Powder paint is also known as dry oil paint, is an environmentally friendly product, can provide a variety of color variety of powder paint varieties, more more industries, more more fields began to apply powder paint. With the rapid development of aluminum profile industry, powder coatings applied to aluminum profiles have become the professional branch of powder coatings, gradually replace electrophoretic paint fluorocarbon paint. With the emergence of transfer printing technology, aluminum profile powder coating varieties more colorful.
Aluminum profiles need to have strong weather resistance decorative, so aluminum surface treatment is necessary. The surface treatment of aluminum profiles is mainly organic coating, including powder coating spraying, fluorocarbon paint spraying wood grain processing. Wood grain processing is carried out on the surface of the powder coating, which is divided into water transfer heat transfer.
Thermal transfer wood printing technology the end of the 1990s into China, in recent years to get a rapid development. The main features of the technology transfer printing image colors, rich layers, the heat transfer effect is equivalent to that of the printing, the difference of thermal transfer printing technology is in high temperature heated sublimation ink, can multicolor pattern is a mapping, need tinted, which form a colorful pattern after sublimation, 40 to 60 can seep into the powder coating (including the interior of the m.
So the heat transfer products durable, transfer printing patterns will fall off, crack fade, because of heat transfer processing change the original product gloss, wear resistance, weather resistance, acid alkaline resistance.
Thermal transfer printing only plays the role of surface decoration, now has basically formed a complete thermal transfer printing supporting system, including powder coating, spraying process, thermal transfer printing equipment, transfer paper transfer film manufacturing.
The emergence of thermal transfer printing technology presents a new challenge to powder coating technology, which requires that the powder coating used for thermal transfer printing must match with the thermal transfer printing paper (film) to ensure a good transfer effect. Therefore, it is necessary to discuss the thermal transfer technology of powder coating study the formula design of thermal transfer powder coating.
Thermal transfer technology
Thermal transfer is also called the sublimation, is the portrait, landscape, wood grain, marble, three-dimensional relief so on all sorts of design, the use of thermal transfer printing ink printed on the high accuracy paper (film), USES the thermal transfer equipment in a short period of time to be heated to set temperature, make the design color on the transfer paper realistically transfer printing on the aluminum material such as a special process.
2.1 transfer paper
Transfer paper is mainly divided into two types, namely wood grain thermal transfer paper PET thermal transfer film. These two materials use the principle of heating sublimation penetration to achieve the purpose of transfer printing, but the two heat transfer printing equipment operation process is different, the use of PET heat transfer film transfer printing production efficiency is higher, especially suitable for the transfer of shaped aluminum aluminum with complex shapes.
2.2 thermal transfer process
Aluminum profile thermal transfer printing process is a simple process with less input equipment, fewer operators, higher production efficiency lower cost than water transfer printing. Heat transfer printing process is: substrate → wood grain heat transfer printing paper PET heat transfer film tightly wrapped substrate → heat transfer printing → surface cleaning → inspection → packaging.
2.2.1 thermal transfer paper technology
Suitable for large area profiled substrate technology 1: take the already sprayed aluminum profile, heat transfer printing glue will heat transfer paper aluminum profile front paste, send to oven baking (180℃, 6min so), tear off the heat transfer printing paper, clean the surface, get transfer wood grain aluminum profile.
Is suitable for large area alien base material process 2: take spray has good aluminum extrusions, attach thermal transfer paper aluminum positive face, interface, with a small amount of high temperature resistant adhesive tape stick paper on the set of high temperature resistant PET plastic bags tighten, fixed on both ends of the bag, both ends of pumping air into vacuum state, sent to the oven to bake (around 180 ℃, 6 min), remove the PET bag, tear off thermal transfer paper, clean surface, namely get transfer grained aluminum.
Applicable to all kinds of plane aluminum process three: take the sprayed good aluminum, heat transfer paper aluminum profile on the front face paste, with a special plate heat transfer machine heating (180℃, 20 seconds so), tear off the heat transfer paper, get transfer wood aluminum profile.
2.2.2 PET thermal transfer film process
The process is suitable for large area profiled aluminum. Process is as follows: take already spraying aluminum, the PET thermal transfer film aluminum positive face, with a bag to be wrapped in transfer of aluminum extrusions, the PET sealed bag printing film with ultrasonic sealing machine, the ends of the bag does seal, fixed at both ends of the bag, PET thermal transfer membrane both ends of pumping air into vacuum state, sent to the oven to bake (around 180 ℃, 6 min), tear off the PET thermal transfer film, transfer of aluminum in grain.
Special powder coating for heat transfer printing
Heat transfer printing process of aluminum profiles usually adopts polyester /TGIC polyurethane powder coatings, which have excellent pattern transfer performance.
3.1 formula design
The softening point of the selected polyester resin should be lower, but the glass transition temperature (Tg) should be 80~110℃. At present, according to the characteristics of heat transfer printing, polyester resin for heat transfer powder coating has been specially developed by polyester manufacturers.
The amount of curing agent must be enough, the right amount of curing catalyst can be added, to ensure that the film curing complete, to prevent the second time into the furnace coating adhesion problem good tear paper;
Leveling agent should be more, but should ensure that the coating has good leveling;
Heat transfer powder coating powder covering power is too high, so the formula in titanium dioxide can be added less, but should ensure that the coating has a good fullness brightness;
When comparing the color of thermal transfer paper film, to choose the same texture, the same position of the contrast sample, with the same transfer conditions, transfer on the same substrate, in the same light source for comparison, directly used before the transfer of paper film surface color for comparison results are accurate.
3.2 technical formulation of powder coating
Due to the cost of polyurethane powder coatings, although there are many advantages, but the current market is seen, most manufacturers still use polyester /TGIC polyester /HAA powder coatings as aluminum profile thermal transfer powder coatings. Table 1~3 is the basic formula of 3 types of powder coatings.