JPH0526457A - Coating composition and oven microwave oven using the same - Google Patents

Abstract

(57) [Abstract] [Purpose] The present invention relates to a punching metal 7 for preventing electric wave leakage from the door 4 of an oven microwave oven 1, which is not clogged even with a punching structure having a hole diameter of 0.7 mm. An object of the present invention is to provide an oven microwave oven in which the inside of the heating chamber 2 is easy to see by providing a coating film forming method that does not have the above. [Structure] To a resin composition composed of 27 parts of a silicone resin and 4 parts of a fluororesin, 19 parts of a color pigment having a particle size of 20 μm or less and an extender pigment and 2 parts of an antisettling agent were added to obtain a resin solid. To this, 48 parts of solvent was added to obtain a coating composition. This coating composition was applied to the punching metal 7 having a hole diameter of 0.7 mm and baked. The obtained coating film had good heat resistance, corrosion resistance, and impact resistance, and did not cause clogging, so that it was possible to provide a practical oven microwave oven 1 in which the inside of the heating chamber 2 was easy to see.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating composition used for coating a substrate having pores, particularly punching metal, and an oven microwave oven using the punching metal coated with this coating composition.

[0002]

2. Description of the Related Art FIG. 1 is an external perspective view of an oven microwave oven 1. 2 is a heating chamber, 3 is an opening of the heating chamber, 4 is an openable / closable door, 5 is an operation panel, and 6 is a cooking chamber 2 in which the material to be cooked is visible to the outside while cooking. It is a window provided for the purpose. The window 6 is usually provided with two heat-resistant glasses on the heating chamber 2 side and the outside of the door 4, and the punching metal 7 is provided between the two heat-resistant glasses. This punching metal 7
In order to prevent high frequency radio waves from leaking out of the window 6 during high frequency heating, as shown in FIG. 2 (a), a large number of holes of about 1.4 mmφ are opened in a plate thickness of 0.8 mm. Punching metal corrodes during use, and when it is damaged and a large hole is opened, radio waves leak and seriously affect the human body. In order to prevent this, the punching metal base material is subjected to a enamel treatment on its surface to improve the corrosion resistance.

[0003]

However, in the above configuration, it is difficult to see the state of the object being heated from the outside. There is a method of increasing the output of a lamp that irradiates the heating chamber in order to make the inside visible from the outside, and by adopting this method, it became easier to see. However, the holes for punching and the non-transparent portions of the holes cast shadows and the object to be heated could not be clearly seen. If the hole diameter is increased, the width of the light non-transmissive portion between the holes is increased due to a manufacturing technology problem, and the above phenomenon is promoted. Therefore, a method is conceivable in which the hole diameter is reduced and the width of the light non-transmissive portion between the holes is reduced. When the aperture ratio (area of the light transmitting portion per unit area) is made as large as possible and the hole diameter is made as small as possible, the presently manufacturable value of the punching metal 7 is 0.7 mm as shown in FIG. 2 (b). The plate thickness at that time is 0.2 mm. When the punching metal 7 having a large number of holes having a hole diameter of 0.7 mm is used, the object to be heated inside the heating chamber 2 can be seen considerably better than the outside. In order to use the punching metal 7 having a hole diameter of 0.7 mm, it is necessary to treat the surface of the punching metal base material with anti-corrosion treatment as described above. If the above-mentioned enamel treatment is performed as this anti-corrosion treatment, clogging occurs and the inside becomes difficult to see. Therefore, there is a problem that the punching metal 7 having a hole diameter of 0.7 mm cannot be used in the oven microwave oven.

The present invention is to solve the above-mentioned problems.
The purpose of (1) is to provide a coating composition which has heat resistance, corrosion resistance and impact resistance and does not cause clogging even when coated, and the second object is to provide a coating composition having the pore size of 0. 7 mm
It is to provide an oven microwave oven with a good view of the inside by using the punching metal of the above as a radio wave shield.

[0005]

In order to solve the above problems, the coating composition of the present invention has the following composition ratios. That is, the weight ratio of silicone resin 4 to fluororesin 1 to 4
8 to 40 parts by weight of the resin composition having a particle size of 20 μ
A solvent was added to a resin solid obtained by mixing 60 to 30 parts of the following pigments and additives to obtain a coating composition.

Further, the above coating composition was applied to a punching metal having any one of a hot dip galvanized steel sheet, a hot dip aluminum plated steel sheet and a galvanium steel sheet as a base material and used for preventing electric wave leakage of a window of an oven microwave oven.

[0007]

Since the present invention uses the coating composition having the above-mentioned composition,
Since the compatibility with the base material is good and the flow is good, it is possible to obtain a coating film which does not cause clogging and has no cracks or pinholes. Therefore, a punching metal having corrosion resistance and high reliability can be obtained.

When the punching metal is used for shielding the electric wave from the window of an oven microwave oven, a large number of small holes with a diameter of 0.7 mm are exposed, and the width of the non-transmissive portion between the holes is small. Because it is narrow, you can see inside without being bothered by this part.

[0009]

EXAMPLES Examples of the present invention will be described below.

The properties required for the coating film of the punching metal 7 used for the window 6 of the microwave oven 1 are excellent heat resistance, corrosion resistance and impact resistance. That is, since the temperature inside the heating chamber 2 reaches nearly 300 ° C. during oven cooking, it is necessary to withstand this temperature. Since the punching metal 7 is provided between the two heat-resistant glass plates provided on the heating chamber 2 side and the outside of the door 4, the punching metal 7 does not come into direct contact with seasonings and cooked food fragments scattered during cooking. . However, it may be corroded by the substance or water vapor entering through the gap. Further, the door 4 is repeatedly opened and closed to receive a shock.

The present invention takes these required performances into consideration,
A resin composition was obtained by using a fluororesin, which has excellent adhesion and flowability and is excellent in corrosion resistance of a silicone resin, as a basic resin. The mixing ratio of these resins is 4 to 8 of silicone resin to 1 of fluororesin by weight. This is because when the silicone resin is smaller than 4 with respect to the fluororesin 1, the adhesiveness of the coating film, particularly the adhesiveness of the pores, decreases. Also, if it is greater than 8, the corrosion resistance will decrease.

To the above resin composition, a pigment, a metal oxide composed of cobalt, chromium, nickel, iron, manganese, copper or the like, and a silicic acid compound were added, and a fluorine-based settling agent was added as an additive to obtain a resin solid. Since the thickness of punching metal is thin and the pore diameter is small, the particle size of these pigments and additives is set to 20 μm or less. If it exceeds 20 μm, the amount of the paint adhered to the periphery of the hole becomes large, the impact resistance is lowered, and clogging easily occurs. Further, when the coating composition obtained by adding a solvent when the particle size becomes small is to be stored and used,
The resin solids are firmly settled at the bottom, and it becomes very difficult to stir the resin solids to form a uniform coating liquid. This tendency is intensified as the number of particles having a particle size of 0.1 μ or less increases.

The ratio of the resin composition to the pigment or the additive is appropriately 60 to 30 parts of the pigment or the additive to 40 to 70 parts of the resin composition. When the amount of the resin composition is less than 40 parts, the coating film becomes brittle, and when the amount of the resin composition exceeds 70 parts, cracks are likely to occur due to temperature change around the holes.

A solvent is added to a resin solid obtained by adding the pigment and the additive to the resin composition to obtain a coating composition. The ratio of resin solids to solvent varies depending on the coating conditions, but in order to obtain a uniform coating film, 1 resin solid to 0.8 to 1.2 solvent
It is good to use it in the ratio of.

The coating composition was applied as a base material to a punching metal consisting of one of SPC steel plate, hot-dip galvanized steel plate, hot-dip aluminum plated steel plate or galvanium steel plate by a spray method and was baked and hardened without clogging. A uniform coating film could be obtained. However, when a thermal cycle test was performed at 300 ° C. and room temperature, the coating film provided on the punching metal using the SPC steel sheet as the base material peeled off after about 300 times. No abnormality was found in the coating films provided on the other steel plates even after 1000 thermal cycling tests.

Specific examples will be described below. 27 parts of a silicone resin as a resin composition, 4 parts of a fluororesin, 8 parts of a composite metal oxide obtained by mixing oxides of cobalt, chromium and copper as a coloring pigment, and a silicate compound 11 as an extender pigment.
Parts and 2 parts of a fluorine-based anti-settling agent as an additive were added to obtain a resin solid. The particle size of the pigments and additives added at this time was 20 μm or less. To 52 parts of this resin solid matter, 48 parts of a mixed solvent of an aromatic solvent and an alcohol solvent was added to obtain a coating composition. As the base material, a hot-dip aluminum-plated steel plate having a thickness of 0.2 mm was used to provide a large number of holes having a hole diameter of 0.7 mm in the base material as shown in FIG. This punching metal was degreased and post-treated, and the coating composition was applied by spraying. After drying at low temperature, 300 ℃
And cured by heating for 10 minutes to obtain a coating film having a thickness of 20 to 25 μm. The coated surface of the punching metal was transparent with no clogging at all, and a coating film of almost uniform thickness without sagging or swelling was obtained. The performance of this coating is 300 ° C 10
No abnormality was observed even after heating for 00 hours. In addition, 48 hours continuous salt spray test, seasoning drop test (60
No abnormality was found even after continuous 48 hours. In the absence of coating, heating at 300 ° C. caused discoloration in several tens of hours, and marked salt discoloration in the salt spray test and seasoning dripping test, with some pitting corrosion. It can be seen that the coating film obtained from the coating composition of the present invention has remarkably high reliability as described above.

When the punching metal having a coating film is used in an oven microwave oven, the inside of the heating chamber can be clearly seen because the gap between the holes is very narrow.

As described above, when the coating composition of the present invention is used, a practical coating film can be obtained without clogging pores having a pore diameter of 0.7 mm. The same effect can be obtained by using this coating composition for a conventional punching metal having pores having a diameter of 1.4 mm or more. Further, in the embodiment of the present invention, the case where the punching metal is coated alone has been described, but the punching metal may be incorporated into the door and then the entire door may be coated.

[0019]

As described above, according to the present invention, the following effects can be obtained. (1) When the coating composition of the present invention is used for a substrate having pores, a coating film having excellent heat resistance, corrosion resistance and impact resistance can be obtained without clogging. (2) When a punching metal having a large number of pores is coated with the coating composition of the present invention, a highly reliable coating film free from clogging can be obtained. Therefore, when this punching metal is used in an oven microwave oven, the inside can be clearly seen due to the large number of small holes.

[Brief description of drawings]

FIG. 1 is an external perspective view of an oven microwave oven.

FIG. 2A is a configuration diagram of a punching portion of punching metal having a hole diameter of 1.4 mm, and FIG. 2B is a configuration diagram of a punching portion of punching metal having a hole diameter of 0.7 mm.

[Explanation of symbols]

1 oven microwave 2 heating chambers 4 doors 6 windows 7 punching metal

Claims (2)

[Claims] 1. A resin solid obtained by mixing 40 to 70 parts of a resin composition having a weight ratio of 1 to a fluororesin of 4 to 8 of a silicone resin with 60 to 30 parts of a pigment having a particle size of 20 μm or less and an additive. A coating composition in which a solvent is added to the product. 2. A hot-dip galvanized steel sheet, a hot-dip aluminum-plated steel sheet or a galvanium steel sheet provided to prevent radio wave leakage from a window of a door attached to the front surface of a heating chamber for heating an object to be heated. An oven microwave oven in which the coating composition according to claim 1 is applied to and baked on a punching metal.