JP7637044B2 - Radiation-shielding resin composition and method for producing radiation-shielding resin composition - Google Patents

Description

The present invention relates to a radiation shielding resin composition that has excellent radiation shielding ability, economic efficiency, and moldability, and a method for producing the radiation shielding resin composition.

Traditionally, lead or materials containing lead have been widely used as materials to shield against radiation, including X-rays, and to protect the human body. However, although lead is exempt from the RoHS Directive for use in radiation shielding, the lead component is harmful to the human body, and it must be treated as specified hazardous industrial waste when disposed of, so special care must be taken when using it.

In recent years, in light of the above issues, the use of relatively heavy metals such as tungsten, antimony, molybdenum, bismuth, and barium, as well as their compounds, has been considered as radiation shielding materials to replace lead. Various radiation shielding products have been proposed and are in use, in which these metals and metal compounds are mixed with polymeric compounds such as rubber and resin and processed into easy-to-handle shapes.

However, among the above radiation shielding materials, barium sulfate is inexpensive and easy to obtain, but its radiation shielding rate is relatively low. Therefore, in order to obtain a shielding rate equivalent to that of lead, the shielding material must be thick. For this reason, it is mainly used as a building material, such as for the walls of X-ray and CT rooms.

On the other hand, tungsten, antimony, molybdenum, bismuth, and other metals with relatively high shielding rates are expensive, so their compounds are also expensive and not economical.

As a result, cerium compounds, especially cerium oxide, have attracted attention as a new radiation shielding material from the standpoint of economy and shielding properties, and their use is being investigated.

Patent Document 1 discloses a radiation shielding sheet that has high radiation shielding properties by filling an organic polymer material with a shielding material at a high filling rate of 40 to 80 volume percent, and describes that cerium oxide powder can be used as the shielding material.

Patent Document 2 discloses a lightweight X-ray shielding material that includes a base material containing an organic polymer material with a specific gravity of 1.0 or less, and a first filler that includes a substance with an effective atomic number of 50 or more and 58 or less.

Patent No. 4686538 JP 2019-56640 A

The radiation shielding sheet described in Patent Document 1 has a high filling rate of the shielding material, so the viscosity of the composition for forming the radiation shielding sheet is high and molding processing is difficult, leaving room for improvement in terms of productivity. In addition, when the radiation shielding sheet is formed by diluting the composition with a volatile component such as a solvent to facilitate molding processing, there is an issue of air bubbles being generated during molding processing.

The X-ray shielding material described in Patent Document 2 is formed by mixing a first filler, which is a shielding material, with an organic polymer material having a specific gravity of 1.0 or less, i.e., a rubber material such as ethylene propylene diene rubber (EPDM). Here, it is not easy to uniformly disperse the first filler in the rubber material, nor to process the mixed composition into various shapes, leaving room for improvement in productivity.

The present invention has been made in consideration of the above problems, and the object of the present invention is to provide a radiation shielding resin composition that has a small environmental impact, is inexpensive, and has excellent productivity.

A radiation-shielding resin composition according to one embodiment of the present invention is a radiation-shielding resin composition having a resin and a radiation-shielding material dispersed in the resin, the resin being a cured product of a liquid resin raw material and having a specific gravity of more than 1.0, the radiation-shielding material being an inorganic powder containing cerium oxide, the inorganic powder having an average particle size of 0.5 μm or more and less than 10 μm, the content of the radiation-shielding material in the radiation-shielding resin composition being less than 40% by volume, and the radiation-shielding resin composition having a specific gravity of 3.0 or more.

In addition, a method for producing a radiation-shielding resin composition according to another aspect of the present invention includes a step of mixing a liquid resin raw material with a radiation-shielding material to prepare a liquid resin raw material blend, and a step of curing the liquid resin raw material blend, wherein the resin obtained by curing the liquid resin raw material has a specific gravity of more than 1.0, the radiation-shielding material is an inorganic powder containing cerium oxide, the inorganic powder has an average particle size of 0.5 μm or more and less than 10 μm, the content of the radiation-shielding material in the radiation-shielding resin composition is less than 40 volume %, and the radiation-shielding resin composition has a specific gravity of 3.0 or more.

The present invention provides a radiation shielding resin composition that is environmentally friendly, inexpensive, and highly productive.

Hereinafter, an embodiment of the present invention will be described.
The radiation-shielding resin composition according to the present invention has a resin and a radiation-shielding material dispersed in the resin. The resin is a cured product of a liquid resin raw material, and when the liquid resin raw material and the radiation-shielding material are mixed, the liquid resin raw material can easily uniformly disperse the radiation-shielding material. In addition, when a liquid resin raw material blend containing the liquid resin raw material and the radiation-shielding material is cured to form the radiation-shielding resin composition, it is possible to easily mold the liquid resin raw material into a complex shape by using a mold. As a result, the radiation-shielding resin composition according to the present invention has excellent productivity.
In the present invention, the term "liquid" means that the material is in a liquid state at room temperature and pressure, unless otherwise specified.

Each component will be described in further detail below.
<Resin>
In the present invention, the radiation-shielding material is dispersed in a resin, which is a cured product of a liquid resin raw material. The resin obtained by curing the liquid resin raw material has a specific gravity of more than 1.0.
In the present invention, the resin for dispersing the radiation-shielding material itself has a specific gravity of more than 1.0, and is therefore advantageous in terms of radiation resistance performance compared to other organic polymer materials, such as rubber materials, which have a specific gravity of 1.0 or less.

Examples of the resin that can be used in the present invention include urethane-based resins, acrylate-based resins, silicone-based resins, and epoxy-based resins.
Among these, epoxy resins are particularly preferred as the resin. Epoxy resins have good dispersibility of the radiation shielding material and are easy to handle. In addition, epoxy resins have excellent moldability because it is easy to adjust the hardness and elongation of the resulting resin and the viscosity of the resin raw material mixture before curing by selecting the types of monomers and oligomers that are raw materials.

Any epoxy resin can be used as long as the raw material mixture before curing is liquid at room temperature. Examples of such epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, phenol novolac type epoxy resins, alicyclic epoxy resins, heterocyclic epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, bromine-containing epoxy resins, cyclohexyl ring-containing epoxy resins, aliphatic epoxy resins such as propylene glycol diglycidyl ether, and urethane-modified epoxy resins. Two or more of these epoxy resins may be mixed together.

In order to adjust the viscosity of the raw material mixture of the epoxy resin, a reactive diluent or dispersant may be used in combination.
Examples of reactive diluents include glycidyl ether compounds such as butyl glycidyl ether, phenyl glycidyl ether, cresyl glycidyl ether, and glycidyl ethers of aliphatic alcohols.
The dispersant may be any known dispersant, such as DISPERBYK-2055, DISPERBYK-2152, DISPERBYK-2155, or DISPERBYK-145 (all manufactured by BYK Japan KK).

Examples of curing agents used to harden epoxy resins include modified amines such as aliphatic amines, aromatic amines, and ketimines.

It is preferable that the liquid resin raw material does not contain any volatile components such as organic solvents.
When a liquid resin raw material blend containing a liquid resin raw material containing a volatile component and a radiation-shielding material is cured at room temperature, the liquid resin raw material may be cured in a state in which the volatile component is not completely removed. As a result, the radiation-shielding resin composition obtained may have non-uniform radiation-shielding performance or insufficient strength.

In addition, when a liquid resin raw material compound containing a liquid resin raw material containing a volatile component and a radiation shielding material is cured at high temperatures, the volatile component may evaporate, causing bubbles and other defects, which may lead to molding defects. This problem is particularly noticeable when producing a thick radiation shielding resin composition.

<Radiation shielding material>
In the present invention, the radiation shielding material is an inorganic powder containing cerium oxide. Cerium oxide has a relatively large specific gravity of 7.22 g/ ^cm3 and has excellent radiation shielding performance. Furthermore, cerium oxide is highly safe for the human body and is abundantly produced, so it can be obtained relatively cheaply.

The inorganic powder has an average particle size of 0.5 μm or more and less than 10 μm. If the average particle size is 0.5 μm or more, aggregation of the inorganic powder when mixed with the liquid resin raw material can be suppressed, and the occurrence of unevenness on the surface of the molded radiation-shielding resin composition can be suppressed. Furthermore, if the average particle size is less than 10 μm, the viscosity does not become too high, and high fluidity can be maintained, making it easy to mold the radiation-shielding resin composition into a desired shape.

In the radiation-shielding resin composition according to the present invention, the content of the radiation-shielding material is less than 40% by volume. This makes it possible to suppress the settling of the radiation-shielding material when it is mixed into the liquid resin raw material, and to obtain uniform shielding performance. In addition, it is possible to suppress an increase in the viscosity of the liquid resin raw material mixture obtained by mixing the radiation-shielding material into the liquid resin raw material, and by maintaining high fluidity, it is possible to obtain good moldability. The content of the radiation-shielding material in the radiation-shielding resin composition is preferably 15% by volume or more and less than 40% by volume. By making the content of the radiation-shielding material 15% by volume or more, a high shielding effect can be obtained.

The inorganic powder may further contain tungsten. Tungsten has a specific gravity of 19.25, which is relatively high among metals, and a small amount of tungsten can exhibit high radiation shielding performance. On the other hand, tungsten is expensive, and there is a problem that a large amount of _CO2 is emitted when smelting metallic tungsten. Therefore, when the inorganic powder contains tungsten, the content of tungsten in the inorganic powder is preferably 70 mass% or less. This can suppress the precipitation of tungsten, which has a high specific gravity, when the liquid resin raw material and the radiation shielding material are mixed, and can also improve the uniformity of the shielding performance of the radiation shielding resin composition after molding.

The inorganic powder may further contain other known metals or metal compounds used for radiation shielding. When the inorganic powder contains a metal or metal compound other than cerium oxide, the content of cerium oxide in the inorganic powder is preferably 30 mass% or more. This makes it possible to obtain a radiation shielding resin composition that is economical and has excellent radiation shielding properties and has a small environmental impact.

<Additives>
The radiation-shielding resin composition according to the present invention may contain other additives as necessary, such as colorants, plasticizers, dispersants, leveling agents, defoamers, antioxidants, and reaction catalysts.

<Radiation-shielding resin composition>
The radiation-shielding resin composition according to the present invention has a specific gravity of 3.0 or more, which allows it to obtain sufficient radiation-shielding performance.

<Method of producing radiation-shielding resin composition>
The method for producing a radiation-shielding resin composition according to the present invention includes the steps of mixing a liquid resin raw material with a radiation-shielding material to prepare a liquid resin raw material blend, and curing the liquid resin raw material blend.

Below, examples of specific work in each step are shown, but the present invention is not limited to these.
First, the liquid resin raw material (for example, the base resin and the curing agent when the resin is an epoxy resin), the radiation shielding material, and other additives as necessary are weighed into a cup or the like, and each material is mixed and stirred to prepare a liquid resin raw material blend. Examples of the mixing method include propeller mixing using a normal motor, a planetary centrifugal mixer (for example, trade name: Rentaro, manufactured by Thinky Corporation), a mixer (for example, trade name: Ultramix, manufactured by Silverson), etc., but are not particularly limited thereto.

Next, the liquid resin raw material mixture is poured into a mold of the desired shape and cured at room temperature or by heating. The cured product is then removed from the mold to obtain the radiation shielding resin composition.

At this time, it is preferable to prepare the liquid resin raw material composition so that it has a viscosity of 20,000 mPa·s or less. It is more preferable to prepare the liquid resin raw material composition so that it has a pot life capable of maintaining a viscosity of 20,000 mPa·s or less for 10 minutes or more. If the viscosity of the liquid resin raw material composition is 20,000 mPa·s or less, bubbles generated during stirring are easily removed, and bubbles are less likely to remain in the radiation shielding resin composition, so that a decrease in shielding performance can be suppressed. In addition, when the liquid resin raw material composition is poured into a mold, the low viscosity allows the surface of the molded body to be made uniform, and molding defects can be suppressed.

It is preferable that the liquid resin raw material formulation does not contain volatile components. For example, if a volatile component such as an organic solvent is added to the liquid resin raw material formulation in order to reduce the viscosity when the liquid resin raw material formulation is prepared, problems may occur when the liquid resin formulation is cured. Specifically, when the liquid curable resin formulation is cured at room temperature, the liquid resin raw material is cured without completely removing the volatile components, and the shielding performance of the obtained radiation-shielding resin composition may become non-uniform and the strength of the radiation-shielding resin composition may be insufficient. In addition, when the liquid curable resin formulation is cured at high temperatures, the volatile components may evaporate, causing bubbles and the like, which may cause molding defects. This problem is particularly noticeable when producing a thick radiation-shielding resin composition.

The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

The materials used in each of the examples and comparative examples are shown below.
Epoxy resin base 1 (product name: jER825, manufactured by Mitsubishi Chemical Corporation, specific gravity: 1.16)
Epoxy resin base agent 2 (product name: ADEKA RESIN EP-4005, manufactured by ADEKA Corporation, specific gravity: 1.08)
Epoxy resin curing agent (amine) (product name: jER Cure 3080, manufactured by Mitsubishi Chemical Corporation, specific gravity: 1.01)
Polycarbonate diol as a polyurethane resin raw material (product name: Duranol T5650E, manufactured by Asahi Kasei Corporation, specific gravity: 1.16)
Isocyanate as a polyurethane resin raw material (product name: Duranate 24A-100, manufactured by Asahi Kasei Corporation, specific gravity: 1.13)
Cerium oxide (product name: AUERPOL FG50, manufactured by TREIBACHER INDUSTRIE AG, average particle size 3.5 μm)
Cerium oxide (product name: AUERPOL PZ110, manufactured by TREIBACHER INDUSTRIE AG, average particle size 0.5 μm)
Cerium oxide (product name: _CeO2 99.95% yellow, manufactured by TREIBACHER INDUSTRIE AG, average particle size 9.5 μm granular product)
Cerium oxide (product name: _CeO2 99.95% yellow, manufactured by TREIBACHER INDUSTRIE AG, average particle size 20.0 μm granular product)
Cerium oxide (product name: Showlox V, manufactured by Showa Denko K.K., average particle size 0.3 μm)
Tungsten (product name: W-4KD, manufactured by Nippon Shinkinzoku Co., Ltd., average particle size 3.0 μm)
Barium sulfate (product name: W-6, manufactured by Takehara Chemical Industry Co., Ltd., average particle size 4.5 μm)

Example 1
The epoxy resin base 1, the epoxy resin curing agent (amine), and cerium oxide (average particle size 3.5 μm) as a radiation shielding material were mixed in a mass ratio of 16.2:8.8:75.0 (base 1:curing agent:cerium oxide). The mixture obtained was stirred with a mixer (product name: Rentaro, manufactured by Thinky Corporation) for a mixing time of 4 minutes to obtain a liquid resin raw material blend.
The obtained liquid curable resin composition was poured into a Teflon (registered trademark) mold having an internal dimension of length: 100 mm × width: 100 mm × depth: 2 mm, and the liquid resin raw material composition was cured under conditions of 100°C and 2 hours, to obtain a radiation-shielding resin composition.

Example 2
In Example 1, the mass ratio when mixing the main agent 1 of the epoxy resin, the curing agent (amine) of the epoxy resin, and cerium oxide (average particle size 3.5 μm) was changed to 12.3:6.7:81.0 (main agent 1:curing agent:cerium oxide). A radiation-shielding resin composition was obtained in the same manner as in Example 1 except for the above.

Example 3
A radiation-shielding resin composition was obtained in the same manner as in Example 2, except that the type of cerium oxide was changed to one having an average particle size of 0.5 μm.

Example 4
A radiation-shielding resin composition was obtained in the same manner as in Example 2, except that the type of cerium oxide was changed to one having an average particle size of 9.5 μm.

Example 5
In Example 1, tungsten was further used as a radiation-shielding material. A base agent 1 of an epoxy resin, a curing agent (amine) of the epoxy resin, cerium oxide, and tungsten were mixed in a mass ratio of 11.0:6.0:58.1:24.9 (base agent 1:curing agent:cerium oxide:tungsten). A radiation-shielding resin composition was obtained in the same manner as in Example 1 except for the above.

Example 6
In Example 5, the mass ratio when mixing the main agent 1 of the epoxy resin, the curing agent (amine) of the epoxy resin, cerium oxide, and tungsten was changed to 9.7:5.3:42.5:42.5 (main agent 1:curing agent:cerium oxide:tungsten). A radiation-shielding resin composition was obtained in the same manner as in Example 5 except for the above.

(Example 7)
In Example 5, the mass ratio when mixing the main agent 1 of the epoxy resin, the curing agent (amine) of the epoxy resin, cerium oxide, and tungsten was changed to 8.4:4.6:34.8:52.2 (main agent 1:curing agent:cerium oxide:tungsten). A radiation-shielding resin composition was obtained in the same manner as in Example 5 except for the above.

(Example 8)
In Example 5, the mass ratio when mixing the main agent 1 of the epoxy resin, the curing agent (amine) of the epoxy resin, cerium oxide, and tungsten was changed to 7.8:4.2:26.4:61.6 (main agent 1:curing agent:cerium oxide:tungsten). A radiation-shielding resin composition was obtained in the same manner as in Example 5 except for the above.

Example 9
In Example 5, the liquid resin raw material was changed to polycarbonate diol (main agent of urethane resin) and isocyanate (curing agent of urethane resin). Polycarbonate diol, isocyanate, cerium oxide, and tungsten were mixed in a mass ratio of 11.9:5.1:58.1:24.9 (main agent:curing agent:cerium oxide:tungsten). Otherwise, the mixture was stirred and cured in the same manner as in Example 5 to obtain a radiation-shielding resin composition.

(Example 10)
In Example 5, the mass ratio of the main component 1 of the epoxy resin, the curing agent (amine) of the epoxy resin, cerium oxide, and tungsten when mixed was changed to 13.6:7.4:15.8:63.2 (main component 1:curing agent:cerium oxide:tungsten). A radiation-shielding resin composition was obtained in the same manner as in Example 1 except for the above.

(Example 11)
In Example 5, the mass ratio of the epoxy resin base 1, the epoxy resin curing agent (amine), cerium oxide, and tungsten when mixing was changed to 11.0:6.0:58.1:24.9 (base 1:curing agent:cerium oxide:tungsten). Then, the same weight of methyl ethyl ketone (MEK) was mixed as a solvent to obtain a liquid resin raw material blend with a solid content concentration of 50 wt%. A radiation-shielding resin composition was obtained in the same manner as in Example 5 except for the above.

Example 12
In Example 5, an epoxy resin base agent 2 was further used. The mass ratio of the epoxy resin base agent 1, the epoxy resin base agent 2, the epoxy resin curing agent (amine), cerium oxide, and tungsten when mixing them was 5.5:5.5:4.0:34.0:51.0 (base agent 1:base agent 2:curing agent:cerium oxide:tungsten). A radiation-shielding resin composition was obtained in the same manner as in Example 5 except for the above.

(Example 13)
In Example 5, the epoxy resin main agent 2 was used instead of the epoxy resin main agent 1. The mass ratio of the epoxy resin main agent 2, the epoxy resin curing agent (amine), cerium oxide, and tungsten when mixing was 12.3:2.3:34.2:51.2 (main agent 2:curing agent:cerium oxide:tungsten). A radiation-shielding resin composition was obtained in the same manner as in Example 5 except for the above.

(Comparative Example 1)
In Example 1, the mass ratio when mixing the main agent 1 of the epoxy resin, the curing agent (amine) of the epoxy resin, and cerium oxide was changed to 9.1:4.9:86.0 (main agent 1:curing agent:cerium oxide). A radiation-shielding resin composition was obtained in the same manner as in Example 1 except for the above.

(Comparative Example 2)
A radiation-shielding resin composition was obtained in the same manner as in Example 2, except that the type of cerium oxide was changed to one having an average particle size of 0.3 μm.

(Comparative Example 3)
A radiation-shielding resin composition was obtained in the same manner as in Example 2, except that the type of cerium oxide was changed to one having an average particle size of 20.0 μm.

(Comparative Example 4)
In Example 1, barium sulfate was used as the radiation-shielding material instead of cerium oxide. In addition, the main agent 1 of the epoxy resin, the curing agent (amine) of the epoxy resin, and barium sulfate were mixed in a mass ratio of 17.5:9.5:73.0 (main agent 1:curing agent:barium sulfate). A radiation-shielding resin composition was obtained in the same manner as in Example 1 except for the above.

(Comparative Example 5)
In Comparative Example 4, the mass ratio when mixing the main agent 1 of the epoxy resin, the curing agent (amine) of the epoxy resin, and barium sulfate was changed to 10.4:5.6:73.0 (main agent 1:curing agent:barium sulfate). A radiation-shielding resin composition was obtained in the same manner as in Comparative Example 4 except for the above.

(Comparative Example 6)
In Example 1, tungsten and barium sulfate were used as the radiation-shielding material instead of cerium oxide. In addition, the main agent 1 of the epoxy resin, the curing agent (amine) of the epoxy resin, tungsten, and barium sulfate were mixed in a mass ratio of 14.3:7.7:23.4:54.6 (main agent 1:curing agent:tungsten:barium sulfate). Otherwise, a radiation-shielding resin composition was obtained in the same manner as in Example 1.

In Examples 1 to 13 and Comparative Examples 1 to 6, the materials used in the production of the radiation-shielding resins and their mixing ratios are shown in Table 1.
The content (vol %) of the radiation-shielding material in the radiation-shielding resin compositions produced in the above Examples and Comparative Examples was calculated from the specific gravity of each of the liquid resin raw material and the radiation-shielding material used.

[Measurement and Evaluation]
The following measurements and evaluations were carried out on the radiation-shielding resin compositions produced in the above Examples and Comparative Examples. The results are shown in Table 2.

<Specific Gravity>
The specific gravity was calculated by measuring the weight of the radiation-shielding resin composition having a size of 100 mm×100 mm×2 mm produced in each of the above examples and comparative examples.

<Viscosity>
The viscosity of the liquid resin raw material blend was measured by placing 500 ml of the liquid resin raw material blend in a cup and using a B-type viscometer (product name: TVB-15, manufactured by Toki Sangyo Co., Ltd.) with an M4 rotor at a rotation speed of 12 rpm at 25°C.

<Method for measuring average particle size of inorganic powder>
The average particle size of the inorganic powder was measured as follows.
After dispersing 10 mg of inorganic powder in 10 mL of MEK for 1 minute using an ultrasonic disperser, the average particle size was measured using a Microtrac (manufactured by Microtrac Bell Co., Ltd.) The D50 (cumulative percent diameter) of the measured value was taken as the average particle size.

<Moldability>
In the evaluation of moldability, the shape of the radiation-shielding resin composition, the presence or absence of bubbles, and the presence or absence of settling of the radiation-shielding material were judged according to the following criteria: A: none of the items were met, B: only one of the items were met, and C: two or more of the items were met.
Shape: The corners of the test piece are poorly formed, and there are uneven parts on the flat surface.
Air bubbles: The test piece contains air bubbles (φ1mm or more).
Sedimentation of radiation shielding material: Sedimentation of radiation shielding material is observed in the test piece.

<Shielding rate (lead equivalent)>
The shielding factor (lead equivalent) was measured in accordance with JIS Z 4501 at a tube voltage of 100 kV.

All of the radiation-shielding resin compositions according to the examples use cerium oxide as a radiation-shielding material, and are therefore environmentally friendly and economically superior. Furthermore, in the production of the radiation-shielding resin compositions according to the examples, all of them had excellent moldability and were also excellent in productivity.
In particular, particularly excellent moldability was obtained in Examples 1 to 9, 12, and 13, excluding two Examples, namely, Example 10 in which the content of cerium oxide in the inorganic powder was less than 30% and Example 11 in which the liquid resin raw material blend contained a volatile component.

In Comparative Examples 1, 5, and 6, the content ratio of the radiation-shielding material in the radiation-shielding resin composition was 40 vol% or more, and the liquid resin raw material blend had a viscosity of more than 20,000, and could not be molded uniformly, resulting in poor moldability.
In Comparative Example 2, since the radiation-shielding material had an average particle size of less than 0.5 μm, the radiation-shielding material aggregated in the liquid resin raw material blend and could not be molded uniformly. As a result, unevenness was generated on the surface of the obtained radiation-shielding resin composition, and the moldability was poor.
In Comparative Example 3, since the radiation-shielding material had an average particle size of 10 μm or more, the liquid resin raw material blend had a viscosity of more than 20,000 mPa·s, and could not be molded uniformly, resulting in poor moldability.
In Comparative Example 4, the specific gravity of the radiation-shielding resin composition was less than 3.0, and a sufficient shielding effect could not be obtained.

Claims (9)

A radiation-shielding resin composition comprising a resin and a radiation-shielding material dispersed in the resin,
The resin is a cured product of a liquid resin raw material and has a specific gravity of more than 1.0;
The radiation shielding material is an inorganic powder containing cerium oxide,
The inorganic powder has an average particle size of 0.5 μm or more and less than 10 μm,
The content of the radiation-shielding material in the radiation-shielding resin composition is less than 40% by volume,
The radiation-shielding resin composition has a specific gravity of 3.0 or more. The radiation shielding resin composition according to claim 1, wherein the inorganic powder further contains tungsten. The radiation shielding resin composition according to claim 2, wherein the tungsten content in the inorganic powder is 70% by mass or less. The radiation-shielding resin composition according to any one of claims 1 to 3, wherein the resin is at least one selected from the group consisting of urethane-based resins, acrylate-based resins, silicone-based resins, and epoxy-based resins. The radiation shielding resin composition according to claim 4, wherein the resin is an epoxy resin. the radiation-shielding resin composition is a cured product of a liquid resin raw material blend containing the liquid resin raw material and the radiation-shielding material,
The radiation shielding resin composition according to any one of claims 1 to 5, wherein the liquid resin raw material blend has a viscosity of 20,000 mPa·s or less. A step of mixing a liquid resin raw material and a radiation shielding material to prepare a liquid resin raw material blend;
curing the liquid resin raw material blend;
A method for producing a radiation-shielding resin composition comprising the steps of:
The resin obtained by curing the liquid resin raw material has a specific gravity of more than 1.0,
The radiation shielding material is an inorganic powder containing cerium oxide,
The inorganic powder has an average particle size of 0.5 μm or more and less than 10 μm,
The content of the radiation-shielding material in the radiation-shielding resin composition is less than 40% by volume,
The radiation-shielding resin composition has a specific gravity of 3.0 or more. The method for producing a radiation shielding resin composition according to claim 7, wherein the liquid resin raw material blend has a viscosity of 20,000 mPa·s or less. The method for producing a radiation shielding resin composition according to claim 7 or 8, wherein the liquid resin raw material blend does not contain any volatile components.