Sheet forming method

Abstract

To provide a molding method capable of suppressing the occurrence of wrinkles at the corners of a molded product when molding a sheet including a composite sheet composed of a woven fabric made of non-melting fibers and a thermoplastic resin, and capable of molding molded products having curved surfaces with nearly right-angled corners such as bags, cases, covers, etc. while ensuring the strength of the curved surfaces without impairing the design of the weave structure of the woven fabric. [Solution] A method for molding a sheet using a male-female interlocking molding die, characterized in that a sheet placed between a male die and a female die is heated to a temperature equal to or higher than the Vicat softening point and lower than the melting point of the thermoplastic resin constituting the sheet, and then the male die and female die are interlocked at a position lower than the position at which the sheet was placed when heated, thereby applying diagonal tension to the four corners of the sheet.

Description

[Technical field]

[0001] The present invention relates to a method for molding a sheet using a male-female interlocking molding die having a male die and a female die. [Background technology]

[0002] As a method for molding a composite sheet composed of a woven fabric and a resin, a method has been disclosed in which a composite sheet composed of a flat yarn woven fabric and a thermoplastic resin is vacuum molded on both sides using a male-female interlocking molding die (Patent Document 1).

[0003] The flat yarn woven fabric disclosed in Patent Document 1 is made by weaving flat yarns composed of polyolefin polymers such as polyethylene, polypropylene, and a mixed resin of polyethylene and polypropylene into a plain weave, twill weave, satin weave, leno weave, alternating weave, etc. Then, a flat yarn laminate sheet having a thermoplastic resin layer with a lower melting point than the flat yarn arranged on both sides of the flat yarn woven fabric is placed between heated male and female mating molding dies, and the flat yarn laminate sheet is brought into contact with the female die and then the male die, and vacuum molding is performed on both sides (Claim 1, Examples, etc. of Patent Document 1).

[0004] However, when a composite sheet is used that is composed of a woven fabric or the like made of non-melting fibers and a thermoplastic resin, unlike the above-mentioned flat yarn laminate sheet, in which the sheet softens due to the heat in the molding die, the non-melting fibers do not soften due to heat, and a problem occurs in that wrinkles occur at the corners when the sheet is molded in a similar manner.

[0005] As a method for improving wrinkles in molded products, a device has been disclosed that performs thermoforming or vacuum forming while holding the running direction of sheet material and the widthwise edges perpendicular to that (the edges in the up-down and left-right directions relative to the sheet plane) with a clamping device (Patent Document 2).

[0006] The device disclosed in Patent Document 2 is provided with clamp devices that grip several points on the sides of a sheet material in the running direction and several points on the sides in the width direction. The sheet material is heated to a predetermined temperature in a heating furnace and softened, and while held by the clamp devices, it is lowered in sync with the movement of the upper forming die to form the sheet material, which applies appropriate tension to the sheet material until the end, making it possible to form products without wrinkles even if they have a complex shape (see, for example,

[0008] of Patent Document 2).

[0007] However, the molding device in Patent Document 2 is for use with a thermoplastic sheet material that is softened by heat, and is not for a sheet material that contains fibers that do not soften or stretch by heat. Therefore, when the molding device is applied to a sheet that contains a woven fabric or the like made of non-melting fibers, there is still a problem that the occurrence of wrinkles at the corners cannot be improved. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2017-196893 A [Patent Document 2] Patent No. 4470190 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been made in consideration of the above problems, and has an object to provide a molding method which, when molding a sheet including a composite sheet composed of a woven fabric made of non-melting fibers and a thermoplastic resin, can suppress the occurrence of wrinkles at the corners of the molded product, and can mold molded products having curved surfaces with corners that are nearly right angles, such as bags, cases, covers, etc., while ensuring the curved surface strength, without compromising the design of the weave structure of the woven fabric. [Means for solving the problem]

[0010] The present inventors conducted extensive research to solve the above problems, and as a result, have succeeded in solving the above problems.

[0011] In other words, the present invention provides a method for molding a sheet using a male-female interlocking molding die, characterized in that a sheet placed in the space between the male and female dies is heated to a temperature equal to or higher than the Vicat softening point and lower than the melting point of the thermoplastic resin constituting the sheet, and then the male and female dies are engaged at a position lower than the position at which the sheet was placed when heated, thereby applying diagonal tension to the four corners of the sheet.

[0012] In the method for forming the sheet, it is preferable to adjust the tension by adjusting the fitting position of the male and female dies of the forming die, and it is preferable to use double-sided vacuum forming.

[0013] In the sheet molding method, it is preferable that the sheet is a moldable sheet including a composite sheet composed of a woven fabric made of non-melting fibers and a thermoplastic resin, or a roving yarn, chopped strands or nonwoven fabric and a thermoplastic resin. In addition, the thermoplastic resin is preferably at least one selected from the group consisting of acrylic resins, polyolefin resins, polyacetal resins, polyamide resins, and modified polyolefin resins, and the thermoplastic resin is preferably contained in an amount of 40% by volume to 90% by volume of the total volume of the composite sheet. Furthermore, the non-melting fiber woven fabric has a basis weight of 30 g / m 2 ~500g / m 2 The fabric preferably has a thread count of 1.74 to 12 threads / 25.4 mm, and the non-melting fibers are preferably carbon fibers or glass fibers. Effect of the Invention

[0014] According to the sheet molding method of the present invention, it is possible to provide a molding method that can suppress the occurrence of wrinkles at the corners of a molded product, without impairing the strength of the curved surface, and that can provide a molded product with excellent design. Furthermore, even in the case of molding a molding sheet including a composite sheet constituted of a woven fabric or the like made of non-melting fibers and a thermoplastic resin, a molding method excellent in strength and design can be provided. The molding method of the present invention is suitable as a molding method for articles or parts having a height of 40 mm or more and a shape including corners that are close to right angles, such as bags such as attache cases and suitcases; cases such as camera cases and instrument cases; automobile parts; and covers for electronic devices. [Brief description of the drawings]

[0015] [Figure 1] FIG. 2 is an explanatory diagram of the molding method of the present invention. [Diagram 2] FIG. 2 is an explanatory diagram of the application of tension to a molding sheet containing a non-melting fiber fabric in the molding method of the present invention. [Diagram 3] FIG. 2 is an explanatory diagram of a molding method in Comparative Example 1. [Figure 4] FIG. 2 is a photograph of the surface of the molded product molded in Example 1. [Diagram 5] FIG. 13 is a diagram showing the results of a bias extension test of sheets used in the present invention examples and comparative examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, a method for molding a sheet using a female-male fitting molding die having a male die and a female die will be described in detail.

[0017] FIG. 1 is an explanatory diagram of the molding method of the present invention, and FIG. 2 is an explanatory diagram for explaining the application of tension to a molding sheet containing a non-melting fiber fabric in the molding method of the present invention.

[0018] [Forming method] The sheet molding method of the present invention is a sheet molding method using a female-male interlocking molding die, and is characterized in that the sheet placed in the space between the male and female dies is heated to a temperature equal to or higher than the Vicat softening point and lower than the melting point of the thermoplastic resin constituting the sheet, and then the male and female dies are interlocked at a position lower than the position at which the sheet was placed when heated, thereby applying diagonal tension to the four corners of the sheet.

[0019] According to the molding method of the present invention, tension can be applied to the sheet in the mold in a direction oblique to the weaving direction, which suppresses the occurrence of wrinkles during deep drawing of the sheet at the four corners (hereinafter referred to as "corner portions") of a molded body formed from one planar portion and four side surfaces (hereinafter simply referred to as "side surfaces") that are connected to the four sides of the planar portion and bent approximately perpendicularly, thereby making it possible to mold a molded product with excellent aesthetics and design without compromising the curved surface strength.

[0020] The sheet molding method of the present invention is a suitable method when molding a moldable sheet (hereinafter simply referred to as "sheet") that includes a composite sheet composed of a non-melting fiber fabric and a thermoplastic resin. As described above, when a sheet made of a woven fabric made of thermally meltable fibers such as polyolefin fibers and a thermoplastic resin is molded, the material is softened by the heat treatment during molding, so wrinkles are unlikely to occur at the corners. On the other hand, in the case of a sheet made of a woven fabric made of non-melting fibers that do not melt with heat such as carbon fibers or glass fibers and a thermoplastic resin, wrinkles occur at the corners because the non-melting fibers do not soften even if the thermoplastic resin softens due to the heat during molding.

[0021] The sheet molding method of the present invention will be specifically described with reference to FIG.

[0022] As shown in FIG. 1(a), in the present invention, first, the four sides and four corners of the sheet 1 are fixed by a frame 10. The frame 10 is composed of an upper frame 11 and a lower frame 12. The upper frame 11 is provided with a convex portion 13, and the lower frame 12 is provided with a concave portion 14 corresponding to the convex portion 13. The convex portion and the concave portion may be upside down, and the number of them is not limited. The material of the frame is not particularly limited, and examples thereof include wood, resin, and metal. The sheet 1 is preferably arranged and fixed so that the warp and weft directions of the woven fabric constituting the sheet are horizontal and vertical to the four sides of the sheet. This eliminates waste in the application of tension, which will be described later, and is effective in suppressing the occurrence of wrinkles. In the case of roving yarn, it is preferable to arrange the yarn so that the length direction of the yarn is parallel to the sides of the sheet. In the case of chopped strands or nonwoven fabric, there is no restriction on the arrangement direction.

[0023] The method of fixing the sheet is preferably to place the sheet 1 between the upper frame 11 and the lower frame 12, and insert the convex parts 13 on the upper frame 11 into the concave parts on the lower frame 12 to fix the four sides and four corners of the sheet 1. Fixing the sheet including the four corners allows tension to be applied efficiently and effectively during forming, making it possible to make wrinkles at the corners less visible.

[0024] As a specific fixing method, there are no particular limitations as long as it is a method in which sheet 1 does not move (does not shift) even when tension is applied during molding, and known fixing methods can be used, such as (a) a method in which a through hole is made in sheet 1 and a convex portion 13 is inserted into the through hole to fix it, (b) a method in which sheet 1 is fixed by pushing it into a concave portion 14 using a convex portion 13, (c) a method in which an adhesive is used, or the like, or (d) a method in which a needle-shaped protrusion such as a rivet is used to fix it.

[0025] 1(b), after the sheet is fixed, the sheet 1 and the frame 10 are placed in the space between the upper die (female die 21) and the lower die (male die 22) of the molding die 20. The position (height) of the sheet 1 at this time is defined as an initial position h0. The sheet 1 thus placed is heated by a heater (not shown) at the initial placement position h0.

[0026] The heater is preferably not provided inside the molding die 20, but is disposed at a position where it can be inserted and removed between the sheet 1 and the die 20. More preferably, it is disposed at a position where it can be inserted and removed between the female die 21 and the sheet 1, and between the male die 22 and the sheet 1. This allows the sheet to be heated from both sides, so that it can be heated efficiently and evenly. In addition, since the molding die can be heated at the same time, it becomes easier to adjust the molding temperature. As the heater, an electric heating wire heater, an infrared heater, a far infrared heater, a ceramic heater, etc. can be used.

[0027] The heating temperature of the sheet by the heater varies depending on the thermoplastic resin used, but is set to a temperature equal to or higher than the Vicat softening point and lower than the melting point of the thermoplastic resin constituting the composite sheet. The specific Vicat softening point and melting point will be described later.

[0028] After the sheet is heated, the heater is moved from between the sheet and the mold, and the molding mold 20 is operated. The heater may be moved and the mold 20 is operated simultaneously. From the viewpoint of molding efficiency, it is preferable that they are done simultaneously. When the molding die 20 is operated, the female die 21 and then the male die 22 come into contact with or into close contact with the sheet 1, and the dies fit together to mold the sheet into a desired shape.

[0029] Specifically, the female die 21 continues to move even after it comes into contact with the sheet 1, and is in a position to press down the sheet 1. On the other hand, the male die 22 comes into contact with the sheet that the female die 21 has pressed down, and then moves to press up the sheet 1. After the sheet 1 in the molding die 20 comes into contact with both dies, tension is applied in a direction oblique to the weaving direction to the parts that correspond to the corners. The dies then fit together to form a molded product.

[0030] FIG. 1(c) is a schematic diagram showing the state in which the molding dies are fitted together.

[0031] As shown in Fig. 1(c), it is essential that the fitting position h1 of the molding die 20 is lower than the initial position h0 of the sheet. By making the fitting position h1 lower than the initial position h0 of the sheet, tension can be applied to the sheet more effectively. The tension applied to the sheet can be adjusted by the difference between the fitting position h1 and the initial position h0, and the greater the difference, the stronger the tension that can be applied to the corners.

[0032] The difference between the fitting position h1 and the initial arrangement position h0 is usually adjusted to 5 mm to 50 mm. If the difference between the fitting position h1 and the initial arrangement position h0 is 5 mm or more, there is no risk of large wrinkles occurring at the corners due to insufficient tension, and if it is 50 mm or less, there is no risk of the strength of the molded product being reduced due to the occurrence of "fiber bundle slippage" described later. It is more preferably 15 mm to 50 mm, and particularly preferably 30 mm to 45 mm. It goes without saying that the value of h0-h1 can be appropriately changed depending on the thickness of the composite sheet and the sheet containing it, the type and weight ratio of the thermoplastic resin in the composite sheet, and the type of non-melting fiber, which will be described later, and can also be appropriately changed depending on the depth (height) of the molded product.

[0033] As shown in FIG. 1(d), after molding, the mold is released from the molding die, and unnecessary portions are cut off to obtain a molded product or part.

[0034] The application of tension in an oblique direction in the molding method of the present invention will be described with reference to Fig. 2. Fig. 2 is an explanatory diagram of the case where the non-melting fibers constituting the molding sheet are a woven fabric.

[0035] In the present invention, the above-mentioned oblique direction refers to a direction oblique to the main axis direction (weaving direction) of the fabric, which is a component of the sheet. The oblique direction is preferably in the range of 45°±15° to the main axis direction of the fabric. If the direction of tension is greater than 60° or less than 30° to the main axis direction, the weave of the fabric cannot deform as desired even when tension is applied to the sheet, and molding defects and wrinkles are likely to occur. The range of 45°±10° is more preferable, and the range of 45°±5° is particularly preferable. When the non-melting fiber constituting the sheet is a roving yarn, the fiber direction is preferably set as the main axis. In addition, for chopped strands and nonwoven fabrics, the orientation direction of the yarn (if oriented) is preferably set as the main axis. When the orientation direction is unclear, any direction may be set as the main axis.

[0036] FIG. 2(a) is an explanatory diagram illustrating the deformation of a sheet (woven fabric) when tension is applied, and FIG. 2(b) is a diagram illustrating the plane and two side faces of a molded product produced by the molding method of the present invention, as well as the corner portions formed by these.

[0037] 2(a), the vertical and horizontal lines in the checkerboard pattern indicate the weaving directions (warp and weft directions) of the fabric constituting sheet 1, and the arrows marked with a cross (×) indicate that the fiber bundles in the fabric are difficult to stretch (difficult to deform) in the corresponding directions. Region (X) indicates the flat surface and side surfaces (two surfaces) of the molded product, and regions (Y) and (Z) indicate the fabric constituting the corners.

[0038] As shown in Figure 2(a), when a tension (F) is applied obliquely to the weaving direction of the fabric, deformation occurs at the corner due to rotation between the fiber bundles that make up the fabric. When this rotational deformation occurs, the shape of the fabric at the corner changes from a square to an approximate diamond or parallelogram, and A moves to position A' (B moves to position B'). The movement distance from A to A' (B to B') varies depending on the tension applied to the sheet, and the greater the tension, the longer the movement distance. Furthermore, the wider the spacing between the fiber bundles that make up the fabric, the easier it is for rotational deformation to occur, and the longer the movement distance becomes. When the non-melting fibers constituting the sheet are roving yarn, chopped strands, or nonwoven fabric, rotational deformation between the fiber bundles does not occur, but the sheet constituting the corner portion is pulled by applying tension (F), thereby suppressing the occurrence of wrinkles.

[0039] As shown in Figure 2(b), by utilizing the rotational deformation of the fiber bundles at the corners (C), even a sheet containing a non-melting fiber fabric can be formed with no wrinkles at the corners, resulting in a molded product with excellent design. Furthermore, a molded product can be obtained with no or only a small decrease in curved surface strength around the corners.

[0040] The tension applied to the fabric can also be determined as the tensile stress in a bias-extension test.

[0041] In the bias extension test, a rectangular test piece is prepared with the weaving direction of the fabric at ±45° to the longitudinal direction, and the upper and lower ends of the test piece are fixed to a testing machine and pulled vertically to generate rotational deformation of the fiber bundles, and the maximum tensile stress, strain, and displacement at that time are measured. When the test begins, the fiber bundles that make up the fabric rotate with each other, and when a certain angle is reached, a locking phenomenon occurs in which the rotating fiber bundles collide with each other, increasing the tensile stress. If the tensile stress is continued after that, "fiber bundle slippage" occurs near the boundary between the fixed end of the test piece and the locked fiber bundle, and the test piece cannot transmit the load, and the tensile stress decreases. In the present invention example, it is presumed that the rocking phenomenon occurs around the displacement of 13 mm to 20 mm shown in FIG. 5 (the point where the slope of the curve changes).

[0042] The molding method of the present invention can effectively apply tension to the corner portions of the molded product by fitting a mold at a position lower than the initial placement position, and in particular, by fixing the four sides and four corners of the sheet to a frame and fitting a mold at a position lower than the initial placement position, tension can be applied to the corner portions more efficiently and effectively. As a result, even in the case of a moldable sheet containing non-melting fibers, which has had the problem of wrinkling in conventional methods, by applying the tension to the corner portions and rotationally deforming the fiber bundles of the woven fabric, it is possible to mold the sheet while suppressing the occurrence of wrinkles in the corner portions, making this a suitable molding method for a moldable sheet including a composite sheet made of a non-melting fiber fabric and a thermoplastic resin.

[0043] In the molding method of the present invention, if the sheet is not fixed sufficiently, or if there is no (0 mm) or only a very small difference between the initial placement position and the fitting position, large wrinkles may occur at the corners of the molded product. Examples of cases in which the seat is not sufficiently secured include when only the four sides of the seat (front-to-back and left-to-right directions) excluding the four corners are secured, or when only the four corners of the seat are secured. When only the four sides of the sheet are fixed, especially when only the four sides of a sheet containing a non-melting fiber fabric are fixed, the fabric is rigid and does not stretch, so when attempting to mold a molded product with height (depth), there is a high possibility that the fabric will gather excessively at the corners (C), causing overlaps and large wrinkles. On the other hand, when only the four corners of the sheet are fixed, the weave of the fabric may become disordered when the molding die is fitted, which may impair the design.

[0044] FIG. 3 is an explanatory diagram of a molding method in which the difference between the initial placement position and the fitting position is 0 mm, simulating a conventional molding method.

[0045] As shown in Fig. 3, the sheet 1 is fixed by an upper frame 11 and a lower frame 12, and the fixed sheet 1 is placed between a female die 31 and a male die 32 of a molding die 30 (Fig. 3(a)). After that, the die is fitted without making a difference between the initial position h0 and the fitting position h1 (Fig. 3(b)), and after molding is completed, the sheet is released from the die (Fig. 3(c)). In the conventional molding method, it is assumed that a small amount of tension is applied to the corners when the male mold pushes up the sheet during mold fitting. In contrast, in the molding method of the present invention, sufficient tension is applied by lowering the fitting position.

[0046] [Molding sheet] In the present invention, the moldable sheet is preferably a moldable sheet including a composite sheet composed of a woven fabric made of non-melting fibers and a thermoplastic resin. The woven fabric includes a unidirectional material (UD sheet). A woven fabric made of non-melting fibers has resistance to tension in the weaving direction, i.e., the warp direction and the weft direction, so that the tensile elongation is small, and ingenuity is required when vacuum molding, but on the other hand, it has the advantage of being beautiful in appearance and excellent in design. Furthermore, since it has excellent impact resistance, it is suitable as a material for applications requiring design on the surface such as bags, cases, and covers.

[0047] In the present invention, the moldable sheet may include a composite sheet composed of a roving yarn, chopped strand, or nonwoven fabric made of non-melting fibers and a thermoplastic resin. Since these have no woven structure, there is no need to worry about the above-mentioned rotational deformation. Therefore, they have excellent moldability compared to non-melting fiber woven fabrics.

[0048] Examples of sheets including the composite sheet of the present invention include those obtained by laminating a surface layer material and / or a back layer material to a composite sheet. Examples of the surface layer material include decorative sheets and print sheets, and examples of the back layer material include nonwoven fabrics.

[0049] [Composite sheet] The composite sheet may generally be a laminate or integral laminate of a non-melting fiber fabric, or a non-melting fiber fabric and a nonwoven fabric, etc., with a thermoplastic resin sheet, and a commercially available product may also be used. The thickness of the composite sheet is preferably 1.0 mm to 3.0 mm. If the thickness is too small, holes are likely to occur in the molded product, and the strength of the molded product is also reduced. On the other hand, if the thickness is too large, molding itself becomes difficult. The thickness of the composite sheet is more preferably 1.2 mm to 2.8 mm, and further preferably 1.5 mm to 2.5 mm.

[0050] [Non-melting fiber] In the present invention, the non-melting fiber means a fiber that does not melt due to the heat of a molding die or a heater during molding. This includes not only fibers that do not melt due to heat, but also fibers that have a melting point higher than the heating during molding and are therefore heat-resistant.

[0051] Specific examples of fibers that do not melt when heated include vegetable fibers such as seed hair fibers (cotton, kapok, etc.), bast fibers (flax, ramie, etc.), vein fibers (Manila hemp, etc.), and fruit fibers (coconut); inorganic fibers such as carbon fibers and glass fibers; animal fibers such as silk; and regenerated fibers such as rayon. Examples of fibers with high melting points include high-strength organic fibers. These fibers may be used alone or in combination of two or more. Among these, carbon fiber, glass fiber, and the like are preferred because they are less susceptible to deformation or expansion due to heat, are easily available, and have excellent processability.

[0052] As the woven fabric made of non-melting fibers, plain weave, twill weave, satin weave, leno weave, alternating weave, etc. woven by a known method can be used. From the viewpoint of excellent shape stability and aesthetic appearance, plain weave, twill weave, and satin weave are preferred, and plain weave and twill weave are more preferred.

[0053] The density of the non-melting fiber fabric is preferably 1.74 to 12 fibers / 25.4 mm in both warp and weft directions. If the density is too low, the curved surface strength of the molded product may be insufficient, or the appearance (design) may be poor. If the density is too high, the gaps between the fiber bundles constituting the fabric may become small, and wrinkles may occur at the corners because the fabric cannot be rotated and deformed when tension is applied. More preferably, it is 4 to 11 fibers / 25.4 mm, and particularly preferably 5 to 10 fibers / 25.4 mm.

[0054] The weight of the non-melting fiber fabric is 30g / m 2 ~500g / m 2 If the basis weight is too large, the formability of the sheet tends to be poor, and conversely, if the basis weight is too small, the strength of the molded product becomes insufficient. More preferably, it is 40 g / m 2 ~450g / m 2 , particularly preferably 50 g / m 2~400g / m 2 It is.

[0055] The width of the yarn constituting the non-melting fiber woven fabric is preferably 1 to 5 mm, more preferably 2 to 5 mm, from the viewpoints of design and formability.

[0056] The density, basis weight and yarn width of the woven fabric may be selected within a range that does not impede the rotational deformation of the fiber bundle in the bias extension test.

[0057] [Thermoplastic resin] The thermoplastic resin used for the molding sheet may have a Vicat softening point lower than the temperature of the mold or the heating temperature by the heater during molding, and a melting point higher than these temperatures.

[0058] The Vicat softening point of the thermoplastic resin is preferably 50° C. or higher. If the Vicat softening point is less than 50° C., the thermoplastic resin in the composite sheet does not soften and cannot withstand the pressure of the mold, which may result in molding defects. It is more preferably 70° C. or higher.

[0059] The melting point of the thermoplastic resin is preferably 300° C. or less. If the melting point exceeds 300° C., the sheet will not be heated sufficiently, and wrinkles may easily occur in the sheet, and the desired molding quality (design, strength, etc.) may not be maintained. The melting point is more preferably 290° C. or less, and particularly preferably 280° C. or less.

[0060] Specific examples of thermoplastic resins include acrylic resins (melting point: about 90 to 110°C), polyolefin resins (melting point: about 80 to 160°C), ABS resins (melting point: about 100 to 120°C), polyamide resins (melting point: about 220 to 260°C), polyester resins (melting point: about 255°C), polyacetal resins (melting point: about 180°C), polyketone resins (melting point: about 220°C), polyvinyl formal resins (melting point: about 85 to 120°C), polyoxymethylene resins (melting point: about 160°C), polyphenylene sulfide resins (melting point: about 290°C), ethylene-ethyl acrylate resins (melting point: about 65 to 100°C), ethylene-vinyl acetate copolymer resins (melting point: about 75 to 100°C), and ethylene-vinyl alcohol copolymer resins. Examples of the resin include cellulose acetate (melting point: about 160 to 190°C), methacrylic resin (melting point: about 90 to 105°C), polystyrene (melting point: about 70 to 90°C), polyvinyl chloride (melting point: about 85 to 210°C), polyvinylidene chloride (melting point: about 210°C), cellulose acetate (cellulose acetate: CA) resin (melting point: about 230°C), syndiotactic polystyrene (melting point: about 270°C), polyamide-imide (melting point: about 275°C), polyarylate (melting point: about 250°C), polysulfone (melting point: about 200°C), fluororesin (melting point: about 220°C), polytetrafluoroethylene (melting point: about 260°C), polybutylene terephthalate (melting point: about 230 to 267°C), and modified resins obtained by modifying these resins. These resins may be used alone or in combination.

[0061] Among the above thermoplastic resins, acrylic resins, polyolefin resins, polyacetal resins, polyamide resins (nylon 6, nylon 66, etc.) and modified polyolefin resins are preferred from the standpoints of cost, light weight, impact resistance, ease of handling, ease of processing, etc. Examples of the polyolefin resin include polyethylene resins such as low-density polyethylene resin and medium-density polyethylene resin, and polypropylene resins such as low-melting-point polypropylene resin. Examples of the modified polyolefin resin include acid-modified polyolefin resins such as maleic anhydride-modified polyethylene resin and maleic anhydride-modified polypropylene resin.

[0062] The thermoplastic resin is preferably contained in an amount of 40 to 90% by volume relative to the total volume of the composite sheet. If the volume content of the resin is too low, the surface of the non-melting fiber fabric may be exposed during molding, which may cause problems in terms of design and safety. On the other hand, if the volume content of the resin is too high, the strength of the molded product may be weakened. It is more preferably 50 to 80% by volume, and particularly preferably 50 to 70% by volume.

[0063] [Male and female interlocking molding die] The molding die used in the molding method of the present invention is preferably a female-male fitting type match mold molding die in which a male die having a convex portion is placed in the lower mold, and a female die having a concave portion corresponding to the male die is placed in the upper mold.

[0064] The molding die is preferably a die for vacuum molding, more preferably a die for double-sided vacuum molding. By using double-sided vacuum molding, the vacuum suction time during molding can be shortened, and traces of suction holes, infiltration spots of thermoplastic resin, and disturbance of the woven fabric shape can be prevented.

[0065] The molding die has a plurality of vacuum holes for vacuum suction on the surfaces of the male and female dies. The number of vacuum holes is not limited, but it is preferable that the male and female dies have vacuum holes at least at locations corresponding to the corners of the molded product. It is more preferable that the vacuum holes are provided on all of the flat and side surfaces. The vacuum holes may be arranged in positions that face each other when the male and female dies are mated, or in different positions.

[0066] The diameter of the vacuum hole is preferably about 0.5 mm to 1.0 mm. If it is 0.5 mm or more, there is no risk of insufficient vacuum suction resulting in reduced moldability, and there is no risk of clogging. If it is 1.0 mm or less, it is possible to prevent traces of the vacuum hole from remaining on the molded product after vacuum suction, and there is no risk of poor appearance.

[0067] The vacuum suction from the surface of the upper mold (female mold) is preferably started before the female mold starts to descend and contacts the sheet, and the vacuum suction is preferably also performed during the vacuum suction from the surface of the lower mold (male mold). Also, the vacuum suction from the surface of the lower mold (male mold) is preferably started immediately after the molds are mated. In this way, by providing a time difference between the vacuum suction of the male and female molds, the thickness distribution of the side walls is affected by the timing of the vacuum suction from both the male and female molds, so that the thickness of the side walls can be easily controlled and wrinkles can be prevented from occurring compared to when the vacuum suction of the male and female molds is started simultaneously. Specifically, the time difference between the start time of the vacuum suction of the male mold and the start time of the vacuum suction of the female mold is preferably 0.5 to 1.0 seconds.

[0068] The vacuum conditions (degree of vacuum) during vacuum molding are not particularly specified, but it is preferable to reduce the pressure of both the male and female molds to about 0.05 MPa to 0.09 MPa (0.5 atm to 0.9 atm). If the degree of vacuum is within the above range, there is no need to worry about molding defects due to insufficient suction force, and there is no risk of the weave of the sheet being disturbed and poor appearance caused by too strong suction force. Furthermore, since the thickness of the sheet can be easily controlled, a molded product of uniform thickness can be obtained.

[0069] The temperature of the molding die during molding is preferably 60°C to 120°C. Within this range, there is no risk of the molded product being deformed due to shrinkage or the like during or after molding. More preferably, it is 80°C to 120°C, and particularly preferably 80°C to 100°C. Since the present invention does not require molding while heating the die to a high temperature, it is possible to speed up the cooling cycle of the molded product and increase the number of molded products produced. It goes without saying that the temperature of the molding die can be appropriately changed depending on the thermoplastic resin used. The molding die can be heated up to a maximum of about 400°C.

[0070] In addition to the above-mentioned heater for heating the sheet, the molding die may be provided with a heater in the die to keep the temperature of the die constant. The heater may be a cartridge type, a heater with a nichrome wire directly embedded, or a heater with other known heating means. A cooling die after molding may or may not be used.

[0071] The molding method of the present invention can be suitably used for molding a moldable sheet including a composite sheet composed of a non-melting fiber fabric and a thermoplastic resin, or a moldable sheet including a composite sheet composed of a roving yarn, chopped strands or nonwoven fabric composed of non-melting fibers and a thermoplastic resin. Specific examples of molded articles that can be molded by the molding method of the present invention include bags such as suitcases and attache cases; cases such as camera cases and musical instrument cases; various covers; trim materials that form door trims and trunk sides, mat materials such as floor mats and trunk mats, automobile parts such as automobile ceiling materials; building materials such as wall materials and ceiling materials; and deep-draw molded articles such as housings for home appliances. EXAMPLES

[0072] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0073] [Measuring method for Vicat softening point and melting point] The Vicat softening point of the resin is a value measured in accordance with JIS K7206: 2016. The melting point of the resin is the maximum peak (Tm) value measured by differential scanning calorimetry (DSC) in accordance with JIS K7121.

[0074] Example 1 The composite sheet was a carbon fiber fabric (manufactured by Mitsui Chemicals, Inc., product name: TOUGHNEX (registered trademark) Tape Cloth, Vf: 50%, basis weight: 350 g / m) laminated on both sides with acid-modified polypropylene resin (Vicat softening point: 115°C, melting point: 130°C). 2, weaving width: 1000 mm, weaving density: 1.74 threads / inch, weaving structure: plain weave) were used.

[0075] As the molding die, a female-male fitting molding die having a female die as an upper die and a male die as a lower die was used.

[0076] [Forming method] The composite sheet and molding die were used to mold the product according to the following molding method. (1) As shown in FIG. 1(a), the composite sheet (1) was sandwiched between upper and lower frames (11, 12) and fixed by inserting the protrusions (13) provided on the frames into the through holes provided in the composite sheet.

[0077] (2) Next, as shown in Fig. 1(b), the fixed composite sheet (1) was placed between the female mold (21) and the male mold (22) so that the center point of the composite sheet was aligned with the center points of the male mold and the female mold. The position (height) of the composite sheet at this time was designated as the initial position h0. After placing the composite sheet, a heater was inserted between the mold and the composite sheet, and the composite sheet was heated from both sides so that the surface temperature of the composite sheet became about 120° C. The surface temperature of the composite sheet was measured using a non-contact thermometer.

[0078] (3) After the composite sheet was heated, the heater was moved from between the mold and the composite sheet to outside the mold, and the mold was operated at the same time, and the female mold (21) and the male mold (22) were brought into contact with the composite sheet (1) in that order to form the composite sheet. The forming method was a double-sided vacuum forming method. The state in which the molds are fitted is shown in Figure 1 (c). The female mold (21) and male mold (22) used had multiple vacuum holes with diameters of 0.5 to 1.0 mm. The temperature of the female and male molds during molding was 80°C to 100°C, the degree of vacuum was 0.085 MPa, and the molding time was 50 to 90 seconds. Vacuum suction began before the female mold began to descend and come into contact with the sheet, and vacuum suction by the male mold began immediately after the molds were mated. As shown in FIG. 1(c), the mating position h1 of the mated female mold (21) and male mold (22) was set to be approximately 20 mm lower than the initial position h0, so that a diagonal tension was applied to the composite sheet when the female mold and male mold were mated.

[0079] (4) After molding, the composite sheet (S) was released from the mold to obtain a molded product, as shown in Figure 1(d). The appearance of the molded product is shown in Figure 4.

[0080] Example 2 The composite sheet was laminated on both sides with acid-modified polypropylene resin (Vicat softening point: 115°C, melting point: 130°C) to form a carbon fiber fabric (manufactured by Mitsui Chemicals, Inc., product name: TOUGHNEX (registered trademark) Tape Cloth, Vf: 50%, basis weight: 350g / m 2 A sheet was formed in the same manner as in Example 1, except that the weaving conditions were as follows: weaving width: 1000 mm, weaving density: 1.74 threads / inch, and weaving structure: twill weave.

[0081] Example 3 A sheet was formed in the same manner as in Example 1, except that the composite sheet was a glass fiber fabric (weave: plain weave) laminated on both sides with acrylic resin (Vicat softening point: 90°C to 110°C, melting point: 165°C).

[0082] Comparative Example 1 The composite sheet (1) used in Example 1 was used, and the molding method was changed as follows.

[0083] [Forming method] (1) As shown in FIG. 3(a), the composite sheet (1) was sandwiched between upper and lower frames (11, 12) and fixed by inserting the protrusions (13) on the frames into the through holes in the composite sheet.

[0084] (2) Next, the fixed composite sheet (1) was placed between the female mold (31) and the male mold (32) so that the center point of the composite sheet was aligned with the center points of the male mold and the female mold. The position (height) of the composite sheet at this time was set as the initial position h0. After placing the composite sheet, a heater was inserted between the mold and the composite sheet, and it was heated in the same manner as in Example 1.

[0085] (3) After the composite sheet was heated, the heater was moved from between the mold and the composite sheet to the outside of the mold, and at the same time, the mold was moved so that the female mold (31) and the male mold (32) were brought into contact with the composite sheet (1) in that order, and the composite sheet was molded by a double-sided vacuum molding method. The difference between the initial position h0 and the mating position h1 was 0 mm. The female mold (31) and male mold (32) used had multiple vacuum holes with a diameter of 0.5 to 1.0 mm. The temperature of the female and male molds during molding was 80 to 100°C, the degree of vacuum was 0.085 MPa, and the molding time was 50 to 90 seconds. Vacuum suction was started before the female mold started to descend and contacted the sheet. Vacuum suction by the male mold was started immediately after the molds were mated. The mated state of the molds is shown in Figure 3(b).

[0086] (4) As shown in FIG. 3(c), after molding, the composite sheet (1) was released from the mold to obtain a molded product.

[0087] [Bias extension test] The composite sheets used in the Examples and Comparative Examples before molding were cut into test pieces with a length of 110 mm and a width of 20 mm. The test pieces were cut out with the weaving direction (warp direction, weft direction) tilted by ±45° with respect to the longitudinal direction. A small tabletop testing machine (Shimadzu Corporation) was used for the test, and the upper and lower ends of the test pieces were fixed to the testing machine so that the distance between the fixtures was 50 mm. In order to approximate the state of the sheet during molding, the cut test pieces were heated to above the Vicat softening point of the thermoplastic resin with a far-infrared ceramic heater before the test. The bias extension test was performed at a tensile displacement rate of 5 mm / min, and the maximum tensile stress (N / mm 2 ) and the displacement (mm) at the maximum tensile stress were calculated.

[0088] The results of the bias extension test are shown in Table 1 and FIG.

[0089] [Table 1]

[0090] As shown in Table 1 and FIG. 5, Example 1-3 had a large displacement at the maximum tensile stress and was able to flexibly respond to the tensile stress during molding, so that a good weave pattern without wrinkles could be molded.

[0091] Although the embodiment of the present invention has been described above, it goes without saying that the present invention is not limited to the above embodiment, and various modifications and changes are possible. [Industrial Applicability]

[0092] The molding method of the present invention is useful as a molding method for sheets including composite sheets composed of a non-melting fiber fabric and a thermoplastic resin, the corners of which cannot be fully designed by ordinary molding methods. According to the molding method of the present invention, it is possible to provide deep drawn molded products which are excellent in appearance, scratch resistance, light weight and design and are suitable for cases, parts, covers and other applications. [Explanation of symbols]

[0093] 1 Composite sheet 10 Frame 11 Upper frame 12 Lower frame 13 Convex 14 Recess 20 Molding mold 21 Female mold (upper mold) 22 Male type (lower type) 30 Molding mold 31 Female mold (upper mold) 32 Male type (lower type) h0 initial placement position h1 mating position C Corner F tension

Claims

1. A molding method for a moldable sheet including a composite sheet composed of a non-melting fiber and a thermoplastic resin using a male-female mating molding die, comprising: The thermoplastic resin is contained in an amount of 40% by volume to 90% by volume based on the total volume of the composite sheet, The molding sheet is placed in the space between the male mold and the female mold (initial placement position (h 0 )); After heating to a temperature equal to or higher than the Vicat softening point and lower than the melting point of the thermoplastic resin constituting the composite sheet, The male and female dies are fitted together at a fitting position (h 1 ) of the molding die that is lower than the initial position (h 0 ) of the molding sheet, thereby applying diagonal tension to the four corners of the molding sheet, A method for forming a sheet, comprising forming the sheet by double-sided vacuum forming.

2. 2. The method for forming a sheet according to claim 1, wherein the tension can be adjusted by changing the fitting position of the male and female halves of the forming die.

3. The method for forming a sheet according to claim 1, wherein the sheet is a formable sheet including a composite sheet constituted of a woven fabric made of non-melting fibers and a thermoplastic resin.

4. The method for forming a sheet according to claim 1, wherein the sheet is a formable sheet comprising a composite sheet constituted of a roving yarn, chopped strand or nonwoven fabric made of non-melting fibers, and a thermoplastic resin.

5. 5. The sheet molding method according to claim 3, wherein the thermoplastic resin is at least one selected from the group consisting of acrylic resins, polyolefin resins, polyacetal resins, polyamide resins and modified polyolefin resins.

6. The weight of the fabric made of the non-melting fibers is 30 g / m ２ Up to 500 g / m ２ The method for forming a sheet according to claim 3, wherein

7. The sheet molding method according to claim 3, wherein the fabric made of the non-melting fibers has an inch count of 1.74 to 12 threads / 25.4 mm.

8. The method for forming a sheet according to claim 1 , wherein the non-melting fibers are carbon fibers or glass fibers.

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