Method for producing carbon fiber bundle composite material and method for producing carbon fiber composite material sheet

Abstract

The manufacturing method of the carbon fiber bundle composite material comprises the following steps: mixing carbon fiber cotton formed by short carbon fibers with a bundling liquid matched with uncured thermosetting resin to obtain a carbon fiber bundle containing the bundling liquid; and enabling the bundling liquid to contain a curing agent so as to enable the bundling liquid to be thermally cured. A method for manufacturing a carbon fiber composite sheet, the method comprising: mixing carbon fiber cotton comprising short carbon fibers with a bundling liquid mixed with an uncured thermosetting resin to obtain a carbon fiber bundle containing the bundling liquid; enabling the bundling liquid to contain a curing agent so as to enable the bundling liquid to be thermally cured; and adhering the plurality of carbon fiber bundles to each other after containing the curing agent in the bundling liquid.

Description

Technical Field

[0001] The present invention mainly relates to a method for manufacturing a carbon fiber bundle composite material (Carbon-fiber Bundle Composite) and a method for manufacturing a carbon fiber composite material sheet. Background Art

[0002] Fiber reinforced plastic (CFRP) using carbon fibers as a reinforcing material is a lightweight material with excellent mechanical properties suitable for parts of transportation equipment such as automobiles, ships, railway vehicles, manned aircraft, and unmanned aircraft, and its importance has been increasing in recent years.

[0003] A method for producing carbon fiber reinforced thermoplastics by adding carbon fiber particles to a thermoplastic resin has been proposed. The carbon fiber particles are produced by mixing short carbon fibers with a solution or suspension of a sizing agent to form a carbon fiber agglomerate, pelletizing the agglomerate with a disc pelletizer, and drying the agglomerate to produce carbon fiber particles (Patent Document 1).

[0004] It is known that by dispersing short carbon fibers in water, further adding a small amount of chloroform and shaking violently, a needle-shaped self-assembled carbon fiber bundle can be obtained; in addition, by dissolving polyetherimide in the chloroform in advance, polyetherimide can be supported on the needle-shaped self-assembled carbon fiber bundle (Non-Patent Document 1).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Publication No. 10-503812

[0008] Non-patent literature

[0009] Non-patent literature 1: JRBaxter, GRPalmese, NJAlvarez, Applied Materials Today 20(2020)100786 Summary of the invention

[0010] Problems to be solved by the invention

[0011] An object of the present invention is to provide a new method for producing a prepreg material using short carbon fibers, which can use either virgin carbon fibers or recycled carbon fibers as a raw material.

[0012] Another object of the present invention is to provide a method for producing a prepreg material using short carbon fibers, the method comprising a step of aggregating the short carbon fibers using a bundling liquid and not requiring a step of removing a solvent in the bundling liquid.

[0013] In this specification, problems that can be solved by each embodiment of the present invention may be explicitly or implicitly shown.

[0014] Methods for solving problems

[0015] According to one embodiment of the present invention, there is provided a method for manufacturing a carbon fiber bundle composite material, which comprises: mixing carbon fiber wool composed of short carbon fibers with a bundling liquid containing an uncured thermosetting resin to obtain a carbon fiber bundle containing the above-mentioned bundling liquid; and allowing the above-mentioned bundling liquid to contain a curing agent so that the above-mentioned bundling liquid can be thermally cured.

[0016] According to another aspect of the present invention, there is provided a method for producing a carbon fiber bundle composite material, comprising: aggregating discontinuous carbon fibers using a bundling liquid to form a carbon fiber bundle containing the bundling liquid, wherein the bundling liquid is a resin composition containing an uncured thermosetting resin and a curing agent.

[0017] According to another embodiment of the present invention, there is provided a method for manufacturing a carbon fiber composite material sheet, comprising: mixing carbon fiber wool composed of short carbon fibers with a bundling liquid formulated with an uncured thermosetting resin to obtain a carbon fiber bundle containing the above-mentioned bundling liquid; allowing the above-mentioned bundling liquid to contain a curing agent so that the above-mentioned bundling liquid can be thermally cured; and after allowing the above-mentioned curing agent to be contained in the above-mentioned bundling liquid, allowing the plurality of the above-mentioned carbon fiber bundles to adhere to each other.

[0018] According to another aspect of the present invention, there is provided a method for producing a carbon fiber composite material sheet, comprising: forming a carbon fiber bundle containing the bundling liquid by agglomerating discontinuous carbon fibers using the bundling liquid; and adhering a plurality of the carbon fiber bundles to each other, wherein the bundling liquid is a resin composition containing an uncured thermosetting resin and a curing agent.

[0019] According to another embodiment of the present invention, there is provided a method for manufacturing a carbon fiber composite material sheet, comprising: making a plurality of carbon fiber bundles contact each other while thickening a bundling liquid contained in each of the plurality of carbon fiber bundles, thereby making the plurality of carbon fiber bundles adhere to each other, wherein in each of the plurality of carbon fiber bundles, discontinuous carbon fibers are agglomerated by the bundling liquid, and the bundling liquid is a resin composition containing an uncured thermosetting resin, a curing agent and a thickener.

[0020] According to another embodiment of the present invention, there is provided a method for manufacturing a carbon fiber composite material sheet, comprising: stacking a plurality of carbon fiber bundles to form a carbon fiber bundle layer; flattening the carbon fiber bundle layer; and then thickening a bundling liquid contained in each of the plurality of carbon fiber bundles, wherein discontinuous carbon fibers in each of the plurality of carbon fiber bundles are condensed by the bundling liquid, and the bundling liquid is a resin composition containing an uncured thermosetting resin, a curing agent, and a thickener.

[0021] Effects of the Invention

[0022] According to one embodiment of the present invention, there is provided a new method for producing a prepreg material using short carbon fibers, which can use either virgin carbon fibers or recycled carbon fibers as a raw material.

[0023] According to one embodiment of the present invention, there is provided a method for producing a prepreg material using short carbon fibers, the method comprising a step of aggregating the short carbon fibers using a bundling liquid and not requiring a step of removing a solvent in the bundling liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] [ Figure 1 ] Figure 1 This is a schematic diagram for explaining the relationship between the bundle length of the carbon fiber bundle composite material and the fiber length of the carbon fibers constituting the carbon fiber bundle composite material.

[0025] [ Figure 2 ] Figure 2 is a photograph of a carbon fiber bundle composite material having a seed-like appearance.

[0026] [ Figure 3 ] Figure 3 This is a conceptual diagram showing an apparatus for producing a carbon fiber composite material sheet.

[0027] [ Figure 4 ] Figure 4 This is a photo showing a carbon fiber bundle composite material being placed in a plastic bag with a chuck and flattened.

[0028] [ Figure 5 ] Figure 5 This is a photograph showing a carbon fiber composite material sheet. DETAILED DESCRIPTION

[0029] When the viscosity value is mentioned in this specification, unless otherwise specified, it means the value measured using a rotational viscometer (for example, HAAKE MARS 40 manufactured by Thermo Fisher Scientific) under the following conditions: measurement mode: constant stress, stress value: 300 Pa, frequency: 1.59 Hz, plate diameter: 25 mm, plate type: parallel plate, plate gap: 0.5 mm.

[0030] Carbon fibers are usually made into continuous fibers with a length that can be wound onto a reel. Short carbon fibers are produced by cutting continuous carbon fibers. Short carbon fibers may be referred to as cut carbon fibers or discontinuous carbon fibers.

[0031] Embodiments of the present invention will be described in detail below.

[0032] 1. Method for manufacturing carbon fiber bundle composite material

[0033] One embodiment of the present invention relates to a method for producing a carbon fiber bundle composite material (hereinafter sometimes referred to as "CBC"). The method comprises: mixing carbon fiber wool composed of short carbon fibers with a bundling liquid containing an uncured thermosetting resin to obtain a carbon fiber bundle containing the bundling liquid; and adding a curing agent to the bundling liquid so that the bundling liquid can be thermally cured.

[0034] Hereinafter, the production method according to the embodiment will be described separately into a method using virgin carbon fiber as a starting material and a method using regenerated carbon fiber as a starting material.

[0035] 1.1. Method using virgin carbon fiber as starting material

[0036] The method using virgin carbon fiber as a starting material typically includes the following steps (i) to (iii).

[0037] (i) Short Cutting Process

[0038] (ii) Defibrination process

[0039] (iii) Bundling process

[0040] Each step will be described in detail below.

[0041] (i) Short Cutting Process

[0042] In the chopping step, a continuous carbon fiber bundle consisting of virgin carbon fibers is cut at predetermined intervals in the fiber direction using, for example, a rotary cutter, thereby forming a chopped carbon fiber bundle.

[0043] The bundle size of the continuous carbon fiber bundle (the number of carbon fiber filaments constituting the bundle) is, for example, 10K or more, and may be 12K or more, 15K or more, 24K or more, 36K or more, 48K or more, or 50K or more. The upper limit is not particularly limited, and is, for example, 100K or less.

[0044] Here, "K" is a symbol representing 1000. For example, 1K means 1000, and 10K means 10000.

[0045] The larger the bundle size of the continuous carbon fiber bundle, the more carbon fiber filaments are contained in one chopped carbon fiber bundle, and thus the higher the production efficiency of CBC. In addition, the production cost of the continuous carbon fiber bundle also decreases with the increase of the bundle size. Therefore, the bundle size of the continuous carbon fiber bundle is preferably 24K or more, more preferably 36K or more, and further preferably 48K or more.

[0046] In the case of PAN-based carbon fibers made from polyacrylonitrile fibers, the diameter of the carbon fiber filaments is generally in the range of 5 μm to 15 μm.

[0047] The fiber length of the chopped carbon fiber bundle can be set to the required length of the carbon fibers constituting the CBC to be manufactured. This is because there is no process of intentionally cutting the carbon fibers after the chopped process.

[0048] The fiber length of the chopped carbon fiber bundle is not limited, and is, for example, 3 mm or more, 5 mm or more, or 10 mm or more, and is, for example, 60 mm or less, 50 mm or less, 40 mm or less, 30 mm or less, or 20 mm or less.

[0049] The longer the fiber length of the chopped carbon fiber bundle, the better the mechanical properties of the CFRP product molded using the manufactured CBC. On the other hand, the shorter the fiber length of the chopped carbon fiber bundle, the more suitable the manufactured CBC is for molding CFRP products with complex shapes. This is because the shorter the carbon fibers contained in the CBC, the easier it is to flow in the molding die.

[0050] like Figure 1 As shown, the bundle length of the CBC formed by a plurality of short carbon fibers having the same fiber length is generally longer than the fiber length of the short carbon fibers. In one example, the bundle length of the CBC may exceed 2 times, and further may exceed 3 times, the fiber length of the short carbon fibers.

[0051] (ii) Defibrination process

[0052] In the defibration step, the chopped carbon fiber bundle obtained in the chopped step is untied to obtain carbon fiber wool.

[0053] The defibration is preferably performed in such a way that all the carbon fibers contained in the chopped carbon fiber bundle are in the form of monofilaments, but this is not essential. That is, the carbon fiber wool obtained in the defibration step may include an ultrafine carbon fiber bundle composed of a small number of filaments, such as less than 100.

[0054] In the defibration step, a general defibration machine may be used, but the present invention is not limited thereto.

[0055] In one example, only chopped carbon fiber bundles are put into a stirring mixer such as a Henschel mixer and stirred in a dry state, thereby defibration can be performed. This method has the advantage that the generated carbon fiber wool can be fed into the next bundling process without taking it out of the stirring mixer.

[0056] In one example, the chopped carbon fiber bundles may be defibrated by immersing them in an organic solvent such as acetone that can dissolve the sizing agent contained in the chopped carbon fiber bundles and irradiating them with ultrasonic waves. After washing away the sizing agent, cotton-like carbon fibers remain.

[0057] (iii) Bundling process

[0058] In the bundling process, the carbon fiber wool obtained in the defibration process is mixed with a bundling liquid, which is a resin composition.

[0059] The carbon fiber filaments or ultrafine carbon fiber bundles constituting the carbon fiber cotton are aggregated by the capillary force based on the surface tension of the bundling liquid, thereby forming a carbon fiber bundle containing the bundling liquid.

[0060] <Viscosity of the Bundling Fluid>

[0061] The lower the viscosity of the bundling liquid, the easier it is to mix with the carbon fiber wool, and the shorter the time required to form the carbon fiber bundle. From this point of view, the viscosity of the bundling liquid when mixed with the carbon fiber wool in the bundling process is preferably 10 Pa·s or less, more preferably 5 Pa·s or less, and further preferably 1 Pa·s or less. There is no particular lower limit for the viscosity, and for example, it can be 0.001 Pa·s or more.

[0062] In the bundling process, the bundling liquid may be heated. For example, a bundling liquid with a viscosity of 10 Pa·s at 25°C may be used without heating when the bundling process is performed in a room at 25°C, but it is preferably heated to a viscosity of 10 Pa·s or less when the bundling process is performed in a room at 15°C.

[0063] In order to prevent the sizing liquid having a viscosity of 10 Pa·s at 50°C from solidifying during the mixing with the carbon fiber wool when heated to 50°C, a curing agent that does not show a curing effect below 50°C may be selected as the curing agent contained in the sizing liquid.

[0064] If the sizing liquid has a viscosity of 10 Pa·s at 40°C, and if a curing agent that does not show a curing effect below 40°C is selected as the curing agent contained in the sizing liquid, it will not cure during the mixing with the carbon fiber wool while being heated to 40°C.

[0065] Thus, the lower the temperature at which the viscosity of the sizing fluid reaches 10 Pa·s, the wider the options for selecting a curing agent that does not cure the sizing fluid when mixed with the carbon fiber wool at the above temperature.

[0066] Therefore, the viscosity of the bundling fluid is preferably 10 Pa·s or less at 50°C, more preferably 10 Pa·s or less at 40°C, and further preferably 10 Pa·s or less at 30°C.

[0067] As described later, the viscosity of the clustering liquid can be adjusted by using a reactive diluent.

[0068] <Thermosetting resin>

[0069] An uncured thermosetting resin is mixed in the bundling liquid. The type of the thermosetting resin is not limited, and preferred examples thereof include epoxy resin, vinyl ester resin, unsaturated polyester resin, and resol type phenolic resin.

[0070] Examples of thermosetting resins that may be contained in the sizing liquid include various (meth)acrylates (compounds having an acryloyl group or a methacryloyl group) and diallyl phthalate other than epoxy vinyl ester. Various (meth)acrylates include alkyl (meth)acrylates that may have a substituent on the alkyl group and urethane acrylates.

[0071] The bundling fluid may contain two or more thermosetting resins.

[0072] <Epoxy resin>

[0073] The type of epoxy resin that can be contained in the clustering liquid is not limited, and various epoxy resins including bisphenol epoxy resin, naphthalene epoxy resin, biphenyl epoxy resin, novolac epoxy resin, glycidylamine epoxy resin, epoxy resin having an oxazolidone ring structure, alicyclic epoxy resin, and aliphatic epoxy resin can be used.

[0074] When epoxy resins having different viscosities are used in combination, generally, the viscosity of the clustering liquid decreases as more epoxy resins having lower viscosities are contained.

[0075] The epoxy resin that can be particularly preferably contained in the clustering liquid is a bisphenol type epoxy resin such as bisphenol A type epoxy resin (epoxy resin containing diglycidyl ether of bisphenol A as a main component) and bisphenol F type epoxy resin (epoxy resin containing diglycidyl ether of bisphenol F as a main component).

[0076] Some commercially available bisphenol epoxy resins have a viscosity of 5 Pa·s or less at 25° C. and can be preferably used.

[0077] In one example, 50 wt % or more, 60 wt % or more, 65 wt % or more, 70 wt % or more, or 75 wt % or more of the total epoxy resin contained in the bulking liquid may be bisphenol epoxy resin.

[0078] Bisphenol epoxy resins, especially bisphenol A epoxy resins, have the advantages of less shrinkage during curing and better heat resistance of cured products. Therefore, the sizing fluid preferably contains at least one of bisphenol A and bisphenol F epoxy resins, and more preferably contains bisphenol A epoxy resin.

[0079] <Vinyl ester resin>

[0080] The type of the vinyl ester resin that can be contained in the sizing liquid is not particularly limited, and typical examples thereof include bisphenol-type vinyl ester resins and novolac-type vinyl ester resins.

[0081] The bisphenol type vinyl ester resin can be produced by esterifying a bisphenol type epoxy resin such as a bisphenol A type epoxy resin with an unsaturated monocarboxylic acid such as acrylic acid or methacrylic acid.

[0082] The novolac vinyl ester resin can be produced by esterifying a novolac epoxy resin such as a phenol novolac epoxy resin with an unsaturated monocarboxylic acid such as acrylic acid or methacrylic acid.

[0083] <Unsaturated polyester resin>

[0084] The type of unsaturated polyester resin that can be contained in the sizing liquid is not particularly limited. The unsaturated polyester resin mainly comprises a polymer having a structure obtained by polycondensation of a dicarboxylic acid including fumaric acid, maleic acid and / or maleic anhydride and a diol.

[0085] <Reactive diluent>

[0086] As described above, the viscosity of the sizing liquid can be adjusted by the reactive diluent. The compound contained as the reactive diluent in the sizing liquid may be only one kind or two or more kinds.

[0087] When epoxy resin is added to the sizing liquid, a known reactive diluent for epoxy resin can be used appropriately. Examples of reactive diluents for epoxy resin having a high viscosity reducing effect include monofunctional epoxy compounds having only one epoxy group in the molecule, but are not limited thereto.

[0088] Methylhexahydrophthalic anhydride and methyltetrahydrophthalic anhydride function as thickeners or curing agents for epoxy resins and also function as diluents, and therefore can be regarded as a type of reactive diluent.

[0089] When at least one of a vinyl ester resin and an unsaturated polyester resin is added to the bulking liquid, a low viscosity compound having one or two ethylenically unsaturated groups in the molecule and preferably 1 Pa·s or less at 25° C. may be preferably added as a reactive diluent.

[0090] Examples of the above-mentioned compounds include styrene compounds such as styrene, methylstyrene, halogenated styrene, and divinylbenzene; methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, benzyl (meth)acrylate, methylbenzyl (meth)acrylate, phenoxyethyl (meth)acrylate, methylphenoxyethyl (meth)acrylate, morpholine (meth)acrylate, phenylphenoxyethyl acrylate, phenylbenzyl (meth)acrylate, methacrylic acid, Monofunctional (meth)acrylates such as phenyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, and dicyclopentanyl methacrylate; hydroxyl-containing (meth)acrylates such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxybutyl (meth)acrylate; difunctional (meth)acrylates such as ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, bisphenol di(meth)acrylate, and 1,4-cyclohexanedimethanol di(meth)acrylate.

[0091] <Thickener>

[0092] In a preferred example, a thickener can be added to the bundling liquid to increase the viscosity of the bundling liquid to, for example, 50 Pa·s or more at 25° C. by adding a thickener to the bundling liquid. By thickening the bundling liquid in this way, the morphology of the CBC formed in the bundling step is stabilized.

[0093] For example, when a large amount of CBC is placed in a large-capacity container for transportation and storage, a strong pressure due to its own weight is applied to the CBC near the bottom of the container. In this case, if the bundle liquid is thickened, it is difficult for the CBC to be destroyed, the CBC to stick to each other, and the liquid component to seep out of the CBC.

[0094] When a thickener is used, it is preferred to mix the thickener into the sizing liquid immediately before mixing the sizing liquid with the carbon fiber wool.

[0095] In one method, the bundling liquid can be divided into two types: a first liquid without a thickener and a second liquid containing a thickener. In this method, the second liquid can be mixed with the mixture obtained after the first liquid is mixed with the carbon fiber wool, or the order can be reversed, and the first liquid can be mixed with the mixture obtained after the second liquid is mixed with the carbon fiber wool. In this method, the bundling liquid is completed by mixing the first liquid and the second liquid in the bundling process.

[0096] The type and amount of the thickener are determined so that the viscosity of the bundling liquid increases during the bundling step and does not hinder the formation of the carbon fiber bundle.

[0097] When the viscosity of the bundling liquid is below 10 Pa·s, the bundling process can be completed within 1 hour. Therefore, in a preferred example, the type and amount of the thickener added to the bundling liquid can be determined in such a way that the viscosity does not exceed 10 Pa·s when maintained at the temperature when mixed with the carbon fiber wool for 1 hour.

[0098] The viscosity of the clustering liquid containing the thickener after thickening at 25°C can be 100 Pa·s or more, further 200 Pa·s or more, further 1000 Pa·s or more, further 2000 Pa·s or more, further 5000 Pa·s or more, and may be a value exceeding the range measurable using a rotational viscometer.

[0099] When the CBC formed in the bundling step is used to produce the carbon fiber composite material sheet described later, the viscosity of the bundling liquid containing the thickener after thickening can be, for example, in the range of 200 Pa·s to 100000 Pa·s. If a bundling liquid having a moderately low viscosity after thickening is used, a soft carbon fiber composite material sheet can be obtained.

[0100] In one example, after the bundling process, the carbon fiber bundle formed in the bundling process may be maintained at a temperature higher than room temperature (temperature within the range of 20°C ± 15°C), that is, at a temperature exceeding 35°C, thereby promoting the thickening of the bundling liquid contained in the carbon fiber bundle. The holding temperature and holding time are set within a range in which the bundling liquid is not solidified by the action of the curing agent.

[0101] In one example, the carbon fiber bundle formed in the stirring tank of the stirring mixer may be not taken out from the stirring tank, but the aggregating liquid contained in the carbon fiber bundle may be thickened while being stirred in the stirring tank.

[0102] In another example, the carbon fiber bundle formed in the stirring tank of the stirring mixer may be transferred to a disc pelletizer, and the bundle liquid contained in the carbon fiber bundle may be thickened while the bundle is tumbled.

[0103] Examples of thickeners that can be used when the epoxy resin is added to the bulking liquid include polyisocyanates, carboxylic anhydrides, and amines.

[0104] Preferred examples of polyisocyanates include diisocyanates having an aromatic ring in the molecular structure, such as bis(4-isocyanatophenyl)methane and toluene diisocyanate, and aliphatic diisocyanates, such as isophorone diisocyanate and hexamethylene diisocyanate. Polymeric MDI (crude MDI) is also included in preferred examples of polyisocyanates.

[0105] Polyisocyanates having a low viscosity (preferably 1 Pa·s or less at 25° C.) can also function as a reactive diluent for a short period of time after being added to the aggregation liquid.

[0106] The polyisocyanate may be formulated in the bulking liquid together with a polyol. Examples of the polyol include ethylene glycol, polyethylene glycol, isosorbide, neopentyl glycol, cyclohexanediol, cyclohexanedimethanol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, and 1,6-hexanediol.

[0107] A polyol having a low viscosity (preferably 1 Pa·s or less at 25° C.) can also function as a reactive diluent for a short period of time after being added to the cluster liquid.

[0108] Preferred examples of carboxylic anhydrides include methylhexahydrophthalic anhydride and methyltetrahydrophthalic anhydride. As described above, these function as reactive diluents even for a short period of time after being added to the clustering liquid.

[0109] Preferred examples of the amine include isophoronediamine, bis(4-aminocyclohexyl)methane, and 1,3-bis(aminomethyl)cyclohexane.

[0110] In the bundle liquid containing epoxy resin, styrene and maleic anhydride as thickeners may be mixed together with a radical polymerization initiator. In this case, styrene and maleic anhydride are copolymerized by the action of the radical polymerization initiator, thereby thickening the bundle liquid. Styrene before polymerization can also function as a reactive diluent.

[0111] Preferred thickeners that can be used when the vinyl ester resin and / or the unsaturated polyester resin is added to the bulking liquid include polyisocyanates, alkaline earth metal hydroxides such as magnesium hydroxide and calcium hydroxide, and alkaline earth metal oxides such as magnesium oxide and calcium oxide.

[0112] Preferred examples of the polyisocyanate are the same as preferred examples of the polyisocyanate that can be used as a thickener when the epoxy resin is blended in the bulking liquid.

[0113] Polyisocyanates having a low viscosity (preferably 1 Pa·s or less at 25° C.) can also function as a reactive diluent for a short period of time after being added to the aggregation liquid.

[0114] The polyisocyanate may be blended together with a polyol in the bulking liquid. Examples of the polyol are the same as those of the polyol that can be blended together with the polyisocyanate when the epoxy resin is blended in the bulking liquid.

[0115] A polyol having a low viscosity (preferably 1 Pa·s or less at 25° C.) can also function as a reactive diluent for a short period of time after being added to the clustering liquid.

[0116] Examples of thickeners that can be preferably used when the resol-type phenolic resin is added to the bulking liquid include hydroxides of alkaline earth metals such as magnesium hydroxide and calcium hydroxide, oxides of alkaline earth metals such as magnesium oxide and calcium oxide, and polyisocyanates.

[0117] When the thermosetting resin added to the sizing liquid is not any of epoxy resin, vinyl ester resin, unsaturated polyester resin and resol type phenolic resin, polyisocyanate can also be suitably used as a thickener. When the thermosetting resin does not contain a hydroxyl group-containing component, polyisocyanate and polyol can be added to the sizing liquid together. Preferred examples of polyisocyanate and polyol are the same as those of polyisocyanate and polyol that can be used when epoxy resin is added to the sizing liquid.

[0118] <Curing Agent>

[0119] The clustering liquid can be thermally cured by containing a curing agent suitable for the thermosetting resin to be blended.

[0120] When the epoxy resin is added to the bundling liquid, a curing agent for the epoxy resin (hereinafter also referred to as “epoxy curing agent”) is contained in the bundling liquid.

[0121] Typical examples of epoxy curing agents include dicyandiamides, phenols including novolacs, amines, carboxylic anhydrides, thiols, and imidazoles.

[0122] The epoxy curing agent that can be particularly preferably used is a latent curing agent, that is, a curing agent that is a solid with low solubility in the epoxy resin at room temperature, but melts or dissolves in the epoxy resin when heated to a predetermined temperature to exhibit a curing action.

[0123] Imidazoles, dicyandiamide and boron trifluoride-amine complexes are typical examples of latent curing agents.

[0124] Imidazoles refer to compounds having an imidazole ring, and include substituted imidazoles in which the hydrogen atom of imidazole is substituted with a substituent, imidazolium salts, imidazole complexes, and the like.

[0125] Examples of substituted imidazoles preferred as latent curing agents include substituted imidazoles having an aromatic ring which may be a heteroaromatic ring in the molecule, such as 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2-phenyl-4-methylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4-benzyl-5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 2-p-tolyl-4-methyl-5-hydroxymethylimidazole, 2-p-tolyl-4,5-dihydroxymethylimidazole, 2-m-tolyl-4-methyl-5-hydroxymethylimidazole, 2-m-tolyl-4,5-dihydroxymethylimidazole and 1-cyanoethyl-2-phenylimidazole.

[0126] Imidazolium salts such as 1-cyanoethyl-2-ethyl-4-methylimidazolium trimellitate, 1-cyanoethyl-2-undecylimidazolium trimellitate and 1-cyanoethyl-2-phenylimidazolium trimellitate are also preferred examples of the imidazole-based latent curing agent.

[0127] Isocyanuric acid adducts of various substituted imidazoles including 2-phenylimidazole, 2-methylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole and 2-phenyl-4-methyl-5-hydroxymethylimidazole, in particular, isocyanuric acid adducts of substituted imidazoles having a triazine ring such as 2,4-diamino-6-(2'-methylimidazolyl-(1'))-ethyl-s-triazine, 1-(4,6-diamino-s-triazine-2-yl)ethyl-2-undecylimidazole and 2,4-diamino-6-[2-(2-ethyl-4-methyl-1-imidazolyl)ethyl]-s-triazine are particularly preferred imidazole-based latent curing agents.

[0128] Amine adducts are also one of the preferred examples of latent curing agents. Amine adducts are obtained by reacting imidazole and / or tertiary amine with epoxy resin and / or isocyanate to increase the molecular weight, and have low solubility in epoxy resin.

[0129] The latent curing agent may be used alone or in combination of two or more.

[0130] When dicyandiamide is used as the epoxy curing agent, it is preferred to use a urea derivative such as 4,4′-methylenebis(phenyldimethylurea) or 2,4-bis(3,3-dimethylureido)toluene as a curing accelerator.

[0131] When the vinyl ester resin and / or the unsaturated polyester resin is added to the sizing liquid, a radical polymerization initiator is contained in the sizing liquid as a curing agent. The radical polymerization initiator may be used alone or in combination of two or more.

[0132] Typical examples of the radical polymerization initiator are organic peroxides such as ketone peroxides, hydroperoxides, diacyl peroxides, dialkyl peroxides, peroxyketals, alkyl peresters and percarbonates.

[0133] Preferred examples of the organic peroxide include 1,1-di(tert-butylperoxy)cyclohexane, tert-butyl peroxyisopropyl carbonate, tert-amyl peroxyisopropyl carbonate, methyl ethyl ketone peroxide, tert-butyl peroxybenzoate, benzoyl peroxide, diisopropylbenzene peroxide, acetylacetone peroxide, and cumene hydroperoxide.

[0134] The radical polymerization initiator preferably has a 10-hour half-life temperature in the range of 70 to 120° C., more preferably in the range of 80 to 110° C., and further preferably in the range of 90 to 100° C. The 10-hour half-life temperature refers to a temperature at which the half-life of a polymerization initiator dissolved in benzene when thermally decomposed at a certain temperature reaches 10 hours, and a benzene solution containing the polymerization initiator at a concentration of 0.2 mol / L is used for the measurement.

[0135] Regarding organic peroxides having a 10-hour half-life temperature within the above preferred range, reference can be made to International Publication No. 2019 / 017254, for example.

[0136] When the sizing liquid contains a radical polymerization initiator, it is preferred that a radical polymerization inhibitor is also contained in the sizing liquid. The radical polymerization inhibitor is well known to those skilled in the art, and preferred examples include catechol, hydroquinone, benzoquinone, and nitroso compounds.

[0137] When a resol type phenolic resin is formulated in the bundling liquid, examples of components that may be contained in the bundling liquid as a curing agent include: organic acids such as benzenesulfonic acid, p-toluenesulfonic acid, xylenesulfonic acid and phenolsulfonic acid; inorganic acids such as phosphoric acid, hydrochloric acid and sulfuric acid; amines such as triethylamine, tri-n-propylamine, diethylamine, n-propylamine, n-butylamine, aniline and benzylamine; and reaction products of isocyanates with primary and / or secondary amines.

[0138] <Optional Ingredients>

[0139] The components that may be contained in the clustering fluid are not limited to the components described above.

[0140] Examples of components that may be contained in the sizing fluid further include low shrinkage agents, antioxidants, internal mold release agents, colorants, modifiers (such as rubber, elastomers, or thermoplastic resins), flame retardants, fillers, and antimicrobial agents.

[0141] Examples of the low shrinkage agent include polyethylene, polystyrene, styrene-based thermoplastic elastomers, cross-linked polystyrene, polyvinyl acetate-polystyrene block copolymers, polyvinyl acetate, polymethyl methacrylate, and saturated polyester resins.

[0142] Examples of fillers include inorganic fillers that may be oxides, hydroxides, carbonates, sulfates, silicates, phosphates, or clay minerals. Other examples of fillers include organic fillers that may be cured products of thermosetting resins such as phenolic resins and resorcinol resins.

[0143] The flame retardant that may be contained in the clustering fluid is described as follows.

[0144] As a preferable flame retardant, a phosphorus-containing flame retardant is mentioned.

[0145] Examples of the phosphorus-containing flame retardant include non-halogen phosphates such as trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, tributoxyethyl phosphate, triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, and aromatic polyphosphates.

[0146] Other examples of phosphorus-containing flame retardants include halogenated phosphoric acid esters such as tris(chloroethyl)phosphate, tris(dichloropropyl)phosphate, tris(chloropropyl)phosphate, bis(2,3-dibromopropyl)2,3-dichloropropyl phosphate, tris(2,3-dibromopropyl)phosphate, bis(chloropropyl)octyl phosphate, halogenated alkyl polyphosphates, and halogenated alkyl polyphosphonates.

[0147] As another example of phosphorus-containing flame retardants, metal salts of phosphinates can be cited. The metal salts of phosphinates mentioned here include not only metal salts of phosphinates without organic groups, but also metal salts of organic phosphinates such as diphenylphosphinates, monophenylphosphinates, dialkylphosphinates, monoalkylphosphinates, and alkylphenylphosphinates, and metal salts of diphosphinates such as methane (dimethylphosphinates) and benzene-1,4-di (methylphosphinates).

[0148] Examples of the dialkylphosphinic acid include dimethylphosphinic acid, ethylmethylphosphinic acid, diethylphosphinic acid, and methyl-n-propylphosphinic acid.

[0149] Examples of the monoalkylphosphinic acid include methylphosphinic acid, ethylphosphinic acid, and n-propylphosphinic acid.

[0150] As an example of the alkylphenylphosphonic acid, methylphenylphosphonic acid can be mentioned.

[0151] The metal salt of phosphinate may be aluminum salt, zinc salt, calcium salt, magnesium salt, etc., but is not limited thereto.

[0152] Another example of the phosphorus-containing flame retardant includes red phosphorus, ammonium polyphosphate, melamine phosphate, guanidine phosphate, guanidine urea phosphate, and the like.

[0153] In addition to the phosphorus-containing flame retardant, a non-phosphorus-containing flame retardant may also be mixed in the clustering fluid.

[0154] Examples of the phosphorus-free flame retardant include melamine compounds such as melamine cyanurate, triazine compounds, guanidine compounds, nitrogen flame retardants such as ammonium carbonate, hydrated metals such as aluminum hydroxide and magnesium hydroxide, and organic metal salt flame retardants such as ferrocene and acetylacetone metal complexes.

[0155] In a preferred example, halogen-free materials are selected for all materials to be blended in the clustering liquid, thereby making it possible to make the CBC as the final product halogen-free.

[0156] Another example of the optional component that may be contained in the sizing liquid is an uncured thermosetting resin powder that is solid at the temperature at which the sizing liquid and the carbon fiber wool are mixed and that is insoluble in the sizing liquid.

[0157] For example, when the bundling liquid contains a liquid epoxy resin, uncured epoxy resin powder can be used as the uncured thermosetting resin powder.

[0158] For example, when the bundling liquid contains a liquid phenolic resin, uncured phenolic resin powder can be used as the uncured thermosetting resin powder.

[0159] <Mixture of carbon fiber wool and clustering fluid>

[0160] The method of mixing the carbon fiber wool and the sizing liquid is not limited, but stirring is preferably performed in order to efficiently mix them in a short time.

[0161] During stirring, a powder stirring mixer known as a Henschel mixer can be preferably used. The stirring mixer can be a type that only has stirring blades (stirring wings) or a type that is provided with a chopper. In a stirring mixer with a jacket, the temperature of the stirring tank can be adjusted by flowing a heat medium inside the jacket.

[0162] When mixing the carbon fiber wool and the bundling liquid, not only a stirring mixer but also a drum mixer without a stirring mechanism may be used.

[0163] In one example, the clustering liquid or the liquid component to be contained in the clustering liquid can be supplied into the mixing tank of the mixer by spraying.

[0164] The temperature T at which the viscosity of the clustering fluid becomes within the above-mentioned preferred range is A Higher than the temperature T of the room where the bundling process is carried out B Before the sizing liquid and the carbon fiber wool are mixed in the stirring tank of the stirring mixer, at least one of the sizing liquid, the carbon fiber wool and the stirring tank, preferably all of them, may be heated to a temperature T A In this case, either the clustering liquid or the carbon fiber wool can be heated to a temperature T in the stirring tank. A .

[0165] The curing agent may be added to the sizing liquid before the sizing liquid is mixed with the carbon fiber wool, or may be added simultaneously with the mixing of the sizing liquid and the carbon fiber wool.

[0166] The bundling liquid may contain all the curing agents at the same time, or may contain a part of the curing agents and another part of the curing agents at different times.

[0167] When two or more types of curing agents are used, the timing of including them in the bundling liquid may be changed depending on the type.

[0168] The curing agent which is liquid at the temperature when the sizing liquid and the carbon fiber wool are mixed or which is dissolved in the sizing liquid is preferably contained in the sizing liquid before the sizing liquid and the carbon fiber wool are mixed.

[0169] The curing agent which is solid at the temperature when the sizing liquid and the carbon fiber wool are mixed and is insoluble in the sizing liquid can be contained in the sizing liquid before the sizing liquid and the carbon fiber wool are mixed, or can be contained in the sizing liquid while the sizing liquid and the carbon fiber wool are mixed. The curing agent is a powder or a micropowder, and its maximum particle size is, for example, 150 μm or less, preferably 100 μm or less, more preferably 50 μm or less, and further preferably 20 μm or less.

[0170] In order to mix the sizing liquid with the carbon fiber wool and contain the curing agent in the sizing liquid, the carbon fiber wool and the curing agent are first mixed, and then the sizing liquid containing components other than the curing agent is added to the obtained mixture.

[0171] There is no particular limitation on the timing of adding components other than the curing agent to the bundling liquid.

[0172] Similar to the curing agent, the components that are liquid at the temperature when the sizing liquid and the carbon fiber are mixed or dissolved in the sizing liquid are preferably contained in the sizing liquid before the sizing liquid and the carbon fiber wool are mixed. However, it is also allowed to contain the above components in the sizing liquid during the sizing process as needed.

[0173] The components that are solid at the temperature when the sizing liquid and the carbon fiber wool are mixed and are insoluble in the sizing liquid can be contained in the sizing liquid before the sizing liquid and the carbon fiber wool are mixed, or can be contained in the sizing liquid while the sizing liquid and the carbon fiber wool are mixed. The above components are usually powders or micropowders, and their maximum particle size is, for example, 150 μm or less, preferably 100 μm or less, more preferably 50 μm or less, and further preferably 20 μm or less.

[0174] The ratio of the weight of the carbon fiber wool to the total weight of the mutually mixed clustering liquid and the carbon fiber wool can be 20% or more and less than 30%, 30% or more and less than 40%, 40% or more and less than 50%, 50% or more and less than 60%, 60% or more and less than 70%, or 70% or more and less than 80%. This ratio is roughly equal to the fiber weight content in the CBC as the final product. In fact, since the carbon fiber wool composed of virgin carbon fiber contains a sizing agent, the value obtained by multiplying the weight ratio of the carbon fiber in the carbon fiber wool by the above ratio becomes the fiber weight content of the CBC.

[0175] When the same carbon fiber wool and bundling liquid are used as raw materials, there is a tendency that the smaller the above ratio is, the coarser the CBC formed is and the longer its bundle length is. When the carbon fiber wool used is the same, there is a tendency that the higher the viscosity of the bundling liquid is, the longer the bundle length of the CBC formed is. According to the results observed in the experiments conducted by the inventors, these two tendencies are weakened when the bundling liquid contains powder and / or fine powder composed of components that are solid and insoluble in the bundling liquid at the temperature when mixed with the carbon fiber wool.

[0176] 1.2. Method using recycled carbon fiber as starting material

[0177] In the method for producing CBC described in 1.1. above, all or part of the virgin carbon fibers as the starting material may be replaced with regenerated carbon fibers.

[0178] A preferred example of regenerated carbon fiber is carbon fiber recovered from waste SMC (sheet molding compound) such as the end material of SMC or waste CFRP (CFRP formed by solidifying SMC) from SMC. Almost all of the carbon fibers contained in SMC have the same fiber length, which is usually in the range of 3mm to 60mm. SMC sometimes contains a small amount of carbon fiber with a longer fiber length than expected due to miscutting of the carbon fiber bundle in the manufacturing process. The proportion of this carbon fiber in all the carbon fibers contained in SMC is usually less than 1% by weight.

[0179] Methods for recovering carbon fibers from waste SMC or waste CFRP derived from SMC are roughly divided into thermal decomposition and chemical decomposition.

[0180] In a preferred example of the thermal decomposition method, waste SMC or waste CFRP from SMC is dry distilled at a temperature preferably above 600°C, and then heated to, for example, 550°C or above, preferably 600°C or above in an oxidizing atmosphere. If the matrix resin is completely thermally decomposed by the above two-stage treatment, carbon fiber wool consisting of regenerated carbon fibers having almost the same fiber length remains. The regenerated carbon fibers are thermally degraded and have a lower strength than virgin carbon fibers, but have sufficient strength when used as a reinforcing material for FRP.

[0181] A typical example of a heating means used in the thermal decomposition method is an electric furnace, and microwave heating, induction heating, etc. may also be used. In one example of the thermal decomposition method, waste CFRP may be treated in superheated water vapor.

[0182] Examples of chemical decomposition methods include normal pressure dissolution method, supercritical fluid method (method of decomposing matrix resin using subcritical fluid or supercritical fluid), semiconductor thermal activation method and electrolytic oxidation method. In order to obtain cotton-like regenerated carbon fibers, the matrix resin needs to be fully removed. Resin residue (residual carbon) that is not completely removed by chemical decomposition can be removed by heat treatment in an oxidizing atmosphere.

[0183] Instead of thermally decomposing the resin residue that has not been completely removed by the first-stage thermal decomposition or chemical decomposition in an oxidative atmosphere, the bonding between the carbon fibers caused by the resin residue is mechanically broken, thereby obtaining a regenerated carbon fiber in a cotton-like state. This operation can be performed using a stirring mixer with rotating blades such as a Henschel mixer.

[0184] As another method for recovering carbon fibers from waste SMC, there is a method of washing out the uncured matrix resin using a solvent that can be a subcritical fluid or a supercritical fluid. According to this method, it is possible to obtain regenerated carbon fibers having the same strength as virgin carbon fibers and without thermal degradation.

[0185] Recycled carbon fibers recovered from waste CFRP or waste SMC from SMC are generally short fibers with a fiber length in the range of 3 mm to 60 mm, and do not require further cutting when used to manufacture CBC, and the sizing agent is also removed. When only such recycle carbon fibers are used as the starting material, unlike when virgin carbon fibers are used as the starting material, (i) the chopping step and (ii) the defibration step are not required, and only the above-mentioned (iii) bundling step is required.

[0186] As the regenerated carbon fibers, carbon fibers recovered from waste UD prepreg or waste CFRP derived from UD prepreg (CFRP obtained by curing UD prepreg) by the above-mentioned thermal decomposition method or chemical decomposition method may be used.

[0187] The regenerated carbon fiber obtained from the waste UD prepreg or the waste CFRP from the UD prepreg is cut into an appropriate length before being used to manufacture the CBC. The length of the regenerated carbon fiber after cutting is, for example, 3 mm or more, 5 mm or more, or 10 mm or more, and is, for example, 60 mm or less, 50 mm or less, 40 mm or less, 30 mm or less, or 20 mm or less.

[0188] The longer the fiber length of the regenerated carbon fiber, the better the mechanical properties of the CFRP product molded using the manufactured CBC. On the other hand, the shorter the fiber length of the regenerated carbon fiber, the more suitable the manufactured CBC is for molding CFRP products with complex shapes. This is because the shorter the carbon fibers contained in the CBC, the easier it is to flow in the molding die.

[0189] Sometimes fibers other than carbon fibers are mixed into the cotton-like regenerated carbon fibers. For example, in the regenerated carbon fiber cotton recovered from CFRP in which a carbon fiber cloth including a coil composed of glass fibers is used as a reinforcement material, mixing of glass fibers can be confirmed.

[0190] When using regenerated carbon fiber as the starting material, it can be used after removing fibers other than carbon fiber mixed in the carbon fiber cotton, but it is not necessary. That is, in the manufacturing method involved in the embodiment, regenerated carbon fiber cotton mixed with fibers other than carbon fiber can also be used as the starting material of CBC.

[0191] 2. Carbon fiber bundle composite materials

[0192] Another embodiment of the present invention is a CBC manufactured by the manufacturing method described in the above 1. The CBC is composed of a plurality of short carbon fibers and a bundling fluid, and the bundling fluid is used to maintain the plurality of short carbon fibers in a bundled state. Due to the manufacturing method, the positions of the front ends of the plurality of short carbon fibers are not aligned at each end of the CBC. The bundling fluid is a resin composition containing an uncured thermosetting resin and a curing agent.

[0193] The number of short carbon fibers (filaments) forming a bundle, that is, the number of short carbon fibers contained in one CBC, may be, for example, 1000 to 10000. More than 99% by weight, preferably all, of the short carbon fibers forming a bundle in one CBC may have a fiber length of 60 mm or less, 50 mm or less, 40 mm or less, 30 mm or less, or 20 mm or less.

[0194] The shorter the fiber length of all short carbon fibers contained in the CBC is, the more suitable it is for molding CFRP products with complex shapes. This is because the shorter the carbon fibers contained in the CBC are, the easier it is to flow in the molding die.

[0195] Carbon fibers with too short a fiber length have low effect as a reinforcing material, and therefore most of the short carbon fibers forming a bundle in one CBC preferably have a fiber length of 3 mm or more, more preferably 5 mm or more, and even more preferably 10 mm or more, based on the weight of the short carbon fibers.

[0196] In a preferred embodiment, the CBC does not contain carbon fibers having a fiber length of less than 3 mm, or even if it does, the amount thereof is less than 5 wt % of all carbon fibers constituting the CBC.

[0197] In another preferred example, the CBC does not contain carbon fibers having a fiber length of less than 5 mm, or even if it contains carbon fibers, the amount thereof is less than 5 wt % of all carbon fibers constituting the CBC.

[0198] In another preferred example, the CBC does not contain carbon fibers having a fiber length of less than 10 mm, or even if it does, the amount thereof is less than 5 wt % of all carbon fibers constituting the CBC.

[0199] A CBC having a majority of fiber lengths of L (mm) or more based on the weight of the short carbon fibers forming the bundle generally has a bundle length exceeding L (mm).

[0200] The shape of CBC can be seed-shaped (spindle-shaped), needle-shaped or thread-shaped. Figure 2 A photograph showing the appearance of a seed-shaped (spindle-shaped) CBC.

[0201] In one embodiment, by making the CBC contain only short carbon fibers having the same fiber length, it is possible to suppress quality variations between production batches. In this case, the difference between the maximum and minimum fiber lengths of the short carbon fibers forming the bundle is preferably within 5 mm, more preferably within 4 mm, and even more preferably within 3 mm.

[0202] The filament diameter of the short carbon fibers forming the bundle is not particularly limited, and may be, for example, within the range of filament diameters generally possessed by PAN-based carbon fibers, that is, within a range of 5 μm to 15 μm.

[0203] The bundling liquid contained in the CBC is the bundling liquid itself used to form the CBC. Therefore, the types and preferred examples of the uncured thermosetting resin that the CBC may contain are the same as the types and preferred examples of the thermosetting resin in the bundling liquid (for example, the preferred examples of the uncured thermosetting resin that the CBC may contain are the same as the preferred examples of the uncured thermosetting resin that may be contained in the bundling liquid, including epoxy resin, vinyl ester resin, unsaturated polyester resin and resol type phenolic resin).

[0204] The types and preferred examples of the components other than the uncured thermosetting resin contained in the CBC are also the same as the types and preferred examples of the components other than the uncured thermosetting resin in the bulking liquid used to form the CBC. However, not all the components contained in the bulking liquid are necessarily contained in the CBC in the same state as when the CBC is formed. In particular, compounds involved in the thickening reaction usually change into other compounds over time after the CBC is formed.

[0205] The fiber weight content in CBC can be, for example, greater than 20wt% and less than 30wt%, greater than 30wt% and less than 40wt%, greater than 40wt% and less than 50wt%, greater than 50wt% and less than 60wt%, greater than 60wt% and less than 70wt%, or greater than 70wt% and less than 80wt%.

[0206] From the viewpoint of improving the mechanical properties of a CFRP product molded using CBC, the fiber content is preferably 30 wt % or more, more preferably 40 wt % or more, and even more preferably 50 wt % or more.

[0207] On the other hand, the lower the fiber content, the easier it is for CBC to flow in a molding die, and thus it is more suitable for molding CFRP products with complex shapes. From this point of view, the fiber content is preferably less than 70wt%, and more preferably less than 60wt%.

[0208] The carbon fibers contained in the CBC may be all virgin carbon fibers, a portion may be virgin carbon fibers and the remainder may be recycled carbon fibers, or all may be recycled carbon fibers.

[0209] The carbon fibers contained in the CBC may be all carbon fibers that have not been thermally degraded, may be carbon fibers that have partially not been thermally degraded and the remaining portion that have been thermally degraded, or may be carbon fibers that have entirely been thermally degraded.

[0210] A typical example of carbon fiber that is not thermally degraded is virgin carbon fiber.

[0211] A typical example of thermally degraded carbon fibers is carbon fibers recovered from waste CFRP, and thermal degradation occurs during the process of thermally decomposing and removing the matrix resin.

[0212] CBC may also contain fibers other than carbon fibers. For example, when regenerated carbon fibers mixed with glass fibers are used as starting materials, a CBC consisting of a plurality of short carbon fibers bundled together with the glass fibers and a resin composition containing an uncured thermosetting resin and a curing agent can be obtained.

[0213] When CBC contains fibers other than carbon fibers, the content thereof is preferably less than 10 wt %, more preferably less than 5 wt %, and further preferably less than 1 wt % relative to the total amount of carbon fibers contained in CBC.

[0214] In this specification, the fiber weight content in a CBC in which fibers other than carbon fibers are mixed refers to the ratio of the total weight of carbon fibers contained in the CBC to the weight of the CBC.

[0215] CBC can be used, for example, as an intermediate material when manufacturing CFRP products by press molding.

[0216] CBC can also be used to produce the carbon fiber composite material sheet described in 3. below.

[0217] 3. Carbon fiber composite sheet

[0218] By using CBC, for example, the following first to third steps are performed in sequence, and thus a carbon fiber composite material sheet which is a sheet-shaped thermosetting molding material can be produced.

[0219] The first step: providing a first protective film and a second protective film.

[0220] Step 2: Spread CBC on the first protective film to accumulate the CBC layer.

[0221] Step 3: After covering the CBC layer with a second protective film, the CBC contained in the CBC layer is allowed to adhere to each other.

[0222] The materials of the first protective film and the second protective film can be appropriately selected from polyolefins such as polyethylene and polypropylene, polyvinylidene chloride, vinyl chloride resin, polyamide, etc. Either or both of the first protective film and the second protective film may be a multilayer film.

[0223] At least one of the first protective film and the second protective film may be a release paper generally used in the production of carbon fiber prepreg.

[0224] In the third step, the CBC layer may be flattened using, for example, a pressing device. The pressing device may be, for example, a double belt press or a roller press. When the CBC is hard, the CBC layer may be heated before or during flattening to reduce the viscosity of the bundled liquid contained in the CBC. In this case, the temperature and heating time are adjusted so that the bundled liquid does not gel and lose fluidity. If the viscosity of the bundled liquid increases by cooling, the CBCs in the flattened CBC layer adhere to each other to form a sheet.

[0225] In the manufacturing method of the preferred example, a thickener is added to the bundling fluid contained in the CBC, and before the effect of the thickener is fully manifested, in addition to the first and second steps, a second protective film is covered on the CBC layer, and then the CBC layer is flattened using, for example, a pressing device, to complete the process. After that, if the bundling fluid is sufficiently thickened, the CBCs in the flattened CBC layer adhere to each other to form a sheet. When the bundling fluid is thickened, the CBC layer can be kept at a temperature higher than room temperature. The holding temperature and holding time are set within a range where the bundling fluid is not solidified due to the action of the curing agent.

[0226] Figure 3 2 is a conceptual diagram of a manufacturing apparatus that can be used to manufacture a carbon fiber composite material sheet according to the above steps.

[0227] The manufacturing device includes: a section for spreading CBC on a first protective film rolled out from a roll to deposit a CBC layer, a section for covering the CBC layer with a second protective film rolled out from a roll, a section for pressurizing the CBC layer, and a section for winding a carbon fiber composite material sheet. In one example, a section for heating the CBC layer may be provided upstream of the section for pressurizing the CBC layer. In another example, the section for pressurizing the CBC layer may also be used as a section for heating the CBC layer.

[0228] The orientation of CBC in the CBC layer can be random or biased in one direction. For example, the lower the travel speed of the first protective film, the closer the orientation of CBC is to random. If the travel speed of the first protective film is increased, the CBC tends to be oriented along its travel direction.

[0229] In one example, the fiber weight content of the carbon fiber composite material sheet can be adjusted by supplementing the components of the bundling liquid when manufacturing the carbon fiber composite material sheet. Therefore, before depositing the CBC layer, the surface of the first protective film may be coated with a paste containing a part or all of the components of the bundling liquid. Alternatively or in addition, the surface of the second protective film may be coated with the same paste before covering the CBC layer.

[0230] In simple terms, the carbon fiber composite material sheet manufactured through the above steps is a sheet composed of a plurality of CBCs adhered to each other. Therefore, the following can be said.

[0231] 99 wt % or more, preferably all, of the carbon fibers contained in the carbon fiber composite material sheet may have a fiber length of 60 mm or less, 50 mm or less, 40 mm or less, 30 mm or less, or 20 mm or less.

[0232] In a preferred example, the carbon fiber composite material sheet does not contain carbon fibers having a fiber length of less than 3 mm, or even if it does, the amount thereof is less than 5 wt % of all carbon fibers contained in the carbon fiber composite material sheet.

[0233] In another preferred example, the carbon fiber composite material sheet does not contain carbon fibers having a fiber length of less than 5 mm, or even if it contains carbon fibers, the amount thereof is less than 5 wt % of all carbon fibers contained in the carbon fiber composite material sheet.

[0234] In another preferred example, the carbon fiber composite material sheet does not contain carbon fibers having a fiber length of less than 10 mm, or even if it contains carbon fibers, the amount thereof is less than 5 wt % of all carbon fibers contained in the carbon fiber composite material sheet.

[0235] The carbon fiber composite material sheet contains a resin composition derived from the sizing fluid contained in the CBC. The components and preferred examples that can be contained in the resin composition are the same as those of the sizing fluid contained in the CBC.

[0236] The fiber weight content in the carbon fiber composite material sheet can be, for example, 20 wt% or more and less than 30 wt%, 30 wt% or more and less than 40 wt%, 40 wt% or more and less than 50 wt%, 50 wt% or more and less than 60 wt%, 60 wt% or more and less than 70 wt%, or 70 wt% or more and 80 wt% or less.

[0237] From the viewpoint of improving the mechanical properties of a CFRP product molded using the carbon fiber composite material sheet, the fiber weight content is preferably 30 wt % or more, more preferably 40 wt % or more, and even more preferably 50 wt % or more.

[0238] On the other hand, the lower the fiber weight content, the easier it is for the carbon fiber composite material sheet to flow in the molding die, and thus it is more suitable for molding CFRP products with complex shapes. From this point of view, the fiber weight content is preferably less than 70wt%, and more preferably less than 60wt%.

[0239] In this specification, the fiber weight content in a carbon fiber composite material sheet mixed with fibers other than carbon fibers refers to the ratio of the total weight of carbon fibers contained in the carbon fiber composite material sheet to the weight of the carbon fiber composite material sheet.

[0240] The weight per unit area of ​​the carbon fiber composite material sheet can be appropriately designed according to the application. The weight per unit area can be, for example, 300 g / m 2 Above and less than 500g / m 2 , 500g / m 2 Above and less than 1000g / m 2 1000g / m 2 Above and less than 2000g / m 2 , 2000g / m 2 Above and less than 4000g / m 2 , 4000g / m 2 Above and less than 6000g / m 2 , 6000g / m 2 Above and less than 8000g / m 2 , or 8000g / m 2 Above and less than 10000g / m 2 .

[0241] The thickness of the carbon fiber composite material sheet can be designed to be, for example, 0.5 mm or more and less than 1.5 mm, 1.5 mm or more and less than 3 mm, or 3 mm or more and 5 mm or less, but is not limited thereto.

[0242] Carbon fiber composite material sheets are prepreg materials used for molding CFRP.

[0243] When a CFRP product is produced using a carbon fiber composite material sheet, press molding can be preferably used as a molding method, but there is no limitation thereto, and molding methods other than press molding such as autoclave molding may also be used.

[0244] 4. Summary of implementation methods

[0245] The embodiments of the present invention include the following, but are not limited thereto.

[0246] [Implementation Method 1] A method for manufacturing a carbon fiber bundle composite material, comprising: mixing carbon fiber wool composed of short carbon fibers with a bundling liquid containing an uncured thermosetting resin to obtain a carbon fiber bundle containing the above-mentioned bundling liquid; and allowing the above-mentioned bundling liquid to contain a curing agent so that the above-mentioned bundling liquid can be thermally cured.

[0247] [Embodiment 2] According to the manufacturing method described in Embodiment 1, the uncured thermosetting resin includes one or more selected from the group consisting of epoxy resin, vinyl ester resin, unsaturated polyester resin and resol type phenolic resin.

[0248] [Implementation 3] According to the manufacturing method described in Implementation 1 or 2, the viscosity of the above-mentioned clustering liquid when mixed with the above-mentioned carbon fiber cotton can be less than 10 Pa·s, preferably less than 5 Pa·s, more preferably less than 1 Pa·s, and can be greater than 0.001 Pa·s.

[0249] [Embodiment 4] According to any one of Embodiments 1 to 3, the clustering liquid has a viscosity of 10 Pa·s or less at 50°C, preferably 40°C, and more preferably 30°C.

[0250] [Embodiment 5] According to any one of Embodiments 1 to 4, a reactive diluent is mixed in the above-mentioned clustering liquid.

[0251] [Embodiment 6] According to any one of Embodiments 1 to 4, an uncured epoxy resin and a monofunctional epoxy compound are mixed into the bundling liquid.

[0252] [Embodiment 7] According to any one of Embodiments 1 to 4 and 6, an uncured epoxy resin and at least one of methylhexahydrophthalic anhydride and methyltetrahydrophthalic anhydride are mixed in the above-mentioned clustering liquid.

[0253] [Implementation 8] According to the manufacturing method described in any one of implementations 1 to 4, 6 and 7, the above-mentioned clustering liquid is mixed with at least one of an uncured vinyl ester resin and an uncured unsaturated polyester resin, and a compound having one or two ethylenically unsaturated groups in the molecule and having a viscosity of less than 1 Pa·s at 25°C.

[0254] [Embodiment 9] According to any one of Embodiments 1 to 8, a thickener is added to the above-mentioned clustering liquid.

[0255] [Embodiment 10] According to any one of Embodiments 1 to 8, the bundling liquid is mixed with an uncured epoxy resin and one or more selected from the group consisting of polyisocyanate, carboxylic anhydride and amine.

[0256] [Embodiment 11] The production method according to any one of Embodiments 1 to 8, wherein at least one of an uncured vinyl ester resin and an uncured unsaturated polyester resin and a polyisocyanate are mixed into the clustering liquid.

[0257] [Embodiment 12] According to the production method described in any one of Embodiments 1 to 8, an uncured resol-type phenolic resin and one or more components selected from alkaline earth metal hydroxides, alkaline earth metal oxides and polyisocyanates are mixed into the above-mentioned clustering liquid.

[0258] [Embodiment 13] A production method according to any one of Embodiments 9 to 12, comprising: after obtaining the above-mentioned carbon fiber bundle and after making the above-mentioned bundling liquid contain the above-mentioned curing agent, thickening the above-mentioned bundling liquid.

[0259] [Implementation 14] A manufacturing method according to any one of implementations 9 to 13, comprising: using a stirring mixer in the above-mentioned mixing, stirring the above-mentioned carbon fiber bundle formed in the stirring tank of the above-mentioned stirring mixer in the above-mentioned stirring tank while thickening the above-mentioned clustering liquid.

[0260] [Implementation 15] A manufacturing method according to any one of implementations 9 to 13, comprising: thickening the above-mentioned bundling liquid while rolling the above-mentioned carbon fiber bundle in a disc pelletizer.

[0261] [Embodiment 16] According to any one of embodiments 1 to 15, an uncured epoxy resin is mixed in the above-mentioned clustering liquid, and the above-mentioned curing agent includes an epoxy curing agent.

[0262] [Implementation 17] According to the manufacturing method described in Implementation 16, the above-mentioned epoxy curing agent contains a latent curing agent.

[0263] [Embodiment 18] According to any one of embodiments 1 to 17, at least one of an uncured vinyl ester resin and an uncured unsaturated polyester resin is added to the above-mentioned clustering liquid, and the above-mentioned curing agent contains a free radical polymerization initiator.

[0264] [Implementation 19] According to any one of the manufacturing methods described in Implementations 1 to 18, an uncured resol-type phenolic resin is added to the above-mentioned clustering liquid, and the above-mentioned curing agent comprises one or more selected from the group consisting of reaction products of at least one of an organic acid, an inorganic acid, an amine, and a primary amine and a secondary amine with an isocyanate.

[0265] [Embodiment 20] The manufacturing method according to any one of Embodiments 1 to 19, further comprising causing the clustering liquid to contain a flame retardant.

[0266] [Embodiment 21] A manufacturing method according to any one of Embodiments 1 to 20, comprising: preparing at least a portion of the above-mentioned carbon fiber cotton by defibration of a chopped carbon fiber bundle.

[0267] [Embodiment 22] According to the manufacturing method described in any one of Embodiments 1 to 20, the short carbon fibers include thermally degraded carbon fibers.

[0268] [Implementation 23] According to any one of the manufacturing methods described in Implementations 1 to 20 and 22, fibers other than carbon fibers are mixed into the carbon fiber cotton, and the fibers other than carbon fibers may be glass fibers.

[0269] [Implementation 24] According to any one of the manufacturing methods described in implementations 1 to 23, all or more than 99 weight % of the above-mentioned short carbon fibers have a fiber length of less than 60 mm, less than 50 mm, less than 40 mm, less than 30 mm or less than 20 mm.

[0270] [Implementation 25] According to any one of the manufacturing methods described in Implementations 1 to 24, the carbon fiber bundle has a bundle length of 3 mm or more, 5 mm or more, or 10 mm or more.

[0271] [Implementation 26] According to any one of the manufacturing methods described in Implementations 1 to 24, the above-mentioned carbon fiber bundle does not contain carbon fibers with a fiber length of less than 3 mm, or even if it does, its content is less than 5wt% of all the carbon fibers in the above-mentioned carbon fiber bundle.

[0272] [Implementation 27] According to any one of the manufacturing methods described in Implementations 1 to 24, the carbon fiber bundle does not contain carbon fibers having a fiber length of less than 5 mm, or even if it does, its content is less than 5wt% of all the carbon fibers in the carbon fiber bundle.

[0273] [Implementation 28] According to any one of the manufacturing methods described in Implementations 1 to 24, the carbon fiber bundle does not contain carbon fibers having a fiber length less than 10 mm, or even if it does, its content is less than 5wt% of all the carbon fibers in the carbon fiber bundle.

[0274] [Implementation 29] According to any one of the manufacturing methods described in implementations 1 to 28, the fiber weight content of the above-mentioned carbon fiber bundle is greater than 20wt% and less than 30wt%, greater than 30wt% and less than 40wt%, greater than 40wt% and less than 50wt%, greater than 50wt% and less than 60wt%, greater than 60wt% and less than 70wt%, or greater than 70wt% and less than 80wt%.

[0275] [Implementation 30] A method for manufacturing a carbon fiber bundle composite material, comprising: forming a carbon fiber bundle containing the bundling liquid by agglomerating discontinuous carbon fibers using the bundling liquid, wherein the bundling liquid is a resin composition containing an uncured thermosetting resin and a curing agent.

[0276] [Implementation 31] According to the manufacturing method described in Implementation 30, the above-mentioned uncured thermosetting resin contains one or more selected from the group consisting of epoxy resin, vinyl ester resin, unsaturated polyester resin, resol type phenolic resin, (meth)acrylate other than epoxy vinyl ester and diallyl phthalate.

[0277] [Implementation 32] According to the manufacturing method described in implementation 30 or 31, the above-mentioned clustering liquid also contains a reactive diluent.

[0278] [Implementation 33] According to the manufacturing method described in any one of implementations 30 to 32, the above-mentioned clustering liquid further contains a thickener.

[0279] [Implementation 34] According to the manufacturing method described in implementation 33, it also includes thickening the above-mentioned bundling liquid after forming the above-mentioned carbon fiber bundle.

[0280] [Implementation 35] According to the manufacturing method described in any one of Implementations 30 to 34, the above-mentioned discontinuous carbon fiber contains regenerated carbon fiber.

[0281] [Implementation 36] According to the manufacturing method described in Implementation 35, the above-mentioned regenerated carbon fiber contains carbon fiber that has been thermally degraded.

[0282] [Implementation 37] According to any one of the manufacturing methods described in implementations 30 to 36, all or more than 99 weight % of the above-mentioned discontinuous carbon fibers have a fiber length of less than 60 mm, less than 50 mm, less than 40 mm, less than 30 mm or less than 20 mm.

[0283] [Implementation 38] According to any one of the manufacturing methods described in Implementations 30 to 37, the carbon fiber bundle has a bundle length of 3 mm or more, 5 mm or more, or 10 mm or more.

[0284] [Implementation 39] According to any one of the manufacturing methods described in Implementations 30 to 37, the above-mentioned carbon fiber bundle does not contain carbon fibers with a fiber length less than 3 mm, or even if it does, its content is less than 5wt% of all the carbon fibers in the above-mentioned carbon fiber bundle.

[0285] [Implementation 40] According to any one of the manufacturing methods described in implementations 30 to 37, the above-mentioned carbon fiber bundle does not contain carbon fibers with a fiber length less than 5 mm, or even if it does, its content is less than 5wt% of all the carbon fibers in the above-mentioned carbon fiber bundle.

[0286] [Implementation 41] According to any one of the manufacturing methods described in implementations 30 to 37, the above-mentioned carbon fiber bundle does not contain carbon fibers with a fiber length less than 10 mm, or even if it does, its content is less than 5wt% of all the carbon fibers in the above-mentioned carbon fiber bundle.

[0287] [Implementation 42] According to any one of the manufacturing methods described in implementations 30 to 41, the fiber weight content of the above-mentioned carbon fiber bundle is greater than 20wt% and less than 30wt%, greater than 30wt% and less than 40wt%, greater than 40wt% and less than 50wt%, greater than 50wt% and less than 60wt%, greater than 60wt% and less than 70wt%, or greater than 70wt% and less than 80wt%.

[0288] [Embodiment 43] According to the manufacturing method described in Embodiment 42, the fiber weight content is greater than 30wt% and less than 70wt%, preferably greater than 40wt% and less than 60wt%.

[0289] [Embodiment 44] A carbon fiber bundle composite material produced by the production method described in any one of Embodiments 1 to 43.

[0290] [Implementation 45] A method for manufacturing a carbon fiber composite material sheet, comprising: mixing carbon fiber wool composed of short carbon fibers with a bundling liquid containing an uncured thermosetting resin to obtain a carbon fiber bundle containing the above-mentioned bundling liquid; allowing the above-mentioned bundling liquid to contain a curing agent so that the above-mentioned bundling liquid can be thermally cured; and after allowing the above-mentioned curing agent to be contained in the above-mentioned bundling liquid, allowing the plurality of the above-mentioned carbon fiber bundles to adhere to each other.

[0291] [Implementation 46] According to the manufacturing method described in Implementation 45, the above-mentioned uncured thermosetting resin contains one or more selected from the group consisting of epoxy resin, vinyl ester resin, unsaturated polyester resin and resol type phenolic resin.

[0292] [Implementation 47] According to the manufacturing method described in implementation 45 or 46, the viscosity of the above-mentioned clustering liquid when mixed with the above-mentioned carbon fiber cotton is less than 10 Pa·s, preferably less than 5 Pa·s, more preferably less than 1 Pa·s, and can be greater than 0.001 Pa·s.

[0293] [Embodiment 48] According to the manufacturing method described in any one of Embodiments 45 to 47, the above-mentioned clustering liquid has a viscosity of 10 Pa·s or less at 50°C, preferably at 40°C, and more preferably at 30°C.

[0294] [Embodiment 49] According to the manufacturing method described in any one of Embodiments 45 to 48, a reactive diluent is added to the above-mentioned clustering liquid.

[0295] [Implementation 50] According to any one of implementations 45 to 48, an uncured epoxy resin and a monofunctional epoxy compound are mixed into the above-mentioned clustering liquid.

[0296] [Embodiment 51] According to the manufacturing method described in any one of Embodiments 45 to 48 and 50, an uncured epoxy resin and at least one of methylhexahydrophthalic anhydride and methyltetrahydrophthalic anhydride are added to the above-mentioned clustering liquid.

[0297] [Implementation 52] According to any one of implementations 45 to 48, 50 and 51, the above-mentioned clustering liquid is mixed with at least any one of an uncured vinyl ester resin and an uncured unsaturated polyester resin, and a compound having one or two ethylenically unsaturated groups in the molecule and having a viscosity of less than 1 Pa·s at 25°C.

[0298] [Implementation 53] According to any one of implementations 45 to 52, a thickener is added to the above-mentioned clustering liquid.

[0299] [Embodiment 54] According to any one of embodiments 45 to 52, an uncured epoxy resin and one or more selected from the group consisting of polyisocyanate, carboxylic anhydride and amine are added to the above-mentioned clustering liquid.

[0300] [Embodiment 55] According to any one of embodiments 45 to 52, at least one of an uncured vinyl ester resin and an uncured unsaturated polyester resin, and a polyisocyanate are mixed into the above-mentioned clustering liquid.

[0301] [Embodiment 56] According to the manufacturing method described in any one of Embodiments 45 to 52, an uncured resol-type phenolic resin and one or more selected from the group consisting of alkaline earth metal hydroxides, alkaline earth metal oxides and polyisocyanates are added to the above-mentioned clustering liquid.

[0302] [Implementation 57] A manufacturing method according to any one of implementations 53 to 56, comprising: after making the above-mentioned bundling liquid contain the above-mentioned curing agent, while making the above-mentioned multiple carbon fiber bundles contact with each other, thickening the above-mentioned bundling liquid.

[0303] [Embodiment 58] According to any one of embodiments 45 to 57, an uncured epoxy resin is mixed into the above-mentioned clustering liquid, and the above-mentioned curing agent includes an epoxy curing agent.

[0304] [Implementation 59] According to the manufacturing method described in Implementation 57, the above-mentioned epoxy curing agent contains a latent curing agent.

[0305] [Implementation 60] According to any one of implementations 45 to 59, at least one of an uncured vinyl ester resin and an uncured unsaturated polyester resin is added to the above-mentioned clustering liquid, and the above-mentioned curing agent contains a free radical polymerization initiator.

[0306] [Implementation 61] According to the manufacturing method described in any one of implementations 45 to 60, an uncured resol-type phenolic resin is added to the above-mentioned clustering liquid, and the above-mentioned curing agent comprises one or more selected from the group consisting of reaction products of at least one of an organic acid, an inorganic acid, an amine, and a primary amine and a secondary amine with an isocyanate.

[0307] [Embodiment 62] The manufacturing method according to any one of Embodiments 45 to 61, further comprising causing the clustering liquid to contain a flame retardant.

[0308] [Implementation 63] A manufacturing method according to any one of implementations 45 to 62, comprising: preparing at least a portion of the carbon fiber cotton by defibration of a chopped carbon fiber bundle.

[0309] [Embodiment 64] According to the manufacturing method described in any one of Embodiments 45 to 62, the above-mentioned short carbon fibers include carbon fibers that have been thermally degraded.

[0310] [Implementation 65] According to any one of the manufacturing methods described in Implementations 45 to 62 and 64, fibers other than carbon fibers are mixed into the above-mentioned carbon fiber cotton, and the fibers other than carbon fibers may be glass fibers.

[0311] [Implementation 66] According to the manufacturing method described in any one of implementations 45 to 65, all or more than 99 weight % of the above-mentioned short carbon fibers have a fiber length of less than 60 mm, less than 50 mm, less than 40 mm, less than 30 mm or less than 20 mm.

[0312] [Implementation 67] According to any one of the manufacturing methods described in Implementations 45 to 66, the carbon fiber bundle has a bundle length of 3 mm or more, 5 mm or more, or 10 mm or more.

[0313] [Implementation 68] According to the manufacturing method described in any one of implementations 45 to 66, the above-mentioned carbon fiber composite material sheet does not contain carbon fibers with a fiber length of less than 3 mm, or even if it does, its content is less than 5wt% of all carbon fibers in the above-mentioned carbon fiber composite material sheet.

[0314] [Implementation 69] According to any one of the manufacturing methods described in Implementations 45 to 66, the above-mentioned carbon fiber composite material sheet does not contain carbon fibers with a fiber length of less than 5 mm, or even if it does, its content is less than 5wt% of all carbon fibers in the above-mentioned carbon fiber composite material sheet.

[0315] [Implementation 70] According to any one of implementations 45 to 66, the carbon fiber composite material sheet does not contain carbon fibers having a fiber length less than 10 mm, or even if it does, its content is less than 5 wt% of all carbon fibers in the carbon fiber composite material sheet.

[0316] [Implementation 71] According to any one of the manufacturing methods described in implementations 45 to 70, the fiber weight content of the above-mentioned carbon fiber composite material sheet is greater than 20wt% and less than 30wt%, greater than 30wt% and less than 40wt%, greater than 40wt% and less than 50wt%, greater than 50wt% and less than 60wt%, greater than 60wt% and less than 70wt%, or greater than 70wt% and less than 80wt%.

[0317] [Implementation 72] A method for manufacturing a carbon fiber composite material sheet, comprising: forming a carbon fiber bundle containing the bundling liquid by utilizing a bundling liquid to agglomerate discontinuous carbon fibers; and adhering a plurality of the carbon fiber bundles to each other, wherein the bundling liquid is a resin composition containing an uncured thermosetting resin and a curing agent.

[0318] [Implementation 73] A method for manufacturing a carbon fiber composite material sheet, comprising: while bringing a plurality of carbon fiber bundles into contact with each other, thickening a bundling liquid contained in each of the plurality of carbon fiber bundles, thereby making the plurality of carbon fiber bundles adhere to each other, wherein in each of the plurality of carbon fiber bundles, discontinuous carbon fibers are condensed by the bundling liquid, and the bundling liquid is a resin composition containing an uncured thermosetting resin, a curing agent and a thickener.

[0319] [Implementation 74] A method for manufacturing a carbon fiber composite material sheet, comprising: stacking a plurality of carbon fiber bundles to form a carbon fiber bundle layer; flattening the carbon fiber bundle layer; and then thickening a bundling liquid contained in each of the plurality of carbon fiber bundles, wherein discontinuous carbon fibers in each of the plurality of carbon fiber bundles are condensed by the bundling liquid, and the bundling liquid is a resin composition comprising an uncured thermosetting resin, a curing agent, and a thickener.

[0320] [Implementation 75] According to the manufacturing method described in any one of implementations 72 to 74, the uncured thermosetting resin comprises one or more selected from the group consisting of epoxy resin, vinyl ester resin, unsaturated polyester resin, resol-type phenolic resin, (meth)acrylate other than epoxy vinyl ester, and diallyl phthalate.

[0321] [Implementation 76] According to the manufacturing method described in any one of implementations 72 to 75, the above-mentioned clustering liquid also contains a reactive diluent.

[0322] [Implementation 77] According to the manufacturing method described in any one of implementations 72 to 76, the above-mentioned discontinuous carbon fiber contains regenerated carbon fiber.

[0323] [Implementation 78] According to the manufacturing method described in Implementation 77, the above-mentioned regenerated carbon fiber contains carbon fiber that has been thermally degraded.

[0324] [Implementation 79] According to the manufacturing method described in any one of implementations 72 to 78, all or more than 99 weight % of the carbon fibers contained in the above-mentioned carbon fiber composite material sheet have a fiber length of less than 60 mm, less than 50 mm, less than 40 mm, less than 30 mm or less than 20 mm.

[0325] [Implementation 80] According to any one of the manufacturing methods described in Implementations 72 to 79, the above-mentioned multiple carbon fiber bundles each have a bundle length of more than 3 mm, more than 5 mm, or more than 10 mm.

[0326] [Implementation 81] According to any one of implementations 72 to 80, the carbon fiber composite material sheet does not contain carbon fibers having a fiber length less than 3 mm, or even if it does, its content is less than 5 wt% of all carbon fibers in the carbon fiber composite material sheet.

[0327] [Implementation 82] According to any one of implementations 72 to 80, the carbon fiber composite material sheet does not contain carbon fibers having a fiber length less than 5 mm, or even if it does, its content is less than 5 wt % of all carbon fibers in the carbon fiber composite material sheet.

[0328] [Implementation 83] According to any one of implementations 72 to 80, the carbon fiber composite material sheet does not contain carbon fibers with a fiber length less than 10 mm, or even if it does, its content is less than 5 wt% of all carbon fibers in the carbon fiber composite material sheet.

[0329] [Implementation 84] According to any one of the manufacturing methods described in implementations 72 to 83, the fiber weight content of the above-mentioned carbon fiber composite material sheet is greater than 20wt% and less than 30wt%, greater than 30wt% and less than 40wt%, greater than 40wt% and less than 50wt%, greater than 50wt% and less than 60wt%, greater than 60wt% and less than 70wt%, or greater than 70wt% and less than 80wt%.

[0330] [Embodiment 85] According to the manufacturing method described in Embodiment 84, the fiber weight content is greater than 30wt% and less than 70wt%, preferably greater than 40wt% and less than 60wt%.

[0331] [Embodiment 86] A carbon fiber composite material sheet manufactured by the manufacturing method described in any one of Embodiments 45 to 85.

[0332] [Embodiment 87] A method for manufacturing a CFRP product, comprising: heating and pressurizing the carbon fiber bundle composite material described in Embodiment 44 or the carbon fiber composite material sheet described in Embodiment 86 in a molding die to solidify it.

[0333] 5. Experimental Results

[0334] The results of experiments conducted by the present inventors are described below.

[0335] The materials used in each experiment are as follows.

[0336] Carbon fiber: A cotton-like carbon fiber obtained by drying chopped carbon fibers having a fiber length of 6 mm sized with water at 120° C. for 1 hour and then unraveling them by hand.

[0337] Epoxy resin 1: jER (registered trademark) 807 manufactured by Mitsubishi Chemical Corporation, which is a bisphenol F-type epoxy resin.

[0338] Epoxy resin 2: TETRAD-X (registered trademark) produced by Mitsubishi Gas Chemical Co., Ltd., containing N,N,N',N'-tetraglycidyl-m-xylenediamine as a component.

[0339] Epoxy curing agent 1: Curezol 2MZA-PW from Shikoku Chemical Industry Co., Ltd., containing 2,4-diamino-6-[2′-methylimidazole-(1′)]-ethyl-s-triazine as a component.

[0340] Epoxy curing agent 2: Amicure (registered trademark) PN-23J manufactured by Ajinomoto Fine Chemicals Co., Ltd., which is an amine adduct-based latent curing agent for epoxy resin.

[0341] Thickener: HN-2200 from Resonac Co., Ltd., containing 3 or 4-methyl-1,2,3,6-tetrahydrophthalic anhydride as a component.

[0342] [Preparation of clustering fluid]

[0343] The epoxy resin, the epoxy curing agent and the thickener were mixed in the weight ratio shown in Table 1 to prepare a bundling liquid.

[0344] [Table 1]

[0345] Element Weight Ratio Epoxy resin 1 95 Epoxy Resin 2 5 Curing agent 1 4 Curing agent 2 4 Thickener 12

[0346] The viscosity of the sizing liquid was measured with a B-type rotational viscometer (Brookfield LVDV-1, Spindle S63, 10 rpm) immediately after preparation, and the result was 4 Pa·s at 22° C. The sizing liquid was left at 22° C. for 6 days, and the viscosity was measured again with a B-type rotational viscometer (Brookfield digital viscometer HBDVE, Spindle S07, 10 rpm), and the result was 470 Pa·s at 22° C.

[0347] [Experiment 1]

[0348] 30g of carbon fiber and 16.2g of bundling liquid were placed in a 500mL plastic container (PP Flat Bottle 500mL from Azowan Co., Ltd.) and shaken by hand for about 5 minutes. The carbon fiber was mixed with the bundling liquid to form a bundle. When the contents of the container were observed after shaking, no carbon fiber that did not participate in the formation of the bundle was confirmed. In addition, all the bundles were seed-shaped (spindle-shaped), and almost all of the bundles were in the range of 10 to 20mm in length, with a maximum diameter in the range of 3 to 5mm. The maximum diameter is the diameter of the bundle at the part where the bundle is the thickest, which can also be said to be the diameter of the bundle at the center of the length direction (fiber direction) (the same applies below).

[0349] [Experiment 2]

[0350] The carbon fibers and the sizing liquid were placed in a container and shaken in the same manner as in Experiment 1 except that the amount of the sizing liquid was increased to 20.0 g. When the contents of the container were observed after shaking, no carbon fibers not involved in the formation of the bundles were confirmed, and all the bundles were seed-shaped (spindle-shaped), and almost all of the bundles were within the range of 15 to 25 mm in length and within the range of 5 to 10 mm in maximum diameter.

[0351] [Experiment 3]

[0352] The carbon fibers and the sizing liquid were placed in a container and shaken in the same manner as in Experiment 1, except that the amount of carbon fibers was reduced to 20 g and the amount of sizing liquid was increased to 20.0 g. When the contents of the container were observed after shaking, no carbon fibers not involved in the formation of bundles were confirmed, and all bundles were seed-shaped (spindle-shaped), and almost all bundles had a length in the range of 20 to 30 mm and a maximum diameter in the range of 10 to 20 mm.

[0353] [Experiment 4]

[0354] A pressing mold consisting of a cavity and a core having a flat bottom surface of 100 mm × 60 mm was used to mold a CFRP plate of 100 mm × 60 mm in length and width from 15 g of the carbon fiber bundle composite material obtained in Experiment 2. The pressing time was set to 1 hour and 30 minutes, with the temperature at 150°C and the pressure at 8 MPa for the first 30 minutes, and the temperature at 180°C and the pressure at 8 MPa for the next hour.

[0355] The obtained CFRP plate has a smooth surface, a thickness of 2.5 mm, and a density of 0.92 g / cm 3 .

[0356] [Experiment 5]

[0357] 15 g of the carbon fiber bundle composite material just produced in the same steps as in Experiment 2 was placed in a plastic bag with a chuck of 100 mm × 70 mm in length and width. The plastic bag was placed on a platform, and the bottom of the beaker was pressed manually, as shown in FIG. Figure 4 As shown, the carbon fiber composite material in the plastic bag is flattened.

[0358] The carbon fiber bundles were not firmly adhered to each other immediately after being flattened, and the contents of the plastic bag could not be handled as a self-supporting sheet.

[0359] However, after being flattened, the contents of the plastic bag were transformed into self-supporting sheets by being placed at 22°C for 6 days. Figure 5 As shown, the sheet will not be damaged even if it is bent.

[0360] Note: If the seed-shaped carbon fiber bundle composite material is left at 22°C for 6 days, it becomes too hard to be crushed by the above method and cannot be bonded to each other.

[0361] [Experiment 6]

[0362] The carbon fiber composite sheet obtained in Experiment 5 was cut into 90 mm × 50 mm in length and width, and the cut carbon fiber composite sheet was used to form a CFRP plate of 100 mm × 60 mm in length and width. The pressing mold and molding conditions used were the same as those in Experiment 4. The area of ​​the carbon fiber composite sheet placed in the pressing mold was 75% of the area of ​​the bottom surface of the cavity of the pressing mold, which shows that the carbon fiber composite sheet flowed during molding.

[0363] The obtained CFRP plate has a smooth surface, a thickness of 1.2 mm, and a density of 1.58 g / cm 3 .

[0364] The present invention has been described above based on specific embodiments, but each embodiment is proposed as an example and does not limit the scope of the present invention. Each embodiment described in this specification can be modified in various ways within the scope of the invention effect, and can be combined with the features described in other embodiments within the scope of implementation.

[0365] This application is based on Japanese Patent Application No. 2022-137548 filed on August 31, 2022, the entirety of which is incorporated by reference.

[0366] Industrial Applicability

[0367] The carbon fiber bundle composite material and carbon fiber composite material sheet obtained by the production method according to each embodiment can be preferably used for the production of various CFRP parts used in the production of sports goods, leisure goods, home appliances, agricultural machinery, building materials, etc., in addition to transportation equipment such as automobiles, motorcycles, bicycles, ships, railway vehicles, manned aircraft, and unmanned aircraft.

Claims

1. A method for manufacturing a carbon fiber bundle composite material, comprising: Mixing carbon fiber wool composed of short carbon fibers with a bundling liquid containing an uncured thermosetting resin to obtain a carbon fiber bundle containing the bundling liquid; as well as The bundling fluid contains a curing agent so that the bundling fluid can be thermally cured. 2 . The production method according to claim 1 , wherein the uncured thermosetting resin comprises at least one selected from the group consisting of epoxy resin, vinyl ester resin, unsaturated polyester resin and resol type phenolic resin.

3. According to the manufacturing method according to claim 1 or 2, the viscosity of the clustering liquid when mixed with the carbon fiber wool is 10 Pa·s or less, preferably 5 Pa·s or less, more preferably 1 Pa·s or less, and can be 0.001 Pa·s or more. 4 . The production method according to claim 1 , wherein the clustering fluid has a viscosity of 10 Pa·s or less at 50° C., preferably 40° C., and more preferably 30° C. 5 . The production method according to claim 1 , wherein a reactive diluent is blended into the focusing liquid. 6 . The production method according to claim 1 , wherein an uncured epoxy resin and a monofunctional epoxy compound are blended into the bundling liquid. 7 . The production method according to claim 1 , wherein an uncured epoxy resin and at least one of methylhexahydrophthalic anhydride and methyltetrahydrophthalic anhydride are blended into the bundling liquid.

8. The production method according to any one of claims 1 to 4, 6 and 7, wherein the bundling liquid contains at least one of an uncured vinyl ester resin and an uncured unsaturated polyester resin and a compound having one or two ethylenically unsaturated groups in its molecule and having a viscosity of 1 Pa·s or less at 25°C. 9 . The production method according to claim 1 , wherein a thickener is blended into the focusing liquid. 10 . The production method according to claim 1 , wherein the clustering liquid contains an uncured epoxy resin and one or more selected from the group consisting of polyisocyanate, carboxylic anhydride and amine. 11 . The production method according to claim 1 , wherein the clustering liquid contains at least one of an uncured vinyl ester resin and an uncured unsaturated polyester resin, and a polyisocyanate. 12 . The production method according to claim 1 , wherein the clustering liquid contains an uncured resol-type phenolic resin and one or more components selected from the group consisting of alkaline earth metal hydroxides, alkaline earth metal oxides and polyisocyanates.

13. The manufacturing method according to any one of claims 9 to 12, comprising: After the carbon fiber bundle is obtained and after the curing agent is contained in the bundling liquid, the bundling liquid is thickened.

14. The manufacturing method according to any one of claims 9 to 13, comprising: The mixing is performed using a stirring mixer, and the carbon fiber bundle formed in a stirring tank of the stirring mixer is stirred in the stirring tank, thereby thickening the bundling liquid.

15. The manufacturing method according to any one of claims 9 to 13, comprising: The agglomerated liquid is thickened while the carbon fiber bundle is tumbled in a disc pelletizer. 16 . The production method according to claim 1 , wherein an uncured epoxy resin is blended into the bundling liquid, and the curing agent includes an epoxy curing agent. The manufacturing method according to claim 16 , wherein the epoxy curing agent comprises a latent curing agent.

18. The production method according to any one of claims 1 to 17, wherein at least one of an uncured vinyl ester resin and an uncured unsaturated polyester resin is blended into the bundling liquid, and the curing agent contains a radical polymerization initiator.

19. The production method according to any one of claims 1 to 18, wherein an uncured resol-type phenolic resin is mixed in the bundling liquid, and the curing agent comprises one or more selected from the group consisting of organic acids, inorganic acids, amines, and reaction products of at least one of primary amines and secondary amines with isocyanates. 20 . The production method according to claim 1 , further comprising adding a flame retardant to the clustering fluid.

21. The manufacturing method according to any one of claims 1 to 20, comprising: At least a portion of the carbon fiber wool is prepared by defibration of chopped carbon fiber bundles. 22 . The production method according to claim 1 , wherein the short carbon fibers include thermally degraded carbon fibers.

23. The production method according to any one of claims 1 to 20 and 22, wherein fibers other than carbon fibers are mixed into the carbon fiber wool, and the fibers other than carbon fibers may be glass fibers.

24. The production method according to any one of claims 1 to 23, wherein all or 99% by weight or more of the short carbon fibers have a fiber length of 60 mm or less, 50 mm or less, 40 mm or less, 30 mm or less, or 20 mm or less. 25 . The production method according to claim 1 , wherein the carbon fiber bundle has a bundle length of 3 mm or more, 5 mm or more, or 10 mm or more.

26. The production method according to any one of claims 1 to 24, wherein the carbon fiber bundle does not contain carbon fibers having a fiber length of less than 3 mm, or even if it does, the content of the carbon fibers is less than 5 wt% of all the carbon fibers in the carbon fiber bundle.

27. The production method according to any one of claims 1 to 24, wherein the carbon fiber bundle does not contain carbon fibers having a fiber length of less than 5 mm, or even if it does, the content of the carbon fibers is less than 5 wt% of all the carbon fibers in the carbon fiber bundle.

28. The production method according to any one of claims 1 to 24, wherein the carbon fiber bundle does not contain carbon fibers having a fiber length of less than 10 mm, or even if it does, the content of the carbon fibers is less than 5 wt% of all the carbon fibers in the carbon fiber bundle.

29. The manufacturing method according to any one of claims 1 to 28, wherein the fiber weight content of the carbon fiber bundle is 20wt% or more and less than 30wt%, 30wt% or more and less than 40wt%, 40wt% or more and less than 50wt%, 50wt% or more and less than 60wt%, 60wt% or more and less than 70wt%, or 70wt% or more and 80wt% or less.

30. A method for manufacturing a carbon fiber bundle composite material, comprising: The carbon fiber bundle containing the bundling liquid is formed by agglomerating discontinuous carbon fibers using the bundling liquid, and the bundling liquid is a resin composition containing an uncured thermosetting resin and a curing agent.

31. The production method according to claim 30, wherein the uncured thermosetting resin comprises one or more selected from the group consisting of epoxy resins, vinyl ester resins, unsaturated polyester resins, resol-type phenolic resins, (meth)acrylates other than epoxy vinyl esters, and diallyl phthalate.

32. The production method according to claim 30 or 31, wherein the clustering liquid further contains a reactive diluent.

33. The production method according to any one of claims 30 to 32, wherein the clustering liquid further contains a thickener.

34. The manufacturing method according to claim 33, further comprising: The bundling fluid is thickened after the carbon fiber bundle is formed. 35 . The production method according to claim 30 , wherein the discontinuous carbon fibers include regenerated carbon fibers. 36 . The manufacturing method according to claim 35 , wherein the recycled carbon fiber comprises thermally degraded carbon fiber.

37. The production method according to any one of claims 30 to 36, wherein all or 99% by weight or more of the discontinuous carbon fibers have a fiber length of 60 mm or less, 50 mm or less, 40 mm or less, 30 mm or less, or 20 mm or less.

38. The production method according to any one of claims 30 to 37, wherein the carbon fiber bundle has a bundle length of 3 mm or more, 5 mm or more, or 10 mm or more.

39. The production method according to any one of claims 30 to 37, wherein the carbon fiber bundle does not contain carbon fibers having a fiber length of less than 3 mm, or even if it does, the content thereof is less than 5 wt% of all carbon fibers in the carbon fiber bundle.

40. The production method according to any one of claims 30 to 37, wherein the carbon fiber bundle does not contain carbon fibers having a fiber length of less than 5 mm, or even if it does, the content thereof is less than 5 wt% of all carbon fibers in the carbon fiber bundle.

41. The production method according to any one of claims 30 to 37, wherein the carbon fiber bundle does not contain carbon fibers having a fiber length of less than 10 mm, or even if it does, the content thereof is less than 5 wt% of all carbon fibers in the carbon fiber bundle.

42. According to the manufacturing method described in any one of claims 30 to 41, the fiber weight content of the carbon fiber bundle is greater than 20wt% and less than 30wt%, greater than 30wt% and less than 40wt%, greater than 40wt% and less than 50wt%, greater than 50wt% and less than 60wt%, greater than 60wt% and less than 70wt%, or greater than 70wt% and less than 80wt%.

43. The production method according to claim 42, wherein the fiber weight content is 30 wt% or more and less than 70 wt%, preferably 40 wt% or more and less than 60 wt%.

44. A carbon fiber bundle composite material produced by the production method according to any one of claims 1 to 43.

45. A method for manufacturing a carbon fiber composite material sheet, comprising: Mixing carbon fiber wool composed of short carbon fibers with a bundling liquid containing an uncured thermosetting resin to obtain a carbon fiber bundle containing the bundling liquid; The bundling fluid contains a curing agent so that the bundling fluid can be thermally cured; as well as After the curing agent is added to the bundling liquid, the plurality of carbon fiber bundles are bonded to each other. 46 . The manufacturing method according to claim 45 , wherein the uncured thermosetting resin comprises at least one selected from the group consisting of epoxy resin, vinyl ester resin, unsaturated polyester resin and resol type phenolic resin.

47. According to the manufacturing method according to claim 45 or 46, the viscosity of the clustering liquid when mixed with the carbon fiber cotton is 10 Pa·s or less, preferably 5 Pa·s or less, more preferably 1 Pa·s or less, and can be 0.001 Pa·s or more.

48. The production method according to any one of claims 45 to 47, wherein the clustering liquid has a viscosity of 10 Pa·s or less at 50°C, preferably 40°C, and more preferably 30°C.

49. The production method according to any one of claims 45 to 48, wherein a reactive diluent is blended into the focusing liquid. 50 . The production method according to claim 45 , wherein an uncured epoxy resin and a monofunctional epoxy compound are blended into the bundling liquid.

51. The production method according to any one of claims 45 to 48 and 50, wherein an uncured epoxy resin and at least one of methylhexahydrophthalic anhydride and methyltetrahydrophthalic anhydride are blended into the bundling liquid.

52. The production method according to any one of claims 45 to 48, 50 and 51, wherein the clustering liquid contains at least one of an uncured vinyl ester resin and an uncured unsaturated polyester resin, and a compound having one or two ethylenically unsaturated groups in its molecule and having a viscosity of 1 Pa·s or less at 25°C.

53. The production method according to any one of claims 45 to 52, wherein a thickener is blended into the bundling liquid.

54. The production method according to any one of claims 45 to 52, wherein an uncured epoxy resin and one or more selected from the group consisting of polyisocyanate, carboxylic anhydride and amine are blended into the clustering liquid.

55. The production method according to any one of claims 45 to 52, wherein the clustering liquid contains at least one of an uncured vinyl ester resin and an uncured unsaturated polyester resin, and a polyisocyanate.

56. The production method according to any one of claims 45 to 52, wherein the clustering liquid contains an uncured resol-type phenolic resin and at least one selected from the group consisting of alkaline earth metal hydroxides, alkaline earth metal oxides and polyisocyanates.

57. The method according to any one of claims 53 to 56, comprising: After the curing agent is added to the bundling liquid, the bundling liquid is thickened while the plurality of carbon fiber bundles are brought into contact with each other.

58. The production method according to any one of claims 45 to 57, wherein an uncured epoxy resin is blended into the bundling liquid, and the curing agent includes an epoxy curing agent.

59. The manufacturing method according to claim 57, wherein the epoxy curing agent comprises a latent curing agent.

60. The production method according to any one of claims 45 to 59, wherein at least one of an uncured vinyl ester resin and an uncured unsaturated polyester resin is blended into the clustering liquid, and the curing agent contains a radical polymerization initiator.

61. The production method according to any one of claims 45 to 60, wherein an uncured resol-type phenolic resin is added to the clustering liquid, and the curing agent comprises one or more selected from the group consisting of organic acids, inorganic acids, amines, and reaction products of at least one of primary amines and secondary amines with isocyanates.

62. The production method according to any one of claims 45 to 61, further comprising adding a flame retardant to the clustering fluid.

63. The production method according to any one of claims 45 to 62, comprising preparing at least a part of the carbon fiber wool by defibration of a chopped carbon fiber bundle.

64. The production method according to any one of claims 45 to 62, wherein the short carbon fibers include thermally degraded carbon fibers.

65. The manufacturing method according to any one of claims 45 to 62 and 64, wherein fibers other than carbon fibers are mixed into the carbon fiber wool, and the fibers other than carbon fibers may be glass fibers.

66. The manufacturing method according to any one of claims 45 to 65, wherein all or more than 99 weight % of the short carbon fibers have a fiber length of 60 mm or less, 50 mm or less, 40 mm or less, 30 mm or less, or 20 mm or less.

67. The production method according to any one of claims 45 to 66, wherein the carbon fiber bundle has a bundle length of 3 mm or more, 5 mm or more, or 10 mm or more.

68. The production method according to any one of claims 45 to 66, wherein the carbon fiber composite material sheet does not contain carbon fibers having a fiber length of less than 3 mm, or even if it does, its content is less than 5 wt% of all carbon fibers in the carbon fiber composite material sheet.

69. The production method according to any one of claims 45 to 66, wherein the carbon fiber composite material sheet does not contain carbon fibers having a fiber length of less than 5 mm, or even if it does, its content is less than 5 wt% of all carbon fibers in the carbon fiber composite material sheet.

70. The production method according to any one of claims 45 to 66, wherein the carbon fiber composite material sheet does not contain carbon fibers having a fiber length of less than 10 mm, or even if it does, its content is less than 5 wt% of all carbon fibers in the carbon fiber composite material sheet.

71. The manufacturing method according to any one of claims 45 to 70, wherein the fiber weight content of the carbon fiber composite material sheet is 20wt% or more and less than 30wt%, 30wt% or more and less than 40wt%, 40wt% or more and less than 50wt%, 50wt% or more and less than 60wt%, 60wt% or more and less than 70wt%, or 70wt% or more and 80wt% or less.

72. A method for manufacturing a carbon fiber composite material sheet, comprising: Forming a carbon fiber bundle containing a bundling fluid by agglomerating discontinuous carbon fibers using the bundling fluid; as well as Adhere a plurality of the carbon fiber bundles to each other, The bundling fluid is a resin composition containing an uncured thermosetting resin and a curing agent.

73. A method for manufacturing a carbon fiber composite material sheet, comprising: While bringing the plurality of carbon fiber bundles into contact with each other, the bundling liquid contained in each of the plurality of carbon fiber bundles is thickened so that the plurality of carbon fiber bundles adhere to each other. In each of the plurality of carbon fiber bundles, discontinuous carbon fibers are aggregated by the aggregating liquid. The clustering fluid is a resin composition containing an uncured thermosetting resin, a curing agent and a thickener.

74. A method for manufacturing a carbon fiber composite material sheet, comprising: stacking a plurality of carbon fiber bundles to form a carbon fiber bundle layer; Flattening the carbon fiber bundle layer; as well as Then, the bundling liquid contained in each of the plurality of carbon fiber bundles is thickened. In each of the plurality of carbon fiber bundles, discontinuous carbon fibers are agglomerated by the aggregating liquid, which is a resin composition containing an uncured thermosetting resin, a curing agent, and a thickener.

75. The manufacturing method according to any one of claims 72 to 74, wherein the uncured thermosetting resin comprises one or more selected from the group consisting of epoxy resins, vinyl ester resins, unsaturated polyester resins, resol-type phenolic resins, (meth)acrylates other than epoxy vinyl esters, and diallyl phthalate.

76. The production method according to any one of claims 72 to 75, wherein the clustering liquid further contains a reactive diluent.

77. The production method according to any one of claims 72 to 76, wherein the discontinuous carbon fibers include recycled carbon fibers.

78. The manufacturing method according to claim 77, wherein the recycled carbon fiber comprises thermally degraded carbon fiber.

79. The production method according to any one of claims 72 to 78, wherein all or 99% by weight or more of the carbon fibers contained in the carbon fiber composite material sheet have a fiber length of 60 mm or less, 50 mm or less, 40 mm or less, 30 mm or less, or 20 mm or less.

80. The production method according to any one of claims 72 to 79, wherein each of the plurality of carbon fiber bundles has a bundle length of 3 mm or more, 5 mm or more, or 10 mm or more.

81. The production method according to any one of claims 72 to 80, wherein the carbon fiber composite material sheet does not contain carbon fibers having a fiber length of less than 3 mm, or even if it does, its content is less than 5 wt% of all carbon fibers in the carbon fiber composite material sheet.

82. The production method according to any one of claims 72 to 80, wherein the carbon fiber composite material sheet does not contain carbon fibers having a fiber length of less than 5 mm, or even if it does, its content is less than 5 wt% of all carbon fibers in the carbon fiber composite material sheet.

83. The production method according to any one of claims 72 to 80, wherein the carbon fiber composite material sheet does not contain carbon fibers having a fiber length of less than 10 mm, or even if it does, its content is less than 5 wt% of all carbon fibers in the carbon fiber composite material sheet.

84. The manufacturing method according to any one of claims 72 to 83, wherein the fiber weight content of the carbon fiber composite material sheet is 20wt% or more and less than 30wt%, 30wt% or more and less than 40wt%, 40wt% or more and less than 50wt%, 50wt% or more and less than 60wt%, 60wt% or more and less than 70wt%, or 70wt% or more and 80wt% or less.

85. The manufacturing method according to claim 84, wherein the fiber weight content is greater than 30 wt% and less than 70 wt%, preferably greater than 40 wt% and less than 60 wt%.

86. A carbon fiber composite material sheet produced by the production method according to any one of claims 45 to 85.

87. A method for manufacturing a CFRP product, comprising: The carbon fiber bundle composite material according to claim 44 or the carbon fiber composite material sheet according to claim 86 is cured by heating and pressurizing the carbon fiber bundle composite material according to claim 44 in a molding die.

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