JP7479630B2 - Manufacturing method of compressed fiber structure material - Google Patents

Description

The present invention relates to a method for producing a compressed fiber structural material formed by compressing metal fibers .

Conventionally, a method for manufacturing a compressed fiber structure material is known in which biocompatible fibers are compressed and sheared at room temperature to form a thin plate-shaped compressed fiber structure material (see, for example, Patent Document 1). In the method for manufacturing a compressed fiber structure material described in Patent Document 1, metal fibers such as titanium fibers are used as the biocompatible fibers. In this manufacturing method, a thin plate-shaped compressed fiber structure material is manufactured by applying a compressive load and a shear load to biocompatible fibers with an average diameter of 5 to 50 μm and an aspect ratio of 20 to 500 at room temperature and in the air.

The method for producing compressed fiber structural material described in Patent Document 1 makes it possible to produce a thin plate-shaped compressed fiber structural material with an average pore size of 60 μm to 100 μm and a porosity of 25% to 50%. In other words, this method for producing compressed fiber structural material makes it possible to produce a thin plate-shaped compressed fiber structural material that has mechanical properties similar to those of living bone and is likely to increase osteoblasts.

JP 2013-78556 A

The method for manufacturing compressed fiber structure material described in Patent Document 1 makes it possible to manufacture a thin plate-shaped compressed fiber structure material with a relatively large average pore size and a relatively high porosity. However, according to the study by the present inventors, it has become clear that the method for manufacturing compressed fiber structure material described in Patent Document 1 makes it possible to manufacture a thin plate-shaped compressed fiber structure material with a thickness of less than 1 mm, but is unable to manufacture a thick, three-dimensional compressed fiber structure material with a thickness significantly exceeding 1 mm.

Therefore, an object of the present invention is to provide a method for producing a compressed fiber structure material having a relatively large average pore diameter and a relatively high porosity, which makes it possible to produce a thick, three-dimensional compressed fiber structure material .

In order to solve the above problems, the present inventors have investigated various methods for manufacturing compressed fiber structural materials. As a result, the present inventors have discovered that, in the compression process for manufacturing compressed fiber structural materials, in which metal fibers contained in a container are compressed in a predetermined compression direction under room temperature conditions to form compressed fiber structural materials, by compressing the metal fibers in the compression direction using a compression tool that rotates with the compression direction as the axial direction of rotation, it is possible to manufacture a thick, three-dimensional compressed fiber structural material that has a relatively large average pore size and a relatively high porosity.

The manufacturing method of the compressed fiber structural material of the present invention is based on this new knowledge and includes a storage step of putting a predetermined amount of metal fibers into a container, and a compression step of compressing the metal fibers in the container in a predetermined compression direction in a room temperature environment after the storage step to form a compressed fiber structural material, characterized in that the compression step compresses the metal fibers in the compression direction using a compression tool that rotates with the compression direction as the axial direction of rotation.

In the manufacturing method of the compressed fiber structure material of the present invention, in the compression step in which the metal fibers in the container are compressed in a predetermined compression direction in a room temperature environment to form a compressed fiber structure material, the metal fibers are compressed in the compression direction by a compression tool that rotates with the compression direction as the axial direction of rotation. Therefore, the manufacturing method of the present invention makes it possible to manufacture a compressed fiber structure material with a relatively large average pore size and a relatively high porosity, and a thick, three-dimensional compressed fiber structure material.

In the present invention, the compression tool is preferably disposed on one side of the metal fibers in the container in the compression direction, and the compression process includes a first compression process in which the compression tool is pressed against one side of the metal fibers, and a second compression process in which the metal fibers are inverted in the compression direction after the first compression process and the compression tool is pressed against the other side of the metal fibers. With this configuration, even if the compression tool is disposed on one side of the metal fibers in the container in the compression direction, it is possible to suppress the variation in the average pore size of the compressed fiber structural material in the compression direction of the metal fibers (i.e., the thickness direction of the compressed fiber structural material) and the variation in the porosity of the compressed fiber structural material in the compression direction of the metal fibers.

In the present invention, the metal fibers are, for example, titanium fibers made of pure titanium or a titanium alloy. In this case, it becomes possible to manufacture compressed fiber structural materials with excellent biocompatibility, strength, and corrosion resistance.

In the present invention, for example, in the containing step, a predetermined amount of powder or fiber other than metal fibers is placed in a container together with a predetermined amount of metal fibers. In this case, it becomes possible to combine different materials to produce a compressed fiber structure material with any mechanical property at any position.

In the present invention, the method for producing a compressed fiber structure material preferably includes a removal step performed after the compression step, in which the powder or fibers are removed. When configured in this manner, the removal step makes it possible to form voids in the compressed fiber structure material having a size corresponding to the size of the powder or fibers. In other words, it becomes possible to control the diameter of the voids formed in the compressed fiber structure material.

As described above, by manufacturing a compressed fiber structure material using the method for manufacturing a compressed fiber structure material of the present invention, it is possible to manufacture a thick, three-dimensional compressed fiber structure material with a relatively large average pore size and a relatively high porosity.

1A is a plan view of a compressed fiber structure manufactured by a method for manufacturing a compressed fiber structure according to an embodiment of the present invention, and FIG. 1B is a side view of the compressed fiber structure shown in FIG. 1 is a schematic diagram for explaining a configuration of a manufacturing apparatus used in a method for manufacturing a compressed fiber structure material according to an embodiment of the present invention. 1A and 1B are graphs showing the mechanical properties of a compressed fiber structure actually manufactured by a method for manufacturing a compressed fiber structure according to an embodiment of the present invention, in which (A) is a graph showing the relationship between the compressive stress applied to the metal fibers in the compression process and the relative density of the compressed fiber structure, and (B) is a graph showing the relationship between the compressive stress applied to the metal fibers in the compression process and the longitudinal elastic modulus of the compressed fiber structure.

The following describes an embodiment of the present invention with reference to the drawings.

(Configuration of compressed fiber structure material and configuration of compressed fiber structure manufacturing device)
Fig. 1(A) is a plan view of a compressed fiber structure material 1 manufactured by a manufacturing method for a compressed fiber structure material according to an embodiment of the present invention, and Fig. 1(B) is a side view of the compressed fiber structure material 1 shown in Fig. 1(A). Fig. 2 is a schematic diagram for explaining the configuration of a manufacturing device 3 used in the manufacturing method for a compressed fiber structure material according to an embodiment of the present invention.

The compressed fiber structural material 1 manufactured by the manufacturing method of the compressed fiber structural material of this embodiment is a structural material formed by compressing the metal fibers 2 without sintering. The metal fibers 2 of this embodiment are titanium fibers made of pure titanium or a titanium alloy. The average diameter of the metal fibers 2 is, for example, 5 to 80 μm, and the aspect ratio of the metal fibers 2 is, for example, 20 to 500. The compressed fiber structural material 1 is formed in a cylindrical shape. The diameter d of the compressed fiber structural material 1 formed in a cylindrical shape is, for example, 12 mm, and the thickness (height) t of the compressed fiber structural material 1 is, for example, 12 mm.

The compressed fiber structural material 1 has mechanical properties similar to those of living bone. More specifically, the compressed fiber structural material 1 has mechanical properties similar to those of cortical bone. The Young's modulus of the compressed fiber structural material 1 is, for example, 5 to 50 GPa. The porosity of the compressed fiber structural material 1 is, for example, 10% to 50%, and the average pore size of the compressed fiber structural material 1 is, for example, 60 μm to 100 μm. In other words, the porosity of the compressed fiber structural material 1 is relatively high. In addition, the average pore size of the compressed fiber structural material 1 is relatively large. In this embodiment, the porosity inside the compressed fiber structural material 1 varies depending on the location of the compressed fiber structural material 1.

When manufacturing the compressed fiber structure material 1, a manufacturing device 3 is used. The manufacturing device 3 includes a die 4, a lower punch 5 fixed to the die 4, an upper punch 6 as a compression tool that rises and falls relative to the die 4, and a punch drive mechanism (not shown) that raises and lowers the upper punch 6 while rotating it. The die 4 is composed of an upper die 7 formed into a thick cylindrical shape, and a lower die 8 that supports the upper die 7 from below. The upper die 7 is positioned so that the axial direction of the cylindrical upper die 7 coincides with the up-down direction.

The lower punch 5 is formed in a cylindrical shape. The lower punch 5 is arranged so that its axial direction coincides with the vertical direction. The upper end of the lower punch 5 is arranged on the inner periphery of the lower end of the upper die 7. The outer diameter of the lower punch 5 is slightly smaller than the inner diameter of the upper die 7. The upper end surface of the lower punch 5 is a flat surface perpendicular to the vertical direction. A pressure sensor (strain gauge) 9 is attached to the lower punch 5 to measure the compressive force when compressing the metal fibers 2.

The upper punch 6 is formed in a stepped cylindrical shape. The upper punch 6 is arranged so that its axial direction coincides with the vertical direction. The upper punch 6 can be inserted from above into the inner periphery of the upper die 7. The outer diameter of the lower end of the upper punch 6 is equal to the outer diameter of the lower punch 5. The lower end surface of the upper punch 6 is a plane perpendicular to the vertical direction. The upper punch 6 can rotate with the vertical direction as the axial direction of the rotation. The punch drive mechanism includes, for example, a rotation mechanism that rotates the upper punch 6 with the vertical direction as the axial direction of the rotation, and a lifting mechanism that lifts and lowers the upper punch 6 together with the rotation mechanism.

When manufacturing the compressed fiber structure material 1, a predetermined amount of metal fibers 2 is placed on the upper surface of the lower punch 5 on the inner circumference of the upper die 7 from above, and then the upper punch 6 is inserted on the inner circumference of the upper die 7 from above. That is, the lower punch 5 is positioned below the metal fibers 2, and the upper punch 6 is positioned above the metal fibers 2. In this embodiment, the lower punch 5 and the upper die 7 form a container 10 in which a predetermined amount of metal fibers 2 is stored.

(Method of manufacturing compressed fiber structural material)
The compressed fiber structural material 1 is manufactured by a manufacturing method including a storage step of putting a predetermined amount of metal fibers 2 into a container 10, and a compression step of compressing the metal fibers 2 in the container 10 in a predetermined compression direction under a room temperature environment after the storage step to form the compressed fiber structural material 1. In this embodiment, the metal fibers 2 in the container 10 are compressed in the up-down direction (vertical direction) in the compression step. That is, the up-down direction in this embodiment is the compression direction.

The storage step and compression step are performed in a room temperature environment. The storage step and compression step are performed in an air atmosphere. In this specification, "room temperature" means that no active heating is performed, and the term "room temperature" is used to include a range of about 20°C to 100°C, but room temperature is usually about 20°C to 80°C. In this specification, "air atmosphere" means an uncontrolled atmosphere, and refers to an air atmosphere that is neither pressurized nor depressurized, but air atmospheres that are pressurized or depressurized are also included in the air atmosphere if they are similar atmospheres.

In the storage process, a predetermined amount of metal fibers 2 is placed on the inner periphery of the upper die 7 and placed on the upper surface of the lower punch 5. In the compression process, the metal fibers 2 are compressed in the vertical direction by the upper punch 6, which rotates with the vertical direction as the axis of rotation. That is, in the compression process, the upper punch 6 is moved downward while rotating, and the metal fibers 2 in the container 10 are compressed into a cylindrical shape by the lower punch 5 and the upper punch 6. In the compression process, because the upper punch 6 rotates with the vertical direction as the axis of rotation, a shear force acts on the inside of the metal fibers 2 in addition to a compression force. When the compression process is completed, a compressed fiber structural material 1 is formed.

In the compression process of this embodiment, first, a first compression process is performed in which the upper punch 6 is pressed against one side of the metal fiber 2 (specifically, the upper side of the metal fiber 2 when it is contained in the container 10 in the containing process). In addition, in the compression process, after the first compression process, the upper punch 6 is moved upward, and the metal fiber 2 is extracted from the inner peripheral side of the upper die 7, and the extracted metal fiber 2 is inverted in the vertical direction and inserted into the inner peripheral side of the upper die 7, and a second compression process is performed in which the upper punch 6 is pressed against the other side of the metal fiber 2 (specifically, the lower side of the metal fiber 2 when it is contained in the container 10 in the containing process).

That is, the compression process of this embodiment includes a first compression process and a second compression process. In the first compression process and the second compression process, the upper punch 6 is rotated at, for example, 50 to 200 rpm. In addition, in the first compression process and the second compression process, the upper punch 6 is pressed against the metal fibers 2 with, for example, a pressing force of 1 to 10 kN. In other words, in the first compression process and the second compression process, the metal fibers 2 are compressed with, for example, a compressive force of 1 to 10 kN. In addition, the first compression process and the second compression process are performed for, for example, 1 to 60 seconds. The pressing force of the upper punch 6 is set based on the measurement value of the pressure sensor 9.

As described above, in this embodiment, the porosity inside the compressed fiber structural material 1 varies depending on the location of the compressed fiber structural material 1. Specifically, the porosity inside the compressed fiber structural material 1 gradually increases from the upper end surface of the compressed fiber structural material 1 toward the lower end surface. In other words, the porosity inside the compressed fiber structural material 1 increases the farther away from the upper end surface of the compressed fiber structural material 1 with which the upper punch 6 performing rotational motion comes into contact. Thus, in this embodiment, the porosity inside the compressed fiber structural material 1 varies, and due to this characteristic, the compressed fiber structural material 1 becomes a functional gradient material with some function.

(Main effects of this embodiment)
As described above, in this embodiment, in the compression step of compressing the metal fibers 2 in the container 10 in a room temperature environment to form the compressed fiber structural material 1, the metal fibers 2 are compressed in the vertical direction by the upper punch 6 that rotates with the vertical direction as the axial direction of rotation. Therefore, in the manufacturing method of this embodiment, it is possible to manufacture a compressed fiber structural material 1 having a relatively large average pore size and a relatively high porosity, and thus a thick, three-dimensional compressed fiber structural material 1.

In this embodiment, the compression process includes a first compression process in which the upper punch 6 is pressed against one side of the metal fiber 2, and a second compression process in which the metal fiber 2 is turned upside down after the first compression process and the upper punch 6 is pressed against the other side of the metal fiber 2. Therefore, in this embodiment, even if the rotating upper punch 6 is positioned only above the metal fiber 2, it is possible to suppress the variation in the average pore size of the compressed fiber structural material 1 in the vertical direction (i.e., the thickness direction of the compressed fiber structural material 1) and the variation in the porosity of the compressed fiber structural material 1 in the thickness direction of the compressed fiber structural material 1.

In this embodiment, the metal fiber 2 is a titanium fiber made of pure titanium or a titanium alloy. Therefore, in this embodiment, it is possible to manufacture a compressed fiber structural material 1 that has excellent biocompatibility, strength, and corrosion resistance.

(Example)
FIG. 3 is a graph showing the mechanical properties of a compressed fiber structure material 1 actually manufactured by a manufacturing method for a compressed fiber structure material according to an embodiment of the present invention, in which (A) is a graph showing the relationship between the compressive stress applied to the metal fibers 2 in the compression process and the relative density of the compressed fiber structure material 1, and (B) is a graph showing the relationship between the compressive stress applied to the metal fibers 2 in the compression process and the longitudinal elastic modulus of the compressed fiber structure material 1.

When the compressed fiber structure material 1 was actually manufactured by the above-mentioned manufacturing method for compressed fiber structure material, the compressed fiber structure material 1 having the mechanical properties shown in FIG. 3 was manufactured. In this example, 3 g of the metal fiber 2, which is titanium fiber, was used to manufacture the compressed fiber structure material 1. The metal fiber 2 is titanium fiber manufactured by Nikko Techno Co., Ltd., and the average diameter of the metal fiber 2 is 20 μm or 80 μm. The length of the metal fiber 2 is 10 mm. In this example, an upper die 7 with an inner diameter of 12 mm was used in the compression process. In this example, the rotation speed of the upper punch 6 was set to 74 rpm in the compression process, and the first compression process and the second compression process were performed once each.

In this example, metal fibers 2 with an average diameter of 20 μm were used, and compressive stresses of 44.2 MPa, 66.3 MPa, 88.4 MPa, 132.6 MPa, and 176.8 MPa were applied to the metal fibers 2 for 10 seconds in the first and second compression steps. In this example, metal fibers 2 with an average diameter of 20 μm were used, and compressive stresses of 66.3 MPa were applied to the metal fibers 2 for 60 seconds in the first and second compression steps. In this example, metal fibers 2 with an average diameter of 80 μm were used, and compressive stresses of 66.3 MPa were applied to the metal fibers 2 for 10 seconds in the first and second compression steps.

The relative density of the compressed fiber structure material 1 produced in this example (the value obtained by dividing the density of the compressed fiber structure material 1 calculated from the volume and mass of the compressed fiber structure material 1 by the density of titanium) fluctuated as shown in Figure 3 (A). In addition, the longitudinal elastic modulus of the compressed fiber structure material 1 produced in this example fluctuated as shown in Figure 3 (B). In FIG. 3, the open circles indicate the relative density and modulus of elasticity of the compressed fiber structure material 1 when a metal fiber 2 with an average diameter of 20 μm is used and a compressive stress is applied to the metal fiber 2 for 10 seconds in the first and second compression steps, the filled circles indicate the relative density and modulus of elasticity of the compressed fiber structure material 1 when a metal fiber 2 with an average diameter of 20 μm is used and a compressive stress is applied to the metal fiber 2 for 60 seconds in the first and second compression steps, and the filled triangles indicate the relative density and modulus of elasticity of the compressed fiber structure material 1 when a metal fiber 2 with an average diameter of 80 μm is used and a compressive stress is applied to the metal fiber 2 for 10 seconds in the first and second compression steps.

In this example, a compressed fiber structural material 1 was produced with a relative density of about 0.5 to about 0.9. In addition, because the relative density of the compressed fiber structural material 1 is about 0.5 to about 0.9, it can be seen that in this example, a compressed fiber structural material 1 was produced with a void ratio of 10 to 50%.

In addition, in this embodiment, when the compressive stress applied to the metal fibers 2 is 44.2 MPa, the modulus of elasticity of the compressed fiber structural material 1 is approximately 10 GPa, when the compressive stress applied to the metal fibers 2 is 88.4 MPa, the modulus of elasticity of the compressed fiber structural material 1 is approximately 17 GPa, when the compressive stress applied to the metal fibers 2 is 132.6 MPa, the modulus of elasticity of the compressed fiber structural material 1 is approximately 22 GPa, and when the compressive stress applied to the metal fibers 2 is 176.8 MPa, the modulus of elasticity of the compressed fiber structural material 1 is approximately 45 GPa.

In addition, in this embodiment, when the compressive stress applied to the metal fibers 2 is 66.3 MPa, the modulus of elasticity of the compressed fiber structural material 1 is approximately 14 GPa when the average diameter of the metal fibers 2 is 20 μm and compressive stress is applied to the metal fibers 2 for 10 seconds in the first and second compression steps, the modulus of elasticity of the compressed fiber structural material 1 is approximately 16 GPa when the average diameter of the metal fibers 2 is 20 μm and compressive stress is applied to the metal fibers 2 for 60 seconds in the first and second compression steps, and the modulus of elasticity of the compressed fiber structural material 1 is approximately 12 GPa when the average diameter of the metal fibers 2 is 80 μm and compressive stress is applied to the metal fibers 2 for 10 seconds in the first and second compression steps.

That is, in this example, a compressed fiber structural material 1 was manufactured with a modulus of elasticity of approximately 10 to approximately 45 GPa. The modulus of elasticity of cortical bone is 10 to 30 GPa. Therefore, this example shows that if the compressive stress applied to the metal fiber 2 in the first compression step and the second compression step is 44 to 133 MPa, the modulus of elasticity of the manufactured compressed fiber structural material 1 can be made approximately the same as that of cortical bone. In this example, a compression test of the compressed fiber structural material 1 based on JIS H7902 "Compression test method for porous metals" was performed to obtain the stress-strain curve of the compressed fiber structural material 1, and then the modulus of elasticity of the compressed fiber structural material 1 was calculated from the stress-strain curve of the compressed fiber structural material 1.

Other Embodiments
In the above-described embodiment, in the containing step, a predetermined amount of powder or fiber other than the metal fibers 2 may be placed in the container 10 together with the predetermined amount of the metal fibers 2. For example, in the containing step, a predetermined amount of pure copper or copper alloy powder, or a predetermined amount of pure copper or copper alloy fiber may be placed in the container 10 together with the metal fibers 2. In this case, it is possible to manufacture a compressed fiber structural material 1 having any desired mechanical property at any desired position by combining different materials.

In the above-mentioned embodiment, a predetermined amount of resin powder may be placed in the container 10 together with a predetermined amount of metal fibers 2 in the storage step. In this case, for example, after the compression step, a removal step is performed to remove the resin powder. In the removal step, the metal fibers 2 after the compression step are heated at a temperature that exceeds the melting point of the resin and is significantly lower than the melting point of the metal fibers 2, and the resin powder is melted and removed without sintering the metal fibers 2. In this case, it becomes possible to form pores in the compressed fiber structural material 1 that have a size corresponding to the size of the resin powder. In other words, it becomes possible to control the diameter of the pores formed in the compressed fiber structural material 1.

In the above-described embodiment, a predetermined amount of powder or fiber of a different type of metal from the metal fibers 2 may be placed in the container 10 together with a predetermined amount of the metal fibers 2 in the storage step. In this case, for example, after the compression step, a removal step is performed to remove the metal powder or fiber. Even in this case, it becomes possible to form voids in the compressed fiber structural material 1 having a size corresponding to the size of the metal powder or fiber. In other words, it becomes possible to control the diameter of the voids formed in the compressed fiber structural material 1.

For example, in the storage step, a predetermined amount of magnesium powder may be placed in the container 10 together with a predetermined amount of metal fibers 2. In this case, in the removal step following the compression step, the magnesium powder contained in the metal fibers 2 after the compression step is dissolved in water and removed. In this case, it becomes possible to form voids in the compressed fiber structural material 1 whose size corresponds to the size of the magnesium powder.

In the above-mentioned embodiment, the metal fibers 2 may be other than titanium fibers. For example, the metal fibers 2 may be aluminum fibers made of pure aluminum or an aluminum alloy, copper fibers made of pure copper or a copper alloy, or iron fibers made of pure iron. In the above-mentioned embodiment, two or more types of metal fibers 2 may be stored in the container 10 in the storage step. In the above-mentioned embodiment, the porosity inside the compressed fiber structural material 1 may be uniform throughout the compressed fiber structural material 1.

In the above-mentioned embodiment, the lower punch 5 may rotate with the vertical direction as the axis of rotation. That is, a rotating upper punch 6 and a rotating lower punch 5 may be arranged on both sides of the metal fiber 2 in the container 10 in the vertical direction. In this case, the rotation direction of the lower punch 5 is opposite to the rotation direction of the upper punch 6. In this case, the lower punch 5 is a compression tool. In the above-mentioned embodiment, the lower punch 5 may rotate without the upper punch 6 rotating.

In the above-mentioned embodiment, only the first compression step may be performed without performing the second compression step. Also, in the above-mentioned embodiment, the vertical direction is the compression direction of the metal fibers 2, but the horizontal direction may be the compression direction of the metal fibers 2, or the direction inclined to the vertical direction and the horizontal direction may be the compression direction of the metal fibers 2.

1 Compressed fiber structural material 2 Metal fiber 6 Upper punch (compression tool)
10 Container

Claims (5)

The method includes a step of placing a predetermined amount of metal fibers in a container, and a step of compressing the metal fibers in the container in a predetermined compression direction in a room temperature environment after the step of placing the metal fibers in the container to form a compressed fiber structural material,
A method for producing a compressed fiber structural material, characterized in that in the compression step, the metal fibers are compressed in the compression direction by a compression tool that rotates with the compression direction as an axial direction of rotation. the compression tool is disposed on one side of the metal fibers in the container in the compression direction;
The method for manufacturing a compressed fiber structural material as described in claim 1, characterized in that the compression process includes a first compression process in which the compression tool is pressed against one side of the metal fibers, and a second compression process in which the metal fibers are reversed in the compression direction after the first compression process and the compression tool is pressed against the other side of the metal fibers. The method for manufacturing a compressed fiber structure material according to claim 1 or 2, characterized in that the metal fibers are titanium fibers made of pure titanium or a titanium alloy. The method for manufacturing a compressed fiber structural material according to any one of claims 1 to 3, characterized in that in the storage step, a predetermined amount of powder or fiber other than the metal fibers is placed in the container together with a predetermined amount of the metal fibers. A removing step is carried out after the compressing step,
5. The method for producing a compressed fiber structure material according to claim 4, wherein the powder or the fiber is removed in the removing step.

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