JP2016019673A - Method of manufacturing water absorbing layer, water absorbing layer, and absorbent article comprising the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a water absorbing layer having a water absorbing material fixed by heat-sealable fibers, which can suppress release of an unusual odor from the water absorbing layer, and provide the water absorbing layer that does not release the unusual odor and that is excellent in absorption performance.SOLUTION: A method of manufacturing a water absorbing layer 26 includes the steps of: manufacturing a molding containing a water absorbing material 27 and hot water-soluble fibers 28; and performing heat treatment after imparting water to the molding. The water absorbing layer contains the water absorbing material and the hot water-soluble fibers, and the water absorbing material is fixed by the hot water-soluble fibers.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a water absorbing layer used for absorbent articles such as disposable diapers and sanitary napkins.

  Absorbent articles such as disposable diapers, sanitary napkins, and incontinence pads are designed to absorb and retain bodily fluids such as urine and menstrual blood excreted from the body, and flexible liquid permeation on the side in contact with the body. And a liquid-impermeable back sheet disposed on the side opposite to the side in contact with the body. The said absorber contains water absorbing materials, such as a pulp fiber. The body fluid passes through the surface sheet made of a nonwoven fabric or the like and is absorbed by the absorber. The absorbed body fluid is absorbed and retained by the water absorbent material inside the absorber.

  Here, as the absorbent body, generally, a liquid-permeable sheet wrapped with a water-absorbing material is used. In such an absorbent body, the water-absorbing material contained in the liquid-permeable sheet is not fixed, and the water-absorbing material easily moves and tends to be biased. If the water-absorbing material is biased, some absorbent materials cannot contribute to the absorption of body fluids and the like, and there is a possibility that the original absorption performance cannot be exhibited. Therefore, for example, in Patent Document 1, 5 to 20 wt% of the thermoplastic fibrous material is 5% to 20% by weight of the pulp, and high melting point fiber having a higher melting point than the thermoplastic fibrous material is 5 to 20% of the pulp. There has been proposed an absorbent body which is mixed by weight and heat-molded at a temperature at which the thermoplastic fibrous material is fused.

  Patent Document 2 discloses a liquid-retaining absorbent comprising pulp fibers and a water-absorbing polymer as main components and containing the pulp fibers and other fibers or flakes. However, the absorption which stabilizes the shape of the said absorption layer by expressing adhesiveness between this another fiber or thin piece or between this another fiber or thin piece, and another structural member by contact with a water | moisture content The body has been proposed.

JP-A-6-105867 JP 10-235190 A

  In the absorbent body as described in Patent Document 1, a hydrophobic resin such as polyethylene or polypropylene is used as a raw material for the thermoplastic fibrous material. Therefore, absorption of body fluids and the like by the water-absorbing material is hindered by these hydrophobic fibers, and the absorption performance is lowered. Moreover, when heat-treating the pulp with the thermoplastic fibrous material, heat treatment is performed. The heat treatment may burn the pulp, or a strange odor (burnt odor) may be generated from the obtained absorbent body. On the other hand, in the absorber as described in Patent Document 2, since the heat treatment is not performed, generation of a bad odor from the absorber can be prevented. However, since the absorbent material is not fixed, there is a problem in that the water absorbent material is biased inside the absorbent body before absorption of body fluid, and sufficient absorbent performance cannot be exhibited.

  The present invention has been made in view of the above circumstances, and is a method for manufacturing a water-absorbing layer in which a water-absorbing material is fixed by heat-fusible fibers, and provides a manufacturing method capable of suppressing the odor of the water-absorbing layer. With the goal. Another object of the present invention is to provide a water-absorbing layer that does not have a strange odor and has excellent absorption performance.

  The method for producing a water-absorbing layer of the present invention includes a step of producing a molded body containing a water-absorbing material and hot water-soluble fibers, and a step of heat-treating the molded body after water is applied thereto. Features. The hot water-soluble fiber has a lower melting point when it comes into contact with water. Therefore, the water-absorbing material can be fixed by heat treatment at a low temperature for a short time by heat-treating the molded article containing the hot water-soluble fiber with water. Therefore, it can suppress that a water absorbing material (pulp etc.) burns at the time of heat processing, or a strange odor (burnt smell) generate | occur | produces from the obtained water absorption layer.

  It is preferable that the usage-amount of the said hot water soluble fiber is 0.01 mass part-20 mass parts with respect to 100 mass parts of said water absorbing materials. The conditions for the heat treatment are preferably that the temperature of the compact is 54 ° C. to 121 ° C. and the heating time is 0.1 second to 60 seconds. The amount of water applied is preferably 5 parts by mass to 150 parts by mass with respect to 100 parts by mass of the molded body. The melting temperature of the hot water-soluble fiber in water is preferably 40 ° C to 80 ° C. The hot water-soluble fiber is preferably a partially saponified polyvinyl alcohol fiber having a saponification degree of 65% to 97%.

  The water-absorbing layer of the present invention contains a water-absorbing material and hot water-soluble fibers, and the water-absorbing material is fixed by the hot water-soluble fibers. By using the hot water-soluble fiber, the water-absorbing material can be fixed by a heat treatment at a low temperature for a short time, so that deterioration of the water-absorbing material can be suppressed. Moreover, since the hot water-soluble fiber is hydrophilic, the water absorption of the water absorbing material is not hindered, and the absorption performance of the water absorbing layer is improved.

The melting temperature of the hot water-soluble fiber in water is preferably 40 ° C to 80 ° C. The hot water-soluble fiber is preferably a partially saponified polyvinyl alcohol fiber having a saponification degree of 65% to 97%. The sum of the basis weight of basis weight and the water absorbent material of the hot water soluble ^{fibers, 50g / m 2 ~300g / m} 2 is preferred. The water absorbing material preferably contains a water absorbing polymer.

  The present invention includes an absorbent body having the water absorbing layer and an absorbent article having the water absorbing layer.

  According to the method for producing a water-absorbing layer of the present invention, when the water-absorbing material is fixed by the heat-fusible fiber, it is possible to suppress the generation of a strange odor in the water-absorbing layer. Moreover, the water absorption layer of this invention does not have a strange odor, and is excellent in absorption performance.

The top view (development figure) of an example of the absorbent article of this invention. The typical sectional view of the II line of Drawing 1. FIG. 2 is a schematic cross-sectional view taken along line II-II in FIG. 1. The typical sectional view of another example of the absorptive article of the present invention.

  The method for producing a water-absorbing layer of the present invention includes a step of producing a molded body containing a water-absorbing material and hot water-soluble fibers, and a step of heat-treating the molded body after imparting water.

  The process for producing the molded body will be described. The method for producing the molded body is not particularly limited, and a conventional method for producing a water-absorbing layer can be employed. For example, a method of mixing a water-absorbing material and hot water-soluble fiber, dispersing the mixture in air, and depositing it on a screen (airlaid method); including a water-absorbing material and hot water-soluble fiber Examples include a method of preparing a dispersion and scraping this dispersion on a screen (wet method). What is necessary is just to adjust suitably the shape of a molded object according to the shape of the desired water absorption layer, for example, a mat form, a sheet form, etc. are mentioned.

  The hot water-soluble fiber has a solubility in water of 40 ° C or higher, preferably 50 ° C or higher, more preferably 55 ° C or higher, preferably 80 ° C or lower, more preferably 78 ° C or lower, Preferably it is 75 degrees C or less. If the dissolution temperature in water is 40 ° C. or higher, dissolution by the body temperature or body fluid of the wearer is suppressed, and if it is 80 ° C. or lower, the amount of heat at the time of molding processing is suppressed and other materials constituting the absorber are burnt. Can be fixed while preventing.

  The melting point of the hot water-soluble fiber (in a state where water is not applied) is preferably 130 ° C. or higher, more preferably 145 ° C. or higher, further preferably 150 ° C. or higher, preferably 250 ° C. or lower, more preferably 240 ° C. Below, it is 230 degrees C or less more preferably. If the melting point is 130 ° C. or higher, the degree of swelling in water is improved and the strength is increased and the function as a binder is improved. If the melting point is 250 ° C. or lower, the decrease in the degree of swelling with respect to water can be suppressed. In addition, melting | fusing point of a hot water soluble fiber can be measured with a differential scanning calorimeter (DSC).

  Examples of the hot water-soluble fiber include polyvinyl alcohol fiber, polyvinyl pyrrolidone fiber, carboxymethyl cellulose fiber, carboxyethyl cellulose fiber, and ethylene vinyl alcohol fiber, and polyvinyl alcohol fiber is preferable. Examples of the polyvinyl alcohol resin constituting the polyvinyl alcohol fiber include a saponified vinyl acetate homopolymer and a saponified copolymer of vinyl acetate and other monomers. When other monomers are used, the content of other monomers in the copolymer is preferably 10 mol% or less. Examples of the other monomer include ethylene, propylene, butadiene, (meth) acrylic acid, (meth) acrylic acid ester, and the like.

  The saponification degree of the polyvinyl alcohol fiber is preferably 65% or more, more preferably 70% or more, further preferably 75% or more, particularly preferably 77% or more, and preferably 97% or less, more preferably 96%. Hereinafter, it is more preferably 95% or less. If the degree of saponification is 70% or more, the polyvinyl alcohol fiber is less likely to become lumpy when water is applied to the molded product, and if it is 97% or less, the surface of the polyvinyl alcohol fiber becomes appropriately hydrophilic, Absorption performance is better. The saponification degree of the polyvinyl alcohol fiber can be measured based on JIS K6726 (1994).

  The average degree of polymerization of the polyvinyl alcohol fiber is preferably 50 or more, more preferably 80 or more, further preferably 100 or more, preferably 4000 or less, more preferably 3000 or less, and still more preferably 2000 or less. If average polymerization degree is 50-4000, adhesiveness, stability, and hot water solubility will become favorable. The average degree of polymerization of the polyvinyl alcohol fiber can be measured based on JIS K6726 (1994).

  The fiber length of the hot water-soluble fiber is preferably 2 mm or more, more preferably 2.1 mm or more, further preferably 2.2 mm or more, preferably 7 mm or less, more preferably 6.8 mm or less, and still more preferably. 6.5 mm or less. When the fiber length is 2 mm or more, the hot water-soluble fiber can be prevented from scattering when the hot water-soluble fiber and the water-absorbing material are mixed or when a molded body is produced. When mixing with a material, it can mix more uniformly.

  The fineness of the hot water-soluble fiber is preferably 0.1 dtex or more, more preferably 0.3 dtex or more, further preferably 0.4 dtex or more, preferably 20 dtex or less, more preferably 18 dtex or less, still more preferably 16 dtex or less. It is. If the fineness of the hot water-soluble fiber is 0.1 dtex or more, the strength as a binder is improved, and if it is 20 dtex or less, the miscibility with other fibers constituting the absorber such as pulp becomes good.

  The amount of the hot water-soluble fiber used is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and further preferably 0.5 parts by mass or more with respect to 100 parts by mass of the water-absorbing material. Yes, 20 parts by mass or less is preferable, more preferably 17 parts by mass or less, and still more preferably 15 parts by mass or less. If the usage-amount of the said hot water soluble fiber is 0.1 mass part-20 mass parts, the adhesive strength and texture as a binder will become favorable.

  Examples of the water absorbent material include water absorbent fibers and water absorbent resin powder. Examples of the water absorbent fiber include pulp fiber, cellulose fiber, rayon, and acetate fiber. As the water absorbent resin powder, those conventionally used for absorbent articles can be used. The water absorbent resin powder may contain additives such as antibacterial agents, antioxidants, ultraviolet absorbers, colorants, fragrances, deodorants, inorganic powders, and organic fibrous materials.

  The water-absorbing material preferably contains pulp fibers as water-absorbing fibers. The content of the pulp fiber in the absorbent material is preferably 40% by mass or more, more preferably 50% by mass or more, still more preferably 60% by mass or more, and preferably 95% by mass or less, more preferably 90% by mass. Hereinafter, it is more preferably 80% by mass or less.

  The molded body may contain a fiber base material in addition to the hot water-soluble fiber. Examples of the fiber base include polyester, acrylic, acrylic (vinyl chloride or vinylidene chloride copolymer), nylon, vinylon, polypropylene, polyvinyl chloride, polyethylene, vinylidene, polyurethane, aramid, polyarylate, polyparaphenylene. Synthetic fibers such as benzoxazole (PBO), acrylates, and polylactic acid; regenerated fibers such as rayon polynosic and cupra; semi-synthetic fibers such as acetate, triacetate, and promix; glass fibers, metal fibers, carbon Inorganic fibers such as fibers; natural fibers such as wool, cotton and hemp. The content of the other fiber base material in the molded body is preferably 50% by mass or less, more preferably 40% by mass or less, and still more preferably 30% by mass or less.

  The process of heat-treating the molded body will be described. In the present invention, it is important to perform heat treatment after imparting water to the compact. When the hot water-soluble fiber comes into contact with water, the melting point decreases. Therefore, by applying water to the molded body, the hot water-soluble fiber and the water-absorbing material can be fixed by a lower temperature heat treatment. Moreover, it can suppress more that a water absorbing material burns by providing water to a molded object.

  A method for applying water to the molded body is not particularly limited, but a method of spraying water from above the molded body is suitable. Examples of spraying water include showers and mists. In addition, when a molded object is produced by a wet method, since the obtained molded object contains water, the process of providing water may be omitted.

  The amount of water applied is preferably 5 parts by mass or more, more preferably 20 parts by mass or more, still more preferably 50 parts by mass or more, and more preferably 150 parts by mass or less, more preferably 100 parts by mass. 100 parts by mass or less, more preferably 70 parts by mass or less. If the application amount of water is 5 parts by mass or more, the melting point of the hot water-soluble fiber is sufficiently lowered and the adhesiveness is improved, and if it is 150 parts by mass or less, a decrease in drying efficiency can be suppressed. Moreover, it is preferable that the moisture content of the hot water-soluble fiber after water provision is 5%-70%.

  The method for heat-treating the molded body is not particularly limited as long as the water-absorbing material can be fixed by the hot water-soluble fiber. Examples of the heat treatment method include a method of sandwiching the molded body with a heated plate or roller, a method of blowing hot air on the molded body, a method of heating the molded body in a heating furnace, and the like. Among these, the method of spraying hot air on the molded body is preferable.

  In the heat treatment, the temperature of the molded body is preferably 54 ° C. or higher, more preferably 60 ° C. or higher, further preferably 65 ° C. or higher, 121 ° C. or lower, more preferably 116 ° C. or lower, more preferably 104 ° C. or lower. Most preferably, it is 99 ° C. or lower. If the temperature of the molded body is 54 ° C. to 121 ° C., the binder effect can be exhibited and molded without scorching the absorber. The temperature of the molded body is a temperature measured by a temperature measurement label (manufactured by Micron, heat label).

  In the heat treatment, the heating time is preferably 0.1 second to 60 seconds, and preferably 0.1 seconds to 15 seconds. When the heating time is 0.1 second to 60 seconds, the binder effect can be obtained while preventing the burn of the absorber. The heating time is a time for blowing hot air and a time for sandwiching between heated plates or rollers.

  By performing the heat treatment, a water-absorbing layer in which a water-absorbing material is fixed by hot water-soluble fibers can be obtained. The water-absorbing layer obtained by the above production method can fix the water-absorbing material by a heat treatment at a low temperature for a short time, so that the pulp is burnt during the heat treatment or a strange odor (burnt odor) is generated from the obtained water-absorbing layer It is suppressed. The obtained water absorption layer may be used as it is or may be cut into a desired shape.

  The thickness of the water absorbing layer is preferably 0.5 mm or more, more preferably 0.7 mm or more, further preferably 1.0 mm or more, preferably 10 mm or less, more preferably 7 mm or less, and further preferably 5 mm or less. is there. In particular, the production method of the present invention is useful for producing a water absorption layer having a thickness of 5 mm or less. A water-absorbing layer having a thickness of 0.5 mm or less easily generates a bad odor when heat-treated at a high temperature. However, by adopting the production method of the present invention, it is possible to suppress the occurrence of such a thin odor.

  Next, the water absorption layer of the present invention will be described. The water-absorbing layer of the present invention contains a water-absorbing material and hot water-soluble fibers, and the water-absorbing material is fixed by the hot water-soluble fibers. By using the hot water-soluble fiber, the water-absorbing material can be fixed by a heat treatment at a low temperature for a short time, so that deterioration of the water-absorbing material can be suppressed. Moreover, since the hot water-soluble fiber is hydrophilic, the water absorption of the water absorbing material is not hindered, and the absorption performance of the water absorbing layer is improved.

The total of the basis weight of the hot water-soluble fiber and the basis weight of the water-absorbing material is preferably 50 g / m ² or more, more preferably 70 g / m ² or more, further preferably 100 g / m ² or more, and 300 g / m ^2. m ² or less is preferable, more preferably 280 g / m ² or less, and still more preferably 250 g / m ² or less. Total balance of absorber strength and absorption performance if ^50g / ^{m 2 ~300g} / m 2 basis weight is easily adjusted.

Basis weight of the water-absorbing material is preferably from 15 g / ^{m 2} or more, more preferably 30 g / ^{m 2} or more, more preferably 40 g / ^{m 2} or more, preferably 300 g / ^{m 2} or less, more preferably 250 g / m ² or less, more preferably 220 g / m ² or less. Intensity of the absorption performance and the absorber if the basis weight is in ^{15g / m 2 ~300g / m 2} , the balance of the texture is easily adjusted.

  The absorbent body of the present invention is characterized in that it comprises a water-absorbing layer or a water-absorbing layer obtained by the method for producing a water-absorbing layer and fixed with hot water-soluble fibers.

  The absorbent body of the present invention includes, for example, a structure in which the water-absorbing layer is wrapped with a liquid-permeable sheet; a liquid-permeable first sheet and a second sheet, and the first sheet and the second sheet The thing in which the said water absorption layer is arrange | positioned between is mentioned.

  As said liquid-permeable sheet | seat, the nonwoven fabric formed with the hydrophilic fiber is mentioned, for example. Examples of such a nonwoven fabric include a point bond nonwoven fabric, an air-through nonwoven fabric, a spunlace nonwoven fabric, a spunbond nonwoven fabric, and an airlaid nonwoven fabric. Examples of the hydrophilic fiber include cellulose, rayon, and cotton. In addition, as the liquid-permeable sheet, a liquid-permeable nonwoven fabric formed of hydrophobic fibers (for example, polypropylene, polyethylene, polyester, polyamide, nylon) whose surface is hydrophilized with a surfactant may be used. .

  The said 1st sheet | seat is a sheet | seat of the side contact | abutted on a skin surface, and permeate | transmits the water | moisture content of the bodily fluid from a wearer rapidly. The liquid permeable sheet can be used as the liquid permeable first sheet. The second sheet may be either a liquid-permeable sheet or a liquid-impermeable sheet depending on how the water-absorbing layer is used. As the liquid-impervious sheet, a water-repellent or liquid-impervious non-woven fabric (for example, spunbond non-woven fabric, melt blown non-woven fabric, SMS (formed of polypropylene, polyethylene, polyester, polyamide, nylon)) Spunbond, meltblown, and spunbond nonwoven fabrics) and water-repellent or liquid-impervious plastic films are used, and the moisture of the excreta that reaches the liquid-impervious sheet oozes out of the water-absorbing layer. To prevent. When a plastic film is used for the liquid-impermeable sheet, it is preferable to use a plastic film having moisture permeability (breathability) from the viewpoint of preventing stuffiness and improving wearer's comfort.

  The present invention includes an absorbent article including the water absorbing layer of the present invention. Specific examples of the absorbent article include absorbent articles that absorb a wearer's body fluid, such as disposable diapers, sanitary napkins, incontinence pads, and breast milk pads.

  Hereinafter, although the absorbent article of this invention is demonstrated referring drawings, this invention is not limited to the aspect shown by drawing.

  1 is a plan view (development view) of an example of the absorbent article of the present invention, FIG. 2 is a schematic cross-sectional view taken along line II in FIG. 1, and FIG. 3 is a schematic cross-sectional view taken along line II-II in FIG. FIG. 4 is a schematic cross-sectional view of another example of the absorbent article of the present invention. 1-4, the arrow A shows the length direction of an absorbent article, the arrow B shows the width direction of an absorbent article, the upper side of the C direction of a paper surface is a skin surface side, and the lower side is an outer surface side.

  In FIG. 1, an example of the underpants type disposable diaper (absorbent article) of this invention was shown (development figure). The pants-type disposable diaper 1 has a front part 2 and a back part 3 in the length direction A, and has a crotch part 4 between the front part 2 and the back part 3. The front abdomen 2 is in contact with the wearer's abdomen, and the back part 3 is in contact with the wearer's buttocks. The crotch part 4 is provided with a notch 5 along the circumference of the wearer's leg. In the pants-type disposable diaper 1 of FIG. 1, the side edge 2a of the front part 2 and the side edge 3a of the back part 3 are joined, and it becomes the pants-type disposable diaper 1 which has a waist opening part and a pair of leg opening part.

  The pants-type disposable diaper 1 has an absorbent main body 20 attached to the skin surface side of the exterior sheet material 6. The absorbent main body 20 extends along the length direction A from the center of the crotch portion 4.

  A front waist elastic member 8 and a rear waist elastic member 9 are attached to the pants-type disposable diaper 1 along the edge 7 of the exterior sheet material 6 in a state of being stretched in the width direction B. Further, along the notch 5, the front leg elastic member 10 and the rear leg elastic member 11 are attached in an extended state. A state where the front waistline elastic member 12 and the back waistline elastic member 13 are extended in the width direction B between the waist elastic member and the leg elastic member in each of the front abdominal part 2 and the back back part 3. It is attached with. The pants-type disposable diaper 1 fits the wearer by contraction of each elastic member.

  FIG. 2 is a diagram schematically illustrating a cross section taken along line II of the pant-type disposable diaper of FIG. With reference to FIG. 2, the structure of the underpants type disposable diaper 1 is demonstrated. The exterior sheet material 6 includes an outer sheet 6a and an inner sheet 6b, and elastic members 8 and 9 for the waist, elastic members 10 and 11 for the legs, and elastic members 12 and 13 for the waistline are stretched between the two sheets. It is attached with. The outer sheet 6a is longer in the length direction than the inner sheet 6b, and is folded back to the inner surface side (skin surface side) at the end edge 7 to form a folded portion 14. In FIG. 2, the right side in the C direction is the outer surface side, and the left side is the inner surface side (skin surface side).

  An absorbent main body 20 is attached to the skin surface side of the exterior sheet material 6. The absorbent main body 20 includes an absorbent body 21, a top sheet 22 made of a nonwoven material disposed on the skin surface side of the absorbent body 21, and a liquid-impermeable back sheet 23 provided on the outer surface side of the absorbent body 21. And have. The said absorber 21 has the 1st sheet | seat 24, the 2nd sheet | seat 25, and the water absorption layer 26 arrange | positioned among these. The water absorbing layer 26 contains a water absorbing material 27 and hot water soluble fibers 28. In the pants-type disposable diaper 1, a front end press sheet 15 and a rear end press sheet 16 are provided so as to cover the lengthwise ends of the absorbent main body 20 at the front abdomen 2 and the back part 3 of the inner surface of the inner sheet 6 b. ing.

  FIG. 3 is a diagram schematically illustrating a cross section taken along line II-II of the pants-type disposable diaper of FIG. As shown in FIG. 3, a side sheet 17 made of a non-woven material is joined to the top of both side edges in the width direction of the top sheet 22 made of a non-woven material. The side seat 17 forms a rising flap that stands up toward the wearer's skin by the contraction force of the elastic member 18 attached in a stretched state in the length direction, and serves as a barrier that prevents lateral leakage of urine and the like. . In FIG. 3, the upper side in the C direction is the skin surface side, and the lower side is the outer surface side.

  FIG. 4 is a schematic cross-sectional view illustrating another preferred embodiment of the disposable diaper 1. The pants-type disposable diaper 1 includes a liquid-permeable top sheet 22, a liquid-impervious back sheet 23, and an absorbent body 21 between the liquid-permeable top sheet 22 and the liquid-impervious back sheet 23. Have. A liquid-impervious side sheet 17 is joined to upper portions of both side edges of the liquid-permeable top sheet 22. The side sheet 17 inward from the joining point 19 forms a rising flap that rises toward the wearer's skin. The side sheet outside the joining point 19 extends outward from the side edge of the absorber 21 and is joined to the back sheet 23. The surface sheet material includes a liquid-permeable top sheet 22 and a liquid-impermeable side sheet 17. The exterior sheet material includes a liquid-impermeable back sheet 23. 2 to 4, the same components as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.

  Hereinafter, the present invention will be described in detail by way of examples. However, the present invention is not limited to the following examples, and all modifications and embodiments without departing from the gist of the present invention are not limited thereto. Included in range.

[Evaluation method]
Dissolution temperature of hot water-soluble fiber in water One end of the hot water-soluble fiber (length: 4 cm) was fixed to a jig, and a weight was suspended from the other end. The weight of the weight was adjusted according to the fineness, and was 2 mg per dtex. The entire hot water-soluble fiber was immersed in water (0 ° C.), the water temperature was raised (temperature increase rate: 2 ° C./min), and the water temperature when the fiber was melted was measured.

Unusual odor test The water absorbing layer was cut into a size of 100 mm x 100 mm, put in a polyethylene bag, and subjected to a sensory test. The case where there was no burnt odor was evaluated as “◯”, and the case where there was a burnt odor was evaluated as “x”.

Shape stability test A compression board was installed on the base of a tensile testing machine (manufactured by A & D, “TENSILON RTG-1210”), and a compression pressure plate was attached to the load cell. A water absorption layer (100 mm × 100 mm) was placed on the compression plate, and a cylindrical jig (inner diameter 25 mm) was placed thereon. Furthermore, a cylindrical jig (15 mm in diameter) is placed on the center of the hole of the cylindrical jig on the water absorption layer, and this cylindrical jig is pushed in by a compression pressure plate (100 mm / min), and the cylindrical jig penetrates the water absorption layer. The load at the time was measured. The case where the measured load was 0.4 N or more was evaluated as “◯”, the case where it was less than 0.4 N, the case where it was 0.3 N or more was evaluated as “Δ”, and the case where it was less than 0.3 N was evaluated as “X”.

Absorbability test A measuring jig (acrylic, cylindrical shape (inner diameter: 15 mm)) was installed at the center of the absorber. 10 ml of physiological saline (concentration: 0.9% by mass) was dropped into the measurement jig, and the absorption time (time from the start of dropping until the physiological saline was completely absorbed by the absorber) was measured (1 Second time). Ten minutes after the start of the first measurement (start of dropping of physiological saline), 10 ml of physiological saline was dropped into the measurement jig, and the absorption time was measured (second time). 20 minutes after the start of the first measurement, 10 ml of physiological saline was dropped into the measurement jig, and the absorption time was measured (third time). For each absorption time, the case of less than 3 seconds was evaluated as “◯”, the case of 3 seconds or more and less than 5 seconds was evaluated as “Δ”, and the case of 5 seconds or more was evaluated as “X”.

[Manufacture of water absorption layer]
Production Example 1
100 parts by mass of pulp fibers as a water-absorbing material and partially saponified polyvinyl alcohol fibers (saponification degree 65%, fiber length 3 mm, fineness 1.1 dtex) (hot water-soluble fibers) 0.005 parts by mass as binder fibers Were mixed. The obtained mixture was directly sprayed onto the transfer conveyor with a basis weight of 100 g / m ² by the air array method, and brought into close contact with the transfer conveyor by a suction force by a blower to obtain a molded body. After spraying water (10 parts by mass with respect to 100 parts by mass of the molded body) to this molded body, hot air (120 ° C.) is blown for 10 seconds to perform heat treatment so that the temperature of the molded body becomes 90 ° C. Was made.

Production Examples 2-12
Water-absorbing layers 2 to 12 were produced in the same manner as in Production Example 1 except that the type of hot water-soluble fiber or the amount added was changed as shown in Table 1.

Production Example 13
100 parts by mass of pulp fibers as a water-absorbing material and 0.05 parts by mass of polyethylene fibers (fiber length 3 mm, fineness 1.2 dtex) as binder fibers were mixed. The obtained mixture was directly sprayed onto the transfer conveyor with a basis weight of 100 g / m ² by the air array method, and brought into close contact with the transfer conveyor by a suction force by a blower to obtain a molded body. Hot air (220 ° C.) was blown onto the molded body for 10 seconds, and heat treatment was performed so that the temperature of the molded body became 150 ° C., and a water absorbing layer 13 was produced.

Production Example 14
A water absorbing layer 14 was produced in the same manner as in Production Example 13 except that the amount of polyethylene fiber added was changed to 20 parts by mass.

Production Example 15
100 parts by mass of pulp fibers as a water absorbing material and 0.05 parts by mass of polypropylene fibers (fiber length 3 mm, fineness 1.2 dtex) as binder fibers were mixed. The obtained mixture was directly sprayed onto the transfer conveyor with a basis weight of 100 g / m ² by the air array method, and brought into close contact with the transfer conveyor by a suction force by a blower to obtain a molded body. Hot air (260 ° C.) was blown onto the molded body for 10 seconds, and heat treatment was performed so that the temperature of the molded body became 190 ° C., thereby producing the water absorbing layer 15.

Production Example 16
A water absorbing layer 16 was produced in the same manner as in Production Example 15 except that the amount of polypropylene fiber added was changed to 20 parts by mass.

Production Example 17
The pulp fibers were directly sprayed on the transfer conveyor with a basis weight of 100 g / m ² by the air lay method, and brought into close contact with the transfer conveyor by the suction force of the blower to obtain the water absorption layer 17.

Production Example 18
Mixing 100 parts by mass of pulp fiber as a water-absorbing material and 20 parts by mass of partially saponified polyvinyl alcohol fiber (saponification degree 65%, fiber length 3 mm, fineness 1.1 dtex) (hot water-soluble fiber) as binder fiber did. The obtained mixture was directly sprayed onto the transfer conveyor with a basis weight of 100 g / m ² by the air array method, and brought into close contact with the transfer conveyor by a suction force by a blower to obtain a molded body. Hot air (120 ° C.) was blown onto the molded body for 10 seconds, and heat treatment was performed so that the temperature of the molded body became 90 ° C., and the water absorption layer 18 was produced.

Production Example 19
Mixing 100 parts by mass of pulp fiber as a water-absorbing material and 20 parts by mass of partially saponified polyvinyl alcohol fiber (saponification degree 97%, fiber length 3 mm, fineness 1.1 dtex) (hot water-soluble fiber) as binder fiber did. The obtained mixture was directly sprayed onto the transfer conveyor with a basis weight of 100 g / m ² by the air array method, and brought into close contact with the transfer conveyor by a suction force by a blower to obtain a molded body. Hot air (120 ° C.) was blown onto the molded body for 10 seconds, and heat treatment was performed so that the temperature of the molded body became 90 ° C., thereby producing a water absorbing layer 19.

Production Example 20
A water absorbing layer 20 was produced in the same manner as in Production Example 19 except that the binder fiber was changed to a completely saponified polyvinyl alcohol fiber (saponification degree 100%, fiber length 3 mm, fineness 1.1 dtex).

  The evaluation results of the water absorption layer obtained are shown in Table 1.

  In Production Examples 1 to 9, water is applied to a molded body containing a water-absorbing material and hot water-soluble fibers, and then heat treatment is performed. The water absorption layers obtained in Production Examples 1 to 9 are excellent in shape stability and have no burning odor. Production Examples 10 to 12 are cases where completely saponified polyvinyl alcohol fiber was used as the binder fiber. The water absorption layers obtained in Production Examples 10 to 12 are inferior in shape stability to the water absorption layers. Production Examples 13 to 16 are cases where heat-fusible binder fibers were used. The water-absorbing layers obtained in Production Examples 13 to 16 had a burning odor because it was necessary to increase the molding temperature. Production Example 17 is a case where no binder fiber is used, but the obtained water-absorbing layer is inferior in shape stability. In Production Examples 18 to 20, a molded body containing a water-absorbing material and partially saponified polyvinyl alcohol or completely saponified polyvinyl alcohol fiber is heat-treated without imparting water. The water absorption layers obtained in Production Examples 18 to 20 are inferior in shape stability because the binder fiber does not dissolve at the molded body temperature (90 ° C.).

[Manufacture of absorber]
Production Example 21
100 parts by mass of pulp fiber as a water absorbing material and 0.1 part by mass of partially saponified polyvinyl alcohol fiber (saponification degree 97%, fiber length 3 mm, fineness 1.1 dtex) as binder fiber (hot water-soluble fiber) Were mixed. The obtained mixture was directly sprayed onto the transfer conveyor with a basis weight of 45 g / m ² by the air lay method, and brought into close contact with the transfer conveyor by a suction force by a blower to obtain a molded body. After spraying 10 parts by mass of water with respect to 100 parts by mass of the molded body, hot air (120 ° C.) was sprayed for 10 seconds, and heat treatment was performed so that the temperature of the molded body was 90 ° C., whereby a water absorbing layer 21 was obtained. The absorbent sheet 1 was prepared by laminating a waterproof sheet, tissue paper, a water absorbent layer 21, a highly water absorbent resin (100 g / m ² ), a water absorbent layer 21, a tissue paper, and a liquid permeable sheet in this order.

Production Examples 22 and 23
Water-absorbing layers 22 and 23 were produced in the same manner as in Production Example 21 except that the addition amount of the binder fiber was changed as shown in Table 2. Using these water-absorbing layers 22 and 23, absorbers 2 and 3 were produced in the same manner as in Production Example 21.

Production Example 24
100 parts by mass of pulp fibers as a water absorbing material and 20 parts by mass of polyethylene fibers (fiber length 3 mm, fineness 1.2 dtex) as binder fibers were mixed. The obtained mixture was directly sprayed onto the transfer conveyor with a basis weight of 45 g / m ² by the air lay method, and brought into close contact with the transfer conveyor by a suction force by a blower to obtain a molded body. Hot air (220 ° C.) was blown onto the molded body for 10 seconds, and heat treatment was performed so that the temperature of the molded body became 150 ° C., and a water absorbing layer 24 was obtained. The absorbent sheet 4 was obtained by laminating the waterproof sheet, tissue paper, water-absorbing layer 24, superabsorbent resin (100 g / m ² ), water-absorbing layer 24, tissue paper, and liquid-permeable sheet in this order.

Production Example 25
100 parts by mass of pulp fibers as a water-absorbing material and 20 parts by mass of polypropylene fibers (fiber length 3 mm, fineness 1.2 dtex) were mixed as binder fibers. The obtained mixture was directly sprayed onto the transfer conveyor with a basis weight of 45 g / m ² by the air lay method, and brought into close contact with the transfer conveyor by a suction force by a blower to obtain a molded body. Hot air (260 ° C.) was blown onto the molded body for 10 seconds, and heat treatment was performed so that the temperature of the molded body was 190 ° C., whereby a water absorbing layer 25 was obtained. The absorbent body 5 was obtained by laminating a waterproof sheet, tissue paper, a water absorbent layer 25, a highly water absorbent resin (100 g / m ² ), a water absorbent layer 25, a tissue paper, and a liquid permeable sheet in this order.

  When the absorbers 1 to 3 are compared, the absorption performance tends to decrease as the amount of the binder fiber added increases. Comparing the absorbent bodies 2, 4 and 5, those using hot water-soluble fibers (partially saponified polyvinyl alcohol fibers) rather than those using heat-fusible fibers (polyethylene fibers, polypropylene fibers) as binder fibers The absorption performance is higher.

  According to the method for producing a water-absorbing layer of the present invention, when the water-absorbing material is fixed by the heat-fusible fiber, it is possible to suppress the generation of a strange odor in the water-absorbing layer. In addition, the water-absorbing layer of the present invention does not produce a strange odor and has excellent absorption performance, and is useful for absorbent articles such as incontinence pads, disposable diapers, sanitary napkins, and breast milk pads.

1: Disposable diaper (absorbent article), 2: front abdomen, 3: back of the back, 4: crotch, 5: notch, 10: liquid-permeable nonwoven sheet, 6: exterior sheet material, 7: edge, 8 : Elastic member for front waist, 9: Elastic member for rear waist, 10: Elastic member for front leg, 11: Elastic member for rear leg, 12: Elastic member for front waist, 13: Elasticity for rear waist Member: 15: Front end pressing sheet, 16: Rear end pressing sheet, 17: Side sheet, 18: Elastic member, 19: Joint part, 20: Water-absorbing body, 21: Absorber, 22: Liquid-permeable top sheet , 23: liquid-impermeable back sheet, 24: first sheet, 25: second sheet, 26: water-absorbing layer, 27: water-absorbing material, 28: hot water-soluble fiber

Claims (14)

Producing a molded body containing a water-absorbing material and hot water-soluble fibers;
And a step of heat-treating the molded body after water is provided.   The method for producing a water absorbing layer according to claim 1, wherein the amount of the hot water soluble fiber used is 0.01 to 20 parts by mass with respect to 100 parts by mass of the water absorbing material.   The method for producing a water-absorbing layer according to claim 1 or 2, wherein the heat treatment conditions are a molded body temperature of 54 ° C to 121 ° C and a heating time of 0.1 second to 60 seconds.   The method for producing a water-absorbing layer according to any one of claims 1 to 3, wherein the applied amount of water is 5 to 150 parts by mass with respect to 100 parts by mass of the molded body.   The method for producing a water-absorbing layer according to any one of claims 1 to 4, wherein a melting temperature of the hot water-soluble fiber in water is 40 ° C to 80 ° C.   The method for producing a water-absorbing layer according to any one of claims 1 to 5, wherein the hot water-soluble fiber is a partially saponified polyvinyl alcohol fiber having a saponification degree of 65% to 97%.   A water-absorbing layer obtained by the method for producing a water-absorbing layer according to any one of claims 1 to 6. Containing water-absorbing material and hot water-soluble fiber,
The water absorbing layer, wherein the water absorbing material is fixed by the hot water soluble fiber.   The water absorption layer according to claim 8, wherein a dissolution temperature of the hot water-soluble fiber in water is 40 ° C to 80 ° C.   The water absorption layer according to claim 8 or 9, wherein the hot water-soluble fiber is a partially saponified polyvinyl alcohol fiber having a saponification degree of 65% to 97%. Wherein the basis weight of the hot water soluble fiber sum of the basis weight of the water-absorbing ^material, the water-absorbing layer according to any one of claims 8-10 is ^{50g / m 2 ~300g / m 2} .   The water absorbing layer according to claim 8, wherein the water absorbing material contains a water absorbing polymer.   The absorber provided with the water absorption layer as described in any one of Claims 7-12.   An absorptive article provided with the water absorption layer according to any one of claims 7 to 12.

Images