アクリレート、Ｎ，Ｎ－ジメチルアミノプロピル（メタ）アクリルアミド、Ｎ，Ｎ－ジエチルアミノエチル（メタ）アクリレート等のアミノ基含有不飽和単量体；メルカプト基含有不飽和単量体；フェノール性水酸基含有不飽和単量体；Ｎ－ビニルピロリドン等のラクタム基含有不飽和単量体等が挙げられる。 Examples of the water-soluble ethylenically unsaturated monomer include (meth) acrylic acid, (anhydride) maleic acid, itaconic acid, cinnamic acid, vinyl sulfonic acid, allyl toluene sulfonic acid, vinyl toluene sulfonic acid, and styrene sulfonic acid. , 2- (meth) acrylamide-2-methylpropanesulfonic acid, 2- (meth) acryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) ) Acrylate, 2-hydroxyethyl (meth) acryloyl phosphate, methoxypolyethylene glycol (meth) acrylate, polyethylene glycol mono (meth) acrylate and other unsaturated monomers containing acid groups; (meth) acrylamide, N-ethyl (meth) ) Acrylamide, N N-dimethyl (meth) acrylamide, Nn-propyl (meth) acrylamide, N-isopropyl (meth) acrylamide, vinylpyridine, N-vinylpyrrolidone, N-acryloylpiperidine, N-acryloylpyrrolidine, N-vinylacetamide and the like Amide group-containing unsaturated monomer; N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide, N, N-diethylamino Amino group-containing unsaturated monomers such as ethyl (meth) acrylate; mercapto group-containing unsaturated monomers; phenolic hydroxyl group-containing unsaturated monomers; lactam group-containing unsaturated monomers such as N-vinylpyrrolidone; Is mentioned.
　なお、上記水溶性エチレン性不飽和単量体の安定性を考慮して、必要に応じて重合禁止剤を水溶性エチレン性不飽和単量体に添加してもよい。該重合禁止剤として、例えば、ｐ－メトキシフェノール、フェノチアジン、Ｖｉｔａｍｉｎ－Ｅ等の公知の重合禁止剤を使用することができる。また、ｐ－メトキシフェノールを使用する場合には、酸素が必要に応じて併用される。なお、上記重合禁止剤の使用量は、水溶性エチレン性不飽和単量体に対して、好ましくは０．１ｐｐｍ～１０００ｐｐｍ、より好ましくは５ｐｐｍ～５００ｐｐｍである。 In addition, in consideration of the stability of the water-soluble ethylenically unsaturated monomer, a polymerization inhibitor may be added to the water-soluble ethylenically unsaturated monomer as needed. As the polymerization inhibitor, for example, a known polymerization inhibitor such as p-methoxyphenol, phenothiazine, and Vitamin-E can be used. When p-methoxyphenol is used, oxygen is used in combination if necessary. The amount of the polymerization inhibitor to be used is preferably 0.1 ppm to 1000 ppm, more preferably 5 ppm to 500 ppm, based on the amount of the water-soluble ethylenically unsaturated monomer.
　上記水溶性エチレン性不飽和単量体の中で、カルボキシル基等の酸基を有する酸基含有不飽和単量体を用いて、吸水性樹脂を製造する場合、該酸基が中和された中和塩を用いることができる。この場合、酸基含有不飽和単量体の塩としては一価のカチオンとの塩であることが好ましく、アルカリ金属塩、アンモニウム塩及びアミン塩から選ばれる少なくとも１種であることがより好ましく、アルカリ金属塩であることがさらに好ましく、ナトリウム塩、リチウム塩及びカリウム塩から選ばれる少なくとも１種であることがよりさらに好ましく、ナトリウム塩が特に好ましい。 Among the water-soluble ethylenically unsaturated monomers, when an acid group-containing unsaturated monomer having an acid group such as a carboxyl group is used to produce a water-absorbing resin, the acid group is neutralized. Neutralizing salts can be used. In this case, the salt of the acid group-containing unsaturated monomer is preferably a salt with a monovalent cation, more preferably at least one selected from alkali metal salts, ammonium salts and amine salts, It is more preferably an alkali metal salt, even more preferably at least one selected from a sodium salt, a lithium salt and a potassium salt, and particularly preferably a sodium salt.
　これらの中でも、得られる吸水性樹脂の吸水性能の観点から、水溶性エチレン性不飽和単量体は、好ましくは酸基含有不飽和単量体及び／又はその塩であり、より好ましくは（メタ）アクリル酸（塩）、（無水）マレイン酸（塩）、イタコン酸（塩）、ケイ皮酸（塩）、さらに好ましくは(メタ)アクリル酸（塩）であり、特に好ましくはアクリル酸（塩）である。 Among them, the water-soluble ethylenically unsaturated monomer is preferably an acid group-containing unsaturated monomer and / or a salt thereof, and more preferably (meth) ) Acrylic acid (salt), (anhydride) maleic acid (salt), itaconic acid (salt), cinnamic acid (salt), more preferably (meth) acrylic acid (salt), particularly preferably acrylic acid (salt) ).
　単量体として酸基含有不飽和単量体を用いる場合、得られる吸水性樹脂の吸水性能の観点から、その酸基含有不飽和単量体の中和塩と併用することが好ましい。吸水性能の観点から、酸基含有不飽和単量体とその中和塩の合計モル数に対する中和塩のモル数（以下、「中和率」と称する）は、好ましくは４０モル％以上、より好ましくは４０モル％～９５モル％、さらに好ましくは５０モル％～９０モル％、さらにより好ましくは５５モル％～８５モル％、特に好ましくは６０モル％～８０モル％である。 (4) When an acid group-containing unsaturated monomer is used as the monomer, it is preferable to use it together with a neutralized salt of the acid group-containing unsaturated monomer from the viewpoint of the water absorbing performance of the resulting water-absorbing resin. From the viewpoint of water absorption performance, the number of moles of the neutralized salt relative to the total number of moles of the acid group-containing unsaturated monomer and the neutralized salt thereof (hereinafter, referred to as "neutralization ratio") is preferably 40 mol% or more, More preferably, it is from 40 mol% to 95 mol%, further preferably from 50 mol% to 90 mol%, still more preferably from 55 mol% to 85 mol%, particularly preferably from 60 mol% to 80 mol%.
　上記中和率を調整する方法としては、酸基含有不飽和単量体とその中和塩とを混合する方法；酸基含有不飽和単量体に公知の中和剤を添加する方法；予め所定の中和率に調整された酸基含有不飽和単量体の部分中和塩（即ち、酸基含有不飽和単量体とその中和塩との混合物）を用いる方法等が挙げられる。また、これらの方法を組み合わせてもよい。 As a method of adjusting the neutralization rate, a method of mixing an acid group-containing unsaturated monomer and a neutralized salt thereof; a method of adding a known neutralizing agent to the acid group-containing unsaturated monomer; A method using a partially neutralized salt of an acid group-containing unsaturated monomer adjusted to a predetermined neutralization ratio (that is, a mixture of an acid group-containing unsaturated monomer and a neutralized salt thereof) is exemplified. Further, these methods may be combined.
　上記酸基含有不飽和単量体を中和するために使用される中和剤としては、特に限定されないが、水酸化ナトリウム、水酸化カリウム、炭酸ナトリウム、炭酸アンモニウム等の無機塩や、アミノ基やイミノ基を有するアミン系有機化合物等の塩基性物質が適宜選択されて用いられる。中和剤として、２種以上の塩基性物質が併用されてもよい。 The neutralizing agent used for neutralizing the acid group-containing unsaturated monomer is not particularly limited, but includes inorganic salts such as sodium hydroxide, potassium hydroxide, sodium carbonate, and ammonium carbonate, and amino groups. And a basic substance such as an amine organic compound having an imino group is appropriately selected and used. As the neutralizing agent, two or more basic substances may be used in combination.
　上記中和剤の添加は、酸基含有不飽和単量体の重合反応開始前に行ってもよいし、酸基含有不飽和単量体の重合反応中で行ってもよいし、酸基含有不飽和単量体の重合反応終了後に得られる含水ゲルに対して行ってもよい。また、重合反応開始前、重合反応中又は重合反応終了後のいずれか一つの段階を選択して中和剤を添加してもよいし、複数の段階で中和率を調整してもよい。なお、紙オムツ等の吸収性物品等、人体に直接接触する可能性のある用途では、好ましくは重合反応の開始前及び／又は重合反応の期間中、より好ましくは重合反応の開始前に、中和剤を添加すればよい。 The addition of the neutralizing agent may be performed before the polymerization reaction of the acid group-containing unsaturated monomer is started, may be performed during the polymerization reaction of the acid group-containing unsaturated monomer, or may be added. It may be carried out on a hydrogel obtained after the completion of the polymerization reaction of the unsaturated monomer. Further, any one of the stages before the start of the polymerization reaction, during the polymerization reaction or after the end of the polymerization reaction may be selected and the neutralizing agent may be added, or the neutralization ratio may be adjusted in a plurality of stages. In applications where there is a possibility of direct contact with the human body, such as absorbent articles such as disposable diapers, preferably, before the start of the polymerization reaction and / or during the polymerization reaction, more preferably before the start of the polymerization reaction, What is necessary is just to add a wetting agent.
　本発明に係る製造方法では、上記例示した単量体のいずれかを単独で使用してもよく、任意の２種以上の単量体を適宜混合して使用してもよい。また、本発明の目的が達成される限り、さらに他の単量体を混合することもできる。 で は In the production method according to the present invention, any one of the monomers exemplified above may be used alone, or two or more arbitrary monomers may be appropriately mixed and used. Further, other monomers can be mixed as long as the object of the present invention is achieved.
　吸水性樹脂を製造する際に２種以上の単量体を併用する場合、主成分として、(メタ)アクリル酸（塩）を含むことが好ましい。この場合、重合に用いられる単量体全体に対する(メタ）アクリル酸（塩）の割合は、得られる吸水性樹脂の吸水性能の観点から、通常は５０モル％以上、好ましくは７０モル％以上、より好ましくは８０モル％以上、さらに好ましくは９０モル％以上（上限は１００モル％）である。 (4) When two or more monomers are used in combination when producing a water-absorbing resin, it is preferable to contain (meth) acrylic acid (salt) as a main component. In this case, the ratio of (meth) acrylic acid (salt) to the entire monomer used for polymerization is usually 50 mol% or more, preferably 70 mol% or more, from the viewpoint of the water absorbing performance of the obtained water-absorbing resin. It is more preferably at least 80 mol%, further preferably at least 90 mol% (the upper limit is 100 mol%).
　単量体溶液中における水溶性エチレン性不飽和単量体の濃度は、水溶性エチレン性不飽和単量体が溶媒に溶解できる範囲内であれば特に限定されるものではないが、１０重量％～飽和濃度以下が好ましく、２０重量％～飽和濃度以下がより好ましく、２５～８０重量％がさらにより好ましく、３０～７０重量％が特に好ましい。 The concentration of the water-soluble ethylenically unsaturated monomer in the monomer solution is not particularly limited as long as the water-soluble ethylenically unsaturated monomer can be dissolved in the solvent. To less than the saturation concentration, more preferably from 20% by weight to the saturation concentration, still more preferably from 25 to 80% by weight, and particularly preferably from 30 to 70% by weight.
　重合工程においては、必要に応じて、内部架橋剤を用いることができる。すなわち、単量体溶液は内部架橋剤をさらに含有していてもよい。内部架橋剤としては、１分子内に２個以上の重合性不飽和基や２個以上の反応性基を有する従来公知の内部架橋剤が挙げられる。内部架橋剤としては、例えば、Ｎ，Ｎ’－メチレンビス（メタ）アクリルアミド、（ポリ）エチレングリコールジ（メタ）アクリレート、（ポリ）プロピレングリコールジ（メタ）アクリレート、トリメチロールプロパントリ（メタ）アクリレート、トリメチロールプロパンジ（メタ）アクリレート、グリセリントリ（メタ）アクリレート、グリセリンアクリレートメタクリレート、エチレンオキサイド変性トリメチロールプロパントリ（メタ）アクリレート、ペンタエリスリトールテトラ（メタ）アクリレート、ジペンタエリスリトールヘキサ（メタ）アクリレート、トリアリルシアヌレート、トリアリルイソシアヌレート、トリアリルホスフェート、トリアリルアミン、ポリ（メタ）アリロキシアルカン、（ポリ）エチレングリコールジグリシジルエーテル、グリセロールジグリシジルエーテル、エチレングリコール、ポリエチレングリコール、プロピレングリコール、グリセリン、１，４－ブタンジオール、ペンタエリスリトール、エチレンジアミン、エチレンカーボネート、プロピレンカーボネート、ポリエチレンイミン、グリシジル（メタ）アクリレート等を挙げることができる。これらの内部架橋剤は１種のみ用いてもよいし２種以上使用してもよい。 内部 In the polymerization step, an internal crosslinking agent can be used, if necessary. That is, the monomer solution may further contain an internal crosslinking agent. Examples of the internal crosslinking agent include conventionally known internal crosslinking agents having two or more polymerizable unsaturated groups or two or more reactive groups in one molecule. Examples of the internal crosslinking agent include N, N′-methylenebis (meth) acrylamide, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, Trimethylolpropane di (meth) acrylate, glycerin tri (meth) acrylate, glycerin acrylate methacrylate, ethylene oxide modified trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, tri Allyl cyanurate, triallyl isocyanurate, triallyl phosphate, triallylamine, poly (meth) allyloxyalkane, (poly) ethylene glycol di Risidyl ether, glycerol diglycidyl ether, ethylene glycol, polyethylene glycol, propylene glycol, glycerin, 1,4-butanediol, pentaerythritol, ethylenediamine, ethylene carbonate, propylene carbonate, polyethyleneimine, glycidyl (meth) acrylate and the like. Can be. These internal crosslinking agents may be used alone or in combination of two or more.
　中でも、得られる吸水性樹脂の吸水特性等から、２個以上の重合性不飽和基を有する化合物を内部架橋剤として用いることが好ましい。所望する吸水性樹脂の物性により適宜決定されればよいが、通常、内部架橋剤の使用量は、単量体に対して０．０００１～５モル％、より好ましくは０．００１～３モル％、さらにより好ましくは０．００５～１．５モル％である。 Above all, it is preferable to use a compound having two or more polymerizable unsaturated groups as the internal cross-linking agent in view of the water absorbing properties of the obtained water-absorbing resin. The amount of the internal cross-linking agent may be appropriately determined depending on the desired physical properties of the water-absorbing resin. Usually, the amount of the internal crosslinking agent is 0.0001 to 5 mol%, more preferably 0.001 to 3 mol%, based on the monomer. And still more preferably 0.005 to 1.5 mol%.
　また、以下に例示する物質（以下、「その他の物質」と称する）を単量体溶液に添加することもできる。 物質 Further, the substances exemplified below (hereinafter, referred to as “other substances”) can be added to the monomer solution.
　その他の物質の具体例として、チオール類、チオール酸類、２級アルコール類、アミン類、次亜リン酸塩類等の連鎖移動剤；炭酸塩、重炭酸塩、アゾ化合物、気泡等の発泡剤；エチレンジアミン４酢酸の金属塩、ジエチレントリアミン５酢酸の金属塩等のキレート剤；ポリアクリル酸（塩）及びこれらの架橋体、澱粉、セルロース、澱粉－セルロース誘導体、ポリビニルアルコール等の増粘剤等が挙げられる。その他の物質は、単独で用いられてもよく、２種以上を組み合わせて用いられてもよい。 Specific examples of other substances include chain transfer agents such as thiols, thiolic acids, secondary alcohols, amines, and hypophosphites; blowing agents such as carbonates, bicarbonates, azo compounds, and bubbles; ethylenediamine Chelating agents such as metal salts of tetraacetic acid and metal salts of diethylenetriaminepentaacetic acid; and thickeners such as polyacrylic acid (salt) and cross-linked products thereof, starch, cellulose, starch-cellulose derivatives, and polyvinyl alcohol. Other substances may be used alone or in combination of two or more.
　その他の物質の使用量は、特に限定されないが、その他の物質の全濃度としては、好ましくは単量体に対して１０重量％以下であり、より好ましくは１重量％以下であり、さらにより好ましくは０．１重量％以下である。また、その他の物質として増粘剤を使用する場合、単量体溶液の粘度（ブルックフィールド型粘度計／２０℃、６ｒｐｍ）が、好ましくは１０ｍＰａ・ｓ～５０００００ｍＰａ・ｓ、より好ましくは２０ｍＰａ・ｓ～３０００００ｍＰａ・ｓ、さらに好ましくは５０ｍＰａ・ｓ～１０００００ｍＰａ・ｓとなる範囲で、増粘剤を添加すればよい。 The use amount of the other substance is not particularly limited, but the total concentration of the other substance is preferably 10% by weight or less, more preferably 1% by weight or less, more preferably 1% by weight based on the monomer. Is 0.1% by weight or less. When a thickener is used as another substance, the viscosity of the monomer solution (Brookfield viscometer / 20 ° C., 6 rpm) is preferably 10 mPa · s to 500,000 mPa · s, more preferably 20 mPa · s. The thickener may be added in a range of from 300 mPa · s to 300,000 mPa · s, and more preferably from 50 mPa · s to 100000 mPa · s.
　「重合開始剤」
　重合開始剤としては、熱分解型重合開始剤が好ましく用いられる。該熱分解型重合開始剤は、熱によって分解しラジカルを発生する化合物を指すが、熱分解型重合開始剤の貯蔵安定性や吸水性樹脂の生産効率の観点から、１０時間半減期温度（以下、「Ｔ１０」と称する）が好ましくは０℃～１２０℃、より好ましくは３０℃～１００℃、さらに好ましくは５０℃～８０℃である水溶性の化合物が重合開始剤として好ましく用いられる。 `` Polymerization initiator ''
As the polymerization initiator, a thermal decomposition type polymerization initiator is preferably used. The thermal decomposition type polymerization initiator refers to a compound which is decomposed by heat to generate radicals. From the viewpoint of the storage stability of the thermal decomposition type polymerization initiator and the production efficiency of the water-absorbing resin, a 10-hour half-life temperature (hereinafter, referred to as a temperature). , "T10") is preferably 0 ° C. to 120 ° C., more preferably 30 ° C. to 100 ° C., and even more preferably 50 ° C. to 80 ° C., is preferably used as a polymerization initiator.
　上記範囲のＴ１０を有する熱分解型重合開始剤として、具体的には、過硫酸ナトリウム、過硫酸カリウム、過硫酸アンモニウム等の過硫酸塩；２，２’－アゾビス（２－メチルプロピオンアミジン）ジヒドロクロリド、２，２’－アゾビス（２－アミジノプロパン）ジヒドロクロリド、２，２’－アゾビス［２－（２－イミダゾリン－２－イル）プロパン］ジヒドロクロリド、２，２’－アゾビス（２－メチルプロピオニトリル）等のアゾ化合物；過酸化水素、ｔ－ブチルパーオキシド、メチルエチルケトンパーオキシド等の過酸化物等が挙げられる。これらのうち、２種以上を併用してもよい。 Specific examples of the thermal decomposition type polymerization initiator having T10 in the above range include persulfates such as sodium persulfate, potassium persulfate and ammonium persulfate; 2,2′-azobis (2-methylpropionamidine) dihydrochloride , 2,2'-azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride, 2,2'-azobis (2-methylpro Azo compounds such as pionitrile); peroxides such as hydrogen peroxide, t-butyl peroxide and methyl ethyl ketone peroxide; Two or more of these may be used in combination.
　中でも、熱分解型重合開始剤の取扱性や吸水性樹脂の物性の観点から、重合開始剤としては、好ましくは過硫酸塩、より好ましくは過硫酸ナトリウム、過硫酸カリウム、過硫酸アンモニウム、さらに好ましくは過硫酸ナトリウムが使用される。 Among them, from the viewpoint of the handleability of the thermal decomposition type polymerization initiator and the physical properties of the water absorbent resin, the polymerization initiator is preferably a persulfate, more preferably sodium persulfate, potassium persulfate, ammonium persulfate, and still more preferably. Sodium persulfate is used.
　上記熱分解型重合開始剤の使用量は、単量体及び重合開始剤の種類等に応じて適宜設定され、特に限定されないが、生産効率の観点から、単量体に対して、好ましくは０．００１ｇ／モル以上、より好ましくは０．００５ｇ／モル以上、さらに好ましくは０．０１ｇ／モル以上である。また、吸水性樹脂の吸水性能向上の観点から、好ましくは２ｇ／モル以下、より好ましくは１ｇ／モル以下である。 The amount of the thermal decomposition type polymerization initiator used is appropriately set according to the type of the monomer and the polymerization initiator, and is not particularly limited. However, from the viewpoint of production efficiency, preferably 0 to the monomer. 0.001 g / mol or more, more preferably 0.005 g / mol or more, and still more preferably 0.01 g / mol or more. In addition, from the viewpoint of improving the water absorbing performance of the water absorbent resin, the amount is preferably 2 g / mol or less, more preferably 1 g / mol or less.
　また、必要に応じて、光分解型重合開始剤等、他の重合開始剤と併用することもできる。すなわち、熱分解型重合開始剤と光分解型重合開始剤とを併用することも、好ましい態様として挙げることができる。該光分解型重合開始剤として、具体的には、ベンゾイン誘導体、ベンジル誘導体、アセトフェノン誘導体（例えば、１－ヒドロキシシクロヘキシルフェニルケトン）、ベンゾフェノン誘導体等が挙げられる。光分解型重合開始剤の使用量は、特に限定されないが、生産効率の観点から、単量体に対して、好ましくは０．００１ｇ／モル以上、より好ましくは０．００５ｇ／モル以上、さらに好ましくは０．０１ｇ／モル以上である。また、吸水性樹脂の吸水性能向上の観点から、好ましくは２ｇ／モル以下、より好ましくは１ｇ／モル以下である。 Further, if necessary, it can be used in combination with another polymerization initiator such as a photodecomposition type polymerization initiator. That is, a combination of a thermal decomposition type polymerization initiator and a photodecomposition type polymerization initiator is also a preferred embodiment. Specific examples of the photolytic polymerization initiator include a benzoin derivative, a benzyl derivative, an acetophenone derivative (eg, 1-hydroxycyclohexyl phenyl ketone), a benzophenone derivative, and the like. The amount of the photodecomposition type polymerization initiator is not particularly limited, but is preferably 0.001 g / mol or more, more preferably 0.005 g / mol or more, more preferably 0.005 g / mol or more, based on the production efficiency. Is 0.01 g / mol or more. In addition, from the viewpoint of improving the water absorbing performance of the water absorbent resin, the amount is preferably 2 g / mol or less, more preferably 1 g / mol or less.
　上記熱分解型重合開始剤と他の重合開始剤とを併用する場合、全重合開始剤に占める熱分解型重合開始剤の割合は、好ましくは６０モル％以上、より好ましくは８０モル％以上である。 When the thermal decomposition type polymerization initiator is used in combination with another polymerization initiator, the ratio of the thermal decomposition type polymerization initiator to the total polymerization initiator is preferably 60 mol% or more, more preferably 80 mol% or more. is there.
　また、上記熱分解型重合開始剤と還元剤とを併用してレドックス系重合開始剤とすることもできる。上記レドックス系重合開始剤では、熱分解型重合開始剤が酸化剤として機能する。用いられる還元剤としては、特に限定されないが、例えば、亜硫酸ナトリウム、亜硫酸水素ナトリウム等の（重）亜硫酸塩；第一鉄塩等の還元性金属塩；Ｌ－アスコルビン酸（塩）、アミン類等が挙げられる。 レ Also, a redox-based polymerization initiator may be used in combination with the above-mentioned thermal decomposition-type polymerization initiator and a reducing agent. In the redox-based polymerization initiator, the thermal decomposition type polymerization initiator functions as an oxidizing agent. The reducing agent used is not particularly limited, but includes, for example, (bis) sulfites such as sodium sulfite and sodium bisulfite; reducing metal salts such as ferrous salt; L-ascorbic acid (salt); amines; Is mentioned.
　なお、上記重合開始剤を使用する代わりに、放射線、電子線、紫外線等の活性エネルギー線を照射することにより重合を行ってもよい。または、これらの活性エネルギー線と重合開始剤とを併用して重合してもよい。 Instead of using the polymerization initiator, the polymerization may be performed by irradiating an active energy ray such as a radiation, an electron beam, or an ultraviolet ray. Alternatively, polymerization may be carried out using these active energy rays and a polymerization initiator in combination.
　「単量体組成物の水溶性エチレン性不飽和単量体濃度」
　本発明において、単量体組成物中の水溶性エチレン性不飽和単量体の濃度は、選択された水溶性エチレン性不飽和単量体および有機溶媒の種類等に応じて選択されるが、生産効率上、下限は、好ましくは１０重量％以上であり、より好ましくは２０重量％以上であり、さらにより好ましくは３０重量％以上であり、また、上限は、好ましくは１００重量％以下であり、より好ましくは９０重量％以下であり、さらに好ましくは８０重量％以下であり、さらにより好ましくは７０重量％以下である。吸水性樹脂の物性及び生産性の観点から、単量体組成物中の水溶性エチレン性不飽和単量体濃度は、好ましくは１０重量％～９０重量％、より好ましくは２０重量％～８０重量％、さらに好ましくは３０重量％～７０重量％である。 "Concentration of water-soluble ethylenically unsaturated monomer in monomer composition"
In the present invention, the concentration of the water-soluble ethylenically unsaturated monomer in the monomer composition is selected according to the type of the water-soluble ethylenically unsaturated monomer and the organic solvent selected, In terms of production efficiency, the lower limit is preferably at least 10% by weight, more preferably at least 20% by weight, even more preferably at least 30% by weight, and the upper limit is preferably at most 100% by weight. , More preferably 90% by weight or less, further preferably 80% by weight or less, and still more preferably 70% by weight or less. From the viewpoints of physical properties and productivity of the water-absorbing resin, the concentration of the water-soluble ethylenically unsaturated monomer in the monomer composition is preferably from 10% by weight to 90% by weight, more preferably from 20% by weight to 80% by weight. %, More preferably 30% to 70% by weight.
　本発明の目的が阻害されない限り、単量体組成物に、内部架橋剤、界面活性剤、密度調整剤、増粘剤等の添加物を配合することも可能である。なお、添加物の種類及び添加量は、用いられる単量体および有機溶媒の組合せにより、適宜選択されうる。 限 り As long as the object of the present invention is not hindered, additives such as an internal cross-linking agent, a surfactant, a density adjuster, a thickener and the like can be added to the monomer composition. The type and amount of the additive can be appropriately selected depending on the combination of the monomer and the organic solvent used.
　［２－２.分散工程］
　水溶性エチレン性不飽和単量体溶液（または単量体組成物）、有機溶媒を、流路に別々に連続的に供給し、有機溶媒中に分散する水溶性エチレン性不飽和単量体を含む液滴を作製する工程である。ここで、水溶性エチレン性不飽和単量体溶液（または単量体組成物）、有機溶媒を、流路に「別々に」供給するとは、水溶性エチレン性不飽和単量体溶液（または単量体組成物）および有機溶媒の混合物を「別々に」流路に供給する意ではなく、水溶性エチレン性不飽和単量体溶液（または単量体組成物）と、有機溶媒と、を独立して「別々に」供給する意である。 [2-2. Dispersion step]
A water-soluble ethylenically unsaturated monomer solution (or monomer composition) and an organic solvent are separately and continuously supplied to a flow path to disperse the water-soluble ethylenically unsaturated monomer in the organic solvent. This is a step of producing a droplet including the liquid. Here, to supply the water-soluble ethylenically unsaturated monomer solution (or monomer composition) and the organic solvent “separately” to the channel means that the water-soluble ethylenically unsaturated monomer solution (or simply Water-soluble ethylenically unsaturated monomer solution (or monomer composition) and the organic solvent are not separately supplied to the flow path "separately". And supply them separately.
　用いられる分散装置としては、間隙を隔てて互いに対向する対向面を有する一対の壁が相対的に移動することによってせん断場を形成する流路を形成でき、せん断場を形成する流路を循環する有機溶媒中に水溶性エチレン性不飽和単量体溶液が連続的に供給される方法を具現化できる形態であれば、特に限定されない。 As a dispersing device to be used, a pair of walls having opposing surfaces opposing each other with a gap can relatively move to form a flow path that forms a shear field, and circulates a flow path that forms a shear field. There is no particular limitation as long as the method can realize a method of continuously supplying a water-soluble ethylenically unsaturated monomer solution in an organic solvent.
　ここに、「流路」は、一対の壁における互いに対向する対向面の間の間隙によって流体（有機溶媒中に水溶性エチレン性不飽和単量体溶液が供給された流体）を流すことができる形態であれば、形状は特に限定されない。例えば、流路は、互いに対向する凹凸形状の対向面によって、屈曲した形状に形成することができる。また、流路は、一方の対向面を周面形状とし、他方の対向面を凹凸形状の対向面とすることによって、屈曲した形状に形成することができる。また、流路は、互いに対向する平坦な対向面によって、直線的な形状に形成することができる。また、流路は、互いに対向する周面形状の対向面によって、円筒形状に形成することができる。 Here, the “flow path” allows a fluid (a fluid in which a water-soluble ethylenically unsaturated monomer solution is supplied in an organic solvent) to flow through a gap between opposing surfaces of a pair of walls. The shape is not particularly limited as long as it is a form. For example, the flow path can be formed in a bent shape by the concavo-convex opposing surfaces opposing each other. Further, the flow path can be formed in a bent shape by making one of the opposing surfaces a peripheral surface shape and the other opposing surface an uneven surface. Further, the flow path can be formed in a linear shape by the flat opposing surfaces opposing each other. Further, the flow path can be formed in a cylindrical shape by opposing peripheral surfaces that oppose each other.
　「壁」の具体的な形状は、流路の形状に応じて、平面形状、羽根形状、ディスク形状、中空円筒形状、あるいは中実円筒形状など種々の形状を有することができる。 具体 The specific shape of the “wall” can have various shapes such as a planar shape, a blade shape, a disk shape, a hollow cylindrical shape, or a solid cylindrical shape, depending on the shape of the flow path.
　「一対の壁が相対的に移動する」形態は、せん断場を形成する流路を形成することができる形態であれば、特に限定されない。例えば、一方の壁を固定壁とし、他方の壁を可動壁として構成することができる。また、移動速度に差が生じるように一対の壁をともに可動壁として構成することができる。 形態 The “movement of the pair of walls relatively” is not particularly limited as long as a flow path that forms a shear field can be formed. For example, one wall can be configured as a fixed wall and the other wall can be configured as a movable wall. Further, both the pair of walls can be configured as movable walls so that a difference occurs in the moving speed.
　本発明において、有機溶媒への単量体液滴の微細化の観点からは、有機溶媒中への水溶性エチレン性不飽和単量体が、比較的狭い流路内に供給されるほうが好ましい。このような観点からは、間隙の寸法は、５ｍｍ以下であることが好ましく、２ｍｍ以下であることが好ましい。また、生産性を考慮すると、間隙の寸法は、０．１ｍｍ以上であることが好ましく、０．５ｍｍ以上であることがより好ましい。また、間隙や一対の壁の相対的な移動速度は、テーラー渦の発生を抑制するように設計されることが好ましい。 に お い て In the present invention, it is preferable that the water-soluble ethylenically unsaturated monomer in the organic solvent be supplied into a relatively narrow channel from the viewpoint of miniaturization of the monomer droplet in the organic solvent. From such a viewpoint, the dimension of the gap is preferably 5 mm or less, and more preferably 2 mm or less. Further, in consideration of productivity, the size of the gap is preferably 0.1 mm or more, and more preferably 0.5 mm or more. Further, it is preferable that the relative movement speed of the gap and the pair of walls is designed to suppress the generation of the Taylor vortex.
　図２～図８を参照して、用いられる種々の分散装置１２Ａ～１２Ｇについて説明する。図示する分散装置１２Ａ～１２Ｇは、高速回転せん断型撹拌機から構成されている。以下、単量体組成物を用いたものを例示するが、これに代えて水溶性エチレン性不飽和単量体溶液であってもよい。分散装置１２Ａ～１２Ｇは、単量体組成物と、有機溶媒と、が別々に連続的に供給され、有機溶媒中に単量体組成物を液滴状に分散する。なお、図２の分散装置１２Ａにおける部材と、図３～図８の分散装置１２Ｂ～１２Ｇにおける部材とが共通する場合には、図２に付した部材符号の添え字「Ａ」に代えて添え字「Ｂ」～「Ｇ」を付し、重複した説明を省略する。 種 々 Various dispersing apparatuses 12A to 12G used will be described with reference to FIGS. The illustrated dispersion devices 12A to 12G are constituted by high-speed rotary shear type stirrers. Hereinafter, an example using a monomer composition will be described, but a water-soluble ethylenically unsaturated monomer solution may be used instead. In the dispersion devices 12A to 12G, the monomer composition and the organic solvent are separately and continuously supplied, and the monomer composition is dispersed in the organic solvent in the form of droplets. When the members of the dispersing apparatus 12A of FIG. 2 and the members of the dispersing apparatuses 12B to 12G of FIGS. 3 to 8 are common, the suffix "A" is added instead of the suffix "A" of the member code given in FIG. Letters “B” to “G” are appended, and redundant description is omitted.
　「分散装置１２Ａ」
　図２は、一例に係る分散装置１２Ａを示す断面図である。分散装置１２Ａは、ロータリーミキサー型の高速回転せん断型撹拌機である。分散装置１２Ａは、間隙を隔てて互いに対向する対向面５１Ａ、５３Ａを有する一対の壁５０Ａ、５２Ａによって形成される流路５４Ａと、一対の壁５０Ａ、５２Ａを相対的に移動する駆動部６０Ａと、を有している。駆動部６０Ａによって一対の壁５０Ａ、５２Ａを相対的に移動することによって、せん断場を形成する流路５４Ａが形成される。分散装置１２Ａはさらに、単量体組成物を流路５４Ａに連続的に供給する第１供給系５５Ａと、有機溶媒を流路５４Ａに連続的に供給する第２供給系５６Ａと、を有している。 "Dispersion device 12A"
FIG. 2 is a cross-sectional view illustrating a dispersion apparatus 12A according to an example. The dispersing device 12A is a rotary mixer type high-speed rotary shear type stirrer. The dispersion device 12A includes a flow path 54A formed by a pair of walls 50A and 52A having opposing surfaces 51A and 53A facing each other with a gap therebetween, and a driving unit 60A that relatively moves the pair of walls 50A and 52A. ,have. By relatively moving the pair of walls 50A and 52A by the driving unit 60A, a flow path 54A that forms a shear field is formed. The dispersion device 12A further has a first supply system 55A that continuously supplies the monomer composition to the flow path 54A, and a second supply system 56A that continuously supplies the organic solvent to the flow path 54A. ing.
　一対の壁５０Ａ、５２Ａは、円筒形状を有している。一方の壁５０Ａは、中心穴を有する非回転の外筒から形成されている。他方の壁５２Ａは、外筒の中心穴内に回転自在に配置された中実の内筒から形成されている。駆動部６０Ａは、例えばモータから構成され、内筒に接続されている。駆動部６０Ａを稼動することによって、内筒が回転駆動される。これによって、一方の壁５０Ａが固定壁を構成し、他方の壁５２Ａが可動壁を構成している。外筒の内周面および内筒の外周面は、互いに対向する対向面５１Ａ、５３Ａを形成している。互いに対向する対向面５１Ａ、５３Ａは、凹凸形状を有している。対向面５１Ａの凸部が対向面５３Ａの凹所に入り込み、対向面５３Ａの凸部が対向面５１Ａの凹所に入り込んでいる。流路５４Ａは、屈曲した形状を有している。 The pair of walls 50A and 52A have a cylindrical shape. One wall 50A is formed of a non-rotating outer cylinder having a center hole. The other wall 52A is formed from a solid inner cylinder rotatably disposed in the center hole of the outer cylinder. The drive unit 60A is composed of, for example, a motor and is connected to the inner cylinder. By operating the driving unit 60A, the inner cylinder is rotationally driven. Thus, one wall 50A forms a fixed wall, and the other wall 52A forms a movable wall. The inner peripheral surface of the outer cylinder and the outer peripheral surface of the inner cylinder form opposing surfaces 51A and 53A that oppose each other. The facing surfaces 51A and 53A facing each other have an uneven shape. The convex portion of the opposing surface 51A enters the concave portion of the opposing surface 53A, and the convex portion of the opposing surface 53A enters the concave portion of the opposing surface 51A. The channel 54A has a bent shape.
　対向面５１Ａ、５３Ａの間の前記間隙は、流路５４Ａにおいて所望のせん断場が生ずる大きさに形成されている。 The gap between the opposing surfaces 51A and 53A is formed in such a size that a desired shear field is generated in the flow path 54A.
　壁５２Ａの底部は下方に向けて先細りの形状を有している。壁５２Ａの底部と壁５０Ａの底部との間に、流路５４Ａと液体排出管５７Ａとを連通する連通路５８Ａが形成されている。この連通路５８Ａの間隙は、流路５４Ａの間隙よりも大きい。これによって、流路５４Ａから排出された液体を液体排出管５７Ａに導出し易くしている。 底 The bottom of the wall 52A is tapered downward. A communication path 58A is formed between the bottom of the wall 52A and the bottom of the wall 50A to communicate the flow path 54A and the liquid discharge pipe 57A. The gap of the communication path 58A is larger than the gap of the flow path 54A. Thus, the liquid discharged from the flow path 54A is easily led to the liquid discharge pipe 57A.
　液体排出管５７Ａは、反応装置１４の上端に接続されている。液体排出管５７Ａの内径と、反応装置１４の内径とはほぼ等しい寸法に形成されている。分散装置１２Ａから反応装置１４への流体の流れを円滑にし、滞留が生じないようにするためである。分散装置１２Ａ内で滞留が生じないことで、単量体組成物が重合し、含水ゲル状体になることを抑制することができる。分散装置１２Ａ内にゲル状体が生成すると、生成する液滴の粒子径が一定となりにくい。 The liquid discharge pipe 57A is connected to the upper end of the reaction device 14. The inner diameter of the liquid discharge pipe 57A and the inner diameter of the reactor 14 are formed to have substantially the same dimensions. This is for smoothing the flow of the fluid from the dispersing device 12A to the reaction device 14 so that no stagnation occurs. Since no stagnation occurs in the dispersing device 12A, it is possible to prevent the monomer composition from polymerizing and becoming a hydrogel. When the gel-like material is generated in the dispersing device 12A, the particle diameter of the generated droplet is difficult to be constant.
　第１供給系５５Ａには配管３１が接続される。混合装置１０において作製した単量体組成物は、配管３１および第１供給系５５Ａを介して、流路５４Ａに連続的に供給される。第２供給系５６Ａには配管３５が接続される。送液ポンプ１８の稼働によって循環する有機溶媒の一部は、配管３５および第２供給系５６Ａを介して、流路５４Ａに連続的に供給される。 配 管 The pipe 31 is connected to the first supply system 55A. The monomer composition produced in the mixing device 10 is continuously supplied to the flow path 54A via the pipe 31 and the first supply system 55A. The pipe 35 is connected to the second supply system 56A. A part of the organic solvent circulated by the operation of the liquid feed pump 18 is continuously supplied to the flow path 54A via the pipe 35 and the second supply system 56A.
　駆動部６０Ａを稼動し、壁５２Ａを回転駆動する。壁５２Ａの対向面５３Ａは、対向する壁５０Ａの対向面５１Ａに対して移動する。壁５２Ａを回転させながら、単量体組成物は、配管３１および第１供給系５５Ａを通って、流路５４Ａに連続的に供給される。 The drive unit 60A is operated to rotationally drive the wall 52A. The opposing surface 53A of the wall 52A moves with respect to the opposing surface 51A of the opposing wall 50A. While rotating the wall 52A, the monomer composition is continuously supplied to the flow path 54A through the pipe 31 and the first supply system 55A.
　このように互いに対向する対向面５１Ａ、５３Ａを有する一対の壁５０Ａ、５２Ａを駆動部６０Ａによって相対的に移動している状態の流路５４Ａに、有機溶媒と、単量体組成物と、が別々に連続的に供給される。流路５４Ａに流れ込んだ有機溶媒には、ローター側の壁５２Ａの対向面５３Ａとステータ側の壁５０Ａの対向面５１Ａとの間の速度差によって、強いせん断力が作用する。単量体組成物は、せん断力が作用している流路５４Ａ内に直接注入され、有機溶媒中に液滴状に速やかに分散される。さらに、液滴状の単量体組成物は、微細化される。 In this way, the organic solvent and the monomer composition are mixed in the channel 54A in a state where the pair of walls 50A and 52A having the opposing surfaces 51A and 53A opposing each other are relatively moved by the driving unit 60A. It is supplied separately and continuously. A strong shearing force acts on the organic solvent flowing into the flow path 54A due to a speed difference between the facing surface 53A of the rotor-side wall 52A and the facing surface 51A of the stator-side wall 50A. The monomer composition is directly injected into the flow path 54A where a shear force is applied, and is quickly dispersed in an organic solvent in the form of droplets. Further, the droplet-shaped monomer composition is miniaturized.
　「分散装置１２Ｂ」
　図３は、他の例に係る分散装置１２Ｂを示す断面図である。分散装置１２Ｂは、ターボミキサー型の高速回転せん断型撹拌機である。 "Dispersion device 12B"
FIG. 3 is a cross-sectional view illustrating a dispersion apparatus 12B according to another example. The dispersing device 12B is a turbo mixer type high-speed rotary shear type stirrer.
　一方の壁５０Ｂは、非回転のケーシングから形成されている。他方の壁５２Ｂは、ケーシング内に回転自在に配置された羽根形状の渦流ファンから形成されている。駆動部６０Ｂは、渦流ファンに接続されている。駆動部６０Ｂを稼動することによって、渦流ファンが回転駆動される。これによって、一方の壁５０Ｂが固定壁を構成し、他方の壁５２Ｂが可動壁を構成している。ケーシングの内周面および渦流ファンの外周面は、互いに対向する対向面５１Ｂ、５３Ｂを形成している。対向面５１Ｂは、周面形状を有している。対向面５３Ｂは、凹凸形状を有している。対向面５３Ｂの羽根が対向面５１Ｂに向かい合っている。流路５４Ｂは、屈曲した形状を有している。 One wall 50B is formed of a non-rotating casing. The other wall 52B is formed of a blade-shaped vortex fan that is rotatably arranged in the casing. The driving unit 60B is connected to the vortex fan. By operating the driving unit 60B, the vortex fan is rotationally driven. Thereby, one wall 50B constitutes a fixed wall, and the other wall 52B constitutes a movable wall. The inner peripheral surface of the casing and the outer peripheral surface of the vortex fan form opposing surfaces 51B and 53B that oppose each other. The facing surface 51B has a peripheral shape. The facing surface 53B has an uneven shape. The blade of the opposing surface 53B faces the opposing surface 51B. The channel 54B has a bent shape.
　送液ポンプ１８の稼働によって循環する有機溶媒の一部は、配管３５および第２供給系５６Ｂを介して、流路５４Ｂに連続的に供給される。 一部 A part of the organic solvent circulated by the operation of the liquid feed pump 18 is continuously supplied to the flow path 54B via the pipe 35 and the second supply system 56B.
　駆動部６０Ｂを稼動し、壁５２Ｂを回転駆動する。壁５２Ｂの対向面５３Ｂは、対向する壁５０Ｂの対向面５１Ｂに対して移動する。壁５２Ｂを回転させながら、単量体組成物は、配管３１および第１供給系５５Ｂを通って、流路５４Ｂに連続的に供給される。 The drive unit 60B is operated to rotationally drive the wall 52B. The opposing surface 53B of the wall 52B moves with respect to the opposing surface 51B of the opposing wall 50B. While rotating the wall 52B, the monomer composition is continuously supplied to the flow path 54B through the pipe 31 and the first supply system 55B.
　このように互いに対向する対向面５１Ｂ、５３Ｂを有する一対の壁５０Ｂ、５２Ｂを駆動部６０Ｂによって相対的に移動している状態の流路５４Ｂに、有機溶媒と、単量体組成物と、が別々に連続的に供給される。流路５４Ｂに流れ込んだ有機溶媒には、ローター側の壁５２Ｂの対向面５３Ｂとステータ側の壁５０Ｂの対向面５１Ｂとの間の速度差によって、強いせん断力が作用する。単量体組成物は、せん断力が作用している流路５４Ｂ内に直接注入され、有機溶媒中に液滴状に速やかに分散される。さらに、液滴状の単量体組成物は、微細化される。 In this way, the organic solvent and the monomer composition are placed in the channel 54B in a state where the pair of walls 50B and 52B having the opposing surfaces 51B and 53B opposing each other are relatively moved by the driving unit 60B. It is supplied separately and continuously. A strong shearing force acts on the organic solvent flowing into the flow path 54B due to a speed difference between the facing surface 53B of the rotor-side wall 52B and the facing surface 51B of the stator-side wall 50B. The monomer composition is directly injected into the flow path 54B where a shear force is applied, and is quickly dispersed in the organic solvent in the form of droplets. Further, the droplet-shaped monomer composition is miniaturized.
　「分散装置１２Ｃ」
　図４は、さらに他の例に係る分散装置１２Ｃを示す断面図である。分散装置１２Ｃは、ディスク型の高速回転せん断型撹拌機である。 "Dispersion device 12C"
FIG. 4 is a sectional view showing a dispersion apparatus 12C according to still another example. The dispersing device 12C is a disk-type high-speed rotary shearing stirrer.
　一方の壁５０Ｃは、非回転のケーシングから形成されている。他方の壁５２Ｃは、ケーシング内に回転自在に配置されたディスク形状の円形プレートから形成されている。駆動部６０Ｃは、円形プレートに接続されている。駆動部６０Ｃを稼動することによって、円形プレートが回転駆動される。これによって、一方の壁５０Ｃが固定壁を構成し、他方の壁５２Ｃが可動壁を構成している。ケーシングの内周面および円形プレートの外周面は、互いに対向する対向面５１Ｃ、５３Ｃを形成している。対向面５１Ｃ、５３Ｃは、ともに周面形状を有している。流路５４Ｃは、円筒形状を有している。 One wall 50C is formed from a non-rotating casing. The other wall 52C is formed of a disk-shaped circular plate rotatably disposed in the casing. The driving unit 60C is connected to the circular plate. The circular plate is rotationally driven by operating the driving unit 60C. Thus, one wall 50C forms a fixed wall, and the other wall 52C forms a movable wall. The inner peripheral surface of the casing and the outer peripheral surface of the circular plate form opposing surfaces 51C and 53C that oppose each other. Both the opposing surfaces 51C and 53C have a peripheral shape. The channel 54C has a cylindrical shape.
　送液ポンプ１８の稼働によって循環する有機溶媒の一部は、配管３５および第２供給系５６Ｃを介して、流路５４Ｃに連続的に供給される。 一部 A part of the organic solvent circulated by the operation of the liquid feed pump 18 is continuously supplied to the flow path 54C via the pipe 35 and the second supply system 56C.
　駆動部６０Ｃを稼動し、壁５２Ｃを回転駆動する。壁５２Ｃの対向面５３Ｃは、対向する壁５０Ｃの対向面５１Ｃに対して移動する。壁５２Ｃを回転させながら、単量体組成物は、配管３１および第１供給系５５Ｃを通って、流路５４Ｃに連続的に供給される。 The drive unit 60C is operated to rotationally drive the wall 52C. The opposing surface 53C of the wall 52C moves with respect to the opposing surface 51C of the opposing wall 50C. While rotating the wall 52C, the monomer composition is continuously supplied to the flow path 54C through the pipe 31 and the first supply system 55C.
　このように互いに対向する対向面５１Ｃ、５３Ｃを有する一対の壁５０Ｃ、５２Ｃを駆動部６０Ｃによって相対的に移動している状態の流路５４Ｃに、有機溶媒および単量体組成物が別々に連続的に供給される。流路５４Ｃに流れ込んだ有機溶媒には、ローター側の壁５２Ｃの対向面５３Ｃとステータ側の壁５０Ｃの対向面５１Ｃとの間の速度差によって、強いせん断力が作用する。単量体組成物は、せん断力が作用している流路５４Ｃ内に直接注入され、有機溶媒中に液滴状に速やかに分散される。さらに、液滴状の単量体組成物は、微細化される。 As described above, the organic solvent and the monomer composition are separately and continuously connected to the channel 54C in which the pair of walls 50C and 52C having the opposing surfaces 51C and 53C opposing each other are relatively moved by the driving unit 60C. Supplied. A strong shearing force acts on the organic solvent flowing into the flow path 54C due to a speed difference between the facing surface 53C of the rotor-side wall 52C and the facing surface 51C of the stator-side wall 50C. The monomer composition is directly injected into the channel 54C where a shear force is acting, and is quickly dispersed in an organic solvent in a droplet form. Further, the droplet-shaped monomer composition is miniaturized.
　「分散装置１２Ｄ」
　図５は、さらに他の例に係る分散装置１２Ｄを示す断面図である。分散装置１２Ｄは、ディスク型の高速回転せん断型撹拌機である。 "Dispersion device 12D"
FIG. 5 is a cross-sectional view illustrating a dispersion apparatus 12D according to still another example. The dispersion device 12D is a disk-type high-speed rotary shearing stirrer.
　一方の壁５０Ｄは、非回転のケーシングから形成されている。他方の壁５２Ｄは、ケーシング内に回転自在に配置された円錘台形状のプレートから形成されている。駆動部６０Ｄは、プレートに接続されている。駆動部６０Ｄを稼動することによって、プレートが回転駆動される。これによって、一方の壁５０Ｄが固定壁を構成し、他方の壁５２Ｄが可動壁を構成している。ケーシングの内周面およびプレートの外周面は、互いに対向する対向面５１Ｄ、５３Ｄを形成している。対向面５１Ｄ、５３Ｄは、ともに周面形状を有している。流路５４Ｄは、円筒形状を有している。 One wall 50D is formed of a non-rotating casing. The other wall 52D is formed of a frustum-shaped plate that is rotatably arranged in the casing. The driving unit 60D is connected to the plate. By driving the driving unit 60D, the plate is rotationally driven. Thus, one wall 50D constitutes a fixed wall, and the other wall 52D constitutes a movable wall. The inner peripheral surface of the casing and the outer peripheral surface of the plate form opposing surfaces 51D and 53D that oppose each other. Both the opposing surfaces 51D and 53D have a peripheral shape. The channel 54D has a cylindrical shape.
　送液ポンプ１８の稼働によって循環する有機溶媒の一部は、配管３５および第２供給系５６Ｄを介して、流路５４Ｄに連続的に供給される。 一部 A part of the organic solvent circulated by the operation of the liquid feed pump 18 is continuously supplied to the flow path 54D via the pipe 35 and the second supply system 56D.
　駆動部６０Ｄを稼動し、壁５２Ｄを回転駆動する。壁５２Ｄの対向面５３Ｄは、対向する壁５０Ｄの対向面５１Ｄに対して移動する。壁５２Ｄを回転させながら、単量体組成物は、配管３１および第１供給系５５Ｄを通って、流路５４Ｄに連続的に供給される。 Activate the driving unit 60D to rotationally drive the wall 52D. The opposing surface 53D of the wall 52D moves with respect to the opposing surface 51D of the opposing wall 50D. While rotating the wall 52D, the monomer composition is continuously supplied to the flow path 54D through the pipe 31 and the first supply system 55D.
　このように互いに対向する対向面５１Ｄ、５３Ｄを有する一対の壁５０Ｄ、５２Ｄを駆動部６０Ｄによって相対的に移動している状態の流路５４Ｄに、有機溶媒と、単量体組成物と、が別々に連続的に供給される。流路５４Ｄに流れ込んだ有機溶媒には、ローター側の壁５２Ｄの対向面５３Ｄとステータ側の壁５０Ｄの対向面５１Ｄとの間の速度差によって、強いせん断力が作用する。単量体組成物は、せん断力が作用している流路５４Ｄ内に直接注入され、有機溶媒中に液滴状に速やかに分散される。さらに、液滴状の単量体組成物は、微細化される。 As described above, the organic solvent and the monomer composition are mixed in the flow path 54D in a state where the pair of walls 50D and 52D having the opposing surfaces 51D and 53D opposing each other are relatively moved by the driving unit 60D. It is supplied separately and continuously. A strong shearing force acts on the organic solvent flowing into the flow path 54D due to a speed difference between the facing surface 53D of the rotor-side wall 52D and the facing surface 51D of the stator-side wall 50D. The monomer composition is directly injected into the channel 54D where a shear force is acting, and is quickly dispersed in an organic solvent in the form of droplets. Further, the droplet-shaped monomer composition is miniaturized.
　「分散装置１２Ｅ」
　図６は、さらに他の例に係る分散装置１２Ｅを示す断面図である。分散装置１２Ｅは、ディスク型の高速回転せん断型撹拌機である。 "Dispersion device 12E"
FIG. 6 is a sectional view showing a dispersion apparatus 12E according to still another example. The dispersion device 12E is a disk-type high-speed rotary shearing stirrer.
　一方の壁５０Ｅは、ケーシング内に回転自在に配置されたディスク形状の円形プレートから形成されている。他方の壁５２Ｅは、ケーシング内に回転自在に配置されたディスク形状の円形プレートから形成されている。駆動部６０Ｅ１、６０Ｅ２は、それぞれの円形プレートに接続されている。駆動部６０Ｅ１、６０Ｅ２を稼動することによって、それぞれの円形プレートが回転駆動される。これによって、一方の壁５０Ｅおよび他方の壁５２Ｅはともに可動壁を構成している。一方の壁５０Ｅの図中下面は平坦面に形成され、他方の壁５２Ｅの図中上面は平坦面に形成されている。一方の壁５０Ｅの下面および他方の壁５２Ｅの上面は、互いに対向する対向面５１Ｅ、５３Ｅを形成している。対向面５１Ｅ、５３Ｅは、ともに円形の平坦形状を有している。流路５４Ｅは、直線的な形状を有している。 One wall 50E is formed of a disk-shaped circular plate that is rotatably arranged in the casing. The other wall 52E is formed of a disk-shaped circular plate rotatably disposed in the casing. The driving units 60E1 and 60E2 are connected to the respective circular plates. By operating the driving units 60E1 and 60E2, the respective circular plates are rotationally driven. Thus, the one wall 50E and the other wall 52E together constitute a movable wall. The lower surface of one wall 50E in the drawing is formed as a flat surface, and the upper surface of the other wall 52E in the drawing is formed as a flat surface. The lower surface of one wall 50E and the upper surface of the other wall 52E form opposing surfaces 51E and 53E which oppose each other. Both the opposing surfaces 51E and 53E have a circular flat shape. The flow path 54E has a linear shape.
　他方の壁５２Ｅの回転軸は、一方の壁５０Ｅの中空形状を有する回転軸の中に挿通されている。回転軸同士の間に形成された通路によって、単量体組成物を流路５４Ｅに連続的に供給する第１供給系５５Ｅと、有機溶媒を流路５４Ｅに連続的に供給する第２供給系５６Ｅとが形成されている。 回 転 The rotation axis of the other wall 52E is inserted into the hollow rotation axis of the one wall 50E. A first supply system 55E for continuously supplying the monomer composition to the flow path 54E by a passage formed between the rotation shafts, and a second supply system for continuously supplying the organic solvent to the flow path 54E. 56E are formed.
　駆動部６０Ｅ１、６０Ｅ２は、それぞれの円形プレートの回転速度に差がつくように、それぞれの円形プレートを回転駆動する。駆動部６０Ｅ１、６０Ｅ２は、それぞれの円形プレートを逆方向に回転させることができる。また、駆動部６０Ｅ１、６０Ｅ２は、それぞれの円形プレートを速度差をもって同じ方向に回転させることができる。 The drive units 60E1 and 60E2 rotationally drive the respective circular plates so that the rotational speeds of the respective circular plates are different. The driving units 60E1 and 60E2 can rotate the respective circular plates in opposite directions. Further, the drive units 60E1 and 60E2 can rotate the respective circular plates in the same direction with a speed difference.
　送液ポンプ１８の稼働によって循環する有機溶媒の一部は、配管３５および第２供給系５６Ｅを介して、流路５４Ｅに連続的に供給される。 一部 A part of the organic solvent circulated by the operation of the liquid feed pump 18 is continuously supplied to the flow path 54E through the pipe 35 and the second supply system 56E.
　駆動部６０Ｅ１、６０Ｅ２を稼動し、壁５０Ｅ、５２Ｅを回転駆動する。壁５２Ｅの対向面５３Ｅは、対向する壁５０Ｅの対向面５１Ｅに対して相対的に移動する。壁５０Ｅ、５２Ｅを回転させながら、単量体組成物は、配管３１および第１供給系５５Ｅを通って、流路５４Ｅに連続的に供給される。 稼 動 The drive units 60E1 and 60E2 are operated to rotationally drive the walls 50E and 52E. The opposing surface 53E of the wall 52E moves relatively to the opposing surface 51E of the opposing wall 50E. While rotating the walls 50E and 52E, the monomer composition is continuously supplied to the flow path 54E through the pipe 31 and the first supply system 55E.
　このように互いに対向する対向面５１Ｅ、５３Ｅを有する一対の壁５０Ｅ、５２Ｅを駆動部６０Ｅ１、６０Ｅ２によって相対的に移動している状態の流路５４Ｅに、有機溶媒と、単量体組成物と、が別々に連続的に供給される。流路５４Ｅに流れ込んだ有機溶媒には、ともにローター側となる壁５０Ｅの対向面５１Ｅと壁５２Ｅの対向面５３Ｅとの間の速度差によって、強いせん断力が作用する。単量体組成物は、せん断力が作用している流路５４Ｅ内に直接注入され、有機溶媒中に液滴状に速やかに分散される。さらに、液滴状の単量体組成物は、微細化される。 The organic solvent and the monomer composition are supplied to the flow path 54E in which the pair of walls 50E and 52E having the opposing surfaces 51E and 53E opposing each other are relatively moved by the driving units 60E1 and 60E2. , Are separately and continuously supplied. A strong shearing force acts on the organic solvent that has flowed into the flow path 54E due to the speed difference between the opposing surface 51E of the wall 50E and the opposing surface 53E of the wall 52E, both of which are on the rotor side. The monomer composition is directly injected into the flow path 54E where a shear force is acting, and is quickly dispersed in the form of droplets in the organic solvent. Further, the droplet-shaped monomer composition is miniaturized.
　「分散装置１２Ｆ」
　図７は、さらに他の例に係る分散装置１２Ｆを示す断面図である。分散装置１２Ｆは、二重円筒型の高速回転せん断型撹拌機である。 "Dispersion device 12F"
FIG. 7 is a cross-sectional view illustrating a dispersion apparatus 12F according to still another example. The dispersion device 12F is a double-cylindrical high-speed rotary shearing stirrer.
　一対の壁５０Ｆ、５２Ｆは、円筒形状を有している。一方の壁５０Ｆは、中心穴を有する非回転の外筒から形成されている。他方の壁５２Ｆは、外筒の中心穴内に回転自在に配置された中実の内筒から形成されている。駆動部６０Ｆは、内筒に接続されている。駆動部６０Ｆを稼動することによって、内筒が回転駆動される。これによって、一方の壁５０Ｆが固定壁を構成し、他方の壁５２Ｆが可動壁を構成している。外筒の内周面および内筒の外周面は、互いに対向する対向面５１Ｆ、５３Ｆを形成している。対向面５１Ｆ、５３Ｆは、ともに周面形状を有している。流路５４Ｆは、円筒形状を有している。 The pair of walls 50F and 52F have a cylindrical shape. One wall 50F is formed from a non-rotating outer cylinder having a center hole. The other wall 52F is formed of a solid inner cylinder rotatably disposed in the center hole of the outer cylinder. The driving unit 60F is connected to the inner cylinder. By operating the driving unit 60F, the inner cylinder is rotationally driven. Thus, one wall 50F constitutes a fixed wall, and the other wall 52F constitutes a movable wall. The inner peripheral surface of the outer cylinder and the outer peripheral surface of the inner cylinder form opposing surfaces 51F and 53F that oppose each other. Both the opposing surfaces 51F and 53F have a peripheral shape. The flow path 54F has a cylindrical shape.
　壁５２Ｆの底部は下方に向けて先細りの形状を有している。壁５２Ｆの底部と壁５０Ｆの底部との間に、流路５４Ｆと液体排出管５７Ｆとを連通する連通路５８Ｆが形成されている。 底 The bottom of the wall 52F is tapered downward. A communication path 58F is formed between the bottom of the wall 52F and the bottom of the wall 50F to communicate the flow path 54F and the liquid discharge pipe 57F.
　送液ポンプ１８の稼働によって循環する有機溶媒の一部は、配管３５および第２供給系５６Ｆを介して、流路５４Ｆに連続的に供給される。 一部 A part of the organic solvent circulated by the operation of the liquid feed pump 18 is continuously supplied to the flow path 54F via the pipe 35 and the second supply system 56F.
　駆動部６０Ｆを稼動し、壁５２Ｆを回転駆動する。壁５２Ｆの対向面５３Ｆは、対向する壁５０Ｆの対向面５１Ｆに対して移動する。壁５２Ｆを回転させながら、単量体組成物は、配管３１および第１供給系５５Ｆを通って、流路５４Ｆに連続的に供給される。 The drive unit 60F is operated to rotationally drive the wall 52F. The opposing surface 53F of the wall 52F moves with respect to the opposing surface 51F of the opposing wall 50F. While rotating the wall 52F, the monomer composition is continuously supplied to the flow path 54F through the pipe 31 and the first supply system 55F.
　このように互いに対向する対向面５１Ｆ、５３Ｆを有する一対の壁５０Ｆ、５２Ｆを駆動部６０Ｆによって相対的に移動している状態の流路５４Ｆに、有機溶媒と、単量体組成物と、が別々に連続的に供給される。流路５４Ｆに流れ込んだ有機溶媒には、ローター側の壁５２Ｆの対向面５３Ｆとステータ側の壁５０Ｆの対向面５１Ｆとの間の速度差によって、強いせん断力が作用する。単量体組成物は、せん断力が作用している流路５４Ｆ内に直接注入され、有機溶媒中に液滴状に速やかに分散される。さらに、液滴状の単量体組成物は、微細化される。 As described above, the organic solvent and the monomer composition are mixed in the flow path 54F in which the pair of walls 50F and 52F having the opposing surfaces 51F and 53F opposing each other are relatively moved by the driving unit 60F. It is supplied separately and continuously. A strong shearing force acts on the organic solvent flowing into the flow path 54F due to a speed difference between the facing surface 53F of the rotor-side wall 52F and the facing surface 51F of the stator-side wall 50F. The monomer composition is directly injected into the flow path 54F where a shear force is applied, and is quickly dispersed in an organic solvent in the form of droplets. Further, the droplet-shaped monomer composition is miniaturized.
　「分散装置１２Ｇ」
　図８は、さらに他の例に係る分散装置１２Ｇを示す断面図である。分散装置１２Ｇは、分散装置１２Ｆと同様に、二重円筒型の高速回転せん断型撹拌機である。 "Dispersion device 12G"
FIG. 8 is a cross-sectional view illustrating a dispersion apparatus 12G according to still another example. The dispersing device 12G is a double-cylindrical high-speed rotary shearing stirrer, like the dispersing device 12F.
　分散装置１２Ｇは、分散装置１２Ｆと異なり、壁５２Ｇの底部は平坦面に形成されている。壁５０Ｇの底面は開口されている。壁５０Ｇの底部開口５９Ｇが液体排出管として機能する。流路５４Ｇから排出された液体は、そのまま落下して反応装置１４に投入される。このように壁５２Ｇが円筒形状で、壁５２Ｇの中心穴の内径と、反応装置１４の内径とがほぼ等しい寸法に形成されていることで、分散装置１２Ｇから反応装置１４への流体の流れを円滑にし、単量体組成物が分散装置内で滞留しにくくなる。ゆえに、１２Ｇの分散装置によれば、装置内で滞留が生じにくいことで、単量体組成物が重合し、含水ゲル状体になることを一層抑制することができ生成する液滴の粒子径が一定となりやすい。分散装置１２Ｇにおける他の構造および作用は、分散装置１２Ｆと同様であるので説明を省略する。 The dispersing device 12G is different from the dispersing device 12F in that the bottom of the wall 52G is formed to be flat. The bottom surface of the wall 50G is open. The bottom opening 59G of the wall 50G functions as a liquid discharge pipe. The liquid discharged from the flow path 54G falls as it is and is charged into the reaction device 14. Since the wall 52G has a cylindrical shape and the inner diameter of the center hole of the wall 52G is substantially equal to the inner diameter of the reaction device 14, the flow of the fluid from the dispersion device 12G to the reaction device 14 is reduced. Smoothness makes it difficult for the monomer composition to stay in the dispersion device. Therefore, according to the 12G dispersing apparatus, since the stagnation does not easily occur in the apparatus, it is possible to further suppress the monomer composition from being polymerized and becoming a hydrated gel, and the particle diameter of the generated droplets Tends to be constant. The other structure and operation of the dispersing device 12G are the same as those of the dispersing device 12F, and thus description thereof is omitted.
　分散装置１２Ｆ、１２Ｇの二重円筒型の高速回転せん断型撹拌機において、外筒が非回転、内筒が回転自在な構成に限定されず（外筒が固定壁、内筒が移動壁を構成する形態）、内筒が非回転、外筒が回転自在な構成でもよい（内筒が固定壁、外筒が移動壁を構成する形態）。また、外筒および内筒のそれぞれが逆方向に回転してもよい（外筒および内筒がともに移動壁を構成する形態）。さらに、外筒および内筒のそれぞれが速度差をもって同じ方向に回転する構成でもよい（外筒および内筒がともに移動壁を構成する形態）。 In the double cylindrical high-speed rotary shearing stirrer of the dispersing devices 12F and 12G, the outer cylinder is not limited to a configuration in which the outer cylinder is non-rotating and the inner cylinder is rotatable. The inner cylinder may be non-rotating and the outer cylinder may be rotatable (the inner cylinder forms a fixed wall, and the outer cylinder forms a moving wall). Further, each of the outer cylinder and the inner cylinder may rotate in the opposite direction (a form in which the outer cylinder and the inner cylinder together form a moving wall). Further, the outer cylinder and the inner cylinder may be configured to rotate in the same direction with a speed difference (a form in which the outer cylinder and the inner cylinder together form a moving wall).
　分散装置１２Ｇにおいて、壁５２Ｇの回転数は特に限定されず、例えば、下記好適なせん断速度となるように、分散装置の構造やスケール等を考慮して、壁５２Ｇの回転数を導きだせばよい。壁５２Ｇの回転数としては、例えば、１００～１０，０００ｒｐｍであり、５００～９，０００ｒｐｍであり、１，０００～８，０００ｒｐｍである。 In the dispersing device 12G, the rotation speed of the wall 52G is not particularly limited. For example, the rotation speed of the wall 52G may be derived in consideration of the structure, scale, and the like of the dispersing device so as to have the following preferable shear rate. . The rotation speed of the wall 52G is, for example, 100 to 10,000 rpm, 500 to 9,000 rpm, and 1,000 to 8,000 rpm.
　「流路におけるせん断速度」
　分散装置の流路におけるせん断速度は、１，０００［１／ｓ］以上であることが好ましい。せん断速度が１，０００［１／ｓ］以上であることで、流路内の単量体が有機溶媒内に分散するのに十分なせん断速度となるため、分散が良好となり、一次粒子径が小さくなる。一次粒子径が小さくなることで、吸水性樹脂の比表面積が大きくなり、吸水速度の向上につながる。また、せん断速度が１，０００［１／ｓ］以上であることで、液滴を生成する時間を短くすることが可能となる。さらには、せん断速度が１，０００［１／ｓ］以上であることで、分散時に界面活性剤の使用量を削減することができる。上記観点からは、分散装置の流路におけるせん断速度は、１,０００［１／ｓ］以上であることが好ましく、２,０００［１／ｓ］以上であることがより好ましく、３,０００［１／ｓ］以上であることがさらに好ましく、３，５００［１／ｓ］以上であることが特に好ましい。一方、分散装置を安定的に稼働させるためには、せん断速度は４０,０００［１／ｓ］以下であることが好ましく、２０,０００［１／ｓ］以下であることがより好ましく、１０,０００［１／ｓ］以下であることがさら好ましく、６，０００[１／ｓ]以下であることが特に好ましい。分散装置の流路におけるせん断速度は、１，０００～４０,０００［１／ｓ］であることが好ましく、２,０００～２０,０００［１／ｓ］であることがより好ましく、３,０００～１０,０００［１／ｓ］であることがさらにより好ましく、３，５００～６，０００［１／ｓ］であることが特に好ましい。また、分散装置が二重円筒型である場合、分散装置の流路におけるせん断速度は、１，０００～４０，０００［１／ｓ］であることが好ましく、２,０００～２０,０００［１／ｓ］であることがより好ましく、３,０００～１０,０００［１／ｓ］であることがさらにより好ましく、３，５００～６，０００［１／ｓ］であることが特に好ましい。 "Shear rate in flow channel"
The shear rate in the flow path of the dispersing device is preferably 1,000 [1 / s] or more. When the shear rate is 1,000 [1 / s] or more, the shear rate is sufficient to disperse the monomers in the flow path in the organic solvent. Become smaller. As the primary particle diameter decreases, the specific surface area of the water-absorbing resin increases, leading to an improvement in the water absorption rate. Further, when the shear rate is 1,000 [1 / s] or more, it is possible to shorten the time for generating droplets. Furthermore, when the shear rate is 1,000 [1 / s] or more, the amount of the surfactant used during dispersion can be reduced. From the above viewpoint, the shear rate in the flow path of the dispersion device is preferably 1,000 [1 / s] or more, more preferably 2,000 [1 / s] or more, and 3,000 [1 / s]. 1 / s] or more, more preferably 3,500 [1 / s] or more. On the other hand, in order to operate the dispersion apparatus stably, the shear rate is preferably 40,000 [1 / s] or less, more preferably 20,000 [1 / s] or less, and It is more preferably at most 000 [1 / s], particularly preferably at most 6,000 [1 / s]. The shear rate in the flow path of the dispersing device is preferably from 1,000 to 40,000 [1 / s], more preferably from 2,000 to 20,000 [1 / s], and 3,000. Even more preferably, it is from 10,000 to 1 / s, and particularly preferably from 3,500 to 6,000 [1 / s]. When the dispersing device is a double cylindrical type, the shear rate in the flow channel of the dispersing device is preferably 1,000 to 40,000 [1 / s], and 2,000 to 20,000 [1 / S], more preferably 3,000 to 10,000 [1 / s], and particularly preferably 3,500 to 6,000 [1 / s].
　せん断速度は、ローター回転数および流路幅（クリアランス、例えば、二重円筒型の分散装置の場合、外筒半径および内筒半径）によって決定される。 The shear rate is determined by the rotor rotation speed and the flow path width (clearance, for example, the outer cylinder radius and the inner cylinder radius in the case of a double cylinder type dispersion device).
　具体的には、せん断速度は、本明細書においては、以下のように算出する。 Specifically, in this specification, the shear rate is calculated as follows.
　せん断速度［１／ｓ］＝分散装置における相対的に移動する壁（ローター、回転子）の移動速度［ｍ／ｓ］／間隙（クリアランス）［ｍ］
　形状が複雑で、移動速度の定義が難しい場合は、移動速度は、一方が固定壁の場合、接液部での最大移動速度とする。また、双方が移動壁の場合は、移動速度は、移動速度の差が最大になる点での移動速度とする。なお、一対の壁の双方が回転する場合には、移動速度の差となる。また、間隙（クリアランス）が複数ある場合は、最狭の距離を用いる。装置の位置によってせん断速度が異なる場合は、最大のせん断速度を本明細書のせん断速度とする。 Shearing speed [1 / s] = moving speed [m / s] / gap (clearance) [m] of a relatively moving wall (rotor, rotor) in the dispersion device
When the shape is complicated and it is difficult to define the moving speed, the moving speed is the maximum moving speed in the liquid contact part when one of the walls is a fixed wall. When both are moving walls, the moving speed is the moving speed at the point where the difference between the moving speeds is maximum. In the case where both of the pair of walls rotate, a difference in the moving speed occurs. When there are a plurality of gaps (clearances), the smallest distance is used. When the shear rate differs depending on the position of the device, the maximum shear rate is defined as the shear rate in the present specification.
　「流路における水溶性エチレン性不飽和単量体溶液の平均滞留時間（以下、単に平均滞留時間とも称する）」
　分散装置においては、有機溶媒および単量体溶液（または単量体組成物）は、速やかに混合され、反応装置に排出される。このため、分散装置内において、単量体溶液（または単量体組成物）の滞留時間は少なくなる。これによって、分散装置内で単量体組成物が重合してゲル状になることが抑制され、該ゲル状物による分散機内での詰まりを抑制することができる。 "Average residence time of the water-soluble ethylenically unsaturated monomer solution in the flow channel (hereinafter, also simply referred to as average residence time)"
In the dispersing device, the organic solvent and the monomer solution (or the monomer composition) are rapidly mixed and discharged to the reaction device. Therefore, the residence time of the monomer solution (or the monomer composition) in the dispersing device is reduced. This suppresses the monomer composition from being polymerized into a gel in the dispersing apparatus, and can suppress clogging in the dispersing machine due to the gel.
　平均滞留時間は、以下の式によって算出される。 The average residence time is calculated by the following formula.
　平均滞留時間［ｓ］＝分散部容積［ｍｌ］／｛（水溶性エチレン性不飽和単量体溶液（または単量体組成物）の流量［ｍｌ／分］＋有機溶媒の流量［ｍｌ／分］）/６０｝
　例えば、二重円筒型分散装置（例えば、図７や図８で示される分散装置）の場合、分散部容積＝（外筒有効容積－回転部有効容積）となる。ここで、分散部とは、二つの流体（有機溶媒および単量体溶液（または単量体組成物））が交わった状態でせん断力が付与される領域である。例えば、図７においては、単量体組成物が供給される第一供給系５５Ｆの高さ方向の中点から壁５２Ｆの円柱形状の終点までの領域（図７におけるＨ）、および、壁５２Ｆの先細りの形状領域（図７におけるＬ）が、分散部であり、当該分散部の容積を分散部容積とする。同様に、図８においては、単量体組成物が供給される第一供給系５５Ｆの高さ方向の中点から壁５２Ｆの底部までの領域（図８におけるＨ）が、分散部であり、当該分散部の容積を分散部容積とする。 Average residence time [s] = dispersion part volume [ml] / ｛(flow rate of water-soluble ethylenically unsaturated monomer solution (or monomer composition) [ml / min] + flow rate of organic solvent [ml / min] ]) / 60｝
For example, in the case of a double-cylindrical dispersion device (for example, the dispersion device shown in FIGS. 7 and 8), the dispersion portion volume = (effective outer cylinder volume−effective rotation portion volume). Here, the dispersion portion is a region where a shearing force is applied in a state where two fluids (an organic solvent and a monomer solution (or a monomer composition)) intersect. For example, in FIG. 7, a region (H in FIG. 7) from a midpoint in the height direction of the first supply system 55F to which the monomer composition is supplied to an end point of the cylindrical shape of the wall 52F, and the wall 52F The tapered shape region (L in FIG. 7) is the dispersion portion, and the volume of the dispersion portion is defined as the dispersion portion volume. Similarly, in FIG. 8, a region (H in FIG. 8) from the midpoint in the height direction of the first supply system 55F to which the monomer composition is supplied to the bottom of the wall 52F is a dispersion portion, The volume of the dispersing part is defined as the dispersing part volume.
　平均滞留時間は０．１～５秒であることが好ましい。このような平均滞留時間となる分散装置を用いることで、水溶性エチレン性不飽和単量体の分散が良好に行われるとともに、ゲル状物の生成を抑制することができ、吸水性樹脂粒子の粒子径がより安定する。また、分散装置が二重円筒型である場合、平均滞留時間は、より好ましくは、０．３～３秒であり、さらに好ましくは０．５～１．５秒である。なお、分散と重合とが一の装置で行われる形態（回分操作）の場合、平均滞留時間は通常６０秒を超える。 The average residence time is preferably 0.1 to 5 seconds. By using a dispersing device having such an average residence time, while the dispersion of the water-soluble ethylenically unsaturated monomer is performed well, the formation of a gel-like substance can be suppressed, and the water-absorbing resin particles Particle size is more stable. When the dispersing device is a double cylinder type, the average residence time is more preferably 0.3 to 3 seconds, and further preferably 0.5 to 1.5 seconds. In the case where the dispersion and the polymerization are performed in one apparatus (batch operation), the average residence time usually exceeds 60 seconds.
　平均滞留時間は、分散装置の形状（ローターサイズ、間隙、単量体溶液の添加位置、反応装置に続く排出口の形状等）および、分散媒量によって制御することができる。 The average residence time can be controlled by the shape of the dispersing device (rotor size, gap, addition position of the monomer solution, shape of the outlet following the reactor, etc.) and the amount of dispersion medium.
　「粒子の液滴径」
　本発明において、水溶性エチレン性不飽和単量体を含む液滴の好ましい体積平均粒子径は、分散や懸濁状態の安定性や有機溶媒の熱移動効率の観点から、２０００μｍ以下であり、より好ましくは１０００μｍ以下であり、さらに好ましくは８００μｍ以下である。また、生産効率の観点から、好ましくは１０μｍ以上であり、より好ましくは２０μｍ以上であり、さらに好ましくは３０μｍ以上である。  `` Drop size of particles ''
In the present invention, the preferable volume average particle diameter of the droplet containing the water-soluble ethylenically unsaturated monomer is 2000 μm or less from the viewpoint of the stability of the dispersed or suspended state and the heat transfer efficiency of the organic solvent. Preferably it is 1000 μm or less, more preferably 800 μm or less. In addition, from the viewpoint of production efficiency, it is preferably 10 μm or more, more preferably 20 μm or more, and further preferably 30 μm or more.
　上記液滴の「体積平均粒子径」は、ＪＩＳ　Ｚ　８８２５：２０１３で規定される「粒子径解析－レーザ回析・散乱法」及びＪＩＳ　Ｚ　８８１９－２：２００１で規定される「粒子径測定結果の表現－第２部：粒子径分布からの平均粒子径又は平均粒子直径及びモーメントの計算」に準拠して算出する方法や、分散状態を撮影した写真の画像解析により算出する方法を用いることが出来る。 The “volume average particle diameter” of the droplet is determined by “particle diameter analysis-laser diffraction / scattering method” specified in JIS Z 8825: 2013 and “particle diameter measurement result” specified in JIS Z 8819-2: 2001. Expression-Part 2: Calculation of average particle diameter or average particle diameter and moment from particle diameter distribution "or a method of calculating the dispersion state by image analysis of a photograph of a photographed image. I can do it.
　「単量体組成物流量／有機溶媒流量比」
　本発明において、分散装置に流入する有機溶媒流量［ｍｌ／分］に対する分散装置に流入する単量体組成物流量［ｍｌ／分］の比（単量体組成物流量［ｍｌ／分］／有機溶媒流量［ｍｌ／分］）は、０．０１以上であることが好ましく、０．０２以上であることがより好ましく、０．０４以上であることがさらに好ましく、０．０４を超えることがさらにより好ましく、０．０８以上であることが特に好ましい。本形態では、せん断場によってせん断力が付与されることで単量体の分散が行われることから、多量の有機溶媒を要しない。ゆえに上記範囲内であっても、分散が良好に行われる。単量体組成物流量［ｍｌ／分］／有機溶媒流量［ｍｌ／分］の上限は特に限定されないが、１．００以下であることが好ましく、０．４０以下であることがより好ましく、０．２０以下であることがさらに好ましい。 "Monomer composition flow rate / organic solvent flow rate ratio"
In the present invention, the ratio of the monomer composition flow rate [ml / min] flowing into the dispersion apparatus to the organic solvent flow rate [ml / min] flowing into the dispersion apparatus (monomer composition flow rate [ml / min] / organic) The solvent flow rate [ml / min]) is preferably 0.01 or more, more preferably 0.02 or more, further preferably 0.04 or more, and more preferably more than 0.04. More preferably, it is particularly preferably 0.08 or more. In the present embodiment, since a monomer is dispersed by applying a shearing force by a shear field, a large amount of an organic solvent is not required. Therefore, even within the above range, the dispersion is favorably performed. The upper limit of the monomer composition flow rate [ml / min] / organic solvent flow rate [ml / min] is not particularly limited, but is preferably 1.00 or less, more preferably 0.40 or less, and .20 or less is more preferable.
　以下、本工程で用いられる材料について説明する。 材料 Hereinafter, the materials used in this step will be described.
　「有機溶媒」
　好ましい有機溶媒としては、脂肪族炭化水素、脂環状炭化水素、芳香族炭化水素、ハロゲン化炭化水素からなる群から選ばれる少なくとも１種類の有機溶媒が挙げられる。具体例には、ｎ－ペンタン、ｎ－ヘキサン、ｎ－ヘプタン、ｎ－オクタン等の脂肪族炭化水素；シクロヘキサン、メチルシクロヘキサン、シクロオクタン、デカリン等の脂環状炭化水素；ベンゼン、トルエン、キシレン等の芳香族炭化水素；クロルベンゼン、ブロムベンゼン、四塩化炭素、１，２－ジクロロエタン等のハロゲン化炭化水素が例示される。これらの中でも、入手容易性及び品質安定性の観点から、ｎ－ヘキサン、ｎ－ヘプタン、シクロヘキサンが好ましい。２種以上を混合した混合溶媒として用いることも可能である。 "Organic solvent"
Preferred organic solvents include at least one organic solvent selected from the group consisting of aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, and halogenated hydrocarbons. Specific examples include aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane and n-octane; alicyclic hydrocarbons such as cyclohexane, methylcyclohexane, cyclooctane and decalin; benzene, toluene, xylene and the like. Aromatic hydrocarbons include, for example, halogenated hydrocarbons such as chlorobenzene, bromobenzene, carbon tetrachloride, and 1,2-dichloroethane. Among these, n-hexane, n-heptane, and cyclohexane are preferable from the viewpoint of availability and quality stability. It is also possible to use a mixture of two or more solvents.
　分散装置内に供給される有機溶媒の温度は、後述するＴｄになるように温度制御される。運転面、重合効率の観点から、有機溶媒の沸点は、７０℃以上であることが好ましく、８０～９５℃であることがより好ましい。 温度 The temperature of the organic solvent supplied into the dispersion device is controlled so as to be Td described later. From the viewpoint of operation and polymerization efficiency, the boiling point of the organic solvent is preferably 70 ° C. or higher, more preferably 80 to 95 ° C.
　本発明によれば、分散助剤を添加することなく、又は非常に少量の分散助剤により、安定な分散状態を達成することが可能であるが、本発明の目的が阻害されない限り、必要に応じて、連続相をなす有機溶媒に、界面活性剤や高分子添加剤等の分散助剤を添加してもよい。分散助剤の種類は、用いられる有機溶媒および単量体の組合せにより、適宜選択されるが、使用できる分散助剤としては、以下の界面活性剤や高分子添加剤が例示される。 According to the present invention, a stable dispersion state can be achieved without adding a dispersing aid or with a very small amount of a dispersing aid. Accordingly, a dispersion aid such as a surfactant and a polymer additive may be added to the organic solvent forming the continuous phase. The type of the dispersing aid is appropriately selected depending on the combination of the organic solvent and the monomer used. Examples of the dispersing aid that can be used include the following surfactants and polymer additives.
　上記界面活性剤として、具体的には、ショ糖脂肪酸エステル、ポリグリセリン脂肪酸エステル、ソルビタン脂肪酸エステル、ポリオキシエチレンソルビタン脂肪酸エステル、ポリオキシエチレングリセリン脂肪酸エステル、ソルビトール脂肪酸エステル、ポリオキシエチレンソルビトール脂肪酸エステル、ポリオキシエチレンアルキルエーテル、ポリオキシエチレンアルキルフェニルエーテル、ポリオキシエチレンヒマシ油、ポリオキシエチレン硬化ヒマシ油、アルキルアリルホルムアルデヒド縮合ポリオキシエチレンエーテル、ポリオキシエチレンポリオキシプロピレンブロックコポリマー、ポリオキシエチレンポリオキシプロピルアルキルエーテル、ポリエチレングリコール脂肪酸エステル、アルキルグルコシド、Ｎ－アルキルグルコンアミド、ポリオキシエチレン脂肪酸アミド、ポリオキシエチレンアルキルアミン、ポリオキシエチレンアルキルエーテルのリン酸エステル、及びポリオキシエチレンアルキルアリルエーテルのリン酸エステル等が挙げられる。これらのうち、２種以上を併用してもよい。また、重合性を有する重合性界面活性剤を使用することもできる。重合性界面活性剤として、具体的には下記の構造を有する化合物が挙げられる。 As the surfactant, specifically, sucrose fatty acid ester, polyglycerin fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene glycerin fatty acid ester, sorbitol fatty acid ester, polyoxyethylene sorbitol fatty acid ester, Polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene castor oil, polyoxyethylene hydrogenated castor oil, alkyl allyl formaldehyde condensed polyoxyethylene ether, polyoxyethylene polyoxypropylene block copolymer, polyoxyethylene polyoxypropyl Alkyl ether, polyethylene glycol fatty acid ester, alkyl glucoside, N-alkyl glucoside Amides, polyoxyethylene fatty acid amides, polyoxyethylene alkyl amines, phosphoric esters of polyoxyethylene alkyl ethers, and phosphoric esters of polyoxyethylene alkyl aryl ether, and the like. Two or more of these may be used in combination. Further, a polymerizable surfactant having polymerizability can also be used. Specific examples of the polymerizable surfactant include compounds having the following structures.
Figure JPOXMLDOC01-appb-C000001
Figure JPOXMLDOC01-appb-C000001
　なお、式中、Ｒ１及びＲ２は、互いに独立して、水素、メチル又はエチルであり、ｎは、３～２０の整数を意味する。 In the formula, R 1 and R 2 are each independently hydrogen, methyl or ethyl, and n represents an integer of 3 to 20.
　上記高分子添加剤として、具体的には、無水マレイン酸変性ポリエチレン、無水マレイン酸変性ポリプロピレン、無水マレイン酸変性エチレン・プロピレン共重合体、無水マレイン酸変性エチレン・プロピレン・ジエン三元共重合体（ＥＰＤＭ）、無水マレイン酸変性ポリブタジエン、無水マレイン酸・エチレン共重合体、無水マレイン酸・プロピレン共重合体、無水マレイン酸・エチレン・プロピレン共重合体、無水マレイン酸・ブタジエン共重合体、ポリエチレン、ポリプロピレン、エチレン・プロピレン共重合体、酸化型ポリエチレン、酸化型ポリプロピレン、酸化型エチレン・プロピレン共重合体、エチレン・アクリル酸共重合体、エチルセルロース、エチルヒドロキシエチルセルロース等が挙げられる。中でも、単量体組成物の分散安定性の観点から、無水マレイン酸変性ポリエチレン、無水マレイン酸変性ポリプロピレン、無水マレイン酸変性エチレン・プロピレン共重合体、無水マレイン酸・エチレン共重合体、無水マレイン酸・プロピレン共重合体、無水マレイン酸・エチレン・プロピレン共重合体、ポリエチレン、ポリプロピレン、エチレン・プロピレン共重合体、酸化型ポリエチレン、酸化型ポリプロピレン、及び酸化型エチレン・プロピレン共重合体が好ましい。これらのうち、２種以上を併用してもよい。また、これらの高分子添加剤と上記界面活性剤とを併用してもよい。中でも、高分子添加剤を用いることが好ましく、無水マレイン酸変性エチレン・プロピレン共重合体を用いることがより好ましい。また、他の好適な形態は、界面活性剤を用いずに高分子添加剤単独で用いることが好ましい。本発明では流路内に高いせん断力がかかるので、高分子添加剤単独で添加した場合であっても液滴の分散が良好となる。 As the polymer additive, specifically, maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene, maleic anhydride-modified ethylene-propylene copolymer, maleic anhydride-modified ethylene-propylene-diene terpolymer ( EPDM), maleic anhydride-modified polybutadiene, maleic anhydride / ethylene copolymer, maleic anhydride / propylene copolymer, maleic anhydride / ethylene / propylene copolymer, maleic anhydride / butadiene copolymer, polyethylene, polypropylene Ethylene-propylene copolymer, oxidized polyethylene, oxidized polypropylene, oxidized ethylene-propylene copolymer, ethylene-acrylic acid copolymer, ethyl cellulose, ethyl hydroxyethyl cellulose, and the like. Among them, from the viewpoint of dispersion stability of the monomer composition, maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene, maleic anhydride-modified ethylene-propylene copolymer, maleic anhydride-ethylene copolymer, maleic anhydride -Propylene copolymer, maleic anhydride-ethylene-propylene copolymer, polyethylene, polypropylene, ethylene-propylene copolymer, oxidized polyethylene, oxidized polypropylene, and oxidized ethylene-propylene copolymer are preferred. Two or more of these may be used in combination. Further, these polymer additives may be used in combination with the above surfactant. Among them, it is preferable to use a polymer additive, and it is more preferable to use a maleic anhydride-modified ethylene / propylene copolymer. In another preferred embodiment, it is preferable to use a polymer additive alone without using a surfactant. In the present invention, since a high shearing force is applied to the inside of the flow channel, the dispersion of the liquid droplets is improved even when the polymer additive is added alone.
　上記分散助剤の使用量は、重合形態、単量体組成物及び有機溶媒の種類等に応じて適宜設定される。具体的には、連続相の有機溶媒中の分散助剤の濃度として、好ましくは０．０００１～２重量％であり、より好ましくは０．０００５～１重量％である。 使用 The amount of the dispersing aid used is appropriately set according to the polymerization form, the type of the monomer composition and the type of the organic solvent. Specifically, the concentration of the dispersing aid in the organic solvent in the continuous phase is preferably 0.0001 to 2% by weight, more preferably 0.0005 to 1% by weight.
　［２－３．重合工程］
　本工程は、上記分散工程において反応装置に供給された水溶性エチレン性不飽和単量体を重合して、含水ゲルを得る工程である。 [2-3. Polymerization step]
This step is a step of obtaining a hydrogel by polymerizing the water-soluble ethylenically unsaturated monomer supplied to the reaction device in the above-mentioned dispersion step.
　（反応装置）
　重合反応が行われる反応装置の形状は特に限定されないが、連続式製造方法の場合、好ましくは、この反応装置内に形成された連続相である有機溶媒中を、上記単量体（組成物）が液滴状の分散相として移動しながら重合反応しうる形状である。このような反応装置として、例えば、管状の反応管を、縦型、横型又は螺旋型に配置した反応装置が挙げられる。本発明の好適な一実施形態は、管状の反応管において水溶性エチレン性不飽和単量体を重合する。反応管が縦型の場合、該反応管の内径Ｄ（ｍｍ）と長さＬ（ｍｍ）との比（Ｌ／Ｄ）は、好ましくは２～１００，０００、より好ましくは３～５０，０００、さらに好ましくは４～２０，０００である。 (Reactor)
The shape of the reactor in which the polymerization reaction is performed is not particularly limited, but in the case of a continuous production method, preferably, the monomer (composition) is mixed with an organic solvent that is a continuous phase formed in the reactor. Are capable of undergoing a polymerization reaction while moving as a droplet-like dispersed phase. As such a reaction device, for example, a reaction device in which a tubular reaction tube is arranged in a vertical type, a horizontal type, or a spiral type is used. One preferred embodiment of the present invention polymerizes a water-soluble ethylenically unsaturated monomer in a tubular reaction tube. When the reaction tube is a vertical type, the ratio (L / D) of the inner diameter D (mm) to the length L (mm) of the reaction tube is preferably 2 to 100,000, more preferably 3 to 50,000. And more preferably 4 to 20,000.
　上記比（Ｌ／Ｄ）を上記範囲内とすることで、上記単量体組成物の液滴が反応装置の内部を良好に移動するため、該液滴の滞留時間のバラつきが減少する。また、最終的に得られるゲル状重合体の粒子径についてもバラつきが少ないものとなるため、得られる吸水性樹脂の諸物性も向上する。 (4) When the ratio (L / D) is within the above range, the droplets of the monomer composition move well inside the reactor, and thus the variation in the residence time of the droplets is reduced. In addition, since the particle size of the gel polymer finally obtained has little variation, various physical properties of the obtained water-absorbing resin are also improved.
　また、上記反応装置には、必要に応じて、外部から反応装置内部の連続相を加熱又は冷却できるように、温度調整手段が備えられていてもよい。該温度調整手段によって、反応装置内の連続相の温度が所定の範囲内に維持される。該温度調整手段としては、特に限定されないが、例えば、反応装置へのジャケットの設置、ヒーターの設置、保温材や断熱材の設置、熱風や冷風の供給等が挙げられる。なお、該反応装置に有機溶媒が再供給される場合、この有機溶媒は、熱交換器によって加熱される。 Further, the reactor may be provided with a temperature adjusting means so that the continuous phase inside the reactor can be heated or cooled from the outside as necessary. The temperature of the continuous phase in the reactor is maintained within a predetermined range by the temperature adjusting means. The temperature adjusting means is not particularly limited, but includes, for example, installation of a jacket in the reactor, installation of a heater, installation of a heat insulating material or heat insulating material, supply of hot air or cold air, and the like. When the organic solvent is resupplied to the reactor, the organic solvent is heated by the heat exchanger.
　また、上記反応装置の材質として、銅、チタン合金、ＳＵＳ３０４、ＳＵＳ３１６、ＳＵＳ３１６Ｌ等のステンレス鋼、ＰＴＥＥ、ＰＦＡ、ＦＥＰ等のフッ素樹脂等を使用することができる。中でも、得られるゲル状重合体の付着性の観点から、好ましくはフッ素樹脂、より好ましくは反応装置の内壁面に、フッ素樹脂加工等の表面加工が施されたものが使用される。 Further, as the material of the reaction apparatus, copper, titanium alloy, stainless steel such as SUS304, SUS316, and SUS316L, and fluorine resin such as PTEE, PFA, and FEP can be used. Among them, from the viewpoint of the adhesion of the obtained gel polymer, a fluororesin is preferably used, and more preferably, one in which the inner wall surface of the reaction apparatus is subjected to surface processing such as fluororesin processing is used.
　「重合温度」
　本発明に係る製造方法では、反応装置内の連続相をなす有機溶媒の温度（以下、「Ｔｄ」と称する）を重合温度とする。 "Polymerization temperature"
In the production method according to the present invention, the temperature of the organic solvent forming the continuous phase in the reactor (hereinafter, referred to as “Td”) is defined as the polymerization temperature.
　上記単量体組成物が液滴状で連続相に分散しているため、単量体組成物の温度は、連続相からの熱移動によって速やかに上昇する。該液滴に含まれる重合開始剤が熱分解型重合開始剤の場合には、上記昇温に伴って熱分解型重合開始剤が分解してラジカルが発生する。発生したラジカルによって重合反応が開始し、重合反応の進行に伴ってゲル状重合体が形成される。 (4) Since the monomer composition is dispersed in the form of droplets in the continuous phase, the temperature of the monomer composition quickly rises due to heat transfer from the continuous phase. When the polymerization initiator contained in the droplet is a thermal decomposition type polymerization initiator, the thermal decomposition type polymerization initiator is decomposed with the above-mentioned temperature rise to generate radicals. The polymerization reaction is started by the generated radical, and a gel polymer is formed with the progress of the polymerization reaction.
　反応装置内の連続相が循環している場合、形成されたゲル状重合体は、循環する連続相によって反応装置の内部を移動し、連続相をなす有機溶媒と共に反応装置から排出される。 When the continuous phase in the reactor is circulating, the formed gel polymer moves inside the reactor by the circulating continuous phase and is discharged from the reactor together with the organic solvent forming the continuous phase.
　上記単量体組成物が熱分解型重合開始剤を含む場合、上記Ｔｄは、重合率の観点から、好ましくは７０℃以上、より好ましくは７５℃以上、さらに好ましくは８０℃以上である。Ｔｄの上限は特に限定されないが、安全性の観点から、連続相をなす有機溶媒の沸点を超えない範囲内で、適宜選択される。 When the monomer composition contains a thermal decomposition type polymerization initiator, the Td is preferably 70 ° C. or higher, more preferably 75 ° C. or higher, and still more preferably 80 ° C. or higher, from the viewpoint of the polymerization rate. The upper limit of Td is not particularly limited, but is appropriately selected from the viewpoint of safety within a range not exceeding the boiling point of the organic solvent constituting the continuous phase.
　また、上記Ｔｄは、重合効率の観点から、使用されている熱分解型重合開始剤のＴ１０と同じであるか、またはＴ１０よりも高くすることが好ましい。具体的には、ＴｄとＴ１０との差ΔＴ２（＝Ｔｄ－Ｔ１０）は、好ましくは０℃以上、より好ましくは５℃以上、さらに好ましくは１０℃以上である。差ΔＴ２の上限値は、エネルギー効率の観点から、好ましくは５０℃以下である。 上 記 From the viewpoint of polymerization efficiency, the Td is preferably the same as or higher than T10 of the thermal decomposition type polymerization initiator used. Specifically, the difference ΔT2 (= Td−T10) between Td and T10 is preferably 0 ° C. or more, more preferably 5 ° C. or more, and further preferably 10 ° C. or more. The upper limit of the difference ΔT2 is preferably 50 ° C. or less from the viewpoint of energy efficiency.
　上記ΔＴ２を上記範囲内とすることで、Ｔ１０よりも低温に維持された単量体組成物が連続相に供給された場合でも、速やかに重合反応が開始され、大きな重合速度が達成される。 こ と By setting ΔT2 within the above range, even when the monomer composition maintained at a temperature lower than T10 is supplied to the continuous phase, the polymerization reaction is started immediately, and a large polymerization rate is achieved.
　なお、上記連続相の温度は、単量体組成物が反応装置に供給されることにより変動する。特に、単量体組成物が供給される領域での温度変化が大きい。そのため、好ましくは、当該領域で所望するＴｄが得られるように、熱交換器で加熱した有機溶媒をこの領域に再供給するか、または、反応装置に設置されたジャケット等の温度調整手段によって反応装置内の連続相を加熱する。これにより、重合反応の開始や進行に寄与する連続相の温度変化を抑制し、より精密にＴｄを制御することができる。 The temperature of the continuous phase fluctuates as the monomer composition is supplied to the reactor. In particular, a temperature change is large in a region where the monomer composition is supplied. Therefore, preferably, the organic solvent heated by the heat exchanger is re-supplied to this region so that a desired Td is obtained in the region, or the reaction is carried out by a temperature adjusting means such as a jacket installed in the reactor. Heat the continuous phase in the apparatus. Thereby, the temperature change of the continuous phase contributing to the initiation and progress of the polymerization reaction can be suppressed, and Td can be controlled more precisely.
　「重合時間」
　本発明に係る吸水性樹脂の製造方法において、「重合時間」とは、連続式製造方法の場合、単量体組成物の反応装置への投入時を起点とし、重合反応で得られたゲル状重合体を反応装置から排出する時を終点として規定される時間である。例えば、単量体組成物が反応装置に液滴状で連続的に供給され、形成されたゲル状重合体が反応装置から連続的に排出される場合、一の単量体組成物の液滴が起点から終点に到達するまでに要する時間を意味する。換言すれば、単量体組成物の反応装置への供給開始から、最初のゲル状重合体の反応装置からの排出までの時間が、重合時間である。該重合時間が液滴の反応装置内の滞留時間に相当する。 "Polymerization time"
In the method for producing a water-absorbent resin according to the present invention, the "polymerization time" refers to the time when the monomer composition is charged into a reaction apparatus in the case of a continuous production method, and a gel state obtained by a polymerization reaction. The time defined as the end point when the polymer is discharged from the reactor. For example, when the monomer composition is continuously supplied to the reaction device in the form of droplets and the formed gel polymer is continuously discharged from the reaction device, the droplets of one monomer composition Means the time required from the start point to the end point. In other words, the time from the start of the supply of the monomer composition to the reactor to the first discharge of the gel polymer from the reactor is the polymerization time. The polymerization time corresponds to the residence time of the droplet in the reactor.
　上記重合時間は、単量体及び重合開始剤の種類等に応じて制御されるが、生産効率の観点から、好ましくは６０分以下、より好ましくは３０分以下、さらに好ましくは２０分以下、特に好ましくは１０分以下、最も好ましくは５分以下に制御される。また、該重合時間の下限値は特に限定されないが、上記反応装置内に供給された単量体組成物の液滴が重合温度まで昇温される際の、連続相からの熱移動効率の観点から、好ましくは３０秒以上に制御される。上記重合時間を上記範囲内に制御することで、反応装置のサイズを小さくすることができるため、好ましい。 The polymerization time is controlled depending on the type of the monomer and the polymerization initiator, etc., but from the viewpoint of production efficiency, preferably 60 minutes or less, more preferably 30 minutes or less, further more preferably 20 minutes or less, particularly preferably 20 minutes or less. It is preferably controlled to 10 minutes or less, most preferably 5 minutes or less. Although the lower limit of the polymerization time is not particularly limited, the viewpoint of the heat transfer efficiency from the continuous phase when the droplets of the monomer composition supplied into the reactor are heated to the polymerization temperature. Therefore, it is preferably controlled to 30 seconds or more. Controlling the polymerization time within the above range is preferable because the size of the reactor can be reduced.
　「重合反応が行われる反応装置における空間速度（ＬＨＳＶ）」
　本発明に係る吸水性樹脂の製造方法において、重合反応が行われる反応装置（以下、重合装置とも称する）における空間速度（ＬＨＳＶ）（単位：ｈｒ－１）とは、重合装置における単量体溶液または単量体組成物（含水ゲル）、および有機溶媒の通過速度を表す指標であり、重合時間を制御する際の目安となる指標である。 "Space velocity (LHSV) in the reactor where the polymerization reaction is performed"
In the method for producing a water-absorbent resin according to the present invention, the space velocity (LHSV) (unit: hr −1 ) in a reactor in which a polymerization reaction is performed (hereinafter also referred to as a polymerization device) refers to a monomer solution in the polymerization device. Alternatively, it is an index indicating the passing speed of the monomer composition (hydrogel) and the organic solvent, and is an index which is a guide when controlling the polymerization time.
　重合率が異なる含水ゲルの接触を防止する観点から、重合装置における空間速度（ＬＨＳＶ）の下限は、２ｈｒ－１以上が好ましく、３ｈｒ－１以上がより好ましく、４ｈｒ－１以上がさらに好ましい。また、得られる含水ゲルの重合率（吸水性樹脂粒子の残存モノマー量）および吸水性樹脂のＤＲＣ５ｍｉｎの観点から、重合装置における空間速度の上限は、１０ｈｒ－１以下が好ましく、９ｈｒ－１以下がより好ましく、８ｈｒ－１以下がさらにより好ましい。すなわち、本発明の一実施形態において、重合装置における空間速度（ＬＨＳＶ）は、２～１０ｈｒ－１であり、好ましくは３～９ｈｒ－１である。なお、重合装置における空間速度（ＬＨＳＶ）（単位：ｈｒ－１）は、重合装置に供給した単量体溶液または単量体組成物（含水ゲル）の容積流量Ｑｍ（単位：ｍ３／ｈｒ）、有機溶媒および分散助剤の合計容積流量Ｑｓ（単位：ｍ３／ｈｒ）を重合装置の容積Ｖ（単位：ｍ３）で除した値であり、下記の式で算出できる。重合装置の容積は、単量体の重合反応が行われている反応場の容積を指し、例えば、縦型の管状反応管の場合、単量体溶液または単量体組成物の流入部（投入部）からゲル状重合体の排出部までの全体の容積を指す。 From the viewpoint of polymerization rate to prevent contact of different hydrogel, the lower limit of space velocity in the polymerization system (LHSV) is preferably from 2 hr -1 or more, more preferably 3 hr -1 or more, 4hr -1 or more is more preferable. From the viewpoint of DRC5min of and the water-absorbent resin (residual monomer amount of the water-absorbing resin particles) polymerization of the resulting water-containing gel, the upper limit of space velocity in the polymerization system is preferably 10 hr -1 or less, 9Hr -1 or less More preferably, it is even more preferably 8 hr -1 or less. That is, in an embodiment of the present invention, the space velocity in the polymerization system (LHSV) is 2 ~ 10 hr -1, preferably 3 ~ 9hr -1. The space velocity (LHSV) (unit: hr −1 ) in the polymerization apparatus is determined by the volume flow rate Qm (unit: m 3 / hr) of the monomer solution or the monomer composition (hydrogel) supplied to the polymerization apparatus. It is a value obtained by dividing the total volume flow rate Qs (unit: m 3 / hr) of the organic solvent and the dispersing aid by the volume V (unit: m 3 ) of the polymerization apparatus, and can be calculated by the following equation. The volume of the polymerization apparatus refers to the volume of the reaction field in which the polymerization reaction of the monomer is performed. For example, in the case of a vertical tubular reaction tube, the inlet of the monomer solution or the monomer composition (injection) Part) to the discharge part of the gel polymer.
Figure JPOXMLDOC01-appb-M000002
Figure JPOXMLDOC01-appb-M000002
　［２－４．分離工程］
　本工程は、上記重合工程において反応装置から排出されたゲル状重合体と有機溶媒とを分離してゲル状重合体（含水ゲル）を得る工程である。 [2-4. Separation process]
This step is a step of separating the gel polymer discharged from the reaction device and the organic solvent in the polymerization step to obtain a gel polymer (hydrogel).
　本発明において、分離装置の種類及び構造については特に限定されないが、例えば、ろ過、沈降、遠心分離、圧搾等の公知の方法を利用することができる。 種類 In the present invention, the type and structure of the separation device are not particularly limited. For example, a known method such as filtration, sedimentation, centrifugal separation, or squeezing can be used.
　「ゲル状重合体の形状」
　本発明において、得られるゲル状重合体の形状は球形である。上記ゲル状重合体の粒子径（以下「ゲル粒子径」と称する）は、得られる吸水性樹脂の用途等に応じて適宜調整される。 `` Shape of gel polymer ''
In the present invention, the shape of the obtained gel polymer is spherical. The particle size of the gel polymer (hereinafter referred to as “gel particle size”) is appropriately adjusted according to the use of the obtained water-absorbent resin.
　上記「球形」とは、真球状以外の形状（例えば、略球状）を含む概念であって粒子の平均長径と平均短径との比（「真球度」とも称する）が好ましくは１．０～３．０である粒子を意味する。該粒子の平均長径と平均短径は、顕微鏡で撮影された画像に基づいて測定される。本発明において、上記ゲル状重合体は、微小な球形ゲルの凝集体として形成されてもよく、微小な球形ゲルと該球形ゲルの凝集体との混合物として得られてもよい。 The “spherical shape” is a concept including a shape other than a true spherical shape (for example, a substantially spherical shape), and the ratio of the average major axis to the average minor axis (also referred to as “sphericity”) is preferably 1.0. Means particles that are ～ 3.0. The average major axis and average minor axis of the particles are measured based on an image taken with a microscope. In the present invention, the gel polymer may be formed as an aggregate of a fine spherical gel, or may be obtained as a mixture of a fine spherical gel and an aggregate of the spherical gel.
　また、上記ゲル状重合体が球形ゲルの凝集体である場合、この凝集体を構成する各球形ゲルの粒子径を、一次粒子径と称する。本発明において、平均一次粒子径は特に制限されないが、乾燥工程において微粉発生を抑制できるという観点から、好ましくは１～２０００μｍ、より好ましくは５～１０００μｍ、さらに好ましくは１０～８００μｍであり、特に好ましくは１０～２００μｍである。なお、ゲル状重合体（含水ゲル）の平均一次粒子径は、下記実施例に記載の方法により測定された値を採用する。 When the gel polymer is an aggregate of spherical gel, the particle size of each spherical gel constituting the aggregate is referred to as a primary particle size. In the present invention, the average primary particle diameter is not particularly limited, but is preferably 1 to 2000 μm, more preferably 5 to 1000 μm, further preferably 10 to 800 μm, and particularly preferably 10 to 800 μm, from the viewpoint of suppressing generation of fine powder in the drying step. Is 10 to 200 μm. The average primary particle diameter of the gel polymer (hydrogel) is a value measured by the method described in the following Examples.
　「ゲル状重合体の固形分濃度」
　後述する乾燥工程に供されるゲル状重合体の固形分率は、特に限定されないが、乾燥コストの観点から、好ましくは２０重量％以上、より好ましくは３０重量％以上、さらに好ましくは４０重量％以上、特に好ましくは４５重量％以上である。該ゲル状重合体の固形分率の上限は、特に限定されないが、好ましくは９０重量％以下、より好ましくは８０重量％以下、さらに好ましくは７０重量％以下、特に好ましくは６０重量％以下である。上記範囲の固形分率であるゲル状重合体を後述の乾燥工程に供することにより、本発明の効果が顕著となる。 "Solid concentration of gel polymer"
The solid content of the gel polymer to be subjected to the drying step described below is not particularly limited, but from the viewpoint of drying cost, is preferably 20% by weight or more, more preferably 30% by weight or more, and further preferably 40% by weight. The content is particularly preferably 45% by weight or more. The upper limit of the solid content of the gel polymer is not particularly limited, but is preferably 90% by weight or less, more preferably 80% by weight or less, further preferably 70% by weight or less, and particularly preferably 60% by weight or less. . By subjecting the gel polymer having a solid content in the above range to a drying step described below, the effect of the present invention becomes remarkable.
　［２－５．その他の工程〕
　本発明に係る吸水性樹脂の製造方法は、上述した各工程以外に、必要に応じて、乾燥工程、粉砕工程、分級工程、表面架橋工程、整粒工程、微粉除去工程、造粒工程及び微粉再利用工程を含むことができる。また、輸送工程、貯蔵工程、梱包工程、保管工程等をさらに含んでもよい。本発明の好適な形態は、さらに、前記重合により得られる含水ゲル状重合体を乾燥して吸水性樹脂粉末を得ることと、前記吸水性樹脂粉末を表面架橋剤により表面架橋を施すことと、を有する。かような操作により、得られる吸水性樹脂の物性を向上させることができる。 [2-5. Other steps)
The method for producing a water-absorbent resin according to the present invention may further include a drying step, a pulverizing step, a classification step, a surface cross-linking step, a sizing step, a fine powder removing step, a granulating step, A recycling step may be included. In addition, it may further include a transportation step, a storage step, a packing step, a storage step, and the like. A preferred embodiment of the present invention further comprises drying the hydrogel polymer obtained by the polymerization to obtain a water-absorbent resin powder, and subjecting the water-absorbent resin powder to a surface crosslinking with a surface crosslinking agent, Having. By such an operation, the physical properties of the obtained water-absorbent resin can be improved.
　（乾燥工程）
　本工程は、上記分離工程で分離されたゲル状重合体を、所望する固形分率まで乾燥して、粒子状の乾燥重合体を得る工程である。該ゲル状重合体を解砕又は造粒することで所望する粒子径又は粒度分布に調整した後に乾燥工程に供してもよい。 (Drying process)
This step is a step of drying the gel polymer separated in the separation step to a desired solid content to obtain a particulate dry polymer. The gel polymer may be crushed or granulated to adjust to a desired particle size or particle size distribution and then subjected to a drying step.
　なお、上記ゲル状重合体を乾燥する公知の方法としては、例えば、伝導伝熱による乾燥、対流伝熱（例えば、熱風）による乾燥、減圧による乾燥、赤外線を用いた乾燥、マイクロ波を用いた乾燥、疎水性有機溶媒との共沸脱水による乾燥、高温の水蒸気（例えば、過熱水蒸気）を用いた過熱水蒸気乾燥等が挙げられる。 In addition, as a known method for drying the gel polymer, for example, drying by conduction heat transfer, drying by convection heat transfer (for example, hot air), drying by reduced pressure, drying using infrared rays, and microwaves are used. Drying, drying by azeotropic dehydration with a hydrophobic organic solvent, and superheated steam drying using high-temperature steam (for example, superheated steam) are exemplified.
　しかしながら、本発明においては、乾燥効率が高く、有機溶媒等の液体成分の回収が容易である攪拌型の伝導伝熱乾燥が好ましく、間接加熱方式を用いた連続式の攪拌型乾燥装置がより好ましく使用される。 However, in the present invention, a stirring-type conduction heat transfer drying that has high drying efficiency and facilitates recovery of a liquid component such as an organic solvent is preferable, and a continuous stirring-type drying apparatus using an indirect heating method is more preferable. used.
　また、上述した通り、本発明に係る製造方法で形成されるゲル状重合体の形状は、球形である。球形のゲル状重合体を上記攪拌型乾燥装置で乾燥することで、球状の粒子からなる乾燥重合体が得られる。なお、本乾燥工程で得られる球状の粒子からなる乾燥重合体を、そのまま吸水性樹脂として各用途に供することもできる。また、この製造方法において吸水性樹脂を製造する場合には、乾燥工程で得られる球状の乾燥重合体を後述する表面架橋工程に供することも可能である。この場合、後述する表面架橋工程に供される乾燥重合体を、便宜上「吸水性樹脂粉末」と称する。 Further, as described above, the shape of the gel polymer formed by the production method according to the present invention is spherical. The dried polymer composed of spherical particles is obtained by drying the spherical gel polymer with the above-mentioned stirring type drying device. In addition, the dry polymer composed of spherical particles obtained in the present drying step can be used as it is as a water-absorbing resin for various uses. When a water-absorbent resin is produced by this production method, the spherical dried polymer obtained in the drying step can be subjected to a surface cross-linking step described later. In this case, the dried polymer that is subjected to the surface cross-linking step described below is referred to as “water-absorbent resin powder” for convenience.
　本発明において、乾燥温度及び乾燥時間は、得られる吸水性樹脂の用途に応じて、その固形分率を指標として適宜調整される。例えば、吸水性樹脂の場合、その固形分率は、吸水性能の観点から、好ましくは８５重量％以上、より好ましくは９０重量％～９８重量％である。なお、吸水性樹脂の固形分率は、試料（吸水性樹脂）を１８０℃で３時間乾燥させた際の、乾燥減量に基づいて算出される値である。 に お い て In the present invention, the drying temperature and the drying time are appropriately adjusted using the solid content as an index according to the use of the obtained water-absorbent resin. For example, in the case of a water-absorbing resin, the solid content is preferably 85% by weight or more, more preferably 90% to 98% by weight, from the viewpoint of water absorbing performance. The solid content of the water-absorbent resin is a value calculated based on the loss on drying when the sample (water-absorbent resin) is dried at 180 ° C. for 3 hours.
　（粉砕工程、分級工程）
　上記乾燥工程で得られた粒子状の乾燥重合体は、必要に応じて、粉砕工程及び分級工程を経ることによって、粒子径又は粒度分布が制御された吸水性樹脂とされる。 (Crushing process, classification process)
The particulate dried polymer obtained in the drying step is subjected to a pulverizing step and a classifying step, if necessary, to obtain a water-absorbent resin having a controlled particle diameter or particle size distribution.
　上記粉砕工程では、例えば、ロールミル、ハンマーミル、スクリューミル、ピンミル等の高速回転式粉砕機、振動ミル、ナックルタイプ粉砕機、円筒型ミキサー等が適宜選択されて用いられる。 で は In the above-mentioned pulverizing step, for example, 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, a cylindrical mixer and the like are appropriately selected and used.
　上記分級工程では、例えば、ＪＩＳ標準篩（ＪＩＳ　Ｚ８８０１－１（２０００））を用いた篩分級や気流分級等が適宜選択されて用いられる。 で は In the classification step, for example, sieving classification using a JIS standard sieve (JIS Z8801-1 (2000)) or air flow classification is appropriately selected and used.
　（表面架橋工程）
　上記乾燥工程を経て得られる粒子状の乾燥重合体、即ち、吸水性樹脂粉末は、必要に応じて表面架橋工程に供される。この表面架橋工程は、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る。なお、本発明においては、公知の表面架橋技術が適宜適用される。 (Surface crosslinking process)
The particulate dry polymer obtained through the drying step, that is, the water-absorbing resin powder, is subjected to a surface cross-linking step as necessary. This surface cross-linking step is a step of providing a portion having a high cross-linking density on the surface layer of the water-absorbent resin powder (a portion several tens of μm from the surface of the water-absorbent resin powder). In the present invention, a known surface crosslinking technique is appropriately applied.
　（整粒工程）
　「整粒工程」とは、上記表面架橋工程を経て緩く凝集した吸水性樹脂粉末を解して粒子径を整える工程を意味する。なお、この整粒工程は、表面架橋工程以降の微粉除去工程、ゲルの解砕工程及び分級工程を含むものとする。 (Sizing process)
The “grain sizing step” means a step in which the water-absorbent resin powder loosely aggregated through the surface cross-linking step is disintegrated to adjust the particle diameter. The sizing step includes a fine powder removing step, a gel crushing step, and a classifying step after the surface crosslinking step.
　（微粉再利用工程）
　「微粉再利用工程」とは、上記各工程で発生した微粉をそのまま、又は微粉を造粒した後に何れかの工程に供給する工程を意味する。 (Fine powder recycling process)
The “fine powder recycling step” refers to a step of supplying the fine powder generated in each of the above steps to any step as it is or after granulating the fine powder.
　〔３．吸水性樹脂の用途〕
　本発明の吸水性樹脂の用途は、特に限定されないが、好ましくは止水防止材、塗料、接着剤、アンチブロッキング剤、光拡散剤、艶消し剤、化粧板用添加剤、人工大理石用添加剤、トナー用添加剤等の樹脂用添加剤が挙げられる。また、吸水性樹脂としての用途は、特に限定されないが、好ましくは紙オムツ、生理用ナプキン、失禁パッド等の吸収性物品の吸収体用途が挙げられる。特に、原料由来の臭気、着色等が問題となっていた高濃度紙オムツの吸収体として使用することができる。さらに、この吸水性樹脂は、吸水時間に優れ、かつ粒度分布が制御されているので、上記吸収体の上層部に使用する場合に、顕著な効果が期待できる。 [3. Use of water absorbent resin)
The use of the water-absorbent resin of the present invention is not particularly limited, but is preferably a water-blocking material, a paint, an adhesive, an anti-blocking agent, a light diffusing agent, a matting agent, a decorative plate additive, and an artificial marble additive. And resin additives such as toner additives. The use as the water-absorbent resin is not particularly limited, but preferably includes absorbent uses for absorbent articles such as disposable diapers, sanitary napkins, incontinence pads, and the like. In particular, it can be used as an absorber for a high-concentration paper diaper that has had problems with odor, coloring, and the like derived from the raw materials. Furthermore, since this water-absorbent resin has excellent water absorption time and a controlled particle size distribution, a remarkable effect can be expected when used in the upper layer of the absorber.
　また、上記吸収体の原料として、上記吸水性樹脂と共にパルプ繊維等の吸収性材料を使用することもできる。この場合、吸収体中の吸水性樹脂の含有量（コア濃度）としては、好ましくは３０重量％～１００重量％、より好ましくは４０重量％～１００重量％、さらに好ましくは５０重量％～１００重量％、さらにより好ましくは６０重量％～１００重量％、特に好ましくは７０重量％～１００重量％、最も好ましくは７５重量％～９５重量％である。 、 Further, as a raw material of the absorbent, an absorbent material such as pulp fiber can be used together with the water absorbent resin. In this case, the content (core concentration) of the water-absorbent resin in the absorber is preferably 30% by weight to 100% by weight, more preferably 40% by weight to 100% by weight, and further preferably 50% by weight to 100% by weight. %, Even more preferably from 60% to 100% by weight, particularly preferably from 70% to 100% by weight, most preferably from 75% to 95% by weight.
　上記コア濃度を上記範囲とすることで、該吸収体を吸収性物品の上層部に使用した場合に、この吸収性物品を清浄感のある白色状態に保つことができる。さらに、該吸収体は尿や血液等の体液等の拡散性に優れるため、効率的な液分配がなされることにより、吸収量の向上が見込める。 (4) By setting the core concentration in the above range, when the absorbent is used for the upper layer of the absorbent article, the absorbent article can be kept in a clean white state. Furthermore, since the absorber has excellent diffusibility for bodily fluids such as urine and blood, an efficient liquid distribution can be expected to improve the absorption amount.
　〔４．吸水性樹脂の物性〕
　「吸水性樹脂の粒子形状」
　本発明においては、いわゆる逆相懸濁重合により重合が行われる。これにより得られる吸水性樹脂は、通常球状重合体粒子となる。ここで、「球状」には、真球状以外の形状も含む。詳細には、「球状」とは、粒子の平均長径と平均短径との比（真球度とも称する）が、好ましくは１．０～３．０の粒子を意味する。粒子の平均長径及び平均短径は、顕微鏡で観察された画像に基づいて、測定される。本発明において、「球状重合体粒子」は単独粒子で存在することに限定されず、球状重合体粒子の凝集体を形成していてもよい。 [4. Physical properties of water absorbent resin)
`` Particle shape of water absorbent resin ''
In the present invention, the polymerization is carried out by so-called reverse phase suspension polymerization. The water-absorbing resin obtained in this way usually becomes spherical polymer particles. Here, the term “spherical” includes shapes other than a true sphere. Specifically, the term “spherical” means particles having a ratio of the average major axis to the average minor axis (also referred to as sphericity) of preferably 1.0 to 3.0. The average major axis and average minor axis of the particles are measured based on an image observed with a microscope. In the present invention, the “spherical polymer particles” are not limited to existing as single particles, and may form aggregates of spherical polymer particles.
　本発明における球状重合体粒子は、その用途・目的に応じて、重合性モノマーを選択することにより設計される。例えば、球状重合体粒子として粉末状又は粒子状の吸水性樹脂を製造する場合、代表的に用いられる重合性モノマーは、（メタ）アクリル酸及び／又はその塩である。 球状 The spherical polymer particles in the present invention are designed by selecting a polymerizable monomer according to the use and purpose. For example, when producing a powdery or particulate water-absorbent resin as spherical polymer particles, a polymerizable monomer typically used is (meth) acrylic acid and / or a salt thereof.
　粒子形状が球状であること、特に球状の凝集体であることで、吸水性樹脂の吸水速度が不定形状よりも速くなる傾向にある。 Because the particle shape is spherical, particularly a spherical aggregate, the water absorption rate of the water-absorbing resin tends to be higher than that of the irregular shape.
　「ＣＲＣ」
　「ＣＲＣ」は、Ｃｅｎｔｒｉｆｕｇｅ　Ｒｅｔｅｎｔｉｏｎ　Ｃａｐａｃｉｔｙ（遠心分離機保持容量）の略称であり、吸水性樹脂の無加圧下での吸水倍率（「吸水倍率」と称する場合もある）を意味する。ＣＲＣ（遠心分離機保持容量）は、ＥＤＡＮＡ法（ＥＲＴ４４１．２－０２）に準拠して測定した。具体的には、吸水性樹脂０．２ｇを不織布製の袋に入れた後、大過剰の０．９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３分間、水切りした後の吸水倍率（単位；ｇ／ｇ）のことをいう。 "CRC"
“CRC” is an abbreviation for Centrifuge Retention Capacity (centrifuge holding capacity), and means the water absorption capacity of the water-absorbent resin under no pressure (sometimes referred to as “water absorption capacity”). CRC (centrifuge holding capacity) was measured according to the EDANA method (ERT441.2-02). Specifically, 0.2 g of the water-absorbing resin is put into a nonwoven bag, and then immersed in a large excess of 0.9% by weight aqueous sodium chloride solution for 30 minutes to freely swell, and then centrifuged (250 G). ) For 3 minutes after water drainage (unit: g / g).
　なお、「ＥＤＡＮＡ」は、Ｅｕｒｏｐｅａｎ　Ｄｉｓｐｏｓａｂｌｅｓ　ａｎｄ　Ｎｏｎｗｏｖｅｎｓ　Ａｓｓｏｃｉａｔｉｏｎｓの略称である。また、「ＥＲＴ」は、ＥＤＡＮＡ　Ｒｅｃｏｍｍｅｎｄｅｄ　Ｔｅｓｔ　Ｍｅｔｈｏｄｓの略称であり、吸水性樹脂の測定方法を規定した欧州標準である。本発明では、特に断りのない限り、ＥＲＴ原本（２００２年改定）に準拠して、吸水性樹脂の物性を測定する。 "EDANA" is an abbreviation for European, Disposables, and Nonwovens Associations. "ERT" is an abbreviation of EDANA Recommended Test Methods and is a European standard that defines a method for measuring a water-absorbent resin. In the present invention, unless otherwise specified, physical properties of the water-absorbent resin are measured based on the original ERT (revised in 2002).
　上記吸水性樹脂のＣＲＣ（遠心分離機保持容量）は、好ましくは１５ｇ／ｇ以上、より好ましくは２５ｇ／ｇ以上である。上限については特に限定されず、より高いＣＲＣが好ましいが、他の物性とのバランスの観点から、好ましくは７０ｇ／ｇ以下、より好ましくは５０ｇ／ｇ以下、さらに好ましくは４０ｇ／ｇ以下である。 ＣＲ The water absorbing resin preferably has a CRC (centrifuge holding capacity) of 15 g / g or more, more preferably 25 g / g or more. The upper limit is not particularly limited, and a higher CRC is preferred, but from the viewpoint of balance with other physical properties, it is preferably 70 g / g or less, more preferably 50 g / g or less, and further more preferably 40 g / g or less.
　上記ＣＲＣが５ｇ／ｇ未満の場合、吸収量が少なく、紙オムツ等の吸収性物品の吸収体としては適さない。また、上記ＣＲＣが７０ｇ／ｇを超える場合、尿や血液等の体液等を吸収する速度が低下するため、高吸水速度タイプの紙オムツ等への使用に適さない。なお、ＣＲＣは、内部架橋剤や表面架橋剤等の種類や量を変更することで制御することができる。 場合 When the CRC is less than 5 g / g, the amount of absorption is small and it is not suitable as an absorbent for absorbent articles such as disposable diapers. On the other hand, if the CRC exceeds 70 g / g, the rate of absorbing body fluids such as urine and blood decreases, so that it is not suitable for use in paper diapers with a high water absorption rate. The CRC can be controlled by changing the type and amount of an internal crosslinking agent, a surface crosslinking agent, and the like.
　「ＤＲＣ５ｍｉｎ」
　「ＤＲＣ」は、Ｄｕｎｋ　Ｒｅｔｅｎｔｉｏｎ　Ｃａｐａｃｉｔｙ（浸漬保持容量）の略称であり、「ＤＲＣ５ｍｉｎ」は、浸漬保持容量５分値（５分での無加圧下での吸水倍率）を意味する。具体的には、吸水性樹脂１．０ｇを、下記ＡＡＰの測定と同様に、底面にメッシュを有する円筒形のセルに均一に散布し、０．９重量％塩化ナトリウム水溶液に５分間接触させて自由膨潤させた後の吸水倍率（単位；ｇ／ｇ）のことをいう。 "DRC5min"
“DRC” is an abbreviation for “Dunk Retention Capacity” (immersion holding capacity), and “DRC5min” means a 5-minute immersion holding capacity (water absorption capacity under no pressure in 5 minutes). Specifically, in the same manner as in the measurement of AAP described below, 1.0 g of the water-absorbent resin was evenly sprayed on a cylindrical cell having a mesh on the bottom surface, and was contacted with a 0.9% by weight aqueous sodium chloride solution for 5 minutes. Water absorption capacity (unit: g / g) after free swelling.
　衛生材料に用いた際の液戻り量の観点から、上記吸水性樹脂のＤＲＣ５ｍｉｎの下限は、好ましくは４６ｇ／ｇ以上、より好ましくは４７ｇ／ｇ以上、さらにより好ましくは５０ｇ／ｇ以上、特に好ましくは５２ｇ／ｇ以上である。また、上記吸水性樹脂のＤＲＣ５ｍｉｎの上限は、特に制限されないが、通常７０ｇ／ｇ以下である。当該ＤＲＣ５ｍｉｎは、吸水倍率、含水ゲルの平均一次粒子径、重合率、粒度等で制御することができる。 From the viewpoint of the liquid return amount when used as a sanitary material, the lower limit of the DRC of the water absorbent resin is preferably 46 g / g or more, more preferably 47 g / g or more, still more preferably 50 g / g or more, and particularly preferably. Is 52 g / g or more. The upper limit of DRC of the water absorbent resin is not particularly limited, but is usually 70 g / g or less. The DRC of 5 min can be controlled by the water absorption ratio, the average primary particle size of the hydrogel, the polymerization rate, the particle size, and the like.
　「残存モノマー量」
　残存モノマー量は、吸水性樹脂中に残存する単量体（モノマー）の量を意味する。以下、吸水性樹脂中に残存する単量体を「残存モノマー」と称する。残存モノマー量は、ＥＤＡＮＡ法（ＥＲＴ４４０．２－０２）に準拠して測定した。具体的には、吸水性樹脂１．０ｇを、０．９重量％塩化ナトリウム水溶液２００ｍｌに添加し、５００ｒｐｍで１時間攪拌した後、水溶液に溶解したモノマー量（単位；ｐｐｍ）のことをいう。残存モノマー量の測定には、高速液体クロマトグラフィー（ＨＰＬＣ）が用いられる。 "Remaining monomer amount"
The residual monomer amount means the amount of the monomer (monomer) remaining in the water absorbent resin. Hereinafter, the monomer remaining in the water absorbent resin is referred to as “residual monomer”. The residual monomer amount was measured according to the EDANA method (ERT440.2-02). Specifically, it refers to the amount (unit: ppm) of a monomer dissolved in an aqueous solution after adding 1.0 g of a water-absorbent resin to 200 ml of a 0.9% by weight aqueous solution of sodium chloride and stirring for 1 hour at 500 rpm. High-performance liquid chromatography (HPLC) is used to measure the amount of residual monomer.
　吸水性樹脂に含まれる残存モノマー量は、安全性の観点から、好ましくは１０００ｐｐｍ以下、より好ましくは４００ｐｐｍ以下、さらに好ましくは３００ｐｐｍ以下である。下限値については低ければ低いほど好ましいため、特に限定されないが、好ましくは０ｐｐｍ、より好ましくは１０ｐｐｍ程度である。上記残存モノマー量を上記範囲内とすることで、人体の皮膚等への刺激が軽減された吸水性樹脂が得られる。 (4) The amount of residual monomers contained in the water-absorbing resin is preferably 1000 ppm or less, more preferably 400 ppm or less, and still more preferably 300 ppm or less, from the viewpoint of safety. The lower limit is preferably as low as possible, and is not particularly limited, but is preferably 0 ppm, and more preferably about 10 ppm. By setting the amount of the residual monomer within the above range, a water-absorbing resin with reduced irritation to the skin or the like of a human body can be obtained.
　当該残存モノマー量は、分散装置内に供給される有機溶媒の温度、ＬＨＳＶ等によって制御することができる。重合時間が適切に確保され、重合率が高いほど、残存モノマー量は低減する。 (4) The amount of the residual monomer can be controlled by the temperature of the organic solvent supplied into the dispersion device, LHSV, or the like. As the polymerization time is appropriately secured and the polymerization rate is higher, the amount of the residual monomer is reduced.
　一実施形態は、上記製造方法によって得られる吸水性樹脂であって、ＤＲＣ５ｍｉｎが４６ｇ／ｇ以上であり、かつ、残存モノマーが４００ｐｐｍ以下である吸水性樹脂である。 One embodiment is a water-absorbent resin obtained by the above production method, wherein the DRC is 5 min or more and the residual monomer is 400 ppm or less.
　本発明の効果を、以下の実施例および比較例を用いて説明するが、本発明はこれらの説明に限定解釈されるものではなく、各実施例に開示された技術的手段を適宜組み合わせて得られる実施例も、本発明の範囲に含まれるものとする。なお、含水ゲル、吸水性樹脂粉末、吸水性樹脂、吸収体の諸物性は以下の方法で測定した。また、実施例において「部」あるいは「％」の表示を用いる場合があるが、特に断りがない限り、「重量部」あるいは「重量％」を表す。また、特記しない限り、各操作は、室温（２５℃）で行われる。 The effects of the present invention will be described with reference to the following examples and comparative examples. However, the present invention is not construed as being limited to these descriptions, and may be obtained by appropriately combining the technical means disclosed in each example. Such embodiments are also included in the scope of the present invention. The physical properties of the hydrogel, the water-absorbent resin powder, the water-absorbent resin, and the absorber were measured by the following methods. In the examples, “parts” or “%” may be used, but unless otherwise specified, “parts” or “% by weight” is used. Each operation is performed at room temperature (25 ° C.) unless otherwise specified.
　［吸水性樹脂の物性］
　「含水ゲルの平均一次粒子径」
　含水ゲルを光学顕微鏡（ＫＨ－３０００、株式会社ハイロックス製）で撮影し、得られた画像から、一次粒子の長径を測定した。一次粒子５０粒について測定し、その平均値を当該含水ゲルの平均一次粒子径とした。 [Physical properties of water absorbent resin]
"Average primary particle size of hydrogel"
The hydrogel was photographed with an optical microscope (KH-3000, manufactured by Hilox Corporation), and the major diameter of the primary particles was measured from the obtained image. The measurement was performed on 50 primary particles, and the average value was defined as the average primary particle size of the hydrogel.
　また、含水ゲルの平均一次粒子径の振れは以下のようにして算出した。 The average primary particle diameter of the hydrogel was calculated as follows.
　（含水ゲルの平均一次粒子径の振れ）＝（運転中に最も大きかった含水ゲルの平均一次粒子径）－（運転中に最も小さかった含水ゲルの平均一次粒子径）
　「含水ゲルの重合率」
　イオン交換水１０００ｇに含水ゲル１．００ｇを投入し、３００ｒｐｍで２時間攪拌した後に、ろ過することにより、不溶分を除去した。上記操作で得られたろ液中に抽出された単量体の量を、液体クロマトグラフを用いて測定した。該単量体の量を残存モノマー量ｍ（ｇ）としたときに、下記（式２）にしたがって、重合率Ｃ（重量％）を求めた。 (Deviation of average primary particle diameter of hydrogel) = (average primary particle diameter of hydrogel that was largest during operation) − (average primary particle diameter of hydrogel that was smallest during operation)
"Polymerization rate of hydrogel"
1.00 g of the hydrogel was added to 1000 g of ion-exchanged water, stirred at 300 rpm for 2 hours, and then filtered to remove insolubles. The amount of the monomer extracted in the filtrate obtained by the above operation was measured using a liquid chromatograph. Assuming that the amount of the monomer was m (g) of the remaining monomer, the polymerization rate C (% by weight) was determined according to the following (Equation 2).
　Ｃ（重量％）＝１００×｛１－ｍ／（α・Ｍ／１００）｝・・・（式２）
　ただし、（式２）中、Ｍは含水ゲルの重量（ｇ）、αは含水ゲルの固形分率（重量％）を意味する。なお、固形分率は以下の手法によって求められる。 C (% by weight) = 100 × {1-m / (α · M / 100)} (Formula 2)
In Formula 2, M represents the weight (g) of the hydrogel, and α represents the solid content (% by weight) of the hydrogel. In addition, a solid content rate is calculated | required by the following methods.
　固形分率
　底面の直径が５０ｍｍのアルミカップに含水ゲル２．００ｇを投入した後、試料（含水ゲル及びアルミカップ）の総重量Ｗ１（ｇ）を正確に秤量した。次に、上記試料を、雰囲気温度１８０℃に設定されたオーブン内に静置した。２４時間経過後、該試料を上記オーブンから取り出し、総重量Ｗ２（ｇ）を正確に秤量した。本測定に供された含水ゲルの重量をＭ（ｇ）としたときに、下記（式３）にしたがって、含水ゲルの固形分率α（重量％）を求めた。 Solid Content After 2.00 g of hydrogel was put into an aluminum cup having a bottom diameter of 50 mm, the total weight W1 (g) of the sample (hydrogel and aluminum cup) was accurately weighed. Next, the sample was allowed to stand in an oven set at an ambient temperature of 180 ° C. After 24 hours, the sample was taken out of the oven, and the total weight W2 (g) was accurately weighed. When the weight of the hydrogel used in this measurement was defined as M (g), the solid content ratio α (% by weight) of the hydrogel was determined according to the following (Equation 3).
　α（重量％）＝１００－｛（Ｗ１－Ｗ２）／Ｍ｝×１００・・・（式３）
　「ＣＲＣ」
　ＥＤＡＮＡ法（ＥＲＴ４４１．２－０２）に準拠して、吸水性樹脂のＣＲＣを測定した。 α (% by weight) = 100 − {(W1−W2) / M} × 100 (formula 3)
"CRC"
The CRC of the water-absorbent resin was measured according to the EDANA method (ERT441.2-02).
　「残存モノマー量」
　ＥＤＡＮＡ法（ＥＲＴ４１０．２－０２）に準拠して吸水性樹脂の残存モノマー量を測定した。 "Remaining monomer amount"
The residual monomer amount of the water-absorbing resin was measured according to the EDANA method (ERT410.2-02).
　「ＤＲＣ５ｍｉｎ」
　国際公開第２０１７／１７０６０５号に記載された方法により、吸水性樹脂（１）のＤＲＣ５ｍｉｎ（浸漬保持容量５分値）を測定した。 "DRC5min"
According to the method described in International Publication No. 2017/170605, the DRC of the water-absorbent resin (1) was measured for 5 minutes (immersion holding capacity 5 minutes value).
　具体的には、図１０に示す装置を用い、内径６０ｍｍのプラスチックの支持円筒２００の底に、ステンレス製４００メッシュの金網２０１（目の大きさ３８μｍ）を融着させ、室温（２０～２５℃）、湿度５０％ＲＨの条件下で、金網２０１上に吸水性樹脂（１）２０２　１．０００±０．００５ｇを均一に散布し、この測定装置一式の重量Ｗａ（ｇ）を測定した。 Specifically, using a device shown in FIG. 10, a 400 mesh stainless steel wire mesh 201 (mesh size: 38 μm) was fused to the bottom of a plastic support cylinder 200 having an inner diameter of 60 mm, and the room temperature (20 to 25 ° C.) ) And a humidity of 50% RH, the water-absorbent resin (1) 202 @ 1.000 ± 0.005 g was evenly sprayed on the wire net 201, and the weight Wa (g) of the set of measuring devices was measured.
　底面積が４００ｃｍ２の円形もしくは正方形のペトリ皿２０３の内側に直径１２０ｍｍのガラスフィルター２０４（株式会社相互理化学硝子製作所社製、細孔直径：１００～１２０μｍ）を置き、０．９０重量％食塩水２０６（２３±０．５℃）をガラスフィルターの上面と同じレベル（ガラスフィルターの外周上に液が表面張力でわずかに浮き上がっている状態、もしくはガラスフィルターの表面の５０％程度が液に覆われている状態）になるように加えた。その上に、直径１１０ｍｍの濾紙２０５（ＡＤＶＡＮＴＥＣ東洋株式会社、品名：ＪＩＳ　Ｐ　３８０１、Ｎｏ．２、厚さ０．２６ｍｍ、保留粒子径５μｍ）を１枚載せ、濾紙の全面が濡れるようにした。 A glass filter 204 having a diameter of 120 mm (manufactured by Mutual Life Science Glass Co., Ltd., pore diameter: 100 to 120 μm) is placed inside a circular or square petri dish 203 having a bottom area of 400 cm 2 , and 0.90 wt% saline. 206 (23 ± 0.5 ° C.) at the same level as the upper surface of the glass filter (the liquid is slightly floating on the outer periphery of the glass filter due to surface tension, or about 50% of the surface of the glass filter is covered with the liquid) State). One sheet of filter paper 205 having a diameter of 110 mm (ADVANTEC Toyo Co., Ltd., product name: JIS P 3801, No. 2, thickness 0.26 mm, diameter of retained particles 5 μm) was placed thereon, and the entire surface of the filter paper was wetted.
　上記測定装置一式を前記湿った濾紙上に載せ、液を吸収させた（測定中も液温度は厳密に２３±０．５℃に管理される）。厳密に５分（３００秒）後、測定装置一式を持ち上げ、その重量Ｗｂ（ｇ）を測定した。そして、Ｗａ、Ｗｂから、下記の式に従ってＤＲＣ５ｍｉｎ（ｇ／ｇ）を算出した。 The above set of measuring devices was placed on the wet filter paper to absorb the liquid (the liquid temperature was strictly controlled at 23 ± 0.5 ° C. even during the measurement). After exactly 5 minutes (300 seconds), the set of measuring devices was lifted and its weight Wb (g) was measured. Then, DRC 5 min (g / g) was calculated from Wa and Wb according to the following equation.
Figure JPOXMLDOC01-appb-M000003
Figure JPOXMLDOC01-appb-M000003
　（実施例１）
　図１に示した製造プロセスに従って含水ゲル（１）を作製した後、得られた含水ゲル（１）を乾燥し、さらに表面架橋することで、球状の吸水性樹脂（１）を製造した。 (Example 1)
After producing the hydrogel (1) according to the production process shown in FIG. 1, the obtained hydrogel (1) was dried and further subjected to surface cross-linking to produce a spherical water-absorbing resin (1).
　まず、有機溶媒としてｎ－ヘプタン（密度：０．６８ｇ／ｍｌ）を、分散装置１２、反応装置１４、分離装置１６及びこれらを接続する配管内に投入した。 {Circle around (1)} First, n-heptane (density: 0.68 g / ml) was charged as an organic solvent into the dispersion device 12, the reaction device 14, the separation device 16, and the piping connecting these components.
　続いて、送液ポンプ１８を稼働させて、流量３００ｍｌ／分で、有機溶媒の循環を開始した。また、熱交換器２０を稼働させて、設定温度が９０℃となるように、上記循環する有機溶媒を加熱した。 Next, the liquid pump 18 was operated to start circulation of the organic solvent at a flow rate of 300 ml / min. In addition, the heat exchanger 20 was operated to heat the circulating organic solvent such that the set temperature was 90 ° C.
　次に分散助剤としてショ糖脂肪酸エステル（商品名：ＤＫエステルＦ－５０／第一工業製薬株式会社）をｎ－ヘプタンに０．００５重量％添加した。 (4) 0.005% by weight of sucrose fatty acid ester (trade name: DK Ester F-50 / Daiichi Kogyo Seiyaku Co., Ltd.) was added to n-heptane as a dispersing aid.
　（１．混合工程）
　アクリル酸、４８．５重量％の水酸化ナトリウム水溶液部及びイオン交換水を混合し、さらに、ポリエチレングリコールジアクリレート（平均重合度：９）及びジエチレントリアミン５酢酸・３ナトリウムを配合することで、単量体水溶液（１）を作製した。また、別途、過硫酸ナトリウム及びイオン交換水を混合することで、６重量％の過硫酸ナトリウム水溶液（１）を作製した。 (1. Mixing process)
Acrylic acid, a 48.5% by weight aqueous solution of sodium hydroxide and ion-exchanged water are mixed, and further, polyethylene glycol diacrylate (average degree of polymerization: 9) and diethylenetriaminepentaacetic acid / 3 sodium are blended to obtain a single monomer. A body aqueous solution (1) was prepared. Separately, sodium persulfate and ion-exchanged water were mixed to prepare a 6% by weight aqueous solution of sodium persulfate (1).
　続いて、上記操作で得られた単量体水溶液（１）と過硫酸ナトリウム水溶液（１）とを、混合装置１０に供給することで、単量体組成物（１）を作製した。該単量体組成物（１）のモノマー濃度は４３重量％、中和率は７３モル％であった。また、内部架橋剤であるポリエチレングリコールジアクリレートは単量体に対して０．０２３モル％、キレート剤であるジエチレントリアミン５酢酸・３ナトリウムは単量体に対して２００ｐｐｍ、重合開始剤である過硫酸ナトリウム（Ｔ１０　７０℃）は単量体に対して０．１ｇ／モルであった。 Subsequently, the monomer aqueous solution (1) and the sodium persulfate aqueous solution (1) obtained by the above operation were supplied to the mixing device 10 to prepare a monomer composition (1). The monomer composition (1) had a monomer concentration of 43% by weight and a neutralization ratio of 73 mol%. In addition, polyethylene glycol diacrylate as an internal cross-linking agent is 0.023 mol% based on the monomer, diethylene triamine pentaacetic acid / 3 sodium as a chelating agent is 200 ppm based on the monomer, and persulfuric acid as a polymerization initiator is used. Sodium (T10 @ 70 ° C.) was 0.1 g / mol based on the monomer.
　（２．分散工程）
　分散装置としては図８に示した二重円筒型の高速回転せん断型攪拌機の分散装置１２Ｇを使用した。ケーシング内径（外筒５０Ｇの内径）２５ｍｍ、ローター外径（内筒５２Ｇの外径）２２ｍｍ、有効ローター長（単量体水溶液投入口５５Ｇから排出口）６５ｍｍである。反応装置としてＰＦＡ（パーフルオロアルコキシアルカン）製チューブ（内径：２５ｍｍ、全長：１０ｍ）を鉛直に配置したものをそれぞれ使用した。 (2. Dispersion step)
As the dispersing device, a dispersing device 12G of a double-cylindrical high-speed rotary shearing stirrer shown in FIG. 8 was used. The inner diameter of the casing (the inner diameter of the outer cylinder 50G) is 25 mm, the outer diameter of the rotor (the outer diameter of the inner cylinder 52G) is 22 mm, and the effective rotor length (from the monomer aqueous solution inlet 55G to the outlet) is 65 mm. As a reaction device, a vertically arranged tube made of PFA (perfluoroalkoxy alkane) (inner diameter: 25 mm, total length: 10 m) was used.
　ローター（内筒５２Ｇ）を回転数４，８００ｒｐｍ（せん断速度３６８６［１／ｓ］）となるように回転させ、次に、単量体組成物（１）を、流量４０ｍｌ／分（４７．２ｇ／分）で、分散装置１２Ｇの配管３１に送液した。供給された上記単量体組成物（１）は、分散装置によって上記有機溶媒中で微細液滴状に分散した（単量体組成物（１）の平均滞留時間１．２７ｓ）。 The rotor (inner cylinder 52G) is rotated at a rotation speed of 4,800 rpm (shear rate 3686 [1 / s]), and then the monomer composition (1) is supplied at a flow rate of 40 ml / min (47.2 g). / Min), the liquid was sent to the pipe 31 of the dispersion device 12G. The supplied monomer composition (1) was dispersed in the form of fine droplets in the organic solvent by a dispersing device (average residence time of the monomer composition (1) 1.27 s).
　（３．重合工程）
　２．で得られた分散液は反応装置１４に排出した。 (3. polymerization step)
2. Was discharged into the reactor 14.
　上記単量体組成物（１）からなる液滴は、上記連続相である有機溶媒が満たされた反応装置内を落下しながら、重合反応の進行に伴って微小な球形ゲルに変化した。これらの微小な球形ゲルは、落下するに従って相互に付着して凝集体を形成した。そして、該反応装置の排出口付近において、微小な球形ゲルの凝集体からなる直径約１ｃｍの含水ゲル（１）を確認した。なお、反応装置１４における空間速度（ＬＨＳＶ）は、４．２ｈｒ－１であった。 The droplet composed of the monomer composition (1) changed into a fine spherical gel as the polymerization reaction proceeded while falling in the reactor filled with the organic solvent as the continuous phase. These small spherical gels adhered to each other as they fell to form aggregates. In the vicinity of the outlet of the reaction apparatus, a hydrogel (1) having a diameter of about 1 cm and consisting of fine spherical gel aggregates was confirmed. The space velocity (LHSV) in the reactor 14 was 4.2 hr -1 .
　上記一連の操作で得られた含水ゲル（１）は、有機溶媒と共に連続的に反応装置１４から排出された。 水 The hydrogel (1) obtained by the above series of operations was continuously discharged from the reactor 14 together with the organic solvent.
　（４．分離工程）
　反応装置１４から排出された含水ゲル（１）と有機溶媒とは、そのまま分離装置１６に連続的に供給された。該分離装置において、該含水ゲル（１）と有機溶媒とを分離した。なお、該分離装置で分離された有機溶媒は、設定温度が９０℃となるように熱交換器２０で調温した後、再度、反応装置１４に供給した。 (4. Separation process)
The hydrogel (1) and the organic solvent discharged from the reaction device 14 were continuously supplied to the separation device 16 as they were. In the separation device, the hydrogel (1) and the organic solvent were separated. The organic solvent separated by the separation device was temperature-controlled by the heat exchanger 20 so that the set temperature became 90 ° C., and then supplied to the reaction device 14 again.
　上記攪拌機への単量体組成物（１）の投入を５時間継続する間、該単量体組成物（１）の送液圧は０．１３ＭＰａＧで一定であり、この攪拌機において詰まりは見られなかった。 While the introduction of the monomer composition (1) into the stirrer was continued for 5 hours, the liquid sending pressure of the monomer composition (1) was constant at 0.13 MPaG, and clogging was observed in this stirrer. Did not.
　上記操作で得られた含水ゲル（１）は、微小な球形の含水ゲルが付着凝集した形状をしていた。また、含水ゲル（１）について運転開始から１００分後から運転終了（５時間）まで２０分毎にサンプリングし、平均一次粒子径を測定したところ、５０～６０μｍであった。 水 The hydrogel (1) obtained by the above operation had a shape in which minute spherical hydrogel was adhered and aggregated. Further, the water-containing gel (1) was sampled every 20 minutes from 100 minutes after the start of the operation to the end of the operation (5 hours), and the average primary particle diameter was measured to be 50 to 60 μm.
　（５．乾燥工程）
　得られた上記含水ゲル（１）を、１８０℃で５０分間攪拌乾燥させた後、得られた乾燥重合体（１）を目開き８５０μｍのＪＩＳ標準篩を用いて分級し、この篩を通過した球状の吸水性樹脂粉末（１）を採取した。 (5. Drying process)
After the obtained hydrogel (1) was stirred and dried at 180 ° C. for 50 minutes, the obtained dried polymer (1) was classified using a JIS standard sieve having openings of 850 μm, and passed through the sieve. The spherical water-absorbent resin powder (1) was collected.
　（６．表面架橋工程）
　５．で得られた吸水性樹脂粉末（１）１００重量部に対して、エチレングリコールジグリシジルエーテル０．０１重量部、プロピレングリコール１．０重量部、及びイオン交換水３．０重量部からなる表面架橋剤溶液をスプレーノズルで噴霧して、連続高速混合機を用いて均一に混合した。 (6. Surface crosslinking step)
5. Surface crosslinking consisting of 0.01 parts by weight of ethylene glycol diglycidyl ether, 1.0 part by weight of propylene glycol, and 3.0 parts by weight of ion-exchanged water with respect to 100 parts by weight of the water-absorbent resin powder (1) obtained in the above. The agent solution was sprayed with a spray nozzle and uniformly mixed using a continuous high-speed mixer.
　その後、表面架橋剤を含む吸水性樹脂粉末（１）を、雰囲気温度を１９５℃±２℃に調温した熱処理機に導入して、３０分間加熱処理した後、粉温が６０℃となるまで強制的に冷却した。当操作によって、吸水性樹脂粒子（１）を得た。 Thereafter, the water-absorbent resin powder (1) containing the surface cross-linking agent is introduced into a heat treatment machine whose atmosphere temperature is adjusted to 195 ° C. ± 2 ° C., and is subjected to heat treatment for 30 minutes, until the powder temperature becomes 60 ° C. Forced cooling. By this operation, water-absorbent resin particles (1) were obtained.
　（７．整粒工程）
　上記吸水性樹脂粒子（１）を目開き８５０μｍのＪＩＳ標準篩に通過させることで整粒し、製品としての吸水性樹脂（１）を得た。吸水性樹脂（１）の形状は球の房状凝集体であった。 (7. Sizing process)
The water-absorbent resin particles (1) were passed through a JIS standard sieve having openings of 850 μm to regulate the particle size, thereby obtaining a water-absorbent resin (1) as a product. The shape of the water-absorbent resin (1) was a tufted aggregate of spheres.
　得られた含水ゲル（１）及び吸水性樹脂（１）について測定した諸物性を表１に示した。 Table 1 shows the physical properties measured for the obtained hydrogel (1) and water-absorbent resin (1).
　［実施例２］
　実施例１において、ローター回転数を３６００ｒｐｍ（せん断速度２７６５［１／ｓ］）へ変更した以外は、実施例１と同様の操作を行い含水ゲル（２）を得た。上記操作で得られた含水ゲル（２）について、運転開始から１００分後から運転終了（５時間）まで２０分毎にサンプリングし、平均一次粒子径を測定したところ、８０～９０μｍであった。 [Example 2]
A water-containing gel (2) was obtained in the same manner as in Example 1, except that the rotor rotation speed was changed to 3600 rpm (shear speed 2765 [1 / s]). The hydrogel (2) obtained by the above operation was sampled every 20 minutes from 100 minutes after the start of the operation to the end of the operation (5 hours), and the average primary particle diameter was measured to be 80 to 90 μm.
　［実施例３］
　実施例１において、ローター回転数を７２００ｒｐｍ（せん断速度５５２９［１／ｓ］）へ、ｎ－ヘプタンに添加する分散助剤を無水マレイン酸変性ポリエチレン（酸価：６０ｍｇＫＯＨ／ｇ）０．００５重量％添加に変更した以外は、実施例１と同様の操作を行い含水ゲル（３）を得た。上記操作で得られた含水ゲル（３）について、運転開始から１００分後から運転終了（５時間）まで２０分毎にサンプリングし、平均一次粒子径を測定したところ、５０～６０μｍであった。 [Example 3]
In Example 1, the rotor rotation speed was set to 7200 rpm (shear rate 5529 [1 / s]), and the dispersing aid to be added to n-heptane was maleic anhydride-modified polyethylene (acid value: 60 mg KOH / g) 0.005% by weight. Except that the addition was changed, the same operation as in Example 1 was performed to obtain a hydrogel (3). The water-containing gel (3) obtained by the above operation was sampled every 20 minutes from 100 minutes after the start of the operation to the end of the operation (5 hours), and the average primary particle diameter was measured to be 50 to 60 μm.
　［実施例４］
　実施例１において、分散媒量を５００ｍｌ／分へ、ローター長さを短く（分散装置１２Ｇの内筒５２Ｇの軸方向長さが下から２．５ｃｍ短い）変更した以外は、実施例１と同様の操作を行い含水ゲル（４）を得た。上記操作で得られた含水ゲル（４）について、運転開始から１００分後から運転終了（５時間）まで２０分毎にサンプリングし、平均一次粒子径を測定したところ、６０～８０μｍであった。 [Example 4]
Example 1 is the same as Example 1 except that the amount of the dispersion medium was changed to 500 ml / min and the rotor length was shortened (the axial length of the inner cylinder 52G of the dispersion device 12G was shorter by 2.5 cm from the bottom). Was carried out to obtain a hydrogel (4). The hydrogel (4) obtained by the above operation was sampled every 20 minutes from 100 minutes after the start of the operation to the end of the operation (5 hours), and the average primary particle diameter was measured to be 60 to 80 μm.
　［実施例５］
　実施例１において、分散装置を図８から図７の分散装置１２Ｆの形状（間隙（クリアランス）３．０ｍｍ、ケーシング内径（外筒５０Ｆの内径）７６ｍｍ、ローター外径（内筒５２Ｆの外径）７０ｍｍ、有効ローター長（単量体水溶液投入口５５Ｆから排出口）３５ｍｍである。）へ、分散媒量を５００ｍｌ／分へ、ローター回転数を４５００ｒｐｍ（せん断速度５４９８［１／ｓ］）に変更した以外は、実施例１と同様の操作を行い含水ゲル（５）を得た。上記操作で得られた含水ゲル（５）について、運転開始から１００分後から運転終了（５時間）まで２０分毎にサンプリングし、平均一次粒子径を測定したところ、６０～８０μｍであった。 [Example 5]
In the first embodiment, the dispersing device is the same as the dispersing device 12F shown in FIGS. 8 to 7 (gap (clearance) 3.0 mm, casing inner diameter (inner diameter of outer cylinder 50F) 76 mm, rotor outer diameter (outer diameter of inner cylinder 52F)). 70 mm, the effective rotor length (35 mm from the monomer aqueous solution inlet 55F to the outlet), the dispersion medium amount to 500 ml / min, and the rotor rotation speed changed to 4500 rpm (shear speed 5498 [1 / s]). Except that, the same operation as in Example 1 was performed to obtain a hydrogel (5). The hydrogel (5) obtained by the above operation was sampled every 20 minutes from 100 minutes after the start of the operation to the end of the operation (5 hours), and the average primary particle diameter was measured to be 60 to 80 μm.
　［実施例６］
　実施例１において、分散装置を図８から図６の分散装置１２Ｅの形状へ変更し、円形プレート５２Ｅを３６００ｒｐｍ（せん断速度９４２５［１／ｓ］、間隙（クリアランス）１．０ｍｍ）で回転した以外は、実施例１と同様の操作を行い含水ゲル（６）を得た。上記操作で得られた含水ゲル（６）について、運転開始から１００分後から運転終了（５時間）まで２０分毎にサンプリングし、平均一次粒子径を測定したところ、７０～１００μｍであった。 [Example 6]
In Example 1, the dispersion device was changed from the shape of FIG. 8 to the shape of the dispersion device 12E of FIG. 6, and the circular plate 52E was rotated at 3600 rpm (shear speed 9425 [1 / s], gap (clearance) 1.0 mm). Was performed in the same manner as in Example 1 to obtain a hydrogel (6). The water-containing gel (6) obtained by the above operation was sampled every 20 minutes from 100 minutes after the start of the operation to the end of the operation (5 hours), and the average primary particle diameter was measured to be 70 to 100 μm.
　［比較例１］
　実施例１において、高速回転せん断型攪拌機の代わりに、図９に示す２流体スプレーノズル（分散装置２００）を用いて分散工程を実施したこと以外は実施例１と同様の操作を行い、比較用含水ゲル（１）および、比較用吸水性樹脂（１）を得た。 [Comparative Example 1]
In Example 1, the same operation as in Example 1 was performed except that the dispersing step was performed using a two-fluid spray nozzle (dispersing apparatus 200) shown in FIG. 9 instead of the high-speed rotary shear type stirrer. A hydrogel (1) and a comparative water-absorbent resin (1) were obtained.
　具体的には、分散装置として、ＰＴＦＥの２流体スプレーノズル（外部混合型、スプレーノズル内径：１．０ｍｍ、形式：ＳＥＴＯＪｅｔ、空気消費量区分０７５、噴量１０、株式会社いけうち製）を使用した。図９において、２流体スプレーは、単量体組成物を連続的に供給する第１供給管２０１と、有機溶媒を連続的に供給する第２供給管２０２と、を有する。単量体組成物は第１ノズル２０３から、有機溶媒は第２ノズル２０４から、それぞれ噴霧分散されて連続的に反応装置に排出される。この際、２流体スプレーの位置を、２流体スプレーのノズルの先端が、重合装置に収容された有機溶媒に浸るように調整した。さらに、循環する有機溶媒および分散助剤の混合液の流量を１０００ｍｌ／分に変更し、循環させた有機溶媒および分散助剤の混合液の経路を、分散装置（２流体スプレーノズル）を介して重合装置に投入する経路と、直接重合装置に投入する経路とに分岐させた。この際、分散装置（２流体スプレーノズル）を介して反応装置に投入される有機溶媒の流量を８００ｍｌ／分とし、直接反応装置に投入される有機溶媒の流量を２００ｍｌ／分とした。次に、上記混合工程で調製した単量体組成物（１）を、速やかに上記２流体スプレーの第１供給管２０１に送液した。その後、上記２流体スプレーを用いて、流量４０ｍＬ／分（４７．２ｇ／分）で、単量体組成物（１）を上記重合装置内を満たしている有機溶媒中に投入した。 Specifically, a PTFE two-fluid spray nozzle (external mixing type, spray nozzle inner diameter: 1.0 mm, type: SETOJet, air consumption classification 075, injection amount 10, manufactured by Ikeuchi Co., Ltd.) was used as a dispersing device. . In FIG. 9, the two-fluid spray has a first supply pipe 201 for continuously supplying the monomer composition and a second supply pipe 202 for continuously supplying the organic solvent. The monomer composition is spray-dispersed from the first nozzle 203 and the organic solvent is sprayed and dispersed from the second nozzle 204, and are continuously discharged to the reactor. At this time, the position of the two-fluid spray was adjusted so that the tip of the two-fluid spray nozzle was immersed in the organic solvent contained in the polymerization apparatus. Further, the flow rate of the circulating mixture of the organic solvent and the dispersing aid was changed to 1000 ml / min, and the path of the circulated mixture of the organic solvent and the dispersing aid was passed through a dispersion device (two-fluid spray nozzle). It was branched into a path to be charged into the polymerization apparatus and a path to be directly charged into the polymerization apparatus. At this time, the flow rate of the organic solvent supplied to the reaction device via the dispersing device (two-fluid spray nozzle) was 800 ml / min, and the flow rate of the organic solvent directly supplied to the reaction device was 200 ml / min. Next, the monomer composition (1) prepared in the mixing step was immediately sent to the first supply pipe 201 of the two-fluid spray. Thereafter, the monomer composition (1) was introduced into the organic solvent filling the polymerization apparatus at a flow rate of 40 mL / min (47.2 g / min) using the two-fluid spray.
　上記２流体スプレーによって投入された上記単量体組成物（１）は、上記有機溶媒中で微細液滴状に分散した。なお、反応装置１４における空間速度（ＬＨＳＶ）は、１２．７ｈｒ－１であった。 The monomer composition (1) charged by the two-fluid spray was dispersed in the organic solvent in the form of fine droplets. The space velocity (LHSV) in the reactor 14 was 12.7 hr -1 .
　なお、上記２流体スプレーノズルによる単量体組成物の投入を３００分間継続したところ、３０分を超えたぐらいから、スプレーノズル先端にゲルの付着、脱離がみられ、生成する液滴サイズに変動が見られるようになった。 In addition, when the introduction of the monomer composition by the two-fluid spray nozzle was continued for 300 minutes, the adhesion and detachment of the gel were observed at the tip of the spray nozzle from about 30 minutes, and the size of the generated droplet was reduced. Fluctuations began to be seen.
　上記操作で得られた比較用含水ゲル（１）は、微小な球形の含水ゲルが付着凝集した形状をしており、運転開始から１００分後から運転終了（５時間）まで２０分毎にサンプリングし、平均一次粒子径を測定したところ、３０～８０μｍと非常に変動していた。 The comparative hydrogel (1) obtained by the above operation has a shape in which minute spherical hydrogel is adhered and agglomerated, and is sampled every 20 minutes from 100 minutes after the start of operation to the end of operation (5 hours). However, when the average primary particle diameter was measured, the average primary particle diameter was extremely varied from 30 to 80 μm.
　得られた比較用含水ゲル（１）及び比較用吸水性樹脂（１）について測定した諸物性を表１に示した。 Table 1 shows various physical properties of the obtained comparative hydrogel (1) and comparative water-absorbent resin (1).
　［実施例７］
　図１１に示した製造プロセスに従って含水ゲル（７）を作製した後、得られた含水ゲル（７）を乾燥し、さらに表面架橋することで、球状の吸水性樹脂（７）を製造した。 [Example 7]
After producing the hydrogel (7) according to the production process shown in FIG. 11, the obtained hydrogel (7) was dried and further subjected to surface crosslinking to produce a spherical water-absorbing resin (7).
　反応装置１４の上部半分には紫外線照射装置２３が装備されている。 紫外線 An ultraviolet irradiation device 23 is provided in the upper half of the reaction device 14.
　まず、有機溶媒としてｎ－ヘプタン（密度：０．６８ｇ／ｍｌ）を、分散装置１２、反応装置１４、分離装置１６及びこれらを接続する配管内に投入した。 {Circle around (1)} First, n-heptane (density: 0.68 g / ml) was charged as an organic solvent into the dispersion device 12, the reaction device 14, the separation device 16, and the piping connecting these components.
　続いて、送液ポンプ１８を稼働させて、流量２００ｍｌ／分で、有機溶媒の循環を開始した。また、熱交換器２０を稼働させて、設定温度が７０℃となるように、上記循環する有機溶媒を加熱した。 Subsequently, the liquid feed pump 18 was operated, and circulation of the organic solvent was started at a flow rate of 200 ml / min. Further, the heat exchanger 20 was operated to heat the circulating organic solvent such that the set temperature was 70 ° C.
　次に分散助剤としてショ糖脂肪酸エステル（商品名：ＤＫエステルＦ－５０／第一工業製薬株式会社）をｎ－ヘプタンに０．０１重量％添加した。 (4) Next, 0.01% by weight of sucrose fatty acid ester (trade name: DK ester F-50 / Daiichi Kogyo Seiyaku Co., Ltd.) was added to n-heptane as a dispersing aid.
　（１．混合工程）
　アクリル酸、４８．５重量％の水酸化ナトリウム水溶液部及びイオン交換水を混合し、さらに、１－ヒドロキシシクロヘキシルフェニルケトン、ポリエチレングリコールジアクリレート（平均重合度：９）及びジエチレントリアミン５酢酸・３ナトリウムを配合することで、単量体水溶液（７）を作製した。また、別途、過硫酸ナトリウム及びイオン交換水を混合することで、６重量％の過硫酸ナトリウム水溶液（７）を作製した。 (1. Mixing process)
Acrylic acid, a 48.5% by weight aqueous sodium hydroxide solution and ion-exchanged water were mixed, and 1-hydroxycyclohexylphenyl ketone, polyethylene glycol diacrylate (average degree of polymerization: 9) and diethylenetriaminepentaacetic acid / 3 sodium were further added. By mixing, a monomer aqueous solution (7) was prepared. Separately, sodium persulfate and ion-exchanged water were mixed to prepare a 6% by weight aqueous solution of sodium persulfate (7).
　続いて、上記操作で得られた単量体水溶液（７）と過硫酸ナトリウム水溶液（７）とを、混合装置１０に供給することで、単量体組成物（７）を作製した。該単量体組成物（７）のモノマー濃度は４５重量％、中和率は７０モル％であった。また、内部架橋剤であるポリエチレングリコールジアクリレートは単量体に対して０．０２０モル％、キレート剤であるジエチレントリアミン５酢酸・３ナトリウムは単量体に対して２００ｐｐｍ、光重合開始剤である１－ヒドロキシシクロヘキシルフェニルケトンは、単量体に対して０．０５ｇ／モル、熱重合開始剤である過硫酸ナトリウム（Ｔ１０　７０℃）は単量体に対して０．１ｇ／モルであった。 Next, the monomer aqueous solution (7) and the sodium persulfate aqueous solution (7) obtained by the above operation were supplied to the mixing device 10 to prepare a monomer composition (7). The monomer composition (7) had a monomer concentration of 45% by weight and a neutralization ratio of 70 mol%. In addition, polyethylene glycol diacrylate as an internal cross-linking agent was 0.020 mol% based on the monomer, diethylene triamine pentaacetic acid / 3 sodium as a chelating agent was 200 ppm based on the monomer, and 1 ppm as a photopolymerization initiator. -Hydroxycyclohexyl phenyl ketone was 0.05 g / mol with respect to the monomer, and sodium persulfate (T10 @ 70 ° C) as the thermal polymerization initiator was 0.1 g / mol with respect to the monomer.
　（２．分散工程）
　分散装置としては図８に示した二重円筒型の高速回転せん断型攪拌機の分散装置１２Ｇを使用した。ケーシング内径（外筒５０Ｇの内径）２５ｍｍ、ローター外径（内筒５２Ｇの外径）２２ｍｍ、有効ローター長（単量体水溶液投入口５５Ｇから排出口）６５ｍｍである。反応装置としてＰＦＡ（パーフルオロアルコキシアルカン）製チューブ（内径：２５ｍｍ、全長：１０ｍ）を鉛直に配置したものをそれぞれ使用した。 (2. Dispersion step)
As the dispersing device, a dispersing device 12G of a double-cylindrical high-speed rotary shearing stirrer shown in FIG. 8 was used. The inner diameter of the casing (the inner diameter of the outer cylinder 50G) is 25 mm, the outer diameter of the rotor (the outer diameter of the inner cylinder 52G) is 22 mm, and the effective rotor length (from the monomer aqueous solution inlet 55G to the outlet) is 65 mm. As a reaction device, a vertically arranged tube made of PFA (perfluoroalkoxy alkane) (inner diameter: 25 mm, total length: 10 m) was used.
　ローター（内筒５２Ｇ）を回転数４，８００ｒｐｍ（せん断速度３６８６［１／ｓ］）となるように回転させ、次に、単量体組成物（７）を、流量４０ｍｌ／分（４７．２ｇ／分）で、分散装置１２Ｇの配管３１に送液した。供給された上記単量体組成物（７）は、分散装置によって上記有機溶媒中で微細液滴状に分散した（単量体組成物（７）の平均滞留時間１．８０ｓ）。 The rotor (inner cylinder 52G) is rotated at a rotation speed of 4,800 rpm (shear rate 3686 [1 / s]), and then the monomer composition (7) is supplied at a flow rate of 40 ml / min (47.2 g). / Min), the liquid was sent to the pipe 31 of the dispersion device 12G. The supplied monomer composition (7) was dispersed in the form of fine droplets in the organic solvent by a dispersing device (average residence time of the monomer composition (7) 1.80 s).
　（３．重合工程）
　２．で得られた分散液は反応装置１４に排出した。 (3. polymerization step)
2. Was discharged into the reactor 14.
　上記単量体組成物（７）からなる液滴は、上記連続相である有機溶媒が満たされた反応装置内を落下し、反応装置上部に設置されている紫外線照射装置で重合が開始され、重合反応の進行に伴って微小な球形ゲルに変化した。これらの微小な球形ゲルは、落下するに従って相互に付着して凝集体を形成した。そして、該反応装置の排出口付近において、微小な球形ゲルの凝集体からなる直径約１～３ｃｍの含水ゲル（７）を確認した。なお、反応装置１４における空間速度（ＬＨＳＶ）は、２．９ｈｒ－１であった。 Droplets composed of the monomer composition (7) fall in a reactor filled with the organic solvent as the continuous phase, and polymerization is started by an ultraviolet irradiation device installed on the upper portion of the reactor, As the polymerization reaction progressed, it changed to a minute spherical gel. These small spherical gels adhered to each other as they fell to form aggregates. Then, in the vicinity of the outlet of the reactor, a hydrogel (7) having a diameter of about 1 to 3 cm and comprising an aggregate of fine spherical gel was confirmed. The space velocity (LHSV) in the reactor 14 was 2.9 hr -1 .
　上記一連の操作で得られた含水ゲル（７）は、有機溶媒と共に連続的に反応装置１４から排出された。 水 The hydrogel (7) obtained by the above series of operations was continuously discharged from the reactor 14 together with the organic solvent.
　（４．分離工程）
　反応装置１４から排出された含水ゲル（７）と有機溶媒とは、そのまま分離装置１６に連続的に供給された。該分離装置において、該含水ゲル（７）と有機溶媒とを分離した。なお、該分離装置で分離された有機溶媒は、設定温度が７０℃となるように熱交換器２０で調温した後、再度、反応装置１４に供給した。 (4. Separation process)
The hydrogel (7) and the organic solvent discharged from the reaction device 14 were continuously supplied to the separation device 16 as they were. In the separation device, the hydrogel (7) and the organic solvent were separated. The organic solvent separated by the separation device was temperature-controlled by the heat exchanger 20 so that the set temperature was 70 ° C., and then supplied to the reaction device 14 again.
　上記攪拌機への単量体組成物（７）の投入を５時間継続する間、該単量体組成物（７）の送液圧は０．１３ＭＰａＧで一定であり、この攪拌機において詰まりは見られなかった。 While the introduction of the monomer composition (7) into the stirrer was continued for 5 hours, the liquid sending pressure of the monomer composition (7) was constant at 0.13 MPaG, and clogging was observed in this stirrer. Did not.
　上記操作で得られた含水ゲル（７）は、微小な球形の含水ゲルが付着凝集した形状をしていた。また、含水ゲル（７）について運転開始から１００分後から運転終了（５時間）まで２０分毎にサンプリングし、平均一次粒子径を測定したところ、７０～８０μｍであった。 (4) The hydrogel (7) obtained by the above operation had a shape in which minute spherical hydrogel was adhered and aggregated. The water-containing gel (7) was sampled every 20 minutes from 100 minutes after the start of the operation to the end of the operation (5 hours), and the average primary particle diameter was measured to be 70 to 80 μm.
　（５．乾燥工程）～（７．整粒工程）
　得られた上記含水ゲル（７）は、実施例１と同様の乾燥および表面処理、整粒工程処理を行い、球状の吸水性樹脂（７）を得た。 (5. Drying process)-(7. Sizing process)
The obtained hydrogel (7) was subjected to the same drying, surface treatment, and sizing process as in Example 1 to obtain a spherical water-absorbing resin (7).
　［実施例８］
　図１に示した製造プロセスに従って下記工程２～５の一連の工程を運転し、含水ゲル（８）を調製した後、得られた含水ゲル（８）を乾燥し、吸水性樹脂（８）を製造した。なお、具体的な運転時間は、下記工程２において分散装置への単量体組成物の送液を開始してから１０時間とした。 Example 8
A series of the following steps 2 to 5 is operated according to the manufacturing process shown in FIG. 1 to prepare a hydrogel (8), and then the obtained hydrogel (8) is dried to remove the water-absorbent resin (8). Manufactured. The specific operation time was set to 10 hours after the start of the supply of the monomer composition to the dispersion device in the following step 2.
　まず、有機溶媒としてｎ－ヘプタン（密度：０．６８ｇ／ｍｌ）を、分散装置１２、重合装置１４、分離装置１６及びこれらを接続する配管内に投入した。 {Circle around (1)} First, n-heptane (density: 0.68 g / ml) as an organic solvent was charged into the dispersion device 12, the polymerization device 14, the separation device 16 and the piping connecting these.
　続いて、送液ポンプ１８を稼働させて、流量３００ｍｌ／分で、有機溶媒の循環を開始した。なお、有機溶媒は、その全量を分散装置１２を介して重合装置１４に投入した。また、熱交換器２０を稼働させて、上記循環する有機溶媒の温度が９０℃となるように加熱した。 Next, the liquid pump 18 was operated to start circulation of the organic solvent at a flow rate of 300 ml / min. In addition, the whole amount of the organic solvent was charged into the polymerization apparatus 14 via the dispersion apparatus 12. Further, the heat exchanger 20 was operated to heat the organic solvent so that the temperature of the circulating organic solvent became 90 ° C.
　次に、別途、分散助剤として無水マレイン酸変性ポリエチレン（酸価：６０ｍｇＫＯＨ／ｇ）をｎ－ヘプタンに混合し、９０℃に加熱して溶解させて、０．０３０重量％の分散助剤溶液（８）を調製した。続いて、上記操作で得られた分散助剤溶液（８）を、配管４３を介して、流量５０ｍｌ／分で３０分間、配管３３を流れるｎ－ヘプタンに添加した。重合開始前の有機溶媒全量に対する無水マレイン酸変性ポリエチレンの含有量の割合は０．００５重量％であった。 Next, a maleic anhydride-modified polyethylene (acid value: 60 mg KOH / g) was separately mixed with n-heptane as a dispersing aid and dissolved by heating to 90 ° C. to obtain a 0.030 wt% dispersing aid solution. (8) was prepared. Subsequently, the dispersion aid solution (8) obtained by the above operation was added to the n-heptane flowing through the pipe 33 via the pipe 43 at a flow rate of 50 ml / min for 30 minutes. The ratio of the content of the maleic anhydride-modified polyethylene to the total amount of the organic solvent before the start of the polymerization was 0.005% by weight.
　（１．混合工程）
　アクリル酸、４８．５重量％の水酸化ナトリウム水溶液及びイオン交換水を混合し、さらに、ポリエチレングリコールジアクリレート（平均重合度：９）及びジエチレントリアミン５酢酸・３ナトリウムを配合することで、単量体水溶液（８）を作製した。また、別途、過硫酸ナトリウム及びイオン交換水を混合することで、６重量％の過硫酸ナトリウム水溶液（８）を作製した。 (1. Mixing process)
Acrylic acid, a 48.5% by weight aqueous sodium hydroxide solution and ion-exchanged water are mixed, and further, polyethylene glycol diacrylate (average degree of polymerization: 9) and diethylenetriaminepentaacetic acid / 3 sodium are added to form a monomer. An aqueous solution (8) was prepared. Separately, sodium persulfate and ion-exchanged water were mixed to prepare a 6% by weight aqueous solution of sodium persulfate (8).
　続いて、上記操作で得られた単量体水溶液（８）と過硫酸ナトリウム水溶液（８）とを、混合装置１０に供給することで、単量体組成物（８）を調製した。該単量体組成物（８）の単量体濃度は４３重量％、中和率は７５モル％であった。また、内部架橋剤であるポリエチレングリコールジアクリレートは単量体に対して０．０１０モル％、キレート剤であるジエチレントリアミン５酢酸・３ナトリウムは単量体に対して２００ｐｐｍ、重合開始剤である過硫酸ナトリウム（Ｔ１０　７０℃）は単量体に対して０．１ｇ／モルであった。 Subsequently, the monomer aqueous solution (8) and the sodium persulfate aqueous solution (8) obtained by the above operation were supplied to the mixing device 10 to prepare a monomer composition (8). The monomer composition (8) had a monomer concentration of 43% by weight and a neutralization ratio of 75 mol%. In addition, polyethylene glycol diacrylate as an internal cross-linking agent is 0.010 mol% based on the monomer, diethylene triamine pentaacetic acid / 3 sodium as a chelating agent is 200 ppm based on the monomer, and persulfate as a polymerization initiator is used. Sodium (T10 @ 70 ° C.) was 0.1 g / mol based on the monomer.
　（２．分散工程）
　分散装置としては図８に示した二重円筒型の高速回転せん断型攪拌機（分散装置１２Ｇ）を使用した。ケーシング内径（外筒５０Ｇの内径）２５ｍｍ、ローター外径（内筒５２Ｇの外径）２２ｍｍ、有効ローター長（単量体水溶液投入口５５Ｇから排出口）６５ｍｍである。重合装置としてＰＦＡ（パーフルオロアルコキシアルカン）製チューブ（内径：２５ｍｍ、全長：１０ｍ）を鉛直に配置したものをそれぞれ使用した。 (2. Dispersion step)
As the dispersing device, a double-cylindrical high-speed rotary shearing stirrer (dispersing device 12G) shown in FIG. 8 was used. The inner diameter of the casing (the inner diameter of the outer cylinder 50G) is 25 mm, the outer diameter of the rotor (the outer diameter of the inner cylinder 52G) is 22 mm, and the effective rotor length (from the monomer aqueous solution inlet 55G to the outlet) is 65 mm. As a polymerization apparatus, a vertically arranged tube made of PFA (perfluoroalkoxyalkane) (inner diameter: 25 mm, total length: 10 m) was used.
　上記の有機溶媒および分散助剤の混合液を分散装置１２Ｇの配管３５に流量３００ｍｌ／分で送液した。重合開始前の分散助剤溶液（８）の投入完了後から３０分後、ローター（内筒５２Ｇ）を回転数７，２００ｒｐｍ（せん断速度５５２９［１／ｓ］）となるように回転させ、次に、単量体組成物（８）を、流量４０ｍｌ／分（４７．２ｇ／分）で、分散装置１２Ｃの配管３１に送液した。供給された上記単量体組成物（８）は、分散装置によって上記有機溶媒中で微細液滴状に分散した。 {Circle around (2)} The mixed solution of the above organic solvent and the dispersing aid was sent to the pipe 35 of the dispersion device 12G at a flow rate of 300 ml / min. Thirty minutes after the completion of the addition of the dispersing aid solution (8) before the start of polymerization, the rotor (inner cylinder 52G) was rotated at 7,200 rpm (shear speed 5529 [1 / s]), and then the rotor was rotated. Then, the monomer composition (8) was sent to the pipe 31 of the dispersion device 12C at a flow rate of 40 ml / min (47.2 g / min). The supplied monomer composition (8) was dispersed as fine droplets in the organic solvent by a dispersing device.
　（３．重合工程）
　２．で得られた分散液を重合装置１４に供給した。 (3. polymerization step)
2. Was supplied to the polymerization apparatus 14.
　上記単量体組成物（８）からなる液滴は、上記連続相である有機溶媒が満たされた重合装置内を落下しながら、重合反応の進行に伴って微小な球形含水ゲル（８）に変化した。これらの微小な球形ゲルは、落下するにしたがって相互に付着して凝集体を形成した。そして、該重合装置の排出口付近において、微小な球形ゲルの凝集体からなる直径１ｃｍ程度の含水ゲル（８）を確認した。なお、重合装置１４における空間速度（ＬＨＳＶ）は、４．２ｈｒ－１であった。 Droplets composed of the monomer composition (8) fall into a polymerization apparatus filled with an organic solvent as the continuous phase, and form fine spherical hydrogels (8) as the polymerization reaction proceeds. changed. These small spherical gels adhered to each other as they fell to form aggregates. In the vicinity of the outlet of the polymerization apparatus, a hydrogel (8) having a diameter of about 1 cm and comprising an aggregate of fine spherical gel was confirmed. The space velocity (LHSV) in the polymerization apparatus 14 was 4.2 hr -1 .
　上記一連の操作で得られた含水ゲル（８）は、有機溶媒と共に連続的に重合装置１４から排出された。 水 The hydrogel (8) obtained by the above series of operations was continuously discharged from the polymerization apparatus 14 together with the organic solvent.
　（４．分離およびリサイクル工程）
　重合装置１４から排出された含水ゲル（８）と有機溶媒とは、そのまま分離装置１６に連続的に供給された。該分離装置において、該含水ゲル（８）と有機溶媒とを分離した。なお、該分離装置で分離された有機溶媒は、配管３２、送液ポンプ１８、配管３３を介して熱交換器２０に供給し、設定温度（有機溶媒温度）が９０℃となるように熱交換器２０で調温した後、配管３５を介して、７０℃以上に維持しながら、分散装置１２および重合装置１４に供給した。その際、補充用の分散助剤として上記分散助剤溶液（８）を、配管４３を介して、流量５ｍｌ／分で、配管３３を流れる有機溶媒を含む連続相に、分散装置への単量体組成物の送液を開始して１０分後から連続的に投入を開始した。すなわち、分散助剤流量［ｍｌ／分］／連続相流量［ｍｌ／分］は０．０１７であった。なお、分散助剤（無水マレイン酸変性ポリエチレン）の添加量は、上記単量体組成物（８）に対して０．００５重量％である。 (4. Separation and recycling process)
The hydrogel (8) and the organic solvent discharged from the polymerization device 14 were continuously supplied to the separation device 16 as they were. In the separator, the hydrogel (8) was separated from the organic solvent. The organic solvent separated by the separation device is supplied to the heat exchanger 20 via the pipe 32, the liquid sending pump 18 and the pipe 33, and heat exchange is performed so that the set temperature (organic solvent temperature) becomes 90 ° C. After adjusting the temperature in the vessel 20, the mixture was supplied to the dispersion apparatus 12 and the polymerization apparatus 14 via a pipe 35 while maintaining the temperature at 70 ° C. or higher. At this time, the dispersion aid solution (8) as a replenishing dispersion aid was added to the continuous phase containing the organic solvent flowing through the pipe 33 at a flow rate of 5 ml / min via the pipe 43 in a single amount to the dispersion device. Feeding was started continuously 10 minutes after the start of the liquid feeding of the body composition. That is, the flow rate of the dispersing aid [ml / min] / the flow rate of the continuous phase [ml / min] was 0.017. The addition amount of the dispersing aid (maleic anhydride-modified polyethylene) is 0.005% by weight based on the monomer composition (8).
　上記操作で得られた含水ゲル（８）は、微小な球形の含水ゲルが付着凝集した形状をしていた。また、含水ゲル（８）について運転開始から１００分後から運転終了（１０時間）まで２０分毎にサンプリングし、平均一次粒子径を測定したところ、６０～７０μｍであった。 水 The hydrogel (8) obtained by the above operation had a shape in which minute spherical hydrogel was adhered and aggregated. Further, the water-containing gel (8) was sampled every 20 minutes from 100 minutes after the start of the operation to the end of the operation (10 hours), and the average primary particle diameter was measured to be 60 to 70 μm.
　（５．乾燥工程）
　分離装置１６から排出された含水ゲル（８）は、そのまま間接加熱式撹拌乾燥装置に連続的に供給すると共に、予め準備したラウリルジメチルアミノ酢酸ベタイン水溶液（濃度３．１重量％）を投入した。含水ゲル（８）に対するラウリルジメチルアミノ酢酸ベタイン水溶液の量は０．５重量％であった。続いて、乾燥装置の熱媒温度を１８０℃に調整して、上記含水ゲル（８）を、ラウリルジメチルアミノ酢酸ベタインと混合しながら、連続乾燥を行って、粒子状の乾燥重合体（８）を得た。得られた乾燥重合体（８）を目開き８５０μｍ及び１５０μｍの金属篩網（ＪＩＳ標準篩）を有する篩い分け装置に連続的に供給して分級し、吸水性樹脂粉末（８）を得た。 (5. Drying process)
The hydrogel (8) discharged from the separation device 16 was continuously supplied to the indirect heating type stirring and drying device as it was, and a previously prepared aqueous solution of betayl lauryl dimethylaminoacetate (concentration: 3.1% by weight) was charged. The amount of the aqueous solution of betayl lauryldimethylaminoacetate based on the hydrogel (8) was 0.5% by weight. Subsequently, the heating medium temperature of the drying device was adjusted to 180 ° C., and the water-containing gel (8) was continuously dried while being mixed with betaine lauryl dimethylaminoacetate, to thereby obtain a particulate dry polymer (8). I got The obtained dried polymer (8) was continuously supplied to a sieving device having a metal sieve mesh (JIS standard sieve) having openings of 850 μm and 150 μm to be classified, thereby obtaining a water-absorbent resin powder (8).
　上記工程１．～５．を１０時間運転し、排出量が安定していない重合開始直後の１時間、および重合停止後のサンプルを除いて混合し吸水性樹脂粉末（８）を得た。 Step 1 above. ~ 5. Was operated for 10 hours, and the mixture was mixed except for 1 hour immediately after the start of the polymerization, in which the discharge amount was not stable, and the sample after the termination of the polymerization, to obtain a water-absorbent resin powder (8).
　（６．表面架橋工程）
　吸水性樹脂粉末（８）１００重量部に対して、エチレングリコールジグリシジルエーテル０．０１５重量部、プロピレングリコール１．０重量部、及びイオン交換水３．０重量部からなる表面架橋剤溶液をスプレーノズルで噴霧して、連続高速混合機を用いて均一に混合した。その後、表面架橋剤を含む吸水性樹脂（８）を、雰囲気温度を１９５℃±２℃に調温した熱処理機に導入して、３０分間加熱処理した後、粉温が６０℃となるまで強制的に冷却し、吸水性樹脂（８）を得た。 (6. Surface crosslinking step)
Spray a surface cross-linking agent solution consisting of 0.015 parts by weight of ethylene glycol diglycidyl ether, 1.0 part by weight of propylene glycol, and 3.0 parts by weight of ion-exchanged water to 100 parts by weight of the water-absorbent resin powder (8). The mixture was sprayed with a nozzle and uniformly mixed using a continuous high-speed mixer. Thereafter, the water-absorbent resin (8) containing the surface cross-linking agent is introduced into a heat treatment machine whose atmosphere temperature is controlled at 195 ° C. ± 2 ° C., and heat-treated for 30 minutes, and then forced until the powder temperature reaches 60 ° C. Cooling was carried out to obtain a water absorbent resin (8).
　（７．整粒工程）
　次いで、目開き８５０μｍの金属篩（ＪＩＳ標準篩）を有する篩い分け装置で分級した。尚、目開き８５０μｍの金属篩上の残留物については再度粉砕を行った後、目開き８５０μｍの金属篩通過物と混合した。以上の操作によって、全量の粒子径が８５０μｍ未満である整粒された吸水性樹脂（８）を得た。得られた吸水性樹脂（８）の諸物性を表１に示す。 (7. Sizing process)
Next, the particles were classified by a sieving apparatus having a metal sieve having an opening of 850 μm (JIS standard sieve). The residue on the metal sieve having an aperture of 850 μm was pulverized again, and then mixed with the metal sieve having an aperture of 850 μm. Through the above operation, a sized water-absorbent resin (8) having a total particle size of less than 850 μm was obtained. Table 1 shows properties of the obtained water-absorbent resin (8).
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000004
　以上の結果より、実施例１～８の製造方法によれば、比較例１の製造方法と比較して、有機溶媒の流量が少ないにもかかわらず、平均一次粒子径が安定した吸水性樹脂を得ることができることがわかる。 From the above results, according to the production methods of Examples 1 to 8, compared to the production method of Comparative Example 1, a water-absorbent resin having a stable average primary particle diameter despite a small flow rate of the organic solvent was obtained. It can be seen that it can be obtained.
　特に、実施例１～３、７および８の吸水性樹脂は、得られる吸水性樹脂の平均一次粒子径の振れが小さいものであった。さらに、実施例１、３、８の吸水性樹脂は、平均一次粒子径が小さく、ＤＲＣ５ｍｉｎが非常に高いものであった。 Especially, the water absorbent resins of Examples 1 to 3, 7 and 8 had small fluctuations in the average primary particle diameter of the obtained water absorbent resin. Furthermore, the water-absorbent resins of Examples 1, 3, and 8 had a small average primary particle diameter and a very high DRC of 5 min.
　本出願は、２０１８年９月２７日に出願された、日本特許出願２０１８－１８２１１４号、２０１９年７月１０日に出願された、日本特許出願２０１９－１２８６６３号に基づいており、その開示内容は、その全体が参照により本明細書に組みこまれる。 This application is based on Japanese Patent Application No. 2018-182114 filed on Sep. 27, 2018, and Japanese Patent Application No. 2019-128663 filed on Jul. 10, 2019, the disclosure of which is as follows. , Which are hereby incorporated by reference in their entirety.
　１０　　　混合装置、
　１２、１２Ａ～１２Ｇ　　分散装置、
　１４　　　反応装置、
　１６　　　分離装置、
　１８　　　送液ポンプ、
　２０　　　熱交換器、
　２２　　　乾燥装置、
　２３　　　紫外線照射装置、
　５０Ａ、５２Ａ　　一対の壁、
　５０Ｂ、５２Ｂ　　一対の壁、
　５０Ｃ、５２Ｃ　　一対の壁、
　５０Ｄ、５２Ｄ　　一対の壁、
　５０Ｅ、５２Ｅ　　一対の壁、
　５０Ｆ、５２Ｆ　　一対の壁、
　５０Ｇ、５２Ｇ　　一対の壁、
　５１Ａ、５３Ａ　　対向面、
　５１Ｂ、５３Ｂ　　対向面、
　５１Ｃ、５３Ｃ　　対向面、
　５１Ｄ、５３Ｄ　　対向面、
　５１Ｅ、５３Ｅ　　対向面、
　５１Ｆ、５３Ｆ　　対向面、
　５１Ｇ、５３Ｇ　　対向面、
　５４Ａ～５４Ｇ　　流路、
　６０Ａ～６０Ｇ　　駆動部、
　５５Ａ～５５Ｇ　　第１供給系、
　５６Ａ～５５Ｇ　　第２供給系。 10 mixing devices,
12, 12A to 12G dispersion device,
14 reactor,
16 separation device,
18 liquid sending pump,
20 heat exchangers,
22 drying equipment,
23 UV irradiation equipment,
50A, 52A a pair of walls,
50B, 52B a pair of walls,
50C, 52C a pair of walls,
50D, 52D a pair of walls,
50E, 52E a pair of walls,
50F, 52F A pair of walls,
50G, 52G a pair of walls,
51A, 53A opposing surface,
51B, 53B opposing surface,
51C, 53C facing surface,
51D, 53D opposing surface,
51E, 53E facing surface,
51F, 53F opposing surface,
51G, 53G facing surface,
54A to 54G channel,
60A-60G drive unit,
55A to 55G first supply system,
56A to 55G Second supply system.

Claims (7)

  1. 　間隙を隔てて互いに対向する対向面を有する一対の壁が相対的に移動することによってせん断場を形成する流路に、水溶性エチレン性不飽和単量体溶液、有機溶媒を別々に連続的に供給し、
    　前記水溶性エチレン性不飽和単量体溶液を含む液滴を作製し、
    　当該水溶性エチレン性不飽和単量体を重合することを有する、吸水性樹脂の製造方法。     A water-soluble ethylenically unsaturated monomer solution and an organic solvent are continuously and separately supplied to a flow path that forms a shear field by a pair of walls having opposing surfaces opposing each other with a gap therebetween. Supply,
    Producing a droplet containing the water-soluble ethylenically unsaturated monomer solution,
    A method for producing a water-absorbing resin, comprising polymerizing the water-soluble ethylenically unsaturated monomer.
  2. 　前記流路におけるせん断速度が、１，０００［１／ｓ］以上である、請求項１に記載の吸水性樹脂の製造方法。 方法 The method for producing a water-absorbent resin according to claim 1, wherein the shear rate in the flow path is 1,000 [1 / s] or more.
  3. 　前記流路における水溶性エチレン性不飽和単量体溶液の平均滞留時間が、０．１～５秒である、請求項１または２に記載の吸水性樹脂の製造方法。 3. The method for producing a water-absorbent resin according to claim 1, wherein the average residence time of the water-soluble ethylenically unsaturated monomer solution in the channel is 0.1 to 5 seconds.
  4. 　管状の反応管において前記水溶性エチレン性不飽和単量体を重合する、請求項１～３のいずれか１項に記載の吸水性樹脂の製造方法。 The method for producing a water-absorbent resin according to any one of claims 1 to 3, wherein the water-soluble ethylenically unsaturated monomer is polymerized in a tubular reaction tube.
  5. 　重合反応が行われる反応装置における空間速度（ＬＨＳＶ）が２～１０ｈｒ－１である、請求項１～４のいずれか１項に記載の吸水性樹脂の製造方法。 The method for producing a water-absorbent resin according to any one of claims 1 to 4, wherein a space velocity (LHSV) in the reactor in which the polymerization reaction is performed is 2 to 10 hr -1 .
  6. 　さらに、前記重合により得られる含水ゲル状重合体を乾燥して吸水性樹脂粉末を得ることと、
    　前記吸水性樹脂粉末を表面架橋剤により表面架橋を施すことと、を有する、請求項１～５のいずれか１項に記載の吸水性樹脂の製造方法。     Further, to obtain a water-absorbent resin powder by drying the hydrogel polymer obtained by the polymerization,
    The method for producing a water-absorbent resin according to any one of claims 1 to 5, further comprising subjecting the water-absorbent resin powder to surface cross-linking with a surface cross-linking agent.
  7. 　請求項１～６のいずれか１項に記載の製造方法によって得られる吸水性樹脂であって、
    　ＤＲＣ５ｍｉｎが４６ｇ／ｇ以上であり、かつ、残存モノマーが４００ｐｐｍ以下である吸水性樹脂。     A water-absorbent resin obtained by the production method according to any one of claims 1 to 6,
    A water-absorbent resin having a DRC of 5 min or more and a residual monomer of 400 ppm or less.
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