JP2005097585A - Process for producing surface-treated particulate water-absorbing resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an excellent process for producing a surface-treated particulate water-absorbing resin, which can realize extremely high levels of properties desired for water-absorbing resins, address conventional problems in terms of safety, and the like and employs a surface treatment method capable of doing sufficient treatment even at reaction temperatures near room temperature. <P>SOLUTION: The process for producing a surface-treated particulate water-absorbing resin according to the present invention comprises adding a treatment solution containing a radical polymerizable compound to a particulate water-absorbing resin as a base polymer, and then surface-treating the particulate water-absorbing resin by irradiating the resin with an active energy ray while flowing the resin. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a particulate water-absorbing resin. In detail, it is related with the manufacturing method of particulate water-absorbing resin surface-treated by the specific surface treatment method.

Conventionally, a water-absorbing resin has been used as a constituent material of sanitary materials that absorb sanitary cotton, disposable diapers, or other body fluids. Examples of such a water-absorbing resin include a hydrolyzate of starch-acrylonitrile graft polymer, a neutralized product of starch-acrylic acid graft polymer, a saponified product of vinyl acetate-acrylic ester copolymer, and an acrylonitrile copolymer. Known are hydrolysates of polymers or acrylamide copolymers, cross-linked products thereof, cross-linked products of partially neutralized polyacrylic acid, and the like.
Properties desired for the water-absorbent resin include a high absorption rate, an excellent absorption rate, a high gel strength, and an excellent suction force for sucking water from the substrate. However, the relationship between these characteristics does not necessarily show a positive correlation, and in particular, there is a contradictory relationship between the absorption magnification and the absorption speed, gel strength, suction force, and the like. For example, when the absorption ratio is improved, so-called “mamako” is formed in contact with the liquid, water does not diffuse throughout the water-absorbent resin particles, and the absorption rate and the like are extremely reduced.

As a method for alleviating such a phenomenon and obtaining a water-absorbing resin having a high absorption rate and a relatively good absorption rate, for example, the surface of the water-absorbing resin particles is made a surfactant or a non-volatile hydrocarbon. A coating method is known. However, although this method improves the dispersibility of the water absorbed in the initial stage, it does not provide a sufficient effect in terms of improving the absorption speed and suction force of each particle.
A method is known in which the surface of the water-absorbent resin is treated with a specific crosslinking agent to increase the crosslinking density of the surface portion (see, for example, Patent Document 1).
Examples of the crosslinking agent used in these methods include polyhydric alcohols, polyvalent glycidyl ethers, haloepoxy compounds, polyvalent aldehydes, polyvalent amines, and polyvalent metal salts. However, among the crosslinking agents often used in the past, there are many crosslinking agents having problems in safety and skin irritation (for example, polyvalent glycidyl ethers), and the surface-treated water-absorbing resin is a sanitary material such as a diaper. When such a crosslinking agent remains on the surface of the water-absorbent resin, it becomes a big problem in terms of safety and the like. On the other hand, among cross-linking agents that are often used in the past, there are cross-linking agents that are relatively less problematic in terms of safety and the like (for example, polyhydric alcohols, etc.). When such cross-linking agents are used, Since the reactivity of the cross-linking agent is low, it is necessary to set the reaction temperature to a high temperature (in some cases, a long period of time). There was a problem of becoming.

As a surface treatment method that can solve the above safety and skin irritation problems while maintaining the desired properties of the water-absorbent resin at the highest possible level, the same monomers and cross-linking agents as those used in the production of the base polymer are used. There has been reported a method of using a treatment liquid containing sucrose for surface treatment of a base polymer (see, for example, Patent Document 2).
However, since the reaction temperature for the surface treatment is still high, a problem remains in that much energy is required.
JP 57-44627 A Japanese Patent No. 2530668

  The problem to be solved by the present invention is that the properties desired for the water-absorbent resin, such as absorption capacity, absorption speed, gel strength, and suction power, can be brought to extremely high levels, and the conventional safety, skin An object of the present invention is to provide an excellent method for producing a surface-treated particulate water-absorbing resin, which can solve the problem of irritation and adopts a surface treatment method that can be sufficiently treated even at a reaction temperature near room temperature.

The present inventor has intensively studied to solve the above problems. As a result, a treatment liquid containing a radical polymerizable compound is used as a treatment liquid for the surface treatment, and after adding it to the particulate water-absorbing resin as a base polymer, irradiation with active energy rays such as ultraviolet rays and electron beams is performed. I thought about surface treatment.
However, when surface treatment was performed by irradiating the particulate water-absorbing resin with active energy rays, there was a problem that a uniform surface treatment with a high crosslinking density could not be developed over the entire surface of the water-absorbent resin depending on conditions.
Therefore, as a result of further intensive studies, the present inventors have found that when the particulate water-absorbing resin to be irradiated is flowed when the surface treatment is performed by irradiating the particulate water-absorbing resin with active energy rays, the water-absorbing property can be obtained. It has been found that a uniform surface treatment with a high crosslink density can be developed over the entire resin surface.

The present invention was thus completed.
That is, in the method for producing a surface-treated particulate water-absorbing resin according to the present invention, a treatment liquid containing a radical polymerizable compound is added to the particulate water-absorbing resin as a base polymer, and then the particulate water-absorbing resin is added. The surface treatment is performed by irradiating active energy rays while flowing.

  According to the present invention, when performing surface treatment of a water-absorbent resin, the conventional safety and skin irritation problems can be solved, and surface treatment can be sufficiently performed even at a reaction temperature near room temperature. The surface-treated particulate water-absorbing resin has extremely high properties desired for the water-absorbing resin, such as absorption capacity, absorption speed, gel strength, and suction force. Further, the obtained surface-treated particulate water-absorbing resin is an aggregate (FSA: fluid stable aggregate) that retains the granulated state even when water is absorbed, for example, water absorption described in JP-A-5-506263. It becomes an agglomerate that keeps the granulated state, and gel blocking hardly occurs. Furthermore, according to this invention, the granulation effect of the fine powder generate | occur | produced at the time of manufacture of a water absorbing resin is large.

Hereinafter, although the manufacturing method of the surface-treated particulate water-absorbing resin according to the present invention will be described in detail, the scope of the present invention is not limited to these explanations, and the present invention is not limited to the following examples. Changes can be made as appropriate without departing from the spirit of the invention.
[Base polymer]
In the present invention, the particulate water-absorbing resin for surface treatment is referred to as a base polymer.
The base polymer is a water-swellable crosslinked polymer in which a crosslinked structure is introduced into the polymer, and its water-swelling property is essentially 3 times or more of its own weight under no load, preferably 5 to 200 times, more preferably The ability to absorb a large amount of physiological saline of 20 to 100 times.

The base polymer that can be used in the present invention is a polymer obtained by polymerization using a conventionally known method using a monomer component that essentially contains a water-soluble ethylenically unsaturated monomer capable of radical polymerization. If there is, it will not be specifically limited.
The water-soluble ethylenically unsaturated monomer used for producing the base polymer is not particularly limited, and examples thereof include (meth) acrylic acid, 2- (meth) acryloylethanesulfonic acid, and 2- (meth) acryloylpropane. Anionic monomers such as sulfonic acid, 2- (meth) acrylamide-2-methylpropanesulfonic acid, vinyl sulfonic acid, styrene sulfonic acid, and salts thereof; (meth) acrylamide, N-substituted (meth) acrylamide, 2 Nonionic hydrophilic group-containing monomers such as hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate; N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate N, N-diethylaminopropyl (meth) acrylate, N, N-di Chill aminopropyl (meth) acrylamide, amino group-containing unsaturated monomers and their quaternized products and the like; or the like can be cited, and may be used alone or two or more selected from these. Preferably, (meth) acrylic acid, 2- (meth) acryloylethanesulfonic acid, 2- (meth) acrylamido-2-methylpropanesulfonic acid, salts thereof, N, N-dimethylaminoethyl (meth) acrylate, N , N-dimethylaminoethyl (meth) acrylate quaternized product, (meth) acrylamide, particularly preferably acrylic acid and / or a salt thereof.

When using a salt of acrylic acid as the water-soluble ethylenically unsaturated monomer, from the viewpoint of physical properties, a monovalent salt of acrylic acid selected from alkali metal salts, ammonium salts and amine salts, more preferably alkali metal acrylates A salt, more preferably an acrylate selected from sodium, lithium and potassium salts.
When producing the base polymer, monomer components other than the water-soluble ethylenically unsaturated monomer, for example, an aromatic ethylenically unsaturated monomer having 8 to 30 carbon atoms, within a range not impairing the effects of the present invention. Mer, aliphatic ethylenically unsaturated monomer having 2 to 20 carbon atoms, alicyclic ethylenically unsaturated monomer having 5 to 15 carbon atoms, (meth) acrylic acid having 4 to 50 carbon atoms in the alkyl group Hydrophobic monomers such as alkyl esters may be used, but the concentration of the water-soluble ethylenically unsaturated monomer in all monomer components is preferably 80% by mass or more, more preferably 90% by mass. As mentioned above, More preferably, it is 95 mass% or more, Most preferably, it is 100 mass%.

The monomer component used when producing the base polymer is preferably used as an aqueous solution. The concentration of the monomer in the aqueous solution can be selected over a wide range, but is preferably 25% by mass or more, more preferably 35% by mass or more.
The base polymer is preferably an internally crosslinked one. The base polymer is based on a cross-linking agent having two or more polymerizable unsaturated groups and / or two or more reactive functional groups in one molecule, rather than a self-crosslinking type obtained without using a cross-linking agent. What is obtained by using the minimum amount necessary for the gel strength of the polymer to reach the desired standard is desirable.
These crosslinking agents are not particularly limited. For example, N, N′-methylenebis (meth) acrylamide, N-methylol (meth) acrylamide, glycidyl (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (Poly) propylene glycol di (meth) acrylate, glycerin tri (meth) acrylate, glycerine acrylate methacrylate, (meth) acrylic acid polyvalent metal salt, trimethylolpropane tri (meth) acrylate, triallylamine, triallyl cyanurate, tri Examples include allyl isocyanurate, triallyl phosphate, ethylene glycol diglycidyl ether, (poly) glycerol glycidyl ether, and polyethylene glycol diglycidyl ether. Two or more of these crosslinking agents may be used in combination.

The amount of these crosslinking agents used is preferably 0.0001 to 1 mol%, more preferably 0.001 to 0.5 mol%, still more preferably based on the monomer component used in producing the base polymer. Is 0.005 to 0.1 mol%.
In order to obtain a base polymer, a monomer component essentially containing the water-soluble ethylenically unsaturated monomer may be polymerized using a water-soluble radical polymerization initiator.
Although it does not specifically limit as a water-soluble radical polymerization initiator which can be used, For example, persulfates, such as potassium persulfate, sodium persulfate, ammonium persulfate; Hydrogen peroxide, t-butyl hydroperoxide, cumene hydroperoxide Hydroperoxides such as 2,2′-azobis-2-amidinopropane dihydrochloride; and the like, and these water-soluble radical polymerization initiators include sulfites and L-ascorbic acid A reducing agent such as a diiron salt may be used in combination as a redox initiator.

The polymerization method is not particularly limited, and well-known methods such as aqueous solution polymerization, reverse phase suspension polymerization, precipitation polymerization, bulk polymerization and the like can be employed. Among these methods, from the viewpoint of ease of control of the polymerization reaction and the performance of the resulting water-absorbent resin, in the present invention, a method in which the monomer is polymerized in an aqueous solution, that is, aqueous solution polymerization or reverse phase suspension polymerization. Is preferred.
The water-containing gel-like polymer obtained by polymerization is preferably pulverized after drying to obtain a particulate water-absorbing resin as a base polymer.
The drying is performed, for example, using a dryer such as a hot air dryer, preferably at 100 to 220 ° C, more preferably at 120 to 200 ° C.

Examples of the pulverizer that can be used for the pulverization include a shear pulverizer and an impact pulverizer among pulverization model names classified in Table 1.10 of the Powder Engineering Handbook (Edition of Powder Engineering, First Edition). Those having one or more grinding mechanisms such as cutting, shearing, impact, and friction can be preferably used, and the cutting and shearing mechanisms are mainly used among the grinding machines corresponding to these models. A pulverizer as a mechanism can be particularly preferably used. For example, a roll mill (roll rotary type) pulverizer is preferable.
The obtained particulate water-absorbing resin as the base polymer may be used as it is for the surface treatment, but is preferably classified so that particles having a particle size of 850 μm or less are 70% by mass or more of the whole, More preferably, it is 80 mass% or more, More preferably, it is 90 mass% or more, Most preferably, it is 98 mass% or more, Most preferably, it is substantially 100 mass%.

Further, according to the production method of the present invention, since the granulation effect of the fine powder generated during the production of the water-absorbent resin is large, even if fine powder is contained in the particulate water-absorbent resin as the base polymer, it does not become a big problem. However, preferably, the particles having a particle size exceeding 100 μm are classified so as to be 70% by mass or more of the whole, more preferably 80% by mass or more, further preferably 90% by mass or more, and particularly preferably 98% by mass. As described above, the most preferable is substantially 100% by mass.
〔surface treatment〕
In the production method of the present invention, after the treatment liquid containing the radical polymerizable compound is added to the particulate water absorbent resin as the base polymer, the surface treatment is performed by irradiating active energy rays while flowing the particulate water absorbent resin. To do.

Examples of the active energy ray include ultraviolet rays, electron beams, infrared rays, and radiation, and ultraviolet rays and electron beams are preferable.
When ultraviolet rays are used as the active energy ray, it is preferable that a polymerization initiator is contained in the treatment liquid. Examples of the polymerization initiator contained in the treatment liquid include photodegradable polymerization initiators such as benzoin derivatives, benzyl derivatives, acetophenone derivatives, benzophenone derivatives, and azo compounds. In addition, persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate; hydroperoxides such as hydrogen peroxide, t-butyl hydroperoxide, cumene hydroperoxide; azonitrile compounds, azoamidine compounds, cyclic azoamidine compounds, azoamides Thermal decomposition polymerization initiators such as compounds, alkylazo compounds, azo compounds such as 2,2′-azobis-2-amidinopropane hydrochloride; Furthermore, these polymerization initiators may be used in combination with a reducing agent such as sulfite and L-ascorbic acid (salt).

The treatment liquid used in the production method of the present invention contains a radical polymerizable compound in order to form a water-absorbing resin layer having a higher crosslinking density than the base polymer in the vicinity of the surface of the water-absorbing resin particles by irradiating active energy rays. .
Examples of the radically polymerizable compound that can be used in the present invention include two or more polymerizable unsaturated groups and / or a crosslinking agent that can be used for producing a particulate water-absorbing resin as a base polymer. Examples thereof include a compound having two or more reactive functional groups and a water-soluble ethylenically unsaturated monomer that can be used for producing a particulate water-absorbing resin as a base polymer.

The treatment liquid used in the production method of the present invention preferably contains a compound having two or more polymerizable unsaturated groups and / or two or more reactive functional groups in one molecule. Examples of the compound having two or more polymerizable unsaturated groups and / or two or more reactive functional groups in one molecule include those exemplified as the crosslinking agent used in the production of the above-mentioned base polymer. .
The treatment liquid used in the production method of the present invention is preferably at least one selected from those exemplified as the water-soluble ethylenically unsaturated monomer used for producing the particulate water-absorbing resin as the base polymer, and / or Or at least 1 sort (s) chosen from what was illustrated as a crosslinking agent used for manufacture of the particulate water-absorbing resin as a base polymer is included. By using such a treatment liquid, the conventional safety and skin irritation problems are solved.

  More preferably, the treatment liquid used in the production method of the present invention is at least one selected from the water-soluble ethylenically unsaturated monomers used in the production of the particulate water-absorbing resin as the base polymer, and / or the base. It contains at least one selected from cross-linking agents used in the production of the particulate water-absorbing resin as a polymer. Thus, the same monomer as the water-soluble ethylenically unsaturated monomer used for the production of the particulate water-absorbing resin as the base polymer, and / or the production of the particulate water-absorbing resin as the base polymer. By using the same cross-linking agent as the cross-linking agent for the surface treatment, a surface treatment layer having the same component composition as the base polymer is formed, so that there is an advantage that a highly safe surface treatment can be performed.

The amount of the radical polymerizable compound contained in the treatment liquid is preferably 1 to 9% by mass, more preferably 1 to 6% by mass, based on the solid content of the particulate water-absorbing resin as the base polymer. More preferably, it is 2 to 5% by mass. If the amount of the radical polymerizable compound contained in the treatment liquid is out of the above range, the effects of the present invention may not be sufficiently exhibited.
The treatment liquid used in the production method of the present invention is preferably used in a state containing water. The concentration of water in the treatment liquid can be selected over a wide range, but is preferably 20% by mass or more, more preferably 40% by mass or more.

  As the treatment liquid used in the production method of the present invention, at least one selected from water-soluble ethylenically unsaturated monomers used for the production of the particulate water-absorbing resin as the base polymer, and the particulate water-absorbing as the base polymer In the case of using a treatment liquid containing at least one selected from the crosslinking agents used for the production of the porous resin, the total amount of at least one selected from the crosslinking agents used for the production of the particulate water-absorbing resin as the base polymer is , Preferably 0.05 to 20 mol%, more preferably based on the total amount of at least one selected from the water-soluble ethylenically unsaturated monomers used for the production of the particulate water-absorbing resin as the base polymer Is 0.1 to 10 mol%, more preferably 0.5 to 5 mol%. That is, the amount used is larger than the amount of the crosslinking agent used for the monomer component when the base polymer is produced.

In the treatment liquid, in order to appropriately control the degree of surface treatment, at least one surfactant selected from the group consisting of a nonionic surfactant having an HLB of 7 or more or an anionic surfactant, or a water-soluble solution is used. A functional polymer may be contained.
Examples of such surfactants include sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyglycerin fatty acid esters, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenol ethers, polyoxyethylene acyl esters, sucrose fatty acid esters, Higher alcohol sulfuric acid ester salts, alkyl naphthalene sulfonates, alkyl polyoxyethylene sulfate salts, dialkyl sulfosuccinates, etc. can be exemplified, and examples of water-soluble polymers include polyvinyl alcohol, polyethylene oxide, polyethylene glycol, polypropylene glycol, Polyacrylamide, polyacrylic acid, sodium polyacrylate, polyethyleneimine, methylcellulose, carboxymethylcellulose Loin, hydroxyethylcellulose, hydroxypropylcellulose, dextrin, sodium alginate, and the like. When these surfactants and water-soluble polymers are used, they are preferably used in an amount of 0.01 to 30% by mass, more preferably 0.1 to 10% by mass, based on the total amount of the treatment liquid.

  The treatment liquid used in the production method of the present invention may contain other components such as a hydrophilic organic solvent as long as the effects of the present invention are not impaired. Examples of the hydrophilic organic solvent include alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol and t-butyl alcohol; ketones such as acetone and methyl ethyl ketone; dioxane and alkoxy (poly) Ethers such as ethylene glycol and tetrahydrofuran; amides such as ε-caprolactam and N, N-dimethylformamide; sulfoxides such as dimethyl sulfoxide; ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, tetraethylene glycol, 1 , 3-propanediol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol, glycerin, 2-butene-1,4 Diol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,2-cyclohexanol, trimethylolpropane, diethanolamine And polyhydric alcohols such as triethanolamine, polyoxypropylene, pentaerythritol, and sorbitol. These may be used alone or in combination of two or more.

In the production method of the present invention, the treatment liquid obtained as described above is added to and mixed with the particulate water-absorbing resin as the base polymer.
The mixing method is not particularly limited, but an ordinary mixer such as a V-type mixer, a ribbon-type mixer, a screw-type mixer, a rotating disk-type mixer, an airflow-type mixer, a batch kneader, a continuous kneader, or a paddle. A method of mixing the treatment liquid with the particulate water-absorbent resin as the base polymer using a mold mixer or the like can be mentioned.
Although the temperature in the case of addition is not specifically limited, Preferably it is 0-120 degreeC, More preferably, it is 0-60 degreeC, More preferably, it is 10-40 degreeC.

In the production method of the present invention, after the treatment liquid is added to the particulate water-absorbing resin as a base polymer, the surface treatment is performed by irradiating active energy rays. It is important to keep By performing surface treatment by irradiating active energy rays while flowing in this way, a uniform surface treatment with a high crosslinking density can be developed over the entire surface of the water absorbent resin. Surface treatment with uniform and high crosslink density over the entire surface of the water-absorbent resin when irradiated with active energy rays with insufficient flow, such as when gently stirring, or when irradiated with active energy rays without flowing. Cannot be expressed.
Examples of the method of allowing the particulate water-absorbing resin to flow when irradiating with active energy rays include, for example, a vibration mixer, a vibration feeder, a ribbon mixer, a conical ribbon mixer, a screw mixing extruder, Examples include a method using an airflow type mixer, a batch type kneader, a continuous type kneader, a paddle type mixer, a high-speed flow type mixer, a floating flow type mixer, and the like.

The conditions of irradiation with an active energy ray can be applied to ordinary general irradiation conditions, for example, the case of using ultraviolet, preferably, irradiation intensity 3~1000mW / cm ^2, irradiation amount in 100~10000mJ / cm ² In the case of using an electron beam, the acceleration voltage is preferably 50 to 800 kV and the absorbed dose is 0.1 to 100 Mrad.
The treatment temperature at the time of surface treatment by irradiating with active energy rays can be set lower than the conventional surface treatment temperature, preferably less than 60 ° C., more preferably 0-55 ° C., more preferably 5-50 ° C., particularly Preferably it is 10-40 degreeC. Moreover, for drying etc., you may heat-process a particulate water absorbing resin at the temperature of 50-250 degreeC after active energy ray irradiation as needed.

In the manufacturing method of this invention, the granulation effect of the fine powder generate | occur | produced at the time of manufacture of a water absorbing resin is large. That is, even if fine powder is contained in the particulate water-absorbing resin as the base polymer, the fine powder is granulated by applying the production method of the present invention, and the fine powder in the surface-treated particulate water-absorbing resin obtained. The amount can be greatly reduced.
[Surface-treated particulate water-absorbing resin]
The surface-treated particulate water-absorbing resin obtained by the production method of the present invention is capable of expressing a surface treatment with a uniform and high crosslinking density over the entire surface of the water-absorbent resin, for example, characteristics desired for the water-absorbing resin, for example, The absorption magnification, absorption speed, gel strength, and suction force can be made extremely high.

The surface-treated particulate water-absorbing resin obtained by the production method of the present invention has a free swelling ratio (GV) of preferably 20 g / g or more, more preferably 22 g / g or more, and further preferably 24 g / g or more. Especially preferably, it is 26 g / g or more.
The surface-treated particulate water-absorbing resin obtained by the production method of the present invention has an absorption capacity under load (AAP) of 4.9 kPa, preferably 10 g / g or more, more preferably 12 g / g or more, Preferably it is 14 g / g or more, More preferably, it is 15 g / g or more, More preferably, it is 17 g / g or more, Most preferably, it is 20 g / g or more.
Since the surface-treated particulate water-absorbing resin obtained by the production method of the present invention has a large granulation effect of fine powder generated during the production of the water-absorbing resin, its particle size distribution is higher than that before the surface treatment. shift. The shift ratio varies depending on the type and amount of the processing liquid, and the ratio of water when the processing liquid is an aqueous solution, the irradiation conditions of the active energy rays, and the flow during irradiation.

  The surface-treated particulate water-absorbing resin obtained by the production method of the present invention becomes an aggregate (FSA: fluid stable aggregate) that maintains a granulated state even when water is absorbed, and gel blocking hardly occurs.

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these. Hereinafter, for convenience, “mass part” may be simply referred to as “part”, and “liter” may be simply referred to as “L”. In addition, “mass%” may be described as “wt%”.
Measurement methods and evaluation methods in Examples and Comparative Examples are shown below.
<Free swelling ratio (GV)>
0.2 g of the water-absorbent resin is uniformly placed in a non-woven bag (60 mm × 60 mm) and placed in a large excess (usually 500 mL) of a 0.9 mass% sodium chloride aqueous solution (saline) at room temperature (25 ± 2 ° C.). ). After 30 minutes, the bag was pulled up, drained at 250 G for 3 minutes using a centrifuge, and then the mass W1 (g) of the bag was measured. Moreover, the same operation was performed without using the water absorbent resin, and the mass W2 (g) of the bag at that time was measured. And free swelling magnification (GV) (g / g) was computed from W1 and W2 by following Formula.

GV (g / g) = [W1 (g) -W2 (g) -mass of water absorbent resin (g)] / mass of water absorbent resin (g)
<Absorption capacity under pressure (AAP)>
A stainless steel 400 mesh wire mesh (mesh size 38 μm) is fused to the bottom of a plastic support cylinder with an inner diameter of 60 mm, and particles are formed on the wire mesh at room temperature (25 ± 2 ° C.) and humidity 50 RH%. 0.9 g of water-absorbing resin was uniformly dispersed, and the outer diameter was adjusted to be able to uniformly apply a load of 4.9 kPa to the particulate water-absorbing resin. A piston and a load, in which no gap is generated between the inner wall surface of the support cylinder and the vertical movement is not hindered, were placed in this order, and the mass Wa (g) of this measuring device set was measured.

A glass filter with a diameter of 90 mm (manufactured by Mutual Riken Glass Co., Ltd., pore diameter: 100 to 120 μm) is placed inside a petri dish with a diameter of 150 mm, and a 0.9 mass% sodium chloride aqueous solution (saline) (20 to 25 ° C.) was added to the same level as the upper surface of the glass filter. On top of that, a sheet of filter paper having a diameter of 90 mm (manufactured by ADVANTEC Toyo Co., Ltd., product name: (JIS P 3801, No. 2), thickness 0.26 mm, retained particle diameter 5 μm) was placed so that the entire surface was wetted. Excess liquid was removed.
A set of measuring devices was placed on the wet filter paper, and the liquid was absorbed under load for a predetermined time. This absorption time was calculated from the start of measurement and was 1 hour later. Specifically, after 1 hour, the measuring device set was lifted and its mass Wb (g) was measured. This mass measurement must be performed as quickly as possible and without vibrations. And the absorption capacity | capacitance under pressure (AAP) (g / g) was computed from Wa and Wb by following Formula.

AAP (g / g) = [Wb (g) -Wa (g)] / mass of particulate water-absorbing resin (g)
<Stability of surface treated product during water absorption>
Among the surface-treated products, relatively large particles (aggregates) were placed under an optical microscope (Nikon, MICROFLEX UFX-II), and the magnification was set to 20 times. Next, water was added to observe whether the aggregates were separated into constituent particles during the swelling process. Furthermore, if necessary, an attempt was made to separate the aggregate into its constituent particles using a needle, and the ease of separation was examined.
<Particle size distribution>
10 g of the water-absorbing resin before and after the surface treatment is sieved with a test sieve (made by IIDA Manufacturing Co., Ltd.) having a diameter of 75 mm and openings of 850 μm, 600 μm and 300 μm, the respective masses are measured, and the mass% of each particle size is obtained. It was. The sieving was performed by shaking for 5 minutes using a SIEVE SHAKER ES-65 type manufactured by IIDA Seisakusho.

[Production Example 1]
Prepare acrylate monomer aqueous solution (monomer concentration: 38 wt%, neutralization rate: 75 mol%) consisting of sodium acrylate, acrylic acid, and water in a kneader equipped with two sigma blades. Then, polyethylene glycol diacrylate (added mole number: n = 8) as an internal cross-linking agent was dissolved so as to be 0.05 mol% with respect to the monomer.
Next, nitrogen gas was blown into the aqueous solution to reduce the oxygen concentration in the aqueous solution and to replace the entire reaction vessel with nitrogen. Subsequently, 0.05 mol% (based on monomer) sodium persulfate and 0.0006 mol% (based on monomer) L-ascorbine were used as polymerization initiators while rotating two sigma blades. An acid was added and stirring polymerization was performed in a kneader. After 40 minutes, a hydrogel polymer having an average particle diameter of 2 mm was obtained.

The obtained hydrogel polymer was dried in a hot air dryer set at 170 ° C. for 45 minutes, and then the dried product was pulverized with a roll mill pulverizer and classified with a sieve having an opening of 850 μm, so that the particle size was 850 μm. By removing larger particles, a particulate water-absorbing resin (A) as a base polymer was obtained.
Various evaluation results of the particulate water-absorbing resin (A) as the obtained base polymer are shown in Table 1.
Further, Table 2 shows the particle size distribution of the particulate water-absorbing resin (A) as the obtained base polymer.

[Example 1]
To 100 g of the particulate water-absorbing resin (A) as the base polymer obtained in Production Example 1, 0.20 g of polyethylene glycol diacrylate (number of added moles: n = 8), 2.6 g of sodium acrylate, and 0.8% of acrylic acid. A processing solution in which 8 g, 5.4 g of water, 0.005 g of sodium persulfate, and 0.036 g of Irgacure 184 (manufactured by Ciba Specialty Chemicals) were mixed in advance was added and mixed.
Next, 10 g of the mixture was set in a Minishaker (manufactured by IKA Works, Inc., MS1S1), and while being vibrated and stirred at 600 times / minute, using an ultraviolet irradiation device (manufactured by Toshiba, TOSCUR401), an irradiation intensity of 4 mW / cm ² For 20 minutes at room temperature to obtain a surface-treated particulate water-absorbing resin (1).

Various evaluation results of the obtained surface-treated particulate water-absorbing resin (1) are shown in Table 1.
[Example 2]
1.0 g of polyethylene glycol diacrylate (number of added moles: n = 8), 2.6 g of sodium acrylate, 0.8 g of acrylic acid, 4.6 g of water, 0.007 g of sodium persulfate, 0.044 g of Irgacure 184 in advance A surface-treated particulate water-absorbing resin (2) was obtained in the same manner as in Example 1 except that the mixed treatment liquid was used.
Various evaluation results of the obtained surface-treated particulate water-absorbing resin (2) are shown in Table 1.
Example 3
Polyethylene glycol diacrylate (number of added moles: n = 8) 0.20 g, sodium acrylate 2.6 g, acrylic acid 0.8 g, water 5.4 g, sodium persulfate 0.005 g, Irgacure 2959 (manufactured by Ciba Specialty Chemicals) ) A surface-treated particulate water-absorbing resin (3) was obtained in the same manner as in Example 1 except that a treatment liquid in which 0.036 g was mixed in advance was used.

Various evaluation results of the obtained surface-treated particulate water-absorbing resin (3) are shown in Table 1.
In addition, Table 2 shows the particle size distribution of the obtained surface-treated particulate water-absorbing resin (3).
Example 4
Other than using a processing solution in which 0.20 g of trimethylolpropane triacrylate, 2.6 g of sodium acrylate, 0.8 g of acrylic acid, 5.4 g of water, 0.005 g of sodium persulfate, and 0.036 g of Irgacure 184 were mixed in advance. Obtained a surface-treated particulate water-absorbing resin (4) in the same manner as in Example 1.
Various evaluation results of the obtained surface-treated particulate water-absorbing resin (4) are shown in Table 1.

Example 5
Other than using a treatment liquid in which 1.0 g of trimethylolpropane triacrylate, 2.6 g of sodium acrylate, 0.8 g of acrylic acid, 4.6 g of water, 0.007 g of sodium persulfate, and 0.044 g of Irgacure 184 were mixed in advance. Obtained a surface-treated particulate water-absorbing resin (5) in the same manner as in Example 1.
Various evaluation results of the obtained surface-treated particulate water-absorbing resin (5) are shown in Table 1.
Example 6
The same procedure as in Example 1 was used except that a treatment liquid in which 1.2 g of trimethylolpropane triacrylate, 3.9 g of acrylic acid, 3.9 g of water, 0.008 g of sodium persulfate, and 0.051 g of Irgacure 184 were mixed in advance was used. Thus, a surface-treated particulate water-absorbing resin (6) was obtained.

Various evaluation results of the obtained surface-treated particulate water-absorbing resin (6) are shown in Table 1.
Example 7
500 g of the particulate water-absorbing resin (A) as the base polymer obtained in Production Example 1 is put into a 2 L batch type kneader equipped with two sigma blades, and the water-absorbing resin is stirred at a blade rotation speed of 73 rpm. However, 1.0 g of polyethylene glycol diacrylate (added mole number: n = 9), 10.0 g of sodium acrylate, 4.0 g of acrylic acid, 30 g of water, 0.0225 g of sodium persulfate, 0.15 g of Irgacure 2959 in advance. The mixed processing liquid was dropped and mixed.

Subsequently, an ultraviolet irradiation device (Ushio Electric Co., Ltd., Lamphouse UVH-1500M, power supply unit VB-1501BY, emission length 125 mm metal halide lamp) is placed on the batch kneader, and the water absorbent resin is stirred at a blade rotation speed of 73 rpm. Then, UV irradiation was performed at room temperature for 10 minutes at an irradiation intensity of 65 mW / cm ² to obtain a surface-treated particulate water-absorbing resin (7).
Various evaluation results of the obtained surface-treated particulate water-absorbing resin (7) are shown in Table 1.
Example 8
1.0 g of polyethylene glycol diacrylate (added mole number: n = 9), 10.0 g of sodium acrylate, 4.0 g of acrylic acid, 45 g of water, 0.0225 g of sodium persulfate, and 0.15 g of Irgacure 2959 were mixed in advance. A surface-treated particulate water-absorbing resin (8) was obtained in the same manner as in Example 7 except that the treatment liquid was used.

Various evaluation results of the obtained surface-treated particulate water-absorbing resin (8) are shown in Table 1.
Example 9
1000 g of the particulate water-absorbing resin (A) as the base polymer obtained in Production Example 1 is put in a Laedige mixer (Matsubo Co., Ltd., type M20), and the water-absorbing resin at a mixer rotation speed of 140 rpm and a chopper rotation speed of 500 rpm. Irgacure of 2.0 g of polyethylene glycol diacrylate (added mole number: n = 9), 20.0 g of sodium acrylate, 8.0 g of acrylic acid, 90 g of water, 0.045 g of sodium persulfate, and 0.3 g. A treatment liquid premixed with 2959 was supplied by spraying and mixed with the water absorbent resin.

Subsequently, the ultraviolet irradiation apparatus used in Example 7 was placed on this Laedige mixer, and while stirring the water absorbent resin at a mixer rotation speed of 180 rpm and a chopper rotation speed of 500 rpm, the irradiation intensity was 42 mW / cm ² for 5 minutes. UV-irradiated at room temperature to obtain a surface-treated particulate water-absorbing resin (9).
Various evaluation results of the obtained surface-treated particulate water-absorbing resin (9) are shown in Table 1.
In addition, Table 2 shows the particle size distribution of the obtained surface-treated particulate water-absorbing resin (9).
Example 10
2.0 g of polyethylene glycol diacrylate (added mole number: n = 4), 20.0 g of sodium acrylate, 8.0 g of acrylic acid, 90 g of water, 0.045 g of sodium persulfate, and 0.30 g of Irgacure 2959 were mixed in advance. A surface-treated particulate water-absorbing resin (10) was obtained in the same manner as in Example 9 except that the treatment liquid was used.

Table 1 shows various evaluation results of the obtained surface-treated particulate water-absorbing resin (10).
Example 11
0.8 g of 2-hydroxy-1-acryloxy-3-methacryloxypropane (Shin Nakamura Chemical Co., Ltd., 701A), sodium acrylate 20.0 g, acrylic acid 8.0 g, water 90 g, sodium persulfate 0.045 g A surface-treated particulate water-absorbing resin (11) was obtained in the same manner as in Example 9, except that a treatment liquid in which 0.30 g of Irgacure 2959 was mixed in advance was used.
Various evaluation results of the obtained surface-treated particulate water-absorbing resin (11) are shown in Table 1.

[Comparative Example 1]
A treatment liquid in which 0.32 g of 1,4-butanediol, 0.5 g of propylene glycol and 2.73 g of water were added in advance to 100 g of the particulate water-absorbing resin (A) obtained as the base polymer in Production Example 1 was added. And mixed.
Subsequently, 10 g of the mixture was heat-treated at 212 ° C. for 20 minutes to obtain a surface-treated particulate water-absorbing resin (c1).
Various evaluation results of the obtained surface-treated particulate water-absorbing resin (c1) are shown in Table 1.
[Comparative Example 2]
When 10 g of the particulate water-absorbing resin mixed with the treatment liquid obtained and mixed in the same manner as in Example 1 was spread on a vat and mixed with a spatula occasionally, UV irradiation was performed under the same conditions as in Example 1. A non-uniform agglomerate containing a granulated product having a diameter of several millimeters or more was formed. The aggregate was passed through a test sieve having a mesh size of 1000 μm (manufactured by IIDA Seisakusho) to obtain a surface-treated particulate water-absorbing resin (c2).

  Various evaluation results of the obtained surface-treated particulate water-absorbing resin (c2) are shown in Table 1.

  According to the present invention, in performing surface treatment of a water-absorbent resin, the conventional safety and skin irritation problems can be solved, and the surface treatment can be sufficiently performed even at a reaction temperature near room temperature. The surface-treated particulate water-absorbing resin has extremely high properties desired for the water-absorbing resin, such as absorption capacity, absorption speed, gel strength, and suction force. Further, the obtained surface-treated particulate water-absorbing resin becomes an aggregate (FSA: fluid stable aggregate) that maintains a granulated state even when water is absorbed, and gel blocking hardly occurs. Furthermore, according to this invention, the granulation effect of the fine powder generate | occur | produced at the time of manufacture of a water absorbing resin is large. Therefore, the surface-treated particulate water-absorbing resin obtained by the present invention can be optimal as a sanitary material that absorbs sanitary cotton, disposable diapers, or other body fluids, or an agricultural water-absorbing resin.

Claims (6)

  The surface is characterized in that after the treatment liquid containing a radical polymerizable compound is added to the particulate water-absorbing resin as a base polymer, the surface treatment is performed by irradiating active energy rays while flowing the particulate water-absorbing resin. A method for producing a treated particulate water-absorbing resin.   The method for producing a surface-treated particulate water-absorbing resin according to claim 1, wherein the treatment liquid contains a polymerization initiator.   The surface-treated particulate water absorption according to claim 1 or 2, wherein the treatment liquid contains a compound having two or more polymerizable unsaturated groups and / or two or more reactive functional groups in one molecule. For producing a functional resin.   The surface-treated particulate water-absorbing agent according to any one of claims 1 to 3, wherein the radically polymerizable compound is used in a proportion of 1 to 9% by mass relative to the solid content of the particulate water-absorbing resin as the base polymer. Manufacturing method of resin.   The treatment liquid is at least one selected from the water-soluble ethylenically unsaturated monomers used for the production of the particulate water-absorbing resin as the base polymer, and / or the production of the particulate water-absorbing resin as the base polymer. The method for producing a surface-treated particulate water-absorbing resin according to any one of claims 1 to 4, comprising at least one selected from the crosslinking agents used in the step.   The production of the surface-treated particulate water-absorbing resin according to any one of claims 1 to 5, wherein the surface-treated particulate water-absorbing resin has an absorption capacity under pressure at 4.9 kPa of 10 g / g or more. Method.