WO2023211009A1 - Radiation shielding film and preparation method therefor - Google Patents

Abstract

The present application relates to a radiation shielding film using tungsten powder and a preparation method for the radiation shielding film. The radiation shielding film is prepared in the form of an ultra-thin film while still including tungsten particles at high density, as eco-friendly radiation shielding materials that replace lead, and thus may be excellent in both flexibility and radiation shielding ratio, thereby being usefully applicable in radiation shielding suits for medical institutions as well as in various fields requiring radiation shielding films. The radiation shielding film includes tungsten powder and a polymer base, wherein the tungsten powder has an average particle size of 80-200 nm, and the film has a thickness of 0.1-0.025 mm.

Description

Radiation shielding film and method of manufacturing the same

This specification relates to radiation shielding films and methods for manufacturing the same.

Lead is mainly used in the manufacture of radiation shielding in medical institutions. Lead has excellent X-ray shielding performance, processability, and economic efficiency, so it is widely used in various forms in medical institutions. However, as lead use increases, there is a risk of lead poisoning because medical staff and patients are exposed to more lead, and lead disposal is also related to environmental problems. To solve this problem, recently, materials mixed with various eco-friendly shielding materials such as tungsten, bismuth, barium sulfate, and antimony and inorganic materials are being used as radiation shields.

Medical institutions generally require shielding suits for radiation shielding, which require lightness and flexibility to facilitate the user's activities. In other words, the shielding material used in the shielding suit must have sufficient flexibility to not interfere with the medical staff's activities. However, to improve the flexibility of the shielding suit, the content of the polymer material used in manufacturing the shielding material must be increased. This reduces the density of the particle structure of the shielding material, thereby lowering the shielding performance. Conversely, if the content of the polymer material is reduced, the shielding material decreases. There was a problem that the bonding strength between them was low and cracks may appear if a thin shielding sheet was used. Therefore, shielding materials used in medical institutions must have a certain thickness, flexibility, and tensile strength, and must meet complex requirements to demonstrate shielding performance similar to lead. The ideal method is to process and use the shielding material alone, but there is a problem that it is difficult to manufacture the material in the desired form because processability is limited depending on the material.

[Prior art literature]

[Patent Document]

(Patent Document 1) Republic of Korea Patent Publication No. 10-1261340

From one perspective, the problem to be solved by the present disclosure is to provide an ultra-thin radiation shielding film that includes an environmentally friendly radiation shielding material and has excellent flexibility.

From one perspective, the problem that the present disclosure aims to solve is to provide a method for manufacturing the radiation shielding film.

One embodiment of the present disclosure is a radiation shielding film containing tungsten powder and a polymer base, wherein the average particle size of the tungsten powder is 80 to 200 nm and the thickness of the film is 0.01 to 0.025 mm. to provide.

Another embodiment of the present disclosure provides a radiation shielding suit including the radiation shielding film.

Another embodiment of the present disclosure provides a building material for a radiation shielding facility including the radiation shielding film.

Another embodiment of the present disclosure is a method of manufacturing the radiation shielding film,

Splitting tungsten powder with an average particle size of 80 to 200 nm, adding a portion of it to a casting solution containing a polymer base, and stirring to disperse the tungsten powder in the solution, repeating the step two or more times; and

Applying the solution in which the tungsten powder is dispersed to a substrate and pressing and molding it by applying heat;

It provides a method for manufacturing a radiation shielding film, including.

One embodiment of the present disclosure can provide a radiation shielding film that contains tungsten powder at high density and is an ultra-thin film several micrometers thick by uniformly dispersing and compressing nanoparticle-sized tungsten powder into a polymer base. Therefore, the present disclosure can be usefully used in various industrial fields and various products that require radiation shielding films, such as medical or construction fields that require ultra-light and ultra-thin films with high radiation shielding rates.

[Correction 24.04.2023 pursuant to Rule 91]
1A and 1B are field emission scanning electron microscope (FESEM) images for confirming the distribution of tungsten powder particles of a radiation shielding film according to an embodiment of the present disclosure and a comparative example manufactured according to the prior art.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings.

The embodiments of the present invention disclosed in the text are illustrative only for illustrative purposes, and the embodiments of the present invention may be implemented in various forms and should not be construed as limited to the embodiments described in the text. . The present invention can make various changes and take various forms, and the embodiments are not intended to limit the present invention to the specific disclosed form, but all changes, equivalents, or substitutes included in the spirit and technical scope of the present invention. It should be understood as including.

Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, terms such as “comprise” or “have” are intended to designate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, and one or more other features The presence or addition of elements, numbers, steps, operations, components, parts or combinations thereof is not excluded.

One embodiment of the present disclosure is a radiation shielding film containing tungsten powder and a polymer base. The average particle size of the tungsten powder contained in the film is 80 to 200 nm, and the film has a thickness of 0.01 to 0.025 mm. can be provided.

As an example, the film may be a lead-free film. More specifically, the film may contain only tungsten as a radiation shielding material. The present disclosure does not contain lead, so it is safe for the human body and harmless to the environment, and can be usefully used in the medical field and other fields that require radiation shielding performance.

As an example, the film may include 88 to 92% by weight of the tungsten powder based on the total weight of the film. Specifically, the tungsten powder may be included in more than 88% by weight, more than 89% by weight, more than 90% by weight, more than 91% by weight, or more than 91.9% by weight, and less than 92% by weight, more than 91% by weight, based on the total weight of the radiation shielding film. % or less, 90% by weight or less, 89% by weight or less, or 88.1% by weight or less. If the tungsten powder is included less than 88% by weight, the radiation shielding ability may be lowered, and if it is more than 92% by weight, the polymer base content may be relatively too small, making it difficult to form a film.

As an example, the tungsten powder may be uniformly dispersed in the film.

As an example, the average particle size of the tungsten powder may be 80 to 200 nm. At this time, the particle size refers to the largest diameter within the particle. The average particle size refers to the average particle size of at least 90% or more of tungsten powder included in the radiation shielding film. Specifically, the average particle size of the tungsten powders included in the radiation shielding film is at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, or 97%. , may mean the average value of the largest diameter within the particles of 98% or more or 99% or more of the powders. More specifically, the average of the particle sizes is 80 nm or more, 85 nm or more, 90 nm or more, 95 nm or more, 100 nm or more, 110 nm or more, 120 nm or more, 130 nm or more, 140 nm or more, 150 nm or more, 160 nm or more. Can be greater than or equal to 170 nm, greater than 180 nm or greater than 190 nm, and less than or equal to 200 nm, less than or equal to 190 nm, less than or equal to 180 nm, less than or equal to 170 nm, less than or equal to 160 nm, less than or equal to 150 nm, less than or equal to 140 nm, less than or equal to 130 nm, and less than or equal to 120 nm. It may be smaller than 110 nm, smaller than 100 nm, smaller than 90 nm, or smaller than 85 nm. If the particle size is outside the above range, radiation shielding performance may be lowered, or the formation or processability of an ultra-thin film may be reduced.

As an example, the thickness of the film may be 0.01 to 0.025 mm. Specifically, the thickness of the film may be 0.01 mm or more, 0.015 mm or more, 0.02 mm or more, or 0.023 mm or more, and may be 0.025 mm or less, 0.022 mm or less, 0.02 mm or less, 0.015 mm or less, or 0.012 mm or less. If the film thickness is less than 0.01 mm, radiation shielding performance may be reduced or the film may crack due to low tensile strength. Even when the film thickness exceeds 0.025 mm, flexibility may decrease and cracks may occur in the film, and an increase in film thickness and weight may cause inconvenience when used in clothing such as radiation shielding suits, limiting the range of use.

As an example, the polymer base is not limited as long as it has excellent thermal stability, but may include, for example, polyethylene, high-density polyethylene, or a combination thereof.

In addition, an embodiment of the present disclosure is a method of manufacturing the radiation shielding film,

Splitting tungsten powder with an average particle size of 80 to 200 nm, adding a portion of it to a casting solution containing a polymer base, and stirring to disperse the tungsten powder in the solution, repeating the step two or more times; and

Applying the solution in which the tungsten powder is dispersed to a substrate and pressing and molding it by applying heat;

A method for manufacturing a radiation shielding film comprising a can be provided.

As an example, the method may further include grinding the tungsten powder to produce tungsten powder having an average particle size of 80 to 200 nm. At this time, the step of pulverizing the tungsten powder may include ultrasonic pulverizing the tungsten powder five or more times to 200 nm or less using a pulverizer.

As an example, the grinding step may further include a drying step after grinding the tungsten powder. Specifically, the drying temperature and time of the drying step may vary depending on the amount of pulverized tungsten powder. For example, the drying temperature may be 40 to 80°C, more specifically 50 to 70°C. For example, the drying time may be 15 to 35 hours, more specifically 20 to 28 hours.

As an example, the manufacturing method may further include preparing a casting solution by dissolving the polymer base in a solvent before dispersing the tungsten powder in the casting solution. As an example, the type of solvent is not limited as long as it can dissolve the polymer base used, and may include, for example, N-dimethylformamide (DMF). As an example, the polymer base may be completely dissolved in a solvent, and the step of removing internal bubbles by leaving the solution for a certain period of time may be further included. The leaving time may be, for example, 12 hours or more, 13 hours or more, 14 hours or more, or 15 hours or more.

As an example, the step of dispersing the tungsten powder in the solution may be performed by a particle dispersion method. As an example, the step of dispersing the tungsten powder in the solution may be repeated 2 or more times, 3 or more times, 4 or more times, or 5 or more times. One embodiment of the present disclosure improves mixing by applying a repetitive time-split stirring technique in which part of the tungsten powder is added to the casting solution and stirred, and then another part is added to the casting solution and stirred. Through this, the present disclosure can prevent agglomeration of tungsten powders and produce a film in which tungsten powders are uniformly dispersed.

As an example, the stirring speed may be 2000 to 4000 rpm, specifically 2000 rpm or more, 2500 rpm or more, 3000 rpm or more, or 3500 rpm or less, and may be 4000 rpm or less, 3500 rpm or less, 3000 rpm or less, or 2500 rpm or less. You can. As an example, the stirring time may be 10 to 15 minutes, specifically 10 minutes or more, 11 minutes or more, 12 minutes or more, 13 minutes or more, or 14 minutes or more, but may be 15 minutes or less, 14 minutes or less, 13 minutes or less, It may be 12 minutes or less or 11 minutes or less.

As an example, the casting solution may further include a plasticizer as an additive to remove micropores of the radiation shielding film and improve flexibility. For example, the plasticizer may include diisononyl phthalate (DINP).

As an example, the step of applying the solution in which the tungsten powder is dispersed to the film may further include removing foreign substances contained in the casting solution using a filter before application.

As an example, the step of compressing and molding by applying heat may be performed using a thermal hydraulic press machine, but is not limited thereto. At this time, the temperature of heat applied in the compression molding step may be 60 to 90°C, and the pressure applied may be 10 to 30 MPa.

Conventionally, an extrusion method was used to manufacture radiation shielding films, but in this case, there was a problem that high-density filling of nanometer-sized tungsten particles was difficult. Accordingly, conventionally, radiation shielding materials were manufactured in the form of sheets over a certain thickness rather than in the form of thin films, and silicone etc. were mixed for flexibility, but in this case, it was not easy to cut them into the desired shape or size due to the thick and hard material of the shielding sheets. In addition, there was a disadvantage in that the density of the radiation shielding material was low and it was not uniformly distributed within the sheet, so it did not show consistent shielding performance. However, the present disclosure uniformly disperses tungsten particles in a solution using a split stirring process and processes them into a film form by extrusion molding, thereby manufacturing an ultra-thin film of 0.01 mm or less while filling nanometer-sized tungsten particles at high density. This not only improves the radiation shielding ability by more than 20% compared to the same thickness, but also improves the tensile strength by more than 30%. In addition, the film according to the present disclosure is not only light and thin, but also has excellent flexibility and is easy to cut with scissors or a knife, so the physical burden can be greatly reduced when used as a lining for clothing such as radiation shielding clothing.

As an example of the present disclosure, the x-ray shielding rate of the radiation shielding film may be 70 to 95% when measured in a tube voltage range of 60 to 120 kVp. Specifically, the x-ray shielding rate of the film is 80 to 90% when measured in a tube voltage range of 60 kVp, 75 to 85% when measured in a tube voltage range of 80 kVp, 70 to 80% when measured in a tube voltage range of 100 kVp, and 120 kVp. When measured in the tube voltage range, it may be 65 to 80%.

As an example, the tensile strength of the radiation shielding film may be 10 to 15 MPa. Specifically, the tensile strength may be 10 MPa or more, 11 MPa or more, 12 MPa or more, or 13 MPa, and may be 15 MPa or less, 14 MPa or less, 13 MPa or less, or 12 MPa or less. Unlike the conventional radiation shielding film, which had a low tensile strength of 8 MPa or less when manufactured at a thickness of 0.01 to 0.025 mm, causing problems in use after processing, the film according to the present disclosure has tensile strength even though it contains a high content of tungsten powder. Since the strength is 10 MPa or more, more specifically 12 MPa or more, processability and usability are excellent.

One embodiment of the present disclosure can provide a radiation shielding suit (radiation shielding clothing) or a building material for a radiation shielding facility including the radiation shielding film described above. For example, the radiation shielding film may be a radiation shielding suit, radiation shielding curtain, protective wall, wallpaper, construction interior material, etc., and may be specifically for use in the medical field, but is not limited thereto.

Hereinafter, the present invention will be described in more detail through examples. These examples are only for illustrating the present invention, and it will be obvious to those skilled in the art that the scope of the present invention should not be construed as limited by these examples.

[Example 1]

A radiation shielding film according to an embodiment of the present disclosure was manufactured in the following manner.

First, tungsten powder pulverized to 200 nm or less (manufacturer: Beijing Tianlong tungsten Technology Co. Ltd., Beijing, China) was placed in an oven and dried at 60°C for 24 hours. In addition, polyethylene as a polymer material was completely dissolved in DMF (N-dimethylformamide, 99.5%) solvent, and then left for at least 12 hours to remove internal bubbles to prepare a caster solution. A portion of the pulverized tungsten powder was added to the prepared caster solution, and stirred using a stirrer at a speed of 3000 rpm for 10-15 minutes to uniformly disperse the tungsten particles in the caster solution. A portion of the remaining tungsten powder was similarly added and stirred into the caster solution, and this division and stirring process was repeated several times. After all the tungsten powder was added and dispersed in the caster solution, DINP (Diisononyl phthalate) was added as a plasticizer to remove micropores.

After removing foreign substances from the caster solution through a filter, it was applied to a film, heated at 60-90°C, pressed and molded at a pressure of 20 MPa, and processed into a film form.

The content of tungsten powder contained in the manufactured film was 92% by weight based on the total weight of the film, and the thickness of the film was 0.01mm.

[Comparative Example 1]

As a comparative example of the present disclosure, a shielding sheet was manufactured according to the prior art using tungsten powder (manufacturer: Beijing Tianlong tungsten Technology Co. Ltd., Beijing, China) ground to an average particle size of 10-200 μm. The content of tungsten powder contained in the manufactured film was 88 to 92% by weight based on the total weight of the film, and the thickness of the film was 0.01 mm.

[Test Example 1]

To confirm the particle distribution of tungsten powder in the radiation shielding film manufactured according to an example of the present disclosure, a field emission scanning electron microscope (FESEM) image was taken and shown in FIGS. 1A and 1B. As a result, as shown in FIG. 1A, the shielding film according to Example 1 of the present disclosure had tungsten powder of 200 nm or less uniformly dispersed at high density within the film, but Comparative Example 1 according to the prior art, as shown in FIG. 1B. It can be seen that the particle size of the tungsten powder is micro-sized and is partially agglomerated and unevenly dispersed within the film. In addition, since Comparative Example 1 omitted the process of solvent dissolution and leaving for 12 hours at a time, there is a greater possibility of voids between particles compared to the film of the present disclosure.

[Test Example 2]

The following experiment was performed to confirm the radiation shielding performance and tensile strength of the tungsten powder in the radiation shielding film manufactured according to an example of the present disclosure.

The radiation shielding rate was performed using Equation 1 below.

[Equation]

Here, S is the shielding ratio, To is the incident dose (mR), and T is the transmitted dose (mR). Specifically, T is the exposure amount measured with a shielding film between the X-rays and the detector, and To is the exposure amount measured without a shielding film between the X-rays and the detector. Under the measured dose conditions, the tube current was 200 mA and the irradiation time was 0.1 seconds. Exposure was measured 10 times using an X-ray generator (DK-525, Toshiba E7239X, Tokyo) and a calibrated ion chamber (Model PM-30, PR-18), and the average value was used.

Tensile strength was measured according to the KS K 0520:2015 test method.

Radiation blocking rate (%)

	60kVp	80kVp	100kVp	120kVp
Example 1	82.09	78.53	73.29	70.8
Comparative Example 1	61.01	50.53	41.02	40.66

	tensile strength (MPa)
Example 1	12.8
Comparative Example 1	8

As a result, as shown in Table 1, Example 1 according to the present disclosure contains tungsten powder of fine particles of 200 nm or less, so that although it has the same thickness as Comparative Example 1, tungsten powder is contained in a high content of 92% by weight. Since it was uniformly dispersed, it was found to have significantly better radiation blocking performance than Comparative Example 1. In addition, as shown in Table 2, under the same thickness conditions, the tensile strength of Comparative Example 1, which is an existing shielding sheet, was 8 MPa, but Example 1 of the present disclosure had a tensile strength of 12.8 even though it contained a high content of 92% by weight of tungsten powder. It has been improved to MPa, and it can be confirmed that it has excellent quality without cracking when used.

Claims (12)

1. It is a radiation shielding film containing tungsten powder and a polymer base,

   The average particle size of the tungsten powder is 80 to 200 nm,

   A radiation shielding film, wherein the film has a thickness of 0.01 to 0.025 mm.
2. The radiation shielding film of claim 1, wherein the film contains 88 to 92% by weight of the tungsten powder based on the total weight of the film.
3. The radiation shielding film of claim 1, wherein the tungsten powder is uniformly dispersed in the film.
4. The radiation shielding film of claim 1, wherein the polymer base includes polyethylene or high-density polyethylene.
5. The radiation shielding film of claim 1, wherein the x-ray shielding rate of the radiation shielding film is 70 to 95% when measured in a tube voltage range of 60 to 120 kVp.
6. The radiation shielding film of claim 1, wherein the radiation shielding film has a tensile strength of 10 to 15 MPa.
7. A radiation-shielding suit comprising the radiation-shielding film according to any one of claims 1 to 6.
8. A building material for a radiation shielding facility comprising the radiation shielding film according to any one of claims 1 to 6.
9. A method for producing the radiation shielding film of claims 1 to 6,

   Splitting tungsten powder with an average particle size of 80 to 200 nm, adding a portion of it to a casting solution containing a polymer base, and stirring to disperse the tungsten powder in the solution, repeating the step two or more times; and

   Applying the solution in which the tungsten powder is dispersed to a film and pressing and molding it by applying heat;

   Method for producing a radiation shielding film, including.
10. The method of claim 9, wherein the stirring speed is 2000 to 4000 rpm and the stirring time is 10 to 15 minutes.
11. The method of claim 9, wherein the temperature of heat applied in the compression molding step is 60 to 90° C., and the pressure applied is 10 to 30 MPa.
12. The method of claim 9, further comprising grinding the tungsten powder to produce tungsten powder having an average particle size of 80 to 200 nm.

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