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

Abstract: Effects on polyester resins and their powder coating properties by the dosing of TMP (trihydroxymethyl propane) and balancing the flexibility and melting of polyester resins by studying chDA (1,4-cyclohexanedone) additions Viscosity, weather resistance and glassing temperature, the synthesis of TGIC system suitable for 170 degrees C low temperature curing of ultra-weather resistant anti-bend polyester resin, and through DSC (differential thermal scanner) to study and analyze the curing behavior of powder coatings.
keywords: low temperature curing, ultra-weather resistance, flexibility, powder coatings
foreword
energy conservation and environmental protection is the main theme of the world today, due to the VOC emissions of powder coatings nearly 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

. Also 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 (interbenzene acid), will lead to powder coating flexibility is very poor, so, to obtain a certain flexibility of ultra-resistant cryogenic cured polyester resin is currently required to study the direction of the industry.
this paper examines the ratio of TMP (trihydroxymethyl propane), CHDA (1,4-cyclohexanedone), PTA (paraben) and IPA (interphenyl xylene) The amount of curing promoter to adjust the properties of polyester, the synthesis of suitable for TGIC 170 degrees C15min curing of ultra-weather-resistant saturated polyester resin, to solve the problem of ultra-weather-resistant polyester resin flexibility.
1 TMP dosing effect on polyester resin reaction activity and levels
To obtain low-temperature cured polyester resins in TGIC systems, there are currently two solutions, one is to increase the amount of TMP to improve the function of polyester, the other Is to increase the content of curing promoter, but too much TMP content will cause polyester viscosity is too high, and then 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 extruded when gel 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 low-temperature cured polyester resins for beta-hydroxyacetamide systems, TMP addition was relatively low viscosity and impact performance at 2.38% of the total formulation mass.
the relevant data, we selected several TMP additions in the following table for the experiment, in which the effects of curing promoters were not considered first.
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 CHDA addition on coating
. ChDA dosing as a percentage of the quality in the formulation, the effect on the toughness of the coating toughness is shown in the table below
Note: The above polyester formulation alcohol is NPG, TMP, acid is IPA and CHDA
above experiments show that First, when chDA addition is less than 5%, the glass temperature of polyester basically does not decrease, but after more than 7.5%, the decline is relatively large; Third, as chDA additions continue to increase, the flexibility of polyester continues to improve. 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 addition increases.
effect of CHDA addition on aging performance is shown in Figure 1 . Note: Polyester 1, 2, 3, 4, 5 CHDA plus 0%, 2.5%, 5%, 7.5%, 12.5%, polyester 6 is a common weather-resistant level of outdoor polyester, aging standard is GSB AL631
Figure 1 we can see that as CHDA additions become longer and worse, polyester aging is getting 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 PTA, but worse than IPA weather resistance. Studies such as Nanrenzhi have shown that the reason for the poor weather resistance of polyester resins synthesized with benzoic acid is the absorption of 297nm of short ultraviolet light on benzoic acid. Choose chDA this monolith because it can be seen as a product of PTA benzene cyclohydration, the maximum absorption wavelength of ultraviolet should not be at 297nm, so weather resistance will be better than TPA.
3 Curing reaction analysis
Figure 2 is a powder coating made of experimentally synthesized ultra-weather-resistant cryogenic cured flexible polyester resin from 10 degrees C to a DSC non-temperature curing curve of 250 degrees C at a heating rate of 10 degrees C/min, powder 1 is a powder made of synthetic ultra-weather-resistant low-gentle polyester resin, powder 2 is a powder made of ordinary ultra-weather-resistant polyester resin. 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 curing PEAK 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 the DSC curve obtained by the synthetic resin from 10 degrees C to 250 degrees C from 10 degrees C/min, 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 glass temperature requirements of outdoor polyester resins to meet the storage stability requirements of polyester.
4 Comparison of the main performance indicators of powder coatings
the table below is a powder performance comparison of synthetic polyester resin and ordinary ultra-weather-resistant polyester resins
it can be seen that the powder coating prepared by synthetic resins is compared to powder coatings prepared by ordinary ultra-weather-resistant polyester, with good flexibility, high hardness and low curing temperature. 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.
Conclusion
Through experimental research, the total determination is that TMP accounted for 1.25% of the amount of feed, while adding the appropriate amount of CHDA and other unconventional monomers, with a certain amount of curing promoter, we can get suitable for 170 degrees C15min low temperature curing ultra-weather-resistant polyester resin, this polyester than ordinary ultra-resistant polyester resin has better bending performance, so it has more energy-saving than ordinary ultra-resistant polyester use.
: 2017 China Powder Coatings Industry Annual Meeting
Hao Haitao, Pan Jianrong, Liu Dongliang, Wang Xi/Zhejiang Guanghua Materials Technology Co.,
.