JP7143473B2 - Prepreg, its manufacturing method, and fiber-reinforced composite material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a prepreg, its manufacturing method, and a fiber-reinforced composite material. More specifically, the present invention relates to a prepreg capable of producing a fiber-reinforced composite material having excellent fracture toughness and a method for producing the same.

Fiber-reinforced composite materials, which consist of reinforcing fibers and resins, have features such as light weight, high strength, and high elastic modulus, and are widely used in aircraft, sports/leisure, and general industries. This fiber-reinforced composite material is often manufactured via a prepreg in which reinforcing fibers and a resin called matrix resin are integrated in advance.

A fiber-reinforced composite material manufactured by molding a prepreg composed of reinforcing fibers and a matrix resin is a heterogeneous material. Generally, in a fiber-reinforced composite material, there is a large difference between the physical properties in the direction in which the reinforcing fibers are arranged and the physical properties in the other directions.

For example, impact resistance, which is a measure of resistance to falling weight impact, is governed by delamination strength quantified by plate edge delamination strength between layers. Therefore, it is known that simply improving the strength of reinforcing fibers does not lead to drastic improvements in physical properties of fiber-reinforced composite materials. In particular, thermosetting resins have low toughness. Therefore, a fiber-reinforced composite material using a thermosetting resin as a matrix resin is likely to break due to stress applied from a direction other than the direction in which the reinforcing fibers are arranged, reflecting the low toughness of the matrix resin. In order to solve this problem, various techniques have been proposed that make it possible to cope with stress applied from a direction other than the direction in which the reinforcing fibers are arranged.

As one of them, a prepreg is proposed in which a resin layer in which resin particles are dispersed is provided on the surface region of the prepreg. Specifically, by using a prepreg in which a resin layer in which thermoplastic resin particles such as nylon are dispersed is used in the surface area, a resin layer with excellent toughness is formed, and the impact resistance of the fiber reinforced composite material is improved. An improvement has been proposed (see Patent Document 1).

In addition, Patent Document 2 discloses a technique for exhibiting a high degree of toughness in a composite material produced by combining a resin composition whose toughness is improved by adding a polysulfone oligomer and thermosetting resin particles. Proposed.

However, when these techniques are used, the resin particles are strongly pressed during impregnation, and as a result, the resin particles may be deformed or the inter-fiber distance of the fiber layer may be reduced. As a result, the uniformity of the fiber layer is reduced, and the mechanical properties of the fiber-reinforced composite material are insufficient.
In addition, the presence of resin particles in the surface region of the prepreg tends to reduce the tackiness of the prepreg.

Thus, there is no prepreg that has excellent tackiness and from which a fiber-reinforced composite material having excellent mechanical properties can be produced.

JP-A-7-41575 JP-A-3-26750

An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a prepreg having excellent tackiness and capable of producing a fiber-reinforced composite material having excellent mechanical properties, and a method for producing the same. to do.

As a result of studies to solve the above problems, the present inventors have found that, in producing a prepreg containing particulate matter, a resin composition containing particulate matter is passed through a layer of a resin composition that does not contain particulate matter. The present inventors have found that a prepreg manufactured by impregnating a reinforcing fiber base material with a reinforced fiber base material and integrating them can solve the above problems, and have completed the present invention.

The present invention for achieving the above objects is described below.

[1] a resin-impregnated fiber layer (I) comprising a reinforcing fiber base material and a thermosetting resin composition impregnated in the reinforcing fiber base material;
a particle-containing resin layer (II) made of a particle-containing resin composition containing particulate matter and formed on one or both sides of the resin-impregnated fiber layer (I);
a resin coating layer (III) made of a thermosetting resin composition and formed on the surface of the particle-containing resin layer (II);
A prepreg consisting of
The average fiber diameter (r) and the average inter-fiber distance (d) of the reinforcing fibers in the resin-impregnated fiber layer (I) are expressed by the following formula (1)
0.04≦d/r≦0.25 Expression (1)
A prepreg characterized by satisfying

The invention described in [1] above is a prepreg having a laminated structure of at least three layers, namely, the resin-impregnated fiber layer (I), the particle-containing resin layer (II), and the resin coating layer (III). The average fiber diameter (r) and the average inter-fiber distance (d) of the reinforcing fibers in the resin-impregnated fiber layer (I) of this prepreg satisfy the relationship of formula (1). That is, the inter-fiber distance of the reinforcing fibers forming the reinforcing fiber substrate is within a predetermined range. This prepreg is manufactured through an impregnation operation, and is a prepreg in which the inter-fiber distance of the reinforcing fiber base material is ensured within a predetermined range by the impregnation operation.

[2] The prepreg according to [1], wherein the average particle size of the particulate matter measured by a laser diffraction method is 2 to 1400 times the average interfiber distance (d).

The invention described in [2] above is a prepreg in which the average particle diameter of the particulate matter is 2 to 1400 times the average inter-fiber distance (d). The fiber-reinforced composite material produced by laminating this prepreg has particularly excellent impact resistance because particulate matter of a predetermined size is present between the reinforcing fiber layers (hereinafter referred to as "existing between the reinforcing fiber layers Particulate matter is also referred to as "interlayer particles").

[3] The prepreg according to [1], wherein the content of the particulate matter is 5 to 60% by mass with respect to the mass of the total resin composition contained in the prepreg.

The invention described in [3] above is a prepreg in which the content of particulate matter in the prepreg is 5 to 60% by mass with respect to the mass of the total resin composition contained in the prepreg. A fiber-reinforced composite material produced by laminating this prepreg has a predetermined amount of interlayer particles between the reinforcing fiber layers, and therefore has particularly excellent impact resistance.

[4] The prepreg according to [1], wherein the coefficient of variation of the inter-fiber distance is 15% or less.

The invention described in [4] above is a prepreg having a small coefficient of variation of the inter-fiber distance. The prepreg of the present invention is manufactured by impregnating a reinforcing fiber base material with a resin in the manufacturing process. The invention described in [4] above is a prepreg in which the impregnation does not substantially cause deformation such that a portion of the fiber-reinforced base material is crushed.

[5] The thermosetting resin composition constituting the resin coating layer (III) contains a thermosetting resin and 10 to 50 parts by mass of a thermoplastic resin per 100 parts by mass of the thermosetting resin. The prepreg according to [1], which is a curable resin composition.

The invention described in [5] above has excellent tackiness because the resin coating layer (III) is modified with a predetermined amount of thermoplastic resin. Moreover, since it contains a predetermined amount of thermoplastic resin and has a high viscosity, sinking into the particle-containing resin layer (II) is suppressed, and the tackiness of the prepreg is maintained.

[6] The prepreg according to [1], wherein the thermosetting resin composition constituting the resin coating layer (III) has a viscosity of 1 to 1000 Pa·s at 100°C.

In the invention described in [6] above, since the resin coating layer (III) has a predetermined viscosity, the resin coating layer (III) is suppressed from sinking into the particle-containing resin layer (II), and the prepreg tackiness is retained.

[7] The prepreg according to [1], wherein the reinforcing fiber base material is a reinforcing fiber base material made of carbon fibers.

[8] stacking a resin film (A) made of a particle-containing resin composition containing a thermosetting resin and particulate matter on one or both sides of a reinforcing fiber base material;
Next, a resin film (B) made of a thermosetting resin composition is stacked on the surface of the resin film (A),
A method for producing a prepreg, wherein the resin film (A) is pressed through the resin film (B) at an impregnation pressure of 1 to 50 kN/cm.

The invention described in [8] above is the method for producing a prepreg described in [1]. In this prepreg manufacturing method, a resin film (A) made of a resin composition containing particulate matter is impregnated with a resin film (B) made of a resin composition containing no particulate matter at an impregnation pressure of 1 to 50 kN / cm. Pressurize with a low pressure. As a result, of the particle-containing resin composition constituting the resin film (A), the resin composition excluding the particulate matter is impregnated into the reinforcing fiber base material, and the particulate matter is applied to the surface of the reinforcing fiber base material. biased. In this prepreg manufacturing method, a pressure member such as a pressure roller does not come into direct contact with the particulate matter during impregnation, and the resin film (B) is used to pressurize the particulate matter at a low pressure. It is possible to suppress the inter-fiber distance of the reinforcing fiber base material from becoming smaller.

[9] A method for producing a prepreg according to [8],
A method for producing a prepreg, wherein the particle-containing resin composition constituting the resin film (A) has a viscosity of 10 to 1000 Pa·s at 100°C.

Since the invention described in [9] above has a predetermined viscosity, the resin coating layer (III) is suppressed from sinking into the particle-containing resin layer (II), and the tackiness of the prepreg is maintained.

[10] A fiber-reinforced composite material comprising a reinforcing fiber base material and a thermosetting resin, wherein particulate matter is present between the layers of the reinforcing fiber base material,
A fiber-reinforced composite material, wherein the coefficient of variation of the distance between fibers in an arbitrary cross section of the reinforcing fiber base material is 15% or less.

The invention described in [10] above is a fiber-reinforced composite material produced using the prepreg of the present invention. Since this fiber-reinforced composite material has a coefficient of variation of the inter-fiber distance of 15% or less, the stress applied to each single fiber of the reinforcing fibers can be dispersed substantially uniformly.

In the prepreg of the present invention, the particle-containing resin layer (II) is formed on the surface of the resin-impregnated fiber layer (I). Therefore, in the fiber-reinforced composite material produced by laminating this prepreg, the particulate matter is dispersed as interlayer particles between the layers of the reinforcing fiber base material. The interlayer particles suppress the propagation of impacts received by the fiber-reinforced composite material. As a result, the impact resistance of the fiber-reinforced composite material is improved.

Since the prepreg of the present invention has the resin coating layer (III) containing no particulate matter, it has excellent tackiness.

In the prepreg of the present invention, the particulate matter-containing resin film (A) is pressure-impregnated through the resin film (B), so direct contact between the particulate matter and the pressing member is unlikely. Therefore, deformation of the particulate matter is suppressed. As a result, the fiber-reinforced composite material produced by laminating this prepreg exhibits high functionality of the interlayer particles.

In the prepreg of the present invention, the particulate matter-containing resin film (A) is pressure-impregnated through the resin film (B), so direct contact between the particulate matter and the pressing member is unlikely. Therefore, deformation of the reinforcing fiber base material due to the particulate matter being pushed into the reinforcing fiber base material is suppressed. That is, the inter-fiber distance of the reinforcing fiber base material is sufficiently secured. As a result, a fiber-reinforced composite material produced using this prepreg can uniformly disperse the stress applied to each single fiber of the reinforcing fibers, and therefore can exhibit high impact resistance.

FIG. 1 is a schematic cross-sectional view showing an example of the prepreg of the present invention. FIG. 2 is a conceptual diagram showing an example of the manufacturing process of the prepreg of the present invention.

The details of the prepreg, the method for producing the same, and the fiber-reinforced composite material of the present invention will be described below.

1. Prepreg The prepreg of the present invention is a resin-impregnated fiber layer (I) comprising a reinforcing fiber base material and a thermosetting resin composition impregnated in the reinforcing fiber base material;
a particle-containing resin layer (II) made of a particle-containing resin composition containing particulate matter and formed on one or both sides of the resin-impregnated fiber layer (I);
A resin coating layer (III) made of a resin composition containing a thermosetting resin and formed on the surface of the particle-containing resin layer (II).

FIG. 1 is a schematic cross-sectional view showing an example of this prepreg. In FIG. 1, 100 is the prepreg of the present invention, and 10 is the resin-impregnated fiber layer (I). The resin-impregnated fiber layer (I) 10 is composed of a reinforcing fiber base material 11 and a thermosetting resin composition 13 impregnated in the reinforcing fiber base material. A particle-containing resin layer (II) 20 is formed on one side or both sides (one side in FIG. 1) of the resin-impregnated fiber layer (I) 10 . Particle-containing resin layer (II) 20 is composed of a particle-containing resin composition containing particulate matter 21 and thermosetting resin composition 23 . A resin coating layer (III) 30 is formed on the surface of the particle-containing resin layer (II) 20 . The resin coating layer (III) 30 is formed from a resin composition 31 containing a thermosetting resin.
The resin-impregnated fiber layer (I) 10, the particle-containing resin layer (II) 20, and the resin coating layer (III) 30 are laminated in this order and integrated.

The prepreg of the present invention is a prepreg in which the entire reinforcing fiber base material is impregnated with a resin. The water absorption rate of the prepreg is preferably 5% or less, more preferably 4% or less, and particularly preferably 3% or less. The lower limit of water absorption is generally preferably 0.5% or more, more preferably 1% or more. In the present invention, the water absorption is an index showing the porosity in the prepreg, and the higher the water absorption, the higher the porosity in the prepreg. When the water absorption rate is high, the prepreg has many voids, which deteriorates the handleability during molding. In addition, voids tend to remain in the manufactured fiber-reinforced composite material, which may adversely affect its mechanical properties. When the water absorption is low, the prepreg has few voids, resulting in poor drapeability. Therefore, good moldability (shape followability) may not be obtained. A method for measuring water absorption will be described later.

The resin content in the entire prepreg is preferably 15 to 60% by mass based on the total mass of the prepreg. If the resin content is less than 15% by mass, voids and the like may occur in the resulting fiber-reinforced composite material, degrading mechanical properties. If the resin content exceeds 60% by mass, the reinforcing effect of the reinforcing fibers may be insufficient, resulting in substantially low mechanical properties relative to mass. The resin content is preferably 20 to 55% by mass, more preferably 25 to 50% by mass.

The content of particulate matter in the entire prepreg is preferably 5 to 60% by mass, more preferably 10 to 40% by mass, based on the mass of the total resin composition contained in the prepreg. If it is less than 5% by mass, the interlaminar particles are insufficient, and the impact resistance of the fiber-reinforced composite material produced by laminating this prepreg tends to be insufficient. If it exceeds 60% by mass, voids are likely to be formed in the fiber-reinforced composite material produced by laminating this prepreg. Also, the content of the particulate matter is preferably 1 to 10% by mass, more preferably 2 to 5% by mass, based on the total mass of the prepreg.

(1) Resin-impregnated fiber layer (I)
The resin-impregnated fiber layer (I) comprises a reinforcing fiber base material and a thermosetting resin composition impregnated in the reinforcing fiber base material. The thickness of the resin-impregnated layer and the average distance between fibers are measured by curing the prepreg by the method described later.

The thickness of the resin-impregnated fiber layer (I) is preferably 100-180 μm, more preferably 120-160 μm. If it is less than 100 μm, the thickness of the fiber layer after molding becomes thin and the tensile strength decreases. If it exceeds 180 μm, the thickness of the resin particle layer after molding becomes thin and the impact resistance decreases.

The resin content in the resin-impregnated fiber layer (I) is preferably 5-30% by mass, more preferably 10-20% by mass. If the content is less than 5% by mass, portions not impregnated with the resin are likely to be formed. If it exceeds 30% by mass, the flexibility (drapability) of the prepreg tends to deteriorate.

The average fiber diameter (r) and the average inter-fiber distance (d) of the reinforcing fibers in the resin-impregnated fiber layer (I) are expressed by the following formula (1)
0.04≦d/r≦0.25 Expression (1)
meet. Here, the lower limit is preferably 0.08, more preferably 0.13. The upper limit is preferably 0.24, more preferably 0.20.
If it is 0.04 to 0.25, the ratio of single fibers in contact with each other is low, and the matrix resin sufficiently permeates between the single fibers. Therefore, the bonding surface between the single fiber surface of the reinforcing fiber and the matrix resin increases. As a result, when stress is applied to a fiber-reinforced composite material produced using this prepreg, the stress transmitted from the matrix resin can be uniformly dispersed among the single fibers. Therefore, the mechanical properties of the fiber-reinforced composite material can be enhanced. If it is less than 0.04, the fiber-reinforced composite material produced using this prepreg will have insufficient mechanical properties because the content of the reinforcing fibers is too small. If it exceeds 0.25, the contact between the single fibers is large, and the fiber-reinforced composite material produced using this prepreg cannot uniformly disperse the stress applied to each single fiber of the reinforcing fibers.
In the present invention, the inter-fiber distance means the distance between the closest fibers in a single reinforcing fiber base layer, and does not mean the distance between adjacent reinforcing fiber layers.

The average fiber-to-fiber distance (d) of the reinforcing fibers in the resin-impregnated fiber layer (I) is preferably 0.4 to 1.2 μm, more preferably 0.65 to 1.0 μm.

The average fiber diameter (r) of the reinforcing fibers in the resin-impregnated fiber layer (I) is preferably 4-20 μm, more preferably 5-10 μm.

The coefficient of variation of the distance between reinforcing fibers in the resin-impregnated fiber layer (I) is preferably 15% or less, more preferably 14% or less, and particularly preferably 13% or less. If it exceeds 15%, the inter-fiber distance varies greatly, and the fiber-reinforced composite material produced using this prepreg cannot uniformly disperse the stress applied to each single fiber of the reinforcing fibers. Although the lower limit of the coefficient of variation is preferably as small as possible, it is generally 0.1% or more.
In order to reduce the coefficient of variation of the inter-fiber distance of the reinforcing fibers, a reinforcing fiber base material having a small variation coefficient of the inter-fiber distance is used, and the inter-fiber distance is not varied as much as possible (particularly, local variation is It is required to impregnate the resin in such a way that it does not occur.

(1-1) Reinforcing fiber substrate The reinforcing fiber substrate used in the present invention is not particularly limited, and examples thereof include carbon fiber, glass fiber, aramid fiber, silicon carbide fiber, polyester fiber, ceramic fiber, alumina fiber, and boron. Fibers, metal fibers, mineral fibers, rock fibers, slag fibers and the like.

Among these reinforcing fibers, carbon fibers, glass fibers, and aramid fibers are preferred. Carbon fiber is more preferable because it has good specific strength and specific modulus, and provides a lightweight and high-strength fiber-reinforced composite material. Polyacrylonitrile (PAN)-based carbon fibers are particularly preferred because of their excellent tensile strength.

When PAN-based carbon fiber is used as the reinforcing fiber, its tensile modulus is preferably 100 to 600 GPa, more preferably 200 to 500 GPa, and particularly preferably 230 to 450 GPa. Also, the tensile strength is preferably 2000 to 10000 MPa, more preferably 3000 to 8000 MPa. The diameter of the carbon fiber is preferably 4-20 μm, more preferably 5-10 μm. By using such carbon fibers, the mechanical properties of the resulting fiber-reinforced composite material can be improved.

It is preferable to form the reinforcing fiber into a sheet for use. Examples of reinforcing fiber sheets include sheets in which a large number of reinforcing fibers are aligned in one direction, bidirectional woven fabrics such as plain weaves and twill weaves, multiaxial woven fabrics, nonwoven fabrics, mats, knits, braids, and paper made from reinforced fibers. can be mentioned. Among these, it is preferable to use a unidirectional aligning sheet, a bidirectional woven fabric, or a multiaxial woven fabric base material in which reinforcing fibers are formed into a sheet form as continuous fibers, since a fiber-reinforced composite material with more excellent mechanical properties can be obtained. The thickness of the sheet-like reinforcing fiber base material is preferably 0.01 to 3 mm, more preferably 0.1 to 1.5 mm. Further, the basis weight of the sheet-like reinforcing fiber base material is preferably 5 to 3000 g/m ² .

(1-2) Thermosetting resin composition constituting resin-impregnated fiber layer (I) In the present invention, the thermosetting resin composition constituting the resin-impregnated fiber layer (I) is not particularly limited and is heat resistant. And from the viewpoint of mechanical properties, it is preferable to include a thermosetting resin that undergoes a cross-linking reaction by heat and at least partially forms a three-dimensional cross-linked structure.

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 blended resins of two or more kinds can also be used. These thermosetting resins may be self-hardening by heating, or may be resins that harden by adding a curing agent or a curing accelerator.

Among these thermosetting resins, epoxy resins and bismaleimide resins are preferable because they have an excellent balance of heat resistance, mechanical properties, and adhesion to carbon fibers. Epoxy resins are more preferable from the viewpoint of mechanical properties. Bismaleimide resin is more preferable from the viewpoint of

Epoxy resins are not particularly limited, but bifunctional epoxies such as bisphenol type epoxy resins, alcohol type epoxy resins, biphenyl type epoxy resins, hydrophthalic acid type epoxy resins, dimer acid type epoxy resins, and alicyclic type epoxy resins can be used. Resins; glycidyl ether type epoxy resins such as tetrakis(glycidyloxyphenyl)ethane and tris(glycidyloxyphenyl)methane; glycidylamine type epoxy resins and naphthalene type epoxy resins such as tetraglycidyldiaminodiphenylmethane; phenol novolac type epoxy resins; Novolac type epoxy resins such as cresol novolak type epoxy resins are included.

Further examples include polyfunctional epoxy resins such as phenol type epoxy resins. Furthermore, various modified epoxy resins such as urethane-modified epoxy resins and rubber-modified epoxy resins can also be used.

Among them, it is preferable to use an epoxy resin having an aromatic group in the molecule, and an epoxy resin having either a glycidylamine structure or a glycidyl ether structure is more preferable. Alicyclic epoxy resins can also be suitably used.

Examples of epoxy resins having a glycidylamine structure include N,N,N',N'-tetraglycidyldiaminodiphenylmethane, N,N,O-triglycidyl-p-aminophenol, N,N,O-triglycidyl-m- Examples include various isomers of aminophenol, N,N,O-triglycidyl-3-methyl-4-aminophenol, and triglycidylaminocresol.

Examples of epoxy resins 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 novolak-type epoxy resins.

These epoxy resins may optionally have a non-reactive substituent on the aromatic ring structure or the like. 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.

These epoxy resins may be used singly or in combination of two or more.

The thermosetting resin composition constituting the resin-impregnated fiber layer (I) may optionally contain a curing agent for curing the curable resin. A known curing agent that cures a curable resin is used as the curing agent. For example, when an epoxy resin is used as the curable resin, curing agents used include dicyandiamide, various isomers of aromatic amine curing agents, and aminobenzoic acid esters. Dicyandiamide is preferable because it is excellent in storage stability of the prepreg. In addition, aromatic diamine compounds such as 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, 4,4'-diaminodiphenylmethane and their derivatives having non-reactive substituents have good heat resistance. It is particularly preferred from the viewpoint of giving a good cured product. Here, the non-reactive substituent is the same as the non-reactive substituent described in the explanation of the epoxy resin.

Preferred aminobenzoic acid esters include trimethylene glycol di-p-aminobenzoate and neopentyl glycol di-p-aminobenzoate. 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 application of the composite material.

The amount of the curing agent contained in the thermosetting resin composition is at least an amount suitable for curing the curable resin compounded in the prepreg. The amount of curing agent may be appropriately adjusted according to the type of curable resin and curing agent used. The amount of the curing agent is appropriately adjusted in consideration of the presence or absence and addition amount of the curing agent/curing accelerator, the stoichiometry of chemical reaction with the curable resin, the curing rate of the composition, and the like. It is preferable to blend 30 to 100 parts by mass, more preferably 30 to 70 parts by mass, of the curing agent with respect to 100 parts by mass of the curable resin contained in the prepreg.

When a low-viscosity curable resin is used as the thermosetting resin composition, a thermoplastic resin may be blended in order to give the thermosetting resin composition an appropriate viscosity. The thermoplastic resin blended in this thermosetting resin composition for viscosity adjustment also has the 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 thermosetting resin composition varies depending on the type of curable resin used in the thermosetting resin composition, and the viscosity of the thermosetting resin composition is adjusted to the appropriate amount described later. It should be adjusted appropriately so that the values are the same. Generally, it is preferable to blend 5 to 100 parts by mass of the thermoplastic resin with respect to 100 parts by mass of the curable resin contained in the thermosetting resin composition. The thermosetting resin composition preferably has a minimum viscosity of 10 to 450 Poise at 80° C., more preferably 50 to 400 Poise.

In the present invention, the thermosetting resin composition contains, in addition to the above components, an acid anhydride, a Lewis acid, dicyandiamide (DICY) and imidazoles, if necessary, as long as the objects and effects of the present invention are not impaired. Basic curing agents such as urea compounds, organic metal salts, curing accelerators, reaction diluents, fillers, antioxidants, flame retardants, pigments, conductive materials, UV absorbers, UV reflectors, thixotropic agents, fillers Various additives such as can be included.

(2) Particle-containing resin layer (II)
The particle-containing resin layer (II) is made of a particle-containing resin composition containing particulate matter.

The thickness of the particle-containing resin layer (II) is preferably 10-50 μm, more preferably 15-40 μm. If it is less than 10 μm, it may be difficult to sufficiently improve the impact resistance. If it exceeds 50 μm, the resin content of the prepreg may decrease, and drape properties may decrease.

The average particle size of the particulate matter contained in the particle-containing resin layer (II) is also preferably 1 to 50 μm, more preferably 5 to 40 μm, even more preferably 10 to 30 μm.

The average particle diameter of the particulate matter contained in the particle-containing resin layer (II) measured by laser diffraction is preferably 2 to 1400 times the average inter-fiber distance (d), preferably 5 to 125 times. is more preferable. Particulate matter having an average particle size within this range does not easily enter between the single fibers of the reinforcing fibers forming the reinforcing fiber base material when mixed with the resin composition and impregnated into the reinforcing fiber base material. Therefore, it remains on the surface of the reinforcing fiber base material. Therefore, by impregnating the reinforcing fiber substrate with a resin composition containing particulate matter having an average particle size within this range, the particulate matter can be arranged on the surface of the reinforcing fiber substrate. If it is less than 2 times, the particulate matter tends to be buried in the reinforcing fiber base material. On the other hand, the larger the particle diameter of the particulate matter, the smaller the surface area per unit mass. Therefore, when a high effect of improving impact resistance is expected, the average particle diameter of the particulate matter is preferably 1400 times or less the average inter-fiber distance (d).

(2-1) Particle-containing resin composition constituting particle-containing resin layer (II) In the present invention, the particle-containing resin composition constituting the particle-containing resin layer (II) is the thermosetting resin composition described above. It contains particulate matter. The particulate matter is appropriately selected depending on the properties to be imparted to the fiber-reinforced composite material, and for example, the following substances are used.

The particulate matter used in the present invention includes thermoplastic resin particles, thermosetting resin particles, elastomer particles, inorganic particles, graphite particles, metal particles and the like. As the thermoplastic resin, if it is a thermoplastic resin that does not dissolve in the matrix resin, it has excellent adhesiveness to the matrix resin, and if it is a thermoplastic resin that dissolves in the matrix resin, it is compatible with the matrix resin. A thermoplastic resin having specific properties is preferable from the viewpoint of improving the toughness of the fiber layer.

Thermoplastic resin particles include polyamide, polyacetal, polyphenylene oxide, polyphenylene sulfide, polyester, polyamideimide, polyimide, polyetherketone, polyetheretherketone, polyethylenenaphthalate, polyethernitrile, polybenzimidazole, polyethersulfone, polysulfone. , polyetherimide, and polycarbonate particles. Among these, polyamide, polyamideimide, polyimide, and polyetherimide are preferred because of their high toughness and heat resistance. These thermoplastic resin particles may be used alone or in combination of two or more. Copolymer particles obtained by copolymerizing the above thermoplastic resins may also be used.

The thermoplastic resin particles are not particularly limited, but particles made of a matrix resin-insoluble thermoplastic resin that does not substantially dissolve in the matrix resin at or below the temperature at which the fiber-reinforced composite material is molded are preferred. The term “substantially insoluble in the matrix resin” refers to a thermoplastic resin that does not change in particle size when the resin particles are added to the matrix resin and stirred at the temperature at which the fiber-reinforced composite material is molded. Specifically, when 10 parts by mass of a thermoplastic resin having an average particle size of 10 to 50 μm is mixed with 100 parts by mass of a matrix resin and stirred at 200° C. for 1 hour, the particle size changes by 10% or more. A thermoplastic resin that does not Incidentally, the temperature for molding the fiber-reinforced composite material is generally 100 to 200°C. Moreover, the particle size is visually measured with a microscope, and the average particle size means the average value of the particle sizes of 100 randomly selected particles.
When an epoxy resin is used as the matrix resin, the matrix resin-insoluble thermoplastic resin includes polyamide, polyacetal, polyphenylene oxide, polyphenylene sulfide, polyester, polyamideimide, polyimide, polyetherketone, polyetheretherketone, polyethylene naphthalate, polyether. Nitriles and polybenzimidazoles are exemplified. Among these, polyamide, polyamideimide, and polyimide are preferred because of their high toughness and heat resistance. Polyamide and polyimide are particularly effective in improving the toughness of fiber-reinforced composite materials. These may be used alone or in combination of two or more. Copolymers of these can also be used.

In particular, amorphous polyimides, crystalline polyamides such as polyamide 6 (polyamide obtained by ring-opening polycondensation reaction of caprolactam), polyamide 12 (polyamide obtained by ring-opening polycondensation reaction of lauryllactam), and amorphous polyamides By using, the heat resistance of the resulting fiber-reinforced composite material can be particularly improved.

Examples of thermosetting resin particles include epoxy resin particles, vinyl ester resin particles, acrylic resin particles, phenol resin particles, and maleimide resin particles.

Elastomer particles include thermosetting elastomer particles and thermoplastic elastomer particles. Thermoplastic elastomer particles are preferred because they tend to improve the toughness of the fiber layer. Examples of thermoplastic elastomer particles include particles of polystyrene-based elastomers, polyolefin-based elastomers, vinyl chloride-based elastomers, polyurethane-based elastomers, polyester-based elastomers, polyamide-based elastomers, polybutadiene-based elastomers, and the like.

Examples of inorganic particles include metal oxide particles and mineral particles. Metal oxides include silicon oxide, titanium oxide, zirconium oxide, zinc oxide, tin oxide, indium oxide, aluminum oxide, antimony oxide, cerium oxide, magnesium oxide, iron oxide, tin-doped indium oxide (ITO), and antimony-doped tin oxide. , fluorine-doped tin oxide, and the like. Minerals include clay minerals such as montmorillonite, talc, mica, boehmite, kaolin, smectite, xonolite, verculite, and sericite. Metal particles include gold, silver, copper, platinum, nickel, zinc, aluminum, iron, tin, lead, and the like. Gold, silver, copper, platinum and nickel are particularly preferred.

These particles may be used alone or in combination of two or more.

The shape of the particulate matter is not particularly limited, and may be particles having a fixed shape such as spherical, polygonal prismatic, cubic, rod-like, or fibrous, or irregular particles having no specific shape such as crushed matter. shape can be adopted. Among these, spherical, amorphous, and fibrous are preferred, and spherical is more preferred.

The composition of the thermosetting resin composition contained in the resin-impregnated fiber layer (I) and the composition of the thermosetting resin composition contained in the particle-containing resin layer (II) are the same except for the presence or absence of particulate matter. is preferably

(3) Resin coating layer (III)
The resin coating layer (III) is made of a thermosetting resin composition.

The thickness of the resin coating layer (III) is preferably 4-15 μm, more preferably 5-10 μm. If it is less than 5 μm, the tackiness of the prepreg tends to deteriorate. In addition, the particulate matter contained in the particle-containing resin layer (II) is easily deformed during pressure molding. Furthermore, the reinforcing fiber base material constituting the resin-impregnated fiber layer (I) is likely to be deformed and the inter-fiber distance is likely to be reduced. If it exceeds 10 μm, the drapeability of the prepreg tends to deteriorate.

(3-1) Thermosetting resin composition constituting the resin coating layer (III) The thermosetting resin composition constituting the resin coating layer (III) is a thermosetting resin and 100 mass of the thermosetting resin. It is preferable that the resin composition contains 10 to 50 parts by mass of a thermoplastic resin per part. The components contained in the thermosetting resin composition constituting the resin coating layer (III) may be the same as the components described above.

The thermoplastic resin modifies the resin coating layer (III) to improve tackiness. In addition, it suppresses migration of the particulate matter contained in the particle-containing resin layer (II) to the surface of the prepreg.
If the content of the thermoplastic resin is less than 10 parts by mass, the effect of improving the tackiness of the prepreg is small. In addition, since the resin coating layer (III) has a low viscosity, the particulate matter contained in the particle-containing resin layer (II) may migrate to the surface of the prepreg and reduce the tackiness of the prepreg. If it exceeds 50 parts by mass, the drapeability of the prepreg tends to deteriorate.
The lower limit of the content of the thermoplastic resin is preferably 15 parts by mass, more preferably 20 parts by mass. The upper limit of the content of the thermoplastic resin is preferably 40 parts by mass, more preferably 35 parts by mass.

The viscosity at 100° C. of the resin composition constituting the resin coating layer (III) is preferably 1 to 1000 Pa·s, more preferably 10 to 500 Pa·s. If it is less than 1 Pa·s, the cohesive force of the resin is weak, so when the prepreg is peeled off from the release paper, the resin tends to remain on the release paper, resulting in poor workability. If it exceeds 1000 Pa·s, the tackiness is lowered due to the high resin viscosity.

2. Prepreg Production Method The prepreg production method of the present invention is produced by a hot-melt method. In the hot melt method, a resin composition is applied to a release paper in the form of a thin film to form a resin film, and then the resin film is peeled off from the release paper and laminated on a reinforcing fiber base material, followed by heating. This is a method of impregnating a reinforcing fiber base material with a resin composition by heating under pressure.

The prepreg of the present invention is prepared by laminating a resin film (A) made of a thermosetting resin composition containing particulate matter on one or both sides of a reinforcing fiber base material, and further comprising a resin coating layer (III). It is produced by stacking resin films (B) made of a curable resin composition and impregnating the reinforcing fiber substrate with the resin film (A) through the resin film (B). A resin film (A) made of a thermosetting resin composition containing particulate matter is laminated on a reinforcing fiber substrate and heated under pressure so that the particulate matter is arranged on the surface of the reinforcing fiber substrate. . That is, of the resin composition constituting the resin film (A), the thermosetting resin composition excluding particulate matter is impregnated into the reinforcing fiber base material to form the resin-impregnated fiber layer (I) in the reinforcing fiber base material. formed in Further, among the resin compositions constituting the resin film (A), a thermosetting resin composition containing particulate matter is disposed on the surface of the reinforcing fiber base material, and the particle-containing resin layer (II) is formed on the reinforcing fiber base material. formed on the surface of Further, on the surface of the particle-containing resin layer (II), a resin coating layer (III) made of a thermosetting resin composition that constitutes the resin film (B) is formed. Therefore, the resin film (A) forms the resin-impregnated fiber layer (I) and the particle-containing resin layer (II) through the impregnation operation.
The basis weight of the resin film (A) is preferably 20 to 45 g/m ² , and the basis weight of the resin film (B) is preferably 2 to 15 g/m ² . It is preferable that the weight ratio between the resin film (A) and the resin film (B) is in the range of 2:1 to 9:1. By setting the film basis weight within this range, the thickness of each layer of the prepreg and the average inter-fiber distance can be easily set within the desired range.

FIG. 2 is a schematic cross-sectional view showing an example of the manufacturing process of this prepreg. In addition, hatching in the figure represents resin. In FIG. 2(a), 40 is a reinforcing fiber substrate layer, and 41 is a reinforcing fiber. 50 is a resin film (A), 51 is particulate matter, and 53 is a thermosetting resin composition. 60 is a resin film (B), and 61 is a resin composition. The resin film (A) 50 is laminated on the reinforcing fiber substrate 40, and the resin film (B) 60 is laminated on the surface of the resin film (A) 50 (FIG. 2(b)). After lamination, the resin film (A) 50 is pressurized and impregnated into the reinforcing fiber substrate 40 via the resin film (B) 60 to produce the prepreg of the present invention (FIG. 2(c)).
The manufacturing method of laminating the resin film (B) 60 on the surface of the reinforcing fiber substrate 40 after the resin film (A) 50 has been impregnated is not the manufacturing method of the present invention.

The method for producing each resin composition is not particularly limited, and any conventionally known method may be used. For example, when an epoxy resin is used, the kneading temperature applied during the production of the resin composition can be exemplified in the range of 10 to 160°C. If the temperature exceeds 160°C, the epoxy resin may be thermally deteriorated or the curing reaction may partially start, and the storage stability of the obtained resin composition and the prepreg produced using the same may be deteriorated. If the temperature is lower than 10°C, the viscosity of the epoxy resin composition is high, and kneading may be substantially difficult. It is preferably 20 to 130°C, more preferably 30 to 110°C.

A conventionally known kneading machine can be used as the kneading machine. Specific examples include roll mills, planetary mixers, kneaders, extruders, Banbury mixers, mixing vessels equipped with stirring blades, and horizontal mixing tanks. Kneading of each component can be performed in air or under an inert gas atmosphere. When kneading is performed in 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 less or in a low-humidity atmosphere with a relative humidity of 50% RH or less.

The method for forming each resin composition into a resin film is not particularly limited, and any conventionally known method can be used. Specifically, using a die extrusion, an applicator, a reverse roll coater, a comma coater, etc., a resin film can be produced by casting a resin composition onto a support such as a release paper or a film. can. The temperature of the resin composition when producing the film is appropriately adjusted according to the resin composition and viscosity. Specifically, the same temperature conditions as the kneading temperature of the resin composition described above are preferably used. The impregnation can be performed not only once but also in multiple steps at arbitrary pressures and temperatures.

The impregnation pressure when impregnating the reinforcing fiber base material with the resin film is 1 to 50 (kN/cm), preferably 5 to 30 (kN/cm). Within this impregnation pressure range, the viscosity of the resin composition constituting the resin film, the resin flow, etc. are taken into account, and the pressure is appropriately determined.
The prepreg of the present invention has a resin coating layer (III). Therefore, compared to a conventional prepreg that does not have the resin coating layer (III), the content of particulate matter in the resin composition impregnated into the reinforcing fiber base material is relatively high (particulate matter content when producing prepregs with the same rate and resin content). That is, the content of particulate matter in the resin film (A) is higher than the content of particulate matter in the total resin constituting the prepreg. Therefore, the viscosity of the resin composition impregnated into the reinforcing fiber substrate tends to increase, and the impregnation pressure tends to increase. When the impregnation pressure becomes high, the inter-fiber distance of the reinforcing fiber substrate tends to increase during the impregnation operation. In the present invention, since the resin film (A) is pressurized through the resin film (B), even if the impregnation pressure is increased, the inter-fiber distance of the reinforcing fiber substrate is unlikely to expand during the impregnation operation.

The impregnation temperature at which the resin film is impregnated into the reinforcing fiber base material is appropriately determined in consideration of the viscosity and resin flow of the resin composition.
When an epoxy resin is used as the thermosetting resin, the impregnation temperature is preferably 50 to 150.degree. C., more preferably 60 to 145.degree. C., and particularly preferably 70 to 140.degree.

The viscosity at 100° C. of the thermosetting resin composition constituting the resin film (A) is preferably 10 to 1000 Pa s, more preferably 50 to 800 Pa s, and more preferably 100 to 600 Pa s. It is particularly preferred to have If it is less than 10 Pa·s, the resin tends to flow out from the prepreg. If it exceeds 1000 Pa·s, the prepreg tends to have non-impregnated portions. As a result, voids and the like are likely to be formed in the resulting fiber-reinforced composite material.

The prepreg obtained using the above method is laminated according to the purpose, molded and cured to produce a fiber-reinforced composite material.

3. Fiber Reinforced Composite Material The fiber reinforced composite material of the present invention is a fiber reinforced composite material in which a reinforcing fiber base material is impregnated with a thermosetting resin and particulate matter is present between layers of the reinforcing fiber base material, The coefficient of variation of the distance between fibers in an arbitrary cross section of the reinforcing fiber base material is 15% or less.
The coefficient of variation of the inter-fiber distance of the reinforcing fibers is preferably 14% or less, more preferably 13% or less. If it exceeds 15%, the inter-fiber distance varies greatly, and the fiber-reinforced composite material produced using this prepreg cannot uniformly disperse the stress applied to each single fiber of the reinforcing fibers. Although the lower limit of the coefficient of variation is preferably as small as possible, it is generally 0.1% or more.
In order to reduce the variation coefficient of the inter-fiber distance of the reinforcing fibers, a reinforcing fiber base material having a small variation coefficient of the inter-fiber distance is used, and the inter-fiber distance is kept as small as possible (especially, the reinforcing fiber base material It is required to produce a fiber reinforced composite material so as not to cause local deformation near the surface of. Such a fiber-reinforced composite material can be produced using the prepreg of the present invention in which the reinforcing fiber base material is not deformed in the impregnation step during the production of the prepreg.

In the fiber-reinforced composite material of the present invention, the average fiber diameter (r ₂ ) and the average inter-fiber distance (d ₂ ) of the reinforcing fibers in the resin-impregnated fiber layer (I) are expressed by the following formula (2)
0.04≤d2/ _r2≤0.25 Expression ( ₂ )
is preferably satisfied. Here, the lower limit is preferably 0.08, more preferably 0.13. The upper limit is preferably 0.24, more preferably 0.20.
When it is 0.04 to 0.25, the inter-fiber distance of the reinforcing fiber base material is within an appropriate range, and the bonding surface between the single fiber surface of the reinforcing fiber and the matrix resin increases. As a result, when stress is applied to the fiber-reinforced composite material, the stress transmitted from the matrix resin can be uniformly distributed to each single fiber. If it is less than 0.04, the contact between the single fibers is large, and the stress applied to each single fiber of the reinforcing fibers cannot be uniformly dispersed. If it exceeds 0.25, the contact between the single fibers is large, and the stress applied to each single fiber of the reinforcing fibers cannot be uniformly distributed.

The average fiber-to-fiber distance (d ₂ ) of the reinforcing fibers in the fiber-reinforced composite material is preferably 0.4 to 1.2 μm, more preferably 0.65 to 1.0 μm.

The size and amount of interlaminar particles and the resin content in the fiber-reinforced composite material of the present invention are as described for the prepreg.

The method for producing the fiber-reinforced composite material of the present invention is not particularly limited, and examples thereof include autoclave molding, press molding, resin transfer molding, and filament winding molding. The fiber-reinforced composite material of the present invention is preferably molded using the prepreg of the present invention.
When the prepreg of the present invention is used to mold the fiber-reinforced composite material of the present invention, the prepregs are layered according to the purpose and then molded and cured. Examples of prepreg lamination methods include manual layup, automated tape layup (ATL), and automated fiber placement.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the examples. Components and test methods used in Examples and Comparative Examples are described below.

〔component〕
(Epoxy resin)
・ Glycidylamine type epoxy resin Huntsman Japan Co., Ltd. “Araldite MY600” (hereinafter, MY600)
・Glycidylamine type epoxy resin
"Araldite MY721" manufactured by Huntsman Japan Co., Ltd. (hereinafter referred to as MY721)
(epoxy resin curing agent)
- Aromatic amine curing agent 3,3'-diaminodiphenylsulfone (manufactured by Konishi Chemical Industry Co., Ltd.) (hereinafter referred to as 3,3'-DDS)
(particulate matter)
・ Polyamide 12 (thermoplastic resin insoluble in epoxy resin) (MSP-A6496 manufactured by Daicel-Evonik (hereinafter referred to as PA12)
・Polyethersulfone (thermoplastic resin soluble in epoxy resin) (hereafter, PES)
"PES-5003P" manufactured by Sumitomo Chemical Co., Ltd. (average particle size 15 μm)

[Evaluation method]
(1) Average particle size (laser diffraction method)
The average particle size of the particulate matter and thermoplastic resin is determined by measuring the particle size distribution using a laser diffraction/scattering particle size analyzer (Microtrac method: MT3300 (manufactured by Nikkiso Co., Ltd.)). The particle diameter ( _D50 ) was defined as the average particle diameter.

(2) Tack Retention Days A prepreg was cut into 100 mm×100 mm pieces, stored in a thermo-hygrostat at a temperature of 25° C. and a relative humidity of 50%, and then the prepregs were laminated and pasted together. After that, the laminated prepreg is attached to an aluminum plate set up vertically, and whether or not the laminated prepreg is peeled off is evaluated.

(3) Water Absorption A prepreg was cut to 100×100 mm, and the mass (W ₁ ) was measured. After that, the prepreg was submerged in water in a desiccator. The pressure inside the desiccator was reduced to 10 kPa or less to replace the air and water inside the prepreg. The prepreg was taken out of the water, the surface water was wiped off, and the mass (W ₂ ) of the prepreg was measured. From these measured values, the following formula Water absorption (%) = [(W ₂ -W ₁ )/W ₁ ] × 100
W ₁ : Mass of prepreg (g)
W ₂ : Mass (g) of prepreg after water absorption
was used to calculate the water absorption.

(4) Distance between fibers Measurement samples were produced using an autoclave molding method. That is, the prepreg was cut into a size of 100 mm×100 mm and laminated to obtain a laminate having a laminate structure of [0] ₆ . This laminate was molded by a normal autoclave molding method. The molding conditions were a pressure of 0.49 MPa, a temperature of 180° C., and 120 minutes. The resulting molded product was cut in the cross-sectional direction of the fiber axis, and the resin layer was observed at a magnification of 100 times (field size: 106 μm × 142 μm) using a laser microscope (manufactured by Keyence Corporation, VK-8710). I photographed mainly the fiber layer so as not to enter. Thereafter, the wall-to-wall distance between each fiber was measured using image analysis software (Azo-kun (trade name)) provided by Asahi Kasei Engineering Co., Ltd., and the fiber-to-fiber distance and its coefficient of variation were determined.

(5) In-Plane Shear (IPS) Yield Point Strength Measurement samples were produced using an autoclave molding method. That is, the prepreg was cut and laminated to obtain a laminate having a laminate structure of [+45/-45] _2S . This laminate was molded by a normal autoclave molding method. The molding conditions were a pressure of 0.49 MPa, a temperature of 180° C., and 120 minutes. The obtained molded product was cut into a size of 25 mm in width×230 mm in length, and measured according to EN6031.

(6) Interlaminar fracture toughness mode I (GIc)
After the obtained prepreg was cut into a square with a side of 30 mm, the prepregs were laminated to prepare two laminates in which 10 layers were laminated in the direction of 0°. In order to generate initial cracks, a release sheet was sandwiched between the two laminates, and the two were combined to obtain a prepreg laminate having a laminate structure of [0] ₂₀ . Molding was carried out for 2 hours at 180° C. under a pressure of 0.59 MPa using a normal vacuum autoclave molding method. The obtained molded product (FRP) was cut into a size of 12.7 mm wide×304.8 mm long to obtain a test piece of interlaminar fracture toughness mode I (GIc).
As a test method for GIc, a double cantilever beam interlaminar fracture toughness test method (DCB method) is used, and a precrack (initial crack) of 12.7 mm is generated from the tip of the release sheet, and then the crack is further propagated. did The test was terminated when the crack growth length reached 127 mm from the tip of the pre-crack. The crosshead speed of the test piece tensile tester was 12.7 mm/min, and the measurement was performed with n=5.
The crack growth length was measured from both end surfaces of the test piece using a microscope, and GIc was calculated by measuring the load and crack opening displacement.

(Example 1)
PAN fiber (24,000 filaments), which is a precursor fiber, was subjected to a flameproofing treatment at 250°C in the air until the specific gravity of the fiber reached 1.35, and then low-temperature carbonization at a maximum temperature of 650°C in a nitrogen gas atmosphere. . After that, the carbon fibers produced by high-temperature carbonization at 1500 ° C. in a nitrogen atmosphere are subjected to surface treatment by electrolytic oxidation using a 10% by mass ammonium sulfate aqueous solution at an electric quantity of 40 C / g, and dried to carbon fiber bundles ( A tensile strength of 5800 MPa, a tensile modulus of elasticity of 290 GPa, the number of filaments of 24000, and an average fiber diameter of 5 μm were obtained. Thereafter, the carbon fiber bundles were aligned in one direction to produce a carbon fiber substrate (basis weight: 190 g/m ² ).
(A) 50 parts by mass of MY600, 50 parts by mass of MY721, and 20 parts by mass of PES were mixed, stirred with a stirrer at 120°C for 30 minutes to completely dissolve, and then the resin was heated to 80°C. Cooled below. After that, 35 parts by mass of particulate matter (PA12 having an average particle diameter of 20 μm) is kneaded, and 45 parts by mass of 3,3'-DDS as a curing agent is kneaded to obtain a particle-containing thermosetting epoxy resin composition. prepared.
The prepared particle-containing thermosetting epoxy resin composition was applied onto release paper using a film coater to prepare two 40 (g/m ² ) resin films (A).
(B) Next, 100 parts by mass of MY600 and 10 parts by mass of PES were mixed and stirred at 120° C. for 30 minutes with a stirrer to completely dissolve them, thereby preparing an epoxy resin composition. The viscosity of this epoxy resin composition at 100° C. was 32 Pa·s.
The prepared epoxy resin composition was applied onto release paper using a film coater to prepare two resin films (B) of 10 (g/m ² ).
The resin film (A) and the resin film (B) are laminated in this order on both sides of the carbon fiber base material, and pressurized and heated using a roller at a temperature of 130 ° C. and an impregnation linear pressure of 30 (kN / cm). Got the prepreg. This prepreg had a resin content of 35 (% by mass), a tack retention period of 33 (days), and a water absorption of 2.3 (%). Table 1 shows the average inter-fiber distance of the obtained prepreg.
The fiber-reinforced composite material produced using this prepreg had an interfiber distance of 1.1 (μm), an IPS yield point strength of 87 (MPa), and a GIc of 660 (J/m ² ).

The prepreg of Example 1 is impregnated with the resin film (A) through the resin film (B). Therefore, the tack retention days were high, and the fiber-reinforced composite material produced using this prepreg had excellent mechanical strength.

(Examples 2 and 3)
A prepreg was obtained in the same manner as in Example 1, except that the impregnation pressure was changed to the value shown in Table 1. By changing the impregnation pressure, the average inter-fiber distance of the obtained prepreg changed to the value shown in Table 1, but all satisfied the requirements of formula (1). The prepregs of Examples 2 and 3 in which the resin film (A) was impregnated through the resin film (B) had high tack retention days, and the fiber-reinforced composite material produced using these prepregs had excellent mechanical strength. rice field.

(Comparative example 1)
PAN fiber (24,000 filaments), which is a precursor fiber, was subjected to a flameproofing treatment at 250°C in the air until the specific gravity of the fiber reached 1.35, and then low-temperature carbonization at a maximum temperature of 650°C in a nitrogen gas atmosphere. . After that, the carbon fibers produced by high-temperature carbonization at 1500 ° C. in a nitrogen atmosphere are subjected to surface treatment by electrolytic oxidation using a 10% by mass ammonium sulfate aqueous solution at an electric quantity of 40 C / g, and dried to carbon fiber bundles ( A tensile strength of 5800 MPa, a tensile modulus of elasticity of 290 GPa, the number of filaments of 24000, and an average fiber diameter of 5 μm were obtained. Thereafter, the carbon fiber bundles were aligned in one direction to produce a carbon fiber substrate (basis weight: 190 g/m ² ).
(A) 50 parts by mass of MY600, 50 parts by mass of MY721, and 20 parts by mass of PES were mixed, stirred with a stirrer at 120°C for 30 minutes to completely dissolve, and then the resin was heated to 80°C. Cooled below. After that, 35 parts by mass of particulate matter (PA12 having an average particle diameter of 12 μm) is kneaded, and 45 parts by mass of 3,3′-DDS as a curing agent is kneaded to obtain a particle-containing thermosetting epoxy resin composition. prepared.
The prepared particle-containing thermosetting epoxy resin composition was applied onto release paper using a film coater to prepare two 40 (g/m ² ) resin films (A).
(B) Next, 100 parts by mass of MY600 and 10 parts by mass of PES were mixed and stirred at 120° C. for 30 minutes with a stirrer to completely dissolve them, thereby preparing an epoxy resin composition. The viscosity of this epoxy resin composition at 100° C. was 32 Pa·s.
The prepared epoxy resin composition was applied onto release paper using a film coater to prepare two resin films (B) of 10 (g/m ² ).
The resin film (A) is laminated on both sides of the carbon fiber base material, pressurized and heated using a roller at a temperature of 130 ° C. and an impregnation linear pressure of 30 (kN / cm), and then the resin film (B) is laminated. I got the prepreg. This prepreg had a resin content of 35 (% by mass), a tack retention period of 33 (days), a water absorption rate of 1.2 (%), and an average interfiber distance (d) of 0.1 (μm). rice field.
The fiber-reinforced composite material produced using this prepreg had an interfiber distance of 0.1 (μm), an IPS yield point strength of 79 (MPa), and a GIc of 560 (J/m ² ).

Since this prepreg had a resin coating layer containing no particulate matter, it had excellent tackiness. However, since this prepreg is produced by directly pressing the resin film (A), the distance between fibers is small. As a result, the resulting fiber-reinforced composite material had low mechanical properties.

(Comparative example 2)
A carbon fiber substrate identical to that of Example 1 was produced.
(A) 50 parts by mass of MY600, 50 parts by mass of MY721, and 20 parts by mass of PES were mixed, stirred with a stirrer at 120°C for 30 minutes to completely dissolve, and then the resin was heated to 80°C. Cooled below. After that, 35 parts by mass of particulate matter (PA12 having an average particle diameter of 20 μm) is kneaded, and 45 parts by mass of 3,3'-DDS as a curing agent is kneaded to obtain a particle-containing thermosetting epoxy resin composition. prepared.
(B) Next, 100 parts by mass of MY600 and 10 parts by mass of PES were mixed and stirred at 120° C. for 30 minutes with a stirrer to completely dissolve them, thereby preparing an epoxy resin composition. The viscosity of this epoxy resin composition at 100° C. was 32 Pa·s. The above two types of resin compositions were mixed so that (A):(B) was 4:1 to prepare a resin composition.
The prepared particle-containing thermosetting epoxy resin composition was applied onto release paper using a film coater to prepare two resin films (A) of 50 (g/m ² ).
The resin film (A) was attached to both surfaces of the carbon fiber base material, and pressure and heat were applied using a roller at a temperature of 130° C. and an impregnation linear pressure of 30 (kN/cm) to obtain a prepreg. This prepreg had a resin content of 35 (% by mass), a tack retention period of 4 (days), a water absorption rate of 6.8 (%), and an average interfiber distance (d) of 0.9 (μm). rice field.
The fiber-reinforced composite material produced using this prepreg had an interfiber distance of 0.9 (μm), an IPS yield point strength of 85 (MPa), and a GIc of 590 (J/m ² ).

This prepreg had poor tackiness because it did not have a resin coating layer containing no particulate matter. In addition, since this prepreg is produced by directly pressing a resin film containing particulate matter, the distance between fibers is slightly reduced. As a result, the resulting fiber-reinforced composite material had low mechanical properties.

(Comparative Example 3)
A prepreg was obtained in the same manner as in Example 1, except that the impregnation pressure was changed to the value shown in Table 1.
By increasing the impregnation pressure, the average inter-fiber distance of the obtained prepreg did not satisfy the requirements of formula (1), as shown in Table 1. Moreover, deformation was observed in the interlayer particles. Therefore, the fiber-reinforced composite material produced using this prepreg has low mechanical strength.

100... Prepreg 10... Resin-impregnated fiber layer (I)
11 Reinforcing fiber base material 13 Thermosetting resin composition 20 Particle-containing resin layer (II)
21 Particulate matter 23 Thermosetting resin composition 30 Resin coating layer (III)
31... Resin composition 40... Reinforcement fiber base layer 41... Reinforcement fiber 50... Resin film (A)
51 Particulate matter 53 Thermosetting resin composition 60 Resin film (B)
61... resin composition

Claims (7)

a resin-impregnated fiber layer (I) comprising a reinforcing fiber base material and a thermosetting resin composition impregnated in the reinforcing fiber base material;
a particle-containing resin layer (II) made of a particle-containing resin composition containing particulate matter and formed on one or both sides of the resin-impregnated fiber layer (I);
a resin coating layer (III) made of a thermosetting resin composition and formed on the surface of the particle-containing resin layer (II);
A prepreg consisting of
The average fiber diameter (r) and the average inter-fiber distance (d) of the reinforcing fibers in the resin-impregnated fiber layer (I) are expressed by the following formula (1)
0.04 < d/r ≤ 0.25 Expression (1)
satisfy the
The average interfiber distance (d) is 0.3 to 1.2 μm,
A prepreg characterized in that the average particle size of the particulate matter measured by a laser diffraction method is 2 to 1400 times the average interfiber distance (d) . The prepreg according to claim 1, wherein the content of the particulate matter is 5 to 60 mass% with respect to the mass of the total resin composition contained in the prepreg. The prepreg according to claim 1, wherein the coefficient of variation of interfiber distance is 15% or less. The thermosetting resin composition constituting the resin coating layer (III) contains a thermosetting resin and 10 to 50 parts by mass of a thermoplastic resin with respect to 100 parts by mass of the thermosetting resin. The prepreg according to claim 1, which is a composition. The prepreg according to claim 1, wherein the thermosetting resin composition constituting the resin coating layer (III) has a viscosity of 1 to 1000 Pa·s at 100°C. The prepreg according to claim 1, wherein the reinforcing fiber base material is a reinforcing fiber base material made of carbon fiber. A fiber-reinforced composite material comprising a reinforcing fiber base material and a thermosetting resin, wherein particulate matter is present between the layers of the reinforcing fiber base material,
The average fiber diameter (r ₂ ) and the average inter-fiber distance (d ₂ ) of the reinforcing fibers are expressed by the following formula (2)
0.04 ≤ d ₂ /r ₂ ≤ 0.25 satisfying the formula (2),
The average interfiber distance (d ₂ ) is 0.3 to 1.2 μm,
The average particle diameter of the particulate matter measured by a laser diffraction method is 2 to 1400 times the average interfiber distance (d ₂ ),
A fiber-reinforced composite material, wherein the coefficient of variation of the distance between fibers in an arbitrary cross section of the reinforcing fiber base material is 15% or less.

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