Molded body production method and molded body

Abstract

This molded body production method comprises a dispersion preparation step for preparing a dispersion in which microfibrillated cellulose is dispersed in water at a concentration of 0.5-3 mass%, a sheet formation step for forming a microfibrillated cellulose-containing sheet-shaped composition by filtering the dispersion such that the content ratio of the microfibrillated cellulose is 5-30 mass%, a winding step for winding the microfibrillated cellulose-containing sheet-shaped composition around a rod-shaped member such that a plurality of layers are formed, a sealing step for sealing the microfibrillated cellulose-containing composition which has been wound around the rod-shaped member, a reduced-pressure drying step for drying the sealed microfibrillated cellulose-containing composition under reduced pressure, and a molded body acquisition step for removing the rod-shaped member after the drying under reduced pressure, thereby acquiring a pipe-shaped molded body which comprises the microfibrillated cellulose.

Description

Method for manufacturing a molded body and molded body

[0001] The present disclosure relates to a method for manufacturing a molded body and a molded body. This application claims priority based on Japanese Application No. 2024-170851 filed on September 30, 2024, and incorporates all the descriptions described in the above Japanese application.

[0002] Techniques related to materials containing cellulose microfibrils are disclosed in Patent No. 3641690 (Patent Document 1). In addition, techniques related to a method for manufacturing a molded body of microfibrillated cellulose are disclosed in JP-A-2018-100466 (Patent Document 2).

[0003] Patent No. 3641690 JP-A-2018-100466

[0004] Recently, regarding molded bodies composed of microfibrillated cellulose, in terms of weight reduction of products using the molded body, etc., pipe-shaped ones are in demand. It is desirable that a pipe-shaped molded body can be manufactured efficiently.

[0005] An object of the present disclosure is to provide a method for manufacturing a molded body that can efficiently manufacture a pipe-shaped molded body.

[0006] The method for manufacturing a molded body according to the present disclosure is a method for manufacturing a molded body composed of microfibrillated cellulose, including a dispersion liquid preparation step of preparing a dispersion liquid in which microfibrillated cellulose is dispersed in water at a concentration of 0.5% by mass or more and 3% by mass or less, a sheet formation step of filtering the dispersion liquid so that the content ratio of microfibrillated cellulose becomes 5% by mass or more and 30% by mass or less to form a sheet-like microfibrillated cellulose-containing composition, a winding step of winding the sheet-like microfibrillated cellulose-containing composition around a rod-shaped member so that a plurality of layers are formed, a sealing step of sealing the microfibrillated cellulose-containing composition wound around the rod-shaped member, a reduced-pressure drying step of drying the sealed microfibrillated cellulose-containing composition under reduced pressure, and a molded body acquisition step of removing the rod-shaped member after drying under reduced pressure to obtain a pipe-shaped molded body composed of microfibrillated cellulose.

[0007] According to this method for manufacturing molded bodies, pipe-shaped molded bodies can be manufactured efficiently.

[0008] Figure 1 is a schematic perspective view showing the appearance of a molded body according to one embodiment of the present disclosure. Figure 2 is a schematic cross-sectional view showing an enlarged portion of the molded body shown in Figure 1. Figure 3 is a schematic perspective view showing a portion of the molded body having a bent portion. Figure 4 is a flowchart showing a typical manufacturing process in the manufacturing method of the molded body 11 according to one embodiment of the present disclosure shown in Figures 1 and 2. Figure 5 is a schematic diagram showing a portion of the winding process. Figure 6 is a schematic diagram showing a portion of the sealing process.

[0009] [Description of Embodiments of the Disclosure] First, embodiments of the Disclosure will be listed and described. A method for manufacturing a molded article according to the Disclosure is a method for manufacturing a molded article containing microfibrillated cellulose (hereinafter sometimes simply referred to as "MFC (Microfibrillated cellulose)"). The method for manufacturing a molded article comprises: a dispersion preparation step of preparing a dispersion in which microfibrillated cellulose is dispersed in water at a concentration of 0.5% by mass or more and 3% by mass or less; a sheet forming step of filtering the dispersion so that the content of microfibrillated cellulose is 5% by mass or more and 30% by mass or less to form a sheet-like microfibrillated cellulose-containing composition; a winding step of winding the sheet-like microfibrillated cellulose-containing composition around a rod-shaped member so that it forms multiple layers; a sealing step of sealing the microfibrillated cellulose-containing composition wound around the rod-shaped member; a vacuum drying step of vacuum drying the sealed microfibrillated cellulose-containing composition; and a molded article acquisition step of removing the rod-shaped member after vacuum drying to obtain a pipe-shaped molded article made of microfibrillated cellulose.

[0010] According to the method for manufacturing a molded article in accordance with this disclosure, the dispersion prepared in the dispersion preparation step has a concentration of microfibrillated cellulose-containing composition of 0.5% by mass or more and 3% by mass or less. With such a dispersion, since the concentration of the microfibrillated cellulose-containing composition is 0.5% by mass or more, it is easier to make the concentration uniform in the planar direction when forming a sheet-like microfibrillated cellulose-containing composition. Furthermore, since the concentration of the microfibrillated cellulose-containing composition is 3% by mass or less, the deterioration of the fluidity of the microfibrillated cellulose can be reduced, making it easier to form a suitable sheet-like microfibrillated cellulose-containing composition. The method also includes a step of filtering the dispersion so that the content of microfibrillated cellulose is 5% by mass or more and 30% by mass or less to form a sheet-like microfibrillated cellulose-containing composition. Therefore, when forming the sheet-like microfibrillated cellulose-containing composition, it is not necessary to prepare bags or sealing tape to create a sealed space. Furthermore, since the sheet-like microfibrillated cellulose-containing composition is formed by filtration, the risk of unevenness in the concentration of microfibrillated cellulose can be reduced. Then, a winding process is carried out on a rod-shaped member, which is selected considering factors such as the ease of removing the rod-shaped member, so that the final product becomes the desired pipe-shaped molded body. After sealing the microfibrillated cellulose-containing composition, it is dried under reduced pressure, and the rod-shaped member is removed to obtain the pipe-shaped molded body. In this case, since the pipe-shaped molded body can be obtained by removing the rod-shaped member, cutting and processing of the block-shaped molded body are unnecessary, thus reducing labor and time. Therefore, the above method for manufacturing a molded body allows for the efficient production of pipe-shaped molded bodies.

[0011] In the above method for manufacturing a molded body, the rod-shaped member may be a hollow cylindrical shape. This makes it easier to remove the rod-shaped member during the molded body acquisition process by shrinking the inner diameter side of the rod-shaped member. Therefore, the molded body acquisition process can be carried out efficiently.

[0012] In the above method for manufacturing a molded article, the rod-shaped member may be a solid cylindrical shape. By doing so, the risk of the rod-shaped member unintentionally bending during the winding process and subsequent processes can be reduced. Furthermore, deformation of the rod-shaped member can be suppressed even if the winding pressure during the winding process is high.

[0013] In the above method for manufacturing a molded body, the rod-shaped member may be flexible. This makes it easier to bend the rod-shaped member together with the molded body when obtaining a bent pipe-shaped body. Therefore, it becomes easier to obtain a pipe-shaped molded body in the shape desired by the user.

[0014] In the above-described method for manufacturing a molded body, the rod-shaped member may be made of metal. By doing so, the rigidity of the rod-shaped member can be increased, and the risk of the rod-shaped member bending unintentionally can be greatly reduced. Therefore, this method is effectively used when the user desires a straight, pipe-shaped molded body.

[0015] In the above method for manufacturing a molded article, the winding step may include a step of winding a microfibrillated cellulose-containing composition to a rod-shaped member with a thickness of 1 mm to 10 mm. By doing so, the strength of the sheet-like microfibrillated cellulose-containing composition can be easily maintained by making the thickness of the microfibrillated cellulose-containing composition in the winding step 1 mm or more. Furthermore, by making the thickness of the microfibrillated cellulose-containing composition in the winding step 10 mm or less, good flexibility can be maintained when performing the bending step, and cracking of the outer surface during bending can be easily suppressed.

[0016] In the above method for manufacturing a molded article, the winding step may include winding a single sheet-like microfibrillated cellulose-containing composition onto a rod-shaped member. By doing so, it becomes easy to obtain a pipe-shaped molded article having layers connected in the circumferential direction. Therefore, it becomes easy to obtain a pipe-shaped molded article that is strong in the circumferential direction as well.

[0017] In the above method for manufacturing a molded article, the winding step may include a step of spirally winding a strip-shaped microfibrillated cellulose-containing composition onto a rod-shaped member. By doing so, it becomes easy to adjust the thickness and length of the microfibrillated cellulose-containing composition while spirally winding it along the longitudinal direction of the rod-shaped member using the strip-shaped microfibrillated cellulose-containing composition. Therefore, it becomes easy to obtain a pipe-shaped molded article with the thickness and length desired by the user.

[0018] In the above method for manufacturing a molded article, the sealing step may include covering the microfibrillated cellulose-containing composition wrapped around a rod-shaped member with a breathable cloth substrate and then sealing it together with the cloth substrate. By doing so, deformation and uneven distribution of the microfibrillated cellulose-containing composition wrapped around the rod-shaped member can be suppressed, and the subsequent vacuum drying step can be carried out smoothly. Therefore, a pipe-shaped molded article can be obtained more efficiently.

[0019] In the above method for manufacturing a molded article, the sealing step may include sealing a microfibrillated cellulose-containing composition wrapped around a rod-shaped member with at least one of film-like polyethylene, film-like polyvinyl chloride, film-like PA6 (nylon 6), and film-like PA66 (nylon 66). Such film-like members are relatively inexpensive and tear-resistant, and are therefore suitable for use in the sealing step.

[0020] In the above method for manufacturing a molded article, the vacuum drying step may include a step of vacuum drying the microfibrillated cellulose-containing composition while maintaining it at a temperature and pressure below the vapor pressure of water so that the water does not freeze and does not boil. By doing so, vacuum drying of the microfibrillated cellulose-containing composition can be carried out more appropriately. Therefore, a pipe-shaped molded article can be obtained more efficiently.

[0021] In the above method for manufacturing a molded article, a bending step may be included after the winding step, in which the microfibrillated cellulose-containing composition wound around the rod-shaped member is bent together with the rod-shaped member. This makes it easier for users to obtain a bent pipe-shaped molded article by performing the bending step. Therefore, it becomes easier to obtain a molded article that better meets the user's needs.

[0022] A molded article according to this disclosure is a molded article composed of microfibrillated cellulose, which is pipe-shaped and formed by laminating layers of microfibrillated cellulose from the inside outwards.

[0023] Such molded bodies are pipe-shaped and formed by laminating layers of microfibrillated cellulose from the inside out, resulting in high rigidity and light weight. Therefore, they can be effectively utilized in applications desired by the user.

[0024] The above-described molded body may be hollow and cylindrical. Because such a molded body is cylindrical, it lacks corners on its outer surface compared to a rectangular tube. Therefore, it suppresses stress concentration and problems caused by corners, allowing for suitable use according to the user's application.

[0025] In the above-described molded body, the ratio S1 / S2 of the bending strength S1 at a first point on the outer surface of the pipe-shaped molded body to the bending strength S2 at a second point on the outer surface rotated 90 degrees from the first point may be 0.9 or more and 1.1 or less. With such a molded body, when assembling or manufacturing a product using the pipe-shaped molded body, the difference between the bending strength at the first point and the bending strength at the second point rotated 90 degrees is relatively small, so when considering the strength of the assembled product, there is no need to be too concerned about the orientation during assembly. Therefore, the convenience of using pipe-shaped molded bodies can be improved.

[0026] The above-described molded body may have a folded portion. Such a molded body makes it easier to effectively utilize the folded portion to meet user needs. Therefore, convenience can be improved.

[0027] [Details of Embodiments of the Disclosure] Embodiments of the Disclosure will be described below. In the following drawings, identical or corresponding parts will be given the same reference numerals and their descriptions will not be repeated.

[0028] Figure 1 is a schematic perspective view showing the appearance of a molded article according to one embodiment of the present disclosure. Figure 2 is a schematic cross-sectional view showing an enlarged portion of the molded article shown in Figure 1. Figure 2 is a cross-sectional view taken along the II-II section shown in Figure 1.

[0029] Referring to Figures 1 and 2, the molded body 11 according to one embodiment of the present invention is pipe-shaped. Specifically, the molded body 11 is hollow cylindrical. In this embodiment, the molded body 11 is a circular tube. The thickness of the molded body 11, that is, the distance from the outer surface 13 to the inner surface 14, is indicated by the arrow T in Figure 2. The thickness of the molded body 11, the outer diameter of the molded body 11, the inner diameter of the molded body 11, and the length of the molded body 11 in the longitudinal direction are arbitrarily determined depending on the application and purpose of use. For example, an inner diameter of 5 mm or more and 80 mm or less, and a thickness of 1 mm or more and 5 mm or less are preferred from the viewpoint of weight and rigidity.

[0030] The molded body 11 is composed solely of microfibrillated cellulose 12. Specifically, the molded body 11 is a hollow cylindrical shape formed by the aggregation of microfibrillated cellulose 12.

[0031] Microfibrillated cellulose 12, also known as cellulose nanofiber, is a cellulose fiber in the form of microfibrils. As raw materials for microfibrillated cellulose 12, for example, plant-derived, animal-derived, or microbial-derived materials can be used. Furthermore, materials derived from chitin or chitosan may also be used.

[0032] The fiber diameter of the microfibrillated cellulose 12 may be between 10 nm and 50 nm. By doing so, the microfibrillated cellulose 12 within the molded body 11 can be more densely intertwined. Therefore, the rigidity can be increased.

[0033] In this embodiment, the molded body 11 is formed by laminating layers 15 of microfibrillated cellulose 12 from the inside outwards.

[0034] Furthermore, in this embodiment, the ratio S1 / S2 of the bending strength S1 at a first point 16 on the outer surface 13 of the pipe-shaped molded body 11 to the bending strength S2 at a second point 17 on the outer surface 13 rotated 90 degrees from the first point 16 is 0.9 or more and 1.1 or less. In this embodiment, this is the bending strength when a load is applied in the direction indicated by arrow F at the first point 16 and the second point 17 located on the same cross-section perpendicular to the longitudinal direction of the pipe-shaped molded body 11. Specifically, for example, the above ratio at the first point 16 and the second point 17 is preferably 0.95 or more and 1.05 or less, and more preferably 0.98 or more and 1.02 or less. The molded body 11 in this embodiment is isotropic. Such a molded body 11 can be obtained, for example, by the manufacturing method shown below. For example, if a composition containing microfibrillated cellulose is made into a sheet, multiple sheets are stacked to form a block, and this block is then machined into a pipe shape, the above ratio will be less than 1 / 20 or greater than 20, more specifically, less than 1 / 80 or greater than 80. Since a molded body formed by machining such a block of stacked material into a pipe shape is anisotropic, the above ratio will be obtained. Furthermore, the machining process itself requires a long time and considerable effort to produce a pipe-shaped molded body. Moreover, when assembling or manufacturing products using such molded bodies, the difference between the bending strength at the first point and the bending strength at the second point rotated 90 degrees becomes large, so when considering the strength of the assembled product, the orientation during assembly must be taken into consideration. Consequently, the convenience of using pipe-shaped molded bodies is reduced.

[0035] Such a molded body 11 is pipe-shaped, and since layers 15 of microfibrillated cellulose 12 are laminated from the inside out, it is highly rigid and lightweight. Therefore, it can be effectively used in applications desired by the user.

[0036] In this embodiment, the molded body 11 is hollow and cylindrical. Because the molded body 11 is cylindrical, there are no corners on the outer surface 13 compared to the case of a rectangular tube. Therefore, stress concentration and problems caused by corners are suppressed, and it can be used suitably according to the user's usage.

[0037] In this embodiment, the ratio S1 / S2 of the bending strength S1 at a first point 16 on the outer surface 13 of the pipe-shaped molded body 11 to the bending strength S2 at a second point 17 on the outer surface 13 rotated 90 degrees from the first point 16 is 0.9 or more and 1.1 or less. With such a molded body 11, when assembling or manufacturing a product using the pipe-shaped molded body 11, the difference between the bending strength at the first point 16 and the bending strength at the second point 17 rotated 90 degrees is relatively small, so when considering the strength of the assembled product, there is no need to be too concerned about the orientation during assembly. Therefore, the convenience of using the pipe-shaped molded body 11 can be improved.

[0038] The molded body may also have a bent portion. Figure 3 is a schematic perspective view showing a part of a molded body having a bent portion. Referring to Figure 3, the molded body 18 is pipe-shaped and is formed by laminating layers 15 of microfibrillated cellulose 12 from the inside to the outside, as shown in Figure 2. The molded body 18 has a bent portion 19, which is a bent portion. The bent portion 19 has a gently curved shape. Such a molded body 18 can be efficiently manufactured by using a hollow cylindrical and flexible rod-shaped member 21. An example of a method for manufacturing such a molded body 18 will be described in detail later.

[0039] Next, an outline of the manufacturing method for the molded article 11 according to one embodiment of the present disclosure will be described. Figure 4 is a flowchart showing a typical manufacturing process in the manufacturing method for the molded article 11 according to one embodiment of the present disclosure shown in Figures 1 and 2.

[0040] Referring to Figure 4, first, in the dispersion preparation step, a dispersion is prepared by dispersing microfibrillated cellulose in water at a concentration of 0.5% by mass or more and 3% by mass or less (in Figure 4, step S11; hereafter, "step" is omitted). In this case, the desired concentration within the above range, for example, 1% by mass, is adjusted by dilution with water or the like.

[0041] Next, as a sheet formation step, the dispersion is filtered so that the content of microfibrillated cellulose is 5% by mass or more and 30% by mass or less to form a sheet-like microfibrillated cellulose-containing composition (S12). In this case, the dispersion is filtered by suction and molded into a sheet-like form. In this way, the dispersion is filtered by suction so that the content of microfibrillated cellulose relative to the whole is 5% by mass or more and 30% by mass or less (water content is 70% by mass or more and 95% by mass or less) to form a sheet-like microfibrillated cellulose-containing composition.

[0042] Next, in the winding step, the sheet-like microfibrillated cellulose-containing composition is wound around the rod-shaped member so that it forms multiple layers (S13). Figure 5 is a schematic diagram illustrating a part of the winding step. Referring to Figure 5, in the winding step, the rod-shaped member 21 is first prepared. In this embodiment, the rod-shaped member 21 is a solid cylinder. The rod-shaped member 21 is made of metal. The sheet-like microfibrillated cellulose-containing composition 22 is wound around this rod-shaped member 21 in the winding step. In this embodiment, one sheet-like microfibrillated cellulose-containing composition 22 is wound around the rod-shaped member 21. Specifically, the strip-shaped microfibrillated cellulose-containing composition 22 is wound in a spiral manner. In this case, it is wound so that adjacent parts overlap in some areas. When it reaches the end of the rod-shaped member 21, it is wound in the opposite direction. In this way, the microfibrillated cellulose-containing composition 22 is wound around the rod-shaped member 21 to the desired thickness.

[0043] Thereafter, as a sealing step, the microfibrillated cellulose-containing composition 22 wound around the rod-shaped member 21 is sealed (S14). FIG. 6 is a schematic diagram schematically showing a part of the sealing step. Referring also to FIG. 6, first, the microfibrillated cellulose-containing composition 22 wound around the rod-shaped member 21 is covered with a breathable cloth substrate 23. In the present embodiment, a non-woven fabric is adopted as the breathable cloth substrate 23. Then, after covering with the cloth substrate 23, the microfibrillated cellulose-containing composition 22 together with the cloth substrate 23 is sealed. In this case, the whole is covered with a film-shaped polyethylene 24, and the opening part is closed with a seal tape 25. In addition, a pipe 26 connected to a vacuum pump is attached in order to depressurize the inside of the film-shaped polyethylene 24. As the one covering the whole, at least any one of film-shaped polyethylene, film-shaped vinyl chloride, film-shaped PA6, and film-shaped PA66 may be used.

[0044] Next, as a depressurization drying step, the sealed microfibrillated cellulose-containing composition 22 is depressurized and dried (S15). The microfibrillated cellulose-containing composition 22 sealed with the polyethylene 24 is disposed in a dryer (not shown). Thereafter, the microfibrillated cellulose-containing composition 22 is depressurized and dried while maintaining the temperature and pressure below the vapor pressure of water so that water does not freeze and water does not boil. In this case, for example, conditions such as a temperature of 25° C. and a pressure of 3.1 kPa or more, or conditions such as a temperature of 60° C. and a pressure of 19.9 kPa or more may be adopted.

[0045] Next, as a molded body acquisition step, after depressurization drying, the rod-shaped member 21 is removed to obtain a pipe-shaped molded body 11 composed of microfibrillated cellulose (S16). In this case, after depressurization drying, the rod-shaped member 21 is removed from the microfibrillated cellulose-containing composition 22 by pulling out the rod-shaped member 21. Regarding the removal of the rod-shaped member 21, depending on the material of the rod-shaped member 21, the rod-shaped member 21 may be dissolved and removed using a solvent. Further, when the rod-shaped member 21 is made of resin, for example, the rod-shaped member 21 may be removed by deforming the rod-shaped member 21 after softening it.

[0046] As described above, according to the method for producing a microfibrillated cellulose-containing composition according to this disclosure, the dispersion prepared in the dispersion preparation step has a concentration of microfibrillated cellulose-containing composition of 0.5% by mass or more and 3% by mass or less. With such a dispersion, since the concentration of the microfibrillated cellulose-containing composition is 0.5% by mass or more, it is easier to make the concentration uniform in the planar direction when forming a sheet-like microfibrillated cellulose-containing composition. Furthermore, since the concentration of the microfibrillated cellulose-containing composition is 3% by mass or less, the deterioration of the fluidity of the microfibrillated cellulose can be reduced, making it easier to form a suitable sheet-like microfibrillated cellulose-containing composition. The method also includes a step of filtering the dispersion so that the content of microfibrillated cellulose is 5% by mass or more and 30% by mass or less to form a sheet-like microfibrillated cellulose-containing composition. Therefore, when forming the sheet-like microfibrillated cellulose-containing composition, it is not necessary to prepare bags or sealing tape to create a sealed space. Furthermore, since the sheet-like microfibrillated cellulose-containing composition is formed by filtration, the risk of unevenness in the concentration of microfibrillated cellulose can be reduced. Then, a winding process is carried out on a rod-shaped member, which is selected considering factors such as the ease of removing the rod-shaped member, so that the final product becomes the desired pipe-shaped molded body. After sealing the microfibrillated cellulose-containing composition, it is dried under reduced pressure, and the rod-shaped member is removed to obtain the pipe-shaped molded body. In this case, since the pipe-shaped molded body can be obtained by removing the rod-shaped member, cutting and processing of the block-shaped molded body are unnecessary, thus reducing labor and time. Therefore, the above method for manufacturing a molded body allows for the efficient production of pipe-shaped molded bodies.

[0047] In the above-described method for manufacturing a molded article, the rod-shaped member is a solid cylinder. Therefore, the risk of the rod-shaped member unintentionally bending during the winding process and subsequent processes can be reduced. Furthermore, deformation of the rod-shaped member can be suppressed even if the winding pressure during the winding process is high.

[0048] In the method for manufacturing the above-described molded body, the rod-shaped member is made of metal. Therefore, the rigidity of the rod-shaped member can be increased, and the risk of the rod-shaped member being inadvertently bent can be greatly reduced. Therefore, it can be effectively used when a user desires a pipe-shaped molded body having a straight shape.

[0049] In the method for manufacturing the above-described molded body, the winding step includes a step of winding a microfibrillated cellulose-containing composition around the rod-shaped member with a thickness of 1 mm or more and 10 mm or less. Therefore, by setting the thickness of the microfibrillated cellulose-containing composition in the winding step to 1 mm or more, the strength of the sheet-like microfibrillated cellulose-containing composition can be easily maintained. Further, by setting the thickness of the microfibrillated cellulose-containing composition in the winding step to 10 mm or less, the flexibility during the bending step can be maintained well, and it becomes easy to suppress cracking of the outer peripheral surface during bending.

[0050] In the method for manufacturing the above-described molded body, the winding step includes a step of winding a single sheet-like microfibrillated cellulose-containing composition around the rod-shaped member. Therefore, it becomes easy to obtain a pipe-shaped molded body having layers continuous in the circumferential direction. Therefore, it becomes easy to obtain a pipe-shaped molded body having high strength in the circumferential direction as well.

[0051] In the method for manufacturing the above-described molded body, the winding step includes a step of spirally winding a belt-like microfibrillated cellulose-containing composition around the rod-shaped member. Therefore, it becomes easy to adjust the thickness of the microfibrillated cellulose-containing composition while spirally winding it using the belt-like microfibrillated cellulose-containing composition in the longitudinal direction of the rod-shaped member. Therefore, it becomes easy to obtain a pipe-shaped molded body having a thickness desired by the user.

[0052] In the above method for manufacturing a molded article, the sealing step includes covering the microfibrillated cellulose-containing composition wrapped around a rod-shaped member with a breathable cloth substrate and then sealing it together with the cloth substrate. This makes it easier to carry out the subsequent vacuum drying step smoothly while suppressing deformation and unevenness of the microfibrillated cellulose-containing composition wrapped around the rod-shaped member. Therefore, a pipe-shaped molded article can be obtained more efficiently.

[0053] In the above-described method for manufacturing a molded article, the sealing step includes sealing a microfibrillated cellulose-containing composition wrapped around a rod-shaped member with at least one of film-like polyethylene, film-like polyvinyl chloride, film-like PA6, and film-like PA66. Such film-like members are relatively inexpensive and tear-resistant, and are therefore suitably used in the sealing step.

[0054] In the above method for manufacturing a molded article, the vacuum drying step includes a step of vacuum drying the microfibrillated cellulose-containing composition while maintaining it at a temperature and pressure below the vapor pressure of water so that the water does not freeze and does not boil. Therefore, vacuum drying of the microfibrillated cellulose-containing composition can be carried out more appropriately. Consequently, pipe-shaped molded articles can be obtained more efficiently.

[0055] In the above embodiment, the microfibrillated cellulose fiber diameter was set to be between 10 nm and 50 nm. However, it is not limited to this, and fiber diameters ranging from a few nm to several hundred and even several thousand nm can be used depending on the application and cost.

[0056] Next, a method for manufacturing the molded body 18 shown in Figure 3 above will be described. As a method for manufacturing the molded body 18 having a bent portion 19, for example, a bending step may be included after the winding step in which the microfibrillated cellulose-containing composition 22 wound around the rod-shaped member 21 is bent together with the rod-shaped member 21. Specifically, for example, the bending step is performed after the winding step and before the sealing step. By doing so, if a user wants to obtain a bent pipe-shaped molded body 18, it becomes easy to respond by performing the bending step. Therefore, it becomes easier to obtain a molded body that is more to the user's liking. Regarding the bending, for example, it may be bent to a near right angle to form an L-shape, or it may be bent to form an S-shape.

[0057] Furthermore, in the above embodiment, the rod-shaped member 21 may be a hollow cylindrical shape. By doing so, when removing the rod-shaped member 21 in the molded body acquisition process, it becomes easier to remove the rod-shaped member 21 by contracting it toward the inner diameter. Therefore, the molded body acquisition process can be carried out efficiently.

[0058] In the above embodiment, the rod-shaped member 21 may be flexible. This makes it easier to bend the rod-shaped member 21 together when obtaining the bent pipe-shaped molded body 18. It also makes it easier to bend the flexible rod-shaped member 21 to a desired angle, anticipating the final shape of the molded body 18. Therefore, it becomes easier to obtain a pipe-shaped molded body 18 with the shape desired by the user.

[0059] In the above embodiment, the winding process involved winding a single sheet of MFC-containing composition onto a rod-shaped member. However, the winding process is not limited to this; it may also involve preparing multiple sheets of MFC-containing composition and winding them together so that they overlap in the radial direction. This allows for a more efficient winding process, especially when obtaining pipe-shaped molded bodies with large inner diameters.

[0060] Furthermore, in the above embodiment, a nonwoven fabric was used as the breathable fabric base material, but the fabric base material is not limited to this, and cotton fabric, synthetic fiber fabric, and glass cloth may also be used. In other words, the fabric base material may include at least one of nonwoven fabric, cotton fabric, synthetic fiber fabric, and glass cloth.

[0061] The embodiments disclosed herein should be understood to be illustrative in all respects and not restrictive in any way. The scope of the invention is defined by the claims and not by the foregoing description, and all modifications within the meaning and scope of the claims are intended to be included.

[0062] 11, 18 Molded body, 12 Microfibrillated cellulose (MFC), 13 Outer surface, 14 Inner surface, 15 Layer, 16 First point, 17 Second point, 19 Bent portion, 21 Rod-shaped member, 22 Microfibrillated cellulose-containing composition, 23 Cloth base material, 24 Polyethylene, 25 Seal tape, 26 Pipe.

Claims

1. A method for manufacturing a molded article composed of microfibrillated cellulose, comprising: a dispersion preparation step of preparing a dispersion in which microfibrillated cellulose is dispersed in water at a concentration of 0.5% by mass or more and 3% by mass or less; a sheet forming step of filtering the dispersion so that the content of microfibrillated cellulose is 5% by mass or more and 30% by mass or less to form a sheet-like microfibrillated cellulose-containing composition; a winding step of winding the sheet-like microfibrillated cellulose-containing composition around a rod-shaped member so that it forms multiple layers; a sealing step of sealing the microfibrillated cellulose-containing composition wound around the rod-shaped member; a vacuum drying step of vacuum drying the sealed microfibrillated cellulose-containing composition; and a molded article acquisition step of removing the rod-shaped member after vacuum drying to obtain a pipe-shaped molded article composed of microfibrillated cellulose.

2. The method for manufacturing a molded article according to claim 1, wherein the rod-shaped member is hollow cylindrical.

3. The method for manufacturing a molded article according to claim 1, wherein the rod-shaped member is a solid cylindrical shape.

4. The method for manufacturing a molded article according to claim 1 or claim 2, wherein the rod-shaped member is flexible.

5. The method for manufacturing a molded article according to claim 1 or claim 3, wherein the rod-shaped member is made of metal.

6. The method for producing a molded article according to claim 1 or claim 2, wherein the winding step includes winding the microfibrillated cellulose-containing composition onto the rod-shaped member to a thickness of 1 mm or more and 10 mm or less.

7. The method for producing a molded article according to claim 1 or claim 2, wherein the winding step includes winding a single sheet of the microfibrillated cellulose-containing composition onto the rod-shaped member.

8. The method for producing a molded article according to claim 1 or claim 2, wherein the winding step includes winding the strip-shaped microfibrillated cellulose-containing composition spirally around the rod-shaped member.

9. The method for producing a molded article according to claim 1 or 2, wherein the sealing step includes a step of covering the microfibrillated cellulose-containing composition wrapped around the rod-shaped member with an air-permeable cloth base material and then sealing it together with the cloth base material.

10. The method for producing a molded article according to claim 1 or 2, wherein the sealing step includes sealing the microfibrillated cellulose-containing composition wrapped around the rod-shaped member with at least one of film-like polyethylene, film-like polyvinyl chloride, film-like PA6, and film-like PA66.

11. The method for producing a molded article according to claim 1 or 2, wherein the vacuum drying step includes a step of vacuum drying the microfibrillated cellulose-containing composition by maintaining it at a temperature and pressure below the vapor pressure of water so that the water does not freeze and does not boil.

12. A method for producing a molded article according to claim 1 or 2, further comprising a bending step of bending the rod-shaped member together with the microfibrillated cellulose-containing composition that has been wrapped around the rod-shaped member, after the winding step.

13. A molded body composed of microfibrillated cellulose, which is pipe-shaped, and is formed by laminating layers of the microfibrillated cellulose from the inside outwards.

14. The molded body according to claim 13, which is hollow and cylindrical.

15. The molded body according to claim 13 or claim 14, wherein the ratio S1 / S2 of the tensile strength S1 at a first point on the outer surface of the pipe-shaped molded body to the tensile strength S2 at a second point on the outer surface rotated 90 degrees from the first point is 1 / 20 or more and 20 or less.

16. The molded article according to claim 13 or claim 14, having a folded portion.

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