Thermoplastic resin composition, thermoplastic resin film, prepreg and fiber-reinforced composite material, and method for producing prepreg and fiber-reinforced composite material

Abstract

The present invention provides a thermoplastic resin composition which is characterized by containing a thermoplastic resin and 0.001 part by mass to 5.0 parts by mass of an inorganic filler relative to 100 parts by mass of the thermoplastic resin, and which is also characterized in that: the thermoplastic resin has a crystal melting point (Tm) of 200°C or higher, or a glass transition temperature (Tg) of 140°C or higher; and the inorganic filler has a plate-like shape.

Description

[Technical Field]

[0001] The present invention relates to a thermoplastic resin composition, a thermoplastic resin film, a prepreg and a fiber-reinforced composite material, and a method for producing the prepreg and the fiber-reinforced composite material. More specifically, the present invention relates to a thermoplastic resin composition containing an inorganic filler of a predetermined shape, a thermoplastic resin film, a prepreg and a fiber-reinforced composite material, and a method for producing the prepreg and the fiber-reinforced composite material. [Background technology]

[0002] Fiber-reinforced composite materials, obtained by combining reinforcing fiber materials such as carbon fiber, glass fiber, and aramid fiber with various matrix resins, are widely used in a variety of fields and applications. Traditionally, in the aerospace and industrial fields, where high mechanical properties and heat resistance are required, thermosetting resins such as unsaturated polyester resin, epoxy resin, and polyimide resin have been mainly used as the matrix resin.

[0003] However, these thermosetting resins have drawbacks such as brittleness and poor impact resistance. Therefore, particularly in the aerospace industry, thermoplastic resins are being considered as matrix resins from the perspectives of the impact resistance of the resulting fiber-reinforced composite materials and molding costs.

[0004] Among thermoplastic resins, polyaryletherketones (PAEKs) such as polyetheretherketone (PEEK) and polyetherketoneketone (PEKK) are expected to play a key role in the aerospace industry due to their excellent heat resistance, chemical resistance, and mechanical strength.

[0005] However, since polyaryletherketones have high melting points, it may be difficult to produce prepregs or process composite materials using the prepregs. Therefore, in order to lower the melting points of polyaryletherketones, the use of copolymerized polyaryletherketones containing a resorcinol skeleton, a biphenol skeleton, or an isophthalic acid skeleton has been investigated.

[0006] Improvement of the mechanical properties of such polyaryl ether ketones has been studied for some time, and examples in which non-fibrous inorganic fillers are added are known. Patent Document 1 discloses that adding sheet-like graphene material improves crystallinity and enhances tensile modulus and mechanical heat resistance. However, this effect comes at the cost of significant degradation of elongation at break and impact resistance. Patent Document 2 discloses that the addition of boron nitride improves the tensile modulus, elongation at break, and mechanical heat resistance. On the other hand, although the impact resistance of the resin composition is not impaired, no significant improvement is observed. Furthermore, although fiber-reinforced composite materials reinforced and filled with short carbon fibers are exemplified, it has been shown that these have little effect on improving the properties of the resin. Although studies have been conducted to improve the mechanical properties of thermoplastic resin compositions, the amount of filler added is relatively large, at only a few percent, and does not contribute to improving toughness factors such as impact resistance, and furthermore, it is unlikely to contribute to the toughness of fiber-reinforced composite materials. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Special Publication 2013-539808 [Patent Document 2] Special Publication 2016-503826 Summary of the Invention [Problem to be solved by the invention]

[0008] According to the investigations of the present inventors, it has been found that when a thermoplastic resin is used as a matrix resin, particularly when a copolymerized polyaryl ether ketone is used, the adhesion between layers of the fiber substrate in the resulting fiber-reinforced composite material may be insufficient. An object of the present invention is to solve the problems of the prior art and to provide a fiber-reinforced composite material having high mode I interlaminar toughness (GIc) and a method for producing the same, as well as to provide a thermoplastic resin composition, a thermoplastic resin film, and a prepreg for producing such a fiber-reinforced composite material, and a method for producing the prepreg. [Means for solving the problem]

[0009] As a result of extensive research into the above-mentioned problems, the present inventors have found that the mode I interlaminar toughness (GIc) of a fiber-reinforced composite material can be improved by blending a predetermined amount of a plate-like inorganic filler into the matrix resin of the fiber-reinforced composite material, and have thus completed the present invention.

[0010] The present invention that solves the above problems will be described below.

[0011] [1] A thermoplastic resin; 0.001 to 5.0 parts by mass of an inorganic filler relative to 100 parts by mass of the thermoplastic resin; and A thermoplastic resin composition, wherein the inorganic filler has a plate-like shape.

[0012] [2] The thermoplastic resin composition according to [1], wherein the thermoplastic resin is a copolymerized polyaryl ether ketone.

[0013] [3] The thermoplastic resin composition according to [1] or [2], wherein the inorganic filler is one or more substances selected from the group consisting of carbonaceous substances, silicate minerals, and nitride substances.

[0014] [4] The thermoplastic resin composition according to [3], wherein the carbon substance is graphene or graphite.

[0015] [5] The thermoplastic resin composition according to [3], wherein the silicate mineral is talc or montmorillonite.

[0016] [6] The thermoplastic resin composition according to [3], wherein the nitride substance is boron nitride.

[0017] The thermoplastic resin compositions described in the above [1] to [6] are thermoplastic resin compositions containing a thermoplastic resin and an inorganic filler of a predetermined shape at a predetermined ratio. When the matrix resin of the composite material is a copolymerized polyaryletherketone, the effect of improving mode I interlaminar toughness (GIc) is particularly enhanced by having this thermoplastic resin composition present at least between the layers of the fiber substrate. The inorganic filler is preferably an inorganic filler having a plate-like shape such as a plate-like carbon material, a plate-like silicate mineral, or a plate-like nitride material, and is particularly preferably graphene, graphite, talc, montmorillonite, or boron nitride.

[0018] [7] A thermoplastic resin film, characterized in that the thermoplastic resin composition according to any one of [1] to [6] is formed into a sheet having a thickness of 10 to 200 μm.

[0019] The thermoplastic resin film described in [7] above can be used when the thermoplastic resin composition is impregnated into a reinforcing fiber substrate as a matrix resin, and can also be used as a resin adhesive film that is placed between prepreg layers and molded, or as a coating film that covers the surface of a prepreg.

[0020] [8] A reinforcing fiber substrate composed of reinforcing fibers; The thermoplastic resin composition according to any one of [1] to [6] impregnated into the reinforcing fiber substrate; A prepreg comprising:

[0021] [9] A method for producing a prepreg, comprising impregnating a reinforcing fiber substrate made of reinforcing fibers with the thermoplastic resin composition according to any one of [1] to [6].

[0022]

[10] A reinforcing fiber substrate composed of reinforcing fibers; The thermoplastic resin composition according to any one of [1] to [6] impregnated into the reinforcing fiber substrate; A fiber-reinforced composite material comprising:

[0023]

[11] A method for producing a fiber-reinforced composite material, characterized by disposing the thermoplastic resin film according to [7] between reinforcing fiber substrates and hot-molding the resultant.

[0024]

[12] A method for producing a fiber-reinforced composite material, characterized by hot molding the prepreg according to [8].

[0025] The inventions described in [8] to

[12] above are prepregs or fiber-reinforced composite materials obtained by impregnating a reinforcing fiber substrate with a thermoplastic resin composition. This fiber-reinforced composite material has improved mode I interlaminar toughness (GIc) because the thermoplastic resin composition contains a plate-shaped inorganic filler. [Effects of the Invention]

[0026] The thermoplastic resin composition, thermoplastic resin film, and prepreg of the present invention contain an inorganic filler of a predetermined shape, and therefore can produce a fiber-reinforced composite material with high mode I interlaminar toughness (GIc). The thermoplastic resin composition of the present invention does not improve mechanical properties such as crystallinity, tensile properties, or impact resistance when used alone. Nevertheless, when the thermoplastic resin composition is disposed at least between layers of a reinforcing fiber substrate in a fiber-reinforced composite material, it significantly improves interlaminar adhesion and exhibits high mode I interlaminar toughness (GIc). DETAILED DESCRIPTION OF THE INVENTION

[0027] The thermoplastic resin composition, thermoplastic resin film, prepreg and fiber-reinforced composite material, and methods for producing the prepreg and fiber-reinforced composite material of the present invention will be described below.

[0028] 1. Thermoplastic resin composition The thermoplastic resin composition of the present invention comprises: A thermoplastic resin, 0.001 to 5.0 parts by mass of an inorganic filler relative to 100 parts by mass of the thermoplastic resin; and The thermoplastic resin composition is characterized in that the inorganic filler has a plate-like shape.

[0029] From the viewpoint of excellent heat resistance of the resulting fiber-reinforced composite material, the thermoplastic resin is preferably a thermoplastic resin having a crystalline melting point (Tm) of 200°C or higher, more preferably 280°C or higher, and particularly preferably 300°C or higher. The upper limit of the crystalline melting point (Tm) is not particularly limited, but from the viewpoint of processability, etc., it is preferably 400°C or lower, more preferably 360°C or lower, and particularly preferably 340°C or lower. Furthermore, the thermoplastic resin used in the present invention is not limited to a thermoplastic resin having a crystalline melting point (Tm) and may be an amorphous thermoplastic resin. In the case of an amorphous thermoplastic resin, from the viewpoint of heat resistance, it is preferably a thermoplastic resin having a glass transition temperature (Tg) of 140°C or higher. Furthermore, from the viewpoint of processability, it is preferably a thermoplastic resin having a glass transition temperature (Tg) of 280°C or lower.

[0030] Examples of such thermoplastic resins include polyphenylene sulfide, polycarbonate, polyethersulfone, polyamide, polyaryletherketone (PAEK), polyphthalamide, etc. Among these, polyaryletherketone (PAEK) such as polyetherketone (PEK), polyetherketoneketone (PEKK), polyetheretherketone (PEEK), polyetheretherketoneketone (PEEKK), and polyetherketoneetherketoneketone (PEKEKK), as well as polycarbonate and polyethersulfone, are preferred due to their excellent melt moldability, heat resistance, chemical resistance, and mechanical strength. Among polyaryletherketone (PAEK), copolymerized polyaryletherketone (copolymerized PAEK) containing a resorcinol skeleton, biphenol skeleton, or isophthalic acid skeleton is preferred. Copolymerized polyaryletherketones have a lower melting point than other polyaryletherketones, resulting in excellent melt moldability. Furthermore, such copolymerized polyaryletherketones have a lower mode I interlaminar toughness (GIc) than other polyaryletherketones, and therefore the effects of the present invention are more pronounced.

[0031] The copolymerized polyaryl ether ketones include those represented by the following chemical formula (1):

[0032] [ka]

[0033] (wherein, in chemical formula (1), X and Y each represent one of the following chemical formulas (2) to (5))

[0034] [ka]

[0035] [ka]

[0036] [ka]

[0037] [ka]

[0038] and a polyether ether ketone copolymer having a structural unit represented by the following chemical formula (6):

[0039] [ka]

[0040] An example of a commercially available product is a polyether ketone ketone copolymer having a structural unit represented by the following formula:

[0033] An example of a commercially available product is "KEPSTAN" manufactured by Arkema.

[0041] The melt viscosity of the thermoplastic resin at 350° C. is preferably from 1 to 3000 Pa·s, more preferably from 100 to 1000 Pa·s, and even more preferably from 100 to 600 Pa·s.

[0042] The inorganic filler used in the thermoplastic resin composition of the present invention must have a plate-like shape. Here, the term "plate-like" encompasses flat, disc-like, and layered shapes formed by stacking these. Specifically, the inorganic filler used in the thermoplastic resin composition of the present invention is an inorganic filler having a three-dimensional dimensional ratio of 2 or more. The dimensional ratio here refers to the ratios x / z and y / z of the dimensions of the smallest dimension of the three-dimensional body, where z is the dimension having the smallest dimension and x and y are the dimensions in directions perpendicular to z and y. Each of these dimensional ratios is preferably 5 or more, more preferably 10 or more, and even more preferably 15 or more.

[0043] Because the inorganic filler is present between layers of the reinforcing fiber substrate and its large dimension ratio, the fracture stress is concentrated at the ends of the inorganic filler, facilitating crack propagation within the thermoplastic resin phase. As a result, fracture at the reinforcing fiber interface is suppressed, and the fracture energy applied between the layers is mitigated by the interface between the thermoplastic resin and the inorganic filler and by the stretching of the thermoplastic resin itself, resulting in high mode I interlaminar toughness (GIc). When the dimension ratio is less than 2, the fracture energy applied between the layers propagates sequentially to adjacent inorganic filler particles in the thickness direction, reaching the interface between the thermoplastic resin and the reinforcing fiber. The energy then propagates through the reinforcing fiber, leading to delamination at the interface between the thermoplastic resin and the reinforcing fiber, which is likely to reduce mode I interlaminar toughness (GIc).

[0044] The inorganic filler is preferably one or more substances selected from the group consisting of carbonaceous materials, silicate minerals, and nitride materials. Examples include plate-like carbonaceous materials such as graphene and flake graphite, plate-like silicate minerals such as pyrophyllite, talc, montmorillonite, nontronite, saponite, vermiculite, mica minerals, chlorite minerals, kaolin minerals, and serpentine minerals, and nitride materials such as boron nitride. Among these, graphene, flake graphite, talc, montmorillonite, and boron nitride are preferred. These may be used alone or in combination. Furthermore, these may be subjected to thermal, electrical, or chemical surface treatment to improve wettability with thermoplastic resins.

[0045] The size of the inorganic filler is preferably such that the average dimension in the longest dimension of the three-dimensional body is 0.1 μm or more, more preferably 0.5 μm or more, and particularly preferably 1.0 μm or more, and the upper limit of the average dimension in the longest dimension is preferably 30 μm or less, more preferably 20 μm or less, and particularly preferably 5.0 μm or less. The size of the inorganic filler is preferably such that the average dimension in the shortest dimension of the three-dimensional body is 1.0 μm or less, more preferably 100 nm or less, and particularly preferably 50 nm or less, and the lower limit of the average dimension in the shortest dimension is preferably 1.0 nm or more, more preferably 2.0 nm or more, and particularly preferably 3.0 nm or more. When the content is within this range, the inorganic filler is less likely to be separated by filtration through the reinforcing fiber substrate when producing a prepreg or fiber-reinforced composite material, and impregnation of the reinforcing fiber substrate is less likely to be hindered.

[0046] The blending ratio of the inorganic filler is 0.001 to 5.0 parts by mass, preferably 0.10 to 2.5 parts by mass, and more preferably 0.20 to 2.0 parts by mass, per 100 parts by mass of the thermoplastic resin. If the blending ratio is less than 0.001 part by mass, the mode I interlaminar toughness (GIc) will not be sufficiently high. If the blending ratio exceeds 5.0 parts by mass, the impregnation into the reinforcing fiber substrate will be reduced and the resin will be prone to brittle fracture during peeling.

[0047] The thermoplastic resin composition of the present invention contains the above-mentioned thermoplastic resin and inorganic filler as essential components, and may contain other optional components. For example, it may contain other thermoplastic resins, spherical fillers, organic fillers, and colorants. It is preferable that the resin composition of the present invention does not contain a thermosetting resin. The thermoplastic resin composition of the present invention preferably contains the above-mentioned thermoplastic resin and inorganic filler in an amount of 60% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 99% by mass or more, based on the total amount of the thermoplastic resin composition, and may naturally contain 100% by mass. The thermoplastic resin composition of the present invention preferably has a melt viscosity at 350°C of 1 to 3000 Pa·s, more preferably 100 to 1000 Pa·s, and even more preferably 100 to 600 Pa·s.

[0048] The thermoplastic resin composition of the present invention can be produced by mixing the above-mentioned thermoplastic resin particles and inorganic filler. The thermoplastic resin particles and inorganic filler may be mixed without heating, in which case the thermoplastic resin and inorganic filler are integrated by heating during prepreg production or molding of the fiber-reinforced composite material. Alternatively, the thermoplastic resin and inorganic filler may be mixed by heating at a temperature equal to or higher than the melting temperature of the thermoplastic resin. Here, the melting temperature of the thermoplastic resin means the melting point if the thermoplastic resin is a crystalline thermoplastic resin, and means the glass transition temperature if the thermoplastic resin is an amorphous thermoplastic resin. Any known kneading device can be used, including, for example, a roll mill, a planetary mixer, a kneader, an extruder, a Banbury mixer, a mixing vessel equipped with stirring blades, and a horizontal mixing tank.

[0049] The thermoplastic resin composition of the present invention is used to bond reinforcing fiber substrates. Bonding here refers to disposing the thermoplastic resin composition between at least the layers of reinforcing fiber substrates, adhering the reinforcing fiber substrates together, and molding them into a desired shape to obtain a fiber-reinforced composite material containing the thermoplastic resin composition of the present invention between at least the layers of the reinforcing fiber substrates. Specific bonding methods include a method in which the thermoplastic resin composition of the present invention is impregnated into the interior of a reinforcing fiber substrate by a conventionally known method to form a prepreg, and a method in which the thermoplastic resin composition of the present invention is disposed between layers of a prepreg made of a conventionally known resin composition and then molded.

[0050] 2. Thermoplastic resin film The thermoplastic resin film of the present invention is formed by forming the above-mentioned thermoplastic resin composition of the present invention into a sheet. The thickness of the thermoplastic resin film is 10 to 200 μm, and preferably 15 to 150 μm.

[0051] The method for producing the thermoplastic resin film of the present invention is not particularly limited, and any conventionally known method can be used. Specifically, the film can be produced by casting a resin composition onto a support such as release paper or film using die extrusion, an applicator, a reverse roll coater, a comma coater, a melt press, or the like. The resin temperature during film production is appropriately determined depending on the composition and viscosity of the resin.

[0052] 3. Prepreg The prepreg of the present invention is characterized in that the thermoplastic resin composition of the present invention is impregnated into a reinforcing fiber substrate made of reinforcing fibers.

[0053] Examples of reinforcing fibers that can be used include known reinforcing fibers such as carbon fiber, glass fiber, aramid fiber, silicon carbide fiber, polyester fiber, ceramic fiber, alumina fiber, boron fiber, metal fiber, mineral fiber, rock fiber, and slag fiber. Among these reinforcing fibers, carbon fiber, glass fiber, and aramid fiber are preferred. Carbon fiber is more preferred because it has good specific strength and specific modulus, and can provide a lightweight, high-strength fiber-reinforced composite material. Polyacrylonitrile (PAN)-based carbon fiber is particularly preferred because it has excellent tensile strength.

[0054] The reinforcing fiber substrate is preferably formed into a sheet. Examples of reinforcing fiber sheets include sheets in which a large number of reinforcing fibers are aligned in one direction, bidirectional fabrics such as plain weave and twill weave, multiaxial fabrics, nonwoven fabrics, mats, knits, braids, and paper made from reinforcing fibers. Among these, the use of unidirectionally aligned sheets in which the reinforcing fibers are formed into a sheet as continuous fibers, bidirectional fabrics, and multiaxial fabric substrates is preferred because they provide fiber-reinforced composite materials with superior mechanical properties. The thickness of the sheet-like reinforcing fiber substrate is preferably 0.01 to 3 mm, more preferably 0.1 to 1.5 mm.

[0055] In the prepreg of the present invention, the volume content of the fibers constituting the reinforcing fiber substrate is preferably 40 to 85%. Note that the volume content of fibers here refers to the volume content of fibers that contribute to maintaining the shape of the reinforcing fiber substrate. When a fibrous material such as short fiber is added as a filler, the volume content of the fibrous material is not included.

[0056] In the prepreg of the present invention, the thermoplastic resin composition of the present invention is impregnated into the reinforcing fiber substrate, and it is preferable that the inorganic filler contained in the thermoplastic resin composition is uniformly dispersed within the reinforcing fiber substrate layer. That is, when the thermoplastic resin composition is impregnated into the reinforcing fiber layer, it is preferable that the inorganic filler contained in the thermoplastic resin composition is filtered by the reinforcing fiber substrate so that the inorganic filler is not localized on the surface of the reinforcing fiber substrate. The surface of the reinforcing fiber substrate becomes the interlayer of the fiber-reinforced composite material. If the inorganic filler is localized on the surface of the reinforcing fiber substrate, the blending amount of the inorganic filler between the layers of the reinforcing fiber substrate becomes inappropriate, which may impair the toughness of the fiber-reinforced composite material. For example, the difference between the content of the inorganic filler on the surface of the reinforcing fiber substrate (between the layers in the fiber-reinforced composite material) and the content of the inorganic filler impregnated within the reinforcing fiber substrate layer is preferably no more than 50%, and more preferably no more than 20%.

[0057] The method for producing the prepreg of the present invention is not particularly limited, and any conventionally known method can be used. Specifically, the hot melt method and the solvent method can be preferably used. The hot melt method is a method in which the thermoplastic resin composition of the present invention is applied in the form of a thin film onto release paper to form a resin composition film, and then the formed film is peeled off from the release paper to obtain a resin composition film. Thereafter, the resin composition film is laminated on a reinforcing fiber substrate and heated under pressure to impregnate the resin composition into the reinforcing fiber substrate layer. The solvent method is a method in which a thermoplastic resin composition is made into a varnish using an appropriate solvent, and the varnish is impregnated into the reinforcing fiber substrate layer. Among these conventional methods, the hot melt method is preferred because it does not use a solvent.

[0058] 4. Fiber-reinforced composite materials The fiber-reinforced composite material of the present invention comprises: The thermoplastic resin composition of the present invention is characterized by comprising a reinforcing fiber substrate made of reinforcing fibers and the thermoplastic resin composition of the present invention disposed at least between layers thereof. The thermoplastic resin composition of the present invention may be disposed only between layers of a reinforcing fiber substrate for bonding the reinforcing fiber substrate, or may be disposed throughout the entire fiber-reinforced composite material as a matrix resin. Except for being molded into a predetermined shape, it is the same as the prepreg described above, and therefore a description thereof will be omitted. The fiber-reinforced composite material of the present invention can be produced by hot molding the prepreg of the present invention. Alternatively, it can be produced by placing the thermoplastic resin film of the present invention between layers of a reinforcing fiber substrate or a known prepreg and hot molding it. The method for molding the fiber-reinforced composite material of the present invention is not particularly limited, and examples include molding methods with excellent productivity such as autoclave molding, press molding, filament winding molding, and stamping molding, and these can be used in combination. [Example]

[0059] The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto. The evaluation methods used in the examples are as follows.

[0060] [Average particle size, size ratio] The average particle size is the D50 particle size determined by a laser diffraction particle size distribution analyzer. The size ratio was measured from two directions for 100 randomly selected inorganic filler particles using an optical microscope or a scanning electron microscope. The size ratio was the average value of the smaller size ratios (x / z) and (y / z), where z is the smallest dimension and x and y are the dimensions in the directions perpendicular to z.

[0061] Mode I Interlaminar Fracture Toughness (GIc) (Examples 1 to 8, Comparative Examples 1 to 6) Reinforced fiber bundles are aligned in one direction, with a fiber weight of 145g / mm 2 A reinforcing fiber substrate of the following formula was obtained. Thermoplastic resin particles made of copolymerized PAEK were dispersed in ethanol to prepare a suspension solution with a concentration of 4.4 mass %. Next, the reinforcing fiber substrate was immersed in the suspension solution for 15 seconds to adhere the thermoplastic resin particles to the reinforcing fiber substrate. The resulting resin-coated reinforcing fiber substrate was dried in a drying oven at 100°C for 1 minute, and then passed through multiple heating bars (370°C) to melt and impregnate the thermoplastic resin into the reinforcing fiber substrate layer, producing a unidirectional thermoplastic resin prepreg (primary prepreg). The carbon fiber content in the entire prepreg was 57% by volume. Separately, a thermoplastic resin composition film (thickness 71 to 100 μm) was produced using a heat press machine using a thermoplastic resin composition (containing an inorganic filler) having the composition described in each Example and Comparative Example. The unidirectional prepreg was cut into a square with a side length of 150 mm, and then laminated to prepare two laminates with eight layers laminated in the 0° direction. The sample thermoplastic resin composition film (containing inorganic filler) was sandwiched between these two laminates to form the laminate configuration [0]. 16 A prepreg laminate of the above formula was obtained. To generate initial cracks, a release sheet (aluminum foil) was sandwiched between two laminates. The prepreg laminate was molded for 20 minutes at a temperature of 380°C and a pressure of 0.15 MPa. The molded product (FRP) obtained was cut to a size of 20 mm wide x 125 mm long to obtain a test piece for mode I interlaminar fracture toughness (GIc). The GIc test method was the double cantilever beam interlaminar fracture toughness test (DCB method) according to ASTM D-5528. A pre-crack (initial crack) was generated 12.7 mm from the tip of the release sheet, and the crack was then allowed to propagate. The test was terminated when the crack propagation length reached 50 mm from the tip of the pre-crack. The crosshead speed of the tensile tester for the test specimen was 1 mm / min, and measurements were performed in duplicate. The crack propagation length was measured from both end faces of the test specimen using a microscope, and GIc was calculated based on the MBT method by measuring the load and crack opening displacement. Although this evaluation method does not use the thermoplastic resin composition of the present invention for the entire prepreg, it is an appropriate evaluation method for evaluating mode I interlaminar fracture toughness (GIc), which focuses only on the interlaminar cracks between layers.

[0062] [Whether or not slip peeling occurs] When measuring the above-mentioned mode I interlaminar fracture toughness (GIc), the presence or absence of a phenomenon in which cracks rapidly propagate during delamination was observed. This is a brittle behavior in which a small crack leads to a large fracture, so it is preferable that slip delamination does not occur.

[0063] [Presence or absence of resin phase destruction] After measuring the above-mentioned mode I interlaminar fracture toughness, the peeled surface of the sample was observed by SEM. When less carbon fiber was exposed than in Comparative Example 1, it was determined that the resin layer between the layers had been broken, and the fracture toughness was evaluated according to the following index. ◯: Compared to Comparative Example 1, the amount of exposed carbon fiber is extremely small. △: Less exposed carbon fiber compared to Comparative Example 1. ×: Compared to Comparative Example 1, the amount of exposed carbon fiber is equal to or greater than that.

[0064] Reinforcement fiber: "Tenax" (trade name) HTS 45 P 12 24K (carbon fiber strand, manufactured by Teijin Limited, 24,000 filaments) Copolymerized PAEK: Produced by the method described in a known document (JP-A-01-198624, Example 1). That is, it is a polyether ether ketone composed of hydroquinone / resorcinol=80 / 20, and has a crystalline melting point of 305°C. PEEK: VESTAKEEP 2000G, a polyether ether ketone manufactured by Daicel-Evonik Co., Ltd., with a crystalline melting point of 343°C. Ketjenblack: EC600JD, manufactured by Lion Specialty Chemicals Co., Ltd., spherical carbon black with an average particle size of 0.034 μm and a size ratio of approximately 1. Nanosilica: Aerosil 300, manufactured by EVONIK, spherical silica particles with an average particle size of 0.007 μm and a size ratio of approximately 1. Microsilica: Seahoster KE-P-250, manufactured by Nippon Shokubai Co., Ltd., spherical silica particles with an average particle size of 2.5 μm and a size ratio of approximately 1. Graphene: Graphene Nanoplatelets 6-8nm (thick), 5μm (wide), Reagent manufactured by Tokyo Chemical Industry Co., Ltd. Plate-shaped graphene with a thickness of 6-8nm and a width of approximately 5μm Graphite: Reagent manufactured by Fujifilm Wako Pure Chemical Corporation, plate-shaped graphite with an average particle size of 15 μm and a dimension ratio of 20. Boron nitride: UHP-15, manufactured by Showa Denko K.K., plate-shaped boron nitride with an average particle size of 11 μm and a dimension ratio of 16 Talc: Nano Ace D-600, manufactured by Nippon Talc Co., Ltd., average particle size 0.6 μm, plate-shaped talc with a size ratio of 15

[0065] Example 1 A thermoplastic resin composition was prepared by adding 1 part by mass of graphene to 100 parts by mass of copolymerized PAEK and mixing at a temperature of 380°C. This thermoplastic resin composition was used to measure and evaluate the mode I interlaminar fracture toughness (GIc) and other properties. The results are shown in Table 1.

[0066] (Examples 2 to 8, Comparative Examples 1 to 6) The thermoplastic resin and inorganic filler were changed as shown in Table 1. Using this thermoplastic resin composition, the mode I interlaminar fracture toughness (GIc) and other properties were measured and evaluated. The results are shown in Table 1.

[0067] [Table 1]

[0068] (Reference examples 1~4) In the above examples, the resin compositions that exhibited good fracture toughness were evaluated for film tensile properties, impact resistance, and crystallinity. The thermoplastic resin films prepared in the above examples were cut into strip specimens measuring 10 mm wide x 110 mm long to evaluate the tensile properties of the films. The tensile modulus, tensile strength, and tensile elongation were evaluated using a chuck distance of 50 mm according to ISO 527-3. The crosshead speed of the specimen tensile tester was 1 mm / min, and measurements were performed on eight specimens. To evaluate impact resistance, strip test pieces measuring 80 mm long x 10 mm wide x 4 mm thick were obtained using an injection molding machine, and then V-notched impact test pieces were prepared using a notching tool, and Charpy impact resistance tests were performed in accordance with ISO 179-1 with n = 3. The following equipment was used to prepare and evaluate the test pieces. Injection molding machine: ThermoFischer Mini-Jet Pro (Melting temperature: 390°C / Mold temperature: 200°C / Holding time: 10 seconds) Notching tool: Toyo Seiki Notching Tool A-4 Impact resistance tester: Toyo Seiki DG-CB To evaluate the crystallinity, differential scanning calorimetry (DSC) was used with a heating and cooling rate of 10°C / min. The sample was heated to 350°C to complete the melting and then cooled, and the crystallization temperature Tc was recorded as the peak temperature of the crystallization exothermic curve.

[0069] [Table 2]

[0070] In Comparative Examples 1 to 3, particularly Comparative Example 2 using copolymerized PAEK, the mode I interlaminar fracture toughness (GIc) was low because no inorganic filler was blended in. Furthermore, in the test pieces after measuring the mode I interlaminar fracture toughness (GIc), there was little fracture in the resin phase, and peeling occurred mainly at the interface between the carbon fiber and the matrix resin. In Comparative Examples 4 to 6, although inorganic fillers were blended, the shape of the fillers was spherical, resulting in low mode I interlaminar fracture toughness (GIc). Furthermore, in the test piece of Comparative Example 6 after measuring the mode I interlaminar fracture toughness (GIc), there was little fracture in the resin phase, and delamination occurred mainly at the interface between the carbon fiber and the matrix resin. Furthermore, when the particle diameter was extremely small as in Comparative Examples 4 and 5, an embrittlement phenomenon (slip delamination) was observed in which cracks rapidly propagate upon delamination. In contrast, in Examples 1 to 8, the mode I interlaminar fracture toughness (GIc) was improved due to the incorporation of a plate-shaped inorganic filler. Furthermore, after measuring the mode I interlaminar fracture toughness (GIc), the test specimens showed fractures mainly in the resin phase, and delamination at the interface between the carbon fiber and the matrix resin was suppressed. Furthermore, even in compositions where improved mode I interlaminar fracture toughness (GIc) was observed, such as the Reference Example, no improvement was observed in the properties of the resin composition itself. In other words, the improvement in mode I interlaminar fracture toughness (GIc) in Examples 1 to 8 was not due to an improvement in the properties of the resin composition. It is presumed that the improvement in mode I interlaminar fracture toughness (GIc) in Examples 1 to 8 was due to the suppression of delamination at the interface between the brittle and fragile carbon fiber and the matrix resin, effectively inducing fracture within the matrix resin phase, which allowed the fracture energy between the layers to be absorbed by the inorganic filler surface and the matrix resin itself, propagating the fracture in a direction parallel to the layers.

[0071] (Examples 9 and 10, Comparative Example 7) The Mode I interlaminar fracture toughness of the laminated molded articles was evaluated for the unidirectional prepregs produced using the thermoplastic resin compositions of Examples 3 and 7 as matrix resins. Note that these unidirectional prepregs differ from Examples 1 to 8, in that the thermoplastic resin of the present invention is impregnated throughout the prepreg, and only exists between the layers. The evaluation method is described below.

[0072] Mode I Interlaminar Fracture Toughness (GIc) (Examples 9 and 10, Comparative Example 7) Reinforced fiber bundles are aligned in one direction, with a fiber weight of 145g / m 2A reinforcing fiber substrate of the above formula was obtained. Furthermore, the inorganic filler and thermoplastic resin described in each of the Examples and Comparative Examples shown in Table 3 were mixed at 380°C and pulverized to obtain thermoplastic resin composition particles. The obtained thermoplastic resin composition particles were dispersed in ethanol to prepare a suspension solution with a concentration of 5.5% by mass. Next, the reinforcing fiber substrate was immersed in the suspension solution for 15 seconds to adhere the thermoplastic resin composition particles to the reinforcing fiber substrate. The obtained resin-coated reinforcing fiber substrate was dried at 100°C for 1 minute using a drying oven, and then passed through multiple heating bars (370°C) to melt and impregnate the thermoplastic resin composition into the reinforcing fiber substrate layer, producing a unidirectional thermoplastic resin prepreg (primary prepreg). The carbon fiber content in the entire prepreg was 57% by volume. The unidirectional prepreg was cut into a square with a side length of 150 mm, and then laminated to prepare two laminates with 12 layers laminated in the 0° direction. To generate initial cracks between the two laminates, a release sheet (aluminum foil) was sandwiched between the two laminates. 24 The prepreg laminate was molded for 20 minutes at a temperature of 380°C and a pressure of 0.15 MPa. The molded product (FRP) was cut into a size of 25 mm wide x 150 mm long to obtain a test piece for mode I interlaminar fracture toughness (GIc). The GIc test method was the double cantilever beam interlaminar fracture toughness test (DCB method) according to ASTM D-5528. A pre-crack (initial crack) was generated 12.7 mm from the tip of the release sheet, and the crack was then allowed to propagate further. The test was terminated when the crack propagation length reached 50 mm from the tip of the pre-crack. The crosshead speed of the tensile tester for the test specimen was 1 mm / min, and measurements were performed on five specimens. The crack propagation length was measured from both end faces of the test piece using a microscope, and the GIc was calculated based on the MBT method by measuring the load and the crack opening displacement. The results are shown in Table 3.

[0073] [Table 3]

Claims

1. A thermoplastic resin, 0.001 to 5.0 parts by mass of an inorganic filler relative to 100 parts by mass of the thermoplastic resin; and The crystalline melting point (Tm) of the thermoplastic resin is 200°C or higher, or the glass transition temperature (Tg) is 140°C or higher, The inorganic filler has a plate-like shape, the inorganic filler is one or more materials selected from the group consisting of silicate minerals and nitride materials; The thermoplastic resin and the inorganic filler are contained in an amount of 90% by mass or more, A thermoplastic resin composition, wherein the thermoplastic resin is a copolymerized polyaryl ether ketone.

2. 2. The thermoplastic resin composition according to claim 1, wherein the silicate mineral is talc or montmorillonite.

3. 2. The thermoplastic resin composition of claim 1, wherein said nitride material is boron nitride.

4. A thermoplastic resin, 0.001 to 5.0 parts by mass of an inorganic filler relative to 100 parts by mass of the thermoplastic resin; and The crystalline melting point (Tm) of the thermoplastic resin is 200°C or higher, or the glass transition temperature (Tg) is 140°C or higher, The inorganic filler has a plate-like shape, the inorganic filler is one or more materials selected from the group consisting of carbonaceous materials, A thermoplastic resin composition, wherein the thermoplastic resin is a copolymerized polyaryl ether ketone.

5. The thermoplastic resin composition according to claim 4, wherein the carbon substance is graphene or graphite.

6. A thermoplastic resin film, which is obtained by molding the thermoplastic resin composition according to any one of claims 1 to 5 into a sheet having a thickness of 10 to 200 µm.

7. A reinforcing fiber substrate made of reinforcing fibers; A thermoplastic resin composition impregnated in the reinforcing fiber substrate; It consists of The thermoplastic resin composition A thermoplastic resin, 0.001 to 5.0 parts by mass of an inorganic filler relative to 100 parts by mass of the thermoplastic resin; and The crystalline melting point (Tm) of the thermoplastic resin is 200°C or higher, or the glass transition temperature (Tg) is 140°C or higher, A prepreg characterized in that the inorganic filler is in the shape of a plate.

8. A thermoplastic resin, 0.001 to 5.0 parts by mass of an inorganic filler relative to 100 parts by mass of the thermoplastic resin; and The crystalline melting point (Tm) of the thermoplastic resin is 200°C or higher, or the glass transition temperature (Tg) is 140°C or higher, A method for producing a prepreg, comprising impregnating a reinforcing fiber substrate made of reinforcing fibers with the thermoplastic resin composition in which the inorganic filler is in the form of a plate.

9. A reinforcing fiber substrate made of reinforcing fibers; A thermoplastic resin composition disposed between layers of the reinforcing fiber substrate; It consists of The thermoplastic resin composition A thermoplastic resin, 0.001 to 5.0 parts by mass of an inorganic filler relative to 100 parts by mass of the thermoplastic resin; and The crystalline melting point (Tm) of the thermoplastic resin is 200°C or higher, or the glass transition temperature (Tg) is 140°C or higher, A fiber-reinforced composite material, characterized in that the inorganic filler has a plate-like shape.

10. A method for producing a fiber-reinforced composite material, comprising placing the thermoplastic resin film according to claim 6 between reinforcing fiber substrates and hot-molding the resulting material.

11. A method for producing a fiber-reinforced composite material, comprising hot-molding the prepreg according to claim 7.

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