Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D123/00—Coating compositions based on homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Coating compositions based on derivatives of such polymers
  • C09D123/02—Coating compositions based on homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Coating compositions based on derivatives of such polymers not modified by chemical after-treatment
  • C09D123/04—Homopolymers or copolymers of ethene
  • C09D123/08—Copolymers of ethene
  • C09D123/0846—Copolymers of ethene with unsaturated hydrocarbons containing other atoms than carbon or hydrogen atoms
  • C09D123/0853—Vinylacetate
  • C09D123/0861—Saponified vinylacetate
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D129/00—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal, or ketal radical; Coating compositions based on hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Coating compositions based on derivatives of such polymers
  • C09D129/02—Homopolymers or copolymers of unsaturated alcohols
  • C09D129/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
  • C09D7/40—Additives
  • C09D7/60—Additives non-macromolecular
  • C09D7/61—Additives non-macromolecular inorganic
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
  • G21F1/00—Shielding characterised by the composition of the materials
  • G21F1/02—Selection of uniform shielding materials
  • G21F1/10—Organic substances; Dispersions in organic carriers
  • G21F1/103—Dispersions in organic carriers
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
  • C08K3/20—Oxides; Hydroxides
  • C08K3/22—Oxides; Hydroxides of metals
  • C08K2003/221—Oxides; Hydroxides of metals of rare earth metal
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/01—Use of inorganic substances as compounding ingredients characterized by their specific function
  • C08K3/013—Fillers, pigments or reinforcing additives

Definitions

• the present invention relates to a radiation shielding composition, a composition, and a paint or coating material.
• Radiation can be broadly divided into electromagnetic radiation and particle radiation.
• the main electromagnetic radiation is gamma rays and X-rays
• neutrons which are electrically neutral, cannot be blocked by matter due to electromagnetic interactions. Therefore, in order to protect the human body and other objects, shielding materials that are specifically tailored to the properties of neutrons will be required.
• Neutrons are produced by nuclear fission in nuclear reactors, and continue to be produced from spent nuclear fuel through spontaneous nuclear fission and ( ⁇ , n) reactions. They are also produced by high-energy particle nuclear reactions in particle accelerators used for medical and research purposes, and photonuclear reactions (nuclear reactions between photons and atomic nuclei) in medical X-ray linacs with energies exceeding 20 million electron volts (20 MeV). In addition to being relevant in a variety of fields such as energy and medicine, neutrons are also used in industry for purposes such as non-destructive testing, and in medicine, such as cancer treatment.
• Neutrons from medical accelerators, nuclear reactors, or spent nuclear fuel are mainly generated in the energy range called fast neutrons, with kinetic energy of about one million electron volts (MeV). Therefore, efficient shielding of fast neutrons is highly effective in reducing external exposure to neutron rays. It is known that deceleration due to elastic scattering with hydrogen atoms, which have almost the same mass as neutrons, is effective in shielding fast neutrons, and materials with a high hydrogen content have been used as fast neutron shielding materials. For example, among resins, polyethylene, especially high-density polyethylene, has a relatively large hydrogen atom ratio and is known to have excellent neutron shielding performance.
• US Pat. No. 5,399,633 describes a neutron absorbing material consisting of ultra-high molecular weight polyethylene in which a boron compound, preferably boron carbide B 4 C, is embedded.
• Patent Document 2 describes a neutron shielding structure comprising an inner layer made of polyethylene containing a substance that absorbs neutrons, an intermediate layer made of polyethylene arranged on the inner layer, and an outer layer made of polyethylene containing a substance that absorbs neutrons arranged on the intermediate layer.
• one of the objectives of the present invention is to provide a radiation shielding composition that has excellent neutron shielding performance.
• a radiation shielding composition using a polyvinyl alcohol-based resin has high neutron shielding performance, leading to the completion of the present invention.
• a first aspect of the present invention is a radiation shielding composition containing a polyvinyl alcohol-based resin.
• a second aspect of the present invention is the radiation shielding composition according to the first aspect, wherein the radiation includes one or more selected from the group consisting of neutrons, protons, and heavy particles.
• a third aspect of the present invention is the radiation-shielding composition according to the first or second aspect, wherein the polyvinyl alcohol-based resin contains a saponified ethylene-vinyl ester-based copolymer.
• a fourth aspect of the present invention is the radiation-shielding composition according to the third aspect, wherein the saponified ethylene-vinyl ester copolymer has an ethylene content of 0.1 to 77 mol %.
• a fifth aspect of the present invention relates to the radiation-shielding composition according to the third aspect, wherein the saponified ethylene-vinyl ester copolymer has an ethylene content of 20 to 60 mol %.
• a sixth aspect of the present invention is the radiation-shielding composition according to any one of the first to fifth aspects, wherein the polyvinyl alcohol-based resin includes a modified polyvinyl alcohol-based resin containing a 1,2-diol structural unit in a side chain.
• a seventh aspect of the present invention is the radiation-shielding composition according to any one of the first to sixth aspects, further comprising an inorganic filler.
• An eighth aspect of the present invention is the radiation-shielding composition according to the seventh aspect, further comprising 30 mass % or more of the inorganic filler.
• a ninth aspect of the present invention is the radiation-shielding composition according to the seventh or eighth aspect, wherein the inorganic filler is at least one selected from the group consisting of Gd 2 O 3 , B 2 O 3 , B 4 C, and LiF.
• a tenth aspect of the present invention is the radiation-shielding composition according to any one of the first to ninth aspects, which is a water-based or solvent-based resin emulsion.
• An eleventh aspect of the present invention is a paint or coating material containing the radiation shielding composition according to any one of the first to tenth aspects.
• a twelfth aspect of the present invention is a molded article comprising the radiation shielding composition according to any one of the first to tenth aspects.
• a thirteenth aspect of the present invention is a medical device having a layer formed using the paint or coating material according to the eleventh aspect.
• a fourteenth aspect of the present invention is an electronic component having a layer formed using the paint or coating material according to the eleventh aspect.
• a fifteenth aspect of the present invention is a component for nuclear power generation having a layer formed using the paint or coating material according to the eleventh aspect.
• a sixteenth aspect of the present invention is an aeronautical or space component having a layer formed using the paint or coating material according to the eleventh aspect.
• a seventeenth aspect of the present invention is a medical device having the molded article according to the twelfth aspect.
• An eighteenth aspect of the present invention is an electronic device having the molded article according to the twelfth aspect.
• a nineteenth aspect of the present invention is a component for nuclear power generation having the molded article according to the twelfth aspect.
• a twentieth aspect of the present invention is an aeronautical or space component having the molded article according to the twelfth aspect.
• a twenty-first aspect of the present invention is a composition containing a polyvinyl alcohol resin and at least one selected from the group consisting of compounds containing at least one of Gd, B, and Li.
• a twenty-second aspect of the present invention is the composition according to the twenty-first aspect, which is used as a radiation shielding composition.
• the present invention provides a radiation shielding composition that has particularly excellent neutron shielding performance.
• the radiation shielding composition according to the embodiment of the present invention contains a polyvinyl alcohol-based resin.
• polyvinyl alcohol-based resins are particularly excellent in neutron shielding performance and are suitable as radiation shielding compositions.
• the inventors have found that polyvinyl alcohol-based resins have better neutron shielding performance than polyethylene, despite having a smaller hydrogen ratio (weight ratio of hydrogen atoms in a molecule) than polyethylene, and have completed the present invention.
• the reason for this is presumably that hydroxyl groups contained in the polyvinyl alcohol-based resin form hydrogen bonds to improve the density of the resin, thereby improving the hydrogen density (intermolecular cohesive force) in the resin.
• the radiation shielding composition according to the embodiment of the present invention has excellent radiation shielding performance.
• the target radiation include neutrons, protons, gamma rays, X-rays, ⁇ rays, ⁇ rays, electrons, protons, heavy particles, and the like.
• the target radiation preferably includes one or more selected from the group consisting of neutrons, protons, and heavy particles.
• neutrons, protons and heavy particles are radiations that are effective for being decelerated by collision with atomic nuclei when shielding. Therefore, the radiation shielding composition according to the embodiment of the present invention is considered to have excellent neutron shielding performance among radiations, and also excellent shielding performance for protons and heavy particles.
• the radiation shielding composition according to the embodiment of the present invention is particularly excellent in the performance of shielding radiation by decelerating it by collision with atomic nuclei. More preferred embodiments of the radiation shielding composition will be further described below.
• the polyvinyl alcohol-based resin (hereinafter, also referred to as PVA-based resin) used in this embodiment has vinyl alcohol structural units corresponding to the degree of saponification and vinyl ester structural units of the unsaponified portion.
• the radiation-shielding composition contains at least a PVA-based resin, and may consist of a PVA-based resin. That is, the proportion of the PVA-based resin in the radiation-shielding composition is preferably, for example, 11% by mass to 100% by mass, although it depends on the content of the inorganic filler described later and the like.
• the proportion of the PVA-based resin is preferably 11% by mass or more, more preferably 20% by mass or more, more preferably 30% by mass or more, more preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, and most preferably 70% by mass or more from the viewpoint of storage stability of the coating material, while the upper limit is preferably 100% by mass or less, more preferably 90% by mass or less, more preferably 80% by mass or less, and most preferably 70% by mass or less from the viewpoint of radiation shielding properties.
• PVA-based resins include unmodified PVA, copolymerized modified PVA obtained by copolymerizing various monomers during the production of vinyl ester-based resins and then saponifying the copolymerized PVA, and various post-modified PVAs in which various functional groups are introduced into unmodified PVA by post-modification. Such modification can be carried out to the extent that the degree of polymerization sufficient for polymer formation of the PVA-based resin is not lost. In some cases, the modified PVA may be further post-modified.
• examples of monomers used in copolymerization with a vinyl ester monomer during the production of a vinyl ester resin include olefins such as propylene, isobutylene, ⁇ -octene, ⁇ -dodecene, and ⁇ -octadecene; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, and itaconic acid, or their salts, or their mono- or dialkyl esters; nitriles such as acrylonitrile and methacrylonitrile; amides such as acrylamide and methacrylamide; olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, and methallyl sulfonic acid, or their salts; alkyl vinyl ethers; N-acrylamidomethyltrimethylammonium chloride
• polyoxyalkylene (meth)allyl ether examples include polyoxyalkylene (meth)acrylates such as polyoxyethylene (meth)acrylate and polyoxypropylene (meth)acrylate; polyoxyalkylene (meth)acrylamides such as polyoxyethylene (meth)acrylamide and polyoxypropylene (meth)acrylamide; polyoxyethylene (1-(meth)acrylamide-1,1-dimethylpropyl) ester; polyoxyalkylene vinyl ethers such as polyoxyethylene vinyl ether and polyoxypropylene vinyl ether; polyoxyalkylene allylamines such as polyoxyethylene allylamine and polyoxypropylene allylamine; polyoxyalkylene vinylamines such as polyoxyethylene vinylamine and polyoxypropylene vinylamine; and hydroxyl group-containing ⁇ -olefins such as 3-buten-1-ol, 4-penten-1-ol, and 5-hexen-1-ol, or derivatives thereof such as acylated products.
• (meth)allyl means allyl or methallyl
• (meth)acrylic means acrylic or methacrylic
• (meth)acrylate means acrylate or methacrylate, respectively.
• monomers usable for copolymerization with vinyl ester monomers include 3,4-dihydroxy-1-butene, 3,4-diacyloxy-1-butene, 3-acyloxy-4-hydroxy-1-butene, 4-acyloxy-3-hydroxy-1-butene, 3,4-diacyloxy-2-methyl-1-butene, 4,5-dihydroxy-1-pentene, 4,5-diacyloxy-1-pentene, 4,5-dihydroxy-3-methyl-1-pentene, 4,5-diacyloxy-3-methyl-1-pentene, 5,6-
• the diol-containing compounds include dihydroxy-1-hexene, 5,6-diacyloxy-1-hexene, glycerin monoallyl ether, 2,3-diacet
• the content of these monomers is preferably 45 mol % or less, more preferably 40 mol % or less, further preferably 35 mol % or less, and particularly preferably 30 mol % or less, of olefins such as propylene.
• Examples of post-modified PVAs in which functional groups have been introduced by post-modification include those that have acetoacetyl groups through reaction with diketene, those that have polyalkylene oxide groups through reaction with ethylene oxide, those that have hydroxyalkyl groups through reaction with epoxy compounds, and those obtained by reacting aldehyde compounds having various functional groups with PVA-based resins.
• a PVA-based resin containing a structural unit having a primary hydroxyl group in the side chain may be used as the modified PVA-based resin.
• a PVA-based resin containing a structural unit having a primary hydroxyl group in the side chain tends to have excellent melt moldability and is therefore preferred.
• Examples of PVA-based resins containing a structural unit having a primary hydroxyl group in the side chain include modified PVA-based resins having a 1,2-diol structural unit in the side chain and modified PVA-based resins having a hydroxyalkyl group structural unit in the side chain, and the like, with modified PVA-based resins having a 1,2-diol structural unit in the side chain being more preferred.
• a modified PVA-based resin containing a 1,2-diol structural unit in the side chain can be produced by a known production method.
• it can be produced by the methods described in Japanese Patent Application Publication No. 2002-284818, Japanese Patent Application Publication No. 2004-285143, and Japanese Patent Application Publication No. 2006-95825.
• the modification rate in the modified PVA-based resin i.e., the content of structural units derived from various monomers in the copolymer or functional groups introduced by post-modification, cannot be generally determined because the characteristics vary greatly depending on the type of functional group, but may be, for example, 0.1 to 20 mol %.
• the PVA-based resin used in this embodiment may be one type or a mixture of two or more types.
• two or more types of PVA-based resins for example, a combination of two or more types of unmodified PVA-based resins differing in saponification degree, viscosity average degree of polymerization, melting point, etc.
• a combination of an unmodified PVA-based resin and a modified PVA-based resin a combination of two or more types of modified PVA-based resins differing in saponification degree, viscosity average degree of polymerization, melting point, type of functional group, modification rate, etc., may be mentioned.
• the PVA resin preferably contains a saponified ethylene-vinyl ester copolymer (hereinafter also referred to as EVOH) from the viewpoint of improving neutron shielding performance.
• EVOH is generally a resin obtained by saponifying a copolymer of ethylene and a vinyl ester monomer (ethylene-vinyl ester copolymer), and corresponds to the copolymer modified PVA mentioned above.
• EVOH is, for example, mainly composed of structural units derived from ethylene and vinyl alcohol structural units, and contains vinyl ester structural units that remain unsaponified.
• the ethylene content in EVOH is preferably 0.1 to 77 mol%, more preferably 20 to 60 mol%, more preferably 23 to 50 mol%, more preferably 25 to 48 mol%, more preferably 25 to 45 mol%, more preferably 25 to 40 mol%, more preferably 25 to 35 mol%, more preferably 25 to 32 mol%, and particularly preferably 29 to 32 mol%. That is, the ethylene content is preferably 0.1 mol% or more, more preferably 20 mol% or more, more preferably 23 mol% or more, more preferably 25 mol% or more, and particularly preferably 29 mol% or more.
• the ethylene content is preferably 77 mol% or less, preferably 60 mol% or less, more preferably 50 mol% or less, more preferably 48 mol% or less, more preferably 45 mol% or less, more preferably 40 mol% or less, even more preferably 35 mol% or less, and particularly preferably 32 mol% or less.
• the ethylene content be equal to or greater than the lower limit, crystallinity is improved and the arrangement of hydroxyl groups can be adjusted to one that facilitates hydrogen bonding, improving radiation shielding properties.
• the ethylene content be equal to or less than the upper limit, the number of hydroxyl groups in the material can be increased, increasing the number of hydrogen bonds between hydroxyl groups and improving radiation shielding properties.
• EVOH may further contain structural units derived from the various monomers mentioned above as monomers used in copolymerization with vinyl ester monomers, in addition to ethylene structural units and vinyl alcohol structural units (including unsaponified vinyl ester structural units). EVOH may also have functional groups introduced therein by the above-mentioned post-modification.
• the saponification degree (measured in accordance with JIS K 6726) of the PVA-based resin used in the present embodiment is preferably, for example, 60 to 100 mol %, including the saponification degree when the PVA-based resin is EVOH.
• the preferred range of the saponification degree varies depending on the type of modification, and for example, in the case of an unmodified PVA-based resin, it is generally 70 mol% or more, and the upper limit is, for example, 99.9 mol% or less. That is, the saponification degree of the unmodified PVA-based resin may be 70 mol% to 99.9 mol%.
• the saponification degree of EVOH is generally from 90 to 100 mol %, preferably from 95.0 to 100 mol %, and particularly preferably from 99 to 100 mol %.
• the saponification degree of the PVA-based resin is equal to or higher than the lower limit, the PVA-based resin can be easily mixed uniformly with an inorganic filler described later.
• the saponification degree is relatively high, the neutron shielding performance can be further improved.
• the saponification degree may be 100 mol%, but may be equal to or lower than the upper limit from the viewpoint of ease of industrial production.
• the melt flow rate (MFR) (210°C, load 2160 g) of PVA-based resin (including EVOH) is usually 0.5 to 100 g/10 min, preferably 1 to 50 g/10 min, and particularly preferably 3 to 35 g/10 min. That is, the MFR of the PVA-based resin may be 0.5 g/10 min or more, preferably 1 g/10 min or more, and particularly preferably 3 g/10 min or more. The MFR of the PVA-based resin may be 100 g/10 min or less, preferably 50 g/10 min or less, and particularly preferably 35 g/10 min or less.
• MFR melt flow rate
• the viscosity average degree of polymerization (measured according to JIS K 6726) of the PVA-based resin used in this embodiment is generally 250 to 3000, preferably 400 to 1700, particularly preferably 450 to 1100, and even more preferably 450 to 800. That is, the viscosity average degree of polymerization of the PVA-based resin may be, for example, 250 or more, preferably 400 or more, and particularly preferably 450 or more.
• the viscosity average degree of polymerization of the PVA-based resin may be 3000 or less, preferably 1700 or less, particularly preferably 1100 or less, and even more preferably 800 or less.
• the viscosity average degree of polymerization be equal to or greater than the above lower limit, the strength of the film, coating film, and other molded products can be ensured.
• a general-purpose molding method can be used, and the product can be used in a variety of applications.
• the PVA resin used in this embodiment can be produced by polymerizing a vinyl ester monomer such as vinyl acetate and then saponifying it.
• a monomer composition containing a vinyl ester monomer and a monomer used in copolymerization is polymerized and then saponified.
• vinyl ester monomer examples include vinyl propionate, vinyl butyrate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, vinyl piperate, vinyl octylate, vinyl monochloroacetate, vinyl adipate, vinyl methacrylate, vinyl crotonate, vinyl sorbate, vinyl benzoate, vinyl cinnamate, and vinyl trifluoroacetate. From the standpoint of cost and availability, vinyl acetate is preferably used as the vinyl ester monomer.
• the polymerization of vinyl ester monomers can be carried out by any known polymerization method, such as solution polymerization, suspension polymerization, or emulsion polymerization.
• solution polymerization which can efficiently remove reaction heat, is preferably carried out under reflux.
• a solvent for solution polymerization for example, alcohol is used, and preferably a lower alcohol having 1 to 3 carbon atoms is used.
• the saponification of the obtained polymer can also be carried out by using a known saponification method, for example, by dissolving the polymer in an alcohol or water/alcohol solvent and using an alkali catalyst or an acid catalyst.
• an alkali catalyst for example, hydroxides or alcoholates of alkali metals such as potassium hydroxide, sodium hydroxide, sodium methylate, sodium ethylate, potassium methylate, and lithium methylate can be used.
• a transesterification reaction using an alkali catalyst in an absolute alcohol solvent is preferably used in terms of the reaction rate and the ability to reduce impurities such as fatty acid salts.
• the reaction temperature for the saponification reaction is, for example, 20 to 60°C. If the reaction temperature is too low, the reaction rate tends to be slow and the reaction efficiency tends to decrease, while if the reaction temperature is too high, the temperature may exceed the boiling point of the reaction solvent, which tends to reduce safety in terms of production.
• saponification is performed under high pressure using a highly pressure-resistant tower-type continuous saponification tower, it is possible to saponify at a higher temperature, for example, 80 to 150°C, and it is possible to obtain a high degree of saponification in a short time even with a small amount of saponification catalyst.
• the radiation shielding composition preferably further contains an inorganic filler.
• the neutron shielding performance of the radiation shielding composition can be further improved by including a compound containing an element having good neutron absorption performance as a filler.
• the inorganic filler preferably includes a compound containing one or more elements selected from the group consisting of Gd, B, and Li.
• the compound is not particularly limited, but examples thereof include oxides, composite oxides, sulfides, hydroxides, etc. containing each element. All of these elements have a high absorption cross section for neutrons.
• the absorption cross section of Gd and B is larger than those of these elements, and it is more preferable that the inorganic filler includes at least one selected from the group consisting of compounds containing at least one of Gd and B.
• the absorption cross section of Gd is the largest among these elements, and it is most preferable that the inorganic filler includes a compound containing Gd.
• the inorganic filler preferably contains at least one selected from the group consisting of Gd 2 O 3 , B 2 O 3 , B 4 C, and LiF.
• Examples of compounds containing Gd include oxides, composite oxides, sulfides, and hydroxides containing Gd. More specifically, gadolinium oxide Gd 2 O 3 , gadolinium gallium garnet Gd 3 Ga 5 O 12 , gadolinium ferrite GdFeO 3 , Gd 3 Fe 5 O 12 , gadolinium hydroxide Gd(OH) 3 , cerium-activated gadolinium silicate Gd 2 SiO 5 : Ce, europium-activated gadolinium borate GdBO 3 : Eu, europium-activated gadolinium oxide Gd 2 O 3 : Eu, europium-activated gadolinium sulfate Gd 2 O 2 S: Eu, and europium-activated gadolinium aluminate Gd 3 Al 5 O 12.
• gadolinium gallate activated with europium Gd 3 Ga 5 O 12 :Eu, gadolinium vanadate activated with europium GdVO 4 :Eu, and gadolinium gallate activated with cerium or chromium Gd 3 Ga 5 O 12 :Ce, Cr, gadolinium oxide activated with terbium Gd 2 O 3 :Tb, gadolinium sulfate activated with terbium Gd 2 O 2 S:Tb, gadolinium sulfate activated with praseodymium Gd 2 O 2 S:Pr, gadolinium gallate activated with terbium Gd 3 Ga 5 O 12 :Tb, gadolinium aluminate activated with terbium Gd 3 Al 5 O 12 From the viewpoint of excellent stability in the air, an oxide of Gd is preferable, and Gd2O3 is more preferable.
• Examples of compounds containing B include oxides, composite oxides, sulfides, hydroxides, carbides, nitrides, phosphides, etc. containing B. More specifically, examples include boron carbide B4C , boron nitride BN, boron phosphide BP, boron sulfide B2S3 , boron phosphate BPO4 , boron oxide B2O3 , etc., with B4C and B2O3 being preferred from the viewpoint of excellent stability in the atmosphere.
• Examples of compounds containing Li include oxides, composite oxides, sulfides, fluorides, and hydroxides containing Li, and examples of such compounds include lithium oxide (Li 2 O), lithium peroxide (Li 2 O 2 ) , lithium aluminate (LiAlO 2 ) , lithium metaborate (LiBO 2 ) , lithium tetraborate (Li 2 B 4 O 7 ) , lithium germanate (Li 2 GeO 3 ) , lithium molybdate (Li 2 MoO 4 ) , lithium niobate (LiNbO 3 ) , lithium metasilicate (Li2SiO 3 ), lithium tantalate (LiTaO 3 ), lithium titanate (Li2TiO 3 ), lithium vanadate (LiVO 3 ), lithium tungstate (LiWO 4 ) , lithium zirconate (Li 2 ZrO 3 ) , lithium fluoride (LiF), and lithium nitrid
• the radiation shielding composition may contain a compound containing an element having an absorption performance against various radiations other than neutrons, protons, and heavy particles, or a known additive as an inorganic filler according to the desired performance.
• the compound containing an element having an absorption performance against various radiations other than neutrons, protons, and heavy particles include compounds containing one or more elements selected from the group consisting of lead, iron, Bi, Y, Zr, Nb, Mo, Hf, Ta, W, and lanthanoid elements.
• examples of compounds containing these elements include composite oxides, sulfides, hydroxides, etc.
• ZrO2 is particularly preferred from the viewpoint of being able to simultaneously absorb gamma rays generated by nuclear reactions and being easy to handle.
• the proportion of the compound containing one or more elements selected from the group consisting of Gd, B, and Li in the inorganic filler may be 0% by mass depending on the desired performance, but from the viewpoint of improving the shielding performance against neutrons and protons, it is preferably 20% by mass or more, more preferably 30% by mass or more, more preferably 40% by mass or more, more preferably 50% by mass or more, particularly preferably 60% by mass or more, and may be 100% by mass.
• the content of the inorganic filler in the radiation shielding composition is preferably, for example, 10 to 90% by mass. That is, from the viewpoint of improving radiation shielding properties, the content of the inorganic filler is preferably 10% by mass or more, more preferably 20% by mass or more, and particularly preferably 30% by mass or more. From the viewpoint of the strength, shape stability, and moldability of various molded products, the content of the inorganic filler in the radiation shielding composition is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 70% by mass or less, even more preferably 50% by mass or less, and particularly preferably 40% by mass or less.
• the shape of the inorganic filler is not particularly limited, but in general, a powdered form is preferably used.
• the average particle size of the inorganic filler is, for example, preferably 1 to 50 ⁇ m, more preferably 2 to 30 ⁇ m, and even more preferably 2 to 20 ⁇ m. That is, the average particle size of the inorganic filler is preferably 1 ⁇ m or more, and more preferably 2 ⁇ m or more.
• the average particle size of the inorganic filler is preferably 50 ⁇ m or less, more preferably 30 ⁇ m or less, and even more preferably 20 ⁇ m or less.
• the inorganic filler can be uniformly dispersed in the coating film or molded product.
• the average particle size refers to the median diameter (d50) measured by a laser diffraction type particle size distribution measuring device in accordance with JIS 8825: Particle size analysis - laser diffraction and scattering method.
• the radiation shielding composition contains a polyvinyl alcohol-based resin and an inorganic filler
• the radiation shielding composition can be produced by mixing them by a known method such as melt kneading, aqueous or solvent-based dispersion of the resin and the filler, or mixing of an aqueous or solvent-based resin emulsion and an inorganic filler.
• aqueous or solvent-based dispersion of the resin and the filler or mixing of an aqueous or solvent-based resin emulsion and an inorganic filler is preferred, and mixing of an aqueous or solvent-based resin emulsion and an inorganic filler is particularly preferred.
• the polyvinyl alcohol-based resin is contained in the radiation shielding composition in the form of an emulsion.
• the heating temperature in the mixing process can be lowered, making it possible to contain a larger amount of filler, thereby further improving the neutron shielding performance.
• examples of methods for producing the aqueous or solvent-based resin emulsion include the high-pressure homogenizer method and the forced extrusion mechanical emulsification method.
• the forced extrusion mechanical emulsification method is advantageous in terms of continuous productivity for efficient production.
• the radiation shielding composition may further contain additives other than the polyvinyl alcohol resin and inorganic filler, as long as the effects of the present invention are not impaired.
• additives include stabilizers (thickeners), surfactants, colorants, plasticizers, lubricants, etc.
• the radiation-shielding composition according to the embodiment of the present invention has excellent radiation shielding performance, particularly excellent neutron shielding performance, and is therefore suitable for use in protecting articles, including people and robots, that may be exposed to radiation. More specifically, the radiation-shielding composition according to the embodiment of the present invention is suitable for use in nuclear power generation-related applications, such as components for nuclear reactors or the periphery of nuclear reactors, vessels and containers for storing nuclear waste and nuclear fuel debris, aviation and space applications, such as components for aircraft and spacecraft, artificial satellites and Moon and Mars-related infrastructure, medical applications, such as components for medical accelerators and peripheral components for medical devices that utilize radiation, and electronic materials containing semiconductors as components.
• nuclear power generation-related applications such as components for nuclear reactors or the periphery of nuclear reactors, vessels and containers for storing nuclear waste and nuclear fuel debris
• aviation and space applications such as components for aircraft and spacecraft, artificial satellites and Moon and Mars-related infrastructure
• medical applications such as components for medical accelerators and peripheral components for medical devices that utilize radiation
• the neutron transmittance of a molded article made of the radiation-shielding composition according to an embodiment of the present invention is preferably less than 25%, particularly preferably less than 22%, and further preferably less than 20%, when the thickness of the molded article is 1 mm.
• the neutron transmittance of the molded article is preferably less than 18%, particularly preferably less than 17.8%, and further preferably less than 17.6%.
• the neutron transmittance is measured by the method described in the Examples.
• the radiation shielding composition may be used as various articles or components by molding into a desired shape, or a paint or coating material containing the radiation shielding composition may be prepared and applied to various components. That is, the present invention also relates to a paint or coating material containing the radiation shielding composition according to an embodiment of the present invention.
• the paint or coating material containing the radiation shielding composition can be produced in the same manner as known paint or coating materials containing PVA-based resins.
• a layer made of the paint or coating material can be formed on various components, and these are suitable for various applications such as medical devices, electronic components, nuclear power generation components, or aviation or space components.
• the radiation shielding composition contains an inorganic filler
• a radiation shielding composition with properties suitable for a paint or coating material by emulsion mixing, for example, a PVA-based resin, an inorganic filler, and additives added as necessary.
• molded articles made from the radiation shielding composition according to the embodiment of the present invention have excellent radiation shielding performance, particularly neutron shielding performance, and are therefore suitable for use as various articles or components constituting them, such as medical devices, electronic components, nuclear power generation components, or aviation or space components.
• composition containing a polyvinyl alcohol resin and at least one selected from the group consisting of compounds containing at least one of Gd, B, and Li The present invention also relates to a composition containing a polyvinyl alcohol-based resin and at least one selected from the group consisting of compounds containing at least one of Gd, B, and Li.
• a PVA-based resin has excellent neutron shielding performance.
• a compound containing at least one of Gd, B, and Li has excellent neutron absorption performance. Therefore, the composition has excellent neutron shielding performance.
• a composition containing a polyvinyl alcohol-based resin and a compound containing Gd has particularly excellent neutron shielding performance.
• a composition containing a polyvinyl alcohol resin and at least one selected from the group consisting of Gd 2 O 3 , B 2 O 3 , B 4 C, and LiF has excellent neutron absorption performance and is also preferable in terms of stability and toxicity. These compositions are suitable for use in radiation shielding compositions.
• Examples 1 to 5 The resins shown in Table 1 were used as the PVA-based resin.
• Gd 2 O 3 powder manufactured by Nippon Yttrium Co., Ltd., product name: gadolinium oxide 99.9%, average particle size 2.32 ⁇ m
• the inorganic filler was used as the inorganic filler, and the PVA-based resin and the filler were mixed so that the filler content in the composition was the value shown in Table 1 to obtain a composition (radiation shielding composition).
• Example 5 a uniformly dispersed kneaded product having a length of 5 cm, a width of 5 cm, and a thickness of 5 mm was obtained by melt kneading (molding temperature 210° C.) using a twin-screw extruder, and was used for the evaluation.
• Example 4 an emulsion of EVOH3 (solid content concentration 22%) prepared separately and an inorganic filler were uniformly stirred and mixed using a batch mixer, and then left to dry, to obtain a uniformly dispersed kneaded product having a length of 5 cm, a width of 5 cm, and a thickness of 5 mm (inorganic filler content 87% by mass), and was used for the evaluation.
• the emulsion used in Example 4 was produced by forced mechanical emulsification using a twin-screw extruder, and was obtained as an emulsion solution of EVOH3 with a solids concentration of 22% and an average particle size of 2 ⁇ m.
• PVA1 "Nichigo G-Polymer (registered trademark) BVE8049P” manufactured by Mitsubishi Chemical Corporation, a modified PVA-based resin containing 1,2-diol structural units in the side chain, saponification degree 99.2%, hydrogen ratio 9.4% by mass
• EVOH1 "Soarnol (registered trademark) DT2904RB” manufactured by Mitsubishi Chemical Corporation, EVOH having an ethylene content of 29 mol%, a saponification degree of 99.9%, and a hydrogen ratio of 10.2 mass%.
• EVOH2 "Soarnol (registered trademark) AT4403B” manufactured by Mitsubishi Chemical Corporation, EVOH having an ethylene content of 44 mol%, a saponification degree of 99.9%, and a hydrogen ratio of 10.8% by mass.
• EVOH3 "Soarnol (registered trademark) DC3212B” manufactured by Mitsubishi Chemical Corporation, EVOH having an ethylene content of 32 mol%, a saponification degree of 99.9%, and a hydrogen ratio of 10.3 mass%.
• EVOH4 Tosoh Corporation, "MERSEN H0051K”, ethylene content: 89 mol%, saponification degree: 99 mol%, MFR: 6.5 g/10 min (190° C., load: 2160 g), hydrogen ratio: 13.1 mass%
• Example 1 Except for using high density polyethylene (manufactured by Mitsubishi Chemical Corporation, “Novatec HD HJ360", hydrogen ratio 14.3 mass%) instead of PVA1, the same procedure as in Example 1 was repeated to uniformly melt-knead the high density polyethylene and the filler to obtain a molded product having a length of 5 cm, a width of 5 cm, and a thickness of 5 mm, which was used for evaluation.
• high density polyethylene manufactured by Mitsubishi Chemical Corporation, "Novatec HD HJ360”, hydrogen ratio 14.3 mass%
• Example 6 As shown in Table 2, in the same manner as in Example 2, a composition (radiation shielding composition) prepared by mixing EVOH1 and an inorganic filler was melt-kneaded (molding temperature: 210° C.) in a twin-screw extruder to obtain a uniformly dispersed kneaded product having a size of 5 cm in length ⁇ 5 cm in width ⁇ 1 mm in thickness, and the product was used for evaluation.
• a composition radiation shielding composition prepared by mixing EVOH1 and an inorganic filler was melt-kneaded (molding temperature: 210° C.) in a twin-screw extruder to obtain a uniformly dispersed kneaded product having a size of 5 cm in length ⁇ 5 cm in width ⁇ 1 mm in thickness, and the product was used for evaluation.
• Example 7 70% by mass of the emulsion solution of EVOH (EVOH3) with a solid content of 22% and an average particle size of 2 ⁇ m used in Example 4 and 30% by mass of inorganic filler (Gd 2 O 3 powder, manufactured by Nippon Yttrium Co., Ltd., product name: gadolinium oxide 99.9%, average particle size 2.32 ⁇ m) were uniformly mixed and stirred in a batch mixer and left to dry to obtain a uniformly dispersed kneaded product (inorganic filler content 66% by mass) with dimensions of 5 cm long x 5 cm wide x 1 mm thick, which was used for evaluation.
• inorganic filler Gadolinium oxide 99.9%
• Example 8 As shown in Table 2, EVOH4 and an inorganic filler were homogeneously melt-kneaded in the same manner as in Example 6, except that EVOH4 was used instead of EVOH1, to obtain a molded product having a length of 5 cm, a width of 5 cm, and a thickness of 1 mm, which was used for evaluation.
• Example 2 As shown in Table 2, the same procedure as in Example 6 was repeated except that high density polyethylene (manufactured by Mitsubishi Chemical Corporation, "Novatec HD HJ360", hydrogen ratio 14.3 mass%) was used instead of EVOH1.
• the high density polyethylene and the inorganic filler were uniformly melt-kneaded to obtain a molded product having a length of 5 cm, a width of 5 cm, and a thickness of 1 mm, which was used for evaluation.
• a plate-shaped molded product for evaluation was prepared as described above, and the neutron transmittance was evaluated.
• Gold foil was set on the front and back (both main surfaces) of the molded sample for evaluation, and neutrons were irradiated from the front side of the sample toward the sample in a direction parallel to the plate thickness direction. It is arbitrary which main surface of the sample is the surface.
• the accelerator neutron source was generated under the following conditions.
• the gold foils set on the front and back of the sample were arranged so that they did not overlap each other when viewed parallel to the plate thickness direction of the sample (i.e., the neutron irradiation direction). When irradiated with neutrons, the gold foil becomes activated.
• the neutron transmittance was evaluated from the ratio of the radioactivity intensity of the gold foil on the front side of the sample, which is directly irradiated with neutrons, to the radioactivity intensity of the gold foil on the back side, which is irradiated with neutrons that have passed through the sample.
• this ratio transmittance
• compositions of Examples 1 to 3 and 5 containing a PVA-based resin exhibited superior neutron shielding performance to the composition of Comparative Example 1 having the same filler content, and were suitable for radiation shielding compositions.
• the reason for this is believed to be that the amount of hydrogen bonds between hydroxyl groups of polyvinyl alcohol derived from the crystalline portion derived from polyethylene increased.
• the composition of Example 2 containing EVOH1 with an ethylene content of 29 mol% and the composition of Example 3 containing EVOH2 with an ethylene content of 44 mol% were superior in neutron shielding performance to the composition of Example 1 containing PVA1 and the composition of Example 5 containing EVOH4 with an ethylene content of 89 mol%.
• Example 4 The composition of Example 4 was obtained as an emulsion-mixed liquid composition before standing and drying, and had properties suitable for use as a paint or coating material.
• the heating temperature in the mixing process could be lowered, making it possible to incorporate more filler, resulting in better neutron shielding performance.

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