JP2018048241A - Radiation-resistant vinyl chloride resin composition and flexible hose and flexible tube containing radiation-resistant vinyl chloride resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a soft vinyl chloride resin composition which suppresses radiation degradation when an absorbed dose of γ rays is in the order of megagray, and to provide a flexible hose and a flexible tube which suppress degradation by radiation rays using the resin composition.SOLUTION: A radiation-resistant vinyl chloride resin composition contains 100 pts.wt. of a vinyl chloride resin, a plasticizer and 5 pts.wt. or more and 50 pts.wt. or less of carbon black or black powder, and has a Duro A hardness before irradiation with γ rays of 50 HDA or more and 95 HDA or less. The radiation-resistant vinyl chloride resin composition preferably contains 1 pts.wt. or more and 15 pts.wt. or less of a phenyl ether-based oil and fat. The radiation-resistant vinyl chloride resin composition preferably contains 20 pts.wt. or more and 110 pts.wt. or less of a benzoic acid-based plasticizer.SELECTED DRAWING: Figure 1

Description

The present invention relates to a radiation-resistant vinyl chloride resin composition in which deterioration due to irradiation is suppressed. In particular, the present invention relates to a soft radiation resistant vinyl chloride resin composition to which a plasticizer is added. Moreover, this invention relates to the flexible hose which contains such a radiation-resistant vinyl chloride resin composition in a hose wall. The present invention also relates to a flexible tube formed from such a radiation-resistant vinyl chloride resin composition.

Vinyl chloride resin is highly versatile and is used in a variety of applications. In particular, a vinyl chloride resin composition containing a plasticizer is soft and flexible, and can be used for various hoses such as hoses for vacuum cleaners and various industrial hoses.

Various resin compositions may be used in environments exposed to radiation. For example, when a vinyl chloride resin is used in a medical device, it is irradiated with radiation during sterilization work by radiation. Further, when a hose or the like using a vinyl chloride resin is used for piping in a medical radiation facility or the like, it is exposed to radiation. Generally, when a vinyl chloride resin is exposed to radiation, physical properties such as strength and elongation of the resin deteriorate, and the life of the product using the vinyl chloride resin is shortened. Therefore, a vinyl chloride resin composition in which deterioration due to radiation is suppressed. Is required.

Patent Document 1 discloses a radiation-resistant polyvinyl chloride resin composition containing di (ethylhexyl) phthalate. This vinyl chloride resin composition is suitable for uses such as medical instruments with little deterioration in physical properties and discoloration.
Patent Document 2 discloses a vinyl chloride resin composition for medical radiation sterilization that contains an epoxy hexahydrophthalate ester plasticizer. This vinyl chloride resin composition has excellent discoloration resistance against radiation sterilization.

JP 05-051630 A JP-A-2015-030773

In recent years, there has been a growing need to use flexible hoses and flexible tubes in nuclear power plants, nuclear reactors, fuel reprocessing plants, disposal facilities and related facilities. On the other hand, in such facilities, since the air dose of radiation may increase or the accumulated dose may increase, soft resins such as those used for general flexible hoses and flexible tubes are not readily available. It has been thought that it is not suitable for use because it deteriorates due to radiation.

In such nuclear facilities, it is necessary to assume a level of 1 MGy (mega gray) to 5 MGy as the total absorbed dose. However, in the conventional soft vinyl chloride resin, for example, as shown in “JAERI-DATA / CODE 2003-015 Polymer Radiation Resistant Properties and Data Collection Page 49 Data Sheet No PVC-2”, in the air Deterioration of properties as a soft resin is remarkable, for example, the tensile elongation of the resin is much less than 100% just by being irradiated with about 1 MGy of gamma (γ) rays. Therefore, it is difficult to use such a vinyl chloride resin for a flexible hose or a flexible tube used in an environment exposed to such a high level of radiation.

In addition, radiation resistant vinyl chloride resin compositions such as Patent Document 1 and Patent Document 2 are mainly used in the case where the irradiation dose is a very limited amount of irradiation of sterilizing radiation for medical use. It is a technology that only suppresses discoloration and the like. Therefore, even the radiation-resistant vinyl chloride resin compositions of these patent documents have not been considered to bring about the suppression of deterioration in physical properties such as strength and elongation against radiation exposure with an absorbed dose of the order of 1 MGy.

In other words, soft vinyl chloride resin has great versatility such as flexibility and moldability, but in an environment exposed to a high level of absorbed total radiation, on the order of 1 to several mega grays, strength and elongation The deterioration of physical properties is remarkable, and it has not been considered that it can be used for applications such as flexible hoses and flexible tubes in nuclear facilities. Further, little research has been made on means for suppressing deterioration of physical properties of the vinyl chloride resin composition in such a high level of absorbed dose region.

An object of the present invention is to suppress radiation deterioration in the order of mega-gray absorbed dose of gamma rays in a soft vinyl chloride resin composition. Another object of the present invention is to provide a flexible hose or a flexible tube in which deterioration due to radiation is suppressed.

As a result of intensive studies, the inventor has found that the radiation resistance of the soft vinyl chloride resin composition can be improved by adding a predetermined amount of carbon black or graphite powder, and has completed the present invention.

The present invention contains 100 parts by weight of a vinyl chloride resin, a plasticizer, 5 parts by weight or more and 50 parts by weight or less of carbon black or graphite powder, and has a duro A hardness of 50 HDA or more and 95 HDA or less before γ-ray irradiation. A radiation-resistant vinyl chloride resin composition (first invention).

In 1st invention, Preferably, 1 to 15 weight part of phenyl ether type fats and oils are contained (2nd invention). In the first invention or the second invention, preferably, the radiation-resistant vinyl chloride resin composition contains 20 parts by weight or more and 110 parts by weight or less of a benzoic acid plasticizer (third invention).

Moreover, this invention is a flexible hose which contains the radiation-resistant vinyl chloride resin composition in any one of 1st invention thru | or 3rd invention in a hose wall (4th invention). Moreover, this invention is a flexible tube formed with the radiation-resistant vinyl chloride resin composition in any one of 1st invention thru | or 3rd invention (5th invention).

The radiation-resistant vinyl chloride resin composition of the present invention (first invention) suppresses deterioration of the strength and elongation of the resin even when the radiation dose of gamma rays is a high level radiation dose on the order of mega gray. In the second and third inventions, the effect of suppressing deterioration is further enhanced. The flexible hose of the fourth invention and the flexible tube of the fifth invention are a flexible hose or a flexible tube in which the radiation resistance of the hose wall or tube is enhanced.

It is a partial cross section figure which shows the structure of the flexible hose regarding this invention.

Hereinafter, embodiments of the invention will be described with reference to the drawings as necessary. The invention is not limited to the individual embodiments shown below, and can be carried out by changing the form.

The radiation resistant vinyl chloride resin composition of the first embodiment contains 100 parts by weight of a vinyl chloride resin, a plasticizer, and 5 parts by weight or more and 50 parts by weight or less of carbon black or graphite powder.

The vinyl chloride resin is not particularly limited, but the average degree of polymerization is preferably 1000 or more and 5000 or less, and the average degree of polymerization is particularly preferably 2000 or more and 3000 or less. Various functional groups may be introduced into the vinyl chloride resin. Further, the vinyl chloride resin is not limited to a polymer of vinyl chloride monomer alone, and may be a copolymer or graft polymer of vinyl chloride monomer and other monomer components. Further, a vinyl chloride resin in this embodiment can be obtained by blending a copolymer or graft polymer of a vinyl chloride monomer with other monomer components and a polymer of a vinyl chloride monomer alone.
As a graft polymer of vinyl chloride monomer and other monomer components, for example, graft copolymer (Sekisui Chemical Co., Ltd.) obtained by grafting vinyl chloride onto EVA (ethylene / vinyl acetate copolymer) as a trunk. Resin sold as PVC-TG series), and resin obtained by complete graft copolymerization of acrylic resin with vinyl chloride resin (resin sold as Plictomer series from Kaneka Corporation).

A plasticizer is blended so that the radiation-resistant vinyl chloride resin composition becomes a so-called soft vinyl chloride resin. What is necessary is just to adjust the compounding quantity of a plasticizer so that the predetermined hardness mentioned later may be obtained. The blending amount of the plasticizer is typically in the range of 20 to 200 parts by weight, more preferably 30 to 150 parts by weight of the plasticizer with respect to 100 parts by weight of the vinyl chloride resin. Adjusted.

The radiation-resistant vinyl chloride resin composition contains fine carbon powder, that is, carbon black or graphite powder. The compounding amount of carbon black or graphite powder is 5 parts by weight or more and 50 parts by weight or less of carbon black or graphite powder with respect to 100 parts by weight of vinyl chloride resin. The type of carbon black is not particularly limited, and carbon such as furnace black, channel black, acetylene black, and thermal black can be used, and those having good dispersibility in vinyl chloride resin are selected and used. be able to. The type of graphite powder is not particularly limited, and artificial graphite powder, powdered expanded graphite, and the like can be used. Both carbon black and graphite powder may be included.

The radiation-resistant vinyl chloride resin composition has a degree of flexibility suitable for use in, for example, a hose wall of a flexible hose, and the degree of flexibility is determined according to JIS K7215 before irradiating γ rays. The Duro A hardness is 50 HDA or more and 95 HDA or less. If it is hardness of this range, it will be in the category of what is called a soft vinyl chloride resin, and it will be easy to apply to the flexible hose by the existing design.

The radiation-resistant vinyl chloride resin composition is preferably blended with phenyl ether oil. As the phenyl ether-based fat and oil, fats and oils such as diphenyl ether and polyphenyl ether can be used. Among diphenyl ethers, alkyl diphenyl ether oils can be preferably used. Functional groups other than alkyl groups may be introduced into the phenyl ether-based fats and oils. Examples of the alkyl diphenyl ether-based fats and oils include oils and fats of model RA-100 and RA-15 sold as lubricants and greases under the trade name of Hirad from MORESCO Co., Ltd. Moreover, as a polyphenyl ether type fats and oils, the fats and oils of model number RP-42R currently sold with the brand name of Hirad from MORESCO, for example are illustrated. These phenyl ether oils and fats are preferably blended in an amount of 1 to 15 parts by weight per 100 parts by weight of the vinyl chloride resin.

As a plasticizer, it is preferable to mix | blend a benzoic acid type plasticizer so that 20 weight part or more and 110 weight part or less may be contained with respect to 100 weight part of vinyl chloride resins. More preferably, the benzoic acid plasticizer is blended in an amount of 30 to 100 parts by weight. Moreover, it is preferable that a benzoic acid type plasticizer is a benzoic acid ester type plasticizer containing a benzoic acid ester. Examples of the benzoic acid ester contained in the benzoic acid plasticizer include diethylene glycol dibenzoate, dipropylene glycol dibenzoate, and 1-4-cyclohexene dimethanol dibenzoate. Examples of the benzoic acid plasticizer include a plasticizer of model number PB-3A and a plasticizer of model number PB-3 sold under the product name of Monosizer from DIC Corporation, and a plasticizer of model number JP120 of J Plus Co., Ltd. And plasticizers of model number 9-88 sold under the product name BENZOFLEX of Eastman Chemical Company.
As the plasticizer, a known plasticizer such as a phthalate ester plasticizer (DOP or the like) may be used, and the benzoic acid plasticizer may be used in combination with another plasticizer.

In the radiation resistant vinyl chloride resin composition, other components may be blended for various purposes such as enhancing dispersibility of blended components, enhancing handleability, or enhancing specific characteristics. For example, in order to increase the stability of the material, particularly the thermal stability, a known stabilizer or a thermal stabilizer may be blended. Similarly, an antioxidant, a processing aid, a lubricant, a pigment, and the like may be blended.

The radiation resistant vinyl chloride resin composition can be obtained by a known method for producing a vinyl chloride resin composition. That is, the desired vinyl chloride resin composition can be obtained by uniformly dispersing the components with a kneading roll or the like while sequentially adding the components to be blended to the base vinyl chloride resin. Depending on the difficulty of kneading each component, a master batch or the like may be used as necessary.

In FIG. 1, the flexible hose 1 which comprised the hose wall 2 with the radiation-resistant vinyl chloride resin composition of the said 1st Embodiment is shown. In FIG. 1, the upper half is shown in cross section and the lower half is shown in appearance. In the present embodiment, the hose wall 2 is formed in a spiral shape that forms a spiral. The flexible hose 1 is configured by embedding a helical reinforcing body 3 made of hard steel wire in a hose wall 2. This hose has moderate flexibility and can be used for various pipes. The material of the reinforcing body 3 may be another material, and the form in which the reinforcing body 3 is integrated with the hose wall 2 is a form in which the reinforcing body 3 is integrally bonded to the inner periphery and outer periphery of the hose wall in addition to the embedded form. It may be. Such a flexible hose 1 can be manufactured by a known hose manufacturing method.

Moreover, a flexible tube can also be formed with the radiation-resistant vinyl chloride resin composition of the first embodiment. The flexible tube typically has a cylindrical tube wall, and the tube wall is formed of a radiation resistant vinyl chloride resin composition. Such flexible tubes are typically manufactured by extrusion. Such a flexible tube has moderate flexibility and can be used for various pipes.
The radiation-resistant vinyl chloride resin composition can also be applied to other uses in which a soft vinyl chloride resin is used, such as a wire coating. In addition, the radiation-resistant vinyl chloride resin composition is blended with a shielding material such as barium sulfate, tungsten, or lead to obtain a resin composition having radiation shielding performance, which is molded into a soft sheet or soft cover and used. You can also.

The action and effect of the radiation resistant vinyl chloride resin composition of the above embodiment will be described. The radiation-resistant vinyl chloride resin composition contains 100 parts by weight of a vinyl chloride resin, a plasticizer, and 5 parts by weight or more and 50 parts by weight or less of carbon black or graphite powder. Even when exposed to radiation (γ rays), the deterioration of the strength and elongation of the resin is suppressed.

Further, among the radiation resistant vinyl chloride resin compositions of the above-described embodiments, those having higher radiation resistance characteristics can maintain the elongation of about 100% even when the absorbed dose of γ rays reaches 3 MGy, for example. Such characteristics are particularly suitable for use in flexible hoses used in environments exposed to high levels of radiation.

The following mechanisms can be considered for changes in the molecular structure of synthetic resins, particularly soft vinyl chloride resins, during radiation degradation. First, it is conceivable that the plasticizer component is destroyed / decomposed or bleed-out by γ-ray irradiation, so that the flexibility of the soft vinyl chloride resin is lost and the strength and elongation of the resin deteriorate. Secondly, it is conceivable that the polymer of vinyl chloride resin has a cross-linking point with each other due to the irradiation of γ-rays and becomes brittle even when the resin is cured, thereby deteriorating the strength and elongation of the resin. Third, as the cross-linking of the vinyl chloride resin proceeds, the resin cannot hold the plasticizer inside, the plasticizer bleeds out to the outside of the resin, the curing of the resin is promoted, and the strength of the resin And a mechanism of deterioration of elongation.

Details of the mechanism by which deterioration of the strength and elongation of the resin when exposed to radiation is suppressed by containing 5 to 50 parts by weight of carbon black or graphite powder with respect to 100 parts by weight of the vinyl chloride resin. Although it is unknown, carbon black and graphite absorb radiation in the resin composition, thereby contributing to suppressing the decomposition of the plasticizer component due to the irradiation of γ rays, which is the first deterioration mechanism. It is presumed that deterioration of strength and elongation is further suppressed.

Further, if carbon black or graphite powder is contained in an amount of 5 parts by weight or more and 50 parts by weight or less with respect to 100 parts by weight of the vinyl chloride resin, the carbon black or the graphite powder inhibits cross-linking between the polymer chains of the vinyl chloride resin. Working in this way contributes to the suppression of the second and third deterioration mechanisms, and the deterioration of the strength and elongation of the resin is suppressed. From the viewpoint of further enhancing the effect of suppressing the deterioration of the strength and elongation of the resin, the blending amount of carbon black or graphite powder with respect to 100 parts by weight of the vinyl chloride resin is preferably 10 parts by weight or more, and more preferably 20 parts by weight or more. It is particularly preferred.
Moreover, it is more preferable to contain graphite powder from the viewpoint of more effectively inhibiting the crosslinking between the polymers of the vinyl chloride resin and suppressing the deterioration of the strength and elongation of the resin.

Further, in the radiation-resistant vinyl chloride resin composition of the above embodiment, the phenyl ether oil / fat is added to the plasticizer in the vinyl chloride resin composition by further blending 1 to 15 parts by weight of the phenyl ether oil / fat. It also functions as a kind of the resin to increase the flexibility of the resin and to further suppress the deterioration of the strength and elongation of the resin.
Phenyl ether fats and oils have a benzene ring and are relatively difficult to decompose when irradiated with γ rays, contributing to the suppression of the degradation of plasticizer components caused by γ rays, which is the first deterioration mechanism. However, such an effect is presumed to occur.

Moreover, when phenyl ether type | system | group fats and oils are used together with a benzoic acid type plasticizer, phenyl ether type | system | group fats and oils come out from a vinyl chloride resin more easily than a benzoic acid type plasticizer. Therefore, in the vinyl chloride resin composition, phenyl ether oils and fats are more likely to bleed out than benzoic acid plasticizers, and more phenyl ether oils and fats are likely to be present on the surface of the molded article of the resin composition. . As a result, phenyl ether-based oils and fats that are difficult to decompose against γ-ray irradiation receive γ-rays on the surface of the molded body like a protective film, and the cross-linking of the vinyl chloride resin inside the molded body and other plasticizers I guess that it works to delay the decomposition of. That is, the phenyl ether fats and oils contribute to the suppression of the second deterioration mechanism and the third deterioration mechanism.

From the viewpoint of enhancing the resistance to degradation of γ-rays of the phenyl ether fats and oils themselves, the phenyl ether fats and oils are made so that the proportion of the benzene ring portion in the molecule increases in the polymers constituting the phenyl ether fats and oils. It is more preferable to perform selection. Further, from the viewpoint of being relatively easy to be blended in a vinyl chloride resin and having high resistance to γ rays, the phenyl ether oil is more preferably an alkyl diphenyl ether oil or a polyphenyl ether oil.

In addition, in the radiation resistant vinyl chloride resin composition of the above embodiment, by further containing 20 parts by weight or more and 110 parts by weight or less of a benzoic acid plasticizer, deterioration of the strength and elongation of the resin with respect to radiation irradiation is further suppressed. The The details of the mechanism by which the degradation of the strength and elongation of the resin when exposed to radiation is suppressed by the benzoic acid plasticizer are unknown, but the benzoic acid plasticizer having a benzene ring is resistant to γ-ray irradiation. Since the decomposability is high, it contributes to suppressing the decomposition of the plasticizer component due to the irradiation of γ rays, which is the first deterioration mechanism, and it is presumed that the deterioration of the strength and elongation of the resin is further suppressed. From the viewpoint of improving the resistance to decomposition of benzoic acid plasticizers against γ rays, benzoic acid is used so that the proportion of the benzene ring moiety in the molecule increases in the polymer constituting the benzoic acid plasticizer. It is more preferable to select a plasticizer or a benzoate component in the plasticizer.

Then, using the radiation resistant vinyl chloride resin composition of the above embodiment, if the flexible hose is configured so that the radiation resistant vinyl chloride resin composition is included in the hose wall, the absorbed dose is as high as the order of mega gray. A flexible hose capable of maintaining a certain strength and flexibility even in an environment receiving a high level of γ-ray irradiation can be obtained. Such a flexible hose is useful in a nuclear facility or a site of decommissioning work. The form using the radiation resistant vinyl chloride resin composition for the hose wall may be a form in which the entire hose wall is composed of the radiation resistant vinyl chloride resin composition, or a metal foil or other film-like material or film. The form which uses a radiation-resistant vinyl chloride resin composition as a material which comprises the one part layer of the hose wall of a laminated structure with a raw material may be sufficient.

Similarly, the flexible tube formed of the radiation-resistant vinyl chloride resin composition of the above embodiment has a certain strength and flexibility even in an environment where high dose γ-ray irradiation with an absorbed dose of the order of mega gray is received. Can be maintained. A reinforcing body may be integrated with such a flexible tube, or a layer made of another material may be provided.

The radiation resistance characteristics against γ-ray irradiation of the radiation resistant vinyl chloride resin composition are illustrated by the following examples.
Tables 1 to 3 show formulation examples of each example and reference examples and changes in physical properties before and after γ-ray irradiation.
The vinyl chloride resin compositions blended in the examples and reference examples were prepared by kneading with rolls so that the blended components were uniformly dispersed. The unit of blending in the table is part by weight. Hereinafter, the compounding materials in the table will be described.

(Vinyl chloride resin)
The types of vinyl chloride resin (PVC) are as follows.
PVC (2500) is a polyvinyl chloride resin having an average degree of polymerization of 2500, and the numerical value in () represents the average degree of polymerization.
Plectomer GX is a kind of graft polymer of a vinyl chloride monomer and other monomer components, and is a resin obtained by completely graft copolymerizing an acrylic resin with a vinyl chloride resin. This resin is sold by Kaneka Corporation as the Plictomer series.

(Plasticizer)
The types of plasticizers are as follows.
DOP is dioctyl phthalate.
PB-3A is a benzoic acid plasticizer and is sold by DIC Corporation under the product name of Monosizer.

(Phenyl ether oil)
The types of phenyl ether fats and oils are as follows.
High Rad RA-15 and RA-100 are alkyl diphenyl ether oils and fats, and are sold as lubricants and greases by MORESCO.

(Carbon powder)
The types of carbon black or graphite powder are as follows.
CB (acetylene) is acetylene black. It is a relatively large diameter carbon black sold as Denka Black HS-100 from Denka Corporation.
CB # 960 is a pyrolytic carbon black, and is a relatively small diameter carbon black sold by Mitsubishi Chemical Corporation under the model number # 960.
Graphite WF-7 is expanded graphite sold by Fuji Graphite Industry Co., Ltd.

(Other ingredients)
ESO (epoxidized soybean oil) is blended as a heat stabilizer.
A barium / zinc stabilizer is blended as a stabilizer.
A polyester processing aid is blended as a processing aid.
Stearic acid is blended as a lubricant.

A No. 5 dumbbell for a tensile test was prepared from the vinyl chloride resin composition of each reference example, and the hardness and tensile test of the resin were performed before and after γ-ray irradiation to measure the mechanical properties. The resin hardness was measured with a durometer in accordance with JIS K7215.

(Tensile test)
In accordance with JIS K7161, elongation deformation was given to a predetermined dumbbell at a tensile speed of 200 mm / min, and the maximum tensile stress, the tensile 100% modulus (tensile 100M), and the tensile elongation were measured.

(Gamma irradiation)
The sample (dumbbell) whose physical properties were to be measured after being exposed to γ rays was irradiated with γ rays. In the irradiation of γ rays, cobalt 60 was used as an irradiation source, and γ rays were irradiated at room temperature in the atmosphere so that the dose rate was 8.35 kGy / h.
The samples listed in Table 1 and Table 2 were irradiated with γ-rays for about 360 hours so that the absorbed dose was 3 MGy. For the samples listed in Table 3, the absorbed dose was 2 MGy. Thus, γ-ray irradiation was performed for about 240 hours.

The following summarizes the test results.
Both the examples and the reference examples have hardness, strength, and elongation preferable as the soft vinyl chloride resin composition before γ-ray irradiation.

According to Table 3, in each Example (Example 9 and Example 10) in which carbon black or graphite powder was blended, the residual tensile elongation after 2MGy irradiation was greatly improved compared to Reference Example 2. I understand that. That is, it can be seen that an improvement in radiation resistance is recognized from the blending of about 5 parts by weight of carbon black or graphite powder.

According to Tables 1 and 2, the following can be understood.
If carbon black or graphite powder is blended as in Example 1, even if DOP is used as a plasticizer, the tensile elongation can be maintained at about 100% even after 3MGy irradiation. This is a considerably high level of radiation resistance for vinyl chloride resin compositions containing DOP. Further, as in Example 2 to Example 7, when carbon black or graphite powder and a benzoic acid plasticizer are used in combination, the tensile elongation can be maintained at about 150% or more even after 3MGy irradiation, which is higher. It becomes a level of radiation resistance.

Further, as can be seen from a comparison between Reference Example 1 and Examples 3 to 7, in these Examples, the residual ratio of tensile elongation after irradiation with 3MGy is considerably improved. Further, when Example 3 and Example 4 are compared, the residual ratio of tensile strength (tensile maximum stress) after irradiation with 3MGy is improved by adding about 50 parts by weight of carbon black over 25 parts by weight. It can be seen that a large amount of carbon black or graphite powder over 25 parts by weight, preferably over 35 parts by weight, is effective in maintaining the tensile strength after irradiation.

Further, as in these examples shown in Table 2, it can be seen that the residual ratio of tensile strength and the residual ratio of tensile elongation can be improved in a well-balanced manner by using carbon black or graphite powder and phenyl ether oil and fat together. .

Further, as can be seen by comparing Example 3, Example 6, and Example 7, Example 7 in which graphite powder was blended had a residual ratio of tensile elongation after irradiation of 3MGy exceeding 70%. It can be seen that the addition is particularly effective for maintaining the tensile elongation after irradiation with γ-ray 3MGy.

Moreover, about the reference example 1 and each Example which were shown in Table 2, after γ-ray irradiation of absorbed dose 3MGy, each sample is immersed in THF (tetrahydrofuran), whether a sample melt | dissolves or how much it swells. Tested. In Reference Example 1 in which no carbon black or graphite was blended, the sample after γ-ray irradiation was substantially insoluble. That is, in Reference Example 1, it means that the polymer chains of the vinyl chloride resin were cross-linked with each other by the irradiation of γ-rays and became insoluble in the solvent. On the other hand, in Examples 3 to 8 in which carbon black or graphite powder was blended, the samples after γ-ray irradiation resulted in “slight dissolution” that slightly dissolved in THF. That is, it was suppressed that the polymer chain of the vinyl chloride resin was cross-linked by blending carbon black or graphite powder.

The radiation-resistant vinyl chloride resin composition can be used for, for example, a flexible hose or a flexible tube, can be used in an environment exposed to radiation, and has high industrial utility value.

DESCRIPTION OF SYMBOLS 1 Flexible hose 2 Hose wall 3 Spiral reinforcement

Claims (5)

100 parts by weight of vinyl chloride resin,
A plasticizer,
Containing 5 parts by weight or more and 50 parts by weight or less of carbon black or graphite powder,
The duro A hardness before γ-ray irradiation is 50 HDA or more and 95 HDA or less,
Radiation resistant vinyl chloride resin composition. The radiation-resistant vinyl chloride resin composition according to claim 1, comprising 1 to 15 parts by weight of a phenyl ether-based fat. The radiation-resistant vinyl chloride resin composition according to claim 1 or 2, comprising 20 to 110 parts by weight of a benzoic acid plasticizer. A flexible hose comprising the radiation-resistant vinyl chloride resin composition according to any one of claims 1 to 3 on a hose wall. A flexible tube formed from the radiation-resistant vinyl chloride resin composition according to any one of claims 1 to 3.

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