Method for producing sheet, and apparatus for producing sheet

Abstract

To provide a method for producing a sheet capable of producing a sheet having sufficient strength dispensing with a resin.SOLUTION: A method for producing a sheet includes: a web-forming process of accumulating a defibrated product by a dry method to form a web; a water-supplying process of supplying water to the web; a pressurizing process of pressurizing the web supplied with water; and a heating process of heating the web supplied with water, where the water content of the web supplied with water in the water-supplying process is 12 mass% or more, the pressure applied to the web in the pressurizing process is 0.2 MPa or more, and the temperature of the web in the heating process is 100°C or lower.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a sheet manufacturing method and a sheet manufacturing apparatus.

Background Art

[0002] For miniaturization and energy saving, a dry sheet manufacturing method has been proposed.

[0003] For example, Patent Document 1 describes a sheet manufacturing method including a fiberizing step of fiberizing a material to be fiberized in the air, a mixing step of mixing an additive containing a resin with the fiberized material in the air, a humidity conditioning step of humidity conditioning a mixture of the fiberized material and the additive, and a heating step of heating the humidity-conditioned mixture.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in Patent Document 1, a resin was required as a binder to manufacture a sheet having sufficient strength. In recent years, a method for manufacturing a sheet having sufficient strength without using a resin has been demanded.

Means for Solving the Problems

[0006] One aspect of the sheet manufacturing method according to the present invention is a web forming step of dry-depositing a fiberized material to form a web, a moisture imparting step of imparting moisture to the web, a pressing step of pressing the web to which moisture has been imparted, a heating step of heating the web to which moisture has been imparted, and includes The moisture content of the web to which moisture is applied in the moisture application step is 12% by mass or more, The pressure applied to the web in the pressing step is 0.2 MPa or more, The temperature of the web in the heating step is 100°C or less.

[0007] One aspect of the sheet manufacturing apparatus according to the present invention is a web forming unit that deposits defibrated materials dry to form a web, a moisture application unit that applies moisture to the web, a pressing unit that presses the web to which moisture has been applied, a heating unit that heats the web to which moisture has been applied, and includes the moisture content of the web to which moisture is applied by the moisture application unit is 12% by mass or more, the pressure applied to the web in the pressing unit is 0.2 MPa or more, the temperature of the web in the heating unit is 100°C or less.

Brief Description of Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0009] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. Note that the embodiments described below do not unduly limit the content of the present invention described in the claims. Also, not all of the configurations described below are essential constituent elements of the present invention.

[0010] The sheet manufacturing method according to the present embodiment includes a web forming step of dry-depositing defibrated materials to form a web, a moisture applying step of applying moisture to the web, a pressing step of pressing the web to which moisture has been applied, and a heating step of heating the web to which moisture has been applied. Hereinafter, first, an example of a sheet manufacturing apparatus capable of implementing the sheet manufacturing method of the present embodiment will be described, and then the sheet manufacturing method will be described.

[0011] 1. Sheet Manufacturing Apparatus An example of a sheet manufacturing apparatus according to the present embodiment suitable for the sheet manufacturing method of the present embodiment will be described with reference to the drawings. FIG. 1 is a diagram schematically showing a sheet manufacturing apparatus 100 according to the present embodiment.

[0012] As shown in FIG. 1, the sheet manufacturing apparatus 100 includes, for example, a supply unit 10, a crushing unit 12, a defibrating unit 20, a sorting unit 40, a first web forming unit 45, a rotating body 49, a mixing unit 50, a depositing unit 60, a second web forming unit 70, a sheet forming unit 80, and a cutting unit 90.

[0013] The supply unit 10 supplies raw materials to the crushing unit 12. The supply unit 10 is, for example, an automatic feeding unit for continuously feeding raw materials to the crushing unit 12. The raw materials supplied by the supply unit 10 include, for example, those containing fibers such as waste paper and pulp sheets.

[0014] The crushing section 12 cuts the raw material supplied by the supply section 10 into small pieces in the air such as the atmosphere. The shape and size of the small pieces are, for example, small pieces with a side length of several centimeters. In the illustrated example, the crushing section 12 has a crushing blade 14, and the crushing blade 14 can cut the input raw material. As the crushing section 12, for example, a shredder is used. The raw material cut by the crushing section 12 is received by the hopper 1 and then transferred to the defibrating section 20 through the pipe 2.

[0015] The defibrating section 20 defibrates the raw material cut by the crushing section 12. Here, "defibrating" means unraveling a raw material formed by binding a plurality of fibers into individual fibers. The defibrating section 20 also has a function of separating substances such as resin particles, ink, toner, and anti-bleeding agents attached to the raw material from the fibers.

[0016] What has passed through the defibrating section 20 is called "defibrated material". The "defibrated material" may contain, in addition to the unraveled defibrated fibers, resin particles separated from the fibers when unraveling the fibers, colorants such as ink and toner, and additives such as anti-bleeding materials and paper strength enhancers. The shape of the unraveled defibrated material is string-like. The unraveled defibrated material may exist in a state where it is not entangled with other unraveled fibers, that is, in an independent state, or in a state where it is entangled with other unraveled defibrated materials to form a lump, that is, in a state where it forms a mass.

[0017] The defibrating section 20 performs defibrating in a dry manner. Here, performing processes such as defibrating in the air such as the atmosphere rather than in a liquid is called dry. As the defibrating section 20, for example, an impeller mill is used. The defibrating section 20 has a function of generating an air flow that sucks the raw material and discharges the defibrated material. Thereby, the defibrating section 20, by the air flow generated by itself, from the inlet 22 The raw materials can be sucked together with the air flow, defibrated, and the defibrated materials can be conveyed to the discharge port 24. The defibrated materials that have passed through the defibrating unit 20 are transferred to the sorting unit 40 via the pipe 3. Note that, for the air flow for conveying the defibrated materials from the defibrating unit 20 to the sorting unit 40, the air flow generated by the defibrating unit 20 may be used, or an air flow generating device such as a blower may be provided and its air flow may be used.

[0018] The sorting unit 40 introduces the defibrated materials defibrated by the defibrating unit 20 from the inlet 42 and sorts them according to the fiber length. The sorting unit 40 has, for example, a drum unit 41 and a housing unit 43 that houses the drum unit 41. As the drum unit 41, for example, a sieve is used. The drum unit 41 has a net, and can separate fibers or particles smaller than the mesh size of the net, that is, the first sorted materials that pass through the net, and fibers, undefibrated pieces, and lumps larger than the mesh size of the net, that is, the second sorted materials that do not pass through the net. For example, the first sorted materials are transferred to the deposition unit 60 via the pipe 7. The second sorted materials are returned to the defibrating unit 20 from the discharge port 44 via the pipe 8. Specifically, the drum unit 41 is a cylindrical sieve that is rotationally driven by a motor. As the net of the drum unit 41, for example, a wire mesh, an expanded metal obtained by stretching a perforated metal plate, or a punching metal in which holes are formed in a metal plate using a press or the like is used.

[0019] The first web forming unit 45 conveys the first sorted materials that have passed through the sorting unit 40 to the pipe 7. The first web forming unit 45 has, for example, a mesh belt 46, a tensioning roller 47, and a suction mechanism 48.

[0020] The suction mechanism 48 can suck the first sorted materials dispersed in the air through the opening of the sorting unit 40 onto the mesh belt 46. The first sorted materials are deposited on the moving mesh belt 46 to form a web V. The basic configurations of the mesh belt 46, the tensioning roller 47, and the suction mechanism 48 are the same as those of the mesh belt 72, the tensioning roller 74, and the suction mechanism 76 of the second web forming unit 70 described later.

[0021] Web V is formed in a state of containing a large amount of air and being soft and swollen by passing through the sorting section 40 and the first web forming section 45. The web V deposited on the mesh belt 46 is put into the pipe 7 and conveyed to the deposition section 60.

[0022] The rotator 49 can cut the web V. In the illustrated example, the rotator 49 has a base 49a and a protrusion 49b protruding from the base 49a. The protrusion 49b has, for example, a plate-like shape. In the illustrated example, four protrusions 49b are provided, and the four protrusions 49b are provided at equal intervals. When the base 49a rotates in the direction R, the protrusion 49b can rotate about the base 49a. By cutting the web V with the rotator 49, for example, the variation in the amount of fiberized material supplied to the deposition section 60 per unit time can be reduced.

[0023] The rotator 49 is provided near the first web forming section 45. In the illustrated example, the rotator 49 is provided near the stretching roller 47a located on the downstream side in the path of the web V. The rotator 49 is provided at a position where the protrusion 49b can contact the web V and does not contact the mesh belt 46 on which the web V is deposited. Thereby, it is possible to suppress the mesh belt 46 from being worn by the protrusion 49b. The shortest distance between the protrusion 49b and the mesh belt 46 is, for example, 0.05 mm or more and 0.5 mm or less. This is a distance at which the web V can be cut without damaging the mesh belt 46.

[0024] The mixing section 50 mixes, for example, the first sorted material that has passed through the sorting section 40 and the additive. The mixing section 50 has, for example, an additive supply section 52 that supplies the additive, a pipe 54 that conveys the first sorted material and the additive, and a blower 56. In the illustrated example, the additive is supplied from the additive supply section 52 to the pipe 54 via the hopper 9. The pipe 54 is continuous with the pipe 7.

[0025] In the mixing section 50, an air current is generated by the blower 56, and in the pipe 54, the first sorted material and the additive can be conveyed while being mixed. Note that the mechanism for mixing the first sorted material and the additive is not particularly limited, and it may be a mechanism that stirs with blades rotating at high speed, or a mechanism that utilizes the rotation of a container like a V-type mixer.

[0026] As the additive supply section 52, a screw feeder as shown in FIG. 1, a disk feeder (not shown), or the like is used.

[0027] The additive supplied from the additive supply section 52 is not particularly limited, and for example, it may contain a resin for binding a plurality of fibers, a water-soluble polysaccharide such as starch. In this case, the additive may contain a resin, but it is better not to contain a resin in terms of further improving the environmental compatibility of the sheet.

[0028] When the additive supplied from the additive supply section 52 contains a resin, at the time when the additive is supplied, the plurality of fibers are not bound. The resin is a thermoplastic resin or a thermosetting resin, and for example, AS (Acrylonitrile Styrene) resin, ABS (Acrylonitrile Butadiene Styrene) resin, polypropylene, polyethylene, polyvinyl chloride, polystyrene, acrylic resin, polyester, polyethylene terephthalate, polyphenylene ether, polybutylene terephthalate, nylon, polyamide, polycarbonate, polyacetal, polyphenylene sulfide, polyether ether ketone, etc. These resins may be used alone or mixed as appropriate. The additive supplied from the additive supply section 52 may be fibrous or powdery.

[0029] Note that the additive supplied from the additive supply section 52 may contain a colorant for coloring the fibers, an aggregation inhibitor for suppressing the aggregation of the fibers and the additive, a flame retardant for making the fibers, etc. difficult to burn, according to the type of the sheet to be manufactured. The mixture that has passed through the mixing section 50 is transferred to the deposition section 60 via the pipe 54.

[0030] The deposition unit 60 introduces the mixture that has passed through the mixing unit 50 from the introduction port 62, loosens the entangled defibrated fibers, and drops them while dispersing them in the air. Further, when the additive resin supplied from the additive supply unit 52 is fibrous, the deposition unit 60 loosens the entangled resin. As a result, the deposition unit 60 can deposit the mixture on the second web forming unit 70 with good uniformity.

[0031] The deposition unit 60 has, for example, a drum unit 61 and a housing unit 63 that houses the drum unit 61. As the drum unit 61, a rotating cylindrical sieve is used. The drum unit 61 has a net and drops fibers or particles smaller than the mesh size of the net contained in the mixture that has passed through the mixing unit 50. The configuration of the drum unit 61 is the same as, for example, the configuration of the drum unit 41.

[0032] Note that the "sieve" of the drum unit 61 does not necessarily have a function of selecting a specific object. That is, the "sieve" used as the drum unit 61 means one equipped with a net, and the drum unit 61 may drop all of the mixture introduced into the drum unit 61.

[0033] The second web forming unit 70 deposits the passing material that has passed through the deposition unit 60 to form a web W. The second web forming unit 70 has, for example, a mesh belt 72, a stretching roller 74, and a suction mechanism 76.

[0034] The passing material that has passed through the opening of the deposition unit 60 is deposited on the mesh belt 72. The mesh belt 72 is stretched by the stretching roller 74 and is configured to be difficult for the passing material to pass through and easy for air to pass through. The mesh belt 72 moves as the stretching roller 74 rotates. While the mesh belt 72 moves continuously, the passing material that has passed through the deposition unit 60 accumulates continuously, and thus the web W is formed on the mesh belt 72.

[0035] The suction mechanism 76 is provided below the mesh belt 72. The suction mechanism 76 can generate a downward airflow. By the suction mechanism 76, the mixture dispersed into the air by the deposition part 60 can be sucked onto the mesh belt 72. Thereby, the discharge speed from the deposition part 60 can be increased. Further, by the suction mechanism 76, a downflow can be formed in the falling path of the mixture, and entanglement of fibrillation and additives during falling can be prevented.

[0036] As described above, by passing through the deposition part 60 and the second web forming part 70, a web W containing a large amount of air and in a soft and swollen state is formed.

[0037] Moisture is imparted to the deposited web W on the way to being conveyed to the sheet forming part 80. The moisture is imparted by the moisture imparting part 78. The moisture imparting part 78 imparts moisture so that a predetermined moisture content of the web W is obtained, and can be constituted by, for example, water vapor, mist, shower, inkjet, etc. Also, in the illustrated example, a suction mechanism 79 is provided at a position facing each other across the web W of the moisture imparting part 78. The suction mechanism 79 can generate a downward airflow. By the suction mechanism 79, the moisture generated from the moisture imparting part 78 can be sucked through the web W. Thereby, moisture can be imparted more uniformly in the thickness direction of the web W.

[0038] The web W to which moisture has been imparted by the moisture imparting part 78 is conveyed to the sheet forming part 80.

[0039] The sheet forming unit 80 forms the sheet S by pressing and heating the web W deposited on the mesh belt 72. In the sheet forming unit 80, pressure and heat are applied to the mixture of defibrated fibers and additives that are mixed, deposited, and provided with moisture. In the sheet forming unit 80, the thickness of the web W decreases and the density increases, and at the same time, the moisture evaporates. The density increases due to the pressure, and the moisture evaporates due to the heat, so that a plurality of fibers are bonded by hydrogen bonds. Thereby, a sheet S with good mechanical strength can be formed. Further, when having a water-soluble polysaccharide as an additive, the density increases due to the pressure, and the temperature of the moisture and the water-soluble polysaccharide rises due to the heat, so that the water-soluble polysaccharide gelatinizes. Then, as the moisture evaporates, a plurality of fibers are bonded through the gelatinized water-soluble polysaccharide. Thereby, a sheet S with better mechanical strength can be formed. Further, when having a resin as an additive, the resin softens due to the heat, and a plurality of fibers are bonded through the softened resin. Thereby, a sheet S with better mechanical strength can be formed.

[0040] The sheet forming unit 80 has a pressure heating unit 84 that pressurizes and heats the web W. The pressure heating unit 84 functions as a pressurizing unit that pressurizes the web W and also functions as a heating unit that heats the web W. Although not shown, the sheet forming unit 80 may have a pressurizing unit that pressurizes the web W and a heating unit that heats the web W as separate mechanisms.

[0041] The pressure heating unit 84 can be configured using, for example, a heating roller, a hot press molding machine. Also, when the pressurizing unit and the heating unit are provided as separate mechanisms, in addition to the aforementioned mechanisms, the heating unit can also be configured using a hot plate, a warm air blower, an infrared heater, a flash fuser. In the illustrated example, the pressure heating unit 84 is a pair of heating rollers 86. Note that the number of the heating rollers 86 is not particularly limited. The pressure heating unit 84 can simultaneously apply pressure and heat to the web W.

[0042] The cutting unit 90 cuts the sheet S formed by the sheet forming unit 80. In the illustrated example, the cutting unit 90 includes a first cutting unit 92 that cuts the sheet S in a direction intersecting the conveyance direction of the sheet S, and a second cutting unit 94 that cuts the sheet S in a direction parallel to the conveyance direction. The second cutting unit 94 cuts, for example, the sheet S that has passed through the first cutting unit 92.

[0043] As described above, a single sheet S of a predetermined size is formed. The cut single sheet S is discharged to the discharge receiving portion 96.

[0044] 2. Sheet manufacturing method Next, the sheet manufacturing method according to the present embodiment will be described with reference to the drawings. FIG. 2 is a flowchart for explaining the sheet manufacturing method according to the present embodiment. The sheet manufacturing method according to the present embodiment can be performed, for example, using the above-described sheet manufacturing apparatus 100.

[0045] As shown in FIG. 2, the sheet manufacturing method according to the present embodiment includes a web forming step (step S1) of forming a web by dry-depositing the defibrated material, a binder adding step (step S2) of adding a binder to at least one of the defibrated material and the web, a moisture applying step (step S3) of applying moisture to the web, a pressing step (step S4) of pressing the web to which moisture has been applied, and a heating step (step S5) of heating the web to which moisture has been applied.

[0046] 2.1. Web forming step In the web forming step, a web is formed by dry-depositing the defibrated material. When using the above-described sheet manufacturing apparatus 100, the defibrated material is formed by the defibrating unit 20. The defibrated material, the depositing unit 60, and the second web forming unit 70 form a web by dry-depositing the defibrated material.

[0047] The defibered material contains fibers. The fibers are not particularly limited, and a wide range of fiber materials can be used. Examples of the fibers include natural fibers (animal fibers, plant fibers), chemical fibers (organic fibers, inorganic fibers, organic-inorganic composite fibers), etc. More specifically, the fibers include fibers made of cellulose, silk, wool, cotton, hemp, kenaf, flax, ramie, jute, Manila hemp, sisal hemp, softwood, hardwood, etc. These may be used alone, may be mixed as appropriate, or may be used as regenerated fibers that have been refined, etc. The fibers used in the sheet manufacturing method of the present embodiment have the ability to form hydrogen bonds.

[0048] Examples of the raw materials of the fibers include pulp, waste paper, waste cloth, etc. Also, the fibers may be subjected to various surface treatments. Further, the material of the fibers may be a pure substance or a material containing a plurality of components such as impurities and other components.

[0049] The length of the fibers is not particularly limited, but for an independent single fiber, the length along the longitudinal direction of the fiber is 1 μm or more and 5 mm or less, preferably 2 μm or more and 3 mm or less, more preferably 3 μm or more and 2 mm or less.

[0050] 2.2. Binder addition step In the binder addition step, a binder is added to at least one of the defibered material and the web. In the binder addition step, the binder may be added only to the defibered material, may be added only to the web, or may be added to both the defibered material and the web. When using the above-described sheet manufacturing apparatus 100, the binder addition step can be performed by the additive supply unit 52. The binder added in the binder addition step may be a resin such as polyester as described above, or may be a water-soluble polysaccharide such as starch. It may also be a water-soluble polysaccharide such as starch.

[0051] Note that the binder addition step may not be performed. By not performing the binder addition step, the process can be shortened. Furthermore, by not adding resin, a more environmentally friendly sheet can be manufactured. On the other hand, if the binder addition step is performed, a sheet with higher strength can be manufactured. Also, if the binder addition step is performed, it may be performed after the moisture application step as long as it is before the pressing step and the heating step.

[0052] 2.3. Moisture Application Step In the moisture application step, moisture is applied to the web. Specifically, in the moisture application step, water is applied to the web. When using the above-described sheet manufacturing apparatus 100, moisture can be applied to the web by the moisture application unit 78.

[0053] The amount of water applied in the moisture application step can be controlled, for example, by the moisture content of the web. The moisture content of the web to which moisture has been applied in the moisture application step is 12% by mass or more and 60% by mass or less, preferably 14% by mass or more and 52% by mass or less, more preferably 14% by mass or more and 40% by mass or less, and still more preferably 15% by mass or more and 30% by mass or less.

[0054] Also, in the moisture application step, it is preferable to apply water vapor or mist to the web. By doing so, moisture can be applied more uniformly onto the web, and a sheet can be manufactured with a simpler apparatus configuration.

[0055] 2.4. Pressing Step In the pressing step, the web to which moisture has been applied is pressed. When using the above-described sheet manufacturing apparatus 100, the pressing can be performed by the sheet forming unit 80.

[0056] In the pressing step, pressure is applied to the web to thin the web and increase the density of the web. The pressure applied to the web in the pressing process is 0.2 MPa or more and 15 MPa or less, preferably 0.2 MPa or more and 13 MPa or less, more preferably 0.3 MPa or more and 10 MPa or less, and still more preferably 0.4 MPa or more and 2.0 MPa or less.

[0057] 2.5. Heating Process In the heating process, the web with moisture applied is heated. When using the above-described sheet manufacturing apparatus 100, the heating process can be performed by the sheet forming unit 80. The pressing process and the heating process are, for example, performed simultaneously. This results in a simpler manufacturing method and simplifies the configuration of the apparatus for performing the manufacturing method. Note that the pressing process and the heating process do not necessarily have to be performed simultaneously. In this case, the heating process may be performed after the pressing process, or the pressing process may be performed after the heating process.

[0058] In the heating process, heat is applied to the web to evaporate the moisture contained in the web. The temperature of the web in the heating process is 100°C or lower. In the heating process, the web is heated such that the temperature of the web is preferably 50°C or higher and 100°C or lower, more preferably 60°C or higher and 98°C or lower, and even more preferably 70°C or higher and 96°C or lower.

[0059] 2.6. Other Processes The sheet manufacturing method of the present embodiment may include, for example, a defibering process, a sorting process, a cutting process, etc. in addition to the above-described processes. If the above-described sheet manufacturing apparatus 100 is used, these processes can be easily performed by the defibering unit 20, the sorting unit 40, the first web forming unit 45, the rotating body 49, the cutting unit 90, etc.

[0060] 2.7. Effects The sheet manufacturing method of the present embodiment includes a web forming process of dry-depositing the defibered material to form a web, a moisture applying process of applying moisture to the web, a pressing process of pressing the web with moisture applied, and a heating process of heating the web with moisture applied. The moisture content of the web with moisture applied in the moisture applying process is 12% by mass or more, the pressure applied to the web in the pressing process is 0.2 MPa or more, and the temperature of the web in the heating process is 100°C or lower.

[0061] Therefore, in the sheet manufacturing method of this embodiment, a plurality of fibers contained in the defibrated material can be bonded by hydrogen bonds. Thereby, a sheet having sufficient strength can be manufactured without using a resin. Specifically, by setting the moisture content of the web to 12% or more and then heating at a temperature of 100°C or lower, hydrogen bonds between the fibers can be formed. For example, when heating at a temperature higher than 100°C, the molecular motion becomes intense and it is difficult to form hydrogen bonds. Furthermore, by pressurizing after setting the moisture content of the web to 12% or more, the density of the web can be increased at a lower pressure, and the size of the apparatus can be reduced. Furthermore, by depositing the defibrated material dry to form a web, the amount of moisture used for forming the web can be reduced compared to the wet papermaking method.

[0062] In the sheet manufacturing method of this embodiment, the moisture content of the web to which moisture is applied in the moisture application step may be 40% by mass or less. If the moisture content of the web is 40% by mass or less, the transportability and formability of the web can be improved.

[0063] In the sheet manufacturing method of this embodiment, the pressure applied to the web in the pressurizing step may be 10 MPa or less. If the pressure applied to the web is 10 MPa or less, deterioration of the fibers can be suppressed. Therefore, a sheet can be manufactured again using the defibrated material obtained by defibrating the manufactured sheet as a raw material.

[0064] In the sheet manufacturing method of this embodiment, the temperature of the web in the heating step may be 60°C or higher. If the temperature of the web is 60°C or higher, the time required for the heating step can be reduced.

[0065] 3. Examples and Comparative Examples 3.1. Production of Sheets A sheet was produced using a device corresponding to the above-described sheet manufacturing apparatus 100. The defibrated material was deposited dry to form a web. After water was applied to the web, the water-applied web was pressure-heated by a pair of rollers to produce a sheet. No binder such as resin or water-soluble polysaccharide was used. The pressurization and heating of the web were performed simultaneously.

[0066] Figure 3 is a table showing the production conditions of the sheets of No. 1 to 10. As shown in Figure 3, the amount of water applied (water content), pressure, and the temperature of the rollers were varied. The basis weights of the sheets of No. 1 to 10 were about 80 g / cm 2 or so. The pressure was calculated based on the following formulas (1) and (2).

[0067] Pressure = Load applied to the roller / Nip area ··· (1) Nip area = Roller width × Nip width ··· (2)

[0068] The nip width was measured by the following method. First, the temperature of a pair of rollers was raised to 100°C. Next, a commercially available laminate sheet was sandwiched between the pair of rollers and nipped (a predetermined load was applied). Next, the nip was released in about 1 second, and the laminate sheet was taken out. Next, since the heated portion of the laminate sheet became transparent, the width of the transparent portion was measured.

[0069] Also, as shown in Figure 4, the sheet temperature was measured with a radiation thermometer at positions A, B, and C away from the nip exit E. The following is an example of the measurement results. The sheet temperature is the temperature of the heated web. Note that Figure 4 is a diagram for explaining the method of calculating the density of the sheet.

[0070] Measurement position Time to reach from nip exit E (s) Sheet temperature (°C) A 1.2 72 B 2.0 64 C 2.8 57

[0071] A graph was created with the arrival time from the nip exit E on the horizontal axis and the sheet temperature on the vertical axis. Then, an approximation curve was created with a quadratic curve, and the temperature at x = 0 (nip exit) was calculated. In the above example, the approximation curve is represented by the following formula (3), and the sheet temperature, which is the y-intercept, was 85.9 °C.

[0072] y = 0.7813x 2 -12.5x + 85.875 ···(3)

[0073] 3.2. Evaluation Conditions The sheets produced as described above were evaluated for strength, density, drying time, and repeated regeneration.

[0074] 3.2.1. Strength In this experimental example, strength refers to the specific tensile strength. A sheet piece with a width of 10 mm × a length of 50 mm was cut out from the produced sheet, and the specific tensile strength was determined based on the following formula (4). The specific tensile strength was evaluated by a tensile test. As the test apparatus, "AGS-X500N" manufactured by Shimadzu Corporation was used. The tensile speed was set at 1 mm / s.

[0075] Specific tensile strength (N·m / g) = maximum tensile load (N) / sheet piece width (mm) / sheet piece basis weight (g / cm 2 ) ···(4)

[0076] The evaluation criteria for the specific tensile strength (N·m / g) are as follows.

[0077] A: 10 or more B: 8 or more and less than 10 C: Less than 8

[0078] 3.2.2. Density A sheet piece with a size of 30 mm × 200 mm was cut out from the produced sheet, the thickness and mass of the sheet piece were measured, and the density was calculated from the following formula (5). The thickness was measured at five locations on the sheet piece in the shape of a circle shown in Fig. 5 with a micrometer, and the average value was calculated. Note that Fig. 5 is a diagram for explaining the method of calculating the sheet temperature.

[0079] Density = Mass / (Thickness × 3 × 20) ···(5)

[0080] Density (g / cm 3 ) The evaluation criteria are as follows.

[0081] A: 0.55 or more B: 0.50 or more and less than 0.55 C: Less than 0.50

[0082] 3.2.3. Drying Time The drying time was based on 0.8 seconds. When drying in 0.8 seconds, it was left as it was (drying time of 0.8 seconds). When there was a lot of moisture and it could not be dried in 0.8 seconds, the rotation speed of the heating roller was decreased to extend the time for the sheet to pass through the nip of the heating roller. The rotation speed at which the moisture content of the dried sheet became 10 mass% or less was adopted, and the drying time at that time was used as an index. Specifically, the drying time was calculated from the following formula (6).

[0083] Drying Time (s) = Nip Width (mm) / Roller Peripheral Speed (mm / s) ···(6)

[0084] As the measuring device for moisture content measurement, "MX-50" manufactured by A&D was used. The heating pattern was set as "the method of keeping the drying time constant". A sheet piece was cut out from the sheet so that the mass of the sheet piece was 1 g for evaluation.

[0085] The evaluation criteria for drying time (s) are as follows.

[0086] A: 1.2 or less B: Greater than 1.2 and 5 or less C: Greater than 5

[0087] 3.2.4. Repeated Reproduction Papermaking was carried out using the recycled paper made as raw material, and this was repeated 2 times to measure the strength. That is, papermaking was carried out a total of 3 times. The method for measuring the strength was as described above. The ratio of the strength of the first-time recycled RC1 to the third-time recycled RC3 (RC3 strength / RC1 strength) was obtained.

[0088] The evaluation criteria for repeated playback are as follows.

[0089] A: The ratio is 0.9 or more B: The ratio is 0.8 or more and less than 0.9 C: The ratio is less than 0.8

[0090] 3.3. Evaluation Results Figure 3 shows the evaluation results of sheets No. 1 to 10. Sheets No. 1, 2, 5, 7 to 10 are sheets according to the examples. Sheets No. 3, 4, 6 are sheets according to the comparative examples.

[0091] As shown in Figure 3, Sheet No. 1 was rated "A" in all evaluation items and had a better evaluation result compared to Sheets No. 2 to 10.

[0092] Sheet No. 2 had high strength and density, but due to the low sheet temperature, it took a long time to dry.

[0093] For Sheet No. 3, since the sheet temperature was too high, hydrogen bonds were not formed, and the strength and density were low.

[0094] For Sheet No. 4, due to the low pressure, the sheet could not be crushed completely, and the density was low. Therefore, the strength was also low.

[0095] The first playback of Sheet No. 5 was good, but due to the too high pressure, the fibers deteriorated, and the evaluation of repeated playback was poor.

[0096] For Sheet No. 6, since the moisture content was low, hydrogen bonds were not formed, and the strength and density were low.

[0097] For Sheet No. 7, the moisture content was too high, and water oozed out from the sheet at the nip, causing dripping. Also, it took a long time to dry.

[0098] The No. 8 sheet had a relatively low moisture content, so its initial strength was slightly low. Additionally, due to the high pressure, the evaluation of repeated recycling was slightly poor.

[0099] The No. 9 sheet had a slightly higher moisture content, so its drying time was slightly long.

[0100] The No. 10 sheet had a slightly higher moisture content but a slightly lower pressure on the other hand, so its initial strength was slightly low. The repeated recycling had a good evaluation.

[0101] The present invention includes a configuration that is substantially the same as the configuration described in the embodiment, for example, a configuration having the same functions, methods, and results, or a configuration having the same objectives and effects. Further, the present invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. Further, the present invention includes a configuration having the same operational effects as the configuration described in the embodiment or a configuration capable of achieving the same objective. Further, the present invention includes a configuration in which known technology is added to the configuration described in the embodiment.

[0102] The following content is derived from the above-described embodiment.

[0103] One aspect of the sheet manufacturing method is a web forming step of depositing defibrated material in a dry state to form a web, a moisture imparting step of imparting moisture to the web, a pressing step of pressing the web to which moisture has been imparted, a heating step of heating the web to which moisture has been imparted, and includes the moisture content of the web to which moisture has been imparted in the moisture imparting step is 12% by mass or more, the pressure applied to the web in the pressing step is 0.2 MPa or more, the temperature of the web in the heating step is 100°C or less.

[0104] According to this sheet manufacturing method, a sheet having sufficient strength can be manufactured without using resin.

[0105] In one aspect of the sheet manufacturing method, The water content rate of the web to which water is imparted in the water imparting step may be 40% by mass or less.

[0106] According to this manufacturing method, the transportability and formability of the web can be improved.

[0107] In one aspect of the sheet manufacturing method, The pressure applied to the web in the pressurizing step may be 10 MPa or less.

[0108] According to this manufacturing method, a sheet can be manufactured again using the defibrated product obtained by defibrating the manufactured sheet as a raw material.

[0109] In one aspect of the sheet manufacturing method, The temperature of the web in the heating step may be 60°C or higher.

[0110] According to this manufacturing method, the time required for the heating step can be reduced.

[0111] In one aspect of the sheet manufacturing method, The pressurizing step and the heating step may be performed simultaneously.

[0112] According to this manufacturing method, the configuration of the apparatus for performing this manufacturing method can be simplified.

[0113] In one aspect of the sheet manufacturing method, Before the pressurizing step and the heating step, a binder adding step of adding a binder to at least one of the defibrated product and the web may be included.

[0114] According to this manufacturing method, a sheet having higher strength can be manufactured.

[0115] In one aspect of the sheet manufacturing method, In the water application step, water vapor or mist may be applied to the web.

[0116] According to this manufacturing method, a sheet can be manufactured with a simpler device configuration.

[0117] One aspect of a sheet manufacturing apparatus is a web forming unit that deposits defibrated material in a dry state to form a web, a water application unit that applies moisture to the web, a pressing unit that presses the web to which moisture has been applied, a heating unit that heats the web to which moisture has been applied, including the moisture content of the web to which moisture has been applied by the water application unit is 12% by mass or more, the pressure applied to the web in the pressing unit is 0.2 MPa or more, the temperature of the web in the heating unit is 100°C or less.

[0118] According to this sheet manufacturing apparatus, a sheet having sufficient strength can be manufactured without using resin.

Explanation of symbols

[0119] 1... Hopper, 2, 3, 7, 8... Pipe, 9... Hopper, 10... Supply section, 12... Crushing section, 14... Crushing blade, 20... Fiber separation section, 22... Inlet, 24... Outlet, 40... Sorting section, 41... Drum section, 42... Inlet, 43... Housing section, 44... Outlet, 45... First web forming section, 46... Mesh belt, 47, 47a... Tension rollers, 48... Suction mechanism, 49... Rotating body, 49a... Base, 49b... Protrusion, 50... Mixing section, 52... Additive supply section, 54... Pipe, 56... Blower, 60... Deposition section, 61... Drum section, 62... Inlet, 63... Housing section, 70... Second web forming section, 72... Mesh belt, 74... Tension roller, 76... Suction mechanism, 78... Moisture application section, 79... Suction mechanism, 80... Sheet forming section, 84... Pressing and heating section, 86... Heating roller, 90... Cutting section, 92... First cutting section, 94... Second cutting section, 96... Discharge receiving section, 100... Sheet manufacturing apparatus

Claims

1. A web forming step of dry-depositing a defibrated material containing fibers made of cellulose to form a web; A moisture applying step of applying moisture to the web; A pressing step of pressing the web to which moisture has been applied; A heating step of heating the web to which moisture has been applied; comprising: The moisture content of the web to which moisture has been applied in the moisture applying step is 12% by mass or more; The pressure applied to the web in the pressing step is 0.2 MPa or more; The temperature of the web in the heating step is 100°C or less; A sheet manufacturing method that does not use a resin as a binder for binding fibers together.

2. In claim 1, The moisture content of the web to which moisture has been applied in the moisture applying step is 40% by mass or less, a sheet manufacturing method.

3. In claim 1 or 2, The pressure applied to the web in the pressing step is 10 MPa or less, a sheet manufacturing method.

4. In any one of claims 1 to 3, The temperature of the web in the heating step is 60°C or more, a sheet manufacturing method.

5. In any one of claims 1 to 4, The pressing step and the heating step are performed simultaneously, a sheet manufacturing method.

6. In any one of claims 1 to 5, Before the pressing step and the heating step, it includes a binder adding step of adding a binder to at least one of the defibrated material and the web, The binder is starch, a sheet manufacturing method.

7. In any one of claims 1 to 6, In the moisture applying step, steam or mist is applied to the web, a sheet manufacturing method.

8. A web forming section for dry-depositing a defibrated material containing fibers made of cellulose to form a web; A moisture applying section for applying moisture to the web; A pressing section for pressing the web to which moisture has been applied; A heating section for heating the web to which moisture has been applied; comprising: The moisture content of the web to which moisture has been applied in the moisture applying section is 12% by mass or more; The pressure applied to the web in the pressing section is 0.2 MPa or more; The temperature of the web in the heating section is 100°C or less; A sheet manufacturing apparatus that does not use a resin as a binder for binding fibers together.

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