Patent Publication Number: US-2023150232-A1

Title: Buffer material

Description:
The present application is based on, and claims priority from JP Application Serial Number 2021-187949, filed Nov. 18, 2021, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a buffer material. 
     2. Related Art 
     For example, JP-A-9-019907 discloses a used paper board molded by heating and pressing a mixture of used paper pulp granules formed into a sponge shape by adding water to a used paper pulp subjected to dry type defibration and a fibrous or powdery synthetic resin having thermoplasticity. The used paper board is used, for example, as a buffer material. 
     However, in the used paper board described in JP-A-9-019907, used paper pulp components and thermoplastic resin components are arranged in a horizontal direction. Therefore, the buffering capacity against an impact in the thickness direction of the used paper board is insufficient when the used paper board is used as a buffer material. Further, with the used paper board described in JP-A 019907, there is a concern that paper powder is scattered during the production or the use of the used paper board as a buffer material. 
     SUMMARY 
     According to an aspect of the present disclosure, there is provided a buffer material including a buffer sheet that contains cellulose fibers and a binding material binding the cellulose fibers and has a sheet shape; and a nonwoven fabric sheet that is provided on at least one surface side of the buffer sheet and is formed of nonwoven fabric, in which the cellulose fibers are aligned in a direction intersecting a thickness direction of the buffer sheet, and the alignment direction of the cellulose fibers is along a direction in which an external force is received. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a view schematically showing an example of a production device capable of producing a buffer material of the present disclosure. 
         FIG.  2    is a perspective view showing the buffer material of  FIG.  1   . 
         FIG.  3    is a partially enlarged cross-sectional view which is a view for describing the buffer function and shows the buffer material of  FIG.  2   . 
         FIG.  4    is a partially enlarged cross-sectional view which is a view for describing the buffer function and shows the buffer material of  FIG.  2   . 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Hereinafter, a buffer material of the present disclosure will be described in detail based on preferred embodiments shown in the accompanying drawings. 
     First, a buffer material will be described. 
     Hereinafter, for convenience of the description, three axes orthogonal to each other are denoted as an x-axis, a y-axis, and a z-axis as shown in  FIGS.  2  to  4   . Further, an xy plane having the x-axis and the y-axis is horizontal, and the z-axis is vertical to the plane. Further, a direction in which an arrow of each axis is oriented is referred to as “+”, and a direction opposite to the direction is referred to as “−”. 
     As shown in  FIG.  2   , a buffer material WS of the present embodiment includes six buffer sheets  1 A and nonwoven fabric sheets  1 B respectively provided on both surface sides of the buffer sheets  1 A. In the present embodiment, the buffer material WS is used in a state where six buffer sheets  1 A provided with the nonwoven fabric sheets  1 B on both surface sides thereof are superimposed in an x-axis direction. 
     First, the buffer sheet  1 A will be described. 
     The buffer sheet  1 A contains a plurality of cellulose fibers and a binding material that binds the cellulose fibers. 
     The cellulose fibers are an abundant natural material derived from a plant, and it is preferable that the cellulose fibers be used as fibers from the viewpoints of suitably dealing with the environmental problems, saving reserve resources, stably supplying the buffer material WS, reducing the cost, and the like. Further, the cellulose fibers have a particularly high theoretical strength among various fibers and are also advantageous from the viewpoint of improving the strength of the buffer material. 
     Typically, cellulose fibers are mainly formed of cellulose, but may contain components other than cellulose. Examples of such components include hemicelluloses and lignin. 
     Here, the content of lignin in the cellulose fibers is preferably 5.0% by mass or less, more preferably 3.0% by mass or less, and still more preferably 1.0% by mass or less. 
     In this manner, buffering performance, particularly compression characteristics, of the buffer material WS is further improved. 
     The content of the cellulose in the cellulose fibers is preferably 50.0% by mass or greater, more preferably 60.0% by mass or greater, and still more preferably 80.0% by mass or greater. 
     For example, fibers which have been subjected to a bleaching treatment or the like may be used as the cellulose fibers. Further, the cellulose fibers may have been subjected to a treatment such as an ultraviolet irradiation treatment, an ozone treatment, or a plasma treatment. 
     As the cellulose fibers, chemical cellulose fibers such as organic cellulose fibers, inorganic cellulose fibers, and organic-inorganic composite cellulose fibers may be used in addition to the natural cellulose fibers such as animal cellulose fibers and plant cellulose fibers. More specifically, examples of the cellulose fibers include cellulose fibers consisting of cellulose, cotton, cannabis, kenaf, linen, ramie, jute, manila hemp, sisal hemp, conifer, and hardwood. These cellulose fibers may be used alone or in the form of a mixture as appropriate, or may be used as regenerated cellulose fibers which have been purified or the like. Further, the cellulose fibers may be subjected to various surface treatments. 
     The average length of the cellulose fibers is not particularly limited, but is preferably 10 μm or greater and 50 mm or less, more preferably 20 μm or greater and 5.0 mm or less, and still more preferably 30 μm or greater and 3.0 mm or less in terms of the length-weighted average fiber length. 
     In this manner, the stability of the shape of the buffer material WS, the strength of the buffer material, and the like can be further improved. Further, the buffering performance of the buffer material WS can be further improved. 
     When the cellulose fibers contained in the buffer sheet  1 A are considered to be one independent cellulose fiber, the average thickness thereof is preferably 1.0 μm or greater and 1000 μm or less and more preferably 2.0 μm or greater and 100.0 μm or less. 
     In this manner, the stability of the shape of the buffer material WS, the strength of the buffer material, and the like can be further improved. Further, the buffering performance of the buffer material WS can be further improved. Further, it is possible to more effectively prevent the surface of the buffer material WS from being unexpectedly uneven. 
     Further, when a cross section of the cellulose fiber is not circular, a circle having the same area as the area of the cross section is assumed, and the diameter of the circle is used as the thickness of the cellulose fiber. 
     The average aspect ratio of the cellulose fibers, that is, the average length with respect to the average thickness is not particularly limited, but is preferably 10 or greater and 1000 or less and more preferably 15 or greater and 500 or less. 
     In this manner, the stability of the shape of the buffer material WS, the strength of the buffer material, and the like can be further improved. Further, the buffering performance of the buffer material WS can be further improved. Further, it is possible to more effectively prevent the surface of the buffer material WS from being unexpectedly uneven. 
     In the present specification, the term “cellulose fibers” denote a single cellulose fiber or an aggregate of a plurality of cellulose fibers. Further, the cellulose fibers may be cellulose fibers loosened into fibers by performing a defibration treatment on a material to be defibrated, that is, a defibrated material. Examples of the material to be defibrated here include cellulose fibers obtained by being entangled or bound, such as pulp sheets, paper, used paper, tissue paper, kitchen paper, cleaners, filters, liquid absorbing materials, sound absorbing bodies, buffer materials, mats, and corrugated cardboard. 
     The content of the cellulose fibers in the buffer sheet  1 A is preferably 63.0% by mass or greater and 90.0% by mass or less, more preferably 67.0% by mass or greater and 88.0% by mass or less, and still more preferably 72.0% by mass or greater and 86.0% by mass or less. 
     In this manner, the strength and the buffering performance of the buffer material WS can be further improved. 
     The buffer sheet  1 A contains a binding material. 
     The binding material has a function of binding a cellulose fiber to a cellulose fiber and may further have other functions. More specifically, the binding material may have a function of suppressing a component other than the cellulose fibers, for example, a colorant or the like described below from falling off from the buffer material. 
     It is preferable that the binding material have thermal plasticity. 
     In this manner, the binding material is melted or softened by applying heat in the process of producing the buffer material to spread between cellulose fibers, and thus the cellulose fibers are likely to be bound to each other. 
     The binding material is melted or softened preferably at 200° C. or lower and more preferably at 160° C. or lower. 
     In this manner, the cellulose fibers can be more suitably bound to each other by carrying out a heat treatment at a relatively low temperature, which is more preferable from the viewpoint of energy saving. 
     The glass transition temperature of the binding material is preferably 45° C. or higher and 95° C. or lower and more preferably 50° C. or higher and 90° C. or lower. 
     In this manner, the cellulose fibers can be more suitably bound to each other by carrying out a heat treatment at a relatively low temperature, which is more preferable from the viewpoint of energy saving. Further, for example, it is possible to effectively prevent the natural binding material from being unexpectedly softened when the buffer material stands in a high temperature environment. 
     The binding material may be a petroleum-based binding material derived from petroleum or a natural binding material derived from the nature. 
     Examples of the petroleum-based binding material include various synthetic resins such as thermoplastic resins, thermosetting resins, and photocuring resins. 
     Examples of the thermoplastic resins among the synthetic resins include an AS resin, an ABS resin, polypropylene, polyethylene, polyvinyl chloride, polystyrene, an acrylic resin, a polyester resin, polyethylene terephthalate, polyphenylene ether, polybutylene terephthalate, nylon, polyamide, polycarbonate, polyacetal, polyphenylene sulfide, and polyether ether ketone. 
     Among the synthetic resins, biodegradable resins such as polylactic acid, polybutylene succinate, and polyhydroxybutanoic acid may be used as the binding materials other than the natural binding material. 
     The environmental suitability of the buffer material can be further improved by using the biodegradable resins. 
     Further, the resins may be, for example, copolymerized or modified. 
     Examples of the natural binding material include natural resins such as rosin, dammar, mastic, copal, amber, a shellac resin, dragon tree, sandarac, and colophonium, starch which is a natural polymer, and modified products thereof, and one or two or more selected from among these can be used in combination, but it is preferable that the natural binding material contain a shellac resin. 
     In this manner, the strength and the buffering performance of the buffer material WS can be further improved, and the workability of the buffer material WS can also be further improved. 
     The starch is a polymer material obtained by polymerizing a plurality of a-glucose molecules with glycoside bonds. The starch may be linear or branched. 
     For example, starch derived from various plants can be used as the starch. Examples of raw materials of starch include cereals such as corn, wheat, and rice, beans such as broad beans, mung beans, and adzuki beans, tubers such as potatoes, sweet potatoes, and tapioca, wild grasses such as dogtooth violet, bracken, and kadzu, and palms such as sago palm. 
     For example, processed starch or modified starch may be used as the starch. Examples of the processed starch include acetylated adipic acid crosslinked starch, acetylated starch, oxidized starch, sodium octenyl succinate starch, hydroxypropyl starch, hydroxypropylated phosphoric acid crosslinked starch, phosphorylated starch, phosphoric acid monoesterified phosphoric acid crosslinked starch, urea phosphorylated esterified starch, sodium starch glycolate, and high amylose cornstarch. Further, examples of the modified starch include pregelatinized starch, dextrin, laurylpolyglucose, cationized starch, thermoplastic starch, and carbamic acid starch. 
     The content of the binding material in the buffer sheet  1 A is preferably 12.0% by mass or greater and 28.0% by mass or less, more preferably 14.0% by mass or greater and 25.0% by mass or less, and still more preferably 15.0% by mass or greater and 22.0% by mass or less. 
     In this manner, the above-described effects are more significantly exhibited. 
     Further, a ratio B/A of a content A of the cellulose fibers in the buffer sheet  1 A to a content B of the binding material in the buffer sheet  1 A is preferably 1/9 or greater and 3/7 or less and more preferably 1/8 or greater and 2/7 or less. In this manner, the cellulose fibers can be more reliably bound while the content of the cellulose fibers is sufficiently ensured. 
     The buffer sheet  1 A is not limited as long as the buffer sheet  1 A contains the cellulose fibers and the binding material, but may further contain other components in addition the above-described components. Hereinafter, such components will also be referred to as “other components”. 
     Examples of the other components include a flame retardant, a colorant, an aggregation inhibitor, a surfactant, a fungicide, a preservative, an antioxidant, an ultraviolet absorbing agent, and an oxygen absorbing agent. 
     The content of the other components in the buffer sheet  1 A is preferably 7.0% by mass or less, more preferably 5.0% by mass or less, and still more preferably 3.0% by mass or less. 
     As shown in  FIG.  2   , the buffer sheet  1 A has a sheet shape. The thickness of the buffer sheet  1 A is not particularly limited, but is preferably 1.0 mm or greater and 100 mm or less, more preferably 1.5 mm or greater and 30 mm or less, and still more preferably 2.0 mm or greater and 20 mm or less. 
     In this manner, the strength and the rigidity of the buffer material WS can be further improved. Further, for example, the workability when the sheet-like buffer material WS is processed into a buffer material WS having a three-dimensional shape by carrying out a process of deep drawing or the like can be further improved, and occurrence of wrinkles or breakage can be more effectively prevented. 
     Next, the nonwoven fabric sheets  1 B will be described. 
     In the present embodiment, the nonwoven fabric sheets  1 B are respectively provided on both surface sides of the buffer sheet  1 A. The nonwoven fabric sheets  1 B are bonded to the buffer sheet  1 A. Since the respective nonwoven fabric sheets  1 B have the same configuration, one nonwoven fabric sheet  1 B will be described below. 
     As described above, the both surfaces of the buffer sheet  1 A are covered with the nonwoven fabric sheet  1 B, and thus it is possible to prevent or suppress powder of the cellulose fibers or the like of the buffer sheet  1 A from being scattered. Therefore, adhesion of powder of the cellulose fibers or the like to an object to be protected can be prevented or suppressed. Further, as described above, it is possible to prevent or suppress paper powder from being scattered in the middle of the production. In addition, the buffer sheet  1 A can be reinforced so that buckling deformation of the buffer sheet  1 A can be prevented or suppressed. 
     The constituent material for the fibers constituting the nonwoven fabric sheet  1 B is not particularly limited, and it is preferable that the nonwoven fabric sheet  1 B be formed of one or two or more kinds of materials selected from the group consisting of resin materials such as nylon, polyethylene terephthalate, polypropylene, and polytetrafluoroethylene, inorganic materials such as glass, alumina, and carbon, and materials derived from the nature (natural fibers) such as metal materials, cellulose, and pulp. 
     Among these, it is preferable that the fibers contained in the nonwoven fabric sheet be natural fibers. In this manner, adverse effects on the environment at the time of disposal of the buffer material WS can be reduced. 
     Particularly, it is preferable that the fibers constituting the nonwoven fabric sheet  1 B be the same as the cellulose fibers used for the buffer sheet  1 A. 
     Further, it is preferable that the average length of the fibers constituting the nonwoven fabric sheet  1 B be greater than the average length of the cellulose fibers contained in the buffer sheet  1 A. In this manner, it is possible to prevent or suppress paper powder from being scattered from the nonwoven fabric sheet  1 B. 
     The average length of the fibers constituting the nonwoven fabric sheet  1 B is not particularly limited, but is preferably 12 μm or greater and 60 mm or less, more preferably 25 μm or greater and 6.0 mm or less, and still more preferably 40 μm or greater and 4.0 mm or less in terms of the length-weighted average fiber length. 
     In this manner, it is possible to effectively prevent or suppress the cellulose fibers of the buffer sheet  1 A from being scattered from between the fibers constituting the nonwoven fabric sheet  1 B. 
     When the fibers constituting the nonwoven fabric sheet  1 B are considered to be one independent cellulose fiber, the average thickness thereof is preferably 1.0 μm or greater and 1000 μm or less and more preferably 2.0 μm or greater and 100.0 μm or less. 
     In this manner, it is possible to effectively prevent or suppress the cellulose fibers of the buffer sheet  1 A from being scattered from between the fibers constituting the nonwoven fabric sheet  1 B. 
     The average aspect ratio of the fibers constituting the nonwoven fabric sheet  1 B, that is, the average length with respect to the average thickness thereof is not particularly limited, but is preferably 10 or greater and 1000 or less and more preferably 15 or greater and 500 or less. 
     Further, the nonwoven fabric sheet  1 B may contain a binding material that binds the fibers. The binding material is not particularly limited and can be appropriately selected from, for example, those exemplified as the binding material contained in the buffer sheet  1 A and then used. 
     The thickness (average thickness) of the nonwoven fabric sheet  1 B is not particularly limited, but is, for example, preferably 0.1 mm or greater and 5 mm or less, more preferably 0.3 mm or greater and 3 mm or less, and still more preferably 0.5 mm or greater and 2 mm or less. 
     In this manner, it is possible to more effectively prevent or suppress powder of the cellulose fibers or the like of the buffer sheet  1 A from being scattered. 
     The thickness of the nonwoven fabric sheet  1 B is preferably 5% or greater and 90% or less and more preferably 10% or greater and 80% or less of the thickness of the buffer sheet  1 A. In this manner, the first projections  11 A and the second projections  12 A can sufficiently exhibit the above-described effects. Further, it is possible to more reliably prevent or suppress powder of the cellulose fibers or the like of the buffer sheet  1 A from being scattered. 
     Further, the density of the nonwoven fabric sheet  1 B is preferably 0.01 g/cm 3  or greater and 0.05 g/cm 3  or less and more preferably 0.02 g/cm 3  or greater and 0.04 g/cm 3  or less. In this manner, it is possible to more effectively prevent or suppress powder of the cellulose fibers or the like of the buffer sheet  1 A from being scattered and to sufficiently ensure the buffering performance of the buffer sheet  1 A. 
     Further, the basis weight of the nonwoven fabric sheet  1 B is less than the basis weight of the cellulose fibers in the buffer sheet  1 A. In this manner, it is possible to prevent or suppress the buffering performance of the buffer sheet  1 A from being decreased due to the nonwoven fabric sheet  1 B. 
     Further, the basis weight of the nonwoven fabric sheet  1 B is preferably 10 g/m 2  or greater and 300 g/m 2  or less, more preferably 20 g/m 2  or greater and 200 g/m 2  or less, and still more preferably 30 g/m 2  or greater and 100 g/m 2  or less. In this manner, it is possible to more effectively prevent or suppress powder of the cellulose fibers or the like of the buffer sheet  1 A from being scattered and to sufficiently ensure the buffering performance of the buffer sheet  1 A. 
     Further, when sixteen nonwoven fabric sheets  1 B each having a thickness of 0.5 mm are superimposed and 300 cc of air is blown thereto at a speed of 10 cm/sec, the time required to permeate the air through the nonwoven fabric sheets  1 B is preferably 0.5 seconds or longer and 2.0 seconds or shorter and more preferably 0.7 seconds or longer and 1.7 seconds or shorter. 
     According to such a nonwoven fabric sheet  1 B, the nonwoven fabric sheet  1 B can prevent or suppress powder (paper powder) of the cellulose fibers or the like of the buffer sheet  1 A from being scattered. Therefore, adhesion of paper powder to an object to be protected can be prevented or suppressed. Further, as described above, it is possible to prevent or suppress paper powder from being scattered in the middle of the production. 
     Further, in the present embodiment, the nonwoven fabric sheets  1 B are respectively provided on both surface sides of the buffer sheet  1 A, but the present disclosure is not limited thereto and the nonwoven fabric sheet  1 B may be provided only on one surface side thereof. 
     As described above, the buffer material WS is formed such that the buffer sheets  1 A provided with the nonwoven fabric sheets  1 B on both surface sides thereof are laminated in the x-axis direction. Further, the upper surface in  FIG.  2   , that is, the surface parallel to the xy plane positioned on a +z-axis side is a pressure receiving surface  200  that receives an external force from an object to be protected. 
     Further, the cellulose fibers in the buffer sheet  1 A are aligned in a plane direction of a yz plane, that is, a direction intersecting the thickness direction of the buffer sheet  1 A. The expression “cellulose fibers are aligned in a direction intersecting the thickness direction of the buffer sheet  1 A” denotes that a main alignment direction of the cellulose fibers is a direction along the plane direction of the buffer sheet  1 A. 
     More specifically, the alignment degree in the x-axis direction is less than the alignment degree in a y-axis direction and the alignment degree in a z-axis direction. Further, the cellulose fibers are randomly aligned in the yz plane. Here, the alignment degree in the z-axis direction may be greater than the alignment degree in the y-axis direction. 
     The alignment direction of the cellulose fibers is acquired by a method of observing the surface of the buffer sheet  1 A under conditions of a magnification of 200 times or greater and 500 times or less using a digital microscope (VHX5000, manufactured by KEYENCE CORPORATION). Further, 50 fibers are randomly selected from the cellulose fibers observed with the digital microscope, the alignment directions using the observed surface as a reference are measured, the average value thereof is calculated, and the obtained direction is defined as the alignment direction of the cellulose fibers. 
     When described from a different viewpoint, the number of fibers in which the alignment direction of the cellulose fiber is a predetermined direction is defined as T1, the number of cellulose fibers in which the alignment direction is a direction different from the predetermined direction is defined as T2, and a ratio T1/T2 is acquired. Therefore, the proportion of the number of cellulose fibers in the predetermined direction can be acquired. Further, a predetermined direction in which the proportion of the number of cellulose fibers is the highest can be defined as the alignment direction of the cellulose fibers. 
     When an external force is applied to such a buffer material WS from an object to be protected, first, the external force is transmitted to the buffer sheet  1 A. In the buffer sheet  1 A, the fibers are aligned in the plane direction of the y-z plane as described above. Therefore, when an external force is applied from the +z-axis side to the buffer sheet  1 A, particularly the cellulose fibers oriented in the z-axis direction move from a state shown in  FIG.  3    to a state shown in  FIG.  4   , that is, to ±x-axis sides or ±y-axis sides in order to avoid the external force. Since the fibers are dissociated from each other from a state where the fibers are bound by the binding material due to the movement of the fibers, the impact energy of the external force is consumed, and the external force is relaxed and absorbed. As a result, an excellent buffer function can be exhibited. 
     Further, the fibers move in a direction different from the direction in which the external force is received, and thus the fibers are unlikely to be densified. Therefore, the buffer function can be sufficiently exhibited even when the buffer material WS is repeatedly used. 
     As described above, the buffer material WS includes the buffer sheet  1 A that contains cellulose fibers and a binding material binding the cellulose fibers and has a sheet shape, and the nonwoven fabric sheet  1 B that is provided on at least one surface side of the buffer sheet  1 A and is formed of nonwoven fabric. Further, the cellulose fibers are aligned in a direction intersecting the thickness direction of the buffer sheet  1 A, and the alignment direction of the cellulose fibers is along a direction in which an external force is received. In this manner, the cellulose fibers easily move when an impact is applied to the buffer material WS, and thus the buffer function can be exhibited due to this movement. Further, since at least one surface of the buffer material sheet  1 A is covered with the nonwoven fabric sheet  1 B, it is possible to prevent or suppress paper powder from being scattered. According to the buffer material WS, it is possible to prevent or suppress paper powder from being scattered while the buffer performance is enhanced, as described above. 
     Further, since the buffer material WS is produced by a production device  100  described below, the buffer material WS does not adversely affect the environment and has excellent recyclability. 
     Further, the alignment direction of the fibers in the nonwoven fabric sheet  1 B is the same as the alignment direction of the cellulose fibers in the buffer sheet  1 A. In this manner, the cellulose fibers easily move even in the nonwoven fabric sheet  1 B when an impact is applied to the buffer material WS, and thus the buffer function can be exhibited due to this movement. Accordingly, the buffering performance of the buffer material WS can be further enhanced. 
     Production device 
     Next, a production device that can be used for production of the buffer material WS will be described. 
       FIG.  1    is a view schematically showing an example of a production device capable of producing the buffer material WS. 
     As shown in  FIG.  1   , a production device  100  includes a supply unit  10 , a crushing unit  12 , a defibrating unit  20 , a sorting unit  40 , a first web forming unit  45 , a rotating body  49 , a mixing unit  50 , an accumulating unit  60 , a second web forming unit  70 , a buffer material forming unit  80 , a cutting unit  90 , and a humidifying unit  78 . 
     The supply unit  10  supplies the raw material to the crushing unit  12 . The supply unit  10  is an automatic charging unit for continuously charging the crushing unit  12  with the raw material. The raw material to be supplied to the crushing unit  12  may contain the cellulose fibers. 
     The crushing unit  12  cuts the raw material supplied by the supply unit  10  in the atmosphere, for example, in the air to form small pieces. As the shape and the size of the small pieces, small pieces with a size of several cm square may be exemplified. In the example shown in the figure, the crushing unit  12  includes crushing blades  14 , and the raw material added to the crushing unit  12  can be cut by the crushing blades  14 . For example, a shredder is used as the crushing unit  12 . The raw material cut by the crushing unit  12  is received by a hopper  1  and transported to the defibrating unit  20  through a pipe  2 . 
     The defibrating unit  20  defibrates the raw material cut by the crushing unit  12 . Here, the term “defibrate” denotes that the raw material formed by binding a plurality of cellulose fibers, that is, a material to be defibrated is loosened into individual cellulose fibers. The defibrating unit  20  also has a function of separating substances, such as resin particles, an ink, a toner, a filler, and a bleeding inhibitor, adhering to the raw material from the cellulose fibers. 
     The material having passed through the defibrating unit  20  is referred to as “defibrated material”. In some cases, “defibrated material” contains, in addition to the loosened cellulose fibers, resin particles separated from the cellulose fibers during loosening of the cellulose fibers, a coloring agent such as an ink, a toner, or a filler, and an additive such as a bleeding inhibitor or a paper strength enhancer. Examples of the resin particles separated from the cellulose fibers include particles containing a resin for binding a plurality of cellulose fibers. 
     The defibrating unit  20  performs dry type defibration. A treatment of performing defibration or the like in the atmosphere, for example, in the air without performing wet type defibration of dissolving a material in a liquid such as water in a slurry form is referred to as dry type defibration. In the present embodiment, an impeller mill is used as the defibrating unit  20 . The defibrating unit  20  has a function of generating an air flow that sucks the raw material and discharges the defibrated material. In this manner, the defibrating unit  20  can suck the raw material from an introduction port  22  together with the air flow, perform the defibration treatment, and transport the defibrated material to a discharge port  24  by the air flow generated by itself. The defibrated material that has passed through the defibrating unit  20  is transferred to the sorting unit  40  through the pipe  3 . Further, as the air flow for transporting the defibrated material to the sorting unit  40  from the defibrating unit  20 , the air flow generated by the defibrating unit  20  may be used or an airflow generating device such as a blower is provided and an air flow generated by the device may be used. 
     The sorting unit  40  introduces the defibrated material defibrated by the defibrating unit  20  from the introduction port  42  and sorts out the defibrated material according to the length of the cellulose fibers. The sorting unit  40  includes a drum portion  41  and a housing unit  43  that accommodates the drum portion  41 . For example, a sieve is used as the drum portion  41 . The drum portion  41  has a net and can divide the defibrated material into a first sorted material that is cellulose fibers or particles having a size smaller than the size of the mesh of the net and thus passing through the net and a second sorted material that is cellulose fibers, undefibrated pieces, or lumps having a size greater than the size of the mesh of the net and thus not passing through the net. For example, the first sorted material is transferred to the mixing unit  50  through the pipe  7 . The second sorted material is returned to the defibrating unit  20  from a discharge port  44  through a pipe  8 . Specifically, the drum portion  41  is a cylindrical sieve rotationally driven by a motor. As the net of the drum portion  41 , for example, a wire net, an expanded metal obtained by expanding a metal plate with cuts, or a punching metal in which holes are formed in a metal plate with a press machine or the like is used. 
     The first web forming unit  45  transports the first sorted material having passed through the sorting unit  40  to the mixing unit  50 . The first web forming unit  45  includes a mesh belt  46 , a stretching roller  47 , and a suction unit  48 . 
     The suction unit  48  can suck the first sorted material having passed through the opening of the sorting unit  40 , that is, the opening of the net and dispersed in the air, onto the mesh belt  46 . The first sorted material is accumulated on the moving mesh belt  46  to form a web V. The basic configurations of the mesh belt  46 , the stretching roller  47 , and the suction unit  48  are the same as the configurations of a mesh belt  72 , a stretching roller  74 , and a suction mechanism  76  of the second web forming unit  70  described below. 
     The web V passes through the sorting unit  40  and the first web forming unit  45  and is thus formed in a soft and inflated state due to containing a large amount of air. The pipe  7  is charged with the web V accumulated on the mesh belt  46 , and the web V is transported to the mixing unit  50 . 
     The rotating body  49  can cut the web V before the web V is transported to the mixing unit  50 . In the example shown in the figure, the rotating body  49  includes a base portion  49   a  and protrusions  49   b  protruding from the base portion  49   a.  The protrusions  49   b  have, for example, a plate shape. In the example shown in the figure, four protrusions  49   b  are provided and the four protrusions  49   b  are provided at equal intervals. Since the base portion  49   a  rotates in a direction R, the protrusions  49   b  can rotate using the base portion  49   a  as an axis. Since the web V is cut by the rotating body  49 , for example, a fluctuation in amount of the defibrated material supplied to the accumulating unit  60  per unit time can be reduced. 
     The rotating body  49  is provided in the vicinity of the first web forming unit  45 . In the example shown in the figure, the rotating body  49  is provided in the vicinity of the stretching roller  47   a  positioned on the downstream in the path of the web V, that is, next to the stretching roller  47   a.  The rotating body  49  is provided at a position where the protrusions  49   b  can come into contact with the web V and does not come into contact with the mesh belt  46  on which the web V is accumulated. The shortest distance between the protrusions  49   b  and the mesh belt  46  is, for example, 0.05 mm or greater and 0.5 mm or less. 
     The mixing unit  50  mixes the first sorted material having passed through the sorting unit  40 , that is, the first sorted material transported by the first web forming unit  45  with an additive containing the natural binding material. The mixing unit  50  includes an additive supply unit  52  that supplies the additive, a pipe  54  that transports the first sorted material and the additive, and a blower  56 . In the example shown in the figure, the additive is supplied to the pipe  54  through the hopper  9  from the additive supply unit  52 . The pipe  54  is connected to the pipe  7 . 
     The mixing unit  50  allows the blower  56  to generate an air flow so that the first sorted material and the additive can be transported while being mixed with each other in the pipe  54 . Further, the mechanism of mixing the first sorted material and the additive is not particularly limited, and the first sorted material and the additive may be mixed by being stirred using a blade rotating at a high speed or may be mixed by using rotation of a container as in a case of a V type mixer. 
     A screw feeder as shown in  FIG.  1    or a disc feeder which is not shown in the figure is used as the additive supply unit  52 . The additive supplied from the additive supply unit  52  contains the above-described natural binding material. The plurality of cellulose fibers have not been bound at the time point when the natural binding material is supplied. The natural binding material is partially melted while passing through the buffer material forming unit  80  so that the plurality of cellulose fibers in the surface region of the buffer material WS are bound. 
     Further, the additive to be supplied from the additive supply unit  52  may contain, in addition to the natural binding material, a colorant for coloring the cellulose fibers, an aggregation inhibitor for suppressing aggregation of the cellulose fibers or aggregation of the natural binding material, and a flame retardant for making the cellulose fibers and the like difficult to burn, depending on the type of the buffer material WS to be produced. The composition for producing a buffer material which is the mixture having passed through the mixing unit  50 , that is, the mixture of the first sorted material and the additive is transferred to the accumulating unit  60  through the pipe  54 . 
     The accumulating unit  60  introduces the mixture having passed through the mixing unit  50  from the introduction port  62 , loosens the defibrated material of the entangled cellulose fibers, and drops the mixture while dispersing the mixture in the air. In this manner, the accumulating unit  60  can uniformly accumulate the mixture on the second web forming unit  70 . 
     The accumulating unit  60  includes a drum portion  61  and a housing unit  63  that accommodates the drum portion  61 . A cylindrical rotating sieve is used as the drum portion  61 . The drum portion  61  has a net and drops the cellulose fibers or particles which are contained in the mixture having passed through the mixing unit  50  and have a size smaller than the size of the mesh of the net. The configuration of the drum portion  61  is the same as the configuration of the drum portion  41 . 
     Further, “sieve” of the drum portion  61  may not have a function of sorting out a specific object. That is, “sieve” used as the drum portion  61  denotes a portion provided with a net, and the drum portion  61  may drop the entire mixture introduced to the drum portion  61 . 
     The second web forming unit  70  accumulates the material having passed through the accumulating unit  60  to form a web W which is an accumulated material serving as the buffer material WS. Further, the alignment direction of the cellulose fibers in the web W is along the plane direction. 
     The second web forming unit  70  includes a nonwoven fabric sheet supply unit  70 A and a nonwoven fabric sheet supply unit  70 B that supply the nonwoven fabric sheet  1 B, the mesh belt  72 , the stretching roller  74 , and the suction mechanism  76 . 
     The nonwoven fabric sheet supply unit  70 A is a roller that develops and delivers the nonwoven fabric sheet  1 B wound in a roll shape. The nonwoven fabric sheet supply unit  70 A is disposed above the mesh belt  72  and on the upstream of the mesh belt  72  in the transport direction. The nonwoven fabric sheet  1 B developed and delivered by the nonwoven fabric sheet supply unit  70 A is supplied onto the mesh belt  72 . 
     The mesh belt  72  accumulates the material having passed through the opening of the accumulating unit  60 , that is, the opening of the net on the molding die while moving. The mesh belt  72  is configured to be stretched by the stretching roller  74  and circulate the air to make the material having passed through the accumulating unit difficult to pass through. The mesh belt  72  moves by rotation of the stretching roller  74 . The mesh belt  72  continuously drops and accumulates the material having passed through the accumulating unit  60  while continuously moving and transporting the nonwoven fabric sheet  1 B on the mesh belt  72 , and thus the web W is formed on the molding die provided on the nonwoven fabric sheet  1 B. The mesh belt  72  is made of, for example, a metal, a resin, cloth, or nonwoven fabric. 
     The suction mechanism  76  is provided below the mesh belt  72 , that is, on a side opposite to the side of the accumulating unit  60 . The suction mechanism  76  can generate an air flow flowing downward, that is, an air flow flowing to the mesh belt  72  from the accumulating unit  60 . The mixture dispersed in the air by the accumulating unit  60  can be sucked onto the nonwoven fabric sheet  1 B on the mesh belt  72  by the suction mechanism  76 . In this manner, the discharge rate of the material from the accumulating unit  60  can be increased. Further, the suction mechanism  76  can form a downflow in the path where the mixture falls, and thus it is possible to suppress the defibrated material and the additive from being entangled with each other during the fall. 
     The nonwoven fabric sheet supply unit  70 B is a roller that develops and delivers the nonwoven fabric sheet  1 B wound in a roll shape. The nonwoven fabric sheet supply unit  70 B is disposed above the mesh belt  72  and on the upstream of the mesh belt  72  in the transport direction. The nonwoven fabric sheet  1 B developed and delivered by the nonwoven fabric sheet supply unit  70 A is supplied onto the web W accumulated on the nonwoven fabric sheet  1 B. In this manner, a laminate S in which the nonwoven fabric sheet  1 B, the web W, and the nonwoven fabric sheet  1 B are laminated in order is generated. The laminate S is transported to the buffer material forming unit  80 . 
     Further, the alignment direction of the fibers in the nonwoven fabric sheet is along the plane direction. 
     As described above, the laminate S in which the nonwoven fabric sheet  1 B, the web W, and the nonwoven fabric sheet  1 B are laminated in order is formed by carrying out the web forming step performed by the accumulating unit  60  and the second web forming unit  70 . 
     The thickness of the web W is preferably 2.0 mm or greater and 150 mm or less, more preferably 3.0 mm or greater and 120 mm or less, and still more preferably 5.0 mm or greater and 100 mm or less. 
     Further, the density of the web W is preferably 0.01 g/cm 3  or greater and 0.05 g/cm 3  or less and more preferably 0.02 g/cm 3  or greater and 0.04 g/cm 3  or less. 
     Further, the basis weight of the web W is preferably 20 g/m 2  or greater and 7500 g/m 2  or less, more preferably 30 g/m 2  or greater and 6000 g/m 2  or less, and still more preferably 50 g/m 2  or greater and 5000 g/m 2  or less. 
     The buffer material forming unit  80  forms the buffer material WS by heating the web W accumulated on the molding die provided on the mesh belt  72 . The buffer material forming unit  80  heats the web W which is the accumulated material of the mixture of the defibrated material and the additive mixed in the second web forming unit  70 , and thus the natural binding material is softened and melted. In this manner, the plurality of cellulose fibers are bound to each other. Further, the fibers of the nonwoven fabric sheet  1 B and the fibers contained in the web W can be bound by the binding material contained in the web W. In this manner, the buffer sheet  1 A and the nonwoven fabric sheet  1 B can be bonded to each other, and thus the buffer material WS to which the buffer sheet  1 A and the nonwoven fabric sheet  1 B have been bonded can be obtained. 
     The buffer material forming unit  80  includes a heating unit  84  that heats the laminate S. For example, a heat press or a heating roller may be used as the heating unit  84 , and an example of using a heating roller will be described below. The number of heating rollers in the heating unit  84  is not particularly limited. In the example shown in the figure, the heating unit  84  includes a pair of heating rollers  86 . The buffer material WS can be molded while the laminate S is continuously transported by configuring the heating unit  84  as the heating rollers  86 . 
     The heating rollers  86  are disposed such that the rotation axes thereof are in parallel with each other. The roller radius of the heating roller  86  is preferably 2.0 cm or greater and 5.0 cm or less, more preferably 2.5 cm or greater and 4.0 cm or less, and still more preferably 2.5 cm or greater and 3.5 cm or less. 
     The heating rollers  86  come into contact with the laminate S and heat the laminate S while transporting the web W in a state of interposing the web W. 
     The rotation speed of the heating rollers  86  is, for example, preferably 20 rpm or greater and 500 rpm or less, more preferably 30 rpm or greater and 350 rpm or less, and still more preferably 50 rpm or greater and 300 rpm or less. 
     In this manner, the surface region of the web W can be sufficiently heated with high accuracy. 
     The heating rollers  86  transport the laminate S in a state of interposing the laminate S to form the buffer material WS having a predetermined thickness. Here, the pressure applied to the web W by the heating rollers  86  is preferably 0.50 MPa or less, more preferably 0.01 MPa or greater and 0.45 MPa or less, and still more preferably 0.05 MPa or greater and 0.40 MPa or less. 
     The surface temperature of the heating rollers  86  when the web W is heated is preferably 160° C. or higher, more preferably 165° C. or higher and 250° C. or lower, and still more preferably 170° C. or higher and 220° C. or lower. 
     The heating and pressing time in the present step is preferably 1 second or longer and 300 seconds or shorter, more preferably 10 seconds or longer and 60 seconds or shorter, and still more preferably 15 seconds or longer and 45 seconds or shorter. 
     In this manner, the productivity of the buffer material WS can be further improved, and the strength, the buffering performance, and the like of the buffer material WS can be further improved. It is also preferable that the heating and pressing time be in the above-described ranges even from the viewpoint of energy saving. 
     The production device  100  of the present embodiment may include the cutting unit  90  as necessary. In the example shown in the figure, the cutting unit  90  is provided on the downstream of the buffer material forming unit  80 . The cutting unit  90  cuts the molding die containing the buffer material WS molded by the buffer material forming unit  80 . In the example shown in the figure, the cutting unit  90  includes a first cutting unit  92  cutting the molding die of the buffer material WS in a direction intersecting the transport direction of the buffer material WS and a second cutting unit  94  cutting the buffer material WS in a direction parallel to the transport direction. The second cutting unit  94  cuts, for example, the molding die containing the buffer material WS having passed through the first cutting unit  92 . 
     Further, the production device  100  of the present embodiment may include the humidifying unit  78 . In the example shown in the figure, the humidifying unit  78  is provided on the downstream of the cutting unit  90  and on the upstream of a discharge unit  96 . The humidifying unit  78  is capable of applying water or water vapor to the buffer material WS. Specific examples of the aspect of the humidifying unit  78  include an aspect of spraying mist of water or an aqueous solution, an aspect of spraying water or an aqueous solution, and an aspect of jetting water or an aqueous solution from an ink jet head for adhesion. 
     Since the production device  100  includes the humidifying unit  78 , the buffer material WS to be formed can be humidified. In this manner, the cellulose fibers are humidified and softened. Therefore, when a container or the like is three-dimensionally molded by using the buffer material WS, wrinkles or breakage is less likely to occur. Further, since a hydrogen bond is easily formed between cellulose fibers by humidifying the buffer material WS, the density of the buffer material WS is increased, and for example, the strength can be improved. 
     In the example of  FIG.  1   , the humidifying unit  78  is provided on the downstream of the cutting unit  90 , and the same effects as described above can be obtained as long as the humidifying unit  78  is provided on the downstream of the buffer material forming unit  80 . That is, the humidifying unit  78  may be provided on the downstream of the buffer material forming unit  80  and on the upstream of the cutting unit  90 . 
     The buffer material WS as shown in  FIG.  1    can be obtained by superimposing a desired number of sheets of buffer materials WS described above, setting a surface in a direction intersecting the direction in which the buffer materials WS are superimposed as a pressure receiving surface, and disposing the superimposed buffer materials WS at an arbitrary location. Further, the configuration thereof is not limited to the configuration shown in the figure, and for example, the function of the buffer material can be sufficiently exhibited even when the number of buffer materials to be superimposed is only one. 
     Hereinbefore, the suitable embodiments of the present disclosure have been described, but the present disclosure is not limited thereto. 
     For example, the present disclosure has configurations that are substantially the same as the configurations described in the embodiments, for example, configurations with the same functions, the same methods, and the same results as described above or configurations with the same purposes and the same effects as described above. Further, the present disclosure has configurations in which parts that are not essential in the configurations described in the embodiments have been substituted. Further, the present disclosure has configurations exhibiting the same effects as the effects of the configurations described in the embodiments or configurations capable of achieving the same purposes as the purposes of the configurations described in the embodiments. Further, the present disclosure has configurations in which known techniques have been added to the configurations described in the embodiments. 
     For example, the buffer material of the present disclosure is not limited to the buffer material produced by the above-described method using the above-described production device.