JPH0810280B2 - Air carrier for irradiation - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to polyethylene-2,6-
The present invention relates to an air carrier made of an oriented film of naphthalene dicarboxylate. More specifically, it is a flexible bag-shaped air carrier used by irradiating various substances with a solid, liquid or gaseous substance or a mixture thereof. The bag-shaped air carrier is further placed in a plastic molding or a metal container and used to study the radiation resistance, chemical reaction or physical change of the irradiated material.

Conventional technology and its problems Conventionally, polyethylene has been used as a material for a pneumatic carrier made of plastic.

In the case of a polyethylene carrier, it is relatively weak against radiation and deteriorates in a relatively short time by irradiation, making it brittle, and it becomes unusable in a short time especially under high dose irradiation conditions such as reactor irradiation. was there.

There is a need for a flexible pouch in the form of a material that will withstand prolonged exposure to high-dose radiation, or even with repeated use, and will not be modified.

In addition, when a material containing an air carrier is irradiated with a neutron beam in a nuclear reactor, for example, an element contained in the air carrier may be activated. For this reason, it is the actual situation that it is very inconvenient due to its radioactivity when the substance to be irradiated is immediately taken out from the air carrier and subjected to other tests after being irradiated. There is a long-felt need for a material that, if not activated or activated, decays in radioactivity in a short time.

Means for Solving the Problems The present inventor has conducted research to provide a radiation irradiation carrier without the above-mentioned defects, and found that polyethylene-2,6-naphthalenedicarboxylate (hereinafter referred to as PEN) having specific characteristics. The present invention has been accomplished by finding that an air carrier made of (abbreviated as -2, 6) is extremely suitable as an irradiation container.

That is, the present invention is a pneumatic carrier composed of an oriented film comprising polyethylene-2,6-naphthalenedicarboxylate containing titanium as a catalyst residue or an additive at a concentration of 50 ppm or less and containing substantially no other metal impurities. It has an intrinsic viscosity of 0.45 to 0.90 and a plane orientation index of 0.10 to
This is an air carrier for irradiation, which has a density of 0.28 and a density of 1.345 to 1.360 g / cm ³ .

The base polymer, which is a material constituting the pneumatic carrier of the present invention,
Any constituent may be used as long as the constituent unit is substantially composed of ethylene-2,6-naphthalene dicarboxylate, and not only PEN-2,6 but also a small amount, for example, 10 mol% or less, preferably 5 mol%. Also included are ethylene-2,6-naphthalene dicarboxylate modified polymers modified by the following third component. PEN-2,6 is generally synthesized by combining naphthalene-2,6-dicarboxylic acid or its functional derivative and ethylene glycol or its functional derivative in the presence of a catalyst under suitable reaction conditions. It
Examples of the modified polymer include those prepared by adding one or more appropriate third component modifiers before completion of the polymerization of PEN-2,6 to prepare a copolymerized or mixed polyester.

Suitable third component is a compound having a divalent ester-forming functional group such as oxalic acid, adipic acid, phthalic acid, isophthalic acid, terephthalic acid, naphthalene-2,7-
Dicarboxylic acids such as dicarboxylic acid and diphenyl ether dicarboxylic acid or lower alkyl esters thereof: oxycarboxylic acids such as P-oxybenzoic acid and P-oxyethoxybenzoic acid or lower alkyl esters thereof: or propylene glycol, trimethylene glycol, tetramethylene glycol , Hexamethylene glycol, neopentyl glycol, and other compounds such as dihydric alcohols.

Further, PEN-2,6 or a modified polymer thereof, for example, benzoic acid, may be one having a terminal hydroxyl group and / or carboxyl group blocked by a monofunctional compound such as methoxypolyalkylene glycol, or For example, it may be modified with a very small amount of a functional ester forming compound such as glycerin or pentaerythritol within a range where a substantially linear copolymer is obtained. The base polymer used in the method of the present invention has an intrinsic viscosity of 0.45 or more measured at 35 ° C. in a tetrachloroethane / phenol [6/4 (polymerization ratio)] mixed solvent. Especially the intrinsic viscosity is 0.55
It is preferable that those having a molecular weight of up to 0.70 have excellent physical properties.

The PEN-2,6 for pneumatic carrier of the present invention can be synthesized, for example, as follows.

2,6 Dimethylnaphthalene dicarboxylate and ethylene glycol are used in a reaction tank with a titanium compound as a catalyst to carry out transesterification under normal pressure or under pressure, and then polycondensation under reduced pressure to give PEN-2,6. Method of obtaining, or PEN-2,6 by 2,3 naphthalene dicarboxylic acid and ethylene glycol by using a titanium compound as a catalyst to carry out a direct esterification reaction under atmospheric pressure or under pressure, and further performing a polycondensation reaction under reduced pressure Method.

Examples of the titanium compound include tetrabutyl titanate or trimellitic acid, hemimellitic acid, and titanium carboxylate, which is a reaction product of titanium tetrabutoxide and the like.

The present invention is a pneumatic carrier molded from the polymer as described above.

Various conventionally known methods can be used for producing the pneumatic element of the present invention from the polymer.

 For example, it can be created by the following method.

In any of the blow stretching method, the tubular stretching method, and the flat film method, it is necessary that the polymer is stretched and oriented in a film form and further heat-fixed. Further, the air carrier needs to be formed into a tubular shape (or a bag shape) by heat sealing or adhesion. Particularly, in the case of forming a bag shape, a heat sealing method or a fusing sealing method is preferable.

The stretching heat treatment conditions of the film stretch-oriented by the above method are adjusted so that the plane orientation index is 0.10 to 0.28 and the density is 1.345 to 1.360 g / cm ³ . If the plane orientation index is less than 0.10, the irradiation resistance will not be sufficiently enhanced and the material will be easily embrittled by irradiation and will not be usable. On the other hand, if the surface compounding index exceeds 0.28, the oriented film is likely to tear, which is not preferable.

Further, if the density is 1.345 or less, the heat resistance is inferior, and it is not preferable because it may not be practically used due to thermal deformation during irradiation. The pneumatic carrier of the present invention has an outer diameter of 15 to 20 m when formed into a tubular shape.
It has dimensions of m, length 50 to 80 mm and thickness 5 to 100 μm.

EFFECTS OF THE INVENTION When the pneumatic carrier made of PEN-2,6 of the present invention is used for irradiation, it has the following advantages.

1. Since it is remarkably less deteriorated than an air carrier made of polyethylene, it can be used under irradiation with a high dose rate. In particular, it is suitable as a pneumatic carrier for nuclear reactor irradiation.

2. The air carrier according to the present invention has an extremely large attenuation of radioactivity when activated, and therefore has an advantage that handling of the object to be radiated becomes extremely easy after irradiation.

3. Since it does not become brittle under low temperature conditions such as liquid nitrogen, it can be used at extremely low temperatures.

4. Since the air carrier according to the present invention is oriented and heat-treated, it can be used at a high temperature of, for example, about 250 ° C.

EXAMPLES Hereinafter, the present invention will be further described with reference to examples. In addition,
The characteristics in the present invention are measured as follows.

(A) Intrinsic viscosity In the present invention, the intrinsic viscosity is calculated from the value measured at 35 ° C in a mixed solvent of tetrachloroethane / phenol in a weight ratio of 6: 4.

(B) Density A small piece was cut from the molded product and used as a sample for density measurement. The density was measured at 25 ° C. with a density gradient tube of carbon tetrachloride to n-heptane system.

(C) Measurement of Refractive Index and Calculation of Plane Orientation Index It was measured using an Abbe refractometer with sodium D line (589 nm) as a light source. Methylene iodide was used as the mount solution, and measurement was performed at 25 ° C and 65% RH.

In the case of a flat film, the refractive index in the length, width and thickness direction of the film was measured. Let these refractive indices be n _M , n
Let _T and n _Z be {(n _M + n _T ) / 2 as the plane orientation index.
It was calculated by −n _Z }. Further, in the case of a blow stretched film or a tubular stretched film, the angular distribution of the refractive index within the film surface was measured, and the value obtained by subtracting the refractive index in the thickness direction from the average value thereof was taken as the plane orientation index.

(D) Radiation resistance test PEN-2, 6 and a test piece made of other comparative materials and a bag-shaped air carrier were prepared, and JRR-2 of Japan Atomic Energy Research Institute
Neutron flux of irradiation hole 5.5 × 10 ¹³ 〜 8.0 × 10
Irradiation was performed at ¹³ n / cm ² · sec. The radioactivity of the neutron-irradiated test piece was measured by an ionization chamber type dose rate meter (IC-247) or a GM dose rate meter.

(E) Measurement of tear strength It was measured using a light load tear strength tester manufactured by Toyo Seiki Seisakusho. This tear strength tester was designed with reference to JIS P8116. The sample for measurement was performed using an oriented flat film.

Examples and Comparative Examples PEN-2,6 containing 15 ppm of titanium as an impurity content and substantially free of other impurities was synthesized. In addition, PEN-2,6 containing 55 ppm of zinc as an impurity content and substantially not containing other impurities was also synthesized. PE containing 302 ppm of antimony, 49 ppm of cobalt, and 83 ppm of phosphorus as impurities.
N-2,6 was synthesized.

These PEN-2, 6 were melt-extruded in a sheet form by a known method and cooled to prepare an unstretched film. This unstretched film was stretched 3.6 times in both the longitudinal and transverse directions, and was stretched at 230 ° C under tension.
Heat set for 30 seconds. Thus, a biaxially oriented film having a thickness of 9 μm was obtained. The intrinsic viscosity of these films is 0.5
7, the plane orientation index was 0.25, the density was 1.354 (Example 1,
Comparative Examples 3 and 4). In Comparative Example 1, an unstretched film of PEN-2,6 containing 15 ppm of titanium as an impurity metal was prepared in the same manner as above, and stretched 2.2 times in both the longitudinal and transverse directions. Then, it was heat-set under tension at 230 ° C. for 30 seconds. The plane orientation index of this film was 0.07 and the density was 1.354 g / cm ³ (Comparative Example 1).

Further, Comparative Example 2 was stretched in the same manner as in Example 1 and heat-set under tension at 135 ° C.

The results are shown in Table 1. The pneumatic child carrier of the present invention shown in Example 1 had little deterioration in tear resistance even at a high irradiation dose, had a large attenuation of the radiation dose rate, and was sufficiently practical. In Comparative Examples 1 and 2, PEN-2,6 having the same composition as in Example 1 was used, but the film resistance was remarkably inferior because of the improper film characteristics. In Comparative Example 3, the decrease in tear resistance is small, but the radiation dose rate is not easily attenuated, so that the object of the present invention cannot be achieved. Further, in Comparative Example 4, since the radiation dose after irradiation was too large to handle, the test was stopped.

As described above, the pneumatic carrier for irradiation of the present invention is extremely useful.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenji Arikane 4-2, Shirane, Shikata, Tokai-mura, Naka-gun, Ibaraki Prefecture Inside the Tokai Research Institute, Japan Atomic Energy Research Institute (72) Tadao Seguchi, 1233 Watanuki-cho, Takasaki-shi, Gunma Prefecture Address, Japan Atomic Energy Research Institute, Takasaki Research Institute (72) Inventor Isao Aoyama, Shirane, Tokai-mura, Naka-gun, Ibaraki Prefecture, 4-2, Shirane, Japan Atomic Energy Research Institute, Tokai Research Laboratory (56) References Japan Atomic Energy Research Institute JAER-M Report , JAERI-M-89-96 (August 1989)

Claims (1)

[Claims] 1. Titanium is used as a catalyst residue or an additive.
A pneumatic element composed of an oriented film consisting of polyethylene-2,6-naphthalenedicarboxylic xylate containing substantially no other metal impurities at a concentration of ppm or less, and having an intrinsic viscosity of 0.45 to 0.90, plane orientation. The index is 0.10 to 0.28,
An air carrier for radiation irradiation, which has a density in the range of 1.345 to 1.360 g / cm ³ .