Manufacturing method of fiber sheets

Abstract

To provide a fiber sheet manufacturing method enabling mechanical strength to be improved and a fiber sheet.SOLUTION: A manufacturing method of a fiber sheet P includes a defibrillation step to generate a fiber F by defibrillating a fabric C under a drying condition, a mixing step to generate a mixture by mixing binder with the fiber F, an accumulation step to generate a web W by accumulating the mixture in the air, and a molding step to mold the web W into sheet-like shape by pressuring and heating.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Conventionally, a method for manufacturing a fiber structure including fibers and a resin has been known. For example, Patent Document 1 discloses a method for manufacturing an elastic fiber structure including fibers derived from natural products and biodegradable heat-fusible synthetic fibers.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the manufacturing method described in Patent Document 1 has a problem that it is difficult to improve the mechanical strength of the fiber structure. Specifically, since various fibers are mixed and carded and then laminated, the longitudinal directions of the fibers tend to align in a direction intersecting the lamination direction, and the entanglement between the fibers decreases. As a result, it has been difficult to improve the mechanical strength. In particular, when the fiber structure is thinly formed into a sheet shape and used, the tear strength is likely to be insufficient, and cracks may occur. That is, a method for manufacturing a fiber sheet with improved mechanical strength has been demanded.

Means for Solving the Problems

[0005] The method for manufacturing a fiber sheet includes a defibrating step of defibrating a fabric dry to generate fibers, a mixing step of mixing a binder with the fibers to generate a mixture, a depositing step of depositing the mixture in air to generate a web, and a forming step of pressing and heating the web to form it into a sheet shape.

[0006] The fiber sheet comprises fibers produced by dry defibration of a fabric including a plain weave or knit fabric, and a biodegradable resin that binds the fibers together. [Brief explanation of the drawing]

[0007] [Figure 1] A flowchart illustrating a method for manufacturing a fiber sheet according to an embodiment. [Figure 2] A schematic diagram showing the configuration of a fiber sheet manufacturing apparatus. [Figure 3] A schematic cross-sectional view showing the state of fibers in a fiber sheet. [Figure 4] A schematic cross-sectional view showing the state of fibers in a fiber sheet. [Figure 5] A schematic cross-sectional view showing the state of fibers in a conventional fiber sheet. [Modes for carrying out the invention]

[0008] The embodiments described below illustrate a method for manufacturing fiber sheets for packaging three-dimensional objects, and will be explained with reference to the drawings. In each of the following figures, the Z-axis, which is a coordinate axis, is added as needed, with the direction indicated by the arrow being the +Z direction and the direction opposite to the +Z direction being the -Z direction. The +Z direction may also be referred to as upward and the -Z direction as downward. In Figure 2, the -Z direction coincides with the vertical direction.

[0009] Also, for illustrative purposes, the sizes of each component are shown to differ from their actual dimensions. In fiber sheet manufacturing equipment, the direction ahead in the conveying direction of raw materials and webs is sometimes called downstream, and the direction upstream in the conveying direction is sometimes called upstream.

[0010] 1. Fiber sheet The fiber sheet according to this embodiment includes fibers and a resin as a binder as raw materials. The fibers and binder are biodegradable from the viewpoint of reducing environmental impact. Furthermore, from the same viewpoint, it is preferable that the fibers and binder are derived from natural products. The fiber sheet is manufactured by the fiber sheet manufacturing method described later.

[0011] Fibers are one of the main components of a fiber sheet and, along with binders, affect the physical properties of the fiber sheet, such as its mechanical strength. The fibers used are those produced by dry defibration of fabrics, including plain weave or knitted fabrics. In addition to knitted and plain weave fabrics, the fabrics may also include pile fabrics and nonwoven fabrics. From the viewpoint of resource recycling, it is preferable to use used fabrics such as old clothes for the fabric.

[0012] Examples of fibers include natural fiber materials such as cotton, hemp, wool, silk, regenerated cellulose, and polylactic acid. These fibers may be used individually or in combination of two or more. In particular, among the above fiber materials, it is preferable that the fabric contains cotton or wool, considering factors such as the ease of obtaining used clothing and the physical properties of the fibers.

[0013] The fibers may include synthetic fibers such as polypropylene, polyester, and polyurethane, but from the viewpoint of reducing environmental impact, it is preferable to use only fibers derived from natural materials.

[0014] The binder resin is used to bond the fibers together in the fiber sheet. The binder resin can be thermoplastic or thermosetting. Examples of such resins include shellac, pine resin, dammar, polylactic acid, plant-derived polybutylene succinate, plant-derived polyethylene, and Kaneka's PHBH® (Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)). One of these resins may be used alone, or two or more may be used in combination. In particular, the binder resin is preferably biodegradable from the viewpoint of reducing environmental impact.

[0015] The fiber sheet may contain additives in addition to fibers and binders. Examples of additives include colorants, flame retardants, antioxidants, UV absorbers, flocculation inhibitors, antibacterial agents, antifungal agents, waxes, and release agents.

[0016] The fiber sheet is manufactured using the above raw materials. The fiber sheet may be secondarily processed into a form such as a bag by welding or the like in order to store and protect a three-dimensional object which is an object to be packaged. Since the fiber sheet has a relatively thin thickness, there is a risk of cracks or the like occurring due to external force. Therefore, mechanical strength is an important physical property in the fiber sheet. Details of the manufacturing method of the fiber sheet will be described later.

[0017] Examples of objects to be packaged by the fiber sheet include information terminal devices such as wristwatches, notebook computers, small game machines, smartphones, printers, projectors, precision parts, models, pottery, porcelain, glassware, household electrical appliances, and fresh produce.

[0018] 2. Manufacturing method of fiber sheet As shown in FIG. 1, the manufacturing method of the fiber sheet according to this embodiment includes a raw material supply step, a crushing step, a fiberizing step, a mixing step, a deposition step, a forming step, and a cutting step.

[0019] In the manufacturing method of the fiber sheet, the fiber sheet is manufactured through each step in the above order from the upstream raw material supply step to the downstream cutting step. Note that the manufacturing method of the fiber sheet of the present invention includes a fiberizing step, a mixing step, a deposition step, and a forming step, and the other steps are not limited to the above. Further, the fiber sheet of the present invention may be formed into a form such as a bag through secondary processing such as welding after the cutting step is completed.

[0020] A specific example of the manufacturing method of the fiber sheet will be described together with a fiber sheet manufacturing apparatus. The fiber sheet manufacturing apparatus 1 according to this embodiment is an example and is not limited thereto.

[0021] As shown in Fig. 2, the fiber sheet manufacturing apparatus 1 includes, from upstream to downstream, a supply unit 5, a crushing unit 10, a fiberizing unit 30, a mixing unit 60, a deposition unit 100, a web conveyance unit 70, a forming unit 150, and a cutting unit 160. Although not shown in the figure, the fiber sheet manufacturing apparatus 1 also includes a control unit that integrally controls the operation of each of the above components. Note that the fiber sheet manufacturing apparatus 1 may be provided with a mechanism for performing secondary processing such as welding on the manufactured sheet-like fiber sheet P.

[0022] In the supply unit 5, a raw material supply process is performed. The supply unit 5 supplies raw materials to the crushing unit 10. The supply unit 5 includes, for example, an automatic feeding mechanism 6 and continuously and automatically feeds the raw material fabric C to the crushing unit 10. The fabric C is a material containing the above-described fibers.

[0023] In the crushing unit 10, a crushing process is performed. The crushing unit 10 shreds the fabric C supplied from the supply unit 5 into small pieces in an atmosphere such as air. The crushing unit 10 is a shredder having a crushing blade 11, a cutter mill, or the like. The fabric C is shredded by the crushing blade 11 into small pieces. The planar shape of the small pieces is, for example, several millimeters square or irregular. The small pieces are collected in the metering supply unit 50.

[0024] The metering supply unit 50 measures the small pieces and supplies them to the hopper 12 in a metered manner. The metering supply unit 50 is, for example, a vibrating feeder. The small pieces supplied to the hopper 12 are conveyed through the pipe 20 and reach the inlet 31 of the fiberizing unit 30.

[0025] In the fiberizing unit 30, a fiberizing process is performed. The fiberizing unit 30 dry-fiberizes the small pieces of the fabric C to generate fibers. The fiberizing unit 30 includes an inlet 31, an outlet 32, a stator 33, a rotor 34, and an air flow generating mechanism (not shown). The small pieces of the fabric C are introduced into the interior of the fiberizing unit 30 through the inlet 31 by the air flow of the air flow generating mechanism. In this specification, "dry" means that it is carried out in air such as air without being carried out in a liquid.

[0026] The stator 33 and rotor 34 are positioned inside the defibration section 30. The stator 33 has a substantially cylindrical inner surface. The rotor 34 rotates along the inner surface of the stator 33. The strips of fabric C are sandwiched between the stator 33 and the rotor 34 and defibrated by the shear force generated between them.

[0027] The defibrated fibers preferably have a length-weighted average fiber length of 1.0 mm or more, and preferably a maximum fiber length of 5.0 mm or more. This prevents the fibers from becoming excessively short, further improving the mechanical strength of the fiber sheet P. The length-weighted average fiber length of the fibers is determined by a method in accordance with ISO 16065-2:2007.

[0028] The longest fiber length is determined by the following method: The fibers are placed on a glass plate so that they do not overlap as much as possible. In this state, the fiber length of the fibers on the glass plate is measured using a Keyence VHX-5000 digital microscope. Specifically, the fiber length is determined from the digital photograph taken with the microscope using the measurement software included with the device. This operation is performed on 50 randomly selected fibers, and the longest fiber length is taken as the longest fiber length. Note that fiber length refers to the distance along the curve if the fiber is curved.

[0029] The fibers preferably have an aspect ratio of 0.9 or less. The aspect ratio of a fiber is the value obtained by dividing the shortest fiber length by the total fiber length. According to this, curved or bent fibers are included in the fiber sheet P. As a result, bias in the orientation direction of the fibers in the fiber sheet P is less likely to occur, and the fibers become more likely to intertwine with each other. This further improves the mechanical strength of the fiber sheet P.

[0030] The aspect ratio of the fiber is determined by the following method: The fiber is imaged on a glass plate in the same manner as the longest fiber length. The shortest fiber length is the straight-line distance between both ends of the fiber. The fiber length and shortest fiber length are determined from this digital image using the measurement software attached to the device. This operation is performed on 50 randomly selected fibers, and the aspect ratio of the fiber is determined as the average value of the 50 fibers.

[0031] The fibers generated in the defibration section 30 are discharged into the pipe 40 from the outlet 32. The pipe 40 communicates with the inside of the defibration section 30 and the inside of the accumulation section 100. The fibers are transported from the defibration section 30 to the accumulation section 100 by the airflow generated by the airflow generation mechanism. A mixing section 60 is provided in the pipe 40 between the defibration section 30 and the accumulation section 100.

[0032] A mixing process is carried out in the mixing section 60. The mixing section 60 mixes fibers with binders and other materials in air to produce a mixture. The mixing section 60 includes hoppers 13 and 14, supply pipes 61 and 62, and valves 65 and 66.

[0033] Hopper 13 communicates with the inside of pipe 40 via supply pipe 61. In supply pipe 61, valve 65 is provided between hopper 13 and pipe 40. Hopper 13 supplies binder into pipe 40. Valve 65 adjusts the weight of binder supplied from hopper 13 to pipe 40. This adjusts the mixing ratio of fibers to binder. The binder may be supplied as a powder or as a molten material.

[0034] Hopper 14 is connected to the inside of pipe 40 via supply pipe 62. Valve 66 is provided between hopper 14 and pipe 40 in supply pipe 62. Hopper 14 supplies additives other than binder into pipe 40. Valve 66 adjusts the weight of additives supplied from hopper 14 to pipe 40. This adjusts the mixing ratio of additives to fibers and binder. Note that additives are not essential components in fiber sheet P, and hopper 14 and supply pipe 62 may be omitted. Alternatively, the additives may be mixed with the binder beforehand and supplied from hopper 13.

[0035] The fibers and binders are mixed as they are transported through the pipe 40 to the deposition section 100 to form a mixture. To promote the formation of the mixture in the pipe 40 and to improve the transportability of the mixture, a blower or the like may be placed in the pipe 40 to generate airflow. The mixture is transported through the pipe 40 to the deposition section 100.

[0036] The deposition process is carried out in the deposition section 100. The deposition section 100 generates a web W by depositing a mixture containing fibers and binders in the air. The deposition section 100 has a drum section 101 and a housing section 102 that houses the drum section 101. The deposition section 100 takes the mixture from the pipe 40 into the drum section 101 and deposits it on the mesh belt 122 in a dry manner.

[0037] Below the stacking section 100, a web transport section 70 is arranged, which includes a mesh belt 122 and a suction mechanism 110. The suction mechanism 110 is positioned opposite the drum section 101, with the mesh belt 122 in between, in the direction along the Z-axis.

[0038] The drum section 101 is a cylindrical sieve that is rotationally driven by a motor (not shown). A mesh that functions as a sieve is provided on the side of the cylindrical drum section 101. The drum section 101 allows particles such as fibers and mixtures that are smaller than the mesh opening size of the sieve to pass from the inside to the outside. The mixture is dispersed into the air inside the housing section 102 after the entangled fibers are loosened by the drum section 101.

[0039] The fibers are dispersed in the air within the housing portion 102, and the fibers are randomly deposited on the mesh belt 122. As a result, the fibers in the web W are less likely to be oriented in a specific direction.

[0040] The sieve in the drum section 101 does not need to have the function of separating large fibers and other particles from the mixture. That is, the drum section 101 may loosen the fibers of the mixture and release all of the mixture into the housing section 102. The mixture dispersed in the air inside the housing section 102 is deposited on the upper surface of the mesh belt 122 by gravity and suction from the suction mechanism 110.

[0041] In the web W, the mass ratio of fibers to binder is preferably in the range of 15:85 to 45:55 in terms of fibers to binder. This ensures that various physical properties, including the mechanical strength, of the fiber sheet P can be secured. Furthermore, the density and thickness of the manufactured fiber sheet P are adjusted by the basis weight of the web W.

[0042] The web conveying section 70 includes a mesh belt 122 and a suction mechanism 110. The suction mechanism 110 facilitates the accumulation of the mixture onto the mesh belt 122. The web conveying section 70 also conveys the web W formed from the mixture downstream by the rotation of the mesh belt 122.

[0043] The suction mechanism 110 is positioned below the drum section 101. The suction mechanism 110 sucks air from inside the housing section 102 through multiple holes in the mesh belt 122. As a result, the mixture released to the outside of the drum section 101 is sucked downward along with the air and deposited on the upper surface of the mesh belt 122. A known suction device such as a blower is used in the suction mechanism 110.

[0044] The multiple holes in the mesh belt 122 allow air to pass through but make it difficult for fibers and binders contained in the mixture to pass through. The mesh belt 122 is an endless belt and is stretched by three tension rollers 121.

[0045] The mesh belt 122 moves downstream as the tension roller 121 rotates, with its upper surface moving downstream. In other words, the mesh belt 122 rotates clockwise in Figure 2. As the mesh belt 122 rotates due to the tension roller 121, the mixture is continuously deposited, forming a web W. The web W contains a relatively large amount of air and is soft and inflated. The web W is transported downstream as the mesh belt 122 moves.

[0046] Here, the web W may be laminated with a nonwoven fabric or the like. Specifically, when the web W is deposited on the mesh belt 122, a nonwoven fabric is interposed between the mesh belt 122 and the web W. Also, the upper surface of the web W is covered with a nonwoven fabric. By continuously supplying the nonwoven fabric to the web W from above and below, the web W is laminated with the nonwoven fabric. A fiber sheet P may be manufactured from the web W in this state.

[0047] The nonwoven fabric used for lamination is preferably made of fibers such as polylactic acid, cellulose, or regenerated cellulose. This, along with the raw materials contained in Web W, promotes a reduction in environmental impact.

[0048] A humidifier 130 may be placed downstream of the deposition section 100 to spray water onto the web W on the mesh belt 122 for humidification. This suppresses the scattering of fibers, binders, and other materials contained in the web W. Alternatively, a water-soluble additive may be added to the water used for humidification, allowing the additive to impregnate the web W in parallel with the humidification process.

[0049] The web W is transported downstream by the mesh belt 122, detached from the mesh belt 122, and drawn into the dancer roller 141. The dancer roller 141 is provided to ensure processing time for the downstream molding process. Specifically, since the molding process following the deposition process is a batch process, the dancer roller 141 is moved up and down to ensure processing time for the molding process for the web W that is continuously supplied from the deposition section 100. The web W passes through the dancer roller 141 to the molding section 150.

[0050] The molding process is carried out in the molding section 150. In the molding process, the web W is heated and pressurized to form a sheet-like fiber sheet P, which is a continuous form. The molding section 150 is a heating press device and comprises an upper substrate 152 and a lower substrate 151. The upper substrate 152 and the lower substrate 151 pressurize the web W between them and heat the web W with a built-in heater.

[0051] The web W is compressed from above and below by pressure, increasing its density, and the binder melts upon heating, wetting and spreading between the fibers. When heating ends and the resin solidifies in this state, the fibers are bonded together by the binder. In the molding process, a continuous process using a heating roller or the like may be used.

[0052] The pressurizing and heating conditions in the molding section 150 are adjusted as appropriate depending on the desired density of the fiber sheet P and the melting point of the resin binder. While not particularly limited, the pressurizing conditions are, for example, 0.1 MPa or higher, and the heating conditions are, for example, 90°C or higher. The molding section 150 transforms the web W into a continuous sheet-like fiber sheet P, which then proceeds to the cutting section 160.

[0053] The cutting process is performed in the cutting unit 160. The cutting unit 160 cuts a continuous sheet of fiber P into single sheets of fiber P. Although not shown in the illustration, the cutting unit 160 includes a vertical blade and a horizontal blade.

[0054] The vertical blade cuts the fiber sheet P in a direction aligned with the direction of travel of the continuous sheet-like fiber sheet P. The horizontal blade cuts the fiber sheet P in a direction intersecting the direction of travel of the continuous sheet-like fiber sheet P. This produces a roughly rectangular fiber sheet P, which is then placed in the tray 170. Note that the single-sheet fiber sheets P cut from the continuous sheet-like fiber sheet P are not limited to being roughly rectangular. The roughly rectangular fiber sheets P may be subjected to secondary processing such as welding using a heating press, for example. The fiber sheet P is thus manufactured.

[0055] The structure of fiber sheets P1 and P2, which are fiber sheets P manufactured through the above process, and the fiber sheet P3 according to the prior art will be described.

[0056] As shown in Figure 5, in the conventional fiber sheet P3, multiple fibers F are oriented substantially along a plane perpendicular to the Z-axis. Furthermore, entanglement between fibers F is minimal, and interference between fibers F is infrequent. These characteristics are derived from the manufacturing method, which involves lamination using a carding machine.

[0057] In fiber sheet P3, cracks are prone to occur along the direction in which the fibers F are oriented. For example, when fiber sheet P3 is welded, if the boundary between the welded and unwelded areas is aligned in the above direction, cracks are likely to occur at that boundary. This is because the orientation and morphology of the multiple fibers F in fiber sheet P3 create areas where the mechanical strength is easily reduced. The morphology of the fibers F referred to here includes the length-weighted average fiber length, the longest fiber length, and the aspect ratio, as described above.

[0058] In contrast, in the fiber sheets P1 and P2 of this embodiment, the orientation directions of the multiple fibers F are not easily aligned and do not tend to be biased towards a particular direction. This is because the deposition process described above is carried out in air, resulting in random deposition of the fibers F compared to when the sheets are laminated using a carding machine. Furthermore, because the fibers undergo a defibration process, the length-weighted average fiber length and the longest fiber length of the fibers F are shorter compared to when the fibers have not undergone a defibration process.

[0059] When knitted fabric is used as the raw material for fiber F, as shown in Figure 3, the fiber sheet P1 contains many curved fibers F. Because knitted fabric is made by looping yarn, curved fibers F are generated from the looped parts of the yarn contained in the knitted fabric. Therefore, fibers F made from knitted fabric tend to have a smaller aspect ratio.

[0060] Furthermore, in this embodiment, the fibers F are dispersed in the air during the deposition process before being deposited to form the web W. Therefore, the fibers F are less likely to be oriented in a specific direction within the fiber sheet P1. As a result, in the fiber sheet P1, multiple relatively short fibers F are randomly dispersed, and curved fibers F and straight fibers F are relatively intertwined. Consequently, the mechanical strength of the fiber sheet P1 is improved compared to the conventional fiber sheet P3.

[0061] When plain weave fabric is used as the raw material for fiber F, as shown in Figure 4, multiple relatively short fibers F are randomly dispersed within the fiber sheet P2. Among the multiple fibers F in the fiber sheet P2, there are also curved fibers F, albeit in smaller quantities compared to knitted fabrics. Because plain weave fabric is woven by intersecting warp and weft threads, curved fibers F tend to be generated from the intersections of warp and weft threads within the plain weave fabric.

[0062] Furthermore, in this embodiment, the fibers F are dispersed in the air during the deposition process before being deposited to form the web W. Therefore, even within the fiber sheet P2, the fibers F are less likely to be oriented in a specific direction. As a result, in the fiber sheet P2, multiple relatively short fibers F are randomly dispersed, and the fibers F are relatively intertwined. Consequently, the mechanical strength of the fiber sheet P2 is improved compared to the conventional fiber sheet P3.

[0063] According to this embodiment, the following effects can be obtained.

[0064] A fiber sheet P with improved mechanical strength can be manufactured. Specifically, since the fabric C is defibrated, the resulting fibers F tend to be relatively short. Also, since the mixture is deposited in air to form a web W, the fibers F within the web W are less likely to be oriented in a particular direction. As a result, within the fiber sheet P, multiple relatively short fibers F are randomly dispersed and intertwined with each other. Therefore, compared to the conventional method where fibers F are laminated oriented in a particular direction, the mechanical strength, such as tear strength, of the fiber sheet P is improved. In other words, a method for manufacturing a fiber sheet P with improved mechanical strength, and the fiber sheet P itself, can be provided.

[0065] 3. Examples and Comparative Examples The effects of the present invention will be explained in more detail below with reference to examples and comparative examples. Table 1 shows the composition of raw materials used in the manufacture, manufacturing conditions, and evaluation results for fiber sheet P1 of Example 1, fiber sheet P2 of Example 2, and fiber sheet P3 of Comparative Example 1. In the raw material composition column of Table 1, a dash (-) indicates that no additive was used. The present invention is not limited in any way by the following examples.

[0066] [Table 1]

[0067] 3.1. Manufacturing of fiber sheets As shown in Table 1, in Example 1, 100% cotton knit fabric was used as the raw material fabric C for fiber F. Specifically, in the coarse crushing step, the knit fabric was coarsely crushed into irregularly shaped fragments with a long side of 1 mm to 30 mm using a cutter mill from Makino Sangyo Co., Ltd. Next, in the defibration step, the fragments were subjected to defibration in the same manner as in the defibration step of the above embodiment to obtain defibrated material.

[0068] Fiber F was extracted from the defibrated material, and its length-weighted average fiber length, longest fiber length, and fiber aspect ratio were determined using the method described above. As a result, the length-weighted average fiber length was 32 mm, the longest fiber length was 60 mm, and the fiber aspect ratio was 0.66.

[0069] Next, in the mixing step, the defibrated fiber F and polylactic acid as a binder were mixed in a mass ratio of 7:3 by air agitation. Then, in the deposition step, the mixture was deposited in air until it reached a basis weight of 300 g / m². 2 A web W was formed. Then, as a molding process, the web W was subjected to a heat press. At this time, the heating conditions were 135°C for 5 minutes, and the press conditions were such that the thickness after manufacturing was 1 mm, thereby producing the fiber sheet P1 of Example 1. The method for manufacturing the fiber sheet P1 of Example 1 is referred to as manufacturing method α.

[0070] In Example 2, a plain weave fabric made of 100% cotton was used as the raw material fabric C for fiber F. Specifically, in Example 2, the fiber sheet P2 was manufactured using manufacturing method α, similar to that of fiber sheet P1 in Example 1, except that the raw material for fiber F was changed.

[0071] Furthermore, in the fiber F extracted from the defibrated material of Example 2, the length-weighted average fiber length was 20 mm, the longest fiber length was 45 mm, and the fiber aspect ratio was 0.72.

[0072] In Comparative Example 1, commercially available absorbent cotton was used as the raw material for fiber F. Specifically, the absorbent cotton was cut into roughly rectangular strips of approximately 30 mm x 30 mm using scissors. Next, compressed air was blown onto these strips to separate the fibers F into individual fibers. The separated fibers F were then collected, and the length-weighted average fiber length, longest fiber length, and fiber aspect ratio were determined using the method described above. As a result, the length-weighted average fiber length was 28 mm, the longest fiber length was 30 mm, and the fiber aspect ratio was 0.93.

[0073] The loosened fibers F and polylactic acid as a binder were mixed in a mass ratio of 7:3 by air agitation. The mixture was then placed on a metal tray, and the fibers F were spread out while minimizing uneven distribution. This process was repeated to form a web of layered mixtures on the metal tray. The web was then subjected to a heat press in the same manner as in Example 1. The heating conditions were 135°C for 5 minutes, and the pressure conditions were such that the fiber sheet thickness was 1 mm, thereby producing the fiber sheet P3 of Comparative Example 1. The method for producing the fiber sheet P3 of Comparative Example 1 is referred to as manufacturing method β.

[0074] 3.2. Evaluation of Fiber Sheets For fiber sheets P1, P2, and P3, tear strength was investigated after welding was performed as a secondary processing step to determine their mechanical strength.

[0075] Specifically, two rectangles measuring 13 cm x 10 cm were prepared from the fiber sheet P1. With the four sides of the two fiber sheets P1 overlapping, the two short sides and the one long side were heat-pressed together within 5 mm from the outer edge. The heating conditions were 135°C for 5 minutes, and the pressing conditions were set so that the thickness of the welded area was 1 mm. As a result, a bag-shaped fiber sheet P1 was obtained in which the outer edges of the two short sides and the one long side were welded with a width of 5 mm. Inside the bag-shaped fiber sheet P1, there is a storage compartment measuring 9.5 cm x 12.0 cm when viewed from above.

[0076] For fiber sheets P2 and P3, bag-shaped fiber sheets P2 and P3 were prepared in the same manner as fiber sheet P1.

[0077] Furthermore, a fiberboard was prepared as the packaged material to be used for evaluation using the following procedure. Specifically, in the manufacturing method α of the fiber sheet P1, the basis weight of the web W was set to 1500 g / m². 2 The fiberboard was formed in the same manner as in manufacturing method α, except that the pressurizing conditions were set to a thickness of 15 mm, and then cut to form a square with a main surface of 10 cm x 10 cm.

[0078] Next, the fiberboard was manually inserted into the internal storage compartment of the bag-shaped fiber sheet P1 from the long side where the outer edge was not welded. At this time, the main surface of the bag-shaped fiber sheet P1 and the main surface of the fiberboard were aligned as closely as possible. After that, the welded area of ​​the bag-shaped fiber sheet P1 was visually observed and evaluated according to the following criteria. The bag-shaped fiber sheets P2 and P3 were also evaluated in the same manner as the bag-shaped fiber sheet P1 by inserting the fiberboard into the internal storage compartment. Evaluation Criteria A: There are no tears in the welded area or its periphery. B: There are cracks in or around the welded area.

[0079] As shown in Table 1, the bag-shaped fiber sheet P1 of Example 1 and the bag-shaped fiber sheet P2 of Example 2 received an A rating. This indicates that mechanical strength is improved in Examples 1 and 2. In contrast, the bag-shaped fiber sheet P3 of Comparative Example 1 received a B rating, indicating inferior mechanical strength. [Explanation of symbols]

[0080] C...Fabric, F...Fiber, P, P1, P2...Fiber sheet, W...Web.

Claims

1. A defibration process comprising: a dry defibration of a fabric made of knitted material to produce a defibration product containing curved fibers; A mixing step of mixing a binder with the defibrated material to produce a mixture, A deposition step of depositing the mixture in air to produce a web containing the curved fibers, A fiber sheet comprising a molding step of pressurizing and heating the web to form it into a sheet. A method for manufacturing this product.

2. The method for producing a fiber sheet according to claim 1, wherein the fabric includes cotton or wool.

3. The method for manufacturing a fiber sheet according to claim 1, wherein the binder is a biodegradable resin.

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