Manufacturing methods of cushioning materials and cushioning materials

Abstract

This invention provides a method for manufacturing a cushioning material with improved mechanical strength, as well as the cushioning material itself. The method for manufacturing the cushioning material P includes: a defiberization step, in which fabric is dry-fibered to generate fibers (F); a mixing step, in which a binding material is mixed into the fibers (F) to generate a mixture; a stacking step, in which the mixture is stacked in air to generate a sheet (W); and a one-step forming step, in which the sheet (W) is pressurized and heated to form a shape.

Description

Technical Field

[0001] This invention relates to a method for manufacturing a cushioning material and the cushioning material itself. Background Technology

[0002] Methods for manufacturing cushioning materials comprising fibers and resins have long been known. For example, Patent Document 1 discloses a method for manufacturing an elastic fiber structure comprising fibers derived from natural materials and biodegradable thermofused synthetic fibers. This elastic fiber structure is intended for use as a cushioning material, etc.

[0003] However, the manufacturing method described in Patent Document 1 has the problem that it is difficult to improve the mechanical strength of the cushioning material. Specifically, various fibers are mixed and then layered on a carding machine. This makes it easy for the length directions of the fibers to align in the direction intersecting the layering direction, thereby reducing fiber entanglement. As a result, it becomes difficult to ensure the mechanical strength of the cushioning material, and there is a possibility that the cushioning material may easily deform under external forces. Therefore, there is a need for a manufacturing method for a cushioning material that can improve its mechanical strength.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2001-226864 Summary of the Invention

[0005] The method for manufacturing cushioning material includes: a defiberization process, in which fabric is defibered in a dry manner to generate fibers; a mixing process, in which a binding material is mixed into the fibers to generate a mixture; a stacking process, in which the mixture is stacked in air to generate a sheet; and a one-time forming process, in which the sheet is pressurized and heated to form a shape.

[0006] The cushioning material comprises: fibers obtained by unwinding a fabric comprising plain woven or knitted fabric; a binding material derived from natural substances that binds the fibers together; and the cushioning material having recesses of a shape corresponding to the three-dimensional shape of the packaged item. Attached Figure Description

[0007] Figure 1 This is a flowchart illustrating a method for manufacturing the cushioning material involved in the embodiment.

[0008] Figure 2 This is a schematic diagram illustrating the structure of a cushioning material manufacturing apparatus.

[0009] Figure 3 A schematic cross-sectional view showing the state of fibers in a plate-shaped cushioning material.

[0010] Figure 4 To indicate that Figure 3A schematic diagram illustrating the following behavior of the cushioning material to the metal mold during compression molding.

[0011] Figure 5 A schematic cross-sectional view showing the state of fibers in a plate-shaped cushioning material.

[0012] Figure 6 To indicate that Figure 5 A schematic diagram illustrating the following behavior of the cushioning material to the metal mold during compression molding.

[0013] Figure 7 A schematic cross-sectional view illustrating the state of fibers in a plate-like cushioning material as described in the prior art.

[0014] Figure 8 To indicate that Figure 7 A schematic diagram illustrating the following behavior of the cushioning material to the metal mold during compression molding. Detailed Implementation

[0015] In the following embodiments, a method for manufacturing a cushioning material for housing three-dimensional objects is illustrated, and the description is provided with reference to the accompanying drawings. In the following drawings, the Z-axis, serving as a coordinate axis, is labeled as needed, and the direction indicated by the arrow is designated as the +Z direction, while the direction opposite to the +Z direction is designated as the -Z direction. Sometimes, the +Z direction is referred to as "up" and the -Z direction as "down." Furthermore, in... Figure 2 In the middle, the -Z direction is consistent with the vertical direction.

[0016] Furthermore, for ease of illustration, the sizes of the components may differ from the actual dimensions. In cushioning material manufacturing equipment, the direction in front of the conveying direction of raw materials or sheets is sometimes referred to as downstream, and the side facing upwards in the opposite direction of conveying is referred to as upstream.

[0017] 1. Cushioning material

[0018] The cushioning material manufactured by the cushioning material manufacturing method according to this embodiment comprises fibers and binding materials as raw materials. From the viewpoint of reducing environmental impact, the fibers and binding materials are made from natural substances. Furthermore, it is preferable that the fibers and binding materials are biodegradable.

[0019] Fibers are a major component of cushioning materials, and together with binding materials, they influence the physical properties of cushioning materials, such as mechanical strength. The fibers used are substances obtained by disintegrating fabric. From a resource reuse perspective, it is preferable to use old fabrics such as old clothes in the fabric.

[0020] Preferably, the fabric includes knitted fabric, plain woven fabric, and napped fabric. In addition, the fabric may also include non-woven fabric.

[0021] Examples of fibers include cotton, linen, wool, silk, and regenerated cellulose, all derived from natural substances. These fibers can be used individually or in combination of two or more substances. In particular, from the viewpoint of the ease of obtaining old clothes and the physical properties of the fibers, fabrics containing cotton or wool are preferred.

[0022] Although fibers can also include synthetic fibers such as polypropylene, polyester, and polyurethane, from the point of view of reducing environmental impact, it is preferable to use only fibers derived from natural materials.

[0023] The bonding material binds the fibers together in the cushioning material. In the bonding material, a thermoplastic or thermosetting resin is used. Examples of resins include shellac, rosin, dammar, polylactic acid, plant-derived polybutylene succinate, plant-derived polyethylene, and Kaneka Corporation's PHBH (registered trademark) (Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate, a copolyester of 3-hydroxybutyric acid and 3-hydroxyacetic acid)). In the bonding material, one of these substances may be used alone, or two or more may be combined. In particular, from the viewpoint of reducing environmental impact, a biodegradable resin is preferred as the bonding material.

[0024] In addition to fibers and bonding materials, cushioning materials can also contain additives. Examples of additives include colorants, flame retardants, antioxidants, UV absorbers, agglomeration inhibitors, antibacterial agents, mildew inhibitors, waxes, and mold release agents.

[0025] The cushioning material is manufactured using the aforementioned raw materials. The cushioning material has recesses that shelter and protect the packaged items. After being formed into a sheet or block shape in one step, the cushioning material undergoes secondary forming, such as compression molding, to create recesses that correspond to the three-dimensional shape of the packaged items. Furthermore, details of the manufacturing method for the cushioning material will be described later.

[0026] Preferably, the shape of the recess is a desired shape corresponding to the three-dimensional shape of the packaged item. Therefore, during compression molding, the shape of the metal mold must be accurately reflected in the recess. Consequently, in cushioning materials, it is necessary to suppress unintended deformation caused by the pressing of the metal mold in order to improve the mold conformity. That is, mold conformity is also a relatively important physical property in the mechanical strength of cushioning materials.

[0027] Examples of items that can be packaged include watches, laptops, small game consoles, smartphones, printers, projectors and other information terminal equipment, precision parts, models, pottery, porcelain, glassware, home appliances, as well as vegetables and fruits.

[0028] 2. Manufacturing method of cushioning material

[0029] like Figure 1 As shown, the method for manufacturing the cushioning material according to this embodiment includes a raw material supply process, a coarse crushing process, a fiber debonding process, a mixing process, a stacking process, a primary forming process, a cutting process, and a secondary forming process.

[0030] In the method for manufacturing cushioning materials, the cushioning material is manufactured through each process in the order described above, from the upstream raw material supply process to the downstream secondary forming process. Furthermore, the method for manufacturing the cushioning material of the present invention includes a fiber unwinding process, a mixing process, a stacking process, and a primary forming process, while other processes are not limited to the above. Moreover, the cushioning material of the present invention can also be used when the primary forming process is completed but the secondary forming process is not. The cushioning material without the secondary forming process is in the form of a sheet or block.

[0031] Specific examples of methods for manufacturing cushioning materials will be described together with the cushioning material manufacturing apparatus. The cushioning material manufacturing apparatus 1 described in this embodiment is an example and is not limited thereto.

[0032] like Figure 2 As shown, the cushioning material manufacturing apparatus 1 includes, from upstream to downstream, a supply unit 5, a coarse crushing unit 10, a fiber-removing unit 30, a mixing unit 60, a stacking unit 100, a sheet conveying unit 70, a one-time forming unit 150, and a cutting unit 160. Furthermore, although not shown in the figure, the cushioning material manufacturing apparatus 1 also includes a control unit that uniformly controls the operation of each of the above structures. In addition, in the cushioning material manufacturing method of this embodiment, a compression molding machine that performs a two-stage forming process is used for the plate-shaped cushioning material P manufactured using the cushioning material manufacturing apparatus 1. A known device can be used in the compression molding machine.

[0033] A raw material supply process is implemented in the supply unit 5. The supply unit 5 supplies raw materials to the coarse crushing unit 10. The supply unit 5 is equipped with, for example, an automatic feeding mechanism 6 to continuously and automatically feed the raw material fabric C into the coarse crushing unit 10. The fabric C is a material containing the aforementioned fibers.

[0034] A coarse crushing process is performed in the coarse crushing section 10. The coarse crushing section 10 shreds the fabric C supplied from the supply section 5 in an atmosphere such as air, turning it into fragments. The coarse crushing section 10 is a shredder, shredder, or the like, equipped with coarse crushing blades 11. The fabric C is shredded by the coarse crushing blades 11, thus becoming fragments. The planar shape of the fragments is, for example, a few millimeters square or irregular. The fragments are collected in the quantitative supply section 50.

[0035] The metering supply unit 50 measures the fragments and supplies them quantitatively to the hopper 12. The metering supply unit 50 is, for example, a vibrating feeder. The fragments supplied to the hopper 12 are conveyed in the pipe 20 and thus reach the inlet 31 of the defiberization unit 30.

[0036] The defibering process is performed in the defibering section 30. The defibering section 30 defibers the fabric C fragments in a dry manner to generate fibers. The defibering section 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 interior of the defibering section 30 via the inlet 31 through the airflow generated by the airflow generating mechanism. Furthermore, in this specification, "dry manner" refers to a method performed not in a liquid but in a gaseous environment such as the atmosphere.

[0037] The stator 33 and rotor 34 are disposed inside the debonding section 30. The stator 33 has a generally cylindrical inner surface. The rotor 34 rotates along the inner surface of the stator 33. Fragments of fabric C are trapped between the stator 33 and the rotor 34 and debonded by the shear force generated between them.

[0038] The length-weighted average fiber length of the unfurled fibers is preferably 1.0 mm or more, and the longest fiber length is preferably 5.0 mm or more. This ensures that the fibers are not excessively short, thereby further improving the mechanical strength of the cushioning material P. The length-weighted average fiber length is determined according to the method in ISO 16065-2:2007.

[0039] The longest fiber length was determined using the following method: The fibers were placed on a glass plate with minimal overlap. In this state, the fiber lengths were measured using a Keyence VHX-5000 digital microscope. Specifically, the fiber lengths were determined from digital photographs taken through the microscope using the included length measurement software. This process was performed on 50 randomly selected fibers, and the longest fiber length was designated as the longest fiber length. Fiber length refers to the distance traveled along the bend when the fiber is bent.

[0040] The aspect ratio of the fibers is preferably 0.9 or less. The aspect ratio is the value obtained by dividing the shortest fiber length by the fiber length. Thus, fibers that have bent or buckled are contained within the cushioning material P. Therefore, uneven distribution of fibers in the orientation direction is less likely to occur in the cushioning material P, and the fibers are more likely to entangle with each other. This further improves the mechanical strength of the cushioning material P.

[0041] The aspect ratio of the fiber is determined using the following method. The fiber, placed on a glass plate, is photographed in the same manner as its longest length. The shortest fiber length refers to the straight-line distance between the two ends of the fiber. The fiber length and the shortest fiber length are then determined from this digital photograph using the length measurement software included with the device. This process is performed on 50 randomly selected fibers, and the aspect ratio is calculated as the average of these 50 fibers.

[0042] The fibers generated by the defiberization section 30 are discharged from the outlet 32 ​​into the pipe 40. The pipe 40 is connected to the interior of the defiberization section 30 and the interior of the stacking section 100. The fibers are transported from the defiberization section 30 to the stacking section 100 by the airflow generated by the airflow generating mechanism. A mixing section 60 is provided on the pipe 40 between the defiberization section 30 and the stacking section 100.

[0043] A mixing process is performed in the mixing section 60. The mixing section 60 mixes bonding materials and the like into the fibers in the air, thereby generating a mixture. The mixing section 60 includes hoppers 13 and 14, supply pipes 61 and 62, and valves 65 and 66.

[0044] The hopper 13 is connected to the interior of the pipe 40 via a supply pipe 61. A valve 65 is disposed between the hopper 13 and the pipe 40 in the supply pipe 61. The hopper 13 supplies the binding material into the pipe 40. The valve 65 adjusts the weight of the binding material supplied from the hopper 13 to the pipe 40. This allows for adjustment of the mixing ratio of the fiber and the binding material. The binding material can be supplied as a powder or in a melted form.

[0045] Hopper 14 is connected to the interior of pipe 40 via supply pipe 62. A valve 66 is disposed between hopper 14 and pipe 40 in supply pipe 62. Hopper 14 supplies additives other than the binding material into pipe 40. Valve 66 adjusts the weight of the additive supplied from hopper 14 to pipe 40. This allows adjustment of the mixing ratio of additives with respect to fibers and binding material. Furthermore, in the cushioning material P, the additive is not a necessary component, and hopper 14 and supply pipe 62 can be omitted. Alternatively, the additive can be pre-mixed with the binding material and supplied from hopper 13.

[0046] Fibers and binding materials are mixed while being conveyed to the stacking section 100 within the pipe 40, thus forming a mixture. To promote the formation of the mixture in the pipe 40 and improve its conveyability, a blower or similar device that generates airflow may be installed in the pipe 40. The mixture is conveyed to the stacking section 100 via the pipe 40.

[0047] A stacking process is performed in the stacking section 100. The stacking section 100 stacks a mixture including fibers and binding materials in air to generate a sheet W. The stacking section 100 has a roller section 101 and a housing section 102 for housing the roller section 101. The stacking section 100 introduces the mixture from the pipe 40 into the interior of the roller section 101 and stacks it on the mesh belt 122 in a dry manner.

[0048] Below the stacking section 100, a sheet conveying section 70 including a mesh belt 122 and a suction mechanism 110 is disposed. The suction mechanism 110 is disposed opposite the roller section 101 in the direction along the Z-axis, across the mesh belt 122.

[0049] The drum section 101 is a cylindrical sieve that is driven to rotate by a motor (not shown). A mesh functioning as a sieve is provided on the side of the cylindrical drum section 101. The drum section 101 allows particles such as fibers or mixtures that are smaller than the mesh size of the sieve mesh to pass from the inside to the outside. The mixture passing through the drum section 101 unravels tangled fibers and disperses them into the air within the housing section 102.

[0050] The fibers are dispersed in the air within the housing portion 102, causing them to accumulate randomly on the mesh belt 122. Therefore, it is difficult to orient the fibers in a specific direction within the sheet W.

[0051] The sieve of the drum section 101 may not have the function of screening larger fibers in the mixture. That is, the drum section 101 may also break down the fibers of the mixture and release the entire mixture into the interior of the housing section 102. The mixture dispersed in the air inside the housing section 102 is accumulated on the surface above the mesh belt 122 by gravity and suction from the suction mechanism 110.

[0052] In the sheet W, the mass ratio of fiber to binding material is preferably set in the range of 15:85 to 45:55. This ensures various physical properties, including the mechanical strength of the cushioning material P. Furthermore, the density or thickness of the manufactured cushioning material P can be adjusted by the weight per unit area of ​​the sheet W.

[0053] The sheet conveying unit 70 includes a mesh belt 122 and a suction mechanism 110. The sheet conveying unit 70 promotes the accumulation of the mixture on the mesh belt 122 by the suction mechanism 110. In addition, the sheet conveying unit 70 conveys the sheet W formed by the mixture downstream by rotating the mesh belt 122.

[0054] A suction mechanism 110 is disposed below the roller section 101. The suction mechanism 110 draws 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 roller section 101 is drawn downwards along with the air, accumulating on the surface above the mesh belt 122. A known suction device such as a blower can be used in the suction mechanism 110.

[0055] The mesh belt 122 has multiple holes that allow air to pass through, but makes it difficult for fibers and binding materials contained in the mixture to pass through. The mesh belt 122 is a seamless belt and is supported by three support rollers 121.

[0056] The mesh belt 122 moves downstream by the rotation of the mounting roller 121. In other words, the mesh belt 122... Figure 2 The conveyor belt 122 rotates clockwise. The conveyor belt 122 is rotated by the support roller 121, thereby continuously piling up the mixture to form a sheet W. The sheet W contains a large amount of air, making it soft and expandable. The sheet W is conveyed downstream along with the movement of the conveyor belt 122.

[0057] Here, the sheet W can also be laminated using nonwoven fabric or the like. Specifically, when the sheet W is stacked on the mesh belt 122, a nonwoven fabric is placed between the mesh belt 122 and the sheet W. Furthermore, the upper surface of the sheet W is covered using the nonwoven fabric. By continuously supplying nonwoven fabric to the upper and lower surfaces relative to the sheet W, the sheet W is laminated with nonwoven fabric. The sheet W in this state can also be used to manufacture the cushioning material P.

[0058] The nonwoven fabric used in the lamination is preferably a nonwoven fabric composed of fibers such as polylactic acid, cellulose, and regenerated cellulose. This, together with the raw materials contained in the sheet W, can contribute to reducing environmental impact.

[0059] A humidifier 130 can also be installed downstream of the stacking section 100 to humidify the material sheets W on the conveyor belt 122 by spraying water in a mist form. This can suppress the scattering of fibers or binding materials contained in the material sheets W. Furthermore, the water used for humidification can contain water-soluble additives, and the material sheets W can be impregnated with these additives in parallel with humidification.

[0060] The sheet W is conveyed downstream via the mesh belt 122, peeled off the mesh belt 122, and introduced to the feed roller 141. The feed roller 141 is provided to ensure the processing time of the downstream primary forming process. Specifically, since the subsequent primary forming process after the stacking process is batch-processed, the feed roller 141 is moved up and down for the sheet W continuously supplied from the stacking section 100 to ensure the processing time of the primary forming process. The sheet W reaches the primary forming section 150 via the feed roller 141.

[0061] A one-time forming process is performed in the one-time forming section 150. In the one-time forming process, the sheet W is heated and pressurized to form a continuous sheet-shaped cushioning material P. The one-time forming section 150 is a heated stamping device, which includes an upper substrate 152 and a lower substrate 151. The upper substrate 152 and the lower substrate 151 are pressurized by clamping the sheet W in the middle, and the sheet W is heated by a built-in heater.

[0062] The sheet W is compressed from top to bottom under pressure, increasing its density, and the bonding material is melted by heating, causing it to wet and spread between the fibers. When heating ends and the resin cures in this state, the fibers are bonded together by the bonding material. Alternatively, in a single molding process, heated rollers or the like can be used for continuous processing.

[0063] The pressure and heating conditions in the one-piece forming section 150 are appropriately adjusted by the desired density of the cushioning material P and the melting point of the binding material resin. Although not particularly limited, the pressure conditions are, for example, 0.1 MPa or more, and the heating conditions are, for example, 90°C or more. Through the one-piece forming section 150, the sheet W is formed into a continuous, single-shaped cushioning material P and moves towards the cutting section 160.

[0064] The cutting process is performed in the cutting section 160. The cutting section 160 cuts the continuous sheet-like cushioning material P into single-sheet and plate-like cushioning material P. Although not shown in the figure, the cutting section 160 includes a longitudinal blade and a transverse blade.

[0065] The longitudinal blade cuts the cushioning material P in the direction of travel of the continuous sheet-like cushioning material P. The transverse blade cuts the cushioning material P in a direction intersecting the direction of travel of the continuous sheet-like cushioning material P. This produces a roughly rectangular sheet-like cushioning material P, which is then stored in the tray 170.

[0066] In the secondary forming process, after the primary forming process, a recess is formed in a predetermined area by pressing the sheet-like cushioning material P. Specifically, a compression forming machine is used to form the recess. As mentioned above, the recess is designed to correspond to the three-dimensional shape of the packaged item. The conformability of the compression forming process to the metal mold is affected by the mechanical strength of the cushioning material P. This mechanical strength is affected by the morphology or dispersion state of the fibers in the cushioning material P. Furthermore, a protrusion may also be formed together with the recess. Additionally, references to the following description... Figures 3 to 8 In this context, the -Z direction is not limited to the vertical direction.

[0067] like Figure 7 As shown, in the plate-shaped cushioning material P3 achieved by existing technology, multiple fibers F are oriented approximately along a plane orthogonal to the Z-axis. Furthermore, the fibers F exhibit minimal entanglement and interference with each other. These morphologies originate from a manufacturing method that involves layering fibers on a carding machine.

[0068] like Figure 8 As shown, when the cushioning material P3 is compressed and shaped in the -Z direction using a metal mold M, the periphery of the area contacted by the metal mold M will significantly indent. This is because, depending on the orientation and morphology of the multiple fibers F of the cushioning material P3, the compressive force of the metal mold M will disperse and affect the periphery. The morphology of the fiber F mentioned here refers to the length-weighted average fiber length, the longest fiber length, and the aspect ratio, etc.

[0069] Furthermore, since the cushioning material P3 is heated during compression molding, the resin in the cushioning material P3 does not contribute to the mechanical strength during compression molding. Therefore, it is difficult to improve the mechanical strength of the existing cushioning material P3, which can easily lead to a deterioration in its conformability to the metal mold.

[0070] In contrast, in the plate-shaped cushioning materials P1 and P2 of this embodiment, the orientation directions of the multiple fibers F are difficult to align, and they do not orient themselves in a specific direction. This is because, in order to perform the above-mentioned stacking process in the air, the fibers F are stacked randomly compared to the case where they are stacked in a carding machine. Furthermore, due to the defibering process, the length-weighted average fiber length and the longest fiber length of the fibers F are shorter compared to the case where the defibering process is not performed.

[0071] When knitted fabrics are used as raw materials for fiber F, such as Figure 3As shown, the cushioning material P1 contains a relatively large number of bent fibers F. Since knitted fabrics are woven from loops of yarn, fibers F that bend from the looped portions of the yarn within the knitted fabric are produced. Therefore, fibers F made from knitted fabric tend to have a smaller aspect ratio.

[0072] Furthermore, in this embodiment, the fibers F are stacked after being dispersed in the air through a stacking process to form a sheet W. Therefore, in the cushioning material P1, the fibers F are difficult to orient in a specific direction. Consequently, in the cushioning material P1, relatively short fibers F are randomly dispersed, and bent fibers F or straight fibers F are relatively intertwined. Therefore, the mechanical strength of the cushioning material P1 can be improved compared to the existing cushioning material P3.

[0073] like Figure 4 As shown, when the cushioning material P1 is compressed and shaped in the -Z direction through the metal mold M, almost no indentation occurs around the area in contact with the metal mold M. This is because, depending on the morphology or dispersion of the multiple fibers F of the cushioning material P1, the compressive force of the metal mold M is unlikely to affect the periphery. Therefore, the cushioning material P1 exhibits superior mechanical strength, thereby improving its conformity to the metal mold.

[0074] When plain weave fabric is used as a raw material for fiber F, such as Figure 5 As shown, in the cushioning material P2, several relatively short fibers F are randomly dispersed. Among the fibers F, there are also a smaller number of bent fibers F compared to knitted fabrics. Since plain weave fabrics are woven by interlacing the warp and weft threads, it is easy to generate fibers F that bend from the intersection of the warp and weft threads contained in the plain weave fabric.

[0075] Furthermore, in this embodiment, the fibers F are dispersed in the air through a stacking process and then stacked to form a sheet W. Therefore, in the cushioning material P2, the fibers F are difficult to orient in a specific direction. Consequently, in the cushioning material P2, multiple shorter fibers F are randomly dispersed and exist entangled together. Therefore, the mechanical strength of the cushioning material P2 is improved compared to conventional cushioning materials.

[0076] like Figure 6As shown, when the cushioning material P2 is compressed in the -Z direction using a metal mold M, although a slight indentation occurs around the area where the metal mold M contacts the material, the degree of indentation is less severe compared to the existing cushioning material P3. This is because, depending on the morphology or dispersion of the multiple fibers F of the cushioning material P3, the compressive force of the metal mold M is less likely to affect the periphery. Therefore, the cushioning material P2 possesses excellent mechanical strength, thereby improving its conformability to the metal mold.

[0077] By using the above method, a cushioning material P with a concave portion is manufactured. According to this embodiment, the following effects can be obtained.

[0078] A cushioning material P with improved mechanical strength can be manufactured. Specifically, by desiccifying the fabric C, the resulting fibers F are more easily shortened. Furthermore, by stacking the mixture in air to form a sheet W, the fibers F are less likely to be oriented in a specific direction within the sheet W. Consequently, within the cushioning material P, multiple shorter fibers F are randomly dispersed and intertwined. Therefore, compared to the prior art where fibers F are oriented in a specific direction and layered, the mechanical strength of the cushioning material P is improved. In other words, a method for manufacturing a cushioning material P with improved mechanical strength, as well as the cushioning material P itself, can be provided.

[0079] Because the cushioning material P has recesses, the packaged items can be contained within these recesses for protection. Furthermore, the increased mechanical strength of the cushioning material P improves its conformability to the metal mold during secondary forming processes such as compression molding. This allows for the precise formation of recesses with the desired shape.

[0080] 3. Examples and Comparative Examples

[0081] The following examples and comparative examples are shown, and the effects of the present invention will be explained in more detail. Table 1 shows the composition of the raw materials used in the manufacturing process, the manufacturing conditions, and the evaluation results for the cushioning materials P of Examples 1 and 2 and the cushioning material of Comparative Example 1. The "-" mark in the raw material composition column of Table 1 indicates that no additives were used. The present invention is not limited in any way by the following examples.

[0082] Table 1

[0083]

[0084] 3.1. Manufacturing of cushioning materials

[0085] As shown in Table 1, in Example 1, a knitted fabric made of 100% cotton was used as the fabric C which is the raw material of the fiber F. Specifically, as the coarse crushing process, the knitted fabric was coarsely crushed into irregular fragments with a long side of 1 mm to 30 mm by a shredder of Mano Sangyo Co., Ltd. (Japanese: 槇野産業社). Next, as the defibrating process, the above-mentioned fragments were defibrated in the same manner as the defibrating process of the above-described embodiment to obtain a defibrated product.

[0086] The fiber F was selected from the defibrated product, and the length-weighted average fiber length, the longest fiber length, and the aspect ratio of the fiber were obtained by the above method. As a result, the length-weighted average fiber length was 32 mm, the longest fiber length was 60 mm, and the aspect ratio of the fiber was 0.66.

[0087] Next, as the mixing process, the defibrated product of the fiber F and polylactic acid as the binding material were made into a mixture by air stirring at a mass percentage of 7:3. Thereafter, as the stacking process, the mixture was stacked in the air to form a sheet W with a unit area weight of 1500 g / m 2 Then, as the primary forming process, the sheet W was subjected to hot stamping. At this time, the heating condition was set to 135 °C for 5 minutes, and the pressing condition was set so that the thickness after manufacturing became 15 mm, and the plate-shaped cushioning material P of Example 1 was manufactured. The manufacturing method of the plate-shaped cushioning material P of Example 1 was set as manufacturing method α.

[0088] In Example 2, a plain woven fabric made of 100% cotton was used as the fabric C which is the raw material of the fiber F. Specifically, in Example 2, except for changing the raw material of the fiber F, the plate-shaped cushioning material P of Example 2 was manufactured by the manufacturing method α in the same manner as the plate-shaped cushioning material P of Example 1.

[0089] In addition, among the fibers F selected from the defibrated product of Example 2, the length-weighted average fiber length was 20 mm, the longest fiber length was 45 mm, and the aspect ratio of the fiber was 0.72.

[0090] In Comparative Example 1, commercially available absorbent cotton was used as the raw material of the fiber F. Specifically, the absorbent cotton was cut into approximately rectangular fragments of about 30 mm × 30 mm with scissors. Next, compressed air was blown onto the fragments to disassemble the fiber F into each single fiber F. Here, the disassembled fiber F was selected, and the length-weighted average fiber length, the longest fiber length, and the aspect ratio of the fiber were obtained by the above method. As a result, the length-weighted average fiber length was 28 mm, the longest fiber length was 30 mm, and the aspect ratio of the fiber was 0.93.

[0091] The disassembled fibers F and polylactic acid, used as a binder, were mixed in a 7:3 mass ratio by air stirring. This mixture was then placed on a metal tray, allowing the fibers F to diffuse while suppressing uneven distribution. This process was repeated to form a sheet of the mixture stacked on the metal tray. The sheet was then subjected to heating and pressing in the same manner as in Example 1. The heating conditions were set at 135°C for 5 minutes, and the pressing conditions resulted in a thickness of 15 mm, thus producing the plate-shaped cushioning material of Comparative Example 1. The manufacturing method of the plate-shaped cushioning material of Comparative Example 1 is designated as manufacturing method β.

[0092] 3.2 Evaluation of cushioning materials

[0093] The mechanical strength index was used to investigate the following of the metal mold in the compression molding process of the secondary forming process for the cushioning material P of Examples 1 and 2 and the cushioning material of Comparative Example 1.

[0094] Specifically, a sheet-like cushioning material P was cut into a square with 10cm sides, which was then used as a test piece. A 4cm diameter, 3cm high iron cylinder was placed at the center of the main surface of this test piece and then placed on the base plate of a hydraulic press. The top and bottom plates of the hydraulic press were preheated to 135°C. Next, the test piece and cylinder were compressed from top to bottom using the hydraulic press, so that the cylinder was submerged 1cm into the test piece. After being left in this state for 5 minutes, the test piece was removed from the hydraulic press while the cylinder was still in place, and then placed at room temperature of approximately 25°C.

[0095] After placement and cooling, the cylinder was removed from the test piece, and the shape of the concave portion of the test piece created by the cylinder was observed. Specifically, the angle between the bottom surface of the approximately circular concave portion, which is in contact with the bottom surface of the cylinder, and the side surface of the concave portion pressed into the test piece by the cylinder was measured. Specifically, a cross-section including the center of the bottom surface of the concave portion and the compression direction during compression molding was cut out. This cross-section was photographed and printed as an image, and the aforementioned angle was measured using a calorimeter. Measurements were performed on each test piece of the embodiments and comparative examples, and evaluations were conducted according to the following criteria.

[0096] Evaluation Criteria

[0097] A: The above angle is 80° or higher.

[0098] B: The angles mentioned above are 70° or higher and less than 80°.

[0099] C: The angles mentioned above are greater than 60° and less than 70°.

[0100] D: The angle mentioned above is less than 60°.

[0101] As shown in Table 1, the cushioning material P of Example 1 was rated A, and the cushioning material P of Example 2 was rated B. Thus, Examples 1 and 2 demonstrate cases where mechanical strength was improved and the conformity to the metal mold during compression molding was excellent. In contrast, the cushioning material of Comparative Example 1 was rated D, indicating that it was difficult to improve mechanical strength and had poor conformity to the metal mold.

[0102] Symbol Explanation

[0103] C…fabric; F…fiber; P…cushioning material; W…sheet material.

Claims

1. A method for manufacturing a cushioning material, wherein the cushioning material is used to store and protect packaged items, wherein... The method for manufacturing the cushioning material includes: The defiberization process involves dry defiberization of the fabric to produce fibers with an aspect ratio of less than 0.

9. The mixing process involves incorporating the binding material into the fibers to generate a mixture. The stacking process involves stacking the mixture in air to form flakes; In a single forming process, the sheet material is pressurized and heated to form the cushioning material; A secondary forming process, which forms a recess in a predetermined area of ​​the cushioning material by applying pressure after the primary forming process. The recess has a shape corresponding to the three-dimensional shape of the packaged item.

2. The method for manufacturing the cushioning material as described in claim 1, wherein, The fabric is a knitted fabric.

3. The method for manufacturing the cushioning material as described in claim 1, wherein, The fabric is a plain weave fabric.

4. The method for manufacturing the cushioning material as described in claim 1, wherein, The fabric may contain cotton or wool.

5. The method for manufacturing the cushioning material as described in claim 1, wherein, The bonding material is a biodegradable resin.

6. A cushioning material used in the method of manufacturing the cushioning material according to claim 1, wherein, Include: Fibers, which are obtained by unwinding fabrics, including plain weave or knitted fabrics; A binding material derived from natural substances binds the fibers together. The cushioning material has a recessed portion with a shape corresponding to the three-dimensional shape of the packaged item.

7. The cushioning material as described in claim 6, wherein, The length-weighted average fiber length is 1.0 mm or more. The longest fiber length of the fiber is 5.0 mm or more.

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