Method for producing vegetable fiber-containing resin board

Abstract

To provide a method for producing a vegetable fiber-containing resin board, by which the vegetable fiber-containing resin board can more simply be produced at a low cost.SOLUTION: A laminated body forming step of sucking the mixed fibers 20 to a holding surface 33 of a sucking machine 32 provided with a plurality of sucking holes 34 to form a laminated body 10L on the holding surface 33, a moving step of moving the sucking machine 32 in a state of holding the laminated body 10L on the holding surface 33 between molding dies 40 having an upper die 41 and a lower die 45, an arranging step of releasing sucking of the sucking machine 32 to arrange the laminated body 10L on a die surface of the lower die 45, and a retracting step of retracting the sucking machine 32 from the molding dies 40; A heat-press forming step of closing the mold 40 and heat-press forming the side 10L of the laminate.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a method for producing a plant fiber-containing resin board. [Background technology]

[0002] A known method for manufacturing board components using plant fibers is described in, for example, Patent Document 1. Patent Document 1 describes a process in which PP resin fibers spun from PP resin and kenaf fibers defibrated from kenaf are mixed in a mixer, formed into a mat using a former, thermo-pressed to a predetermined thickness using a press, and cut to the desired web dimensions using a cutter to obtain a thermoformable fiberboard. The resulting thermoformable fiberboard is then heated using a heater, placed in upper and lower cold-press molding dies, and clamped to form an interior substrate with the desired curved surface shape. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-179716 Summary of the Invention [Problem to be solved by the invention]

[0004] The above-described conventional manufacturing method can produce a board member that is high in rigidity and easy to handle even with a low basis weight. However, the manufacturing process involves many steps, which is time-consuming and requires high equipment costs, and therefore manufacturing costs. Therefore, there has been a demand for a simpler and more cost-effective manufacturing method.

[0005] The technology disclosed in this specification was developed based on the above circumstances, and aims to provide a method for manufacturing a plant fiber-containing resin board that is easier to manufacture and allows for lower costs. [Means for solving the problem]

[0006] The technology disclosed in this specification, which was completed to solve the above-mentioned problems, is a method for manufacturing a plant fiber-containing resin board, which sequentially carries out the following steps: a mixing step of mixing plant fibers and thermoplastic resin fibers; a laminate formation step of sucking the mixed plant fibers and thermoplastic resin fibers onto a holding surface of a suction machine provided with a plurality of suction holes to form a laminate on the holding surface; a moving step of moving the suction machine, with the laminate held on the holding surface, between a molding die having an upper mold and a lower mold; an arrangement step of releasing the suction of the suction machine and placing the laminate on the mold surface of the lower mold; an evacuation step of retracting the suction machine from between the upper mold and the lower mold; and a heat-press molding step of closing the upper mold and the lower mold and heat-press molding the laminate at a temperature at which the thermoplastic resin fibers melt.

[0007] According to the above manufacturing method, the number of steps required to manufacture a plant fiber-containing resin board can be significantly reduced compared to the conventional method of hot press molding using a thermoforming fiberboard, thereby reducing manufacturing costs.

[0008] The suction force of the suction device may have a strength distribution within the holding surface. With this configuration, the basis weight within the surface of the plant fiber-containing resin board can be controlled, for example, by increasing the basis weight in areas where the strength of the plant fiber-containing resin board is desired to be relatively high, such as bent portions and component attachment portions, and decreasing the basis weight in areas where strength is not required, thereby reducing the weight.

[0009] The suction force of the suction machine may have a strength distribution within the holding surface such that when the laminate is placed on the mold surface of the lower mold, the suction force is greater in areas where the distance between the upper mold and the lower mold is greater.

[0010] According to the above configuration, even if the plant fiber-containing resin board has portions where the board thickness varies within its surface, it can have a nearly uniform weight per unit area as a whole. [Effects of the Invention]

[0011] According to the technology disclosed in this specification, it is possible to provide a method for producing a plant fiber-containing resin board that can be produced more easily and at lower cost. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a diagram illustrating a method for manufacturing a trim board according to the first embodiment, and is an explanatory diagram illustrating a mixing step. [Figure 2] An explanatory diagram showing a laminate formation process [Figure 3] An explanatory diagram showing the movement process [Figure 4] An explanatory diagram showing the placement process [Figure 5] An explanatory diagram showing the evacuation process [Figure 6] An explanatory diagram showing the hot press molding process [Figure 7] An explanatory diagram showing the mold opened state [Figure 8] Cross-sectional view of a trim board according to a second embodiment [Figure 9] An explanatory diagram showing the placement process [Figure 10] An explanatory diagram showing the hot press molding process DETAILED DESCRIPTION OF THE INVENTION

[0013] <Embodiment 1> Embodiment 1 will be described with reference to Figures 1 to 7. The plant fiber-containing resin board manufactured by the manufacturing method of this embodiment is a trim board 10 that forms part of a door trim that constitutes the interior design surface of a vehicle door such as an automobile, and as shown in Figure 7, has a configuration in which a reinforcing rib 12 is provided on the back surface (upper surface in Figure 7) of a flat, plate-shaped base material 11. The front side (lower surface in Figure 7) of the base material 11 forms the interior design surface 11A, and the back side forms the back surface 11B.

[0014] The trim board 10 is made of plant fibers and thermoplastic resin. Specifically, the plant fibers are bonded together with the thermoplastic resin. Therefore, the trim board 10 is a lightweight member while maintaining a predetermined rigidity.

[0015] Plant fibers are fibers derived from plants. Examples of plant fibers include fibers obtained from various plants such as kenaf, flax, hemp, jute, Manila hemp, sisal, gampi, mitsumata, kozo, banana, pineapple, coconut, corn, sugarcane, bagasse, palm, papyrus, reed, esparto, sabaigrass, wheat, rice, bamboo, various coniferous trees (such as cedar and cypress), broadleaf trees, and cotton. The part of the plant used as the plant fiber is not particularly limited, and may be any part of the plant, such as non-woody parts, stems, roots, leaves, and woody parts, as long as fiber can be extracted.

[0016] Kenaf fiber is preferred as the plant fiber. Kenaf is an annual plant that grows extremely quickly and has excellent carbon dioxide absorption properties, which can contribute to reducing the amount of carbon dioxide in the atmosphere and making effective use of forest resources. Furthermore, bast plant fibers such as kenaf have voids in the fiber itself, making them preferable in terms of weight reduction. In this embodiment, kenaf fiber with an average fiber diameter of 80 μm to 100 μm is used as the plant fiber.

[0017] On the other hand, the thermoplastic resin constituting the trim board 10 of this embodiment mainly functions as a binder resin, and various thermoplastic resins can be used. Examples of thermoplastic resins include polyolefin resin, polyester resin, polystyrene, acrylic resin (resin obtained using methacrylate and / or acrylate, etc.), polyamide resin, polycarbonate resin, polyacetal resin, and ABS resin. Examples of polyolefin resins include polypropylene, polyethylene, and ethylene-propylene copolymers (ethylene-propylene block copolymers and ethylene-propylene random copolymers). Examples of polyester resins include aliphatic polyester resins such as polylactic acid, polycaprolactone, and polybutylene succinate, as well as aromatic polyester resins such as polyethylene terephthalate, polytrimethylene terephthalate, and polybutylene terephthalate. These thermoplastic resins may be used alone or in combination. In this embodiment, polypropylene is used as the thermoplastic resin.

[0018] Next, a method for manufacturing the trim board 10 of this embodiment will be described. The trim board 10 of this embodiment is manufactured by sequentially performing a mixing process, a laminate forming process, a moving process, a arranging process, a retracting process, and a hot press molding process. Each process will be described in detail below.

[0019] <Mixing process> In the mixing process, as shown in Figure 1, kenaf fibers (an example of plant fibers) 21 and polypropylene fibers (an example of thermoplastic resin fibers) 22 are placed in an appropriate ratio into a box-shaped mixing tank 30 that opens upward, and air is blown into the mixed fibers 20 to defibrate the kenaf fibers 21 and polypropylene fibers 22. As shown in Figure 2, a blower 31 is installed near the bottom of the mixing tank 30, and the mixed fibers 20 that have accumulated at the bottom are blown up and circulated within the mixing tank 30 by the air blown in from the blower 31. The entangled mixed fibers 20 collide with each other and fall as they circulate, gradually defibrating and homogenizing them.

[0020] During circulation of the mixed fiber 20, the opening of the mixing tank 30 is closed by a suction machine 32, which will be described later. The length of the kenaf fiber 21 obtained by defibration is about 1 to 100 mm, and the length of the polypropylene fiber 22 is about 1 to 100 mm.

[0021] <Laminate formation process> Air is blown into the mixing tank 30, and after a predetermined time has passed and the mixed fibers 20 (kenaf fibers 21 and polypropylene fibers 22) have been defibrated, the above-mentioned suction machine 32 is turned on and the mixed fibers 20 in the mixing tank 30 are sucked onto the holding surface 33 (bottom surface) of the suction machine 32.

[0022] As shown in Figure 2, the aspirator 32 is shaped like a thick plate having dimensions that enable it to block the opening of the mixing tank 30 from above, and has a plurality of suction holes 34. Each suction hole 34 is connected to a vacuum chamber (not shown) formed inside the aspirator 32, and an air compressor such as a pump is connected to the vacuum chamber. The aspirator 32 sucks air through the plurality of suction holes 34, thereby sucking some of the mixed fibers 20 circulating in the mixing tank 30 onto the holding surface 33 and stacking them. A filter 35 is attached to the holding surface 33, making it difficult for the mixed fibers 20 to enter the suction holes 34.

[0023] The suction device 32 is configured so that the suction force at each of the plurality of suction holes 34 can have a strength distribution within the holding surface 33. FIG. 2 is a schematic diagram showing this state, with larger upward arrows indicating relatively strong suction force and smaller upward arrows indicating relatively weak suction force. As shown in the figure, a large amount of mixed fiber 20 is laminated in areas with strong suction force, and a relatively small amount of mixed fiber 20 is laminated in areas with weak suction force. In this embodiment, the suction force in the area where the rib 12 is formed of the laminate 10L is set to be greater than that in other areas (areas where only the base material 11 is formed).

[0024] In this embodiment, the suction force of the suction device 32 is set to a strength capable of holding mixed fibers 20 of various lengths and diameters on the holding surface 33. In the areas where suction force is strong, mixed fibers 20 containing fibers with longer fiber lengths or larger fiber diameters, i.e., relatively heavy fibers, are sucked in compared to areas where suction force is weak. In this embodiment, the length of the mixed fibers 20 layered in the areas where suction force is weak on the holding surface 33 is approximately 1 to 40 mm, and the length of the mixed fibers 20 layered in the areas where suction force is strong is 1 to 100 mm.

[0025] <Movement process> Once the laminate 10L (kenaf fibers 21 and polypropylene fibers 22) has a predetermined thickness on the holding surface 33 of the suction machine 32, the suction machine 32 holding the laminate 10L on the holding surface 33 is moved between the open molding dies 40 (upper die 41 and lower die 45) (see FIG. 3). The molding die 40 has a mold surface that follows the shape of the trim board 10 of this embodiment.

[0026] Specifically, as shown in Fig. 3, the mold surface (upper surface) of the lower mold 45 is composed of a lower base 46 extending in the horizontal direction. The lower mold 45 is a fixed mold that does not move. On the other hand, the mold surface (lower surface) of the upper mold 41 is set so that a predetermined distance (a distance equal to the thickness of the substrate 11) is provided between the mold surface (lower base 46) of the lower mold 45 in the mold closed state, and is composed of an upper base 42 extending in the horizontal direction and a recess 43 that is recessed upward from the upper base 42 and forms the above-mentioned rib 12. This upper mold 41 is a movable mold that can be moved in the vertical direction by a driving device (e.g., an electric motor, an air cylinder, a hydraulic cylinder, etc.) not shown.

[0027] <Placement process> When the suction device 32 reaches a predetermined position between the upper mold 41 and the lower mold 45, the suction of the suction device 32 is turned off. The laminate 10L held on the holding surface 33 of the suction device 32 falls by gravity and is placed on the mold surface (lower base 46) of the lower mold 45 (see FIG. 4).

[0028] <Evacuation process> Next, as shown in FIG. 5, the suction device 32 is retracted from between the upper mold 41 and the lower mold 45 to the outside of the mold.

[0029] <Hot press molding process> 6, the upper mold 41 is moved by a drive device in a direction (downward) approaching the lower mold 45, and the laminate 10L is hot-press molded by the upper mold 41 and the lower mold 45. The temperature of the molding mold 40 at this time is set to a temperature higher than the melting point of polypropylene.

[0030] At this time, as described above, the thickness dimension of the laminate 10L pressed by the mold 40 at the portion where the rib 12 of the trim board 10 is formed is larger than that of the other portions (portions where the base material 11 is formed), so that the trim board 10 (base material 11 and rib 12) formed by press molding has a nearly uniform basis weight overall.

[0031] After the molten resin (polypropylene) has cooled and solidified, the upper mold 41 and the lower mold 45 are separated to open the molding die 40, thereby obtaining a trim board 10 with ribs 12 integrally formed on the back surface 11B side of the base material 11 (see Figure 7).

[0032] The manufacturing method of the trim board 10 of this embodiment sequentially includes the following steps: a mixing step of mixing the kenaf fibers 21 and the polypropylene fibers 22; a laminate forming step of sucking the mixed kenaf fibers 21 and the polypropylene fibers 22 onto a holding surface 33 of a suction device 32 having a plurality of suction holes 34 to form a laminate 10L on the holding surface 33; a moving step of moving the suction device 32, with the laminate 10L held on the holding surface 33, between a molding die 40 having an upper die 41 and a lower die 45; an arrangement step of releasing the suction of the suction device 32 and placing the laminate 10L on the mold surface of the lower die 45; a retracting step of retracting the suction device 32 from between the upper die 41 and the lower die 45; and a hot-press molding step of closing the upper die 41 and the lower die 45 and hot-press molding the laminate 10L at a temperature at which the polypropylene fibers 22 melt.

[0033] According to the above manufacturing method, the number of steps required to manufacture the trim board 10 can be significantly reduced compared to the conventional method of hot press molding using a thermoforming fiberboard, thereby reducing manufacturing costs.

[0034] Furthermore, the suction force of the suction device 32 has a strength distribution within the holding surface 33. With this configuration, the basis weight within the surface of the trim board 10 can be controlled by, for example, increasing the basis weight in areas where the strength of the trim board 10 needs to be relatively high, such as bent portions and component mounting portions, and decreasing the basis weight in areas where strength is not required, thereby reducing the weight.

[0035] In addition, the suction force of the suction device 32 has a strength distribution within the holding surface 33 such that when the laminate 10L is placed on the mold surface of the lower mold 45, the suction force is greater in areas where the distance between the upper mold 41 and the lower mold 45 is greater.

[0036] According to the above configuration, even if the trim board 10 has portions where the board thickness varies within its surface, it is possible to achieve a nearly uniform weight as a whole.

[0037] <Embodiment 2> Next, a second embodiment will be described with reference to Figures 8 to 10. Note that only the parts that are different from the first embodiment will be described below, and parts that are the same as those in the first embodiment will be given the same reference numerals, and duplicated explanations will be omitted.

[0038] 8, a trim board 110 manufactured by the manufacturing method according to this embodiment has a plate-shaped base material 111 and a resin bracket 13 provided on the back side of the base material 111. The front side of the base material 111 is an interior design surface 111A, and the back side is a back surface 111B.

[0039] Bracket 13 is made of, for example, ABS resin, is formed separately from base material 111, and is joined to the center of back surface 111B of base material 111. Bracket 13 is, for example, a clip seat for attaching a clip for locking a door panel.

[0040] The manufacturing method of the trim board 110 of this embodiment first performs the same steps from the mixing step to the retracting step as in the above-described embodiment 1. Then, in the subsequent hot press molding step, the configuration of the molding die 140 differs from that in the above-described embodiment 1. The molding die 140 and the hot press molding step will be specifically described below.

[0041] As shown in FIG. 9, the molding die 140 of this embodiment differs from the first embodiment in that the mold surface (lower surface) of the upper die 141 does not have a recess. After the retraction step, in the hot press molding step, the laminate 110L is hot press molded by the upper die 141 and the lower die 145, as shown in FIGS. 8 and 9. The relatively thick central portion of the laminate 110L is pressed against the horizontal mold surface to form a reinforcement portion 111C that has a larger basis weight and higher strength than the other peripheral portions. After the base material 111 is completed, the bracket 13 described above is adhered to this reinforcement portion 111C to form a durable bracket-equipped trim board 110.

[0042] <Other embodiments> The technology disclosed in this specification is not limited to the embodiments described above and illustrated in the drawings, and the following embodiments, for example, are also included in the technical scope.

[0043] (1) In the above embodiment, the mixed fiber 20 is defibrated in the mixing step, but if defibration is not necessary, it may be omitted.

[0044] (2) In the above embodiment, in the laminate formation process, the suction force at each of the multiple suction holes 34 of the suction device 32 has a strength distribution within the holding surface 33, but a form in which the suction force is constant within the holding surface is also included in the technical scope.

[0045] (3) The technology disclosed in this specification is not limited to the trim boards 10, 110 of vehicle door trim, but can be modified and applied to other vehicle interior materials such as pillar garnishes, ceiling materials, console boxes, dashboards, various instrument panels, deck trim, etc., as well as vehicle interior materials for trains, airplanes, ships, etc., and applications other than vehicle interior materials. [Explanation of symbols]

[0046] 10, 110: Laminated body 10L, 110L: Laminated body 11, 111: Base material 11A, 111A: Interior design surface 11B, 111B: Back surface 12: Rib 13: Bracket 20: Mixed fiber 21: Kenaf fiber (plant fiber) 22: Polypropylene fiber (thermoplastic resin fiber) 30: Mixing tank 31: Blower 32: Vacuum machine 33: Holding surface 34: Vacuum hole 35: Filter 40, 140: Molding mold 41, 141: Upper mold 42: Upper base 43: Recess 45, 145: Lower mold 46: Lower base 111C: Reinforcement part

Claims

1. a mixing step of mixing plant fibers and thermoplastic resin fibers; a laminate forming step of sucking the mixed plant fibers and the thermoplastic resin fibers onto a holding surface of a suction machine having a plurality of suction holes to form a laminate on the holding surface; a moving step of moving the suction machine with the laminate held on the holding surface between a molding die having an upper die and a lower die; a placement step of releasing the suction of the suction device and placing the laminate on the mold surface of the lower mold; a retracting step of retracting the suction device from between the upper mold and the lower mold; and a heat press molding step of closing the upper mold and the lower mold and heat press molding the laminate at a temperature at which the thermoplastic resin fibers melt.

2. The method for producing a plant fiber-containing resin board according to claim 1 , wherein the suction force of the suction machine has a strength distribution within the holding surface.

3. A method for manufacturing a plant fiber-containing resin board as described in claim 1 or claim 2, wherein the suction force of the suction machine has a strength distribution within the holding surface such that when the laminate is placed on the mold surface of the lower mold, the suction force is greater in areas where the distance between the upper mold and the lower mold is greater.

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