Composite Sheet

Abstract

Provided is a composite sheet that can achieve both high levels of mechanical properties and bending fatigue resistance. [Solution] A composite sheet (10) comprising a reinforcing fabric (A) (12) and a matrix resin (B) (11) formed on at least one surface of the reinforcing fabric, wherein the reinforcing fabric (A) is composed of organic fibers having a single yarn fineness of 2.0 dtex or less and a basis weight of 330 g / m as measured by the method described in JIS L1096. 2 More than 600g / m 2 The composite sheet is characterized in that the impregnation rate of the composite sheet measured by a water pick-up method is 55.0% or more and 90.0% or less.

Description

[Technical Field]

[0001] The present invention relates to a composite sheet comprising a reinforcing fabric (A) and a matrix resin (B) formed on at least one surface of the reinforcing fabric. [Background technology]

[0002] BACKGROUND ART Composite sheets made of organic fiber fabric and a matrix resin are lightweight and have excellent mechanical properties, and therefore are used in a wide range of fields, such as aircraft materials, vehicle components, electrical and electronic components, and various housings for home appliances, and are effectively used in fields that require lightweight, high rigidity, high strength, abrasion resistance, etc.

[0003] Among these, composite sheets used to repair and reinforce fatigue cracks that occur in areas where stress is concentrated due to repeated live loads are required to have both fatigue resistance and mechanical properties.

[0004] A composite sheet using fine organic fibers can provide a composite sheet with excellent flexibility, but has the drawback of having a small basis weight and poor sheet strength, while a composite sheet using thick organic fibers can provide a composite sheet with a large basis weight and excellent sheet strength, but has the drawback of being prone to thread breakage at bent portions with repeated use and poor durability.

[0005] Patent Document 1 proposes a composite sheet with excellent impact resistance and penetration resistance, which is made by integrating a fabric containing organic long fiber bundles with a resin. However, although there are regions inside the sheet that are made only of organic long fibers, the resin impregnation rate is high, and the composite sheet has poor resistance to bending fatigue.

[0006] Patent Document 2 proposes a laminated molded product that is excellent in impact resistance and shatter resistance, which is made by integrating a hard composite and a soft composite. However, there is no description regarding the resin impregnation state of the soft composite, and it is unclear whether it can exert a sufficient effect on bending fatigue resistance.

[0007] Patent Document 3 proposes a composite material with excellent interfacial adhesion containing a woven fabric of high-elasticity fibers and a thermoplastic elastomer resin. However, the high-elasticity fibers have a large single-filament fineness, which tends to reduce the bending processability of the composite material.

[0008] Patent Document 4 proposes a flexible laminate with excellent flexibility that includes a fiber fabric and one or more resin layers. However, it uses a combination of spun yarn and multifilament yarn, has a low basis weight of the base fabric, and has insufficient rigidity. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2022-006988 [Patent Document 2] WO2010 / 035453 publication [Patent Document 3] WO2023 / 132307 publication [Patent Document 4] Japanese Patent Publication No. 2022-057803 Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention has been made in view of the above circumstances, and has an object to provide a composite sheet that can achieve both high levels of fatigue resistance and mechanical properties. [Means for solving the problem]

[0011] The present inventors have conducted extensive research to achieve the above object, and as a result have found that a composite sheet having excellent resistance to bending fatigue and mechanical properties can be provided by controlling the resin impregnation rate of the organic fibers within the composite sheet and further using a reinforcing fabric having a high basis weight and composed of organic fibers having a single filament fineness of not more than a certain level, thereby arriving at the present invention.

[0012] That is, the present invention provides a composite sheet comprising a reinforcing fabric (A) and a matrix resin (B) formed on at least one surface of the reinforcing fabric, wherein the reinforcing fabric (A) is composed of organic fibers having a single yarn fineness of 2.0 dtex or less and a basis weight of 330 g / m as measured by the method described in JIS L1096. 2 More than 600g / m 2 and the composite sheet has an impregnation rate of 55.0% or more and 90.0% or less as measured by a water pick-up method. [Effects of the Invention]

[0013] According to the present invention, a composite sheet can be obtained that can improve the flexural fatigue resistance and mechanical properties of a fiber-resin composite. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view showing an example of a composite sheet of the present invention. [Figure 2] FIG. 1 is a cross-sectional view showing the water pickup method. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present invention will be described in detail.

[0016] The composite sheet according to the present invention is a composite sheet comprising a reinforcing fabric (A) and a matrix resin (B) formed on at least one surface of the reinforcing fabric, wherein the reinforcing fabric (A) is composed of organic fibers having a single yarn fineness of 2.0 dtex or less and a basis weight of 330 g / m as measured by the method described in JIS L1096. 2 More than 600g / m 2 The composite sheet is characterized in that the impregnation rate measured by the water pick-up method is 55.0% or more and 90.0% or less.

[0017] <Organic fiber> Examples of organic fibers constituting the reinforcing fabric (A) used in the present invention include aramid (fully aromatic polyamide) fibers, polyphenylene sulfide fibers, polyimide fibers, polyparaphenylene benzobisoxazole fibers, polyparaphenylene benzobisthiazole fibers, polyether ether ketone fibers, polytetrafluoroethylene fibers, high-strength polyethylene fibers, liquid crystal polyester fibers, and polyarylate fibers. These organic fibers may be used alone or in combination of two or more. All of the organic fibers have a tensile strength of 10 cN / dtex or more. By constituting the reinforcing fabric with organic long fiber bundles obtained by bundling such high-strength organic long fibers, the strength and rigidity of the composite sheet can be sufficiently improved, and regions consisting only of organic long fiber bundles without resin can be effectively created within the composite sheet.

[0018] Among these, high-strength organic fibers with a tensile strength of 18 cN / dtex or more, as measured by the method described in JIS L1013:2021 "Testing Methods for Chemical Fiber Filament Yarn," are preferred, with those with a tensile strength of 20 cN / dtex or more being more preferred. Specifically, aramid (fully aromatic polyamide) fibers, polyparaphenylene benzobisoxazole fibers, high-strength polyethylene fibers, liquid crystal polyester fibers, and polyarylate fibers are preferred. Using these organic fibers with a tensile strength of 18 cN / dtex or more will ensure that the composite sheet has sufficient strength and rigidity. Furthermore, using organic fibers with a high melting point or decomposition temperature (150°C or higher) is preferred because it improves adhesion to the matrix resin during composite sheet preparation.

[0019] The aramid fiber is not particularly limited as long as it is a fiber having at least one divalent aromatic group, which may be substituted, in the repeating unit of the polymer forming the fiber and has at least one amide bond, and may be what is called a wholly aromatic polyamide fiber or an aramid fiber. The "divalent aromatic group, which may be substituted" means a divalent aromatic group, which may have one or more identical or different substituents. Examples of aramid fibers include para-aramid fibers and meta-aramid fibers, with para-aramid fibers being preferred due to their excellent tensile strength. Such aramid fibers are commercially available, and specific examples of para-aramid fibers include polyparaphenylene terephthalamide fibers (manufactured by DuPont USA, Toray DuPont Co., Ltd., trade name "Kevlar" (registered trademark)) and copolyparaphenylene-3,4'-oxydiphenylene terephthalamide fibers (manufactured by Teijin Limited, trade name "Technora" (registered trademark)). Among these para-aramid fibers, polyparaphenylene terephthalamide fibers are particularly preferred due to their excellent tensile strength.

[0020] The liquid crystalline polyester constituting the liquid crystalline polyester fiber is a polyester that can form an anisotropic molten phase (liquid crystallinity) when melted. This property can be confirmed, for example, by placing a sample on a hot stage, heating it under a nitrogen atmosphere, and observing the transmitted light through the sample under polarized light.

[0021] Examples of liquid crystal polyesters include (i) polymers of aromatic hydroxycarboxylic acids, (ii) polymers of aromatic dicarboxylic acids and diols selected from aromatic diols or aliphatic diols, and (iii) copolymers of the above (i) and (ii), which are produced by conventionally known methods. Among the above (co)polymers, those composed only of aromatic compounds are preferred. (Co)polymers composed only of aromatic compounds exhibit excellent strength when made into fibers.

[0022] Examples of the aromatic oxycarboxylic acid include hydroxybenzoic acid, hydroxynaphthoic acid, etc., and alkyl, alkoxy, and halogen-substituted derivatives thereof. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, diphenyldicarboxylic acid, naphthalenedicarboxylic acid, diphenyletherdicarboxylic acid, diphenoxyethanedicarboxylic acid, diphenylethanedicarboxylic acid, etc., and alkyl, alkoxy, and halogen-substituted derivatives thereof. Examples of the aromatic diol include hydroquinone, resorcinol, dihydroxybiphenyl, naphthalenediol, etc., and alkyl, alkoxy, and halogen-substituted derivatives thereof. Examples of the aliphatic diol include ethylene glycol, propylene glycol, butanediol, and neopentyl glycol.

[0023] Examples of commercially available liquid crystal polyester fibers include "Zexion (registered trademark)" manufactured by KB Seiren Co., Ltd., "Vectran (registered trademark)" manufactured by Kuraray Co., Ltd., and "Sumikasuper (registered trademark) LCP" manufactured by Sumitomo Chemical Co., Ltd. These liquid crystal polyester fibers can be used alone or in combination of two or more.

[0024] The organic fibers used in the composite sheet of the present invention preferably have a breaking elongation of 4.0% or more, as measured by the method described in JIS L1013:2021, "Testing Methods for Chemical Fiber Filament Yarns." The composite sheet of the present invention is composed of a reinforcing fabric (A) made of organic fibers and a layer of matrix resin (B) formed on at least one surface of the reinforcing fabric (A), and the organic fibers are responsible for most of the mechanical properties of the composite sheet. Therefore, if the breaking elongation of the organic fibers is less than 4.0%, the fiber structure will be unfavorable for flexural fatigue resistance, depending on the configuration of the fiber sheet, and there is a disadvantage that the composite sheet may be prone to breakage when subjected to repeated bending loads.

[0025] On the other hand, if the breaking elongation of the organic fiber is 4.0% or more, the stress concentration on the sheet due to the bending load can be reduced when the composite sheet is prepared, and therefore a composite sheet with excellent fatigue resistance can be obtained. The breaking elongation of the organic fiber is preferably 4.1% or more, and more preferably 4.2% or more.

[0026] The organic fibers used in the composite sheet of the present invention preferably have a tensile modulus of 400 cN / dtex or more and 700 cN / dtex or less, as measured by the method described in JIS L1013:2021 "Testing Methods for Chemical Fiber Filament Yarns." Using organic fibers with these characteristics allows the composite sheet to exhibit a sufficient modulus of elasticity. If the tensile modulus exceeds 700 cN / dtex, the composite sheet will be less flexible, potentially reducing the flexibility of the sheet's rigidity.

[0027] The total fineness of the organic fibers is not particularly limited, but is typically 50 to 10,000 dtex, preferably 500 to 7,000 dtex, more preferably 1,000 to 5,000 dtex, and even more preferably 1,500 to 4,000 dtex. If the total fineness is less than 50 dtex, the fabric yield strength may decrease, potentially impairing mechanical properties. If the total fineness exceeds 10,000 dtex, the surface smoothness of the fabric may decrease, resulting in poor interfacial adhesion to the matrix resin and the risk of interfacial peeling. Furthermore, organic fibers such as air-entangled yarns that have been subjected to taslan processing or interlacing processing, twisted-heat-set-untwisted yarns (crimped yarns), false-twist textured yarns, and push-textured yarns may also be used, provided that the effects of the present invention are not impaired.

[0028] The organic fibers used in the composite sheet of the present invention must have a single filament fineness of 2.0 dtex or less. The use of multifilament yarns with a small fiber diameter improves the cycle fatigue life of the composite sheet, resulting in a composite sheet with excellent fatigue resistance. The single filament fineness of the organic fibers is preferably 1.7 dtex or less, more preferably 1.5 dtex or less. From the viewpoint of production efficiency in the spinning production process, the single filament fineness of the organic fibers is preferably 0.8 dtex or more.

[0029] Pretreatment may be carried out as necessary to improve the adhesion between the organic fibers constituting the reinforcing fabric (A) and the matrix resin (B), thereby improving the properties of the resulting composite sheet. The pretreatment may be carried out on the entire organic fibers or fabric, or on only a portion of the organic fibers or fabric, preferably only on the adhesive surface. Suitable examples of the pretreatment include a method of applying a reactive organic compound together with an oil to organic fibers (e.g., Japanese Patent No. 5676337), a treatment of preheating organic fibers or fabrics, corona discharge treatment, electron irradiation treatment, ultraviolet irradiation treatment, flame plasma treatment, atmospheric pressure plasma treatment, or low pressure plasma treatment. The pretreatment may be performed using known means, such as treatment with a corona discharge device, hot air heating, or heating with a heater. These means may be used alone or in combination of two or more means. Such treatment generates a certain number of activation points on the bonding surface of the organic fibers or fabric, enabling the formation of strong adhesion with the matrix resin.

[0030] <Reinforcement fabric (A)> The form of the reinforcing fabric (A) can be at least one selected from the group consisting of woven fabrics, knitted fabrics, and non-crimp fabrics (NCFs), and short or long fibers processed by known methods can be used. Among these, woven fabrics with excellent mechanical properties are preferred. The thickness of the fabric is not particularly limited, but from the viewpoints of reducing the weight, cost, and performance of the composite sheet, a preferred thickness is 0.3 mm to 2.0 mm, more preferably 0.4 mm to 1.0 mm.

[0031] Examples of woven fabrics include tow sheets in which organic long-fiber bundles are oriented in one direction, unidirectional or bidirectional woven fabrics in which organic long-fiber yarns are oriented in one or two directions, and triaxial woven fabrics in which organic long-fiber yarns are oriented in three directions. From the viewpoint of achieving both mechanical properties and bending fatigue resistance, unidirectional or bidirectional woven fabrics are preferred.

[0032] The reinforcing fabric (A) preferably has a cover factor (CF) represented by the following formula (I) of 1,200 to 2,200, more preferably 1,500 to 2,000. If the cover factor (CF) is 1,200 or more, there is no risk of the fabric structure being disturbed when the matrix resin (B) is bonded, resulting in a deterioration in the product condition. If the cover factor (CF) exceeds 2,200, the surface smoothness of the reinforcing fabric (A) is impaired, making it difficult to bond the matrix resin (B), and the product thickness may increase. CF = √Dp × Np + √Df × Nf (I) Where Dp: warp fineness (dtex) Np: Warp density (threads / 25.4mm) Df: Weft fineness (dtex) Nf: Weft density (count / 25.4mm)

[0033] The weight per unit area of ​​the reinforcing fabric is 330 g / m2 in order to provide sufficient strength and rigidity to the resulting composite sheet. 2 More than 600g / m 2 It is desirable that the weight is 600g / m or less. 2 If the weight exceeds 350 g / m, the thickness of the fabric increases and the flexibility may be poor. 2 More than 550g / m 2 Less than 400 g / m 2 More than 500g / m 2 The following is the result.

[0034] The tensile strength of the fabric measured by the method described in JIS L1096 is preferably 300 to 1,500 kgf / 25.4 mm or more, more preferably 500 to 1,200 kgf / 25.4 mm, from the viewpoint of imparting sufficient strength and rigidity to the resulting composite sheet.

[0035] The fabric density (warp and weft density) measured by the method described in JIS L1096 is preferably 15 to 25 threads / 25.4 mm, more preferably 16 to 24 threads / 25.4 mm. If the fabric density is less than 15 threads / 25.4 mm, the fabric structure may be disrupted when the matrix resin (B) is bonded, which may result in a deterioration in the product quality. If the fabric density exceeds 25 threads / 25.4 mm, the surface smoothness of the reinforcing fabric (A) may be impaired, making it difficult to bond the matrix resin (B), and the mechanical strength of the composite sheet may be reduced.

[0036] <Matrix resin (B)> In the present invention, the matrix resin (B) is an essential component of the composite sheet of the present invention, and is used by being stuck onto at least one surface of the reinforcing fabric made of organic fibers. The matrix resin (B) used in the present invention is not particularly limited, and may be a known thermosetting resin, thermoplastic resin, thermoplastic elastomer, etc. Examples of the thermoplastic resin include thermoplastic resins such as polyethylene resin, ethylene-propylene copolymer resin, ethylene-vinyl acetate copolymer resin, polybutylene terephthalate resin, and polyvinyl chloride resin; thermoplastic elastomers such as polyolefin-based, polyester-based, and polyurethane-based elastomers; copolymer resins or modified resins thereof; and thermoplastic resin compositions containing one or more of these resins in combination.

[0037] Among the matrix resins, thermoplastic elastomers are preferred because they can be processed in various ways and have excellent durability against repeated deformation, and among them, polyolefin-based or polyurethane-based thermoplastic elastomers are preferred. By using these thermoplastic resins, it is possible to maximize the effect of improving the flexural fatigue resistance of the composite sheet of the present invention.

[0038] Examples of polyolefin-based thermoplastic elastomers include copolymers of two or more monomers selected from α-olefins such as ethylene, propylene, 1-butene, 1-pentene, and 1-octene, and these copolymers may be used alone or in combination. Examples include ethylene-propylene copolymer (EPR), ethylene-1-butene copolymer (EBR), ethylene-1-pentene copolymer, ethylene-1-octene copolymer (EOR), propylene-1-butene copolymer (PBR), propylene-1-pentene copolymer, and propylene-1-octene copolymer (POR).

[0039] The polyurethane-based thermoplastic elastomer is composed of a hard segment composed of a low-molecular-weight glycol and a diisocyanate, and a soft segment composed of a high-molecular-weight diol and a diisocyanate. Examples of the low molecular weight glycol include C1-10 diols such as ethylene glycol, 1,4-butanediol, and 1,6-hexanediol. Examples of the high molecular weight diol include poly(1,4-butylene adipate), poly(1,6-hexane adipate), polycaprolactone, polyethylene glycol, polypropylene glycol, and polyoxytetramethylene glycol. Examples of the diisocyanate include tolylene diisocyanate, 4,4-diphenylmethane diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate.

[0040] The matrix resin (B) used in the present invention can be blended with various additives as needed, provided that the effects of the present invention are not impaired. Examples of additives include heat stabilizers, light stabilizers, UV absorbers, hydrolysis inhibitors, antioxidants, lubricants, nucleating agents, plasticizers, color inhibitors, delustering agents, flame retardants, antistatic agents, mold release agents, fillers (glass fiber, carbon fiber, glass beads, hollow glass, talc, and other fillers), pigments, and dyes. One or more additives selected from these additives can be blended. The amounts of these additives to be blended may be those typically used.

[0041] The matrix resin (B) preferably has a flexural modulus of 0.05 GPa or more and 1.00 GPa or less, as measured by the method described in JIS K7171. If the flexural modulus is less than 0.05 GPa, buckling deformation may occur under large loads, which may lead to cracks. If the flexural modulus is more than 1.00 GPa, the composite sheet may be less flexible and may have poor flex fatigue resistance when prepared. The flexural modulus of the matrix resin (B) is preferably 0.10 GPa or more and 0.80 GPa or less, more preferably 0.15 GPa or more and 0.60 GPa or less.

[0042] <Composite sheet> The composite sheet of the present invention comprises a reinforcing fabric (A) and a matrix resin (B) formed on at least one surface thereof, but the means for bonding them together is not particularly limited, and they can be produced using known production methods. For example, a method of overlapping a matrix resin sheet on a reinforcing fabric and pressing them under pressure, or an impregnation method, a coating method, a transfer method, etc. can be used. Specifically, a method of impregnating a fiber substrate with a varnish prepared by dissolving the matrix resin in a solvent and then drying the varnish, a method of impregnating a fabric with a liquid matrix resin prepared without using a solvent and at room temperature or in a heated state, a method of fixing a powdered matrix resin to a fabric, a method of forming a matrix resin layer on a film or sheet with releasability and then transferring the layer to a fabric, etc. When the matrix resin impregnated into or attached to the fabric is dried, it is preferable to dry it in a non-contact manner using a vertical dryer.

[0043] The composite sheet of the present invention has a water pickup rate of 55.0% to 90.0%, more preferably 58.0% to 85.0%, even more preferably 60.0% to 80.0%, and particularly preferably 60.0% to 75.0%. If the rate of impregnation is less than 55.0%, the matrix resin (B) is impregnated into the reinforcing fabric (A) containing organic fibers, or the reinforcing fabric (A) containing organic fibers is strongly constrained by the matrix resin (B), resulting in insufficient flexural fatigue resistance of the composite sheet. Furthermore, if the rate of impregnation is greater than 90.0%, the adhesion between the reinforcing fabric (A) containing organic fibers and the matrix resin (B) is weak, resulting in the composite sheet structure not being maintained and possibly separation. The rate of impregnation can be adjusted by the temperature and / or pressure during pressurization.

[0044] The water pickup method is an index of impregnation obtained by immersing a composite sheet in water and calculating the weight percentage (impregnation rate) of water that has entered the voids in the composite sheet due to capillary action. In the present invention, as described below, one composite sheet of 100 × 100 mm is prepared, its weight is measured, and then it is vertically submerged in a beaker containing water to a depth of 6 mm. After immersion for 5 minutes, the weight is measured, and the increase in weight after immersion is divided by the weight of the reinforcing fabric (A) containing organic fibers that constitutes the composite sheet, and the value expressed as a percentage is the impregnation rate (%). [Example]

[0045] The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto. In the following examples, "parts by weight" will be abbreviated to "parts" unless otherwise specified. The evaluation methods described in the examples are as follows.

[0046] (1) Single yarn fineness of organic fibers The test was conducted in accordance with 8.3 B method (simplified method) of JIS L1013:2021 "Testing methods for chemical fiber filament yarns."

[0047] (2) Tensile properties of organic fibers The test was conducted in accordance with 8.5 tensile strength of JIS L1013:2021 "Testing methods for chemical fiber filament yarns."

[0048] (3) Basis weight, weaving density, and thickness of reinforcing fabric The method described in JIS L1096:2020 "Testing methods for woven and knitted fabrics" was followed.

[0049] (4) Flexural modulus of matrix resin The method described in JIS K7171:2022 "Plastics - Determination of bending properties" was followed.

[0050] (5) Impregnation rate of composite sheet The resulting composite sheet was cut into a shape that exposed the fabric made of organic fiber bundles on the cross section to prepare a 100 x 100 mm composite sheet. After measuring the weight before the test, the sheet was immersed vertically to a depth of 6 mm in a beaker containing ion-exchanged water at room temperature (20°C). After immersion for 5 minutes, the weight increase after immersion was divided by the weight of the fabric (A) containing organic long fiber bundles that constituted the composite sheet, and the value was expressed as a percentage.

[0051] (6) Mechanical properties of composite sheets According to the method described in JIS K7164:2005 "Plastics - Testing methods for tensile properties," the tensile strength (X) was measured at a chuck distance of 20 mm and a test speed of 2 mm / min, and the evaluation was carried out as follows. 〇: The tensile strength (X) of the composite sheet is 3,000N / 10mm or more ×: Tensile strength (X) of the composite sheet is less than 3,000 N / 10 mm

[0052] (7) Flexural fatigue resistance of composite sheet According to the method described in JIS K6260:2017 "Determination of flex crack resistance and flex crack growth resistance," measurements were carried out using a DeMatcha flexural fatigue tester manufactured by Toyo Seiki Seisakusho Co., Ltd. under the following conditions: room temperature, chuck distance: stroke between 25mm and 5mm, flex speed: 300Hz, processing time: 30 minutes, flexed surface: fiber side convex, resin side concave (direction does not matter for composite sheets made by bonding both sides). The retention rate (R) was calculated from the measured tensile strength of the composite sheet before and after flexion using the following formula, and evaluation was carried out based on the retention rate (R) as follows. R = B / A × 100 A: Tensile strength before bending (N / 10mm) B: Tensile strength after bending (N / 10mm) R: Retention rate (%) 〇: The composite sheet tensile strength retention rate (R) before and after bending is 70.0% or more ×: The retention rate (R) of the tensile strength of the composite sheet before and after bending is less than 70.0%

[0053] [Manufacturing Example 1] 1 kg of paraphenylene terephthalamide (molecular weight approximately 20,000) obtained by a conventional method was dissolved in 4 kg of concentrated sulfuric acid, and the solution was passed through a die with 1,000 holes of 0.1 mm diameter at a shear rate of 30,000 sec -1 The resulting mixture was spun into water at 25°C, neutralized with a 10% by weight aqueous solution of sodium hydroxide at 10°C for 15 seconds, and then heated and dried at 170°C for 15 seconds. An oil was then applied, and two strands were then paralleled and bundled to obtain polyparaphenylene terephthalamide fiber (total fineness 3,300 dtex) with a moisture content of 7.0% by weight.

[0054] [Manufacturing Example 2] The same procedure as in Production Example 1 was carried out except that the spinning temperature was 4°C and the heat drying conditions were 150°C x 30 seconds, to obtain polyparaphenylene terephthalamide fibers (total fineness 3,300 dtex) with a moisture content of 7.0% by weight.

[0055] [Manufacturing Example 3] The same procedure as in Production Example 1 was carried out except that the two strands were not plyed together after application of the oiling agent, to obtain polyparaphenylene terephthalamide fibers (total fineness 1,670 dtex) having a moisture content of 7.0% by weight.

[0056] [Manufacturing Example 4] The same procedure as in Production Example 1 was carried out except that a spinneret having 1,333 holes was used and the spinning temperature was set to 4°C, to obtain polyparaphenylene terephthalamide fiber (total fineness 3,300 dtex) with a moisture content of 7.0% by weight.

[0057] [Manufacturing Example 5] "Izanas SK60" (high strength polyethylene fiber; 1,760 dtex) manufactured by Toyobo MC Co., Ltd. was used.

[0058] Details of the polyparaphenylene terephthalamide fibers obtained in Production Examples 1 to 4 and the high-strength polyethylene fibers obtained in Production Example 5 are shown in Table 1.

[0059] [Table 1]

[0060] [Example 1] A plain weave fabric (basis weight: 461 g / m) using the polyparaphenylene terephthalamide fiber (Production Example 1) shown in Table 1 was used. 2 A reinforcing fabric (A-1) was made of a polyvinyl chloride sheet (thickness: 0.45 mm, warp density: 16.5 / 25.4 mm, weft density: 17.0 / 25.4 mm, thickness: 0.61 mm), and a polyvinyl chloride sheet (thickness: 0.45 mm) was used as the matrix resin (B-1). A urethane adhesive was applied to one side of the reinforcing fabric (A-1), and the fabric was attached by pressing (100°C x 2 MPa x 5 minutes) to obtain a composite sheet.

[0061] [Example 2] Plain woven fabric (basis weight: 448 g / m) using polyparaphenylene terephthalamide fiber (Production Example 2) shown in Table 1 2A reinforcing fabric (A-2) was made of a flexible urethane sheet (thickness: 0.58 mm), warp density: 15.5 / 25.4 mm, weft density: 16.5 / 25.4 mm, thickness: 0.55 mm), and a soft urethane sheet (thickness: 0.58 mm) was used as the matrix resin (B-2). A urethane adhesive was applied to both sides of the reinforcing fabric (A-2), and the fabric was bonded by pressing (120°C x 2 MPa x 5 minutes) to obtain a composite sheet.

[0062] [Example 3] A plain weave fabric (basis weight: 350 g / m) was prepared using two twisted high-strength polyethylene fibers (Production Example 5) shown in Table 1. 2 A reinforcing fabric (A-3) was prepared using a flexible urethane sheet (B-2) manufactured in accordance with Example 1. The reinforcing fabric (A-3) was a flexible urethane sheet (B-2) manufactured in accordance with Example 1. The flexible urethane sheet (B-2) was used as the matrix resin. A urethane adhesive was applied to one side of the reinforcing fabric (A-3) and the fabric was attached by pressing (120°C x 2 MPa x 5 minutes) to obtain a composite sheet.

[0063] [Comparative Example 1] A plain weave fabric (basis weight: 319 g / m) using the polyparaphenylene terephthalamide fiber (Production Example 3) shown in Table 1 was used. 2 A reinforcing fabric (A-4) was prepared from a polyvinyl chloride sheet (B-1) of a 100% polyester fiber reinforced plastic (100% polyester fiber, warp density: 24.0 threads / 25.4 mm, weft density: 24.5 threads / 25.4 mm, thickness: 0.43 mm), and the matrix resin used in Example 1 was the same polyvinyl chloride sheet (B-1). A urethane adhesive was applied to one side of the reinforcing fabric (A-4) and the fabric was attached by pressing (100°C x 2 MPa x 5 minutes) to obtain a composite sheet.

[0064] Comparative Example 2 The soft urethane sheet (B-2) used in Example 2 was used as the matrix resin (B) instead of the polyvinyl chloride sheet (B-1) used in Example 1. A urethane adhesive was applied to both sides of the reinforcing fabric (A-1), and the fabric was attached by pressing (150°C x 5 MPa x 5 minutes) to obtain a composite sheet.

[0065] Comparative Example 3 Plain woven fabric (basis weight: 455 g / m) using polyparaphenylene terephthalamide fiber (Production Example 4) shown in Table 1 2 A reinforcing fabric (A-5) was prepared using a flexible urethane sheet (B-2) manufactured in accordance with Example 1. The reinforcing fabric (A-5) was a flexible urethane sheet (B-2) manufactured in accordance with Example 1. The flexible urethane sheet (B-2) was used as the matrix resin. A urethane adhesive was applied to one side of the reinforcing fabric (A-5) and the fabric was attached by pressing (120°C x 2 MPa x 5 minutes) to obtain a composite sheet.

[0066] [Examples 1 to 3, Comparative Examples 1 to 3] The evaluation results for the reinforcing fabric (A) and composite sheet made of each fiber type listed in Table 1 are shown in Table 2.

[0067] [Table 2]

[0068] As shown in Table 2, the fiber weight is 330 g / m 2 It can be seen that the composite sheet having a tensile strength of less than 100 MPa has insufficient tensile strength (Comparative Example 1). On the other hand, the fiber weight is 330g / m 2 It can be seen that even if a composite sheet has excellent mechanical properties exceeding 55.0%, if the impregnation rate measured by the water pickup method is less than 55.0% or the single fiber fineness exceeds 2.0 dtex, the composite sheet cannot fully exhibit the effect of improving bending fatigue resistance (Comparative Examples 2 and 3).

[0069] In contrast, the composite sheet of the present invention uses a high-basis-weight reinforcing fabric made of organic fibers with a controlled single-fiber fineness, and by controlling the impregnation rate of the matrix resin into the fabric, it is possible to improve both the mechanical properties and flexural fatigue resistance of the composite sheet, demonstrating the usefulness of the present invention. [Industrial Applicability]

[0070] The composite sheet of the present invention has excellent mechanical properties and flexural fatigue resistance, and can therefore be widely used in a wide range of applications, including aircraft and space parts, pressure vessels, industrial equipment parts, printed circuit boards, and sporting goods, particularly for repairing and reinforcing fatigue cracks that occur in stress-concentrated areas where live loads are repeatedly applied, as well as in applications where durability against such fatigue cracks is required. [Explanation of symbols]

[0071] 10 Composite Sheet 11 Matrix resin (B) 12 Reinforcing fabric containing organic fibers (A) 13 Top surface of composite sheet 14 Underside of composite sheet

Claims

1. A composite sheet comprising a reinforcing fabric (A) and a matrix resin (B) formed on at least one surface of the reinforcing fabric, The reinforcing fabric (A) is made of organic fibers having a single yarn fineness of 2.0 dtex or less, and has a basis weight of 330 g / m as measured by the method described in JIS L1096. ２ More than 600g / m ２ is as follows: A composite sheet characterized in that the impregnation rate of the composite sheet measured by a water pick-up method is 55.0% or more and 90.0% or less.

2. 2. The composite sheet according to claim 1, wherein the matrix resin (B) has a flexural modulus of 1.00 GPa or less as measured by the method described in JIS K7171.

3. 2. The composite sheet according to claim 1, wherein the matrix resin (B) sheet is bonded to one or both sides of the reinforcing fabric (A).

4. 4. The composite sheet according to claim 1, wherein the reinforcing fabric (A) is a woven fabric, and the woven fabric density of warp and weft yarns measured by the method described in JIS L1096 is 15 to 25 yarns / 25.4 mm.

5. 4. The composite sheet according to claim 1, wherein the organic fibers have a breaking elongation of 4.0% or more as measured by the method specified in JIS L1013.

6. 6. The composite sheet according to claim 5, wherein the organic fibers are aramid (wholly aromatic polyamide) fibers, polyphenylene sulfide fibers, polyimide fibers, polyparaphenylene benzobisoxazole fibers, polyparaphenylene benzobisthiazole fibers, polyether ether ketone fibers, polytetrafluoroethylene fibers, high-strength polyethylene fibers, liquid crystal polyester fibers, or polyarylate fibers.

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