Research and application of matte transparent powder coating for automotive hub cover light (I.)

Abstract: According to the index requirements of the light powder coating for automotive aluminum hub cover, the type of anti-light system, the weather resistance of resin, the type of anti-light agent, the transparency of leveling agent, the use of UV absorber for weather resistance, latent promoter, obtained the matte transparent powder coating for automotive aluminum hub light, and studied the construction and application of light transparent powder coating in automotive aluminum hub. The compatibility and baking temperature adaptability of the matte transparent powder coating and the high-gloss acrylic transparent powder coating for automotive aluminum wheel cover were also studied, and finally obtained the matte transparent powder coating which can be shared with the high-gloss oxyoxypropyl acrylic transparent powder coating, and its comprehensive performance is comparable, which is more advantageous in terms of health and environmental protection, energy saving, cost and storage stability.Introduction
The pollution of the environment and the consumption of non-renewable resources from large quantities of volatile organic matter emitted by solvent-based coatings has become a matter of great concern to all countries in the world, and the development of low-polluting coatings is
21st century
An important research direction, powder coatings with
4E (
economy, efficiency, environmental protection and performance excellence
)
and other advantages, has become the main force in solvent-based coatings .
With the increasing demand for aesthetics, a new coating process has emerged in the coating of aluminum wheels, namely, aluminum hub base
-
-color paint
-plus
-fine car
-
matte high-weather transparent powder process, which requires matte transparent powder with excellent leveling, high transparency, high weather resistance and high corrosion resistance.
At present, aluminum hub cover light transparent powder market in large quantities is high-gloss transparent powder, is made of epoxy acrylic acid as the base system, after the cover light aluminum hub surface formed a high-gloss mirror effect, with people appreciate the concept of change, the market appeared on the matt transparent powder cover light aluminum wheel demand, and matte transparent powder in the market has not been used in bulk.
1
1
raw
materials
dual-component saturated pyride polyester resin
A/a
,
B/b
,
C/c
,
D/d
;
TGIC
: Anshan Runde Fine Chemical Co., Ltd., industrial grade
ultraviolet absorbents: benzodiazepines,
(Ciba)

Company; Light Stabilizers: Blocked Amines, Ciba
(Ciba)
Company; Domestic Polyester Resin
A
,
B
,
C
, Imported Polyester Resin
D
,
E
; Acrylic leveling agent:
TROY
, industrial grade; anti-light agent:
A9
, Zehe company, industrial grade High and low hydroxy polyurethane resin: imported; isocyanate:
B1400
, win-win; epoxy acrylic resin:
XG665
, South China Sea Fenghua.
1.2
main equipment 30
twin screw extruder,
ACM
grinding powder system, omnium Chinese medicine shredder, laser particle size spreader, small electrostation spraying equipment, impact tester, salt spray test box, xenon lamp artificial accelerated aging tester and other coating and coating performance testing equipment.
1.3
Powder coating and coating preparation
according to the preset formula called to take each raw material, with a lmspoon Chinese medicine shredder premixed after the use of twin screw extruder in the set temperature range melt extruded, extruded film material after cooling, crushing, screening, electrostectrical spray, heat curing into a film, and finally test the coating performance. The spray process parameters are shown
table
1.2
results and discussion
weather-resistant sublight transparent powder can be made by two-part pure polyester dry mixed light, polyester
/GMA
anti-light acrylic reaction, high and low hydroxy polyurethane dlighting, pure polyester
/TGIC
adding physical anti-lighting agents and other methods, this paper will be explored from these systems.2.1
Two-part polyester dry mixed light system
mainly through the faster reactive high acid content and the slower reaction of the low acid value group dry mixed light, through the difference between the curing speed of the two to form a microscopic incompatible surface, so as to obtain de-lighting. The glossy transparent powder coating obtained by this method usually does not require the addition of additional anti-lighting agents and is dissipated by the curing system itself, thus preserving a higher transparency of the coating.
(1)
Polyester resin selection
by the automotive aluminum hub cover light powder ultra-weather-resistant, high level, high transparency characteristics, you can know that polyester resin needs to have ultra-high weather resistance, high level performance, better transparency and no other color. High acid resins generally choose acid values in
45 to 55 mg KOH/g
, low acid resins generally choose acid values in the
20 to 25 mg KOH/g
range of resins. The specific performance status can be found in
2
.by Table
2
it can be known that when the acid reaction activity of the resin is too large, the coating is prone to orange peel, when the reaction activity is small, the mechanical performance of the coating is poor, so it is advisable to choose a medium-active high acid resin
B
. Ordinary two-group dry mixed anti-light resin weather resistance is poor, can not meet the requirements of aluminum hub coating, and general transparency is less than ultra-weather-resistant polyester resin, ultra-weather-resistant resin in the content of interbenzene is relatively more than
. Therefore, it is advisable to choose the medium-active ultra-weather-resistant two-group polyester resin as the substrate resin of matte transparent powder for aluminum hub cover light.
(2)
the main types of
and acrylic flattening agents are selected for the main types of silicone and acrylic. Because silicone class will mostly reduce surface stress, to a certain extent, affect the coating of inter-layer adhesion, commonly used polyether polyester modified silicone oxane, and car cover light transparent powder often need to do rework treatment, so it is necessary to investigate the re-painting rework performance of powder coating, inter-layer adhesion is particularly important, so generally do not use silicone type leveling agent.
Automotive aluminum hub cover light powder should use wire resin polymer as the main body of acrylic leveling agent, not only can promote the flow and leveling of the coating film, but also will not affect the film's inter-layer adhesion, and also de-foaming effect.the carrier of
acrylates leveling agent is mostly silicon dioxide, calcium carbonate and so on, but the leveling agent with these two substances as the carrier has a certain color, to a certain extent, affect the transparency of transparent powder, in transparent powder needs to choose transparent substances as the carrier of acrylic leveling agent.(3)
UV absorber use
pure polyester resin
/TGIC
system weather resistance is not as good as acrylic transparent powder system, so in practice, automotive aluminum hub cover light transparent powder usually need to add UV absorbers and light stabilizers to compensate for the lack of weather resistance, can add benzodiazepine UV absorbers with blocked amine light stabilizers to improve the resistance of the coating. The effects of the addition of UV absorbers and light stabilizers on coating weather resistance are
4
.As can be seen from Table
4
, UV absorbers and light stabilizers added at
0.5% to 0.8%
, the weather resistance of the coating reached a peak, and when adding both additions, there was no significant increase in weather resistance, so the additions were suitable for the range of
0.5% to 0.8%
.(4)
Use of hydrophobic silica
Copper-accelerated acetate mist experiment
(CASS)
is an important corrosion resistance indicator for transparent powder coatings, and this study found that by adding a certain amount of hydrophobic silica can improve the hydrophobic properties of the coating, thereby improving the coating's copper-resistant
(
table
5)
.the results of Table
5
show that as the content of hydrophobic silica increases, the
CASS
performance of the coating is getting better and better, when the content is at
1
%, the best effect, the content reaches
2%
when the transparency of the coating is affected, so the best addition is about
1%
.
two-part pure polyester dry mixed light transparent powder recommended formula as table 6
6
.
: 2018 China Powder Coatings and Coatings Industry Annual Conference / Paper Essay Selection First Prize, Article Ma Huanming
1/ Gao Qingfu
2/ Li Guang
2/ Zhang Shengchao
1/ Qin Zhiwei
1
(1.CITIC Daika Co., Ltd.); 2. Guangzhou Dynasky Materials Technology Co., Ltd.)