Special thermal transfer powder coating for aluminum profiles.

Abstract:
this paper introduces the thermal transfer powder coating applied to aluminum profiles. The thermal transfer process and powder coating formulation design are briefly described, and the powder-making materials affecting the clarity of wood texture are tested one by one. The factors affecting the quality of thermal transfer are analyzed and

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1, Overview
Powder Coatings, also known as dry paints, is an environmentally friendly product that offers a wide variety of powder coatings in color and variety. More and more industries, more and more fields began to apply powder coatings.
with the rapid development of the aluminum profile industry, powder coatings used in aluminum profiles have become a professional branch of powder coatings, and gradually replace electrophoresis paint and fluorocarbon paint. With the emergence of transfer technology, aluminum profiles dedicated powder coating varieties are more colorful.aluminum profiles need to be highly weather-resistant and decorative, aluminum surface treatment is required. The surface treatment of aluminum profiles is dominated by organic coatings, including powder coating, fluorocarbon paint and wood grain treatment.
wood grain treatment is carried out on the surface of powder coating, divided into water transfer and thermal transfer. Thermal transfer wood grain technology from the late 1990s into China, in recent years has been a rapid development.
The main features of this technology is that the transfer image color is bright, rich in layers, transfer effect can be comparable with printing, and printing technology is different in the heat transfer is in the high temperature so that the ink heat sublimation, can multi-color pattern once into a picture, no set of colors, after the condensation will form a bright color pattern, and can seep into the powder coating 40 to 60 m of the interior.
So thermal transfer products durable, transfer patterns will not fall off, crack and fade, will not be due to thermal transfer treatment and change the product's original gloss, wear resistance, weather resistance, acidity and alkalinity.
thermal transfer only plays a role in surface decoration, has now basically formed a perfect thermal transfer supporting system, including powder coatings, spraying process, thermal transfer equipment, transfer paper and transfer film manufacturing.the emergence of thermal transfer technology presents a new challenge to powder coating technology, which requires that powder coatings for thermal transfer must match the thermal transfer paper (film) to ensure good transfer results.
, it is necessary to explore the thermal transfer process of powder coating film and to study the formulation design of thermal transfer powder coating.
2, thermal transfer technology . Thermal transfer is also known as thermal sublimation, is the image, landscape, wood, marble, three-dimensional relief and other patterns, the use of thermal transfer ink printed on high-precision paper (film), and the use of thermal transfer equipment in a short period of time to heat it to set the temperature, so that the printed paper on the pattern and color realistic transfer to aluminum profiles and other materials on a special process.
2.1 transfer paper . Transfer paper is divided into two main types, namely wood-printed thermal transfer paper and PET thermal transfer film. Both materials use the principles of heat sublimation and osmosis for transfer purposes.
However, the transfer equipment and operating process used by the two in thermal transfer are different, and the use of PET thermal transfer film transfer is more productive, especially suitable for transfer of special aluminum or complex shape aluminum.
2.2 thermal transfer process . Aluminum profile thermal transfer process is a low input equipment, fewer operators, than water transfer production efficiency, low cost of simple process. Thermal transfer process is: the selection of substrates→ with wood-printed thermal transfer paper or PET thermal transfer film tightly wrapped the substrate →heating transfer→ surface cleaning→ inspection → packaging.
2.2.1 Thermal transfer paper process
- suitable for large areas and special-shaped substrate process one: take the sprayed aluminum profile, with thermal transfer special glue will be hot transfer paper front and aluminum profile face-to-face paste, sent to the oven baking (180 degrees C, about 6min), tear off the hot transfer paper, clean the surface, get the transfer of wood or stone-printed aluminum profile.- Suitable for large areas and special-shaped substrate process II: take the sprayed aluminum profile, the thermal transfer paper front and aluminum profile face-to-face paste, with a small amount of high temperature-resistant tape glue paper interface, set up high-temperature-resistant PET plastic bag and fasten;
Fix both ends of the plastic bag, vacuum from both ends, sent to the oven baking (180 degrees C, 6min or so), remove the PET plastic bag, tear off the hot transfer paper, clean the surface, that is, get the transfer of wood or stone aluminum profile.- Suitable for a variety of flat aluminum profile process three: take the sprayed aluminum profile, the front of the thermal transfer paper and aluminum profile face-to-face paste, with a special plate heat transfer machine heating (180 degrees C, about 20s), tear off the thermal transfer paper, get the transfer of wood or stone-printed aluminum sheet.
2.2.2 PET thermal transfer film process
suitable for large areas and shaped aluminum. The process is as follows: take the sprayed aluminum profile, the PET thermal transfer film front and aluminum profile face-to-face.
wrap the aluminum profile to be transferred in a bag, seal the PET transfer film into a bag with an ultrasonic sealer, the ends of the bag are not sealed, fixed at both ends of the PET thermal transfer film bag, vacuum from both ends, sent to the oven baking (180 degrees C, 6min or so), tear off the PET thermal transfer film, get the transfer of wood or stone aluminum profile.
3, heat transfer special powder coating . The thermal transfer process of aluminum profiles typically uses polyester/TGIC and polyurethane powder coatings, both of which have excellent pattern transfer properties.
3.1 Recipe Design . The soft point of the selected polyester resin should be lower, but the glucification temperature (Tg) should be 80 to 110 degrees C. At present, polyester manufacturer root thermal transfer characteristics, specifically introduced the thermal transfer powder coating polyester resin; curing agent must be added enough, can be added to the curing catalyst in moderation, to ensure that the coating film curing completely, to prevent the secondary furnace coating back to stick problems and not good tear paper; leveling agent should not be added, but should ensure that the coating has good leveling; Thermal transfer powder coating base cover need not be too high, so the formula of titanium dioxide can be less, but should ensure that the coating has a good fullness and freshness; compared to the color of thermal transfer paper or hot transfer film To choose the same texture, the same location of the contrast sample, with the same transfer conditions, transfer on the same base color substrate, under the same light source for comparison, directly using the paper sample or membrane sample surface color before transfer for comparison results are not accurate.
3.2 Powder coating technology . Polyurethane powder coatings due to cost problems, although there are many advantages, but at present the market is rare, most manufacturers still use polyester/TGIC type and polyester/HAA powder coating as aluminum profiles dedicated to thermal transfer powder coatings. Table 1 to 3 is the basic formula for powder coatings in 3 models.
Table 1 Outdoor lightless wood grain powder coating formulation and process conditions
formula
raw material name
quality parts
polyester
600
XG665 anti-light curing agent
140
TGIC curing agent
15
PV88
10
resting incense
4
precipitation
300
R-902
00
polyethylene wax
7
pigment
moderate amount
curing and thermal transfer conditions
curing conditions
200 degrees C/10min
thermal transfer conditions

180C/5min gloss
3%
Table 2 Outdoor highlight wood-print powder coating formulation and process conditions
picion
raw material name
mass
. Polyester
600
333 curing agent
32
PV88
9
701
11
resting incense
4
precipitation


300
R-902
100
Polyethylene wax
7
pigments
appropriate amount
curing and thermal transfer conditions
curing conditions
2 Thermal transfer conditions

180 degrees C/5min
60 degrees gloss
90% Table 3 Polyurethane light wood coating formulation and process conditions Formula

quality
hydroxy resin (high hydroxy)
200
hydroxy resin (low hydroxy)
460
B1530
310.



270
R902
240
Other additives
30
pigments
appropriate amount
curing and thermal transfer conditions
curing conditions
200C/10min
Thermal transfer conditions
180 degrees C/5min
60 degrees gloss
6%
4, factors affecting the clarity of the transfer texture

effect of filler addition on wood grain clarity can be seen in Table 6, the effect of different brands of polyester resin on wood grain clarity can be seen in Table 7, and the effect of hydroxyamide HAA curing agent on wood grain clarity can be seen in Table 8.
The effect of wax powder on wood grain clarity can be seen in Table 9, the effect of filler varieties on wood grain clarity can be seen in Table 10, the effect of leveling agent on grain clarity can be seen in Table 11, the effect of degassing agent on wood grain clarity can be seen in Table 12, and the effect of titanium white powder filling on wood grain clarity can be seen in Table 13.
4 Effects of Physical Anti-lighting agents on wood grain clarity
Note: Excellent- Wood-printed clarity; Good-wood-blurred; and poor-wood-printed clarity.
effect of table 5 6600A polyester/catalyst matching on wood grain clarity
The effect of table 6 filler addition on wood grain clarity
Table 7 Effect of polyester resin from different manufacturers on wood grain clarity
8 Effect of hydroxyamine HAA curing agent on wood grain clarity
Effect of Table 9 wax powder on wood grain clarity
Effect of Table 10 filler varieties on wood grain clarity
Table 11 Leveling agent on grain clarity Impact
Table 12 Degassing Agent's Effect on Wood grain Clarity
Table 13 Titanium White Powder Addition Effect on Woodline Clarity The larger the addition, the less clear the texture of the wood grain, the greater the impact of catalyst varieties and additions on the clarity of the wood grain, the different clarity of the wood grain formed by the polyester provided by
manufacturers, and the amount of filler has an effect on the clarity of the wood grain, not much good. There are some differences in wood grain clarity produced by different amounts of HAA curing agent,
but different wax powder varieties have little effect on wood texture clarity, different varieties of wood texture texture clarity formed by the selection of different varieties of niobium sulfate or calcium carbonate are also different,
change the variety and dosage of leveling agent and degassing agent has little effect on wood texture clarity, but the amount of titanium white powder has a great impact on wood texture clarity.
5, thermal transfer quality problems and reasons analysis
Table 14 thermal transfer quality problems and cause analysis
seed quality problems
cause analysis
thermal transfer after not good paper or film
1 the surface of the transferred substrate has quality problems, such as high temperature resistance, sticky paper or mucous membrane phenomenon.
coating on the surface of the transfer substrate after 2 powder injection is not fully cured, and the heat transfer is cured again and glued back.
3 thermal transfer glue quality is poor, the ratio concentration and the amount of brush improper directly affect the effect of paper stripping.
4 recommends adding a suitable amount of diatom (silicon oil) to the hot transfer glue water to solve the problem of paper-stripping.
transfer paper (film) fragile or zoom
transfer temperature is too high or too long caused by thermal transfer paper (film) too fast aging.
The same kind of thermal transfer paper (film) transfer products have color difference
1 color comparison did not comply with the "choose the same texture, the same location of the contrast sample, with the same transfer conditions, transfer on the same base color substrate, under the same light source for comparison" principle.
2 Transfer substrate has a color difference.
3 transfer device performance is not stable.
4 The temperature and time of the improved printing are not controlled during thermal transfer, usually the transfer temperature is 120 to 190 degrees C, and the transfer temperature and time are directly related to the depth of the color of the
transfer texture. Cannot be transferred below 120 degrees C, and the texture color of the transfer on the substrate becomes lighter over time when it is higher than 190 degrees C.
the product after thermal transfer of spots or foggy block phenomenon
1 the surface of the transferred substrate originally has spots or foggy block.
2 the surface of the transferred substrate is not resistant to high temperatures, there is a sticky paper or mucous membrane phenomenon.
3 The powder coating on the surface of the transferred substrate is not fully cured.
4 The quality of thermal transfer glue is poor, the ratio concentration and the amount of brushing is not proper, the normal thermal transfer glue after high temperature will
automatically volatile, leaving no traces.
5 If the use of thermal transfer glue sticky paper caused this phenomenon, it is recommended to transfer the substrate used.