METHOD FOR MANUFACTURING AND DEVICE FOR MANUFACTURING ULTRAFINE FIBER NONWOVEN FABRIC

Abstract

A spinning die for producing ultrafine fiber nonwoven fabric is made miniaturized and its productivity thereof is enhanced. The spinning die has a substantial cuboid shape and a plurality of nozzle holes is disposed in a longitudinal direction. A slit for jetting hot air is disposed only in one side of the nozzle holes. Thermoplastic polymer is melt blown from the nozzle of the spinning die to obtain ultrafine fibers. Hot air is jetted from the slit disposed at only one side of the nozzle holes. The result is that the ultrafine fibers melt blown in a direction inclined with respect to an axis direction of the nozzle. The blown ultrafine fibers are accumulated by sucking to downward to obtain ultrafine fiber nonwoven fabric.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Phase application filed under 35 USC 371 of PCT International Application No. PCT/JP2016/070580 with an International Filing Date of Jul. 12, 2016, which claims under 35 U.S.C. § 119(a) the benefit of Japanese Application No. 2015-144966 filed on Jul. 22, 2015, the entire contents of which are incorporated herein by reference.

BACKGROUND

(a) Technical Field

The present disclosure relates to a method for producing ultrafine fiber (or filament) nonwoven fabric and an apparatus therefor, in particular to the method which has excellent productivity and the apparatus therefor with a reduced size.

(b) Description of the Related Art

Hitherto, ultrafine fiber nonwoven fabric has been produced with using a spinning die of a substantial cuboid shape, which has nozzle holes for melt blowing thermoplastic polymer and slits for jetting hot air in both sides of the nozzle holes. The nozzle holes are linearly arranged in a longitudinal direction of the substantial cuboid spinning die. The spinning die is set to adjust the longitudinal direction of the spinning die to a width direction of the ultrafine fiber nonwoven fabric. A lot of ultrafine fibers are blown from the nozzle holes and accumulated to form ultrafine fiber nonwoven fabric.

A schematic cross sectional view of the spinning die is shown in FIG. 1. The longitudinal direction of the spinning die 1 is the direction from the front side to the back side of the paper sheet on which FIG. 1 is drawn. A plurality of nozzle holes 2 are aligned in a determined space distance along the longitudinal direction of the spinning die 1 (the direction from the front side to the back side of the paper sheet). Molten thermoplastic polymer is flowed from a polymer passage 3 to downward, and passed through an upper end of a nozzle to reach the nozzle hole 2. Hot air is flowed in pipes 6, 6 in a pressurized condition and passed through hot air passages 5, 5 to jet from slits 4, 4 which are disposed to both side of the nozzle hole 2. Thus, the molten thermoplastic polymer at the nozzle hole 2 is blown to a direction of an axis line of the nozzle with hot air jetted from the slits 4, 4 to obtain ultrafine fibers. A spinning die similar to the above is disclosed in Japanese Publication 2015-14065.

However, the spinning die 1 needs to have the pipes 6, 6, the hot air passages 5, 5 and the slits 4, 4 in both sides of the nozzle hole, to result in a drawback of a large-sized apparatus. The object of the present disclosure is to overcome the drawback and to make a small-sized apparatus. In addition, the spinning die is small-sized and a plurality of the spinning dies may be arranged in parallel, thus a productivity of ultrafine fiber nonwoven fabric may be enhanced.

SUMMARY

In order to solve the above problems, according to the present disclosure, it is not always necessary to include the slits in both sides of the nozzle hole. Accordingly, the reason why the conventional spinning die includes the slits in both sides of the nozzle hole is considered that the thermoplastic polymer is melt blown from the nozzle hole 2 by jetting hot air to the axis direction of the nozzle and the melt blown ultrafine fiber is extended to the direction of the axis to enhance the strength of the ultrafine fiber. However, it has been found that, even if hot air is jetted to the direction of axis of the ultrafine fiber in the condition, because the ultrafine fiber is floating in the air, almost no extension effects of the fiber are obtained.

Accordingly, in the present disclosure, hot air has been jetted from only one side of the nozzle hole to produce ultrafine fiber nonwoven fabric, and it was found that the resultant ultrafine fiber nonwoven fabric has almost the same properties as the conventional ultrafine fiber nonwoven fabric. Thus, the present disclosure provides a method for producing ultrafine fiber nonwoven fabric, which comprises: a step of melt blowing thermoplastic polymer from a plurality of nozzle holes which are disposed in a longitudinal direction at a longitudinal lower end of a spinning die having a substantial cuboid shape to obtain ultrafine fibers, a step of jetting out hot air from a slit disposed in only one side of the nozzle holes to blow the ultrafine fibers at an angle inclining with respect to the direction of an axial line of the nozzles, and a step of accumulating the blown ultrafine fibers which are sucked downward from the spinning die to form the ultrafine fiber nonwoven fabric.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic cross sectional view of a conventional spinning die for a producing apparatus for ultrafine fiber nonwoven fabric.

FIG. 2 shows a schematic cross sectional view of an example of the spinning die employed in the producing apparatus for the ultrafine fiber nonwoven fabric of the present invention.

FIG. 3 is a conceptual diagram showing a relation of an axial line of the nozzle with a blowing direction of the ultrafine fiber or a jetting direction of hot air.

FIG. 4 shows a schematic cross sectional view of another embodiment of the spinning die employed in the producing apparatus for the ultrafine fiber nonwoven fabric of the present invention. FIG. 5 shows a schematic cross sectional view of the producing apparatus of ultrafine fiber nonwoven fabric, which combines two of the spinning dies of FIG. 2.

FIG. 6 shows a schematic cross sectional view of the producing apparatus of ultrafine fiber nonwoven fabric, which combines two of the spinning dies of FIG. 4.

FIG. 7 shows a schematic cross sectional view of the producing apparatus of ultrafine fiber nonwoven fabric, which combines the spinning die of FIG. 2 with the spinning die of FIG. 4, in which the jetting directions of hot air are faced with each other.

FIG. 8 shows a schematic cross sectional view of the producing apparatus of ultrafine fiber nonwoven fabric, which combines the spinning die of FIG. 2 with the spinning die of FIG. 4, in which the jetting directions of hot air are leaving apart with each other.

DETAILED DESCRIPTION OF THE DISCLOSURE

The production method of the present disclosure is conducted with using a specific spinning die. The specific spinning die may include an embodiment shown in FIG. 2. FIG. 2 shows a schematic cross sectional view of a spinning die having a cuboid shape and a direction from the front side to the back side of the paper sheet on which FIG. 2 is drawn is a longitudinal direction of the spinning die 1. A plurality of nozzle holes 2 are aligned in the longitudinal direction (the direction from the front side to the back side of the paper sheet) in a determined space distance. Thermoplastic polymer is melt blown from the nozzle holes to form ultrafine fibers.

A slit is provided in only a right side of the nozzle hole 2. Hot air is flowed in pipes 6 in a pressurized condition and passed through hot air passage 5, thus jetting from slit 4. Accordingly, the ultrafine fibers from the nozzle 2 are blown to a left side to the axis line direction of the nozzle by jetting hot air. FIG. 3 schematically shows the direction of the axis line of the nozzle and the direction of blowing ultrafine fibers. The direction of blowing ultrafine fibers inclines a determined angle of θ with respect to the direction of the axis line of the nozzle. The angle of θ can be any value and may generally be preferred to be within a range of 30° to 60°. For setting an angle of the direction of blowing ultrafine fibers to θ, it is needless to say that a jetting angle of hot air is made θ with respect to the direction of the axis line of the nozzle.

Hot air is jetted to the ultrafine fibers at an angle of θ inclining with respect to the direction of the axis line of the nozzle. In this air jetting, it is necessary that the ultrafine fibers are sucked downward of the spinning die 1. Without sucking, it is not so easy that the ultrafine fibers are uniformly accumulated on a conveyer provided under the spinning die 1, thus deteriorating qualities of the resultant ultrafine fiber nonwoven fabric. The sucking can generally be conducted by a reduced pressure using a suction box from a lower portion of a breathable conveyer, such as a wire mesh chain conveyer and the like.

In FIG. 2 the slit is disposed in only a right side of the nozzle hole 2, but it can be disposed only in a left side. Accordingly, the die is symmetrical with the spinning die of FIG. 2 and its cross sectional view is shown in FIG. 4 as a spinning die 1 using same number.

The apparatus for the production method of the present disclosure is comprised of the spinning die 1 shown in FIG. 2 and/or FIG. 4. Accordingly, the spinning die 1 comprises a pipe for providing hot air and a passage for providing thermoplastic polymer.

Actually, the production of the ultrafine fiber nonwoven fabric may be conducted by an apparatus of only one of the spinning die 1 as shown in FIG. 2 or FIG. 4, or an apparatus of a combination of more than two spinning dies 1 shown in FIG. 2 (for example as shown in FIG. 5). It may also be conducted by an apparatus of a combination of more than two spinning dies of shown in FIG. 4 (for example as shown in FIG. 6). In addition, it may be an apparatus of a combination of the spinning die 1 shown in FIG. 2 and the spinning die 1 shown in FIG. 4 (for example as shown in FIG. 7 and FIG. 8). The combined apparatus shown in FIG. 7 has the jetting directions of hot air, which are faced with each other. The combined apparatus shown in FIG. 8 has the jetting directions of hot air, which are left apart with each other. Further, the combined apparatus can be assembled with two or more apparatuses or can be manufactured as one body.

The term “ultrafine fiber” as used herein means fiber having a fiber diameter of about 1 to about 15 μm. The thermoplastic polymer employed herein can be polyolefin, polyamide, polyester or the like. The nozzle hole 2 can generally have a diameter of about 0.1 to about 0.5 mm. Number of the nozzle holes can be 30 to 100 dies/inch and the nozzle holes are arranged in a longitudinal direction at a longitudinal lower end of a spinning die 1. The nozzle generally has a length of about 1 to about 5 mm.

In the combined apparatus of the present disclosure, a mixed ultrafine fiber nonwoven fabric can be obtained by changing the sorts of the thermoplastic polymer melt blown from each of the apparatuses. For example, polyester fiber is melt blown from one of the combined apparatus and polypropylene is melt blown from the other of the combined apparatus, thus obtaining a polyester/polypropylene ultrafine fiber nonwoven fabric. In the combined apparatus of the present disclosure, another mixed ultrafine fiber nonwoven fabric can be obtained by changing each diameter of the nozzle hole 2, thus obtaining a ultrafine fiber nonwoven fabric having different fiber diameter. For example, a thermoplastic polymer is melt blown from one of the combined apparatus which provides nozzle holes having a diameter of 0.1 mm and a thermoplastic polymer is melt blown from the other of the combined apparatus which provides nozzle holes having a diameter of 0.5 mm, thus obtaining a ultrafine fiber nonwoven fabric having a mixed fiber diameter.

The ultrafine fiber nonwoven fabric obtained by the production method of the present disclosure can be used for applications, such as filter material, cleaning cloth or the like.

The apparatus of the present disclosure has technical effects of making it miniaturized because it has the pipe flowing hot air, the passage for hot air and the slit only in one side of the nozzle holes, as it is clear when comparing with the conventional apparatus of FIG. 1. In addition, even if two of the apparatuses of the present disclosure are combined, the resulting combined apparatus has the same size with the conventional apparatus. According, the present disclosure has excellent technical effects in that the productivity of the ultrafine fiber nonwoven fabric of the present disclosure can be double in comparison with that of the conventional apparatus.

Claims

1. A method for producing ultrafine fiber nonwoven fabric, comprising:

a step of melt blowing thermoplastic polymer from a plurality of nozzle holes which are disposed in a longitudinal direction at a longitudinal lower end of a spinning die having a substantial cuboid shape to obtain ultrafine fibers,

a step of jetting out hot air from a slit disposed in only one side of the nozzle holes to blow the ultrafine fibers at an angle inclining with respect to the direction of an axial line of the nozzles, and

a step of accumulating the blown ultrafine fibers which are sucked downward from the spinning die to form the ultrafine fiber nonwoven fabric.

2. The method for producing ultrafine fiber nonwoven fabric according to claim 1, wherein the slit is provided in either a right side or a left side of a line of the nozzle holes.

3. The method for producing ultrafine fiber nonwoven fabric according to claim 1, wherein the ultrafine fibers are blown with hot air at an angle inclining 30° to 60° with respect to the axis line of the nozzles.

4. An apparatus for producing ultrafine fiber nonwoven fabric, comprising a plurality of nozzle holes disposed in a longitudinal direction at a longitudinal lower end of a spinning die having a substantial cuboid shape, and a slit for jetting hot air disposed in only one side of a line of the nozzle holes.

5. The apparatus for producing ultrafine fiber nonwoven fabric according to claim 5, wherein the slit is provided in only a right side of a line of the nozzle holes.

6. The apparatus for producing ultrafine fiber nonwoven fabric according to claim 5, wherein the slit is provided in only a left side of a line of the nozzle holes.

7. A combined apparatus for producing ultrafine fiber nonwoven fabric is disposing at least two of the apparatus according to claim 5 in parallel.

8. A combined apparatus for producing ultrafine fiber nonwoven fabric is disposing at least two of the apparatus according to claim 6 in parallel.

9. A combined apparatus for producing ultrafine fiber nonwoven fabric of claim 4, further comprising a first apparatus in which the slit is provided in only a right side of a line of the nozzle holes and a second apparatus in which the slit is provided in only a left side of a line of the nozzle holes.

10. The apparatus of producing ultrafine fiber nonwoven fabric according to claim 4, wherein the hot air from the slit is jetted at an angle inclining 30° to 60° with respect to the axis direction of the nozzles.