CN117136127A

CN117136127A - Spindle-type carbon fiber aggregate and method for producing same, and carbon fiber-reinforced thermoplastic resin pellet containing regenerated carbon fibers and method for producing same

Info

Publication number: CN117136127A
Application number: CN202280025751.1A
Authority: CN
Inventors: 乳井真吾
Original assignee: Teijin Ltd
Current assignee: Teijin Ltd
Priority date: 2021-03-31
Filing date: 2022-03-28
Publication date: 2023-11-28
Also published as: JP2022170581A

Abstract

The present invention provides a carbon fiber aggregate exhibiting improved feeding properties. A method of manufacturing a fusiform aggregate, the method comprising: providing a mixture of at least carbon fibers and a binder-containing liquid; producing a spindle-shaped precursor by rotating the above mixture in a container; and drying the precursor.

Description

Spindle-type carbon fiber aggregate and method for producing same, and carbon fiber-reinforced thermoplastic resin pellet containing regenerated carbon fibers and method for producing same

Technical Field

The present disclosure relates to a spindle-shaped carbon fiber aggregate and a method for producing the same ("invention 1"). The present disclosure relates to a spindle-shaped carbon fiber aggregate excellent in feeding property and produced from regenerated carbon fibers (recycled carbon fibers) and a method for producing the same ("invention 1 a").

In addition, the present disclosure relates to spindle-shaped assemblies of thermoplastic resin fibers and carbon fibers, and methods of making the same ("invention 1 b").

In addition, the present disclosure also relates to carbon fiber reinforced thermoplastic resin particles containing regenerated carbon fibers produced using waste materials of carbon fiber reinforced resin molded products or the like ("invention 2").

Background

(regarding invention 1, invention 1a and invention 1 b)

Carbon fibers are lightweight and excellent in specific strength/specific elastic modulus, and are used as reinforcing fibers for thermosetting resins and thermoplastic resins (particularly thermoplastic resins). Carbon fiber reinforced resin composite materials (or carbon fiber reinforced plastics, CFRP) are used not only for sports/general industrial applications but also for a wide range of applications such as aerospace applications, automotive applications, and the like.

Regarding carbon fibers as a raw material of carbon fiber-containing products such as carbon fiber reinforced resin composite materials, a method of producing a granular carbon fiber aggregate from carbon fibers, a sizing agent, and the like has been studied. Such a carbon fiber aggregate can exhibit better feedability (feedability) when a carbon fiber-containing product is produced by extrusion molding or the like, compared with the case where carbon fibers are directly used.

Patent document 1 describes: a method of manufacturing carbon fiber particles by bringing an aggregate of carbon fibers bundled by a bundling agent into contact with an inclined rotating surface.

In recent years, demand for recycled carbon fibers (recycled carbon fibers) recovered from used carbon fiber-containing products and the like has increased. For such regenerated carbon fibers, a method of granulating a carbon fiber aggregate has also been studied.

Patent document 2 describes: a method of making carbon fiber particles from recycled carbon fibers using a mixer with an inclined rotating vessel.

Patent documents 3 and 4 describe: a method for manufacturing a cylindrical carbon fiber aggregate from recycled carbon fibers by wet extrusion granulation.

(invention 2)

As one embodiment of the carbon fiber reinforced resin composite material, there are carbon fiber reinforced thermoplastic resin particles. The carbon fiber-reinforced thermoplastic resin particles have the following two types: long fiber-reinforced particles produced by coating continuous carbon fibers with a thermoplastic resin and cutting the obtained resin strands; and short fiber-reinforced particles produced by kneading and dispersing discontinuous carbon fibers in a thermoplastic resin, and cutting the obtained resin strands. Although the mechanical properties of the short fiber-reinforced thermoplastic resin particles are poor relative to those of the long fiber-reinforced thermoplastic resin particles, the method is widely used as a method that can be inexpensively produced.

Patent document 5 and patent document 6 describe: a method for producing a composite body containing recycled carbon fibers from carbon fibers by melt kneading. The carbon fibers used in this method are attached with residual carbon which is carbonized as a matrix component recovered from waste materials of the carbon fiber reinforced resin composite material by a thermal decomposition method.

Patent document 7 describes a carbon fiber aggregate in which a fiber treatment agent is added to recycled carbon fibers recovered from a carbon fiber-reinforced composite material, and the carbon fiber aggregate is formed into a cylindrical shape by using an extrusion granulator, thereby improving the feeding properties.

Prior art literature

Patent literature

Patent document 1: japanese patent No. 3452363;

patent document 2: european patent application publication No. 2902433;

patent document 3: japanese patent application laid-open No. 2020-180218;

patent document 4: japanese patent application laid-open No. 2020-196882;

patent document 5: japanese patent laid-open No. 2020-49218;

patent document 6: japanese patent application laid-open No. 2019-155634;

patent document 7: japanese patent application laid-open No. 2021-55198.

Disclosure of Invention

Problem to be solved by the invention (related to invention 1)

The conventional carbon fiber aggregate may have insufficient feeding properties.

The invention 1 according to the present disclosure aims to: provided is a carbon fiber aggregate exhibiting improved feeding properties.

(invention 1 a)

The conventional carbon fiber aggregate produced using the regenerated carbon fiber may have insufficient feeding properties.

The invention 1a according to the present disclosure aims to: provided is a carbon fiber aggregate which contains regenerated carbon fibers and exhibits improved feeding properties.

(invention 1 b)

In general, when a carbon fiber-containing molded article is produced using the carbon fiber aggregate as described above, a thermoplastic resin is supplied to a kneader or the like in addition to the carbon fiber aggregate (intermediate material 1 time), and kneaded to produce pellets (intermediate material 2 times) containing carbon fibers and the thermoplastic resin. Then, the pellets are supplied to an injection molding machine or the like to produce a carbon fiber-containing molded article.

However, carbon fibers sometimes break when manufacturing 2 times of intermediate materials. In addition, if the thermoplastic resin can be added to the carbon fiber aggregate in advance, the kneading step for producing the intermediate material 2 times can be omitted, and the molded article can be produced directly using the carbon fiber and thermoplastic resin aggregate, but it is not easy to contain the thermoplastic resin in the carbon fiber aggregate while maintaining the operability of the aggregate.

The invention 1b according to the present disclosure aims to: provided are an aggregate of carbon fibers and a thermoplastic resin, which is excellent in handleability and can be used directly for producing a carbon fiber-containing molded article, and a method for producing the same.

(invention 2)

The method for decomposing the used carbon fiber-reinforced resin composite material and obtaining the regenerated carbon fiber comprises the following steps: as a method of decomposing a resin component by heat treatment (thermal decomposition method), a method of dissolving and removing the resin component by a solvent, a method of performing electric decomposition, and the like, there are listed as a method which has been widely spread conventionally: and a method of decomposing by heat treatment.

In the case of producing a short fiber reinforced thermoplastic resin pellet using the conventional regenerated carbon fiber obtained by the method of decomposition by heat treatment, it is difficult to exhibit sufficient reinforcing performance.

The invention 2 according to the present disclosure aims to: the regenerated carbon fiber reinforced thermoplastic resin particles which are obtained by the method of decomposition by heat treatment are used as raw materials and can be used for producing molded articles having excellent mechanical strength.

Means for solving the problems (invention 1)

The following means according to invention 1 of the present disclosure can solve the above-described problem according to invention 1:

< scheme 1>

A method for producing a spindle-shaped aggregate, the method comprising:

providing a mixture of at least carbon fibers and a binder-containing liquid;

producing a spindle-shaped precursor by rotating the above mixture in a container; and

the precursor is dried.

< scheme 2>

A spindle-shaped aggregate comprising carbon fibers and a binder.

(invention 1 a)

The problems described above relating to the invention 1a can be solved by the following means A1 to a13 relating to the invention 1a of the present disclosure:

< protocol A1>

A method for producing a spindle-shaped carbon fiber aggregate, comprising:

Providing a mixture of at least regenerated carbon fibers and a binder-containing liquid;

producing a spindle-shaped precursor by rotating the mixture in a vessel in a gap between an inner wall of the vessel and a rotating body in the vessel; and

the precursor is dried to obtain a dried product,

wherein the regenerated carbon fiber contains a residual carbon component, and the content of the residual carbon component is more than 0 wt% and not more than 5.0 wt% relative to the regenerated carbon fiber; and

the regenerated carbon fiber has an average length of 1mm or more and less than 30mm.

< protocol A2>

The method according to the embodiment A1, wherein the average length of the carbon fiber aggregate is 1.5mm to 60mm.

< protocol A3>

The method according to the embodiment A1 or A2, wherein the amount of the binder-containing liquid in the mixture is 20 to 60% by weight relative to the mixture.

< protocol A4>

The method according to any one of aspects A1 to A3, wherein the binder is contained in the binder-containing liquid in an amount of 0.1 to 10% by weight relative to the regenerated carbon fiber.

< protocol A5>

The method of any one of schemes A1 to A4, comprising: the regenerated carbon fiber is produced by decomposing a plastic component contained in a carbon fiber-containing plastic product by a semiconductor heat activation method.

< protocol A6>

The method according to any one of aspects A1 to A5, wherein an average length of the carbon fiber aggregate is 1.2 to 4.0 times an average length of the regenerated carbon fibers contained in the carbon fiber aggregate.

< protocol A7>

The method according to any one of aspects A1 to A6, wherein the rotating body is a stirring blade.

< protocol A8>

The method according to any one of aspects A1 to A7, wherein the precursor is produced in a container that is not tilted.

< protocol A9>

A fusiform carbon fiber assembly characterized in that: which is a carbon fiber aggregate composed of at least regenerated carbon fibers and a binder,

wherein the average length of the regenerated carbon fiber is more than 1mm and less than 30mm; and

the average length of the carbon fiber aggregate is 1.5mm to 60mm.

< protocol A10>

The carbon fiber assembly according to the aspect A9, wherein the average length of the spindle-shaped carbon fiber assembly in the longitudinal direction is 1.2 to 4.0 times the average length of the regenerated carbon fibers contained in the spindle-shaped carbon fiber assembly.

< protocol A11>

The carbon fiber assembly according to claim A9 or a10, wherein the regenerated carbon fibers contained in the spindle-shaped carbon fiber assembly are oriented in the longitudinal direction of the spindle-shaped carbon fiber assembly.

< protocol A12>

The carbon fiber assembly according to any one of aspects A9 to a11, wherein the binder is contained in an amount of 0.1 to 10% by weight relative to the spindle-shaped carbon fiber assembly.

< protocol A13>

The carbon fiber assembly according to any one of the aspects A9 to A12, wherein the regenerated carbon fiber contains a residual carbon component,

the content of the residual carbon component is more than 0% by weight and not more than 5.0% by weight relative to the regenerated carbon fiber.

(invention 1 b)

The following aspects B1 to B14 according to the invention 1B of the present disclosure can solve the above-described problems according to the invention 1B:

< protocol B1>

An aggregate, which is a spindle-shaped aggregate of thermoplastic resin fibers and carbon fibers, comprising carbon fibers, thermoplastic resin fibers and a binder,

the carbon fibers and the thermoplastic resin fibers contained in the aggregate are oriented in the longitudinal direction of the aggregate.

< protocol B2>

The aggregate according to claim B1, wherein the average length of the aggregate is 1.5mm to 60mm.

< protocol B3>

The aggregate according to claim B1 or B2, wherein the average length of the carbon fiber and the thermoplastic resin fiber is 1mm or more and less than 30mm, respectively.

< protocol B4>

The aggregate according to any one of the aspects B1 to B3, wherein an average length of the aggregate is 1.2 to 5.0 times an average length of the carbon fibers and an average length of the thermoplastic resin fibers contained in the aggregate.

< protocol B5>

The aggregate according to any one of the aspects B1 to B4, wherein the content of the binder is 0.1 to 10% by weight based on the aggregate.

< protocol B6>

The aggregate according to any one of the aspects B1 to B5, wherein the thermoplastic resin fibers are selected from the group consisting of polyolefin resin fibers, polyester resin fibers, polyamide resin fibers, polyether ketone resin fibers, polycarbonate resin fibers, phenoxy resin fibers, polyphenylene sulfide resin fibers, and mixtures thereof.

< protocol B7>

The aggregate according to any one of aspects B1 to B6, wherein the carbon fibers comprise regenerated carbon fibers.

< protocol B8>

The aggregate according to any one of aspects B1 to B7, wherein the carbon fiber is a regenerated carbon fiber.

< protocol B9>

The aggregate according to claim B7 or B8, wherein the regenerated carbon fiber contains a residual carbon component, and the residual carbon component is more than 0% by weight and not more than 5.0% by weight relative to the regenerated carbon fiber.

< protocol B10>

The method for producing an aggregate according to any one of aspects B1 to B9, comprising:

providing a mixture of at least carbon fibers, thermoplastic resin fibers and a binder-containing liquid;

the precursor is dried.

< protocol B11>

The method according to item B10, wherein the spindle-shaped precursor is produced by rotating the mixture in a container in a gap between an inner wall of the container and a rotating body in the container.

< protocol B12>

The method according to embodiment B10 or B11, wherein the carbon fibers comprise regenerated carbon fibers.

< protocol B13>

The method according to embodiment B12, wherein the carbon fiber is a regenerated carbon fiber.

< protocol B14>

The method of scheme B12 or B13, comprising: the regenerated carbon fiber is produced by decomposing a plastic component contained in a carbon fiber-containing plastic product by a semiconductor heat activation method.

(invention 2)

The following aspects C1 to C7 according to invention 2 of the present disclosure can solve the above-described problems according to invention 2:

< protocol C1>

Carbon fiber reinforced thermoplastic resin particles characterized in that: which are carbon fiber-reinforced thermoplastic resin particles comprising regenerated carbon fibers and a thermoplastic resin,

Wherein the regenerated carbon fiber has a single fiber tensile strength of 3.0GPa or more and a Weber shape factor of 6.0 or more; and

the regenerated carbon fiber contains a residual carbon component, and the content of the residual carbon component is more than 0 wt% and not more than 5.0 wt% with respect to the regenerated carbon fiber.

< protocol C2>

The carbon fiber-reinforced thermoplastic resin particles according to the aspect C1, wherein the content of the regenerated carbon fibers is 5% by weight or more and 30% by weight or less relative to the carbon fiber-reinforced thermoplastic resin particles.

< protocol C3>

The carbon fiber-reinforced thermoplastic resin particles of item C1 or C2, wherein the thermoplastic resin is selected from the group consisting of polyolefin resins, polyester resins, polyamide resins, polyether ketone resins, polycarbonate resins, phenoxy resins, and polyphenylene sulfide resins, and mixtures thereof.

< protocol C4>

The carbon fiber-reinforced thermoplastic resin particles according to any one of the aspects C1 to C3, wherein the length in the longitudinal direction is 3mm or more and 10mm or less.

< protocol C5>

The carbon fiber-reinforced thermoplastic resin particles according to any one of aspects C1 to C4, characterized in that: the regenerated carbon fibers contained in the carbon fiber-reinforced thermoplastic resin particles have a residual average fiber length of 300 μm or more.

< protocol C6>

The carbon fiber-reinforced thermoplastic resin particles according to any one of aspects C1 to C5, characterized in that: for producing a molded article having a tensile strength of 90MPa or more, a flexural strength of 140MPa or more, and a flexural modulus of 7100MPa or more.

< protocol C7>

The carbon fiber-reinforced thermoplastic resin particles according to any one of aspects C1 to C6, characterized in that: the frequency of occurrence of the single fibers of 300 μm or less in the regenerated carbon fibers in the carbon fiber-reinforced thermoplastic resin particles is 40% or less.

Effects of the invention (regarding invention 1)

According to invention 1 of the present disclosure, a carbon fiber aggregate exhibiting improved feeding properties can be provided.

(invention 1 a)

According to the invention 1a of the present disclosure, a carbon fiber aggregate containing regenerated carbon fibers and exhibiting improved feeding properties can be provided.

(invention 1 b)

According to the invention 1b of the present disclosure, an aggregate of carbon fibers and thermoplastic resins, which is excellent in handleability and can be used directly for producing molded articles containing carbon fibers, and a method for producing the same can be provided.

(invention 2)

According to invention 2 of the present disclosure, a regenerated carbon fiber-reinforced thermoplastic resin pellet which can be used for producing a molded article having excellent mechanical properties can be provided from a regenerated carbon fiber obtained by a method of decomposition by heat treatment as a raw material.

In particular, according to the carbon fiber-reinforced thermoplastic resin particles of invention 2 according to the present disclosure, a molded article having mechanical strength equivalent to that of a molded article produced from carbon fiber-reinforced thermoplastic resin particles produced from virgin carbon fibers (virgin carbon fiber) (ordinary carbon fibers other than recycled carbon fibers) as a raw material can be produced.

Drawings

Fig. 1 is a schematic diagram of 1 embodiment of an agitating granulator that may be used in the present disclosure.

Fig. 2 is a conceptual sectional view for explaining an decomposition method according to invention 2 of the present disclosure.

Fig. 3 is a schematic cross-sectional view schematically showing 1 embodiment of the decomposition method according to invention 2 of the present disclosure.

Fig. 4 is a photograph of a plurality of carbon fiber assemblies according to example A1.

FIG. 5A photograph of 1 carbon fiber aggregate according to example A1.

FIG. 6A photograph of the carbon fiber aggregate obtained in comparative example A2.

Fig. 7 is a photograph of a plurality of assemblies according to example B2.

FIG. 8A photograph of 1 aggregate according to example B2.

Fig. 9 is a photograph showing a material obtained as a result of comparative example B1.

FIG. 10 is a photograph of a CFRP sheet prior to heat treatment.

Fig. 11 is a photograph of the CFRP board after the treatment according to reference example 4.

Fig. 12 is a photograph of the CFRP board after the treatment according to the reference comparative example 2.

Detailed Description

(invention 1)

The method for manufacturing the spindle-shaped aggregate according to the invention 1 of the present disclosure includes:

providing a mixture of at least carbon fibers and a binder-containing liquid;

the precursor is dried.

In addition, the invention 1 of the present disclosure includes:

a spindle-shaped aggregate comprising carbon fibers and a binder.

The aggregate according to invention 1 of the present disclosure contains carbon fibers and a binder, and has a spindle shape. In the case where the carbon fiber-containing aggregate is spindle-shaped, contact resistance is reduced, and as a result, the flow characteristics of the carbon fiber aggregate are improved, and as a result, it is considered that the feeding property can be improved. In the present disclosure, a spindle shape means a shape in which a central portion is thicker and tapers toward both ends.

The spindle-shaped aggregate (spindle-shaped carbon fiber aggregate) according to the invention 1 of the present disclosure is particularly a spindle-shaped carbon fiber aggregate or a spindle-shaped aggregate of thermoplastic resin fibers and carbon fibers.

The aggregate according to invention 1, the method for producing the aggregate, and the constituent elements and specific embodiments thereof can be referred to the following description of inventions 1a and 1 b.

(invention 1 a)

The method for producing a carbon fiber aggregate according to invention 1a of the present disclosure is characterized by comprising the steps of:

providing a mixture of at least regenerated carbon fibers and a binder-containing liquid (providing step);

producing a spindle-shaped precursor by rotating the mixture in a vessel in a gap between an inner wall of the vessel and a rotating body in the vessel (granulating step); and

the precursor is dried (drying step),

wherein the regenerated carbon fiber contains a residual carbon component, and the content of the residual carbon component exceeds 0 wt% and is 5.0 wt% or less relative to the regenerated carbon fiber; and

the average length of the regenerated carbon fiber is more than 1mm and less than 30mm.

In general, when molding a carbon fiber-containing product, carbon fibers may be fed into an extrusion molding machine or the like using a feeder, and in particular, the carbon fibers may be quantitatively fed using a quantitative feeder. In order to stably and precisely manufacture a molded article, stable supply of carbon fibers is important.

Such feeding properties (feedability) of carbon fibers can be improved by mixing/granulating carbon fibers, a bundling agent, and the like to form a carbon fiber aggregate having a specific shape. For example, it is considered that the feeding property can be improved by forming the carbon fiber aggregate into a spindle-shaped particle shape having a small contact resistance, thereby improving the flow characteristics of the carbon fiber aggregate.

However, when such a carbon fiber aggregate is produced from regenerated carbon fibers, it is difficult to obtain a spindle-like shape excellent in feeding properties.

That is, since the regenerated carbon fiber is generally obtained by thermally decomposing a carbon fiber-reinforced resin composite material, the fiber is relatively firmly bonded to each other because the regenerated carbon fiber has a certain amount or more of residual carbon from the resin material. Without being limited by theory, it is thought that the carbon fiber aggregate having a spindle shape cannot be obtained because the binder-containing liquid cannot penetrate between the fibers because the bonded state is not easily released under the stress applied by the granulator (particularly, the rotary agitator).

In contrast, in the method of invention 1a of the present disclosure, regenerated carbon fibers having a residual carbon content of 5 wt% or less are used as a raw material of the carbon fiber aggregate. Without intending to be limited by theory, in such regenerated carbon fibers, the fibers are weakly bonded (or not bonded) to each other, and thus it is thought that the binder-containing liquid easily penetrates between the fibers under the stress applied by the granulator or the like. In this case, a spindle-shaped carbon fiber aggregate excellent in flow characteristics can be obtained.

In addition, the length of the regenerated carbon fiber as a raw material may also affect the feeding properties. That is, when the average length of the regenerated carbon fibers as a raw material is too short, it is considered that it is not easy to orient the fibers in one direction, and it is difficult to obtain a carbon fiber aggregate having a spindle shape. In addition, when the average length of the regenerated carbon fibers is too long, it is considered that the fibers are entangled with each other, and the fibers are not easily uniformly oriented.

In contrast, in the method of invention 1a of the present disclosure, the average length of the regenerated carbon fibers is 1mm or more and less than 30mm, and thus it is considered that the uniform orientation of the fibers is promoted.

As described above, according to the manufacturing method of the invention 1a of the present disclosure, a carbon fiber aggregate excellent in feeding property can be obtained. Since the carbon fiber aggregate produced by the production method according to the invention 1a of the present disclosure has a spindle-shaped particle shape having good flow characteristics, for example, in the case of being fed to a quantitative feeder, the quantitative feeder is not clogged, and stable quantitative feeding is possible.

< carbon fiber Assembly >

The spindle-shaped carbon fiber aggregate manufactured by the method according to the invention 1a of the present disclosure is an aggregate composed of at least regenerated carbon fibers and a binder. Preferably, the carbon fiber aggregate is substantially composed of regenerated carbon fibers and a binder. In the carbon fiber aggregate, the regenerated carbon fibers are bonded to each other by a binder.

The amount of the binder in the carbon fiber aggregate is preferably 0.1 to 10% by weight, and particularly may be 0.5 to 8% by weight or 1 to 6% by weight, based on the carbon fiber aggregate.

The carbon fiber aggregate obtained by the method according to invention 1a of the present disclosure has a spindle-like shape. The carbon fiber aggregate having a spindle shape exhibits good feeding properties. Without being limited by theory, it is believed that carbon fiber aggregates having a spindle shape have a small contact resistance, and thus do not clog the feeder, and can flow relatively smoothly into the feeder.

(orientation of fibers)

In the carbon fiber aggregate obtained by the method according to invention 1a of the present disclosure, the regenerated carbon fibers are preferably oriented in the long axis direction of the spindle shape. The orientation of the regenerated carbon fibers is not necessarily the same as (parallel to) the long axis direction of the carbon fiber aggregate, but is preferably substantially parallel, and more specifically, the average extending direction of the regenerated carbon fibers has an angle of 45 ° or less, 40 ° or less, 30 ° or less, 20 ° or less, 10 ° or less, 5 ° or less, 2 ° or less, 1 ° or less, 0.5 ° or less, or 0.1 ° or less with respect to the long axis direction of the carbon fiber aggregate. The average extension direction of the regenerated carbon fibers is preferably approximately 0 ° with respect to the long axis direction of the carbon fiber aggregate, and the lower limit is not particularly limited, and may be, for example, more than 0 ° or 0.01 ° or more.

The average extending direction of the fibers in the carbon fiber aggregate can be determined by using a digital camera, an optical microscope, or the like in a cross section of the carbon fiber aggregate parallel to the long axis direction.

(average Length)

The average length of the carbon fiber aggregate may be 1.5mm to 60mm. The average length of the carbon fiber aggregate is preferably 1.8mm or more, 2mm or more, 3mm or more, 4mm or more, 5mm or more, 6mm or more, 7mm or more, 8mm or more, 9mm or more, 10mm or more, 11mm or more, or 12mm or more, and/or 50mm or less, 40mm or less, 30mm or less, or 25mm or less. When the average length of the carbon fiber aggregate is within the above range, good feedability can be obtained.

The average length of the carbon fiber aggregate can be calculated by measuring the length of 50 carbon fiber aggregates in the longitudinal direction from an image obtained by visually using a caliper or the like or by using a digital camera, an optical microscope or the like, and averaging the measured values.

Preferably, the average length of the carbon fiber aggregate is 1.2 to 4.0 times the average length of the regenerated carbon fibers.

Particularly preferably, the average length of the carbon fiber aggregate is 1.4 times or more, 1.5 times or more, or 1.6 times or more, and/or 3.5 times or less, or 3.0 times or less the average length of the regenerated carbon fibers. When the average length of the carbon fiber aggregate is within the above range, particularly good feedability can be obtained.

(average maximum width of aggregate)

The average maximum width of the carbon fiber aggregate may be 0.1mm to 3.0mm. Preferably, the average length of the aggregate is 0.2mm or more, 0.3mm or more, 0.4mm or more, or 0.5mm or more and/or 2.5mm or less, 2.0mm or less, 1.8mm or less, or 1.6mm or less. The average maximum width of the carbon fiber aggregate means an average of the maximum lengths (widths) in a direction perpendicular to the longitudinal direction. When the average maximum width of the carbon fiber aggregate is within the above range, good feedability can be obtained.

The average maximum width of the carbon fiber aggregate can be calculated by measuring the maximum length in the short axis direction of 50 carbon fiber aggregates by visual observation using a caliper or the like, or by measuring the maximum length in the short axis direction of 50 carbon fiber aggregates in an image obtained by a digital camera, an optical microscope or the like, and averaging the measured values.

(aspect ratio)

The aspect ratio of the carbon fiber aggregate may be 2 to 150, 2 to 100, or 2 to 50. The aspect ratio of the carbon fiber aggregate is preferably 2 to 20 or 3 to 15, or particularly 4 to 10. When the aspect ratio is within this range (particularly preferred range), a carbon fiber aggregate having particularly excellent shape stability and feeding properties may be obtained.

The aspect ratio is a value obtained by dividing the long diameter of the spindle-shaped carbon fiber aggregate by the short diameter, that is, the long diameter/short diameter. With an increase in the elongation, the aspect ratio becomes high.

The aspect ratio can be obtained by measuring the long diameter and the short diameter of the carbon fiber aggregate visually using a caliper or the like, or by measuring the long diameter/short diameter using a digital camera or an optical microscope or the like. The length (width) that is the largest in the direction perpendicular to the longitudinal direction may be referred to as the "short diameter".

< providing procedure >

In the method according to the invention 1a of the present disclosure, a mixture composed of at least regenerated carbon fibers and a binder-containing liquid is provided.

The amount of binder-containing liquid in the mixture is preferably 20 to 60% by weight, particularly preferably 25 to 55% by weight or 30 to 50% by weight. In this case, the regenerated carbon fibers are particularly well bundled due to the liquid contained in the binder. In this case, the amount of the liquid contained in the binder is not excessive, so that the load of the drying process can be reduced. The binder-containing liquid contains a solvent or a dispersion medium. Preferably, the solvent or dispersion medium (in particular water) is present in the mixture in an amount of 20% to 60% by weight, in particular 25% to 55% by weight or 30% to 50% by weight. More preferably, the solvent or dispersion medium (especially water) is present in the mixture in an amount of 20 to 45 wt.%, 20 to 40 wt.%, or 20 to 30 wt.%. In this way, in the case where the content of the solvent or the dispersion medium (particularly water) is low, the load for drying can be particularly preferably reduced.

(regenerated carbon fiber)

The regenerated carbon fiber is a raw material for a carbon fiber aggregate, and contains a carbon fiber component and a residual carbon component. In general, in the regenerated carbon fiber, the residual carbon component adheres to the surface of the carbon fiber component.

The regenerated carbon fiber is not particularly limited, and may be, for example, a regenerated carbon fiber obtained by heat-treating a carbon fiber-containing plastic product such as Carbon Fiber Reinforced Plastic (CFRP). The regenerated carbon fiber may be the regenerated carbon fiber described later in relation to invention 2.

Particularly preferably, the regenerated carbon fiber is a regenerated carbon fiber obtained by a semiconductor heat activation method. That is, a particularly preferred embodiment of the method according to the present disclosure comprises: the regenerated carbon fiber is produced by decomposing a plastic component contained in a carbon fiber-containing plastic product by a semiconductor heat activation method.

The "semiconductor thermal activation method" (TASC method) is a method of decomposing a compound to be decomposed such as a polymer by thermal activation of a semiconductor (Thermal Activation ofSemi-conductors, TASC). For the method of producing regenerated carbon fibers by decomposing the plastic component contained in the carbon fiber-containing plastic product by the semiconductor heat activation method, for example, refer to the descriptions of japanese patent No. 4517146 and japanese patent application laid-open No. 2019-189674, and the like. The method for producing the regenerated carbon fiber by the semiconductor heat activation method can also be referred to the description of invention 2 of the present disclosure described below.

(carbon fiber component)

The carbon fiber component in the regenerated carbon fiber is generally derived from carbon fibers contained in a carbon fiber-containing product or the like as a raw material of the regenerated carbon fiber. The carbon fiber component in the regenerated carbon fiber may be modified by subjecting to heat treatment or the like in the production process of the regenerated carbon fiber.

The carbon fiber component in the regenerated carbon fiber may be, for example, PAN-based carbon fiber or pitch-based carbon fiber.

The form of the carbon fiber component in the regenerated carbon fiber is not particularly limited, and may be a form of a carbon fiber bundle composed of a plurality of monofilaments (monofilaments, filaments). The number of filaments constituting the carbon fiber bundle may be in the range of 1,000 to 80,000 or 3,000 to 50,000. The diameter of the filaments constituting the carbon fiber component in the regenerated carbon fiber may be 0.1 μm to 30 μm, 1 μm to 10 μm, or 3 μm to 8 μm.

(residual carbon component)

The residual carbon component contained in the regenerated carbon fiber is especially residual carbon from a resin contained in a carbon fiber-containing plastic product used as a raw material in manufacturing the regenerated carbon fiber.

In the method according to the invention 1a of the present disclosure, the residual carbon content is more than 0% by weight and not more than 5.0% by weight relative to the regenerated carbon fiber. In this case, a carbon fiber aggregate with improved feeding properties can be obtained.

In addition, when the residual carbon content exceeds 0% by weight and is 5.0% by weight or less, contamination due to a large amount of carbon content (particularly carbon) can be avoided, carbon content which can be a foreign substance when a carbon fiber-containing product is produced from a carbon fiber aggregate can be reduced, and uniform distribution of fibers in the carbon fiber-containing product can be improved.

Preferably, the residual carbon content is 4.0 wt% or less, 3.0 wt% or less, or 2.0 wt% or less, relative to the regenerated carbon fiber. The residual carbon content is preferably reduced as much as possible, and may be 0.1 wt% or more, 0.2 wt% or more, 0.4 wt% or more, 0.6 wt% or more, 0.8 wt% or more, 1.0 wt% or more, or 1.2 wt% or more, based on the regenerated carbon fiber.

The content of the residual carbon component in the regenerated carbon fiber can be measured by thermogravimetric analysis (TGA method).

The measurement of the residual carbon content based on thermogravimetric analysis can be performed in the following order:

(i) For 1 to 4mg sample pieces obtained by pulverizing regenerated carbon fibers, a thermogravimetric analysis was performed for a total of 300 minutes at an air supply rate of 0.2L/min, a heating rate of 5 ℃/min, and a recording rate of 1/6 seconds in a thermogravimetric analyzer, and the method comprises the steps of:

Raising the temperature from room temperature to 100℃,

Maintaining at 100deg.C for 30 min,

Heating from 100deg.C to 400deg.C, and

maintaining at 400 ℃;

(ii) In the graph of the weight reduction rate plotted against time, an inflection point of the slope was determined, and the weight reduction rate during the holding at 100 ℃ was subtracted from the value of the weight reduction rate at the inflection point, thereby calculating the residual carbon amount.

In the case where the slope inflection point cannot be specified under the above conditions, instead of the thermogravimetric analysis for 300 minutes in total, the thermogravimetric analysis for about 600 minutes in total accompanied by the holding at 400 ℃ for 480 minutes may be performed, and further, the temperature may be held at a specific temperature in the range of more than 400 ℃ and 500 ℃ or less for 480 minutes instead of the holding at 400 ℃.

In addition, in the case where the regenerated carbon fiber has a resin by a sizing treatment or the like, the residual carbon component can be measured by the above method after the resin is removed.

(average Length)

The regenerated carbon fiber has an average length of 1mm or more and less than 30 mm. The regenerated carbon fiber having a length in this range can be obtained, for example, by subjecting a regenerated carbon fiber having a long size to a cutting process. The average length of the regenerated carbon fibers may be 2mm or more, 3mm or more, or 4mm or more, and/or 29mm or less, 28mm or less, 27mm or less, 26mm or less, 25mm or less, 24mm or less, 23mm or less, 22mm or less, 21mm or less, 20mm or less, 15mm or 10mm or less. In particular, the average length of the regenerated carbon fibers may be 8mm to 25mm or 9mm to 20mm.

In a preferred embodiment of the invention 1a of the present disclosure, the average length of the regenerated carbon fibers is 2mm or more and 20mm or less, particularly 3mm or more and 15mm or less. In this case, particularly good feedability can be obtained.

In 1 embodiment of the invention 1a of the present disclosure, the average length of the regenerated carbon fiber is more than 6mm and less than 30mm, particularly 8mm or more and 25mm or less. In this case, when a carbon fiber-containing product is produced using a carbon fiber aggregate, a carbon fiber-containing product having particularly excellent physical properties such as strength may be obtained.

The average length of the regenerated carbon fibers can be calculated by measuring the lengths of 50 regenerated carbon fibers visually using a caliper or the like or in an image obtained by a digital camera, an optical microscope or the like, and averaging the measured values.

(adhesive-containing liquid)

The binder-containing liquid is a binder dispersion or binder solution containing a binder and a solvent or dispersion medium.

(adhesive)

The binder has a function of bundling the regenerated carbon fibers in the carbon fiber aggregate and maintaining the shape of the carbon fiber aggregate. The binder is not particularly limited, and is preferably a thermoplastic resin or a thermosetting resin. More specifically, as the binder, there may be mentioned: epoxy resin, urethane-modified epoxy resin, polyester resin, phenolic resin, polyamide resin, polyurethane resin, polycarbonate resin, polyetherimide resin, polyamideimide resin, polyimide resin, bismaleimide resin, polysulfone resin, polyethersulfone resin, epoxy-modified urethane resin, polyvinyl alcohol resin, polyvinylpyrrolidone resin. These resins may be used singly or in combination of 2 or more.

Further, as the binder, there may be mentioned: bentonite, lignosulfonate, molasses, carboxymethyl cellulose, konjaku flour, sodium alginate, polyacrylamide, polyvinyl acetate, polyvinyl alcohol and starch. These may be used alone or in combination of 2 or more kinds, and may be used in combination with the above-mentioned resins.

(solvent, dispersion Medium)

The solvent or dispersion medium is not particularly limited as long as it is a liquid in which the binder is soluble or dispersible. As the solvent or dispersion medium, there may be mentioned: water, alcohols (e.g., methanol or ethanol), ketones (e.g., butanone or acetone), hydrocarbons (e.g., cyclohexane, toluene or xylene), halogenated hydrocarbons (e.g., methylene chloride), amides (e.g., N-methylpyrrolidone or dimethylformamide), ethers (e.g., tetrahydrofuran). The solvent or dispersion medium is particularly preferably water.

The binder-containing liquid used in the present disclosure can be prepared, for example, by further adding a solvent or a dispersion medium to a commercially available sizing agent having a relatively high concentration composed of a binder and a solvent or a dispersion medium. In particular, the binder-containing liquid can be prepared by adding a dispersion medium (in particular, water) to a sizing agent having a binder and a dispersion medium (in particular, water).

The sizing agent (and the binder-containing liquid obtained by adding a solvent or a dispersion medium to the sizing agent) may be, for example, in the form of an aqueous emulsion in which the binder is dispersed in water, and in particular, may be an aqueous polyurethane.

The concentration of the binder in the sizing agent is not particularly limited, and may be, for example, 10 to 80 wt%, 20 to 60 wt%, or 30 to 50 wt%.

The amount of the binder may be 0.1 wt% or more, 0.5 wt% or more, 1 wt% or more, or 1.5 wt% or more, and/or 20 wt% or less, 15 wt% or less, 10 wt% or less, 8 wt% or 7 wt% or less, with respect to the binder-containing liquid. The amount of binder is particularly preferably 1 to 10% by weight or 2 to 8% by weight relative to the binder-containing liquid. The amount of the solvent or the dispersion medium (particularly water) may be 80 wt% or more, 85 wt% or more, 90 wt% or more, 92 wt% or more, or 93 wt% or more, and/or 99.9 wt% or less, 99.5 wt% or less, 99 wt% or less, or 98.5 wt% or less, with respect to the binder-containing liquid.

The amount of the binder is preferably 0.1 to 10 wt%, particularly preferably 0.5 to 8 wt%, or 1 to 7 wt% based on the regenerated carbon fiber.

(open fiber)

The regenerated carbon fiber may be subjected to a fiber-opening treatment in advance. By performing the opening treatment, entanglement of fibers with each other is eliminated, and the fibers may be sometimes promoted to be oriented in one direction with each other in the granulation process.

The method of the opening treatment is not particularly limited, and may be performed by, for example, rotating a blade. The rotating blades for opening the fibers may be auxiliary blades provided in the granulator.

The fiber-opening treatment may be performed by stirring at a high speed.

(mixing)

The method for obtaining the mixture from the regenerated carbon fiber and the binder-containing liquid is not particularly limited. The regenerated carbon fiber and the binder-containing liquid may be fed as a mixture into a vessel used in the granulation process. For example, a binder-containing liquid may be injected into a block of regenerated carbon fibers, and the mixture may be obtained by stirring at will, and the mixture may be put into a container. Alternatively, the regenerated carbon fiber and the binder-containing liquid may be separately put into a container, and mixed in the container to prepare a mixture. Mixing and granulating may be performed simultaneously.

The regenerated carbon fibers and binder-containing liquid in the mixture need not necessarily be uniformly distributed within the mixture. The mixture may be stirred during the pelletization process to improve uniformity.

< granulating Process >

In the method according to the present disclosure, a spindle-shaped precursor is produced by rotating the mixture in a vessel in a gap between an inner wall of the vessel and a rotating body in the vessel (hereinafter, this treatment is also sometimes referred to as "granulation treatment").

Without being bound by theory, it is believed that by rotating the mixture comprising regenerated carbon fibers and the binder-containing liquid in the gap between the inner wall of the container and the rotating body within the container, the fibers are oriented in a specific direction while being bonded to each other via the binder, and as a result, a precursor having a spindle shape can be obtained.

The method for rotating the mixture in the gap between the inner wall of the container and the rotating body in the container is not particularly limited. An example method for this is described below with reference to fig. 1.

Fig. 1 is a schematic illustration of 1 embodiment of an agitating granulator that may be used in the present disclosure. The mixer granulator 100 of fig. 1 has a cylindrical container part 120 as a container and a stirring blade 140 as a rotating body. The mixer granulator 100 of fig. 1 is horizontal, and in a normal use state, the opening of the container 120 is opened laterally. Fig. 1 is a view from a point of view looking into the interior of the container portion. A shaft 160 is attached to an inner wall (a wall on the back side from the viewpoint) of the container 120 facing the opening. The shaft portion 160 extends in the horizontal direction. The stirring blade 140 is rotatable about the shaft 160 (in the example of fig. 1, the rotation may be counterclockwise ("a"), but may be clockwise). That is, the stirring blade 140 in fig. 1 is configured to rotate in a plane parallel to the gravitational direction. Although not shown in fig. 1, an auxiliary blade for opening the fibers may be provided in the container portion 120.

In the granulation process, the mixture containing the regenerated carbon fiber and the binder-containing liquid is optionally mixed/stirred by the stirring blade 140 rotating in the container part 120, and is rotated in a gap (denoted by symbol "C" in fig. 1) between the inner wall of the container part 120 and the stirring blade 140 in the container part 120.

The granulation process may be performed at ambient temperature or with heat. The granulation treatment may be carried out, for example, for 1 minute to 1 hour, 5 minutes to 20 minutes, or 8 minutes to 15 minutes.

(Container)

The container of the present disclosure is not particularly limited as long as the mixture can be held therein and the mixture is suitably subjected to the above-described granulation treatment. The container is preferably made of a material excellent in rigidity and durability. In particular, the inner wall of the container is preferably made of a material that does not wear or the like during rotation of the mixture, or is surface-treated for this purpose.

In 1 embodiment of the disclosure, the container is not tilted, and is substantially parallel to the horizontal direction. For example, the portion of the inner wall of the container located below in the gravitational direction may not be inclined and may be substantially parallel to the horizontal direction.

(rotating body)

The rotating body is configured such that the mixture containing the regenerated carbon fiber and the binder-containing liquid can be rotated between the rotating body itself and the inner wall of the container by rotating in the container. The rotating body is attached to a shaft portion provided in the container, for example, and is configured to be rotatable about the shaft portion.

The rotating body preferably has a blade (root) shape. The rotating body is particularly preferably a stirring blade (stirring plume). The stirring blade is preferably made of a material excellent in rigidity and durability, and particularly preferably made of a material which does not cause abrasion or the like during rotation of the mixture, or is subjected to surface treatment for this purpose.

(gap)

The size of the gap between the inner wall of the container and the rotating body, i.e. the distance between the inner wall of the container and the rotating body, may be constant or of various values, continuous or discontinuous.

The size of the gap between the inner wall of the container and the rotating body in the container, that is, the distance between the inner wall of the container and the rotating body may be appropriately set according to the desired size of the carbon fiber aggregate or the like, and may be, for example, 1 to 10mm.

(stirring granulator)

As the apparatus having the container and the rotating body described above, a known stirring granulator can be used. The stirring granulator is not particularly limited, and for example, a henschel granulator (henschel mixer), a Bagmill granulator, or an Eirich stirring granulator may be used. The mixer granulator may be used in either of a vertical type and a horizontal type.

(spindle-shaped precursor)

The spindle precursor contains regenerated carbon fibers and a binder, and contains a liquid (particularly water) from the binder-containing liquid. The liquid (particularly, moisture) in the precursor may be removed by a drying process described below.

< drying Process >

In the methods according to the present disclosure, the resulting spindle precursor is dried.

The method for drying the precursor is not particularly limited, and the temperature conditions, time conditions, and the like may be appropriately determined according to the moisture content and the like of the obtained precursor. In order to reduce the drying load, the spindle-shaped precursor may be dehydrated after the granulation step and before the drying step.

Carbon fiber aggregate

The invention 1a of the present disclosure includes the following carbon fiber aggregate:

the average length of the carbon fiber aggregate is 1.5mm to 60mm.

The carbon fiber aggregate exhibits particularly good feeding properties due to its shape. The method for producing the carbon fiber aggregate is not particularly limited. The carbon fiber aggregate according to the invention 1a of the present disclosure can be produced by the method described above according to the present disclosure, for example. For each constituent element of the carbon fiber aggregate, the above description of the method for producing the carbon fiber aggregate can be referred to.

< bulk Density >

The carbon fiber aggregate according to the invention 1a of the present disclosure preferably has a bulk density of 50g/L or more, 75g/L or more, or 100g/L or more, and/or 500g/L or less, 400g/L or more, 300g/L or less, or 200g/L or less.

Bulk density can be measured as follows:

the sample was poured from a height of 63mm into a 200ml container having an inner diameter of 63mm using a funnel having an inner diameter of 18mm at the outlet, and filled to a full state. The weight of the sample at the shredding capacity is then determined. The bulk density was calculated from the weight and the volume of the container.

(invention 1 b)

The thermoplastic resin fibers and the spindle-shaped aggregate of carbon fibers according to invention 1b of the present disclosure include carbon fibers, thermoplastic resin fibers, and a binder,

wherein the carbon fibers and the thermoplastic resin fibers contained in the aggregate are oriented in the long axis direction of the aggregate.

The aggregate according to the invention 1b of the present disclosure contains thermoplastic resin fibers, that is, fibrous thermoplastic resins. Without being limited by theory, it is thought that the thermoplastic resin is fibrous, and the carbon fibers and the thermoplastic fibers are easily aligned in a predetermined direction, and as a result, are easily concentrated into a granular aggregate, and further, are in a spindle shape. When the aggregate is granular, the operability is improved, for example, when a molded article containing carbon fibers is produced using the aggregate. In addition, it is considered that an aggregate having a spindle shape has particularly good feeding properties (feedability) when a carbon fiber-containing product is produced using the aggregate. Without being limited by theory, it is believed that the aggregate having a spindle shape has a small contact resistance, and therefore does not clog the supply port of the extruder or the like, and can flow into the supply port relatively smoothly.

Further, since the aggregate according to the invention 1b of the present disclosure has thermoplastic resin fibers in addition to carbon fibers, unlike the conventional carbon fiber aggregate including only carbon fibers, the step of kneading the carbon fiber aggregate and the thermoplastic resin to produce pellets can be omitted, and the production of molded articles containing carbon fibers can be directly performed.

Further, according to the aggregate according to the invention 1b of the present disclosure, the step of producing particles, which is required in the case of the conventional carbon fiber aggregate, can be omitted, and therefore breakage of carbon fibers at the time of producing particles can be avoided. Accordingly, it is considered that a molded article having improved physical properties can be obtained by producing a molded article containing carbon fibers using the aggregate according to the present disclosure.

The invention according to the invention 1b of the present disclosure will be described in detail below.

< aggregate of thermoplastic resin fiber and carbon fiber >

The aggregate of the thermoplastic resin fibers and the carbon fibers according to the invention 1b of the present disclosure is spindle-shaped,

comprises carbon fiber, thermoplastic resin fiber and adhesive,

the carbon fibers and the thermoplastic resin fibers contained in the aggregate are oriented in the long axis direction of the aggregate.

The aggregate according to invention 1b of the present disclosure includes carbon fibers, thermoplastic resin fibers, and a binder. In the aggregate, fiber components composed of carbon fibers and thermoplastic resin are bonded to each other by a binder. The aggregate is preferably substantially composed of carbon fibers, thermoplastic resin fibers, and a binder, and particularly preferably composed of these constituent elements.

The amount of the binder in the aggregate is preferably 0.1 to 10 wt%, particularly 0.5 to 9 wt%, or 1 to 8 wt% with respect to the aggregate.

The aggregate may contain 1 to 1000 parts by weight, 5 to 900 parts by weight, 10 to 750 parts by weight, 20 to 500 parts by weight, or 50 to 250 parts by weight of thermoplastic resin fibers with respect to 100 parts by weight of carbon fibers.

The aggregate according to the present disclosure has a spindle shape. As described above, the spindle shape refers to a shape in which the central portion is thicker and tapers toward both ends.

(orientation of fibers)

In the aggregate according to the invention 1b of the present disclosure, the fiber components (carbon fibers and thermoplastic resin fibers) contained in the aggregate are oriented in the long axis direction of the spindle shape. In the case where the aggregate is a deformed spindle (for example, a curved spindle), the term "the fibers are oriented in the long axis direction of the spindle" means that the fibers contained in the aggregate are oriented along the axis of the deformed spindle. The orientation of the fibers need not necessarily be the same (parallel) as the long axis direction of the aggregate, and is preferably substantially parallel, and more specifically, the average direction of extension of the fibers has an angle of 45 ° or less, 40 ° or less, 30 ° or less, 20 ° or less, or 10 ° or less with respect to the long axis direction of the spindle-shaped aggregate. The average extension direction of the fibers is preferably approximately 0 ° with respect to the long axis direction of the spindle-shaped aggregate, and the lower limit is not particularly limited, and may be, for example, more than 0 °, 1 ° or more, or 2 ° or more.

The average extending direction of the fibers in the long axis direction of the aggregate can be determined by calculating an average value from the measured values of the randomly selected fibers n=30 in a cross section of the aggregate parallel to the long axis direction using a digital camera, an optical microscope, or the like. In this calculation, the fluffed fibers (fibers partially distant from the aggregate) were not included.

The average extending direction of the fibers in the long axis direction of the aggregate may be determined by calculating an average value from the measured values of the randomly selected fibers of n=30 on the surface of the aggregate, using a digital camera, an optical microscope, or the like. In this case, the fiber is not formed (partially away from the aggregate) by fluffing.

In the case where the aggregate is in a deformed spindle shape (for example, a bent spindle shape), the orientation of the fibers and the extending direction of the fibers may be determined with respect to the axis of the aggregate. The length and aspect ratio of the aggregate may be similarly determined.

(average Length of aggregate)

The average length of the aggregate according to invention 1b of the present disclosure may be 1.5mm to 60mm. Preferably, the average length of the aggregate is 1.8mm or more, 2.0mm or more, 3.0mm or more, 4.0mm or more, 5.0mm or more, 6.0mm or more, 7.0mm or more, 8.0mm or more, 9.0mm or more, 10mm or more, 11mm or more, 12mm or more, or 15mm or more, and/or 50mm or less, 40mm or less, 30mm or less, or 25mm or less. When the average length of the aggregate is within the above range, particularly good feedability is considered to be obtained.

The average length of the aggregate can be calculated by measuring the length of 50 aggregates in the longitudinal direction by visual observation using a caliper or the like, or by measuring the length of 50 aggregates in the longitudinal direction in an image obtained by a digital camera, an optical microscope, or the like, and averaging the measured values.

Preferably, the average length of the aggregate is 1.2 to 5.0 times the average length of the carbon fibers and the average length of the thermoplastic resin fibers contained in the aggregate. When the average length of the aggregate is within the above range, particularly good feedability may be obtained.

Particularly preferably, the average length of the aggregate is 1.4 times or more, 1.5 times or more, or 1.6 times or more, and/or 4.5 times or less, 4.0 times or less, 3.5 times or less, 3.0 times or less, or 2.5 times or less the average length of the carbon fibers and the average length of the thermoplastic resin fibers. When the average length of the aggregate is within the above range, particularly good feedability may be obtained.

The average length of the carbon fibers and the average length of the thermoplastic resin fibers can be calculated by measuring the lengths of 50 fibers by visual observation using calipers or the like, or in an image obtained by a digital camera, an optical microscope or the like, and averaging the measured values.

(average maximum width of aggregate)

The average maximum width of the carbon fiber aggregate may be 0.1mm to 5.0mm. Preferably, the average length of the aggregate is 0.2mm or more, 0.3mm or more, 0.4mm or more, 0.5mm or more, 1.0mm or more, 1.5mm or more, or 2.0mm or more, and/or 4.5mm or less, or 4.0mm or less. The average maximum width of the carbon fiber aggregate is an average of the maximum lengths (widths) in the direction perpendicular to the longitudinal direction. When the average maximum width of the carbon fiber aggregate is within the above range, good feedability can be obtained.

(aspect ratio)

The carbon fiber aggregate may have an aspect ratio of 2 to 150, 2 to 100, or 2 to 50. The aspect ratio of the aggregate is preferably 2 to 20, 3 to 15, or 4 to 10. When the aspect ratio is within this range (particularly, the preferred range), an aggregate having particularly excellent shape stability and feeding properties may be obtained.

The aspect ratio is a value obtained by dividing the long diameter of the spindle-shaped aggregate by the short diameter, that is, the long diameter/short diameter. As the degree of elongation increases, the aspect ratio becomes higher.

The aspect ratio can be obtained by measuring the long diameter and the short diameter of the aggregate visually using a caliper or the like, or by measuring the long diameter and the short diameter of the aggregate using a digital camera, an optical microscope, or the like, and calculating the long diameter/the short diameter. The maximum length (width) in the direction perpendicular to the longitudinal direction may be referred to as "short diameter".

The method for producing the aggregate according to invention 1b of the present disclosure is not particularly limited. The aggregate according to the invention 1b of the present disclosure can be manufactured by, for example, a method according to the invention 1b of the present disclosure described below.

< bulk Density >

The aggregate according to invention 1b of the present disclosure preferably has a bulk density of 50g/L or more, 75g/L or more, or 100g/L or more, and/or 500g/L or less, 400g/L or less, 300g/L or less, or 200g/L or less.

The method for measuring the bulk density can be referred to the above description of invention 1 a.

(carbon fiber)

Carbon fibers are raw materials for an aggregate, and examples thereof include: common carbon fibers (carbon fibers other than regenerated carbon fibers, so-called virgin carbon fibers), regenerated carbon fibers, and mixtures thereof. The carbon fibers may be PAN-based carbon fibers or pitch-based carbon fibers, for example.

The form of the carbon fiber is not particularly limited, and may be a form of a carbon fiber bundle composed of a plurality of monofilaments (monofilaments, filaments). The number of filaments constituting the carbon fiber bundle may be in the range of 1,000 to 80,000, or 3,000 to 50,000. The filaments constituting the carbon fibers may have a diameter of 0.1 μm to 30 μm, 1 μm to 10 μm, or 3 μm to 8 μm.

(regenerated carbon fiber)

The regenerated carbon fiber (recycled carbon fiber) includes a carbon fiber component and a carbon component other than the carbon fiber component (in particular, a residual carbon component). In general, in the regenerated carbon fiber, carbon components other than the carbon fiber component are attached to the surface of the carbon fiber component.

Particularly preferably, the regenerated carbon fiber is a regenerated carbon fiber obtained by a semiconductor heat activation method. Particularly preferred embodiments of the following methods according to the present disclosure include: the regenerated carbon fiber is produced by decomposing a plastic component contained in a carbon fiber-containing plastic product by a semiconductor heat activation method.

The "semiconductor thermal activation method" (TASC method) can be referred to the above description of invention 1 a.

The carbon fiber component in the regenerated carbon fiber may be modified by subjecting to heat treatment or the like in the production process of the regenerated carbon fiber. For details of the carbon fiber component in the regenerated carbon fiber, reference may be made to the description of the carbon fiber.

The residual carbon component in the regenerated carbon fiber is generally derived from a resin contained in a carbon fiber-containing plastic product used as a raw material in manufacturing the regenerated carbon fiber. In general, in the heat treatment of a carbon fiber-containing plastic product, the plastic component is thermally decomposed, and residual carbon remains on the surface of the carbon fiber component.

In the present disclosure, the residual carbon content is preferably more than 0% by weight and 5.0% by weight or less with respect to the regenerated carbon fiber. In this case, an aggregate with improved feeding properties may be obtained.

In addition, when the residual carbon content exceeds 0% by weight and is 5.0% by weight or less, contamination due to a large amount of carbon content (particularly carbon) can be avoided, and carbon content which can be a foreign substance can be reduced when a carbon fiber-containing product or the like is produced from the aggregate as a material. In addition, the uniform distribution of fibers in the carbon fiber-containing product can be improved.

Preferably, the residual carbon content is 4.0 wt% or less, 3.0 wt% or less, or 2.0 wt% or less, relative to the regenerated carbon fiber. The residual carbon content is preferably reduced as much as possible, and may be 0.1 wt% or more, 0.2 wt% or more, 0.4 wt% or more, 0.6 wt% or more, 0.8 wt% or more, 1.0 wt% or more, or 1.2 wt% or more, based on the carbon fiber.

The method for measuring the residual carbon content by thermogravimetric analysis can be referred to the above description of invention 1 a.

(thermoplastic resin fiber)

As the thermoplastic resin fiber, there may be mentioned: polyolefin resin fibers (e.g., polypropylene resin fibers and polyethylene), polyester resin fibers (e.g., polyethylene terephthalate resin fibers, polybutylene terephthalate resin fibers and polylactic acid), polyamide resin fibers, polyetherketone resin fibers, polycarbonate resin fibers, phenoxy resin fibers, and polyphenylene sulfide resin fibers. The thermoplastic resin fibers may be 1 type only, or a mixture of 2 or more types of thermoplastic resin fibers.

(average length of fiber)

The carbon fibers may have an average length of 1mm or more and less than 30 mm. Fibers having a length in this range can be obtained, for example, by subjecting fibers having a longer size to a cutting process. The average length of the carbon fibers may be 2mm or more, 3mm or more, or 4mm or more, and/or may be 29mm or less, 28mm or less, 27mm or less, 26mm or less, 25mm or less, 24mm or less, 23mm or less, 22mm or less, 21mm or less, 20mm or less, 15mm or 10mm or less, respectively. In particular, the average length of the carbon fibers may be 8mm to 25mm, or 9mm to 20mm.

In a preferred embodiment according to invention 1b of the present disclosure, the average length of the carbon fibers is 2mm or more and 20mm or less, particularly 3mm or more and 15mm or less. In this case, particularly good feedability can be obtained.

In 1 embodiment of the invention 1b of the present disclosure, the average length of the carbon fibers is more than 6mm and less than 30mm, particularly 8mm or more and 25mm or less. In this case, when a carbon fiber-containing product is produced using the aggregate according to the present disclosure, a carbon fiber-containing product having particularly excellent physical properties such as strength may be obtained.

The thermoplastic resin fibers may have an average length of 1mm or more and less than 30 mm. Fibers having a length in this range can be obtained, for example, by subjecting fibers having a longer size to a cutting process. The average length of the thermoplastic resin fibers may be 1.5mm or more, 2mm or more, or 3mm or more, and/or may be 28mm or less, 26mm or less, 24mm or less, 22mm or less, 20mm or less, 18mm or less, 16mm or less, 14mm or less, 12mm or less, 10mm or 8mm or less, respectively.

When the average length of the carbon fibers and the thermoplastic resin fibers is 1mm or more and less than 30mm, it is considered that uniform orientation of the fibers is promoted, and a spindle-shaped aggregate having particularly good feeding properties can be obtained. Without being limited by theory, it is believed that the average length of the fibers as the raw material is long enough to allow the fibers to be easily oriented in one direction with respect to each other, resulting in a spindle-shaped aggregate. In addition, since the average length of the fibers is sufficiently short, the fibers are prevented from intertwining with each other, and as a result, it is considered that uniform orientation of the fibers is promoted.

The average lengths of the carbon fiber and the thermoplastic resin fiber can be calculated by measuring the lengths of 50 fibers by visual observation using a caliper or the like, or in an image obtained by a digital camera, an optical microscope or the like, and averaging the measured values.

Method for producing aggregate

The invention 1b of the present disclosure includes a method for producing an aggregate according to the invention 1b of the present disclosure, the method including:

providing a mixture of at least carbon fibers, thermoplastic resin fibers and a binder-containing liquid (providing step);

producing spindle-shaped precursors by rotating the mixture in a container (pelletization process); and

the precursor is dried (drying step).

The above description of the aggregate according to the invention 1b of the present disclosure can be referred to for each component related to the above manufacturing method.

< providing procedure >

In the method according to the invention 1b of the present disclosure, a mixture composed of at least carbon fibers, thermoplastic resin fibers, and a binder-containing liquid is provided. The mixture is composed in particular of carbon fibers, thermoplastic resin fibers and a binder-containing solution.

The amount of binder-containing liquid in the mixture is preferably 20 to 70 wt%, particularly preferably 25 to 60 wt%, or 30 to 50 wt%. In this case, the fibers are particularly well bundled due to the liquid contained in the binder. In this case, the amount of the liquid contained in the binder is not excessive, so that the load of the drying process can be reduced. The binder-containing liquid contains a solvent or a dispersion medium. Preferably, the solvent or dispersion medium (in particular water) is present in the mixture in an amount of 20% to 70% by weight, in particular 25% to 60% by weight, or 30% to 50% by weight. More preferably, the solvent or dispersion medium (especially water) is present in the mixture in an amount of 20 to 45 wt.%, 20 to 40 wt.%, or 20 to 30 wt.%. In this way, in the case where the content of the solvent or the dispersion medium (particularly, water) is low, the load for drying can be reduced particularly effectively.

The amounts of carbon fibers and thermoplastic resin fibers in the mixture may be appropriately set so that the weight ratio of these fibers in the resulting aggregate is a desired value. In particular, the carbon fiber and thermoplastic resin fiber may be contained in the mixture in an amount of 2.5 to 80 wt%, 5 to 70 wt%, or 10 to 60 wt%, respectively.

(adhesive-containing liquid)

The binder-containing liquid and its components can be referred to the above description of invention 1 a.

The amount of the binder may be 0.5 wt% or more, 1 wt% or more, 1.5 wt% or more, 2.0 wt% or more, or 3.0 wt% or less, and/or may be 20 wt% or less, 15 wt% or less, 10 wt% or less, 9 wt% or less, or 8 wt% or less, with respect to the binder-containing liquid. Particularly preferably, the amount of binder is 1 to 10 wt.%, or 2 to 8 wt.%, relative to the binder-containing liquid. The amount of the solvent or the dispersion medium may be 80 wt% or more, 85 wt% or more, 90 wt% or more, 92 wt% or more, or 93 wt% or more with respect to the binder-containing liquid, and/or may be 99.9 wt% or less, 99.5 wt% or less, 99 wt% or less, or 98.5 wt% or less.

The amount of the binder is preferably 0.1 to 10 wt%, particularly preferably 0.5 to 9.0 wt%, 1.0 to 8.0 wt%, or 2.0 to 7.0 wt%, based on the total amount of the carbon fibers and the thermoplastic resin fibers.

(open fiber)

The fiber component, particularly the carbon fiber, may be subjected to a fiber opening treatment in advance. For the fiber opening treatment, the above description of the invention 1a can be referred to.

(mixing)

The method for obtaining the mixture from the carbon fiber, the thermoplastic resin fiber and the binder-containing liquid is not particularly limited. The carbon fiber, the thermoplastic resin fiber and the binder-containing liquid may be fed as a mixture into a container used in the granulation step. For example, a binder-containing liquid may be poured into a block of carbon fibers and thermoplastic resin fibers, and the mixture may be obtained by stirring at will, and the mixture may be poured into a container. Alternatively, the carbon fiber, the thermoplastic resin fiber and the binder-containing liquid may be separately put into a container, and mixed in the container to prepare a mixture. Mixing and granulating may be performed simultaneously.

The carbon fibers, thermoplastic resin fibers, and binder-containing liquid in the mixture need not be uniformly distributed within the mixture. The mixture may be stirred during the pelletization process to improve uniformity.

< granulating Process >

In the method according to the invention 1b of the present disclosure, a spindle-shaped precursor is produced by rotating the mixture in a container (hereinafter, this treatment may be also referred to as "granulation treatment").

The method of rotating the mixture in the container is not particularly limited, and a known method (particularly a known granulating method) can be employed.

In particular, the spindle-shaped precursor is produced by rotating the mixture in the vessel in a gap between the inner wall of the vessel and the rotating body within the vessel. Without being limited by theory, it is thought that by rotating the mixture comprising the carbon fiber and the thermoplastic resin fiber and the binder-containing liquid in the gap between the inner wall of the container and the rotating body in the container, the fibers are oriented in a specific direction while being bonded to each other via the binder, and as a result, a precursor having a spindle shape can be obtained particularly effectively.

The method for rotating the mixture in the gap between the inner wall of the container and the rotating body in the container is not particularly limited. In this method, the mixture contains carbon fibers, thermoplastic resin fibers, and a binder-containing liquid, and the above description of the invention 1a is referred to.

(spindle-shaped precursor)

The spindle-shaped precursor contains carbon fibers and thermoplastic resin fibers and a binder, and contains a liquid (particularly water) from a binder-containing liquid. The liquid (particularly, moisture) in the precursor may be removed by the following drying process.

< drying Process >

(invention 2)

The carbon fiber-reinforced thermoplastic resin particles according to invention 2 of the present disclosure are characterized in that: comprises regenerated carbon fiber and thermoplastic resin,

the regenerated carbon fiber has a single fiber tensile strength of more than 3.0GPa and a Weber shape factor of more than 6.0; and

the carbon fiber contains a residual carbon component, and the content of the residual carbon component is more than 0 wt% and not more than 5.0 wt% relative to the regenerated carbon fiber.

Generally, carbon fiber-reinforced thermoplastic resin pellets are obtained by melt-kneading a thermoplastic resin and carbon fibers using a twin-screw extruder or the like, but in some cases, the carbon fibers are pulverized in an extruder in order to carry out kneading with high shear. If the average fiber length of the carbon fibers in the obtained particles is less than 300. Mu.m, the mechanical property-enhancing effect is reduced.

Without being bound by theory, it is believed that the regenerated carbon fiber according to invention 2 of the present disclosure has a high weibull shape factor at the tensile strength of the single fiber, and therefore the variation in tensile strength is small, and even when compared with a normal, unused carbon fiber having the same tensile strength, the single fiber having a low tensile strength is small, and therefore the breakage of the single fiber of the regenerated carbon fiber is comparatively suppressed.

In general, when the variation in tensile strength of the carbon fibers fed into the extruder is large, the low-strength fibers are pulverized to be finer, and therefore, the proportion of carbon fibers of 300 μm or less remaining in the pellets is relatively large. On the other hand, as described above, since the regenerated carbon fiber of the invention 2 of the present disclosure has a high weibull shape factor and a small variation in tensile strength, the proportion of fibers pulverized to 300 μm or less is reduced, and as a result, it is considered that a great mechanical property enhancing effect is obtained.

In particular, as a supply source of regenerated carbon fibers in producing the particles according to invention 2 of the present disclosure, a carbon fiber aggregate can be used. The carbon fiber aggregate includes regenerated carbon fibers and a binder. For example, refer to Japanese patent No. 3452363 and Japanese patent application laid-open No. 2020-180218 for the production method thereof. A particularly preferred embodiment of the method according to the present disclosure is a spindle-shaped carbon fiber aggregate. The method for obtaining the fusiform carbon fiber aggregate can be referred to the above description of the invention 1 a.

By using the spindle-shaped carbon fiber aggregate as a supply source of the regenerated carbon fiber, even the regenerated carbon fiber having a low residual carbon content can be supplied particularly stably to the thermoplastic resin.

Further, without being limited by theory, the spindle-shaped carbon fiber aggregate is relatively easily defibrated by kneading in an extruder, and can be properly dispersed in the thermoplastic resin, and the short fiber-reinforced thermoplastic resin pellets can be produced without excessive kneading. Therefore, it is considered that the proportion of carbon fibers having a long fiber length in the short fiber-reinforced thermoplastic resin particles can be further increased, and that particles exhibiting particularly excellent mechanical properties can be produced.

The invention according to invention 2 of the present disclosure will be described in further detail below. < regenerated carbon fiber (regenerated carbon fiber Material) >

The regenerated carbon fiber (recycled carbon fiber) contains a carbon fiber component and a carbon component other than the carbon fiber component (in particular, a residual carbon component). In general, in the regenerated carbon fiber, carbon components other than the carbon fiber component are attached to the surface of the carbon fiber component.

The regenerated carbon fiber according to the present disclosure is characterized in that: has a single fiber tensile strength of 3.0GPa or more and a Weber shape factor of 6.0 or more; and a carbon-containing component that contains the regenerated carbon fiber, wherein the content of the carbon-containing component exceeds 0 wt% and is 5.0 wt% or less.

The regenerating method is not particularly limited as long as it is a regenerated carbon fiber having such characteristics, and may be, for example, a regenerated carbon fiber obtained by heat-treating a carbon fiber-containing plastic product such as Carbon Fiber Reinforced Plastic (CFRP).

Particularly preferably, the regenerated carbon fiber is a regenerated carbon fiber obtained by a semiconductor thermal activation method (TASC method). That is, a particularly preferred embodiment of the present disclosure includes regenerated carbon fibers that are manufactured by decomposing plastic components contained in a carbon fiber-containing plastic product by a semiconductor heat activation method.

The method for obtaining the regenerated carbon fiber having the characteristics of invention 2 of the present disclosure by the semiconductor heat activation method will be described later.

< residual average fiber Length >

Preferably, the residual average fiber length of the regenerated carbon fibers in the carbon fiber-reinforced thermoplastic resin particles (i.e., the average fiber length of the regenerated carbon fibers present in the particles) is 300 μm or more. The residual average fiber length of the regenerated carbon fiber is more preferably 320 μm or more, 330 μm or more, or 340 μm or more. The upper limit of the residual average fiber length of the regenerated carbon fiber is not particularly limited, and may be 600 μm or less or 500 μm or less.

The residual average fiber length of the regenerated carbon fibers in the carbon fiber-reinforced thermoplastic particles can be calculated as a number average value by removing matrix resin in the particles by a known decomposition method (for example, sulfuric acid decomposition method, thermal decomposition method or solvent decomposition method), filtering, and measuring the fiber length of 300 or more single fibers by a microscope.

< frequency of occurrence of Single fiber of 300 μm or less >

Regarding the regenerated carbon fibers in the carbon fiber-reinforced thermoplastic resin particles, the frequency of occurrence of single fibers of 300 μm or less is preferably 40% or less. The frequency of occurrence of the single fiber of 300 μm or less is particularly preferably 39% or less, 38% or less, 37% or less, or 36% or less. The lower limit of the frequency of occurrence of the single fiber of 300 μm or less is not particularly limited, and may be, for example, 1% or more or 10% or more.

The frequency of occurrence of single fibers of 300 μm or less can be obtained by measuring the fiber length of single fibers and calculating the ratio of the number of fibers of 300 μm or less in the same manner as the measurement of the residual average fiber length.

< tensile Strength of Single fiber >

The tensile strength of the filaments is preferably 3.1GPa or more, 3.2GPa or more, 3.3GPa or more, or 3.4GPa or more. The upper limit of the tensile strength of the single fiber is not particularly limited, and may be 6.0GPa or less.

The tensile strength of the single fiber can be measured according to JIS R7606 as follows:

at least 30 individual fibers are collected from the fiber bundle,

the diameter of the single fiber was measured in a side image of the single fiber taken by a digital microscope, and the cross-sectional area was calculated,

the sampled filaments were fixed to an apertured liner paper using an adhesive,

the slip sheet with the single fibers fixed thereon was mounted on a tensile tester, and a tensile test was performed at a specimen length of 10mm and a strain rate of 1 mm/min to measure tensile breaking stress,

the tensile strength was calculated from the cross-sectional area and tensile breaking stress of the filaments,

the tensile strength of the filaments is taken as the average of the tensile strength of at least 30 filaments.

< Weber shape factor >

The weibull shape factor is preferably 6.5 or more, 7.0 or more, 7.5 or more, 8.0 or more, or 8.5 or more. The upper limit of the weibull shape coefficient is not particularly limited, and may be 15.0 or less. The high weibull shape factor of the tensile strength of the single fiber means that the variation in tensile strength of the single fiber is small.

The weibull shape factor can be calculated as follows:

lnln{1/(1-F)}＝m×lnσ+C

wherein F is a failure probability obtained by a symmetric sample cumulative distribution method, sigma is a single fiber tensile strength (MPa), m is a Weber shape factor, and C is a constant.

The weibull shape factor m can be found from 1-order approximation slope by performing weibull plot with lnln { 1/(1-F) } and lnσ.

< carbon fiber component >

The form of the carbon fiber component in the regenerated carbon fiber is not particularly limited, and may be a form of a carbon fiber bundle composed of a plurality of single fibers (monofilaments and filaments). The number of filaments constituting the carbon fiber bundle may be in the range of 1,000 to 80,000, or 3,000 to 50,000. The diameter of the filaments constituting the carbon fiber component in the regenerated carbon fiber may be 0.1 μm to 30 μm, 1 μm to 10 μm, or 3 μm to 8 μm.

< residual carbon component >

The residual carbon component contained in the regenerated carbon fiber is derived in particular from: residual carbon of resin contained in a carbon fiber-containing plastic product used as a raw material in the production of the regenerated carbon fiber.

For the measurement method of the residual carbon component by the thermogravimetric analysis method, the above description of the invention 1a can be referred to.

< thermoplastic resin >

Examples of the thermoplastic resin contained in the carbon fiber-reinforced thermoplastic resin particles according to invention 2 of the present disclosure include: polyolefin resins (e.g., polypropylene resins and polyethylene resins), polyester resins (e.g., polyethylene terephthalate resins, polybutylene terephthalate resins and polylactic acid resins), polyamide resins, polyetherketone resins, polycarbonate resins, phenoxy resins, and polyphenylene sulfide resins. The thermoplastic resin may be only 1 kind, or may be a mixture of 2 or more kinds of thermoplastic resins.

Granule (granule)

The carbon fiber-reinforced thermoplastic resin particles according to invention 2 of the present disclosure contain regenerated carbon fibers and a thermoplastic resin.

The shape of the carbon fiber-reinforced thermoplastic resin particles according to invention 2 of the present disclosure is not particularly limited, and the length of the particles in the longitudinal direction is preferably 3mm to 10 mm. Particularly preferably, the diameter may be 5mm or less.

(content of regenerated carbon fiber)

The content of the regenerated carbon fibers in the carbon fiber-reinforced thermoplastic resin particles according to invention 2 of the present disclosure is preferably 30 wt% or less, less than 30 wt%, 20 wt% or less, 15 wt% or less, and/or 5 wt% or more, 7 wt% or more, 8 wt% or more, or 10 wt% or more, based on the carbon fiber-reinforced thermoplastic resin particles.

If the content of the regenerated carbon fibers is 30% by weight or less with respect to the carbon fiber-reinforced thermoplastic resin particles, the carbon fibers can be particularly uniformly dispersed in the particles. In addition, if the content of the regenerated carbon fiber is 5 wt% or more with respect to the carbon fiber-reinforced thermoplastic resin particles, particularly good mechanical property reinforcing effect of the particles can be obtained.

< method for producing particles >

The method for producing the carbon fiber-reinforced thermoplastic resin particles according to invention 2 of the present disclosure is not particularly limited, and can be obtained, for example, by a production method including the following steps:

providing regenerated carbon fibers;

providing a thermoplastic resin; and

mixing the regenerated carbon fiber and the melted thermoplastic resin,

here the number of the elements is the number,

the regenerated carbon fiber has a single fiber tensile strength of 3.0GPa or more and a Weber shape factor of 6.0 or more, and

The regenerated carbon fiber contains a residual carbon component, and the content of the residual carbon component is more than 0 wt% and not more than 5.0 wt% relative to the regenerated carbon fiber.

The regenerated carbon fibers and thermoplastic resin used to produce the carbon fiber-reinforced thermoplastic resin particles according to invention 2 of the present disclosure may be referred to the above description concerning the carbon fiber-reinforced thermoplastic resin particles according to invention 2 of the present disclosure.

In the step of supplying the regenerated carbon fiber, a spindle-shaped carbon fiber aggregate may be used as a supply source of the regenerated carbon fiber. That is, when the regenerated carbon fiber is provided, a spindle-shaped carbon fiber aggregate containing the regenerated carbon fiber may be provided as the regenerated carbon fiber. The spindle-shaped carbon fiber aggregate can be referred to the above description of the spindle-shaped carbon fiber aggregate according to the invention 1a of the present disclosure. By using the spindle-shaped carbon fiber aggregate as a supply source of the regenerated carbon fiber, the supply property at the time of producing the pellets may be further improved than in the case of using the short fiber as a supply source of the regenerated carbon fiber. The method for producing the spindle-shaped carbon fiber aggregate is not particularly limited, and preferably, the spindle-shaped carbon fiber aggregate can be produced according to the above-described method for producing a carbon fiber aggregate according to the invention 1a of the present disclosure.

In 1 exemplary embodiment for producing the carbon fiber-reinforced thermoplastic resin pellets according to the present disclosure, a thermoplastic resin as a base resin is fed via a main feeder of a twin-screw kneading extruder, a regenerated carbon fiber (in particular, a spindle-shaped regenerated carbon fiber aggregate) is fed into the resin kneaded and melted in the extruder via the twin-screw feeder, and the extruded kneaded product is cooled by a water cooling path and then cut to obtain carbon fiber-reinforced thermoplastic resin pellets.

Molded article

The carbon fiber-reinforced thermoplastic resin particles according to the present disclosure can be molded by using an extrusion molding machine or the like to produce molded articles. Molded articles molded using the pellets according to the present disclosure exhibit good physical properties, particularly good mechanical properties.

< tensile Strength >

The molded article produced according to the method shown in examples preferably exhibits a tensile strength of 90MPa or more, particularly preferably 92MPa to 110MPa, or 95MPa to 100MPa, according to ISO 527.

< bending Strength >

The molded article produced according to the method shown in the examples preferably exhibits a flexural strength of 140MPa or more, particularly preferably 140MPa to 160MPa, 140MPa to 150MPa, or 140MPa to 145MPa, according to ISO 178.

< flexural modulus of elasticity >

The molded article produced according to the method shown in examples preferably has a flexural modulus of at least 7100MPa, particularly preferably 7100MPa to 8000MPa, 7100MPa to 7500MPa, or 7100MPa to 7400MPa, according to ISO 178.

Method for producing regenerated carbon fiber by semiconductor thermal activation method

Hereinafter, a method for obtaining regenerated carbon fibers having the characteristics of invention 2 of the present disclosure by a semiconductor thermal activation method will be described. Hereinafter, a method of decomposing a plastic-containing material will be described first, and then, a method of recovering an inorganic material (carbon fiber) from a plastic-containing material containing plastic and an inorganic material (carbon fiber) by using the decomposition method will be described.

< method for decomposing Plastic-containing Material >

The decomposition method of the plastic-containing material comprises the following steps:

in an environment in a heating furnace into which a low oxygen concentration gas having an oxygen concentration of less than 10% by volume is introduced, a plastic-containing material is heated to a 1 st surface temperature in the presence of a semiconductor material, and plastics in the plastic-containing material are decomposed.

Fig. 2 is a conceptual sectional view for explaining an decomposing method according to the present invention. The mechanism of decomposition of the plastic-containing material according to the present invention will be described below. It should be noted that the present invention is not limited by theory.

It is considered that if the semiconductor material 11 is heated in an oxygen atmosphere, positive holes h are generated in the semiconductor material 11 ⁺ And electron e ^- The electron e ^- With oxygen O in the environment ₂ Reaction to produce O ₂ ^- Free radicals (reactive oxygen species). Then, radical propagation occurs in the plastic-containing material 12 disposed adjacent to the semiconductor material 11, and the plastic-containing material 12 is decomposed into small molecular components, and further oxidized and decomposed into CO ₂ 、H ₂ O、CH ₄ And the like. Radicals are believed to promote oxidative decomposition of plastics by extracting hydrogen from the plastics.

By using a semiconductor material, heat introduced for decomposition of plastic can be reduced as compared with the case where the semiconductor material is not used, and as a result, the energy consumption can be reduced.

Existing semiconductor-based heat-activated plastic decomposition processes sometimes produce excessive oxidative heating during the heat treatment. In the conventional method, since the heat treatment is performed in an atmosphere having an uncontrolled oxygen concentration, excessive radicals are generated, and as a result, excessive oxidative heat generation is considered to be generated.

In contrast, the present inventors found that: by setting the oxygen concentration to a low value even in the presence of the semiconductor material, heat treatment of the plastic can be effectively performed while suppressing excessive oxidative heat generation.

In particular, in the initial stage of thermal decomposition of plastics, excessive oxidative heat generation is likely to occur because the amount of plastics is large. In contrast, according to the method of the present disclosure, since the heat treatment is effectively performed at a low oxygen concentration, excessive oxidation heat generation can be suppressed even in the early stage of decomposition.

Therefore, according to the method of the present disclosure, since the heat treatment is performed in the presence of the semiconductor material, a good decomposition efficiency can be obtained even at a low oxygen concentration, and by setting the oxygen concentration in the heating furnace to a low value, excessive oxidation heat generation can be suppressed, and a decomposition treatment with improved stability can be realized.

The decomposition method according to the present invention will be described with reference to the drawings depicting exemplary embodiments.

Fig. 3 is a sectional view schematically showing 1 embodiment of the decomposition method according to the present disclosure. The heating furnace 20 shown in fig. 3 has a heat source (heater) 23, a gas supply portion 24, an exhaust port 25, and an internal space 26. A porous carrier 21 is disposed in the internal space 26 of the heating furnace 20, and a semiconductor material is carried on the surface of the carrier 21. In the embodiment of fig. 3, a plastic-containing material 22 is arranged in contact with the carrier 21.

The surface temperature of the plastic-containing material 22 can be brought to a specific temperature by controlling the ambient temperature of the internal space 26 of the heating furnace 20 via the heat source (heater) 23 of the heating furnace 20. The surface temperature of the plastic-containing material 22 may be measured via a temperature sensor 27 arranged within 5mm from the surface of the plastic-containing material 22.

A low oxygen concentration gas having an oxygen concentration of less than 10% by volume is introduced into the internal space 26 of the heating furnace 20 through the gas supply portion 24. By setting the introduction rate of the low oxygen concentration gas according to the amount of the furnace content, the oxygen concentration of the environment in the heating furnace 20 can be controlled. The low oxygen concentration gas may be pushed into the heating furnace via a gas supply portion provided in the heating furnace, or may be sucked into the heating furnace by applying a suction pressure to the exhaust port 25.

The low oxygen concentration gas is, for example, a mixed gas of air and nitrogen. By selecting the ratio of air to nitrogen, the oxygen concentration in the furnace can be controlled.

In an environment in which the oxygen concentration is controlled to be less than 10% by volume by introducing a low oxygen concentration gas, the plastic-containing material is heated to a 1 st surface temperature, for example 300 ℃ to 600 ℃. Accordingly, the plastic contained in the plastic-containing material 22 is decomposed into a decomposition gas such as steam, carbon dioxide, and methane, and the decomposition gas is discharged from the exhaust port 25 of the heating furnace 20.

After the heat treatment at the oxygen concentration of less than 10% by volume, the heat treatment may be further performed in which the oxygen concentration has been increased to 10% by volume or more.

In addition, after the heat treatment, the inorganic material contained in the plastic-containing material may be recovered.

Hereinafter, the decomposition method according to the present disclosure will be described in more detail.

< Plastic-containing Material >

The plastic-containing material comprises plastic. The plastic-containing material may be a plastic material or a plastic composite.

The plastics contained in the plastic-containing material include: thermoplastic resins and thermosetting resins.

Examples of the thermoplastic resin contained in the plastic-containing material include: polycarbonate (PC) resin, polyethylene (PE) resin, polypropylene (PP) resin, polyvinyl chloride (PVC) resin, polystyrene (PS) resin, polyethylene terephthalate (PET) resin, acrylonitrile-butadiene-styrene (ABS) resin, polyamide (PA) resin, polylactic acid (PLA) resin, polyimide (PI) resin, polymethyl methacrylate (PMMA) resin, methacrylic acid resin, polyvinyl alcohol (PVA) resin, polyacetal resin, petroleum resin, AS resin, modified polyphenylene ether resin, polybutylene terephthalate (PBT) resin, polybutylene (PB) resin, fluorine resin, polyacrylate resin, polyether ether ketone (PEEK) resin, polyphenylene Sulfide (PPs) resin.

Examples of the thermosetting resin contained in the plastic-containing material include: phenolic resins, urethane foam resins, polyurethane resins, urea resins, epoxy resins, unsaturated polyester resins, melamine resins, alkyd resins, vinyl ester resins, cyanate resins.

The plastic-containing material may contain at least 1 selected from the thermoplastic resins and thermosetting resins described above.

(Plastic composite Material)

Comprising plastic materials, in particular plastic composites. The plastic composite is, for example, a fiber reinforced plastic (FRP: fiber Reinforced Platic). The reinforcing fibers contained in the fiber-reinforced plastic include: carbon fiber (CarbonFibre).

(carbon fiber reinforced plastics)

Plastic composites are in particular carbon fiber-containing plastic products such as Carbon Fiber Reinforced Plastics (CFRP). The carbon fiber reinforced plastic contains plastic and carbon fiber material (carbon fiber). The carbon fiber reinforced plastic may include other members and/or materials (e.g., reinforcing fibers other than carbon fibers, resin molded articles, metals, ceramics, etc.).

The carbon fibers contained in the carbon fiber reinforced plastic are not particularly limited, and examples thereof include: PAN-based carbon fibers and pitch-based carbon fibers. The carbon fibers may be 1 kind or 2 or more kinds.

The carbon fiber material contained in the carbon fiber reinforced plastic may be in any form, and may be, for example, carbon fiber bundles, a fabric formed of carbon fiber bundles, or a nonwoven fabric of carbon fibers.

< introduction of Low oxygen concentration gas >

In the method according to the present disclosure,

a low oxygen concentration gas having an oxygen concentration of less than 10% by volume is introduced into the environment of the heating furnace.

Preferably, the oxygen concentration of the low oxygen concentration gas introduced into the environment of the heating furnace exceeds 0% by volume and is 1% by volume or more, 2% by volume or more, 3% by volume or more, or 4% by volume or more, and/or 9% by volume or less, 8% by volume or less, or 7% by volume or less.

The timing of introducing the low oxygen concentration gas into the heating furnace can be determined by the type of plastic contained in the plastic-containing material, the surface temperature at which the plastic starts to decompose, and the like. The timing of introducing the low oxygen concentration gas into the heating furnace can be determined based on data acquired in advance regarding self-heat generation of the plastic-containing material.

In 1 preferred embodiment according to the present disclosure, the low oxygen concentration gas is introduced into the above-described environment of the heating furnace during the period when the surface temperature of the plastic-containing material held in the heating furnace is below 300 ℃.

It is further preferable that the low oxygen concentration gas having an oxygen concentration of less than 10% by volume is introduced into the atmosphere of the heating furnace during the period in which the surface temperature of the plastic-containing material held in the heating furnace is 250 ℃ or less, 200 ℃ or less, or 150 ℃ or less.

It is further preferred that the low oxygen concentration gas having an oxygen concentration of less than 10% by volume is introduced into the environment of the heating furnace holding the plastic-containing material having a surface temperature of less than 300 ℃, whereby the oxygen concentration of the environment within the heating furnace is made to be less than 10% by volume. When a low oxygen concentration gas having an oxygen concentration of less than 10% by volume is introduced into the environment of the heating furnace, the lower limit of the surface temperature of the plastic-containing material held in the heating furnace is not particularly limited, and may be, for example, 0 ℃ or higher, 10 ℃ or higher, 20 ℃ or higher, or room temperature or higher.

It is further preferable that the low oxygen concentration gas having an oxygen concentration of less than 10% by volume is introduced into the environment of the heating furnace, particularly into the environment of the heating furnace holding the plastic-containing material having a surface temperature of less than 300 ℃, whereby the oxygen concentration in the environment within the heating furnace is controlled to be more than 0% by volume and 1% by volume or more, 2% by volume or more, 3% by volume or more, or 4% by volume or more, and/or 9% by volume or less, 8% by volume or less, or 7% by volume or less.

The oxygen concentration in the heating furnace may be directly measured using an oxygen concentration meter (oxygen monitor), or may be determined based on the volume of the furnace and the gas introduction amount in the furnace. The oxygen concentration in the heating furnace is preferably the average oxygen concentration during the heat treatment.

The introduction of the low oxygen concentration gas into the furnace may be performed, for example, by pressing the low oxygen concentration gas into the furnace through a gas supply portion provided in the heating furnace, or may be performed by sucking the low oxygen concentration gas from a suction port (or an exhaust port) provided in the furnace, thereby allowing the gas to flow into the furnace from a gas supply portion provided at a position different from the suction port. The gas supply portion of the heating furnace may have an opening, for example, and/or may have a gas permeable material.

The amount of gas introduced into the furnace may be set based on the unit resin amount of the resin (e.g., epoxy resin) to be decomposed, according to the capacity of the heating furnace, the desired oxygen concentration, and the like.

For example, the gas introduction amount in the furnace per unit amount of resin is in the range of 1 to 1000 (L/min)/kg or less, and may be preferably determined in the range of 2 to 700 (L/min)/kg or less. In addition, the time for replacing the furnace interior environment with the introduced gas may be determined based on the determined gas introduction amount and the volume of the heating furnace to be used.

In particular, by setting the amount of the introduced low oxygen concentration gas relative to the furnace volume, the environment in the heating furnace can be replaced with the introduced low oxygen concentration gas during the period when the surface temperature of the plastic-containing material held in the heating furnace is lower than 300 ℃.

The low oxygen concentration gas introduced into the heating furnace may include a diluent gas, particularly a mixed gas of air and the diluent gas. Examples of the diluent gas include: nitrogen, carbonic acid gas, water vapor and superheated water vapor. The superheated steam is steam heated to a temperature equal to or higher than the boiling point. The superheated steam has an advantage of high heat transfer to the object to be decomposed.

(heating furnace)

The heating furnace may be a combustion furnace or an electric furnace. The heating furnace may have, for example: an internal space for accommodating a plastic material and a semiconductor material, a heat source (heater) for heating the environment in the heating furnace, a gas supply unit for introducing a low oxygen concentration gas into the heating furnace, an exhaust port for exhausting a decomposed gas, and a suction port for optionally applying suction pressure to the inside of the heating furnace. It should be noted that 1 structure may be used as the exhaust port and the suction port. As the exhaust port and/or the suction port, for example, 1 or more openings provided in the heating furnace can be used.

(surface temperature)

The "surface temperature" of the plastic-containing material may be determined by measuring the temperature within 5mm of the surrounding plastic-containing material in the heating process.

The surface temperature of the plastic-containing material may be controlled, for example, by controlling the temperature in the heating furnace via the heat source of the heating furnace, and/or may be controlled by introducing a low-temperature gas into the heating furnace and/or reducing the oxygen concentration to suppress oxidative heat generation.

Further, the surface temperature of the plastic-containing material may be measured by a temperature sensor disposed within 5mm from the surface of the plastic-containing material, and the measured value may be fed back to the heat source of the heating furnace, whereby the surface temperature may be controlled with further high accuracy.

Further, for example, data concerning the temperature in the heating furnace and/or the output power of the heat source and the surface temperature measured by the sensor may be acquired in advance, and the heating process may be performed based on the data.

< heat treatment >

The method related to the disclosure comprises the following steps:

Preferably, the heating treatment is performed in an environment in which the oxygen concentration is made to be less than 10% by volume by introducing a low oxygen concentration gas having an oxygen concentration of less than 10% by volume, in particular, at an oxygen concentration of more than 0% by volume, 1% by volume or more, 2% by volume or more, 3% by volume or more, or 4% by volume or more, and/or at an oxygen concentration of 9% by volume or less, 8% by volume or less, or 7% by volume or less.

(1 st surface temperature)

"surface temperature 1" refers to the surface temperature of the plastic-containing material. As with the "surface temperature" described above, the "1 st surface temperature" can be determined by measuring a temperature within 5mm of the periphery of the plastic-containing material in the heating process.

The 1 st surface temperature may be 300 ℃ or more, 325 ℃ or more, or 350 ℃ or more, and/or may be 600 ℃ or less, 550 ℃ or less, 500 ℃ or less, or 450 ℃ or less. The 1 st surface temperature is, for example, 300℃to 600℃at 300℃to 550℃at 300℃to 500℃or 300℃to 450 ℃.

If the 1 st surface temperature is lower than the above range, decomposition of the plastic may not occur. If the 1 st surface temperature exceeds the above range, degradation and/or burnout of valuable substances such as carbon fibers may be noticeable by heating in the presence of oxygen when the plastic-containing material contains valuable substances such as carbon fibers. By setting the 1 st surface temperature to a low temperature, the effect of suppressing excessive oxidation heat generation is further improved.

In a preferred embodiment of the present disclosure, the 1 st surface temperature is brought to a temperature above 450 ℃ during the heat treatment with an oxygen concentration of less than 10% by volume. When the heating temperature is low, further decomposition of the plastic may be suppressed due to the carbide formed on the surface of the plastic-containing material, and by bringing the surface temperature to a temperature of 450 ℃ or higher, the carbide can be removed even if the oxygen concentration is low. Therefore, the decomposition efficiency of the plastic can be further improved.

Preferably, the heating treatment is performed for a predetermined time in a state where a low oxygen concentration gas having an oxygen concentration of less than 10% by volume is introduced. The predetermined time may be 1 minute to 600 minutes, preferably 30 minutes to 300 minutes, and more preferably 60 minutes to 180 minutes. The time point when the temperature of the heating furnace reaches 300 ℃ or the time point when the decomposition of the plastic is confirmed may be set as the start point of the "predetermined time" described above.

(semiconductor material)

The semiconductor material may be disposed in the heating furnace together with the plastic-containing material, or the semiconductor material may be disposed in the heating furnace in advance, and then the plastic-containing material may be disposed adjacent to or in contact with the semiconductor material.

In 1 embodiment of the present disclosure, the plastic-containing material and the semiconductor material subjected to the heat treatment are disposed apart from each other at a distance of 50mm or less. For this purpose, for example, spacers arranged between the plastic-containing material and the semiconductor material can be used. In this case, the lower limit of the distance is not particularly limited, and may be more than 0mm, more than 1mm, more than 5mm, or more than 10mm.

The distance between the plastic-containing material and the semiconductor material can be measured in the closest proximity of the two.

In a preferred embodiment of the present disclosure, the plastic-containing material subjected to the heat treatment is disposed in contact with the semiconductor material.

The contact method between the plastic-containing material and the semiconductor material is not particularly limited. For example, the two may be brought into contact by disposing a plastic-containing material over the semiconductor material. In addition, a plastic-containing material may be disposed on the semiconductor material supported on the surface of the carrier. Furthermore, the two may be brought into contact by surrounding or covering at least a portion or the whole of the plastic-containing material with the semiconductor material.

The semiconductor material is not particularly limited as long as it is stable at the temperature and oxygen concentration of the present invention. The semiconductor material contains, for example, at least 1 selected from the group consisting of:

BeO、MgO、CaO、SrO、BaO、CeO ₂ 、ThO ₂ 、UO ₃ 、U ₃ O ₈ 、TiO ₂ 、ZrO ₂ 、V ₂ O ₅ 、Y ₂ O ₃ 、Y ₂ O ₂ S、Nb ₂ O ₅ 、Ta ₂ O ₅ 、MoO ₃ 、WO ₃ 、MnO ₂ 、Fe ₂ O ₃ 、MgFe ₂ O ₄ 、NiFe ₂ O ₄ 、ZnFe ₂ O ₄ 、ZnCo ₂ O ₄ 、ZnO、CdO、Al ₂ O ₃ 、MgAl ₂ O ₄ 、ZnAl ₂ O ₄ 、Tl ₂ O ₃ 、In ₂ O ₃ 、SiO ₂ 、SnO ₂ 、PbO ₂ 、UO ₂ 、Cr ₂ O ₃ 、MgCr ₂ O ₄ 、FeCrO ₄ 、CoCrO ₄ 、ZnCr ₂ O ₄ 、WO ₂ 、MnO、Mn ₃ O ₄ 、Mn ₂ O ₃ 、FeO、NiO、CoO、Co ₃ O ₄ 、PdO、CuO、Cu ₂ O、Ag ₂ O、CoAl ₂ O ₄ 、NiAl ₂ O ₄ 、Tl ₂ O、GeO、PbO、TiO、Ti ₂ O ₃ 、VO、MoO ₂ 、IrO ₂ 、RuO ₂ 、CdS、CdSe、CdTe、Cu ₂ O、Sb ₂ O ₃ 、MnO ₃ and CoCrO ₄ 。

Preferably, the semiconductor material is an oxide semiconductor material. As a preferable oxide semiconductor material, there can be mentioned: chromium oxide, titanium oxide, zinc oxide, vanadium oxide, tungsten oxide, molybdenum oxide, cobalt oxide, iron oxide, and copper oxide.

The form of the semiconductor material is not particularly limited, and may be, for example, plate-like, granular or honeycomb. From the viewpoint of promoting the decomposition of plastics, the semiconductor material is preferably supported on the surface of a carrier having air permeability. The support having air permeability may be a porous body made of ceramic or the like, a honeycomb support, or the like. The semiconductor material may be a sintered body of semiconductor.

< two-stage heating >

The heat treatment method according to 1 preferred embodiment of the present disclosure includes:

the plastic-containing material subjected to the heat treatment at the 1 st surface temperature is heated in an atmosphere having an oxygen concentration of 10% by volume or more in the presence of the semiconductor material.

The heat treatment with an oxygen concentration of 10 vol% or more is preferably performed at an oxygen concentration of more than 10 vol%, 12 vol% or more, 15 vol% or more, or 20 vol% or more, and/or at an oxygen concentration of 30 vol% or less, or 25 vol% or less.

In this variant, which is also mentioned as two-stage heating, the plastic-containing material after the heat treatment at a lower oxygen concentration is further heat-treated at an increased oxygen concentration.

In the initial stage of thermal decomposition of plastics, excessive oxidative heat generation is likely to occur due to a large amount of plastics. In contrast, in the above embodiment accompanied by two-stage heating, the heating treatment performed at a lower oxygen concentration is followed by the heating treatment for increasing the oxygen concentration. That is, since heating is performed to increase the oxygen concentration in a stage where the plastic is decomposed to reduce the amount of plastic, excessive oxidation heat generation can be suppressed.

In addition, in the heating treatment at a relatively low oxygen concentration, a part of the plastic may not be gasified and remain as carbide. In contrast, in the above embodiment accompanied by two-stage heating, since the oxygen concentration is increased to further perform the heating treatment, the remaining carbide can be effectively decomposed/removed, and as a result, the decomposition efficiency can be further improved.

The heat treatment in a state where a low oxygen concentration gas having an oxygen concentration of less than 10% by volume is introduced and the heat treatment having an oxygen concentration of 10% by volume or more can be continuously performed in the same heating furnace. That is, for example, after heating the plastic-containing material to the 1 st surface temperature, the oxygen concentration may be increased to 10% by volume or more in the same heating furnace, and then the heating treatment may be further performed. In the conventional plastic decomposition method, it is necessary to perform the batch processing followed by the processing such as the fine cutting of the object to be processed, but the heating processing in a state where a low oxygen concentration gas having an oxygen concentration of less than 10% by volume is introduced and the heating processing having an oxygen concentration of 10% by volume or more are continuously performed in the same heating furnace, whereby the number of steps can be saved.

The environment having an oxygen concentration of 10% by volume or more may be formed by introducing a high oxygen concentration gas having an oxygen concentration of 10% by volume or more into the heating furnace, for example, and particularly may be formed by introducing air and/or oxygen into the heating furnace. The oxygen concentration of the high oxygen concentration gas may be more than 10% by volume, 12% by volume or more, 15% by volume or more, or 20% by volume or more, and/or 30% by volume or less, or 25% by volume or less.

In the heating treatment with the oxygen concentration of 10% by volume or more, a semiconductor material used in the heating treatment at the 1 st surface temperature may be used.

(surface temperature 2)

In particular, the plastic-containing material subjected to the heat treatment at the 1 st surface temperature is heated to the 2 nd surface temperature in an environment in which the oxygen concentration is 10% by volume or more in the presence of the semiconductor material.

"surface temperature 2" means the surface temperature of the plastic-containing material to be treated. As with the "surface temperature" and "surface temperature 1" described above, the "surface temperature 2" can be determined by measuring a temperature within 5mm of the periphery of the plastic-containing material in the heating process.

The 2 nd surface temperature may be in the range of 400 ℃ to 600 ℃. Further preferably, the 2 nd surface temperature is 425 ℃ to 575 ℃, or 450 ℃ to 550 ℃.

If the 2 nd surface temperature is lower than the above range, the improvement of the decomposition efficiency may not be observed. If the 2 nd surface temperature exceeds the above range, degradation and/or burning of valuable substances such as carbon fibers may be noticeable by heating in the presence of oxygen when the plastic-containing material contains valuable substances such as carbon fibers.

The 2 nd surface temperature may be substantially the same temperature as the 1 st surface temperature.

In addition, the 2 nd surface temperature may be above the 1 st surface temperature or at least 5 ℃, at least 10 ℃, at least 25 ℃, at least 50 ℃, or at least 75 ℃ higher than the 1 st surface temperature. The upper limit of the difference between the 1 st surface temperature and the 2 nd surface temperature is not particularly limited, and may be, for example, 200 ℃ or less, or 100 ℃ or less.

The heat treatment with an oxygen concentration of 10 vol% or more can be performed for a predetermined period of time. The predetermined time may be, for example, 1 minute to 600 minutes, 60 minutes to 360 minutes, or 90 minutes to 300 minutes.

< use >

According to the decomposition method of the plastic-containing material according to the present disclosure, plastics of a wide variety can be effectively gasified and decomposed. The decomposition method according to the present disclosure is applicable to Volatile Organic Compounds (VOCs), smoke emission, particulate Matters (PMs), and the like, and also applicable to exhaust gas treatment.

Method for recovering inorganic Material

Hereinafter, a method according to the present disclosure for recovering an inorganic material contained in a plastic composite will be described.

In 1 embodiment of the recycling method according to the present disclosure, the plastic-containing material as the plastic composite contains a plastic and an inorganic material, the recycling method comprising:

the plastics in the plastics-containing material are decomposed by the decomposition method described above, and the inorganic material is recovered.

The decomposition method according to the present disclosure, which can be used in the recycling method according to the present disclosure, and details thereof can be referred to the above description of the decomposition method of the plastic-containing material.

As described above, according to the decomposition method according to the present disclosure, plastics can be effectively decomposed. Therefore, according to the recycling method of the present disclosure, plastics contained in the plastic composite material can be efficiently and selectively decomposed, and thus an inorganic material having good physical properties can be efficiently recycled.

In addition, in the recycling method according to the present disclosure, the inorganic material can be recycled without pulverizing the plastic composite material. The plastic composite material to be pulverized is not particularly limited, and may be optionally pulverized.

Further, in the case of recovering an inorganic material from a plastic composite material, it is necessary to suppress the influence of heat treatment on the inorganic material as much as possible from the viewpoint of maintaining the quality of the recovered inorganic material. In this regard, in the decomposition method according to the present disclosure, excessive oxidative heat generation is suppressed by a lower oxygen concentration. Therefore, according to the recovery method of the present disclosure, an inorganic material having relatively good physical properties can be recovered.

(two stage heating)

In other embodiments of the recycling process according to the present disclosure, the plastic-containing material as a plastic composite is provided for two-stage heating. That is, the plastic composite material is subjected to heating in a state where a low oxygen concentration gas is introduced (oxygen concentration is less than 10%) and then a heating treatment in which the oxygen concentration is 10 vol% or more, whereby the plastic is decomposed and an inorganic material is recovered.

In the case of recovering an inorganic material, it is desirable to suppress deterioration of physical properties of the inorganic material due to excessive oxidation heat generation, and further, it is preferable to suppress deterioration of physical properties of the inorganic material due to carbonization of plastic, adhesion to the inorganic material, and residue. In this regard, in the case where the plastic composite is heated in two stages, the deterioration of the physical properties of the inorganic material due to excessive oxidation heat generation is suppressed by achieving a low oxygen concentration in the initial stage where excessive oxidation heat generation is likely to occur. Further, since the heating treatment for increasing the oxygen concentration is performed thereafter, the carbonized resin remaining on the inorganic material can be effectively removed. As a result, by the method of recovering the inorganic material by the two-stage heat treatment, more favorable physical properties of the recovered inorganic material can be ensured.

(inorganic Material)

As the plastic composite material containing an inorganic material and a plastic, there can be mentioned: fiber Reinforced Plastics (FRP), in particular carbon fiber reinforced plastics.

The inorganic material is especially carbon fiber (carbon fiber material).

(carbon fiber)

The carbon fibers contained in the carbon fiber reinforced plastic may be in any form, and may be, for example, carbon fiber bundles, a woven fabric formed of carbon fiber bundles, or a nonwoven fabric of carbon fibers.

(recyclate)

According to 1 embodiment of the recycling method according to the present disclosure, the residual carbon from the plastic recycled with the inorganic material is reduced, in particular the residual carbon is below 5% by weight of the recycled inorganic material. Preferably, the residual carbon is 4 wt% or less, 3 wt% or less, 2 wt% or less, 1 wt% or less, 0.9 wt% or less, 0.5 wt% or less, or 0.1 wt% or less of the recovered inorganic material. The residual carbon is preferably reduced as much as possible, and the lower limit thereof may be 0.001 wt% or more. The amount of the residual carbon in the recovered inorganic material can be measured in the same manner as the amount of the residual carbon in the regenerated carbon fiber described later.

Further, according to the recovery method of the present disclosure, carbon fibers having more excellent physical properties than carbon fibers before the production of the carbon fiber-reinforced plastic can be recovered.

In particular, according to the recovery method of the present disclosure, carbon fibers having a single fiber tensile strength of 3.0GPa or more and a weibull shape factor of 6.0 or more can be obtained from carbon fiber reinforced plastics as inorganic materials.

(tensile Strength of Single fiber)

at least 30 individual fibers are collected from the fiber bundles,

in a side image of a single fiber taken by a digital microscope, the diameter of the single fiber was measured, and the cross-sectional area was calculated,

the sampled filaments were fixed to an apertured liner paper using an adhesive,

(Weber shape factor)

The weibull shape factor can be calculated as follows:

lnln{1/(1-F)}＝m×lnσ+C

< use >

According to the recovery method of the present disclosure, for example, only matrix resins such as Fiber Reinforced Plastics (FRP), solar panels, electronic circuits, and the like can be decomposed effectively, and valuable substances such as strong fibers and rare metals can be recovered effectively.

Regenerated carbon fiber

The regenerated carbon fiber (regenerated carbon fiber material) according to the present disclosure can be produced by recovering carbon fiber from carbon fiber reinforced plastic. In 1 embodiment of the present disclosure, the regenerated carbon fiber may have more excellent physical properties than the carbon fiber before the carbon fiber reinforced plastic is manufactured.

The method for producing the regenerated carbon fiber is not particularly limited. For example, the regenerated carbon fiber may be manufactured by recovering the regenerated carbon fiber from a carbon fiber reinforced plastic according to the recovery method related to the present disclosure.

In 1 embodiment, the regenerated carbon fiber has a single fiber tensile strength of 3.0GPa or greater and a weibull shape factor of 6.0 or greater. The tensile strength and the weibull shape factor of the filaments can be measured and determined as described above.

The tensile strength of the regenerated carbon fiber is preferably 3.1GPa or more, 3.2GPa or more, 3.3GPa or more, or 3.4GPa or more. The upper limit of the tensile strength of the single fiber is not particularly limited, and may be 6.0GPa or less.

The weibull shape factor of the regenerated carbon fiber is preferably 6.5 or more, 7.0 or more, 7.5 or more, 8.0 or more, or 8.5 or more. The upper limit of the weibull shape coefficient is not particularly limited, and may be 15.0 or less.

(method for producing regenerated carbon fiber)

In particular, a method for producing a regenerated carbon fiber having a single fiber tensile strength of 3.0GPa or more and a Weber shape factor of 6.0 or more, and a content of a residual carbon component exceeding 0% by weight and 5.0% by weight or less relative to the regenerated carbon fiber, the method comprising:

In an environment in a heating furnace into which a low oxygen concentration gas having an oxygen concentration of less than 10% by volume is introduced, a plastic-containing material is heated to a 1 st surface temperature in the presence of a semiconductor material to decompose plastics in the plastic-containing material,

here, the plastic-containing material is a carbon fiber reinforced plastic containing carbon fibers.

In addition, in particular, a method for producing a regenerated carbon fiber having a single fiber tensile strength of 3.0GPa or more and a weibull shape factor of 6.0 or more, and a content of a residual carbon component exceeding 0% by weight and 5.0% by weight or less relative to the regenerated carbon fiber, the method comprising:

heating a plastic-containing material to a 1 st surface temperature in the presence of a semiconductor material in an atmosphere in a heating furnace into which a low oxygen concentration gas having an oxygen concentration of less than 10% by volume is introduced, and heating the plastic-containing material subjected to the heating treatment at the 1 st surface temperature in the presence of the semiconductor material in an atmosphere having an oxygen concentration of 10% by volume or more to decompose plastics in the plastic-containing material,

here, the plastic-containing material means a carbon fiber reinforced plastic containing carbon fibers.

In 1 preferred embodiment of the method for producing a regenerated carbon fiber according to the present disclosure, a low oxygen concentration gas is introduced into the environment of the heating furnace during the period when the surface temperature of the plastic-containing material is lower than 300 ℃.

(residual carbon)

Preferably, in the regenerated carbon fiber according to the present disclosure, the amount of residual carbon is reduced, and in particular, the amount of residual carbon is 5 wt% or less with respect to the regenerated carbon fiber. Further preferably, the residual carbon is 4 wt% or less, 3 wt% or less, 2 wt% or less, 1 wt% or less, 0.9 wt% or less, 0.5 wt% or less, or 0.1 wt% or less, based on the regenerated carbon fiber.

The "residual carbon" is a carbonized component derived from a plastic contained in a carbon fiber reinforced plastic as a raw material in the production of a regenerated carbon fiber.

The amount of residual carbon in the regenerated carbon fiber may be determined by thermogravimetric analysis (TGA).

For the measurement of residual carbon content by thermogravimetric analysis, the above description of invention 1a can be referred to.

Method for producing fusiform carbon fiber aggregate

Regarding invention 2, regarding the spindle-shaped carbon fiber aggregate and the method for producing the same, the above description relating to invention 1a can be referred to. The details of the regenerated carbon fibers contained in the carbon fiber aggregate may be referred to the above description of the invention 1a, and the above description of the regenerated carbon fibers of the invention 2 may be referred to.

Examples

The present application will be described in more detail with reference to examples. The embodiment is an example, and the present application is not limited thereto.

Example A1 of application 1a

< modulation of Material >

(regenerated carbon fiber)

As the regenerated carbon fiber, a regenerated carbon fiber having a residual carbon content of 1.4 wt% obtained by a semiconductor thermal activation method was used.

The amount of residual carbon components in the regenerated carbon fiber was determined by thermogravimetric analysis (TGA method) as follows:

(i) For a sample piece of 1 to 4mg obtained by pulverizing the regenerated carbon fiber, a total of about 600 minutes of thermogravimetric analysis was performed in a thermogravimetric analyzer, and the thermogravimetric analysis comprises the steps of: at an air supply rate of 0.2L/min, a heating ramp rate of 5 ℃ per minute, and a recording rate of 1/6 seconds, from room temperature to 100 ℃, at 100 ℃ for 30 minutes, from 100 ℃ to 400 ℃, and at 400 ℃ for 480 minutes;

(ii) In a graph obtained by plotting the weight reduction rate against time, an inflection point of the slope was determined, and the weight reduction rate during the holding at 100 ℃ was subtracted from the value of the weight reduction rate at the inflection point, thereby calculating the amount of residual carbon.

The regenerated carbon fiber has an average length of 5 mm.

(adhesive-containing liquid)

A binder-containing liquid having 297g of water as a dispersion medium with respect to 5.05g of the urethane resin as a binder was prepared.

< granulating treatment >

For the granulation treatment, a henschel-type horizontal stirring granulator (20L Loedige mixer, manufactured by Matsubo) was used. The mixer granulator has a mixing blade. The stirring vane is formed by the following modes: is connected to a shaft portion horizontally attached to a side inner wall of a container portion of the mixer granulator, and rotates around the shaft portion. The stirring blade is configured to have a gap of about 2mm minimum and about 5mm maximum between the stirring blade and the inner wall of the container portion.

The mixer-granulator also has auxiliary blades for promoting the opening of the fibres.

While the stirring blade was started to rotate, 500g of the regenerated carbon fiber and 302g of the binder-containing liquid were charged into the vessel portion of the stirring granulator, and mixing and granulating treatments were performed at ambient temperature for 10 minutes, to obtain a spindle-shaped precursor.

The moisture content of the mixture was 37.0 wt%. The rotation speed of the stirring blade was 320rpm, and the rotation speed of the auxiliary blade was 3000rpm.

< drying treatment >

The obtained precursor was dried in a dryer to obtain a carbon fiber aggregate according to example A1.

< carbon fiber Assembly >

Photographs of the carbon fiber assembly according to example A1 are shown in fig. 4 and 5. As can be seen from these figures, the carbon fiber aggregate according to example A1 has a spindle-like shape.

(adhesive content)

The binder content was 1.0 wt% relative to the carbon fiber aggregate of example A1.

(aspect ratio)

The long diameter and the short diameter of the carbon fiber aggregate of example A1 were measured using calipers, and the aspect ratio (long diameter/short diameter) of the carbon fiber aggregate was calculated. The short diameter was measured at a position where the width of the carbon fiber aggregate reached the maximum. As a result of measurement of sample number 50 (n=50), the aspect ratio was 7.5.

(average Length, average maximum Width)

When measured with a caliper at a sample number of 50 (n=50), the carbon fiber aggregate according to example A1 had an average length of 13.5mm and an average maximum width of 1.8mm. Since the average length of the regenerated carbon fibers is 5mm, the average length of the carbon fiber aggregate is 2.7 times the average length of the regenerated carbon fibers.

(bulk Density)

The bulk density of the carbon fiber aggregate according to example A1 was measured. Specifically, a funnel with an outlet having an inner diameter of 18mm was used to allow a sample to flow from a height of 63mm into a 200ml container with an inner diameter of 63mm, and the container was filled to a full state. The sample weight at the shredding capacity is then determined. The bulk density was calculated from the weight and the volume of the container. As a result, the bulk density was 181g/L.

< evaluation of feeding Property >

The carbon fiber aggregate of example A1 was evaluated for feeding properties. Specifically, the carbon fiber aggregate according to example A1 was fed to a capacity coil feeder (CFD-111, manufactured by Technovel Co.) at a feed rate of 1 g/min, and the feeding property was evaluated. In table 1 below, the case where supply can be performed for 10 minutes is indicated as "o".

The conditions for producing the carbon fiber aggregate according to example A1 and the evaluation results are shown in table 1 below.

Example A2 of invention 1a

The production and evaluation of the carbon fiber aggregate according to example A2 were performed in the same manner as in example A1, except that the amount of binder and the water content were changed as shown in table 1. The production conditions and the evaluation results are shown in table 1.

Example A3 of invention 1a

The production and evaluation of the carbon fiber aggregate according to example A3 were performed in the same manner as in example A1, except that the amount of binder and the water content were changed as shown in table 1. The production conditions and the evaluation results are shown in table 1.

Example A4 of invention 1a

The production and evaluation of the carbon fiber aggregate according to example A4 were performed in the same manner as in example A2, except that the average length of the regenerated carbon fibers was 10 mm. The production conditions and the evaluation results are shown in table 1.

Comparative example A1 concerning invention 1a

Production of a carbon fiber assembly was attempted in the same manner as in example A2, except that the average length of the regenerated carbon fibers was 30 mm. However, the regenerated carbon fibers are entangled with each other in the granulator, and a granular carbon fiber aggregate cannot be obtained. The production conditions and results are shown in Table 1 below.

Comparative example A2 concerning invention 1a

A carbon fiber assembly was produced in the same manner as in example A4, except that the regenerated carbon fiber having a residual carbon content of 7.1 wt% was used.

Fig. 6 shows a photograph of the carbon fiber aggregate according to comparative example A2. As shown in fig. 6, the carbon fiber aggregate obtained in comparative example A2 had a flat plate-like shape, and a carbon fiber aggregate having a spindle-like shape could not be obtained. Most of the carbon fiber aggregates obtained in comparative example A2 were formed into bundles by bonding the regenerated carbon fibers to each other while maintaining the shape of the cut regenerated carbon fibers. In addition, in comparative example A2, oval particles having a non-uniform size were also seen. The production conditions and results are shown in Table 1 below.

TABLE 1

Example B1 of invention 1B

< modulation of Material >

(carbon fiber)

As the carbon fiber, a regenerated carbon fiber having a residual carbon content of 1.4 wt% obtained by a semiconductor heat activation method was used.

The amount of residual carbon components in the regenerated carbon fiber is determined by thermogravimetric analysis (TGA method) as follows:

(i) For a 4mg sample piece obtained by pulverizing the regenerated carbon fiber, a total of about 600 minutes of thermogravimetric analysis was performed in a thermogravimetric analyzer, and the thermogravimetric analysis had the steps of: at an air supply rate of 0.2L/min, a heating ramp rate of 5 ℃ per minute, and a recording rate of 1/6 seconds, from room temperature to 100 ℃, at 100 ℃ for 30 minutes, from 100 ℃ to 400 ℃, and at 400 ℃ for 480 minutes;

(ii) In a graph obtained by plotting the weight reduction rate against time, an inflection point of the slope was determined, and the weight reduction rate during the holding period at 100 ℃ was subtracted from the value of the weight reduction rate at the inflection point, thereby calculating the amount of residual carbon.

The regenerated carbon fiber has an average length of 10 mm.

(thermoplastic resin fiber)

As the thermoplastic resin fiber, polyphenylene sulfide resin fiber (PPS resin fiber, single filament fineness of 4.4 denier) having an average length of 5mm was used.

(fiber component)

The PPS resin fiber as the thermoplastic resin fiber used in example B1 was 70g, and the regenerated carbon fiber as the carbon fiber was 30g.

(adhesive-containing liquid)

A binder-containing liquid (aqueous emulsion sizing agent) having 88.5g of water as a dispersion medium with respect to 6.5g of a urethane resin as a binder was prepared.

< granulating treatment >

For the granulation treatment, a Henschel horizontal mixer granulator (Pam Apex mixer, manufactured by DaPacific Co., ltd.) was used. The mixer granulator has a mixing blade. The stirring vane is formed by the following modes: is connected to a shaft portion horizontally attached to a side inner wall of a container portion of the mixer granulator, and rotates around the shaft portion. The stirring blade was formed so as to have a gap of about 2mm between the stirring blade and the inner wall of the container portion.

While the stirring blade was started to rotate, 30g of the regenerated carbon fiber, 70g of the PPS resin fiber, and 95g of the binder-containing liquid were charged into the vessel portion of the stirring granulator, and mixing and granulating were performed at ambient temperature for 15 minutes, to obtain a spindle-shaped precursor.

The moisture content of the mixture was 45.4 wt%. The rotation speed of the stirring blade was 600rpm, and the rotation speed of the auxiliary blade was 600rpm.

< drying treatment >

The obtained precursor was dried in a dryer to obtain an aggregate according to example B1.

< aggregate >

The aggregate of the thermoplastic resin fibers and the carbon fibers according to example B1 has a spindle shape. The thermoplastic resin fibers and the carbon fibers contained in the aggregate are oriented in the long axis direction of the aggregate.

In order to quantify the extending direction of the fibers in the aggregate, the aggregate was cut parallel to the longitudinal direction, the absolute value of the angle of the fibers with respect to the longitudinal direction of the aggregate was measured for each of the fibers of n=30 randomly selected in the cross section taken with a digital camera, and then the obtained measured values were averaged to calculate the average extending direction of the fibers with respect to the longitudinal direction of the aggregate (the "fiber orientation degree" in table 2 below). The fluffed fibers (fibers partially distant from the aggregate) were not included in this calculation. The degree of fiber orientation was 9 ° with respect to example B1.

(adhesive content)

The binder content relative to the aggregate of example B1 was 6.1 wt%.

(aspect ratio)

The aspect ratio (long diameter/short diameter) of the aggregate of example B1 was calculated using a caliper. The major axis is the length of the aggregate. The minor diameter is measured at the point where the width of the aggregate is maximized. As a result of measuring the average value for the number of samples 50 (n=50), the aspect ratio was 5.4 (average value: long diameter=20.0 mm, see below; short diameter=3.7 mm).

(average Length, average maximum Width)

The average length of the aggregate according to example B1 was 20.0mm and the average maximum width was 3.7mm when measured with a caliper at a sample number of 50 (n=50). Since the average length of the regenerated carbon fibers is 10mm, the average length of the aggregate is 2.0 times the average length of the regenerated carbon fibers. Further, since the average length of the PPS resin fibers is 5mm, the average length of the aggregate is 4.0 times the average length of the PPS resin fibers.

(bulk Density)

The bulk density of the aggregate according to example B1 was measured. Specifically, a funnel with an outlet having an inner diameter of 18mm was used to allow a sample to flow from a height of 63mm into a 200ml container with an inner diameter of 63mm, and the container was filled to a full state. The sample weight at the shredding capacity is then determined. The bulk density was calculated from the weight and the volume of the container. As a result, the bulk density was 164g/L.

The conditions for producing the aggregate and the evaluation results of the aggregate according to example B1 are shown in table 2 below.

Example B2 of invention 1B

An aggregate according to example B2 was produced in the following manner.

< modulation of Material >

(carbon fiber)

As the carbon fiber, a regenerated carbon fiber having a residual carbon content of 1.4 wt% obtained by the semiconductor heat activation method was used in the same manner as in example B1. The regenerated carbon fiber has an average length of 5 mm.

(thermoplastic resin fiber)

As the thermoplastic resin fiber, polyphenylene sulfide resin fiber (PPS resin fiber, single filament fineness 4.4 denier) having an average length of 5mm was used.

(fiber component)

The PPS resin fiber as the thermoplastic resin fiber used in example B2 was 350g, and the regenerated carbon fiber as the carbon fiber was 150g.

(adhesive-containing liquid)

A binder-containing liquid (aqueous emulsion sizing agent) containing 256g of water as a dispersion medium with respect to 21.0g of a urethane resin as a binder was prepared.

< granulating treatment >

For the granulation treatment, a horizontal stirring granulator (30L MTI mixer, manufactured by Yueisland mechanical Co., ltd.) was used.

The mixer granulator has a mixing blade and an auxiliary blade for opening the fibers.

150g of the regenerated carbon fiber, 350g of the PPS resin fiber, and 277g of the binder-containing liquid were charged into a vessel portion of a mixer-granulator while the stirring blade was started to rotate, and mixing and granulating were performed at ambient temperature for 15 minutes to obtain a spindle-shaped precursor.

The moisture content of the mixture was 32.9 wt%. The rotation speed of the stirring blade was 235rpm, and the rotation speed of the auxiliary blade was 3,000rpm.

< drying treatment >

The obtained precursor was dried in a dryer to obtain an aggregate according to example B2.

< aggregate >

Fig. 7 and 8 are photographs of an aggregate according to example B2. As can be seen from these figures, the aggregate of the thermoplastic resin fibers and the carbon fibers according to example B2 has a spindle-like shape. The thermoplastic resin fibers and the carbon fibers contained in the aggregate are oriented in the long axis direction of the aggregate. In the same manner as in example B1, the degree of fiber orientation was calculated in example B2, and was found to be 7 °.

(adhesive content)

The binder content was 4.0 wt% relative to the aggregate of example B2.

(aspect ratio)

The aspect ratio (long diameter/short diameter) of the aggregate of example B2 was calculated using a caliper. The major axis is the length of the aggregate. The short diameter is measured at a position where the width of the aggregate is maximized. As a result of measuring the average value for the number of samples 50 (n=50), the aspect ratio was 6.7 (average value: long diameter=17.4 mm, see below; short diameter=2.6 mm).

(average Length, average maximum Width)

When measured with a caliper at a sample number of 50 (n=50), the average length of the aggregate according to example B2 was 17.4mm, and the average maximum width was 2.6mm. Since the average length of the regenerated carbon fibers was 5mm, the average length of the aggregate was 3.5 times the average length of the regenerated carbon fibers. Further, since the average length of the PPS resin fibers is 5mm, the average length of the aggregate is 3.5 times the average length of the PPS resin fibers.

(bulk Density)

The bulk density of the aggregate according to example B2 was measured in the same manner as in example B1. As a result, the bulk density was 189g/L.

The conditions for producing the aggregate and the evaluation results of the aggregate according to example B2 are shown in table 2 below.

Comparative example B1 concerning invention 1B

In the same manner as in example B2 above, except that polyphenylene sulfide resin powder (PPS powder, median diameter 270 μm) was used instead of PPS resin fibers, a spindle-shaped aggregate could not be obtained when an attempt was made to produce an aggregate.

Fig. 9 is a photograph showing a material obtained as a result of comparative example B1. The material obtained in comparative example B1 was mainly composed of carbon fiber aggregates and PPS powder, which were not uniform in shape and size, and they were present separately from each other. Since the material of comparative example B1 does not become a dispersion mixture of PPS resin and carbon fiber, it is necessary to granulate the material of comparative example B1 in a kneading step in order to produce a molded product containing carbon fiber.

TABLE 2

Example C1 of invention 2

< modulation of Material >

(regenerated carbon fiber)

As the regenerated carbon fiber, a regenerated carbon fiber having an average length of 5mm, an average filament diameter of 7.0 μm, a filament tensile strength of 4.2GPa, a weibull shape factor of 8.7, and a residual carbon content of 0.3% by weight, which was regenerated by the semiconductor heat activation method according to the method of invention 2 of the present disclosure, was used as a raw material.

(tensile Strength of Single fiber)

The tensile strength of the single fiber was measured according to JIS R7606 as follows:

at least 30 individual fibers are collected from the fiber bundle,

the diameter of the single fiber was measured in a side image of the single fiber taken with a digital microscope, and the cross-sectional area was calculated,

the sampled filaments were fixed to an apertured liner paper using an adhesive,

(Weber shape factor)

The weibull shape factor is calculated according to the following formula:

lnln{1/(1-F)}＝m×lnσ+C

(wherein F is the failure probability obtained by the symmetric sample cumulative distribution method, σ is the tensile strength (MPa) of the single fiber, m is the Weber shape factor, and C is a constant.)

Weber mapping was performed using lnln { 1/(1-F) } and lnσ, and the Weber shape factor m was determined from 1-order approximation slope.

(residual carbon amount)

The amount of residual carbon components in the regenerated carbon fiber was determined according to thermogravimetric analysis (TGA method) as follows:

(i) For a 4mg sample piece obtained by pulverizing the regenerated carbon fiber, a thermogravimetric analysis was performed for a total of about 600 minutes in a thermogravimetric analyzer, and the thermogravimetric analysis had a process comprising: at an air supply rate of 0.2L/min, a heating ramp rate of 5 ℃ per minute, and a recording rate of 1/6 seconds, from room temperature to 100 ℃, at 100 ℃ for 30 minutes, from 100 ℃ to 400 ℃, and at 400 ℃ for 480 minutes;

According to the method of the present invention, a spindle-shaped carbon fiber aggregate is obtained from the regenerated carbon fiber. Specifically, the regenerated carbon fibers were defibrated by a mixer, and then stirred and mixed with an aqueous dispersion of an epoxy resin as a binder by using a stirring granulator, and the obtained spindle-shaped precursor was dried in a dryer to obtain a spindle-shaped carbon fiber assembly. The regenerated carbon fiber was given 2% by weight of an epoxy resin.

The obtained spindle-shaped carbon fiber aggregate was measured in the same manner as in example A1 of the above-mentioned invention 1a, and the average length of the aggregate was 10.8mm, the average maximum width of the aggregate was 1.4mm and the bulk density of the aggregate was 132g/L. The aspect ratio of the aggregate was 7.7.

(thermoplastic resin)

As the base thermoplastic resin, a polycarbonate resin (L1225 WP, manufactured by Di Kagaku Co., ltd.: molecular weight 21.8 ten thousand) was used.

< production of carbon fiber-reinforced thermoplastic resin particles >

The polycarbonate as the thermoplastic resin was fed to a twin-screw kneading extruder, and the regenerated carbon fiber aggregate obtained as described above was fed from a side feeder, dispersed in a polycarbonate resin as a base material, and pelletized, whereby carbon fiber-reinforced thermoplastic resin pellets according to example C1 were obtained.

The weight of the thermoplastic resin and the regenerated carbon fiber fed into the extruder was measured, and the fiber weight ratio (wt%) of the particles according to example C1 was calculated as (regenerated carbon fiber (g)/(regenerated carbon fiber (g) +thermoplastic resin (g))) ×100.

The obtained pellets were molded into dumbbell pieces (molded articles according to example C1) having a length of 170 mm. Times.10 mm in width. Times.4 mm in thickness using an injection molding machine (Toshiba machine, 130T injection molding machine, cylinder temperature 300 ℃ C., mold temperature 100 ℃ C.).

The tensile strength, flexural strength and flexural modulus of the resulting dumbbell sheet were 99MPa, 142MPa and 7.2GPa, respectively. Tensile strength, flexural strength and flexural modulus of elasticity were measured as follows.

(tensile Strength)

Using the above dumbbell pieces, the tensile strength was determined according to ISO 527.

(flexural Strength)

Using the dumbbell pieces described above, flexural strength was determined in accordance with ISO 178.

(flexural modulus of elasticity)

The flexural modulus of elasticity was determined according to ISO178 using the dumbbell pieces described above.

The average fiber length of the regenerated carbon fibers in the particles was 348 μm and the occurrence frequency of single fibers of 300 μm or less was 36%. Their measurement methods are as follows.

(residual average fiber Length)

The average fiber length (residual average fiber length) of the regenerated carbon fibers in the carbon fiber-reinforced thermoplastic resin particles was calculated as a number average value by removing the matrix resin of the matrix resin in the particles by sulfuric acid decomposition, filtering, and measuring the fiber length of 300 or more single fibers by a microscope.

(frequency of occurrence of single fiber of 300 μm or less)

The frequency of occurrence of the single fibers of 300 μm or less was calculated by measuring the fiber length of the single fibers and calculating the ratio of the number of single fibers of 300 μm or less in the same manner as the measurement of the average fiber length.

The results of example C1 are shown in Table 3 below.

Comparative example C1 concerning invention 2

In comparative example C1, a regenerated carbon fiber having a residual carbon content of 7.1 wt% obtained by a conventional thermal decomposition method without using a semiconductor was used. Since the residual carbon content was 5 wt% or more, the tensile strength of the single fiber and the weibull shape factor could not be measured.

In comparative example C1, the production and evaluation of pellets and dumbbell plates were performed in the same manner as in example C1 except that the mixer treatment and the production of the carbon fiber aggregate were not performed, but that the regenerated carbon fibers as short (chopped) recycled carbon fibers were supplied to the twin-screw extruder. The results are shown in Table 3 below. The carbon fibers regenerated by the conventional thermal decomposition method (short recycled carbon fibers according to comparative example C1) were bundled by the remaining carbide, and thus, the carbon fibers could be fed from the side feeder to the twin-screw kneading extruder.

Comparative example C2 concerning invention 2

In comparative example C2, the production and evaluation of pellets and dumbbell pieces were performed in the same manner as in example C1, except that short fibers of commercially available virgin carbon fibers (HT C422, manufactured by teh corporation) were used instead of the regenerated carbon fibers.

The results are shown in Table 3 below. The physical properties of the raw carbon fiber according to comparative example C2 are shown in table 3 below.

The molded article of example C1 exhibited more excellent mechanical properties than the molded article of comparative example C1. Without intending to be limited by theory, as a reason for this, there may be mentioned: compared with the regenerated carbon fiber of comparative example C1, the regenerated carbon fiber of example C1 has a smaller residual carbon content and has good adhesion between the carbon fiber and the resin.

The molded article of example C1 contained the regenerated carbon fiber, but showed mechanical properties equivalent to those of the molded article of comparative example C2. In example C1, the occurrence frequency of the single fibers pulverized to 300 μm or less was 36%, which was lower than that of 55% of comparative example C2. Thus, in example C1, a high mechanical property enhancing effect was obtained, and it was considered that the regenerated carbon fiber having a low tensile strength of single fiber was used, but the same mechanical properties as those of comparative example C2 using the virgin carbon fiber were exhibited. It should be noted that, not being limited by theory, the reason why the occurrence frequency of the single fibers pulverized to 300 μm or less in example C1 becomes low is that: since the regenerated carbon fiber used in example C1 was regenerated by the semiconductor heat activation method, the deviation in the tensile strength of the filaments was small compared with comparative example C2, and the weibull shape factor was high (8.7).

TABLE 3

Reference examples 1 to 3 and reference comparative example 1

In reference examples 1 to 3 and reference comparative example 1, carbon Fiber Reinforced Plastic (CFRP) plates as plastic-containing materials were subjected to heat treatment, and the plastic decomposition efficiency was evaluated.

< reference example 1>

Reference example 1 was performed as follows.

(provision and configuration of materials)

As the semiconductor material, a material obtained by applying chromium oxide (Cr ₂ O ₃ Purity of 99% or more, manufactured by positive chemical company). The support with honeycomb structure was 13 cells/25 mm.

As the plastic-containing material, CFRP plates having an epoxy resin content of 41 wt% were used.

The internal volume of the heating furnace was 9L. Inside the heating furnace, a CFRP plate is disposed on a carrier carrying chromium oxide as a semiconductor material. The carrier and the CFRP plate are disposed in contact with each other.

The surface temperature of the CFRP plate was measured by a sensor arranged within 5mm from the surface of the CFRP plate.

(heating treatment)

The internal temperature of the heating furnace is controlled by the output power of the heater of the heating furnace, and the internal temperature of the heating furnace is raised.

Before the surface temperature of the CFRP plate reached 300 ℃, a mixed gas of air and nitrogen having an oxygen concentration of 6% by volume was introduced into the heating furnace. The mixed gas was introduced into the heating furnace by sucking the mixed gas from a suction port provided in the upper part of the heating furnace at a gas introduction amount of 70L/min, and flowing the mixed gas into a gas supply port provided in the lower part of the heating furnace. The oxygen concentration in the heating furnace was measured by an oxygen monitor.

The heating treatment was performed for 30 minutes in an atmosphere in which the oxygen concentration was controlled to 6% by volume by introducing the above mixed gas. During the heat treatment, the heater output of the heating furnace was adjusted so that the surface temperature of the CFRP plate was raised to the 1 st surface temperature of 376 ℃.

(evaluation)

The evaluation of the plastic decomposition efficiency in the method according to reference example 1 was performed by calculating the weight reduction rate (wt%) from the difference between the weight of the CFRP sheet before the heat treatment and the weight of the CFRP sheet after the heat treatment. The results are shown in Table 4.

< reference example 2>

The heat treatment and evaluation of reference example 2 were performed in the same manner as in reference example 1, except that the carrier and the CFRP plate were disposed at a distance of 30mm from each other in the heating furnace, and the surface temperature of the CFRP plate was raised to 377 ℃ during the heat treatment. The results are shown in Table 4.

< reference example 3>

The heat treatment and evaluation of reference example 3 were performed in the same manner as in reference example 1, except that the time of the heat treatment was set to 60 minutes, and the surface temperature of the CFRP plate was raised to 371 ℃ during the heat treatment. The results are shown in Table 4.

< reference comparative example 1>

The heat treatment and evaluation of reference comparative example 1 were performed in the same manner as in reference example 1, except that a semiconductor material was used and the surface temperature of the CFRP plate was raised to 370 ℃ during the heat treatment. The results are shown in Table 4.

TABLE 4

TABLE 4 Table 4

As seen from table 4, in reference examples 1 to 3, in which a low oxygen concentration gas having an oxygen concentration of 6% by volume was introduced in the presence of the semiconductor material, the decomposition efficiency of the plastic-containing material was higher than that of reference comparative example 1, in which the semiconductor material was not used, in which the surface temperature was heated to 371 to 377 ℃.

In reference example 3, although the treatment time was prolonged to 60 minutes, the increase in the weight reduction rate was limited as compared with reference example 1 in which the treatment time was 30 minutes. This is thought to be due to: the sample surface is covered with carbide during the heat treatment, and as a result, the decomposition efficiency is lowered.

Reference example 4 and reference comparative example 2

< reference example 4>

The treatment and evaluation of reference example 4 were performed in the same manner as in reference example 1, except that heating was performed at a surface temperature of 500 ℃ for 60 minutes. The results are shown in Table 5 below.

< reference comparative example 2>

The process and evaluation of reference comparative example 2 were performed in the same manner as in reference example 4, except that the semiconductor material was not used. The results are shown in Table 5 below.

TABLE 5

Photographs of the samples subjected to the treatments related to reference example 4 and reference comparative example 2 are shown in fig. 11 and 12, respectively. In addition, a photograph of the sample before the treatment is shown in FIG. 10.

As seen from table 5, in reference example 4 in which the heat treatment was performed under the semiconductor material in a state where the low oxygen concentration gas having the oxygen concentration of 6% by volume was introduced, a high plastic decomposition efficiency was exhibited as compared with reference comparative example 2 in which the heat treatment was performed without the semiconductor material in a state where the low oxygen concentration gas having the oxygen concentration of 6% by volume was introduced.

As shown in fig. 12, the surface of the treated sample of reference example 2 had a block-like residual carbon from the plastic, while as shown in fig. 11, the surface of the treated sample of reference example 4 had a relatively smooth and highly uniform surface, similar to the surface of the sample before treatment shown in fig. 10, without confirming the adhesion of such residual carbon.

Reference examples 5 to 9

In reference examples 5 to 9, a CFRP plate or a pressure vessel containing a plastic material was subjected to a two-stage heat treatment. Then, the decomposition efficiency was evaluated, and the physical properties of the carbon fiber (carbon fiber material) obtained by the heat treatment were evaluated.

< reference example 5>

Reference example 5 was performed as follows.

(provision and configuration of materials)

As the semiconductor material, a material obtained by applying chromium oxide (Cr ₂ O ₃ Manufactured by pure chemical company) with a purity of 99% or more. The support with honeycomb structure was 13 cells/25 mm.

As the plastic-containing material, CFRP plates having an epoxy resin content of 41 wt% were used. Physical properties of carbon fibers contained in the CFRP sheet before treatment are shown in table 6 as reference example 1.

The internal volume of the heating furnace is 0.0525m ³ . Inside the heating furnace, a CFRP plate is disposed on a carrier carrying chromium oxide as a semiconductor material. The carrier and the CFRP plate are disposed in contact with each other.

(heating treatment)

The internal temperature of the heating furnace is controlled by the output power of the heater of the heating furnace, and the internal temperature of the heating furnace is raised. Then, before the surface temperature of the CFRP plate reached 300 ℃, a mixed gas of air and nitrogen having an oxygen concentration of 8% by volume was introduced into the heating furnace. The mixed gas was introduced into the heating furnace by sucking the mixed gas at a gas introduction amount of 190L/min and then flowing the mixed gas from a gas supply unit provided in the heating furnace.

In reference example 5, reference example 6 and reference comparative example 4 described below, the oxygen concentration in the heating furnace was measured by an oxygen monitor provided in the heating furnace. With reference to examples 7 to 9, the oxygen concentration in the furnace was calculated from the volume of the furnace and the gas introduction amount.

At the point in time when the surface temperature of the CFRP plate was 300 ℃, the generation of decomposed gas was confirmed.

The heating treatment was performed for 120 minutes in an atmosphere in which the oxygen concentration was controlled to 8% by volume by introducing the above-mentioned mixed gas. During the heat treatment, the heater output of the heating furnace was adjusted so that the surface temperature of the CFRP plate was raised to the 1 st surface temperature of 450 ℃.

(secondary heating treatment)

Then, the gas suction pressure was kept constant, the supply of nitrogen was stopped, only air was supplied, and it was confirmed that the oxygen concentration in the heating furnace was 10 vol% or more, and then the heating treatment was performed. During the heating treatment for 260 minutes, the surface temperature of the CFRP plate was raised to 500 ℃. The average oxygen concentration in 260 minutes was 14% by volume, and the maximum oxygen concentration was 18% by volume.

In reference example 5, 0.8kg of CFRP plate was treated. The throughput with respect to the internal volume of the furnace was 15.2kg/m ³ 。

(residual carbon amount)

The amount of residual carbon from the plastic in the carbon fiber (regenerated carbon fiber) recovered after the heat treatment was determined by thermogravimetric analysis. The values of the amounts of residual carbon in table 6 below represent the amounts of residual carbon (wt%) relative to the carbon fibers.

Thermogravimetric analysis was performed as follows:

(i) For 1 to 4mg of the sample piece obtained by pulverizing the recovered carbon fibers, a total of 300 minutes of thermogravimetric analysis was performed in a thermogravimetric analyzer, and the thermogravimetric analysis had the following steps: at an air supply rate of 0.2L/min, a heating up rate of 5 ℃/min, and a recording rate of 1/6 seconds, from room temperature to 100 ℃, at 100 ℃ for 30 minutes, from 100 ℃ to 400 ℃, and at 400 ℃;

(ii) In a graph plotting the weight reduction rate against time, an inflection point of the slope was determined, and the weight reduction rate during the holding at 100 ℃ was subtracted from the value of the weight reduction rate at the inflection point, thereby calculating the amount of residual carbon.

Further, the fiber filament diameter and the filament tensile strength were measured for the carbon fibers recovered after the heat treatment, and the weibull shape factor was calculated.

(tensile Strength of Single fiber)

The tensile strength of the single fiber was measured in accordance with JIS R7606 as follows:

At least 30 individual fibers are collected from the fiber bundle,

the sampled filaments were fixed to an apertured liner paper using an adhesive,

(Weber shape factor)

The weibull shape factor is calculated according to the following formula:

lnln{1/(1-F)}＝m×lnσ+C

The Weibull shape factor m was obtained from the 1 st approximation efficiency by performing Weibull plot with lnln { 1/(1-F) } and lnσ.

The evaluation results are shown in Table 6. The fiber filament diameter is an average of diameters of filaments measured on at least 30 filaments by the above operation.

< reference example 6>

The process was performed in the same manner as in reference example 5, except that a pressure vessel was used as the plastic-containing material, the mixed gas was sucked at a gas introduction amount of 127L/min, and the oxygen concentration, the surface temperature, and the time of the heat treatment were set as shown in table 6 below.

The pressure vessel treated in reference example 6 had an aluminum liner and 44% by weight of FRP (fiber reinforced plastic) containing 31% by weight of reinforcing fibers and 13% of epoxy resin. The reinforcing fiber is mainly composed of carbon fiber and contains a small amount of glass fiber. The capacity of the pressure vessel was 2.0L.

The amount of FRP treated in referential example 6 was 0.47kg. The throughput with respect to the internal volume of the furnace was 9.0kg/m ³ 。

The evaluation results of the plastic decomposition efficiency and the physical properties of the recovered carbon fiber are shown in Table 4. After 180 minutes of the secondary heat treatment, the average oxygen concentration was 18 vol% and the maximum oxygen concentration was 20 vol%.

The physical properties of the carbon fibers contained in the pressure vessel before the treatment are shown in table 6 as reference example 2.

< reference example 7>

The internal volume of the heating furnace is 0.1435m ³ A heat treatment was performed in the same manner as in reference example 5, except that a mixed gas of superheated steam and air was introduced into the heating furnace at a gas introduction amount of 29L/min, and the surface temperature and the time of the heat treatment were set as shown in table 6 below.

The internal temperature of the heating furnace and the surface temperature of the sample were controlled by the heater output of the heating furnace and the temperature of the superheated steam.

In reference example 7, 1.0kg of CFRP plate was treated. The throughput with respect to the internal volume of the furnace was 7.0kg/m ³ 。

The evaluation results of the plastic decomposition efficiency and the physical properties of the recovered carbon fiber are shown in Table 6. In the secondary heating treatment, only 29L/min of air was pushed into the furnace.

< reference example 8>

The treatment was performed in the same manner as in reference example 7, except that a pressure vessel was used as the plastic-containing material, and the surface temperature and the heat treatment time were set as shown in table 6 below.

The pressure vessel used in reference example 8 was the same as the pressure vessel used in reference example 6.

The FRP amount treated in referential example 8 was 0.47kg. The throughput with respect to the internal volume of the furnace was 3.3kg/m ³ 。

The evaluation results of the plastic decomposition efficiency and the physical properties of the recovered carbon fiber in reference example 8 are shown in Table 6. In the secondary heating treatment, only 29L/min of air was pushed into the furnace.

< reference example 9>

The internal volume of the heating furnace is 0.049m ³ The process was performed in the same manner as in reference example 7, except that a mixed gas of superheated steam and air was introduced into the heating furnace at a gas introduction amount of 25L/min, and the surface temperature and the heat treatment time were set as shown in table 6 below.

In reference example 9, a CFRP plate having an epoxy resin ratio of 38% was treated. The throughput relative to the internal volume of the furnace was 1.6kg/m ³ 。

The evaluation results of the plastic decomposition efficiency and the physical properties of the recovered carbon fiber in reference example 9 are shown in table 6. In the secondary heating treatment, the amount of air was increased while continuously supplying superheated steam, and a gas having an oxygen concentration of 11% by volume was introduced into the furnace at 38L/min.

Physical properties of carbon fibers contained in the CFRP sheet of reference example 9 before treatment are shown in table 6 as reference example 3.

Reference comparative example 3

In reference example 3, the supply and arrangement of the continuous material were performed in the same manner as in reference example 5, and then the internal temperature of the heating furnace was raised without performing adjustment of the oxygen concentration of the environment in the heating furnace.

As a result, when the heater output is not changed at the time point when the surface temperature of the CFRP plate reaches 300 ℃, excessive self-heating occurs, and the surface temperature of the CFRP plate increases to 485 ℃. The results are recorded in table 6.

In reference comparative example 3, 0.8kg of CFRP plate was treated. The throughput with respect to the internal volume of the furnace was 15.2kg/m ³ 。

Reference comparative example 4

The same procedure as in reference example 6 was conducted except that the semiconductor material was not used.

The FRP amount treated in reference comparative example 4 was 0.47kg. The throughput with respect to the internal volume of the furnace was 9.0kg/m ³ 。

The results of evaluating the physical properties of the recovered carbon fibers are shown in Table 6 with reference to comparative example 4. After 180 minutes of secondary heating treatment, the average oxygen concentration was 18% by volume and the maximum oxygen concentration was 20% by volume.

TABLE 6

As seen from table 6, reference examples 5 to 9, in which a low oxygen concentration gas having an oxygen concentration of 6 to 8% by volume was introduced, heat-treated 1 time in the presence of a semiconductor material, and then heat-treated 2 times further at an elevated oxygen concentration, were low in residual carbon content (residual carbon content), and exhibited very excellent plastic decomposition efficiency.

In reference comparative example 3 in which oxygen concentration control was not performed, excessive self-heating was generated, whereas in reference examples 5 to 9 in which low oxygen concentration gas having an oxygen concentration of 6 to 8% by volume was introduced into the heating furnace, excessive self-heating was not observed. In reference comparative example 3, since the decomposition treatment was started without reducing the oxygen concentration in advance, the oxygen concentration was excessive, and as a result, it was considered that the decomposition temperature could not be properly controlled in the presence of the semiconductor material.

Further, the carbon fibers recovered in reference examples 5 to 9 were kept at the same level in terms of fiber filament diameter and filament tensile strength and the weibull shape factor of the filament tensile strength was increased as compared with the carbon fibers before treatment (reference examples 1 to 3). That is, in reference examples 5 to 9, carbon fibers having more excellent physical properties than the carbon fibers before the production of the carbon fiber reinforced plastic were recovered.

Further, the carbon fiber recovered in reference example 6 accompanied by heat treatment under the semiconductor material has more excellent quality than the carbon fiber material recovered in reference comparative example 4 subjected to heat treatment without the semiconductor material, in particular, in terms of tensile strength of single fiber and weibull shape factor.

Symbol description

100: a stirring granulator;

120: a container part;

140: stirring blades;

160: a shaft portion;

a: a rotation direction;

c: a gap;

11: a semiconductor material;

12: a plastic-containing material;

20: a heating furnace;

21: a carrier having a semiconductor material;

22: a plastic-containing material;

23: a heat source (heater);

24: a gas supply unit;

25: an exhaust port;

26: an inner space of the heating furnace;

27: a temperature sensor.

Claims

1. A method for producing a spindle-shaped aggregate, the method comprising:

Providing a mixture of at least carbon fibers and a binder-containing liquid;

the precursor is dried.

2. The method for producing a spindle-shaped aggregate according to claim 1, wherein,

the spindle-shaped aggregate is a spindle-shaped carbon fiber aggregate,

the carbon fibers are regenerated carbon fibers and,

the manufacturing method is characterized by comprising the following steps: producing a spindle-shaped precursor by rotating the mixture in a vessel in a gap between an inner wall of the vessel and a rotating body in the vessel,

3. The method according to claim 2, wherein the average length of the carbon fiber aggregate is 1.5mm to 60mm.

4. A method according to claim 2 or 3, wherein the amount of the binder-containing liquid in the mixture is 20 to 60% by weight relative to the mixture.

5. The method according to any one of claims 2 to 4, wherein the binder is contained in the binder-containing liquid in an amount of 0.1 to 10% by weight relative to the regenerated carbon fiber.

6. The method according to any one of claims 2 to 5, wherein an average length of the carbon fiber aggregate is 1.2 to 4.0 times an average length of the regenerated carbon fibers contained in the carbon fiber aggregate.

7. The method for producing a spindle-shaped aggregate according to claim 1, wherein,

the spindle-shaped aggregate is a spindle-shaped aggregate of thermoplastic resin fibers and carbon fibers,

the above mixture further comprises thermoplastic resin fibers.

8. The method of claim 7, wherein the spindle precursor is produced by rotating the mixture in a vessel in a gap between an inner wall of the vessel and a rotating body within the vessel.

9. The method of claim 7 or 8, wherein the carbon fibers comprise regenerated carbon fibers.

10. The method of claim 9, wherein the carbon fibers are regenerated carbon fibers.

11. The method of claims 2-6, 9 or 10, comprising: the regenerated carbon fiber is produced by decomposing a plastic component contained in a carbon fiber-containing plastic product by a semiconductor heat activation method.

12. A spindle-shaped aggregate comprising carbon fibers and a binder.

13. The spindle assembly of claim 12, wherein:

The spindle-shaped aggregate is a spindle-shaped carbon fiber aggregate composed of at least regenerated carbon fibers and a binder, wherein,

the average length of the regenerated carbon fiber is more than 1mm and less than 30mm; and

the average length of the carbon fiber aggregate is 1.5mm to 60mm.

14. The assembly according to claim 13, wherein an average length of the spindle-shaped carbon fiber assembly in a longitudinal direction is 1.2 to 4.0 times an average length of the regenerated carbon fibers contained in the spindle-shaped carbon fiber assembly.

15. The aggregate according to claim 13 or 14, wherein the regenerated carbon fibers contained in the fusiform carbon fiber aggregate are oriented in the longitudinal direction of the fusiform carbon fiber aggregate.

16. The spindle assembly of claim 12, wherein the spindle assembly comprises thermoplastic resin fibers and carbon fibers, and comprises carbon fibers, thermoplastic resin fibers and a binder,

17. The aggregate according to claim 16, wherein the average length of the aggregate is 1.5 to 60mm.

18. The aggregate according to claim 16 or 17, wherein the average length of each of the carbon fiber and the thermoplastic resin fiber is 1mm or more and less than 30mm.

19. The aggregate according to any one of claims 16 to 18, wherein an average length of the aggregate is 1.2 to 5.0 times an average length of the carbon fibers and an average length of the thermoplastic resin fibers contained in the aggregate.

20. The aggregate according to any one of claims 12 to 19, wherein the binder is contained in an amount of 0.1 to 10% by weight relative to the spindle aggregate.

21. The assembly of any one of claims 16 to 20, wherein the thermoplastic resin fibers are selected from the group consisting of polyolefin resin fibers, polyester resin fibers, polyamide resin fibers, polyether ketone resin fibers, polycarbonate resin fibers, phenoxy resin fibers, and polyphenylene sulfide resin fibers, and mixtures thereof.

22. The aggregate according to any one of claims 16 to 21, wherein the carbon fibers comprise regenerated carbon fibers.

23. The aggregate according to any one of claims 16 to 22, wherein the carbon fibers are regenerated carbon fibers.

24. The aggregate according to claim 13 to 15, 22 or 23, wherein the regenerated carbon fiber contains a residual carbon component, and the residual carbon component is more than 0% by weight and not more than 5.0% by weight relative to the regenerated carbon fiber.

25. Carbon fiber reinforced thermoplastic resin particles characterized in that: which are carbon fiber-reinforced thermoplastic resin particles comprising regenerated carbon fibers and a thermoplastic resin,

26. The carbon fiber-reinforced thermoplastic resin particles according to claim 25, wherein the content of the regenerated carbon fiber is 5% by weight or more and 30% by weight or less with respect to the carbon fiber-reinforced thermoplastic resin particles.

27. The carbon fiber-reinforced thermoplastic resin particles of claim 25 or 26, wherein the thermoplastic resin is selected from the group consisting of polyolefin resins, polyester resins, polyamide resins, polyetherketone resins, polycarbonate resins, phenoxy resins, and polyphenylene sulfide resins, and mixtures thereof.

28. The carbon fiber-reinforced thermoplastic resin particles according to any one of claims 25 to 27, wherein the length in the longitudinal direction is 3mm or more and 10mm or less.

29. The carbon fiber-reinforced thermoplastic resin particles according to any one of claims 25 to 28, characterized in that: the regenerated carbon fibers contained in the carbon fiber-reinforced thermoplastic resin particles have a residual average fiber length of 300 μm or more.

30. The carbon fiber-reinforced thermoplastic resin particles according to any one of claims 25 to 29, characterized in that: for producing a molded article having a tensile strength of 90MPa or more, a flexural strength of 140MPa or more, and a flexural modulus of 7100MPa or more.

31. The carbon fiber-reinforced thermoplastic resin particles according to any one of claims 25 to 30, characterized in that: the frequency of occurrence of the single fibers of 300 μm or less in the regenerated carbon fibers in the carbon fiber-reinforced thermoplastic resin particles is 40% or less.

32. A method for producing carbon fiber-reinforced thermoplastic resin particles, comprising:

providing regenerated carbon fibers;

providing a thermoplastic resin; and

mixing the regenerated carbon fiber and the melted thermoplastic resin,

wherein the regenerated carbon fiber has a single fiber tensile strength of 3.0GPa or more and a Weber shape factor of 6.0 or more, and

33. The method of claim 32, wherein the regenerated carbon fiber is provided using a spindle-shaped carbon fiber aggregate containing the regenerated carbon fiber.