Transparent radiation-shielding composition, radiation-shielding material, and method for manufacturing the same

Abstract

This disclosure provides a low-cost radiation shielding composition with superior transparency to visible light compared to conventional methods. The disclosure relates to a transparent radiation shielding composition comprising: a base material containing a polar solvent, a polar polymer, or a combination thereof; and ions of a metal compound ionized in the base material, wherein the metal compound is a water-soluble metal compound capable of ionizing in the polar solvent and dissolving in ionic form, and the polar polymer is a water-soluble polymer capable of dissolving in the polar solvent.

Description

Technical Field

[0001] This invention relates to a transparent radiation shielding composition, a radiation shielding material, and a method for manufacturing the same. Background Technology

[0002] Radiation shielding is required in medical settings, health checkups, X-ray devices, nuclear facilities, and other applications. Lead was previously used, but it is opaque and harmful; therefore, in recent years, composites of metal compound particles and resins have become widely used as a replacement.

[0003] For the purpose of providing transparent radiation shielding materials against neutron rays and gamma rays / X-rays, an epoxy resin molded article has been proposed, which is formed by curing an epoxy resin composition containing nanoparticles mixed with elemental metals and / or metal compounds with acid anhydride (Patent Document 1).

[0004] For the purpose of providing a radiation protection device for protecting the hippocampus from radiation, a radiation protection device has been proposed that includes a head shield for shielding radiation entering from the head and a face shield for shielding radiation entering from the face (Patent Document 2).

[0005] To provide a radiation shielding material with high density while suppressing the refractive index to near that of transparent resin, a density of 6 g / cm³ is proposed. 3 Radiation shielding materials consisting of solid solutions of fluorides with a refractive index of 1.55 or less (Patent Document 3).

[0006] For the purpose of providing lead-free radiation shielding materials, a radiation shielding material comprising heavy metal components such as bismuth and polymer components in a matrix combined with or embedded in polymer components has been proposed (Patent Document 4).

[0007] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2022-037678 Patent Document 2: Japanese Patent Application Publication No. 2012-225702 Patent Document 3: Japanese Patent Application Publication No. 2018-179679 Patent Document 4: Japanese Patent Application Publication No. 2019-138915 Summary of the Invention

[0008] The problem that the invention aims to solve However, in the prior art, including patent documents 1-4, radiation shielding materials are made by dispersing metal or metal compound particles with an average diameter of several μm to tens of μm in a solid such as a liquid or plastic. Alternatively, nanoscale metal oxide particles with wavelengths smaller than visible light are used to make the X-ray shielding material transparent under visible light. However, substances containing dispersed metal or metal compound particles have low transparency to visible light. Even when using nanoscale particles, if a large number of particles are added for use as a radiation shielding material, the nanoscale particles tend to aggregate, resulting in insufficient transparency to visible light. Furthermore, using nanoscale metal oxide particles incurs costs for raw materials and dispersion control, making it difficult to achieve both radiation shielding and transparency to visible light at a low cost. Therefore, there is a need for a low-cost radiation shielding composition with superior transparency to visible light compared to conventional methods.

[0009] Solution for solving the problem The main points of this invention are as follows.

[0010] (1) A transparent radiation shielding composition comprising: a base material comprising a polar solvent, a polar polymer or a combination thereof; and ions of a metal compound ionized in the base material, the metal compound being a water-soluble metal compound capable of ionization in the polar solvent and dissolving in ionic form, and the polar polymer being a water-soluble polymer capable of dissolving in the polar solvent.

[0011] (2) The radiation shielding composition according to (1) above, wherein the polar solvent is water, glycerol, ethylene glycol, propylene glycol, methanol, ethanol, biomass ethanol or a combination thereof.

[0012] (3) The radiation shielding composition according to (1) or (2) above, wherein the metal compound is barium acetate, barium bromide, barium chloride, barium hydroxide, barium nitrate, sodium tungstate, polytungstate, potassium tungstate, bismuth acetate, bismuth bromide, sodium borate, polyborate, or a combination thereof.

[0013] (4) The radiation shielding composition according to any one of (1) to (3) above, wherein the polar polymer is starch, polyacrylic acid, carrageenan, polyvinyl alcohol, polyvinylpyrrolidone, cellulose nanofibers, carboxymethyl cellulose, hydroxyethyl cellulose, polyacrylamide, agarose, agar, water-dispersible rubber latex or a combination thereof.

[0014] (5) The radiation shielding composition according to any one of (1) to (4) above, wherein the content of the metal compound is 3 to 50% by mass based on the total amount of the composition.

[0015] (6) A radiation shielding material comprising the radiation shielding composition as described in any one of (1) to (5) above.

[0016] (7) The radiation shielding material according to (6) above, wherein the radiation shielding material is a radiation shielding curtain.

[0017] (8) A method for manufacturing a transparent radiation shielding composition, comprising: mixing a polar solvent and a water-soluble metal compound soluble in the polar solvent to form a first composition containing ions ionized from the water-soluble metal compound in the polar solvent.

[0018] (9) The manufacturing method according to (8) above, wherein the method comprises: mixing the first composition and a polar polymer soluble in the polar solvent, dissolving the polar polymer in the polar solvent of the first composition, to form a second composition containing ions ionized from the water-soluble metal compound in the solution of the polar solvent and the polar polymer.

[0019] (10) The manufacturing method according to (9) above, wherein the method comprises: removing at least a portion of the polar solvent from the second composition, and preparing a third composition containing ions ionized from the water-soluble metal compound in the solution of the polar solvent and the polar polymer or in the polar polymer.

[0020] Invention Effects According to the present invention, an inexpensive radiation shielding composition with superior transparency to visible light compared to conventional methods can be provided. Attached Figure Description

[0021] Figure 1 This is an example of the appearance of the first composition placed in a glass bottle, along with a schematic diagram.

[0022] Figure 2 These are photographs and schematic diagrams of the appearance of radiation shielding materials containing metal particles or metal compound particles, which were previously placed in glass bottles.

[0023] Figure 3 This is a photograph showing the appearance of an example of the particles of this composition.

[0024] Figure 4 These are photos of the appearance of previous radiation shielding materials.

[0025] Figure 5 This is a photograph showing the appearance of particles of a composition that does not contain metal compounds.

[0026] Figure 6 This composition, Figure 4The conventional radiation shielding materials shown are as follows Figure 4 The diffraction pattern was obtained by measuring the raw material powder (barium sulfate powder) of the metal compound contained in the previous radiation shielding materials using a powder X-ray diffraction device.

[0027] Figure 7 This is a schematic diagram illustrating a method for determining the X-ray shielding efficiency of a liquid, gel, or other substance that cannot maintain a certain shape when placed in a container.

[0028] Figure 8 This is a schematic diagram illustrating a method for determining the radiation shielding efficiency of a sample (the object of measurement) alone.

[0029] Figure 9 This is a schematic diagram illustrating the method for determining the radiation shielding efficiency of the composition when it is a solid or other self-supporting material.

[0030] Figure 10 This is a graph showing the X-ray shielding efficiency of the compositions prepared in the examples and comparative examples at tube voltages of 40–120 kV.

[0031] Figure 11 This is a graph showing the X-ray shielding efficiency of the compositions (particles) prepared in Examples and Comparative Example 5 at tube voltages of 40–120 kV.

[0032] Figure 12 This is a chart showing the X-ray shielding efficiency of liquid compositions prepared with a metal compound content of 1 mmol and the metal compounds being barium acetate, barium chloride, and barium bromide, respectively.

[0033] Figure 13 This is a chart showing the X-ray shielding efficiency of liquid compositions prepared with a metal compound content of 2.5 mmol and the metal compounds being barium acetate, barium chloride, and barium bromide, respectively.

[0034] Figure 14 This is a chart showing the X-ray shielding efficiency of liquid compositions prepared with a metal compound content of 5 mmol and the metal compounds being barium acetate, barium chloride, and barium bromide, respectively.

[0035] Figure 15 This is a graph showing the X-ray shielding efficiency of the compositions prepared in the examples.

[0036] Figure 16 This is a graph showing the visible light transmittance of particles produced in the embodiments and comparative examples in the visible light region.

[0037] Figure 17 This is a photograph of the appearance of radiation protection gloves previously used for measuring X-ray shielding efficiency.

[0038] Figure 18 These are photographs showing the appearance of the compositions (particles) prepared in the examples.

[0039] Figure 19 This is a photograph of the appearance of the composition (particles) that does not contain metal compounds.

[0040] Figure 20 This is a graph showing the X-ray shielding efficiency of the compositions (particles) prepared in the examples and comparative examples.

[0041] Figure 21 This is a graph showing the visible light transmittance of the compositions (particles) prepared in the examples and comparative examples. Detailed Implementation

[0042] This disclosure relates to a transparent radiation shielding composition (hereinafter also referred to as "the composition") comprising: a base material containing a polar solvent, a polar polymer, or a combination thereof; and ions of a metal compound ionized in the base material, the metal compound being a water-soluble metal compound capable of ionizing in the polar solvent and dissolving in ionic form, and the polar polymer being a water-soluble polymer capable of dissolving in the polar solvent.

[0043] The inventors have discovered that when a polar solvent and a water-soluble metal compound (hereinafter also referred to as a metal compound) that can dissolve in the polar solvent are mixed, the metal compound ionizes and dissolves in the polar solvent in ionic form. The resulting composition (hereinafter referred to as the first composition or the two-component system) exhibits high transparency to visible light and radiation shielding properties. The first composition can be a liquid. The viscosity of the first composition can be adjusted according to the type of polar solvent and the content of the metal compound.

[0044] The inventors have also discovered that the composition obtained by adding a polar polymer to the first composition and dissolving it in a polar solvent (hereinafter also referred to as the second composition or the three-component system) possesses the same visible light transparency and radiation shielding properties as described above. In the second composition, the metal compound exists in ionic form in the mixture of the polar solvent and the polar polymer. The second composition can be a high-viscosity liquid or gel. The state of the second composition can be liquid, gel, or solid. The state of the second composition can be adjusted according to the type and content of the polar solvent and polar polymer, as well as the content of the metal compound.

[0045] The inventors further discovered that the composition obtained by removing at least a portion of the polar solvent from the second composition described above (hereinafter also referred to as the third composition or three-component system) also possesses the same visible light transparency and radiation shielding properties as described above. The third composition can be a solid. The third composition is obtained by removing at least a portion of the polar solvent from the second composition, but may or may not contain residual polar solvent. The state of the third composition can be adjusted according to the residual amount of polar solvent, the type of polar solvent and polar polymer, the content of polar polymer, and the content of metal compound. In the third composition, the metal compound exists in the polar polymer in ionic form. By including a polar polymer in this composition, the viscosity or strength of the radiation shielding material constituted by this composition can be changed; furthermore, even when this composition is a solid, it can still possess transparency.

[0046] This composition may be the first composition, the second composition, the third composition, or a combination thereof described above.

[0047] In this composition, it is known that the metal compound ionizes and exists in the form of ions in polar solvents, polar polymers, or a matrix containing a combination thereof, and therefore does not shield visible light. Furthermore, depending on the metal content of the metal compound contained in this composition, radiation shielding properties equivalent to those of conventional radiation shielding materials containing metal particles or metal compound particles can be obtained.

[0048] Conventional radiation shielding materials containing metallic components contain metallic particles or metal compound particles. These particles block visible light, thus reducing transparency even at nanoscale. Furthermore, nanoscale particles tend to aggregate, potentially affecting transparency. In contrast, in this composition, the metal compound is ionized and present as ions, resulting in high transparency to visible light. Moreover, since the metal compound exists as ions in this composition, nanoscale metal compound particles are unnecessary for achieving transparency, offering advantages in terms of cost and operation.

[0049] Transparency can be assessed visually. Figure 1 The image shows an example of the appearance of the first composition placed in a glass bottle, along with a schematic diagram. Figure 2 The image shows photographs and schematic diagrams of conventional radiation shielding materials containing metal particles or metal compound particles placed in glass bottles. Figure 1 and Figure 2It is known that, in conventional radiation shielding materials containing metal particles or metal compound particles, the metal particles or metal compound particles are dispersed in the solvent and do not dissolve, thus making them opaque. However, in the first composition, the metal compound ionizes in the polar solvent and dissolves in the form of ions, thus making it transparent. The second composition containing a polar polymer and the third composition without a polar solvent are also transparent.

[0050] Figure 3 The image shows an example of the appearance of particles of a near-solid gel-like second composition made of 26% by mass of glycerol, 26% by mass of sodium polytungstate (SPT), and 47% by mass of starch. Figure 4 The image shows a photograph of the appearance of particles of a conventional radiation shielding material (47% by mass of polystyrene / 53% by mass of barium sulfate particles). Figure 5 The image shows the appearance of particles of a composition (36% by mass glycerol / 64% by mass starch) that does not contain metal compounds. Figure 4 It is known that, in the case of previous radiation shielding materials, metal compound particles are dispersed and insoluble in nonpolar solvents, and therefore opaque. However, due to... Figure 3 It is known that in the second composition, the water-soluble metal compound exists in the polar polymer in ionic form, and therefore interacts with the non-metallic polymer. Figure 5 The particles are also transparent.

[0051] The transparency can be evaluated by measuring the visible light transmittance using a UV-Vis spectrophotometer. This composition exhibits excellent visible light transmittance in the visible light region of 400–800 nm. The third composition exhibits even higher visible light transmittance. This composition preferably shows a visible light transmittance of 50% or more, more preferably 60% or more, further preferably 70% or more, and even more preferably 80% or more. It should be noted that the visible light transmittance of ordinary glass is approximately 90%, while the visible light transmittance of conventional radiation shielding materials containing metal particles or metal compounds is approximately 30%.

[0052] Whether a metal compound is ionized and exists in ionic form in a polar solvent, polar polymer, or a combination thereof can be evaluated using powder X-ray diffraction. When analyzing conventional radiation shielding materials containing metal particles or metal compound particles using a powder X-ray diffraction apparatus, diffraction patterns with peaks reflecting the crystal structure of the metal particles or metal compound particles are obtained. However, when analyzing this composition in which the metal compound is ionized and dissolved in the matrix using a powder X-ray diffraction apparatus, no peaks originating from the metal compound are observed in the diffraction pattern. Thus, while the ionized metal compound contained in this composition does not show peaks in the powder X-ray diffraction pattern, qualitative and quantitative analysis of the metal compound can be performed by SEM-EDS (scanning electron microscopy-energy dispersive X-ray spectroscopy).

[0053] Figure 6 The image shows particles of a second composition made of a gel-like substance consisting of 23% by mass of glycerol, 36% by mass of barium bromide, and 41% by mass of starch. Figure 4 The particles of the conventional radiation shielding materials shown are as follows Figure 4 The diffraction pattern was obtained by measuring the raw material powder (barium sulfate powder) of the metal compound contained in the previous radiation shielding materials using a powder X-ray diffraction device.

[0054] In the X-ray diffraction patterns obtained from measurements of conventional radiation shielding materials, peaks reflecting the crystal structure of barium sulfate, identical to those obtained from measurements of the raw material powder, were observed. In conventional radiation shielding materials, the metal compound particles (barium sulfate powder) exist in polystyrene as crystalline particles, thus being opaque, and peaks reflecting the crystal structure of the metal compound were observed. However, in the X-ray diffraction patterns obtained from measurements of the second composition, no diffraction peaks reflecting the metal compound were observed. In the second composition, the metal compound (barium bromide) exists in ionic form in a solution of glycerol (a polar solvent) and starch (a polar polymer), and is substantially non-crystalline; therefore, no peaks reflecting the crystal structure of the metal compound were observed in the diffraction patterns. Similarly, no peaks reflecting the crystal structure of the metal compound were observed in the diffraction patterns of the first and third compositions.

[0055] It should be noted that when a metal compound is ionized in the parent material and exists in the form of ions, it becomes transparent. Therefore, transparency can also be evaluated by the presence or absence of diffraction peaks based on powder X-rays.

[0056] This composition exhibits excellent radiation shielding characteristics over a wide range of tube voltages. The photoelectric effect weakens with increasing energy; therefore, the higher the tube voltage, the less effective the radiation shielding becomes. However, for example, in the case of a 10mm thick radiation shielding material composed of this composition, an X-ray shielding efficiency of at least 20%, more preferably at least 25%, further preferably at least 30%, even more preferably at least 35%, and even more preferably at least 45% is preferred at an X-ray tube voltage of 120kV. At an X-ray tube voltage of 40kV, an X-ray shielding efficiency of at least 30%, more preferably at least 40%, further preferably at least 50%, even more preferably at least 60%, and even more preferably at least 70% is preferred. For instance, in the case of a 0.5mm thick radiation shielding material composed of this composition, an X-ray shielding efficiency of at least 30%, more preferably at least 40%, and even more preferably at least 50% is preferred at an X-ray tube voltage of 40kV. For example, in the case of a radiation shielding material with a thickness of 0.3 mm composed of this composition, an X-ray shielding rate of preferably 5% or more, more preferably 10% or more, further preferably 15% or more, and even more preferably 20% or more can be displayed at an X-ray tube voltage of 40 kV.

[0057] Figures 7-9 The method for determining radiation shielding efficiency is shown in the figure. Figure 7 This is a schematic diagram illustrating a method for measuring the X-ray shielding efficiency of the composition when it is a liquid, gel, or similar substance that cannot maintain a certain shape without being placed in a container. A lead plate 30 with a diameter of 15 mm and a thickness of 4.5 mm is placed on a detector. The composition, serving as the sample 20 (the object of measurement), is placed in a glass container to a depth of 10 mm. The glass container containing the composition is placed on the lead plate 30. Radiation is irradiated from a radiation source 10, such as an X-ray source, at a distance of 1000 mm from the detector 40, using a prescribed tube voltage. The first radiation intensity is measured using the detector 40. Furthermore, as... Figure 8 As illustrated in the diagram, in order to determine only the radiation shielding efficiency of the sample, an empty glass container was placed on a lead plate 30 and irradiated with radiation in the same manner as described above, and the second radiation intensity was measured using a detector 40.

[0058] The radiation intensity of the transmitted sample is obtained by adding the difference between the measured first radiation intensity and the second radiation intensity to the first radiation intensity. The radiation transmittance can be determined by the following formula (1).

[0059] Radiant transmittance (%) = (radiation intensity transmitted through the sample) / (radiation intensity toward the sample) × 100 (1) The radiation shielding efficiency can be calculated using the following formula (2).

[0060] Radiation shielding rate (%) = 100% - radiation transmittance (%) (2) Figure 9 This is a schematic diagram illustrating a method for determining the radiation shielding efficiency of this composition when it is a self-supporting high-viscosity gel, solid, or other similar substance. The composition can be directly placed on a lead plate 30 as a sample 20 (the object of measurement), and the radiation shielding efficiency can be determined using the same method as described above.

[0061] The radiation intensity used to determine the radiation shielding efficiency can be adjusted by the tube voltage. The tube voltage can be determined based on the radiation intensity to be shielded by this composition; for example, it can be 40–120 kV when the radiation is X-ray. Typically, the tube voltage is around 40 kV for X-ray images of clapping hands and around 120 kV for X-ray images of the chest.

[0062] The radiation that can be shielded by this composition can be X-rays, gamma rays, alpha rays, beta rays, or neutron rays.

[0063] In the past, lead glass was used to shield radiation in applications such as medical settings and the nuclear industry. However, while a higher lead content results in better radiation shielding, its transparency to visible light is sometimes insufficient. Furthermore, lead glass contains a large amount of lead, so a higher lead content means a heavier glass. Additionally, as glass, lead glass is easily broken.

[0064] In contrast, this composition possesses radiation shielding properties while also exhibiting excellent transparency to visible light, making it well-suited for applications requiring transparency equivalent to or exceeding that of lead glass. Because this composition is transparent, it allows for easy visualization of the shielded interior during operation, resulting in high workability and safety. This composition can, for example, replace or be used in combination with lead glass previously used in medical settings, nuclear applications, etc., enabling the reduction or elimination of lead usage.

[0065] This composition can be used, for example, as lenses and frame materials for radiation-protective eyeglasses used to shield the lens from radiation during catheterization examinations in medical settings, and as window materials for viewing the interior of examination devices using X-rays or other radiation. This composition is lead-free, making it easier to reduce weight compared to conventional lead glass. Furthermore, this composition is a liquid, gel, or resin-based solid, making it less prone to breakage and ensuring high safety. In addition, in examinations using isotopes, higher energies such as gamma rays are sometimes used. In such examinations, the radiation shielding effect of lead glass is sometimes insufficient. Combining the shielding material made of this composition with lead glass provides excellent radiation shielding.

[0066] Radiation shielding materials containing this composition (hereinafter also referred to as radiation shielding materials) can be obtained. Radiation shielding materials containing this composition can be the composition alone or a composite material with other materials.

[0067] Radiation shielding material can be a sheet-like component having layers of this composition. The sheet component can also be a strip-shaped component. The layers of this composition can be flexible and have elastic, deformable rubber-like elasticity. Therefore, the layers of this composition can be bent or rolled like cloth, and are not easily damaged or missing even when bent or rolled. In this application, flexibility means that it is not easily damaged or missing even when bent or rolled.

[0068] Radiation shielding materials may, for example, have a double-layer structure of the composition disposed on at least a portion of one side of a first substrate, or a triple-layer structure of the composition disposed on at least a portion of both sides, and these layer structures may further include other layers. Radiation shielding materials may, for example, have a triple-layer structure of the composition disposed on at least a portion between a first substrate and a second substrate, and these layer structures may further include other layers.

[0069] The first and second substrates can be independently made of soft sheet or film materials such as woven fabrics, non-woven fabrics, paper, or resin. Alternatively, they can be independently made of harder sheet materials such as glass or plastic sheets. The first and second substrates can be the same material or different materials. The thickness of the first and second substrates can be the same as or different from the thickness of the composition.

[0070] A transparent radiation shielding material can be formed by disposing a liquid first composition between a first substrate and a second substrate that are transparent to visible light. If the second composition is a liquid or a gel with low strength and cannot be self-supporting, a transparent radiation shielding material can still be formed by disposing it between the first substrate and the second substrate that are transparent to visible light. If the second composition is a gel with high strength or a solid, it can be self-supporting and therefore can be used alone as a radiation shielding material or sandwiched between the first substrate and the second substrate that are transparent to visible light. A third composition is a solid and self-supporting, therefore it can be used alone as a radiation shielding material or sandwiched between the first substrate and the second substrate that are transparent to visible light.

[0071] The second composition can be used in liquid, gel, or solid form, or as a third composition formed by drying a polar solvent to form a solid. It is transparent to visible light and possesses radiation shielding properties in any of its liquid, gel, or solid states. Therefore, the second composition can be disposed in a liquid state between a first substrate and a second substrate that are transparent to visible light to form a transparent radiation shielding material; it can be used as a self-supporting radiation shielding material in a gel or solid state; or it can be used as a radiation shielding material as a solid and transparent third composition formed by drying a polar solvent. The solid third composition can form a transparent radiation shielding material even in areas where a liquid cannot be used.

[0072] Two or three of the first, second, and third compositions may also be used in combination.

[0073] The radiation shielding material preferably has a substantially constant thickness throughout the entire area, and its surface is generally flat. There are no particular limitations on the thickness of the radiation shielding material; the upper limit can be less than 100 mm, less than 50 mm, less than 10 mm, less than 1.0 mm, less than 0.8 mm, or less than 0.5 mm. The lower limit of the thickness can be more than 0.1 mm or more than 0.3 mm. The thickness of the first and second substrates in the radiation shielding material can independently be 0.005 mm to 0.2 mm or 0.01 mm to 0.1 mm.

[0074] The thickness of the composition contained in the radiation shielding material can be a thickness corresponding to the application. The first composition is preferably used for applications with a larger thickness, for example, a thickness of 1-100 mm, 2-50 mm, 3-20 mm, 4-15 mm, or 5-10 mm. The second and third compositions are preferably used for applications with a thinner thickness, for example, a thickness of 0.1-1 mm, 0.2-0.9 mm, 0.3-0.8 mm, or 0.4-0.7 mm. The second and third compositions, at the thin thicknesses described above, exhibit mechanical properties such as flexibility and high strength.

[0075] Radiation shielding materials can be used in clothing such as radiation protective suits, and other products besides clothing, such as gloves or neck braces, which are worn on the body. They can also be used in various other items besides those worn on the body.

[0076] The preferred radiation shielding material is a radiation shielding curtain. This curtain can be used for X-ray inspection devices for baggage in airports. It can be installed at the entrance and exit of the X-ray inspection device. This composition provides both radiation shielding and flexibility, thus the radiation shielding curtain containing this composition provides both radiation shielding to prevent X-rays emitted from inside the X-ray inspection device from leaking to the outside and flexibility to allow baggage transported by conveyor belt to pass smoothly in and out.

[0077] This composition can be transparent, therefore the radiation shielding curtain containing this composition can also be transparent. Conventional radiation shielding curtains used in X-ray inspection equipment are opaque, making it impossible to observe the interior of the X-ray inspection equipment. However, by using a radiation shielding curtain containing this composition, the interior of the X-ray inspection equipment irradiating luggage can be visually confirmed. Therefore, even in the event of a malfunction such as luggage failing to exit the X-ray inspection equipment, the status of the luggage inside the X-ray inspection equipment can be easily confirmed through the transparent radiation shielding curtain without stopping the X-ray inspection equipment.

[0078] For example, the composition can be sandwiched between the first substrate and the second substrate, and the laminate containing the composition can be pressed together using a press and rollers, and then dried using a hot air drying oven. Heating and drying can also be carried out using a hot air drying oven.

[0079] The first substrate and the second substrate can be conveyed by a supply roller or the like, the composition is supplied to the upper surface of the first substrate on the lower side being conveyed, and the second substrate is overlapped from above the supplied composition, and the first substrate and the second substrate with the composition sandwiched in them are pressed together by a press or roller.

[0080] The laminate of the first substrate, the present composition, and the second substrate, after being pressed together, is dried with hot air. As a result, the present composition sandwiched between the first and second substrates is dried, forming a layer of the present composition between the first and second substrates. Thus, a sheet-like radiation shielding material having a layer of the present composition tightly adhered between the first and second substrates can be produced.

[0081] Radiation shielding materials can also consist of a single layer of the composition. In this case, the radiation shielding material can be produced by molding only the layer of the composition, or it can be produced by forming the layer of the composition on a first substrate and then peeling off the first substrate. In this case, the first substrate can be used as a release liner.

[0082] The preferred polar solvent is water, glycerol, ethylene glycol, propylene glycol, methanol, ethanol, biomass ethanol, or combinations thereof. Using these preferred polar solvents allows for good dissolution of the metal compound. The polar solvent is preferably a low molecular weight liquid, more preferably having a molecular weight of 18 to 92. Within this preferred molecular weight range, the metal compound can be dissolved more effectively.

[0083] The polar solvent is more preferably biodegradable. From the viewpoint of biodegradability, water, glycerol, or bioethanol are further preferred polar solvents. In addition, for example, glycerol has a high boiling point, and is therefore preferred in that it can dissolve metal compounds while heating and can dissolve higher concentrations of metal compounds.

[0084] The polar solvent preferably has a relative permittivity of 3 or higher, more preferably 10 or higher, further preferably 20 or higher, even more preferably 30 or higher, and even more preferably 40 or higher. By using a polar solvent with a relative permittivity within the aforementioned preferred range, more metal compounds can be dissolved. The relative permittivity of water is 80, that of glycerol is 47, that of ethylene glycol is 39, that of propylene glycol is 32, that of methanol is 33, and that of ethanol is 24. The relative permittivity can be determined based on JIS C2138:2007.

[0085] The polar solvent preferably has a boiling point of 100°C or higher, more preferably 180°C or higher, even more preferably 190°C or higher, and even more preferably 200°C or higher. By using a polar solvent with a boiling point within the aforementioned preferred range, heating can be performed while suppressing evaporation, thus enabling higher concentrations of metal compounds to dissolve in the polar solvent.

[0086] When it is desired to remove the solvent from this composition, the polar solvent may have a boiling point below 100°C, below 90°C, below 80°C, or below 70°C. By using a polar solvent with a boiling point within the aforementioned range, it is easier to remove the polar solvent through natural evaporation, heat treatment, or the like. By removing the solvent, it is easier to form a high-viscosity composition or a solid composition. In particular, in the case of a second composition containing a polar polymer, even after removing the polar solvent, the metal compound exists in the polar polymer in ionic form, thus obtaining a transparent and solid third composition with radiation shielding properties.

[0087] This composition can contain multiple polar solvents with different boiling points. Alternatively, a third composition can be obtained by evaporating only the polar solvents with lower boiling points from a second composition containing multiple polar solvents with different boiling points. For example, a second composition can be generated by heating and stirring two or more polar solvents, such as water with a boiling point below 100°C and glycerol with a boiling point above 100°C, along with a polar polymer and a metal compound. Then, the polar solvent, such as water with a boiling point below 100°C, is evaporated to obtain a third composition containing a polar solvent, such as glycerol with a boiling point above 100°C, a polar polymer, and a metal compound. The polar solvents remaining in the third composition can ionize the metal compound and contain it in the form of metal ions, and can impart softness to the composition. Removing a portion of the polar solvents from the multiple polar solvents contained in the second composition can be done by utilizing the differences in the boiling points of the polar solvents.

[0088] The boiling point of water is 100℃, the boiling point of glycerol is 290℃, the boiling point of ethylene glycol is 197℃, the boiling point of propylene glycol is 188℃, the boiling point of methanol is 64℃, and the boiling point of ethanol is 78℃.

[0089] The content of polar solvents in this composition, based on the total amount of the composition, can be, for example, 0% by mass, or more than 0-97% by mass, 5-96% by mass, 10-95% by mass, 15-94% by mass, 20-90% by mass, or 25-85% by mass. The content of polar solvents in this composition, based on the total amount of the composition, can be, for example, 20-30% by mass, 60-95% by mass, 70-90% by mass, or 90-97% by mass. Regarding the content of polar solvents, in the formation of this composition and in the first composition, it is acceptable as long as it is within the range capable of dissolving the added metal compound. In the second composition, it can be adjusted within the range capable of dissolving the metal compound according to the amount of polar polymer added. The third composition may contain or may not contain a portion of the polar solvents contained in the second composition.

[0090] In the third composition, the content of residual polar solvents can be varied according to the desired softness. For example, when the third composition is obtained by evaporating a low-boiling-point polar solvent such as water from the various polar solvents contained in the second composition, the higher the content of residual polar solvents with higher boiling points such as glycerol, ethylene glycol, and propylene glycol, the greater the softness of the third composition. To make the third composition soft, it contains 20–60% by mass, 25–55% by mass, or 30–50% by mass of high-boiling-point polar solvents such as glycerol, ethylene glycol, and propylene glycol relative to the total composition. To make the third composition non-soft, the content of residual polar solvents can be reduced to 15% by mass or less, 10% by mass or less, 5% by mass or less, or substantially zero relative to the total composition.

[0091] Metal compounds are water-soluble metallic compounds that can ionize in polar solvents and dissolve in ionic form. Metal compounds possess both positive and negative charges and can exist as ions ionized from the parent material. The metallic element contained in the metallic compound is preferably an element from the sixth period or boron. Metal compounds containing elements from the sixth period are effective at shielding against X-rays, gamma rays, alpha rays, and beta rays, while metallic compounds containing boron are effective at shielding against neutron rays. The elements from the sixth period are preferably those from barium to bismuth, namely barium, lanthanum, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, mercury, thallium, lead, and bismuth. Elements with higher atomic numbers have higher radiation shielding properties, but elements with atomic numbers greater than the sixth period may become radiation sources when irradiated; therefore, the metallic element contained in the metallic compound is preferably an element from the sixth period.

[0092] The metallic element contained in the metallic compound is further preferably barium, tungsten, lead, bismuth, boron or a combination thereof, and is further preferably barium, tungsten or bismuth in terms of environmental (non-toxicity) and tungsten or barium in terms of cost and environmental (non-toxicity) even more preferably.

[0093] The preferred metal compound is barium acetate, barium bromide, barium chloride, barium hydroxide, barium nitrate, sodium tungstate, polytungstate (SPT), potassium tungstate, bismuth acetate, bismuth bromide, sodium borate, polyborate, or a combination thereof. The preferred metal compound is more readily soluble in polar solvents.

[0094] The content of the metal compound can be an amount corresponding to the desired radiation shielding characteristics within a range that allows it to dissolve in polar solvents. A higher content of metal compound in this composition results in stronger radiation shielding characteristics. Furthermore, a higher content of metal compound in this composition makes it less likely for the radiation shielding characteristics to decrease even with increased tube voltage. It should be noted that a greater thickness of the radiation shielding material formed using this composition results in stronger radiation shielding characteristics, thus allowing for a lower content of metal compound. Conversely, a smaller thickness of the radiation shielding material formed using this composition results in weaker radiation shielding characteristics, thus allowing for a higher content of metal compound.

[0095] The thickness of the radiation shielding material formed using this composition is not particularly limited, and can be a thickness corresponding to the desired radiation shielding characteristics, for example, 1-1000 mm, 2-750 mm, 3-500 mm, 4-250 mm or 5-100 mm.

[0096] The content of the metal compound, based on the total amount of the composition, is preferably 3–50% by mass, 5–48% by mass, 10–46% by mass, 15–44% by mass, or 20–42% by mass. By maintaining the metal compound content within the above ranges, the metal compound can dissolve more effectively in polar solvents in ionic form, resulting in a radiation shielding effect. Furthermore, the content of the metal compound in this composition relative to the total mass per 3 cm³ is [not specified in the original text]. 3 The composition is preferably 0.5–10 mmol, more preferably 1–8 mmol, even more preferably 2–6 mmol, and still more preferably 2.5–5 mmol. By ensuring the content of the metal compound is within the above-mentioned preferred range, the metal compound with radiation shielding effect can be more effectively dissolved in the polar solvent in ionic form.

[0097] The metal compound prepared for dissolution in polar solvents can be any powder that is soluble in polar solvents, and it can also be agglomerated; for example, commercially available metal compound powders of about 100 μm to 1 mm are sufficient. In this composition, the metal compound exists in ionic form, thus eliminating the need for nano-sized metal compound particles for transparency, which is advantageous in terms of cost and operation.

[0098] Polar polymers are water-soluble polymers that can dissolve in polar solvents. A polar polymer only needs to be soluble in a polar solvent and can have the same relative permittivity as the polar solvent. Depending on the content or molecular weight of the polar polymer, the viscosity of this composition can be adjusted to be high or low, or the hardness of the gel composition can be adjusted, thus obtaining a substantially solid composition. Furthermore, crosslinking the polar polymer yields a hard composition.

[0099] The polar polymer is preferably starch, polyacrylic acid, carrageenan, polyvinyl alcohol, polyvinylpyrrolidone, cellulose nanofibers, carboxymethyl cellulose, hydroxyethyl cellulose, polyacrylamide, agarose, agar, water-dispersible rubber latex, or combinations thereof. Furthermore, the polar polymer is preferably biodegradable. From the viewpoint of biodegradability, starch, carrageenan, agarose, and agar are more preferred polar polymers.

[0100] A biodegradable first composition can be obtained by using a biodegradable polar solvent in the formation of the first composition. A biodegradable second composition can be obtained by using a biodegradable polar solvent and a biodegradable polar polymer in the formation of the second composition. For example, glycerol and starch are both biodegradable; therefore, by using glycerol as a polar solvent and starch as a polar polymer, a composition that is transparent to visible light, has radiation shielding properties, and is biodegradable can be obtained. When the polar solvent is removed from the second composition to form a third composition, a biodegradable third composition can be obtained by using a biodegradable polar polymer.

[0101] By using cellulose nanofibers as a polar polymer, cellulose nanofibers can be dispersed in a polar solvent to form a transparent dispersion liquid. At least a portion of the polar solvent can be removed by drying or heat treatment to obtain a transparent and biodegradable fibrous third composition.

[0102] The content of the polar polymer can be an amount corresponding to the desired viscosity or strength of the resulting composition. The content of the polar polymer, based on the total amount of the composition, can be, for example, 0.1–60% by mass, 0.5–57% by mass, 1–54% by mass, 10–52% by mass, 20–50% by mass, or 30–48% by mass. With the polar polymer content within the above ranges, a second or third composition can be well formed.

[0103] The content ratio (mass ratio) of the polar polymer to the polar solvent can be determined based on the desired viscosity or hardness of the resulting composition, as long as the polar polymer is soluble in the polar solvent. The preferred content ratio (mass ratio) of the polar polymer to the polar solvent is 1.5 to 2.0, more preferably 1.6 to 1.9, and even more preferably 1.7 to 1.8. By setting this preferred ratio, the polar polymer and the metal compound can be dissolved in the polar solvent, and a composition with the desired viscosity or hardness can be formed more easily.

[0104] This composition may also contain any other ingredients. Other ingredients may include, for example, gelling agents, thickeners, and polysaccharides, in addition to those mentioned above.

[0105] Furthermore, this disclosure relates to a method for manufacturing a transparent radiation shielding composition (hereinafter also referred to as the manufacturing method), comprising: mixing a polar solvent and a water-soluble metal compound soluble in the polar solvent to form a first composition containing ions ionized from the metal compound.

[0106] By mixing a polar solvent with a water-soluble metal compound that is soluble in the polar solvent, the metal compound can be ionized in the polar solvent and dissolved in ionic form. The method of mixing the polar solvent and the metal compound is not particularly limited; it can be carried out at room temperature or while heating. By mixing the polar solvent and the metal compound while heating, a higher concentration of the metal compound can be dissolved in the polar solvent in a shorter time. The heating temperature can be adjusted according to the boiling point of the polar solvent, for example, from 60 to 200°C.

[0107] Preferably, the first composition and the polar polymer are mixed, causing the polar polymer to dissolve in the polar solvent of the first composition, forming a second composition. In the second composition, the metal compound exists in ionic form in the solution of the polar solvent and the polar polymer. The mixing method of the first composition and the polar polymer is not particularly limited and can be carried out at room temperature or while heating. Mixing the first composition and the polar polymer while heating allows for better dissolution of the polar polymer in the polar solvent. The heating temperature can be adjusted according to the boiling point of the polar solvent, for example, from 60 to 200°C. When mixing the polar solvent and the metal compound, polar polymers such as carrageenan can also be mixed simultaneously. As described above, by mixing the first composition and the polar polymer, the polar polymer is easily and uniformly dissolved in the polar solvent.

[0108] More preferably, the first composition and the polar polymer are mixed at room temperature, and the mixture is heated and melt-kneaded to form the second composition. This prevents the polar polymer from clumping when added, such as starch. The melt-kneading temperature is preferably adjusted according to the boiling point of the polar solvent, for example, from 60 to 200°C.

[0109] Preferably, at least a portion of the polar solvent is removed from the second composition to prepare the third composition. In the third composition, the metal compound exists in ionic form in the solution of the polar solvent and the polar polymer or in the polar polymer. The third composition can be a solid. The method for removing at least a portion of the polar solvent from the second composition is not particularly limited and can be carried out at room temperature or while heating. Heating allows for the removal of at least a portion of the polar solvent from the second composition in a shorter time. The heating temperature can be adjusted according to the boiling point of the polar solvent, for example, 60–300°C or 80–200°C.

[0110] The second or third composition can be processed to obtain molded articles such as granules. Processing can be conventional resin molding methods such as injection molding and stamping. For example, it can also be a compression molding method where the second or third composition is added to a heated mold, and pressure is applied while it has softened and has moderate fluidity to fill the mold, followed by further heating and pressure to solidify it within the mold. In the granulated second or third composition, the metal compound also exists in the parent material in ionic form.

[0111] The above description applies to the composition of the polar solvents, metal compounds, and polar polymers used in this manufacturing method. Furthermore, the above description also applies to the composition of this composition, which includes the first composition, the second composition, and the third composition obtained by this manufacturing method.

[0112] Example (Example of a two-component system) (Example 1) 93.5% by weight of glycerol (manufactured by Kanto Chemical Co., Ltd., product number: 56-81-5, hereinafter the same) and 6.5% by weight of barium acetate (manufactured by FUJIFILM Wako Pure Chemical Co., Ltd., product number: 543-80-6, hereinafter the same) were mixed while heating to 80°C to form a transparent liquid composition.

[0113] (Example 2) 92.6% by weight of glycerol and 7.4% by weight of barium bromide (manufactured by FUJIFILM Wako Pure Chemical Co., Ltd., product number: 10553-31-8, hereinafter the same) were mixed while heating to 80°C to form a transparent liquid composition.

[0114] (Example 3) 93.8% by weight of glycerol and 6.2% by weight of barium chloride (manufactured by FUJIFILM Wako Pure Chemical Co., Ltd., product number: 10326-27-9, hereinafter the same) were mixed while heating to 80°C to form a transparent liquid composition.

[0115] (Example 4) 91.8% by weight of glycerol and 8.2% by weight of sodium tungstate (manufactured by FUJIFILM Wako Pure Chemical Co., Ltd., product number: 10213-10-2, hereinafter the same) were mixed while heating to 80°C to form a transparent liquid composition.

[0116] (Example 5) 91.8% by weight of glycerol and 8.2% by weight of sodium polytungstate (SPT) (manufactured by MEASURE WORKS Co., Ltd., product number: 12141-67-2, hereinafter the same) were mixed while heated to 80°C to form a transparent liquid composition.

[0117] Table 1 shows the types and amounts of polar solvents and metal compounds used in Examples 1-5, as well as the transparency and X-ray shielding efficiency of the resulting compositions. The X-ray shielding efficiency was determined by... Figure 7 and Figure 8 The method shown is performed (composition depth 10 mm). (Examples 6-10) A transparent liquid composition was formed by using water instead of glycerol as a polar solvent, otherwise by the same method as in Examples 1-5. Figure 1 The image shows the appearance of the liquid composition formed in Example 6 placed in a glass bottle.

[0118] Table 2 shows the types and amounts of polar solvents and metal compounds used in Examples 6-10, as well as the transparency and X-ray shielding efficiency of the resulting compositions. The X-ray shielding efficiency was determined by... Figure 7 and Figure 8 The method shown is performed (composition depth 10 mm). (Example of a three-component system) (Example 11) 24% by weight of glycerol and 34% by weight of barium acetate were mixed while heating to 80°C to form a transparent first composition. Next, 42% by weight of starch powder (manufactured by Sanwa Starch Industry Co., Ltd., pregelatinized cassava flour, hereinafter the same) was added to the first composition at room temperature and mixed. The mixture was then heated to 120°C for melt kneading to form a transparent second composition. The resulting second composition was stamped to form transparent, solid granules (film-like composition) in the shape of discs with a thickness of 0.5 mm and a diameter of 20 mm.

[0119] (Example 12) 23% by weight of glycerol and 36% by weight of barium bromide were mixed while heating to 80°C to form a transparent first composition. Then, 41% by weight of starch was added to the first composition while heating to 120°C and mixed to form a transparent second composition in the same manner as in Example 11, resulting in transparent and solid particles (film composition) in the shape of a disc with a thickness of 0.5 mm and a diameter of 20 mm.

[0120] (Example 13) 26% by weight of glycerol and 28% by weight of barium chloride were mixed while heating to 80°C to form a transparent first composition. Then, 46% by weight of starch was added to the first composition while heating to 120°C and mixed to form a transparent second composition in the same manner as in Example 11, resulting in transparent and solid particles (film composition) in the shape of a disc with a thickness of 0.5 mm and a diameter of 20 mm.

[0121] (Example 14) 26% by weight of glycerol and 26% by weight of sodium tungstate were mixed while heating to 80°C to form a transparent first composition. Then, 47% by weight of starch was added to the first composition while heating to 120°C and mixed to form a transparent second composition in the same manner as in Example 11, resulting in transparent and solid particles (film composition) in the shape of a disc with a thickness of 0.5 mm and a diameter of 20 mm.

[0122] (Example 15) 26% by weight of glycerol and 26% by weight of sodium polytungstate (SPT) were mixed while heated to 80°C to form a transparent first composition. Next, 47% by weight of starch was added to the first composition while heating to 120°C and mixed to form a transparent second composition in the same manner as in Example 11, resulting in transparent and solid particles (film composition) in the shape of a disc with a thickness of 0.5 mm and a diameter of 20 mm. Figure 3 The image shows the appearance of the obtained particles.

[0123] (Example 16) 81% by mass of water and 18% by mass of sodium polytungstate (SPT) were mixed while heating to 80°C to form a transparent first composition. Next, 1% by mass of carrageenan (manufactured by Tokyo Chemical Co., Ltd., 11114-20-8) was added to the first composition while heating to 80°C and mixed to form a transparent second composition. The resulting second composition was cooled at room temperature to obtain transparent, gel-like particles (film-like composition) in the shape of discs with a thickness of 0.5 mm and a diameter of 20 mm.

[0124] Table 3 shows the types and contents of polar solvents, metal compounds, and polar polymers used in Examples 11-16, as well as the transparency and X-ray shielding efficiency of the resulting compositions. The X-ray shielding efficiency was determined by... Figure 9 The method shown is performed (composition thickness 0.5 mm). (Comparative Example 1) Prepare 100% by weight of glycerin.

[0125] (Comparative Example 2) Prepare 100% water by mass.

[0126] (Comparative Example 3) A liquid composition was formed by mixing 94.1% by weight of glycerol and 5.9% by weight of barium sulfate (manufactured by Takehara Chemical Industry Co., Ltd., W-10, average particle size 10 μm, hereinafter the same) while heating to 120°C. The barium sulfate particles are insoluble in glycerol and are in a dispersed state, resulting in an opaque composition.

[0127] (Comparative Example 4) 94.2% by weight of glycerol and 5.8% by weight of tungsten oxide (manufactured by FUJIFILM Wako Pure Chemical Co., Ltd., 1314-35-8, average particle size 10 μm, the same applies below) were mixed while heating to 120°C to form a liquid composition. The tungsten oxide particles are insoluble in glycerol and are in a dispersed state, so the prepared composition is opaque.

[0128] (Comparative Example 5) 47% by mass of polystyrene (manufactured by Toyo Styrene Co., Ltd., G100, relative permittivity 2.4) and 53% by mass of barium sulfate were mixed while heating to 200°C to form a composition (particles). The resulting composition was opaque. The resulting composition was cooled at room temperature to obtain gel-like particles (film-like composition) with a thickness of 0.5 mm and a diameter of 20 mm. Figure 4 The image shows the appearance of the obtained particles.

[0129] (Comparative Example 6) A liquid composition was formed by mixing 94.2% by mass water and 5.9% by mass barium sulfate while heating to 80°C. The barium sulfate particles are insoluble in water and exist in a dispersed state, resulting in an opaque composition. Figure 2 The image shows the appearance of the liquid composition being placed into a glass bottle.

[0130] Table 4 shows the types and contents of polar solvents and metal compounds in Comparative Examples 1-6, as well as the transparency and X-ray shielding efficiency of the obtained compositions. Regarding the determination of X-ray shielding efficiency, for Comparative Examples 1-4 and Comparative Example 6, the X-ray shielding efficiency was determined by... Figure 7 and Figure 8 The method shown (composition depth 10 mm) was performed. For Comparative Example 5, it was carried out by... Figure 9 The method shown was performed (composition thickness 0.5 mm). The X-ray shielding efficiency of Comparative Example 1 was 29%, while Example 1 above maintained transparency and showed an X-ray shielding efficiency of 56%, achieving a shielding performance 1.93 times better. (Comparative Example 7) 36% by weight of glycerol and 64% by weight of starch were mixed while heating to 120°C to form a transparent composition (granules) with a thickness of 0.5 mm and a diameter of 20 mm. Figure 5 The image shows the appearance of the obtained particles.

[0131] (Comparative Example 8) 17% by weight of glycerol and 53% by weight of barium sulfate were mixed at room temperature to form a composition. Then, 30% by weight of starch was mixed while heating to 120°C to form a composition (granules) with a thickness of 0.5 mm and a diameter of 20 mm. The resulting composition was opaque.

[0132] (Comparative Example 9) 17% by weight of glycerol and 53% by weight of tungsten oxide were mixed at room temperature to form a composition. Then, 30% by weight of starch was mixed while heating to 120°C to form a composition (granules) with a thickness of 0.5 mm and a diameter of 20 mm. The resulting composition was opaque.

[0133] Table 5 shows the types and contents of polar solvents, metal compounds, and polar polymers in Comparative Examples 7-9, as well as the transparency and X-ray shielding efficiency of the resulting compositions. The X-ray shielding efficiency was determined by... Figure 9 The method shown is performed (composition thickness 0.5 mm). (Evaluation based on diffraction patterns from powder X-ray diffraction) Figure 6 The diagram shows the diffraction patterns obtained by measuring the particles (glycerol / barium bromide / starch) prepared in Example 12, the particles (polystyrene / barium sulfate) prepared in Comparative Example 5, and the barium sulfate powder used in Comparative Example 5 using a sample horizontal multi-purpose X-ray diffractometer (Ultima IV, Rigaku Co., Ltd.).

[0134] In the X-ray diffraction pattern obtained by measuring the particles prepared in Comparative Example 5, peaks reflecting the crystal structure of barium sulfate, identical to those obtained by measuring barium sulfate powder, were observed. On the other hand, in the X-ray diffraction pattern obtained by measuring the particles prepared in Example 12, no peaks of metal compounds were observed.

[0135] (Evaluation of X-ray shielding efficiency) Figure 10The graph shows the X-ray shielding efficiency of the liquid compositions prepared in Example 1 (glycerol / barium acetate), Example 4 (glycerol / sodium tungstate), Comparative Example 3 (glycerol / barium sulfate), and Comparative Example 4 (glycerol / tungsten oxide) at tube voltages of 40–120 kV. The X-ray shielding efficiency was determined by… Figure 7 and Figure 8 The method shown was followed. The liquid compositions prepared in Examples 1 and 4 were transparent, but exhibited the same X-ray shielding efficiency as the opaque liquid compositions prepared in Comparative Examples 3 and 4.

[0136] The X-ray shielding efficiency was approximately the same in the liquid composition containing CH3COOBa in glycerol in ionic form (Example 1) and the liquid composition containing BaSO4 in glycerol in particle form (Comparative Example 3).

[0137] Furthermore, the X-ray shielding efficiency was approximately the same in the liquid composition containing Na2WO4·2H2O in glycerol in ionic form (Example 4) and the liquid composition containing WO3 in glycerol in particle form (Comparative Example 4).

[0138] Figure 11 The graph shows the X-ray shielding efficiency of the particles (glycerol / sodium polytungstate (SPT) / starch) prepared in Example 15, the particles (polystyrene / barium sulfate) prepared in Comparative Example 5, and the particles (glycerol / starch) prepared in Comparative Example 7 at tube voltages of 40–120 kV. The X-ray shielding efficiency was determined by… Figure 9 The method shown was followed. The particles prepared in Example 15 were transparent but exhibited the same X-ray shielding efficiency as the opaque particles prepared in Comparative Example 5. The composition prepared in Comparative Example 7, which did not contain any metal compound, had an X-ray shielding efficiency of approximately 0%.

[0139] (Evaluation of X-ray shielding efficiency based on the type and content of metal compounds) (Example 17) 91.9% by mass of water and 1 mmol (8.1% by mass) of barium acetate were mixed while heating to 80°C to form a transparent liquid composition.

[0140] (Example 18) 90.8% by mass of water and 1 mmol (9.2% by mass) of barium bromide were mixed while heating to 80°C to form a transparent liquid composition.

[0141] Table 6 shows the types and amounts of polar solvents and metal compounds used in Examples 17 and 18, as well as the transparency and X-ray shielding efficiency of the resulting compositions. The X-ray shielding efficiency was determined by... Figure 7 and Figure 8 The method shown is performed (composition depth 10 mm). Figure 12 The diagram shows graphs illustrating the X-ray shielding efficiency of liquid compositions prepared in Examples 17 and 18 with barium acetate and barium bromide as the metal compounds, and with the metal compound content uniformly set at 1 mmol. The composition with barium bromide as the metal compound exhibits a higher X-ray shielding efficiency compared to the composition with barium acetate. The X-ray shielding efficiency tends to decrease as the tube voltage increases.

[0142] (Example 19) 81.1% by mass of water and 2.5 mmol (18.9% by mass) of barium acetate were mixed while heating to 80°C to form a transparent liquid composition.

[0143] (Example 20) 84.6% by mass of water and 2.5 mmol (15.4% by mass) of barium chloride were mixed while heating to 80°C to form a transparent liquid composition.

[0144] (Example 21) 79.3% by mass of water and 2.5 mmol (20.7% by mass) of barium bromide were mixed while heating to 80°C to form a transparent liquid composition.

[0145] Table 7 shows the types and amounts of polar solvents and metal compounds used in Examples 19-21, as well as the transparency and X-ray shielding efficiency of the resulting compositions. The X-ray shielding efficiency was determined by... Figure 7 and Figure 8 The method shown is performed (composition depth 10 mm). Figure 13 The diagram shows the X-ray shielding efficiency of liquid compositions prepared by using barium acetate, barium chloride, and barium bromide as the metal compounds in Examples 19-21, with a uniform metal compound content of 2.5 mmol. The composition with barium bromide as the metal compound has a high X-ray shielding efficiency, while the compositions with barium acetate and barium chloride as the metal compounds have similar X-ray shielding efficiency. The X-ray shielding efficiency tends to decrease slightly as the tube voltage increases.

[0146] (Example 22) 66.0% by weight of water and 5 mmol (34.0% by weight) of barium acetate were mixed while heating to 80°C to form a transparent liquid composition.

[0147] (Example 23) 72.4% by mass of water and 5 mmol (27.6% by mass) of barium chloride were mixed while heating to 80°C to form a transparent liquid composition.

[0148] (Example 24) 64.4% by mass of water and 5 mmol (35.6% by mass) of barium bromide were mixed while heating to 80°C to form a transparent liquid composition.

[0149] Table 8 shows the types and amounts of polar solvents and metal compounds used in Examples 22-24, as well as the transparency and X-ray shielding efficiency of the resulting compositions. The X-ray shielding efficiency was determined by... Figure 7 and Figure 8 The method shown is performed (composition depth 10 mm). Figure 14 The diagram shows the X-ray shielding efficiency of liquid compositions prepared by setting the metal compounds in Examples 22-24 to barium acetate, barium chloride, and barium bromide, and uniformly setting the metal compound content to 5 mmol. The composition with barium bromide as the metal compound has a high X-ray shielding efficiency, while the compositions with barium acetate and barium chloride as the metal compounds have similar X-ray shielding efficiency. The X-ray shielding efficiency is stable regardless of tube voltage.

[0150] (Evaluation of carrageenan as a polar polymer) Figure 15 The graph shows the X-ray shielding efficiency of the composition (particles) prepared in Example 16. The X-ray shielding efficiency is above 60%, unaffected by tube voltage.

[0151] (Evaluation of visible light transmittance) Figure 16 The graph shows the visible light transmittance of particles prepared in Example 15 (glycerol / sodium polytungstate (SPT) / starch), Comparative Example 5 (polystyrene / barium sulfate), and Comparative Example 7 (glycerol / starch) in the visible light region of 400–800 nm, based on a UV-Vis spectrophotometer (Hitachi High-Tech Co., Ltd., U-4100). The particles prepared in Example 15 contain metal compounds in ionic form, and therefore show a visible light transmittance of over 65%, equivalent to that of the particles prepared in Comparative Example 7, which does not contain metal compounds. The visible light transmittance of the particles prepared in Comparative Example 5, which contains barium sulfate in particle form, is approximately 30%.

[0152] (Comparative Example 10) for Figure 17 The X-ray shielding efficiency of the previously used 0.5 mm thick radiation protection gloves (manufactured by Social Security Division, G-3) was measured at a tube voltage of 100 kV, covering the entire wrist, back of hand, and fingertips. As shown in Table 9, the X-ray shielding efficiency of the radiation protection gloves is approximately 50%. (Example 25) 90.4% by weight of water, 2.8% by weight of glycerol, 1.5% by weight of barium bromide, and 5.3% by weight of starch powder were stirred at 90°C for 2 hours to form a transparent second composition. Next, the second composition was placed in a dish and dried at 40°C for 24 hours to evaporate the water, forming a transparent solid third composition. The obtained third composition was then stamped to form a product with a thickness of 0.3 mm, a diameter of 50 mm, and a density of 1.4 g / cm³. 3 Disk-shaped, transparent, and solid particles (film composition). Figure 18 The image shows the appearance of the obtained particles.

[0153] (Comparative Example 10) 91.7% by weight of water, 2.8% by weight of glycerol, and 5.4% by weight of starch powder were stirred at 90°C for 2 hours to form a transparent second composition. Next, the second composition was placed in a dish and dried at 40°C for 24 hours to evaporate the water, forming a transparent solid third composition. The resulting third composition was then stamped to form a product with a thickness of 0.3 mm, a diameter of 50 mm, and a density of 1.2 g / cm³. 3 Disk-shaped, transparent, and solid particles (film composition). Figure 19 The image shows the appearance of the obtained particles.

[0154] Table 10 shows the types and amounts of polar solvents and metal compounds used in Example 25 and Comparative Example 10, as well as the transparency and X-ray shielding efficiency of the resulting compositions. The X-ray shielding efficiency was determined by... Figure 9 The method shown is performed (the thickness of the composition is 0.3 mm). Figure 20 The graph shows the X-ray shielding efficiency of the particles (glycerol / starch / barium bromide) prepared in Example 25 and the particles (glycerol / starch) prepared in Comparative Example 10 at tube voltages of 40–120 kV. Both the particles prepared in Example 25 and Comparative Example 10 are transparent, but the particles prepared in Comparative Example 10, which does not contain any metal compounds, have a low X-ray shielding efficiency, while the particles prepared in Example 25 exhibit a high X-ray shielding efficiency.

[0155] Figure 21 The graph shows the visible light transmittance of particles (glycerol / starch / barium bromide) prepared in Example 25 and Comparative Example 10 (glycerol / starch) in the visible light region of 400–800 nm, based on a UV-Vis spectrophotometer (Hitachi High-Tech Co., Ltd., U-4100). The particles prepared in both Example 25 and Comparative Example 10 showed a visible light transmittance of approximately 90%.

[0156] Explanation of reference numerals in the attached figures 10: Radioactive source; 20: Sample; 30: Lead plate; 40: Detector.

Claims

1. A transparent radiation shielding composition comprising: A base material comprising polar solvents, polar polymers, or combinations thereof; and The ions of the metal compound ionized in the parent material, The metal compound is a water-soluble metal compound that can ionize in the polar solvent and dissolve in ionic form. The polar polymer is a water-soluble polymer that can dissolve in the polar solvent.

2. The radiation shielding composition according to claim 1, wherein, The polar solvent is water, glycerol, ethylene glycol, propylene glycol, methanol, ethanol, biomass ethanol, or a combination thereof.

3. The radiation shielding composition according to claim 1 or 2, wherein, The metal compound is barium acetate, barium bromide, barium chloride, barium hydroxide, barium nitrate, sodium tungstate, polysodium tungstate, potassium tungstate, bismuth acetate, bismuth bromide, sodium borate, polysodium borate, or a combination thereof.

4. The radiation shielding composition according to claim 1 or 2, wherein, The polar polymer is starch, polyacrylic acid, carrageenan, polyvinyl alcohol, polyvinylpyrrolidone, cellulose nanofibers, carboxymethyl cellulose, hydroxyethyl cellulose, polyacrylamide, agarose, agar, water-dispersible rubber latex, or a combination thereof.

5. The radiation shielding composition according to claim 1 or 2, wherein, The content of the metal compound is 3 to 50% by mass, based on the total amount of the composition.

6. A radiation shielding material comprising the radiation shielding composition as described in claim 1 or 2.

7. The radiation shielding material according to claim 6, wherein, The radiation shielding material is a radiation shielding curtain.

8. A method for manufacturing a transparent radiation shielding composition, wherein, comprising: A polar solvent and a water-soluble metal compound that can dissolve in the polar solvent are mixed to form a first composition containing ions ionized from the water-soluble metal compound in the polar solvent.

9. The manufacturing method according to claim 8, wherein, comprising: The first composition is mixed with a polar polymer that is soluble in the polar solvent, such that the polar polymer dissolves in the polar solvent of the first composition, to form a second composition containing ions ionized from the water-soluble metal compound in the solution of the polar solvent and the polar polymer.

10. The manufacturing method according to claim 9, wherein, include: At least a portion of the polar solvent is removed from the second composition to prepare a third composition containing ions ionized from the water-soluble metal compound in the solution of the polar solvent and the polar polymer or in the polar polymer.

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