JP3016879B2 - Method for producing superabsorbent resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a superabsorbent resin. More specifically, the present invention relates to a method for producing a superabsorbent resin having high water absorbency even under a pressurized state.

[0002]

2. Description of the Related Art In recent years, superabsorbent resin powders have been used in various fields such as sanitary materials that absorb body fluids and water retention agents, such as menstrual cotton and paper diapers. Examples of such superabsorbent resin include, for example, a hydrolyzate of starch-acrylonitrile graft polymer (Japanese Patent Publication No. 49-49).
-43,395), a neutralized product of a starch-acrylic acid graft polymer (JP-A-51-125468), and a saponified product of a vinyl acetate-acrylic acid ester copolymer (JP-A-52-14, JP-A-52-14). No. 689), a hydrolyzate of an acrylonitrile copolymer or an acrylamide copolymer (JP-B-53-15959), or a cross-linked product thereof or a cross-linked polyacrylic acid partially neutralized product (JP-A-55-84). , 30
No. 4) is known.

[0003] Desirable characteristics of a highly aqueous resin include a high absorption capacity and an excellent absorption rate when in contact with an aqueous liquid, a high gel strength of a water-containing swelling gel, and the ability to absorb water from a substrate containing an aqueous liquid. And excellent suction power. However, the relationship between these properties does not necessarily show a positive correlation, and in particular, the absorption capacity and the absorption rate, the gel strength and the suction force are in conflicting relation, and the higher the absorption capacity, the lower these properties are. I will. In addition, some materials with high absorption capacity are so-called "Mamako" when they come in contact with aqueous liquids.
Is formed, water does not diffuse throughout the superabsorbent resin particles, and the absorption rate is extremely low.

[0004] As a method for obtaining a superabsorbent resin having a high absorption capacity and a relatively good absorption rate, a method of coating the surface of the superabsorbent resin with a surfactant or a non-volatile hydrocarbon is known. ing. However, in this method, although the dispersibility of the superabsorbent resin in the aqueous liquid is improved, a sufficient effect is not obtained in terms of improving the absorption speed and suction power of each superabsorbent resin particle.

As a method for improving the above properties in a well-balanced manner, there is also known a method in which the surface of a highly water-absorbent resin is crosslinked with a hydrophilic crosslinking agent. Such hydrophilic crosslinking agents include polyhydric alcohols, polyhydric glycidyl ethers,
Haloepoxy compounds, polyhydric aldehydes, polyvalent amines, and polyvalent metal salts are used, but it is necessary to uniformly distribute and react this hydrophilic cross-linking agent on the surface of the superabsorbent resin. It is important to form a suitable crosslinked layer and enhance the improvement effect.

As a method of uniformly distributing the hydrophilic crosslinking agent on the surface of the superabsorbent resin, a method of directly mixing the superabsorbent resin powder and the hydrophilic crosslinking agent and performing a heat treatment if necessary (Japanese Patent Application Laid-Open No. 58-1983) 180,233, JP-A-59-18
9, 103, JP-A-61-16903, JP-A-6
No. 1-46,241), a highly water-absorbing resin is prepared by dispersing a hydrophilic organic dispersion medium of alcohol and ketones or water and alcohol;
There is known a method of dispersing in a mixture with a ketone, adding a crosslinking agent and reacting the mixture (Japanese Patent Application Laid-Open No. 58-42602).

However, in the former method in which the superabsorbent resin powder and the crosslinker are directly mixed, it is difficult to uniformly distribute the crosslinker on the surface of the resin powder. Tends to be uneven.

In the latter method, when a mixture of water and a hydrophilic organic solvent is used, the hydrophilic cross-linking agent becomes soluble in the dispersion medium and may be distributed uniformly on the surface of the superabsorbent resin. However, when heated at the time of crosslinking, the hydrophilic organic solvent is distilled off, which is not preferable in view of the danger of fire in the apparatus and the problem of avoiding the problem of pollution due to emission into the atmosphere as waste gas. Furthermore, there is a high possibility that the hydrophilic organic solvent remains as impurities in the superabsorbent resin.

On the other hand, a method of mixing and reacting a superabsorbent resin powder with a crosslinking agent in the presence of water and an inert inorganic powder (JP-A-60-163956 and JP-A-60-255) 814) is known, but it is industrially difficult to use expensive inorganic powder because of low economic efficiency. On the other hand, if a very small amount of the inorganic powder is to be added to the superabsorbent resin powder, it is difficult to form a uniform mixture, and the effect of using the inorganic powder cannot be obtained.

[0010]

As described above, in order to improve the various properties of the superabsorbent resin in a well-balanced manner, methods such as forming a surface cross-linked layer on the superabsorbent resin have been tried. Also have the problems described above,
It did not show a sufficient improvement effect.

Accordingly, it is an object of the present invention to provide a novel method for producing a superabsorbent resin. Another object of the present invention is to provide a method for producing a superabsorbent resin having high water absorbency even in a pressurized state.

[0012]

The above objects are achieved by charging a superabsorbent resin powder having a functional group from the upper part of a cylindrical body having a lower end opened, and from the upper part to the lower part of the cylindrical body. A liquid material of a compound having a group capable of reacting with two or more functional groups of the superabsorbent resin is sprayed in the form of droplets, and the superabsorbent resin powder flowing down toward the lower part of the cylindrical body is The droplets, which are radially diffused toward the lower part of the cylindrical body and flow down, are brought into contact with each other in a co-current state, and the highly water-absorbent resin powder in which the droplets are uniformly adsorbed is brought into the cylindrical shape. From the bottom of the body
The superabsorbent resin powder is then subjected to a heat treatment at a temperature of 40 ° C. or higher, which is achieved by a method for producing a superabsorbent resin.

[0013]

Hereinafter, the method of the present invention will be described in more detail with reference to the drawings.

FIG. 1 is a view showing an apparatus embodying a method for continuously producing a superabsorbent resin powder of the present invention. As shown in the figure, a cylindrical body 10 having an opening 11 at its lower end is provided facing up and down, and at the upper center of the cylindrical body 10, a conical dispersion plate 12 spreading downward is installed. ing. The supply member 13 for supplying the superabsorbent resin powder A toward the dispersion plate 12 and supplying the resin powder A into the cylinder 10 from the entire lower periphery of the dispersion plate 12 is located above the cylinder 10. It is provided in.

At the center of the dispersion plate 12, a pipe 14 is mounted.
The nozzle 15 is mounted at a position below the nozzle 15. Air and a liquid (hereinafter referred to as liquid B) of a compound having a group capable of reacting with two or more functional groups of the superabsorbent resin are simultaneously ejected from the nozzle 15. The liquid material B is sprayed downward as fine droplets in the cylindrical body 10. The superabsorbent resin powder A and the fine liquid droplets sprayed from the nozzles 15 supplied from the dispersing plate 12 flow down due to the spraying force and their own weight while diffusing toward each other below the cylindrical body 10. Will be.
As a result, the resin powder A flowing down while diffusing
Flows down from the upper portion to the lower portion, while the droplets of the liquid material B flow down from the upper portion to the lower portion while diffusing at a predetermined angle in the radial direction of the liquid material B in the cylindrical body 10, so that the resin powder A and the liquid material B And a mixture in which the liquid B is uniformly dispersed on the surface of the resin powder A. At this time, a bonded granule in a state in which the plurality of resin powders A are bonded may be formed using droplets attached to the resin powder A as a medium.

FIG. 2 shows another embodiment of the present invention. Members common to the members shown in FIG.
The same reference numerals are given. In the apparatus shown in FIG. 1, the superabsorbent resin powder A was separately charged into the dispersion plate 12. However, in the apparatus shown in FIG. They are distributed.

For this purpose, as shown in FIG.
Is a tapered portion 16 whose diameter decreases as it goes downward.
a and a straight portion 16b extending downward from the lower end of the tapered portion 16a. Compressed air from a nozzle 19 provided at the tip of a pneumatic pipe 18 is blown onto the superabsorbent resin powder A charged from the charging member 13 on the upper surface of the tapered portion 16a. Will also flow down due to the action of.
In this case, the mixing ratio between the resin powder A and the airflow is 0.1 to 5
It is preferable to be in the range of kg / Nm ³ . When the amount of the resin powder A is more than 5 kg / Nm ³ , the dispersion or diffusion of the resin powder A by an air current becomes insufficient,
Uniform contact with the droplets of the liquid material B cannot be achieved. On the other hand, if the ratio is less than 0.1 kg / Nm ³ , an enormous amount of gas is introduced, so that an excessive facility is required for disposal of the gas, which is not practical. In addition, when the exhaust is insufficient, the amount of the mixture adhering to the inner peripheral surface of the cylindrical body 10 increases, making continuous operation difficult. By controlling the flow rate of the airflow together with the ratio between the airflow and the resin powder A, the residence time of the airflow in the cylindrical body 10 is determined. The residence time is about 0.1 to 30 seconds. It is preferable to set.

FIG. 3 shows a modification of the apparatus shown in FIG. 2. In this case, a jacket 31 is formed in the wall of the cylindrical body 10, and steam is circulated through a steam pipe 32 in this. The inner surface of the cylindrical body 10 is heated. In the case shown, steam of about 2 kg / cm ² G was circulated, and the temperature of the inner surface was kept at about 100 ° C. This prevents the mixture from adhering to the inner surface of the cylindrical body 10. In the experiment, 60
The apparatus was operated for minutes, and no generation of deposits was observed. In this case, the basic form is the same as that of the apparatus shown in FIG. 2 except that the above-described jacket 31 is provided and the position of the nozzle 19 at the tip of the pneumatic pipe 18 is different. is there.

FIG. 4 is a view showing still another specific example, and this basic form has the commonality with the apparatus shown in FIG. 2, but in this case, the nozzle 33 for ejecting the liquid B is used. Are arranged on the inner peripheral surface of the cylindrical body 10. The droplets from these nozzles 33 flow down because the respective nozzles are inclined downward at a predetermined angle.
, And flows downward while crossing at a predetermined angle. In this case, the same operation and effect as those described above were obtained. Even if the droplets are sprayed from these nozzles 33 toward the center of the cylindrical body 10 in the horizontal direction, the influence of the air flow for charging the resin powder A causes
As a result of the restriction of the flow of the droplet, the droplet and the resin powder A become co-current with each other in the downward direction in the cylindrical body 10, and the droplet and the resin powder A are uniformly mixed to form a mixture.

In each of the above embodiments, the cylindrical body 10 is used as the cylindrical body. However, a rectangular cylindrical body having a quadrangular cross section or a polygon having a larger cross section may be used. Alternatively, a cylindrical body having a cone shape such as a cone shape or a pyramid shape may be used.

In a preferred embodiment of the present invention, the highly water-absorbent resin powder A is charged by a gas stream from a dispersing member provided on the upper portion of a cylindrical body having a lower end opened. In the charging method without using an air flow, the superabsorbent resin powder A may be insufficiently dispersed, and the absorbent under pressure may be deteriorated during continuous operation. Further, it is preferable that the nozzle for spraying the liquid material B is provided inside, preferably substantially at the center of the dispersion member of the superabsorbent resin powder A. When installed outside the dispersing member, the contact between the superabsorbent resin powder A and the liquid material B may become uneven, and the absorbency under pressure of the superabsorbent resin obtained during continuous operation may deteriorate. Sometimes. Further, since the liquid material B diffuses and wets the inner wall of the cylinder, the superabsorbent resin powder A
Easily adhere to the wall.

The inner wall of the cylindrical body is preferably kept at 50 to 200 ° C., more preferably 70 to 200 ° C., by providing a heat retaining means. Thereby, it is possible to prevent the superabsorbent resin powder A from adhering to the inner surface of the cylindrical body, and to obtain a superabsorbent resin having stable performance even in continuous operation. The adhesion of the superabsorbent resin powder A to the inner wall of the cylinder causes an excessively or unevenly mixed state of the liquid material B on the adhered portion, and lowers the quality of the superabsorbent resin obtained during continuous operation. And stability will be reduced.

In the present invention, the mixture of the superabsorbent resin powder A and the liquid B taken out from the lower part of the cylindrical body is heated at 40 ° C.
Heat treatment is performed at the above temperature.

As the heating device used in the present invention, there are a usual dryer and a mixer with a jacket. For example, a ribbon blender, a fluidized-bed dryer, a paddle-type dryer, an infrared dryer, and the like are given.

The ribbon blender includes a horizontal type and a vertical type. The horizontal type has a single axis or a double axis. The ribbon blender is used for both batch and continuous operations. The movement of the granular material is in the ribbon blade, while the outer blade is
In general, the inner blade has a double-wound ribbon structure that moves outward, but it is necessary to change the ribbon shape according to the target substance, its properties, or operation (batch or continuous). Shearing and circulation promote mixing,
Discharge the mixture from the bottom or side of the tank.

The fluidized-bed dryer is a device for drying the powdery and granular wet raw material on the perforated plate by performing a heat exchange by flotting the raw material with hot air from below and mixing vigorously. A typical example is a horizontal fluidized bed type, in which a crusher is provided in the fluidized bed, and the aggregates in the supplied raw material are crushed and heat is exchanged with hot air at the same time. Although the number of revolutions, the shape of the blades, and the mounting location are determined each time depending on the state of the raw material, the crusher is typically mounted in a fluidized bed below the supply port. The raw material crushed by the crusher and fluidized by the hot air in the lower part is prevented from being short-passed by the adjustable weir provided in the machine. As a result, the average residence time distribution of the feedstock is narrowed, and a uniform product can be obtained. In addition, the dwell time can be adjusted by tilting the weir. As the drying proceeds, the raw material moves by the inlet to the outlet.

As a mixer with a jacket, for example, a horizontal U-shaped trough-shaped drying chamber with a heating jacket is provided in the main body, a raw material supply port is provided on one upper surface, and a product discharge port is provided on the other lower surface. A large number of a pair of hollow fan-shaped heat transfer blades and stirring blades for stirring and transporting the raw material are mounted at equal intervals and rotated at a low speed. The raw material is continuously stirred, heated, and transferred in the machine, and is discharged after overflowing the movable weir at the discharge port. The residence time in the machine is adjusted by changing the angle of the stirring blade.

In the present invention, the heat treatment temperature of the superabsorbent resin powder to which the liquid material B adheres is 40 ° C. or higher, preferably 80 to 220 ° C., but the optimum heating temperature depends on the hydrophilic crosslinking agent used. Are usually different. Also,
The heating time depends on the heating method, but is usually 0.1
５5 hours, preferably 0.5-2 hours.

The superabsorbent resin powder to be used in the present invention is a conventionally known powdery superabsorbent resin which absorbs a large amount of water in water and swells to form a hydrogel.
For example, hydrolyzate of starch-acrylonitrile graft copolymer, saponified product of acrylic acid ester-vinyl acetate copolymer, hydrolyzed product of acrylonitrile copolymer or acrylamide copolymer, and starch-acrylic acid graft polymer Examples include a neutralized product, a neutralized product of a self-crosslinked polyacrylic acid, a crosslinked product of a polyacrylate, and a neutralized product of a crosslinked isobutylene-maleic anhydride copolymer.

Such a superabsorbent resin powder is generally obtained by polymerizing a water-soluble ethylenically unsaturated monomer having a functional group. The monomer constituting the superabsorbent resin powder used in the present invention is a water-soluble ethylenically unsaturated monomer having a functional group, for example, acrylic acid, methacrylic acid, maleic acid, fumaric acid. Acid, itaconic acid, protonic acid, citraconic acid, α-hydroxyacrylic acid, aconitic acid, 2- (meth) acryloylethanesulfonic acid, 2- (meth) acrylamide-2-methylpropanesulfonic acid and the like can be mentioned. And an acrylate monomer comprising at least one unsaturated carboxylic acid and a salt thereof, and more preferably an acrylate monomer composed of 1 to 50 mol% of acrylic acid and 99 to 50 mol% of acrylate. Of course, the ratio of the acrylic acid to the acrylate may be such that the polyacrylic acid obtained by polymerizing the acrylic acid is partially neutralized to have the above molar ratio.

In addition, the superabsorbent resin powder contains a smaller amount of a crosslinkable monomer having two or more polymerizable unsaturated groups or reactive functional groups than a self-crosslinkable resin powder that does not use a crosslinkable monomer. Those reacted are more desirable.

Examples of these crosslinking agents include, for example, N,
N'-methylenebis (meth) acrylamide, N-methylol (meth) acrylamide, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, glycerin tri (meth) acrylate, glycerin di (meth) ) Acrylate, (meth) acrylic acid polyvalent metal salt, trimethylolpropane tri (meth) acrylate, triallylamine,
Triallyl cyanurate, triallyl isocyanurate, triallyl phosphate, glycidyl (meth) acrylate, ethylene glycol diglycidyl ether,
Glycerin tri (di) glycidyl ether, polyethylene glycol diglycidyl ether and the like can be mentioned. These crosslinking agents may be used as a mixture of two or more kinds. The use amount of these crosslinking agents is generally about 0.001 mol% to 0.5 mol%, preferably about 0.01 to 0.3 mol%.

As a polymerization method for obtaining the superabsorbent resin powder, various methods such as aqueous solution polymerization, reversed phase suspension polymerization, precipitation polymerization, bulk polymerization and the like can be adopted. Among them, aqueous solution polymerization or reversed-phase suspension polymerization is preferred, and aqueous solution polymerization is particularly preferred, from the viewpoints of workability during polymerization and handleability when mixing the obtained superabsorbent resin powder and liquid B.

When the superabsorbent resin powder is synthesized by aqueous solution polymerization or reverse phase suspension polymerization, the monomer concentration in the aqueous monomer solution is as follows:
The choice can be made over a wide range, but is generally from 20% by weight or more, more preferably from 25% by weight to the saturation concentration.

Examples of the polymerization initiator used in the polymerization include commonly used water-soluble radical polymerization initiators such as potassium persulfate, sodium persulfate and ammonium persulfate, hydrogen peroxide, t Hydroperoxides such as -butyl hydroperoxide and cumene hydroperoxide; and azo compounds such as 2,2'-azobis-2-amidinopropane hydrochloride. These polymerization initiators can be used as a mixture of two or more kinds. Further, a redox initiator system may be used in combination with a reducing agent such as sulfite, 1-ascorbic acid, and ferric salt. it can. The amount of the polymerization initiator used is 0.001 to 1.0% by weight, preferably 0.005% by weight, based on the monomer.
~ 0.5% by weight.

The compound having a group capable of reacting with two or more functional groups of the superabsorbent resin powder used in the present invention (hereinafter referred to as a surface cross-linking agent) is preferably hydrophilic, and more preferably hydrophilic. There is no particular limitation as long as it is a water-soluble compound, for example, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, glycerin, polyglycerin, propylene glycol, diethanolamine,
Polyhydric alcohols such as triethanolamine, polyoxypropylene, oxyethyleneoxypropylene block copolymer, pentaerythritol and sorbitol; ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol polyglycidyl ether, diglycerol polyglycidyl ether Glycidyl ethers such as polyglycerol polyglycidyl ether, sorbitol polyglycidyl ether, pentaerythritol polyglycidyl ether, propylene glycol diglycidyl ether and polypropylene glycol diglycidyl ether; 2.2-bishydroxymethylbutanol-tris [3 -(1-aziridinyl) propionate], 1,6-hexamethylenediethyleneurea , Diphenylmethane - bis-4,4
Polyvalent aziridine such as' -N, N'-diethyleneurea; haloepoxy compounds such as epichlorohydrin and α-methylchlorohydrin; polyaldehydes such as glutaraldehyde and glyoxal; ethylenediamine, diethylenetriamine, triethylenetetramine, tetra Polyvalent amines such as ethylenepentamine, pentaethylenehexamine and polyethyleneimine; polyvalent isocyanates such as 2,4-toluylene diisocyanate and hexamethylene diisocyanate; aluminum chloride, magnesium chloride, calcium chloride, aluminum sulfate, magnesium sulfate; Examples thereof include polyvalent metal salts such as calcium sulfate. Particularly preferred are polyhydric alcohols, polyglycidyl ethers, polyamines, and polyvalent metal salts.

The amount of the surface cross-linking agent to be used depends on the type of the cross-linking agent.
0% by weight is suitable, preferably 0.5 to 10% by weight
It is. If the amount is less than 0.1% by weight, the effect of the present invention will not be exhibited, and if it exceeds 30% by weight, the absorption capacity may be significantly reduced.

The compound having a group capable of reacting with two or more functional groups of the superabsorbent resin powder used in the present invention is as follows:
If the substance itself is liquid, it can be used alone, but it is usually diluted with a diluent and used as a liquid substance B. The diluent can be used without any limitation as long as it can dissolve or disperse the compound and does not affect the performance of the superabsorbent resin. For example, water, methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol,
Lower alcohols such as isobutyl alcohol and t-butyl alcohol; ketones such as acetone and methyl ethyl ketone; ethers such as dioxane and tetrahydrofuran; amides such as N, N'-dimethylformamide; and sulfoxides such as dimethyl sulfoxide. be able to.

However, a feature of the present invention is that the compound and the superabsorbent resin powder are uniformly mixed without using any organic solvent. That is, it is preferable that the diluent be water alone from the viewpoints of economy, fire, and pollution.

The fine droplets of the liquid material B used in the present invention preferably have an average diameter of 300 μm or less, more preferably 250 μm or less. Usually, it has an average diameter of 50 to 200 μm. If the average diameter exceeds 300 μm, it becomes difficult to uniformly diffuse or disperse the liquid material B, resulting in a high-density mass or a large amount of the superabsorbent resin powder that does not contact the liquid material B in the cylinder. May be undesirable. As a method of generating fine droplets having an average diameter of 300 μm or less, a rotating disk method,
Although a pressurized nozzle method and a two-fluid nozzle method can be mentioned, in the present invention, since the superabsorbent resin powder is introduced from the upper part, a gas is ejected to a droplet sprayer to prevent granulation adhesion. Suitable is a two-fluid nozzle capable of performing the following. Examples of such a product include Lumina (made by Fuso Seiki Co., Ltd.).
Fluid nozzles and spray vectors (manufactured by Kobe Cast Iron Co., Ltd.) can be mentioned.

[0041]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to Examples, but the scope of the present invention is not limited only to these Examples. Unless otherwise specified, all “%” and “parts” in the following examples represent% by weight and “parts” by weight, respectively.

Example 1 A jacketed stainless steel double-armed kneader provided with two sigma-type blades having an inner volume of 10 liters and a blade rotation diameter of 120 mm was provided with a lid, and an aqueous solution of sodium acrylate was placed in the kneader. 5500 parts of an aqueous solution of an acrylate monomer composed of 4380 parts, 414 parts of acrylic acid and 706 parts of ion-exchanged water (monomer concentration: 37% by weight, neutralization rate: 75 mol%), and 3.4 parts of trimethylolpropane triacrylate And the inside of the reaction system was purged with nitrogen by blowing nitrogen gas. Then, two sigma-type blades were
While rotating at a speed of rpm and passing warm water at 35 ° C. into the jacket, 2.8 parts of sodium persulfate and 0.14 part of 1-alcorbic acid were added as polymerization initiators. After the addition of the initiator, the polymerization was started in 5 minutes, the temperature in the reaction system reached 83 ° C. in 20 minutes, and the hydrogel was about 5 mm.
And the polymerization was completed in 60 minutes to take out a hydrogel polymer.

This hydrogel polymer was spread in a hot air drier to a thickness of 50 mm and dried with hot air at a temperature of 150 ° C. for 90 minutes. This was pulverized with a hammer type pulverizer and sieved with a 20-mesh wire net to obtain superabsorbent resin powder A.

A liquid material B composed of 0.5 part of glycerin and 10 parts of water was mixed with 100 parts of the superabsorbent resin powder A by using the apparatus shown in FIG. 3, heated and then sieved with a 20 mesh wire mesh. The un-passed material was pulverized by a roll mill-type granulator to obtain a water-absorbing agent (1) by passing the whole amount through 20 mesh.

That is, in the apparatus shown in FIG. 3, compressed air from an airflow generating means comprising a nozzle 19 provided at the end of a pneumatic pipe 18 is applied to the superabsorbent resin powder A charged from the charging member 13. Sprayed superabsorbent resin powder A
Was diffused in the radial direction of the cylindrical body 10 by the action of its own weight and this airflow, and flowed down below the cylindrical body 10.

A pipe 14 was attached to the center of the dispersing member 16, and a nozzle 15 was attached to the tip of the pipe at a position below the dispersing member 16. Air and the liquid material B were simultaneously ejected from the nozzle 15, and the liquid material B was sprayed downward as fine droplets in the cylindrical body 10. The sprayed droplets of the liquid material B flow down below the cylindrical body 10 while diffusing in the radial direction of the cylindrical body 10,
Due to the adjustment of the nozzle position and the liquid absorption of the superabsorbent resin powder A, the diffusion of the cylindrical body 10 in the radial direction at any position in the height direction of the cylindrical body 10 is performed by the superabsorbent resin powder. It was not larger than A. The droplets are absorbed by the highly water-absorbent resin powder A during the flow, and the liquid
At the lower end of 0, the existence of the droplet was hardly recognized. At this time, the mixing ratio between the superabsorbent resin powder A and the airflow was 1 kg / Nm ³ . The average droplet diameter of the liquid B is
It was about 100 μm. The residence time of the superabsorbent resin powder A in the cylindrical body 10 was 10 seconds. The inner wall temperature of the cylindrical body 10 was maintained at 90 ° C. by external heating.

The superabsorbent resin powder A and the liquid material B come into contact with each other in a co-current state, and the droplets of the liquid material B adhered to the resin powder A are used as a medium to form the liquid material B on the surface of the plurality of resin powders A. Resulted in a uniformly dispersed mixture.

The resin powder thus formed into a mixture was placed in a ribbon blender in which a jacket provided below the cylindrical body 10 was heated to 200 ° C. with a heating medium and subjected to a heat treatment. The material temperature of the water-absorbing agent (1) taken out of the mixture after the heat treatment for 60 minutes was 180 ° C.

The resin powder A and the water-absorbing agent (1) thus obtained had (a) absorption capacity, (b) suction power, (c) absorbency under pressure, and (d) particle size (the weight of a powder passing through a 100 mesh standard sieve). %) Was evaluated as follows.

(A) Absorption Ratio About 0.2 g of the obtained resin powder A or the water absorbing agent (1) is uniformly placed in a non-woven tea bag type bag (40 mm × 150 mm) and immersed in 0.9% saline solution. After 30 minutes, the weight was measured. The water absorption capacity of the water-absorbing agent (1) was calculated according to the following mathematical formula 1, using the weight of the liquid absorption of only the tea bag type bag as a blank.

[0051]

(Equation 1)

(B) Suction force The artificial urine 20 was placed on a tissue paper (55 mm × 75 mm).
ml (composition: urea 1.9%, NaCl 0.8%, CaC
l ₂ 0.1% and MgSO ₄ 0.1%) was added to create a substrate containing synthetic urine, on the substrate, 0 high water-absorbent resin powder A or water-absorbing agent (1). 1 g was placed.
After 10 minutes, the swollen gel was collected, and its weight was measured to determine the suction force of the liquid from the tissue paper. Further, the presence or absence of mamako in the superabsorbent resin powder A or the water absorbing agent (1) added at the same time was observed. (C) Absorbency under pressure The absorbency under pressure was measured using the apparatus shown in FIG. The upper port 22 of the burette 21 was plugged with a stopper 23, and the measuring table 24 and the air port 25 were set at the same position. Diameter 70 in measuring table 24
The filter paper, the superabsorbent resin powder A or 0.2 g of the water-absorbing agent (1) and the filter paper 27 are placed on a glass filter (No. 1) 26 mm in size, and the weight 28 of 20 g / cm ² is further placed thereon. The amount of artificial urine absorbed (m
As 1), absorbency under pressure (ml / g) was calculated by the following mathematical formula 2.

[0053]

(Equation 2)

(D) A JIS standard screen having a viscosity of 70 mm has a mesh of 20 mesh,
0 mesh and three types of trays are placed on top of each other, and the resulting superabsorbent resin powder A or water absorbing agent (1) is placed on top of it.
Was shaken with a classifier for 10 minutes, and the classified material was weighed and expressed as% by weight.

Table 1 shows the results.
As compared with the water absorbing agent (1), the water absorbing agent (1) was remarkably improved in absorbency under pressure, and an easy-to-handle water absorbing agent having a small amount of fine powder (100 mesh passing amount) was obtained. The absorption rate under pressure was as shown in FIG.

Comparative Example 1 A liquid material B consisting of 0.5 part of glycerin and 10 parts of water was mixed with 100 parts of the resin powder A obtained in Example 1 using a paddle type mixer, and the obtained mixture was mixed with Example 1. The same treatment was performed to obtain a comparative water-absorbing agent (1). The obtained comparative water absorbing agent (1) was evaluated in the same manner as in Example 1.

The results are shown in Table 1. The comparative water-absorbing agent (1) has improved absorptivity as compared to the superabsorbent resin powder A, but has a higher absorbency under pressure and a higher water-absorbing agent (1). The viscosity was poor. The absorption rate under pressure was as shown in FIG.

Example 2 A liquid substance B consisting of 0.5 part of glycerin and 10 parts of water was added to 100 parts of the superabsorbent resin powder A obtained in Example 1,
It mixed by the following method. That is, in the apparatus shown in FIG.
Into the nozzle 15 through the pipe 14
While spraying the liquid material B, compressed air was blown from the nozzle 19 through the pneumatic pipe 18, and the resin powder A was caused to flow downward by the action of this air flow. At this time, resin powder A
The mixing ratio between the air and the air current was 1 kg / Nm ³ . The residence time was 10 seconds. The mixture thus obtained was treated in the same manner as in Example 1 to obtain a water absorbing agent (2). The obtained water absorbing agent (2) was evaluated in the same manner as in Example 1. Table 1 shows the results.

Example 3 A water-absorbing agent (3) was obtained in the same manner as in Example 1, except that Liquid B-1 consisting of 0.5 part of glycerin and 5 parts of water was used. The obtained water-absorbing agent (3) was evaluated in the same manner as in Example 1, and the results were shown in Table 1.
Shown in

Comparative Example 2 In Example 3, superabsorbent resin powder A and liquid material B-1 were used.
Was mixed in a paddle type mixer, and the same operation as in Example 3 was carried out to obtain a comparative water absorbing agent (2). The obtained comparative water absorbing agent (2) was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Example 4 A liquid substance B-2 consisting of 0.5 part of glycerin and 20 parts of water was added to 100 parts of the superabsorbent resin powder A obtained in Example 1.
Was mixed in the following manner. That is, in the apparatus shown in FIG. 4, the superabsorbent resin powder A is charged into the cylindrical body 10 from the charging member 13 and the liquid B
While spraying -2, compressed air was blown from the nozzle 19 through the pneumatic pipe 18, and the resin powder A was caused to flow downward by the action of this air flow. The mixture thus obtained was heated in the same manner as in Example 1 to obtain a water absorbing agent (4). The obtained water absorbing agent (4) was evaluated in the same manner as in Example 1. Table 1 shows the results.

Example 5 The superabsorbent resin powder A obtained in Example 1 was mixed with a liquid B-3 composed of 0.5 part of ethylene glycol diglycidyl ether and 10 parts of water using the apparatus shown in FIG. After mixing and heat treatment, the mixture was sieved with a 20-mesh wire gauze, and the unpassed material was pulverized with a roll mill-type granulator to obtain a water-absorbing agent (5) with the whole amount passed through a 20-mesh material.

That is, in the apparatus shown in FIG. 1, the superabsorbent resin powder A was charged into the cylindrical body 10 from the charging member 13, and the liquid B-3 was sprayed from the nozzle 15 through the pipe 14. The fine droplets sprayed from the nozzle 15 are spread downward and flow down by the spraying force and their own weight as they go down the cylindrical body 10, and the resin powder A and the liquid material B-3 are co-flowed. Contact, resin powder A
A liquid B-3 was uniformly dispersed on the surfaces of the plurality of resin powders A using the droplets of the liquid B-3 attached to the medium as a medium. The resulting mixture was lightly placed on a belt conveyor, passed through an infrared dryer, and subjected to heat treatment to obtain a water absorbing agent (5). At this time, the average heating time was 10 minutes, and the material temperature at the outlet of the dryer was 120 ° C.
The obtained water absorbing agent (5) was evaluated in the same manner as in Example 1. Table 1 shows the results.

Example 6 A liquid B-4 composed of 0.5 part of glycerin and 60 parts of water was mixed with 100 parts of the superabsorbent resin powder A obtained in Example 1 in the same manner as in Example 1, and heat-treated. Thus, a water absorbing agent (6) was obtained. The obtained water absorbing agent (6) was evaluated in the same manner as in Example 1. Table 1 shows the results.

Example 7 In Example 1, 1460 parts of acrylic acid and 220 parts of 2-acrylamido-2-methylpropanesulfonic acid were dissolved in 2970 parts of distilled water and neutralized by adding 850 parts of sodium carbonate in a kneader. , N'-methylenebisacrylamide (1.0 part) was added and dissolved. Subsequent operations were performed in the same manner as in Example 1 to obtain a hydrogel polymer. The obtained hydrogel polymer was dried with a hot air drier, and then dried in Example 1.
In the same manner as described above, the mixture was pulverized and classified to obtain a 20-mesh passing product (superabsorbent resin powder B). A liquid substance B consisting of 0.5 part of glycerin and 10 parts of water is added to 100 parts of the superabsorbent resin powder B.
Was mixed and heated in the same manner as in Example 1 to obtain a water absorbing agent (7). Example 1 about the obtained water absorbing agent (7)
The evaluation was performed in the same manner as described above. Table 1 shows the results.

Example 8 250 ml of cyclohexane was placed in a 500 ml four-neck separable flask equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen gas inlet tube and a dropping funnel, and sorbitan monostearate (HLB 4.7) was used as a dispersant. ) 2.0 g was added and dissolved, and nitrogen gas was blown in to drive out dissolved oxygen. Separately in a flask 28.2% sodium acrylate
g, 7.21 g of acrylic acid and 0.004 g of methylenebisacrylamide are dissolved in 65.79 g of ion-exchanged water, and 0.05 g of potassium persulfate is added and dissolved, and then dissolved in the aqueous solution by blowing nitrogen gas. I expelled oxygen.

Next, the aqueous monomer solution in this flask was added to the above separable flask and dispersed by stirring at 250 rpm. Thereafter, the bath temperature was raised to 60 ° C. to start the polymerization reaction, and then the temperature was maintained for 2 hours to complete the polymerization. After completion of the polymerization, most of the water was distilled off by azeotropic dehydration to obtain a cyclohexane suspension of the polymer. The suspension was filtered to obtain superabsorbent resin powder C. This resin powder C was mixed with the liquid B in the same manner as in Example 1 and heat-treated to obtain a water absorbing agent (8). Table 1 shows the results of the evaluation of the obtained water absorbing agent (8).

[0068]

[Table 1]

As is evident from the results shown in Table 1, the water-absorbing agent obtained by the production method of the present invention does not become mamaco, and has a high suction power and a high water-absorbing ability with excellent water-absorbing ability under pressure. Resin. In addition, 10
It can be seen that the amount of 0 mesh passing is small and workability is good.

(Particle Strength Test) The superabsorbent resin powder A and the water absorbing agent (1) obtained in Example 1 and Comparative Example 1 were used.
Each of the comparative water-absorbing agents (1) obtained in
5 g of a glass ball having a diameter of 5 mm was charged into a 100 ml mayonnaise bottle of 0 g each, and the mixture was shaken with a paint shaker for 30 minutes. Each particle size after shaking was checked. Table 2 shows the results.

[0071]

[Table 2]

It can be seen that the water absorbing agent obtained in the present invention has high strength against vibration and abrasion.

[0073]

As described above, according to the present invention, a highly water-absorbent resin powder having a functional group is charged from the upper part of a cylindrical body having an open lower end, and the powder is directed from the upper part to the lower part of the cylindrical body. The superabsorbent resin powder, which is formed by spraying a liquid of a compound having a group capable of reacting with two or more functional groups of the superabsorbent resin in the form of droplets and flowing down toward the lower part of the cylindrical body When,
The droplets, which are radially diffused toward the lower portion of the cylindrical body and flow down, are brought into contact with each other in a co-current state, and the highly water-absorbent resin powder in which the droplets are uniformly adsorbed is formed in the cylindrical body. Take out from the lower part of the superabsorbent resin, and then the superabsorbent resin powder obtained is subjected to a heat treatment at a temperature of 40 ° C. or more. It is excellent in all of the absorption capacity upon contact with a liquid, the absorbency under pressure, and the suction power of moisture from a substrate containing an aqueous liquid.

Further, the method of the present invention can be carried out even when a hydrophilic organic solvent is not used, and therefore provides an industrially safe and economical production method. Furthermore, the superabsorbent resin obtained by the present invention has a high quality and a particle size within a desired range, and contains no fine powder. Deterioration of work environment, etc. is eliminated.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an apparatus for performing a method for producing a superabsorbent resin according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing an apparatus for performing a production method according to an embodiment in which a superabsorbent resin powder is dispersed and introduced by an air current.

FIG. 3 is a cross-sectional view showing a modification of the apparatus for performing the manufacturing method according to the embodiment in which the superabsorbent resin powder is dispersed and introduced by an air current.

FIG. 4 is a cross-sectional view showing an apparatus for performing a manufacturing method according to another embodiment of the present invention.

FIG. 5 is a schematic sectional view of an apparatus for measuring the absorbency under pressure of a superabsorbent resin.

FIG. 6 is a graph showing the absorption rate under pressure of a superabsorbent resin.

[Explanation of symbols]

10: cylindrical body (cylindrical body), 11: opening, 1
2, 16 ... dispersing plate, 13 ... input member, 14 ...
· Pipes, 15, 33 ··· Nozzle, 18 ··· Pneumatic piping, 19 ··· Compressed air nozzle, 21 ··· Bullet, 23 ··· Plug, 25 ··· Air port, 24 ··· Measuring table, 28 ... weight.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification code FI C08F 265/06 A61F 13/18 307A C08J 3/12 (72) Inventor Yoshio Irie 992 No. 1, Nishioki, Okihama, Aboshi-ku, Himeji, Hyogo Inside the Himeji Research Laboratory, Catalytic Chemical Industry Co., Ltd. (72) Inventor, Akiaki Fujiwara 992, Nishioki, Akihama-ku, Himeji-shi, Hyogo Pref. Shuichi Kanzaki, Nippon Shokubai Chemical Industry Co., Ltd. Himeji Works, (72) Inventor Shuji Kanzaki 992, Nishioki, Okihama-shi, Abashiri-ku, Himeji-shi, Hyogo Pref. (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C08F 8/00 C08J 3/12 C08F 26 5/00-265/06

Claims (9)

(57) [Claims] (1) When the inner wall temperature is maintained at 50 to 200 ° C.
Together it becomes lower end turns on the high water-absorbent resin powder having a functional group from the top of the opened tubular body, and two or more functional groups of the super absorbent polymer toward the bottom from the top of the cylindrical body A liquid material of a compound having a group capable of reacting is sprayed in the form of fine droplets, and the highly water-absorbent resin powder flowing down toward the lower portion of the cylindrical body, and radially flowing toward the lower portion of the cylindrical body. The droplets flowing down while diffusing are brought into contact with each other in a co-current state, and the superabsorbent resin powder in which the droplets are uniformly adsorbed is taken out from the lower part of the cylindrical body, and then the taken out is taken out. A method for producing a superabsorbent resin, comprising heating the superabsorbent resin powder at a temperature of 40 ° C. or higher. 2. A water-absorbing resin in which fine droplets are formed by a two-fluid nozzle.
The method according to claim 1, wherein the mixture is mixed. 3. The method according to claim 1, wherein said tubular body is cylindrical. 4. The method according to claim 1, wherein said droplets are sprayed downward from a nozzle located at the upper center of said cylindrical body, and said superabsorbent resin powder is injected downward from outside of said nozzle. Item 1. The method according to Item 1. 5. The droplet is sprayed downward from a nozzle provided on the upper inner wall surface of the cylindrical body, and the superabsorbent resin powder is injected downward from the center of the upper part of the cylindrical body. The method of claim 1 comprising: 6. The method according to claim 1, wherein the superabsorbent resin powder is supplied by an air stream. 7. The method according to claim 6, wherein the mixing ratio of the superabsorbent resin powder and the gas stream is 0.1 to 5 kg / Nm ³ . 8. The residence time of the airflow in the tubular body is set to be equal to or less than 0.
5. The method of claim 4, wherein the time is between 1 and 30 seconds. 9. The inner wall of the cylinder into which the water-absorbent resin powder is
Water-absorbent resin characterized by keeping the temperature at 50 to 200 ° C
A method for preventing powder from adhering to the inner wall of the cylinder.