JP5467895B2 - Fiber assembly and method for producing the same - Google Patents

Description

  The present invention relates to a fiber assembly using an electrospinning method (electrospinning method) and a method for producing the same.

  Conventionally, as another method for obtaining ultrafine fibers, an electrospinning method in which a high voltage is applied to a polymer solution or a polymer melt to spin the ultrafine fibers is known. The electrospinning method is free from problems such as removal and disposal of sea components such as sea-island fibers, is easy to process, and is advantageous in terms of cost. As the electrospinning method, a solution method and a melting method are known from the raw material supply means. The solution method is a method in which an aqueous solution in which a raw material resin is dispersed or a fluid raw material resin liquid is supplied, the raw material resin is charged by being charged, and then fiberized by electric attraction. On the other hand, the melting method is a method of supplying a solid raw material resin molded product, charging the raw material resin by charging, heating and melting it, and stretching it by electric attractive force to form a fiber.

  For example, Japanese Patent Application Laid-Open No. 2005-154927 discloses a method of using a rod-shaped polymer to irradiate a supplied rod-shaped polymer with a laser to melt the polymer, and elongate it by electric attraction to obtain ultrafine fibers. (Patent Document 1). In JP 2009-299212 A, a sheet material such as a film or a sheet material in which fiber bundles are arranged in parallel is irradiated with laser light in a line along the width direction of the surface and heated. A method for obtaining ultrafine fibers by melting and stretching by electric attraction is disclosed (Patent Document 2).

JP 2005-154927 A JP 2009-299212 A

  Because of such raw material supply properties, ultrafine fibers can be easily obtained by the solution electrospinning method, but there is a problem that the practical strength is inferior and applications are limited. Also in the melt electrospinning method, the productivity of the rod-shaped polymer is inferior and the productivity tends to be improved if the sheet-shaped material is supplied, but the single-component sheet material has higher strength than the solution method. However, sufficient practical strength has not been obtained.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a fiber assembly including an ultrafine composite fiber obtained by an electrospinning method having high productivity and high practical strength.

The fiber assembly of the present invention supplies a composite resin raw material containing at least two component polymers, applies a voltage between the supply side electrode and the collection side electrode, gives electric charge to the molten composite resin raw material, and performs electrospinning ( A fiber assembly obtained by accumulating ultrafine composite fibers stretched by electrospinning, wherein the composite resin material includes a polymer having a volume resistivity of 10 ¹⁵ Ω · cm or less. And a sheet-like product in which at least two layers of the second polymer layer containing another polymer are laminated.

The method for producing a fiber assembly of the present invention is a composite resin raw material including at least two polymers, and includes a first polymer layer including a polymer having a volume resistivity of 10 ¹⁵ Ω · cm or less and another polymer. It is selected from the step of supplying a solid or molten sheet-like composite resin raw material in which at least two layers of the second polymer layer are laminated, before the supply side electrode, and between the supply side electrode and the collection side electrode A process of heating and melting in at least one region, and applying a voltage between the supply side electrode and the collection side electrode, applying an electric charge to the composite resin raw material in a molten state, and elongating it by electrospinning into an ultrafine composite fiber, It is characterized by including the process of accumulating on a collector.

In the present invention, the composite resin raw material supplied in the melt electrospinning method includes at least two layers of a first polymer layer containing a polymer having a volume resistivity of 10 ¹⁵ Ω · cm or less and a second polymer layer containing another polymer. By forming a laminated sheet-like material, a fiber assembly including ultrafine composite fibers having high productivity and high practical strength can be obtained.

It is a schematic explanatory drawing of the electrospinning apparatus of one Embodiment in this invention. It is a photograph of the scanning electron microscope (SEM, magnification 5000 times) of the surface of the fiber assembly after the electrospinning of Example 1 in this invention. It is a photograph of the scanning electron microscope (SEM, magnification 4000 times) of the cross section of the fiber assembly after the electrospinning of Example 1 in this invention.

The fiber assembly of the present invention is obtained by applying a voltage between the supply side electrode and the collection side electrode, giving electric charge to the composite resin material in a molten state, and stretching it by electrospinning to form an ultrafine composite fiber, which is obtained by accumulation. It is a fiber assembly. In general, in melt electrospinning as described above, the resin charged when passing through the supply-side electrode is stretched at high speed toward the collection-side electrode by electric attraction, so that the volume resistivity value is 10 ^15. Those having a resistance exceeding Ω · cm are difficult to be charged, so that they are difficult electrospinning resins unsuitable for electrospinning. However, according to the present invention, it is possible to obtain an ultrafine composite fiber assembly having a high practical strength by using a laminated sheet-like material as a first polymer layer containing a polymer having a volume resistivity of 10 ¹⁵ Ω · cm or less. I found it. Further, even when an electrospinning resin having a high volume resistivity is used as the second polymer layer, it can be stretched by electrospinning with the influence of a polymer having a volume resistivity of 10 ¹⁵ Ω · cm or less. This is because when the sheet-shaped composite resin material is heated and melted before and / or between the supply-side electrodes between the electrodes, for example, the composite resin material stays in the vicinity of the supply-side electrodes until it has a certain charge or more. At that time, when the heat-melted composite resin raw material sheet-like end surface is collapsed and the tailor cone is instantaneously alloyed, and the polymer component having a volume resistivity value of a predetermined value or less is elongated. It is presumed that the other polymer components combined are spun while stretching.

In the present invention, the polymer used for the first polymer layer has a volume resistivity of 10 ¹⁵ Ω · cm or less (hereinafter also referred to as a first component). This is because the composite resin material is easily charged when passing through the supply-side electrode. Preferably, it is 10 ⁶ to 10 ¹⁴ Ω · cm, more preferably 10 ⁷ to 10 ¹⁴ Ω · cm.

In addition, even in a polymer having a high volume resistivity such that the volume resistivity exceeds 10 ¹⁵ Ω · cm, a masterbatch kneading (for example, carbon or metal salts) that reduces the volume resistivity in the polymer. Master batches containing fillers such as), corona processing, fluorine processing, electret processing, and other treatment techniques that lower the resistance value of the resin, or oil agents that reduce the volume resistivity (for example, anionic surfactants) , Cationic surfactants, nonionic surfactants, etc.) on the surface of the composite resin, by using a single or a combination of treatment techniques, apparent volume resistivity before electrospinning. By lowering the value, a resin suitable for electrospinning can be obtained. In the case of resin, the volume resistivity is usually measured by ASTM D-257.

  The apparent volume resistivity value is a value obtained by measuring a volume resistivity (ASTM D-257), which is generally measured with a resin, with a sample obtained by treating the resin portion with the above-described treatment technique. That is, the apparent volume specific resistance value indicates not the volume specific resistance value of the resin itself but the volume specific resistance value of the treated resin.

The content of the first component in the first polymer layer is preferably 10% by mass or more. More preferably, it is 30 mass% or more, Still more preferably, it is 50 mass% or more, Most preferably, it is 100 mass%. If it is this range, an ultrafine fiber can be obtained stably. If the blending ratio of the first component is 10% by mass or more, a resin having a volume resistivity value of 10 ¹⁵ Ω · cm or less even if a resin with a volume resistivity value exceeding 10 ¹⁵ Ω · cm is added. When the material is electrospun by electrification, it can be simultaneously electrospun and stretched by its influence to form an ultrafine composite fiber.

The polymer having a volume resistivity of 10 ¹⁵ Ω · cm or less is not particularly limited, and examples thereof include ethylene vinyl alcohol copolymer (hereinafter also referred to as EVOH), polyesters such as polyethylene terephthalate, nylon, and polyurethane. Among them, EVOH is preferable because it is highly charged and has high extensibility by electrospinning. The volume resistivity value of the EVOH is preferably 10 ⁶ to 10 ¹⁵ Ω · cm, more preferably 10 ⁷ to 10 ⁹ Ω · cm, and still more preferably 10 ^7.5 to 10 ^8.5 Ω · cm.

  The EVOH can be obtained by saponifying an ethylene vinyl acetate copolymer. The content of ethylene in EVOH is not particularly limited, but is generally 29 to 47 mol (mol)%. Examples of commercially available products include Kuraray's trade name “EVAL”, Nippon Synthetic Chemical Industry's trade name “Soarnol”, and the like, and these commercially available products can be used in the present invention. The melting point of EVOH varies depending on the contents of ethylene and vinyl alcohol contained therein. For example, when 38 mol% of ethylene is contained, the melting point is 171 ° C. In addition, EVOH having a different ethylene content may be appropriately selected and used depending on the combination with other components contained in the composite resin raw material.

The first component may have a volume resistivity value of 10 ¹⁵ Ω · cm or less, and is not particularly limited. However, the melting point is preferably 100 to 300 ° C, and more preferably 120 to 200 ° C.

The second polymer layer including the other polymer laminated with the first polymer layer is not particularly limited, and a polymer having a volume resistivity value of 10 ¹⁵ Ω · cm or less and a volume resistivity value exceeding 10 ¹⁵ Ω · cm. Any of polymers may be used. As the other polymer, a polymer having a volume resistivity exceeding 10 ¹⁵ Ω · cm is preferably used. In the conventional method, an ultrafine fiber containing a polymer having a volume resistivity value exceeding 10 ¹⁵ Ω · cm could not be obtained. However, by combining a polymer having a volume resistivity value of 10 ¹⁵ Ω · cm or less, the ultrafine fiber can be obtained. This is because the obtained polymer can sufficiently exhibit the characteristics of a polymer having a volume resistivity exceeding 10 ¹⁵ Ω · cm. Examples of the polymer having a volume resistivity exceeding 10 ¹⁵ Ω · cm include polyolefins such as polyethylene, polypropylene, and polybutene or copolymers thereof, polystyrene, and the like.

The content of the polymer component having a volume resistivity exceeding 10 ¹⁵ Ω · cm with respect to the entire sheet is preferably 10 to 95% by mass. More preferably, it is 30-85 mass%. When the polymer having a volume resistivity exceeding 10 ¹⁵ Ω · cm is within the above range, electrospinning can be satisfactorily performed and a predetermined ultrafine composite fiber can be obtained.

  In order to increase the practical strength, high-adhesive polymers include linear low density polyethylene, low density polyethylene, high density polyethylene, ethylene-propylene copolymer, polypropylene, copolymer polyester, polylactic acid, polybutylene succin Polymers having a low melting point or adhesion temperature such as polyesters such as nates or copolymers thereof are preferred. As the polymer having high adhesiveness, it is preferable to use a polymer component having a melting point or an adhesion temperature of 70 to 180 ° C. More preferably, it is 90-160 degreeC, More preferably, it is 100-140 degreeC. When such a polymer having high adhesiveness is used, it is easy to stably obtain an ultrafine composite fiber, and good adhesiveness can be obtained.

It is preferable that content with respect to the whole sheet-like material in a polymer component with high adhesiveness is 10-90 mass%. More preferably, it is 20-80 mass%. When the polymer having a volume resistivity value exceeding 10 ¹⁵ Ω · cm is within the above range, it is possible to perform electrospinning well, to obtain a predetermined ultrafine composite fiber, and to obtain a fiber aggregate having high practical strength. can get.

  In addition, as the second polymer layer, it is preferable to use a polymer component having a melting point lower by 10 ° C. or more than the first component. More preferably, it is a polymer component whose melting point is 20 ° C. or more lower than that of the first component. With this configuration, the ultrafine composite fibers can be self-adhered to each other by adhesion of the polymer component (polymer having high adhesiveness) constituting the second polymer layer, and a fiber assembly having high practical strength such as tensile strength and puncture strength. You can get things. Also, when the fiber assembly is subjected to an adhesion treatment, an ultrafine composite fiber containing a highly adhesive polymer is formed. Therefore, if heat treatment is performed at a temperature lower than the melting point of the first component, a highly adhesive polymer component Only the first material can be adhered, and the first component can maintain the fiber shape without forming a film.

  The sheet-like material of the present invention is not particularly limited as long as at least two layers of the first polymer layer and the second polymer layer are laminated. The sheet-like material may be a laminate of three layers, four layers, or more. For example, as the three layers, a third polymer layer containing a polymer different from the first and second polymer layers may be used, or the third polymer layer may be formed of the same polymer component as the first polymer layer or the second polymer layer. Also good. The same applies to four or more layers.

  The form of the sheet-like material of the present invention is not particularly limited as long as it is a sheet in which at least two layers of a first polymer layer and a second polymer layer are laminated. For example, composite sheet-like articles, such as a composite film, a composite nonwoven fabric, and a composite knitted fabric, are mentioned. Among them, the composite film is preferable because it has high homogeneity such as thickness as a composite resin raw material and can be easily supplied to the nozzle stably.

  The composite resin raw material is preferably a sheet-like material in which the first polymer layer is disposed on at least one surface. More preferably, the first polymer layer is a sheet-like material disposed on both surfaces. When the first polymer layer is disposed on at least one surface, the first polymer layer is easily charged, and a predetermined ultrafine fiber aggregate is obtained.

  The lamination ratio of the first polymer layer is preferably 10 to 90% by mass with respect to the entire sheet-like material. More preferably, it is 20-80 mass% of the whole sheet-like material. When the lamination ratio of the first polymer layer is within the above range, electrospinning can be satisfactorily performed, and a predetermined ultrafine composite fiber can be obtained.

  The sheet material preferably has a thickness of 10 to 5000 μm. More preferably, it is 20-1000 micrometers. When the thickness of the sheet-like material is within the above range, the first component resin can be charged, which is preferable in that stable electrospinning is possible.

The sheet-like material preferably has a basis weight of 10 to 5000 g / m ² . More preferably 20~1000g / m ^2. It is preferable that the basis weight of the sheet-like material is within the above range because the first component resin can be charged and stable electrospinning is possible.

  In the present invention, the composite resin material only needs to be in a molten state when it is charged. Although the state at the time of supply of a composite resin raw material is not specifically limited, It is preferable that it is a solid state or a molten state. When the composite resin raw material is supplied in a solid state, an ultrafine composite fiber containing at least two component polymers can be easily obtained. Further, when the composite resin raw material is supplied in a molten state, the composite resin raw material is easily charged, and an ultrafine composite fiber containing at least two component polymers can be easily obtained.

  Next, the manufacturing method of the molten electrospinning of this invention is demonstrated. FIG. 1 is a schematic explanatory diagram of an electrospinning apparatus according to an embodiment of the present invention. The electrospinning device 11 applies a voltage from the voltage generator 3 between the supply side electrode 1 and the collection side electrode 2, and an arrow passes from the laser irradiation device 4 directly below the supply side electrode 1 through the laser widening device. A line-shaped laser beam widened along A is irradiated. The sheet-shaped composite resin material 7 is drawn from the roll 6, passes through the guides 8 and 9, and is supplied from the supply roller 10 to the electrospinning device 11. The composite resin material 7 is charged when passing through the supply-side electrode. In this charged state, the composite resin material 7 is heated and melted by being irradiated with a laser beam from the laser irradiation device 4 along the arrow A immediately below the supply-side electrode 1, and is stretched to the collection-side electrode together with the electric attractive force. The At this time, the composite resin raw material 7 extends in the direction of arrow B to be extremely fine, and becomes an ultrafine composite fiber. Reference numeral 12 denotes a fiber assembly in which ultrafine composite fibers are accumulated.

  In the present invention, a voltage is applied between the supply-side electrode and the collection-side electrode between the electrodes. A preferable applied voltage is 20 to 100 kV, and more preferably 30 to 50 kV. If the voltage is 20 kV or more, the resistance between the electrodes is small in the space (between the electrodes) in the atmosphere, the flow of electrons is good, and the resin is easily charged. Moreover, if it is 100 kV or less, a spark does not occur between electrodes and there is no possibility of igniting resin.

  The distance between the electrodes is preferably 2 to 25 cm, more preferably 5 to 20 cm. If the distance between the electrodes is 2 cm or more, no spark occurs between the electrodes, and there is no possibility of igniting the resin. Moreover, if it is 25 cm or less, the resistance between electrodes is not high, the flow of electrons is not deteriorated, and the resin is easily charged.

  When supplying the supply side electrode, the composite resin raw material may be supplied in a solid state or a molten state. For example, it is supplied in the state of a composite film. On the other hand, when passing through the supply-side electrode, it may be a composite resin material that is heated and melted or semi-molten (softened). When the composite resin raw material is in a molten state, it can be supplied in a composite film state.

  The sheet-like material may be supplied with a width of 1 mm or more when supplied to the supply-side electrode. A preferable width of the sheet is 5 to 2000 mm. When the width of the sheet is within the above range, good electrospinning is possible.

  In order to supply such a sheet-like material stably, a nozzle may be used. As the shape of the nozzle, it is preferable to use a nozzle having a slit hole having a size equal to or larger than the thickness and width of the sheet-like material. When a slit hole having a size 1 to 5 times the thickness and width of the sheet-like material is used, the sheet-like material can be supplied more stably.

  The composite resin material immediately after passing through the supply-side electrode may be irradiated with, for example, a laser beam or near-infrared ray, and heated and melted so that the composite resin material has a viscosity that is easy to electrospin. Even when the composite resin raw material is supplied in a molten state, or when the solid composite resin raw material is supplied and the composite resin raw material is previously melted or semi-molten, the composite resin is heated and melted between the electrodes. The viscosity of the resin raw material can be reduced, and the extensibility can be increased.

  The heating and melting method is preferably laser beam irradiation or near-infrared irradiation that is widened in the same direction as the width direction of the sheet-like material because the viscosity of the sheet-like material having a thickness and width is instantaneously reduced. Specifically, at least one selected from near-infrared line condensing heating and linear laser beam irradiation is more preferable. Near-infrared line condensing heating is performed using the method described in JP 2007-32246 A using a line heater HYP series (parallel irradiation type), HYL series (line condensing type), etc., manufactured by Hibeck. Good. Near-infrared line condensing heating is preferable because it can easily cope with the width of generally produced sheet-like materials.

The laser beam includes a laser beam generated from a light source such as a YAG laser, a carbon dioxide (CO ₂ ) laser, an argon laser, an excimer laser, or a helium-cadmium laser. Of these laser beams, a laser beam using a carbon dioxide laser is preferable because of its high power efficiency and high meltability of the composite fiber. The wavelength of the laser beam is, for example, 200 nm to 20 μm, preferably 500 nm to 18 μm, more preferably 1 to 16 μm, and even more preferably 5 to 15 μm. The laser beam irradiation method is preferably one that generates line-shaped laser light. Specifically, an optical system that uses a beam expander and a cylindrical lens, an optical system that scans a laser beam using a motor and a mirror, an optical system that uses a multistage phase beam branching diffractive optical component (DOE), and a callide Examples include an optical system that uses a scope.

  Thus, when heat-melting in a line shape, it is preferable that the line length is 1 to 100 times the length of the sheet-like material. More preferably, the length is 2 to 10 times. When the line length is within the above range, the sheet-like material can be stably heated and melted, and a predetermined ultrafine composite fiber can be obtained.

  When the composite resin raw material is heated and melted by irradiating a laser beam or the like after passing through the supply side electrode, the end of the supply side electrode on the side where the composite resin raw material exits and the line heating of the laser beam or the like in the composite resin raw material are performed. The distance between the parts is preferably 1 to 6 mm. More preferably, it is 2-4 mm. If the distance is 1 mm or more, the line heating part is not too close to the electrode, the temperature of the electrode does not increase, and resin decomposition tends to hardly occur. On the other hand, if the thickness is 6 mm or less, the charge amount of the resin molded product charged when passing through the supply-side electrode is not attenuated, and if the resin is heated and melted by line heating, the molten resin tends to easily extend toward the collection-side electrode. It is in.

  The output of the laser beam necessary for melting the composite resin raw material to be extendable is equal to or higher than the melting point of the first component constituting the composite resin raw material, and any of the resins constituting the composite resin raw material is ignited or What is necessary is just to control to the range used as the temperature which does not decompose | disassemble. That is, the composite resin raw material only needs to be in a viscous state. The temperature at which the composite resin material is heated to have a viscosity varies depending on the supply speed of the composite resin material, the output of the laser beam, the distance between the line heating unit and the composite resin material, and the size of the composite resin material. For example, the heating temperature in the case of near infrared heating or laser beam is preferably 160 to 1200 ° C, more preferably 600 to 800 ° C. If the heating temperature is 160 ° C. or higher, the amount of heat to be heated is sufficient, so that the melting is good, the viscosity is easily obtained, and it is easy to make it ultrafine. Moreover, if it is 1200 degrees C or less, resin will not ignite or decompose | disassemble and the fiberization of resin will become favorable. The specific output of the laser beam can be appropriately selected according to the physical property value (melting point), thickness, supply rate, etc. of the composite resin raw material to be used, but is, for example, 3 to 50 mA, preferably 6 to 40 mA, more preferably. It is about 10-30 mA. If the output of the laser beam is less than 3 mA, it is difficult to make the resin into a molten state that can be electrospun well, and if it exceeds 50 mA, the viscosity becomes too low and beads (resin balls) tend to occur frequently.

  The composite resin raw material melted to such an extent that it can be stretched is stretched together with the electric attractive force to the collecting side electrode to generate a tailor cone and stretch, so that it becomes a fibrous material containing ultrafine composite fibers. This tailor cone is randomly generated, for example, at about 1 to 3 mm.

  In the present invention, the fiber diameter of the obtained ultrafine composite fiber is preferably 0.1 to 10 μm. More preferably, it is 0.3-5 micrometers, More preferably, it is 0.5-3 micrometers. Here, the fiber diameter is obtained from the diameter of the fiber in the case of a circular fiber. The fiber diameter (diameter) is measured from the fiber cross section or from the fiber side surface. In addition, in irregular cross-section fibers such as polygons, ellipses, hollows, C-types, Y-types, X-types, and irregular shapes, the fiber diameter is determined by measuring the diameter assuming that the fiber cross-sectional shape is a circle having the same area. Ask. Therefore, in the case of a modified cross-section fiber, the fiber diameter cannot be obtained from the fiber side surface.

  The fibrous material containing the ultrafine composite fiber is accumulated on the collector of the collecting electrode to obtain a fiber assembly. The fiber aggregate may be collected directly on the collection side electrode (collector), or the collection side electrode (collector) is in the shape of a conveyor, and the position of continuous accumulation is moved. The sheet-like fiber assembly may be continuously produced. As another method for collecting fiber aggregates, a metal mesh, woven fabric, non-woven fabric, paper, or the like is placed on a collection-side electrode (collector), and ultrafine composite fibers are accumulated on the sheet-like material. As a result, a fiber assembly having a laminated structure can be obtained. Further, it may be accumulated in a non-sheet type such as an article having a certain thickness such as a cartridge type filter.

  The objects to be accumulated are preferably grounded to eliminate the potential difference from the collection side electrode. However, if there is no particular problem in production, there is no need to take a separate ground, and the object may be held in a state of being slightly lifted from the collection side electrode.

  In the fiber assembly, it is preferable that the ultrafine composite fibers are self-adhering to each other. The self-adhesion of the ultrafine composite fiber is not particularly limited, but can be performed by the following heat treatment. When an adhesive polymer is included as a polymer component constituting the fiber assembly, the ultrafine composite fibers are self-adhered by the adhesion of the adhesive polymer, and a fiber assembly having high practical strength can be obtained. For example, by performing a heat treatment at a temperature below the melting point of the polymer component other than the adhesive polymer, it is possible to obtain a heat-bonded nonwoven fabric in which the adhesive polymer is bonded and the ultrafine composite fibers are self-bonded. Although it does not specifically limit as a heat processing method, For example, the drying system by an air through dryer, a cylinder dryer, a hot roll (including embossing) etc. is mentioned.

The basis weight of the fiber aggregate is preferably 0.5 to 200 g / m ² . More preferably, it is 1-150 g / m < ² >, More preferably, it is 1-50 g / m < ² >. If the basis weight is 0.5 g / m ² or more, the fiber aggregate is hardly broken. On the other hand, if the basis weight is 200 g / m ² or less, the collection becomes stable. Here, the basis weight of the nonwoven fabric refers to that measured according to JIS L 1906 (2000).

  The thickness of the fiber aggregate is preferably 1 to 300 μm, more preferably 5 to 200 μm. If the thickness is 1 μm or more, the fiber aggregate does not break, while if it is 300 μm or less, the collection is stable. Here, the thickness of the nonwoven fabric refers to a thickness measured according to JIS B 7502.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, this invention is not limited to the following Example.

  The measurement methods used in Examples and Comparative Examples are as follows.

<Fiber diameter>
Using a scanning electron microscope (SEM, trade name “S-3500N” manufactured by Hitachi, Ltd., magnification of 1500 times), the fiber side surface was observed, and an average value was obtained from the measurement results of arbitrary 30 single fibers.

<Tensile strength>
According to JIS L 1096 6.12.1 (strip method), the tensile strength in the length direction of the sheet was measured using a test piece of a sheet having a width of 5 cm and a length of 15 cm.

<Raw resin>
(1) EVOH: Nippon Synthetic Chemical Co., Ltd. Soarnol ET3803 (MFR 3.2, 210 degreeC 2160g load)
(2) PP: Novatec EA9 (MFR 0.5, JIS K 7210 (1999)) manufactured by Nippon Polypro Co., Ltd.
(3) EP: Novatec EG7FT (MFR 1.3, JIS K 7210 (1999)) manufactured by Nippon Polypro Co., Ltd.
(4) LLDPE: Nippon Polypro, Novatec UF440 (MFR 1.7, JIS K 6922-2)
(5) Adhesive PP: Mitsubishi Chemical PAP553A (MFR 2.4, 230 ° C., 21.2 N load)
(6) Adhesive PE: Modic AP M545 manufactured by Mitsubishi Chemical Corporation (MFR 6, 190 ° C., 21.2 N load)

<Manufacture of composite resin raw materials>
The composite resin raw material produced the sheet-like material of the composite film shown in Table 1 according to the conventional composite film manufacturing method.

<Electrospinning method>
The electrospinning apparatus used the apparatus shown in FIG. 1, and the conditions were as follows.
Voltage between electrodes: 32.5 kV
Distance between electrodes: 10cm
Spinning speed: 30mm / min
Atmospheric temperature: 23 ° C
Laser device: PIN-30R manufactured by Onizuka Glass Co., Ltd. (rated output 30 W, wavelength 10.6 μm, beam diameter 6 mm)
Laser widening device: Beam homogenizer manufactured by Nippon Laser Co., Ltd. (for CO ₂ gas laser)
Distance between supply side electrode and laser irradiation part: 4mm
Supply side electrode: UNI series 20G × 15 manufactured by Unicontrols, Inc. Laser intensity: 20 mA

(Examples 1-4, Comparative Examples 1-2)
The sheet-like material (film) of Production Examples 1 to 6 was used as a resin raw material, supplied at a film width of 10 mm, and spun under the above electrospinning conditions to obtain a fiber aggregate containing the ultrafine composite fiber of the present invention. At this time, the CO ₂ gas laser was irradiated with a beam expander widened to a width of 35 mm with respect to the width direction of the film. Table 2 shows the characteristics of the obtained fiber assembly.

As apparent from Table 2, in Production Examples 1 to 4, the first polymer layer of the composite film, which is a composite resin raw material, used EVOH having a volume specific resistance value of 10 ¹⁵ Ω · cm or less. A fiber assembly containing spinning properties and ultrafine composite fibers was obtained. Moreover, when the surface and cross section of the fiber assembly were observed with an electron microscope, it was confirmed that the ultrafine composite fibers were self-adhering. On the other hand, Production Examples 5 and 6 using a single resin film having a volume resistivity exceeding 10 ¹⁵ Ω · cm as a raw material could not be spun.

  In addition, when the fiber aggregates of Examples 1 to 4 were bonded using an air-through dryer at a temperature 5 ° C. higher than the melting point of each lowest melting point component, the self-adhesion between the ultrafine composite fibers became stronger. It was.

  The fiber assembly of the present invention includes a filter, a battery separator (for example, a separator for a lithium ion battery, an electric double layer capacitor, etc.), a biocompatible material (for example, a tissue medical engineering material (artificial membrane), a scaffold for cell proliferation, etc.) ), Useful as an alternative to conventional paper and non-woven fabrics such as clothing, wipers, sound absorbing materials, heat insulating materials, and oil adsorbing materials.

DESCRIPTION OF SYMBOLS 1 Supply side electrode 2 Collection side electrode 3 Voltage generator 4 Laser irradiation apparatus 5 Laser widening apparatus 6 Roll 7 Composite resin raw material 8,9 Guide 10 Supply roller 11 Electrospinning apparatus 12 Fiber aggregate containing ultra fine composite fiber

Claims (6)

Elongate by supplying composite resin material containing at least two polymers, applying voltage between supply side electrode and collection side electrode, applying electric charge to molten composite resin material and electrospinning It is a fiber assembly obtained by accumulating ultrafine composite fibers,
The composite resin material includes a first polymer layer volume resistivity comprising the following polymer 10 ¹⁵ Ω · cm, Ri sheet der at least two layers are stacked in the second polymer layer containing other polymers ,
The melting point of the polymer component constituting the second polymer layer is 10 ° C. or more lower than the melting point of the polymer component constituting the first polymer layer,
A fiber assembly in which the ultrafine composite fibers are self-adhered by a polymer component constituting the second polymer layer .   The fiber assembly according to claim 1, wherein the composite resin material is a sheet-like material in which a first polymer layer is disposed on at least one surface. The fiber assembly according to claim 1 or 2, wherein the composite resin material is a sheet-like product in which a second polymer layer containing a polymer having a volume resistivity value exceeding 10 ¹⁵ Ω · cm is laminated.   The fiber assembly according to any one of claims 1 to 3, wherein the composite resin material is a composite film. A composite resin raw material containing at least two component polymers, wherein at least two layers of a first polymer layer containing a polymer having a volume resistivity value of 10 ¹⁵ Ω · cm or less and a second polymer layer containing another polymer are laminated. Supplying a solid or molten sheet-shaped composite resin material having a melting point of the polymer component constituting the second polymer layer that is 10 ° C. or more lower than the melting point of the polymer component constituting the first polymer layer ;
Heating and melting in at least one region selected from before the supply side electrode and between the supply side electrode and the collection side electrode;
And applying a voltage between the supply-side electrode and the collection-side electrode, applying a charge to the composite resin raw material in a molten state and stretching it by electrospinning to form an ultrafine composite fiber, and collecting it on the collector ,
The fiber assembly includes a step of heat-treating the ultrafine composite fiber at a temperature lower than the melting point of the polymer component constituting the first polymer layer and causing the ultrafine composite fiber to self-adhere with the polymer component constituting the second polymer layer . Manufacturing method.   6. The method for producing a fiber assembly according to claim 5, wherein the heat melting is at least one selected from near-infrared line condensing heating and line-shaped laser beam irradiation.