JPS6113871B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention mainly relates to a surface treatment method for box-shaped cooking utensils such as various ovens, which are disliked because oil, food residue, etc. can scatter, generate strange odors, and become sticky and filthy. The inner surface of the box is coated with a paint-type catalyst that has the ability to decompose and remove oils such as salad oil. Conventionally, a coating having such a catalytic effect has been formed by forming an enamel or glass material on a base metal. As this coating layer,
Vitrified catalytic coatings were applied to electric ovens and other box-shaped cookware by adding catalytic materials based on manganese, iron, cobalt, zirconium, chromium, copper, or rare earth metal oxides. . As these conventional catalysts, oxidation catalysts with strong catalytic ability are used. During cooking, these oxidation catalysts completely oxidize oil, protein, fat, and various other organic compounds that scatter from cooked foods such as meat and fish into carbon dioxide gas and water, cleaning the interior walls of the refrigerator. The aim is to prevent this and keep it clean at all times. It is questionable that salad oil can be completely oxidized to water and carbon dioxide while it is in liquid state and in contact with the surface of these oxidation catalysts. The catalyst coating was thermally decomposed in the air while in contact with salad oil (soybean oil), and the gas produced was analyzed using a gas chromatograph. Although evaluation was performed under various conditions (e.g., raising the temperature to 350°C and leaving it for 1 hour), no carbon dioxide gas was detected. Therefore, it is considered that these oxidation catalysts do not contribute at all to complete oxidation. The process in which oil heated in the air turns into tar is partially oxidized to obtain intermediates such as peroxides and polymerized, or hydrogen is extracted to form olefins, etc. The process of depolymerization can be considered. In both processes, the effect of the strong oxidation catalyst (which is thought to act as a hydrogen abstraction catalyst at the same time) actually acts to accelerate this tar formation, decomposing the reaction intermediates related to tar formation. Based on the idea that catalysts with this ability would be effective, we searched for catalysts, and as a result, we discovered and proposed a catalyst in a completely new direction. In fact, manganese dioxide (MnO ₂ ), which is known to have strong ability as an oxidation catalyst,
In the case of copper oxide (CuO), etc., it has the effect of promoting tar formation particularly markedly. In addition, regarding what is conventionally called self-cleaning enamel, when salad oil or the like is dropped onto the surface of a catalyst that has been left in high-temperature air, the salad oil quickly spreads on the surface, and under 300℃ conditions, , after 20 to 30 minutes, the traces become difficult to see, but when viewed on a microscopic scale,
It is thought that the carbon content has not disappeared, but rather that the carbon has been deposited in the porous and thick enamel bottom in a state that is difficult to see. Even when evaluated from the weight change before and after the test, there was no significant difference numerically from oil tarred on an ordinary iron plate, supporting the above idea. In this way, conventional self-cleaning enamels are not only inadequate in terms of purification effect, but also have drawbacks in terms of adhesion and abrasion because the catalyst layer itself is quite porous. ing. An embodiment of the present invention will be described in detail below. In order to search for catalytically active substances that effectively act on oil decomposition, we used a gas chromatograph and a pyrolysis device to bring salad oil (soybean oil) into contact with various metal oxides in the air. The resulting gas was analyzed by gas chromatography, and metal oxides with particularly excellent thermal decomposition ability were evaluated. Although carbon monoxide and formaldehyde were identified as decomposition gases, we also detected decomposed hydrocarbons, which are different from the components contained in salad oil itself. The test conditions were approximately 2mg of metal oxide mixed with 1.0μ of salad oil using a microsyringe, and heated to 300℃ in a sealed glass container.
After decomposition for 10 minutes, the produced gas was introduced into a gas chromatograph and analyzed. The analysis conditions are 60ml/ _N2 carrier.
Min _H2 flow rate with FID detector: 60ml/min, air flow rate
0.5/min Column conditions were a 3 mmφ x 3 m stainless steel column using silicone GE SE-305% liquid phase (Simalite W carrier), held at 150°C for 5 minutes, and then heated at a heating rate of 5°C/min. Analysis was carried out at a temperature raised to 250°C, and decomposition gas was detected. Under the above conditions, decomposition products were detected at retention time positions of 100, 106, 139, and 173, although they have not yet been identified. Table 1 shows the area integration results for typical metal oxides (values integrated using a digital integrator, sum of counts of the above four decomposition products).

【table】

[Table] From Table 1, metal oxides or compounds that exhibit good catalytic activity for the decomposition of salad oil (soybean oil) in the presence of air are metal oxides or compounds from Group 1 to Group 4 of the periodic table.
Mention may be made of oxides of metals of groups 1 and 2, especially alkali and alkaline earth metals of groups 1A and 2A. An even more excellent compound is (M _A ) x (M
_B ) A compound represented by y(O)z, where M _A is a group A or an element of group A, M _B is a group B,
Or, it can be seen that elements of group B are suitable. In particular, M _A is composed of Na, K, Ca, and Mg, and M _B
It turns out that this is the best when using a compound consisting of C, Si, and Al. In the case of conventional enamel type coating, cracks occur when the film is thickened, and the enamel film tends to crack.Especially, in the case of the enamel type, if it is applied directly to the box, the film on the corner parts may crack. There was a problem with the film becoming too thick and peeling off. Therefore, we adopted a method of forming the coating by removing one side, spotting the remaining four sides and the first side separately, masking the other parts, applying the coating, and then assembling it as a box. . In the case of this enamel type coating, basically a 2-coat, 2-bake method was used to obtain adhesion to the base metal, so masking was required twice for each, making the process extremely complicated. It was hot. Therefore, in this embodiment, taking a microwave oven box as an example, the microwave oven box has an open central portion on the front 1, and a door is attached to this portion. It has a structure in which five faces, a face 2 facing the front face 1, a right side face 3, a top face 4, a left side face 5, and a bottom face 6, are closed with plates. Details such as the projection provided on the bottom surface 6 for setting the turntable or the window provided on the top surface 4 for irradiation of microwaves from the magnetron are omitted. The main parts of this oven box are made of aluminum-treated steel. The painting procedure was carried out as follows. The water glass-based heat-resistant paint "Sumiceram P-100" (pigment black) was used as the paint, and after mixing the main agent and curing agent in the specified formulation, the following was added as a catalyst additive to 100 parts of this paint: Alumina cement (JIS No. 2 product) 4
1 part of calcium silicate, and further added about 10 parts of glycerin, and a mixture was used for coating. After the box was subjected to the usual alkaline degreasing, water washing, draining and drying, surface 4 was masked using a jig, and surface 1 and the other four inner cylindrical surfaces, namely surfaces 3, 4, 5, 2 to 3 minutes after coating No. 6, the masking was removed and side No. 4 was applied. After coating the entire inner surface and front surface, it was placed in a hot air oven at 300°C and baked for 1 hour to harden. The boxes treated in this manner were assembled into an oven/range set, and tests such as cooking experiments were conducted. Even when cooking chicken thighs, where contamination inside the refrigerator was a problem, there was almost no dirt inside the refrigerator, and the refrigerator was thoroughly cleaned. This paint-based coating dries relatively quickly and has a thin coating film compared to the enamel type, so compared to the conventional enamel method, which is basically a 2-coat, 2-bake method, 1 coat is 1 coat. This is a baking method, and compared to the former, which requires masking four times, this method only requires one masking, and has a great practical economical effect. Another advantage of this method is that the finished surface is relatively smooth, so even if the inside of the refrigerator is contaminated with contaminants other than oil, it can be easily cleaned with a cloth or the like. In addition, in the case of the enamel method, the color can only be black (because metal oxides are used as catalysts), but with this method, it is possible to color any color that the pigment allows, improving the aesthetic appearance and product quality. It has a remarkable effect on sex, etc. As described above, the present invention has extremely excellent practical characteristics as a surface treatment with a catalytic action applied to the inner surface of a cooking appliance box.

[Brief explanation of the drawing]

The figure is a schematic diagram of a cooker box.

Claims (1)

[Claims] 1. On the inner surface of a cooking box with one or more sides open,
A method for surface treatment of a cooker box, in which a heat-resistant paint is used as a base, and at least one compound selected from Groups A and B below is added to the paint, which is applied in two or more parts through a masking operation, and then baked. . A A group A or an oxide of group A of the periodic table, B A compound containing an oxide of group A with the formula (M _A ) x
(M _B )y(O)z, where M _A is a group A or an element of the A group, M _B is a group B or an element of the B group, O is oxygen, x, y,
z indicates an integer.