JPH088986B2 - Self-cleaning coated surface - Google Patents

Description

TECHNICAL FIELD The present invention provides a coated surface for self-cleaning, which has a catalytic action of decomposing oil stains on a cooking device such as an oven.

2. Description of the Related Art Conventionally, when oil and fat adhered to the wall surface of such a cooking device, it was difficult to wash it with water and remove it, or to mechanically remove what was carbonized and fixed.

In order to eliminate such an inconvenience, it has been attempted to coat the surface to which dirt is attached with a coating having a catalytic action to decompose oil, and it has already been put to practical use. This is a catalyst that is dispersed in a binder such as enamel frit or dye, and this is applied to form a film on the surface of the vessel wall by baking and curing. It is applied to the wall surface of the heating chamber of the container.

For example, an inorganic heat-resistant polymer such as an inorganic phosphate is used as a binder, and a coating layer obtained from a composition in which a solid acid or a metal oxide is dispersed therein is formed on the inner surface of the cooking chamber, or is transitioned into enamel. There has been a technique of adding a metal oxide and forming an enameled coating layer on the inner surface of the cooking chamber. In this case, solid acids and transition metal oxides are catalysts that oxidize and decompose oils above a certain temperature, and by forming a coating layer having such a catalytic action, it is possible to eliminate oil stains adhering to the inside of the cooking chamber. It is what In addition, there is a method of eliminating oil stains only by thermal decomposition without using a catalyst, but in this case, a temperature of about 500 ° C. requires 1 to 2 hours.

Problems to be Solved by the Invention However, the conventional techniques have problems in the following points.

The basic structure of oil is a triglyceride of a higher fatty acid, but the solid acid or transition metal oxide does not decompose the oil unless the temperature is raised to 450 ° C or higher. Furthermore, by dispersing such a catalyst in a binder or enamel, the catalyst surface is covered and the exposed area is reduced, the contact area between the oil and the catalyst surface is reduced, and it becomes difficult to decompose the oil. At the same time, the diffusion of oxygen deteriorates, which causes a decrease in activity. Further, if the oil itself is heated to 450 ° C or higher and 500 ° C or so, it is thermally decomposed, so that the effect of the coating layer becomes unclear. When the coating layer temperature is maintained at about 400 ° C, the oil is carbonized, and as a result, the surface of the coating layer is covered with tar.

A high temperature of about 800 ° C. is required to obtain a enamel coating layer, and at such a high temperature, the surface area of the metal oxide becomes small and the activity also decreases.

As described above, with respect to the conventional coating layer, there is a problem that the activity is low and the oil stain cannot be completely decomposed at 400 ° C. or lower, and the cause is that the activity of the catalyst itself is low,
Further, the catalyst surface was not exposed so much, the contact portion between the oil and the catalyst surface was reduced, and the diffusion of oxygen into the film was suppressed.

The present invention solves the above problems and provides a self-cleaning coated surface that decomposes oil stains at a relatively low temperature.

Means for Solving the Problems In order to solve the above problems, the present invention comprises a support, an adhesive layer and a fiber layer, the fiber layer is adhered to the support by an adhesive layer, SiO ₂ , Al ₂ O _3, of ZrO _2, are those formed by carrying Ce, Cu, a composite oxide of Mn and at least any one of an oxide fibrous porous body mainly composed,
Ce, Cu, Mn ratio of the composite oxide, Ce: Cu in molar ratio:
Provide a catalytically coated surface with Mn = 1: X: 1-X, where 0 <X <1.

Action The action of the self-cleaning coating surface by the above means will be described. The decomposition of oil stains, which is the object of the present invention, requires increasing the surface area of the catalyst and increasing the supply of oxygen. In the present invention, a coating layer having a high porosity is formed by using inorganic fibers so that oxygen easily diffuses into the coating and the surface area is much larger than that of the conventional coating. This facilitates the desired reaction to proceed more advantageously.

What is called a ceramic paver using inorganic fibers has a density of about 0.15 to 0.69 g / cm ³ and a porosity of about 7
It is about 0 to 90%. By supporting the catalyst on the fiber having such a high porosity, the supply of oxygen is improved and the catalytic activity can be sufficiently exhibited.

The inorganic fibers have been described above, but the activity of the supported catalyst is described below.
In the complex oxide of e, Cu, Mn, the ratio of Ce, Cu, Mn is Ce: Cu: Mn = 1: X: 1-X (where 0 <X <1), , Shows a higher activity for the oxidation of hydrocarbons than a single element or a composite oxide of two or more elements. This is because in the three-element system oxide of Ce, Cu, and Mn, the element on the surface of the oxide takes many valences (for example, Mn is trivalent and tetravalent, Cu is monovalent and divalent, etc.). ), That is, valence control between different elements that is not found in a single or binary system is performed, and a surface more suitable for reaction is created. This is confirmed by XPS (X-ray photoelectron spectroscopy). By supporting such a highly active catalyst on the inorganic fibers, the oxidative decomposition activity is further improved, and a coated surface that decomposes oil and the like at an unprecedented low temperature can be obtained.

Example One example of the present invention will be described below.

A test piece having a coating layer was prepared in the present invention, and an oxidative decomposition test of salad oil was carried out under heating conditions.

An inorganic heat resistant binder (for example, Sumiceram (S-18) manufactured by Sumitomo Chemical Co., Ltd.
C)) and silica / alumina fibers (S
iO ₂ : Al ₂ O ₃ = 53: 47, average fiber diameter 2.8 μm, porosity 92%,
A thickness of 1.0 mm) was used. The test piece size is 50 x 50m
It was m. Spray gun on the support (Devilbiss spray gun, nozzle diameter 1.4mmφ, air pressure 4-4.5kg / c
In m ^2), SUMICERAM the (S-18C) 0.020g / cm 2 was applied,
The silica-alumina fiber is pressure-bonded and heated at 110 ° C for 30
After heat curing for a minute, a mixed solution of Ce, Cu and Mn nitrates (Ce: Cu: Mn = 1.0: 0.3: 0.7mol / l) was spray gun (Devilbiss spray gun, nozzle diameter 1.4mmφ, air pressure 1.5).
~ ² kg / cm ² ) at 0.50 g / cm ^{2 and} baked at 450 ° C for 30 minutes. At a temperature distribution of the test piece of 300 ± 10 ° C., when 10 mg / cm ^{2 of} salad oil was dropped and left for 60 minutes, the salad oil completely disappeared. On the contrary,
The coating layer containing MnO _X and CuO _X was not completely burned out even at 350 ± 10 ° C. In addition, a composite oxide of Ce, Cu, and Mn (Ce: Cu:
For the test piece with Mn = 1.0: 0.3: 0.7 mol / l), the test piece with salad oil completely disappeared no matter how many times it was tested. FIG. 1 shows a conceptual view of the cross-sectional structure of the self-cleaning coating surface of the present invention.

Next, the effect of the amount of oxygen supplied to the catalyst was examined. The oxidation activity of the salad oil of the composite oxide of Ce, Cu, Mn, which is the catalyst of the present invention, was measured by DTA. The measurement is
A commercially available salad oil and oxide were mixed at a weight ratio of 2.5: 1.0, mixed well, and placed in a quartz cell to obtain a DTA curve. FIG. 2 shows the results of measurement of a complex oxide having a ratio of Ce, Cu and Mn (Ce: Cu: Mn = 1.0: 0.3: 0.7) in an oxygen atmosphere and a nitrogen atmosphere. As can be seen from the figure, when the supply amount of oxygen is large, the oil can be burned out at a lower temperature and the activity of the catalyst can be increased.

Next, silica / alumina fiber (SiO ₂ , Al ₂ O ₃ = 53: 47,
Porosity of average fiber diameter 2.8μm, thickness 1.0mm) from 68% to 94
%, The baking test with salad oil was performed, and the result was as shown in Table 1.

From Table 1, it can be seen that the oil can be burned out at a lower temperature than the conventional cell cleaning. Porosity 85
%, It is possible to burn off oil at a low temperature of 300 ℃.

Also, instead of silica / alumina fiber, zirconia fiber (ZrO ₂ , Y ₂ O ₃ = 89: 6, average fiber diameter 5.0 μm, thickness 0.5
mm, porosity 84%). Using SUS304 as a support, as an adhesive, Sumiceram (S-18
C), zirconia fiber is pressure-bonded, and at 110 ℃ 30
After heat-curing for a minute, a mixed aqueous solution of Ce, Cu and Mn nitrates (Ce: Cu: Mn = 1.0: 0.3: 0.7mol / l) was applied and fired. , It completely disappeared in 60 minutes.

Although silica-alumina SUMICERAM was used as the adhesive, polyborosiloxane polymers and polytitanosiloxane polymers that do not react with the complex oxides of Ce, Cu, and Mn can also be used.

The effect of supporting the catalyst on the inorganic fiber has been described above. Next, the activity of the composite oxide of Ce, Cu and Mn will be described.

Table 2 shows the surface area by the BET method. C for comparison
The single oxides of e, Cu and Mn are also shown. Firing is 450
Performed at ° C.

Regarding 1) and 2), oxides having an oxidation number other than CuO and Mn ₂ O ₃ are also included.

The reason why the total surface area is as large as about 70 to 120 m ² / g is that the firing temperature is 450 ° C. and the temperature of the oxide is low. Further, the surface area of the composite oxide is larger than that of the single oxide. This is considered to be due to the effect of CeO ₂ . Actually, Ce / Cu Oxide and Ce / Mn Oxide were larger than the surface areas of CuO and Mn ₂ O _{3 in} Table 2, respectively. Table 2 shows that the surface area of CeCu _0.5 Mn _0.5 O _y is large.
Ce, Cu, Mn composite oxide (molar ratio Ce, Cu, Mn = 1.0: X:
The dependence of the surface area of (1-X) (where 0 <X <1) on X is shown in FIG. From Fig. 3, the peak of the surface area is X
It was found to be around 0.3.

Ratio of Ce, Cu and Mn mentioned above (Ce: Cu: Mn = 1.0: X: 1-
The oxidative activity of the mixed oxide salad oil of X) was measured by DTA. The measurement was performed by mixing the commercially available salad oil and oxide at a weight ratio of 2.5: 1.0, mixing them well, and placing them in a quartz cell.
Got a TA curve. FIG. 4 shows TG curves of the four kinds of oxides shown in Table 2. In FIG. 4, it can be said that the oxidation activity is high when the weight reduction rate is high and the weight reduction is completed at the lower temperature side. Therefore, it is clear that CeCu _0.5 Mn _0.5 O _y has high activity and is effective as an oxidation catalyst. Figure 5 shows the ratio of Ce, Cu and Mn (Ce: Cu: Mn = 1.0: X: 1).
-X (where 0 <X <1) X of TG curve of complex oxide
Dependence on. X = 0.3 seems to have the highest activity. This is considered to correspond to the dependence of the surface area on X. It can be seen from FIGS. 4 and 5 that the activity of the complex oxide of Ce, Cu, Mn is only powder and has the ability to decompose salad oil at 400 ° C. Will be able to break down the salad oil.

EFFECTS OF THE INVENTION As described above, the self-cleaning coated surface of the present invention can form a coating layer having a high porosity by using inorganic fibers, can supply more oxygen, and can be used as a salad. If it is applied to equipment that has high oxidative decomposition activity for triglycerides such as oil and oil stains are generated, for example, the wall surface inside the refrigerator of a cooking device, it is possible to eliminate oil stains by raising the temperature to around 300 ° C. . This allows the cooker to always be used in a clean state. Also, since oil stains can be decomposed at around 300 ° C, there is no need to reduce the heat insulation structure (a thermal decomposition temperature of around 500 ° C is required if a catalyst is not used) and the heater capacity is increased in the design of the cooking device. As it is completed, it also saves energy.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a self-cleaning coating surface in one embodiment of the present invention, and FIGS. 2, 3, 4, and 5 are characteristic diagrams thereof, respectively. 1 ... fiber layer, 2 ... adhesive layer, 3 ... support, 4 ... complex oxide.

Claims (1)

[Claims] 1. A support and a fiber layer, wherein the fiber layer is adhered to the support by an adhesive layer, and SiO ₂ , Al ₂ O ₃ , and Z.
Of the rO ₂ , at least one fibrous porous body containing at least one oxide as a main component, Ce, Cu, is a composite oxide of Mn is carried, Ce, Cu of the composite oxide, The molar ratio of Mn is Ce: Cu: Mn = 1: X: 1-X (where 0 <x1).
Self-cleaning coated surface with catalytic action.