Development status of international color coating
Color coated plate production technology pioneered in the United States in 1927. Since 1960s, the production of color coated plate has been developed rapidly, and the United States and Japan color plate production line up to the maximum capacity, the most complete varieties. Abroad, the color plate has been widely used in construction, home appliances, automobile manufacturing and other industries. With Caitu consumption growth and the expansion of the application field, and user requirements of the product quality and the improvement of the performance of all kinds of new technology, the production of color sheet have been developed and applied, the color plate varieties also gradually toward the direction of diversification and high.
In Chinese, late 90s began to rise in consumption and production of color plate, its growth rapidly, by the end of 2003 124 enterprises into the coating unit 169, production capacity of 8 million 740 thousand tons, the iron and Steel Industry Association member China unit 7, production capacity of 1 million 40 thousand tons; non member unit 162, production capacity of 7 million 700 thousand tons. But because most of the production line is affected by the low level of equipment, technical strength is weak, the raw material supply is not stable and other factors, so the operating rate is low. At present, the domestic market is still in the production of color plates, half half imported, the state of supply. 2003 total domestic output of 1 million 454 thousand and 600 tons, imports 1 million 101 thousand and 600 tons, exports 16 thousand and 200 tons, the total apparent consumption of 2 million 539 thousand and 900 tons.
Domestic low level of repeated construction makes the color coated market vicious competition, but also makes a lot of investment tens of millions of units put into operation on production. China Iron and steel industry association is expected in 2005 the domestic demand for color plate up to 4 million 300 thousand tons, in 2010 will reach 8 million tons, of which the proportion of the construction of the board will be greatly improved. According to the ECCA2003 annual data show that in North America painted steel and painted aluminum as building board respectively 66% and 53.3%, and the current consumer market of our country mainly in the architectural decoration industry, in 2003 the proportion of construction for the color plate up to more than 95%, in the home appliance industry is still in the small batch trial should be used stage of application in the transportation industry basically did not start. Therefore, the color coated plate still has broad market prospects in the country.
Production technology and coating of color coated plate
Color coated plate mainly has two kinds of common coating plate and special color coated plate, the current domestic ordinary coated steel plate mainly used in the construction industry, the process flow diagram is as follows:
The basic production process: coating plate, double cut, book sewing machine, (pre degreasing), looping, degreasing and cleaning, coating, drying, coating, drying and curing early cooling (water, air) to fine coating curing, drying, cooling (water, air), looping, coiling.
Color coated substrate with cold rolled annealed sheet, ordinary zinc spend the whole hot dip galvanized sheet, small zinc spend the entire hot dip galvanized sheet, galvanized sheet and galvanized sheet. The cold rolled plate number for color coated substrate is dwindling, galvanized board is gradually replaced by the number of hot galvanized plate, for Galfan, Galvalume, Gal-vanneal substrate and plating steel in Zn-Ni increased, appeared on stainless steel substrates coated board, especially with the next two years, the domestic steel production of WISCO Galvalume the line of succession after the operation, using GL as the substrate of the color coated sheet will replace imported. In addition, the construction of color coated substrates to the thin specification (<5mm), large width (>1500mm) and high strength (UTS>600MPa) development. The requirement of color coated substrate for household electrical appliances to surface quality is becoming higher and higher. The maximum width of the color plate China for the production of 1600mm (line No. 2).
Epoxy primer is the most classic primer type, 1990 years ago was used for almost all types of color plate. It has the best corrosion resistance film, and pretreatment layer and most paint adhesion. But the PMT curing high, high energy consumption, can reach 0T and 1T with paint. Polyester primer is a new type of primer developed by European and North American paint companies in recent years. The corrosion resistance of the epoxy primer to be roughly the same, low PMT (<200 C), and the high flexibility is especially suitable for the production of T bending demanding appliances with color plate. Water based acrylic acid primer is another new type of primer, which belongs to environmental protection product. Its PMT is lower (160 degrees C), and the other properties are similar to that of the polyester primer. But it is easy to cause the decline of chemical stability of paint, so still can not be widely accepted.
Polyester in all aspects of corrosion resistance, decorative and cost advantages to occupy the leading position in the paint color plate, consumption accounted for more than 50% of the top coat. In addition, the European PVC plastisol for outdoor building paint, paint accounted for 31% of the total consumption; and the use of modified polyester, accounting for 39%.
Roll coating method is the most widely used in the production of color coated plate, accounting for about 85% ~ 90%. The process is by roller coating machine with roller with liquid coating, coated roll coating to the steel after pretreatment on the surface, and then enter the oven heating and baking, the coating of the solvent volatilizes completely out, and the waste gas containing solvent discharged and sent to the incinerator processing. The coating curing after water quenching, hot air drying. Roll coating process is usually affected by the coating thickness of the roller coating machine and baking curing furnace capacity of the restrictions, if the product requires a large thickness of the film, it requires multiple coating and curing. Therefore, in order to meet the requirements of different coating thickness, roller process has a coating of one, two, two, three or even three. At present, the widely used roller coating process is two - two. At present, the domestic color coating unit maximum process speed of 160m/min, many units in the United States can be open to more than 180m/min speed, greatly improved the production capacity.
Powder coating is a new technology: substrate surface pretreatment was coated with powder binder, curing by induction heating, water cooling roll through the substrate cooling.