JPH1121753A - Production of slit-spun melt-blow nonwoven fabric - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a melt-blow nonwoven fabric, allowing to stably produce the uniform ultrafine fiber nonwoven fabric in high productivity from a resin having a large extrusion resistance and easy to generate shear heat. SOLUTION: This method for producing a slit-spun melt-blown nonwoven fabric comprises extruding a thermoplastic resin from a die having a slit 9 having a lip width of 0.1-2.0 mm, simultaneously obliquely blowing a heated gas on the extruded filmy melted thermoplastic from adjacent slits 11 disposed on both the sides of the slit 9 to thin the filmy thermoplastic resin into fiber-like products, and simultaneously collecting the fiber-like products on a moving collection surface disposed in the downstream direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a slit-spun melt-blown nonwoven fabric having a high productivity of a thermoplastic resin.

[0002]

2. Description of the Related Art Conventionally, a fibrous molten polymer discharged from a plurality of orifices is injected with heated air or another gas from a propellant gas port provided adjacent to the orifice to melt the molten polymer. The method for producing a melt-blown nonwoven fabric for forcibly pulling the coalesced, effectively thinning, forming fibers of substantially 10 μm or less, and collecting the fiber flow to produce a nonwoven fabric is used as a method for producing a microfine nonwoven fabric. Have been

However, when the discharge amount per hole of the polymer orifice is increased in order to increase the production amount per unit space, there is a problem that the fibers gradually become larger and the formation of balls called shots is promoted. . In addition, for resins that have high extrusion resistance and tend to generate shear heat, the molecular structure changes due to cross-linking degradation during spinning, and the melt flow rate changes significantly before and after spinning, making spinning difficult and uniform spinning. There was a problem that can not be.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a resin having a high extrusion resistance, a resin which is liable to generate shear heat and a high productivity, and a stable production of a uniform ultrafine fiber nonwoven fabric. It is to provide a manufacturing method of.

[0005]

In order to achieve the above-mentioned object, the present inventors use a wide slit having a specific lip width in place of a plurality of spinning orifices, and use a high-speed gas having a specific flow rate to form a film. The present inventors have found that a nonwoven fabric made of ultrafine fibers having a narrow fiber diameter distribution can be easily produced by collecting a fiber stream by simultaneously drawing and narrowing the fibrous molten resin, thereby completing the present invention.

That is, according to the present invention, a thermoplastic resin is discharged in the form of a film from a die having a slit with a lip width of 0.1 to 2.0 mm, and the slit is applied to the discharged film-like molten thermoplastic resin. The heating gas is obliquely injected from the slits provided adjacent to both sides of the film so that the film-like thermoplastic resin is collected in a sheet shape on the moving collection surface provided in the downstream direction while being thinned into a fibrous shape. A method for producing a slit-spun melt-blown nonwoven fabric.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a thermoplastic resin is discharged from a spinning slit having a wide slit, and a high-speed heating gas is blown from both sides of the slit onto a wide plastic film obtained from the wide slit, whereby the film is made extremely fine. This is a method for producing a nonwoven fabric by separating and stretching fibers and collecting these ultrafine fiber flows. The configuration of the present invention will be described in detail below.

In the present invention, as a slit die for discharging a resin, a generally used T die or a coat hanger die of a flat die used for manufacturing a sheet or a film can be used. Of these,
A coat hanger die is preferred. The lip width of the slit die is 0.1 to 2.0 mm, preferably 0.2 to 1.
5 mm. When the width is less than 0.1 mm, the resin cannot be discharged smoothly, and when the width is more than 2.0 mm, the fiber of the film cannot be reduced, which is not preferable. The width of the heated high-speed gas slit provided adjacent to the slit for discharging the resin depends on the high-speed gas velocity, but may have the same width as the resin slit.

As the thermoplastic resin applicable to the slit-spun melt-blown nonwoven fabric method of the present invention, any thermoplastic resin can be used. In particular, extrusion resistance is high, shear heat is easily generated, and cross-linking deterioration at the time of spinning is caused. Polyolefin-based resins, elastomer-based resins, and the like, which are resins whose molecular flow changes easily change the melt flow rate before and after spinning. For example, as the polyolefin-based resin, polyethylene, ethylene-vinyl acetate copolymer, ethylene-α-olefin random copolymer, atactic polypropylene, polybutene, and the like, and the α-olefin of the ethylene-α-olefin copolymer As the olefin having 3 to 12 carbon atoms, propylene,
Butene-1, pentene-1, hexene-1, 4-methyl-pentene-1, 3-methyl-butene-1, heptene-
1, octene-1, nonene-1, decene-1 and the like. Further, examples of the elastomer resin include thermoplastic polyurethane, polyester / ether copolymer elastomer, polyester / lactone copolymer heavy elastomer, and the like. Of these resins, polyethylene is preferred. Further, these resins may be used by blending resins such as polypropylene, polyester, polyamide and the like used in a melt blow method for manufacturing from a large number of ordinary orifice dies.

[0010] The time during which the thermoplastic convects into the heated high velocity inert gas stream and turns into fibers is relatively short, and therefore it is relatively unlikely that the thermoplastic will decompose when heated. Few. However, in general, thermoplastics
Convection in the heated part of the die head for a longer time than in a high-speed inert gas stream, and is easily decomposed by both the residence time in the die head and the temperature at which the thermoplastic resin is held, The slit die of the present invention is characterized in that the residence time of the polymer in the die head is short and polymer decomposition is unlikely to occur.

As the high-speed gas used in the present invention, any inert gas which does not react with the thermoplastic resin is used. However, the high-speed gas stream used to make the film into fine fibers or microfibers is air. Is preferred. The flow rate of the high-speed gas must be such that it is necessary to decompose the formed film into ultrafine fibers immediately after leaving the wide slit spinning nozzle and collect these fibers as a nonwoven fabric.
It is necessary to spray from the slit at 1 to 5 kg / cm ² , preferably 1 to 3 kg / cm ² . 0.1kg / cm
^If it is less than ² , the fiber of the film cannot be formed and 5 kg / cm ²
Exceeding this is not preferable because it becomes difficult to collect as a nonwoven fabric. An advantage of the present invention is that these speeds can be increased throughout. The temperature of the high-speed gas suitable for microfibrillation is usually higher than the melting point of the thermoplastic resin, especially in the case of polyethylene, higher than its softening point, and a temperature of at least about 200 ° C is required.

The details will be described below with reference to the drawings. FIG. 1 is a schematic view of a nonwoven fabric manufacturing apparatus of the method according to the present invention. FIG. 1 shows an extruder 1 for thermoplasticizing a thermoplastic resin, a nonwoven fabric 2 obtained by the present invention, a spinning slit unit 3, a collector 4, and a winding device 5 for the nonwoven fabric 2. The apparatus operates by the melt blow method. Therefore, the spinning slit unit 3 is connected to the co-pressor 6, which acts on the air heater 7. In this way, the heated air can be sent to the spinning slit unit 3.

FIG. 2 is an enlarged view of the vicinity of the melt blow die slit. The base 8 and the gas slit adjusting plate 13 are combined, and the gap forms the gas injection slit 11 on both sides. The spinning slit 9 at the tip of the spinneret may be on the same plane as the gas injection slit, protruding, or intruding into the inside, but can be used properly depending on the properties of the nonwoven fabric to be obtained.

FIG. 3 is a view showing an example of a slit structure according to the melt blowing device of the present invention. FIG. 3 is a plan view of a slit portion near the discharge surface of the die as viewed from the discharge direction side. The gas ejection slits 11 are adjacent to each other.

In such an apparatus, the thermoplastic resin is supplied from the extruder 1 to the slit die unit 3 and is discharged from the slit 9 in the form of a film.
Accelerates the heated air introduced through the narrow gap,
Inject from the slit 11. The high-velocity gas hits the film-shaped molten resin at an oblique angle from both sides to cause turbulence in the flow and to form fine fibers. In addition, since the speed of the high-speed gas is overwhelmingly higher than the moving speed in the resin discharge direction, the molten resin is strongly pulled and stretched in the polymer discharge direction. It is particularly preferable that the gap in the high-speed gas supply flow path intersects the resin flow at an angle of 15 to 90 degrees.

The drawn fibers preferably have an average of 1
It has a fiber diameter of less than 5 μm, more preferably 1 to 15 μm, but can be easily changed by changing spinning conditions, and also easily by changing the distance between the die and the collector. . Other fibers and the like may be mixed into the fibrous nonwoven fabric of the present invention. For example, staple fibers, particulate matter, etc. can be introduced into the fiber stream before reaching the collector, and may be combined with the fibers in a subsequent heat treatment, molding operation.

The thickness of the nonwoven fabric of the present invention can vary greatly. For most applications, about 0.05-5c
Those having a thickness of m are used. Depending on the application, two or more nonwoven fabrics separately formed may be used in a stacked manner.
Also, the nonwovens of the present invention may be made by depositing the fiber stream directly onto another sheet material, such as another porous nonwoven. Special structures, such as other films, can be laminated to the sheet nonwoven fabric of the present invention by mechanical entanglement, heat bonding, or adhesives. The nonwoven fabric of the present invention may be further processed after being collected by a collector. For example, the pore size and thickness of the nonwoven fabric sheet may be controlled by heat treatment and pressure treatment, a pattern may be given to the nonwoven fabric, or particulate matter may be fixed.

The slit spinning meltblowing technique of the present invention is subject to the action of the gas stream over a larger surface area than the polymer stream extruded from the circular outlet of the orifice having the same discharge rate, so that even high viscosity polymers can be used. This can be applied, and the number of shots can be reduced as compared with the case where the circular discharge port of the orifice is used. Furthermore, when a nonwoven fabric made of fine fibers is collected on a flat surface, there is an advantage that the nonwoven fabric can be produced at a significantly higher efficiency because the rate of change in thickness is small.

[0019]

Embodiments of the present invention will be described below in detail. The present invention is not construed as being limited to the following examples. The measurement of the physical properties in the examples was performed according to the following methods. (1) Weight: 100 × 100 mm from the sample length direction
Of the test piece was taken, and the weight of the water equilibrium state was measured.
^It was converted to ^two . (2) Thickness: 100 × 100 mm from the sample length direction
Of the test specimen and dial thickness gauge (Co., Ltd.)
It was measured by 7321 manufactured by Mitoyo Seisakusho, 1 mm / 1 rotation). (3) Average fiber diameter: Five photographs were taken of any five points of the test piece with an electron microscope, the diameter of 20 fibers was measured for each photograph, and these were performed for the five photographs.
The average fiber diameter of 100 fibers was determined.

EXAMPLE 1 A single-screw extruder having a ratio (L / D) of the length L and the diameter D of the screw of the extruder of 25 to 3 inches shown in FIG. 2 and the lip width of the slit for discharging resin were used. A melt flow rate (hereinafter, sometimes abbreviated as MFR) is 50 (g / 1) using a melt-blowing slit spinneret having a gas discharge slit of 0.60 mm and 0.25 mm width on both sides thereof.
0 minutes, 190 ° C.), melt extrusion of a linear low density polyethylene resin having a melting point of 124 ° C. at an extrusion temperature of 260 ° C.
The mixture was melt-blown at a die temperature of 270 ° C. to obtain a slit-spun melt-blown nonwoven fabric. The discharge amount at this time is 100
g / hour / inch, the temperature of the air used for meltblowing is 280 ° C. at the inlet, and the pressure is 3.0 kg / cm ^2.
Met. The obtained slit-spun meltblown nonwoven fabric made of linear low-density polyethylene has a basis weight of 62.3 g / m ² ,
The thickness was 0.56 mm, and the average fiber diameter was 12.5 μm.

Comparative Example 1 Using the extruder used in Example 1 and a normal melt-blowing die, a melt-blowing spinneret having a total of 95 holes, in which spinning holes having a hole diameter of 0.4 mm are arranged in a line. Example 1
The linear low-density polyethylene resin used in
0 ° C., mouth temperature 250 ° C., discharge rate 100 g / h / inch, heated air 280 ° C., pressure 3.1 kg /
The melt blown non-woven fabric was obtained by blowing out at a density of ² cm ² . The obtained melt-blown nonwoven fabric made of linear low-density polyethylene had a basis weight of 56.5 g / m ² , a thickness of 0.61 mm, and an average fiber diameter of 23.7 μm, and a nonwoven fabric of fine fibers was not obtained. In addition, when the extrusion temperature was increased to 280 ° C. and the die temperature to 280 ° C. in order to obtain a nonwoven fabric of fine fibers, spinning could not be performed because the molten resin pressure in the die increased.

Example 2 The lip width of the slit spinneret for melt blowing was 0.8 m.
Using a device similar to that used in Example 1 except that the m was 21 m, a high-density polyethylene resin having an MFR of 21 (g / 10 minutes, 190 ° C.) and a melting point of 129 ° C. was extruded at 270 ° C.
Then, melt extrusion was performed at a die temperature of 280 ° C. to obtain a slit-spun melt-blown nonwoven fabric.
The discharge rate at this time was 100 g / hour / inch, and the temperature of the air used for melt blowing was 290 ° C. at the inlet,
The pressure was 3.0 kg / cm ² . The resulting high density polyethylene slit-spun meltblown nonwoven fabric has a basis weight of 58.5 g / m ² , a thickness of 0.51 mm, and an average fiber diameter of 1
It was 4.1 μm.

Comparative Example 2 Using the extruder used in Example 1 and a normal melt-blowing die, a melt-blowing spinneret having a total of 48 holes, in which spinning holes having a hole diameter of 0.8 mm are arranged in a line, Example 2
The high-density polyethylene resin used at
° C, base temperature 270 ° C, discharge rate 100 g / h / inch, heated air 280 ° C, pressure 3.1 kg / c
m ² was blown out to obtain a melt-blown nonwoven fabric. The resulting high-density polyethylene melt-blown nonwoven fabric has a basis weight of 60.0 g / m ² , a thickness of 0.63 mm, and an average fiber type of 2.
8.2 μm, and a nonwoven fabric of fine fibers could not be obtained. In order to obtain a non-woven fabric of fine fibers, the extrusion temperature is set to 3
When the temperature was raised to 00 ° C and the die temperature to 300 ° C, spinning could not be performed because the molten resin pressure in the die increased.

[0024]

According to the slit spinning melt blow technique of the present invention, the spinning temperature can be increased because the die internal pressure is lower than the melt blowing method using a nozzle die having a plurality of orifices. As a result, high-viscosity resins and resins with high extrusion resistance, which tend to generate heat due to shearing, and which tend to undergo a molecular structure change due to cross-linking degradation during spinning, are melt-blown to produce a stable, highly productive, uniform microfiber nonwoven fabric. can do.

[Brief description of the drawings]

FIG. 1 is a schematic view of a nonwoven fabric manufacturing apparatus.

FIG. 2 is an enlarged sectional view near a melt blow die slit.

FIG. 3 is a schematic plan view of the melt blow die slit as viewed from a discharge direction side.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Extruder 2 Nonwoven fabric 3 Spinning slit unit 4 Collector 5 Winding device 6 Compressor 7 Air heater 8 Cap part 9 Spinning slit 10 Resin introduction passage 11 Gas injection slit 12 Gas introduction port 13 Gas slit adjusting plate

Claims (2)

[Claims] 1. A thermoplastic resin having a lip width of 0.1 to
While discharging in the form of a film from a die having a 2.0 mm slit, the discharged film-shaped molten thermoplastic resin, by obliquely injecting a heating gas from a slit provided adjacent to both sides of the slit, A method for producing a slit-spun melt-blown nonwoven fabric, comprising collecting a film-shaped thermoplastic resin into a sheet on a moving collection surface provided in a downstream direction while reducing the film-shaped thermoplastic resin into a fiber. 2. The method for producing a slit-spun melt-blown nonwoven fabric according to claim 1, wherein a heated gas is injected at a rate of 0.1 to 5 kg / cm ² to thin the film-like molten thermoplastic resin into a fibrous shape.