JP2020062573A - Manufacturing method of regenerated reinforcement fiber and manufacturing apparatus thereof - Google Patents

Abstract

To provide a manufacturing method of a regenerated reinforcement fiber and a manufacturing apparatus thereof, capable of obtaining a regenerated reinforcement fiber from an intermediate product of a fiber-reinforced plastic with good productivity.SOLUTION: The manufacturing method of a regenerated reinforcement fiber is a method to obtain a reinforcement fiber as a regenerated reinforcement fiber from an intermediate product 100 of a fiber-reinforced plastic including a reinforcement fiber and a matrix resin. By heating a long continuous intermediate product 100 while moving with its traveling direction being in its longer direction, the matrix resin is thermally decomposed to obtain a heat treatment product 102 including a regenerated reinforcement fiber.SELECTED DRAWING: Figure 1

Description

  TECHNICAL FIELD The present invention relates to a method and an apparatus for producing recycled reinforcing fibers.

For example, the following method has been proposed as a method of recovering reinforced fibers from waste materials of intermediate products generated from the manufacturing process of fiber reinforced plastics and the manufacturing process of intermediate products (prepregs, etc.) of fiber reinforced plastics.
(1) A method in which a prepreg containing carbon fibers impregnated with a resin is cut, and the cut prepreg is heat-treated to thermally decompose the resin (Patent Document 1).
(2) A method of curing a prepreg containing carbon fibers impregnated with a resin, crushing the cured product, and heat-treating the crushed cured product to thermally decompose the resin (Patent Document 1).

JP-A-11-290822

However, in the method (1), since the prepreg is cut before the resin is thermally decomposed, it is difficult to handle the prepreg after cutting, and the number of steps for filling the tray with the prepreg after cutting is increased. Sex decreases. Moreover, since the cut prepreg is heat-treated in a batch system, the prepreg cannot be continuously heat-treated, and the productivity of the recycled carbon fiber is not good. Further, when the cut prepreg is thermally decomposed to remove the matrix resin, the carbon fibers are easily scattered by a slight air flow in the furnace, and the inside of the furnace is contaminated. Further, in the layer of prepreg pieces filled in the tray, the matrix resin is not uniformly removed to the inside of the layer during thermal decomposition, and the matrix resin removal efficiency is poor.
In the method (2), since the steps of hardening the prepreg and filling the crushed hardened material into the tray are increased, the productivity of the recycled carbon fiber is not good. Further, since the crushed hardened material is heat-treated in a batch system, the hardened material cannot be continuously heat-treated, resulting in poor productivity of the recycled carbon fiber. Further, when the crushed hardened material is thermally decomposed to remove the matrix resin, the carbon fibers are easily scattered by a slight air flow in the furnace and the inside of the furnace is contaminated. Further, in the layer of the cured product pieces filled in the tray, the matrix resin is not uniformly removed to the inside of the layer during thermal decomposition, and the matrix resin removal efficiency is poor.

  The present invention provides a method and an apparatus for producing regenerated reinforced fibers, which enables regenerated reinforced fibers to be produced with high productivity from intermediate products of fiber reinforced plastics.

The present invention has the following aspects.
<1> A method for obtaining the above-mentioned reinforcing fibers as recycled reinforcing fibers from an intermediate product of a fiber-reinforced plastic containing a reinforcing fiber and a matrix resin, wherein a continuous long intermediate product is formed such that its longitudinal direction is the traveling direction. A method for producing regenerated reinforcing fibers, in which the matrix resin is thermally decomposed to obtain a heat-treated product containing the regenerated reinforcing fibers by heating while moving it to the above.
<2> Manufacture of the regenerated reinforcing fiber according to <1>, in which the intermediate product is moved by a feed roll composed of a pair of rolls, a belt conveyor having a mesh-shaped endless belt, or a double belt press composed of a pair of belt conveyors. Method.
<3> The method for producing regenerated reinforcing fibers according to <1> or <2>, wherein the heat-treated product is cut while being moved so that the longitudinal direction thereof is the traveling direction.
<4> The heat-treated product is cut with at least one selected from the group consisting of a slitter, a guillotine cutter, a cutter mill, a roving cutter, a flying shear, an ultrasonic cutter, a laser cutter, and a water jet cutter, <3> The method for producing a recycled reinforcing fiber.
<5> The method for producing a recycled reinforcing fiber according to any one of <1> to <4>, wherein the reinforcing fiber is a carbon fiber.
<6> The method for producing a recycled reinforcing fiber according to any one of <1> to <5>, wherein the intermediate product is a prepreg, a sheet molding compound, a tow prepreg, or a carbon fiber cable.
<7> A device for obtaining the reinforced fiber as a regenerated reinforced fiber from an intermediate product of a fiber reinforced plastic containing a reinforced fiber and a matrix resin, and a supply unit for storing the continuous long intermediate product, and the supply unit. By transporting the withdrawn intermediate product so that its longitudinal direction is the traveling direction and heating the intermediate product withdrawn and moved from the supply unit to thermally decompose the matrix resin, An apparatus for producing recycled reinforcing fibers, comprising: a heating unit for obtaining a heat-treated product containing the recycled reinforcing fibers.
<8> The apparatus for producing regenerated reinforcing fibers according to <7>, wherein the heating unit has a tunnel-shaped heating furnace.
<9> Reinforcement of regeneration of <7> or <8>, in which the transport section has a feed roll including a pair of rolls, a belt conveyor including a mesh-shaped endless belt, or a double belt press including a pair of belt conveyors. Fiber manufacturing equipment.
<10> The apparatus for producing regenerated reinforcing fibers according to any one of <7> to <9>, further including a cutting unit that cuts the moving heat-treated product.
<11> In the above <10>, the cutting portion has at least one selected from the group consisting of a slitter, a guillotine cutter, a cutter mill, a roving cutter, a flying shear, an ultrasonic cutter, a laser cutter, and a water jet cutter. Equipment for manufacturing recycled fiber.

According to the method for producing regenerated reinforcing fibers of the present invention, it is possible to obtain regenerated reinforcing fibers with high productivity from an intermediate product of fiber reinforced plastic.
According to the apparatus for producing recycled reinforcing fiber of the present invention, the recycled reinforcing fiber can be obtained with high productivity from the intermediate product of the fiber reinforced plastic.

It is a schematic block diagram which shows an example of the manufacturing apparatus of the reproduction | regeneration reinforcement fiber of this invention. It is a schematic block diagram which shows the other example of the manufacturing apparatus of the reproduction | regeneration reinforcement fiber of this invention.

The following definitions of terms apply throughout the specification and claims.
“Intermediate product of fiber reinforced plastic” refers to a material that can be processed into fiber reinforced plastic by molding or the like.
The “non-oxidizing atmosphere” refers to an atmosphere containing no oxygen gas or an atmosphere containing substantially no oxygen gas. “Substantially free of oxygen gas” means that even if oxygen gas is inevitably mixed in the atmosphere when heating the intermediate product, the amount of oxygen gas is almost the same as the deterioration of the reinforcing fiber due to oxygen gas. It means that the amount is not within the range.
The “oxidizing atmosphere” is an atmosphere containing oxygen gas and means an atmosphere other than the non-oxidizing atmosphere.
The "superheated steam" means steam heated to a temperature equal to or higher than the boiling point.
The “resin residue content” of the heat-treated product is a value obtained from the equation (1).
(B−A × X) / (B) × 100 Formula (1)
A: Mass of intermediate product of fiber-reinforced plastic before heat treatment B: Mass of heat-treated product X: Content of reinforcing fiber in intermediate product of fiber-reinforced plastic before heat treatment Numerical range in the present specification and claims "-" Shown means to include the numerical values described before and after it as the lower limit value and the upper limit value.
The dimensional ratios in FIGS. 1 and 2 are different from actual ones for convenience of description.

<Intermediate product of fiber reinforced plastic>
The intermediate product of the fiber-reinforced plastic in the present invention contains a reinforcing fiber and a matrix resin.
The intermediate product may include other materials (such as an inorganic filler) other than the reinforcing fiber and the matrix resin.

  Examples of intermediate products include UD (one direction) and cloth (fabric) prepregs, tow prepregs, sheet molding compounds, and carbon fiber cables. As the intermediate product, a prepreg, a sheet molding compound, a tow prepreg, or a carbon fiber cable is preferable, because a continuous long product can be easily obtained and continuous heat treatment can be easily performed.

(Reinforcing fiber)
The reinforcing fiber may be one that is not thermally decomposed or is not easily thermally decomposed, and can retain the shape of the fiber even when subjected to heat treatment.
Examples of the reinforcing fiber include carbon fiber (including graphite fiber), glass fiber, silicon carbide fiber, alumina fiber, boron fiber, tungsten carbide fiber, metal fiber, and the like. Fibers are preferred.

Examples of the carbon fibers include PAN-based carbon fibers using polyacrylonitrile fiber as a raw material, pitch-based carbon fibers using coal pitch or petroleum pitch as a raw material, and the mechanical properties of recycled carbon fibers are good. PAN-based carbon fiber is preferred.
The reinforcing fibers may be used alone or in combination of two or more.

The form of the reinforcing fiber may be a reinforcing fiber base material such as a fiber bundle or a woven fabric, or may be a reinforcing fiber (milled reinforcing fiber etc.) not constituting the reinforcing fiber base material. As a form of the reinforcing fiber, a reinforcing fiber base material is preferable because it can be easily recovered as a recycled reinforcing fiber from an intermediate product.
The number of layers of the reinforcing fiber base material contained in the intermediate product is appropriately set depending on the use and characteristics of the intermediate product, and is not particularly limited.
The reinforcing fiber base material may be in a sheet shape or a chip shape.

Examples of the form of the sheet-like reinforcing fiber base material include a fiber bundle (tow) in which a plurality of reinforcing fibers are aligned in one direction, a woven fabric using the reinforcing fiber bundle for warp and weft, and a non-woven fabric of reinforcing fiber. To be
Examples of the form of the chip-shaped reinforcing fiber base material include chopped reinforcing fibers obtained by cutting a fiber bundle, and chip-shaped woven fabrics.

  The form of the reinforcing fiber base contained in the intermediate product may be only one type, or may be two or more types. The plurality of reinforcing fiber base materials included in the intermediate product are, for example, a combination of a sheet-like reinforcing fiber base material and a chip-like reinforcing fiber base material.

The number of reinforcing fibers constituting the fiber bundle is appropriately set depending on the use and characteristics of the fiber reinforced plastic and is not particularly limited.
The length and fiber diameter of the reinforcing fiber are appropriately set depending on the application, characteristics, etc. of the fiber-reinforced plastic and are not particularly limited.
The ratio of the reinforcing fiber contained in the intermediate product is appropriately set according to the application, characteristics, etc. of the fiber-reinforced plastic and is not particularly limited.

(Matrix resin)
The matrix resin may be a thermosetting resin or a thermoplastic resin. The thermosetting resin may be an uncured one or a cured one.

As the thermosetting resin, epoxy resin, unsaturated polyester resin, vinyl ester resin, phenol resin, cyanate resin, melamine resin, urea resin, diallyl phthalate resin, benzoguanamine resin, alkyd resin, vinyl ester resin, diallyl terephthalate, silicone resin , Urethane resin, furan resin, ketone resin, xylene resin, thermosetting polyimide resin and the like.
The thermosetting resins may be used alone or in combination of two or more.

As the thermoplastic resin, polyamide (nylon, etc.), polyolefin (polyethylene, polypropylene, etc.), polyester (polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, etc.), polycarbonate, acrylic resin (polymethyl methacrylate (PMMA) ) Etc.), acrylonitrile-butadiene-styrene copolymer, polyphenylene sulfide, polystyrene resin, polyphenylene ether, polyoxymethylene, polyvinyl chloride, polyurethane, polyimide, polyamideimide, polyetherimide, polysulfone, polyether sulfone, polyketone, poly Ether ketone, polyether ether ketone, polyarylate, polyether nitrile, phenoxy resin , Polybutadiene resins, polyisoprene resins, thermoplastic elastomers, copolymers thereof, modified products, blends resins. Further, a resin added with an elastomer or a rubber component may be used.
The thermoplastic resins may be used alone or in combination of two or more.

The matrix resin may contain an additive as needed. Examples of the additive include a curing agent, a curing aid, an internal release agent, a flame retardant, an antioxidant, a light stabilizer, an ultraviolet absorber and a colorant.
The ratio of the matrix resin contained in the intermediate product is appropriately set depending on the use and characteristics of the fiber reinforced plastic and is not particularly limited.

<Recycled fiber manufacturing equipment>
The apparatus for producing regenerated reinforcing fibers of the present invention comprises a conveying section for moving a continuous long intermediate product so that its longitudinal direction is the traveling direction, and heating the moving intermediate product to thermally decompose the matrix resin. And a heating unit for obtaining a heat-treated product containing regenerated reinforcing fibers.
The apparatus for producing regenerated reinforcing fibers of the present invention may further include a cutting unit for cutting the moving heat-treated product, if necessary.
The apparatus for producing regenerated reinforcing fibers of the present invention may further include a supply unit that stores a continuous long intermediate product, if necessary.

  Examples of the transport unit include those having a feed roll (nip roll, unit roll), a belt conveyor, a roller conveyor, a double belt press, and the like. As the feed roll, for example, one having a pair of rubber rolls adjacent to each other and at least one roll being rotationally driven can be mentioned. Examples of the belt conveyor include one having a pair of spaced rollers and a mesh-shaped endless belt bridged between the rollers, and at least one of the rollers is rotationally driven. Examples of the mesh-shaped endless belt include an endless belt made of a metal mesh. As the roller conveyor, for example, a roller conveyor having a plurality of rolls arranged in parallel at a predetermined interval, and each roll being rotationally driven, can be mentioned. The double belt press includes, for example, a press which presses a material between a pair of belt conveyors arranged vertically. A feed roll, a belt conveyor, or a double belt press is preferable as the transport unit.

As the heating unit, any unit can be used as long as it can heat-treat a continuous long intermediate product to thermally decompose the matrix resin of the intermediate product. As the heating unit, a unit having a tunnel-shaped heating furnace is preferable from the viewpoint that it is easy to continuously heat-treat a continuous long intermediate product.
The heating furnace may include a heat treatment unit that heats the intermediate product, and a cooling unit that cools the heat treatment products that are arranged in parallel on the downstream side of the heat treatment unit. The heating furnace may further include gas seal chambers arranged in parallel on the upstream side of the heat treatment section and on the downstream side of the cooling section. The heating furnace may further include a burner that burns exhaust gas discharged from the heat treatment unit or the gas seal chamber. A nitrogen gas supply source, an air supply source, a superheated steam generator, and the like are connected to the heat treatment section. A cooling pipe is arranged in the cooling unit, and a heat exchanger is connected to the cooling pipe. A nitrogen gas supply source or the like is connected to the gas seal chamber.

  Examples of the cutting unit include those having a slitter, a guillotine cutter, a cutter mill, a roving cutter, a flying shear, an ultrasonic cutter, a laser cutter, a water jet cutter, and the like. As the cutting portion, it is preferable to have a slitter, a guillotine cutter, a cutter mill, a roving cutter, a flying shear, an ultrasonic cutter, a laser cutter, or a water jet cutter from the viewpoint that a regenerated carbon fiber bundle with a regular fiber length can be obtained. .

  As the supply unit, an unwind roll around which a continuous long intermediate product is wound, a case where the continuous long intermediate product is folded and stored, and a tow-shaped continuous long intermediate product is rolled up. Examples of such a bobbin include a wound bobbin and a reel around which a cable-shaped continuous long intermediate product is wound.

FIG. 1 is a schematic configuration diagram showing an example of an apparatus for producing a recycled reinforcing fiber of the present invention.
The apparatus 1 for producing recycled reinforcing fibers is a winding roll 10 around which a continuous long intermediate product 100 is wound; the intermediate product 100 is pulled out from the winding roll 10 and the intermediate product 100 advances in the longitudinal direction. A feed roll 12 that is moved in the same direction; a heat treatment product by heating an intermediate product 100 that is provided between the unwind roll 10 and the feed roll 12 and moves from the unwind roll 10 toward the feed roll 12. A heating furnace 14 for obtaining 102; a slitter 16 for longitudinally cutting the heat-treated product 102 that has passed through the heating furnace 14 and has been sent out from the feed roll 12; and a short cut for the heat-treated product 102 cut by the slitter 16. The guillotine cutter 18 is provided.

FIG. 2 is a schematic configuration diagram showing another example of the apparatus for producing recycled reinforcing fibers of the present invention.
The regenerated reinforcing fiber manufacturing apparatus 2 is provided with a winding roll 10 around which a continuous long intermediate product 100 is wound; a heating roll 14 is provided in the heating furnace 14 so that both ends thereof project from the winding roll 10. A belt conveyor 20 that pulls out the intermediate product 100 and moves the intermediate product 100 so that its longitudinal direction is the traveling direction; heating the intermediate product 100 moving on the belt conveyor 20 to obtain a heat-treated product 102 Furnace 14; slitter 16 that cuts heat-treated product 102 that has passed through heating furnace 14 and is sent from the end of belt conveyor 20 in the longitudinal direction; and guillotine that cuts heat-treated product 102 that has been cut by slitter 16 And a cutter 18.

  The apparatus for producing regenerated reinforcing fibers according to the present invention includes a conveyor for moving a continuous long intermediate product so that its longitudinal direction is the traveling direction, and heating the moving intermediate product to heat the matrix resin. It is only required to have a heating unit for obtaining a heat-treated product containing regenerated reinforcing fibers by decomposing, and the present invention is not limited to the apparatus for producing regenerated reinforcing fibers of the illustrated example.

(Mechanism of action)
In the recycled reinforcing fiber manufacturing apparatus of the present invention described above, the longitudinal direction of the supply unit that stores the continuous long intermediate product and the intermediate product pulled out from the supply unit is the traveling direction. Since it is provided with a transporting unit for moving the intermediate product and a heating unit for heating the intermediate product that is pulled out from the supply unit and moving to obtain a heat-treated product containing regenerated reinforcing fibers, Can be produced continuously. Moreover, since the intermediate product is not cut in advance, it is easy to handle the intermediate product. Therefore, it is possible to obtain regenerated reinforcing fibers from an intermediate product with high productivity, as compared with a conventional apparatus that heat-processes cut prepregs in a batch process.

<Method of manufacturing recycled reinforcing fiber>
The method for producing regenerated reinforced fibers of the present invention is a method of recovering reinforced fibers from an intermediate product of fiber reinforced plastic and regenerating them as regenerated reinforced fibers.
The method for producing regenerated reinforcing fiber of the present invention specifically includes the following steps.
Step (a): a step of heating a continuous long intermediate product while moving it so that its longitudinal direction is the traveling direction to thermally decompose the matrix resin to obtain a heat-treated product containing regenerated reinforcing fibers. .
Step (b): A step of collecting a heat-treated product piece containing regenerated reinforcing fibers by cutting the heat-treated product while moving the longitudinal direction of the heat-treated product as the traveling direction, if necessary.
Step (c): A step of further heating the heat-treated piece under an oxidizing atmosphere to reduce the resin residue, if necessary.
Step (d): A step of processing the heat-treated product piece, if necessary.

  Hereinafter, an example of a method for producing a recycled reinforcing fiber of the present invention will be described in detail with reference to FIG.

(Process (a))
The intermediate product 100 is unwound from the unwinding roll 10, passed through a tunnel-shaped heating furnace 14, and then passed between a pair of feed rolls 12.
By rotating the feeding roll 12, the continuous long intermediate product 100 is pulled out from the unwinding roll 10, and the intermediate product 100 is directed from the unwinding roll 10 toward the feeding roll 12 so that the longitudinal direction of the intermediate product 100 is the traveling direction. To move inside the heating furnace 14.
By heating the intermediate product 100 while moving it in the heating furnace 14, the matrix resin contained in the intermediate product 100 is thermally decomposed (gasification, carbonization, etc.) to obtain a heat-treated product 102 containing regenerated reinforcing fibers.

  The length of the intermediate product is preferably a furnace length plus 2 m or more, more preferably a furnace length plus 5 m or more, still more preferably a furnace length plus 10 m or more, from the viewpoint that the productivity of the recycled reinforcing fiber is further increased. The longer the intermediate product, the better, and the upper limit is not particularly limited.

  The inside of the heating furnace is in an oxidizing atmosphere or a non-oxidizing atmosphere. A non-oxidizing atmosphere is preferable because the deterioration of the reinforcing fiber surface due to oxidation can be suppressed. As the non-oxidizing atmosphere, any atmosphere containing no oxygen gas or an atmosphere containing substantially no oxygen gas can be adopted. An inert gas containing no oxygen gas or substantially no oxygen gas may be appropriately introduced into the heating furnace. The inert gas is preferably a nitrogen gas atmosphere or a superheated steam atmosphere from the viewpoints of being able to sufficiently thermally decompose the matrix resin and being economical and safe.

  The temperature for heating the intermediate product may be appropriately set in the range of 300 to 1000 ° C. The heating temperature is preferably 300 to 700 ° C, more preferably 400 to 700 ° C, and further preferably 500 to 700 ° C. When the heating temperature is at least the lower limit value of the above range, the matrix resin can be sufficiently thermally decomposed. When the heating temperature is equal to or lower than the upper limit value of the above range, energy cost can be suppressed and equipment specifications can be reduced. The heating temperature is the temperature in the atmosphere in the heating furnace.

  The time for heating the intermediate product (the residence time of the intermediate product in the heating furnace) may be appropriately set within the range of 10 to 180 minutes depending on the heating temperature. The heating time is preferably 10 to 180 minutes, more preferably 10 to 120 minutes, still more preferably 10 to 60 minutes. When the heating time is at least the lower limit value of the above range, the matrix resin can be sufficiently thermally decomposed. When the heating time is not more than the upper limit value of the above range, the throughput can be increased and the productivity is further improved.

  The resin residue content of the heat-treated product is preferably 0.01 to 30.0% by mass, more preferably 3 to 25% by mass, still more preferably 5 to 20% by mass, relative to 100% by mass of the heat-treated product. When the resin residue content of the heat-treated product is at least the lower limit value of the above range, the heat-treated product can sufficiently retain its form as a reinforcing fiber bundle, and the handleability of the heat-treated product is improved. Therefore, the heat-treated product is easily cut, and the productivity of the recycled reinforcing fiber is further increased. In addition, the recycled reinforcing fibers obtained by cutting the heat-treated product can sufficiently maintain the form as a reinforcing fiber bundle. If the resin residue content of the heat-treated product is at most the upper limit value of the above range, the heat-treated product will not be too hard. Therefore, the heat-treated product is easily cut, and the productivity of the recycled reinforcing fiber is further increased. Further, the resin residue which is an impurity is reduced, and the quality of the recycled reinforcing fiber is improved.

(Process (b))
After the heat-treated product 102 that has passed through the heating furnace 14 and has been sent out from the feed roll 12 is cut in the longitudinal direction by the slitter 16, the heat-treated product 102 cut by the slitter 16 is cut into short pieces by the guillotine cutter 18. Thus, the heat-treated product piece 104 containing the recycled reinforcing fibers is collected.

  Since the heat-treated material piece obtained by cutting the heat-treated material contains a small amount of resin residue, the plurality of reinforcing fibers are fixed by the resin residue. Therefore, the heat-treated piece can retain the form of a reinforcing fiber bundle, a woven fabric, a non-woven fabric, or the like. Therefore, the heat-treated material piece can be reused for the purpose according to each form. For example, a chip-shaped reinforcing fiber bundle can be reused as a chopped recycled reinforcing fiber bundle.

(Process (c))
The heat-treated product piece contains a resin residue. In order to obtain a recycled reinforcing fiber having a reduced resin residue, the heat-treated piece may be further heated in an oxidizing atmosphere to oxidize and reduce the resin residue. Any oxidizing atmosphere can be used as long as it contains oxygen gas. The concentration of oxygen gas is preferably 0.1 to 21% by volume.
The heat-treated material piece heated in an oxidizing atmosphere becomes a reinforcing fiber bundle when the resin residue is not sufficiently removed, and becomes a cotton-like reinforcing fiber when the resin residue is sufficiently removed.

  300-700 degreeC is preferable, as for the temperature at the time of heating a heat-processed piece, 400-600 degreeC is more preferable, and 450-550 degreeC is further more preferable. When the heating temperature is at least the lower limit value of the above range, the resin residue can be sufficiently removed. When the heating temperature is at most the upper limit value of the above range, the recycled reinforcing fibers are less likely to deteriorate, and the mechanical properties of the recycled reinforcing fibers are less likely to deteriorate.

  The time for heating the heat-treated piece may be appropriately set within the range of 10 to 180 minutes depending on the heating temperature. The heating time is preferably 10 to 180 minutes, more preferably 10 to 120 minutes, and further preferably 10 to 60 minutes. When the heating time is at least the lower limit value of the above range, the resin residue can be sufficiently removed. If the heating temperature is at most the upper limit value of the above range, the throughput can be increased.

(Process (d))
The heat-treated piece may be finely crushed using a known crusher to obtain a milled regenerated reinforcing fiber.

(Mechanism of action)
In the method for producing regenerated reinforcing fibers of the present invention described above, a continuous long intermediate product is heated while being moved so that the longitudinal direction thereof is the traveling direction, whereby the matrix resin is thermally decomposed. Since the heat-treated product containing the regenerated reinforcing fibers is obtained, the heat-treated product containing the regenerated reinforcing fibers can be continuously produced. Moreover, since the intermediate product is not cut in advance, it is easy to handle the intermediate product. Therefore, as compared with the conventional method in which the cut prepreg is heat-treated in a batch system, the recycled reinforcing fibers can be obtained from the intermediate product with high productivity.

<How to use recycled reinforcing fibers>
Regenerated reinforcing fibers can be reused as reinforcing fibers for intermediate products of fiber-reinforced plastics.
The following method (α) may be mentioned as a specific method for producing the intermediate product.
Method (α): A method of kneading the recycled reinforcing fibers and the thermoplastic resin to obtain a kneaded product, and processing the kneaded product into pellets.

Examples of the form of the recycled reinforcing fibers that can be used in the method (α) include long fiber bundles, short fiber bundles, reinforcing fiber woven fabrics, chip-like reinforcing fiber bundles, cotton-like reinforcing fibers, and milled reinforcing fibers.
The thermoplastic resin that can be used in the method (α) includes polyamide (nylon, etc.), polyolefin (polyethylene, polypropylene, etc.), polyester (polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, etc.), polycarbonate. , Acrylic resin (polymethylmethacrylate (PMMA) etc.), acrylonitrile-butadiene-styrene copolymer, polyphenylene sulfide, polystyrene resin, polyphenylene ether, polyoxymethylene, polyvinyl chloride, polyurethane, polyimide, polyamideimide, polyetherimide, Polysulfone, polyether sulfone, polyketone, polyether ketone, polyether ether ketone, polyarylate, poly Terunitoriru, phenoxy resins, polybutadiene resins, polyisoprene resins, thermoplastic elastomers, copolymers thereof, modified products, blends resins. Further, a resin added with an elastomer or a rubber component may be used.

  In the method (α), for example, pellets are obtained by kneading the recycled reinforcing fibers and the thermoplastic resin with an extruder, extruding the kneaded product as a strand from a die, cooling the strand, and then cutting the strand with a pelletizer.

  Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

<Measurement>
(Resin residue content of heat treated pieces)
The resin residue content of the heat-treated piece was calculated from the formula (1) by calculating the mass of the reinforcing fiber contained in the intermediate product of the fiber-reinforced plastic before the heat treatment from the content of the reinforcing fiber.

<Intermediate product>
As an intermediate product, a prepreg (length: 20 m, width: 30 cm, thickness: 0.12 mm, type of reinforcing fiber: PAN-based carbon fiber, type of carbon fiber substrate: 0 ° oriented fiber bundle single layer, matrix resin Two types of unwinding rolls around which (uncured epoxy resin) was wound were prepared.

<Example 1>
An apparatus 2 for producing recycled reinforcing fibers shown in FIG. 2 was prepared.
Two continuous long prepregs were arranged on the endless belt made of metal mesh of the belt conveyor 20 and moved in the heating furnace 14 (length: 4 m) at 12 m / h. The prepreg was heated at 600 ° C. while maintaining the nitrogen gas atmosphere in the heating furnace 14 to obtain a heat-treated product. The heat-treated product was cut with a slitter 16 and cut with a guillotine cutter 18 to obtain a heat-treated product piece containing regenerated carbon fibers. The resin residue content of the heat-treated piece was 10% by mass. It was possible to continuously obtain pieces of the heat-treated product containing the regenerated carbon fiber.

<Comparative Example 1>
The tray was filled with prepreg which was previously cut with a slitter and a guillotine cutter, and heated at 600 ° C. for 120 minutes to obtain a heat-treated product. The resin residue content of the heat-treated material piece was 16% by mass, and the matrix resin removability was poor as compared with the heat-treated material piece of Example 1.

  INDUSTRIAL APPLICABILITY The method for producing recycled reinforcing fibers of the present invention is useful as a method for recovering reinforcing fibers from recycled fiber-reinforced plastic intermediate products as recycled reinforcing fibers.

  1 Recycled Reinforcement Fiber Manufacturing Equipment, 2 Recycled Reinforcement Fiber Manufacturing Equipment, 10 Unwinding Roll, 12 Feeding Roll, 14 Heating Furnace, 16 Slitter, 18 Guillotine Cutter, 20 Belt Conveyor, 100 Intermediate Product, 102 Heat Treated Product, 104 Heat-treated piece.

Claims (11)

A method of obtaining the above-mentioned reinforcing fibers as recycled reinforcing fibers from an intermediate product of a fiber-reinforced plastic, including reinforcing fibers and a matrix resin,
By heating the continuous long intermediate product while moving it so that its longitudinal direction is the traveling direction, the matrix resin is thermally decomposed to obtain a heat-treated product containing the regenerated reinforcing fiber. Fiber manufacturing method.   The method for producing recycled reinforcing fibers according to claim 1, wherein the intermediate product is moved by a feed roll including a pair of rolls, a belt conveyor including a mesh-shaped endless belt, or a double belt press including a pair of belt conveyors.   The method for producing regenerated reinforcing fibers according to claim 1, wherein the heat-treated product is cut while being moved so that the longitudinal direction thereof is the traveling direction.   The heat-treated product is cut using at least one selected from the group consisting of a slitter, a guillotine cutter, a cutter mill, a roving cutter, a flying shear, an ultrasonic cutter, a laser cutter, and a water jet cutter. A method for producing the regenerated reinforcing fiber described.   The method for producing a recycled reinforcing fiber according to claim 1, wherein the reinforcing fiber is a carbon fiber.   The method for producing a recycled reinforcing fiber according to claim 1, wherein the intermediate product is a prepreg, a sheet molding compound, a tow prepreg, or a carbon fiber cable. A device for obtaining the reinforcing fibers as recycled reinforcing fibers from an intermediate product of a fiber-reinforced plastic, including reinforcing fibers and a matrix resin,
A supply unit for storing the continuous long intermediate product,
The intermediate product pulled out from the supply unit, a transport unit that moves so that the longitudinal direction is the traveling direction,
And a heating unit for heating the intermediate product pulled out of the supply unit and moving to thermally decompose the matrix resin to obtain a heat-treated product containing the regenerated reinforcing fiber. .   The apparatus for producing regenerated reinforcing fibers according to claim 7, wherein the heating unit has a tunnel-shaped heating furnace.   9. The apparatus for producing regenerated reinforcing fibers according to claim 7, wherein the transport unit has a feed roll including a pair of rolls, a belt conveyor including a mesh-shaped endless belt, or a double belt press including a pair of belt conveyors. .   The apparatus for producing regenerated reinforcing fibers according to any one of claims 7 to 9, further comprising a cutting unit that cuts the moving heat-treated product.   The regeneration strengthening according to claim 10, wherein the cutting portion has at least one selected from the group consisting of a slitter, a guillotine cutter, a cutter mill, a roving cutter, a flying shear, an ultrasonic cutter, a laser cutter, and a water jet cutter. Fiber manufacturing equipment.

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