JP2005307398A - Water-absorbing composite composition and water-absorbing sheet-shaped material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-absorbing composite composition suitable for use as a water-absorbing element of a water-absorbing article such as a paper diaper and sanitary goods. <P>SOLUTION: The water-absorbing composite composition consists essentially of water-absorbing composites formed out of nearly spherical water-absorbing resin particles and fibers bonded to the particles and extended outward from the particles, and capable of being formed into a sheet shape by the entanglement of the fibers, and is regulated so that the content of the composites each composed of one particle and the fibers may be ≥50%, and the content of the composites each composed of four or more particles and the fibers may be ≤10%. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a water absorbent composite composition mainly comprising a water absorbent composite comprising water absorbent resin particles and fibers bonded thereto, and a water absorbent sheet-like material formed using the same. This water-absorbent sheet is suitable for use as a water-absorbing element such as paper diapers and sanitary products.

  Paper diapers and sanitary products that use water-absorbing resin particles as a water-absorbing element (hereinafter, these may be collectively referred to as water-absorbing articles) are widely used. The basic structure of the water-absorbent article is such that pulp or non-woven fabric is placed on a water-impermeable resin sheet, water-absorbing resin particles are dispersed thereon, and further, pulp or non-woven fabric is stacked thereon. . One of the problems with this water-absorbent article is that the water-absorbent resin particles easily move inside due to an impact applied during handling or wearing. As a result, a portion having poor water absorption capability is locally generated in the water-absorbent article, and urine leakage or the like may occur despite having sufficient water absorption capability as a whole.

As a solution to this problem, use of a composite in which water-absorbing resin particles are bonded to a nonwoven fabric or the like as a water-absorbing element has been studied (see Patent Documents 1 to 3). This composite is typically dropped from the top of the polymerization tower as a droplet of a partially neutralized acrylic acid solution containing a polymerization catalyst, while a non-woven fabric is placed at the bottom of the polymerization tower. It can be produced by placing the liquid droplets while dropping while adhering to the nonwoven fabric and completing the polymerization on the nonwoven fabric. In addition, it is also considered to produce a composite by supplying the fiber itself in the middle of the polymerization tower instead of the non-woven fabric, causing the falling droplets to adhere to the fiber and depositing on the bottom of the polymerization tower (patent) Reference 4).
JP-A-2-138306 JP 2000-198805 A JP 2000-328456 A In these composites, the water-absorbing resin particles are bonded to the fibers, so that the problem that the water-absorbing resin particles move in the water-absorbing article is solved by using these composites. It is done. However, in these composites, the fibers and the water-absorbing resin particles are combined to form a three-dimensional network with a coarse mesh as a whole, so that the rigidity and elasticity are large. Therefore, even if the composite is compressed and thinned when it is processed into a water-absorbent article, it returns to its original thickness when it is uncompressed, and it is bulky and tends to cause inconvenience in wearing. In addition, since the composite generally has a low bulk density, there is also a problem that the water absorption capacity per unit volume of the composite is small.

  The present invention inherits the advantages of the conventional composite that can provide a water-absorbent article in which the water-absorbent resin particles do not move inside, and has improved the point that has been a problem with the conventional composite. An object of the present invention is to provide a water absorbent element and a water absorbent sheet using the same.

The water-absorbing element according to the present invention is formed of substantially spherical water-absorbing resin particles and one or a plurality of fibers bonded to the water-absorbing resin particles and extending outward from the fibers. A water-absorbing composite composition mainly comprising a water-absorbing composite that can be formed into a sheet shape by entanglement of the water-absorbing composite, wherein the water-absorbing composite formed from one water-absorbing resin particle and fiber is a water-absorbing composite 50% by weight or more of the total, and the water-absorbing composite formed of four or more water-absorbing resin particles and fibers is 10% by weight or less of the whole water-absorbing composite It is.

  Further, the water-absorbent sheet material according to the present invention is composed of the water-absorbent composite composition or the fiber (= fiber not bonded to the water-absorbent resin particles), and is formed into a sheet shape by the entanglement of the fibers. It is characterized by that.

  The water-absorbent composite composition according to the present invention is basically composed of one, at most about four, water-absorbent resin particles and fibers bonded to the water-absorbent composite particles. Since it is an assembly of a conductive composite, it can be formed into a sheet-like material having an arbitrary thickness by entanglement of fibers. Moreover, this sheet-like material is extremely flexible and has low elasticity. In addition, as the water-absorbing composite composition, those containing fibers (= free fibers) that are not bonded to the water-absorbing resin particles are used, or when forming into a sheet-like material, free fibers are mixed into the water-absorbing composite composition. By doing so, the water absorption capacity per unit volume can be changed greatly.

  The water-absorbent composite forming the water-absorbent composite composition according to the present invention is composed of one or at most about four substantially spherical water-absorbent resin particles, bonded to the water-absorbent resin particles and from now on. It consists of fibers that extend to the outside. Most of the water-absorbing composites contain only one water-absorbing resin particle, and there are few, if any, water-absorbing composites containing more than four water-absorbing resin particles.

  That is, 50% by weight or more of the entire water-absorbing composite is composed of one water-absorbing resin and fibers bonded thereto. It is preferable that 70% by weight or more, particularly 85% by weight or more of the entire water-absorbent composite contains only one water-absorbent resin particle. On the other hand, those containing 4 or more water-absorbing resin particles are 10% by weight or less, 5% by weight or less, more preferably 1% by weight or less of the total water-absorbing composite. The number of fibers bonded to one water-absorbent resin particle is arbitrary, but is usually about several to 30. The mode of bonding between the water-absorbing resin particles and the fiber is arbitrary as long as it has a bonding strength that prevents the water-absorbing resin particles and the fiber from being separated by an impact applied during normal handling. That is, the fibers may be bonded so as to adhere to the surface of the water-absorbent resin particles, or a part of the fibers may be embedded in the water-absorbent resin particles so that the yarn is passed through the beads. In the water-absorbing composite, the water-absorbing resin particles impart water absorbing ability, and the fibers impart sheet-form forming ability. The weight ratio of the water-absorbent resin particles to the fibers in the water-absorbent composite is arbitrary, but is usually 1: 1 to 100: 1, and preferably 2: 1 to 20: 1. If the fiber ratio is small, the sheet-like product forming ability of the water-absorbing composite is reduced. This is because the water-absorbing composite composition contains free fibers or the water-absorbing composite in forming the sheet-like product. It can be supplemented by using free fibers in combination with the body composition.

  The average particle diameter of the water-absorbent resin particles is usually 50 to 3,000 μm. In view of ease of production and convenience in use of the water-absorbent composite, the average particle diameter is preferably 100 μm or more, more preferably 200 μm or more. The upper limit of the average particle diameter is preferably 2,000 μm or less, more preferably 1,000 μm or less. In general, the average particle diameter of the water-absorbent resin particles is most preferably 200 to 800 μm, although it depends on the application. The water-absorbing resin particles are substantially spherical. The substantially spherical shape means that an aqueous solution of a partially neutralized salt of acrylic acid is dropped in the form of droplets while being dropped, and is attached to fibers during polymerization. It means a shape that is rounded as a whole, such as water-absorbing resin particles formed by polymerization, and is not angular like crushed particles.

The length of the fiber forming the water-absorbing composite is usually 100 to 30,000 μm. The length of the fiber is preferably not less than twice the average particle diameter of the water-absorbent resin particles, more preferably not less than 5 times, since the fiber forms a sheet-like material by entanglement. The length of the fiber is preferably 200 μm or more, more preferably 500 μm or more. The longer the fibers, the better the entanglement between them, and the greater the ability of the water-absorbent composite to form a water-absorbent sheet. However, when the length of the fiber becomes long, the ratio of the fiber to the water-absorbing composite increases, and the water absorption capacity of the water-absorbing composite decreases. If the fibers are long, when a water-absorbing composite is produced by the method described later, a product in which a plurality of water-absorbing resin particles are bonded to one fiber is likely to be produced. Accordingly, the length of the fiber is preferably 20,000 or less, and more preferably 10,000 μm or less. In general, the fiber length is most preferably 500 to 5000 μm.

  The fiber may be either a hydrophilic material such as cellulose, or a hydrophobic material such as polyester or polyolefin, or both may be used in combination. Preferably, a hydrophilic fiber obtained by modifying the surface of cellulose fiber or hydrophobic fiber to be hydrophilic with a surfactant or the like is used. In the water-absorbent composite using hydrophilic fibers, water can be expected to reach the water-absorbent resin particles through the fibers and penetrate into the water-absorbing resin particles. As the hydrophilic fiber, it is preferable to use one having a water contact angle of 60 ° or less, which is a hydrophilic index. More preferably, the contact angle is 50 ° or less, particularly 40 ° or less.

  The water-absorbing composite is obtained by bringing the water-absorbing resin particles being polymerized into contact with the fibers to bond them together, and in this state, in the known water-absorbing composite manufacturing method, the fibers opened as fibers are used. It can be manufactured by controlling the ratio of the fibers and the water-absorbent resin particles so that the plurality of water-absorbent resin particles are not in contact with one fiber. The product usually comprises free fibers, i.e., fibers that have not been bonded to the water-absorbent resin particles, in addition to those composed of water-absorbent resin particles and fibers bonded thereto. The product is opened to disperse the fibers and free fibers to which the water-absorbing resin particles are bound to individual units, and then sieved or wind-classified to bind the fibers and the free fibers to which the water-absorbing resin particles are bound. And can be separated. The water absorbent composite comprising the water absorbent resin particles thus obtained and the fibers bonded thereto has a weight ratio of the water absorbent resin particles to the fibers of 1: 1 to 100: 1, particularly 2: 1 to 1. It is preferably 20: 1. When the ratio of the water absorbent resin particles is small, the water absorption capacity of the water absorbent composite is reduced. On the contrary, if the ratio of the fibers is too small, the entanglement between the fibers becomes weak, and the strength of the water-absorbent sheet-like material formed from this water-absorbent composite becomes weak. Note that it is not necessary to completely separate the fibers and the free fibers to which the water-absorbent resin particles are bonded. This is because mixing free fibers in the water-absorbing composite composition decreases the water-absorbing capacity of the water-absorbing composite composition, but conversely forms a water-absorbing sheet with the water-absorbing composite composition. This is because there is also an advantage of increasing the strength of the water-absorbent sheet by increasing the entanglement between the fibers. Therefore, what is necessary is just to determine the grade of the isolation | separation of the fiber which the water absorbing resin particle couple | bonded, and the free fiber according to the use of the water absorbing sheet-like material formed using a water absorbing composite composition.

In one of the typical methods for producing a water-absorbing composite, droplets of a polymerizable monomer aqueous solution containing a catalyst are formed at the top of a polymerization tower and dropped while polymerizing inside the polymerization tower. On the other hand, the fibers are supplied to the polymerization tower in the open state, and the particles in the process of polymerization are brought into contact with the fibers in the air to bond them together. At this time, the density of the particles in the polymerization column in the polymerization tower is reduced, and conversely, the density of the fibers is increased so that a plurality of particles in the polymerization process are not attached to one fiber as much as possible. The particles in the process of polymerization combined with the fibers continue to be polymerized and fall inside the tower, accumulate together with free fibers on a belt conveyor provided at the bottom of the tower, and are taken out of the tower. The polymerization is preferably allowed to proceed to such an extent that the particles lose their adhesive strength before falling to the bottom of the tower. However, when a large amount of fibers are attached to the particles in the middle of polymerization, even if they fall to the bottom of the tower in a sticky state, they are blocked by other fibers on the surface and bound to other resin particles. There is little risk of forming a water-absorbing composite containing a plurality of resin particles by combining with existing fibers. Alternatively, instead of supplying fibers from the middle of the polymerization tower, a thin layer of fibers opened on a belt conveyor at the bottom of the tower is formed, and particles in the course of polymerization are dropped roughly on this. You may make it adhere to a fiber. The type of polymerizable monomer, the concentration of the polymerizable monomer aqueous solution, the type and concentration of the catalyst contained in this aqueous solution, the method of forming droplets, the polymerization conditions such as the atmosphere and temperature in the polymerization tower, and the resulting water-absorbing composite What is necessary is just to select suitably the removal method of the residual monomer from a body, the modification method by surface crosslinking, etc. from a well-known range. When the fibers are brought into contact with the particles being polymerized, the polymerization rate of the particles, that is, the monomer conversion rate, is suitably 40 to 95% when the particles are dropped and bonded onto the fiber at the bottom of the column. If the monomer conversion is less than 40%, the particles are generally too soft to maintain their shape on the fiber against gravity. On the other hand, when the monomer conversion rate exceeds 95%, the adhesiveness of the particles becomes weak, and it becomes difficult to firmly adhere the particles to the fibers. In general, it is preferable to contact the particles and fibers during polymerization in a state where the monomer conversion is 45 to 90%, particularly 50 to 80%. When particles and fibers are bonded in the air, there is no need to consider maintaining the shape of the particles against gravity, so the monomer conversion may be lower than 40%.

  The mode of bonding between the water-absorbent resin particles and the fibers is basically determined by the monomer conversion rate of the particles when they are in contact with each other, and the lower the monomer conversion rate, the easier the fibers to get into the particles. Accordingly, when the monomer conversion rate of the particle is low, the particle and the fiber are brought into contact with each other, the fiber is entrapped inside the particle, and when the monomer conversion rate becomes high, the particle and the fiber are brought into contact again. A water-absorbing composite having fibers encroached on the inside and fibers bonded on the surface can be generated.

  The water-absorbent sheet-like material according to the present invention is obtained by molding a water-absorbent composite composition mainly composed of the above-mentioned water-absorbent composite into a sheet shape by entanglement of fibers. Depending on the properties required for the water-absorbent sheet, a water-absorbent composite composition containing any amount of free fibers can be used. In forming the water-absorbent sheet-like material, free fibers can be used in combination with the water-absorbent composite composition. As the free fibers, the same fibers as those used in the production of the water-absorbent composite can be used, but it is preferable to use relatively long fibers in order to improve the entanglement and to develop the strength. Usually, a length of 100 to 30,000 μm is used. It is preferable to use one having a length of 200 to 10,000 μm, particularly 500 to 5,000 μm.

  The weight ratio of the water-absorbent resin particles and the fibers in the water-absorbent sheet material, that is, the total of the fibers to which the water-absorbent resin particles are bonded and the fibers not bonded, is usually 1: 1 to 10: 1. It is preferably 2: 1 to 9: 1. If the ratio of the water-absorbent resin particles in the water-absorbent sheet is small, the water-absorbing capacity is small, and conversely if the ratio is too large, the strength of the water-absorbent sheet is weakened. The thickness of the water-absorbent sheet is arbitrary, but is usually 0.5 to 10 mm, preferably 1 to 5 mm. The thickness is measured as follows in accordance with JISI-1096.

Measuring the thickness of the water absorbent sheet;
As shown in FIG. 1, an adapter 11 having a diameter of 30 mm is attached to a rheometer (manufactured by FUDOH, model number NRM-2003J). The sample stage 12 is raised at a speed of 2 cm / min and set to stop when a pressure of 0.2 psi is applied. The water-absorbent sheet-like material 13 is placed on the sample table. The sample table is raised, and the distance L (mm) from the upper surface of the adapter to the lower surface of the sample table at the stopped position is measured with a caliper. Measure five samples and determine the average value. The same measurement is performed without placing the water-absorbent sheet on the sample table as a blank, and the distance L ′ (mm) is measured.
Thickness (mm) = L−L ′
Further, the water-absorbent sheet-like material usually has a restoration rate calculated by the following formula of 50% or less.

Restoration rate (%) = {(A−B) / A} × 100
(In the formula, A is a water-absorbent sheet material after a load of 100 kg / cm ² was applied to the water-absorbent sheet material for 10 minutes, the load was removed, and the product was stored for 30 days in an atmosphere at a temperature of 25 ° C. and a humidity of 50%. (B is the thickness of the water-absorbent sheet immediately before the load is removed. The measurement is performed on five 5 cm × 5 cm samples, and the average value is obtained.)
That the restoration rate of the water-absorbent sheet-like material according to the present invention is 50% or less means that the water-absorbent sheet material is flexible and has a small repulsive force against compression. This is based on the fact that the water-absorbent sheet is formed by non-fixed bonds such as entanglement of short fibers, such as a water-absorbing composite in which water-absorbing resin particles are bonded to a conventional non-woven fabric or the like. This is a great difference from the case where the bonding point is fixed, such as a water-absorbing composite in which the particles in the polymerization are closely attached to the deposit and the fibers are bonded to each other by the particles.

  It is preferable that the water-absorbent sheet-like material according to the present invention has a heart loop stiffness L applied to a relatively soft fabric defined in JISL-1096 in the range of 5.0 to 9.5 cm. For measurement, 5 samples of 2 cm × 25 cm were cut out from the water-absorbent sheet, stored in an atmosphere at a temperature of 25 ° C. and a humidity of 50% for 24 hours, and then the sample 22 was put on the horizontal bar grip 21 shown in FIG. Attach it in the shape of a heart loop so that is 20cm. After 1 minute, the distance L (mm) between the top of the horizontal bar and the lowest point of the loop is measured. Rigidity is displayed as an average value of five samples. The softer the sample, the greater the flexibility L.

  The water-absorbent sheet-like material according to the present invention is combined with a water-impermeable resin film, paper, fluff pulp, non-woven fabric, etc. in the same manner as a conventional non-woven fabric bonded with water-absorbent resin particles. It can be used for the manufacture of articles. The basic structure is that at least three layers of a layer made of pulp, paper or non-woven fabric, a water-absorbent sheet according to the present invention, and a layer made of pulp, paper or non-woven fabric are formed on this water-impermeable resin sheet. They are sequentially stacked in order. Since the water-absorbent sheet-like material according to the present invention has a weak repulsive force against compression as described above, it constitutes a water-absorbent article in combination with a material having a similarly low repulsive force, and compresses and packs it strongly. Even if the compression is released, the water-absorbent article can be obtained with little expansion.

In the water-absorbent composite according to the present invention, the fibers can be entrapped inside the water-absorbent resin particles as described above to firmly bond the two. Therefore, a water-absorbent article using a water-absorbent sheet-like material formed of such a water-absorbent composite as a water-absorbing element exhibits an excellent performance that the water-absorbent resin particles hardly fall off from the fiber even in the water-absorbing state. For example, according to the present invention, it is possible to easily obtain a water-absorbing article having a water-absorbing particle dropout rate measured below of less than 10%.
Measurement of water absorption particle drop-off rate;
A water-absorbing article (100 mm × 400 mm) is placed on a smooth table with the water-absorbing surface facing up. A cylinder with a circular diameter of 40 mm is attached to the center of a square acrylic plate (100 × 100 × 10 mm), and seven through-holes with a diameter of 5 mm are provided at almost equal intervals in the acrylic plate portion surrounded by the cylinder. A thing (weight 150 g) is placed in the center of the water-absorbent article. 150 ml of artificial urine is placed in a cylinder and left at room temperature for 30 minutes to absorb the artificial urine in the water-absorbent article. Next, a portion (100 × 100 mm) that was under the acrylic plate is cut out from the water-absorbent article, and its weight is measured. The cut sample is placed at the center of a 200 × 200 mm acrylic plate, and a load (3 kg) having a bottom area of 100 × 100 mm is placed thereon so that the sample does not protrude. Set this on a shaker (product of Inoue Seieido, Model No. MS-1) so that the cut end of the sample is perpendicular to the moving direction, and amplitude is 50 mm, frequency is 80 times / min. Shake. The load is removed, the weight of the water-absorbing particles dropped from the sample is measured, and the particle drop-off rate is calculated by the following formula.

Artificial urine having the following composition is used. % Is% by weight.
Urine 1.94%
Sodium chloride 0.80%
Calcium chloride 0.06%
Magnesium sulfate 0.11%
Distilled water 97.09%
The particle weight in the sample before shaking is calculated on the assumption that all of the water absorption of the water absorbent article (100 mm × 400 mm) is due to the water absorbent resin particles. That is, 1/4 of the total of the weight of the water-absorbent resin particles in the water-absorbent article (100 mm × 400 mm) and the amount of water absorbed is taken as the particle weight in the sample (100 mm × 100 mm) before shaking.

The present invention will be described more specifically with reference to the following examples.
Example 1 (Production of a water-absorbing composite composition)
While cooling a mixture of 100 parts by weight of acrylic acid and 3.3 parts by weight of water to 25 ° C. or lower, 133.3 parts by weight of a 25% aqueous sodium hydroxide solution was added thereto. Solution A was prepared by adding 0.14 parts by weight of N, N'-methylenebisacrylamide and 4.55 parts by weight of 31% by weight aqueous hydrogen peroxide solution to this partially neutralized acrylic acid aqueous solution (monomer concentration: 50% by weight, medium 60% sum).

Separately, 0.14 parts by weight of N, N'-methylenebisacrylamide and 0.57 parts by weight of L-ascorbic acid were added to 100 parts by weight of a partially neutralized acrylic acid aqueous solution prepared in the same manner as above to prepare Solution B.
The solution A and the solution B were heated to 40 ° C., respectively, and flowed out at 4.5 m / second from the nozzles facing each other in the nozzle apparatus shown in FIG. 3 installed at the top of the polymerization tower. Each nozzle has an inner diameter of 0.125 mm, and five nozzles are arranged at intervals of 1 cm. The crossing angle of the nozzles is 30 degrees, and the distance between the nozzle tips is 4 mm. The inside of the polymerization tower is controlled at 50 ° C. The solution flowing out from each nozzle collided in the air to form droplets, and dropped in the tower while polymerizing. At a position where the monomer conversion rate of the droplets is about 15% and about 40%, pulp fibers (length: about 2500 μm, thickness: 2.2 decidex) are supplied to the polymerization tower, and the droplets are attached to the fibers. It was. The fiber / resin supply ratio, that is, the supply weight ratio of pulp fibers to the water-absorbent resin particles (dry basis) generated from the solution A and the solution B is 2.5 / l, respectively. The fallen matter was taken out from the bottom of the polymerization tower, and after the polymerization was completed, it was dried until the water content became 5%. Next, after opening the fiber, it was sieved and separated into a water-absorbing composite composed of water-absorbing resin particles and fibers bonded thereto, and free fibers to obtain a water-absorbing composite composition. The weight ratio of the water absorbent resin particles to the fibers of the water absorbent composite was 55:45. The measurement was performed according to the following method.

Measurement of the resin-to-fiber ratio of the water-absorbing composite;
About 1 g of the dried water-absorbing complex is taken, and its weight w ₁ g is precisely weighed and put into a 50 ml glass container. A solution in which 0.03 g of L-ascorbic acid is dissolved in 25 ml of pure water is added to a glass container to swell the water-absorbent composite, sealed and kept at 40 ° C. for 24 hours to decompose the water-absorbent resin. Filter the contents of the glass container through an 80 mesh wire mesh. Thoroughly wash the fibers on the wire mesh. After drying the fibers at 100 ° C. for 5 hours, the weight w ₂ g is precisely weighed. The weight ratio of the water-absorbent resin to the fiber of the water-absorbent composite is calculated as follows.

Weight of water absorbent resin / weight of fiber = (w ₁ −w ₂ ) / w ₂
In the microscopic observation, the water-absorbing composite is composed of one water-absorbing resin particle and 2 to 20 to 30 fibers bonded to the water-absorbing resin particle, and the water-absorbing water is not bonded to the fibers. Resin particles were not found. The average particle diameter of the resin particles of this water-absorbing composite composition was 360 μm. In addition, 100 water-absorbing composites were selected at random from the microphotograph (50 times magnification) of the water-absorbing composites, and the average particle diameter was displayed as an arithmetic average of the long diameters.

  In addition, the measurement of the monomer conversion rate of the droplet in the course of polymerization is performed by receiving the falling droplet in a beaker containing methanol and analyzing the amount of acrylic acid (Mm) eluted in the methanol by liquid chromatography. On the other hand, the polymer in methanol was dried under reduced pressure at 130 ° C. for 3 hours and then weighed to determine the weight (Mp) as an acrylic acid polymer, and the monomer conversion rate was calculated by the following formula.

Monomer conversion (%) = {Mp / (Mp + Mm)} × 100
Further, the water absorption capacity of the physiological saline according to the following measurement method of this water-absorbent composite composition was 45 g / g.

Measurement of saline absorption capacity;
Place 1,000 ml of 0.9 wt% saline in a 2,000 ml beaker. About 1 g (w ₁ g) of the dried water-absorbing composite composition is placed in a 250-mesh nylon bag (10 cm × 20 cm in size), and the whole bag is placed in the above physiological saline and held at room temperature for 30 minutes. Pull up the nylon bag, hold it in the air for 15 minutes, drain it, and then measure its weight w ₂ g.
Further, the same operation on the nylon bag that does not put a water-absorbent composite composition, measuring the weight w ₃ after draining. The physiological saline absorption capacity of the water-absorbing complex is calculated by the following equation.
Saline absorption capacity (g / g) = (w ₂ −w ₃ ) / w ₁

Examples 2 to 4 (Production of water-absorbing composite)
In Example 1, except that the type of fiber supplied to the polymerization tower, the fiber supply ratio to the water-absorbent resin, the monomer conversion rate at the fiber supply position, etc. were changed as shown in Table 1, and Example 1 Similarly, a water-absorbing composite composition was produced. The obtained water-absorbing composite is composed of one water-absorbing resin particle and two to 20 to 30 fibers bonded to the water-absorbing resin particle, and the water-absorbing resin particles to which no fiber is bonded. Was hardly found.

Comparative Example 1 (Production of water-absorbing composite composition)
45.0 g of acrylic acid and 1.5 g of distilled water were put in a 200 ml beaker, and 60.0 g of 25% aqueous sodium hydroxide solution was added to the solution while cooling to 35 ° C. or lower to prepare a partially neutralized aqueous acrylic acid solution. To this was further added 41.9 mg of N, N'-methylenebisacrylamide and 0.31 g of L-ascorbic acid. After completely covering the top surface of a 300 ml stainless steel beaker with a polyester sheet, a rubber tube was inserted into the sheet, and nitrogen gas was fed through the rubber tube to replace the inside of the beaker with nitrogen. The solution prepared previously was put in a beaker, and while being immersed in a hot water bath at 50 ° C., 0.84 g of a 30% hydrogen peroxide solution was added to the solution with stirring to perform polymerization. The temperature of the polymer reached a maximum temperature of 110 ° C. after about 1 minute. After polymerizing for 2 hours, it was cooled to 20 ° C. to obtain a water-containing water-absorbent resin.

  70 g of this water-containing water-absorbing resin, 200 g of water and 15 g of pulp were kneaded for about 2 hours using a screw rotary mixer. The kneaded product was dried with a vacuum dryer at 100 ° C. for 8 hours, and then pulverized with a rotary blade pulverizer. The pulverized product was sieved to remove free fibers to obtain a water-absorbing composite. Under microscopic observation, the fiber was partially embedded in resin particles.

Examples 6 to 15 and Comparative Example 2
The water-absorbing composite compositions obtained in Examples 1 to 5 and Comparative Example 1 were entangled with each other to prepare water-absorbing sheet-like materials. Table 2 shows the thickness, flexibility and restoration rate of this water-absorbent sheet.
Further, this water-absorbent sheet-like material was stacked on a stainless steel plate so as to be 300 g / m ² , consolidated at a pressure of 10 MPa at room temperature for 10 minutes, and then cut into a size of 10 cm × 40 cm.

On a water-impermeable polyethylene sheet (weight per unit area: 18 g / m ² ), tissue (weight per unit area: 14 g)
/ M ² ), fluff pulp (weight per unit area 110 g / m ² ), the above-mentioned compacted water-absorbent sheet, tissue (weight per unit area 14 g / m ² ), and water-permeable polyester fiber nonwoven fabric (weight per unit area 23 g)
/ M ² ) in order. This was sandwiched between stainless plates, left to stand for 20 minutes under a load of 0.4 MPa, and consolidated. After removing the load, the four sides were thermocompression bonded to obtain a water-absorbing article of about 10 cm × 40 cm. Table 2 shows the water-absorbing particle drop-off rate of the water-absorbing article, and the water absorption rate and water discharge amount measured as follows.

Measurement of water absorption rate and water discharge amount;
A water-absorbing article is placed on a smooth table with the water-absorbing surface facing up. A cylinder with an inner diameter of 40 mm is attached to the center of an acrylic plate (10 cm × 10 cm × 1 cm), and seven through holes with a diameter of 5 mm are provided at almost equal intervals in the acrylic plate surrounded by the cylinder. (Total weight 150 g) is placed in the center of the water-absorbent article. A disc (weight: 500 g) having a diameter of 100 mm and a hole having a diameter of 45 mm in the center is inserted into the cylinder and placed on the acrylic plate. 25 ml of artificial urine is put into a cylinder, and the time from when the artificial urine is absorbed until the cylinder becomes empty is measured with a stopwatch to obtain the water absorption speed.

  Ten minutes after placing artificial urine in the cylinder, the acrylic plate on the water-absorbent article is removed, and 20 sheets of filter paper (ADVANTEC NO.424, 100 × 100 mm, manufactured by Toyo Roshi Kaisha, Ltd.) are stacked on the acrylic sheet on the water-absorbent article. Place the plate where it was, and place a load (bottom area 10 cm x 10 cm, weight 4 kg) on it. After 5 minutes, the load is removed, the weight of the filter paper is measured, and the increase in the weight of the filter paper is taken as the water discharge amount. The measurement of the water absorption rate and the water discharge amount is repeated three times and displayed as the average value. Artificial urine having the following composition is used. % Is% by weight.

Urine 1.94%
Sodium chloride 0.80%
Calcium chloride 0.06%
Magnesium sulfate 0.11%
Distilled water 97.09%

It is a figure of the apparatus which measures the thickness of a water absorbing sheet-like material. It is a figure of the apparatus which measures the flexibility of a water absorbing sheet-like material. It is a figure of the nozzle apparatus used in the Example. It is a microscope picture of one example of a water absorbing composite.

Explanation of symbols

11 Adapoo 12 Sample stand 13 Water-absorbent sheet 21 Grip 22 Sample

Claims (25)

  It is formed from substantially spherical water-absorbing resin particles and one or a plurality of fibers bonded to the water-absorbing resin particles and extending to the outside, and can be formed into a sheet by entanglement of the fibers. A water-absorbent composite composition mainly comprising a water-absorbent composite, wherein the water-absorbent composite formed of one water-absorbent resin particle and fiber accounts for 50% by weight or more of the entire water-absorbent composite. A water-absorbing composite composition, wherein the water-absorbing composite formed of four or more water-absorbing resin particles and fibers is 10% by weight or less of the entire water-absorbing composite.   It is formed from substantially spherical water-absorbing resin particles and one or a plurality of fibers bonded to the water-absorbing resin particles and extending to the outside, and can be formed into a sheet by entanglement of the fibers. A water-absorbent composite composition mainly comprising a water-absorbent composite, wherein the water-absorbent composite formed of one water-absorbent resin particle and fiber accounts for 70% by weight or more of the entire water-absorbent composite. A water-absorbing composite composition, wherein the water-absorbing composite formed of four or more water-absorbing resin particles and fibers is 10% by weight or less of the entire water-absorbing composite.   It is formed of substantially spherical water-absorbing resin particles and one or a plurality of fibers bonded to the water-absorbing resin particles and extending to the outside, and can be formed into a sheet by entanglement of the fibers. A water-absorbent composite composition mainly comprising a water-absorbent composite, wherein the water-absorbent composite formed of one water-absorbent resin particle and fiber accounts for 85% by weight or more of the entire water-absorbent composite. A water-absorbing composite composition, wherein the water-absorbing composite formed of four or more water-absorbing resin particles and fibers is 5% by weight or less of the entire water-absorbing composite.   The water-absorbent composite composition according to any one of claims 1 to 3, wherein the water-absorbent resin particles have an average particle size of 50 to 3,000 µm.   The water absorbent composite composition according to any one of claims 1 to 3, wherein the water absorbent resin particles have an average particle diameter of 100 to 1,000 µm.   The water absorbent composite composition according to any one of claims 1 to 3, wherein the water absorbent resin particles have an average particle size of 200 to 800 µm.   The water absorbent composite composition according to any one of claims 1 to 6, wherein the fiber has a length of 100 to 30,000 µm and is at least twice the average particle diameter of the water absorbent resin particles. .   The water-absorbing composite composition according to any one of claims 1 to 6, wherein the fiber has a length of 200 to 10,000 µm and is at least twice the average particle diameter of the water-absorbing resin particles. .   The water-absorbing composite composition according to any one of claims 1 to 6, wherein the fiber has a length of 500 to 5,000 µm and is at least twice the average particle diameter of the water-absorbing resin particles. .   The water-absorbent composite composition according to any one of claims 1 to 9, wherein the weight ratio of the water-absorbent resin particles to the fibers bonded thereto is 1: 1 to 100: 1.   The water-absorbent composite composition according to any one of claims 1 to 9, wherein the weight ratio of the water-absorbent resin particles to the fibers bonded thereto is 2: 1 to 20: 1.   The water-absorbent composite composition according to any one of claims 1 to 11, comprising fibers that are not bonded to the water-absorbent resin particles.   A water-absorbent composite material according to any one of claims 1 to 12, or a water-absorbent composite material or a fiber, and formed into a sheet shape by entanglement of fibers.   14. The water-absorbent sheet-like material according to claim 13, comprising fibers not bonded to the water-absorbent resin particles and having a length of 100 to 30,000 μm.   The water-absorbent sheet-like material according to claim 13, which contains fibers not bonded to the water-absorbent resin particles and has a length of 200 to 10,000 µm.   16. The weight ratio of the water-absorbent resin particles to the fibers (the sum of the fibers bonded to the water-absorbent resin particles and the fibers not bonded) is 1: 1 to 10: 1. The water-absorbent sheet-like material according to any one of the above.   16. The weight ratio of the water-absorbent resin particles to the fibers (the total of fibers bonded to the water-absorbent resin particles and fibers not bonded) is 2: 1 to 9: 1. The water-absorbent sheet-like material according to any one of the above.   A substantially spherical water-absorbent resin particle having an average particle diameter of 100 to 1,000 μm, and one or a plurality of fibers bonded to the water-absorbent resin particle and extending to the outside thereof, the average length thereof A water-absorbing composite composition mainly comprising a water-absorbing composite formed of fibers having a length of 200 to 10,000 μm and a length of at least twice the average particle diameter of the water-absorbing resin particles. The water-absorbent composite formed from one water-absorbent resin particle and fiber accounts for 50% by weight or more of the entire water-absorbent composite, and is formed from four or more water-absorbent resin particles and fiber. A water-absorbing composite composition in which the water-absorbing composite is 10% by weight or less of the entire water-absorbing composite, or a fiber comprising the water-absorbing composite composition and fibers, and not bonded to the water-absorbing resin particles Length of 100-30,000μ The weight ratio of the water-absorbent resin particles and the fibers (the total of the fibers bonded to the water-absorbent resin particles and the fibers not bonded) is 1: 1 to 10: 1, and the sheet is formed by the entanglement of the fibers. A water-absorbent sheet-like material characterized in that it is formed.   A substantially spherical water-absorbing resin particle having an average particle diameter of 200 to 800 μm, and one or a plurality of fibers bonded to the water-absorbing resin particle and extending outward from the water-absorbing resin particle. A water-absorbent composite composition mainly comprising a water-absorbent composite formed of fibers having a length of 500 to 5,000 μm and having a length twice or more the average length of the water-absorbent resin particles, The water-absorbing composite formed from one water-absorbing resin particle and fiber accounts for 85% by weight or more of the entire water-absorbing composite, and is formed from four or more water-absorbing resin particles and fibers. The water-absorbing composite composition having a water-absorbing composite content of 5% by weight or less of the entire water-absorbing composite, or the length of the fiber not composed of the water-absorbing resin particles, comprising the water-absorbing composite composition and fibers. Is 100-30,000 μm The weight ratio of the water-absorbent resin particles to the fibers (the total of the fibers bonded to the water-absorbent resin particles and the fibers not bonded) is 2: 1 to 9: 1, and is formed into a sheet shape by the entanglement of the fibers. A water-absorbent sheet-like material characterized by   The water-absorbent sheet-like material according to any one of claims 13 to 19, wherein the thickness is 0.5 to 10 mm.   The water-absorbent sheet-like material according to any one of claims 13 to 19, wherein the thickness is 1 to 5 mm. The water-absorbent sheet-like material according to any one of claims 13 to 21, wherein a restoration rate calculated by the following formula is 50% or less.
Restoration rate (%) = {(A−B) / A} × 100
(In the formula, A is a water-absorbent sheet material after a load of 100 kg / cm ² was applied to the water-absorbent sheet material for 10 minutes, the load was removed, and the product was stored for 30 days in an atmosphere at a temperature of 25 ° C. and a humidity of 50%. And B is the thickness of the water-absorbent sheet just before the load is removed)   The water-absorbent sheet-like material according to any one of claims 13 to 22, wherein the stiffness according to the heart loop method specified in JISL-1096 is 5.0 to 9.5 cm.   A water absorbent article having a laminated structure, wherein the water absorbent article according to any one of claims 13 to 23 is contained as at least one layer thereof.   At least three layers of a layer made of pulp, paper or nonwoven fabric, a water-absorbent sheet-like material according to any one of claims 13 to 23, and a layer made of pulp, paper or nonwoven fabric are formed on the water-impermeable resin sheet. A water-absorbent article characterized by having a structure laminated in order.

Images