Synthesis and Research of TGIC System Powder Coatings Low Temperature Super Weatherproof Flexible Polyester Resin

Abstract: Effects on polyester resin and its powder coating properties by the dosing of TMP (trihydroxymethyl propane) and the flexibility and melting of polyester tree moons by studying chDA (1,4-cyclohexanedone) additions Melt viscosity, weather resistance and glassification temperature, the synthesis of TGIC system suitable for 170 degrees C low temperature curing of ultra-weather resistant anti-bend polyester resin, and through the DSC (differential thermal scanner) to study and analyze the curing behavior of powder coatings.
foreword
energy conservation and environmental protection is the main theme of today's world, because the VOC emissions of powder coatings near zero and other environmental performance outstanding, so that powder coatings will gradually replace solvent-based coatings. In recent years, with the increasing requirements of energy conservation and emission reduction, at the same time, powder coatings are used in outdoor buildings, automobiles, road facilities and other occasions are becoming more and more common, so that the demand for low temperature ultra-weather-resistant powder coatings is also increasingAlso because the powder coating to obtain ultra-weather-resistant low-temperature curing performance and relatively low price, the key factor is the development and research of low-temperature ultra-weather-resistant polyester resin.
Now on the market TGIC system low temperature ultra-weather-resistant polyester resin has appeared, because to ensure weather resistance, so the formulation of binary acid will choose a large number of IPA (interbenzene acid), but because of the rigid structure of IPA (inter-benzoic acid), will lead to powder coating flexibility is very poor, so, to obtain a certain flexibility of ultra-weather-resistant cured polyester resin is currently required to study the direction of the industry. In this paper, by examining the dosage of TMP (trihydroxymethyl propane), CHDA (1,4-cyclohexane methamphetamine), TPA (benzoic acid) and IPA (interbenzene) ratio, curing promoter dosage, to adjust the properties of polyester, synthesis suitable for TGIC 170 degrees C15min curing ultra-weather-resistant saturated polyester resin, to solve the problem of ultra-resistant polyester.
1 Experimental Part
1.1 Raw Materials
NPG (New Glycol), Industrial Grade, BASF Glycol Co., Ltd.; T (for parabens), Industrial Grade, Zhuhai BP Chemical Co., Ltd.; IPA (Interbenzene), Industrial Grade, Lotte Chemical Co., Ltd.; CHDA (1,4-Cyclo- Alkydyl acid), industrial grade, Eastman Chemical Co., Ltd.; TMP (trihydroxymethyl propane), industrial grade, Shandong Fufeng Baisto Chemical Co., Ltd.; 4100 (single butyl tin oxide), Jiangsu Haimen long-term; TGIC; curing promoter, titanium white powder, sulphate, sabbath, leveling agent, brightener, market.
1.2 Polyester resin synthesis process
add alcohols, acids and catalysts to the 30L homemade reactor, heat up to 240 degrees C under nitrogen protection, keep warm for about 3 hours, control acid values at 12-16mgKOH/g, after sampling acid values, cool down to 220C, add an acid extractor Heating up to 240 degrees C, insulation, 2 hours, control acid value in 47-50 or so, acid value qualified, began to vacuum, pressure at -0.095Mpa, until the acid value at 30-36KOH/g, after adding a curing promoter, stirring evenly after cooling to 200 degrees C.
1.3 Powder coating preparation
ingredients according to Table 1.
Then, after premixing, extrusion, cooling, grinding powder, screening, and then sprayed with manual electrostature powdering equipment on the descaled iron plate, and then put in a constant temperature oven at 170 degrees C cured 15min, wait until the powder coating, and then test the properties of the coating.
1.4 Performance characteristics
polyester resin acid value according to GB/T 6743-2008 test; The vitrification temperature and curing behavior of the powder are tested with the METLER-Tolido DSCI tester, the bend resistance is tested with the GB/T 6742-2007 standard type I. bending tester, and the viscosity test is tested at 200 degrees C with the U.S. Bole Fei CAP 2000-H plate viscosity meter.
2 Results and Discussion
2.1 TMP Dosing effects on polyester reaction activity and leveling
To obtain a low-temperature cured polyester resin from the TGIC system, there are currently two solutions, one is to increase the amount of TMP to increase the amount of polyester Energy, the other is to increase the content of curing promoter, but too much content will cause polyester viscosity is too high, and thus seriously affect the flow of powder coating, if the curing promoter dosage is too much, so that the activity of the powder is too high, easy to melt out when glued out or seriously affect the storage stability of the powder. So you have to find a suitable TMP plus. Chen Longcai and other studies have studied the relationship between TMP addition and powder gel time in polyester, and believe that the TMP addition of conventional short gelding polyester resin is generally 1.5%-1.6% of the total quality of the formula. Ma Zhiyi found that in the synthesis of polyester resins for cryogenic curing of the β-hydroxyacetalamide system, the TMP addition was relatively low viscosity and impact performance at 2.38% of the total mass of the formula.
the relevant data, we selected the following table 2 TMP addition to carry out the experiment, the test does not consider the effects of curing promoter.
after the above experiments, we found that the addition of TMP in 1.0%-1.5% is more reasonable, can get a more suitable viscosity, so that under the conditions of low temperature curing there is a relatively satisfactory plate level.
effect of the 2.2 CHDA addition on coating
ChDA dosing as a percentage of the quality in the formulation has an effect on the toughness of the coating toughness as shown in Table 3.
above experiments show that, first, the glass temperature of polyester did not decrease until chDA addition was 5%, but the decrease was relatively large after more than 7.5%. Second, with the increase of CHDA addition, the gel time does not change much, basically remains unchanged. Third, with the increasing amount of CHDA, the flexibility of polyester is getting better. Due to the influence of polyester cost and glass temperature, the experiment did not further increase the amount of CHDA. Studies such as jaundice show that polyester resins synthesized with CHDA have good hardness and elasticity. In terms of viscosity in the table, the viscosity of polyester resins remains basically the same as chDA additions increase.
effect of CHDA addition on aging performance is shown in Figure 1.
From Figure 1, we can see that as CHDA additions become longer and worse, polyester aging is getting worse and worse, but much better than the general general weather resistance level of outdoor polyester, which also from another level, CHDA weather resistance level is better than TPA, but worse than IPA weather resistance. Studies such as Nanrenzhi show that the reason for the poor weather resistance of polyester resins synthesized with benzoic acid is the absorption of 297nm of short ultraviolet rays on benzoic acid. Choose chDA this monolith because it can be seen as a product of TPA benzene cyclohydration, the maximum absorption wavelength of ultraviolet should not be at 297nm, so weather resistance will be better than TPA.
2.3 Curing reaction analysis
Figure 2 is an experimental synthesis of ultra-weather-resistant cryogenic curing flexible polyester resin powder coating from 10 degrees C to 250 degrees C heating rate of DSC non-temperature curing curve, powder 1 is a synthetic ultra-weather-resistant low-gentle polyester resin made of powder coating. From this we can see that the glass temperature of powder 1 is 53.17 degrees C, slightly lower than the glass temperature of powder 2 55.31 degrees C, but higher than the safe value of the storage stability of the powder at 50 degrees C. In terms of curing temperature, the cured PEA value of powder 1 is 161.92 degrees C, and the curing PEAK value of powder 2 is 186.87 degrees C, so powder 1 can be cured completely under the condition of 170 degrees C15min.
Figure 3 is a DSC curve obtained by the synthetic resin from 10 degrees C to 250 degrees C, and we can see from the figure that the glass temperature of the synthetic polyester resin is 61.96 degrees C, which also meets the glassing temperature requirements of the outdoor polyester resin to meet the storage stability requirements of polyester.
2.4 main performance indicators for powder coatings
Table 4 is a powder performance comparison between synthetic polyester resins and common ultra-weather-resistant polyester resins.
from Table 4, it can be seen that the powder coating prepared by synthetic resin is better flexible, has a high hardness and has a low curing temperature compared to the powder coating prepared by ordinary ultra-weather-resistant polyester. Due to the addition of an unconventional monomer such as CHDA, the weather resistance aspect is slightly sacrificed, but as can be seen from Figure 1, the weather resistance of synthetic resin-prepared powders is far ahead of ordinary outdoor weather-resistant polyester resins, and ultra-weather-resistant powder coatings can still be prepared.
3 Conclusion
Through experimental research, the most generally determined is that TMP accounts for 1.25% of the amount of feed, while adding the appropriate amount of CHDA and other unconventional monosomes, with a certain amount of curing promoter, we can get suitable for 17 Ultra-weather-resistant polyester resins cured at low temperatures of 0C/15min, which in turn have better bending properties than ordinary ultra-weather-resistant polyester resins, so they have a wider range of use areas and energy-saving and environmental protection properties than ordinary ultra-weather-resistant polyester.
Wen/Yu Haitao, Pan Jianrong, Liu Dongliang, Wang Xi
Zhejiang Guanghua Materials Technology Co.,