WO2020203932A1

WO2020203932A1 - Melt-blown nonwoven fabric manufacturing method and melt-blown nonwoven fabric

Info

Publication number: WO2020203932A1
Application number: PCT/JP2020/014392
Authority: WO
Inventors: 和也永峰; 貴幸宮本; 武和前田
Original assignee: 株式会社カネカ
Priority date: 2019-03-29
Filing date: 2020-03-27
Publication date: 2020-10-08
Also published as: EP3943655B1; JPWO2020203932A1; CN113950547A; EP3943655A1; EP3943655A4

Abstract

Provided are: a melt-blown nonwoven fabric manufacturing method that enables manufacturing of a melt-blown nonwoven fabric having high strength without performing a calendering process; and a melt-blown nonwoven fabric that can be manufactured by the manufacturing method. This melt-blown nonwoven fabric manufacturing method includes setting, in the respective suitable ranges, the temperature of a resin to be discharged from a spinning die head, the amount and the temperature of hot air to be blown to a nozzle hole from which the resin is discharged, the amount of the resin discharged from the nozzle hole, and a distance between the nozzle hole and a conveyor for conveying a melt-blown nonwoven fabric.

Description

Manufacturing method of melt-blown non-woven fabric and melt-blown non-woven fabric

The present invention relates to a method for producing a melt-blown non-woven fabric and a melt-blown non-woven fabric.

A resin discharge process that discharges molten resin from a spinning die head equipped with nozzles with multiple holes,
A fiber forming process in which hot air flowing from the nozzle hole toward a conveyor provided facing the spinning die head is blown toward the nozzle hole to fibrate the discharged molten resin to form fibers.
A melt-blown non-woven fabric is manufactured by a so-called melt-blown method including a non-woven fabric forming step of depositing the fibers on a conveyor by a stream of hot air to form a melt-blown non-woven fabric.

According to such a method, a non-woven fabric made of ultrafine fibers and having a large specific surface area can be produced inexpensively and easily. The melt-blown non-woven fabric produced by such a method has a problem in terms of strength because the fibers are weakly adhered to each other in the state of being deposited on the conveyor. For this reason, the melt blown non-woven fabric is used in a state where the strength is increased by heat compression processing with a calendar roll, which is so-called calendar processing (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 06-136656

However, although the calendar-processed melt-blown non-woven fabric has high strength, its surface is crushed and its breathability is reduced. Breathability is an important performance when melt blown non-woven fabric is used for filter applications and the like.

The present invention has been made in view of the above problems, and is a method for producing a melt-blown non-woven fabric capable of producing a melt-blown non-woven fabric having good strength without calendar processing, and a melt-blown that can be produced by the manufacturing method. An object of the present invention is to provide a non-woven fabric.

As a result of diligent studies to solve the above problems, the present inventors have completed the present invention.

That is, the present invention provides the following (1) to (8).
(1) A resin discharge process in which molten resin is discharged from a spinning die head equipped with nozzles having a plurality of holes.
A fiber forming process in which hot air flowing from the nozzle hole toward a conveyor provided facing the spinning die head is blown toward the nozzle hole to fibrate the discharged molten resin to form fibers.
Including a non-woven fabric forming step of depositing fibers on a conveyor to form a melt-blown non-woven fabric by a stream of hot air.
After the non-woven fabric forming process, no calendar processing is performed,
The temperature of the hot air is above the melting point of the resin and below (melting point + 100 ° C).
The air volume of hot air is 1000 NL / min / m or more and 7000 NL / min / m or less.
Discharge rate of the resin per one nozzle hole, and a 0.006 cm ³ / min or more 0.3 cm ³ / min or less,
The temperature of the resin in the nozzle hole is equal to or higher than the melting point of the resin (melting point + 100 ° C) or lower.
The shortest distance between the nozzle hole and the conveyor is 10 mm or more and 75 mm or less.
A method for producing a melt-blown non-woven fabric, wherein the temperature of the atmosphere between the nozzle hole and the conveyor is 110 ° C. or higher and 160 ° C. or lower.
(2) The method for producing a melt-blown non-woven fabric according to (1), wherein the resin is a polyester-based resin or a polyolefin-based resin.
(3) The values of ultrasonic reflection intensity on both sides of the melt blown non-woven fabric are different from each other.
The larger reflection intensity value is 1.2 times or more and 3.0 times or less than the smaller reflection intensity value.
The reflection intensity is as follows:
Distance between ultrasonic transmitter / receiver and non-woven fabric surface: 155 mm
Frequency: 360kHz
Measurement temperature: 22 ° C
Applied voltage: 500V
Wavenumber: 5 (burst wave)
Sharp ratio: 100%
The method for producing a melt-blown non-woven fabric according to (1) or (2), which is an average value of 100 or more measured values measured according to 100 or more points within a range of 25 mm × 40 mm.
(4) The values of the reflection intensity of ultrasonic waves on both sides are different from each other.
The larger reflection intensity value is 1.2 times or more and 3.0 times or less than the smaller reflection intensity value.
The reflection intensity is as follows:
Distance between ultrasonic transmitter / receiver and non-woven fabric surface: 155 mm
Frequency: 360kHz
Measurement temperature: 22 ° C
Applied voltage: 500V
Wavenumber: 5 (burst wave)
Sharp ratio: 100%
Number of measurement points: A melt-blown non-woven fabric which is an average value of 100 or more points measured according to 100 points or more within a range of 25 mm × 40 mm.
(5) The meltblown non-woven fabric according to (4), which has a thickness of 0.1 mm or more and 0.4 mm or less.
(6) The melt-blown non-woven fabric according to (4) or (5), wherein the apparent density is 50 kg / m ³ or more and 350 kg / m ³ or less.
(7) The meltblown non-woven fabric according to any one of (4) to (6), wherein the average pore diameter measured by a palm poromometer is 2.5 μm or more and 5.0 μm or less.
(8) Any one of (4) to (7), wherein the average fiber diameter, which is the average value of the fiber diameters of 100 or more fibers obtained from the electron microscope image, is 0.5 μm or more and 3.0 μm or less. Melt blown non-woven fabric described in.

According to the present invention, it is possible to provide a method for producing a melt-blown non-woven fabric capable of producing a melt-blown non-woven fabric having good strength without performing calendar processing, and a melt-blown nonwoven fabric that can be produced by the manufacturing method.

It is a figure which shows the outline of the structure of the manufacturing apparatus of the melt blown non-woven fabric. It is a perspective view which shows the outline of the spinning die head provided in the melt blown non-woven fabric manufacturing apparatus. It is a graph which shows the relationship between the position in the thickness direction of the melt blown non-woven fabric of Example 2 and Example 4 analyzed by X-ray CT, and the occupancy rate of a fiber. It is a graph which shows the relationship between the position in the thickness direction of the melt blown non-woven fabric of Comparative Example 6 and Comparative Example 7 and the occupancy rate of a fiber analyzed by X-ray CT. It is a grayscale image in the central portion in the thickness direction of the meltblown nonwoven fabric of Example 2 acquired by X-ray CT analysis.

≪Manufacturing method of melt blown non-woven fabric≫
Hereinafter, a method for producing a melt-blown non-woven fabric will be described with reference to the drawings as necessary. FIG. 1 shows an outline of a melt blown non-woven fabric manufacturing apparatus. FIG. 2 shows an outline of a spinning die head provided in a melt blown non-woven fabric manufacturing apparatus as a perspective view.

The manufacturing method of melt blown non-woven fabric is
A resin ejection process in which molten resin is ejected from a spinning die head 10 having a plurality of nozzle holes 11.
A fiber that forms fibers by blowing hot air flowing from the nozzle hole 11 toward a conveyor 12 provided facing the spinning die head 10 toward the nozzle hole 11 and fibrating the discharged molten resin. The formation process and
It is a method including a non-woven fabric forming step of forming a melt blown non-woven fabric by depositing fibers on a conveyor by an air flow of hot air.
In addition, no calendar processing is performed after the non-woven fabric forming step.

<Resin discharge process>
In the resin discharge step, the molten resin is discharged from the spinning die head 10 having a plurality of nozzle holes 11.

The method of supplying the molten resin to the spinning die head 10 is not particularly limited. As a typical method, a method of melting the resin supplied from the hopper 100 by passing it through an extruder 101 and supplying the melted resin to the spinning die head 10 through a kneader 104 can be mentioned.

The type of extruder 101 is not particularly limited as long as the resin can be melted. Types of extruder 101 include, for example, single-screw extruder, same-direction meshing twin-screw extruder, same-direction non-meshing twin-screw extruder, different-direction non-meshing twin-screw extruder, multi-screw extruder and the like. Machines can be used. Among them, the single-screw extruder is preferable because the resin retention portion in the extruder is small, so that it is possible to prevent thermal deterioration of the resin during extrusion, and the equipment cost is reduced. Further, when a resin that generates residual volatile matter is used, the extruder 101 may have a vent structure.

As the raw material form of the resin to be put into the extruder 101, a solid resin is preferable. More preferably, a pellet-shaped resin is used. The pellet-shaped resin is generally supplied into the extruder 101 via a hopper 100 attached to a raw material supply port of the extruder 101.

The resin supplied to the extruder 101 is preferably heat-dried in advance so as not to cause hydrolysis or oxidative deterioration of the resin. The amount of water in the resin is preferably 200 mass ppm or less. The drying conditions are preferably 100 ° C. for 3 hours or more, although it depends on the resin.

At the time of drying, it is preferable to remove oxygen in the atmosphere to be dried or remove oxygen in the resin. The atmosphere at the time of drying is preferably an atmosphere of an inert gas such as nitrogen.
For drying, in consideration of the required drying time and resin consumption time, a method using a hopper type dryer provided with a drying mechanism in the hopper 100 that supplies pellets to the extruder 101, or using a dryer before supplying the resin to the hopper 100. A method of supplying the resin to the hopper 100 so as not to dry the hopper and absorb moisture, or a method of using both of them can be preferably used.

Of these methods, the method using a hopper type dryer is preferable because the resin can be kept in a dry state until just before the resin is supplied to the extruder 101.
By using a dryer in front of the hopper 100, the dryer in front of the hopper 100 dries quickly at a high temperature, and the hopper type dryer creates a dehumidifying atmosphere so that moisture does not enter, because moisture does not mix even at low temperatures. More preferred.
If the temperature of the hopper 100 is excessively high, blocking problems and the like may occur. Therefore, specifically, after drying the resin at 120 ° C. for 3 hours or more in the dryer in front of the hopper 100, the temperature inside the hopper type dryer is set to 40 to 100 ° C. to suppress the water content of the resin. And extrusion stability are easy to achieve at the same time.

Regarding the extruder 101, for example, as a screw (not shown) used in a single-screw extruder or the like, a screw having a general full-flight configuration with a compression ratio of about 2 to 3 for an extruder without or with a vent is used. Can be done. It is also possible to adopt a special kneading mechanism such as barrier flight so that unmelted material does not exist.

The resin discharge step, from each of the nozzle holes 11 a spinning die head 10 is provided, as the discharge amount of resin is 0.006 cm ³ / min or more 0.3 cm ³ / min or less, the molten resin is discharged. The above discharge amount is the discharge amount from one nozzle hole 11.
The amount of resin discharged from one nozzle hole 11 is 0.01 cm ³ / min or more because it is easy to stably extrude the resin and it is easy to form fibers having excellent crystallization and strength. 0.2 cm ³ / min or less is preferable, and 0.02 cm ³ / min or more and 0.1 cm ³ / min or less is more preferable.

Further, in the resin discharge step, the molten resin is discharged so that the temperature of the resin in the nozzle hole 11 is equal to or higher than the melting point of the resin (melting point + 100 ° C.) or lower.
Therefore, the extrusion conditions of the extruder 101, such as the cylinder temperature, the resin residence time, and the extrusion amount, are adjusted so as to satisfy the above conditions regarding the discharge amount and the temperature of the discharged resin.
In the subsequent fiber forming step, the temperature of the resin in the nozzle hole 11 is preferably equal to or higher than the melting point of the resin (melting point + 70 ° C.) or lower because the discharged resin can be easily fiberized.

The molten resin obtained by a melting means such as an extruder 101 is preferably supplied to a spinning die head using a gear pump 102. By using the gear pump 102, fluctuations in the discharge amount in the extruder 101 are absorbed, the supply quantification is remarkably improved, and the resin discharge from the nozzle hole 11 provided in the spinning die head 10 is also stable.
The molten resin quantitatively supplied by the gear pump 102 or the molten resin directly supplied from the extruder 101 is supplied to the spinning die head 10 through, for example, a tubular flow path, and is supplied from a plurality of nozzle holes 11 included in the spinning die head 10. It is discharged.

A foreign matter removing device such as a filter 103 should be provided in the resin flow path from the gear pump 102 to the die, or in the resin flow path from the melting means such as the extruder 101 to the spinning die head 10 when the gear pump 102 or the like is not used. Is preferable.
As a result, it is possible to trap the foreign matter contained in the raw material resin and the foreign matter generated by the extruder or the gear pump 102, and reduce the mixing of the foreign matter into the non-woven fabric.

As the filter 103 as a foreign matter removing device, a screen mesh, a pleated filter, a leaf disc filter, or the like can be used. Among these, the leaf disc type filter is preferable in terms of filtration accuracy, filtration area, pressure resistance, time until filter clogging due to foreign matter, and the like. As the filter medium of the filter 103, for example, a sintered non-woven fabric of metal fibers can be used.

The molten resin discharged from the gear pump 102 is supplied to the spinning die head 10 with or without the filter 103. The supply of the molten resin from the gear pump 102 or from the filter 103 to the spinning die head 10 is performed, for example, through the kneader 104.

The molten resin supplied to the spinning die head 10 by the method as described above is discharged from a plurality of nozzle holes 11 included in the spinning die head 10 as shown in FIG.
The arrangement of the plurality of nozzle holes 11 in the spinning die head 10 is not particularly limited as long as the melt blown non-woven fabric 2 having desired characteristics can be produced. Typically, the plurality of nozzle holes 11 are arranged so as to form rows at appropriate intervals in the same direction as the width direction of the melt blown nonwoven fabric 2 formed on the conveyor 12 described later. The distance between the nozzle holes 11 is, for example, preferably 0.10 mm or more and 1.0 mm or less, and more preferably 0.25 mm or more and 0.75 mm or less. The spacing between the nozzle holes 11 may or may not be uniform, but is preferably uniform in that a homogeneous non-woven fabric can be easily produced.

The shape of the opening of each nozzle hole 11 is not particularly limited, but is usually circular, substantially circular, elliptical, substantially elliptical, or the like. The opening diameter of each nozzle hole 11 is not particularly limited, and is appropriately selected according to the fiber diameter of the fibers constituting the non-woven fabric.

The resin used as a raw material for the melt-blown non-woven fabric 2 used in the resin discharge step is not particularly limited as long as it is a resin conventionally used as a raw material for the melt-blown non-woven fabric.
Examples of the resin include polyolefin-based resins, polystyrene-based resins, (meth) acrylic-based resins, polyester-based resins, polyamide-based resins, polycarbonate-based resins, and the like.

Examples of the polyolefin resin include low-density polyethylene, high-density polyethylene, polypropylene, ethylene-propylene copolymer, poly1-butene, and poly4-methyl-1-pentene. Examples of the (meth) acrylic resin include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, phenyl (meth) acrylate, and benzyl (meth) acrylate. Examples thereof include polymers of one or more (meth) acrylate monomers selected from the (meth) acrylates. As the (meth) acrylic resin, polymethyl (meth) acrylate is preferable. Examples of the polyester resin include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PNE), and polylactic acid (PLA). Examples of the polyamide-based resin include nylon 6, nylon 6, 6, nylon 12, nylon 6, 12, and MXD nylon.

Among these resins, polyolefin-based resins and polyester-based resins are preferable, and polypropylene, polyethylene terephthalate, and polybutylene terephthalate are more preferable, because they have good processability when producing melt-blown non-woven fabrics.

<Fiber formation process>
In the fiber forming step, hot air flowing from the nozzle hole 11 toward the conveyor 12 provided facing the spinning die head 10 is blown toward the nozzle hole 11 to fibrate the discharged molten resin to form fibers. To form.

When hot air is blown near the nozzle hole 11, the molten resin discharged from the nozzle hole 11 is stretched by the hot air and made into fibers.
Further, the hot air flows from the vicinity of the nozzle hole 11 toward the conveyor 12 provided facing the spinning die head 10. Therefore, the fibers stretched by the hot air are deposited on the conveyor 12 along with the air flow of the hot air in the subsequent non-woven fabric forming step to form the melt blown non-woven fabric 2.

The method of blowing hot air is not particularly limited. Typically, hot air can be generated by heating an inert gas such as air or nitrogen pressurized by a compressor (not shown) with a heater (not shown).
Further, by colliding the hot air on the traveling direction side of the conveyor 12 and the hot air on the opposite side of the traveling direction of the conveyor 12 in the vicinity of the nozzle hole 11, the direction of the hot air flowing toward the vicinity of the nozzle hole 11 is changed from the nozzle hole 11 to the conveyor 12. Can be changed in the direction toward.

The temperature of the hot air is preferably (melting point + 30 ° C.) or lower, (melting point + 30 ° C.) or higher, (melting point + 90 ° C.) or lower, and (melting point + 40 ° C.) or higher, (melting point + 80 ° C.) or lower. preferable.
When the temperature of the hot air is within the above range, the resin discharged from the nozzle hole 11 can be easily stretched, and in the subsequent non-woven fabric forming step, the fibers can be easily heat-sealed on the conveyor 12.

The air volume of hot air is 1000 NL / min / m or more and 7,000 NL / min / m or less, preferably 2000 NL / min / m or more and 6800 NL / min / m or less, and more preferably 3000 NL / min / m or more and 6500 NL / min / m or less. ..
When the air volume of the hot air is within the above range, the resin discharged from the nozzle hole 11 can be easily stretched, and in the subsequent non-woven fabric forming step, the fibers can be easily heat-sealed on the conveyor 12.

<Non-woven fabric forming process>
In the non-woven fabric forming step, the fibers are deposited on the conveyor 12 by the air flow of hot air generated in the fiber forming step to form the melt blown non-woven fabric 2.

In the non-woven fabric forming step, the shortest distance between the nozzle hole 11 and the conveyor 12 is set to be 10 mm or more and 75 mm or less.
Further, the non-woven fabric forming step is carried out so that the temperature of the atmosphere between the nozzle hole 11 and the conveyor 12 is 110 ° C. or higher and 160 ° C. or lower.
By setting the shortest distance between the nozzle hole 11 and the conveyor 12 within the above range and setting the temperature of the atmosphere between the nozzle hole 11 and the conveyor 12 within the above range, the vicinity of the surface of the conveyor 12 The heat-sealing property of the resin fibers in the above can be within a good range in which a melt-blown non-woven fabric having good mechanical properties can be formed.
As a result, the melt-blown non-woven fabric 2 having good strength can be produced even if the calendar processing is not performed. Further, when the calendar processing is not applied, the air permeability of the melt blown non-woven fabric is good.

The method of setting the temperature of the atmosphere between the nozzle hole 11 and the conveyor 12 within the above range is not particularly limited. For example, the space between the nozzle hole 11 and the conveyor 12 may be surrounded by a wall for the purpose of preventing a decrease in temperature. As such a wall, it suffices to prevent the inflow of outside air into the space between the nozzle hole 11 and the conveyor 12. The material of the wall may be a heat-resistant heat insulating material such as glass wool, rock wool, or porous ceramic. Further, a heater may be provided so as to heat the space between the nozzle hole 11 and the conveyor 12. If the temperature of the space between the nozzle hole 11 and the conveyor 12 becomes too high due to the relationship between the hot air temperature and the resin temperature, a cooler is provided so as to cool the space between the nozzle hole 11 and the conveyor 12. May be good.

The shortest distance between the nozzle hole 11 and the conveyor 12 is appropriately set within a range of 10 mm or more and 75 mm or less in consideration of the thickness and strength of the melt blown non-woven fabric. The longer the shortest distance between the nozzle hole 11 and the conveyor 12, the thicker the obtained melt blown non-woven fabric 2 tends to be, and the lower the apparent density and the tensile strength tend to be.
If the shortest distance between the nozzle hole 11 and the conveyor 12 exceeds 75 mm, the apparent density of the obtained melt-blown non-woven fabric becomes significantly small, and the desired strength of the melt-blown non-woven fabric cannot be maintained without calendar processing.

The temperature of the atmosphere between the nozzle hole 11 and the conveyor 12 is 110 ° C. or higher and 160 ° C. or lower, preferably 115 ° C. or higher and 155 ° C. or lower, and more preferably 125 ° C. or higher and 150 ° C. or lower.
The temperature of the atmosphere between the nozzle hole 11 and the conveyor 12 can be measured, for example, according to the following method. Specifically, the temperature of the atmosphere between the nozzle hole 11 and the conveyor 12 is measured by thermography from a position 2 m away from the front surface of the spinning die head 10 (a surface parallel to the width direction of the manufactured melt blown non-woven fabric 2). To do. More specifically, the thermography of the atmosphere between the nozzle hole 11 and the conveyor 12 at an arbitrary position near directly above the non-woven fabric within a range ± 250 mm in the width direction from the center position in the width direction of the spinning die head 10. The temperature data of 100 pixels corresponding to 2.5 mm square in actual size is measured. The average value of the obtained temperature data of 100 points is taken as the temperature of the atmosphere between the nozzle hole 11 and the conveyor 12.

The material of the conveyor 12 is not particularly limited as long as it has heat resistance to the same temperature conditions for producing the melt-blown non-woven fabric 2, does not excessively fuse with the melt-blown non-woven fabric 2, and can peel off the melt-blown non-woven fabric 2.
Further, it is preferable that the conveyor 12 is made of a breathable material, and hot air is sucked from the surface on which the melt blown non-woven fabric of the conveyor 12 is formed by suction (not shown) toward the back surface. By doing so, it is easy to prevent the fibers made of resin from bouncing back on the conveyor 12, and it is easy to form the melt blown non-woven fabric 2 in which the fibers are well fused with each other.

The conveyor 12 is driven by a roller 13 and conveys the melt blown non-woven fabric 2 formed on the conveyor 12 to the winding device 14. The moving speed of the conveyor 12 is appropriately determined in consideration of the discharge amount of the resin and the apparent density of the obtained melt blown non-woven fabric 2. Typically, the moving speed of the conveyor is in the range of 1.5 m / min or more and 6.0 m / min or less. The melt blown non-woven fabric 2 formed in the non-woven fabric forming step is wound into a roll by the winding device 14.
The melt-blown non-woven fabric 2 may be cut to a predetermined length and collected as a product in a sheet-like form instead of a roll-like form.

According to the method described above, the melt-blown non-woven fabric 2 having good strength can be produced even if the calendar processing is not performed.
After the non-woven fabric forming step, the melt blown non-woven fabric 2 can be subjected to various treatments and processes conventionally performed on the non-woven fabric. However, after the non-woven fabric forming step, the melt blown non-woven fabric 2 is not subjected to calendar processing. This is because when the calendar processing is performed, the air permeability of the melt blown non-woven fabric 2 is lowered.

In the melt-blown non-woven fabric 2 manufactured by the above-mentioned method for manufacturing a melt-blown non-woven fabric, the surface state is different between the surface in contact with the conveyor 12 and the surface opposite to the surface in contact with the conveyor 12.
In a non-woven fabric, the reflection intensity of ultrasonic waves is determined by the elastic modulus and density of the surface. In melt-blown non-woven fabrics, there is usually a difference between the front and back sides of the non-woven fabric immediately after production. The fact that the difference between the front and back sides of the non-woven fabric is reduced by the calendar processing indicates that the elastic modulus and density of at least one side are changed. This is considered to be the reason why the ventilation performance is lowered by the calendar processing.

As a result, when measuring the reflection intensity of ultrasonic waves on both sides of the melt blown non-woven fabric 2, the values of the reflection intensity of ultrasonic waves on both sides are different from each other.
Specifically, the larger reflection intensity value is preferably 1.2 times or more and 3.0 times or less, and more preferably 1.2 times or more and 2.5 times the smaller reflection intensity value. It is as follows. Melt-blown non-woven fabrics in which the magnification of the reflection intensity of ultrasonic waves on both sides is within the above range tends to be excellent not only in strength but also in breathability.

The reflection intensity of the above ultrasonic waves is an average value of 100 or more measured values measured according to the following measurement conditions. If the reflected wave is weak, a gain may be set for the output signal as needed.
(Reflection intensity measurement conditions)
Distance between ultrasonic transmitter / receiver and non-woven fabric surface: 155 mm
Frequency: 360kHz
Measurement temperature: 22 ° C
Applied voltage: 500V
Wavenumber: 5 (burst wave)
Sharp ratio: 100%
Number of measurement points: 100 points or more within the range of 25 mm x 40 mm

The thickness of the melt blown non-woven fabric satisfying the above-mentioned predetermined reflectance ratio is preferably 0.1 mm or more and 0.4 mm or less, and more preferably 0.1 mm or more and 0.3 mm or less. When the thickness of the melt-blown non-woven fabric is within the above range, stable production of the melt-blown non-woven fabric is easy, and it is easy to obtain a homogeneous non-woven fabric after fabrication.

The apparent density of the melt-blown non-woven fabric satisfying the above-mentioned predetermined reflectance ratio is preferably 50 kg / m ³ or more and 350 kg / m ³ or less, and more preferably 100 kg / m ³ or more and 350 kg / m ³ or less. When the apparent density of the melt-blown non-woven fabric is within the above range, it is easy to achieve both good strength and good ventilation performance in the melt-blown non-woven fabric.

The average pore size measured by a palm poromometer of a melt-blown non-woven fabric that satisfies the above-mentioned predetermined reflectance ratio is preferably 2.5 μm or more and 5.0 μm or less, and more preferably 2.5 μm or more and 4.6 μm or less. When the average pore diameter of the melt-blown non-woven fabric is within the above range, it is easy to achieve both good ventilation performance and good collection performance in the melt-blown non-woven fabric.

For the melt-blown non-woven fabric that satisfies the above-mentioned predetermined reflectance ratio, the average fiber diameter, which is the average value of the fiber diameters of 100 or more fibers determined from the electron microscope image, is 0.5 μm or more and 3.0 μm or less. It is preferably 0.5 μm or more and 2.5 μm or less, more preferably.

Tensile strength in the MD direction of the meltblown nonwoven fabric which satisfies the ratio of the predetermined reflection factor described above, preferably 2.0 N / ^{m 2} or more 15.0 N / ^{m 2} or less, 3.0 N / ^{m 2} or more 10.0 N / ^{m 2} The following is more preferable. The tensile elastic modulus in the MD direction is preferably 100 MPa or more and 400 MPa or less, and more preferably 120 MPa or more and 350 MPa or less. Tensile strength in the TD direction is preferably 2.0 N / ^{m 2} or more 8.0 N / ^{m 2} or less, 2.5 N / ^{m 2} or more 6.0 N / ^{m 2} or less is more preferable. The tensile elastic modulus in the TD direction is preferably 50 MPa or more and 200 MPa or less, and more preferably 70 MPa or more and 130 MPa or less.
The tensile strength and the tensile elastic modulus are values measured according to the measuring method in the examples described later.
The MD direction is a direction along the direction in which the melt-blown non-woven fabric moves when the melt-blown non-woven fabric is manufactured. The TD direction is a direction perpendicular to the MD direction.

Further, for the melt-blown non-woven fabric, the melt-blown non-woven fabric is scanned in the thickness direction of the melt-blown non-woven fabric according to the method described later in the examples, and the data of the fiber distribution in the plane perpendicular to the thickness direction in the melt-blown non-woven fabric is acquired. By performing the X-ray CT analysis, the fiber occupancy rate at each position in the thickness direction of the meltblown non-woven fabric can be known.
According to the above X-ray CT analysis, for the melt-blown non-woven fabric, the average fiber occupancy FO1 in the region 15% from the surface of one surface and the average fiber occupancy FO2 in the region 15% from the surface of the other surface are obtained. The average occupancy rate of the fibers of the melt blown non-woven fabric AFO can be calculated.
The melt-blown non-woven fabric tends to have excellent strength and breathability by having a gradient in the fiber occupancy in the plane perpendicular to the thickness direction. Specifically, the occupancy rate change rate calculated by the following formula is preferably 10% or more, more preferably 12% or more and 30% or less, and further preferably 13% or more and 25% or less. .. Meltblown non-woven fabrics having an occupancy rate change rate within the above range tend to be excellent in strength and breathability.
Occupancy rate change rate (%) = (│FO1-FO2│) / AFO x 100

The melt-blown non-woven fabric described above can be easily produced by the above-mentioned method. The meltblown non-woven fabric described above has both good strength and good breathability, and is therefore preferably used for filters.
More specifically, the above-mentioned melt-blown non-woven fabric is preferably used as a filter used for extracorporeal circulation therapy, antibody drug purification, virus purification for gene therapy, and the like.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[Examples 1 to 4 and Comparative Examples 1 to 7]
Using the melt-blown non-woven fabric manufacturing apparatus 1 having the configuration shown in FIG. 1, a melt-blown non-woven fabric having a width of 600 mm was manufactured under the conditions shown in Table 1. As the resin, polyethylene terephthalate (PET, melting point 260 ° C.) was used. Regarding the spinning nozzle used, the nozzle hole diameter was 0.25 mm, the hole spacing was 0.25 mm, and the number of holes was 1200. The moving speed of the conveyor was 2.9 m / min.

In the examples, no calendar processing was performed after the acquisition of the melt blown non-woven fabric.
As for the comparative example, the melt-blown non-woven fabric was calendar-processed under the condition of the clearance between rolls of 0.10 to 0.11 mm using the calendar rolls having the roll temperatures shown in Table 1.

The thickness and apparent density of the melt-blown non-woven fabrics obtained in Examples 1 to 4 and the calendar-processed melt-blown non-woven fabric obtained in Comparative Examples 1 to 7 were measured. In addition, the average pore diameter, average fiber diameter, coefficient of variation, tensile strength, tensile elastic modulus, ultrasonic reflection strength, and air permeability were measured according to the following methods. The measurement results are shown in Tables 2 to 4.

<Average hole diameter>
The mean flow pore size measured using a palm polo meter (manufactured by PMI) was adopted as the average pore size.

<Average fiber diameter, coefficient of variation>
A scanning electron microscope observation was performed using a part of the melt blown non-woven fabric as a sample. Based on the obtained electron microscopic images, the diameters of 100 or more randomly selected fibers were measured. The average number of measured values of 100 or more was defined as the average fiber diameter. The coefficient of variation was calculated by dividing the standard deviation of the fiber diameter by the average fiber diameter.

<Tensile strength, tensile elastic modulus>
For the melt-blown non-woven fabric, the tensile strength and the tensile elastic modulus were measured in each of the MD direction and the TD direction.
The MD direction is a direction along the direction in which the melt-blown non-woven fabric moves when the melt-blown non-woven fabric is manufactured. The TD direction is a direction perpendicular to the MD direction.
A test piece having a width of 8 mm and a length of 40 mm was cut out from the obtained melt blown non-woven fabric. Using a universal testing machine (A & D Co., Ltd., RTG-1210), fix both ends of the test piece with chucks, pull the test piece with a chuck spacing of 20 mm and a tensile speed of 20 mm / min, and the distance between the chucks. -The load relationship was plotted, and the tensile strength and tensile elastic modulus were calculated based on the following formulas.
Tensile strength (N / m ² ) = (load at break) / Cross-sectional area of test piece Tensile elastic modulus (MPa) = (load change when the distance between chucks is extended by 0 to 2% before the start of the test / test piece Cross-sectional area) / (0-2% elongation / initial length of test piece)

<Ultrasonic reflection intensity>
In a region of 75 mm × 75 m in the melt blown non-woven fabric, 100 or more measured values of ultrasonic reflection intensity were obtained according to the following measurement conditions. The average value of the ultrasonic reflection intensity of 100 points or more is defined as the ultrasonic reflection intensity. The ultrasonic reflection intensity was measured on the surface that was in contact with the conveyor 12 and the surface that was in contact with the nozzle hole 11 when the meltblown non-woven fabric was manufactured.

(Reflection intensity measurement conditions)
Distance between ultrasonic transmitter / receiver and non-woven fabric surface: 155 mm
Frequency: 360kHz
Measurement temperature: 22 ° C
Applied voltage: 500V
Wavenumber: 5 (burst wave)
Sharp ratio: 100%
Number of measurement points: 100 points or more within the range of 25 mm x 40 mm

Specifically, ultrasonic waves were transmitted and received from an ultrasonic vibrator (ultrasonic transmitter / receiver) connected to a pulsar receiver (ULTRA SONIC RECEIVER JPR600C manufactured by Japan Probe Co., Ltd.) to measure the ultrasonic reflection intensity. .. The pulsar receiver was connected to a high-speed digitizer (NI PIX-1033 (chassis), NI PIX-5114, manufactured by National Instruments Co., Ltd.), and the high-speed digitizer was connected to a personal computer for data processing.

<Breathability>
The melt blown non-woven fabrics obtained in Examples and Comparative Examples are stacked in 4 or 8 layers, and 300 mL of air is passed through a ventilation surface having an area of 642 mm ² with a weight of 567 g, and the time required for passing the total amount of 300 mL of air. (Seconds) was measured and the air permeability was evaluated. A Gale type densometer (manufactured by TOYOSEIKI) was used to evaluate the air permeability.
Regarding the melt-blown non-woven fabric, when the surface in contact with the conveyor 12 at the time of manufacturing the melt-blown non-woven fabric is the A-side and the surface of the melt-blown non-woven fabric facing the nozzle hole 11 is the B-side, the A-sides or the B-sides are used. Are stacked so that they do not touch.
In addition, air was supplied from the B side.
In Example 2 and Comparative Example 1, the air permeability of the 32-layer melt-blown non-woven fabric was also evaluated.

For example, comparing the melt-blown non-woven fabric of Example 2 and the melt-blown non-woven fabric of Comparative Example 2 and Comparative Example 3 in which the thickness, the apparent density, the average pore diameter, and the average fiber diameter are close to each other, the melt-blown non-woven fabric of Example 2 is compared. It can be seen that the tensile strength and tensile elastic modulus of Comparative Example 2 and Comparative Example 3 are equal to or superior to the tensile strength and tensile elastic modulus of the meltblown non-woven fabrics of Comparative Example 2 and Comparative Example 3.
Further, according to a comparison between the melt-blown non-woven fabric of Example 2 and the melt-blown non-woven fabric of Comparative Example 2, the melt-blown non-woven fabric of Example 2 which has not been calendar-processed is more ventilated than the melt-blown non-woven fabric of Comparative Example 2 which has been calendar-processed. It can be seen that it is excellent in sex.

From Table 4, it can be seen that the ratio of the reflection intensities of the ultrasonic waves on both sides in the melt-blown non-woven fabric of the example is 1.2 or more and 3.0 or less because the calendar processing is not performed.
Further, from Tables 1 to 3, it can be seen that in Comparative Example 1 in which the distance between the nozzle hole and the conveyor exceeds 75 mm, the apparent specific gravity of the obtained melt-blown non-woven fabric is low, and the strength of the melt-blown non-woven fabric is inferior.

[Example 5, Example 6, and Comparative Examples 8 to 10]
The melt-blown non-woven fabric was manufactured under the conditions shown in Table 5 using the melt-blown non-woven fabric manufacturing apparatus 1 having the configuration shown in FIG. As the resin, polypropylene (PP, melting point 160 ° C.) was used.
The thickness, apparent density, average pore diameter, average fiber diameter, and coefficient of variation of the melt-blown non-woven fabrics obtained in Examples 5, 6 and 8 to 10 were measured in the same manner as in Example 1. The measurement results are shown in Tables 2 to 6.

For the melt-blown non-woven fabrics of Examples 5 and 6, the ratio of the reflection intensities of ultrasonic waves on both sides was measured in the same manner as in Example 1, and both were 1.2 or more and 3.0 or less.
Further, since the melt blown non-woven fabrics of Comparative Examples 8 to 10 were manufactured under the condition that the distance between the nozzle hole and the conveyor exceeds 75 mm, the apparent density is remarkably low. Therefore, the melt blown non-woven fabrics of Comparative Examples 8 to 10 cannot guarantee the desired strength unless they are calendar-processed.

Further, the melt blown non-woven fabrics of Example 2, Example 4, Comparative Example 6 and Comparative Example 7 were analyzed by X-ray CT. This analysis reveals the fiber occupancy at each position in the thickness direction of the meltblown non-woven fabric. The graphs of the analysis results are shown in FIGS. 3 and 4.
In the graphs of FIGS. 3 and 4, with respect to the axis in the thickness direction (μm), the plus side is the direction facing the surface on the conveyor side in the thickness direction of the meltblown non-woven fabric. Further, the minus side is the direction facing the surface on the nozzle side in the thickness direction of the melt blown non-woven fabric.

The analysis by X-ray CT was specifically performed by the following method.
As the X-ray CT apparatus, a micro X-ray CT scanner (MicroXCT-400) manufactured by Xradia was used. With this device, the melt-blown non-woven fabric was scanned in the thickness direction, and the distribution data of the fibers in the melt-blown non-woven fabric was acquired. From the scan data, two-dimensional data on the distribution of fibers was obtained at intervals of 0.05 mm in thickness. Then, the obtained two-dimensional data was grayscaled. As an example of the grayscaled image, FIG. 4 shows a grayscale image of the central portion of the meltblown nonwoven fabric of Example 2 in the thickness direction. Pixel values were generated from the grayscaled image data. Based on the obtained pixel values, a predetermined binarization process was performed on the grayscale image. For the binarized grayscale image, the ratio of the total area of the fiber portion to the total area of the image (fiber occupancy rate (%)) was determined.

Hereinafter, the binarization process will be described. When the binarization process was performed, first, a histogram was obtained for the distribution of pixels for each brightness (256-step gradation (0 to 255) in an 8-bit image) of the grayscale image. In the obtained histogram with the brightness as the horizontal axis, there are two peaks. From the obtained histogram, the maximum value I _max of the brightness, the minimum value I _min of the brightness, and the average value μ _{0 of the} brightness were obtained. Arbitrary threshold T was selected between I _max and I _min . The histogram was divided into two classes, class 1 and class 2, with the threshold value T as a boundary. Class 1 and class 2 each contain one peak. The variance σ ₁ ² for class 1, the mean μ _1, and the frequency n ₁ were determined. And variance sigma ₂ ² for class 2, was determined as the average mu _2, and a frequency _{n 2.}

Next, the intra-class variance σ _w ² and the inter-class variance σ _b ² were obtained from the following equations.

From the obtained intraclass variance σ _w ² and the interclass variance σ _b ² , the degree of separation S was obtained by the following equation.

The degree of separation S was determined according to the above method for all threshold values T between the maximum value I _max and the minimum value I _min . The threshold value T when the degree of separation S becomes maximum was adopted as the threshold value in the binarization method.

Table 7 below shows the average value (AFO) of the fiber occupancy (%) at each position in the thickness direction of the melt blown non-woven fabric, which was obtained from the above X-ray CT analysis results, and 15% from the surface on the nozzle hole side. The average value of the fiber occupancy within the range of (FO1), the average value of the fiber occupancy within the range of 15% from the surface of the surface on the conveyor side (FO2), and both sides (15% from the surface of each surface). The difference between the average value of the fiber occupancy rate (│ (FO1-FO2│)) and the occupancy rate change rate (%) calculated by the following formula are described.
Occupancy rate change rate (%) = (│FO1-FO2│) / AFO x 100

As described above, the meltblown non-woven fabrics of Examples 2 and 4 which are excellent in strength and breathability show a high occupancy rate change rate of 10% or more.

1: Melt blown non-woven fabric manufacturing equipment 2: Melt blown non-woven fabric 10: Spinning die head 11: Nozzle hole 12: Conveyor 13: Roller 14: Winding device 100: Hopper 101: Extruder 102: Gear pump 103: Filter 104: Kneader

Claims

A resin discharge process that discharges molten resin from a spinning die head equipped with nozzles with multiple holes,
Hot air flowing from the nozzle hole toward the conveyor provided facing the spinning die head is blown toward the nozzle hole, and the discharged resin in a molten state is fibrotic to form fibers. Process and
A non-woven fabric forming step of depositing the fibers on the conveyor to form a melt blown non-woven fabric by the air flow of the hot air is included.
After the non-woven fabric forming step, no calendar processing is performed,
The temperature of the hot air is equal to or higher than the melting point of the resin (the melting point + 100 ° C.) or lower.
The air volume of the hot air is 1000 NL / min / m or more and 7000 NL / min / m or less.
Discharge rate of the resin per the nozzle holes one is, it is 0.006 cm 3 / min or more 0.3 cm 3 / min or less,
The temperature of the resin in the nozzle hole is equal to or higher than the melting point of the resin (the melting point + 100 ° C.) or lower.
The shortest distance between the nozzle hole and the conveyor is 10 mm or more and 75 mm or less.
A method for producing a melt-blown non-woven fabric, wherein the temperature of the atmosphere between the nozzle hole and the conveyor is 110 ° C. or higher and 160 ° C. or lower.
The method for producing a melt-blown non-woven fabric according to 1, wherein the resin is a polyester-based resin or a polyolefin-based resin.
The values of ultrasonic reflection intensity on both sides of the melt blown non-woven fabric are different from each other.
The larger value of the reflection intensity is 1.2 times or more and 3.0 times or less of the smaller value of the reflection intensity.
The reflection intensity is the following measurement conditions:
Distance between ultrasonic transmitter / receiver and non-woven fabric surface: 155 mm
Frequency: 360kHz
Measurement temperature: 22 ° C
Applied voltage: 500V
Wavenumber: 5 (burst wave)
Sharp ratio: 100%
The method for producing a meltblown nonwoven fabric according to claim 1 or 2, which is an average value of 100 or more measured values measured according to 100 or more points within a range of 25 mm × 40 mm.
The value of the reflection intensity of ultrasonic waves on both sides is different from each other,
The larger value of the reflection intensity is 1.2 times or more and 3.0 times or less of the smaller value of the reflection intensity.
The reflection intensity is the following measurement conditions:
Distance between ultrasonic transmitter / receiver and non-woven fabric surface: 155 mm
Frequency: 360kHz
Measurement temperature: 22 ° C
Applied voltage: 500V
Wavenumber: 5 (burst wave)
Sharp ratio: 100%
Number of measurement points: A melt-blown non-woven fabric which is an average value of 100 or more points measured according to 100 points or more within a range of 25 mm × 40 mm.
The meltblown non-woven fabric according to claim 4, which has a thickness of 0.1 mm or more and 0.4 mm or less.
The melt-blown non-woven fabric according to claim 4 or 5, wherein the apparent density is 50 kg / m 3 or more and 350 kg / m 3 or less.
The melt-blown non-woven fabric according to any one of claims 4 to 6, wherein the average pore diameter measured by a palm poromometer is 2.5 μm or more and 5.0 μm or less.
The melt-blown non-woven fabric according to any one of claims 4 to 7, wherein the average fiber diameter, which is the average value of the fiber diameters of 100 or more fibers obtained from an electron microscope image, is 0.5 μm or more and 3.0 μm or less. ..
It was obtained from the result of X-ray CT analysis which scans the melt-blown non-woven fabric in the thickness direction of the melt-blown non-woven fabric and acquires the data of the fiber distribution in the plane perpendicular to the thickness direction in the melt-blown non-woven fabric. From the average fiber occupancy FO1 in the region 15% from the surface of one surface, the average fiber occupancy FO2 in the region 15% from the surface of the other surface, and the average fiber occupancy AFO in the fiber of the meltblown non-woven fabric, the following formula is used. :
Occupancy rate change rate (%) = (│FO1-FO2│) / AFO x 100
Melt blown non-woven fabric having an occupancy rate change rate of 10% or more calculated based on.
It was obtained from the result of X-ray CT analysis which scans the melt-blown non-woven fabric in the thickness direction of the melt-blown non-woven fabric and acquires the data of the fiber distribution in the plane perpendicular to the thickness direction in the melt-blown non-woven fabric. From the average fiber occupancy FO1 in the region 15% from the surface of one surface, the average fiber occupancy FO2 in the region 15% from the surface of the other surface, and the average fiber occupancy AFO in the fiber of the meltblown non-woven fabric, the following formula:
Occupancy rate change rate (%) = (│FO1-FO2│) / AFO x 100
The melt-blown non-woven fabric according to any one of claims 4 to 8, wherein the occupancy rate change rate calculated based on the above is 10% or more.