JP7575576B2 - Method for manufacturing spunbond nonwoven fabric with improved fiber opening quality and no residual harmful substances - Google Patents

Description

The present invention relates to a spunbond nonwoven fabric that does not contain residual harmful substances and has improved fiber opening quality, as well as a manufacturing method and manufacturing apparatus for the same.

Generally, the manufacturing process for spunbond nonwoven fabrics proceeds in the following order: spinning, cooling, stretching, web formation, bonding, and winding. The spunbond method, which is carried out as a continuous process, has high productivity and excellent economic properties.

The manufacturing process for spunbond nonwoven fabrics is divided into the Docan system and the Reicofil system based on the difference from the spinning process to the drawing process, and is further subdivided based on the filament opening technology used to form the web.

In the Lycofil system, molten polymer discharged from a rectangular spinning pack passes through a closed cooling/drawing section and is spun in the form of a filament curtain, which is then separated by aerodynamic force or corona charge to form a web. The Lycofil system has the advantages of high production volume and fast production speed, and low manufacturing costs for nonwoven fabrics. It is being applied in the fields of sanitary materials, protective clothing, and filters using olefin raw materials such as polyethylene and polypropylene. However, PET has difficulty entering the high value-added market due to its poor mechanical properties and appearance quality.

In the Dokan system, molten polymer discharged from a circular spin pack passes through an open cooling/drawing section and is fiberized into a filament bundle, which is then opened by mechanical force, electrostatic charge, or a combination method to form a web. The Dokan system has excellent mechanical properties and a uniform appearance, making it suitable for high value-added products. However, it has the disadvantage of being more expensive to manufacture than the Lycofil system, as it has lower productivity.

Under the Dokan system, various spreading methods have been developed, such as forced charging by corona discharge and triboelectric charging by collision with a frictional material (e.g., metal). However, even if the spreading method improves the spreading of filament bundles, there is still a need to improve the unevenness of the web's areal density (i.e., the unevenness of the weight per unit area of the web).

On the other hand, the performance of the friction charging method is controlled according to the charging sequence of the friction material. For example, the polyester filaments are made to have a negative charge by friction (collision) between the polyester filaments and the metal plate material. The filaments are opened by the Coulomb repulsive force between the filaments that have the same charge due to the friction.

Lead (Pb) has traditionally been used as the metal plate material in the frictional charging method. However, lead is brittle and easily wears away due to friction with the filaments. As a result, residual lead may be present in spunbond nonwoven fabrics manufactured using lead as the friction material in the frictional charging method.

Lead (Pb) is one of the six major hazardous substances listed in the European Union's (EU) Restriction of Hazardous Substances (RoHS) guidelines, and poses a potential risk to the human body. As a result, lead (Pb) has permissible limits for different uses in life science materials, and it is currently recommended that it not be used.

The present invention provides a method for producing a spunbond nonwoven fabric with improved fiber opening quality using a friction material that has the same level of negative charge donating ability as lead (Pb) but is not harmful to the human body.

The present invention provides a manufacturing apparatus for the spunbond nonwoven fabric.

The present invention provides a spunbond nonwoven fabric that does not contain any residual harmful substances and has improved fiber opening quality.

According to one embodiment of the present invention,
melt spinning a thermoplastic resin to obtain a continuous filament bundle;
impacting the continuous filament bundle against a metal member containing bismuth (Bi) or a bismuth alloy to obtain filaments opened by triboelectric charging;
concentrating the opened filaments on a continuous conveyor net to form a fibrous web.

According to another embodiment of the present invention,
a plurality of nozzle units arranged and configured to discharge a continuous filament bundle;
an impingement unit adjacent each of the nozzle units in a position for impinging with the continuous filament bundle discharged by the nozzle units;
and a continuous conveyor net for collecting and transporting the filaments opened by frictional charging with the collision unit,
The collision unit includes a collision surface that is a metal member containing bismuth (Bi) or a bismuth alloy;
An apparatus for producing a spunbond nonwoven fabric is provided.

According to yet another embodiment of the present invention,
A fibrous web including thermoplastic filaments,
having a residual amount of bismuth (Bi) of 0.01 ppmw to 10.0 ppmw;
A spunbond nonwoven fabric is provided.

The following provides a more detailed explanation of the method for producing spunbond nonwoven fabric, the apparatus for producing spunbond nonwoven fabric, and the spunbond nonwoven fabric produced using the apparatus according to an embodiment of the present invention.

Unless otherwise defined herein, all technical and scientific terms have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention belongs. The terms used in the description of the present invention are merely for the purpose of effectively describing specific examples and are not intended to limit the present invention.

As used herein, the singular forms include the plural forms unless the context clearly indicates to the contrary.

As used herein, the meaning of "comprise" is to embody certain properties, regions, integers, steps, operations, elements, and/or components, and does not exclude the presence or inclusion of other certain properties, regions, integers, steps, operations, elements, components, and/or groups.

The present invention may be modified in various ways and may take various forms, but a specific embodiment will be described in detail below. However, this is not intended to limit the present invention to the specific disclosed embodiment, and it should be understood that the present invention includes all modifications, equivalents, and alternatives within the spirit and technical scope of the invention.

In this specification, when the positional relationship between two parts is described using, for example, "on", "at the top", "below", "to the side", etc., the expressions "directly" or "indirectly" are not used, so one or more other parts may be located between the two parts.

In this specification, when a temporal relationship is described using expressions such as "after," "next to," "after," or "before," the expressions "directly" or "in person" are not used, and therefore non-consecutive cases may also be included.

As used herein, the term "at least one" should be understood to include all possible combinations of one or more associated items.

I. Method for Producing Spunbond Nonwoven Fabric According to one embodiment of the invention,
melt spinning a thermoplastic resin to obtain a continuous filament bundle;
impacting the continuous filament bundle against a metal member containing bismuth (Bi) or a bismuth alloy to obtain filaments opened by triboelectric charging;
concentrating the opened filaments on a continuous conveyor net to form a fibrous web.

Conventionally, the Docan system's opening process is controlled by the generation of electrostatic force due to friction between the filament bundle and the lead plate material, and the kinetic energy of the filaments causes the lead plate material to wear away, leaving trace amounts of lead remaining in the nonwoven fabric produced.

However, unlike industrial materials, residual lead may be exposed in consumer products through the mouth, respiratory system or skin, and these potential risks have made it difficult to enter the market.

However, as a result of the inventors' ongoing research, it was confirmed that when a metal component containing bismuth (Bi) or a bismuth alloy is used as the friction material in the production of spunbond nonwoven fabric using the Dokan system, it is possible to produce a spunbond nonwoven fabric that exhibits the same level of negative charge donating properties as conventional metal components made of lead (Pb), does not contain residual harmful substances, and has improved fiber opening quality.

Figure 1 is a schematic diagram of a spunbond nonwoven fabric manufacturing apparatus according to one embodiment of the present invention.

First, (i) a step is performed in which a thermoplastic resin is melt spun to obtain a continuous filament bundle.

As the thermoplastic resin, any resin commonly used in the technical field to which the present invention pertains can be used without any particular restrictions.

The thermoplastic resin may have a melting point of 200°C or higher, which may be advantageous in ensuring the mechanical properties of the filament.

Preferably, the thermoplastic resin may be one or more resins selected from the group consisting of polyester, polyamide, polyolefin, and polyphenylene sulfide.

Specifically, the thermoplastic resin may be one or more resins selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate, polycyclohexane terephthalate, polyethylene naphthalate, nylon, polyethylene, polypropylene, polybutylene, and polyphenylene sulfide.

The thermoplastic resin is melted in a continuous extruder having a screw and a heater, and is continuously extruded through a spinneret to form a continuous filament bundle.

The continuous filament bundle is stretched by compressed air and an ejector in the cylindrical pipe of the nozzle unit 10 and then discharged through a jet nozzle.

The denier and cross-sectional shape of the filaments constituting the continuous filament bundle are not particularly limited. As a non-limiting example, the filaments may have a fineness of 1 to 10 denier and a circular or irregular cross section.

Continuing, (ii) the continuous filament bundle is collided with a metal member containing bismuth (Bi) or a bismuth alloy to obtain filaments that are opened by frictional charging.

The step (ii) is a step in which the continuous filament bundle 11 discharged through the jet nozzle of the nozzle unit 10 is collided with the collision surface of the collision unit 20, thereby inducing frictional charging due to the charge sequence between the material of the collision surface and the filament bundle, and opening the filaments due to the Coulomb repulsion between the filaments that now have the same charge.

In step (ii), one of the main factors that determines the dispersion form and fiber spreading quality of the filament bundle 11 is the type of material that forms the collision surface of the collision unit 20.

Lead (Pb) has traditionally been used as the material for the impact surface of the impact unit 20. However, trace amounts of lead that fall off due to friction with the filaments remain in the nonwoven fabric, posing a potential risk of harm to the human body.

According to an approach based on solid-state physics, lead (Pb) is classified as follows: Lead (Pb) has a conductivity of 5×10 ⁶ S/m, and is therefore electrically classified as a "conductor" among conductors, semiconductors, and nonconductors. Lead (Pb) has a magnetic susceptibility of -23.0×10 ^-6 cm ³ /mol (at 298 K), and is therefore magnetically classified as a "diamagnetic material" among ferromagnetic materials, paramagnetic materials, and diamagnetic materials. Lead (Pb) has a melting point of 600.61 K (327.46° C., 621.43° F.), and is therefore thermally classified as a "low-temperature melt" among high-temperature melts and low-temperature melts. Lead (Pb) has a Vickers hardness (Hv) of 8.11, and is therefore mechanically classified as "soft" among hard and soft materials, and as "tough" among brittle and tough materials.

According to one embodiment of the invention, the continuous filament bundle 11 is struck against a metal member containing bismuth (Bi) or a bismuth alloy.

Bismuth (Bi) is classified electrically as a "conductor" with an electrical conductivity of 7.7×10 ⁵ S/m; magnetically as a "diamagnetic material" with a magnetic susceptibility of -280.1×10 ^-6 cm ³ /mol (at 298 K); thermally as a "low melt" with a melting point of 544.7 K (271.5° C., 520.7° F.); and mechanically as "soft" and "tough" with a Vickers hardness (Hv) of 11.55.

Bismuth (Bi) can provide a similar level of negative charge compared to lead (Pb), but is harder and is not classified as a hazardous substance under the European Union's Restriction of Hazardous Substances (RoHS) guidelines.

Therefore, by applying bismuth or a bismuth alloy to the collision surface of the collision unit 20, a spunbond nonwoven fabric that does not contain residual harmful substances and has improved fiber opening quality can be obtained.

Preferably, a metal member made of bismuth can be applied to the collision surface of the collision unit 20.

A metal member made of a bismuth alloy can be applied to the collision surface. Preferably, the bismuth alloy contains 10% or more by weight, or 20% or more by weight, or 30% or more by weight, or 40% or more by weight, or 45% or more by weight, or 50% or more by weight of bismuth based on the weight of the bismuth alloy, which may be advantageous for realizing the effects of the present invention. Specifically, the bismuth alloy may contain 10% to 80% by weight, or 20% to 80% by weight, or 20% to 70% by weight, or 30% to 70% by weight, or 30% to 60% by weight, or 40% to 60% by weight, or 45% to 60% by weight, or 45% to 55% by weight of bismuth based on the weight of the bismuth alloy.

In addition to bismuth, the bismuth alloy further contains a metal that is not a harmful substance according to the RoHS guidelines and does not impair the properties of bismuth. For example, the bismuth alloy may contain one or more metals selected from the group consisting of copper (Cu), zinc (Zn), tin (Sn), aluminum (Al), molybdenum (Mo), and titanium (Ti). As a non-limiting example, the bismuth alloy may contain 50% by weight of bismuth (Bi) and 50% by weight of copper (Cu). Metals other than bismuth contained in the bismuth alloy can be selected in consideration of the physical properties of the metal and the physical properties to be imparted to the collision surface.

According to one embodiment of the invention, the continuous filament bundle 11 can collide with the metal member at a linear velocity of 4,000 m/min to 6,000 m/min, alternatively 4,500 m/min to 6,000 m/min, alternatively 4,500 m/min to 5,500 m/min.

The continuous filament bundle 11 can be impinged on the metal member at a mass flow rate of 2.0 kg/hr to 8.0 kg/hr, or 3.0 kg/hr to 8.0 kg/hr, or 3.0 kg/hr to 6.0 kg/hr per nozzle that sprays the continuous filament bundle.

It is preferable that the continuous filament bundle 11 collide with the metal member within the linear velocity range and mass flow rate range in order to ensure sufficient generation of frictional electrification due to collision with the metal member while also ensuring fiber spreading quality and operability.

According to one embodiment of the invention, the filaments 22 opened by frictional charging can have a charge generation amount (measured by the Faraday cage method) of -3500 nC/sec to -500 nC/sec, or -3400 nC/sec to -600 nC/sec, or -3400 nC/sec to -700 nC/sec.

The filaments 22 that are opened by the frictional charging have a charge generation amount within the above range, and are opened with a wide opening width and excellent quality.

The amount of charge generated by the opened filament 22 is the amount of electrostatic discharge that the filament has due to collision with the metal member, and can be measured using a Faraday cage method.

The Faraday cage is divided into an inner cage and an outer cage. The insulated inner cage is installed to confine the filaments 22 that collide with the metal member and are opened. The grounded outer cage is installed to surround the entire surface of the inner cage. A digital coulomb meter is placed in contact with the inner cage. The time it takes for the charge difference between the inner cage and the outer cage to reach -9,000 nC is measured with the digital coulomb meter and standardized by time to obtain the amount of electrostatic discharge possessed by the opened filaments.

According to one embodiment of the invention, the jet nozzle that sprays the filament bundle in step (ii) is connected to the shaft of a step motor and can be controlled with a nozzle rotation angle range of -15±5° to +15±5° and a nozzle reciprocating speed of 3 counters/sec to 12 counters/sec.

Continuing, (iii) the step of converging the opened filaments 22 onto a continuous conveyor net 30 to form a fibrous web 33 is performed.

The filaments, which have become negatively charged by the frictional charging, are opened by the Coulomb repulsion between the filaments and fall below where the metallic continuous conveyor net 30 is located. The negatively charged filaments are placed on the grounded conveyor net 30 by electrostatic forces to form a fiber web 33.

According to one embodiment of the invention, the spread filaments 22 can be concentrated on the continuous conveyor net 30 with a spread width of 500 mm or more under the conditions of a rotation angle range of -15±5° to +15±5° of the nozzle spraying the filament bundle and a reciprocating speed of the nozzle of 3 counters/sec to 12 counters/sec.

To ensure excellent spreading quality, the spread width of the spread filaments 22 is preferably 500 mm or more. Preferably, the spread width may be 500 mm or more, or 500 mm to 700 mm, or 500 mm to 650 mm, or 520 to 650 mm.

Here, the spread width refers to the maximum width based on the moving direction of the spread filaments 22 gathered on the continuous conveyor net 30. The spread width is based on the value indicated by the spread filaments obtained from one nozzle unit and its corresponding collision unit.

Then, the spunbonded nonwoven fabric is obtained by bonding the fiber web by thermal bonding or the like. The bonding is carried out using a calendar roll or an embossing roll.

II. According to another embodiment of the invention, a spunbond nonwoven fabric manufacturing apparatus includes:
a plurality of nozzle units 10 configured and arranged to deliver a continuous filament bundle 11;
an impingement unit 20 adjacent each of the nozzle units 10 in a position for impinging with the continuous filament bundle 11 discharged by the nozzle units 10;
a continuous conveyor net 30 for collecting and transporting the filaments 22 opened by frictional charging with the collision unit 20;
The collision unit 20 includes a collision surface that is a metal member containing bismuth (Bi) or a bismuth alloy.
An apparatus for producing a spunbond nonwoven fabric is provided.

The spunbond nonwoven fabric manufacturing apparatus is used to carry out the above-mentioned "I. Method for manufacturing spunbond nonwoven fabric."

Figure 1 is a schematic diagram of a spunbond nonwoven fabric manufacturing apparatus according to one embodiment of the present invention.

A spunbond nonwoven fabric manufacturing apparatus according to an embodiment of the invention includes a plurality of nozzle units 10 arranged and configured to eject a continuous filament bundle 11.

The thermoplastic resin raw material is melted in a continuous extruder (not shown in FIG. 1) that has a screw and a heater, and is continuously extruded through a spinneret to form a continuous filament bundle.

The nozzle unit 10 includes a cylindrical pipe connected to the spinneret and a jet nozzle formed on one side of the cylindrical pipe.

The continuous filament bundle is stretched by compressed air and an ejector within the cylindrical pipe of the nozzle unit 10 and then discharged through a jet nozzle.

The jet nozzle is connected to the shaft of a step motor and controlled with a nozzle rotation angle range of -15±5° to +15±5° and a nozzle reciprocating speed of 3 counters/sec to 12 counters/sec.

The jet nozzle can extrude the continuous filament bundle 11 at a linear velocity of 4,000 m/min to 6,000 m/min, or 4,500 m/min to 6,000 m/min, or 4,500 m/min to 5,500 m/min.

The continuous filament bundle 11 can collide with the metal member of the collision unit 20 at a mass flow rate of 2.0 kg/hr to 8.0 kg/hr, or 3.0 kg/hr to 8.0 kg/hr, or 3.0 kg/hr to 6.0 kg/hr per jet nozzle that sprays the continuous filament bundle.

The spunbond nonwoven fabric manufacturing apparatus according to an embodiment of the invention includes collision units 20 adjacent to each of the nozzle units 10 in a position for collision with the continuous filament bundles 11 discharged by the nozzle units 10.

The collision unit 20 includes a collision surface that is a metal member containing bismuth (Bi) or a bismuth alloy. The collision surface refers to a surface of the collision unit 20 that directly collides with the continuous filament bundle 11.

Preferably, a metal member made of bismuth can be applied to the collision surface of the collision unit 20.

A metal member made of a bismuth alloy can be applied to the collision surface. Preferably, the bismuth alloy contains 10% or more by weight, or 20% or more by weight, or 30% or more by weight, or 40% or more by weight, or 45% or more by weight, or 50% or more by weight of bismuth based on the weight of the bismuth alloy, which may be advantageous for realizing the effects of the present invention. Specifically, the bismuth alloy may contain 10% to 80% by weight, or 20% to 80% by weight, or 20% to 70% by weight, or 30% to 70% by weight, or 30% to 60% by weight, or 40% to 60% by weight, or 45% to 60% by weight, or 45% to 55% by weight of bismuth based on the weight of the bismuth alloy.

In addition to bismuth, the bismuth alloy further contains a metal that is not a harmful substance according to the RoHS guidelines and does not impair the properties of bismuth. For example, the bismuth alloy may contain one or more metals selected from the group consisting of copper (Cu), zinc (Zn), tin (Sn), aluminum (Al), molybdenum (Mo), and titanium (Ti). As a non-limiting example, the bismuth alloy may contain 50% by weight of bismuth (Bi) and 50% by weight of copper (Cu). The metal other than bismuth contained in the bismuth alloy can be selected in consideration of the physical properties of the metal and the physical properties to be imparted to the collision surface.

The collision unit 20 can be installed at a predetermined angle so that the filaments 22 opened by frictional charging can be collected on a continuous conveyor net 30 at a position for collision with the continuous filament bundle 11 discharged by the nozzle unit 10.

The spunbond nonwoven fabric manufacturing apparatus according to an embodiment of the invention includes a continuous conveyor net 30 that collects and transports the filaments 22 that have been opened by frictional charging with the collision unit 20.

The continuous conveyor net 30 is preferably grounded. In other words, it is preferable that the opened filaments 22, which have become negatively charged due to frictional charging with the collision unit 20, can be fixed on the continuous conveyor net 30 by electrostatic forces.

The continuous conveyor net 30 continuously transports the fiber web 33 formed by collecting the opened filaments 22.

In addition, the spunbond nonwoven fabric manufacturing apparatus according to an embodiment of the invention may include a bonding unit for adjusting and bonding the fiber web 33 to a predetermined thickness.

The bonding unit may have a typical configuration, such as a calendar roll and an embossing roll, used in the technical field to which the present invention pertains for bonding nonwoven fabrics.

III. According to yet another embodiment of the spunbond nonwoven fabric invention,
Obtained by the above-mentioned production method,
A fibrous web including thermoplastic filaments,
having a residual amount of bismuth (Bi) of 0.01 ppmw to 10.0 ppmw;
A spunbond nonwoven fabric is provided.

The spunbond nonwoven fabric may be obtained by the above-mentioned "I. Manufacturing method of spunbond nonwoven fabric."

The spunbond nonwoven fabric may be obtained using the above-mentioned "II. Spunbond nonwoven fabric manufacturing apparatus."

According to an embodiment of the invention, the spunbond nonwoven fabric comprises a fibrous web that includes thermoplastic resin filaments.

The thermoplastic resin filament is obtained using a thermoplastic resin.

As the thermoplastic resin, any resin commonly used in the technical field to which the present invention pertains can be used without any particular restrictions.

The thermoplastic resin may have a melting point of 200°C or higher, which may be advantageous in ensuring the mechanical properties of the filament.

Preferably, the thermoplastic resin may be one or more resins selected from the group consisting of polyester, polyamide, polyolefin, and polyphenylene sulfide.

Specifically, the thermoplastic resin may be one or more resins selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate, polycyclohexane terephthalate, polyethylene naphthalate, nylon, polyethylene, polypropylene, polybutylene, and polyphenylene sulfide.

The denier and cross-sectional shape of the thermoplastic resin filaments are not particularly limited. As a non-limiting example, the filaments may have a denier of 1 to 10 and a circular or irregular cross section.

To ensure good mechanical properties, the spunbond nonwoven fabric may have a weight per unit area of 20 to 150 g/m ² , or 50 to 120 g/m ² .

In particular, the spunbond nonwoven fabric is obtained by the above-mentioned "I. Manufacturing method of spunbond nonwoven fabric" and is substantially free of residual harmful substances such as lead (Pb), and exhibits improved fiber opening quality.

According to one embodiment of the invention, the spunbond nonwoven fabric may have a residual amount of lead (Pb) of 0.1 ppmw (ppm by weight) or less. Preferably, the spunbond nonwoven fabric does not contain residual lead.

According to one embodiment of the invention, the spunbond nonwoven fabric includes filaments that are opened by collision with a metal member containing bismuth (Bi) or a bismuth alloy, and may have a residual amount of bismuth (Bi) of 0.01 ppmw to 10.0 ppmw, or 0.05 ppmw to 5.0 ppmw, or 0.1 ppmw to 2.5 ppmw.

The residual amount of metals other than bismuth contained in the bismuth alloy in the spunbond nonwoven fabric may be 0.1 ppmw or less. The bismuth alloy may contain one or more metals selected from the group consisting of copper (Cu), zinc (Zn), tin (Sn), aluminum (Al), molybdenum (Mo), and titanium (Ti).

According to one embodiment of the invention, the spunbond nonwoven fabric may have a quality index (Q) of 350 or less, as defined by the following formula 1:

[Formula 1]
Quality index (Q) = SD/OD

In the above formula 1,
OD is the optical density of the spunbond nonwoven fabric, measured using a formation tester;
SD is the standard deviation of the optical density.

The optical density (OD) is a value obtained by the transmittance of a light source per unit area of the spunbond nonwoven fabric and the distribution of the transmittance. The quality index (Q) is a value obtained by standardizing the standard deviation (SD) of the optical density by the optical density (OD). The OD and SD are obtained using a conventional quality evaluation device in the technical field to which the present invention pertains.

To ensure uniform and excellent quality, the spunbond nonwoven fabric preferably has a quality index (Q) of 350 or less. More preferably, the quality index (Q) of the spunbond nonwoven fabric may be 250 to 350, or 270 to 350, or 275 to 300.

According to the present invention, a method and apparatus for producing spunbond nonwoven fabric with improved fiber opening quality is provided using a friction material that has the same level of negative charge donating ability as lead (Pb) but is not harmful to the human body. The apparatus makes it possible to extend the replacement cycle of the friction material, which also contributes to improving operability. The spunbond nonwoven fabric produced by the apparatus and method does not contain residual harmful substances and has improved fiber opening quality, and can be applied to industrial materials as well as life science materials, eliminating potential risks of harmfulness to the human body.

1 is a schematic diagram of a spunbond nonwoven fabric manufacturing apparatus according to one embodiment of the present invention;

Below, preferred examples are presented to aid in understanding the invention. However, the following examples are merely for the purpose of illustrating the invention, and are not intended to limit the invention to these examples.

Example 1
A spunbond nonwoven fabric was produced using the apparatus according to FIG.

First, a polyethylene terephthalate resin having an intrinsic viscosity (IV) of 0.665 dl/g and a melting point (T _m ) of 254°C was melted at 284°C and continuously extruded. The filament bundle obtained by the extrusion was extruded through an electric distribution jet nozzle (EDJ nozzle) while being stretched at a speed of 5,000 m/min using compressed air and an ejector in a cylindrical pipe of a nozzle unit. The EDJ nozzle was connected to the shaft of a step motor, and the rotation angle range of the nozzle was controlled to -15±5° to +15±5° and the reciprocating speed of the nozzle was controlled to 10 counter/sec.

The extruded filament bundle collided at the speed with a collision unit positioned at a predetermined angle adjacent to the nozzle unit. A metal member (metal plate with a thickness of 2.0±0.15 mm) made of bismuth (Bi) was used as the collision surface of the collision unit. In this case, the mass flow rate of the filaments colliding with the metal member was 5.0 kg/hr per nozzle spraying the continuous filament bundle, and the linear velocity of the filaments was controlled to 5,000 m/min.

The filaments, which have become negatively charged due to frictional charging with the collision unit, are opened by the Coulomb repulsion between the filaments and fall below where the conveyor net is located. The negatively charged filaments are fixed by electrostatic forces onto the grounded continuous conveyor net to form a fiber web.

The fibrous web was passed between calendar rollers maintained at 130° C. and 35 N/mm to obtain an appropriate thickness. Next, hot air was applied to the fibrous web to thermally bond it, thereby obtaining a spunbonded nonwoven fabric (thickness 0.27±0.03 mm, weight 60±2.0 g/m ² ).

Example 2
A spunbond nonwoven fabric was obtained in the same manner as in Example 1, except that a metal member made of a bismuth/copper alloy (Bi 50 wt %, Cu 50 wt %) was used instead of the bismuth metal member on the collision surface of the collision unit.

Comparative Example 1
A spunbond nonwoven fabric was obtained in the same manner as in Example 1, except that a metal member made of lead (Pb) was used on the collision surface of the collision unit instead of the bismuth metal member.

Comparative Example 2
A spunbond nonwoven fabric was obtained in the same manner as in Example 1, except that a metal member made of copper (Cu) was used on the collision surface of the collision unit instead of the bismuth metal member.

Comparative Example 3
A spunbond nonwoven fabric was obtained in the same manner as in Example 1, except that a metal member made of tin (Sn) was used on the collision surface of the collision unit instead of the bismuth metal member.

Comparative Example 4
A spunbond nonwoven fabric was obtained in the same manner as in Example 1, except that a metal member made of aluminum (Al) was used on the collision surface of the collision unit instead of the bismuth metal member.

Comparative Example 5
A spunbond nonwoven fabric was obtained in the same manner as in Example 1, except that a metal member made of zinc (Zn) was used on the collision surface of the collision unit instead of the bismuth metal member.

Comparative Example 6
A spunbond nonwoven fabric was obtained in the same manner as in Example 1, except that a metal member made of molybdenum (Mo) was used on the collision surface of the collision unit instead of the bismuth metal member.

Comparative Example 7
A spunbond nonwoven fabric was obtained in the same manner as in Example 1, except that a metal member made of titanium (Ti) was applied to the collision surface of the collision unit instead of the bismuth metal member.

Test Example (1) Amount of Charge Generated (nC/sec)
The amount of electrostatic discharge per unit time of the opened filaments was measured using a Faraday cage method.

The Faraday cage is divided into an inner cage and an outer cage. The insulated inner cage is installed so that it collides with the metal member and traps the opened filaments 22. The grounded outer cage is installed so as to surround the entire surface of the inner cage. A digital coulomb meter (NK-1002, KASUGA DENKI, Inc.) is placed in contact with the inner cage. The time it takes for the charge difference between the inner cage and the outer cage to reach -9,000 nC is measured with the digital coulomb meter and standardized by time to obtain the average amount of electrostatic discharge per unit time possessed by the opened filaments.

(2) Spreading width (mm)
The width of the filaments spread by the frictional charging with the collision unit was measured. Here, the width of the spread was measured in the moving direction of the spread filaments converged on the continuous conveyor net. The spread width refers to the maximum width based on the standard. The spread width is based on the value of the spread filaments obtained from one nozzle unit and the corresponding collision unit. The spread width is The values were expressed as average values after 10 measurements were made under the conditions of a rotation angle range of the EDJ nozzle of −15±5° to +15±5° and a reciprocating speed of the EDJ nozzle of 10 counters/sec.

(3) Quality index (Q)
Using a quality evaluation device (Formation tester, FMT-III, manufactured by NOMURA SHOJI CO.), the optical density (OD) and the distribution of the transmittance of the light source per unit area of the spunbond nonwoven fabric were calculated. The standard deviation (SD) of the optical density was measured. The quality index was calculated according to the above formula 1.

The quality evaluation device (FMT-III) is an image analysis type quality analyzer that uses a two-dimensional CCD camera. A nonwoven fabric sample is placed on a stage that is illuminated from below. The CCD camera captures an image of 320x230 pixels, and the light intensity is measured by each pixel. A PC linked to the CCD camera converts the light intensity into transmittance (%) and optical density (OD).

(4) Use period of metal components (days)
In the manufacturing process of a spunbond nonwoven fabric, the time when perforations in the thickness direction occurred in a metal member (a metal plate having a thickness of 2.0±0.15 mm) included in a collision unit, or the time when operability decreased due to the occurrence of unevenness caused by wear, was measured. In this case, the mass flow rate of the filaments colliding with the metal member was 5.0 kg/hr per nozzle spraying the continuous filament bundle, and the linear velocity of the filaments was controlled in the range of 5,000 m/min.

(5) Amount of residual inorganic matter (ppmw)
The amount of inorganic residues in spunbond nonwoven fabric was measured using inductively coupled plasma (ICP). The test pieces of spunbond nonwoven fabric were pretreated with an aqueous solution that had been used to remove particles and organic matter by acid digestion. Inorganic residues were primarily measured using inductively coupled plasma-atomic emission spectrometry (ICP-AES) and, when residual inorganics were undetectable, inductively coupled plasma-mass spectrometry (ICP-MS). ) was used to increase the resolution and perform the measurements again.

Referring to Table 1 above, Comparative Example 1 had excellent quality index and spread width, but residual lead was detected in the nonwoven fabric, making it unsuitable for use in life science materials.

In the example, the quality index and spread width were at the same level as those in Comparative Example 1, but no residual harmful substances were detected in the nonwoven fabric. Furthermore, the metal members used in the example had a usage cycle that was approximately twice as long as those in Comparative Example 1, confirming that operability was significantly improved.

In Comparative Examples 2 and 3, the amount of inorganic matter remaining in the nonwoven fabric was low, but the quality index and spread width were poor. In Comparative Examples 4 to 7, no residual inorganic matter was detected in the nonwoven fabric, but it was confirmed that the filaments were poorly spread.

10: Nozzle unit 11: Filament bundle 20: Collision unit 22: Spread filament 30: Conveyor net 33: Fiber web

Claims (7)

melt spinning a thermoplastic resin to obtain a continuous filament bundle;
impacting the continuous filament bundle against a metal member containing bismuth (Bi) or a bismuth alloy to obtain filaments opened by triboelectric charging;
and concentrating the spread filaments on a continuous conveyor net to form a fibrous web,
The continuous filament bundle is collided with the metal member at a linear speed of 4,000 m/min to 6,000 m/min and at a mass flow rate of 2.0 kg/hr to 8.0 kg/hr per nozzle spraying the continuous filament bundle. The method for producing a spunbond nonwoven fabric according to claim 1, wherein the bismuth alloy contains 10% by weight or more of bismuth based on the weight of the bismuth alloy. The method for producing a spunbond nonwoven fabric according to claim 1, wherein the bismuth alloy contains one or more metals selected from the group consisting of copper (Cu), zinc (Zn), tin (Sn), aluminum (Al), molybdenum (Mo), and titanium (Ti). The method for producing a spunbond nonwoven fabric according to claim 1, wherein the opened filaments have a charge generation amount due to the frictional charging of -3500 nC/sec to -500 nC/sec (measured by the Faraday cage method). The method for producing a spunbond nonwoven fabric according to claim 1, wherein the spread filaments are collected on the continuous conveyor net with a spread width of 500 mm or more under the conditions of a rotation angle range of -15±5° to +15±5° of the nozzle spraying the filament bundle and a reciprocating speed of the nozzle of 3 counters/sec to 12 counters/sec (here, the spread width means the maximum width based on the moving direction of the spread filaments collected on the continuous conveyor net). The thermoplastic resin has a melting point of 200° C. or higher,
The thermoplastic resin is one or more resins selected from the group consisting of polyester, polyamide, polyolefin, and polyphenylene sulfide.
A method for producing the spunbond nonwoven fabric according to claim 1. The method for producing a spunbond nonwoven fabric according to claim 1, wherein the thermoplastic resin is one or more resins selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate, polycyclohexane terephthalate, polyethylene naphthalate, nylon, polyethylene, polypropylene, polybutylene, and polyphenylene sulfide.

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