JP3059584B2 - Radiation-resistant container - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation-resistant container.

[0002]

2. Description of the Related Art Conventionally, various samples have been irradiated with radiation for the purpose of developing radiation-resistant materials, producing isotope compounds, synthesizing substances using radiation as an energy source, and modifying polymer substances. Is performed in a nuclear reactor or the like. In order to irradiate the sample with radiation, a capsule for accommodating the sample is required. In addition, when filling a capsule with a plurality of types of samples, a flexible film or a peripheral portion of the film is used to prevent mixing of the capsules or to absorb an impact during transfer of the sample-containing capsule into the reactor. A welded bag-like packaging material is required.

Conventionally, as the capsule, film or bag-like packaging material, those made of polyethylene or aluminum have been used.

[0004] However, polyethylene capsules and film / bag-like packaging materials are effective when irradiating a sample with a low dose of radiation, but are severely degraded when irradiating a sample with a high dose of radiation. There is a disadvantage that. On the other hand, aluminum capsules and film / bag-shaped packaging materials are used when irradiating high doses of radiation.However, they are activated by neutrons during irradiation, and the decay of radioactivity is slow. There is a drawback that a sample cannot be immediately taken out to perform another measurement / operation.

[0005] As an alternative to polyethylene or aluminum capsules, films and bag-like packaging materials,
Polyimide materials are also used.Since capsules, films, and bag-like packaging materials made of polyimide resin have low activation even when exposed to high doses of radiation, they can be used to remove samples even after irradiation. Is relatively easy to handle. For this reason, the above-mentioned polyimide is preferably used as a capsule, a film, or a bag-like wrapping material when irradiating a sample with a high dose of radiation, since activation upon exposure to radiation is small. ing.

However, polyimide resin, which is a thermosetting resin, has poor molding processability, so that the productivity of capsules, film and bag-like packaging materials made of polyimide resin is low. For this reason,
In recent years, containers made of polyethylene-2,6-naphthalenedicarboxylate, which have better moldability than polyimide resins, have been developed as containers (pneumatic tubes) for irradiating high-dose radiation ( JP-A-2-278
No. 200). This polyethylene-2,6-naphthalenedicarboxylate has a small activation when exposed to radiation, and is superior to a polyimide resin in terms of moldability since it is a thermoplastic resin. Also, because it has higher radiation resistance than polyethylene,
It can be used when irradiating a sample with a high dose of radiation.

[0007]

However, when a molded article of polyethylene-2,6-naphthalenedicarboxylate is exposed to a high dose of radiation, the decrease in mechanical strength of the molded article is relatively large. In other words, the radiation resistance to high doses of radiation is relatively low. Therefore, when used as a high-dose radiation irradiation container (capsule, film, or bag-like packaging material), there is a drawback that it cannot be used repeatedly.

Accordingly, an object of the present invention is to provide a radiation-resistant container which is made of a resin having excellent moldability, has low radioactivity even when exposed to a high dose of radiation, and has high radiation resistance to a high dose of radiation. To provide.

[0009]

The radiation-resistant container of the present invention that achieves the above object has the following formula:

Embedded image And a melt flow rate at 400 ° C. under a load of 5 kg (based on JIS K7210) of 0.1 to 500.
It is characterized by being composed of an aromatic ether copolymer having a g / 10 minutes.

Hereinafter, the present invention will be described in detail. As described above, the radiation-resistant container of the present invention comprises the aromatic ether-based copolymer represented by the above formula. That is, this aromatic ether copolymer is composed of a repeating unit group

Embedded image And the repeating unit group

Embedded image And the ratio (x / y) between the former repeating unit group and the latter repeating unit group is 10/90 to 70 /
30. The reason why the lower limit of the value of x / y is limited to 10/90 is that if x / y is smaller than 10/90, the melting point increases and the moldability decreases. The reason for limiting the ratio to 70/30 is that if x / y is greater than 70/30, the radiation resistance decreases, and the irradiation time to the container or the number of times the container can be used repeatedly decreases. Particularly preferred values of x / y are 15/85 to 60/40.
It is.

The aromatic ether copolymer may be a block copolymer in which two types of repeating units each constitute a block, or a random type in which two types of repeating units are randomly bonded. It may be a copolymer or an alternating copolymer in which two types of repeating units are alternately bonded, but it is preferable to use a block copolymer. The aromatic ether copolymer used as the material of the radiation-resistant container of the present invention has a melt flow rate (based on JIS K7210) of 400 ° C. under a load of 5 kg of 0.
It is required to be 1 to 500 g / 10 minutes. The reason is that if the melt index is less than 0.1 g / 10 minutes, the moldability is insufficient and molding of the container is difficult.
If it exceeds 00 g / 10 minutes, the mechanical strength of the obtained container is insufficient, and the container cannot be used as a radiation-resistant container. The fact that the melt flow rate under a load of 5 kg at a temperature of 400 ° C. is 0.1 to 500 g / 10 minutes substantially corresponds to a melt viscosity of 500 poise or more at the same temperature. A particularly preferred melt flow rate is 0.2 to 200 g / 10
Minutes.

The above-mentioned copolymer which is a material of the radiation-resistant container of the present invention can be produced by a method disclosed in Japanese Patent Application Laid-Open No. 2-255833. That is,
As starting monomers, dihalogenobenzonitrile such as 2,6-dichlorobenzonitrile, 2,6-difluorobenzonitrile, 2,4-dichlorobenzonitrile, and dihydric phenol such as 4,4'-biphenol; And dihalogenobenzophenones such as 4'-difluorobenzophenone and 4,4'-dichlorobenzophenone. The molar ratio of the starting monomer and the molar ratio is appropriately determined such that x / y in the obtained aromatic ether-based copolymer falls within the above range (10/90 to 70/30).

In obtaining the above aromatic ether copolymer by reacting the starting monomer and
An alkali metal carbonate such as potassium carbonate, sodium carbonate and lithium carbonate or an alkali metal bicarbonate such as potassium bicarbonate and sodium bicarbonate is present in the system. The amount of these alkali compounds is usually preferably 1.03 to 2.5 equivalents per one hydroxyl group of the starting monomer. This polymerization reaction is usually performed using NMP (N-methylpyrrolidone), DMI (N, N-dimethylimidazolidinone), DMAc (dimethylacetamide), DMF
(Dimethylformamide), diphenylsulfone, or another neutral polar solvent. The amount of the neutral polar solvent used is preferably 200 ml per 0.05 to 1 mol of the total amount of the starting monomer and the neutral polar solvent.

The reaction is carried out for 0.1 to 10 hours by simultaneously or sequentially adding the above-mentioned starting monomer and a solvent to a solvent.
It is carried out by heating to a temperature of 50 to 380 ° C. After the reaction, washing with water and washing with methanol are performed to obtain an aromatic ether copolymer.

The aromatic ether copolymer thus obtained has excellent radiation resistance to high doses of radiation. And, since the melt flow rate under a load of 5 kg at 400 ° C. is 0.1 to 500 g / 10 minutes, it can be easily formed by extrusion, injection molding, press molding, inflation molding or the like at a resin temperature of 370 to 430 ° C. can do. In addition, the aromatic ether copolymer can control the crystallization of the resin by controlling the copolymerization ratio, the mold temperature during molding, the presence or absence of annealing after molding, and the like. And chemical resistance can be controlled. For example, copolymerization ratio (x / y)
Is 40/60 or near the above, the aromatic ether copolymer is amorphous, and the copolymerization ratio (x / y) is 25/60.
The above-mentioned aromatic ether copolymer having a ratio of / 75 or its vicinity can be made crystalline by forming it into a desired shape and then performing annealing as necessary. Crystallized ones have better heat resistance and chemical resistance than amorphous ones.

The radiation-resistant container of the present invention comprises an aromatic ether-based copolymer having the above-mentioned properties,
The shape and size are appropriately selected according to the application. For example, the radiation-resistant container of the present invention may be a closed container capable of blocking the inside from the outside, or may be an open container having the inside communicating with the outside.

Examples of the closed container include a capsule, a container with a stopper or a lid, and examples of the open container include:
Examples include hermetically sealed or lidless containers, films, and bag-like packaging materials. Extrusion molding, injection molding, press molding, and the like are used when molding a closed container such as a capsule, a hermetic stopper, or a container with a lid, and when molding a hermetic stopper or a container without a lid among open containers. The formation of the film or the bag-like packaging material in the open container is performed as follows. That is, the aromatic ether copolymer is 370-4
First, a film is formed at a resin temperature of 30 ° C. by a film forming method such as extrusion, press or inflation. The film may be uniaxially or biaxially (simultaneously or sequentially) stretched and heat-treated as necessary. Next, the above-mentioned film is cut into an arbitrary shape, then folded, and the periphery is sealed with heat or an adhesive to obtain a bag-like packaging material.

Since the radiation-resistant container of the present invention is made of resin, it hardly activates when exposed to radiation. Also,
Even when exposed to high doses of radiation, it can be used repeatedly due to a small decrease in mechanical strength. And
As described above, since a resin having excellent moldability is used as a material, a high degree of freedom in a shape that can be adopted and high productivity are obtained. Therefore, the radiation-resistant container of the present invention can also be used as an irradiation container in a nuclear reactor irradiated with a high dose of radiation.

[0019]

Embodiments of the present invention will be described below. Example 1 (1) Production of Aromatic Ether Copolymer 1548 g (9 mol) of 2,6-dichlorobenzonitrile was placed in a 200-liter reactor equipped with a stirrer and an argon gas blowing tube. '-Biphenol 5580 g (30 mol), potassium carbonate 4561 g (3
3 mol) and 50 liters of N-methylpyrrolidone, and the mixture was blown with 195 argon gas for 1 hour.
The temperature was raised to ° C. After the temperature was raised, a small amount of toluene was added, and generated water was removed by azeotropic distillation. Next, at a temperature of 195 ° C.
After reacting for 30 minutes, a solution prepared by dissolving 4,58'-difluorobenzophenone (4582 g, 21 mol) in N-methylpyrrolidone (70 L) was added, and the reaction was further carried out for 1 hour. After completion of the reaction, the product was pulverized with a blender, washed with water and methanol in that order, dried, and 10.0 kg (98% yield) of a white copolymer was obtained.
I got

When the properties of this copolymer were measured, the melt flow rate (according to JIS K7210) at a temperature of 400 ° C. and a load of 5 kg was 20.0 g / 10 minutes. The melt viscosity (zero shear viscosity) measured at a temperature of 400 ° C. was 13,000 poise, and the glass transition temperature was 1
82 ° C, crystal melting point: 379 ° C, thermal decomposition onset temperature: 562
° C (5% weight loss in air). This copolymer is a crystalline aromatic ether copolymer represented by the following formula.

[0021]

Embedded image (2) Production of radiation-resistant container The aromatic ether-based copolymer obtained in (1) was melt-kneaded at 390 ° C with a twin screw extruder manufactured by Sugai Kagaku to pelletize. Thereafter, using an IS45P injection molding machine manufactured by Toshiba Corporation, injection molding was performed under the conditions of a resin temperature of 390 ° C. and a mold temperature of 220 ° C., and an outer diameter of 30 mm having a bottom at one end.
A cylindrical container having a length (outside dimension) of 100 mm and a thickness of 3 mm was obtained. Similarly, an inner diameter of 30 mm having a bottom at one end,
A cylindrical cap having a length (outside dimension) of 20 mm and a thickness of 3 mm was obtained.

(3) Radiation resistance test The cylindrical container obtained in (2) equipped with the cap obtained in (2) (hereinafter referred to as a test container)
After irradiation in the reactor with fast neutrons and γ-rays having the absorbed doses shown in Table 1, changes in appearance were visually observed. Also, 20
Immediately after irradiation with the absorbed dose of MGy, the surface dose equivalent rate was measured using a GM type survey meter [NSM-15202 manufactured by Fuji Electric Co., Ltd.] to evaluate the induced radioactivity of the test container. Further, in order to check the strength of the test container after irradiation, the crosshead was set at right angles to the longitudinal direction of the container using an INSTRON4301 type compression tester (trade name, manufactured by Instron, USA), and the test speed was set at 5 mm. The test container was subjected to a compression test at / min. Table 1 shows the results.

Example 2 (1) Production of aromatic ether-based copolymer 2,6-dichlorobenzonitrile was charged at 2064.
9.9 kg of a white copolymer in the same manner as in Example 1 (1) except that the charged amount of 4,4'-difluorobenzophenone was changed to 3927 g (18 mol), respectively. (99% yield). When the properties of this copolymer were measured, the temperature was 400 ° C. and 5 k.
The melt flow rate (based on JIS K7210) under a load of g was 13.2 g / 10 minutes. Temperature 400
The melt viscosity (zero shear viscosity) measured at 0 ° C is 1950
The temperature was 0 poise, the glass transition temperature was 187 ° C, and the thermal decomposition onset temperature was 561 ° C (5% weight loss in air). This copolymer is an amorphous aromatic ether copolymer represented by the following formula.

[0024]

Embedded image (2) Manufacture of radiation-resistant container The melt-kneading temperature was 395 ° C, and the resin temperature during injection molding was 39.
Example 1 (2) except that the mold temperature was 170 ° C. and 5 ° C.
In the same manner as in Example 1, a test container having the same shape as in Example 1 was obtained.

(3) Radiation resistance test The test vessel was irradiated with the absorbed dose shown in Table 1 in the reactor in the same manner as in Example 1 (3), and then the appearance of the test vessel in the same manner as in Example 1 (3) Was visually observed, the surface dose equivalent rate was measured, and the test container was subjected to a compression test. Table 1 shows the results.

Comparative Example 1 A test container having the same shape as in Example 1 was obtained in the same manner as in Example 1 (2), using polyethylene-2,6-naphthalenedicarboxylate as the material for the container. After irradiating the test container with the absorbed dose shown in Table 1 in the reactor in the same manner as in Example 1 (3), visual observation of the change in the external appearance of the test container and the surface were performed in the same manner as in Example 1 (3). Measurement of dose equivalent rate and compression test of the test container were performed. Table 1 shows the results.

[0027]

[Table 1] As is clear from Table 1, the radiation-resistant containers of Examples 1 and 2 did not change their appearance even when irradiated with an absorbed dose of 20 MGy in the reactor, and irradiated with an absorbed dose of 40 to 220 MGy in the reactor. Even if it is done, there is little discoloration of the appearance. The degree of activation is low. And, even when the absorbed dose of 100 MGy is irradiated in the reactor, a decrease in mechanical strength is hardly recognized. From this, when the radiation-resistant container of the present invention is used, handling when removing the sample in the container after irradiation is easy, and the same container can be used repeatedly as an irradiation container for high-dose radiation. It can be seen that it is. On the other hand, the appearance of the test container of Comparative Example 1 was changed regardless of the irradiation dose in the reactor. Further, when the absorbed dose of 40 to 100 MGy is irradiated in the reactor, the mechanical strength is greatly reduced. From this,
It turns out that repeated use as an irradiation container for high-dose radiation is impossible.

Example 3 The aromatic ether copolymer obtained in Example 1 (1) was melt-kneaded at 390 ° C. with a twin screw extruder manufactured by Sugai Kagaku Co., Ltd. to obtain extruded pellets. Using these pellets, a film having a width of 250 mm and a thickness of 100 μm was obtained by T-die extrusion molding. Then, the peripheral portion of the film was heat-sealed to produce a bag-like container, and the bag was inserted into an aluminum capsule, sent to a reactor irradiation section and irradiated with radiation for 10 seconds. 26 minutes, 76 minutes and 136 minutes after the irradiation, the radioactivity intensity (mSv / h) was measured with a GM type survey meter, and the attenuation of the radiation dose rate was examined. Table 2 shows the measurement results. Table 3 shows the results of a 180-degree bending test and appearance observation after irradiation for a maximum of 100 hours.

Example 4 A bag-like container was prepared in the same manner as in Example 3 except that the aromatic ether copolymer obtained in Example 2 (1) was used as a material for the bag-like container. Tested in the same manner as 3. The measurement results of the radioactivity intensity are shown in Table 2, and the results of the bending test and the appearance observation are shown in Table 3.

Comparative Example 2 A bag-like container was prepared in the same manner as in Example 3 except that polyethylene-2,6-naphthalenedicarboxylate was used as the material for the bag-like container. The appearance was observed. Table 3 shows the results.

[0031]

[Table 2]

[Table 3] As is evident from Table 2, the bag-shaped containers of Examples 3 and 4 have little activation after irradiation, have a rapid decay of radioactivity, and can take out samples at an early stage after irradiation. It became clear that it was.

As is clear from Table 3, the bag-like containers of Examples 3 and 4 exhibited good bending tests and good appearance after irradiation, and showed little deterioration due to irradiation. On the other hand, the bag-shaped container of Comparative Example 2 was inferior in both the bending test and the appearance.

[0033]

As described above, the radiation-resistant container of the present invention is made of a resin having excellent moldability, has low activation even when exposed to a high dose of radiation, and has a reduced radioactivity. It is fast and has high radiation resistance.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akitoshi Otomo 2-4 Shirakata Shirane, Tokai Village, Naka-gun, Ibaraki Pref. Japan Atomic Energy Research Institute Tokai Research Laboratory (72) Inventor Shigeru Matsuo 1280 Kamiizumi 1280 Kamiizumi, Sodegaura City, Chiba Prefecture Idemitsu Kosan Inside (72) Inventor Shigeru Murakami 1280 Kamiizumi, Sodegaura-shi, Chiba Idemitsu Kosan Co., Ltd. (58) Field surveyed (Int.Cl. ⁷ , DB name) G21K 5/08 G21C 23/00

Claims (2)

(57) [Claims] 1. The following formula: And a melt flow rate at 400 ° C. under a load of 5 kg (based on JIS K7210) of 0.1 to 500.
A radiation-resistant container comprising an aromatic ether copolymer having a g / 10 minutes. 2. The radiation-resistant container according to claim 1, wherein the container is a closed container or an open container.