JP5679519B2 - Sealing glass - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a sealing glass used for a metal double container, and particularly in an intermediate temperature range of 500 to 800 ° C., the exhaust port of a metal double container such as an electric pot, a lunch jar, a heat-insulating cooking pot, etc. The present invention relates to a sealing glass that can be sealed.

  FIG. 1 shows an electric pot 10 which is an example of a metal double container. As shown in FIG. 1, the electric pot 10 is arranged so that the outer container 1 and the inner container 2 overlap each other, and has a structure in which the outer container 1 and the inner container 2 are sealed with a sealing glass 3. Yes. In the electric pot 10, a hollow portion 4 is formed between the outer container 1 and the inner container 2, and the hollow portion 4 is kept in a vacuum state.

  FIG. 2 is an enlarged conceptual diagram of the encircled portion of FIG. 1 before the sealing step. As shown in FIG. 2, the sealing glass 3 is in a state of being accommodated in a recess formed in a metal double container before being sealed. In addition, the sealing of the metal double container is usually performed in a reduced pressure atmosphere in order to prevent metal oxidation.

  The metal material used for the metal double container is selected according to durability (heat resistance, acid resistance) against heat treatment and acid treatment in the production process, steel material price, and the like. Considering these matters comprehensively, the metal material of the electric pot is not SUS304 of general austenite type (18% Cr / 8% Ni) but SUS430 of ferrite type (18% Cr), martensite SUS436 and SUS403 of the system (12 to 14% Cr) are used.

  In addition, as a method for producing a metal double container, for example, Patent Document 1 discloses a method in which an exhaust port is provided in either an outer container or an inner container and the exhaust port is sealed with a brazing material. Further, lead borosilicate glass is disclosed as a brazing material made of a glass material, that is, sealing glass, and aluminum, tin, and nickel are disclosed as a brazing material made of a metal material.

When sealing glass is used, advantages such as shortening the process time by lowering the sealing temperature and weight reduction by reducing the thickness of the steel material can be enjoyed. As a result, the cost of the metal double container can be reduced. . In addition, PbO—B ₂ O ₃ -based glass containing a large amount of lead is widely used as a sealing glass for this application (see, for example, Patent Document 2). In contrast, as a sealing glass containing no lead, _SnO-P 2 _{O 5} based glass has been proposed (e.g., see Patent Document 3-7).

JP 2000-166777 A JP 2002-345655 A JP-A-2005-350314 Japanese Patent No. 2628007 JP 2000-72479 A JP 2001-139344 A JP 2008-30972 A

By the way, in the case of a metal double container, for example, an electric pot, sealing is performed in an intermediate temperature range of 500 to 800 ° C. However, when the above SnO—P ₂ O ₅ based glass is used and sealed in the middle temperature range of 500 to 800 ° C., a large number of bubbles are generated in the glass due to the low melting point. As a result, leakage from bubbles occurs due to long-term use, and the airtightness of the sealed portion is impaired, or the possibility that the sealed portion peels increases.

In recent years, Bi ₂ O ₃ —B ₂ O ₃ glass has been used as a lead-free substitute for PbO—B ₂ O ₃ glass. However, Bi ₂ O ₃ —B ₂ O ₃ -based glass has a property that a bismuth component is easily reduced in a sealing step in a reduced-pressure atmosphere, and it is difficult to ensure a stable state. In addition, metal sealing (including sealing between metal and metal, metal and ceramic, metal and glass, etc.) is usually performed in a non-oxidizing atmosphere such as a reduced pressure atmosphere in order to prevent metal oxidation (for example, , See Patent Document 8).

Accordingly, the present invention may be a reduced pressure atmosphere, inventing a sealing glass consisting satisfactorily sealable SnO-P ₂ O ₅ based glass metallic double container in a temperature range within 500 to 800 ° C. Thus, it is a technical problem to ensure the airtightness of the metal double container over a long period of time.

The present inventor conducted various experiments, and strictly controlled the glass composition range of SnO—P ₂ O ₅ glass, so that even in a reduced pressure atmosphere, the metal in the middle temperature range of 500 to 800 ° C. The present inventors have found that the double container can be well sealed and that the reaction between the glass and the metal can be optimized at the time of sealing, and are proposed as the present invention. That is, the sealing glass of the present invention has a glass composition in terms of mol%, SnO 15-30% (however, not including 30%), P ₂ O ₅ 20-40%, WO ₃ 5-20% ( However, 5% is not included), ZnO 3.4 to 30% (however, 30% is not included), the molar ratio SnO / ZnO is 1 or more and 4.5 or less, and a metal double container It is used for sealing.

  The glass composition range of the sealing glass of the present invention is regulated as described above. If it does in this way, it will become possible to seal well in the middle temperature range of 500-800 ° C. That is, it flows properly in the middle temperature range of 500 to 800 ° C., and can prevent the occurrence of a large number of bubbles in the glass while closing the exhaust port of the metal double container, and the sealing glass is made of metal. It reacts properly and can secure strong adhesiveness. Moreover, even when sealed in a reduced-pressure atmosphere, it is possible to prevent a situation where the surface of the sealed portion is devitrified and deteriorated, and as a result, ensure the airtightness of the metal double container over a long period It becomes possible.

  Second, it is preferable that the sealing glass of the present invention does not substantially contain PbO. In this way, environmental demands in recent years can be satisfied. Here, “substantially free of PbO” refers to a case where the content of PbO in the glass composition is 1000 ppm (mass) or less.

Thirdly, the sealing glass of the present invention is preferably used for sealing in a reduced pressure atmosphere of 1.0 × 10 ⁻² Torr or less.

  Fourthly, the sealing glass of the present invention is preferably used for sealing at 500 to 800 ° C.

  Fifth, the sealing glass of the present invention preferably has a glass transition point of 350 to 500 ° C. The glass transition point can be measured with a push rod thermal dilatometer or the like.

  Sixth, the sealing glass of the present invention is preferably formed by a drop forming method.

  Seventhly, it is preferable that the sealing glass of the present invention is cut after molding. If it does in this way, it will become easy to adjust to a desired shape.

It is the cross-sectional schematic which shows the structure of an electric pot. FIG. 2 is an enlarged schematic cross-sectional view of a circled portion in FIG.

The reason for limiting the glass composition range of SnO—P ₂ O ₅ based glass as described above will be described below. In addition, in description of the containing range of each component,% display points out mol%.

  SnO is a component that lowers the melting point of glass, and its content is 15 to 30% (however, not including 30%), preferably 20 to 28%. When the SnO content is less than 15%, the viscosity of the glass increases, and the fluidity tends to decrease in the middle temperature range. Note that when the SnO content is 20% or more, the fluidity is improved in the middle temperature range, so that high airtightness is easily secured. On the other hand, if the SnO content is more than 30%, the glass softens at a low temperature, so that the glass flows too much at the time of sealing, making it difficult to seal the exhaust port of the metal double container in the middle temperature range.

P ₂ O ₅ is a glass-forming oxide, and its content is 20 to 40%, preferably 25 to 35%. If the content of P ₂ O ₅ is less than 20%, the glass becomes unstable. On the other hand, when the content of P ₂ O ₅ is more than 40%, the moisture resistance is lowered. Incidentally, when the content of P ₂ O ₅ is more than 25%, the glass is more stable, if 35% or less, it is possible to improve the weather resistance.

WO ₃ is an essential component of the present invention, and is a component that optimizes the reactivity with the metal and increases the adhesive strength and air tightness. Further, when WO ₃ is added, the weather resistance is improved, so that the long-term reliability of the sealed portion can be improved. The content of WO ₃ is 5 to 20% (not including 5%), preferably 10 to 15%. When the content of WO ₃ is 5% or less, it is impossible to obtain the above effect. On the other hand, when the content of WO ₃ is more than 20%, the phase separation tendency becomes strong at the time of melting, and the glass becomes unstable. Incidentally, the content of WO ₃ is 10 to 15% improves the fluidity at the middle temperature range. Further, when the content of WO ₃ is more than 5%, the above effect can be enjoyed. However, when sealing is performed in an air atmosphere, the glass tends to be devitrified at the time of sealing. For this reason, the sealing glass of the present invention is preferably used for sealing in a reduced-pressure atmosphere of 1.0 × 10 ⁻² Torr or less.

  ZnO is an intermediate oxide and a component having a great effect of stabilizing the glass, and its content is 3.4 to 30% (however, not including 30%), preferably 5 to 28%. . In consideration of overall glass stability (devitrification resistance, phase separation, etc.), the ZnO content is preferably 5% or more. However, when the ZnO content is 30% or more, the component balance of the glass composition is impaired, and devitrification is likely to occur on the glass surface during sealing. If the ZnO content is 28% or less, the stability of the glass is improved in the middle temperature range.

  The molar ratio SnO / ZnO is 1 or more and 4.5 or less, preferably 1 or more and 4 or less. When the molar ratio SnO / ZnO is smaller than 1, the glass tends to be unstable. On the other hand, if the molar ratio SnO / ZnO is greater than 4.5, the glass flows too much at the time of sealing, making it difficult to seal the exhaust port of the metal double container in the middle temperature range, and there are bubbles in the glass. It tends to occur.

  The following components can be added as optional components.

  MgO is a network-modifying oxide and a component that stabilizes the glass. The content of MgO is preferably 0 to 20%, particularly preferably 0 to 5%. When the content of MgO is more than 20%, devitrification tends to occur on the glass surface during sealing.

Al ₂ O ₃ is an intermediate oxide, a component that stabilizes the glass, and a component that further reduces the thermal expansion coefficient. The content of Al ₂ O ₃ is preferably 0 to 10%, and particularly preferably 0.5 to 5% in consideration of glass stability, thermal expansion coefficient, fluidity, and the like. When the content of Al ₂ O ₃ is more than 10%, the softening temperature rises, the fluidity tends to decrease at medium temperature range.

SiO ₂ is a glass-forming oxide and a component that suppresses devitrification, and its content is preferably 0 to 15%, particularly preferably 0 to 8%. If the content of SiO ₂ is more than 15%, the softening temperature rises and the fluidity tends to decrease in the middle temperature range.

B ₂ O ₃ is a glass-forming oxide and a component that stabilizes the glass, and its content is 0 to 25%. If the content of B ₂ O ₃ is more than 25%, the viscosity of the glass becomes too high, and the fluidity is remarkably lowered at the time of sealing, and the airtightness of the sealing part may be impaired. In particular, in the glass composition system according to the present invention, when the content of B ₂ O ₃ is more than 25%, the glass is likely to undergo phase separation. B ₂ O ₃ tends to increase the viscosity of the glass. For this reason, when it is desired to greatly reduce the softening temperature, it is preferable that B ₂ O ₃ is not substantially contained, that is, 0.1% or less.

R ₂ O (R is any one of Li, Na, K, and Cs) is not an essential component, but when at least one of R ₂ O components is added, adhesion to a metal such as stainless steel is improved. . The content of R ₂ O is preferably 0 to 20%, particularly preferably 0.1 to 10%. When the content of R ₂ O is more than 20%, the glass tends to be devitrified at the time of sealing. Further, the content of Li ₂ O, Na ₂ O, K ₂ O, and Cs ₂ O is preferably 0 to 12%, particularly preferably 0.1 to 10%. Of the R ₂ O components, Li ₂ O has a great effect of improving the adhesion to metal.

The lanthanoid oxide is a network-modified oxide, and its content is preferably 0 to 25%, 0.1 to 20%, particularly preferably 0.5 to 15%. When the content of the lanthanoid oxide is more than 25%, the sealing temperature becomes high, and the fluidity tends to decrease in the middle temperature range. As the lanthanoid oxide, La ₂ O ₃ , CeO ₂ , Nd ₂ O ₃ or the like can be used. Moreover, weather resistance can be improved if content of a lanthanoid oxide shall be 0.1% or more.

In addition to the lanthanoid oxide, the addition of other rare earth oxides such as Y ₂ O ₃ can further enhance the weather resistance. The total content of rare earth oxides excluding lanthanoid oxides is preferably 0 to 5%.

Furthermore, in order to stabilize the glass, MoO ₃ , Nb ₂ O ₅ , TiO ₂ , ZrO ₂ , CuO, MnO, In ₂ O ₃ , R′O (R ′ is any of Mg, Ca, Sr, and Ba). ) Etc. may be added up to 35% in total. In addition, when there is more content of these components than 35% in total, the component balance of a glass composition will be impaired, glass will become unstable conversely, and manufacture of sealing glass will become difficult. In addition, if content of these components is 25% or less in total, glass will not become unstable easily.

The content of MoO ₃ is preferably 0 to 20%, particularly preferably 0 to 10%. When the content of MoO ₃ is more than 20%, the viscosity of the glass becomes high and the glass hardly flows in the middle temperature range.

The contents of Nb ₂ O ₅ , TiO ₂ and ZrO ₂ are each preferably 0 to 15%, particularly preferably 0 to 10%. If these components are each more than 15%, the component balance of the glass composition is impaired, and conversely, the glass tends to be unstable.

  The contents of CuO and MnO are each preferably 0 to 10%, particularly preferably 0 to 5%. If each of these components is more than 10%, the component balance of the glass composition is impaired, and the glass tends to be unstable.

In ₂ O ₃ is a component that can be used for the purpose of obtaining high weather resistance when the cost is not taken into consideration. The content of In ₂ O ₃ is preferably 0 to 5%.

  The total content of R′O is preferably 0 to 15%, particularly preferably 0 to 5%. When the content of R'O is more than 15% in total, the component balance of the glass composition is impaired, and conversely, the glass tends to become unstable.

  In addition to the above components, other components can be added up to 5%, for example. Moreover, as mentioned above, it is preferable that PbO is not included substantially from an environmental viewpoint.

The SnO—P ₂ O ₅ glass having the above glass composition has a glass transition point of about 350 to 500 ° C., a deformation point of about 380 to 530 ° C., and a thermal expansion coefficient of about 60 × in a temperature range of 30 to 300 ° C. 10 ^{−7 to} 110 × 10 ⁻⁷ / ° C. In a reduced-pressure atmosphere of 1.0 × 10 ⁻² Torr or less, the metal double container exhaust port is well sealed in a temperature range of 500 to 800 ° C. Is possible.

  In the sealing glass of the present invention, the glass transition point is preferably 350 to 500 ° C, particularly preferably 400 to 450 ° C. When the glass transition point is lower than 350 ° C., the glass flows too much in the middle temperature range, and it becomes difficult to seal the exhaust port of the metal double container, and bubbles are easily generated in the glass. On the other hand, when the glass transition point is higher than 500 ° C., the softening temperature increases, and the fluidity tends to decrease in the middle temperature range.

  In the sealing glass of the present invention, the yield point is preferably 380 to 530 ° C, particularly preferably 440 to 480 ° C. When the yield point is lower than 380 ° C., the glass flows too much in the middle temperature range, and it becomes difficult to seal the exhaust port of the metal double container, and bubbles are easily generated in the glass. On the other hand, if the yield point is higher than 530 ° C., the softening temperature rises and it becomes difficult to seal in the middle temperature range. The yield point can be measured with a push rod thermal dilatometer or the like.

In the sealing glass of the present invention, the thermal expansion coefficient in the temperature range of 30 to 300 ° C. is preferably 60 × 10 ^{−7 to} 110 × 10 ⁻⁷ / ° C., particularly preferably 70 × 10 ^{−7 to} 85 × 10 ⁻⁷ / ° C. . By doing so, it becomes easy to match the thermal expansion coefficient of a metal such as stainless steel, so that the stress applied to the sealed portion can be reduced. The thermal expansion coefficient in the temperature range of 30 to 300 ° C. can be measured with a push rod type thermal dilatometer or the like.

The sealing glass of the present invention can be satisfactorily sealed against various metal double containers. The sealing glass of the present invention is preferably used for sealing in a reduced pressure atmosphere of 1.0 × 10 ⁻² Torr or less in order to prevent metal oxidation during sealing.

  In order to adjust the thermal expansion coefficient, the sealing glass of the present invention may be combined with a filler powder and used. When mixing filler powder, the mixing amount is 45-100 volume% of sealing glass (glass powder), and 0-55 volume% of filler powder is preferable. When the content of the filler powder is more than 55% by volume, the ratio of the glass powder is relatively reduced, and it becomes difficult to ensure necessary fluidity.

Various materials can be used as the filler powder, such as quartz, cordierite, zircon, tin oxide, niobium oxide, zirconium phosphate, willemite, and mullite. The NbZr _{(PO 4) 3} based ceramic powder, since it contains phosphoric acid in component compatible with _SnO-P 2 _{O 5} based glass is excellent. In addition, it is preferable that a small amount (for example, 0.1 to 2 mass%) of MgO is added to the NbZr (PO ₄ ) ₃ ceramic powder as a sintering aid.

  Hereinafter, the manufacturing method of the sealing glass of this invention is explained in full detail.

For producing the sealing glass of the present invention and a composite material using the same, first, a glass raw material is prepared so as to have the above glass composition, and then melted at 850 to 1000 ° C. to produce a molten glass. In the case of the glass composition range according to the present invention, there is no problem even if it is melted in the atmosphere, but it is necessary to pay attention so that SnO in the glass composition is not oxidized to SnO ₂ at the time of melting. Since the SnO in the glass composition is prevented from oxidizing to SnO _2, or melted in N _2, etc. to N ₂ bubbling in the molten glass, it is preferable to perform the melt in a non-oxidizing atmosphere. Further, in the case of melting at the laboratory level, it is preferable from the viewpoint of workability that the melting crucible is covered and melted.

  As a melting furnace (melting crucible) material, refractories such as platinum and its alloys, zirconium and its alloys, quartz glass, alumina, and zirconia can be used.

  Sealing glass used for metal double containers is often used alone without mixing refractory fillers. In this case, (1) the molten glass is drawn out into a rod shape and cut into a predetermined length, (2) a predetermined volume of molten glass is dropped into a molding die and molded into a predetermined size, or (3) a block shape After molding into a solid, sealing glass can be produced by solidifying. The block-shaped sealing glass is used after being cut into a predetermined size. When the sealing glass of the present invention is used alone, a shape such as a rectangular parallelepiped, a cylinder, a sphere, an elliptical sphere, a hemisphere, an egg shape, and a repellent shape is preferable. In this case, the binder removal described later is not necessary, and the sealing process can be simplified. However, since it cannot be made into a paste, it is sealed at the portion to be sealed of the metal double container, particularly at the exhaust port. It is preferable to provide a recess for installing the stop glass.

  The sealing glass of the present invention is preferably formed by a dropping molding method (the method (2) above). When this method is used, machining such as cutting can be omitted or simplified, so that the sealing glass can be manufactured at low cost. In addition, if molten glass is pressurized with a shaping | molding die etc. after dripping of molten glass, the height etc. of sealing glass can be adjusted to a desired range.

  In the case of the drop molding method, a dropping nozzle is required, and it is necessary to weld the melting furnace and the nozzle. Considering the weldability of the melting furnace and the nozzle, platinum and its alloy, zirconium and its alloy are suitable as the melting furnace material and nozzle material.

  In the case of the drop molding method, the volume of the sealing glass can be controlled by adjusting the nozzle outer diameter and the viscosity of the molten glass. When sealing the exhaust port of the metal double container, the volume of the sealing glass is preferably equal to or less than the volume of the recess formed around the exhaust port. When the volume of the sealing glass is too larger than the volume of the recess, the sealing glass part is easily cracked due to the difference in expansion between the sealing glass and the metal (for example, SUS430 series), and the airtightness of the hollow part is increased. It becomes difficult to maintain. In addition, if the volume of the sealing glass is a minimum volume that reaches the exhaust port, the exhaust port may not be reliably sealed. Considering the above points, the volume of the sealing glass is preferably 50 to 120% of the volume of the recess formed around the exhaust port.

  It is preferable that the sealing glass of this invention is provided to the sealing process, after accommodated in the recessed part formed in the metal double container. If it does in this way, while being able to mount sealing glass stably, an exhaust port can be sealed efficiently.

  The sealing glass of the present invention is preferably used for sealing an electric pot, a lunch jar, and a heat-insulating cooking pan, and particularly preferably used for sealing an electric pot. Since these metal double containers are sealed at an intermediate temperature range of 500 to 700 ° C., the sealing glass of the present invention is suitable.

  The sealing glass of the present invention is preferably used for a metal double container in which the metal material is SUS430 of ferrite type (18% Cr), or SUS436 or SUS403 of martensite type (12 to 14% Cr). Since these metal materials are often sealed at an intermediate temperature range of 500 to 700 ° C., the sealing glass of the present invention is suitable.

  Hereinafter, a method of sealing a metal double container using a paste material will be described. After the molten glass is formed into a film shape, it is processed into a powder shape by pulverization and classification. When the filler powder is mixed with the obtained glass powder, a composite powder can be produced. Next, the obtained glass powder or composite powder (which often contains a colorant) and a vehicle are kneaded to produce a paste material.

As the resin in the vehicle, aliphatic polyolefin carbonates, particularly polyethylene carbonate and polypropylene carbonate are preferred. These resins have properties that make it difficult to alter the SnO—P ₂ O ₅ glass during sealing. On the other hand, when general-purpose ethyl cellulose is used as the resin, there is a high possibility that the SnO—P ₂ O ₅ glass will be altered. The solvent in the vehicle is preferably one or more selected from N, N′-dimethylformamide, ethylene glycol, dimethyl sulfoxide, dimethyl carbonate, propylene carbonate, butyrolactone, caprolactone, and N-methyl-2-pyrrolidone. These solvents have properties that make it difficult to alter the SnO—P ₂ O ₅ glass during sealing.

Subsequently, a paste material is applied to the metal surface and dried. The paste material may be applied using a dispenser, a screen printer, or the like. Next, if necessary, firing (primary firing) is performed for debinding, and then firing (secondary firing) is performed to seal the metal double container. Here, the primary firing is preferably performed in an inert atmosphere such as nitrogen or argon, particularly in a nitrogen atmosphere, in order to prevent deterioration of the SnO—P ₂ O ₅ glass. Further, it is necessary to perform secondary firing under conditions sufficient for the glass powder or the composite material to wet the adhesion surface of the metal.

The sealing glass of the present invention is preferably used for sealing in a reduced-pressure atmosphere of 1.0 × 10 ⁻² Torr or less. If the reduced pressure atmosphere is 1.0 × 10 ⁻² Torr or less, oxidation of the metal can be prevented while maintaining the degree of vacuum of the hollow portion. Further, in order to surely prevent metal oxidation, it is more preferable to seal in a reduced pressure atmosphere of 1.0 × 10 ⁻³ Torr or less. On the other hand, if the pressure is greater than 1.0 × 10 ⁻² Torr, the glass tends to devitrify and deteriorate during sealing. In addition, as long as the pressure is 1.0 × 10 ⁻² Torr or less, it can be reached by a commonly used rotary pump.

In actual production of a metal double container, the sealing atmosphere is often decompressed with an oil diffusion pump (diffusion pump) in order to increase the degree of vacuum in the hollow portion. In this case, the degree of vacuum in the sealing atmosphere is 1.0 × 10 ⁻³ Torr or less. The upper limit of the degree of vacuum of the sealing atmosphere is not particularly limited. In addition, when the sealing test was performed by reducing the pressure to 1.0 × 10 ⁻⁶ Torr by using a rotary pump and a turbo molecular pump together, no devitrification or alteration was observed in the sealing glass of the present invention. It has been confirmed that However, in actual production, the degree of vacuum in the sealing atmosphere is difficult to be 1.0 × 10 ⁻⁶ Torr or less due to the influence of the gas released from the sealing glass or metal.

  The sealing glass of the present invention is preferably subjected to sealing at 500 to 800 ° C., particularly 550 to 700 ° C. If it does in this way, adhesive strength and airtightness can be raised.

  Hereinafter, based on an Example, the sealing glass of this invention is explained in full detail. The following examples are merely illustrative. The present invention is not limited to the following examples.

  Tables 1 and 2 show examples (Nos. 1 to 11) of the present invention, and Table 3 shows comparative examples (Nos. 12 to 16).

  Each sample was prepared as follows. First, glass raw materials were prepared so as to have the glass composition in the table. Further, as the phosphorus introduction raw material, orthophosphoric acid (orthophosphoric acid), which is a liquid raw material, was not used, but stannous pyrophosphate and zinc metaphosphate were used, and the phosphorus introduction raw materials were all solid raw materials. When all the raw materials for introducing phosphorus are made into solid raw materials, there is an advantage that the same production equipment as other glass systems can be used. In addition, if a liquid raw material is directly put into a melting furnace and melted as a raw material for introducing phosphorus, a problem of spilling easily occurs. And in order to avoid the problem of spilling, the glass raw material must be once dried.

  Next, the prepared glass raw material was melted at 950 ° C. for 2 hours. In addition, in order to suppress the oxidation of SnO during melting, nitrogen was passed through the melting furnace. The residual oxygen concentration in the melting furnace at the time of nitrogen inflow was 1% or less.

  Subsequently, the molten glass was formed into a cylindrical shape having a diameter of 5 mm and a length of 20 mm using a carbon jig. This molded sample was annealed, and the glass transition point, yield point, and thermal expansion coefficient in the temperature range of 30 to 300 ° C. were measured by a push rod type thermal dilatometer (TMA, manufactured by Rigaku). A similar cylindrical sample (annealed) was processed to a length of 3 mm and used for the evaluation of adhesion.

  The presence or absence of adhesiveness was evaluated as follows. As a metal for evaluation, high heat resistance ferrite-based SUS430 was used. The shape of the metal for evaluation was a flat plate shape of 40 mm × 40 mm. Next, the above-mentioned sample for evaluation was placed on this metal plate and fired by “reduced pressure firing” in the table.

The “reduced pressure firing” in the table is a result of firing while continuously reducing the pressure with a rotary pump. At the time of firing under reduced pressure, there was a change in pressure due to the foaming gas generated from the sealing glass, but it was confirmed by a pressure gauge that the pressure was 1.0 × 10 ⁻² Torr or less. The firing conditions were a firing temperature of 650 ° C. for 10 minutes, a heating rate of 20 ° C./min from room temperature to the firing temperature, and a cooling rate of 15 ° C./min to room temperature.

As is apparent from the table, sample No. 1 to 11 have a thermal expansion coefficient of 69.6 × 10 ^{−7 to} 83.7 × 10 ⁻⁷ / ° C. in a temperature range of 30 to 300 ° C., a glass transition point of 402 to 431 ° C., and a yield point of 416 to 472. C., and there was no devitrification or alteration after firing under reduced pressure, and the metal showed good adhesion. Therefore, sample no. 1-11 were suitable as sealing glass used for metal vacuum double containers.

  On the other hand, sample No. Nos. 12, 13, and 16 were not devitrified and altered after firing under reduced pressure, but were not adhesive to the metal and peeled off from the metal plate after sealing. Sample No. 14 had no devitrification or alteration after firing under reduced pressure, but because the molar ratio SnO / ZnO was larger than 5, it flowed excessively on the metal plate, and the glass protruded from the metal plate. Could not do. Sample No. No. 14 is considered to be unable to seal the exhaust port of the metal double container in the middle temperature range because the flow is excessive. Sample No. No. 15 was not devitrified or altered after firing under reduced pressure, but it hardly flowed on the metal plate, so the adhesion could not be evaluated.

  The sealing glass of this invention can be used conveniently for metal double containers, such as an electric pot, a lunch jar, and a heat-insulating cooking pot.

DESCRIPTION OF SYMBOLS 1 Outer container 2 Inner container 3 Sealing glass 4 Hollow part 10 Electric pot

Claims (7)

As a glass composition, in mol%, SnO 15 to 30% (not inclusive of _{30%), P 2 O 5} 20~40%, WO 3 5~20% ( not inclusive of 5%), ZnO It contains 3.4 to 30% (but not 30%), has a molar ratio SnO / ZnO of 1 or more and 4.5 or less, and is used for sealing a metal double container. Sealing glass. The sealing glass according to claim 1, wherein the content of PbO is 0.1% by mass or less . The sealing glass according to claim 1, wherein the sealing glass is used for sealing in a reduced pressure atmosphere of 1.0 × 10 ⁻² Torr or less.   It uses for sealing in 500-800 degreeC, The sealing glass as described in any one of Claims 1-3 characterized by the above-mentioned.   The glass transition point is 350-500 degreeC, The sealing glass as described in any one of Claims 1-4 characterized by the above-mentioned.   The sealing glass according to any one of claims 1 to 5, wherein the sealing glass is formed by a drop forming method. The sealing glass according to any one of claims 1 to 5, wherein the sealing glass is cut after the molding.