JP2004149970A - Method for producing water-absorbing composite - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a water-absorbing composite having a large water-absorbing rate, a high water absorption and flexible feeling, and suitable for an application such as a paper diaper. <P>SOLUTION: The water-absorbing composite is obtained by attaching an aqueous solution of a monomer consisting essentially of acrylic acid and/or a salt thereof so as to form a fine particle shape on a water-absorbing composite material obtained by fixing fine particles of a water-absorbing resin on a fibrous substrate, and polymerizing the monomer attached to the water-absorbing composite material. <P>COPYRIGHT: (C)2004,JPO

Description

【００８７】
【発明の効果】
本発明の吸水性複合体の製造方法においては、吸水性樹脂を固着した繊維質基材に更に単量体水溶液を担持させ、単量体を重合させるようにしているので、得られる吸水性複合体は、吸水性樹脂の固着量が大きい。更に、更に本発明の吸水性複合体の製造方法においては、繊維質基材に単量体水溶液を噴霧し、繊維質基材に担持された単量体水溶液を重合させるようにしているので、基材の繊維に吸水性樹脂粒子を確実に互いに独立していわゆる数珠繋ぎの状態で付着できる。このようにして製造した吸水性複合体は、その内部に吸水性樹脂粒子が互いに独立して均一に分散されているので、吸水速度が高く、吸水量が大きく、且つ柔軟性が高い。このため本発明方法により製造する吸水性複合体は、例えば紙おむつ等の衛生材料に好適である。また更に、繊維質基材を予め加熱による起毛処理をする場合は、更に高性能な吸水性複合体を製造できる。また、得られる吸水性複合体を熱圧縮して吸水性複合体の表面に凹凸模様を付ける場合は、吸水速度、吸水量等を更に高めることができる。
【図面の簡単な説明】
【図１】本発明の吸水性複合体の連続的製造方法に用いる製造装置の一例を示す構成図である。
【符号の説明】
２ 繊維質基材ロール
４ 繊維質基材
５ 吸水性複合材料
６ 起毛処理部
７、１４ スプレーノズル
８ 単量体水溶液槽
１０ 添加剤槽
１２、１６、２２ 紫外線ランプ
１８ 表面処理剤槽
２０ 表面処理剤塗工用スプレーノズル
２４ 吸水性複合体
２６ 熱圧縮ロール
２７ 圧縮吸水性複合体
２８ 製品吸水性複合体ロール
１００ 第１重合処理部
１１０ 第２重合処理部
１２０ 第３重合処理部
１３０ 保温部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a water-absorbing composite useful for producing disposable diapers, sanitary napkins, and the like. According to the present production method, it is possible to produce a water-absorbing composite having a high water absorption rate and a high water absorption while maintaining the flexibility of the fibrous base material.
[0002]
[Prior art]
Conventionally, water-absorbing composites used for disposable diapers, sanitary napkins, etc. are generally formed by uniformly dispersing and adsorbing a water-absorbing resin powder such as cross-linked polyacrylic acid on a fibrous base material such as paper, pulp, or nonwoven fabric. It has been manufactured. However, according to this manufacturing method, it is difficult to securely fix the water-absorbing resin powder to the fibrous base material. The operation is complicated in handling powder.
[0003]
In order to solve the above problem, after spraying an aqueous solution of a monomer mixture comprising acrylic acid and an acrylate onto a fibrous base material, irradiating the fibrous base material with ionizing radiation or fine particle ionizing radiation, etc. There is known a method in which a body mixture is polymerized to fix a water absorbent resin to a fibrous base material.
[0004]
Patent Document 1 discloses a method for producing a water-absorbing composite similar to that described above by using a means of polymerizing an aqueous monomer solution supported on fibers constituting a base material by UV irradiation. I have. The publication states that, after polymerization, most of the monomers are polymerized by UV polymerization so that no unreacted monomers remain after polymerization, and then irradiated with an electron beam, and then irradiated with UV. Is described as being preferred. As described above, in order to produce a water-absorbing composite in which unreacted monomers do not remain even when the UV polymerization method is employed, at present, a complicated production process must be employed.
[0005]
Patent Literature 2 discloses that a monomer aqueous solution droplet being polymerized is dropped and adhered to a fibrous base material, and redox-based polymerization is completed on the fibrous base material, so that water absorption and water retention are high. A method for obtaining the complex is described.
[0006]
Patent Literature 3 discloses that a similar water-absorbent composite has a porosity of 50 to 99.5% as a fibrous base material, and a primary particle size of water-absorbent resin particles supported on the base material. Is preferably 50 to 1000 μm, and the amount of the water-absorbing resin carried per 1 m ^{2 of the} base material is preferably 10 to 500 g.
[0007]
According to the inventions described in Patent Documents 2 and 3, since the aqueous monomer solution is polymerized on the fibers constituting the base material, the obtained water-absorbent resin particles are fixed to the fibers and integrated. Many of the above-mentioned problems that occur when a powdery water-absorbing resin is applied to a fibrous base material have been solved.
[0008]
However, in the inventions described in the above publications, there is a problem that even if the amount of water-absorbing resin adhered per 1 m ² of the base material is increased, the amount of water absorbed by the manufactured water-absorbing composite does not increase in proportion thereto. Was. That is, when the amount of the water-absorbing resin adhered was 100 g / m ² or more, even if the amount of the water-absorbing resin was further increased, the increase in the amount of water absorbed could not be obtained. Further, when the amount of fixation is large, there has been a problem that unreacted monomers tend to remain.
[0009]
[Patent Document 1]
JP-A-1-292103 (pages 1-3)
[Patent Document 2]
JP-A-2000-328456 (Claim 1)
[Patent Document 3]
JP-A-9-67403 (Claims)
[0010]
[Problems to be solved by the invention]
In the present invention, a water-absorbing composite which can fix a large amount of a water-absorbing resin, is excellent in water absorption amount and water absorption rate, and contains only a small amount of unreacted monomer, and has high flexibility is produced on an industrial scale. The task was to provide a method.
[0011]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to solve the above problems, and as a result, further sprayed a monomer aqueous solution such as acrylic acid on a water-absorbing composite material in which fine particles of a water-absorbing resin were fixed to a fibrous base material. After that, by adopting a means of polymerizing the aqueous monomer solution supported in fine particles on the fibrous base material, the resulting water-absorbent resin is substantially independently separated from the center of the fibers of the fibrous base material. The amount of water-absorbent resin adhered can be greatly increased while maintaining the state in which beads are adhered to the fiber as spherical fine particles. While having flexibility, the amount of water absorption increases in proportion to the amount of the water-absorbent resin adhered. Further, when the fibrous base material is subjected to a brushing treatment in advance, the amount of the water-absorbent resin adhered is further increased while maintaining the flexibility. Can be like this In the case where the fibrous base material to which the water-absorbent resin is fixed further is subjected to a heat compression treatment, it has been found that the diffusion rate of the liquid and the anti-return property are significantly improved, and the present invention has been completed. .
[0012]
That is, the present invention provides a water-absorbing composite material obtained by fixing fine particles of a water-absorbing resin to a fibrous base material, in which a monomer aqueous solution containing acrylic acid and / or a salt thereof as a main component is supported in the form of fine particles. And then polymerizing the monomer supported on the water-absorbing composite material.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
The feature of the method for producing a water-absorbent composite of the present invention is that, in fixing the water-absorbent resin particles on the fibrous base material, the monomer aqueous solution is applied on the base material surface in a plurality of times, As an embodiment thereof, when a monomer aqueous solution is applied on a substrate surface twice or more in a series of manufacturing steps (after most of the monomers first applied on the substrate are polymerized, When the operation of applying and polymerizing an aqueous monomer solution on the same surface is repeated), and using a water-absorbing composite material to which water-absorbing resin particles are fixed as a starting material, and then applying and polymerizing the aqueous monomer solution on top of it. There is a case.
[0014]
The water-absorbing composite material of the starting material may be manufactured by any method, but a fibrous base material that has not been subjected to a raising treatment as described below, or an acrylic acid and It can be suitably produced by a method in which a monomer aqueous solution mainly containing a salt thereof is supported in fine particles, and then the monomer supported on the fibrous base material is polymerized.
[0015]
As the fibrous base material, a nonwoven fabric is preferable. In the present invention, the nonwoven fabric is a general term of a nonwoven fabric in a narrow sense, that is, a fibrous web to which base fibers are fixed by a binder, a carded or airlaid web, and a loose pad of fibers. The nonwoven fabric used in the present invention is more preferably manufactured by heat-sealing a base fiber with a binder fiber. This nonwoven fabric is more preferable because it can be subjected to a raising process described later.
[0016]
The nonwoven fabric is preferably manufactured using a base fiber having a fineness (thickness of fiber) of 2.0 to 20 dtex and a fiber length of 32 to 128 mm. When the fineness of the base fiber is less than 2.0 dtex, the resulting nonwoven fabric tends to have insufficient air permeability. On the other hand, when it exceeds 20 dtex, it is difficult to increase the adhesion amount of the water-absorbing resin.
[0017]
If the fiber length of the base fiber is less than 32 mm, the strength of the nonwoven fabric tends to decrease. In the case of performing the raising process by heating, which will be described later, the raising of the fibers is insufficient, and the amount of the water-absorbing resin adhered tends to be insufficient. On the other hand, if it exceeds 128 mm, the carding treatment performed in the production of the nonwoven fabric becomes difficult.
[0018]
As basis weight of the nonwoven fabric is suitably 10 to 100 g / ^{m 2.} The bulkiness of the nonwoven fabric is preferably 0.1 × 10 ^{2 to} 2.0 × 10 ² ml / g in volume per 1 g of the nonwoven fabric, that is, in specific volume.
[0019]
As a base fiber material, a non-hydrophilic resin is used in that when the monomer aqueous solution is atomized and supported on the substrate surface as described later, the monomer aqueous solution adheres to the fibers in the form of independent fine particles. Is preferred. Specific examples include polyethylene, polypropylene, ethylene-propylene copolymer, polyethylene terephthalate, polyamide, polystyrene, polyacrylonitrile, polyvinyl chloride, polyvinylidene chloride, and the like. Further, a nonwoven fabric using hydrophilic fibers such as rayon, cotton, and regenerated cellulose fibers as a small component is also preferable. A nonwoven fabric produced using a fiber made of such a non-hydrophilic resin as a base fiber is preferable in that a water-absorbent resin obtained by polymerizing an aqueous monomer solution can be fixed to the fiber in fine particles. If there is no hydrophilic property to some extent, paper diapers, sanitary products, and the like manufactured using the resulting water-absorbing composite are likely to leak when used. Therefore, the nonwoven fabric used in the present invention is a nonwoven fabric subjected to a hydrophilic treatment, for example, polyoxyethylene alkyl ether, polyoxyethylene phenol ether, polyoxyethylene sorbitan ester, polyoxyethylene alkyl fatty acid ester or polyoxyethylene oxypropylene. A nonwoven fabric coated with an anionic surfactant such as a nonionic surfactant such as a block polymer, a higher fatty acid salt, an alkyl naphthalene sulfonate, a dialkyl succinate or an alkyl sulfate is preferred.
[0020]
As a specific hydrophilic treatment method, the above-mentioned surfactant, that is, a hydrophilic agent may be mixed in advance with the spinning raw material resin when spinning the base fiber, and then spinning may be performed. Further, a hydrophilizing agent dissolved in a solvent or the like may be sprayed on the fiber after spinning.
[0021]
In the present invention, the above fibrous base material may be used as it is, but it is preferably used by raising the hair by heating. The heating temperature is preferably near the softening point of the base fiber of the fibrous base material, and practically a temperature in the range of 70 to 150 ° C is selected. The heating time varies depending on the heating temperature, but is usually several seconds to 180 seconds. More preferable heating conditions are heating at 80 to 110 ° C for 20 to 60 seconds. The heating means is not limited. For example, the fibrous base material may be passed through a heating furnace for a predetermined time, hot air may be blown on the fibrous base material, or the fibrous base material may be irradiated with an infrared lamp or the like. May be heated.
[0022]
As a result of the above-described heating method and the like, some of the fibers constituting the fibrous base material are oriented in a direction perpendicular to the base material surface, so that the fibrous base material varies depending on the fiber length of the base fiber used therein. Usually, the volume swells to about 1.3 to 3.0 times the volume before the raising treatment. By appropriately selecting the fiber length of the base fiber and the heating conditions, it is preferable that the volume of the fibrous base material be increased by 1.5 to 2.5 times the volume before the raising process by the raising process by heating.
[0023]
In addition, as a raising treatment means such as a nonwoven fabric or a fiber web, for example, a raising treatment means using a roll with a needle ridge is known in addition to heating. However, in the case of employing a mechanical raising treatment means other than heating, it is difficult to carry a large amount of the aqueous monomer solution described below as fine particles on the fiber. And the water absorption rate becomes inferior.
[0024]
Monomer containing acrylic acid and / or a salt thereof (hereinafter collectively referred to as an acrylic acid monomer) as a main component in the fibrous base material or the raised fibrous base material (usually in the form of a sheet). An aqueous solution of the body is sprayed and carried by spraying. A preferred monomer is a mixture of acrylic acid and acrylate wherein 20-90 mol% of acrylic acid has been converted to an alkali metal or ammonium salt. Monomers other than acrylic acid monomers can also be used in combination, and specific examples include methacrylic acid or a salt thereof, (meth) acrylamide, 2-hydroxyethyl (meth) acrylate and 2-acrylamido-2-methyl And propanesulfonic acid or a salt thereof. The preferred use amount of such a monomer is 20 mol% or less based on the total amount of the monomer and the acrylic acid-based monomer.
[0025]
The preferred concentration of the monomer in the aqueous monomer solution is 20 to 80% by mass, more preferably 40 to 60% by mass. When the monomer concentration is high, a large amount of the water-absorbing resin can be easily fixed on the fibrous base material, and the heat energy required for the drying treatment after the polymerization of the monomer can be reduced. Therefore, it is preferable to use an aqueous monomer solution having the highest possible concentration. Usually, a concentration near the saturation solubility of the monomer is selected.
[0026]
It is preferable to add a crosslinking agent, a polymerization initiator, and the like to the aqueous monomer solution in addition to the monomer.
[0027]
As a crosslinking agent, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, glycerin tri (meth) acrylate , N, N'-methylenebisacrylamide, diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, triallyl phosphate and the like.
[0028]
The proportion of the crosslinking agent added is preferably from 100 to 1000 ppm, particularly preferably from 300 to 750 ppm, based on the total mass of the monomers.
[0029]
The polymerization of the monomer can be performed by a general radical polymerization method, and the polymerization initiation method at that time is a thermal polymerization method using a compound that generates a radical by heat as a polymerization initiator, or an ultraviolet ray, an electron beam. For example, a method of initiating polymerization by irradiation with active energy rays. Preferably, it is a thermal polymerization method or a method of irradiating ultraviolet rays in the presence of a photopolymerization initiator (hereinafter referred to as UV irradiation polymerization method), and particularly preferably a UV irradiation polymerization method.
[0030]
Examples of the thermal polymerization initiator include water-soluble radical polymerization initiators such as hydrogen peroxide, ammonium persulfate, potassium persulfate, t-butyl hydroperoxide and cumene hydroperoxide. These compounds may be used as a redox polymerization initiator in combination with a reducing compound such as sodium bisulfite, sodium thiosulfate, L-ascorbic acid or an amine.
[0031]
The photopolymerization initiator used for polymerization by the UV irradiation polymerization method is not particularly limited, and any photopolymerization initiator that can generate radicals by ultraviolet rays can be used. The initiator can be appropriately selected and used according to the purpose. Specifically, azo compounds such as 2,2'-azobis (2-aminodipropane) salt, ketones such as 1-benzoyl-1-hydroxycyclohexane and benzophenone, benzoin and its alkyl ethers, benzyl ketals, and anthraquinone Derivatives and the like can be exemplified.
[0032]
Benzoyl compounds such as 1-hydroxy-cyclohexyl-phenyl-ketone and azo compounds such as 2,2′-azobis {2- (2-imidazolin-2-yl) propane} are preferred.
[0033]
The addition amount of the photopolymerization initiator is preferably from 100 to 2000 ppm based on the monomer. When the concentration of the photopolymerization initiator is less than 100 ppm, polymerization does not sufficiently occur, and when it exceeds 2,000 ppm, the degree of polymerization of the obtained polymer decreases.
[0034]
It is preferable to use a thermal decomposition type radical polymerization initiator in addition to the photopolymerization initiator. When this initiator is used in combination, thermal polymerization occurs in parallel with UV polymerization, and as a result, the polymerization conversion rate increases, and the amount of unreacted monomer remaining can be reduced. The amount of the thermal decomposition type radical polymerization initiator to be added is preferably from 100 to 5,000 ppm, particularly preferably from 500 to 2,000 ppm, based on the monomer.
[0035]
The polymerization temperature is preferably from 50 to 80 ° C. Therefore, as the thermal decomposition type radical polymerization initiator, a compound which decomposes in water at 80 ° C or less to generate radicals is preferable. Specific examples include persulfates such as ammonium persulfate and sodium persulfate.
[0036]
If necessary, a chain transfer agent, a surfactant and the like may be further added to the monomer aqueous solution.
[0037]
As described above, the monomer aqueous solution can be supported in the form of fine particles independently on the fibrous base material by spraying (coating) on the fibrous base material in the form of a mist as described above. As a method for atomizing the monomer aqueous solution, a known atomization technique can be used. Examples of the method include a dropletization method, a dropletization method using a spray nozzle, a dropletization method using a rotary disk atomizer, and an ultrasonic method.
[0038]
The average diameter of the spray droplet is preferably 50 to 500 μm. If the average diameter is less than 50 μm, droplets sprayed on the fibrous base material may easily penetrate to the back side without adhering to the fibrous base material, and thus may not easily adhere to the fibrous base material. When the average diameter of the droplets exceeds 500 μm, the adhesion of the droplets becomes uneven, and as a result, the water absorption amount and the water absorption rate of the water-absorbing composite material obtained by polymerization may be insufficient. The monomer aqueous solution having a size of 50 to 500 μm is subjected to polymerization and drying steps to become water-absorbent resin particles having a size of approximately 30 to 300 μm, and is fixed to the fibrous base material.
[0039]
The amount of the monomer aqueous solution carried is such that the amount of fixation of the water-absorbent resin obtained by the polymerization to the fibrous base material is 5 to 500 g / m ² , preferably 20 to 300 g / m ² .
[0040]
The fibrous base material carrying the aqueous monomer solution as described above is irradiated with ultraviolet light (UV) or the base material is heated to a predetermined temperature to convert the acrylic acid-based monomer into a crosslinking agent. Polymerize in the presence.
[0041]
At the time of polymerization, it is preferable to replace the atmosphere surrounding the monomer aqueous solution with an inert gas such as nitrogen gas to eliminate oxygen as much as possible.
[0042]
As the ultraviolet lamp, a high-pressure mercury lamp, a metal halide lamp or the like capable of irradiating a wavelength of 250 to 450 nm, and a mercury lamp having a lamp input of 30 to 240 W / cm is preferable. The amount of ultraviolet irradiation is 100 to 10000 mj / cm ² , more preferably 2000 to 6000 mj / cm ² . A number of mercury lamps can be used side by side depending on the required dose.
[0043]
By the above-mentioned UV irradiation, the majority (about 90% or more) of the monomer completes the polymerization in about 5 to 60 seconds. At this time, the polymerization temperature is estimated to be about 80 to 90 ° C. as the temperature of the fine particles of the aqueous monomer solution applied to the base material. In this way, hydrated polymer particles containing about 15 to 30% by weight of water and 0.1 to 10% by weight of unreacted monomer are formed on the fibrous base material.
[0044]
Thereafter, the heating is continued for a further appropriate period of time to reduce the unreacted monomers and to dry the hydropolymer particles, whereby a water-absorbing composite material as a starting material of the present invention is obtained.
[0045]
As described above, in the present invention, a fibrous base is obtained by further applying and polymerizing an aqueous monomer solution capable of forming a water-absorbing resin on the surface of the water-absorbing composite material produced by the above-described method or the like. Increase the amount of water absorbent resin on the material. Further, the operation of applying and polymerizing the aqueous monomer solution to the fibrous base material in a series of manufacturing steps may be repeated a plurality of times without using the water-absorbing composite material as a starting material.
[0046]
The coating amount of the aqueous monomer solution when per the latter is preferably 10 to 1000 g / ^{m 2,} more preferably from 50 to 500 g / ^{m 2.} Further, it is preferable to apply the next monomer aqueous solution when the polymerization of the previous monomer aqueous solution has progressed and the polymerization rate has reached 50% or more. When the next monomer aqueous solution is applied at a stage where the polymerization rate of the previously applied monomer is less than 50%, the droplets of the monomer aqueous solution unite with the semi-polymer to form large particles. The resulting water-absorbent composite sheet tends to be hard and the water absorption tends to be insufficient.
[0047]
The number of repetitions of the operation of carrying the monomer aqueous solution and the polymerization may be one or more, and the number of repetitions is appropriately determined in consideration of the purpose of use of the resulting water-absorbing composite.
[0048]
For details of operations such as supporting the aqueous monomer solution and polymerizing the monomer, the method described in the production of the water-absorbing composite material as the starting material can be used as it is.
[0049]
According to the production process for a water-absorbent composite of the present invention, the amount of sticking against the fibrous substrate of the water-absorbent resin becomes 100 g / ^{m 2} or more, preferably 150~1000g / ^{m 2.}
[0050]
After producing the water-absorbing composite by the above method, it is desirable to spray an aqueous solution of a crosslinking agent (hereinafter referred to as a surface treatment agent) having a plurality of epoxy groups reactive with a carboxyl group on the composite. By this operation, the degree of crosslinking of the surface layer of the water-absorbent resin particles can be further increased.
[0051]
Examples of the surface treatment agent include glycidyl ethers such as ethylene glycol diglycidyl ether and polyethylene glycol diglycidyl ether, polyols such as diethylene glycol, triethylene glycol, propylene glycol, glycerin and pentaerythritol, and polyamines such as ethylene diamine. The addition amount of the surface treatment agent is preferably 100 to 1000 ppm based on the water-absorbing resin particles.
[0052]
The resulting water-absorbing composite is preferably further heat-compressed for the purpose of further improving the water-absorbing performance (water-absorbing speed, water-absorbing amount, liquid diffusivity, liquid reversion preventing property, etc.). The thermal compression is preferably performed using a hot press, a hot roll, an emboss roll, or the like.
[0053]
The heat compression temperature is preferably from 50 to 150C, more preferably from 70 to 120C. When the heat compression temperature is lower than 50 ° C., a sufficient compression effect cannot be obtained. When the heat compression temperature is higher than 150 ° C., the flexibility of the water-absorbing composite obtained by hot-melting the fibrous base material may be impaired. It is not preferred.
[0054]
The thermal compression pressure is preferably from 0.01 to 100 MPa, more preferably from 0.1 to 10 MPa. The heat compression time varies depending on the heat compression temperature and the heat compression pressure, but is preferably 1 to 100 seconds.
[0055]
When performing thermal compression on an industrial scale, it is particularly preferable to use a hot roll. Specifically, the water-absorbent composite is continuously guided between the rolls while pressing the pair of rolls so as to have a linear pressure of 1 to 100 kg / cm, and is thermally compressed between the rolls.
[0056]
The gap between the pair of rolls used for thermal compression depends on the thickness of the water-absorbing composite to be thermally compressed, but is usually preferably 10 to 500 µm. When it is less than 10 μm, the fibrous base material may be cut, and when it exceeds 500 μm, the compression effect becomes insufficient.
[0057]
The pair of rolls preferably have at least one of the rolls formed with an uneven pattern. The depth of the concavo-convex pattern is preferably 0.001 mm or more, and more preferably 0.01 to 1 mm. It is preferable that the concavo-convex pattern is a pattern in which the concavo-convex pattern is repeated at intervals of 10 mm or less, or a pattern that fits in a circle having a diameter of 10 mm is formed continuously at intervals of 10 mm or less. In the case of a pattern in which the repetition interval exceeds 10 mm or a pattern which does not fit in a circle of 10 mm, the advantage of the present invention caused by compressing the fibrous base material may not be sufficiently exhibited.
[0058]
Hereinafter, an example of a continuous process for producing a water-absorbing composite sheet, which incorporates the method for producing a water-absorbing composite of the present invention, will be described with reference to FIG. This production process includes a process 1 for producing a water-absorbing composite material as a main raw material, and a process 2 for polymerizing a monomer after again supporting an aqueous monomer solution on the water-absorbing composite material.
[0059]
(Step 1)
Reference numeral 2 in FIG. 1 denotes a fibrous base material roll made of a wound nonwoven fabric. The fibrous base material wound around the roll 2 is preferably excellent in liquid permeability and gas permeability.
[0060]
The fibrous base material 4 fed from the roll 2 is then sent to a raising treatment section 6, where it is heated and subjected to a raising treatment. The processing conditions for the raising treatment have already been described in detail.
[0061]
The aqueous solution of a monomer containing a crosslinking agent, a polymerization initiator, and the like is applied by the spray nozzle 7 to the fibrous base material 4 that has been continuously raised by the heat treatment. In FIG. 1, reference numeral 8 denotes a monomer aqueous solution tank for storing an aqueous solution of a monomer and a cross-linking agent, and 10 denotes an additive tank for storing an aqueous solution of an additive such as a polymerization initiator. The aqueous solution of the crosslinking agent and the monomer in each of these tanks and the aqueous solution of an additive such as a polymerization initiator are mixed and supplied to the spray nozzle 7.
[0062]
In this example, a thermal decomposition type radical polymerization initiator is used in addition to the photopolymerization initiator as the polymerization initiator.
[0063]
The fibrous base material 4 on which the monomer aqueous solution is carried as described above is then sent to the first polymerization processing section 100 provided with a plurality of ultraviolet lamps 12 on the upper side, where the ultraviolet light is irradiated from above. As a result, the monomer applied to the fibrous base material 4 is polymerized. The inside of the first polymerization section 100 is kept in an atmosphere of an inert gas such as nitrogen gas, and oxygen is eliminated as much as possible. As the ultraviolet lamp 12, a mercury lamp or a metal halide lamp is preferable.
[0064]
Thereby, the water-absorbing composite material 5 of the starting material of the present invention is obtained.
[0065]
(Step 2)
Thereafter, the same aqueous monomer solution as described above is applied again to the water-absorbing composite material 5 obtained by passing through the first polymerization treatment section 100 using the spray nozzle 14. As a result, a sufficient amount of the monomer is supported on the fibrous base material 4.
[0066]
Next, the water-absorbing composite material 5 to which the aqueous monomer solution has been applied again is sent to the second polymerization processing section 110. The second polymerization processing section 110 has an interior maintained in an inert atmosphere similarly to the first polymerization processing section 100, and is provided with a plurality of ultraviolet lamps 16 at an upper portion thereof. This causes the re-coated monomer to polymerize.
[0067]
A spray nozzle 20 for applying a surface treatment agent that sprays the surface treatment agent stored in the surface treatment agent tank 18 is provided downstream of the second polymerization treatment unit 110. The coating spray nozzle 20 applies a surface treatment agent to the water-absorbing composite material 5 that has passed through the second polymerization treatment section 110.
[0068]
A third polymerization treatment section 120 is provided downstream of the spray nozzle 20 for applying the surface treatment agent. The third processing unit 120 is maintained in an inert gas atmosphere similarly to the second processing unit 110, and has a plurality of ultraviolet lamps 22 mounted thereon.
[0069]
The water-absorbing composite material 5 coated with the surface treatment agent is irradiated with ultraviolet rays when passing through the third processing section, and is subjected to photo-radical polymerization and polymerization heat generated as the photo-radical polymerization proceeds. As a result, the thermal polymerization is initiated by the action of a thermal polymerization initiator, whereby the residual monomers are almost completely eliminated. Furthermore, the crosslink density near the surface of the water-absorbent resin particles is increased by the surface treatment agent.
[0070]
Below the third polymerization processing section 120, a heat retaining section 130 is formed, and the water absorbing composite material 5 to which the water absorbing resin particles are adhered passes therethrough to dry the water absorbing resin particles. Thus, the water-absorbing composite 24 is obtained.
[0071]
(Heat compression processing)
Reference numeral 26 denotes a heat compression roll, by which the water-absorbing composite is heat-compressed.
[0072]
As a method of applying heat compression to the water-absorbing composite 24, various conventionally known methods can be adopted. As shown in FIG. 1, the water-absorbing composite 24 is provided between a pair of opposed rolls 26 provided with heating means. A method in which the heat compression treatment is continuously performed by passing through the body 24 is preferable.
[0073]
After the heat compression treatment, the compressed water-absorbent composite 27 is wound up, whereby a product water-absorbent composite roll 28 is obtained.
[0074]
Hereinafter, the present invention will be described more specifically with reference to examples.
[0075]
【Example】
Example 1
In a monomer aqueous solution composed of 70 mol% of sodium acrylate and 30 mol% of acrylic acid (total content of monomers: 42 mass%), tetraethylene glycol diacrylate (Aronix M-240 manufactured by Toagosei Co., Ltd.) was used as a crosslinking agent. 05% by mass (based on the mass of the monomer) was added, and the aqueous monomer solution was cooled to 20 ° C. Next, nitrogen gas was blown into the monomer aqueous solution to reduce the dissolved oxygen concentration to 1 ppm or less.
[0076]
In this monomer aqueous solution, 1-hydroxycyclohexyl-phenyl-ketone (0.02% by mass (based on monomer mass)) as a photopolymerization initiator, and sodium persulfate (0.15% by mass) (monomer (Based on the amount).
[0077]
On the other hand, the prepared monomer aqueous solution was applied to an air-through nonwoven fabric (basis weight 40 g / m ² ) composed of PE / PP using a spray nozzle so as to be 190 g / m ² (in the amount of the aqueous solution). The non-woven fabric sprayed with the monomer aqueous solution was irradiated with ultraviolet rays using a high-pressure mercury lamp under a nitrogen atmosphere. The amount of ultraviolet light was 1000 mj / cm ² .
[0078]
The obtained water-absorbing composite material was further sprayed with the above monomer aqueous solution at 190 g / m ² (in the amount of the aqueous solution). Thereafter, ultraviolet irradiation was performed using a high-pressure mercury lamp under a nitrogen atmosphere. The amount of ultraviolet light was 2500 mj / cm ² . The obtained water-absorbent composite had flexibility with the water-absorbent resin fixed at 160 g / m ² .
[0079]
Example 2
The same procedure as in Example 1 was repeated except that the monomer aqueous solution was sprayed at 127 g / m ² and then polymerized three times in total, and the amount of the water-absorbing resin fixed was 160 g / m ² . A water-absorbing composite was obtained.
[0080]
Comparative Example 1
A water-absorbing composite having a water-absorbing resin fixed to 160 g / m ² was obtained in the same manner as in Example 1 except that 380 g / m ^{2 of the} aqueous monomer solution was sprayed at a time.
[0081]
The water-absorbing composites of Examples 1 and 2 and Comparative Example 1 were evaluated by the test methods described below. The results are shown in Table 1. The artificial urine (per 10 kg) has the following composition.
[0082]
Urea _{/ NaCl / MgSO 4 · 7H 2} O / CaCl 2 · 2H 2 O / pure water = 200g / 80g / 8.0g / 3.0g / 9709g
(Amount of artificial urine absorbed)
The water-absorbing complex cut into 6 cm × 7 cm and 200 ml of artificial urine were placed in a 300 ml beaker and left at room temperature for 30 minutes. After that, the water-absorbing complex swollen by absorbing the artificial urine was taken out from the artificial urine, and the artificial urine attached thereto was wiped off with a 200-mesh filter cloth, and the mass was measured. The artificial urine water absorption A (kg / m ² ) was calculated by the following equation.
[0083]
(Equation 1)
A = (W1-W2) /0.42
Here, W1 represents the mass of the water-absorbing composite after water absorption, and W2 represents the mass of the water-absorbing composite before water absorption.
[0084]
(Artificial urine absorption rate)
The water-absorbing complex cut into 6 cm × 7 cm and 200 ml of artificial urine were placed in a 300 ml beaker and left at room temperature for 5 minutes. Thereafter, the water-absorbing composite or the water-absorbent resin-supporting fibrous base material swollen by the artificial urine was taken out from the artificial urine, and the artificial urine attached thereto was wiped off with a 200-mesh filter cloth, and the mass was measured. The artificial urine water absorption rate B (kg / m ² ) was calculated by the following equation.
[0085]
(Equation 2)
B = (W1-W2) /0.42
(Artificial urine suction speed)
The results are shown in Table 1.
[0086]
[Table 1]

[0087]
【The invention's effect】
In the method for producing a water-absorbent composite of the present invention, the fibrous base material to which the water-absorbent resin is fixed further supports an aqueous monomer solution, and the monomer is polymerized. The body has a large amount of water-absorbing resin adhered. Furthermore, in the method for producing a water-absorbing composite of the present invention, since the aqueous monomer solution is sprayed on the fibrous base material, and the aqueous monomer solution supported on the fibrous base material is polymerized. The water-absorbent resin particles can be reliably attached to the fibers of the base material independently in a so-called rosary connection state. The water-absorbing composite thus produced has a high water absorption rate, a large amount of water absorption, and a high flexibility since the water-absorbing resin particles are uniformly and independently dispersed therein. Therefore, the water-absorbing composite produced by the method of the present invention is suitable for sanitary materials such as disposable diapers. Further, when the fibrous base material is subjected to a raising treatment by heating in advance, a more sophisticated water-absorbing composite can be produced. In the case where the resulting water-absorbing composite is thermally compressed to form an uneven pattern on the surface of the water-absorbing composite, the water absorption speed, the water absorption, and the like can be further increased.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an example of a production apparatus used for a continuous production method of a water-absorbing composite of the present invention.
[Explanation of symbols]
2 fibrous base material roll 4 fibrous base material 5 water-absorbing composite material 6 napping treatment part 7, 14 spray nozzle 8 monomer aqueous solution tank 10 additive tank 12, 16, 22 ultraviolet lamp 18 surface treatment agent tank 20 surface treatment Spray nozzle for agent coating 24 Water-absorbing composite 26 Hot compression roll 27 Compressed water-absorbing composite 28 Product water-absorbing composite roll 100 First polymerization processing section 110 Second polymerization processing section 120 Third polymerization processing section 130 Insulation section

Claims (3)

After a monomer aqueous solution containing acrylic acid and / or a salt thereof as a main component is supported in fine particles on a water-absorbing composite material obtained by fixing fine particles of a water-absorbing resin to a fibrous base material, A method for producing a water-absorbing composite, comprising polymerizing a monomer supported on a water-soluble composite material. A method for producing a water-absorbing composite, comprising the following steps 1 and 2.
(Step 1) An aqueous monomer solution containing acrylic acid and / or a salt thereof as a main component was supported in fine particles on a fibrous substrate that had been subjected to a raising treatment, and then supported on the fibrous substrate. Step of polymerizing the monomer to obtain a water-absorbing composite material (Step 2) In addition to the water-absorbing composite material obtained in Step 1, a monomer aqueous solution containing acrylic acid and / or a salt thereof as a main component is formed into fine particles. And then polymerizing the monomer supported on the water-absorbing composite material Method for producing a water-absorbing composite according to claim 1 or 2 fine particles of the water-absorbing resin to obtain a 100 g / m ² or more fixed water-absorbent composite fibrous base material.

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