JP2001248057A - Porous sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porous sheet having soft touch feeling and proper air permeability which are not achieved by a film, and hardly forming fluff when being rubbed. SOLUTION: This porous sheet made from a thermoplastic polymer has 30-90% filling rate of a polymer, 2-100 polymer cross sections having <=50.001 mm2 per mm sheet cross section, and a network structure present on the surface of the sheet, formed out of linear objects, and obtained by fusing the polymer constituting each of the linear objects to each other at the crossing points so as to be integrated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous sheet made of a thermoplastic polymer, and more particularly, to a porous sheet having a specific porous structure in the cross section of the sheet and having a network-like uneven structure on at least one surface of the sheet. And a porous sheet having the same.

[0002]

2. Description of the Related Art Conventionally, nonwoven fabrics in which fibers are accumulated are known. The nonwoven fabric is integrated by bonding or fusing at the points where the fibers are in contact with each other, and although the cross-sectional shape of the fibers may be slightly deformed by heat, the fibers also retain their shape on the surface and inside of the nonwoven fabric It has a structure that is integrated and arranged in a state. Further, there is also known a nonwoven fabric in which fibers are entangled by needle punching or water entanglement to maintain the form without bonding the fibers by an adhesive or heat. These nonwoven fabrics are flexible, have good air permeability, have a calm appearance, and are used in a wide range of clothing and non-clothing. However,
Depending on the application, a conventional nonwoven fabric may not be used as it is.For example, generation of fluff from a nonwoven fabric during use may be a problem, or a controlled air permeability lower than that of a normal nonwoven fabric may be required. .

On the other hand, a porous film is known as a material having air permeability. A method for forming a porous film by adding a pore-forming agent to a thermoplastic polymer, stretching the film, forming the film-forming pore-forming agent, forming a porous structure by extracting and removing the pore-forming agent after the film is formed, It is manufactured by extruding a solution containing a thermoplastic polymer and a pore-forming agent into a coagulating liquid, and coagulating the thermoplastic polymer solution to form a porous structure. According to such a method, it is easy to adjust the microstructure of the porous film, but it is necessary to select an appropriate pore-forming agent to be added to the thermoplastic polymer, and the production method is relatively complicated. is there. Further, even if a pore-forming agent is added to the thermoplastic polymer to obtain a desired air permeability, it is difficult to form a film depending on the amount of addition, or even if the film can be formed, the strength is highly practical. However, there remains a problem that a product having the above-mentioned is not obtained. As described above, at present, a material satisfying desired performance cannot be obtained depending on the use of both the nonwoven fabric and the porous film.

For example, as a specific application, a base cloth of an emergency bandage is given. Most of the sheets having a low friction and abrasion resistance which have been conventionally used as an emergency bandage base cloth are films and air permeable. There was no thing. In order to provide air permeability, it is necessary to make a hole in the film or use a porous film as described above, but the film usually has a drawback that the feel is poor and the texture is poor. In order to solve such problems of the feeling of touch and air permeability of the film, for example, Japanese Utility Model Registration No. 1917955 proposes to use a fiber sheet made of polyurethane elastic fiber as a first aid base fabric. . However, since it is a fiber sheet, when it is used as a base fabric for an emergency bond, there has been a problem that fluff comes out due to rubbing of the surface. In order to reduce the fluff, it is conceivable to make the fibers thicker and to fuse them at the intersections.However, it is possible that the texture becomes rough, and it is also possible to heat-treat the fiber sheet surface. It is necessary to pass through another process for performing the process.

[0005]

DISCLOSURE OF THE INVENTION The present invention eliminates the drawback of the generation of fluff in a nonwoven fabric and the poor tactile sensation of a porous film, and has a moderate air permeability and a soft tactile sensation. The purpose is to provide a reasonable porous sheet.

[0006]

That is, the present invention relates to a porous sheet made of a thermoplastic polymer, which has a polymer filling rate of 30 to 90% and an arbitrary cross section of 0.001 mm ^{2 in} any cross section of the sheet. The following polymer cross section is 2 to 10
0 / mm and a porous sheet characterized by having the following network structure (a) and / or (b) on at least one surface of the sheet. (A) a network structure in which the intersections of the linear bodies are formed from linear bodies, and the polymers constituting the respective linear bodies are melted and integrated into one body; (b) formed by linear ridges Network structure

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The porous sheet of the present invention will be described with reference to the drawings. FIG. 1 is an enlarged schematic view showing an example of a cross section of the porous sheet of the present invention.
It is characterized in that a space (void) where the polymer does not exist, a portion where the polymer exists in a relatively large area (2), and a portion where the polymer exists in a small area (3) are observed. In the present invention, it is important that the cross section of the sheet is filled with the polymer at a ratio of 30 to 90%. When the polymer filling rate is less than 30%, the ratio of voids in the sheet is too large, and the sheet having such a low filling rate has a portion where the polymer is present in a small area when the cross section is observed (3). Tends to increase,
It is not preferable because the abrasion resistance of the sheet is reduced, which leads to the generation of fluff. On the other hand, if the filling rate exceeds 90%, it becomes impossible to obtain a desired air permeability. From such a viewpoint, the filling rate is preferably from 30 to 85%, particularly preferably from 40 to 8%.
0% is preferred. The filling rate of the polymer in the sheet cross section can be determined by a method described later,
The sheet cross-sectional area at that time is calculated as, for example, a dotted line drawn on the front and back surfaces of the sheet at predetermined intervals as shown in FIG.

In the porous sheet of the present invention,
When viewed at an arbitrary cross section of the sheet as shown in FIG. 1, the cross-sectional area is within a unit length (1 mm) in the sheet surface direction.
² independent polymer cross sections equivalent to 0.001 mm ² or less
It is important that there are １００100, particularly preferably 3 こ と が 75. The polymer cross-section having a specific cross-sectional area here corresponds to, for example, the cross-section of the portion (3) where the polymer has a small area in the sheet cross-section of FIG. ^Two
When the number of the following polymer cross sections (3) exceeds 100, the strength of the sheet tends to decrease, and fluff is easily generated by friction. Conversely, such a sheet having one or less cross-sections has a reduced thickness and poor tactile sensation. In addition,
The polymer cross section refers to a polymer having an area of 0.00001 mm ² as a lower limit value.

FIG. 2 is a photograph of an example showing the surface of the porous sheet of the present invention. On the sheet surface, linear bodies are irregularly arranged to form a network structure (a), and at the point where the linear bodies intersect, the respective polymers are almost completely melted and fused together by melting. State. FIG. 3 is a photograph showing another example of the surface of the porous sheet of the present invention. FIG. 3 shows FIG.
It is in a more advanced molten state, and a network structure (b) is formed by the linear ridges.
In the present invention, since the network structure as described in (a) and / or (b) exists only on the sheet surface, there is no or very little fuzz at the time of friction, and the appearance is like cloth. It has a soft touch texture.

[0010] While the weight of the sheet of the present invention is not particularly limited, considering the actual use when 10 to 200 g / m ^2, preferably from 30 to 150 g / m ^2. Also, the thickness can be appropriately changed according to the application, but in consideration of practicality,
0.03 mm to 0.5 mm is preferred. More preferably, it is 0.05 mm to 0.4 mm. Especially 0.1mm
~ 0.4 mm is preferred.

The thermoplastic polymer used in the present invention is not particularly limited, and may be a polyolefin elastomer such as an ethylene-α-olefin copolymer, a polyurethane elastomer, a polystyrene copolymer, a polyester elastomer, or a polyamide elastomer. It is possible to use various thermoplastic polymers such as thermoplastic elastomers such as elastomers, polyolefin-based resins such as polypropylene and polyethylene, and ethylene-vinyl alcohol-based copolymers. Considering this, a thermoplastic elastomer is preferably used. In addition, additives such as a lubricant may be added to the thermoplastic polymer in order to improve the releasability from a net or a roll and the self-adhesiveness of the formed porous sheet itself in a manufacturing process described later. When a thermoplastic elastomer is used, after forming the porous sheet, there is a high possibility that peeling from a net or a roll becomes difficult. Therefore, it is desirable to perform a treatment for improving the peelability on the surface.

The method for producing the porous sheet of the present invention is not particularly limited as long as the above-described sheet structure can be formed. For example, the porous sheet can be produced through the steps shown in FIGS. . (4) in the figure is a melting and discharging apparatus having nozzles arranged in a line, and the apparatus (4)
The molten polymer is extruded from the nozzle, and at the same time, high-temperature, high-pressure air is blown out from slits formed on both sides of the nozzle outlet to form a fine linear object from the discharged polymer, as shown in FIG. It can be manufactured by collecting and stacking on a collecting device such as a simple conveyor net (5) or a roll (8) as shown in FIG. 5 and winding it up by a winding device (7). At this time, if the distance from the nozzle to the collection device (collection distance) is long, the obtained sheet becomes a nonwoven fabric, and the sheet intended for the present invention cannot be manufactured.

The most important features of the present invention are that the collection distance of the polymer in the cross section of the sheet, the proportion of the specific minute cross section, and the specific network structure on the sheet surface are extremely reduced. And the distance between the outlet of the melting and discharging device (4) and the collecting surface is within 8 cm, preferably within 5 cm, particularly preferably 4.5 cm.
It is better to be within. If the collecting distance is too short, the polymer adheres to the nozzle surface or it becomes difficult to form a sheet. Therefore, it is preferable to keep the collecting distance of 1 cm or more.

As a collecting device, a conveyor net (5) as shown in FIG. 4 can be used. However, after forming a porous sheet, it is difficult to peel it off by winding. Preferably, the net surface is subjected to a treatment for improving releasability, such as oil application, Teflon (registered trademark) treatment, release agent application, and water spraying. Further, as a collecting device, for example, a diameter of 5 to 100 cm as shown in FIG.
Using a metal collecting roll (8), a supporting roll (9)
You may take up while supporting with. In order to improve the releasability as in the case of the net, the roll itself may be water-cooled and the surface may be subjected to a treatment such as Teflon processing. In some cases, the roll may be heated, for example, to promote film formation. When a roll is used, its surface may be a mirror surface, and a pattern may be applied to the surface of the collection device such as a roll or a net in order to impart design properties.

In FIG. 5, a conveyor net may be installed under the collecting roll (8) instead of the supporting roll (9). However, fly net easily adheres to the net and hinders stable production of sheets. In such a case, the rotation direction of the collecting roll is set to the opposite direction to that shown in FIG.
In addition, it is preferable to collect the discharged polymer by moving the central axis of the collecting roll about 1 mm to 50 mm upstream of the nozzle position in the sheet flow direction.

The temperature of the nozzle portion in the melting / discharging apparatus can be appropriately changed according to the type of the polymer to be used and the structure of the target sheet. Melt viscosity at the time of discharging from 5 to 50 Pa · s, particularly 5 to 30 Pa
It is preferable to set the nozzle temperature so as to be s. The high-pressure air discharged from the slit preferably has a temperature substantially equal to the nozzle temperature, and the amount of air per unit length of the slit is 0.01 to 0.2.
Nm ³ / (cm · min) is preferable from the viewpoint of stably producing a high quality sheet. Further, it is preferable that the temperature of the collection surface be lower by about 100 to 200 ° C. than the nozzle temperature.

The porous sheet of the present invention produced in this manner can be used in a 0.1 sheet by appropriately changing the production conditions and the like.
3 to 100 cc / (cm ² · s), preferably 0.5 to 3
It has a moderate air permeability of 0 cc / (cm ² · s),
The texture is soft touch, the generation of fluff at the time of friction is extremely improved, and it can be widely used from clothing to non-clothing applications, alone or in combination with other nonwoven fabrics. Can be effectively used as a base material for emergency bandages, a base material for patches, a wound covering material, a disposable diaper member, and other medical and sanitary materials, foods, and packaging materials for other products.

[0018]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples.

"Measurement of Polymer Filling Ratio in Cross Section of Porous Sheet"
The photograph was magnified to 0 times, and the respective cross-sectional areas occupied by the polymer, the sum total thereof, and the cross-sectional area of the sheet were calculated using an image analyzer manufactured by Toyobo, and the polymer filling rate was calculated by the following equation. Further, the number of polymer cross sections having a cross sectional area of 0.001 mm ² or less within the range of the sheet cross sectional area was also calculated. (1) Calculation of Sheet Cross-Section Area An arbitrary cross section of the porous sheet is observed under a magnification of 500 times with an electron microscope, and both sides of the front and back sides of the sheet are 50 μm ± over a length of 1 mm or more in the sheet surface direction. 10
The two line segments on the front and back sides obtained by connecting points on the outermost surface of the sheet at an interval of μm were regarded as the apparent sheet surface, and the sheet cross-sectional area (apparent cross-sectional area) was determined from the portion sandwiched between these line segments. . When the sheets were laminated to form a composite, the cross section was observed with the composite as it was, and the cross-sectional area of the sheet was calculated from the cross-sectional portion of the porous sheet in the same manner as described above. (2) Calculation of polymer filling rate The polymer filling rate was calculated by the following equation. Polymer filling rate (%) = ｛(total polymer cross-sectional area) /
(Sheet cross-sectional area)｝ × 100

"Measurement of abrasion resistance" Based on JIS L 1076, pilling test method (ART method), the presence or absence of fluff was confirmed and evaluated.

"Measurement of Air Permeability" Measured with a Frazier-type air permeability measuring tester according to JIS L 1096.

"Measurement of breaking strength and breaking elongation" JIS L
According to 1096, it was measured using a tensile tester (Autograph, manufactured by Shimadzu Corporation).

Example 1 A thermoplastic polyurethane "Kuramilon U" (manufactured by Kuraray Co., Ltd.) was used as a raw material, and 400 pieces were arranged in a row with a diameter of 0.3 mm.
The above polymer is melt-discharged at a nozzle temperature of 240 ° C. and a rate of 0.5 g per minute per single hole using a melt-discharge device having slits for injecting heated gas (slit width: 1.2 mm) on both sides of the round nozzle. Then, air (air amount: 0.1 Nm ³ / (cm · min)) heated to the same temperature as the nozzle temperature is jetted from the slit, and the thinned linear object having a diameter of 16 cm provided below the nozzle is placed below the nozzle. The sample was collected on a steel roll so that the collection distance was 2.5 cm, and was taken up by a take-up device to obtain a weight of 64.2 g / m ² and a thickness of 0.14.
An 8 mm porous sheet was obtained. The polymer filling rate of this porous sheet was 76.0%, and the number of cross-sections of polymers having 0.001 mm ² or less was 5 / mm. Further, when the sheet surface was observed with a scanning electron microscope, a network structure formed from linear ridges was recognized. This sheet did not generate any fluff in the pilling test.
Furthermore, when this porous sheet was used as a patch base fabric, a patch base fabric excellent in wearing feeling without stuffiness and fluff was obtained while suppressing early drying of the patch.

Example 2 The method of Example 1 except that the collection distance was 3.5 cm.
According to the weight 62.9 g / m^Two, 0.135mm thick porous
Quality sheet was obtained. The polymer filling rate of this porous sheet is
70.1%, 0.001mm^Two0.0001mm or less ^TwoMore polymer
-The number of cross sections was 35 / mm. In addition, scanning
Observation of the sheet surface with a microscope
And the intersections of the linear bodies are
The polymers that make up the
Network formed from network structure and linear ridge
The structure was recognized in about a half ratio. This sheet
No fluff was generated in the pilling test. Furthermore, this
When the porous sheet is used as a base cloth for emergency bandages,
A first-aid rescue plaster with no stuffiness, no fluff, and excellent wearing feeling
Was done.

Example 3 A porous sheet having a weight of 70.2 g / m ² and a thickness of 0.173 mm was produced according to the method of Example 2 except that the nozzle temperature was changed to 250 ° C. The polymer filling rate is 81.6%, 0.4%.
The number of cross sections of the polymer having a size of 001 mm ² or less was 3 / mm. There was no fluff in the pilling test. Further, when the sheet surface was observed with a scanning electron microscope, a network structure formed from linear ridges was recognized.

Example 4 A porous sheet having a weight of 62.0 g / m ² and a thickness of 0.137 mm was produced according to the method of Example 1 except that the collecting distance was 7.5 cm. Polymer filling rate 47.1%, 0.1
The number of cross sections of the polymer having a size of 001 mm ² or less was 58 / mm. No fluff was generated by the pilling test. Also,
When the sheet surface was observed with a scanning electron microscope,
A network structure is formed from the linear bodies, and the intersections of the linear bodies are recognized as a network structure in which the polymers constituting the respective linear bodies are melted and integrated, and further partially formed from the linear ridges. The observed network structure was also observed.

Example 5 The procedure of Example 2 was repeated except that the polyolefin elastomer "Engage" (manufactured by Dupont Dow Elastomer Co., Ltd.) was used as a raw material and the nozzle temperature was 310 ° C. and the single hole discharge rate was 0.45 g / min. Weight 100.1g /
A porous sheet having m ² and a thickness of 0.308 mm was produced.
The polymer filling rate was 69.3%, and the number of cross-sections of polymers having 0.001 mm ² or less was 10 pieces / mm. No fluff was generated by the pilling test. When the sheet surface was observed with a scanning electron microscope, it was found that the network structure was formed from linear bodies, and the intersections of the linear bodies were integrated with each other by melting the polymers constituting the linear bodies. In addition, a network structure partially formed from linear ridges was observed.

Example 6 The procedure of Example 2 was repeated, except that polypropylene was used as a raw material and the nozzle temperature was 310 ° C., and the single hole discharge rate was 0.3 g / min. The weight was 17.9 g / m ² and the thickness was 0.078 mm. A porous sheet was manufactured. 53.3% polymer loading, 0.
The number of cross sections of the polymer having a size of 001 mm ² or less was 28 / mm. No fluff was generated by the pilling test. Also,
When the sheet surface was observed with a scanning electron microscope,
A network structure is formed from the linear bodies, and the intersections of the linear bodies are recognized as a network structure in which the polymers constituting the respective linear bodies are melted and integrated, and further partially formed from the linear ridges. The observed network structure was also observed.

Comparative Example 1 A porous sheet having a weight of 58.8 g / m ² and a thickness of 0.156 mm was produced in the same manner as in Example 1 except that the collection distance was 15 cm. Polymer filling rate 28.9%, 0.001m
The number of cross sections of the polymer having a size of m ² or less was 110 / mm. Many fluffs were generated by the pilling test. When the sheet surface was observed with a scanning electron microscope, a typical nonwoven fabric structure formed of fibers and adhering at intersections without fusing and integrating was observed. Table 1 shows the physical properties of the porous sheets obtained in the above Examples and Comparative Examples.

[0030]

[Table 1]

Reference Example 1 Weight of 20.0 g / m ^{2 made of} thermoplastic polyurethane,
When the air permeability of the extruded film having a thickness of 34 μm was measured, it was 0.1 cc / (cm · s) or less.

Reference Example 2 Weight: 21.8 g / m ^{2 made of} polypropylene, thickness: 3
When the polymer filling rate and air permeability of a 4 μm porous film (manufactured by 3M) were measured, the polymer filling rate was 70% and the air permeability was 0.1 cc / (cm · s) or less.

It can be seen that the porous sheet of the present invention has a suitable gap in the sheet, has a soft touch feeling that cannot be achieved with a porous film, and is excellent in air permeability and abrasion resistance. .

[0034]

According to the present invention, it is possible to easily produce a soft touch porous sheet having a suitable air permeability without generation of fluff due to friction, and when this sheet is used as a base cloth for an emergency bandage or the like, it becomes stuffy. An emergency bandage with no fluff and excellent wearing feeling can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a porous sheet of the present invention.

FIG. 2 is an electron micrograph showing an example of the surface of the porous sheet of the present invention.

FIG. 3 is an electron micrograph showing another example of the surface of the porous sheet of the present invention.

FIG. 4 is a schematic process diagram illustrating an example of a method for producing a porous sheet according to the present invention.

FIG. 5 is a schematic process diagram for explaining another example of the method for producing a porous sheet of the present invention.

[Explanation of symbols]

 1: Cross section of porous sheet 2: Part where polymer is present in a relatively large area 3: Part where polymer is present in a small area 4: Melt discharge device 5: Conveyor net 6: Porous sheet 7: Winding device 8: Capture Collection roll 9: Support roll

Claims (5)

[Claims] 1. A porous sheet made of a thermoplastic polymer, having a polymer filling rate of 30 to 90%, and an arbitrary cross section of the sheet having 2 to 100 polymer cross sections having a cross sectional area of 0.001 mm ² or less. / Mm, and at least one surface of the sheet has the following network structure (a) and / or (b). (A) a network structure in which the intersections of the linear bodies are formed from linear bodies, and the polymers constituting the respective linear bodies are melted and integrated into one body; (b) formed by linear ridges Network structure 2. An air permeability of 0.3 to 100 cc / (cm ² .cm).
The porous sheet according to claim 1, which is s). 3. The porous sheet according to claim 1, wherein the thermoplastic polymer is a thermoplastic elastomer. A patch base fabric comprising the porous sheet according to any one of claims 1 to 3. 5. A first aid base fabric comprising the porous sheet according to claim 1.