JP7200828B2 - METHOD FOR MANUFACTURING FIBER CONTAINING RESIN MOLDED PRODUCT - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a fiber-containing resin molding .

BACKGROUND ART A plant fiber composite material (hereinafter referred to as a composite material) having a structure in which plant fibers are bound together by a thermoplastic resin as a base material is known (for example, Patent Document 1). Composite materials of this type are widely used as interior materials for vehicles, such as door trims, because they are lightweight and have high rigidity.

The composite material is formed by molding a preboard containing vegetable fibers and a thermoplastic resin using a predetermined mold. The preboard is formed by heating and compressing a fiber mat formed by mixing vegetable fibers and thermoplastic resin fibers (thermoplastic resin fibers). Since such a preboard is heated at a temperature equal to or higher than the melting point of the thermoplastic resin immediately before molding, the plant fibers, which have been compressed and gathered small until then, expand and become thicker. Such a preboard is molded into a predetermined shape by being sandwiched between molds.

JP 2009-234129 A

At the time of molding the preboard, the thermoplastic resin, which is the base material, is in a molten state within the mold. Therefore, the vegetable fibers are in a state of being soaked in the molten thermoplastic resin. When the preboard in such a state is bent along the molding surface in the mold, if the bending angle is large, no vegetable fibers remain in the bent portion, and the finally obtained molded product has thermoplasticity. A part consisting only of resin may be formed. This is because the vegetable fibers are rigid and less entangled with each other, and when pulled in a direction away from each other at the bent portion, the entanglement between the fibers is easily unraveled and the vegetable fibers are torn. Occur.

Such a portion has no vegetable fiber and can be seen through, which sometimes causes design problems in the molded product. In addition, the mechanical properties of the molded product may be deteriorated due to such a portion.

An object of the present invention is to provide a fiber-containing resin base material and a fiber-containing resin molded article in which the occurrence of vegetable fiber-absent portions is suppressed.

The fiber-containing resin base material according to the present invention includes a thermoplastic resin, a vegetable fiber, and a high-strength fiber having a melting point higher than that of the thermoplastic resin and a tensile modulus of 4000 MPa or more, and the high-strength fiber has an average fiber diameter of 30 μm or less.

In the fiber-containing resin base material, the content of the high-strength fibers in the fiber-containing resin base material is preferably 2 to 25% by mass.

In the fiber-containing resin base material, the maximum load in a hot tensile test is preferably 100 to 300N.

In the fiber-containing resin base material, the average fiber diameter of the vegetable fibers is preferably larger than the average fiber diameter of the high-strength fibers.

Further, the fiber-containing resin molded article according to the present invention includes a thermoplastic resin, a vegetable fiber, and a high-strength fiber having a melting point higher than that of the thermoplastic resin and a tensile elastic modulus of 4000 MPa or more, The average fiber diameter of the strong fibers is 30 µm or less.

According to the present invention, it is possible to provide a fiber-containing resin base material and a fiber-containing resin molded article in which the occurrence of vegetable fiber-absent portions is suppressed.

Explanatory drawing schematically showing the cross-sectional configuration of the fiber-containing resin molding of the present embodiment. Explanatory drawing schematically showing a method for producing a fiber-containing resin base material Explanatory drawing showing a step of heating a fiber-containing resin substrate using a hot platen press. Explanatory drawing showing a fiber-containing resin substrate in a state of being expanded in the thickness direction by being heated by a hot platen press. Explanatory diagram schematically showing the configuration of the press molding device Explanatory drawing showing the process of molding a fiber-containing resin base material using a press molding apparatus to obtain a molded body.

A fiber-containing resin molded article 1 and a fiber-containing resin substrate 10 of the present embodiment will be described with reference to FIGS. 1 to 6. FIG. FIG. 1 is an explanatory view schematically showing the cross-sectional structure of a fiber-containing resin molded article 1 of this embodiment. As shown in FIG. 1, the fiber-containing resin molded article 1 (hereinafter, sometimes simply referred to as "molded article 1") has a central portion that protrudes upward in FIG. It has a shape and is used as an interior material for vehicles (door trim). The molded body 1 is formed by molding a fiber-containing resin base material (preboard) containing vegetable fibers, thermoplastic resin, and high-strength fibers into a predetermined shape.

Vegetable fibers are fibers derived from plants. Vegetable fibers include, for example, kenaf, jute hemp, manila hemp, sisal hemp, gampi, mitsumata, mulberry, banana, pineapple, coconut palm, corn, sugar cane, bagasse, palm, papyrus, reed, esparto, sabaigrass, barley, rice, Fibers obtained from various plants such as bamboo, various coniferous trees (such as cedar and cypress), broad-leaved trees, and cotton. These vegetable fibers may be used alone or in combination of two or more. As the vegetable fiber, kenaf fiber is preferred. Kenaf is an annual plant that grows extremely fast and has excellent carbon dioxide absorption, so it can contribute to the reduction of carbon dioxide in the atmosphere and the effective use of forest resources. In addition, the part of the plant body to be used as the vegetable fiber is not particularly limited as long as the fiber can be collected. good. Furthermore, only a specific site may be used, or two or more different sites may be used in combination.

Vegetable fibers are usually solid bodies. The upper limit of the fiber length of vegetable fibers is preferably 150 mm. The average fiber length (average fiber length) is preferably 10 mm to 100 mm, more preferably 30 mm to 80 mm. In addition, this average fiber length is determined by randomly taking out single fibers one by one by a direct method in accordance with JIS L1015, stretching them straight without stretching, and measuring the fiber length on a set ruler. It is the average value measured for books. The average fiber length of other fibers, which will be described later, can also be determined by the same method.

The upper limit of the fiber diameter of the vegetable fiber is not particularly limited as long as the object of the present invention is not impaired. The lower limit of the average fiber diameter (average fiber diameter) is preferably larger than the average fiber diameter of the high-strength fibers described later, for example, 35 μm or more, more preferably 45 μm or more. In addition, this average fiber diameter is the value obtained by measuring the fiber diameter at the center of the fiber length direction with an optical microscope (average value measured for a total of 200 fibers) for the vegetable fiber whose fiber length was measured. be. The average fiber diameters of other fibers, which will be described later, are also determined by the same method.

The shape of the vegetable fiber is not particularly limited. The shape in the length direction can be linear, polygonal, curved, spiral, or modified shapes thereof. The cross-sectional profile can be circular, elliptical, polygonal, or variations thereof.

The content (% by mass) of vegetable fibers in the molded article 1 is 35% by mass or more, preferably 40% by mass or more, and 55% by mass or less, preferably 50% by mass or less. When the content rate (%) of the vegetable fiber is in such a range, the lightness of the molded article 1 is ensured, and the generation of the non-vegetable fiber-absent portions is suppressed.

The thermoplastic resin mainly functions as a binder resin, and various thermoplastic resins can be used. Examples of thermoplastic resins include polyolefin resins, polyester resins, polystyrene, acrylic resins (resins obtained using methacrylate and/or acrylate, etc.), polyamide resins, polycarbonate resins, polyacetal resins, ABS resins, and the like. Among these, polyolefin resins include polypropylene, polyethylene, ethylene/propylene copolymers (ethylene/propylene block copolymers, ethylene/propylene random copolymers), and the like. Polyester resins 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.

Moreover, you may use an acid-modified thermoplastic resin as a thermoplastic resin. In this specification, among thermoplastic resins, thermoplastic resins other than acid-modified thermoplastic resins may be referred to as "non-acid-modified thermoplastic resins".

An acid-modified thermoplastic resin is a thermoplastic resin into which an acid-modified group has been introduced by acid modification. The type of acid-modifying group introduced into this thermoplastic resin is not particularly limited, but it is usually a carboxylic anhydride residue (--CO--O--OC--) and/or a carboxylic acid residue (--COOH). The acid-modifying group may be introduced by any compound, and the compounds include maleic anhydride, itaconic anhydride, succinic anhydride, glutaric anhydride, adipic anhydride, maleic acid, itaconic acid, Examples include fumaric acid, acrylic acid, and methacrylic acid. These may use only 1 type and may use 2 or more types together. Among these, maleic anhydride and itaconic anhydride are preferred, and maleic anhydride is particularly preferred.

Furthermore, the type of thermoplastic resin that forms the skeleton of the acid-modified thermoplastic resin is not particularly limited, and various thermoplastic resins can be used. Specifically, as described above, various thermoplastic resins exemplified as thermoplastic resins (non-acid-modified thermoplastic resins) can be used.

The thermoplastic resin that forms the skeleton of the acid-modified thermoplastic resin and the non-acid-modified thermoplastic resin may be of the same type or different types, but are preferably the same, and both are polyolefin resins. is preferably Polyolefin resins are easy to handle and can improve productivity. In addition, high flexibility and excellent formability can be obtained. Among polyolefin resins, polypropylene, polyethylene, ethylene-propylene copolymers, and mixed resins (alloys) of polypropylene and polyethylene are preferable. Furthermore, as the non-acid-modified thermoplastic resin, polypropylene or the mixed resin is particularly preferable, and as the thermoplastic resin serving as the skeleton of the acid-modified thermoplastic resin, polypropylene is particularly preferable.

When the total thermoplastic resin is 100% by mass, the proportion of the acid-modified thermoplastic resin is preferably 15% by mass or less (usually 0.3% by mass or more). If the blending amount is within this range, smooth spinning can be performed, and the mechanical properties of the molded article 1 can be improved by using the resin together with the non-acid-modified thermoplastic resin. The blending amount is preferably 0.5 to 15% by mass, more preferably 1 to 10% by mass, and particularly preferably 2 to 7% by mass.

The thermoplastic resin content (% by mass) in the molded article 1 is 38% by mass or more, preferably 40% by mass or more, more preferably 42% by mass or more, and 55% by mass or less, preferably 53% by mass or less, More preferably, it is 51% by mass or less. When the content (% by mass) of the thermoplastic resin is within such a range, it is possible to exhibit the function as a binder resin and to suppress the occurrence of areas where vegetable fibers are absent.

The high-strength fiber is made of a resin having a higher melting point than the thermoplastic resin and has a tensile modulus of 4000 MPa or more as measured according to JIS L 1013. As high-strength fibers, synthetic fibers, particularly thermoplastic resin fibers can be preferably used. By using a predetermined amount of high-strength fiber together with a predetermined amount of vegetable fiber, it is possible to suppress the occurrence of areas where vegetable fiber is absent.

High-strength fibers include high-strength polyester fibers (high-strength polyethylene terephthalate fibers, etc., referred to as "high-strength PET fibers"), aromatic polyamide fibers (meta-aramid fibers, etc.), aliphatic polyamide fibers (nylon 66, nylon 6, nylon 46, etc.) can be exemplified. As polyamide fibers, highly heat-resistant aromatic polyamide fibers are more preferable than aliphatic polyamide fibers. Moreover, from the viewpoint of the productivity of the molded article 1, high-strength PET fibers, which are generally less expensive than polyamide fibers, are particularly preferred. As the high-strength PET fiber, a high-strength fiber that has a higher tensile modulus than non-reinforced polyethylene terephthalate resin (normal PET fiber with a tensile modulus of elasticity of about 3000 to 3700 MPa) and is also used for airbags and seat belts is suitable. can be used for

High tenacity fibers are usually solid. The average fiber length of the high-strength fibers is not particularly limited as long as it does not impair the purpose of the present invention, but is, for example, 150 mm. The average fiber length of the high-strength fibers is preferably 10 mm to 150 mm, more preferably 30 mm to 100 mm, still more preferably 50 mm to 80 mm.

Moreover, the average fiber diameter of the high-strength fibers is 30 μm or less. The lower limit of the average fiber diameter of the high-strength fibers is not particularly limited as long as the object of the present invention is not impaired, but is preferably 3 μm or more, for example. When the average fiber diameter of the high-strength fibers is within such a range, the high-strength fibers are likely to be entangled with the vegetable fibers, and the generation of areas without vegetable fibers is suppressed during molding of the fiber-containing resin substrate (preboard).

The tensile modulus of the high-strength fibers is preferably 8000 MPa or higher, more preferably 12000 MPa or higher. The upper limit of the tensile modulus of the high-strength fiber is not particularly limited as long as the object of the present invention is not impaired.

The content (%) of the high-strength fibers in the molded article 1 is 1.5% by mass or more, preferably 2% by mass or more, and 20% by mass or less, preferably 18% by mass or less. When the content (%) of the high-strength fibers is within such a range, occurrence of areas absent vegetable fibers can be suppressed. The content of the high-strength fiber is set to be lower than the content of the thermoplastic resin and the vegetable fiber.

Note that in other embodiments, a skin material may be attached to the surface of the molded body 1 . In addition, layers (members) other than the skin material may be appropriately formed on the molded body 1 .

In addition, the molded article 1 may contain components (for example, coloring agents, fillers, additives, etc.) in addition to the vegetable fibers, thermoplastic resins and high-strength fibers, as long as the object of the present invention is not impaired.

In the molded article 1 of the present embodiment, as shown in FIG. 1, vegetable fibers are present even at the corner C1 that is bent to protrude outward and the corner C2 that is bent to protrude inward. , the occurrence of vegetable fiber absent locations (so-called see-through) is suppressed.

The molded body 1 is manufactured using a fiber-containing resin base material (preboard) 10 containing vegetable fibers, thermoplastic resins and high-strength fibers. Here, the fiber-containing resin base material 10 will be described.

FIG. 2 is an explanatory view schematically showing a method for manufacturing the fiber-containing resin substrate 10. As shown in FIG. As shown in FIG. 2, the fiber-containing resin base material 10 is a fiber mat 11 formed by mixing vegetable fibers, thermoplastic resin fibers (thermoplastic resin fibers), and high-strength fibers. are compressed to a predetermined thickness while being heated at a predetermined temperature using a pair of hot plates 12 . In other embodiments, thermoplastic resin pellets or the like may be used instead of thermoplastic resin fibers.

The thermoplastic resin fiber is manufactured by a known method or a method based thereon. Regarding the average fiber length and average fiber diameter of the thermoplastic resin fibers, those equivalent to those of high-strength fibers and vegetable fibers can be used. For example, the thermoplastic resin fiber preferably has a fiber length of 30 mm or more, more preferably 30 mm to 100 mm, and even more preferably 30 mm to 70 mm. When the average fiber length of the thermoplastic resin fibers is within such a range, sufficient entanglement between the thermoplastic resin fibers and between the thermoplastic resin fibers and the vegetable fibers and high-strength fibers are easily obtained.

The above-mentioned "mixed fibers" means that vegetable fibers, thermoplastic resin fibers, and high-strength fibers are mixed to obtain a fiber mixture (for example, a fiber mat). The method of mixing fibers at this time is not particularly limited, and various methods can be used, and usually a dry method or a wet method is used. A dry method is preferable as the mixed fiber method. Examples of the dry method include an air lay method and a card method. After the fibers are mixed with each other, entangling by needle punching or the like may be performed as necessary.

When forming the fiber mat, the blending amounts of the vegetable fibers, the thermoplastic resin fibers and the high-strength fibers are such that the content (%) of each of the vegetable fibers, the thermoplastic resin fibers and the high-strength fibers in the molded body 1 is , are set to the values described above.

The temperature for heating the fiber mat is a temperature higher than the temperature at which the thermoplastic resin fibers melt (soften) and at which the high-strength fibers can maintain their fibrous state. For example, when the thermoplastic resin fibers are polypropylene fibers (PP fibers), the heating temperature is set to 170 to 240° C. (preferably 180 to 200° C.). The temperature for heating the fiber mat is determined so that the vegetable fibers in the fiber mat do not deteriorate such as decomposition.

In addition to the hot plate 12, a known press such as a double belt press or a press equipped with a mold is used for compressing the fiber mat. When the fiber mat is compressed to a predetermined thickness and then appropriately cooled, a preboard (fiber-containing resin base material 10) for forming the molded body 1 is obtained. The thickness of the preboard is not particularly limited as long as it does not impair the purpose of the present invention, but it is preferably 2 mm to 3.5 mm, for example.

Also, the maximum load in the hot tensile test of the fiber-containing resin base material 10 is preferably 100N to 300N. When the maximum load is within such a range, the occurrence of areas where vegetable fibers are absent is suppressed during molding of the fiber-containing resin base material 10 .

Next, a method for manufacturing the molded body 1 using the fiber-containing resin base material 10 will be described with reference to FIGS. 3 to 5. FIG. The method for producing the molded body 1 includes heating a fiber-containing resin base material 10 as a preboard at a temperature higher than the temperature at which the thermoplastic resin melts and at a temperature at which the high-strength fibers can maintain the fiber state, thereby forming a fiber-containing resin base material. A step of expanding the material 10 in the thickness direction and a step of compressing the expanded fiber-containing resin base material 10 using a press molding device are provided.

When the fiber-containing resin base material 10 is heated using a heating device such as a hot platen press device 20 immediately before manufacturing the molded body 1, the thermoplastic resin is melted (or softened) and compressed until then. The thickness of the vegetable fibers and the high-strength fibers that have been gathered into a small size is increased due to expansion and the like. The thickness of the fiber-containing resin base material 10 after expansion is larger than the clearance of the mold used for molding.

FIG. 3 is an explanatory view showing the process of heating the fiber-containing resin substrate 10 using the hot platen press device 20. As shown in FIG. The hot platen press device 20 includes a fixed hot plate 21 shown in the lower side of FIG. 3 and a movable hot plate 22 shown in the upper side of FIG. , are provided with heaters 23 and 24, respectively. As shown in FIG. 3, the fiber-containing resin substrate 10 is placed on the lower heating plate 21 while the upper heating plate 22 is waiting above the lower heating plate 21 . After that, the upper heating plate 22 is lowered to sandwich the fiber-containing resin base material 10 with the lower heating plate 21, whereby the fiber-containing resin base material 10 is hot-pressed. At that time, the hot platen press device 20 heats the fiber-containing resin substrate 10 at a temperature higher than the temperature at which the thermoplastic resin melts and at which the high-strength fibers can maintain the fiber state.

FIG. 4 is an explanatory view showing the fiber-containing resin base material 10 in a state of being expanded in the thickness direction by being heated by the hot platen press device 20. As shown in FIG. After that, as shown in FIG. 4, when the upper heating plate 22 is lifted and the pressing of the hot plate press device 20 is completed, a fiber containing fiber expanded in the thickness direction by heating is formed on the lower heating plate 21. A resin substrate 10 appears. Thus, the fiber-containing resin base material 10 expanded in the thickness direction can be obtained. This fiber-containing resin base material 10 is molded using a press molding device 30 while the thermoplastic resin is being melted (or softened).

FIG. 5 is an explanatory diagram schematically showing the configuration of the press molding device 30. As shown in FIG. The fiber-containing resin base material 10 after heating is molded into a predetermined shape using a press molding device 30 . The press molding device 30 includes a stationary lower mold 31 having a convex mold surface 31a and a movable upper mold 32 having a concave mold surface 32a. As shown in FIG. 5, while the upper mold 32 is standing by above the lower mold 31, the heated fiber-containing resin substrate 10 is placed on the convex mold surface 31a of the lower mold 31. be done.

FIG. 6 is an explanatory view showing the process of molding the fiber-containing resin base material 10 using the press molding device 30 to obtain the molding 1. As shown in FIG. As shown in FIG. 6, in the press molding device 30 in the clamped state, the distance (clearance) between the mold surface 31a of the lower mold 31 and the mold surface 32a of the upper mold 32 is It is set to be smaller than the thickness of 10. When the fiber-containing resin substrate 10 is sandwiched between the lower mold 31 and the upper mold 32 having such a clearance, the fiber-containing resin substrate 10 is compressed in the thickness direction so that the thickness becomes smaller. It will be crushed.

The fiber-containing resin substrate 10 in such a state is cooled while sandwiched between the upper mold 32 and the lower mold 31, and the thermoplastic resin contained in the fiber-containing resin substrate 10 is solidified. After that, the upper mold 32 and the lower mold 31 are opened, and the molded product is taken out from the press molding device 30 to obtain the molded product 1 as shown in FIG. At the corners C1 and C2 of the molded body 1 obtained in this way, as described above, the occurrence of areas where vegetable fibers are absent (so-called see-through) is suppressed. This is because the high-strength fibers are entangled with the vegetable fibers, so that even if the mixed fibrous body composed of the plant fiber and the high-strength fibers is pulled in a direction away from each other, the mixed fibrous body does not unravel and shape. is retained. Since the molten thermoplastic resin spreads evenly between the upper mold 32 and the lower mold 31 in such a mixed fibrous body, the occurrence of defects such as see-through in the molded body 1 is suppressed.

The present invention will be described in more detail below based on examples. In addition, the present invention is not limited at all by these examples.

[Example 1]
(material)
High-strength PET fibers having an average fiber diameter of 30 μm, an average fiber length of 60 mm, a tensile modulus of elasticity of 10000 MPa, a tensile elongation at break of 18% and a melting temperature of 260° C. were used as high-strength fibers.

As a thermoplastic resin fiber (non-acid-modified thermoplastic resin fiber), a polypropylene fiber (PP fiber) having an average fiber length of 51 mm obtained by melt-spinning a polypropylene resin "Novatec SA01" (trade name) manufactured by Japan Polypro Co., Ltd. Using.

As a thermoplastic resin fiber (acid-modified thermoplastic resin fiber), 95% by mass of the above polypropylene resin and 5% by mass of maleic anhydride-modified polypropylene resin "Modic P908" (trade name) manufactured by Mitsubishi Chemical Corporation are dry-blended. Acid-modified polypropylene fibers (acid-modified PP fibers) obtained by melt spinning and having an average fiber diameter of 30 μm and an average fiber length of 51 mm were used.

As vegetable fibers, kenaf fibers with an average fiber diameter of 50 μm and an average fiber length of 70 mm were used.

(Manufacture of pre-board)
48 parts by mass of kenaf fiber, 47.5 parts by mass of PP fiber, 2.5 parts by mass of acid-modified PP fiber, and 2 parts by mass of high-strength PET fiber are mixed by a carding method to form a fiber mat. formed. The resulting fiber mat was heated and compressed using a press with a mold temperature of 235° C. until the internal temperature reached 210° C., and a preboard (fiber-containing resin base) of Example 1 having a thickness of 2.5 mm was obtained. material) was obtained. In addition, two preboards were produced. Two preboards were prepared for each of the following examples and comparative examples.

[Examples 2 and 3]
Example 1 was carried out in the same manner as in Example 1, except that the compounding ratio (mass ratio) of kenaf fiber, PP fiber, acid-modified PP fiber, and high-strength PET fiber was changed to the value shown in Table 1. A few preboards were made.

[Example 4]
As the high-strength fibers, 15 parts by mass of high-strength PET fibers having an average fiber diameter of 12 μm, an average fiber length of 60 mm, a tensile modulus of elasticity of 10000 MPa, a tensile elongation at break of 18%, and a melting temperature of 260 ° C. were used. A preboard of Example 3 was produced in a similar manner.

[Comparative Example 1]
A preboard of Comparative Example 1 was produced in the same manner as in Example 1, except that the blending amount of kenaf fiber was changed to 50 parts by mass and the high-strength PET fiber was not used.

[Comparative Example 2]
In place of the high-strength PET fiber, 15 parts by mass of normal PET fiber made of ordinary PET resin is used, and the compounding ratio (mass ratio) of kenaf fiber, PP fiber and acid-modified PP fiber is shown in Table 1. A preboard of Comparative Example 2 was produced in the same manner as in Example 1, except that the values were changed. As the normal PET fiber, a commercially available product (average fiber diameter: 30 μm) manufactured by Toray Industries, Inc. was used.

[Comparative Example 3]
Except for using 15 parts by mass of rayon instead of high-strength PET fibers and changing the compounding ratios (mass ratios) of kenaf fibers, PP fibers, and acid-modified PP fibers to the values shown in Table 1, A preboard of Comparative Example 3 was produced in the same manner as in Example 1. As the rayon, a commercially available product (average fiber diameter: 30 μm) manufactured by Mitsubishi Chemical Corporation was used.

[Comparative Example 4]
As the high-strength fibers, 15 parts by mass of high-strength PET fibers having an average fiber diameter of 50 μm, an average fiber length of 60 mm, a tensile modulus of 10000 MPa, a tensile elongation at break of 18%, and a melting temperature of 260 ° C. were used. A comparative example 4 preboard was produced in the same manner.

[Hot tensile test]
One preboard of each example and each comparative example was subjected to a hot tensile test by the method shown below. The test results are shown in Table 1.

The preboard was heated in an oven until the PP fibers (PP resin) melted. Then, the preboard in which the PP fibers were in a molten state was subjected to a tensile test according to JIS K7161. The results are shown in Table 1.

[Manufacturing of molded products]
For one preboard of each example and each comparative example, a molded article was produced by the method shown below. First, the obtained preboard was sandwiched in a hot platen press device equipped with a heater, and heat-pressed. At this time, the hot platen press was heated to a temperature 20 to 40° C. higher than the melting point of the PP fibers to melt the PP fibers and the acid-modified PP fibers in the preboard. After that, the pressing of the hot platen press was released to obtain a preboard that was heated and expanded in the thickness direction.

Then, the preboard in a heated state was supplied to a press molding device equipped with an upper mold and a lower mold. The upper and lower dies of the press molding machine were clamped and cold pressed for 60 seconds until the internal temperature reached 25°C. After that, the mold was opened to obtain a molded article having a thickness of about 2.5 mm. A convex portion is formed in the center of each molded product.

[Confirmation of locations where vegetable fibers are absent]
For the molded articles of each example and each comparative example, it was visually confirmed whether or not there was a portion through which light was transmitted (so-called see-through), which was a portion where vegetable fibers were not present. In particular, in order to form a convex portion, the bent portion (curvature radius R=3) of the plate-like portion was carefully checked. The results are shown in Table 1.

As shown in Table 1, no see-through was observed in the molded articles (fiber-containing resin moldings) of Examples 1 to 4. Further, the maximum load of the preboards (fiber-containing resin substrates) of Examples 1 to 4 was 100 N or more. In particular, in Examples 3 and 4 containing a large amount of high-strength PET fibers, the maximum load of the preboard was 200 N or more.

Comparative Example 1 is the case where high-strength PET fibers are not included, and Comparative Examples 2 and 3 are the cases where other fibers (normal PET fibers, rayon) are included instead of the high-strength PET fibers. See-through was observed in the molded articles of Comparative Examples 1 to 3. Comparative Example 4 is a case of using high-strength PET fibers having a large average fiber diameter (50 μm). In the molded article of Comparative Example 4, see-through was observed. It is presumed that this is because the high-strength PET fibers used in Comparative Example 4 were too thick and did not entangle well with kenaf fibers (vegetable fibers) and the like, and the fibers unraveled. The maximum load of the preboard of Comparative Example 4 was 150.3N.

<Other embodiments>
The present invention is not limited to the embodiments explained by the above description and drawings, and the following embodiments are also included in the technical scope of the present invention.

(1) The fiber-containing resin base material and the fiber-containing resin molding of the above embodiments are widely used in the fields of vehicles, ships, aircraft, construction, etc., and are suitable as interior materials, exterior materials, structural materials, etc. in these fields. used for In the field of automobiles, door substrates, package trays, pillar garnishes, switch bases, quarter panels, core materials for armrests, door trims, seat structural materials, console boxes, dashboards, various instrument panels, deck trims, Bumpers, spoilers, cowlings and the like can be mentioned. Furthermore, for example, it is also suitable for interior materials, exterior materials and structural materials such as buildings and furniture. Specific examples include door covering materials, door structural materials, covering materials for various kinds of furniture (desks, chairs, shelves, chests of drawers, etc.), structural materials, and the like. In addition, it is also suitable as a package, container (tray, etc.), protective member, partition member, and the like.

DESCRIPTION OF SYMBOLS 1... Fiber-containing resin molding, 10... Fiber-containing resin base material, 20... Hot platen press device, 21, 22... Hot plates, 23, 24... Heater

Claims (3)

A thermoplastic resin, a plant fiber, and a high-strength fiber having a higher melting point than the thermoplastic resin and a tensile modulus of 4000 MPa or more and 10000 MPa or less,
The average fiber diameter of the high-strength fibers is 30 μm or less,
A fiber-containing resin base material in which the average fiber diameter of the vegetable fibers is larger than the average fiber diameter of the high-strength fibers,
a step of heating at a temperature equal to or higher than the temperature at which the thermoplastic resin melts and at which the high-strength fibers can maintain their fibrous state;
The fiber-containing resin base material after heating is sandwiched between a first mold having a convex mold surface and a second mold having a concave mold surface to form a plate-like portion of the fiber-containing resin base material. forming a plurality of corners by bending outward or inward. 2. The method for producing a fiber-containing resin molding according to claim 1, wherein the content of the high-strength fibers in the fiber-containing resin base material is 2 to 25% by mass. 3. The method for producing a fiber-containing resin molded product according to claim 1 , wherein the fiber-containing resin substrate before the heating step has a maximum load of 100 to 300 N in a hot tensile test.

Images