JP2013127021A - High density composite material - Google Patents

Abstract

A high-density composite material that can be suitably used for a member that requires flexibility and high density, such as a weight shielding member and a balance member, including a radiation shielding member.
A composite material in which high-density particles are dispersed in a flexible material having at least one of an elastomer material and a vulcanized rubber material, and the elastomer material is a styrene material. Selected from at least one of polyamide, urethane, polyester, vinyl chloride and olefin thermoplastic elastomers, vulcanized rubber materials are fluoro rubber, silicon rubber, ethylene / propylene rubber, nitrile rubber, natural The material is selected from a material vulcanized into at least one of rubber, isoprene rubber and styrene-butadiene rubber, and the high-density particles are selected from at least one of tungsten, tungsten alloy and tungsten carbide.
[Selection figure] None

Description

  The present invention relates to a high-density composite material suitably used for a member that requires high density and flexibility, such as a shielding member and a weight member.

  Plants equipped with nuclear power plants and reactors, or experimental facilities that handle radiation, handle radiation sources necessary for business. These facilities properly manage radiation based on high security and rules. In addition, radiation management beyond what is stipulated in the regulations is also performed. In such a situation, facilities that handle these radiation often perform a process of shielding radiation from the radiation source even in a place that is generally regarded as safe.

  The shielding member that shields radiation often uses a dense material such as heavy metal or a compound thereof. A well-known shielding member uses lead or an alloy containing lead as a main component. Such a dense substance can shield the radiation by absorbing most of the energy of the passing radiation. Such a shielding member is used for the shielding member in the facility which needs to handle the above-mentioned radiation, and the protective clothing of the worker.

  On the other hand, facilities that handle radiation have characteristics that radiation sources are provided at various sites, and that workers work at various positions. For this reason, the shielding member needs to be attached according to the shape, structure, and characteristics of various parts. That is, the shielding member needs flexibility according to a target site (a site including a radiation source) to be attached. Of course, the shielding member needs to be flexible in accordance with the relationship between the target part to be attached and the worker who needs protection from radiation from the target part. In addition, lead used as a material for the shielding member is an environmentally hazardous substance, and its handling is large, and there is a problem that it is difficult to exhibit the outer shape flexibility in the installation and installation of the shielding member. Of course, if the material is not dense, it cannot be used as a radiation shielding member.

From the above, for radiation shielding members, high density composite materials having outer shape flexibility while using materials that are not environmentally hazardous substances such as lead as a raw material are required.
Further, not only a radiation shielding member but also a weight member, a balance member, a vibration isolating member, a heat radiating member, a shot, etc., a high density composite material having a high density and a flexible outer shape is required. This is because these members also require a sufficient weight, and depending on the installation location and the state of handling, the outer shape and the flexibility of the shape are required.

  That is, there is a demand for a high-density composite material satisfying (1) to (3) that (1) high density, (2) environmentally hazardous substances are not used, (3) the outer shape and shape are flexible. Yes.

  As such a high-density composite material, a high-density metal that is easily deformable and easy to process, particularly a composite material of tungsten and an organic material has been proposed (for example, Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4).

Japanese National Patent Publication No. 10-153687 JP 2001-187829 A JP 2001-183100 A JP-A-10-153687 JP-A-7-33905 JP-A-11-279415

Patent Document 1 discloses a high-density flexible material in which rubber is a mixed substance with other organic materials and has a density of 9 g / cm ³ or more (density is 9 or more). The high-density flexible material disclosed in Patent Document 1 uses a high-density powder having two types of average particle diameters to increase the density, but the density of 9 g / cm ³ is lead. In addition to being lower than (11.3), there is no clear disclosure as to under what conditions a high density powder is mixed to achieve a sufficient density. For this reason, the high-density flexible material disclosed in Patent Document 1 has a problem that it is not suitable for use as a radiation shielding member. It is natural that both flexibility and density can be achieved by mixing a flexible material such as rubber and heavy metal, but if the detailed conditions are not clarified, the required density will be achieved. It is difficult. The same applies to Document 2 described later.

  Patent Document 2 discloses a tungsten-containing composite material that includes an unvulcanized rubber and a tungsten powder, and is formed by imparting a shape to the tungsten powder via the unvulcanized rubber. Here, Patent Document 2 discloses that the weight ratio of unvulcanized rubber and tungsten powder is 1:10 because the tungsten-containing composite material has a density equivalent to that of lead.

  Here, the tungsten-containing composite material disclosed in Patent Document 2 realizes flexibility by unvulcanized rubber and realizes high density by tungsten powder, but has a structure of an opposite structure that gives priority to either one. As such, it has the problem that it is difficult to create an optimal balance between flexibility and density. In particular, only the technique of mixing tungsten powder cannot actually adjust the filling degree of tungsten powder per unit volume, and has a problem that it is difficult to use as a radiation shielding member.

  Patent Document 3 describes the interfacial adhesion between a thermoplastic resin composition obtained by adding a plasticizer to a thermoplastic polymer resin, a granular heavy metal for adjusting the density of bullets, and a thermoplastic resin composition and a heavy metal. It is a bullet for small firearms characterized in that a bullet material is composed of a coupling agent for improvement, and this bullet material is formed into a bullet of a predetermined shape, and this heavy metal bullet uses tungsten etc. Is disclosed.

  However, Patent Document 3 has the same problem as Patent Documents 1 and 2.

  Patent document 4 discloses the radiation shielding material by the mixture of tungsten powder and vulcanized rubber. In particular, a radiation shielding material is disclosed in which tungsten powder of 5 μm or more and 50 μm or less and tungsten powder of 0.5 μm or more and 5 μm or less are mixed with vulcanized rubber.

  However, the technique disclosed in Patent Document 4 intends to achieve both density and flexibility by mixing tungsten powder and vulcanized rubber, but does not disclose detailed conditions for that purpose. For this reason, there is no sufficient disclosure on how to achieve both density and flexibility. Moreover, in order to adjust the density, a technique of mixing tungsten powder of 5 μm or more and 50 μm or less and tungsten powder of 0.5 μm or more and 5 μm or less is disclosed, but to what extent the particle size range is too wide It is unclear whether it can be adjusted. That is, it cannot be said that the ease of manufacturing a radiation shielding agent having a desired result is taken into consideration. Tungsten or the like is a rare earth, and it is difficult to obtain a large particle size or a small particle size, and in order to produce a sufficient density, it is necessary to control the particle size in consideration of availability. Patent Document 4 has a problem that does not consider such ease of manufacture and availability.

  Patent Document 5 discloses a balance weight composition for an instrument pointer characterized by containing 86 to 96% by weight of heavy metal powder having an average particle diameter of 1 to 30 μm and 4 to 14% by weight of a thermoplastic resin. The composition disclosed in Patent Document 5 specifies a composition that can be used as a weight by specifying the composition ratio of a heavy object such as tungsten powder.

  However, as in Patent Document 4, it does not disclose a technique for achieving both density and flexibility. In addition, since it is a mixture of metal powder having a very wide particle diameter, it has a problem that it is difficult to adjust the density to a desired range.

  Patent Document 6 discloses a method for producing a high-density resin composition, comprising kneading and granulating 82 to 96% by weight of heavy metal powder having an average particle size of 1 μm to 15 μm and 4 to 18% by weight of thermoplastic resin powder. Is disclosed. Similar to Patent Document 6, it is a composition used for a weight member, and does not sufficiently disclose compatibility between density and flexibility and adjustment to a desired density range.

  As described above, the high-density composite material disclosed in each of Patent Documents 1 to 6 achieves both flexibility and density by mixing a flexible material such as rubber and a high-density tungsten powder. I am trying to let you. Of course, environmental load such as lead is not generated.

However, if a substance such as rubber is increased, the flexibility increases, but the density decreases. Conversely, if the tungsten powder is increased more than a certain level, the density increases but the flexibility decreases. In particular, in order for a high-density composite material to be used as a radiation shielding member, a density of 8 g / cm ³ or more is desirable. This value ignores the type of resin and the particle size of tungsten, and is simply rubber and tungsten powder. It cannot be realized simply by mixing.

  On the other hand, it has also been proposed to increase the density by mixing tungsten powders having a plurality of different particle sizes so that voids formed between the large tungsten powders are filled with the tungsten powder having a small particle size. However, for example, ultrafine powder having a particle size of 0.3 μm or less and coarse powder having a particle diameter exceeding 15 μm are hardly distributed as raw material powders, which is difficult in terms of stable supply.

In view of the above, a high-density composite material that satisfies the following requirements is required.
(Requirement 1) The outer shape and shape must be flexible.
(Requirement 2) It has a density (8 g / cm ³ or more) that can be used for a radiation shielding member.
(Requirement 3) It is easy to adjust the high density particles to be mixed, and the acquisition cost is low.
(Requirement 4) Stable supply is possible in terms of securing high-density particles and manufacturing cost of high-density composite materials.

  In particular, in order to form a member satisfying these (Requirement 1) to (Requirement 4), the composition ratio for balancing the flexibility and the density, the particle diameter and the composition ratio of the high-density particles are simultaneously set. And it needs to be adjusted very finely.

  In view of the above-described problems, the present invention satisfies (Requirement 1) to (Requirement 4) and is suitable for members that require flexibility and high density, such as weight members and balance members, including radiation shielding members. It aims at providing the high-density composite material which can be utilized for.

  In view of the above problems, the high-density composite material of the present invention is a composite material in which high-density particles are dispersed in a flexible material having at least one of an elastomer-based material and a vulcanized rubber-based material. The elastomer material is selected from at least one of styrene, polyamide, urethane, polyester, vinyl chloride and olefin thermoplastic elastomers, and the vulcanized rubber material is fluoro rubber, silicon rubber, The high-density particles selected from materials vulcanized into at least one of ethylene / propylene rubber, nitrile rubber, natural rubber, isoprene rubber and styrene / butadiene rubber are tungsten, tungsten alloy and tungsten carbide (hereinafter referred to as “WC”). The total volume of the composite material. The flexible material is 35-60% by volume and the high-density particles are 40-65% by volume. The first particles having a particle size of 1.5 μm or more and less than 6 μm are the entire high-density particles. The second particles having a particle diameter of 18 to 74% by volume and having a particle size of 0.5 μm or more and less than 1.5 μm are 9 to 19% by volume of the first particles, Contains 2 particles and inevitable mixtures.

  The high-density composite material of the present invention can achieve both flexibility and high density. Furthermore, it does not cause an environmental load such as lead.

  In addition, since the high-density composite material of the present invention uses high-density particles having two types of particle sizes, it is possible to reduce the acquisition cost of the high-density particles, the labor for manufacturing the high-density composite material, and the manufacturing cost. In addition, the high-density composite material is stably supplied, and convenience for various members using the high-density composite material is increased.

It is an expansion schematic diagram of the high-density composite material in Embodiment 1 of this invention. It is a graph which shows the measurement result of the green compact density in Embodiment 2 of this invention.

  The high-density composite material according to the first aspect of the present invention is a composite material in which high-density particles are dispersed in a flexible material having at least one of an elastomer-based material and a vulcanized rubber-based material. The elastomeric material is selected from at least one of styrenic polyamide-based, urethane-based, polyester-based, vinyl chloride-based and olefin-based thermoplastic elastomers, and the vulcanized rubber-based material is fluororubber, silicon rubber, The high-density particles selected from materials vulcanized into at least one of ethylene / propylene rubber, nitrile rubber, natural rubber, isoprene rubber and styrene / butadiene rubber are tungsten, tungsten alloy and tungsten carbide (hereinafter referred to as “WC”). For the total volume of the composite material The flexible material is 35 to 60% by volume and the high-density particles are 40 to 65% by volume. The high-density particles have the first particles having a particle size of 1.5 μm or more and less than 6 μm in the entire high-density particles. On the other hand, the second particles having a particle diameter of 18 to 74% by volume and having a particle size of 0.5 μm or more and less than 1.5 μm are 9 to 19% by volume with respect to the entire high-density particles, Contains particles and inevitable mixtures.

  With this configuration, the high-density composite material can achieve both flexibility and high density.

  In the high-density composite material according to the second aspect of the present invention, in addition to the first aspect, the inevitable mixture includes high-density particles having a particle size of 10 μm or more.

  With this configuration, the high-density composite material facilitates management in the manufacturing process while realizing flexibility and high density.

  In the high-density composite material according to the third aspect of the present invention, in addition to the first or second aspect, the gap formed by the adjacent first particles is less than 1.5 μm.

  With this configuration, the second particles are easily focused on the voids formed by the first particles.

  In the high-density composite material according to the fourth aspect of the present invention, in addition to any one of the first to third aspects, the second particles are filled in the voids between the adjacent first particles.

  This configuration allows the high density composite material to contain high density particles at a high density.

  In the high-density composite material according to the fifth aspect of the present invention, in addition to any of the first to fourth aspects, the high-density particles are tungsten, and the first particles are based on the entire high-density particles. 65 volume% or more and less than 74 volume%, and the second particles are 6 volume% or more and less than 19 volume% with respect to the entire high density particles.

  With this configuration, the high-density composite material can have a high density applicable to radiation shielding or the like.

  In the high-density composite material according to the sixth invention of the present invention, in addition to any of the first to fifth inventions, the shape of the high-density composite material is a sheet shape, a plate shape, a film shape, a cylindrical shape, a corner shape. It has at least one of shapes and combinations thereof.

  With this configuration, the high-density composite material can be applied to various uses.

  In the high-density composite material according to the seventh aspect of the present invention, in addition to any of the first to sixth aspects, the high-density composite material is used as a radiation shielding member.

  With this configuration, the radiation shielding member has a high radiation shielding ability due to the high-density composite material having both flexibility and density.

The high density composite material according to the eighth aspect of the present invention, in addition to the seventh aspect, the high-density composite material ^has a density of ^{8g / cm 3 ~13g / cm 3} .

  With this configuration, the high-density composite material can sufficiently shield radiation.

  In the high-density composite material according to the ninth aspect of the present invention, in addition to any of the sixth to eighth aspects of the invention, in the high-density composite material in the form of a sheet, the thickness of the sheet is 2.2 mm or less, When the radius of curvature is 10 mm, no crack is generated when the bending angle is in the range of 0 to 180 degrees.

  With this configuration, the high-density composite material can be easily applied to various uses.

  In the high-density composite material according to the tenth aspect of the present invention, in addition to any of the first to sixth inventions, the high-density composite material includes a weight member, a vibration isolating member, a balance member, a heat radiating member, and a weight. Used for at least one of the counterweights.

  With this configuration, the high-density composite material is applied to a member that requires weight.

  Hereinafter, embodiments will be described with reference to the drawings.

  (Embodiment 1)

  Embodiment 1 will be described.

(Overview)
The high-density composite material of Embodiment 1 is formed of a composite material in which high-density particles are dispersed and composited in a flexible material having at least one of an elastomeric material and a vulcanized rubber material. The high density particles are dispersed and combined in the flexible material, so that the high density composite material achieves sufficient density while maintaining flexibility, and can be used as a weight member or balance member such as a radiation shielding member. Applicable.

  The elastomer material is selected from at least one of styrene, polyamide, urethane, polyester, vinyl chloride and olefin thermoplastic elastomers. These materials are excellent in moldability, have high flexibility, and can impart high flexibility to the high-density composite material. The vulcanized rubber material is selected from rubbers vulcanized into at least one of fluorine rubber, silicon rubber, ethylene / propylene rubber, nitrile rubber, natural rubber, isoprene rubber and styrene / butadiene rubber. These materials, like the elastomeric materials, are excellent in moldability, have high flexibility, and can impart high flexibility to the high-density composite material.

  The high-density particles are selected from at least one of tungsten, a tungsten alloy, and tungsten carbide (hereinafter referred to as “WC”). These materials have high density and strength, and can be given high density and strength to a high-density composite material by being dispersed in a flexible material.

  Here, in the composite material forming the high-density composite material, the flexible material is 35% by volume to 60% by volume with respect to the total volume of the composite material, and the high-density particle has a particle size of 1.5 μm or more and 6 μm or less. The second particles having a particle size of 18 to 74% by volume and 0.5 μm or more and less than 1.5 μm with respect to the whole high-density particles are 9% to the whole high-density particles. ~ 19% by volume. In addition, the dense particles can contain unavoidable mixtures.

  In addition, the high-density particles may include particles of 6 μm or more and particles of less than 0.5 μm in the balance of the first particles and the second particles. As a result, the high density particles may include first particles, second particles, particles of 6 μm or more, particles of less than 0.5 μm, and inevitable mixtures. In this case, these particles and the inevitable mixture constitute 100% of the high density particles.

  In addition, the high-density particles are not necessarily composed of only the first particles and the second particles having the particle sizes as described above, and may include particles other than these particle sizes. In short, each of the first particles and the second particles has the volume ratio described above, and particles other than the first particles and the second particles in other volume ratios are classified as high-density particles. May be included. As a result, the composite material forming the high-density composite material may contain high-density particles other than the first particles and the second particles.

  As described above, the inclusion of particles having a particle size other than the first particles and the second particles depends on the problem of obtaining high-density particles or depends on variations in the produced high-density particles. .

  Since the high-density composite material in Embodiment 1 has the above-described configuration and materials, flexibility and high density can be achieved in a balanced manner. In addition, the high-density particles include two types of first particles and second particles, so that other types of high-density particles are not required actively, and materials and materials necessary for high-density composite materials. The acquisition cost and acquisition risk can be reduced. In particular, tungsten is a rare metal that often needs to be imported, resulting in an acquisition risk. Even in such a situation, the high-density composite material of Embodiment 1 can reduce such an acquisition risk by being able to handle the high-density particles with two types of first particles and second particles. Of course, the acquisition cost can be reduced, and the manufacturing cost of the high-density composite material is reduced.

  Further, the high density particles are dispersed and composited in a flexible material. In the high-density composite material thus obtained, the high-density particles are hardly exposed on the surface. Since the high-density particles are hardly exposed on the surface, the high-density particles do not fall off the surface when the high-density composite material is shipped or distributed.

  In order to prevent high-density particles from being exposed on the surface of the high-density composite material, a method of reducing the surface roughness when pressure is applied to the high-density composite material or the outlet of the molded body during extrusion molding is used. It is preferable to reduce the surface roughness. At this time, it is preferable that the surface roughness of the outlet for extrusion shaping is Ra 1.0 μm or less. In this way, by not exposing the high density particles on the surface of the high density composite material, it is not necessary to put a protective film on the surface when shipping or distributing the high density composite material, and manufacturing costs and distribution costs can be reduced. There are benefits.

  In addition, the value of the volume% defined here does not have to be very strictly limited. For example, when it is 35 volume% to 60 volume%, 34.8 volume% or 60.3% volume% It is not intended to include any errors that may occur according to manufacturing errors or manufacturing convenience.

(Elastomer material)
The elastomeric material is a material that becomes a flexible material of the high-density composite material, and is selected between the vulcanized rubber material (at least one of the elastomeric material and the vulcanized rubber material is selected as the flexible material). That is, either one may be selected, or both may be selected and mixed.) The elastomer material is selected from at least one of styrene, polyamide, urethane, polyester, vinyl chloride and olefin thermoplastic elastomers. All of these are thermoplastic and disperse smoothly in a composite with high density particles. As a result, the high-density composite material using the elastomer-based material has good moldability and gives high flexibility.

  Styrenic thermoplastic elastomers have particularly high flexibility among elastomers and have a low softening temperature. For this reason, the styrene-based thermoplastic elastomer can produce a composite material having high density and flexibility in the compounding by kneading with high density particles. Furthermore, since the styrenic thermoplastic elastomer has thermoplasticity, it can be regenerated and the amount of waste after use can be reduced. Styrenic thermoplastic elastomers are styrene / isoprene copolymer, hydrogenated styrene / isoprene copolymer, styrene / butadiene copolymer, hydrogenated styrene / butadiene copolymer, styrene / isoprene / butadiene copolymer. Or a hydrogenated product of styrene / isoprene / butadiene copolymer. One material listed here may be selected, or a plurality of materials may be selected. This is because these materials have thermoplasticity and can exhibit high flexibility. Of course, the materials listed here are examples of styrenic thermoplastic elastomers, and other materials having similar characteristics may be selected as the materials for styrenic thermoplastic elastomers.

  Polyamide-based thermoplastic elastomers, like styrene-based thermoplastic elastomers, have high flexibility, and can be combined with high-density particles to produce high-density and flexible composite materials. it can. It also has excellent oil and chemical resistance. The polyamide-based thermoplastic elastomer is selected from at least one of copolymerized nylons such as nylon 6, nylon 66, and polyesteramide block copolymer. One material listed here may be selected, or a plurality of materials may be selected. This is because these materials have thermoplasticity and can exhibit high flexibility.

  Urethane-based thermoplastic elastomers are excellent in wear resistance and have high tensile strength and tear strength, so that a composite material that is strong against scratches and tough can be produced. Further, like the styrene-based thermoplastic elastomer, it can be regenerated and the amount of waste after use can be reduced.

  Polyester thermoplastic elastomers are also excellent in wear resistance, like urethane thermoplastic elastomers. In addition, since it is excellent in oil resistance and weather resistance, it is characterized by being hardly affected by the use environment. Like styrenic thermoplastic elastomers, they can be recycled and require less waste after use.

  Vinyl chloride-based thermoplastic elastomer is the most widely produced material and is inexpensive. In addition to being excellent in heat resistance, weather resistance, oil resistance, etc., it also has acid resistance. Because it is resistant to repeated bending, it is suitable for applications such as wrapping around piping.

  Olefin-based thermoplastic elastomers also have high flexibility and a low softening temperature. For this reason, the olefinic thermoplastic elastomer has excellent moldability, oil resistance, heat resistance, and tensile strength. As a result, the olefinic thermoplastic elastomer can give high flexibility and strength to a high-density composite material using the olefin-based thermoplastic elastomer. Since the high-density composite material using the olefinic thermoplastic elastomer is thermoplastic, it can be recycled and the amount of waste after use can be reduced. Olefin-based thermoplastic elastomers include ethylene / butene copolymer, propylene / butene copolymer, ethylene / propylene copolymer, butene or ethylene, propylene and α-olefin copolymer, amorphous ethylene / propylene copolymer, etc. Is selected from at least one of the following. One material listed here may be selected, or a plurality of materials may be selected. Of course, the materials listed here are only examples of olefinic thermoplastic elastomers, and other materials having similar characteristics may be selected as the material of the olefinic thermoplastic elastomer.

  It is also preferable that various additives such as commonly used resins such as ABS resin, polystyrene resin, and polycarbonate resin, flame retardant, thickener, and ozone-resistant additive are added to the elastomeric material. This is because the addition of these materials appropriately adjusts the hardness and strength of the finally obtained high-density composite material. In addition, since a high-density composite material having functions such as flame retardancy and ozone resistance can be manufactured, a weight member and a radiation shielding member having these functions can be provided.

(Vulcanized rubber)
Further, a vulcanized rubber material may be used as the flexible material. The vulcanized rubber material is selected from materials downstream of at least one of fluorine rubber, silicon rubber, ethylene / propylene rubber, nitrile rubber, natural rubber, isopropylene rubber and styrene / butadiene rubber. Of course, the materials listed here are merely examples, and other materials are not excluded.

  For example, when fluororubber is selected, the high-density composite material can be used in an environment of an average of 200 ° C. In addition, the high-density composite material has an elastic deformation capability that can withstand most organic solvents and chemicals except ketones. In this case, the high-density composite material can form a sheet member rich in flexibility and elasticity.

  In addition, as a vulcanizing agent for vulcanizing the fluororubber, a peroxide or the like is used. When baroxide is used, the vulcanized rubber material (high density composite material) is particularly excellent in chemical resistance. Alternatively, a polyol is used as a vulcanizing agent. In this case, the vulcanized rubber material (high density composite material) is particularly excellent in heat resistance and can be suitably applied to a radiation shielding material. For materials other than fluororubbers, it is sufficient that a peroxide or polyol is used as a vulcanizing agent. Since the characteristics of the resulting vulcanized rubber material change depending on the vulcanizing agent, an appropriate vulcanizing agent may be used according to the specifications of the high-density composite material.

  The flexible material is selected from at least one of an elastomeric material and a vulcanized rubber material, and which one is used may be determined based on the cost of the material and availability. Or it is necessary to mix so that a high-density particle may disperse | distribute in a flexible raw material, but you may determine based on the ease of dispersion | distribution of this high-density particle. For example, when one of the elastomeric material and the vulcanized rubber material is difficult to disperse depending on the material of the high-density particles and the particle size, the material that is difficult to disperse may not be selected. These may be determined as appropriate.

(High density particles)
The high density particles are dispersed and composited in a flexible material. Due to the composite of the high-density particles, the high-density composite material has high density, strength, and the like. The high-density particles are selected from at least one of tungsten, a tungsten alloy, and tungsten carbide (hereinafter referred to as “WC”). This is because tungsten has a high density, and the manufactured high-density composite material is suitably applied to a weight member and a radiation shielding member that require a high density. Moreover, these tungsten is mixed with a flexible material in the state of particle | grains. This is because the particles are dispersed and compounded in the flexible material. In addition, tungsten is a rare metal and has a high acquisition cost and an acquisition risk, but the acquisition cost and the acquisition risk can be reduced by controlling the particle size and the like.

  Here, the high-density composite material has a balance between flexibility and density by two stages: (1) a mixing ratio of flexible material and high-density particles, and (2) a mixing ratio of particle sizes in high-density particles. Optimize.

  First, as for (1), the flexible material is 35 to 60% by volume with respect to the total volume of the high-density composite material, and the high-density particles are 40 to 40% with respect to the total volume of the high-density composite material. 65% by volume. When the mixing ratio of the flexible material and the high-density particles is within this range, the balance between the flexibility and the density of the high-density composite material is optimized.

  Next, as for (2), in the high-density particles, the first particles having a particle size of 1.5 μm or more and less than 6 μm are 18 to 74% by volume with respect to the entire high-density particles, and The 2nd particle which has a particle size of 5 micrometers or more and less than 1.5 micrometers is 9-19 volume% to the whole high-density particle. By being in this range, high-density particles are finely dispersed inside the flexible material and combined. That is, high-density particles are composited at a high density over the entire high-density composite material. As a result, the high density composite material will exhibit a high density.

  It should be noted that the inevitable mixture is not excluded. Here, the inevitable mixture may include high-density particles having a particle size of 10 μm or more. For example, when tungsten or tungsten alloy particles are used as the high-density particles, the first particles and the second particles described above are mixed with the flexible material. At this time, particles that do not belong to the first particle or the second particle having a particle diameter of 6 μm or more may be mixed as an inevitable mixture. For example, depending on the environment for obtaining high-density particles, not only the first particles and the second particles but also particles of 6 μm or more may be obtained. In order to reduce the manufacturing cost of the high-density composite material, it may be necessary to mix the particles of 6 μm or more. As described above, high density particles of 6 μm or more may be mixed as an inevitable mixture. Similarly, particles having a particle size of less than 0.5 μm may be mixed as high-density particles in addition to the first particles and the second particles.

  The first particles and the second particles are distinguished and mixed by classification. For example, classification may be performed using a sieve or classification using a flow rate. Of course, classification is not essential.

  The high density particles achieve the high density of the high density composite material that is produced. Tungsten and its compounds themselves have a high density, but when mixed into a high density composite material, they need to be mixed at a high density. When high-density particles having a single particle size are mixed, voids are formed between adjacent high-density particles, and the density decreases due to the voids. , The density is inevitably lowered.

  On the other hand, by mixing the first particles having a large particle size and the second particles having a small particle size, the gaps between the first particles and the gaps having a size that the first particles cannot enter. Since the two particles are finely combined, the density increases and the density also increases. FIG. 1 is an enlarged schematic diagram of a high-density composite material according to Embodiment 1 of the present invention. As shown in FIG. 1, the second particles 11 enter the voids 12 between the first particles 10.

  The high-density composite material 1 is manufactured by mixing the first particles 10 and the second particles 11. The first particles 10 are large particles having a particle size of 1.5 μm or more and less than 6 μm, and voids 12 are formed between the adjacent first particles 10. On the other hand, the second particles 11 are small particles having a particle size of 0.5 μm or more and less than 1.5 μm, and can enter the void 12. Thus, by mixing the first particles 10 and the second particles 11 having different particle sizes, the high-density particles are finely filled, and the high-density composite material has a high density. .

  Moreover, it is also preferable that the voids 12 formed by the first particles 10 have a size of less than 1.5 μm. Since the void 12 is formed adjacent to each other of the first particles 10 having a particle diameter of 1.5 μm or more and less than 6 μm, the void 12 tends to have a size of less than 1.5 μm. Of course, the gap 12 slightly exceeding 1.5 μm may be formed. On the other hand, since the second particles 11 have a particle size of 0.5 μm or more and less than 1.5 μm, the second particles 11 easily enter the voids 12 of about 1.5 μm. That is, the second particles 11 are filled in the voids 12 formed by the adjacent first particles 10. By this filling, as shown in FIG. 1, the first particles 10 and the second particles 11 are mixed in a fine state. As a result, the high-density composite material 1 has a high density. In addition, particles that are not included in the particle diameters of the first particles and the second particles may be included in the high-density particles in the remainder other than the mixing ratio of the first particles and the second particles.

  For example, if only the first particles having a large particle size are mixed with the flexible material, a large number of voids are generated, and the density is lowered. On the other hand, even if only the second particles having a small particle size are mixed with the flexible material, each of the voids is small, but many voids are formed, and the density is eventually lowered. As in the high-density composite material of the first embodiment, the first particles and the second particles having an optimal particle size balance are mixed to reduce the number of voids to be formed. Therefore, the high-density composite material has a high density.

  The first particles have a particle size of 1.5 μm or more and less than 6 μm, and the particle size is not very large. For example, when tungsten particles having a particle size of about 100 μm are used, the high-density composite material does not have flexibility. A high-density composite material may be folded in the form of a sheet or film, but may be cracked or damaged when folded without flexibility. For this reason, it is considered that the particle size of the first particles is appropriate.

  Since such high-density particles are dispersed and composited in a flexible material, the density of the finally produced high-density composite material is a density obtained by adding the flexible material to the high-density particles. Here, when the mixing ratio of the high density particles and the flexible material is defined as described above, the density of the high density particles due to the composite of the first particles and the second particles is too low due to the flexible material. There is no.

  If the mixing ratio of the high-density particles exceeds 65% by volume, the high-density composite material will not be completely taken into the flexible material such as an elastomeric material (it will not be dispersed in the flexible material). The flexibility and elastic deformability cannot be maintained. Conversely, when the mixing ratio of the high-density particles is less than 40% by volume, there is a problem that the flexible material becomes rich and the density of the high-density composite material decreases. Also from this viewpoint, the ratio of the flexible material to the entire high-density composite material is 35% to 60% by volume, and the ratio of the high-density particles to the entire high-density composite material is 40% to 65% by volume. It is preferable that Combined with the ratio of the first and second particles, the high density composite material can achieve a balance between flexibility and high density.

  In addition, the 1st particle | grains and 2nd particle | grains demonstrated here correspond to each of raw materials, such as enumerated tungsten and WC, and are not limited to either.

(Manufacturing and properties of high-density composite materials)
A manufacturing process of the high-density composite material will be described.

  In the production of the high-density composite material in the first embodiment, first, high-density particles that are powders including the first particles and the second particles are mixed in advance. Here, the high-density particles, which are powders including the first particles and the second particles, include first particles having a particle size of 1.5 μm or more and 6 μm or less, or a particle size of 0.5 μm or more and less than 1.5 μm. In other words, the particles may contain particles of other particle sizes.

  The high-density particles that are elements of the high-density composite material are a mixture of the first particles and the second particles having a predetermined volume ratio defined by the above-mentioned particle size. However, in the actual production of particles, the particle size may vary, and the high-density particles are not composed of only the first particles and the second particles. For this reason, the high-density particles are defined as powders including the first particles and the second particles as described above.

  The high-density particles defined in the present invention are powders including first particles having a particle size of 1.5 μm or more and 6 μm or less and second particles of 0.5 μm or more and less than 1.5 μm. The particle | grains other than the particle size of particle | grains and 2nd particle | grains may be included. When the total volume ratio of the first particles and the second particles to the high-density particles does not reach the entire high-density particles, the high-density particles include particles other than the particle sizes of the first particles and the second particles. It is in a state. That is, the high-density particles in the present invention are not limited to the state containing only the first particles and the second particles, and the particles other than the first particles and the second particles are premised on the volume ratio of the first particles to the second particles. May be included.

  For example, the first particles and the second particles are adjusted in particle size by classification and then uniformly dispersed and mixed by a mixer to obtain a mixed powder. Alternatively, the first particles and the second particles having different particle diameters (when particles whose particle diameters are adjusted in advance are available) are mixed while being uniformly dispersed by a mixer to obtain a mixed powder.

  Next, this mixed powder is mixed with the flexible material. The flexible material is an elastomeric material or a vulcanized rubber material as described above. When an elastomeric material is used as the flexible material, the mixed powder is kneaded by a kneader or a screw in a molding apparatus. This kneading produces a high-density composite material. The obtained high-density composite material can be molded into various shapes such as pellets, blocks, sheets, wires, and pipes by various molding apparatuses such as press molding, extrusion molding, and roll molding. Furthermore, continuous sheet forming such as a die extruder and a calender roll, forming into a complex shape product using an injection molding machine, embedding of metal parts, or forming using a screw may be performed.

  When a vulcanized rubber-based material is used as the flexible material, the rubber-based material in which additives such as a vulcanizing agent, a vulcanization accelerator, a softening agent, and a reinforcing agent are blended with unvulcanized rubber, The blended powder is mixed to obtain a high density composite material. The obtained composite material is molded into various shapes by press molding or extrusion molding as in the case of the elastomeric material.

  As a result, the shape of the high-density composite material has at least one of a sheet shape, a plate shape, a film shape, a cylindrical shape, a square shape, and a combination thereof. As a result, the high-density composite material can be suitably used for a weight member (weight member), a balance member, a radiation shielding member, and the like that require weight. Of course, when it is used for these members, it may be formed into a necessary shape, structure, thickness and the like.

  By being processed into such various shapes, even when applied to a weight member, a radiation shielding member, etc., it is possible to optimally cope with a specific application and application mode. When the aspect requiring radiation shielding is a thin planar shape, the high-density composite material is suitably formed by being formed into a sheet shape or a film shape. Alternatively, when a three-dimensional weight member is required, it is preferable that the high-density composite material is processed into a prismatic shape.

  Here, in the high-density composite material, high-density particles are mixed in a flexible material including an elastomer material and a vulcanized rubber material. For this reason, if only a flexible material is used, cutting is difficult, but by mixing high-density particles, micro cracks connected to the network are formed, so that cutting can be easily performed. For this reason, a high-density composite material becomes excellent in cutting workability, and can be processed into various members. Further, when a thermoplastic elastomer is used, since it is plastically deformed by heating, a member having a desired shape can be easily obtained. Furthermore, there is an advantage that material joining becomes easy by thermocompression bonding and the workability of the member is excellent.

Since the high density composite material has a high density of 8 g / cm ³ or more, it can be used as at least one of a weight member, a vibration isolating member, and a balance member. A density of 8 g / cm ³ or more is the highest density among flexible materials, and has a very suitable performance as a weight member or a vibration isolation member. Since the performance of the weight member and the vibration isolation member is determined by the density (density), the high-density composite material of the first embodiment is optimally used as the weight member and the vibration isolation member.

Naturally, the high-density composite material has a high radiation shielding ability because it has a density of 8 g / cm ³ or more. Of course, the density of 8 g / cm ³ or more is an example, and the density of 8 g / cm ³ or more may be preferable depending on the shape and application of the high-density composite material, and may be more preferable. . Considering application to a radiation shielding member, the high-density composite material preferably has a density of 8 g / cm ³ or more and 13 g / cm ³ or less.

  In addition, the high-density composite material has high flexibility. For example, in the sheet-like high-density composite material, when the thickness of the sheet is 2.2 mm or less and the radius of curvature is 10 mm, no crack is generated when the bending angle is in the range of 0 to 180 degrees. It has a degree of flexibility.

  Thus, the high-density composite material in Embodiment 1 has a high radiation shielding capability, and can be suitably used as a radiation shielding member.

  (Embodiment 2)

Next, a second embodiment will be described.
In the second embodiment, an example in the case where a high-density composite material is actually manufactured will be described.

  As an example, tungsten will be described as the high-density particles.

  A tungsten raw material powder having an average particle diameter of 5 μm is used as the raw material powder containing the first particles (particle diameter of 1.5 μm or more and less than 6 μm) in the high-density particles. The powder having an average particle diameter of 5 μm is composed of about 3% by volume of particles less than 1.5 μm, about 96.5% by volume of particles of 1.5 μm to 6 μm, and about 0.5% by volume of particles of more than 6 μm. Tungsten raw material powder having an average particle size of 1 μm is used as the second particles (particle size of 0.5 μm or more and less than 1.5 μm). This raw material powder comprises about 9% by volume of particles less than 0.5 μm, about 75% by volume of particles of 0.5 μm to 1.1, and about 26% by volume of particles greater than 1.1 μm. In order to produce a comparative example, tungsten raw material powder having an average particle diameter of about 15 μm is used as particles larger than the first particles (defined as third particles). These particles were mixed in a mixing time of 30 minutes using a Henschel mixer (FM10B, manufactured by Mitsui Miike Machine) to obtain a mixed powder.

  Four mixed powders of Comparative Example 1, Comparative Example 2, Example 1, and Example 2 were produced. Table 1 shows a list of blending conditions for the tungsten particles of Comparative Examples 1 and 2.

  First, the filling properties of the mixed powders of Comparative Examples 1 to 2 using these first to third particles were evaluated. Particles based on the respective ratios of Comparative Example 1 to Example 2 shown in Table 1 were mixed, and a press body was manufactured at a pressure of 100 MPa using a φ14 mm press mold. The density of the green compact filled was measured from the volume of the press body. The measurement results are shown in FIG. FIG. 2 is a graph showing measurement results of the green density in the second embodiment of the present invention.

  As is clear from FIG. 2, the density of the green compact is small or insufficient for each of the first particle, the second particle, and the third particle. Moreover, it turns out that the mixed powder which mixed all the 1st particle | grains to the 3rd particle | grains by the predetermined ratio like the comparative example 1 and the comparative example 2 has a high green compact density. It can be seen that mixing more types of particles with different particle sizes is effective in increasing the green density (ie, the degree of packing of high density particles). However, although mixing many kinds of particles with a large particle size increases the density of the green compact, obtaining high-density particles with a large number of particle sizes involves acquisition costs and risks. In particular, tungsten is a rare metal and often carries import risks.

Here, the mixed powders of Example 1 and Example 2, which are mixed powders of two kinds of particles, the first particles and the second particles, have a green compact density of about 11 g / cm ³ . This is a sufficient value although it is lower than the green density of Comparative Examples 1 and 2 which are mixed powders of three kinds of particles.

  In consideration of the green compact density with respect to the acquisition cost and the acquisition risk, Example 1 and Example 2 included in the mixing ratio of the high-density particles of the present invention are sufficiently and excellent as compared with Comparative Examples 1 and 2. It is thought to be a mixed powder. That is, the high-density composite material in which this mixed powder is used can exhibit a high density.

  Next, the mixed powder produced was mixed with the flexible material to produce a high-density composite material. As the flexible material, an olefin-based elastomer (Mitsubishi Chemical Corporation Thermorun) was used. Moreover, the mixed powder produced in Comparative Example 1-Example 2 was knead | mixed and mixed with the olefin type elastomer using the hindered phenolic antioxidant (Nippon Cytec Industries Inc. Syanox) as an additive. For the kneading, a lab plast mill (ME-50 manufactured by Toyo Seiki Seisakusho) was used. The kneading conditions were a kneading temperature of 180 ° C., a blade rotation speed of 25 rpm, and a kneading time of 30 minutes. The kneaded body taken out after kneading was chopped into small pieces with a spatula during cooling. Further, a kneading blending table was set in advance according to the target density, and a kneaded body, that is, a high-density composite material was manufactured. Table 2 is a recipe.

  In accordance with the conditions shown in Table 2, the mixed powders of Comparative Examples 1 to 2 were mixed with the olefin elastomer to obtain a high density composite material. The appearance properties and density of these high-density composite materials were measured. Table 3 shows the measurement results.

  As is apparent from Table 3, in Examples 1 and 2, it is considered that the target density is achieved. That is, the high density required for the high-density composite material is also realized in the first and second embodiments. In mixing the high density particles and the flexible material by mixing the first particles and the second particles, a sufficient density can be obtained by appropriately adjusting the mixing ratio. Compared with Comparative Examples 1 and 2 in which three kinds of particles are mixed, the density of Examples 1 and 2 is sufficient. That is, the sufficient density of the high-density composite material of the present invention that can reduce the acquisition cost and the acquisition risk was confirmed from the experimental results.

  The fluidity of the manufactured high-density composite material was also evaluated. A melt indexer (F-F01 manufactured by Toyo Seiki Seisakusho) was used to perform numerical evaluation of fluidity. A high-density composite material, which is a material, is put into a cylinder heated to a predetermined temperature, and the high-density composite material is extruded using a die. At this time, the fluidity of the high-density composite material can be quantified by measuring the extrusion weight per unit time.

  At this time, JIS standard (JIS K7210-1999) is applied mutatis mutandis, and the cylinder diameter is φ9.55 mm and the die hole diameter φ2 mm × L8 mm. As a unit of fluidity, g / 10 min is used.

This unit is MFR (g / 10 min) represented by the following formula.
MFR (g / 10 min) = 600 × m / t
MFR Melt mass flow rate (g / 10min)
m ² ... average mass of cut pieces (g)
t ... Sample cutting time interval (s)
600 ... seconds of standard time (= 10 minutes)

The high-density composite material of the present invention has a high density of 8 to 13 g / cm ³ and cannot be measured with a filling amount and sampling time according to JIS K7210-1999. The measurement sample prepared 45-50g of what made the high-density composite material of Comparative Example 1-Example 2 into the granular form of about 5 mm at maximum by grind | pulverizing. The measurement conditions were a temperature of 190 ° C. and a load of 21.6 kg.

  In actual measurement, a sample of a high-density composite material is put into the cylinder and preheated for 4 minutes until the temperature stabilizes. A load due to the weight is applied, and the sample starts to be extruded. Thereafter, the sample was cut according to a predetermined sampling time, three extruded pieces were collected, and the fluidity was calculated by measuring the weight of each extruded piece. This time, the collection time was adjusted between 10 seconds and 60 seconds.

  Table 4 shows the results of fluidity measurement.

  In Table 4, when the MFR value is 20 or more, it is determined that the fluidity is high. In this way, both Examples 1 and 2 are considered to have fluidity. In Example 1, when the density is high, the fluidity is low, but in Example 2, it can be seen that the fluidity is constant (the fluidity is not inferior to that of Comparative Example 2). It is determined that the high-density composite material is at a level sufficient for use as a sheet or plate. As described above, the high-density composite material of the present invention using the two types of first particles and second particles has a good balance of flexibility in addition to the density, and includes a weight member, a vibration-proof member, a balance member, and a shot. It was proved that it can be suitably used for applications such as members and radiation shielding members.

(Example 3)
Subsequently, Example 3 was produced in which the same powder blend ratio as in Example 2 was used and the flexible material was changed. As flexible materials, styrene-based (Aronkasei Elastomer AR), urethane-based (Nippon Miractolan Co., Ltd. Miractolan), polyester-based (Toyobo Co., Ltd., Perprene), silicon rubber (Shin-Etsu Chemical KE-551-U) Was used. The target specific gravity was set to 10, and the mixed powder and the flexible material were mixed to obtain a high-density composite material. The appearance properties and density of these high-density composite materials were measured. Table 5 shows the measurement results.

  As is apparent from Table 5, it is considered that the target density is also achieved in Example 3. That is, the high density required for the high-density composite material is also realized in the third embodiment. In mixing the high density particles and the flexible material by mixing the first particles and the second particles, a sufficient density can be obtained by appropriately adjusting the mixing ratio.

(Experiment in an embodiment closer to the manufacturing site)
Next, tests using various kinds of raw material tungsten were conducted. In an actual manufacturing site, a high-density composite material is manufactured using raw material powders obtained from various material manufacturers. Commercially available raw material powders have different particle distributions depending on the product name, manufacturer, and production lot. Even if it is the raw material powder with the indication of “average particle diameter of 1.0 μm”, when taking the particle size distribution, some of them are composed of particles less than 1.0 μm, and others are 0 Actually, the particle distribution cannot be determined from the average particle diameter, such as two peak particle diameters around 0.5 μm and 2.0 μm.

  Considering these, the experiment was conducted here by an example that imitated a state closer to the manufacturing site. In this experiment, various commercially available tungsten powders were prepared, each particle size distribution was measured before use, and the particles were classified as “smaller than 0.5 μm”, “0.5 μm or more and less than 1.5 μm (= second particles). ) ”“ 1.5 μm or more and 6 μm or less (= first particle) ”“ greater than 6 μm ”and managed in four parts, and by using a mixture of the controlled powders, each particle in the molded body The ratio was managed.

  Based on the various elastomers and the particle distributions described above, the other parts described in Example 1 were mixed in the same manner and the results of molding experiments are shown in Table 6.

Examples 11 to 66 shown in Table 6 are all practiced within the scope of the present invention, all can be kneaded, have no appearance or pores or discoloration, and have a density of 8 to 12 (g / cm). ³ ) A molded product could be obtained.

  In the above experiments, tungsten was used as high-density particles, but it is considered that the same tendency can be obtained with tungsten alloys and WC.

  As described above, the high-density composite material described in Embodiments 1 and 2 can achieve sufficient density and flexibility even when confirmed by the examples. In addition, as can be seen from the comparison with Comparative Examples 1 and 2, a high-density composite material having sufficient density and flexibility can be obtained even with two types of high-density particles. That is, a high-density composite material can be manufactured with reduced acquisition cost and acquisition risk. As a result, a high-density composite material that can be stably supplied at low cost can be provided.

(Aspect when shipping, etc.)
It is also preferable that the high-density composite material is shipped in a form in which at least one of the front surface and the back surface is sandwiched between films. When shipping and distributing, various loads can be applied. The film can prevent damage due to such a load. The film may be removed when shipping and distribution are finished and the film is used in an actual application such as a radiation shielding member or a weight member. Of course, you may use it with the state covered with the film. In this case, the film serves as a protective film during use.

  Similarly, the high density composite material may be shipped or distributed in a packaged manner. In this case as well, the high-density composite material is protected from damage and the like, like the film. Of course, it may be used in a packaged state. For example, when the shape of the high-density composite material is not neatly molded, it can be used as a weight member by being packaged. As described above, the high-density composite material can be protected from damage by being covered with a film or packed in a bag, or can have an aspect according to the application.

  As described above, the high-density composite material described in Embodiments 1 and 2 is an example for explaining the gist of the present invention, and includes modifications and alterations without departing from the gist of the present invention.

1 High-density composite material 10 First particle 11 Second particle 12 Void

Claims (11)

A composite material in which high-density particles are dispersed and composited in a flexible material having at least one of an elastomer material and a vulcanized rubber material,
The elastomer material is selected from at least one of a styrene, polyamide, urethane, polyester, vinyl chloride and olefin thermoplastic elastomer,
The vulcanized rubber material is selected from materials vulcanized into at least one of fluorine rubber, silicon rubber, ethylene / propylene rubber, nitrile rubber, natural rubber, isoprene rubber and styrene / butadiene rubber,
The high-density particles are selected from at least one of tungsten, a tungsten alloy, and tungsten carbide (hereinafter referred to as “WC”).
The flexible material is 35-60% by volume and the high-density particles are 40-65% by volume with respect to the total volume of the composite material,
The high density particles are:
First particles having a particle size of 1.5 μm or more and 6 μm or less are 18 to 74% by volume with respect to the entire high-density particles,
The second particles having a particle size of 0.5 μm or more and less than 1.5 μm are 9 to 19% by volume with respect to the entire high-density particles,
A high density composite material comprising first particles, second particles and an inevitable mixture.   The high-density composite material according to claim 1, wherein the inevitable mixture includes the high-density particles having a particle diameter of 10 μm or more.   3. The high-density composite material according to claim 1, wherein a gap formed between the adjacent first particles is less than 1.5 μm.   The high-density composite material according to any one of claims 1 to 3, wherein the second particles are filled in a space between the adjacent first particles. The high-density particles are tungsten,
The first particles are 65% by volume or more and less than 74% by volume with respect to the entire high-density particles,
The second particles are 6% by volume or more and less than 19% by volume with respect to the entire high-density particles.
The high-density composite member according to any one of claims 1 to 4.   The high-density composite material according to any one of claims 1 to 5, wherein the high-density composite material has at least one of a sheet shape, a plate shape, a film shape, a cylindrical shape, a square shape, and a combination thereof. .   The high-density composite material according to any one of claims 1 to 6, wherein the high-density composite material is used as a radiation shielding member. The high density composite material ^has a density of ^{8g / cm 3 ~13g / cm 3} , high density composite material according to claim 7 wherein.   In the sheet-shaped high-density composite material, when the thickness of the sheet is 2.2 mm or less and the radius of curvature is 10 mm, the bending angle is in the range of 0 to 180 degrees, and no cracks are generated. The high-density composite material according to any one of claims 6 to 8.   The high-density composite material according to any one of claims 1 to 6, wherein the high-density composite material is used for at least one of a weight member, a vibration isolating member, a balance member, a heat radiating member, a weight, and a counterweight. The high-density composite material according to any one of claims 1 to 10, having at least one of a sheet shape and a plate shape,
A radiation shielding member comprising: a protective film coated on at least one of a front surface and a back surface of the high-density composite material.

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