JP2013170836A - Radiation shield glass laminate having resistance to discoloration - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation shield glass laminate 10 having resistance to discoloration, which allows a resin layer 13 to be hardly discolored for a long period, so that the transparency of the whole glass laminate can be maintained for a long period.SOLUTION: A glass laminate includes a CeOcontaining glass plate 11 and a radiation shield glass plate 12 which are stuck each other and laminated through a resin layer 13. The CeOcontaining glass plate 11 is arranged adjacent to a radiation source RS.

Description

  The present invention relates to a radiation shielding glass laminate suitable for glass for windows in, for example, nuclear facilities, medical facilities, research facilities and the like.

  As is well known, radiation shielding glass is a medical facility equipped with nuclear facilities such as storage facilities and processing facilities for spent nuclear fuel, heavy machinery such as forklifts used outdoors with high radioactive concentration, CT scanning devices, X-ray devices, etc. It is used as glass for windows in related facilities or research facilities equipped with X-ray diffractometers and particle accelerators. This radiation shielding glass is required to have high transparency for observing the inside of a facility or the like, as well as shielding various radiations to ensure safety to the human body and the environment.

  Conventionally, as a glass block body having both radiation shielding ability and transparency, it is used in the above-described applications. For example, a glass block body described in Patent Document 1 is disclosed. However, such a block-shaped radiation shielding glass needs to be cooled very slowly so as not to cause distortion inside after pouring molten glass into a large mold. Time was required, leading to a delay in delivery and an increase in manufacturing costs.

  Therefore, to date, the following patent is a glass laminate that combines radiation shielding ability and transparency at a high level, and is laminated with a plurality of radiation shielding glasses having different compositions as transparent glass layers. The radiation shielding glass laminate described in Document 2 is disclosed.

Japanese Patent Laid-Open No. 6-127773 JP 2008-286787 A

  However, the radiation shielding glass laminate described in Patent Document 2 is transparent for bonding radiation shielding glass, although each radiation shielding glass itself constituting the glass laminate has resistance to browning due to radiation irradiation. There was a problem that the resin layer was discolored by long-term use and the transparency of the entire glass laminate was lowered.

  The present invention has been made in view of the above-mentioned problems in the conventional radiation shielding glass laminate, and the glass is difficult to be colored and the resin layer is also difficult to discolor over a long period of time. It is an object to provide a hardly discolorable radiation shielding glass laminate capable of maintaining the transparency of the entire glass laminate for a long period of time.

  As a result of intensive studies on the reduction in transparency of the radiation shielding glass laminate, the present inventors formed a glass network structure or a resin layer by irradiating γ rays, X rays, or ultraviolet light having a wavelength of 400 nm or less. It was noted that the radicals generated by breaking the bonds of the polymer compounds and other organic compounds, and the bonds formed between the radicals are the main factors for the discoloration of the resin layer. In particular, ultraviolet light with a wavelength of 10 to 400 nm can be effectively absorbed by cerium oxide contained in the glass, so that coloring of the resin can be suppressed, and cerium oxide is added even when the glass is irradiated with radiation such as γ rays or X rays. As a result, it has been found that it is difficult to be colored brown, and the present invention has been made.

  That is, the hardly discolorable radiation shielding glass laminate of the present invention is a radiation shielding glass laminate in which a plurality of radiation shielding glasses are laminated by a resin layer, and one outermost layer contains cerium oxide. It is characterized by being.

  Further, the hardly discolorable radiation shielding glass laminate of the present invention is characterized in that the glass containing cerium oxide is radiation shielding glass.

  In addition, the hardly discolorable radiation shielding glass laminate of the present invention is characterized in that the glass-containing thickness of the glass containing cerium oxide is 3 mm or more.

  Further, the hardly discolorable radiation shielding glass laminate of the present invention is characterized in that the thickness of the glass in the lamination direction is 30 mm or less.

  The radiation shielding glass laminate according to the present invention not only can prevent browning of the glass itself when irradiated with radiation from the glass side because the outermost glass layer contains cerium oxide. By efficiently absorbing ultraviolet light having a wavelength of 400 nm or less with cerium oxide, coloring of the resin layer by ultraviolet light can be suppressed, and the transparency of the entire glass laminate can be maintained over a long period of time. In addition, although originally uncolored glass depends on the type, it can effectively absorb light having a wavelength shorter than 300 nm, but often cannot sufficiently absorb ultraviolet light having a wavelength of 300 to 400 nm. When cerium oxide is contained in the glass, there is almost no absorption at wavelengths longer than the wavelength of about 400 nm in the visible region, but light having a shorter wavelength than the wavelength of about 400 nm in the ultraviolet region is almost absorbed. Therefore, almost no coloration of the glass itself can be confirmed, and it is possible to effectively prevent the resin from being irradiated with ultraviolet rays. The content of cerium oxide is preferably 0.1 to 3.0%, and if it is less than 0.1%, it is difficult to sufficiently obtain an ultraviolet light shielding effect, and if it is more than 3.0%, it results from cerium oxide. The transparency of the glass tends to be impaired by coloring.

  In addition, since the radiation shielding glass laminate according to the present invention is formed by bonding glass with a resin, even when used in a humid environment, moisture does not directly contact the glass surface, so that the surface such as alkali blown or burned is used. Degradation is unlikely to occur.

  In addition, according to the hardly discolorable radiation shielding glass laminate having a thickness of 3 mm or more in the direction of lamination of the glass containing cerium oxide, it is difficult to break because it is easy to obtain sufficient rigidity, and absorbs ultraviolet light sufficiently. Therefore, it is not necessary to extremely increase the content of cerium oxide, and coloring due to cerium oxide can be suppressed, and a glass with high transmittance can be obtained. Furthermore, even if there is little content of cerium oxide, since it has sufficient thickness, it can fully absorb an ultraviolet-ray and can prevent discoloration of a resin layer more effectively.

  Further, according to the hardly discolorable radiation shielding glass laminate having a thickness in the laminating direction of the radiation shielding glass of 30 mm or less, each radiation shielding glass is obtained by various molding methods such as a rollout method that is more productive than the casting method. Even when the total thickness of the hardly discolorable radiation shielding glass laminate exceeds 200 mm, the radiation shielding glass produced by the above molding method can be laminated and bonded together. Therefore, the productivity can be remarkably improved and it can be provided to the market at a lower cost.

  Radiation shielding glass emits electrons due to the Compton effect when it is irradiated with high dose density of γ-rays or X-rays, and it tends to be charged. Although it may be destroyed, if it is a block-like laminate produced by laminating and sticking radiation shielding glass with a plate thickness of 30 mm or less, dielectric breakdown occurs more than an integrated block produced by casting. It tends to be difficult.

It is a schematic sectional drawing of the hardly discolorable radiation shielding glass laminated body of this embodiment. It is a schematic sectional drawing of the hardly discolorable radiation shielding glass laminated body of this embodiment.

As shown in FIG. 1, the hardly discolorable radiation shielding glass laminate 10 of the present embodiment is configured by laminating a CeO ₂ -containing glass 11 and a radiation shielding glass 12 by laminating them with a resin layer 13. In the present embodiment, the CeO ₂ -containing glass 11 and the radiation shielding glass 12 are bonded together by a single resin layer 13, and the CeO ₂ -containing glass 11 is disposed on the radiation source RS side.

The CeO ₂ -containing glass 11 of the present embodiment can be used even if the radiation shielding ability is not high, such as glass (glass A) obtained by adding a predetermined amount of CeO ₂ to window glass, but radiation shielding is possible. High performance is preferable because coloring and deterioration of the resin due to γ rays and X rays can be prevented. Note that having radiation shielding ability means that the lead equivalent is 0.03 mmPb / mm or more with respect to X-rays having a tube voltage of 150 kV.

The CeO ₂ -containing glass 11 having radiation shielding ability not containing PbO is, for example, a mass percentage in terms of oxide, SiO ₂ 40 to 70%, CeO ₂ 0.1 to 3%, Al ₂ O ₃ 0 to 4%. BaO 7 to 27%, ZnO 0 to 20%, ZrO ₂ 0 to 3%, Na ₂ O 0 to 12%, K ₂ O 0 to 12%, and a glass B.

  The reason for limiting the composition range of the radiation shielding glass 11 as described above is as follows.

SiO ₂ is essential as a glass network structure forming component. When the content is less than 40%, the weather resistance is deteriorated. On the other hand, when the content exceeds 70%, a component for increasing the density and a component having a high radiation shielding ability cannot be contained sufficiently.

CeO ₂ is a component that prevents browning of the glass due to irradiation and absorbs ultraviolet rays having a wavelength of 400 nm or less. Therefore, when CeO ₂ is contained, light having a wavelength of 400 nm or less is absorbed, so that discoloration of the resin layer 13 can be prevented. If the content is less than 0.1%, the action is poor, and if it exceeds 3%, the glass is colored yellow by the light absorption of CeO ₂ itself, and the light transmittance is lowered.

If Al ₂ O ₃ exceeds 4%, the meltability deteriorates.

  BaO is an essential component for increasing the density of the glass and having a high radiation shielding ability. However, when the content is less than 7%, its action is poor, and when it exceeds 27%, it tends to devitrify. .

  ZnO is a component that increases the density of glass and is a component that has a high radiation shielding ability. However, when the content exceeds 20%, it tends to devitrify.

ZrO _{2 is} also a component that increases the density and has a high radiation shielding ability. However, if the content exceeds 3%, surface devitrification is likely to occur. Moreover, it is also a component which improves a weather resistance.

Na 2 _{O, K} 2 _O, as well as a component to increase the melting property of the glass, a component to lower the respective electrical resistance, be a component having an effect of preventing the dielectric breakdown because it hardly charges accumulate in the glass , If necessary. When these contents exceed 12%, the weather resistance deteriorates, and the contents of components that increase the density of the glass and components that can increase the radiation shielding ability are decreased, and the shielding ability tends to be lowered.

In addition to the above components, alkali metal oxides such as Li ₂ O, alkaline earth oxides such as MgO, CaO, and SrO, components having absorption in the ultraviolet region of wavelength 300 to 400 nm, such as TiO ₂ , B Components for forming a glass skeleton such as ₂ O ₃ and P ₂ O ₅ and fining agents such as As ₂ O ₃ , Sb ₂ O ₃ and Cl may be added as necessary.

The CeO ₂ containing glass 11 having a radiation shielding ability containing PbO, for example, in percent by mass of oxide _{equivalent, PbO 15~45%, SiO 2 40~60} %, CeO 2 0.1~3%, B _{2 O 3 0~10%, Na 2} O 0~10%, may be used those having a composition of K 2 O 0~10% (glass C).

The CeO ₂ -containing glass 11 is formed into a flat plate shape by a roll-out method, and the thickness in the stacking direction is 3 to 30 mm. If it is smaller than 3 mm, the ultraviolet rays may reach the resin layer 13 because the ultraviolet rays may not be sufficiently absorbed by the cerium oxide contained in the CeO ₂ -containing glass 11, and the discoloration suppressing action becomes poor. When it exceeds 30 mm, it becomes difficult to produce the CeO ₂ -containing glass 11 efficiently by a molding method such as a roll-out method.

The radiation shielding glass 12 of the present embodiment is, for example, a mass percentage in terms of oxide, SiO ₂ 10 to 40%, PbO 45 to 80%, B ₂ O ₃ 0 to 10%, Na ₂ O 0 to 10%, A composition of K ₂ O 0 to 10% is mentioned as glass D. Thus, the radiation shielding glass 12 has a high radiation shielding ability because PbO is 45% or more.

  By having such a glass composition, it is possible to obtain a sufficient γ-ray shielding ability as a glass characteristic, and no devitrification occurs even if a large amount of PbO is contained in the glass composition.

  The reason why the composition range of the radiation shielding glass 12 is limited as described above is as follows.

SiO ₂ is a component that forms a network structure of glass. Its content is 10 to 40%, preferably 15 to 35%, more preferably 20 to 30%. When the content of SiO ₂ is more than 40%, the high temperature viscosity of the glass becomes high, melting and molding become difficult, and the content of PbO having a high radiation shielding ability tends to decrease, so that the radiation shielding ability is lowered. To do. On the other hand, when the content of SiO ₂ is less than 10%, the components forming the skeleton of the glass become too small, the glass becomes structurally unstable, and the water resistance of the glass is lowered.

  PbO is a component having a high ability to shield radiation. Its content is 45-80%, preferably 50-80%, more preferably 60-80%, most preferably 70-80%. When the content of PbO exceeds 80%, components other than PbO are relatively reduced, and the glass becomes thermally unstable. On the other hand, if the PbO content is less than 45%, the radiation shielding ability is lowered.

B ₂ O ₃ is a component that lowers the high-temperature viscosity of the glass to improve the meltability and formability, and to increase the thermal stability. Its content is 0-10%, preferably 0.1-8%, more preferably 0.1-5%. When the content of B ₂ O ₃ is more than 10%, the water resistance of the glass is lowered.

Na ₂ O and K ₂ O are components that lower the high-temperature viscosity of the glass and increase the meltability and moldability. The content is 0 to 10%, preferably 0 to 8%, more preferably 1 to 5%. When these contents are more than 10%, the radiation shielding ability is lowered because the PbO content tends to be lowered.

Components forming a glass skeleton such as Al ₂ O ₃ and P ₂ O ₅ , alkaline earth oxides such as MgO, CaO, SrO and BaO, and clarification such as As ₂ O ₃ , Sb ₂ O ₃ and Cl An agent may be added as necessary.

  Moreover, the radiation shielding glass 12 is shape | molded by the roll-out method at flat form, and the thickness of a lamination direction is 30 mm or less. If it exceeds 30 mm, it becomes difficult to form the radiation shielding glass 12 by the roll-out method which is excellent in productivity. The hardly discolorable radiation-shielding glass laminate 10 of the present embodiment has two radiation-shielding glasses (11, 12) having different compositions and the same thickness bonded together, but those having the same composition may be bonded together. Different thicknesses may be bonded together.

  The resin layer 13 consists of transparent resin, and the thickness of the lamination direction is 10-2000 micrometers. The resin layer 13 of the present embodiment is made of a polyvinyl alcohol resin. In addition to the resin layer 13, fluorine resin, polyethylene terephthalate resin, polybutylene terephthalate resin, polyethylene naphthalate resin, polyamide resin, polyacetal resin, polyethylene (including low density and high density), polypropylene resin, and polyethylene-polypropylene A transparent resin such as a polymerization resin, an acrylonitrile-butadiene-styrene copolymer resin, a polycarbonate resin, or a vinyl acetate resin can be employed. Conductivity is imparted to these synthetic resins by mixing and dispersing fine particles of tin-containing indium oxide (ITO) and antimony-containing tin oxide (ATO) and metal fine particles such as gold, silver, copper, nickel, and platinum. May be.

  Below, the manufacturing method of the hardly discolorable radiation shielding glass laminated body 10 of this embodiment is demonstrated.

“Production of CeO ₂ -containing glass 11 and radiation shielding glass 12”
First, glass raw materials are respectively prepared so as to have the above composition, melted at 1000 to 1500 ° C., and then a glass plate having a thickness of about 3 to 30 mm is produced by a roll-out method. CeO ₂ -containing glass 11 and radiation shielding glass 12 are obtained by subjecting this glass plate to annealing (slow cooling) treatment, cutting, polishing and the like as necessary. In addition, as a method for forming the CeO ₂ -containing glass 11 and the radiation shielding glass 12, a press forming method, a down draw method, a fusion method, or the like can be employed.

“Lamination of CeO ₂ -containing glass 11 and radiation shielding glass 12”
A resin sheet made of a polyvinyl alcohol resin and having a thickness of about 10 to 2000 μm is stacked so as not to sandwich air between the CeO ₂ -containing glass 11 and the radiation shielding glass 12, and is heat-treated at a temperature about the glass transition point of the resin sheet. By doing so, the CeO ₂ -containing glass 11 and the radiation shielding glass 12 are laminated together by the resin layer 13. At this time, it is preferable to pressurize the CeO ₂ -containing glass 11 and the radiation shielding glass 12 in the laminating direction in order to bring the resin layer 13 into close contact with each other.

Further, in place of the resin sheet, it may be performed bonding of CeO ₂ containing glass 11 and radiation shielding glass 12 by using a liquid resin. For example, after defoaming a two-component mixed type liquid resin in which a main agent and a curing agent (initiator) are mixed, an appropriate amount is poured onto the main surface of the CeO ₂ -containing glass 11, and the radiation shielding glass 12 is placed on the air. The CeO ₂ -containing glass 11 and the radiation shielding glass 12 are bonded together by superimposing them so as not to sandwich them, and applying external stimuli such as heat and ultraviolet rays as necessary to cure the resin. Thereafter, excess resin protruding from the end is removed. Thus, the hardly discolorable radiation shielding glass laminate 10 of the present embodiment can be produced. As the liquid resin to be cured after lamination, other transparent resins such as an epoxy resin, an unsaturated polyester resin, and an acrylic resin can be used.

Incidentally, when attaching the CeO ₂ containing glass 11 and radiation shielding glass 12, to improve the adhesion strength, be surface treated with the bonding surface of CeO ₂ containing glass 11 and radiation shielding glass 12 with a silane coupling agent or the like preferable. As the silane coupling agent, an aminosilane group having an amino group, an epoxysilane group having an epoxy group, an acrylicsilane group having an acrylic group, or the like can be employed.

After fixing one of the hardly discolorable radiation shielding glass laminates 10 thus obtained, or a laminate obtained by repeatedly laminating the resin layer 13 and the radiation shielding glass 12 to the radiation shielding glass 12, to a metal frame, from concrete or steel material, etc. The radiation shielding window can be formed by disposing the opening in the wall and filling the gap between the opening and the metal frame with a joint agent or the like. Note that when configuring the radiation shielding windows, to position the CeO ₂ containing glass 11 to the radiation source RS side.

Thus, the hardly discolorable radiation shielding glass laminate 10 of the present embodiment can not only prevent browning of the CeO ₂ -containing glass 11 itself when irradiated with radiation from the CeO ₂ -containing glass 11 side, Since cerium oxide can effectively absorb ultraviolet rays having a wavelength of 400 nm or less, the ultraviolet rays hardly reach the resin layer 13 and can effectively prevent discoloration of the resin layer 13, and the transparency of the entire glass laminate can be maintained for a long time. Can be maintained over a period of time.

In addition, the hardly discolorable radiation shielding glass laminate 10 of the present embodiment has a thickness of 3 mm or more in the lamination direction of the CeO ₂ -containing glass 11, so that the resin layer 13 can be more effectively prevented from being discolored, and impact can be prevented. This is preferable because it is difficult to break.

Moreover, since the thickness in the lamination direction of the CeO ₂ -containing glass 11 and the radiation shielding glass 12 is 30 mm or less, the hardly discolorable radiation shielding glass laminate 10 of the present embodiment has a float bath molding method other than the rollout method, Various molding methods such as a downdraw method and a press molding method can be appropriately selected for molding. In general, since it is difficult to form a glass plate having a thickness of 30 mm or more by a roll-out method or the like, it is necessary to use a casting method. Therefore, a glass plate having a thickness of 30 mm or more is formed with an inner surface and an outer surface of the glass plate. It must be cooled slowly while preventing damage due to temperature differences. In particular, when it exceeded 200 mm, it had to be gradually cooled over several months, and the productivity was not high. On the other hand, the hardly discolorable radiation shielding glass laminate 10 of the present embodiment laminates the CeO ₂ -containing glass 11 and the radiation shielding glass 12 having a thickness of 30 mm or less even when the total thickness exceeds 200 mm. Therefore, the productivity can be greatly improved, and it can be provided to the market at a lower cost.

In the above embodiment, only the CeO ₂ containing glass 11 to be positioned in the radiation source RS side and contain a cerium oxide, a radiation shielding glass 12 to be positioned on the opposite of the observer side of the radiation source RS However, the present invention is not limited to this, and the radiation shielding glass 12 may contain cerium oxide.

Combination of CeO ₂ containing glass 11 and radiation shielding glass 12 of discoloring radiation shielding glass laminate 10 of the present embodiment, the glass A- Glass B, Glass A- Glass C, glass A- Glass D, glass B- A combination of glass B, glass B-glass C, glass B-glass D, glass C-glass C, glass C-glass D is possible. Further, in the same glass combination, the same thickness or different thicknesses may be used.

  As mentioned above, although the hard-discoloration radiation shielding glass laminated body 10 of this embodiment was demonstrated, this invention can be implemented also with another form.

As shown in FIG. 2, the hardly discolorable radiation shielding glass laminate 20 of the present embodiment has a CeO ₂ containing glass 21 and a plurality of radiation shielding glasses (22, 23) bonded together by resin layers (24, 25). The CeO ₂ -containing glass 21 is arranged on the radiation source RS side.

As the CeO ₂ -containing glass 21 of this embodiment, one having the same composition as the CeO ₂ -containing glass 11 of Example 1 can be used.

As the radiation shielding glass 22 of the present embodiment, any one having the same composition as the CeO ₂ -containing glass 11 or the radiation shielding glass 12 of Example 1 can be used.

  As the radiation shielding glass 23 of this embodiment, one having the same composition as the radiation shielding glass 12 of Example 1 can be used.

The combination of the CeO ₂ -containing glass 21 and the radiation shielding glass (22, 22) of the hardly discolorable radiation shielding glass laminate 20 of the present embodiment is glass A-glass B-glass B, glass A-glass B-glass C, Glass A-glass B-glass D, glass A-glass C-glass C, glass A-glass C-glass D, glass A-glass D-glass D, glass B-glass B-glass B, glass B-glass B -Glass C, Glass B-Glass B-Glass D, Glass B-Glass C-Glass C, Glass B-Glass C-Glass D, Glass B-Glass D-Glass D, Glass C-Glass C-Glass C, Glass Combinations of C-glass C-glass D and glass C-glass D-glass D are possible. Further, in the same glass combination, the same thickness or different thicknesses may be used.

  The resin layers 24 and 25 can be the same as the resin layer 13 of the first embodiment. Further, the resin layer 24 and the resin layer 25 may have different thicknesses or resins having different compositions.

  The present invention can be carried out in other modes without various modifications, modifications, and variations based on the knowledge of those skilled in the art without departing from the spirit of the present invention. In addition, any invention-specific matters may be replaced with other technologies within the scope where the same action or effect occurs, and the integrally-configured invention-specific matters are constituted by a plurality of members. Alternatively, the invention specific items configured by a plurality of members may be implemented in an integrated configuration.

  The hardly discolorable radiation shielding glass laminate according to the present invention is suitable for a window material of a nuclear facility where strong radiation is irradiated, a window material of a research facility equipped with a large accelerator, and the radiation protection window of a medical device. In view of the characteristics that are difficult to deteriorate even when exposed to ultraviolet rays or moisture, the lens cover that protects the camera mounted on the robot working inside the nuclear reactor or the scattered radioactive material For applications where it is necessary to work outdoors or in places with high humidity and to shield radiation, such as vehicles for heavy-duty collection (for example, window materials for heavy machinery such as forklifts) and window materials for robots, etc. Particularly preferred.

10, 20 Difficult color-changing radiation shielding glass laminate 11, 21 CeO ₂ containing glass 12, 22, 23 Radiation shielding glass 13, 24, 25 Resin layer

Claims (4)

  A radiation-shielding glass laminate in which a plurality of glasses are laminated by laminating with a resin layer, wherein the one outermost layer glass contains cerium oxide, .   The hardly discolorable radiation shielding glass laminate according to claim 1, wherein the glass containing cerium oxide is radiation shielding glass.   The hardly discolorable radiation shielding glass laminate according to claim 2, wherein the radiation shielding glass containing cerium oxide has a thickness in the laminating direction of 3 mm or more.   4. The hardly discolorable radiation shielding glass laminate according to claim 2, wherein a thickness of the radiation shielding glass in a laminating direction is 30 mm or less. 5.

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