n the color coating construction, the top coat has the most critical role in product performance. The utility model not only provides the decoration of the color coated plate, but also enables the color coated plate to have various practical functions.
The color coated plate can be applied in different fields, such as color coated plate for building materials, color coated plate for household appliances, color coated plate for automobiles, etc. Therefore, the research of finishing coat in coil coating
is the most thorough one. At present, there are mainly the following types of coil top coating that have been industrialized.
A plyester finish
According to the definition, polyester resin refers to the polymer materials with ester bond on the main chain, including three types: alkyd resin, saturated polyester and unsaturated polyester. Polyester used in coil industry
refers to saturated polyester.
The paint film formed by polyester resin has excellent comprehensive performance and wide adjustable range of performance, and can be made into different application forms, such as solvent based, water-based, powder,
drying or self drying paint products. It is widely used in household appliances, automobiles, metal furniture, building materials, cans and other industries. The polyester resin for roll is mainly composed of aromatic, aliphatic and aliphatic polyols
Polyester Topcoat for color coating plate is a coating prepared with polyester as the basic raw material. The main crosslinking resin is butanol etherified melamine formaldehyde resin (amino resin). Amino resin cured Polyester
Topcoat has good flexibility, hardness and durability, as well as good processability. People use the heterogeneity technology of this kind of resin in the paint film to improve its performance. Therefore, it is the most commonly used coil finish.
B polyurethane finish
Polyurethane coating is widely used in different fields for its excellent comprehensive properties. In 1972, the polyurethane coating composed of blocked polyisocyanate and hydroxypolyester was first used as the top coat
of precoated coil for aluminum coil in Germany. In 1997, polyurethane topcoat accounted for 5% of the pre coated coil topcoat. In 1999, polyurethane topcoat ranked fourth among the synthetic resins used for pre coated coil coating, mainly used for coating
building materials, household appliances and pre coated metal coils for vehicles. Polyurethane finish (especially polyurethane finish made of aliphatic and alicyclic polyisocyanate) has a better balance between flexibility, hardness and durability than
amino polyester finish. Another characteristic of polyurethane finish is that it can be baked or self drying at room temperature. For the coating with the same formula, the polyisochlorous acid component used is used in the production line of precoating
coil after being sealed, while the unclosed component is used in the self drying two-component coating, and finally the paint film with the same structure and performance can be obtained, which is very beneficial to the repair work of precoating coil
for building materials in the use site.
C polyacrylate finish
Polyacrylate coating is a kind of widely used coating. The main chain of polyacrylate resin is carbon carbon bond, which is very stable to light, heat, acid, alkali, etc. the coating
made of polyacrylate resin has excellent outdoor durability and light and color retention. In addition, through the copolymerization of various acrylates, the mechanical properties of the resin can be adjusted, so the comprehensive properties are relatively
At present, there are three main types of polyacrylate coating used for color coating: solvent based heat curable polyacrylate coating, water diluted polyacrylate coating and radiation curable polyacrylate coating.
thermosetting polyacrylate coating has good stain resistance, scratch resistance, high gloss and hardness, as well as excellent weather resistance and chemical resistance. The disadvantage of this kind of coating is that it is difficult to obtain products
that meet the requirements of hardness and toughness at the same time. When the hardness meets the requirements, the paint film can not generally withstand deep processing and forming. At present, this kind of coating is mainly used as the matching primer
of PVC plastisol topcoat.
In order to further improve the outdoor durability of polyacrylate coating, organosilicon modified polyacrylate coating was developed in the mid-1960s, trying to replace the fluorine-containing coating with the price advantage
part to manufacture the precoated metal coil for exterior wall and roof. The organosilicon component in the coating generally accounts for more than 30% of the film-forming resin. In practical application, it is found that the introduction of organosilicon
can not only improve the weatherability, but also reduce the processability, and it is difficult to find a satisfactory balance point in this contradiction, and the improvement of weatherability is not worth comparing with the increased cost. Therefore,
at present, this kind of coating has been less used in the production of color coated plates.