JP2007145976A - Radiation-proof resin composition and radiation-proof electric wire/cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a radiation-proof resin composition having excellent mechanical properties even after severe radiation exposure of about 1MGy, exhibiting a suitable radiation resistance even with a small amount of additive added and has a slight concern for bloom of additive and to provide a radiation-proof electric wire/cable. <P>SOLUTION: The radiation-proof resin composition is obtained by adding 0.1-5 parts by mass of a salicylate-based ultraviolet light absorber and 0.1-5 parts by mass of a hindered amine-based light stabilizer to 100 parts by mass of a polyolefin-based resin. The radiation-proof electric wire/cable are obtained by using the same as an insulator or a sheath material. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a radiation resistant resin composition obtained by adding a salicylate ultraviolet absorber and a hindered amine light stabilizer to a polyolefin resin, and a radiation resistant electric wire / cable using the same as an insulator or sheath material. About.

  Radiation irradiation is applied to insulators / sheaths of electric wires and cables, resin pipes and other resin products laid in places where radiation is present, such as nuclear power plants, radioactive waste storage facilities, and research / medical facilities that handle radioactive materials. As a result, deterioration may occur and the mechanical characteristics may gradually deteriorate, leading to dielectric breakdown.

  Patent Document 1 discloses a resin composition such as an electric wire / cable insulator / sheath used in a place where such radiation irradiation is applied, and includes an antioxidant and a salicylate ultraviolet absorber specific to the polyolefin resin. A radiation-resistant resin composition that protects against irradiated radiation by blending is proposed.

In order to impart light resistance to polyolefin resins, benzotriazole ultraviolet absorbers and hindered amine light stabilizers are widely used. For example, Non-Patent Document 1 discloses specific hindered amine light stabilizers. In the commentary on the above, there is a description that a synergistic effect is exhibited in a combination system of an antioxidant and an ultraviolet absorber.
Japanese Patent Laid-Open No. 3-24137 "Additive dotcom, light stabilizer", [online], 2005, Ciba Specialty Chemicals Co., Ltd., [searched on November 9, 2005], Internet <URL: http://tenkazai.com/ciba /syousai_taikou.html#a7_2>

  However, in the case of the polyolefin resin composition using the blend described in Patent Document 1, mechanical properties after irradiation of about 1 MGy are satisfactory, but mechanical properties after irradiation of about 2 MGy are satisfactory. It wasn't. In addition, when the amount of the additive is increased in order to improve radiation resistance, the additive bloom becomes a problem.

  In addition, a resin composition in which a benzotriazole ultraviolet absorber and a hindered amine light stabilizer are used in combination with a polyolefin resin can be expected to have an effect on light resistance, but a tensile test is performed after radiation resistance irradiation. As a result, the mechanical properties were significantly lower than before irradiation. Further, when the amount of the additive is increased in order to improve the radiation resistance, the additive bloom also becomes a problem.

  Therefore, the present invention has been made in view of the above-mentioned problems of the prior art, and the problem to be solved by the present invention is excellent in mechanical characteristics even after being subjected to severe irradiation of about 1 MGy, and more An object of the present invention is to provide a radiation-resistant resin composition that exhibits a suitable radiation resistance with a small amount of additive blending, and has little risk of additive bloom.

That is, in the radiation resistant resin composition of the present invention, 0.1 to 5 parts by mass of a salicylate ultraviolet absorber and 0.1 to 5 parts by mass of a hindered amine light stabilizer are added to 100 parts by mass of a polyolefin resin. It is characterized by.
The present invention also provides a radiation-resistant electric wire / cable using the radiation-resistant resin composition as an insulator or a sheath material.

  According to the present invention, by using a salicylate-based UV absorber and a hindered amine light stabilizer in combination, a high additive amount to the polyolefin-based resin can be obtained with a small amount of additive without fear of bloom due to the synergistic effect of both. Radiation resistance can be imparted, and mechanical properties are maintained even after harsh irradiation of about 1 MGy. Therefore, the radiation-resistant electric wires / cables and other resin products using the radiation-resistant resin composition of the present invention can be suitably used even in places that receive radiation, such as in nuclear facilities.

  The radiation-resistant resin composition of the present invention is obtained by adding 0.1 to 5 parts by mass of a salicylate ultraviolet absorber and 0.1 to 5 parts by mass of a hindered amine light stabilizer to 100 parts by mass of a polyolefin resin. . The polyolefin resin, salicylate ultraviolet absorber, hindered amine light stabilizer, antioxidant, and other additives used in the radiation-resistant resin composition of the present invention are described in detail below.

<Polyolefin resin>
In the present invention, the polyolefin resin means an ethylene homopolymer, a copolymer of ethylene and vinyl acetate or ethyl acrylate, or a copolymer of an α-olefin other than ethylene and a vinyl monomer.

  Examples of the polyolefin resin used in the present invention include low density polyethylene (LDPE), very low density polyethylene (VLDPE), high pressure method low density polyethylene, gas phase method ultra low density polyethylene, and linear low density polyethylene (LLDPE). ), Vapor phase linear low density polyethylene, medium density polyethylene (MDPE), high density polyethylene (HDPE), ethylene-vinyl acetate copolymer (EVA), ethylene-ethylene acrylate copolymer (EEA), ethylene Propylene rubber (EPDM), ethylene / propylene diene rubber, isobutylene-isoprene rubber, polypropylene (PP), polybutene-1, etc. are used alone or as a mixture.

<Salicylate UV absorber>
Salicylate-based UV absorbers used as additives for polyolefin resins are originally intended to absorb ultraviolet rays and impart light resistance, but salicylate-based UV absorbers used in the present invention are hindered amine light stabilizers and The synergistic action of this imparts radiation resistance to the polyolefin resin.
Examples of the salicylate ultraviolet absorber used in the present invention include the following general formula (1):

(However, R ¹ , R ² , R ³ and R ⁴ are each independently a hydrogen atom or a linear or branched alkyl group having 1 to 10 carbon atoms.)
What is represented by these is used preferably.
R ¹ , R ² , R ³ and R ⁴ are preferably a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms, more preferably a hydrogen atom or 3 to 3 carbon atoms. Up to 5 linear or branched alkyl groups.

  As the salicylate-based ultraviolet absorber represented by the general formula (1), 2 ′, 4′-di-tert-butylphenyl 3,5-di-tert-butyl-4-hydroxybenzoate, 4- tert-butylphenyl salicylate, phenyl salicylate, and the like.

  As the salicylate-based ultraviolet absorber used in the present invention, in addition to these, for example, amyl salicylate, menthyl salicylate, homomenthyl salicylate, octyl salicylate, 4-octyl salicylate, Benzyl salicylate, dipropylene glycol salicylate, ethylene glycol salicylate, p-isopropanol phenyl salicylate, phenyl 2-hydroxy-3- (1-propenyl) benzoate, 2-ethylhexyl salicylate, triethanolamine Salicylate, etc. can also be used.

  In order to obtain excellent radiation resistance, the addition amount of the salicylate UV absorber added to the radiation resistant resin composition of the present invention needs to be 0.1 parts by mass or more with respect to 100 parts by mass of the polyolefin resin. And preferably 0.5 parts by mass or more. In order to prevent the bloom from bleeding, it is necessary to be 5 parts by mass or less with respect to 100 parts by mass of the polyolefin resin.

<Hindered amine light stabilizer>
The hindered amine light stabilizer (HALS) used in the present invention imparts radiation resistance to the polyolefin resin by synergistic action with the salicylate ultraviolet absorber.
The hindered amine light stabilizer (HALS) is roughly classified into low molecular weight type HALS and high molecular weight type HALS, and any of them may be used for the radiation resistant resin composition of the present invention. Absent.

  For example, as low molecular weight type HALS, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1-octyloxy-2,2,6,6 tetramethyl-4-piperidyl) sebacate Bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, 2- (3,5-di-tert-butyl-4-hydroxybenzyl) -2-n-butylmalonic acid bis (1 , 2,2,6,6-pentamethyl-4-piperidyl), tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) 1,2,3,4-butanetetracarboxylate, 1,2 , 2,6,6-pentamethyl-4-piperidyl / tridecyl-1,2,3,4-butanetetracarboxylate, {1,2,2,6,6-pentamethyl-4-piperidyl / , Β, β ′, β′-tetramethyl-3,9- [2,4,8,10-tetraoxaspiro (5,5) undecane] diethyl} -1,2,3,4-butanetetracarboxylate, Etc.

  For example, high molecular weight type HALS includes dimethyl succinate-1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate, N, N′-bis (3 -Aminopropyl) ethylenediamine-2,4-bis [N-butyl-N- (1,2,2,6,6-pentamethyl-4piperidyl) amino] -6-chloro-1,3,5-triazine condensate , Poly [[6-[(1,1,3,3-tetramethylbutyl) amino] -1,3,5-triazine-2,4-diyl] [(2,2,6,6-tetramethyl- 4-piperidinyl) imino]], poly [{6- (1,1,3-trimethylpentyl) amino-1,3,5-triazine-2,4-diyl} {(N-methyl-2,2,6 , 6-Tetramethyl-piperidyl) imino} o Tamethylene {(N-methyl-2,2,6,6-tetramethyl-piperidyl) imino}], poly [(6-morpholino-S-triazine-2,4-di) [1,2,2,6, 6-pentamethyl-4-piperidyl] imino] -hexamethylene [(1,2,2,6,6-pentamethyl-4-piperidyl) imino]], poly [{6- (1,1,3,3-tetra Methylbutyl) amino-1,3,5-triazine-2,4-diyl} {(2,2,6,6-tetramethyl-piperidyl) imino} hexamethylene {(2,2,6,6-tetramethyl) -Piperidyl) imino}], and the like.

  The amount of the hindered amine light stabilizer added to the radiation resistant resin composition of the present invention should be 0.1 parts by mass or more with respect to 100 parts by mass of the polyolefin resin in order to obtain excellent radiation resistance. And preferably 0.5 parts by mass or more. In order to prevent the bloom from bleeding, it is necessary to be 5 parts by mass or less with respect to 100 parts by mass of the polyolefin resin.

<Antioxidant>
The radiation-resistant resin composition of the present invention can contain an antioxidant as an additive. It is preferable to include a phenolic antioxidant, particularly a hindered phenolic antioxidant. Examples of the phenolic antioxidant include pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], thiodiethylenebis (3- (3,5-di-). tert-butyl-4-hydroxyphenyl) propionate), octadecyl-1- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate), 1,3,5-tris (3,5-di-tert) -Butyl-4-hydroxybenzyl) -1,3,5-triazine-2,4,6 (1H, 3H, 5H) trione, isooctyl (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 1,3,5-tris (4-tert-butyl-3-hydroxy-2,6-dimethyl-benzyl) -sym-tria -2,4,6 (1H, 3H, 5H) trione, 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, Tris (2,4-di-tert-butylphenyl) phosphite, and the like.

  The addition amount of the antioxidant added to the radiation-resistant resin composition of the present invention is preferably 0.1 parts by mass or more, and more preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the polyolefin resin.

<Other additives>
In addition to the above, the radiation-resistant resin composition of the present invention can contain various auxiliary materials commonly used in known resin compositions as additives. Such auxiliary materials include stabilizers, fillers, colorants, carbon black, crosslinking agents, lubricants, processability improvers, antistatic agents and the like.

<Radiation resistant wires and cables>
The radiation-resistant resin composition of the present invention can be used as an insulator or a sheath material, and can be used as an electric wire or a cable by covering a conducting wire according to a usual method.

  Examples of the present invention will be described below. The compositions and evaluation results of the radiation resistant resin compositions of the examples are shown in Table 1 together with the compositions and evaluation results of the comparative examples.

[Preparation of radiation-resistant resin composition]
(1) About the various compositions shown in Table 1, it was made to disperse | distribute uniformly with an open roll of 170 degreeC, and the polyolefin-type resin composition was obtained (Examples 1-9 and Comparative Examples 1-7).
(2) A press sheet having a thickness of 2 mm was produced from each polyolefin resin composition obtained in (1) with a compression molding machine at 160 ° C. and 150 kgf / cm ² (pressing for 10 minutes).

[Evaluation methods]
(Radiation irradiation)
About each press sheet produced by said (2), the gamma ray which uses cobalt 60 as a radiation source was irradiated to 1MGy and 2MGy at room temperature and the dose rate of 5 kGy / h.

(Mechanical property evaluation)
Each press sheet before and after the radiation irradiation was evaluated for mechanical properties by the following method. A JIS No. 3 dumbbell was punched from each press sheet, and a tensile test was performed at a tensile speed of 200 mm / min. As a guideline for preventing cracks when wound with a self-diameter, a tensile elongation of 50% or more was accepted (O), and a tensile elongation of less than 50% was rejected (X).

(Broom property evaluation)
Each press sheet produced in (2) above was stored in a thermostatic bath at 50 ° C for 14 days. If the white powder did not ooze out on the surface, it was accepted (○), and oozing was confirmed. Was rejected (x).

[Evaluation results]
(Examples 1-4)
Examples 1-4 are 0.5-5 mass parts salicylate with respect to 100 mass parts polyolefin resin (EVA resin (EV270 by Mitsui DuPont Polychemical Co., Ltd.) containing 28% vinyl acetate component) as a base resin. UV absorber (2 ′, 4′-di-tert-butylphenyl 3,5-di-tert-butyl-4-hydroxybenzoate, SEESORB 712 manufactured by Cypro Kasei Co., Ltd.), 0.5 to 5 parts by mass of a hindered amine light stabilizer (Bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, high molecular weight type HALS, Chimassorb 944FDL manufactured by Ciba Specialty Chemicals), and 0.5 parts by mass of a hindered phenol-based antioxidant (penta Erythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphen Le) propionate], tetraester type high-molecular weight hindered phenol, manufactured by Asahi Denka Kogyo KK AO-60) the radiation-proof resin composition that was added. Each of Examples 1 to 4 exhibited excellent mechanical properties even after performing extremely severe irradiation of about 2MGy. There was also no problem with the bloom property.

  Moreover, the polyolefin resin composition of Example 1 was used as a granulated product. Thereafter, a 9 mmφ lead wire 11 was coated with a crosslinked polyethylene to form a 12 mmφ insulator 12, and the above granulated product was further coated thereon to form a sheath 13 to produce a 15 mmφ radiation resistant cable 1 (FIG. 1). .

(Examples 5 to 9)
In Examples 5 to 8, 0.5 to 5 parts by mass of a hindered amine light stabilizer in Examples 1 to 4 was added to poly [[6-[(1,1,3,3-tetramethylbutyl) amino]- 1,3,5-triazine-2,4-diyl] [(2,2,6,6-tetramethyl-4-piperidinyl) imino]] (low molecular weight type HALS, Tinuvin 770DF manufactured by Ciba Specialty Chemicals) It has been replaced with. Examples 5 to 8 all exhibited excellent mechanical properties and low bloom properties even after performing extremely severe irradiation of about 2 MGy. In Example 9, 0.25 parts by mass of a salicylate UV absorber and 0.25 parts by mass of a hindered amine light stabilizer were added to 100 parts by mass of a polyolefin resin. Excellent mechanical properties were exhibited even after irradiation. There was also no problem with the bloom property.

(Comparative Examples 1-5)
Comparative Example 1 lacks both a salicylate UV absorber and a hindered amine light stabilizer, and Comparative Examples 2 to 5 lack either a salicylate UV absorber or a hindered amine light stabilizer. is there. In Comparative Examples 4 and 5, a benzotriazole ultraviolet absorber (2- (3,5-di-tert-pentyl-2-hydroxyphenyl) -2H-benzotriazole, SEESORB 704 manufactured by Cypro Kasei Co., Ltd.) was used. . Comparative Examples 1 to 3 and 5 were all inferior in radiation resistance (mechanical properties) as compared to the Examples. In Comparative Example 4, the mechanical properties were maintained to some extent after the irradiation of about 1 MGy, but the mechanical properties were significantly deteriorated after the irradiation of about 2 MGy. As can be seen by comparing Comparative Example 4 with Examples 1, 2, and 9, in order to achieve a certain level of radiation resistance using a benzotriazole-based UV absorber and a hindered amine-based light stabilizer, salicylate-based UV It can be seen that a larger amount of additive is required than when both the absorbent and the hindered amine light stabilizer are blended.

(Comparative Examples 6-8)
In Comparative Examples 6 and 7, the addition amount of the ultraviolet absorber and the hindered amine light stabilizer (HALS) is excessive. Although the radiation resistance was the same, all had difficulty in bloom compared to the examples.
Comparative Example 8 uses an antioxidant (Nocrack 300, 4,4′-thiobis (3-methyl-6-tert-butylphenol) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.) and a salicylate ultraviolet absorber. The effect is verified. Although mechanical characteristics were maintained to some extent after irradiation of about 1 MGy, mechanical characteristics deteriorated significantly after irradiation of about 2 MGy. As can be seen by comparing Comparative Example 8 with Examples 1, 2, and 9, a certain amount of radiation resistance was obtained using 4,4′-thiobis (3-methyl-6-tert-butylphenol) and a salicylate ultraviolet absorber. It can be seen that, in order to achieve the properties, a large amount of additive is required as compared with the case where both the salicylate ultraviolet absorber and the hindered amine light stabilizer are blended.

FIG. 1 is a schematic view showing a radiation resistant cable of the present invention.

Explanation of symbols

1: Radiation-resistant cable, 11: Conductor, 12: Insulator, 13: Sheath

That is, the radiation-resistant resin composition of the present invention is 0.5 to 5 parts by mass of a salicylate ultraviolet absorber and 0.5 to 5 parts by mass of a hindered amine-based light stabilizer with respect to 100 parts by mass of a polyolefin resin. An agent is added (however, metal hydrate is not included).
The present invention also provides a radiation-resistant electric wire / cable using the radiation-resistant resin composition as an insulator or a sheath material.

That is, the radiation resistant resin composition of the present invention comprises 1 to 5 parts by mass of a salicylate ultraviolet absorber and 1 to 5 parts by mass with respect to 100 parts by mass of a polyolefin resin (however, the polyolefin resin does not contain polypropylene) . 5 parts by mass of a hindered amine light stabilizer is added (however, metal hydrate is not included).
The present invention also provides a radiation-resistant electric wire / cable using the radiation-resistant resin composition as an insulator or a sheath material.

[Preparation of Radiation Resistant Resin Composition] (1) The various compositions shown in Table 1 were uniformly dispersed with an open roll at 170 ° C. to obtain polyolefin resin compositions (Examples 1 to 6 and Comparative Examples). 1-8 ).
(2) A press sheet having a thickness of 2 mm was produced from each polyolefin resin composition obtained in (1) with a compression molding machine at 160 ° C. and 150 kgf / cm ² (pressing for 10 minutes).

[Evaluation results] (Examples 1 to 3 )
Examples 1 3, with respect to (EVA resin containing 28% vinyl acetate component (Mitsui Du Pont Poly Chemical Co. EV270)) a polyolefin resin 100 parts by weight of the base resin, of 1-5 parts by salicylates UV absorber (2 ′, 4′-di-tert-butylphenyl 3,5-di-tert-butyl-4-hydroxybenzoate, SEESORB 712 manufactured by Cypro Kasei Co., Ltd.), 1 to 5 parts by mass of a hindered amine light stabilizer (Bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, high molecular weight type HALS, Chimassorb 944FDL manufactured by Ciba Specialty Chemicals), and 0.5 parts by mass of a hindered phenol-based antioxidant (penta Erythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphen Nyl) propionate], tetraester type high molecular weight hindered phenol, AO-60) manufactured by Asahi Denka Kogyo Co., Ltd. Each of Examples 1 to 3 exhibited excellent mechanical properties even after performing extremely severe irradiation of about 2MGy. Also, there was no problem with the bloom property.

(Examples 4 to 6 )
In Examples 4 to 6 , in Examples 1 to 3 , 1 to 5 parts by mass of a hindered amine light stabilizer was added to poly [[6-[(1,1,3,3-tetramethylbutyl) amino]- 1,3,5-triazine-2,4-diyl] [(2,2,6,6-tetramethyl-4-piperidinyl) imino]] (low molecular weight type HALS, Tinuvin 770DF manufactured by Ciba Specialty Chemicals) It has been replaced with. Each of Examples 4 to 6 exhibited excellent mechanical properties and low bloom properties even after performing extremely severe irradiation of about 2 MGy .

That is, the radiation-resistant resin composition of the present invention is 1 to 5 parts by mass of a salicylate ultraviolet absorber and 1 to 5 parts by mass of a hindered amine-based light stabilizer with respect to 100 parts by mass of ethylene / vinyl acetate copolymer. And 0.1 to 0.5 parts by mass of a phenolic antioxidant (but not including a metal hydrate).
The present invention also provides a radiation-resistant electric wire / cable using the radiation-resistant resin composition as an insulator or a sheath material.

Claims (5)

  A radiation-resistant resin composition comprising 0.1 to 5 parts by mass of a salicylate ultraviolet absorber and 0.1 to 5 parts by mass of a hindered amine light stabilizer to 100 parts by mass of a polyolefin resin. .   The radiation resistance according to claim 1, wherein 0.5 to 5 parts by mass of a salicylate ultraviolet absorber and 0.5 to 5 parts by mass of a hindered amine light stabilizer are added to 100 parts by mass of the polyolefin-based resin. Resin composition.   The radiation-resistant resin composition according to claim 1 or 2, further comprising 0.1 to 5 parts by mass of a phenolic antioxidant added to 100 parts by mass of the polyolefin-based resin. The salicylate-based ultraviolet absorber is represented by the general formula (1)

(However, R ¹ , R ² , R ³ and R ⁴ are each independently a hydrogen atom or a linear or branched alkyl group having 1 to 10 carbon atoms.)
The radiation-resistant resin composition according to claim 1, which is represented by: A radiation-resistant electric wire / cable using the radiation-resistant resin composition according to claim 1 as an insulator or a sheath material.

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