Metal sheet coating technology

Metal sheet coating technology

From Yang Wenliang Xin Qiaojuan, "Metal Packaging Container Metal Can Manufacturing Technology"

The metal plate coating technology is a processing technique in which a plastic film and a metal plate are subjected to high-temperature hot pressing to adhere the film to a metal plate. The film-coating technology was born in Japan in 1977. It was originally used for canning. It can replace the inner coating and outer coating technology. Up to now, it has developed into various fields such as interior and exterior decoration of building materials, home appliances, and automobiles. Since the film processing does not use an adhesive or a solvent, it does not contain formaldehyde, and the plastic film can be treated with landscaping, antibacterial, anti-dyeing, etc., ensuring the safety and health of the human body and at the same time playing an environmental protection role.
Laminating sheets used in the canning industry, commonly known as Laminated Steel, are made by laminating PP film with tinplate. The inside of the traditional metal can has to be painted, and the materials contained in the coating method have harmful effects on the human body and the environment, especially the canned food. The current treatment method is to apply resin on the inner wall of the can. However, the paint used in this coating process contains an environmental hormone-containing substance, Bis-phenol A, which is an internationally recognized environmental hormone and may cause dissolution problems once dissolved. Exceeding the standard will have an adverse effect on the human body. And the serious consequences caused by this problem have attracted the attention of both domestic and foreign.

The birth of metal sheet coating technology is a revolutionary advancement in the production of metal cans. With its wide application, traditional metal can production processes and technologies will be subverted, and productivity, production costs, sanitation, and environmental protection will all take a big step forward.

First, the characteristics of the film board

The laminated board is a metal material which has the characteristics of deep-drawing, abrasion resistance, corrosion resistance and decoration which are superior to the traditional printed tinplate, and has the dual characteristics of a polymer resin film and a metal sheet. This feature determines that the coated sheet can be used as a substrate by using a cold-rolled sheet to quickly cover the printed film with an overprint, so that the coated sheet greatly reduces the material cost.

1. The laminated board has excellent performance.

(1) The corrosion resistance and rust resistance of the coated board are unmatched by the paint board. Because it is a composite board of plastic film, the coating board has the contradiction between corrosion resistance and adhesion. It is easy to solve for the laminating board. For the food cans such as tomato cans and two-piece cans, the laminating board is The ideal material.

(2) The appearance of the coated sheet is smooth, smooth, decorative, and feels good.

(3) The laminated board has good chemical stability, weather resistance and aging resistance, and can adapt to harsh environments without falling off and rusting.

(4) The coated sheet has excellent processing performance, deep drawing resistance and wear resistance, and is not easily damaged during processing. Due to its smooth surface and lubricity, it is easier to form in the processing of metal cans.

2, the cost of the laminate material is lower

(1) Since the laminated sheet is a metal material having both the characteristics of a plastic film and a metal sheet, in general, it is not necessary to use a tinplate as a substrate to produce a laminated sheet. The cost advantage of using cold rolled sheet coating is obvious.

(2) The production of laminated sheets is a continuous high-speed production line of coiled sheets. Compared with the traditional printing process, the production speed is three times faster.

(3) The production process of the laminating board can be completed at one time because the printing plastic film and the laminating film are compared, so compared with the traditional printing iron process, it has the characteristics of low energy consumption, high speed and less material consumption.

(4) Metal sheet laminating equipment is easy to operate and easy to maintain. The traditional tinplate printing and painting relies on the experience of the technical operators to control the various processes. The laminating board production process and equipment are simple, the whole process of production is automatically controlled, the operation and maintenance are convenient, and the production can be mastered without special professional training. And maintenance technology.

(5) Compared with the traditional tinplate printing, the equipment is less, the investment is smaller, the floor space is smaller, and the use of workers is less. This saves a lot of equipment investment and labor costs.

3. Environmental protection, energy conservation and sanitation

(1) The production of coated sheets is solvent-free and exhaust-free, and does not require paint drying. It has less environmental pollution and is also very energy-saving.

(2) Since the coated sheet is not thermally coated with a chemical coating and ink, but is covered with a plastic film, the coated sheet does not contain various chemicals harmful to the human body. Adhesives and solvents are not used to ensure human health and safety. Solved the problem of environmental hormones and volatile organic compounds.

(3) It does not contain harmful substances such as citric acid or phthalic acid esters, and can be fully utilized as renewable resources. The production of carbon dioxide is reduced at the time of manufacture, and no dioxins are generated when the resources are regenerated. The waste film can is reused as iron resource, and the recovery rate is 100%. When the film is recycled together with iron, the film is burned into water and CO2 due to heating, and this part is converted into natural gas, which is used as the power for iron heating. Energy is used. The waste film can also be used as a regeneration.

The can body of the metal can is usually welded, and the exposed portion of the metal after welding must be coated. Figure 1 is a schematic diagram of the film filling of the metal can weld. The application of the non-adhesive coating technology is to repair the welded portion by using a polypropylene resin of the same material as the film to complete the filming and melting repair of the exposed portion of the metal. The characteristics of the polypropylene film heating and melting are fully utilized, and a vacuum bag-like effect is formed, and the contents are not leaked at all. Since the adhesive and the lubricant are not used in the can making process, the risk of dissolution of the physical properties, residual solvents, plasticizers, and the like due to the additional materials can be avoided. Moreover, problems such as poor resistance to contents, weak adhesion, and incorporation of air bubbles which occur during the coating and recoating process do not occur.

Figure 1 Metal can weld seam film

It is also possible to use tape refilling or powder recoating, that is, using a resin tape or powder having the same composition as the film, and the steel plate is covered with a PP white film, and a white PP powder is required for refilling.

China's self-developed automatic welding film laminating device is installed at the back of the seam welding machine. Through special process, the film can be automatically filled immediately after seam welding, which effectively solves the problem of the quality of the weld.

5, film quality control

For the quality inspection of the laminated board, the JISK6854-1 adhesive strength peeling test is generally used; the distillation test method; the first checkerboard method; the original thermal modification method of the film coating industry and the like.

(1) Appearance quality inspection The purpose of using the laminating board is to decorate only, so that the appearance does not change is an important requirement.

The quality change of the appearance was observed. The ISO0877 was used as the standard, and EMMAQUA-NTW (outdoor light collection and promotion exposure test) was selected, and the experimental energy was applied until the surface became fibrillated and microfibrillated. Observe the changes in gloss, brightness and chromatic aberration of the surface.

1 Gloss gloss did not change, and the mirror state remained at 86%.

2 The brightness of the brightness has not changed, and the stability of the composite technology after printing has not been damaged.

The 3 color difference indicates high weather resistance within the color difference ΔE2. The known PMMA film has high durability and has the same high weather resistance as a fluorine-based plastic film.

(2) Physical durability test The physical strength change test was used to promote degradation in a high temperature environment (85 ° C) for 90 days, and the residual rate of tensile strength and elongation was measured. Tables 4-6 show the physical strength of the laminated film.

Table 4-6 Comparison of Durable Physical Strength Values ​​of Commonly Covered Membrane

(3) The physical laminated film of the laminated film should be subjected to physical properties such as refractive index and heat resistance, and the laminated film should have certain optical and heat-resistant physical properties. Table 4-7 shows the physical properties of the laminated film.

Third, the application of the film board

At present, the laminated board has been widely used in various industries, especially in Japan, and it is the most widely used.

1, food cans

The main applications in food metal cans are: food cans, beverage cans, four-caps, candy cans, tea cans, easy-open lids, etc.

2, chemical tank

The main applications in chemical tanks are: chemical tanks, paint cans, paint cans, two aerosol cans and various top and bottom covers. In particular, the film-free processing technology can be applied to the canning of various three-piece cans.

3, decorative cans, gift cans

The main applications in decorative cans are: portable ashtrays, gift boxes, pencil cases, jewelry boxes, cigarette cases, wine boxes, and so on.

4. Applications in other industries

Applications in other industries include: building panels, walls, ceilings, security doors, floors, awnings, etc.

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