JPS6351194B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a coating surface that coats the inner wall of a cooking device and has the ability to decompose oil to catalytically purify stains from foods and the like. A coating surface formed by decomposing an oxidation catalyst into glass frit has been proposed and put into practical use, but it has not been sufficient. The present inventors investigated the catalyst system used to catalytically purify food stains formed on the inner walls of cooking equipment, and found that oxidation catalysts with strong oxidation ability were unsuitable. We have already found and proposed that a catalyst that simply activates the thermal decomposition of fatty acids, which are the main cause of food stains, has little or very weak oxidizing ability and is extremely effective. Most of these catalysts are composed of basic substances, and a water glass-based binder has been used as a binder to disperse the catalyst and form a surface. However, the weakness of water glass-based inorganic paints is that in high-temperature atmospheres with a lot of water vapor and carbon dioxide, the alkali remaining in the paint film reacts and produces white products such as sodium bicarbonate. It was hot. Although this drawback can be fully resolved by controlling the coating conditions, the above problems can become difficult in practice due to environmental conditions and the shape of the object to be coated, where such control is difficult. . The present inventors have focused on phosphoric acid-based paints such as phosphoric acid and acidic metal phosphates as binders for dispersing and supporting the catalyst system, and have conducted various studies on the formation of coated surfaces. When using an acidic metal phosphate binder, the addition of large amounts of basic substances, especially alkaline earth metals, has the disadvantage of causing a curing (gelling) reaction of the paint and reducing the film-forming properties of the paint. (1) Oxides of Group 1A or Group 2A of the Peripheral Table. (2) A compound represented by the formula (MA) _x (MB) _y (O) _z . However, MA: Group 1A or 2A element. MB: Group 3B or 4B element. O: Oxygen x, y, z: Indicates an integer. one or more catalysts selected from the group consisting of Ti,
It has been found that when coexisting with one or more catalysts selected from the group of oxides of Fe, Ni, Co, Cr, and Ag, an extremely excellent effect is exhibited and it is also good as a surface treatment. The main components of organic compounds that pollute are fatty acids with a carbon number of 15 to 22, mainly palmitic acid, stearic acid, oleic acid, linoleic acid,
Such as linoleic acid. When heated, these substances turn into tar, turn black, and become stains, but the following two types of processes can be considered for this tar reaction. One is a process of polymerization via an intermediate of an incompletely oxidized compound such as a peroxide, and the other is a process of thermal decomposition, dehydrogenation, and polymerization via an olefin. The present invention does not use a conventional oxidation catalyst to combust, that is, completely oxidize, the polluting organic compounds generated during cooking, but because dirt such as oil exists on the surface in a liquid or solid state. ,
Since it would be undesirable if that part were to turn into tar, this oil is changed into a gaseous state and released from the surface. For this purpose, it is desirable that the surface be in a state where the evaporation of the oil itself can be effectively utilized; however, relying only on evaporation is insufficient for the gasification of the oil. Considering that only evaporation is active, oil will spread well on a highly smooth metal surface and the evaporation rate will be extremely fast, but in this case tar formation is unavoidable. When increasing the surface area by making the surface uneven, it may seem that the evaporation rate is faster, but the unevenness itself inhibits the diffusion of oil, and if the surface is made three-dimensionally porous, Rather, its structure becomes a hindrance, and the evaporation rate is slower than in the flat case. Therefore, for the purpose of complete purification, some qualitative contribution of the surface to the gasification of oil is necessary. An embodiment of the present invention will be described in detail below regarding a gasification and decomposition reaction of salad oil. We identified that methane, ethylene, ethane, carbon monoxide, formaldehyde, etc. are generated as gases generated when salad oil is decomposed at 200 to 300℃, but there are also other components contained in the salad oil itself. analyzed that different decomposed hydrocarbons were produced during pyrolysis in the presence of air. The test conditions were as follows: Approximately 2mg of compound powder was mixed with 1.0μ of salad oil using a microsyringe, and 300mg of compound powder was mixed with 1.0μ of salad oil in a sealed glass container.
After decomposition at ℃ for 10 minutes, the generated gas was introduced into a gas chromatogram and analyzed. The analysis conditions are _N2 carrier (60ml/min)
The _H2 flow rate was 60 ml/min and the air flow rate was 0.5/min with the F--D detector.The column conditions were 3 mmφ x 3 m silicon G, E, SE-30,
150 using a 5% liquid phase (Silamite W as carrier)
After holding at ℃ for 5 minutes, increase temperature at 5℃/min.
Decomposition gas was detected by temperature raising analysis to 250℃. Under the above conditions, decomposition products were detected at retention times of 100, 106, 139, and 173 (seconds), although they were not identified. The results of integrating the areas of detected peaks for representative materials (values integrated using a digital integrator, ie, the sum of counts of the four decomposition products mentioned above) are shown in the table. From this table, metal oxides or compounds that exhibit good catalytic activity in the decomposition of salad oil (soybean oil) in the presence of air include oxides of metals from groups 1 to 4 of the periodic table, especially group 1A, Examples include Group 2A alkali and alkaline earth metals and their oxides. An even better compound is (MA) _x (MB) _y
A compound represented by (O) _z , where MA is group 1A,
Or, it is found that elements of group 2A, MB of group 3B, or group 4B are good. Note that O is oxygen,
x, y, z represent integers. Especially when MA is Na, K,
It is found that it is best to use a compound consisting of CaMg and MB consisting of C, Si, and Al.

[Table] As a catalyst used for gasification decomposition reaction, MnO ₂
It is necessary to avoid using Ti, CuO and CuO in an active form as they interfere with the reaction, and even metal oxides such as Ti,
Metal oxides such as Fe, Ni, Co, Cr, and Ag exhibit gasification and decomposition activity, and Fe in particular has excellent activity. Sumitomo Chemical's phosphate-based inorganic heat-resistant paint "Sumiceram P Type" was used as a binder, and the catalyst compound described above was blended with this to form a paint.The paint was applied to an aluminum-treated steel plate and then tested. . "Sumisaram P type" is a two-component system consisting of a main binder (phosphate) and a hardening agent consisting of reactive metal oxides, fillers, and pigments, and is formulated using a ball mill. , when a gasification decomposition catalyst showing obvious activity in the gasification decomposition reaction is added, when the binder is acidic and the gasification decomposition catalyst is a basic compound or an alkaline earth metal salt, The gasification decomposition catalyst reacts with the binder and causes the paint to gel, which is undesirable. First, the paint was applied onto a 10 cm square, 0.4 mm thick aluminum-treated steel plate (the film thickness after drying was approx.
After drying at 100℃ for 10 minutes, baking at 200℃ for 10 minutes, and finally at 300℃ for 30 minutes.
I baked it separately. This coating has good adhesion, water resistance, abrasion resistance, thermal shock resistance, heat resistance, steam resistance,
It showed properties such as chemical resistance, but almost no oil purification performance was observed. The oil purification ability was evaluated by the following test. That is, a 10 cm square test piece was placed on a hot plate set at a temperature of 250°C, and
Approximately 50 spots of salad oil were dispersed and placed on the coating surface, and changes in the oil stains were visually tracked and evaluated. In the case of using only the above-mentioned paint, in this test, the residue of salad oil was stuck to almost the entire surface of the test piece and turned into tar. Next, 5% by weight of calcium silicate, which is one of the most efficient catalysts among gasification and decomposition catalysts, was added. In this case, the binder gelled significantly, but ca.
% of water was added to adjust the viscosity, and the coating was applied under the above-mentioned coating conditions. The resulting coated surface had noticeable cracks, and when testing adhesion by peeling off the tape, some parts peeled off in the form of pinholes, and adhesion was insufficient on some surfaces, but other physical properties were generally good. In an oil purifying ability test, it showed good purifying performance, cleaning almost no stains in about 5 minutes. Almost the same results were obtained for lime aluminate. Next, the same test was conducted with the addition of 10% iron oxide (Fe ₂ O ₃ ), which is thought to be the most effective catalyst additive among gasification decomposition catalysts and does not cause the paint to gel. In this case, good physical properties of the coating film were obtained, which were almost the same as those obtained with paint alone. In the purification ability test, tarry traces of about 2 mmφ remained at a few points, but a certain level of ability was obtained. Next, similarly, 5% iron oxide and 1% lime aluminate.
A similar test was conducted for the case where . In this case, a coated film surface with almost the same surface condition as the case of paint alone was obtained, except that the surface was rough. This coating surface exhibits extremely excellent surface physical properties, and is no different from that of paint alone.
Rather, it showed excellent properties such as impact resistance.
This coated surface showed particularly remarkable cleaning performance; stains disappeared within a few minutes, and no trace of tar remained on the surface even after the same test was repeated seven times. The reason for this excellent effect is not the synergistic effect of both catalysts, but rather the addition of a small amount of alkaline earth metal causes the paint to partially gel, causing the catalytic compound to disintegrate, especially in its surface layer. This seems to be due to the fact that a structure was achieved that exposed the surface layer without reacting with the binder. The amount of gasification decomposition catalyst added is preferably 5% or more in the case of transition metal oxides and 1% or less in the case of alkaline earth metal salts, and it is especially best to use both in combination. be. The present invention can be applied to any surface that can be coated with a phosphate-based binder, such as general metal surfaces or ceramic surfaces, and can also be applied over an undercoat to improve corrosion resistance. It is also possible to apply the coating using the same method, or if a thicker film is desired, it is also possible to apply multiple coats after baking the main coating film. As described above, the present invention has great industrial value in that it forms a surface that can easily clean food stains and the like.

Claims (1)

[Claims] 1 5wt% to 50wt% of one or more oxides selected from the group of Ti, Fe, Ni, Co, Cr, Ag and CaO,
Na ₂ O, K ₂ O, MgO, K ₂ CO ₃ , CaSiO ₃ ,
CaAl ₂ O ₄ , MgSiO ₃ , BaSiO ₃ , BaTiO ₃ ,
One or more compounds selected from the group of Li ₂ SiO ₃ , Na ₂ CO ₃ , and Ca(OH) ₂ are dispersed in a phosphate binder at a concentration of 1 wt% or less and have the ability to decompose oil. coated surface.