JPS5915017B2 - Coated surface with catalytic action - Google Patents

Description

[Detailed Description of the Invention] The present invention provides a coated surface that has a catalytic effect to suppress the generation and formation of tar-based carbon, for metal surfaces where there is a concern that carbonaceous tar-based materials may be formed. The purpose is to

As equipment that causes troubles due to the formation of carbonaceous matter in tar, for example, oil, food residue, etc. can be scattered, producing a strange odor, and it is unpleasant to apply forceful force in a sticky and filthy state. Typical examples include box-shaped cooking utensils such as the various types of open cooking utensils that are commonly used in cooking, and oil-burning utensils that generate carbon and cause various problems related to safety and reduced combustion. It is mentioned as.

5. Conventionally, the catalytic coating surface used in such devices has been a hollow or vitreous coating formed on the substrate.

This coating layer is made of manganese, iron, cobalt, zirconium, chromium, copper, or rare earth metal oxides.
It was made vitrified by adding a catalytic material whose main component was a substance. As these conventional catalysts, oxidation catalysts with strong catalytic ability are used.
The aim is to use these oxidation catalysts to completely oxidize organic compounds into carbon dioxide gas and water, thereby preventing stains on the internal walls of the refrigerator and keeping them clean at all times.

The inventors have doubts about whether salad oil, for example, can be completely oxidized to -30 water and carbon dioxide gas while it is in contact with the surface of these oxidation catalysts in a liquid state, and have not actually found it. A catalyst coating layer, which is commercially available as a self-cleaning enamel, was brought into contact with salad oil (soybean oil) and thermally decomposed in the air, and the generated gas was analyzed using a Gas 35 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 air turns into tar is partially oxidized to obtain an intermediate such as peroxide, which is then polymerized, or hydrogen is extracted to form an olefin, which then depolymerizes. A strong oxidation catalyst (
At the same time, it is also used as a hydrogen abstraction catalyst), which promotes this tar formation, and is considered to be in no way suitable for self-cleaning purposes; rather, it decomposes reaction intermediates related to tar formation. We discovered that catalysts that have the ability to do so are effective.

In fact, in the case of manganese dioxide MnO2, copper oxide CuO, etc., which are known to have strong abilities as oxidation catalysts, they are particularly effective in promoting tar formation.

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 spreads quickly on the surface and under 300 saC conditions. 20～
After 30 minutes, the trace becomes difficult to see.

This does not mean that the carbon content has disappeared, but rather that carbon is deposited in the porous and thick enamel bottom in a hidden state that is difficult to see. There is not much difference numerically from that on a regular iron plate when oil is turned into tar, which confirms that the above considerations are correct. The present invention uses a enamel frit as a catalyst base,
This is provided with a catalyst-coated surface containing a catalyst that effectively decomposes oil. An example of this will be described in detail below.

In order to search for catalytically active substances that are effective in decomposing oil, we pyrolyzed salad oil in the air by contacting it with various metal oxides using a gas chromatograph and a pyrolysis device, and the resulting gas was Analyzed by gas chromatography, metal oxides with particularly excellent thermal decomposition ability were evaluated.

Although carbon monoxide and formaldehyde were identified as decomposition gases, they also detected decomposed hydrocarbons that are different from the components contained in salad oil itself. The test was carried out using a microsyringe for about 2W9 metal oxide, and 10 μl of salad oil was mixed with the metal oxide in a sealed glass container for 3 minutes.
After decomposition at 00°C for 10 minutes, the resulting gas was introduced into a gas chromatograph and analyzed.

The analysis conditions were as follows: N2 carrier (60 m1/min) was used. I. D detector: H2 flow rate: 60 m1/min, air flow rate: 0.51/min, column conditions: 3 mmφ x 3 m
Silicon G. E. SE-30.5
After holding at 150° C. for 5 minutes using a % liquid phase simalite w carrier, the temperature was raised to 250° C. at a heating rate of 5 C/min, and analysis was performed to detect decomposition gas.

Under the above conditions, decomposition products were detected at retention time positions of 100, 106, 139, and 173, although they were not yet identified.

Area integration results for typical metal oxides Table 1 shows the sum of the counts of the above four decomposition products as values integrated using a digital integrator. Table 1 shows that metal oxides or compounds that exhibit good catalytic activity for the decomposition of salad oil in the presence of air include metal oxides from Groups I to Groups of the Periodic Table, especially those from Group I A and Group II B. Examples include oxides of alkali and alkali metals.

These substances have a weak partial oxidation ability, and it is presumed that the decomposition mechanism of unsaturated fat, which is the main component of salad oil, is decomposed through intermediates of partially oxidized compounds. Partial oxidation catalysts activate this reaction and decompose and evaporate the oil before the reaction that progresses from hydrogen abstraction to polymerization, which results in suppressing the formation of oil into tar, so-called Demonstrates a self-cleaning effect. Furthermore, as an excellent compound from Table 1, the compound MA expressed in the form (MA) x (MB) y (0) z is an element of group IA or group A, and MB is C, Si, A
It was found that a compound consisting of 1 is good, and in particular, it is found that it is best when a compound consisting of Na, K, Ca, and Mg is used as MA.

Next, Al2O3, SlO2, B2O3, Li2O, N
a, O, K2O, CaO, ZnO, BaO, COO, N
iO, MnO2 (63 parts by weight of Al2O3+SiO2,
14 parts by weight of B2O3, 16 parts by weight of Li,O+Na2O+K2O, 4 parts by weight of CaO+ZnO+BaO, CO
100 parts by weight of a frit for enamel obtained by melting a mixture of metal oxides (O, NiO, MnO2 (3 parts by weight)) in a glass bowl at high temperature and pouring it into water and the above-mentioned Mix catalytic active material and 50 parts by weight of water, and the size is 40W! I×80m1Lx0.6m7! A coating layer was formed by spraying onto the iron plate soil of L and heating it. The type and composition ratio of the catalytic active material are shown in Table 2, and the weight percentage of the catalytic active material is the weight ratio to the enamel frit. Approximately 30m of salad oil was dropped onto the various test pieces prepared in this way with a spot down distribution so that the area was approximately 1m9, and the pieces were left on a hot plate set at a temperature of 250°C for 30 minutes. The cleanup was evaluated. Table 2 shows the results.

The purification rates in the table were determined as follows. If the purification rate is C, then C-{Ws-AVt-(W-W2)}×100/(Ws
-W1) Ws: Weight of test piece after dropping salad oil Wt
:2500C Weight of test piece with salad oil added after being left for 130 minutes (on hot plate) W1: Weight of test piece only (no salad oil) W2:
25 "Weight of test piece only after standing for Cl3O (on hot plate) (no salad oil)" Here, (W1-W2) is the weight change of only the coating layer and means correction of the purification rate C.

・Looking at the purification ability of each system, 3% by weight of potassium carbonate and 1.5% by weight of frit? of calcium oxide, 3
The system containing 3% by weight of calcium silicate and 3% by weight of alumina cement was the best, and all traces disappeared completely after a test period of 30 minutes. Judging from the ingredients of salad oil, the boiling point is 27.
It also contains palmitic acid at 1°C, which is 10°C.
The fact that 0% purification was achieved is thought to be due to the decomposition ability of the catalytic active substance, which caused it to be thermally decomposed even at 250°C and evaporated as a low-boiling point substance. Furthermore, a similar test was conducted using lard (pork fat) and the same results were obtained.

However, lard has a higher purification rate, and the total amount of catalyst added to the frit is about 10% by weight.
It is preferable that the following (relative to the frit weight):
If more than that is added, the catalyst will exist in powdered form on the surface.
This is undesirable because the adhesion of the coating film becomes significantly poor. Furthermore, we conducted a series of tests on temperature stability, heat shock, corrosion resistance, etc., but the amount of catalyst added was 10% by weight. It was also confirmed that if it is below, the physical properties of the conventional coating film are hardly impaired.

According to the above test results, the catalyst coating of this example has almost the same characteristics as the conventional self-cleaning enamel treated product, and the only difference is that the catalyst coating of this example has excellent wear resistance. In terms of thermal shock, on the other hand, it can be said that the self-quenched product is superior. This is because conventional self-cleaning enamel products are porous, emphasizing porosity rather than catalytic effect, but in the case of the coating in this example, the catalytic effect is well exhibited, which is why conventional self-cleaning enamel products are porous. This is because there is no need for porosity that sacrifices strength like self-cleaning hollow products. As described above, the present invention exhibits an extremely excellent self-cleaning effect in practical use, and has great industrial value as the quality of the coating is on the same level as conventional self-cleaning enamel products.

Claims (1)

[Claims] 1. A frit for enamel made of metal oxide and the following A,
A coated surface comprising at least one compound selected from Group B and having a catalytic action to suppress the formation of tar-like carbon due to thermal decomposition. A, an oxide consisting of an element in group I A or IIA of the periodic table B, a compound containing an oxide in group A, expressed as (M_A) x (M_B)_yO_2, where M_A is an element in group I A or IIA group element, M_B is C
, Si, Al, and O represent oxygen, and x, y, and z represent integers. 2 Group A: Na_2O, K_2O, CaO, MgO
, The coated surface having a catalytic action according to claim 1, wherein M_A is composed of Na, K, Ca, and Mg and M_B is composed of C, Si, and Al as the B group.