JPS63275680A - Coating composition - Google Patents

Abstract

PURPOSE:To provide a coating compsn. which has an excellent oil stain decomposing activity on the inner surface of a cooking utensil heated in use, such as an oven, by dispersing a particular powdery mixture of a perovskite oxide and a heteropolyacid in a heat-resistant binder. CONSTITUTION:A powder mixture of a porovskite oxide of formula I or II (wherein 0<=x<1) and a heteropolyacid of formula III is dispersed in a heat- resistant binder, thereby obtaining the desired coating compsn. Oil decomposition can be performed at 400 deg.C by forming a coating layer derived from the coating compsn. on the inner surface of a cooking utensil heated in use, such as an oven, whereas at least 500 deg.C is required according to the conventional burning off method. Thus, it becomes possible to choose design parameters more freely. Moreover, since oil stain can be completely decomposed, it is possible to keep the interior of the oven clean. a silica sol is suitably used as the heat-resistant binder.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a composition for providing a coated surface to prevent oil stains on the inner surface of a cooking device such as an oven.

Conventional Technology Preventing oil stains in ovens can be broadly divided into two methods: burn-off methods, which use heat to burn off the oil and decompose it, and catalytic methods, which use oxidation catalysts to decompose the oil. Also, instead of breaking down the oil, we use fluororesin to make it non-stick in the cooking room (
There is also a method of applying oil to the surface (hereinafter referred to as the inside of the refrigerator) to make it difficult for oil to adhere, but this method is based on the ratio.

The burn-off method heats the inner surface of the refrigerator to a high temperature of about 500'C and uses that thermal energy to decompose the oil, which takes 1 to 2 hours to completely decompose.

On the other hand, the rapid medium method uses Mn, Cu,
Go.

Oxides or composite oxides such as Nl, Cr, and Fe are used, and solid acids such as zeolite, acid clay, activated clay, and silica alumina are used as catalysts. It is said that these catalysts are dispersed in an inorganic binder to form a porous coating layer on the inner surface of the refrigerator, and that the oil is decomposed at a temperature of 300 to 350'C.

Problems to be Solved by the Invention However, there are some problems with the above method. First, in the burn-off method, the inner surface of the refrigerator is
A high-output heater is required to maintain the temperature above C, a new thermal structure is required to prevent heat release, and the interior material of the refrigerator is susceptible to thermal deterioration, making it difficult to use materials with excellent heat resistance. The problem is that the cost is high.

On the other hand, in the catalytic method, there is a problem that the oil is not completely decomposed at a temperature of 300 to 350°C, and undecomposed residues enter the porous membrane. temperature to 400
It does not decompose completely even if raised above °C. This means that
This suggests that the catalyst is not effective.

Means for Solving the Problems In order to solve the above problems, the present invention provides a perovskite oxide La1-XCl! lXCOO3 or Lal
-xSr XCOO3 (0<x<1) and heteropolyacid H3PMo 12040 mixed powder dispersed in a heat-resistant binder A coated surface is formed on the inner surface of the refrigerator, and this surface decomposes oil. be.

For production The following effects can be obtained by the above means.

First, perovskite oxides will be explained.

A perovskite-type oxide represented by the general formula Aday03 (A: rare earth element, alkaline earth metal, B: transition metal) has an activity comparable to that of platinum. Regarding the oxidation reaction of hydrocarbons such as oil, the hydrocarbons are adsorbed to Bn+ in the bulk, and the bulk oxygen reacts with the hydrocarbons to proceed with the oxidation reaction.

The consumed oxygen is replenished by oxygen adsorbed in the bulk. Wait, the A site of ABO3 is La + Ce s
B site is Go La□, g Ce□, I C
oO3 is highly active. This is the CoG+ involved in the reaction.
This is because it is the structure that most easily appears on the bulk surface.

Next, heteropolyacid (hereinafter referred to as HPA) will be explained.

The action of HPA as a proton flux is stronger than that of normal acids (eg HNO3). This is because HPA anions create reaction substrates and intermediates and stabilize them, thereby further promoting the reaction.

Examples of HPA include H3PMo12040, H3PW1
It consists of a heteroatom (P) such as 2040, a polyatom (Mo, W), oxygen, and hydrogen, and also has crystal water. H
The acid of PA is a Bronsted acid, and the acid strength varies depending on the constituent atoms. The acid strength is in the following order, but depending on the reaction, the optimal activity PW12 > 5iW12 > PM
o12~5102 eA#203 > SiMo12
>> H3PO4 >> HPA with 5lo2 changes. This is because the magnitude of acid strength greatly affects side reactions or product selectivity for the desired reaction, and it is necessary to find the optimal HPA for the reaction side.

Example Examples will be described below.

The compositions shown in Table 1 were prepared, and a coating layer was formed on the surface of an alumina plate as a test piece.

Table 1 The coating layer made of the above five types of compositions was maintained at 400°C, and a constant amount of salad oil was added dropwise to the coating layer to monitor changes over time.

After 30 minutes, Composition 4 completely decomposed the oil, but the other four types left carbonized residue. The residue remained even after 60 minutes had passed. From this, L a O0
It can be seen that the mixed system of 9Coo, I Coo 3, H3PMo12040, and silica sol is suitable for decomposing oil.

FIG. 1 shows a cross section of a coating layer made of composition 4.

In Fig. 1, 1 is La□, gCe□, I CoO3,
2 is H3PMo12040, and 3 is silica.

Figure 2 shows La□0gce□, 1. CoO3, H3PM
It is a differential thermal curve of salad oil according to o12040, H3PW, and 12040. In Figure 2, 5 is Lo 0.9
Curve by Coo, I Coo 3, 6 is H3PMo
12040, 7 is the curve for H3PW12040, and 8 is the curve for salad oil alone.

In the case of La□9gCe□, ICoO3, 420℃~4
There is a strong exothermic peak at 50'C. This is thought to be due to oxidation of carbide. l#'Mot204o
, 450-500° also in H3PW12040
Although an exothermic peak is seen at C, La□0gCe□, I C
Not as strong as oO3. This means that La □, g Co
□ indicates that I Coo 3 promotes the oxidation reaction of carbides, which can be seen from the very weak exothermic peak around 500°C when salad oil is used alone. However, La0,9 C
a 0. In the case of I Coo 3, it was found that although the oxidation reaction was promoted, a small amount of carbide residue remained which was not oxidized and decomposed. On the contrary, there was no residue in H3PMo12040.

Next, FIG. 3 is an IR absorption spectrum showing the adsorption state of salad oil on the catalyst. 1700-1750z-t
Only that part is shown. The temperature is room temperature. In Figure 3, 9 is the IR absorption spectrum of salad oil adsorption to La□, gCo□, ICo03, and 10 is the same <H3
PMo12040, 11 are the same <83PW1204)
belongs to. 12 is the absorption spectrum of salad oil. The absorption of 1745 cu-1 and 1705 cil in Figure 3 is due to carboxylic acid \C=O, and the components of salad oil are saturated with octopus such as syristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, and lilunic acid. Due to being an unsaturated carboxylic acid. It is thought that 1745CrIL-1 is due to a free carboxylic acid, and 17Q5Crn1 is due to an associated carboxylic acid. As you can see from Figure 3, only when H3P1iQo1204010 is 170
A peak is shown at 5crrL1.

La□, gCe□, ICoO39, H3PW1204
011, there is no peak at 1705 Cml, and the adsorption state is clearly different. Also, 1 of H3PMo 12040
H3PV21VI01 with part of Vlo replaced with V or W
0040 and H3PW6Mo604) is 1705cm-
It was found that the absorption strength of 1 became weaker and was influenced by 1ν1°.

Figure 4 shows the IR of gas generated when salad oil decomposes.
This is an absorption spectrum. 13 is La□, 90e□, l
Spectrum of salad oil decomposition gas caused by Co03i, 14
15 is the spectrum of the salad oil cracked gas due to H3PM120ao, 15 is the spectrum of the salad oil cracked gas due to H3PM12040, and 16 is the spectrum of the cracked gas from salad oil alone, and the temperature is about 370°C.

Unlike the peak in FIG. 3, the absorption of t705cr/L-1 is strong. However, in the case of salad oil alone, the absorption of 1745Cut is also strong. This is thought to indicate that there are many components that simply evaporate when salad oil is heated alone. La0,9
Ca0. If I CoO3 or HPA is used, 1745C
! The n-1 peak is lost and is not shown in Figure 4, but judging from the changes in other peaks, it can be considered that the decomposition reaction progresses due to heating. Comparing the spectrum of such decomposed gas (Fig. 4) and the spectrum of the adsorbed state of salad oil (Fig. 3), it can be seen from the coincidence of the absorption wave numbers of the spectra that H3PMo12040 is advantageous for decomposition.

Now, returning to Table 1, Composition 4 completely decomposes salad oil. This is as shown above (La□, gCe□, l
CoO3 carbide oxidation reaction promotion effect, H3PMo12
This may be due to the specificity of 040 and other HPAs.

Next, we will explain La1-1sr) (Co03. According to the thermogravimetric change with salad oil, it is 450 to 480 °C
An exothermic peak due to oxidation of carbides can be seen. Although this temperature was slightly higher than that of La□, gce□, and ICoO3, almost the same results as composition 4 of Table 1 were obtained with the coating layer of composition 6 shown in Table 2.

(Left below) As detailed in Table 2, the present invention provides the following effects on oil stains in ovens etc. due to the catalytic effect of the perovskite oxide and heteropolyacid. Can be done.

(1) The conventional burn-off method required a temperature of 500°C or more, but according to the present invention, this can be lowered to 400°C, allowing flexibility in design conditions. Moreover, if catalysts are improved, it will become possible to burn out at temperatures below 400°C, 350'C and 300°C.

(2) Since oil stains can be completely broken down, the inside of the oven can be kept clean.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of a cross section of a coating composition according to an embodiment of the present invention, and FIG. 2 is a differential heat curve diagram of salad oil using a catalyst.
FIG. 3 is an IR spectrum diagram showing the adsorption state of salad oil on the catalyst, and FIG. 4 is an IR spectrum diagram of gas generated when salad oil is decomposed using the catalyst. 1 °= La□0gca□, I CoO3, 2---
H3PMo120403...Silica, 4...Base material (
alumina), 5...La□, gce□, I Co
Curve due to O3, 6---- H3PIVlo1204
Curve according to 01, 7 ・Curve according to H3PW12040, 8 ・Curve without catalyst, 9-- La□0gca
□, I Adsorption to CoO3, 10...H3PIVlo
Adsorption to 12040, 11...H3P, W18O49
Adsorption to, 12... Salad oil alone, 13...La
□, gCe□, decomposed gas by I CoO3, 14...
...Cracked gas by H3PMo12040, 15 ・
・-H3P, decomposition gas by W18O49, 16-...
No catalyst. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2: Temperature

Claims (1)

[Claims] La_1_-_xCe_ as perovskite type oxide
xCoO_3 (O≦x<1) or La_1_-_x
A coating composition in which a mixed powder of Sr_xCoO_3 (0≦x<1) and H_3PMo_1_2O_4_0 as a heteropolyacid is dispersed in a heat-resistant binder.