JPH04246403A - Production of highly water-absorptive resin - Google Patents

Abstract

PURPOSE:To obtain the title resin with highly water-absorptive properties even under a compressed condition by a bringing a highly water-absorptive resin powder having functional groups into contact with a liq. product of a compd. having a group reactive with the above resin in a cylindrical body with a specified constitution under a specified condition, taking out the product, and heat- treating the product. CONSTITUTION:A highly water-absorptive resin powder A having functional groups (e.g. acrylic acid-sodium acrylate-trimethylolpropane triacrylate copolymer resin) is fed in a cylindrical body 10 wherein the lower end is opened from the top and a liq. product B (e.g. a watery soln.) of a compd. having a group reactive with two or more functional groups of the resin A (e.g. glycerol) is sprayed in a fine liq. droplet from the top of the cylindrical body 10 toward the lower part to bring the powder A flowing down toward the lower part of the cylindrical body 10 into contact with the liq. droplet B flowing down while it diffuses in the radial direction each other under a parallel flow condition. The powder A contg. absorbed liq. droplet B is taken out of the lower part of the cylindrical body 10 and heat-treated at 40 deg.C or higher.

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 superabsorbent resins. More specifically, the present invention relates to a method for producing a super absorbent resin that has high water absorbency even under pressure.

0002

BACKGROUND OF THE INVENTION In recent years, superabsorbent resin powders have come to be used in various fields such as sanitary materials that absorb body fluids and water retention agents, such as sanitary cotton and disposable diapers. Examples of such super absorbent resins include hydrolysates of starch-acrylonitrile graft polymers (Japanese Patent Publication No. 49
-43,395), neutralized product of starch-acrylic acid graft polymer (JP-A-51-125,468), saponified product of vinyl acetate-acrylic acid ester copolymer (JP-A-52-14, 689), hydrolysates of acrylonitrile copolymers or acrylamide copolymers (Japanese Patent Publication No. 53-15,959), crosslinked products thereof or partially neutralized polyacrylic acid crosslinked products (Japanese Patent Publication No. 55-84) ,30
No. 4) etc. are known.

[0003] Desired properties of highly aqueous resins include high absorption capacity and excellent absorption rate when in contact with aqueous liquids, high gel strength of hydrous swelling gels, and ability to absorb water from base materials containing aqueous liquids. The excellent suction power, etc. However, the relationship between these properties does not necessarily show a positive correlation; in particular, absorption capacity and absorption rate, gel strength, and suction power have contradictory relationships, and the higher the absorption capacity, the lower these physical properties. Put it away. In addition, some substances with high absorption capacity may cause so-called "mamako" when they come into contact with aqueous liquids.
In some cases, water is not diffused throughout the superabsorbent resin particles, resulting in an extremely low absorption rate.

[0004] As a method for obtaining a superabsorbent resin that has a high absorption capacity and a relatively good absorption rate, a method is known in which the surface of the superabsorbent resin is coated with a surfactant or a non-volatile hydrocarbon. ing. However, although this method improves the dispersibility of the superabsorbent resin in an aqueous liquid, a sufficient effect cannot be obtained in terms of improving the absorption rate and suction power of each superabsorbent resin particle.

[0005] Furthermore, as a method for improving the above-mentioned properties in a well-balanced manner, a method of crosslinking the surface of a superabsorbent resin with a hydrophilic crosslinking agent is also known. Such hydrophilic crosslinking agents include polyhydric alcohols, polyglycidyl ethers,
Haloepoxy compounds, polyvalent aldehydes, polyvalent amines, and polyvalent metal salts are used, but it is important to uniformly distribute and react this hydrophilic crosslinking agent on the surface of the superabsorbent resin. This is important in forming a crosslinked layer to enhance the improvement effect.

[0006] A method for uniformly distributing the hydrophilic crosslinking agent on the surface of the superabsorbent resin is to directly mix the superabsorbent resin powder and the hydrophilic crosslinking agent, and if necessary, heat treatment (
JP-A-58-180,233, JP-A-59-189,
No. 103, JP-A-61-16,903, JP-A-61-
46,241), a method in which a super absorbent resin is dispersed in a hydrophilic organic dispersion medium of alcohol and ketones, or a mixture of water, alcohol, and ketones, and a crosslinking agent is added and reacted (JP-A-58-42 , No. 602), etc. are known.

However, in the former method of directly mixing the superabsorbent resin powder and the crosslinking agent, it is difficult to uniformly distribute the crosslinking agent on the surface of the resin powder, and the surface crosslinked layer of the superabsorbent resin obtained tends to become uneven.

In addition, in the latter method, when a mixture of water and a hydrophilic organic solvent is used, the hydrophilic crosslinking agent becomes soluble in the dispersion medium, and there is a possibility that it can be uniformly distributed on the surface of the superabsorbent resin. However, heating during crosslinking distills off the hydrophilic organic solvent, which is undesirable from the standpoint of risk of fire within the apparatus and avoidance of pollution problems caused by release into the atmosphere as waste gas. Furthermore, there is a high possibility that the hydrophilic organic solvent will remain as an impurity in the superabsorbent resin.

On the other hand, a method in which a crosslinking agent is mixed and reacted with a super absorbent resin powder in the presence of water and an inert inorganic powder (JP-A-60-163,956 and JP-A-60-255) , No. 814) is known, but the use of expensive inorganic powder is uneconomical and industrially difficult. On the other hand, if an extremely small amount of inorganic powder is added to superabsorbent resin powder, it is difficult to form a homogeneous mixture, and the effect of using inorganic powder cannot be obtained.

0010

[Problems to be Solved by the Invention] As described above, in order to improve the various properties of superabsorbent resins in a well-balanced manner, methods such as forming a surface crosslinked layer on superabsorbent resins have been attempted, but none of them have been successful. It also has the problems mentioned above,
It did not show sufficient improvement effect.

[0011] Therefore, an object of the present invention is to provide a novel method for producing a super absorbent resin. Another object of the present invention is to provide a method for producing a super absorbent resin that has high water absorbency even under pressure.

0012

[Means for Solving the Problems] The above-mentioned objects are such that superabsorbent resin powder having a functional group is introduced from the upper part of a cylindrical body whose lower end is open, and the superabsorbent resin powder having a functional group is introduced from the upper part of the cylindrical body toward the lower part. A liquid substance of a compound having a group capable of reacting with two or more functional groups of the super absorbent resin is sprayed in the form of droplets, and the super absorbent resin powder flows down toward the lower part of the cylindrical body. , the droplets flowing down while diffusing in the radial direction toward the bottom of the cylindrical body are brought into contact with each other in a cocurrent state, and the superabsorbent resin powder with the droplets uniformly adsorbed is placed in the cylindrical body. Take it out from the bottom of the body,
This is achieved by a method for producing a super absorbent resin, which is characterized in that the super absorbent resin powder taken out is then heat-treated at a temperature of 40° C. or higher.

[0013]

[Operation] The method of the present invention will be explained in more detail below with reference to the drawings.

FIG. 1 is a diagram showing an apparatus embodying the method for continuously producing superabsorbent resin powder of the present invention. As shown in the figure, a cylindrical body 10 having an opening 11 at the lower end is provided facing in the vertical direction, and a conical dispersion plate 12 that expands downward is installed in the upper center of this cylindrical body 10. ing. A charging member 13 is provided above the cylindrical body 10 for supplying the superabsorbent resin powder A toward the dispersing plate 12 and injecting the resin powder A into the cylindrical body 10 from the entire circumference of the lower part of the dispersing plate 12. It is set in.

A pipe 14 is attached to the center of the dispersion plate 12, and the dispersion plate 12 is attached to the tip of the pipe 14.
A nozzle 15 is mounted below the nozzle. From this nozzle 15, air and a liquid substance of a compound having a group capable of reacting with two or more functional groups of the superabsorbent resin (hereinafter referred to as liquid substance B) are ejected simultaneously. The liquid substance B becomes fine droplets and is sprayed downward into the cylindrical body 10. The super-absorbent resin powder A introduced from the dispersion plate 12 and the fine droplets sprayed from the nozzle 15 spread downward from each other in the cylindrical body 10 and flow down due to the spray force and their own weight. It turns out. As a result, the resin powder A flows down while diffusing.
flows down from the top to the bottom, while droplets of the liquid substance B flow down from the top to the bottom while diffusing at a predetermined angle in the radial direction of the cylinder 10, so that the resin powder A and the liquid substance B The resin powder A is brought into contact with the resin powder A in a parallel flow state, and a mixture is formed in which the liquid substance B is uniformly dispersed on the surface of the resin powder A. At this time, a plurality of resin powders A may be caked to form a caking granule using the droplets attached to the resin powder A as a medium.

FIG. 2 shows another embodiment of the present invention, and the members common to those shown in FIG. 1 include:
The same reference numerals are given. In the device shown in FIG. 1, the superabsorbent resin powder A was put into the dispersion plate 12 alone, but in the device shown in FIG. I try to distribute the input.

For this purpose, as shown in the figure, the dispersion plate 16
is a tapered portion 16 whose diameter decreases toward the bottom.
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 the pneumatic piping 18 is blown onto the super absorbent resin powder A fed from the feeding member 13 onto the upper surface of the tapered portion 16a, and the resin powder A is blown by this air flow. It also flows downward due to the action of In this case, the mixing ratio of resin powder A and the air flow is 0.1 to 5.
It is preferable to set it within the range of kg/Nm3. If the ratio of the amount of resin powder A exceeds 5 kg/Nm3, the resin powder A will not be sufficiently dispersed or diffused by the airflow, and uniform contact with droplets of liquid material B will not be achieved. On the other hand, if the ratio is less than 0.1 kg/Nm3, a huge amount of gas will be injected, and excessive equipment will be required to dispose of it, which is impractical. Furthermore, if the exhaust is insufficient, the amount of the mixture adhering to the inner circumferential surface of the cylindrical body 10 will increase, making continuous operation difficult. The residence time of the airflow within the cylindrical body 10 is determined by controlling the flow rate of the airflow as well as the ratio of the airflow to the resin powder A described above, and this residence time is approximately 0.1 to 30 seconds. It is preferable to set

FIG. 3 shows a modification of the apparatus shown in FIG. 2, in which a jacket 31 is formed within the wall of the cylindrical body 10, and steam is circulated through the jacket 31 through a steam pipe 32. , the inner surface of the cylindrical body 10 is heated. In the case shown in the figure, about 2 kg/cm2G of steam was circulated to maintain the inner surface temperature at about 100°C. This prevents the mixture from adhering to the inner surface of the cylindrical body 10. In the experiment, the apparatus was operated continuously for 60 minutes under the above-mentioned conditions, but no deposits were observed. In this case, the basic configuration is the same as the device shown in FIG. 2, except that the jacket 31 described above is provided and the position of the nozzle 19 at the tip of the pneumatic pipe 18 is different. be.

FIG. 4 is a diagram showing still another specific example, and this basic form is common to the device shown in FIG. are arranged in large numbers on the inner peripheral surface of the cylindrical body 10. Since each nozzle is tilted downward at a predetermined angle, the droplets from these nozzles 33 flow down into the resin powder A.
It will diffuse and flow downward while intersecting at a predetermined angle. In this case as well, the same effects as in the case described above were obtained. Even if droplets are sprayed horizontally from these nozzles 33 toward the center of the cylindrical body 10, due to the influence of the airflow for injecting the resin powder A,
As a result of regulating the flow of the droplets, the droplets and the resin powder A become cocurrent as they move downward into the cylindrical body 10, and the droplets and the resin powder A are uniformly mixed to form a mixture.

In each of the embodiments described above, the cylindrical body 10 is used as the cylindrical body, but a rectangular cylindrical body whose cross section is a quadrangle or a larger polygon may also be used. Alternatively, a cone-shaped cylinder such as a conical shape or a pyramid shape may be used.

A preferred embodiment of the present invention is that the superabsorbent resin powder A is introduced by airflow from a dispersion member installed at the top of a cylinder whose bottom end is open. If the charging method does not use airflow, the superabsorbent resin powder A may not be sufficiently dispersed, and the absorbency under pressure may deteriorate during continuous operation. Further, it is preferable that the nozzle for spraying the liquid substance B be installed inside the dispersion member for the superabsorbent resin powder A, preferably approximately at the center. If it is installed outside the dispersion member, the contact between the superabsorbent resin powder A and the liquid B may become uneven, and the absorbency under pressure of the superabsorbent resin obtained during continuous operation will deteriorate. Sometimes. In addition, in order for the liquid B to diffuse and wet the inner wall of the cylinder, the super absorbent resin powder A
will easily adhere to the wall.

[0022] The inner wall of the cylinder is preferably maintained at a temperature of 50 to 200°C, more preferably 70 to 200°C, by providing a heat insulating means. Thereby, it is possible to prevent the super absorbent resin powder A from adhering to the inner surface of the cylinder, and it is possible to obtain a super absorbent resin with stable performance even during continuous operation. Adhesion of the superabsorbent resin powder A to the inner wall of the cylinder causes excessive or non-uniform mixing of the liquid substance B to the adhesion area, resulting in a decrease in the quality of the superabsorbent resin obtained during continuous operation. and reduce stability.

[0023] In the present invention, the mixture of super absorbent resin powder A and liquid substance B taken out from the lower part of the cylindrical body is heated to 40°C.
Heat treatment is performed at the above temperature.

[0024] Examples of the heating device used in the present invention include a conventional dryer and a jacketed mixer. Examples include ribbon blenders, fluidized bed dryers, paddle dryers, infrared dryers, and the like.

[0025] Ribbon blenders are available in horizontal and vertical types, with the horizontal type having a single shaft or multiple shafts, and these ribbon blenders can be used in both batch and continuous operations. Ribbon blades generally have a double-wound ribbon structure in which the powder particles move inward on the outer blades and outward on the inner blades, but depending on the target material, its properties, or operation (batch or continuous) A corresponding change in ribbon shape is required, and forced shear and circulation of the ribbon vanes facilitates mixing and discharges the mixture from the center bottom of the tank or from the sides.

The fluidized bed dryer is a device that performs drying by floating the powdery wet raw material on a perforated plate with hot air from below and vigorously mixing it to perform heat exchange. A typical example is the horizontal fluidized bed type, in which a crusher is installed in the fluidized bed, and the agglomerates in the supplied raw material are crushed and at the same time heat exchanged with hot air. The rotation speed, blade shape, and installation location of the crusher are determined each time depending on the raw material condition, but the crusher is normally installed in the fluidized bed below the supply port. The raw material crushed by the crusher and fluidized by the hot air at the bottom is prevented from short-pathing by the adjustable weir provided inside the machine. This narrows the average residence time distribution of the feedstock and results in a uniform product. In addition, the residence time can be adjusted by tilting the weir. As drying progresses, the raw material is moved by the inlet to the outlet.

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

[0028] In the present invention, the heat treatment temperature of the super absorbent resin powder to which the liquid substance B is attached is 40°C or higher, preferably 80 to 220°C, but the optimum heating temperature may be determined depending on the hydrophilic crosslinking agent used. Usually, they are different. Also,
The heat treatment time depends on the heat treatment method, but is usually 0.1
-5 hours, preferably 0.5-2 hours.

[0029] The superabsorbent resin powder targeted in the present invention is a conventionally known powdered superabsorbent resin that absorbs a large amount of water in water and swells to form a hydrogel.
For example, hydrolysates of starch-acrylonitrile graft copolymers, saponified products of acrylic acid ester-vinyl acetate copolymers, hydrolysates of acrylonitrile copolymers or acrylamide copolymers, and starch-acrylic acid graft copolymers. Examples include neutralized products of self-crosslinking polyacrylic acid, crosslinked polyacrylates, and neutralized products of crosslinked isobutylene-maleic anhydride copolymers.

[0030] Such a super absorbent 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, such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, etc. acids, itaconic acid, protonic acid, citraconic acid, α-hydroxyacrylic acid, aconitic acid, 2-(meth)acryloylethanesulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, etc. , an unsaturated carboxylic acid and a salt thereof, and more preferably an acrylate monomer containing 1 to 50 mol% of acrylic acid and 99 to 50 mol% of an acrylate. Of course, the molar ratio between acrylic acid and acrylic acid salt may be adjusted to the above molar ratio by partially neutralizing polyacrylic acid obtained by polymerizing acrylic acid.

[0031] In addition, super absorbent resin powder contains a very small amount of crosslinkable monomers having two or more polymerizable unsaturated groups or reactive functional groups, compared to self-crosslinkable ones that do not use crosslinkable monomers. A reaction product is preferable.

Examples of these crosslinking agents include, for example, N,
N'-methylene bis(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, ) acrylate, (meth)acrylic acid polyvalent metal salt, trimethylolpropane tri(meth)acrylate, triallylamine, triallyl cyanurate, triallyl isocyanurate,
Examples include triallyl phosphate, glycidyl (meth)acrylate, ethylene glycol diglycidyl ether, glycerin tri(di)glycidyl ether, polyethylene glycol diglycidyl ether, and the like. Further, two or more of these crosslinking agents may be used in combination. The amount of these crosslinking agents used is generally 0.001 mol%
~0.5 mol%, preferably about 0.01~0.3 mol%.

[0033] As the polymerization method for obtaining the superabsorbent resin powder, various methods such as aqueous solution polymerization, reverse phase suspension polymerization, precipitation polymerization, and bulk polymerization can be employed. Among these, from the viewpoint of workability during polymerization and ease of handling when mixing the obtained superabsorbent resin powder and liquid material B, aqueous solution polymerization or reversed-phase suspension polymerization is preferred, and aqueous solution polymerization is particularly preferred.

[0034] The monomer concentration in the monomer aqueous solution when synthesizing super absorbent resin powder by aqueous solution polymerization or reverse phase suspension polymerization method is as follows:
Selection is possible over a wide range, but generally from 20% by weight or more, more preferably 25% by weight or more up to saturation concentration.

In addition, the polymerization initiators used in the polymerization include persulfates such as potassium persulfate, sodium persulfate, and ammonium persulfate, which are commonly used water-soluble radical polymerization initiators, hydrogen peroxide, t Examples include hydroperoxides such as -butyl hydroperoxide and cumene hydroperoxide, and azo compounds such as 2,2'-azobis-2-amidinopropane hydrochloride. It is also possible to use a mixture of two or more of these polymerization initiators, and it is also possible to use a redox initiator system in combination with a reducing agent such as sulfite, l-ascorbic acid, or ferric salt. can. The amount of the polymerization initiator used is 0.001 to 1.0% by weight based on the monomer, preferably 0.005% by weight.
~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 crosslinking agent) is preferably hydrophilic, and more preferably There are no particular restrictions on water-soluble compounds, such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, glycerin, polyglycerin, propylene glycol, diethanolamine,
Polyhydric alcohols such as triethanolamine, polyoxypropylene, oxyethylene oxypropylene block copolymer, pentaerythritol, sorbitol; ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol polyglycidyl ether, diglycerol polyglycidyl ether , polyglycidyl ethers such as polyglycerol polyglycidyl ether, sorbitol polyglycidyl ether, pentaerythritol polyglycidyl ether, propylene glycol dicrycidyl ether, polypropylene glycol diglycidyl ether; 2.2-bishydroxymethylbutanol-tris [3 -(1-aziridinyl)propionate], 1,6-hexamethylene diethylene urea, diphenylmethane-bis-4,4
Polyvalent aziridines such as '-N,N'-diethyleneurea; haloepoxy compounds such as epichlorohydrin and α-methylchlorohydrin; polyvalent aldehydes such as glutaraldehyde and glyoxal; ethylenediamine, diethylenetriamine, triethylenetetramine, tetra Polyvalent amines such as ethylene pentamine, pentaethylene hexamine, polyethylene imine; polyvalent isocyanates such as 2,4-toluylene diisocyanate and hexamethylene diisocyanate; aluminum chloride, magnesium chloride, calcium chloride, aluminum sulfate, magnesium sulfate, Examples include polyvalent metal salts such as calcium sulfate. Particularly preferably polyhydric alcohols,
These are polyvalent glycidyl ethers, polyvalent amines, and polyvalent metal salts.

[0037] The amount of these surface crosslinking agents used depends on the type of the agent, but is generally 0.1 to 3% of the super absorbent resin powder.
0% by weight is suitable, preferably 0.5-10% by weight
It is. If this amount is less than 0.1% by weight, the effect of the present invention will not be achieved, and if it is used in excess of 30% by weight, the absorption capacity may decrease significantly.

[0038] The compound having a group capable of reacting with two or more functional groups of the super absorbent resin powder used in the present invention is as follows:
If it is liquid itself, it can be used alone, but it is usually diluted with a diluent and used as liquid material B. As the diluent, any diluent that can dissolve or disperse the above-mentioned compound and does not affect the performance of the superabsorbent resin can be used without any restriction. For example, water, methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol,
Examples include 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, the feature of the present invention is that the above compound and superabsorbent resin powder can be mixed uniformly without using any organic solvent. That is, it is preferable to use water alone as the diluent from the viewpoint of economy and avoidance of fire and pollution problems.

The fine droplets of 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, the average diameter is 50 to 200 μm. If this average diameter exceeds 300 μm, uniform diffusion or dispersion of liquid material B becomes difficult, resulting in formation of high-density lumps, or a large amount of superabsorbent resin powder remaining in the cylinder that does not come into contact with liquid material B. This is not desirable. Methods for generating fine droplets with an average diameter of 300 μm or less include the rotating disk method,
Examples include the pressurized nozzle method and the two-fluid nozzle method, but in the present invention, since the super absorbent resin powder is introduced from the top, gas is ejected into the droplet sprayer to prevent granulation and adhesion. A two-fluid nozzle that can do this is suitable. For example, Lumina (manufactured by Fuso Seiki Co., Ltd.) 2
Examples include fluid nozzles and spray vectors (manufactured by Kobe Cast Iron Co., Ltd.).

[0041]

[Examples] The present invention will be explained in detail with reference to Examples below, but the scope of the present invention is not limited only to these Examples. In the following examples, unless otherwise specified, all "%" and "parts" indicate parts by weight, respectively.

Example 1 A lid was attached to a jacketed stainless steel double-arm kneader equipped with two sigma-type blades with an internal volume of 10 liters and a blade rotation diameter of 120 mm, and a sodium acrylate aqueous solution was placed in the kneader. 4380 parts, acrylic acid 414
5,500 parts of an aqueous solution of acrylate monomers (monomer concentration 37% by weight,
(neutralization rate: 75 mol %) and 3.4 parts of trimethylolpropane triacrylate were added, and nitrogen gas was blown to replace the inside of the reaction system with nitrogen. Next, two sigma type impellers were attached to a 56r. p. m. While rotating at a speed of
．． 14 parts were added. After adding the initiator, polymerization started in 5 minutes, the temperature in the reaction system reached 83°C in 20 minutes, the water-containing gel was made into fine particles with a diameter of about 5 mm, and polymerization was completed in 60 minutes. A hydrogel polymer was taken out.

[0043] This hydrogel polymer was spread out in a hot air dryer 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 through a 20-mesh wire gauze to obtain superabsorbent resin powder A.

100 parts of this superabsorbent resin powder A was mixed with liquid B consisting of 0.5 parts of glycerin and 10 parts of water using the apparatus shown in FIG. 3, heated, and then sieved through a 20-mesh wire mesh. The unfiltered material was pulverized using a roll mill type sieve, and the entire amount was made into a 20 mesh material to obtain a water absorbing agent (1).

That is, in the apparatus shown in FIG. 3, the super absorbent resin powder A introduced from the input member 13 is filled with compressed air from the airflow generating means consisting of the nozzle 19 provided at the tip of the pneumatic pipe 18. Sprayed super absorbent resin powder A
was diffused in the radial direction of the cylindrical body 10 due to its own weight and the action of this airflow, and flowed down below the cylindrical body 10.

A pipe 14 was attached to the center of the dispersion member 16, and a nozzle 15 was attached to the tip of the pipe, positioned below the dispersion member 16. Air and liquid material B were simultaneously ejected from this nozzle 15, and liquid material B was sprayed downward into the cylindrical body 10 in the form of fine droplets. The droplets of the sprayed liquid substance B diffused in the radial direction of the cylindrical body 10 and flowed down below the cylindrical body 10, but
By adjusting the nozzle position and absorbing the super absorbent resin powder A, at any position in the height direction of the cylindrical body 10,
The diffusion in the radial direction of the cylindrical body 10 was not greater than that of the super absorbent resin powder A. Further, the droplets were absorbed by the superabsorbent resin powder A while flowing down, and the presence of the droplets was hardly recognized at the lower end of the cylindrical body 10. At this time, the mixing ratio of super absorbent resin powder A and air flow is 1
kg/Nm3. The average droplet diameter of liquid B is approximately 1
It was 00 μm. Further, the residence time of the super absorbent 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 substance B are brought into contact with each other in a cocurrent state, and the liquid substance B is spread onto the surfaces of the plurality of resin powders A using the droplets of the liquid substance B attached to the resin powder A as a medium. became a homogeneously dispersed mixture.

[0048] The resin powder thus obtained as a mixture is heated through a jacket installed below the cylindrical body 10 using a heating medium.
It was put into a ribbon blender heated to 00°C and heat treated. The material temperature of the water absorbing agent (1) taken out after heating the mixture for 60 minutes was 180°C.

(a) Absorption capacity, (b) suction power, (c) absorbency under pressure, and (d) particle size (weight of the particles passed through a 100 mesh standard sieve) of the obtained resin powder A and water absorbing agent (1) %) was evaluated as follows.

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

[0051]

[Math 1]

(b) Suction force 20 ml of artificial urine (composition: urea 1.9%, NaCl 0.8%) was placed on tissue paper (55 mm x 75 mm).
, CaCl2 0.1% and MgSO4 0.1
%) to create a base material containing artificial urine, and on top of that base material, add 0.1% of super absorbent resin powder A or water absorbing agent (1).
I put g. The swollen gel was collected after 10 minutes and its weight was measured to determine the suction force of the liquid from the tissue paper. In addition, the presence or absence of superabsorbent resin powder A or 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. A plug 23 was attached to the upper opening 22 of the burette 21, and the measuring table 24 and the air port 25 were set at equal positions. Diameter 70 in measuring stand 24
A filter paper, 0.2 g of super absorbent resin powder A or water absorbing agent (1), and a filter paper 27 were placed on a 20 mm glass filter (No. 1) 26, and then a 20 g/cm2 weight 28 was placed on top of the filter, and then the absorption was carried out for 60 minutes. Amount of artificial urine (ml)
), the absorbency under pressure (ml/g) was calculated using the following formula 2.

[0053]

[Math 2]

(d) JIS standard sieve with a viscosity of 70 mm, 20 mesh, 1
Layer three types of classification plates: 00 mesh and saucer, and place the obtained super absorbent resin powder A or water absorbent (1) on top of them.
After adding 30 g of the mixture and shaking it in a classifier for 10 minutes, the classified product was weighed and expressed in weight %.

The results are shown in Table 1. Super absorbent resin powder A
Compared to the water absorbing agent (1), the absorbency under pressure was significantly improved, and a water absorbing agent that was easy to handle and contained less fine powder (amount passing through 100 mesh) was obtained. In addition, the absorption rate under pressure was as shown in FIG.

Comparative Example 1 0 parts of glycerin was added to 100 parts of the resin powder A obtained in Example 1.
．． Liquid B consisting of 5 parts and 10 parts of water was mixed using a paddle mixer, and the resulting mixture was treated in the same manner as in Example 1 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. Comparative water-absorbing agent (1) has improved absorbency compared to super absorbent resin powder A, but has lower absorbency under pressure than water-absorbing agent (1). The viscosity was poor. In addition, the absorption rate under pressure was as shown in FIG.

Example 2 Liquid material B consisting of 0.5 parts of glycerin and 10 parts of water was added to 100 parts of super absorbent resin powder A obtained in Example 1.
It was mixed in the following manner. That is, in the apparatus shown in FIG.
0 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 piping 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 of the air flow and the air flow was 1 kg/Nm3. Moreover, 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. The results are shown in Table 1.

Example 3 A water-absorbing agent (3) was obtained in the same manner as in Example 1 except that liquid material B-1 consisting of 0.5 parts 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 are shown in Table 1.
Shown below.

Comparative Example 2 In Example 3, super absorbent resin powder A and liquid material B-1
A comparative water-absorbing agent (2) was obtained by performing the same operation as in Example 3, except that the mixture was mixed with a paddle-type mixer. 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 Liquid material B-2 was added to 100 parts of the superabsorbent resin powder A obtained in Example 1, consisting of 0.5 parts of glycerin and 20 parts of water.
were mixed in the following manner. That is, in the apparatus shown in FIG.
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 heat treated 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. The results are shown in Table 1.

Example 5 100 parts of the superabsorbent resin powder A obtained in Example 1 was mixed with liquid B-3 consisting of 0.5 parts of ethylene glycol diglycidyl ether and 10 parts of water using the apparatus shown in FIG. After mixing and heat-treating, the mixture was sieved through a 20-mesh wire gauze, and the unfiltered material was pulverized using a roll mill type sieving machine to obtain a water-absorbing agent (5) as a 20-mesh sieve.

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 material B-3 was sprayed from the nozzle 15 through the pipe 14. The fine droplets sprayed from the nozzle 15 diffuse as they go downwards in the cylindrical body 10 and flow down due to the spray force and their own weight, and the resin powder A and the liquid substance B-3 are in a cocurrent state. A mixture was obtained in which the liquid B-3 was uniformly dispersed on the surfaces of the plurality of resin powders A using the droplets of the liquid B-3 adhering to the resin powder A as a medium. The obtained mixture was thinly placed on a belt conveyor, passed through an infrared dryer, and heated to obtain a water absorbing agent (5). At this time, the average heating time was 10 minutes, and the temperature of the material taken out 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. The results are shown in Table 1.

Example 6 Liquid material B-4 consisting of 0.5 parts 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 the mixture was heated. A water absorbing agent (6) was obtained. The obtained water absorbing agent (6) was evaluated in the same manner as in Example 1. The results are shown in Table 1.

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 in a kneader, and 850 parts of sodium carbonate was added to neutralize the solution. , N'-methylenebisacrylamide (1.0 part) was added and dissolved. The subsequent operations were performed in the same manner as in Example 1 to obtain a hydrogel polymer. After drying the obtained hydrogel polymer with a hot air dryer, Example 1
The mixture was crushed and classified in the same manner as above to obtain a 20-mesh material (super absorbent resin powder B). Liquid B consisting of 100 parts of this super absorbent resin powder B, 0.5 parts of glycerin and 10 parts of water.
were mixed and heated in the same manner as in Example 1 to obtain a water absorbing agent (
7) was obtained. The obtained water absorbing agent (7) was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 8 250 ml of cyclohexane was placed in a 500 ml four-necked separable flask equipped with a stirrer, reflux condenser, thermometer, nitrogen gas inlet tube and dropping funnel, and sorbitan monostearate (HLB 4.7) was added as a dispersant. ) was added and dissolved, and nitrogen gas was blown in to drive out dissolved oxygen. Separately in a flask 28.
2g of acrylic acid, 7.21g of acrylic acid, and 0.004g of methylenebisacrylamide are dissolved in 65.79g of ion-exchanged water, then 0.05g of potassium persulfate is added and dissolved, and then nitrogen gas is blown into the aqueous solution. Driven out oxygen.

Next, the monomer aqueous solution in this flask was added to the separable flask and heated at 250 rpm. p. m.
The mixture was dispersed by stirring. After that, increase the bath temperature to 60
After the temperature was raised to .degree. C. to initiate the polymerization reaction, this temperature was maintained for 2 hours to complete the polymerization. After the polymerization was completed, most of the water was distilled off by azeotropic dehydration to obtain a cyclohexane suspension of the polymer. This suspension was filtered and superabsorbent resin powder C
I got it. This resin powder C was mixed with 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 evaluating the obtained water absorbing agent (8).

[0068]

[Table 1]

As is clear from the results shown in Table 1, the water-absorbing agent obtained by the production method of the present invention is highly water-absorbent, does not become bulky, and has an excellent water-absorbing ability with a large suction force and absorbency under pressure. It is resin. Furthermore, 100% of fine powder
It can be seen that the amount of mesh passing through is small and workability is good.

(Particle strength test) Super water absorbent resin powder A and water absorbing agent (1) obtained in Example 1 and Comparative Example 1
Regarding the comparative water absorbing agent (1) obtained in
0 g each was placed in a 100 ml mayonnaise bottle along with 5 g of glass balls with a diameter of 5 mm, and the mixture was shaken in a paint shaker for 30 minutes. The particle size of each sample was examined after shaking. The results are shown in Table 2.

[0071]

[Table 2]

It can be seen that the water absorbing agent obtained according to the present invention has strong resistance to vibration and abrasion.

[0073]

Effects of the Invention As described above, according to the present invention, superabsorbent resin powder having a functional group is introduced from the upper part of a cylindrical body with an open bottom end, and the superabsorbent resin powder is introduced from the upper part of the cylindrical body to the lower part. A liquid substance of a compound having a group capable of reacting with two or more functional groups of the super absorbent resin is sprayed in the form of droplets, and the super absorbent resin powder flows down toward the lower part of the cylindrical body. and,
The droplets flowing down while diffusing in the radial direction toward the bottom of the cylindrical body are brought into contact with each other in a cocurrent state, and the superabsorbent resin powder with the droplets uniformly adsorbed is transferred to the cylindrical body. The method for producing a super absorbent resin is characterized by taking out the super absorbent resin powder from the lower part of the bottle, and then heat-treating the super absorbent resin powder taken out at a temperature of 40°C or higher. It has excellent absorption capacity when in contact with liquid, absorbency under pressure, and ability to absorb water from a base material containing an aqueous liquid.

Furthermore, the method of the present invention can be carried out without using a hydrophilic organic solvent, so it provides an industrially safe and economically superior manufacturing method. Furthermore, the superabsorbent resin obtained in the present invention is of high quality and has a particle size within a desired range, and does not contain fine powder, so there is no possibility of dust generation when using the superabsorbent resin powder. Deterioration of the working environment will be eliminated.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an apparatus for carrying out a method for producing a super absorbent resin according to an embodiment of the present invention.

FIG. 2 is a sectional view showing an apparatus for carrying out a manufacturing method according to an embodiment in which super absorbent resin powder is dispersed and introduced by air current.

FIG. 3 is a sectional view showing a modified example of an apparatus for carrying out the manufacturing method according to the embodiment in which super absorbent resin powder is dispersed and introduced by airflow.

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

FIG. 5 is a schematic cross-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 super absorbent resin.

[Explanation of symbols]

10... Cylindrical body (cylindrical body), 11... Opening, 12
, 16... Dispersion plate, 13... Injection member, 14...
Pipe, 15, 33... Nozzle, 18... Pneumatic piping, 19... Compressed air nozzle, 21... Bullet,
23... Plug, 25... Air port, 24... Measuring table,
28... Weight.

Claims (18)

[Claims] Claim 1: Powder of a super absorbent resin having a functional group is introduced from the top of a cylindrical body with an open bottom end, and two or more powders of the super absorbent resin are poured from the top to the bottom of the cylindrical body. A liquid substance of a compound having a group capable of reacting with the functional group of The superabsorbent resin powder with the droplets uniformly adsorbed thereon is taken out from the lower part of the cylindrical body, and then the droplets are brought into contact with each other in a parallel flow state. A method for producing a super absorbent resin, which comprises heat-treating the super absorbent resin powder taken out at a temperature of 40° C. or higher. Claim 2: Claim 1, wherein the liquid substance is a dilution of a compound having a group capable of reacting with two or more functional groups with a diluent.
The method described in. 3. The method according to claim 1 or 2, wherein the ratio of the liquid substance to 100 parts by weight of the superabsorbent resin powder is 1 to 50 parts by weight. 4. The method of claim 2, wherein the diluent is water. 5. The method according to claim 4, wherein the compound capable of reacting with two or more functional groups is water-soluble. 6. The method according to claim 5, wherein the compound capable of reacting with two or more functional groups is a polyhydric alcohol. 7. The polyhydric alcohol is the super absorbent resin powder 10
7. The method according to claim 6, wherein the amount is 0.1 to 30 parts by weight per 0 parts by weight. 8. The method according to claim 1, wherein the functional group of the superabsorbent resin powder is a carboxyl group. (9) The super absorbent resin powder having a functional group is a crosslinked polymer of acrylic acid monomers consisting of 1 to 50 mol% of acrylic acid and 99 to 50 mol% of acrylate.
The method described in. 10. A superabsorbent resin powder having a functional group contains 100 parts by weight of an acrylate monomer and 0 parts by weight of a crosslinking monomer.
The method according to claim 9, which is an acrylate-based polymer obtained by heating and drying a gel-like hydrous polymer formed by polymerizing ~5 parts by weight at a monomer concentration of 20% by weight or more. . 11. The method according to claim 1, wherein the temperature of the inner wall of the cylindrical body is maintained at 50 to 200°C. 12. The method according to claim 1, wherein the cylindrical body is cylindrical. 13. A claim in which the droplets are sprayed downward from a nozzle located at the center of the upper part of the cylindrical body, and the super absorbent resin powder is introduced downward from the outside of the nozzle. The method described in Section 1. 14. The droplets are sprayed downward from a nozzle provided on the inner wall surface of the upper part of the cylindrical body, and the super absorbent resin powder is injected downward from the center of the upper part of the cylindrical body. The method according to claim 1, comprising: 15. The method according to claim 1, wherein the superabsorbent resin powder is supplied by airflow. 16. The method according to claim 15, wherein the mixing ratio of the superabsorbent resin powder and the air flow is 0.1 to 5 kg/Nm3. 17. The residence time of the air flow within the cylindrical body is 0.
14. The method according to claim 13, wherein the time is 1 to 30 seconds. 18. The method according to claim 1, wherein the droplets of the liquid material have a diameter of 300 μm or less.