Sheet manufacturing apparatus and sheet manufacturing method

Abstract

To provide an apparatus for producing a sheet capable of reducing an amount of paper powder.SOLUTION: An apparatus for producing a sheet includes: an accumulation part of accumulating a defibrated product in a dry method to form a web; a water application part of applying water from one face side of the formed web so that the water content of the web becomes 12 mass% or more and 40 mass% or less; and a heating part of heating the web having water applied thereto. The heating part has a first part contacting one face of the web, and a second part contacting another face of the web. The heating part heats the web in such a state that the surface temperature of the first part is higher than a surface temperature of the second part.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

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

[0003] For example, Patent Document 1 describes a paper recycling apparatus including a dry defibrillation unit that pulverizes and defibrillates paper, a paper forming unit that forms paper from the defibrillated material defibrillated in the dry defibrillation unit, a moisture sprayer that sprays moisture onto the formed paper, and a heater roller that heats the paper sprayed with moisture by the moisture sprayer.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when moisture is applied and heated from one surface side of the defibrillated material deposited as described above, depending on the temperature of the heater roller, a large amount of paper dust may be generated in the manufactured sheet.

Means for Solving the Problems

[0006] One aspect of the sheet manufacturing apparatus according to the present invention is a deposition unit that dry-deposits defibrillated material to form a web, a moisture application unit that applies moisture from one surface side of the formed web to make the moisture content of the web 12% by mass or more and 40% by mass or less, a heating unit that heats the web to which moisture has been applied, and includes the heating unit is A first portion that contacts one surface of the web, a second portion that contacts the other surface of the web, and the heating unit heats the web in a state where the surface temperature of the first portion is higher than the surface temperature of the second portion.

[0007] One aspect of the sheet manufacturing method according to the present invention is a step of depositing shredded fibers dry to form a web, a step of imparting moisture from one surface side of the formed web to make the moisture content of the web 12% by mass or more and 40% by mass or less, a step of heating the web with moisture imparted thereto by a heating unit, and the heating unit has a first portion that contacts one surface of the web, a second portion that contacts the other surface of the web, and in the step of heating by the heating unit, the web is heated in a state where the surface temperature of the first portion is higher than the surface temperature of the second portion.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments 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] 1. Sheet manufacturing apparatus 1.1. Overall configuration First, the sheet manufacturing apparatus according to the present embodiment will be described with reference to the drawings. FIG. 1 is a diagram schematically showing the sheet manufacturing apparatus 100 according to the present embodiment.

[0011] As shown in FIG. 1, the sheet manufacturing apparatus 100 includes, for example, a supply unit 10, a crushing unit 12, a defibering unit 20, a sorting unit 40, a first web forming unit 45, a rotating body 49, a mixing unit 50, a deposition unit 60, a second web forming unit 70, a moisture application unit 78, a sheet forming unit 80, and a cutting unit 90.

[0012] 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.

[0013] The crushing unit 12 cuts the raw materials supplied by the supply unit 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 unit 12 has a crushing blade 14, and the crushing blade 14 can cut the input raw materials. As the crushing unit 12, for example, a shredder is used. The raw materials cut by the crushing unit 12 are received by the hopper 1 and then transferred to the defibering unit 20 through the pipe 2.

[0014] The defibering unit 20 defibers the raw materials cut by the crushing unit 12. Here, "defibering" means unraveling a raw material formed by binding a plurality of fibers into individual fibers. The defibering unit 20 also has a function of separating substances such as resin particles, ink, toner, and anti-bleeding agents attached to the raw materials from the fibers.

[0015] What has passed through the defiberization unit 20 is called "defiberized material". The "defiberized material" may contain, in addition to the defiberized fibers that have been loosened, resin particles separated from the fibers when the fibers are loosened, colorants such as ink and toner, and additives such as anti-bleeding agents and paper strength enhancers. The shape of the loosened defiberized material is string-like. The loosened defiberized material may exist in a state where it is not intertwined with other loosened fibers, that is, in an independent state, or in a state where it is intertwined with other loosened defiberized materials to form a lump, that is, in a state where a ball is formed.

[0016] The defiberization unit 20 performs defiberization in a dry manner. Here, performing processes such as defiberization and deposition in the air such as in the atmosphere rather than in a liquid is called dry. As the defiberization unit 20, for example, an impeller mill is used. The defiberization unit 20 has a function of generating an air flow that sucks in the raw material and discharges the defiberized material. Thereby, the defiberization unit 20 can suck in the raw material from the inlet 22 together with the air flow by the air flow generated by itself, perform defiberization processing, and convey the defiberized material to the outlet 24. The defiberized material that has passed through the defiberization unit 20 is transferred to the sorting unit 40 via the pipe 3. Note that the air flow for conveying the defiberized material from the defiberization unit 20 to the sorting unit 40 may utilize the air flow generated by the defiberization unit 20, or an air flow generating device such as a blower may be provided and its air flow may be utilized.

[0017] The sorting unit 40 introduces the defibrated material defibrated by the defibrating unit 20 from the inlet 42 and sorts it 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 mesh, and separates fibers or particles smaller than the mesh opening size, that is, the first sorted material that passes through the mesh, from fibers, undefibrated pieces, and lumps larger than the mesh opening size, that is, the second sorted material that does not pass through the mesh. For example, the first sorted material is transferred to the deposition unit 60 via the pipe 7. The second sorted material is 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 mesh 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.

[0018] The first web forming unit 45 conveys the first sorted material that has 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.

[0019] The suction mechanism 48 can suck the first sorted material dispersed into the air through the opening of the sorting unit 40 onto the mesh belt 46. The first sorted material accumulates on the moving mesh belt 46 to form the 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.

[0020] The web V is formed in a state of containing a large amount of air, being soft and swollen by passing through the sorting unit 40 and the first web forming unit 45. The web V deposited on the mesh belt 46 is put into the pipe 7 and conveyed to the deposition unit 60.

[0021] The rotating body 49 can cut the web V. In the illustrated example, the rotating body 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. By rotating the base 49a in the direction R, the protrusion 49b can rotate about the base 49a. By cutting the web V with the rotating body 49, for example, fluctuations in the amount of fiberized material supplied to the deposition portion 60 per unit time can be reduced.

[0022] The rotating body 49 is provided in the vicinity of the first web forming portion 45. In the illustrated example, the rotating body 49 is provided in the vicinity of the stretching roller 47a located on the downstream side in the path of the web V. The rotating body 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 the mesh belt 46 being damaged.

[0023] The mixing unit 50 mixes, for example, the first sorted material that has passed through the sorting unit 40 and the additive. The mixing unit 50 has, for example, an additive supply unit 52 that supplies an 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 unit 52 to the pipe 54 via the hopper 9. The pipe 54 is continuous with the pipe 7.

[0024] In the mixing unit 50, an air flow can be generated by the blower 56, and the first sorted material and the additive can be conveyed while being mixed in the pipe 54. 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.

[0025] As the additive supply unit 52, a screw feeder as shown in FIG. 1, a disk feeder (not shown), or the like is used. The additive supplied from the additive supply unit 52 is not particularly limited, but includes, for example, a binder for binding a plurality of fibers. Details of the binder will be described later. The additive supplied from the additive supply unit 52 may be fibrous or powdery.

[0026] In addition, the additive supplied from the additive supply unit 52 may include a colorant for coloring the fibers, an aggregation inhibitor for suppressing the aggregation of the fibers and the additive, and a flame retardant for making the fibers and the like difficult to burn, depending on the type of the sheet to be manufactured. The mixture that has passed through the mixing unit 50 is transferred to the deposition unit 60 via the pipe 54.

[0027] The deposition unit 60 introduces the mixture that has passed through the mixing unit 50 from the inlet 62, loosens the entangled defibrated materials, and drops them while dispersing them in the air. The deposition unit 60 deposits the defibrated materials in a dry manner to form the web W. Further, when the resin of the additive supplied from the additive supply unit 52 is fibrous, the deposition unit 60 loosens the entangled resin. Thereby, the deposition unit 60 can deposit the mixture on the second web forming unit 70 with good uniformity.

[0028] 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.

[0029] 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.

[0030] The second web forming unit 70 forms a web W by depositing the material that has passed through the deposition unit 60. The second web forming unit 70 has, for example, a mesh belt 72, a stretching roller 74, and a suction mechanism 76.

[0031] The 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 material to pass through but easy for air to pass through. The mesh belt 72 moves as the stretching roller 74 rotates. As the mesh belt 72 continuously moves and the material that has passed through the deposition unit 60 continuously accumulates, the web W is formed on the mesh belt 72.

[0032] 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 in the air by the deposition unit 60 can be sucked onto the mesh belt 72. Thereby, the discharge speed from the deposition unit 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 the fibrillated material and the additive during falling can be prevented. By the suction mechanism 76, a downflow can be formed in the falling path of the mixture, and entanglement of the fibrillated material and the additive during falling can be prevented.

[0033] As described above, by passing through the deposition unit 60 and the second web forming unit 70, the web W in a state of containing a large amount of air, being soft and swollen is formed.

[0034] Water is applied to the deposited web W on the way to being conveyed to the sheet forming unit 80. The water is applied by the water application unit 78. Details of the water application unit 78 will be described later.

[0035] The web W to which water has been applied by the water application unit 78 is conveyed to the sheet forming unit 80.

[0036] The sheet forming unit 80 forms the sheet S by pressing and heating the web W deposited on the mesh belt 72. The sheet forming unit 80 has a heating unit 82 that presses and heats the web W. Details of the heating unit 82 will be described later.

[0037] The cutting unit 90 cuts the sheet S formed by the sheet forming unit 80, that is, the heated web W. In the illustrated example, the cutting unit 90 has 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.

[0038] As described above, a single sheet S of a predetermined size is formed. The cut single sheet S is discharged to the discharge receiving unit 96.

[0039] 1.2. Additive Supply Unit The additive supply unit 52 is, for example, a binder application unit that applies a binder to at least one of the defibrated material and the web W. The binder binds a plurality of fibers. The additive supply unit 52 may apply the binder to the defibrated material and not to the web W, or may apply the binder to the web W and not to the defibrated material, or may apply the binder to both the defibrated material and the web W. Further, the additive supply unit 52 may apply the binder to the web V.

[0040] Examples of the binder supplied from the additive supply unit 52 include water-soluble polysaccharides and resins. However, in terms of being able to further improve the environmental compatibility of the sheet, it is preferable that the additive does not contain resin.

[0041] Water-soluble polysaccharides refer to polysaccharides that dissolve in water, warm water, or hot water. Examples of water-soluble polysaccharides include starch and dextrin.

[0042] Starch is a polymer in which a plurality of α-glucose molecules are polymerized by glycosidic bonds. Starch may be linear or may contain branches. Starches derived from various plants can be used. Examples of starch raw materials include grains such as corn, wheat, and rice, beans such as broad beans, mung beans, and adzuki beans, tubers such as potatoes, sweet potatoes, and tapioca, wild grasses such as arrowroot, bracken, and kudzu, and palms such as sago palms.

[0043] Furthermore, modified starches or denatured starches may be used as the starch. Examples of modified starches include acetylated adipic acid crosslinked starch, acetylated starch, acetylated starch, oxidized starch, sodium octenyl succinate starch, hydroxypropyl starch, hydroxypropylated phosphate crosslinked starch, phosphorylated starch, phosphate esterified phosphate crosslinked starch, urea phosphorylated esterified starch, sodium starch glycolate, high amylose corn starch, etc. Examples of denatured starches include α-starch, dextrin, lauryl polyglucose, cationized starch, thermoplastic starch, starch carbamate, etc. In addition, dextrin obtained by processing or modifying starch can be preferably used.

[0044] The resin is a thermoplastic resin or a thermosetting resin, 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.

[0045] The content of the binder in the sheet 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, more preferably 1% by mass or more and 30% by mass or less.

[0046] 1.3. Moisture Application Unit The moisture application unit 78 applies moisture to the web W from the first surface Wa side of the formed web W. Specifically, the moisture application unit 78 applies water to the web W from the first surface Wa side. The web W has a first surface Wa and a second surface Wb facing in opposite directions. The first surface Wa is one surface of the web W and is the lower surface in the illustrated example. The second surface Wb is the other surface of the web W and is the upper surface in the illustrated example.

[0047] The moisture application unit 78 applies water vapor or mist such as ultrasonic mist to the first surface Wa of the web W. The moisture application unit 78 is constituted by, for example, a humidifier, an inkjet, a shower, or the like. In the illustrated example, the moisture from the moisture application unit 78 is discharged upward from below.

[0048] The moisture application unit 78 applies moisture to the web W to make the moisture content of the web W 12% by mass or more and 40% by mass or less, more preferably 14% by mass or more and 35% by mass or less, and even more preferably 15% by mass or more and 30% by mass or less. The moisture content of the web W is measured by, for example, a heated drying type moisture meter. If the moisture content of the web W is 12% by mass or more, a plurality of fibers contained in the defibrated material can be bound by hydrogen bonds. If the moisture content of the web is 40% by mass or less, the transportability and formability of the web W can be improved.

[0049] 1.4. Heating Unit The heating unit 82 heats the web W to which moisture has been imparted by the moisture imparting unit 78. As the moisture in the web W evaporates due to the heat of the heating unit 82, a plurality of fibers are bonded by hydrogen bonds. Thereby, a sheet S with good mechanical strength can be formed. Further, when a water-soluble polysaccharide is included as an additive, as the temperature of the moisture and the water-soluble polysaccharide rises due to the heat of the heating unit 82, the water-soluble polysaccharide gelatinizes, and then, as the moisture evaporates, a plurality of fibers are bonded via the gelatinized water-soluble polysaccharide. Thereby, a sheet S with better mechanical strength can be formed. Further, when a resin is included as an additive, the resin softens due to heat, and a plurality of fibers are bonded via the softened resin. Thereby, a sheet S with better mechanical strength can be formed.

[0050] The heating unit 82 has a first portion 84 that contacts the first surface Wa of the web W and a second portion 86 that contacts the second surface Wb of the web W. The first portion 84 and the moisture imparting unit 78 are provided on the first surface Wa side. In the illustrated example, the first portion 84 is provided below the web W, and the second portion 86 is provided above the web W.

[0051] The heating unit 82 is configured using, for example, a heating roller, a hot press molding machine, a hot plate, a hot air blower, an infrared heater, or a flash fuser. In the illustrated example, the heating unit 82 is a pair of rollers, the first portion 84 is one of the pair of rollers, and the second portion 86 is the other of the pair of rollers. The rollers constituting the first portion 84 and the second portion 86 are, for example, those in which a rubber layer is formed on an aluminum core and a fluorine layer is formed on the surface of the rubber layer. By configuring the heating unit 82 as a pair of rollers, the sheet S can be formed while continuously conveying the web W, as compared with the case where the heating unit 82 is configured as a plate-shaped pressing device.

[0052] The heating unit 82 heats the web W in a state where the surface temperature of the first portion 84 is higher than the surface temperature of the second portion 86. The surface of the first portion 84 refers to the surface that contacts the web W of the first portion 84. The surface of the second portion 86 refers to the surface that contacts the web W of the second portion 86.

[0053] The heating unit 82 heats the web W in a state where the surface temperature of the first portion 84 is, for example, 80°C or higher and 130°C or lower, preferably 85°C or higher and 120°C or lower, more preferably 90°C or higher and 110°C or lower.

[0054] The heating unit 82 heats the web W in a state where the surface temperature of the second portion 86 is, for example, 100°C or higher and 160°C or lower, preferably 110°C or higher and 150°C or lower, more preferably 120°C or higher and 140°C or lower.

[0055] The heating unit 82 heats the web W in a state where the difference between the surface temperature of the first portion 84 and the surface temperature of the second portion 86 is, for example, 10°C or higher and 50°C or lower, preferably 15°C or higher and 40°C or lower, more preferably 20°C or higher and 30°C or lower.

[0056] The heating unit 82 heats the web W in a state where the sum of the surface temperature of the first portion 84 and the surface temperature of the second portion 86 is, for example, 180°C or higher and 240°C or lower, preferably 210°C or higher and 240°C or lower, more preferably 230°C or higher and 240°C or lower.

[0057] The heating unit 82 further presses the web W to which moisture has been applied. In the illustrated example, the heating unit 82 presses the web W by sandwiching it between the first portion 84 and the second portion 86. The heating unit 82 presses the web W at a pressure of, for example, 0.2 MPa or higher and 10 MPa or lower, preferably 0.3 MPa or higher and 5 MPa or lower, more preferably 0.4 MPa or higher and 1 MPa or lower. In the illustrated example, since the sheet manufacturing apparatus 100 has a function of the heating unit 82 pressing the web W, it does not have a mechanism for separately pressing the web W.

[0058] 1.5. Effects In the sheet manufacturing apparatus 100, there are included a deposition unit 60 that deposits defibrated materials in a dry state to form a web W, a moisture application unit 78 that applies moisture from one surface Wa side of the formed web W to make the moisture content of the web W 12 mass% or more and 40 mass% or less, and a heating unit 82 that heats the web to which moisture has been applied. The heating unit 82 has a first portion 84 that contacts one surface Wa of the web W and a second portion 86 that contacts the other surface Wb of the web W, and the heating unit 82 heats the web W in a state where the surface temperature of the first portion 84 is higher than the surface temperature of the second portion 86.

[0059] Therefore, in the sheet manufacturing apparatus 100, as shown in the examples and comparative examples described later, for example, compared with the case where the web W is heated in a state where the surface temperature of the first portion and the surface temperature of the second portion are the same, the amount of paper dust generated in the sheet S can be reduced. In the sheet manufacturing apparatus 100, by heating the side of the surface Wa with a larger amount of moisture at a higher temperature than the side of the other surface Wb, an appropriate amount of water can be obtained to generate hydrogen bonds on the side of the surface Wa and the side of the other surface Wb. This enables a plurality of fibers to be firmly bonded by hydrogen bonds, and the amount of paper dust can be reduced.

[0060] In the sheet manufacturing apparatus 100, the heating unit 82 heats the web W in a state where the difference between the surface temperature of the first portion 84 and the surface temperature of the second portion 86 is 10°C or more and 50°C or less. Therefore, in the sheet manufacturing apparatus 100, the amount of paper dust can be made even less.

[0061] In the sheet manufacturing apparatus 100, the heating unit 82 heats the web W in a state where the sum of the surface temperature of the first portion 84 and the surface temperature of the second portion 86 is 180°C or higher and 240°C or lower. By setting the sum of the surface temperature of the first portion 84 and the surface temperature of the second portion 86 to 180°C or higher, the production efficiency of the sheet S can be increased. When the sum of the surface temperature of the first portion 84 and the surface temperature of the second portion 86 is less than 180°C, the hydrogen bonds cannot be sufficiently generated unless the passing speed of the web W in the heating unit 82 is reduced, resulting in low production efficiency. By setting the sum of the surface temperature of the first portion 84 and the surface temperature of the second portion 86 to 240°C or lower, the amount of paper dust can be further reduced.

[0062] In the sheet manufacturing apparatus 100, the heating unit 82 pressurizes the web W at a pressure of 0.2 MPa or higher and 10 MPa or lower. Therefore, in the sheet manufacturing apparatus 100, there is no need to separately provide a mechanism for pressurizing the web W, and the apparatus can be downsized. Furthermore, by pressurizing the web W at a pressure of 0.2 MPa or higher, the strength of the sheet S can be increased. By pressurizing the web W at a pressure of 10 MPa or lower, the deterioration of the fibers can be suppressed. Therefore, the sheet can be manufactured again using the defibrated product obtained by defibrating the manufactured sheet as a raw material.

[0063] The sheet manufacturing apparatus 100 includes an additive supply unit 52 as a binder application unit that applies a binder to at least one of the defibrated product and the web W. Therefore, in the sheet manufacturing apparatus 100, the strength of the sheet S can be increased.

[0064] In the sheet manufacturing apparatus 100, the moisture application unit 78 applies water vapor or mist to the web W. Therefore, in the sheet manufacturing apparatus 100, the web W can be uniformly supplied with moisture.

[0065] The sheet manufacturing apparatus 100 includes a cutting unit 90 that cuts the heated web W. In the sheet manufacturing apparatus 100, since the heating unit 82 heats the web W in a state where the surface temperature of the first portion 84 is higher than the surface temperature of the second portion 86, even if the heated web W is cut by the cutting unit 90, the amount of paper dust generated can be reduced.

[0066] 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 using, for example, the above-described sheet manufacturing apparatus 100.

[0067] As shown in FIG. 2, the sheet manufacturing method according to the present embodiment includes, for example, a step of depositing defibrated materials in a dry state to form a web W (step S1), a step of applying moisture from one surface Wa side of the formed web W to make the moisture content of the web W 12% by mass or more and 40% by mass or less (step S2), a step of heating the web W with moisture applied by a heating unit 82 (step S3), and a step of cutting the heated web W (step S4).

[0068] The step of forming the web W (step S1) can be performed by, for example, the deposition unit 60 of the sheet manufacturing apparatus 100.

[0069] The step of applying moisture from one surface Wa side of the formed web W (step S2) can be performed by, for example, the moisture application unit 78 of the sheet manufacturing apparatus 100.

[0070] In the step of heating with the heating unit 82 (step S3), the web W is heated in a state where the surface temperature of the first portion 84 is higher than the surface temperature of the second portion 86.

[0071] The step of cutting the heated web W (step S4) can be performed by, for example, the cutting unit 90 of the sheet manufacturing apparatus 100.

[0072] The sheet manufacturing method according to this embodiment may include a step of applying a binder to at least one of the defibrated material and the web W before the step of heating the web W. The step of applying the binder can be performed, for example, by the additive supply unit 52 of the sheet manufacturing apparatus 100.

[0073] Furthermore, the sheet manufacturing method of this embodiment may include, in addition to the above-described steps, for example, a defibrating step, a sorting step, and the like. These steps can be performed by the defibrating unit 20, the sorting unit 40, etc. of the sheet manufacturing apparatus 100.

[0074] 3. Examples and Comparative Examples 3.1. Production of Sheets Sheets were produced using an apparatus corresponding to the above-described sheet manufacturing apparatus 100. Specifically, the defibrated material was deposited dry to form a web, moisture was applied to the web from the moisture application unit, and then the web with moisture applied was pressurized and heated by the heating unit to produce a sheet. The moisture was applied from the lower side of the web. Also, sheets were produced separately in cases where a binder was applied to the defibrated material and where no binder was applied.

[0075] As the raw material, Fuji Film Business Innovation's recycled paper GR70W (basis weight 67 g / cm 2 ) was used. The moisture application unit injected ultrasonic mist from the lower side of the web so that the moisture content of the sheet would be 20% by mass. As the binder, starch "Lastergen FK" manufactured by Nisshin Chemical Co., Ltd. was used. 13% by mass of the binder was applied based on the total amount of the defibrated material before moisture was applied. As the heating unit, a pair of rollers with a rubber layer and a fluorine layer formed on an aluminum mandrel with a diameter of 100 mm was used. The web was sandwiched between the pair of rollers and the web was pressurized at a pressure of 0.6 MPa. The surface temperature of the rollers was varied.

[0076] 3.2. Evaluation Method The amount of paper dust of the sheets produced as described above was measured. FIG. 3 is a diagram for explaining the method of measuring the amount of paper dust of the produced sheets.

[0077] As shown in FIG. 3, the fabricated sheet S was cut out into pieces of 50 mm × 25 mm. Further, a self-adhesive film F manufactured by Panasonic Industry Co., Ltd. was cut out into pieces of 20 mm × 40 mm.

[0078] Next, the sheet S was sandwiched between the protective film and the base film of the self-adhesive film F, and without heating, the self-adhesive film F was pressed at 10 kN for 3 seconds using a hand press. Then, within 3 minutes after the pressing, while holding up the self-adhesive film F, the right half of the sheet S was held and the sheet S was vigorously peeled upward. Next, the surface of the base film was protected again with the protective film.

[0079] Next, the brightness of the digital microscope "VHX-5000" manufactured by Keyence Corporation was set to "Manual 6 msec", and the base film was observed at a magnification of 20 times, and an image was acquired. Next, HDR (High Dynamic Range) image processing was performed on the acquired image, and then automatic area measurement processing was performed to measure the area, and the image was saved. The HDR image processing was performed under the condition of "brightness / texture / contrast / color = 30 / 0 / 100 / 0". The automatic area measurement processing was performed under the condition of "brightness 90-255, maximum area > 2500". Regarding the brightness of the HDR image processing and the automatic area measurement processing, when there was a lot of noise, it was adjusted each time. Next, binarization processing was performed on the saved image, the number of paper dust particles was calculated, and the amount of paper dust was obtained. The evaluation criteria for the amount of paper dust are as follows.

[0080] A: 120 or less

[0081] B: More than 121 and less than or equal to 150 C: More than 151 and less than or equal to 200 D: 201 or more.

[0082] 3.3. Evaluation Results FIG. 4 is a table showing the evaluation results of the amount of paper dust of the fabricated sheet.

[0083] In FIG. 4, "Tu" represents the surface temperature of the upper roller among a pair of rollers (hereinafter also referred to as "upper roller temperature"). "Td" represents the surface temperature of the lower roller among a pair of rollers (hereinafter also referred to as "lower roller temperature"). "Td - Tu" represents the value obtained by subtracting the upper roller temperature from the lower roller temperature. "Td + Tu" represents the total value of the lower roller temperature and the upper roller temperature.

[0084] As shown in FIG. 4, in Examples 1 to 5 where the lower roller temperature is higher than the upper roller temperature, the amount of paper dust was less compared to Comparative Example 1 where the lower roller temperature and the upper roller temperature are the same, and Comparative Example 2 where the upper roller temperature is higher than the lower roller temperature. Thus, it was found that the amount of paper dust can be reduced by making the temperature of the roller on the side where moisture is applied higher than the temperature of the roller on the side where moisture is not applied.

[0085] Also, in Examples 2 and 4 where the difference between the lower roller temperature and the upper roller temperature is 20°C and 30°C respectively, the amount of paper dust was less than that in Examples 1, 3, and 5. Thus, it was found that the amount of paper dust can be further reduced by setting the difference between the lower roller temperature and the upper roller temperature to be 20°C or more and 30°C or less.

[0086] The present invention includes configurations that are substantially the same as the configurations described in the embodiments, for example, configurations having the same functions, methods, and results, or configurations having the same objectives and effects. In addition, the present invention includes configurations in which non-essential parts of the configurations described in the embodiments are replaced. Further, the present invention includes configurations that exhibit the same operational effects as the configurations described in the embodiments or configurations that can achieve the same objectives. Also, the present invention includes configurations in which known technologies are added to the configurations described in the embodiments.

[0087] The following content is derived from the above-described embodiments.

[0088] One aspect of the sheet manufacturing apparatus is a deposition unit that dry-deposits defibrated materials to form a web, A moisture-imparting section that imparts moisture from one surface side of the formed web to make the moisture content of the web 12% by mass or more and 40% by mass or less; A heating section that heats the web imparted with moisture; comprising The heating section has a first portion that contacts one surface of the web, and a second portion that contacts the other surface of the web; and the heating section heats the web in a state where the surface temperature of the first portion is higher than the surface temperature of the second portion.

[0089] According to this sheet manufacturing apparatus, the amount of paper dust can be reduced.

[0090] In one aspect of the sheet manufacturing apparatus, the heating section may heat the web in a state where the difference between the surface temperature of the first portion and the surface temperature of the second portion is 10°C or more and 50°C or less.

[0091] According to this sheet manufacturing apparatus, the amount of paper dust can be made even less.

[0092] In one aspect of the sheet manufacturing apparatus, the heating section may heat the web in a state where the sum of the surface temperature of the first portion and the surface temperature of the second portion is 180°C or more and 240°C or less.

[0093] According to this sheet manufacturing apparatus, the production efficiency can be increased and the amount of paper dust can be made even less.

[0094] In one aspect of the sheet manufacturing apparatus, the heating section may press the web at a pressure of 0.2 MPa or more and 10 MPa or less.

[0095] According to this sheet manufacturing apparatus, there is no need to separately provide a mechanism for pressing the web, and the apparatus can be downsized.

[0096] In one aspect of the sheet manufacturing apparatus, it may include a binder application unit that applies a binder to at least one of the defibrated material and the web.

[0097] According to this sheet manufacturing apparatus, the strength of the sheet can be increased.

[0098] In one aspect of the sheet manufacturing apparatus, the moisture application unit may apply water vapor or mist to the web.

[0099] According to this sheet manufacturing apparatus, moisture can be uniformly applied to the web.

[0100] In one aspect of the sheet manufacturing apparatus, it may include a cutting unit that cuts the heated web.

[0101] According to this sheet manufacturing apparatus, since the heating unit heats the web in a state where the surface temperature of the first part is higher than the surface temperature of the second part, even if the heated web is cut by the cutting unit, the amount of paper dust generated can be reduced.

[0102] One aspect of the sheet manufacturing method is a step of depositing the defibrated material dry to form a web, a step of applying moisture from one surface side of the formed web to make the moisture content of the web 12% by mass or more and 40% by mass or less, a step of heating the web with moisture applied thereto by a heating unit, and includes the heating unit has a first part that contacts one surface of the web, and a second part that contacts the other surface of the web, and in the step of heating by the heating unit, Heat the web with the surface temperature of the first part being higher than that of the second part.

[0103] According to this sheet manufacturing method, the amount of paper dust can be reduced.

[0104] In one aspect of the sheet manufacturing method, Before the step of heating by the heating unit, a step of applying a binder to at least one of the defibrated material and the web may be included.

[0105] According to this sheet manufacturing method, the strength of the sheet can be increased.

[0106] In one aspect of the sheet manufacturing method, A step of cutting the heated web may be included.

[0107] According to this sheet manufacturing method, since the heating unit heats the web with the surface temperature of the first part being higher than that of the second part, even if the heated web is cut by the cutting unit, the amount of paper dust generated can be reduced.

Explanation of reference numerals

[0108] 1... Hopper, 2, 3, 7, 8... Tubes, 9... Hopper, 10... Supply unit, 12... Crushing unit, 14... Crushing blade, 20... Defibrating unit, 22... Inlet, 24... Outlet, 40... Sorting unit, 41... Drum unit, 42... Inlet, 43... Housing unit, 44... Outlet, 45... First web forming unit, 46... Mesh belt, 47, 47a... Tension rollers, 48... Suction mechanism, 49... Rotating body, 49a... Base, 49b... Protrusion, 50... Mixing unit, 52... Additive supply unit, 54... Tube, 56... Blower, 60... Deposition unit, 61... Drum unit, 62... Inlet, 63... Housing unit, 70... Second web forming unit, 72... Mesh belt, 74... Tension roller, 76... Suction mechanism, 78... Moisture application unit, 80... Sheet forming unit, 82... Heating unit, 84... First part, 86... Second part, 90... Cutting unit, 92... First cutting unit, 94... Second cutting unit, 96... Discharge receiving unit, 100... Sheet manufacturing apparatus

Claims

1. A deposition section that dry-deposits defibrated material to form a web, a moisture application section that applies moisture from one surface side of the formed web to make the moisture content of the web 12% by mass or more and 40% by mass or less, a heating section that heats the web to which moisture has been applied, comprising, the heating section has a first portion that contacts one surface of the web, and a second portion that contacts the other surface of the web, and has, the heating section heats the web in a state where the surface temperature of the first portion is 10°C or more and 50°C or less higher than the surface temperature of the second portion, a sheet manufacturing apparatus.

2. In claim 1, the heating section heats the web in a state where the difference between the surface temperature of the first portion and the surface temperature of the second portion is 20°C or more, a sheet manufacturing apparatus.

3. In claim 1 or 2, the heating section heats the web in a state where the difference between the surface temperature of the first portion and the surface temperature of the second portion is 30°C or less, a sheet manufacturing apparatus.

4. In any one of claims 1 to 3, the heating section heats the web in a state where the sum of the surface temperature of the first portion and the surface temperature of the second portion is 180°C or more and 240°C or less, a sheet manufacturing apparatus.

5. In any one of claims 1 to 4, the surface temperature of the first portion of the heating section is 130°C and the surface temperature of the second portion is 100°C or more and 110°C or less, a sheet manufacturing apparatus.

6. In any one of claims 1 to 5, a binder application section that applies a water-soluble polysaccharide to at least one of the defibrated material and the web, a sheet manufacturing apparatus.

7. In any one of claims 1 to 6, a sheet manufacturing apparatus including a defibrating section that defibrates waste paper or a pulp sheet to create defibrated material.

8. A step of dry-depositing defibrated material to form a web, a step of applying moisture from one surface side of the formed web to make the moisture content of the web 12% by mass or more and 40% by mass or less, a step of heating the web to which moisture has been applied by a heating section, comprising, the heating section has a first portion that contacts one surface of the web, and a second portion that contacts the other surface of the web, and has, in the step of heating by the heating section, the web is heated in a state where the surface temperature of the first portion is 10°C or more and 50°C or less higher than the surface temperature of the second portion, a sheet manufacturing method.

9. In claim 8, A sheet manufacturing method including a step of cutting the heated web.

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