JPH08113653A - Granulation method for super absorbent polymer powder - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a method for granulating a super absorbent polymer powder capable of efficiently producing a granulated product having a strong granulation strength, an appropriate particle size and a narrow particle size distribution. Constitution: 0.1 to 10 parts by weight of inorganic powder, 0.05 to 10 parts by weight of ethylene-acrylic acid copolymer powder or emulsion and 100 parts by weight of water-absorbent resin powder and the water content of the resin powder are A method for granulating a highly water-absorbent resin powder, which comprises mixing water in an amount of 20 to 70% by weight, and then drying the mixture.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing granules from superabsorbent resin powder. More specifically, the present invention relates to a granulation method which gives a highly water-absorbent resin granulated product having a large particle strength and an appropriate particle size and having a narrow particle size distribution.

[0002]

2. Description of the Related Art In recent years, superabsorbent resins have been used for sanitary items such as disposable diapers, sanitary items, disposable rags, and water retention agents, agricultural and horticultural items such as soil conditioners, coagulants for sludge, and dew condensation inhibitors for building materials. It is used for various purposes such as dehydrating agents for oils.

Among these, there is an increasing demand for highly water-absorbent resins, especially in the field of sanitary products such as sanitary products and diapers.

Conventionally, a super absorbent polymer such as an acrylic resin is generally prepared by synthesizing a polymer by a polymerization method such as reverse phase suspension polymerization, reverse phase emulsion polymerization or aqueous solution polymerization, and then drying the polymer as it is, or It is manufactured by crushing after drying.

However, the highly water-absorbent resin powder produced by the above method generally has a wide particle size distribution and contains a considerable amount of fine powder. For this reason, the following problems occur. (A) Dust is liable to be generated, which easily deteriorates the working environment and lowers the product yield. (B) Poor mixability and dispersibility when mixing other materials. (C) It is easy to create a so-called "mamako" when it comes into contact with a liquid. (D) Since the fluidity is poor, bridge formation in the hopper and flash phenomenon are likely to occur.

As a solution to these problems, a method in which fine powder is removed and then granulated with an organic binder (Japanese Patent Laid-Open No. 63-154766, Japanese Patent Laid-Open No. 2-154766).
No. 308820), a method of adding an inorganic powder in the presence of a surfactant (JP-A-62-132936, JP-A-2-284927, JP-B-3-26204) and the like. ..

Although all of these have provided some solutions, to the knowledge of the inventors,
It seems to contain some problems.

That is, the method of removing fine powder requires a new separation device for that purpose, and the separated fine powder must be disposed of. Therefore, it is not economically advantageous in any case. And, in the method of using an organic solvent-based binder, there is a risk of ignition in the drying step after granulation and, when the drying is insufficient, adverse effects on human health due to the organic solvent remaining in the product. ..

On the other hand, when the water-soluble binder is used, the above problems when using an organic solvent-based binder do not occur, but the granulated material has a high water absorption property and rapidly absorbs the aqueous liquid. Due to this property, it is difficult to uniformly disperse and mix the aqueous liquid, easily generate large lumps of high density, and it is difficult to obtain a homogeneous granulated product. Therefore, after granulation, it is necessary to pulverize or the like to obtain an appropriate particle size.

In addition, in the method of adding the inorganic powder in the presence of the surfactant, unevenness of addition tends to occur when the substantially insoluble inorganic fine powder is added, and the quality in terms of particle size, bulk density, etc. is accompanied. Since unevenness is likely to occur and the mechanical strength of the obtained granular material is weak, there seems to be a problem that it is easily broken.

In addition to the above, a method of granulating by spraying an aqueous solution on the surface of the water-absorbent resin powder (JP-A-61-97)
333), a method in which a dry resin is mixed with a liquid containing a water-absorbent resin, and the mixture is heated and dried in a drier with stirring (JP-A-57-117551). However, the one described in JP-A-61-97333 seems to have a problem that it becomes a granular polymer having a wide particle size distribution due to slight variations in the size of the droplets, the spraying method and the like. Further, in the one described in JP-A-57-117551, when the particles are dried with stirring, fine particles are again generated due to friction between the particles, and as a result, a uniform granulated product is produced. Seems to be difficult.

[0012]

SUMMARY OF THE INVENTION As described above,
The highly water-absorbent resin powder has various problems such as generation of dust, low fluidity, and poor mixing/dispersing property with other materials due to non-uniformity of powder particle size and high content of fine powder. Even in the above-mentioned various granulation methods proposed as solutions to these problems, it is difficult to obtain granules having a uniform particle size and concern about adverse effects on human health due to the use of organic solvents. There are problems such as

Therefore, the present invention does not have the above-mentioned problems, and is a highly water-absorbent resin powder having a large particle strength and an appropriate particle size and capable of efficiently producing a granulated product having a narrow particle size distribution. The purpose of the present invention is to provide a granulation method.

[0014]

[Means for Solving the Problems]

[Summary of the Invention] <Summary> The present invention provides a highly water-absorbent resin containing a certain amount of inorganic powder,
It is based on the discovery of the fact that the above objective is achieved by a method in which a certain amount of ethylene-acrylic acid copolymer and a certain amount of water are mixed and then the mixture is dried.

That is, the method of granulating the super absorbent polymer powder according to the present invention is as follows: 0.1 to 10 parts by weight of inorganic powder, ethylene-acrylic acid copolymer powder or 100 parts by weight of super absorbent polymer powder or 0.05 to 10 parts by weight of an emulsion and water in an amount such that the water content of the resin powder is 20 to 70% by weight are mixed, and then the mixture is dried. <Effect> According to the granulation method of the present invention, a highly water-absorbent resin granulated product having a large particle strength and an appropriate particle size and a narrow particle size distribution width can be obtained in a high yield. The granulated product according to the present invention,
Since it is granulated in a system containing substantially no organic solvent, it is hygienic and safe, and further, the water absorption performance of the super absorbent polymer is not substantially reduced before and after granulation.

Therefore, the product obtained by the granulation method of the present invention can be suitably used for various purposes such as sanitary products and agricultural and horticultural products. [Detailed Description of the Invention] <Superabsorbent Resin> The superabsorbent resin powder to which the granulation method of the present invention is applied is not particularly limited, and the present invention is applicable to any superabsorbent resin. Specific examples thereof include cross-linked acrylic acid salt polymers such as sodium polyacrylate, saponified products of cross-linked acrylic acid ester-vinyl acetate copolymer, cross-linked products of starch-acrylic acid salt graft copolymer, starch-acrylonitrile. Examples include saponified products of cross-linked graft copolymers and cross-linked products of maleic anhydride-grafted polyvinyl alcohol. The effect of the present invention is particularly remarkable in a cross-linked acrylate polymer such as sodium polyacrylate.

The highly water-absorbent resin powder is obtained by synthesizing a polymer by a method such as reverse phase suspension polymerization, reverse phase emulsion polymerization, aqueous solution polymerization, etc., and then drying it as it is, or after drying and pulverizing, It is generally produced by surface-crosslinking with a crosslinking agent having two or more functional groups reactive with a group, but the superabsorbent resin to which the present invention is applicable is limited to those produced by these methods. It is not produced, and is produced by any method.

The super absorbent polymer has an average particle size of 10 to 500.
It is preferable that the thickness is μm, particularly 50 to 300 μm. The particle size is measured by using a JIS standard sieve to obtain a mass-based particle size distribution and a mass-based 50% particle size. <Inorganic powder> In the present invention, the inorganic powder is mixed when granulating the super absorbent polymer powder. When the inorganic powder is mixed, appropriate strength is imparted to the superabsorbent resin particles obtained, and the water absorption rate of the granulated product is increased. Examples of preferred inorganic powders used in the present invention include silicon dioxide, aluminum oxide, titanium dioxide, calcium phosphate, calcium carbonate, talc, magnesium phosphate, calcium sulfate, diatomaceous earth, bentonite, zeolite, and other metal oxides. Be done. Particularly, silicon dioxide, aluminum oxide and titanium dioxide are preferable. The particle size of these inorganic powders is generally 0.001 to 2
It is preferably 00 μm, particularly 0.01 to 100 μm. This particle size is measured by a Coulter counter or the like.

The addition amount of the inorganic powder is 1
It is generally 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight, based on 00 parts by weight. If the addition amount of the inorganic powder is less than 0.1 part by weight, the effect is not sufficiently expressed,
If the amount is more than 10 parts by weight, the water absorption performance is adversely affected, which is not preferable. <Ethylene-acrylic acid copolymer> In the granulation method according to the present invention, an ethylene-acrylic acid copolymer is mixed.

Although a granulated body may be obtained only by adding water to the superabsorbent resin mixed with the inorganic powder, absorbing water while mixing, and then drying, insufficient strength of the produced particles and local It is apt to be accompanied by a defect that the particle size of the granulated product is not uniform due to the formation of blocks. By mixing the ethylene-acrylic acid copolymer according to the present invention, it is possible to obtain a granulated product which does not have such drawbacks and has a large strength and a uniform particle size.

The ethylene-acrylic acid copolymer used in the present invention has a number average molecular weight of 1,000 to 100,000.
0, preferably 2,000 to 50,000, more preferably 5,000 to 30,000. Also,
The content of acrylic acid in this copolymer is 3 to 50 by weight.
%, preferably 5 to 30 wt %. The copolymer may be a block copolymer, but a random copolymer is preferable. Also,
The "ethylene-acrylic acid copolymer" in the present invention includes a small amount of a comonomer in addition to the above-mentioned two monomers, and "acrylic acid" is in the form of a salt. It includes things.

The ethylene-acrylic acid copolymer used in the present invention should form a uniform mixture with the fine superabsorbent resin and the inorganic powder prior to the water-added granulation step. It should be in a suitable form. That is, in particular, the forms are powders and emulsions, especially aqueous emulsions.

When added in the form of fine powder, this ethylene-
The acrylic acid copolymer has a particle size of 0.01 to 1000 μm.
m, especially 1 to 100 μm is preferable.

On the other hand, when it is added as an emulsion,
The water is used as a part or all of the water for granulation.

The aqueous emulsion of ethylene-acrylic acid copolymer may be prepared by any method, and the emulsion contains an emulsifying agent and an emulsifying aid to give a stable emulsion. Good. When the ethylene-acrylic acid copolymer is used in the form of an aqueous emulsion, the emulsifier and the emulsification aid contained in the emulsion are also brought to the granulation process. The types and/or amounts of emulsifiers and emulsification auxiliaries, such as are customary for emulsions, are practically not found to give any particular impediment to the granulation and/or use of the resulting granulate.

The ethylene-acrylic acid copolymer is added to 100 parts by weight of the superabsorbent resin powder as the weight of the ethylene-acrylic acid copolymer alone, regardless of whether it is used as a powder or as an emulsion. On the other hand, 0.
It is used in an amount of 05 to 10 parts by weight, preferably 0.5 to 5 parts by weight. If it is less than 0.05 parts by weight, the granulation strength may be weakened, or local blocks may be generated, and large agglomerates of particles may be generated after drying. On the other hand, if the amount exceeds 10 parts by weight, a particle having an appropriate particle size may not be obtained or the water absorption performance may decrease. <Water Content> The amount of water to be added in the method of the present invention depends on the performance of the super absorbent polymer powder,
Preferably, the water content of the resin powder [water content (%)=water content/
(Highly water-absorbent resin powder weight + water content) x 100] is 20%
˜70%, more preferably 30 to 60%. If the water content is less than 20%, the granulation efficiency and the strength of the granulated product may decrease. If the water content exceeds 70%, local blocks may occur, the drying efficiency may decrease, and the water absorption performance of the granulated product may decrease. May occur.

As mentioned above, at least a part of this may be supplied from an aqueous emulsion of ethylene-acrylic acid copolymer. <Granulation/Mixing and Drying> When the superabsorbent resin powder, the inorganic powder, the ethylene-acrylic acid copolymer and water are mixed by the method of the present invention, the mixing order is arbitrary. However, the preferred order is to mix the powder ingredients before adding water. For example, the super absorbent polymer powder is mixed with the inorganic powder, the powdery ethylene-acrylic acid copolymer is mixed therewith, and then water is added. It goes without saying that when the ethylene-acrylic acid copolymer is an aqueous emulsion, the addition of water may be unnecessary.

As the superabsorbent resin, any known mixing device can be used as a device for mixing the inorganic powders as long as it can mechanically mix or disperse two or more kinds of powders. .. Examples of usable mixing devices include a ribbon blender, a Henschel mixer, a super mixer, a Nauter mixer, and a paddle type mixer.

When an ethylene-acrylic acid copolymer in the form of fine powder is used, it may be mixed in the same manner as when the inorganic powder is mixed with the superabsorbent resin powder. As a device for mixing the ethylene-acrylic acid copolymer in the form of a block, the same device used for mixing the inorganic powder with the superabsorbent resin powder can be used.

Water or water, that is, oil-in-water type ethylene, is added to a superabsorbent resin powder prepared by mixing an inorganic powder and a fine powdery ethylene-acrylic acid copolymer, or a superabsorbent resin powder prepared by mixing an inorganic powder. -As an apparatus for dropping and mixing an emulsion of an acrylic acid copolymer, a double-arm kneader, a paddle-type mixer or a Henschel mixer, a super mixer and the like can be mentioned, preferably a double-arm kneader and a paddle-type mixer. Is used.

The superabsorbent resin powder composite obtained by the above mixing is then dried to an appropriate water content (usually 15% or less, preferably 10% or less), but the drying method is not particularly limited. Instead, any method can be adopted as long as it does not impair the functions of the super absorbent polymer powder, the inorganic powder and the ethylene-acrylic acid copolymer.

Specifically, using an appropriate drying device such as a paddle type drier, a rotary type drier or a fluidized bed drier, for example, 80° C. to 180° C., preferably 1
It can be dried at a drying temperature ranging from 00°C to 150°C.

As an example of a preferred embodiment in the above-mentioned granulation step, as the super absorbent polymer powder, the inorganic powder is mixed with a ribbon blender, and then the oil-in-water type ethylene-acrylic acid copolymer emulsion is mixed with the paddle type. A method of dropping the mixture in a machine and then drying the mixture in a rotary dryer to obtain a granulated product can be mentioned.

The dried granulated product can be pulverized and classified as necessary to adjust the particle size to an appropriate value.

[0035]

[Production of Pearl-Shaped Polyacrylic Sodium Acrylate Crosslinked Products by Reverse Phase Suspension Polymerization]

Take 124.5g of acrylic acid in a 500cc beaker,
This is cooled to 35° C. or less and 25% caustic soda aqueous solution 1
Neutralization with 93.4 g gave a partially neutralized acrylic acid monomer to 70%. To this, 0.05 g of potassium persulfate (KPS) and 0.07 g of N,N'-methylenebisacrylamide were added and mixed well to prepare a preparation solution.
N ₂ bubbling was performed for 15 minutes.

Separately, 350 g of cyclohexane was placed in a 1-liter separable flask to dissolve 1.75 g of sorbitan monostearate, and then at 20° C., N ₂ was added.
After bubbling for 15 minutes, the total amount of the acrylic acid partially neutralized monomer preparation liquid was added dropwise with stirring. Then, the temperature inside the system was raised to 75° C. at a heating rate of 50° C./hour, and the temperature was maintained at 75° C. for an additional 1 hour to complete the polymerization.
The bath temperature was set to 100° C., and cyclohexane and water were azeotropically distilled for dehydration. 150 g of the obtained dehydrated polymer was placed in a 1 liter eggplant-shaped flask, and cyclohexane 18
0 g was added to make a slurry. While stirring this slurry, 28 g of water and 1.2 g of γ-glycidoxypropyltrimethyloxysilane were added, and the mixture was stirred at room temperature for 30 minutes.
Then, it is immersed in a bath at 105° C. for 30 minutes, reduced in pressure while maintaining the bath temperature, and evaporated to dryness to give an average particle size of 14
A 0 μm pearl-shaped sodium polyacrylate crosslinked product was obtained.
The water content of this resin was about 3%. Superabsorbent Resin Production Example 2 [ Production of polysodium acrylate crosslinked product by stationary aqueous solution polymerization] By the same operation as in Production Example 1, partially neutralized acrylic acid/K
A mixed aqueous solution of PS/N,N'-methylenebisacrylamide was prepared. Flat bottom stainless steel vat (150 mm x 200
(mm) the top sheet was perforated and the system was thoroughly replaced with N ₂ through a rubber tube.

After pouring the mixed aqueous solution into the vat, the vat was immersed in a hot bath at 70° C. for polymerization. A maximum temperature of 110° C. was exhibited after about 10 minutes. Thereafter, the sheet was kept in a hot bath at 70° C. for 2 hours and then cooled to 20° C. to obtain a sheet-shaped acrylic acid polymer cross-linked product (sodium polyacrylate cross-linked product).

The polymer was taken out of the vat, formed into small pieces, and dried in a vacuum dryer at 90° C. for about 3 hours.

The thus dried fine pieces were crushed by a crusher, and a cross-linked product of sodium polyacrylate having a particle size of 40 to 325 mesh was collected. The water content of this resin is
It was about 3%. Example 1 Superabsorbent Resin 100 parts of superabsorbent resin obtained in Production Example 1 was mixed with 1 part of finely powdered silica (Fuji Silysia Chemical Ltd., “Sylysia #770”, average particle size 6 μm) with a ribbon blender. After that, paddle 64 parts of an oil-in-water emulsion having an ethylene-acrylic acid copolymer solid content of 3.0% by weight (ethylene-acrylic acid copolymer component: average molecular weight 20,000, acrylic acid weight ratio 18%). The mixture was added dropwise using a mold mixer (the amount of added water corresponds to an amount at which the water content of the super absorbent polymer powder is 40% by weight).
Subsequently, the granulated product was dried in a rotary dryer while flowing a carrier gas under an atmosphere of 120° C. until the water content became 3% to obtain a granulated product A. Example 2 Superabsorbent Resin 100 Superabsorbent Resin 100 obtained in Production Example 1 was replaced with Superabsorbent Resin 100 obtained in Superabsorbent Resin Production Example 2.
By the same method as in Example 1 except that parts are used,
Granulated product B was obtained. The amount of water added corresponds to the amount by which the water content of the super absorbent polymer powder becomes 40% by weight. Example 3 Replacing 64 parts of an oil-in-water emulsion having an ethylene-acrylic acid copolymer solid content of 3.0% by weight with an oil-in-water emulsion having an ethylene-acrylic acid copolymer solid content of 0.8% by weight A granulated product C was obtained by the same method as in Example 1 except that 62 parts of the emulsion was used. The amount of water added corresponds to the amount by which the water content of the super absorbent polymer powder becomes 40% by weight. Example 4 64 parts of an oil-in-water emulsion having an ethylene-acrylic acid copolymer solid content of 3.0 wt% was replaced with an ethylene-acrylic acid copolymer solid content of 7.3 wt% oil-in-water emulsion. A granulated product D was obtained in the same manner as in Example 1 except that 67 parts of the emulsion was used. The amount of water added corresponds to the amount by which the water content of the super absorbent polymer powder becomes 40% by weight. Example 5 An ethylene-acrylic acid copolymer having an average molecular weight of 3,0
Granule E was obtained in the same manner as in Example 1 except that the amount of acrylic acid was changed to 00 and the weight ratio of acrylic acid was 18%. The amount of water added corresponds to the amount by which the water content of the super absorbent polymer powder becomes 40% by weight. Example 6 An ethylene-acrylic acid copolymer having an average molecular weight of 20,0
Granules F were obtained in the same manner as in Example 1 except that the weight ratio of acrylic acid and acrylic acid was changed to 00 and 7.0%, respectively. The amount of water added corresponds to the amount by which the water content of the super absorbent polymer powder becomes 40% by weight. Example 7 An oil-in-water emulsion having an ethylene-acrylic acid copolymer solid content of 3.0 wt% and an oil-in-water emulsion having an ethylene-acrylic acid copolymer solid content of 3.8 wt% were used instead of 64 parts of the oil-in-water emulsion. A granulated product G was obtained in the same manner as in Example 1 except that 51 parts of the emulsion was used. The amount of water added corresponds to the amount that the water content of the super absorbent polymer powder is 35% by weight. Example 8 64 parts of oil-in-water emulsion having an ethylene-acrylic acid copolymer solid content of 3.0 wt% was replaced with 64 parts of an ethylene-acrylic acid copolymer solid content of oil-in-water emulsion of 2.5 wt %. A granulated product H was obtained in the same manner as in Example 1 except that 78 parts of the emulsion was used. The amount of water added corresponds to the amount by which the water content of the super absorbent polymer powder becomes 45% by weight. Example 9 Example 1 except that the amount of finely divided silica was changed to 0.5 part.
Granules I were obtained by the same method as described above. The amount of water added corresponds to the amount by which the water content of the super absorbent polymer powder becomes 40% by weight. Example 10 A granulated product J was obtained in the same manner as in Example 1 except that the amount of finely divided silica was changed to 5 parts. The amount of water added corresponds to the amount by which the water content of the super absorbent polymer powder becomes 40% by weight. Example 11 Superabsorbent Resin 1 part of finely powdered silica ("Sylysia #770" manufactured by Fuji Silysia Chemical Ltd., average particle size 6 µm) and ethylene-
Acrylic acid copolymer fine powder (average molecular weight 10,000,
Acrylic acid weight ratio 5%, average particle size 10 μm) 1 part was mixed by a ribbon blender, and then 62 parts of water was added dropwise using a paddle type mixer (the amount of water added was
It corresponds to the amount of water content of the super absorbent polymer powder of 40% by weight). Then, the carrier gas was made to flow with solid air and dried at 150° C. for 20 minutes to obtain a granulated product K. Comparative Example 1 Superabsorbent Resin 100 parts of the superabsorbent resin obtained in Production Example 1 was mixed with 1 part of finely powdered silica (Fuji Silysia Chemical Ltd., “Sylysia #770”, average particle size 6 μm) with a ribbon blender. After that, 62 parts of water was mixed while being dropped using a paddle type mixer (the amount of added water corresponds to an amount at which the water content of the super absorbent polymer powder is 40% by weight). Then, it was dried in a rotary polymerization dryer under a 120° C. atmosphere for 2 hours while flowing a carrier gas to obtain a granulated product L. Comparative Example 2 Ethylene-acrylic acid copolymer solid content was changed to 64 parts of oil-in-water emulsion of 3.0% by weight, and resin solid content of 3.
0% by weight PVA aqueous solution (PVA: saponification degree 88%, P
A granulated product M was obtained by the same method as in Example 1 except that 64 parts of VA content 94%) was used. The amount of water added corresponds to the amount by which the water content of the super absorbent polymer powder becomes 40% by weight. Comparative Example 3 A granulated product N was obtained in the same manner as in Example 1 except that finely divided silica was not mixed. Comparative Example 4 A granulated product O was obtained in the same manner as in Example 1 except that the amount of finely divided silica was changed to 15 parts. Comparative Example 5 Instead of 64 parts of an oil-in-water emulsion having an ethylene-acrylic acid copolymer solid content of 3.0% by weight, an ethylene-acrylic acid copolymer solid content of 19.1% by weight was added. A granulated product P was obtained in the same manner as in Example 1 except that 76 parts of the emulsion was used. The amount of water added corresponds to the amount by which the water content of the super absorbent polymer powder becomes 40% by weight. Comparative Example 6 Instead of 64 parts of an oil-in-water emulsion having an ethylene-acrylic acid copolymer solid content of 3.0% by weight, an oil-in-water emulsion having an ethylene-acrylic acid copolymer solid content of 12.1% by weight was used. A granulated product Q was obtained in the same manner as in Example 1 except that 16 parts were used. The amount of water added corresponds to the amount by which the water content of the super absorbent polymer powder becomes 15% by weight. Comparative Example 7 0.22% by weight in place of 64 parts of an oil-in-water emulsion having an ethylene-acrylic acid copolymer solid content of 3.0% by weight
A granulated product R was obtained in the same manner as in Example 1 except that 872 parts of the oil-in-water emulsion of 1 was used. The amount of water added is such that the water content of the super absorbent polymer powder is 90% by weight.
Is equivalent to Comparative Example 8 Superabsorbent Resin 100 parts of the superabsorbent resin powder obtained in Production Example 1 was mixed with 64 parts of an oil-in-water emulsion having an ethylene-acrylic acid copolymer solid content of 3.0% by weight in a paddle type mixture. The mixture was added dropwise using a machine. Subsequently, 1 part of fine powder silica was mixed with a ribbon blender, but many fine particles were formed without dispersing the fine powder silica. The amount of water added corresponds to the amount by which the water content of the super absorbent polymer powder becomes 40% by weight. [Results] The following measurements were carried out on the superabsorbent resin powders obtained in the above-mentioned superabsorbent resin production examples, examples and comparative examples and the granulated products thereof. <Granulation Yield> The weight ratio of 80#-oversized product was determined as the granulation yield using a classification sieve. <Agglomeration rate> The weight ratio of the agglomerates having a diameter of 10 mm or more was defined as the agglomeration rate. <Impact strength> 20 g of granulated product (80# over and 20# under product) is put in a cylindrical container having an internal volume of 50 cc, and one plastic ball having a diameter of 10 mm is further put therein,
Shake vigorously for 5 minutes on a shaker, then
The weight ratio of #under is the impact strength. <Compressive strength> The granulated product (80# over and 20# under product) is evenly dispersed on the metal plate so that the granulated product does not overlap, and the metal plate is placed on top of it and 10 kg/
After applying a load of cm ² , the weight ratio of 80# under in the granulated product was taken as the compressive strength. <Water absorption capacity> 1 g of the granulated product is put into a 400 mesh nylon bag (10 cm x 10 cm) and 0.9% of 1 liter
Immerse in physiological saline for 30 minutes. After 30 minutes, the nylon bag was pulled up, drained for 15 minutes, weighed, blank-corrected, and the weight of 0.9% physiological saline absorbed by 1 g of the granulated product was defined as the water absorption capacity. <Water absorption rate (normal pressure)> The water absorption rate was measured using the apparatus shown in FIG. 1.0 g of the granulated product 1 is placed on the non-woven fabric 3 on the support plate 2 having small holes. The water absorption rate (normal pressure) was defined as the amount of the granulated product 1 absorbing 0.9% physiological saline in 10 minutes when brought into contact with 0.9% physiological saline 4 from the lower surface. <Water absorption rate (pressurization)> It was measured using the apparatus shown in FIG. 1.0 g of the granulated product 1 is placed on the non-woven fabric 3 on the support plate 2 having small holes. Further, when a guide 10 was provided around the granulated product, a weight 11 (corresponding to 12 g/cm ² ) was placed on the granulated product, and when 0.9% physiological saline 4 was brought into contact with the granulated product from the lower surface, the granulated product 1 was adjusted to 0. The amount of water absorbed by 9% physiological saline was defined as the water absorption speed (pressurization).

Granulation yield, lump ratio, impact strength, compression strength of the granules obtained in Examples 1 to 11 and Comparative Examples 1 to 7,
Water absorption capacity, water absorption speed (normal pressure) and water absorption speed (pressurized), and water absorption capacity, water absorption speed (normal pressure) and water absorption speed of the crosslinked polyacrylic acid soda powder obtained in Production Example 1 or 2 The results of measuring (pressurization) by the above method are as shown in Table 1.

[0041]

[Table 1]

[0042]

[Table 2]

[0043]

According to the granulation method of the present invention, a highly water-absorbent resin granulated product having a strong granulation strength and an appropriate particle size and a narrow particle size distribution width can be obtained in a high yield, and is hygienic. Is highly safe, and
The fact that a granulated product in which the water absorption performance of the super absorbent polymer is not substantially reduced before and after granulation can be obtained is as described above in the section "Outline of the Invention".

Therefore, the product obtained by the granulation method of the present invention can be suitably used for various purposes such as sanitary products and agricultural and horticultural products.

[Brief description of drawings]

FIG. 1 is a schematic view of an apparatus for measuring a water absorption rate (normal pressure) of a granulated material.

FIG. 2 is a schematic view of an apparatus for measuring a water absorption rate (pressurization) of a granulated material.

[Explanation of symbols]

1 Granule (1 g) 2 Support plate with small holes 3 Nonwoven fabric 4 0.9% saline solution 5 Burette 6 Rubber stopper 7 Valve 8 Valve 9 Air inlet 10 Guide 11 Weight

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hisao Ito 1 Toho-cho, Yokkaichi-shi, Mie Mitsubishi Chemical Co., Ltd. Yokkaichi Research Institute

Claims (4)

[Claims] 1. To 100 parts by weight of superabsorbent resin powder, 0.1 to 10 parts by weight of inorganic powder, 0.05 to 10 parts by weight of ethylene-acrylic acid copolymer powder or emulsion and water content of the resin powder. A method for granulating a super absorbent polymer powder, which comprises mixing water in an amount such that the ratio is 20 to 70% by weight, and then drying the mixture. 2. The method for granulating a super absorbent polymer powder according to claim 1, wherein the ethylene-acrylic acid copolymer is in the form of fine powder. 3. The method for granulating a super absorbent polymer powder according to claim 1, wherein the ethylene-acrylic acid copolymer is an aqueous emulsion. 4. The highly water-absorbent resin according to claim 1, wherein an inorganic powder is mixed with the highly water-absorbent resin powder, and the ethylene-acrylic acid copolymer and water are mixed with the mixture. Of powdery resin powder.