JP6494162B2 - Textile material and manufacturing method thereof - Google Patents

Description

  The present invention relates to a fiber material and a manufacturing method thereof, and more particularly to a fiber material coated with nanofibers and a manufacturing method thereof.

  In recent years, fiber materials have attracted attention as materials having a large specific surface area. In particular, vigorous studies have been conducted in Japan and overseas to increase the specific surface area based on the surface processing of fibers and to develop materials using them.

  Patent Document 1 discloses a fiber material for a filter having a large specific surface area, in which a core fiber is coated with a nanofiber having a functional group applied by applying a high voltage to the core fiber. Here, a high specific surface area is achieved by performing surface processing of the fiber by coating with nanofibers. That is, a fiber material (nanofiber-coated fiber material) coated with nanofibers manufactured by jetting nanofibers onto core fibers while winding thin fibers as core fibers has a large specific surface area. Therefore, a plurality of the nanofiber-coated fiber materials are twisted and converged to form a fiber bundle, and this fiber bundle is wound around the outer periphery of a cylinder having a permeable cylinder wall. Thus, it is disclosed that a pincushion filter having excellent filtration performance can be obtained.

JP 2009-219952 A

  However, the nanofiber-covered fiber material described in Patent Document 1 is configured such that the core fiber and the nanofiber covering the core fiber or the core fibers are physically entangled with each other. For this reason, there are problems in the following application aspects. First, the peeling resistance between the nanofiber and the core fiber is low, and the nanofiber is easily peeled and dropped due to external factors such as rubbing, and the specific surface area of the fiber material is reduced. Secondly, the mechanical strength of the fiber material is low, and the core fibers are easily frayed, which is disadvantageous for long-term use.

  The present invention has been made in view of such a background art, and provides a fiber material coated with nanofibers having excellent peeling resistance between nanofibers and core fibers and high mechanical strength, and a method for producing the same. It is.

The fiber material that solves the above problem is a fiber membrane that is formed by collecting a plurality of nanofiber-covered polymer fibers formed by coating polymer nanofibers on polymer fibers that are core fibers,
The nanofiber-coated polymer fiber is obtained by spinning the polymer fiber and the polymer nanofiber by an electrospinning method ,
The polymer fibers and the polymer nanofibers covering the polymer fibers are fused, and the plurality of polymer fibers constituting the fiber film have a structure in which the polymer films are fused at least partially to each other. Have
The polymer fiber has an average diameter of 10 μm or more and 50 μm or less, and the polymer nanofiber has an average diameter of 1 nm or more and less than 1 μm.

A method for producing a fiber material that solves the above problems includes a spinning step in which a polymer fiber that is a core fiber made of a polymer material is coated with a polymer nanofiber made of a polymer material to obtain a nanofiber-covered polymer fiber;
A fusion step of fusing the polymer fiber and the polymer nanofiber covering the polymer fiber, and fusing the plurality of polymer fibers forming the fiber material to each other at least partially; And
The spinning step may include Ri紡 yarn by the said polymer fibers and the polymer nanofibers electrospinning method,
The polymer fiber has an average diameter of 10 μm or more and 50 μm or less, and the polymer nanofiber has an average diameter of 1 nm or more and less than 1 μm.

  ADVANTAGE OF THE INVENTION According to this invention, the fiber material which was excellent in the peeling tolerance between a nanofiber and a core fiber, and the mechanical strength of the fiber material was high, and coated the nanofiber, and its manufacturing method can be provided.

It is the schematic which shows one Embodiment of the fiber material of this invention. It is the schematic which shows one Embodiment of the manufacturing method of the fiber material of this invention. It is an optical microscope photograph of the fiber material of Example 5 of this invention.

  Embodiments of the present invention will be described below.

(About the fiber material according to the present invention)
First, the fiber material according to the present invention will be described.

  The fiber material according to the present invention is a fiber material formed by collecting a plurality of nanofiber-covered polymer fibers formed by coating polymer fibers as core fibers with polymer nanofibers, the polymer fibers and the polymer The polymer nanofibers covering the fibers are fused, and the plurality of polymer fibers forming the fiber material have a structure fused at least partially to each other.

  In the present invention, the core fibers and the diameters of the coated fibers covering the core fibers each have an average diameter of 1 μm or more and 50 μm or less, and 1 nm or more and less than 1 μm. The core fibers include conventionally known fiber materials such as, for example, Carbon fiber materials and fiber materials can be used alone or in combination as appropriate.

  In the present embodiment, a fiber (fiber) having a mean diameter of 1 μm or more and 50 μm or less composed of a polymer is called a polymer fiber, and a fiber having an average diameter of 1 nm or more and less than 1 μm is called a nanofiber. A fiber having an average diameter of 1 nm or more and less than 1 μm is also referred to as polymer nanofiber (abbreviated as polymer fiber).

  Further, the fiber according to the embodiment of the present invention has a longer length than the thickness of the fiber. The cross-sectional shape of the fiber is not particularly limited, and may be a circle, an ellipse, a quadrangle, a polygon, a semicircle, or the like, and may not be an accurate shape, or may have a different shape in an arbitrary cross section.

  The fiber thickness (diameter) refers to the diameter of the circle of the cross section when the fiber cross section is cylindrical, but otherwise the length of the longest straight line passing through the center of gravity of the fiber cross section. That is. The length of the polymer fiber is at least 10 times the thickness.

  In addition, since the structure which consists of fibers has the feature that a specific surface area increases, so that the diameter becomes thin, since the fiber material with a high specific surface area is obtained, so that a fiber diameter is thin, it is effective. In addition, in nanofibers with a nano-sized diameter, the additive added to the nanofibers in a fine space, called the supramolecular alignment effect, is aligned in the longitudinal direction of the fiber during the nanofiber manufacturing process. In the case of a polymer (polymer fiber), there is an effect that the molecular chains of the polymer are aligned. As a result, a fiber having high mechanical strength can be obtained.

  Next, the fiber material which coat | covered the polymer nanofiber of this invention is demonstrated using FIG.

  FIG. 1 is a schematic view showing an embodiment of the fiber material of the present invention. FIG. 1A is a schematic cross-sectional view of one nanofiber-coated polymer fiber, and FIG. 1B is a perspective view of a fiber material. In the figure, 1 is a nanofiber-coated polymer fiber, 2 is a polymer fiber, 3 is a polymer nanofiber, and 4 is a fiber material.

  The fiber material 4 coated with the nanofibers of the present embodiment inevitably has irregularities on the surface, and is composed of the nanofiber-coated polymer fibers 1, so that the specific surface area is high. One of the nanofiber-coated polymer fibers 1 in the fiber material of the present invention is formed by fusing a polymer nanofiber 3 composed of at least a polymer material on the surface of a core fiber 2 composed of at least the polymer material. Yes. As a result, the peeling resistance between the polymer nanofiber 3 and the polymer fiber 2 that is the core fiber is high, and the polymer nanofiber 3 is easily peeled and dropped due to external factors such as rubbing, and the specific surface area of the fiber material is reduced. There is nothing.

  In addition, although the specific surface area and surface unevenness | corrugation in a nanofiber coating polymer fiber depend on the coating ratio of a polymer nanofiber, the number of the coated polymer nanofiber, etc., these should just be selected suitably according to a desired characteristic.

  In the fiber material of the present invention, the number of nanofiber-covered polymer fibers 1 in any cross section, the adjacent interval, and the number of laminated layers can be appropriately selected according to the desired characteristics of the fiber material. For example, FIG. 1B shows a configuration in which a plurality of nanofiber-covered polymer fibers 1 are randomly arranged and the nanofiber-covered polymer fibers 1 are fused at least partially.

  That is, these adjacent nanofiber-covered polymer fibers forming the fiber material 4 are fused to each other at least partially to form a strong and flexible network. As a result, the fiber material obtained by the present invention has high mechanical strength, and the core fibers are not easily frayed, which is advantageous for long-term use.

  From the above, the present invention can provide a fiber material coated with polymer nanofibers, which has a high specific surface area, high resistance to peeling between the polymer fibers that are core fibers and polymer nanofibers, high mechanical strength of the fiber material. .

  The fiber material of the present invention can be a fiber material having a high specific surface area that can be used over a long period of time even when external factors such as rubbing are applied. Can be suitably used.

(About polymer fibers that are core fibers)
The polymer fiber that is the core fiber in the present invention is not particularly limited, and may be at least a fiber made of a polymer material, and an organic polymer is preferable. As the organic polymer, conventionally known organic polymer materials can be appropriately used alone or in combination. Further, it may be a polymer material containing fine particles or a conventionally known filler, and may be constituted by appropriately combining them.

  In addition, the polymer fiber in this invention has at least 1 or more types of polymer, and the length is longer than the thickness of the polymer fiber.

  The thickness of the polymer fiber is preferably larger than that of the polymer nanofiber to be coated, and the average diameter is preferably 1 μm or more and 50 μm or less. A more preferable average diameter is 10 μm or more and 50 μm or less.

  In order to coat the polymer nanofiber, if the core fiber is thinner than the polymer nanofiber, it is difficult to handle from the viewpoint of manufacturing, and it becomes difficult to coat the polymer nanofiber on the outer peripheral surface of the core fiber well. There is a case. Therefore, the thickness of the polymer fiber is thicker than the polymer nanofiber to be coated, more preferably at least 10% thicker than the polymer nanofiber, and the average diameter is preferably 1 μm or more.

  In addition, in order to obtain a fiber material with a high specific surface area, it is easy to obtain a high specific surface area by coating the core fiber with a polymer nanofiber having a small diameter, so the average diameter of the polymer fiber is 50 μm or less. It is preferable that

  The cross-sectional shape of the polymer fiber is not particularly limited, and may be a circle, an ellipse, a quadrangle, a polygon, a semicircle, or the like, and may not be an accurate shape, or may have a different shape in an arbitrary cross section.

  The thickness of the polymer fiber refers to the diameter of the circle of the cross section when the cross section of the polymer fiber is circular, but otherwise the length of the longest straight line passing through the center of gravity in the fiber cross section. It is. The length of the polymer fiber is 10 times or more the thickness.

  The polymer material of the polymer fiber in the present invention is not particularly limited as long as it is at least partially meltable and forms a fibrous structure, and is an inorganic material such as an organic material such as a resin material, silica, titania, clay mineral, etc. Alternatively, a material obtained by hybridizing the organic material and the inorganic material may be used.

Examples of the polymer material include fluorine-containing polymers such as tetrafluoroethylene and polyvinylidene fluoride, such as polyvinylidene fluoride (PVDF), a copolymer of PVDF and hexafluoropropylene (PVDF-HFP), polyethylene, Polyolefin polymers such as polypropylene; polystyrene (PS); polyarylenes such as polyparaphenylene oxide, poly (2,6-dimethylphenylene oxide) and polyparaphenylene sulfide (aromatic polymers); polyolefin polymers, polystyrene, polyimide, polyarylene ethers (aromatic polymers), sulfonic acid _(-SO 3 H), carboxyl group (-COOH), a phosphoric acid group, a sulfonium group, ammonium group, or guiding a pyridinium group Perfluorosulfonic acid polymer or perfluorocarboxylic acid polymer in which a sulfonic acid group, carboxyl group, phosphoric acid group, sulfonium group, ammonium group, or pyridinium group is introduced into the skeleton of polytetrafluoroethylene or a fluorine-containing polymer , Perfluorophosphoric acid polymers; polybutadiene compounds; polyurethane compounds such as elastomers and gels; silicone compounds; polyvinyl chloride; polyethylene terephthalate; nylon; polyarylate; (PCL) and polylactic acid, as well as ethers such as polyethylene oxide (PEO) and polybutylene oxide, and polyesters (PES) such as polyethylene terephthalate (PET). Yes. These may be used singly or in combination, may be functionalized, or may be a copolymer with another polymer. In addition, in the case of a polymer material that is difficult to melt, such as polyimide, polyamide, polyamideimide (PAI), and polybenzimidazole (PBI), for example, a thermoplastic resin can be used in combination.

Examples of the inorganic material include Si, Mg, Al, Ti, Zr, V, Cr, Mn, Fe, Co, Ni, Cu, Sn, and Zn oxides, and more specifically, the following metal oxides. . Examples thereof include silica (SiO ₂ ), titanium oxide, aluminum oxide, alumina sol, zirconium oxide, iron oxide, chromium oxide and the like. A clay mineral such as montmorillonite (MN) can also be used.

  In addition, when an inorganic material is contained in the polymer fiber, the mechanical strength tends to be remarkably improved by fusing the fibers together, which is preferable from the viewpoint of improving durability.

  In the present invention, when the polymer fiber contains at least the polymer material constituting the polymer nanofiber, the compatibility between the fibers is high and the fibers tend to be firmly fused.

  In the present invention, “the polymer fiber contains at least the polymer material constituting the polymer nanofiber” means that the polymer material formed from the same kind of skeleton structure constituting the polymer nanofiber is included in the polymer fiber. It need only be at least contained and need not be the same polymeric material.

  By setting it as the above material structures, since there exists a tendency for the mechanical strength of the fiber material in this invention to improve remarkably, it is preferable from a viewpoint of a durable improvement.

When the melting temperature (melting point: Tm ₁ ) of the polymer material forming the polymer fiber is lower than the Tm _{2 of} the polymer material forming the polymer nanofiber and the difference is large, the polymer fiber and It becomes possible to fuse the polymer nanofiber to be coated by fusing the polymer fiber side preferentially. That is, it is preferable because the shape (unevenness) of the polymer nanofiber is maintained and the effect of increasing the specific surface area of the fiber material based on the coating of the polymer nanofiber is easily exhibited.

Here, the temperature difference (Tm ₂ −Tm ₁ ) between the melting points of the polymer fiber and the polymer nanofiber is 5 ° C. or more, preferably 30 ° C. or more, from the viewpoint of temperature control. That is, when the temperature difference is less than 5 ° C., the shape of the polymer nanofiber tends to be difficult to maintain.

  In addition, when the melting point (Tm) of the polymer material forming the polymer fiber is equal to or lower than the glass transition point (Tg) of the polymer material forming the polymer nanofiber, the shape of the polymer nanofiber is extremely maintained during the fusing process. It is more suitable because it is easy to cause.

  In the present invention, when polymer fibers or polymer nanofibers are each formed from a plurality of polymer materials, the Tm and Tg of the composite material are the lower value of each Tm and each Tg. Indicates.

  The polymer fiber also preferably has at least a material having a high sharp melt property from the viewpoint of easy handling in the fusing process. As the material having high sharp melt property, conventionally known materials can be used alone or in combination, and for example, a hot melt agent or a low melt agent can be suitably used. Specifically, as the hot melt agent, PES310S30, PES360S30, PES375S40 (above, manufactured by Toa Gosei Co., Ltd.), 3738, 3747, 3762, 3764 (above, made by 3M), etc. 3792LM, 3798LM (manufactured by 3M) or the like can be used alone or in combination as appropriate.

(About polymer nanofibers that are coated fibers)
The material of the polymer nanofiber that is the coated fiber in the present invention is not particularly limited, and may be a fiber made of at least a polymer material, and an organic polymer is preferable. As the organic polymer, a conventionally known polymer material can be appropriately used. Further, it may be a polymer material containing fine particles or a conventionally known filler, and may be constituted by appropriately combining them.

  In addition, the polymer nanofiber according to the embodiment of the present invention includes at least one type of polymer, and the length is longer than the thickness of the polymer nanofiber.

  The polymer nanofiber is preferably thinner than the polymer fiber that is the core fiber. In particular, from the viewpoint of increasing the specific surface area by coating the core fiber, the thickness of the polymer nanofiber is the average diameter. Is preferably 1 nm or more and less than 1 μm. More preferably, the average diameter is 30 nm or more and less than 1 μm.

  In order to coat the outer surface of the core fiber with the polymer nanofiber, if the polymer nanofiber is thicker than the core fiber, it is difficult to handle from the viewpoint of manufacturing. The polymer nanofiber is also coated on the outer surface of the core fiber. May be difficult to do. Therefore, it is preferably thinner than the polymer fiber that is the core fiber and the average diameter is less than 1 μm, and more specifically, it is preferably at least 10% thinner than the polymer fiber.

  In addition, polymer nanofibers having an average diameter of less than 1 nm generally need to be manufactured by a special technique such as a self-assembly method or a phase separation method, and tend to be expensive to manufacture in large quantities. Therefore, the thickness of the polymer nanofiber is preferably 1 nm or more.

  The cross-sectional shape of the polymer nanofiber is not particularly limited, and may be a circle, an ellipse, a rectangle, a polygon, a semicircle, or the like, and may not be an exact shape, or may have a different shape in an arbitrary cross section. .

  The thickness of the polymer nanofiber refers to the diameter of the circle of the cross section when the cross section of the nanofiber is circular, but otherwise, the length of the longest straight line passing through the center of gravity of the cross section of the polymer nanofiber. That's it. The length of the polymer nanofiber is not less than 10 times the thickness.

  The polymer material used for the polymer nanofiber according to the present invention is not particularly limited except for the relationship with the polymer material used as the polymer fiber described above, and the polymer material of the polymer fiber can be used as appropriate.

  Moreover, it is preferable that the polymer nanofiber which coat | covers a polymer fiber contains the polymer material which comprises the said polymer fiber at least.

  From the viewpoint of maintaining the shape of the polymer nanofiber in the fusion process, a polymer material that is difficult to melt, such as polyimide, polyamide, polyamideimide (PAI), or polybenzimidazole (PBI), is combined with, for example, a thermoplastic resin. It is also preferable to use it alone. In other words, polyimide, polyamide, polyamideimide (PAI), polybenzimidazole (PBI), etc. are called engineering plastics, and they have a Tg higher than that of general thermoplastic polymer materials. Is preferable because it tends to maintain the shape of the polymer nanofiber in the fusion process.

(Coating amount of polymer nanofiber coated on polymer fiber)
The coating amount of the polymer nanofiber coated on the polymer fiber as the core fiber may be appropriately adjusted according to the desired performance. For example, it is 1 part by weight or more and 95 parts by weight or less, preferably 100 parts by weight of the polymer fiber. Is preferably 5 parts by weight or more and 90 parts by weight or less. If the polymer nanofiber is less than 1 part by weight, the increase in specific surface area may not be large, which is not preferable. On the other hand, if the polymer nanofiber exceeds 95 parts by weight, the polymer fibers may not be fused to each other at least in part, which is not preferable.

(About the manufacturing method of the fiber material which concerns on this invention)
Next, the manufacturing method of the fiber material which concerns on this invention is demonstrated.

  The method for producing a fiber material according to the present invention comprises a spinning step of coating a polymer fiber, which is a core fiber made of a polymer material, with a polymer nanofiber made of a polymer material to obtain a nanofiber-coated polymer fiber, and the polymer fiber, The polymer nanofiber covering the polymer fiber is fused, and a plurality of polymer fibers forming the fiber material are fused at least partially to each other.

  The method for producing the fiber material according to the present invention is not particularly limited. For example, polymer fibers and polymer nanofibers are compositely spun by electrospinning (electrospinning / electrostatic spinning), and then heated in an oven. Rather than using a method of fusing fibers and polymer nanofibers and polymer fibers, or composite spinning using the electrospinning method alone, a combination of electrospinning and meltblowing may be used.

  The electrospinning method applies a high voltage between the polymer solution contained in the syringe and the collector electrode, so that the solution extruded from the syringe is charged and scattered in the electric field to become thin, and the polymer fiber This is a method for producing a polymer fiber that adheres to the collector.

  Among the above-mentioned production methods, various polymers can be spun into a fiber shape, the fiber shape control is relatively simple, and an average diameter of several tens of μm to a nano-sized fiber can be easily obtained. Furthermore, since the manufacturing process is simple, it is preferable to perform composite spinning by electrospinning.

  The spinning process by the composite spinning of polymer fiber and polymer nanofiber by electrospinning, which is an embodiment of the present invention, will be described with reference to FIG.

  FIG. 2 is a schematic view showing an embodiment of the method for producing a fiber material of the present invention. It is the schematic which shows the composite spinning using the electrospinning method which is an example of the manufacturing method of the nanofiber covering polymer fiber of this invention especially.

  As shown in FIG. 2, this is performed using a head 17 in which a plurality of polymer solution storage tanks 12, 13, and 14 are arranged and a grounded collector 15 through a connection portion 11 connected to a high-voltage power supply 16. Reference numeral 10 denotes a fiber material manufacturing apparatus.

  The polymer solution is extruded from the tanks 12, 13, 14 to the spinning ports 22, 23, 24 at a constant speed. A voltage of 1 to 50 kV is applied to each spinning port 22, 23, 24, and when the electric attractive force exceeds the surface tension of the polymer solution, the polymer solution jets 18, 19, 20 are jetted toward the collector 15. Is done. At this time, the solvent in the jet gradually evaporates, and when it reaches the collector, the corresponding fiber is obtained. Here, the polymer solution set to the conditions for forming the polymer nanofibers is introduced into the tanks 12 and 13, while the polymer solution set to the conditions for forming the polymer fibers is introduced into the tank 14 to perform composite spinning.

  Here, not a polymer solution but a molten polymer heated to a melting point or higher may be used.

  In addition, a polymer nanofiber and a polymer fiber can be confirmed by direct observation by a scanning electron microscope (SEM) or laser microscope measurement.

  The average fiber diameter (average diameter) of polymer nanofibers and polymer fibers is determined by measuring the corresponding composite fiber membrane with a scanning electron microscope (SEM), and importing the image into image analysis software “Image J”. This can be determined by measuring the widths of the 50 polymer nanofibers and polymer fibers.

(Polymer nanofiber and polymer fiber, and fusion process between polymer fibers)
In the present invention, “the polymer fiber and the polymer nanofiber covering the polymer fiber are fused” or “a plurality of polymer fibers forming the fiber material are fused to each other at least partially. “To wear” means that at least the polymer fiber is softened and adhered to the coated polymer nanofiber or the adjacent polymer fiber, and the bonding boundary is planar or the bonding boundary is lost. That means.

  The fusion process is not particularly limited. In addition to thermal fusion, ultrasonic fusion, and frictional fusion, fusion by thermocompression (hot press) may be used. Wear is preferred. There is no particular limitation on the method of heat fusion, for example, a method of hot pressing, a method of fusing by heating with an industrial dryer or an oven, or a post-heating in an oven after heating once with a heater. Thus, a method of fusing can be suitably used. Among them, the method of fusing using an oven can be used particularly suitably because the temperature of the whole material is uniform and easy to make uniform.

  The fusing temperature is not particularly limited as long as it is equal to or lower than the decomposition temperature of the polymer material. As described above, the fusing temperature may be appropriately selected according to the polymer material to be used, the desired fiber material, etc. The temperature is preferably 30 to 250 ° C., and more preferably at least near the melting point of the polymer fiber or both the polymer fiber and the polymer nanofiber. As described above, when the fusion temperature is not lower than the melting point (Tm) of the polymer material forming the polymer fiber and not higher than the glass transition point (Tg) of the polymer material forming the polymer nanofiber, This is very suitable because it is easy to maintain the shape of the polymer nanofiber. The heating time is preferably from 0.1 minute to 60 minutes.

  Method of confirming “fusion of polymer fiber and polymer nanofiber covering the polymer fiber” and “fusion of polymer fibers (polymer fibers are fused to each other at least partially)” Can be confirmed by direct observation using a laser microscope or an electron microscope (SEM) before and after the fusion process.

  That is, as described above, at least a part of the polymer fibers in the present invention are fused to each other, that is, the fusion of at least a part of the polymer fibers is that the polymer fibers are softened and bonded to the adjacent polymer fibers. The state where the bonding boundary portion is planar or the bonding boundary disappears. Therefore, the polymer fibers or polymer nanofibers soften, and the adjacent polymer fibers or polymer fibers adhere to the polymer nanofibers covering them, so that the bonding boundary is planar or the bonding boundary disappears. If it is observed that it is bent, it can be confirmed that they are fused.

  In FIG. 3, the optical micrograph of the nanofiber covering polymer fiber material of Example 5 is shown as an example which shows the fusion | melting of the polymer nanofiber and polymer fiber which concern on this invention, and polymer fibers. In FIG. 3, a polymer nanofiber having an average diameter of about 700 nm formed from polyamideimide (PAI) is fused and coated to the surface of a polymer fiber having an average diameter of about 35 μm formed from a polyester-based material (PES). In addition, it can be confirmed that the polymer fibers adjacent to each other are at least partially fused to each other.

(Evaluation of degree of fusion between polymer fiber and polymer nanofiber covering the polymer fiber)
In the present invention, the degree of fusion of the polymer nanofibers coated with the polymer fibers is evaluated by using an adhesive tape (NICHIBAN CO., LTD .: CT-18, 0.401 N / mm) on both sides of the produced fiber material. And a simple tape peeling test in which an Instron tester (Shimadzu: EZ-test) was used to peel the film vertically.

In other words, arbitrary 10 points (observation points) on the surface of the fiber material are marked in advance, and the degree of peeling of the polymer nanofibers covering the polymer fibers before and after the simple tape peeling test at the observation point is observed with a laser microscope. The evaluation was made in the following three stages A to C.
A: Peeling of the polymer nanofiber covering the polymer fiber is not observed at all observation points.
B: Peeling of the polymer nanofiber covering the polymer fiber is observed at 1 to 4 observation points.
C: Peeling of the polymer nanofiber covering the polymer fiber is observed at five or more observation points.

  Note that the degree of fusion is high in the order of A >> B> C, and as a result, the peel resistance between the polymer nanofiber and the polymer fiber is high. Therefore, in the order of A >> B> C, polymer nanofibers can be easily peeled and dropped due to external factors such as rubbing, and a polymer nanofiber-coated polymer fiber material in which the specific surface area of the fiber material does not decrease can be obtained. .

(Evaluation of the degree of fusion between polymer fibers)
Confirmation of improvement in mechanical strength of fiber material by fusing polymer fibers in nanofiber coated polymer fiber material can be easily performed by measuring the Young's modulus of the corresponding fiber material before and after the fusing process. is there.

  In the present invention, the evaluation of the degree of fusion between polymer fibers is performed by measuring the tensile strength measurement using an autograph (AG-Xplus) manufactured by Shimadzu Corporation for the mechanical strength change of the fiber material before and after the fusion process.

  Specifically, in the sample after the fusion process, it is confirmed by direct observation using a laser microscope or an electron microscope (SEM) that the polymer fibers are fused to each other at least partially. Thereafter, the Young's modulus of the fiber material in a state where the polymer nanofibers are only physically coated and the Young's modulus of the sample after the fusion process are measured, and the increase rate of the Young's modulus is calculated.

  In addition, the higher the Young's modulus increase rate, the higher the degree of fusion that the polymer fibers are fused to each other at least in part. As a result, the mechanical strength of the fiber material is improved. Is possible.

(Evaluation of polymer nanofiber shape change before and after the fusion process)
The evaluation of the shape change of the polymer nanofiber before and after the fusion process in the present invention can be performed using a scanning electron microscope (SEM).

That is, the fiber material before and after the fusing process is observed using an SEM, and those images are taken into the image analysis software “Image J”, and then the direction perpendicular to the thickness direction of the fiber material before and after the fusing process ( The fiber widths of 50 arbitrary polymer nanofibers are measured from the upper surface), and the shape change ratio of the polymer nanofibers is calculated by comparing the fiber widths before and after fusing. Based on the results, the degree of the shape change rate was evaluated in the following three stages I to III.
I: No change in polymer nanofibers is observed at all observation points.
II: A slight change (within +5 to + 10%) of the polymer nanofiber is observed.
III: Changes in polymer nanofibers are observed to be very large (greater than + 10%).

Examples of the present invention will be described below. In addition, Example 2 is a reference example.

  In addition, although the Example of this invention is described in detail below, these are only illustrations and do not limit this invention. The technology of the present invention includes various modifications and changes of the specific examples illustrated below.

<Example 1>
This example is a fiber material in which polymer fibers are formed from polycaprolactone (PLC) and polymer nanofibers are formed from polyethylene oxide (PEO). The production of the fiber material is performed as follows.

  First, PCL adjusted to 8 wt% using a solution obtained by mixing polycaprolactone (PCL, weight average molecular weight 80000, manufactured by Aldrich), THF (tetrahydrofuran) and DMF (dimethylformamide) at a ratio of 6: 4 (volume ratio). Use 1 mL of diluent A. 2 mL of PEO diluent B prepared by adjusting polyethylene oxide (manufactured by Aldrich) to 6 wt% using pure water is used.

  Next, the nanofiber-coated polymer in which the polymer nanofibers made of PEO are physically coated on the PLC polymer fiber, which is the core fiber, by simultaneously injecting these dilute solutions by electrospinning and performing composite spinning. Get fiber.

  That is, first, an electrospinning apparatus (manufactured by MEC) is equipped with a head (clip spinneret, see FIG. 2) capable of spinning a plurality of solutions.

  Next, a tank filled with the PCL diluted solution A is provided at the center of the head, and a tank filled with the PEO diluted solution B is provided at both ends. Then, each diluted solution is jetted toward the collector by moving left and right at 50 mm / s while applying a voltage of 19 kV to the spinneret. By spraying for 15 minutes, a nanofiber-covered polymer fiber in which a polymer fiber of PCL is coated with a polymer nanofiber of PEO can be obtained.

  Then, after sandwiching the obtained nanofiber-coated polymer fiber with a glass plate, it was placed in an oven and heat-treated at 65 ° C. for 0.5 minutes, so that the polymer fiber and the polymer nanofiber were fused and the adjacent A fiber material is obtained in which the polymer fibers are at least partially fused together.

  The thickness of the polymer fiber in the fiber material thus obtained has an average diameter of 18 μm, and the thickness of the polymer nanofiber has an average diameter of 650 nm.

<Example 2>
This example is a modification of Example 1, and was produced in the same manner as Example 1 except that the material of the polymer fiber or polymer nanofiber was changed and the following conditions were changed.

  As a polymer fiber material, a mixture of polystyrene (PS, weight average molecular weight 280000, manufactured by Aldrich) and polyethylene terephthalate (PET, weight average molecular weight 10,000, manufactured by Aldrich) (9: 1 by volume) using DMF. Use 1 mL of PS / PET diluted solution C adjusted to a 30 wt% solution. Further, as a polymer nanofiber material, PET diluted solution D and 2 mL adjusted to 13 wt% using a solution in which PET is mixed with dichloromethane (DCM) and trifluoroacetic acid (TA) at 1: 1 (volume ratio) are used. .

  The voltage is applied to the spinneret at 22 kV. Also, in the fusion process, a fiber material in which the polymer fiber and the polymer nanofiber are fused in an oven at 260 ° C. for 0.5 minutes, and the adjacent polymer fibers are fused to each other at least partially. Is obtained.

  The thickness of the polymer fiber in the fiber material thus obtained has an average diameter of 1.5 μm, and the thickness of the polymer nanofiber has an average diameter of 300 nm.

<Example 3>
This example is a modification of Example 1, and was produced in the same manner as Example 1 except that the material of the polymer fiber or polymer nanofiber was changed and the following conditions were changed.

  As a polymer fiber material, polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) (Kayner 2750, manufactured by Kyner) was adjusted to a 10 wt% solution using dimethylacetamide (DMAc), a PVDF-HFP diluted solution E, Use 1 mL.

  As a material for the polymer nanofiber, a mixture of polyvinylidene fluoride (PVDF, Kyner 460, manufactured by Kyner) and montmorillonite (MN, Nanoclay, manufactured by Aldrich) was used. The mixture was prepared by the following procedure.

  10 mg of montmorillonite (MN) as a filler and 1 mL of organic solvent (DMAc) are put in a container. A zirconia ball having a particle diameter of 2 mm is added to 1/3 of the capacity of the container, and a dispersion treatment is performed using a ball mill (Fritchsch, planetary fine pulverizer) at 200 rpm / 30 minutes. Next, a solution in which 200 mg of PVDF as a base material was dissolved in 2 mL of DMAc was added, and further a dispersion treatment was performed under conditions of 500 rpm / 60 minutes. In this way, 2 mL of PVDF-MN diluted mixed solution E, which is a material of the polymer nanofiber, is prepared.

  The voltage is applied to the spinneret at 18 kV. Also, the fusion process is a fiber material in which the polymer fiber and the polymer nanofiber are fused in an oven at 155 ° C. for 0.5 minutes, and the adjacent polymer fibers are fused at least partially to each other. Is obtained.

  The thickness of the polymer fiber in the fiber material thus obtained has an average diameter of 20 μm, and the thickness of the polymer nanofiber has an average diameter of 220 nm.

<Example 4>
This example is a modification of Example 1, and was produced in the same manner as Example 1 except that the material of the polymer fiber or polymer nanofiber was changed and the following conditions were changed.

  The material of the polymer fiber is adjusted as follows.

In a container, 10 parts by weight of thermoplastic polyester-based hot melt material (PES, Aron Melt PES375S40, manufactured by Toa Gosei Co., Ltd., solid content 40 wt%, solvent (toluene: MEK = 8: 2)), silica particles (SiO ₂ , Nanopowder with an average particle diameter of 10 to 20 nm (manufactured by Aldrich) is added and mixed. Next, zirconia balls having a particle size of 2 mm are added to 1/3 of the container volume, and dispersion treatment is performed using a ball mill (Fritchsch, planetary fine pulverizer) under conditions of 500 rpm / 30 minutes, and PES-SiO Prepare 1 mL of ₂ diluted mixed solution E.

  In addition, as a material of the polymer nanofiber, a PBI diluted solution F, in which polybenzimidazole (PBI, manufactured by Aldrich) was adjusted to 20 wt% in a DMAc solution in which 4 wt% lithium chloride (LiCl) was dissolved, Use 2 mL.

  The voltage is applied to the spinneret at 23 kV. Also, in the fusion process, heat treatment is performed at 130 ° C. for 1 minute in an oven to obtain a fiber material in which the polymer fiber and the polymer nanofiber are fused, and the adjacent polymer nanofiber-covered polymer fiber is fused. It is done.

  The thickness of the polymer fiber in the fiber material thus obtained has an average diameter of 40 μm, and the thickness of the polymer nanofiber has an average diameter of 150 nm.

<Example 5>
This example is a modification of Example 1, and was produced in the same manner as Example 1 except that the material of the polymer fiber or polymer nanofiber was changed and the following conditions were changed.

  As the polymer fiber material, 1 mL of a thermoplastic polyester-based hot melt material (PES, Aron Melt PES375S40, manufactured by Toa Gosei Co., Ltd., solid content 40 wt%, solvent (toluene: MEK = 8: 2)) is prepared.

  As a material for the polymer fiber, a polyamideimide (PAI, Pyromax HR-13NX) with a solid content concentration of 25 wt% using DMF was used.

  The voltage is applied to the spinneret at 19 kV. Also, in the fusion process, heat treatment is performed at 130 ° C. for 1 minute in an oven to obtain a fiber material in which the polymer fiber and the polymer nanofiber are fused, and the adjacent polymer nanofiber-covered polymer fiber is fused. It is done.

  The thickness of the polymer fiber in the fiber material thus obtained has an average diameter of 35 μm, and the thickness of the polymer nanofiber has an average diameter of 700 nm. In FIG. 3, the optical microscope photograph of the fiber material of Example 5 of this invention is shown. The length between two points indicated by “1” in FIG. 3 is 33 μm.

<Comparative Example 1>
This comparative example is a modification of Example 1, and a fiber material was produced in the same manner as in Example 1 except that it was produced without performing the fusing process in Example 1.

  The thickness of the polymer fiber in the fiber material thus obtained has an average diameter of 9 μm, and the thickness of the polymer nanofiber has an average diameter of 500 nm.

  Table 1 below shows melting points (Tm) and glass transition points (Tg) of polymer materials used in Examples and Comparative Examples.

(Fiber material performance evaluation)
The fiber materials in Examples 1 to 5 have a structure in which polymer fibers and polymer nanofibers covering the polymer fibers are fused, and a plurality of polymer fibers forming the fiber material are fused to each other. It was observed by SEM.

  The peel resistance between the nanofiber and the core fiber was examined by “evaluation of the degree of fusion between the polymer fiber and the polymer nanofiber covering the polymer fiber” by the tape peel test described above.

  The mechanical strength of the fiber material was examined by “evaluation of the degree of fusion between polymer nanofiber-coated polymer fibers” by a tensile strength test.

  In addition, a fiber material with a large specific surface area can be obtained by coating polymer nanofibers, but the coated polymer nanofibers are maintained before and after fusion (maintenance of irregularities of nanofiber-coated polymer fibers). Were examined by the above-mentioned "Evaluation of shape change of polymer nanofiber before and after the fusion process".

  Table 2 below shows the results of the materials used, the peel test results, the strength increase rate, and the degree of change in the shape of the polymer nanofibers before and after the fusion process in Examples and Comparative Examples.

[Evaluation of degree of fusion between polymer fiber and polymer nanofiber covering the polymer fiber]
From the results of Examples 1 to 5 and Comparative Example 1, in Examples 1 to 5, the polymer fibers and the polymer nanofibers covering the polymer fibers were fused, and in the tape peeling test, (A ) Or very little (B), the polymer nanofibers are peeled off, and a remarkable performance improvement in the peel resistance between the nanofibers and the core fibers can be confirmed.

  In particular, from Example 1 and Comparative Example 1, even in the same polymer fiber / polymer nanofiber material system, the polymer fiber and the polymer nanofiber covering the polymer fiber are fused, so that the tape peeling test is performed. It can be confirmed that a significant performance improvement can be achieved (C → B).

  In addition, from Example 2 and Example 3, if the same polymer material (same structure constituting the polymer material) is contained in the polymer fiber material and the polymer nanofiber material, the polymer fiber and the polymer fiber By fusing polymer nanofibers coated with polymer, it was confirmed that in the tape peeling test, the polymer nanofibers were not peeled off at all (A), and the performance of peeling resistance between the polymer nanofibers and the core fibers could be significantly improved. I can do it.

  Therefore, it turns out that the fiber material in this invention has high peeling tolerance between a polymer nanofiber and a core fiber. In other words, the polymer nanofiber is not easily peeled off or dropped off due to external factors such as rubbing, and the specific surface area of the fiber material does not decrease.

[Evaluation of degree of fusion between polymer fibers]
The plurality of polymer fibers forming the fiber material of Examples 1 to 5 have a structure in which the fiber materials are fused to each other, so that the tensile strength is improved several times before and after the fusion, and the mechanical strength of the fiber material Can be confirmed to be significantly higher.

Incidentally, the inorganic filler (MN, SiO ₂₎ and engineering plastics (PBI, PAI) in case where the fiber material by using a material was also confirmed tend to exhibit improved high mechanical strength before and after fusion process ( Examples 3 to 5).

  Therefore, it turns out that the mechanical strength of the fiber material in this invention is high. That is, the core fibers are not easily frayed, which is advantageous for long-term use.

[Evaluation of shape change of polymer nanofiber before and after fusion process]
From the results of Examples 1 to 3, the melting point (Tm ₁ ) of the polymer material forming the polymer fiber is lower than the melting point (Tm ₂ ) of the polymer material forming the polymer nanofiber, and the temperature difference (Tm ₂ −Tm). ₁ ) is 5 ° C. or higher (Example 1: PCL (Tm ₁ : 60 ° C.), PEO (Tm ₂ : 65 ° C.)), and the shape of the polymer nanofiber is maintained well before and after the fusion process (II) You can see that

Further, from the results of Examples 2 and 3, the temperature difference _(Tm 2 -Tm ₁₎ is 30 ° C. or higher (Example _{2: PS (Tm 1: 230} ℃), PET (Tm 2: 260 ℃) In Example 3, PVDF-HFP (Tm ₁ : 130 ° C.) and PVDF (Tm ₂ : 160 ° C.)), it can also be confirmed that the change rate is as low as less than 10%.

Further, from the results of Example 4 and Example 5, when Tm ₁ of the polymer material forming the polymer fiber is equal to or lower than the glass transition point (Tg) of the polymer material forming the polymer nanofiber (Example 4: PES) (Tm ₁ : 130 ° C.), PBI (Tg: 473 ° C.), Example 5: PES (Tm ₁ : 130 ° C.), PAI (Tg: 290 ° C.) has a shape of the polymer nanofiber during the fusing process. It can be confirmed that it can be maintained.

When the melting temperature (melting point: Tm ₁ ) of the polymer material forming the polymer fiber is lower than the Tm _{2 of} the polymer material forming the polymer nanofiber and the difference is large, the polymer fiber and It becomes possible to fuse the polymer nanofiber to be coated by fusing the polymer fiber side preferentially.

  Therefore, according to the present invention, it is possible to manufacture a fiber material in which a polymer fiber and a polymer nanofiber covering the polymer fiber are fused while maintaining the shape (unevenness) of the polymer nanofiber. It is easy to exhibit the effect of increasing the specific surface area based on the coating.

  As shown in each of the above examples, according to the configuration of the present invention, the nanofiber having a high specific surface area and high peel strength between the polymer nanofiber and the core fiber and the mechanical strength of the fiber material are coated. A fiber material can be provided.

  The fiber material coated with the nanofiber of the present invention can be a fiber material having a high specific surface area that can be used for a long time even if external factors such as rubbing are applied. It can be used as a friction charging material.

DESCRIPTION OF SYMBOLS 1 Nanofiber coating polymer fiber 2 Polymer fiber 3 Polymer nanofiber 4 Fiber material

Claims (5)

A fiber membrane composed of a plurality of nanofiber-covered polymer fibers formed by coating polymer fibers as core fibers with polymer nanofibers,
The nanofiber-coated polymer fiber is obtained by spinning the polymer fiber and the polymer nanofiber by an electrospinning method ,
The polymer fibers and the polymer nanofibers covering the polymer fibers are fused, and the plurality of polymer fibers constituting the fiber film have a structure in which the polymer films are fused at least partially to each other. Have
An average diameter of the polymer fibers is 10 μm or more and 50 μm or less, and an average diameter of the polymer nanofibers is 1 nm or more and less than 1 μm.   The fiber membrane according to claim 1, wherein the polymer nanofiber covering the polymer fiber contains at least a polymer material constituting the polymer fiber.   The fiber membrane according to claim 1 or 2, wherein a melting point of the polymer material forming the polymer fiber is below a glass transition point of the polymer material forming the polymer nanofiber. A spinning step of coating a polymer fiber, which is a core fiber made of a polymer material, with a polymer nanofiber made of a polymer material to obtain a nanofiber-coated polymer fiber;
A fusion step of fusing the polymer fiber and the polymer nanofiber covering the polymer fiber, and fusing the plurality of polymer fibers forming the fiber material to each other at least partially; And
The spinning step may include Ri紡 yarn by the said polymer fibers and the polymer nanofibers electrospinning method,
The average diameter of the polymer fibers is 10 μm or more and 50 μm or less, and the average diameter of the polymer nanofibers is 1 nm or more and less than 1 μm.   5. The method for producing a fiber membrane according to claim 4, wherein the fusing step is performed by fusing by heat fusing, ultrasonic fusing, friction fusing, or thermocompression bonding.