Method for producing particle-containing fiber bundles and particle-containing fiber bundles

Abstract

Provided are: a particle-containing fiber bundle that is highly uniform and has further improved feeding efficiency; and a production method for the same. A particle-containing fiber bundle production method according to the present invention is for producing a particle-containing fiber bundle having a prolate spheroidal shape or a strand shape, the method comprising a step for mixing a plurality of shortened fibers, particles having a median diameter of at most 100 μm, an organic binder, and a liquid. Carbon fibers are included as the fibers, and at least 10 parts by mass of the particles are used with respect to 100 parts by mass of the fibers.

Description

[Technical Field]

[0001] This invention relates to a method for producing particle-containing fiber bundles and to particle-containing fiber bundles. This application claims priority based on Japanese Patent Application No. 2022-200735 and Japanese Patent Application No. 2022-201050, both filed in Japan on December 16, 2022, and the contents thereof are incorporated herein by reference. [Background technology]

[0002] Carbon fibers have been used in a variety of applications as an industrially important material, mixed and dispersed in matrices such as resins to improve mechanical and electrical properties such as high strength, high rigidity, low specific gravity, high electrical conductivity, and high wear resistance.

[0003] Generally, when obtaining fiber-reinforced resin compositions by mixing and dispersing short carbon fibers in various resins, carbon fiber forms are used that facilitate handling and improve the efficiency of the mixing and dispersion processes. In particular, it is required that the carbon fibers be fed into kneaders and molds stably and smoothly. Methods for achieving this include cutting continuous carbon fiber bundles obtained by treating them with sizing agents to produce so-called chopped carbon fibers, or granulating the cut carbon fibers to form carbon fiber bundles.

[0004] Carbon fiber reinforced thermoplastics can be manufactured by adding carbon fiber pellets to a thermoplastic resin. One method for manufacturing carbon fiber pellets is disclosed (Patent Document 1), which involves mixing short carbon fibers with a sizing agent solution or suspension to form carbon fiber aggregates, then pelletizing these aggregates in a disc pelletizer and drying them. This yields carbon fiber pellets with high density and a streamlined shape, enabling stable and smooth feeding of carbon fibers.

[0005] A method for obtaining carbon fiber pellets using recycled fibers is disclosed, which includes cutting and / or crushing the carbon fibers to a predetermined average length, mixing the carbon fibers with a solution or suspension in a mixer to form aggregates, concentrating the aggregates by bringing them into contact with an inclined rotating surface, and further drying the aggregates to obtain carbon fiber pellets, wherein the carbon fibers are thermally decomposed before cutting or crushing (Patent Document 2). Furthermore, as a method to improve the feed efficiency of carbon fiber pellets using recycled fibers, a method for producing carbon fiber pellets by rolling a mixture consisting of carbon fibers and a binder-containing liquid in a container is disclosed, in which the mixture further includes thermoplastic resin fibers (Patent Document 3). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japan Special Publication No. 10-503812 [Patent Document 2] European Patent Application Publication No. 2902433 [Patent Document 3] International Publication No. 2022 / 210591 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Our investigations have revealed that, in the method described in Patent Document 1, sufficient feed efficiency may not be obtained when recycled fibers are used as the raw material carbon fibers. One of the objectives of the present invention is to provide a particle-containing fiber bundle with high uniformity and further improved feed efficiency, and a method for producing the same. Another objective of the present invention is to provide a particle-containing fiber bundle with high uniformity and further improved feed efficiency, and a method for producing the same, even when recycled fibers are used as the raw material carbon fibers. [Means for solving the problem]

[0008] The present invention includes the following embodiments.

[0009] [1]: A method for producing a fiber bundle containing elongated spherical or strand-shaped particles, The process includes mixing multiple shortened fibers, particles with a median diameter of 100 μm or less, an organic binder, and a liquid. The aforementioned fiber includes carbon fiber, A method for producing a particle-containing fiber bundle, wherein the particles are used in an amount of 10 parts by mass or more per 100 parts by mass of the fibers. [2]: The method for producing a particle-containing fiber bundle according to [1], wherein the median diameter of the particles is 3 μm or more. [3]: A method for producing a particle-containing fiber bundle according to [1] or [2], wherein the solubility of the particles in the liquid is 0.01 g / 100 g or less. [4]: A method for producing a particle-containing fiber bundle according to any one of [1] to [3], wherein the solubility of the particles in water is 0.0001 g / 100 g or less. [5]: The method for producing a particle-containing fiber bundle according to [4], wherein the solubility of the organic binder in water is greater than 0.0001 g / 100 g. [6]: A method for producing a particle-containing fiber bundle according to any one of [1] to [5], comprising organic particles as the particles. [7]: A method for producing a particle-containing fiber bundle according to any one of [1] to [6], wherein the particles are used in an amount of 20 parts by mass or more and 80 parts by mass or less per 100 parts by mass of the fiber. [8]: A method for producing a particle-containing fiber bundle according to any one of [1] to [7], wherein the particles are used in an amount of 55 parts by mass or more and 75 parts by mass or less per 100 parts by mass of the fiber. [9]: A method for producing a particle-containing fiber bundle according to any one of [1] to [8], comprising at least one resin selected from the group consisting of polyamide resin, epoxy resin, unsaturated polyester resin, vinyl ester resin, and polyurethane resin as the organic binder.

[10] : A method for producing a particle-containing fiber bundle according to any one of [6] to [9], comprising thermoplastic resin particles as the organic particles.

[11] : A method for producing a particle-containing fiber bundle according to

[10] , wherein the thermoplastic resin particles include at least one selected from the group consisting of polyamide resin, polyolefin resin, polyester resin, polycarbonate resin, polyethersulfone resin, polyetheretherketone resin, polyetherimide resin, and polyphenylene sulfide resin.

[12] : A method for producing a particle-containing fiber bundle according to any one of [6] to

[11] , comprising thermosetting resin particles as the organic particles.

[13] : A method for producing a particle-containing fiber bundle according to

[12] , wherein the thermosetting resin particles include at least one selected from the group consisting of epoxy resin, vinyl ester resin, unsaturated polyester resin, cyanate ester resin, polyimide resin, maleimide resin, silicone resin, melamine resin, urea resin, alkyd resin, urethane resin, and phenolic resin.

[14] : A method for producing a particle-containing fiber bundle according to any one of [6] to

[13] , comprising curing agent particles as the organic particles.

[15] : A method for producing a particle-containing fiber bundle according to

[14] , comprising at least one selected from the group consisting of dicyandiamides, phenols, amines, carboxylic acid anhydrides, thiols, imidazoles, phosphines, peroxides, and organometallic salts as the curing agent particles.

[16] : A method for producing a particle-containing fiber bundle according to any one of [1] to

[15] , comprising inorganic particles as the aforementioned particles.

[17] : A method for producing a particle-containing fiber bundle according to

[16] , wherein the inorganic particles include at least one selected from the group consisting of metal particles, metal oxide particles, silica particles, silicate particles, carbonate particles, sulfate particles, hydroxide particles, glass particles, ceramic particles, graphite, and carbon black.

[18] : A method for producing a particle-containing fiber bundle according to any one of [1] to

[17] , wherein the particle size D90 at which the cumulative value in the volume-based particle size distribution of the particles becomes 90% is 250 μm or less.

[19] : A method for producing a particle-containing fiber bundle according to any one of [1] to

[18] , wherein the particle size D10 at which the cumulative value in the volume-based particle size distribution of the particles becomes 10% is 50 μm or less.

[20] : The production method of the particle-containing fiber bundle according to any one of [1] to

[19] , wherein the particle size D90 at which the integrated value in the volume-based particle size distribution of the particles is 90% is 0.5 μm or more.

[21] : The production method of the particle-containing fiber bundle according to any one of [1] to

[20] , wherein the particle size D10 at which the integrated value in the volume-based particle size distribution of the particles is 10% is 0.05 μm or more.

[22] : The production method of the particle-containing fiber bundle according to any one of [1] to

[21] , wherein the ratio (D75 / D25) of the particle size D75 at which the integrated value in the volume-based particle size distribution of the particles is 75% to the particle size D25 at which the integrated value is 25% is 1 to 15.

[23] : The production method of the particle-containing fiber bundle according to any one of [1] to

[22] , using a fiber batting containing the fibers.

[24] : The production method of the particle-containing fiber bundle according to any one of [1] to

[23] , using an agitation granulator.

[25] : The production method of the particle-containing fiber bundle according to

[24] , wherein the agitation granulator includes an agitation tank.

[26] : The production method of the particle-containing fiber bundle according to

[25] , wherein an agitation blade is provided inside the agitation tank.

[27] : The production method of the particle-containing fiber bundle according to

[25] or

[26] , wherein the agitation tank includes a scraper.

[28] : The production method of the particle-containing fiber bundle according to

[26] or

[27] , wherein the distance between the agitation blade and the wall surface of the agitation tank is 1 mm or less.

[29] : The production method of the particle-containing fiber bundle according to any one of

[26] to

[28] , wherein the distance between the agitation blade and the wall surface of the agitation tank is 10 mm or more.

[30] : The production method of the particle-containing fiber bundle according to any one of

[25] to

[29] , rotating the agitation tank.

[31] : The production method of the particle-containing fiber bundle according to any one of [1] to

[30] , wherein the average fiber length of the fibers is 12 to 50 mm.

[32] : The production method of the particle-containing fiber bundle according to any one of [1] to

[30] , wherein the average fiber length of the fibers is 2 to 12 mm.

[33] : The bulk density of the fibers is 0.01 to 0.1 g / cm 3The method for producing a particle-containing fiber bundle according to any one of [1] to

[32] .

[34] : The method for producing a particle-containing fiber bundle according to any one of [1] to

[33] , wherein the positions of the tips of the fibers constituting the particle-containing fiber bundle are uneven.

[35] : The method for producing a particle-containing fiber bundle according to any one of [1] to

[34] , wherein the length of the particle-containing fiber bundle is longer than the average fiber length of the fibers contained in the particle-containing fiber bundle.

[36] : The method for producing a particle-containing fiber bundle according to any one of [1] to

[35] , comprising mixing the particles, the organic binder, and the liquid to obtain a mixture 1, and mixing the mixture 1 and the fibers to obtain a mixture 2.

[37] : The method for producing a particle-containing fiber bundle according to any one of [1] to

[36] , comprising removing the liquid.

[38] : The method for producing a particle-containing fiber bundle according to any one of [1] to

[37] , wherein 60 to 200 parts by mass of the liquid is used per 100 parts by mass of the fibers.

[39] : The method for producing a particle-containing fiber bundle according to any one of [1] to

[38] , wherein 1 to 40 parts by mass of the organic binder is used per 100 parts by mass of the fibers.

[40] : The method for producing a particle-containing fiber bundle according to any one of [1] to

[39] , wherein the particles and the organic binder are used such that the mass ratio of the particles to the organic binder (mass of particles / mass of organic binder) is 2.5 to 100.

[0010]

[41] : A method for producing a particle-containing fiber bundle, comprising a plurality of shortened fibers, particles having a median diameter of 100 μm or less, and an organic binder, wherein the fibers are aligned and have an ellipsoidal shape or a strand shape.

[42] : The method for producing a particle-containing fiber bundle according to

[41] , wherein the fibers include carbon fibers.

[43] : The method for producing a particle-containing fiber bundle according to

[41] or

[42] , wherein the median diameter of the particles is 3 μm or more.

[44] : The method for producing a particle-containing fiber bundle according to any one of

[41] to

[43] , wherein the solubility of the particles in water is 0.0001 g / 100 g or less.

[45] : A method for producing a particle-containing fiber bundle according to

[44] , wherein the solubility of the organic binder in water is greater than 0.0001 g / 100 g.

[46] : A method for producing a particle-containing fiber bundle according to any one of

[41] to

[45] , wherein the average fiber length of the fiber is 12 to 50 mm.

[47] : A method for producing a particle-containing fiber bundle according to any one of

[41] to

[45] , wherein the average fiber length of the fiber is 2 to 12 mm.

[48] : A method for producing a particle-containing fiber bundle according to any one of

[41] to

[47] , wherein the positions of the tips of the fibers constituting the particle-containing fiber bundle are irregular.

[49] : A method for producing a particle-containing fiber bundle according to any one of

[41] to

[48] , wherein the length of the particle-containing fiber bundle is longer than the average fiber length of the fibers contained in the particle-containing fiber bundle.

[50] : A method for producing a particle-containing fiber bundle according to any one of

[41] to

[49] , wherein the ratio of the length of the particle-containing fiber bundle to the average fiber length of the fibers contained in the particle-containing fiber bundle (length of the particle-containing fiber bundle / average fiber length of the fibers contained in the particle-containing fiber bundle) is 1.1 to 2.5.

[51] : A method for producing a particle-containing fiber bundle according to any one of

[41] to

[50] , wherein the mass content of the particles in the particle-containing fiber bundle is 20 to 80% by mass.

[52] : A method for producing a particle-containing fiber bundle according to any one of

[41] to

[51] , wherein the mass content of the organic binder in the particle-containing fiber bundle is 0.5 to 20% by mass.

[53] : A method for producing a particle-containing fiber bundle according to any one of

[41] to

[52] , wherein the mass ratio of the particles to the organic binder in the particle-containing fiber bundle (mass of particles / mass of organic binder) is 2.5 to 100.

[0011]

[54] : A method for producing a particle-containing fiber bundle, comprising mixing a mixture containing carbon fiber cotton containing multiple shortened fibers, particles having a median diameter of 100 μm or less, at least one resin selected from the group consisting of polyamide resin, epoxy resin, unsaturated polyester resin, vinyl ester resin, and polyurethane resin, and water.

[55] : A method for producing a particle-containing fiber bundle according to

[54] , wherein the solubility of the particles in water is 0.0001 g / 100 g or less.

[56] : A method for producing a particle-containing fiber bundle according to

[54] or

[55] , comprising, as the particles, at least one resin particle selected from the group consisting of polyamide resin, polyetheretherketone resin, polyetherimide resin, polyphenylene sulfide resin, epoxy resin, and vinyl ester resin.

[0012]

[57] : A particle-containing fiber bundle comprising multiple shortened fibers, particles with a median diameter of 100 μm or less, and an organic binder, having an elongated spherical or strand shape, The aforementioned fiber includes carbon fiber, A particle-containing fiber bundle comprising 10 parts by mass or more of the aforementioned particles per 100 parts by mass of the fiber.

[58] : The particle-containing fiber bundle according to

[57] , wherein the fibers are aligned.

[59] : The particle-containing fiber bundle according to

[57] or

[58] , comprising organic particles as the particles.

[60] : The particle-containing fiber bundle according to

[59] , comprising thermoplastic resin particles as the organic particles.

[61] : The particle-containing fiber bundle according to

[60] , wherein the thermoplastic resin particles include at least one selected from the group consisting of polyamide resin, polyolefin resin, polyester resin, polycarbonate resin, polyethersulfone resin, polyetheretherketone resin, polyetherimide resin, and polyphenylene sulfide resin.

[62] : A particle-containing fiber bundle according to any one of

[59] to

[61] , comprising thermosetting resin particles as the organic particles.

[63] : The particle-containing fiber bundle according to

[62] , wherein the thermosetting resin particles include at least one selected from the group consisting of epoxy resin, vinyl ester resin, unsaturated polyester resin, cyanate ester resin, polyimide resin, maleimide resin, silicone resin, melamine resin, urea resin, alkyd resin, urethane resin, and phenolic resin.

[64] : A particle-containing fiber bundle according to any one of

[59] to

[63] , comprising curing agent particles as the organic particles.

[65] : The particle-containing fiber bundle according to

[64] , comprising at least one selected from the group consisting of dicyandiamides, phenols, amines, carboxylic acid anhydrides, thiols, imidazoles, phosphines, peroxides, and organometallic salts as the curing agent particles.

[66] : A particle-containing fiber bundle according to any one of

[57] to

[65] , wherein the median diameter of the particles is 3 μm or more.

[67] : A particle-containing fiber bundle according to any one of

[57] to

[66] , wherein the average fiber length of the fibers is 12 to 50 mm.

[68] : A particle-containing fiber bundle according to any one of

[57] to

[66] , wherein the average fiber length of the fibers is 2 to 12 mm.

[69] : The particle-containing fiber bundle according to any one of

[57] to

[68] , wherein the positions of the tips of the fibers constituting the particle-containing fiber bundle are irregular.

[70] : The particle-containing fiber bundle according to any one of

[57] to

[69] , wherein the length of the particle-containing fiber bundle is longer than the average fiber length of the fibers contained in the particle-containing fiber bundle.

[71] : A particle-containing fiber bundle according to any one of

[57] to

[70] , wherein the ratio of the length of the particle-containing fiber bundle to the average fiber length of the fibers contained in the particle-containing fiber bundle (length of the particle-containing fiber bundle / average fiber length of the fibers contained in the particle-containing fiber bundle) is 1.1 to 2.5.

[72] : The particle-containing fiber bundle according to any one of

[57] to

[71] , wherein the mass content of the particles in the particle-containing fiber bundle is 20 to 80% by mass.

[73] : The particle-containing fiber bundle according to any one of

[57] to

[72] , wherein the mass content of the organic binder in the particle-containing fiber bundle is 0.5 to 20% by mass.

[74] : The particle-containing fiber bundle according to any one of

[57] to

[73] , wherein the mass ratio of the particles to the organic binder in the particle-containing fiber bundle (mass of particles / mass of organic binder) is 2.5 to 100.

[75] : A particle-containing fiber bundle according to any one of

[57] to

[74] , comprising recycled fiber as the fiber.

[76] : The particle-containing fiber bundle according to any one of

[57] to

[75] , wherein the organic binder comprises at least one resin selected from the group consisting of polyamide resin, epoxy resin, unsaturated polyester resin, vinyl ester resin, and polyurethane resin.

[77] : A particle-containing fiber bundle according to any one of

[57] to

[76] , using fiber cotton containing the aforementioned fibers.

[78] : A particle-containing fiber bundle according to any one of

[57] to

[77] , wherein the particle size D10 at which the cumulative value in the volume-based particle size distribution of the particles becomes 10% is 50 μm or less.

[79] : A particle-containing fiber bundle according to any one of

[57] to

[78] , wherein the particle size D90 at which the cumulative value in the volume-based particle size distribution of the particles becomes 90% is 0.5 μm or larger.

[80] : A particle-containing fiber bundle according to any one of

[57] to

[79] , wherein the particle size D10 at which the cumulative value in the volume-based particle size distribution of the particles becomes 10% is 0.05 μm or larger.

[81] : A particle-containing fiber bundle according to any one of

[57] to

[80] , wherein the ratio (D75 / D25) of particle size D75, which accounts for 75% of the volume-based particle size distribution of the particles, to particle size D25, which accounts for 25%, is 1 to 15.

[82] : A particle-containing fiber bundle according to any one of

[57] to

[81] , wherein the ratio of the average fiber diameter of the fiber to the median diameter of the particle (average fiber diameter of the fiber (μm) / median diameter of the particle (μm)) is 0.01 to 0.4.

[0013]

[83] : A particle-containing fiber bundle comprising several shortened fibers, polyetheretherketone resin particles, and an organic binder, having an elongated spherical or strand shape.

[84] : The particle-containing fiber bundle according to

[83] , comprising carbon fiber as the fiber.

[85] : The particle-containing fiber bundle according to

[83] or

[84] , wherein the median diameter of the resin particles is 0.1 μm or more and 100 μm or less.

[86] : A particle-containing fiber bundle according to any one of

[83] to

[85] , wherein the ratio of the length of the particle-containing fiber bundle to the average fiber length of the fibers contained in the particle-containing fiber bundle (length of the particle-containing fiber bundle / average fiber length of the fibers contained in the particle-containing fiber bundle) is 1.1 to 2.5.

[87] : A particle-containing fiber bundle according to any one of

[83] to

[86] , wherein the average fiber length of the fibers is 1 to 100 mm.

[88] : A particle-containing fiber bundle according to any one of

[83] to

[87] , wherein the average fiber length of the fibers is 12 to 50 mm.

[89] : A particle-containing fiber bundle according to any one of

[83] to

[87] , wherein the average fiber length of the fibers is 2 to 12 mm.

[90] : The particle-containing fiber bundle according to any one of

[83] to

[89] , comprising at least one resin selected from the group consisting of polyamide resin, epoxy resin, and polyurethane resin as the organic binder. [Effects of the Invention]

[0014] According to one embodiment of the present invention, a particle-containing fiber bundle with high uniformity and further improved feed efficiency can be provided, as well as a method for producing the same. According to one embodiment of the present invention, in particular, even when recycled materials are used as the raw material carbon fibers, a particle-containing fiber bundle with high uniformity and further improved feed efficiency can be provided, as well as a method for producing the same. According to a preferred embodiment of the present invention, a particle-containing fiber bundle with improved feed efficiency can be obtained. Furthermore, the size of the particle-containing fiber bundle can be easily adjusted. Even when using fiber cotton raw material, a particle-containing fiber bundle with improved feed efficiency and resin impregnation properties can be easily obtained. [Brief explanation of the drawing]

[0015] [Figure 1A] Figure 1A shows an embodiment of a stirring granulator, and is a horizontal cross-sectional view of the stirring tank. [Figure 1B] Figure 1B is a cross-sectional view along line bb in Figure 1A. [Figure 2]Figure 2 is an internal perspective view showing an embodiment of a rolling agitation granulator. [Figure 3] Figure 3 is a photograph showing an example of the form of recycled fibers. [Figure 4] Figure 4 is a photograph showing an example of the morphology of virgin fibers. [Figure 5] Figure 5 is an image of the particle-containing fiber bundle obtained in Example 1. [Figure 6] Figure 6 is an image showing the appearance of the particle-containing fiber bundle obtained in Example 1. [Figure 7] Figure 7 is an image showing a cross-section of the particle-containing fiber bundle obtained in Example 1. [Modes for carrying out the invention]

[0016] The present invention will be described in detail below. [Method for producing particle-containing fiber bundles] One embodiment of the present invention relates to a method for producing particle-containing fiber bundles. The method for producing particle-containing fiber bundles includes a mixture of several shortened fibers, particles with a median diameter of 100 μm or less, an organic binder, and a liquid, and produces particle-containing fiber bundles in the shape of elongated spheres or strands. The fibers include carbon fibers, and the particles are used in amounts of 10 parts by mass or more per 100 parts by mass of the fibers. The median diameter is defined as the particle size (D50) at which the cumulative value in the volume-based particle size distribution is 50%.

[0017] A method using multiple shortened fibers as starting materials typically involves the following steps (i) to (iii): (i) Mixing process (ii) Bundling process (iii) Drying process The timing of mixing the fibers, particles, organic binder, and liquid is not limited, but from the viewpoint of manufacturing efficiency, it is preferable to mix the particles, organic binder, and liquid to obtain mixture 1, and mix mixture 1 and fibers to obtain mixture 2. Mixture 1 can be produced in (i) the mixing step, but may also be prepared separately. Mixture 2 can be produced in (i) the mixing step, but (ii) the bundling step may be carried out simultaneously with the production of mixture 2. The amount of raw materials used until a particle-containing fiber bundle is produced can be, for example, 10 to 200 parts by mass of particles, 1 to 200 parts by mass of liquid, and 1 to 40 parts by mass of organic binder per 100 parts by mass of fiber.

[0018] From the viewpoint of maintaining the shape of the fiber bundle, the amount of organic binder used is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 6 parts by mass or more, per 100 parts by mass of fiber. From the viewpoint of maintaining the shape of the particle-containing fiber bundle, the amount of organic binder used is preferably 40 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of fiber. The above upper and lower limits can be combined arbitrarily. For example, it may be 1 to 40 parts by mass, 3 to 20 parts by mass, or 6 to 10 parts by mass.

[0019] From the viewpoint of reducing the total length of the particle-containing fiber bundle, the amount of particles used is 10 parts by mass or more per 100 parts by mass of fiber, preferably 20 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 40 parts by mass or more, particularly preferably 50 parts by mass or more, and most preferably 55 parts by mass or more. From the viewpoint of making the shape of the particle-containing fiber bundle uniform, the amount of particles used is preferably 150 parts by mass or less per 100 parts by mass of fiber, more preferably 100 parts by mass or less, even more preferably 90 parts by mass or less, particularly preferably 80 parts by mass or less, and most preferably 75 parts by mass or less. The above upper and lower limits can be combined arbitrarily. For example, it may be 10 to 150 parts by mass, 20 to 150 parts by mass, 30 to 100 parts by mass, 40 to 90 parts by mass, 50 to 80 parts by mass, or 55 to 75 parts by mass.

[0020] From the viewpoint of uniformly dispersing the particles within the particle-containing fiber bundle, it is preferable to use raw materials such that the mass ratio of particles to organic binder (mass of particles / mass of organic binder) is 2.5 to 100, and more preferably 5.0 to 50.

[0021] From the viewpoint of efficiently promoting liquid crosslinking, the amount of liquid used is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 30 parts by mass or more, particularly preferably 60 parts by mass or more, and most preferably 80 parts by mass or more, per 100 parts by mass of fiber. From the viewpoint of facilitating drying, the amount of liquid used is preferably 200 parts by mass or less, more preferably 180 parts by mass or less, and even more preferably 160 parts by mass or less, per 100 parts by mass of fiber. The above upper and lower limits can be combined arbitrarily. For example, it may be 5 to 200 parts by mass, 10 to 200 parts by mass, 30 to 180 parts by mass, 60 to 180 parts by mass, or 80 to 160 parts by mass.

[0022] The details of each step are explained below.

[0023] (i) Mixing process In the mixing step, fibers, particles, organic binder, and liquid are mixed to obtain a mixture. A general defibrillator can be used in the mixing step, but is not limited to it. For example, the fibers and particles can be placed in a stir granulator, such as a Henschel mixer, and mixed by stirring in a dry state. This method has the advantage of allowing the resulting mixture to proceed to the next bundling step without removing it from the stir granulator. The bundling step may also be omitted.

[0024] (ii) Bundling process In the bundling process, fiber bundles are formed by mixing the mixture obtained in the mixing process with a liquid. The particles, organic binder, and liquid can also be mixed in this process to form a mixture. From the viewpoint of ensuring that particles and organic binders are present inside the fiber bundles, it is preferable that the particles and organic binders are mixed before the fiber bundles are formed, that is, before the start of mixing in the bundling process or (i) in the mixing process. The fibers and particles constituting the mixture aggregate due to capillary forces based on the surface tension of the liquid, forming fiber bundles containing the liquid. A mixture of the liquid and an organic binder may also be used for bundling. Hereinafter, the liquid alone or the mixture will be referred to as the bundling solution. There are no particular restrictions on the bundling solution, but for example, a solvent such as an organic solvent can be used, and it may contain an organic binder and other components. The organic binder and other components may be dissolved in the solvent, mechanically dispersed, or dispersed by a surfactant. Furthermore, a bundling solution whose viscosity has been reduced by heating can be used. The amount of the bundling solution is, for example, 70 to 210 parts by mass per 100 parts by mass of the raw material fibers used in the production of particle-containing fiber bundles (hereinafter sometimes referred to as "raw material fibers"), but is not limited to that amount. The amount of the bundling solution can be adjusted as appropriate while observing the state of the mixture.

[0025] The viscosity of the bundling solution can ensure uniformity of the particle-containing fiber bundles if it is 10 Pa·s or less at 23°C. The viscosity can be 8 Pa·s or less, 5 Pa·s or less, 2 Pa·s or less, or 0.5 Pa·s or less. On the other hand, the viscosity can be 0.0001 Pa·s or more. The above upper and lower limits can be combined arbitrarily. For example, it may be 0.0001 to 10 Pa·s, 0.0001 to 8 Pa·s, 0.0001 to 5 Pa·s, 0.0001 to 2 Pa·s, or 0.0001 to 0.5 Pa·s. When bundling by heating, a bundling solution within the viscosity range described above at the current temperature can be used. Viscosity is measured using a B-type rotational viscometer (e.g., Brookfield LVDV-1 Pri) at a rotational speed of 50 rpm.

[0026] If the surface tension of the bundling solution is 120 mN / m or less, liquid crosslinks can be formed between fibers, facilitating fiber movement and enabling fiber orientation. The surface tension can be 110 mN / m or less, 100 mN / m or less, 90 mN / m or less, 72 mN / m or less, 60 mN / m or less, 50 mN / m or less, or 40 mN / m or less at 23°C. On the other hand, the surface tension can be 10 mN / m or more, 15 mN / m or more, 20 mN / m or more, or 30 mN / m or more. The above upper and lower limits can be combined arbitrarily. For example, it may be 10-120 mN / m, 10-110 mN / m, 15-100 mN / m, 15-90 mN / m, 20-72 mN / m, 20-60 mN / m, 30-50 mN / m, or 30-40 mN / m. The surface tension is measured using the plate method (vertical plate method). When bundling by heating, a bundling solution within the above tension range at the current temperature can be used.

[0027] Regarding the degree of fiber length maintenance, since the uniformity of the fiber bundle is increased, the ratio (Y / X) of the average fiber length Y of the particle-containing fiber bundle to the average fiber length X of the raw fibers is preferably 0.55 or higher, more preferably 0.70 or higher, even more preferably 0.80 or higher, and particularly preferably 0.90 or higher. This ratio (Y / X) can be 1 or less. The above upper and lower limits can be arbitrarily combined. For example, it may be 0.55 to 1, 0.70 to 1, 0.80 to 1, or 0.90 to 1.

[0028] The following describes a stirring granulator suitable for use in (i) the mixing process and (ii) the bundling process, with reference to Figures 1A and 1B. The stirring granulator, as shown in Figure 1A, preferably has a rotating shaft 2 on the central axis inside a bottomed cylindrical stirring tank 1, from which multiple (three in Figure 1A) propeller-shaped stirring blades extend radially at equal intervals. The stirring blades may also be disc-shaped and perpendicular to the rotating shaft. They may also be discs with undulations and protrusions.

[0029] As shown in Figure 1B, the stirring blade 3 is installed at an angle in the rotational direction with respect to the bottom surface 1A of the stirring tank 1. The angle θ between the rear surface 3A with respect to the rotational direction R and the bottom surface 1A of the stirring tank 1 (hereinafter sometimes simply referred to as the "angle of inclination") is preferably in the range of 1 to 60°. If the angle of inclination θ of the stirring blade 3 is 1° or more, it is possible to stir the mixture while circulating it within the stirring tank. If the angle of inclination θ of the stirring blade 3 is 60° or less, it is possible to adjust the rotational speed within a range that does not put a load on the device by suppressing resistance to the stirring blade. The angle of inclination θ is more preferably 10 to 50°, and even more preferably 20 to 40°.

[0030] In Figure 1A, the stirring blade 3 is bent at an angle α in the middle of its longitudinal direction. For example, the distance between the bottom surface of the stirring blade 3 and the bottom surface 1A of the stirring tank 1 may be set to 1 mm or less to stir up the raw material that has accumulated at the bottom. The distance between the tip of the stirring blade 3 and the side (wall) of the stirring tank 1 may be set to 10 mm or more to suppress damage to the raw materials due to shearing. The stirring blade is not limited to such a bent shape; it may also be a straight, plate-shaped blade. The stirring blade may also be bent in an arc shape. The agitator may be equipped with a propeller-type auxiliary stirring blade (chopper) on the wall of the stirring tank for auxiliary stirring. The stirring tank of the agitator may be equipped with a scraper on the bottom or side. The stirring tank may have a horizontally rotating stirring blade (agitator) and a vertically rotating propeller-type auxiliary stirring blade (chopper) as stirring blades, and efficient agitator granulation can be performed by stirring with the horizontally rotating stirring blade and the vertically rotating propeller-type auxiliary stirring blade. The vertically rotating auxiliary stirring blade plays a role in crushing granules that have become too large and making the size of the particle-containing fiber bundles uniform.

[0031] In a stirring granulator, the rotation conditions of the stirring blade are preferably such that the peripheral speed of the tip of the stirring blade (part 3a in Fig. 1a) (hereinafter simply referred to as "peripheral speed") is in the range of 1 to 20 m / sec. If the peripheral speed is 1 m / sec or more, it is possible to stir the mixture while circulating it in the stirring tank. If the peripheral speed is 20 m / sec or less, it is possible to make the particle shape of the particle-containing fiber bundles uniform. The peripheral speed of the stirring blade is more preferably 4 to 12 m / sec, and even more preferably 4 to 8 m / sec. The peripheral speed of the chopper should preferably be in the range of 5 to 30 m / s.

[0032] Below, with reference to Figure 2, we will describe another type of stirring granulator that is suitably used in the method for producing particle-containing fiber bundles. One embodiment of a rolling agitation granulator, as shown in Figure 2, includes a rotatable container 40 that houses raw material fibers, particles, an organic binder, and a liquid, and a rotating shaft 42 positioned inside the container 40 and eccentrically from the central axis 41 of the container 40, parallel to the central axis 41. Preferably, the rotating shaft 42 is rotatable in the opposite direction to the rotation direction of the container 40. By rotating in the opposite direction, the impact force between the agitator blades and the raw material fibers is increased, making it possible to align the fibers in a short time by strong shearing. The rotation direction of the rotating shaft 42 may be the same as that of the container 40. When the direction of rotation of the stirring blade is opposite to the direction of rotation of the container, the number of filaments in the fiber bundle tends to be small, and the distribution of the number and shape of filaments in the fiber bundle tends to be uniform. When the direction of rotation is the same as the direction of rotation of the container, the number of filaments in each fiber bundle tends to be large, and the fibers tend to clump together easily. After stirring with the impeller rotating in the opposite direction to the container's rotation, stirring again with the impeller rotating in the same direction as the container's rotation is thought to promote liquid crosslinking between fiber bundles with a small number of filaments and a uniform distribution. This makes it possible to obtain a fiber bundle that is uniform and has high bulk density.

[0033] The rotating shaft portion 42 extends to the vicinity of the bottom plate 43 of the container 40 and has a stirring blade 44 that moves within the region where the mixture can exist. The rotation of the container 40 circulates the mixture, and the rotation of the stirring blade 44 shears the mixture, making it possible to align the fibers. The blades of the stirring blade 44 can be configured in the same way as described for the stirring granulator. For example, the distance between the bottom surface 49 of the stirring blade 44 and the bottom plate 43 of the stirring tank may be set to 10 mm or more to efficiently bring the stirring blade into contact with the raw material scraped up by the scraper. The distance between the tip 46 of the stirring blade 44 and the side surface 47 of the stirring tank may be set to 10 mm or more to suppress damage to the raw material due to shearing.

[0034] A scraper 45 is provided on the side of the container 40. A scraper may also be provided on the inner side 47, the bottom plate 43, or both of the container 40. The scraper 45 can be used to scrape off any adhering raw materials.

[0035] Regarding the rotation conditions, the peripheral speed of the container 40 (container peripheral speed) can be in the range of 0.4 to 1.2 m / sec. If the peripheral speed is 0.4 m / sec or higher, the mixture can be stirred while circulating it within the stirring tank. On the other hand, if the peripheral speed is 1.2 m / sec or lower, the mixture can be efficiently brought into contact with the stirring blades and scrapers, thereby shortening the processing time. The peripheral speed can be 0.5 to 1.0 m / sec or 0.7 to 0.9 m / sec. The peripheral speed of the tip of the stirring blade 44 (tip peripheral speed) can be in the range of 1 to 30 m / s. If the tip peripheral speed is 1 m / s or more, it is possible to align the fibers in a short time and increase the density of the fiber bundle. On the other hand, if the tip peripheral speed is 30 m / s or less, it is possible to make the shape of the fiber bundle uniform. The peripheral speed of the stirring blade 44 can be 10 to 20 m / s or 1 to 8 m / s.

[0036] There are no particular restrictions on the stirring time in the stirring granulator; stirring should be performed for as long as the desired fiber bundle is obtained. By using cotton fibers as an intermediate step, the time required for the bundling process can be shortened. There are no particular restrictions on the temperature during stirring, and it can be done at room temperature (e.g., 5-40°C). A rise in temperature of the container or mixture due to stirring is acceptable. When bundling, stirring can be performed at a temperature above the melting or softening point of the organic binder so that the organic binder becomes solid during the stage when the granulated product is maintained, and then it can be cooled once particle-containing fiber bundles are formed.

[0037] The stirring conditions are preferably adjusted to obtain a bundle of fibers that are aligned rather than a spherical carbon fiber ball formed by the crimping of the fibers. To obtain a bundle of fibers that are aligned, for example, methods include increasing the amount of liquid, increasing the peripheral speed of the stirring blade tip, or using raw fibers with an average fiber length greater than 1 mm. There are no particular restrictions on when granulation is completed, but it is preferable that it be at a time when the fiber bundles can be confirmed to the extent that the particle size distribution can be identified.

[0038] (iii) Drying process In the drying process, the particle-containing fiber bundles formed in the bundling process are dried to remove the liquid contained in the bundling solution. Even if the liquid evaporates due to drying, the shape of the particle-containing fiber bundles can be maintained due to the adhesion of the organic binder. Drying may be forced or natural. In one example, particle-containing fiber bundles formed in the stirring tank of a stirring granulator can be dried while being stirred in the stirring tank without being removed from the tank. In another example, the particle-containing fiber bundles formed in the stirring tank of a stirring granulator may be removed from the stirring tank and dried elsewhere. This other location could be, for example, a hot air dryer, or it could be inside a transport pipe or on a conveyor belt. If using a dryer, the process can be carried out at 50-150°C for 1-5 hours. Examples of drying equipment include box dryers, belt conveyor dryers, tunnel dryers, fixed tank agitation dryers, drum rotary dryers, rotary kilns, fluidized bed dryers, agitated hot air dryers, airflow dryers, infrared dryers, microwave dryers, and vacuum dryers.

[0039] Other processes may include classification and chopping. The classification process can be introduced in any of steps (i) to (iii), but introducing it after step (iii) can improve the uniformity of the fiber bundles containing multiple particles. A sieve used for classification can be configured, for example, to include a vibrating mechanism, a container coupled to the vibrating mechanism, and a sieve mesh that partitions the internal space of the container. The mesh shape and opening of the sieve mesh are adjusted so that particle-containing fiber bundles can be sieved to a desired size. When the particle-containing fiber bundles are elongated spherical in shape, the mesh shape is preferably rectangular or rhombic. The mesh shape may also be square or circular.

[0040] The chopping process is preferably introduced before (i), and for example, a continuous fiber bundle made of virgin fibers is cut at predetermined intervals in the fiber direction using a rotary cutter to form a chopped fiber bundle. The bundle size of a continuous fiber bundle (the number of fiber filaments constituting the bundle) can be, for example, 10K or more and 100K or less. Here, "K" is a symbol representing 1000, for example, 1K means 1000 and 10K means 10000. From the viewpoint of production efficiency, the bundle size of a continuous fiber bundle is preferably 24K or more, more preferably 36K or more, and even more preferably 48K or more. For example, it may be 24K or more and 100K or less, 36K or more and 100K or less, or 48K or more and 100K or less. The fiber length of the chopped fiber bundle is not limited, but may be, for example, 3 mm or more, 5 mm or more, or 10 mm or more, or, for example, 60 mm or less, 50 mm or less, 40 mm or less, 30 mm or less, or 20 mm or less. The above upper and lower limits can be combined arbitrarily. For example, it may be 3 to 60 mm, 3 to 50 mm, 5 to 40 mm, 5 to 30 mm, or 10 to 20 mm or less. If the chopped fiber bundle contains water or sizing agents, it is preferable to remove the water or sizing agents by solvent or thermal decomposition to obtain dried fiber cotton.

[0041] <Textiles> It is preferable to use a fiber cotton containing multiple shortened fibers as the raw material. By using fiber cotton, it is possible to bundle the fibers from a state where they are separated into monofilaments, making it easier to efficiently obtain a uniform particle-containing fiber bundle. The fibers include carbon fibers. Carbon fibers are useful in the production of fiber-reinforced resin compositions, and it is possible to provide fiber-reinforced resin compositions with high specific strength and specific modulus. Carbon fibers include PAN-based and pitch-based types, with PAN-based being more readily available. From the viewpoint of specific strength and specific modulus, the proportion of carbon fibers in the raw material fibers is preferably 70% by mass or more, and more preferably 90-100% by mass.

[0042] The raw fibers are not limited to virgin fibers; recycled fibers may also be used. Figure 3 shows an example of the form of recycled fibers. Recycled fibers are fibrous cotton in which monofilaments are randomly stacked. Figure 4 shows an example of the form of virgin fibers. Virgin fibers are clumps of fiber bundles in which the fibers are aligned. The raw fibers may have sizing agents or FRP matrix resin attached to them. The amount of resin residue on raw fibers such as carbon fibers is, for example, in the range of 0.01 to 10%.

[0043] By following the previously described method for manufacturing particle-containing fiber bundles, even if the raw material fibers include recycled fibers, it is possible to produce particle-containing fiber bundles with controlled size, where the fibers are aligned and maintain their length without cutting the fibers. Examples of recycled fibers include fibers obtained by decomposing the matrix using heat, subcritical fluid, or supercritical fluid, and fibers obtained by cutting off pieces of fiber substrate. The matrix can be completely removed from the recycled fibers until they become cotton-like. If there are any remaining resin residues, they may be removed by heat treatment in an oxidizing atmosphere.

[0044] The fibers contained in the particle-containing fiber bundle may be partially or entirely thermally degraded. For example, thermally degraded carbon fibers are recycled carbon fibers recovered from CFRP waste, which have been thermally degraded during the process of removing the matrix resin through thermal decomposition. The raw material fibers are preferably cotton-like, consisting of multiple short fibers (discontinuous fibers) bundled together. Because they are cotton-like, they are separated into monofilaments in the dry state, eliminating the need for energy to undo the orientation that would occur if the fibers were wet and had developed a certain orientation. This allows for efficient size control of the particle-containing fiber bundles. The raw material fibers may include groups of fibers that are already aligned, but it is preferable that, for example, 50% or more by mass of the fiber raw material is cotton fiber.

[0045] Shortened fibers may be obtained by cutting a continuous bundle of fibers, or by using fibers in a discontinuous form. The continuous fibers may be tow fibers, or fibers extracted from prepregs or molded products. For example, recycled fibers obtained by decomposing the matrix with heat are in a dry, cotton-like fiber state immediately after heating. By using a stirring granulator, it is possible to obtain particle-containing fiber bundles with aligned fibers without changing the fiber form from the fiber recycling process. The raw fibers may be defibrated before being stirred with a stirring granulator or similar device. For example, before adding the fiber treatment agent to the stirring tank, the raw fibers are defibrated by stirring the liquid-free fibers in the tank with a stirring blade. The rotation of the stirring blade breaks down the fibers bound together by adhering substances such as resin carbides, creating smaller fiber units, which makes it easier to align the fibers when stirring with the stirring blade after adding the fiber treatment agent. At the same time, the uniformity of the fiber bundles can be improved.

[0046] There are no particular restrictions on the fiber diameter of the raw material fibers, but for example, it is in the range of 3 μm to 100 μm, with 5 μm to 15 μm being the most readily available. The bulk density of the raw fibers is, for example, 0.01 to 0.90 g / cm³. 3 This is within the range of the bulk density of the raw fiber, which is 0.01 to 0.10 g / cm³. 3 Therefore, it is easier to convert it into a fiber bundle with a higher bulk density than the raw fiber. For example, fiber cotton is an example of a material with a bulk density in the range of 0.01 to 0.10 g / cm³. From the viewpoint of uniformly bundling the raw fibers, the fiber length is preferably 100 mm or less, more preferably 60 mm or less, and even more preferably 50 mm or less, but may also be 20 mm or less or 12 mm or less.

[0047] From the viewpoint of strength when used in a molded article, the fiber length contained in the particle-containing fiber bundle is preferably 1 mm or more, and more preferably 2 mm or more. The fibers may not contain fibers with a length of less than 1 mm, or they may contain them in a content of less than 5 wt%.

[0048] When used in fiber-reinforced resin compositions (pellets) for extrusion molding, the average fiber length of the raw materials is preferably 2 to 12 mm. When used in fiber-reinforced resin materials (prepregs) for press molding, the average fiber length of the raw fibers is preferably 12 to 50 mm, and more preferably 12 to 30 mm, from the viewpoint of facilitating the uniform deposition of particle-containing fiber bundles by scattering them during prepreg manufacturing. If the fiber length of the raw material fibers is above the lower limit mentioned above, the strength of the fiber-reinforced resin composition can be sufficiently increased, and the fiber orientation can be controlled to a high degree. If the average fiber length of the raw material fibers is below the upper limit mentioned above, entanglement in the equipment when manufacturing particle-containing fiber bundles can be suppressed, thereby increasing production efficiency, and the shape of the particle-containing fiber bundles can be uniformly controlled.

[0049] The weighted average fiber length is used as the average fiber length. The average fiber length can be measured by the method described in the Examples section below. Alternatively, the average fiber length can be calculated by binarizing images taken by microscopic observation using image processing software such as ImageJ. By constructing the particle-containing fiber bundle from only fibers having equivalent fiber lengths, variations in the quality of the particle-containing fiber bundle between manufacturing lots can be suppressed. Between the multiple short fibers constituting the particle-containing fiber bundle, the difference between the maximum and minimum fiber lengths is preferably within 5 mm, more preferably within 4 mm, and even more preferably within 3 mm.

[0050] <particle> By using particles with a median diameter of 100 μm or less, it is possible to adjust the overall length of the particle-containing fiber bundles while maintaining a uniform shape. The shorter the overall length of the particle-containing fiber bundles, the less fiber interference occurs at the tips of the bundles, making it easier to improve the feed efficiency from the hopper to the feeder. The presence of particles in the particle-containing fiber bundles creates spaces between the fibers, making it easier for the resin to impregnate them.

[0051] In this specification, the particles have a solubility in water at 23°C of 0.0001 g / mL or less and are materials used separately from the organic binder described later in the section on <organic binders>. Furthermore, it is preferable that the particles can maintain their shape both in the presence and absence of the liquid component, which will be explained later in the section on <liquid>. From the viewpoint of adjusting the overall length of the particle-containing fiber bundle to be short, it is preferable that the particles are not easily soluble in the liquid described later. For example, if the solubility in the liquid at 23°C is 0.01 g / 100 g or less, the particles will be incorporated into the fiber bundle while maintaining their shape during mixing.

[0052] The median diameter of the particles is the particle size (D50) at which the cumulative value in the volume-based particle size distribution becomes 50%, and is preferably 0.1 μm or larger, more preferably 3 μm or larger, and even more preferably 10 μm or larger. This allows for adjustment to shorten the overall length of the particle-containing fiber bundle. Furthermore, during injection molding or press molding of the resulting particle-containing fiber bundle, the fibers unravel easily and are uniformly dispersed, resulting in a good appearance of the molded product. The median diameter of the particles is preferably 90 μm or smaller, more preferably 80 μm or smaller, and even more preferably 60 μm or smaller. This allows for a uniform shape of the particle-containing fiber bundle. Furthermore, during injection molding or press molding of the resulting particle-containing fiber bundle, the interfaces between the fiber bundles become uniform, improving the strength of the molded product. The above upper and lower limits can be combined in any way. For example, they may be 0.1 to 90 μm, 3 to 80 μm, or 10 to 60 μm.

[0053] The particle size D90 at which the cumulative value in the particle size distribution based on particle volume reaches 90% is preferably 350 μm or less, more preferably 250 μm or less, and even more preferably 100 μm or less. This ensures a uniform distribution of particles and fibers within the particle-containing fiber bundle. Furthermore, during injection molding or press molding of the resulting particle-containing fiber bundle, the fibers unravel easily and disperse uniformly, resulting in a good appearance of the molded product. The particle size D90 is preferably 0.5 μm or more, and more preferably 30 μm or more. This allows for adjustment to shorten the overall length of the particle-containing fiber bundle. Furthermore, during injection molding or press molding of the resulting particle-containing fiber bundle, the fibers unravel easily and disperse uniformly, resulting in a good appearance of the molded product. The above upper and lower limits can be combined in any way. For example, they may be 0.5 to 350 μm, 0.5 to 250 μm, or 30 to 100 μm.

[0054] The particle size D10 at which the cumulative value in the particle size distribution based on particle volume reaches 10% is preferably 70 μm or less, more preferably 50 μm or less, and even more preferably 30 μm or less. This allows for a uniform distribution of particles and fibers within the particle-containing fiber bundle. Furthermore, during injection molding or press molding of the resulting particle-containing fiber bundle, the interfaces between fiber bundles become uniform, improving the strength of the molded product. The particle size D10 is preferably 0.05 μm or more, and more preferably 1 μm or more. This allows for adjustment to shorten the overall length of the particle-containing fiber bundle. Furthermore, during injection molding or press molding of the resulting particle-containing fiber bundle, the fibers unravel easily and disperse uniformly, resulting in a good appearance of the molded product. The above upper and lower limits can be combined in any way. For example, they may be 0.05 to 70 μm, 0.05 to 50 μm, or 1 to 30 μm.

[0055] The ratio (D75 / D25) of particle size D75, where the cumulative value in the particle size distribution based on volume is 75%, to particle size D25, where it is 25%, is preferably 1 to 15, and more preferably 1 to 10. This allows for a uniform distribution of particles and fibers within the particle-containing fiber bundle. Furthermore, during injection molding or press molding of the resulting particle-containing fiber bundle, the interfaces between the fiber bundles become uniform, improving the strength of the molded product.

[0056] The relationship between particle size D84, where the cumulative value in the particle size distribution based on volume is 84%, and particle size D16, where it is 16%, is expressed as (D84-D16) / 2, which can be expressed in the range of 1 to 150 or 5 to 100.

[0057] The particle size distribution based on particle volume can be obtained by laser diffraction / scattering or image analysis. Particle size distribution measurement by laser diffraction / scattering can be performed, for example, by the method described in the examples. Particle size distribution measurement by image analysis can be performed, for example, by determining the particle size of 50 or more particles from images obtained using an optical microscope. When using commercially available particles, you may use the median diameters D90, D10, D75, D25, D84, and D16 as specified in the catalog. Furthermore, it is also possible to use two or more particles with different particle sizes, i.e., particles having two or more peaks with different particle sizes in the particle size distribution measured by the above method. When using particles with peaks of 1000 μm or larger, the median diameter, D90, D10, D75, D25, D84, and D16 shall be determined from the particle size distribution obtained by separating the peaks of 1000 μm or larger by peak separation.

[0058] The ratio of the average fiber length of the raw material fibers to the median diameter of the particles (average fiber length of raw material fibers (μm) / median diameter of particles (μm)) is preferably 10 to 150, and more preferably 30 to 130. This allows for adjustment to shorten the overall length of the particle-containing fiber bundle. Furthermore, during injection molding or press molding of the resulting particle-containing fiber bundle, the fibers are easily unraveled and uniformly dispersed, resulting in a good appearance of the molded product. The ratio of the average fiber diameter of the raw material fibers to the median diameter of the particles (average fiber diameter of raw material fibers (μm) / median diameter of particles (μm)) is preferably 0.01 to 0.4, and more preferably 0.07 to 0.3. This allows for a uniform distribution of particles and fibers within the particle-containing fiber bundle. Furthermore, during injection molding or press molding of the resulting particle-containing fiber bundle, the interfaces between the fiber bundles become uniform, improving the strength of the molded product.

[0059] Particle shapes can include spherical, flattened, needle-shaped, and amorphous. However, a spherical shape is preferred because a shape different from that of fibers makes it easier to shorten the overall length of the fiber bundle containing the particles. Furthermore, a spherical shape allows the fibers to unravel easily during injection molding or press molding, resulting in uniform dispersion and a good appearance of the molded product. The aspect ratio of the particles can be between 1 and 1.5. The maximum Ferret diameter of the particles can be 0.1 μm to 100 μm, or 3 to 80 μm. The maximum Ferret diameter can be determined by analyzing 50 or more particles from images obtained using a transmission electron microscope (TEM), and using the median of the maximum distance between parallel tangents touching opposing contour lines.

[0060] The types of particles include organic particles and inorganic particles. Examples of organic particles include thermoplastic resin particles, thermosetting resin particles, and curing agent particles. Curing agent particles are capable of curing thermosetting resins. Thermoplastic resin particles and thermosetting resin particles can be components of the matrix resin of a fiber-reinforced resin composition or its molded product. Organic particles and inorganic particles may be used in combination.

[0061] Examples of resins that make up thermoplastic resin particles include polyamide resins, polyolefin resins, polyester resins, polycarbonate resins, polyethersulfone resins, polyetheretherketone resins, polyetherimide resins, and polyphenylene sulfide resins. When used as a matrix resin in a fiber-reinforced resin composition, polyamide resin, polyetheretherketone resin, polyetherimide resin, or polyphenylene sulfide resin is preferred from the viewpoint of impact resistance of the molded article. In particular, when using polyetheretherketone resin particles, it becomes possible to impregnate even high-viscosity polyetheretherketone resins that are difficult to impregnate into fibers, thereby improving the mechanical properties of the molded product. Thermoplastic resin particles are used in amounts of, for example, 1 to 200 parts by mass per 100 parts by mass of the total amount of raw fiber. However, if the resulting particle-containing fiber bundle is used as is as a molding material, 30 to 300 parts by mass is preferred, and if the particle-containing fiber bundle is converted into another molding material, 1 to 100 parts by mass is preferred.

[0062] Examples of resins that make up thermosetting resin particles include epoxy resins, vinyl ester resins, unsaturated polyester resins, cyanate ester resins, polyimide resins, maleimide resins, silicone resins, melamine resins, urea resins, alkyd resins, urethane resins, and phenolic resins. When used as a matrix resin in a fiber-reinforced resin composition, epoxy resin, vinyl ester resin, cyanate ester resin, or phenolic resin is preferred from the viewpoint of the strength of the cured product. Thermosetting resin particles are used in amounts of, for example, 1 to 200 parts by mass per 100 parts by mass of the total amount of raw fiber. However, if the resulting particle-containing fiber bundle is used as is as a molding material, 30 to 300 parts by mass is preferred, and if the particle-containing fiber bundle is converted into another molding material, 1 to 100 parts by mass is preferred.

[0063] Examples of curing agent particles include dicyandiamides, phenols, amines, carboxylic acid anhydrides, thiols, imidazoles, phosphines, peroxides, and organometallic salts. The curing agent particles are used in amounts of, for example, 1 to 100 parts by mass per 100 parts by mass of the total amount of raw fiber, but 2 to 10 parts by mass are preferred from the viewpoint of reducing the amount remaining so as not to become a point of fracture in the molded article.

[0064] Examples of inorganic particles include metal particles, metal oxide particles, silica particles, silicate particles, carbonate particles, sulfate particles, hydroxide particles, glass particles, ceramic particles, graphite, and carbon black. Inorganic particles are used in amounts of, for example, 1 to 200 parts by mass per 100 parts by mass of the total amount of raw fiber. However, from the viewpoint of reducing the amount remaining so as not to become a point of fracture in the molded body, 2 to 150 parts by mass is preferred. These particles may be used individually or in combination of two or more types.

[0065] <Organic Binder> The organic binder is not particularly limited as long as it is an organic substance that can bind fibers together. A suitable example of an organic binder material is the resin used for sizing in commercially available general fiber bundles. In other words, it can be called the component resin of a sizing agent. Examples of such resins include, but are not limited to, polyamide resins, epoxy resins, unsaturated polyester resins, vinyl ester resins, and polyurethane resins. These resins may be used individually or in combination of two or more. The organic binder may contain the same resin as the resin that makes up the particles, but it is used separately from the particles to bind the fibers together. Typically, the solubility of organic binders in water at 23°C is greater than 0.0001 g / mL. Also, typically, the solubility of organic binders in liquids at 23°C is greater than 0.01 g / mL.

[0066] In addition to the resins mentioned above, the organic binder may also contain surfactants. Examples of surfactants include anionic surfactants such as alkyl ether carboxylates, cationic surfactants such as aliphatic quaternary ammonium salts and imidazolinium salts, amphoteric surfactants such as carboxylates, and nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene glycerin fatty acid esters, and polyethylene glycol fatty acid esters.

[0067] <Liquid> By using a liquid, liquid crosslinks can be formed between fibers, allowing them to be bundled. From the viewpoint of being able to form liquid crosslinks between fibers at room temperature, it is preferable that the liquid is liquid at room temperature (25°C). Examples of liquids include alcohols such as methanol, ethanol, and propanol; ketones such as acetone and methyl ethyl ketone; organic solvents such as hydrocarbons such as hexane, cyclohexane, benzene, toluene, and styrene; and water. Water is preferred from the viewpoint of eliminating the need for explosion-proof equipment during the manufacturing process.

[0068] [Particle-containing fiber bundle] Another embodiment of the present invention relates to particle-containing fiber bundles. A particle-containing fiber bundle according to one embodiment of the present invention comprises a plurality of shortened fibers, particles with a median diameter of 100 μm or less, and an organic binder, and has an elongated spherical shape or a strand shape. The fibers also include carbon fibers, and the particles are present in an amount of 10 parts by mass or more per 100 parts by mass of the fibers.

[0069] Another embodiment of the present invention provides a particle-containing fiber bundle comprising a plurality of shortened fibers, polyetheretherketone resin particles, and an organic binder, and having an elongated spherical or strand shape. In particle-containing fiber bundles, it is preferable that the fibers are aligned to form a fiber bundle. Furthermore, it is preferable that the fibers present on the surface of the fiber bundle are curved and oriented along the contour of an elongated sphere.

[0070] Particle-containing fiber bundles can be manufactured, for example, by the method for manufacturing particle-containing fiber bundles described above. According to the method for manufacturing particle-containing fiber bundles described above, since the fiber bundle is formed by the aggregation of multiple fibers, the positions of the tips of the fibers constituting the particle-containing fiber bundle become uneven.

[0071] When used as a raw material for injection molding or pellets, the shape of the particle-containing fiber bundle is preferably elongated spherical from the viewpoint of feed efficiency to the kneader. When used in SMC, the shape of the fiber bundle is preferably strand-shaped from the viewpoint of strength when formed into a molded product. The longer the fiber length of the fibers contained in the particle-containing fiber bundle, the more likely it is to form a strand shape.

[0072] Figures 5-7 show the appearance and cross-section of the particle-containing fiber bundles obtained in the embodiments described in detail below. In one example, the particle-containing fiber bundle has an elongated spherical shape with the fibers aligned, as shown in Figure 5, and particles and fibers are uniformly present on the surface (appearance) and inside (cross-section) of the particle-containing fiber bundle, as shown in Figures 6 and 7.

[0073] The length of the particle-containing fiber bundle may be 3 mm or more, 6 mm or more, 12 mm or more, 20 mm or more, 50 mm or more, or 70 mm or more. The length of the particle-containing fiber bundle may be 100 mm or less, 70 mm or less, 50 mm or less, 40 mm or less, 25 mm or less, 12 mm or less, or 6 mm or less. The above upper and lower limits can be combined arbitrarily. For example, it may be 3 to 100 mm, 6 to 70 mm, 12 to 50 mm, 20 to 40 mm, 50 to 100 mm, 70 to 100 mm, 3 to 25 mm, 3 to 12 mm, or 3 to 6 mm. The length of the particle-containing fiber bundle can be determined by the method described in the examples.

[0074] When particle-containing fiber bundles are used as raw materials for injection molding or pellets, the length of the particle-containing fiber bundles is preferably 3 mm to 12 mm. When particle-containing fiber bundles are used as raw materials for press molding or SMC, the length of the particle-containing fiber bundle is preferably between 12 mm and 50 mm. The diameter of the thickest part of the particle-containing fiber bundle can be 0.1 mm to 10 mm, and the cross-sectional shape can be, for example, circular or elliptical.

[0075] From the viewpoint of strength when formed into a molded body, it is preferable that the length of the particle-containing fiber bundle is longer than the average fiber length of the fibers in the particle-containing fiber bundle. The ratio of the length of the particle-containing fiber bundle to the average fiber length of the fibers contained in the particle-containing fiber bundle (length of particle-containing fiber bundle / average fiber length of the fibers contained in the particle-containing fiber bundle) is preferably 1.1 to 5.0 from the viewpoint of feed efficiency. In particular, when the feeder is a screw feeder equipped with a hopper, a ratio of 1.1 to 2.5 is more preferable because it makes it easier to stably supply a constant amount without clogging the supply port.

[0076] When the particle-containing fiber bundle is elongated spherical in shape, it is preferable that the diameter of the thickest part is between 2 mm and 7 mm. Furthermore, the length of the long axis of the particle-containing fiber bundle is longer than the average fiber length of the fibers contained in the bundle, preferably between 3 mm and 18 mm. The ratio (length of the long axis of the particle-containing fiber bundle / average fiber length of the fibers contained in the bundle) is preferably between 1.1 and 5.0.

[0077] When used in SMC, the shape of the particle-containing fiber bundle is preferably such that the diameter of the thickest part is 2 mm to 10 mm if it is in the form of a strand. Furthermore, the length of the long axis of the particle-containing fiber bundle is longer than the average fiber length of the fibers contained in the particle-containing fiber bundle, preferably between 12 mm and 150 mm. The ratio (length of the long axis of the particle-containing fiber bundle / average fiber length of the fibers contained in the particle-containing fiber bundle) is preferably between 1.1 and 3.0.

[0078] The fibers contained in the particle-containing fiber bundle function as reinforcing material for the molded body. The number of filaments contained in the particle-containing fiber bundle can be, for example, between 8,000 and 800,000. The central part of the long axis of the particle-containing fiber bundle has more filaments than the terminal part of the long axis, which allows it to form an elongated spherical shape.

[0079] In all fibers contained in the particle-containing fiber bundle, from the viewpoint of fluidity during molding, the fiber length is preferably 60 mm or less, more preferably 40 mm or less, and even more preferably 30 mm or less, but may also be 20 mm or less or 12 mm or less. From the viewpoint of strength when used in a molded article, the fiber length contained in the particle-containing fiber bundle is preferably 1 mm or more, and more preferably 2 mm or more. The fiber bundle may not contain fibers with a fiber length of less than 1 mm, or may contain them in a content of less than 5 wt%. The above upper and lower limits can be combined in any way. For example, they may be 1 to 60 mm, 1 to 40 mm, 1 to 30 mm, 2 to 20 mm, or 2 to 12 mm.

[0080] From the viewpoint of uniform bundling, the average fiber length is preferably 1 to 80 mm, and more preferably 2 to 50 mm. When used in a fiber-reinforced resin composition (pellets) for extrusion molding, the average fiber length of the fibers is preferably 2 to 12 mm. When used in a fiber-reinforced resin composition (prepreg) for press molding, the average fiber length of the fibers is preferably 12 to 50 mm. The average fiber length is the weighted average fiber length. It is also possible to perform binarization processing on the image taken by microscopic observation using image processing software such as imageJ to calculate the fiber length. By configuring the particle-containing fiber bundle to consist only of fibers having the same fiber length, it is possible to suppress variations in the quality of the particle-containing fiber bundle between production lots. Among the plurality of fibers constituting the particle-containing fiber bundle, the difference between the maximum value and the minimum value of the fiber length is preferably within 5 mm, more preferably within 4 mm, and still more preferably within 3 mm.

[0081] The bulk density of the particle-containing fiber bundle can be, for example, 0.03 to 0.7 g / cm 3 It depends on the raw fibers used. From the perspective of the transport efficiency of the particle-containing fiber bundle, the bulk density is preferably 0.1 g / cm 3 or more, particularly preferably 0.2 g / cm 3 or more. For applications of molded articles with a low fiber content, the bulk density may be 0.1 g / cm 3 or more and less than 0.3 g / cm 3 For applications of molded articles where strength is required, the bulk density may be 0.3 g / cm 3 to 0.6 g / cm 3 In any case, since the amount that can be fed at one time can be increased, the bulk density is preferably 0.15 g / cm 3 or more, particularly preferably 0.2 g / cm 3 or more. The bulk density of the particle-containing fiber bundle is measured in accordance with JIS Z2512 and JIS R1628.

[0082] The angle of repose of the particle-containing fiber bundle is preferably 60° or less, and more preferably 50° or less. The angle of repose of the particle-containing fiber bundle can be 10° or more. For example, it may be between 10 and 60°, or between 10 and 50°. The angle of repose of a particle-containing fiber bundle can be determined by dropping a 200g fiber bundle from a height of 100mm onto a horizontally held disk of diameter φ95mm, measuring the height of the fiber bundle after 10 seconds, and using the formula θ = tan-1(T / R), where R is the radius of the disk and T is the height of the bundle.

[0083] As for the type of fiber, the fibers described above under <Fibers> can be used. In terms of specific strength and specific modulus of elasticity, the mass content of carbon fibers in the total fibers of the particle-containing fiber bundle is preferably 70% by mass or more, more preferably 70-100% by mass, and even more preferably 90-100% by mass.

[0084] The particles can be those described earlier in the section on <Particles>. By including particles, it becomes possible to impart functions derived from the particles to the molding material or molded product, and to facilitate the impregnation of the matrix resin into the fibers during the manufacturing of the molding material or during molding. The particle size distribution of the particles in the particle-containing fiber bundle can be measured by washing the particle-containing fiber bundle with a solvent that dissolves the organic binder, separating the fibers and particles by filtration or the like, and then measuring it using the method described earlier in the section on <Particles>.

[0085] The organic binder can be the one described earlier in the section on <Organic Binders>. By including an organic binder, the fibers are bound together, and the shape of the particle-containing fiber bundle can be maintained.

[0086] Furthermore, the particle-containing fiber bundle may also contain fillers such as silica, calcium silicate, alumina, calcium carbonate, talc, and barium sulfate; flame retardants such as phosphinate metal salts, aluminum hydroxide, and magnesium hydroxide; and release agents such as silicone oil, wetting and dispersing agents, defoaming agents, natural waxes, synthetic waxes, metal salts of linear fatty acids, acid amides, esters, and paraffins.

[0087] The mass content of fibers in the particle-containing fiber bundle can be, for example, 10 to 99% by mass. The volume content of fibers in the particle-containing fiber bundle can be, for example, 7 to 99% by volume. When used in pellet manufacturing, the fiber mass content in the particle-containing fiber bundle can be, for example, 80-99% by mass. When particle-containing fiber bundles are directly fed into a mold or the like for molding, the fiber mass content in the particle-containing fiber bundle can be, for example, 10 to 70% by mass.

[0088] The total mass content of particles in the particle-containing fiber bundle can be, for example, 20 to 80% by mass, and from the viewpoint of moldability and functional imparting, 30 to 70% by mass is preferred. In the case of thermoplastic resin particles or thermosetting resin particles, the amount can be 20 to 80% by mass. In the case of hardening agent particles or inorganic particles, the amount can be 1 to 70% by mass.

[0089] The mass content of the organic binder in the particle-containing fiber bundle can be, for example, 0.1 to 90% by mass, and is preferably 0.5 to 20% by mass from the viewpoint of maintaining the shape of the fiber bundle.

[0090] The mass content of liquid in the particle-containing fiber bundle can be, for example, 5% by mass or less, or 1% by mass or less, and the particle-containing fiber bundle may be dried so that it does not contain any liquid. From the viewpoint of use as a molding material, the moisture content (by mass) of the particle-containing fiber bundle is preferably 5% by mass or less, or 1% by mass or less.

[0091] The mass ratio of particles to organic binder in the particle-containing fiber bundle (mass of particles / mass of organic binder) is preferably 2.5 to 100, and more preferably 5 to 50, from the viewpoint of uniformly dispersing the particles within the particle-containing fiber bundle.

[0092] [Application] The particle-containing fiber bundles produced by the method for producing particle-containing fiber bundles described above can be used as reinforcing fibers in various fiber-reinforced resin compositions and molding materials such as prepregs (random, unidirectional), pellets, and stampable sheets. When particle-containing fiber bundles are used as an intermediate material for molding, a molded body can be formed by fusing multiple particle-containing fiber bundles together.

[0093] When organic particles are used as the matrix resin material, the organic particles can be melted to fuse adjacent particle-containing fiber bundles together. When organic particles are included as an additive, adjacent particle-containing fiber bundles can be fused together by melting or reacting an organic binder. Since the content of reinforcing fibers can be adjusted, thermoplastic resins or thermosetting resins may be added during the fusion process. For example, a molded body can be obtained by scattering multiple particle-containing fiber bundles into a mold and compression molding. The particle-containing fiber bundles can also be heated and fused together in an oven or similar device without applying pressure.

[0094] When particle-containing fiber bundles are used as the fiber material contained in pellets, pellets can be manufactured by melting and kneading multiple particle-containing fiber bundles. Examples of pellet manufacturing methods include a method of melt-kneading multiple particle-containing fiber bundles without adding other components such as resin, a method of dry-blending a thermoplastic resin and particle-containing fiber bundles and then melt-kneading them, and a method of supplying particle-containing fiber bundles to a molten thermoplastic resin and kneading them. Melt kneading is performed using an extruder such as a single-screw extruder or a twin-screw extruder. By feeding the particle-containing fiber bundles described above into a hopper attached to the extruder, it is possible to suppress fiber bridging when the particle-containing fiber bundles are fed from the hopper to the kneading zone. Particle-containing fiber bundles can also be used directly as raw materials for injection molding, similar to pellets. [Examples]

[0095] The present invention will be described in more detail below based on examples, but the present invention is not limited in any way by the following examples.

[0096] [Measurement and Evaluation Methods] The various measurement and evaluation methods were as follows:

[0097] <Particle size distribution> The particle size distribution was measured by suspending 0.1 g of particles in 10 mL of a 0.1% by mass aqueous solution of surfactant, dropping it onto a laser diffraction / scattering particle size distribution analyzer (Horiba: LA-960V2, wet measurement, aqueous solvent) so that the transmittance ranged from 65% to 95%, and irradiating it with ultrasound for 1 minute. <Surface tension> The surface tension of the bundled solution at 23°C was measured using an automated surface tensimeter (Kyowa Interface Science: CBVP-A3, plate method).

[0098] <Viscosity> The viscosity of the bundled liquid at 23°C was measured using a B-type rotational viscometer (Brookfield: LVDV-1 Pri, spindle S61) at a rotational speed of 50 rpm.

[0099] <Length of fiber bundle> Fiber bundles were placed on a white plate, and images were taken from a vertical direction opposite to the white plate. The resulting images were binarized using the image analysis software ImageJ (Wayne Rasband), and the ferret diameter of the fiber bundles was measured. The ferret diameters of 60 or more fiber bundles were averaged to determine the length of the fiber bundle.

[0100] <Standard deviation and coefficient of variation (CV) of fiber bundle length> The Ferret diameter of more than 60 fiber bundles was measured using the same method as for the length of the fiber bundles, and the mean μ and standard deviation σ of the Ferret diameter were determined. The coefficient of variation CV was calculated by dividing the standard deviation σ by the mean μ, as shown in the formula below. CV = σ / μ

[0101] [Example 1] Carbon fiber (product name: Pyrofil Chopped Fiber TR03CM, manufactured by Mitsubishi Chemical Corporation, average fiber length 3.1 mm) was used as the raw material fiber. PEEK particles (product name: Keetasspire KT-800SFP, manufactured by Solway, powder, median diameter 27.4 μm) were used as the particles. First, 350g of carbon fiber and 250g of PEEK particles were placed into a stirring granulator (product name: SP Granulator SPG25T, manufactured by Dalton, equipment volume: 25 liters, stirring blade inclination angle θ: 30°, stirring blade diameter: 396mm). Next, 480g of a bundled liquid (surface tension at 23℃: 57.7mN / m, viscosity at 23℃: 0.003Pa·s) consisting of 462g of water as the liquid and 18g of polyamide resin as the organic binder was placed into the stirring granulator and mixed for 6 minutes at a speed of 400 rpm for the stirring blade (peripheral speed of stirring blade: 8m / sec) and 3000 rpm for the chopper (peripheral speed of stirring blade: 11m / sec) to obtain a fiber bundle W1 containing liquid particles. The particle-containing fiber bundle W1 was dried in a box-type dryer at 120°C for 2 hours to obtain a particle-containing fiber bundle P1 with a fiber bundle length of 4.5 mm and an elongated spherical shape as shown in Figure 5. Table 1A shows the standard deviation and coefficient of variation CV of the fiber bundle length when 179 particle-containing fiber bundles P1 were measured. As shown in Figure 6, particles were present on the surface of the fiber bundle P1. When the particle-containing fiber bundle P1 was torn apart and the internal state was observed, particles were uniformly distributed inside the fiber bundle as shown in Figure 7.

[0102] [Example 2] Except for changing the amount of carbon fiber used to 383g and replacing the PEEK particles with PA11 particles 1 (product name: RILSAN-ES, manufactured by RLKEMA, powder, median diameter 32.9μm) 217g, a fiber bundle containing elongated spherical particles with a fiber bundle length of 5.3mm was obtained in the same manner as in Example 1. Table 1A shows the standard deviation and coefficient of variation CV of the fiber bundle length when 156 particle-containing fiber bundles P2 were measured.

[0103] [Example 3] Except for changing the amount of carbon fiber used to 369 g and replacing the PEEK particles with 231 g of PA10T particles 1 (median diameter 92.2 μm), the same procedure as in Example 1 was followed to obtain a fiber bundle P3 containing elongated spherical particles with a fiber bundle length of 4.4 mm. PA10T particles 1 were obtained by removing coarse powder from PA10T particles (product name: XecoT-XN500, manufactured by Unitika Corporation, powder, median diameter 192 μm) using a sieve with a mesh size of 250 μm (product name: electromagnetic sieve shaker A-3, manufactured by Fritsch Japan). Table 1A shows the standard deviation and coefficient of variation CV of the fiber bundle length when 153 particle-containing fiber bundles P3 were measured.

[0104] [Comparative Example 1] An amorphous particle-containing fiber bundle P4 with a fiber bundle length of 8.4 mm was obtained in the same manner as in Example 2, except that PA11 particle 1 was replaced with PA11 particle 2 (product name: RILSAN-T, manufactured by RLKEMA, powder, median diameter 111.6 μm). Table 1B shows the standard deviation and coefficient of variation CV of the fiber bundle length when 67 particle-containing fiber bundles P4 were measured.

[0105] [Comparative Example 2] An irregularly shaped particle-containing fiber bundle P5 with a fiber bundle length of 9.4 mm was obtained in the same manner as in Example 3, except that PA10T particle 1 was replaced with PA10T particle 2 (median diameter 176.3 μm). PA10T particle 2 was obtained by removing coarse powder from PA10T particles (product name: XecoT-XN500, manufactured by Unitika Corporation, powder, median diameter 192 μm) using a sieve with a mesh size of 500 μm (product name: electromagnetic sieve shaker A-3, manufactured by Fritsch Japan). Table 1B shows the standard deviation and coefficient of variation CV of the fiber bundle length when 67 particle-containing fiber bundles P5 were measured.

[0106] [Example 4] Carbon fiber (product name: Pyrofil Chopped Fiber TR03CM, manufactured by Mitsubishi Chemical Corporation, average fiber length 3.1 mm) was used as the raw material fiber. Glass beads (product name: EJ-2500, manufactured by Potters Barotini, powder, median diameter 4.9 μm) were used as the particles. First, 84g of carbon fiber and 116g of glass beads were placed into a stirring granulator (product name: Henschel Mixer FM10B, manufactured by Mitsui Miike Seisakusho Co., Ltd., device volume: 9 liters). Next, 160g of a bundled liquid (surface tension at 23°C: 57.7 mN / m, viscosity at 23°C: 0.003 Pa·s), which consisted of 154g of water as the liquid and 6g of polyamide resin as the organic binder, was placed into the stirring granulator and mixed by stirring at a speed of 1195 rpm (peripheral speed of stirring blade: 13 m / sec) for 2 minutes to obtain a fiber bundle W2 containing liquid particles. The fiber bundle W2 was dried in a box-type dryer at 120°C for 2 hours to obtain a fiber bundle P6 containing elongated spherical particles with a fiber bundle length of 11.7 mm. Table 1B shows the standard deviation and coefficient of variation CV of the fiber bundle length when 60 particle-containing fiber bundles P6 were measured.

[0107] [Example 5] Except for replacing the glass beads with glass beads (product name: J-800, manufactured by Potters Barotini, powder, median diameter 24.6 μm), a long spherical particle-containing fiber bundle P7 with a fiber bundle length of 12.2 mm was obtained in the same manner as in Example 4. Table 1B shows the standard deviation and coefficient of variation CV of the fiber bundle length when 112 particle-containing fiber bundles P7 were measured.

[0108] [Example 6] Except for replacing the glass beads with glass beads (product name: J-320, manufactured by Potters-Barotini, powder, median diameter 51 μm), the same procedure as in Example 4 was used to obtain a particle-containing fiber bundle P8 with a fiber bundle length of 12.6 mm in the shape of an elongated sphere. Table 1B shows the standard deviation and coefficient of variation CV of the fiber bundle length when 73 particle-containing fiber bundles P8 were measured.

[0109] [Examples 7-10] Except for changing the amounts of raw material fibers, particles, liquid, and organic binder used as shown in Table 1A, elongated spherical particle-containing fiber bundles P9-12 with the fiber bundle lengths shown in Table 1A were obtained in the same manner as in Example 1. Table 1A shows the standard deviation and coefficient of variation CV of the fiber bundle length when particle-containing fiber bundles P9-12 were measured.

[0110] [Table 1A]

[0111] [Table 1B]

[0112] As is clear from the results in Table 1, in Examples 1 to 10, elongated spherical particle-containing fiber bundles were obtained, and the coefficient of variation (CV), an index indicating the uniformity of fiber bundle length, was 0.19 to 0.32. In Comparative Examples 1 and 2, irregularly shaped particle-containing fiber bundles were obtained under the same stirring conditions as in Experimental Examples 1 to 3, and the CV exceeded 0.43. [Explanation of symbols]

[0113] 1. Agitation tank 2 rotation axes 3. Agitator blades 40 containers 42 Rotating shaft section 44. Agitator blades 45 Scrapers

Claims

1. A method for producing fiber bundles containing elongated spherical or strand-shaped particles, The process includes mixing multiple shortened fibers, particles with a median diameter of 100 μm or less, an organic binder, and a liquid. The aforementioned fiber includes carbon fiber, A method for producing a particle-containing fiber bundle, wherein the particles are used in an amount of 10 parts by mass or more per 100 parts by mass of the fibers.

2. The method for producing a particle-containing fiber bundle according to claim 1, wherein the median diameter of the particle is 3 μm or more.

3. The method for producing a particle-containing fiber bundle according to claim 1, wherein the solubility of the particles in the liquid is 0.01 g / 100 g or less.

4. The method for producing a particle-containing fiber bundle according to claim 1, wherein the solubility of the particles in water is 0.0001 g / 100 g or less.

5. The method for producing a particle-containing fiber bundle according to claim 4, wherein the solubility of the organic binder in water exceeds 0.001 g / 100 g.

6. A method for producing a particle-containing fiber bundle according to claim 1, wherein the particles include organic particles.

7. The method for producing a particle-containing fiber bundle according to claim 1, wherein the particles are used in an amount of 20 parts by mass or more and 80 parts by mass or less per 100 parts by mass of the fibers.

8. The method for producing a particle-containing fiber bundle according to claim 1, wherein the particles are used in an amount of 55 parts by mass or more and 75 parts by mass or less per 100 parts by mass of the fibers.

9. The method for producing a particle-containing fiber bundle according to claim 1, wherein the organic binder comprises at least one resin selected from the group consisting of polyamide resin, epoxy resin, unsaturated polyester resin, vinyl ester resin, and polyurethane resin.

10. The method for producing a particle-containing fiber bundle according to claim 6, wherein the organic particles include thermoplastic resin particles.

11. The method for producing a particle-containing fiber bundle according to claim 10, wherein the thermoplastic resin particles include at least one selected from the group consisting of polyamide resin, polyolefin resin, polyester resin, polycarbonate resin, polyethersulfone resin, polyetheretherketone resin, polyetherimide resin, and polyphenylene sulfide resin.

12. The method for producing a particle-containing fiber bundle according to claim 6, wherein the organic particles include thermosetting resin particles.

13. The method for producing a particle-containing fiber bundle according to claim 12, wherein the thermosetting resin particles include at least one selected from the group consisting of epoxy resin, vinyl ester resin, unsaturated polyester resin, cyanate ester resin, polyimide resin, maleimide resin, silicone resin, melamine resin, urea resin, alkyd resin, urethane resin, and phenolic resin.

14. The method for producing a particle-containing fiber bundle according to claim 6, wherein the organic particles include curing agent particles.

15. The method for producing a particle-containing fiber bundle according to claim 14, wherein the curing agent particles include at least one selected from the group consisting of dicyandiamides, phenols, amines, carboxylic acid anhydrides, thiols, imidazoles, phosphines, peroxides, and organometallic salts.

16. The method for producing a particle-containing fiber bundle according to claim 1, wherein the particles include inorganic particles.

17. The method for producing a particle-containing fiber bundle according to claim 16, wherein the inorganic particles include at least one selected from the group consisting of metal particles, metal oxide particles, silica particles, silicate particles, carbonate particles, sulfate particles, hydroxide particles, glass particles, ceramic particles, graphite, and carbon black.

18. The method for producing a particle-containing fiber bundle according to claim 1, wherein the particle size D90 at which the cumulative value in the volume-based particle size distribution of the aforementioned particles reaches 90% is 250 μm or less.

19. The method for producing a particle-containing fiber bundle according to claim 1, wherein the particle size D10 at which the cumulative value in the volume-based particle size distribution of the aforementioned particles reaches 10% is 50 μm or less.

20. The method for producing a particle-containing fiber bundle according to claim 1, wherein the particle size D90 at which the cumulative value in the volume-based particle size distribution of the aforementioned particles reaches 90% is 0.5 μm or larger.

21. The method for producing a particle-containing fiber bundle according to claim 1, wherein the particle size D10 at which the cumulative value in the volume-based particle size distribution of the aforementioned particles reaches 10% is 0.05 μm or larger.

22. The method for producing a particle-containing fiber bundle according to claim 1, wherein the ratio (D75 / D25) of particle size D75, which accounts for 75% of the cumulative particle size distribution based on volume of the particles, to particle size D25, which accounts for 25%, is 1 to 15.

23. A method for producing a particle-containing fiber bundle according to claim 1, wherein a fiber cotton containing the aforementioned fibers is used.

24. A method for producing a particle-containing fiber bundle according to claim 1, using a stirring granulator.

25. The method for producing particle-containing fiber bundles according to claim 24, wherein the stirring granulator is equipped with a stirring tank.

26. The method for producing a particle-containing fiber bundle according to claim 25, wherein a stirring blade is provided inside the stirring tank.

27. The method for producing a particle-containing fiber bundle according to claim 25, wherein the stirring tank is equipped with a scraper.

28. The method for producing a particle-containing fiber bundle according to claim 26, wherein the distance between the bottom surface of the stirring blade and the bottom surface of the stirring tank is 1 mm or less.

29. The method for producing a particle-containing fiber bundle according to claim 26, wherein the distance between the tip of the stirring blade and the wall surface of the stirring tank is 10 mm or more.

30. The method for producing a particle-containing fiber bundle according to claim 25, wherein the stirring tank is rotated.

31. The method for producing a particle-containing fiber bundle according to claim 1, wherein the average fiber length of the aforementioned fibers is 12 to 50 mm.

32. The method for producing a particle-containing fiber bundle according to claim 1, wherein the average fiber length of the aforementioned fibers is 2 to 12 mm.

33. The bulk density of the aforementioned fibers is 0.01 to 0.1 g / cm³. ３ The method for producing a particle-containing fiber bundle according to claim 1.

34. The method for producing a particle-containing fiber bundle according to claim 1, wherein the positions of the tips of the fibers constituting the particle-containing fiber bundle are uneven.

35. The method for producing a particle-containing fiber bundle according to claim 1, wherein the length of the particle-containing fiber bundle is longer than the average fiber length of the fibers contained in the particle-containing fiber bundle.

36. A method for producing a particle-containing fiber bundle according to claim 1, comprising mixing the particles, the organic binder, and the liquid to obtain a mixture 1, and mixing the mixture 1 and the fibers to obtain a mixture 2.

37. A method for producing a particle-containing fiber bundle according to claim 1, comprising removing the aforementioned liquid.

38. The method for producing a particle-containing fiber bundle according to claim 1, wherein 60 to 200 parts by mass of the liquid is used per 100 parts by mass of the fiber.

39. The method for producing a particle-containing fiber bundle according to claim 1, wherein the organic binder is used in an amount of 1 to 40 parts by mass per 100 parts by mass of the fiber.

40. A method for producing a particle-containing fiber bundle according to claim 1, wherein the particles and the organic binder are used such that the mass ratio of the particles to the organic binder (mass of particles / mass of organic binder) is 2.5 to 100.

41. A particle-containing fiber bundle comprising multiple shortened fibers, particles with a median diameter of 100 μm or less, and an organic binder, having an elongated spherical shape or a strand shape, The aforementioned fiber includes carbon fiber, A particle-containing fiber bundle comprising 10 parts by mass or more of the aforementioned particles per 100 parts by mass of fiber.

42. The particle-containing fiber bundle according to claim 41, wherein the aforementioned fibers are aligned.

43. The particle-containing fiber bundle according to claim 41, wherein the particles include organic particles.

44. The particle-containing fiber bundle according to claim 41, wherein the median diameter of the particles is 3 μm or more.

45. The particle-containing fiber bundle according to claim 41, wherein the average fiber length of the fibers is 12 to 50 mm.

46. The particle-containing fiber bundle according to claim 41, wherein the average fiber length of the fibers is 2 to 12 mm.

47. The particle-containing fiber bundle according to claim 41, wherein the positions of the tips of the fibers constituting the particle-containing fiber bundle are irregular.

48. The particle-containing fiber bundle according to claim 41, wherein the length of the particle-containing fiber bundle is longer than the average fiber length of the fibers contained in the particle-containing fiber bundle.

49. The particle-containing fiber bundle according to claim 41, wherein the ratio of the length of the particle-containing fiber bundle to the average fiber length of the fibers contained in the particle-containing fiber bundle (length of particle-containing fiber bundle / average fiber length of the fibers contained in the particle-containing fiber bundle) is 1.1 to 2.

5.

50. The particle-containing fiber bundle according to claim 41, wherein the mass content of the particles in the particle-containing fiber bundle is 20 to 80% by mass.

51. The particle-containing fiber bundle according to claim 41, wherein the mass content of the organic binder in the particle-containing fiber bundle is 0.5 to 20% by mass.

52. The particle-containing fiber bundle according to claim 41, wherein the mass ratio of the particles to the organic binder in the particle-containing fiber bundle (mass of particles / mass of organic binder) is 2.5 to 100.

53. The particle-containing fiber bundle according to claim 41, wherein the fiber includes recycled fiber.

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