JPH05331775A - Absorbing article and its production - Google Patents

Abstract

PURPOSE:To obtain an absorbing article suitable as a drip sheet for fresh foods, sanitary goods, disposable diaper, or concrete curing sheet, by setting water- absorptive resin particles in a holding layer consisting of thermoplastic fibers. CONSTITUTION:Thermoplastic fibers such as polyester, polyolefin or polyamide fibers, or conjugate fibers thereof are interlaced in a three-dimensional manner to form a holding layer 0.005-0.05g/m<2> in apparent density, and one side of this holding layer is laminated with a supporting sheet consisting of nonwoven fabric. Thence, water-absorptive resin particles (e.g. crosslinked polyacrylic acid salt) 10-2000 (pref. 100-1000)mu in diameter are dispersed at 10-200g/m<2> in the holding layer but blocked by the above supporting sheet. The resulting laminate is then pressed and deformed in the width direction at such a temperature as to soften the thermoplastic fibers to set the water-absorptive resin particles in the holding layer, thus affording the objective absorbing article.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an absorbent article useful as a raw material for products requiring water absorption, such as fresh food drip sheets, sanitary items, disposable diapers and concrete curing sheets, and a method for producing the same. is there.

[0002]

2. Description of the Related Art Conventionally, as an absorbent article as described above, for example, as shown in FIG. 5 (a), an absorbent article having a structure in which a water-absorbent resin powder 21 is sandwiched between supporting sheets 22 having water permeability is known. Has been. However, in such a structure, as shown in FIG. 5B, when the water-absorbent resin powder 21 absorbs water and swells, the sandwiched support sheets 22 and 22 are peeled off and the structure collapses. , Support sheet 22
The water-absorbent resin powder 21 extruded from between 22 to cause a problem of poor appearance and feeling of use.

Therefore, in order to avoid the above problem, a structure has been proposed in which the side portions of the support sheets 22 are sealed as shown in FIG. 6 (a). However, as shown in FIG. 6 (b), the above-mentioned structure is such that as the water-absorbent resin powder 21 absorbs water and swells, each support sheet 22.
2 swells in a substantially cylindrical shape, and the water-absorbent resin powder 21 swollen between the support sheets 22 and 22 can easily move, which makes it difficult to handle. Further, when cut to be applied to a diaper or the like, water is absorbed from the cut surface. Since the resinous resin powder 21 spills out, a sealing step such as heat sealing is required along the cut. Therefore, the sealing step with a complicated shape is difficult, which causes a problem that free cutting cannot be performed. It was

Therefore, in order to avoid the above problems, as shown in FIG.
A structure has been proposed in which each water-absorbent resin powder 21 is firmly bonded while sandwiching each water-absorbent resin powder 21 with an adhesive portion 23 such as an adhesive or heat seal. Further, there is disclosed an absorbent body in which a powdery or fibrous water-absorbing polymer is carried in a nonwoven fabric, and the nonwoven fabric is compressed in the thickness direction to bond the fibers of the nonwoven fabric and the water-absorbing polymer (Japanese Patent Laid-Open Publication No. Sho. 61-28003).

[0005]

However, in the conventional structure shown in FIG. 7A, the distance between the support sheets 22 is restricted by the adhesive portion 23.
As shown in (b), the swelling of the water-absorbent resin powder 21 which absorbs water and tries to swell is hindered. Further, also in the absorbent body disclosed in the above publication, since each water-absorbent polymer is bonded to each fiber in the nonwoven fabric, swelling of each water-absorbent polymer is inhibited.

As a result, in each of the above-mentioned constitutions, the water absorption rate and the water absorption amount of the water absorbent resin powder 21 and the water absorbent polymer are lowered, and the water absorption characteristics originally possessed by the water absorbent resin powder 21 and the water absorbent polymer cannot be exhibited, so that the water absorbent resin powder 21 and the water absorbent polymer cannot be predetermined. However, there is a problem in that the size is increased in order to secure the water absorption of the.

[0007]

In order to solve the above problems, the absorbent article according to claim 1 has a holding layer made of a fibrous thermoplastic resin for holding water-absorbent resin particles. In the above, the water-absorbent resin particles are held in the holding layer which is deformed by being pressed at a temperature at which the thermoplastic resin is softened.

A method for manufacturing an absorbent article according to claim 2 is
In order to solve the above problems, a holding layer made of a fibrous thermoplastic resin is formed so as to have a gap in which the water-absorbent resin particles can enter the holding layer, and then the water-absorbing material is formed on one surface of the holding layer. After laminating a support sheet for preventing the passage of the resin particles, after distributing the water-absorbent resin particles in the holding layer, press the holding layer in the thickness direction at a temperature at which the thermoplastic resin softens. It is characterized in that the water-absorbent resin particles are held in the holding layer by being deformed.

[0009]

According to the above-mentioned structure, the holding layer is pressed and deformed at the temperature at which the thermoplastic resin is softened, so that the welding between the fibrous thermoplastic resins in the holding layer is avoided. Thus, the water absorbent resin particles are held in the holding layer.

Therefore, when the above structure is applied to various products such as diapers, even if the product is cut at an arbitrary position, the water-absorbent resin particles held from the cut surface can be prevented from scattering. It is possible to omit a sealing step such as heat sealing for preventing the water-absorbent resin particles from scattering from the cut surface, which has been conventionally required.

In addition, in the above-mentioned constitution, even if the water-absorbent resin particles held in the holding layer absorb water and swell, the fiber-shaped thermoplastic resins can be elastically deformed and expanded. It is possible to prevent the swelling of the water absorbent resin particles from being hindered.

According to the method described in claim 2, it is possible to manufacture an absorbent article having the action of the structure described in claim 1 described above, and it is possible to freely cut the article. An absorbent article having a large area can be manufactured, and mass production can be easily performed.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following will describe one embodiment of the present invention with reference to FIGS. The method of manufacturing the absorbent article will be sequentially described. First, as shown in FIG. 2, the nonwoven fabric-like holding layer 1 is manufactured. This holding layer 1
As described later, the synthetic fibers 1a made of a thermoplastic synthetic resin are three-dimensionally intertwined with each other, or are produced by point bonding or a mixture of them.

At this time, since the holding layer 1 disperses the water-absorbent resin particles 2 to be described later and distributes the water-absorbent resin particles 2 in the holding layer 1 substantially uniformly, the synthetic fibers 1a larger than the particle diameter of the water-absorbent resin particles 2 are ... It is manufactured so as to have an interspace.

Next, a composite nonwoven fabric is prepared by sticking a support sheet 3 which is clogged to the extent that the water-absorbent resin particles 2 do not pass through, on one side of the holding layer 1. Such composite non-woven fabric preferably has predetermined water resistance and peel strength, and as such a sticking method, a physical / mechanical method such as needle punching, an emulsion adhesive or a hot melt adhesive is used. Such a chemical method, a method using heat bonding by melting, or the like can be mentioned.
Further, such a composite nonwoven fabric is used by being wound up in a roll shape.

Next, the composite non-woven fabric is drawn out, and a predetermined amount of the water-absorbent resin particles 2 are sequentially sprinkled from above while moving horizontally with the support sheet 3 as the lower side. Then, the composite nonwoven fabric is heated and compressed in the thickness direction, and
As shown in, the synthetic fiber 1a in the holding layer 1 is plastically deformed to thin the thickness of the holding layer 1 to about 1/5.

At this time, the heating temperature is the above-mentioned synthetic fiber 1a.
Is set to a temperature at which it does not melt but softens, so that the synthetic fibers 1a ... Are not welded even at the contact points between the synthetic fibers 1a. Therefore, in the above-mentioned thinned retaining layer 1,
Since the distance between the synthetic fibers 1a ...
The water-absorbent resin particles 2 are held between a and so that the synthetic fibers 1a do not scatter outside. In this way, a water-absorbing article in which each water-absorbent resin particle 2 is held can be manufactured.

During the above heat compression, as shown in FIG. 4, a thermoplastic resin fiber having a melting point lower than the above heating temperature, a thermoplastic resin powder, and a composite fiber described below are further provided on the holding layer 1. The sandwiching sheets 3 ′ such as non-woven fabric containing at least one selected from the group consisting of may be laminated and laminated.

Further, although not shown, a hydrophilic sheet such as valp paper may be laminated on the sandwiching sheet 3'and simultaneously attached at the time of the above-mentioned heat compression. Such a sandwiching sheet 3'is melted at each contact at the time of heating and compression, so that it is adhered to the holding layer 1 and / or the hydrophilic sheet.

Instead of welding the sandwiching sheet 3'as described above, an emulsion-based or hot-melt adhesive is used between the sandwiching sheet 3'and the holding layer 1 and / or the hydrophilic sheet. May be adhered.

Further, when the holding layer 1 is sandwiched between the support sheet 3 and the sandwiching sheet 3 ', one of the support sheet 3 and the sandwiching sheet 3'is water-impermeable, depending on the application. Alternatively, it may be water repellent. In this way, an absorbent article including the water-absorbent resin particles 2 held between the supporting sheet 3 and the sandwiching sheet 3'by one-time heat compression,
Alternatively, an absorbent article in which a hydrophilic sheet is further laminated can be manufactured.

Next, the method for manufacturing the above-mentioned holding layer 1 will be described in more detail. The manufacturing method is not particularly limited as long as it is a method of performing entanglement or spot adhesion between the synthetic fibers 1a ... In the holding layer 1 so that the synthetic fibers 1a. General manufacturing methods, such as mechanical and physical entanglement of needle punch, spunlace, etc., and chemical bonding with an adhesive (resin bond),
For example, point adhesion by fusion using a heat-fusible fiber is used.

The fineness of the synthetic fiber 1a is 0.5 to 30 denier, preferably 1 to 30 in terms of cost and strength.
The fiber length is 15 denier, and the fiber length of the synthetic fiber 1a is preferably 10 to 100 mm, more preferably 10 to 60 mm, from the viewpoint of availability and strength.

The holding layer 1 preferably has an apparent thickness of 1 to 10 mm in terms of maximum water absorption, ease of handling after water absorption, and strength. The density of the holding layer 1 is the strength of the holding layer 1, the particle size of the water-absorbent resin particles 2 used, the manufacturing process of the holding layer 1,
From the viewpoint of manufacturing cost, 0.01 to 0.1 g / cm ³ , more preferably
The holding layer 1 has an apparent density of 0.03 to 0.07 g / cm ³ .
005-0.05g / cm ³ , more preferably 0.075-0.04g / cm
^{Is 3} .

The apparent thickness (cm) is measured by stacking 10 test pieces of about 10 × 10 mm and measuring the thickness,
The thickness per sheet was calculated. In addition, the thickness (cm) was measured according to JIS-L1086, and each measured value was measured at 5 points of the sample for 10 seconds at 10 kgf / cm ² (loading area is 10 cm ² ) with a thickness measuring instrument. The average value of

The above-mentioned apparent density is 1 m ^{2 of the} holding layer 1.
It is a value obtained by converting the mass per unit (g / m ² ) into (g / cm ² ) and dividing by the above apparent thickness. The above-mentioned density is a value obtained by converting the mass (g / m ² ) per 1 m ^{2 of the} holding layer 1 into (g / cm ² ) and dividing by the above-mentioned thickness.

Retaining layer 1 satisfying the respective standard values
The water absorbent resin particles 2 can easily enter the voids formed between the synthetic fibers 1a.

Examples of the synthetic fiber 1a made of a thermoplastic resin used for the holding layer 1 include polyesters such as polyethylene terephthalate and low melting point polyethylene terephthalate, polyolefins such as polyethylene and polypropylene, polyamides such as nylon and the like. The synthetic fibers made of a single resin, or polyethylene terephthalate / polypropylene, polyethylene terephthalate / polyethylene, polyethylene terephthalate / low melting point polyethylene terephthalate, polyethylene / polypropylene, etc., are preferable. As such a composite fiber, it is desirable to use a resin having a high melting point as a core and a resin having a low melting point as a rod, since the heat fusion is easy and the shape during heating and compression is easily maintained.

Next, the water absorbent resin particles 2 described above will be described. The material of the water-absorbent resin particles 2 is a graft copolymer of starch acrylate, a carboxymethyl cellulose cross-linked product, a vinyl alcohol alcohol salt copolymer, a polyacrylonitrile hydrolyzate, a cross-linked polyacrylic acid salt, a modified polyvinyl alcohol, Examples thereof include acrylic acid polymers, acrylic acid acrylamide copolymers, and isobutylene maleic anhydride copolymers. It should be noted that these polymers may be used as a mixture of two or more kinds.

Of these polymers, crosslinked polyacrylic acid salts are particularly preferably used, and such crosslinked polyacrylic acid salts consist of acrylic acid, methacrylic acid, and alkali metal salts thereof. It is obtained by partially cross-linking an acrylic acid-based monomer polymerized by selecting at least one kind from the group.

The alkali metal salt means acrylic acid and / or
Alternatively, it is a salt obtained by neutralizing the carboxyl group of methacrylic acid with an alkali metal hydroxide such as sodium hydroxide, potassium hydroxide or lithium hydroxide in an amount of 50 to 90 mol%.

Water-absorbent resin particles 2 made of such a resin
Is formed to have a particle size of 10 to 2000 μ, preferably 100 to 1000 μ, and the amount used is appropriately set depending on the application, but is 10 to 200 g / m ² with respect to the holding layer 1, More preferably, it is in the range of 30 to 100 g / m ² . Such water-absorbent resin particles 2 can absorb about 200 times as much deionized water as their own weight before absorbing water, and the volume at maximum absorption is about 100 times that before absorbing water. The above μ represents 10 ⁻⁶ m.

The supporting sheet 3 and the sandwiching sheet 3'described above.
As a material of the thermoplastic resin fiber, a thermoplastic resin fiber having a melting point lower than that of the constituent fibers of the holding layer 1 at the time of heat welding,
A non-woven fabric or cloth containing at least one selected from the group consisting of the thermoplastic resin powder and the above-mentioned composite fiber is used, and when an adhesive is used, in order to facilitate the adhesion, the holding layer 1 and A non-woven fabric or cloth containing thermoplastic resin fibers having a similar or closely related composition is desirable.

As the above-mentioned adhesive, an emulsion type or hot type such as acrylic type, urethane type, EVA (ethylene-vinyl acetate copolymer) type which is easy to handle and has little influence on the water-absorbent resin particles 2 is used. Melt type is preferable.

The heating temperature during the heating and compression is set so that the synthetic fibers 1a of the holding layer 1 are easily plastically deformed to be thinned, and the sandwiching sheet 3'is also welded at the same time. At this time, at a heating temperature that causes welding between the sandwiching sheet 3 ′ and the synthetic fibers 1 a of the holding layer 1, the synthetic fibers 1 a of the holding layer 1 are easily plastically deformed. Then, it is set to be thinned. Therefore, the heating temperature in the above example is set to be lower than the melting point and higher than the softening point of the synthetic fiber 1a, for example, 100 to 180 ° C.
Is set to.

As described above, in the structure of the above embodiment, the water absorbent resin is contained in the holding layer 2 in which each synthetic fiber 1a is plastically deformed by being pressed at a temperature at which the thermoplastic resin forming the synthetic fiber 1a is softened. The particles 2 are held.

Therefore, in the above structure, even when the water-absorbent resin particles 2 ... Are swollen 3 to 4 times in diameter at the time of maximum water absorption, the thickness is reduced to about 1/5 as shown in FIG. The synthetic fibers 1a ... of the thin retaining layer 1 are held and held.

That is, each swollen water-absorbent resin particle 2 ...
Each of the synthetic fibers 1a, which retains the fibers, can be restored to the original three-dimensional structure before thinning even when they are point-bonded to each other, and can be elastically deformed with a slight force with a sufficient margin. On the other hand, even when the synthetic fibers 1a are entangled with each other, the entanglement can be maintained while the synthetic fibers 1a are slid and elastically deformed.
Can be swollen while being held by the respective synthetic fibers 1a.

As a result, the above structure does not have the swelling inhibition of the water absorbent resin particles 2 caused by the adhesion between the synthetic fibers constituting the holding layer and the water absorbent resin particles as in the conventional case, and
Inhibition of swelling of the water-absorbent resin particles 2 caused by firmly adhering each water-absorbent resin powder while sandwiching each water-absorbent resin powder between the support sheets as in the conventional case with an adhesive or heat-sealed adhesive portion is avoided.

By the way, conventionally, since the swelling of the water-absorbent resin powder was hindered, the water-absorbent resin particles were sometimes filled more than necessary in order to secure the water absorbability.

However, the above-mentioned constitution can sufficiently exhibit the water absorption originally possessed by the water-absorbent resin particles 2, and the amount of the water-absorbent resin particles 2 to be filled can be reduced as compared with the conventional one, and the size can be reduced.

In addition, the above structure can prevent the absorbent article 2 from bulging from the side of the absorbent article when the absorbent resin particles 2 are swollen, and can prevent deterioration of the feeling of use.

By the way, in the past, a feeling of use and the like may be deteriorated due to a local increase in thickness such that only the central portion of the absorbent article is thickened.

However, in the above structure, even when water is absorbed, the amount of increase in the thickness becomes uniform as a whole, the local increase in the thickness can be prevented, and the deterioration of the feeling of use can be avoided.

Further, in the above structure, as shown in FIG. 1, since the water-absorbent resin particles 2 ... Are held between the synthetic fibers 1a. The water absorbent resin particles 2 are prevented from scattering from the surface to the outside.

Therefore, in order to prevent the water-absorbent resin particles from scattering from the cut surface, it is possible to omit the sealing step such as heat sealing along the cut surface before the cutting as in the conventional case. Therefore, the absorbent article can be easily applied to any complicated cut.

As a result, the absorbent article and the method for producing the same can be easily applied to other products, such as sanitary ware and diapers, which require cutting in a complicated shape, even if they are manufactured in a wide band shape. Therefore, mass production can be easily performed, and the manufacturing cost can be reduced.

In the structure and method of the above embodiment,
An example was given in which the holding layer 1 was heated and compressed so as to have a thickness of about ⅕ when thinning the holding layer 1, but the degree of thinning is not limited to the above, and may be ½ to 1 as necessary. It may be prepared in the range of / 10.

[0049]

The absorbent article according to claim 1 of the present invention comprises:
As described above, the holding layer made of a fibrous thermoplastic resin, in the absorbent article holding the water-absorbent resin particles, in the holding layer deformed by being pressed at the softening temperature of the thermoplastic resin, This is a configuration in which the water-absorbent resin particles are held.

Therefore, with the above structure, when the obtained absorbent article is applied to various products, such as diapers, even if the absorbent article is cut at any position, it is held from the cut surface. Since it is possible to prevent the water-absorbent resin particles from scattering, it is possible to omit a sealing step such as heat sealing for preventing the water-absorbent resin particles from scattering from the cut surface, which has been conventionally required.

Further, in the above-mentioned constitution, even if the water-absorbent resin particles held in the holding layer absorb water and swell, the fibrous thermoplastic resins can be elastically deformed and expanded. It is possible to prevent the swelling of the water absorbent resin particles from being hindered. From this, the water-absorbing resin particles can sufficiently exhibit the water-absorbing property, so that the conventional water-absorbing property is secured, and therefore, there is an effect that it is not necessary to fill the water-absorbing resin particles more than necessary and the size can be reduced.

In the method for producing an absorbent article according to the second aspect of the present invention, as described above, the holding layer made of the fibrous thermoplastic resin is provided with the gap through which the water-absorbent resin particles can enter the holding layer. After being formed so as to have, after laminating a support sheet for preventing the passage of the water-absorbent resin particles on one surface of the holding layer, after distributing the water-absorbent resin particles in the holding layer, the holding layer In this method, the water absorbent resin particles are held in the holding layer by pressurizing and deforming the thermoplastic resin in the thickness direction at a softening temperature.

Therefore, the method comprises the above-mentioned claim 1.
Since it is possible to easily manufacture an absorbent article having the effect of the described configuration, and because it can be freely cut, it is possible to manufacture an absorbent article having a large area, and mass production is possible. There is an effect that it can reduce.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts of an absorbent article obtained by a method for manufacturing an absorbent article of the present invention.

FIG. 2 is a cross-sectional view of essential parts of the absorbent article before the heating and compression step in the method for manufacturing the absorbent article.

FIG. 3 is a cross-sectional view of relevant parts showing a state of the absorbent article at the time of absorbing water.

FIG. 4 is a cross-sectional view of essential parts showing a step of further stacking sandwiching sheets in the method for manufacturing an absorbent article.

FIG. 5 is a cross-sectional view of a main part of a conventional absorbent article.

FIG. 6 is a cross-sectional view of a main part of another conventional absorbent article.

FIG. 7 is a cross-sectional view of a main part of still another conventional absorbent article.

[Explanation of symbols]

 1 Retaining Layer 1a Synthetic Fiber (Thermoplastic Resin) 2 Water-Absorbent Resin Particles

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location D04H 1/54 A 7199-3B D06M 23/08 D06M 17/00 K

Claims (2)

[Claims] 1. In an absorbent article holding a water-absorbent resin particle, a holding layer made of a fibrous thermoplastic resin is contained in the holding layer deformed by being pressed at a temperature at which the thermoplastic resin is softened. An absorbent article, wherein water-absorbent resin particles are held. 2. A holding layer made of a fibrous thermoplastic resin is formed so as to have a gap through which the water-absorbent resin particles can enter the holding layer, and then the one side of the holding layer is filled with the water-absorbent resin particles. After stacking the support sheets that prevent passage,
After the water-absorbent resin particles are distributed in the holding layer, the holding layer is pressed and deformed in the thickness direction at a temperature at which the thermoplastic resin is softened, whereby the water-absorbent resin is contained in the holding layer. A method for producing an absorbent article, which comprises retaining particles.