JP2015147906A - Fiber-reinforced composite material, prepreg and method for producing them - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fiber-reinforced composite material having excellent interlaminar toughness.SOLUTION: The fiber-reinforced composite material according to the present invention is a fiber-reinforced composite material composed of at least thermoplastic resin particles, a curable resin and a reinforcing fiber base material, the thermoplastic resin particles being thermoplastic resin particles which have been subjected to a heat treatment. The thermoplastic resin particles are preferably a curable resin insoluble thermoplastic resin. A method for producing a fiber-reinforced composite material according to the present invention includes: a step of subjecting thermoplastic resin particles to a heat treatment; a step of integrating the thermoplastic resin particles which have been subjected to the heat treatment, a curable resin, and a fiber base material; and a step of curing the curable resin. The step of subjecting the thermoplastic resin particles to the heat treatment is preferably a step of subjecting the thermoplastic resin particles to the heat treatment in a fluid.

Description

  The present invention relates to a fiber-reinforced composite material composed of a curable resin and reinforcing fibers, a prepreg used for manufacturing fiber reinforcement, and a method for manufacturing them.

  Fiber reinforced composite materials using reinforcing fibers such as carbon fibers and aramid fibers have been used for structural materials for aircraft and automobiles, sports and general industrial applications because of their high specific strength and specific elastic modulus. In the production of these fiber-reinforced composite materials, a method using a prepreg which is a sheet-like intermediate base material in which reinforcing fibers are impregnated with a matrix resin is often used. As the matrix resin used for the fiber-reinforced composite material, a curable resin is often used from the viewpoint of process and handleability.

  The fiber reinforced composite material is a heterogeneous material composed of reinforced fibers and a matrix resin, and there is a great difference between the physical properties in the arrangement direction of the reinforced fibers and the physical properties in other directions. For example, the impact resistance of a composite material is governed by the interlaminar toughness, which is an index of the difficulty of delamination between laminated fiber layers. Therefore, simply improving the strength of the reinforcing fiber does not lead to a drastic improvement. It is known. In particular, a fiber-reinforced composite material using a curable resin as a matrix resin has a property that the matrix resin has a low toughness, and thus is easily broken by stress from other than the direction in which the reinforcing fibers are arranged. For this reason, various techniques have been proposed for the purpose of improving the physical properties of composite materials that can cope with stresses from other than the direction in which the reinforcing fibers are arranged, in addition to improving tensile strength and compressive strength in the fiber direction.

  Conventionally, as a method for improving the toughness of the curable resin composite material, a method of blending a thermoplastic resin having excellent toughness has been tried. As a method of blending a thermoplastic resin with a curable resin, there is no loss of mechanical properties of the curable resin by dissolving a thermoplastic resin such as polyethersulfone, polysulfone and polyetherimide in the curable resin. It is known to improve toughness (see, for example, Patent Document 1). However, in this method, it is necessary to blend a large amount of thermoplastic resin. By blending a large amount of thermoplastic resin, the viscosity of the curable resin composition is significantly increased, making it difficult for the curable resin composition to impregnate the reinforcing fiber base material, resulting in voids in the resulting fiber reinforced composite material. Problems that are likely to arise. For this reason, the fiber-reinforced composite material obtained by such a method has not been satisfactory in strength and impact resistance.

A composite material using a prepreg in which fine particles are dispersed on the surface of a prepreg composed of reinforcing fibers and a curable resin composition has been proposed. Specifically, fine particles such as thermoplastic resin and rubber that do not dissolve in the matrix resin such as polyamide and polyurethane are dispersed on the surface of the prepreg to form a resin layer called an interlayer resin layer in the carbon fiber reinforced composite material. It is a technology that gives high toughness and good heat resistance to composite materials. (For example, see Patent Document 2)
However, when considering the demand for further weight reduction and high toughness, which will increase further in the future, the above method is not necessarily sufficient.

Japanese Examined Patent Publication No. 6-43508 JP 2012-193322 A

  An object of the present invention is to provide a fiber-reinforced composite material having excellent interlayer toughness and excellent impact resistance.

  The inventors of the present invention have intensively studied a fiber reinforced composite material having excellent interlayer toughness, and as a result, the interlayer toughness of a fiber reinforced composite material containing heat-treated thermoplastic resin particles as a constituent element is remarkably improved. I found it.

  That is, the fiber reinforced composite material of the present invention is a fiber reinforced composite material comprising at least thermoplastic resin particles, a curable resin, and a reinforced fiber base material, wherein the thermoplastic resin particles are heat-treated. It is a fiber reinforced composite material which is a plastic resin particle. In the present invention, it is preferable that the thermoplastic resin particles are resin particles made of a curable resin-insoluble thermoplastic resin, and the thermoplastic resin has a higher elongation at break than the cured elongation of the curable resin. The resin particles are preferably made of

  The method for producing a fiber-reinforced composite material of the present invention is a method for producing a fiber-reinforced composite material comprising at least thermoplastic resin particles, a curable resin, and a reinforced fiber base material, and heat-treats the thermoplastic resin particles. And a step of integrating the heat-treated thermoplastic resin particles, the curable resin, and the reinforcing fiber substrate, and the step of curing the curable resin. . In the present invention, the step of heat-treating the thermoplastic resin particles is preferably a step of heat-treating the thermoplastic resin particles in a fluid.

The prepreg which is another embodiment of the present invention is a prepreg comprising at least thermoplastic resin particles, a curable resin, and a reinforcing fiber base material, and the thermoplastic resin particles are heat-treated thermoplastic resin. It is a prepreg that is a particle.
The method for producing a prepreg of the present invention is a method for producing a prepreg comprising at least thermoplastic resin particles, a curable resin, and a reinforcing fiber base, and a step of heat-treating the thermoplastic resin particles, and a heat treatment. And a step of integrating a thermoplastic resin particle, a curable resin, and a reinforcing fiber substrate.

Since the fiber reinforced composite material of the present invention is excellent in interlayer toughness, it becomes a fiber reinforced composite material excellent in impact resistance.
According to the method for producing a fiber-reinforced composite material of the present invention, a fiber-reinforced composite material having excellent interlayer toughness can be obtained.
When the prepreg of the present invention is used, a fiber-reinforced composite material having excellent interlayer toughness can be produced.
According to the method for producing a prepreg of the present invention, a prepreg that provides a fiber-reinforced composite material having excellent interlayer toughness can be produced.

The fiber-reinforced composite material of the present invention is a fiber-reinforced composite material comprising at least thermoplastic resin particles, a curable resin, and a reinforced fiber base material, and the thermoplastic resin particles are heat-treated thermoplastic resin. It is a fiber-reinforced composite material that is a particle.
By providing the heat-treated thermoplastic resin particles as a constituent element, the interlayer toughness of the composite material is improved, and a fiber-reinforced composite material exhibiting excellent impact resistance is obtained.

  In the present invention, the thermoplastic resin particles are preferably resin particles made of a curable resin-insoluble thermoplastic resin. Further, the resin particles are preferably made of a thermoplastic resin having a higher elongation at break than the cured elongation of the curable resin, and further, a tensile modulus lower than the tensile modulus after the curing of the curable resin. More preferably, the resin particles are made of a thermoplastic resin. The elongation at break and the tensile modulus of elasticity referred to in the present invention are the tensile elongation at break of a resin obtained by molding a thermoplastic resin or a curable resin into a dumbbell-shaped test piece and performing a tensile test according to ISO 527. And tensile modulus.

The method for producing a fiber-reinforced composite material of the present invention is a method for producing a fiber-reinforced composite material comprising at least thermoplastic resin particles, a curable resin, and a reinforced fiber base material, and heat-treats the thermoplastic resin particles. And a step of integrating the heat-treated thermoplastic resin particles, the curable resin, and the reinforcing fiber substrate, and the step of curing the curable resin. .
In the present invention, the step of heat-treating the thermoplastic resin particles is preferably a step of heat-treating the thermoplastic resin particles in a fluid.

  In the present invention, the method for integrating the heat-treated thermoplastic resin particles, the curable resin, and the reinforcing fiber base is not particularly limited. For example, the heat-treated thermoplastic resin particles are added to the curable resin. A curable resin composition, a method of impregnating the reinforced fiber base material with the curable resin composition, and after attaching the heat-treated thermoplastic resin particles to the reinforced fiber base material, the curable resin is used as the reinforced fiber base material. For example, a method of impregnating a reinforcing fiber base material with a curable resin, and a method of adhering the heat-treated thermoplastic resin particles to the reinforcing fiber base material impregnated with the curable resin. A method of impregnating a reinforcing fiber base material with a curable resin composition to which heat-treated thermoplastic resin particles are added, because the heat-treated thermoplastic resin is easily dispersed uniformly in the resin layer of the fiber-reinforced composite material. Is more preferable. As a method for impregnating the fiber reinforced substrate with the curable resin composition, conventionally known methods can be used, and examples thereof include a hand lay-up method, a resin transfer method, and a prepreg method. Among these methods, the prepreg method is preferred because it is easy to obtain a fiber-reinforced composite material having high strength.

The prepreg which is another embodiment of the present invention is a prepreg comprising at least thermoplastic resin particles, a curable resin, and a reinforcing fiber base material, and the thermoplastic resin particles are heat-treated thermoplastic resin. It is a prepreg that is a particle.
The method for producing a prepreg of the present invention is a method for producing a prepreg comprising at least thermoplastic resin particles, a curable resin, and a reinforcing fiber base, and a step of heat-treating the thermoplastic resin particles, and a heat treatment. And a step of integrating a thermoplastic resin particle, a curable resin, and a reinforcing fiber substrate.

Hereinafter, preferred embodiments of the present invention will be described.
(Reinforced fiber substrate)
The reinforcing fiber substrate used in the present invention is a substrate obtained by processing reinforcing fibers into various shapes. The reinforcing fiber substrate is preferably in the form of a sheet. As the reinforcing fiber, for example, carbon fiber, glass fiber, aramid fiber, silicon carbide fiber, polyester fiber, ceramic fiber, alumina fiber, boron fiber, metal fiber, mineral fiber, rock fiber and slug fiber can be used. Among these reinforcing fibers, carbon fibers, glass fibers, and aramid fibers are preferable. Carbon fiber is particularly preferable, and PAN-based carbon fiber having high tensile strength is most preferable because a composite material having high specific strength and high specific modulus, light weight and high strength can be obtained.

The carbon fiber preferably has a tensile modulus of 170 to 600 GPa, particularly preferably 220 to 450 GPa. The tensile strength of the carbon fiber is preferably 3920 MPa (400 kgf / mm ² ) or more. By using such a carbon fiber, the mechanical properties of the composite material can be particularly improved.
As a sheet-like reinforcing fiber base material, a sheet made by arranging a large number of reinforcing fibers in one direction, bi-directional woven fabrics such as plain weave and twill, multi-axial woven fabrics, non-woven fabrics, mats, knits, braids, and reinforcing fibers Paper. The thickness of the sheet material is preferably 0.01 to 3 mm, more preferably 0.1 to 1.5 mm.

(Thermoplastic resin particles)
The thermoplastic resin particles used in the present invention are heat-treated thermoplastic resin particles. In the present invention, the thermoplastic resin particles are heat-treated before being integrated with the reinforcing fiber base and the curable resin. Such heat treatment will be described later.
The thermoplastic resin particles used in the present invention are particles made of a thermoplastic resin, and conventionally known thermoplastic resins can be used as the thermoplastic resin constituting the particles. Thermoplastic resins are roughly classified into curable resin-soluble thermoplastic resins and curable resin-insoluble thermoplastic resins. In the present invention, it is preferable that the thermoplastic resin particles to be heat-treated are a curable resin-insoluble thermoplastic resin because the toughness of the composite material to be obtained is easily improved.

  In the present invention, the curable resin-soluble thermoplastic resin refers to a thermoplastic resin that can be partially or wholly dissolved in the curable resin at a temperature at which the composite material is molded or at a temperature lower than that. “Partially dissolved” means to exclude “a thermoplastic resin that does not substantially dissolve”, which will be described later. On the other hand, in the present invention, the curable resin-insoluble thermoplastic resin refers to a thermoplastic resin that does not substantially dissolve in the curable resin at a temperature at which the composite material is molded or at a temperature lower than that. That is, it refers to a thermoplastic resin in which the size or shape of the particles does not change when the thermoplastic resin is put into the curable resin and stirred at the temperature at which the composite material is molded. In addition, although the temperature at the time of shape | molding a composite material changes with curable resin to be used, it is 100-190 degreeC generally.

  Part of the curable resin-insoluble thermoplastic resin or curable resin-soluble thermoplastic resin (the curable resin-soluble thermoplastic resin remaining undissolved in the matrix resin after curing) is contained in the matrix resin of the composite material. (Hereinafter, the dispersed particles are also referred to as “interlayer particles”). The interlayer particles suppress the propagation of the impact received by the composite material. As a result, the impact resistance of the composite material is improved. The interlayer particles are preferably present in an amount of 5 to 60 parts by mass with respect to 100 parts by mass of the curable resin contained in the composite material.

Specific examples of the curable resin-soluble thermoplastic resin include polyethersulfone, polysulfone, polyetherimide, and polycarbonate when an epoxy resin is used as the curable resin. These may be used alone or in combination of two or more.
Examples of the curable resin insoluble thermoplastic resin include polyamide, polyacetal, polyphenylene oxide, polyphenylene sulfide, polyester, polyamideimide, polyimide, polyetherketone, polyetheretherketone, polyethylene naphthalate, polyaramid, polyethernitrile, and polybenzimidazole. Illustrated. Among these, polyamide, polyamideimide, and polyimide are preferable because of high toughness and heat resistance. Polyamide and polyimide are particularly excellent in improving the toughness of the composite material. These may be used alone or in combination of two or more. Moreover, these copolymers can also be used.

  Amorphous polyimide, nylon 6 (trademark) (polyamide obtained by ring-opening polycondensation reaction of caprolactam), polyamide 12 (polyamide obtained by ring-opening polycondensation reaction of lauryl lactam), amorphous nylon (transparent nylon) Polyamide, which is also referred to as nylon which does not cause crystallization of the polymer or has a very low crystallization rate of the polymer, has a particularly high effect of improving the heat resistance of the composite material.

  In this invention, it is preferable that the thermoplastic resin used as a thermoplastic resin particle is a resin particle which consists of a thermoplastic resin which has a higher breaking elongation than the breaking elongation after hardening of curable resin. The breaking elongation of the thermoplastic resin is more preferably 10 to 2000%, further preferably 50 to 1000%, and particularly preferably 200 to 400%. When the breaking elongation of the thermoplastic resin is within this range, the interlayer toughness of the composite material can be further improved. Moreover, it is preferable that the thermoplastic resin used by this invention is a thermoplastic resin which has a tensile elasticity modulus lower than the tensile elasticity modulus after hardening of curable resin. The tensile elastic modulus of the thermoplastic resin is more preferably 3000 MPa or less, and still more preferably 1000 to 2000 MPa.

Among these thermoplastic resins, polyamide is more preferable, and polyamide 12 is particularly preferable.
The average particle diameter of the thermoplastic resin particles is preferably 1 to 50 μm, and particularly preferably 3 to 30 μm. If the thickness is less than 1 μm, the viscosity of the curable resin composition tends to be high, and it may be difficult to add a sufficient amount of the curable resin-insoluble thermoplastic resin to the curable resin composition. is there. When exceeding 50 micrometers, when processing an epoxy resin composition into a sheet form, it may become difficult to obtain a sheet of uniform thickness.

(Curable resin)
There is no restriction | limiting in particular in curable resin used by this invention, For example, a thermosetting resin and energy-beam curable resin can be used. Among these, a thermosetting resin is preferable because a fiber-reinforced composite material having high heat resistance can be produced. As the thermosetting resin, from the viewpoint of heat resistance and mechanical properties, a thermosetting resin in which a crosslinking reaction proceeds by heat and at least partially forms a three-dimensional crosslinked structure is preferable.

  Examples of such thermosetting resins include unsaturated polyester resins, vinyl ester resins, epoxy resins, bismaleimide resins, benzoxazine resins, phenol resins, urea resins, melamine resins, and polyimide resins. Furthermore, these modified bodies and two or more kinds of blend resins can also be used. These thermosetting resins may be those that are self-cured by heating, or resins that are cured by blending a curing agent or a curing accelerator.

Among these thermosetting resins, an epoxy resin having an excellent balance of heat resistance, mechanical properties, and adhesion to carbon fibers is preferable.
The epoxy resin is not particularly limited, but bifunctional epoxy resins such as bisphenol type epoxy resin, alcohol type epoxy resin, biphenyl type epoxy resin, hydrophthalic acid type epoxy resin, dimer acid type epoxy resin, and alicyclic epoxy resin, Glycidyl ether type epoxy resins such as tetrakis (glycidyloxyphenyl) ethane, tris (glycidyloxyphenyl) methane, glycidylamine type epoxy resins such as tetraglycidyldiaminodiphenylmethane, naphthalene type epoxy resins, and phenols that are novolak type epoxy resins Examples thereof include novolac type epoxy resins and cresol novolac type epoxy resins.

Furthermore, polyfunctional epoxy resins, such as a phenol type epoxy resin, etc. are mentioned. Furthermore, various modified epoxy resins such as urethane-modified epoxy resins and rubber-modified epoxy resins can also be used.
Especially, it is preferable to use the epoxy resin which has an aromatic group in a molecule | numerator, and the epoxy resin which has either a glycidylamine structure or a glycidyl ether structure is more preferable. Moreover, an alicyclic epoxy resin can also be used suitably.

Examples of the epoxy resin having a glycidylamine structure include N, N, N ′, N′-tetraglycidyldiaminodiphenylmethane, N, N, O-triglycidyl-p-aminophenol, N, N, O-triglycidyl-m-. Examples include aminophenol, N, N, O-triglycidyl-3-methyl-4-aminophenol, and various isomers of triglycidylaminocresol.
Examples of the epoxy resin having a glycidyl ether structure include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, phenol novolac type epoxy resins, and cresol novolac type epoxy resins.
These epoxy resins may have a non-reactive substituent in the aromatic ring structure or the like as necessary. Examples of non-reactive substituents include alkyl groups such as methyl, ethyl and isopropyl, aromatic groups such as phenyl, alkoxyl groups, aralkyl groups, and halogen groups such as chlorine and bromine.

Examples of the bisphenol type epoxy resin include bisphenol A type resin, bisphenol F type resin, bisphenol AD type resin, bisphenol S type resin and the like. Specifically, jER815 (product name), jER828 (product name), jER834 (product name), jER1001 (product name), jER807 (product name) manufactured by Japan Epoxy Resin Co., Ltd., and EPOMIC R-710 (product name) manufactured by Mitsui Petrochemical Co., Ltd. ), EXA1514 (trade name) manufactured by Dainippon Ink and Chemicals, and the like.
Examples of the alicyclic epoxy resin include Araldite CY-179 (trade name), CY-178 (trade name), CY-182 (trade name), and CY-183 (trade name) manufactured by Huntsman. .

As a phenol novolac type epoxy resin, Japan Epoxy Resin's jER152 (trade name), jER154 (trade name), Dow Chemical's DEN431 (trade name), DEN485 (trade name), DEN438 (trade name), DIC Corporation As cresol novolak type epoxy resin such as Epicron N740 (trade name), Araldite ECN1235 (trade name), ECN1273 (trade name), ECN1280 (trade name), EOCN102 (trade name), EOCN103, manufactured by Nippon Kayaku Co., Ltd. (Product name), EOCN104 (Product name), etc. are exemplified.
Examples of the various modified epoxy resins include Adeka Resin EPU-6 (trade name) and EPU-4 (trade name) manufactured by Asahi Denka as urethane-modified bisphenol A epoxy resins.

  These epoxy resins can be appropriately selected and used alone or in combination of two or more. Among these, bifunctional epoxy resins represented by bisphenol type include various grades of resins from liquid to solid depending on the difference in molecular weight. Therefore, these resins are conveniently blended for the purpose of adjusting the viscosity of the prepreg matrix resin.

(Curing agent)
In the present invention, the curable resin composition may contain a curing agent for curing the curable resin, if necessary. As the curing agent, a known curing agent is used.
For example, examples of the curing agent used when an epoxy resin is used as the curable resin include dicyandiamide, various isomers of aromatic amine curing agents, and aminobenzoic acid esters. Dicyandiamide is preferable because of excellent storage stability of the prepreg. In addition, aromatic diamine compounds such as 4,4′-diaminodiphenylsulfone, 3,3′-diaminodiphenylsulfone, and 4,4′-diaminodiphenylmethane and derivatives having non-reactive substituents have good heat resistance. From the viewpoint of providing a cured product. Here, the non-reactive substituent is the same as the non-reactive substituent described in the description of the epoxy resin.

  As the aminobenzoic acid esters, trimethylene glycol di-p-aminobenzoate and neopentyl glycol di-p-aminobenzoate are preferably used. Composite materials cured using these are inferior in heat resistance to various isomers of diaminodiphenylsulfone, but are excellent in tensile elongation. Therefore, the type of curing agent to be used is appropriately selected according to the use of the composite material.

  The amount of the curing agent contained in the curable resin composition is appropriately adjusted according to the type of the curable resin and the curing agent to be used, and at least an amount suitable for curing the curable resin blended in the resin composition. That's fine. The blending amount can be appropriately used in a desired blending amount in consideration of the presence / absence and addition amount of a curing agent / curing accelerator, the chemical reaction stoichiometry with the curable resin, the curing rate of the composition, and the like. From the viewpoint of storage stability, it is preferable to add 30 to 100 parts by mass of the curing agent, and more preferably 30 to 70 parts by mass with respect to 100 parts by mass of the curable resin contained in the resin composition.

  As the curing agent, it is also possible to use a curing agent microencapsulated with a coating agent (for example, DDS coat 10 (manufactured by Matsumoto Yushi Co., Ltd.)). In order to prevent the microencapsulated curing agent from reacting with an uncured curable resin at room temperature, the surface layer of the curing agent is made less reactive with the curable resin by physical and chemical bonding. Specifically, it is coated with a coating agent such as polyamide, modified urea resin, modified melamine resin, polyolefin, polyparaffin (including modified products). These coating agents may be used alone or in combination, and curing agents microencapsulated with various coating agents other than those described above can also be used.

(Other additives)
When a curable resin having a low viscosity is used as the curable resin, a thermoplastic resin other than the heat-treated thermoplastic resin particles may be blended in order to give an appropriate viscosity to the resin composition. The thermoplastic resin blended in the resin composition for viscosity adjustment has an effect of improving the impact resistance of the finally obtained fiber-reinforced composite material.

The amount of the thermoplastic resin to be blended in the resin composition varies depending on the type of curable resin used in the resin composition, and may be appropriately adjusted so that the viscosity of the resin composition becomes an appropriate value described later. Usually, it is preferable to mix | blend a thermoplastic resin so that it may become 5-100 mass parts with respect to 100 mass parts of curable resin contained in a resin composition. The resin composition preferably has a minimum viscosity of 10 to 450 poise at 80 ° C., more preferably a minimum viscosity of 50 to 400 poise.
In addition to the above components, the curable resin used in the present invention may be a base such as an acid anhydride, Lewis acid, dicyandiamide (DICY), or imidazoles, as appropriate, as long as the purpose and effect of the present invention are not impaired. Various additives such as a functional curing agent, a urea compound, and an organic metal salt can be included.

  Specifically, examples of the acid anhydride include phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, and the like. Examples of the Lewis acid include boron trifluoride salts, and more specifically, BF3 monoethylamine, BF3 benzylamine, and the like. Examples of imidazoles include 2-ethyl-4-methylimidazole, 2-ethylimidazole, 2,4-dimethylimidazole, and 2-phenylimidazole. Moreover, 3- [3,4-dichlorophenyl] -1,1-dimethylurea (DCMU) that is a urea compound, Co [III] acetylacetonate that is an organometallic salt, and the like can be exemplified. Examples of the reactive diluent include reactive diluents such as polypropylene diglycol / diglycidyl ether and phenyl glycidyl ether.

(Heat treatment process)
In the present invention, heat treatment is performed on the thermoplastic resin particles. By using the thermoplastic resin particles subjected to such heat treatment, a fiber-reinforced composite material having excellent interlayer toughness can be obtained. Such heat treatment is preferably performed in a fluid such as a liquid or a gas, and more preferably performed in a gas. By performing the heat treatment in the fluid, the entire surface of the thermoplastic resin particles can be uniformly heat-treated.

  When heat treatment is performed in a gas, the gas to be used is not particularly limited. For example, an oxidizing gas such as air, oxygen, ozone, or nitrogen dioxide, a reducing gas such as carbon monoxide or nitrogen monoxide, nitrogen, helium, An inert gas such as argon can be used. The heat treatment temperature can be appropriately adjusted according to the thermoplastic resin particles to be used, and is preferably a temperature equal to or higher than the melting point of the thermoplastic resin particles to be used, more preferably 100 to 800 ° C., still more preferably 250 to 600. ° C.

As a heat treatment method, it is preferable that the thermoplastic resin particles are dispersed and sprayed in a fluid heated to a treatment temperature. By dispersing and spraying the thermoplastic resin particles in the fluid, the entire resin particles can be uniformly heat-treated. If dispersing spraying resin in a fluid, the fluid flow rate (if a gas flow rate) is preferably 0.1 to 10 m ³ / min, more to be 0.5 to 5 m ³ / min preferable. Moreover, it is preferable that the supply amount of resin sprayed by dispersion is 1 to 100 g / min with respect to 1 m ³ of the heating fluid.

(Integration process)
In the present invention, the method for integrating the heat-treated thermoplastic resin particles, the curable resin, and the reinforcing fiber base is not particularly limited. For example, the heat-treated thermoplastic resin particles are added to the curable resin. A curable resin composition, a method of impregnating the reinforced fiber base material with the curable resin composition, and after attaching the heat-treated thermoplastic resin particles to the reinforced fiber base material, the curable resin is used as the reinforced fiber base material. For example, a method of impregnating a reinforcing fiber base material with a curable resin, and a method of adhering the heat-treated thermoplastic resin particles to the reinforcing fiber base material impregnated with the curable resin.

Among them, there is a method of impregnating a reinforced fiber base material with a curable resin composition to which heat-treated thermoplastic resin particles that are easily dispersed uniformly in a resin layer of a fiber-reinforced composite material that can obtain a heat-treated thermoplastic resin is added. preferable.
The method for producing the curable resin composition by adding the heat-treated thermoplastic resin particles to the curable resin is not particularly limited, and any conventionally known method may be used. For example, a curable resin composition is prepared by mixing thermoplastic resin particles, a curable resin, and optionally a curing agent and other additives, and dispersing the thermoplastic resin particles in the curable resin, preferably uniformly. Can be manufactured.

  The kneading method of the curable resin composition is not particularly limited, and any conventionally known method may be used. For example, when an epoxy resin is used as the curable resin, examples of the kneading temperature include a range of 10 to 160 ° C. If it is the range of 10-160 degreeC, the thermal deterioration of a resin and a partial hardening reaction can be suppressed, and a resin composition can be knead | mixed suitably. Preferably it is 20-130 degreeC, More preferably, it is the range of 30-110 degreeC.

  A conventionally well-known thing can be used as a kneading machine apparatus. Specific examples include a roll mill, a planetary mixer, a kneader, an extruder, a Banbury mixer, a mixing vessel provided with a stirring blade, a horizontal mixing vessel, and the like. Each component can be kneaded in the air or in an inert gas atmosphere. When kneading is performed in the air, an atmosphere in which temperature and humidity are controlled is preferable. Although not particularly limited, for example, it is preferable to knead in a temperature controlled at a constant temperature of 30 ° C. or lower or in a low humidity atmosphere with a relative humidity of 50% RH or lower.

(Resin impregnation process)
As a method for impregnating the fiber reinforced substrate with the curable resin composition, conventionally known methods can be used, and examples thereof include a hand lay-up method, a resin transfer method, and a prepreg method. Among these methods, the prepreg method is preferred because it is easy to obtain a fiber-reinforced composite material having high strength.
When the resin is impregnated by the prepreg method, the resin impregnation method is not particularly limited, and any conventionally known method can be employed. Specifically, a hot melt method or a solvent method can be suitably employed.
In the hot melt method, the resin composition is coated on a release paper in a thin film to form a resin composition film, and then the formed film is peeled from the release paper to obtain a resin composition film. In this method, a resin composition film is laminated on a reinforcing fiber substrate and heated under pressure to impregnate the reinforcing fiber substrate with the resin composition.

  The method for forming the resin composition into a resin composition film is not particularly limited, and any conventionally known method can be used. Specifically, it can be obtained by casting and casting a resin composition on a support such as a release paper or a film using a die extrusion, an applicator, a reverse roll coater, a comma coater or the like. The resin temperature for producing the film is appropriately determined according to the composition and viscosity of the resin for producing the film. Specifically, the same temperature conditions as the kneading temperature in the above-described method for producing a curable resin composition are preferably used. The impregnation can be performed in multiple stages at an arbitrary pressure and temperature in a plurality of times instead of once.

The solvent method is a method in which a curable resin composition is made into a varnish using an appropriate solvent, and this reinforcing varnish is impregnated with the varnish. Among these conventional methods, the prepreg of the present invention can be preferably produced by a hot melt method which is a conventionally known production method.
The impregnation pressure for impregnating the reinforcing fiber base material with the resin composition using the resin composition film is appropriately determined in consideration of the viscosity, resin flow, and the like of the resin composition.
The impregnation temperature when an epoxy resin is used as the curable resin and the reinforcing fiber base material is impregnated with the epoxy resin composition film by a hot melt method is preferably in the range of 50 to 150 ° C. If it is the range of 50-150 degreeC, it will be easy to impregnate resin to a reinforcement fiber base material uniformly, suppressing the curing reaction of curable resin. The impregnation temperature is more preferably 60 to 145 ° C, and particularly preferably 70 to 140 ° C.
By the method as described above, the prepreg of the present invention that gives the fiber-reinforced composite material of the present invention having excellent interlayer toughness can be produced.

  The form of the prepreg of the present invention is not particularly limited as long as the reinforcing fiber base is impregnated with the resin composition. However, a prepreg comprising a reinforcing fiber layer comprising a reinforcing fiber, a curable resin composition impregnated between the reinforcing fibers, and a resin coating layer coated on the surface of the reinforcing fiber layer is preferred. The thickness of the resin coating layer is preferably 2 to 50 μm. When the thickness of the resin coating layer is less than 2 μm, the tackiness becomes insufficient, and the molding processability of the prepreg may be significantly lowered. When the thickness of the resin coating layer exceeds 50 μm, it is difficult to wind the prepreg into a roll with a uniform thickness, and the molding accuracy may be significantly reduced. The thickness of the resin coating layer is more preferably 5 to 45 μm, and particularly preferably 10 to 40 μm.

The content (RC) of the resin composition is preferably 15 to 60% by mass based on the total mass of the prepreg. When the content is less than 15% by mass, voids or the like are generated in the obtained composite material, and the mechanical properties may be deteriorated. When the content exceeds 60% by mass, the reinforcing effect by the reinforcing fibers becomes insufficient, and the mechanical properties relative to mass may be substantially low. Preferably, the content is 20 to 50% by mass, more preferably 25 to 50% by mass.
The prepreg of the present invention is laminated according to the purpose, molded and cured to produce a fiber reinforced composite material. This manufacturing method itself is known. The fiber-reinforced composite material produced by the prepreg of the present invention is a fiber-reinforced composite material having excellent interlayer toughness and excellent impact resistance.

(Resin curing process)
In the present invention, the heat-treated thermoplastic resin particles, the curable resin, and the reinforcing fiber base material are integrated, and subsequently the curable resin is cured to produce the fiber-reinforced composite material of the present invention. can do. When integration is performed by the prepreg method, the prepreg molding and curing method is a conventionally known method such as manual layup, automatic tape layup (ATL), automatic fiber placement, vacuum bagging, autoclave curing, and other than autoclave. , Fluid assisted processing, pressure assisted processes, match mold processes, simple press curing, press clave curing, or methods using continuous band presses.

For example, when a fiber-reinforced composite material is molded by an autoclave curing method using a prepreg having a thermosetting resin as a matrix resin, the prepreg is laminated and pressurized to 0.2 to 1.0 MPa in the autoclave, By heating at 204 ° C. for 1 to 8 hours, a molded fiber-reinforced composite material can be produced.
By the method as described above, the fiber-reinforced composite material of the present invention having excellent interlayer toughness can be produced. The fiber-reinforced composite material of the present invention thus obtained is a fiber-reinforced composite material having excellent interlayer toughness and excellent impact resistance.

  EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely, this invention is not limited to an Example. The components and test methods used in the examples and comparative examples are described below.

〔component〕
[Reinforced fiber substrate]
-The tensile strength and elastic modulus of the carbon fiber strand (Tenax IMS60 (brand name)) by Toho Tenax used were as follows.
・ Tensile strength: 5800 MPa (590 kgf / mm ² )
-Elastic modulus 290 GPa (30 tf / mm ² )

[Curable resin composition]
(Epoxy resin)
Glycidylamine type epoxy resin (4 functional groups) [jER604 manufactured by Mitsubishi Chemical Corporation] (tensile modulus after curing: 3500 MPa, elongation at break after curing: 5%)
(Epoxy resin curing agent)
・ 3,3′-Diaminodiphenylsulfone [3,3′-DAS manufactured by Konishi Chemical Industries, Ltd.]

[Thermoplastic resin particles]
Polyamide 12 (pulverized product) having an average particle size of 20 μm [VESTOSINT 2158 (trade name) manufactured by Daicel-Evonik Co., Ltd. (tensile elastic modulus: 1400 MPa, elongation at break: 300%, melting point: 184 ° C., density: 1.016 g / cm ³ )] (Thermoplastic resin particles insoluble in epoxy resin)

[Other additives]
Polyethersulfone having an average particle size of 20 μm [PES-5003P (trade name) manufactured by Sumitomo Chemical Co., Ltd.] (a thermoplastic resin soluble in an epoxy resin)

〔Measuring method〕
(1) Average particle diameter The average particle diameter was measured by using a laser diffraction / scattering particle size analyzer (Microtrack method) MT3300 manufactured by Nikkiso Co., Ltd., and its 50% particle diameter (D50). Was defined as the average particle size.

(2) Interlaminar toughness (GIc)
The obtained prepreg was cut to a predetermined size and then laminated to produce two laminates in which 10 layers were laminated in the 0 ° direction. In order to generate an initial crack, a release film was sandwiched between two laminates, and both were combined to obtain a prepreg laminate having a laminate configuration [0] ₂₀ . Using a normal vacuum autoclave molding method, molding was performed for 2 hours at 180 ° C. under a pressure of 0.59 MPa. The obtained molded product (composite material) was cut into a size of 12.7 mm width × 304.8 mm length to obtain a test piece of interlaminar fracture toughness mode I (GIc). As a test method, a twin cantilever beam interlaminar fracture toughness test method (DCB method) was used, and the GIc was calculated by measuring the crack propagation length, load, and crack opening displacement.

(3) Interlaminar fracture toughness mode II (GIIc)
The obtained prepreg was cut to a predetermined size and then laminated to produce two laminates in which 10 layers were laminated in the 0 ° direction. In order to generate an initial crack, a release film was sandwiched between two laminates, and both were combined to obtain a prepreg laminate having a laminate configuration [0] ₂₀ . Using a normal vacuum autoclave molding method, molding was performed for 2 hours at 180 ° C. under a pressure of 0.59 MPa. The obtained molded product (composite material) was cut into a size of 12.7 mm width × 304.8 mm length to obtain a test piece of interlaminar fracture toughness mode II (GIIc). A GIIc test was performed using this test piece.
As a GIIc test method, an ENF (end notched flexure test) test that applies a three-point bending load was performed. Place the test piece at a position where the tip of the crack made of PTFE film with a fulcrum distance of 101.6 mm and a thickness of 25 μm is 38.1 mm from the fulcrum, and give a bending load at a speed of 2.54 mm / min. Initial cracks were formed. Thereafter, the test piece was placed so that the tip of the crack caused by the initial crack was located at a position 25.4 mm from the fulcrum, and the test was performed by applying a bending load at a speed of 2.54 mm / min. Similarly, the test piece is arranged so that the tip of the crack is at a position 25.4 mm from the fulcrum, a bending load is applied at a speed of 2.54 mm / min, and the bending test is performed three times. GIIc was calculated from the load-stroke of the bending test.

Example 1
In the air (hot air flow rate: 1.2 m ³ / min) in which polyamide 12 particles (thermoplastic resin particles) were heated to 550 ° C. using a surface reformer, Meteorenbo MR-10, manufactured by Nippon Pneumatic Industry Co., Ltd. Spraying was performed at a supply rate of 1.0 kg / hr, and heat treatment was performed to obtain heat-treated thermoplastic resin particles.
In a kneading apparatus, PES-5003P (30 parts by mass), which is a curable resin-soluble thermoplastic resin, is added to jER604 (100 parts by mass), which is an epoxy resin, and stirred with a stirrer at 120 ° C. for 60 minutes. After completely dissolving 5003P in epoxy resin, the resin temperature was cooled to 80 ° C or lower. Thereafter, the heat-treated polyamide 12 particles (30 parts by mass) were added and kneaded with the epoxy resin, and the curing agent (40 parts by mass) was further kneaded to prepare a curable resin composition.
The prepared curable resin composition was applied onto release paper using a film coater to prepare ^two 51 g / m ² resin films. Next, the two produced resin films were stacked on both sides of a carbon fiber sheet in which carbon fiber bundles were arranged in one direction. By heating and pressurizing, a carbon fiber sheet was impregnated with the resin, and a unidirectional prepreg having a basis weight of carbon fiber of 190 g / m ² and a mass fraction of matrix resin of 35.0% was produced.
A composite material was produced using the produced unidirectional prepreg, and its toughness was evaluated. The obtained composite material showed excellent toughness such as GIc: 4.0 in-lb / in ² and GIIc: 13 in-lb / in ² .

(Comparative Example 1)
A unidirectional prepreg was prepared in the same manner as in Example 1 except that the thermoplastic resin particles were not heat-treated. A composite material was produced using the produced unidirectional prepreg, and its toughness was evaluated. The obtained composite material was GIc: 3.5 in-lb / in ² and GIIc: 10 in-lb / in ² and was a composite material inferior in toughness as compared with Example 1.

Claims (7)

At least a fiber-reinforced composite material comprising thermoplastic resin particles, a curable resin, and a reinforcing fiber base,
The fiber-reinforced composite material, wherein the thermoplastic resin particles are heat-treated thermoplastic resin particles.   The fiber-reinforced composite material according to claim 1, wherein the thermoplastic resin particles are a curable resin-insoluble thermoplastic resin.   The fiber-reinforced composite material according to claim 1 or 2, wherein the thermoplastic resin particles are resin particles made of a thermoplastic resin having a higher breaking elongation than the breaking elongation after curing of the curable resin. A method for producing a fiber-reinforced composite material comprising at least thermoplastic resin particles, a curable resin, and a reinforcing fiber substrate,
A step of heat-treating the thermoplastic resin particles;
A step of integrating the heat-treated thermoplastic resin particles, the curable resin, and the reinforcing fiber base;
Curing the curable resin;
The manufacturing method of the fiber reinforced composite material characterized by including this.   The method for producing a fiber-reinforced composite material according to claim 4, wherein the step of heat-treating the thermoplastic resin particles is a step of heat-treating the thermoplastic resin particles in a fluid. A prepreg comprising at least thermoplastic resin particles, a curable resin, and a reinforcing fiber base,
The prepreg characterized in that the thermoplastic resin particles are heat-treated thermoplastic resin particles. A method for producing a prepreg comprising at least thermoplastic resin particles, a curable resin, and a reinforcing fiber substrate,
A step of heat-treating the thermoplastic resin particles;
A step of integrating the heat-treated thermoplastic resin particles, the curable resin, and the reinforcing fiber base;
The manufacturing method of the prepreg characterized by including.