JP2615212B2 - Perforated meltblown nonwoven fabric and method for producing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a perforated meltblown nonwoven fabric having excellent air permeability and water permeability, and a method for producing the same.

[Conventional technology]

BACKGROUND ART Conventionally, as a nonwoven fabric used for a diaper top sheet or the like, a dry nonwoven fabric in which thermoplastic resin fibers are bonded to each other has been known.

On the other hand, JP-B-57-17081 discloses an absorbent structure having a structure in which a surface sheet of a resin film is laminated on an absorbent. Here, the resin film is perforated, and a tapered capillary is protruded around the hole, and the capillary extends from the surface to the inside of the absorbent. This absorbent structure is mainly used for diapers, sanitary napkins, bed pads and the like.

Japanese Patent Application Laid-Open No. 57-193311 describes a plastic film or web in which a large number of holes are uniformly scattered.

JP-A-64-65565 discloses that a film made of a thermoplastic resin is swelled and ruptured so that a large number of holes are provided in the film. Exploded debris remains in the form of protrusions.

[Problems to be solved by the invention]

By the way, the melt blown nonwoven fabric has a flexible feel and a high flexibility, but has low air permeability and water permeability. For this reason, it is not suitable for applications requiring large water permeability, such as a top sheet of a disposable diaper, which requires urine to immediately pass through a water absorbing material.

In addition, even if it is excellent in flexibility, for example, medical patches for protecting wounds, diapers for infants who do not need to cause rash, beds for long-term medical care patients who do not need to cause skin soaking It is desired that the pad for use and the like have high water permeability and air permeability, as well as flexibility and rich cushioning.

In response to such demands, the surface sheets described in JP-B-57-17081, JP-A-57-193311, and JP-A-64-64655 are formed of a film, so Although it has water permeability and air permeability due to the holes,
The film has a cold feeling unique to the film, lacks in flexibility, and is not preferable as it directly touches the skin.

Certainly, in order to impart air permeability and water permeability to the nonwoven fabric, it can be thought that it is sufficient to provide a large number of holes in the nonwoven fabric,
In reality, for example, if holes are punched out mechanically in a non-woven fabric, the material of the punched portion becomes more wasteful as the number of holes increases,
It is uneconomical and unrealistic. If the nonwoven fabric is thermally melted with a needle to form a hole, the periphery of the hole is melted and hardened, and the texture is impaired at the hardened portion. Further, there is also a problem that flexibility cannot always be imparted only by a method of making a hole.

The present invention provides a nonwoven fabric having high water permeability, air permeability, hygroscopicity, and flexibility and a cushioning property, and a method for producing such a nonwoven fabric in order to solve the above-described conventional problems. Subject.

[Means for solving the problem]

The melt-blown nonwoven fabric of the present invention that solves the above-described problems has a large number of holes 1a in a base cloth portion 1 formed of a fiber group of a thermoplastic resin, and a base cloth portion 1 around each hole 1a. Cylindrical protrusion 2 at the tip opening made of a group of fibers of the same quality
The protrusion height of the projection 2 is at least twice the thickness of the base cloth 1.

The method for producing a melt-blown nonwoven fabric according to the present invention comprises:
Fibers are sprayed and deposited from the perforated plate
In a state where the pressure on the opposite side is smaller than the pressure on the resin spraying side with respect to 12, a part of the fiber group is made to protrude from the opening 12a, and the protrusion bulges in a cylindrical shape and the tip 2a Blows through to form the projections 2 and then the perforated plate
Remove from 12

 Hereinafter, the present invention will be described in more detail.

The invention is formed from a meltblown nonwoven. As shown in FIG. 2, the melt-blown nonwoven fabric of the present invention has a large number of holes 1a in a base cloth portion 1 composed of a thermoplastic resin fiber group.

The thermoplastic resin used as a material of the base cloth portion 1 provided with a large number of holes 1a is a monopolymer such as low density polyethylene, high density polyethylene, polypropylene, poly 1-butene, poly 4-methyl-1-pentene or ethylene. Is mentioned. Further, a random or block copolymer of α-olefins such as propylene 1-butene and 4-methyl-1-pentene may be used. Further, ethylene / vinyl compound copolymers such as ethylene / acrylic acid copolymer, ethylene / vinyl acetate copolymer, ethylene / vinyl alcohol copolymer, ethylene / vinyl chloride copolymer, and polystyrene, acrylonitrile / styrene Copolymer, acrylonitrile butadiene
Styrene resins such as styrene copolymers, methyl methacrylate / styrene copolymers, α-methylstyrene / styrene copolymers, and also chlorides such as polyvinyl chloride, polyvinylidene chloride vinyl chloride / vinylidene chloride copolymers Vinyl resins and polyacrylates such as polymethyl acrylate and polymethyl methacrylate are also included. Further, in addition to polyamides such as nylon 6, nylon 6-6, nylon 6-10, nylon 11, nylon 12, and polyamide, polyethylene terephthalate,
Examples thereof include thermoplastic polyesters such as polybutylene terephthalate, and further, polycarbonates, polyphenylene oxides, and the like. These may be used alone or in combination.

In the present invention, the velocity of the air flow blowing off the fibers,
The fiber length and fiber diameter can be changed by the viscosity of the molten resin, the melt flow rate, the diameter of the die orifice, and the like. The fiber length of the nonwoven fabric in the present invention is continuous, a long fiber of 10 cm or more, or 1 cm to 10 cm.
Short fibers.

Regarding the fiber diameter, not limited to the present invention, the melt blown nonwoven fabric is generally 1 μm to 10 μm, and often 2 μm.
５5 μm. The present invention may also be manufactured in this range.
When the nonwoven fabric of the present invention is manufactured from fibers having such a fiber diameter with the same basis weight as a melt-blown nonwoven fabric by a general manufacturing method, air permeability and water permeability are improved as compared with general nonwoven fabrics.

The base cloth portion 1 has a large number of holes 1a as shown in FIGS. The shape of the hole 1a is not limited to a circle, but may be an ellipse, a square, or any other shape.
The hole diameter of the hole 1a is 0.2 mm to 6 mm, preferably 0.4 mm to 2 mm.
mm is desirable. When the hole 1a is other than a circle, the hole diameter here refers to a circle that encompasses the entire hole 1a having an arbitrary shape, that is, a diameter of a minimum circumscribed circle. If the pore diameter is less than 0.2 mm, the air permeability and water permeability become inferior, which is not preferable.
If it exceeds 6 mm, the feeling is impaired, which is not preferable.

The number of holes in the base cloth portion 1 is desirably 2 or more, preferably 5 or more per 1 cm ² , but may be appropriately selected according to the hole diameter.

Around the hole 1a of the base cloth portion 1, there is provided a cylindrical projection 2 having an opening at the tip 2a made of a fiber group of the same quality as the base cloth portion 1. The protrusion height (h) of the cylindrical projection 2 is
If the thickness (t) of the base cloth portion 1 is at least twice (see FIG. 3), preferably at least four times, sufficient bulkiness may be secured both tactilely and visually. That is, the apparent density is small and light, and there is a sufficient thickness to make the whole very flexible. If the protrusion height is less than twice, sufficient bulkiness is lost.

Due to the presence of such projections 2, elasticity, cushioning,
Flexibility is good, and a nonwoven fabric with good skin is obtained.

The melt blown nonwoven fabric of the present invention is manufactured by the following manufacturing method.

The equipment for the melt blow method is equipped with a die at the tip of the extruder.
A gas orifice 11 is provided around the die orifice, which is the resin discharge port of the die 10 (when a capillary tube is used as the resin discharge port), and a gas discharge orifice 11 is provided from the gas discharge orifice 11. A perforated plate configured to blow high-pressure heating gas toward the orifice, and to catch and collect the stretched fiber group that is blown by the blown gas flow at the end of the blowing direction
12 are arranged. Here, the perforated plate 12 is not limited to a flat plate, but may be a mesh-shaped one such as a wire mesh. Further, the perforated plate 12 is movable so as to move while depositing the fiber group, so that the nonwoven fabric can be formed in a belt shape. Specifically, moving the flat perforated plate 12 can be exemplified,
It is more preferable that the perforated plate 12 has a rotatable cylindrical shape. It is also possible to form an endless belt.

The opening 12a provided in the perforated plate 12 has a shape and a size necessary for forming the above-described hole 1a of the nonwoven fabric.

In general, since the drawing force due to the gas flow is weak, it is preferable that the fiber temperature on the porous plate 12 extruded so that the fibers can be uniformly drawn and broken even with such a weak force is higher than the softening point.

In manufacturing the nonwoven fabric, at the same time as the molten resin is extruded, high-pressure heating gas is blown from the gas blowing orifice 11 to fiberize the thermoplastic resin in a molten state, and the porous plate 12
Before the temperature of the scattered fibers drops below the softening point, the fibers are continuously collided with the rotating perforated plate 12, and a group of fibers is continuously formed into a film on the perforated plate 12. To be deposited.

At that time, the pressure on the side opposite to the side on which the fibers are sprayed is set to be smaller than the pressure on the side on which the fibers are sprayed with the perforated plate 12 as a boundary (hereinafter, simply referred to as a pressure difference). is there).

Specifically, the side opposite to the side where the fibers are sprayed is depressurized by the decompression means, and a part of the fiber group is sucked and protruded from the opening 12a of the perforated plate 12 to the opposite side to form the projection 2. This can be shown as a preferred example. A vacuum suction device or the like is used as the pressure reducing means.

Even without using such a pressure reducing means, simply bringing the perforated plate 12 close to the melt blow die 10 makes the pressure on the side opposite to the side on which the fibers are sprayed smaller than the pressure on the side on which the fibers are sprayed. be able to. That is, the pressure relationship is established by the wind pressure of the high-pressure heating gas blown out from the gas blowing orifice 11, and the wind pressure pushes a part of the fiber group from the opening 12a of the perforated plate 12 to the opposite side to project the protrusion. Form 2

When the perforated plate 12 is brought close to the melt blow die 10, the fibers in the molten state are collected in a state of not being cooled so much that the adhesion rate between the fibers increases, and if the fibers are too close, the film is formed. Be careful.

The accumulation of the fibers on the perforated plate 12 causes the opening 12
The base cloth portion 1 is formed at a portion other than the portion a, and a hole 1a is formed at the opening 12a due to the pressure difference, and the same fibers as the fiber group constituting the base cloth portion 1 are formed around the hole 1a. The cylindrical projection 2 is formed to be raised. Due to the above pressure difference, a part of the fiber group rides on the gas flow passing through the opening 12a due to the pressure difference and protrudes in the flow direction of the gas flow. Part 2
The tip 2a is formed by blowing through and opening. Therefore, there is a need for a pressure difference sufficient to create such a gas flow. After such protrusions 2 are formed, the fiber aggregate formed on the perforated plate 12 is peeled off from the perforated plate 12 to obtain a melt-blown nonwoven fabric.

As described above, when the nonwoven fabric is formed, especially when the projections 2 are formed, the viscosity and the melt flow rate of the molten resin are related, or the diameter and strength of the fiber, and the die 10 and the porous plate
The distance (collection distance) between them and the pressure difference influences. When the resin viscosity, fiber diameter, or fiber strength is large, it is necessary to suck or extrude the fiber with a large pressure difference. When the viscosity is small, the fiber can be sucked or extruded with a small pressure difference. In any case, die
The collection distance is adjusted so that the fibers blown out by 10 accumulate on the perforated plate 12 while the temperature is equal to or higher than the softening point. The pressure difference is adjusted in such a manner.

Depending on the viscosity, melt flow rate, fiber diameter, fiber strength, collection distance, and pressure difference of these molten resins, a nonwoven fabric having a different texture and a projection 2 having a different form are formed.

The melt-blown nonwoven fabric manufactured by such a method may be subjected to a hydrophilic treatment with a surfactant or a water-repellent treatment with a water-repellent agent according to the purpose of use. A film, paper, or other nonwoven fabric may be attached to the flat surface side without the protrusion 2.

Melt blown nonwoven fabric obtained by the above method,
It is used as a top sheet for disposable diapers, a top sheet for sanitary napkins, a cushioning material, a draining sheet, and the like. Projection 2
If you attach a film, paper, or other non-woven fabric to the surface with
It can be made into a sheet with properties like corrugated paper, and can also be used as a heat insulating and soundproofing material.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Example 1> As shown in FIGS. 4 to 7, a melt blow die 10 used in the present example was formed into a die block 15 having a resin chamber 14 for accommodating a molten resin to be extruded, and a flat plate. A plurality of capillary tubes 16 (capillaries) each having a base end held by the die block 15 and communicated with the resin chamber 14 in a lined state, and a tip of the capillary tube 16 is pressed flat by a lip portion 17. Surface and form a gas blowing orifice 11 between the holding surface and the capillary tube 16 and communicate with the gas blowing orifice 11 between the die block 15 and the die block 15. Gas plate with gas chamber 18
19 is provided.

Then, the tip of the capillary tube 16 is
It is in a slightly protruding state.

Opposite to the capillary tube 16, in front of the melt blow die 10, a collecting device 13 having a rotatable perforated roll having a perforated plate 12 formed in a cylindrical shape is disposed. The collection device 13 is movable toward and away from the die 10 so that the distance (collection distance) between the tip of the capillary tube 16 and the surface of the perforated plate 12 can be adjusted.
Further, inside the porous roll, a partition 22 for forming a negative pressure chamber 21 is provided at a portion behind the fiber receiving portion, and a contact portion between the inner surface of the porous roll and the partition 22 has a porous portion. A slide seal 23 is provided to allow rotation of the roll and to prevent air from leaking into the negative pressure chamber 21. Then, a vacuum suction device 24 is connected to the negative pressure chamber 21, so that the inside of the negative pressure chamber 21 is maintained at a constant negative pressure state.

Further, a press roll 25 for holding the nonwoven fabric is provided on the outside of the porous roll corresponding to the portion of the porous roll that has passed through the negative pressure chamber 21, and the formed nonwoven fabric is
And is peeled off from the porous roll.

In the above apparatus, the diameter of each opening 12a of the porous roll is
1.5 mm, 18 holes / cm ² , perforated plate 12 with perforated roll
Was 0.5 mm.

The resin used is polypropylene with a melt flow rate of 300, and the discharge rate per minute from a capillary tube with a hole diameter of 0.4 mm and a pitch of 0.7 mm is 0.06 gr / min.
Extruded at 280 ° C. resin / hole, resin temperature. Air at a temperature of 280 ° C and a pressure of 0.7 kg / cm ² is used as the stretching gas, and the collection distance is 5 c.
m, the degree of vacuum in the negative pressure chamber 21 on the back side of the perforated plate 12 was melt-blown as a −1000 mm water column. At this time, the ambient temperature of collection is about
80 ° C.

The obtained perforated meltblown nonwoven fabric had a weight per unit area (basis weight) of 40 gr / m ² , an average fiber diameter of 6 μm, and a pore diameter of 1.3.
mm, the number of holes is 18 / cm ² , the apparent height of the projection 2 is about 1.5 mm,
The apparent thickness of the base cloth 1 was about 0.13 mm. FIGS. 8 to 10 show micrographs of 30 times magnification showing a front surface, a back surface, and a cross section of the nonwoven fabric of this example. As is clear from these photographs, the projections 2 are made of a group of fibers of the same quality as the base cloth 1.

This perforated melt-blown non-woven fabric is hydrophilically treated with a surfactant, laid on a water-absorbent material of a diaper, and laid on top.
When water was poured, it was confirmed that water was absorbed instantaneously and water permeability was good.

Moreover, the obtained nonwoven fabric was rich in breathability and flexibility, and had a good feel.

<Example 2> The perforated plate 12 has a wire diameter of 0.3 mm and an opening of 0.54 mm x 0.60 mm.
Was used to manufacture the nonwoven fabric of the present invention. Other conditions are the same as in the first embodiment.

The obtained melt blown nonwoven fabric has a weight per unit area (basis weight) of 40 gr / m ² , an average fiber diameter of 6 μm, a pore diameter of 0.6 mm,
The number of holes was 130 / cm ² , the apparent height of the protrusion 2 was about 0.9 mm, and the apparent thickness of the base cloth 1 was about 0.13 mm. The 30th microscopic photograph showing the front and back surfaces of the nonwoven fabric of this example is shown in FIGS.
Figure 12 shows.

This perforated meltblown nonwoven fabric is treated hydrophilically with a surfactant, and the surface without protrusions is laid on a diaper's water-absorbing material. Was confirmed to be good.

Moreover, the obtained nonwoven fabric was rich in breathability and flexibility, and had a good feel.

〔The invention's effect〕

The present invention can be formed into a nonwoven fabric having high water permeability, air permeability, flexibility, and cushioning property because it is formed with the above-described configuration.

Therefore, it can be widely used as a top sheet of a disposable diaper, a top sheet of a sanitary napkin, a cushioning material, a heat insulating material, a soundproofing material, a draining sheet and the like.

[Brief description of the drawings]

FIG. 1 is a perspective view of the melt-blown nonwoven fabric of the present invention viewed from the front, FIG. 2 is a perspective view of the meltblown nonwoven fabric of the present invention viewed from the back, FIG. 3 is a cross-sectional view of the meltblown nonwoven fabric of the present invention, FIG. FIG. 5 is a cross-sectional view of the melt blow apparatus according to the present invention, FIG. 5 is a front view of the die, FIG. 6 is a partially enlarged view thereof, and FIG. FIGS. 8 to 12 are micrographs showing the shapes of the fibers constituting the nonwoven fabric of the embodiment of the present invention, and FIG. 8 is the state of the surface-side fibers of the nonwoven fabric of the embodiment 1. , FIG. 9 is a plan view showing the back side fiber state of the non-woven fabric of Example 1, FIG. 10 is a cross-sectional view showing the fiber state of the protrusion, and FIG. 11 is the non-woven fabric of Example 2. FIG. 12 is a plan view showing the state of the front side fiber of FIG. 12, and FIG. 12 shows the state of the back side fiber of the nonwoven fabric of Example 2. It is a plan view. DESCRIPTION OF SYMBOLS 1 ... Base cloth part, 1a ... Hole 2a ... Protrusion tip, 2 ... Projection part 10 ... Melt blow die, 12 ... Perforated plate 12a ... Open hole

Claims (5)

(57) [Claims] 1. A base fabric portion formed of a fiber group of a thermoplastic resin has a large number of holes, and a cylindrical projection having a tip end made of a fiber group of the same quality as the base fabric portion is provided around each of the holes. A perforated melt-blown nonwoven fabric, wherein the protrusion height of the protrusion is at least twice the thickness of the base cloth. 2. The perforated melt-blown non-woven fabric according to claim 1, wherein the diameter of the hole is from 0.2 mm to 6 mm. 3. A group of fibers is sprayed and deposited from a melt blow die toward a perforated plate provided with a large number of apertures.
As the pressure on the opposite side is smaller, a part of the fiber group is made to protrude from the opening, and the protrusion bulges up in a cylindrical shape and the tip blows out to form a projection, and then the fiber assembly is porous. A method for producing a perforated melt-blown nonwoven fabric, characterized in that it is peeled off from a plate. 4. A method in which the pressure on the side opposite to the fiber blowing side is smaller than the pressure on the fiber blowing side with respect to the perforated plate as a boundary. The method for producing a perforated melt-blown nonwoven fabric according to claim 3, wherein a part of the fiber group is sucked and protruded from the opening of the plate. 5. A method for making the pressure on the opposite side smaller than the pressure on the fiber blowing side from the perforated plate as a boundary, wherein the perforated plate is brought close to a melt blow die, and the perforated plate is blown by the wind pressure blown from the melt blow die. The method for producing a perforated melt-blown nonwoven fabric according to claim 3, wherein a part of the fiber group is projected from the opening.