Fiber-reinforced resin hollow molding and manufacturing method thereof

Abstract

A fiber-reinforced resin hollow molded body 30 in which a resin-integrated fiber sheet is used, wherein: the resin-integrated fiber sheet includes unidirectional continuous fibers in which continuous fiber groups are opened and arranged in parallel in one direction, and a thermoplastic resin present at least on the surface of the unidirectional continuous fibers; the hollow molded body 30 is wound so as to create an overlapped portion in a state in which one or a plurality of the resin-integrated fiber sheets are laminated; the unidirectional continuous fibers are impregnated with the thermoplastic resin; and the resin-integrated fiber sheet is integrated.

Description

[Technical field]

[0001] The present invention relates to a fiber-reinforced hollow resin molding using semipreg and a method for producing the same. [Background technology]

[0002] Carbon fiber, a reinforcing fiber material, is composited with various matrix resins, and the resulting fiber-reinforced plastics have come to be widely used in various fields and applications. In the aerospace and space fields, which require high mechanical properties and heat resistance, and in the general industrial fields, unidirectional continuous fibers with thermoplastic resin as the matrix resin are used. Conventionally, prepregs in which the carbon fiber substrate is completely impregnated with resin have been used, and it has been suggested that when made into a composite material, it has excellent impact resistance, short molding time, and the possibility of reducing molding costs. However, prepregs that are completely impregnated with resin have high hardness and poor flexibility, and are difficult to round. For this reason, semipregs in which the resin is not impregnated in the reinforcing fiber substrate have attracted attention. Semipregs are unimpregnated substrate sheets in which the matrix resin is attached or fused to the fiber substrate or in a semi-impregnated state, and are soft and have excellent formability. In addition, they can be molded directly, so they have excellent molding efficiency.

[0003] However, when molding reinforced fiber resin, it is necessary to impregnate the fiber substrate with thermoplastic resin, but in the case of short fibers, it is necessary to process them into nonwoven fabric, which is extremely inefficient. In addition, in the case of continuous fibers, the orientation may shift and become disordered, and defects such as voids and wrinkles may occur. Therefore, a more suitable semi-preg substrate that can be used for direct molding is required.

[0004] Patent Document 1 proposes integrating a fiber-reinforced resin preform with a metal molded body using an expandable mandrel. Patent Document 2 proposes a method for manufacturing a golf shaft in which a long fiber oriented prepreg sheet is wound around the outer periphery of a mandrel with an internal pressure holding tube, a short fiber two-dimensional random prepreg sheet is further wound around the joints, and the internal pressure holding tube is expanded in a mold to perform heat and pressure molding. Patent Document 3 proposes a method for manufacturing a pipe in which a tape-shaped fiber-reinforced composite material containing a specific fluororesin and reinforcing fibers is wound around the outer periphery of the first layer. Patent Document 4 proposes using a sheet-shaped molding substrate in which a nonwoven fabric made of a thermoplastic resin is layered on a sheet material in which reinforcing fibers are aligned in one direction as the molding substrate for the pipe. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2018-172116 A [Patent Document 2] JP 2013-106782 A [Patent Document 3] WO2017 / 191735 Specification [Patent Document 4] JP 2011-62818 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the above-mentioned conventional techniques have the problem that the raw material base material is hard or cannot be handled alone, and blow molding processing is also difficult.

[0007] In order to solve the above-mentioned problems of the conventional art, the present invention provides a fiber-reinforced hollow resin molding that is thin and has excellent shapeability, and a method for producing the same, using a semipreg that is easy to handle. [Means for solving the problem]

[0008] The present invention relates to a fiber-reinforced resin hollow molding using a resin-integrated fiber sheet, the resin-integrated fiber sheet comprising unidirectional continuous fibers in which a group of continuous fibers is spread and arranged in parallel in one direction, and a thermoplastic resin present on at least the surface of the unidirectional continuous fibers, and the hollow molding is a fiber-reinforced resin hollow molding in which one or more of the resin-integrated fiber sheets are stacked and wound so as to create overlapping portions, the thermoplastic resin is impregnated into the unidirectional continuous fibers, and the resin-integrated fiber sheets are integrated.

[0009] The method for producing a fiber-reinforced resin hollow molding of the present invention uses a resin-integrated sheet containing unidirectional continuous fibers in which a group of continuous fibers has been spread and arranged in parallel in one direction, and a thermoplastic resin present on at least the surface of the unidirectional continuous fibers, and wraps one or more of the resin-integrated fiber sheets around the surface of an elastic body so that overlaps are created, places the elastic body with the resin-integrated fiber sheet wrapped around it in a heated mold having a hollow shape, and supplies a pressurized fluid into the inside of the elastic body to perform pressure molding, melting the thermoplastic resin, impregnating the unidirectional continuous fibers with the thermoplastic resin and integrating the resin-integrated fiber sheet. Effect of the Invention

[0010] The fiber-reinforced resin hollow molding of the present invention uses a resin-integrated fiber sheet containing unidirectional continuous fibers in which continuous fiber groups are spread and aligned in parallel in one direction, and a thermoplastic resin present at least on the surface of the unidirectional continuous fibers, thereby providing a thin fiber-reinforced resin hollow molding that is easy to handle and has excellent shapeability, and a method for producing the same. In addition, the method for producing the hollow molding of the present invention has a fast molding cycle and can produce a high-quality hollow molding in a short time. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1A is a schematic perspective view of a fiber-reinforced hollow resin molded article according to one embodiment of the present invention, and FIG. 1B is a schematic cross-sectional view of the same. [Diagram 2] FIG. 2 is a schematic explanatory view showing a method of laminating the resin-integrated carbon fiber sheets used in molding the fiber-reinforced resin hollow molded article of FIG. [Diagram 3] FIG. 3A is a schematic perspective view of a mandrel used in blow molding, FIG. 3B is a schematic perspective view of the mandrel wound with a resin-integrated carbon fiber sheet, and FIG. 3C is a cross-sectional view of FIG. 3B. [Figure 4] FIG. 4A is a schematic plan view showing a state in which a mandrel around which a resin-integrated carbon fiber sheet is wound is placed in a molding die, and FIG. 4B is a cross-sectional view taken along line II in FIG. 4A. [Diagram 5] FIG. 5 is a schematic perspective view of a resin-integrated carbon fiber sheet used for molding a fiber-reinforced resin hollow molded article according to one embodiment of the present invention. [Figure 6] FIG. 6 is a schematic cross-sectional view in the width direction of the resin-integrated carbon fiber sheet shown in FIG. [Figure 7] FIG. 7 is a schematic process diagram showing a method for producing the resin-integrated carbon fiber sheet shown in FIG. [Figure 8] FIG. 8 is a graph showing the test force-displacement measurement at the end and center of the fiber-reinforced hollow resin molding of Example 1. [Figure 9] FIG. 9 is a graph showing the test force-displacement measurement at the end and center of the fiber-reinforced hollow resin molding of Example 2. [Explanation of symbols]

[0012] 1. Resin-integrated carbon fiber sheet 2. Unidirectional carbon fiber 3,3a,3b crosslinked fiber 4. Resin 5 Parts where resin is not attached 6 Opening device 7 Supply bobbin 8 Carbon fiber filament group (carbon fiber unspread tow) 9a, 9b Nip roll 12a-12b Bridge Roll 13a-13g Guide roll 14,17 Powder supply hopper 15,18 Dry powder resin 16,19 Heating device 20 Winding Roll 21a-21j Spreading roll 23 Roll opening process 24 Cross-linked fiber generation process 25 Powder resin application process 30 Hollow molded body 31 Fiber reinforced resin part 32 Overlapped part of resin-integrated carbon fiber sheet 33a, 33b Resin-integrated carbon fiber sheet 34 Overlap 35 Mandrel 36 Jig 37 Resin-integrated carbon fiber sheet 39 Lower mold 40 Upper mold 41 Air supply port DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present invention relates to a fiber-reinforced resin hollow molding using a resin-integrated fiber sheet (hereinafter, the fiber-reinforced resin hollow molding may be abbreviated as "hollow molding"). The resin-integrated fiber sheet includes unidirectional continuous fibers in which continuous fiber groups are opened and arranged in parallel in one direction, and a thermoplastic resin present at least on the surface of the unidirectional continuous fibers. The hollow molding of the present invention is formed by winding one or more resin-integrated fiber sheets in a laminated state so as to generate overlapping portions, impregnating the fiber sheets with a thermoplastic resin, and integrating the resin-integrated fiber sheets. The resin-integrated fiber sheet used in the manufacture of the hollow molding includes crosslinked fibers in a direction intersecting with the unidirectional continuous fibers, and the thermoplastic resin preferably integrates the unidirectional continuous fibers and the crosslinked fibers. The resin-integrated fiber sheet may include auxiliary threads arranged in the other direction on the unidirectional continuous fibers. The auxiliary threads are those that keep the orientation of the fiber sheet constant, and examples of the auxiliary threads include glass fibers, aramid fibers, polyester fibers, nylon fibers, and vinylon fibers.

[0014] The main component of the fiber of the resin-integrated fiber sheet used in the present invention is unidirectional continuous fiber that is opened and arranged in parallel in one direction, and is unidirectional long fiber. The secondary component of the fiber is preferably crosslinked fiber arranged in a direction intersecting with the unidirectional continuous fiber. Here, the main component is preferably 75 to 99 mass%, and the secondary component is preferably 1 to 25 mass%, when the fiber contained in the resin-integrated fiber sheet is 100 mass%. It is preferable that the thermoplastic resin is attached in powder form from above the unidirectional continuous fiber and the crosslinked fiber, and is heat-fused at least on the surface of the unidirectional continuous fiber, and the unidirectional continuous fiber and the crosslinked fiber are integrated. Since the unidirectional continuous fiber and the crosslinked fiber are integrated by the heat-fused thermoplastic resin, this sheet has good handleability and good operability when stacking (including stacking accompanying winding) and molding.

[0015] The resin-integrated fiber sheet is preferably a semipreg in which a thermoplastic powder resin that serves as a matrix is ​​attached to the surface of unidirectional continuous fibers and then heat-fused. When this semipreg is molded, the thermoplastic resin on the surface uniformly permeates and diffuses into the resin-integrated fiber sheet and between the resin-integrated fiber sheets. This allows for the production of a hollow molded product that is excellent in formability (moldability) and does not cause voids.

[0016] When the total of the unidirectional continuous fibers and the crosslinked fibers is taken as 100% by mass, the unidirectional continuous fibers are preferably 75 to 99% by mass, more preferably 80 to 97% by mass, and even more preferably 85 to 97% by mass. The crosslinked fibers are preferably 1 to 25% by mass, more preferably 3 to 20% by mass, and even more preferably 3 to 15% by mass. If the mass proportions are within the above ranges, the integrity of the unidirectional continuous fibers is high, and a resin-integrated fiber sheet with high tensile strength in the width direction is obtained.

[0017] The fiber volume (Vf) of the resin-integrated fiber sheet is preferably 20 to 65 volume % and the thermoplastic resin is preferably 35 to 80 volume %, more preferably 25 to 60 volume % of fiber and 40 to 75 volume % of resin. This allows the resin component of the resin-integrated fiber sheet to be used as it is as the matrix resin component of the hollow molded body. In other words, when producing a hollow molded body, it is not necessary to add new resin. The mass per unit area of ​​the resin-integrated fiber sheet is 10 to 3000 g / m 2 is preferable, and more preferably 20 to 2000 g / m 2 and more preferably 30 to 1000 g / m 2 It is.

[0018] The fiber is preferably at least one selected from carbon fiber, glass fiber, and high modulus fiber having a modulus of elasticity of 380 cN / dtex or more. Examples of the high modulus fiber include aramid fiber, particularly para-aramid fiber (modulus of elasticity: 380-980 cN / dtex), polyarylate fiber (modulus of elasticity: 600-741 cN / dtex), heterocyclic polymer (PBO, modulus of elasticity: 1060-2200 cN / dtex) fiber, high molecular weight polyethylene fiber (modulus of elasticity: 883-1413 cN / dtex), polyvinyl alcohol fiber (PVA, strength: 14-18 cN / dtex) (Encyclopedia of Fibers, p. 522, March 25, 2002, Maruzen). These fibers are useful as resin-reinforced fibers. Carbon fiber is particularly useful.

[0019] The thickness of each of the resin-integrated fiber sheets is preferably 0.01 to 5.0 mm. A resin-integrated fiber sheet having a thickness in this range is easy to mold. When molding a hollow molded product, one or more of the resin-integrated fiber sheets are layered and wound. The preferred number of layers is 2 to 20, and more preferably 3 to 15.

[0020] The thermoplastic resin may be, but is not limited to, a polyamide-based resin, a polycarbonate-based resin, a polypropylene-based resin, a polyester-based resin, a polyethylene-based resin, an acrylic-based resin, a phenoxy resin, a polystyrene-based resin, a polyimide-based resin, or a polyether ether ketone-based resin.

[0021] The resin-integrated fiber sheet of the present invention is preferably in a state in which the resin is melted and solidified and adheres to the surface of the spread fiber sheet, and the resin does not penetrate into the inside of the spread fiber sheet or only partially penetrates into the inside of the spread fiber sheet. This state is preferable for laminating and molding a plurality of resin-integrated fiber sheets.

[0022] The width of the spread fiber sheet (hereinafter also referred to as "spread sheet") is preferably 0.1 to 5.0 mm per 1000 constituent fibers in the case of carbon fiber. Specifically, the width of the spread sheet is about 0.1 to 1.5 mm per 1000 constituent fibers in the case of large tow such as 50K or 60K, and about 0.5 to 5.0 mm per 1000 constituent fibers in the case of regular tow such as 12K or 15K. Here, K indicates 1000 constituent fibers. As the number of constituent fibers per tow increases, the fibers become more twisted and more difficult to spread, so the width of the spread sheet becomes narrower. In this way, the unspread tow sold by the carbon fiber manufacturer is spread to form an easy-to-use spread sheet, which can be supplied for molding various hollow molded bodies. The carbon fiber bundles (tows) supplied for producing a resin-integrated fiber sheet preferably have 5,000 to 50,000 fibers per bundle, and it is preferable to supply 10 to 280 of these carbon fiber bundles (tows) to the fiber spreading means. When a plurality of carbon fiber bundles (tows) are supplied and spread in this manner to form a single sheet, the spaces between the carbon fiber bundles (tows) tend to split, but when crosslinked fibers having various orientations are bonded and fixed to the spread sheet by resin, splitting between the tows can also be prevented.

[0023] The average length of the crosslinked fibers is preferably 1 mm or more, and more preferably 5 mm or more. If the average length of the crosslinked fibers is within the above range, the carbon fiber sheet has high strength in the width direction and is easy to handle.

[0024] The method for producing the resin-integrated fiber sheet used in the production of the hollow molded article of the present invention includes, for example, the following steps: The fiber sheet will be described by taking a carbon fiber sheet as an example. (1) When a group of carbon fiber filaments is spread by at least one means selected from passing through a plurality of rolls, passing through a spreading bar, and air spreading, and arranged in parallel in one direction, crosslinked fibers are generated from the group of carbon fiber filaments during or after spreading, or crosslinked fibers are dropped onto a carbon fiber sheet during or after spreading. The crosslinked fibers are formed on a surface of the carbon fiber sheet of 10 mm2 or more. 2 The average number of filaments per filament is one or more. When the carbon fiber filaments are spread by passing through a roll or a spreading bar, tension is applied to the carbon fiber filaments, so that crosslinked fibers can be generated from the carbon fiber filaments during spreading. The tension of the carbon fiber filaments can be, for example, in the range of 2.5 to 30 N per 15,000 filaments. When air spreading is employed, it is preferable to generate crosslinked fibers thereafter using a roll or a spreading bar. When crosslinked fibers are generated from the carbon fiber filaments, the crosslinked fibers are in a state of being intertwined with the carbon fibers constituting the carbon fiber sheet. Here, intertwining includes entanglement. For example, a part or all of the crosslinked fibers are present in the carbon fiber sheet and are three-dimensionally intertwined with the carbon fibers arranged in one direction. (2) Powdered resin is applied to the opened carbon fiber sheet. (3) The powder resin is heated and melted in a pressure-free state (without pressure), and then cooled to cause the resin to be partially present on at least a part of the surface of the carbon fiber sheet. During this process, the crosslinked fibers are bonded and fixed to the carbon fiber sheet by the resin on the surface.

[0025] The hollow molded body of the present invention is obtained by laminating one or more of the resin-integrated fiber sheets on the surface of an elastic body, winding the sheet so as to generate an overlapping portion, and molding the sheet. The resin-integrated fiber sheets are preferably wound at least two times in a state where one or more sheets are laminated. The width of the overlapping portion is preferably 3 mm or more, more preferably 10 mm or more. In the present invention, when the sheet is wound two times, an overlapping portion having a width equal to the circumference is generated, and when the sheet is wound three times, an overlapping portion having a width twice the circumference is generated. When two or more resin-integrated fiber sheets are laminated, the sheets may be laminated so that the directionality of the unidirectional continuous fibers (the longitudinal direction of the fibers of the unidirectional continuous fibers) is different. The elastic body may be a mandrel. For example, when two sheets are laminated, the angle can be 0° / 90°. This makes it possible to obtain a hollow molded body having the mechanical properties required for the hollow molded body. When one resin-integrated fiber sheet is used, for example, a long molded body can be obtained by winding it obliquely to the length direction of the mandrel, or a hollow molded body can be obtained by winding it multiple times at 90° to the length direction of the mandrel. The hollow molded body can be a pipe, shaft, frame, etc., and the cross section can be a circular hollow, a rectangular hollow, or various other shapes.

[0026] The hollow molded article of the present invention is preferably molded with a fluid that expands outward from the hollow portion, for example, a pressurized fluid such as compressed air.

[0027] In one embodiment, the method for producing a blown molded article of the present invention includes the following steps. (a) A step of winding one or more of the resin-integrated fiber sheets on the surface of an elastic body so as to create overlapping portions. (b) A process in which the elastomer wrapped with the resin-integrated fiber sheet is placed in a heated mold having a hollow shape, and pressure fluid is supplied into the inside of the elastomer to perform pressure molding (for example, the resin-integrated fiber sheet is pressed against the heated mold with compressed air to obtain the desired shape). (c) A step of melting a thermoplastic resin and integrating the resin-integrated fiber sheet that has been impregnated and wound around the unidirectional continuous fibers.

[0028] In another embodiment, the method for producing a blown molded article of the present invention includes the following steps. (a') A step of winding one or more resin-integrated fiber sheets around the surface of an elastomer body. (b') A process of placing the elastic body with the resin-integrated fiber sheet wrapped around it in a heated mold having a hollow cavity. (c') A process of supplying a pressurized fluid into the inside of the elastomer, expanding the resin-integrated fiber sheet from the elastomer toward the outside to perform hollow molding, and melting the thermoplastic resin to impregnate the entire laminate (the entire wound resin-integrated fiber sheet). (d´) The subsequent step is cooling.

[0029] In the steps (a) and (a'), when multiple resin-integrated fiber sheets are wound, the multiple resin-integrated resin sheets are preferably laminated and wound so that the unidirectional continuous fibers have different orientations. This makes it possible to obtain a hollow molded body having the mechanical properties required for the hollow molded body. The resin-integrated fiber sheet may be wound directly on the surface of the elastic body, or the resin-integrated fiber sheet may be wound to form a preform, which is then placed on the surface of the elastic body.

[0030] The following description will be given with reference to the drawings. In the following drawings, the same reference numerals denote the same objects. FIG. 1A is a schematic perspective view of a hollow molded body 30 according to one embodiment of the present invention, and FIG. 1B is a schematic cross-sectional view of the same. This hollow molded body 30 is hollow in the length direction, and a fiber-reinforced resin part 31 is formed by laminating and integrating a plurality of resin-integrated carbon fiber sheets. Reference numeral 32 denotes an overlap part of the resin-integrated carbon fiber sheets. The hollow molded body 30 has a preferred diameter (outer diameter) of 10 to 200 mm, a preferred length of 50 to 5000 mm, a preferred thickness of 0.03 to 5 mm, and a more preferred thickness of 0.04 to 5 mm.

[0031] Fig. 2 is a schematic explanatory diagram showing a method of laminating the resin-integrated carbon fiber sheets used in molding the fiber-reinforced resin hollow molded article of Fig. 1. The resin-integrated carbon fiber sheet 33a has unidirectional continuous fibers at an angle of 0°, and the resin-integrated carbon fiber sheet 33b has unidirectional continuous fibers at an angle of 90°. An overlapping portion 34 of the resin-integrated carbon fiber sheets 33a and 33b is cut out and wrapped around a mandrel. The wrapping may be done once or multiple times. When wrapping once, a portion is overlapped.

[0032] FIG. 3A is a schematic perspective view of a mandrel 35 used in blow molding, FIG. 3B is a schematic perspective view of the mandrel 35 wound with a resin-integrated carbon fiber sheet 37, and FIG. 3C is a cross-sectional view of FIG. 3B. A jig 36 is attached to the tip of the mandrel 35 to seal the pressure fluid in the mandrel. The mandrel is, for example, a tube made of fluororubber (heat resistance limit temperature 230°C) or silicone rubber (heat resistance limit temperature 230°C), and has, for example, an outer diameter of 19 mm, an inner diameter of 15 mm, and a length of 500 mm. FIG. 3C shows a case where the resin-integrated carbon fiber sheet is wound n turns, and the width of the overlap part is the sum of the circumference length for n-1 turns and the length of the part indicated by 38 in the figure.

[0033] FIG. 4A is a schematic plan view showing a state in which a mandrel 35 around which a resin-integrated carbon fiber sheet 37 is wound is placed in a molding die, and FIG. 4B is a cross-sectional view taken along line II in FIG. 4A. The molding die is composed of a lower die 39 and an upper die 40, and is heated. The mandrel 35 around which the resin-integrated carbon fiber sheet 37 is wound is placed in the die, and compressed air is supplied from an air supply port 41 fixed to one end of the mandrel 35 to expand the mandrel. As a result, the resin-integrated carbon fiber sheet 37 wound around the mandrel 35 expands up to the die, and the thermoplastic resin on the surface of the resin-integrated carbon fiber sheet 37 is melted by heat from the die and impregnated into the entire laminate (the entire wound resin-integrated carbon fiber sheet 37). Next, the die is cooled with water. As a result, a fiber-reinforced resin hollow molding is obtained.

[0034] FIG. 5 is a schematic perspective view of a resin-integrated carbon fiber sheet 1 used for producing a hollow molded body according to one embodiment of the present invention, and FIG. 6 is a schematic cross-sectional view of the resin-integrated carbon fiber sheet 1 in the width direction. On the surface of the spread unidirectional carbon fibers 2, the crosslinked fibers 3 are arranged in various directions. In addition, the resin 4 is melted and solidified and adheres to the vicinity of the surface of the unidirectional carbon fibers 2, and the resin 4 does not impregnate the inside of the unidirectional carbon fibers 2, or only partially impregnates the inside of the unidirectional carbon fibers 2. The resin 4 adheres and fixes the crosslinked fibers 3 to the surface of the unidirectional carbon fibers 2. As shown in FIG. 6, the crosslinked fibers 3a and 3b are present on the surface of the unidirectional carbon fibers 2. The crosslinked fibers 3a are all present on the surface of the unidirectional carbon fibers 2. The crosslinked fibers 3b are partially present on the surface of the unidirectional carbon fibers 2, and partially enter the inside and cross the carbon fibers. The resin 4 adheres and fixes the crosslinked fibers 3 to the surface of the unidirectional carbon fibers 2. In addition, the surface of the unidirectional carbon fibers 2 has a portion to which the resin 4 adheres and a portion 5 to which the resin does not adhere. When multiple resin-integrated carbon fiber sheets 1 are stacked and heated to form a fiber-reinforced plastic molded product, the resin-free portion 5 becomes a passageway through which the air inside the fiber sheet escapes, and the resin on the surface easily permeates the entire fiber sheet when pressurized. As a result, the resin 4 becomes the matrix resin of the fiber-reinforced plastic hollow molded product.

[0035] Fig. 7 is a schematic process diagram showing a method for producing a resin-integrated carbon fiber sheet used for producing a hollow molded body according to one embodiment of the present invention. A group of carbon fiber filaments (tow) 8 is drawn from a number of supply bobbins 7 (only one is shown in Fig. 7, and the others are omitted), and is spread by passing between spreading rolls 21a-21j (roll spreading process 23). Air spreading may be used instead of roll spreading. The spreading rolls may be fixed or rotated, and may vibrate in the width direction.

[0036] After the fiber-spreading step, the spread tow is nipped between nip rolls 9a and 9b, and passed between a plurality of bridge rolls 12a-12b installed between the nip rolls, and a tension of, for example, 2.5 to 30 N per 15,000 tows (corresponding to a group of carbon fiber filaments supplied from one supply bobbin) is applied to generate cross-linked fibers (cross-linked fiber generating step 24). The bridge rolls may rotate or vibrate in the width direction. The bridge rolls are, for example, a plurality of rolls with matte, uneven, or mirror surfaces, and the bridge rolls are arranged in a bent state with respect to the group of carbon fiber filaments, fixed, rotated, vibrated in the width direction, or a combination of these to generate cross-linked fibers. 13a-13g are guide rolls.

[0037] Then, dry powder resin 15 is sprinkled on the surface of the spread sheet from powder supply hopper 14, and is supplied to heating device 16 in a pressure-free state and heated, the dry powder resin 15 is melted, and cooled between guide rolls 13e-13g. Then, dry powder resin 18 is sprinkled from powder supply hopper 17 to the back surface of the spread sheet, and is supplied to heating device 19 in a pressure-free state and heated, the dry powder resin 18 is melted, cooled, and wound up by winding roll 20 (powder resin application process 25). Dry powder resins 15 and 18 are, for example, polypropylene resin (melting point: 150 to 165°C), and the temperatures in heating devices 16 and 19 are, for example, +5 to +60°C of the melting point, softening point, or fluidization point of the dry powder resin, and the residence time is, for example, 4 seconds each. As a result, the carbon fiber spread sheet has high strength in the width direction, and the constituent carbon fibers do not fall apart, and can be handled as a sheet.

[0038] The powder resin can be applied by a powder coating method, an electrostatic coating method, a spraying method, a fluidized bed dipping method, etc. The powder coating method in which the powder resin is dropped onto the surface of the carbon fiber spread sheet is preferred. For example, the powder resin in the form of a dry powder is sprinkled onto the spread carbon fiber sheet.

[0039] The advantages of the present invention can be summarized as follows: (1) Unlike prepregs, resin-integrated carbon fiber sheets are semipregs, which allows direct molding. Therefore, a hollow molded body can be molded without softening the material before molding and transferring the softened material to a molding die. In addition, shaping the resin-integrated carbon fiber sheet and impregnation of the entire fiber base material with the thermoplastic resin can be performed almost simultaneously. (2) Unlike prepregs, resin-integrated carbon fiber sheets are semipregs, which allows for high-cycle molding and has excellent formability and moldability. (3) The powdered thermoplastic resin is heat-sealed, so it has good impregnation between fibers. In other words, unlike film-like resin, it has excellent air escape during molding of the hollow molded product, and voids are less likely to occur. (4) The main component of the fiber-integrated resin sheet is continuous fiber (not short fiber), such as carbon fiber, which allows the production of a thin, high-strength hollow molded body. (5) As can be seen from the following comparison, the present invention uses semi-preg, which reduces the thermal history of the resin, thereby preventing deterioration of the resin. Prepreg: Long time during sheet production + Preheating (softening of prepreg) + Molding + Heat curing Semipreg: Heat only for a short time when making the sheet and when molding As described above, semipreg allows for faster molding times. (6) In the case of prepreg, after softening, it cools when it is transferred to the molding die, so the smoothness of the molded product surface (mold transferability) is poor. In contrast, the present invention allows direct molding, so the molded product surface is smooth. (7) In the case of prepregs, after softening, they cool when they are transferred to the molding die, so the molded product needs to have a certain thickness (thin molded products cannot be made). Since the present invention allows direct molding, there is no need to transfer the base material (prepreg) to the molding die after preheating before molding. This makes it possible to manufacture thin hollow molded products. EXAMPLES

[0040] The present invention will be specifically described below using examples, but the present invention is not limited to the following examples.

[0041] Example 1 (1) Carbon fiber unspread tow The carbon fiber unspread tow used was manufactured by Mitsubishi Chemical Corporation, product number: PYROFILE TR 50S15L, shape: regular tow filament 15K (15,000 filaments), single fiber diameter 7 μm. An epoxy compound was attached to the carbon fibers of this carbon fiber unspread tow as a sizing agent. (2) Means for spreading unspread tow The fibers were spread using the spreading means shown in Fig. 7 (spreading process). In the spreading process, the tension of the carbon fiber filaments (tow) was 15 N per 15,000 filaments. In this way, a spread sheet with 15K carbon fiber filaments, a spread width of 500 mm, and a thickness of 0.08 mm was obtained. The crosslinked fiber was 3.3% by mass. (3) Semipreg Polypropylene (melting point: 150-165°C (Prime Polymer)) was used as the dry powder resin. The average particle size of the dry powder resin was 80 μm. 2 The average weight of the resin-integrated fiber sheet was 132.4 g / m. The temperature in the heating devices 16 and 19 was 220°C, and the residence time was 8 seconds (powdered resin application step). 2 The thickness was 0.2 mm, the fiber volume (Vf) was 40 vol. %, and the thermoplastic resin was 60 vol. %. (4) Lamination conditions Number of layers of resin-integrated fiber sheet: 2 (overlapped part is 4 layers, overlapped part width 53.9mm) Fiber direction of resin-integrated fiber sheet: Bidirectional (laminated in perpendicular directions), 0° / 90° (outer side is 90°) (5) Hollow molding Blow molding was carried out using the equipment shown in Figure 4 under the following conditions. Mold temperature 200℃ Air pressure 0.6MPa Heat molding time: 3 minutes Water cooling time 5 minutes After cooling, the air line was cut and the hollow molded body was demolded.

[0042] Example 2 The lamination conditions were as follows, and the experiment was carried out in the same manner as in Example 1, except that the heat molding time was 5 minutes. Number of layers of resin-integrated fiber sheet: 4 sheets (overlapped part is 8 sheets, overlapped part width 53.1mm) Fiber direction of resin-integrated fiber sheet: Bidirectional (laminated in perpendicular directions), 0° / 90° / 0° / 90° (outside is 90°) (evaluation) The size of the hollow molded body (pipe) of Examples 1 and 2 was measured. The diameter (outer diameter) and length were measured using a vernier caliper, and the thickness was measured using a micrometer. The thickness was measured at five points and the average value was calculated. The results are shown in Table 1.

[0043] [Table 1]

[0044] Further, a compression test was performed in the diameter direction on the hollow molded bodies of Examples 1 and 2. The compression test was performed by pressing a disk of φ50 mm against the hollow molded body (end or center) using an autograph (Model: AG-50kNXplus, manufactured by Shimadzu Corporation). Compression was performed with a stroke of 2.5 mm and 5.0 mm in Example 1, and compression was performed with a stroke of 2.5 mm in Example 2, but the hollow molded bodies of Examples 1 and 2 were not broken or deformed. The results of the compression test are shown in Table 2 and Figures 8 and 9. Figure 8 is a graph showing the test force-displacement measurement at the end and center of the hollow molded body of Example 1, and Figure 9 is a graph showing the test force-displacement measurement at the end and center of the hollow molded body of Example 2. In Figures 8 and 9, a shows the measurement result at the end of the hollow molded body, and b shows the measurement result at the center of the hollow molded body.

[0045] [Table 2]

[0046] As described above, it was found that the hollow molded articles of Examples 1 and 2 had sufficient performance for practical use. [Industrial Applicability]

[0047] The hollow molded article of the present invention is a pipe, a shaft, a frame, etc., and may have a cross section of a circular hollow, a rectangular hollow, or various other shapes. The present invention can be widely applied to general industrial applications such as building materials, sporting goods, windmills, bicycles, automobiles, railways, ships, aviation, and space.

Claims

1. A method for producing a fiber-reinforced hollow resin molding, A semipreg is used as a resin-integrated fiber sheet, in which a thermoplastic powder resin is sprinkled on the surfaces of unidirectional continuous fibers in which continuous fibers are spread and arranged in parallel in one direction, and the molten resin adheres to the surfaces of the unidirectional continuous fibers, A single resin-integrated fiber sheet or a plurality of resin-integrated fiber sheets are laminated on a surface of an elastic body, and the sheet is wound so as to generate an overlapping portion; The elastic body around which the resin-integrated fiber sheet is wound is placed in a heated mold having a hollow shape; A method for producing a fiber-reinforced resin hollow molded body, comprising the steps of: supplying a pressurized fluid into the inside of the elastic body to perform compressed air molding; heating the elastic body to melt the resin; and impregnating the entire resin-integrated fiber sheet wrapped around the elastic body with the resin, so that the resin serves as a matrix resin for the fiber-reinforced resin hollow molded body.

2. The method for producing a fiber-reinforced resin hollow molding according to claim 1 , wherein the resin-integrated fiber sheets are a plurality of sheets, and the resin-integrated fiber sheets are stacked and wound so that the unidirectional continuous fibers have different orientations.

3. 3. The method for producing a fiber-reinforced resin hollow molding according to claim 1, wherein the resin-integrated fiber sheet used for producing the fiber-reinforced resin hollow molding contains crosslinked fibers in a direction intersecting with the unidirectional continuous fibers, and the resin integrates the unidirectional continuous fibers and the crosslinked fibers.

4. 4. The method for producing a fiber-reinforced resin hollow molding according to claim 3, wherein the unidirectional continuous fibers are 75 to 99% by mass and the bridging fibers are 1 to 25% by mass when the total of the unidirectional continuous fibers and the bridging fibers is 100% by mass.

5. The method for producing a fiber-reinforced resin hollow molding according to any one of claims 1 to 4, wherein the resin-integrated fiber sheet has a thickness of 0.01 to 5.0 mm.

6. The method for producing a fiber-reinforced resin hollow molding according to any one of claims 1 to 5, wherein the fiber volume content (Vf) of the resin-integrated fiber sheet is 20 to 65 volume%, and the resin volume content is 35 to 80 volume%.

7. The resin-integrated fiber sheet is a plurality of sheets, The method for producing a fiber-reinforced resin hollow molding according to any one of claims 1 to 6, wherein the plurality of resin-integrated fiber sheets are stacked, the overlapping portions are cut off, and the stacked portions are wound so as to generate overlapping portions.

8. A method for manufacturing a fiber-reinforced resin hollow molding described in any of claims 1 to 7, wherein the multiple resin-integrated fiber sheets include a resin-integrated fiber sheet in which the direction of the unidirectional continuous fibers is 0° relative to the longitudinal direction of the elastomer.

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