JP2000198805A - Water-absorbing complex and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-absorbing complex that has excellent water absorption and high water absorption rate, with almost all part of the high water- absorption polymer stably fixed to the fibrous base material and shows excellent fixation of the swollen gel after water absorption. SOLUTION: This water absorption complex is prepared by fixing the particles of water-absorption polymer to the fibrous base material. In this case, at least a part of the water absorption polymer particles comprises primary particles with an average particle size of 50-1,000 μm, more than 30 wt.% of the primary particles bind with each other, as they retain almost their shapes and is constituted with the coagulation particles having the shapes satisfying the following conditions and a part of the constituting particles are adhered to the fibrous base material: The average particle size (D): 100<=D<=3,000 μm; The declination angle according to the declination analysis (θ): 10<=θ<=25; 5 Hz/20 Hz intensity rate in the frequency analysis; 0.6<=k<=0.9; the rate of the major axis (L) to the minor axis (l): 1.2<=L/l<=15.0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-absorbing composite in which water-absorbing polymer particles are immobilized as agglomerates on a fibrous base material and a method for producing the same. More specifically, the present invention provides a method for fixing a swollen gel after absorbing water, in which agglomerated granules composed of water-absorbing polymer particles are fixed to a fibrous base material with good stability, good water absorption and a high water absorption rate. TECHNICAL FIELD The present invention relates to a water-absorbing composite having excellent properties and a method for producing the same.

[0002]

2. Description of the Related Art Paper, pulp, non-woven fabric, sponge-like urethane resin, etc. have high water absorbency, and have been used as a water retention agent in various sanitary products such as sanitary napkins, disposable diapers, and agricultural materials. It has been. However, these water-absorbing materials have a water absorption of only about 10 to 50 times their own weight. For this reason, in order to absorb or hold a large amount of water, a large amount of material is required, and there has been a problem that the material becomes extremely bulky. In addition, there is also a drawback such that when pressure is applied to the material that has absorbed water, water is easily released.

In order to improve the above-mentioned disadvantages of this type of water-absorbing material, various high-water-absorbing polymer materials have been proposed in recent years. For example, graft polymers of starch (JP-B-53-46199, etc.), modified cellulose (JP-A-50-80376, etc.), crosslinked products of water-soluble polymers (JP-B-43-23462, etc.) ), Self-crosslinking type alkali metal acrylate polymer (JP-B-54-30)
No. 710, etc.) have been proposed.

[0004] Although the water-absorbing performance of these water-absorbing polymers has reached a considerably high level, most of them are in powder form, and therefore, for use as sanitary materials such as sanitary napkins and disposable diapers, tissue, It is necessary to uniformly disperse the water-absorbing polymer powder on a substrate such as a nonwoven fabric or cotton. However, a water-absorbing polymer dispersed by a known method
It is difficult to fix powder on a fibrous base material with good stability, and it often tends to partially aggregate even after being uniformly dispersed. There is a drawback that it is easily fixed to the fibrous base material without being fixed on the fibrous base material.

Further, in the method of obtaining an absorbent body by uniformly dispersing a powdery polymer in a fibrous base material as described above, not only the polymer powder easily leaks from the fibrous base material but also the handling of the powder. Due to the complexity involved in the process and problems in the process of efficiently performing the uniform dispersion, the cost must be extremely high.

As a method of solving these problems, for example, a method of fixing a polymer powder on a fibrous base material with a binder, or a method of coating an aqueous solution of a metal polyacrylate on the base material, followed by heating and drying. Although a method of introducing cross-linking in the process is known, the former has a drawback that the process is complicated by using a binder, and the latter has a drawback that it is difficult to sufficiently exhibit water absorption performance.

Further, a composite is prepared by applying an aqueous solution of an acrylic acid monomer to a formed fibrous substrate in a predetermined pattern, and the composite is irradiated with electromagnetic radiation or ionizing radiation of fine particles to form an acrylic acid-based monomer. A method of producing a water-absorbing composite by converting a monomer into a water-swellable polymer has been reported (Japanese Patent Publication No. 3-67712). According to this method, although a considerable improvement is seen in terms of uniform dispersion in handling the powder and stable immobilization on the fibrous base material, the acrylic acid-based monomer absorbs water. In the conversion to the polymer, the use of electromagnetic radiation or particulate ionizing radiation makes the self-crosslinking reaction of the water-absorbing polymer extremely easy to proceed.
The performance as a water-absorbing body, especially the water-absorbing ability is significantly reduced,
Usually, there is a drawback that the water absorption capacity is reduced to half or less as compared with the case where the powdery superabsorbent polymer is used. In particular, since the fibrous base material itself absorbs the polymerizable acrylic acid-based monomer-water solution, the composite after polymerization becomes a plate-like extremely hard material, and the plate-like material is crushed in practical use. Must be used. In addition, when the water-absorbing polymer swells, a swelling inhibitory effect of the fibrous base material and the like are generated, and the absorption capacity, particularly the water absorption capacity, is significantly reduced.

Further, there has been proposed an absorbent article comprising a fibrous base material and a water-absorbing polymer, wherein a part of the water-absorbing polymer wraps the base material in a substantially spherical shape and is discontinuously adhered thereto (Japanese Patent Publication No. Hei 5- No. 58030). Although this absorbent article has some improved water absorbing properties as compared with the conventional article, hydrophilic fibers are unsuitable as a fibrous base material in spite of being a water absorbent article. There is a problem that the adhesiveness afterwards is weak and easily falls off.

The applicant of the present invention has proposed a method in which droplets composed of a mixture obtained by initiating polymerization of an aqueous solution of an acrylic acid-based polymerizable monomer with a redox-type initiator are supported on a fibrous base material and polymerized, whereby the water absorption and water absorption rate are increased. It has been found that a water-absorbent composite in which the superabsorbent polymer particles are excellently fixed and fixed on a fibrous base material with good stability can be produced (Japanese Patent Laid-Open No. 9-674).
03 publication). However, depending on the application of the product, there is a demand for an absorbent material having higher performance than the absorbent composite.

[0010]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above-mentioned disadvantages of the prior art, has excellent water absorption, has a high water absorption rate, and has a high stability of the superabsorbent polymer on a fibrous base material. An object of the present invention is to provide a water-absorbing composite which is well fixed and has excellent fixability of a swollen gel after absorbing water, and a method for producing the same.

[0011]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have found that the following effects can be obtained according to the present invention. .

The present invention relates to a water-absorbing composite having a water-absorbing polymer particle fixed to a fibrous base material, wherein at least a part of the water-absorbing polymer particle has an average particle diameter of 50 to 100.
0 μm primary particles, 30% by weight or more of the primary particles are bonded to each other while maintaining substantially the particle shape, constituting an aggregated granular material having a shape satisfying the following conditions, In addition, the present invention provides a water-absorbing composite, wherein a part of the constituent particles of the aggregated granular material is not attached to the fibrous base material. Average particle diameter (D) 100 ≦ D ≦ 3000 μm Declination (θ) by declination analysis 10 ≦ θ ≦ 25 5 Hz / 20 Hz intensity ratio of frequency analysis (k) 0.6 ≦ k ≦ 0.9 Ratio of long diameter (L) to shortest diameter (l) 1.2 ≦ L / l ≦ 15.0

As a preferred embodiment of the water-absorbing composite of the present invention, an embodiment in which 50% by weight or more, more preferably 80% by weight or more of the water-absorbing polymer particles constitute the agglomerated granules; Wherein one or more selected from synthetic fibers, natural fibers, semi-synthetic fibers and inorganic fibers is used; wherein the agglomerated particles are formed by dropping an aqueous solution of an ethylenically unsaturated monomer with a redox polymerization initiator. An embodiment formed by polymerizing with
By mixing an aqueous solution of a polymerizable monomer that gives a water-absorbing polymer and a redox-based polymerization initiator, droplets of a reaction mixture in which polymerization is started are formed in a gas phase, and a droplet is formed in the gas phase and / or the fibrous base material. The droplets are bonded to each other while maintaining their shapes substantially to form aggregated granules, and after the aggregated granules formed in the gas phase are supported on the fibrous base material,
An embodiment obtained by completing the polymerization of the aggregated granular material on the fibrous base material and fixing the aggregated granular material to the fibrous base material can be mentioned.

The present invention also provides a method of forming a droplet of a reaction mixture in which a polymerization is initiated by mixing an aqueous solution of a polymerizable monomer to give a water-absorbing polymer and a redox-based polymerization initiator in a gas phase. The droplets are bonded to each other while maintaining their shapes substantially in the middle and / or fibrous base material to form aggregated granules, and the aggregated granules formed in the gas phase are supported on the fibrous base material. After that, the present invention provides a method for producing a water-absorbent composite, wherein the polymerization of the aggregated granules is completed on a fibrous base material to fix the aggregated granules on the fibrous base material.

In a preferred embodiment of the production method of the present invention, the polymerization rate of the polymerizable monomer at the time of contact with the fibrous base material is 20 to 97%; A first liquid containing an oxidizing agent and a polymerizable monomer aqueous solution constituting a polymerization initiator, and a second liquid containing a reducing agent and a polymerizable monomer aqueous solution constituting a redox-based polymerization initiator are mixed in a gas phase. An embodiment in which the mixing is such that the first liquid and the second liquid are collision-mixed in a liquid column state; and wherein the polymerizable monomer is mainly composed of an aliphatic unsaturated carboxylic acid or a salt thereof. Embodiment in which the polymerizable monomer has a carboxyl group of 20
An embodiment mainly composed of acrylic acid in which at least mol% is neutralized with an alkali metal salt or an ammonium salt; the oxidizing agent constituting the redox polymerization initiator is hydrogen peroxide, and the reducing agent is L-ascorbic acid Or an embodiment in which the fibrous base material is one or two or more selected from synthetic fibers, natural fibers, semi-synthetic fibers, and inorganic fibers.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the water-absorbing composite of the present invention and a method for producing the same will be described in detail with reference to preferred embodiments.

The water-absorbing composite of the present invention is obtained by immobilizing water-absorbing polymer particles on a fibrous base material (hereinafter sometimes abbreviated as “base material”). At least a part of the water-absorbing polymer particles is composed of primary particles having an average particle diameter of 50 to 1000 μm. Average particle size of primary particles is 100-900μ
m is preferable, and 200 to 800 μm is more preferable. In this specification, “to” indicates a range including numerical values described before and after it as a minimum value and a maximum value.

At least 30% by weight of the primary particles have their particles bound together to form aggregated particles while maintaining their particle shape. The primary particles constituting the aggregated granular material are 5
It is preferably at least 0% by weight, more preferably at least 80% by weight. Some of the primary particles constituting the aggregated granular material do not adhere to the fibrous base material. That is,
The agglomerated particles are composed of primary particles directly attached to the fibrous base material and primary particles not attached to the fibrous base material at all. Since such agglomerated particles have a large specific surface area, the water absorption rate is high, and only a part of the primary particles constituting the agglomerated particles are bound to the fibrous base material. It is less constrained by the porous substrate and has excellent water absorption capacity. In addition, since the bonding surfaces of the primary particles constituting the aggregated granular material are integrated, the aggregated granular material may be broken down into primary particles and fall off from the fibrous base material not only before water absorption but also after water absorption. Less is.

The agglomerated particles have an average particle diameter (D),
Declination (θ) by declination analysis, 5 Hz / 20 of frequency analysis
The Hz intensity ratio (k) and the ratio between the longest diameter (L) and the shortest diameter (l) of the aggregated granules are within the specific ranges defined above. The average particle diameter (D) of the aggregated granules is 100 to 3000 μm
And preferably 200 to 2000 μm, and 250 to 2 μm.
000 μm is more preferred. If the average particle size is smaller than 100 μm, the water absorption performance is not sufficiently exhibited. On the other hand, when the average particle diameter is larger than 3000 μm, the adhesive strength with the fibrous base material becomes weak.

The argument (θ) obtained by the argument analysis is 10 to 25.
And 12 to 24 are preferable, and 14 to 22 are more preferable. The 5 Hz / 20 Hz intensity ratio (k) of the frequency analysis is 0.6 to 0.9, preferably 0.65 to 0.85, and more preferably 0.65 to 0.80. The ratio between the longest diameter (L) and the shortest diameter (l) of the aggregated granules is 1.2 to 15.0, preferably 1.5 to 10.0, and more preferably 1.5 to 8.0. About these average particle diameter (D), declination (θ) by declination analysis, 5 Hz / 20 Hz intensity ratio (k) of frequency analysis, and ratio of longest diameter (L) and shortest diameter (l) of aggregated granular material, Can be determined by a method described in Test Examples described later.

The water-absorbing composite of the present invention is characterized in that polymer particles whose primary particles are truly spherical are bound to each other and secondary particles are in a grape shape, so that there is no angularity and a soft feeling can be maintained. . As in the present invention, a water-absorbing composite in which a water-absorbing polymer is immobilized on a fibrous base material has been developed as described in JP-A-9-67403. The water-absorbing resin in the body is one in which angular single particles are adhered to fibers. For this reason, the feel to the skin is rough or tingling, and it may be lacking in softness. However, the water-absorbing complex of the present invention significantly improves the feel to the skin.

The water-absorbing polymer particles are usually contained in the water-absorbing composite at 50 to 300 g / m ^2.
The content is preferably set to be from 00 to 250 g / m ² , particularly from 130 to 220 g / m ² . When the content of the water-absorbing polymer particles is small, the water absorbing ability naturally becomes small. Further, if the content is too large, it is uneconomical, and the ratio of the primary particles that bind to the fibrous base material decreases, so that the binding force with the base material decreases.

The method for producing the water-absorbing composite of the present invention is not particularly limited. What is manufactured by any method is included in the scope of the present invention as long as it satisfies the conditions described in claim 1. Further, the material of the water-absorbing polymer particles and the fibrous base material constituting the water-absorbing composite of the present invention is not particularly limited. Therefore, conventionally known water-absorbing polymers and fibrous base materials can be used. Further, a plurality of types may be used in combination. Specific examples of the water-absorbing polymer and the fibrous base material will be described later.
In the water-absorbing composite of the present invention, the water-absorbing polymer may be immobilized on only one surface of the fibrous base material, or the water-absorbing polymer may be immobilized on both surfaces. It can be determined appropriately according to the use of the water-absorbing composite. For example, a water-absorbing polymer can be immobilized on both surfaces of the fibrous base material to increase the basis weight of the fibrous base material and to share the functions of the front and back surfaces.

Method for Producing a Water-Absorbing Composite A water-absorbing composite for the purpose of the present invention can be produced simply and inexpensively by the production method of the present invention. The production method of the present invention forms droplets of a reaction mixture in which polymerization is started by mixing an aqueous solution of a polymerizable monomer that gives a water-absorbing polymer and a redox polymerization initiator, and forms droplets in a gas phase. And / or binding the droplets to each other on the fibrous base material while maintaining their shapes substantially to form aggregated granules, and carry the aggregated granules formed in the gas phase on the fibrous base material. Thereafter, the polymerization of the aggregated granular material is completed on the fibrous base material to fix the aggregated granular material to the fibrous base material.

<Polymerizable Monomer> The polymerizable monomer used in the present invention may be of any type as long as it provides a water-absorbing polymer and as long as its polymerization is initiated by a redox-based initiator. Regardless. The monomer must be water-soluble because it is used as an aqueous solution, but the monomer that provides the water-absorbing polymer is generally water-soluble.

A representative example of such a monomer, which is also preferable for use in the present invention, is an aliphatic unsaturated carboxylic acid or a salt thereof. Specific examples include unsaturated monocarboxylic acids or salts thereof such as acrylic acid or salts thereof, methacrylic acid or salts thereof, and unsaturated dicarboxylic acids or salts thereof such as maleic acid or salts thereof, itaconic acid or salts thereof. These may be used alone or as a mixture of two or more. Among them, preferred are acrylic acid or a salt thereof, and methacrylic acid or a salt thereof, and particularly preferred is acrylic acid or a salt thereof.

As the polymerizable monomer for providing the water-absorbing polymer in the present invention, an aliphatic unsaturated carboxylic acid or a salt thereof is preferable as described above.
As the aqueous solution of (1), an aqueous solution containing an aliphatic unsaturated carboxylic acid or a salt thereof as a main component is preferable. here,
The phrase "having an aliphatic unsaturated carboxylic acid or a salt thereof as a main component" means that the aliphatic unsaturated carboxylic acid or a salt thereof is contained in an amount of 50 mol% or more, preferably 80 mol% or more, based on the total amount of the polymerizable monomer. Means that

As the salt of the aliphatic unsaturated carboxylic acid, a water-soluble salt, for example, an alkali metal salt, an alkaline earth metal salt, an ammonium salt and the like are usually used. The degree of neutralization is appropriately determined according to the purpose. In the case of acrylic acid, it is preferable that 20 to 90 mol% of the carboxyl group is neutralized with an alkali metal salt or an ammonium salt. The degree of partial neutralization of acrylic acid monomer is 20 mol%
If it is less than 3, the water-absorbing ability of the produced water-absorbing polymer tends to be remarkably reduced.

For neutralization of the acrylic acid monomer, an alkali metal hydroxide, bicarbonate or the like, or ammonium hydroxide can be used. Preferred is an alkali metal hydroxide. Include sodium hydroxide and potassium hydroxide.

In the present invention, in addition to the above-mentioned aliphatic unsaturated carboxylic acids, polymerizable monomers copolymerizable therewith, such as (meth) acrylamide and (poly) ethylene glycol (meth) acrylate , 2-hydroxyethyl (meth) acrylate, or a low water-soluble monomer
However, alkyl acrylates such as methyl acrylate and ethyl acrylate may be copolymerized in an amount that does not decrease the performance of the resulting water-absorbing polymer. In this specification, the term “(meth) acryl” shall mean both “acryl” and “methacryl”.

Among these polymerizable monomers, the one that gives a water-absorbing polymer is not used as an auxiliary component for an aliphatic unsaturated carboxylic acid or a salt thereof, but is an aqueous solution of a polymerizable monomer that gives a water-absorbing polymer. ] Can be used as the main monomer.

The aliphatic unsaturated carboxylic acid or a salt thereof, particularly acrylic acid or a salt thereof, may form a self-cross-linked polymer by itself. However, a cross-linking agent is used in combination to positively form a cross-linked structure. You can also. When a cross-linking agent is used in combination, the water-absorbing performance of the resulting water-absorbing polymer is generally improved. Examples of the crosslinking agent include divinyl compounds copolymerizable with the polymerizable monomer, such as N, N'-methylenebis (meth) acrylamide, (poly) ethylene glycol (meth) acrylates, and carboxylic acids. A water-soluble compound having two or more functional groups capable of reacting with water, for example, polyglycidyl ethers such as ethylene glycol diglycidyl ether and polyethylene glycol diglycidyl ether are preferably used. Among them, particularly preferred is N, N'-methylenebis (meth) acrylamide. The amount of the crosslinking agent to be used is 0.001 to 1% by weight, preferably 0.01 to 1% by weight, based on the charged amount of the monomer.
0.5% by weight.

The concentration of the polymerizable monomer in the aqueous polymerizable monomer solution containing the above-mentioned aliphatic unsaturated carboxylic acid or its salt as a main component is 20% by weight or more, preferably 25% by weight or more. If the concentration is less than 20% by weight, it is difficult to form droplets having an appropriate viscosity, and furthermore, it is not preferable because the water absorbing ability of the water-absorbing polymer after polymerization cannot be sufficiently obtained. The upper limit is preferably about 80% by weight from the viewpoint of handling the polymerization reaction solution.

<Redox-based polymerization initiator> The polymerization initiator used in the present invention is a redox-based one obtained by combining an oxidizing radical generator and a reducing agent, and exhibits a certain degree of water solubility. Must.
Examples of such an oxidizing agent include hydrogen peroxide, persulfates such as ammonium persulfate and potassium persulfate, peroxides such as hydroperoxides such as t-butyl hydroperoxide and cumene hydroperoxide, and others. , Ceric salts, permanganates, chlorites, hypochlorites, etc., of which hydrogen peroxide is particularly preferred. The amount of the oxidizing agent to be used is 0.01 to 10% by weight, preferably 0.1 to 2% by weight, based on the polymerizable monomer.

The reducing agent is capable of forming a redox system with the above-mentioned oxidizing agent. Specific examples thereof include sulfites such as sodium sulfite and sodium hydrogen sulfite, sodium thiosulfate, cobalt acetate, copper sulfate, and ferrous sulfate. , L-ascorbic acid or alkali metal salts of L-ascorbic acid. Among them, L-ascorbic acid or L-ascorbic acid alkali metal salt is particularly preferred. The amount of these reducing agents used is 0.1 to the polymerizable monomer.
001 to 10% by weight, preferably 0.01 to 2% by weight.

<Polymerization method> In the present invention, an aqueous solution of a polymerizable monomer which gives a water-absorbing polymer, specifically,
A redox-based polymerization initiator is disposed in an aqueous solution of a polymerizable monomer containing an aliphatic unsaturated carboxylic acid or a salt thereof as a main component to start polymerization of the monomer, and the monomer and the polymer after the reaction is started are converted. The reaction mixture during the progress of polymerization is formed into droplets in the gas phase, and the droplets are bound together in the gas phase and / or on the fibrous base material to form aggregated granules. The polymerization is completed on the substrate. Therefore, after the aggregated granules formed in the gas phase are supported on the fibrous base material (in some cases, the fibrous base material on which the aggregated granules are supported), the aggregated granules on the fibrous base material The body completes the polymerization as it is. In this specification, "on the fibrous base material" includes on the surface of the formed fibrous base material, on the base fiber, and also on the inner surface of the void between the fibers constituting the base material. is there.

In such a polymerization system, a monomer is used.
When the redox system is formed in the coexistence, polymerization is started practically immediately, and the time until the polymerization by the redox initiator reaches a predetermined polymerization rate corresponding to the chain polymerization, that is, the monomer-containing aqueous solution Care must be taken that the time required for the viscosity to reach the predetermined level is relatively short, and the monomer-containing aqueous solution after the initiation of the polymerization forms droplets of the predetermined viscosity, forming aggregated particles and causing It is necessary to select operating conditions so as to produce strong adhesion.

Under such considerations, one preferred method is to use a first solution comprising a polymerizable monomer-water solution containing one of an oxidizing agent and a reducing agent constituting a redox polymerization initiator and a redox polymerization initiator. Initiating the polymerization by mixing the second and, if desired, a second liquid comprising an aqueous solution containing a polymerizable monomer in the gas phase.

As a specific means, for example, the intersection angle between the liquids flowing out of the first liquid and the second liquid from the nozzle is 1
There is a method of jetting from separate nozzles so as to collide at an angle of 5 degrees or more and in a liquid column state. In this way, by making the two liquids have an intersection angle and collide with each other, a part of the outflow energy from the nozzle is used for mixing. The intersection angle between the first liquid and the second liquid flowing out of each nozzle is determined by the properties of the polymerizable monomer used,
Select as appropriate according to the flow rate ratio and the like. For example, if the linear velocity of the liquid is high, the intersection angle can be reduced. To obtain a sufficient mixing effect, 15 degrees or more is required, and a particularly preferable angle is 20 degrees or more. As long as a liquid column is formed after the collision between the first liquid and the second liquid (details will be described later), the upper limit of the angle is not particularly limited, but is 120 ° or less, particularly preferably 100 ° or less for an industrial apparatus.

In this method, it is necessary to collide in a liquid column state so that the two liquids, the first liquid and the second liquid, coming out of the respective nozzles merge to form a liquid column. By colliding in the liquid column state in this way, liquids can be mixed at a set flow rate ratio, and the polymerization reaction is favorably performed. If the first liquid and the second liquid collide after becoming particulate, the mixing ratio is different from the set flow rate ratio, and a favorable result is hardly obtained. Further, the distance between the nozzle tips can be set freely within a range where the fluid can collide in a liquid column state, and the tips of the nozzles may be in contact. The inner diameter of the nozzle may be appropriately selected according to the properties of the polymerizable monomer to be used and the shape of the intended water-absorbing composite, but is preferably 0.15 to 0.15.
It is 2.0 mm, more preferably in the range of 0.1 to 1.0 mm.

In this case, the temperature of the first liquid is usually from room temperature to about 60 ° C., preferably from room temperature to about 40 ° C.
The temperature of the second liquid is also usually from room temperature to about 60 ° C, preferably from room temperature to about 40 ° C. As described above, the respective aqueous solutions ejected from the nozzles collide in a liquid column state to combine the two liquids. After the merging, a liquid column is formed, and this state is maintained for a certain period of time. Thereafter, the liquid column is disassembled into a droplet. The resulting droplets fall in the gas phase or onto the substrate, where they form aggregated particulates.

The time for forming and holding the liquid column after the coalescence, the length of the liquid column, and the size of the liquid droplet vary depending on the setting conditions such as the nozzle inner diameter, but generally the holding time is 0.1 to 3 seconds and the liquid column length is The size is 3 to 50 mm and the size of the droplet is about 5 to 300 in diameter.
0 μm. In order for the polymerization of the droplets to proceed and bind to each other to form appropriate aggregated granules, the size of the droplets is particularly 5
It is preferable to set it in the range of 0 to 1000 μm.

As a gas in the gaseous phase which provides a place for starting the polymerization and forming droplets during the progress of the polymerization, nitrogen, helium, carbon dioxide gas or the like which is inert to the polymerization is preferable. Good. Also, the humidity in the gas is not particularly limited, including the case of only water vapor.However, if the humidity is too low, the water in the aqueous solution of the monomer evaporates before the polymerization proceeds, and the monomer is precipitated. There is a possibility that the polymerization rate is remarkably reduced or the polymerization is stopped halfway. The temperature condition of the gas is from room temperature to 150 ° C., preferably 1
It is below 00 ° C. The flow direction of the gas may be either countercurrent or cocurrent with respect to the direction of travel of the liquid column and the droplet, but when it is necessary to extend the residence time of the droplet in the gas phase, that is, the polymerization rate of the polymerizable monomer is reduced. If it is necessary to raise the viscosity of the liquid droplets, and thus increase the viscosity of the liquid droplets, countercurrent (anti-gravity direction) is better.

The droplets undergoing polymerization collide with each other and bind together in the gas phase or on the fibrous base material while maintaining their shapes to form aggregated granules. The above aggregated granules are left as is, and the aggregated granules formed in the gas phase are supported on a fibrous base material, and then the polymerization is completed on the base material. Is immobilized on the fibrous base material by surrounding or in contact with the base fiber. At least a portion of the constituent particles of the aggregated granules fixed to the fibrous base material constitute aggregated granules joined to each other while substantially maintaining the particle shape, and the constituent particles of the aggregated granules are Some have a structure that does not adhere to the fibrous base material.

The polymerization rate at the time when the droplets during the polymerization are in contact with the substrate in the gas phase or on the substrate to form aggregated granules is 20 to 20.
97%, preferably 30-97%, more preferably 5%
Various conditions are set so as to be 0 to 95%. If the polymerization rate is too low, even if the droplets collide with each other in the gas phase, they will not form aggregated granules but will be integrated into large particles, or the liquid will fall when the droplets fall onto the substrate. It becomes impossible to adhere to the base material in the form of agglomerated granules by spreading or being absorbed or impregnated on the base material. On the other hand, if it is too high, the adhesive strength to the base material does not appear, and the base material and the water-absorbing polymer
And the fixability becomes worse.

The polymerization rate and the formation of agglomerated particles are determined by the angle of intersection between the first liquid and the second liquid flowing out of the nozzle, the diameter of the nozzle,
Depending on the type and amount of the polymerization initiator, the distance between the nozzle and the substrate, the temperature and humidity of the gas phase, the number and arrangement of the nozzles, and the relative position or distance between the nozzle and the substrate, the probability of collision between the liquids can be increased, It is possible to control by controlling the degree of polymerization progress in the phase. A method other than using two opposing nozzles is also possible. As an example of such a case, a binding type nozzle in which the tip positions of the two nozzles are aligned,
One example is a double nozzle in which one nozzle is inserted into the other nozzle.

The components of the respective liquids ejected from the nozzles collide and mix in a liquid column state to form droplets, and the droplets are polymerized while falling onto the substrate or on the substrate as polymerization proceeds to form aggregated granular materials. And the final stage of polymerization proceeds on the substrate.

If necessary, the remaining monomer may be treated in order to react the unreacted monomer remaining in the aggregated granules. Examples of the method of treating the remaining monomer include 1) a method of promoting polymerization of the monomer, 2) a method of leading the monomer to another derivative, and 3) a method of removing the monomer.

Examples of the method of 1) for promoting the polymerization of the monomer include a method of further heating the composite of the aggregated granular material and the base material, and adding a catalyst or a catalyst component for accelerating the polymerization of the monomer to the aggregated granular material. Examples of the method include a method of heating later, a method of irradiating ultraviolet rays, and a method of irradiating electromagnetic radiation or particulate ionizing radiation.

The method of further heating the composite of the aggregated granular material and the base material includes the step of heating the composite of the aggregated granular material and the base material to 100 to 2 times.
Heat treatment is performed at 50 ° C. to polymerize the monomers remaining in the aggregated granules. A method of adding a catalyst or a catalyst component that promotes the polymerization of a monomer to the aggregated particles is, for example, when polymerization is performed using a redox polymerization initiator, since a radical generator often remains, What is necessary is just to apply a reducing agent solution to a granular material. As the reducing agent, sodium sulfite, sodium hydrogen sulfite, L-ascorbic acid, or the like used as a redox-based initiator may be used, and these are usually applied to the aggregated granules as a 0.5 to 5% by weight aqueous solution. The amount of the reducing agent applied may be 0.1 to 2% by weight based on the dry resin. The application of the reducing agent solution can be performed by an arbitrary method such as spraying using a sprayer or dipping in the reducing agent solution. The aggregated particles to which the reducing agent has been added are then heated to polymerize the polymerizable monomer. Heating is performed at 100 to 150 ° C. for 10 to
It may be performed for about 30 minutes. This heating lowers the water content of the aggregated granules, but if the water content is high, it is further dried with a dryer to obtain a water-absorbing composite of the product.

In the method of irradiating the composite of the aggregated particles and the base material with ultraviolet light, an ordinary ultraviolet lamp may be used.
The irradiation intensity, irradiation time and the like vary depending on the type of the fibrous substrate used, the amount of the residual monomer impregnated, and the like, but are generally from 10 to 200 w / cm, preferably from 30 to 12 UV lamps.
0 w / cm, irradiation time 0.1 second to 30 minutes, lamp-composite interval 2 to 30 cm. The amount of water in the composite at this time is generally 0.01 to 40 parts by weight, preferably 0.1 to 1.0 part by weight, per 1 part by weight of the polymer. A water content of less than 0.01 part by weight or more than 40 parts by weight is not preferred because it has a significant effect on the reduction of the residual monomer. As an atmosphere for irradiating ultraviolet rays, any of a vacuum, in the presence of an inorganic gas such as nitrogen, argon, and helium, or in air can be used.
The irradiation temperature is not particularly limited, and the object can be sufficiently achieved at room temperature. There is no particular limitation on the ultraviolet irradiation apparatus to be used, and any method such as a method of irradiating for a fixed time in a stationary state or a method of continuously irradiating with a belt conveyor can be used.

In the method of irradiating the composite of the aggregated granular material and the substrate with radiation, high-energy radiation such as accelerated electrons or gamma rays is used. The dose to be applied varies depending on the amount of residual monomer in the composite, the amount of water, etc.,
Generally, 0.01 to 100 megarads, preferably 0.1 to 100 megarads.
1 to 50 megarads. At a dose exceeding 100 megarads, the water absorption becomes extremely small, and when it is less than 0.01 megarads, the water absorption capacity and water absorption rate aimed at by the present invention are large,
It is difficult to obtain a particularly small residual monomer. Also,
At this time, the amount of water in the composite is generally 40 parts by weight or less, preferably 10 parts by weight with respect to 1 part by weight of the fibrous substrate.
Parts by weight or less are employed. If the amount of water exceeds 40 parts by weight, the effect of improving the water absorption rate is small, and in particular, the amount of unpolymerized monomer is significantly affected, which is not preferable. The atmosphere for irradiating the composite with high-energy radiation in the present invention may be any of a vacuum, in the presence of an inorganic gas such as nitrogen, argon, and helium, or in air. The preferred atmosphere is air. Irradiation in the air increases the water absorption capacity and water absorption rate and reduces the residual monomer in particular. The irradiation concentration is not particularly limited, and the object can be sufficiently achieved at room temperature.

Examples of the method 2) for introducing the monomer into another derivative include a method of adding an amine, ammonia and the like, and a method of adding a reducing agent such as bisulfite, sulfite and pyrosulfite.

As a method of removing the monomer of 3),
For example, a method of extracting and distilling with an organic solvent may be mentioned. In the method of extracting with an organic solvent, the complex of the aggregated granular material and the substrate is immersed in a water-containing organic solvent to extract and remove the remaining monomer. Ethanol, methanol, acetone and the like can be used as the water-containing organic solvent, and the water content thereof is preferably from 10 to 99% by weight, particularly preferably from 30 to 60% by weight. In general, the higher the water content, the higher the ability to remove residual monomers. However, when a water-containing organic solvent having a high water content is used, energy consumption in the subsequent drying step increases. The time for immersing the composite of the aggregated granular material and the base material in the aqueous organic solvent is usually sufficient for about 5 to 30 minutes, and the extraction of the residual monomer such as shaking the composite of the aggregated granular material and the base material is sufficient. It is also preferable to employ means for promoting. After the immersion treatment, it is usually treated by a dryer and dried.

As a method of distilling off the monomer,
The composite of the aggregated particles and the substrate is treated with superheated steam or a steam-containing gas. For example, saturated steam of 110 ° C.
By heating to 20 to 150 [deg.] C. and bringing it as superheated steam into contact with the composite of the aggregated granular material and the base material, the residual monomer in the aggregated granular material can be reduced. In this method, it is considered that when water in the aggregated granules evaporates as water vapor, the remaining monomer is also vaporized and escapes from the aggregated granules. According to this method, both the removal of the residual monomer and the drying of the product can be performed.

The surface of the aggregated particles on the substrate can be cross-linked with a cross-linking agent for the purpose of improving the water absorption performance. In general, it is known to improve the properties of resin particles by applying a crosslinking agent to the surface of the powdery water-absorbent resin particles and then heating and crosslinking the surface to form a crosslinked structure selectively on the surface. As a result, when swelling by absorbing water, it is considered that the shape can be maintained without inhibiting swelling. In this step, first, a solution of the surface cross-linking agent is applied to the aggregated granules of the composite of the aggregated granules and the substrate. Examples of the surface crosslinking agent include polyfunctional compounds copolymerizable with polymerizable monomers such as N, N'-methylenebis (meth) acrylamide, (poly) ethylene glycol bis (meth) acrylate, and (poly) ethylene glycol diglycidyl ether. A compound having a plurality of functional groups capable of reacting with the carboxylic acid group of the above is used. These surface cross-linking agents are usually used in an amount of 0.1 to the aggregated granules (dry basis).
To 1% by weight, preferably 0.2 to 0.5% by weight. These surface cross-linking agents are diluted with water, ethanol, methanol or the like to 0.1 to 1% by weight, particularly 0.2 to 0.5% by weight, so as to be uniformly applied to the entire surface of the aggregated granular material. % Solution is preferred. The application of the cross-linking agent solution is usually performed by spraying the cross-linking agent solution onto the aggregated granules using a sprayer, or inverting the composite of the aggregated granules and the base material so that the resin particle adhesion surface is on the lower surface. It is preferable to apply the method by applying the crosslinking agent solution with a roll brush whose lower part is immersed in a tank containing the crosslinking agent solution. After the crosslinker solution is applied in excess, the excess crosslinker solution may be removed by squeezing the resin particles lightly with a squeeze roll or blowing air to such an extent that the resin particles are not crushed. The application of the crosslinking agent solution may be performed at room temperature. The composite of the aggregated granular material and the substrate to which the crosslinking agent solution has been applied is then heated to cause a crosslinking reaction to proceed, thereby selectively forming a crosslinked structure on the surface of the aggregated granular material. The conditions for the cross-linking reaction may be appropriately selected depending on the cross-linking agent to be used, but the reaction is usually performed at a temperature of 100 ° C. or higher for 10 minutes or longer.

The water-absorbing composite produced by the production method of the present invention is excellent in water absorption, has a high water absorption rate, and most of the superabsorbent polymer is fixed on the fibrous base material with good stability. Moreover, the swelling gel after absorbing water is also excellent in fixability. Japanese Patent Laid-Open No. 9-23 which is a prior art related to the present invention
No. 9912 discloses that after disposing a water-soluble ethylenically unsaturated monomer-impregnated water-absorbing polymer particle on or in a fibrous substrate, polymerizing the ethylenically unsaturated monomer in the water-absorbing polymer particle. Discloses a method for producing a water-absorbing composite, comprising immobilizing water-absorbing polymer particles on or in the fibrous base material. Since this method uses the water-absorbent resin polymer particles which have been polymerized in advance, the bonding with the fibers of the fibrous base material is performed by point bonding with the surface of the primary particles constituting the aggregated granular material. On the other hand, since the present invention binds to the fibers of the fibrous base material before the polymerization is not completed, the fibers of the fibrous base material penetrate through some of the primary particles constituting the aggregated granular material. JP-A-9-2
When comparing the water-absorbent resin of the water-absorbing composite of the present invention with that of JP-A-39912, the adhesive strength at the time of water absorption of the present invention is greatly improved as is apparent from the bonding mechanism.

<Fibrous Substrate> As the fibrous substrate to which droplets or agglomerated particles of the above-mentioned reaction mixture undergoing polymerization are to be adhered, a molded fibrous substrate is preferable. As used herein, the term "fibrous base material" refers to a pad formed by loosely forming fibers, a carded or air-layed web, a woven fabric such as a tissue paper, a cotton gauze, or a meliath fabric. Or, it is a non-woven fabric having a specific shape. Molded fibrous base material means that cutting, joining, shaping, etc. may be necessary in order to incorporate the fibrous base material into the product, but there is no need to further perform web forming work. I do.

The fibers constituting the base material are wood pulp,
Hydrophilic fibers such as Yong, cotton, regenerated cellulose and other cellulosic fibers are preferred, and are those which best enjoy the benefits of the present invention, and are primarily composed of such hydrophilic fibers. These are particularly preferred substrates in the present invention. In addition, it is also preferable to use a fibrous base material mainly composed of polyester fibers, and other types of non-hydrophilic fibers such as polyethylene, polypropylene, polystyrene, polyamide, and polyvinyl alcohol. -It is also possible to use a fibrous base material containing polyester, polyvinyl chloride, polyvinylidene chloride, polyacrylonitrile, polyurea, polyurethane, polyfluoroethylene, and polyvinylidene cyanide fibers as main components. It is. Also, a relatively dense fibrous base material can be used as the fibrous base material. Specific examples include paper, wood, backskin, and leather.

<Production of water-absorbing composite> An example of an actual method for producing a water-absorbing composite is as follows.
That is, the sheet of the fibrous base material is transferred to a belt conveyor.
The liquid column of the reaction mixture undergoing polymerization in which the polymerization of the polymerizable monomer-water solution has been started is dropped from above, and the generated droplets are combined in the gas phase or on the fibrous base material sheet. After a predetermined period of time has passed since the aggregated granular material that has been attached and supported on the substrate sheet, the polymerization is completed. Since the produced water-absorbing polymer contains water, it is subjected to a drying treatment for removing water to obtain a raw material of the water-absorbing composite. This is cut into a predetermined shape and size to produce a water-absorbing composite.

<Water-absorbing composite> The water-absorbing composite thus obtained is obtained by forming the water-absorbing polymer into aggregated granules,
At least a part of the agglomerated granular material is fixed to the fibrous base material around the base fiber or in contact with the base fiber, and penetrates through some of the primary particles constituting the base material. Carried on top. Therefore, the polymer is firmly fixed to the fibrous base material not only before the water absorption but also after the water absorption and the gel state, and the agglomerated granular material is further composed of the aggregated primary particles. Since the bonding surfaces are integrated and have no adhesive interface, they do not easily return to single particles even after swelling by absorbing water, and have excellent shape retention as an absorber.

Further, since the water-absorbing polymer becomes agglomerated particles, and a part of the constituent primary particles do not adhere to the base fiber, the polymer is less restricted by the base fiber, so that the polymer absorbs water. The swelling inhibition received from the fiber when swelling is reduced, and a water-absorbing composite having excellent water-absorbing ability can be obtained.

The water-absorbing complex according to the present invention should be satisfactory in terms of water-absorbing capacity and water-absorbing rate, as is clear from the physiological saline water-absorbing capacity and absorption rate tests described in the following Examples (and Comparative Examples). Has performance. According to the present invention, the water absorption capacity is generally 20 (fold) or more, usually 30 times.
(Times) or more, and often 35 (times) or more. The water absorption rate is generally 15 g / 5 min or more, usually 20 g / 5 min or more, and often 25 g / 5 min or more.

Further, the water-absorbing composite according to the present invention is satisfactory in that the amount of residual unreacted monomer is small. According to the present invention, the residual unreacted monomer concentration is
Generally less than 500 ppm, usually less than 300 ppm, often less than 100 ppm.

The water-absorbing composite of the present invention can be used for applications where a water-absorbing resin has been conventionally used. "Water-absorbing polymer", pp. 81-111 (Fusayoshi Masuda, Kyoritsu Shuppan, 198
7), "Development trend of super water absorbent resin and its application development" (Eizo Omori, Techno Forum, 1987), Kenji Tanaka,
“Industrial Materials”, Vol. 42, No. 4, pp. 18-25, 1994, Nobuyuki Harada, Tadao Shimomura, pp. 26-30, introduces various uses of water-absorbing resins and can be used as appropriate. For example, disposable diapers, sanitary products, freshness preserving materials, humectants, cold preservatives, anti-condensation agents, soil improvement materials and the like can be mentioned.

Further, JP-A-63-267370, JP-A-63-10667, and JP-A-63-29
No. 5251, Japanese Patent Application Laid-Open No. 270801, and Japanese Patent Application Laid-Open
JP-A-3-294716, JP-A-64-64602, JP-A-1-231940, JP-A-1-243
927, JP-A-2-30522 and JP-A-2
-153731, JP-A-3-21385,
JP-A-4-133728, JP-A-11-1561
It can also be used for the use of the sheet-shaped water-absorbing composite proposed in JP-A-18 / 18 and the like.

<Additives> Various additives can be added to the water-absorbing polymer or the water-absorbing composite in order to impart a desired function according to the intended use. These additives include polymer stabilizers by absorbing liquids, stabilizers to prevent deterioration, antibacterial agents, deodorants, deodorants, fragrances,
Blowing agents and the like can be mentioned.

Among the stabilizers, excrement (ie, human urine,
And a stabilizer that prevents the water-absorbent resin from decomposing and deteriorating due to feces) and body fluids (body fluids such as human blood, menstrual blood, and secreted fluid).
JP-A-63-118375 discloses a method of incorporating an oxygen-containing reducing inorganic salt and / or an organic antioxidant in a polymer, and JP-A-63-153060 discloses a method of containing an oxidizing agent. JP-A-63-127754 discloses a method of incorporating an antioxidant, and JP-A-63-2723.
No. 49, a method of containing a sulfur-containing reducing agent, JP-A-63-146964, a method of containing a metal chelating agent, and JP-A-63-15266, a method of containing a radical chain inhibitor. JP-A-1-27566
No. 1 discloses a method for containing an amine compound containing a phosphinic acid group or a phosphonic acid group or a salt thereof.
JP-A-29257 discloses a method of containing a polyvalent metal oxide, JP-A-2-255804, JP-A-3-179.
No. 008 proposes a method in which a water-soluble chain transfer agent coexists during polymerization. Also, JP-A-6-30620
No. 2, JP-A-7-53884, JP-A-7-6
No. 2252, Japanese Unexamined Patent Publication No. Hei 7-113048, Japanese Unexamined Patent Publication No. Hei 7-145326, Japanese Unexamined Patent Publication No. 7-145263, Japanese Unexamined Patent Publication No. 7-228788, Japanese Unexamined Patent Publication No. 7-22
The materials and methods described in 8790 can also be used. Specific examples include potassium oxalate titanate, tannic acid, titanium oxide, amine phosphinate (or a salt thereof), amine phosphonate (or a salt thereof), and metal chelate. Of these, especially human urine,
Stabilizers for human blood and menstrual blood may be called human urine stabilizers, human blood stabilizers, and menstrual blood stabilizers, respectively.

An antibacterial agent is used to prevent spoilage due to the absorbed liquid. Examples of antibacterial agents include "New Development of Sterilization and Antibacterial Technology", pp. 17-80 (Toray Research Center (1994)), "Testing and Evaluation Methods and Product Design of Antibacterial and Antifungal Agents", pp. 128-344 (NTT)・ S (19
97)), Japanese Patent No. 2760814,
179114, JP-A-56-31425,
JP-A-57-25813, JP-A-59-1898
No. 54, JP-A-59-105448, JP-A-60-158861, JP-A-61-181532
JP-A-63-135501, JP-A-63-135501
JP-139556, JP-A-63-156540, JP-A-64-5546, JP-A-64-554
7, JP-A-1-153748, JP-A-1-153748
JP-A-221242, JP-A-2-253847,
JP-A-3-59075, JP-A-3-103254
JP, JP-A-3-221141, JP-A-4-14-1
1948, JP-A-4-92664, JP-A-4-138165, JP-A-4-266947, JP-A-5-9344, JP-A-5-68694
JP, JP-A-5-161671, JP-A-5-15-1
79053, JP-A-5-269164, and JP-A-7-165981 can be appropriately selected.

Examples thereof include alkylpyridinium salts, benzalkonium chloride, chlorhexidine gluconate, zinc pyridione, and silver-based inorganic powder. Representative examples of quaternary nitrogen-based antibacterial reagents include methylbenzethonium chloride, benzalkonium chloride, dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide and hexadecyltrimethylammonium bromide. Can be. Heterocyclic quaternary nitrogen-based antibacterial reagents include dodecylpyridinium chloride, tetradecylpyridinium chloride, cetylpyridinium chloride (CPC), tetradecyl-4-ethylpyridinium chloride and tetradecyl-4-chloride.
Methylpyridinium chloride can be mentioned.

Other preferred antibacterial reagents include bis-biguanides. The bis-biguanides are also known as antibacterial reagents. These are, for example, U.S. Pat.Nos. 2,684,924, 2,990,425,
Nos. 2,830,006 and 2,863,019. The most preferred bis-biguanides include 1,
6-bis (4-chlorophenyl) diguanide hexane, which is known as chlorhexidine and its water-soluble salt. Particularly preferred are the hydrochloride, acetate and gluconate salts of chlorohexidine.

[0072] Several other types of antibacterial reagents are also useful. Examples include carbanilides, substituted phenols, metal compounds, and rare earth salts of surfactants. Carbanilide includes 3,4,
4'-trichlorocarbanilide (TCC, triclocarban) and 3- (trifluoromethyl-4,4'-dichlorocarbanilide (IRGASAN). Substituted phenols include 5-chloro-2- (2 , 4-dichlorophenoxy) phenol (IRGASAN DP-300) Metal compounds include salts of graphite and tin such as zinc chloride, zinc sulfide and tin chloride Rare earth salts of surfactants include This is disclosed in European Patent Publication No. 10819. Examples of this type of rare earth salt include a lanthanum salt of a linear C10-18 alkylbenzene sulfonate.

Further, deodorants, deodorants, and fragrances are used to prevent or reduce the unpleasant odor of the absorbed liquid. Deodorants, deodorants, and fragrances are described, for example, in "New Deodorants and Deodorants, Techniques and Prospects", pp. 38-20 (Toray Research Center (1994)), JP-A-59-105448, JP-A-60-1985. No. 158861, JP-A-61-1986
No. 181532, Japanese Patent Application Laid-Open No. 1-153748,
JP-A-1-221242, JP-A-1-26595
No. 6, JP-A-2-41155, JP-A-2-2-2
JP-A-53847, JP-A-3-103254, JP-A-5-269164, JP-A-5-277143
Can be selected as appropriate. Specifically, examples of deodorants and deodorants include iron complexes, tea extract components, and activated carbon. As the fragrance, for example, fragrance-based (citral, cinnamaldehyde, heliotopin, camphor, bornyl acetate) wood vinegar, paradichlorobenzene, surfactant, higher alcohol, terpene-based compound (limonene, pinene, camphor, borneol, eucalyptol, Eugenol).

Further, a foaming agent and a foaming aid can be used in combination for making the water absorbing resin porous and increasing the surface area for improving the water absorbing performance. Examples of the foaming agent and foaming assistant include “rubber / plastic compounding chemicals” (Rubber Digest, 1989, 2).
Pp. 59-267) can be selected as appropriate. For example, sodium bicarbonate, a nitroso compound, an azo compound, sulfonyl hydrazide and the like can be mentioned. These additives are appropriately added in the production process of the water-absorbent resin or the water-absorbent composite according to the purpose and mechanism of action. For example, the foaming agent is suitably added in the process of producing the water-absorbent resin, that is, before or during the polymerization step. Human urine stabilizer, human blood stabilizer,
Antibacterial agents, deodorants, and fragrances can be added in each step of the water-absorbent resin manufacturing process or the water-absorbing composite manufacturing process. Of course, it is also possible to apply it to a fibrous base material in advance.

[0075]

The present invention will be described more specifically below with reference to examples and comparative examples. Materials, reagents, ratios, operations, and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the following specific examples.

(Example 1) 58.3 parts by weight of a 48.5% by weight aqueous solution of sodium hydroxide, 6.4 parts by weight of water, 125% by weight of an aqueous solution of acrylic acid of 80% by weight, a crosslinking agent (N,
N'-methylenebisacrylamide) 0.15 part by weight and an aqueous solution of 30% by weight of hydrogen peroxide 5.0 as an oxidizing agent.
Solution A was prepared by adding parts by weight. Solution A had a monomer concentration of 60% by weight and a degree of neutralization of 50 mol%. Separately, to 125 parts by weight of an 80% by weight aqueous solution of acrylic acid,
57.3 parts by weight of a 48.5% by weight aqueous sodium hydroxide solution, 9.9 parts by weight of water, 0.15 part by weight of a crosslinking agent (N, N'-methylenebisacrylamide) and L as a reducing agent
-Solution B was prepared by adding 1.5 parts by weight of ascorbic acid. The monomer concentration and degree of neutralization of solution B were the same as solution A.

The prepared solution A and solution B were mixed using the nozzle shown in FIG. The inner diameter of the nozzle of FIG.
3 mm, and five nozzles for each solution are arranged at intervals of 1 cm. Solution A and solution B flowing out of the nozzle
Was adjusted to 30 degrees, and the distance between the nozzle tips was adjusted to 4 mm. The solution A and the solution B were heated at a liquid temperature of 40 ° C., respectively, and supplied by a pump so that the flow rate was 5 m / sec.

The solution A and the solution B join at the exit of each of the nozzle pairs, and each of them
After the formation of the liquid column, the liquid drops were dropped in the gas phase (in air, at a temperature of 50 ° C.) while the polymerization proceeded as droplets. Some of the droplets collide with each other in the gas phase to form agglomerated particles, and fall onto a polyester nonwoven fabric substrate (basis weight: 30 g / m ² ) located 3 m below the tip of the nozzle, and The polymerization was completed on the material. At the same time, a part of the liquid droplets fell on the substrate, and after forming aggregated particles on the substrate, polymerization was completed on the substrate. Thus, the water-absorbing polymer was supported on the substrate. The supported polymer was dried until the water content of the polymer became 5% to obtain a water-absorbing composite A having a polymer loading of 200 g / m ² . Optical micrographs of this water-absorbing composite A are shown in FIGS.

(Example 2) Instead of the solution A used in Example 1, 125 parts by weight of an aqueous solution of 80% by weight of acrylic acid was used.
88.5 parts by weight of 48.5% by weight potassium hydroxide, 2.0 parts by weight of water, 0.15 part by weight of a crosslinking agent (N, N'-methylenebisacrylamide) and 30% by weight of peroxide as an oxidizing agent Using a solution prepared by adding 5.0 parts by weight of a hydrogen aqueous solution, 48.5% by weight was added to 125 parts by weight of an aqueous solution of 80% by weight acrylic acid instead of the solution B used in Example 1.
80.4 parts by weight of potassium hydroxide, 5.5 parts by weight of water, and a crosslinking agent (N, N'-methylenebisacrylamide) 0.1
5 parts by weight and 1.5% of L-ascorbic acid as a reducing agent
A water-absorbing complex B was obtained by performing the same operation as in Example 1 except that a solution prepared by adding parts by weight was used.

Example 3 The same operation as in Example 1 was carried out except that the nonwoven fabric substrate made of polypropylene / polyethylene (basis weight: 100 g / m ² ) was used instead of the nonwoven fabric substrate made of polyester used in Example 1. Was performed to obtain a water-absorbing composite C.

(Example 4) The same operation as in Example 1 was carried out except that a rayon nonwoven fabric substrate (basis weight: 50 g / m ² ) was used instead of the polyester nonwoven fabric substrate used in Example 1. Was performed to obtain a water-absorbing composite D.

Example 5 The water-absorbing composite A (water content of polymer: 20%) obtained in Example 1 before drying was 1000 m
After irradiation with ultraviolet rays of J / cm ² , the supported polymer
Was dried until the water content became 5% to obtain a water-absorbing complex E.

Example 6 An absorbent composite F was prepared in the same manner as in Example 1 except that the inner diameters of the nozzles for Solution A and Solution B used in Example 1 were changed to 0.20 mm. Obtained.

Example 7 Instead of the solution A used in Example 1, 100 parts by weight of an 80% by weight aqueous solution of acrylic acid was added to
27.4 parts by weight of maleic anhydride, 68.9 parts by weight of 48.5% by weight sodium hydroxide, 18.0 parts by weight of water, 0.15 of a crosslinking agent (N, N'-methylenebisacrylamide)
Using a solution prepared by adding 5.0 parts by weight of a 30% by weight aqueous hydrogen peroxide solution as an oxidizing agent and 100 parts by weight of an 80% by weight aqueous solution of acrylic acid instead of the solution B used in Example 1 , Maleic anhydride 27.4 parts by weight, 4
8.5% by weight of 68.9 parts by weight of sodium hydroxide, water 2
Example 1 except that a solution prepared by adding 1.5 parts by weight, 0.15 parts by weight of a crosslinking agent (N, N'-methylenebisacrylamide) and 1.5 parts by weight of L-ascorbic acid as a reducing agent was used. By performing the same operation as described above, an absorbent composite G was obtained.

Example 8 A 5% aqueous solution of ethylene glycol diglycidyl ether was sprayed on the water-absorbing complex A obtained in Example 1 with a spray nozzle to impregnate the polymer. The polymer was dried until the water content of the polymer became 5% to obtain a water-absorbing complex H.

Example 9 An absorbent composite I was obtained in the same manner as in Example 1 except that the amount of the polymer was changed to 100 g / m ² .

(Comparative Example 1) Solution A prepared in Example 1 was heated to a liquid temperature of 40 ° C, and supplied by a pump at a flow rate of 5 m / sec using a nozzle having an inner diameter of 0.13 mm. The solution A formed a liquid column from the tip of the nozzle, then dropped as a droplet in the gas phase (in air, at 50 ° C.). The droplets were received on a polyester nonwoven fabric substrate (basis weight: 30 g / m ² ) placed 3 m below the tip of the nozzle, and the solution B prepared in Example 1 was sprayed by the same operation as the solution A. .
The solution A and the solution B reacted on the substrate, and the polymerization proceeded to form a water-absorbing polymer. This was dried until the water content became 5% to obtain a water-absorbing composite J having a polymer loading of 200 g / m ² . FIG. 5 shows an optical micrograph of the water absorbing composite J. The scale in the photograph is 1.5 mm.

(Comparative Example 2) The same operation as in Example 1 was performed except that the polyester nonwoven fabric substrate was placed 20 cm below the tip of the nozzle in Example 1, and polymerization proceeded on the substrate. A water-absorbing composite L without forming aggregated granules was obtained.

Comparative Example 3 The same operation as in Example 1 was carried out except that the polyester nonwoven fabric substrate was placed 5 m below the tip of the nozzle in Example 1, and the polymerization on the substrate was almost completed. Water-absorbent composite M with aggregated granules falling
I got

Comparative Example 4 A water-absorbing complex N was obtained by the method described in Example 1 of JP-A-9-67403. FIG. 6 shows an optical micrograph of the water absorbing composite N. The scale in the photograph is 500 μm.

Comparative Example 5 A water-absorbing composite P was obtained by the method described in Example 1 of JP-A-9-239912.

(Test Examples) Examples 1 to 9 and Comparative Examples 1 to
The respective water-absorbing composites obtained in 5 were measured and tested by the following methods. (1) Ratio of Polymer as Agglomerated Granules After scanning microscopic photographs (SEM photographs) of a plurality of portions of the water-absorbing composite, 100 particles were arbitrarily selected to determine the presence or absence of aggregation. Assuming that the density of agglomerated particles is uniform,
The ratio of the polymer in the form of agglomerated particles was calculated.

(2) Average Particle Size of Agglomerated Particles After taking SEM photographs of a plurality of portions of the water-absorbing composite, 100 particles were arbitrarily selected, the particle diameter was measured, and the average of the measured values was determined. .

(3) Residual unreacted polymerizable monomer concentration 0.5 g of the water-absorbing complex was precisely weighed, and this was
The solution was added to 1 liter of ion-exchanged water in the car, and sufficiently swollen while stirring for about 10 hours. The polymer gel after swelling was filtered off with a 200 mesh sieve, and the filtrate was analyzed by high performance liquid chromatography. Separately, a monomer standard solution having a known concentration was prepared, and a calibration curve was prepared therefrom to determine the absolute concentration.

(4) Loading strength of the water-absorbing polymer on the fibrous base material The water-absorbing composite is 60 mm × 300 mm (thickness: 0.5 to 0.5 mm).
A sheet sample (20 mm) was saturated and absorbed with physiological saline, and then placed on a stone table. A roller having a diameter of 105 mm, a width of 60 mm and a weight of 4 kg was placed on the sample.
When the polymer was reciprocated 5 times at a speed of cm / sec, the weight of the water-absorbing polymer dropped from the sample after drying was weighed and evaluated by the loading A expressed by the following formula. Those having a loading ratio of 60% or more are preferable because they have a practical loading strength.
% Or more is more preferable.

A (%) = [(W0−w) / W0] × 100 where W0 represents the dry weight of the water-absorbing polymer in the sample, and w represents the dry weight of the water-absorbing polymer dropped off.

(5) Absorption capacity of physiological saline About 1.0 g of the water-absorbing complex and about 200 g of 0.9% -concentrated physiological saline were weighed and placed in a 300 ml beaker, and allowed to stand for about 4 hours. The polymer was sufficiently swollen with physiological saline. Next, after draining with a 100-mesh sieve, physiological saline water absorption capacity B was calculated according to the following formula, and the water absorption capacity of the water-absorbing polymer carried was evaluated.

B = (W1-W2) / W3 where W1 is the weight of the water-absorbing composite after water absorption, W2 is the weight of the base material alone after water absorption, and W3 is carried on the water-absorbing composite. Shows the weight of the water-absorbing polymer.

(6) Water absorption rate In a 300 ml beaker, about 1.0 g of the water-absorbing complex and about 200 g of physiological saline having a concentration of 0.9% were weighed, respectively, and left for 5 minutes. Polymer by water
Was swollen. Next, after draining with a 100-mesh sieve, the physiological saline water absorption capacity B was calculated according to the above equation, and this was used as the water absorption rate to evaluate the water absorption rate of the water-absorbing polymer carried.

(7) Polymerization rate when dropped onto a substrate A beaker containing weighed methanol was placed at a position where the substrate was placed so that the liquid level of methanol was positioned, and the reaction mixture was allowed to start polymerization. Droplets were formed in the gas phase, and the aggregated granules during the polymerization dropped into the beaker containing methanol. The amount of the monomer in methanol was measured by liquid chromatography. Further, the polymer in methanol was dried under reduced pressure at 130 ° C. for 3 hours, and then the weight was measured. The polymerization rate was calculated from the respective weights according to the following formula (Mp is the weight of the polymer, Mm is the weight of the monomer).

## EQU3 ## Polymerization ratio = Mp / (Mm + Mp) × 100

(8) Frequency Intensity Ratio Using a scanning electron microscope (S2400 manufactured by Hitachi, Ltd.), a photograph of a magnification of 160 or 300 was obtained for the aggregated granular material. The particle contours of these photographs were faithfully traced on a tracing paper with a mechanical pencil (HB, 0.5 mm diameter), and the obtained trace image was further reduced by half.
The original reduced for image analysis. Next, an image was captured at a resolution of 75 dpi using a scanner (CanoScan 300, manufactured by Canon Inc.). The resolution of the measurement length in the captured image at this time is 2.3 μm (80
Times) or 1.25 μm (150 times). Further, after filling in the inside of the captured outline image (for example, commercially available software Adobe Beeshophop and NIH
image can be used), and converted to a text file.

A figure in which the inside including the contour is filled is defined as a binary figure (0, 1), and the center of gravity (Gx, y) is obtained. If all of the four pixels on the upper, lower, left, and right sides of the target black pixel are “1”, the outline (closed curve of the graphic boundary line) is obtained as a pixel inside the graphic. Next, the black pixels constituting the contour are continuously traced, and m
The coordinate array (Yi, Xi) of the contour line composed of the pieces of data was obtained. The distance from the center of gravity to the pixels forming the contour was determined for all contour coordinate arrays, and then the distance from the center of gravity was normalized. For normalization, the distance from the center of gravity was divided by the average distance, and “1” was subtracted to obtain the normalized distance.

## EQU4 ## Normalized distance = (distance from center of gravity / average distance) -1

Before performing the frequency analysis of the normalized distance, the number of data points differs for each particle.
It was standardized to 12 points. 5 data from m normalized distance data
In order to convert the data into twelve data, interpolation was performed using two points of data sandwiching the desired data. The normalized distances in the 512 data array were subjected to Fourier transform to obtain a power spectrum. The power spectrum was integrated from the low frequency side to the high frequency side to obtain an integrated value of the power spectrum. In order to define the characteristics of the figure, the ratio of the integral value of the frequency 5 (Ipw, 5) to the integral value of the frequency 20 (Ipw, 20) as the integral value of the power spectrum was defined as the frequency intensity ratio. The frequency intensity ratio is large for a figure like an ellipse (a figure with many low frequency components), and a small value for a complicated contour (a figure with many high frequency components).

## EQU00005 ## Frequency intensity ratio = (Ipw, 5) / (Ipw, 20)

(9) Declination by Declination Analysis The deviation (Δi) from the coordinate array (Yi, Xi) of the contour
θ) was determined. The variation of the argument is defined by the following equation.
That is, the declination change (Δθi) of the i-th contour data is n times smaller than the i-th data (Xi, Yi) and the i-th data.
A vector connecting the data (Xi + n, Yi + n) preceding the data and the data (Xi-n,
Yi-n) and the direction of the vector connecting the i-th data (Xi, Yi). If the direction is the same, the angle of change of the argument is 0 degree. The direction of change is not distinguished between right and left.

(Equation 6) In the case of n = 1, the minimum change angle is 45 degrees (π / 4 radian), so that the step width is too large and is easily affected by the digitization error. The change angle average angle of the argument was obtained by the following equation.

(7) Average angle of change of declination = (ΣΔθi−360)
xn) / number of data (m)

Here, the correction term "360xn" in the equation was corrected because the total change in the argument becomes 360 degrees even in the case of a circle. n is the sum of all data, so
As a result, the correction is performed so that the change amount of the deflection angle is summed n times. The variation angle average angle of the declination is a value that defines the complexity of the particle contour, and is a large value for a complex shape having many irregularities in the contour. In these data processing, since the coordinate data is a contour and a closed curve, the coordinate array (X
(1, Y1) and (Xm, Ym) were calculated in consideration of their continuity. Numerical values were randomly selected.
The average of more than one particle was used.

(10) Ratio of Longest Diameter to Shortest Diameter The longest diameter and the shortest diameter of the aggregated granular material were determined from the image processing diagram of the aggregated granular material. Here, the longest diameter and the shortest diameter indicate the longest distance and the shortest distance as the diameter of the aggregated granular material, and the longest diameter and the shortest diameter are not necessarily orthogonal. The ratio between the longest diameter and the shortest diameter was determined by dividing the longest diameter by the shortest diameter. If the ratio of the longest diameter to the shortest diameter is less than 1.2, the shape is not a cohesive granular structure. The following table summarizes these measurement and test results.

[0105]

[Table 1]

[0106]

According to the water-absorbing composite of the present invention, most of the superabsorbent polymer is a moderately agglomerated particle, and is fixed to the fibrous base material with good stability. Moreover, it is excellent in water absorption, high in water absorption speed, and excellent in fixability of the swollen gel after absorbing water. According to the production method of the present invention,
Such a water-absorbing composite exhibiting excellent performance can be easily and inexpensively produced, and is extremely industrially useful because there are few residual monomers.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a nozzle structure used for performing a mixing step in a manufacturing method of the present invention.

FIG. 2 is an optical micrograph of the water-absorbing composite A produced in Example 1.

FIG. 3 is an optical micrograph of the water-absorbing composite A produced in Example 1.

FIG. 4 is an optical micrograph of the water-absorbing composite A produced in Example 1.

FIG. 5 is an optical micrograph of the water-absorbing composite J produced in Comparative Example 1.

FIG. 6 is an optical micrograph of the water-absorbing composite N produced in Comparative Example 4.

[Explanation of symbols]

 1: Nozzle for first liquid 2: Nozzle for second liquid 3: Solution A 4: Solution B

Claims (14)

[Claims] 1. A water-absorbent composite comprising water-absorbent polymer particles fixed to a fibrous base material, wherein at least a part of the water-absorbent polymer particles is composed of primary particles having an average particle diameter of 50 to 1000 μm. 30% by weight or more of the primary particles constitute an aggregated granular material having a shape satisfying the following conditions, wherein the particles are bonded to each other while maintaining substantially the particle shape, and the configuration of the aggregated granular material A water-absorbing composite, wherein some of the particles are not attached to the fibrous base material. Average particle diameter (D) 100 ≦ D ≦ 3000 μm Declination (θ) by declination analysis 10 ≦ θ ≦ 25 5 Hz / 20 Hz intensity ratio of frequency analysis (k) 0.6 ≦ k ≦ 0.9 Ratio of long diameter (L) to shortest diameter (l) 1.2 ≦ L / l ≦ 15.0 2. The water-absorbing composite according to claim 1, wherein 50% by weight or more of the water-absorbing polymer particles constitute the aggregated granules. 3. The water-absorbing composite according to claim 1, wherein 80% by weight or more of the water-absorbing polymer particles constitute the aggregated granules. 4. The water-absorbing material according to claim 1, wherein the fibrous base material comprises one or more selected from synthetic fibers, natural fibers, semi-synthetic fibers, and inorganic fibers. Complex. 5. The agglomerated granule is formed by polymerizing an aqueous solution of an ethylenically unsaturated monomer with a redox polymerization initiator in the form of droplets.
5. The water-absorbing composite according to any one of 4. 6. Droplets of a reaction mixture in which polymerization is initiated by mixing an aqueous solution of a polymerizable monomer to give a water-absorbing polymer and a redox-based polymerization initiator are formed in a gas phase. Or on the fibrous base material, the droplets are bound to each other while maintaining their shapes to form aggregated granules, and after the aggregated granules formed in the gas phase are supported on the fibrous base material, The water-absorbent composite according to any one of claims 1 to 5, which is obtained by completing the polymerization of the aggregated granular material on the fibrous base material and fixing the aggregated granular material to the fibrous base material. 7. Droplets of a reaction mixture in which polymerization is initiated by mixing an aqueous solution of a polymerizable monomer to give a water-absorbing polymer and a redox-based polymerization initiator are formed in a gas phase. Or on the fibrous base material, the droplets are bound to each other while maintaining their shapes to form aggregated granules, and after the aggregated granules formed in the gas phase are supported on the fibrous base material, A method for producing a water-absorbing composite, comprising: completing polymerization of the aggregated granules on a fibrous base material and fixing the aggregated granules to the fibrous base material. 8. The method for producing a water-absorbing composite according to claim 7, wherein the polymerization rate of the polymerizable monomer at the time of contact with the fibrous base material is 20 to 97%. 9. A droplet of the reaction mixture is mixed with an oxidizing agent constituting a redox-based polymerization initiator and a first solution containing an aqueous solution of a polymerizable monomer, a reducing agent constituting a redox-based polymerization initiator, and a polymerizable monomer. The method for producing a water-absorbing composite according to claim 7 or 8, wherein the method is formed by mixing a second liquid containing an aqueous solution in a gas phase. 10. The method for producing a water-absorbent composite according to claim 9, wherein the mixing is a step of colliding and mixing the first liquid and the second liquid in a liquid column state. 11. The method for producing a water-absorbing composite according to claim 7, wherein the polymerizable monomer contains an aliphatic unsaturated carboxylic acid or a salt thereof as a main component. 12. The polymerizable monomer according to claim 7, wherein the polymerizable monomer is mainly composed of acrylic acid in which at least 20 mol% of carboxyl groups are neutralized with an alkali metal salt or an ammonium salt. A method for producing the water-absorbing composite according to the above. 13. The method according to claim 7, wherein the oxidizing agent constituting the redox polymerization initiator is hydrogen peroxide, and the reducing agent is L-ascorbic acid or an alkali metal salt of L-ascorbic acid. 3. The method for producing a water-absorbing composite according to item 2. 14. The water-absorbing material according to claim 7, wherein the fibrous base material is composed of one or more selected from synthetic fibers, natural fibers, semi-synthetic fibers, and inorganic fibers. A method for producing a composite.