KR940003194B1 - Coating composition - Google Patents

Abstract

4-30 wt.% of the binder complex comprising organic binding agent of silicone resin type and inorganic binding agent formed by hydrolysis of colloidal alumina and org. functional silane cpd.; 5-15 wt.% of alumina cpd. contg. water of crystallization; 30-50 wt.% of oxydating catalyst; 0.5-1 wt.% of dispersing agent; 0.5-2 wt.% of precipitation preventing agent; 2-15 wt.% of lower melting temp. glass frit for 400 deg.C; 2-15 wt.% of higher melting temp. glass frit for 600 deg.C; and 5-20 wt.% of org. solvent. The obtd. compsn. is useful for coating of inner faces of the electronic oven.

Description

High temperature self-cleaning film composition

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating composition to be coated inside household appliances, in particular microwave ovens, and the like, and particularly to a high temperature self-cleaning coating composition having a heat resistance of 600 ° C or higher.

Various cookers using gas, electricity, microwave, etc. are special paints that decompose these products into water vapor and carbon dioxide because oils, carbohydrates, proteins, etc. which are scattered when cooking food are attached to the inner wall and cause rot or odor. Phosphorus self-cleaning paint is applied to the inner wall, and sometimes the temperature is applied to the inside of the microwave oven at a high temperature of about 600 ° C. to remove contaminants attached to the wall for cleaning the inside of the microwave oven. Such high-temperature self-cleaning paint or coating composition includes an oxidation catalyst for oxidatively decomposing the above-mentioned products in the coating composition because it functions to absorb the oil-like products on the surface of the coating and decomposes them into water vapor and carbon dioxide gas. Not only must the surface area of the coating film be large so as to absorb the above-mentioned by-products, but also it must not be carbonized while maintaining adhesion with the workpiece even at a high temperature of 600 ° C or higher.

Conventionally, such self-cleaning paints have been used as coatings such as law-based, Teflon-based and inorganic-based paints, or paints in which an oxidation catalyst, a curing accelerator, and a polymerization inhibitor have been added to a heat-resistant synthetic resin. In this case, the coating was uniform or carbonized.

Japanese Patent Publication No. 56-14545 uses glass frit used as a self-cleaning paint for high temperature that can be used at 600 ° C, phosphoric acid-based compound as a binder, and MnC ₂ , zeolite, etc. as an oxidation promoter. High temperature self-cleaning compositions are described. Since the resin composition used as the binder is a phosphoric acid-based compound, the heat-resistance of the coating composition is high. However, since the coating film is cured, the coating film has a high surface density.

In addition, Japanese Patent Publication No. 55-80763 uses inorganic water-based silicate as a binder for high-temperature self-cleaning paint that can be used at 600 ° C, MnC ₂ as a catalyst, and an alumina compound as a polymerization inhibitor. Purified coating compositions are described. These coating compositions have the advantage of very high heat resistance and low temperature cure due to the use of inorganic binders, but the pot life of the paint is limited because the phosphate hardener must be used because the water-soluble silicates themselves lack water resistance. There is a problem that the oil decomposition rate is low because it is impossible.

An object of the present invention is to provide a high-temperature self-cleaning coating composition that can maintain the adhesion of the coating film even at a high temperature of 600 ℃ or more, does not discolor, can be a thick film and excellent oil decomposition rate.

The above object of the present invention is to improve heat resistance by using organic binder of silicone resin and organic / inorganic composite binder composed of hydrolysis reaction of colloidal alumina and organic functional silane compound to improve heat resistance of low melting point glass frit and high melting point glass frit. A mixture composition is used to promote high temperature adhesion and is achieved by a coating composition which allows for workability and thick film using silicone resin.

The present invention is an organic-inorganic composite binder 4-30% by weight of an inorganic binder produced by the hydrolysis of a silicon-based organic binder and colloidal alumina and an organic functional silane compound, and 5-15 weight of an alumina compound containing crystal water. %, Oxidation catalyst 30-50 wt% Dispersant 0.5-1 wt%, Sedimentation inhibitor 0.5-2 wt%, Low melting glass frit (for 400 ° C) 2-15 wt%, High melting glass frit (for 600 ° C) 2- It consists of the high temperature self-cleaning film composition which consists of 15 weight% and 5-20 weight% of organic solvents.

According to one embodiment of the present invention, as the silicone resin used as the organic binder, phenyl siloxane and methyl siloxane are used. In particular, it is preferable to use methylphenyl siloxane having a ratio of methyl group and phenyl group of 1: 0.5 to 1: 1. However, other silicone resins having heat resistance and not having high water repellency can also be used. These organic binders not only enable workability and thick film, but also phenyl or methyl groups at the time of baking (450-500 ° C.) can be carbonized to increase the surface area of the coating to increase the oil decomposition rate. As the inorganic binder used together with the siloxane-based organic binder described above, a hydrolyzable reaction product obtained by hydrolyzing colloidal alumina with an organic functional silane compound is used. In preparing such hydrolyzate, colloidal alumina and organic The ratio of the functional silane compound is hydrolyzed in the range of 1: 2 to 2: 1. If the colloidal organic functional silane compound content is more than twice the alumina content in the preparation of the hydrolysis reaction product, there is a problem in that the heat resistance of the film is lowered. The above-mentioned inorganic binder improves heat resistance and fire resistance. When the amount of the inorganic binder used is 2% by weight or less of the whole composition, the heat resistance of the coating film is lowered. When the amount of the inorganic binder is 15% by weight or more, the coating film formation is impossible and the coating film may be cracked. It is preferred to use within the range of 2-15% by weight of the total composition. In addition, the blending ratio of the organic binder and the inorganic binder is in the range of 1: 5 to 5: 1, and when it is out of the above range, there is a problem in that heat resistance and wear resistance are lowered.

The organic-inorganic composite binder of the aforementioned organic binder and inorganic binder should not exceed 30% or more of the total composition weight, and particularly preferred is to be used in the range of 4-30% by weight. If the organic-inorganic composite binder is 4% or less of the total weight of the composition, the thick film may not be possible.

Oxidation catalysts used to promote oil decomposition in the present invention include r-MnO ₂ , r-Mn ₂ O ₃ , rhodonite (MnO ₂ ㆍ SiO ₂ ), tefroid (MnSiO ₄ ) alleghite (5MnO ₂ the manganese oxides such as 2SiO ₂₎ is used. These oxidation catalysts are also used in conventional self-cleaning coating compositions, but when used in large amounts, they improve oil decomposition rate, but because their specific gravity is heavy, they precipitate during storage to form cake-like precipitates with other additives and auxiliaries. It should be used at less than%.

According to the present invention, the amount of the oxidation catalyst is used up to 30-50% to promote the oxidation rate of the oil, but an antisettling agent and a dispersant are added to prevent the precipitation of the oxidation catalyst. As the anti-settling agent, homed silica having a fine SiO ₂ as a matrix and a methyl group bonded to the silica surface is used, and a representative example is Aerosil R-972 (trade name of Degu Co., Ltd.). Such anti-settling agent is added within the range of 0.5-2% of the total weight of the composition, the above-mentioned anti-settling agent is used when 2% or more of the oil degradation rate is lowered, if less than 0.5%, the anti-settling effect is lowered, the above-mentioned formulation range Must be used within. Moreover, although a zirco aluminate, r-amino propyl triethoxysilane, methyl triethoxysilane, r-methacryloxypropyl trimethoxysilane, etc. are used as a dispersing agent, it is preferable to use the dispersing agent of a silane compound system among these. . The amount of dispersant used is within the range of 0.5-1% of the total composition. When using more than 1%, the coating film is discolored. When the dispersant is less than 0.5%, the dispersibility between the organic resin and the inorganic material is poor, resulting in poor painting workability.

According to the present invention, a low melting point glass frit for 400 ° C. and a high melting point glass frit for 600 ° C. are used to improve high temperature adhesion. Low-melting glass frit has 20-30% by weight of Al ₂ O ₃ , 40-50% by weight of P ₂ O ₅ , and 20-30% by weight of RO.R'O (wherein R is an alkali metal and R 'is an alkaline earth Metal) and have a softening point of 370-400 ° C. and a thermal expansion coefficient of 300-310 × 10 ⁻⁶ . These low melting glass frits are melted at temperatures above the melting point to improve adhesion between the paint composition and the base. Let's do it. The high melting point glass frit used in the above-mentioned low melting point glass frit has a matrix of 65-75% by weight of SiO ₂ and 20-30% by weight of RO.R ' ₂ O. 3-5% by weight of MnO ₂ (wherein R and R' Has a softening point of 550-600 ° C. and a thermal expansion coefficient of 310-330 × 10 ⁻⁷ and improves the high temperature adhesion force of 600 ° C. or higher and prevents discoloration. Therefore, when the high melting point glass frit is mixed with the low melting point glass frit, the adhesive force at 400 ° C., which is a normal use temperature of the microwave oven, is excellent as well as the high temperature adhesion force of 600 ° C. or higher can be obtained to obtain the most efficient adhesion.

In particular, when mixing two kinds of glass frit, the mixing ratio and the particle size play an important role. It is preferable to mix the glass frit for 400 ° C and 600 ° C so that the ratio of 1: 1 to 1: 2, and the particle size is 20-. It is suitable in the range of 50 µm. If the frit for 400 ℃ is higher than the frit content for 600 ℃, there is a possibility that the film peeling phenomenon may occur due to thermal expansion between the base and the coating film at a high temperature of 600 ℃ or higher and if the frit content for 600 ℃ exceeds 1: 2, Adhesion at the service temperature of 400 ° C. may be a problem. In addition, when the particle size of the glass frit is 20 μm or less, the coating film surface density and adhesion are adversely affected. When the glass frit is 50 μm or more, the appearance of the coating may be a problem. Such glass frit content is suitably 5-30% by weight of the total coating film composition. When the glass frit content is 30% or more of the total paint composition, the oil decomposition rate is lowered. When the glass frit content is 5% or less, it does not affect adhesion at high temperature (600 ° C.). An example of the method of manufacturing the above-mentioned coating composition is as follows.

In the method of the present invention, 1 part of the dispersant is uniformly mixed with 10 parts of an inorganic binder, homogeneously mixed by adding 5 parts of a silicone resin, and then 50 parts of an oxidation catalyst, 20 parts of glass frit for 400 ° C and 600 ° C, 5 parts of extender pigment, A high temperature self-cleaning coating composition is prepared after milling at 30-60 RPM for about 2-10 hours after adding 1 part of antisettling agent and 8 parts of organic solvent.

In general, the bonding force between the elements in the maintenance molecule can be broken by the energy of the wavelength in the far-infrared region, and when these bonds are broken, they are decomposed into CO ₂ and H ₂ O.

The oil decomposition mechanism is described in stages as follows.

(1) is the ionization reaction of fatty acids,

Equation (2) is a reaction in which the metal cation of the surface modifier and R-COO ^- ionized in Eq. (1) form a metal salt called R-COOMe. The reaction is a reversible reaction.

(3) is the R-COOMe created in (2). Is a reaction to decompose ketone and Me ₂ CO ₃

(4) is a reaction in which Me ₂ CO ₃ generated in formula (3) is decomposed into metal oxides (Me ₂ O) and CO ₂ ,

Equation (5) is a reaction in which Me ₂ O reacts with a surface modifier or water in the air and changes to metal hydroxide and H ₂ ,

Formula (6) is a reaction in which the ketone compound produced in Formula (3) reacts with hydrogen generated in Formula (5) to form an alcohol,

Equation (7) is a reaction in which the alcohol produced in formula (6) is decomposed into CO ₂ and H ₂ O by MnO ₂ and oxygen, which are oxidation catalysts.

This chemical reaction occurs instantaneously (1)-(7) when the contaminant touches the coating.

Oils and the like are adsorbed on the surface of the porous coating film formed by carbonization of methyl and phenyl groups of the lycon resin and evaporation of the crystallized water in the coating composition. Decomposes easily even at low temperatures. In particular, the activated alumina, which is produced when the crystal water of Al (OH ₃ ) ₃ and [Al ₂ ㆍ (OH) ₅ ㆍ Cl] _X , is extracted during the baking process, is included in the fat and oil component. This prevents the polymerization, which further improves the oil decomposition rate. When the alumina compound is used in an amount of 0.5% by weight or less with respect to the total coating composition, the effect of preventing the polymerization of the oil and fat component is lowered, and when 15% by weight or more is used, the heat resistance of the overall coating properties is reduced.

Hereinafter, examples and comparative examples are described so that the present invention can be understood in more detail.

Comparative Example 1 is described in Japanese Patent Publication No. 59-14545, and Comparative Example 2 is described in Korean Patent Application No. 89-8919.

Example 1-5

According to the mixing ratio of Table 1, the dispersant is uniformly mixed with the inorganic binder, homogeneously mixed with the addition of silicone resin, and then the oxidation catalyst, low temperature and high temperature glass frit, sieving pigment, sedimentation inhibitor and organic solvent are added. Milling at -60 RPM for 5 hours to form a coating composition.

200 μm by hairline treatment of the resulting coating composition on stainless steel

TABLE 1

TABLE 2

Physical property test of coating film

Note: 1) All specimens were subjected to hairline treatment on stainless steel and baked for 20 minutes at 450 ℃ based on 200㎛ thickness.

2) ΔE is the color difference between the sample and the color before the test and the sample for 2 hours in 5% NaOH solution.

3) In the stain resistance test, 4-5 mg of cooking oil was added dropwise to the surface of the coating film, distributed, and then placed in a drying oven for 30 minutes at 250 ° C.

4) Adhesion is measured by 2mm cross cut.

5) Flexibility is the degree of cracking when folded at 15 ° φ.

6) The oil decomposition rate is measured at 300 ℃ / 30 minutes by treating cooking oil such as pollution resistance and using differential thermal analysis (TG-DAT).

7) Heat resistance is the state after air cooling after heating for 1 hour in 600 ℃ oven.

Claims (4)

4-30% by weight of organic-inorganic binder made of inorganic binder produced by hydrolysis of organic binder, colloidal alumina and organic functional silane compound of silicone resin system, 5-15% by weight of alumina compound containing crystal water, oxidation Catalyst 30-50 wt%, Dispersant 0.5-1 wt%, Sedimentation inhibitor 0.5-2 wt%, Low melting point glass frit 2-15 wt% for 400 ° C High melting point glass frit 2-15 wt% for 600 ° C, Organic solvent 5 High temperature self-cleaning coating composition composed of -20% by weight. The self-cleaning coating composition according to claim 1, wherein the inorganic binder is an inorganic binder hydrolyzed in a ratio of colloidal alumina and an organofunctional silane compound in the range of 1: 2 to 2: 1. The coating composition according to claim 1, wherein the ratio of the organic binder to the inorganic binder is included in a weight ratio of 1: 5 to 5: 1. In claim 1, the low melting glass frits are Al ₂ O ₃ , P ₂ O ₅ , RO.R '| ₂ O (wherein R is an alkali metal and R 'is an alkaline earth metal Im) that will have the composition and the coefficient of thermal expansion of the 370-400 ℃ softening point and 300 -310 × 10 ^-6 high melting point glass frit is SiO ₂ and MnO | ₂ , RO.R ' ₂ O (R, R' has the meaning described above) and has a softening point of 550-600 ℃ and a softening point of 310-330 × 10 ^-7 , the mixing ratio thereof is 1: A composition, characterized in that it is used in a ratio of 1 to 1: 2.