JPS6237973B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a vacuum double container made of stainless steel. Traditionally, vacuum double-walled glass containers have been commonly used as thermos flasks and other heat-insulating containers, but in recent years, these containers have become less resistant to mechanical shock.
Vacuum double containers using stainless steel and other metal materials have been proposed. Among these metal materials, stainless steel has the advantage of excellent corrosion resistance and strong mechanical strength, but like other metal materials, when the space formed between the inner container and the outer container is placed in a high vacuum, In addition to the problem of releasing gas from the inside and gradually reducing the degree of vacuum, it is impossible to cause a silver mirror reaction even if you try to form a silver mirror plating like in a glass vacuum double container to prevent heat loss due to radiation. It was hot. For the purpose of preventing heat loss due to gas release and radiation from inside this stainless steel to the vacuum space, for example,
Publication No. 22571 discloses a structure in which a vitreous layer containing silicon dioxide as a main component is formed on the surface of the inner and outer metal bottles that form the space of the vacuum double container, and a silver mirror layer is laminated on the vitreous layer. , also, JP-A-57-
No. 75621 proposes a structure in which nickel plating is applied to the surfaces of the inner and outer bottles that form the space, and a silver mirror layer is laminated thereon. These vacuum double containers can obtain practically sufficient heat retention through the action of a silver mirror layer with a vitreous layer or a nickel plating layer, and can maintain heat retention over a long period of time, but they are made of stainless steel. The vitreous layer interposed between the silver mirror layer and the silver mirror layer tends to become non-uniform, resulting in variations in product quality. However, since each bottom member must be plated and then joined, the manufacturing process is complicated and requires a large number of man-hours. The purpose of the present invention is to provide a homogeneous vacuum double container made of stainless steel with excellent heat retention and productivity. In a stainless steel vacuum double container that has a heavy wall structure and has a space formed between both containers that is evacuated, an oxide film is formed on at least the outer surface of the inner container among the walls forming the space. A vacuum double container made of stainless steel is characterized in that a silver mirror layer is formed on the oxide film. That is, in the present invention, although it is impossible to cause a silver mirror reaction with the raw material of stainless steel,
This method was developed based on the knowledge that when the surface is appropriately oxidized, a film made of ferric oxide is formed on the surface, and this film enables silver mirror reactions. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be specifically described with reference to the accompanying drawings showing an embodiment in which the present invention is applied to a stainless steel thermos flask. In the figure, 1 is an inner bottle made of stainless steel, 2 is an outer bottle made of stainless steel, and both are joined at the mouth part 3 by brazing, contact, or other means to form a double wall structure, and the inner bottle is made of stainless steel. A space 4 formed between the bottle 1 and the outer bottle 2 is evacuated and made into a vacuum.
The inner bottle 1 is formed by joining the body part 1a and the bottom part 1b by means such as brazing, and the outer bottle 2
is formed by joining the body part 2a, the bottom part 2b and the shoulder part 2c. Bottom part 2b of outer bottle 2
A tip tube 5, which serves as an exhaust port when evacuating the space 4, is bonded to the tip tube 5 by brazing or the like, and a bottom cover 6 is attached to the bottom portion 2b with a bonding agent to protect the tip tube 5. There is. On the other hand, according to the present invention, in order to improve the heat retention ability of the stainless steel vacuum double container, the walls of the inner and outer bottles forming the space 4, that is, the outer surface of the inner bottle 1 and the inner surface of the outer bottle 2, are provided with grooves. As shown in FIG. 2, an oxide film 7 is formed, and a silver mirror layer 8 is laminated thereon. In addition, in the illustrated embodiment, the silver mirror layer 8
Although the silver mirror layer is formed on the outer surface of the inner bottle and the inner surface of the outer bottle, the silver mirror layer may be formed only on the outer surface of the inner bottle. This is particularly advantageous in reducing costs in the case of containers with large contents. According to the present invention, the oxide film and silver mirror layer in the thermos flask having the above structure are formed as follows. That is, the oxide film on the walls of the inner and outer bottles forming the space 4 of the thermos flask is formed by firing the inner bottle 1 and the outer bottle 2 in an oxidizing atmosphere such as air or an atmosphere containing oxygen. This firing process is usually performed in the oxidizing atmosphere at 250 to 550
5-120 minutes at ℃, preferably 10-120 minutes at 300-450℃
It will be held for 60 minutes. The degree of oxidation of the stainless steel surface is preferably such that the photoselectivity of the stainless steel surface after firing is 10 to 50 lower than the photoselectivity of the polished surface before firing. This is because oxidation that causes a decrease in photo selectivity of less than 10 will not cause a silver mirror reaction on the stainless steel surface, and excessive oxidation that causes a decrease in photo selectivity of more than 50 will not cause a silver mirror reaction. This is because it becomes difficult. The reason why this phenomenon occurs is that in unfired or similar conditions, the silver mirror reaction is inhibited by chromic oxide that coexists with ferric oxide, and if it is excessively oxidized, ferric oxide forms on the surface. It is presumed that this is because chromium oxide ceases to exist and becomes almost only chromium oxide. The silver mirror layer is formed on the oxide film, and can be formed by the same method as in manufacturing a glass thermos flask. In other words, in order to speed up silver precipitation and ensure uniform precipitation,
The oxide film is formed by wetting and activating the oxide film with an activating solution containing a stannous halide as a main component, and then treating it with a silver mirror solution. Although the activation treatment can be omitted, it is desirable to perform it in order to shorten the time required to form the silver mirror layer. Example Inner bottle 1 made of 0.5mm thick stainless steel plate (SUS304)
At the same time, the shoulder member 2c, body member 2a, and bottom member 2b of the outer bottle 2 are made from 0.6 mm thick stainless steel plates, and the shoulder members 2c of the inner bottle 1 and outer bottle 2 are welded at their mouth parts 3. Then, bake it in air at 350℃ for 30 minutes. Next, separately from this, the body member 2a and bottom member 2b of the outer bottle 2 are welded to form an integrated assembly, which is then welded to the fired inner bottle 1 to form a double wall structure.
From the tip tube 5 connected to the outer bottle bottom 2b to the space 4
An aqueous solution containing 10 ppm of stannous chloride is injected into the inner bottle 1 to activate the outer surface of the inner bottle 1, and after discharging the aqueous solution, the inner bottle 1 is washed with water. Next, a commonly used silver mirror solution, for example, a silver mirror solution prepared according to the following formulation, is poured into the space from the tip tube 5, and the double bottle is held horizontally in the axial direction, as in the case of a glass thermos flask, and the bottle is held at high speed. The silver mirror is deposited by injecting the solution while rotating, thereby forming the silver mirror layer shown in FIG. After that, it is washed with water, dried, and vacuum treated in the same manner as for glass thermos flasks, and the tip is melt-sealed. (Prescription of silver mirror solution) Dissolve 10g of silver nitrate in a small amount of water and add 28%
Aqueous solution made by adding 500ml of ammonia water and water to make 4800ml, and further dissolving 10g of sodium hydroxide.
Add 200ml to make the total volume 5000ml, and use this as Solution A. Separately, 0.25 ml of concentrated nitric acid was added to an aqueous solution of 20 g of sucrose dissolved in 50 ml of water and boiled. After adding 5 ml of a 37% formaldehyde aqueous solution to this,
Add water to bring the total volume to 5000ml, and use this as Solution B. The above liquid A and liquid B are mixed at a volume ratio of 1:1 to obtain a silver mirror liquid. Attach the bottom cover 6 to the bottom of the double bottle obtained in this way.
Join them to obtain a thermos flask with an internal capacity of 0.75. In order to investigate the heat retention ability of this thermos flask, we measured it under the following conditions using the test method specified in JIS2005, and the heat retention effect for 6 hours and 24 hours was 82.5℃ and 59.9℃, respectively.
It was hot. [Test conditions] Pouring temperature: 95°C Hot water amount: Full Plug: Sealed plug (45mmφ) Ambient temperature: 20°C The gloss of the outer surface of the inner bottle after buffing and degreasing is 122, which is the same as the gloss of the firing process. The temperature was 101, a decrease of 21 points compared to before firing. This gloss value is JIS
Based on the measurement method specified in Z8741, the angle of incidence is 60
゜、The glossiness of the standard sample is 91.1, which is 1/4 of that, 22.8.
This is the value obtained by setting . Separately, after firing 0.3 mm thick stainless steel (SUS 304) test pieces under various firing conditions shown in Table 1, the gloss was measured, and electroless plating was performed using the silver mirror solution. did. The results are also shown in Table 1.

【table】

[Table] As is clear from the above description, the stainless steel vacuum double container according to the present invention has significantly improved heat retention ability compared to the conventional container in which a nickel plating layer is interposed on a glassy layer. Moreover, unlike the case of forming a glassy layer or a nickel plating layer, there is no need for complicated processes, and the silver mirror layer can be formed by simply firing, and the silver mirror layer can be formed by electroless plating, which improves workability and reduces manufacturing costs. It has excellent advantages such as being able to

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a stainless steel thermos flask showing an embodiment of the present invention, and FIG. 2 is an enlarged view of section A in FIG. 1. 1...Inner bottle, 2...Outer bottle, 4...Space, 5...
...Chip tube, 6...Bottom cover, 7...Oxide coating,
8...Silver mirror layer.

Claims (1)

[Claims] 1. In a stainless steel vacuum double container having a double wall structure consisting of an inner container and an outer container made of stainless steel, and in which the space formed between the two containers is evacuated, the space is formed. A vacuum double container made of stainless steel, characterized in that an oxide film is formed on at least the outer surface of the inner container among the wall surfaces, and a silver mirror layer is formed on the oxide film.