Manufacturing method of long foam sheet, manufacturing method of composite material, and long foam sheet

Abstract

In order to provide a method for manufacturing a long foam sheet with which it is possible to manufacture a long foam sheet with a high-precision thickness without being limited to the material or the thickness of a foam, a method for manufacturing a long foam sheet 12 comprises: a slicing step of slicing a foam block 35 to generate a foam sheet 14; and a sheet pasting step of arranging a plurality of the foam sheets 14 generated by the slicing step and pasting the same on one surface of a long base material sheet 11A. Thus, the long foam sheet 12 in which the foam sheets 14 are continuous in the length direction of the base material sheet 11A is manufactured.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a long foam sheet used in materials such as composite materials. [Background technology]

[0002] Conventionally, composite materials having a core material provided between skin materials have been known. A foam can be suitably used as the material for this core material. Patent Document 1 describes a fiber-reinforced composite laminate having a core containing a foamed resin and a surface layer having a thermosetting resin containing carbon fiber.

[0003] On the other hand, Patent Document 2 describes a method for producing a thermoplastic resin foam film laminated on an aluminum foil, in which a rectangular foam is cut (sliced) using a cutting machine. Patent Document 3 describes a method for producing a foam sheet from a cylindrical foam block. In this method, a long, thin foam sheet is produced by continuously slicing the cylindrical foam block with a slicing blade in a manner similar to peeling a skin from the outer periphery. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-6037 [Patent Document 2] WO2010 / 047274 International Publication Pamphlet [Patent Document 3] Japanese Unexamined Patent Publication No. 63-19235 Summary of the Invention [Problem to be solved by the invention]

[0005] Some foam sheets are produced in thin sheet form from the time of foam molding using a method such as extrusion foaming. However, most foam sheets are produced by cutting a foam block to a predetermined thickness. In this case, the foam sheet is inevitably in the form of a sheet. The foam film (foam sheet) produced by the method for producing a thermoplastic resin foam film described in Patent Document 2 is also in the form of a sheet.

[0006] Meanwhile, the present inventor has invented and filed a patent application (Japanese Patent Application No. 2020-24756) relating to a composite material having an island structure in which a core layer is composed of numerous plate-like pieces. One method for obtaining a core layer composed of numerous plate-like pieces is, for example, punching a foam sheet. However, when the foam sheet is in a sheet form, it is difficult to perform punching continuously. Furthermore, when the foam sheet is in a sheet form, continuous processing is difficult even when it is desired to continuously bond the foam sheet to a long roll material such as a metal film or fiber-reinforced resin.

[0007] Therefore, the inventors of the present application considered preparing a long foam sheet to realize continuous processing and improve productivity. However, the method for manufacturing a long foam sheet described in Patent Document 3 requires the foam to be formed into a cylindrical shape. Furthermore, when processing using a slicing machine that is designed to process such a cylindrical foam, the material, thickness, and precision of the foam that can be processed are extremely limited.

[0008] The present invention has been made in consideration of these circumstances, and aims to provide a method for manufacturing long foam sheets that is capable of producing long foam sheets with highly accurate thicknesses without being limited by the material or thickness of the foam. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems, the first invention is a method for manufacturing a long foam sheet, which involves carrying out a sheet attachment process in which a number of foam sheets are lined up and attached to one side of a long base sheet, thereby producing a long foam sheet in which a number of foam sheets are connected in the longitudinal direction of the base sheet.

[0010] The second invention is the same as the first invention, except that, before the sheet attachment step, a slicing step is carried out to create a foam sheet by slicing a foam block, and a sheet stretching step is carried out to reduce the curling tendency of the foam sheet created by the slicing step, and in the sheet attachment step, the foam sheet whose curling tendency has been reduced by the sheet stretching step is attached to a base sheet.

[0011] The third invention is the first invention, which further includes a slicing process in which a foam block is sliced ​​to create a foam sheet before the sheet pasting process, and an inspection process in which the foam sheet created in the slicing process is inspected for at least one of weight and thickness, and foam sheets that meet the selection criteria are selected, and in the sheet pasting process, foam sheets that meet the selection criteria in the inspection process are pasted onto a base sheet.

[0012] A fourth invention is the product according to any one of the first to third inventions, wherein the foam sheet is a hard foam sheet.

[0013] The fifth invention is a method for producing a composite material, which comprises the steps of: a cutting step of dividing a foam sheet constituting a long foam sheet produced by the manufacturing method of any one of the first to fourth inventions into a number of plate-like pieces by cutting; and a lamination step of sandwiching the plate-like pieces divided by the cutting step between a pair of skin sheets to produce a composite material.

[0014] A sixth aspect of the present invention is the method of the fifth aspect of the present invention, further comprising the step of connecting adjacent foam sheets on the base sheet with a connecting member after the sheet adhering step and before the cutting step.

[0015] According to a seventh aspect of the present invention, in the sixth aspect of the present invention, the cutting chips of the foam sheet other than the numerous plate-like pieces are removed by winding up.

[0016] The eighth invention is any one of the fifth to seventh inventions, wherein in the cutting step, an intermediate sheet is prepared in which a number of plate-like pieces are attached to a base sheet, and after the cutting step, a transfer step is carried out in which the number of plate-like pieces on the intermediate sheet are transferred to one of a pair of skin material sheets, and in the laminating step, the other of the pair of skin material sheets is laminated on the number of plate-like pieces transferred in the transfer step.

[0017] A ninth invention is any one of the fifth to seventh inventions, wherein in the cutting process, an intermediate sheet is produced in which a number of plate-like pieces are attached to a base sheet, and in the laminating process, the intermediate sheet is sandwiched between a pair of skin material sheets.

[0018] The tenth invention is a method for producing a long foam sheet, which comprises carrying out a sheet connecting process in which a number of foam sheets are arranged in a certain direction and connected with connecting members to produce a long foam sheet comprising a number of connected foam sheets.

[0019] The eleventh invention is a long foam sheet comprising a long base sheet and a number of foam sheets attached to one side of the base sheet in a line in the longitudinal direction of the base sheet, and wound into a roll. [Effects of the Invention]

[0020] In the present invention, a long foam sheet is produced by arranging and attaching a large number of foam sheets to one side of a long base sheet. While it is difficult to produce a long foam sheet with a highly accurate thickness from a cylindrical foam block without being limited by the foam material or thickness, it is possible to prepare a large number of short foam sheets with a highly accurate thickness. Therefore, by arranging and attaching a large number of foam sheets, a long foam sheet with a highly accurate thickness can be produced without being limited by the foam material or thickness. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a perspective view of a composite material according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view of a composite material according to an embodiment. [Figure 3] FIG. 3 is a plan view of the core layer of the composite material according to the embodiment, showing the side on which the chamfered portion is formed. [Figure 4] FIG. 4 is a cross-sectional view of the transfer sheet according to the embodiment. [Figure 5] FIG. 5 is a cross-sectional view for explaining a slicing step in the first manufacturing process according to the embodiment. [Figure 6] FIG. 6 is a schematic diagram illustrating the sheet stretching step in the first manufacturing process according to the embodiment. [Figure 7] FIG. 7 is a perspective view for explaining a sheet pasting step in the first manufacturing process according to the embodiment. [Figure 8] FIG. 8 is a schematic diagram of a manufacturing line used in the second manufacturing process according to the embodiment. [Figure 9] FIG. 9 is a cross-sectional view for explaining a cutting step in the second manufacturing process according to the embodiment. [Figure 10] FIG. 10 is a cross-sectional view for explaining a transfer step in the third manufacturing process according to the embodiment. [Figure 11] FIG. 11 is a cross-sectional view illustrating a stacking step in the third manufacturing process according to the embodiment. [Figure 12] FIG. 12 is a cross-sectional view of the composite material according to the embodiment when the gaps are filled with a cured resin. [Figure 13] FIG. 13 is a cross-sectional view of a laminated material in the manufacturing process of a composite material according to the first modified example. [Figure 14] FIG. 14 is a cross-sectional view illustrating a transfer step in the manufacturing process of an adhesive core sheet according to the second modified example. [Figure 15] FIG. 15 is a cross-sectional view of a composite material manufacturing sheet according to a third modified example. [Figure 16] FIG. 16 is a cross-sectional view of a composite material according to a fourth modified example. [Figure 17] FIG. 17 is a perspective view of a composite material according to the fifth modified example. [Figure 18]FIG. 18 is a cross-sectional view of a cylindrical body using a composite material according to the fifth modification. [Figure 19] FIG. 19 is a cross-sectional view illustrating how notches are formed between adjacent plate-like pieces during press cutting in a composite material according to another modified example. [Figure 20] FIG. 20 is a perspective view illustrating the sheet connecting step in the first manufacturing process in the manufacturing method of a long foam sheet according to another modified example. [Figure 21] FIG. 21 is a diagram for explaining a slicing step in the first manufacturing process according to another modified example. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the following embodiments are merely examples of the present invention and are not intended to limit the scope of the present invention, its applications, or its uses.

[0023] This embodiment is a method for manufacturing a composite material 30 that applies the method for manufacturing a long foam sheet (long foam film) 12 according to the present invention. Below, the configuration of the composite material 30 and the configuration of the transfer sheet 10 used in manufacturing the composite material 30 will be explained, and then the method for manufacturing the composite material 30 will be explained.

[0024] [Composite material composition] As shown in FIGS. 1 and 2 , the composite material 30 is a sandwich-structured panel. The composite material 30 includes a core layer (also referred to as an "intermediate layer") 20, a first skin material 31 laminated on the core layer 20, and a second skin material 32 laminated on the side of the core layer 20 opposite the first skin material 31 and sandwiching the core layer 20 together with the first skin material 31. The composite material 30 can be used, for example, as a panel material where light weight and rigidity are more important than strength. Specifically, the composite material 30 can be used as a structural material for mobile objects such as aircraft, automobiles, and bicycles (such as sports bicycles), as well as for electrical equipment, electronic devices, office equipment, home appliances, medical equipment, or building panel materials. In the case of mobile objects, the composite material 30 can be used as an aerodynamic component constituting the exterior.

[0025] Each of the skin materials 31, 32 is made of a different material from the core layer 20, for example, a skin material or a panel material. The material of each of the skin materials 31, 32 may be metal, plastic, or inorganic. In this embodiment, each of the skin materials 31, 32 is made of fiber-reinforced plastic. As the fiber-reinforced plastic, fiber-reinforced plastic reinforced with carbon fiber can be used. As this fiber-reinforced resin, prepreg (for example, "Pyrofil Prepreg (registered trademark)" manufactured by Mitsubishi Chemical Corporation) in which carbon fiber is impregnated with resin (matrix) can be used. The matrix of this prepreg is made of thermosetting epoxy resin.

[0026] The fibers of the fiber-reinforced plastic may be any of inorganic fibers, organic fibers, or metal fibers, such as glass fibers, carbon fibers, aramid fibers, polyethylene fibers, polyester fibers, tungsten fibers, steel fibers, boron fibers, etc. The matrix of the fiber-reinforced plastic may be any of thermosetting resins or thermoplastic resins, such as polyester resin, epoxy resin, phenolic resin, vinyl ester resin, polyimide resin, polypropylene resin, nylon resin, polyether ether ketone resin, polybutylene terephthalate resin, or bismaleimide resin.

[0027] The core layer 20 is laminated on each of the skin materials 31, 32. In the core layer 20, a large number of plate-like pieces 13 of the same thickness are arranged on a two-dimensional plane as a core material. The large number of plate-like pieces 13 are lined up along the surface of each of the skin materials 31, 32. Each plate-like piece 13 is a small, thin, flat piece. Each plate-like piece 13 is made of the same material and has the same shape and size. In this specification, the term "large number" in "large number of plate-like pieces" means 10 or more. The number of plate-like pieces 13 in the core layer 20 is at least 10 or more. This number may be 50 or more.

[0028] The plate-like piece 13 can be made of a material having a lower density than the skin materials 31 and 32. In this embodiment, a hard resin foam is used as the material for the plate-like piece 13. The density of the plate-like piece 13 is, for example, 30 kg / m 3 More than 500kg / m 3 The value is in the following range:

[0029] Examples of hard resin foams used as the material for the plate-like pieces 13 include polystyrene foam, polyvinyl chloride foam, cellulose acetate foam, polyurethane foam, phenol foam, epoxy foam, acrylic foam, polymethacrylimide foam, polypropylene foam, polyethylene terephthalate foam, polycarbonate foam, polyamideimide foam, and polyphenylene sulfide foam. Among these, for example, with regard to polymethacrylimide foam, polymethacrylimide (PMI) closed-cell foam (e.g., "ROHACELL (registered trademark)" (EVONIC Industries AG)) can be used.

[0030] In the core material layer 20, as shown in FIG. 3, the planar shape (peripheral shape) of the plate-like pieces 13 is a regular polygon (a regular hexagon in this embodiment). When a large number of plate-like pieces 13 are uniformly laid out, the planar shape of the plate-like pieces 13 can be selected to be a triangle, a rectangle, a hexagon, or an equilateral pentagon. The planar shape of the plate-like pieces 13 may also be other than these shapes, and other polygons, circles, ellipses, etc. can also be selected. When the planar shape of the plate-like pieces 13 is basically a polygon, each corner may be chamfered.

[0031] The thickness of the plate-like piece 13 can be, for example, in the range of 0.05 mm to 10 mm (e.g., 0.05 mm to 2 mm). Furthermore, with regard to the planar dimensions of the plate-like piece 13, the average value of the distance from the center of gravity to the outer periphery (average value over 360 degrees; radius in the case of a circle) can be in the range of 3 mm to 50 mm (e.g., 5 mm), and if the plate-like piece 13 is a regular hexagon, the length of one side can be in the range of 3 mm to 10 mm (e.g., 5 mm). However, the dimensions of the plate-like piece 13 may be outside the ranges described in this paragraph.

[0032] In the core layer 20, all of the plate-like pieces 13 are separated from one another and are separate entities. The entire periphery of each plate-like piece 13 is separated from all of the adjacent plate-like pieces 13 by gaps 16. Each plate-like piece 13 has an island-like structure independent of the others. Adjacent plate-like pieces 13 are not connected to each other by connecting parts made of the same material as the plate-like pieces 13. The composite material 30 is a multi-web panel in which the skin materials 31, 32 function as flanges in an I-beam structure and the plate-like pieces 13 function as webs, and is a sandwich-structure panel in which the plate-like pieces 13 function as the core material.

[0033] Adjacent plate-like pieces 13 face each other with a gap 16 between their sides. The width W of the gap 16 varies depending on factors such as the size of the gap between adjacent blades 24 in the upper die 23, which will be described later. The width W of the gap 16 is constant along the opposing sides. Furthermore, in each plate-like piece 13, the width W of the gap 16 between each side is equal to each other. The dimension of the width W of the gap 16 is designed appropriately depending on factors such as the size of the composite material 30, and can be, for example, in the range of 0 mm to 10 mm.

[0034] In the core layer 20, a large number of plate-like pieces 13 are arranged regularly. The large number of plate-like pieces 13 are evenly spread out. In this embodiment, the plate-like pieces 13 are arranged in a staggered pattern, with the plate-like pieces 13 being offset by half a pitch between adjacent plate-like piece rows 13L. In this embodiment, the planar shape of each plate-like piece 13 is a regular hexagon, and the arrangement of the plate-like pieces 13 can also be described as a honeycomb arrangement in which gaps are formed between adjacent plate-like pieces 13.

[0035] A chamfered portion 13c is formed around the entire periphery of one of the main surfaces 13a (the bottom surface in FIG. 2 ) of each plate-like piece 13 (one of the surfaces 13a, 13b parallel to the arrangement surface of each plate-like piece 13). The chamfered portion 13c is a trace (cut mark) indicating that the plate-like piece 13 has been formed by punching, and is an arc-shaped curved surface (for example, a rounded surface of about 0.05 mm) or a curved surface that bulges outward like an arc. The shape of the chamfered portion 13c varies depending on the shape of the tip of the blade 24 used in the punching process. In each plate-like piece 13, the dimensions of the chamfered portion 13c are approximately uniform around the entire periphery. In this specification, the "main surface" of the plate-like piece 13 refers to the front or back surface.

[0036] Furthermore, the many plate-like pieces 13 (for example, all of the plate-like pieces 13 of the core layer 20) have the same cutting direction in the thickness direction, as determined from cutting marks formed on the periphery as traces of manufacturing using the transfer sheet 10 described below. Specifically, the many plate-like pieces 13 have chamfered portions 13c formed on the periphery of the main surface 13a on the same side in the thickness direction.

[0037] [Transfer sheet composition] Next, the transfer sheet 10 used in the production of the composite material 30 will be described. The transfer sheet 10 is a sheet that can transfer a large number of plate-like pieces 13 from a base sheet 11 to another structural material (a structure with a sticky or adhesive surface). The transfer sheet 10 corresponds to an intermediate sheet. In this specification, the term "intermediate sheet (intermediate material)" refers to a sheet that is produced in an intermediate step in the production process of the composite material 30.

[0038] As shown in FIG. 4, the transfer sheet 10 includes a core layer 20 and a base sheet 11 on which the core layer 20 is laminated. The base sheet 11 is produced by cutting a long base sheet 11A, which will be described later. On the surface of the base sheet 11 facing the core layer 20, cut marks (V-shaped grooves) 43 remain, which were created when the numerous plate-like pieces 13 were cut (see FIG. 9). In the core layer 20, adjacent plate-like pieces 13 are separated by gaps 16. In the core layer 20, a chamfered portion 13c is formed on the outer periphery of the main surface 13a on the same side of each plate-like piece 13 in the thickness direction.

[0039] The numerous plate-like pieces 13 are removably attached to the surface of the base sheet 11. Each plate-like piece 13 is held to the base sheet 11 with a certain adhesive force by an adhesive layer 18. Each plate-like piece 13 has a main surface 13b opposite to the main surface 13a on the chamfered portion 13c side attached to the base sheet 11. If the surface of the base sheet 11 is adhesive, the adhesive layer 18 may be omitted.

[0040] The arrangement of the plate-like pieces 13 on the base sheet 11 is the basis for the arrangement of the plate-like pieces 13 in the core material layer 20 of the composite material 30. The plan view of the core material layer 20 of the transfer sheet 10 is the same as that shown in FIG.

[0041] [Manufacturing method for composite materials] The method for manufacturing the composite material 30 includes a first manufacturing step of manufacturing a foam roll 12, a second manufacturing step of manufacturing a transfer sheet 10 using the foam roll 12 obtained in the first manufacturing step, and a third manufacturing step of manufacturing the composite material 30 using the transfer sheet 10 obtained in the second manufacturing step, in this order. The foam roll 12 corresponds to a long foam sheet.

[0042] In the first manufacturing process, a slicing process is performed to slice a foam block 35 to produce foam sheets 14. A sheet attaching process is performed to attach a plurality of foam sheets 14 (single-leaf foam sheets) produced in the slicing process to the surface of a long base sheet 11A. These processes are performed in this order to produce a foam roll 12 in which a plurality of foam sheets 14 are wound in a roll shape along the length of the base sheet 11A. In addition to these processes, in this embodiment, a sheet stretching process and an inspection process are performed between the slicing process and the sheet attaching process. In this specification, the term "a plurality of foam sheets" refers to five or more. That is, the number of foam sheets 14 in the foam roll 12 is at least five or more (when a foam block 35 having the dimensions described in the next paragraph is used, the length of the foam roll 12 is 5,000 mm or more). The number may be ten or more (when the length of the foam roll 12 is 10,000 mm or more).

[0043] In the first manufacturing step, a foam block 35 and a base sheet 11A are prepared as materials. A substantially rectangular parallelepiped hard resin foam (e.g., polymethacrylimide (PMI) closed-cell foam) can be used for the foam block 35. The dimensions of the foam block 35 are, for example, 2000 mm in length, 1000 mm in width, and 50 mm in thickness.

[0044] On the other hand, base sheet 11A is a long sheet wound into a roll. Base sheet 11A has a uniform thickness along its length, for example, in the range of 0.01 mm to 0.5 mm. The width of base sheet 11A must be equal to or greater than the width of foam sheet 14, and in this embodiment, it is equal to the width of foam sheet 14.

[0045] The base sheet 11A is, for example, a resin sheet or film (such as a thermoplastic resin sheet). A variety of resins can be used for the base sheet 11, including polyethylene, polypropylene, urethane, polyester, polyethylene terephthalate (PET), and polycarbonate. In this embodiment, an acrylic, urethane, or silicone adhesive is applied to the entire surface of one side of the base sheet 11A. In other words, the long base sheet 11A is an adhesive tape (or a slightly adhesive tape). The base sheet 11A may have a separate sheet (not shown) laminated on the back side. The base sheet 11 may be a rubber or paper sheet (or film) in addition to a resin.

[0046] In the slicing step, a slicing process is performed to cut foam block 35 into uniform thicknesses (a value in the range of 0.05 mm to 10 mm (for example, 0.05 mm to 2 mm)). In this slicing process, foam block 35 is cut by slicing blade 36 while at least one of foam block 35 and slicing blade 36 is moved in a certain direction. In FIG. 5, cutting is performed while moving foam block 35, out of the slicing blade 36 and foam block 35. In the slicing step, slicing is repeatedly performed on each of multiple foam blocks 35, and a large number of foam sheets 14 of the same thickness are created. Note that in FIG. 5, the member that secures slicing blade 36 is not shown.

[0047] Here, each foam sheet 14 obtained by slicing retains a curling tendency and is curled in the slicing direction. Therefore, in this embodiment, a sheet stretching process is performed before the sheet attachment process to reduce the curling tendency of the foam sheet 14. In addition, the density of the foam block 35 is usually not uniform, and there is a risk of variation in weight among the many foam sheets 14 produced in the slicing process. Furthermore, since the foam block 35 varies in hardness due to the variation in density, there is a risk of variation in thickness among the many foam sheets 14 produced in the slicing process. Therefore, in this embodiment, an inspection process is performed before the sheet attachment process to sort the foam sheets 14 by inspecting at least one of the weight and the thickness.

[0048] Both the sheet stretching step and the inspection step may be omitted, or only one may be performed. Furthermore, in the inspection step, only one of the weight and thickness may be inspected. Furthermore, the order of the sheet stretching step and the inspection step may be such that the sheet stretching step is performed first, or the inspection step is performed first. Furthermore, the sheet stretching step may be performed between the weight inspection step and the thickness inspection step.

[0049] In the sheet stretching process, the curled foam sheets 14 are fed one by one into a stretching device 55 shown in Fig. 6, and the foam sheets 14 are stretched. The stretching device 55 is a device that stretches the foam sheet 14 by driving a belt 56 to convey the foam sheet 14 fed between adjacent rollers 72, 74, between the belt 56 and the roller 74, and between adjacent rollers 73, 74. In the stretching device 55, some of the rollers 73, 74 are heated rollers, and the foam sheet 14 is heated by the rollers 73, 74, so that the curled foam sheet 14 is effectively removed.

[0050] Specifically, the stretching device 55 includes a plurality of rollers 71 to 74, an endless belt 56, and a drive motor (not shown) that rotates at least one roller 71 to rotate the belt 56. The belt 56 is wound around a first roller 71 and a second roller 72 and a third roller 73 that are spaced apart from the first roller 71. The belt 56 has a running track that is recessed inward by a fourth roller 74 that is located between the second roller 72 and the third roller 73. The second roller 72, the third roller 73, and the fourth roller 74 are arranged adjacent to each other in the vertical direction with gaps between them. In the stretching device 55, the foam sheet 14 introduced between the second roller 72 and the fourth roller 74 is sandwiched between the fourth roller 74 and the belt 56, transported around the fourth roller 74 and stretched, and then passes through the gap between the third roller 73 and the fourth roller 74 and transported around the third roller 73 and stretched. The foam sheet 14 stretched substantially straight is then conveyed to the first roller 71 side and picked up by a worker.

[0051] In the inspection process, the foam sheets 14 are inspected for weight and thickness, and the foam sheets 14 are selected. In this selection, selection criteria established for each of weight and thickness are used. The selection criteria for weight are that the measured weight of the foam sheet 14 falls within an error range (for example, a range of ±10%) of the designed weight value. On the other hand, the selection criteria for thickness are that the measured thickness of the foam sheet 14 falls within an error range (for example, a range of ±10%) of the designed thickness value. In the inspection process, the weight and thickness of each foam sheet 14 are measured, and foam sheets 14 that do not meet the selection criteria for either the weight or thickness measurement are excluded, and only foam sheets 14 that meet both selection criteria are selected.

[0052] Next, in the sheet bonding process, as shown in FIG. 7, the roll-shaped base sheet 11A placed on the first reel 81 is unwound and wound around the second reel 82. In this state, the base sheet 11A is wound around the second reel 82, and the base sheet 11A moves between the two reels 81 and 82. In the sheet bonding process, the base sheet 11A repeatedly moves and stops, and while the base sheet 11A is stopped, the foam sheet 14 is bonded to the base sheet 11A between the two reels 81 and 82. In the sheet bonding process, multiple foam sheets 14 are bonded to the base sheet 11A in a line without overlapping each other, without any gaps (or with only small gaps) along the length of the base sheet 11A. Then, the base sheet 11A to which multiple foam sheets 14 are bonded is wound around the second reel 82, and a foam roll 12 is completed.

[0053] After the sheet adhering step, a sheet connecting step may be further carried out in which adjacent foam sheets 14 on the long base sheet 11A are connected with tape 85, as in Fig. 20. In this case, tape 85 corresponds to a connecting member, and is attached along the seams of adjacent foam sheets 14 to connect the adjacent foam sheets 14 to each other.

[0054] Next, the second manufacturing process will be described.

[0055] In the second manufacturing process, a cutting process is carried out in which each foam sheet 14 constituting the foam roll 12 is divided into a large number of plate-like pieces 13 by cutting. In the cutting process, the foam sheet 14 attached to the base sheet 11A is subjected to a punching process (press cut) to manufacture the transfer sheet 10 shown in FIG.

[0056] In the cutting process, the foam roll 12 is placed on a reel 51 of a production line 50 shown in FIG. 8. The foam sheet 14 is then unwound from the foam roll 12 in the longitudinal direction together with the base sheet 11A and passed through a press device 15 shown in FIG. 9(a). The foam sheet 14 on the lower mold 22 of the press device 15 is then press-cut by being vertically cut by the blade 24 of the upper mold 23. As shown in FIG. 9(b), the base sheet 11A is not completely cut but is instead half-cut (i.e., cut only enough to prevent the sheet from penetrating completely). Swarf 39 is formed between the blades 24 (see FIG. 9(c)). In this embodiment, a large number of plate-like pieces 13 are formed on the base sheet 11A to produce the transfer sheet 10. The planar shape of the blade 24 corresponds to the outer peripheral shape of the plate-like pieces 13. For example, when forming regular hexagonal plate-like pieces 13, a blade 24 having a regular hexagonal shape in plan view is used. In the upper die 23, a large number of blades 24 are arranged at intervals on a two-dimensional plane. In addition, during the punching process, depending on the cutting conditions, burrs may be formed on the outer periphery of the main surface 13a of each plate-like piece 13 instead of chamfered portions 13c.

[0057] In this embodiment, after cutting, scraps 39 of the foam sheet 14 other than the numerous plate-like pieces 13 become a mesh sheet 38. The mesh sheet 38 made up of the scraps 39 is taken up by the take-up reel 25 and removed (see FIG. 8). A protective film 27 unwound from a roll provided on another reel 26 is laminated on the plate-like piece 13 side of the transfer sheet 10. The numerous plate-like pieces 13 are covered with the protective film 27. In this embodiment, the long transfer sheet 10 is cut to a predetermined length by the cutter 28 and divided into multiple transfer sheets 10. Note that the steps of taking up by the take-up reel 25, covering with the protective film 27, and cutting by the cutter 28 may be omitted.

[0058] In this embodiment, the upper die 23 moves up and down relative to the lower die 22 during press cutting, but press cutting may also be performed by rotary pressure applied by a rotary die (die-cut roll).

[0059] Next, the third manufacturing process will be described.

[0060] In the third manufacturing process, a transfer process is performed in which the numerous plate-like pieces 13 on the transfer sheet 10 are transferred to a first skin sheet 31A, and a lamination process is performed in this order in which a second skin sheet 32A is laminated onto the numerous plate-like pieces 13 transferred in the transfer process to create a laminate 30B in which the numerous plate-like pieces 13 are sandwiched between a pair of skin sheets 31A, 32A, to produce a composite material 30. The skin sheets 31A, 32A are made of the material of the above-mentioned skin materials 31, 32 (see FIG. 2), and for example, semi-cured prepreg (prepreg sheet) can be used.

[0061] In the transfer step, first, a first skin sheet 31A is placed on a mold (e.g., a metal die) 33. Next, as shown in FIG. 10(a), the transfer sheet 10 obtained in the second manufacturing step is placed on the first skin sheet 31A on the mold 33, with the plate-like pieces 13 facing it. Next, as shown in FIG. 10(b), the multiple plate-like pieces 13 of the transfer sheet 10 are pressed against the first skin sheet 31A. The surface of the first skin sheet 31A is adhesive. Therefore, the multiple plate-like pieces 13 are attached to the first skin sheet 31A. Then, as shown in FIG. 10(c), the base sheet 11 is peeled off from the multiple plate-like pieces 13. In this case, the adhesive strength of the first skin sheet 31A to the numerous plate-like pieces 13 is greater than the adhesive strength of the adhesive layer 18 to the numerous plate-like pieces 13, so that the numerous plate-like pieces 13 are transferred from the base sheet 11 to the first skin sheet 31A.

[0062] Next, in the lamination step, as shown in FIG. 11(a), a second skin sheet 32A is first placed at a distance from the laminate 30A obtained in the transfer step so as to face the plate-like pieces 13 side. Then, as shown in FIG. 11(b), the second skin sheet 32A is laminated on the plate-like pieces 13 side of the laminate 30A. The surface of the second skin sheet 32A is adhesive. Therefore, the numerous plate-like pieces 13 are attached to the second skin sheet 32A. As a result, a laminate 30B is obtained in which the numerous plate-like pieces 13 are sandwiched between the pair of skin sheets 31A, 32A.

[0063] If the matrix of the prepreg used for each of the skin sheets 31A and 32A is a thermosetting resin (e.g., epoxy resin), a molding process is carried out. In the molding process, the laminate 30B obtained in the lamination process is sealed using a bagging film. The laminate 30B sealed with the bagging film is then heated in an autoclave at a predetermined temperature and pressure (e.g., 0.2 MPa, 130°C) for a predetermined time (e.g., 2 hours). During this heating process, the semi-cured skin sheets 31A and 32A become the fully cured skins 31 and 32. As a result, the composite 30 is formed into a predetermined shape (a flat plate in the case of FIG. 11(b)) and cured.

[0064] In the molding process, when the laminated material 30B is heated, the resin (matrix) of the prepreg flows into the gaps 16 between the plate-like pieces 13, filling the gaps 16 in the core layer 20. The resin that flows in hardens in the gaps 16, thereby preventing localized reductions in strength of the composite material 30. Furthermore, when the gaps 16 are large, the prepregs used as the material for the skin materials 31, 32 can have a large amount of resin per unit area.

[0065] Alternatively, a curable resin (e.g., a thermosetting, two-component, or moisture-reactive adhesive) may be injected into the gaps 16 between the plate-like pieces 13 using a pressure difference, separate from the prepreg matrix. The injected resin is cured in the gaps 16. Alternatively, a film-like adhesive may be added between the two skin materials 31 and 32. In this case, the film-like adhesive melts when the laminate 30B is heated, and the molten adhesive (resin) flows into the gaps 16 and eventually hardens. In these cases, as shown in FIG. 12, the gaps 16 between adjacent plate-like pieces 13 are filled with the cured resin 6, which prevents localized strength reduction in the composite material 30 and improves its rigidity. Filling with the curable resin can be performed even when prepreg is not used as the material for the skin materials 31 and 32.

[0066] When the matrix of the prepreg used for each of the skin sheets 31A, 32A is a thermoplastic resin (for example, polyamide resin, polypropylene resin, or polyether ether ketone resin), after a molding process such as pressurized and heated press molding, a curing process is carried out by cooling the laminate 30B in an atmosphere at a temperature lower than the curing temperature of the matrix (for example, room temperature), and the composite material 30 is completed.

[0067] [Effects of this embodiment] In this embodiment, a large number of foam sheets 14 prepared by the slicing process are aligned and attached to one side of a long base sheet 11A to produce a long foam sheet 12. As described above, it is possible to prepare a large number of short foam sheets 14 with a substantially uniform thickness. Therefore, by aligning and attaching a large number of foam sheets 14, a long foam sheet 12 with a substantially uniform thickness in the longitudinal direction can be produced.

[0068] Furthermore, in this embodiment, the curling tendency of the foam sheet 14 is reduced by the sheet stretching step, so that the foam sheet 14 can be attached to an accurate position in the sheet attachment step.

[0069] Furthermore, in this embodiment, the inspection process allows only foam sheets 14 that meet the selection criteria for weight and mass to be attached to the base sheet 11A, thereby further uniforming the weight and thickness in the longitudinal direction of the foam sheet 14 layers of the long foam sheet 12.

[0070] Furthermore, in this embodiment, the chips 39 become the mesh sheet 38 and can be easily removed, so that the intermediate sheet 10 and the composite material 30 can be produced efficiently.

[0071] In this embodiment, the transfer sheet 10 is used to arrange the numerous plate-like pieces 13 in the core layer 20. Therefore, it is not necessary to arrange the numerous plate-like pieces 13 individually, and the core layer 20 can be easily formed.

[0072] <First Modification> In this modified example, the transfer step is not performed, and the intermediate sheet 10 is sandwiched directly between a pair of skin sheets 31A, 32A in the lamination step to produce the laminate 30B shown in Fig. 13. In this case, the intermediate sheet 10 is used as an adhesive core sheet into which the base sheet 11 is dissolved. When the intermediate sheet 10 is used as a transfer sheet, an adhesive is used to enable the plate-like pieces 13 to be peeled from the base sheet 11. However, when the intermediate sheet 10 is used as an adhesive core sheet, an adhesive other than an adhesive can be used to attach the foam sheet 14 to the base sheet 11.

[0073] Specifically, in the third manufacturing step, an intermediate sheet 10 and a second skin sheet 32A are laminated in this order on a first skin sheet 31A on a mold 33. The intermediate sheet 10 may be laminated with the plate-like piece 13 attached to the first skin sheet 31A, as shown in FIG. 13 . Alternatively, the base sheet 11 may be attached to the first skin sheet 31A (not shown). The second skin sheet 32A is then laminated to obtain a laminate 30B. The method for manufacturing a composite 30 from the laminate 30B is the same as in the above-described embodiment, and therefore a description thereof will be omitted. If the amount of resin required to fill the gaps 16 is insufficient, a resin sheet (e.g., a sheet adhesive, prepreg, etc.) may be laminated on one or both sides of the core layer 20. A single composite 30 may be manufactured using multiple intermediate sheets 10 as adhesive core sheets.

[0074] <Second Modification> In this modification, in the transfer step, the numerous plate-like pieces 13 on the transfer sheet 10 are transferred to the sheet-like adhesive 111, rather than to the first skin sheet 31A.

[0075] Specifically, in the transfer step, as shown in Figures 14(a) and 14(b), a sheet-like adhesive 111 is attached to the side of the plate-like pieces 13 of the transfer sheet 10 (first intermediate sheet). The sheet-like adhesive 111 has a separation sheet 141 laminated on its back surface. Next, as shown in Figure 14(c), the base sheet 11 is peeled off from the many plate-like pieces 13, thereby transferring the many plate-like pieces 13 to the sheet-like adhesive 111, and an adhesive core sheet 60 is produced as a second intermediate sheet. Then, in the lamination step, the adhesive core sheet 60 is sandwiched between a pair of skin sheets 31A, 32A, similar to the adhesive core sheet 10 of the first modified example, to produce a laminate 30B.

[0076] <Third Modification> In this modified example, in the transfer step, a large number of plate-like pieces 13 on a transfer sheet (first intermediate sheet) 10 are transferred to a prepreg 31A to produce a composite material manufacturing sheet (second intermediate sheet) 70 shown in FIG. 15. That is, in the second intermediate sheet, semi-cured prepreg 31A is used instead of the sheet-like adhesive 111 of the second modified example. The prepreg 31A may have a separator sheet 141 laminated on its back surface. The prepreg 31A corresponds to a skin sheet. Then, in the lamination step, the composite material manufacturing sheet 70 is placed on a mold with the prepreg 31A facing downward, and a prepreg 31B corresponding to the skin sheet is laminated from above.

[0077] <Fourth Modification> 16, a composite material 130 further includes a second core layer 21 having a large number of plate-like pieces 13 arranged along the surface of a second skin material 32, and an intermediate adhesive layer 17 disposed between the first core layer 20 and the second core layer 21. The intermediate adhesive layer 17 is formed using a sheet-like adhesive (also referred to as a film-like adhesive or adhesive sheet) that melts when heated and then thermosets, and bonds the first core layer 20 and the second core layer 21 together.

[0078] In a method for producing a composite material 130 according to this modified example, the laminated material before the molding step can be produced by laminating an adhesive core sheet, in which the first core layer 20 and intermediate adhesive layer 17 are integrated, onto a first skin sheet 31A on a mold, then transferring a large number of plate-like pieces 13 from a transfer sheet 10 to the intermediate adhesive layer 17, and then laminating a second skin sheet 32A on top. Alternatively, the composite material can be produced by placing a composite manufacturing sheet 70 according to the third modified example on a mold with the prepreg 31A facing downwards, and then laminating the adhesive core sheet 10 and prepreg 32A according to the first modified example on top of it in that order.

[0079] In this modification, the core material layers 20, 21 are two layers, but the core material layers 20, 21 may be three or more layers. In this case, an intermediate adhesive layer 17 is also provided between the core material layers 20, 21 adjacent to each other in the thickness direction. Furthermore, instead of using a sheet-like adhesive, the intermediate adhesive layer 17 may be made of prepreg or a thermosetting resin sheet (such as epoxy resin).

[0080] In this modification, the plate-like pieces 13 have a two-layer structure in the core layer 20. Here, when forming a curved composite material 30, the thicker the plate-like pieces 13, the greater the tensile strain on one side of the plate-like pieces 13. Depending on the thickness of the plate-like pieces 13 and the degree of bending, there is a risk that one side of the plate-like pieces 13 may be damaged by the tensile strain. In contrast, in this modification, when compared with composite materials of the same thickness, each plate-like piece 13 is thinner than a composite material 30 having a single-layer plate-like piece 13. Therefore, the tensile strain on one side of each plate-like piece 13 is smaller, and damage is less likely to occur even when low-toughness hard resin foam is used for the plate-like pieces 13. This modification makes it possible to provide a composite material 30 with excellent moldability into three-dimensional shapes.

[0081] <Fifth Modification> In this modified example, as shown in Fig. 17, a composite material 131 has a canapé structure. In addition, in the core material layer 20 on the skin material 31, rectangular plate-like pieces 13 are arranged in a fixed direction. Gaps 16 are formed between adjacent plate-like pieces 13. Note that, although the plate-like pieces 13 are not divided in the length direction in Fig. 17, the plate-like pieces 13 may also be divided in the length direction.

[0082] In this modification, in the cutting step, the foam sheet 14 attached to the base sheet 11A is punched (press cut) to produce a transfer sheet (not shown) in which rectangular plate-like pieces 13 are arranged in a fixed direction on the base sheet 11A. Then, in the transfer step, the numerous plate-like pieces 13 on the transfer sheet are transferred to a skin sheet 31A such as a prepreg.

[0083] The cylindrical body 100 can be manufactured by rolling the composite material 131 into a cylindrical shape. When the composite material 131 is rolled with the skin material 31 side facing inward, the cylindrical body 100 shown in FIG. 18 is obtained. In this case, the core material layer 20 is not laminated on both end portions 31a of the skin material 31, and one end portion 31a serves as an attachment margin on the inner circumferential surface (a location attached to the skin material 31 one layer away from the center), while the other end portion 31a is laminated so as to cover the outermost plate-like piece 13. The cylindrical body 100 can also be obtained when the composite material 131 is rolled with the skin material 31 side facing outward. In this case, one end portion 31a is laminated so as to cover the innermost plate-like piece 13, and the other end portion 31a serves as an attachment margin on the outer circumferential surface (a location attached to the skin material 31 one layer away from the center). The end portion 31a of the skin material 31 is laminated on the innermost side so as to cover the multiple plate-like pieces 13.

[0084] <Other variations> In the above-described embodiment, foam sheet 14 may be cut by laser cutting instead of press cutting to divide it into multiple plate-like pieces 13. Alternatively, foam sheet 14 may be cut and divided into multiple plate-like pieces 13 using a cutting device (cutting plotter) that moves a blade along the cutting shape.

[0085] In the above-described embodiment, adjacent plate-like pieces 13 in the core material layer 20 are separated by a gap 16, but adjacent plate-like pieces 13 may be separated by a notch 40. In this case, as shown in Figures 19(a) and 19(b), adjacent plate-like pieces 13 are cut by the same blade 24. For example, when forming regular hexagonal plate-like pieces 13, blades 24 with a regular hexagonal arrangement pattern are used. Then, as shown in Figure 19(c), when the blade 24 is pulled out, the plate-like pieces 13 that were elastically deformed in the state of Figure 19(b) return to their original shape, and notches 40 remain between adjacent plate-like pieces 13.

[0086] In the above-described embodiment, a long base sheet 11 is used to manufacture a long foam sheet, but the base sheet 11 may be omitted. That is, the method for manufacturing a long foam sheet may include a sheet connecting step in which a number of foam sheets 14 are arranged in a certain direction and connected with connecting members (tapes) 85 to manufacture a long foam sheet in which a number of foam sheets 14 are connected together (see FIG. 20).

[0087] In the above-described embodiment, a large number of foam sheets 14 may be attached to the base sheet 11 after connecting a plurality of foam sheets 14 (for example, 2 to 10 sheets) with connecting members 85 so that they are aligned in a certain direction.

[0088] In the above embodiment, the inner portion of the blade 24 used in punching of the foam sheet 14 of the long foam sheet 12 is used as the core material to form the island-shaped core layer 20. However, the inner portion of the blade 24 may be used as the cutting chip, and the outer portion of the blade 24 may be used as the core material. In this case, the punching process is not performed by half-cutting as described above, but by full-cutting, in which the blade 24 cuts both the foam sheet 14 and the base sheet 11 in the thickness direction. The core layer 20 has a structure in which many chambers (chambers in the planar shape of the blade 24) are formed, and when the planar shape of the blade 24 is a regular hexagon, it has a honeycomb structure.

[0089] In the above-described embodiment, a slicing process may be performed using a slicing technique called a slicing technique. In this slicing process, as shown in FIG. 21(a), the foam block 35 is passed across the straight portion of a rotating, endless, thin band knife 80 in the width direction of the band knife 80, slicing the foam block 35 to produce a foam sheet 14. In this case, as shown in FIG. 21(b), the foam block 35 may be fed toward the band knife 80 by a roller 81. Alternatively, as shown in FIG. 21(c), the foam block 35 may be fed toward the band knife 80 by moving a table 82 carrying the foam block 14. In the case of the slicing process, the foam sheet 14 hardly develops a curl, so the sheet stretching step may be omitted. Note that FIG. 21(a) is a perspective view, and FIGS. 21(b) and 21(c) are cross-sectional views. Also, pulleys and other components for rotating the band knife 80 are omitted from FIG. 21(a).

[0090] In the above-described embodiment, a metal-based material may be used as the material of the skins 31 and 32. In this case, each plate-like piece 13 is joined to the skins 31 and 32 by an adhesive.

[0091] In the above embodiment, a hard resin foam is used as the material for the plate-like pieces 13, but when a slicing process is performed, any type of foam that can be formed into a foam block 35 in a substantially rectangular parallelepiped shape by foam molding can be suitably used, and types of foam other than hard resin foam may also be used. Furthermore, even when a slicing process is not performed, types of foam other than hard resin foam may also be used.

[0092] In the above-described embodiment, the shapes of all the plate-like pieces 13 in the core layer 20 do not have to be the same. For example, the planar shape of the plate-like pieces 13 in a region of the composite material 30 may be determined depending on the curvature of that region.

[0093] In the above-described embodiment, the composite material 30 shown in Fig. 2 may have a canapé structure, omitting the second skin material 32. In this case, the plate-like piece 13 side of the composite material 30 is attached to the structural material to be reinforced. The core layer 20 is sandwiched between the first skin material 31 and the structural material to be reinforced. Note that the core layer 20 in the canapé structure does not form a central layer as in a sandwich structure, but after being attached to the structural material to be reinforced, a central layer is formed between the first skin material 31 and the structural material to be reinforced. [Industrial Applicability]

[0094] The present invention is applicable to a method for producing a long foam sheet used in composite materials and the like. [Explanation of symbols]

[0095] 10 Transfer sheet (intermediate sheet) 11 Base sheet 11A Long base sheet 12 Foam roll (long foam sheet) 13 Plate-like pieces 14 foam sheets 20 Core layer 30 Composite materials 31,32 Skin material 31A, 32A Skin sheet 35 foam blocks 36 Slicing knife

Claims

1. a sheet attaching step of attaching a number of foam sheets to one surface of a long base sheet in the length direction of the base sheet without gaps or overlaps with each other; A long foam sheet is produced in which the multiple foam sheets are connected in the length direction of the base sheet, A method for producing a roll of long foam sheets, comprising winding the long foam sheets into a roll without providing an adhesive layer or a bonding layer on the surface of each of the multiple foam sheets opposite to the base sheet.

2. A sheet attaching step is carried out in which a number of foam sheets are aligned and attached to one side of a long substrate sheet, A long foam sheet is produced in which the multiple foam sheets are connected in the length direction of the base sheet, Before the sheet attaching step, a slicing step of slicing the foam block to produce a foam sheet, and a sheet stretching step of reducing curling of the foam sheet produced by the slicing step are further carried out; In the sheet attaching step, the foam sheet whose curling tendency has been reduced by the sheet stretching step is attached to the base sheet.

3. A sheet attaching step is carried out in which a number of foam sheets are aligned and attached to one side of a long substrate sheet, A long foam sheet is produced in which the multiple foam sheets are connected in the length direction of the base sheet, Before the sheet attaching step, a slicing step of slicing the foam block to produce foam sheets, and an inspection step of inspecting the foam sheets produced by the slicing step for at least one of weight and thickness to select foam sheets that meet a selection criterion are further carried out, In the sheet attaching step, a foam sheet that satisfies the selection criteria in the inspection step is attached to the base sheet.

4. A sheet attaching step is carried out in which a number of foam sheets are aligned and attached to one side of a long substrate sheet, A long foam sheet is produced in which the multiple foam sheets are connected in the length direction of the base sheet, a cutting step of dividing the foam sheet constituting the long foam sheet produced by the sheet attaching step into a plurality of plate-like pieces by cutting; a lamination step in which the numerous plate-like pieces obtained by the cutting step are sandwiched between a pair of skin sheets, Manufacturing composite materials, manufacturing methods for composite materials.

5. The method for producing a composite material according to claim 4 , further comprising a sheet connecting step of connecting adjacent foam sheets on the base sheet with a connecting member after the sheet attaching step and before the cutting step.

6. The method for producing a composite material according to claim 5, wherein scraps other than the numerous plate-like pieces are removed from the foam sheet after the cutting process by winding it up.

7. In the cutting step, an intermediate sheet is prepared in which the numerous plate-like pieces are attached to the base sheet, After the cutting step, a transfer step is carried out in which the numerous plate-like pieces on the intermediate sheet are transferred to one of the pair of skin sheets; 7. The method for manufacturing a composite material according to claim 4, wherein in the laminating step, the other of the pair of skin material sheets is laminated onto the numerous plate-like pieces transferred in the transferring step.

8. In the cutting step, an intermediate sheet is prepared in which the numerous plate-like pieces are attached to the base sheet, 7. The method for manufacturing a composite material according to claim 4, wherein in the laminating step, the intermediate sheet is sandwiched between the pair of skin sheets.

9. A long base sheet; a plurality of foam sheets attached to one surface of the base sheet in a longitudinal direction of the base sheet without gaps and without overlapping each other; the plurality of foam sheets are connected to each other only by the base sheet on the base sheet side, The long foam sheet is wound into a roll without providing an adhesive layer or a bonding layer on the surface of the foam sheets opposite to the base sheet.

10. A sheet connecting step is carried out in which a number of foam sheets are arranged in a certain direction and connected with connecting members, A long foam sheet is produced in which the multiple foam sheets are connected together, a cutting step of dividing the foam sheet constituting the long foam sheet produced by the sheet attaching step into a plurality of plate-like pieces by cutting; a lamination step in which the numerous plate-like pieces obtained by the cutting step are sandwiched between a pair of skin sheets, Manufacturing composite materials, manufacturing methods for composite materials.

11. A sheet connecting step is carried out in which a number of foam sheets are arranged in a certain direction and connected with connecting members, A long foam sheet is produced in which the multiple foam sheets are connected together, Before the sheet attaching step, a slicing step of slicing the foam block to produce a foam sheet, and a sheet stretching step of reducing curling of the foam sheet produced by the slicing step are further carried out; In the sheet connecting step, the foam sheets whose curling tendency has been reduced by the sheet stretching step are connected by the connecting member.

12. A sheet connecting step is carried out in which a number of foam sheets are arranged in a certain direction without gaps or overlaps and connected with connecting members, A long foam sheet is produced in which the multiple foam sheets are connected together, Before the sheet attaching step, a slicing step of slicing the foam block to produce foam sheets, and an inspection step of inspecting the foam sheets produced by the slicing step for at least one of weight and thickness to select foam sheets that meet a selection criterion are further carried out, In the sheet connecting step, foam sheets that meet the selection criteria in the inspection step are connected by the connecting member.

Images