JP2019056640A - X-ray shielding material - Google Patents

Abstract

To provide an X-ray shielding material having a light weight and sufficient X-ray shielding capability.SOLUTION: An X-ray shielding material 10 includes a base material 20 containing an organic polymer material having a specific gravity of 1.0 or less, a first filler 30 containing a substance having an effective atomic number of 50 or more and 58 or less distributed in the base material 20. The content of the first filler 30 is 20% by volume or more and less than 50% by volume.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an X-ray shielding material.

  Radiation represented by gamma rays and X-rays is widely used in scenes such as inspection and analysis. When using radiation, it is required to appropriately shield the radiation that reaches the outside of the radiation use range and avoid unnecessary exposure. Therefore, a shielding material for shielding radiation is used.

  Examples of such a shielding material include a radiation shielding material in which an oxide powder of at least one lanthanoid element selected from lanthanum, cerium, praseodymium, neodymium, samarium, europium, and gadolinium is dispersed in an organic polymer material. It is disclosed (see Patent Document 1 and Patent Document 2).

International Publication No. 2006/090629 JP 2007-86865 A

  Among radiation, X-rays are widely used in the medical field and science and engineering field. When using X-rays, an X-ray shielding material is used as a member constituting an X-ray protective garment, an inner wall of an X-ray irradiation chamber, or the like. The X-ray shielding material is required to be lightweight in addition to having a sufficient X-ray shielding ability.

  Accordingly, an object is to provide an X-ray shielding material that is lightweight but has sufficient X-ray shielding ability.

  The X-ray shielding material of the present application includes a base material containing an organic polymer material having a specific gravity of 1.0 or less, and a first filler containing a substance having an effective atomic number of 50 or more and 58 or less dispersed in the base material. . The content of the first filler in the X-ray shielding material is 20% by volume or more and less than 50% by volume.

  According to the X-ray shielding material, it is possible to provide an X-ray shielding material that is lightweight and has sufficient X-ray shielding ability.

It is a schematic perspective view which shows an example of the laminated body for X-ray shielding containing an X-ray shielding material. It is a schematic sectional drawing which shows an example of the laminated body for X-ray shielding containing an X-ray shielding material.

[Description of Embodiment of Present Invention]
First, embodiments of the present invention will be listed and described. The X-ray shielding material of the present application includes a base material containing an organic polymer material having a specific gravity of 1.0 or less, and a first filler containing a substance having an effective atomic number of 50 or more and 58 or less dispersed in the base material. . The content of the first filler in the X-ray shielding material is 20% by volume or more and less than 50% by volume.

  In radiation shielding materials, generally, the larger the atomic number of an element contained in a filler, the higher the radiation shielding properties. Moreover, there exists a tendency for radiation shielding property to increase, so that many fillers are included. However, there is a problem that a radiation shielding material containing a large amount of filler containing an element having a large atomic number is heavy.

  The radiation shielding material containing a large amount of filler containing an element having a large atomic number as described above is designed to shield not only X-rays but also other radiation such as γ-rays having higher energy than X-rays. Has been. On the other hand, in the medical field and the science and engineering field, there are many cases where X-rays are used among radiation. In such a field, it is sufficient if X-rays can be shielded.

  The present inventors have found through examination that a substance having a specific effective atomic number has a high shielding ability against X-rays. Specifically, it has been found that a substance having a relatively low effective atomic number of 50 to 58 has a high X-ray shielding ability. By using such a substance as a filler dispersed in an organic polymer material, the X-ray shielding property per unit mass of the X-ray shielding material can be increased. As a result, it is possible to reduce the mass of the X-ray shielding material necessary to ensure the necessary X-ray shielding properties, and it is possible to provide an X-ray shielding material that is lightweight and has sufficient X-ray shielding ability. . This is expected to expand the applications of X-ray shielding materials.

  The base material may further contain at least one of a plasticizer and a softener. When the base material contains at least one of a plasticizer and a softener, the flexibility of the X-ray shielding material is improved, and processing and handling are facilitated.

  The X-ray shielding material may have a specific gravity of 2.0 or more and less than 4.0. By having such specific gravity, it becomes easier to provide a lightweight X-ray shielding material while maintaining sufficient X-ray shielding ability.

  The first filler may be cerium oxide or metallic tin. By containing cerium oxide or metallic tin as the first filler, X-rays can be shielded more efficiently.

  In the X-ray generator in which the target metal is tungsten, the X-ray shielding material may shield X-rays generated under a tube voltage of 80 kV to 150 kV. The X-ray shielding material shields such X-rays particularly efficiently.

  The X-ray shielding material may further contain a substance containing at least one element of tungsten and bismuth as a second filler. By including such a substance as a filler, the wavelength range of X-rays to be shielded can be broadened.

  The organic polymer material may be at least one selected from the group consisting of ethylene propylene diene rubber (EPDM), butyl rubber (isobutylene isoprene rubber: IIR), chlorinated butyl rubber, and brominated butyl rubber. . By providing a base material composed of at least one of these rubbers, an X-ray shielding material that is easy to process can be obtained.

  The X-ray shielding material may be a sheet-like molded body. A sheet-like molded body is preferable because it can be easily applied to various uses.

[Details of the embodiment of the present invention]
Next, an embodiment of the X-ray shielding material of the present application will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated.

[Configuration of X-ray shielding material]
The configuration of the X-ray shielding material will be described with reference to FIGS. FIG. 1 is a schematic perspective view showing an example of an X-ray shielding laminate including an X-ray shielding material. FIG. 2 is a schematic sectional view showing an example of an X-ray shielding laminate including an X-ray shielding material.

  With reference to FIG. 1 and FIG. 2, the laminated body 100 for X-ray shielding contains the X-ray shielding sheet 10 which is one form of the X-ray shielding material of this application shape | molded by the sheet form, and the protective layer 40. FIG. X-ray shielding sheet 10 includes base material 20, first filler 30, and second filler 60. The protective layer 40 protects the surface of the X-ray shielding sheet 10 and reinforces the X-ray shielding sheet 10. The protective layer 40 is an organic polymer film layer, for example. The protective layer 40 and the second filler 60 can be omitted.

  The base material 20 contains an organic polymer material having a specific gravity of 1.0 or less. Examples of such an organic polymer material include ethylene propylene diene rubber (EPDM), butyl rubber (isobutylene isoprene rubber: IIR), chlorinated butyl rubber, and brominated butyl rubber. The base material 20 may include these alone, or may include a plurality of these in combination. The specific gravity of the organic polymer material is preferably 0.7 or more, more preferably 0.8 or more.

  The ethylene propylene diene rubber may be used in the state of oil-extended ethylene propylene diene rubber. The oil-extended ethylene propylene diene rubber is a rubber whose viscosity is adjusted by adding a saturated hydrocarbon compound such as paraffinic oil acting as a softening agent to a high molecular weight ethylene propylene diene rubber. By using ethylene propylene diene rubber in the state of oil-extended ethylene propylene diene rubber, an X-ray shielding material having higher flexibility and higher strength can be obtained.

The first filler 30 includes a substance having an effective atomic number of 50 or more and 58 or less. The effective atomic number is a value obtained by converting a compound into an atomic number for an element. In the case of a simple metal, the effective atomic number basically matches the atomic number of the metal. Although there are various methods for calculating the effective atomic number, an example is a method of calculating the effective atomic number Z _eff for the photoelectric effect by the following equation.

式中、Ｚ_ｉはｉ番目の原子を表す。ｆ_ｉはその化合物全体の電子に対するＺ_ｉの電子の割合を表し、Σｆｉ＝１である。ｍは注目する相互作用等によって様々な値をとり得る係数である。本願明細書においては、Ｍａｙｎｅｏｒｄが提唱したｍ＝２．９４という値を用いる。

In the formula, Z _i represents the i-th atom. f _i represents the ratio of the electron of Z _{i to} the electron of the entire compound, and Σfi = 1. m is a coefficient that can take various values depending on the interaction of interest. In the present specification, the value m = 2.94 proposed by Mayneord is used.

Examples of the substance having an effective atomic number of 50 or more and 58 or less include cerium oxide (Ce ₂ O ₃ , effective atomic number 54.4), metallic tin (Sn) (effective atomic number 50.0), and the like.

  Content of the 1st filler 30 in the X-ray shielding sheet 10 is 20 volume% or more and less than 50 volume%. If the content is 20% by volume or more, X-rays can be sufficiently shielded. Moreover, the specific gravity of the 1st filler 30 is usually larger than the organic polymer material of specific gravity 1.0 or less. Therefore, when the content of the first filler 30 increases, the X-ray shielding sheet 10 becomes heavy. When the content of the first filler 30 is less than 50% by volume, the X-ray shielding sheet 10 having a sufficient X-ray shielding ability while being lightweight is provided. The lower limit of the content of the first filler 30 in the X-ray shielding sheet 10 is preferably 30% by volume. The upper limit is preferably 40% by volume.

  The second filler 60 is made of a material containing at least one element of tungsten and bismuth. Tungsten and bismuth shield X-rays and other radiation with shorter wavelengths (higher energy). Therefore, by using together the first filler made of a substance having an effective atomic number of 50 or more and 58 or less and the second filler made of a substance containing at least one element of tungsten and bismuth, the range of X-rays to be shielded can be reduced. Can be spread. Since tungsten and bismuth are relatively expensive, the content is selected in consideration of cost and necessary shielding properties. Specifically, the content of the second filler 60 in the X-ray shielding sheet 10 is preferably 1% by volume or more and 20% by volume or less.

  The base material 20 may further include at least one of a plasticizer and a softener. The types of plasticizer and softener are not particularly limited, but phthalic plasticizers such as bis (2-ethylhexyl) phthalate (Di (2-ethylhexyl) phthalate: DEHP) and diisononyl phthalate (DINP) And adipic acid plasticizers such as adipic acid esters and hydrocarbon plasticizers such as paraffinic oils.

  The content of the plasticizer or softening agent in the X-ray shielding material, that is, in the X-ray shielding sheet 10 is appropriately selected. The amount is 200 parts by mass or less.

  The base material 20 may contain a necessary amount of other additives such as a plasticizer and a softener. Such additives include coupling agents, colorants, antistatic agents, stabilizers, pigments and the like.

  Although not particularly limited, the X-ray shielding sheet 10 can be produced by, for example, the following method. First, at least one of an organic polymer material that forms the base material 20, a plasticizer and a softening agent that are added as necessary, a first filler 30, and a second filler 60 as needed, respectively. A predetermined amount is weighed and kneaded in a melt-kneading apparatus such as a roll, a kneader, or a Banbury mixer to form a composition for a radiation shielding material. The X-ray shielding sheet 10 is produced by processing the obtained composition for radiation shielding material into a sheet having a desired thickness using a calender roll. The X-ray shielding sheet 10 may be further vulcanized using a press or a vulcanizing can. By stacking the protective layer 40 on one or both surfaces of the X-ray shielding sheet 10, the X-ray shielding laminate 100 is formed.

[X-ray shielding ability of X-ray shielding material]
The X-ray shielding sheet 10 effectively shields X-rays. The X-ray shielding sheet 10 shields X-rays incident on the surface of the X-ray shielding sheet 10 in a practically sufficient amount. The X-ray shielding sheet 10 shields, for example, 30% or more of X-rays reaching the X-ray shielding sheet 10, more preferably 50% or more, further preferably 70% or more, and particularly preferably 90% or more. Further, among X-rays, in an X-ray generator in which the target metal is tungsten, X-rays generated under conditions where the tube voltage is 80 kV to 150 kV, preferably 100 kV to 130 kV are effectively shielded.

[Usage]
The X-ray shielding material according to the present embodiment can be used as a wall material for a room where X-rays are used. Since the X-ray shielding material according to the present embodiment is lightweight, the construction is easy and the burden on the operator is small. In addition, although it is lightweight, it exhibits practically sufficient X-ray shielding properties.

  Moreover, it can also be used as an X-ray protective garment by using the X-ray shielding material according to the present embodiment as a covering material. Since the weight can be reduced by using the X-ray shielding material according to the present embodiment as the X-ray protective clothing, it is possible to provide an X-ray protective clothing that is easy for the wearer to move and has a low burden.

  Next, in order to confirm the effect of the present invention, the following experiment was performed to evaluate the characteristics. The results are shown below.

[Preparation of sample for evaluation]
A sample for evaluation was produced as follows. Each organic polymer material shown in Table 1, the first filler, if necessary, at least one of a plasticizer or a softener, and other powder sulfur, vulcanization accelerator, zinc oxide, stearic acid, aging A predetermined amount of each additive such as an inhibitor was weighed. They were kneaded using a kneader to form a radiation shielding composition. This radiation shielding material composition was processed into a sheet shape using a calender roll, and further vulcanized using a press or a vulcanizing can to obtain a sheet-like sample having a thickness of 1 mm. A sample for evaluation was obtained by cutting the sheet-like molded body into a required size.

[1. Relationship between content of first filler and physical properties]
The relationship between the content of the first filler and the specific gravity, flexibility, and X-ray shielding property of the X-ray shielding material was examined. The results are shown in Table 1. Experiment No. Nos. 3 to 7 are working examples. 1 and 2 and experiment no. 8 is a comparative example. The total of the content of the base material and the content of the first filler does not become 100% by volume because the additive is included in addition.

  The evaluation sheet is an oil-extended ethylene propylene diene rubber (oil-extended EPDM, grade: Esprene 670F, manufactured by Sumitomo Chemical Co., Ltd., specific gravity 0.86, including paraffin oil as a plasticizer) as an organic polymer material, and a first filler. Was prepared based on the method described in “Preparation of Evaluation Sample” above. The “content of the base material” is the total amount of the organic polymer material and the plasticizer (or softener) (when oil-extended EPDM is used, it is the content as oil-extended EPDM).

  About each produced evaluation sheet | seat, specific gravity as an X-ray shielding material was calculated | required, and the lightweight property was evaluated. Further, flexibility and X-ray shielding properties were evaluated by the methods shown below. The results are shown in Table 1.

[Evaluation of flexibility]
A sample cut into a 100 mm × 50 mm rectangle was folded 180 ° into a 50 mm × 50 mm folded shape. Further, a 3 kg weight was placed thereon and held for 30 seconds. The weight was removed, and both the front and back surfaces of the bent portion were visually observed to check for cracks and discoloration.

The flexibility was evaluated according to the following criteria.
Excellent: Cracks on both front and back sides, no discoloration not possible: Cracks or discoloration

[Evaluation of X-ray shielding properties (X-ray shielding properties per unit mass)]
In an X-ray generator in which the target metal is tungsten, the tube voltage is 100 kV, the current is 1 mA, the sample is irradiated with X-rays filtered through a copper additional filter plate having a thickness of 0.5 mm, and the sample is irradiated. The X-ray dose (luminance) transmitted through was measured. The distance between the X-ray source and the detector was 600 mm, and the distance between the X-ray source and the sample was 300 mm. Similar measurements were performed on lead plates of various thicknesses, and calibration curves related to the thickness and brightness of the lead plates were prepared. Using the calibration curve, the thickness of the lead plate corresponding to the luminance of the sample was calculated. The thickness of this lead plate was defined as a lead equivalent (mmPb), which was used as an index of X-ray shielding properties.

Further, the X-ray shielding property per unit mass was determined from the X-ray shielding property. The X-ray shielding per unit mass (indicated as “X-ray shielding” in Table 1) was evaluated according to the following criteria.
Excellent: Lead equivalent (mmPb) / specific gravity (g / cm ³ ) is 0.08 or more Impossible: Lead equivalent (mmPb) / specific gravity (g / cm ³ ) is less than 0.08

  As shown in Table 1, as the content of the first filler increases, the specific gravity of the evaluation sheet as the X-ray shielding material increases and the X-ray shielding properties also increase. On the other hand, the flexibility becomes insufficient when the content of the first filler exceeds 50% by volume. As can be seen from the results in Table 1, the range in which flexibility and X-ray shielding properties are compatible is a range in which the content of the first filler is 20% by volume or more and 50% by volume or less. If the content of the first filler is within this range, the specific gravity of the X-ray shielding material is in an appropriate range of 2.0 or more and less than 4.0.

[2. Characterization]
Next, the formulation was changed and the physical properties were compared. Table 2 shows the composition and evaluation results of each of the examples and comparative examples. In Table 2, Experiment No. 9 to Experiment No. 12 is an example. In addition, Experiment No. 13 to Experiment No. 15 is a comparative example.

  Table 2 shows the type of organic polymer material used, the presence or absence of a plasticizer or softener, the type of filler, and the specific gravity of the X-ray shielding material. The organic polymer materials used are oil-extended ethylene propylene diene rubber (oil-extended EPDM), ethylene propylene diene rubber (EPDM), butyl rubber (IIR), and chlorinated PE (chlorinated polyethylene).

※１ 油展ＥＰＤＭを使用。
※２ 油展ＥＰＤＭ中に、可塑剤としてのパラフィンオイルを含む。

* 1 Oil-extended EPDM is used.
* 2 Oil-extended EPDM contains paraffin oil as a plasticizer.

  As shown in Table 2, Experiment No. 9 to Experiment No. In all the examples shown in No. 12, the X-ray shielding per unit mass was sufficient. In contrast, Experiment No. 13 to Experiment No. In all of the comparative examples shown in FIG. 15, the X-ray shielding properties (X-ray shielding properties per unit mass) were insufficient.

  In addition, Experiment No. containing no plasticizer. In comparison with Experiment No. 11, Experiment No. 9 and experiment no. In 10, the flexibility was improved. Such a lightweight and flexible X-ray shielding material is preferable in that it has high workability and is particularly lightweight and easy to move when applied to an X-ray protective clothing.

  Thus, according to the X-ray shielding material according to the present embodiment, it is possible to provide an X-ray shielding material that is lightweight and has sufficient X-ray shielding ability.

  It should be understood that the embodiments and examples disclosed herein are illustrative in all respects and are not restrictive in any respect. The scope of the present invention is defined by the terms of the claims, rather than the meaning described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The X-ray shielding material of the present application can be applied particularly advantageously in a field where an X-ray shielding material that is lightweight and has sufficient X-ray shielding properties is required.

10 X-ray shielding sheet 20 Base material 30 First filler 40 Protective layer 60 Second filler 100 X-ray shielding laminate

Claims (8)

A base material containing an organic polymer material having a specific gravity of 1.0 or less;
A first filler containing a substance having an effective atomic number of 50 or more and 58 or less dispersed in the base material,
X-ray shielding material whose content of the said 1st filler is 20 volume% or more and less than 50 volume%.   The X-ray shielding material according to claim 1, wherein the base material further contains at least one of a plasticizer and a softening agent.   The X-ray shielding material according to claim 1 or 2, wherein the specific gravity is 2.0 or more and less than 4.0.   The X-ray shielding material according to any one of claims 1 to 3, wherein the first filler is cerium oxide or metallic tin.   The X-ray shielding material according to any one of claims 1 to 4, wherein in the X-ray generator in which the target metal is tungsten, X-rays generated under a tube voltage condition of 80 kV to 150 kV are shielded.   The X-ray shielding material according to any one of claims 1 to 5, further comprising a substance containing at least one element of tungsten and bismuth as the second filler.   The X of any one of claims 1 to 6, wherein the organic polymer material is at least one selected from the group consisting of ethylene propylene diene rubber, butyl rubber, chlorinated butyl rubber, and brominated butyl rubber. Wire shielding material.   The X-ray shielding material according to any one of claims 1 to 7, which is a sheet-like molded body.

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