JP2000328456A - Continuous production of water absorbent composite - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for continuously and efficiently producing a water absorbent complex having a high water absorbent ability and a high water holding ability. SOLUTION: This method for continuously producing a water absorbent composite comprises a compounding step of dropping an aqueous solution of a polymerizable monomer consisting essentially of an unsaturated carboxylic acid in which >=20% of carboxyl groups are neutralized in the form of droplets while polymerizing the monomer, feeding a fibrous substrate into a dropping point, thereby making resin particles in the course of polymerization stick to the fibrous substrate, completing the polymerization after the sticking and forming a particle-substrate composite and a surface cross-linking step of adding a cross-linking agent having two or more functional groups reactive with carboxyl groups and/or carboxylate groups in the presence of water in an amount of 1-100 pts.wt. based on 100 pts.wt. of the resin particles derived from the polymerizable monomer in the composite and reacting the cross-linking agent therewith.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for continuously producing a water-absorbing composite in which water-absorbing resin particles are bound to a fibrous base material such as a nonwoven fabric. The water-absorbing composite produced by the production method of the present invention is suitable for use in producing a water-absorbing article such as a so-called disposable diaper or sanitary napkin.

[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 articles 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 resin powder on a substrate such as a nonwoven fabric or cotton. However, the water-absorbent resin powder dispersed by a known method is difficult to fix with good stability on the fibrous base material, and often aggregates partially even after being uniformly dispersed, In addition, there is a disadvantage that the swollen gel after water absorption is not fixed on the fibrous base material with good stability and easily moves from the fibrous base material. When the water-absorbent resin powder is adhered to fluff pulp or the like with an adhesive to prevent such movement, the water-absorbent resin powder absorbs water by the adhesive and inhibits swelling. Will be gone.

[0005] Further, in the method of obtaining an absorbent body by uniformly dispersing a water-absorbent resin powder 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 becomes difficult. Due to the complications involved and the problems in the process of efficiently performing the uniform dispersion, the cost had to be extremely high.

As a method for solving these problems, there is provided a method in which droplets composed of a mixed solution obtained by initiating polymerization of an aqueous solution of an acrylic acid-based polymerizable monomer with a redox initiator are supported on a fibrous base material and polymerized. (Japanese Patent Laid-Open No. 9-6)
No. 7403). According to this method, it is possible to produce a water-absorbing composite having excellent water-absorbing properties and a high water-absorbing rate and in which highly water-absorbing polymer particles are stably fixed on a fibrous base material. However, depending on the application of the product, there is a demand for an absorbent material having higher performance than the absorbent composite.

[0007]

SUMMARY OF THE INVENTION Accordingly, the present invention is to provide a method for manufacturing a water-absorbent resin particle, and simultaneously fixing the water-absorbent resin particle to a fibrous base material so that the water-absorbent resin particle can exhibit its original water absorbing performance and water retaining performance. It is an object of the present invention to provide an efficient method for continuously producing a water-absorbing composite comprising: Another object of the present invention is to provide a highly practical water-absorbing article using a water-absorbing composite having such properties.

[0008]

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found the following steps: (A) unsaturated carboxylic acid in which at least 20% of carboxyl groups are neutralized; The polymerizable monomer aqueous solution containing as a main component is dropped while being polymerized in the form of droplets, and the fibrous base material is fed into the drop point, thereby adhering the polymer particles being polymerized to the fibrous base material, and polymerizing after the adhesion. (B) a cross-linking agent having two or more functional groups capable of reacting with a carboxyl group and / or a carboxylate group is added to the composite. Resin particles 1 derived from polymerizable monomers in the body
The present invention has provided a method for continuously producing a water-absorbing composite according to the present invention, which comprises a surface crosslinking step of adding and reacting in the presence of 1 to 100 parts by weight of water per 100 parts by weight.

In the continuous production method of the present invention, a water content adjusting step of adjusting the water content of the resin particles constituting the particle-substrate composite to 10 to 40% by weight can be performed before the surface crosslinking step. After the compounding step, a residual monomer treatment step of treating the polymerizable monomer remaining on the resin particles constituting the particle-substrate composite can be performed. In the continuous production method of the present invention, the water content of the resin particles constituting the particle-substrate composite subjected to the surface crosslinking step is preferably 10 to 40% by weight. Further, particles obtained in the compounding step
At least a part of the resin particles of the substrate composite is agglomerated particles in which the resin particles are bonded to each other, and a part of the resin particles constituting the agglomerated particles are directly attached to the fibrous base material. Preferably not.

[0010] The present invention also provides a water-absorbing composite produced by the above continuous production method. The water-absorbing composite of the present invention has a water absorption amount of, for example, 15 g or more per 1 g of the water-absorbing polymer carried on the water-absorbing composite when physiological saline is absorbed for 10 minutes under a pressure of 40 g / cm ^2. Preferably, there is. Further, the present invention also provides a water-absorbing article characterized by using these water-absorbing composites.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a method for continuously producing a water-absorbing composite, a water-absorbing composite, and a water-absorbing article of the present invention will be described in detail. The method for producing a water-absorbent composite of the present invention includes the above-described composite step and surface cross-linking step. In the complexing step, the polymerization is performed in a gas phase in a state where the aqueous solution of the polymerizable monomer is dispersed in the form of droplets. Such a polymerization method is known, and usually, a polymerization is performed while supplying a polymerizable monomer aqueous solution containing a polymerization initiator to a liquid dispersing device provided at an upper portion of a polymerization chamber, and dropping the droplets in the polymerization chamber as droplets. .

As the polymerizable monomer used in the complexing step, any one can be used as long as it gives a water-absorbing resin. Usually, acrylic acid, methacrylic acid,
Unsaturated carboxylic acids such as maleic acid and itaconic acid are used. If desired, some of these may be used in combination, or other monomers such as (meth) acrylamide and 2-hydroxyethyl (meth) acrylate may be used in combination. Among these, it is preferable to use acrylic acid or methacrylic acid. Acrylic acid is particularly preferred, and it is preferable to use acrylic acid alone or a monomer mixture in which acrylic acid accounts for 50 mol% or more, particularly 80 mol% or more.

Preferably, at least a part of these unsaturated carboxylic acids is used as a water-soluble salt, for example, an alkali metal salt or an ammonium salt, thereby improving the water absorbing ability of the water-absorbing resin obtained. be able to. For example, in the case of acrylic acid, 20% or more, preferably 20 to 90%, is subjected to polymerization as an alkali metal salt or ammonium salt, whereby the water absorbing ability of the resulting water-absorbing resin can be remarkably improved.

In the present invention, a small amount of a crosslinking agent can be contained in the solution of the polymerizable monomer used for the polymerization, if desired. As the crosslinking agent, for example, N, N'-methylenebis (meth) acrylamide, (poly) ethylene glycol diglycidyl ether, or the like can be used.
It is 1% by weight, preferably 0.05 to 0.5% by weight.
If the amount of the crosslinking agent is too large, the water absorption capacity of the resulting resin particles tends to decrease.

The concentration of the polymerizable monomer in the monomer solution is as follows:
The total weight of the free form and the salt form is usually 20% by weight or more, preferably 25% by weight or more. If the monomer concentration is too low, it is difficult to form droplets having an appropriate viscosity, and when the resin particles adhere to the fibrous base material, the shape is likely to collapse, and thus the water-absorbing composite finally obtained. Physical properties are likely to be inferior. The upper limit of the monomer concentration is about 80% by weight from the viewpoint of handleability and the like.

As the polymerization initiator, it is preferable to use a redox polymerization initiator comprising a combination of an oxidizing radical generator and a reducing agent. As the radical generator, it is preferable to use hydrogen peroxide, but persulfates such as ammonium persulfate and potassium persulfate; hydroperoxides such as t-butyl hydroperoxide and cumene hydroperoxide; Cerium salts, permanganates, chlorites, hypochlorites and the like can be used. These radical generators are preferably used in an amount of 0.01 to 10% by weight, particularly 0.1 to 2% by weight, based on the polymerizable monomer.

As the reducing agent, it is preferable to use L-ascorbic acid or an alkali metal salt thereof. In addition, sulfites such as sodium sulfite and sodium hydrogen sulfite, sodium thiosulfate, cobalt acetate, copper sulfate, and sulfate sulfate Iron or the like can also be used. These reducing agents are used in an amount of 0.01 to 10% by weight, especially 0.1 to 10% by weight, based on the polymerizable monomer.
Preferably, it is used so as to be 2% by weight.

The polymerization reaction can be carried out by various known methods. According to the method described in Japanese Patent Application No. 10-330283, an aqueous polymerizable monomer solution containing a radical generator and a polymerizable monomer solution containing a reducing agent are used. A method is used in which a monomer aqueous solution is jetted out from each nozzle installed opposite to the upper part of the polymerization chamber in the form of a liquid column, and the two liquids collide and mix in the air while being dispersed in the form of droplets. Preferred (FIG. 2). For example, a first liquid containing an oxidizing agent and a polymerizable monomer aqueous solution constituting a redox polymerization initiator, and a second liquid containing a reducing agent and a polymerizable monomer aqueous solution constituting a redox polymerization initiator are subjected to a gas phase. The method of mixing in the above can be exemplified as a preferable method. The size of the droplet is 5
3000 μm, particularly preferably 50 to 1000 μm, is preferred. As soon as the two liquids are mixed, polymerization is started, and the liquid drops in the polymerization chamber while the polymerization proceeds in the droplet. The atmosphere in the polymerization chamber is arbitrary as long as it does not hinder the polymerization reaction. Normally, nitrogen, helium, carbon dioxide, or the like is used as the atmospheric gas, but air or water vapor can also be used. The temperature of the atmosphere is usually from room temperature to 150 ° C., preferably from room temperature to 100 ° C.
It is. When sending steam into the atmosphere,
What is necessary is just to set from what point the water evaporation from a monomer aqueous solution will be based on the density | concentration of the monomer aqueous solution used for reaction, the desired water content of the produced resin particles, etc.

In the present invention, the sheet-like fibrous base material is fed into the polymerization chamber, and is moved in parallel with the floor of the polymerization chamber.
It is preferable that resin particles falling during polymerization are adhered thereon. As the fibrous base material, any material may be used as long as it is formed in a certain shape and easily adheres to resin particles during polymerization, and cloth, paper, pulp, nonwoven fabric, and the like can be used. Above all, it is preferable to use fluff pulp or nonwoven fabric in which the fibrous base material is coarsely integrated, the resin particles can easily enter the inside, and the resin particles can strongly adhere to the fibrous base material. Particularly preferred is a nonwoven fabric made of (semi) synthetic fibers such as polyester, polyolefin, polyamide, acetate and the like, which have high strength even in a wet state. The fiber thickness of the fibrous base material constituting the nonwoven fabric is preferably 10 to 50 μm, and the basis weight of the nonwoven fabric is 10 to 100 g / m ² , particularly 20 to 50 g / m ² .
g / m ² .

The polymerization rate at the time when the droplets undergoing polymerization contact in the gas phase or on the substrate to form agglomerated granules is 3 to 9
7%, preferably 20-97%, more preferably 50%
Various conditions are set so as to be ~ 95%. If the polymerization rate is too low, even if the droplets collide with each other, they will not form aggregated granules but will be integrated into large particles, or when the droplets fall onto the substrate, the liquid will fall on the substrate. It becomes impossible to adhere to the substrate in the form of agglomerated granules by spreading or being absorbed or impregnated. On the other hand, if it is too high, the adhesion to the substrate will not be exhibited, and the fixability between the substrate and the water-absorbing polymer will be poor. In the compounding step, the polymerization rate of the polymerizable monomer at the time of contact with the fibrous base material is 20 to 9
Preferably it is 7%.

The resin particles are adhered to the fibrous base material so as to be 50 to 400 g / m ² in the water-absorbing composite finally obtained. Generally 80 to 300 g / m, depending on the application
^It is preferable to adhere so as to be ² . When the content of the resin particles in the water-absorbing composite is small, the water absorbing ability naturally becomes small. Further, if the content is too large, it is generally uneconomical, and the proportion of the portion bonded to the fibrous base material is reduced, and the bonding strength with the fibrous base material is weakened.

In the resin particles constituting the water-absorbing composite produced by the continuous production method of the present invention, at least a part of the resin particles (primary particles) in the course of polymerization are bonded to each other to form an aggregated granular material. Preferably, some of the resin particles (primary particles) constituting the aggregated granular material are not directly bonded to the fibrous base material. Such agglomerated granules have a large specific surface area and therefore have a high water absorption rate, and only a part of the primary particles constituting the agglomerated granules are bonded to the fibrous base material. The restraint received from the base material is small, and the water absorption ability is excellent. In addition, since the bonding surfaces of the primary particles constituting the aggregated particles are integrated, not only before water absorption but also after water absorption, the aggregated particles can be broken down into primary particles and fall off from the fibrous base material. Few. It is preferable that 30% by weight or more of the resin particles are agglomerated particles, more preferably 50% by weight or more, particularly 80% by weight or more. In general, the larger the ratio of the aggregated particles, the better the performance as a water absorbing material. The particle size of the agglomerated particles is substantially 100 to 3000 μm
Is preferably within the range. If the particle size is smaller than 100 μm, the water absorption performance tends not to be sufficiently exhibited. On the other hand, when the particle size is larger than 3000 μm, the adhesive strength to the sheet-like substrate tends to be weak. The ratio and particle size of the aggregated particles can be controlled mainly by appropriately adjusting the density, distribution state, flow state, and the like of the particles during polymerization in the gas phase. For example, in order to increase the ratio of agglomerated particles, the amount of falling resin per unit cross-sectional area of the polymerization chamber may be increased or the polymerization chamber may be increased so that the particles in the course of polymerization may come into contact with each other during the fall. May be generated to reduce the falling speed of the resin particles.
Another method is to generate a drift in the polymerization chamber to cause the distribution of falling resin particles to be offset.

The particle-substrate composite obtained by adhering the resin particles being polymerized to the fibrous substrate obtained as described above is then brought into contact with a hydrophilic organic solvent to remove a part of the water content of the resin particles. It is preferable to remove and subject it to a subsequent moisture content adjustment step of adjusting the moisture content to a level suitable for performing surface crosslinking. In the present invention, a crosslinking agent is added and reacted in the presence of 1 to 100 parts by weight of water per 100 parts by weight of resin particles derived from the polymerizable monomer in the particle-base composite. In particular, the water content of the resin particles when the crosslinking agent is added is preferably 10 to 40% by weight. If the water content is too high or too low, it tends to be difficult to obtain resin particles having excellent water absorption performance. In addition,
The “water content” in the present specification indicates the weight of water contained in the resin particles as a percentage by weight when the weight of the resin particles in a water-containing state is 100% by weight.

The hydrophilic organic solvent used in the water content adjusting step is preferably ethanol, methanol or acetone having a water content of 30% by weight or less, particularly 10% by weight or less. For example, after immersing the particle-substrate composite in a dehydration tank containing such ethanol or methanol, the resin particles are gently passed through a squeezing roll or blown to such an extent that the resin particles are not crushed. It is possible to employ a method for removing ethanol or methanol that has been present. The removal of the alcohol may be performed to such an extent that the subsequent application of the surface crosslinking agent solution is not hindered, and it is not necessary to completely remove the adhering alcohol. The immersion conditions vary depending on the moisture content of the resin particles to be subjected to dehydration and the target moisture content of the resin particles, but usually, immersion may be performed at room temperature for about 30 seconds to 5 minutes. Since the polymerization of the particle-substrate composite taken out of the polymerization chamber is almost completed in the transportation process before being introduced into the dehydration tank, and the temperature is usually at room temperature, it is necessary to introduce the particles into the dehydration tank. There is no need for forced cooling.

In the complexing step, by controlling the concentration of the aqueous monomer solution to be subjected to the polymerization reaction, the temperature and humidity of the atmosphere in the polymerization chamber, and the like, the particles taken out of the polymerization chamber are controlled.
The water content of the resin particles of the substrate composite is adjusted to a value suitable for surface crosslinking.
It is also possible to set the water content to 0 to 40% by weight, and according to this method, the above-mentioned step of adjusting the water content is unnecessary.

The particle-substrate composite in which the water content of the resin particles has been reduced to a desired value in the water content adjusting step is then sent to a surface crosslinking step. It is known that the properties of the resin particles are improved by applying a crosslinking agent to the surface of the water-absorbent resin particles and then heating and cross-linking the surface to form a crosslinked structure selectively on the surface. It is believed that the shape can be maintained without inhibiting swelling upon swelling. In this step, first, a solution of the surface crosslinking agent is applied to the resin particles of the particle-substrate composite. N, N'-methylenebis (meth) acrylamide as a surface crosslinking agent,
A polyfunctional compound copolymerizable with a polymerizable monomer such as (poly) ethylene glycol bis (meth) acrylate,
A compound having a plurality of functional groups capable of reacting with a carboxylic acid group such as (poly) ethylene glycol diglycidyl ether is used. Preferred are crosslinking agents having a glycidyl group, and it is particularly preferred to use polyglycidyl ether. These surface cross-linking agents are usually used in an amount of 0.1 to 1% by weight, preferably 0.2 to 1% by weight, based on the resin particles (dry basis).
It is used to be 0.5% by weight. In addition, these surface cross-linking agents are water or alcohol (such as ethanol and methanol) so as to be uniformly applied to the entire surface of the resin particles.
And then used as an alcohol solution of 0.1 to 1% by weight, particularly 0.2 to 0.5% by weight. The application of the cross-linking agent solution is usually performed by spraying the cross-linking agent solution onto the resin particles using a sprayer, or by moving the particle-substrate composite so that the resin particle adhesion surface is on the lower surface, and It is preferable to carry out the method by applying a cross-linking agent solution with a roll brush whose lower part is immersed in a tank containing the cross-linking agent solution. After excessively applying the crosslinking agent solution, the excess crosslinking agent solution may be removed by squeezing the resin particles lightly with a squeezing roll to the extent that the resin particles are not crushed or blowing air. The application of the crosslinking agent solution may be performed at room temperature. The particle-substrate composite to which the crosslinking agent solution has been applied is then heated to cause a crosslinking reaction to proceed to selectively form a crosslinked structure on the surface of the resin particles. 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 performance of the water-absorbing composite produced by the continuous production method of the present invention is substantially determined up to the surface crosslinking step.

The particle-substrate composite that has undergone the surface crosslinking step is preferably sent to a residual monomer treatment step. Particles
Although unreacted polymerizable monomers remain in the resin particles of the substrate composite, these polymerizable monomers are harmful to the human body. To be reduced to

For example, when partially neutralized acrylic acid is used as a polymerizable monomer, generally, several hundred ppm, and in many cases, 1000 ppm or more of the monomer remains, but it is used for disposable diapers and sanitary napkins. When providing, generally, the residual amount is preferably 500 ppm or less, and the residual amount is 300 ppm or less, particularly 100 p
Most preferably, it is reduced to below pm.

The treatment of the polymerizable monomer can be performed in several ways. As one of the methods, there is a method in which the treatment is performed by advancing the polymerization of the residual monomer. For example, a method of heat-treating the particle-substrate composite at a temperature of 100 to 250 ° C. to polymerize the remaining monomer, a method of imparting a catalyst or a catalyst component for accelerating the polymerization of the polymerizable monomer to resin particles, and then heating the polymer to obtain a polymerizable polymer There is a method of polymerizing a monomer. For example, when polymerization is carried out using the above-described redox-based polymerization initiator, a radical generator is often left, so that a reducing agent solution may be applied to the resin particles. As a reducing agent, sodium sulfite, sodium hydrogen sulfite, L-ascorbic acid or the like used as a redox polymerization initiator may be used, and these are usually used in an amount of 0.5 to
A 5% by weight aqueous solution is applied to the resin particles. The amount of the reducing agent applied may be 0.1 to 20 parts by weight per 100 parts by weight of 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 resin particles provided with the reducing agent are then heated to polymerize the polymerizable monomer. Heating is for example 10
It may be performed at 0 to 150 ° C. for about 10 to 30 minutes. Although the water content of the resin particles is reduced by this heating, when the water content is still high, the resin particles can be further dried by a dryer to form a water-absorbing composite of the product. Further, after adding 0.01 to 1 part by weight of a peroxide and / or an azo compound per 100 parts by weight of the resin particles in the particle-substrate composite, heating can be performed to reduce the amount of the residual monomer.

Further, as a method of promoting the polymerization of the residual monomer, there is a method of irradiating ultraviolet rays or radiation.
In the method of irradiating the ultraviolet rays, a normal ultraviolet lamp may be used, and the irradiation intensity, the irradiation time, and the like are determined depending on the type of the fibrous substrate used, the amount of the polymerizable monomer impregnated, and the like. Generally, the irradiation intensity of an ultraviolet lamp is 10 to 200 W / c.
m, preferably 30 to 120 W / cm, the irradiation time is 0.1 second to 30 minutes, and the distance between the lamp and the complex is 2
３０30 cm. 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 a method of irradiating for a fixed time in a stationary state, a method of continuously irradiating with a belt conveyor, or the like can be used.

The amount of water in the composite at this time is generally 0.01 to 40 parts by weight per 1 part by weight of the polymer.
Preferably, it is 0.1 to 1.0 part by weight. A water content of less than 0.01 part by weight or more than 40 parts by weight tends to affect the reduction of the unpolymerized monomer. This water content can be realized by controlling the water content in the complexing step and / or the surface crosslinking step, or by adjusting the water content after the surface crosslinking step.

In the method of irradiating radiation, high energy radiation such as electromagnetic radiation or particulate ionizing radiation is used. Specifically, accelerated electrons and gamma rays can be exemplified. The dose to be irradiated varies depending on the amount of unpolymerized monomer in the composite, the amount of water and the like, but is generally 0.01 to 100 Mrad, preferably 0.1 to 50 Mrad. When the dose exceeds 100 megarads, the water absorption becomes extremely small. When the dose is less than 0.01 megarads, the water absorption capacity and water absorption rate aimed at in the present invention are large, and it is difficult to obtain an unpolymerized monomer having a particularly small amount.

The amount of water in the composite at this time is generally 40 parts by weight or less, preferably 10 parts by weight or less based on 1 part by weight of the fibrous substrate. 40
If the amount of water exceeds the weight part, the effect of improving the water absorption rate is small, and it is not preferable because the effect on the reduction of the unpolymerized monomer is particularly remarkable.

The atmosphere for irradiating the composite with high-energy radiation in the present invention may be under vacuum, in the presence of an inorganic gas such as nitrogen, argon or helium, or in air. The preferred atmosphere is air, and irradiation in the air results in a large water absorption capacity and a high water absorption rate and a particularly small amount of unpolymerized monomer. The irradiation temperature is not particularly limited, and the object can be sufficiently achieved at room temperature.

Another method for treating unreacted polymerizable monomers is to remove residual monomers. For example, the particle-substrate composite taken out from the surface crosslinking step,
After cooling, there is a method of immersing in a water-containing organic solvent to extract a polymerizable monomer. Ethanol, methanol and acetone can be used as the water-containing organic solvent, and the water content thereof is preferably 10 to 90% by weight, particularly preferably 30 to 60% by weight. Generally, the higher the water content, the higher the ability to remove the polymerizable monomer. However, when a water-containing organic solvent having a high water content is used, the energy consumption in the subsequent drying step increases. The time for immersing the particle-substrate complex in the water-containing organic solvent is usually sufficient for about 5 to 30 minutes, and a means for promoting the extraction of the polymerizable monomer, such as rocking the particle-substrate complex, is employed. Is also preferred. After the immersion treatment, the mixture is treated with a dryer and dried to obtain a water-absorbing composite of the product. Usually, drying may be performed so that the water content of the resin particles is about 10%.

Still another method for removing the polymerizable monomer is to treat the particle-substrate composite with superheated steam or a steam-containing gas. For example, the polymerizable monomer in the resin particles can be reduced by heating a saturated steam at 110 ° C. to 120 to 150 ° C. and contacting the steam as superheated steam with the particle-substrate composite. In this method, it is considered that when water in the resin particles evaporates as water vapor, the polymerizable monomer also vaporizes and escapes from the resin particles. According to this method, both the removal of the polymerizable monomer and the drying of the product can be performed.

In the present invention, the above-described complexing step and surface cross-linking step are essential steps, and the water content adjustment step and the residual monomer treatment step are performed as preferred steps. The order can be performed in any order after the composite process is performed for the first time. A preferred order of the steps is a step of sequentially performing a compounding step, a surface cross-linking step, and a residual monomer processing step, a step of sequentially performing a compounding step, a residual monomer processing step, and a surface cross-linking step, a compounding step, a residual monomer processing step, and a water content. Steps of sequentially performing an adjusting step and a surface cross-linking step, steps of sequentially performing a compounding step, a water content adjusting step, a surface cross-linking step, and a residual monomer processing step, a step of forming a compounding step, a water content adjusting step, a residual monomer processing step, and a surface cross-linking step. Are sequentially performed.

One example of a method for producing a water-absorbent composite according to the continuous production method of the present invention will be described with reference to FIG. 1. A polyester nonwoven fabric (2) having a basis weight of 35 g / m ² wound on a roll (1) is wound. While returning, it is fed into the polymerization chamber (3) at a rate of 30 m / min. Parallel to the floor surface. A pair of two nozzles facing each other, in which a nozzle for ejecting an aqueous solution of polymerizable monomer A containing a reducing agent and a nozzle for ejecting an aqueous solution of polymerizable monomer B containing an oxidizing agent are downwardly opposed to an upper portion of the polymerization chamber. Are provided at 1 cm intervals. The conditions are as follows: the inner diameter of the nozzle is 0.18 mm, the opposing angle of the nozzle is 30 degrees, the opposing interval between the nozzles is 3.5 mm, and the height from the nonwoven fabric surface to the end of the nozzle opening is 3 m.

The following polymerizable monomer aqueous solutions are supplied to the nozzles at room temperature, and are ejected from each nozzle at 5.0 m / sec. The atmosphere in the polymerization chamber is at a temperature of about
Air containing water vapor is supplied from the lower portion so that the humidity is about 30 to 100%, and the air is exhausted from the upper portion. The exhaust gas is introduced into an exhaust gas treatment device. Polymerizable monomer aqueous solution A: A 50% by weight aqueous solution of acrylic acid and sodium acrylate (acrylic acid: sodium acrylate = 4: 6 (molar ratio)) was prepared by adding hydrogen peroxide to the total of acrylic acid and sodium acrylate. Aqueous solution containing 2.8% by weight. Polymerizable monomer aqueous solution B: a 50% by weight aqueous solution of acrylic acid and sodium acrylate (acrylic acid: sodium acrylate = 4: 6 (molar ratio)) and sodium L-ascorbate in total of acrylic acid and sodium acrylate An aqueous solution containing 1.1% by weight of the aqueous solution.

The polymerizable monomer aqueous solutions A and B ejected from the nozzle collide with each other to form droplets, fall onto the nonwoven fabric while polymerizing, and adhere to the nonwoven fabric as resin particles having a polymerization rate of about 95% or more. . The adhesion amount of the resin particles is about 200 g / m ² on a dry resin basis. The size of the resin particles is about 200 ~
1500 μm, and about 90% of the resin particles are agglomerated particles.

The nonwoven fabric to which the resin particles have adhered is sent to the dewatering tank (4). 96% ethanol is stored in the dehydration tank, and the nonwoven fabric is retained in the ethanol for 5 minutes and dehydrated so that the water content becomes about 20% on the basis of the water-containing resin. A part of the ethanol in the dehydration tank is continuously extracted and dehydrated and distilled in the distillation column (5) so as to maintain a constant water content, and then circulated to the dehydration tank.

The non-woven fabric to which the resin particles taken out from the dewatering tank adhere is removed from the non-woven fabric by blowing air through the air, and then sent to the surface cross-linking device (6). Here, first, a 0.5% by weight ethanol solution of ethylene glycol diglycidyl ether is sprayed on the resin particles so as to give 0.35% by weight of ethylene glycol diglycidyl ether on a dry resin basis to the resin particles. Then, it is heated to about 110 ° C. for 30 minutes to crosslink the surface.

The non-woven fabric drawn from the surface cross-linking device is cooled by blowing air, and then sent to an unreacted polymerizable monomer extraction tank (7). The extraction tank (7) contains 50% by weight aqueous ethanol at room temperature, and the nonwoven fabric is kept in the aqueous ethanol for 20 minutes. Thereby, the content of the polymerizable monomer in the resin particles is about 80 p on a dry resin basis.
pm. The non-woven fabric taken out of the extraction tank is brought into contact with a drying drum (8) into which steam is fed, and the ethanol and water are removed by evaporation. The water-absorbing composite thus produced is wound up by a winder (9) and shipped as a product. A part of the water-containing ethanol in the extraction tank (7) is continuously withdrawn so that the monomer does not accumulate, and fresh water-containing ethanol is supplied.

The water-absorbing composite produced by the continuous production method of the present invention shows high water absorption. The water absorption of the water-absorbing composite is a multifaceted property, and is evaluated by various evaluation methods according to the purpose of use of the water-absorbing composite. Specifically, water, physiological saline, artificial urine, or the like is used as the liquid to be absorbed, and the water absorption capacity (the amount of liquid that can be absorbed over a certain period of time is defined as the weight per unit weight of the water-absorbing polymer. ), Water retention capacity (the amount of liquid retained after dehydrating the water-absorbing composite that once absorbed the liquid under certain conditions is expressed as the weight per unit weight of the water-absorbing polymer), under normal pressure Water absorption rate (The amount of liquid that can be absorbed during the short-term specified time is expressed as the weight per unit weight of the water-absorbing polymer), Water absorption rate under pressure (Short-term specified time under constant pressure The amount of liquid that can be absorbed during the reaction can be evaluated by measuring the amount of the liquid, expressed as the weight per unit weight of the water-absorbing polymer).

According to the continuous production method of the present invention, for example,
The present invention provides a water-absorbing complex that exhibits the following water-absorbing properties when the water-absorbing rate under pressure with physiological saline is measured using an apparatus according to JIS K-7224. Specifically, 40
g / amount of water absorption when allowed to absorb water for 10 minutes saline under pressure of cm ² is absorbent composite is supported water-absorbing polymer per 1g 15g above the water-absorbing composite, 40 g / cm ² The water-absorbing complex has a water absorption amount of 18 g or more per 1 g of the water-absorbing polymer supported on the water-absorbing composite when the physiological saline is absorbed for 20 minutes under the pressure of 40 g / cm ² . A water-absorbing complex having a water absorption of 22 g or more per gram of the water-absorbing polymer supported on the water-absorbing composite when the physiological saline is absorbed for 60 minutes, and 10 g under a pressure of 60 g / cm ^2.
Water-absorbing complex having a water absorption of 13 g or more per gram of the water-absorbing polymer supported on the water-absorbing composite for 20 minutes under a pressurized pressure of 60 g / cm ² for 20 minutes. Of the water-absorbing polymer supported by the water-absorbing composite is 1%.
5 g or more of the water-absorbing composite, the amount of water absorbed when physiological saline is absorbed for 60 minutes under a pressure of 60 g / cm ² is 19 g or more per 1 g of the water-absorbing polymer supported on the water-absorbing composite. A water-absorbing composite is preferably provided.

In particular, under pressure of 40 g / cm ² ,
The amount of water absorbed when physiological saline was absorbed for 0 minutes, and 60 g
Water-absorbing composite having a sum of water absorption of 28 g or more per 1 g of the water-absorbing polymer supported on the water-absorbing composite, when the physiological saline is absorbed for 10 minutes under a pressure of / cm ² , 40 g / and water absorption amount when allowed to absorb water for 20 minutes saline under pressure of cm ^2, the sum of the water absorption amount when allowed to absorb water for 20 minutes saline under pressure of 60 g / cm ^2, water-absorbing 40 g of a water-absorbing composite that is 33 g or more per 1 g of a water-absorbing polymer supported on the composite
/ A water absorption amount when the pressure of cm ² to water for 60 minutes saline, the sum of the water absorption amount when allowed to absorb water for 60 minutes saline under pressure of 60 g / cm ^2, water-absorbent The water-absorbing composite is preferably provided in an amount of 40 g or more per 1 g of the water-absorbing polymer supported on the water-soluble composite. These water-absorbing composites can be appropriately selected and used according to the purpose of use.

These water-absorbing composites can be used in various applications in which water-absorbing resins have been used. "Water-absorbing polymer", pp. 81-111 (Tatsuyoshi Masuda, Kyoritsu Shuppan, 1987), "Development trend of superabsorbent resin and its application development" (Eizo Omori, Techno Forum, 198)
7), Kenji Tanaka, "Industrial Materials", Vol. 42, No. 4, 18-25.
Pages, 1994, Nobuyuki Harada, Tadao Shimomura, pp. 26-30 describe various uses of water-absorbent resins, which 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.

[0049]

The present invention will be described more specifically below with reference to examples, comparative examples and test examples. Materials, usage amounts, ratios, processing contents, processing procedures, 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 specific examples described below.

Example 1 125 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 solution of sodium hydroxide, 6.4 parts by weight of water, and 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 parts 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 the degree of neutralization of the solution B were the same as those of the solution A.

In the structure shown in FIG.
Solutions A and B flowing out of the nozzles in pairs
The nozzle A has a crossing angle of 30 degrees and the distance between the nozzle tips is adjusted to 4 mm. The two liquid nozzles are arranged in five pairs at 1 cm intervals. Were heated to a liquid temperature of 40 ° C., respectively, and supplied at a flow rate of 5 m / sec by a pump. The liquid A and the liquid B join at the point where they are discharged in the form of a liquid column from the nozzles of each pair of nozzles. After forming a liquid column of about 10 mm each, they form droplets and undergo polymerization in the gas phase (in air). At a temperature of 50 ° C.), and some of the droplets collide in the gas phase to form agglomerated particles, which are located below the tip of the nozzle.
m of polyester non-woven fabric substrate (basis weight: 30
g / m ² ) to complete the polymerization on the substrate.
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. Through such a complexing step, the water-absorbing polymer was supported on the substrate. The water content of the water-absorbing polymer supported on the substrate was 20% by weight.

Further, an ethanol solution of 0.5% by weight of ethylene glycol diglycidyl ether (EGDGE) was sprayed on the composite so that the weight of the polymer carrying EGDGE (based on the dry polymer) was 3000 ppm by weight. The complex to which the ethanol solution of EGDGE has been applied is further dried by a hot air dryer at 110 ° C. until the moisture content of the supported polymer becomes 5%, and the water-absorbing complex applied with 200 g / m ² as the supported polymer amount. I got

Example 2 The same procedure as in Example 1 was performed up to the complexing step to obtain a substrate (composite) supporting a water-absorbing polymer having a water content of 20% by weight. The complex contains 0.5% by weight ethylene glycol diglycidyl ether (EGD).
The ethanol solution of GE) was added to the EGDGE-supported polymer (dry polymer base) at 3000 weight pp.
m. The composite to which the ethanol solution of EGDGE was applied was further vertically blown with steam having a temperature of 130 ° C. and a dew point of 120 ° C. on a substrate by a ventilation band type drier equipped with a steam supply device. The contact time between the steam and the substrate was 2 minutes, and the linear velocity was 0.5 m / sec. Thus, a water-absorbing composite was obtained. The polymer supported on the obtained composite had a water content of 5%, and a water-absorbing composite having a polymer loading of 200 g / m ² was obtained.

(Example 3) 125 parts by weight of an aqueous solution of 80% by weight of acrylic acid, 57.3 parts by weight of a 48.5% by weight aqueous solution of sodium hydroxide, 68.8 parts by weight of water, and a crosslinking agent (N, N ') Solution A was prepared by adding 0.15 parts by weight of (methylenebisacrylamide) and 5.0 parts by weight of a 30% by weight aqueous hydrogen peroxide solution as an oxidizing agent. Solution A had a monomer concentration of 45% by weight and a degree of neutralization of 50 mol%.
Separately, 125 parts by weight of an aqueous solution of 80% by weight of acrylic acid and an aqueous solution of 48.5% by weight of sodium hydroxide
3 parts by weight, 72.5 parts by weight of water, 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 were added to the solution B.
Was prepared. The monomer concentration and the degree of neutralization of the solution B were the same as those of the solution A.

In the structure shown in FIG.
Solutions A and B flowing out of the nozzles in pairs
The nozzle A has a crossing angle of 30 degrees and the distance between the nozzle tips is adjusted to 4 mm. The two liquid nozzles are arranged in five pairs at 1 cm intervals. Were heated to a liquid temperature of 50 ° C., respectively, and supplied by a pump so as to have a flow rate of 5 m / sec. The liquids A and B join at the exit of each pair of nozzles, form a liquid column of about 10 mm each, and then form droplets in the gas phase (in air, at a temperature of 50
° C), and a part of the liquid droplets collide in the gas phase to form agglomerated granules, and is placed on a polyester nonwoven fabric substrate (basis weight: 30 g / m ² ) installed 3 m below the tip of the nozzle. It fell and completed the polymerization on the substrate. At the same time, a part of the droplets fall on the base material, and after forming aggregated granules on the base material,
The polymerization was completed on the substrate. Through such a complexing step, the water-absorbing polymer was supported on the substrate. The water content of the water-absorbing polymer supported on the substrate was 45% by weight.

Subsequently, potassium persulfate (KP
A 1% by weight aqueous solution of S) was weighed at 2000 wt.
pm. Thereafter, the complex is heated to 110 ° C.
Water content of polymer supported by hot air dryer is 20%
Dry until dry. 0.5% by weight of the composite
Ethylene glycol diglycidyl ether (EGDG
E) Ethanol solution is 3000 ppm by weight based on the polymer carrying EGDGE (dry polymer base)
Sprayed so that The complex to which the ethanol solution of EGDGE has been applied is further dried by a hot air dryer at 110 ° C. until the moisture content of the supported polymer becomes 5%, and the water-absorbing complex applied with 200 g / m ² as the supported polymer amount. I got

Example 4 A 0.5% by weight aqueous solution of sodium bisulfite (NaHSO ₃ ) was loaded on a substrate (composite) on which a water-absorbing polymer having a water content of 45% by weight was loaded. A water-absorbing composite was obtained in the same manner as in Example 3, except that the sprayed amount was 1000 ppm by weight (dry polymer base) with respect to the polymer obtained.

Example 5 The same procedure as in Example 1 was carried out up to the complexing step to obtain a substrate (composite) supporting a water-absorbing polymer having a water content of 20% by weight. 1000 m for the complex
After irradiating with ultraviolet rays of J / cm ² , an ethanol solution of 0.5% by weight of ethylene glycol diglycidyl ether (EGDGE) was sprayed onto the EGDGE-supported polymer (dry polymer base) so as to have a concentration of 3000 ppm by weight. . The composite to which the ethanol solution of EGDGE was applied was further dried by a 110 ° C. hot air dryer until the water content of the supported polymer became 5%, and the water-absorbing composite to which 200 g / m ² was applied as the supported polymer amount was applied. I got a body.

Example 6 The same procedure as in Example 1 was performed up to the composite step to obtain a substrate (composite) supporting a water-absorbing polymer having a water content of 20% by weight. An electron beam device equipped with a Dynamitron accelerator on the complex
Irradiation with an electron beam at a dose of 0 megarad gave a water-absorbing composite. Subsequently, an ethanol solution of 0.5% by weight ethylene glycol diglycidyl ether (EGDGE) was added to E
GDGE was sprayed to the polymer on which it was carried (dry polymer base) so as to be 3000 ppm by weight. EGD
The complex to which the ethanol solution of GE was applied was further heated to 110 ° C.
5% moisture content of the polymer supported by the hot air dryer
And dried to a polymer loading of 200 g / m
² was obtained.

Example 7 The same procedure as in Example 3 was carried out up to the composite step to obtain a substrate (composite) on which a water-absorbing polymer having a water content of 45% by weight was supported. The composite was added to 1 part by weight of the supported polymer (dry polymer base),
It was immersed in 0 parts by weight of a 30% by weight aqueous ethanol solution and left at room temperature for 30 minutes. Thereafter, the complex was taken out from the aqueous ethanol solution, immersed in 10 parts by weight of ethanol, and left at room temperature for 30 minutes. The complex removed from ethanol was further sprayed with an ethanol solution of 0.5% by weight of ethylene glycol diglycidyl ether (EGDGE) to the polymer carrying EGDGE (dry polymer basis) so as to have a concentration of 3000 ppm by weight. The complex to which the EGDGE ethanol solution was applied was further dried by a 110 ° C. hot air dryer until the supported polymer had a water content of 5%, and the polymer loading was 2%.
A water-absorbing composite applied with 00 g / m ² was obtained.

Example 8 A solution A and a B solution were prepared in the same manner as in Example 1. 0.13 inner diameter of the structure shown in FIG.
mm using two nozzles, the angle between the nozzles is 30 degrees,
The distance between the tips of the nozzles is set to 4 mm. The liquid A is heated from one nozzle and the liquid B is heated from the other nozzle to a liquid temperature of 40 ° C., and is supplied by a pump so as to have a flow rate of 5 m / sec. did. The liquids A and B merged when they came out of the nozzle, formed a liquid column of about 10 mm, and then fell as droplets in a rising air current of air (60 ° C.). The droplet was dropped on a polyester nonwoven fabric substrate (basis weight: 30 g / m ² ) placed 100 cm below the tip of the nozzle, and polymerization was completed on the substrate.

The water content of the water-absorbing polymer supported on the substrate was 30% by weight. Further, the complex contains 0.5% by weight of ethylene glycol diglycidyl ether (EGDG).
E) The ethanol solution of EGDGE was applied to the polymer carrying EGDGE (dry polymer base) at 3000 weight pp
m. The complex to which the EGDGE ethanol solution was applied was further dried until the water content of the water-absorbing polymer supported on the hot air dryer at 110 ° C. became 5%, and the water-absorbing property was applied at 200 g / cm ² as the polymer supported amount. The complex was obtained.

Example 9 The same procedure as in Example 3 was performed up to the composite step to obtain a substrate (composite) supporting a water-absorbing polymer having a water content of 45% by weight. The complex contains 0.5
Wt% ethylene glycol diglycidyl ether (EG
DGE) ethanol solution to the EGDGE-supported polymer (dry polymer basis)
pm. The composite to which the ethanol solution of EGDGE was applied was further dried by a 110 ° C. hot air dryer until the water content of the supported polymer became 5%, and the water-absorbing composite to which 200 g / m ² was applied as the supported polymer amount was applied. I got a body.

Example 10 The same procedure as in Example 1 was carried out up to the composite step to obtain a substrate (composite) on which a water-absorbing polymer having a water content of 25% by weight was supported. The complex is treated with 110
℃ hot air dryer, the moisture content of the supported polymer is 5
%, And the polymer loading amount is 200 g /
m ² was obtained. Further, an ethanol solution of 0.5% by weight of ethylene glycol diglycidyl ether (EGDGE) was added to the obtained complex by EGDG.
E was sprayed to the supported polymer (dry polymer base) so that the concentration became 3000 ppm by weight. A water-absorbing composite having a polymer loading of 200 g / m ² was obtained.

(Comparative Example 1) The same procedure as in Example 1 was carried out up to the complexing step to obtain a substrate (composite) supporting a water-absorbing polymer having a water content of 20% by weight. The supported polymer was dried until the water content of the polymer became 5% to obtain a water-absorbing composite having a polymer loading of 200 g / m ² .

Comparative Example 2 13.1 g of sodium hydroxide (purity: 96% by weight) was placed in a 100 ml conical flask.
Was dissolved in pure water (39.0 g) under ice-cooling. To this, 30 g of acrylic acid was gradually added to neutralize. About 7 neutralization
5% and the monomer concentration in the aqueous solution was about 45% by weight. 0.05 g of potassium persulfate was taken as a radical polymerization initiator, dissolved in the above monomer aqueous solution, and degassed with N ₂ .

Separately, a polyester nonwoven fabric (basis weight: 30 g)
/ M ² ) was taken, and the above monomer aqueous solution was applied to the whole surface of the nonwoven fabric by a roll coater to give a linear pattern along the fibers. The amount of the impregnated monomer was 6.8 times the weight of the nonwoven fabric. This was put into a constant temperature reaction tank which had been degassed with N ₂ to 90 ° C. in advance. Polymerization immediately occurred, and a composite was obtained in which the superabsorbent polymer composed of the self-crosslinked product of the partially neutralized sodium polyacrylate was stably fixed to the polyester nonwoven fabric in a linear pattern along the fibers.

Next, the water content of this complex was set to about 25% by weight (based on the weight of the superabsorbent polymer, the same applies hereinafter), and 0.012 g of ethylene glycol diglycidyl ether (3,000 ppm of dry polymer) was added to the composite.
Spray as a 5 wt% ethanol solution, then 110 ° C
Using a hot air dryer, the water content of the supported polymer was 5
%, And the polymer loading amount is 200 g /
m ² was obtained.

(Test Example) Examples 1 to 10 and Comparative Example 1
The following measurements and tests were performed on each of the water-absorbing composites obtained in Nos. 1 to 2. (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 Diameter of Agglomerated Particles After taking SEM photographs of a plurality of locations 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) Polymerization rate when dropped onto a substrate A beaker containing methanol weighed so that the liquid level of methanol is positioned at the position where the substrate is placed is placed, and the reaction mixture obtained by initiating polymerization is placed in a beaker. 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 by the following formula (Mp is the weight of the polymer, Mm was the weight of the monomer, unit: g).

(Equation 1)

(4) Absorption capacity of physiological saline About 1.0 g of a 300 ml beaker water-absorbing complex and about 200 g of 0.9% physiological saline were weighed and put, respectively, and left to stand for about 4 hours. The polymer was sufficiently swollen with saline. Next, after draining with a 100-mesh sieve, the physiological saline absorption capacity was calculated according to the following equation. All weight units in the formula are g.

(Equation 2)

(5) Water holding capacity of physiological saline The composite was cut so that the weight W ₁ of the water-absorbing polymer supported on the composite became ₁ g, and the cut composite was placed in a 250-mesh nylon bag (20 cm × 10 cm). Was immersed in 500 ml of physiological saline (concentration: 0.9% by weight) for 30 minutes. Next, the nylon bag was pulled up, suspended for 15 minutes, drained, and then dehydrated at 90 G for 90 seconds using a centrifuge. The weight W ₂ of the nylon bag after the dehydration was measured. In addition, the nonwoven fabric not carrying the water-absorbing polymer was cut into the same size as the raw composite, and the same operation was performed to obtain the weight W ₃
Was measured. The water retention capacity of the physiological saline was calculated according to the following equation. Here, the units of W _{1 to} W ₃ are all g.

(Equation 3)

(6) Absorbing speed under normal pressure About 1.0 g of the water-absorbing complex and about 200 g of 0.9% concentration physiological saline were weighed and placed in a 300 ml beaker, and then left standing for 5 minutes. The polymer was swollen with saline. Next, after draining with a 100-mesh sieve, the physiological saline water absorption capacity was calculated according to the above equation, and this was defined as the water absorption rate.

(7) Water absorption rate under pressure According to JIS K-7224, the water absorption rate under physiological saline was measured using the apparatus shown in FIG. The composite, previously cut to 10 cm x 10 cm, is laid on a support plate with small holes, so that the water-absorbing polymer carried on the nonwoven fabric is placed on top, and further laid under the support plate on the same nonwoven fabric. On top. Further, a predetermined weight is placed thereon, and a predetermined pressure (40 g / cm ² or 60 g / c
m ² ) was applied to the conjugate. The lower surface of the complex was brought into contact with 0.9% physiological saline, and the amount of the complex absorbing physiological saline was measured. The water absorption rate under pressure was defined as the amount of 0.9% physiological saline absorbed at 10 minutes, 20 minutes and 60 minutes after the start.

(8) Residual unreacted polymerizable monomer concentration (residual monomer concentration) 0.5 g of the water-absorbing complex was precisely weighed, and added to 1 liter of ion-exchanged water in a 2 liter beaker. The mixture was sufficiently swollen under stirring for 10 hours. After swelling the polymer gel to 20
The mixture was filtered through a 0-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. The test results are shown in the table below.

[0077]

[Table 1]

Each of the water-absorbing composites of Examples 1 to 10 produced by the continuous production method of the present invention has satisfactory water absorption capacity of physiological saline, water retention capacity, water absorption rate under normal pressure, water absorption rate under pressure, and residual monomer concentration. It was within a possible range. In particular, Example 1
The water-absorbing composites of Nos. To 7 exhibited excellent effects. On the other hand, the water-absorbing composites of Comparative Examples 1 and 2 were particularly inferior in water absorption rate under pressure, and were not satisfactory.

[0079]

According to the present invention, a water-absorbing composite having high water-absorbing ability and water-holding ability can be continuously and efficiently produced.

[Brief description of the drawings]

FIG. 1 is an example of a flow sheet when a water-absorbing composite is continuously produced by the method of the present invention.

FIG. 2 is a schematic view showing an example of a nozzle structure used for performing a mixing step in the manufacturing method of the present invention.

FIG. 3 is a schematic view of a device for measuring a water absorption rate under pressure used in a test example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Nonwoven fabric roll 2 Nonwoven fabric 3 Polymerization chamber 4 Dehydration tank 5 Distillation tower 6 Surface cross-linking device 7 Polymerizable monomer extraction tank 8 Dryer 9 Water-absorbing composite winding machine 11 Nozzle for A liquid 12 Nozzle for B liquid 13 A liquid 14 B liquid 21 Bullet 22 Rubber stopper 23 Support plate with small holes 24 Non-woven fabric 25 Resin particles

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) B01J 20/30 C08F 2/00 C C08F 2/00 20/04 22/02 20/04 C08J 3/24 CEYZ 22/02 5/04 CEY C08J 3/03 CEY A61F 13/18 307G 3/075 CEY C08J 3/03 CEY 3/24 CEY 5/04 CEY // C08L 33:02

Claims (41)

[Claims] 1. The following steps: (A) A polymerizable monomer aqueous solution containing an unsaturated carboxylic acid as a main component, in which 20% or more of carboxyl groups are neutralized, is dropped while polymerizing in the form of droplets. A composite step of adhering the polymer particles being polymerized to the fibrous base material by feeding the fibrous base material into the fibrous base material, and completing the polymerization after the adhesion to form a particle-substrate composite (B) The composite And a cross-linking agent having two or more functional groups capable of reacting with a carboxyl group and / or a carboxyl group is added to the resin particles 1 derived from the polymerizable monomer in the composite.
A continuous process for producing a water-absorbing composite, comprising a surface crosslinking step of adding and reacting in the presence of 1 to 100 parts by weight of water per 100 parts by weight. 2. The continuous production method according to claim 1, wherein the water content of the resin particles constituting the particle-substrate composite subjected to the surface crosslinking step is 10 to 40% by weight. 3. The continuous production method according to claim 2, further comprising a water content adjusting step of adjusting the water content of the resin particles constituting the particle-substrate composite to 10 to 40% by weight before the surface crosslinking step. . 4. The continuous production according to claim 1, further comprising a residual monomer treatment step of treating a polymerizable monomer remaining on the resin particles constituting the particle-substrate composite after the composite step. Method. 5. The continuous production method according to claim 4, wherein the compounding step, the surface crosslinking step, and the residual monomer treatment step are sequentially performed. 6. The continuous production method according to claim 4, wherein the compounding step, the residual monomer treatment step, and the surface crosslinking step are sequentially performed. 7. The continuous production method according to claim 4, wherein a composite step, a residual monomer treatment step, a water content adjustment step, and a surface cross-linking step are sequentially performed. 8. The continuous production method according to claim 4, wherein a compounding step, a water content adjusting step, a surface crosslinking step, and a residual monomer treatment step are sequentially performed. 9. The continuous production method according to claim 4, wherein a compounding step, a water content adjusting step, a residual monomer treatment step, and a surface cross-linking step are sequentially performed. 10. The continuous production method according to claim 1, wherein the unsaturated carboxylic acid is acrylic acid. 11. 20% of the carboxyl groups of acrylic acid
The continuous production method according to claim 10, wherein the above is neutralized to an alkali metal salt or an ammonium salt. 12. The continuous production method according to claim 1, wherein the polymerization of the aqueous polymerizable monomer solution in the complexing step is initiated by a redox polymerization initiator. 13. A droplet comprising a redox-based polymerization initiator, an oxidizing agent constituting a redox-based polymerization initiator and an aqueous solution of a polymerizable monomer, a reducing agent comprising a redox-based polymerization initiator, and a polymerizable monomer. The continuous production method according to claim 12, wherein the second production method is formed by mixing a second liquid including an aqueous solution in a gas phase. 14. The continuous production method according to claim 13, wherein the liquid-column-shaped first liquid and the liquid-column-shaped second liquid are subjected to collision mixing. 15. In the complexing step, the polymerization rate of the polymerizable monomer at the time of contact with the fibrous base material is 20 to 97.
%, The continuous production method according to claim 1. 16. At least a part of the resin particles of the particle-substrate composite obtained in the compounding step is agglomerated particles in which the resin particles are bonded to each other, and the resin constituting the agglomerated particles is The continuous production method according to any one of claims 1 to 13, wherein a part of the particles does not directly adhere to the fibrous base material. 17. The continuous production method according to claim 16, wherein the ratio of the resin particles constituting the aggregated granules is 30% by weight or more of all the resin particles. 18. The agglomerated granular material has a particle size of 100 to 3000.
The continuous production method according to claim 16 or 17, wherein the diameter is μm. 19. The continuous production method according to claim 1, wherein the resin particles are immobilized on the fibrous base material at 50 to 400 g / m ² by the complexing step. 20. The continuous production method according to claim 1, wherein the crosslinking agent is a compound having a glycidyl group as a group that reacts with a carboxyl group and / or a carboxylate group. 21. The continuous production method according to claim 20, wherein the compound having a glycidyl group is polyglycidyl ether. 22. The continuous production method according to claim 1, wherein the crosslinking agent is sprayed onto the particle-substrate composite in an aqueous solution or an alcohol solution. 23. The method according to claim 3, wherein in the water content adjusting step, the water contained in the resin particles is reduced by heating the particle-substrate composite to remove water.
23. The continuous production method according to any one of the above items. 24. The water content adjusting step, wherein the particle-substrate composite is brought into contact with a hydrophilic organic solvent to reduce the water content in the resin particles.
The continuous production method according to any one of the above. 25. A method in which the hydrophilic organic solvent has a water content of 30% by weight.
The continuous production method according to claim 24, which is any of the following ethanol, methanol, and acetone or a mixture thereof. 26. The continuous method according to claim 4, wherein in the residual monomer treatment step, the particle-substrate composite is heated to 100 to 250 ° C. to reduce the amount of the residual monomer. Production method. 27. In the residual monomer treatment step, 0.01 to 100 parts by weight of resin particles in the particle-substrate composite.
The continuous production method according to any one of claims 4 to 25, wherein after adding 1 to 1 part by weight of a peroxide and / or an azo compound, the mixture is heated to reduce the amount of residual monomers. 28. The continuous production method according to claim 4, wherein in the residual monomer treatment step, the particle-substrate composite is irradiated with ultraviolet rays to reduce the amount of residual monomer. 29. The residual monomer treatment step of irradiating the particle-substrate composite with electromagnetic radiation or particulate ionizing radiation to reduce the amount of residual monomer. 3. The continuous production method according to item 1. 30. In the residual monomer treatment step, 0.1 to 100 parts by weight of resin particles in the particle-substrate composite.
The continuous production method according to any one of claims 4 to 25, wherein after adding 20 parts by weight of a reducing agent, heating is performed to reduce the amount of residual monomers. 31. In the residual monomer treatment step, the particle-substrate complex is brought into contact with a water-containing organic solvent capable of dissolving the polymerizable monomer to extract the polymerizable monomer contained in the composite into the water-containing organic solvent. The continuous production method according to any one of claims 4 to 25, wherein the amount of the residual monomer is reduced. 32. The continuous production method according to claim 31, wherein the aqueous organic solvent is any one of aqueous methanol, aqueous ethanol, and aqueous acetone, or a mixture thereof. 33. In the residual monomer treatment step, the particle-substrate composite is subjected to a temperature of 80 to 250 ° C. and a dew point of 50 to 2
The continuous production method according to any one of claims 4 to 25, wherein the method is brought into contact with superheated steam or a steam-containing gas at a temperature in the range of 50 ° C. 34. The continuous production method according to claim 1, wherein the fibrous base material is made of a nonwoven fabric. 35. The continuous production method according to claim 34, wherein the nonwoven fabric is made of fibers having a diameter of 10 to 50 μm. 36. The nonwoven fabric has a basis weight of 10 to 100 g / m.
The continuous process according to claim 34 or 35, characterized in that it is ^2. 37. A water-absorbing composite produced by the continuous production method according to claim 1. 38. A water-absorbing composite comprising a water-absorbing polymer and a fibrous base material, wherein the water-absorbing composite satisfies at least one of the following conditions (1) to (3): (1) The amount of water absorbed when physiological saline is absorbed for 10 minutes under a pressure of 40 g / cm ² is 15 g or more per 1 g of the water-absorbing polymer supported on the water-absorbing composite. (2) The amount of water absorbed when physiological saline is absorbed for 20 minutes under a pressure of 40 g / cm ² is 18 g or more per 1 g of the water-absorbing polymer supported on the water-absorbing composite. (3) The amount of water absorbed when physiological saline is absorbed for 60 minutes under a pressure of 40 g / cm ² is 22 g or more per 1 g of the water-absorbing polymer supported on the water-absorbing composite. 39. A water-absorbing composite comprising a water-absorbing polymer and a fibrous base material, wherein the composite satisfies at least one of the following conditions (1) to (3): (1) The amount of water absorbed when physiological saline is absorbed for 10 minutes under a pressure of 60 g / cm ² is 13 g or more per 1 g of the water-absorbing polymer supported on the water-absorbing composite. (2) The amount of water absorbed when physiological saline is absorbed for 20 minutes under a pressure of 60 g / cm ² is 15 g or more per 1 g of the water-absorbing polymer supported on the water-absorbing composite. (3) The amount of water absorbed when physiological saline is absorbed for 60 minutes under a pressure of 60 g / cm ² is 19 g or more per 1 g of the water-absorbing polymer supported on the water-absorbing composite. 40. A water-absorbing composite comprising a water-absorbing polymer and a fibrous base material, wherein the composite satisfies at least one of the following conditions (1) to (3): (1) Sum of the amount of water absorbed when physiological saline was absorbed under pressure of 40 g / cm ² for 10 minutes and the amount of water absorbed when physiological saline was absorbed under pressure of 60 g / cm ² for 10 minutes. Is 28 g or more per 1 g of the water-absorbing polymer supported on the water-absorbing composite. (2) the sum of the water absorption amount when allowed to absorb water for 20 minutes saline under pressure of 40 g / cm ^2, and the water absorption amount when allowed to absorb water for 20 minutes saline under pressure of 60 g / cm ² Is 33 g or more per 1 g of the water-absorbing polymer supported on the water-absorbing composite. (3) The water-absorbing complex, the amount of water absorbed when physiological saline was absorbed for 60 minutes under a pressure of 40 g / cm ² ,
The sum of the amount of water absorbed when physiological saline is absorbed for 60 minutes under a pressure of g / cm ² is 40 g or more per 1 g of the water-absorbing polymer supported on the water-absorbing composite. 41. A water-absorbent article using the water-absorbent composite according to any one of claims 37 to 40.