JP2001281396A - Neutron shielding material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a neutron shielding material secondarily shapeable as occasion demands, and easily moldable in a large size in a relatively short time without requiring any large-scaled injection device or mixing and dispersing device. SOLUTION: This neutron shielding material is obtained by mixing a neutron absorbable fine powder to metathetic polymerizable cycloolefins followed by polymerization in the presence of a metathetic polymerization catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a neutron shielding material having a function of absorbing and shielding neutrons and having predetermined physical properties.

[0002]

2. Description of the Related Art In recent years, with the development of the nuclear industry, the shielding and protection of neutrons generated from nuclear facilities such as nuclear reactors, nuclear fuel reprocessing plants, fast breeder reactors, fusion facilities, etc. has been affected by the amount of neutrons received by the human body. It is regarded as important for the purpose of minimizing air pollution and protecting structural materials and equipment materials of various nuclear facilities from damage by neutron radiation. In addition, it has become indispensable for safety management for people working in the facility. For this reason, the development of neutron shielding materials has become an important issue that must be simultaneously contributed with the development of the nuclear industry.

As a neutron shielding material, an inorganic boron compound has conventionally been a typical component. The use form includes a neutron shielding material containing a boron compound. For example, a product in which boron carbide is dispersed in silicone (Japanese Patent Application Laid-Open No. 53-73000), a product in which boron carbide and a low melting point glaze are mixed in a silicone resin at a specific ratio (Japanese Patent Application Laid-Open No.
176998), a neutron shielding material in which a natural boron mineral is contained in an acrylic resin, an epoxy resin, a silicone resin, and the like (Japanese Patent Application Laid-Open No. 9-176496).

In general, concrete is often used as a neutron beam shielding material. In addition, a material having a high hydrogen density is considered effective for shielding neutrons, and water, paraffin, polyethylene, and the like are also used. For weight reduction, it has been proposed to use a boron compound mixed with a polyolefin-based thermoplastic resin or the like. For example, an epoxy resin blended with polyethylene powder (JP-A-60-194394), ethylene-polyvinyl alcohol Epoxy resin containing copolymer powder (JP-A-3-25398)
A neutron shielding material composed of, for example, has been proposed.

[0005]

It has been clarified that natural boron minerals can be stably coated and mortared with various resin binders as neutron absorbers. On the other hand, it has been clarified that a composition obtained by adding an epoxy resin or a curing agent, and further adding a boron compound and an inorganic filler can be obtained. However, in order to protect structural materials and equipment materials of various nuclear facilities from damage by neutron beams, large-sized molded products are required, which requires molding equipment for large-scale equipment and large-scale injection equipment and Requires a mixing and dispersing device. There has been no neutron shielding material that can be easily formed at a low pressure and has a complicated shape and a large size.

[0006] The present invention does not require a large-scale injection device or mixing and dispersing device, is relatively large in a relatively short time, is capable of performing neutron shielding material and, if necessary, secondary shaping, and is easy to mold. It is to provide a neutron shielding material that can be used.

[0007]

The present invention provides (1) a neutron shielding material obtained by mixing a metathesis-polymerizable cycloolefin with a fine powder having a neutron absorbing ability and polymerizing in the presence of a metathesis polymerization catalyst. It is. (2) The neutron shielding material according to the above (1), wherein the fine powder having a neutron absorbing ability is a boron compound. (3) The neutron shielding material according to the above (1) or (2), wherein the fine powder having a neutron absorbing ability is a natural boron mineral. (4) Cycloolefins 100 capable of metathesis polymerization
The neutron ray shielding material according to any one of the above (1) to (3), wherein 20 to 500 parts by weight of a fine powder (boron compound or natural boron mineral) having a neutron absorbing ability is blended with respect to parts by weight. (5) Cycloolefins 100 capable of metathesis polymerization
The neutron shielding material according to any one of the above (1) to (4), further comprising 0.05 to 5 parts by weight of an antioxidant based on parts by weight. (6) Cycloolefins 100 capable of metathesis polymerization
0.001 to 10
The neutron shielding material according to any one of the above (1) to (5), which is blended by weight. (7) The neutron shielding material according to any one of the above (1) to (6), wherein the metathesis polymerization catalyst is at least one of the metathesis polymerization catalysts represented by the general formulas (a) and (b).

Embedded image (In the formulas (a) and (b), M is ruthenium or osmium; R and R ¹ are each independently hydrogen, having 1 to 2 carbon atoms.
0 alkyl group, alkenyl group having 2 to 20 carbon atoms, alkynyl group having 2 to 20 carbon atoms, aryl group, 1 to 2 carbon atoms
0 carboxylate group, C1-20 alkoxy group, C2-20 alkenyloxy group, aryloxy group, C2-20 alkoxycarbonyl group, C1-20 alkylthio group, carbon number An alkylsulfonyl group having 1 to 20 carbon atoms, an alkylsulfinyl group having 1 to 20 carbon atoms, an alkylseleno group having 1 to 20 carbon atoms, an alkylseleninyl group having 1 to 20 carbon atoms, or an alkylselenonyl group having 1 to 20 carbon atoms Selected, each with 1 carbon
5 to 5 alkyl groups, halogens, alkoxy groups having 1 to 5 carbon atoms or phenyls, wherein the phenyls are halogens, alkyl groups having 1 to 5 carbon atoms, alkoxy groups having 1 to 5 carbon atoms. X and X ^{1 each} represent an anionic ligand; L and L ^{1 each} represent a neutral electron donating group. )

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The neutron absorbing fine powder constituting the neutron shielding material of the present invention is preferably a boron compound. As boron compounds, boric acid, borate,
Examples include various materials such as borax, colemanite, boron oxide, boron nitride, barium borate, zinc borate, borides with various metals such as zirconium and titanium (ZrB ₂ , TiB ₂ ). Minerals containing boric acid and borate
It is a neutron-absorbing fine powder made of natural boron minerals such as dendite, syberite, cotolite, borax, kahnite, colemanite, and pryceite (collemanite, urexite, tincal, carnite).

As the metathesis polymerizable cycloolefin used in the present invention, at least one selected from bicyclic or more norbornenes and C4 or more monocyclic cycloolefins can be used. Above all, norbornene such as substituted or unsubstituted norbornene, dicyclopentadiene and dihydrodicyclopentadiene are preferably used.

The norbornenes include norbornene,
Norbornadiene, methyl norbornene, dimethyl norbornene, ethyl norbornene, ethylidene norbornene, butyl norbornene, 5-acetyl-2-norbornene, dimethyl-5-norbornene-2,3-dicarboxylate, N-hydroxy-5-norbornene-2,
3-dicarboximide, 5-norbornene-2-carbonitrile, 5-norbornene-2-carboxaldehyde, 5-norbornene-2,3-dicarboxylic acid monomethyl ester, 5-norbornene-2,3-dicarboxylic acid dimethyl ester, 5-norbornene-2,3-dicarboxylic acid diethyl ester, 5-norbornene-2,3
Dicarboxylic acid di-n-butyl ester, 5-norbornene-2,3-dicarboxylic acid dicyclohexyl ester, 5-norbornene-2,3-dicarboxylic acid dibenzyl ester, 5-norbornene-2,3-dicarboxylic anhydride, 3,6-epoxy-1,2,3,6-tetrahydrophthalic anhydride, 5-norbornene-2,3-dicarboxylic acid, 5-norbornene-2-methanol, 6-triethoxysilyl-2-norbornene, Bicyclic norbornene such as -norbornen-2-ol, dicyclopentadiene (a dimer of cyclopentadiene), tricyclic norbornene such as dihydrodicyclopentadiene, methyldicyclopentadiene, dimethyldicyclopentadiene, and tetracyclododecene; Methyltetracyclododecene, dimethylcyclote Tetracyclic norbornene such Radodesen, tricyclopentadiene (trimer of cyclopentadiene) (tetramer cyclopentadiene) tetra cyclopentadiene include pentacyclic or more norbornene like.

A compound having two or more norbornene groups, for example, tetracyclododecadiene, symmetric tricyclopentadiene or the like can also be used. Cyclobutenes other than norbornene, cyclopentene, cyclooctene, cyclododecene, 1,5-cyclooctadiene,
1,3,5,7-cyclooctatetraene, 1,5,7
-Cyclododecatriene, 5,6-epoxy-1-cyclooctene, 3,4-epoxy-1-cyclooctene,
5-methoxy-1-cyclooctene, 5-bromo-1-
Cyclooctene, 5-isopropoxy-1-cyclooctene, 5-formyl-1-cyclooctene, 5-methoxy-1-cyclooctene, ethyl-cyclooct-1-
Cycloolefins such as ene-5-carboxylate, (trimethylsilyl) cyclooct-1-ene-5-carboxylate, tetrahydroindene and methyltetrahydroindene can also be used. The above compounds can be used alone or as a mixture of a plurality of compounds.

As the metathesis polymerization catalyst used in the present invention, at least one of the metathesis polymerization catalysts represented by the general formulas (a) and (b) is preferably used.

[0013]

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[0014]

Embedded image (Where M is ruthenium or osmium; R and R ¹
Are each independently hydrogen, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an aryl group, a carboxylate group having 1 to 20 carbon atoms, ~ 20 alkoxy groups, 2 carbon atoms
-20 alkenyloxy group, aryloxy group, C2-20 alkoxycarbonyl group, C1-20
An alkylthio group, an alkylsulfonyl group having 1 to 20 carbon atoms or an alkylsulfinyl group having 1 to 20 carbon atoms,
It is selected from an alkyl seleno group having 1 to 20 carbon atoms, an alkyl seleninyl group having 1 to 20 carbon atoms and an alkyl selenonyl group having 1 to 20 carbon atoms, each of which is an alkyl group having 1 to 5 carbon atoms, a halogen, and a carbon number. X may be substituted with 1 to 5 alkoxy groups or phenyls, and the phenyls may be substituted with halogen, an alkyl group having 1 to 5 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms; X ¹ each independently represents an anionic ligand. An anionic ligand is a group that has a negative charge when decoordinated to the central metal. Such groups include, for example, hydrogen,
Halogen, CF ₃ CO ₂ , CH ₃ CO ₂ , CFH ₂ CO ₂ ,
(CH ₃ ) ₃ CO, (CF ₃ ) ₂ (CH ₃ ) CO, (CF ₃ ) (CH ₃ ) ₂
CO, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a phenyl group, a phenoxy group, a tosyl group, a mesyl group, a trifluoromethanesulfonate group, and the like. , Chlorine).

L and L ¹ each independently represent a neutral electron donating group. A neutral electron donating group is a group that has a neutral charge when decoordinated to a central metal. Examples of such a group include, for example, PR ² R ³ R ⁴ (where R ² is a secondary alkyl group or a cycloalkyl group, R ³ and R ⁴ are each independently an aryl group, a group having 1 to 10 carbon atoms. A phosphine-based electron donating group represented by a primary alkyl group, a secondary alkyl group, or a cycloalkyl group of
Pyridine, p-fluoropyridine, imidazolylidene compounds and the like. Preferred L and L ¹ are both -P
(Cyclohexyl) ₃ , —P (cyclopentyl) ₃ , or —P (isopropyl) ₃ , but L and L ¹ may be different electron donating groups.

These catalysts are different from the conventionally known two-component metathesis catalyst system in which a catalyst component and an activator are combined, without easily losing the catalytic activity due to oxygen or moisture in the air. The metathesis polymerizable compound can be subjected to ring-opening polymerization by a metathesis (metathesis) reaction. Specific examples of the compound (catalyst) include compounds represented by formulas (1) to (8)
The catalysts described in (3) above are particularly preferable.

[0017]

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[0018]

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[0019]

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[0020]

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[0021]

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[0022]

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[0023]

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[0024]

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The metathesis polymerization catalysts can be used alone or in combination of two or more. At this time, the amount of the catalyst is 0.001 to 20 parts by weight, preferably 0.01 to 20 parts by weight, based on 100 parts by weight of the metathesis-polymerizable cycloolefin.
5 parts by weight.

The above metal carbene compound can be obtained by a known synthesis method. For example, Organometallics
Vol. 16, No. 18, p. 3867 (1997) using propargyl chloride. An example of the synthesis of the catalyst is shown below. (Synthesis example) 500 ml Fisher-Porter
The bottle was charged with cyclooctadiene ruthenium dichloride (21 mmol), tricyclohexylphosphine (42 mmol), sodium hydroxide (7.2 g), and 250 ml of sec-butanol from which oxygen had been removed. Heat with. Pressurization is repeated several times until the absorption of hydrogen is completed, and stirring is continued overnight. Cool to room temperature while applying hydrogen pressure,
A pale yellow precipitate is obtained. 30 ml of water was added and the precipitate was filtered, dried in a stream of hydrogen and dried over Ru (H) ₂ (H ₂ ) ₂ (P
cy ₃ ) ₂ is obtained (yield about 80%, cy represents cyclohexyl). Next, this Ru (H) ₂ (H ₂ ) ₂ (Pcy ₃ )
₂ (1.5 mmol) is dissolved in 30 ml of dichloroethane solution and cooled to -30 ° C. Add 3-chloro-3-methyl-1-butyne (1.5 mmol). The solution immediately turns reddish purple and is allowed to react for 15 minutes. The cooling bath was removed and degassed methanol (20 ml) was added to precipitate purple crystals. After washing with methanol and drying, the Ru carbene catalyst (Cl) ₂ (P
_{cy 3) 2 Ru = CH-} CH = C (CH 3) obtaining ₂ (95% yield). (Reference: Organometallics Vol. 16, 18
Issue, p. 3867 (1997))

If the above-mentioned metathesis polymerization catalyst is used,
The rate of the polymerization (metathesis) reaction can be arbitrarily adjusted by appropriately selecting the conditions (the amount of the catalyst used, the reaction temperature, the use of the reaction adjusting (suppressing) agent, etc.).

In the neutron beam shielding material of the present invention, the above-mentioned cycloolefins capable of metathesis polymerization and a metathesis polymerization catalyst are essential components. However, fillers and glass fibers can be mixed as necessary. In addition, a silane coupling agent, an antioxidant, a flame retardant, a release agent, a colorant, a light stabilizer and the like can be added as long as the object of the present invention is not impaired. In addition, additives such as a modifier and a reaction regulator can be added as needed. As a modifier,
Rubber-based elastomer, polystyrene, saturated polyester,
Polyethylene, polyimide, acrylic resin, methacrylic resin, vinyl resin and the like can be used. As the reaction modifier, triphenylphosphine, tricyclohexylphosphine, tricyclopentylphosphine, tributylphosphine, triisopropylphosphine and the like can be used.
0.001 to 10 parts by weight can be added to the parts by weight.

The neutron ray shielding material of the present invention can be filled and mixed with a boron compound and a fine powder having a neutron absorbing ability, which is a natural boron mineral. Usually, 20 to 500 parts by weight can be added to 100 parts by weight of the cycloolefin.

The neutron shielding material of the present invention can be easily cast at low pressure. Further, since the reaction rate can be adjusted by the reaction modifier, a large-sized molded product can be produced.

[0031]

The present invention will be specifically described below with reference to examples. In the examples, “parts” means “parts by weight” unless otherwise specified. In addition, the test pieces of the cured products obtained in each of Examples and Comparative Examples were evaluated by the following methods. (A) Evaluation method of degree of curing of cured product Using TG-DTA (thermal balance analyzer) manufactured by Vacuum Riko, the temperature was raised from room temperature to 500 ° C. at 10 ° C./min under a nitrogen atmosphere, and the heating loss at 250 ° C. Was measured, and the degree of cure of the test sample was calculated by the following formula. Curing degree (%) = 100−weight loss rate (%) (b) Deflection under load Using Toyo Seiki S3-H type (HDT test apparatus), J
The measurement was performed according to IS K7191-1. Test piece size: 12.7 × 3.0 × 127 mm, n =
3. The temperature at which the temperature rise rate was 2 ° C./min and the standard deflection was 0.26 mm was defined as the deflection temperature under load.

Example 1 (DCPD resin solution) 0.125 parts by weight of triphenylphosphine was added to 100 parts by weight of commercially available dicyclopentadiene (hereinafter referred to as DCPD) having a purity of about 99% by weight.
A resin solution was prepared. (Catalyst dispersion) 92 parts by weight of liquid paraffin was added to 8 parts by weight of the Ru carbene catalyst to prepare a catalyst dispersion. (Preparation of test piece) The catalyst dispersion was added to 100 parts by weight of the DCPD resin solution and stirred for 1 minute to completely dissolve the catalyst dispersion. Further, 150 parts by weight of boron oxide was added to the resin solution, and the mixture was stirred for 3 minutes to be completely dispersed. The boron oxide-filled resin solution was poured into a cast aluminum plate having two aluminum plates and a spacer having a thickness of 3 mm and molded. The curing conditions were 40 ° C. × 1 hour in the first step and 14 ° C. in the second step.
The temperature was raised to 0 ° C in 30 minutes, and 140 ° C x 1 in the third step.
Cured for a long time (1000 × 2000 × 3mm)
Was prepared. This cured product has sufficient neutron absorption ability,
Functioned as a neutron beam shielding plate.

(Comparative Example 1) (DCPD resin solution) Preparation was carried out in the same manner as in Example 1. (Catalyst dispersion liquid) Prepared in the same manner as in Example 1. (Preparation of test piece) The catalyst dispersion was added to the DCPD resin solution, and the mixture was stirred for 1 minute to completely dissolve the catalyst dispersion.
This resin liquid is applied to a glass plate (300 mm × 300 mm × 6
mm) It was poured into a cast glass plate having a thickness of 2 sheets and a spacer having a thickness of 3 mm. The curing condition is 40 ° C x 1st step.
1 hour, the temperature is raised to 140 ° C. in 30 minutes in the second step,
In the third step, the composition was cured at 140 ° C. for 1 hour to produce a cured product. Table 1 shows the evaluation results of the respective cured products obtained in Example 1 and Comparative Example 1.

[0034]

[Table 1] Item Curing degree (%) Deflection temperature under load (° C) Example 1 98.7 140.7 Comparative example 1 98.7 140.8 150 parts by weight of boron oxide was added to Comparative example 1 in which boron oxide was not filled. In Example 1, where the boron oxide was added, there was no change in the degree of curing and the deflection temperature under load, and the molding was successfully performed.

[0035]

According to the present invention, a large-sized molded article can be formed from a material excellent in neutron beam shielding.

Claims (7)

[Claims] 1. A neutron ray shielding material obtained by mixing a fine powder having a neutron absorbing ability with a metathesis-polymerizable cycloolefin and polymerizing the mixture in the presence of a metathesis polymerization catalyst. 2. The neutron shielding material according to claim 1, wherein the fine powder capable of absorbing neutrons is a boron compound. 3. The neutron shielding material according to claim 1, wherein the fine powder having a neutron absorbing ability is a natural boron mineral. 4. The neutron shielding according to claim 1, wherein 20 to 500 parts by weight of a fine powder having a neutron absorbing ability is blended with 100 parts by weight of cycloolefins capable of metathesis polymerization. material. 5. An antioxidant is further added at 0.05 to 100 parts by weight of metathesis-polymerizable cycloolefin.
The neutron shielding material according to any one of claims 1 to 4, wherein the neutron shielding material is blended in an amount of 5 to 5 parts by weight. 6. A reaction modifier is further added to 0.00100 parts by weight of a metathesis polymerizable cycloolefin.
The neutron shielding material according to any one of claims 1 to 5, wherein the neutron shielding material is contained in an amount of 1 to 10 parts by weight. 7. The neutron shielding material according to claim 1, wherein the metathesis polymerization catalyst is at least one of the metathesis polymerization catalysts represented by the general formulas (a) and (b). Embedded image Embedded image (In the formulas (a) and (b), M is ruthenium or osmium; R and R ¹ are each independently hydrogen, an alkyl group having 1 to 20 carbon atoms, and 2 carbon atoms.
-20 alkenyl group, 2-20 carbon atoms alkynyl group, aryl group, 1-20 carbon atoms carboxylate group, 1-20 carbon atoms alkoxy group, 2-20 carbon atoms alkenyloxy group, aryloxy group , Having 2 to 2 carbon atoms
0 alkoxycarbonyl group, an alkylthio group having 1 to 20 carbon atoms, an alkylsulfonyl group having 1 to 20 carbon atoms,
An alkylsulfinyl group having 1 to 20 carbon atoms,
20 alkyl seleno groups, alkyl selenyl groups having 1 to 20 carbon atoms or alkyl selenonyl groups having 1 to 20 carbon atoms, each being an alkyl group having 1 to 5 carbon atoms, halogen, X and X ¹ may be substituted with an alkoxy group or a phenyl, and the phenyl may be substituted with a halogen, an alkyl group having 1 to 5 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms; L and L ^{1 each} represent a neutral electron donating group. )