JP7467906B2 - Fiber-reinforced resin molded body and composite molded body - Google Patents

Description

The present invention relates to a fiber-reinforced resin molding that contains both thermosetting and thermoplastic resins.

Fiber-reinforced resins, which use thermosetting or thermoplastic resins as a matrix resin and combine them with reinforcing fibers such as carbon fiber or glass fiber, are lightweight yet have excellent mechanical properties such as strength and rigidity, as well as heat resistance and corrosion resistance, and are therefore used in many fields such as aerospace, automobiles, railway vehicles, ships, civil engineering and construction, and sporting goods.

In general, fiber-reinforced resin is not suitable for manufacturing parts or molded bodies with complex shapes in a single molding process. To form complex shapes, it is necessary to create a component made of fiber-reinforced resin and then join it to another component. When used as structural or semi-structural components for aircraft or automobiles, currently, joining methods using adhesives or mechanical fastening methods such as rivets are used. However, when adhesives are used, there is a risk of poor joining due to peeling at the interface between the fiber-reinforced resin molded body and the other component. In addition, when mechanical fastening is used, holes are drilled in the fiber-reinforced resin and the other component, which poses the issue of the strength of the holes being reduced.

Fiber-reinforced resins that use thermoplastic resins as the matrix resin can be joined by welding to components that use other thermoplastic resins, so it can be said that the process is relatively easy to simplify. For example, Patent Document 1 discloses a fiber-reinforced resin laminate in which a thermosetting resin layer and a thermoplastic resin layer are joined by forming an uneven boundary surface, and describes that such a laminate exhibits excellent joining strength and can be easily disassembled in a high-temperature environment.

International Publication No. WO 2004/060658

The method described in Patent Document 1 does not require drilling holes, can effectively utilize the strength, rigidity, and other properties of fiber-reinforced resin moldings, and has high productivity due to the simple joining process. However, further improvements in joining strength are required to expand the range of applications for products.

The objective of the present invention is to provide a fiber-reinforced resin molding that has high bonding properties and a wide range of applications as a final product.

The present invention, which aims to solve the above problems, is a fiber-reinforced resin molding that includes reinforcing fibers (A), a thermosetting resin (B), a thermoplastic resin (C), and an inorganic filler (D), and is a composite of a reinforcing fiber group consisting of continuous reinforcing fibers (A) and a matrix resin having a region mainly composed of a thermosetting resin (B) and a region mainly composed of a thermoplastic resin (C), in which a part of the reinforcing fibers (A) and a part of the inorganic filler (D) are in contact with both the region mainly composed of the thermosetting resin (B) and the region mainly composed of the thermoplastic resin (C), and the region mainly composed of the thermoplastic resin (C) is present on at least one surface of the fiber-reinforced resin molding.

1 is a schematic diagram of a fiber-reinforced resin molding according to the present invention. 1 is a schematic cross-sectional view of a fiber-reinforced resin molded body according to the present invention. FIG. 2 is a schematic diagram for explaining the aggregate structure length of an inorganic filler (D).

The present invention is described below.

<Fiber-reinforced resin molded body>
The fiber-reinforced resin molded article of the present invention (hereinafter, sometimes simply referred to as "molded article") is a composite of a reinforcing fiber group composed of continuous reinforcing fibers (A) and a matrix resin having a thermosetting resin (B ) region and a thermoplastic resin (C ) region . Hereinafter, in this specification, the reinforcing fiber group composed of continuous reinforcing fibers (A) will be abbreviated as "reinforcing fiber group", the thermosetting resin (B ) region will be abbreviated as "thermosetting resin region", and the thermoplastic resin (C ) region will be abbreviated as "thermoplastic resin region".

Figure 2 is a schematic diagram showing a cross section of one embodiment of the fiber-reinforced resin molded body of the present invention, cut at an angle of 45 degrees to the orientation direction of the reinforcing fiber (A) as shown in Figure 1 and perpendicular to the surface direction of the molded body. In Figure 2, the reinforcing fiber (A) 6 constitutes a reinforcing fiber group consisting of a large number of reinforcing fibers (A) 6 oriented at an angle of 45 degrees from the direction perpendicular to the paper surface. Then, the reinforcing fiber group is compounded with a matrix resin consisting of a thermosetting resin region 8 and a thermoplastic resin region 7, and as a whole, the reinforced fiber resin molded body is constituted. Thus, in the fiber-reinforced resin molded body of the present invention, the thermosetting resin region and the thermoplastic resin region are in contact while forming an interface.

In the molded article of the present invention, the thermoplastic resin region is present on at least one surface. By doing so, when the molded article is joined to another member, the thermoplastic resin region becomes the joining surface, and joining can be achieved by a simple process such as injection molding or heat welding. The thermoplastic resin region preferably occupies 50% or more of the surface area, more preferably 80% or more, and particularly preferably 100%, i.e., the entire surface is a thermoplastic resin region. It is also preferable that the thermoplastic resin region exists on both sides.

As shown in FIG. 2, it is preferable that the thermoplastic resin region and the thermosetting resin region have a layered structure. In other words, it is preferable that the thermoplastic resin layer and the thermosetting resin layer are laminated while forming an interface. By adopting such a layered structure, it is possible to improve the bonding strength when the molded body is bonded to another member.

As for the interface between the thermosetting resin region and the thermoplastic resin region, as shown in FIG. 1, when the molded body is observed in a cross section that is at an angle of 45 degrees to the orientation direction of the reinforcing fibers (A) and perpendicular to the surface direction of the molded body, it is preferable that the curve formed by the interface between the two resin regions (hereinafter referred to as the "interface curve") in the cross section has a roughness average length RSm of 100 μm or less and a roughness average height Rc of 3.5 μm or more. Here, the roughness average length RSm and the roughness average height Rc are parameters that represent the roughness of the contour curve, calculated in accordance with JIS B0601 (2013).

In such cross-sectional observation, if the roughness average length RSm of the interface curve is 100 μm or less, not only chemical and/or physical bonding forces but also mechanical bonding forces of entanglement are likely to be applied, making it difficult for the two resin regions to peel off. There are no particular limitations on the lower limit of RSm, but from the viewpoint of avoiding a decrease in mechanical bonding strength due to stress concentration, it is preferably 15 μm or more.

Furthermore, by having the roughness average height Rc of the interface curve be 3.5 μm or more, in addition to the mechanical bonding strength due to the above-mentioned entanglement, the reinforcing fiber (A) present on the interface is more likely to form a physical uneven shape with both the thermosetting resin region and the thermoplastic resin region, improving the adhesion strength of both resin regions. The preferred range of Rc is 10 μm or more, which allows the reinforcing fiber (A) and the inorganic filler (D) described later to easily come into contact with both resin regions, thereby further improving the adhesion strength, and more preferably 20 μm or more. The upper limit is not particularly limited, but from the viewpoint of avoiding a decrease in the mechanical bonding strength due to stress concentration, it is preferably 100 μm or less.

Here, as a method for obtaining a cross section for measuring the roughness average height Rc and roughness average length RSm of the interface curve, as shown in FIG. 1, the direction of the reinforcing fibers oriented on the outermost surface of the molded body having the thermoplastic resin region is set as 0 degrees as a reference, and the observation cross section can be obtained by cutting and polishing using a diamond cutter or the like so that the angle is 45 degrees with respect to the perpendicular direction (the direction in which the cross section of the reinforcing fibers is observed as a perfect circle). At this time, a preferred example of the wet abrasive paper is finish polishing with an abrasive grain size of about #1500 so that the observation image of the desired cross section can be observed sharply. Methods for measuring the roughness average height Rc and roughness average length RSm of the interface curve from the obtained cross section include, for example, a method of obtaining a cross section image using X-ray CT, a method of using an elemental analysis mapping image of the cross section using an energy dispersive X-ray spectrometer (EDS), or a method of using a cross section observation image using an optical microscope, a scanning electron microscope (SEM), or a transmission electron microscope (TEM). In the observation, the thermosetting resin (B) and/or the thermoplastic resin (C) may be dyed to adjust the contrast between the two resin regions. In the image obtained by any of the above methods, the roughness average height Rc and roughness average length RSm of the interface curve are measured within an area of 500 μm square.

The method for measuring the roughness average height Rc and roughness average length RSm of the interface curve (method for measuring interface curve elements) is as follows. Using the end 11 on the resin region side containing thermosetting resin (B) of the rectangular observation image 9 as a reference line, vertical base lines 12 are drawn at 5 μm intervals from the resin region 8 containing thermosetting resin (B) toward the resin region 7 containing thermoplastic resin (C). The point where the vertical base line drawn from the reference line first intersects with the thermoplastic resin (C) is plotted, and the line connecting the plotted points is taken as the interface curve 13. The obtained interface curve 13 is subjected to a filtering process based on JIS B0601 (2013), and the roughness average height Rc and roughness average length RSm of the interface curve 13 are calculated.

In the present invention, some of the reinforcing fibers (A) constituting the reinforcing fiber group are in contact with both the thermosetting resin region and the thermoplastic resin region. Referring to FIG. 2, reinforcing fibers (A) 6A and 6B, which are part of the reinforcing fiber (A) 6, are in contact with both the thermosetting resin region and the thermoplastic resin region in a part of their cross section. Note that, although the explanation has been given based on only a specific cross section using FIG. 2, some reinforcing fibers (A) can be said to be in contact with both resin regions even if they are not in contact with both resin regions in a specific cross section, as long as they are in contact with both resin regions somewhere along their entire length. In this case, in the cross section of the part where such reinforcing fiber (A) straddles both resin regions, the cross section of the reinforcing fiber (A) is observed in a state of contact with both resin regions, like reinforcing fibers (A) 6A and 6B in FIG. 2.

The reinforcing fibers (A) may be continuous throughout the entire molded body or may be interrupted, but preferably have a length of 10 mm or more, and more preferably are continuous throughout the entire molded body.

The fiber-reinforced resin molding of the present invention further contains an inorganic filler (D), and a portion of the inorganic filler (D) is also in contact with both the thermosetting resin region and the thermoplastic resin region. Referring to FIG. 2, the inorganic filler (D) 14A is in contact with both the thermosetting resin region and the thermoplastic resin region, as is clear from the cross section. Here, although the inorganic filler (D) is generally shorter and smaller than the reinforcing fiber (A), the explanation of the state in which it is in contact with both resin regions is omitted because it is the same as the case of the reinforcing fiber (A) described above.

In the fiber-reinforced resin molding of the present invention, not only the reinforcing fiber (A) but also a portion of the inorganic filler (D) is in contact with both the thermosetting resin region and the thermoplastic resin region, so that when the fiber-reinforced resin molding is formed, both resin regions exhibit excellent bonding properties.

The basis weight of the thermoplastic resin region in the fiber-reinforced resin molded body is preferably 10 g/m2 or more. The basis weight of the thermoplastic resin region is preferably 50 g/m2 or more because it is easier to obtain a sufficient thickness to achieve better bonding strength, and is more preferably 100 g/m2. There is no particular upper limit to the basis weight, but from the viewpoint of obtaining a laminate with excellent specific strength and specific elastic modulus, it is preferably 500 g/m2 or less. Here, the basis weight of the thermoplastic resin region refers to the mass (g) of thermoplastic resin (C) contained per 1 m2 of the molded body.

The amount of reinforcing fibers per unit area of the fiber-reinforced resin molded body is preferably 30 to 2,000 g/m2. If the amount of reinforcing fibers is 30 g/m2 or more, the number of layers required to obtain a desired thickness during laminate molding can be reduced, making the process easier. On the other hand, if the amount of reinforcing fibers is 2,000 g/m2 or less, the drapeability of the fiber-reinforced resin molded body is more likely to be improved.

The mass content of the reinforcing fiber (A) in the fiber-reinforced resin molding is preferably 30 to 90 mass%, more preferably 35 to 85 mass%, and even more preferably 40 to 80 mass%. If the mass content is 30 mass% or more, the amount of resin is not too large compared to the fiber, making it easier to obtain the advantages of a fiber-reinforced resin molding having excellent specific strength and specific elastic modulus, and also making it difficult for the amount of heat generated during curing during molding to be excessively high. Furthermore, if the mass content is 90 mass% or less, impregnation failure of the thermosetting resin is unlikely to occur, and voids in the obtained fiber-reinforced resin molding are likely to be reduced.

<Reinforcing fiber (A)>
In the molded article of the present invention, the reinforcing fiber group can be in a state in which the reinforcing fibers (A) oriented in one direction are arranged in one or more layers, or in a state in which they are arranged in a woven structure. In order to obtain a molded article that is lightweight and has higher durability, it is preferable that the reinforcing fiber group is in a state in which the reinforcing fibers (A) oriented in one direction are arranged in one or more layers. In addition, in the case of a form in which the reinforcing fibers (A) oriented in one direction are arranged in multiple layers, the reinforcing fiber group constituting each layer may be oriented in the same direction or may be oriented perpendicularly.

From the viewpoints of strength, elastic modulus, and economy of the molded body itself, it is preferable that the reinforcing fiber (A) is at least one type of reinforcing fiber selected from the group consisting of carbon fiber and glass fiber. In addition to the above, metal fibers, aromatic polyamide fibers, polyaramid fibers, alumina fibers, silicon carbide fibers, boron fibers, basalt fibers, etc. may also be used as the reinforcing fiber (A) within the scope that does not impair the effects of the present invention. These may be used alone or in combination of two or more types as appropriate.

These reinforcing fibers (A) may be surface-treated. Examples of surface treatments include metal deposition treatment, treatment with a coupling agent, treatment with a sizing agent, and treatment with an additive. Some of these reinforcing fibers have electrical conductivity.

As the reinforcing fiber (A), carbon fiber is preferably used because of its low specific gravity, high strength, and high elastic modulus. Commercially available carbon fiber products include "TORAYCA (registered trademark)" T800G-24K, "TORAYCA (registered trademark)" T800S-24K, "TORAYCA (registered trademark)" T700G-24K, "TORAYCA (registered trademark)" T700S-24K, "TORAYCA (registered trademark)" T300-3K, and "TORAYCA (registered trademark)" T1100G-24K (all manufactured by Toray Industries, Inc.).

In addition, it is preferable that the strand tensile strength of the reinforcing fiber (A), measured in accordance with the resin-impregnated strand test method of JIS R7608 (2007), is 3.5 GPa or more, since this results in a laminated fiber-reinforced composite material that has excellent bonding strength in addition to tensile strength. It is even more preferable that the strand tensile strength is 4.5 GPa or more.

<Thermosetting resin (B)>
The thermosetting resin (B) is preferably at least one thermosetting resin selected from the group consisting of epoxy, phenol, unsaturated polyester, vinyl ester, thermosetting polyimide, cyanate ester resin, bismaleimide resin, and benzoxazine resin, from the viewpoint of expanding the range of choices of strength and elastic modulus when made into a fiber-reinforced resin molded body and heat resistance when made into a product. In this specification, the term "thermosetting resin (B)" is intended to include even compositions containing curing agents and additives.

Thermosetting resins (B) include, for example, unsaturated polyester resins, vinyl ester resins, epoxy resins, phenolic resins, urea resins, melamine resins, polyimide resins, cyanate ester resins, bismaleimide resins, benzoxazine resins, copolymers or modified products thereof, and resins in which at least two of these types are blended. To improve impact resistance, elastomers or rubber components may be added to the thermosetting resins.

Among them, epoxy resins are preferred because of their excellent mechanical properties, heat resistance, and adhesion to reinforcing fibers. Examples of the main component of epoxy resins include bisphenol type epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD type epoxy resin, and bisphenol S type epoxy resin; brominated epoxy resins such as tetrabromobisphenol A diglycidyl ether; epoxy resins having a biphenyl skeleton, epoxy resins having a naphthalene skeleton, epoxy resins having a dicyclopentadiene skeleton, novolac type epoxy resins such as phenol novolac type epoxy resin and cresol novolac type epoxy resin; and N,N,O-triglycidyl-m-aminophenol. Examples of glycidyl amine type epoxy resins include phenol, N,N,O-triglycidyl-p-aminophenol, N,N,O-triglycidyl-4-amino-3-methylphenol, N,N,N',N'-tetraglycidyl-4,4'-methylenedianiline, N,N,N',N'-tetraglycidyl-2,2'-diethyl-4,4'-methylenedianiline, N,N,N',N'-tetraglycidyl-m-xylylenediamine, N,N-diglycidylaniline, and N,N-diglycidyl-o-toluidine, resorcinol diglycidyl ether, and triglycidyl isocyanurate.

Examples of epoxy resin curing agents include dicyandiamide, aromatic amine compounds, phenol novolac resins, cresol novolac resins, polyphenol compounds, imidazole derivatives, tetramethylguanidine, thiourea-added amines, carboxylic acid hydrazides, carboxylic acid amides, and polymercaptans.

<Thermoplastic resin (C)>
It is preferable that the thermoplastic resin (C) be a thermoplastic resin that is in a molten state within the curing reaction temperature range of the thermosetting resin (B), because this makes it easier for the reinforcing fiber (A) and the inorganic filler (D) to come into contact with the boundary surface consisting of (B) and (C) within the fiber-reinforced resin molding.

The melting temperature of a thermoplastic resin can be measured as follows. The peak melting temperature of a thermoplastic resin is measured in accordance with the "Method for measuring transition temperature of plastics" specified in JIS K7121 (1987). Before the measurement, the sample is dried for 24 hours or more in a vacuum dryer controlled at an oven temperature of 50°C. The melting temperature according to the above standard is obtained using a differential scanning calorimeter, and the peak top is defined as the melting temperature. In this specification, the term "thermoplastic resin (C)" is also used to include compositions containing fillers and additives.

Examples of the thermoplastic resin (C) include polyester-based resins such as polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, and liquid crystal polyester; polyolefins such as polyethylene, polypropylene, and polybutylene; styrene-based resins; urethane resins; polyamides such as polyoxymethylene, polyamide 6, and polyamide 66; polycarbonate; polymethyl methacrylate; polyvinyl chloride; polyarylene sulfides such as polyphenylene sulfide; polyphenylene ether, modified polyphenylene ether, polyimide, polyamideimide, polyetherimide, polysulfone, modified polysulfone, polyethersulfone; polyarylene ether ketones such as polyketone, polyether ketone, polyether ether ketone, and polyether ketone ketone; polyarylate; polyether nitrile; phenolic resins; and phenoxy resins. These thermoplastic resins may also be copolymers or modified bodies of the above-mentioned resins, and/or resins blended with two or more of them.

Among these, from the viewpoint of the balance between moldability, heat resistance, and mechanical properties, it is preferable to use at least one thermoplastic resin selected from the group consisting of polyolefin, polycarbonate, polyester, polyarylene sulfide, polyamide, polyoxymethylene, polyetherimide, polyethersulfone, and polyarylene ether ketone.

Furthermore, the thermoplastic resin (C) may contain other fillers and additives as appropriate depending on the application, etc., within the scope of the present invention. Examples include flame retardants, electrical conductivity imparting agents, crystal nucleating agents, ultraviolet absorbers, antioxidants, vibration dampers, antibacterial agents, insect repellents, deodorants, coloring inhibitors, heat stabilizers, release agents, antistatic agents, plasticizers, lubricants, colorants, pigments, dyes, foaming agents, foam control agents, coupling agents, etc.

<Inorganic filler (D)>
In the present invention, the inorganic filler (D) preferably has an aspect ratio of 5 or more. By using such an inorganic filler (D), it is possible to easily form a structure in which the inorganic filler (D) contacts both regions at the interface between the thermosetting resin region and the thermoplastic resin region, and it is also easy to control the roughness average length RSm and roughness average height Rc of the interface curve at the interface within a predetermined range. For the same reason, the aspect ratio is more preferably 50 or more, more preferably 100 or more, and from the viewpoint of the handleability of the inorganic filler, the upper limit is preferably 1000 or less.

Furthermore, it is preferable that the aggregate structure length L of the inorganic filler (D) is not more than twice the single fiber diameter of the reinforcing fiber (A). Here, the aggregate structure length L of the inorganic filler (D) is a value measured as follows. As a premise, "structure" refers to the inorganic filler (D) forming a chain-like or block-like state by aggregation. As shown in FIG. 1, a cross section including both the thermosetting resin region and the thermoplastic resin region of the fiber-reinforced resin molded body and the molded body is cut out, and it is magnified by a microscope such as a scanning electron microscope by 1000 times or more, and an aggregate of the inorganic filler that randomly forms an aggregate (observed in the form exemplified in FIG. 3, the shape of the inorganic filler (D) is shown as an ellipse for simplicity) is selected, and a circumscribed circle passing through the outermost position (for example, 16) is drawn, and the diameter of the circumscribed circle is measured and taken as the aggregate structure length. Here, the number of measurements is 50 (n = 50) or more, and the arithmetic average value is taken as the aggregate structure length. When the inorganic filler (D) is present in such an aggregated state, the roughness average length RSm and roughness average height Rc of the interface curve between the thermosetting resin region and the thermoplastic resin region tend to fall within the specified range.

When the inorganic filler (D) is contained within the range of 0.01 to 2.0 mass% relative to 100 mass% of the fiber-reinforced resin molding, it is possible to easily bring the thermosetting resin region and the thermoplastic resin region into contact with each other at the boundary surface between the two resin regions, and it is also preferable because it is easier to control the roughness average length RSm and roughness average height Rc of the interface curve within a predetermined range. Furthermore, it is particularly preferable that the inorganic filler (D) is contained within the range of 0.05 to 1.0 mass% because it is easier to blend with the thermosetting resin (B) and the thermoplastic resin (C).

Examples of the inorganic filler (D) that can be used include fibrous fillers such as carbon black, carbon fibers, carbon nanotubes, carbon nanohorns, potassium titanate whiskers, zinc oxide whiskers, calcium carbonate whiskers, wollastonite whiskers, aluminum borate whiskers, aramid fibers, alumina fibers, silicon carbide fibers, ceramic fibers, asbestos fibers, gypsum fibers, and metal fibers; and non-fibrous fillers such as fullerenes, talc, wollastonite, zeolite, sericite, mica, kaolin, clay, pyrophyllite, silica, bentonite, asbestos, and silicates such as alumina silicate, silicon oxide, magnesium oxide, alumina, zirconium oxide, titanium oxide, and iron oxide, carbonates such as calcium carbonate, magnesium carbonate, and dolomite, sulfates such as calcium sulfate and barium sulfate, hydroxides such as calcium hydroxide, magnesium hydroxide, and aluminum hydroxide, glass beads, glass flakes, glass powder, ceramic beads, boron nitride, silicon carbide, carbon black, and silica and graphite. Among them, at least one inorganic filler selected from the group consisting of carbon black, graphite powder, vapor-grown carbon fiber, carbon nanotube, milled carbon fiber, milled glass fiber, wollastonite, talc, and mica is preferred from the viewpoints of improving adhesive strength, ease of incorporation into various resins, versatility, and economy. In particular, carbon black, carbon nanotube, wollastonite, and talc are particularly preferred from the viewpoints of adhesive properties with resins and versatility. Two or more of these inorganic fillers can also be used in combination. Furthermore, these inorganic fillers may be pretreated with a coupling agent such as an isocyanate compound, an organic silane compound, an organic titanate compound, an organic borane compound, or an epoxy compound before use.

<Composite Molded Body>
The molded article of the present invention can be made into a composite molded article by joining other members to the thermoplastic resin region present on the surface of the fiber-reinforced resin molded article. Examples of the other members include members containing thermoplastic resin. Such other members containing thermoplastic resin may contain reinforcing fibers, fillers, etc. The integration method is not particularly limited, and examples thereof include heat welding, vibration welding, ultrasonic welding, laser welding, resistance welding, induction welding, insert injection molding, and outsert injection molding. In this case, it is preferable that the thermoplastic resin contained in the other members is the same type of resin as the thermoplastic resin (C) contained in the molded article.

An example of another embodiment of the member is the fiber-reinforced resin molded product of the present invention. This is an embodiment in which the thermoplastic resin regions of the fiber-reinforced resin molded product of the present invention are joined together. By joining in this manner, since the thermoplastic resin (C) used in the fiber-reinforced resin molded product is the same type, it is easy to dissolve in the melt, and strong joining characteristics can be obtained.

<Applications>
The fiber-reinforced resin molded product of the present invention and a composite molded product using said molded product are preferably used for aircraft structural members, wind turbine blades, automobile exterior panels, IC trays, notebook computer housings, and further for sporting goods such as golf shafts and tennis rackets.

The present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited to these examples.

All measurements of various characteristics were performed in an environment with a temperature of 23°C and a relative humidity of 50%, unless otherwise noted.

<Abbreviations used in the table>
[Reinforcing fiber (A)]
CF-1
A continuous carbon fiber with a total of 24,000 single fibers obtained by spinning, baking, and surface oxidation treatment from a copolymer whose main component is polyacrylonitrile. The characteristics are as follows.
Single fiber diameter: 7 μm
Density: 1.8g/cm3
Tensile strength: 4600 MPa
Tensile modulus: 220 GPa
CF-2
A continuous carbon fiber with a total of 24,000 single fibers obtained by spinning, baking, and surface oxidation treatment from a copolymer whose main component is polyacrylonitrile. The characteristics are as follows.
Single fiber diameter: 5 μm
Density: 1.8g/cm3
Tensile strength: 5900 MPa
Tensile modulus: 294 GPa
・GF-1
A continuous E-glass fiber with a total of 1,600 single yarns that have been bundled. The characteristics are as follows:
Single fiber diameter: 13 μm
Tensile strength: 3400 MPa
Tensile modulus: 72 GPa
Tensile elongation: 3%
Density: 2.6 g/cm3.

[Thermosetting resin (B)]
・EP
Epoxy resin (more on this later)
[Thermoplastic resin (C)]
・PA
Polyamide resin (details below)
[Inorganic filler (D)]
・CNT-1
"Signis (registered trademark)" CG-200 (manufactured by Chemical Advanced Materials, Inc., average diameter 1.3 nm, center length 1 μm, aspect ratio 769)
・CNT-2
"NANOCYL (registered trademark)" NC-3000 (manufactured by Nanocyl, average diameter 9.5 nm, length 1.5 μm, aspect ratio 158)
・CB-1
"Printex (registered trademark)" L6 (manufactured by Orion Engineered Carbons, average particle size 23 nm)
・CB-2
"Ketjen Black" EC300J (manufactured by Lion Specialty Chemicals Co., Ltd., average particle size 39.5 nm)
・CB-3
"GRANOC (registered trademark)" HC-600 (manufactured by Nippon Graphite Fiber Co., Ltd., average diameter 12.5 μm, length 100 μm, aspect ratio 8)
IF-1
"Wollastonite"FPW#400 (Kinsei Matec Co., Ltd., average diameter 8 μm, average length 40 μm, aspect ratio 5)
IF-2
"Talc" JM-209 (manufactured by Asada Flour Milling Co., Ltd., average particle size 3.9 μm, aspect ratio 7)
<Evaluation method>
(1) State of inorganic filler (D) in fiber-reinforced resin molded body and aggregate structure length Using a scanning electron microscope (S-4000 manufactured by Hitachi, Ltd.), a cross section in the thickness direction of the fiber-reinforced resin molded body part of the composite structure was photographed at a magnification of 5000 times or more, and inorganic filler (D) forming aggregates (observed in the form exemplified in FIG. 3) was randomly selected and a circumscribed circle was drawn. The diameter of the circumscribed circle was measured as the structure length of the aggregate. The number of measurements was 50 (n = 50) or more, and the average value was taken as the aggregate structure length.

(2) Method for measuring the bonding strength of a fiber-reinforced resin molded body The molded body produced in each Example and Comparative Example was cut into two pieces with a width of 250 mm and a length of 92.5 mm, with the 0° direction as the length direction of the test piece, and dried in a vacuum oven for 24 hours. Thereafter, the two panels cut into a width of 250 mm and a length of 92.5 mm were overlapped with a width of 25 mm x a length of 12.5 mm, with the 0° direction as the length direction, and a pressure of 3 MPa was applied at a temperature 20° C. higher than the melting point of the thermoplastic resin (C) used, and held for 1 minute to weld the overlapped surfaces to obtain the molded product. A tab was attached to the obtained molded product in accordance with ISO4587:1995 (JIS K6850 (1994)), and the target test piece was obtained by cutting it to a width of 25 mm.

The obtained test pieces were dried in a vacuum oven for 24 hours, and a bonding strength evaluation experiment based on ISO4587:1995 (JIS K6850 (1994)) was performed. The surfaces of the test pieces that were divided after destruction were observed under a microscope, and the adhesion area of the thermoplastic resin was calculated from the image. Based on the measurement results, the following evaluation was performed.
Good: More than 80% of the thermoplastic resin (C) was attached to both fracture surfaces of the test piece.
Fair: 60% or more but less than 80% of the thermoplastic resin (C) is adhered to both fracture surfaces of the test piece, and the thermosetting resin (B) is observed on the remaining surfaces.
Bad: Less than 60% of the thermoplastic resin (C) was adhered to both fractured surfaces of the test piece, and the thermosetting resin (B) was observed on the remaining surfaces.
Worst: Thermoplastic resin (C) is 100% adhered to one of the fractured surfaces of the test piece, and thermosetting resin (B) is observed on the other surface.

(3) Method for measuring the bonding strength of a composite molded product bonded to another member The molded body produced in each Example and Comparative Example was cut into a shape of 250 mm wide and 92.5 mm long with the 0° direction as the length direction of the test piece, and dried in a vacuum oven for 24 hours. Then, it was set between the molds of an injection molding machine, and the material prepared as shown below was used as the injection molding material, and the cylinder temperature and mold temperature were set as shown in Table 4 to obtain a composite molded body that was injection molded and bonded to the surface of the thermoplastic resin (C) side in the fiber reinforced resin molded body.

NY6 Injection Material 80 parts of NY6 ("Amilan (registered trademark)" CM1007, manufactured by Toray Industries, Inc.) and 20 parts of CF-1 were put into a twin-screw extruder and mixed at 250°C to obtain pellets for injection molding. The number average fiber length of CF-1 in the pellets was 0.1 mm.

PP Injection Material 80 parts of PP (a dry blend of 79% by mass of "Prime Polypro" (registered trademark), manufactured by Prime Polymer Co., Ltd., J105G and 20% by mass of "Admer" (registered trademark) QB510, manufactured by Mitsui Chemicals, Inc.) and 20 parts of CF-1 were placed in a twin-screw extruder and heated and kneaded at 200°C to obtain pellets for injection molding. The number average fiber length of CF-1 in the pellets was 0.1 mm.

PEKK injection molding material 80 parts of PEKK ("KEPSTAN (registered trademark)" 7002, manufactured by Arkema Co., Ltd., melting point 331°C) and 20 parts of CF-1 were placed in a twin-screw extruder and heated and kneaded at 320°C to obtain pellets for injection molding. The number average fiber length of CF-1 in the pellets was 0.1 mm.

Tabs were attached to the resulting composite molding in accordance with ISO4587:1995 (JIS K6850 (1994)) and the product was cut to a width of 25 mm to obtain the desired test specimen.

The obtained test pieces were dried in a vacuum oven for 24 hours, and a bonding strength evaluation experiment was performed based on ISO4587:1995 (JIS K6850 (1994)). The surface of the test pieces divided after destruction was observed under a microscope, and the adhesion area of the thermoplastic resin was calculated from the image. Based on the measurement results, the evaluation was performed as follows. The results are shown in Table 4.
Good: More than 80% of the thermoplastic resin (C) was attached to both fracture surfaces of the test piece.
Fair: 60% or more but less than 80% of the thermoplastic resin (C) is adhered to both fracture surfaces of the test piece, and the thermosetting resin (B) is observed on the remaining surfaces.
Bad: Less than 60% of the thermoplastic resin (C) was adhered to both fractured surfaces of the test piece, and the thermosetting resin (B) was observed on the remaining surfaces.
Worst: Thermoplastic resin (C) is 100% adhered to one of the fractured surfaces of the test piece, and thermosetting resin (B) is observed on the other surface.

(4) Roughness average length RSm and roughness average height Rc of the interface curve
Using the fiber-reinforced resin molded body or composite molded product prepared above, the fiber-reinforced resin molded body was cut perpendicular to the planar direction of the fiber-reinforced resin molded body at an angle of 45 degrees in a plan view of the fiber-reinforced resin molded body with respect to any orientation direction of the reinforcing fiber [A] contained in both resin regions, using a diamond cutter. The cross section obtained by the cut was cut and polished using wet abrasive paper (#1500) to finish polish the observed cross section. An image of the cross section was taken at a magnification of 1000 times using an optical microscope. In an arbitrary observation range of 500 μm square in the obtained image, the roughness average length RSm and roughness average height Rc of the interface curve element obtained by the measurement method 1 of the interface curve element, as defined in JIS B0601 (2013), were measured.

Example 1
[Thermoplastic prepreg (PP+C)]
As polypropylene (PP) resin, 79% by mass of unmodified polypropylene resin (Prime Polymer Co., Ltd. "Prime Polypro" (registered trademark) J105G, melting point 161 ° C.) and 20% by mass of acid-modified polypropylene resin (Mitsui Chemicals Co., Ltd. "Admer" (registered trademark) QB510, melting point 164 ° C.) resin were added to a twin-screw extruder, and 1% by mass of CNT-1 was added as an inorganic filler (D). The mixture was prepared to be 100 g / m2 and sandwiched between two metal plates, and pressurized and heated together with the metal plates at a surface pressure of 3 MPa in a press machine with a hot platen temperature adjusted to 200 ° C. After 5 minutes, the pressurization of the press machine was stopped and released, and the metal plates were moved to a press machine with a hot platen temperature adjusted to 50 ° C., and pressurized and cooled at a surface pressure of 3 MPa to obtain a resin sheet (PP).

A resin sheet (PP) was placed on a reinforcing fiber sheet (193 g/m2) in which CF-1 was aligned in one direction as reinforcing fibers (A), and the sheet was heated to 200°C with an IR heater to melt the resin sheet and adhere it to the entire surface of one side of the continuous reinforcing fiber sheet. The sheet was then pressed with nip rolls whose surface temperature was kept at 80°C, below the melting point of the thermoplastic resin (C), and cooled to obtain a thermoplastic prepreg (PP+C), which is an intermediate for a fiber-reinforced resin molded product.

[Thermosetting resin film (EP)]
As the thermosetting resin (B), the same thermosetting resin (EP) as in Example 1 was coated on a release paper while adjusting the resin basis weight to 50 g/m2 using a knife coater, to produce a thermosetting resin film (EP).

[Fiber-reinforced resin molded body]
The thermosetting resin film (EP) was placed on the surface of the thermoplastic prepreg (PP+C) opposite to the surface impregnated with the resin sheet, and the intermediate was impregnated with the resin film while being heated and pressurized by a heat roll, thereby obtaining a composite prepreg for molding a fiber-reinforced resin molding.

Six sheets of the thermosetting prepreg and two sheets of the composite prepreg were laminated at [0°/90°]2s (the symbol s indicates mirror symmetry), with the orientation direction of the reinforcing fiber (A) defined as 0° and the axially perpendicular direction defined as 90°, to produce a preform. At this time, the two outermost layers on each side were laminated to form the composite prepreg, and the surface layers on both sides of the preform were arranged to form thermoplastic resin layers. This preform was set in a press molding die, and a pressure of 0.6 MPa was applied with a press machine and heated at 180°C for two hours to produce a fiber-reinforced resin molded body.

Example 2
[Thermosetting prepreg (EP)]
50 parts by mass of bisphenol A type epoxy resin ("jER" (registered trademark) 825 (manufactured by Mitsubishi Chemical Co., Ltd.)), 50 parts by mass of tetraglycidyl diaminodiphenylmethane ("Sumiepoxy (registered trademark)" ELM434 (manufactured by Sumitomo Chemical Co., Ltd.)), and 8 parts by mass of polyethersulfone ("Sumikaexcel (registered trademark)" PES5003P (manufactured by Sumitomo Chemical Co., Ltd.)) were added and heated and kneaded to dissolve the polyethersulfone. Next, while continuing the kneading, the temperature was lowered to a temperature of 100°C or less, and 45 parts by mass of 4,4'-diaminodiphenylsulfone (Seikacure S (manufactured by Wakayama Seika Kogyo Co., Ltd.)) was added and stirred to obtain a thermosetting resin (EP).

Thermosetting resin (EP) was used as the thermosetting resin (B) and coated on release paper with a resin weight of 50 g/m2 using a knife coater to produce a thermosetting resin film. This thermosetting resin film was superimposed on both sides of a reinforcing fiber sheet (weight 193 g/m2) in which carbon fiber CF-1 was aligned in one direction, and a heat roll was used to apply heat and pressure while impregnating the reinforcing fiber (A) with the thermosetting resin film to produce a thermosetting prepreg (EP).

[Resin sheet (PA+C)]
In the twin-screw extruder, 99% by mass of polyamide (PA) resin "Amilan (registered trademark)" CM4000 (manufactured by Toray Industries, Inc., ternary copolymer polyamide resin, melting point 155 ° C.) was used as the thermoplastic resin (C), and 1% by mass of CNT-2 was used as the inorganic filler (D), and the mixture was heated and kneaded at 180 ° C. The resulting kneaded product was prepared to be 100 g / m2, sandwiched between two metal plates, and pressed and heated together with the metal plates at a surface pressure of 3 MPa in a press machine with a hot platen temperature adjusted to 180 ° C. After 5 minutes, the press machine was stopped and released, and the metal plates were moved to a press machine with a hot platen temperature adjusted to 50 ° C., and pressed and cooled at a surface pressure of 3 MPa to obtain a resin sheet (PA + C).

[Fiber-reinforced resin molded body]
Next, the orientation direction of the reinforcing fiber (A) contained in the thermosetting prepreg was defined as 0°, and the axial orthogonal direction was defined as 90°, and eight thermosetting prepregs were laminated at [0°/90°]2s (the symbol s indicates mirror symmetry). Then, one resin sheet (PA+C) was placed on each side to obtain a preform. The preform was set in a press molding die, and a pressure of 0.6 MPa was applied with a press machine and heated at 180°C for 2 hours to produce a fiber-reinforced resin molded body.

<Examples 3 to 5>
A fiber-reinforced resin molded body was produced in the same manner as in Example 2, except that the inorganic filler (D) shown in Table 1 was used instead of CNT-2.

Example 6
Except for using CF-2 instead of CF-1 as the reinforcing fiber (A) and adjusting the amount of inorganic filler (D) CNT-1 to 1.7 mass% relative to the thermoplastic resin (C), a fiber-reinforced resin molded body was produced in the same manner as in Example 1.

Example 7
A fiber-reinforced resin molding was produced in the same manner as in Example 1, except that the amount of the inorganic filler (D) CNT-1 was adjusted to 0.5% by mass relative to the thermoplastic resin (C).

Example 8
A fiber-reinforced resin molded body was produced in the same manner as in Example 7, except that CF-2 was used instead of CF-1 as the reinforcing fiber (A) and CNT-2 was used as the inorganic filler (D).

<Example 9>
A fiber-reinforced resin molded body was produced in the same manner as in Example 7, except that GF-1 was used instead of CF-1 as the reinforcing fiber (A) and CNT-2 was used as the inorganic filler (D).

Example 10
[Thermosetting prepreg (EP+C)]
50 parts by mass of bisphenol A type epoxy resin ("jER" (registered trademark) 825 (manufactured by Mitsubishi Chemical Corporation)), 50 parts by mass of tetraglycidyldiaminodiphenylmethane ("Sumiepoxy" (registered trademark) ELM434 (manufactured by Sumitomo Chemical Co., Ltd.)), and 8 parts by mass of polyethersulfone ("Sumikaexcel" (registered trademark) PES5003P (manufactured by Sumitomo Chemical Co., Ltd.)) were added and heated and kneaded to dissolve the polyethersulfone, thereby obtaining a kneaded product.

Next, 1% by mass of CNT-2 was weighed out as an inorganic filler and fed into a twin-screw extruder together with the above kneaded material, and kneading was continued. Next, while continuing kneading, the temperature was lowered to 100°C or lower, and 45 parts by mass of 4,4'-diaminodiphenyl sulfone (Seikacure S (Wakayama Seika Kogyo Co., Ltd.)) was added and stirred to obtain a thermosetting resin composition containing CNT-2.

The thermosetting resin composition was coated on release paper with a knife coater at a resin weight of 50 g/m2 to produce a thermosetting resin film. This thermosetting resin film was superimposed on both sides of a reinforcing fiber sheet (weight 193 g/m2) aligned in one direction, and the thermosetting resin film was impregnated into the reinforcing fiber (A) while applying heat and pressure using a heat roll, obtaining a thermosetting prepreg (EP+C) containing inorganic filler (D).

[Resin sheet (PA)]
A resin sheet (PA) was produced using "Amilan (registered trademark)" CM4000 (manufactured by Toray Industries, Inc., ternary copolymer polyamide resin, melting point 155 ° C.) as a PA resin. The resin sheet (PA) was prepared by preparing CM4000 at 100 g / m2, sandwiching it between two metal plates, and pressing and heating it together with the metal plate at a surface pressure of 3 MPa in a press machine with a hot plate temperature adjusted to 180 ° C. After 5 minutes, the pressure of the press machine was stopped and released, and the metal plate was moved to a press machine with a hot plate temperature adjusted to 50 ° C., and pressed and cooled at a surface pressure of 3 MPa to obtain a resin sheet (PA).

Next, the thermosetting prepreg (EP+C) and the resin sheet (PA) were laminated and press molded in the same manner as in Example 1 to produce a fiber-reinforced resin molded body.

Example 11
[Thermoplastic prepreg (PP+C)]
As polypropylene (PP) resin, 79% by mass of unmodified polypropylene resin (Prime Polymer Co., Ltd. "Prime Polypro" (registered trademark) J105G, melting point 161 ° C.) and 20% by mass of acid-modified polypropylene resin (Mitsui Chemicals Co., Ltd. "Admer" (registered trademark) QB510, melting point 164 ° C.) resin were added to a twin-screw extruder, and 1% by mass of CNT-2 was added as an inorganic filler (D). The mixture was prepared to be 100 g / m2 and sandwiched between two metal plates, and pressurized and heated together with the metal plates at a surface pressure of 3 MPa in a press machine with a hot platen temperature adjusted to 200 ° C. After 5 minutes, the pressurization of the press machine was stopped and released, and the metal plates were moved to a press machine with a hot platen temperature adjusted to 50 ° C., and pressurized and cooled at a surface pressure of 3 MPa to obtain a resin sheet (PP).

A resin sheet (PP) was placed on a reinforcing fiber sheet (193 g/m2) in which CF-1 was aligned in one direction as reinforcing fibers (A), and the sheet was heated to 200°C with an IR heater to melt the resin sheet and adhere it to the entire surface of one side of the continuous reinforcing fiber sheet. The sheet was then pressed with nip rolls whose surface temperature was kept at 80°C, below the melting point of the thermoplastic resin (C), and cooled to obtain a thermoplastic prepreg (PP+C), which is an intermediate for a fiber-reinforced resin molded product.

[Thermosetting resin film (EP)]
As the thermosetting resin (B), the same thermosetting resin (EP) as in Example 1 was coated on a release paper while adjusting the resin basis weight to 50 g/m2 using a knife coater, to produce a thermosetting resin film (EP).

[Fiber-reinforced resin molded body]
The thermosetting resin film (EP) was placed on the surface of the thermoplastic prepreg (PP+C) opposite to the surface impregnated with the resin sheet, and the intermediate was impregnated with the resin film while being heated and pressurized by a heat roll, thereby obtaining a composite prepreg for molding a fiber-reinforced resin molding.

Six sheets of the thermosetting prepreg and two sheets of the composite prepreg were laminated at [0°/90°]2s (the symbol s indicates mirror symmetry), with the orientation direction of the reinforcing fiber (A) defined as 0° and the axially perpendicular direction defined as 90°, to produce a preform. At this time, the two outermost layers on each side were laminated to form the composite prepreg, and the surface layers on both sides of the preform were arranged to form thermoplastic resin layers. This preform was set in a press molding die, and a pressure of 0.6 MPa was applied with a press machine and heated at 180°C for two hours to produce a fiber-reinforced resin molded body.

Example 12
[Thermoplastic prepreg (NY6+C)]
In a twin-screw extruder, "Amilan (registered trademark)" CM1007 (manufactured by Toray Industries, Inc., melting point 225 ° C.) was prepared to be 99% by mass, and CNT-2 was prepared to be 1% by mass as an inorganic filler (D), and was heated and kneaded at 250 ° C. The obtained kneaded product was prepared to be 100 g / m2, sandwiched between two metal plates, and pressurized and heated together with the metal plates at a surface pressure of 3 MPa in a press machine with a hot platen temperature adjusted to 250 ° C. After 5 minutes, the pressurization of the press machine was stopped and released, and the metal plates were moved to a press machine with a hot platen temperature adjusted to 80 ° C., and pressed and cooled at a surface pressure of 3 MPa to form a sheet, and a resin sheet (NY6) was produced.

A resin sheet made of thermoplastic resin (C) was placed on a reinforcing fiber sheet (193 g/m2) in which CF-1 reinforcing fibers (A) were aligned in one direction, and the sheet was heated to 250°C with an IR heater to melt the resin sheet and adhere it to the entire surface of one side of the continuous reinforcing fiber sheet. The sheet was then pressed with nip rolls kept at 80°C, which is below the melting point of (C), and cooled to obtain a thermoplastic prepreg (NY6+C), which is an intermediate for a fiber-reinforced resin molded product.

[Fiber-reinforced resin molded body]
A thermosetting resin film (EP) produced by the method described in Example 11 was laminated on the surface of the thermoplastic prepreg (NY6+C) opposite to the surface impregnated with the resin sheet, and the resin film was impregnated into the intermediate while heating and pressurizing with a heat roll, thereby obtaining a composite prepreg for molding a fiber-reinforced resin molded body.

Six sheets of the thermosetting prepreg and two sheets of the composite prepreg were laminated at [0°/90°]2s (the symbol s indicates mirror symmetry), with the orientation direction of the reinforcing fiber (A) defined as 0° and the axially perpendicular direction defined as 90°, to produce a preform. At this time, the two outermost layers on each side were laminated to form the composite prepreg, and the surface layers on both sides of the preform were arranged to form thermoplastic resin layers. This preform was set in a press molding die, and a pressure of 0.6 MPa was applied with a press machine and heated at 180°C for two hours to produce a fiber-reinforced resin molded body.

Example 13
[Thermoplastic prepreg (PEKK+C)]
In a twin-screw extruder, "KEPSTAN (registered trademark)" 7002 (manufactured by Arkema Co., Ltd., melting point 331 ° C.) was prepared to 99 mass%, CNT-2 was prepared as an inorganic filler (D) to 1 mass%, and heated and kneaded at 350 ° C. The obtained kneaded product was prepared to 100 g / m2, sandwiched between two metal plates, and pressurized and heated together with the metal plates at a surface pressure of 3 MPa in a press machine with a hot platen temperature adjusted to 350 ° C. After 5 minutes, the pressurization of the press machine was stopped and released, and the metal plates were moved to a press machine with a hot platen temperature adjusted to 120 ° C., and pressed and cooled at a surface pressure of 3 MPa to form a sheet, and a resin sheet (PEKK) was produced.

A resin sheet made of thermoplastic resin (C) was placed on a reinforcing fiber sheet (weight 193 g/m2) in which CF-1 was aligned in one direction as reinforcing fiber (A), and the sheet was heated to 350°C with an IR heater to melt the resin sheet and adhere it to the entire surface of one side of the continuous reinforcing fiber sheet. The sheet was then pressed with nip rolls kept at 120°C, which is below the melting point of (C), and cooled to obtain a thermoplastic prepreg (PEKK+C), which is an intermediate for a fiber-reinforced resin molded body.

[Thermosetting resin film (EP+C)]
50 parts by mass of bisphenol A type epoxy resin ("jER" (registered trademark) 825 (manufactured by Mitsubishi Chemical Corporation)), 50 parts by mass of tetraglycidyldiaminodiphenylmethane ("Sumiepoxy" (registered trademark) ELM434 (manufactured by Sumitomo Chemical Co., Ltd.)), and 8 parts by mass of polyethersulfone ("Sumikaexcel" (registered trademark) PES5003P (manufactured by Sumitomo Chemical Co., Ltd.)) were added and heated and kneaded to dissolve the polyethersulfone, thereby obtaining a kneaded product.

Next, 1% by mass of CNT-2 was weighed out as an inorganic filler and put into a twin-screw extruder together with the above kneaded product, and kneading was continued. Next, while continuing kneading, the temperature was lowered to 100°C or less, and 45 parts by mass of 4,4'-diaminodiphenyl sulfone (Seikacure S (Wakayama Seika Kogyo Co., Ltd.)) was added and stirred to obtain a thermosetting resin composition containing CNT-2. The thermosetting resin composition was coated on release paper using a knife coater while adjusting the resin basis weight to 50 g/m2, and a thermosetting resin film (EP+C) was produced.

[Fiber-reinforced resin molded body]
The thermosetting resin film (EP+C) was superimposed on the surface of the thermoplastic prepreg (PEKK+C) opposite to the surface impregnated with the resin sheet, and the intermediate was impregnated with the resin film while being heated and pressurized with a heat roll, thereby obtaining a composite prepreg for molding a fiber-reinforced resin molded body.

Six sheets of the thermosetting prepreg and two sheets of the composite prepreg were laminated at [0°/90°]2s (the symbol s indicates mirror symmetry), with the orientation direction of the reinforcing fiber (A) defined as 0° and the axially perpendicular direction defined as 90°, to produce a preform. At this time, the two outermost layers on each side were laminated to form the composite prepreg, and the surface layers on both sides of the preform were arranged to form thermoplastic resin layers. This preform was set in a press molding die, and a pressure of 0.6 MPa was applied with a press machine and heated at 180°C for two hours to produce a fiber-reinforced resin molded body.

<Example 14>
A fiber-reinforced resin molding was produced in the same manner as in Example 3, except that the blending amount of the inorganic filler (D) CB-1 was 5 mass %.

Example 15
A thermosetting prepreg (EP+C) was produced in the same manner as in Example 10, except that CB-3 was used as the inorganic filler (D) and the amount of the filler blended with the thermosetting resin (B) was 5% by mass.

A resin sheet (PA+C) was produced in the same manner as described in Example 5, except that the amount of inorganic filler (D) CB-3 was adjusted to 5 mass%.

Next, the orientation direction of the reinforcing fibers contained in the thermosetting prepreg (EP+C) was defined as 0°, and the direction perpendicular to the axis was defined as 90°, and eight thermosetting prepregs were laminated at [0°/90°]2s (the symbol s indicates mirror symmetry). A resin sheet (PA+C) was then placed on each side of the prepreg to obtain a preform. The preform was set in a press molding die, and a pressure of 0.6 MPa was applied with a press machine and heated at 180°C for two hours to produce a fiber-reinforced resin molded body.

<Example 16>
A fiber-reinforced resin molded body was produced in the same manner as in Example 1 except that IF-1 was used instead of CNT-1 as the inorganic filler (D) and the amount blended into the thermoplastic resin sheet was 2% by mass.

<Example 17>
A fiber-reinforced resin molded body was produced in the same manner as in Example 1 except that IF-2 was used instead of CNT-1 as the inorganic filler (D) and the amount blended into the thermoplastic resin sheet was 2% by mass.

<Comparative Example 1>
A substrate to be used for a fiber-reinforced resin molded product and a molded product were prepared in the same manner as in Example 1 except that the inorganic filler (D) was not blended, and were subjected to evaluation.

<Comparative Example 2>
In the same manner as in Example 1, a thermosetting prepreg (EP) and a resin sheet (PA+C) were prepared.

Eight sheets of the thermosetting prepreg were laminated at [0°/90°]2s (the symbol s indicates mirror symmetry), with the orientation direction of the reinforcing fibers defined as 0° and the direction perpendicular to the axis defined as 90°, and then set in a press molding die. A pressure of 0.6 MPa was applied using a press machine, and the prepreg was heated at 180°C for two hours to harden the prepreg, yielding a thermosetting resin molded body.

Then, thermoplastic resin sheets were placed on both sides of the thermosetting resin molded body, and the body was set on a press molding platen surface adjusted to the temperature at which the thermoplastic resin (C) melts (180°C). A pressure of 0.6 MPa was applied using a press machine, and the body was heated at 150°C for 5 minutes to adhere the thermosetting resin molded body and the thermoplastic resin sheets together, producing a fiber-reinforced resin molded body.

<Consideration>
The outline and evaluation results of each of the examples and comparative examples are shown in Tables 1 to 4.

Comparing Examples 1 to 17 and Comparative Examples 1 and 2, when inorganic filler (D) is used in the fiber-reinforced resin molding, and the shape of the reinforcing fiber (A) and the shape of the inorganic filler (D) at the boundary surface between the thermosetting resin (B) and the thermoplastic resin (C) in the fiber-reinforced resin molding satisfy the range of the present invention, and the aggregate structure length, roughness average length RSm, and roughness average height Rc of the inorganic filler (D) are satisfied, the bond strength evaluation was satisfactory. Furthermore, when the fracture surface after the bond strength evaluation was observed, thermoplastic resin (C) was observed on both sides of the test piece after fracture, and the bond strength was equal to or greater than the strength of the thermoplastic resin (C), so it was clear that sufficient bond strength was provided.

In particular, the effect of adding inorganic filler (D) became clear by comparing Example 1 with Comparative Example 1. Furthermore, in Examples 1 to 5, by satisfying the amount of inorganic filler (D) added and the length of the aggregate structure, it was possible to achieve the improvement in bonding strength, which is the objective of the present invention, regardless of the type of inorganic filler.

It became clear that there was an optimum amount of inorganic filler (D) to be blended, as compared with Examples 6, 7, 16, and 17 and Examples 14 and 15. This was thought to be because, since the fracture surface of the test piece in the adhesion evaluation was destroyed by the thermosetting resin (B), the length of the aggregated structure increased due to the blending amount of inorganic filler (D) being excessive, and the boundary surface between the thermosetting resin region and the thermoplastic resin region became weak.

In Comparative Example 2, the thermoplastic resin (C) was applied to an intermediate product obtained by previously curing the thermosetting resin (B) blended in the fiber-reinforced resin molded body, but the effect was limited. This was thought to be because the reinforcing fiber (A) could not be shared at the boundary between the thermosetting resin region and the thermoplastic resin region in the fiber-reinforced resin molded body.

Compared with Example 2 and Examples 11 to 13, it was suggested that, according to the present invention, it is possible to use thermoplastic resins (C) with different melting points as adhesive layers without being significantly affected by the type of thermoplastic resin.

The fiber-reinforced resin molded body and its composite molded body according to the present invention can provide a fiber-reinforced resin molded body having a thermoplastic resin welding layer and high bonding properties with thermoplastic resin, and a composite molded body using the same.

1: Fiber-reinforced resin molding 2: Reinforced fiber (A)
3: Thermosetting resin (B) or thermoplastic resin (C)
4: Orientation direction of any fiber bundle 5: Cross-sectional observation surface 6: Reinforcement fiber (A)
7: Thermosetting resin (B ) region 8: Thermoplastic resin (C ) region 9: Observed image 10: Boundary 11: Reference line 12: Vertical base line 13: Interface curve 14: Inorganic filler (D)
15: Aggregate of inorganic filler (D) 16: Inorganic filler (D)
17: Circumscribed circle L: length of coagulation structure

Claims (10)

A fiber-reinforced resin molded body comprising reinforcing fibers (A), a thermosetting resin (B), a thermoplastic resin (C) and an inorganic filler (D),
A reinforcing fiber group composed of continuous reinforcing fibers (A) is composited with a matrix resin having a thermosetting resin (B) region and a thermoplastic resin (C) region,
The thermosetting resin (B) region and the thermoplastic resin (C) region form a layer structure,
The average aggregate structure length of the inorganic filler (D) is not more than twice the single fiber diameter of the reinforcing fiber (A);
A portion of the reinforcing fiber (A) and a portion of the inorganic filler (D) are in contact with both the thermosetting resin (B) region and the thermoplastic resin (C) region, and the thermoplastic resin (C) region is present on at least one surface. A fiber-reinforced resin molded body. When a cross section perpendicular to the plane of the fiber-reinforced resin molded body is obtained from a direction at an angle of 45 degrees different from the orientation direction of the reinforcing fibers (A), the interface curve formed by the boundary between the thermosetting resin (B) region and the thermoplastic resin (C) region in the cross section has a roughness average length RSm defined in JIS B0601 (2013) of 100 μm or less and a roughness average height Rc of 3.5 μm or more. The fiber-reinforced resin molded body according to claim 1 . The fiber-reinforced resin molding according to claim 1 or 2 , wherein the inorganic filler (D) has an aspect ratio of 5 or more. The fiber-reinforced resin molded body according to any one of claims 1 to 3 , wherein the inorganic filler (D) is contained in a range of 0.01 to 2.0 mass% relative to 100 mass% of the fiber-reinforced resin molded body. The fiber-reinforced resin molding according to any one of claims 1 to 4, wherein the inorganic filler (D) is at least one selected from the group consisting of carbon black, graphite powder, vapor -grown carbon fiber, carbon nanotubes, milled carbon fiber, milled glass fiber, wollastonite, talc, and mica. The fiber-reinforced resin molding according to any one of claims 1 to 5 , wherein the reinforcing fiber (A) is at least one selected from the group consisting of carbon fiber and glass fiber. The fiber-reinforced resin molding according to any one of claims 1 to 6, wherein the thermosetting resin (B) is at least one thermosetting resin selected from the group consisting of epoxy, phenol, unsaturated polyester, vinyl ester, thermosetting polyimide, cyanate ester resin, bismaleimide resin , and benzoxazine resin. The fiber-reinforced resin molding according to any one of claims 1 to 7 , wherein the thermoplastic resin (C) is a thermoplastic resin that is in a molten state within the curing reaction temperature range of the thermosetting resin (B). The fiber-reinforced resin molded body according to any one of claims 1 to 8 , wherein the thermoplastic resin (C) region covers 50% or more of an area of the surface layer. A composite molded body obtained by bonding another member to a surface of the thermoplastic resin (C) in the fiber-reinforced resin molded body according to any one of claims 1 to 9 by heating.

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