JP2013241544A - Radiation-resistive resin composition, and cable using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin composition excellent in heat resistance and radiation resistance, and having flame retardancy and oil resistance; and to provide a cable using the same.SOLUTION: A radiation-resistive resin composition includes a mixed polymer of a chlorine-based polymer and an ethylene-vinyl acetate copolymer, wherein the content of chlorine is ≥5 mass% and ≤10 mass%; and the content of the vinyl acetate in the mixed polymer is ≥40 mass% and ≤50 mass%.

Description

  The present invention relates to a radiation-resistant resin composition and a cable using the same.

  Since electric wires and cables used in nuclear power plants are exposed to heat and radiation during steady operation of the nuclear power plants, resistance to these is required. In addition, when a possible loss of cooling water accident (hereinafter referred to as LOCA) occurs, the specified cable function must be maintained for a certain period even if it is exposed to heat, radiation, and hot water or superheated steam. Radiation is required.

  In addition, in the unlikely event of a fire, the cable is required to have high flame retardance that simulates a cable fire installed in a vertical tray.

  In cables used for such applications, flame retardant polyolefin is used because the insulator is required to have high insulation and flame resistance. In addition, the sheath formed around the insulator and positioned on the outermost surface is required to have flame resistance, heat resistance, radiation resistance, oil resistance and the like as well as mechanical characteristics. For this reason, chlorinated polymers such as polychloroprene (CR), chlorosulfonated polyethylene (CSM), and chlorinated polyethylene (CM) are generally used as the base polymer for the sheath. Chlorine polymers contain chlorine and have a high molecular weight, so that they have predetermined heat resistance and radiation resistance. Further, chlorine in the structure exhibits a radical trap effect and generates a non-flammable gas, thereby exhibiting a predetermined flame retardance to suppress combustion.

  However, when the chlorine-based polymer is exposed to heat or radiation (especially γ rays), chlorine in the structure is desorbed and a zipper reaction occurs, so that deterioration of the sheath proceeds.

  In this regard, a method for suppressing deterioration of the polymer by adding a stabilizer to the chlorine-based polymer has been proposed (for example, see Patent Document 1). The stabilizer can stabilize the chlorine or the generated hydrogen chloride in the skeleton of the chlorinated polymer to suppress the deterioration of the polymer. For example, a lead-based stabilizer such as tribasic lead sulfate or lead stearate, Hydrotalcite, Ca / Zn stabilizers and the like are mentioned. According to Patent Document 1, by adding a stabilizer to a polymer containing chlorine having a chlorination degree of 30% to 40% (chlorine polymer), such as heat resistance, radiation resistance, and flame retardancy of the chlorine polymer. The characteristics can be improved.

JP 2010-27291 A

  By the way, in recent years, nuclear power plants have been aging (60 years), and along with this, long life is required for cables that are used in reactor containment vessels and cannot be easily replaced. . For this reason, the sheath material used for the cable is required to have higher heat resistance and radiation resistance than before.

  However, in the method of adding a stabilizer to a chlorine-based polymer as in Patent Document 1, it is difficult to stably obtain higher heat resistance and radiation resistance than before.

  On the other hand, as a method of suppressing deterioration of the sheath, there is a method of using a polyolefin resin that does not contain halogen (chlorine or the like) that promotes deterioration, but flame retardancy is inferior because it does not contain halogen. Moreover, many polyolefin resins have a small polarity, and the oil resistance against nonpolar mineral oil necessary as a sheath material is lowered.

  The present invention has been made in view of such problems, and the purpose thereof is a radiation-resistant resin composition having excellent heat resistance and radiation resistance, and having flame resistance and oil resistance, and the use thereof. To provide a cable.

  A first aspect of the present invention includes a mixed polymer of a chlorine-based polymer and an ethylene vinyl acetate copolymer, and a content of a chlorine component in the mixed polymer is 5% by mass or more and 10% by mass or less, and the mixing A radiation-resistant resin composition having a vinyl acetate component content of 40 to 50% by mass in a polymer.

  According to a second aspect of the present invention, in the radiation-resistant resin composition according to the first aspect, the chlorinated polymer is any one of chlorinated polyethylene, chlorosulfonated polyethylene, and polychloroprene, or a mixture of two or more. It is a radiation resistant resin composition of a polymer.

  According to a third aspect of the present invention, in the radiation-resistant resin composition of the first aspect or the second aspect, the ethylene vinyl acetate copolymer has an ethylene acetate content of 60% by mass or more. A radiation resistant resin composition comprising a mixed polymer of a vinyl copolymer and an ethylene vinyl acetate copolymer having a vinyl acetate component content of 45% by mass or less.

  According to a fourth aspect of the present invention, in the radiation resistant resin composition according to any one of the first to third aspects, a radiation resistance containing an anti-aging agent, a stabilizer, a halogen flame retardant, and a flame retardant aid. It is a resin composition.

  According to a fifth aspect of the present invention, there is provided a cable having an electric wire and a sheath that covers a core formed by twisting the electric wire or a plurality of the electric wires, wherein the sheath has any one of the first to fourth aspects. A cable made of a radiation resin composition.

  ADVANTAGE OF THE INVENTION According to this invention, the resin composition and cable which are excellent in heat resistance and radiation resistance, and have a flame retardance and oil resistance can be obtained.

It is sectional drawing of the cable concerning one Embodiment of this invention. It is a figure which shows the LOCA simulation test conditions of a cable.

The heat resistance and radiation resistance of the resin composition constituting the sheath are evaluated by degrading the sheath by a sequential degradation method, a reverse sequential degradation method, a simultaneous degradation method, or the like. The sequential degradation method is a method of irradiating radiation after the thermal degradation of the resin composition. The reverse sequential deterioration method is a method in which the procedure of the sequential deterioration method is reversed, and is a method in which heat deterioration is performed after radiation irradiation. The simultaneous degradation method is a method for simultaneously applying heat and radiation.
These three methods differ in the degree of progress of deterioration, and the degree of progress of deterioration increases in the order of reverse sequential deterioration method, simultaneous deterioration method, and sequential deterioration method. The sheath to be evaluated requires higher heat resistance and radiation resistance as the degradation rate of the method increases.

  In this regard, it has been confirmed that conventional resin compositions have predetermined heat resistance and radiation resistance with respect to the sequential degradation method. However, it has been difficult to obtain stable heat resistance and radiation resistance for the reverse sequential deterioration method having a larger deterioration progress rate. As a reason for this, it is considered that the conventional resin composition has a large content of chlorine component, and deterioration (desorption of chlorine) cannot be sufficiently suppressed only by adding a stabilizer. Therefore, the present inventors have studied a method for reducing the content of the chlorine component in the resin composition and suppressing a decrease in heat resistance and radiation resistance. As a result, we found a method to improve the characteristics by reducing the content of chlorine component in the resin composition by mixing a chlorine-free polymer with a conventionally used chlorine polymer to make a mixed polymer. It was. By using ethylene vinyl acetate copolymer with heat resistance and radiation resistance as a polymer that does not contain chlorine, the resin composition's heat resistance, radiation resistance, flame resistance, oil resistance and other properties are well balanced. The inventors have found that it has been improved and have created the present invention.

  Below, the radiation resistant resin composition which concerns on one Embodiment of this invention is demonstrated.

<Radiation resistant resin composition>
The radiation resistant resin composition of the present embodiment contains a mixed polymer of a chlorine-based polymer and an ethylene vinyl acetate copolymer as a base polymer. In the mixed polymer, the content of the chlorine component derived from the chlorine-based polymer is 5% by mass to 10% by mass, and the content of the vinyl acetate component is 40% by mass to 50% by mass.

(Chlorine polymer)
The chlorine-based polymer contains chlorine and is a polymer that imparts predetermined flame retardancy to the radiation-resistant resin composition. The chlorinated polymer is mixed with an ethylene vinyl acetate copolymer to form a mixed polymer. The chlorine polymer is not particularly limited as long as the content of the chlorine component in the mixed polymer can be adjusted to 5% by mass or more and 10% by mass or less. For example, chlorinated polyethylene, chlorosulfonated polyethylene, polychloroprene, etc. Can be suitably used. Moreover, as content of the chlorine component of the chlorine-type polymer to be used, 25 to 40 mass% is preferable, for example. In the case of less than 25% by mass, particularly in chlorinated polyethylene, chlorosulfonated polyethylene, polychloroprene and the like, the flame retardancy is remarkably reduced. On the other hand, when it exceeds 40 mass%, especially in chlorinated polyethylene, the deterioration of mechanical properties is remarkable.

  Chlorinated polyethylene is a polymer obtained by making powdered linear polyethylene (from high density to low density) into an aqueous suspension and blowing chlorine gas into the system at a temperature near the crystal melting point of the raw polyethylene. Chlorinated polyethylene is a thermoplastic elastomer having a wide range of properties from amorphous rubbery to semicrystalline and crystalline plastics because it is obtained by heterogeneous reaction. Chlorinated polyethylene is commercially available with a degree of chlorination (content of the chlorine component of the polymer) of about 25 to 45%, but those with low chlorination or high chlorination are not rubbery, Suitable is 30 to 40% of rubber elasticity.

  Chlorosulfonated polyethylene is a polymer produced by dissolving raw polyethylene in a solvent and chlorinating and chlorosulfonated it. As can be judged from the structure, unlike polychloroprene, there is no double bond in the main chain, so that it is excellent in ozone resistance and electric characteristics. This material has the characteristics that it can be crosslinked by various methods due to its structure, such as (1) peroxide, (2) acceptor / sulfur-containing accelerator, (3) maleimide / crosslinking aid + acid acceptor, etc. Cross-linked by Chlorosulfonated polyethylene has a grade of each brand up to a chlorine content of about 29 to 43%, and any of them can be used.

The polychloroprene is of a dry type (solid), and is roughly classified into a sulfur-modified type and a non-sulfur-modified type depending on the molecular weight, uniformity, and stability regulator during polymerization.
In addition, when polychloroprene is left at a low temperature, it loses its characteristic elasticity and increases its rigidity. This is because the polymer segments are regularly arranged in a certain direction to form a crystal structure, and the phenomenon of forming such a structure is called crystallization. Each brand is classified according to easiness of crystallization, and it is as follows when arranged according to type from those which are difficult to crystallize.
GRT, WD, WRT, WXJ, WK <GN, GS, GNA, WB, WX <W, WM-1, WHV <HC, AD, AG, CG
In this embodiment, any grade of polychloroprene rubber can be used because any of the above grades can be used because the effect is not greatly changed.

  Other chlorinated polymers include vinyl chloride-ethylene vinyl acetate copolymers that are grafted with ethylene vinyl acetate as the backbone, or those grafted with ethylene vinyl acetate as the backbone of polyvinyl chloride. Can be used.

  The molecular weight of the chlorine-based polymer is not particularly limited, but the Mooney viscosity (ML (1 + 4) 100 ° C.) as a measure of the molecular weight is preferably 40 or more and 110 or less. If it is less than 40, not only the heat resistance and radiation resistance are not satisfied, but also stickiness occurs and workability deteriorates. On the other hand, when it exceeds 110, the fluidity of the chlorinated polymer is deteriorated and extrusion molding becomes difficult. The Mooney viscosity is measured according to JIS K6300.

(Ethylene vinyl acetate copolymer)
An ethylene vinyl acetate copolymer (hereinafter referred to as EVA) is mixed with the above chlorine polymer to adjust the content (ratio) of the chlorine component in the mixed polymer. EVA is a thermoplastic resin produced by copolymerizing ethylene and vinyl acetate (hereinafter referred to as VA), and has predetermined heat resistance and radiation resistance. EVA has different properties such as flexibility, rubber elasticity, oil resistance, and flame retardancy depending on the content (VA amount) of the VA component. For example, EVA having a VA amount of 40% by mass or more is called EVM or VAE, has no melting point, and exhibits flexibility close to rubber. In addition, it exhibits excellent flame resistance and oil resistance. However, in EVA, the molecular weight tends to decrease as the VA amount increases, and EVA having a VA amount exceeding 50% is difficult to achieve a high molecular weight and has a low molecular weight. For this reason, in EVA in which the amount of VA exceeds 50%, when the main chain is cut by irradiation with heat or radiation, and deterioration progresses, mechanical properties such as elongation tend to decrease. That is, EVA having a VA amount exceeding 50% is inferior in heat resistance and radiation resistance as compared with, for example, EVA having a VA amount of 40%. Moreover, since EVA with a VA amount exceeding 50% has a low molecular weight, the low molecular weight component bleeds on the surface of the resin or molded product, resulting in poor workability.

  The EVA to be used is not particularly limited as long as the VA amount in the mixed polymer can be adjusted to 40% by mass or more and 50% by mass or less. When the VA amount in the mixed polymer is 40% by mass or more and 50% by mass or less, EVA having a VA amount of 60% by mass or more and a low molecular weight EVA and a high molecular weight EVA having a VA amount of 45% by mass or less are combined. It is preferable. By combining EVA having different VA amounts, the proportion of EVA having a VA amount of 60% by mass or more and a low molecular weight can be reduced, so that the heat resistance and radiation resistance of the radiation resistant resin composition are improved, Stickiness (bleed) can be suppressed.

(Mixed polymer)
The radiation-resistant resin composition of the present embodiment contains a mixed polymer composed of the two polymers, and the mixed polymer has a chlorine component content of 5% by mass to 10% by mass, and a vinyl acetate component. Content is 40 mass% or more and 50 mass% or less. The contents of the chlorine component and the vinyl acetate component are calculated as follows.

The content of the chlorine component in the mixed polymer uses the content of the chlorine component of the chlorine polymer measured by wavelength dispersive X-ray fluorescence analysis and the ratio of the chlorine polymer in the mixed polymer. ).
(Content of chlorine component in mixed polymer [% by mass]) =
(Content of chlorine component of chlorine-based polymer [% by mass]) × (ratio of chlorine-based polymer in mixed polymer) Formula (1)

  As shown in Formula (1), a predetermined amount of chlorine component is contained in the mixed polymer by addition of the chlorine-based polymer, and the content of the chlorine component is 5% by mass or more and 10% by mass or less. When the content of the chlorine component in the mixed polymer is less than 5% by mass and the chlorine component in the resin composition is small, the radical trap effect due to the chlorine component and the generation of nonflammable gas are insufficient. The flame retardancy is reduced. And since there are few chlorine components, the polarity in a resin composition is small and the oil resistance of a resin composition will fall. On the other hand, when the content is larger than 10% by mass and the chlorine component in the resin composition is large, the chlorine component that is released when exposed to heat or radiation increases, so that a zipper reaction easily occurs, and the resin composition The heat resistance and radiation resistance of the will be reduced.

The content (VA amount) of the vinyl acetate (VA) component in the mixed polymer is calculated by the following formula (2) using the VA amount in EVA measured by JISK7192 and the ratio of EVA in the mixed polymer. The
(VA amount [% by mass] in mixed polymer) =
(VA amount of EVA [mass%]) × (ratio of EVA in the mixed polymer) Formula (2)

  As shown in the formula (2), the mixed polymer contains a predetermined amount of VA by adding EVA, and the VA amount in the mixed polymer is 40% by mass or more and 50% by mass or less. When the amount of VA in the mixed polymer is less than 40% by mass and the amount of VA in the resin composition is small, the polarity of the resin composition becomes low, so that the oil resistance is lowered. On the other hand, when the amount of VA is larger than 50% by mass and the amount of VA in the resin composition is large, the resin composition becomes difficult to have a high molecular weight and has a low molecular weight, so that the heat resistance and radiation resistance are deteriorated. In addition, it is difficult to suppress bleed to the surface of the resin composition having a low molecular weight component.

  The mixing ratio of the chlorine-based polymer and EVA is not particularly limited, and is adjusted so that the contents of the chlorine component and the vinyl acetate component of the mixed polymer are within the above numerical range.

  The method for crosslinking and vulcanizing the chlorinated polymer and the ethylene vinyl acetate copolymer is not particularly limited, but is preferably peroxide crosslinking excellent in heat resistance and radiation resistance. In order to increase the degree of crosslinking, a crosslinking aid such as a polyfunctional monomer such as triallyl cyanurate (TAC), triallyl isocyanurate (TAIC), or trimethylolpropane trimethacrylate (TMPT) may be used in combination.

  The radiation-resistant resin composition preferably contains various additives such as an anti-aging agent, a stabilizer, a halogen flame retardant, and a flame retardant aid.

(Anti-aging agent)
Anti-aging agents (antioxidants) are generally used for maintaining heat resistance, but also play an important role in radiation resistance. As the anti-aging agent, it is possible to use a primary anti-aging agent such as phenol or amine, or a secondary anti-aging agent such as sulfur or phosphorus, and a combination of the primary anti-aging agent or secondary anti-aging agent. Can be used together. Among these anti-aging agents, amines can be preferably used.

Phenolic antioxidants are classified into three types, monophenol, bisphenol, and polyphenol, depending on the number of hydroxyl groups (—OH) present in the molecule. Monophenol includes 2,6-di-terbutyl-4-methylphenol, 2,6-di-terbutyl-4-ethylphenol, mono (α-methylbenzyl) phenol, and bisphenol includes 2,2 '-Methylenebis (4-methyl-6-ter-butylphenol), 2,2'-methylenebis (4-ethyl-6-ter-butylphenol), 4,4'-butylidenebis (3-methyl-6-ter-butylphenol) 4,4'-thiobis (3-methyl-6-ter-butylphenol), di (α-methylbenzyl) phenol, etc., and polyphenols include 2,5'-di-ter-butylhydroquinone, 2,5 ' -Di-ter-amylhydroquinone, tri (α-methylbenzyl) phenol, p-cresol and dicyclopentadi Emissions, and the like.

  Amine-based antioxidants are broadly classified into quinoline-based and aromatic secondary amines, and the former is 2,2,4-trimethyl-1,2-dihydroquinoline, 6-ethoxy-1,2-dihydro-2, An example is 2,4-trimethylquinoline. The latter include phenyl-1-naphthylamine, alkylated diphenylamine, octylated diphenylamine, 4,4′-bis (α, α-dimethylbenzyl) dienylamine, p- (p-toluenesulfonylamido) diphenylamine, N, N-di- 2-naphthyl-p-phenylenediamine, N, N′-diphenyl-p-phenylenediamine, N-phenyl-N′-isopropyl-p-phenylenediamine, N-phenyl-N ′-(1,3-dimethylbutyl) -P-phenylenediamine, N-phenyl-N '-(3-methacryloyloxy-2-hydroxypropyl) -p-phenylenediamine, and the like.

  Sulfur antioxidants are classified into benzimidazole, dithiocarbamate, and thiurea, and benzimidazole includes 2-mercaptobenzimidazole, 2-mercaptomethylbenzimidazole, zinc salt of 2-mercaptobenzimidazole, etc. The dithiocarbamate system includes nickel diethyldithiocarbamate and nickel dibutyldithiocarbamate, and the thiourea system includes bis (dimethylaminopropyl) -2-thiourea and tributylthiourea.

  Examples of the phosphorus-based antioxidant include tris (norylphenyl) phosphite as a phosphorous acid-based agent.

  The addition amount of the anti-aging agent is not particularly limited, but is preferably 1 part by weight or more and 15 parts by weight or less with respect to 100 parts by weight of the mixed polymer. If the amount is less than 1 part by weight, it is difficult to sufficiently obtain the radiation resistance of the resin composition, and if the amount is more than 15 parts by weight, the effect is saturated and only the cost increases.

(Stabilizer)
The stabilizer can stabilize chlorine or hydrogen chloride and suppress deterioration of the radiation-resistant resin composition. Known stabilizers can be used, and examples thereof include lead stabilizers such as tribasic lead sulfate, tin compounds, epoxy stabilizers, hydrotalcite, and Ca / Zn stabilizers. . In consideration of water resistance at the time of LOCA, a lead-based stabilizer or hydrotalcite is preferable.

(Halogen flame retardant)
The halogen flame retardant imparts flame retardancy to the radiation resistant resin composition. As the halogen-based flame retardant, it is preferable to use decabromodiphenylethane from the viewpoint of environment and flame retardancy, but tetrabromobisphenol A-bis (2,3-dibromopropyl ether), decabromodiphenyl oxide, octabromodiphenyl. Oxide, pentabromodiphenyl oxide, tetrabromobisphenol A, tetrabromobisphenol A-
Bis (allyl ether), tetrabromobisphenol A bis (2-hydroxyether), hexabromocyclodecane, bis (tribromophenoxy) ethane, tetrabromobisphenol A epoxy oligomer, tetrabromobisphenol A carbonate oligomer, ethylenebistetrabromo Phthalimide, poly-dibromophenylene oxide, 2,4,6-tribromophenol, tetrabromobisphenol A mono-bis (acrylate), tetrabromophthalic anhydride, tetrabromophthalate diol, 2,3-dibromopropanol, tribromostyrene, Tetrabromophenylmaleimide, poly (pentabromobenzyl) acrylate, tris (tribromoneopentyl) bosfate, tris (dibromophe L) phosphate, tris (tribromophenyl) phosphate, 1,2,3,4,7,8,9,10,13,13,14,14-dodecachloro-1,4,4a, 5,6,6a, 7,10,10a, 11,12,12a-dodecahydro-1,4,7,10-dimethanodibenzo (a, e) cyclooctene, chlorinated paraffin, perchlorocyclopentadecane, tetrachlorophthalic anhydride, chlorendic acid, dodeca Chlorocyclooctane or the like may be used.

  The addition amount of the halogen-based flame retardant is preferably 10 parts by weight or more and 30 parts by weight or less with respect to 100 parts by weight of the mixed polymer. When the amount is less than 10 parts by weight, it is difficult to obtain a predetermined flame retardancy. When the amount is more than 30 parts by weight, water may be absorbed during LOCA, which may adversely affect electrical characteristics and mechanical characteristics.

(Flame retardant aid)
It is known that the halogen-based flame retardant further exhibits its effect when used in combination with the flame retardant auxiliary antimony trioxide, and the present invention is not an exception, and antimony trioxide may be added. The amount of addition is not particularly limited, but it is preferable to add the antimony at a ratio of 1 atom to 3 halogen atoms.

  Other additives include process oils, lubricants, processing aids, fillers (reinforcing agents including carbon black), colorants, light stabilizers (hindered amine light stabilizers, etc.) A well-known thing, such as a ultraviolet absorber, can be used. In particular, the use of an aromatic mineral oil as a process oil has an effect as a radiation resistance-imparting agent (anti-rad) in addition to the purpose of stabilizing the workability during kneading and extrusion. Conventional methods for kneading, extrusion, and crosslinking can be applied.

(cable)
Next, a cable according to an embodiment of the present invention will be described. The cable of this embodiment has a sheath composed of the radiation-resistant resin composition. As shown in FIG. 1, the cable 1 has a sheath 3 formed on the outer periphery of a core in which a plurality of (two in FIG. 1) electric wires 2 are twisted or bundled. The electric wire 2 includes a conductor 21 and a flame retardant insulator 22 that covers the conductor 21.

The conductor 21 is formed of, for example, a conductive material such as copper or a copper alloy, and has a predetermined conductor cross-sectional area. The conductor diameter of the conductor 21 is not particularly limited, and an optimal numerical value is appropriately selected according to the application.
The conductor 21 is covered with a flame retardant insulator 22 to which a predetermined compounding agent is added. The thickness of the flame retardant insulator 22 is not particularly limited, and an optimum thickness is selected according to the application. The base polymer of the flame retardant insulator 22 is, for example, ethylene-propylene-diene rubber (EPDM), polyethylene, crosslinked polyethylene, ethylene-vinyl acetate copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, A polymer such as natural rubber, ethylene-propylene rubber, butyl rubber, chlorosulfonated polyethylene, or chlorinated polyethylene can be used. The base polymer can also be formed from a mixed polymer composed of two or more types of polymers selected from these polymers.

  Then, the manufacturing method of the cable 1 is demonstrated.

  First, a plurality of electric wires 2 in which a conductor 21 is coated with a flame retardant insulator 22 are prepared. The prepared plurality of wires 2 are twisted together to form a twisted insulated wire (core). Subsequently, the radiation resistant resin composition is extruded and coated around the core using an extruder or the like. The radiation resistant resin composition is adjusted so that the contained chlorine component and vinyl acetate component are in a predetermined amount.

  Thereafter, the radiation resistant resin composition covering the core is subjected to a crosslinking treatment (for example, treatment with high-pressure steam at a predetermined temperature) to make the radiation resistant resin composition a sheath. Thereby, the cable which concerns on this embodiment is obtained. In addition, although FIG. 1 demonstrated the case of the cable provided with two electric wires, it can manufacture similarly about the case where one electric wire is provided. When only one electric wire is provided, the radiation-resistant resin composition is extruded and coated around one electric wire, and the subsequent process goes through the same process as that of the cable according to the present embodiment. Cable is obtained.

(Effect of this embodiment)
According to the present embodiment, the following one or more effects are achieved.

The radiation-resistant resin composition of this embodiment contains a mixed polymer of a chlorine-based polymer and an ethylene vinyl acetate copolymer (EVA), and the content of the chlorine component in the mixed polymer is 5% by mass or more and 10% by mass. Hereinafter, the content of the vinyl acetate component in the mixed polymer is 40% by mass or more and 50% by mass or less.
According to this configuration, the heat resistance and radiation resistance of the radiation resistant resin composition are improved by mixing EVA with chlorine polymer and reducing the content of chlorine component that promotes deterioration of the resin. Can do. Further, since the mixed polymer contains a predetermined amount of chlorine component, the radiation resistant resin composition can obtain a predetermined flame retardancy. Furthermore, since the mixed polymer contains a predetermined amount of vinyl acetate component and a predetermined amount of chlorine component and has polarity, the radiation resistant resin composition can obtain oil resistance.
Therefore, according to the configuration of the present embodiment, it is possible to provide a radiation-resistant resin composition having excellent heat resistance and radiation resistance, and having flame retardancy and oil resistance.

  In this embodiment, the chlorinated polymer is preferably any one of chlorinated polyethylene, chlorosulfonated polyethylene, and polychloroprene, or a mixed polymer of two or more. According to this configuration, various properties such as heat resistance can be further improved, and ozone resistance and electrical properties can be improved.

  In this embodiment, the ethylene vinyl acetate copolymer comprises an ethylene vinyl acetate copolymer having a vinyl acetate component content of 60% by mass or more and an ethylene vinyl acetate component having a vinyl acetate component content of 45% by mass or less. A mixed polymer with a copolymer is preferred. According to this structure, the ratio of a low molecular weight ethylene vinyl acetate copolymer can be reduced, heat resistance and radiation resistance can be further improved, and stickiness (bleeding) can be suppressed.

  Moreover, in this embodiment, it is preferable that a radiation resistant resin composition contains an anti-aging agent, a stabilizer, a halogenated flame retardant, and a flame retardant aid. According to this configuration, various characteristics such as heat resistance can be further improved.

Moreover, it is preferable that a cable has the sheath which consists of a radiation resistant resin composition of this embodiment. According to this structure, it can be set as the cable excellent in heat resistance, radiation resistance, a flame retardance, and oil resistance.

  The radiation resistant resin compositions of the examples according to the present invention were prepared by the following methods and conditions. These examples are examples of the radiation-resistant resin composition according to the present invention, and the present invention is not limited to these examples.

Example 1
12.5 parts by weight of chlorinated polyethylene (Mooney viscosity (ML (1 + 4) 100 ° C.): 100, chlorine component content: 40% by mass, Elaslene 401A, Showa Denko) as a chlorinated polymer and vinyl acetate (VA) ) 60% EVA by weight (Mooney viscosity (ML (1 + 4) 100 ° C.): 27, Revaprene 600, manufactured by LANXESS) and 27.5% EVA (YX-21, manufactured by Tosoh) 27.5 In addition, 100 parts by weight of the mixed polymer including the parts by weight were charged with various additives excluding the crosslinking agent in a 75-liter Banbury mixer and kneaded to obtain a 1st compound. Thereafter, the 1st compound was put into a 50 liter kneader maintained at about 60 ° C., and dicumyl peroxide as a crosslinking agent was added and mixed, whereby the radiation resistant resin composition of Example 1 (2nd compound). Got.
The additives are 6 parts by weight of hydrotalcite (Mugceller 1, Kyowa Chemical Industry) as a stabilizer, 0.5 parts by weight of an epoxy stabilizer (epoxidized soybean oil), and 0.5 parts by weight of stearic acid Ba as a lubricant. , 20 parts by weight of a halogen-based flame retardant (Cytex 8010, manufactured by Albemarle), 10 parts by weight of antimony trioxide, 15 parts by weight of carbon black (thermal carbon) as a filler, 15 parts by weight of calcined clay (SP-33, manufactured by BASF) Parts and 1 part by weight of an amine-based anti-aging agent (ANTAGE DDA, manufactured by Kawaguchi Chemical) were added. The respective addition amounts are shown in Table 1 below.

  Subsequently, a flame-retardant insulating material covering the conductor was prepared. Specifically, with respect to 100 parts by weight of EPDM (EPT3045, manufactured by Mitsui Chemicals), 3.5 parts by weight of di (2-ter-butylperoxyisopropyl) benzene as a peroxide crosslinking agent and 2 parts by weight of trimethylolpropane trimethacrylate. Parts, zinc oxide (3 types) 5 parts by weight, amine-based anti-aging agent (NOCRACK 224, manufactured by Ouchi Shinsei Chemical) 2 parts by weight, sulfur-based anti-aging agent (NOCRACK 400, manufactured by Ouchi Shinsei Chemical) 10 parts by weight, Stearic acid 0.5 parts by weight, aroma-based operating oil (Diana Process Oil AH-16, manufactured by Idemitsu Kosan) 20 parts by weight, calcined clay (SP-33, manufactured by BASF) 40 parts by weight, halogen flame retardant (Cytex 8010) And 30 parts by weight of Albemarle) and 20 parts by weight of antimony trioxide were added and adjusted. Table 2 below shows the amount of the compound constituting the flame-retardant insulating material.

Subsequently, the cable of Example 1 was manufactured using the radiation-resistant resin composition and the flame-retardant insulating material obtained above. First, a flame-retardant insulating material was extruded and coated with a thickness of 0.8 mm on a conductor (conductor cross-sectional area of 2.0 mm ² ), and crosslinked with high-pressure steam at about 190 ° C. to produce an electric wire. Next, after twisting two wires obtained to form a core, the core was extruded and coated with a radiation-resistant resin composition by an extruder and crosslinked with high-pressure steam at about 190 ° C. The cable of Example 1 (outer diameter 10.5 mm) was produced.

  The cable of Example 1 obtained was evaluated for heat resistance, radiation resistance, flame resistance, oil resistance, and bleed (with stickiness). Each evaluation method will be described below. In addition, the evaluation method of the present embodiment described below was performed using the facility operation system of the Japan Atomic Energy Agency.

(Heat resistance and radiation resistance)
The cable was subjected to heat resistance and radiation resistance tests to evaluate the characteristics of the cable.

  The cable obtained in Example 1 was irradiated with 2 MGy of radiation at a dose rate of 5 kGy / h using cobalt 60 as a γ-ray source, and then thermally deteriorated under conditions of 140 ° C. × 9 days. A tensile test was performed on the cable of Example 1 which had been thermally deteriorated according to JISC3005, and the elongation at break after γ-ray and heat deterioration was measured.

  In addition, the cable of Example 1 that was thermally deteriorated was exposed to high-pressure steam under the LOCA simulation test conditions, and the swelling of the sheath material was visually observed, and the mandrel that was 40 times the cable self-diameter was pressed and bent once, Furthermore, the presence or absence of cracks when bending again in the opposite direction was confirmed.

As shown in FIG. 2, the LOCA simulation test conditions are performed by heating to 171 ° C. and 0.427 MPaG in 5 minutes using superheated steam, and maintaining this state for 9 hours. Then, it switches to saturated steam and is exposed to steam at 121 ° C. for 13 days.
In addition, this test condition has a life span of 40 years. The Institute of Electrical Engineers of the Institute of Electrical Engineers of Japan Technical Report (Part H) No. 139 “Recommended Proposal for Environmental Test Method and Fire-Flame Resistance Test Method of Wires and Cables for Nuclear Power Stations” ”By referring to the test conditions for the boiling water nuclear reactor power plant containment cable of”, the radiation dose during normal operation is 1.5 times, the radiation dose for the LOCA test is 500 kGy, and the thermal degradation conditions are in accordance with the Arrhenius plot. 6 of boiling water nuclear power plant extended to 60 years
It looks like it has been in operation for 0 years.

In the evaluation of heat resistance and radiation resistance, an absolute value of elongation at break was 50% or more, and a crack that did not occur in the confirmation of the crack after the LOCA simulation test shown in FIG.
When the heat resistance and radiation resistance of the cable of Example 1 were measured, as shown in Table 3, the elongation at break after γ-rays and thermal deterioration was 60%, and no cracks were observed after the LOCA simulation test. It was confirmed to have sufficient heat resistance and radiation resistance.

(Flame retardance)
The cable was subjected to a vertical tray combustion test based on IEEE std 1202-1991 to evaluate the flame retardancy of the cable.
When the flame retardance of the cable of Example 1 was measured, it was confirmed that the cable had sufficient flame retardancy.

(Oil resistance)
The cable was tested according to JISC3005 to evaluate the oil resistance of the cable. Specifically, IRM902 oil was used, a tensile test was carried out at a heating temperature of 120 ° C. and a heating time of 18 hours, and those having a tensile strength and a residual ratio of elongation at break of 60% or more were considered acceptable.
When the oil resistance of the cable of Example 1 was evaluated, it was confirmed that the residual tensile strength was 83% and the residual elongation at break was 82%, so that the cable had sufficient oil resistance.

(Bleed test)
The stickiness (bleed) was confirmed by tactile sensation. When the bleed test was performed on the cable of Example 1, no bleed was confirmed.

  From the above results, the cable of Example 1 satisfied all the characteristics and passed. The results of the evaluation are shown in Table 3 below.

(Examples 2 to 7)
In Examples 2 to 7, as shown in Table 1, the types and addition amounts of the chlorine-based polymer and EVA in Example 1 were changed, and the content of the chlorine component and the content of the vinyl oxide component were changed as appropriate. Produced a radiation-resistant resin composition and a cable in the same manner as in Example 1. As chlorinated polymers, chlorosulfonated polyethylene (Mooney viscosity (ML (1 + 4) 100 ° C.): 53, chlorine component content 35 mass%, TS-530, manufactured by Tosoh Corporation), polychloroprene (Mooney viscosity (ML (1 + 4)) 100 ° C.): 42 to 51, content of chlorine component 40% by mass, Showrene W, Showa Denko). As the EVA, EVA having a VA amount of 80% (Mooney viscosity (ML (1 + 4) 100 ° C.): 27, Revaprene 800, manufactured by LANXESS) was used.

  The characteristics of the cables of Examples 2 to 7 were measured in the same manner as in Example 1. As shown in Table 3, all of heat resistance, radiation resistance, flame resistance, oil resistance, and bleed (with stickiness) were obtained. The characteristics were acceptable.

(Comparative Examples 1-6)
In Comparative Examples 1 to 6, as shown in Table 4 below, the radiation resistant resin was the same as in Example 1 except that the content of the chlorine component and the content of the vinyl acetate component were outside the scope of the present invention. The composition was adjusted to produce a cable. Moreover, the characteristics of the obtained cable were evaluated in the same manner as in Example 1. The results are shown in Table 5. In Table 4, numerical values that fall outside the scope of the present invention are underlined. In Table 5, items for which characteristics were not obtained are underlined.

  In Comparative Example 1, sufficient flame retardancy was not obtained because the content of the chlorine component contained in the mixed polymer was small. Moreover, the low molecular weight component bleeds to the surface, causing stickiness.

  In Comparative Example 2, since the content of the chlorine component contained in the mixed polymer is large, sufficient flame retardancy was obtained, but heat resistance and radiation resistance were insufficient, and cracks occurred after the LOCA simulation test. It was.

  In Comparative Example 3, sufficient oil resistance was not obtained because the content of the vinyl acetate component contained in the mixed polymer was small.

  In Comparative Example 4, EVA that does not contain chlorine was used alone without using a high molecular weight chlorine polymer, so that sufficient flame retardancy could not be obtained. Moreover, since the VA amount of EVA to be used is high, the polarity in the radiation resistant resin composition is large, and oil resistance can be obtained. However, since the molecular weight of the mixed polymer in the radiation resistant resin composition is low due to the high VA amount, heat resistance and radiation resistance cannot be obtained, and low molecular weight components bleed on the surface and become sticky. Has occurred.

  In Comparative Example 5, as in Comparative Example 4, EVA containing no chlorine was used alone, so that sufficient flame retardancy and oil resistance could not be obtained.

  In Comparative Example 6, since a chlorine-based polymer was used alone, sufficient heat resistance and radiation resistance could not be obtained.

  From the above, in the radiation-resistant resin composition, by using a mixed polymer of a chlorine-based polymer and an ethylene vinyl acetate copolymer, and by setting the chlorine component and the vinyl acetate component in the mixed polymer to a predetermined content, It was found that excellent heat resistance, radiation resistance, flame retardancy and oil resistance can be obtained.

1 Cable 2 Electric wire 21 Conductor 22 Flame retardant insulator 3 Sheath

Claims (5)

  A mixed polymer of a chlorine-based polymer and an ethylene vinyl acetate copolymer is contained, the content of the chlorine component in the mixed polymer is 5% by mass to 10% by mass, and the content of the vinyl acetate component in the mixed polymer Is a radiation-resistant resin composition characterized by being 40 mass% or more and 50 mass% or less.   The radiation-resistant resin composition according to claim 1, wherein the chlorinated polymer is any one of chlorinated polyethylene, chlorosulfonated polyethylene, and polychloroprene, or a mixed polymer of two or more.   The ethylene vinyl acetate copolymer comprises an ethylene vinyl acetate copolymer having a vinyl acetate component content of 60% by mass or more and an ethylene vinyl acetate copolymer having a vinyl acetate component content of 45% by mass or less. The radiation-resistant resin composition according to claim 1 or 2, comprising a mixed polymer.   The radiation resistant resin composition according to any one of claims 1 to 3, further comprising an antiaging agent, a stabilizer, a halogen flame retardant, and a flame retardant aid. In the cable which has an electric wire and the sheath which coat | covers the core formed by twisting together the said electric wire or the said electric wire, the said sheath consists of a radiation-resistant resin composition in any one of Claims 1-4. Characteristic cable.

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