He Tao 1.2, Gu Yuxuan 1, Xie Jing 1.2, Lin Xien 1.2, Yan Deliang 1.2, Liang Baorong 1.2
1. China Electrical Science Research Institute Co., Ltd.
2. Guangzhou Dynasky Materials Technology Co., Ltd.
introduced a set of high, low acid-resistant terminal urethane resin based on the single system of benzoic acid, with the resin prepared powder coating through dry mixing electrostectric spraying can obtain a good anti-light effect (gloss for 21 to 26), coating appearance delicate, excellent weather resistance, anti-aging time significantly better than the control.
weather-resistant polyester powder coatings are mainly used in the field of anti-light curtain wall, outdoor construction, construction machinery, outdoor solar panel support, automotive parts and other fields for this type of powder coating polyester resin is usually composed of methylphenidate, cycloethylene and other monomers.
anti-light powder coating as a better decorative varieties, widely used, powder coating anti-light methods are mainly 2 kinds:
(1) by adding physical or chemical anti-lighting agent to achieve the way of anti-light;
(2) After using high acid resin and low acid resin respectively prepared into powder coating, according to the quality ratio of 1:1 dry mixing spray, using the difference between the curing rate of the two groups to achieve a rough surface on the microscopic surface to eliminate light, without the need to add anti-light additives can obtain 18 to 45 gloss
This study prepared a set of high and low acid-based biphenyl acid-based two-component end pyride polyester resin, through the second way with the curing agent TGIC prepared dry mixed anti-light powder coating, because the organic materials used are weather-resistant components, no need to add a large number of anti-light agents to ensure the overall excellent weather resistance of the powder coating.
1, the experimental part
1.1 main raw material
xin glycol: BASF Gichua new glycol Co., Ltd.;
2-ethyl-2-butyl-1,3-propylene glycol, trihydroxymethyl propane, 1,4-cyclohexanedone-methylene-dhamphetamine: Bairstow, Sweden;
benzoic acid: Korea KP Chemical Co., Ltd.;
catalyst: Nanjing Dingchen Technology Development Co., Ltd.
-resistant polyester resin NH - 3307: Guangzhou Dynasky Materials Technology Co., Ltd.
two-group polyester resin CRYLCOATE04131 /E04132: Industrial products, formerly Cyanide;
, antioxidants, curing promoter, TGIC, titanium dioxide, vanadium sulfate, leveling agent, sabbath: industrial products, commercially available.
1.2 Instruments and equipment
homemade 100 L synthetic reactor;
reel cone viscosity meter: Research Equipment (London) UK;
SLJ - 30AF twin screw extruder: Yantai Donghui Powder Equipment Co., Ltd.
high-voltage electrostectrulative spraying equipment: Foshan City, the South China Sea large-step spraying plant;
QUV UV artificial accelerated aging instrument: Q - Lab Company;
MP41 permeable polarity microscope: Guangzhou Mingmei Photoelectric Technology Co., Ltd.;
gel permeation chromatography: Japan's Izu Corporation.
1.3 resin synthetic
Add a variety of polyols, polyic acid monosomes (based on mesobenzene, no parabens) and catalysts to the 100 L synthetic reactor by ratio, open the agitator, and heat up to about 250 degrees C;
reaction to 95% esterified water distillation, and then add acid antidote, reaction to resin transparent, then vacuum shrinkage, and then add antioxidants and other additives, stirred evenly after the material, respectively, to obtain 2 different acid value polyester resins: high acid resin A and low acid resin B, basic performance parameters see Table 1.
1.4 Preparation of powder coatings and coatings
1.4.1 two-component anti-light powder coating preparation
the synthetic A and B polyester resins are mixed with TGIC, pigments and other additives according to the ratio of Table 2, melting extrusion, cooling crushing, crushing through sieve to make powder coating.
A, B powder coating will be obtained, according to the quality ratio of 1:1 mixing after spraying can get the anti-light powder coating. Spray the powder coating static on a cold-rolled steel plate and bake a 10min coating model at 200 degrees C.
1.4.2 two-component powder coating control sample preparation
with high acid resin CC04131 as A resin, low acid resin CC04132 as B resin, using 1.4.1 method to prepare two-component powder coating control sample (later referred to as control sample) and control coating sample.
1.4.3 Conventional anti-light powder coating preparation
the weather-resistant polyester resin NH3307 and TGIC, pigments, anti-lightening agents and other additives in accordance with the ratio of Table 3 after mixing, melting extrusion, cooling broken, crushed screening into a powder coating. Static spray is applied to the cold-rolled steel plate and the 10min instant coating model is baked at 200 degrees C.
1.5 weather resistance test
Put the cured powder coating model in the aging box for an artificial accelerated aging test of ultraviolet light, the aging condition is QUV-B (313nm), irradiance: 0. 71 W/m2 /nm, light segment: 60 degrees C /4h, condensation segment: 50 degrees C /4h.
2, Results and Discussion
2.1 Coating Basic Performance Study
Table 4 is the basic performance of weather-resistant two-component powder coating.
from Table 4, the anti-light performance of the coating is relatively ideal, the gloss is 23. This is mainly due to the large difference in reactivity between the two powder coatings, and the large difference in the curing speed between the two groups, resulting in a rougher surface.
In addition, because the resin synthesized in this study is based on methyl xylene acid, interbenzene acid relative to benzoic acid, synthetic resin brittleness, hardness is greater, so impact resistance will be based on the difference between benzoic acid monosome, flexibility is also poor, high hardness.
, in the interlesced structure formed by dry-curing, the rapidly curing parts easily form a relative stress concentration, which has a negative effect on impact resistance.
In terms of acid and alkali resistance, it can be found that the acid resistance of the coating passes through, but the resistance to alkali is not good, mainly because the organic body of the coating still belongs to polyester, easy to soapy reaction after prolonged alkali immersion.
2.2 coating anti-light performance study
Micro-observation of the appearance of the coating at the microscope was made to examine the de-lighting of the ultra-weather-resistant two-component coating, and in order to better observe the surface effect of the coating, a high-gloss coating with a gloss of 90 and a coating with a gloss of 21 prepared by adding a de-glossing agent were used as a score, as shown in Figure 1.
can be seen from Figure 1, the surface of the high-gloss coating is smaller particles, high flatness; The coating obtained by the anti-light agent and the surface of the two-component anti-light coating are relatively rough, in which the two-component anti-light coating surface structure is uniform, misplaced and worn through each other, the pattern is obviously much larger.
the appearance of the coating obtained by the anti-light agent is relatively light and dense, the two-component anti-light coating surface protruding is relatively large and loose.
general, the rougher the coating surface, the more conducive to diffuse reflection, the lower the gloss; The more uniform the anti-light surface structure and the shallower the pattern, the more delicate the coating.
, the coating obtained by the anti-light agent and the two-component anti-light coating have a low gloss; In addition, the experiment shows that the greater the difference in the activity of the two-part powder, the greater the surface roughness of the formation, the better the anti-light effect.
2.3 Coating water-resistant boiling study
Because the two-component powder coating is commonly used in aluminum profile curtain wall, outdoor building, hard metal components and other fields, so the water resistance of the coating is more concerned.
This study compared the heat-resistant two-component with the two-component powder coating, in which the gloss of the weather-resistant two-component coating prepared in this study was 23 and the gloss of the two-component coating was 32. Figure 2 shows a comparison of the water-cooking preservation rate of the weather-resistant two-component and the two-component powder coating.
From Figure 2, it can be seen that with the extension of the boiling time, the overall preservation rate of the coating gradually decreased, wherein the weather-resistant two-component coating in the initial 8h appeared after boiling the first rise and then decline trend, may be related to the boiling of water after the surface roughness decreased.
the temperature-resistant coating water cooking 24 h after the preservation rate remained above 50%, while the temperature preservation rate after the coating water boiling 6h is less than 50%.
This is mainly due to the weather-resistant coating resin body part of the water-resistant mesobenzene monosynthetic synthesis, and because of the high degree of energy containing the base group, cross-link density, so excellent water resistance.
2.4 Weather Resistance Study
In order to evaluate the weather resistance of the weather-resistant two-component coating more quickly, the coating was artificially accelerated UV aging test, and the experimental results were shown in Figure 3.
can be seen from Figure 3, weather-resistant two-group coating at 100h, the loss rate is less than 3%, no loss of light phenomenon, loss of light 0 level; At 360h, the loss rate is less than 15%, very slightly lost light, loss of 1 level;
to 500h, the loss rate is about 20% to 30%, there is a slight loss of light, loss of light 2 levels; By 600h, the loss rate is about 51% to 56%, severe loss of light, loss of light level 4, indicating a sharp decline in the weather resistance of the coating at this stage, serious degradation of the organic coating film.
two-group coating in 240h preservation rate of 61%, obvious loss of light, loss of light level 3; At 360h, the preservation rate is 33%, severe loss of light, loss of light level 4. By comparison, it can be found that the anti-aging time of the two-component coating is significantly longer than that of the two-component coating layer.
4 shows that the color difference under the aging of the weather-resistant two-component coating QUVB varies with the aging time.
From Figure 4, it can be seen that the color difference of the weather-resistant two-component coating is divided into two stages: before
500h, with the aging time increase the color difference also increased, slightly lost light to obvious loss of light, the color difference of the weather-resistant coating surface reached the maximum value at about 500h, this point in time the coating is basically at a critical point of rapid destruction;
500h to 700h, the weather resistance of the coating drops sharply, the organic coating film degrades seriously, and the surface powder increases.
Under the washing of condensate, resulting in a decrease in the concentration of organic coating phase changes, color difference changes mainly containing a small number of organic film fragments of inorganic fillers and after the color changes, the color difference is smaller
the color difference of the phosphor coating reaches the apes at 250 h, which is similar to the weather-resistant two-component coating, followed by further aging, the organic coating is powdered severely, the color difference decreases rapidly, and then changes little.
(1) Through the introduction of multi-official groups of the branching agent, obtained the inter-benzoic acid as the main unit, the viscosity of the appropriate two-part weather-resistant powder coating resin;
(2) by controlling the activity of the reaction system, high and low acid value dry mixed light can obtain a relatively ideal anti-light effect, after the glare of 21 to 26;
(3) The ultra-weather-resistant powder coating developed based on inter-benzoic acid has superior water-resistant cooking performance, water-resistant performance is better than that of the two-component coating of inter-weather resistance, and the water-cooking preservation rate after boiling 24h can still reach more than 50%;
(4) The preservation rate after 500h of the artificially accelerated UV aging test of a weather-resistant powder coating based on interphenyl xylene acid is about 70%, which is more than 2 times the aging-resistant time of the two-part resistance of the participants.