Method for manufacturing plant fiber-containing resin boards

Abstract

The present invention provides a method for manufacturing a plant fiber-containing resin board that can form a uniform layer of pulverized material and obtain stable quality. [Solution] The process involves the following steps in order: a grinding step of grinding a fibrous resin body containing plant fiber A and thermoplastic resin to obtain a pulverized material containing plant fiber B and thermoplastic resin; a plate-forming step of forming a first plate-like body containing plant fiber C, which has a longer fiber length than plant fiber B, and thermoplastic resin, and which is breathable; a scattering step of scattering the pulverized material onto the first plate surface of the first plate-like body; a removal step of removing the second pulverized material accumulated on the first pulverized material by sucking the pulverized material from the second plate surface side with a first suction force and sucking the pulverized material from the first plate surface side with a second suction force; a lamination step of laminating the second plate-like body containing plant fiber C and thermoplastic resin onto the first pulverized material; and a heating and pressing step of heating and pressing the laminate.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a plant fiber-containing resin board.

Background Art

[0002] Conventionally, for example, as a method for manufacturing an interior material for a vehicle (a molding method for an interior material for a vehicle), the technique described in Patent Document 1 is known. Specifically, Patent Document 1 discloses heating a fiber resin member (an interior base material) formed by mixing a thermoplastic resin such as PE or PP into glass fibers, wood fibers, etc. (hereinafter sometimes simply referred to as fibers), and inserting it between the upper mold and the lower mold of a press molding die and performing press molding.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Recently, with the pursuit of realizing a recycling-based society and contributing to carbon neutrality, in the interior base material manufactured by the process disclosed in Patent Document 1, since the thermoplastic resin is bound to the fibers, it is difficult to recover and reuse the fibers from this interior base material due to fluffs or the like. On the other hand, it is conceivable to pulverize the interior base material and mold the pulverized material, for example, into a plate shape and reuse it as a base material. However, when the interior base material is pulverized, the length of the fibers becomes shorter, so there is a concern about a decrease in strength of the base material produced from the pulverized material.

[0005] Therefore, it is conceivable to improve the strength of the substrate by laminating a layer containing fibers longer than the length of the pulverized material fibers onto the pulverized material layer. For example, a substrate with a sandwich structure and increased strength can be obtained by sandwiching a layer of pulverized material between two fiber mats, each containing relatively longer fibers than the pulverized material fibers and thermoplastic resin fibers, and then heating and pressing to melt the thermoplastic resin. Such a substrate can be obtained, for example, by forming a layer of pulverized material by scattering it on one fiber mat, and then placing the other fiber mat on top and heating and pressing it.

[0006] However, when manufacturing the base material using the above manufacturing method, it is not easy to uniformly distribute the pulverized material onto the fiber mat. If the pulverized material is unevenly distributed onto the fiber mat, there is a problem in that the resulting base material will have large variations in weight and thickness, as well as variations in physical properties such as rigidity.

[0007] This disclosure is a technology completed based on the circumstances described above, and aims to provide a method for manufacturing a plant fiber-containing resin board that can form a uniform layer of pulverized material and obtain stable quality. [Means for solving the problem]

[0008] The technology of this disclosure, completed to solve the above problems, comprises: a grinding step of grinding a fiber resin body comprising at least plant fiber A and a thermoplastic resin that binds the plant fiber A to obtain a pulverized material comprising plant fiber B having a shorter fiber length than the plant fiber A and to which the thermoplastic resin is bound; a plate-forming step of forming a first plate-shaped body that is breathable and comprises plant fiber C having a longer fiber length than the plant fiber B and a thermoplastic resin; a scattering step of scattering the pulverized material onto the first plate surface of the first plate-shaped body; and in the first plate-shaped body The method for manufacturing a plant fiber-containing resin board involves sequentially performing the following steps: a removal step of removing the second pulverized material that has accumulated on the first pulverized material from the scattered pulverized material by sucking the pulverized material from the second board surface side opposite to the first board surface with a first suction force, while sucking the pulverized material from the first board surface side with a second suction force smaller than the first suction force; a lamination step of laminating a second board-like body containing the plant fiber C and thermoplastic resin onto the first pulverized material after the removal step; and a heating press step of heating and pressing the laminate formed by the lamination step.

[0009] According to the above manufacturing method, of the pulverized material scattered on the first surface of the first plate-like body, only the first pulverized material that can remain on the first plate-like body due to the first suction force, despite the second suction force, remains on the first plate-like body side. Therefore, a pulverized material layer with small dispersion variations can be formed, and a uniform fiber-containing resin board with stable quality can be obtained. In this disclosure, "suction" may also include suction by gravity. In the removal step, the second pulverized material may be removed by gravity by directing the first plate surface vertically downward while maintaining the state in which the pulverized material is sucked from the second plate surface side by the first suction force.

[0010] Furthermore, in the removal step, the second pulverized material may be removed by suction from the first plate surface side using a suction device.

[0011] The first plate-like body may be a fiber mat composed of the plant fibers C and thermoplastic resin fibers. Alternatively, the first plate-like body may be a pre-board in which the plant fibers C are bound together with the thermoplastic resin. [Effects of the Invention]

[0012] The technology disclosed herein provides a method for producing a plant fiber-containing resin board that can form a uniform layer of pulverized material and achieve stable quality. [Brief explanation of the drawing]

[0013] [Figure 1] Diagram showing the cross-sectional configuration of the substrate according to Embodiment 1. [Figure 2] An explanatory diagram showing a fibrous resin body and its pulverized product (a diagram showing the pulverization process). [Figure 3] Diagram showing the spraying process [Figure 4] Diagram showing the reversal process (before reversal) [Figure 5] Diagram showing the reversal process (after reversal) [Figure 6] Diagram showing the lamination process [Figure 7] Diagram showing the pre-board formation process. [Figure 8] Diagram showing the substrate formation process. [Figure 9] Diagram showing the suction process in Embodiment 2 (during suction) [Figure 10] Diagram showing the suction process (after suction) [Modes for carrying out the invention]

[0014] <Embodiment 1> Embodiment 1 will be described with reference to Figures 1 to 8. In this embodiment, a method for manufacturing a base material (an example of a plant fiber-containing resin board) 10 that constitutes a door trim attached to an automobile door will be described. As shown in Figure 1, the base material 10 of this embodiment has a sandwich structure in which a third fiber resin layer 13 is sandwiched between a first fiber resin layer 11 and a second fiber resin layer 12.

[0015] First, starting from the description of the third fiber resin layer 13, the third fiber resin layer 13 is a laminated body formed based on the crushed material 13T of the fiber resin body 14 described later, and contains at least plant fiber B and a thermoplastic resin. The plant fiber B is obtained by crushing the fiber resin body 14 containing the plant fiber A, and has a fiber length shorter than that of the plant fiber A. Although the plant fiber A and the plant fiber B are not particularly limited, for example, among the fibers possessed by plants such as kenaf, flax, hemp, jute, manila hemp, sisal hemp, ganpi, mitsuba, kozo, banana, pineapple, coconut palm, corn, sugarcane, bagasse, palm, papyrus, reed, esparto, sabi grass, wheat, rice, bamboo, coniferous trees (such as cedar and cypress), broad-leaved trees, and cotton, one or more of them can be adopted.

[0016] Although the fiber length of the plant fiber A is not particularly limited, for example, the average fiber length calculated according to JIS L1015 may be 10 mm or more, 50 mm or more, or 100 mm or more. Although the fiber length of the plant fiber B is not particularly limited as long as it is shorter than the fiber length of the plant fiber A, for example, the average fiber length calculated according to JIS L1015 may be 0.5 mm or more, 1 mm or more, or 2 mm or more. It may also be less than 10 mm, less than 7 mm, or less than 5 mm.

[0017] Although the thermoplastic resin contained in the third fiber resin layer 13 is not particularly limited, one or more of polyolefin resins (such as polypropylene and polyethylene), polyester resins (such as aliphatic polyester resins such as polylactic acid and polycaprolactone, and aromatic polyester resins such as polyethylene terephthalate), etc. can be adopted.

[0018] On the other hand, the first fiber resin layer 11 and the second fiber resin layer 12 are composed of at least plant fibers C having a longer fiber length than the plant fibers B described above, and a thermoplastic resin. The first fiber resin layer 11 and the second fiber resin layer 12 have a lower modulus of elasticity than the third fiber resin layer 13. The plant fibers C are not particularly limited, but for example, one or more types of fibers from plants such as kenaf, flax, hemp, jute, Manila hemp, sisal, ganpi, mitsumata, kozo, banana, pineapple, coconut, corn, sugarcane, bagasse, palm, papyrus, reed, esparto, sabaigrass, wheat, rice, bamboo, coniferous trees (cedar, cypress, etc.), broad-leaved trees, and cotton can be used. The fiber length of plant fiber C is not particularly limited as long as it is longer than the fiber length of plant fiber B, but for example, the average fiber length calculated in accordance with JIS L1015 may be 10 mm or more, 50 mm or more, or 100 mm or more.

[0019] The thermoplastic resins included in the first fiber resin layer 11 and the second fiber resin layer 12 are not particularly limited, but one or more types from polyolefin resins (polypropylene, polyethylene, etc.), polyester resins (aliphatic polyester resins such as polylactic acid and polycaprolactone, aromatic polyester resins such as polyethylene terephthalate, etc.) can be used. The first fiber resin layer 11 and the second fiber resin layer 12 may contain the same plant fiber C and thermoplastic resin, or they may contain different plant fiber C and thermoplastic resins.

[0020] The base material 10 of this embodiment is manufactured by sequentially performing a crushing step, a fiber mat formation step (an example of a plate-like body formation step), a spreading step, an inversion step (an example of a removal step), a lamination step, a pre-board formation step (an example of a heat-pressing step), and a base material formation step (an example of a heat-pressing step), using a discarded fiber resin body 14 and a mixed fiber obtained by mixing plant fiber C and thermoplastic resin fiber as raw materials. Each step will be described in detail below.

[0021] <Grinding process> The crushing process involves crushing a fibrous resin body 14, which is formed by binding plant fibers A with a thermoplastic resin, to obtain crushed material 13T. The fibrous resin body 14 is not particularly limited as long as it contains at least plant fibers A and a thermoplastic resin that binds the plant fibers A. For example, as shown in Figure 2, one or more types of materials can be used from off-spec base materials 14X, base material scraps 14Y, and vehicle interior materials 14Z recovered through recycling. The crushing method for the fibrous resin body 14 is not particularly limited and can be done by cutting, tearing, smashing, etc. The crushed material 13T contains plant fibers B that are shorter in length than plant fibers A, as a result of crushing the fibrous resin body 14, that is, plant fibers A bound with thermoplastic resin. Furthermore, thermoplastic resin is bound to the plant fibers B contained in the crushed material 13T. It is also possible to reuse the base material 10 formed in this embodiment as the fibrous resin body 14. The dimensions of the crushed material obtained in this crushing process are approximately 5 mm.

[0022] <Fiber mat formation process (an example of a plate-like body formation process)> The fiber mat formation process involves, for example, mixing plant fibers C, which have a longer fiber length than plant fiber B, with fibrous thermoplastic resin fibers to form a mixed fiber web. This web is then defibrated using a carding machine and laminated to form a mat. This process is then entangled using needle punching to obtain nonwoven fiber mats (examples of first and second plate-like bodies) 11M and 12M. However, the method for forming fiber mats 11M and 12M is not limited to this method.

[0023] <Spraying process> In the spreading process, as shown in Figure 3, the first fiber mat 11M obtained in the fiber mat formation process is arranged so that its surface extends approximately horizontally (facing vertically), and the pulverized material 13T is spread onto the first surface 11A, which is the upper surface of the first fiber mat 11M, by the spreading device 20. This forms a laminate 10A1 in which a layer of pulverized material 13T (referred to as the pulverized material layer 13S1) is laminated onto the first fiber mat 11M. At this time, it is not easy to spread the pulverized material 13T uniformly in the planar direction of the first fiber mat 11M, and the formed pulverized material layer 13S1 may be uneven with large variations in thickness. The thickness of the formed pulverized material layer 13S1 is approximately 5 to 15 mm.

[0024] <Inversion process (an example of a removal process)> Next, as shown in Figure 4, the entire laminate 10A1 is sucked up by the suction device 25 from the second plate surface 11B side, which is the bottom surface of the first fiber mat 11M (laminated body 10A1), and the laminate 10A1 is inverted upside down together with the suction device 25 (see Figure 5). The suction force of the suction device 25 at this time (an example of the first suction force) is set to be greater than gravity (an example of the second suction force). As a result, of the pulverized material 13T laminated on the first fiber mat 11M, the portion where the suction force of the suction device 25 is greater than gravity (first pulverized material 13T1) remains on the first fiber mat 11M, and the portion where the suction force is less than gravity (second pulverized material 13T2) falls downward. Thus, a laminate 10A2 is obtained in which the dispersion state of the pulverized material 13T (thickness of the pulverized material layer 13S2) is uniform. The thickness of the formed pulverized material layer 13S2 is set to be approximately 5 to 8 mm.

[0025] <Lamination process> Subsequently, the inverted laminate 10A2 is stacked such that the crushed material layer 13S2 is superimposed on the second fiber mat 12M described above, thereby forming a laminate 10S consisting of the first fiber mat 11M, the crushed material layer 13S2, and the second fiber mat 12M (see Figure 6).

[0026] <Pre-board forming process (an example of a heated pressing process)> Next, the resulting laminate 10S is heated to a temperature above which the thermoplastic resin contained in the first fiber mat 11M, the second fiber mat 12M, and the pulverized material layer 13S2 (in the first pulverized material 13T1) can melt, and then pressed between the upper mold 31 and the lower mold 32 of the first molding die 30 (see Figure 7). As a result, the plant fibers B and C are bound together by the molten thermoplastic resin, and a three-layer plate-shaped pre-board 11P with a relatively thin thickness is formed. Since this pre-board 10P is flat, it is suitable for situations such as storing or transporting multiple pre-boards together.

[0027] <Substrate Forming Process (Example of Heat Pressing Process)> Finally, the pre-board 10P is reheated to a temperature above which it can be softened, and then pressed between the upper die 36 and lower die 37 of the second molding die 35 to form the base material 10 (see Figure 8). The pre-board formation step may be omitted; in that case, the base material 10 can be formed directly from the laminate 10S2 by heating the laminate 10S2 and then pressing it with the second molding die 35.

[0028] Next, the effects of this embodiment will be described. This embodiment includes a grinding step of grinding a fiber resin body 14 which is composed of at least plant fibers A and a thermoplastic resin that binds the plant fibers A to obtain a pulverized material 13T which contains plant fibers B that have a shorter fiber length than plant fibers A and to which the thermoplastic resin is bound; a plate-shaped body forming step of forming a plate-shaped first fiber mat 11M which contains plant fibers C that have a longer fiber length than plant fibers B and a thermoplastic resin and is breathable; a scattering step of scattering the pulverized material 13T onto the first plate surface 11A of the first fiber mat 11M; and in the first fiber mat 11M, the first plate surface 11A is opposite to the first plate surface 11A. This is a method for manufacturing a substrate 10, comprising: an inversion step in which crushed material 13T is sucked from the opposite side, the second plate surface 11B, with a first suction force, while gravity less than the first suction force is applied from the first plate surface 11A, thereby removing the second crushed material 13T2 that has accumulated on the first crushed material 13T1 from the scattered crushed material 13T; a lamination step in which a second fiber mat 12M containing plant fibers C and thermoplastic resin is laminated on the first crushed material 13T1 after the inversion step; and a pre-board forming step and a substrate forming step in which the laminate 10S formed by the lamination step is heated and pressed.

[0029] According to the above manufacturing method, of the pulverized material 13T scattered on the first surface 11A of the first fiber mat 11M, only the first pulverized material 13T1 that can remain on the first fiber mat 11M due to the first suction force against gravity remains on the first fiber mat 11M side. Therefore, a pulverized material layer 13S2 with small dispersion variations can be formed, and a uniform and stable quality base material 10 can be obtained.

[0030] Furthermore, during the inversion process, while maintaining the state in which the pulverized material 13T is sucked in by the first suction force from the second plate surface 11B side, the first plate surface 11A is directed vertically downward, thereby causing the second pulverized material 13T2 to fall and be removed by gravity.

[0031] <Embodiment 2> Next, Embodiment 2 will be described with reference to Figures 9 and 10. In the following, only the steps that differ from Embodiment 1 will be described, and the same steps as in Embodiment 1 will be omitted to avoid redundant explanation. In the above embodiment, an inversion step was performed as an example of a removal step after the spraying step, but in this embodiment, a suction step is performed as an example of a removal step.

[0032] <Suction process> In the suction process following the scattering process, as shown in Figure 9, while maintaining a state of suction of the entire laminate 10A1 from the second plate surface 11B side, which is the lower surface of the first fiber mat 11M (laminated laminate 10A1), a portion of the scattered pulverized material 13T (second pulverized material 13T2) is removed by suction from the first plate surface 11A side, which is the upper surface of the laminate 10A1, using the second suction device 26. At this time, it is desirable to start suction by the first suction device 25 before suction by the second suction device. Also, at this time, by setting the second suction force of the second suction device 26 to be smaller than the first suction force of the first suction device 25, it is possible to leave only the necessary portion (first pulverized material 13T1) of the pulverized material 13T and remove the unnecessary portion (second pulverized material 13T2). Even by this method, a laminate 10A2 with a uniform dispersion state of the pulverized material 13T (thickness of the pulverized material layer 13S2) can be obtained.

[0033] <Other Embodiments> The technologies disclosed herein are not limited to the embodiments described above in the description and drawings, but also include, for example, the following embodiments.

[0034] (1) In the above embodiment, the crushed material 13T is shown to be scattered on a fiber mat 11M, but instead of a fiber mat, the crushed material can also be scattered on a breathable pre-board (an example of a first plate-like body).

[0035] (2) In addition to the embodiments described above, the fibrous resin body 14, which is a precursor of the pulverized material 13T, can be changed as appropriate. In other words, in the embodiments described above, the fibrous resin body 14 was made from substandard base material 40X, base material scraps 40Y, and vehicle interior material 40Z recovered through recycling, but is not limited to these. For example, the fibrous resin body may be carpet or its scraps, or fiber-containing resin components such as building materials for houses.

[0036] (3) The pre-board formation step may be omitted, and the substrate formation step may be carried out directly after the removal step.

[0037] (4) In the above embodiment, a base material 10 that constitutes a vehicle door trim was described as a plant fiber-containing resin board, but the plant fiber-containing resin board of this technology is not limited to a base material for interior materials for vehicles. [Explanation of symbols]

[0038] 10: Base material (plant fiber-containing resin board) 10P: Pre-board 10S: Laminate 11: First fiber resin layer 11A: First board surface 11B: Second board surface 11M: First fiber mat (first plate-like body) 11P: Pre-board 12: Second fiber resin layer 12M: Second fiber mat (second plate-like body) 13: Third fiber resin layer 13T1: First crushed material 13T2: Second crushed material 13T: Crushed material 14: Fiber resin body 26: Second suction device (suction device)

Claims

1. A grinding step of grinding a fiber resin body comprising at least plant fiber A and a thermoplastic resin that binds the plant fiber A to obtain a pulverized product containing plant fiber B having a shorter fiber length than the plant fiber A and to which the thermoplastic resin is bound; A plate-forming step to form a first plate-shaped body that is breathable and contains plant fiber C having a longer fiber length than the aforementioned plant fiber B and a thermoplastic resin, A scattering step of scattering the pulverized material onto the first plate surface of the first plate-shaped body, In the first plate-like body, a removal step is performed to remove the second pulverized material that has accumulated on top of the first pulverized material from the scattered pulverized material by sucking the pulverized material from the second plate surface side opposite to the first plate surface with a first suction force, while sucking the pulverized material from the first plate surface side with a second suction force smaller than the first suction force, After the removal step, a lamination step is performed in which a second plate-like body containing the plant fiber C and thermoplastic resin is laminated onto the first pulverized material, A method for manufacturing a plant fiber-containing resin board, comprising sequentially performing a heating and pressing step for heating and pressing the laminate formed by the lamination step, and a step of heating and pressing the laminate formed by the lamination step.

2. The method for manufacturing a plant fiber-containing resin board according to claim 1, wherein in the removal step, the second pulverized material is removed by gravity by directing the first board surface vertically downward while maintaining the state in which the pulverized material is sucked from the second board surface side by the first suction force.

3. The method for producing a plant fiber-containing resin board according to claim 1, wherein in the removal step, the second pulverized material is removed by suction from the first board surface side using a suction device.

4. A method for producing a plant fiber-containing resin board according to any one of claims 1 to 3, wherein the first plate-like body is a fiber mat composed of the plant fiber C and thermoplastic resin fibers.

5. The method for producing a plant fiber-containing resin board according to any one of claims 1 to 3, wherein the first plate-like body is a pre-board in which the plant fibers C are bound together with the thermoplastic resin.

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