JP7844895B2 - Manufacturing method of fiber sheets - Google Patents

Description

This invention relates to a method for manufacturing a fiber sheet, and to a fiber sheet itself.

Conventionally, methods for manufacturing fibrous structures containing fibers and resins have been known. For example, Patent Document 1 discloses a method for manufacturing an elastic fibrous structure containing naturally derived fibers and biodegradable heat-fusible synthetic fibers.

Japanese Patent Publication No. 2001-226864

However, the manufacturing method described in Patent Document 1 had the problem of difficulty in improving the mechanical strength of the fiber structure. Specifically, because various fibers are mixed and then processed through a carding machine before lamination, the length direction of the fibers tends to align in a direction intersecting the lamination direction, and entanglement between fibers decreases. This makes it difficult to improve mechanical strength. In particular, when the fiber structure is formed into a thin sheet, the tear strength tends to be insufficient, sometimes resulting in tearing. In other words, there was a need for a manufacturing method for fiber sheets that could improve mechanical strength.

The method for manufacturing a fiber sheet comprises a defibration step of dry-processing a fabric to produce fibers, a mixing step of mixing a binder with the fibers to produce a mixture, a deposition step of depositing the mixture in air to produce a web, and a molding step of pressurizing and heating the web to form it into a sheet.

The fiber sheet comprises fibers produced by dry defibration of a fabric, including a plain weave or knitted fabric, and a biodegradable resin that binds the fibers together.

A flowchart illustrating a method for manufacturing a fiber sheet according to an embodiment. A schematic diagram showing the configuration of a fiber sheet manufacturing apparatus. A schematic cross-sectional view showing the state of fibers in a fiber sheet. A schematic cross-sectional view showing the state of fibers in a fiber sheet. A schematic cross-sectional view showing the state of fibers in a conventional fiber sheet.

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, a Z-axis (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.

Furthermore, for illustrative purposes, the sizes of each component are depicted differently from their actual dimensions. In fiber sheet manufacturing equipment, the direction of transport of raw materials and webs is sometimes referred to as downstream, while the direction of transport going upstream is sometimes referred to as upstream.

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.

Fibers are one of the main components of a fiber sheet and, along with binders, influence 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. Besides knitted and plain weave fabrics, the fabric may also include pile fabrics or nonwoven fabrics. From the viewpoint of resource recycling, it is preferable to use recycled fabrics such as used clothing for the fabric.

Examples of fibers include natural fiber materials such as cotton, hemp, wool, silk, regenerated cellulose, and polylactic acid. These fibers can 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.

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.

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

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.

Fiber sheets are manufactured using the raw materials described above. Fiber sheets may be further processed, such as by welding, to form bags or other shapes in order to enclose and protect three-dimensional objects being packaged. Because fiber sheets are relatively thin, they are susceptible to tearing under external force. Therefore, mechanical strength is an important property of fiber sheets. Details of the fiber sheet manufacturing method will be described later.

Examples of items packaged in fiber sheets include information terminal devices such as watches, laptops, small game consoles, smartphones, printers, and projectors, as well as precision parts, models, ceramics, porcelain, glassware, home appliances, and fresh produce.

2. Method for Manufacturing Fiber Sheets As shown in Figure 1, the method for manufacturing fiber sheets according to this embodiment comprises a raw material supply step, a crushing step, a defibration step, a mixing step, a piling step, a molding step, and a cutting step.

In the method for manufacturing fiber sheets, the fiber sheet is produced by following the above-described steps from the upstream raw material supply process to the downstream cutting process. The fiber sheet manufacturing method of the present invention includes a defibration process, a mixing process, a deposition process, and a molding process, but other processes are not limited to those described above. Furthermore, the fiber sheet of the present invention may be formed into a bag-like shape or other form after secondary processing such as welding is completed after the cutting process is finished.

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

As shown in Figure 2, the fiber sheet manufacturing apparatus 1 includes, from upstream to downstream, a supply unit 5, a crushing unit 10, a defibration unit 30, a mixing unit 60, a stacking unit 100, a web conveying unit 70, a molding 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 comprehensively controls the operation of each of the above components. Furthermore, the fiber sheet manufacturing apparatus 1 may also include a mechanism for performing secondary processing, such as welding, on the manufactured sheet-like fiber sheet P.

In the supply unit 5, the raw material supply process takes place. The supply unit 5 supplies raw materials to the crushing unit 10. The supply unit 5, for example, is equipped with an automatic feeding mechanism 6, which continuously and automatically feeds the raw material fabric C into the crushing unit 10. Fabric C is a material containing the aforementioned fibers.

The coarse crushing section 10 performs the coarse crushing process. The coarse crushing section 10 shreds the fabric C supplied from the supply section 5 into fine pieces in an atmosphere such as air. The coarse crushing section 10 is a shredder, cutter mill, etc., having coarse crushing blades 11. The fabric C is shredded into fine pieces by the coarse crushing blades 11. The planar shape of the fine pieces is, for example, a few millimeters square or irregular. The fine pieces are collected in the quantitative supply section 50.

The quantitative feeding unit 50 weighs the flakes and supplies them to the hopper 12 in a fixed quantity. The quantitative feeding unit 50 is, for example, a vibrating feeder. The flakes supplied to the hopper 12 are transported through the pipe 20 and reach the inlet 31 of the defibration unit 30.

The defibration process is performed in the defibration unit 30. The defibration unit 30 generates fibers by dry defibration of the fabric C fragments. The defibration unit 30 includes an inlet 31, an outlet 32, a stator 33, a rotor 34, and an airflow generating mechanism (not shown). The fabric C fragments are introduced into the defibration unit 30 via the inlet 31 by the airflow from the airflow generating mechanism. In this specification, "dry process" means that the process is carried out in air, such as atmosphere, rather than in a liquid.

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 fine strips of fabric C are trapped between the stator 33 and rotor 34 and defibrated by the shear force generated between them.

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 is determined by a method compliant with ISO 16065-2:2007.

The longest fiber length is determined by the following method: The fibers are placed on a glass plate, ensuring 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 photographs taken with the microscope using the measurement software included with the device. This procedure is performed on 50 randomly selected fibers, and the longest fiber length is considered the longest fiber length. Note that fiber length refers to the distance along the curve of the fiber if it is curved.

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. Therefore, bias in the orientation direction of the fibers in the fiber sheet P is less likely to occur, and the fibers become more easily intertwined. This further improves the mechanical strength of the fiber sheet P.

The aspect ratio of the fiber is determined by the following method: The fiber is imaged on a glass plate, similar to how the longest fiber length is measured. The shortest fiber length refers to 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 included with the device. This operation is performed on 50 randomly selected fibers, and the aspect ratio of the fiber is calculated as the average value of the 50 fibers.

The fibers generated in the defibration section 30 are discharged into the pipe 40 through the outlet 32. The pipe 40 communicates with the interior of the defibration section 30 and the interior 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.

The mixing process takes place in the mixing unit 60. The mixing unit 60 mixes fibers with binders and other materials in air to produce a mixture. The mixing unit 60 includes hoppers 13 and 14, supply pipes 61 and 62, and valves 65 and 66.

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

The hopper 14 communicates with the inside of the pipe 40 via a supply pipe 62. A valve 66 is provided between the hopper 14 and the pipe 40 in the supply pipe 62. The hopper 14 supplies additives other than the binder into the pipe 40. The valve 66 adjusts the weight of the additives supplied from the hopper 14 to the pipe 40. This adjusts the mixing ratio of the additives to the fibers and binder. Note that additives are not essential components in the fiber sheet P, and the hopper 14 and supply pipe 62 may be omitted. Alternatively, the additives may be pre-mixed with the binder and supplied from the hopper 13.

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

The deposition process takes place in the deposition section 100. The deposition section 100 deposits a mixture containing fibers and binders in air to generate a web W. The deposition section 100 has a drum section 101 and a housing section 102 that accommodates the drum section 101. The deposition section 100 takes the mixture from the pipe 40 into the drum section 101 and deposits it onto the mesh belt 122 in a dry manner.

Below the accumulation section 100, a web conveying section 70 is arranged, including 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.

The drum section 101 is a cylindrical sieve driven by a motor (not shown). A mesh screen, which 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 smaller than the mesh opening 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 drum section 101 loosens the entangled fibers.

The fibers are dispersed in the air within the housing portion 102, and the fibers accumulate randomly on the mesh belt 122. Therefore, the fibers in the web W are less likely to orient in a specific direction.

The sieve in the drum section 101 does not necessarily need to have the function of separating large fibers 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 within the housing section 102 accumulates on the upper surface of the mesh belt 122 due to gravity and the suction of the suction mechanism 110.

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

The web conveying unit 70 comprises a mesh belt 122 and a suction mechanism 110. The suction mechanism 110 facilitates the deposition of the mixture onto the mesh belt 122. Furthermore, the web conveying unit 70 conveys the web W formed from the mixture downstream by the rotation of the mesh belt 122.

The suction mechanism 110 is positioned below the drum section 101. The suction mechanism 110 draws air from within 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 drawn downwards along with the air and deposited on the upper surface of the mesh belt 122. A known suction device, such as a blower, is employed in the suction mechanism 110.

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 taut by three tension rollers 121.

The mesh belt 122 moves downstream as the tension roller 121 rotates. 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 conveyed downstream as the mesh belt 122 moves.

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 the 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.

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.

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 and binders contained in the web W. Alternatively, water-soluble additives may be added to the water used for humidification, allowing the additives to impregnate the web W in parallel with the humidification process.

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 sufficient 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 sufficient processing time for the molding process as the web W is continuously supplied from the deposition section 100. The web W then passes through the dancer roller 141 to the molding section 150.

The molding process is performed in the molding unit 150. In the molding process, the web W is heated and pressurized to form a continuous sheet of fiber P. The molding unit 150 is a heating press device comprising 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 using a built-in heater.

The web W is compressed from above and below by pressure, increasing its density. Heating melts the binder, which then spreads between the fibers. When heating ends and the resin solidifies, the fibers are bonded together by the binder. Note that the molding process may be a continuous process using a heating roller or similar device.

The pressurization and heating conditions in the molding section 150 are appropriately adjusted depending on the desired density of the fiber sheet P and the melting point of the resin binder. While not particularly limited, the pressurization condition is, for example, 0.1 MPa or higher, and the heating condition is, 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.

The cutting unit 160 performs the cutting process. The cutting unit 160 cuts the continuous-form fiber sheet P into single-sheet fiber sheets P. Although not shown in the illustration, the cutting unit 160 includes both a vertical blade and a horizontal blade.

The vertical blade cuts the fiber sheet P in a direction aligned with the direction of travel of the continuous fiber sheet P. The horizontal blade cuts the fiber sheet P in a direction intersecting the direction of travel of the continuous 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 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 heat press device. The fiber sheet P is then manufactured.

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 below.

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 low. These characteristics stem from the manufacturing method, which involves lamination using a carding machine.

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 aligns with the aforementioned 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 mechanical strength is easily reduced. Here, the morphology of the fibers F refers to the length-weighted average fiber length, longest fiber length, and aspect ratio, as described above.

In contrast, in the fiber sheets P1 and P2 of this embodiment, the orientation directions of the multiple fibers F are less likely to align, and they do not align unevenly in a particular direction. This is because, since the aforementioned deposition process is performed in air, the fibers F are deposited randomly compared to when they are laminated using a carding machine. Furthermore, because the fiber defibration process is performed, the length-weighted average fiber length and the longest fiber length of the fibers F are shorter compared to when the fiber defibration process is not performed.

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 areas of the yarn within the knitted fabric. Therefore, fibers F produced from knitted fabric tend to have a smaller aspect ratio.

Furthermore, in this embodiment, the fibers F are dispersed in 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 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.

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 a small number of curved fibers F compared to knitted fabric. Because plain weave fabric is woven by intersecting warp and weft threads, curved fibers F tend to form easily at the intersections of the warp and weft threads within the plain weave fabric.

Furthermore, in this embodiment, the fibers F are dispersed in 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.

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

A fiber sheet P with improved mechanical strength can be manufactured. Specifically, because the fabric C is defibrated, the resulting fibers F tend to be relatively short. Furthermore, since the mixture deposits in air to form a web W, the fibers F within the web W are less likely to be oriented in a specific 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 conventional methods where fibers F are oriented in a specific direction and laminated, 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.

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 column for raw material composition in Table 1, a dash (-) indicates that no additive was used. The present invention is not limited in any way by the following examples.

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.

Fiber F was extracted from the defibrated material, and its length-weighted average fiber length, longest fiber length, and aspect ratio were determined using the method described above. The results showed a length-weighted average fiber length of 32 mm, a longest fiber length of 60 mm, and an aspect ratio of 0.66.

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 to form a web W with a basis weight of 300 g/ ^m² . Then, in the molding step, 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 producing the fiber sheet P1 of Example 1 is referred to as manufacturing method α.

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, except for a change in the raw material of fiber F, the fiber sheet P2 of Example 2 was manufactured using the same manufacturing method α as the fiber sheet P1 of Example 1.

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.

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.

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 operation was repeated to form a web of layered mixtures on the metal tray. Then, the web was 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.

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 to indicate mechanical strength.

Specifically, two rectangular pieces of fiber sheet P1 measuring 13 cm x 10 cm were prepared. With the four sides of the two fiber sheets P1 overlapping, the two short sides and one long side were heat-pressed together within 5 mm of 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. This resulted in a bag-shaped fiber sheet P1 with the outer edges of the two short sides and one long side 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.

The fiber sheets P2 and P3 were also fabricated in the same manner as fiber sheet P1, creating bag-shaped fiber sheets P2 and P3.

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

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: No cracks in the welded area or surrounding area.
B: There are cracks in or around the welded area.

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 demonstrates 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.

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

Claims (3)

A defibration process involves dry defibration of a knitted fabric to produce a defibrated material 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 method for manufacturing a fiber sheet, comprising a molding step of pressurizing and heating the web to form it into a sheet. The method for producing a fiber sheet according to claim 1 , wherein the fabric includes cotton or wool. The method for manufacturing a fiber sheet according to claim 1 , wherein the binder is a biodegradable resin.