JPH0126736B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an absorbent (meaning absorption and water absorption, sometimes represented by water absorption) material. More specifically, the present invention relates to an absorbent material made of a tufted mass of fiber aggregates holding a water-insoluble resin having high water absorption performance. Recently, resins with high water absorption performance have been applied to disposable products such as sanitary napkins and disposable diapers, and there are signs that they will become widespread. However, since superabsorbent resins are generally in powder form, they are difficult to handle, and their uses and uses are limited. As a method of commercializing this, a method of forming it into a sheet or a fiber has been developed. However, since the water-absorbing resin gels when absorbed, the strength of the sheet is extremely reduced when wet, and it is difficult to maintain the sheet shape, so it cannot be used alone. Furthermore, fibrous materials are too weak and brittle to be called fibers. On the other hand, there is a method of immobilizing such powdered water-absorbing resin in a sandwich structure with a support such as absorbent paper or non-woven fabric, but this method is difficult because the water-absorbing resin is crimped between the supports. However, it has the disadvantage that it reduces the absorbing and swelling power of the water-absorbing resin, making it unable to fully demonstrate its original absorbing power. Furthermore, there is a method of simply mixing a water-absorbent resin with a fiber aggregate such as pulverized pulp, but although this method improves the absorbing power compared to the Sanderch structure, it is not sufficient and also prevents the absorbed liquid from diffusing in the lateral direction. Since the amount is small, the absorption rate is also insufficient. The inventors of the present invention have conducted various studies with the aim of eliminating such drawbacks, fully demonstrating the water absorption function of superabsorbent resin, and providing an easy-to-handle superabsorbent resin-containing absorbent material. The present invention is based on the invention that a specific form of a mixture of a powdered super absorbent resin and a fiber aggregate such as crushed pulp has an extremely high water absorbing power and has the property of instantaneously absorbing water. Reached. That is, the present invention provides a mixture of a uniformly dispersed water-insoluble water-absorbing resin () and fiber aggregates (), the weight of each of which is 0.5 g.
The apparent specific gravity is divided into the following: 0.1g/cm ³
This is an absorbent material characterized by being composed of the above tufted masses. The water-absorbing material of the present invention consists of tufted masses. In the present invention, a tuft-like mass refers to a tuft of curled fibers of different lengths entwined like a strand of hair, and is particularly often seen when the fibers are beaten. Regarding tufts, "Nonwoven Fabric Essentials" (written by Yoshito Miura, published by Kobunshi Publishing Co., Ltd., published on May 15, 1970)
It is described on page 13, and it can be the same as this.
The size of the tufted mass is usually 0.1 to 10 mm, preferably 1
~5mm. Further, the shape of the tufted mass is not particularly limited, and examples include spherical, ellipsoidal, prismatic, and spindle shapes. The water-absorbing material in the present invention is a mixture of a water-insoluble water-absorbing resin () and a fiber aggregate (). In the present invention, the water-insoluble water-absorbent resin () used as one component of the mixture includes a water-soluble monomer and/or a monomer (A) that becomes water-soluble upon hydrolysis, a polysaccharide (B) and Examples include polymers obtained by polymerizing with/or a crosslinking agent (C) as an essential component and hydrolyzing as necessary. (A) Used in the production of water-soluble water absorbent resin ()
The water-soluble monomer has at least one hydrophilic group (for example, a carboxyl group, a carboxylic acid anhydride group,
Carboxylic acid group, sulfonic acid group, sulfonic acid group, hydroxyl group, ether group, amide group, amino group,
Examples include monoethylenically unsaturated monomers having a quaternary ammonium base). Examples of monomers that become water-soluble upon hydrolysis include monomers having at least one hydrolyzable group (ester group, nitrile group, etc.). Among (A), preferred are water-soluble monomers. Preferred water-soluble monomers from the viewpoint of providing high water absorption are monomers containing a carboxyl group, a carboxylic acid anhydride group, a carboxylic acid group,
For example, (meth)acrylic acid, maleic anhydride,
Sodium (meth)acrylate, (meth)acrylic acid trimethylamine acid, (meth)acrylic acid triethanolamine salt; and quaternary ammonium base-containing monomers such as N,N,N-trimethyl-
N-(meth)acryloyloxyethylammonium chloride. Polysaccharides (B) used in the production of water-insoluble water-absorbing resins include starch, cellulose, carrageenan, guar gum, and sodium alginate. Starch includes natural starch and modified starch (pregelatinized starch, oxidized starch, cationized starch, etc.), and cellulose includes cellulose and modified cellulose (carboxymethyl cellulose, carboxymethyl cellulose, etc.) obtained from wood, leaves, stems, gin bark, seed hair, etc. hydroxyethylcellulose, methylcellulose). Among these, preferred are natural starch and pregelatinized starch. The crosslinking agent (C) used in the production of the water-insoluble water-absorbent resin is (1) a compound having at least two polymerizable double bonds (non-conjugated), (2) a compound that reacts with the monomer (A). monoolefin having a functional group capable of reacting with a compound having at least one functional group to be obtained and at least one polymerizable double bond, such as a carboxyl group, a carboxylic acid anhydride group, a hydroxyl group, an amino group or an amide group. (3) A compound having at least two functional groups that can react with the monomer (A), such as a group that can react with a carboxyl group, a carboxylic acid anhydride group, a hydroxyl group, an amino group, or an amide group. (4) polyvalent metal compounds capable of forming ionic crosslinks, such as oxides, hydroxides and weak acid salts (carbonates, acetates, etc.) of alkaline earth metals (calcium, magnesium, etc.) and zinc; can be given. Among the crosslinking agents (C), preferred are alkylene (C ₂ - _{C 6} ) glycols, di(meth)acrylates of polyoxyalkylene (C ₂ -C ₄ ) glycols (molecular weight 400 or less), and alkylene bis(meth) Acrylamide and alkaline earth metal or zinc oxides. (A),
In addition to (B) and (C), monomers that can be copolymerized with these (e.g. styrene, ethylene, propylene, butene)
It is also possible to copolymerize. Details of (A), (B), and (C) used in the production of the above water-absorbing resin, the method for producing the polymer, and specific examples of the water-absorbing resin can be found in JP-A-53-149190.
No., JP-A-51-125468, JP-A-52-25886 and JP-A-52-59690. The water-absorbing resin used in the present invention has a water-absorbing capacity of at least 60 ml/g (preferably 70 ml/g or more,
100 to 500 ml/g) is particularly suitable. The ratio (weight ratio) of polysaccharide (B):monomer (A):crosslinking agent (C) is usually 100:10 to 3000:0.0001 to 20, preferably 100:
50-1000: 0.001-10, more preferably 100:
100-500: 0.01-5. (A), (B) and (C) above
Examples of water-absorbing resins other than those obtained by polymerizing (A) and (B) include hydrolysates of starch-acrylonitrile graft polymers, hydrolysates of cellulose-acrylonitrile graft polymers;
Copolymers with (C) such as polyacrylamide crosslinked with divinyl compounds (such as methylene bisacrylamide) and its partial hydrolysis, crosslinked sulfonated polystyrene, crosslinked poval, JP-A-52-14689 and JP-A-Sho. Examples include saponified crosslinked vinyl ester-unsaturated carboxylic acid copolymers and crosslinked polyethylene oxide described in No. 52-27455. Two or more of these water-absorbing resins may be used in combination. The water-absorbing resin is usually used in the form of powder to granules. The particle size is usually 10 to 300 mesh, preferably 32 to 150 mesh. The fibers in the fiber aggregate used in the present invention include natural fibers such as cotton, wool, jute,
Semi-synthetic fibers such as viscose rayon, acetate, triacetate, etc.; synthetic fibers such as nylon, acrylic, polyester, polypropylene, etc., and mixtures of these fibers. Among these, hydrophilic fibers such as wood pulp, cotton, wool, and viscose rayon are preferable as the absorbent material of the present invention. Also particularly preferred are wood pulp, cotton pulp and viscose rayon. Although the fiber length is not particularly limited, it is usually 0.1 to 50 mm, preferably 0.5 to 10 mm. Examples of the shape of the fiber aggregate include pulp (soft lump), staple, or filament. It may also be in the form of a web, sheet, or mat. In the mixture of water-insoluble resin () and fiber aggregate () in the present invention, the mixing ratio of () and () is usually (): () 100:
1~10000, preferably ():()=100:~
20000. The method of mixing the water-insoluble water-absorbent resin () and the fiber aggregate () in the present invention is not particularly limited as long as the water-insoluble water-absorbent resin is uniformly dispersed and mixed in the fiber aggregate. For example, a method in which a fiber aggregate and a water-absorbing resin are mixed using a machine with a mixing function such as a mixer or a screw rotary mixer; the fiber aggregate absorbs water into water or an organic solvent (methanol, isopropyl alcohol, acetone, etc.). A method of dispersing the water-absorbing resin, stirring, mixing, and then filtering and drying; A method of opening the fiber aggregate using a card machine or the like and mixing it with the water-absorbent resin in an air stream using a jet airflow mill or the like; A method in which a water-absorbing resin is dispersed onto a fiber aggregate in the form of a web, a sheet, or a mat, and the water-absorbing resin is dispersed in the fiber aggregate by suctioning from the bottom of the fiber aggregate; Examples include a method in which a water-absorbing resin is spread on a mat-like fiber aggregate and then opened. When mixing the fiber aggregate () and the water-absorbing resin () using the above method, adding a small amount of water at any stage will cause the surface of the water-absorbing resin to swell and soften, making it strongly adhere to the fibers. Possible and preferable. In the present invention, there is no particular limitation on the method for producing the tufted mass of the mixture of the water-absorbing resin (2) and the fiber aggregate (2). For example, (1) a method in which a mixture of () and () is made into a web, sheet, or mat shape, then compressed with a press and cut into chips; (2)
A method of adding some moisture to a mixture of () and () and stirring at high speed with a mixer (in this case, fibers adhere and aggregate to the water-absorbing resin that has swollen and softened with moisture, forming tuft-like lumps). (3) A method of applying shear stress by placing a mixture of () and () between two belt conveyors with different vertical operating speeds; (4)
Add a mixture of () and () to water or an adhesive (acrylic emulsion, vinegar emulsion, etc.)
An example of this method is to form a sheet using a binder and then spread the sheet non-uniformly. In the present invention, each tuft-like mass of the mixture of the water absorbent resin () and the fiber aggregate () weighs 0.5 g or less, preferably 0.001 to 0.5 g. Apparent specific gravity is 0.1g/ ^cm3 or more, preferably 0.3-2
g/ ^cm3 . If the weight of one piece is more than 0.5g or the apparent specific gravity is less than 0.1g/cm ³ , its absorption power and absorption rate are greatly reduced, and it is not much different from a simple mixture of fiber aggregate and water-absorbing resin. . The tuft-like lumps do not necessarily have to satisfy the above-mentioned weight per unit and apparent specific gravity, and usually only need to contain these as a main component. The absorbent material of the present invention consists of multiple tufts. When using it, the tufts may be used as is in place of conventional absorbent materials (pulverized pulp, absorbent paper, etc.), or the tufts may be formed into a shape, for example, the tufts may be further formed into a sheet. Alternatively, the tufted mass may be further molded into a sandwich shape using a support such as absorbent paper or nonwoven fabric. As a method for further forming the tufted mass into a sheet shape, there is a method of laminating the tufted mass in layers and further fixing the layered product using a needle punch, a press machine, etc. so that the tufted mass does not move. It will be done. In addition, a method for further forming the tufted mass into a sandwich-like shape is to laminate the tufted mass on a support such as absorbent paper or nonwoven fabric, and then layer another support.Then, the resulting laminate is needle-punched. , a method of fixing using a press or the like. The absorbent material of the present invention is suitable for aqueous liquids such as water, urine,
When in contact with blood, emulsion, etc., the fiber components in the tufts absorb aqueous liquid and swell rapidly, and at the same time, the water-absorbing resin in the tufts also absorbs liquid and swells, causing a An unexpected synergistic effect appears. In other words, the absorption rate is significantly higher than that of the fiber aggregate or the water-absorbent resin alone, and the absorption capacity and pressure retention capacity (liquid retention capacity when pressurized after absorption) are also significantly greater than when each is used alone. do. When the absorbent material of the present invention is laminated in sheet form, there are spaces between each tufted mass, so it has cushioning properties and can also create a voluminous feel with a small amount of absorbent material. In addition, because the absorbent material of the present invention has high absorbing power and pressure holding power, less absorbent material is required when it is made into a final product, so the product form can be made smaller, which not only reduces raw material costs but also helps to store the product. It also reduces costs and transportation costs, making it possible to significantly reduce costs. The absorbent material of the present invention can be used for disposable diapers, sanitary napkins,
Suitable for medical pads, etc. In addition, it can be used for various purposes such as industrial water absorption and water retention materials (oil/water separation materials, water absorption materials in solvents, etc.) and soil water retention materials. The present invention will be explained below with reference to Examples. The water absorbent resins (resins) used in the examples are as follows. Resin According to the method of the example of JP-A No. 54-125468,
A white powdery water-insoluble water-absorbing resin produced from corn starch, acrylic acid, sodium acrylate, and N,N'-methylenebisacrylamide. The water absorption amount of this resin is ion exchange water 342
ml/g, 0.9% NaCl 77ml/g, water absorption rate 10ml/g
Less than 1 second at g time, 18.2 seconds at 50ml/g Pressure retention amount 328
It was ml/g. (The measurement method is described in Example 9). Example 1 100 g of flat pulp pulp and 30 g of resin were mixed using a jet air flow mill, and this was dispersed in 2 methanol, and then poured uniformly onto a 1 m ² horizontal wire mesh (100 meshes) and filtered. this
A web-like mixture was obtained by drying with circulating air at 80°C for 3 hours. This mixture was pressurized at 5 kg/cm ² using a press and then cut into square pieces of 3 mm x 3 mm using a cutter to obtain a tufted absorbent material [A]. The average weight of each cluster is 0.024g, and the apparent specific gravity is 0.61g/
It was warm at ^cm3 . Example 2 A tufted block of absorbent material [B] was obtained in the same manner as in Example 1, except that the amount of resin was changed to 10 g. The average weight of each cluster was 0.021 g, and the apparent specific gravity was 0.65 g/cm ³ . Example 3 A tufted block of absorbent material [C] was obtained in the same manner as in Example 1 except that the amount of resin was changed to 20 g.
The average weight of each cluster was 0.023 g, and the apparent specific gravity was 0.66 g/cm ³ . Example 4 In the same manner as in Example 1, 100 g of fluff pulp and 30 g of resin were mixed using a jet jet mill, and this was dispersed in the methanol/water mixed solvent (methanol/water = 8/2 volume ratio) of 2. After
The mixture was poured uniformly onto a 1 m ² horizontal wire mesh (100 meshes), filtered, and dried with circulating air at 80° C. for 3 hours to obtain a web-like mixture. After uniformly spraying 20 g of water onto this mixture, two belt conveyors with a length of 5 m and a width of 50 cm were stacked one on top of the other, and the upper belt conveyor was operated at a speed of 1 m/min and the lower one at a speed of 5 m/min. Then, the water-sprayed mixture was thrown between two conveyors to obtain a tuft-like absorbent material [D]. The average weight of each cluster was 0.27 g, and the apparent specific gravity was 0.14 g/cm ³ . Example 5 A tuft-like absorbent material [E] was obtained in the same manner as in Example 1 except that 100 g of viscose rayon fiber was used instead of the flat pulp. The weight of each tuft is 0.022g, and the apparent specific gravity is
It was 0.61 g/cm ³ . Example 6 A tuft-like absorbent material [F] was obtained in the same manner as in Example 1 except that 100 g of cotton linter pulp was used instead of the flat pulp. Each tufted mass is 0.020g, and the apparent specific gravity is 0.60g/
It was warm at ^cm3 . Example 7 Tuft-like absorbent material [G] was produced in the same manner as in Example 1 except that the pressure of the press was 1 Kg/cm ²
I got it. The weight of each cluster was 0.008 g, and the apparent specific gravity was 0.18 g/cm ³ . Example 8 Absorbent material of the present invention obtained in Example 1 [A] 2.0 g
The mixture was uniformly spread on 100 cm ² of rayon nonwoven fabric weighing 20 g/m ² , and another sheet of rayon nonwoven fabric was layered and the surrounding area was sewn to obtain a sheet-like absorbent material [H]. Example 9 Absorbent materials [A] to [H] obtained in Examples 1 to 8
About water absorption rate, ion exchange water and 0.9%
The saturated water absorption amount of water-soluble NaCl and the amount of pressure retention under a 5 kg load were measured, and the results shown in Table 1 were obtained. In addition, Comparative Example 1 uses flat pulp alone, Comparative Example 2 uses 100 g of flat pulp and resin, 30 g
g and a mixture prepared in the same manner as in Example 1 were also measured. To measure the water absorption rate and saturated water absorption amount, 1 g of each water absorbing material was placed on 100 mesh nodes and administered into water.
25 seconds, 10 seconds, 25 seconds, 50 seconds, 75 seconds, 15 minutes, and 25 minutes later, take it out, leave it on the filter paper for 1 minute, measure the weight to determine the amount of water absorbed (ml/g), and calculate the amount of water absorbed and time. This was done by plotting the relationship and determining each water absorption rate and saturated water absorption amount. The amount of pressure retained is calculated by spreading 1 g of each water-absorbing material evenly on 100 mesh knots of 100 cm ² and placing them in water for 15 minutes, then taking them out and placing them on filter paper.Then, the water-absorbing material is made by swelling an acrylic plate with the same shape as the knots. Place it on top, and place a 5Kg weight on top of it.
It was determined by measuring the weight after 1 minute. 【table】

[Brief explanation of drawings]

FIGS. 1a and 1b are enlarged perspective views of the tufted mass according to the present invention, and FIG. 2 is a perspective view of the tufted mass further formed into a sheet shape. In the figure, 1 is a fiber aggregate, 2
3 indicates a water-absorbing resin, and 3 indicates a tufted mass.

Claims (1)

[Claims] 1 A mixture of a water-insoluble absorbent resin uniformly dispersed between the fibers and a fiber aggregate, where the mixture is divided into many pieces and the curled fibers are entwined in a tuft shape. The tufted lumps each have a weight of 0.001 to 0.5 g and an apparent density specific gravity of 0.1.
g/cm ³ or more, and a weight ratio of the water-absorbing resin to the fiber aggregate is 100:1 to 10.000.