What are the functions of tinplate inner coating?
Tips for making tinplate lids
- Coating purpose and requirements
Tinned plate, chrome plated and aluminum alloy thin plate made of cans are susceptible to corrosion and cause the contents to deteriorate. Therefore, most food cans require coatings inside the cans. Different food cans have different coating requirements.
1.Purpose of coating
- Certain anthocyanin-containing fruits, such as strawberries, cherries, and bayberry, use general coating material to prevent anthocyanins from corroding cans and contents from fading due to tin reduction.
- Steamed fish and luncheon meat are easy to stick to the cans. The coating containing anti-sticking agent makes the contents easy to pour out and keep the shape complete and beautiful.
- The acidic tomato sauce and pickled cucumber adopt acid-resistant paint to prevent acid corrosion of the cans and ensure that the canned food has a certain shelf life.
- Protein-rich aquatic products, poultry and meat cans use anti-sulfur coatings to prevent sulfidation corrosion caused by thermal decomposition of proteins, such as vulcanization spots and iron sulfide.
- Canned beer coating material is (spraying after weaving) to eliminate pores and prevent iron ions from dissolving, which affects the flavor and transparency of beer.
- The coating should be non-toxic after film formation, without affecting the flavor and color of the contents.
- The coating material has good storage stability.
- Convenient construction, simple operation, and a good coating film can be formed after drying.
- The coating material and solvent price are cheap.
- After sterilization of the canned product, the coating film will not change color, soften and fall off.
- The coating has good adhesion after film formation, has the required hardness, punch resistance and solder heat resistance, etc., which can meet the requirements of can making process.
- After the coating film is formed, it can effectively prevent the contents from corroding the cans.
The selection of can lids making equipment should first consider product specifications, output scale, quality requirements, followed by is equipment costs, labor costs, operating costs, plant conditions and other factors.
Generally speaking, for the production of metal covers with few specifications and varieties, large output, and high quality requirements, equipment with high production efficiency and high degree of automation should be selected, such as various types of multi-function combined machines configured as automatic production lines. Due to the small specifications, it is not necessary to change molds and debugging equipment frequently, and it is easy to take advantage of the large-scale production of high-speed automatic production lines to avoid the damage caused by the handling of semi-finished products in the semi-automatic production process. At present, more advanced lid-making equipment can be provided in China, such as corrugated plate shearing machine, double-head automatic punching machine, glue injection drying combined machine, etc. For the production of special-shaped lids with quality requirements, it is best to choose a full lids curl machine to improve the sealing quality. The small size special-shaped cover can be directly selected the automatic curl & glue lining combined machine.The large-size special-shaped cover lining machine is relatively in low production speed. So, For large-size lids lining can use multi-gun semi-automatic lining machine or automatic lining machine. The dryer can be preferred to use a vertical dryer, and its drying quality is better than that of tunnel dryer. For products with many specifications and a lack of large quantity demand, and the production of metal covers with general quality requirements, you can consider choosing multiple semi-automatic stand-alone equipment.On the one hand, you can reduce the number of mold replacements and machine adjustments.On the other hand, you can also reduce the equipment. Investment costs. The rounded edge of the special-shaped cover can be considered to use half-curl or full-curl. As far as possible, the glue injection should not use the printing glue that is facing elimination. The tunnel dryer is suitable for any size and shape of metal cover, but it covers a large area and has high energy consumption. The drying quality is not as good as the vertical dryer, and it needs manual loading and unloading. The aluminum easy-open cover has fewer varieties and specifications, but the output is extremely large, so it requires a high-speed large-scale automatic production line, which is not yet available in China. The current demand for tinplate full opening is relatively small. The production capacity of domestic production lines has reached more than 80 pieces / min. The product quality also meets the requirements for use. Compared with similar foreign products, the price is low and should be preferred.