Method for molding sheet

Abstract

To provide a molding method capable of suppressing an occurrence of wrinkles at 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 a strength of curved surfaces without impairing a design of a weave structure of the woven fabric.SOLUTION: In a sheet molding method using a male-female engaged molding die, 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 a thermoplastic resin constituting the sheet, and then the male die and the female die are engaged at a position lower than the position of the sheet when heated, thereby applying diagonal tension to four corners of the sheet.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for forming a sheet using a male-female fitting mold having a male type and a female type.

Background Art

[0002] As a method for forming a composite sheet composed of a fabric and a resin, a method of double-sided vacuum forming a composite sheet composed of a flat yarn woven fabric and a thermoplastic resin using a male-female fitting mold has been disclosed (Patent Document 1).

[0003] The flat yarn woven fabric disclosed in Patent Document 1 is obtained by weaving flat yarns composed of polyolefin polymers such as polyethylene, polypropylene, and a mixed resin of polyethylene and polypropylene into plain weave, twill weave, satin weave, interlaced weave, or change weave. Then, a flat yarn laminate sheet having a thermoplastic resin layer with a melting point lower than that of the flat yarn is disposed on both sides of the flat yarn woven fabric, and the flat yarn laminate sheet is disposed between heated male-female fitting molds, and is brought into contact with the flat yarn laminate sheet in the order of the female mold and the male mold, and double-sided vacuum forming is performed (Claim 1, Examples, etc. of Patent Document 1).

[0004] However, when using a composite sheet composed of a fabric made of non-molten fibers and a thermoplastic resin, unlike the case where the sheet softens by heat in the forming mold like the flat yarn laminate sheet, since the non-molten fibers do not soften by heat, there is a problem that wrinkles are generated at the corner portions when formed by the same method.

[0005] As a method for improving the wrinkling of a molded product, a device for thermoforming or vacuum forming in a state where sides in the running direction of the sheet material and the width direction orthogonal thereto (sides in the vertical and horizontal directions with respect to the sheet plane) are gripped by a clamping device has been disclosed (Patent Document 2).

[0006] The apparatus disclosed in Patent Document 2 is provided with a clamp device that grips several locations on the sides in the running direction of the sheet material and several locations on the sides in the width direction. Then, the sheet material heated to a predetermined temperature and softened in the heating furnace is lowered while being synchronized with the movement of the forming upper die while being gripped by the clamp device, and formed. By doing so, an appropriate tension is applied to the sheet material until the end, and it is claimed that a product without wrinkles can be formed even with a complex shape (see

[0008] of Patent Document 2, etc.).

[0007] However, Patent Document 2 is a forming apparatus used for a thermoplastic sheet material that softens with heat, and is not a forming apparatus for a sheet material containing fibers that do not soften or expand and contract with heat. Therefore, when applied to a sheet including a fabric made of non-molten fibers, there has been a problem that the generation of wrinkles at the corner portions cannot be improved still.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0009] The present invention has been made in view of the above problems, and when forming a sheet including a composite sheet composed of a fabric made of non-molten fibers and a thermoplastic resin, it is possible to suppress the generation of wrinkles at the corner portions of the molded product, and without impairing the designability of the weave structure of the fabric, an object of the present invention is to provide a forming method capable of forming while ensuring the surface strength of a molded product having a curved surface with an angle almost close to a right angle, such as bags, cases, covers, etc.

Means for Solving the Problems

[0010] As a result of intensive studies to solve the above problems, the inventors of the present invention have arrived at a solution to the above problems.

[0011] That is, the present invention is a method for forming a sheet using a male-female fitting type molding die, wherein a sheet disposed in a space 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 the female die are fitted at a position lower than the arrangement position of the sheet during heating, thereby adding a tension in an oblique direction to the four corners of the sheet. A method for forming a sheet is provided.

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

[0013] In the method for forming the sheet, it is preferable that the sheet is a molding sheet including a composite sheet composed of a fabric made of non-molten fibers and a thermoplastic resin, or a roving yarn, chopped strand or non-woven fabric and a thermoplastic resin. Further, the thermoplastic resin is preferably at least one selected from the group consisting of an acrylic resin, a polyolefin resin, a polyacetal resin, a polyamide resin, and a modified polyolefin resin, and the thermoplastic resin is preferably contained in an amount of 40% to 90% by volume based on the total volume of the composite sheet. Furthermore, the non-molten fiber fabric has a basis weight of 30 g / m 2 ~500 g / m 2 It is preferably, and the number of warp yarns of the fabric is preferably 1.74 to 12 per 25.4 mm, and the non-molten fiber is preferably carbon fiber or glass fiber.

Advantages of the Invention

[0014] According to the method for forming a sheet of the present invention, it is possible to suppress the generation of wrinkles at the corner portions of the molded product, and to provide a molding method excellent in the design of the molded product without impairing the curved surface strength. Moreover, even when a molding sheet including a composite sheet composed of a fabric or the like made of non-melted fibers and a thermoplastic resin is molded, a molding method excellent in strength and designability can be provided. The molding method of the present invention is suitable as a molding method for an article or a part having a shape with a height of 40 mm or more and having a corner portion close to a right angle, for example, bags such as an attaché case and a suitcase; cases such as a camera case and a musical instrument case; automotive parts; covers of electronic devices; and the like.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

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

[0017] FIG. 1 is an explanatory view of the molding method of the present invention, and FIG. 2 is an explanatory view for explaining the tension addition of the molding sheet including the non-melted fiber fabric in the molding method of the present invention.

[0018] [Molding Method] The sheet forming method of the present invention is a sheet forming method using a male-female fitting type forming die, wherein a sheet disposed in the space between the male die and the 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 the female die are fitted at a position lower than the arrangement position of the sheet during heating, whereby an oblique tension is applied to the four corners of the sheet.

[0019] According to the forming method of the present invention, an oblique tension can be applied to the sheet in the forming die in a direction oblique to the weaving direction. As a result, at the four corners (hereinafter simply referred to as "corner portions") of a molded body formed from one flat portion and four side surfaces (hereinafter simply referred to as "side surfaces") that are continuous with the four sides of the one flat portion and bend substantially vertically, the generation of wrinkles during the deep drawing forming of the sheet is suppressed, and a molded product excellent in aesthetic appearance and design properties can be formed without impairing the curved surface strength.

[0020] The sheet forming method of the present invention is a suitable method for forming a forming sheet (hereinafter simply referred to as "sheet") including a composite sheet composed of a non-molten fiber fabric and a thermoplastic resin. As described above, when forming a sheet composed of a fabric made of heat-meltable fibers such as polyolefin fibers and a thermoplastic resin, the material softens due to the heat treatment during forming, so wrinkles are less likely to occur at the corners. On the other hand, in the case of a sheet composed of a fabric made of non-molten fibers that do not melt with heat, such as carbon fibers and glass fibers, and a thermoplastic resin, the non-molten fibers do not soften even when the thermoplastic resin softens due to heating during forming, resulting in wrinkles at the corner portions.

[0021] The sheet forming method of the present invention will be specifically described with reference to FIG. 1.

[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 body 10. The frame body 10 is composed of an upper frame body 11 and a lower frame body 12. A convex portion 13 is provided on the upper frame body 11, and a concave portion 14 corresponding to the convex portion 13 is provided on the lower frame body 12. The convex portion and the concave portion may be reversed up and down, and their numbers are not limited. The material of the frame body is not particularly limited, and examples include wooden, resin-made, and metal-made. The sheet 1 is preferably arranged and fixed such that the warp direction and weft direction of the fabric constituting the sheet are in the horizontal direction and vertical direction with respect to the four sides of the sheet. Thereby, there is no waste in the addition of tension described later, and it is effective in suppressing the generation of wrinkles. In the case of roving yarn, it is preferable to arrange the yarn such that the length direction of the yarn is parallel to the side of the sheet. In the case of chopped strands or non-woven fabric, the arrangement direction is not limited.

[0023] As a method for fixing the sheet, it is preferable to arrange the sheet 1 between the upper frame body 11 and the lower frame body 12, insert the convex portion 13 provided on the upper frame body 11 into the concave portion provided on the lower frame body 12, and fix the four sides and four corners of the sheet 1. By fixing including the four corners, when forming, the tension to the sheet is efficiently and effectively added, and the wrinkles at the corner portions can be made less visible.

[0024] As a specific fixing method, there is no particular limitation as long as the sheet 1 does not move (shift) even when tension is applied during forming. (A) A method of providing through holes in the sheet 1 and inserting the convex portion 13 into the through holes for fixing; (B) A method of fixing the sheet 1 by pushing it into the concave portion 14 using the convex portion 13; (C) A method of fixing using an adhesive or the like; (D) Known fixing methods such as a method of fixing using needle-like protrusions such as nails can be used.

[0025] As shown in Fig. 1(b), after fixing the sheet, the sheet 1 and the frame body 10 are arranged in the space between the upper mold (female mold 21) and the lower mold (male mold 22) of the forming mold 20. The arrangement position (height) of the sheet 1 at this time is set as the initial arrangement position h 0 and. The arranged sheet 1 is at the initial arrangement position h0 It is heated by a heater (not shown).

[0026] The heater is preferably disposed at a position where it can be inserted and removed between the sheet 1 and the mold 20 and is not installed inside the molding die 20. More preferably, it is disposed at a position where it can be inserted and removed between the female mold 21 and the sheet 1 and between the male mold 22 and the sheet 1. Thereby, since the sheet can be heated from both sides, it can be heated efficiently without unevenness. In addition, since the molding die can be heated together, the temperature adjustment of the molding temperature becomes easy. As the heater, a heating wire heater, an infrared heater, a far-infrared heater, a ceramic heater, or the like can be used.

[0027] The heating temperature of the sheet by the heater varies depending on the thermoplastic resin used, but it 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 composite sheet. Specific Vicat softening points and melting points will be described later.

[0028] After the sheet is heated, the heater is moved from between the sheet and the mold, and the molding die 20 is operated. The movement of the heater and the operation of the mold 20 may be simultaneous. From the viewpoint of molding efficiency, it is preferably simultaneous. When the molding die 20 is operated, it comes into contact with or adheres to the sheet 1 in the order of the female mold 21 and the male mold 22, and the mold is fitted and the sheet is molded into a desired shape.

[0029] Specifically, the female mold 21 continues to move even after coming into contact with the sheet 1 and takes a shape that presses down the sheet 1. On the other hand, the male mold 22 moves so as to push up the sheet 1 after coming into contact with the sheet pushed down by the female mold 21. The sheet 1 in the molding die 20 is tensioned in a direction oblique to the weaving direction at a portion that hits the corner portion after coming into contact with both molds. Then it is fitted and molded into a molded product.

[0030] FIG. 1(c) is a diagram schematically showing a state where the molding die is fitted.

[0031] As shown in FIG. 1(c), the fitting position h of the molding die 20 1 is importantly lower than the initial placement position h of the sheet 0 . By making the fitting position h lower than the initial placement position h of the sheet, the tension applied to the sheet can be more effectively imparted. The tension applied to the sheet can be adjusted by the difference between the fitting position h 1 and the initial placement position h of the sheet 0 . The greater the difference, the stronger the tension that can be added to the corner portion. 1 The difference between the fitting position h 0 and the initial placement position h is adjusted usually between 5 mm and 50 mm. If the difference between the fitting position h

[0032] and the initial placement position h 1 is 5 mm or more, there is no risk of large wrinkles occurring in the corner portion due to insufficient tension. If it is 50 mm or less, there is no risk of the strength of the molded product decreasing due to the occurrence of "sliding of the fiber bundle" described later. More preferably, it is 15 mm to 50 mm, and particularly preferably 30 mm to 45 mm. Incidentally, it goes without saying that the value of h 0 -h 1 and the initial placement position h 0 can be appropriately changed depending on the thickness of the composite sheet and the sheet including the same described later, the type and weight ratio of the thermoplastic resin in the composite sheet, and the type of non-molten fiber, and can also be appropriately changed depending on the depth (height) of the molded product. 0 -h 1 The value of can be appropriately changed depending on the thickness of the composite sheet and the sheet including the same described later, the type and weight ratio of the thermoplastic resin in the composite sheet, and the type of non-molten fiber, and can also be appropriately changed depending on the depth (height) of the molded product.

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

[0034] The addition of tension in the diagonal direction in the molding method of the present invention will be described with reference to FIG. 2. FIG. 2 is an explanatory view in the case where the non-molten fibers constituting the molding sheet are a fabric.

[0035] In the present invention, the diagonal direction means a direction diagonal to the main axis direction (weaving direction) of the fabric which is a component of the sheet. The diagonal direction is preferably in the range of 45° ± 15° with respect to the main axis direction of the fabric. When the direction of the tension is greater than 60° or less than 30° with respect to the main axis direction, even if tension is applied to the sheet, the weave structure of the fabric cannot be deformed as desired, and molding defects and wrinkles are likely to occur. More preferably, it is in the range of 45° ± 10°, particularly preferably in the range of 45° ± 5°. When the non-molten fiber constituting the sheet is a roving yarn, it is preferable to set the fiber direction as the main axis direction. Further, for chopped strands and non-woven fabrics, it is preferable to set the yarn orientation direction (when oriented) as the main axis. When the orientation direction is not clear, any direction may be set as the main axis direction.

[0036] FIG. 2(a) is an explanatory diagram for explaining the deformation of the sheet (fabric) when tension is applied, and FIG. 2(b) is a diagram showing a plane and a side surface of a molded article manufactured by the molding method of the present invention, and a corner portion formed therefrom.

[0037] In FIG. 2(a), the grid-like vertical and horizontal lines indicate the weaving directions (warp direction, weft direction) of the fabric constituting the sheet 1, and the arrow marked with a cross (×) means that the fiber bundles in the fabric are difficult to extend (deform) in the said direction. Region (X) shows the plane portion and the side surface (two surfaces) of the molded article, and regions (Y) and (Z) show the fabric constituting the corner portion.

[0038] As shown in FIG. 2(a), when a diagonal tension (F) is applied to the fabric in the weaving direction, deformation due to the rotation of the fiber bundles constituting the fabric occurs at the corner portion. When the rotational deformation occurs, the shape of the fabric at the corner portion deforms from a square shape to a substantially rhombus shape or a parallelogram shape, and A moves to the position of A´ (B moves to the position of B´). The moving distance from A to A´ (from B to B´) varies depending on the tension applied to the sheet, and the moving distance becomes longer as the tension increases. Further, since the rotational deformation becomes easier as the interval between the fiber bundles constituting the fabric becomes wider, the moving distance also becomes longer. When the non-molten fibers constituting the sheet are roving yarns, chopped strands or non-woven fabrics, rotational deformation between fiber bundles does not occur, but when tension (F) is applied, the sheet forming the corner portion is pulled, suppressing the generation of wrinkles.

[0039] As shown in Fig. 2(b), by utilizing the rotational deformation between fiber bundles, the corner portion (C) can suppress the generation of wrinkles in the corner portion even in a sheet including a non-molten fiber fabric, and a molded product with excellent design can be obtained. Furthermore, a molded product with no or little decrease in the curved surface strength around the corner portion can be obtained.

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

[0041] The bias-extension test involves preparing a strip-shaped test piece with the weaving direction of the fabric at ±45° with respect to the longitudinal direction, fixing the upper and lower ends to a testing machine and pulling in the vertical direction to generate rotational deformation of the fiber bundles, and determining the maximum tensile stress, strain, and displacement at that time. At the beginning of pulling, the fiber bundles constituting the fabric rotate, and when a certain angle is reached, a locking phenomenon occurs where the rotating fiber bundles collide with each other, increasing the tensile stress. If the tensile stress is continuously applied thereafter, "sliding of the fiber bundles" occurs near the boundary between the fixed end portion of the test piece and the fiber bundles in the locked state, and thereafter the test piece cannot transmit the load, and the tensile stress decreases. In the example of the present invention, it is presumed that the vicinity of the displacement of 13 mm to 20 mm shown in Fig. 5 (the point where the slope of the curve changes) is the point where the locking phenomenon occurs.

[0042] The molding method of the present invention can effectively apply tension to the corner portion of the molded product by fitting the mold at a position lower than the initial arrangement position. In particular, by fixing the four sides and four corners of the sheet to the frame body and fitting the mold at a position lower than the initial arrangement position, tension can be applied to the corner portion more efficiently and effectively. Thus, even for a molding sheet containing non-melt fibers that had a problem of wrinkles occurring with conventional methods, by applying the tension to the corner portions and rotationally deforming the fiber bundles of the fabric, it is possible to suppress the occurrence of wrinkles in the corner portions and perform molding. Therefore, it is suitable as a molding method for a molding sheet including a composite sheet composed of a non-melt fiber fabric and a thermoplastic resin.

[0043] In the molding method of the present invention, when the fixing of the sheet is insufficient, or when the difference between the initial placement position and the fitting position is zero (0 mm) or extremely small, there is a risk of large wrinkles occurring in the corner portions of the molded product. Examples of the case where the fixing of the sheet is insufficient include, for example, when only the four sides of the sheet excluding the four corners (front-back direction and left-right direction) are fixed, or when only the four corners of the sheet are fixed. When only the four sides of the sheet are fixed, particularly when only the four sides of the sheet containing the non-melt fiber fabric are fixed, since the fabric does not stretch rigidly, when attempting to mold a molded product with a certain height (depth), the fabric tends to gather excessively at the corner portions (C), increasing the possibility of folding and large wrinkles occurring. On the other hand, when only the four corners of the sheet are fixed, there is a possibility that the fabric texture of the fabric will be disturbed when the molding die is fitted, impairing the design quality.

[0044] FIG. 3 is an explanatory diagram of a molding method when 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 the upper frame body 11 and the lower frame body 12, and the fixed sheet 1 is placed between the female die 31 and the male die 32 of the molding die 30 (FIG. 3(a)). Then, without creating a difference between the initial placement position h 0 and the fitting position h 1 , the die is fitted (FIG. 3(b)), and after molding is completed, the die is removed (FIG. 3(c)). In the conventional molding method, it is presumed that a small amount of tension is applied to the corner portions during the process of the male die pushing up the sheet when the die is fitted. In contrast, in the molding method of the present invention, sufficient tension is applied by lowering the fitting position.

[0046] [Forming sheet] In the present invention, the forming sheet preferably includes a composite sheet composed of a fabric made of non-melt fibers and a thermoplastic resin. The fabric includes a unidirectional material (UD sheet). A fabric woven from non-melt fibers has a small tensile elongation because it is resistant to tensile forces in the weaving direction, i.e., the warp and weft directions, and thus requires some ingenuity when performing vacuum forming. On the other hand, it has the advantages of being aesthetically beautiful and having excellent design properties. Furthermore, since it also has excellent impact resistance, it is suitable as a material for applications that require design properties on the surfaces of bags, cases, covers, etc.

[0047] Also in the present invention, the forming sheet may include a composite sheet composed of a roving yarn, chopped strand, or non-woven fabric made of non-melt fibers and a thermoplastic resin. Since these do not have a woven structure, there is no need to worry about the rotational deformation described above. Therefore, they have better formability than non-melt fiber fabrics.

[0048] Examples of the sheet including the composite sheet of the present invention include those in which a surface layer material and / or a back layer material are laminated on the composite sheet. Examples of the surface layer material include a decorative sheet, a printed sheet, etc., and examples of the back layer material include a non-woven fabric, etc.

[0049] [Composite sheet] Generally, as the composite sheet, a laminated or laminated-integrated product of a non-melt fiber fabric, or a non-melt fiber fabric and a non-woven fabric, etc., and a thermoplastic resin sheet can be used, and commercially available products can also be used. The thickness of the composite sheet is preferably 1.0 mm to 3.0 mm. If the thickness is too small, the formed product is likely to have holes and the strength of the formed product also decreases. On the other hand, if the thickness is too large, the forming itself becomes difficult. The thickness of the composite sheet is more preferably 1.2 mm to 2.8 mm, and even more preferably 1.5 mm to 2.5 mm.

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

[0051] Specific examples of fibers that do not melt by heat include plant fibers such as seed hair fibers (cotton, kapok, etc.), bast fibers (flax, ramie, etc.), leaf 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. In addition, examples of high melting point fibers include high-strength organic fibers. These fibers may be used alone or in combination of two or more. Among these, carbon fibers, glass fibers, etc. are preferable because they have little deformation or expansion due to heat, are easily available, and have excellent processability.

[0052] As the fabric made of non-melting fibers, plain weave, twill weave, damask weave, knitted fabric, and change weave woven by known methods can be used. Plain weave, twill weave, and damask weave are preferable, and plain weave and twill weave are more preferable, because of their excellent shape stability and aesthetic appearance.

[0053] The density of the non-melting fiber fabric is preferably 1.74 to 12 threads per 25.4 mm in both warp and weft. If the density is too small, the curved surface strength of the molded product may be insufficient, or the appearance (design) may be poor. On the other hand, if the density is too large, the gap between the fiber bundles constituting the fabric becomes small, and when tension is applied, it may not be able to rotate and deform, and wrinkles may occur at the corners. More preferably, it is 4 to 11 threads per 25.4 mm, and particularly preferably 5 to 10 threads per 25.4 mm.

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

[0055] From the viewpoints of designability and formability, the yarn width constituting the non-molten fiber fabric is preferably 1 to 5 mm, more preferably 2 to 5 mm.

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

[0057] [Thermoplastic resin] As the thermoplastic resin used for the forming sheet, a thermoplastic resin having a Vicat softening point lower than the temperature of the mold during forming or the heating temperature by a heater and a melting point higher than the said temperature can be used.

[0058] The Vicat softening point of the thermoplastic resin is desirably 50°C or higher. When the Vicat softening point is less than 50°C, the thermoplastic resin in the composite sheet remains soft and cannot withstand the pressure of the mold, which may cause molding defects. More desirably, it is 70°C or higher.

[0059] The melting point of the thermoplastic resin is desirably 300°C or lower. When the melting point exceeds 300°C, the heating of the sheet becomes insufficient, wrinkles are likely to occur in the sheet, and there is a risk that the desired molding quality (designability, strength, etc.) cannot be maintained. More desirably, it is 290°C or lower, and particularly desirably 280°C or lower.

[0060] Specific examples of the thermoplastic resin 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), ethylene vinyl alcohol copolymer resins (melting point: about 160 to 190 °C), methacrylic resins (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 (CA) resins (melting point: about 230 °C), syndiotactic polystyrene (melting point: about 270 °C), polyamideimide (melting point: about 275 °C), polyarylate (melting point: about 250 °C), polysulfone (melting point: about 200 °C), fluororesins (melting point: about 220 °C), polytetrafluoroethylene (melting point: about 260 °C), polybutylene terephthalate (melting point: about 230 to 267 °C), etc., or modified resins obtained by modifying these resins, and the like. These resins may be used alone or in combination of two or more.

[0061] Among the above thermoplastic resins, from the viewpoints of cost, light weight, impact resistance, ease of handling, ease of processing, etc., acrylic resins, polyolefin resins, polyacetal resins, polyamide resins (nylon 6, nylon 66, etc.) or modified polyolefin resins are preferable. 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 based on the total volume of the composite sheet. If the volume content of the resin is too low, the surface of the non-molten 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. More preferably, it is 50 to 80% by volume, and particularly preferably 50 to 70% by volume.

[0063] [Male-female fitting type molding die] As the molding die used in the molding method of the present invention, a male-female fitting type match mold molding die in which a male die having a convex portion is disposed as a lower die and a female die having a concave portion corresponding to the male die is disposed as an upper die is preferable.

[0064] The molding die is preferably a die for vacuum molding, and more preferably a die for double-sided vacuum molding. By performing double-sided vacuum molding, the vacuum suction time during molding can be shortened, and in addition, the remaining traces of the suction holes, the penetration marks of the thermoplastic resin, and the disturbance of the fabric form can be prevented.

[0065] The molding die is provided with a plurality of vacuum holes for vacuum suction on the surfaces of the male die and the female die. The number of the vacuum holes is not limited, but it is preferable that the vacuum holes are provided at least at positions corresponding to the corners of the molded product in both the male die and the female die. More preferably, the vacuum holes are further provided on all of the flat portions and the side surfaces. Regarding the arrangement of the vacuum holes, they may be arranged at positions facing each other when the male die and the female die are mated, or may be arranged at different positions.

[0066] The aperture 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 that the vacuum suction will not be sufficiently performed and the moldability will deteriorate, and there is no concern about clogging. Also, if it is 1.0 mm or less, it is possible to prevent the traces of the vacuum holes from remaining on the molded product after vacuum suction, and there is no concern about the occurrence of appearance defects.

[0067] The vacuum suction performed from the surface of the upper mold (female mold) is preferably started before the female mold begins to descend and comes into contact with the sheet, and this vacuum suction is preferably also performed during the vacuum suction performed from the surface of the lower mold (male mold). Also, the vacuum suction performed from the surface of the lower mold (male mold) is preferably started immediately after the molds are aligned. In this way, by providing a time difference in the vacuum suction of the male and female molds, since the wall thickness distribution of the side walls is affected by the timing of the vacuum suction from both the male and female molds, compared to the case where the vacuum suction is started simultaneously for the male and female, the wall thickness of the side surface becomes easier to control and the occurrence of wrinkles can be prevented. Specifically, the time difference between the vacuum suction start time of the male mold and the vacuum suction start time of the female mold is preferably 0.5 seconds to 1.0 seconds.

[0068] The vacuum conditions (vacuum degree) during vacuum forming are not particularly specified, but it is preferable to reduce the pressure to about 0.05 MPa to 0.09 MPa (0.5 atm to 0.9 atm) for both the male and female molds. If the vacuum degree is within the above range, there is no concern about molding defects due to insufficient suction force, and also, the texture of the sheet is not disturbed due to the suction force being too strong, and no appearance defects occur. Furthermore, since the control of the thickness of the sheet is easy, a molded product with a uniform thickness can be obtained.

[0069] The temperature of the molding die during molding is preferably 60°C to 120°C. If it is within the above range, there is no risk of the molded product deforming due to shrinkage or the like during and 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 heating the mold to a high temperature during molding, the cooling cycle of the molded product can be accelerated, and the production quantity of the molded product can be improved. Needless to say, the temperature of the molding die can be appropriately changed depending on the thermoplastic resin used. The molding die can be heated up to about 400°C at most.

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

[0071] The molding method of the present invention can be suitably used for molding a molding sheet including a composite sheet composed of a non-molten fiber fabric and a thermoplastic resin, or a molding sheet including a composite sheet composed of a roving yarn, chopped strand or non-woven fabric made of non-molten fiber and a thermoplastic resin. Specific examples of the molded article molded by the molding method of the present invention include bags such as suitcases and attache cases; cases such as camera cases and instrument cases; various covers; automotive parts such as door trims, trim materials forming the trunk side, mat materials such as floor mats and trunk mats, and ceiling materials for automobiles; building members such as wall materials and ceiling materials; and deep drawing molded articles such as housings of household appliances.

Example

[0072] Hereinafter, the present invention will be described more specifically by way of examples, but the present invention is not limited only to the following examples.

[0073] [Measurement method of 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) As the composite sheet, a carbon fiber fabric (manufactured by Mitsui Chemicals, Inc., trade name: Toughnex (registered trademark) tape cloth, Vf: 50%, basis weight: 350 g / m) laminated with acid-modified polypropylene resin (Vicat softening point: 115 ° C, melting point: 130 ° C) on both sides 2, a fabric width of 1000 mm, a fabric density of 1.74 threads per inch, and a plain weave were used.

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

[0076] [Molding Method] Using the composite sheet and the molding die, molding was performed by the following molding method. (1) As shown in Fig. 1(a), the convex portion (13) provided on the frame was inserted into and fixed to the through hole provided in the composite sheet so that the composite sheet (1) was sandwiched between the upper and lower frames (11, 12).

[0077] (2) Next, as shown in Fig. 1(b), the fixed composite sheet (1) was placed between the female die (21) and the male die (22) so that the center point of the composite sheet, the center points of the male die and the female die were aligned. The arrangement position (height) of the composite sheet at this time was set as the initial arrangement position h 0 . After arranging the composite sheet, a heater was inserted between the die and the composite sheet, and the composite sheet was heated from both sides so that the surface temperature of the composite sheet reached about 120°C. The surface temperature of the composite sheet was measured using a non-contact thermometer.

[0078] (3) After heating the composite sheet, the heater was moved out of the die-composite sheet gap to the outside of the die, and at the same time the die was operated, and the composite sheet (1) was brought into contact with the female die (21) and the male die (22) in this order for molding. The molding method was a double-sided vacuum molding method. The state where the dies were fitted is shown in Fig. 1(c). As the female die (21) and the male die (22), those provided with a plurality of vacuum holes having a diameter of 0.5 to 1.0 mm were used. The temperature of the male and female dies 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. The vacuum suction started before the female die started to descend and contact the sheet, and the vacuum suction performed from the male die started immediately after the dies were fitted. As shown in Fig. 1(c), the fitting position h 1 of the fitted female die (21) and male die (22) 0It was set to be about 20 mm lower so that when the female mold and the male mold were fitted, an oblique tension was applied to the composite sheet.

[0079] (4) As shown in Fig. 1(d), after molding, the molded product was obtained by demolding the composite sheet (S) from the mold. The appearance of the obtained molded product is shown in Fig. 4.

[0080] (Example 2) The composite sheet was a carbon fiber fabric (manufactured by Mitsui Chemicals, Inc., trade name: Toughnex (registered trademark) Tape Cloth, Vf: 50%, basis weight: 350 g / m 2 , fabric width: 1000 mm, fabric density: 1.74 threads / inch, fabric weave: twill weave) with acid-modified polypropylene resin (Vicat softening point: 115 °C, melting point: 130 °C) laminated on both sides. The sheet was molded in the same manner as in Example 1 except for this.

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

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

[0083] [Molding Method] (1) As shown in Fig. 3(a), the convex portion (13) provided on the frame was inserted into and fixed to the through hole provided in the composite sheet so that the composite sheet (1) was sandwiched between the upper and lower frames (11, 12).

[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 and the center points of the male and female molds were aligned. The arrangement position (height) of the composite sheet at this time was set as the initial arrangement position h 0 . After arranging the composite sheet, a heater was inserted between the mold and the composite sheet and heated in the same manner as in Example 1.

[0085] (3) After heating the composite sheet, the heater was moved out of the mold to the outside of the mold while moving the mold, and the mold was brought into contact with the composite sheet (1) in the order of the female mold (31) and the male mold (32) and formed by a double-sided vacuum forming method. Initial placement position h 0 and the fitting position h 1 The difference from was 0 mm. As the female mold (31) and the male mold (32), those provided with a plurality of vacuum holes having a diameter of 0.5 to 1.0 mm were used. The temperature of the male and female 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 starts before the female mold starts to descend and comes into contact with the sheet. Also, the vacuum suction performed from the male mold starts immediately after the mold is fitted. The state where the mold is fitted is shown in Fig. 3(b).

[0086] (4) As shown in Fig. 3(c), after molding, the molded product was obtained by releasing the composite sheet (1) from the mold.

[0087] [Bias Extension Test] The composite sheets before molding used in the examples and comparative examples were cut into pieces with a length of 110 mm × width of 20 mm to obtain test pieces. The test pieces were cut out with the weaving direction (warp direction, weft direction) inclined at ± 45 ° with respect to the longitudinal direction. For the test, a small tabletop testing machine (Shimadzu Corporation) was used, and the upper and lower ends of the test piece were fixed to the testing machine so that the distance between the fixtures was 50 mm. In order to approximate the cut test piece to the situation of the sheet during molding, it was heated with a far-infrared ceramic heater to a temperature above the Vicat softening point of the thermoplastic resin and then the test was performed. 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 determined.

[0088] The results of the bias extension test are shown in Table 1 and Fig. 5.

[0089] [Table 1]

[0090] As shown in Table 1 and FIG. 5, in Examples 1-3, the displacement at the maximum tensile stress was large, and they could flexibly respond to the tensile stress during molding. Therefore, a woven pattern without wrinkles was successfully molded in a good state.

[0091] As described above, the embodiments of the present invention have been explained. Needless to say, the present invention is not limited to the above embodiments, and various modifications and changes are possible.

Industrial Applicability

[0092] The molding method of the present invention is useful as a molding method for a sheet including a composite sheet composed of a non-melt fiber fabric and a thermoplastic resin, in which the designability of the corner portion cannot be fully exhibited by a normal molding method. According to the molding method of the present invention, it is possible to provide a deep drawing molded product suitable for cases, parts, covers, and other applications that are excellent in appearance, scratch resistance, light weight, and designability.

Explanation of Signs

[0093] 1 Composite sheet 10 Frame 11 Upper frame 12 Lower frame 13 Protrusion 14 Recess 20 Molding die 21 Female die (upper die) 22 Male die (lower die) 30 Molding die 31 Female die (upper die) 32 Male die (lower die) h 0 Initial arrangement position h 1 Fitting position C Corner portion F Tension

Claims

1. A method for forming a sheet using a male-female fitting mold, comprising: heating a sheet disposed in the space between the male mold and the female mold 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 fitting the male mold and the female mold at a position lower than the arrangement position of the sheet during heating, thereby applying a diagonal tension to the four corners of the sheet. A method for forming a sheet, characterized by this.

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

3. The method for forming a sheet according to claim 1, wherein the forming method is double-sided vacuum forming.

4. The method for forming a sheet according to claim 1, wherein the sheet is a forming sheet including a composite sheet composed of a fabric made of non-molten fibers and a thermoplastic resin.

5. The method for forming a sheet according to claim 1, wherein the sheet is a forming sheet including a composite sheet composed of a roving yarn, chopped strand or non-woven fabric made of non-molten fibers and a thermoplastic resin.

6. The method for forming a sheet according to claim 4 or 5, wherein the thermoplastic resin is at least one selected from the group consisting of an acrylic resin, a polyolefin resin, a polyacetal resin, a polyamide resin, and a modified polyolefin resin.

7. The method for forming a sheet according to claim 4 or 5, wherein the thermoplastic resin is contained in an amount of 40% to 90% by volume based on the total volume of the composite sheet.

8. The basis weight of the fabric made of the non-melt fiber is 30 g / m ２ to 500 g / m ２ The method for forming a sheet according to claim 4, wherein the basis weight is as described above.

9. The method for forming a sheet according to claim 4, wherein the number of wefts of the fabric made of non-molten fibers is 1.74 to 12 per 25.4 mm.

10. The method for forming a sheet according to claim 4 or 5, wherein the non-molten fibers are carbon fibers or glass fibers.

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