Natural fiber molded article and method for manufacturing the same

Abstract

This invention provides a novel natural fiber molded article and a method for producing the same. [Solution] The present invention provides a method for producing a natural fiber molded article, comprising obtaining a slurry containing natural fibers and a liquid medium, and removing the liquid by freeze-drying the slurry. The natural fiber molded article of the present invention has a nonwoven fabric-like surface and a density of 0.50 g / cm³. 3 The following, and with a thickness of 5 mm or more:

Description

[Technical Field]

[0001] The present invention relates to a natural fiber molded article and a method for producing the same. [Background technology]

[0002] To maintain a sustainable global environment, there is a global movement to restrict the use of petroleum-derived plastic products. For example, in Europe, the use of expanded polystyrene (Styrofoam) in packaging and cushioning materials is prohibited.

[0003] Therefore, molded products derived from natural fibers have been attracting attention in recent years. Examples of such natural fiber molded products include pulp molds and cellulose sponges.

[0004] Pulp molds are used for cushioning materials, packaging containers, etc. Pulp molds are usually manufactured by pouring pulp slurry into a mold, suctioning to dewater it, and then drying it. Cellulose sponges are used for kitchen sponges, etc. Cellulose sponges usually use viscose-converted cellulose for purposes such as improving durability. Cellulose sponges are usually manufactured by adding a foaming agent to a viscose slurry, pouring this into a mold, foaming it, and heating it.

[0005] In addition, molded articles derived from cellulose, such as those described in Patent Documents 1 to 3, are also known. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2019-166698 [Patent Document 2] Japanese Patent Publication No. 2020-180395 [Patent Document 3] Japanese Patent Publication No. 2022-088181 [Overview of the project] [Problems that the invention aims to solve]

[0007] This invention provides a novel natural fiber molded article and a method for producing the same. [Means for solving the problem]

[0008] The present invention has the following aspects:

[0009] 《Aspect 1》 To obtain a slurry containing natural fibers and a liquid medium, and The liquid is removed by freeze-drying the slurry. A method for producing a molded product of natural fibers containing [unspecified fibers]. 《Aspect 2》 The method for producing a natural fiber molded article according to embodiment 1, wherein the slurry includes a binder. 《Aspect 3》 The method for producing a natural fiber molded article according to embodiment 2, wherein the liquid medium is an aqueous medium and the binder is a hydrophilic binder. Appearance 4 A method for producing a molded natural fiber article according to Embodiment 1, wherein the natural fiber is water-dispersible. 《Aspect 5》 A method for producing a molded natural fiber article according to Embodiment 1, wherein the freeness value of the natural fiber measured in accordance with JIS-P-8121-2:2012 is 400 mL or less. 《Aspect 6》 The method for producing a molded natural fiber article according to Embodiment 1, wherein the natural fiber is a pulp fiber. Appearance 7 The surface is nonwoven fabric-like, with a density of 0.50 g / cm³. 3 The following are examples of natural fiber molded bodies having a thickness of 5 mm or more. 《Aspect 8》 Density is 0.10 g / cm³ 3 The following is a natural fiber molded body according to embodiment 7, wherein the material has a thickness of more than 10 mm. 《Aspect 9》 A natural fiber molded article according to embodiment 7, wherein the natural fiber content is 50% by mass or more. 《Aspect 10》 The natural fiber formed body according to aspect 7, wherein the natural fiber has water dispersibility. 《Aspect 11》 The natural fiber formed body according to aspect 7, wherein the natural fiber is pulp fiber.

Advantages of the Invention

[0010] According to the present invention, a novel natural fiber formed body and a method for manufacturing the same can be provided.

Brief Description of the Drawings

[0011] [Figure 1] FIG. 1 shows a photograph of the slurry used to obtain the natural fiber formed body manufactured in the example. [Figure 2] FIG. 2 shows a photograph of the natural fiber formed body manufactured in the example.

Modes for Carrying Out the Invention

[0012] The present invention will be specifically described below by taking the following embodiments as examples, but the present invention is not limited thereto. When there is no particularly detailed mention of the configuration of each embodiment, those skilled in the art can use well-known configurations for these.

[0013] 《Method for Manufacturing Natural Fiber Formed Body》 The method for manufacturing a natural fiber formed body includes obtaining a slurry containing natural fiber and a liquid, and removing the liquid by freeze-drying the slurry.

[0014] The present inventor has found that by freeze-drying a slurry containing natural fiber, a novel natural fiber formed body having thickness and light weight can be obtained. Such a formed body can not only provide biodegradability by natural fiber, but also can be easily recycled by taking out natural fiber from the formed body, which is extremely effective in constructing a sustainable society.

[0015] The natural fibers used in this method are not particularly limited as long as they are of natural origin, but biodegradable natural fibers can be used in particular. For example, natural fibers include plant fibers and animal fibers. Plant fibers include cellulose fibers such as cotton, hemp, and pulp, and animal fibers include protein fibers such as wool, silk, mohair, and cashmere. In addition to the natural cellulose fibers mentioned above, regenerated cellulose fibers such as viscose rayon and cupro can also be used.

[0016] Among these, water-dispersible fibers are particularly noteworthy. By using water-dispersible fibers, the molded product can be dispersed in an aqueous medium to form a slurry. Since the molded product contains natural fibers, in one embodiment, the method for manufacturing the natural fiber molded product includes a method for regenerating the natural fiber molded product.

[0017] In this specification, "water-dispersible fibers" refers to fibers that dissolve and disperse when immersed in water. For example, a woven or nonwoven garment made of such fibers will disperse to the extent that it cannot be reused as clothing after a single wash in a normal washing machine. Water-dispersible fibers do not include cotton, linen, wool, silk, mohair, cashmere, viscose rayon, cupro, etc., but do include pulp fibers. Such pulp fibers can be obtained by beating pulp and have a relatively short fiber length.

[0018] The average fiber length of water-dispersible fibers may be, for example, 10 mm or less, 5.0 mm or less, 3.0 mm or less, or 2.0 mm or less, or it may be 0.3 mm or more, 0.5 mm or more, 1.0 mm or more, or 2.0 mm or more. The average fiber length of the fibers is determined by observing 100 or more fibers under a microscope.

[0019] The amount of natural fibers in the slurry may be 1% or more by mass, 3% or more by mass, 5% or more by mass, or 10% or more by mass of the total slurry, and may also be 30% or less by mass, 20% or less by mass, 10% or less by mass, or 8% or less by mass. In particular, when water-dispersible fibers are used, it is easy to produce a homogeneous slurry within these ranges.

[0020] Water dispersibility can be quantitatively evaluated by the freeness value of the fiber, measured in accordance with JIS P 8121-2:2012. The freeness value of natural fibers may be, for example, 500 mL or less, 400 mL or less, 350 mL or less, 300 mL or less, or 250 mL or less, or 50 mL or more, 100 mL or more, 150 mL or more, or 200 mL or more.

[0021] When obtaining the slurry, a liquid medium that can uniformly disperse the natural fibers and can be easily removed by freeze-drying is preferred. The type of liquid medium is not particularly limited as long as it can uniformly disperse the natural fibers and can be easily removed by freeze-drying, but examples include aqueous media and organic solvent media. Among these, the use of an aqueous medium is particularly preferred.

[0022] Examples of aqueous media include water, water-miscible solvents, and mixtures thereof. Examples of water-miscible solvents include alcohols, dimethylformamide, tetrahydrofuran, cellosolves, lower ketones, or esters. Examples of alcohols include methanol, isopropanol, or ethylene glycol. Examples of lower ketones include acetone or methyl ethyl ketone. Examples of esters include ethyl acetate. These may be used individually or in combination of two or more. Among these, water, alcohols, or mixtures thereof are preferred, and water and tert-butanol are particularly preferred because they are easily freeze-dried.

[0023] A binder can be included in the slurry. By using a binder to bind natural fibers during manufacturing, toughness can be imparted to the natural fiber molded body. For example, cellulose sponges are given toughness by adding reinforcing fibers such as cotton, but in this embodiment, toughness can be imparted to the natural fiber molded body without adding reinforcing fibers. This is thought to be because, when the liquid is gradually removed during freeze-drying, the binder present between the natural fibers acts as a binding point. If a binder and reinforcing fibers are not used, the natural fiber molded body may become brittle, and such a natural fiber molded body may have limited applications.

[0024] Such binders are not particularly limited as long as they can be dissolved or substantially uniformly dispersed in the liquid medium used. Examples of binders include: plant-based binders such as methylcellulose, cellulose fiber, cellulose nanofiber, starch, seaweed such as corn starch, guar gum, karaya gum, and hibiscus; structural proteins such as keratin, fibroin, and collagen; water-soluble polymers such as polyvinyl alcohol, polyacrylamide, and polyethylene glycol; polymer resins (synthetic resin binders) such as modified resin binders mainly composed of resins used as binders, including acrylic resin emulsions, vinyl acetate resins, latex, SBR (styrene-butadiene-latex) resin, vinyl chloride resin, acrylic-styrene resins, acrylic-silicone resins, and ethylene-vinyl acetate resins; inorganic binders such as gypsum, cement, lime, and water glass, as well as derivatives thereof. One type of binder may be used, or two or more types may be used in combination.

[0025] When using an aqueous medium in the slurry, a hydrophilic binder can be used. Examples of such hydrophilic binders include the plant-derived binders, structural proteins, and water-soluble polymers mentioned above. Such hydrophilic binders are advantageous when using cellulose-based fibers as natural fibers because they can form hydrogen bonds with the cellulose-based fibers, and using cellulose nanofibers is particularly advantageous.

[0026] The amount of binder added may be 0.1 parts by mass or more, 0.5 parts by mass or more, 1 part by mass or more, or 3 parts by mass or more per 100 parts by mass of natural fiber, and may also be 20 parts by mass or less, 10 parts by mass or less, 8 parts by mass or less, or 5 parts by mass or less.

[0027] By mixing various additives into the slurry, various functions can be imparted to the natural fiber molded body. For example, coloring pigments can be mixed into the slurry to color the natural fiber molded body; reinforcing fibers can be mixed in to improve mechanical properties; boric acid can be mixed in to impart antifungal and insecticidal properties; inorganic fibers such as glass fibers can be mixed in to impart flame retardancy; and activated carbon can be mixed in to impart deodorizing properties. These additives can be supported in the gaps between the natural fibers in the nonwoven three-dimensional structure of natural fibers after freeze-drying.

[0028] For example, when an additive is included in the slurry, the amount of the additive may be 0.1 parts by mass or more, 1 part by mass or more, 10 parts by mass or more, 30 parts by mass or more, 50 parts by mass or more, 100 parts by mass or more, or 200 parts by mass or more per 100 parts by mass of natural fiber, or it may be 500 parts by mass or less, 300 parts by mass or less, 200 parts by mass or less, 100 parts by mass or less, 50 parts by mass or less, 20 parts by mass or less, 10 parts by mass or less, 5 parts by mass or less, or 4 parts by mass or less.

[0029] When reinforcing fibers are included in the slurry, the amount of additives may be 0.1 parts by mass or more, 0.5 parts by mass or more, 1 part by mass or more, or 3 parts by mass or more per 100 parts by mass of natural fibers, or it may be 20 parts by mass or less, 10 parts by mass or less, 5 parts by mass or less, or 4 parts by mass or less. The reinforcing fibers can be specified as fibers with a long fiber length, for example, their average fiber length may be 10 mm or more, 15 mm or more, 20 mm or more, or 30 mm or more.

[0030] By freeze-drying while surrounding other structures with a slurry, other structures can be incorporated into the molded body. For example, by freeze-drying a reinforcing material, such as a mesh or rod, in the slurry, a molded body with the reinforcing material incorporated can be obtained. In such embodiments, it is preferable to select natural fibers with short fiber lengths.

[0031] The solid content in the slurry may be 1% or more by mass, 3% or more by mass, 5% or more by mass, or 10% or more by mass of the total slurry, and may also be 50% or less by mass, 30% or less by mass, 20% or less by mass, or 10% or less by mass.

[0032] This manufacturing method may include placing the slurry described above into a mold or container. The liquid in the slurry can then be sublimated and removed by freeze-drying the mold or container.

[0033] The depth of the slurry placed in the mold or container substantially determines the thickness of the molded body. The slurry depth may be, for example, 3 mm or more, 5 mm or more, 10 mm or more, 20 mm or more, or 30 mm or more, and may be 500 mm or less, 300 mm or less, 100 mm or less, 80 mm or less, or 50 mm or less. Within this range, a molded body with sufficient thickness can be obtained, and the liquid can be removed relatively easily during freeze-drying.

[0034] A molded body can be obtained by pouring a slurry into a mold or container with sheets laid inside and then freeze-drying it, thereby creating a laminated body of sheets.

[0035] The lyophilization carried out by this manufacturing method can be performed by a generally known method. Lyophilization is a method of rapidly freezing at a temperature below the freezing point, reducing the pressure below the vapor pressure of the frozen product to sublimate and remove the liquid, and drying the substance. For example, when the liquid is an aqueous medium, the slurry can be rapidly frozen in an environment of -30°C or lower, and the aqueous medium can be removed by reducing the pressure.

[0036] 《Natural Fiber Formed Body》 The natural fiber formed body is not limited by the manufacturing method, but can be manufactured by the manufacturing method of the natural fiber formed body as described above. For each component of the natural fiber formed body, reference can be made to each component described in the manufacturing method of the natural fiber formed body above. Also, for each component of the manufacturing method of the natural fiber formed body above, reference can be made to each component described with respect to the natural fiber formed body.

[0037] The natural fiber formed body has a surface in the form of a non-woven fabric and a density of 0.50 g / cm 3 or less and a thickness of 5 mm or more. [[ID=I16]]

[0038] The density of the natural fiber formed body may be 0.01 g / cm 3 or more, 0.02 g / cm 3 or more, 0.05 g / cm 3 or more, or 0.10 g / cm 3 or more, and may be 0.50 g / cm 3 or less, 0.30 g / cm 3 or less, 0.20 g / cm 3 or less, or 0.10 g / cm 3 or less.

[0039] The thickness of the natural fiber formed body may be 3 mm or more, 5 mm or more, 10 mm or more, 20 mm or more, or 30 mm or more, and may be 500 mm or less, 300 mm or less, 100 mm or less, 80 mm or less, or 50 mm or less.

[0040] The inventors have found that, as described above, a novel natural fiber molded body that is extremely light and thick can be provided by the manufacturing method. For example, with pulp molds, increasing the thickness requires lamination, which increases the specific gravity. Cellulose sponges can be made thick and low in specific gravity, but their surface does not become nonwoven fabric-like.

[0041] Furthermore, natural fiber molded bodies are porous materials with a nonwoven-like surface and can possess elasticity similar to expanded polystyrene, whereas cellulose sponges are sponge-like foams and cannot possess elasticity similar to expanded polystyrene. Note that "nonwoven-like" refers to a surface similar to that of a nonwoven fabric, and the surface of pulp molds is also nonwoven-like.

[0042] Natural fiber molded articles can include the natural fibers described above, but if the article is manufactured using water-dispersible natural fibers, particularly pulp fibers, it can be easily recycled simply by immersing it in water. In other words, this article can be easily returned to a slurry simply by immersing it in water. A natural fiber molded article that is elastic like expanded polystyrene, yet very light, thick, easily recyclable, and biodegradable has not existed before, making it extremely advantageous. Moreover, such a natural fiber molded article can be manufactured at a very low cost. Therefore, such a natural fiber molded article has the potential to replace molded articles made from petroleum-derived products such as expanded polystyrene and expanded polyurethane.

[0043] Natural fiber molded materials possess elasticity similar to expanded polystyrene, yet can form a non-woven, three-dimensional porous material. Unlike expanded polystyrene, they can have breathability and moisture permeability. Furthermore, when natural fiber molded materials are manufactured using cellulose fibers, they can also possess deodorizing and moisture-absorbing properties, which is extremely advantageous.

[0044] The natural fiber molded article may have an LC value of 0.5 or higher, 0.6 or higher, 0.7 or higher, or 0.8 or higher in the compression properties test by the KES method, and may also have an LC value of 1.2 or lower, 1.1 or lower, 1.0 or lower, or 0.9 or lower. Furthermore, the natural fiber molded article may have an LC value (gf·cm / cm) in the compression properties test by the KES method. 2 The RC value (%) of the natural fiber molded body in the compression properties test by the KES method may be 0.5 or higher, 0.8 or higher, 1.0 or higher, or 1.5 or higher, and may be 3.0 or lower, 2.5 or lower, 2.0 or lower, or 1.6 or lower. Furthermore, the RC value (%) of the compression properties test by the KES method of the natural fiber molded body may be 30 or higher, 35 or higher, 40 or higher, or 45 or higher, and may be 70 or lower, 60 or lower, 50 or lower, or 45 or lower. Here, the measurement conditions are that the pressurized area is 1 cm². 2 The maximum load is 50 gf / cm². 2 The compression speed is 20 μ / sec.

[0045] A natural fiber molded article may contain natural fibers in amounts of 25% or more by mass, 50% or more by mass, 60% or more by mass, 70% or more by mass, 80% or more by mass, 90% or more by mass, or 95% or more by mass, and may be substantially composed entirely of natural fibers, or may contain natural fibers in amounts of 99% or less by mass, 98% or less by mass, 95% or less by mass, 90% or less by mass, or 90% or less by mass.

[0046] Furthermore, the natural fiber molded article can contain the binder-derived substance described above in the amount described above. As a result, at least a portion of the natural fiber molded article can have bonding points between the fibers, derived from the binder, thereby increasing the toughness of the entire molded article.

[0047] Furthermore, the natural fiber molded body can contain the various additives mentioned above in the amounts described above.

[0048] Natural fiber molded products can be used in a variety of applications as they are, and by manufacturing them with the additives mentioned above, they can be given various functions and thus used in an even wider range of applications. Natural fiber molded products can be used, for example, as cushioning material, packaging material, filler, various containers or parts of containers, and as thermal insulation and soundproofing material for buildings or vehicles.

[0049] The present invention will be described in more detail by the following examples, but the present invention is not limited thereto. [Examples]

[0050] Experiment 1: Natural fiber molded body consisting essentially of pulp fibers <Manufacturing Examples> Pulp sheets were disintegrated using a beater to obtain pulp fibers. 60 grams of these pulp fibers and 2.4 grams of cellulose nanofiber (4.0% by mass relative to the weight of the final molded product) as a binder were added to 1 liter of water and thoroughly mixed to obtain a slurry. This slurry was placed in a container and spread to a uniform thickness. The slurry in this state is shown in Figure 1.

[0051] The container was rapidly frozen to -30°C, and then placed in a freeze-dryer under vacuum and reduced pressure, gradually increasing the temperature from -30°C to remove moisture and dry it. The resulting natural fiber molded body was removed from the container. The resulting natural fiber molded body is shown in Figure 2.

[0052] The natural fiber molded body obtained in this way was a three-dimensional porous body with a nonwoven surface and possessed elasticity similar to expanded polystyrene. The density of this molded body was approximately 0.06 g / cm³. 3 It was approximately 1.5 cm thick.

[0053] Similarly, the natural fiber molded article of Example 1 was produced without using a binder. Furthermore, the natural fiber molded articles of Examples 2 and 3 were produced using varying amounts of hydrolyzed keratin (EF) as a binder. In addition, the natural fiber molded articles of Examples 4-7 were produced using varying amounts of cellulose nanofiber (CNF) as a binder. For reference, pulp sheets with the same basis weight as these molded articles were also prepared.

[0054] <evaluation> The following physical properties were evaluated by Unitika Garmentec Co., Ltd. (Research Lab Division).

[0055] For each example, a compression characteristic test was performed using the KES method. The measurement conditions were as follows: Pressurized area: 1 cm² 2 The maximum load is 50 gf / cm². 2 The compression rate was 20 μ / sec.

[0056] The deodorizing properties of ammonia gas were evaluated using the detector tube method for Example 3 and the Reference Example.

[0057] For Examples 1 and 7 and the Reference Example, the hygroscopic properties were evaluated under conditions of 20°C and 65% relative humidity, and 30°C and 90% relative humidity.

[0058] Examples 2 and 7 and the reference example were tested using the dry contact method with a Thermolab Type II tester at 20°C and 65% relative humidity, with a blank heat consumption of 11.6 W / m². 2 The heat retention performance was evaluated under the conditions of °C.

[0059] Examples 1 and 4, as well as the reference example, were evaluated for their moisture permeability in accordance with JIS-L1099:2012.

[0060] <result> The results are shown in the table below:

[0061] [Table 1]

[0062] The Linearity of Compression (LC) of the compression properties indicates the linearity of the compression characteristics, representing how linear the relationship between compressive stress and compressive deformation is. An LC value closer to 1 indicates that compression progresses linearly, while a larger LC value indicates that the material becomes stiffer in the initial stages of compression. Adding a binder increases the overall LC, indicating increased stiffness.

[0063] The Work of Compression (WC) characteristic indicates the amount of work required for compression. In the example using 2% protein fiber as a binder, the surface was fuzzy and a soft layer formed on the surface. Similarly, when the amount of cellulose nanofiber was high, a soft layer resembling a thin film formed on the surface, and it is thought that the high value was obtained because the measurement was taken on this surface layer. The WC measurement values ​​obtained by the KES method tended to be unstable.

[0064] The RC (Recovery from Compression) value of the compression characteristics indicates the recovery rate from compression; a higher value means that the material is more easily returned to its original shape. The molded body of Example 6 showed increased resilience.

[0065] Although Example 1 did not show a significant difference in compression characteristics, it lacked toughness and was brittle.

[0066] The deodorizing test results showed that in Example 3, the deodorizing performance was significantly improved compared to a pulp sheet of the same basis weight. In deodorizing tests, a 70% success rate is considered sufficient, and the result for Example 3 was very high because it reached the measurement limit.

[0067] The water absorption was found to be higher compared to pulp sheets of the same basis weight. This indicates that these molded materials have humidity control properties. Furthermore, these molded materials were found to have very high heat retention and moisture permeability. These results are thought to be due to the fact that these molded materials have a very low specific gravity compared to pulp sheets and constitute the majority of the volume.

[0068] These results suggest that the molded product in question is particularly useful as interior material for homes and vehicles.

[0069] Experiment 2: Natural fiber molded body containing various additives <Noncombustible material> A molded article was obtained in the same manner as in the above manufacturing example, except that 150 grams of glass fiber were added to prepare the slurry. A flame retardancy test was performed on the obtained molded article, and it passed the test.

[0070] Furthermore, the resulting molded product was heavy and rigid due to the high amount of glass fiber. For typical wallpaper, flame retardancy can be achieved with approximately 15% glass fiber by mass. Therefore, it is considered that a molded product can pass the flame retardancy test if it contains 30 parts by mass or more of glass fiber per 100 parts by mass of natural fiber.

[0071] <Coloring pigments> A molded body was obtained in the same manner as in the above manufacturing example, except that 4 grams of blue coloring pigment (DIC Corporation, FASTOGEN® BLUE AR-7EF PB15) were added to the slurry. The resulting molded body was light blue. To obtain a darker color, it is possible to pre-dye the pulp with a cotton reactive dye.

[0072] <Laminated molded body> A molded body was obtained in the same manner as the above manufacturing example, except that hydrolyzed keratin was used as the binder and the slurry was added after the silk fabric was placed in the container. By manufacturing in this manner, a laminated molded body having the design properties of silk fabric on its surface was obtained.

[0073] Furthermore, when the silk fabric was washed with a small amount of surfactant to increase its affinity for water before use, the adhesion between the silk fabric and the molded body was further improved.

[0074] <Reinforcement material> After placing the slurry in the container, we inserted disposable chopsticks as reinforcement and manufactured the product in the same manner as in the example, and we were able to obtain a molded body reinforced with disposable chopsticks.

Claims

1. To obtain a slurry containing natural fibers and a liquid medium, and The liquid is removed by freeze-drying the slurry. A method for producing a molded product of natural fibers containing [unspecified fibers].

2. The method for producing a natural fiber molded article according to claim 1, wherein the slurry includes a binder.

3. The method for producing a natural fiber molded article according to claim 2, wherein the liquid medium is an aqueous medium and the binder is a hydrophilic binder.

4. The method for producing a molded natural fiber article according to claim 1, wherein the natural fiber is water-dispersible.

5. A method for producing a molded natural fiber article according to claim 1, wherein the freeness value of the natural fiber measured in accordance with JIS-P-8121-2:2012 is 400 mL or less.

6. The method for producing a molded natural fiber article according to claim 1, wherein the natural fiber is a pulp fiber.

7. The surface is non-woven fabric-like, with a density of 0.50 g / cm³. ３ The following are examples of natural fiber molded articles containing natural fibers, having a thickness of 5 mm or more.

8. Density is 0.10 g / cm³ ３ The following is a natural fiber molded body according to claim 7, having a thickness of more than 10 mm.

9. A natural fiber molded article according to claim 7, wherein the natural fiber content is 50% by mass or more.

10. The natural fiber molded article according to claim 7, wherein the natural fiber is water-dispersible.

11. The natural fiber molded article according to claim 7, wherein the natural fiber is a pulp fiber.

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