JPH05140848A - Water-absorbing structure and its production - Google Patents

Abstract

PURPOSE:To obtain the title structure causing no decline in its water-absorbing performance due to deviation of water-absorbing form by developing crimps of a web containing fibers having such potential through heat treatment and by holding water-absorbing granules inside the resulting spiral structure. CONSTITUTION:Firstly, the following structure is made; i.e., a structure consisting of a card web comprising (A) hydrophilic fibers such as rayon and (B) >=50wt.% of crimp-developing fibers capable of spirally crimping consisting of eccentric sheath-core type or side-by-side type conjugate fibers made up of an olefin resin like polypropylene or polyethylene, polyester resin like polyethylene terephthalate, nylon resin, or a structural combination thereof. This structure is then heat treated to weakly develop crimps followed by scattering water- absorbing granules composed of pulp and a water-absorbing polymer in the structure while making width expansion and/or longitudinal stretching. The resultant structure is heat treated again to firmly develop crimps and the granules are held inside the resulting spiral structure, thus preventing deviation of the granules due to external force on the structure in its use.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an absorbent structure suitable for use in absorbent articles such as sanitary napkins, disposable diapers, wound dressings, bandages, incontinence pads and the like, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, an absorbent structure used in an absorbent article is a structure in which pulp and water-absorbing polymer powder or particles are mixed. , It is known that it may cause the structure to be twisted and cannot exert its function sufficiently.

In order to solve the above problems, a method of mixing a binder and a thermoplastic resin in the structure (Japanese Patent Laid-Open No. 3-6).
3049), a method in which a water-absorbing polymer is sandwiched between papers and pressure-bonded under a wet condition so as to fix the water-absorbing polymer (JP-A-3-1-1).
73562), or a method in which a water-absorbing polymer is made into a fiber to form a composite (Japanese Patent Laid-Open No. 3-45769).

[0004]

However, in the method using an adhesive component such as a binder, if an attempt is made to obtain shape stability by increasing the adhesive component, on the contrary, the expansion of the water-absorbing polymer is inhibited and the absorption performance is reduced. Will lower it. Further, it is difficult to control the wetting by a method of pressing the water-absorbing polymer under a wet condition, and the fixation to the hydrophilic fiber is not always stable and reliable.

Further, in the method of making the water-absorbing polymer into fibers, the technique of making the water-absorbing polymer into fibers is difficult and handling of the fibers is not easy, and the water-absorbing capacity is smaller than that of the surface layer of the spherical polymer, resulting in poor water-absorbing speed. .. Therefore, an object of the present invention is to easily fix the water-absorbing polymer in the structure without a decrease in the water-absorbing polymer's water-absorbing capacity and water-absorbing speed, and to generate a twist of the structure itself due to an external force received during use, Another object of the present invention is to provide an absorbent structure in which the deterioration of the absorption performance due to the deviation of the polymer or the like is hardly observed, and a method for producing the same.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides an absorbent structure containing crimp-expressing fibers that are crimped in a spiral shape, and a water-absorbing particulate material inside the crimped spiral structure of the crimp-expressing fibers. The above object is achieved by providing an absorbent structure characterized by being retained.

[0007]

According to the absorbent structure of the present invention, since the water-absorbing granular material is held by the crimp-forming fibers, there is no occurrence of twisting or deviation during its use, and the use of an adhesive agent Since it does not suffer from swelling inhibition, etc., there is little deterioration in absorption performance. The water-absorbing granules can be fixed simply by expressing the crimp-developing fibers, and the water-absorbing granules can be spherical to increase the water absorption rate.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to an absorptive structure (web etc.) containing crimp-expressing fibers that are crimped in a spiral shape. Things are being held. It is preferable that the crimp-developing fibers constituting the absorbent structure of the present invention have crimp-developing properties, and the physical properties of the structure after crimp-developing are 20% or more and the recovery rate after stretching is 80% or more. .. If it is less than 80%, the elastic recovery rate of the structure is insufficient, the external force applied to the absorbent structure cannot be completely followed, and the holding power of the water-absorbing particulate matter (water-absorbing polymer etc.) is also insufficient.

Further, the absorbent structure of the present invention preferably contains at least 50% or more of the fibers, and 50% or more.
If it is less than this, sufficient absorption cannot be obtained and sufficient stretchability is not exhibited. In the absorbent structure of the present invention, the area shrinkage ratio of the structure after the crimp development is preferably 30% or more with respect to the structure before the crimp development (or in the card web state), and when it is less than 30%. The elasticity is insufficient, and the holding power of the water-absorbing particles is also low.

Further, the absorbent structure of the present invention is preferably mixed with water-absorbing or hydrophilic material. By mixing a water-absorbing or hydrophilic material such as rayon cloth or pulp, even if the crimp-expressing fiber is hydrophobic, it functions as a water-conducting material to the water-absorbing particles, and the water-absorbing particles can be effectively used. .. Further, a water absorbing resin may be kneaded into the crimp expressing fiber itself.

As the crimp-forming fiber, the thickness of the fiber is 6d (denier) in order to retain the water-absorbing particulate matter before swelling.
The following is preferable, and it is more preferably 1 to 3 d in consideration of processability. The fiber length is preferably 20 to 76 mm. If the fiber is too thick or the fiber length is too short, the water-absorbing particulate matter cannot be held and the shrinkage rate of the web is low. On the other hand, if it is too thin or if the fiber length is too long, the cardability will deteriorate.

The fibers according to the present invention include polyolefin resins such as polypropylene and polyethylene, polyester resins such as polyethylene terephthalate, nylon resins, or eccentric core / sheath or sand-by-side type structurally combining these. Can be used. Examples of the water-absorbing granular material include starch-based, cellulose-based, and synthetic polymer-based materials. For example, starch-acrylic acid (salt) graft copolymer, starch-
Saponified products of acrylonitrile copolymer, crosslinked products of sodium carboxymethyl cellulose, acrylic acid (salt) polymers and the like are preferable. The shape may be any shape as long as the crimp-expressing fibers can be gripped, such as spherical shape and scale shape, but the particle diameter is preferably 50 to 400 μm,
It is more preferably 150 to 250 μm.

A preferred method for producing the absorbent structure of the present invention is to form a card web (structure) by a known method containing 50% or more of the crimp expressing fibers, and then to form a water-absorbing granular material. Sprinkle on. After that, a heat treatment is performed at a crimp development temperature or higher to make the area shrinkage of the structure 30% or more, whereby a fibrous structure incorporating the water-absorbing particles can be formed. In addition, the mesh of the web conveyor for spraying the water-absorbing particles is coarse, and excess water-absorbing particles are dropped and collected. Furthermore, by spraying a large amount of water-absorbing granules on the structure, when making an absorbent structure having a higher water-absorbing performance, the crimps are weakly expressed by heat treatment, and then the water-absorbing granules are sprayed after increasing the fiber density, Then, it is possible to fix a larger amount of the water-absorbent particles by re-heat-treating and crimping strongly. Further, after the crimps of the crimp-expressing fibers are sufficiently expressed, the absorbent structure can be obtained by expanding and stretching the absorbent structure to disperse the water-absorbing particulate matter to obtain the same absorbent structure. The ratio is 1.1 to 3.0 times, and the stretching ratio is 1.0.
It is desirable to be in the range of 2.0 to 2.0 times.

The absorbent structure according to the present invention configured as described above is used not only as a sheet or other suitable shape but also as one constituent layer of another laminated absorbent structure. be able to. Moreover, it can be suitably used for absorbent articles such as sanitary napkins, diapers, wound dressings, bandages and incontinence pads.

[0015]

EXAMPLES Next, the present invention will be described with reference to examples.
The invention is not limited to these examples. (Example 1) Daiwabo Co., Ltd. CPP fiber (thickness 2d, fiber length 20 mm, material: polypropylene) and PET fiber (thickness 2 d, fiber length 51 mm) were mixed at a mixing ratio of 80:20, 50:50, 30:50. Make a card web to be 70,
A water-absorbing polymer (average particle size: 100 μm, material: polyacrylate cross-linked product) was sprayed, and heat treatment was performed at 130 ° C. for 5 to 90 seconds to prepare samples having different area shrinkage rates with respect to each mixing rate.

Mixing ratio of CPP fiber and PET fiber 80:20
Samples with shrinkage ratios of 80, 30 and 20% are samples 1, 2 and 3, respectively, with a mixing ratio of 50:50 and a shrinkage ratio of 8
0, 30, 20% of samples are sample 4,
Samples 5 and 6 and a mixing ratio of 30:70 and shrinkage ratios of 30 and 20% were designated as Samples 7 and 8, respectively. (Example 2) The fiber mixed with the CPP fiber was rayon 1.5d × 32 mm (Daiwa Boseki Co., Ltd.).
Sample 9 was created under the same conditions as above.

(Example 3) A card web made of 100% CPP fiber was prepared, and then a mixture of a water-absorbing polymer and pulp was sprinkled and heat-treated at 130 ° C for 1 minute to prepare a sample. Table 1 shows the sample characteristics of each example and comparative example.

[0018]

[Table 1] If the CPP fiber is less than 50% and the area shrinkage is less than 30%,
The recovery rate, falling-off property, and twisting property were insufficient. Also, CP
When the P content was 30%, a shrinkage ratio of 80% was not obtained.

Example 4 The CPP fiber (thickness 2d,
A mixture of polymer and pulp was sprinkled on a 100% card web having a fiber length of 20 mm and heat-treated at 130 ° C. for 90 seconds to prepare Sample 10. (Comparative Example 1) A normal pulp and a polymer were laminated and wrapped with absorbent paper to prepare a structure as Comparative Product 1.

(Comparative Example 2) A card web was prepared from 100% thermoplastic fiber NBF (H) of Daiwabo Co., Ltd. (thickness 2d, fiber length 51 mm) and then sprinkled with a polymer.
Comparative product 2 is prepared by heat treatment at 35 ° C. for 90 seconds. (Comparative Example 3) A card web was prepared in the same manner as in Comparative Example 2 and heat treated at 135 ° C for 90 seconds as it was, and then a polymer was sprayed to prepare Comparative Product 3.

(Comparative Example 4) Spunlace N.V. manufactured by DuPont. W. "Sontara 8423" was used to apply a hot-melt adhesive on one side, and then a polymer was sprinkled to apply N. W. Comparative product 4 is prepared by fixing the polymer on top. (Comparative Example 5) A pulp, a polymer, and a thermoplastic resin were mixed, heat-treated, and treated for 30 minutes at a temperature 5 ° C higher than the melting point of the thermoplastic resin to prepare Comparative product 5.

Table 2 shows a performance comparison between the example sample and the comparative example sample.

[0023]

[Table 2] Note) The amount of polymer sprayed in this example is the same. Physical property measurement method * 1 Area shrinkage: When the web area S1 before shrinkage and the web area S2 after shrinkage are taken, each area is measured by an image analyzer. Shrinkage = S2 / S1 * 100 * 2 20% Recovery after elongation: A test piece having a width of 50 mm is set at a chuck interval of 150 mm in a Tensilon tensile tester. The length L of the absorptive structure is read at the point where the restoring stress becomes 0 at the same speed when the chuck is stretched at a speed of 300 mm / min and the chuck interval becomes 180 mm. Recovery rate = (1
80-L) / 30 * 100 Other evaluation criteria ◎: High practical level ○: Satisfaction of practical level △: Level of practical anxiety ×: Level of practical problem

[0024]

[Effect] The absorbent structure according to the present invention is capable of easily fixing the water-absorbing polymer in the structure without any decrease in the water-absorbing ability and water-absorbing speed of the absorbent polymer, and absorbing the absorbent body by an external force received during use. It is also possible to prevent deterioration of the absorption performance due to generation of twist or deviation of the polymer.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location D04H 1/40 B 7199-3B 1/50 7199-3B

Claims (9)

[Claims] 1. An absorbent structure containing crimp-expressing fibers that are spirally crimped, wherein water-absorbing particles are held inside the crimped spiral structure of the crimp-expressing fibers. And an absorbent structure. 2. The absorbent structure according to claim 1, containing 50 wt% or more of the crimp developable fiber. 3. The absorbent structure according to claim 1, which has a recovery rate of 80% or more after 20% elongation in the machine direction or the transverse direction. 4. The absorbent structure according to claim 1, wherein the crimp developable fiber is capable of changing its three-dimensional structure in accordance with the swelling of the water-absorbent particles when absorbing the liquid. 5. The absorbent structure according to claim 1, which contains hydrophilic fibers. 6. The method for manufacturing an absorbent structure according to claim 1, wherein the absorbent structure containing the crimp-developing fibers comprises:
Production of an absorbent structure comprising a step of spraying the water-absorbent particles and a step of expressing crimps of the fibers, wherein the water-absorbent particles are held in the water-absorbent structure. Method. 7. The method for producing an absorbent structure according to claim 1, wherein the absorbent structure composed of the crimp developable fibers is heat-treated at a crimp development temperature or higher to weakly develop crimps. After that, the method comprises a step of spraying the water-absorbent particles and a step of heat-treating the absorbent structure to strongly develop crimps, and the water-absorbing particles are held inside the spiral structure of the fibers. A method for manufacturing an absorbent structure, comprising: 8. The method for manufacturing an absorbent structure according to claim 1, wherein the absorbent particles are spread while the absorbent structure is widened and / or stretched, and the fiber is wound. And a step of causing shrinkage, wherein the absorbent structure is held by the absorbent granules. 9. The method for manufacturing an absorbent structure according to claim 1, wherein the shrinkable fibers have a shrinkage ratio of 30% or more before and after crimp development. And a method for manufacturing an absorbent structure.