JP2004175042A - Molded article and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a molded article capable of dispersing well a smaller amount of a solvent. <P>SOLUTION: The method comprises a process of positioning a supporting material 14 holding a solvent near to a molding material 12 composed of a bundle of slip materials so as to transfer the solvent in the supporting material 14 to the molding material 12. In this method, an amount of the solvent per surface area to be supplied can be determined regardless of a thickness and a density of the molding material 12 because the solvent is held in the supporting material 14, and further the solvent held in each part of the supporting material 14 can be supplied securely to each surface of the molding material 12 positioned near to the supporting material 14. Thus, the solvent can be supplied to the whole surface of the molding material 12 with preventing generation of undesirable unevenness in the molding material 12. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a molded article formed by binding a strip of woody material such as kenaf fiber with a binder and a method for producing the molded article.
[0002]
[Prior art]
A molded body made of a woody material such as a chip or a fiber bonded by a binder resin can be used, for example, as an interior material of a building or an automobile. Such a molded body is formed, for example, by laminating a woody material processed into a fibrous shape, forming a mat shape, and, as appropriate, temporarily forming by needle punching or pressing, then applying a liquid binder, and heating in a heated state. It can be manufactured by press molding. Here, as a method of applying a binder to the mat-like molding material, there are various methods such as immersion, application, and spraying, and various devices have been devised so that the binder penetrates into the inside of the mat. For example, in supply from a predetermined direction such as coating or spraying, suctioning from the opposite side to the supply direction has been proposed. As a method of applying a liquid agent in which spray and suction are combined, for example, a method of spraying a thermosetting resin for improving water resistance from one side of a fiberboard and suctioning air from the other side is known. (For example, see Patent Document 1).
[0003]
[Patent Document 1]
JP 10-323809 A
[Problems to be solved by the invention]
In recent years, particularly in vehicles, weight reduction has been promoted, and there is a demand for lightweight interior materials while maintaining strength and rigidity. In the molded body in which the wooden materials are combined with the binder, the weight of the wooden materials is reduced, and the wooden materials are securely combined with each other with a smaller amount of the binder. However, in the application method by immersion, the amount of the binder tends to be excessive. Further, since the spray tends to cause unevenness, there is a possibility that a portion where the binder is insufficient may be formed when an attempt is made to add a smaller amount of the binder.
[0005]
Then, in this invention, it aims at providing the manufacturing method of the molded object which can disperse | distribute a small amount of liquid agents favorably.
Another object of the present invention is to provide a molded article in which a binder is well dispersed.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, in the present invention, a liquid material applying step of moving a liquid material in a holding member to a molding material by adjoining a holding member holding a liquid material to a molding material formed by gathering strip-shaped materials. A method for producing a molded article, comprising:
In this method, since the liquid material is held by the holding member, the amount of the liquid material to be applied per unit area can be determined regardless of the thickness or the basis weight of the molding material. Further, the liquid agent held by each part of the holding member can be reliably applied to each surface of the molding material adjacent to the holding member. Therefore, it is possible to suppress the occurrence of undesirable unevenness in the molding material and apply the liquid agent to the entire molding material.
[0007]
Further, when a component capable of dispersing or dissolving the liquid agent is supplied in the liquid agent applying step, the fluidity of the liquid agent is improved, and the liquid agent can be favorably transferred to the molding material.
In addition, in the liquid agent application step, when an airflow for transferring the liquid agent to the molding material is supplied, the liquid agent can be favorably moved to the inside of the molding material.
Further, when the holding member is a fiber entangled member, it can hold a larger amount of liquid agent, can hold the liquid agent movably by airflow, compression, or the like, and can move the liquid agent satisfactorily to the molding material.
[0008]
Further, in the present invention, in any one of the above-mentioned manufacturing methods, the liquid agent is a binder, and the method further includes a step of solidifying the binder in a state where the holding member is laminated on the molding material. Thus, a laminated molded article can be formed.
[0009]
Further, in the present invention, the base material in which the strip-shaped materials are gathered, and the sheet-shaped fiber entangled member are laminated and integrated, and the fiber entangled member is bonded by a binder that binds the strip-shaped material of the base material. Provided is a molded article that is integrated with a substrate and contains the binder at a higher density in the substrate.
In this molded article, the fiber entangled member is integrated with the substrate by a binder that binds the strip-shaped materials of the substrate, and a laminated molded article is formed of a smaller number of materials. Further, the rigidity and strength of the fiber entangled member are reinforced by the binder, and the strength of the molded body is improved.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described in detail with reference to the drawings.
A molded body 1 shown in FIG. 1 is a molding board molded into a predetermined shape by pressure molding. The molded body 1 is integrated with a base material 2 made of a strip-shaped material and laminated on both sides of the base material 2. And a surface material 4.
The base material 2 is formed by joining strip-shaped materials with a binder. The strip-shaped material is in a chip shape, a fiber shape, or a flake shape, and various shapes of materials that can be combined into a compact to form a molded body can be selected. Specifically, a fibrous shape or a flaky shape which is easily caught by each other is preferable. The strip material can be composed of inorganic materials such as glass, thermosetting resin materials such as urethane and nylon, thermoplastic elastomer materials, thermoplastic resin materials such as polyester and polyolefin, and wood materials. Alternatively, a mixture of two or more kinds may be used. From the viewpoint of effective use of resources, wood materials made of non-oil resources are preferable.For woody plants such as wood, herbs such as cotton, kenaf, hemp, and rice, and other uses such as sugarcane bagasse, pulp, and sawdust. Materials that are discarded can be used. Annual grasses such as kenaf and sisal are more preferable, and tubular materials obtained by cutting these cores (vascular bundle portions) to a predetermined length and fiber materials obtained by fiber opening are preferable. The base material 2 in FIG. 1 uses a kenaf fiber material.
[0011]
The strip-like materials are joined together by a binder. The binder is a variety of materials that can be bonded to the strip-like material, for example, a thermosetting resin such as a phenol resin or an epoxy resin, an ester such as polyethylene terephthalate or an aliphatic polyester, or a polyolefin such as polyethylene or polypropylene. Can be used. From the viewpoint of effective use of resources, aliphatic polyesters derived from non-petroleum resources, for example, hydroxycarboxylic acid aliphatic polyesters such as polycaprolactone, polyalkylene succinate, polyalkylene adipate and polylactic acid are preferred. Polylactic acid is more preferable because it is derived from non-petroleum resources, is easily available, and can be prepared into an aqueous solution.
In addition, it is also preferable to use so-called biodegradable resins such as chemically modified starches as non-petroleum resources, esterified celluloses, and the like, and materials obtained by using these as the binder.
[0012]
In addition, the base material 2 may contain various auxiliary materials such as a preservative, a waterproofing agent, a coloring agent, and a filler. For example, when polylactic acid is used as a binder and an inorganic filler such as talc or clay is contained, crystallization of polylactic acid can be promoted, and heat resistance and rigidity can be improved, which is preferable.
[0013]
The surface layer material 4 is integrated with the base material 2 using the same material as the binder in the base material 2. The surface layer material 4 is made of a material that can easily hold a liquid material (liquid material), and is formed of, for example, a member such as a nonwoven fabric, a woven cloth, a knitted cloth, or a sponge, which has many voids that can store the liquid material. Is preferred. Specifically, a fiber entangled material is preferable. For example, a hydroentangled nonwoven fabric (spunlace) is preferable because it is bulky and can absorb more liquid agent. In addition, a member having a flocked surface or a material that easily retains the liquid agent on the substrate 2 side, for example, a member having a foamed material of polyolefin and having a surface that is difficult to retain the liquid agent, such as a film or a synthetic leather May be used.
The surface layer material 4 has a void portion in which the binder resin has penetrated, and the density of the binder resin is higher than that of the base material 2.
[0014]
In the molded body 1, the surface layer material 4 is surely integrated with the base material 2 by the binder resin. Further, since the binder resin is present in the surface material 4 at a higher density, the surface material 4 is harder than the base material 2. For this reason, the base material 2 is protected by the surface material 4. Further, the molded body 1 provided with the surface layer material 4 on both sides of the base material 2 has a cardboard structure, and has improved bending rigidity and bending strength.
[0015]
Next, a method for manufacturing the molded body 1 in the method for manufacturing a molded body according to one embodiment of the present invention will be described with reference to FIGS.
First, a molding material 12 (see FIGS. 6 and 7) is formed by assembling the above-mentioned strip-like materials into a predetermined shape. For example, in the case of a fiber material, the fibers can be laminated using a known fiber-opening process such as an air-lay, card, or fleece, and can be held in a predetermined shape by entanglement such as a pressing roller or needle punching. In the case of a powdery or flaky material, by filling it in a mold or the like, it is possible to stabilize the material into a predetermined shape.
[0016]
In the liquid agent application step, a holding member holding the liquid agent is prepared.
First, a liquid 20 (see FIGS. 2 to 5) is prepared. The liquid agent 20 contains one or more components imparted to the molding material, for example, a binder, a crosslinking agent, a waterproofing agent, a coloring agent, a filler, a preservative, and the like. When the above-mentioned material is liquid, the liquid 20 may be used as it is, or may be a solution or a dispersion (suspension, emulsion, colloid solution, etc.). It is preferable to select a type of the solvent or the dispersion medium that is easily compatible with the strip-shaped material and the holding member. Further, it is preferable to use an aqueous system because deterioration of the production environment can be suppressed. For example, the solution 20 containing polylactic acid as a binder contains a solution in which polylactic acid is dissolved in methylene chloride or acetone, or polyvinyl alcohol as a dispersion stabilizer and a cationic polymer compound or an anionic polymer compound. It can be an aqueous dispersion.
[0017]
The holding member 14 (see FIGS. 2 to 7) is a sheet member that can hold the liquid agent 20, and is a member that has a gap portion that can store the liquid agent 20. In addition to the above-described members that can be used as the surface material 4, the holding member 14 can use a porous material or a nonwoven fabric that is not used as the surface material 4, for example, a nonwoven fabric made of an inorganic fiber material. For example, a nonwoven fabric of a fibrous material made of at least one of materials such as polypropylene, polyolefin, polyester, cotton, and rayon can be suitably used. As the porous material, a foamed material such as polyolefin, polyester such as polyethylene terephthalate, or polyurethane can be used. The holding member 14 preferably has a property (lipophilicity, hydrophilicity, or the like) that easily holds the liquid agent 20. For example, when the liquid agent 20 is an aqueous dispersion, a fiber material such as cotton and rayon having high hydrophilicity and high water absorption is preferable.
[0018]
The supply of the liquid agent 20 to the holding member 14 can be performed by various known methods such as spraying, impregnation, and application. For example, as shown in FIG. 2, the liquid agent 20 may be sprayed from the outlets 34 arranged at equal intervals to the holding member 14. In order to evenly apply the liquid 20, it is preferable to use a contact-type application method such as a doctor knife coat shown in FIG. 3 or a gravure coat or a roll coat shown in FIG. When a large amount of liquid is supplied or when the holding member is made of a porous material, the holding member 14 is preferably immersed in the liquid tank 36 as shown in FIG.
[0019]
In the liquid agent application step, as shown in FIG. 6, the liquid agent is moved to the molding material 12 with the holding member 14 holding the liquid agent 20 adjacent to the molding material 12. Here, “adjacent to the molding material” means that the liquid material is arranged at a distance that can be applied to the molding material, and is not limited to the case where the liquid material is in direct contact with the molding material, and also includes the case where the liquid material is arranged with a predetermined gap. The holding member 14 may be adjacent to at least one surface of the molding material. However, in order to apply the liquid agent more uniformly, it is preferable that the holding member 14 is adjacent to a plurality of surfaces. As shown in FIG. 6, when the molding material 12 has a mat shape, a sheet shape, or the like, it is preferable to arrange the molding material 12 so as to sandwich the molding material 12 between a pair of holding members 14.
[0020]
The transfer of the liquid agent is typically performed by blowing with an air current. Preferably, it is moved by airflow prior to leaching by compression. The transfer of the liquid agent is preferably performed at a temperature at which the viscosity of the liquid agent decreases, so that the liquid agent can flow smoothly. If a component capable of dissolving or dispersing a liquid agent (including only a component such as a binder) is supplied to the void portion in the molding material 12, the liquid agent can be favorably moved to the molding material. In the movement of the liquid agent by the air flow, the liquid agent can be moved while keeping the gap portion without compressing the molding material 12, and a portion where the liquid agent can be stored and moved is secured, which is preferable. It is more preferable to use an air stream containing the solvent of the liquid agent or the vapor of the dispersion medium. The liquid agent may be moved by directly applying a force to the member, such as compressing and leaching the holding member 14 such as pressing (preforming) the molding material 12.
[0021]
In the embodiment shown in FIG. 6, the molding material 12 and the holding member 14 are arranged in a mold 30 as an airflow supply unit, and a liquid agent is applied. The mold 30 has a cavity having a width substantially equal to the thickness of the mat-shaped molding material 12 and the holding member 14, and a plurality of holes 32 for gas ejection are formed on the cavity surface at equal intervals. I have.
After the molding material 12 and the holding member 14 are arranged adjacent to each other in the mold 30, a gas containing water vapor is ejected from the hole 32 of the mold 30, so that the airflow from the holding member 14 toward the molding material 12 is increased. Can be formed. Due to this airflow, the liquid agent held by the holding member 14 moves to the molding material 12 side. Since the gas stream contains water vapor, the liquid agent can be more stably present in the gas stream and moves well.
[0022]
Further, since the gas ejected from the hole 32 of the mold 30 has a temperature of about 100 ° C. or higher, the liquid material is heated and the viscosity is reduced. Thereby, the liquid agent moves to the molding material 12 more quickly. Further, the air current passes through the inside of the molding material 12 made of a fiber material and escapes in the thickness direction. Therefore, the liquid agent can be applied to the inside of the molding material 12, and the liquid agent can be satisfactorily dispersed in the surface direction of the inside of the molding material 12 by the air current.
[0023]
After that, the molding material 12 is molded under pressure alone or together with the holding member 14 or together with another sheet member to form the molded body 1. In the present embodiment, as shown in FIG. 7, the molding material 12 is pressed into a plate shape together with the pair of holding members 14 that are adjacently arranged in a stacked manner in the liquid agent application step. The pressure molding is preferably performed at a temperature at which the polylactic acid used as a binder is softened or melted. Thereby, the compact 1 having a predetermined thickness, in which the strip-shaped materials of the molding material 12 are combined, can be formed.
[0024]
By holding the holding member 14 adjacent to the molding material 12 at the time of pressure molding, the liquid agent in the holding member 14 can be leached toward the molding material 12 and moved by the molding pressure. Further, the liquid agent arranged in the molding material 12 in the liquid agent applying step by the air flow is expected to move so as to have a more uniform distribution by receiving a uniform pressure in the molding material.
[0025]
The holding member 14 can be integrated with the molding material 12 by the binder by keeping the holding member 14 adjacent to the molding material 12 during the binder solidification step, cold pressing, or cooling after pressing. Thereby, the laminated molded body 1 as shown in FIG. 1 is obtained. On the other hand, by separating the holding member 14 from the molding material 12 before the binder is solidified, it is possible to mold a molded body (only the base material 2 in FIG. 1) made of a strip-shaped material.
[0026]
In the manufacturing method of the present embodiment, since the liquid material is held by the holding member and then applied by being moved to the molding material, the influence of the shape of the molding material and the amount of the void portion is reduced, so that various amounts of the liquid material are reduced. Can be given. In addition, by pressing the holding member against the molding material using the pressure of the pressure molding, the liquid material can be reliably moved from the holding member to the molding material.
In particular, by including a component such as a binder that can dissolve or disperse a liquid agent in the airflow, the liquid agent can be favorably transferred to the molding material. In addition, it is possible to disperse well by using a smaller amount of liquid agent. In particular, by moving the liquid agent by an air flow containing a component that can dissolve or disperse the liquid agent in a heated state in order to reduce the viscosity of the liquid agent itself, a smaller amount of the liquid agent can be satisfactorily dispersed and applied in the molding material.
Further, in this manufacturing method, since the liquid material is held on the holding member and moved to the molding material 12, the binder density in the holding member, that is, the surface layer material 4 of the molded body 1 shown in FIG. Can be higher. Therefore, the binder is better dispersed in the base material 2, and a molded body having a binder density in the surface material 4 higher than that of the base material 2 can be easily manufactured.
[0027]
The molded body 1 shown in FIG. 1 is a molding board that can be pressure-molded into a predetermined shape by softening (including melting) a binder resin. The pressure-molded body obtained in this manner has more rigidity and strength even when the density (specific gravity) in the base material 2 is small because the surface layer material 4 contains more binder resin. The molded body 1 is obtained. For this reason, the specific gravity in the base material 2, that is, the amount of the flaky material and / or the amount of the binder resin is reduced, so that the pressure-molded body is reduced in weight and has good rigidity and strength. be able to. Further, the surface material 4 may be given various properties such as water resistance, heat resistance, and mirror surface by a binder resin or another auxiliary material contained in the liquid agent. In addition, by selecting a design material having a design such as a pattern or a color as the holding member 14 serving as the surface material 4 in advance, it is possible to obtain a laminated molded body including a design skin material.
In addition, the surface material 4 can be separated by heating the molded body 1 and softening the binder resin. Various compacts can also be obtained by pressing. For example, an interior material of a building or a vehicle can be obtained by laminating a film or a skin material and performing pressure molding.
[0028]
In the production method according to the present invention, a molded article can be produced by variously changing the amount (basis weight) of the flaky material and the amount of the liquid agent (binder). For example, a base material ^{2 made} of a kenaf fiber material having a basis weight of 300 to 700 g / m ² , a holding member 14 made of a nonwoven fabric made of polyester having a basis weight of 30 to 50 g / m ² , and an aqueous dispersion containing polylactic acid as a binder ( Solid content 40%), and adding this aqueous dispersion to each holding member 14 in the range of 50 to 250 wet · g / m ² (solid content 20 to 100 g / m ² ), and by the method described above. Various molded articles can be obtained. In the method of the present embodiment, the molded body 1 can be favorably molded using a binder solid content (solid content of the liquid agent) of 10% to 30% based on the total weight of the molded body 1. Further, it is preferable that the binder is 30 to 50% at the interface between the surface layer material 4 and the base material 2.
[0029]
Note that the liquid agent application step is not limited to the present embodiment, and for example, may be moved from the holding member to the molding material by a pressure applied by a compression molding machine. In this embodiment, the liquid agent preferably has good fluidity, and is preferably performed in a heated state. In particular, when the main component of the liquid preparation is a binder, it is preferable that the liquid preparation be softened or melted. In addition, even when the liquid agent is applied by this method, by solidifying the binder in a compressed state, it is possible to manufacture a molded body in which the holding member is laminated and integrated with the molding material. Also, only the molding material can be molded by solidifying the binder after separating the holding member from the molding material.
Needless to say, after the liquid agent is moved by an air flow or compressed by a pressure molding machine, the molded product may be directly molded into a predetermined shape without being molded into a molding mat.
[0030]
【Example】
Polylactic acid was dispersed in water to prepare an aqueous dispersion having a solid content of 40% to obtain a liquid preparation. Next, a nonwoven fabric made of polyester having a basis weight of 50 g / m ² formed by a needle punch (a water punch may be used) is used as a holding member, and an aqueous dispersion of 125 wet · g is obtained by a doctor knife method so that the solid content becomes 50 g / m ^2. / M ² was applied.
Next, the fiber material collected from the kenaf is opened and laminated with a card, an air lay, and a fleece, and the holding members are arranged on both surfaces of a mat-shaped molding material having a basis weight of 200 g / m ² obtained by entanglement with a needle punch. Then, while maintaining the thickness, the steam is set in a mold capable of ejecting steam, and alternately steamed at about 80 ° C. for 30 seconds on each side from both sides of the holding member, and the liquid material in the holding member is applied to the molding material. Uniformly applied.
Thereafter, while the holding member and the molding material are arranged adjacent to each other, the film is set in a hot press having a mold heated to 220 to 230 ° C. and compressed for about 90 seconds to form a polylactic acid film.
Thereafter, the holding member and the molding material were cold-pressed to solidify the polylactic acid and demolded to obtain a plate-shaped preform.
The obtained preformed body is heated to 220 to 230 ° C. by a contact heater to melt the polylactic acid, and then set in a cold press (20 ° C., normal temperature) and pressure-formed into a predetermined three-dimensional shape. A molded article was obtained.
[0031]
The bending elasticity gradient (the inclination of the first straight line portion of the load deflection curve) of this molded body was measured. However, it was 15 to 20 N / cm.
The bending elastic gradient was measured by measuring a rectangular molded body of 50 mm × 150 mm at a position of 25 mm from each short side, and a plate-like member having a tip cross-sectional shape formed into an arc of R = 3.2 mm. At a speed of 50 mm / min from the upper side, a plate-like member having a tip cross-sectional shape formed into an arc of R = 3.2 mm is brought into contact, a load deflection curve is measured, and a linear portion at the beginning of the deflection is measured. When the inclination was calculated, it was 15 to 20 N / cm.
[0032]
Further, an aqueous dispersion of polylactic acid (solid content 40%) 300 wet · g / m ² was added to a mat-shaped molding material having a basis weight of 280 g / m ^{2 made} of a kenaf fiber material so that the solid content became 120 g / m ^2. The spray-applied product was preformed at the same temperature, and the preformed product was pressure-formed in the same manner to obtain a formed product having a basis weight of 400 g / m ² . When the bending elasticity gradient of this molded body was measured in the same manner, it was 5 N / cm.
Further, the same aqueous dispersion of polylactic acid (solid content 40%) of 100 wet g / m ² as described above was added to a mat-shaped molding material having a basis weight of 160 g / m ^{2 made} of a kenaf fiber material and a solid content of 40 g / m ² . It was applied by spraying as before, and preformed and pressed in the same manner as described above to obtain a formed body. Next, a non-woven fabric made of polyester having a basis weight of 20 g / m ² is welded to both surfaces of the molded body with a hot melt film having a basis weight of 80 g / m ² containing polyester as a main component to obtain a laminated molded body having a basis weight of 400 g / m ^2. Was. When the bending elasticity gradient of this molded body was measured in the same manner, it was 10 to 12 N / cm.
[0033]
All of the above three molded articles had a basis weight of 400 g / m ² as a whole, but it was revealed that the molded article molded by the production method of the present invention was most difficult to bend. From this, it was found that such a molded product was a molded product that was resistant to bending even though it was lighter.
[0034]
【The invention's effect】
In the present invention, by providing a method for producing a molded article capable of favorably dispersing a smaller amount of a liquid agent, a lighter molded article can be produced using less resources.
Further, in the present invention, by providing a molded article in which a binder is well dispersed, a lightweight molded article using a smaller amount of a binder is provided, in which deterioration of performance such as bending is suppressed. it can.
[Brief description of the drawings]
FIG. 1 is a perspective view of a molded article according to an embodiment of the present invention.
FIG. 2 is a schematic view of an embodiment of a method for supplying a liquid agent to a holding member.
FIG. 3 is a schematic view of another embodiment of a method for supplying a liquid agent to a holding member.
FIG. 4 is a schematic view of another embodiment of a method for supplying a liquid agent to a holding member.
FIG. 5 is a schematic view of another embodiment of a method for supplying a liquid agent to a holding member.
FIG. 6 is a schematic view showing a liquid agent application step.
FIG. 7 is a schematic view showing a pressure forming step.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 molded body 2 base material 4 surface layer material 12 molding material 14 holding member 20 liquid material 30 mold 32 hole 34 blowout port 36 liquid material tank

Claims (6)

A method for producing a molded article, comprising a liquid agent application step of moving a liquid agent in a holding member to a molding material by adjoining a holding member holding the liquid agent to a molding material formed by gathering strip-shaped materials. The method for producing a molded article according to claim 1, wherein a component capable of dispersing or dissolving the liquid agent is supplied in the liquid agent applying step. The method for producing a molded article according to claim 1, wherein in the liquid agent applying step, an airflow for transferring the liquid agent to the molding material is supplied. The method for manufacturing a molded article according to any one of claims 1 to 3, wherein the holding member is a fiber entangled member. The method according to any one of claims 1 to 4, further comprising a step of solidifying the binder in a state where the liquid agent is a binder and the holding member is laminated on the molding material. The base material in which the strip-shaped materials are gathered, and the sheet-like fiber entangled member are laminated and integrated,
A molded article in which the fiber entangled member is integrated with the base material by a binder that binds the strip-like material of the base material, and contains the binder at a higher density in the base material.

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