JPH05112654A - Producti0n of water-containing gelatinous polymer particle and water-absorbing resin - Google Patents

Abstract

PURPOSE:To obtain water-containing gelatinous polymer particles having high water-absorption ratio and low content of water-soluble component by applying a load on a water-containing gelatinous polymer having a cross-linked structure in a vessel under heating and repeatedly applying shearing force to the polymer. CONSTITUTION:A water-containing gelatinous polymer having cross-linked structure is heated at 40-110 deg.C in a vessel and a shearing force is repeatedly applied to the polymer under a load of 0.01-1.5kg/cm<2> to obtain the objective water-containing gelatinous polymer particles. The above vessel is preferably a kneader having a plurality of rotary stirring shafts.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a particulate hydrogel polymer and a water absorbent resin. More specifically, the present invention relates to a method for producing a particulate hydrous gel polymer, which comprises repeatedly applying a shearing force to a hydrogel polymer having a crosslinked structure at a specific temperature while applying a load in a specific range.
Further, the present invention relates to a method for producing a water-absorbent resin by drying the particulate hydrogel polymer.

[0002]

Water-absorbent resins include crosslinked polyacrylic acid salts, saponified acrylic acid ester-vinyl acetate copolymers, crosslinked polyvinyl alcohol modified products, crosslinked isobutylene-maleic anhydride copolymers, starch-acrylic acid. Graft polymer and the like are known, and are widely applied to sanitary napkins, sanitary absorbents such as paper diapers, or water retention agents, dehydrating agents and the like in the fields of agriculture and horticulture and the field of civil engineering.

As a method for producing these water-absorbent resins, a reverse-phase suspension polymerization method is disclosed, for example, in JP-A-56-161408 and JP-A-56-161.
-94,011, No. 57-158,209 and No. 57-198,714 known methods, also, as an aqueous solution polymerization method,
For example, JP-A-57-34,101, JP-B-48-42,466, JP-A-58-49,714, JP-B-59-37,003, USP 4,286,08
2 and the method described in USP 4,625,001 are known.

However, since the reversed phase suspension polymerization method uses an organic solvent, not only the working environment is deteriorated but also there is a risk of ignition and explosion. In addition, the cost is high in addition to the cost for removing it. Further, since a small amount of this organic solvent remains in the product, it is more costly to completely remove it. Furthermore, since the water-absorbent resin obtained by the reverse phase suspension polymerization method has a spherical shape and a small particle size, when it is used in, for example, a paper diaper, it is not retained by a fibrous absorbent core component such as pulp and easily falls off. Moreover, handling is inconvenient.

On the other hand, the aqueous solution polymerization method does not have the above-mentioned problems, and the methods disclosed in JP-A-57-34,101 and USP 4,625,001 are known. JP-A-57-34,101
The method described in U.S. Pat. No. 4,625,001 is a method of polymerizing an aqueous solution of a monomer that forms a crosslinked structure during aqueous solution polymerization to form a hydrogel polymer and a polymerization initiator in a container equipped with a stirring blade. It is a method for producing a crosslinked polymer, which comprises carrying out radical aqueous solution polymerization while subdividing a hydrous gel-like polymer produced as it progresses by the shearing force of a stirring blade caused by rotation of the stirring shaft. According to these manufacturing methods,
Not only the workability is extremely good, but also a finely divided hydrogel polymer having a crosslinked structure in the molecule can be produced with high productivity. However, even in such a method, a water-absorbent resin having a high water absorption capacity and a low water-soluble content may have low productivity.

It is well known to those skilled in the art that the water absorption capacity is increased by decreasing the crosslink density, and when the water-absorbent resin is manufactured by the work of decreasing the crosslink density, it is soluble in water. It is also known that the minutes increase. The water-soluble component is leached from the water-absorbent resin when it contacts a liquid to be absorbed such as water, urine or body fluid to form a hydrogel structure. Thus, the water-soluble component extracted by the liquid to be absorbed not only lowers the water absorption capacity of the water absorbent resin, but also accelerates the deterioration of the water absorbent resin. In addition, unpleasant sensation is caused due to the sliminess, and an unfavorable situation such as contaminating the liquid to be absorbed is created.

Therefore, there has been a demand for a method for producing a water absorbent resin having a high water absorption capacity and a low water-soluble content.

US Pat. No. 4,654,039 and Japanese Patent Laid-Open No. 1-144,404 describe a method for producing a water-absorbent resin having a high water absorption capacity and a low water-soluble content by polymerizing a free acid type or a monomer having a specific neutralization ratio in an aqueous solution. is suggesting. However, these production methods require post-neutralization, complicated operations and low productivity, and restrictions on polymerization conditions.

On the other hand, the hydrogel polymer obtained by polymerization is generally marketed as a powdery product after being pulverized through a drying step. Conventionally, in order to efficiently dry such a hydrous gel polymer, measures have been taken to increase the surface area of the hydrous gel polymer as much as possible. For example,
A method of crushing a hydrous gel polymer by extruding it from a porous plate (Japanese Patent Publication No. 54-32,176, JP-A No. 50-136,348, etc.) is known, but in the conventional method, it was finely crushed and extruded. The hydrated gel polymer reattached to form a string, and a particulate hydrated gel polymer could not be obtained.

A method of adding an additive such as a lubricant for the purpose of preventing redeposition of the hydrogel polymer when the hydrogel polymer is extruded from a porous plate and crushed (JP-A-59-30,826).
JP-A-59-119,172), but additives remaining in the polymer sometimes adversely affect the performance of the product.

The above-mentioned Japanese Patent Laid-Open No. 57-34,101 and
According to the method disclosed in USP 4,625,001, a hydrogel polymer having a relatively small particle size can be obtained, but the size is 10 or less.
Coarse gel particles having a size of mm or more are produced from several wt% to several tens wt%, the particle size distribution is wide, and the drying efficiency and the uniformity of the degree of drying are insufficient.

Furthermore, it has been difficult to obtain a particulate hydrous gel polymer having a sufficiently small average particle size by the conventional method for pulverizing a hydrous gel polymer, or the productivity is remarkably low. When drying the particulate hydrogel polymer to obtain a product having a desired particle size, it is necessary to grind the dried product when the average particle diameter of the particulate hydrogel polymer is large, and at the time of grinding A fine powder smaller than the desired particle size is generated. It is well known to those skilled in the art that this fine powder is not preferable in terms of performance and handleability of the water absorbent resin.

As described above, a method for producing a particulate hydrogel polymer and a water-absorbent resin with a simple process, high productivity, high water absorption capacity, and low water-soluble content has not been established. Further, a method for obtaining a highly productive particulate hydrogel polymer which does not contain additives such as a lubricant and has a narrow particle size distribution and good drying efficiency has not been established. Further, a method for efficiently producing a particulate hydrogel polymer having a sufficiently small average particle diameter has not been established so far.

[0014]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method for producing a particulate hydrogel polymer and a water absorbent resin which have a high water absorption capacity and a low water-soluble content.

Another object of the present invention is a simple process,
Moreover, it is an object of the present invention to provide a method for producing a particulate hydrogel polymer and a water-absorbent resin which have good productivity, a high water absorption capacity, and a low water-soluble content.

Another object of the present invention is to provide a method for producing a particulate hydrous gel polymer which does not contain additives such as a lubricant and has a narrow particle size distribution and good drying efficiency with high productivity. To do.

Still another object of the present invention is to provide a method for efficiently producing a particulate hydrogel polymer having a sufficiently small average particle diameter.

[0018]

In view of the above circumstances, the inventors of the present invention have conducted extensive studies on a method for producing a particulate hydrogel polymer and a water absorbent resin, and as a result, have completed the present invention. It was

That is, an object of the present invention is to provide a method for producing a particulate hydrogel polymer, which comprises subjecting a hydrogel polymer having a crosslinked structure to a shearing force to subdivide into particles in a container. A method for producing a particulate hydrous gel polymer, which comprises repeatedly applying a shearing force to a hydrous gel polymer heated to a temperature of ˜110 ° C. while applying a load of 0.01 to 1.5 kg / cm ^2. And a method for producing a water-absorbent resin, which comprises drying the particulate hydrogel polymer.

[0020]

The hydrogel polymer of the present invention is not particularly limited as long as it is a hydrogel having a crosslinked structure and showing a gel state in the hydrous state, but the water content is usually 40 to 90% by weight, more preferably 50% by weight. It is a -80% by weight hydrogel polymer. In the present invention, the water content of the water-containing gel polymer means the content of water in the total weight of the water-containing gel polymer in% by weight. Further, it is essential that the hydrogel polymer used in the present invention has a crosslinked structure. If it does not have a crosslinked structure, the object of the present invention cannot be achieved.

The hydrogel polymer of the present invention is prepared by, for example, forming a crosslinked structure in a mold by aqueous solution polymerization, and adding a monomer component to form the hydrogel polymer, and polymerizing the mixture. 55-133,413) or a method of polymerizing the monomer component in a kneader or the like having a stirring shaft capable of subdividing the hydrogel polymer formed inside (JP-A-57-34,101). And the like.

Among the monomer components used in the above polymerization method, examples of the water-soluble unsaturated monomer include (meth)
Acrylic acid, (anhydrous) maleic acid, fumaric acid, crotonic acid, itaconic acid, 2- (meth) acryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid, 2- (meth) acrylamido-2-methylpropanesulfone Acid, vinyl sulfonic acid, styrene sulfonic acid,
Anionic monomers and salts thereof such as; (meth) acrylamide, N-substituted (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, Nonionic hydrophilic group-containing monomers such as polyethylene glycol (meth) acrylate; N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-dimethylaminopropyl Amino group-containing unsaturated monomers such as (meth) acrylamide and their 4
Specific examples thereof include graded products. In addition, an amount of acrylic acid ester such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate or vinyl acetate in an amount that does not extremely hinder the hydrophilicity of the resulting hydrogel polymer. Alternatively, a hydrophobic monomer such as vinyl propionate may be used. As the monomer component, one kind or two or more kinds can be selected and used from these, but considering various water absorption characteristics of the finally obtained water-absorbent resin, (meth) acrylic acid (salt), 2- (meth) acryloylethanesulfonic acid (salt), 2- (meth) acrylamido-2-methylpropanesulfonic acid (salt), (meth) acrylamide, methoxypolyethylene glycol (meth) acrylate, N, N-dimethylaminoethyl One or more selected from the group consisting of (meth) acrylate or a quaternary compound thereof is preferable, and one further containing (meth) acrylic acid (salt) as an essential component is more preferable. In this case, 3 of (meth) acrylic acid
Most preferably, 0 to 90 mol% is neutralized with a basic substance.

The water-containing gel-like polymer of the present invention is a self-crosslinking type polymer obtained without using a crosslinking agent, and is a water-absorbing polymer having a crosslinking agent having a polymerizable unsaturated group and / or a reactive functional group. It may be obtained by using the resin in such a range that various properties reach desired standards. Usually, the amount used is 0.001 to 1.0 mol% with respect to the monomer component, and preferably 0.1.
It is from 01 to 0.5 mol%.

Examples of these crosslinking agents include, for example, N,
N'-methylenebis (meth) acrylamide, (poly)
Ethylene glycol (meth) acrylate, glycerin tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, triallylamine, triallyl cyanurate, triallyl isocyanurate, glycidyl (meth) acrylate, (poly) ethylene glycol, diethylene glycol, (Poly) glycerin, propylene glycol, diethanolamine, trimethylolpropane, pentaerythritol, (poly) ethylene glycol diglycidyl ether, (poly) glycerol polyglycidyl ether, epichlorohydrin, ethylenediamine, polyethyleneimine, (poly) aluminum chloride, aluminum sulfate, Specific examples include calcium chloride and magnesium sulfate. Of these, considering reactivity, It can be used alone or in combination.

In order to obtain a hydrogel polymer, the above-mentioned monomer components are polymerized in the presence of a hydrophilic polymer such as starch, cellulose and polyvinyl alcohol to form a graft bond or a complex simultaneously with the polymerization. You may let me.

Upon polymerization of these monomer components, as a polymerization initiator, ammonium persulfate, potassium persulfate, hydrogen peroxide, t-butyl hydroperoxide, 2,2'-azobis-amidinopropane dihydrochloride and the like are used. The water-soluble radical polymerization initiator may be used.

The hydrogel polymer of the present invention may be any hydrogel having a hydrogel state, and may be either one in which the polymerization reaction of the above-mentioned monomer components is in progress or one in which the polymerization reaction is completed. .. Generally, a hydrogel polymer having a crosslinked structure exhibits a hydrogel state at a polymerization rate of about several%, so that the shearing force under a load is arbitrary for the hydrogel polymer having a polymerization rate of several% or more. It's good if the time comes. The polymerization rate is preferably 10 to 100%, more preferably 20 to 100%.
Is a hydrogel polymer. Needless to say, a usual stirring operation may be added to the monomer component before it has a hydrogel state. However, when applying shearing force at the time when the polymerization rate of the monomer component is low, it is expected that unfavorable phenomena such as decrease in basic molecular weight will occur if the application of shearing force is excessive. Requires.

The method for producing the particulate hydrous gel polymer of the present invention can be achieved by applying a shearing force to the hydrous gel polymer under the above conditions. Any embodiment can be adopted as appropriate. Typical specific embodiments include, for example: 1. A shear force is applied to the hydrogel polymer after completion of the polymerization reaction under the above conditions. 2. A shearing force is applied to the hydrogel polymer in the course of the polymerization reaction under the above conditions. An embodiment may be mentioned in which a shearing force is applied to the produced hydrogel polymer under the above conditions while the polymerization reaction proceeds.

The apparatus shown in FIG. 1 is an example of a preferable apparatus for carrying out 2 or 3 of the above embodiments. FIG. 2 is a schematic sectional view taken along the line aa of FIG. As shown in FIGS. 1 and 2, in the container 7 of the present embodiment, rotary arms 10 and 11 for applying shearing force to the hydrogel polymer are respectively rotated and stirred shafts 12,
12 'and 13, 13' (not shown) are fixed along the longitudinal direction in the container 7, and the pressure lid 5 for applying a load has a rotating arm 10 even when it is lowered to the lowermost end. , 11 has a shape adapted to the peripheral part of the rotating arm so as not to hinder the rotation of the rotating arms 11, and is installed at the opening of the container 7. In the state of FIG. 1, that is, by the pressure lid 5, the container 7
Is kept substantially closed, and the liquid supply port 1 and the gas supply port 2 are in an open state with respect to the container 7, and the aqueous solution of the monomer component and the inert gas are stored in the container 7. Supplied. At this time, the charged amount of the aqueous solution of the monomer component is usually the effective shear volume (the remaining space volume obtained by subtracting the volume of the rotary stirring shaft and the rotary arm from the space volume formed by the rotation of the rotary arm of the rotary stirring shaft). ) Of 50-150%
Is. The inert gas supplied from the gas supply port 2 passes through the container 7 and is discharged from the gas discharge port 1'or the nozzle 2 '. Polymerization of the monomer components is started, and at any time when the hydrogel polymer is formed, the cylinder 8 is moved by hydraulic pressure or air pressure, and the pressure lid 5 is lowered onto the hydrogel polymer. It is applied to the water-containing gel polymer and subjected to repeated shearing force by the rotation of the rotating arms 10 and 11. An example of this state is shown in FIG. At this time,
The liquid supply port 1 and the gas supply port 2 are closed by the pressure lid 5, so that the water-containing gel polymer does not enter.
On the other hand, the inert gas supplied from the gas supply port 2 is supplied to the stirring space 14 through the gap between the wall of the container 7 and the wall of the pressure lid 5. As described above, from the charging of the aqueous solution of the monomer component, through the polymerization, applying a shearing force while applying a load to the hydrous gel polymer, until the removal of the particulate hydrogel polymer under an inert gas atmosphere Can be done at. The positions of the liquid supply port 1 and the gas supply port 2 are preferably provided at positions higher than the surface of the hydrogel polymer when the load is removed. 1 to 3, a cover 4 is attached to the outside of the pressure lid 5 so as to be vertically movable relative to the lid. The cover 4 has a box shape having an opening at the lower end, and a flange portion facing the flange portion provided on the container 7 is provided at the lower end portion, and a sealing material 9 is provided at the flange portion. It is equipped. When the pressure lid 5 is raised, the cover 4 contacts the pressure lid 5 and is raised. On the other hand, when the pressure lid 5 is moved down by the cylinder 8, the flange portion of the cover 4 is inserted into the flange portion of the container 7 via the sealing material 9 at the position where the lower end portion of the pressure lid 5 starts to be fitted into the container 7. The space inside the cover 4 is sealed from the outside by the abutment and its own weight. After the flanges of both the cover 4 and the container 7 come into contact with each other via the sealing material 9, only the pressure lid 5 is moved down by the cylinder 8. The cover 4 is provided with a gas supply port 3 and a gas discharge port 3 '.
In this state, by supplying an inert gas from the gas supply port 3, the inside of the cover 4 can be replaced with an inert gas atmosphere. This cover 4 is not always necessary, but the container 7
This is a preferred embodiment when the inert gas atmosphere inside is more complete.

As the apparatus equipped with the container used in the present invention, specifically, an ordinary batch kneader having a member (pressurizing lid) at the opening thereof, a mechanical pressure kneader,
An internal mixer, a Banbury mixer, etc. can be used. Of these, a mechanical pressure kneader can be preferably used.

In the present invention, it is preferable that there are two or more rotating arms, and it is particularly preferable that the rotating arms are of a double-arm type. Specific examples of the shape of the rotary arm used in the present invention include a sigma (δ) shape, a zet (Z) shape, a spiral (S) shape, a masticator shape, a fish tail shape, and a convex lens shape in cross section. Can be used. Further, when the rotary arm is a double-arm type, as a combination of the shapes of these rotary arms, for example, there is a combination of a sigma type and a spiral type or a zet type,
These two rotating arms rotate in opposite directions at a constant speed or a non-constant speed. The combination method includes an overlap type and a tangential type, and these are appropriately selected depending on various properties such as viscosity of the hydrogel polymer, but generally, the hydrogel polymer has a high viscosity. If it is a substance, the tangential type is more suitable. When the rotary arm is used for an internal mixer, the phases of two pairs of rolls are changed to rotate in the same direction, and pressure is applied from above as in a pressure kneader or a Banbury mixer. Shearing force can be applied to the hydrogel polymer.

As the material of the rotating arm used in the present invention, stainless steel or the like is specifically used.

The rotation speed of the rotating arm used in the present invention depends on various properties such as viscosity of the hydrogel polymer, but is 0.01 to 10 m / s, preferably 0.
It is 1-5 m / s.

In the above embodiment, the jacket 6 is provided to heat or cool the hydrous gel polymer, but the jacket is not limited as long as the hydrogel polymer can be heated or cooled. The pressure lid 5 or the rotating arm may have a structure in which a temperature controlling liquid medium can flow.

The shape of the pressure lid used in the present invention is shown in FIGS. 4 (a) and 4 (b) in addition to the shape adapted to the peripheral portion of the rotary arm as shown in FIG. As described above, it may have a flat plate shape (FIG. 4 (a)) or a shape (FIG. 4 (b)) adapted to the circumferential moving portion only on the wall surface side of the container. Among these, it is preferable that the entire hydrogel polymer is stirred and the shear force is evenly applied to the entire hydrogel polymer. Therefore, considering that the hydrogel polymer is unlikely to stay in the container, the pressure lid having the shape shown in FIG. 1 is preferable. In addition,
The above equality means that the specific hydrous gel polymer does not continuously stay at a specific position in the container, and that the shearing force cannot be continuously applied only to a part of the hydrous gel polymer. means.

In the present invention, the pressure lid is used to apply a load of 0.01 to 1.5 kg / cm ² to the hydrogel polymer. The load is applied by applying pressure by air pressure or hydraulic pressure from above the pressure lid in addition to the load of the pressure lid itself. The load applied to the water-containing gel polymer needs to be in the range of 0.01 to 1.5 kg / cm ² . More preferably 0.05 to 1.0 kg / cm ²
Is. 0.01kg load on hydrogel polymer
If it is less than / cm ² , the hydrogel polymer will not be effectively subjected to shearing force, and it will be difficult to obtain the particulate hydrogel polymer aimed at by the present invention, or it will take a long time to obtain it. Or cost. On the other hand, when the load applied to the hydrogel polymer exceeds 1.5 kg / cm ² , the power required to apply the shearing force to the hydrogel polymer is too large and the hydrogel polymer is kneaded. Therefore, the physical properties of the resulting hydrogel polymer are deteriorated, which is not preferable.

In the pressure lid used in the present invention, the volume inside the container is 1.1 of the volume V ₀ of the hydrogel polymer.
~ 1.8 times, more preferably 1.2 to 1.7 times,
And 1.0 to 2.0 times, more preferably 1.0 to 2.0 times the spatial volume V _{1 to which} a shear force is applied (hereinafter referred to as the effective shear volume).
It is desirable to position it in the container so that it becomes about 1.8 times. At this time, the space volume to which the shearing force is applied refers to the remaining space volume obtained by subtracting the volumes of the rotary stirring shaft and the rotary arm from the space volume formed by the maximum rotation circle of the rotary arm of the rotary stirring shaft. When the volume inside the container is less than 1.1 times the volume V ₀ of the hydrous gel polymer, the power required to apply the shearing force to the hydrous gel polymer is too large, and the hydrous gel polymer is too large. However, there is a drawback that the physical properties are deteriorated because of the kneading state. On the other hand, when the volume inside the container exceeds 1.8 times the volume V ₀ of the hydrogel polymer, the hydrogel polymer is not effectively subjected to shearing force,
It is not preferable because it is difficult to obtain the particulate hydrogel polymer which is the object of the present invention, and it takes a long time to obtain the polymer.

If the volume inside the container exceeds 2.0 times the effective shear volume V ₁ , the hydrogel polymer is not effectively subjected to shearing force, and the particulate hydrogel form of the present invention is intended. It is not preferable because it is difficult to obtain the polymer or it takes a long time to obtain the polymer.

The hydrogel polymer of the present invention is not particularly limited as long as it has a size that can be put into a container for carrying out the present invention. Further, for example, even for the finely divided hydrogel polymer obtained by the method described in JP-A-57-34,101, etc., the method of the present invention is applied to these hydrogel polymers. Thereby, the object of the present invention can be achieved.

In the present invention, it is an essential requirement that the temperature of the hydrogel polymer be heated to a temperature of 40 to 110 ° C, preferably 40 to 100 ° C, more preferably 50 to 95 ° C. .. The heating temperature of the hydrous gel polymer is 4
If the temperature is less than 0 ° C, the shearing surface and the water-containing gel-like polymer,
Alternatively, the friction between the water-containing gel-like polymers becomes large, and the physical properties of the water-containing gel-like polymer tend to deteriorate. On the other hand, when the heating temperature of the hydrogel polymer exceeds 110 ° C., water from the hydrogel polymer evaporates violently and the hydrogel polymer foams. Is not sufficiently added, therefor there is a possibility that a particulate hydrogel polymer having a sufficiently small particle size may not be obtained, and there is a case where an increase in soluble content may occur due to deterioration of the hydrogel polymer. Absent.

In the present invention, the time for applying the shearing force is not particularly limited. Generally, the time for applying the shearing force may be shorter as the rotational speed of the rotary stirring shaft is increased and the load applied to the hydrous gel polymer is increased. However,
Applying the repeated shearing force described in the claims of the present invention means applying a repeated shearing force to a specific hydrous gel polymer, for example, using a screw type extruder for the hydrous gel polymer. This is different from the method of applying a temporary shearing force as in the case of extruding from a perforated plate. With a transient shearing force, a particulate hydrous gel polymer having various physical properties, especially a water absorption rate, cannot be obtained.

FIG. 5 is a sectional view schematically showing another embodiment of the container used for applying a shearing force to the hydrogel polymer in the present invention.

The container 7 shown in FIG. 5 has a bottom portion 16 of the pressure lid 5.
Has a structure similar to that shown in FIG. 1 except that the upper part 17 of the pressure lid 5 is provided with a tube 18 for decompressing the atmosphere in the container. In a container having such a structure, by depressurizing the atmosphere in the container through a mesh, it becomes possible to proceed with the polymerization while suppressing an increase in the temperature in the container due to the heat generated during the polymerization. When the heat of polymerization generated when a shearing force is applied to the hydrogel polymer while polymerizing the above-mentioned monomer components to generate a hydrogel polymer is insufficient, the system temperature is high. In some cases, bumping may occur, and the quality of the obtained polymer may be deteriorated, which is not preferable. In order to increase the heat removal effect, it is possible to increase the heat transfer surface for heat removal by flowing cooling water or the like inside the pressure lid and / or the rotating arm in addition to the jacket, but still the heat removal is insufficient. Sometimes the method of reducing pressure is effectively used.

The degree of pressure reduction in the container when using the container shown in FIG. 5 is 1 to 500 mmHg, more preferably 1 to 40 mmHg.
It is preferably about 0 mmHg.

In the production method of the present invention, for the purpose of facilitating the adjustment of the particle diameter of the hydrous gel polymer or improving the handleability of the obtained hydrous gel polymer, Additives such as a surfactant may be added at any time, including before and after the step of applying shearing force to the coalescence. Further, in order to impart a new function to the resulting particulate hydrogel polymer and water-absorbent resin, a water-soluble polymer, a deodorant, a fragrance, a plant growing aid, a bactericide, a fungicide,
It is also possible to apply shearing force in the coexistence of a hydrous gel polymer with a foaming agent, pigment, dye, activated carbon, hydrophilic short fiber, and the like.

The method for producing a water-absorbent resin of the present invention is characterized by drying the particulate hydrogel polymer obtained by the above-mentioned production method of the present invention.

In the present invention, a conventionally known method can be adopted for drying. For example, a box dryer, an aeration box dryer, an aeration band dryer, an aeration vertical dryer, a rotary dryer and the like can be mentioned.

The drying temperature for drying the hydrogel polymer may be a conventionally known temperature, but is in the range of 80 to 250 ° C, preferably 100 to 200 ° C. If the temperature exceeds 250 ° C, the polymer may be deteriorated or decomposed. In any of the above methods, the time required for drying is significantly shorter in the particulate hydrogel polymer obtained by the method of the present invention than in the conventional hydrogel polymers.

A particularly advantageous embodiment of the process according to the invention is to carry out the drying process described in JP-A 64-26,604. This method is a suitable method for obtaining a polymer having a low residual monomer, but has a drawback that its drying efficiency (productivity) becomes low when a low level of residual monomer is achieved. there were. By using the particulate hydrogel polymer obtained by the production method of the present invention, its drying efficiency is remarkably improved, and the object of the present invention is to have a high water absorption capacity and a low water-soluble content. In addition, it is possible to obtain a water-absorbent resin having a significantly small amount of residual monomer with high productivity.

The method for producing a water-absorbent resin of the present invention is characterized by drying, pulverizing and / or crushing the particulate hydrogel polymer obtained by the above-mentioned production method of the present invention. In the present invention, a conventionally known pulverization method can be adopted to obtain the powdery water-absorbent resin. For example, a high speed rotary crusher (pin mill, hammer mill, etc.), screw mill (coffee mill), roll mill, etc. may be mentioned. Among them, since the dried product of the particulate hydrogel polymer obtained by the production method of the present invention is a uniform dried product, it is crushed (crushed) by a roll mill without undergoing a step such as removal of an undried portion. By doing so, it is possible to obtain a water absorbent resin having a small content of fine powder.

The water-absorbent resin thus obtained can be made into a water-absorbing agent whose surface properties are modified by subjecting the water-absorbing resin to a conventionally known surface treatment method. For example, at least 2 which can react with the water-absorbent resin and the functional group of the water-absorbent resin
Mixing with a cross-linking agent having one or more functional groups in one molecule, a modification method of increasing the cross-linking density in the vicinity of the surface of the water-absorbent resin by reacting, mixing the water-absorbent resin and a hydrophobic substance,
A modification method may be mentioned in which a reaction is carried out if necessary to carry out a hydrophobic treatment.

Further, the water-absorbent resin obtained by carrying out the method of the present invention or the water-absorbing agent subjected to the above surface treatment may be subjected to a conventionally known granulation method.

Water-absorbent resin or water-absorbent obtained by the method of the present invention and water-soluble polymer, deodorant, fragrance, drug, plant growth aid, bactericide, fungicide, foaming agent, pigment, dye , Carbon black, activated carbon, single fiber, etc.,
It is also possible to impart a new function to the obtained water absorbent resin.

[0054]

The present invention will be described in more detail with reference to the following examples and comparative examples, but the scope of the present invention is not limited by these examples.

Further, the particle size distribution of the particulate hydrogel polymer described in these examples in dry conversion, the particle size distribution of the dry pulverized product, the water absorption capacity of the dry pulverized product as a water absorbent resin, the water-soluble content, and The water absorption rate is a value measured by the following test method.

A: Particle size distribution of the particulate hydrous gel polymer in terms of dryness: 25 g of the sampled hydrous gel polymer (solid content α% by weight) was added to a 20% by weight sodium chloride aqueous solution 12
It was put into 100 g and the stirrer chip was rotated at 300 rpm and stirred for 60 minutes. After stirring, sieve (opening 9.5 mm, 2.0 mm, 0.85 mm, 0.60
mm, 0.30 mm, 0.075 mm), the above dispersion was charged, and 6000 g of a 20 wt% sodium chloride aqueous solution was slowly poured from above to classify the particulate hydrogel polymer. The classified hydrogel polymer particles on each sieve were thoroughly drained and then weighed. The sieve opening was converted to a sieve opening R (100) corresponding to 100% by weight of the solid content of the particulate hydrogel polymer according to the following mathematical formula 1. The particle size distribution of the particulate hydrous gel polymer corresponding to a solid content of 100% by weight, that is, in terms of dry matter was plotted on a logarithmic probability paper.

[0057]

[Equation 1]

(In the formula, R (100): sieve opening (mm) when converted to a particulate hydrogel polymer having a solid content of 100% by weight, w: hydrogel polymer after classification and draining) (G), γ: mesh size (mm) of sieve classified by hydrous gel polymer swollen in 20% aqueous sodium chloride solution) B: particle size distribution of dry ground product JIS standard sieve A mesh of meshes of 16 mesh, 30 mesh, 50 mesh, 100 mesh and a saucer was placed on top of this, and the dried pulverized product of the hydrogel polymer was placed on top of it.
After adding 0 g and shaking with a sieve shaker for 10 minutes, the classified matter on each sieve was weighed and displayed in% by weight.

C: Water absorption capacity of dry pulverized product Approximately 0.2 g of dry pulverized product of hydrous gel polymer classified according to JIS standard sieve mesh 16 mesh to 100 mesh
Precisely weighed, and made of non-woven tea bag type bag (40mm × 1
50 mm) and soak in 0.9% saline solution for 60
The weight after the minute was measured, and the water absorption capacity was determined according to the following mathematical formula 2.

[0060]

[Equation 2]

D: Water-soluble content of dry pulverized product 0.5 g of dry pulverized product of hydrous gel-like polymer classified from JIS standard sieve mesh 16 mesh to 100 mesh was dispersed in 1000 ml of deionized water for 16 hours. After stirring, filter with a filter paper (TOYO # 6) to obtain at least 100
g of filtrate was obtained. Exactly 100 g of the filtrate was concentrated to about 2 to 3 ml with a rotary evaporator, deionized water was added, and the filtrate was transferred to a petri dish (W0 g). This was dried at 120 ° C. (W1g). The water-soluble content was determined according to the following mathematical formula 3.

[0062]

[Equation 3]

E: Water absorption rate of dried pulverized product 50 ml of 0.9% saline solution (30 ml in a 100 ml beaker)
(° C.) and a stirrer chip were put in and stirred at 600 rpm. Dry pulverized product of hydrous gel polymer classified from JIS standard sieve mesh 16 mesh to 100 mesh 2.0
g was immediately put into the beaker, and the stopwatch was started. The stopwatch was stopped when the stirrer chip exposed at the center of the saline flow was hidden by the swollen hydrogel polymer, and the obtained time was defined as the water absorption rate.

Example 1 A thermometer (15) having a dual-arm Z wing shown in FIGS. 1 and 2 with a total volume of 75 liters and an effective shearing volume of 24.9 liters.
The pressure lid (5) and cover (4) of the pressure kneader (7) made of stainless steel with a jacket (6) equipped with are shown in FIG.
In the state shown in, the liquid supply port (1) and the nozzle (2 ')
Is closed, 50 liters / from the gas supply port (2)
Nitrogen was added in minutes, and the gas was discharged from the gas discharge port (1 '). At this time, the cover (4) is in close contact with the pressure kneader (7) through the sealing material (9) by its own weight. On the other hand, nitrogen was introduced from the gas supply port (3) at 80 liters / minute, and the gas was discharged from the gas discharge port (3 '). The above operation was continued for 10 minutes, the system was replaced with nitrogen, and then the gas outlet (3 ') was closed. 30 kg aqueous solution of monomer component consisting of 75 mol% sodium acrylate and 25 mol% acrylic acid in another container (37 wt% monomer component)
Then, nitrogen gas was blown into an aqueous solution of 18.6 g (0.05 mol% relative to the monomer component) of trimethylolpropane triacrylate as a cross-linking agent to expel dissolved oxygen.
The resulting aqueous solution of the monomer component was charged from the liquid supply port (1) while pressing with nitrogen. Next, the blades of the two kneaders were rotated at 30 rpm, and hot water at 35 ° C was passed through the jacket (6) and the jacket (5 ') inside the pressure lid to heat the monomer components. Then, an aqueous solution containing 15.0 g of sodium persulfate as a polymerization initiator and an aqueous solution containing 0.75 g of L-ascorbic acid were added from the liquid supply port (1). After the addition was completed, the liquid supply port (1) was closed. Polymerization started 4 minutes after the addition of the polymerization initiator and 89 minutes after 13 minutes.
A polymerization peak temperature of ° C was reached. Further, stirring was continued at 30 rpm, and 25 minutes after the initiation of the polymerization, a particulate hydrogel polymer (A) was obtained. At this time, about 10% by weight of the hydrogel polymer (A) was a hydrogel polymer having a size of 10 mm or more. The amount of the water-containing gel-like polymer having a size of 10 mm or more was determined by sampling 500 g of the water-containing gel-like polymer and visually selecting the water-containing gel-like polymer having a size of 10 mm or more. .. The warm water temperature of the jacket was raised to 70 ° C., and while the blade was rotated at 30 rpm, the cylinder (8) was moved by the hydraulic device to the hydrogel polymer (A) adjusted to about 65 ° C. ) Was lowered to the state shown in FIG. That is, a hydrogel polymer (A) having a surface pressure of 0.40 kg / cm ²
The hydraulic pressure of the cylinder (8) is adjusted so as to affect the pressure, and the hydrous gel polymer (A) is loaded under a load for 10 minutes under a nitrogen atmosphere.
A shearing force was applied to to obtain a hydrogel polymer (1) finely divided into particles. At this time, the pressure lid was lifted by 43 mm from the completely closed position (namely, gel stirring space (14) / effective shearing volume = 1). Gel stirring space (14) / effective shear volume = 1.33, gel stirring space (14) /
The charged gel volume was 1.35. The hydrogel polymer (1) thus obtained was moved by moving a cylinder (8) with a hydraulic device to raise a pressure lid (5), and a pressure kneader (7).
Was tilted and taken out. 1 kg each of the resulting hydrogel polymer (A) and hydrogel polymer (1)
Each of them was put in a wire net of 200 mm × 280 mm × 80 mm and dried with hot air at 160 ° C. for 30 minutes. The hydrogel polymer (A) was not uniformly dried, had undried portions, and could not be pulverized. Then, the hydrogel polymer (A) was dried for additional 35 minutes. The obtained dried product was pulverized with a roll mill to obtain 16 mesh (1000 mμ)
A dry ground product (A) and a dry ground product (1) were obtained. The particle size distribution of the obtained hydrous gel polymer and the particle size distribution of the dried and pulverized product, the water absorption capacity as a water absorbent resin, the water-soluble content and the water absorption rate were measured by the above test methods, and the results are shown in Tables 1 to 4. It was shown to.

COMPARATIVE EXAMPLE 1 In Example 1, the pressure lid (5) was not lowered to the state of FIG. 3, and the hydrogel polymer (A) was loaded under a nitrogen atmosphere for 10 minutes in the state of FIG. 1 under no load. The same operation as in Example 1 was carried out except that shearing force was applied to the comparative hydrogel polymer (1
a) was obtained. The obtained comparative hydrogel polymer (1a) was dried in the same manner as in Example 1 at 160 ° C. for 30 minutes with hot air. However, the dry state was non-uniform, there were undried portions, and crushing was impossible. Therefore, a comparative hydrogel polymer (1
The a) was further dried for 30 minutes, and the obtained comparative dried product was pulverized in the same manner as in Example 1 to obtain a comparative dried pulverized product (1a). The obtained comparative hydrogel polymer and the comparative dry pulverized product were evaluated by the same test method as in Example 1, and the results are shown in Tables 1 to 4.

Example 2 In Example 1, except that when the polymerization peak temperature of 89 ° C. was reached, the cylinder (8) was moved by the hydraulic device and the pressure lid (5) was lowered to the state of FIG. The same operation as in Example 1 was performed to obtain a hydrogel polymer (2). The obtained hydrogel polymer (2) was dried with hot air and pulverized in the same manner as in Example 1 to obtain a dry pulverized product (2). The obtained hydrogel polymer and dried and pulverized product were evaluated by the same test method as in Example 1, and the results are shown in Tables 1 to 4.

Example 3 In Example 1, the pressure lid (5) was placed immediately after the initiation of polymerization,
The same operation as in Example 1 was carried out except that it was lowered from the completely closed position to a position lifted by 20 mm. The polymerization started 3 minutes after the addition of the polymerization initiator, and reached the polymerization peak temperature of 86 ° C. 12 minutes later. Further, stirring was continued at 30 rpm, and 40 minutes after initiation of the polymerization, a particulate hydrogel polymer (3) at 60 ° C. was obtained. From the viewpoint of heat generated by the heat of polymerization, pressure started to be applied to the hydrogel polymer at a polymerization rate of about 60%, and the surface pressure was adjusted to 0.12 kg / cm ² . Finally, the pressure lid (5) is stabilized at a position 73 mm above the completely closed position, and the gel stirring space (14) at that time is stabilized.
/ Effective volume of shear = 1.57, and the gel stirring space (1
4) / Prepared gel volume = 1.59. The obtained hydrogel polymer (3) was dried with hot air and pulverized in the same manner as in Example 1 to obtain a dry pulverized product (3). The obtained hydrogel polymer and dried and pulverized product were evaluated by the same test method as in Example 1, and the results are shown in Tables 1 to 4.

Example 4 In Example 1, 36 kg of an aqueous solution of a monomer component (37% by weight of a monomer component) and 22.3 g (0.05 mo of trimethylolpropane triacrylate as a crosslinking agent) were used.
1% relative to the monomer component) and the same operation as in Example 1 was carried out except that the pressure lid (5) was lowered to a position 35 mm above the completely closed position immediately after the initiation of polymerization. The polymerization started 3 minutes after the addition of the polymerization initiator, and reached the polymerization peak temperature of 94 ° C. 12 minutes later. Further 30 rpm
Stirring was continued for 25 minutes after initiation of polymerization to obtain a particulate hydrogel polymer (4) at 70 ° C. From the viewpoint of heat generated by the heat of polymerization, pressure started to be applied to the hydrogel polymer at a polymerization rate of about 60%, and the surface pressure was adjusted to 0.40 kg / cm ² . Finally, the pressure lid (5) is 6
It was stable at a position where it was lifted by 3 mm, and the gel agitation space (14) / effective shearing volume = 1.49 at that time, and the gel agitation space (14) / charged gel volume = 1.25. The resulting hydrogel polymer (4) was dried with hot air and pulverized in the same manner as in Example 1 to obtain a dry pulverized product (4). The obtained hydrogel polymer and dried and pulverized product were evaluated by the same test method as in Example 1, and the results are shown in Tables 1 to 4.

Example 5 Polymerization was carried out in the same manner as in Example 1 to obtain a hydrogel polymer (A) similar to that obtained in Example 1. The water-containing gel polymer (A) was adjusted to about 50 ° C. and the blade was adjusted to 20.
While rotating at rpm, pressurizing lid (5) by hydraulic system
Lowered. The hydraulic pressure of the cylinder (8) was adjusted so that the surface pressure of 0.12 kg / cm ² was applied to the hydrous gel polymer (A), and the hydrous gel polymer (A) was sheared for 15 minutes under a nitrogen atmosphere. Was added to obtain a hydrogel polymer (5) finely divided into particles. At this time, the pressure lid (5) was lifted up 73 mm from the completely closed position, and the gel stirring space / effective shear volume = 1.57 and the gel stirring space / charged gel volume = 1.59. The obtained hydrogel polymer (5) was dried with hot air and pulverized in the same manner as in Example 1.
A dry ground product (5) was obtained. The obtained hydrogel polymer and dried and pulverized product were evaluated by the same test method as in Example 1, and the results are shown in Tables 1 to 4.

Example 6 In Example 5, the temperature of the hydrogel polymer (A) was adjusted to 7
The same procedure as in Example 5 was carried out except that the temperature was 0 ° C., the rotation speed of the blades was 10 rpm, and the surface pressure applied to the hydrous gel polymer (A) was 1.0 kg / cm ^2. 6) was obtained. At this time, the pressure lid (5) was lifted by 15 mm from the completely closed position, and the gel stirring space / effective shear volume = 1.12 and the gel stirring space / charged gel volume = 1.13. The obtained hydrogel polymer (6) was dried with hot air and pulverized in the same manner as in Example 5 to obtain a dry pulverized product (6). The obtained hydrogel polymer and dried pulverized product were evaluated by the same test method as in Example 5, and the results are shown in Tables 1 to 4.

Comparative Example 2 Polymerization was carried out in the same manner as in Example 1 to obtain a hydrogel polymer (A) similar to that obtained in Example 1. The hydrogel polymer (A) was adjusted to 37 ° C., and the subsequent operations were performed in the same manner as in Example 1. The hydrous gel polymer (A) is
A kneaded state was not obtained and a particulate hydrogel polymer was not obtained.

Comparative Example 3 The same operation as in Example 1 was conducted except that the surface pressure of 1.52 kg / cm ² was applied to the hydrous gel polymer (A) in Comparative Example 3. The ammeter of the blade drive motor greatly exceeded the rated value, making it impossible to operate the kneader.

Comparative Example 4 In Example 1, immediately after the initiation of polymerization, the pressure lid (5) was
The same operation as in Example 1 was carried out except that it was lifted to a position where it was lifted 115 mm from the completely closed position. Polymerization started 3 minutes after the addition of the polymerization initiator, and after 12 minutes the polymerization peak at 88 ° C. Reached temperature. Further 30 rpm
The stirring was continued at 25 ° C., and a comparative hydrogel polymer (4a) having a temperature of 62 ° C. was obtained 25 minutes after the initiation of the polymerization. As seen from the movement of the pressure lid (5) and the ammeter of the blade drive motor, the pressure lid (5) is in contact with the hydrogel polymer, but the hydrogel polymer is almost loaded. It didn't seem to depend. At this time, the gel stirring space / effective shear volume = 1.89 and the gel stirring space / charged gel volume = 1.91. The obtained comparative hydrogel polymer (4a) was used in Example 1
In the same manner as above, hot air drying was performed at 160 ° C. for 30 minutes. However, the dry state was non-uniform, there were undried portions, and crushing was impossible. Therefore, the comparative hydrogel polymer (4a) was further dried for 30 minutes, and the obtained comparative dried product was pulverized in the same manner as in Example 1 to obtain a comparative dried pulverized product (4a). The obtained comparative hydrogel polymer and comparative dry ground product were used in Example 1.
Evaluation was carried out by the same test method as described in Table 1 and the results are shown in Tables 1 to 4.

Example 7 A stainless steel kneader equipped with a thermometer and equipped with a double-armed sigma blade having a total volume of 10 liters and an effective shearing volume of 5.5 liters, and 75 mo of sodium acrylate.
1. Aqueous solution of monomer component consisting of 1% and 2-acrylamido-2-methylpropanesulfonic acid 25 mol% 6.
6 kg (35% by weight of the monomer component) and 2.3 g of N, N'-methylenebisacrylamide as a crosslinking agent (0.
(08 mol% relative to the monomer component), and nitrogen gas was blown into the reaction system to replace the atmosphere in the reaction system with nitrogen. Then, while rotating the blades of the two kneaders at 45 rpm and heating the jacket with warm water of 35 ° C., 2.3 g of sodium persulfate and 0.1 g of L-ascorbic acid were added as polymerization initiators. Polymerization started 2 minutes after the polymerization initiator was added, and
A polymerization peak temperature of 89 ° C. was reached after 0 minutes. 4 more
Stirring was continued at 5 rpm, and 25 minutes after the initiation of polymerization, a particulate hydrogel polymer (B) was obtained. At this time, about 15% by weight of the gel polymer (B) was a hydrous gel polymer having a size of 10 mm or more. Set the hot water temperature of the jacket to 7
The temperature was raised to 5 ° C., and the hydrogel polymer (B) adjusted to about 70 ° C. was loaded with a pressure lid while rotating the blade at 45 rpm. It was adjusted so that a surface pressure of about 0.06 kg / cm ² was applied to the hydrogel polymer (B), and shearing force was applied to the hydrogel polymer (B) for 15 minutes in a nitrogen atmosphere to subdivide it into particles. A hydrated gel polymer (7) was obtained. At this time, the pressure lid should be in a completely closed position (ie gel stirring space /
It was lifted by 25 mm from the effective shear volume = 1), the gel stirring space / effective shear volume = 1.25, and the gel stirring space / charged gel volume = 1.25. The obtained hydrogel polymer (7) was dried with hot air and pulverized in the same manner as in Example 1 to obtain a dry pulverized product (7). The obtained hydrogel polymer and dried and pulverized product were evaluated by the same test method as in Example 1, and the results are shown in Tables 1 to 4.

Example 8 In Example 7, the same kneader as in Example 7 was used except that the bottom of the pressure lid had a mesh shape and the pressure inside the reaction system could be reduced. An aqueous solution of the same monomer component as in Example 7 was charged, and nitrogen gas was blown into the reaction system to replace it with nitrogen. Then 45 kneader blades
1. Rotate at rpm and heat the jacket with hot water of 35 ° C., while heating, sodium persulfate as a polymerization initiator 2.
3 g and L-ascorbic acid 0.1 g were added. Immediately after the start of polymerization, the pressure lid was lowered to a position 10 mm above the completely closed position. At this time, the atmospheric pressure in the reaction system is set to 1
The pressure was reduced to 00 mmHg. The polymerization started 2 minutes after the addition of the polymerization initiator, and reached the polymerization peak temperature of 70 ° C. 10 minutes later. Furthermore, the temperature of the hydrogel polymer is about 70.
The temperature of the hot water in the jacket was raised to 75 ° C so that the temperature was maintained at 0 ° C, and stirring was continued under reduced pressure. At this time, the pressure lid was lifted by 25 mm from the completely closed position, gel stirring space / effective shear volume = 1.25, and gel stirring space / charged gel volume = 1.25. After 20 minutes from the start of polymerization, the reaction system is returned to normal pressure (760 mmHg), and further 2
Stirring was continued at 0 rpm, and 50 minutes after the initiation of polymerization, a hydrogel polymer (8) finely divided into particles was obtained. The obtained hydrogel polymer (8) was dried with hot air and pulverized in the same manner as in Example 7 to obtain a dry pulverized product (8). The obtained hydrogel polymer and dried pulverized product were evaluated by the same test method as in Example 7, and the results are shown in Tables 1 to 4.

Comparative Example 5 The same as Example 7 except that the hydrogel polymer (B) was subjected to shearing force under a load for 15 minutes in a nitrogen atmosphere without lowering the pressure lid. The same operation was performed to obtain a comparative hydrogel polymer (5a). The obtained comparative hydrous gel polymer (5a) was treated in the same manner as in Example 7 at 160 ° C. for 3 times.
It was dried with hot air for 0 minutes. However, the dry state was non-uniform, there were undried portions, and crushing was impossible. Therefore, the comparative hydrogel polymer (5a) was further dried for 30 minutes, and the dried product obtained was pulverized in the same manner as in Example 7 to obtain a comparative dry pulverized product (5a). The obtained comparative hydrogel polymer and the comparative dry pulverized product were evaluated by the same test method as in Example 7, and the results are shown in Tables 1 to 4.

Example 9 A hydrogel polymer (9) was obtained in the same manner as in Example 1 except that 37.5 g of sodium persulfate was used as a polymerization initiator. The obtained hydrogel polymer (9) was spread in a hot air drier (aeration type drier, see FIG. 6) to a thickness of 35 mm. Then, the gas from the fresh air introduction pipe and the steam introduction pipe is introduced into the heat exchanger, and heated by the heat transfer medium introduced from the heat medium introduction pipe to change the temperature from 105 ° C. and the dew point 85 ° C. from the steam-air mixed gas. Hot air of 0.8 m / sec. When sprayed at a wind speed of, a dried product was obtained in which the water content was dried to about 8% in 50 minutes. A part of the mixed gas was exhausted from an exhaust pipe and circulated in a heat exchanger by a blower. The dried product thus obtained was pulverized in the same manner as in Example 1 to obtain a dry pulverized product (9). The obtained hydrogel polymer and dried and pulverized product were evaluated by the same test method as in Example 1, and the results are shown in Tables 1 to 4. The amount of residual monomer in the dried and pulverized product was quantified by the following method and found to be 20 ppm.

Method for Quantifying Residual Monomer Amount 0.50 g of the dried and ground product was dispersed in 1000 ml of deionized water, stirred for 2 hours, and then filtered through Whatman filter paper GF / F (particle retention capacity 0.7 micron), It was measured by liquid chromatography.

Comparative Example 6 The procedure of Comparative Example 1 was repeated except that 37.5 g of sodium persulfate was used as the polymerization initiator to obtain a comparative hydrogel polymer (6a). The obtained comparative hydrogel polymer (6a) was dried in the same manner as in Example 9. However, the dry state was non-uniform, there were undried portions, and crushing was impossible. Therefore, the comparative hydrogel polymer (6a) was further dried for 70 minutes, and the obtained dried product was pulverized in the same manner as in Example 9 to obtain a comparative dried pulverized product (6a). The obtained comparative hydrogel polymer and the comparative dry pulverized product were evaluated by the same test method as in Example 9, and the results are shown in Tables 1 to 4. Further, the amount of residual monomer of the dried pulverized product was quantified by the same test method as in Example 9, and it was 2
It was 0 ppm.

Example 10 100 parts by weight of the dry ground product (1) obtained in Example 1 were mixed with an aqueous mixture consisting of 1 part by weight of glycerin, 2 parts by weight of water and 8 parts by weight of isopropanol. The resulting mixture was placed in a bowl immersed in an oil bath (195 ° C.) and heat-treated for 45 minutes under stirring to give a water-absorbing agent (1
0) was obtained. The water absorbent obtained was evaluated by the same test method as in Example 1, and the results are shown in Tables 1 to 4. The water absorption performance under pressure was evaluated by the following method. 5 minutes and 30
Water absorption capacity under pressure is 17 ml / g and 26
It was ml / g.

Evaluation Method of Water Absorption Under Pressurization The water absorption under pressure for 5 minutes and 30 minutes was measured using the apparatus shown in FIG. 7, and the water absorption rate under pressure and the water absorption capacity under pressure were evaluated. The upper port 32 of the buret 31 is capped with a plug 33, and the measuring table 34 and the air port 35 are set at a constant height. The filter paper 37, 0.2 g of the water absorbing agent 39 and the filter paper 37 were placed on the glass filter 36 having a diameter of 70 mm in the measuring table 34, and further the weight 38 of 20 g / cm ² was placed thereon, and artificial urine absorbed in a predetermined time (composition: Urea 1.9%, NaCl
0.8%, CaCl ₂ 0.1% and MgSO ₄
The value of 0.1%) was taken as the water absorption capacity under pressure (ml / g).

Comparative Example 7 Comparative Example 7 was carried out in the same manner as in Example 10, except that the comparative dry crushed product (1a) obtained in Comparative Example 1 was used in place of the dry crushed product (1). A water absorbing agent (7a) was obtained. The water absorbent obtained was evaluated by the same test method as in Example 1, and the results are shown in Tables 1 to 4. When the water absorption performance under pressure was evaluated by the same method as in Example 10, the water absorption capacity under pressure for 5 minutes and 30 minutes were 11 ml / g and 25 ml / g, respectively.

[0083]

[Table 1]

[0084]

[Table 2]

[0085]

[Table 3]

[0086]

[Table 4]

[0087]

INDUSTRIAL APPLICABILITY As described above, by carrying out the method of the present invention, a particulate hydrogel polymer and a water absorbent resin having a high water absorption capacity and a low water-soluble content are produced with high productivity. It becomes possible. Further, it becomes possible to obtain a particulate hydrogel polymer which does not contain additives such as a lubricant and has a narrow particle size distribution and good drying efficiency with high productivity. Further, it becomes possible to obtain a water absorbent resin having a high water absorption rate and a small content of fine powder. Further, it becomes possible to obtain a water absorbent resin having a high water absorption rate under pressure. Furthermore, it becomes possible to obtain a water absorbent resin having a remarkably small amount of residual monomer with high productivity.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing an embodiment of a container used for applying a shearing force to a hydrogel polymer according to the present invention.

FIG. 2 is a schematic cross-sectional view taken along the line aa of FIG.

FIG. 3 is a cross-sectional view schematically showing another embodiment of the container used to apply the shearing force to the hydrogel polymer according to the present invention.

4 (a) and 4 (b) are cross-sectional views schematically showing another embodiment of the container used in the present invention.

FIG. 5 is a cross-sectional view schematically showing another embodiment of the container used for applying a shearing force to the hydrogel polymer according to the present invention.

FIG. 6 is a schematic view of an apparatus used for drying the particulate hydrous gel polymer obtained according to the present invention.

FIG. 7 is a schematic view of an apparatus used for measuring the water absorption under pressure of the particulate hydrous gel polymer obtained according to the present invention.

[Explanation of symbols]

1 ... Liquid supply port 2, 3 ... Gas supply port 1 ', 3' ... Gas discharge port 2 '... Nozzle 4 ... Cover 5 ... Pressurizing lid 5', 6 ... Jacket 7 ... Container (pressurizing kneader) 8 ... Cylinder 9 ... Sealing material 10, 11 ... Rotating arm 12, 12 ', 13
... Rotating stirring shaft 14 ... Gel stirring space 15 ... Thermometer 16 ... Pressure lid bottom 17 ... Pressure lid top 18 ... Tube 21 ... Hydrogel polymer 22 ... Fresh air introduction pipe 23 ... Steam introduction pipe 24 ... Exhaust exhaust pipe 25 ... Blower 26 ... Heat exchanger 27 ... Heat medium introduction pipe 31 ... Burette 32 ... Burette upper port 33 ... Plug 34 ... Measuring stand 35 ... Air port 36 ... Glass filter 37 ... Filter paper 38 ... Weight 39 ... Water absorbent

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location C08L 33/02 LHR (72) Inventor Kazumasa Kimura 5-8 Nishimitabicho Suita City Osaka Prefecture Co., Ltd. Central Research Institute of Nippon Shokubai

Claims (12)

[Claims] 1. A method for producing a particulate hydrogel polymer in which a hydrogel polymer having a crosslinked structure is subjected to shearing force to be subdivided into particles in a container, at a temperature of 40 to 110 ° C. 0.01-1.5k to warm hydrogel polymer
A method for producing a particulate hydrogel polymer, which comprises repeatedly applying a shearing force while applying a load of g / cm ² . 2. The method for producing a particulate hydrogel polymer according to claim 1, wherein the container is a kneader having a plurality of rotary stirring shafts. 3. The remaining space volume (shear effective volume) of the container, wherein the volume inside the container is formed by subtracting the volumes of the rotary stirring shaft and the rotary arm from the space volume formed by the rotation of the rotary arm of the rotary stirring shaft. The method for producing a particulate hydrogel polymer according to claim 1, which is 1.0 to 2.0 times V ₁ and 1.1 to 1.8 times the volume V ₀ of the hydrogel polymer. .. 4. A hydrated gel-like polymer formed by advancing the polymerization of a monomer component containing an ethylenically unsaturated monomer which becomes a hydrated gel by polymerization and a crosslinking agent. The method for producing a particulate hydrogel polymer according to claim 1, which is a polymer. 5. The method for producing a particulate hydrogel polymer according to claim 4, wherein the hydrogel polymer is a hydrogel polymer having a polymerization rate of a monomer component of 10 to 100%. 6. The method for producing a particulate hydrogel polymer according to claim 4, wherein the polymerization of the monomer component is allowed to proceed under reduced pressure. 7. The method for producing a particulate hydrogel polymer according to claim 6, wherein the degree of reduced pressure is 1 to 500 mmHg. 8. A method for producing a water absorbent resin, which comprises drying the particulate hydrogel polymer according to claim 1. 9. A method for producing a water-absorbent resin, which comprises drying, crushing and / or crushing the particulate hydrogel polymer according to claim 1. 10. Drying gas containing at least water vapor and having a dew point of 50 to 100 ° C., 80 to 250
The method for producing a water absorbent resin according to any one of claims 8 to 9, which is carried out by contacting at a temperature of ° C. 11. The method for producing a water absorbent resin according to claim 9, wherein the crushing and / or crushing is performed by a roll mill (roll rotary crusher). 12. The water-absorbent resin according to claim 8, which is mixed with a cross-linking agent having at least two functional groups capable of reacting with the functional group of the water-absorbent resin, to react with the water-absorbent resin. A method for producing a water absorbing agent, which comprises increasing the crosslink density in the vicinity of the surface of a resin.