Method for manufacturing composite molded products and composite molded products

Abstract

We aim to manufacture relatively high-strength composite molded products while making effective use of surplus prepreg. [Solution] The manufacturing method of the present invention includes a first step of laminating a prepreg (40) comprising continuous reinforcing fibers and a pre-impregnated resin therein, and virgin fibers (30) consisting of continuous reinforcing fibers that are not impregnated with resin, onto each other; a second step of attaching an uncured matrix resin (25) to the prepreg (40) and virgin fibers (30), respectively; and a third step of heating the prepreg (40) and virgin fibers (30), to which the matrix resin (25) is attached and which are laminated onto each other, while passing them through a mold (53), thereby obtaining a composite molded product (1) in which the prepreg (40) and virgin fibers (30) are integrated via the matrix resin (25).

Description

Technical Field

[0001] The present invention relates to a composite molded product containing reinforcing fibers and a resin.

Background Art

[0002] As one method for manufacturing a composite molded product, the one disclosed in Patent Document 1 below is known. Specifically, Patent Document 1 discloses a method for manufacturing a long composite molded product (FRP molded product) having a predetermined thickness by passing reinforcing fibers (continuous reinforcing fibers) derived from a plurality of rollers through a resin bath while laminating them on each other, and passing the reinforcing fibers that have passed through the resin bath through a heated mold.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Here, a prepreg containing reinforcing fibers and a resin impregnated therein may be used as a reinforcing material for reinforcing a product. Depending on the situation, surplus prepreg may occur, for example, when the prepreg is not used as planned. If this surplus prepreg can be used as a raw material when manufacturing a composite molded product by a method (drawing molding) such as that of Patent Document 1 above, effective utilization of the surplus prepreg can be achieved. However, since the prepreg originally contains resin, if it is further passed through a resin bath and introduced into a molding die, the content ratio of the reinforcing fibers in the obtained composite molded product may decrease, and sufficient strength may not be obtained.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to manufacture a composite molded product having relatively high strength while achieving effective utilization of surplus prepreg.

Means for Solving the Problems

[0006] To solve the above problems, a method for manufacturing a composite molded article according to one aspect of the present invention includes: a first step of laminating a prepreg, which comprises continuous reinforcing fibers and a pre-impregnated resin impregnated therein, and virgin fibers, which consist of continuous reinforcing fibers that are not impregnated with resin; a second step of attaching an uncured matrix resin to the prepreg and the virgin fibers, respectively; and a third step of heating the prepreg and the virgin fibers, to which the matrix resin is attached and which are laminated together, while passing them through a mold to obtain a composite molded article in which the prepreg and the virgin fibers are integrated via the matrix resin.

[0007] According to the present invention, a matrix resin is again attached to a prepreg containing reinforcing fibers and pre-impregnated resin, and the prepreg is then drawn through a mold. This allows the prepreg, which has been further impregnated with uncured matrix resin, to be molded within the mold, and a composite molded product can be appropriately manufactured from the prepreg. In this case, if surplus prepreg is used as the prepreg, this surplus prepreg can be effectively utilized as a raw material for the composite molded product. Moreover, since not only prepreg but also virgin fibers are prepared as raw materials, and both these virgin fibers and the prepreg are drawn through the mold, the volume content of reinforcing fibers in the composite molded product can be increased, and the strength of the composite molded product can be made relatively high.

[0008] Here, as time passes, the pre-impregnation resin in the excess prepreg hardens, making it difficult to use as a raw material for composite molded products. In contrast, according to the manufacturing method of the present invention described above, even excess prepreg that has aged over time, i.e., waste prepreg, can be used as a raw material. That is, in the present invention, it is preferable that the prepreg is waste prepreg in which the pre-impregnation resin has hardened.

[0009] Preferably, in the first step, a plurality of the waste prepregs and a plurality of the virgin fibers are laminated such that the waste prepregs and virgin fibers are alternately stacked on top of each other.

[0010] In this embodiment, virgin fibers and waste prepreg can be arranged in a balanced manner along the thickness direction of the composite molded product, thereby stabilizing the physical properties of the composite molded product.

[0011] Preferably, in the first step, a plurality of the waste prepregs and a plurality of the virgin fibers are laminated such that the virgin fibers are located in the outermost layer.

[0012] Thus, when virgin fibers are placed in the outermost layer, unlike when waste prepreg, which is prone to deterioration over time, is placed in the outermost layer, the surface of the composite molded product can be finished smoothly.

[0013] Furthermore, a composite molded article according to another aspect of the present invention comprises a plurality of first composite layers including continuous first reinforcing fibers and a first resin containing them, and a plurality of second composite layers including continuous second reinforcing fibers and a second resin containing them, wherein the first composite layers and the second composite layers are laminated together with the first composite layer being the outermost layer, and the uniformity of the distribution of the first reinforcing fibers within the first composite layer is higher than the uniformity of the distribution of the second reinforcing fibers within the second composite layer.

[0014] Such composite molded products can be manufactured by the manufacturing method described above. The manufactured composite molded products have relatively high strength even when surplus prepreg is used as a raw material.

[0015] In the composite molded product, preferably, the second reinforcing fiber is a recycled reinforcing fiber, and the volume content of the second reinforcing fiber is greater than the volume content of the first reinforcing fiber.

[0016] Thus, when the proportion of recycled reinforcing fibers (second reinforcing fibers) derived from surplus prepreg is relatively increased, the surplus prepreg can be effectively utilized sufficiently.

[0017] The total volume content ratio of the first reinforcing fiber and the second reinforcing fiber is preferably 50% or more and 80% or less.

[0018] In this aspect, the reinforcing effect by the reinforcing fibers can be sufficiently exerted, and a composite molded product with high strength can be obtained.

Advantages of the Invention

[0019] As described above, according to the present invention, it is possible to manufacture a composite molded product with relatively high strength while effectively utilizing surplus prepreg.

Brief Description of the Drawings

[0020] [Figure 1] It is a cross-sectional view schematically showing a composite molded product according to an embodiment of the present invention. [Figure 2] It is a photograph showing a partially enlarged cross-section of the composite molded product. [Figure 3] It is a side view schematically showing a manufacturing apparatus for manufacturing the composite molded product. [Figure 4] It is a schematic cross-sectional view of waste prepreg used as a raw material for the composite molded product. [Figure 5] It is a flowchart summarizing the manufacturing procedure of the composite molded product by the manufacturing apparatus. [Figure 6] It is a table showing the characteristics of an example of the composite molded product while comparing with a comparative example.

Embodiments for Carrying Out the Invention

[0021] Hereinafter, with reference to the drawings, preferred embodiments of the composite molded article of the present invention and a method for manufacturing the same will be described. The composite molded article of the present invention is a molded article including continuous reinforcing fibers and a matrix resin containing the same, and is molded by draw molding. The composite molded article can have various shapes, and for example, it can be in a plate shape. Further, the use of the composite molded article is not particularly limited, and for example, it can be used as a structural material or a reinforcing material for products such as vehicles, aircraft, ships, electronic devices, medical devices, civil engineering and building materials, household appliances, tools, and the like.

[0022] [Structure of the composite molded article] FIG. 1 is a cross-sectional view schematically showing a composite molded article 1 according to an embodiment of the present invention. As shown in this figure, the composite molded article 1 is a plate-like body having a certain thickness T and width W. The composite molded article 1 includes continuous reinforcing fibers 10 extending in the same direction and a base resin 20 containing the reinforcing fibers 10.

[0023] The base resin 20 is a thermosetting resin cured through heat treatment. Various thermosetting resins can be used as the base resin 20, and for example, an epoxy resin is suitable.

[0024] The reinforcing fibers 10 are continuous fibers arranged to extend in the longitudinal direction, which is a direction orthogonal to the plane of FIG. 1, that is, a direction orthogonal to both the thickness direction D1 and the width direction D2 of the composite molded article 1. That is, the reinforcing fibers 10 are contained in the base resin 20 in a state aligned in the longitudinal direction of the composite molded article 1. The reinforcing fibers 10 are widely dispersed and arranged inside the base resin 20.

[0025] Various fibers that contribute to reinforcing the composite molded product 1 can be used as the reinforcing fiber 10, but carbon fiber is preferred, for example. In the case of carbon fiber, it is more preferable to use PAN (polyacrylonitrile) based carbon fiber, which has relatively high strength, as the reinforcing fiber 10. Of course, pitch-based carbon fiber may also be used as the reinforcing fiber 10. It is also possible to use fibers other than carbon fiber, such as glass fiber, ceramic fiber, aramid fiber, basalt fiber, PBO fiber (poly(p-phenylenebenzoxazole) fiber), etc., as the reinforcing fiber 10.

[0026] The composite molded product 1 has multiple layers with different degrees of uniformity in the distribution of reinforcing fibers 10. That is, the composite molded product 1 comprises multiple first composite layers 2 with a relatively high degree of uniformity in the distribution of reinforcing fibers 10, and multiple second composite layers 3 with a relatively low degree of uniformity in the distribution of reinforcing fibers 10. Note that the cross-sectional view in Figure 1 is schematic, and the shape, number, and thickness ratio of each layer 2,3 may differ from the actual dimensions. For example, the thickness of each layer 2,3 may be smaller in comparison to the width W of the composite molded product 1. Also, the actual number of each of the first composite layers 2 and second composite layers 3 may be larger.

[0027] The stacking order of the first composite layer 2 and the second composite layer 3 can be set as appropriate, but in this embodiment, multiple first composite layers 2 and multiple second composite layers 3 are stacked in an order in which the first composite layer 2 and the second composite layer 3 overlap alternately. In other words, multiple first composite layers 2 and multiple second composite layers 3 are stacked on top of each other such that a second composite layer 3 is always interposed between adjacent first composite layers 2, and a first composite layer 2 is always interposed between adjacent second composite layers 3. Furthermore, the two outermost layers (outermost layers) in the thickness direction D1 that constitute the surface of the composite molded product 1 are both first composite layers 2 with a high degree of uniformity in the distribution of reinforcing fibers 10.

[0028] If we define the boundary between the adjacent first composite layer 2 and second composite layer 3 as BL, then in Figure 1, this boundary BL is schematically shown as a planar surface. However, in reality (especially microscopically), the boundary BL can be formed to undulate along the width direction D2 (see Figure 2, described later). That is, the first composite layer 2 and second composite layer 3 may have a shape in which their thickness changes depending on the position in the width direction D2. On the other hand, the surface of the composite molded product 1, that is, the upper surface of the uppermost first composite layer 2 and the lower surface of the lowermost first composite layer 2 in Figure 1, can be flat surfaces as shown in the figure.

[0029] Here, the reinforcing fibers 10 included in the first composite layer 2 are designated as the first reinforcing fibers 11, and the reinforcing fibers 10 included in the second composite layer 3 are designated as the second reinforcing fibers 12. Similarly, the base resin 20 included in the first composite layer 2 is designated as the first resin 21, and the base resin 20 included in the second composite layer 3 is designated as the second resin 22. In other words, the reinforcing fibers 10 include the first reinforcing fibers 11 included in the first composite layer 2 and the second reinforcing fibers 12 included in the second composite layer 3. Furthermore, the base resin 20 includes the first resin 21 included in the first composite layer 2 and the second resin 22 included in the second composite layer 3.

[0030] As the second reinforcing fiber 12, so-called recycled reinforcing fiber is used, and as the first reinforcing fiber 11, new, non-recycled reinforcing fiber is used. As will be described in detail later, in this embodiment, as raw materials for the composite molded product 1, surplus prepreg containing reinforcing fiber and resin impregnated therein (waste prepreg 40, described later) and new, unimpregnated reinforcing fiber (virgin fiber 30, described later) are used. As a result, recycled reinforcing fiber derived from the former is formed as the second reinforcing fiber 12 within the second composite layer 3, and new, unimpregnated reinforcing fiber derived from the latter is formed as the first reinforcing fiber 11 within the first composite layer 2.

[0031] The first reinforcing fiber 11 and the second reinforcing fiber 12 may be reinforcing fibers of different materials, but in this embodiment, the same material is used for both the first reinforcing fiber 11 and the second reinforcing fiber 12. Similarly, the first resin 21 and the second resin 22 may be resins of different materials, but in this embodiment, the same thermosetting resin is used for both the first resin 21 and the second resin 22. For example, both the first reinforcing fiber 11 and the second reinforcing fiber 12 can be carbon fibers, and both the first resin 21 and the second resin 22 can be epoxy resins.

[0032] The fiber diameters of the first reinforcing fiber 11 and the second reinforcing fiber 12 may be the same, but in this embodiment, the fiber diameters of the first reinforcing fiber 11 and the second reinforcing fiber 12 are different. Specifically, in this embodiment, the fiber diameter of the first reinforcing fiber 11 is larger than the fiber diameter of the second reinforcing fiber 12.

[0033] The volume content (Vf) of reinforcing fibers 10 in the composite molded product 1, that is, the total volume content of the first reinforcing fibers 11 and the second reinforcing fibers 12, is set to be between 50% and 80%. Here, the volume content of reinforcing fibers 10 refers to the volume ratio of reinforcing fibers 10 to the composite molded product 1, and is calculated by dividing the total volume of the first reinforcing fibers 11 and the second reinforcing fibers 12 by the total volume of the composite molded product 1. The higher this volume content, the denser the reinforcing fibers 10 are contained within the composite molded product 1.

[0034] Furthermore, if the volume ratio of the first reinforcing fiber 11 in the composite molded product 1 is defined as the first volume content, and the volume ratio of the second reinforcing fiber 12 in the composite molded product 1 is defined as the second volume content, then in this embodiment, the second volume content is greater than the first volume content. That is, in the composite molded product 1 of this embodiment, the reinforcing fibers 11 and 12 are blended such that the volume ratio of the second reinforcing fiber 12, which is made of recycled reinforcing fiber, is greater than the volume ratio of the first reinforcing fiber 11, which is made of new reinforcing fiber. In other words, in this embodiment, the ratio of the second reinforcing fiber 12 to the total reinforcing fibers 10, including the first reinforcing fiber 11 and the second reinforcing fiber 12, that is, the ratio of the second volume content to the sum of the first and second volume content, is set to exceed 50%. More specifically, it is preferable that this ratio is 51% or more.

[0035] The thicknesses (dimensions in the thickness direction D1) of the first composite layer 2 and the second composite layer 3 can be set as appropriate, but in this embodiment, the thickness of the second composite layer 3 is set to be greater than or equal to the thickness of the first composite layer 2. Specifically, the thickness ratio of the first composite layer 2 and the second composite layer 3 can be set to, for example, 40:60 to 50:50. From the viewpoint of realizing the above-mentioned relationship between the first volume content and the second volume content, it is preferable that the thickness of the second composite layer 3 is greater than the thickness of the first composite layer 2. Figure 1 shows an example in which the thickness of the second composite layer 3 is relatively large in this way. That is, in the example shown in Figure 1, the thickness of the second composite layer 3 containing the second reinforcing fiber 12 (recycled reinforcing fiber) is greater than the thickness of the first composite layer 2 containing the first reinforcing fiber 11 (new reinforcing fiber).

[0036] Figure 2 is a magnified photograph of the cross-section of the composite molded product 1, showing the portion including the boundary BL between the first and second composite layers 2 and 3. As shown in this figure, the distribution of the second reinforcing fibers 12 in the second composite layer 3 is relatively variable. For example, within the second composite layer 3, there are several regions A1, A2, A3, and A4 with different degrees of uniformity in the distribution of the second reinforcing fibers 12. Region A1 is a dense region with a relatively high density of the second reinforcing fibers 12. That is, in this dense region A1, the ratio of reinforcing fibers (second reinforcing fibers 12) to resin (second resin 22) is large. On the other hand, regions A2, A3, and A4 are sparse regions with a relatively low density of the second reinforcing fibers 12. In these sparse regions A2, A3, and A4, the ratio of reinforcing fibers to resin is smaller compared to the dense region A1. The sparse regions A2, A3, and A4 surround the dense region A1.

[0037] In contrast, the uniformity of the distribution of reinforcing fibers in the first composite layer 2 is higher than in the second composite layer 3. That is, in the first composite layer 2, the density of the first reinforcing fibers 11 does not vary significantly from place to place, and the first reinforcing fibers 11 are distributed relatively uniformly throughout the entire first composite layer 2.

[0038] [Manufacturing method] The composite molded product 1 described above can be manufactured by the following method. Figure 3 is a schematic side view showing a manufacturing apparatus 50 for manufacturing the composite molded product 1. As shown in this figure, the manufacturing apparatus 50 is a so-called pultrusion machine for manufacturing the composite molded product 1 from virgin fibers 30 and waste prepreg 40.

[0039] As shown in Figure 4, the waste prepreg 40 includes a fiber bundle 41, which is a continuous bundle of reinforcing fibers, and a pre-impregnated resin 42 that has been pre-impregnated into the fiber bundle 41. The pre-impregnated resin 42 is a thermosetting resin and has already begun to harden. In other words, the waste prepreg 40 was originally a so-called tow prepreg, which included the fiber bundle 41 and the unhardened thermosetting resin impregnated therein. Tow prepregs have been widely used as raw materials for various composite molded products. Over time, the unhardened thermosetting resin in the tow prepreg naturally hardens, forming waste prepreg 40 containing the hardened thermosetting resin (pre-impregnated resin 42). Since the pre-impregnated resin 42 in the waste prepreg 40 has hardened (naturally hardened), it cannot normally be used as a raw material for composite molded products and is often discarded. In this embodiment, in order to recycle and effectively utilize such waste prepreg 40, the waste prepreg 40 is deliberately used to manufacture the composite molded product 1. Furthermore, waste prepreg 40 is prepreg that was left over without being used in the product, and is a type of surplus prepreg.

[0040] The virgin fiber 30 consists of continuous, new, unimpregnated reinforcing fibers. The virgin fiber 30 is supplied, for example, in a bundled strip.

[0041] As shown in Figure 3, the manufacturing apparatus 50 comprises a feeder 51, a resin tank 52, a mold 53, and a take-up machine 54. The feeder 51, resin tank 52, mold 53, and take-up machine 54 are arranged in this order from the upstream side (left side in Figure 3) in the withdrawal direction. Here, the top and bottom of the manufacturing apparatus 50 are defined as shown in Figure 3, but this is not intended to limit the installation orientation of the manufacturing apparatus 50.

[0042] The feeder 51 is a device that supplies virgin fibers 30 and waste prepreg 40 to the resin tank 52. The feeder 51 includes a plurality of first discharge rollers 511 around which the virgin fibers 30 are wound, a plurality of second discharge rollers 512 around which the waste prepreg 40 are wound, and a guide 513 that guides the virgin fibers 30 and waste prepreg 40 discharged from each discharge roller 511, 512 to the downstream side.

[0043] The first feed roller 511 and the second feed roller 512 are arranged so as to be approximately equal in length in the vertical direction. In this embodiment, the order of the rollers is set such that the first feed roller 511 and the second feed roller 512 are arranged alternately in the vertical direction, and the first feed roller 511 is positioned at the top and bottom. This order of rollers corresponds to the lamination order of the first composite layer 2 and the second composite layer 3 shown in Figure 1. That is, in this embodiment, the first composite layer 2 is a layer derived from virgin fibers 30, and the second composite layer 3 is a layer derived from waste prepreg 40. Therefore, the first feed roller 511 and the second feed roller 512 are arranged in the order shown in Figure 3 so as to realize the cross-sectional structure of the composite molded product 1 shown in Figure 1, that is, a structure in which the first composite layer 2 and the second composite layer 3 overlap alternately and the first composite layer 2 is the outermost layer.

[0044] For simplicity, Figure 3 shows an example where a total of five delivery rollers are arranged, namely three first delivery rollers 511 and two second delivery rollers 512. However, the number of both delivery rollers 511 and 512, in other words, the number of virgin fibers 30 and waste prepreg 40 to be laminated, can be appropriately set according to the target thickness T of the composite molded product 1 (Figure 1) and the target volume content (Vf) of the reinforcing fibers 10, and in practice, it can be set to a number significantly larger than five, such as several tens.

[0045] The first discharge roller 511 rotates to feed virgin fibers 30 downstream. Similarly, the second discharge roller 512 rotates to feed waste prepreg 40 downstream. Multiple virgin fibers 30 and multiple waste prepreg 40 fed from both discharge rollers 511 and 512 are guided by guides 513 and led towards the resin tank 52 downstream. By passing through guides 513, the virgin fibers 30 and waste prepreg 40 are guided so that the distance between them decreases as they move downstream. As a result, the virgin fibers 30 and waste prepreg 40 are stacked vertically (in the thickness direction) downstream of guides 513 and upstream of the resin tank 52.

[0046] The direction in which the virgin fibers 30 and waste prepreg 40 are fed by the first and second feed rollers 511 and 512 corresponds to the longitudinal direction of both elements 30 and 40, or in other words, the fiber direction of the continuous reinforcing fibers contained in both elements 30 and 40. That is, the feeder 51, including each of the feed rollers 511 and 512, is configured to feed multiple virgin fibers 30 and multiple waste prepreg 40 along their respective longitudinal directions (fiber directions).

[0047] The resin tank 52 is a tank for impregnating (adhering) the matrix resin 25 to the virgin fibers 30 and the waste prepreg 40. The matrix resin 25 is an uncured thermosetting resin. In this embodiment, the matrix resin 25 is the same thermosetting resin as the pre-impregnation resin 42 of the waste prepreg 40. For example, both the matrix resin 25 and the pre-impregnation resin 42 can be epoxy resins.

[0048] Multiple guide rollers 521 and 522 are arranged inside and outside the resin tank 52. The upstream guide roller 521 guides both elements 30 and 40 so that the virgin fibers 30 and waste prepreg 40 are introduced into the resin tank 52 after lamination. The downstream guide roller 522 leads the laminate of virgin fibers 30 and waste prepreg 40, which has been impregnated with matrix resin 25, to the downstream side of the resin tank 52 and guides it toward the mold 53. Hereinafter, the laminate of virgin fibers 30 and waste prepreg 40 led out of the resin tank 52, that is, the laminated virgin fibers 30 and waste prepreg 40 impregnated with matrix resin 25, will be referred to as resin-impregnated prepreg 100.

[0049] The mold 53 is a mold that receives and heats the resin-impregnated prepreg 100. The mold 53 has a cavity that penetrates in the drawing direction and incorporates a heating device that raises the temperature of the inner wall of the cavity (neither of which are shown in the figure). Upstream of the mold 53, there are several guides 531 that guide the resin-impregnated prepreg 100 so that it is introduced into the cavity of the mold 53. The resin-impregnated prepreg 100 introduced into the cavity is heated by the heating device and shaped to have a cross-sectional shape corresponding to the cavity.

[0050] In this embodiment, the mold 53 has a rectangular cross-sectional cavity corresponding to the composite molded product 1 shown in Figure 1. The heating device heats the resin-impregnated prepreg 100 at least downstream of the mold 53 until the temperature of the matrix resin 25 exceeds its curing temperature. That is, the uncured matrix resin 25 contained in the resin-impregnated prepreg 100 hardens due to heating inside the mold 53. As a result, a composite molded product 1 with a rectangular cross-section is produced in which the virgin fibers 30 and the waste prepreg 40 are integrally bonded via the matrix resin 25.

[0051] The take-up machine 54 is a device that takes up the composite molded product 1 discharged from the mold 53 and sends it further downstream. In this embodiment, the take-up machine 54 includes a plurality of pairs of rollers 541 and a pair of endless belts 542 that are arranged opposite each other vertically and wrapped around the rollers 541. However, the take-up machine 54 is not limited to one using such endless belts 542, and any type of take-up machine that is appropriate to the shape of the composite molded product 1, such as a clamp type, can be used.

[0052] Figure 5 is a flowchart summarizing the manufacturing procedure for the composite molded product 1 using the manufacturing apparatus 50 described above. As shown in this figure, the manufacturing method for the composite molded product 1 generally includes a first step S1, a second step S2, and a third step S3.

[0053] The first step S1 is a process of laminating multiple virgin fibers 30 and multiple waste prepregs 40 in a predetermined order. This first step S1 is carried out by a feeder 51.

[0054] The second step S2 is a process in which the laminated virgin fibers 30 and waste prepreg 40 are passed through a resin tank 52, thereby impregnating the virgin fibers 30 and waste prepreg 40 with uncured matrix resin 25, and thereby obtaining resin-impregnated prepreg 100. This second step S2 is realized by the resin tank 52 and the guide rollers 521 and 522 before and after it.

[0055] The third step S3 is a process of obtaining a composite molded product 1 in which virgin fibers 30 and waste prepreg 40 are integrated in layers by heating the resin-impregnated prepreg 100 while passing it through the mold 53. This third step S3 is realized by the mold 53 and the take-up machine 54.

[0056] Through the processes S1 to S3 described above, a composite molded product 1 having a cross-sectional shape schematically shown in Figure 1 is manufactured. Specifically, a composite molded product 1 is manufactured in which a plurality of first composite layers 2 containing first reinforcing fibers 11 and first resin 21 and a plurality of second composite layers 3 containing second reinforcing fibers 12 and second resin 22 are alternately laminated.

[0057] The first composite layer 2 is a layer containing virgin fibers 30 supplied from the first delivery roller 511 of the feeder 51. That is, as the virgin fibers 30 pass through the resin tank 52 and the mold 53, the matrix resin 25 impregnates and hardens into the virgin fibers 30, thereby forming the first composite layer 2. In other words, the first composite layer 2 is a layer containing continuous first reinforcing fibers 11 derived from the virgin fibers 30 and a thermosetting first resin 21 derived from the matrix resin 25.

[0058] The second composite layer 3 is mainly composed of waste prepreg 40 containing fiber bundles 41 and pre-impregnated resin 42, supplied from the second delivery roller 512 of the feeder 51. Here, the waste prepreg 40 passes through the resin tank 52 and the mold 53, and in the process, some matrix resin 25 is also impregnated into the waste prepreg 40. The matrix resin 25 impregnated into the waste prepreg 40, together with the pre-impregnated resin 42 originally contained in the waste prepreg 40, forms the second resin 22. In other words, the second composite layer 3 is a layer containing continuous second reinforcing fibers 12 derived from the fiber bundles 41 and a thermosetting second resin 22 derived from the pre-impregnated resin 42 and matrix resin 25.

[0059] [Effects and Effects] As described above, in this embodiment, waste prepreg 40, which includes a fiber bundle 41 that is a continuous bundle of reinforcing fibers and a pre-impregnated resin 42 impregnated therein, and virgin fibers 30 that are not impregnated with resin, are laminated together and then passed through a resin tank 52 to form resin-impregnated prepreg 100 in which the virgin fibers 30 and waste prepreg 40 are impregnated with matrix resin 25. Subsequently, the resin-impregnated prepreg 100 is passed through a mold 53 to produce a composite molded product 1 in which the virgin fibers 30 and waste prepreg 40 are integrated in layers. With this configuration, there is an advantage in that a relatively high-strength composite molded product 1 can be manufactured while effectively utilizing waste prepreg 40 (surplus prepreg).

[0060] In other words, in this embodiment, the waste prepreg 40, which cannot be used as raw material as is because the pre-impregnated resin 42 has hardened, is passed through the resin tank 52 again and then drawn into the mold 53. This allows the waste prepreg 40, which has been further impregnated with unhardened matrix resin 25, to be molded in the mold 53. As a result, a composite molded product 1 can be properly manufactured from the waste prepreg 40, and the waste prepreg 40 can be effectively utilized. Moreover, since not only waste prepreg 40 but also virgin fibers 30 are prepared as raw materials, and both the virgin fibers 30 and the waste prepreg 40 are passed through the resin tank 52 and then into the mold 53, the volume content of reinforcing fibers 10 in the composite molded product 1 can be increased, and the strength of the composite molded product 1 can be made relatively high.

[0061] Furthermore, in this embodiment, since the virgin fibers 30 and the waste prepreg 40 are laminated in an alternating manner, the virgin fibers 30 and the waste prepreg 40 can be arranged in a balanced manner along the thickness direction of the composite molded product 1, thereby stabilizing the physical properties of the composite molded product 1.

[0062] Furthermore, in this embodiment, the virgin fibers 30 and the waste prepreg 40 are laminated in an order such that the virgin fibers 30 are located in the outermost layer. Unlike the case where the waste prepreg 40, which is prone to deterioration over time, is placed in the outermost layer, the surface of the composite molded product 1 can be finished smoothly. For example, it is possible to effectively suppress the fuzzing of the reinforcing fibers 10 on the surface of the composite molded product 1.

[0063] Furthermore, in this embodiment, since the pre-impregnation resin 42 of the waste prepreg 40 and the matrix resin 25 in the resin tank 52 are both the same thermosetting resin (for example, epoxy resin), the affinity between the waste prepreg 40 and the matrix resin 25 is improved, and the integrity of the composite molded product 1 can be enhanced. In other words, a composite molded product 1 with excellent integrity can be obtained in which the first composite layer 2 and the second composite layer 3 are well bonded to each other.

[0064] In this embodiment, in the first composite layer 2 of the composite molded product 1, obtained by impregnating virgin fibers 30 with matrix resin 25, the reinforcing fibers 10 (first reinforcing fibers 11) derived from the virgin fibers 30 tend to be uniformly distributed within the layer. In contrast, in the second composite layer 3, obtained by additionally impregnating waste prepreg 40 with matrix resin 25, variations tend to occur in the distribution of the reinforcing fibers 10 (second reinforcing fibers 12). As a result, the uniformity of the distribution of the first reinforcing fibers 11 within the first composite layer 2 is higher than the uniformity of the distribution of the second reinforcing fibers 12 within the second composite layer 3. Thus, in this embodiment, where the first composite layer 2, in which the reinforcing fibers 10 are more uniformly distributed, is placed as the outermost layer, the surface of the composite molded product 1 can be finished to have a good appearance, and the marketability of the composite molded product 1 can be improved.

[0065] Furthermore, in this embodiment, the volume content (Vf) of the reinforcing fibers 10 in the composite molded product 1, that is, the total volume content of the first reinforcing fibers 11 and the second reinforcing fibers 12, is set to a range of 50 to 80%. This allows the reinforcing effect of the reinforcing fibers 10 to be fully realized, resulting in a composite molded product 1 with high strength.

[0066] Furthermore, in a comparison between the first reinforcing fiber 11 and the second reinforcing fiber 12, the volume content of the second reinforcing fiber 12 (second volume content) is made greater than the volume content of the first reinforcing fiber 11 (first volume content). In this way, by relatively increasing the proportion of the second reinforcing fiber 12 (recycled reinforcing fiber) derived from the waste prepreg 40, the waste prepreg 40 can be fully utilized.

[0067] [Examples] Figure 6 shows an example of a composite molded product 1 actually manufactured using the method of the embodiment described above. Specifically, a composite molded product 1 was manufactured using the manufacturing apparatus 50 shown in Figure 3, with both virgin fibers 30 and waste prepreg 40 as raw materials, and one of the resulting products is designated as Example 1. In Example 1, PAN-based carbon fiber was used as the material for the reinforcing fibers 10 (first and second reinforcing fibers 11, 12), and thermosetting epoxy resin was used as the material for the base resin 20 (first and second resins 21, 22). In Example 1, the volume content (Vf) of the reinforcing fibers 10 in the composite molded product 1 was set to 70%. The breakdown was that the volume content (first volume content) of the first reinforcing fiber 11, which is a new reinforcing fiber derived from virgin fibers 30, was 34%, and the volume content (second volume content) of the second reinforcing fiber 12, which is a recycled reinforcing fiber derived from waste prepreg 40, was 36%. In other words, in Example 1, the first and second reinforcing fibers 11 and 12 were blended such that the total volume content of the first and second reinforcing fibers 11 and 12 was 70%, and the second reinforcing fiber 12 (recycled reinforcing fiber) was contained in 2% more volume than the first reinforcing fiber 11.

[0068] Figure 6 shows two comparative examples 1 and 2 with different reinforcing fiber compositions. In comparative example 1, all reinforcing fiber raw materials were new reinforcing fibers derived from virgin fibers 30, with a volume content of 70%. In comparative example 2, all reinforcing fiber raw materials were recycled reinforcing fibers derived from waste prepreg 40, with a volume content of 50%. The reason why the volume content of reinforcing fibers in comparative example 2 is 50%, which is lower than 70%, is that, due to the manufacturing method of additionally impregnating the waste prepreg 40 with matrix resin, it was not possible to manufacture a composite molded product with a high volume content of reinforcing fibers of about 70% using only waste prepreg. Other elements in comparative examples 1 and 2, such as the materials of the reinforcing fibers and base resin, were the same as those in Example 1.

[0069] Figure 6 shows the results of measuring the bending strength and bending modulus of Example 1 and Comparative Examples 1 and 2 as described above. As shown in the figure, Comparative Example 1, which was manufactured using only virgin fibers 30, had the highest bending strength and bending modulus, with a bending strength of 1640 MPa and a bending modulus of 146 GPa. Comparative Example 2, which was manufactured using only waste prepreg 40, had the lowest bending strength and bending modulus, with a bending strength of 974 MPa and a bending modulus of 80.7 GPa. In contrast, Example 1, which was manufactured using both virgin fibers 30 and waste prepreg 40, showed intermediate characteristics between Comparative Examples 1 and 2, with a bending strength of 1405 MPa and a bending modulus of 148 GPa. These characteristics are somewhat closer to those of Example 1. That is, Example 1 has a strength that is not significantly different from the high-strength Comparative Example 1, which was manufactured using only virgin fibers 30, despite the ratio of new reinforcing fibers derived from virgin fibers 30 to recycled reinforcing fibers derived from waste prepreg 40 being close at 34:36. In particular, the flexural modulus was almost the same between Example 1 and Comparative Example 1. From this, it was confirmed that the advantage of Example 1 is that it has relatively high strength despite containing waste prepreg 40 (excess prepreg) as a raw material.

[0070] [Differentiation] Although preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and the following modifications are possible, for example.

[0071] In the above embodiment, the virgin fibers 30 and waste prepreg 40 supplied from the feeder 51 are passed through the resin tank 52 in a laminated state, but the method is not limited to this. For example, the virgin fibers 30 and waste prepreg 40 may be laminated together in the resin tank 52, or the virgin fibers 30 and waste prepreg 40 may be laminated together after passing through the resin tank 52. In other words, in the present invention, the step of laminating the virgin fibers and waste prepreg (first step) and the step of passing the virgin fibers and waste prepreg through the resin tank (second step) may be performed in this order, in the reverse order, or simultaneously.

[0072] In the above embodiment, the matrix resin 25 was applied (impregnated) to the virgin fibers 30 and waste prepreg 40 by passing them through a resin tank 52 storing uncured matrix resin 25. However, the method of applying the matrix resin 25 is not limited to this. For example, the matrix resin 25 may be applied to the virgin fibers 30 and waste prepreg 40 inside the mold 53 by injecting the uncured matrix resin 25 into the upstream part of the mold 53. In other words, the apparatus for applying the matrix resin 25 to the virgin fibers 30 and waste prepreg 40 (resin application apparatus) can be any apparatus that can supply the matrix resin 25 so that it adheres to the virgin fibers 30 and waste prepreg 40 in or upstream of the mold 53, and the resin tank 52 is merely one example.

[0073] In the above embodiment, the virgin fibers 30 and waste prepregs 40 supplied from the feeder 51 were stacked in an order in which the virgin fibers 30 and waste prepregs 40 overlapped alternately, but the order is not limited to this. For example, the stacking order may be such that at least some of the virgin fibers 30 overlap directly with each other, or at least some of the waste prepregs 40 overlap directly with each other.

[0074] In the above embodiment, the same thermosetting resin as the pre-impregnation resin 42 contained in the waste prepreg 40 was used as the matrix resin 25 to impregnate the virgin fibers 30 and the waste prepreg 40. However, a thermoplastic resin different from the pre-impregnation resin 42 may be used as the matrix resin 25. That is, the matrix resin 25 only needs to be able to integrate the virgin fibers 30 and the waste prepreg 40 and satisfy the mechanical properties required for the composite molded product 1. In that respect, the matrix resin can be appropriately selected from various thermosetting resins.

[0075] In the above embodiment, the fiber diameter of the first reinforcing fiber 11 derived from virgin fiber 30 is larger than the fiber diameter of the second reinforcing fiber 12 derived from waste prepreg 40. However, the fiber diameters of both reinforcing fibers 11 and 12 may be the same, or the fiber diameter of the first reinforcing fiber 11 may be smaller than the fiber diameter of the second reinforcing fiber 12.

[0076] In the above embodiment, a plate-shaped composite molded product 1 having a rectangular cross-section was manufactured by passing resin-impregnated prepreg 100 through a mold 53 having a rectangular cross-sectional cavity. However, the manufacturing method of the present invention can also be applied to the manufacture of composite molded products having various cross-sectional shapes other than rectangles, such as polygons and circles. [Explanation of Symbols]

[0077] 1 Composite molded product 2. First composite layer 3. Second composite layer 10 Reinforced Fibers 11. First reinforcing fiber 12 Second Reinforcement Fiber 21 First resin 22 Second resin 25 Matrix resin 30 virgin fibers 40 Waste prepreg 41 Fiber bundles (reinforcement fibers) 42 Pre-impregnated resin 52 Resin tank 53 Molding mold

Claims

1. A first step involves laminating a prepreg, which includes continuous reinforcing fibers and a pre-impregnated resin, with virgin fibers, which consist of continuous reinforcing fibers that are not impregnated with resin. A second step involves attaching an uncured matrix resin to the prepreg and the virgin fibers, respectively. A method for manufacturing a composite molded product, comprising: a third step of heating the prepreg and virgin fibers, to which the matrix resin is attached and which are laminated together, while passing them through a mold to obtain a composite molded product in which the prepreg and virgin fibers are integrated via the matrix resin.

2. In the method for manufacturing a composite molded article according to claim 1, A method for manufacturing a composite molded product, wherein the prepreg is a waste prepreg in which the pre-impregnation resin has undergone curing.

3. In the method for manufacturing a composite molded article according to claim 2, A method for manufacturing a composite molded product, wherein in the first step, a plurality of the waste prepregs and a plurality of the virgin fibers are laminated such that the waste prepregs and virgin fibers are alternately stacked on top of each other.

4. In the method for manufacturing a composite molded article according to claim 2 or 3, A method for manufacturing a composite molded product, wherein in the first step, a plurality of the waste prepregs and a plurality of the virgin fibers are laminated such that the virgin fibers are located in the outermost layer.

5. A plurality of first composite layers comprising continuous first reinforcing fibers and a first resin containing them, It comprises a plurality of second composite layers, each containing a continuous second reinforcing fiber and a second resin encompassing it, With the first composite layer positioned as the outermost layer, the first composite layer and the second composite layer are stacked on top of each other. A composite molded product in which the uniformity of the distribution of the first reinforcing fibers within the first composite layer is higher than the uniformity of the distribution of the second reinforcing fibers within the second composite layer.

6. In the composite molded article according to claim 5, The second reinforcing fiber is a recycled reinforcing fiber, A composite molded article in which the volume content of the second reinforcing fiber is greater than the volume content of the first reinforcing fiber.

7. In the composite molded article according to claim 5 or 6, A composite molded article in which the total volume content of the first reinforcing fiber and the second reinforcing fiber is 50% or more and 80% or less.

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