Board component

Abstract

To provide a board material with excellent sound absorption properties. [Solution] A board member comprising an inner layer having porous properties due to intertwined fibers, and an outer layer covering both sides of the inner layer and having lower porous properties compared to the inner layer, laminated together.

Description

Technical Field

[0001] The technology disclosed in this specification relates to board members.

Background Art

[0002] Conventionally, as a board member having sound absorption properties, the one disclosed in Patent Document 1 below is known. This board member is a side trim of an automobile trunk room, and is configured such that a sound absorption material having sound absorption properties is adhered to the back side (outdoor side) of a laminate of a fiber skin material and a high specific gravity plastic sheet. The sound absorption material is obtained by press-forming a laminate in which a fiber skin material is pressure-bonded to a high specific gravity plastic sheet into the shape of a side trim, and then adhered to the high specific gravity plastic sheet side (outside the vehicle room) of the laminate by an adhesive or heat adhesion.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, it is known that a board member obtained by laminating and entangling fibers including plant fibers and thermoplastic resin fibers to form a mat and then heat press-forming the mat has porosity and can be lightweight. Such a board member having porosity is also useful from the viewpoint of sound absorption properties, and there is a desire to improve the sound absorption properties of the board member itself by making better use of the porous characteristics.

[0005] The technology disclosed in this specification has been completed based on the above circumstances, and an object thereof is to provide a board member having excellent sound absorption properties.

Means for Solving the Problems

[0006] In view of the above circumstances, the completed board member disclosed herein comprises an inner layer having entangled fibers and being porous, and an outer layer covering both sides of the inner layer and having lower porousness compared to the inner layer, which are laminated together.

[0007] According to the above configuration, a high sound absorption effect can be obtained due to the inner layer, which has higher porosity compared to the outer layer. On the other hand, although the outer layer has lower porosity compared to the inner layer, it can maintain rigidity, thus maintaining the overall strength of the board member. Here, the level of porosity refers to the volume ratio of pores per unit volume in the inner or outer layer.

[0008] The inner layer may contain at least plant fibers. With this configuration, the sound absorption effect can be further enhanced because the plant fibers themselves are porous. In addition, although the plant fibers contained in the inner layer may emit a plant-specific odor, even in such cases, the less porous outer layer covering the inner layer can suppress the generation of the odor.

[0009] The outer layer may contain at least a thermoplastic resin. With such a configuration, when the inner layer and the outer layer are bonded together, the bonding can be easily performed by utilizing the anchoring effect of the thermoplastic resin contained in the outer layer.

[0010] The inner layer may be made of intertwined plant fibers and thermoplastic resin fibers, and the outer layer may be made of plant fibers bound together with thermoplastic resin.

[0011] The inner layer and the outer layer may contain the same raw materials in the same proportions. With this configuration, the board member can be manufactured more simply and easily compared to when the inner layer and the outer layer are formed from different raw materials or in different proportions.

[0012] At least one of the outer layers, on the front and back, may be provided with a plurality of through-holes that penetrate the outer layer in the thickness direction. With such a configuration, by adjusting the diameter of the through-holes, sounds of specific frequencies can be attenuated by the resonance effect, thus further improving sound absorption. [Effects of the Invention]

[0013] According to the technology disclosed herein, a board member with excellent sound absorption properties can be provided. [Brief explanation of the drawing]

[0014] [Figure 1] Cross-sectional view of the deck board of Embodiment 1 [Figure 2] Diagram illustrating the fiberboard formation process (before pressing) [Figure 3] Diagram illustrating the fiberboard formation process (after pressing) [Figure 4] Diagram illustrating the heating process [Figure 5] Diagram illustrating the press forming process. [Figure 6] Cross-sectional view of the deck board of Embodiment 2 [Modes for carrying out the invention]

[0015] <Embodiment 1> Embodiment 1 will be explained with reference to Figures 1 to 5. In this embodiment, as an example of a board member, a deck board 10 that constitutes the floor surface of the cargo area of ​​an automobile (vehicle) will be described.

[0016] Figure 1 is a cross-sectional view of a deck board 10. This deck board 10 has a three-layer structure (sandwich structure) base material 11 in which an inner layer 12 made of intertwined plant fibers and thermoplastic resin fibers is sandwiched between outer layers 13, 13 in which plant fibers are bound together with thermoplastic resin (binder resin). The front and back of this base material 11 are covered with a surface material 15. This deck board 10 is a lightweight material while maintaining a predetermined rigidity.

[0017] The plant fiber used for the deck board 10 of this embodiment is a fiber derived from plants. Examples of plant fibers include kenaf, flax, hemp, jute, manila hemp, sisal hemp, ganpi, sansho, kozo, banana, pineapple, coconut, corn, sugarcane, bagasse, palm, papyrus, reed, esparto, sabi grass, wheat, rice, bamboo, various coniferous trees (such as cedar and cypress), broad-leaved trees, and cotton, etc., which are fibers obtained from various plant bodies. The part of the plant body used as the plant fiber is not particularly limited as long as the fiber can be collected, and it may be any part constituting the plant body, such as non-xylem, stem, root, leaf, and xylem.

[0018] In addition, kenaf fiber is preferable as the plant fiber. Kenaf is an annual plant with extremely fast growth and has excellent carbon dioxide absorbency, so it can contribute to reducing the amount of carbon dioxide in the atmosphere and the effective use of forest resources. Also, bast plant fibers such as kenaf are preferable in terms of weight reduction because the fibers themselves have voids. In this embodiment, kenaf fibers with an average fiber diameter of 80 μm to 100 μm are used as the plant fiber.

[0019] On the one hand, examples of the thermoplastic resin fiber and thermoplastic resin (binder resin) used for the deck board 10 of the present embodiment 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. Among these, examples of the polyolefin resin include polypropylene, polyethylene, ethylene-propylene copolymer (ethylene-propylene block copolymer, ethylene-propylene random copolymer), etc. Examples of the polyester resin include aliphatic polyester resins such as polylactic acid, polycaprolactone, and polybutylene succinate, and aromatic polyester resins such as polyethylene terephthalate, polytrimethylene terephthalate, and polybutylene terephthalate. These thermoplastic resins may be used alone or in combination of two or more. In the present embodiment, polypropylene is adopted as the thermoplastic resin fiber and thermoplastic resin (binder resin).

[0020] The deck board 10 of the present embodiment uses the same kind of raw materials for the inner layer 12 and the outer layers 13, 13. Specifically, the inner layer 12 is a layer formed by the entanglement of kenaf fibers and polypropylene fibers, and the outer layer 13 is a layer formed by binding kenaf fibers with polypropylene.

[0021] Also, the content ratio (mass) of kenaf fibers and polypropylene (including fibers) is the same for the inner layer 12 and the outer layer 13. Specifically, the content ratio (mass) of kenaf fibers and polypropylene is 5:5 in both the inner layer 12 and the outer layer 13. As a result, compared with a conventional resin-made deck board having the same degree of rigidity, the mass can be reduced by about 25 to 35%.

[0022] On the other hand, the thickness dimensions and densities of the inner layer 12 and the outer layer 13 are different. The thickness dimension of the inner layer 12 is greater than that of the outer layer 13 (one side), and the density of the outer layer 13 is greater than that of the inner layer 12. Specifically, the thickness dimensions of the inner layer 12 and the outer layer 13 are given as follows: inner layer = 3.0 mm, outer layer (one side) = 1.5 mm, and total = 6 mm. The density ratio is given as inner layer:outer layer = 1:2.

[0023] Next, the method for manufacturing the deck board 10 will be described. The deck board 10 of this embodiment is manufactured by sequentially performing the following steps: a mat forming step for forming the mat 12M; a fiberboard forming step for forming the fiberboard 13F; a heating step for heating the fiberboard 13F; and a press forming step for sandwiching the front and back surfaces of the mat 12M between the fiberboard 13F and joining them while press forming. Each step will be described in detail below.

[0024] <Mat Formation Process> First, in the mat formation process, kenaf fibers and fibrous polypropylene (PP fibers) are defibrated using a carding machine and laminated. Then, the laminated fibers are intertwined by needle punching to form mat 12M. The mat 12M obtained in this way is porous. Note that "having porous properties" refers to a porous state. The mat 12M is cut to a predetermined size using a cutting machine as needed.

[0025] <Fiberboard Formation Process> Next, as shown in Figures 2 and 3, one of the obtained mats 12M is heated to a temperature at which the PP fibers contained in the mat 12M can melt, and is then hot-pressed to a predetermined thickness using a pair of press molds 20 (upper mold 21 and lower mold 22) to obtain a fiberboard 13F in which kenaf fibers are bound together with PP.

[0026] In this embodiment, the thickness of the fiberboard 13F is approximately half the thickness of the mat 12M. That is, the density of the fiberboard 13F is higher than that of the mat 12M. Furthermore, the fiberboard 13F possesses porosity, although it is lower than that of the mat 12M. "Low porosity" means that the volume ratio of pores per unit volume is low. In addition, the fiberboard 13F has higher rigidity than the mat 12M.

[0027] <Heating process and press molding process> Next, the two fiberboards 13F formed as described above are heated to melt the PP on their surfaces (see Figure 4), and the two fiberboards 13F are positioned so that their molten surfaces face the front and back of the mat 12M. These are then set into the upper and lower molds 30 for cold press molding (upper mold 31, lower mold 32), and the molds 30 are clamped to form a deck board 10 with the desired curved shape, which is a sandwich structure in which the mat 12M is sandwiched between the two fiberboards 13F (see Figure 5). As a result, the molten PP on the surface of the fiberboard 13F (the surface facing the mat 12M) penetrates the surface layer of the mat 12M through an anchoring effect, acting as an adhesive and bonding and integrating the fiberboard 13F and the mat 12M.

[0028] Then, after the PP has cooled and solidified, the upper and lower molds 30 for cold press molding are opened and the molds are removed, completing a deck board 10 with a sandwich structure in which the front and back of the inner layer 12, which is made up of entangled kenaf fibers and PP fibers, are covered by outer layers 13, 13, to which kenaf fibers are bound by PP (see Figure 1).

[0029] Furthermore, when clamping the upper and lower molds 30 for cold press molding, by placing the surface material 15 between the mold surface of the upper and lower molds 30 and the fiberboard 13F, the adhesion of the fiberboard 13F to the mat 12M and the adhesion of the surface material 15 to the fiberboard 13F (base material 11) can be performed simultaneously (see Figure 5). In such cases, the molten PP can be used as an adhesive by heating both sides of the fiberboard 13F in the heating process to melt the PP on both sides. Alternatively, the surface material 15 may be attached with an adhesive or the like after the completed base material 11 has been demolded from the upper and lower molds 30 for cold press molding.

[0030] Next, the effects will be explained. The deck board 10 of this embodiment is made by laminating an inner layer 12 which is made of intertwined fibers and has porous properties, and an outer layer 13 which covers both sides of the inner layer 12 and has lower porous properties compared to the inner layer 12.

[0031] According to the above configuration, a high sound absorption effect can be obtained due to the inner layer 12, which has higher porosity than the outer layer 13. On the other hand, although the outer layer 13 has lower porosity than the inner layer 12, it can maintain rigidity, thus maintaining the overall strength of the deck board 10. Here, the high or low level of porosity refers to the volume ratio of pores per unit volume in the inner or outer layer.

[0032] Furthermore, since the deck board 10 itself has high sound absorption properties, there is no need to add additional sound-absorbing material, and the construction of the deck board 10 can be simplified.

[0033] Furthermore, the inner layer 12 contains kenaf fibers. With this configuration, the sound absorption effect can be further enhanced because the kenaf fibers themselves are porous. In addition, although the kenaf fibers contained in the inner layer 12 may emit a kenaf-specific odor, even in such cases, the less porous outer layer 13 covering the inner layer 12 can suppress the generation of the odor.

[0034] Furthermore, the outer layer 13 contains polypropylene (PP). With this configuration, when the inner layer 12 and the outer layer 13 are bonded together, the bonding can be easily performed by utilizing the anchoring effect of the PP contained in the outer layer 13.

[0035] Furthermore, the inner layer 12 is made of kenaf fibers and PP fibers intertwined together, and the outer layer 13 is made of kenaf fibers bound together with PP.

[0036] Furthermore, the inner layer 12 and the outer layer 13 contain the same raw materials in the same proportions. With this configuration, the deck board 10 can be manufactured more simply and easily compared to when the inner layer 12 and the outer layer 13 are formed from different raw materials or in different proportions.

[0037] <Embodiment 2> Next, Embodiment 2 will be described with reference to Figure 6. The deck board 110 of this embodiment differs from the deck board 10 of Embodiment 1 in that, in addition to the configuration, a plurality of through holes 14 are formed in one of the outer layers 13A and 13B. Components similar to those of the deck board 10 of Embodiment 1 are denoted by the same reference numerals, and redundant explanations are omitted. Furthermore, the upper surface of the deck board 110 shown in Figure 6 will be referred to as the upper surface when the deck board 110 is placed in the cargo compartment of a vehicle, and the opposite surface will be referred to as the lower surface.

[0038] Of the outer layers 13A and 13B of the deck board 110, the outer layer 13B, which is located on the lower side, has multiple through-holes 14 formed in the outer layer 13B that penetrate in the thickness direction. The diameters of the multiple through-holes 14 are all different, and because the diameters of the through-holes 14 are different, each through-hole 14 is able to attenuate sound of a specific frequency through a resonance effect (energy reduction due to air vibration and friction within the hole). In other words, the sound absorption effect can be enhanced compared to a configuration in which no through-holes 14 are formed (Embodiment 1).

[0039] Furthermore, the area of ​​these through holes 14 in a plan view accounts for approximately 30% of the total area of ​​the outer layer 13B in a plan view. This configuration reduces the mass of the outer layer 13B located on the lower side, and consequently, reduces the overall mass of the deck board 110.

[0040] Furthermore, by providing the through-holes 14 only in the outer layer 13B of the deck board 110 and not in the outer layer 13A, it is possible to avoid the through-holes 14 affecting the floor surface, which is the design surface of the cargo compartment, and thus avoid compromising its aesthetic appeal.

[0041] <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.

[0042] (1) In the above embodiment, a deck board was shown in which both the inner and outer layers contained plant fibers and thermoplastic resin (including fibers). However, for example, the inner layer may not contain thermoplastic resin fibers, or the outer layer may not contain plant fibers and may be a simple resin board that does not have porous properties.

[0043] (2) In addition, even if both the inner and outer layers contain plant fibers and thermoplastic resin (fibers), these raw materials may not be contained in the same proportion in the inner and outer layers.

[0044] (3) In Embodiment 2 described above, the through-hole 14 is provided only in one outer layer 13B, but the technical scope also includes providing the through-hole 14 in both the front and back outer layers 13A and 13B. In addition, in Embodiment 2 described above, the diameters of the multiple through-holes 14 are all different, but if it is desired to attenuate sound of a specific frequency, a configuration in which multiple through-holes of the same diameter capable of attenuating that sound are provided may be used.

[0045] (4) The surface material 15 may be omitted.

[0046] (5) The technology disclosed herein is not limited to the vehicle deck board 10, but can be suitably applied to removable parts such as package tray trims and tonneau covers to which aftermarket sound-absorbing materials cannot be attached. Furthermore, it can be applied in various ways to vehicle interior materials such as pillar garnishes, ceiling materials, console boxes, dashboards, various instrument panels, and deck trims, as well as to interior materials for vehicles such as railways, airplanes, and ships, and to applications other than vehicle interior materials. [Explanation of Symbols]

[0047] 10,110: Deck board 11: Base material 12: Inner layer 12M: Mat 13,13A,13B: Outer layer 13F: Fiberboard 14: Through hole 15: Surface material

Claims

1. An inner layer having porous properties due to intertwined fibers, A board member comprising an outer layer that covers both sides of the inner layer and has lower porousness compared to the inner layer, and which is laminated together.

2. The board member according to claim 1, wherein the inner layer contains at least plant fibers.

3. The board member according to claim 1 or claim 2, wherein the outer layer comprises at least a thermoplastic resin.

4. The inner layer is made by intertwining plant fibers and thermoplastic resin fibers. The board member according to claim 1 or claim 2, wherein the outer layer is made of plant fibers bonded together with a thermoplastic resin.

5. The board member according to claim 1 or claim 2, wherein the inner layer and the outer layer contain the same raw materials in the same proportions.

6. The board member according to claim 1 or claim 2, wherein at least one of the front and back outer layers is provided with a plurality of through holes that penetrate the outer layer in the thickness direction.

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