Solderless gamma ray shielding sheet and manufacturing method thereof

Abstract

The present invention relates to a solderless gamma ray shielding sheet that is lightweight yet provides a high gamma ray shielding rate, and a manufacturing method thereof.

Description

[Technical field]

[0001] The present invention relates to a lead-free gamma ray shielding sheet and a manufacturing method thereof, and more particularly, to a lead-free gamma ray shielding sheet that is not heavy but provides a high gamma ray shielding rate and a manufacturing method thereof. [Background technology]

[0002] Radiation has existed since the Earth was formed, and we still live in an environment full of radiation. There are many different types of radioactive materials, some of which exist naturally and some which are artificially created for industrial and medical purposes.

[0003] Ionizing radiation refers to radiation such as alpha, beta, protons, neutrons, gamma rays, and X-rays that cause ionization when they pass through matter. Alpha rays are absorbed and blocked by materials as thick as paper and are stopped instantly in the air, so no special shielding is required. Beta rays are known to be larger than alpha rays, but can generally be blocked by thin aluminum foil or plastic sheets.

[0004] On the other hand, gamma rays are electromagnetic waves generated by nuclear decay and transformation, and have higher energy than X-rays, and are characterized by their strong penetrating power. For example, medical X-rays have a photon of about 2,000 eV, while cosmic gamma rays are usually 10 million eV (10 MeV) or 300 billion eV (300 GeV), meaning that gamma rays have 10,000 to 100 million times the energy of X-rays. Therefore, gamma rays can be blocked by materials with higher density and thickness than X-ray shielding materials.

[0005] Korean Patent Publication No. 10-2014-0086201 discloses a first metal sheet (lead) of a thin metal film that blocks gamma rays and a second metal sheet (cadmium) of a thin metal film that blocks neutrons as a shielding material for shielding radiation generated in a nuclear reactor. As in the Korean Patent Publication, thick lead sheets and heavy water are generally used as gamma ray shielding materials in nuclear reactors. In addition, workers at nuclear power plants generally use lead gowns. Such lead gowns are used in sheet form by dispersing lead components in polyvinyl chloride (PVC) and squeezing it out, but they are heavy (5kg to 10kg), uncomfortable to wear, and restrict activity, making them very inconvenient to wear. In addition, lead is a heavy metal substance that is highly harmful and difficult to dispose of.

[0006] Recently, tungsten has been widely used as a radiation shielding material that can replace lead. For example, Korean Patent No. 10-1605319 discloses a radiation shielding rubber composition containing 80-200 parts by weight of tungsten powder and 5-50 parts by weight of additives in 100 parts by weight of acrylonitrile-butadiene rubber (NBR), and Korean Patent No. 10-1804295 discloses a radiation shielding rubber composition containing 80-200 parts by weight of tungsten powder, 100-300 parts by weight of tantalum powder, and 5-50 parts by weight of additives in 100 parts by weight of acrylonitrile-butadiene rubber (NBR). The above two Korean patents only provide test data on the X-ray shielding rate (75-95%), and do not specifically mention test data on gamma ray shielding, which has more than 100 million times the energy of X-rays, or its applicability. In addition, in Korean Patent No. 10-1804295, when using a large amount of metals such as tungsten powder and tantalum powder, the tungsten powder and tantalum powder are coated with an adipic acid ether ester type (RS-107) plasticizer to prevent the metals from hardening (Claim 1).

[0007] Figure 1 is a catalog of radiation shielding products currently available from Yamamoto Chemical Industry Co., Ltd. of Japan. According to the catalog, the thickness of the product is 4mm, but the gamma ray (Cs 137) shielding rate is only 4%. As such, existing radiation shielding products have a low gamma ray shielding rate, making it difficult to safely protect workers from gamma rays. DISCLOSURE OF THEINVENTION technical challenges

[0008] The present invention provides a sheet that has an increased gamma ray shielding rate without using lead.

[0009] The present invention provides a shielding sheet that can be used in shielding films, blankets, and protective clothing for gamma ray shielding in nuclear power plants.

[0010] The present invention relates to

[0011] masticating the solid rubber in a mixing roll;

[0012] adding tungsten and additives to the mixing roll and kneading them together with the rubber;

[0013] The mixed solid is compressed to a constant thickness using a rolling roll to produce a sheet;

[0014] The sheet is rolled and vulcanized,

[0015] The kneading step is related to a method for producing a gamma ray shielding sheet, in which 100 parts by weight of rubber and 600 to 1900 parts by weight of tungsten are mixed.

[0016] According to another aspect, the present invention comprises:

[0017] A gamma ray shielding sheet made of a rubber base mixed with tungsten and antimony oxide.

[0018] The gamma ray shielding sheet is related to a gamma ray shielding sheet containing 100 parts by weight of rubber, 600 to 1900 parts by weight of tungsten, and 5 to 15 parts by weight of antimony oxide.

[0019] The radiation shielding sheets manufactured according to the present invention have gamma ray (Cs-137) shielding rates of 10.3% (thickness 1.1 mm) and 18.6% (thickness 2.2 mm), which are approximately 10 times higher than the gamma ray (Cs-137) shielding rate of 4% (thickness 4 mm) of conventional products (see Figure 1) (comparison converted to the same thickness). In addition, the sheet of Example 1 is very thin at 1.1 mm, but has a high shielding rate and is comfortable to wear, making it possible to provide a protective product.

[0020] The gamma ray shielding sheet of the present invention uses a large amount of high-density tungsten (600-1900 parts by weight relative to 100 parts by weight of base rubber), but the tungsten is uniformly dispersed within the sheet, thereby increasing the gamma ray shielding rate. In the method for manufacturing the gamma ray shielding sheet of the present invention, the temperatures of the rollers and the mixed solid (rubber + tungsten) of the mixing roll are maintained at 35-40°C and 75-85°C, respectively, and the mixed solid is repeatedly fed into the mixing roll, thereby dispersing a large amount of tungsten uniformly in the rubber. [Brief description of the drawings]

[0021] Figure 1 is a catalog of radiation shielding products currently available from Yamamoto Chemical Industry Co., Ltd. of Japan.

[0022] FIG. 2 is a schematic diagram of the mastication and kneading equipment.

[0023] Figure 3 shows a photograph of the mixed solid material after the kneading process.

[0024] FIG. 4 shows the final vulcanized product (Sheet (1, 1 mm) of Example 1).

[0025] 5 to 7 are test results of the gamma ray shielding sheet manufactured in Example 1.

[0026] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings in order to enable those skilled in the art to easily carry out the present invention.

[0027] The terms used in this application are merely used to describe certain embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, terms such as "include" or "have" are intended to specify the presence of features, numbers, steps, operations, components, or combinations thereof described in the specification, and should be understood as not precluding the presence or additional possibility of one or more other features, numbers, steps, operations, components, or combinations thereof.

[0028] The lead-free gamma ray shielding sheet of the present invention includes a mastication step, a kneading step, a sheet manufacturing step (calendering step), and a vulcanization step.

[0029] The mastication step is a step in which solid rubber is put into a mixing roll to crush and pulverize the rubber. The rubber mastication step is a process in which the molecular chains of raw rubber (e.g., raw rubber) are mechanically cut using a mixing roll (e.g., a kneader), releasing the twists between molecules in the chain state, lowering the degree of polymerization, decreasing viscoelasticity, and increasing plasticity.

[0030] The solid rubber may be at least one of natural rubber, styrene butadiene rubber, nitrile butadiene rubber, chloroprene rubber, butyl rubber, ethylene propylene rubber, and butadiene rubber.

[0031] The mixing roll used in the mastication and kneading steps refers to equipment that has two rolls and can crush or squeeze rubber. Referring to Figure 2, the mixing roll rotates two rolls in opposite directions, and crushes solid rubber that is put between the rollers.

[0032] The kneading step is a step of feeding tungsten and additives into the mixing roll and mixing them with the rubber (see FIG. 2a).

[0033] The mixing rolls may be the same as or different from the mixing rolls in the mastication stage.

[0034] The tungsten is a metal with high density (19.25 g / cm3) and high specific gravity. In the present invention, 600 to 1900 parts by weight of tungsten is used per 100 parts by weight of rubber.

[0035] If the tungsten content is less than 600 parts by weight, the gamma ray shielding rate is low, and if it exceeds 1900 parts by weight, it is difficult to uniformly disperse the tungsten in the kneading step and difficult to extrude with a uniform thickness in the calendering process.

[0036] In the present invention, tungsten having a purity of 97% to 99.9% and a particle size of 0.01 μm to 100 μm can be used.

[0037] The additives used in the kneading step can be zinc oxide (zinc oxide), an oxidizing agent (vulcanizing agent), or a mixture thereof.

[0038] The oxidizing agent (vulcanizing agent) can be sulfur, a thiocarbamate accelerator, a thiuram accelerator or a thiourea accelerator.

[0039] The additives may be mixed in an amount of 0.1 to 20 parts by weight based on 100 parts by weight of rubber.

[0040] The gamma ray shielding sheet of the present invention can increase not only durability but also elasticity, tear strength and tensile strength by mixing additives such as zinc oxide into rubber.

[0041] In the kneading step, 5 to 15 parts by weight of flame-retardant antimony oxide may be additionally mixed based on 100 parts by weight of rubber.

[0042] The antimony oxide may have a particle size of 0.1 μm to 100 μm.

[0043] The antimony oxide enhances the flame retardancy of the gamma ray shielding sheet.

[0044] The kneading step may be performed by compressing and dispersing the mixed solids several times using the mixing roll.

[0045] The kneading step may be repeated several times by cutting the mixed solid material that has passed through the mixing roll and re-introducing it into the mixing roll so that the tungsten is uniformly dispersed in the rubber. Here, the mixed solid is a mixture containing rubber, tungsten, additives, antimony oxide, etc., and is a paste in a solid state that maintains viscosity rather than being liquid.

[0046] At this time, the surface temperature of the mixing roll during the kneading step may be 35-40°C, and the temperature of the mixed solids attached to the roll surface may be 75-85°C. If the roll surface temperature exceeds 40°C and rotates for a long period of time, the rubber being pressed may easily ripen or a scotch phenomenon (a phenomenon in which vulcanization proceeds under undesirable conditions, causing changes in the properties of the rubber) may occur. Therefore, the present invention maintains the temperature of the mixed solids at 75-85°C while controlling the roll surface temperature within the range of 35-40°C. If the temperature of the roll and mixed solids is lower than this temperature, sufficient dispersion is difficult.

[0047] The method for producing a gamma ray shielding sheet of the present invention may further include a maturing step of cutting the mixed solid in sheet form after the kneading step into a predetermined thickness and size and storing it for a predetermined time.

[0048] The aging step may be for 12 hours or more, preferably for 24 hours or more.

[0049] The aging step may be carried out at room temperature.

[0050] If the mixed solids do not undergo the aging step, problems may occur such as a high reject rate or a shortened product lifespan over time.

[0051] The sheet manufacturing step (calendering step) is a step of squeezing the mixed solid material produced in the kneading step to a uniform thickness using a rolling roll.

[0052] In the sheet manufacturing step, a calender (a piece of equipment with an inverted L-shape, two rolling rolls on top and two on the bottom) is used to manufacture sheets with a uniform thickness.

[0053] In the manufacturing method of the present invention, the mixed solid (shield) that has been aged and hardened before the sheet manufacturing step is put into a kneader and made into a paste state by heat and pressure. At this time, the surface temperature of the kneader roll and the mixed solid (shield) are maintained at 35 to 40°C and 75 to 85°C, respectively, to prevent the Scotch phenomenon.

[0054] In the sheet manufacturing step, a mixed solid (shield) maintained at 75 to 85° C. may be poured into the rolling rolls of the calender.

[0055] In the sheet producing step, the roll surface temperature of the rolling roll may be 35 to 40°C, and the mixed solid material attached to the roll surface may be 75 to 85°C, similar to the kneading step.

[0056] The vulcanizing step is a step of vulcanizing the sheet by placing it in a rolling roll.

[0057] The vulcanization step is a step in which heat and pressure are applied to the bonded sheet using equipment called a rotocure, causing additives such as sulfur to react with the rubber. The sheet produced through the vulcanization step can become a gamma ray shielding sheet with excellent durability and elasticity.

[0058] In the method for manufacturing the gamma ray shielding sheet of the present invention, even though a large amount of tungsten having high density is used, the kneading step of maintaining a specific temperature is repeated several times, so that the tungsten can be uniformly dispersed in the rubber.

[0059] In another aspect, the present invention relates to a lead-free gamma radiation shielding sheet.

[0060] The lead-free gamma ray shielding sheet of the present invention is a sheet in which a large amount of tungsten is dispersed in a base rubber and molded.

[0061] The base rubber is at least one of natural rubber, styrene butadiene rubber, nitrile butadiene rubber, chloroprene rubber, butyl rubber, ethylene propylene rubber, and butadiene rubber.

[0062] The sheet may contain 600 to 1900 parts by weight of tungsten relative to 100 parts by weight of base rubber.

[0063] The tungsten may have a purity of 97% to 99.9% and a particle size of 0.01 μm to 100 μm.

[0064] The lead-free gamma ray shielding sheet of the present invention may contain an additive and antimony oxide. The additive can be zinc oxide (using zinc oxide), an oxidizing agent (vulcanizing agent), or a mixture thereof.

[0065] The additives may be mixed in an amount of 0.1 to 20 parts by weight based on 100 parts by weight of rubber.

[0066] The antimony oxide may be additionally mixed in an amount of 5 to 15 parts by weight based on 100 parts by weight of rubber.

[0067] The additive and antimony oxide can be referred to the above description. (Mode for carrying out the invention)

[0068] An embodiment of the present invention is disclosed below.

[0069] Example 1

[0070] 100g of chloroprene rubber was placed in a mixing roll and kneaded for 30 minutes. Then, 700g of tungsten, 5g of antimony oxide, 3g of zinc oxide, and 1g of Thjuram accelerator (TT) were placed in the mixing roll and kneaded for 30 minutes. During kneading, the surface temperature of the mixing roll was maintained at 35-40°C, and the temperature of the mixed solid attached to the roll surface was maintained at 75-85°C. The mixed solid in the form of a compressed sheet was cut into a certain thickness and size by the mixing roll and aged at a constant temperature for about one day. The matured and hardened mixed solid was placed in a kneader and made into a paste state while maintaining the surface temperature of the kneader roll and the surface temperature of the mixed solid (shield) at 35-40°C and 75-85°C, respectively. The mixed solid kneaded from the kneader was calendered (4 rolls) and pressed to a certain thickness. The sheets were pressed to a certain thickness and vulcanized using equipment called a roto-cure. In the end, two sheets of 1.1mm and 2.2mm thickness were acquired.

[0071]

[0072] Figures 4 to 7 are test results of the gamma ray shielding sheet manufactured in Example 1. Referring to Figures 4 to 7, the gamma ray (Cs-137) shielding rate of Example 1 is 10.3% (thickness 1.1 mm) and 18.6% (thickness 2.2 mm), respectively, which is about 10 times higher than the gamma ray (Cs-137) shielding rate of 4% (thickness 4 mm) of a conventional product (see Figure 1) (comparison converted to the same thickness). In addition, the sheet of Example 1 is very thin at 1.1 mm, but has a high shielding rate and is comfortable to wear, making it possible to provide a protective product.

[0073] We have looked at specific examples of the present invention. Those skilled in the art will understand that the present invention can be embodied in modified forms without departing from the essential characteristics. The scope of the present invention is defined in the claims, not the above description, and all differences within the scope of the present invention should be interpreted as being included in the present invention. [Industrial Applicability]

[0074] The present invention can be used as a gamma ray shielding sheet. The shielding sheet of the present invention can be applied to protective products that are comfortable to wear.

Claims

1. masticating the solid rubber in a mixing roll; adding tungsten and additives to the mixing roll and kneading them together with the rubber; The mixed solid is compressed to a constant thickness using a rolling roll to produce a sheet; The method for producing a lead-free gamma ray shielding sheet includes a step of vulcanizing the sheet by placing the sheet in a rolling roll, and the kneading step is a step of mixing 100 parts by weight of rubber with 600 to 1900 parts by weight of tungsten.

2. 2. The method of claim 1, wherein the kneading step further comprises mixing 5 to 15 parts by weight of flame-retardant antimony oxide with respect to 100 parts by weight of rubber.

3. The method for producing a lead-free gamma ray shielding sheet according to claim 1, characterized in that the additive is zinc oxide (zinc white), an oxidizing agent or a mixture thereof.

4. In the kneading step, the roll surface temperature of the mixing roll is 35 to 40° C., and the temperature of the mixed solid material attached to the roll surface is 75 to 85° C., The method for manufacturing a lead-free gamma ray shielding sheet according to claim 1, wherein the mixed solid material comprises rubber, tungsten and an additive.

5. 2. The method for manufacturing a lead-free gamma ray shielding sheet according to claim 1, wherein, in the sheet manufacturing step, a roll surface temperature of the rolling roll is 35 to 40° C., and a temperature of the mixed solid material attached to the roll surface is 75 to 85° C.

6. 2. The method of claim 1, wherein the rubber is at least one selected from the group consisting of natural rubber, nitrile butadiene rubber, styrene butadiene rubber, chloroprene rubber, butyl rubber, ethylene propylene rubber, and butadiene rubber.

7. A lead-free gamma ray shielding sheet in which tungsten and antimony oxide are mixed in a base rubber, the gamma ray shielding sheet comprising 600 to 1900 parts by weight of tungsten and 5 to 15 parts by weight of antimony oxide per 100 parts by weight of rubber.

8. 8. The lead-free radiation shielding sheet according to claim 7, wherein the lead-free gamma ray shielding sheet contains an additive which is zinc oxide (zinc white), an oxidizing agent, or a mixture thereof.

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