JPS61147025A - High frequency heating device - Google Patents

Abstract

PURPOSE:To develop a processing method for oven shaped product without using fusion weld by forming painted films on the walls of high frequency heating oven in such a way that on the steel plate with Zn or Zn alloy plating, films of one or more layers are formed with special resin mixed with one of polyester or phenolepoxy resins. CONSTITUTION:Both sides of a steel plate 1 are plated by Zn or Zn alloy 2 and the painted films 3 have one or more layers. The materials of films are made in such a way that one of polyester resin or phenol epoxy is added with pigment, filler and supplementary material to the base materials which are composed of one or more resins selected from melamine, isocyanate, epoxy and silicon resins and is 30wt% of the aforementioned resin, and films can be colored. The thickness of 15-50mum is desirable and the films have poor anti-pollution property under 15mum thick and also poor painting operability over 50mum thick due to the generation of foaming.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a high frequency heating device equipped with an oven.

BACKGROUND OF THE INVENTION Conventionally, the material used for the oven of a high-frequency heating device has been stainless steel, enamel, or zinc steel plate, the surface of which is coated with melamine acrylic resin or epoxy resin.

However, these materials are stainless steel.

Enamel has the drawbacks of high cost and limited color tones. In addition, when using a galvanized steel plate and applying epoxy resin powder coating on it, the processing method is to first process the iron plate or galvanized steel plate into an oven shape, and then pre-paint treatment.

However, since the inner surface of the box-shaped box was painted, it was not possible to coat the film with a uniform thickness, and defects such as scratches and wrinkles were likely to occur, especially at the corners. Furthermore, some disadvantages include paint powder scattering, resulting in a rough finish, poor painting efficiency and uneconomical results, and the box-shaped finished product taking up space. Ta. In particular, when knocking down and assembling in a faraway place such as overseas, there is a drawback that the transportation costs are high.

In order to eliminate such drawbacks, it is possible to use pre-painted steel sheets. Already in conventional double-layered microwave ovens, pre-painted steel plates are bent into a U-shape as the exterior material.
On the other hand, it is used by covering it from above.

By using pre-painted steel plate, ■ High coating efficiency and resource saving.

■ By shortening the baking time, the process can be shortened and fuel consumption can be saved.

■ Painting can be automated, eliminating the need for skilled painting workers 0 ■ Disposal 1 Safety, hygiene, and pollution control can be easily implemented in terms of the work environment.

0　Logistics costs can be reduced because it is a flat painted plate.

The O coating film distribution is uniform and the coating film performance is easily stable.

There are many advantages such as. Despite this, plate steel sheets were not used for oven walls because the conventional oven processing method used welding (spot), and because the coating performance required for oven walls could not be achieved using conventional pre-coated steel sheets. That's because I wasn't satisfied.

Problems to be Solved by the Invention When using a pre-coated steel plate as an oven wall material for a high-frequency heating device, a processing method that does not involve welding to the oven shape becomes a problem. The oven can be configured by folding, crimping, screwing, etc. Naturally, pre-painted steel sheets must withstand these processes (post-processing). Melamine acrylic resin and epoxy resin, which have been conventionally used for coating inside ovens, cannot withstand such processing.

Further properties required of the coating film include high hardness and resistance to scratches on the coating film, little deterioration of the coating film due to electrical discharge, and good stain resistance to withstand food.

However, the above-mentioned hardness and stain resistance, workability and stain resistance are contradictory properties, and it is difficult to balance them. In other words, soft resins with low hardness have excellent processability, but
It has poor stain resistance, and hard materials with good stain resistance have poor workability. In particular, regarding stain resistance, sauce, ketchup,
If high-frequency heating is continued with lemon juice etc. spilled on the paint film, most of the paint film will blister in about 30 minutes, making it extremely difficult to create physical properties that can withstand this process. This is to the extent that even acid anhydride curing type epoxy resin powder coating with a film thickness of about 80 μm may cause blisters.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides an oven wall material for a high-frequency heating device having a center line average roughness of 1.2 μm.
on a zinc or zinc-based alloy plated steel sheet that is less than m.
0 to 30 parts by weight of one or more resins selected from the group of melamine resins, isocyanate resins, epoxy resins, and silicone resins are added to either the polyester resin or the phenol epoxy resin, as necessary. A pre-coated steel plate is used, which has one or more layers of coating film added with pigments, fillers, and auxiliaries.

Since a smooth substrate with low surface roughness is used, a dense and smooth coating film is easily formed on the substrate. The surface is glossy and very clean, and is in excellent appearance as an exterior material. Even when this pre-coated steel sheet is subjected to post-processing, the coating film has a lubricating effect on the mold surface, making press working easier.

Polyester resins and phenol epoxy resins are examples of hard resins with a good balance between workability and hardness. These resins are not used alone, but also include melamine resin, isocyanate resin, epoxy resin, silicone resin, etc., to achieve hardness and chemical resistance.

It is used with improved physical properties such as slip resistance and corrosion resistance.

The amount of these resins added is from 0 to
30 parts by weight is reasonable.

For pre-coated steel sheets used for general home appliances, galvanized steel sheets are usually used as the base sheet due to the required level of corrosion resistance. There are two types of galvanized steel sheets: electroplating and hot-dip galvanizing, but electroplating has a smoother surface. In order to achieve a beautiful appearance, the steel sheet is usually dulled and the surface is roughened during temper rolling, so the average centerline roughness of the smoothest electrogalvanized steel sheet is 1.2 to 1. The thickness is 3 μm, and is usually 1.2 μm or more.

The most difficult property for oven wall materials for high-frequency heating devices is resistance to contamination by foods and seasonings during high-frequency heating. Even with an epoxy powder coating having a film thickness of 70 to 80 μm and excellent chemical resistance, blistering may occur after heating for 30 minutes.

The occurrence of blisters is thought to be due to the following reasons.

(1) First stage: Diffusion of hydrogen ions (H+) in food (seasoning) into the coating film (++) Second stage: Electrochemical reaction on the plated surface Generation of hydrogen by (at the anode) Zn-*Zn +2e (at the cathode)
2 H++ 2 e --H2↑θ11) 3rd stage... 7 creases in the coating film due to expansion of hydrogen. In both cases where the above-mentioned polyester resin and phenol epoxy resin are used, the center line average roughness is 1.2 μm or more. In some cases, regardless of whether it is solvent-based, powder-based, or the type of additive, blistering occurs during a 30-minute high-frequency heating stain resistance test, and the paint film peels off. This problem of blistering does not change even if the zinc plating of the original plate is replaced with an alloy plating containing one or more of nickel, cobalt, and aluminum, or the surface is subjected to chromate treatment.

When the center line average roughness is set to 1.2 μm or less, the occurrence of blisters is solved. This is considered to be due to the following reasons.

■ Since the coating film is smooth and dense, it is difficult for hydrogen ions to diffuse through the coating film.

■ Because the plated surface is smooth, zinc is not activated.
Since the contact area with hydrogen is small, the rate of hydrogen generation is slow and the coating film does not swell. Due to the above actions, the most difficult characteristics required for oven wall materials can be met.

Since the surface is smooth, seamer processing can be performed smoothly without damaging the coating film.

Embodiment FIG. 1 shows a sectional view of a main part of an oven wall material of a high-frequency heating device of the present invention. In FIG. 1, a steel plate 1 is plated with zinc or a zinc-based alloy on both sides. 3
is the coating layer on the oven side. The coating layer 3 may consist of one layer, or two or more layers as shown by 3' and 3'. In the coating layer 3, one or more resins selected from the group of melamine resins, isocyanate resins, epoxy resins, and silicone resins are added to either polyester resin or phenol epoxy resin in an amount of 0 to 30% by weight based on the resin. It may be used in a clear form using the added resin system as a paste, or it may be optionally colored by adding pigments, fillers, and auxiliary agents.

Regarding the high-frequency heating device of the present invention, it may be used in a single layer structure by using a coating layer 4 similar to the coating layer 3 on the back surface so that the coating layer 4 serves as an exterior material, or It is also possible to use the conventional double structure without providing any special structure.

FIG. 2 shows a perspective view of the high-frequency heating device with the door 6 open. In FIG. 2, the oven wall 1 may have a double structure with the exterior body 5, or may have a single layer structure with the exterior body 5 on the back side of the oven wall 1. This device opens a door 6 that can be opened and closed, stores food to be cooked in the oven through the opening, and sets switches, timers, etc. provided on the operating section 7 with the door 6 closed. This allows food to be irradiated with microwaves and cooked.

The oven wall of the high frequency heating device of the present invention is made of a galvanized steel plate of the required dimensions and coated with a roll coater.

After forming a coating film using a flow coater, spraying, electrostatic coating, etc., baking is performed by using a pre-coated steel sheet manufactured by hardening, post-processing it into a predetermined shape, and baking it in an oven.

The coating thickness is preferably in the range of 15 to 50 μm. When the thickness is less than 15 μm, stain resistance decreases. If it exceeds 50 μm,
Wrinkles, etc. are likely to occur, reducing painting workability.

Although the original plate of the present invention can be applied to both hot-dip plating and electroplating, electroplating is preferable from the viewpoint of ease of post-processing and aesthetic finish.
- It is desirable to use the above.

This is because if the porosity of the plating layer is 10y/- or less, it increases and it becomes difficult to make the center line average roughness 1.2 μm or less.

Table 1 shows the results of an evaluation test of high-frequency heating contamination when the surface roughness of the original plate was changed. Center line surface roughness is 1.
There is a clear significant difference in the occurrence of blisters between the case of 2 μm or less and the case of larger than 1.2 μm. The paint used here is a highly processable PCM paint used for single-serve cans for home appliances, manufactured by Sakuramiya Chemical, 5K-110-
26.

P-1o, Dainippon Paint Co., Ltd. VNITSU) #6100, etc.

Precoated steel sheets coated with these paints exhibit good coating film properties as shown in Table 2. Table 2 is for polyester paints.

Effects of the Margin Invention As described above, the following effects can be obtained by applying the oven wall material of the invention.

■ Since the coating is applied on a flat plate, the coating efficiency is high and resources are saved.

■ The coating film distribution is uniform and the coating performance is stable.

■ Since the oven is made of a flat painted plate, logistics costs can be reduced.O In addition to the many advantages of being able to configure the oven at low cost, the interior color can be chosen as desired.

Further, the oven of the high frequency heating device can be manufactured in a small space, and the high frequency heating device of the present invention has the advantage that it can be manufactured at low cost and with better quality than conventional ones.

[Brief explanation of drawings]

FIG. 1 is an enlarged sectional view of a main part of the oven wall of the high-frequency heating device of the present invention, and FIG. 2 is a perspective view of the high-frequency heating device of the present invention with the door opened. 1... Steel plate, 2... Plating, 3...
...paint layer.

Claims (2)

[Claims] (1) As an oven wall material for high-frequency heating equipment, melamine resin or isocyanate resin is applied to either polyester resin or phenol epoxy resin on a zinc or zinc-based alloy plated steel plate with an average centerline roughness of 1.2 μm or less. , epoxy resin, and silicone resin in an amount of 0 to 30% relative to the resin.
A high-frequency heating device using a pre-coated steel plate on which one or more coating layers are formed by adding parts by weight and, if necessary, pigments, fillers, and auxiliary agents. (2) The high-frequency heating device according to claim 1, which uses a pre-coated steel plate whose coating layer has a thickness of 15 to 50 μm.