JPH0415686B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a method for manufacturing a stainless steel thermos flask. Prior Art In recent years, thermos flasks made of stainless steel have been put into practical use in place of glass thermos flasks that are susceptible to mechanical shock. In general, stainless steel has the advantages of not only high mechanical strength but also excellent corrosion resistance and low thermal conductivity, but like other metal materials, it releases gas from inside in a high vacuum, so it reduce the vacuum level of
Moreover, it has the disadvantage of large heat loss due to radiation. For this reason, attempts have been made to form a silver mirror on the wall of the thermos flask that forms the vacuum space between the inner container and the outer container, but unlike the case of glass thermos flasks, it is not possible to directly plate the stainless steel surface with a silver mirror. Since this is possible, it was proposed in JP-A-57-75621 to improve heat retention by applying nickel plating to the stainless steel surface and laminating a silver mirror plating layer thereon. The same publication also proposes laminating a chemical copper plating layer on the nickel plating layer. These thermos flasks have a plating layer that prevents heat dissipation due to radiation and suppresses gas release, so they exhibit sufficient heat retention performance for practical use and can maintain this temperature for a long period of time. Forming the plating layer requires a lot of attention and man-hours, and the process is complicated.
There was a problem with high manufacturing costs. As a result of various studies to solve this problem, we found that, contrary to the conventional wisdom that when plating a metal surface, the oil and oxide film on the metal surface must be removed to make the surface clean, it is necessary to sinter stainless steel. They discovered that by oxidizing the surface appropriately, it became possible to directly silver mirror plate the stainless steel surface.
We proposed a stainless steel vacuum double container using this technology. According to the manufacturing method described in the same specification, there is no need to nickel plate the stainless steel surface, and silver mirror plating can be achieved just by firing, reducing manufacturing costs and achieving good heat retention performance. However, since it is made of stainless steel, it was inevitable that the manufacturing cost would be higher than that of glass thermos flasks. Therefore, an inexpensive method of chemical copper plating instead of silver mirror plating was proposed in Japanese Patent Application No. 167207/1983. In this method, chemical copper plating is performed after firing stainless steel or by contacting it with an aqueous solution of a noble metal salt and then contacting it with stannous halide. When this method is applied to the manufacture of thermos flasks, It has become clear that although it is possible to form a chemical copper plating layer on the walls forming the vacuum space, this results in a fatal problem of significantly inferior heat retention compared to silver mirror plating. As a result of research into the cause, it was found that in the above method, undissolved noble metal salt particles exist in the noble metal salt aqueous solution that is contacted after firing, and these particles adhere to the surface of the substrate and roughen the plating layer, resulting in a homogeneous layer. It has become clear that heat dissipation due to radiation cannot be suppressed because the heat dissipation is not possible. OBJECT OF THE INVENTION The object of the present invention is to provide a method for manufacturing an inexpensive stainless steel thermos flask that has heat retention performance equal to or better than that of a stainless steel thermos flask whose walls forming a vacuum space are plated with silver mirrors. The technical problem is to prevent the surface of the chemical copper plating layer from becoming rough and to form a chemical copper plating layer with high emissivity. The gist of the present invention is to manufacture a stainless steel thermos flask that has 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. or the components thereof are fired in an oxidizing atmosphere, and then, among the surfaces of both containers forming the space, at least the surface of the inner container or the component parts of the inner container is sensitized, and then the noble metal salt is contained. A method for manufacturing a stainless steel thermos flask, characterized by activating it with an activating liquid and then chemically copper plating the flask. In other words, in the present invention, even if the stainless steel substrate is chemically plated with copper, the hydrogen generated on the surface of the substrate by the chemical reaction described below inhibits the precipitation of copper, and even if it does precipitate, it will crack or peel. Therefore, in order to form a copper plating layer with good adhesion to the surface of the stainless steel substrate, the inner container and the outer container, or the components of both containers, are oxidized. By firing in an atmosphere, a thin oxide film is formed on the surface forming the vacuum space, and a copper plating layer with high emissivity is uniformly deposited.
By sensitizing the oxide film and activating the surface with an aqueous solution of a precious metal salt such as an extremely low concentration of silver salt or palladium salt, or a solution containing a noble metal salt and an acid such as hydrochloric acid, chemical copper plating is performed. This solves the above technical problem. The chemical reaction in alkaline divalent copper solution is as follows. Cu ⁺⁺ +2e ^- →Cu↓ 2HCHO+2OH ^- → 2HCOO ^- +2H ₂ O+2e ^- +H ₂ ↑ In a preferred embodiment of the present invention, in order to ensure strong adhesion of the copper plating layer to the stainless steel surface, the firing treatment is not performed. 250-550℃, preferably
It is carried out at 300 to 450°C, and the time varies depending on the temperature, but is usually 5 to 180 minutes, preferably
It lasts 10 to 60 minutes. Generally, the firing process is
in air or in an oxidizing atmosphere such as an oxygen-containing atmosphere at 250 to 550°C for 5 to 120 minutes, preferably,
It is carried out at 300-450°C for 10-60 minutes. This is because if the firing temperature is less than 250°C, a sufficient oxide film will not be formed or it will take a long time to form, inhibiting copper precipitation and increasing manufacturing costs; if the firing temperature exceeds 550°C, This is because the stainless steel base undergoes metamorphosis. The firing time can be set arbitrarily as long as it is within the above temperature range, but if it is less than 5 minutes, it will be difficult to form a sufficient oxide film when the firing temperature is low, and if it exceeds 180 minutes, it will not be necessary when the firing temperature is high. It is desirable to perform the firing within the above range because the above firing treatment increases energy loss and also inhibits the precipitation of copper again. The degree of oxidation of the stainless steel surface by this firing treatment is preferably such that the glossiness of the stainless steel surface after firing is 10 to 50 lower than the glossiness of the polished surface before firing. This means that the gloss reduction is 10
If the degree of oxidation is less than
This is because excessive oxidation, which decreases by more than 20%, makes it difficult to cause a copper precipitation reaction. The cause of this phenomenon has not been completely elucidated, but in unfired or similar conditions, sufficient ferric oxide, which contributes to copper precipitation, is not formed, and excessive oxidation causes surface This is presumed to be because ferric oxide ceases to exist in the steel, leaving almost only chromium oxide, which inhibits the precipitation of copper. Usually, as long as the firing is carried out under the above-mentioned firing conditions, the change in the glossiness of the stainless steel surface will fall within the above-mentioned range, so there is no need to particularly measure the glossiness after firing. Further, as the stainless steel, there is no problem in using any type of stainless steel such as austenitic, ferrite, steanite thread, etc. A chemical copper plating layer is formed on the oxide film, and can be formed by the following method. In other words, while increasing the copper precipitation rate,
In order to deposit uniformly, the oxide film is sensitized by wetting it with a sensitizing solution mainly composed of tin halide, and then activated with an activating solution containing a noble metal such as silver salt or palladium chloride. Formed by processing with copper plating solution. As the sensitizing solution, a bath containing stannous halide as the main component is used, and the sensitizing treatment is carried out for a short time, usually 1 to 5 minutes at room temperature, by immersion in the bath or by contacting with the sensitizing solution. This is done by As the activating solution, an aqueous solution containing precious metal salts such as silver salts and palladium salts at extremely low concentrations, or solutions containing noble metals and acids are used, but as noble metal salts, palladium chloride and silver oxides are economically advantageous. It is particularly preferred to use silver nitrate. In addition, the concentration of noble metal salt in the activation solution is 0.1 to 0.0001
% by weight, preferably from 0.01 to 0.005% by weight. This is because if the concentration of noble metal salt exceeds 0.1% by weight, not only will it cause an increase in cost, but it will also be difficult to dissolve it unless acid is added, making it difficult to obtain a uniform copper plating layer with high emissivity. This is because if it is less than 0.0001% by weight, it cannot be activated sufficiently, making it impossible to form a good chemical copper plating layer, and no improvement in heat retention can be expected. In addition, when using noble metal salts at a concentration of 0.01% by weight or more, it is necessary to add hydrochloric acid, etc. to the solution to prevent undissolved salts from remaining. Good too. The chemical copper plating bath is not particularly limited as long as it is an alkaline copper solution, regardless of whether it contains additives, and any commercially available bath may be used. Hereinafter, a detailed explanation will be given with reference to the accompanying drawings showing a stainless steel narrow neck thermos manufactured by the method of the present invention. In the figure, 1 is an inner container made of stainless steel, 2 is an outer container made of stainless steel, and both are joined at the mouth 3 by brazing, welding, or other means to form a double wall structure, and the inner container A space 4 formed between the container 1 and the outer container 2 is evacuated and made into a vacuum. The inner container 1 has a body part 1a and a bottom part 1b welded together,
The outer container 2 is formed by joining the body part 2a, the bottom part 2b, and the shoulder part 2c together by means such as brazing.
A tip tube 5, which serves as an exhaust port for evacuating the space 4, is bonded to the bottom 2b of the outer container 2 by brazing or the like, and a bottom cover 6 is bonded to the bottom 2b to protect the tip tube 5. It is attached by an agent. Although not shown, a getter may be provided in the space 4 for safety to ensure high vacuum over a long period of time. On the other hand, according to the present invention, in order to improve the heat retention ability of the stainless steel vacuum double container, among the walls of both the inner and outer containers forming the space 4, that is, the outer surface of the inner container 1 and the inner surface of the outer container 2, As shown in FIG. 2, an oxide film 7 is formed on the outer surface of the inner container, and a chemical copper plating layer 8 is laminated thereon. In the illustrated embodiment, the chemical copper plating layer is formed only on the outer surface of the inner container, but the chemical copper plating layer 8 is formed on the outer surface of the inner container and the inner surface of the outer container. Good too. This is particularly advantageous for improving heat retention in the case of containers with small contents. Examples of the present invention will be described below. Example 1 0.5mm thick stainless steel (SUS 304) with internal capacity
While manufacturing the 750ml inner container 1, the shoulder member 2c and body member 2 of the outer container 2 were made of 0.6 mm thick stainless steel plate.
a. The bottom member 2b is manufactured, the shoulder members 2c of the inner container 1 and the outer container 2 are welded together at their mouth portions 3, and this is baked in air at 350° C. for 30 minutes. Next, the body member 2a of the outer container 2 is welded to the fired inner container 1 and the bottom member 2b is welded to form a double wall structure, and 10 ppm is injected into the space 4 from the chip tube 5 joined to the outer container bottom 2b. An aqueous solution containing stannous chloride is injected to sensitize the outer surface of the inner container 1, and after the aqueous solution is discharged, it is washed with water. Next, an activation liquid prepared according to the following recipe is injected into the space 4 from the tip tube 5, and the double bottle is held horizontally in the axial direction and rotated at high speed to activate the inner container 1 and the outer surface. . (Prescription of activation liquid) Dissolve 10g of silver nitrate in a small amount of water, 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, 25 ml of a 15% aqueous solution of glucose
Add water to make a total volume of 5000ml, and use this as Solution B. After mixing the liquid A and liquid B at a volume ratio of 1:1, 900 ml of water is added to 100 ml of the mixed liquid to obtain an activation liquid containing 0.01% by weight of silver nitrate. After activation treatment, drain the liquid, wash with water, and remove _CuSO4 .
Chemical copper plating solution 240, which is a mixture of 120 ml of a solution containing 35 g/5H ₂ O, 50 g/NaOH, and 170 g Rotussel salt and 120 ml of 3.7% formalin solution.
ml was injected into the space 4 through the tip tube 5, the double bottle was held horizontally in the axial direction, and rotated at high speed for 5 minutes at 40°C to inject the chemical copper shown in Figure 2 onto the outer surface of the inner container 1. Form a plating layer. Next, after washing with water and drying at 150° C., vacuum treatment was performed, the tip tube 5 was melt-sealed, and a bottom cover 6 was joined to the bottom of the tube to obtain a stainless steel thermos flask having an internal capacity of 0.75. In order to examine the heat retention ability of the stainless steel thermos flask thus obtained, measurements were made under the following conditions using the test method specified in JISS2005, and the heat retention effect for 24 hours was 63.0°C. [Test conditions] Pouring temperature: 95℃ Hot water amount: Full Stopper: Sealed stopper (45mmφ) Ambient temperature: 20℃ The gloss of the test piece surface after buffing and degreasing was 122, and the gloss after baking treatment The temperature was 101, a decrease of 21 points compared to before firing. This gloss value is
Based on the measurement method specified in JIS Z8741, a digital variable angle gloss meter (Model: UGV-) manufactured by Suga Test Instruments Co., Ltd.
4D), the incident angle is 60°, and the standard sample's glossiness of 91.1 is set to 22.8, which is 1/4. 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] Example 2 A stainless steel thermos flask with a content capacity of 750 ml was manufactured in the same manner as in Example 1 except that a 0.001% by weight palladium chloride solution was used as the activating liquid in Example 1, and its heat retention effect was measured. It turned out to be 62.5
It was warm at ℃. The 0.001% palladium chloride solution was prepared by dissolving 1 g of palladium chloride in 10 parts of water and diluting it 10 times. Comparative Example 1 The same procedure as in Example 1 was carried out, except that instead of the 0.01% silver nitrate solution in Example 1, a 0.1% aqueous palladium chloride solution having the following composition was used, under the same conditions, stainless steel with an internal volume of 750 ml was used. I made a thermos flask. (Activation liquid prescription) Palladium chloride 1.0g Water 1000ml The heat retention effect of this thermos bottle for 24 hours was 50.6°C. Example 3 0.5mm thick stainless steel (SUS 304) with internal capacity
While manufacturing the 350ml inner container 1, the shoulder member 2c and body member 2 of the outer container 2 are made of 0.6 mm thick stainless steel plate.
a. The bottom member 2b is manufactured, the shoulder members 2c of the inner container 1 and the outer container 2 are welded at their mouth portions 3, and this is baked in air at 300° C. for 30 minutes. Next, separately from this, the inner container 1 is produced by firing an assembly in which the body member 2a and the bottom member 2b of the outer container 2 are welded and integrated.
An aqueous solution containing 10 ppm of stannous chloride is injected into the space 4 from the chip tube 5 connected to the bottom part 2b of the outer container to sensitize the outer surface of the inner container 1. After draining the aqueous solution, wash with water. Next, 0.01% silver nitrate activation solution prepared in the same manner as in Example 1 was injected into the space 4 from the tip tube 5, and the double bottle was held horizontally in the axial direction and rotated at high speed to open the inner container 1. Activates the outer surface. After the activation treatment, the liquid was drained and washed with water, and 130 ml of the chemical copper plating solution prepared in Example 1 was injected into the space 4 through the tip tube 5, and the double bottle was held horizontally in the axial direction and heated to 40°C. Rotate at high speed for 5 minutes, then remove inner container 1.
A chemical copper plating layer shown in FIG. 2 is formed on the outer surface of the substrate. Then, after washing with water and drying at 110°C for 20 minutes,
Vacuum treatment was performed in the same manner as in Example 1, the chip tube 5 was melt-sealed, and the bottom cover 6 was bonded to the bottom of the tube to determine the internal capacity.
I got a 0.35 stainless steel thermos. When we investigated the heat retention ability of the stainless steel thermos flask obtained in this way, the heat retention effect for 24 hours was 45.0℃.
It was hot. The test conditions are as follows. [Test conditions] Water pouring temperature: 95℃ Hot water amount: Full stopper: Sealed stopper (35mmφ) Ambient temperature: 20℃ Example 4 In Example 3, 130ml of a 0.001% by weight silver nitrate solution that does not contain glucose was used as the activation liquid. A stainless steel thermos flask was produced in the same manner as in Example 2, except that the activation treatment was carried out using the same method as in Example 2. The heat retention effect for 24 hours was 45°C. By the way, the temperature of the one with the silver mirror layer was 44.9°C. Effects As is clear from the above explanation, according to the present invention, the inner and outer bottle components are fired and assembled into a double-walled structure without the need for a complicated process unlike the case of using conventional nickel plating. After that, it is only necessary to apply chemical copper plating, which improves work efficiency.Moreover, copper plating is cheaper than forming a silver plating layer, and it has excellent heat retention properties that are equal to or better than those with a silver plating layer. It has excellent effects such as being able to manufacture thermos flasks. Additionally, in the process of firing the inner and outer bottles, there is also a degassing effect from the stainless steel, which has the effect of shortening the evacuation time.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a stainless steel thermos flask manufactured by the method of the present invention, and FIG. 2 is an enlarged view of section A in FIG. 1. 1 - inner container, 2 - outer container, 4 - space, 7 - oxide film, 8 - chemical copper plating layer.

Claims (1)

[Scope of Claims] 1. When manufacturing a stainless steel thermos flask that has 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, After firing the container or its component parts in an oxidizing atmosphere, and then sensitizing at least the surface of the inner container or the component parts of the inner container among the surfaces of both containers forming the space, containing the noble metal salt. A method for producing a stainless steel thermos flask, which comprises activating the flask with an activating solution and then chemically copper plating the flask. 2. The method according to claim 1, wherein the firing is performed in air at 250 to 550°C. 3. The method according to claim 1 or 2, in which only the inner container is fired. 4. The method according to any one of claims 1 to 2, wherein the sensitization treatment is performed with a solution containing stannous chloride. 5. The method according to any one of claims 1 to 4, wherein the activating solution contains 0.1 to 0.0001% by weight of silver nitrate. 6. The method according to any one of claims 1 to 5, wherein the activation liquid contains 0.1 to 0.0001% by weight of palladium chloride.