JPH0335546Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Industrial Application Field] The present invention is a coated aluminum alloy structure, particularly a coated aluminum alloy sheet material suitable for deep drawing forming of an inner pot for a rice cooker, and this sheet material.
This invention relates to an inner pot for a rice cooker having a coating film on the inner surface, which is deep-drawn with a drawing ratio of 1 and 2.5:1. [Problems to be solved by the invention] There is a particular need for a non-adhesive coating film for the inner pot of a rice cooker. Such inner pots are usually deep drawn from an aluminum alloy and anodized to give the outer surface a durable and attractive finish. Such inner pots are used in electric rice cookers that can maintain heat for several hours or even continuously during the day when used in the kitchen. In the presence of steam generated during cooking, the seaweed from the cooked rice and other ingredients used tend to become sticky and stick to the inner pot. Currently available coatings on rice cooker inner pots are prone to cracking during deep drawing, develop oil and water stains during manufacture and use, and cause blistering during use. [Prior Art] Such a coating is applied in one coat to an electrolytically etched aluminum alloy plate, ie, a disk, before deep drawing of the inner pot, and a transparent polytetrafluoroethylene is coated on the surface. The disc with the shape is rolled or pressed. Better coating systems are desirable. US Patent No.
Satisfactory coating techniques are known, including the undercoat films of U.S. Pat. Nos. 4,011,361 and 4,049,863, and the systems of U.S. Pat. The optimal integrated coating system is not known. Each of the above patents is incorporated herein by reference. [Means for Solving the Problems] The present invention is a rice cooker manufactured from a painted aluminum alloy structure, particularly a painted aluminum alloy sheet material (blank) and outer sheet material suitable for deep drawing of an inner pot for a rice cooker. The coating film is an undercoat that facilitates the removal of food residue from the surface-finished inner pot for rice cookers.
It is a multi-layered non-adhesive coating consisting of an intermediate coat and a top coat. The basecoat consists of polytetrafluoroethylene and polyamide-imide in a weight ratio of 4:1 to 10:1 with the addition of 1.5 to 10% by weight colloidal silica, based on the solids content of the basecoat; The coating consists of polytetrafluoroethylene, a pigment, and a coalescing agent that can be decomposed by heat at the temperatures used to cure the coating system;
The topcoat consists of polytetrafluoroethylene, a coalescing agent that can be decomposed by heat at the temperatures used to cure the coating system, a catalyst to promote this decomposition, and mica flakes or pigment-coated mica flakes. In a preferred embodiment, the weight ratio of polytetrafluoroethylene to polyamide-imide in the basecoat is about 7:1 and the colloidal silica is about 3.1% by weight. Preferably, the total dry film thickness of the coating is from about 12.5 to
87.5 μm, and the dry film thickness of the undercoat is approximately 2.5 to 15 μm.
The ratio of the dry film thickness of the intermediate coat to that of the top coat is about 1:3 to 3:1. More preferably, the thickness of the undercoat is about 7.5-10μm
The ratio of the thickness of the intermediate coat to the top coat is approximately 1:1. The structure of the present invention, especially the plate, has a ratio of 1.4:1 and
The inner pot is deep drawn with a drawing ratio of between 2.5:1 to provide a coating on the inner surface and is therefore also within the scope of the present invention. A three-coat coating system is required to achieve the desired improvement in coating performance. In this case, the basecoat is selected for the purpose of good adhesion to the substrate and intermediate coat, the intermediate coat is selected to provide satisfactory concealment of stains and barrier properties, and the topcoat is selected for optimal pick resistance and appearance. Select as follows. The entire system must be fairly formable to allow deep drawing of the coated board, and the coating system resists the effects of anodization on the outer surface of the inner pot after deep drawing. It must be durable and resistant to blistering, pinhole formation and other coating defects. It has been found that the basecoat should contain a relatively large proportion of polytetrafluoroethylene to polyamide-imide and a small amount of colloidal silica.
Preferably, the thickness of the coating is kept small enough so as not to interfere with deep drawing, but large enough to provide the desired properties of the coating. As used herein, the terms polytetrafluoroethylene and polyamide-imide include modifications of each polymer that are understood in the art to be the common equivalents of such polymers. The accompanying drawings require little explanation. In FIGS. 1 and 2, 1 is an aluminum alloy substrate. The selection of alloy for such applications is based on factors known in the art, and preferably 3003Al alloy according to the Aluminum Institute (USA) or Japanese Industrial Standards (JIS) is used. In Figure 2, 2 indicates the coating system, 3 indicates the undercoat, and 4
5 represents an intermediate coat, and 5 represents a top coat. In Figure 3, the deep drawn aluminum inner pot is 1
A, the coating system is shown in 2A and the position of the anodized layer is shown in 6. In practice, the outer edge of a deep-drawn inner pot is usually rolled downward. This deforms the coating film even more severely than the original drawing process. In the Examples and elsewhere, parts, percentages and ratios are by weight unless otherwise indicated. The three-coat system described herein applies a base coat, then an intermediate coat, and then a top coat to grit blasted aluminum. It is not necessary to dry or cure each coat before applying the next, however some drying between each coat is acceptable and sometimes preferred. Sufficient basecoat is preferably applied to provide a coating thickness of about 5 to 15 micrometers. The total membrane forming all three layers is preferably about 12.5-87.5 μm, more preferably 30-40 μm
It is. The thickness ratio of intermediate coat to top coat is preferably from 25:75 to 75:25, more preferably about 50:50. After applying all three layers of coating, the coated substrate is preferably heated to 340-470°C, more preferably 385-470°C.
1, most preferably at a temperature of about 425°C.
Calcinate to cause coalescence (promoted by a catalyst such as triethanolamine oleate or cerium octoate) to cure the coating for up to an hour, preferably about 10 minutes, but long enough depending on the temperature. The coating is cured by decomposition and volatilization of a degradable polymer, preferably an acrylic resin. 〔Example〕

[Effect of idea]

Boiling for 1 hour, 1 hour 73 for the coated product of the present invention and prior art products with various mixed components
According to repeated tests at ~77°C, the prior art product stains after 3 cycles and blister after 15 cycles.
However, the product of the present invention did not cause any stains or blisters even after 20 repetitions. As specific examples of the painted aluminum alloy structure of the present invention, we have so far mainly explained plates for deep drawing of rice cooker inner pots and rice cooker inner pots, but the present invention is limited to these. However, any material having the above-mentioned multilayer coating on an aluminum alloy is included within the scope of the present invention, regardless of its shape.
Specific examples include hot plates for cooking, utensils and equipment for manufacturing and processing bread and other foods that require non-stick properties, molds for molding and processing plastics and rubber, and such molds. Examples include plates for manufacturing.

[Brief explanation of the drawing]

Figure 1 is a plan view of the plate material for the inner pot of the present invention, Figure 2
The figure is a side view of FIG. 1, and FIG. 3 is a schematic sectional view of the inner pot formed by deep drawing the plate material of the present invention. 1... Aluminum alloy substrate, 2... Coating film system,
3...Undercoat, 4...Intermediate coat, 5...Top coat,
1A... Deep drawn aluminum alloy inner pot, 2A... Paint film system, 6... Anodized layer.

Claims (1)

[Claims for Utility Model Registration] 1. A multilayer non-adhesive coating film consisting of an undercoat, an intermediate coat, and a topcoat, where the undercoat is composed of polytetrafluoroethylene and polyamide in a weight ratio of 4:1 to 10:1. It consists of an imide with the addition of 1.5 to 10% colloidal silica, based on the solids content of the basecoat, and is heat-resistant at temperatures used to cure polytetrafluoroethylene, pigments, and coating systems. and the topcoat comprises polytetrafluoroethylene, a coalescing agent capable of being decomposed by heat at the temperatures used to cure the coating system, a catalyst to promote this decomposition, and mica. Painted aluminum alloy structure consisting of flakes or mica flakes coated with pigments. 2 Utility model registration claim 1 characterized in that the aluminum alloy structure is in the form of a plate material
Structure described in section. 3. The structure of claim 2, wherein the basecoat has a weight ratio of polytetrafluoroethylene to polyamide-imide of about 7:1 and contains about 3.1% by weight of colloidal silica. 4. The total dry thickness of the coating film is about 12.5 to 87.5 μm, the dry film thickness of the undercoat is about 2.5 to 15 μm,
The structure according to claim 2, wherein the ratio of the dry film thickness of the intermediate coat to that of the top coat is about 1:3 to 3:1. 5. The structure according to claim 4, wherein the thickness of the undercoat is about 7.5 to 10 μm, and the ratio of the thickness of the intermediate coat to the top coat is about 1:1. 6. The structure according to claim 1, wherein the aluminum alloy structure is in the form of an inner pot for a rice cooker.