JP7132735B2 - Metal Vacuum Double Container Sealing Glass Composition and Metal Vacuum Double Container - Google Patents

Description

The present invention can vacuum seal a glass composition for sealing a metal vacuum double container and a metal vacuum double container, more specifically, a thermos bottle, a portable heat-retaining bottle, or the like, at a low temperature. The present invention relates to a glass composition for sealing a vacuum double container made of metal capable of holding well, and a vacuum double container made of metal sealed with the glass composition.

The metal vacuum double container is manufactured by performing a so-called degassing process, in which the gas between the inner and outer containers is evacuated from the exhaust hole while heating the metal double container in a vacuum furnace, followed by further high temperature treatment. Then, a so-called sealing process is performed to close the exhaust hole by causing the glass installed in the exhaust hole to flow.
A vacuum furnace needs to be used for the vacuum sealing process, but the only heat transfer in the vacuum furnace is radiation, and the temperature tends to vary more within the furnace than in a general furnace.
In addition, crystal nuclei may be generated in the glass during the degassing treatment prior to the sealing treatment, and crystal precipitation is promoted around these nuclei during the sealing treatment at high temperature. If crystal precipitation is accelerated, flowability deteriorates and sealing becomes incomplete.
Therefore, if the degree of crystal precipitation differs due to variations in the furnace during degassing, variations in flowability occur. In addition, variations in the furnace during the sealing process also affect the degree of crystal precipitation and the flowability, so the conditions of the sealing process also greatly affect the sealing performance. Therefore, in order to suppress variations in sealing performance, it is necessary to develop a composition that makes it difficult for glass crystals to crystallize and that has a low softening point for sealing at a low temperature.
Conventionally, lead glass has been used for sealing metal vacuum double containers from the above viewpoints, but lead-free glass has been desired in view of recent environmental problems. Examples of lead-free glass include bismuth-based glass and phosphate glass. In the case of bismuth-based glass, a composition containing a large amount of bismuth must be used in order to lower the softening point. In order not to crystallize, the amount of bismuth must be limited, which tends to increase the softening point.
As for bismuth-based glasses, there are the following prior art documents.

JP-A-2000-128574 JP 2006-321665 A JP 2008-24558 A

Patent Document 1 discloses a bismuth-based glass composition that can be fired at a temperature of 500° C. or lower for sealing applications.
However, the glass composition disclosed in Patent Document 1 may be non-crystalline glass or crystalline glass depending on the selected composition, and therefore lacks stability and has problems with the flowability of the glass. , so there is a problem with the sealing performance.
Further, Patent Document 2 discloses a bismuth-based lead-free glass composition that does not exhibit a crystallization peak up to 500°C.
However, in the case of Patent Document 2, since a composition having a crystallization temperature is presented, crystals may precipitate when used for vacuum sealing.
Further, Patent Document 3 discloses a bismuth-based lead-free sealing glass composition suitable for vacuum sealing of a metal vacuum double container.
However, since the glass composition disclosed in Patent Document 3 does not contain SiO ₂ , it has a problem of water resistance. Also, since the amount of Bi ₂ O ₃ is large, there is a high possibility that crystals will precipitate during vacuum sealing.

Therefore, the present invention solves the above-mentioned problems of the prior art, and performs vacuum sealing of a metal vacuum double container at a low temperature, favorably, and with a high yield without crystal precipitation during firing such as degassing and vacuum sealing. It is an object of the present invention to provide a glass composition for sealing a vacuum double container made of metal, which can be used to seal a vacuum double container made of metal and has excellent adhesiveness and adhesion to metal, and a vacuum double container made of metal sealed with the glass composition.

As a result of repeated research to solve the above problems, the present inventors added Na ₂ O, which is an alkali metal, to bismuth glass instead of increasing the amount of bismuth, and when it was within a certain range of components, The inventors have found that the composition does not crystallize and has a low softening point.

That is, the glass composition for sealing a metal vacuum double container of the present invention does not substantially contain PbO, and in terms of mass%, Bi ₂ O ₃ : 72 to 76%, excluding 72% and 76%. B ₂ O ₃ : 2 to 17%, SiO ₂ : 0.1 to 9%, ZnO: 5 to 20%, Na ₂ O: 0.9 to 2%, at least one of MgO, CaO, SrO and BaO 0.1 to 5% in total of more than seeds , and further, the total content of CuO and CoO is in the range of 4% or less, not including 0%, and the total content of Li ₂ O and K ₂ O A first feature is that the amount is set to a range that includes 0% and does not exceed 1% .
In addition to the first feature, the glass composition for sealing a double vacuum container made of a metal according to the present invention has a second feature that it contains 2% or less of Al ₂ O ₃ in terms of % by mass .
A third feature of the metal vacuum double container of the present invention is that it is vacuum-sealed with the glass composition for sealing a metal vacuum double container according to claim 1 or 2 .

According to the glass composition for sealing a metal vacuum double container according to claim 1, a lead-free metal vacuum double container that is resistant to precipitation of crystals during firing, has excellent flowability, and can be reliably sealed at a low temperature. The glass for sealing heavy containers can be provided, and it is suitable for keeping good heat retention. Since the total content of CuO and CoO is in the range of 4% or less, not including 0%, the softening point of the glass can be lowered and the fluidity can be improved. In addition, since the total content of Li ₂ O and K ₂ O is set to a range that includes 0% and does not exceed 1%, crystallization of the glass does not easily occur during sealing, and sealing may not be performed well. disappears.

According to the glass composition for sealing a double vacuum container made of metal according to claim 2, in addition to the effects of the configuration according to claim 1, the content of Al ₂ O ₃ is 2% or less in terms of mass%. By containing it, it is possible to provide a glass for sealing a metal vacuum double container in which crystals are much less likely to precipitate .

According to the metal vacuum double container of the present invention, by vacuum sealing with the glass composition for sealing a metal vacuum double container according to claim 1 or 2, the metal vacuum is actually well sealed. A double container can be provided at low cost.

The glass composition for sealing a metal vacuum double container according to the embodiment of the present invention can be suitably applied as a sealing glass capable of vacuum-sealing a metal vacuum double container by firing at a low temperature and maintaining a good vacuum.
Reasons for limiting the content of each component of the glass composition for sealing a metal vacuum double container of the present embodiment will be described below. All the following are mass %.

Bi ₂ O ₃ is an oxide that forms the network of the glass of the present invention and is contained in the range of 70 to 77%.
If the Bi ₂ O ₃ content is less than 70%, glass can be obtained, but sealing at a low temperature may not be possible due to the high softening point.
On the other hand, if it exceeds 77%, crystals may precipitate, and sealing may become unstable, which is not preferable.
The content of Bi ₂ O ₃ is preferably 72 to 76%, more preferably 73 to less than 75%, in consideration of the softening point of the glass, crystallization, and the like.

B ₂ O ₃ is an oxide that forms a network of glass and is contained in the range of 2 to 17%.
If the B ₂ O ₃ content is less than 2%, the glass may not be obtained, and even if it is obtained, the formability of the glass may be poor, or crystals may precipitate.
On the other hand, if it exceeds 17%, the softening point becomes high, and there is a possibility that sealing at a low temperature may not be possible, which is not preferable.
The content of B ₂ O ₃ is preferably 5 to 12%, more preferably 6 to 10%, in consideration of moldability, softening point, etc. of the glass.

SiO ₂ is an oxide that forms a network of glass, is a component that improves the formability of glass, and is contained in the range of 0.1 to 9%.
If _SiO2 is less than 0.1%, there is no effect of improving the moldability of the glass.
On the other hand, if the SiO ₂ content exceeds 9%, the softening point of the glass becomes high, and sealing at a low temperature may not be possible, which is not preferable.
The content of SiO ₂ is preferably 0.6 to 7%, more preferably 1 to 5%, in consideration of moldability, softening point, etc. of the glass.

ZnO is a component that has the effect of lowering the softening point of glass and increasing fluidity, and is contained in the range of 5 to 20%.
If the ZnO content is less than 5%, the glass may not be obtained, and even if it is obtained, the moldability of the glass may be poor, or crystals may precipitate.
If it exceeds 20%, glass may not be obtained, and even if it is obtained, crystals may precipitate.
The content of ZnO is preferably 10 to 15%, more preferably 11 to 14%, in consideration of the moldability and softening point of the glass.

MgO, CaO, SrO, and BaO are components that improve the stability of the glass by coexistence with ZnO, and the total amount thereof is contained within the range of 0.1 to 5%.
If the total amount is less than 0.1%, the effect of improving stability may not be obtained.
On the other hand, if it exceeds 5%, glass cannot be obtained or crystals are precipitated, which is not preferable.
The total amount of MgO, CaO, SrO and BaO is preferably 0.4 to 3%, more preferably 0.4 to 1.5%, in consideration of the stability and crystallization of the glass.

Na ₂ O is a component that lowers the softening point of the glass and increases the fluidity of the glass, and is contained in the range of 0.1 to 2.5%.
If the Na ₂ O content is less than 0.1%, the effect of lowering the softening point may not be obtained.
On the other hand, when Na ₂ O exceeds 2.5%, glass may not be obtained, and even if it is obtained, crystals may precipitate.
The content of Na ₂ O is preferably 0.4 to 2.0%, more preferably 0.9 to 2%, in consideration of the moldability and softening point of the glass.

Al ₂ O ₃ is an oxide that forms a network of glass and is a component that improves formability of glass, and may be contained up to 2%.
If the content of Al ₂ O ₃ exceeds 2%, the softening point of the glass becomes high, and sealing at a low temperature may not be possible, or the Al 2 O 3 may not dissolve in the glass, which is not preferable.
When it is contained, it is preferably 0.1 to 1%, more preferably 0.1 to 0.5%.

CuO and CoO are components that lower the softening point of glass and increase fluidity. It may be contained up to 4% in total.
If the total amount of CuO and CoO exceeds 4%, crystals may precipitate and sealing may not be performed well.
The total content of CuO and CoO is preferably 2% or less in consideration of crystallization and the like. Further, the total content of CuO and CoO is more preferably 0.1 to 2%.

Li ₂ O and K ₂ O can be contained up to 1% in total. Li ₂ O and K ₂ O are more effective than Na ₂ O in lowering the liquidus viscosity, so if they are added alone, the stability of the glass is lowered and crystallization is likely to occur during sealing. On the other hand, when Li ₂ O and K ₂ O are added together with Na ₂ O, the mixed alkali effect stabilizes the glass and lowers the softening point of the glass. Therefore, when Li ₂ O and K ₂ O are contained, it is preferable to contain them together with Na ₂ O.
When the total amount of Li ₂ O and K ₂ O exceeds 1%, the liquidus viscosity is lowered, so crystallization is likely to occur, and sealing may not be performed well.
Li ₂ O and K ₂ O are preferably not added in consideration of crystallization of the glass.

In addition to the above components, Fe ₂ O ₃ , La ₂ O ₃ , Y ₂ O ₃ , Yb ₂ O ₃ , CeO are added for the purpose of improving stability during glass production, suppressing reaction with metals, and improving adhesion. ₂ , TiO ₂ and ZrO ₂ can be contained in a total amount of 2% or less.

Lead oxide (PbO) is not substantially contained. Here, the expression "substantially does not contain" means that the raw material containing lead oxide (PbO) as an active ingredient is not used in the present invention. It does not exclude those in which a trace amount of water is mixed as an impurity. In other words, it does not mean that even those contained as impurities do not fall within the scope of the present invention. Specifically, if lead oxide (PbO) is contained in the sealing glass composition of the present invention in a total amount of 1000 ppm or less in terms of oxide, there is no possibility of substantially causing a problem. It corresponds to "substantially not including" in the invention.

The glass composition for sealing a double metal vacuum container of the present invention has a glass softening point Ts of 480°C or less and an average thermal expansion coefficient α of 90 to 120 × 10 ^-7 /°C in the range of room temperature to 300°C. , suitable for vacuum sealing of metal vacuum double containers.
The metal vacuum double container of the present invention is obtained by keeping the space between the double containers in a decompressed state and sealing the insertion hole with the glass composition.
Metal materials constituting the vacuum double container to be sealed include stainless steel, other steels, iron materials, titanium materials, aluminum materials, and other metal materials.
The sealing glass of the present invention can be used, for example, in spherical, hemispherical, marble-like, or similar shapes.

EXAMPLES The present invention will be described in more detail below with reference to examples. The present invention is by no means limited by these examples.

(Manufacture of glass)
Bismuth oxide, zinc oxide, magnesium hydroxide, calcium carbonate, strontium carbonate, barium carbonate, lithium carbonate, sodium carbonate, potassium carbonate, silicon oxide, boric acid, aluminum hydroxide, copper oxide, cobalt oxide, etc. were used as raw materials. .
As shown in Tables 1 to 5, raw materials were prepared and mixed so as to obtain the glass compositions shown in Examples 1 to 27 and Comparative Examples 1 to 3.
The resulting mixture is placed in a platinum crucible, melted at a temperature of 850 to 950° C. for 1 hour, then quenched by a twin roll method to obtain glass flakes, and poured onto a preheated carbon plate to form a block. made.
After that, the block was placed in an electric furnace set to a temperature about 50° C. higher than the expected glass transition point Tg, and slowly cooled.
The produced glass flakes are remelted in a temperature range of 900 to 1000 ° C., lowered to a temperature 200 to 300 ° C. higher than the softening point to an appropriate viscosity, and then cut down, having a diameter of about 5 mm, a height of about 2 mm, A hemispherical molded body weighing about 140 mg was molded.

(evaluation)
For Examples 1 to 27 and Comparative Examples 1 to 3, the glass transition point, softening point, crystallization temperature, and thermal expansion coefficient α of the glass block were measured by the following methods, and the flowability of the glass was determined. .
The results are shown in Tables 1-5.

(1) Glass transition point Tg, softening point Ts, crystallization temperature Tp
The glass flakes were pulverized in a mortar to obtain glass powder. About 60 to 80 mg of the glass powder is filled in a platinum cell, and a DTA measuring device (Thermo Plus TG8120 manufactured by Rigaku Corporation) is used to raise the temperature from room temperature at a rate of 20 ° C./min to measure the glass transition point (° C.) and softening point. (°C) was measured. Also, it was determined whether the crystallization temperature (°C) was detected by the DTA measuring device.

(2) Thermal expansion coefficient α
The obtained glass block was cut into a size of about 5×5×15 mm and polished to obtain a sample for measurement. A thermal expansion coefficient (×10 ⁻⁷ /° C.) based on two points at 50° C. and 300° C. was obtained from a thermal expansion curve obtained when the temperature was raised from room temperature at a rate of 10° C./min using a TMA measurement device. .

(3) Flow Diameter of Glass The obtained hemispherical compact was pulverized, 10 g of the compact was put into a mold with an inner diameter of 20 mm, and press-molded at 3 MPa for 10 seconds to obtain a powder compact. This green compact was placed on a SUS plate and fired at a firing temperature of 500° C. for a holding time of 15 minutes, and the flowed diameter was measured.

(4) Crystallinity after flow The compact after flow was evaluated by X-ray diffraction analysis (XRD) to determine whether it was "amorphous", "containing microcrystals", or "crystalline".
Here, "amorphous" means a state in which only a halo can be seen by XRD and no crystals are precipitated, and "microcrystalline content" means a crystal peak in the halo that is too small to be identified. The state "crystalline" indicates a state in which an identifiable crystalline peak is observed.

(Example 1)
As raw materials, bismuth oxide, boric acid, silicon oxide, zinc oxide, barium carbonate, sodium carbonate, aluminum hydroxide, and copper oxide are used. After melting at a temperature of 950° C. for 1 hour, the mixture was quenched by a twin roll method to obtain glass flakes, and poured onto a preheated carbon plate to prepare a block. After that, the block was placed in an electric furnace set to a temperature about 50° C. higher than the expected glass transition point, and slowly cooled.
The resulting glass flakes were pulverized in a mortar to obtain glass powder, about 80 mg was filled in a platinum cell, and the temperature was raised from room temperature at a rate of 20 ° C./min using a DTA measurement device to measure the glass transition point and softening point. When measured, they were 369°C and 438°C, respectively. No crystallization temperature was detected.
Further, when the thermal expansion coefficient α of the sample cut out from the glass block was obtained based on two points of 50°C and 300°C, it was 105 × 10 ^-7 /°C.
The produced glass flakes were re-melted at 1000° C., the temperature was lowered until an appropriate viscosity was achieved, and the glass flakes were added dropwise to produce a hemispherical molded body. After producing a green compact by pulverizing the obtained compact, it was fired at 500° C. for 15 minutes. When the flow diameter after firing was measured, it was 25.5 mm. Further, when the state of crystallization was determined by XRD, it was found to be amorphous.

(Examples 2 to 27, Comparative Examples 1 to 3)
Examples 2 to 27 and Comparative Examples 1 to 3 were prepared in the same manner as in Example 1, and were measured and evaluated.
No crystallization temperature was detected in any of the compositions of Examples 1 to 27, and the XRD after flow showed that the composition was either amorphous or contained microcrystals, and had good flow properties.
On the other hand, in Comparative Examples 1 and 2, the crystallization temperature was detected, and crystals were confirmed by XRD after the flow. In addition, in Comparative Example 3 containing Li ₂ O but not containing Na ₂ O, crystallization was remarkable at a temperature 200 to 300° C. higher than the softening point, so that a hemispherical compact could not be produced. rice field.

The glass composition for sealing a metal vacuum double container and the metal vacuum double container of the present invention can be widely used in the industry for manufacturing stainless steel and other metal vacuum double containers.

Claims (3)

substantially free of PbO, expressed in mass %,
Bi ₂ O ₃ : 72-76%, except 72% and 76%;
_B2O3 : _2-17 %,
SiO ₂ : 0.1 to 9%,
ZnO: 5-20%,
Na ₂ O: 0.9-2%,
At least one or more of MgO, CaO, SrO, and BaO in total of 0.1 to 5%, and
The total content of CuO and CoO is in the range of 4% or less, not including 0%,
The total content of Li ₂ O and K ₂ O is set to a range including 0% and not exceeding 1%,
A glass composition for sealing a metal vacuum double container, characterized by: 2. The glass composition for sealing a double vacuum metal container according to claim 1, containing ₂ % or less of _Al2O3 in terms of % by mass. A metal vacuum double container vacuum-sealed with the glass composition for sealing a metal vacuum double container according to claim 1 or 2 .