Metal packaging industry environmental protection and development synchronization

Tinplate is the common name for tin-plated cold-rolled steel sheet in the Packaging industry. It used to be divided into hot dip tinplate and electroplated tinplate.

In the development of tinplate production, lowering the production cost of tinplate is a strategic goal of the manufacturer. Therefore, by the 1970s, the hot dip tinplate was eliminated due to large consumption of tin. With the advancement of can manufacturing technology, people's demand for Metal Containers is increasing.

By the 1990s, the main varieties of electroplated tinplate used were: CC steel grades, large-size coarse-grained iron, low-tin or chrome-plated cold-rolled steel sheets, and secondary cold-rolled thin steel sheets 0.14 to 0.18 mm in thickness. The appearance of these types of tinplate not only reduces the cost for manufacturers and can makers, but also more importantly meets various types of cans such as resistance welding cans, adhesive cans, DRD cans, DI cans, and crown caps, caps, etc. The needs of the packaging of metal containers for food cans, various beverages, oleochemicals, household chemicals, medical and health, cultural and educational supplies and cosmetics and other industries provide the necessary packaging materials.

The above-mentioned various types of tinplates generally must be decorated with printed iron before they can enter the market as products. In China, printed iron refers to external printing, and coating refers to internal coating. The outer coating of the inner coating ensures that the tinplate has good canning, canning and decorative appearance. However, the thickness of this coated organic film is usually only a few microns thick, and it is difficult to completely cover the surface of the tinplate.

Therefore, in order to prevent the occurrence of concentrated corrosion in organic film defects, tinplate must be required to have high corrosion resistance, the surface oxide film to provide the coating film density, the surface oil layer to ensure the leveling of the coating film and so on. To this end, in the late 1990s, tinplate manufacturers developed and invented the "film iron" of hot PET film, which solved the above problems and is currently in the market development stage. However, tinplate, chrome-plated iron, and laminated iron cannot be separated from high-quality inks and coatings.

Iron printing ink must have the following characteristics:

◎ Heat resistance: The ink must have good adhesion with tinplate after being cured by heat, and the pigment does not change color after baking.
◎Processability: Can withstand bending, stamping, drawing, etc.
◎ Lead-free: The ink components do not contain lead.
◎Drying: Generally, 1% desiccant has been added to the ink in the ink factory. It is necessary to add 1~2% desiccant when printing, but it should not be too much, otherwise the ink is easy to crust when coating. Overbaked.
◎ Wet imprinting: No ink loss, fading, and coloring are found.
◎ High-temperature sterilization: The ink does not change when the canned food is sterilized.
◎ lightfastness, weather resistance: especially when the metal container ink coating (without the surface coating) is particularly important.
透明 Transparency: When the metal surface gloss is used as a printing body, the transparency of the ink is very important.
◎ White Ink: Primer on the metal surface and then coat it.

Printing iron decorative coatings are classified by resin system as oily, phenolic, epoxy, vinyl, polyester, acrylic, amino and other resins; inner coating, outer coating, white coating, and glazing coating are classified according to applications. The general anti-sulfur coating is a zinc oxide oleoresin, the acid-resistant coating is an epoxy phenolic resin, a glazing coating, and the white coating is an acrylic resin or a polyester resin. The above-mentioned various types of coatings and inks are coated on tinplates and become metal containers. However, due to the release of a large amount of solvent gas during the high-temperature baking process, the paint has obvious odor and the concentration of benzene-containing gas is exceeding the standard, causing serious pollution to the environment.

Therefore, while developing tinplate printing technology, the environmental protection of waste gas treatment cannot be ignored. In fact, foreign countries have a long exploration process for this waste gas treatment, which consumes a lot of manpower and financial resources. From the high-altitude emissions in the 1960s (expedient measures), the adsorption method in the 1970s (high cost and incompleteness), and the catalytic combustion method in the 1980s (high cost), it was not until the 1990s that the incineration method completely resolved.

Nowadays, there are research institutes and manufacturers of environmental protection equipment in the country that are committed to the research of the aforementioned exhaust gas treatment. The realization of the catalytic combustion method and incineration method has brought good news to the printing iron industry. In particular, the implementation of the incineration method not only makes up for domestic gaps, but also reduces the operating costs of waste gas treatment and has a broader market prospect.

The economy in the 21st century is a knowledge economy and an environmental economy. This is an inevitable trend of the development of the times. The rapid economic development brought about by reform and opening up has also caused serious damage and pollution to the ecological environment. Therefore, environmental protection has become the supporting point and growth point for sustained economic development.

According to preliminary statistics, there are nearly 1,000 printing and coating lines in China. Among them, the coating drying room with serious exhaust gas pollution accounts for about 1/2, each coating drying room has 214 coating tinplate in the smallest production size (512×721mm), the coating thickness is 5.5 g/m2, and the production speed is 4600 sheets/hour. To calculate, about 20kg of waste gas will be emitted every hour. Every day, 15 hours (second class), 300kg of waste gas will be discharged.

As a result, the degree of pollution of the environment can be imagined. In view of this, China Packaging Technology Association has set up a designated factory for environmental protection equipment in Shanghai. It specializes in the development and production of incinerators to solve the problem of exhaust gas pollution that has not been solved in the printing iron industry for many years. This has given tinplate packaging industry greater support and a broader scope. Prospects.