JPS6173099A - Neutron fluorescent screen - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [I] Object of the Invention (Industrial Application Tn) The present invention relates to a neutron fluorescent screen. Furthermore, it is an object of the present invention to provide a neutron fluorescent screen that is not only sophisticated but also has high elasticity and excellent abrasion resistance.

[II] Background of the Invention (Prior Art) With the recent remarkable development of the nuclear power industry, radiation M shielding in nuclear facilities has become important. Furthermore, radiation is increasingly used in fields such as analytical chemistry and medicine, and there is an urgent need to develop radiation shielding materials and materials with radiation sensing performance. In particular, radiation-sensing materials are widely required not only to protect radiation workers from the danger of radiation exposure, but also in fields such as various analyzes that use radiation, structural analysis, and measurement of integrated intensity of radiation.

Traditionally, fluorescent pigments that emit light due to radiation (e.g.
Calcium tungstate, silver-activated zinc sulfide) containing compositions (e.g.

A method of coating the surface of a sheet-like material is used.

However, these radiation-emitting fluorescent pigments have a so-called low sensitivity and can therefore only be detected by considerable radiation. Furthermore, it is not very effective as a sensing material for trace amounts of radiation due to problems such as generation of secondary radiation. In particular, the use of fluorescent pigments has naturally been limited due to safety problems such as radiation shielding and environmental pollution, including the generation of secondary radiation.

[I11] As a result of various searches to solve these problems, the present inventors found that ('A) 1002 parts of olefin rubber containing ethylene and propylene as main components, (B ) Inorganic boron compound 100-400 parts by weight, (C)
Zinc sulfide-based phosphor 100 to 600 parts by weight It was discovered that it does not generate secondary radiation, is not only effective in shielding radiation, but also has excellent radiation (especially neutron) sensing, and has arrived at the present invention. did.

[IV] Detailed description of the invention (A) Olefin rubber The olefin rubber used in the present invention is mainly composed of ethylene and propylene, that is, EPR and E
At least one rubber-like material selected from the group consisting of PDM. EPR is obtained by copolymerizing ethylene and propylene. On the other hand, EPDM
is ethylene and propylene, 1,4-pentadiene, 1,5-hexadiene and 3,3-dimethyl 1.
Linear or branched diolefins containing two double bonds at the end, such as 5-hexadiene, and only one double bond, such as 1,4-hexadiene and 6-methyl-1,5-hebutadiene. terminally containing double bonds such as linear or branched diolefins or cyclic diene hydrocarbons such as bicyclo[2,2,l]-hebutene-2 (norbornene) and its derivatives (e.g. ethylidene norbornene) It is a multicomponent copolymer rubber obtained by copolymerizing a small amount of monomers. The weight ratio of one unit of ethylene monomer to one unit of propylene monomer in EPR and EPOM is preferably from 20 to 80 to 80 to 20. Further, the copolymerization ratio of the monomer having double bonds in EPDM is at most 10% by weight. These rubber-like materials are industrially produced and widely used with a catalyst system containing a transition metal compound and an organometallic compound (generally an organoaluminum compound) as main components. The Mooney viscosity of these rubbery substances is 20 to 14.
A number of 0 is preferred, and a number of 30 to 120 is particularly preferred. Also, M, 1. (ASTM [1-123
Measured according to 8, temperature 190°C 1 load 2.16k
g) is generally 0.1 to 8 g/10 minutes.

In manufacturing the neutron fluorescent screen of the present invention, only the above-mentioned olefin rubber may be used, but other types of polymeric substances that are miscible with the olefin rubber may also be blended.

Examples of the polymeric substance include rubbery substances such as silicone rubber, ethylene-ethyl acrylate copolymer, ethylene-methyl methacrylate copolymer, and ethylene-ethyl acrylate copolymer.
Examples include resinous materials such as acrylic acrylate copolymers. When blending these polymeric substances, the blending ratio of other polymeric substances to 100 parts by weight of olefin rubber is at most 50 parts by weight.

(B) Inorganic boron compound Among the inorganic boron compounds used in the present invention, inorganic boron compounds that do not contain metal are desirable. Representative examples of desirable inorganic boron compounds include boron carbide, boron nitride, boric anhydride, and orthoboric acid.

Examples include metaboric acid and tetraboric acid. Among these inorganic boron compounds, boron nitride is preferred.

The weight average diameter of these inorganic boron compounds is 0.5 to 500.
A powder with a micron size is preferable, especially 3.0~
300 microns is preferred. Boron nitride, which is a preferred inorganic boron compound, has a true density of 1.88 to 2.27 g/am, a weight average diameter of 0.7 to 6.0 microns, and a surface area of 14 to 35 m'/am depending on the degree of crystal development.
g is preferable, especially true specific gravity is 2.0 g/cm
Those with a weight average diameter of 3.0 microns or more are preferable. Further, it is optimal to use a material containing a large number of particles 10 having a large neutron absorption cross section.

Examples of the phosphor include zinc sulfide activated with metals such as silver, manganese, and lead, and silver-activated zinc sulfide is preferred in the present invention. These zinc sulfide-based phosphors are preferably powders with a weight average diameter of 1.0 to 50 microns, particularly preferably 5 to 10 microns.

(D) Organic peroxide The organic peroxide used in the present invention is not particularly limited, but it is particularly desirable to have a decomposition temperature (temperature at which the half-life is 1 minute) of 120°C or higher, particularly 140°C.
℃ or higher is preferable. Representative examples of suitable organic peroxides include ketone peroxides such as 1,1-bis-tertiary-butylperoxy-3,3,5-)limethylcyclohexane, 2,5-dimethylhexane-2 ,5
-hydroperoxides such as cybidroba-oxide, peroxyesters such as 2,5-dimethyl-2,5-di-tertiary-butylperoxyhexane, thudiasilver oxide such as benzoyl peroxide, and dicumyl peroxide. Examples include sialgyl peroxide.

Furthermore, polyfunctional substances such as triallyl isocyanurate and triallyl isocyanurate, which are used as crosslinking aids in the conventional rubber field, may be blended.

In producing the neutron fluorescent screen of the present invention, a mixture (composition) consisting of these olefin rubbers, inorganic boron compounds, zinc sulfide phosphors, and organic peroxides may be molded as described below. Furthermore, by adding (blending) the lubricant described later to these, it is possible to not only improve crosslinking caused by organic peroxides, but also improve kneading properties when producing a single composition, and further improve processability. It can be improved.

(E) Lubricant The lubricant used in the present invention is not particularly limited, but
Particularly preferred are fatty acids and fatty acid amides. Representative examples of suitable lubricants include stearic acid, hydroxystearic acid, complex stearic acid, stearamide,
oleylamide, erucylamide, ricinolamide,
Behenamide? Mention may be made of the methylolamide, ethylenebis-stearoamide, tatilenebis-stearobehenamide and stearoamide systems.

The physical properties, product names, etc. of these lubricants are described in detail in Rubber Digest Co., Ltd., “Handbook of Rubber Fist Plastic Compound Chemicals” (1971, published by Rubber Digest Co., Ltd.), pages 303 to 312. ing.

(F) Composition ratio (mixing ratio) The blending ratio of the inorganic boron compound to 100 parts by weight of resin rubber (if other polymeric substances are included, the same shall apply hereinafter) is 100 to 400 parts by weight. and particularly preferably 200 to 350 parts by weight. If the blending ratio of the inorganic boron compound to 100 parts by weight of olefin rubber is less than 100 parts by weight, the amount of alpha rays emitted by the rubber will be small, and no matter how much zinc sulfide is filled, it will not be possible to effectively generate fluorescence. In addition, the ability to detect neutrons is weak, and the resolution, especially when using a photographic plate, is reduced.

On the other hand, if the amount exceeds 400 parts by weight, not only will it be difficult to mold the resulting composition, but the loading amount of the most important zinc sulfide phosphor will be reduced to 1 part by weight per 100 parts by weight of the olefin rubber.
00 parts by weight or more, making it impossible to obtain the composition of the present invention.

In addition, the blending ratio of the zinc sulfide phosphor to 100 parts by weight of olefin rubber (including other polymeric substances, if any) is 100 to 600 parts by weight,
Particularly preferably 200 to 400 parts by weight, 100 ii
If the blending ratio of the zinc sulfide-based phosphor to the olefin-based rubber is less than 100 parts by weight, even if alpha rays are emitted by the inorganic boron compound, zinc sulfide will remain in the vicinity of the inorganic boron compound in an amount sufficient to generate fluorescence. Because it is not present, the intensity of fluorescence generated is weak and the resolution is significantly reduced. On the other hand, if the amount exceeds 600 parts by weight, it is not only difficult to exceed 200 parts by weight of the inorganic boron compound per 100 parts of olefin rubber, but also it is difficult to obtain a uniform composition of both. Furthermore, it becomes difficult to mold the resulting composition.

Furthermore, the blending ratio of organic peroxide to 1.00 parts by weight of olefin rubber is 0.1-10 parts by weight, and 0.
．． 2 to 5.0 parts by weight is desirable, especially 0.5 to 5.0 parts by weight.
0 parts by weight is preferred. If the blending ratio of organic peroxide to 100 parts by weight of olefin rubber is less than 0.1 parts by weight, crosslinking properties will be poor and a neutron fluorescent screen with excellent abrasion resistance will not be obtained.

On the other hand, if the amount exceeds 10 parts by weight, it is not only difficult to control crosslinking, but also a neutron fluorescent screen with appropriate elasticity cannot be obtained, and the radioactivity sensing performance is deteriorated.

When a lubricant is added, the amount is at most 5.0 parts by weight and 0.00 parts by weight per 100 parts by weight of resin rubber.
It is preferably 1 to 3.0 parts by weight, particularly preferably 0.2 to 2.0 parts by weight. Even if more than 5.0 parts by weight of lubricant is added to 100 parts by weight of olefin rubber,
It acts as a lubricant and further reduces radiation sensing performance.

(G) Manufacture of composition, molding method, etc. In manufacturing the composition comprising the olefin rubber of the present invention, an inorganic boron compound, a zinc sulfide phosphor and an organic peroxide, or these and a lubricant, A boron compound, a zinc sulfide phosphor and an organic peroxide, or a portion of these and a lubricant, are tri-blended in advance and then melted and kneaded uniformly, and then the remaining inorganic boron compound, zinc sulfide phosphor and organic It is preferable to carry out melt mixing while sequentially adding peroxide or these and a lubricant so that they are uniform. When melt-kneading the inorganic boron compound, zinc sulfide phosphor, organic peroxide, or a lubricant with the above-mentioned reflex rubber, first put the olefin rubber into a plastic bender or nygu to soften the olefin rubber. The olefin rubber is sufficiently kneaded by maintaining the temperature at or above the point. After this kneading has been sufficiently performed, an inorganic boron compound, a zinc sulfide phosphor, an organic peroxide, or a portion of these and a lubricant are added and thoroughly kneaded. Once this kneading has been sufficiently performed, the remaining inorganic boron compound and zinc sulfide phosphor are added while kneading to form the final blended components. In this mixing, a mixing method commonly used in the field of use of olefin rubbers is used, for example, tri-blending is performed in advance using a mixer such as a ribbon mixer or a tumbler, and then the resulting mixture is transferred to an oven roll or an extruder. Even if melt mixing is performed using a mixer such as
It may not be possible to fill more than 0 parts by weight of inorganic boron compounds.

As described above, in order to fill the olefin rubber of the present invention with an inorganic boron compound, zinc sulfide, an organic peroxide, or a lubricant together with an inorganic boron compound, zinc sulfide, an organic peroxide, or a part of these and a lubricant. It is important to fill the olefin rubber with olefin rubber and knead it almost uniformly, then add the inorganic boron compound, zinc sulfide and organic peroxide, or these and a lubricant to this mixture while kneading them almost uniformly. It is.

In any of the above cases, it is important that the olefin rubber is not essentially crosslinked by the organic peroxide when melt crosslinking occurs.

The composition obtained as described above is prepared using a molding machine such as a press molding machine, an extrusion molding machine, or an injection molding machine used in the fields of synthetic resins and rubbers at a temperature above the softening point of olefin rubber (generally (140-200°C)
What is necessary is just to crosslink and mold it into a desired shape.

When the resin composition obtained in the present invention is molded into a neutron detection plate, the thickness is 100 microns to 1 mm.
It may be formed into a sheet or film. If this molded product is thick, the inorganic boron compound in the surface layer converts neutrons into alpha rays, so neutrons do not penetrate deeply. Therefore, if the molded product is thicker than 1 mm, it generally does not contribute to fluorescence generation. However, if the composition of the present invention is required to have a neutron shielding effect at the same time, the thickness may be increased by 1.
There is no problem even if the thickness is made larger than mm, and it may be advantageous in some cases because it increases the shielding ability.

When the sheet or film-like product obtained as described above is used as a neutron detection plate, these molded products are usually adhered to -H of a plate-like product (for example, an aluminum plate) via an adhesive layer. As an adhesion method, it is sufficient to use a commonly used molding adhesive, but in order to make the surface of the molded product uniform and smooth, it is necessary to use an unsaturated compound (for example, an unsaturated compound) as the adhesive layer. The adhesive effect can be further enhanced by using an adhesive polyethylene film or sheet modified with saturated carboxylic acid. In particular, when aluminum is used as a plate-like material, the adhesive film or sheet is sandwiched between the sheet or film of the olefin rubber composition of the present invention and an aluminum plate, and the adhesive film or sheet is pressed using a heat press machine. If so, it can be easily bonded. In addition, a good product with less unevenness on the surface can be obtained.

[V] Effects of the invention The neutron fluorescent screen obtained by the invention exhibits the following effects (characteristics).

(1) Excellent neutron sensing performance (sensitivity and resolution).

(2) It has excellent elasticity.

(3) Good ITFJ abrasion resistance.

(4)'91 [Due to its strength, it is difficult to break.

(5) It is lightweight and convenient to carry.

(6) It is inexpensive.

4hi (7) A large area is possible.

The neutron detection plate obtained as described above can be widely used not only in various analytical and medical fields that use neutrons, but also in neutron detection batches to protect neutron workers from neutron exposure.

The neutron detection plate is an example of the use of the fluorescent plate obtained by the present invention, but it can be molded into various shapes and used as neutron diffraction slits and detection equipment parts in the fields of instrument analysis and medicine.

[VI] Examples and/or Comparative Examples The present invention will be explained in more detail with reference to Examples below.

Example 1 Mooney (M L +44 (
100 parts by weight of ethylene-propylene-non-coterminous diene ternary copolymer rubber (non-coterminous diene component: ethylidene norbornene, iodine value: 25.hereinafter referred to as r EPDMJ) with a temperature of 45 was placed on a roll set at 50℃. wrap around,
Melting crosstalk was performed. 200 parts by weight of boron nitride (manufactured by Showa Denko Co., Ltd., trade name: Showbinis) (PS, density 2,
27 g/cmq weight average diameter 3.5 microns) was gradually added while kneading almost uniformly, and uniformly dispersed and mixed. Next, 300 parts by weight of silver-activated zinc sulfide (manufactured by Kasei Obtonics Co., Ltd., white powder, weight average diameter 7 microns, ZnS; Ag) was mixed and kneaded into this mixture so that the mixture was almost uniform. After adding the entire amount, add 3.0 parts by weight of dicumyl peroxide and 1.0 parts by weight of dicumyl peroxide.
Parts by weight of stearic acid were added. After kneading, a sheet having a thickness of lam was formed. Thereafter, the sheet of the composition obtained as described above was stacked on a cabinet-sized aluminum plate (thickness: 1.5 mm). 165
Pressure was applied for 5 minutes using the above-mentioned press machine set at .degree. C., and the sheet of the resin composition was thermally bonded to the aluminum plate without crosslinking. When the resulting adhesive was exposed to thermal neutrons emitted from a Trigger II nuclear reactor, it was confirmed that the photosensitive paper placed in front of the adhesive was exposed to light.

Example 2 To the ioo parts by weight used in Example 1, 2.0 weight of high molecular weight polyester (trioctyl trinuritate) was added. Next, the amount of boron nitride used in Example 1 was changed to 300 parts by weight, and the amount of silver-activated zinc sulfide was changed to 4 parts by weight.
A homogeneous mixture (composition) was prepared by gradually adding these ingredients while kneading them almost uniformly in the same manner as in Example 1, except that the amount was changed to 0.00 parts by weight. The same amounts of dicumyl peroxide and stearic acid as in Example 1 were added to the composition thus obtained and kneaded. It was then hot pressed to obtain a sheet with a thickness of 200 microns. Next, in the same manner as in Example 1, it was thermally bonded to an aluminum plate (thickness: 2 am) having a diameter of 400 arms while being crosslinked. When this adhesive was irradiated with thermal neutrons in the same manner as in Example 1, it was confirmed that zinc sulfide was emitting light.

Example 3 Silicone rubber (manufactured by Shin-Etsu Silicone Co., Ltd., trade name) was added to 100 parts by weight of the olefin rubber used in Example 1.
KE 752-U) was added in an amount of 30 parts by weight.

Furthermore, 2.0 parts by weight of high molecular weight polyester (trioctyl trimellitate) was added. Next, the amount of boron nitride used in Example 1 was changed to 300 parts by weight, and the amount of silver-activated zinc sulfide was changed to 400 parts by weight.
These were gradually added while being uniformly kneaded in the same manner as in Example 1 to create a uniform mixture (composition). The same amounts of dicumyl peroxide and stearic acid as in Example 1 were added to the mixture thus obtained, and crosstalk was performed. The composition thus obtained was hot-pressed to produce a sheet in the same manner as in Example 2, and the sheet was heat-welded without crosslinking to an aluminum plate.

When this adhesive was irradiated with thermal neutrons in the same manner as in Example 1, it was confirmed that zinc sulfide was emitting light.

Example 4 Mixing was carried out in the same manner as in Example 1, except that only the stearic acid used in producing the mixture in Example 1 was not blended (other ingredients were blended in the same amounts as in Example 1). . The resulting mixture was hot pressed under the same conditions as in Example 3 to produce a sheet. The obtained sheet was used in Example 1.
When the zinc sulfide was thermally welded while cross-linked to an aluminum plate and irradiated with thermal neutrons, it was confirmed that the zinc sulfide was emitting light. However, the workability is slightly inferior.

Claims (1)

Scope of Claims: (A) 100 parts by weight of an olefin rubber containing ethylene and propylene as main components, (B) 100 to 400 parts by weight of an inorganic boron compound, (C) 100 to 600 parts by weight of a zinc sulfide-based phosphor, and (D) A neutron fluorescent screen formed by crosslinking a composition comprising 0.1 to 10 parts by weight of an organic peroxide.