JP3415036B2 - Method for granulating hydrogel crosslinked polymer - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for atomizing a hydrous gel-like crosslinked polymer, such as pulverizing a hydrous gel-like crosslinked polymer which is preferably used as a material for a water absorbent resin.

[0002]

2. Description of the Related Art A water-containing gel-like cross-linked polymer is obtained as a hydrophilic and water-absorbing cross-linked polymer by polymerizing a water-soluble ethylenically unsaturated monomer in an aqueous solution in the presence of a trace amount of a cross-linking agent. It is well known that

The above-mentioned hydrogel crosslinked polymer (hereinafter, simply referred to as hydrogel) is a semisolid, highly elastic gel, which is rarely used as it is, and in many cases, improves the drying efficiency. For this purpose, one end is pulverized by pulverization or the like, then dried, and further pulverized appropriately. After that, the hydrous gel in a dry powder state is used in various applications as a resin having hydrophilicity and water absorption, that is, a water absorption resin.

Conventionally, as a method for making the hydrous gel finer, for example, a method in which the hydrous gel after polymerization is pulverized by a screw type extruder such as a meat chopper is used.

As a technique for pulverizing a hydrous gel using the above-mentioned screw type extruder, there is a method for producing a water-absorbent resin disclosed in JP-A-5-70597.
In this method, a hydrous gel is heated at a temperature of 45 ° C. to 90 ° C. and extruded from a screw type extruder equipped with a perforated plate having pores with a pore diameter of 6.5 mm to 18 mm, and then the extruded hydrous gel is roll-milled. It is crushed and finely crushed with a stick.

In the above method, the average gel particle size is 0.5 mm.
Within the range of ˜3 mm, a particulate hydrogel having a narrow particle size distribution can be obtained. Therefore, the drying efficiency is significantly improved, and a water absorbent resin having a remarkably small amount of residual monomer can be obtained with high productivity.

[0007]

Here, when the hydrogel is made into fine particles, it is preferable that mechanical external force does not act as much as possible. This is because the cross-linked polymer chains in the hydrous gel may be broken by mechanical external force, and the water-soluble component amount of the finally obtained water-absorbent resin may increase.

However, in the method of the above-mentioned Japanese Patent Laid-Open No. 5-70597, the hydrous gel is very likely to stay in the casing during extrusion from the screw type extruder, which is carried out when the hydrous gel is made into fine particles (grinding treatment). Become. Therefore, the mechanical external force excessively acts on the hydrogel along with the rotation of the screw, which causes a problem that the hydrogel is kneaded.

The present invention has been made in view of the above problems, and an object thereof is to treat a water-containing gel-like cross-linked polymer in a pulverization process of the water-containing gel-like cross-linked polymer using a screw type extruder. An object of the present invention is to provide a finely pulverizing method capable of performing uniform pulverization with almost no mechanical external force applied.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems, and as a result, in the vicinity of the extrusion port of a screw type extruder, hydrous gel-like cross-linking was formed in the casing of the extruder. It has been found that the water-containing gel-like cross-linked polymer can be satisfactorily extruded and pulverized by applying a structure for preventing the polymer from reversing, with almost no mechanical external force applied.

The inventors of the present invention also filled the casing of a screw type extruder with as many hydrogel-like crosslinked polymers as possible and pulverized them to carry out a pulverization treatment, thereby giving almost no hydrous force. The inventors have found that the gelled crosslinked polymer can be satisfactorily extruded and crushed, and have completed the present invention.

That is, in order to solve the above problems, the method for finely granulating a water-containing gel-like crosslinked polymer according to the present invention uses a screw containing a water-containing gel-like crosslinked polymer (hereinafter, appropriately abbreviated as a water-containing gel). In the method for atomizing a hydrogel-like crosslinked polymer, which is supplied from a supply port of a type extruder and extruded from an extrusion port provided with a porous plate, the hydrogel-type crosslinked polymer is used as the screw type extruder. It is characterized by using a member provided with a reversion prevention member for preventing reversion to the supply port side at least in the vicinity of the extrusion port.

In the above method, since the screw type extruder used is provided with the reversion preventing member, the water-containing gel does not revert to the supply port side and is smoothly extruded from the extrusion port.
Therefore, the hydrous gel does not stay in the casing of the screw type extruder, and it is possible to prevent the hydrous gel from being kneaded by applying a mechanical external force. as a result,
The hydrogel can be easily made into fine particles without deteriorating the physical properties.

Moreover, the fact that the hydrous gel does not stay in the screw type extruder means that the hydrous gel introduced is promptly extruded from the extrusion port. for that reason,
It is also possible to improve the efficiency of atomizing the hydrous gel. That is, it is possible to greatly improve the treatment amount for making the hydrogel finer.

It is preferable that the reversion preventing member is a band-shaped projection formed in a spiral shape or a concentric shape in the casing of the screw type extruder.

If the reversion preventing member has the above-mentioned structure, it is possible to effectively prevent the water-containing gel from reversing without hindering the rotation of the screw in the casing. Further, it is possible to avoid complication of the structure of the screw type extruder.

In the method for finely granulating a hydrogel-like crosslinked polymer according to the present invention, the hydrated gel-like crosslinked polymer is completely filled in the casing of the screw type extruder at the time of pulverization treatment using the screw type extruder. When the processing amount per unit time in the case of performing the pulverization process is A, and the supply amount of the hydrogel crosslinked polymer supplied in the state where the screw rotates at the same rotation speed as this time is B It is preferable that the filling factor C defined by the following equation, C = (B / A) × 100, be within the range of 30% to 100%.

According to the above method, it is possible to avoid applying an unnecessary force to the rotation of the screw rotating in the screw type extruder. Therefore, during the pulverization treatment, the hydrous gel is not kneaded by applying a mechanical external force, and the physical properties of the hydrous gel are not deteriorated, and the granules can be more finely pulverized.

In the crushing treatment, the filling rate C is set within the range of 30% to 100% depending on the amount of the hydrogel crosslinked polymer fed to the screw type extruder. It is preferable to change the rotation speed of the screw.

According to the above method, the screw rotates so as to correspond to the amount of the hydrogel present in the casing of the screw type extruder. As a result, no excessive mechanical external force is applied to the hydrous gel due to the excessive number of rotations, and it is possible to more reliably prevent the hydrous gel from being kneaded.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The method for atomizing a hydrogel crosslinked polymer according to the present invention will be described in detail below with reference to FIGS. 1 to 5, but the present invention is not limited thereto. . The hydrogel-like crosslinked polymer to be finely granulated in the present invention is preferably used as a water absorbent resin, for example, and an ethylenically unsaturated monomer is polymerized in an aqueous solution so as to form a crosslinked structure. It is obtained by

The ethylenically unsaturated monomer used as a raw material for the hydrogel crosslinked polymer is a water-soluble monomer, and specific examples thereof include (meth) acrylic acid and β-acryloyl. Oxypropionic acid, maleic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, cinnamic acid, 2- (meth) acryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid,
Acid group-containing monomers such as 2- (meth) acrylamido-2-methylpropanesulfonic acid, vinylsulfonic acid, styrenesulfonic acid, allylsulfonic acid, vinylphosphonic acid, and 2- (meth) acryloyloxyethylphosphoric acid, and These alkali metal salts, alkaline earth metal salts, ammonium salts, alkylamine salts; N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-dimethylaminopropyl Dialkylaminoalkyl (meth) acrylates such as (meth) acrylamide and their quaternary compounds (for example, reaction products with alkyl hydride,
Reaction products with dialkyl sulfuric acid, etc.); N-alkylvinylpyridinium halides; hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl (meth) acrylate; acrylamide, methacrylamide, N-ethyl (meth ) Acrylamide, N-n-propyl (meth) acrylamide, N-isopropyl (meth) acrylamide,
N, N-dimethyl (meth) acrylamide; alkoxy polyethylene glycol (meth) acrylate such as methoxy polyethylene glycol (meth) acrylate,
Polyethylene glycol mono (meth) acrylate; vinyl pyridine, N-vinyl pyridine, N-vinyl pyrrolidone, N-acryloyl piperidine; N-vinyl acetamide; and the like. These ethylenically unsaturated monomers may be used alone or in a suitable mixture of two or more kinds.

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

The water-soluble salts of acrylic acid have a neutralization ratio in the range of 30 mol% to 100 mol%, preferably 5%.
The alkali metal salt, the alkaline earth metal salt, the ammonium salt, the hydroxyammonium salt, the amine salt, and the alkylamine salt of acrylic acid in the range of 0 mol% to 99 mol% are shown. Among the water-soluble salts exemplified above, sodium salt and potassium salt are more preferable.

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

The above hydrogel crosslinked polymer can be obtained by polymerizing a monomer composition containing the above ethylenically unsaturated monomer as a main component in the presence of a crosslinking agent. The monomer composition contains another monomer (copolymerizable monomer) copolymerizable with the above ethylenically unsaturated monomer to such an extent that the hydrophilicity of the resulting hydrogel crosslinked polymer is not impaired. You can leave.

Specific examples of the above-mentioned copolymerizable monomer include (meth) acrylic acid esters such as methyl (meth) acrylate, ethyl (meth) acrylate and butyl (meth) acrylate; vinyl acetate and propion. Hydrophobic monomers such as vinylate; and the like. These copolymerizable monomers may be used alone,
Further, two or more kinds may be appropriately mixed and used.

The cross-linking agent used when polymerizing the above-mentioned monomer components is, for example, a compound having a plurality of vinyl groups in the molecule; a functional group capable of reacting with a carboxyl group or a sulfonic acid group in the molecule. Compounds containing a plurality of groups; and the like. These cross-linking 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-diallyl acrylamide,
Examples thereof include triallyl cyanurate, triallyl isocyanurate, triallyl phosphate, triallylamine, diallyloxyacetic acid, N-methyl-N-vinylacrylamide, bis (N-vinylcarboxylic acid amide), and tetraallyloxyethane.

Examples of the compound having a plurality of functional groups capable of reacting with a carboxyl group or a sulfonic acid group in the molecule include (poly) ethylene glycol, (poly) propylene glycol, 1,3-propanediol, 2,2,2. 4-
Trimethyl-1,3-pentanediol, (poly) glycerin, 2-butene-1,4-diol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexane Dimethanol,
Polyhydric alcohol compounds such as trimethylolpropane, diethanolamine, triethanolamine, pentaerythritol, sorbitol; (poly) ethylene glycol diglycidyl ether, (poly) glycerol polyglycidyl ether, diglycerol polyglycidyl ether, (poly) propylene glycol di Epoxy compounds such as glycidyl ether and glycidol; polyvalent amine compounds such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyamide polyamine and polyethyleneimine, and condensation of these polyvalent amines with haloepoxy compounds Polyisocyanates such as 2,4-tolylene diisocyanate and hexamethylene diisocyanate Compounds; 1,2-ethylene bisoxazoline polyvalent oxazoline compounds such as; .gamma.-glycidoxypropyltrimethoxysilane, silane coupling agents such as .gamma.-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-dioxolane-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, 1,3-dioxopan-2-one and other alkylene carbonate compounds; such as epichlorohydrin Haloepoxy compounds; hydroxides or chlorides of zinc, calcium, magnesium, aluminum, iron, zirconium and the like can be mentioned.

The amount of the above-mentioned cross-linking agent used is not particularly limited, but it is 0.
It is preferably in the range of 0001 mol% to 10 mol%, and more preferably in the range of 0.001 mol% to 1 mol%.

In the present invention, the method for polymerizing the above-mentioned 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 used. Can be adopted. Among them, aqueous solution polymerization in which the above-mentioned monomer component is used as an aqueous solution is preferable from the viewpoint of improving the water absorption property of the resulting water-absorbent resin and facilitating the control of polymerization.

During the above-mentioned polymerization reaction, it is preferable to allow the monomer components to stand and polymerize without stirring. Further, in the aqueous solution polymerization of the above ethylenically unsaturated monomer, any method of continuous polymerization or batch polymerization may be adopted, and any of normal pressure, reduced pressure and increased pressure may be used. It may be carried out under pressure. The polymerization reaction is preferably carried out in a stream of an inert gas such as nitrogen, helium, argon or carbon dioxide.

At the initiation of polymerization in the above-mentioned polymerization reaction, for example, a polymerization initiator or activation energy rays such as radiation, electron rays, ultraviolet rays and electromagnetic rays 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, 2,2'-azobis (2 -Amidinopropane) or a salt thereof, 4,4'-azobis-
Radical polymerization initiators such as azo compounds such as 4-cyanovaleric acid;

These polymerization initiators may be used alone or in combination of two or more kinds. When a peroxide is used as the polymerization initiator, redox polymerization may be performed by using a reducing agent such as sulfite, bisulfite, and L-ascorbic acid (salt) together. .

In the present invention, the water-containing gel-like crosslinked polymer obtained by polymerizing the above-mentioned monomer components can improve the water-absorbing property of the water-absorbent resin obtained by containing bubbles therein. Therefore, it is particularly preferable. The hydrogel-like crosslinked polymer containing bubbles therein can be easily obtained by polymerizing the above-mentioned monomer component in the presence of a crosslinking agent so as to contain bubbles. Examples of such a polymerization method include a polymerization method in the presence of an azo initiator; a carbonate as a foaming agent (JP-A-5-237378, JP-A-7-
No. 185331); a polymerization method in which a water-insoluble foaming agent such as pentane or trifluoroethane is dispersed in a monomer (US Pat. No. 5,328,935).
JP, US Pat. No. 5,338,766); Polymerization method using solid fine particle foaming agent (International Publication WO96 / 17).
No. 884); a method of polymerizing while dispersing an inert gas in the presence of a surfactant; and various conventionally known methods can be employed.

When the above monomer component is polymerized in the presence of a crosslinking agent, water is preferably used as a solvent. That is, it is preferable that the monomer component and the crosslinking agent be an aqueous solution. This is to improve the water absorption properties of the resulting water absorbent resin and to efficiently perform foaming with the foaming agent.

The above aqueous solution (hereinafter referred to as "monomer aqueous solution")
The concentration of the monomer component therein is more preferably in the range of 20% by weight to 60% by weight. When the concentration of the monomer component is less than 20% by weight, the amount of the water-soluble component of the resulting water-absorbent resin may increase and the foaming agent may cause insufficient foaming to improve the water absorption rate. You may not be able to. 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.

Further, water is used as a solvent for the aqueous monomer solution,
A water-soluble organic solvent can also be used in combination. Specific examples of the organic solvent include methyl alcohol, ethyl alcohol, acetone, dimethyl sulfoxide, ethylene glycol monomethyl ether, and the like. These organic solvents may be used alone or in combination of two or more.

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

The amount of the foaming agent used with respect to the monomer may be appropriately set depending on the combination of the monomer and the foaming agent and is not particularly limited. However, it is more preferably within 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 out of the above range, the water-absorbent resin obtained may have insufficient water absorbing properties.

The water content of the hydrogel obtained as described above is generally in the range of 10 to 90% by weight, preferably 20 to 80% by weight. Water content is 10% by weight
If it is less than the range, it may be difficult to pulverize the hydrous gel, or in the case of a hydrous gel containing bubbles, the bubbles may be crushed. When the water content is higher than 90% by weight, it takes too long to dry after pulverization.

The above-mentioned hydrogel can be made into a water-absorbent resin by making it into a particulate hydrogel obtained by crushing to a predetermined size (hereinafter referred to as a fine-grain hydrogel) and then drying. At the time of the above-mentioned granulation, the hydrogel must be crushed so that it is uniform and cannot be kneaded. This is because the physical properties of the resulting water absorbent resin will be reduced.

Specifically, when the hydrous gel is not uniformly pulverized, the particle size distribution of the particles of the finely granulated hydrous gel is widened, and the hydrous gel cannot be dried uniformly, so that undried substances are generated. Invite. Since this undried material has a very large adhesive force, it adheres to the inside of the crusher in the crushing step after drying and hinders crushing. Further, if the undried product is mixed with the water absorbent resin as the final product, the physical properties of the water absorbent resin will be deteriorated.

Further, if the hydrous gel is kneaded in the crushing process, the cross-linked chains of the hydrous gel will be broken, resulting in an increase in the amount of soluble components and deteriorating the physical properties of the water absorbent resin as the final product. When the hydrogel has bubbles, the bubbles are kneaded in the crushing process, which also deteriorates the physical properties of the water absorbent resin.

Therefore, it is necessary to uniformly pulverize the hydrous gel so that the particle size distribution becomes sharp and prevent the hydrous gel from being kneaded during the pulverization. In order to perform such pulverization of the hydrous gel, the present invention uses a screw type extruder having a reversion preventing member at least near the extrusion port.

The above-mentioned screw type extruder used in the present invention is provided with a reversion preventing member at least in the vicinity of the extrusion port, and is particularly preferable as long as it has a rotating uniaxial or multiaxial screw in a cylindrical casing. It is not limited. As the screw type extruder, for example, as shown in FIG. 1, a casing 11, a base 12, a screw 13, a supply port 14, a hopper 15, an extrusion port 16,
It is possible to preferably use a structure having a porous plate 17, a rotary blade 18, a ring 19, a backward movement preventing member 20, a motor 21, a streak 22, and the like.

The casing 11 has a cylindrical shape, and a screw 13 is arranged inside the casing 11 along the longitudinal direction of the casing 11. Cylindrical casing 11
An extrusion port 16 for extruding and crushing the hydrous gel is provided at one end of the
A motor 21 and a drive system for rotating the screw 13 are provided. Below the casing 11 is a table 1
2 is provided so that the screw type extruder can be stably placed on the floor. On the other hand, above the casing 11, a supply port 14 for supplying the hydrous gel is provided, and preferably, a hopper 15 for facilitating the supply of the hydrogel is provided.

The shape and size of the casing 11 are not particularly limited as long as it has a cylindrical inner surface corresponding to the shape of the screw 13. The number of revolutions of the screw 13 is not particularly limited because it varies depending on the shape of the screw type extruder, but as will be described later, the number of rotations of the screw 13 depends on the supply amount of the hydrogel.
It is preferable to change the number of rotations.

The rotation direction of the screw 13 is not particularly limited. In the present invention, the motor 21
The screw 13 is configured to rotate clockwise when viewed from the end on the side connected with.

The extrusion port 16 is shown in FIGS.
A perforated plate 17 having a plurality of holes 17a is arranged as shown in FIG. The perforated plate 17 is detachably fixed to the extrusion port 16 by a ring 19. This is because the size of the particles of the fine hydrous gel is determined by the diameter of the holes 17a of the perforated plate 17. Therefore, in order to control the size of the particles of the hydrous gel, the perforated plate 1 having different diameters of the holes 17a is used.
This is because it becomes necessary to replace 7 as appropriate.

The perforated plate 17 has a thickness of 1 mm to 20 mm.
Within the range of. The diameter of the plurality of holes 17a ...
It is preferably in the range of 8 mm to 28 mm and 5 m
More preferably, it is in the range of m to 24 mm. Hole 1
If the diameter of 7a is within the above range, excessive external mechanical force will not be applied to the hydrogel during extrusion,
The hydrogel can be satisfactorily granulated.

Conventionally, when the hydrous gel is extruded by a screw type extruder, the diameter of the holes of the perforated plate is 6.5.
It has been preferred to be in the range of mm-18 mm. This is because in the screw type extruder not equipped with the reversion preventing member, if the diameter of the hole is out of the above range, the hydrous gel cannot be finely pulverized.

Specifically, in the past, if the pore diameter was smaller than the above range, a very large force was required to push out the hydrogel from the perforated plate, and the hydrogel was kneaded in the casing to improve the physical properties. Productivity declines as it declines.
On the other hand, when the diameter of the pores is larger than the above range, the size of the particles of the obtained hydrous gel is not uniform, the drying after the granulation is not performed uniformly in the production of the water absorbent resin,
This will reduce the physical properties of the water absorbent resin.

On the other hand, in the method of atomizing the hydrogel crosslinked polymer according to the present invention, since the reversion preventing member 20 is provided in the vicinity of the porous plate 17, that is, the extrusion port 16, the diameter of the hole 17a. Even if the value is small, the hydrogel does not revert. Therefore, the water-containing gel is extruded smoothly, and the productivity is not lowered. Also, hole 1
Even if the diameter of 7a is large, more uniform and efficient pulverization is possible.

The aperture ratio of the porous plate 17 is preferably 25% or more, more preferably in the range of 30% to 40%, particularly preferably about 35%. When the opening ratio is less than 25%, the hydrogel is less likely to be extruded and the productivity is reduced. Further, since the hydrous gel is less likely to be extruded, the hydrous gel may be excessively finely crushed at the pressure-feeding portion to the porous plate 17, which is not preferable. The above-mentioned opening ratio means the perforated plate 17
Indicates the ratio of the total area of all the holes 17a to the total area of.

Although the end of the screw 13 on the side not connected to the motor 21 is close to the extrusion port 16, a perforated plate is provided between the perforated plate 17 and the end of the screw 13. The rotary blade 18 is arranged so as to operate substantially in contact with the surface of 17. The rotary blade 18
Although the structure is not particularly limited, for example, a cross-shaped structure as shown in FIG. 3 can be preferably used.

The rotating direction of the rotary blade 18 is not particularly limited. In the present invention, the rotary blade 18 is adapted to rotate in the same direction as the rotation direction of the screw 13. Moreover, the number of rotations of the rotary blade 18 is not particularly limited.

In the present invention, the hydrous gel is conveyed to the extrusion port 16 side by the screw 13 and pulverized by being extruded from the perforated plate 17 provided in the extrusion port 16, but the rotary blade 18 is used. As a result, the size of the particles of the finely granulated hydrous gel can be made smaller and the particle size can be made uniform.

The screw type extruder used in the present invention is provided with a reversion preventing member 20 for preventing the water-containing gel from returning to the supply port 14 side, at least in the vicinity of the extrusion port 16.

The structure of the above-mentioned reversion preventing member 20 is not particularly limited as long as it can suppress the reversion of the water-containing gel at least in the vicinity of the extrusion port 16. For example, a spiral-shaped or concentric-circular strip-shaped projection, the screw 13 is provided. And parallel to the traveling direction of the, the granular, spherical or angular projections.

When the hydrogel is crushed by the screw type extruder having the perforated plate 17, the hydrogel is extruded through the small holes 17a provided in the perforated plate 17. Therefore, the pressure in the vicinity of the extrusion port 16 becomes high, and the hydrous gel tends to return toward the supply port 14. According to the present invention, the protrusions having the above-described shapes are provided as the reversion preventing member 20, whereby the rehydration of the hydrous gel is prevented and the hydrous gel is made finer.

Among the projections of the above-described shapes, the reversion preventing member 20 has a belt-shaped projection 20a formed in a spiral shape in the casing 11 as shown in FIG. 1, FIG. 4 and FIG. 1 and FIG. 4) or a band-shaped protrusion 20b formed in a concentric shape (see FIG. 5).
Is preferred.

If the above-mentioned reversion preventing member 20 has such band-like projections 20a and 20b, it is possible to effectively prevent the reversion of the hydrous gel without hindering the rotation of the screw 13 in the casing 11. Further, it is possible to avoid complication of the structure of the screw type extruder. Further, since the strip-shaped projections 20a and 20b are arranged so as to be in harmony with the rotating spiral formed on the screw 13, no unnecessary friction is generated when the hydrous gel is pushed out by the rotation of the screw 13, and the hydrous The gel can be extruded smoothly and efficiently.

In particular, some of the hydrogels used for the water-absorbent resin have a very high adhesiveness, but in the method of finely granulating the hydrogel-like crosslinked polymer according to the present invention, the screw type extruder is used for the above-mentioned strip-shaped projections. Since the water-containing gel is provided, the water-containing gel will not be kneaded and adhered to the inside of the casing 11 when the water-containing gel is extruded. therefore,
Even if the water-containing gel is pulverized, the temperature of the water-containing gel is not increased and the physical properties of the water-containing gel are not deteriorated, and the water-containing gel can be efficiently ground.

As shown in FIG. 1, the strip-shaped projections 20a and 20b are provided at least in the extrusion port 1 of the casing 11.
It is necessary to be provided in the vicinity of 6 (in FIG. 1, the strip-shaped projection 20a is taken as an example), but it may be provided on the entire inner surface of the casing 11. The band-shaped projections 20a / 20
Since b is provided in the vicinity of the extrusion port 16, the extrusion port 1
The return of the hydrous gel can be prevented in the vicinity of 6, but if the strip-shaped projections 20a and 20b are provided on the entire inner surface of the casing 11, the reversion of the hydrous gel can be avoided at all parts in the casing 11, and the water-containing gel is mechanical It is possible to effectively avoid applying external force.

On the inner surface of the casing 11 where the strip-shaped projections 20a and 20b are not provided, for example, streak-shaped projections 22 parallel to the axial direction of the screw 13 as shown in FIG. 1 may be provided. In addition, the streak 22 as described above
It may be a smooth surface not provided. The streak 22
Specific examples thereof include a structure formed on the inner surface of the casing of a screw type extruder used in a conventional granulation method. Furthermore, this streak 22
Also, when it is provided in the vicinity of the extrusion port 16, it can function as the reversion preventing member 20.

The gap between the band-shaped projections 20a and 20b and the screw 13 is preferably within the range of 0.1 mm to 5 mm. If it is less than 0.1 mm, the band-shaped protrusion 20
It is not preferable because the a and 20b hinder the rotation of the screw 13. On the other hand, if it exceeds 5 mm, the band-shaped projections 20a and 20b do not function as the reversion preventing member 20, which is not preferable.

The finely granulated hydrous gel obtained by pulverizing with the above-mentioned screw type extruder has a sharp particle size distribution and is of good quality with no extra mechanical external force applied during pulverization. Here, the average particle size of the finely granulated hydrous gel is preferably in the range of 0.5 mm to 3 mm, more preferably in the range of 0.5 mm to 2 mm, and if the hydrous gel is hard, 1 mm to 2 mm The range of is particularly preferable.

The smaller the particle size of the finely granulated hydrogel is, the more uniform and good the subsequent drying process can be made. However, when the hydrogel is hard, it is coarsely ground rather than finely ground. It is preferable. This is because if the hard hydrous gel is crushed too finely, clogging or the like will occur in the subsequent drying step, etc., and it will be difficult to dry it uniformly, which may lead to the generation of undried matter. If the finely granulated hydrous gel is too large, undried matter will be generated. Therefore, the average particle size of the finely granulated hydrous gel is 1 mm to 2 m.
It is particularly preferable that it is within the range of m.

In the method of finely granulating the hydrogel-like crosslinked polymer according to the present invention, it is preferable that the casing 11 of the screw type extruder is filled with the hydrogel at a predetermined amount or more, if possible, almost completely, and pulverized. By crushing like this,
It is possible to prevent the hydrous gel from being kneaded in the casing 11, and it is possible to improve the productivity of the pulverization process.

In the present invention, the predetermined amount of the hydrogel filled in the casing 11 is defined by the following filling rate. Casing 1 of the screw type extruder
A is the amount of treatment per unit time when the hydrated gel is completely filled in 1 and crushed, and the supply of the hydrated gel is supplied with the screw 13 rotating at the same number of revolutions as this time. When the amount is B, the filling rate C is calculated by the following equation (1).
Is defined.

C = (B / A) × 100 (1) In the present invention, the crushing process may be carried out with the filling rate C set within the range of 30% to 100%. Preferably
It is particularly preferable that the filling rate C be close to 100%. When the filling rate C is less than 30%, an extra mechanical external force is applied to the hydrogel in the casing 11 as the screw 13 rotates, and the hydrogel is kneaded.

Here, depending on the amount of hydrous gel produced, the filling rate C may be less than 30%, and mechanical external force tends to be applied to the hydrous gel. Therefore, in order to avoid this problem, in the method of atomizing the hydrogel crosslinked polymer according to the present invention, depending on the change in the feed amount of the hydrogel supplied to the screw type extruder, the filling rate C is 30% ~
The rotation speed of the screw 13 is changed so as to be 100%.

Specifically, for example, in the case where the hydrogel is continuously supplied, if the supply amount is small, the hydrogel is crushed in such a state that the filling rate C is 30% or less. A situation will occur. Therefore, according to the width of the decrease in the supply amount (that is, the decrease in the filling rate C), the screw 1
The number of rotations of 3 is reduced.

Since the hydrogel of the present invention has a crosslinked structure, the treatment amount A per unit time can be reduced by lowering the rotation speed of the screw 13. As a result, the filling rate C is 30% even when the supply amount is reduced.
The hydrogel can be finely divided while maintaining the content within the range of -100%. In the present invention, the relationship between the rotation speed and the processing amount A is parameterized, the rotation speed of the screw 13 is changed according to the change in the supply amount of the hydrous gel, and the filling rate C is 30% to 30%.
The hydrogel can be finely granulated while keeping it within the range of 100%.

According to the above method, even if the filling rate C is less than 30%, it is possible to prevent an extra mechanical external force from being applied to the hydrogel due to the rotation of the screw 13. . As a result, the hydrogel can be crushed so that it cannot be kneaded further. In addition, the filling rate C is 3
If the filling rate C is 0% or more, for example, even if the filling rate C is 40%, if the rotation speed of the screw 13 is reduced according to the reduction width of the filling rate with the filling rate C being 100% as a reference. The effect of mechanical external force on the hydrous gel can be more reliably avoided.

In the present invention, as described above, the change in the supply amount of the hydrous gel is defined as the change in the filling rate C.
The supply amount is not limited to this, and when the supply amount can be specified by other parameters, the reduction rate of the rotation speed of the screw 13 can be appropriately specified according to the parameter.

Further, the range of change in the number of revolutions of the screw 13 corresponding to the change in the supply amount of the hydrous gel is not limited to a certain specific range, and the conditions for atomization, for example, the screw type extrusion used. The optimum change width can be defined by the shape of the machine (the volume of the casing 11, the shape of the screw 13, the diameter of the holes 17a of the perforated plate 17, the shape of the rotary blade 18 used), the physical properties of the hydrous gel, and the like. Therefore, it is preferable that the number of revolutions is appropriately defined according to the screw type extruder and the hydrogel used.

Note that the above-mentioned filling rate C and the regulation of the supply amount at the time of the crushing treatment of the hydrous gel are not limited to the screw type extruder equipped with the reversion preventing member 20, but other screw type extruders. It is also applicable to the crushing treatment by.

In the method of finely granulating the hydrogel crosslinked polymer according to the present invention, the lump hydrogel may be appropriately coarsely pulverized before supplying the hydrogel to the screw type extruder.
This makes it easier to supply the hydrogel and to fill the casing 11 more easily. The coarse pulverizing means used for the coarse pulverization is not particularly limited as long as it can pulverize the hydrogel so as not to knead it, and examples thereof include a guillotine cutter.

The size of the coarsely pulverized product of the hydrous gel obtained by the coarse pulverization is not particularly limited as long as it can be supplied from the supply port 14 and can be sent to the extrusion port 16 by the screw 13. Although not limited, in general, it is preferably in the range of 5 mm to 500 mm, more preferably in the range of 10 mm to 150 mm. If it is less than 5 mm, there is no point in crushing with a screw type extruder. On the other hand, if it exceeds 500 mm, the water-containing gel cannot be filled into the casing 11 without any gap (that is, the filling rate C is lowered), which is not preferable.

The water-absorbent resin obtained by drying the atomized hydrogel obtained by the atomizing method according to the present invention as described above has excellent water-absorbing performance, and can be used, for example, in disposable diapers and sanitary napkins. Sanitary materials such as incontinence pad, wound protection material, wound healing material (body fluid absorbent article); absorbent article such as urine for pets; construction material, water retention material for soil, water blocking material, packing material, civil engineering construction such as gel water bag Materials; Food products such as drip absorbents, freshness-retaining materials, and cold insulation materials; Oil-water separation materials, condensation prevention materials,
Various industrial articles such as coagulation materials; agricultural and horticultural articles such as water-retaining materials for plants and soil, etc. have been suitably used for various purposes.

The method for making fine particles of the hydrogel-like crosslinked polymer according to the present invention is not only applied to the production of the water-absorbent resin, and the hydrogel is pulverized so as not to be uniformly and kneaded. This method is preferably used when the step of performing is required.

[0085]

EXAMPLES The method of atomizing a hydrogel crosslinked polymer according to the present invention will be described more specifically based on the following examples and comparative examples. The present invention is based on these examples and comparative examples. It is not limited.

In the following Examples and Comparative Examples, the method for making fine particles of the hydrogel crosslinked polymer according to the present invention is applied to the production of the water absorbent resin. First, various physical properties of the water-absorbent resins obtained in the following Examples and Comparative Examples and the state of the finely granulated hydrous gel were measured as follows. In addition,% described in the following Examples and Comparative Examples means% by weight.

[Water absorption capacity] First, the weight of the water absorbent resin is weighed, and then sodium sulfate 0.02% and potassium chloride 0.2
00%, magnesium chloride hexahydrate 0.050%, calcium chloride dihydrate 0.025%, ammonium dihydrogen phosphate 0.035%, diammonium hydrogen phosphate 0.0
It was immersed for 60 minutes in an artificial urine composed of 15% and 99.475% deionized water.

Then, the water-absorbent resin was taken out, drained by a centrifuge, the weight of the water-absorbent resin was weighed, and the water absorption capacity was determined by comparing with the weight before absorbing artificial urine.

[Soluble Content] In a 100 mL beaker, 1 g of the water-absorbent resin was swollen with 25 mL of a 0.9% sodium chloride aqueous solution (physiological saline), and the solution was capped and left at 37 ° C. for 16 hours. Then, the swollen gel was dispersed in 975 mL of deionized water, stirred for 1 hour, and then filtered through a filter paper. The obtained filtrate was titrated by colloid titration to calculate the soluble content (%) of the water absorbent resin.

[Degradable soluble content] Degradable soluble content (%) was measured in the same manner as in the measurement of the soluble content except that 1 g of the water absorbent resin was swollen in 25 mL of physiological saline containing 0.005% of L-ascorbic acid. Was calculated.

[Average Gel Particle Size of Fine-Grained Hydrous Gel] 30 g of a sample having a solid content of α% by weight was put into 1000 g of 20% by weight NaCl aqueous solution, and a stirrer tip was rotated at 300 rpm.
Stir for 120 minutes by spinning at. After stirring, 6 types of sieves (opening 9.5, 2.0, 0.85, 0.6, 0.3,
The sample (fine-grained hydrous gel) was put into 0.07 mm), and further 6000 g of 20 wt% NaCl aqueous solution was put into it for classification. The sample on the classified sieve was thoroughly drained and then weighed.

The weight of the sample after classification and draining was W and the mesh size of the sieve was r, and the particle size distribution of the hydrous gel was plotted on a logarithmic probability paper based on the following equation (2).

R (α) = (30 / W) ^1/3 × r (2) The particle diameter corresponding to 50% by weight of% R on the cumulative sieving of the plot was calculated as follows: The average gel particle size was used.

[Example 1] 65% neutralized sodium acrylate and polyethylene glycol diacrylate (average number of ethylene oxide units: 8) 0.04 mol%
An aqueous monomer solution containing (to sodium acrylate) was prepared. The concentration of sodium acrylate at this time is 35
% By weight. Nitrogen was blown into the aqueous monomer solution to adjust the dissolved oxygen concentration in the aqueous solution to 0.1 ppm or less.

Next, a water-soluble azo initiator (manufactured by Wako Pure Chemical Industries, Ltd .: product number V-50) 0.02 g / mol (to sodium acrylate monomer), L-ascorbic acid 0.002 g / mol ( Polymerization was carried out by successively adding 0.001 g / mol of hydrogen peroxide (to sodium acrylate monomer) and hydrogen peroxide (to sodium acrylate monomer). The polymerization initiation temperature was 22 ° C, and the temperature reached 82 ° C after 12 minutes.

After polymerization, the obtained hydrous gel was roughly crushed into 25 to 50 mm square with a guillotine cutter, and then charged into a screw type extruder as shown in FIG. 1 so that the filling rate was almost 100%. It was extruded from the perforated plate 17 and crushed.

As the screw type extruder, a casing 11 having an inner diameter of 210 mm and a length of 900 mm was used. Further, as the reversion preventing member 20, four spiral band-shaped projections 20a are provided in the casing 11 in the vicinity of the extrusion port 16. The height of the strip-shaped projection 20a from the inner surface of the casing 11 was 9 mm.

The perforated plate 17 has a thickness of 15 mm,
A hole 17a having a diameter of 9.5 mm and an aperture ratio of 35% was used (see FIG. 2A). Further, as the rotary blade 18,
A cross-shaped type as shown in FIG. 3 was used. The rotary blade 18 is arranged on the screw 13 side of the perforated plate 17 (see FIG. 1). The screw 13 and the band-shaped projection 20
The gap with a was about 3 mm.

The hydrous gel was extruded and pulverized by using the above-mentioned screw type extruder to obtain fine hydrous gel. The crushed hydrous gel was glass-like transparent particles. Table 1 shows the fine-graining conditions at that time. During the pulverization, the screw 13 was taken out from the casing 11 and the state of the hydrous gel in the casing 11 was observed.
The hydrogel just before reaching 7 was crushed into fine particles, but other than that, it was hardly crushed and remained transparent. Table 1 shows the state of the obtained fine-grained hydrous gel.

The finely granulated hydrous gel was dried at 180 ° C. for 30 minutes and then pulverized to obtain the water absorbent resin (1) of the present invention. Table 2 shows the physical properties of the water absorbent resin (1).

Example 2 In Example 1, 0.08 mol% of polyethylene glycol diacrylate was used,
A perforated plate 17 having a hole 17a having a diameter of 24 mm was used (see FIG. 2).
A water absorbent resin (2) in the present invention was obtained in the same manner except that (see (b)). Table 1 shows the conditions of fine-graining and the state of the fine-grained hydrous gel at this time. Also, a water absorbent resin (2)
The physical properties of are shown in Table 2.

[Example 3] In Example 2, the rotation speed of the screw 13 was set to 35 rpm, and the water-containing gel was set to 2300.
A water absorbent resin (3) of the present invention was obtained in the same manner except that it was pulverized while being supplied at kg / h. Table 1 shows the conditions of fine-graining and the state of the fine-grained hydrous gel at this time. Also,
Table 2 shows the physical properties of the water absorbent resin (3).

Example 4 In Example 2, the coarsely pulverized hydrogel was fed at 2300 kg / h, that is,
A water absorbent resin (4) of the present invention was obtained in the same manner except that the hydrated gel was filled at a filling rate of 35% and the pulverization was performed. Table 1 shows the conditions of fine-graining and the state of the fine-grained hydrous gel at this time. In addition, Table 2 shows the physical properties of the water absorbent resin (4).

Example 5 In Example 1, the rotation speed of the screw 13 was set to 18 rpm, and the water-containing gel was set to 1000 rpm.
A water absorbent resin (5) according to the present invention was obtained in the same manner except that it was pulverized while being supplied at a rate of kg / h. Table 1 shows the conditions of fine-graining and the state of the fine-grained hydrous gel at this time. Also,
Table 2 shows the physical properties of the water absorbent resin (5).

[Embodiment 6] Water absorption was performed in the same manner as in Embodiment 1 except that a screw type extruder in which eight streak projections 22 were provided on the inner surface of the casing 11 along the axial direction of the screw 13 was used. Resin (6) was obtained. Table 1 shows the conditions of fine-graining and the state of the fine-grained hydrous gel at this time.
In addition, Table 2 shows the physical properties of the water absorbent resin (6).

Further, when the screw 13 was taken out from the casing 11 during the pulverization and the appearance of the hydrous gel in the casing 11 was observed, it was found that not only immediately before the perforated plate 17 but also in the hydrous gel in the middle of the screw 13. Some were crushed and the surface was white.

[Embodiment 7] In Embodiment 2, Embodiment 6
A water-absorbent resin (7) was obtained in the same manner except that the screw type extruder used in step 1 was used. Table 1 shows the conditions of fine-graining and the state of the fine-grained hydrous gel at this time. In addition, Table 2 shows the physical properties of the water absorbent resin (7).

Example 8 In Example 2, the coarsely pulverized hydrogel was supplied at 1000 kg / h, that is,
A water absorbent resin (8) was obtained in the same manner except that the hydrated gel was filled at a filling rate of 15% and pulverized. Table 1 shows the conditions of fine-graining and the state of the fine-grained hydrous gel at this time. In addition, Table 2 shows the physical properties of the water absorbent resin (8).

Comparative Example A comparative water absorbent resin was obtained in the same manner as in Example 1 except that a smooth screw type extruder having no protrusion on the inner surface of the casing 11 was used. Perforated plate 1
The hydrogel extruded from No. 7 was in the form of a kneaded white string. Table 1 shows the conditions of fine-graining and the state of the fine-grained hydrous gel at this time. In addition, Table 2 shows the physical properties of the comparative water absorbent resin.

During the pulverization, the screw 13 was taken out from the casing 11 and the appearance of the hydrous gel in the casing 11 was observed. The hydrous gel immediately before the perforated plate 17 and in the middle of the screw 13 was also kneaded to be pure white. It was a part of a white lump.

[0111]

[Table 1]

[0112]

[Table 2]

As described above, in Examples 1 to 5 using the grain refining method according to the present invention, the reversion preventing member 20 is used.
Since the crushing process is performed by using the screw type extruder having the (belts 20a), the particle size distribution of the finely granulated hydrous gel becomes very sharp, and the average gel particle size also becomes large, so that the drying can be performed. It was confirmed that a finely granulated hydrous gel that could be satisfactorily obtained was obtained.

In particular, as in Examples 1 and 2, according to the atomizing method of the present invention, the hydrogel can be favorably atomized regardless of the diameter of the holes 17a of the porous plate 17. It was confirmed that it was possible. Further, as in Examples 3 and 5, even if the amount of hydrous gel supplied was small, the screw 13
It was confirmed that fine graining could be achieved by reducing the number of rotations. Further, as in Example 4, the filling rate C
It was also confirmed that if the ratio is 30% or more, good grain refinement is possible.

In addition, the water-absorbent resins (1) to (5) obtained in the above Examples 1 to 5 are high-quality ones having a very small amount of soluble components and degraded soluble components and exhibiting very good physical properties. Was confirmed.

Further, the water-absorbent resins (6) to (8) obtained in Examples 6 to 8 do not use the band-shaped projection 20a, which is a particularly preferable structure as the reversion preventing member 20, and therefore the water-absorbent resin (1 It was confirmed that, although a slight deterioration in quality was observed as compared with those in (5) to (5), it showed good physical properties.

On the other hand, in the comparative example, since the crushing process was performed using the screw type extruder not equipped with the reversion preventing member 20, the particle size distribution of the finely granulated hydrous gel was widened, and the average gel particle size was also increased. It was confirmed that the diameter was also small. Furthermore, the obtained hydrous gel was in the form of a kneaded white string. It was also confirmed that the comparative water-absorbent resin obtained in the above Comparative Example had a large amount of soluble components and deteriorated soluble components, and thus the quality of the water-absorbent resin was low.

[0118]

As described above, the method for making fine particles of the hydrogel-like crosslinked polymer according to the present invention includes at least a pushback preventing member for preventing the hydrogel-like crosslinked polymer from returning to the supply port side. It is a method of pulverizing a hydrogel crosslinked polymer using a screw type extruder provided near the outlet.
At this time, it is preferable that the reversion preventing member is a band-shaped projection formed in a spiral shape or a concentric shape.

According to the above method, it is possible to prevent the hydrogel from being kneaded by applying a mechanical external force and to make it possible to uniformly pulverize the hydrogel. It can be granulated. In addition, the amount of finely treated hydrogel can be significantly improved.

Further, in the crushing treatment by the screw type extruder, the filling rate C defined by the above-mentioned formula (1) is preferably within the range of 30% to 100%. Within this range, application of mechanical external force to the hydrous gel is more reliably suppressed. Further, the filling rate C
Even when the water content is less than 30%, it is possible to reliably suppress the application of mechanical external force to the hydrous gel by changing the rotation speed of the screw according to the amount of the hydrous gel supplied. be able to.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a screw type extruder used for a method of atomizing a hydrogel crosslinked polymer according to an embodiment of the present invention.

2A and 2B are perspective views showing an example of a configuration of a perforated plate included in the screw type extruder shown in FIG.

FIG. 3 is a perspective view showing an example of the configuration of a rotary blade of the screw type extruder shown in FIG.

FIG. 4 is an explanatory diagram showing an example of a configuration of a band-shaped projection as a reversion preventing member provided in the screw type extruder shown in FIG.

FIG. 5 is an explanatory view showing another example of the configuration of the band-shaped projection as the reversion preventing member provided in the screw type extruder shown in FIG. 1.

[Explanation of symbols]

11 casing 13 Screw 14 Supply port 16 Extrusion port 17 Perforated plate 17a hole 18 rotary blades 20 Reverse return prevention member 20a Band-shaped projection (return prevention member) 20b Band-shaped protrusion (return prevention member) 22 Streak

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takumi Hatsuda 1 Nishi-oki, 952, Okihama, Aboshi-ku, Himeji-shi, Hyogo Prefecture Nippon Shokubai Co., Ltd. (56) Reference JP-A-54-106568 (JP, A) JP-A-5 -70597 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08J 3/00-3/28 B29B 9/06

Claims (8)

(57) [Claims] 1. A method for finely granulating a hydrogel-like crosslinked polymer, which comprises supplying the hydrogel-like crosslinked polymer through a supply port of a screw type extruder and extruding through a extrusion port equipped with a perforated plate to carry out a pulverization treatment. As the screw type extruder, a hydrous gel-like cross-linked polymer characterized by using a hydrogel-like cross-linked polymer provided with at least a reversion prevention member for preventing reversion to the supply port side in the vicinity of the extrusion port Atomization method. 2. The water-containing gel-like cross-linked polymer according to claim 1, wherein the reversion preventing member is a band-shaped projection formed in a spiral shape or a concentric shape in a casing of a screw type extruder. Atomization method. 3. In the crushing treatment, the amount of treatment per unit time when the hydrated gel-like cross-linked polymer is completely filled in the casing of the screw type extruder and the crushing treatment is performed is defined as A. Assuming that the feed amount of the hydrogel crosslinked polymer supplied in the state where the screw rotates at the same rotation speed as that of B is B, the filling factor C defined by the following formula, C = (B / A) × 100 The method of finely granulating a hydrogel-like crosslinked polymer according to claim 1 or 2, wherein the content is in the range of 30% to 100%. 4. The filling rate C is set within the range of 30% to 100% according to the change in the feed amount of the hydrogel crosslinked polymer fed to the screw type extruder during the pulverization treatment. The method for atomizing a hydrogel crosslinked polymer according to claim 3, wherein the number of revolutions of the screw is changed. 5. A water-absorbent resin obtained by drying a finely divided hydrogel cross-linked polymer has a soluble content of 15% by weight or less and a degraded soluble content of 28% by weight or less. The method for finely granulating a hydrogel-like crosslinked polymer according to any one of claims 1 to 4. 6. A hydrogel-like crosslinked polymer which has been made into fine granules having a particle size of 10
mm No mesh pass-through and / or fine
The average particle diameter of the granulated hydrogel cross-linked polymer is 0.5
It is within the range of 3 mm to 3 mm.
6. The method for finely granulating a hydrogel crosslinked polymer according to any one of items 1 to 5 . 7. The hydrogel crosslinked polymer before being fed to the screw type extruder is roughly pulverized within a range of 5 mm to 500 mm, according to any one of claims 1 to 6. A method for making fine particles of the hydrogel-like crosslinked polymer described. 8. The thickness of the perforated plate is in the range of 1 mm to 20 mm.
The inside diameter is 0.8 mm to 28 mm.
And the aperture ratio of the perforated plate is 25% or more, wherein the hydrogel-like crosslinked polymer according to any one of claims 1 to 7 is atomized. Method.