JP7385814B2 - Method for manufacturing molded bodies - Google Patents

Description

The technology disclosed herein relates to a method for manufacturing a molded article.

BACKGROUND ART Conventionally, as a method for manufacturing a molded body, a method of manufacturing a plate-shaped molded body by hot pressing a sheet-like fibrous body is known. As a method for producing a fibrous body, a method using an opening cylinder and a conveyor is known (see Patent Document 1 below). Patent Document 1 discloses that after a sheet-like fibrous body is formed by opening fibers using an opening cylinder and releasing them into the air, and depositing the released fibers on a conveyor, the fibers constituting the fibrous body are separated from each other. A method of interlacing by needle punching is described.

Japanese Patent Application Publication No. 2004-339653

In the above method, the thickness of the fibrous body can be further reduced by needle punching the fibrous body. This facilitates handling (for example, transportation) of the fibrous body. Further, by reducing the thickness of the fibrous body, the fibrous body can be heated efficiently. However, when the fibrous body is needle punched, holes are formed in the fibrous body. Such holes may be visible as a pattern, causing a deterioration in design quality. Under these circumstances, there is a need for a method that can reduce the thickness of a fibrous body without needle punching the fibrous body.

The technology disclosed in this specification was developed based on the above circumstances, and aims to reduce the thickness of the fibrous body without needle punching the fibrous body. .

As a means for solving the above problems, the method for manufacturing a molded article disclosed in this specification includes vegetable fibers, first thermoplastic resin fibers, and a thermoplastic resin fiber having a melting point lower than that of the first thermoplastic resin fibers. a fibrous body forming step of forming a sheet-like fibrous body by laminating mixed fibers having a second thermoplastic resin fiber having a melting point portion, and a fibrous body forming step performed after the fibrous body forming step, a pressing step in which the thickness of the fibrous body is reduced by heating and pressing the fibrous body at a temperature at which the first thermoplastic resin fibers are melted and the first thermoplastic resin fibers are not melted; A molded body forming step of reducing the thickness of the fiber body by hot pressing the fiber body at a temperature at which the first thermoplastic resin fiber melts, and forming a plate-shaped molded body. have

According to the above method, the low melting point portion of the second thermoplastic resin fiber is melted in the pressing step. As a result, the molten low melting point portion is cooled and solidified, thereby fulfilling the function of a binder and binding the fibers included in the fibrous body. As a result, the fibrous body is maintained in its pressed shape. Therefore, the thickness of the fibrous body can be reduced without needing to needle punch the fibrous body. In the pressing process, by reducing the thickness of the fibrous body, handling (transportation, etc.) of the fibrous body becomes easier. Furthermore, by reducing the thickness of the fibrous body, the fibrous body can be heated more efficiently in the next step (molded body forming step). Furthermore, in the pressing process, since the low melting point portion, which has a lower melting point than the first thermoplastic resin fiber, is melted, the heating temperature of the fiber body is lower than when the first thermoplastic resin fiber is melted and used as a binder. heating time can be reduced. In addition, in the pressing process, since the first thermoplastic resin fibers are heated at a temperature at which they do not melt, the first thermoplastic resin fibers maintain their fiber state. As a result, the fibrous body after the pressing process has higher flexibility than the molded body. Therefore, fibrous bodies are easier to change shape and to be stored than molded bodies. Further, when cutting the fibrous body into a predetermined size, the cutting operation can be easily performed (compared to cutting a molded body into a predetermined size).

Further, the second thermoplastic resin fiber is a fiber having a core-sheath structure having a core portion and a sheath portion having a lower melting point than the core portion, the low melting point portion is the sheath portion, and the press In the step, the fibrous body may be heated and pressed at a temperature at which the sheath portion melts but the core portion does not melt.

By melting the sheath, other fibers can be bound to the second thermoplastic resin fibers. In the pressing process, only the sheath portion, which has a lower melting point, needs to be melted, so the heating temperature and heating time for the fibrous body must be lowered and the heating time shorter than when both the core and sheath portions are melted. I can do it. It should be noted that if the fibrous body is heated too much, there is a concern that the vegetable fibers will be burnt and the design will be deteriorated, but such a situation can be suppressed.

Further, the core portion may be made of polyethylene terephthalate, and the sheath portion may be made of low melting point polyethylene terephthalate, which has a lower melting point than the polyethylene terephthalate. By configuring the second thermoplastic resin fibers with polyethylene terephthalate, it is possible to increase the light transmittance, and since the second thermoplastic resin fibers are difficult to be visually observed, it is possible to further improve the design of the molded article. can.

Moreover, the mass per unit area of the molded body can be 200 g/m ² or more and 600 g/m ² or less. By setting the mass per unit area to 200 g/m ² or more, the rigidity of the molded object can be ensured, and by setting the mass per unit area to 600 g/m ² or less, the molded object can have light transmittance. Since the molded body has light transparency, for example, by irradiating the molded body with light, the pattern of the vegetable fibers can be illuminated, and the design can be enhanced. Such a molded body is suitable for use in, for example, a vehicle interior material equipped with a light source. In the case where the molded object has light transmittance, if holes are formed in the molded object by needle punching, the holes will be easily visible when the molded object is irradiated with light, and the design will deteriorate. There are concerns. In this respect, the above method is preferable because it does not require the use of a needle punch, and therefore no holes are formed in the molded body.

According to the present invention, the thickness of the fibrous body can be reduced without needle punching the fibrous body.

Diagram showing the fibrous body forming process and pressing process Diagram showing the molded body forming process An enlarged view of a part of mixed fibers Diagram showing the molding process of molding a molded object into a predetermined product shape Cross-sectional view showing a vehicle interior material including a molded body Diagram showing a comparative example manufacturing device (manufacturing device equipped with a needle punch device)

An embodiment of the present invention will be described with reference to FIGS. 1 to 6. In this embodiment, a molded body 10 used as a vehicle interior material (vehicle interior material) such as a door trim is exemplified. As shown in FIG. 2, the molded body 10 has a plate shape and contains vegetable fibers and a thermoplastic resin.

Next, the manufacturing apparatus 20 (molded body manufacturing apparatus) for manufacturing the molded body 10 will be explained. The manufacturing apparatus 20 is configured to be able to manufacture a plate-shaped molded body 10 from mixed fibers 12 containing vegetable fibers and thermoplastic resin fibers. As shown in FIGS. 1 and 2, the manufacturing device 20 includes a fiber supply section 23, a feed conveyor 24, an opening cylinder 25, a conveyor 26, a press device 40, a cutter 29, and a press device 50 (see FIG. (see 2).

The feed conveyor 24 is capable of conveying the mixed fibers 12 fed into the fiber supply section 23 to the opening cylinder 25. The opening cylinder 25 includes a cylinder main body 25A having a cylindrical shape and a plurality of protrusions 25B formed on the surface (outer peripheral surface) of the cylinder main body 25A. The plurality of protrusions 25B are constituted by, for example, metallic wires wound around the surface of the cylinder body 25A.

The opening cylinder 25 can rotate about the central axis L1 so that the upper part of the opening cylinder 25 faces toward the right side in FIG. 1 . The rotating opening cylinder 25 is capable of opening the mixed fibers 12 sent from the feed conveyor 24 by scratching them with the projections 25B. Further, as the opening cylinder 25 rotates, the mixed fibers 12 are hooked on the surface of the opening cylinder 25 (protrusions 25B) and are conveyed upward, and then due to the centrifugal force caused by the rotation of the opening cylinder 25. , released into the air.

The manufacturing apparatus 20 also includes a stripper roller 30 and a walker roller 31 provided along the outer periphery of the opening cylinder 25. On each surface of the stripper roller 30 and the walker roller 31, protrusions (not shown) made of metallic wire or the like are formed similarly to the opening cylinder 25. The walker roller 31 has a function of spreading the mixed fibers 12 by passing the mixed fibers 12 between the walker roller 31 and the walker roller 31 . It has a function of peeling off the mixed fibers 12 attached to the surface.

The conveyor 26 has an upper surface 26A on which the mixed fibers 12 discharged into the air from the opening cylinder 25 can be deposited. The conveyor 26 is configured to be able to form a fiber web 13 (sheet-like fiber body) by conveying the mixed fibers 12 to the right side in FIG. 1 while depositing the mixed fibers 12 on the upper surface 26A.

The press device 40 heat-presses the fibrous web 13 sent from the conveyor 26 using a pair of belts 41 and 42, thereby reducing the thickness of the fibrous web 13 and making it possible to form a fibrous mat 14 (fibrous body). The structure is as follows. In this embodiment, the sheet-like fibrous body before the pressing process using the press device 40 is referred to as the fibrous web 13, and the fibrous body after the pressing process using the press device 40 (fibrous web 13) A fibrous body with a thickness smaller than 13) is called a fibrous mat 14 to distinguish it.

The press device 40 is a double belt press device, and includes a pair of belts 41 and 42 facing each other, a pair of rollers 41A and 41B that drive the belt 41, and a pair of rollers 42A and 42B that drive the belt 42. , a heating section 43, and a cooling section 45. The pair of belts 41 and 42 are made of metal such as stainless steel, for example. The fibrous web 13 is conveyed to the right side in FIG. 1 by a pair of belts 41, 42. The opposing interval T2 between the pair of belts 41 and 42 is set to a value smaller than the thickness T1 of the fibrous web 13 on the conveyor 26. As a result, the thickness of the fiber web 13 decreases in the process of passing between the pair of belts 41 and 42. Note that the facing interval T2 between the pair of belts 41 and 42 may gradually become smaller as the fibrous web 13 is conveyed.

The heating unit 43 is provided on each of the pair of belts 41, 42, and can heat the belts 41, 42 by, for example, blowing hot air onto the belts 41, 42. This makes it possible to heat the fiber web 13 located between the pair of belts 41 and 42 in the region where the heating section 43 is arranged. Note that by forming the pair of belts 41 and 42 into a mesh shape, heat can be easily transmitted through the fiber web 13. Note that the heating method of the heating section 43 is not limited to using hot air. For example, the heating unit 43 may include a heater that can heat the belt 41 (or belt 42).

The cooling unit 45 is provided on each of the pair of belts 41, 42, and is capable of cooling the belts 41, 42. This makes it possible to cool the fiber web 13 located between the pair of belts 41 and 42 in the area where the cooling unit 45 is arranged. As shown in FIG. 1, the cooling unit 45 may be, for example, a water-cooled roller disposed inside the belt 41 (or belt 42). A refrigerant (for example, cold water) can be circulated inside the cooling section 45, and the belt 41 (or belt 42) is cooled by the cooling section 45 coming into contact with the belt 41 (or belt 42). ing. Note that the heating section 43 is disposed on the upstream side in the conveyance direction D1 (right side in FIG. 1) of the fiber web 13 by the pair of belts 41 and 42, and the cooling section 45 is disposed on the downstream side in the conveyance direction D1. .

The press device 50 is configured to heat-press the fiber mat 14 using a pair of belts 51 and 52, thereby reducing the thickness of the fiber mat 14 and making it possible to form the flat molded body 10. Note that the molded body 10 shown in FIG. 2 is in a state before being molded into the product shape of a vehicle interior material, and is sometimes referred to as a pre-board. The press device 50 is a double belt press device, and includes a pair of belts 51 and 52 facing each other, a pair of rollers 51A and 51B that drive the belt 51, and a pair of rollers 52A and 52B that drive the belt 52. , a heating section 53, and a cooling section 55. The pair of belts 51 and 52 are made of metal such as stainless steel, for example. The fiber mat 14 is conveyed to the right side in FIG. 2 by a pair of belts 51 and 52. The opposing interval T4 between the pair of belts 51 and 52 is set to a value smaller than the thickness T3 of the fiber mat 14. As a result, the thickness of the fiber mat 14 decreases in the process of passing between the pair of belts 51 and 52.

The heating unit 53 is provided on each of the pair of belts 51, 52, and can heat the belts 51, 52 by, for example, blowing hot air onto the belts 51, 52. This makes it possible to heat the fiber mat 14 located between the pair of belts 51 and 52 in the area where the heating section 53 is arranged. Note that the heating method of the heating section 53 is not limited to one using hot air. For example, the heating unit 53 may include a heater that can heat the belt 51 (or belt 52).

The cooling unit 55 is provided on each of the pair of belts 51 and 52, and is capable of cooling the belts 51 and 52. This makes it possible to cool the fiber mat 14 located between the pair of belts 51 and 52 in the area where the cooling unit 55 is arranged. As shown in FIG. 2, the cooling unit 55 may be, for example, a water-cooled roller disposed inside the belt 51 (or belt 52). A refrigerant (for example, cold water) can be circulated inside the cooling section 55, and the belt 51 (or belt 52) is cooled by the cooling section 55 coming into contact with the belt 51 (or belt 52). ing. Note that the heating section 53 is disposed on the upstream side in the conveyance direction D2 (right side in FIG. 2) of the fiber mat 14 by the pair of belts 51 and 52, and the cooling section 55 is disposed on the downstream side in the conveyance direction D2. .

Next, a method for manufacturing the molded body 10 of this embodiment will be explained. The method for manufacturing the molded body 10 of the present embodiment includes a fibrous body forming step (fibrous web forming step) in which a fibrous web 13 (sheet-like fibrous body) is formed by laminating mixed fibers 12, and a fibrous body forming step. A press step is executed after the press step in which the fibrous web 13 is heated and pressed using the press device 40 to reduce the thickness of the fibrous web 13 (fiber body) to form the fibrous mat 14; A molded body forming step is provided in which the thickness of the fiber mat 14 is reduced by heating and pressing the fiber mat 14 using a press device 50 to form a plate-shaped molded body 10.

(fibrous body formation process)
In the fibrous body forming step, as shown in FIG. The mixed fibers 12 (spread fibers) released into the air are deposited on the upper surface 26A of the conveyor 26 in operation. In addition, in FIG. 1, the rotation direction of the opening cylinder 25 is shown by arrow A2. The mixed fibers 12 deposited on the upper surface 26A are conveyed to the right side (press device 40 side) in FIG. 1 by the operation of the conveyor 26. Therefore, by continuously depositing the mixed fibers 12 on the upper surface 26A and conveying the deposited mixed fibers, a fiber web 13 in which the mixed fibers 12 are layered is formed.

The mixed fiber 12 is a mixture of a vegetable fiber 70, a first thermoplastic resin fiber 71, and a second thermoplastic resin fiber 72, as shown in FIG. Examples of the vegetable fiber 70 include bast vegetable fibers such as kenaf, wood fibers obtained by defibrating fiber wood, and the like. In the following description, a case where kenaf fiber is used as the vegetable fiber 70 will be exemplified.

Examples of the first thermoplastic resin fiber 71 include polyolefin resins (polypropylene, polyethylene, etc.), polyester resins (aliphatic polyester resins such as polylactic acid and polycaprolactone, aromatic polyester resins such as polyethylene terephthalate), etc. I can do it. In the following description, a case where polypropylene is used as the first thermoplastic resin fiber 71 will be exemplified.

As shown in FIG. 3, the second thermoplastic resin fiber 72 is a fiber with a core-sheath structure having a core portion 72A and a sheath portion 72B having a lower melting point than the core portion 72A. The sheath portion 72B is arranged to cover the outer peripheral surface of the core portion 72A. The core portion 72A is made of, for example, polyethylene terephthalate (PET), and the sheath portion 72B is made of, for example, low melting point polyethylene terephthalate (low melting point PET), which has a lower melting point than polyethylene terephthalate. The sheath portion 72B has a melting point lower than that of the first thermoplastic resin fiber 71. In other words, the second thermoplastic resin fiber 72 has a low melting point portion (sheath portion 72B) whose melting point is lower than that of the first thermoplastic resin fiber 71. Note that the melting point of the core portion 72A is, for example, higher than the melting point of the first thermoplastic resin fiber 71.

Note that the melting point of the polypropylene forming the first thermoplastic resin fiber 71 is, for example, about 160 to 170°C, and the melting point of the polyethylene terephthalate forming the core portion 72A is, for example, about 260°C, and the melting point of the polyethylene terephthalate forming the core portion 72A is, for example, about 260°C. The melting point of low melting point polyethylene terephthalate is, for example, about 110 to 120°C, but is not limited thereto.

In addition, in the case where kenaf fiber is used as the vegetable fiber 70, polypropylene is used as the first thermoplastic resin fiber 71, polyethylene terephthalate is used as the core portion 72A, and low melting point polyethylene terephthalate is used as the sheath portion 72B, the total mass of the mixed fibers 12 is 100 wt. %, the vegetable fiber 70 is contained in a proportion of 40 to 60 wt%, the first thermoplastic resin fiber 71 is contained in a proportion of 20 to 40 wt%, and the second thermoplastic resin fiber 72 is contained in a proportion of 10 to 30 wt%. . Note that the proportion of each fiber contained in the mixed fibers 12 is not limited to this.

(Press process)
In the pressing process (fiber mat forming process), as shown in FIG. 1, the fibrous web 13 is heated and pressed using a press device 40 to reduce the thickness of the fibrous web to form a fibrous mat 14. Specifically, the thickness (board thickness) of the fibrous web 13 is reduced by passing the fibrous web 13 between the pair of belts 41 and 42 and pressing. In the pressing process, the fibrous web 13 is heated in the process of passing between the pair of belts 41 and 42 heated by the heating section 43. The heating temperature of the fiber web 13 in the pressing step is a temperature at which the sheath portion 72B (low melting point portion) of the second thermoplastic resin fiber 72 melts, and a temperature at which the first thermoplastic resin fiber 71 does not melt and the core portion 72A. It is said to be the temperature at which the temperature does not melt. That is, in the pressing process, the fiber web 13 is heated and pressed at a temperature at which the sheath portion 72B melts, but at a temperature at which the first thermoplastic resin fibers 71 do not melt. In other words, in the pressing step, the fiber web 13 is heated and pressed at a temperature higher than the melting point of the sheath portion 72B and lower than the melting point of the first thermoplastic resin fiber 71, thereby forming the first thermoplastic resin fiber 71 and the core portion 72A. Only the sheath portion 72B is melted without being melted.

The fiber web 13 heated by the heating section 43 is cooled in the process of passing through a region of the pair of belts 41 and 42 where the cooling section 45 is arranged. As a result, the molten sheath portion 72B is cooled and solidified, thereby functioning as a binder and binding the fibers included in the fibrous web 13 to each other. As a result, the fibrous web 13 is maintained in the pressed shape by the pair of belts 41 and 42, resulting in a fibrous mat 14 (hard cotton mat) having a smaller thickness.

As described above, in the pressing process, only the sheath portion 72B is melted. Therefore, in the fiber mat 14, the first thermoplastic resin fibers 71 and the core part 72A are in the state of fibers, and the vegetable fibers 70, the first thermoplastic resin fibers 71, the core part 72A are connected through the sheath part 72B. is in a bound state. Further, the formed fiber mat 14 is cut into a predetermined length by a cutter 29, for example, and then sent to the next process (molded body forming process).

(Molded body forming process)
In the molded body forming step, the fiber mat 14 is heated and pressed using the press device 50 to form the molded body 10. Specifically, the fiber mat 14 is passed between a pair of belts 51 and 52 and pressed, thereby reducing the thickness (board thickness) of the fiber mat 14 and forming the plate-shaped molded body 10. As shown in FIG. 2, in the molded body forming process, the fiber mat 14 is heated in the process of passing between a pair of belts 51 and 52 heated by a heating section 53. The heating temperature of the fiber mat 14 in the molded body forming process is set to a temperature at which the first thermoplastic resin fibers 71 are melted. In other words, in the molded body forming step, the fiber mat 14 is heated and pressed at a temperature at which the first thermoplastic resin fibers 71 melt.

Note that when polypropylene is used as the first thermoplastic resin fiber 71 and polyethylene terephthalate is used as the core portion 72A, the melting point of the first thermoplastic resin fiber 71 is lower than the melting point of the core portion 72A. If the melting point of the first thermoplastic resin fibers 71 is lower than the melting point of the core portion 72A, the fiber mat 14 may be heated at least at a temperature at which the first thermoplastic resin fibers 71 melt in the molded body forming step. The fiber mat 14 may be heated to a temperature at which both the first thermoplastic resin fibers 71 and the core portion 72A melt. However, it is preferable to melt only the first thermoplastic resin fibers 71 because the heating time for the fiber mat 14 can be further reduced.

The fiber mat 14 heated by the heating section 53 is cooled while passing through a region of the pair of belts 51 and 52 where the cooling section 55 is arranged. As a result, the molten first thermoplastic resin fibers 71 are cooled and solidified to function as a binder, and the fibers included in the fiber mat 14 are bound together. As a result, the fiber mat 14 is maintained in the pressed shape by the pair of belts 51 and 52, resulting in the molded body 10 having a smaller thickness.

In this embodiment, the molded body 10 is molded so that the mass per unit area of the molded body 10 is, for example, 200 g/m ² or more and 600 g/m ² or less. By reducing the mass per unit area of the molded body 10, the molded body 10 can be imparted with light transmittance. By setting the mass per unit area of the molded body 10 to 600 g/m ² or less, the molded body 10 can be more reliably imparted with light transmittance. The mass per unit area of the molded body 10 can be adjusted, for example, by adjusting the amount of mixed fibers 12 (more specifically, the basis weight of the fiber web 13) stacked on the conveyor 46. Note that by setting the mass per unit area of the molded body 10 to 400 g/m ² or less, the molded body 10 can be more reliably imparted with light transmittance.

Moreover, the molded body 10 (preboard) is molded into a predetermined product shape in a molding process performed after the molded body forming process. In this molding process, the thermoplastic resin (more specifically, the first thermoplastic resin fiber 71 is melted and then solidified) constituting the molded body 10 is melted by heating the molded body 10 with a heating furnace, a heater, etc. By doing so, the molded body 10 is softened, and as shown in FIG. 4, the molded body 10 in the softened state is pressed by a pair of molds 61 and 62, thereby molding the molded body 10 into a predetermined product shape. .

The molded body 10 formed into a product shape is used, for example, as a component of a vehicle interior material 80 (for example, a plate-shaped interior material main body as shown in FIG. 5), as shown in FIG. As described above, in this embodiment, after the mixed fibers 12 are made into the fiber web 13 and the fiber web 13 is made into the fiber mat 14, the fiber mat 14 is made into the molded body 10, and the molded body 10 is molded into a predetermined product shape. This is a component of the vehicle interior material 80. In other words, the method for manufacturing the vehicle interior material 80 includes a fibrous body forming process, a pressing process, a molded body forming process, and a molding process.

The molded body 10 constitutes a design surface (a surface on the interior side of the vehicle) in the vehicle interior material 80. A vehicle interior material 80 shown in FIG. 5 includes a light source 82 (such as an LED) disposed on the outside of the vehicle interior of the molded body 10 (on the right side in FIG. 5). Note that examples of the vehicle interior material 80 include those used as vehicle door trims, instrument panels, roof linings, cowl side trims, pillar garnishes, and the like.

Further, as shown in FIG. 5, the vehicle interior material 80 may include a plate material 81 that is attached to the molded body 10. The plate material 81 is made of, for example, a light-transmitting resin (eg, acrylic resin, etc.). By attaching the plate material 81 to the molded body 10, the rigidity can be further increased. In addition, in the molded body 10, the vegetable fibers 70 are visible as a pattern. The light emitted from the light source 82 passes through the plate material 81 and the molded body 10. In this way, when light passes through the molded body 10, the vegetable fibers 70 contained inside the molded body 10 can be illuminated as a pattern, and the design can be further improved. The vehicle interior material 80 only needs to include at least the molded body 10, and may be configured without the plate material 81.

Next, the effects of this embodiment will be explained. According to the method for manufacturing the molded body 10 of this embodiment, the sheath portion 72B (low melting point portion) of the second thermoplastic resin fiber 72 is melted in the pressing step. As a result, the molten sheath portion 72B is cooled and solidified, thereby functioning as a binder and binding the fibers included in the fibrous web 13 to each other. As a result, the fibrous web 13 is maintained in its pressed shape and becomes a fibrous mat 14. Therefore, the thickness of the fibrous web 13 can be reduced (more specifically, the fibrous web 13 can be maintained in a small thickness state) without needing to needle punch the fibrous web 13 (fibrous body). The fibrous web 13 can be a fibrous mat 14.

In the pressing process, by reducing the thickness of the fiber web 13 to form the fiber mat 14, handling (transportation, etc.) of the fiber mat 14 becomes easier. Further, by reducing the thickness of the fiber web 13 to form the fiber mat 14, the fiber mat 14 can be heated more efficiently in the next step (molded body forming step). Furthermore, by changing the fiber web 13 to a fiber mat 14 with a smaller thickness, it is possible to save space when storing the fiber mat 14 compared to storing the fiber web 13. . Furthermore, in the pressing process, since the sheath portion 72B having a lower melting point than the first thermoplastic resin fibers 71 is melted, the heating of the fiber web 13 is faster than when the first thermoplastic resin fibers 71 are melted to form a binder. It is possible to lower the temperature and shorten the heating time.

In addition, in the pressing step, since the first thermoplastic resin fibers 71 are heated at a temperature at which they do not melt, the first thermoplastic resin fibers 71 are included in the state of fibers. As a result, the fiber mat 14 after the pressing process has higher flexibility than the molded body 10. Therefore, the fiber mat 14 can change its shape more easily than the molded body 10, and can be wound into a roll for easy storage, for example. Furthermore, when cutting the fiber mat 14 into a predetermined length using the cutter 29, for example, the cutting operation can be easily performed (compared to cutting the molded body 10 into a predetermined length). I can do it.

Further, FIG. 6 shows a manufacturing apparatus 120 of a comparative example. The manufacturing apparatus 120 in FIG. 6 includes a needle punch device 140 instead of the press device 40. When manufacturing the molded body 10 using the manufacturing device 120, the fibers included in the fiber web 13 are entangled with each other by the needle punch device 140 to reduce the thickness and form the fiber mat 14. In this case, since the needle provided in the needle punch device 140 pierces the fiber web 13, countless holes are formed in the fiber mat 14. As a result, in the molded body 10, there is a concern that the countless holes will be visible as a pattern, and the design quality will be degraded. In contrast, in this embodiment, the thickness of the fibrous web 13 can be reduced without performing needle punching on the fibrous web 13. Therefore, it is possible to suppress the formation of countless holes in the fiber mat 14.

Further, in the present embodiment, the second thermoplastic resin fiber 72 is a fiber with a core-sheath structure having a core portion 72A and a sheath portion 72B having a lower melting point than the core portion 72A. The fiber web 13 heated at a temperature at which the core portion 72B melts but does not melt the core portion 72A is pressed. By melting the sheath portion 72B that constitutes the surface of the second thermoplastic resin fiber 72, other fibers can be bound to the second thermoplastic resin fiber 72 (sheath portion 72B). In the pressing process, it is only necessary to melt the sheath portion 72B, which has a lower melting point, so the heating temperature of the fiber web 13 may be lowered and the heating time may be lower than when both the core portion 72A and the sheath portion 72B are melted. can be made smaller. It should be noted that if the fiber web 13 is heated too much, there is a concern that the vegetable fibers 70 will be scorched and the design quality will deteriorate, but such a situation can be suppressed.

Further, the core portion 72A is made of polyethylene terephthalate, and the sheath portion 72B is made of low melting point polyethylene terephthalate, which has a lower melting point than polyethylene terephthalate. By forming the second thermoplastic resin fiber 72 with polyethylene terephthalate, the light transmittance can be increased and the second thermoplastic resin fiber 72 is difficult to be seen, so only the pattern of the vegetable fiber 70 can be molded. It can be exposed to the design surface of the body 10, and the design of the molded body 10 can be further improved. For example, as shown in FIG. 5, when a light source 82 is used, it is possible to particularly illuminate only the vegetable fibers 70 as a pattern, thereby making it possible to further enhance the design.

Further, in the present embodiment, the mass (fabric weight) per unit area of the molded body 10 is 200 g/m ² or more and 600 g/m ² or less. In other words, according to the method for manufacturing the molded body 10 of this embodiment, the molded body 10 is manufactured so that the mass per unit area of the molded body 10 is 200 g/m ² or more and 600 g/m ² or less. By setting the mass per unit area to 200 g/m ² or more, the rigidity of the molded object 10 can be ensured, and by setting the mass per unit area to 600 g/m ² or less, the molded object 10 can have light transmittance. Since the molded body 10 has light transparency, the pattern of the vegetable fiber 70 can be illuminated by irradiating the molded body 10 with light using a light source 82 as shown in FIG. can be made higher. In addition, in the case where the molded body 10 has optical transparency, if holes are formed in the molded body 10 by needle punching, the holes may become easily visible when the molded body 10 is irradiated with light. The light source 82 may be visible through the hole, and there is a concern that the design quality may deteriorate. In this respect, the method described above is preferable because no needle punch is used, so no holes are formed in the molded body 10.

Furthermore, when the fibrous web 13 is needle punched, there is a concern that the fibers constituting the fibrous web 13 will be cut, resulting in a decrease in rigidity. In this respect, in this embodiment, since no needle punch is used, it is possible to prevent the fibers constituting the fiber web 13 from being cut, which is preferable.

Further, when needle punching the fibrous web 13, there is a concern that foreign matter on the surface of the fibrous web 13 may be pushed into the fibrous web 13 by being pressed by the needle. If there is a foreign substance inside the fiber web 13, when the molded article 10 is irradiated with light, the foreign substance will be illuminated, resulting in a decrease in design. However, it is difficult to remove foreign matter pushed into the fiber web 13. In this respect, the present embodiment is preferable because it does not use a needle punch, so that it is possible to prevent foreign matter from entering the inside of the fiber web 13.

<Other embodiments>
The present invention is not limited to the embodiments described above and illustrated in the drawings; for example, the following embodiments are also included within the technical scope of the present invention.
(1) In the above embodiment, a configuration is illustrated in which a part of the second thermoplastic resin fiber 72 (the sheath portion 72B) is a low melting point portion having a lower melting point than the first thermoplastic resin fiber 71, but it is limited to this. Not done. The second thermoplastic resin fiber 72 may be composed only of a low melting point portion having a lower melting point than the first thermoplastic resin fiber 71. For example, when the first thermoplastic resin fiber 71 is made of polypropylene, the second thermoplastic resin fiber 72 may be made of low melting point polypropylene, which has a lower melting point than polypropylene. Note that the materials and proportions of the vegetable fiber 70, first thermoplastic resin fiber 71, and second thermoplastic resin fiber 72 illustrated in the above embodiment are merely examples, and can be changed as appropriate.
(2) In the above embodiment, in the pressing step and the molded body forming step, a method of pressing the fibrous body (fiber web 13 or fiber mat 14) using a double belt press device was exemplified, but the method is not limited thereto. For example, the fibrous body (fibrous web 13 or fibrous mat 14) may be pressed using a pair of press dies.
(3) In the above-mentioned pressing process, a method of pressing while heating the fibrous web 13 was exemplified, but the fibrous web 13 may be heated and then pressed before the fibrous web 13 cools down.
(4) In the above-mentioned molded body forming step, a method of pressing the fiber mat 14 while heating it was exemplified, but it may be pressed after heating the fiber mat 14 and before the fiber mat 14 cools down.

DESCRIPTION OF SYMBOLS 12... Mixed fiber, 13... Fiber web (fibrous body before the press process), 14... Fiber mat (fibrous body after the press process), 70... Vegetable fiber, 71... First thermoplastic resin fiber, 72... Second Thermoplastic resin fiber, 72A... Core part, 72B... Sheath part (low melting point part)

Claims (2)

By laminating mixed fibers obtained by mixing vegetable fibers, first thermoplastic resin fibers, and second thermoplastic resin fibers having a low melting point portion whose melting point is lower than that of the first thermoplastic resin fibers, a sheet-like fiber is formed. a fibrous body forming step of forming a fibrous body;
Performed after the fibrous body forming step, the thickness of the fibrous body is reduced by heating pressing the fibrous body at a temperature at which the low melting point portion melts and at a temperature at which the first thermoplastic resin fibers do not melt. A pressing process to
Forming a molded body, which is performed after the pressing step, and reduces the thickness of the fiber body by heating pressing the fiber body at a temperature at which the first thermoplastic resin fiber melts, thereby forming a plate-shaped molded body. comprising a process and,
The second thermoplastic resin fiber is a fiber with a core-sheath structure having a core and a sheath having a melting point lower than that of the core,
the low melting point part is the sheath part,
In the pressing step, the fibrous body is heated and pressed at a temperature at which the sheath portion melts but the core portion does not melt;
The core is made of polyethylene terephthalate,
The method for producing a molded article, wherein the sheath portion is made of low melting point polyethylene terephthalate having a melting point lower than that of the polyethylene terephthalate. By laminating mixed fibers obtained by mixing vegetable fibers, first thermoplastic resin fibers, and second thermoplastic resin fibers having a low melting point portion whose melting point is lower than that of the first thermoplastic resin fibers, a sheet-like fiber is formed. a fibrous body forming step of forming a fibrous body;
Performed after the fibrous body forming step, the thickness of the fibrous body is reduced by heating pressing the fibrous body at a temperature at which the low melting point portion melts and at a temperature at which the first thermoplastic resin fibers do not melt. A pressing process to
Forming a molded body, which is performed after the pressing step, and reduces the thickness of the fiber body by heating pressing the fiber body at a temperature at which the first thermoplastic resin fiber melts, thereby forming a plate-shaped molded body. comprising a process and,
A method for producing a molded body, wherein the mass per unit area of the molded body is 200 g/m ² or more and 600 g/m ² or less.

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