SHEET MANUFACTURING METHOD AND SHEET MANUFACTURING APPARATUS

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 technology]

[0002] For the purpose of 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 defibration step in which the defibrated material is defibrated in the atmosphere, a mixing step in which an additive containing a resin is mixed with the defibrated material in the atmosphere, a humidity adjustment step in which the humidity of the mixture of the defibrated material and the additive is adjusted, and a heating step in which the humidity-adjusted mixture is heated. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-137437 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in Patent Document 1, a resin was required as a binder to produce a sheet having sufficient strength. In recent years, there has been a demand for a method of producing a sheet having sufficient strength without using a resin. [Means for solving the problem]

[0006] One aspect of the sheet manufacturing method according to the present invention is to a web forming step of depositing the defibrated material in a dry manner to form a web; a moisture imparting step of imparting moisture to the web; a pressurizing step of pressing the web to which moisture has been added; a heating step of heating the web to which moisture has been added; Including, The moisture content of the web to which moisture has been added in the moisture adding step is 12% by mass or more; The pressure applied to the web in the pressurizing 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 to a web forming section that deposits the defibrated material in a dry manner to form a web; A moisture applying unit that applies moisture to the web; a pressurizing unit that pressurizes the web to which moisture has been added; A heating section that heats the web to which moisture has been added; Including, The moisture content of the web to which moisture has been added in the moisture adding section is 12% by mass or more, The pressure applied to the web in the pressurizing section is 0.2 MPa or more, The temperature of the web in the heating section is 100° C. or less. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating a sheet manufacturing apparatus according to an embodiment of the present invention. [Diagram 2] 4 is a flowchart illustrating a sheet manufacturing method according to the embodiment. [Diagram 3] 1 is a table showing preparation conditions and evaluation results. [Figure 4] FIG. 4 is a diagram for explaining a method of calculating the density of a sheet. [Diagram 5] FIG. 4 is a diagram for explaining a method of calculating a seat temperature. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Preferred embodiments of the present invention will be described in detail below with reference to the drawings. Note that the embodiments described below do not unduly limit the contents of the present invention described in the claims. In addition, not all of the configurations described below are necessarily essential components of the present invention.

[0010] The sheet manufacturing method according to this embodiment includes a web forming step of dry-accumulating defibrated material to form a web, a moisture imparting step of imparting moisture to the web, a pressurizing step of pressurizing the moisture-imparted web, and a heating step of heating the moisture-imparted web. Hereinafter, first, an example of a sheet manufacturing apparatus capable of implementing the sheet manufacturing method according to this embodiment will be described, and then the sheet manufacturing method will be described.

[0011] 1. Sheet manufacturing equipment 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 schematic diagram 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 section 10, a crushing section 12, a defibrating section 20, a sorting section 40, a first web forming section 45, a rotating body 49, a mixing section 50, a deposition section 60, a second web forming section 70, a sheet forming section 80, and a cutting section 90.

[0013] The supply unit 10 supplies raw material to the crushing unit 12. The supply unit 10 is, for example, an automatic input unit for continuously inputting raw material to the crushing unit 12. The raw material supplied by the supply unit 10 is, for example, a fiber-containing raw material such as waste paper or a pulp sheet.

[0014] The crushing unit 12 cuts the raw material supplied by the supply unit 10 into small pieces in air, such as the atmosphere. The small pieces have a shape and size of, for example, several centimeters square. In the example shown in the figure, the crushing unit 12 has crushing blades 14, which can cut the input raw material. For example, a shredder is used as the crushing unit 12. The raw material cut by the crushing unit 12 is received in a hopper 1 and then transferred to the defibrating unit 20 via a pipe 2.

[0015] The defibrating unit 20 defibrates the raw material cut by the coarse crushing unit 12. Here, "defibrating" refers to unraveling the raw material, which is made up of multiple fibers bound together, into individual fibers. The defibrating unit 20 also has the function of separating substances such as resin particles, ink, toner, and anti-bleeding agents attached to the raw material from the fibers.

[0016] The material that has passed through the defibration unit 20 is called the "defibrated material." In addition to the defibrated material fibers, the "defibrated material" may also contain additives such as resin particles that have separated from the fibers when the fibers are defibrated, coloring agents such as ink and toner, and anti-bleeding agents and paper strength enhancers. The defibrated material has a string-like shape. The defibrated material may exist in a state where it is not entangled with other defibrated fibers, i.e., in an independent state, or it may exist in a state where it is entangled with other defibrated material and forms a lump, i.e., in a state where it forms lumps.

[0017] The defibrator unit 20 performs defibration in a dry manner. Here, the term "dry manner" refers to processing such as defibration in air, such as in the atmosphere, rather than in a liquid. An impeller mill, for example, is used as the defibrator unit 20. The defibrator unit 20 has the function of sucking in the raw material and generating an airflow that discharges the defibrated material. As a result, the defibrator unit 20 uses the airflow it generates to blow the raw material through the inlet 22. The raw material can be sucked in together with the airflow from the defibrator, defibrated, and transported to the discharge outlet 24. The defibrated material that has passed through the defibrator unit 20 is transferred to the sorting unit 40 via the pipe 3. The airflow for transporting the defibrated material from the defibrator unit 20 to the sorting unit 40 may be an airflow generated by the defibrator unit 20, or an airflow generating device such as a blower may be provided and that airflow may be used.

[0018] The sorting unit 40 introduces the defibrated material defibrated by the defibration unit 20 from an inlet 42 and sorts it according to the length of the fibers. The sorting unit 40 has, for example, a drum unit 41 and a housing unit 43 that houses the drum unit 41. For example, a sieve is used as the drum unit 41. The drum unit 41 has a net and can separate fibers or particles smaller than the size of the mesh of the net, i.e., a first sorted material that passes through the net, from fibers, undefibrated pieces, and lumps larger than the size of the mesh of the net, i.e., a second sorted material that does not pass through the net. For example, the first sorted material is transferred to the deposition unit 60 via a pipe 7. The second sorted material is returned to the defibration unit 20 from the discharge port 44 via a pipe 8. Specifically, the drum unit 41 is a cylindrical sieve that is rotated by a motor. The mesh of the drum portion 41 may be, for example, a wire mesh, an expanded metal made by stretching a metal plate with slits, or a punched metal made by forming holes in a metal plate using a press or the like.

[0019] 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 tension roller 47, and a suction mechanism 48.

[0020] The suction mechanism 48 can suck the first sorted material that has passed through the openings of the sorting unit 40 and been dispersed in the air onto the mesh belt 46. The first sorted material is deposited on the moving mesh belt 46 to form a web V. The basic configurations of the mesh belt 46, tension roller 47, and suction mechanism 48 are similar to those of the mesh belt 72, tension roller 74, and suction mechanism 76 of the second web forming unit 70, which will be described later.

[0021] The web V is formed into a soft and puffy state containing a lot of air by passing through the screening unit 40 and the first web forming unit 45. The web V accumulated on the mesh belt 46 is input into the pipe 7 and transported to the accumulation unit 60.

[0022] The rotating body 49 can cut the web V. In the illustrated example, the rotating body 49 has a base 49a and protrusions 49b protruding 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 provided at equal intervals. By rotating the base 49a in the direction R, the protrusions 49b can rotate around the base 49a as an axis. By cutting the web V with the rotating body 49, for example, it is possible to reduce the fluctuation in the amount of defibrated material supplied per unit time to the deposition section 60.

[0023] The rotating body 49 is provided in the vicinity of the first web forming section 45. In the illustrated example, the rotating body 49 is provided in the vicinity of the tension roller 47a located downstream in the path of the web V. The rotating body 49 is provided in a position where the protrusions 49b can contact the web V but do not contact the mesh belt 46 on which the web V is deposited. This makes it possible to prevent the mesh belt 46 from being worn by the protrusions 49b. The shortest distance between the protrusions 49b and the mesh belt 46 is, for example, 0.05 mm or more and 0.5 mm or less. This is the 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 with an additive. The mixing section 50 has, for example, an additive supply section 52 that supplies the additive, a pipe 54 that transports the first sorted material and the additive, and a blower 56. In the illustrated example, the additive is The material is supplied from the supply section 52 through the hopper 9 to the pipe 54. The pipe 54 is continuous with the pipe 7.

[0025] In the mixing section 50, an air flow is generated by a blower 56, and the first sorted material and the additives can be transported while being mixed in the pipe 54. The mechanism for mixing the first sorted material and the additives is not particularly limited, and may be one that uses a blade that rotates at high speed to mix, or one that utilizes the rotation of a container such as a V-type mixer.

[0026] The additive supplying section 52 may be a screw feeder as shown in FIG. 1 or a disk feeder (not shown).

[0027] The additive supplied from the additive supply unit 52 is not particularly limited, and may include, for example, a resin for binding a plurality of fibers, a water-soluble polysaccharide such as starch, etc. In this case, the additive may include a resin, but it is preferable that the additive does not include a resin in order to further improve the environmental compatibility of the sheet.

[0028] When the additive supplied from the additive supply unit 52 contains a resin, the fibers are not bonded together at the time the additive is supplied. The resin is a thermoplastic resin or a thermosetting resin, such as an AS (Acrylonitrile Styrene) resin, an ABS (Acrylonitrile Butadiene Styrene) resin, polypropylene, polyethylene, polyvinyl chloride, polystyrene, an 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 in appropriate mixture. The additive supplied from the additive supply unit 52 may be in the form of a fiber or a powder.

[0029] The additives supplied from the additive supply unit 52 may contain a colorant for coloring the fibers, an aggregation inhibitor for inhibiting aggregation of the fibers and the additives, and a flame retardant for making the fibers, etc. less flammable, depending on the type of sheet to be manufactured. The mixture that has passed through the mixing unit 50 is transferred to the deposition unit 60 via a pipe 54.

[0030] The deposition unit 60 introduces the mixture that has passed through the mixing unit 50 from an inlet 62, loosens the tangled defibrated material, and drops it while dispersing it in the air. Furthermore, when the resin of the additive supplied from the additive supply unit 52 is fibrous, the deposition unit 60 loosens the tangled resin. This allows the deposition unit 60 to deposit the mixture in 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. A rotating cylindrical sieve is used as the drum unit 61. The drum unit 61 has a mesh and causes fibers or particles smaller than the mesh size contained in the mixture that has passed through the mixing unit 50 to fall. The configuration of the drum unit 61 is the same as that of the drum unit 41, for example.

[0032] The "sieve" of the drum unit 61 does not have to have the function of separating out a specific object. In other words, the "sieve" used as the drum unit 61 means one equipped with a net, and the drum unit 61 may allow all of the mixture introduced into the drum unit 61 to fall.

[0033] The second web forming section 70 accumulates the material that has passed through the accumulation section 60 to form a web W. The second web forming section 70 has, for example, a mesh belt 72, a tension roller 74, and a suction mechanism 76.

[0034] Materials passing through the openings of the deposition section 60 are deposited on the mesh belt 72. The mesh belt 72 is stretched by tension rollers 74 and is configured to prevent materials from passing through but allow air to pass through. The mesh belt 72 moves as the tension rollers 74 rotate. Materials passing through the deposition section 60 are continuously deposited on the mesh belt 72 while the mesh belt 72 is continuously moving, forming a web W 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. The suction mechanism 76 can suck the mixture dispersed in the air by the deposition unit 60 onto the mesh belt 72. This can increase the discharge speed from the deposition unit 60. Furthermore, the suction mechanism 76 can form a downflow in the falling path of the mixture, preventing the defibrated material and additives from becoming entangled during the fall.

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

[0037] Moisture is added to the accumulated web W while it is being transported to the sheet forming unit 80. The moisture is added by a moisture adding unit 78. The moisture adding unit 78 adds moisture to the web W so that the web W has a predetermined moisture content, and can be configured by, for example, steam, mist, shower, inkjet, or the like. In the illustrated example, a suction mechanism 79 is provided at a position facing the moisture adding unit 78 with the web W sandwiched therebetween. The suction mechanism 79 can generate an airflow that faces downward. The suction mechanism 79 can suck the moisture generated from the moisture adding unit 78 by passing it through the web W. This allows moisture to be added more uniformly in the thickness direction of the web W.

[0038] The web W to which moisture has been applied by the moisture applying unit 78 is transported to the sheet forming unit 80.

[0039] The sheet forming unit 80 pressurizes and heats the web W deposited on the mesh belt 72 to form a sheet S. In the sheet forming unit 80, pressure and heat are applied to the mixture of defibrated material and additives that have been mixed, deposited, and given moisture. In the sheet forming unit 80, the thickness of the web W is reduced to increase the density, and moisture evaporates. The density is increased by pressure, and moisture evaporates by heat, so that multiple fibers are bonded by hydrogen bonds. This makes it possible to form a sheet S with good mechanical strength. Furthermore, in the case where water-soluble polysaccharide is included as an additive, the density is increased by pressure, and the temperature of the moisture and water-soluble polysaccharide is increased by heat, so that the water-soluble polysaccharide is gelatinized, and then the moisture evaporates, so that multiple fibers are bonded via the gelatinized water-soluble polysaccharide. This makes it possible to form a sheet S with better mechanical strength. Furthermore, in the case where resin is included as an additive, the resin is softened by heat, and multiple fibers are bonded via the softened resin. This makes it possible to form a sheet S with better mechanical strength.

[0040] The sheet forming unit 80 has a pressurizing and heating unit 84 that pressurizes and heats the web W. The pressurizing and 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 pressurizing and heating unit 84 can be configured using, for example, a heating roller or a heat press molding machine. When the pressurizing unit and the heating unit are provided as separate mechanisms, the heating unit can be configured using a hot plate, a hot air blower, an infrared heater, and a flash fixing unit in addition to the above-mentioned mechanisms. In the illustrated example, the pressurizing and heating unit 84 is a pair of heating rollers 86. There is no particular limitation on the number of heat rollers 86. The pressurizing and 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 has a first cutting unit 92 that cuts the sheet S in a direction intersecting the conveying direction of the sheet S, and a second cutting unit 94 that cuts the sheet S in a direction parallel to the conveying direction. The second cutting unit 94 cuts the sheet S that has passed through the first cutting unit 92, for example.

[0043] In this manner, a single sheet S of a predetermined size is formed. The cut single sheet S is discharged to a discharge receiving portion 96.

[0044] 2. Sheet manufacturing method Next, a 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, by using the sheet manufacturing apparatus 100 described above.

[0045] As shown in FIG. 2, the sheet manufacturing method according to this embodiment includes a web formation step (step S1) of dry-stacking defibrated material to form a web, a binder addition step (step S2) of adding a binder to at least one of the defibrated material and the web, a moisture addition step (step S3) of adding moisture to the web, a pressurizing step (step S4) of pressing the web to which moisture has been added, and a heating step (step S5) of heating the web to which moisture has been added.

[0046] 2.1. Web forming process In the web forming process, the defibrated material is deposited in a dry manner to form a web. When using the above-mentioned sheet manufacturing apparatus 100, the defibrated material is formed by the defibrated unit 20. The deposition unit 60 and the second web forming unit 70 deposit the defibrated material in a dry manner to form a web.

[0047] The defibrated material includes fibers. The fibers are not particularly limited, and a wide variety of fiber materials can be used. Examples of fibers include natural fibers (animal fibers, plant fibers), chemical fibers (organic fibers, inorganic fibers, organic-inorganic composite fibers), and the like. More specifically, examples of fibers include fibers made of cellulose, silk, wool, cotton, hemp, kenaf, flax, ramie, jute, Manila hemp, sisal, coniferous trees, broadleaf trees, and the like, and these may be used alone or in appropriate mixtures, or may be used as regenerated fibers that have been purified, etc. The fibers used in the sheet manufacturing method of this embodiment have the ability to form hydrogen bonds.

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

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

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

[0051] The binder adding step does not have to be performed. By not performing the binder adding 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 adding step is performed, a stronger sheet can be manufactured. Furthermore, the binder adding step may be performed after the moisture imparting step, as long as it is performed before the pressurizing step and the heating step.

[0052] 2.3. Moisture addition process In the moisture imparting step, moisture is imparted to the web. Specifically, in the moisture imparting step, water is imparted to the web. When the above-described sheet manufacturing apparatus 100 is used, moisture can be imparted to the web by the moisture imparting unit 78.

[0053] The amount of water added in the moisture adding step can be controlled, for example, by the moisture content of the web. The moisture content of the web to which moisture has been added in the moisture adding 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 even more preferably 15% by mass or more and 30% by mass or less.

[0054] In addition, in the moisture imparting step, it is preferable to impart water vapor or mist to the web, which allows moisture to be imparted more uniformly onto the web and enables the sheet to be produced with a simpler device configuration.

[0055] 2.4. Pressurization process In the pressurizing step, the web to which moisture has been imparted is pressed. The pressurizing step can be performed by the sheet forming unit 80 when the above-mentioned sheet manufacturing apparatus 100 is used.

[0056] The pressing step applies pressure to the web to thin the web and increase the density of the web. The pressure applied to the web by the pressing step 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 even more preferably 0.4 MPa or more and 2.0 MPa or less.

[0057] 2.5. Heating process In the heating step, the web to which moisture has been added is heated. When the above-mentioned sheet manufacturing apparatus 100 is used, the heating step can be performed by the sheet forming unit 80. The pressurizing step and the heating step are performed, for example, simultaneously. This makes the manufacturing method simpler and simplifies the configuration of the apparatus that performs the manufacturing method. Note that the pressurizing step and the heating step do not have to be performed simultaneously. In this case, the heating step may be performed after the pressurizing step, or the pressurizing step may be performed after the heating step.

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

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

[0060] 2.7. Effects The sheet manufacturing method of the present embodiment includes a web forming step of dry-accumulating defibrated material to form a web, a moisture imparting step of imparting moisture to the web, a pressurizing step of pressurizing the moisture-imparted web, and a heating step of heating the moisture-imparted web. The moisture content of the web imparted with moisture in the moisture imparting step is 12 mass% or more, the pressure applied to the web in the pressurizing step is 0.2 MPa or more, and the temperature of the web in the heating step is 100°C or less.

[0061] Therefore, in the sheet manufacturing method of this embodiment, multiple fibers contained in the defibrated material can be bonded by hydrogen bonds. This makes it possible to manufacture a sheet with sufficient strength without using resin. Specifically, hydrogen bonds can be formed between the fibers by increasing the moisture content of the web to 12% or more and then heating it at a temperature of 100°C or less. For example, if the web is heated at a temperature higher than 100°C, molecular motion becomes intense and hydrogen bonds are difficult to form. Furthermore, by increasing the moisture content of the web to 12% or more and then applying pressure, the density of the web can be increased at a lower pressure, and the device can be made smaller. Furthermore, by forming a web by piling the defibrated material in a dry manner, the amount of moisture used to form the web can be reduced compared to wet papermaking methods.

[0062] In the sheet manufacturing method of the present embodiment, the moisture content of the web to which moisture has been added in the moisture adding 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 the present 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 produced sheet can be defibrated to obtain defibrated material, which can be used as a raw material to manufacture a sheet again.

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

[0065] 3. Examples and Comparative Examples 3.1. Sheet preparation A sheet was produced using an apparatus corresponding to the above-mentioned sheet manufacturing apparatus 100. Defibrated material was piled up in a dry manner to form a web, moisture was added to the web, and then the moisture-added web was pressurized and heated by a pair of rollers to produce a sheet. No binder such as resin or water-soluble polysaccharide was used. Pressurization and heating of the web were performed simultaneously.

[0066] FIG. 3 is a table showing the manufacturing conditions of sheets No. 1 to 10. As shown in FIG. 3, the amount of water applied (moisture content), pressure, and roller temperature were varied. The basis weight of sheets No. 1 to 10 was 80 g / cm. 2 The pressure was calculated based on the following formulas (1) and (2).

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

[0068] The nip width was measured by the following method. First, a pair of rollers was heated 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 removed. Next, the heated part of the laminate sheet became transparent, and the width of the transparent part was measured.

[0069] As shown in FIG. 4, the sheet temperature was measured by 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. FIG. 4 is a diagram for explaining a method of calculating the sheet density.

[0070] Measurement position Arrival time from nip exit E (s) Sheet temperature (℃) 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. An approximation curve was then created using a quadratic curve, and the temperature at x=0 (nip exit) was calculated. In the above example, the approximation curve is expressed by the following formula (3), and the sheet temperature, which is the intercept, was 85.9°C.

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

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

[0074] 3.2.1. Strength In this experimental example, the strength refers to the tensile strength index. A sheet piece measuring 10 mm wide and 50 mm long was cut out from the prepared sheet, and the tensile strength index was calculated based on the following formula (4). The tensile strength index was evaluated by a tensile test. The test equipment used was Shimadzu Corporation's "AGS-X500N." The tensile speed was 1 mm / s.

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

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

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

[0078] 3.2.2. Density A 30 mm x 200 mm piece was cut out from the prepared sheet, and the thickness and mass of the piece were measured to calculate the density using the following formula (5). The thickness was measured with a micrometer at five points on the piece as shown by the circles in Fig. 5, and the average value was calculated. 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 for 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 standard drying time was 0.8 seconds, and when drying was possible in 0.8 seconds, the drying time was left as it was (drying time 0.8 seconds). When the moisture content was too high to dry in 0.8 seconds, the rotation speed of the heating roller was reduced to extend the time the sheet passed through the nip of the heating roller. The rotation speed at which the moisture content of the dried sheet was 10% by 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] The moisture content was measured using an A&D MX-50. The heating pattern was set to a 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 and evaluated.

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

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

[0087] 3.2.4. Repeat playback The recycled paper was used as the raw material to make paper, and this process was repeated twice to measure the strength. In other words, paper was made three times in total. The strength measurement method was as described above. The strength ratio (RC3 strength / RC1 strength) of the once recycled RC1 and the three times recycled RC3 was calculated.

[0088] The evaluation criteria for repeat playback are as follows:

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

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

[0091] As shown in FIG. 3, sheet No. 1 received an "A" in all evaluation items, and had better evaluation results than sheets No. 2 to 10.

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

[0093] In the case of sheet No. 3, the sheet temperature was too high, so hydrogen bonds were not formed and the sheet had low strength and density.

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

[0095] Sheet No. 5 performed well the first time it was recycled, but because the pressure was too high, the fibers deteriorated and it received a poor evaluation after repeated recycling.

[0096] Sheet No. 6 had a low moisture content, which meant that hydrogen bonds were not formed and the sheet had low strength and density.

[0097] The No. 7 sheet had too much moisture, so water leaked out of the sheet at the nip, causing dripping, and it took a long time to dry.

[0098] The No.8 sheet had a low moisture content, so the strength was slightly low the first time. In addition, the pressure was high, so the evaluation of repeated regeneration was slightly poor.

[0099] The No.9 sheet had a slightly higher moisture content, so it took a little longer to dry.

[0100] Sheet No. 10 had a slightly higher moisture content but a slightly lower pressure, so the strength was slightly lower the first time. Repeated reuse was rated as good.

[0101] The present invention includes configurations that are substantially the same as the configurations described in the embodiments, for example, configurations with the same functions, methods, and results, or configurations with the same purpose and effects. The present invention also includes configurations in which non-essential parts of the configurations described in the embodiments are replaced. The present invention also includes configurations that achieve the same effects as the configurations described in the embodiments, or configurations that can achieve the same purpose. The present invention also includes configurations in which publicly known technology is added to the configurations described in the embodiments.

[0102] The following can be derived from the above-described embodiment.

[0103] One aspect of the sheet manufacturing method includes: a web forming step of depositing the defibrated material in a dry manner to form a web; a moisture imparting step of imparting moisture to the web; a pressurizing step of pressing the web to which moisture has been added; a heating step of heating the web to which moisture has been added; Including, The moisture content of the web to which moisture has been added in the moisture adding step is 12% by mass or more; The pressure applied to the web in the pressurizing 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 embodiment of the sheet manufacturing method, The moisture content of the web to which moisture has been added in the moisture adding 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 embodiment of the sheet manufacturing method, The pressure applied to the web in the pressing step may be 10 MPa or less.

[0108] According to this manufacturing method, a manufactured sheet is defibrated, and the defibrated material is used as a raw material to manufacture a sheet again.

[0109] In one embodiment 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 embodiment of the sheet manufacturing method, The pressurizing step and the heating step may be carried out simultaneously.

[0112] According to this manufacturing method, the configuration of the device for carrying out the manufacturing method can be simplified.

[0113] In one embodiment of the sheet manufacturing method, The method may include a binder adding step of adding a binder to at least one of the defibrated material and the web, prior to the pressurizing step and the heating step.

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

[0115] In one embodiment of the sheet manufacturing method, In the moisture imparting step, water vapor or mist may be imparted to the web.

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

[0117] One aspect of the sheet manufacturing apparatus is a web forming section that deposits the defibrated material in a dry manner to form a web; A moisture applying unit that applies moisture to the web; a pressurizing unit that pressurizes the web to which moisture has been added; A heating section that heats the web to which moisture has been added; Including, The moisture content of the web to which moisture has been added in the moisture adding section is 12% by mass or more, The pressure applied to the web in the pressurizing section is 0.2 MPa or more, The temperature of the web in the heating section 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] Reference Signs List 1...hopper, 2,3,7,8...pipe, 9...hopper, 10...supply section, 12...crushing section, 14...crushing blade, 20...defibration section, 22...inlet, 24...discharge outlet, 40...screening section, 41...drum section, 42...inlet, 43...housing section, 44...discharge outlet, 45...first web forming section, 46...mesh belt, 47,47a...tension roller, 48...suction mechanism, 49...rotating body, 49a...base, 49b...projection, 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 applying section, 79... suction mechanism, 80... sheet forming section, 84... pressure 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 process in which a mixture of defibrated material containing cellulose fibers and a binder is added thereto is dry-laid to form a web; a moisture imparting step of imparting moisture to the web; a pressurizing step of pressing the web to which moisture has been added; a heating step of heating the web to which moisture has been added; Including, The moisture content of the web to which moisture has been added in the moisture adding step is 12% by mass or more, The pressure applied to the web in the pressurizing step is 0.2 MPa or more, The temperature of the web in the heating step is 100° C. or less, The sheet manufacturing method, wherein the binder is a water-soluble polysaccharide.

2. In claim 1, The moisture content of the web to which moisture has been added in the moisture adding step is 40 mass % or less.

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

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

5. In any one of claims 1 to 4, The sheet manufacturing method, wherein the pressurizing step and the heating step are carried out simultaneously.

6. In any one of claims 1 to 5, The sheet manufacturing method, wherein the moisture imparting step applies water vapor or mist to the web.

7. A mixing section that adds a binder to defibrated material containing cellulose fibers to generate a mixture; a web former for dry-laying the mixture to form a web; A moisture applying unit that applies moisture to the web; a pressurizing unit that pressurizes the web to which moisture has been added; A heating section that heats the web to which moisture has been added; Including, The moisture content of the web to which moisture has been added in the moisture adding section is 12% by mass or more, The pressure applied to the web in the pressure applying section is 0.2 MPa or more, The temperature of the web in the heating section is 100° C. or less, The sheet manufacturing apparatus, wherein the binder is a water-soluble polysaccharide.

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