KR102334663B1 - Lead free gamma radiation sheilding sheet and method for preparing the same - Google Patents

Abstract

The present invention relates to a lead-free gamma radiation shielding sheet that is light and provides a high gamma radiation shielding rate, and a method for manufacturing the same. The method for manufacturing a lead-free gamma radiation shielding sheet comprises the steps of: putting solid rubber into a mixing roll to perform mastication on the same; adding tungsten and an additive to the mixing roll, and kneading the same with the rubber; manufacturing a sheet by pressing a mixed solid material to a predetermined thickness by using a rolling roll; and vulcanizing the sheet by putting the same in the rolling roll.

Description

LEAD FREE GAMMA RADIATION SHEILDING SHEET AND METHOD FOR PREPARING THE SAME

The present invention relates to a lead-free gamma-ray shielding sheet and a method for manufacturing the same, and more particularly, to a lead-free gamma-ray shielding sheet that is not heavy and provides a high gamma-ray shielding rate, and a method for manufacturing the same.

Radiation has existed since the earth was created, and we are still living in an environment full of radiation. There are various types of radioactive materials, including those that exist in nature and those that are artificially created for use in industry and medicine.

Ionizing radiation refers to radiation such as alpha, beta, proton, neutron, gamma, and X-rays that cause ionization when passing through a material. There is no need for shielding, and although beta rays are known to be larger than alpha rays, they can generally be blocked by thin aluminum foil or plastic plates.

On the other hand, gamma rays are electromagnetic waves that are generated from the decay or transformation of a nucleus and have higher energy than X-rays, and have a very strong penetrating power. For example, in medical X-rays, one photon is about 2,000 eV, whereas cosmic gamma rays are usually about 10 million eV (10 MeV) to 300 billion eV (300 GeV), and gamma rays produce 10,000 to 100 million times the energy of X-rays. Have. Therefore, it is possible to block gamma rays only when the density or thickness is higher than that of the X-ray shielding material.

Korean Patent Laid-Open Patent No. 10-2014-0086201 discloses a first metal sheet (lead) of a metal thin film that shields gamma rays as a shielding body for shielding radiation generated in a nuclear reactor and a second metal sheet (cadnium) of a metal thin film that shields neutrons is starting As in the Korean Patent Laid-Open Patent Publication, a thick lead sheet and heavy water are generally used as a gamma ray shielding agent in a nuclear reactor. In addition, it was common for workers at nuclear power plants to use lead robes. Such a lead gown is used in the form of a sheet by dispersing the lead component in vinyl chloride resin (PVC) and extruding it, but it is heavy with a weight of 5 to 10 kg, so it is uncomfortable to wear and has poor activity. In addition, lead is a heavy metal and is highly hazardous, so it is difficult to dispose of it.

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 comprising 80 to 200 parts by weight of tungsten powder and 5 to 50 parts by weight of additives to 100 parts by weight of acrylonitrile-butadiene rubber (NBR), , Korea Patent No. 10-1804295 is a radiation shielding rubber containing 80 to 200 parts by weight of tungsten powder, 100 to 300 parts by weight of tantalum powder, and 5 to 50 parts by weight of additives to 100 parts by weight of acrylonitrile-butadiene rubber (NBR) compositions are disclosed. The above two Korean patents only present test data for the X-ray shielding rate (75 to 95%), and specific test data for gamma-ray shielding, which has more than 100 million times the energy of X-rays, or the applicability thereof no mention In addition, Korean Patent No. 10-1804295 discloses adipic acid ether ester type (RS-107) to prevent aggregation of metals such as tungsten powder and tantalum powder when using a large amount of metals. Tungsten powder and tantalum powder are coated with a plasticizer (Claim 1).

1 is a catalog of radiation shielding products of Sanbon Chemical Industry in Japan that are currently commercially available. Referring to the catalog, the thickness of the product is 4 mm, but the shielding rate of gamma rays (Cs 137) is only 4%. As such, existing radiation shielding products have a low gamma ray shielding rate, so it is difficult to safely protect workers from gamma rays.

An object of the present invention is to provide a sheet having an increased gamma-ray shielding rate without using lead.

An object of the present invention is to provide a shielding sheet usable as a screen, blanket, and protective clothing for gamma-ray shielding in a nuclear power plant.

the present invention

Putting the solid rubber in a mixing roll to Soviet (素煉);

kneading with the rubber by adding tungsten and an additive to the mixing roll;

manufacturing a sheet by pressing the resulting mixed solid material to a predetermined thickness using a rolling roll;

Putting the sheet into a rolling roll and vulcanizing,

The kneading step relates to a method of manufacturing a gamma ray shielding sheet, which is a step of mixing 600 to 1900 parts by weight of tungsten with respect to 100 parts by weight of rubber.

In another aspect, the present invention

A gamma ray shielding sheet in which tungsten and antimony oxide are mixed with base rubber,

The gamma ray shielding sheet relates to a gamma ray shielding sheet containing 600 to 1900 parts by weight of tungsten and 5 to 15 parts by weight of antimony oxide based on 100 parts by weight of rubber.

The radiation shielding sheet prepared in the present invention has a gamma ray (Cs-137) shielding rate of 10.3% (thickness 1.1mm) and 18.6% (thickness 2.2mm), respectively, and the gamma rays (Cs- 137) The shielding rate is 4% (thickness 4mm) and it is about 10 times higher (comparison with the same thickness). In addition, although the sheet of Example 1 is very thin with a thickness of 1.1 mm, it is possible to provide a protective product with excellent wearing comfort due to a high shielding rate.

The gamma-ray shielding sheet of the present invention increases the gamma-ray shielding rate by allowing the tungsten to be uniformly dispersed in the sheet even though high-density tungsten is used in a large amount (600 to 1900 parts by weight compared to 100 parts by weight of the base rubber). The gamma ray shielding sheet manufacturing method of the present invention maintains the temperature of the roller of the mixing roll and the mixed solid (rubber + tungsten) at 35 to 40 ° C and 75 to 85 ° C, respectively, and repeatedly injects the mixed solid into the mixing roll to produce a large amount of tungsten. It can be uniformly dispersed in rubber.

1 is a catalog of radiation shielding products of Sanbon Chemical Industry in Japan that are currently commercially available.
2 is a schematic diagram of the Soviet Union and the kneading apparatus.
3 is a photograph of a mixed solid material that has undergone a kneading process.
4 is a vulcanized final product (sheet (1,1 mm) of Example 1).
5 to 7 are test results of the gamma ray shielding sheet prepared in Example 1.

Hereinafter, embodiments and embodiments of the present invention will be described in detail so that those of ordinary skill in the art to which the present invention pertains can easily carry out the present invention.

The terminology used herein is used only to describe specific embodiments, and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present application, terms such as "comprise" or "have" are intended to designate that a feature, number, step, operation, element, or combination thereof described in the specification exists, and includes one or more other features or It should be understood that the possibility of the presence or addition of numbers, steps, acts, elements, or combinations thereof is not precluded in advance.

The lead-free gamma-ray shielding sheet of the present invention includes a USSR step, a kneading step, a sheet manufacturing step (calendar step), and a vulcanization step.

The Soviet step is a step of crushing and pulverizing the rubber by putting the solid rubber in a mixing roll. In the rubber Soviet stage, the molecular chain of raw rubber (eg, raw rubber) is mechanically cut using a mixing roll (eg, a kneader), and the kinking between the molecules in the chain state is loosened to lower the polymerization degree and viscoelasticity. (粘彈性) is lowered and plasticity (可塑性) is increased.

The solid rubber may be any one or more of natural rubber, styrene butadiene rubber, nitrile butadiene rubber, chloroprene rubber, butyl rubber, ethylene propylene rubber, and butadiene rubber.

The mixing roll used in the Soviet stage and the kneading stage refers to a facility capable of crushing or compressing rubber by having two rolls. Referring to FIG. 2 , the mixing roll rotates two rollers in opposite directions, and when solid rubber is inserted between the rollers, the mixing roll is pulverized.

In the kneading step, tungsten and an additive are added to the mixing roll and mixed together with the rubber (refer to FIG. 2A ).

The mixing roll may be the same as or different from the mixing roll of the Soviet stage.

The tungsten is a high density (19.25 g/cm ³ ), high specific gravity metal. In the present invention, 600 to 1900 parts by weight of tungsten is used based on 100 parts by weight of rubber.

When the content of tungsten is less than 600 parts by weight, the gamma-ray shielding rate is low, and when it exceeds 1900 parts by weight, it is difficult to uniformly disperse in the kneading step, and it is difficult to extrude to a certain thickness in the calendar process.

In the present invention, tungsten having a purity of 97% to 99.9% and a particle size (particle size) of 0.01 μm to 100 μm may be used.

The additive used in the kneading step may be zinc oxide (using zinc oxide), an oxidizing agent (vulcanizing agent), or a mixture thereof.

The oxidizing agent (vulcanizing agent) may be sulfur, a digiocarbamate accelerator, a Thjuram or a Thiourea accelerator.

The additive may be mixed in an amount of 0.1 to 20 parts by weight based on 100 parts by weight of the rubber.

The gamma ray shielding sheet of the present invention can improve elasticity, tear strength and tensile strength as well as durability by mixing an additive such as zinc oxide with rubber.

In the kneading step, 5 to 15 parts by weight of flame-retardant antimony oxide may be additionally mixed with respect to 100 parts by weight of rubber.

The antimony oxide may have a particle size (particle size) of 0.1 μm to 100 μm.

The antimony oxide increases the flame retardancy of the gamma ray shielding sheet.

The kneading step may be compressed and dispersed by repeating the mixed solid material several times with the mixing roll.

In the kneading step, the process of cutting the mixed solid that has passed through the mixing roll and re-injecting it back into the mixing roll may be repeated several times so that tungsten is uniformly dispersed in the rubber. Here, the mixed solid is a mixture containing rubber, tungsten, an additive, antimony oxide, and the like, and is a paste in a solid state maintaining viscosity, not in a liquid state.

At this time, in the kneading step, the temperature of the mixed solid adhering to the surface of the roll of the mixing roll may be 75 ~ 85 ℃. If the temperature of the mixed solid material is lower than the above temperature, sufficient dispersion is difficult, and if the temperature of the mixed solid material is higher than the above range, the rubber easily ripens or scorch phenomenon (vulcanization proceeds under undesired conditions, changing the properties of the rubber) appear.

The method for manufacturing a gamma ray shielding sheet of the present invention may further include a maturation step of cutting the mixed solid material in the form of a sheet that has undergone the kneading step to a predetermined thickness and size and storing it for a predetermined time.

The aging step may be 12 hours or more, preferably 24 hours or more.

The aging step may be performed at room temperature.

Mixed solids that have not undergone the aging step may have problems with a high defect rate or a shortened product life over time.

The sheet manufacturing step (calendar step) is a step of pressing the mixed solid material generated in the kneading step to a predetermined thickness using a rolling roll.

In the sheet manufacturing step, a sheet with a constant thickness can be manufactured using a calendar (in an inverted L-shape, with two rolling rolls on top and two on the bottom).

In the manufacturing method of the present invention, the aged and hardened mixed solid (shielding body) is put into a kneader before the sheet manufacturing step to make a paste by heat and pressure. At this time, the surface temperature of the mixed solid (shielding body) is maintained at 75-85° C. to prevent scorching.

In the sheet manufacturing step, a mixed solid material (shielding body) maintained at 75 to 85° C. may be injected into the rolling roll of the calendar.

In the sheet manufacturing step, similarly to the kneading step, the temperature of the mixed solid adhering to the surface of the roll of the rolling roll may be 75 to 85°C.

The vulcanization step is a step of vulcanizing the sheet by putting it in a rolling roll.

The vulcanization step is a step in which the rubber reacts with additives such as sulfur by applying heat and pressure to the compressed sheet using a device called a rotor Q. The sheet manufactured through the vulcanization step may be a gamma-ray shielding sheet having excellent durability and elasticity.

In the method for manufacturing a gamma ray shielding sheet of the present invention, tungsten can be uniformly dispersed in rubber by repeating the kneading step of maintaining a specific temperature several times despite using a large amount of high-density tungsten.

In another aspect, the present invention relates to a lead-free gamma ray shielding sheet.

The lead-free gamma-ray shielding sheet of the present invention is a sheet formed by dispersing a large amount of tungsten in a base rubber.

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.

The sheet may contain 600 to 1900 parts by weight of tungsten based on 100 parts by weight of the base rubber.

The tungsten may have a purity of 97% to 99.9%, and a particle size (particle size) of 0.01 μm to 100 μm.

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

The additive may be mixed in an amount of 0.1 to 20 parts by weight based on 100 parts by weight of the rubber.

5 to 15 parts by weight of the antimony oxide may be additionally mixed with respect to 100 parts by weight of the rubber.

The additive and antimony oxide may refer to the above-mentioned contents.

Example 1

100 g of chloroprene rubber was put on a mixing roll and stirred for 30 minutes. Then, 700 g of tungsten, 5 g of antimony oxide, 3 g of zinc oxide, and 1 g of Thjuram accelerator (TT) were added to the mixing roll and kneaded for 30 minutes. During kneading, the temperature of the mixed solid adhering to the roll surface of the mixing roll was maintained at 75-85°C. The mixed solid material in the form of a sheet compressed on the mixing roll was cut to a certain thickness and size and aged at room temperature for about 1 day. The aged and hardened mixed solids were put into a kneader to make a paste while maintaining the surface temperature of the mixed solids (shielding body) at 75-85°C. The mixed solids kneaded from the kneader were calendered (four rolls) and compressed to a certain thickness. The sheet pressed to a certain thickness was vulcanized using a device called RotorQ. Two sheets of 1.1 mm and 2.2 mm thickness were finally obtained.

4 to 7 are test results of the gamma-ray shielding sheet prepared in Example 1. Referring to FIGS. 4 to 7, the gamma-ray (Cs-137) shielding rate of Example 1 is 10.3% (thickness 1.1mm), respectively, As 18.6% (thickness 2.2mm), it is about 10 times higher than that of a conventional commercially available product (refer to FIG. 1) of 4% (thickness 4mm) shielding rate of gamma ray (Cs-137) (comparison with the same thickness). In addition, although the sheet of Example 1 is very thin with a thickness of 1.1 mm, it is possible to provide a protective product with excellent wearing comfort due to a high shielding rate.

So far, specific embodiments of the present invention have been described. Those of ordinary skill in the art to which the present invention pertains will understand that the present invention can be implemented in a modified form without departing from the essential characteristics. The scope of the present invention is indicated in the claims rather than the foregoing description, and all differences within the scope equivalent thereto should be construed as being included in the present invention.

Claims (8)

Putting the solid rubber in a mixing roll to Soviet (素煉);
adding tungsten and an additive to the mixing roll and kneading with the rubber;
manufacturing a sheet by pressing the resulting mixed solid material to a predetermined thickness using a rolling roll;
Putting the sheet into a rolling roll and vulcanizing,
The additive is zinc oxide (zincification), an oxidizing agent, or a mixture thereof,
The mixed solid is a paste in a solid state including rubber, tungsten and additives, but maintaining viscosity,
The solid rubber is any one or more of natural rubber, nitrile butadiene rubber, styrene butadiene rubber, chloroprene rubber, butyl rubber, ethylene propylene rubber, butadiene rubber,
In the kneading step, 600 to 1900 parts by weight of the tungsten and 0.1 to 20 parts by weight of the additive are mixed with respect to 100 parts by weight of rubber,
The kneading step is a lead-free gamma ray shielding sheet, characterized in that by repeating the process of cutting the mixed solid material in the paste state that has passed through the mixing roll and re-injecting it back into the mixing roll several times so that the tungsten is uniformly dispersed in the solid rubber. manufacturing method. The method of claim 1, wherein in the kneading step, 5 to 15 parts by weight of flame-retardant antimony oxide are additionally mixed with respect to 100 parts by weight of rubber. delete The method of claim 1, wherein in the kneading step, the temperature of the mixed solid adhering to the surface of the mixing roll is 75-85°C. The method of claim 1, wherein in the sheet manufacturing step, the temperature of the mixed solid adhering to the surface of the rolling roll is 75 to 85°C. delete A lead-free gamma-ray shielding sheet manufactured according to any one of claims 1, 2, 4 and 5. delete

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