JP2012025104A - Fiber bundle and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fiber bundle that eliminates the need for use of resin film and low-melting-point fiber and the use of heat-curable resin solution, moreover, has an excellent function as a fiber bundle, is efficiently manufactured at a low cost, and is suitable for a writing instrument and an applicator for make-up implement or the like for applying cosmetics, and to provide a method for manufacturing the same.SOLUTION: The fiber bundle is made of thermoplastic resin fibers 11 and allows impregnation with an ink composition. The thermoplastic resin fibers 11 are neatly aligned to one another, solidified, and bound together, thereby forming a fiber bundle. The entire circumferential surface of the fiber bundle is provided with a fiber fusion layer formed from a molten body of the thermoplastic resin.

Description

  The present invention relates to a fiber bundle that can be suitably used as a relay core or batting (occlusion body) of an applicator such as a writing instrument such as a water-based ballpoint pen, a marking pen, or a sign pen, or a cosmetic that applies cosmetics, and a method for producing the same. About.

Conventionally, a wide variety of applicators such as writing tools and cosmetic tools to which a fiber bundle made of fiber bundles such as synthetic resin fibers and natural fibers is attached are known.
The fiber bundles used in these writing instruments and cosmetics are used as batting, pen cores, and relay cores. For example, a resin film is wound around the outer periphery of a fiber bundle made of thermoplastic fibers and attached to the fiber bundle. However, there have been problems in terms of production efficiency, cost, efficient penetrability of the ink composition and coating liquid, and the like.

  On the other hand, as a technique for manufacturing a fiber bundle without winding with a resin film, for example, 1) The outer wall of a thermoplastic synthetic fiber is heat-processed to form a film-like wall on the outer periphery, and the inside is a flexible fiber The tip of the synthetic fiber is constructed so that the fiber part is infiltrated with liquid and written (for example, refer to Patent Document 1). 2) One kind or two or more kinds of synthetic fibers that are weak against heat (low melting point) are mixed. A cylindrical rod-like fibrous body having an arbitrary diameter is formed using a mixture of the above-mentioned fibers and other various fibers, and the fibrous body is heated to dissolve the peripheral fiber layer, and the dissolved portion is solidified. Forming a film on the peripheral surface of the cylindrical rod-shaped fiber body, and cutting the continuous rod-shaped fiber body covered with the film into a desired length to provide a core material for a magic pen. Manufacturing method of core material for magic pen 3) A bundling body made of thermoplastic fibers is integrated with a thermosetting resin to form a rod-shaped pen core, and the thermoplastic fibers are formed on the entire outer periphery of the pen core. There is known a nib material (for example, see Patent Document 3) characterized by uniformly forming an ink-impermeable thermoplastic resin layer by melting.

  However, the techniques described in Patent Documents 1 and 2 described above are to manufacture a coated pen core or the like by heating a thermoplastic resin fiber with a processing tube having a trumpet-shaped entrance and melting the surface. However, it is unclear if there is no particular description as to whether or not the bundle of coated inner fibers is aligned and uniform. In addition, when trying to manufacture an extremely fine fiber bundle, it can be easily inferred that all the inner fiber bundles have melted, and the function as a fiber bundle cannot be exhibited. If the bundle is not sufficiently heated and pressurized, the fibers inside may not be uniformly aligned. In the techniques described in Patent Documents 1 and 2, it is possible to produce a layer in which inner fibers are arranged at an appropriate density, are evenly aligned in the cross-sectional direction and the longitudinal direction, and a molten layer is provided on the surface. It can be said that it is difficult.

  The nib material of Patent Document 3 described above is a method of applying a solution of a thermosetting resin monomer to a thermoplastic fiber bundle, evaporating and curing a solvent portion by heating, and further heating, this time a fiber thermoplastic resin. It becomes a pen tip material that becomes a coated pen core that completely covers the entire outer periphery with a thermoplastic resin, and a thermosetting resin is added separately from the thermoplastic resin fibers that make up the fiber bundle. Further, since a solvent for dissolving the monomer of the thermosetting resin is also added, the number of manufacturing steps is increased, the cost is increased, and the structural characteristics are also different from those of the present invention.

Japanese Patent Publication No. 36-18027 (Claims, Examples, etc.) JP 51-46226 (Claims, Examples, etc.) JP-A-2004-243561 (Claims, Examples, etc.)

  The present invention has been made in view of the above-mentioned problems of the prior art, and is intended to solve this problem. It has an excellent function as a fiber bundle without causing ink adhering to the fiber bundle to ooze out to the surface, and a resin. Relay cores and batting (occlusion) for applicators such as writing instruments and cosmetics that can be manufactured easily and efficiently at low cost without the use of films, low-melting fibers, or the use of thermosetting resin solutions. It is an object of the present invention to provide a fiber bundle suitable for the above and a manufacturing method thereof.

  In view of the above-described conventional problems and the like, the present inventors intend to solve this problem, and are a fiber bundle made of a thermoplastic resin fiber and infiltrated with an ink composition, the thermoplastic resin fiber. The above-mentioned target fiber bundle and its manufacturing method can be obtained by forming a fiber bundle having a specific structure and forming a fiber fusion layer having specific physical properties on the entire outer peripheral portion of the fiber bundle. The headline and the present invention have been completed.

That is, the present invention resides in the following (1) to (6).
(1) A fiber bundle made of a thermoplastic resin fiber, infiltrated with an ink composition, which forms a fiber bundle in which the thermoplastic resin fibers are aligned and solidified and bound together, and the fiber bundle A fiber bundle, wherein a fiber fusion layer made of a melt of the thermoplastic resin is formed on the entire outer surface.
(2) The fiber bundle according to claim 1, wherein the resin composing the fiber fusion layer of the fiber bundle is the same type of resin as the thermoplastic resin composing the fiber.
(3) The molecular weight and molecular weight distribution of the thermoplastic resin composing the fiber fusion layer of the fiber bundle and the molecular weight and molecular weight distribution of the thermoplastic resin composing the fiber are substantially equal. The fiber bundle according to 1 or 2.
(4) The thermoplastic resin fibers constituting the fiber bundle are made of a single type of fiber, and the inside of the fiber fusion layer is a fiber bundle having a substantially uniform density. The fiber bundle body as described in any one of 1-3.
(5) The fiber bundle according to any one of claims 1 to 4, wherein the diameter is 10 mm or less.
(6) Fibers made of thermoplastic resin are aligned and bundled, the fiber bundle is heated to form a fiber bundle in which the fibers are solidified and bundled, and the entire outer periphery of the fiber bundle is heated to produce a fiber. A method for producing a fiber bundle, wherein a fiber fusion layer is formed on the entire outer periphery of the fiber bundle by melting of the fiber bundle.

  In addition, “molecular weight is substantially equal” defined in the present invention means that the result of measuring the weight molecular weight of the resin is about ± 10%. “Molecular weight distribution is substantially equal” means that the numerical value of number average molecular weight / weight average molecular weight is about ± 10%. Further, “a fiber bundle having a substantially uniform density” means that the flow path resistance value measured by measuring the pressure loss of the capillary tube of the pen core is substantially equal in the longitudinal direction.

  According to the present invention, the ink adhering to the fiber bundle does not ooze out on the surface, and has an excellent function as a fiber bundle, using a resin film, using a low-melting fiber together, or a thermosetting resin solution A fiber bundle suitable for a relay core or batting (occlusion body) of an applicator such as a writing instrument or a cosmetic that can be easily and efficiently manufactured at low cost without using a metal, and a method for manufacturing the same. In particular, by constituting with a single resin type, it can be manufactured at low cost with ease and efficiency.

(A) is the schematic which shows an example of embodiment of the manufacturing process for manufacturing the fiber bundle of this invention in a cross-sectional aspect. It is an electron micrograph which shows an example of the fiber bundle obtained by this invention method. (A) Schematic which shows the fiber used by the fiber bundle of the comparative example 1 in a cross-sectional aspect, (b) is an electron micrograph of the fiber bundle obtained in the comparative example 1. (A) Schematic which shows the fiber used by the fiber bundle of the comparative example 2 in a cross-sectional aspect, (b) is an electron micrograph of the fiber bundle obtained in the comparative example 2.

Hereinafter, embodiments of the present invention will be described in detail.
The fiber bundle of the present invention is a fiber bundle made of thermoplastic resin fibers and infiltrated with the ink composition, and the fibers of the thermoplastic resin are aligned to form a solidified and bundled fiber bundle. At the same time, a fiber fusion layer made of a melt of the thermoplastic resin is formed on the entire outer periphery of the fiber bundle.
Further, the method for producing a fiber bundle according to the present invention includes arranging and bundling fibers made of thermoplastic resin, heating the bundle of fibers to form a fiber bundle in which the fibers are solidified and bundled, The entire outer periphery of the fiber bundle is heated, and the fiber fusion layer is formed on the entire outer periphery of the fiber bundle by melting the fiber.
Hereinafter, the “present invention” includes both the fiber bundle and the method for producing the same.

The fiber used in the present invention is at least one kind of thermoplastic resin fiber, preferably at least 150 ° C. or higher, more preferably at least one thermoplastic resin fiber having a melting point of 150 ° C. or higher and 300 ° C. or lower. And polyester synthetic resins (polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.), polyamide synthetic resins (6,6-nylon, 6-nylon, 6,10-nylon, 6,12-nylon, etc.) ), Polyolefin-based synthetic resins [polyethylene (PE), polypropylene (PP), etc.], polyurethane-based synthetic resins, polyacrylonitrile-based synthetic resins (polyacrylonitrile, acrylonitrile-styrene copolymers, acrylonitrile-butadiene-styrene copolymers, etc.) , Polymethacrylic resin (polymethacrylate) Methyl Resin: PMMA), can be selected from such a polyacetal resin (POM).
Among these, a polyester synthetic resin having a melting point of 150 ° C. or higher is preferable. In addition, the thermoplastic resin fibers are composed of a single type from the standpoints of flexibility, melting point or glass transition point, and management advantages in the manufacturing process, and further performance as a fiber bundle. Is desirable.

The thermoplastic resin fibers used in the present invention include filaments (monofilaments, multifilaments) and slivers. Monofilaments or multifilaments are preferred to obtain a fiber bundle having a uniform density in the longitudinal direction. Furthermore, a multifilament is preferable in terms of ease of handling when individual yarns are combined, drawn, and bundled. And, taking advantage of the property of having heat shrinkability in the longitudinal direction and expanding the diameter by heat, it can be molded into a uniform cylindrical shape in the first thermoforming machine. It is preferable to use crimped fibers made of at least one of plastic resin fibers. Note that crimped fibers are those that are bulky by imparting two-dimensional or three-dimensional crimps and strains to the fibers, fixing the strains in an appropriate manner, and disturbing the parallelism between the fibers. A fiber that has been given elasticity.
The fineness of these fibers is 20 denier or less, preferably 2 to 5 denier.
In addition, it is difficult to obtain the target fiber bundle efficiently by using side-by-side type, core-sheath type, or a fiber in which low-melting fiber and high-melting fiber are mixed. Use of the above fibers is not preferable because it is difficult to mix them.

  The fiber bundle of the present invention is a bundle of at least one fiber made of a thermoplastic resin having the above-mentioned characteristics, preferably at least one fiber of a thermoplastic resin having a melting point of 150 ° C. or higher, and bundles the fibers. Heating (first thermoforming) is performed to form a fiber bundle in which the fibers are solidified by heating and pressurizing without using a binder resin or solvent, that is, a fiber bundle in which the fibers are solidified and bound. For example, as shown in FIG. 1, the first thermoforming machine 10 has a fiber 11 made of a thermoplastic resin having the above-mentioned characteristics and the like aligned while being pulled by a pulling roller 12 arranged in the front direction. Placed, bundled and heated and pressed to solidify the fibers without using a binder resin or solvent, the roundness of the cross section is high, the fibers are solidified and bound, and the outer periphery is melted A fiber bundle in which a film is not yet formed is formed. In this case, it is important that the heating method is within a range in which the fibers do not fuse with each other, and the heating temperature and time are the purpose of the first thermoforming to solidify and bind the fibers by heat and pressure. If it is a range that can form a fiber bundle having a binding force superior to the die pulling resistance and varies depending on the fiber type and the size of the fiber bundle to be manufactured, if the fiber to be used is composed of a single type, By heating at a temperature equal to or higher than the heat shrinking completion temperature from the melting point of the crimped fiber to be used, a fiber bundle is formed by solidifying and binding the fibers together by heat. For example, if a fiber made of thermoplastic resin is PET-based fiber and the heat shrinkage completion temperature is 200 ° C., the fibers are solidified and bound by heating at 200 ° C. or higher and below the melting point. Can do.

Next, a fiber fusion layer is formed on the entire outer periphery of the fiber bundle in which the fibers are solidified and bundled by heat. The resin constituting the fiber fusion layer formed on the entire outer periphery of the fiber bundle is the same type of resin as the thermoplastic resin constituting the fiber used, preferably the fiber fusion layer of the fiber bundle. It is desirable to use those in which the molecular weight and molecular weight distribution of the thermoplastic resin to be composed, and the molecular weight and molecular weight distribution of the thermoplastic resin that composes the fiber are substantially equal.
In this case, the fiber fusion layer is formed by preparing in advance a resin of the same type as the thermoplastic resin composing the fiber to be used on the entire outer periphery of the fiber bundle in which the fibers are solidified and bound by heat. It can be carried out by melting and uniformly applying to the entire outer periphery of the fiber bundle using a discharge nozzle.

More preferably, from the standpoint of production efficiency and obtaining a fiber bundle having the same physical properties, the entire outer periphery of the fiber bundle obtained by solidifying and binding the above fibers with heat is heated to a temperature equal to or higher than the melting point of the resin constituting the fiber. It is desirable to form the fiber fusion layer on the entire outer periphery of the fiber bundle by melting the entire outer periphery of the fiber bundle and then cooling it. For example, as shown in FIG. 1, the first thermoforming machine 10 continuously pulls the solidified and bundled fiber bundles from the first thermoforming machine 13 with a pulling roller 12 arranged on the front side. However, by heating the entire outer periphery of the fiber bundle with a high-temperature die 14 to a temperature equal to or higher than the melting point of the resin constituting the fiber, drawing the diameter down and melting only the outside without destroying the structure inside the fiber bundle. An ink impermeable layer is formed.
The heating method in this case is not particularly limited, and the heating temperature and time may be within the range in which the purpose of this thermoforming is to form a uniform fiber fusion layer on the entire outer periphery of the fiber bundle, and the fiber type and production Depending on the size of the fiber bundle, if the fiber used is composed of a single type, after heating at a high temperature (melting temperature) that is equal to or higher than the melting point of the fiber used, leave it at room temperature. A fiber fusion layer is formed.

The thickness of the fiber fusion layer obtained by each of the above methods can be set to an arbitrary thickness according to the use of the fiber bundle, for example, the use of a batting, a pen core, a relay core, or the like.
The fiber bundle in which the fiber fusion layer is formed by each of the above methods is cut into an arbitrary length according to the use of the fiber bundle, for example, a pen core, a relay core, etc. The target fiber bundle can be obtained by processing to a desired value.

In the obtained fiber bundle, it is preferable that a fiber bundle having a substantially uniform density is formed inside the fiber fusion layer. In order to obtain a fiber bundle having a substantially uniform density, a fiber bundle having a yarn density of 1000 to 7000 d / mm ² at the time of the first forming can be formed.
Further, in such a production method, a fiber bundle having a fiber fusion layer having a diameter of 1 mm or more and a fiber density of 1,000 d / mm ² or more can be produced satisfactorily. When the finish is less than 1 mm in diameter and the fiber density is less than 1,000 d / mm ^2, when the outer shell is melted in the second thermoforming machine, the melt adhesion generated between the inner wall of the die causes the first molding. There is a possibility that the bundles of the homogenized fibers are broken and the shape is broken. It is desirable in the present invention that the finished dimensions are 1 mm or more and the fiber density is 1,000 d / mm ² or more.

  In the fiber bundle according to the present invention configured as described above, the minimum strength required at the time of writing instrument production is maintained, and has an excellent function as a fiber bundle, the use of a resin film or a combination of low-melting fibers, Alternatively, a fiber bundle suitable for an applicator such as a writing instrument and a cosmetic tool that can be easily and efficiently manufactured at low cost without using a thermosetting resin solution, and a method for manufacturing the same are provided. In particular, by constituting with a single resin species, the fiber fusion layer is further formed by heating and melting the entire outer periphery of the fiber bundle fused by heat between fibers. If it is formed on the entire outer surface of the bundle, it can be manufactured easily and efficiently at a lower cost. Moreover, since the binder resin such as a thermosetting resin solution is not used in the method of the present invention, there is a merit that the problem of air pollution due to the atmospheric release of VOC (volatile organic compound) gas or the like can be overcome during the production. .

  EXAMPLES Next, although an Example and a comparative example demonstrate this invention further in full detail, this invention is not limited by the following Example etc.

Example 1
Using a fiber made of the following thermoplastic resin, a fiber bundle was obtained by the method shown below.
(Physical properties of fibers made of thermoplastic resin)
Polyethylene terephthalate (PET) fiber (multifilament, thickness 5 denier, melting point 260 ° C., crimp heat shrink completion temperature 220 ° C.) is used.

(Manufacturing method of fiber bundle)
As shown to Fig.1 (a), with the 1st thermoforming machine 10, the fibers were aligned in the longitudinal direction, and the fiber bundle which solidified and bound the fibers of the thermoplastic resin was formed. At this time, the temperature for solidification and binding is 240 ° C., and the time for passing the die is 25 seconds. Further, the obtained fiber bundle was a fiber bundle having a yarn density of 4200 d / mm ² .
Next, using a second thermoforming machine, the fiber bundle obtained by fusing the obtained fibers together is heated with a high-temperature die and drawn while reducing the diameter. By melting only the outer skin portion without breaking the structure, a fiber bundle having a fiber fusion layer thickness of 30 μm and a diameter of 1.75 mm and a fiber density of 4200 d / mm ² was obtained.
When this fiber bundle was confirmed by an electron microscope (SEM), the inside of the fiber fusion layer was a fiber bundle having a substantially uniform density, and as shown in FIG. It was confirmed that a fiber fusion layer was formed.

  When this fiber bundle was cut to a length of 100 mm and manufactured as a relay core for a water-based ballpoint pen “UB-200” (ink type: black ink) manufactured by Mitsubishi Pencil Co., Ltd., a normal binder resin was blended. Compared to the case where a relay core is used, since there is no winding process for a film or the like, it can be manufactured inexpensively and easily. Even when the ballpoint pen was manufactured, since the relay core itself had a fiber fusion layer, its strength was sufficient, and there was no accident such as bending or bending, and it could be manufactured without problems. Further, the manufactured ballpoint pen itself also improved the ink pick-up property. As a result, the ink arrival time to the tip of the ball was shortened, and writing was possible immediately after assembly.

(Example 2)
Using the same fibers as in Example 1, an ink occlusion body (filling) was obtained by the method shown below.
(Manufacturing method of batting)
Although it is the same as that of the manufacturing method of the relay core in the said Example 1, with the 1st thermoforming machine 10 which made the diameter of die | dye 6 mm, fibers were aligned in the longitudinal direction and the fibers of thermoplastic resin were solidified. A bound fiber bundle was formed. At this time, the temperature for solidification and binding is 240 ° C., and the time for passing the die is 25 seconds. Further, the obtained fiber bundle was a fiber bundle having a yarn density of 1600 d / mm ² .
Next, using a second thermoforming machine with a die diameter of 5.5 mm, the fiber bundle obtained by fusing the obtained fibers together is heated with a high-temperature die. The diameter of the fiber fusion layer is 30 μm and the fiber density is 5.5 mm and the fiber density is 1600 d / mm ² by pulling out the diameter and melting only the outer skin without breaking the structure inside the fiber bundle. A fiber bundle was obtained.
When this batting was confirmed by an electron microscope (SEM), the inside of the fiber fusion layer was a fiber bundle having a substantially uniform density, and was uniform on the outer peripheral front surface of the fiber bundle as in the above-described example of the relay core. It was confirmed that a fiber fusion layer having a thickness was formed.

  When this batting was cut into a length of 79.5 mm and manufactured as a batting of an oil-based dye marker “PA-152TR (trade name: piece)” (ink type: black ink) manufactured by Mitsubishi Pencil Co., Ltd. Compared to using batting with a binder resin, there is no film wrapping process, so it is inexpensive and has sufficient strength to withstand handling by an automatic machine, and can be easily manufactured and assembled. did it. Further, the manufactured marker itself was able to write a sufficient writing distance as a result of improving the ink sucking property of the batting.

(Comparative Example 1)
Using a fiber made of the following thermoplastic resin, a relay core was obtained in the same manner as in Example 1 above.
As shown in FIG. 3A, “low melting point (100 to 140 ° C.) amorphous copolymer nylon fiber, multifilament, 5 denier thickness” and polyester fiber (thickness of 240 ° C.) melting point 5 denier), an example in which binderless production is attempted by thermoforming using a mixture of multifilaments.

When the obtained fiber bundle was confirmed with an electron microscope (SEM), as shown in FIG. 3B, the combined state of “multifilaments” (aggregates of plural single yarns) was uneven in the fused portion. It was found that the ink impermeable layer could not be formed and the fiber bundle was not formed.
When this fiber bundle was used in the same manner as in Example 1, the outflow of ink was not constant, and mottling was observed in normal use, and blurring was frequently observed.

(Comparative Example 2)
Using a fiber made of the following thermoplastic resin, a relay core was obtained in the same manner as in Example 1 above.
As shown in FIG. 4A, a core-sheath type composite fiber and a side-by-side type low melting point composite fiber were used.
Core-sheath type composite fiber: Composite fiber (thickness) in which the sheath part is a polyetherester block copolymer (melting point: 150 ° C.) and the core part is polybutylene terephthalate (melting point: 255 ° C.). 5 denier).
Side-by-side type composite fiber: One side is a polyether ester block copolymer (melting point: 150 ° C.), and the other side is a polybutylene terephthalate (melting point: 255 ° C.) weight ratio of 1: 1 to a composite fiber (thickness 5 denier) ).
In the batting using the core-sheath type fiber, a relay core having a diameter of 2 mm with a fiber fusion layer thickness of about 100 μm was obtained.
In addition, a relay core having a diameter of 2 mm with a fiber fusion layer thickness of about 100 μm was obtained even with a side-by-side fiber bundle.
When the relay core using the obtained core-sheath fiber was confirmed by an electron microscope (SEM), as shown in FIG. 4B, the ink impermeable layer was a relatively thick layer in which the fibers were folded tightly. Thus, it was found that the ink flow path was relatively narrow. In this case, the biggest problem in the case of a fiber bundle having a substantially uniform density using low melting point fibers is the fusion of pores due to "generation of grinding heat during grinding". It has been found that it becomes impossible to serve as a writing instrument part as a fiber bundle such as a core.
Further, it was found that a side-by-side type relay core has the same result as the core-sheath fiber.

(Comparative Example 3)
In Example 1 above, fibers made of the same thermoplastic resin as in Example 1 were used, the fibers were aligned in the longitudinal direction, and the first thermoforming machine 10 was not used (the fibers of the thermoplastic resin were fused together) However, when the second thermoforming machine 12 was used and heat treatment was performed in the same manner as in Example 1 to try to form a fiber fusion layer, a part of the fiber fusion layer was torn and It was found that a uniform fiber fusion layer with high circularity cannot be obtained. It was also found that the “crimping effect” (improving the bulkiness) by heating the crimped fiber cannot maintain uniformity.
The above cause is due to the fact that the first molding machine is not used, so that the fibers cannot be fused together.

(Comparative Example 4)
Filling (fiber: polyester (thickness: 3 denier), outer peripheral film: polypropylene, conventionally used for oil-based dye marker “PA-152TR (trade name: piece)” (ink type: black ink) manufactured by Mitsubishi Pencil Co., Ltd. When the performance was compared with the batting of Example 2 using a length of 79.5 mm, a diameter of 13.0 mm, and an ink-impermeable layer thickness (outer skin thickness) of 200 μm), the difference as described above was observed. .
When this batting was confirmed by an electron microscope (SEM), the inside of the ink impermeable layer was a fiber bundle having a substantially uniform density, and the film on the entire outer periphery of the fiber bundle was uniform as in Example 2 above. The thickness was confirmed.

  As is clear from the results of Examples 1 and 2 and Comparative Examples 1 to 4 above, the relay core and the batting according to the present invention have the ink passing through the relay core or the ink occluded in the batting on the surface. It has been found that it has an excellent function of maintaining a constant ink flow rate as a relay core and having a high occlusion amount as a batting without bleeding, and in any case, it can be manufactured easily and efficiently at low cost.

  A relay core or batting suitable for an applicator such as a writing instrument or a cosmetic applicator is obtained.

DESCRIPTION OF SYMBOLS 10 1st thermoforming machine 11 Fiber of thermoplastic resin 13 2nd thermoforming machine

Claims (6)

  A fiber bundle made of thermoplastic resin fibers and infiltrated with the ink composition, forming a fiber bundle in which the thermoplastic resin fibers are aligned and solidified and bound together, and the entire outer peripheral portion of the fiber bundle Further, a fiber bundle comprising a fiber fusion layer made of a melt of the thermoplastic resin.   2. The fiber bundle according to claim 1, wherein the resin composing the fiber fusion layer of the fiber bundle is the same type of resin as the thermoplastic resin composing the fiber.   3. The molecular weight and molecular weight distribution of a thermoplastic resin composing the fiber fusion layer of the fiber bundle and the molecular weight and molecular weight distribution of the thermoplastic resin composing the fiber are substantially equal. The fiber bundle as described in 2.   The thermoplastic resin fibers constituting the fiber bundle are made of a single type of fiber, and the inside of the fiber fusion layer is a fiber bundle having a substantially uniform density. A fiber bundle according to any one of the above.   The fiber bundle according to any one of claims 1 to 4, wherein a diameter is 10 mm or less.   Fibers made of thermoplastic resin are aligned and bundled, this fiber bundle is heated to form a fiber bundle in which the fibers are solidified and bundled, and the entire outer periphery of this fiber bundle is heated to melt the fiber. A method for producing a fiber bundle, wherein a fiber fusion layer is formed on the entire outer periphery of a fiber bundle.