JP2005081204A - Method for manufacturing water absorbing resin composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a water absorbing resin composition in which a water absorbing resin can be mixed homogeneously without damaging the water absorbing resin. <P>SOLUTION: A static mixer is used as a mixing apparatus when an additive is added to the water absorbing resin and the additive-added water absorbing resin is mixed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a water absorbent resin composition. More specifically, the present invention relates to a method for producing a water absorbent resin composition by mixing a water absorbent resin and an additive added to the water absorbent resin using a static mixer.

  It is well known that a water-containing gel-like polymer can be obtained as a water-absorbing polymer by aqueous polymerization of a water-soluble ethylenically unsaturated monomer. This water-containing gel-like polymer is a semi-solid and highly elastic gel-like material and is rarely used as it is. In many cases, it is once crushed and crushed to increase the drying efficiency. Then, it is dried and crushed. Thereafter, the crushed product of the hydrogel polymer in a dry powder state is used as a water absorbent resin, that is, an absorbent.

  In order to use the water-absorbent resin as an absorbent, the water-absorbent resin preferably has a high water-absorbing ability, and such a water-absorbent resin has been developed. However, the higher the water absorption capacity, the stronger the affinity with water, so when these materials come into contact with water, gelation occurs only at the contact area, preventing uniform penetration of water and rapid water absorption speed. Has a problem that cannot be obtained. In order to solve this problem, it is known to mix a polyvalent metal salt with a water-absorbent resin (for example, refer to Patent Documents 1 and 2).

  In Patent Document 1, a small amount of polyvalent metal salt and / or hydroxide is mixed with polymer particles, and a small amount of water is added. Thus, the water-absorbed liquid can easily pass between the polymer particles without adhesion between the polymer particles, and the water absorption speed of the water-absorbing material can be improved. Examples of the mixing apparatus used in the above mixing include a V-type mixer, a nauter mixer, and a ball mill.

In Patent Document 2, a superabsorbent polymer is prepared by dry blending a superabsorbent polymer with a polyvalent metal salt and then bringing the mixture into contact with a binder. Thereby, it is supposed that the gel layer resiliency characteristic of a superabsorbent polymer can be improved. Examples of the blending equipment used in the dry blend include a jar tumbler, a plow shear mixer, a paddle blender, a ribbon blender, a rotary blender, and a high-speed rotary blender.
JP 61-257235 A (published on November 14, 1986) Special Table 2001-523289 (announced on November 20, 2001)

  However, the mixing apparatus and the blending equipment described in Patent Documents 1 and 2 all have a driving portion for mixing such as a rotary blade, a stirring blade, and a screw, and mixing is performed by driving these. Is going. That is, mixing of the water absorbent resin and the polyvalent metal salt is performed mechanically. For this reason, when mechanical energy is added to the water absorbent resin, the water absorbent resin itself or its surface is damaged. If the water-absorbing resin is damaged, the physical properties such as the water-absorbing ability, which is the main function as the water-absorbing resin, and other functions provided to make the water-absorbing resin high-quality are reduced. Has the problem.

  The water-absorbent resin is generally fine particles having a particle size distribution of, for example, 150 to 850 μm. For this reason, when it mixes using drive mixers, such as a stirring type mixer, segregation tends to occur in the water-absorbent resin in the mixer or when discharged from the mixer. That is, when a drive mixer is used for mixing the water absorbent resin and additives such as polyvalent metal salts, the particle size and composition of the water absorbent resin are biased and become non-uniform. Sometimes. When this water-absorbent resin is used for a diaper or the like, the performance of the diaper varies, which is not preferable.

  On the other hand, it is conceivable to use a static mixer which is a mixing device that does not have a driving part and does not perform mechanical mixing. However, the static mixer generally assumes a case where the fluid to be mixed is a liquid-liquid, gas-solid, or liquid-gas combination, and does not assume solid-solid dry mixing. For this reason, it is not known to use a static mixer for dry mixing of solids and solids, and when a static mixer is used for dry mixing of a water absorbent resin and a powdered additive. It was unclear whether uniform mixing was possible even if it was.

  The present invention has been made in view of the above problems, and its purpose is to use a static mixer to mix fine particles such as a water-absorbent resin and a powdery additive. Thus, it is to realize a method for producing a water-absorbent resin composition that can be uniformly mixed without damaging the water-absorbent resin.

  In order to solve the above problems, a method for producing a water-absorbent resin composition according to the present invention includes the steps of adding an additive to the water-absorbent resin and mixing the water-absorbent resin and the additive. The method is characterized in that the water-absorbent resin and the additive are mixed using a static mixer.

  The method for producing a water absorbent resin composition according to the present invention is characterized in that, in addition to the above configuration, the water absorbent resin and the additive move in the static mixer by gravity and / or pressure of a pressurizing means. .

  The method for producing a water absorbent resin composition according to the present invention is characterized in that, in addition to the above configuration, the surface of the water absorbent resin is crosslinked using a crosslinking agent.

  As described above, in the method for producing a water absorbent resin composition according to the present invention, the water absorbent resin and the additive are mixed using a static mixer. A static mixer is a mixer having no drive parts. For this reason, mechanical mixing is not performed, the water-absorbent resin can be prevented from being damaged by receiving mechanical energy, and the decrease in physical properties of the water-absorbent resin composition can be suppressed. Play. Further, by using a mixer having no driving part, it is possible to prevent the occurrence of trouble during continuous mixing. In addition, since the static mixer has good piston flow properties, the water-absorbent resin and the additive can be mixed uniformly, and the effect that segregation occurs in the mixture can also be suppressed. Play. Furthermore, by adding an additive to the water-absorbent resin, for example, there is an effect that various functions according to the additive can be imparted to the water-absorbent resin.

  As described above, the method for producing a water-absorbent resin composition according to the present invention allows the water-absorbent resin and the additive to move in the static mixer by gravity and / or the pressure of the pressurizing means. While being able to move a water absorbing resin and an additive, it can also be moved at a desired speed. For this reason, when moving by gravity, transport means such as a pressurizing means for moving the water-absorbent resin and the additive are not required, and there is an effect that they can be easily mixed. Moreover, when moving by the pressure of a pressurizing means, since both are moved by applying a pressure with respect to a water absorbing resin and an additive, a moving speed can be adjusted freely. Furthermore, when moving by both the weight and the pressure of the pressurizing means, the pressure is increased in addition to the gravity. Therefore, compared with the case of moving only by the pressure of the pressurizing means, the pressure is smaller. The moving speed can be freely adjusted by pressurization. Therefore, the speed can be adjusted so that the mixed state of the water-absorbent resin and the additive becomes a desired mixed state, and the speed can be adjusted according to the type of the additive.

  As described above, the method for producing the water-absorbent resin composition according to the present invention is a water-absorbent resin having an increased cross-linking density in the vicinity of the surface because the surface of the water-absorbent resin is crosslinked using a crosslinking agent. be able to. Thereby, the liquid permeability of the water absorbent resin, the water absorption speed, the water absorption magnification under pressure, and the liquid permeability can be further improved, so that the physical properties of the water absorbent resin composition can be further improved. Play.

[Embodiment 1]
The first embodiment of the present invention will be described as follows. Note that the present invention is not limited to this. The method for producing the water-absorbent resin composition of the present invention comprises mixing a water-absorbent resin and an additive such as an inorganic powder or an organic powder using a static mixer, so that the physical properties are not lowered. This is a method for obtaining a water-absorbent resin composition mixed with the above.

  The water-absorbent resin according to the present invention is produced by crushing a hydrogel crosslinked polymer that is a precursor thereof. The hydrogel crosslinked polymer can be obtained by polymerizing an ethylenically unsaturated monomer in an aqueous solution in the presence of a trace amount of a crosslinking agent. The ethylenically unsaturated monomer used as a raw material for the hydrogel crosslinked polymer is a monomer having water solubility, and specifically, for example, (meth) acrylic acid, β-acryloyloxypropionic acid. , Maleic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, cinnamic acid, 2- (meth) acryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid, 2- (meth) acrylamide-2- Acid group-containing monomers such as methylpropanesulfonic acid, vinylsulfonic acid, styrenesulfonic acid, allylsulfonic acid, vinylphosphonic acid, 2- (meth) acryloyloxyethylphosphoric acid, (meth) acryloxyalkanesulfonic acid, and These alkali metal salts, alkaline earth metal salts, ammonium salts, alkylamine salts; N, N-di Dialkylaminoalkyl (meth) acrylates such as tilaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide and the quaternized compounds thereof (for example, alkyl Reaction products with hydride, reaction products with dialkyl sulfuric acid, etc.); dialkylaminohydroxyalkyl (meth) acrylates and their quaternized products; N-alkylvinylpyridinium halides; hydroxymethyl (meth) acrylate, 2-hydroxyethyl methacrylate , Hydroxyalkyl (meth) acrylates such as 2-hydroxypropyl (meth) acrylate; acrylamide, methacrylamide, N-ethyl (meth) acrylamide, Nn-propyl (meth) Acrylamide, N-isopropyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, alkoxy polyethylene glycol such as methoxypolyethylene glycol (meth) acrylate (Meth) acrylate, polyethylene glycol mono (meth) acrylate; vinyl pyridine, N-vinyl pyridine, N-vinyl pyrrolidone, N-acryloyl piperidine; N-vinyl acetamide; Only one kind of these ethylenically unsaturated monomers may be used, or two or more kinds may be appropriately mixed.

  Among the ethylenically unsaturated monomers exemplified above, when a monomer containing an acrylate monomer as a main component is used, the water absorption property and safety of the resulting hydrogel crosslinked polymer are further improved. Therefore, it is preferable. Here, the acrylate monomer refers to acrylic acid and / or water-soluble salts of acrylic acid.

  The water-soluble salts of acrylic acid are alkali metal salts and alkaline earths of acrylic acid having a neutralization rate in the range of 30 mol% to 100 mol%, preferably in the range of 50 mol% to 99 mol%. Metal salt, ammonium salt, hydroxyammonium salt, amine salt, alkylamine salt are shown. Of the water-soluble salts exemplified above, sodium salts and potassium salts are more preferable.

  These acrylate monomers may be used alone or in combination of two or more. In addition, the average molecular weight (degree of polymerization) of the water absorbent resin is not particularly limited.

  The above water-containing gel-like crosslinked polymer can be obtained by polymerizing the monomer composition containing the ethylenically unsaturated monomer as a main component in the presence of a crosslinking agent. The product contains other monomer (copolymerizable monomer) copolymerizable with the ethylenically unsaturated monomer to such an extent that the hydrophilicity of the resulting hydrogel crosslinked polymer is not impaired. Also good.

  Specific examples of the copolymerizable monomer include (meth) acrylic acid esters such as methyl (meth) acrylate, ethyl (meth) acrylate, and butyl (meth) acrylate; vinyl acetate, vinyl propionate, and the like. And the like. These copolymerizable monomers may be used alone or in combination of two or more.

  Examples of the crosslinking agent used in polymerizing the monomer component include a compound having a plurality of vinyl groups in the molecule; a plurality of functional groups capable of reacting with a carboxyl group or a sulfonic acid group in the molecule. And the like. These crosslinking agents may be used alone or in combination of two or more.

  Specific examples of the compound containing a plurality of vinyl groups in the molecule include N, N-methylenebis (meth) acrylamide, (poly) ethylene glycol di (meth) acrylate, and (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, N, N-diallylacrylamide, triallyl cyanurate, triallyl isocyanurate, triallyl phosphate, triary Amine, diallyloxyacetic acid, bis (N- vinylcarboxamides), such as tetraallyloxyethane, and the like.

  As a compound having a plurality of functional groups capable of reacting with a carboxyl group or a sulfonic acid group in the molecule, (poly) ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, tetraethylene glycol, 1,3-propanediol, Dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol, polypropylene glycol, (poly) glycerin, 2-butene-1,4-diol, 1,4-butanediol, 1,5-pentanediol 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,2-cyclohexanol, trimethylolpropane, diethanolamine, triethanolamine, polyoxypropylene, oxyethyleneoxypropylene block copolymer, Polyhydric alcohol compounds such as intererythritol and sorbitol; Epoxy compounds such as (poly) ethylene glycol diglycidyl ether, (poly) glycerol polyglycidyl ether, diglycerol polyglycidyl ether, (poly) propylene glycol diglycidyl ether, glycidol; ethylenediamine , Diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyamidepolyamine, polyethyleneimine and other polyvalent amine compounds, and condensates of these polyvalent amines with haloepoxy compounds; 2,4-tolylene diisocyanate, Polyvalent isocyanate compounds such as hexamethylene diisocyanate; polyvalent oxazoline compounds such as 1,2-ethylenebisoxazoline Silane coupling agents such as γ-glycidoxypropyltrimethoxysilane and γ-aminopropyltrimethoxysilane; 1,3-dioxolan-2-one, 4-methyl-1,3-dioxolan-2-one, 4 , 5-dimethyl-1,3-dioxolan-2-one, 4,4-dimethyl-1,3-dioxolan-2-one, 4-ethyl-1,3-dioxolan-2-one, 4-hydroxymethyl- 1,3-dioxolan-2-one, 1,3-dioxan-2-one, 4-methyl-1,3-dioxan-2-one, 4,6-dimethyl-1,3-dioxan-2-one, Alkylene carbonate compounds such as 1,3-dioxopan-2-one; haloepoxy compounds such as epichlorohydrin; zinc, calcium, magnesium, aluminum, iron, di Koniumu like hydroxides or chlorides, such as.

  The amount of the crosslinking agent used is not particularly limited, but is preferably in the range of 0.0001 mol% to 10 mol% with respect to the monomer component, and 0.001 mol. More preferably, it is in the range of% to 1 mol%.

  In the present invention, the method for polymerizing the above monomer components is not particularly limited, and various conventionally known polymerization methods such as bulk polymerization, precipitation polymerization, aqueous solution polymerization or reverse phase suspension polymerization are employed. be able to. Among them, aqueous polymerization using the above monomer component as an aqueous solution is preferable from the viewpoint of improving the water absorption characteristics of the water-absorbing resin to be obtained and controlling the polymerization easily.

  The above polymerization reaction can be carried out while stirring the monomer component in a kneader, or allowed to stand in a belt or box reactor for polymerization. Furthermore, when the above ethylenically unsaturated monomer is polymerized in an aqueous solution, any one of continuous polymerization or batch polymerization may be employed, and any of normal pressure, reduced pressure, and pressurized pressure may be employed. You may implement under pressure. The polymerization reaction is preferably carried out under an inert gas stream such as nitrogen, helium, argon, carbon dioxide.

  At the start of polymerization in the polymerization reaction, for example, a polymerization initiator or activation energy rays such as radiation, electron beam, ultraviolet ray, electromagnetic ray, or the like can be used. Specific examples of the polymerization initiator include inorganic compounds such as sodium persulfate, ammonium persulfate, potassium persulfate, and hydrogen peroxide; t-butyl hydroperoxide, benzoyl peroxide, cumene hydroperoxide, and the like. Organic peroxide: 2,2′-azobis (N, N′-methyleneisobutylamidine) or a salt thereof, 2,2′-azobis (2-methylpropionamidine) or a salt thereof, 4,4′-azobis-4 -Radical polymerization initiators such as azo compounds such as cyanovaleric acid;

  These polymerization initiators may be used alone or in combination of two or more. Moreover, when using a peroxide as a polymerization initiator, you may perform oxidation-reduction (redox) polymerization using reducing agents, such as a sulfite, a bisulfite, and L-ascorbic acid, for example.

  In the present invention, the water-containing gel-like cross-linked polymer obtained by polymerizing the above monomer components is particularly preferable since it can improve the water-absorbing properties of the water-absorbing resin obtained when it contains bubbles. . The water-containing gel-like crosslinked polymer containing bubbles inside can be easily obtained by polymerizing the monomer component in the presence of a crosslinking agent so as to contain bubbles.

  As such a polymerization method, a polymerization method in the presence of an azo initiator; a polymerization method using carbonates (JP-A-5-237378 and JP-A-7-185331) as a foaming agent; pentane Polymerization method in which a water-insoluble blowing agent such as trifluoroethane is dispersed in a monomer (US Pat. No. 5,328,935, US Pat. No. 5,338,766); polymerization method using a solid particulate foaming agent ( Internationally known WO96 / 17884); various conventional methods such as a method of polymerizing while dispersing an inert gas in the presence of a surfactant;

  When the monomer component is polymerized in the presence of a crosslinking agent, it is preferable to use water as a solvent. That is, it is preferable to make the monomer component and the crosslinking agent into an aqueous solution. This is to improve the water absorption characteristics of the obtained water absorbent resin and to efficiently perform foaming with the foaming agent.

  The concentration of the monomer component in the aqueous solution (hereinafter referred to as the monomer aqueous solution) is more preferably in the range of 20 wt% to 60 wt%. When the concentration of the monomer component is less than 20% by weight, the water-soluble component amount of the resulting water-absorbent resin may increase, and foaming by the foaming agent may be insufficient, thereby improving the water absorption rate. There is a risk that it will not be possible. On the other hand, when the concentration of the monomer component exceeds 60% by weight, it may be difficult to control the reaction temperature and foaming by the foaming agent.

  Moreover, water and the organic solvent soluble in water can also be used together as a solvent of monomer aqueous solution. Specific examples of the organic solvent include methyl alcohol, ethyl alcohol, acetone, dimethyl sulfoxide, ethylene glycol monomethyl ether, glycerin, (poly) ethylene glycol, (poly) propylene glycol, and alkylene carbonate. These organic solvents may be used alone or in combination of two or more.

  As the foaming agent added to the monomer aqueous solution, one that is dispersed or dissolved in the monomer aqueous solution can be used. Specific examples of the blowing agent include n-pentane, 2-methylpropane, 2,2-dimethylpropane, hexane, heptane, benzene, substituted benzene, chloromethane, chlorofluoromethane, 1,1. Volatile organic compounds that are dispersed or dissolved in the above monomer aqueous solution such as, 2-trichlorotrifluoromethane, methanol, ethanol, isopropanol, acetone, azodicarbonamide, azobisisobutyronitrile; sodium bicarbonate, ammonium carbonate, Examples thereof include carbonates such as ammonium bicarbonate, ammonium nitrite, basic magnesium carbonate, and calcium carbonate; dry ice; and acrylates of amino group-containing azo compounds. The said foaming agent may be used independently and may use 2 or more types together.

  What is necessary is just to set suitably the usage-amount of the foaming agent with respect to a monomer according to the combination of a monomer and a foaming agent, etc., and it is not specifically limited. However, it is more preferable that the amount be in the range of 0.001 to 10 parts by weight with respect to 100 parts by weight of the monomer. If the amount of the foaming agent used is outside the above range, the water-absorbing property of the resulting water-absorbent resin may be insufficient.

  The water absorbent resin according to the present invention can be obtained by crushing the water-containing gel-like crosslinked polymer. The crushing method is not particularly limited. For example, a method of crushing the hydrated gel-like crosslinked polymer using a crusher having a rotary blade; the hydrated gel-like crosslinked polymer. The method of crushing after freezing is mentioned. Moreover, as a method of crushing the hydrated gel-like crosslinked polymer using a crushing apparatus having a rotating blade, a method of crushing the hydrated gel-like crosslinked polymer by shearing with a fixed blade and a rotating blade. A method of crushing the hydrated gel-like crosslinked polymer by cutting with a cutting machine provided with a pair of rotating blades provided on different shafts and rotating while at least partially overlapping; And a method of crushing the coalescence by cutting with a cutter equipped with a rotary blade using a lubricant.

  Moreover, the crushed hydrogel crosslinked polymer can be made into a particulate water-absorbing resin through a drying and pulverization step if necessary. Examples of the drying method of the crushed hydrogel crosslinked polymer include known drying methods such as hot air drying, infrared drying, microwave drying, drum dryer drying, and azeotropic dehydration in a hydrophobic organic solvent. It can be used and is not particularly limited. The drying conditions may be appropriately set so that the solid content of the water-absorbent resin is within a desired range, preferably the water content is 10% by weight or less.

  The crushed hydrogel crosslinked polymer may be further dried, and then the particle size of the resulting water-absorbent resin may be adjusted by pulverization, granulation or classification. The weight average particle diameter of the water absorbent resin is not particularly limited, but is preferably 100 to 800 μm, more preferably 250 to 600 μm. The particle size distribution of the water-absorbent resin is preferably narrow. For example, when classification is performed using a sieve having an opening of 850 μm and a sieve of 150 μm, the ratio of the unpassed material having an opening of 850 μm is 1%. Or less, preferably 0.5% or less, more preferably 0.1% or less, and the ratio of the sieve passing material having an opening of 150 μm is 10% or less, preferably 5% or less, more preferably 3% or less, particularly Preferably it is 1% or less. Absorption performance can be further improved by adjusting the particle size of the water-absorbent resin to the above range. The water absorbent resin may have various shapes such as a spherical shape, a scale shape, an irregular crushed shape, and a granular shape.

  Various functions can be imparted to the water-absorbent resin by adding a powdery additive to the water-absorbent resin particles obtained by the above method and mixing them. The additive is not particularly limited as long as it is capable of imparting various functions to the water-absorbent resin and is in a powder form at room temperature, but is not limited to inorganic powder, organic powder, or other The water-absorbent resin particles can be used. The functions that can be imparted are, for example, fluidity, stability over time, deodorization / antibacterial properties, hydrophilicity / absorption rate, coloring, and the like. By adding and mixing additives, these functions can be newly imparted to the water-absorbent resin, or can be further improved when already having the functions. Moreover, the functional provision by the additive is achieved by the presence of the additive on the surface of the water absorbent resin.

  Specifically, the inorganic powder includes sulfur-containing inorganic compounds such as sodium sulfite and sodium hydrogen sulfite; phosphorus-based inorganic compounds such as phosphates; apatite, activated carbon, alumina, silica, zeolite, bentonite, cement, fine particle silica , Kaolin, talc, clay, diatomaceous earth, sodium carbonate, calcium carbonate, magnesium carbonate, sodium sulfate, aluminum sulfate, alum, calcium oxide, magnesium oxide, zinc oxide, titanium oxide, zinc sulfide and the like.

  Further, the organic powder specifically includes surfactants such as polyoxyethylene alkyl ether and sorbitan fatty acid ester; water-soluble polymers such as polyethylene oxide, polyacrylic acid, sodium polyacrylate, and polyvinylpyrrolidone; polyethylene; cellulose Powder; Organic acid (salt) such as L-ascorbic acid (salt), oxalic acid (salt), succinic acid (salt); Radical inhibitor such as hydroquinone and methoquinone; ethylenediaminetetraacetic acid (salt), diethylenepentaaminepentaacetic acid (Salts), chelating agents such as ethylenediamine disuccinic acid (salts); cyclodextrins; plant-derived powders such as tea leaves, bamboo powder and cypress sawdust;

  The other water absorbent resin particles are water absorbent resins different from the water absorbent resin used in the present invention. Even when such other water-absorbent resin particles are mixed, the water-absorbent resin according to the present invention can be provided with a function. Further, as the other water-absorbing resin, it is preferable to use a water-absorbing resin having physical properties and shapes different from those of the water-absorbing resin used in the present invention. For example, absorbent resins having different particle size distributions can be mixed, or a spherical water-absorbing resin obtained by reverse-phase suspension polymerization can be mixed with an irregularly crushed water-absorbing resin obtained by aqueous solution polymerization. . By adding such water-absorbing resin particles having different physical properties and shapes, bulk density, liquid permeability, and gel blocking, which have been difficult to achieve with a single water-absorbing resin, can be controlled.

  The water-absorbent resin and the additive are mixed using a static mixer. The static mixer is composed of a housing and a mixing member. This mixing member is fixed to the housing and is not driven. That is, the static mixer according to the present invention is a mixer having no drive part. As the mixing member, for example, a right element obtained by twisting a rectangular plate 180 ° in the right direction and a left element twisted 180 ° in the left direction can be arbitrarily connected. Specifically, the right element and the left element can be alternately arranged in a straight line. Further, as the mixing member, a plurality of protruding members may be used. The protruding member may be, for example, a plate shape or a rod shape. The plurality of projecting members may be arbitrarily arranged in the housing, but it is preferable to arrange the mounting angle difference between the lattice-like or projecting members to be 10 ° to 90 °.

  In addition, the static mixer has an input port for supplying water-absorbing resin and additives, and an output port for discharging the mixed mixture. By supplying the water-absorbing resin and the additive to the inlet and passing through the static mixer, both are uniformly mixed and discharged from the outlet. The supply amount of the water absorbent resin and the additive is not particularly limited. However, in order to mix the water-absorbent resin and the additive more uniformly, the supply amount may be appropriately adjusted in advance according to the type of the additive to be added. That is, when liquid-liquid, gas-solid, and liquid-gas fluids are mixed using a static mixer, it is necessary to adjust the supply amount of each fluid in order to mix uniformly. When the solid-solid is mixed as in the present invention, it can be mixed uniformly without adjusting the supply amount, and can be mixed more uniformly when the supply amount is adjusted.

  When adjusting the supply amount of the water absorbent resin and the additive, the supply amount is 25 to 100%, preferably 50 to 100%, more preferably the maximum discharge amount of the water absorbent resin composition in the static mixer. Is 70 to 100%. If the supply amount is less than 25% of the maximum discharge amount, uniform mixing becomes difficult. Further, when the supply amount exceeds 100% of the maximum discharge amount, mixing cannot be performed. The maximum discharge amount can be obtained by supplying water-absorbing resin to the static mixer under natural fall or pressure. The additive may be added to the water-absorbing resin before the water-absorbing resin is added to the static mixer. You may carry out by throwing directly into a mixer.

  The mixing ratio of the water absorbent resin and the additive is preferably such that the water absorbent resin: additive is within the range of 99.99: 0.01 to 0.01: 99.99, and 99.9: 0. More preferably, it is in the range of 1 to 0.1-99.9. When the mixing ratio of the water absorbent resin or additive is less than 0.01, it is difficult to mix the two uniformly.

  The water-absorbent resin and the additive can be mixed by placing the static mixer in a substantially vertical position so that the inlet is upward and the outlet is downward. In this case, the water-absorbent resin and the additive supplied to the charging port of the static mixer are naturally dropped by gravity inside the static mixer and discharged from the discharge port. That is, in this case, since the water-absorbing resin and the additive move due to natural fall, it is not necessary to use a transporting means (for example, a pressurizing means) for transporting the water-absorbing resin and the additive. Moreover, when it mixes by natural fall, compared with the case where it mixes using a transport means, generally the damage given to a water absorbing resin can be reduced. Note that the above-mentioned “substantially vertical” may be an angle at which all of the water-absorbing resin and additives supplied to the charging port of the static mixer can be naturally dropped by gravity and moved to the discharging port. It is more preferable that the resin is vertical so that all of the resin and the additive can move to the discharge port by natural fall.

  However, there are cases where the static mixer cannot be arranged substantially vertically due to design reasons in a manufacturing apparatus including the static mixer. Further, the speed at which the water-absorbing resin and the additive move in the static mixer is made faster or slower than the natural fall so that a mixed state of the water-absorbing resin composition having more preferable physical properties is obtained (that is, static mixing). It may be necessary to shorten or increase the residence time in the machine. In these cases, the water-absorbing resin and the additive may be mixed using a transportation means. By using the transportation means, the water absorbent resin and the additive can be transported at a desired rate.

  Therefore, when mixing using a transportation means, it may be arranged at any angle (direction), for example, it may be arranged horizontally, or it may be arranged so that the inlet is downward and the outlet is upward. You may arrange | position vertically and may arrange | position so that it may have another fixed angle. For this reason, when using it for a manufacturing apparatus etc., the freedom degree of design increases. In addition, even if it is in a state of being arranged substantially vertically so that the above-mentioned input port is upward and the discharge port is possible, if it is necessary to pass through faster than a natural drop, water absorption is performed using a transportation means. The transporting resin and additives may be transported. When transporting means is used, the damage given to the water-absorbent resin is slightly larger than when moving by natural fall, but is sufficiently reduced compared to when using a drive-type mixer. can do.

  Examples of the method of transporting using the transporting means include a method of transporting by applying pressure to the water-absorbent resin and the additive using a pressurizing means as the transporting means. Specifically, the method of pumping air can be mentioned. By pumping air from the inlet to the outlet of the static mixer, the water absorbent resin and the additive can be transported by the pressure of the air. The air pressure may be set as appropriate so that the water absorbent resin and the additive are in a desired mixed state, but can be adjusted by the air flow rate. The air flow rate can be adjusted by changing the air flow rate, and the air flow rate is preferably 1 to 40 m / s, and more preferably 5 to 20 m / s. When the air flow rate is less than 1 m / s, it becomes difficult to stably transport the water absorbent resin, and as a result, uniform mixing becomes difficult. When the air flow rate exceeds 40 m / s, the water-absorbent resin is pulverized and the object of the present invention cannot be achieved.

  As described above, the water-absorbing resin and the additive can be made uniform and homogeneous by simply dividing the water-absorbing resin and the additive through the static mixing machine by dividing, converting, or reversing the mixing member. Can be made. In addition, since the static mixer has good piston flow properties, it is possible to uniformly mix the water-absorbent resin and other additives, and also suppress segregation of the resulting mixture (water-absorbent resin composition). can do. Furthermore, since a mixing device having no drive part is used, no mechanical mixing is performed. For this reason, since it can mix without giving damage to a water absorbing resin, the water absorbing resin composition mixed uniformly can be obtained, without reducing a physical property.

  In addition, it is preferable that the weight average particle diameter of the water-absorbent resin composition obtained by the production method of the present invention is in the range of 250 μm to 600 μm. Therefore, in the production method of the present invention, classification is preferably performed so as to be within the above range. The classification may be performed so as to have the above-described preferable weight average particle diameter, and for example, it is preferable to use a sieve having an opening of 850 to 600 μm. Further, in addition to the sieve having an aperture of 850 to 600 μm, the use of a sieve having an aperture of 100 to 300 μm can remove a water absorbent resin composition having a fine particle size. As a result, a water absorbent resin composition having a narrow particle size distribution can be obtained. As means for removing the water-absorbent resin composition having a fine particle size, not only the above sieve classification but also known classification means such as airflow classification can be used. In the following, the step of adding an additive is referred to as an addition step, the step of mixing the water absorbent resin and the additive is referred to as a mixing step, and the step of performing classification is referred to as a classification step.

  Said classification process may be performed before a mixing process, and may be performed after a mixing process. Furthermore, when performing a classification process before a mixing process, a classification process may be performed before an addition process and may be performed after it. In the case where the classification step is performed before the mixing step, the additive can be mixed with the water absorbent resin classified to a desired weight average particle size, so that the mixing can be performed efficiently. In addition, when the classification step is performed after the mixing step, the water-absorbing resin and the additive can be classified in a uniformly mixed state, and the residence time of the water-absorbing resin and the additive can be increased. Can be secured. That is, in the classification step, the water-absorbing resin and the additive are stirred and mixed, so that more mixing time can be secured. As a result, it is possible to obtain a water absorbent resin composition in which additives are more uniformly mixed.

  In addition, the weight average particle diameter of the water absorbent resin or the water absorbent resin composition can be measured as follows. Screen the water-absorbent resin or water-absorbent resin composition with a JIS standard sieve (mesh size 850 μm, 710 μm, 600 μm, 500 μm, 425 μm, 300 μm, 212 μm, 150 μm, 45 μm, etc.), and plot the residual percentage R on logarithmic probability paper . By reading the particle diameter corresponding to R = 50% by weight as the weight average particle diameter (D50), the weight average particle diameter (D50) can be obtained. The sieving when measuring the weight average particle diameter (D50) is, for example, 10.0 g of a water absorbent resin or a water absorbent resin composition under conditions of room temperature (20 to 25 ° C.) and humidity of 50 RH%. A JIS standard sieve (trade name: THE IIDA TESTING SIEVE, diameter 8 cm) with a mesh size of 850 μm, 710 μm, 600 μm, 500 μm, 425 μm, 300 μm, 212 μm, 150 μm, 45 μm is charged, and a vibration classifier (trade name: IIDA SIVEVE SHAKER, : ES-65 type, SER No. 0501) and sieving for 5 minutes.

  The water-absorbent resin composition uniformly mixed in the static mixer is transported to a product hopper and then packed into a bag or the like to become a product.

[Embodiment 2]
A second embodiment of the present invention will be described. In the present embodiment, the surface of the water-absorbent resin is secondarily crosslinked in advance with a surface cross-linking agent, and then the water-absorbent resin and the additive are mixed using a static mixer. The present embodiment is mainly different from the first embodiment in whether or not the water-absorbent resin mixed with the additive is subjected to surface cross-linking in advance. Mainly explained.

  The water-absorbent resin particles obtained by the same method as in the first embodiment can be cross-linked in the vicinity of the surface of the water-absorbent resin particles by secondary cross-linking the surface with a surface cross-linking agent. . The water-absorbent resin obtained by the method of the present invention is further treated with a surface cross-linking agent to further improve the liquid permeability, water absorption rate, water absorption capacity under pressure, and liquid permeability of the water-absorbent resin. To do.

  The surface cross-linking agent may be any compound that has a plurality of reactive groups and reacts with a functional group such as a carboxyl group that the water-absorbent resin has, and generally employs a known surface cross-linking agent that is used for the application. can do. Specific examples of the surface cross-linking agent include (poly) ethylene glycol, diethylene glycol, (poly) propylene glycol, triethylene glycol, tetraethylene glycol, 1,3-propanediol, dipropylene glycol, 2, 2,4-trimethyl-1,3-pentanediol, (poly) glycerin, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2- Cyclohexanedimethanol, 1,2-cyclohexanol, trimethylolpropane, diethanolamine, triethanolamine, polyoxypropylene, oxyethylene-oxypropylene block copolymer, pentaerythritol, sorbitol, polyvinyl alcohol, gluco- Polyhydric alcohols such as mannitol, sucrose and glucose; ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, (poly) propylene glycol diglycidyl Polyvalent epoxy compounds such as ether; polyvalent amine compounds such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine and polyethyleneimine; polyvalent isocyanates such as 2,4-tolylene diisocyanate and hexamethylene diisocyanate Compound; Polyvalent oxazoline compound such as 1,2-ethylenebisoxazoline; 1,3-dioxolan-2-one, 4 Methyl-1,3-dioxolan-2-one, 4,5-dimethyl-1,3-dioxolan-2-one, 4,4-dimethyl-1,3-dioxolan-2-one, 4-ethyl-1, 3-dioxolan-2-one, 4-hydroxymethyl-1,3-dioxolan-2-one, 1,3-dioxan-2-one, 4-methyl-1,3-dioxan-2-one, 4,6 -Alkylene carbonate compounds such as dimethyl-1,3-dioxan-2-one and 1,3-dioxopan-2-one; haloepoxy compounds such as epichlorohydrin, epibromohydrin and α-methylepichlorohydrin; And polyvalent metal compounds such as hydroxides and chlorides of polyvalent metals such as zinc, calcium, magnesium, aluminum, iron and zirconium; There. These surface cross-linking agents may be used alone or in combination of two or more.

  The processing method at the time of processing a water absorbing resin using a surface crosslinking agent is not specifically limited. Specifically, for example, 1) a method in which the water-absorbing resin and the surface cross-linking agent are mixed without solvent, and 2) the water-absorbing resin is dispersed in a hydrophobic solvent such as cyclohexane or pentane, and then the surface cross-linking agent is mixed. And 3) a method in which a surface cross-linking agent is dissolved or dispersed in a hydrophilic solvent, and then this solution or dispersion is sprayed or added dropwise to a water-absorbent resin. Of the above processing methods, it is more preferable to use the method 3). As the hydrophilic solvent, water or a mixture of water and an organic solvent soluble in water is preferable.

  Thus, by introducing secondary crosslinking into the water absorbent resin using the surface cross-linking agent, the water absorption capacity under pressure of the water absorbent resin is further improved. In addition, the amount of a component that elutes into the aqueous liquid when contacted with the aqueous liquid, that is, a so-called water-soluble component can be reduced. The amount of the surface cross-linking agent used, the processing temperature, and the processing time may be appropriately set according to the type and combination of the water-absorbing resin and the surface cross-linking agent used, the desired degree of surface cross-linking, etc., and are particularly limited. It is not something.

  Moreover, in this Embodiment, in order to adjust the moisture content of the water absorbing resin after the said surface treatment, water can also be added. In this case, the amount of water added is preferably less than 5%. In addition, in order to adjust the water content of the water-absorbent resin, metal salts such as aluminum sulfate, alum, sodium chloride, sodium hydrogen sulfite and sodium phosphate; antioxidants; deodorants such as tea leaf dry-distilled products and extracts An antibacterial agent; a preservative; a fragrance; a chelating agent; and an aqueous solution of a water-soluble compound such as a surfactant.

  When the surface treatment of the water-absorbent resin is performed by the method using the hydrophilic solvent, it is common to evaporate the hydrophilic solvent by heating during or after the surface treatment. Thereby, the water absorbent resin can be dried. However, when the hydrophilic solvent is evaporated, especially when water is evaporated, the water-absorbing resins may be aggregated. This is presumed to be because water that has migrated to the surface during evaporation acts as a plasticizer for the water-absorbent resin, and as a result, the water-absorbent resins easily aggregate. When the size of these aggregates is larger than 1 mm, it is not suitable for sanitary materials such as diapers. This is because there is a risk of being stiff when worn or breaking through the top sheet of the diaper. For this reason, in order to make a water-absorbent resin into an absorptive resin composition, the water-absorbent resin containing this aggregate needs to be sized separately so as to be the water-absorbent resin of the original primary particles. In the following, the step of sizing the water absorbent resin is referred to as a sizing step.

  Although it does not specifically limit as a sizing apparatus used for the said sizing, In this Embodiment, the rotary granulator is used. Examples of the rotary sizing machine include a knife cutter sizing machine. Specifically, a new speed mill (trade name, manufactured by Okada Seiko Co., Ltd.), a flash mill (trade name; Nippodar Co., Ltd.), speed mill (trade name, manufactured by Showa Engineering Co., Ltd.) and the like.

  The rotary granulator has a rotary blade, and the water-absorbent resin receives mechanical energy due to the high-speed rotation of the rotary blade, and the aggregates of the water-absorbent resin are separated from each other to adjust the individual water absorbent resin particles. Be grained. The rotary granulator is provided with an inlet and an outlet. In the granulation step, the water-absorbing resin containing aggregates is continuously added little by little from the inlet, and the granulation is continuously performed. It is supposed to be. And the water absorbent resin obtained by sizing is discharged from the discharge port. It is more efficient to discharge the water-absorbent resin after sizing while sucking with a blower or the like.

  Moreover, it is preferable that the rotation speed of the rotary blade of the rotary sizing machine in the above sizing is in the range of 100 to 1000 rpm, and more preferably in the range of 300 to 700 rpm. When the rotational speed is less than 100 rpm, the rotational speed of the rotary blade of the rotary granulator is slow, and the aggregate of the water absorbent resin composition cannot be sized, and the water absorbent resin containing the aggregate is It is not preferable because it is simply mixed. On the other hand, when the rotational speed is higher than 1000 rpm, the rotational speed of the rotary blade of the rotary granulator is high and a large amount of fine powder is generated, which is not preferable.

  By the above sizing, the water-absorbent resin agglomerates are separated from each other and sized to the original primary water-absorbent resin particles or the water-absorbent resin particles passing through a sieve having a predetermined particle size, for example, 850 to 600 μm. .

  Even in the above sizing, all of the aggregates of the water-absorbent resin may not be sized. In this case, the agglomerated water-absorbing resin that is not sized remains. The weight average particle diameter of the sized water absorbent resin is 100 μm to 800 μm, and the preferred weight average particle diameter of the water absorbent resin composition as a product is 250 μm to 600 μm. For this reason, it is preferable to classify the water-absorbent resin after sizing. The classification may be performed so as to obtain a preferable weight average particle diameter as in the first embodiment. For example, the classification is preferably performed using a sieve having an opening of 850 to 600 μm. Further, the measurement of the weight average particle diameter may be performed in the same manner as in the first embodiment.

  By the classification, agglomerates of the water absorbent resin that have not been sized are separated and introduced again into the rotary sizing machine. Thereby, all the aggregates of the remaining water absorbent resin can be sized. Moreover, the water-absorbent resin containing the aggregate which does not pass a sieve with an opening of 850-600 micrometers can be removed by classification. The removed water-absorbing resin is again introduced into the rotary granulator by a transportation means such as a bucket conveyor, a flight conveyor, a screw conveyor, and pneumatic transportation. Moreover, in addition to the sieve of the said mesh opening 850-600 micrometers, a water absorbent resin composition with a fine particle size can be removed by using a sieve of 100-300 micrometers. As a result, a water absorbent resin composition having a narrow particle size distribution can be obtained. As means for removing the water-absorbent resin composition having a fine particle size, not only the above sieve classification but also known classification means such as airflow classification can be used.

  Then, the sized water-absorbing resin and additive, or the sized and classified water-absorbing resin and additive are mixed using a static mixer. Also in the present embodiment, the static mixer to be used, the additive to be added, the mixing conditions, and the like can be performed in the same manner as in the first embodiment. However, when a sizing step is included as in the present embodiment, the addition step of adding an additive is performed before the sizing step, during the sizing step, or after the sizing step. Just do it.

  In addition, what is necessary is just to add an additive with respect to the water absorbing resin before thrown into a rotary granulator, when performing an addition process before a granulation process. In addition, when the addition step is performed during the sizing step, when the water-absorbent resin is sized by the rotary sizing machine, the additive is added (added) directly to the rotary sizing machine. Good. Furthermore, what is necessary is just to add with respect to the water absorbing resin which passed through the granulation process (or granulation process and classification process), when performing an addition process after a granulation process. In addition, when performing a classification process after a granulation process, you may perform an addition process again, when the water absorbing resin isolate | separated by classification is re-introduced into a rotary granulator.

  Since the sizing of the water-absorbent resin is performed by the above-described rotary granulator, when the addition step is performed before the sizing step or during the sizing step, the sizing of the water-absorbing resin is performed. In this case, the water absorbent resin and the additive are mixed. That is, the sizing process and the mixing process are performed simultaneously. Then, the water absorbent resin and the additive are mixed simultaneously with the sizing of the water absorbent resin, and then further mixed in a static mixer. Therefore, the residence time for mixing the water-absorbent resin and the additive can be made longer and can be mixed more uniformly. Moreover, since the water-absorbent resin and the additive are also stirred and mixed in the above classification, it is possible to secure a longer mixing time. Therefore, when performing a classification process after a granulation process, a water absorbing resin and an additive can be mixed further more uniformly. In addition, when performing an addition process before a granulation process or during a granulation process, an additive may be crushed with a rotary granulator, and it is not necessary to crush. The additive can give various functions to the water-absorbent resin without being crushed, but when the additive is crushed, the additive becomes finer particles. The mixing property with the functional resin is increased, and the function is imparted more efficiently.

  Moreover, when performing an addition process after a sizing process, since an additive is added with respect to the water absorbing resin which passed through the sizing process (or sizing process and classification process), a weight average particle diameter is desired. The water absorbent resin having a narrow particle size distribution and an additive can be mixed.

  By the above mixing, the water absorbent resin and the additive can be uniformly mixed without deteriorating the physical properties of the water absorbent resin, and the water absorbent resin composition of the present invention can be produced. The manufactured water-absorbent resin composition is transported to a product hopper and then packed into a bag or the like to become a product.

  The production method of the water-absorbent resin composition of the present invention will be described more specifically based on the following examples and comparative examples, but the present invention is not limited to these examples. In addition, the absorption capacity under no pressure and the absorption capacity under pressure of the water absorbent resin composition (water absorbent resin when the amount of the additive is extremely small) and the absorption capacity under pressure were measured by the following methods.

[Absorption capacity of the water-absorbent resin composition under no pressure]
0.2 g (Wp1) of the water-absorbent resin composition (or water-absorbent resin) is uniformly placed in a non-woven bag (60 mm × 60 mm), and physiological saline at 23 ° C. (composition: 0.9% by weight aqueous solution of sodium chloride) ). After 60 minutes, the bag was pulled up, drained at 250 G for 3 minutes using a centrifuge, and the weight Wa (g) of the bag was measured. The same operation was performed without using the water absorbent resin composition, and the weight Wb (g) at that time was measured. And from these weights Wa and Wb,
Absorption capacity under no pressure (g / g)
= {(Weight Wa (g) -Weight Wb (g) -Weight of water-absorbent resin composition Wp1 (g)
/ Weight of water absorbent resin composition Wp1 (g)}-1
The absorption capacity (g / g) of the water-absorbent resin composition under no pressure was calculated.

[Absorption capacity under pressure of water-absorbent resin composition]
First, a measurement apparatus used for measuring the absorption capacity under pressure of a water absorbent resin composition (or water absorbent resin) will be briefly described below with reference to FIG.

  As shown in FIG. 1, the measuring apparatus includes a balance 1, a container 2 having a predetermined capacity placed on the balance 1, an outside air intake pipe 3, a conduit 4, a glass filter 6, and the glass filter 6. It consists of the measurement part 5 mounted on the top. The container 2 has an opening 2a on its top and an opening 2b on its side, and an outside air suction pipe 3 is fitted into the opening 2a, while a conduit 4 is attached to the opening 2b. It has been.

  The container 2 contains a predetermined amount of physiological saline 12 (the composition is referred to as “absorption capacity under non-pressure of the water-absorbent resin composition”), and the lower end portion of the outside air suction pipe 3 is the physiological saline. Submerged in water 12. The glass filter 6 is formed with a diameter of 70 mm, and the container 2 and the glass filter 6 communicate with each other by a conduit 4. Further, the upper part of the glass filter 6 is fixed so as to be positioned slightly higher than the lower end of the outside air suction pipe 3.

  The measurement unit 5 includes a filter paper 7, a support cylinder 8, a wire mesh 9 attached to the bottom of the support cylinder 8, and a weight 10. The measuring unit 5 has a filter paper 7 and a support cylinder 8 (that is, a wire mesh 9) placed on the glass filter 6 in this order, and a weight 10 is placed inside the support cylinder 8, that is, on the wire mesh 9. It has become. The support cylinder 8 has an inner diameter of 60 mm. The metal mesh 9 is made of stainless steel and has a mesh size of 400 (mesh size: 38 μm). A predetermined amount of the water-absorbent resin composition 11 is uniformly distributed on the wire mesh 9. The weight of the weight 10 is adjusted so that a load of 4.83 kPa (0.7 psi) can be uniformly applied to the wire mesh 9, that is, the water absorbent resin composition 11.

  The absorption capacity under pressure of the water absorbent resin composition 11 was measured using the measuring apparatus having the above-described configuration. The measurement method will be described below.

  First, a predetermined preparatory operation such as putting a predetermined amount of physiological saline 12 into the container 2 and inserting the outside air suction pipe 3 into the container 2 was performed. Next, the filter paper 7 was placed on the glass filter 6. On the other hand, in parallel with these placing operations, 0.44 g (Wp2) of the water absorbent resin composition 11 is uniformly distributed inside the support cylinder 8, that is, on the wire mesh 9, and the weight is placed on the water absorbent resin composition 11. 10 was placed.

Next, the weight Wc (g) of the physiological saline 12 absorbed by the water absorbent resin composition 11 over 30 minutes from the time when the support cylinder 8 was placed on the filter paper 7 was measured using the balance 1. From these weights Wp2 · Wc,
Absorption capacity under pressure (g / g) = weight Wc (g) / weight of water-absorbent resin composition Wp2 (g)
Thus, the absorption capacity (g / g) under pressure 30 minutes after the start of absorption was calculated.

[Example 1]
In a kneader equipped with two sigma blades, an aqueous monomer solution having a monomer concentration of 38 wt% and a neutralization rate of 75 mol% was prepared. In this monomer aqueous solution, polyethylene glycol diacrylate (average number of ethylene glycol units: 9) was dissolved as an internal crosslinking agent so as to be 0.03 mol% (with respect to the monomer).

  Subsequently, nitrogen gas was blown into the monomer aqueous solution to reduce dissolved oxygen in the monomer aqueous solution, and the entire reaction vessel was purged with nitrogen. Subsequently, the temperature of the aqueous monomer solution was adjusted to 22 ° C. while rotating two sigma blades, and then 0.12 g / mol of sodium persulfate (as a monomer) and 0.005 g of L-ascorbic acid as a polymerization initiator. / Mol (vs. monomer) was added.

  The polymerization started immediately and the aqueous monomer solution became cloudy, so the rotation of the blade was stopped. After the polymerization temperature reached 50 ° C., the blade was rotated again, and polymerization was continued with stirring in a kneader. After about 50 minutes, a hydrogel polymer having a weight average particle diameter of about 2 mm was obtained.

  The obtained hydrogel polymer was dried in a hot air dryer at 170 ° C. for about 60 minutes. Next, the dried product was pulverized with a roll mill pulverizer and classified with a sieve having an opening of 850 μm and 180 μm to obtain a water absorbent resin having a water content of 3% by weight and a weight average particle diameter of 400 μm. The obtained water-absorbent resin contained 1% by weight of fine particles of 150 μm.

  A continuous high-speed stirring mixer (100 parts by weight of a water absorbent resin and 3.23 parts by weight of a surface cross-linking agent composed of ethylene glycol diglycidyl ether: propylene glycol: water = 0.03: 0.5: 2.7) (Trade name: Turbulizer, manufactured by Hosokawa Micron Co., Ltd.).

  A mixture of a water-absorbent resin and a surface cross-linking agent is mixed into a biaxial stirring dryer (trade name: paddle dryer, Nara Machinery Co., Ltd.) The average residence time was 60 minutes. Subsequently, the inner wall, the stirring board, and the rotating shaft were cooled with a biaxial stirring dryer in which water of 35 ° C. was passed (average residence time 30 minutes) to obtain a surface-crosslinked water-absorbing resin.

  The surface-crosslinked water-absorbent resin after cooling was sieved with a 850 μm sieve. Aggregates that did not pass through the 850 μm sieve were crushed with a crusher and then sieved again with an 850 μm sieve. Then, 0.8 parts by weight of aluminum sulfate 14-18 hydrate was added to 100 parts by weight of the surface-crosslinked water-absorbing resin that passed through a 850 μm sieve, and a static mixer (11 / 2-N33-131- P (trade name), manufactured by Noritake Co., Ltd.) to obtain an absorbent resin composition of the present invention. The maximum discharge amount of the water-absorbent resin in the static mixer was 233 kg / h, the water-absorbent resin supply amount was 150 kg / h, and the aluminum sulfate 14-18 hydrate supply amount was 1.2 kg / h. .

  The physical properties of the obtained water absorbent resin composition were measured at five points. The results are shown in Table 1. As shown in Table 1, the physical properties of the water absorbent resin composition were stable.

〔比較例１〕
実施例１において得られた、８５０μｍの篩いを通過した表面架橋された吸収性樹脂１００重量部に対して、硫酸アルミニウム１４−１８水和物０．８重量部を、円錐型スクリュー混合機にて１５分間混合して、比較吸収性樹脂組成物を得た。得られた比較吸水性樹脂組成物の物性を５点測定した。その結果を表２に示す。

[Comparative Example 1]
For 100 parts by weight of the surface-crosslinked absorbent resin obtained in Example 1 and passed through a 850 μm sieve, 0.8 part by weight of aluminum sulfate 14-18 hydrate was added using a conical screw mixer. By mixing for 15 minutes, a comparative absorbent resin composition was obtained. The physical properties of the obtained comparative water absorbent resin composition were measured at five points. The results are shown in Table 2.

〔実施例２〕
実施例１において、硫酸アルミニウム１４−１８水和物に代えてセルロースパウダー（商品名：ＫＣフロック、日本製紙株式会社製）１重量部を混合した他は、実施例１と同様にして本発明の吸水性樹脂組成物を得た。なお、吸収性樹脂の供給量は１５０ｋｇ／ｈであり、セルロースパウダーの供給量は１．８ｋｇ／ｈであった。

[Example 2]
In Example 1, in place of aluminum sulfate 14-18 hydrate, 1 part by weight of cellulose powder (trade name: KC Flock, manufactured by Nippon Paper Industries Co., Ltd.) was mixed. A water absorbent resin composition was obtained. The supply amount of the absorbent resin was 150 kg / h, and the supply amount of the cellulose powder was 1.8 kg / h.

  The resulting water-absorbent resin composition had an absorption capacity without pressure of 36 (g / g), an absorption capacity under pressure of 25 (g / g), and an absorption rate (measured according to JIS K7224) of 55 seconds.

  The manufacturing method according to the present invention as described above is a method of mixing solids, which suppresses a decrease in physical properties and enables uniform mixing. Can be widely applied. In addition, the water-absorbent resin composition obtained by the production method according to the present invention has excellent water-absorbing performance, for example, sanitary materials (body fluids) such as paper diapers, sanitary napkins, incontinence pads, wound protection materials, and wound healing materials. Absorbing articles); Absorbing articles such as urine for pets; Construction materials such as water retaining materials for soil, water-stopping materials, packing materials, gel water sacs; foods such as drip absorbents, freshness-keeping materials, and cold insulation materials Articles for industrial use; various industrial articles such as oil-water separators, anti-condensation agents, coagulants, etc .; agricultural and horticultural articles such as water-retaining materials such as plants and soils.

It is a schematic sectional drawing which shows the structure of the measuring apparatus which measures the absorption capacity under pressure used in the Example of this invention.

Claims (3)

A method for producing a water absorbent resin composition comprising adding an additive to a water absorbent resin and mixing the water absorbent resin and the additive,
The method for producing a water-absorbent resin composition, wherein the water-absorbent resin and the additive are mixed using a static mixer.   The method for producing a water-absorbent resin composition according to claim 1, wherein the water-absorbent resin and the additive move in the static mixer by gravity and / or pressure of a pressurizing means.   The method for producing a water absorbent resin composition according to claim 1, wherein the surface of the water absorbent resin is crosslinked using a crosslinking agent.

Images