阅读说明：本技术 再生碳纤维束、再生碳纤维、再生碳纤维粉碎物的制造方法以及再生碳纤维束的制造装置、碳纤维强化树脂的制造方法、以及再生碳纤维束 (Regenerated carbon fiber bundle, regenerated carbon fiber, method for producing crushed regenerated carbon fiber, device for producing regenerated carbon fiber bundle, method for producing carbon fibe) 是由 豊岛宏一 武田彻 原贵久 增田浩二郎 山口泰雄 中村仁俊 丸田阳介 佐藤正希 于 2018-05-08 设计创作，主要内容包括：本发明提供一种即使不在800℃以上对碳纤维强化树脂进行加热也可保持包含于碳纤维强化树脂中时的形态来回收碳纤维基材,并可减小所回收的碳纤维基材中的树脂残渣含量的偏差的再生碳纤维的制造方法,以及提供该制造方法中可使用的再生碳纤维束的制造装置及可有效利用再生碳纤维的碳纤维强化树脂的制造方法。一种再生碳纤维束的制造方法,其为从包含多个碳纤维基材及基质树脂的碳纤维强化树脂(100)中,以再生碳纤维束的形式得到所述碳纤维基材的方法,该方法包括：通过对所述碳纤维强化树脂(100)进行加热,使所述基质树脂发生热分解而得到加热处理物(102),通过对所述加热处理物(102)进行解碎而分离所述多个碳纤维基材。(The invention provides a method for producing regenerated carbon fibers, which can recover a carbon fiber base material while maintaining the form of the carbon fiber base material contained in the carbon fiber reinforced resin without heating the carbon fiber reinforced resin at 800 ℃ or higher and can reduce the variation in the content of resin residue in the recovered carbon fiber base material, and provides a device for producing a regenerated carbon fiber bundle usable in the production method and a method for producing a carbon fiber reinforced resin capable of effectively utilizing the regenerated carbon fibers. A method for producing a regenerated carbon fiber bundle, which is a method for obtaining a carbon fiber substrate in the form of a regenerated carbon fiber bundle from a carbon fiber-reinforced resin (100) comprising a plurality of carbon fiber substrates and a matrix resin, the method comprising: the carbon fiber-reinforced resin (100) is heated to thermally decompose the matrix resin to obtain a heat-treated product (102), and the heat-treated product (102) is disintegrated to separate the plurality of carbon fiber base materials.)

1. A method for producing a regenerated carbon fiber bundle, which is a method for obtaining a carbon fiber substrate in the form of a regenerated carbon fiber bundle from a carbon fiber-reinforced resin containing a plurality of carbon fiber substrates and a matrix resin, comprising:

heating the carbon fiber-reinforced resin to thermally decompose the matrix resin to obtain a heat-treated product,

separating the plurality of carbon fiber base materials by disintegrating the heat-treated material.

2. A method for producing a regenerated carbon fiber bundle, which is a method for obtaining a carbon fiber substrate as a regenerated carbon fiber bundle from a laminate formed by laminating a plurality of prepregs including the carbon fiber substrate and a matrix resin, the method comprising:

heating the laminate to thermally decompose the matrix resin to obtain a heat-treated product,

separating the plurality of carbon fiber base materials by disintegrating the heat-treated material.

3. The method for producing a regenerated carbon fiber bundle according to claim 1 or 2, wherein the temperature at which the carbon fiber-reinforced resin is heated is 300 ℃ to 700 ℃.

4. The method for producing a regenerated carbon fiber bundle according to any one of claims 1 to 3, wherein the carbon fiber-reinforced resin is heated in a non-oxidizing atmosphere.

5. The method for producing a regenerated carbon fiber bundle according to claim 4, wherein the non-oxidizing atmosphere is a nitrogen atmosphere or a superheated steam atmosphere.

6. The method for producing a regenerated carbon fiber bundle according to any one of claims 1 to 5, wherein the heat-treated material is disintegrated by a biaxial roller disintegrator, a multiaxial roller disintegrator, or a hammer disintegrator.

7. The method for producing a regenerated carbon fiber bundle according to any one of claims 1 to 6, wherein the carbon fiber base material separated by disintegration is cut to obtain a chip-like fiber bundle.

8. A method for producing regenerated carbon fiber, comprising: a regenerated carbon fiber bundle obtained by the production method according to any one of claims 1 to 7,

the regenerated carbon fiber bundle is further heated under an oxidizing atmosphere.

9. A method for producing a pulverized regenerated carbon fiber, comprising: a regenerated carbon fiber bundle or a regenerated carbon fiber obtained by the production method according to any one of claims 1 to 8,

and crushing the regenerated carbon fiber bundle or the regenerated carbon fiber to obtain a carbon fiber crushed material.

10. A method for producing a carbon fiber-reinforced resin, comprising: any one of a regenerated carbon fiber bundle, regenerated carbon fiber, or a crushed regenerated carbon fiber obtained by the production method according to any one of claims 1 to 9;

producing a carbon fiber-reinforced resin containing any one of the regenerated carbon fiber bundle, the regenerated carbon fiber, or the crushed regenerated carbon fiber and a matrix resin.

11. A method for producing carbon fiber-reinforced resin particles, comprising: any one of a regenerated carbon fiber bundle, regenerated carbon fiber, and a crushed regenerated carbon fiber obtained by the production method according to any one of claims 1 to 9,

kneading a thermoplastic resin and either the regenerated carbon fiber bundle, the regenerated carbon fiber or the crushed regenerated carbon fiber to obtain a kneaded product,

processing the kneaded mixture into granules.

12. A manufacturing device of regenerated carbon fiber bundles, which is a device for obtaining a carbon fiber base material from carbon fiber reinforced resin in the form of regenerated carbon fiber bundles,

the device includes:

a heating furnace for obtaining a heat-treated product by heating the carbon fiber-reinforced resin; and the number of the first and second groups,

and a disintegrator for disintegrating the heat-treated material.

13. The apparatus for manufacturing regenerated carbon fiber bundle according to claim 12, wherein the crusher is a biaxial roller crusher, a multiaxial roller crusher or a hammer crusher.

14. A regenerated carbon fiber bundle, wherein the average value of the thickness of the regenerated carbon fiber bundle is 0.01mm to 1 mm.

15. The recycled carbon fiber bundle of claim 14, wherein the standard deviation of the thickness of the recycled carbon fiber bundle is 0.01mm to 0.5 mm.

16. The regenerated carbon fiber bundle according to claim 14 or 15, wherein the average resin residue amount after the thermal decomposition treatment is 0.1 to 30 mass% with respect to the carbon fiber-reinforced resin.

Technical Field

The present invention relates to a regenerated carbon fiber bundle, regenerated carbon fibers, a method for producing a crushed regenerated carbon fiber, an apparatus for producing a regenerated carbon fiber bundle, a method for producing a carbon fiber-reinforced resin, and a regenerated carbon fiber bundle.

The present application claims priority based on japanese patent application No. 2017-097990 filed in japan on 5/17/2017, and the contents of which are incorporated herein by reference.

Background

As a method for recovering carbon fibers from a product (molded product) of a used carbon fiber-reinforced resin, an intermediate product (prepreg) of a carbon fiber-reinforced resin produced in a production step, or the like, for example, the following methods have been proposed.

(1) A method for manufacturing a carbon fiber block, characterized in that: the carbon fiber-reinforced plastic is subjected to dry distillation at a temperature of 300 to 1000 ℃ in a substantially non-oxidizing atmosphere, and then crushed into a flake shape, whereby the carbon fiber block is constituted such that a portion having a maximum size of 30mm or less in the matrix accounts for 90 mass% or more, and a portion having a thickness ratio to the maximum size of the carbon fiber block of 3 or more accounts for 60 mass% or more (patent document 1).

(2) A method for recovering carbon fibers, characterized by: a method for manufacturing a carbon fiber-reinforced plastic composite material, which comprises removing plastic in a carbon fiber-reinforced plastic material by treating an object to be treated having a carbon fiber-reinforced plastic material comprising a laminated carbon fiber base cloth formed by laminating carbon fiber base cloth layers made of fiber bundles obtained by bundling carbon fibers, in superheated steam at 800 ℃ or higher, and removing the carbon fiber-reinforced plastic material, wherein the base cloth layers of the laminated carbon fiber base cloth are delaminated, and the carbon fibers are recovered by maintaining the fiber bundles. (patent document 2).

Drawings

Fig. 1 is a schematic configuration diagram showing an example of a heat treatment apparatus.

Fig. 2 is a schematic configuration diagram showing another example of the heat treatment apparatus.

Fig. 3 is a perspective view showing an example of a mode of accommodating the carbon fiber reinforced resin in a tray (tray).

FIG. 4 is a schematic view showing a mode of disintegrating a heat-treated material by a twin-shaft roller crusher.

Fig. 5 is a schematic view showing another example of the double-shaft roller crusher.

Fig. 6 is a photograph showing an example of a carbon fiber base material (long fiber bundle) separated by disintegration of a heat-treated product.

Fig. 7 is a photograph showing an example of a carbon fiber base material (short fiber bundle) separated by disintegration of a heat-treated product.

Fig. 8 is a photograph showing an example of a carbon fiber substrate (chopped carbon fiber) separated by the disintegration of a heat-treated product.

Detailed Description

The following definitions of terms apply to all ranges of this specification and the claims.

The term "carbon fiber-reinforced resin" refers to a resin containing carbon fibers and a matrix resin, and includes a molded product and an intermediate product before molding.

The term "disintegration" refers to a process in which a heat-treated product obtained by consolidating resin residues such as thermal decomposition products of matrix resins between a plurality of carbon fiber substrates is pressed to thereby untwist the carbon fiber substrates into individual carbon fiber substrates while suppressing breakage of the carbon fiber substrates.

The "carbon fiber bundle" refers to a bundle of carbon fibers in which individual plain threads of carbon fibers are bonded by a resin or a thermal decomposition product of a resin, and includes a woven fabric.

"fracture" refers to breaking up the carbon fibers to break them.

"pulverizing" refers to finely breaking up the carbon fibers into powder.

"non-oxidizing atmosphere" means an atmosphere containing no oxygen gas, or an atmosphere containing substantially no oxygen gas. "substantially not containing oxygen" means that the amount of oxygen gas is in a range in which deterioration of carbon fibers due to oxidation by oxygen gas cannot be observed even if oxygen gas is inevitably mixed into the atmosphere in which the carbon fiber-reinforced resin is heated.

The "oxidizing atmosphere" is an atmosphere containing oxygen gas and refers to an atmosphere other than a non-oxidizing atmosphere.

"superheated steam" refers to steam heated to a temperature above its boiling point.

The resin residue content in the carbon fiber bundle was determined in accordance with JIS K7075: 1991, the fiber mass content of the carbon fiber bundle is determined by the sulfuric acid decomposition method, and the value is determined from the 100-fiber mass content.

The average value of the thickness toxicity of the regenerated carbon fiber bundle is a value calculated by measuring the thickness of the regenerated carbon fiber bundle at an arbitrary 30 points of the unspecified regenerated carbon fiber bundle and averaging these values.

The standard deviation of the thickness of the regenerated carbon fiber bundle is a value calculated from the following equation (1) by measuring the thickness x of the regenerated carbon fiber bundle at an arbitrary 30 points of the unspecified regenerated carbon fiber bundle.

The average value of the resin residue content of the regenerated carbon fiber bundle is a value calculated by measuring the resin residue content at an arbitrary 5 points of the unspecified regenerated carbon fiber bundle and averaging these values.

The standard deviation of the resin residue content of the regenerated carbon fiber bundle is a value calculated from the following formula (1) by measuring the resin residue content x at an arbitrary 5 points of the unspecified regenerated carbon fiber bundle.

[ mathematical formula 1]

In the present specification and claims, "to" indicating a numerical range means to include numerical values recited before and after the range as a lower limit value and an upper limit value.

For convenience of explanation, the dimensional ratio in fig. 1 to 5 is different from the actual dimensional ratio.

< carbon fiber reinforced resin >

The carbon fiber-reinforced resin in the present invention includes a plurality of carbon fiber base materials and a matrix resin.

The carbon fiber-reinforced resin may include carbon fibers (pulverized carbon fibers and the like) which do not constitute the carbon fiber base material, carbon fibers, and other materials (reinforcing fibers other than carbon fibers, inorganic fillers and the like) other than the matrix resin.

The carbon fiber-reinforced resin may be a molded product (molded product) or an intermediate product before molding (prepreg, prepreg strand (tow), sheet molding compound (sheet molding compound), stampable sheet (or the like)). Further, a laminate in which a plurality of prepregs each including a single-layer carbon fiber substrate and a matrix resin are laminated may be used. In the case of using a laminate in which a plurality of prepregs are laminated as the carbon fiber-reinforced resin, the amount of prepregs that can be recycled can be increased at the same time, and the recycling can be performed at low cost. When a sheet-like molding material is used as the carbon fiber-reinforced resin, the resin residue content of the recovered carbon fiber base material can be increased, and the form as a carbon fiber bundle can be easily maintained. Further, since the carbon fiber base material in a chip form can be recovered by performing only the disintegration treatment, the regeneration treatment can be performed at low cost without performing the cutting treatment.

The carbon fiber-reinforced resin may be in the form of a composite with other members (a fiber-reinforced resin containing reinforcing fibers other than carbon fibers, a resin molded article containing no reinforcing fibers, a metal, a ceramic, and the like).

The shape of the carbon fiber-reinforced resin is not particularly limited. Examples of the shape of the carbon fiber-reinforced resin include: a sheet shape, a plate shape, a cross-sectional L-shape (angular shape), a cross-sectional T-shape, a cross-sectional C-shape (channel shape), a cross-sectional H-shape, a square tube shape, a round tube shape, an arbitrary three-dimensional shape, and the like.

(carbon fiber substrate)

The number of carbon fiber base material layers contained in the carbon fiber-reinforced resin is 2 or more. The number of carbon fiber substrate layers may be set as appropriate depending on the use, properties, and the like of the carbon fiber-reinforced resin, and is not particularly limited as long as it is 2 or more.

The carbon fiber substrate may be in the form of a sheet or a chip.

Examples of the form of the carbon fiber substrate in a sheet form include: a fiber bundle (tow) in which a plurality of carbon fibers are aligned in one direction; a fabric using fiber bundles of carbon fibers in the warp or weft; non-woven fabrics of carbon fibers, and the like.

Examples of the form of the carbon fiber substrate in the form of chips include chopped carbon fibers obtained by cutting fiber bundles, and woven fabrics in the form of chips.

As the fiber bundle, there can be mentioned: long fiber bundles arranged along the longitudinal direction of the carbon fiber-reinforced resin; short fiber bundles arranged along the width direction of the carbon fiber reinforced resin or in a direction inclined with respect to the longitudinal direction of the carbon fiber reinforced resin.

The carbon fiber base material contained in the carbon fiber reinforced resin may be in one form alone or in two or more forms. Examples of the plurality of carbon fiber substrates contained in the carbon fiber-reinforced resin include a combination of long fiber bundles and short fiber bundles, a combination of long fiber bundles, short fiber bundles, and woven fabric, and a combination of long fiber bundles, short fiber bundles, and chips.

Examples of the carbon fiber include PAN-based carbon fibers using polyacrylonitrile fibers as a raw material, pitch-based carbon fibers using coal pitch or petroleum pitch as a raw material, and PAN-based carbon fibers are preferable from the viewpoint of good mechanical properties of regenerated carbon fibers.

The carbon fiber may be used alone or in combination of two or more.

The number of carbon fibers constituting the fiber bundle is not particularly limited, and may be appropriately set according to the use, characteristics, and the like of the carbon fiber-reinforced resin.

The length and fiber diameter of the carbon fibers may be appropriately set according to the use, properties, and the like of the carbon fiber-reinforced resin, and are not particularly limited.

The proportion of the carbon fibers contained in the carbon fiber-reinforced resin may be appropriately set according to the use, characteristics, and the like of the carbon fiber-reinforced resin, and is not particularly limited.

(matrix resin)

The matrix resin may be a thermosetting resin or a thermoplastic resin. The thermosetting resin may be a cured product.

Examples of the thermosetting resin include: epoxy resins, unsaturated polyester resins, vinyl ester resins, phenolic resins, cyanate ester resins, polyimide resins, and the like.

The thermosetting resin may be used alone or in combination of two or more.

As the thermoplastic resin, there can be mentioned: polyamides, polyolefins, polyesters, polycarbonates, acrylics, acrylonitrile-butadiene-styrene copolymers, polyetheretherketones, polyphenylene sulfides, and the like.

The thermoplastic resin may be used alone or in combination of two or more.

The matrix resin may also contain additives as needed. Examples of additives include: curing agents, curing aids, internal mold release agents, flame retardants, antioxidants, light stabilizers, ultraviolet absorbers, colorants, and the like.

The proportion of the matrix resin contained in the carbon fiber-reinforced resin may be appropriately set according to the use, characteristics, and the like of the carbon fiber-reinforced resin, and is not particularly limited.

< manufacturing method of regenerated carbon fiber bundle, regenerated carbon fiber, and crushed regenerated carbon fiber

The method for producing a regenerated carbon fiber bundle, regenerated carbon fibers, or a crushed regenerated carbon fibers of the present invention is a method for recovering and regenerating a carbon fiber base material from a carbon fiber-reinforced resin in the form of a regenerated carbon fiber bundle, regenerated carbon fibers, or a crushed regenerated carbon fibers.

Specifically, the method for producing a regenerated carbon fiber bundle, a regenerated carbon fiber, and a crushed regenerated carbon fiber of the present invention includes the following steps.

Step (a): and cutting the carbon fiber reinforced resin as required.

Step (b): and a step of heating the carbon fiber-reinforced resin to thermally decompose the matrix resin to obtain a heat-treated product.

Step (c): and a step of separating the plurality of carbon fiber base materials into individual regenerated carbon fiber bundles by crushing the heat-treated material.

Step (d): and a step of discriminating the regenerated carbon fiber bundles separated by the disintegration according to the form of the regenerated carbon fiber bundles as required.

A step (e): and processing the regenerated carbon fiber bundle separated by the disintegration into other forms as required.

Step (f): and if necessary, further heating the regenerated carbon fiber bundle separated by the disintegration in an oxidizing atmosphere to reduce resin residue.

Step (g): and (3) processing the regenerated carbon fiber bundle separated by disintegration or the regenerated carbon fiber obtained by further heating in an oxidizing atmosphere as necessary into a crushed regenerated carbon fiber.

(step (a))

In the case where the carbon fiber-reinforced resin is a large molded article or the like, the carbon fiber-reinforced resin may not be directly fed to the heat treatment apparatus in the following step (b) or may not pass through the disintegrator in the step (c), and therefore the carbon fiber-reinforced resin may be cut into an appropriate size by a cutter as needed.

In the case of cutting the carbon fiber-reinforced resin, it is preferable to cut the carbon fiber-reinforced resin along the longitudinal direction of the long fiber bundle contained in the carbon fiber-reinforced resin, from the viewpoint that the long fiber bundle can be recovered as long as possible.

(step (b))

The heat-treated product is obtained by heating the carbon fiber-reinforced resin to thermally decompose (gasify, carbonize, etc.) the matrix resin.

The heat-treated product is obtained by consolidating a plurality of carbon fiber base materials with a resin residue such as a thermal decomposition product (carbide or the like) of the matrix resin. The heat treatment causes voids between the carbon fiber substrates of the heat-treated material, and the thickness of the heat-treated material is generally larger than that before the heat treatment.

The carbon fiber-reinforced resin can be heated by using a heat treatment apparatus having a heating furnace, for example.

Examples of the heat treatment apparatus include the following.

Fig. 1 is a schematic configuration diagram showing an example of a heat treatment apparatus. The heat treatment apparatus 1 includes a feeding chamber and gradually cooling chamber 10, which is replaced with nitrogen gas for feeding the carbon fiber reinforced resin 100 and discharging the heat treatment object 102, and a heating furnace 12 for heating the carbon fiber reinforced resin 100.

Fig. 2 is a schematic configuration diagram showing another example of the heat treatment apparatus. The heat treatment apparatus 2 includes a feed chamber 20 for feeding the carbon fiber reinforced resin 100 and replacing with nitrogen gas, a heating furnace 22 for heating the carbon fiber reinforced resin 100, and a gradually cooling chamber 24 for discharging the heat-treated material 102 and replacing with nitrogen gas.

As shown in fig. 3, for example, the carbon fiber reinforced resin 100 is loaded in the mesh tray 30 and fed into the heat treatment apparatus.

Examples of the heating furnace include: batch-type heating furnaces such as electric furnaces; a continuous heating furnace for pusher conveyance or belt conveyance.

A nitrogen gas supply source, a superheated steam generator, and the like are connected to the heating furnace.

The gradual cooling chamber and the feeding chamber are connected to a nitrogen gas supply source and the like.

The heat treatment apparatus may include a burner or the like for performing combustion treatment on the exhaust gas discharged from the heating furnace.

The heating furnace may be either an oxidizing atmosphere or a non-oxidizing atmosphere. The non-oxidizing atmosphere is preferable in that deterioration due to oxidation of the carbon fiber surface can be suppressed. The non-oxidizing atmosphere may be any atmosphere containing no oxygen or an atmosphere containing substantially no oxygen. It is preferable to introduce an inert gas containing no oxygen or substantially no oxygen into the heating furnace. The inert gas is preferably a nitrogen atmosphere or a superheated steam atmosphere in view of sufficiently thermally decomposing the matrix resin. The superheated steam atmosphere is more preferable in terms of high thermal conductivity.

In the present invention, since the heat-treated product is disintegrated to separate the plurality of carbon fiber substrates into individual regenerated carbon fiber bundles in the step (c) described below, it is not necessary to heat the carbon fiber bundles to 800 ℃ or higher by the method described in patent document 2 to sufficiently reduce the resin residue adhering between the plurality of carbon fiber substrates.

The temperature at which the carbon fiber-reinforced resin is heated is preferably 300 to 700 ℃, more preferably 400 to 700 ℃, and still more preferably 500 to 700 ℃. When the heating temperature is not less than the lower limit of the above range, the matrix resin can be sufficiently thermally decomposed. If the heating temperature is not more than the upper limit of the above range, the energy cost can be suppressed and the equipment specification can be made inexpensive. The heating temperature is a temperature in the atmosphere in the heating furnace.

The pressure at which the carbon fiber-reinforced resin is heated is usually slightly increased to slightly negative (reduced) pressure.

The time for heating the carbon fiber-reinforced resin may be set as appropriate within a range of 10 minutes to 180 minutes depending on the heating temperature. The heating time is preferably 10 minutes to 180 minutes, more preferably 30 minutes to 120 minutes. When the heating time is not less than the lower limit of the above range, the matrix resin can be thermally decomposed sufficiently. If the heating time is not more than the upper limit of the above range, the throughput (throughput) can be improved, and the regeneration treatment can be performed at low cost.

(step (c))

The heat-treated product is disintegrated to cause at least a part of the resin residue consolidated between the plurality of carbon fiber base materials to fall off, thereby separating the plurality of carbon fiber base materials into individual regenerated carbon fiber bundles. In addition, the variation in the content of the resin residue in the regenerated carbon fiber bundle recovered by the excess resin residue falling off becomes small.

The disintegration of the heat-treated product can be carried out by: while suppressing the breakage of the carbon fiber base material, the heat-treated material is subjected to pressure application, compression, tension, shear stress application, and impact application.

Examples of the disintegrator for disintegrating the heat-treated material include: a double-shaft roller type crusher, a multi-shaft roller type crusher with more than three shafts, a hammer type crusher and the like. The arrangement of the rollers in the multi-shaft roller crusher may be arranged in a quadrilateral or in a kilo-bird grid. In the case of the bird's nest arrangement, since sufficient stress can be applied to the heat-treated material, the roller surface can be free from irregularities. Preferably a twin-shaft roller crusher or a hammer crusher. Multiple defragmentators may be combined. In order to suppress the breakage of the carbon fiber base material, it is preferable that a sharp member such as a cutter is not included in a portion of the shredder which comes into contact with the heat-treated object.

Fig. 4 is a schematic view showing a mode of crushing a heat-treated object by a twin-shaft roller crusher.

The twin-roll crusher 40 is a device in which two rolls 42 having concave and convex surfaces are fitted and arranged. The two rollers 42 rotate in directions opposite to each other along the traveling direction of the heat-treated object 102 (in the case of the illustrated example, the direction from the top to the bottom). By passing the heat-treated object 102 between the two rollers 42, the heat-treated object 102 is pressed by the irregularities on the surfaces of the rollers 42, and the heat-treated object 102 is disintegrated and separated into a plurality of carbon fiber base materials (regenerated carbon fiber bundles) 104.

The twin-shaft roll crusher is not limited to the material of fig. 4. For example, as shown in fig. 5, two rollers 44 having a cross-sectional shape may be fitted and arranged.

(step (d))

When the carbon fiber base material contained in the carbon fiber reinforced resin is in two or more types, it is preferable to separate the regenerated carbon fiber bundles separated by disintegration of the heat-treated material in the form of regenerated carbon fiber bundles in order to improve the utility value as regenerated carbon fibers.

For example, the regenerated carbon fiber bundles separated by disintegration are divided into long fiber bundles arranged along the longitudinal direction of the carbon fiber-reinforced resin as shown in fig. 6; short fiber bundles arranged along the width direction of the carbon fiber-reinforced resin or in a direction inclined with respect to the longitudinal direction of the carbon fiber-reinforced resin as shown in fig. 7; a woven fabric such as a plain woven fabric (not shown); as shown in fig. 8, a carbon fiber bundle (chopped carbon fiber) in a chip form can be reused as a regenerated carbon fiber bundle for each application according to each form.

Since a small amount of resin residue is contained in the regenerated carbon fiber bundle separated by the disintegration, a plurality of carbon fibers constituting the carbon fiber bundle are solidified by the resin residue. Therefore, the long fiber bundle or the short fiber bundle is difficult to separate into individual carbon fibers, and can be maintained in the form of a carbon fiber bundle after being disintegrated. Therefore, the regenerated carbon fiber bundles separated by the disintegration can be easily distinguished according to the form of the regenerated carbon fiber bundles.

The average thickness of the recovered regenerated carbon fiber bundle is 0.01 to 1mm, preferably 0.01 to 1mm, more preferably 0.1 to 0.8mm, and still more preferably 0.2 to 0.7 mm. If the average value of the thicknesses of the regenerated carbon fiber bundles is equal to or more than the lower limit of the above range, the form of the carbon fiber bundles can be sufficiently maintained. When the average value of the thicknesses of the regenerated carbon fiber bundles is equal to or less than the upper limit of the above range, secondary processing such as cutting, crushing, and pulverization is facilitated, and wear of the cutter can be reduced. In addition, the regenerated carbon fiber bundle subjected to the crushing treatment has a significantly increased surface area as compared with the case where the regenerated carbon fiber not subjected to the crushing is subjected to the secondary heating treatment in the oxidizing atmosphere, and therefore, the uniform heating treatment can be performed. In addition, the quantitative charging property is improved.

The standard deviation of the thickness of the recovered regenerated carbon fiber bundle is 0.01 to 0.5mm, preferably 0.03 to 0.3mm, and more preferably 0.05 to 0.2 mm. If the standard deviation of the thickness of the regenerated carbon fiber bundle is not less than the lower limit of the above range, productivity is good. When the standard deviation of the thickness of the regenerated carbon fiber bundle is not more than the upper limit of the above range, secondary processing such as cutting, crushing, and pulverization is facilitated, and wear of the cutter can be reduced. In addition, the regenerated carbon fiber bundle subjected to the disintegration treatment has a significantly increased surface area as compared with the case where the secondary heat treatment is performed on the regenerated carbon fibers not subjected to the disintegration in the oxidizing atmosphere, and therefore, the uniform heat treatment can be performed. In addition, the quantitative charging property is improved.

The resin residue content of the recovered regenerated carbon fiber bundle is preferably 0.1 to 30 mass% based on 100 mass% of the carbon fiber base material. More preferably 10 to 28% by mass. More preferably 13 to 26% by mass. More preferably 20 to 25% by mass. When the resin residue content of the regenerated carbon fiber bundle is not less than the lower limit of the above range, the form of the carbon fiber bundle can be sufficiently maintained even after the long fiber bundle or the short fiber bundle is disintegrated. When the resin residue content of the regenerated carbon fiber bundle is not more than the upper limit of the above range, the resin residue as impurities is reduced, and the quality of the regenerated carbon fiber bundle is improved.

The standard deviation of the resin residue content of the recovered regenerated carbon fiber bundle is preferably 0% to 3%, more preferably 0% to 2%, and still more preferably 0% to 1%. When the standard deviation of the resin residue content of the regenerated carbon fiber bundle is not more than the upper limit value of the above range, the deviation of the resin residue content in the recovered regenerated carbon fiber bundle becomes small, and a regenerated carbon fiber bundle having high uniformity can be obtained.

(step (e))

The regenerated carbon fiber bundle separated by the disintegration may be processed into other forms.

For example, the separated regenerated carbon fiber bundle may be cut with a cutter such as a slitter (slitter), a guillotine (guillotine), or a rotary cutter (rotary cutter) to obtain a scrap-like regenerated carbon fiber bundle. Preferably, the carbon fiber woven fabric in the regenerated carbon fiber bundle is separated and cut to obtain a scrap-like regenerated carbon fiber bundle. Preferably, the long fiber bundles of the regenerated carbon fiber bundles are separated and cut to obtain short-cut regenerated carbon fiber bundles.

(step (f))

The regenerated carbon fiber bundles separated by the disintegration contain resin residues. In order to obtain regenerated carbon fibers with reduced resin residues, the regenerated carbon fiber bundles separated by disintegration may be further heated in an oxidizing atmosphere to oxidize and reduce the resin residues. As the oxidizing atmosphere, any atmosphere can be used as long as it contains oxygen. The concentration of oxygen is preferably 0.1 to 25 vol%.

The regenerated carbon fiber bundle heated in an oxidizing atmosphere becomes a carbon fiber bundle when the removal of the resin residue is insufficient, and becomes a flocculent carbon fiber when the removal of the resin residue is sufficient.

The temperature at which the regenerated carbon fiber bundle is heated is preferably 300 to 700 ℃, more preferably 400 to 600 ℃, and still more preferably 450 to 550 ℃. When the heating temperature is not less than the lower limit of the above range, the resin residue can be sufficiently removed. When the heating temperature is not more than the upper limit of the above range, the regenerated carbon fiber is less likely to be deteriorated by oxidation, and the mechanical properties and the like of the regenerated carbon fiber are less likely to be lowered.

The pressure at which the regenerated carbon fiber bundle is heated is usually slightly increased to slightly negative (reduced) pressure.

The time for heating the regenerated carbon fiber bundle may be appropriately set in the range of 10 minutes to 180 minutes depending on the heating temperature. Preferably 10 minutes to 180 minutes, more preferably 30 minutes to 120 minutes. When the heating time is not less than the lower limit of the above range, the resin residue can be sufficiently removed. If the heating temperature is not more than the upper limit of the above range, the yield can be improved.

(step (g))

The separated regenerated carbon fiber bundle may be finely pulverized by a known pulverizer to obtain a pulverized product of regenerated carbon fiber.

(mechanism of action)

In the above-described method for producing a regenerated carbon fiber bundle, regenerated carbon fibers, and a crushed regenerated carbon fiber product of the present invention, the matrix resin is thermally decomposed by heating the carbon fiber-reinforced resin to obtain a heat-treated product, and the heat-treated product is disintegrated to separate the plurality of carbon fiber base materials into individual regenerated carbon fiber bundles, so that it is not necessary to sufficiently reduce the resin residue that is heated to 800 ℃ or higher and is consolidated between the plurality of carbon fiber base materials. Therefore, even if the carbon fiber-reinforced resin is not heated at 800 ℃ or higher, the carbon fiber base material can be recovered as a regenerated carbon fiber bundle while maintaining the form when contained in the carbon fiber-reinforced resin. The recovered regenerated carbon fiber bundle (long fiber bundle, short fiber bundle, woven fabric, etc.), regenerated carbon fiber, or crushed regenerated carbon fiber can be reused as regenerated carbon fiber in various applications.

In the method for producing a regenerated carbon fiber bundle, regenerated carbon fibers, and a crushed regenerated carbon fiber product according to the present invention, at least a part of the resin residue consolidated between the plurality of carbon fiber substrates falls off because the heat-treated product is crushed. Therefore, the variation in the content of the resin residue in the recycled carbon fiber bundle recovered by the excess resin residue falling off becomes small.

< method for producing carbon fiber-reinforced resin >

The method for producing a carbon fiber-reinforced resin according to the present invention is a method for producing a carbon fiber-reinforced resin including the regenerated carbon fiber bundle, the regenerated carbon fiber, and the regenerated carbon fiber pulverized material obtained by the method for producing a regenerated carbon fiber bundle, a regenerated carbon fiber, and a regenerated carbon fiber pulverized material according to the present invention.

Specific examples of the method for producing the carbon fiber-reinforced resin include the following method (α).

Method (a): a method of processing a kneaded product into pellets, the method comprising kneading a regenerated carbon fiber bundle, a regenerated carbon fiber, a crushed product of a regenerated carbon fiber, and a thermoplastic resin to obtain a kneaded product.

Examples of the regenerated carbon fiber bundle, regenerated carbon fiber, and regenerated carbon fiber pulverized material that can be used in method (α) include: long fiber bundles, short fiber bundles, carbon fiber woven fabrics, chip-like carbon fiber bundles, flocculent carbon fibers, carbon fiber pulverized products, and the like.

Examples of the thermoplastic resin that can be used in the method (α) include: polyamides, polyolefins, polyesters, polycarbonates, acrylics, acrylonitrile-butadiene-styrene copolymers, polyetheretherketones, polyphenylene sulfides, and the like.

In the method (α), for example, the regenerated carbon fibers and the thermoplastic resin are kneaded by an extruder, the kneaded product is extruded from a die in the form of strands (strand), and after the strands are cooled, the strands are cut by a pelletizer (pelletier) to obtain pellets.

< apparatus for producing regenerated carbon fiber >

An apparatus for producing a regenerated carbon fiber bundle according to the present invention is an apparatus for obtaining a carbon fiber base material as regenerated carbon fibers from a carbon fiber-reinforced resin, the apparatus including: a heating furnace for obtaining a heat-treated product by heating the carbon fiber-reinforced resin; and a disintegrator for disintegrating the heat-treated material.

The heating furnace may be one of the above-described heat treatment apparatuses.

Examples of the crusher include the above-mentioned double-shaft roller crusher, a multi-shaft roller crusher having three or more shafts, and a hammer crusher. The arrangement of the rollers in the multi-shaft roller crusher may be arranged in a quadrilateral or a kilo-bird grid arrangement. In the case of the bird's nest arrangement, since sufficient stress can be applied to the heat-treated material, the roller surface can be free from irregularities. Preferably a twin-shaft roller crusher or a hammer crusher. Multiple defragmentators can also be combined. In order to suppress the breakage of the carbon fiber base material, it is preferable that a part of the shredder which comes into contact with the heat-treated material does not include a sharp member such as a cutter.

The manufacturing device of the regenerated carbon fiber bundle can be provided with a feeding chamber or a gradually cooling chamber at the same time in a heating furnace according to requirements; a supply source for supplying nitrogen gas to the heating furnace, the feed chamber, the gradually cooling chamber, and the like; a superheated steam generator for supplying superheated steam to a heating furnace or the like; and a burner for burning the exhaust gas discharged from the heating furnace.