Analysis of the development trend of polyester resins used in powder coatings in China

China Coatings Online News News First, environmental protection
In recent years, by the impact of TGIC toxicity, as well as people's environmental awareness, the use of non-toxic environmentally friendly hydroxyalinelamide (HAA) solidification system polyester resin Demand is growing, according to 2012 industry statistics, compared to 2009 HAA polyester growth of 12.1%, while TGIC curing type increased by only about 2%, it can be clearly felt that environmentally friendly polyester more and more attention. Because the HAA system has a high reaction activity, and when cured, the by-product water is released, which can easily cause the phenomenon of thick membrane pinholes. On the other hand, due to the high reaction activity, the curing speed is fast, and the leveling performance of the system is also poor. Moreever, due to the poor performance of the HAA system against yellowing, it is easy to yellow when cured and baked. Domestic research, mainly focused on solving or circumventing the shortcomings of HAA to study alternative TGIC varieties. When synthesizing polyester resins for β-hydroxyacetalamide-cured weather-resistant powder coatings, the Tg, viscosity and reaction activity of the resin are controlled mainly by designing different reactant monomers, and the viscosity of the system is reduced by the selection of the polyester monomer structure of the resin to obtain the resins that meet the conditions of use.
trend towards environmental protection is the study of polyester resins that do not contain organo tin. At present, polyester resin synthesis of powder coatings using single-butyl tin oxide as a catalyst, because of the high catalytic efficiency of such catalysts, uniform synthesis reaction, synthetic resin color, at present in the domestic polyester plant has been widely used. In recent years, by Europe and the United States and other developed countries market influence, there have been many countries issued relevant regulations or standards to limit the use of organo tin. The organotin compounds of concern in Appendix VXII of the EU REACH regulations include TBT, tribenzene tin compounds and butyltin (DBT) and DSDt (DOT) compounds, the first of which is officially limited to 1 July 2010 and the 1 January 2012; Downstream manufacturers such as IKEA have proposed that the content of coated organotin needs to be controlled below 1ppm, pan-art, etc., through the study of non-butyl tin catalyst synthetic powder coating polyester to obtain a resin equivalent to the performance of conventional organic tin catalysts.
2. Energy saving
With the increasing national demand for energy conservation and emission reduction, more and more enterprises and institutions began to attach importance to the research and development and application of energy saving and emission reduction technology, in the field of powder is mainly manifested in the application and promotion of low-temperature curing type and rapid curing type powder coating, for the current low-temperature cured powder coating mainly depends on the research and development of low-temperature cured polyester resin. At present, the curing temperature of traditional powder coatings is generally 180 degrees C-200 degrees C/10 to 20min, the general baking temperature is reduced by 10 degrees C, can save about 10%. For low temperature curing, the more mature varieties in the mixing type (epoxy curing type), mainly reached the curing level of 160 degrees C/10-15min, the appearance of orange peel is heavier, mainly obtained by adding curing promoter; Primid system mainly has 95/5 type of acid value of about 30, can achieve 160 degrees C /15min curing, and 160 degrees C/10min more acid value of about 50 93/7 type, by increasing the acid value, to obtain a higher reaction activity; The more mature varieties on the TGIC system can meet the curing of 160 degrees C/15min, mainly through the combination of flexible monosome selection and curing promoter, suitable for low-temperature curing curing promoter mainly have 4 categories: the alkali represented by seramine, halogenation? Represented by buzzing salts, cation compounds represented by acetyl acetone cobalt on behalf of metal chelates and boron teflon. At present, Li Yong and so on through the introduction of different reaction activity and soft monomers such as hexydiacid, methyl propylene glycol, cyclohexane methamphetamine, etc., to reduce the viscosity of the system, change the molecular structure of polyester resin, synthesis suitable for β-hydroxyacetamide curing agent 160 degrees C / 15min curing use of end-oxycodone polyester resin, the basic performance and conventional resin 180 degrees C / 15min equivalent. Should Mingyou and other studies of acid value of 90 to 110mgKOH/g, melt viscosity of 5000 to 15000cp (at 130 degrees C), Tg is 42 to 52 degrees C of mixed polyester resin, by adding a ringstructure of RB31 curing promoter dosage of 2%, can meet 130/25min. Wang Zhiguo and so on through the use of antibutene dicing acid, shunbutene disic and other monoglycerides to raise low temperature reaction activity, in the soft good monogamed hedic acid, sunflower acid and curing promoter with the synthesis of acid values of 30 to 40 mg KOH/g, Polyester resins for outdoor powder coatings with Tgs of 55 to 62 degrees C can be used for curing TGIC systems at 140 degrees C/30min, 150 degrees C/20min, and 160 degrees C/15min.
, another aspect of energy conservation is rapid curing. This is concentrated in achieving energy savings by reducing the curing reaction time and achieving high turnover efficiency. Powder downstream manufacturers of the curing temperature is generally prone to fluctuations, often low, in order to better obtain a stable degree of curing, many manufacturers often in the conventional curing temperature of the product based on the addition of curing promoter, or directly choose low-temperature curing or rapid curing products.
Third, functional
with the increasingly fierce competition of powder coatings, the general industry profits are getting lower and lower, in order to obtain better profit returns, more and more enterprises began to turn to higher value-added market segments; On the other hand, with the expansion of powder coatings, market demand is becoming more and more diversified, which also provides an opportunity for the polyester industry to develop in a new direction. In general, more and more polyester resin research and development tend to functional development. Specifically reflected in the ultra-weather-resistant powder coating polyester series (large curtain wall, small flower, solar water heater), high temperature powder coating with polyester, thermal transfer powder coating with polyester, high decorative powder coating with polyester, high toughness (roll) / impact-resistant attenuation of powder coatings with polyester, thin Polyester for powder coatings, polyester for water-resistant powder coatings, polyester modified technology research (silicone, acrylic, fluoro monomer and other modified), one extrusion of anti-light powder coatings with polyester, overspending polyester, semi-crystalline polyester, etc.
Among them, the synthesis of polyester on high temperature-resistant powder coating mainly takes the method of increasing molecular weight, increasing cross-link density, adding antioxidants to improve the temperature resistance level, when using ordinary pigments such as niobium sulfate, titanium dioxide, etc., can generally reach 300 degrees C level, if polyester using silicone modified and talcum powder, hollow powder, quartz powder, mica powder as a filler to prepare powder paint can obtain a higher temperature level. Overspending polyester generally uses multi-function groups such as dihydroxymethyl propane (DTMP) and glucodol as nuclear monomers, and AB-type monomers such as dihydroxymethyl acid (DMPA) as branch-like growth chains Synthesis, because the overspending molecule is spherical, and the end base is mostly a hydroxyl or hydroxyl class of the official energy group, melting viscosity is also low, so it has a high reaction activity, so in low temperature curing and high level powder coating has a greater prospect. Semi-crystalline resin is also one of the hot topics in recent years, characterized by high Tg, low melt viscosity, excellent leveling performance after curing, and high potential value in solving powder leveling bottlenecks.
In the research of polyester modified powder coating, Fan Hong and so on added a small amount of silicone active resin Z-6018 in the fusion polymerization process of polyester, obtained silicone modified polyester, the glass temperature of modified resin, melting viscosity decreased slightly, the weather resistance of the cured coating film improved, when the added amount of 1%, the comprehensive performance was better. In the fluorine-containing modified polyester, Jinyunquan reacts with alkyl binary alcohol, cyclic acid anhydride, fluorine-free monocyclic oxygen-based compounds and fluorine-containing monocyclic oxygen-based compounds, and the reaction product is diluted with acetone. Stir to add to the precipitation of distilled water to obtain fluoro polyester resin, prepared into a powder coating, the hardness of the coating film, boiling water, acid and alkalinity have been improved, and the adhesion to the substrate has not been reduced.
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