Sheet manufacturing apparatus

Abstract

A sheet manufacturing apparatus capable of forming a smooth sheet is provided. The sheet manufacturing apparatus includes: a piling section that causes a material containing fibers to pile up by an air flow to form a web; a humidifying section that gives moisture from one face side of the web; and a pressurizing section that pressurizes the web that has been humidified to form a sheet, the pressurizing section having a first roller that contacts the one face of the web and a second roller that contacts the other face of the web, the surface of the first roller being harder than the surface of the second roller.

Description

Technical Field

[0001] This invention relates to a sheet manufacturing apparatus. Background Technology

[0002] As shown in Patent Document 1, a sheet manufacturing apparatus has been known, comprising: a defiberizing unit for defiberizing a material in the atmosphere; a mixing unit for adding an additive containing a resin to the defiberized material in the atmosphere; a humidification unit for humidifying a mixture formed by mixing the defiberized material and the additive; a pressurizing unit for pressurizing the humidified mixture; and a heating unit for heating the pressurized mixture.

[0003] However, in the aforementioned apparatus, a resin is required as an adhesive in order to manufacture a sheet with sufficient strength. In recent years, there has been a demand for a method to manufacture a sheet with sufficient strength even without the use of resin.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2015-137437 Summary of the Invention

[0005] A sheet manufacturing apparatus includes: a stacking section that stacks fibrous material by airflow to form a sheet; a humidifying section that supplies moisture from one side of the sheet; and a pressurizing section that presses the humidified sheet to form a sheet. The pressurizing section has a first roller in contact with the one side of the sheet and a second roller in contact with the other side of the sheet, wherein the surface of the first roller is harder than the surface of the second roller. Attached Figure Description

[0006] Figure 1 This is a schematic diagram illustrating the structure of a sheet manufacturing apparatus.

[0007] Figure 2 This is a schematic diagram showing the pressurized section and its surrounding structure.

[0008] Figure 3 This is a schematic diagram illustrating the clamping state of the material sheet in the pressure section. Detailed Implementation

[0009] First, the structure of the sheet manufacturing apparatus 1 will be described. The sheet manufacturing apparatus 1 is an apparatus for forming sheet S.

[0010] like Figure 1As shown, the sheet manufacturing apparatus 1 includes, for example, a feeding unit 10, a coarse crushing unit 11, a fiber unwinding unit 20, a screening unit 40, a first sheet forming unit 45, a rotating body 49, a mixing unit 50, a stacking unit 60, a sheet conveying unit 80, a humidifying unit 90, a pressurizing unit 100, and a cutting unit 120. Furthermore, the sheet manufacturing apparatus 1 includes a control unit (processor) that controls the drive mechanisms of each of the above-mentioned parts.

[0011] The supply unit 10 supplies raw materials to the coarse crushing unit 11. The supply unit 10 is, for example, an automatic feeding unit for continuously feeding raw materials into the coarse crushing unit 11. The raw materials supplied by the supply unit 10 are materials containing various fibers.

[0012] As a fiber, it is not particularly limited and a wide range of fiber materials can be used. Examples of fibers include natural fibers (animal fibers, plant fibers) and chemical fibers (organic fibers, inorganic fibers, organic-inorganic composite fibers). More specifically, fibers can be listed as those composed of cellulose, silk, wool, cotton, hemp, kenaf, flax, ramie, jute, Manila hemp, shisar hemp, coniferous trees, broad-leaved trees, etc. These fibers can be used alone, or they can be appropriately blended, or they can be used as regenerated fibers that have undergone refining.

[0013] Raw materials for fibers include, for example, pulp, waste paper, and old cloth. Furthermore, fibers can undergo various surface treatments. In addition, fibers can be made from pure substances or from materials containing impurities and other components. Furthermore, fibers can also be obtained by dry defibering waste paper or pulp sheets.

[0014] Although the length of the fiber is not particularly limited, in an individual fiber, the length of the fiber along the length direction is more than 1 μm and less than 5 mm, preferably more than 2 μm and less than 3 mm, and more preferably more than 3 μm and less than 2 mm.

[0015] In the sheet manufacturing apparatus 1, since moisture is supplied in the humidification section 90, the mechanical strength of the formed sheet S can be improved if a fiber capable of forming hydrogen bonds is used. Cellulose is an example of such a fiber.

[0016] The fiber content in the sheet S is, for example, 50% by mass or more and 99.9% by mass, preferably 60% by mass or more and 99% by mass, and more preferably 70% by mass or more and 99% by mass or less. Such a content can be achieved by blending during the formation of the mixture.

[0017] The coarse shredder 11 breaks down the raw material supplied by the supply section 10 into fragments in the atmosphere. The fragments are, for example, square fragments a few centimeters in size. The coarse shredder 11 has coarse shredding blades 12, which can break down the input raw material. For example, a paper shredder is used as the coarse shredder 11. The raw material, after being broken down by the coarse shredder 11, is received by the hopper 14 and then transferred to the debonding section 20 via the pipe 15.

[0018] The defiberization section 20 defibers the raw material that has been divided by the coarse crushing section 11. Here, "defiberization" means breaking down the raw material, which is composed of multiple fibers bonded together, into individual fibers. The defiberization section 20 also has the function of separating resin particles, inks, pigments, anti-seepage agents, and other substances adhering to the raw material from the fibers.

[0019] The substance passing through the defiber section 20 is called "defiber material". The "defiber material" may contain, in addition to the disassembled fibers, resin particles, inks, pigments, or additives such as anti-bleeding agents and paper strength enhancers separated from the fibers during the disassembly process. The disassembled defiber material is rope-like in shape. The disassembled defiber material can exist either independently, without intertwining with other disassembled fibers, or in a clump-like state, intertwined with other disassembled defiber material.

[0020] The defiber section 20 performs defibering in a dry manner. Here, the method of performing defibering and other processes in air, such as the atmosphere, rather than in a liquid is called dry. For example, an impeller mill is used as the defiber section 20. The defiber section 20 has the function of generating an airflow that draws in the raw material and discharges the defibered material. Thus, the defiber section 20 can draw in the raw material and airflow together from the inlet 22 through its own generated airflow, perform defibering processing, and then transport the defibered material to the outlet 24. The defibered material passing through the defiber section 20 is transferred to the screening section 40 via the pipe 16. Furthermore, the airflow used to transport the defibered material from the defiber section 20 to the screening section 40 can utilize the airflow generated by the defiber section 20, or it can utilize the airflow from an airflow generating device such as a blower.

[0021] The screening section 40 introduces the defibered material, which has been defibered by the defibering section 20, through the inlet 42 and performs screening based on the length of the fibers. The screening section 40 includes, for example, a roller section 41 and a housing section 43 for housing the roller section 41. The roller section 41 is, for example, a sieve. The roller section 41 has a mesh and is capable of separating fibers or particles smaller than the mesh opening (i.e., the first screening material that passes through the mesh) from fibers or undefibered pieces or clumps larger than the mesh opening (i.e., the second screening material that does not pass through the mesh). For example, the first screening material is conveyed to the accumulation section 60 via the pipe 17. The second screening material is returned to the defibering section 20 from the outlet 44 via the pipe 18. Specifically, the roller section 41 is a sieve that is a cylinder driven by a motor. The mesh used in the roller section 41 can be, for example, a wire mesh, a porous metal mesh formed by stretching a slit metal plate, or a perforated metal mesh formed by forming holes in a metal plate using a stamping press.

[0022] The first sheet forming section 45 conveys the first screened material that has passed through the screening section 40 to the pipe 17. The first sheet forming section 45 includes, for example, a mesh belt 46, a support roller 47, and a suction mechanism 48.

[0023] The suction mechanism 48 is capable of drawing the first screened material, which has passed through the opening of the screening section 40 and dispersed in the air, onto the mesh belt 46. This causes the first screened material to accumulate on the moving mesh belt 46.

[0024] A first screened material passing through the opening of the screening section 40 is deposited on the mesh belt 46. The mesh belt 46 is structured such that it is supported by a support roller 47, making it difficult for the first screened material to pass through while allowing air to pass through. The mesh belt 46 moves by rotating on its own axis via the support roller 47. By continuously moving the mesh belt 46 while the first screened material passing through the screening section 40 continuously falls and accumulates, a material sheet V is formed on the mesh belt 46.

[0025] A suction mechanism 48 is disposed below the mesh belt 46. The suction mechanism 48 generates a downward airflow. Through the suction mechanism 48, the first screened material dispersed in the air by the screening section 40 can be drawn onto the mesh belt 46. As a result, the discharge velocity discharged from the screening section 40 can be increased.

[0026] The sheet V is formed into an air-rich, soft, and fluffy state by passing through the screening section 40 and the first sheet forming section 45. The sheet V stacked on the mesh belt 46 is fed into the pipe 17 and conveyed to the stacking section 60.

[0027] The rotating body 49 is capable of cutting the sheet V. In the illustrated example, the rotating body 49 has a base 49a and protrusions 49b extending from the base 49a. The protrusions 49b have, for example, a plate-like shape. In the illustrated example, four protrusions 49b are provided, and the four protrusions 49b are arranged at equal intervals. By rotating the base 49a in the direction R, the protrusions 49b can rotate about the base 49a as an axis. By using the rotating body 49 to cut the sheet V, the variation in the amount of fiber supplied to the stacking section 60 per unit time can be reduced, for example.

[0028] The rotating body 49 is disposed near the first sheet forming section 45. In the illustrated example, the rotating body 49 is disposed near the support roller 47a on the downstream side of the sheet V's path. The rotating body 49 is disposed at a position where the protrusion 49b can contact the sheet V, but not in contact with the conveyor belt 46 on which the sheet V is deposited. This suppresses wear on the conveyor belt 46 caused by the protrusion 49b. The shortest distance between the protrusion 49b and the conveyor belt 46 is, for example, 0.05 mm or more and 0.5 mm or less. This is a distance at which the sheet V can be cut without damaging the conveyor belt 46.

[0029] The mixing section 50 mixes the first screened material (fiber) that has passed through the screening section 40 with starch as a binder. The mixing section 50 includes a starch supply section 52 for supplying starch, a pipe 54 for conveying the first screened material and starch, and a blower 56. In the illustrated example, starch is supplied from the starch supply section 52 to the pipe 54 via the hopper 19. The pipe 54 is connected to the pipe 17.

[0030] In the mixing section 50, an airflow is generated by a blower 56, and the first screened material and starch are conveyed in the pipe 54 while being mixed. Furthermore, the mechanism for mixing the first screened material and starch is not particularly limited; it can be a mechanism that stirs the mixture using high-speed rotating blades, or a mechanism that utilizes the rotation of a container, such as a V-type mixer.

[0031] As part of the starch supply unit 52, a screw feeder or a disc feeder is used.

[0032] The starch supplied from starch supply unit 52 is a polymer composed of multiple α-glucose molecules polymerized through glycosidic bonds. Starch can be linear or branched.

[0033] Starch can be made from a variety of plant-based materials. Examples of raw materials for starch include grains such as corn, wheat, and rice; legumes such as broad beans, mung beans, and red beans; tubers such as potatoes, sweet potatoes, and cassava; wild grasses such as ferns and kudzu; and palm trees such as coconut palms.

[0034] In addition, processed starch and modified starch can also be used as starch. Examples of processed starch include acetylated adipic acid crosslinked starch, acetylated starch, oxidized starch, sodium octenyl succinate starch, hydroxypropyl starch, hydroxypropyl phosphate crosslinked starch, phosphorylated starch, phosphorylated esterified phosphate crosslinked starch, urea phosphorylated esterified starch, sodium starch glycolate, and high-amino corn starch. Furthermore, dextrin, as a modified starch, can be a material obtained by processing or modifying starch.

[0035] In the sheet manufacturing apparatus 1, by using starch as a binder, the environmental impact can be reduced compared to using synthetic resins. Furthermore, by pressurizing and heating the starch-containing fibers (first screening material) after they have been moistened, at least one of the fiber-to-fiber bonding caused by starch gelatinization and the fiber-to-fiber hydrogen bonds can be generated, thereby enabling the sheet S to have sufficient strength. Additionally, if the sheet S can have sufficient strength solely through the fiber-to-fiber hydrogen bonds, the sheet S can also be manufactured without using starch. In the case of manufacturing the sheet S without using starch, the sheet manufacturing apparatus 1 may not include a starch supply unit 52.

[0036] The starch content in the sheet S is, for example, 0.1% by mass or more and 50% by mass or less, preferably 1% by mass or more and 40% by mass or less, and more preferably 1% by mass or more and 30% by mass or less. Such a content can be achieved by blending during the formation of the mixture.

[0037] In addition to starch, the starch supply section 52 may contain, depending on the type of sheet S being manufactured, a colorant for coloring fibers, a aggregation inhibitor for inhibiting fiber and starch aggregation, and a flame retardant for making fibers less flammable. The mixture passing through the mixing section 50 is transferred to the stacking section 60 via the pipe 54.

[0038] The stacking section 60 introduces the mixture that has passed through the mixing section 50 through the inlet 62 to untangle the intertwined fibers and allow them to fall while being dispersed in the air. As a result, the stacking section 60 enables the mixture to be stacked uniformly on the second sheet forming section 70.

[0039] The accumulation section 60 includes, for example, a roller section 61 and a cover section 63 for housing the roller section 61. The roller section 61 is a rotating cylinder sieve. The roller section 61 has a mesh and allows fibers or particles smaller than the mesh opening size contained in the mixture passing through the mixing section 50 to fall off. The structure of the roller section 61 is, for example, the same as that of the roller section 41.

[0040] Furthermore, the "sieve" of the roller section 61 may not have the function of screening a specific object. That is, the "sieve" used as the roller section 61 refers to a component with a mesh, and the roller section 61 can also allow all the mixture introduced into the roller section 61 to fall.

[0041] The stacking section 60 includes a second sheet forming section 70. The second sheet forming section 70 stacks the mixture that has passed through the roller section 61 to form a sheet W. The second sheet forming section 70 includes, for example, a first mesh belt 72, a support roller 74, and a suction mechanism 76.

[0042] A mixture passing through the opening in the accumulation section 60 is deposited on the first mesh belt 72. The first mesh belt 72 is structured so that air passes through but the mixture is difficult to pass through. The first mesh belt 72 moves by rotating on its own axis via the support roller 74. By continuously moving the first mesh belt 72 while the mixture passing through the accumulation section 60 continuously falls and accumulates, a sheet W is formed on the first mesh belt 72.

[0043] A suction mechanism 76 is disposed below the first mesh belt 72. The suction mechanism 76 generates a downward airflow. Through the suction mechanism 76, the mixture dispersed in the air by the roller section 61 is drawn onto the first mesh belt 72. This increases the discharge velocity from the accumulation section 60. Furthermore, the suction mechanism 76 creates a downward airflow along the falling path of the mixture, thereby preventing fibers or starch from entangled during the falling process.

[0044] As described above, the material sheet W is formed in a soft and fluffy state with rich air by passing through the stacking section 60.

[0045] A sheet conveying section 80 is disposed downstream of the sheet W on the first mesh belt 72 in the conveying direction. The sheet conveying section 80 peels the sheet W off the first mesh belt 72 and conveys it toward the pressurizing section 100.

[0046] like Figure 2 As shown, the sheet conveying unit 80 includes a second mesh belt 81 as a conveyor belt, multiple rollers 82, and a suction mechanism 83 as a suction unit. The second mesh belt 81 is structured such that air passes through it, supported by the multiple rollers 82. The second mesh belt 81 is configured to be driven to rotate by the rotation of the rollers 82. The suction mechanism 83 is positioned opposite the sheet W across the second mesh belt 81. The suction mechanism 83 includes a suction fan (not shown), and the suction force of the suction fan generates an upward (+Z direction) airflow on the second mesh belt 81. The sheet W is suctioned by this airflow.

[0047] Thus, the sheet W can be peeled off from the first mesh belt 72, and the other side Wb of the sheet W peeled off from the first mesh belt 72 comes into contact with the second mesh belt 81. Moreover, since the other side Wb of the sheet W is in contact with the second mesh belt 81, the sheet W is conveyed in a held state.

[0048] A humidifying unit 90 is disposed below the sheet conveying section 80. The humidifying unit 90 is disposed opposite to the second mesh belt 81. The humidifying unit 90 supplies moisture from one side Wa of the lower surface of the sheet W, which is in contact with the second mesh belt 81. In the humidifying unit 90, humidifying air (e.g., water vapor or mist) is supplied to the sheet W as moisture.

[0049] like Figure 2 As shown, the humidifying unit 90 includes a container 91 capable of storing water and a piezoelectric vibrator 92 disposed on the bottom of the container 91. An outlet 93 for discharging humidified air is formed at the upper part of the container 91. The container 91 is arranged such that the outlet 93 faces one surface Wa of the material sheet W. By driving the piezoelectric vibrator 92, ultrasonic waves are generated in the water, and mist (humidified air) is generated inside the container 91. The generated mist is supplied to one surface Wa of the material sheet W through the outlet 93 of the container 91. By supplying water from below the material sheet W, even if condensation occurs in or near the humidifying unit 90, water droplets will not fall onto the material sheet W. That is, for example, if water is supplied to the material sheet W from above, there is a possibility that water adheres to or near the humidifying unit 90 and falls as water droplets, causing water droplets to adhere to the material sheet W. In this case, the supply of water to the material sheet W becomes uneven. However, in this embodiment, the falling of water droplets can be suppressed, thereby avoiding any impact on the quality of the sheet S.

[0050] The suction mechanism 83 is positioned opposite the humidifying section 90, separated by the second mesh belt 81. The suction mechanism 83 draws in the mist discharged from the humidifying section 90. The mist discharged from the outlet 93 is also drawn in by the suction mechanism 83, which is positioned opposite the outlet 93. Thus, since the mist is drawn in by the suction mechanism 83 via the sheet W, moisture can be supplied in the thickness direction of the sheet W.

[0051] The moisture content of the sheet W, which is supplied with moisture in the humidification section 90, is, for example, 12% by mass or more and 40% by mass or less. Based on this moisture content, hydrogen bonds between fibers can be effectively formed, thereby increasing the strength of the sheet S.

[0052] A pressurizing unit 100 is disposed downstream of the sheet conveying unit 80 and the humidifying unit 90. The sheet W, which has been given moisture, is conveyed to the pressurizing unit 100.

[0053] The pressure unit 100 applies pressure to the humidified sheet W to form a sheet S. The pressure unit 100 has a first roller 101 that contacts one surface Wa of the sheet W, and a second roller 102 that contacts the other surface Wb of the sheet W. The sheet W is fed in and pressed using the first roller 101 and the second roller 102 to form the sheet S. The detailed structure of the pressure unit 100 will be described later.

[0054] A cutting section 120 is disposed downstream of the pressurizing section 100. The sheet S formed by the pressurizing section 100 is conveyed to the cutting section 120.

[0055] The cutting section 120 cuts the sheet S formed by the pressure section 100. In the illustrated example, the cutting section 120 has a first cutting section 122 that cuts the sheet S in a direction intersecting the conveying direction of the sheet S, and a second cutting section 124 that cuts the sheet S in a direction parallel to the conveying direction. The second cutting section 124 cuts the sheet S that has passed through the first cutting section 122.

[0056] Through the above process, a single sheet S of a predetermined size is formed. The cut single sheet S is discharged to the receiving part 130.

[0057] Next, the detailed structure of the pressurizing section 100 will be explained. First, the shape of the clamping section Np (pressurizing part) in the pressurizing section 100 will be explained.

[0058] As described above, in this embodiment, a sheet manufacturing apparatus 1 can be realized that uses starch as a binder to form a sheet S. Here, in the sheet manufacturing process using starch, it is necessary to add water to the starch-containing sheet W. Since the sheet W contains a relatively large amount of water, it is easy to produce wrinkles, for example, when pressure is applied, making it difficult to maintain the smoothness of the sheet S.

[0059] Therefore, the pressure section 100 in this embodiment is configured to form a smooth sheet S. This will be described in detail below.

[0060] like Figure 2 and Figure 3 As shown, the pressure unit 100 includes a first roller 101 and a second roller 102. The rotation axes of the first roller 101 and the second roller 102 are arranged along the X-axis. The length of the first roller 101 and the second roller 102 along the X-axis is longer than the length of the conveyed sheet W along the X-axis. Therefore, the entire area of ​​the sheet W along the X-axis can be clamped using the first roller 101 and the second roller 102.

[0061] Furthermore, in this embodiment, the surface of the first roller 101 is configured to be harder than the surface of the second roller 102. Specifically, the first roller 101 is made of metal, and the second roller 102 is made of metal and rubber covering its surface.

[0062] More specifically, the first roller 101 has a hollow core 111, such as aluminum, iron, or stainless steel. A surface layer 112, formed of a fluoropolymer such as PTFE (polytetrafluoroethylene), PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), FEP (tetrafluoroethylene-hexafluoropropylene copolymer), or ETFE (tetrafluoroethylene-ethylene copolymer), or a silicone resin, is provided on the surface of the first roller 101. By providing the surface layer 112, the release properties relative to the sheet W (sheet S) can be improved. Furthermore, wear or damage to the core 111 can be suppressed.

[0063] The second roller 102 includes, for example, a hollow core 114 made of aluminum, iron, stainless steel, etc. The surface of the core 114 is covered by an elastic layer 115 formed of silicone resin or polyurethane rubber, which is a type of rubber. The hardness of the elastomer is preferably ASKER C 30 or higher and 70 or lower, more preferably ASKER C 40 or higher and 60 or lower. The thickness of the elastic layer is 1 mm or higher and 10 mm or lower, more preferably 1 mm or higher and 5 mm or lower. Furthermore, the surface of the elastic layer 115 is covered by a fluoropolymer layer such as PTFE (polytetrafluoroethylene), PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), FEP (tetrafluoroethylene-hexafluoropropylene copolymer), ETFE (tetrafluoroethylene-ethylene copolymer), or a surface layer 116 made of a flexible tube containing fluoropolymer. By providing the surface layer 116, the release properties relative to the sheet W (sheet S) can be improved. Furthermore, wear or damage to the elastic layer 115 can be suppressed.

[0064] By applying pressure to the sheet W using the first roller 101 and the second roller 102, the sheet W is thinned, and the fiber density within the sheet W is increased. The pressure applied to the sheet W by the first roller 101 and the second roller 102 is preferably 0.1 MPa or more and 15 MPa or less, more preferably 0.2 MPa or more and 10 MPa or less, and even more preferably 0.4 MPa or more and 8 MPa or less. If the pressure is within such a range, fiber deterioration can be suppressed, and the defiber obtained by defibering the manufactured sheet S can be used as raw material to remanufacture a sheet S with good strength.

[0065] Furthermore, in this embodiment, the first roller 101 and the second roller 102 are respectively equipped with heaters 113 and 117 (e.g., halogen heaters) for heating, serving as heating mechanisms. The first roller 101, the second roller 102, and each heater 113 and 117 acquire their respective temperatures via a temperature detection unit, and the drive of each heater 113 and 117 is controlled based on the acquired temperatures. This allows the surface temperatures of the first roller 101 and the second roller 102 to be maintained at predetermined temperatures. For example, the surface temperature of the first roller 101 is preferably 100°C or higher and 130°C or lower, and the surface temperature of the second roller 102 is preferably 80°C or higher and 100°C or lower.

[0066] Since the pressurizing unit 100 of this embodiment simultaneously applies pressure and heat to the sheet W, the productivity of the sheet S can be improved. Furthermore, the structure of the sheet manufacturing apparatus 1 can be simplified. In addition, the moisture contained in the sheet W evaporates after the temperature rises, and the thickness of the sheet W decreases, thereby increasing the fiber density. Besides the increase in temperature due to heat and the increase in fiber density due to pressure, multiple fibers are bonded together by the gelatinized starch through starch gelatinization and subsequent moisture evaporation. Furthermore, multiple fibers are bonded together by hydrogen bonds through moisture evaporation due to heat and the increase in fiber density due to pressure.

[0067] Here, when moisture is applied to the sheet W containing starch and fiber, it is necessary to reliably bond the fibers within the sheet W in the pressure section 100 to form a sheet S. This is because when moisture remains in the sheet W, the bonding of the fibers becomes insufficient, which easily leads to wrinkles and the like in the sheet S.

[0068] Therefore, in the clamping section Np where the sheet W is clamped using the first roller 101 and the second roller 102, it is necessary to ensure a sufficient clamping width Nw. The clamping section Np refers to the pressure section where the sheet W is pressurized using the first roller 101 and the second roller 102, and the clamping width Nw is the dimension of the sheet W in the conveying direction within the clamping section Np. That is, the clamping width Nw is the length dimension from the clamping start position of the sheet W formed by the first roller 101 and the second roller 102 to the clamping end position. Furthermore, the clamping width Nw is formed along the X-axis of the clamping section Np with a substantially fixed dimension.

[0069] By ensuring a sufficient clamping width Nw, the heating and pressurizing time of the sheet W can be guaranteed, thus reliably bonding the fibers contained in the sheet S together, resulting in a sheet S with better mechanical strength. Furthermore, to ensure the clamping width Nw, a structure where both the first roller 101 and the second roller 102 are made of rubber can be considered. The clamping width Nw is thus ensured through the elastic deformation of each roller. However, since each roller undergoes elastic deformation, the pressure deviation in the clamping portion Np increases, making wrinkles more likely. Therefore, a smooth sheet S cannot be formed. On the other hand, if both the first roller 101 and the second roller 102 are metal rollers (hard rollers), since no elastic deformation occurs, the clamping width Nw cannot be sufficiently ensured, and the pressurizing and heating time of the sheet W cannot be guaranteed, resulting in insufficient fiber bonding.

[0070] According to this embodiment, when the sheet W is clamped using a first roller 101 and a second roller 102 with different hardnesses, the surface of the second roller 102 becomes stably concave due to the pressure of the first roller 101. This maintains a fixed clamping width Nw, thereby stabilizing the pressure within the clamping portion Np. Since the sheet W can be heated and pressurized in this state, the fibers within the sheet W can be reliably bonded, resulting in the formation of a smooth sheet S.

[0071] Furthermore, since moisture is supplied from one side Wa of the sheet W, the Wa side contains more moisture than the Wb side in the thickness direction of the sheet W. Therefore, when the sheet W is clamped, the moisture can be moved from one side Wa to the other side Wb by heating the relatively hard first roller 101 made of a metal with good thermal conductivity. As a result, since the sheet W is pressurized and heated in a state where moisture is distributed throughout the thickness direction, the uniformity of strength within the sheet S surface can be improved.

[0072] Furthermore, since the first roller 101 side of the sheet W is heated at a high temperature, the vapor in the sheet W can easily diffuse to the other surface Wb, which is in contact with the second roller 102 side, which is at a lower temperature. In addition, by heating the surface Wa side, which has more moisture in the sheet W, at a higher temperature, the diffusion of moisture to the other surface Wb can be promoted, thereby improving the heating efficiency.

[0073] Furthermore, when both the first roller 101 and the second roller 102 are configured to use soft rollers, the thickness of the sheet S will be uneven due to the expansion and contraction of the surfaces of each soft roller in the clamping part Np. According to this embodiment, the side Wa of the sheet W containing more moisture tends to adhere to the harder side of the first roller 101, thereby allowing the sheet W to be clamped in a state conforming to the first roller 101. At this time, since one side Wa of the sheet W is pressed down on the side of the first roller 101, and the other side Wb is clamped in a slipping state on the side of the second roller 102, a smooth sheet S can be formed.

[0074] Furthermore, the surface of the first roller 101 in this embodiment has an uneven surface. In this case, the surface roughness measured by the surface roughness gauge, in terms of Ra (arithmetic mean roughness), is preferably 2 μm or more and 8 μm or less, more preferably 3 μm or more and 6 μm or less. Furthermore, in terms of Rz (maximum height), it is preferably 15 μm or more and 70 μm or less, more preferably 25 μm or more and 50 μm or less. The unevenness of the surface of the first roller 101 is formed, for example, by sandblasting or spray coating.

[0075] Because the surface of the first roller 101 has very small irregularities, the surface texture difference between the first surface Sa (the surface corresponding to one surface Wa of the sheet W) and the second surface Sb (the surface corresponding to the other surface Wb of the sheet W) of the sheet S can be reduced while ensuring the smoothness of the sheet S. Specifically, when the sheet W is pressed between the first roller 101 and the second roller 102, the portion of the sheet W with high fiber density is thicker, and the portion with low fiber density is thinner. Here, when both the first roller 101 and the second roller 102 are made of soft rollers, since both rollers undergo elastic deformation, the irregularities within the sheet W are generated approximately equally on one surface Wa and the other surface Wb. This reduces the surface texture difference between the first surface Sa and the second surface Sb of the sheet S. However, since the first roller 101 in this embodiment is made of metal, it does not undergo elastic deformation, and therefore, during clamping, the irregularities within the sheet W tend to favor the second roller 102, which has a soft surface. Therefore, the second surface Sb on the second roller 102 side of the sheet S becomes a relatively rough surface, while the first surface Sa on the first roller 101 side becomes a smooth surface, resulting in a surface quality difference between the first surface Sa and the second surface Sb in the sheet S. Therefore, by forming minute irregularities on the surface of the first roller 101, the first surface Sa on the first roller 101 side also becomes a relatively rough surface. Thus, the surface quality difference between the first surface Sa and the second surface Sb of the sheet S can be reduced. Furthermore, when touching the first surface Sa and the second surface Sb of the sheet S with a finger, the texture of the first surface Sa and the second surface Sb of the sheet S is the same, thereby reducing any sense of disharmony. Moreover, for example, when forming an image on the sheet S using a printer, the same image quality can be maintained in both the first surface Sa and the second surface Sb.

[0076] Next, the winding method of the sheet W in the pressure section 100 will be explained.

[0077] As described above, this embodiment employs a sheet manufacturing process using starch. Here, since the sheet W is supplied with moisture through the humidification section 90, it is prone to deformation or breakage, making it difficult to process.

[0078] Therefore, the pressurizing unit 100 of this embodiment is configured to process the sheet W in a stable state. This will be described in detail below.

[0079] The pressure section 100 has a first roller 101 that contacts one side Wa of the sheet W at the clamping section Np (pressure section) and a second roller 102 that contacts the other side Wb of the sheet W at the clamping section Np.

[0080] like Figure 3As shown, sheet W is conveyed such that one side Wa of sheet W contacts the surface of the first roller 101, starting from the clamping part Np and extending a predetermined length. Furthermore, during the period when one side Wa of sheet W is in contact with the surface of the first roller 101, the first roller 101 heats the sheet W. That is, sheet W is heated in the clamping part Np and in the winding area Ta that is wound by the first roller 101 extending a predetermined length from the clamping part Np. A sheet S is thus formed via the winding area Ta.

[0081] In this embodiment, since moisture is supplied from one side Wa of the sheet W, it contains more moisture than the other side Wb, making it easier for the Wa side of the sheet W to adhere. Utilizing this characteristic, by conveying the sheet W with one side Wa adhered to the first roller 101 (in a wound state), the sheet W can be processed stably. Furthermore, since the Wa side of the sheet W, containing more moisture, is wound on the first roller 101, heating can be performed efficiently.

[0082] Furthermore, moisture remains inside the sheet W discharged from the clamping part Np, making it susceptible to deformation or breakage. In this embodiment, by providing a winding area Ta on the first roller 101 downstream of the clamping part Np in the conveying direction, the conveyability of the sheet W is improved, thereby enabling reliable drying of the sheet W.

[0083] Furthermore, by utilizing the weight of the sheet W to be wound onto the first roller 101 located below the conveyed sheet W, the conveying posture of the sheet W after the clamping part Np can be stabilized, thereby suppressing the occurrence of deformation, etc.

[0084] A third roller 103 is provided opposite to the first roller 101 and downstream of the clamping section Np in the conveying direction of the sheet W. Furthermore, a pair of conveying rollers 118 is arranged downstream of the third roller 103. The sheet W (sheet S) is conveyed downstream by driving the conveying rollers 118. Moreover, the sheet W, which passes from the clamping section Np through the winding area Ta, is peeled off from the first roller 101 at a predetermined position and is conveyed downstream after contacting the lower part of the third roller 103.

[0085] Since the sheet W is conveyed via the third roller 103, the predetermined length (winding area Ta) of the sheet W wound by the first roller 101 can be kept fixed.

[0086] In addition, since the surface of the first roller 101 has unevenness, the pressing and fixing effect (anchoring effect) achieved by the unevenness can suppress the deformation or breakage of the sheet W after the clamping part Np, and also suppress the undulation of the sheet W caused by shrinkage during the heating of the winding area Ta.

[0087] Here, the first roller 101 is the driving roller, and the second roller 102 is the driven roller. Since the first roller 101 on the side with the material sheet W is the driving roller, the conveying speed of the material sheet W and the tension applied to the material sheet W are relatively stable, thus forming a smooth sheet S.

[0088] Furthermore, in this embodiment, the diameter of the first roller 101 is larger than the diameter of the second roller 102. The diameter of the first roller 101 is, for example, 110 mm or more and 150 mm or less, and the diameter of the second roller 102 is, for example, 80 mm or more and less than 110 mm.

[0089] By increasing the diameter of the first roller 101, the winding area Ta can be ensured. That is, the heating time of the sheet W can be ensured. The winding size of the sheet W in the winding area Ta is, for example, about 1 / 8 to 1 / 2 of the outer circumference of the first roller 101, preferably about 1 / 8 to 1 / 4. In addition, the winding area Ta can be appropriately set and changed according to the heating conditions of the heater 113, etc.

[0090] Because the sheet W is conveyed in a manner that conforms to the larger circumference of the roller, the edge curling of the sheet S is less when it is dried.

[0091] Furthermore, by reducing the size of the second roller 102, the structure of the pressure section 100 can be miniaturized.

[0092] Symbol Explanation

[0093] 1…Sheet manufacturing apparatus; 10…Feeding section; 11…Crushing section; 20…Defiberizing section; 40…Screwing section; 50…Mixing section; 52…Starch feeding section; 60…Accumulation section; 70…Second sheet forming section; 80…Sheet conveying section; 90…Humidification section; 91…Container; 92…Piezoelectric vibrator; 93…Discharge port; 100…Pressurization section; 101…First roller; 102…Second roller; 103…Third roller; 111…core iron; 112…surface layer; 113…heater; 114…core iron; 115…elastic layer; 116…surface layer; 117…heater; 118…conveyor roller pair; 120…cutting section; 130…receiving section; W…sheet; Wa…one side; Wb…other side; S…sheet; Sa…first side; Sb…second side; Np…clamping section; Nw…clamping width; Ta…winding area.

Claims

1. A sheet manufacturing apparatus, characterized in that, have: The stacking section uses airflow to stack fibrous materials to form sheets; A humidification section that supplies moisture from one side of the sheet; The pressurizing section applies pressure to the humidified material sheet to form a thin sheet. The pressurizing section has a first roller that contacts one side of the sheet and a second roller that contacts the other side of the sheet. The first roller heats one surface, and the second roller heats the other surface. The surface of the first roller is harder than the surface of the second roller. The surface of the first roller has irregularities.

2. The sheet manufacturing apparatus as claimed in claim 1, wherein, The first roller is made of metal, and the second roller is made of metal and rubber covering the surface of the metal.

3. The sheet manufacturing apparatus as claimed in claim 1, wherein, The first roller is a drive roller, and the second roller is a driven roller.

4. The sheet manufacturing apparatus as claimed in claim 1, wherein, The first roller and the second roller are each equipped with a heater for heating.

5. The sheet manufacturing apparatus as claimed in claim 1, wherein, A starch supply unit that supplies starch for binding the fibers; The mixing section mixes the starch and the fiber.

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