KR102052421B1 - Manufacturing Method For Radiation Protecting Sheet And Radiation Protecting Sheet Using The Same - Google Patents

Abstract

The present invention discloses a method of manufacturing a radiation shielding sheet for manufacturing a radiation shielding sheet comprising a skin coating film made of a urethane resin material and a multilayer radiation shielding film coated on one side of the skin coating film. According to one aspect of the present invention, there is provided a method of manufacturing a radiation shielding sheet: a urethane solution containing a urethane resin and a solvent is applied to a surface of a release paper and thermally dried to form the skin coating film. Skin coating film coating step; And repeatedly applying a radiation shielding solution containing a urethane resin, a solvent, and bismuth powder on the skin coating film and drying the film a plurality of times, to form a shielding film on the skin coating film.
According to the present invention, by using bismuth powder instead of lead harmful to the human body, it is possible to lighten the radiation shielding garment and have a good feeling of wearing, and the flexibility can be improved as compared with the lead rubber sheet, so it is easy to handle and store. In addition, the flexibility and ease of operation of the seat can be applied to various designs of clothing and protective equipment for various uses.

Description

Method for manufacturing radiation shielding sheet and radiation shielding sheet using the same {Manufacturing Method For Radiation Protecting Sheet And Radiation Protecting Sheet Using The Same}

The present invention relates to a method of manufacturing a radiation shielding sheet and a radiation shielding sheet produced thereby, and more particularly, to a radiation shielding sheet having a radiation shielding film having a multilayer structure containing urethane resin-bismuth powder, and a method of manufacturing the same. will be.

In places where radiation occurs or exists, for example, x-ray imaging and radiotherapy rooms in hospitals, radiation zones in nuclear power plants, radiation transmission laboratories, and sites that handle x-ray clearance inspection equipment, a person at that location is exposed to radiation. You are in danger of becoming.

In general, it is well known that radiation such as X-rays and gamma rays causes many serious diseases and disorders, including carcinogenesis, genetic disorders, and cataracts.

Accordingly, in 1934, the International Commission on Radiation Protection was launched to limit the use of radiation (0.2 R / day), and in 1977 the International Recommendation on Radiation Protection (ICRP-26) was adopted, followed by X-ray diagnosis, treatment and nuclear Guidelines for reducing the exposure of patients, workers and carers to medicine have been published, and countries have enacted laws on the use of radiation.

As described above, radiation exposure is very harmful to the human body, so it should be limited as much as possible.However, those who directly or indirectly deal with radiation, such as those in hospitals, doctors, nurses, and nuclear facility personnel, may continue to be exposed to radiation due to their work characteristics. Be particularly careful.

In addition, exposure to radiation should be minimized even in patients undergoing radiographic imaging or radiation therapy due to disease, and human tissues such as organs vulnerable to radiation or other areas except the target area for examination or treatment, that is, the target area. It is preferable to protect suitably from silver radiation.

Currently, in order to protect workers who perform work in places exposed to radiation, such as repair or inspection of nuclear power plants, radiation shielding clothing is worn to protect them from the danger of exposure. Is being provided.

As a method for shielding the radiation exposure, it is common to wear a gown (radiation protective gown) to which a lead component is dispersed and then extruded and molded into a rubber.

Lead rubber, also known as rubber lead, is a rubber that contains a large amount of lead. It is usually manufactured in the form of sheets to be used as a radiation protection material, and as a radiation protection product to which lead rubber is applied, apron made of lead rubber (lead-rubber apron), gloves (lead-rubber gloves) and radiographic clothing (radiation gowns).

Radiation shielding garments, such as gowns made of lead rubber, are effective for shielding radiation, but are very heavy, inconvenient to handle and provide a firm fit. More specifically, the lead rubber radiation shielding sheet should have a thickness sufficient to block radiation according to the purpose of use, but the radiation shielding suit to which the lead rubber radiation shielding sheet is applied has a heavy and hardness. Therefore, it is difficult to wear and very uncomfortable behavior in the worn state.

In particular, the radiation used in hospitals is relatively low dose compared with radiation generated in nuclear power plants, and the risk of direct radiation exposure is high and the risk of indirect exposure due to radiation diffraction is high. You have to bear the inefficiency of wearing and handling your work.

On the other hand, for lighter radiation shielding clothing, US Patent No. 3,194,239 discloses a method of manufacturing radiation absorbing fibers using an alloy wire for radiation absorption, but this is a problem of poor flexibility and radiation shielding have.

Republic of Korea Patent No. 10-1145703 U.S. Patent No. 3,194,239

An object of the present invention is to provide a method for producing a radiation shielding sheet capable of appropriate radiation protection without using lead harmful to a human body, and a radiation shielding sheet thereby.

A specific object of the present invention is a method for producing a flexible and excellent radiation shielding sheet using a fine bismuth powder and a urethane resin, and a radiation shielding sheet produced by a radiation shielding composition comprising a fine bismuth powder and a urethane resin. It is to provide.

One embodiment of the present invention provides a method of manufacturing a radiation shielding sheet: a radiation containing urethane resin, solvent and bismuth powder in order to form a multilayered radiation shielding film on one side of the base sheet; It provides a method of manufacturing a radiation shielding sheet comprising a shielding film forming step of laminating a plurality of radiation shielding film by applying a shielding solution to one side of the base sheet and repeating a plurality of times.

The manufacturing method of the radiation shielding sheet: before the shielding film forming step, the urethane solution containing a urethane resin and a solvent is applied to the surface of the base sheet and thermally dried to coat the radiation shielding film on the surface of the base sheet Skin coating film forming step of forming a skin coating film of the urethane resin material may be further included.

Accordingly, one embodiment of the present invention provides a method of manufacturing a radiation shielding sheet for producing a radiation shielding sheet comprising a skin coating film made of a urethane resin material and a multilayer radiation shielding film coated on one side of the skin coating film: Urethane Resin Skin coating film coating step of forming a skin coating film by applying a urethane solution containing a) and a solvent (Solvent) to the surface of the base sheet and heat-dried; And repeatedly forming a radiation shielding solution containing a urethane resin, a solvent, and bismuth powder on the skin coating film and drying a plurality of times, thereby forming a shielding film forming the multilayer radiation shielding film on the skin coating film. Provided is a method for producing a shielding sheet.

The skin coating layer coating step; The urethane solution is applied to the release paper in a thickness of 0.12mm to 0.18mm. More specifically, the skin coating film coating step; The urethane solution may include the step of applying a thickness of 0.14mm to 0.16mm on the release paper.

The base sheet is an embossed release paper having an embossed convex surface and detachable from the skin coating film; The skin coating layer coating step may include applying a urethane solution to a surface of the release paper to a predetermined thickness and then drying the film.

The urethane solution to form the skin coating film; With respect to 100 parts by weight of the urethane resin, but includes 50 to 70 parts by weight of the solvent, but is not limited thereto.

Forming the shielding film; Sequentially laminating the radiation shielding solution on the skin coating film N (natural number; 3 ≦ N ≦ 8) so that the cumulative coating thickness of the radiation shielding solution applied on the skin coating film is 1 mm to 1.7 mm. do.

More specifically, the shielding film forming step; Forming a first shielding coating film on the skin coating film to a thickness of 0.13 mm to 0.27 mm and thermally drying; A second shielding film forming step of applying the radiation shielding solution to a thickness of 0.18mm to 0.32mm on the first shielding film and then heat-drying it; A third shielding coating film forming step of applying the radiation shielding solution to a thickness of 0.18mm to 0.32mm on the second shielding coating film and then thermally drying the film; A fourth shielding film forming step of applying the radiation shielding solution to a thickness of 0.23mm to 0.37mm on the third shielding film and then heat-drying it; And a fifth shielding coating film forming step of applying the radiation shielding solution to a thickness of 0.28mm to 0.42mm on the fourth shielding coating film and then thermally drying the film.

Forming the shielding film; Sequentially laminating the radiation shielding solution on the skin coating film N (4 ≦ N ≦ 6) times so that the cumulative coating thickness of the radiation shielding solution applied on the skin coating film is 1.25 mm to 1.45 mm. Can be.

The radiation shielding solution; It may include 30 to 38% by weight of the urethane resin, 15 to 27% by weight of the solvent, and 40 to 50% by weight of the bismuth powder.

The bismuth powder of the radiation shielding solution forming the multilayered radiation shielding film includes fine particles having an average particle size (r) of 0 <r ≦ 5 μm, more specifically granular bismuth nanoparticles. Preferred for

Method for producing a radiation shielding sheet according to the present invention; In order to manufacture the radiation shielding solution, further comprising a milling step of milling the raw material composition containing the urethane resin and the bismuth powder to mix the urethane resin and the bismuth powder and to grind and disperse the bismuth powder can do.

As the bismuth powder of the raw material composition, fine particles having an average particle size of 0.5 μm to 6 μm may be used, but are not limited thereto.

Another embodiment of the present invention is a skin coating film made of urethane resin coated on the surface of the release paper having a convex surface of the embossed shape; And a radiation shielding film comprising a plurality of radiation shielding films including a plurality of shielding films laminated on the skin coating film. The shielding films may include 110 to 160 parts by weight of bismuth powder based on 100 parts by weight of a urethane resin. It includes.

The sum of the thickness of the skin coating film and the thickness of the radiation shielding film is 0.28 mm to 0.32 mm; The radiation shielding film is a laminated structure of 4 to 6 layers, but is not limited thereto.

The radiation shielding film may include a first shielding film formed on the skin coating film, a second shielding film formed on the first shielding film, a third shielding film formed on the second shielding film, and the third shielding film A fourth shielding coating film formed thereon and a fifth shielding coating film formed on the fourth shielding coating film; The amount of bismuth powder contained in the fifth shielding coating film is greater than the amount of bismuth powder contained in the first shielding coating film; The amount of the bismuth powder contained in the second to fourth shielding coatings is greater than or equal to that of the bismuth powder contained in the first shielding coating.

The bismuth powder of the shielding coating film may include fine particles having an average particle size r of 0 <r ≦ 5 μm, more specifically nanoparticles.

According to the method for producing a radiation protection sheet and the radiation protection sheet according to the present invention has the following effects.

First, according to the present invention, by using bismuth powder instead of lead harmful to the human body, it is possible to reduce the weight of the radiation shielding suit and to manufacture a protective clothing with good fit, and to improve flexibility compared to the lead rubber sheet, thus handling and storage are convenient. . In addition, the flexibility and ease of operation of the sheet allows it to be applied to clothing of various designs and radiation protection equipment for various purposes.

Secondly, according to the present invention, it is possible to sufficiently secure the thickness of the radiation protection sheet, to prevent the phenomenon of cracking or crushing of the radiation protection sheet when the radiation protection sheet is bent or folded, and the structural stability of the radiation shielding film is secured, Since the bismuth powder can be evenly dispersed, the occurrence of variation in protection performance for each site can be minimized or prevented.

Third, according to the present invention, an excellent property in which the thickness and weight of the radiation shielding sheet is differentiated from existing lead rubber sheets and other lead-free protective fabrics (radiation shielding sheet) can be realized. More specifically, a single shielding sheet or a plurality of shielding sheets may be superimposed in order to satisfy radiation protection standards and have similar shielding ability, and have a lead equivalent value of, for example, 0.50 mm Pb. The present invention can be reduced in weight by 40% or more compared with lead rubber, compared with other shielding materials such as lead-free radiation shielding sheets, for example, antimony.

Fourth, according to the present invention, since a urethane skin coating film is formed on a release paper having an embossed surface shape, and a radiation shielding film having a multilayer structure is formed on the skin coating film, the thickness deviation of each part of the shielding film forming an individual layer of the radiation shielding film. Can be minimized or prevented, the interlayer bonding force of the skin coating film and the radiation shielding film and the interlayer bonding force of the radiation shielding film can be secured, and the divergence of solvent from the low layer shielding film to the high layer shielding film (evaporation) ) Can be made stable, so that the thickness of the radiation shielding film can be increased, and variations in the thickness direction of the radiation shielding film can be minimized or prevented.

Fifth, the radiation shielding sheet according to the present invention has a single layer of radiation shielding film produced using the same radiation shielding solution as the present invention and has a higher flexibility and flexibility than the radiation shielding sheet having the same overall thickness. This phenomenon of opening or splitting and separation of the interlayer bonding interface of the radiation shielding film can be prevented, and can have excellent radiation shielding performance.

The features and advantages of the present invention may be better understood with reference to the following drawings in conjunction with the following detailed description of embodiments of the invention, of which:
1 is a cross-sectional view showing a radiation shielding sheet (protective sheet) according to an embodiment of the present invention;
2 is an enlarged photograph of the surface of a base sheet (release paper) having an emboss surface;
3 is a schematic view of a three roll mill;
4 is a view schematically showing the grinding / dispersion process of particles by a three roll mill;
5 is a photograph showing granular bismuth powder having an average particle size of 3 μm to 5 μm;
6 is a photograph showing granular bismuth powder having an average particle size of 1 μm to 4 μm;
FIG. 7 is a photograph showing a state in which granular bismuth powder having an average particle size of 4 µm to 20 µm and a bismuth powder having a rod-like shape are mixed;
8 is a photograph showing a dispersion state of bismuth powder shown in FIG. 5;
9 is a photograph showing a dispersion state of bismuth powder shown in FIG. 6;
10 is a photograph showing a dispersion state of bismuth powder shown in FIG. 7;
11 is an enlarged photograph of the surface of a radiation protection sheet according to Example 1;
12 is an enlarged photograph of the surface of a radiation protection sheet according to Example 2;
13 is a diagram illustrating a shielding performance inspection position of the radiation shielding sheet; And
14 is a durability test report of the radiation shielding sheet according to the present invention.

Hereinafter, preferred embodiments of the present invention, in which the object of the present invention can be specifically realized, are described with reference to the accompanying drawings. In describing the present embodiment, the same name and the same reference numerals are used for the same configuration and additional description thereof will be omitted below.

First, a method of manufacturing a radiation shielding sheet and a radiation shielding sheet 1 (protective sheet) according to an embodiment of the present invention will be described with reference to FIG. 1.

Manufacturing method of the radiation shielding sheet 1 according to an embodiment of the present invention (hereinafter referred to as "protective sheet manufacturing method"), in order to form a radiation shielding film of a multilayer on one side of the base sheet (Base Sheet 10), Applying a radiation shielding solution containing a urethane resin, a solvent (Solvent) and bismuth powder to one side of the base sheet and drying a plurality of times, the radiation shielding film 100 of the multilayer A shielding film forming step of forming a laminate is included.

The radiation shielding film 100 may be directly coated on the surface of the base sheet 10, but may be indirectly coated on the surface of the base sheet 10 through another layer as described below. .

In the method of manufacturing a radiation shielding sheet according to the present embodiment, before the shielding film forming step, a urethane solution containing a urethane resin and a solvent is applied to the surface of the base sheet 10 and thermally dried to form the base sheet 10. Skin coating film forming step of forming a skin coating film 200 of the urethane resin material for the coating of the radiation shielding film 100 on the surface of the).

The base sheet 10 is a sheet forming a bottom frame for forming a radiation shielding sheet, but may be a fabric, for example, a woven fabric, a knitted fabric or a nonwoven fabric, but in this embodiment, the radiation shielding film 100 having a multilayer structure is stably implemented. To this end, a release paper is exemplified as the base sheet 10.

The base sheet 10 is a release paper, that is, an embossed release paper, which has an embossed convex surface and is detachable from the skin coating film 200. In addition, the skin coating film coating step may include applying a urethane solution to a surface of the release paper 10 to a predetermined thickness and then drying the film.

Accordingly, one embodiment of the present invention is a method of manufacturing a radiation shielding sheet for producing a radiation shielding sheet comprising a skin coating film made of a urethane resin material and a multilayer radiation shielding film coated on one side of the skin coating film. Skin coating film coating step of forming the skin coating film 200 by applying a urethane solution containing to the base sheet 10, for example, the surface of the release paper described above and heat-dried, and radiation containing a urethane resin, a solvent and bismuth powder And a shielding film forming step of laminating and forming the shielding solution on the skin coating film 200 and drying the plurality of times, laminating the radiation shielding film 100 on the skin coating film 200.

The skin coating layer coating step may include applying the urethane solution to the surface of the base sheet 10 in a thickness of 0.12 mm to 0.18 mm. That is, the urethane solution for forming the skin coating film 200 is applied to the surface of the release paper in a thickness of 0.12mm to 0.18mm, when the solvent contained in the urethane solution by heat drying (evaporation) urethane solution coating layer As the thickness of the (base coating layer) shrinks, a urethane resin skin coating film 200 is formed on the surface of the release paper 10.

The skin coating film 200 stably bonds the radiation shielding solution containing bismuth particles dispersed therein, more specifically, the radiation shielding film 100 to the release paper 10, and the surface curved state of the release paper 100 is multilayered. It helps to be transferred to the interlayer interface of the radiation shielding film 100 having the structure. Therefore, the interlayer bonding force of the radiation shielding sheet 1 according to the present embodiment may be enhanced.

When the skin coating film 200 is formed, if the coating thickness of the urethane solution is less than 0.12 mm, the coating workability of the urethane solution is lowered and the radiation shielding film 100 cannot be stably fixed. Partial thickness variation may occur, affecting the thickness of the protective sheet and preventing the smooth dissipation of the solvent.

More specifically, in view of the coating workability of the urethane solution, the fixing force of the radiation shielding film 100 and the thickness variation of each part in the skin coating film and the smooth dissipation of the solvent, the urethane solution is on the base sheet 10, that is, the release paper. It is preferable to apply the thickness of 0.14mm to 0.16mm.

The urethane solution for forming the skin coating film 200 includes 50 to 70 parts by weight of the solvent, more specifically 55 to 65 parts by weight based on 100 parts by weight of the urethane resin, but is not limited thereto.

In order to form the skin coating film 200, a urethane solution of about 2,000 to 2,500 cps may be applied to the release paper 10, but the viscosity of the urethane solution is not limited thereto, and may be changed according to process conditions. . For example, the viscosity of the urethane solution for skin coating film can be adjusted by mixing a solvent in the urethane resin of 50,000-80,000 cps.

Using the embossed release paper described above as the base sheet 10 has the following advantages.

First, the surface having an embossed shape, that is, the embossed surface, is urged toward one side from the surface of the base sheet when the urethane solution is applied to the surface of the base sheet 10 (release paper) or the base sheet is not parallel to the urethane. Minimize or prevent the flow of the solution from the surface of the base sheet to one side, and the thickness of the radiation shielding solution (bismuth-urethane resin-solvent containing solution) applied on the skin coating film 200 is not partially thinned. It can lead to even dispersion and application.

Second, while the urethane solution is embedded in the uneven structure while being applied to the surface of the base sheet to prevent the skin coating film and the radiation shielding film to be processed thinner than the set thickness, to prevent the phenomenon of under-radiation or partial deviation of the radiation shielding effect Can be.

Third, the stability of the radiation shielding solution is evenly applied during the formation of the multilayered radiation shielding film, and the mass and viscosity of the radiation shielding solution in the additional lamination process are induced by inducing a smooth dispersion of the solvent in the heat drying process of the radiation shielding solution. Depending on the physical properties can be given to vary the coating layer.

Examples of the embossed release paper include DN-TP release paper (Ajinomoto, Non-silicon type release paper developed by Dai Nippon Printing Co., Ltd.), and FIG. 2 shows an enlarged photograph of the surface of DN-TP release paper. It is.

Next, the shielding film forming step, N (natural water) on the skin coating film 200, the radiation shielding solution so that the cumulative coating thickness of the radiation shielding solution is applied on the skin coating film 200 is 1mm to 1.7mm; Laminating and applying 3 ≤ N ≤ 8 times sequentially to form a radiation shielding film 100 of the N layer.

More specifically, in the forming of the shielding film, forming the first shielding film 110 to apply the radiation shielding solution on the skin coating film 200 to a thickness of 0.13 mm to 0.27 mm (first step coating thickness) and to heat-dry it. And forming a second shielding coating layer 120 which is thermally dried after applying the radiation shielding solution on the first shielding coating layer 110 to a thickness of 0.18 mm to 0.32 mm (second step coating thickness). Forming a third shielding coating layer 130 to heat and dry the radiation shielding solution on the second shielding coating layer 120 at a thickness of 0.18 mm to 0.32 mm (third step coating thickness); and the third shielding coating layer. Forming a fourth shielding coating layer 140 which is applied to the radiation shielding solution at a thickness of 0.23 mm to 0.37 mm (fourth step coating thickness), and then heat-dried on the fourth shielding coating layer 140. Applying the radiation shielding solution in a thickness (the fifth step coating thickness) of 0.28mm to 0.42mm To heat drying may include the fifth-shielding film 150 formed in step.

That is, in this embodiment, a protective sheet having five radiation shielding films 100 and a single skin layer 200 is disclosed, but the number of layers of the radiation shielding film is not limited thereto. According to the present invention, the radiation shielding film 100 is formed in a plurality of layers through the continuous stacking of the shielding coating film, so that the total thickness of the radiation shielding film is the same as that of the present embodiment using the same material (radiation shielding solution). The curing of the radiation shielding film 100 can be facilitated (diffusion of solvent), the structure stability of the shielding film 100 can be realized, and the bismuth powder is uniformly dispersed in each layer of the radiation shielding film 100 to improve the radiation shielding effect. The thickness of the radiation shielding film 100 can be increased while maintaining tissue stability.

For example, the forming of the shielding film may include N (4 ≦ N ≦ 6) on the skin coating film such that the cumulative coating thickness of the radiation shielding solution applied on the skin coating film is 1.25 mm to 1.45 mm. It may comprise the step of laminating the coating sequentially.

The radiation shielding solution forming the above-mentioned shielding coating films (110, 120, 130, 140, 150), 30 to 38% by weight of the urethane resin, 15 to 27% by weight of the solvent, and 40 to 50% by weight of the bismuth powder It may include. More specifically, based on 100% by weight of the radiation shielding solution, may include 32 to 36% by weight of the urethane resin, 18 to 24% by weight of the solvent, and 43 to 47% by weight of the bismuth powder.

The viscosity of the urethane solution applied for forming the skin coating film and the viscosity of the radiation shielding solution applied in steps for forming the shielding film may be appropriately adjusted according to the conditions such as the particle size and shape of the bismuth powder and the application environment. Since the method for adjusting the known is an additional description is omitted.

The shielding films 110, 120, 130, 140, and 150 described above may be formed by a radiation shielding solution having the same component / content, and may include at least one of the shielding films 110, 120, 130, 140, and 150. One may be formed by another radiation shielding solution in a content of at least one component within the ranges exemplified above. For example, the content ratio of bismuth powder may be applied differently for each layer. In the present embodiment, the same components / contents of the radiation shielding solution are used for the formation of the shielding films 110, 120, 130, 140, and 150, but the present invention is not limited thereto. Can vary.

The urethane resin is a binder, and the polyurethane resin has excellent bonding strength with the base sheet 10 such as a fiber material or the above-described release paper, and is suitable as a shielding material due to its high durability and flexibility, and has a high hydrogen density and high speed. Effective for slowing neutrons Urethane resin, that is, polyurethane resin itself and a manufacturing method, etc. are well known, and further description thereof is omitted.

The solvent includes dimethylformamide (DMF), isopropyl alcohol (IPA), methyl ethyl ketone (MEK), toluene, and the like, which may be used alone or as a mixed solvent.

The heat drying of the urethane solution applied for the skin coating film forming and the radiation shielding solution applied stepwise for forming the shielding film may be performed in a heat dryer (dry oven) of 100 ℃ ~ 130 ℃ However, the present invention is not limited thereto and may be variously changed under conditions capable of implementing a predetermined dry state. For example, when the strip type long base sheet 10 (release paper) is continuously transported by a roller and the skin coating film 200 and the radiation shielding film 100 are stacked / molded thereon, 115 ° C A predetermined speed that can be cured in a heat drying environment of ˜120 ° C., for example, may be passed through a heat dryer of approximately 15 m to 30 m length at a speed of 10 m to 18 m per minute.

More specifically, the first drying is performed while the portion coated with the urethane solution to form the skin coating film 200 passes through a 17m heat dryer, and the first shielding coating film 110 is directly laminated to the skin coating film 200. The secondary drying is performed while the portion to which the radiation shielding solution is applied in the first step for formation passes through a 22m heat dryer, and the second shielding film 120 is directly stacked on the first shielding film. In the step, while the portion to which the radiation shielding solution is applied passes through the 25 m heat dryer, the third drying is performed, so that the solvent may be diverged, that is, the thermal drying may be performed. As described above, after the skin coating layer 200, the first shielding coating layer 110, and the second shielding coating layer 120 are sequentially formed, the third shielding coating layer 130 may be formed on the second shielding coating layer 120. The process of sequentially stacking / forming the fourth shielding film 140 and the fifth shielding film 150 may also be performed in the same process as the above-described process of forming the skin coating film, the first shielding film, and the second shielding film. However, the above-described heat drying environment, that is, the heating temperature and the transfer speed and the length of the heat drying section may be variously changed within a range capable of sufficient heat drying.

The bismuth powder of the radiation shielding solution forming the multilayer radiation shielding film 100 may be fine particles having an average particle size r of 0 <r ≦ 5 μm, more specifically granular bismuth nano having a maximum size of 1,000 nm. It is preferred for the even dispersion of bismuth powders in urethane resins to include nanoparticles, for example spherical bismuth powders having a size of 10 nm ≦ r ≦ 1 μm. However, since it may be expensive to grind the bismuth particles into nano size, bismuth powder having an average particle size in the range of 50 nm to 100 nm and a maximum of 1000 nm or less, more specifically, a bismuth powder of 500 nm to 1000 nm level in view of cost. This can be considered.

Examples of the bismuth powder include bismuth compounds such as bismuth oxide, more specifically bismuth trioxide (Bi ₂ O ₃ ), sodium bismuth (BiNaO ₃ ) and bismuth nitrate (BiN ₃ O ₉ ), and the like, May be mixed.

In the manufacturing method of the radiation shielding sheet according to the present embodiment, in order to manufacture the radiation shielding solution, by milling the raw material composition for radiation shielding containing the urethane resin and the bismuth powder, the urethane resin and the The method may further include a milling step of mixing the bismuth powder and grinding and dispersing the bismuth powder. As the bismuth powder of the raw material composition, fine particles (micro particles) having an average particle size of 0.5 μm to 6 μm, more specifically 1 μm to 5 μm are used, but are not limited thereto.

The particle size and shape of the bismuth powder can play an important role in the ability of the bismuth to disperse and evenly spread over the entire surface when mixed with the urethane resin used as a substrate. The size of the bismuth powder is below a certain level, for example nano-sized granular powders (nano particles) may be more effective for the uniform dispersion of bismuth powders in urethane resins, but this can greatly increase the cost of purchasing raw materials. It becomes a factor.

Thus, an effective shielding effect is obtained by pulverizing the bismuth powder and dispersing it evenly in the urethane resin using a micro-sized powder (micro particles) using a milling apparatus such as a 3 roll mill.

The raw material composition for radiation shielding (composition supplied to the milling) is a liquid substance in which a urethane resin, bismuth powder, and a solvent are mixed, and a viscosity of about 2,000 to 2,500 cps is not limited thereto. It may be changed by a manufacturing environment, such as a conveyance speed of the base sheet 10, thermal drying conditions, etc. The radiation shielding raw material composition may include 30 to 38 wt% of the urethane resin, 15 to 27 wt% of the solvent, and 40 to 50 wt% of the bismuth powder. More specifically, based on 100% by weight of the raw material composition, may include 32 to 36% by weight of the urethane resin, 18 to 24% by weight of the solvent, and 43 to 47% by weight of the bismuth powder.

Therefore, in the present embodiment, assuming that there is no loss of each component in the milling process, the bismuth powder compared to the urethane resin in the radiation shielding solution used in the raw material composition before milling and the shielding film to form a radiation shielding film after milling The content ratio of the solvent is the same.

3 and 4, the urethane resin and the bismuth powder mixture, that is, the above-described radiation shielding raw material composition are milled to mix the bismuth powder and the urethane resin, and the bismuth powder is milled. ) And dispersion.

When the paste of high-viscosity urethane resin is passed between three rollers rotating at different speeds, it is rubbed by the difference in the rotation speed between the rollers so as to have optimized density and stiffness during the milling process by the 3 roll mill. Loads can be generated to achieve the effect of precise grinding and dispersion.

Each roller in the above-mentioned 3 Roll Mill is rotated at a constant rate of rotation (rpm) to apply pressure and shear force to the sample to enable the above-mentioned mixing, milling, and dispersion. Through this, the size of the bismuth particles can be made small and the colloidal colloids in the urethane resin can be present evenly dispersed in the urethane resin without being precipitated and settled by gravity by gravity.

For reference, the three-roll mill is a structure in which three rolls rotating at opposite speeds and at different speeds (V1, V2, and V3) are arranged side by side in a horizontal manner, and a middle roll in which a sample (shielding raw material composition) is located in the middle. It passes between the first and draw-in rolls and transfers to the last scraper roll. The dispersed sample passes through the last scraper roll and is discharged by the scraper. Since the three-roll mill apparatus itself is known, further description is omitted.

One embodiment of the radiation shielding sheet, that is, the protective sheet according to the present invention, the skin coating film 200 made of a urethane resin material coated on the surface of the release paper 10 having an embossed shape of the convex surface, and the It may include a plurality of radiation shielding film 100 including a plurality of shielding coating film (110, 120, 130, 140, 150) sequentially stacked on the skin coating film 200. The shielding coating films may include a urethane resin and bismuth powder, and more specifically 110 to 160 parts by weight of bismuth powder based on 100 parts by weight of the urethane resin.

The radiation shielding film 100 is a multilayer structured film as described above, and includes a first shielding film 110 formed on the skin coating film and a second shielding film 120 formed on the first shielding film. A third shielding coating layer 130 formed on the second shielding coating film, a fourth shielding coating film 140 formed on the third shielding coating film, and a fifth shielding coating film 150 formed on the fourth shielding coating film. It includes.

In the present embodiment, the amount of the bismuth powder contained in the fifth shielding coating film 150 is greater than the amount of the bismuth powder contained in the first shielding coating film 110, and the second shielding coating film 120 to the fourth shielding film. The amount of bismuth powder contained in the coating film 140 is greater than or equal to the amount of bismuth powder contained in the first shielding coating film 110. Therefore, in the case of forming the above-described shielding films using the same component / content of the radiation shielding solution, if the amount of bismuth powder is larger than other shielding films, the thickness of the radiation shielding solution applied to form the shielding film is It can be seen that it is relatively thicker.

The bismuth powder of the shielding coating film is composed of fine particles having an average particle size r of 0 <r ≦ 5 μm, more specifically nanoparticles. For example, the average particle size of the bismuth powder dispersed in the shielding film may be in the range of several nanometers to less than 1 micrometer, specifically, 50 nm to 1,000 nm, and may be 500 nm to 1000 nm in consideration of cost. have.

In the present embodiment, the bismuth powder having an average particle size of about 500 nm to 1000 nm may be dispersed in the urethane resin by the above-mentioned three roll mill, but the size of the bismuth powder of the shielding film, that is, the bismuth powder contained in the radiation shielding solution is It is not limited to this.

The bismuth powder can be pulverized to less than 1/2 of the size before milling by means of the three-roll mill described above. In this embodiment, the middle roll and the middle roll are placed in the middle of the first roll. Naturally, the rotation ratio (V1: V2: V3) of the scraper roll is 1: 2: 3 but is not limited thereto.

The sum of the thickness of the skin coating film 200 and the thickness of the radiation shielding film 100 is 0.28 mm to 0.32 mm, and the radiation shielding film has a laminated structure of 4 to 6 layers, but is not limited thereto. For example, in order to form the skin coating film 100 of one layer and the radiation shielding film of five layers, the urethane solution and the radiation shielding solution which are divided and applied in six steps so that the total cumulative coating thickness on a release paper will be approximately 1.5 mm are heat-dried. As the solvent is released, the thickness shrinks to about one fifth. Of course, in addition to the bismuth powder, the radiation shielding film 100 may further contain one or more other protective particles such as tungsten particles.

The above-mentioned radiation shielding sheet 1 may be implemented by embedding (embedding) in the protective clothing, that is, the fibers of the radiation shielding clothing to implement radiation protection. The radiation shielding sheet 1 may be used in a state in which one sheet is used or a plurality of sheets are stacked in accordance with the required protection performance.

The radiation shielding sheet 1 may be fixed to the protective clothing cloth by sewing or bonding. The plurality of radiation shielding sheets 1 may be integrated by sewing or bonding.

When manufacturing the radiation shielding material, that is, the shielding sheet 1 by the method of manufacturing a protective sheet disclosed in the above-described embodiment, it is economical, excellent radiation shielding effect, easy to recycle, it can be excellent in environmentally friendly effect compared to lead, It is possible to manufacture a radiation shielding sheet excellent in light weight and flexibility.

Hereinafter, the configuration and operation of the present invention through the preferred embodiment of the present invention will be described in more detail. However, the following examples are only illustrated to aid the understanding of the present invention, and the scope of the present invention is not limited to the following examples. In addition, the contents not described in the present specification may be sufficiently inferred by those skilled in the art through sufficiently known techniques, and thus description thereof will be omitted.

1. Preparation of Examples and Comparative Examples of Radiation Shielding Solutions

In order to prepare a radiation shielding solution containing a urethane resin, a solvent, and bismuth powder, three kinds of radiation are prepared using three kinds of bismuth powder raw materials and three kinds of radiation shielding raw material compositions (samples) as follows. A shielding solution was obtained.

The content ratio of urethane resin (manufacturer, product name), solvent (manufacturer, product name), and bismuth powder raw material used in three kinds of radiation shielding raw material compositions (samples) is 35% by weight of urethane resin, 20% by weight of solvent, and bismuth. 45 wt% of powder raw materials were the same for all three, and the viscosity was set to 2,200 to 2,300 cps.

In addition, the rotation speeds of the first roll, middle roll and scraper roll in the 3 roll mill were 500, 1,000, and 1,500 RPM, respectively. The gap Gap between rolls was about 5 micrometers in 10 micrometers or less.

Example 1

To prepare a radiation shielding solution according to Example 1, as shown in FIG. 5, granular bismuth powder (Bi ₂ O ₃ , Orange Yellow Powder, Qingdao Xiguanya International) having an average particle size of 3 μm to 5 μm and a purity of 99.98% Trade Co., Ltd, China), and the radiation shielding solution according to Example 1 was obtained by milling a raw material composition for radiation shielding containing granular bismuth powder having a thickness of 3 µm to 5 µm with a three-roll mill apparatus, In Example 1, the dispersion state of the bismuth powder was confirmed.

Example 2

To prepare a radiation shielding solution according to Example 2, as shown in FIG. 6, granular bismuth powder (Bi ₂ O ₃ , Light Yellow Powder, Changsha Santech Materials) having an average particle size of 1 μm to 4 μm and a purity of 99.9% Co., Ltd, China), and the radiation shielding solution according to Example 2 was obtained by milling a radiation shielding raw material composition containing granular bismuth powder having a size of 1 µm to 4 µm under the same conditions as in Example 1. And the dispersion state of the bismuth powder was confirmed in Example 2.

Comparative Example 1

In order to prepare a radiation shielding solution according to Comparative Example 1, as shown in FIG. 7, a bismuth powder (Bi ₂ O ₃ , Light Yellow) having a purity of 99.9% and an average particle size of 4 µm to 20 µm was mixed. Power, Changsha Santech Materials Co., Ltd, China) and the radiation shielding solution according to Comparative Example 1 by milling the radiation shielding raw material composition containing granular and acicular mixed bismuth powder under the same conditions as in Example 1 Was obtained, and the dispersion state of the bismuth powder was confirmed in Comparative Example 1.

8 to 10 are enlarged photographs showing dispersion states of bismuth powders in Examples 1 and 2 and Comparative Example 1, wherein the granular particles having a particle size of 3 μm to 5 μm are pulverized and the bismuth powder as shown in FIG. The colloids were formed like colloids without particle precipitation and uniform distribution throughout the particle size.

In addition, the granular particles having a particle size of 1 μm to 4 μm are pulverized so that the bismuth powder is uniformly mixed with the urethane resin at the nano particle size and uniformly dispersed as shown in FIG. 9, and colloid like colloid without precipitation. Formed.

However, in the powder in which granular particles and acicular particles are mixed in a particle size of 4 µm to 20 µm, granular powder and acicular powder (bar powder) are separated in the urethane resin as shown in FIG. The phase powder was present in the upper layer (see Fig. 7 (a)) and the needle powder was present in the precipitated state in the lower layer of the urethane resin (see Fig. 7 (b)). This precipitation phenomenon shows that the urethane powder does not form a colloid in the urethane resin and shows a heterogeneous state, which is not sufficient to be used as a raw material for radiation shielding.

Accordingly, the particles of the powder usable in the manufacture of the radiation shielding sheet are granular powders of evenly dispersible size, for example, nano-spherical bismuth powders. It can be seen that it should be enlarged to achieve even mixing and dispersion in the urethane resin.

2. Preparation of Examples and Comparative Examples of Radiation Shielding Sheets

Example of radiation shielding sheet using embossed release paper (DN-TP release paper, Ajinomoto, Non-silicon type release paper developed by Dai Nippon Printing Co., Ltd.) of 1m × 1m (width × length) as follows 1 and 2 and Comparative Examples were prepared.

Embodiment 1 of the radiation shielding sheet

A urethane solution was applied to the surface of the embossed release paper to form a base coating layer having a thickness of 0.15 mm, and then thermally dried at a temperature of 105 ° C. for 30 seconds in a thermal drying chamber to form a skin coating film made of urethane.

The urethane solution applied to the embossed release paper to form the skin coating film is a solution in which a solvent is mixed with a urethane resin as described above, and the mixing ratio of the urethane resin and the solvent in the urethane solution for skin coating film is 100 parts by weight of a urethane resin. About 60 weight part of solvents, it was set as the viscosity of 2,000-2,200 cps. The urethane solution may be prepared by mixing a solvent (DMF) in a urethane resin having a viscosity of 50,000 to 80,000 cps. MEK and toluene may be used as the solvent. More specifically, at least one solvent selected from the group consisting of DMF, MEK, toluene, and the like may be used.

Then, Example 1 of the above-mentioned radiation shielding solution was applied to the skin coating film at the thickness shown in the following [Table 1], followed by heat drying (heat drying for 30 seconds at 105 ° C.) five times. 1, a radiation shielding sheet having a single layer skin coating film and a five layer radiation shielding film (first shielding film to fifth shielding film) was manufactured in the same manner as the structure shown in FIG. 1. The thickness of the sheet was 0.28 mm to 0.31 mm (average 0.29 mm).

At this time, the cumulative coating thickness of the radiation shielding solution is a total of 1.35mm from the first step to the fifth step, as shown in Table 1 below, the thickness of the hood of the urethane solution for forming a skin coating, that is, the thickness of the base coating layer and the radiation The cumulative coating thickness of the shielding solution totaled 1.5 mm. The first stage coating layer for forming the radiation shielding film forms a first shielding coating film, the second stage coating layer forms a second shielding coating film, the third stage coating layer forms a third shielding coating film, and the fourth It can be seen that the step coating layer forms a fourth shielding coating film, and the fifth step coating layer forms a fifth shielding coating film. In other words, the radiation shielding film has a structure in which five protective layers are successively stacked on the skin coating film from the first shielding film to the fifth shielding film.

division Base
Coating layer First stage 2nd step 3rd step 4th step 5th step Application thickness 0.15mm 0.20mm 0.25mm 0.25mm 0.30mm 0.35mm

The embossed release paper was peeled / removed from the skin coating film, and the radiation shielding performance of Example 1 of the radiation shielding sheet was examined. 11 is an enlarged photograph of the surface of the radiation shielding sheet according to Example 1, and FIG. 11 (a) is an enlarged photograph showing the surface (surface of the skin coating film) from which the embossed release paper is removed, and FIG. As an enlarged photograph showing the opposite surface (surface of the fifth shielding coating film), it can be seen that the pin hole formed as the solvent is released in FIG. 11B is formed.

Example 2 of the radiation shielding sheet

The skin coating film was formed on the surface of the said embossed release paper using the same urethane solution as Example 1 mentioned above with the same coating thickness and heat-drying method as Example 1. And the radiation shielding sheet which apply | coated Example 2 of the above-mentioned radiation shielding solution, and has a skin coating film of one layer and a radiation shielding film of five layers in the same manner as Example 1 of a radiation shielding sheet (same application | coating thickness and heat drying conditions are the same). Example 2 was prepared.

Then, the embossed release paper was peeled / removed from the skin coating film of Example 2, and the radiation shielding performance of Example 2 of the radiation shielding sheet was examined. 12 is an enlarged photograph of the surface of the radiation shielding sheet according to Example 2, and FIG. 12A is an enlarged photograph showing the surface (surface of the skin coating film) from which the embossed release paper is removed, and FIG. As an enlarged photograph of the opposite surface (surface of the fifth shielding coating film), it can be seen that FIG. 12B shows a pin hole formed while the solvent is released.

Comparative example of radiation shielding sheet

The skin coating film was formed on the surface of the said embossed release paper using the same urethane solution as Example 1 and 2 mentioned above by the same coating thickness and heat-drying method.

In addition, a radiation shielding solution using an antimony powder instead of bismuth powder (hereinafter referred to as an 'antimony solution') was prepared, and the antimony solution was applied in the same manner as in Example 1 of the radiation shielding sheet described above to obtain a radiation shielding sheet. A comparative example of a radiation shielding sheet having a skin coating film of one layer and a radiation shielding film of five layers was prepared in the same manner as in Example 1 (same coating thickness and thermal drying conditions).

In order to prepare an antimony solution, a radiation shielding raw material composition comprising 35% by weight of a urethane resin, 20% by weight of a solvent (DMF), and 45% by weight of granular antimony powder having a size of 3 μm to 5 μm were used. The antimony solution was obtained by milling using a three roll mill under the same conditions as in the manufacturing procedures of Examples 1 and 2. That is, with Example 1 In comparison, in the comparative example, bismuth powder was replaced with antimony powder (Minochem, DFR-555N, Korea), and the content ratio and remainder are the same.

Then, the embossed release paper was peeled / removed from the skin coating film of Example 2, and the radiation shielding performance of Example 2 of the radiation shielding sheet was examined.

3. Experimental Example of Radiation Shielding Sheet

The radiation shielding performance (shielding rate) of Examples 1 and 2 and Comparative Examples of the radiation shielding sheet was examined. The inspector was a radiation safety inspector affiliated with the Korea Medical Equipment Inspection Institute.

Examples 1 and 2 of the radiation shielding sheet and the comparative example were cut into sizes of 30 cm in width and 30 cm in length, respectively, to obtain test specimens. The equipment described in the following [Table 2] was used for the shielding rate inspection, and the dose measurement method for the attenuation characteristics of the radiation shielding sheet was performed according to the KS standard (KS C IEC 61331-1).

The shielding rate test results of Example 1 of the radiation shielding sheet are shown in Table 3 below, and the shielding rate of the plurality of parts on the test specimen according to Example 1 was examined and the average value was calculated for the shielding rate test. It was.

* Dose reduction: the dose value measured by the detector through the test specimen

* Shielding rate (%) = ((Dose-Low dose) / Reference dose) × 100,

Next, the shielding rate test results for Example 2 of the radiation shielding sheet is as shown in Table 4 below, and the shielding rate is tested for the plurality of parts on the test specimen according to Example 2 for the shielding rate test and the average value is determined. Calculated and shown.

And, the shielding rate test results for the comparative example (antimony applied) of the radiation shielding sheet is as shown in [Table 5] below, and the shielding rate is tested for a plurality of parts on the test specimen according to Example 2 for the shielding rate test The average value was calculated and shown.

As can be seen from the above [Table 3] to [Table 5], Examples 1 and 2 of the radiation shielding sheet using the bismuth powder shows a superior shielding performance than the comparative example using the antimony powder. In addition, it was confirmed that the test specimens according to Examples 1 and 2 of the radiation shielding sheet were not evenly different in portions of the shielding rate but appeared evenly.

[Table 6] below shows the partial shielding performance of one of the plurality of test specimens for the shielding rate test for Example 1 of the radiation shielding sheet, as shown in FIG. The shielding performance of four corners is measured. Baseline doses for the test are shown in Table 3.

Measuring position kVp Reduced dose Shielding rate
A
60 550.0 54.66 80 1273.7 45.97 100 2344.7 39.26
B
60 543.0 55.23 80 1267.0 46.25 100 2341.0 39.35
C
60 542.0 55.32 80 1257.0 46.68 100 2326.3 39.73
D
60 552.0 54.49 80 1299.7 44.87 100 2351.3 39.08
E
60 544.0 55.15 80 1284.0 45.53 100 2352.3 39.06

As shown in Table 6, in the test specimen according to Example 1 of the radiation shielding sheet, the shielding ratio of each part was measured evenly without a large difference, and it can be confirmed that the bismuth powder was evenly dispersed in the urethane resin.

And, [Table 7] below shows the shielding performance for each part of one of the plurality of test specimens for the shielding rate test for Example 2 of the radiation shielding sheet, the edge of one arbitrarily selected Radiation shielding performance was measured at and center. Baseline dose for the test is shown in [Table 4].

Measuring position Center Corner kVp 60 80 100 60 80 100 Reduced dose 507.7 1219.7 2293.0 519.3 1236.0 2328.0 Shielding rate 59.68 50.75 43.94 58.75 50.09 43.08

As shown in [Table 7], even the test specimens according to Example 2 of the radiation shielding sheet were measured evenly without a large difference, and thus the bismuth powder was evenly distributed in the urethane resin in Example 2 of the radiation shielding sheet. You can see that it is dispersed.

The radiation shielding sheet according to the present invention can be used by stacking a plurality of sheets according to the required radiation shielding performance. Table 8 shows the radiation shielding performance by overlapping the test specimens of Examples 1 and 2.

As can be seen from [Table 8], the radiation shielding rate increases as the test specimens of Example 1 overlap each other, and the radiation shielding rate increases as the test specimens of Example 2 further overlap one by one. The rate increased. Therefore, the radiation shielding sheet according to the present invention can be used in a state of being superimposed on an appropriate number of sheets according to the use environment.

Test specimen
Number of overlap Example 1 Example 2 60kVp 80 kVp 100kVp 60kVp 80 kVp 100kVp 2 75.21 64.63 56.02 79.27 69.46 60.98 3 86.39 76.10 66.86 86.42 77.86 69.92 4 91.24 82.57 73.99 93.25 85.19 77.38 5 92.94 87.27 78.94 96.21 90.05 83.10 6 96.74 90.05 82.59 98.09 93.66 87.58 7 97.56 91.80 85.09 98.41 94.05 89.14 8 98.28 93.51 86.97 99.76 96.16 91.21 9 98.53 95.00 89.44 99.99 96.97 92.53 10 99.42 95.81 90.90 100.00 97.13 93.77

Considering that the thickness of the radiation shielding sheet according to Example 1 and Example 2 is about 0.28 mm to about 0.31 mm, the thickness of the radiation shielding sheet is about 3 mm even if 10 layers of radiation shielding sheets overlap.

On the other hand, according to the durability test of the radiation shielding sheet according to the present invention, as shown in Figure 14, in the bending test (ISO 7854: 1995 B method) 6 grade (KS K ISO 16602: 2010 6. 16 Table 15 The EKfms test performance standard, Class 6 (highest grade), satisfies more than 100,000 flexural tests (repetitive bending and unfolding tests). It was confirmed. The durability test was conducted by the Korea Apparel Testing Institute (KATRI, Anyang-si, Gyeonggi-do).

As described above, a preferred embodiment according to the present invention has been described, and the fact that the present invention can be embodied in other specific forms in addition to the above-described embodiments without departing from the spirit or scope thereof has ordinary skill in the art. It is obvious to them.

Therefore, the above-described embodiments are to be considered as illustrative and not restrictive, and thus, the invention is not limited to the above description, but may vary within the scope of the appended claims and their equivalents.

1: radiation shielding sheet 10: base sheet (release paper)
100: multilayer radiation shielding film 110: first shielding coating film
120: second shielding coating 130: third shielding coating
140: fourth shielding coating 150: fifth shielding coating
200: skin coating film

Claims (18)

As a method of manufacturing the radiation shielding sheet:
In order to form a multilayered radiation shielding film on one side of the base sheet for forming the radiation shielding sheet, a radiation shielding solution containing a urethane resin, a solvent and a bismuth powder is used. A shielding film forming step of laminating and forming the radiation shielding film of the multilayer by repeating a process of applying and drying to one side of the base sheet a plurality of times; And
Before the shielding film forming step, a urethane solution containing a urethane resin and a solvent is applied to the surface of the base sheet and heat-dried to form a skin coating film made of a urethane resin material for coating the radiation shielding film on the surface of the base sheet. Skin coating coating step;
The base sheet is an embossed release paper having an embossed convex surface and detachable from the skin coating film;
The skin coating film coating step includes applying a urethane solution to a surface of the release paper to a predetermined thickness and then drying the film;
The shielding film forming step,
Forming a first shielding coating film on the skin coating film with a thickness of 0.13 mm to 0.27 mm and thermally drying;
A second shielding film forming step of applying the radiation shielding solution to a thickness of 0.18mm to 0.32mm on the first shielding film and then heat-drying it;
A third shielding film forming step of applying the radiation shielding solution to a thickness of 0.18mm to 0.32mm on the second shielding film and then drying the film;
A fourth shielding coating film forming step of applying the radiation shielding solution to a thickness of 0.23mm to 0.37mm on the third shielding coating film and then thermally drying the film;
And a fifth shielding coating film forming step of applying the radiation shielding solution to a thickness of 0.28mm to 0.42mm on the fourth shielding film and then thermally drying the film. delete The method of claim 1,
The skin coating layer coating step; Method for producing a radiation shielding sheet comprising the step of applying the urethane solution to the surface of the base sheet in a thickness of 0.12mm to 0.18mm. The method of claim 3,
The skin coating layer coating step; And applying the urethane solution to the surface of the base sheet in a thickness of 0.14 mm to 0.16 mm. delete The method of claim 1,
The urethane solution to form the skin coating film; The manufacturing method of the radiation shielding sheet containing 50-70 weight part of said solvents with respect to 100 weight part of said urethane resins. delete delete delete The method of claim 1,
The radiation shielding solution; 30 to 38% by weight of the urethane resin, 15 to 27% by weight of the solvent, and 40 to 50% by weight of the bismuth powder manufacturing method of the radiation shielding sheet. The method of claim 1,
The bismuth powder of the said radiation shielding solution which forms the said radiation shielding film of said multilayer has an average particle size r of 0 <r <= 5micrometer, The manufacturing method of the radiation shielding sheet characterized by the above-mentioned. The method of claim 11,
The bismuth powder of the said radiation shielding solution which forms the said multilayer shielding film contains the granular bismuth nanoparticle, The manufacturing method of the radiation shielding sheet characterized by the above-mentioned. The method of claim 1,
In order to manufacture the radiation shielding solution, a milling step of milling the radiation shielding raw material composition containing the urethane resin and the bismuth powder to mix the urethane resin and the bismuth powder and to grind and disperse the bismuth powder Method for producing a radiation shielding sheet further comprising. The method of claim 13,
Bismuth powder of the raw material composition used in the milling process is a method for producing a radiation shielding sheet, characterized in that the average particle size of 0.5㎛ 6㎛. delete delete delete delete

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