Radiation-protective nonwoven fabric and fiber product

Abstract

Radiation-protective nonwoven fabric (1), comprising: a sheet- or web-shaped nonwoven fabric in which metal fibers (2) are stacked three-dimensionally and randomly, wherein the metal fibers (2) each comprise a metal material having a relative density higher than the relative density of lead, wherein the radiation-shielding nonwoven fabric (1) felt is, the metal fibers (2) contain a pure tungsten wire as the metal fiber, and The pure tungsten wire has a wire diameter of less than 100 µm.

Description

[Technical field]

[0001] The present invention relates to a radiation-protective or radiation-shielding nonwoven fabric and to a fiber product containing the radiation-protective nonwoven fabric. [State of the art]

[0002] Radioactive rays (e.g., gamma rays and X-rays) are emitted by radioactive materials and other materials in medical radiotherapy facilities, nuclear power plants, etc. Therefore, to provide radiation protection, radiation-shielding articles containing a material that shields radioactive rays have been used in environments where radioactive rays are emitted.

[0003] Conventionally, lead has been used as a material that shields radioactive rays. A lead plate, a lead evaporation sheet on which lead is deposited by an evaporation process, or the like are known as radiation-shielding articles containing lead. For example, Patent Literature (PTL) 1 discloses a radiation-shielding sheet containing sheet-like lead.

[0004] WO 2013 / 039 195 A1 describes a radiation protection fabric used to block radiation, wherein the radiation protection fabric is characterized in that it comprises metal fibers with a tungsten or molybdenum content of 95 wt% or more.

[0005] JP 2 534 646 Y2 describes a radiation shielding mat comprising an inner component made of a lead fiber nonwoven fabric as the main material and a resin-coated base fabric covering the entire surface of the inner component. [Literature list][Patent literature]

[0006] [PTL 1] JP 2015 - 206 643 A [Summary of the invention][Technical problem]

[0007] A radiation protection article containing lead is heavy because the radiation protection article requires sufficient thickness to achieve a desired radiation protection effectiveness, or a radiation protection article containing lead cannot be used in a place having a high temperature because the radiation protection article has a low melting point.

[0008] In particular, a lead plate is difficult to cut or work with, or it is damaged when bent because the lead plate is hard and cannot be folded. A lead evaporation sheet or plate is damaged by folding, which causes it to peel off or detach when bent.

[0009] The present invention has an object to provide a radiation-protective nonwoven fabric and a fiber product which have superior radiation-protective effectiveness and yet are not damaged when folded. [Solution to the problem]

[0010] The underlying problem is solved by a radiation-protective nonwoven fabric and a fiber product having the features disclosed in claims 1 and 7. Further embodiments are defined in the dependent claims. [Advantageous effects of the invention]

[0011] The present invention makes it possible to provide, for example, a radiation-protective nonwoven fabric and a fiber product which have better radiation-protective effectiveness and yet are not damaged when folded. [Brief description of the drawings] [ Fig. 1] Fig. 1 is a perspective view illustrating a radiation-shielding nonwoven fabric according to Embodiment 1. [ Fig. 2] Fig. 2 is a cross-sectional view illustrating the radiation-shielding nonwoven fabric according to Embodiment 1. [ Fig. 3] Fig. 3 is a diagram illustrating a method for manufacturing a radiation-shielding nonwoven fabric according to Embodiment 1. [ Fig. 4] Fig. 4 is a diagram illustrating needle punching in the method for manufacturing a radiation-shielding nonwoven fabric according to Embodiment 1. [ Fig. 5] Fig. 5 is a diagram illustrating a prior art method for manufacturing a plate-like radiation-shielding sheet in which fine metal particles are fused with a resin. [ Fig. 6] Fig. 6 is a plan view illustrating a radiation-shielding nonwoven fabric according to Embodiment 2. [ Fig. 7] Fig. 7 is a cross-sectional view illustrating the radiation-shielding nonwoven fabric according to Embodiment 2. [Description of an embodiment]

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that each of the embodiments described below shows a specific example. Therefore, numerical values, shapes, materials, structural components, the arrangement and connection of the structural components, etc. shown in the following embodiments are merely examples and are not intended to limit the scope of the present invention. Moreover, among the structural components in the following embodiments, structural components not recited in any of the independent claims indicating the broadest concepts of the present invention are described as optional structural components.Furthermore, the figures are schematic diagrams and are not necessarily precise illustrations. (Embodiment 1)

[0013] First, a radiation-shielding nonwoven fabric 1 according to an embodiment 1 will be described with reference to Fig. 1 and Fig. 2 are described. Fig. 1 is a perspective view illustrating a radiation-shielding nonwoven fabric 1 according to Embodiment 1. Fig. 2 is a cross-sectional view illustrating the radiation-shielding nonwoven fabric 1 according to Embodiment 1.

[0014] As this is Fig. 1 and Fig. As illustrated in Figure 2, a radiation-shielding nonwoven fabric 1 according to Embodiment 1 is a sheet having radiation-shielding effectiveness for shielding radioactive rays. In other words, the radiation-shielding nonwoven fabric 1 shields radioactive rays by blocking (completely shielding) or attenuating the radioactive rays. The radiation-shielding nonwoven fabric 1 has a thickness of, for example, 5 to 20 mm, but is not limited to this thickness.

[0015] The radiation-shielding nonwoven fabric 1 according to Embodiment 1 is a felt and a cloth-like sheet or web having flexibility. Accordingly, the radiation-shielding nonwoven fabric 1 can be folded like a cloth and will not break or shatter even when folded.

[0016] The radiation-shielding nonwoven fabric 1 has a structure in which metal fibers 2 are three-dimensionally and randomly stacked. Specifically, the metal fibers 2 are interwoven and densified. In Embodiment 1, the metal fibers 2 are bonded together by interlacing them without using an adhesive including a resin. Accordingly, even when folded, the radiation-shielding nonwoven fabric 1 is not folded by plastic deformation of each metal fiber 2, and the radiation-shielding nonwoven fabric 1 as a whole is allowed to easily return to a pre-folded shape like a cloth.

[0017] The metal fibers 2 contained in the radiation-shielding nonwoven fabric 1 are each a metal wire (metal wire material) containing a metal material that is a shielding material for shielding radioactive rays and has a higher specific gravity than lead. Examples of metal materials that have a higher specific gravity than lead include tungsten (W) and molybdenum (Mo). Such a metal material shields radioactive rays by absorbing the radioactive rays.

[0018] In Embodiment 1, the metal fibers 2 contained in the radiation-shielding nonwoven fabric 1 include a tungsten wire (tungsten fiber or filament). Each of the metal fibers 2 may be a single strand of a tungsten filament (tungsten wire) or a composite strand of tungsten filaments formed by twisting or parallelly arranging two or more strands of tungsten filaments. In other words, each metal fiber 2 may be a monofilament fiber or a multifilament fiber.

[0019] Furthermore, the metal fibers 2 contained in the radiation-shielding nonwoven fabric 1 may contain a metal wire other than the tungsten wire, such as a molybdenum wire (molybdenum fiber). In this case, each of the metal fibers 2 may be a composite strand made by twisting or paralleling a single strand of a tungsten filament and a metal wire of a different type, or may be a composite strand containing a tungsten wire and a fiber other than a metal fiber (e.g., a chemical fiber).

[0020] In Embodiment 1, the metal fibers 2 contained in the radiation-shielding nonwoven fabric 1 are only tungsten wires. For example, a tungsten wire comprises pure tungsten (at a purity of greater than 99.00%), but the purity of the tungsten wire is not limited thereto. In Embodiment 1, tungsten wires comprising tungsten at a purity of nearly 100% are used as the metal fibers 2.

[0021] Each metal fiber 2 is an ultrafine thin metal wire, and a diameter of the metal fiber (metal wire) 2 is, for example, less than 1 mm. As an example, each metal fiber 2 has a diameter of less than 150 µm, preferably less than or equal to 50 µm, more preferably less than or equal to 20 µm, or even more preferably less than or equal to 10 µm. In addition, each metal fiber 2 is a short fiber having a length of at least 10 mm and at most 100 mm. More preferably, metal fibers 2 having a length of at least 30 mm and at most 80 mm can be used.

[0022] Next, a method for producing the radiation-shielding nonwoven fabric 1 will be described with reference to Fig. 3 are described. Fig. 3 is a diagram illustrating the method for manufacturing the radiation-shielding nonwoven fabric 1 according to Embodiment 1.

[0023] First, fine metallic particles 2a (metal powder) are prepared as shown in (a) of Fig. 3. Then, the metal wire 2b is made from the fine metal particles 2a as shown in (b) of Fig. 3. Subsequently, the metal wire 2b is cut to a predetermined length. Accordingly, the short metal fiber 2 can be manufactured as shown in (c) in Fig. 3 is illustrated.

[0024] For example, when producing tungsten wires as metal fibers 2, fine tungsten particles (tungsten powder) having a particle diameter of approximately 5 μm are prepared as fine metal particles 2a. Next, these fine tungsten particles are press-formed and sintered to form a tungsten ingot. Then, the sintered body of the tungsten ingot is forged into a wire by press-forging and stretching from its periphery. After that, the wire is plastically deformed by repeatedly drawing using dies (wire drawing) having progressively reduced pore sizes, and is wound, thereby producing the metal wire 2b (tungsten wire). Subsequently, the metal wire 2b is sequentially cut to a length of at least 20 mm and at most 80 mm, thereby producing many tungsten wires as metal fibers 2.In Embodiment 1, the metal fibers 2 are produced by cutting the metal wire 2b to a length of approximately 20 to 30 mm. In this case, the metal fibers 2 can be produced as a monofilament or non-monofilament by cutting them.

[0025] The tensile strength of the tungsten wires thus produced is increased as a result of hardening processing through repeated drawing using dies in the process of producing an ultra-thin wire. In other words, the use of tungsten wires makes it possible to obtain metal wires that are less likely to break, even when the metal wires are made ultra-fine. Furthermore, although metal wires typically become more flexible with the increase in flexibility of the metal wires as a result of making the metal wires thinner, the tungsten wires become flexible when the diameter of the tungsten wires is approximately less than or equal to 100 µm.

[0026] Next, the metal fibers 2 resulting from the cutting are three-dimensionally and randomly stacked into a sheet. In Embodiment 1, a sheet-like nonwoven fabric is produced by needle-punching the metal fibers 2.

[0027] Hereinafter, a step of needle punching metal fibers 2 will be described in detail with reference to Fig. 4 are described. Fig. 4 is a diagram illustrating the step of needling in the method for producing the radiation-shielding nonwoven fabric 1 according to Embodiment 1.

[0028] As this is Fig. As illustrated in Figure 4, the needling machine 100 is capable of processing the metal fibres 2 into a nonwoven fabric.

[0029] The short metal fibers 2 are fed into a feeder 110. The feeder 110 opens and agitates the supplied metal fibers 2 by blowing air and feeds the metal fibers 2 onto a belt conveyor. The metal fibers 2 supplied to the belt conveyor are sent out in a certain amount by a carding machine 120, etc., and fed as a web 2A to the needle-punching processing machine 130.

[0030] The needle punch 132, equipped with needles 131, compacts the metal fibers 2 (web 2A) fed to the needle punch processing machine 130 while interweaving the metal fibers 2. Specifically, by causing the needle punch 132 to continuously move upward and downward at a high speed, the needles 131 of the needle punch 132 repeatedly pierce the metal fibers 2 (web 2A). Here, small barbs provided on the needles 131 interweave the metal fibers 2. Accordingly, a nonwoven fabric 1A having a sheet-like and felted structure is formed. It should be noted that needling may be performed on stacked metal fibers 2 (webs 2A) according to the purpose or intended use.

[0031] An elongated, sheet-like nonwoven fabric 1A formed by the needle-punching processing machine 130 is wound up by a take-up roll 140. Subsequently, the sheet-like radiation-shielding nonwoven fabric 1 can be produced by pulling or unwinding the nonwoven fabric 1A from the take-up roll 140 and cutting the nonwoven fabric 1A accordingly.

[0032] It should be noted that the needle 131 of the needle-punching processing machine 130 is easily broken during processing, and the needle 131 may be mixed into the nonwoven fabric 1A. In this case, although a metal detector is capable of detecting and removing the broken needle 131 when chemical fibers are needle-punched instead of metal fibers, the metal detector is unable to detect the broken needle 131 in the nonwoven fabric 1A containing the metal fibers 2. For this reason, the broken needle 131 mixed into the nonwoven fabric 1A can be detected and removed by determining a type of metal based on the magnetic field distribution of the needle-punched nonwoven fabric 1A.

[0033] Hereinafter, the advantageous effects of the radiation-shielding nonwoven fabric 1 according to Embodiment 1 will be described.

[0034] A configuration in which fine metal particles are molded or cast with resin or plastic is conceivable as a radiation shielding sheet containing fine metal particles, such as tungsten particles. Such a radiation shielding sheet can be produced, for example, as described in Fig. 5 is illustrated. Fig. 5 is a diagram illustrating a method for manufacturing a radiation shielding sheet in which fine metal particles are molded with resin.

[0035] Fine metal particles 2a, such as fine tungsten particles, are prepared as described in (a) of Fig. 5. By molding the fine metal particles 2a with a resin and curing the resin, a plate-like radiation-shielding sheet 1X can be manufactured as shown in (b) of Fig. 5 is illustrated.

[0036] The radiation shielding sheet 1X thus manufactured exhibits radiation shielding effectiveness according to the amount of fine metal particles 2a contained therein. However, the radiation shielding sheet 1X is broken or chipped when folded because the radiation shielding sheet 1X has a structure in which the fine metal particles 2a are dispersed within the cured resin. Furthermore, the radiation shielding sheet 1X manufactured by molding the fine metal particles 2a with the resin is difficult to use in a high-temperature environment because the resin melts at a high temperature.

[0037] In contrast, the radiation-shielding nonwoven fabric according to Embodiment 1 is a sheet in which metal fibers are three-dimensionally and randomly stacked, the metal fibers each containing a metallic material having a specific gravity higher than a specific gravity of lead.

[0038] The radiation-shielding nonwoven fabric 1 constructed in this way exhibits superior radiation-shielding effectiveness, yet is neither broken nor shattered even when folded. Accordingly, the radiation-shielding nonwoven fabric 1 can be sewn in the same manner as a nonwoven fabric and a woven fabric, thereby facilitating the production of a fiber product exhibiting superior radiation-shielding effectiveness.

[0039] Examples of a fiber product produced by sewing the radiation-shielding nonwoven fabric 1 include a garment, a hat, gloves, and a cloth. Examples of garments include work clothes used in a workspace and ordinary clothing such as a coat and trousers, but the present invention is not limited to these examples. In particular, since the radiation-shielding nonwoven fabric 1 has the same texture as a cloth, the radiation-shielding nonwoven fabric 1 can be used for gloves, a neck wrap, etc., to provide radiation protection to parts of a person's body that are thin and require flexibility.

[0040] Furthermore, since the radiation-shielding nonwoven fabric 1 does not contain resin, the radiation-shielding nonwoven fabric 1 does not melt even when the radiation-shielding nonwoven fabric 1 is used in a high-temperature environment. In addition, the radiation-shielding nonwoven fabric 1 has high strength and high cutting resistance because the radiation-shielding nonwoven fabric 1 has a structure in which the metal fibers 2 are three-dimensionally stacked and interwoven. For this reason, the radiation-shielding nonwoven fabric 1 is less likely to break even if a knife is applied to the radiation-shielding nonwoven fabric 1, and thus, it is possible to use the radiation-shielding nonwoven fabric 1 as a padding, etc., for stopping the rotation of an electric chain saw.

[0041] Furthermore, in the radiation-shielding nonwoven fabric 1 according to Embodiment 1, the metal fibers 2 comprise a tungsten wire.

[0042] Thus, it is possible to easily obtain the radiation-protective nonwoven fabric 1 which has better radiation-protective efficacy and yet is not damaged even if it is folded.

[0043] Furthermore, in the radiation-shielding nonwoven fabric 1 according to Embodiment 1, each of the metal fibers 2 has a diameter of at most 1 mm and a length of at least 20 mm and at most 80 mm.

[0044] This makes it possible to easily produce the radiation-protective nonwoven fabric 1 which has better radiation-protective effectiveness and yet is not damaged even if it is folded, for example, by needling the metal fibers 2.

[0045] Furthermore, the radiation-shielding nonwoven fabric 1 according to the embodiment 1 is felt.

[0046] Thus, since the radiation-shielding nonwoven fabric 1 can be used as a felt, a fiber product can be manufactured in the same manner as a felt fabric by performing a conventional sewing process on the radiation-shielding nonwoven fabric 1. (Embodiment 2)

[0047] Hereinafter, a radiation-protective nonwoven fabric 10 according to an embodiment 2 will be described with reference to Fig. 6 and Fig. 7 are described. Fig. 6 is a plan view illustrating the radiation-shielding nonwoven fabric 10 according to Embodiment 2. Fig. 7 is a cross-sectional view illustrating the radiation-shielding nonwoven fabric 10 according to Embodiment 2.

[0048] In the radiation-shielding nonwoven fabric 10 according to Embodiment 2, metal fibers 2 are made woolly and packaged. For example, in the radiation-shielding nonwoven fabric 10, woolly metal fibers 2 are innumerable and randomly distributed throughout. Examples of the shape of the woolly metal fibers 2 include an S shape, an O shape, a C shape, and a curved shape.

[0049] As this is Fig. 6 and Fig.As illustrated in Fig. 7, the radiation-shielding nonwoven fabric 10 according to Embodiment 2 is configured as a quilt including a front cloth 11, a back cloth 12, and a filler 13, and metal fibers 2 bundled to be woolly are arranged as the filler 13 between the front cloth 11 and the back cloth 12. In other words, the woolly metal fibers 2 are packed between the front cloth 11 and the back cloth 12. The front cloth 11 and the back cloth 12 are sewn with a thread 14.

[0050] In the radiation-shielding nonwoven fabric 10, the metal fibers 2 are a shielding material that shields radioactive rays, and, similarly to Embodiment 1, tungsten wires, for example, can be used as the metal fibers 2. In this case, the woolly metal fibers 2 are cotton-like tungsten wool.

[0051] As stated above, the radiation-shielding nonwoven fabric 10 according to Embodiment 2 is the quilt, which includes the front sheet 11, the back sheet 12, and the filling 13. In addition, the metal fibers 2 are woolly and are arranged between the front sheet 11 and the back sheet 12 as the filling 13 of the quilt.

[0052] As described above, the use of the wool-like metal fibers 2 as the radioactive ray shielding material makes it possible to obtain the radiation-shielding nonwoven fabric 10 which has a high shielding factor and yet can be easily folded.

[0053] Furthermore, the woolly metal fibers 2 can be evenly distributed throughout by packing them. Furthermore, it is possible to reduce the degree of difficulty in subsequent processing by packing the woolly metal fibers 2.

[0054] It should be noted that the woolly metal fibers 2 are packed by quilting in Embodiment 2, but the present invention is not limited thereto. (variations)

[0055] Although the radiation-shielding nonwoven fabrics according to the present invention have been described based on the above-mentioned embodiments, the present invention is not limited to the above-mentioned embodiments.

[0056] For example, in the above-mentioned embodiments, the fiber products containing the radiation-shielding nonwoven fabrics are not limited to products worn by people and may be products other than the products worn by people, and the radiation-shielding nonwoven fabrics are not limited to use in fiber products and may be for use in products other than the fiber products.

[0057] Furthermore, radiation-protective nonwovens are not limited to commercial or trade products, but can also be industrial products. For example, radiation-protective nonwovens can be used as filters.

[0058] In particular, the radiation-shielding nonwoven fabrics according to the above-mentioned embodiments exhibit superior thermal resistance and can thus be used as filters in high-temperature environments. Furthermore, since the radiation-shielding nonwoven fabrics according to the above-mentioned embodiments each contain only metal fibers and do not contain an organic material such as a resin, the radiation-shielding nonwoven fabrics according to the above-mentioned embodiments can be used as chemical filters that transmit an acidic solution, an alkaline solution, or the like.

[0059] Forms obtained by various modifications to the above-mentioned embodiments which can be devised by a person skilled in the art, as well as forms realized by optionally combining structural components and functions in the above-mentioned embodiments, which are within the scope of the spirit of the present invention, are included in the present invention. [List of reference symbols] 1, 10 nonwoven fabric 2 metal fiber 11 front cloth or front fabric 12 back cloth or back fabric 13 Filling or insert

Claims

[1] Radiation-protective nonwoven fabric (1), comprising: a sheet- or web-shaped nonwoven fabric in which metal fibers (2) are three-dimensionally and randomly stacked, wherein the metal fibers (2) each comprise a metal material having a relative density higher than a relative density of lead, wherein the radiation-protective nonwoven fabric (1) is felt, the metal fibers (2) contain a pure tungsten wire as the metal fiber, and the pure tungsten wire has a wire diameter of less than 100 µm. [2] The radiation-shielding nonwoven fabric according to claim 1, wherein the metal fibers (2) further comprise a molybdenum wire. [3] Radiation-shielding nonwoven fabric according to claim 1, wherein the metal fibers (2) are only tungsten wires. [4] Radiation-protective nonwoven fabric according to one of claims 1 to 3, which a quilt comprising a front cloth (11), a back cloth (12) and a filling (13) containing metal fibers (2) and arranged between the front cloth (11) and the back cloth (12), wherein the metal fibers (2) are three-dimensionally and randomly stacked, the metal fibers (2) each comprise a metal material having a relative density higher than a relative density of lead, and the metal fibers (2) are wool-like. [5] The radiation-shielding nonwoven fabric according to any one of claims 1 to 4, wherein each of the metal fibers (2) is not a monofilament or continuous yarn. [6] Radiation-shielding nonwoven fabric according to one of claims 1 to 5, wherein each of the metal fibers (2) has a length of at least 20 mm and at most 80 mm. [7] A fiber product obtained by sewing the radiation-shielding nonwoven fabric (1) according to any one of claims 1 to 6.

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