New breakthrough in HAA system matting

New breakthrough in HAA system matting

Zhou Shaoying Hu Sijun (Wuhan Yincai Technology Co., LTD.)

Abstract: This paper evaluates the performance and influencing factors of L2019, a novel HAA matting curing agent developed by Wuhan Yincai Technology Co., Ltd., while assessing its advantages and limitations. The L2019 HAA matting curing agent effectively reduces production costs, enables single-extrusion with sustained and reliable matting effects, simplifies process steps, and delivers excellent surface smoothness of coatings. It achieves a minimum gloss level of 15°.

I. Background

The outdoor powder coating market currently features two primary curing systems: TGIC and HAA. Due to TGIC's potential genotoxicity and irritancy, the EU has banned its use in curing agents, with HAA being the preferred alternative. China is also phasing out TGIC applications, while HAA systems are gaining prominence in outdoor coatings. Although HAA systems still face challenges like yellowing, pinhole formation, and poor gloss control, technological advancements make their replacement inevitable. After years of development, TGIC systems have well-established in gloss control techniques, utilizing methods including filler-based, wax-based additives, dry-mixing, acrylic curing agents, and composite physical matting agents that cover most gloss ranges. However, HAA systems still struggle with rapid carboxylate polyester reaction rates due to the absence of suitable accelerators. Currently, the most common HAA curing method involves combining acrylic curing agents with HAA to produce gloss coatings below 10%, while other wax-based or filler-based methods struggle to achieve gloss levels below 40%. Maintaining gloss between 10-40% remains a persistent challenge. The current mainstream method for achieving 10-40% gloss through matting primarily relies on dry-mixing techniques. This process requires separately preparing two powder coatings with different reaction rates, followed by thorough blending to produce matte finishes. While the HAA system remains a viable solution until better matting methods emerge, it faces challenges including complex production processes, poor stability, and insufficient film fineness. Wuhan Yincai Technology Co., Ltd. (hereinafter "Wuhan Yincai") has been dedicated to HAA-based matting research, with their preliminary breakthrough being the L2019 matting curing agent. This innovative formulation enables single-extrusion production of matte coatings exceeding 15% gloss. Compared to conventional blending methods, the L2019 curing agent simplifies the production process by allowing direct extrusion of matting agents, offering greater operational efficiency, better gloss reproducibility, with superior film leveling and fineness. However, the L2019 matting curing agent still has many areas requiring refinement and enhancement. This paper summarizes our research findings on the L2019 matting curing agent. Overall, the L2019 matting curing agent demonstrates significant potential as an HAA-based system matting agent. Given the growing emphasis on environmental sustainability, it is projected to have promising market prospects.

II. THE EXPERIMENTAL PART

2.1 Main equipment and experimental instruments

DE-500g Universal High-Speed Grinder (Zhejiang Hongjingtian Industry & Trade Co., Ltd.); ACM-02 Experimental Mill (Yantai Jiecheng Powder Equipment Co., Ltd.); TSE26C Twin-Screw Extruder (Yantai Yuanfeng Electromechanical Equipment Co., Ltd.); SLJ-30A Twin-Screw Extruder (Yantai Donghui Powder Equipment Co., Ltd.); SJ-5 Compact Electrostatic Spray System with Electrostatic Spray Gun; QCJ Paint Film Impact Tester (Changzhou Weiye Coatings Machinery Factory); DHG-2 Advanced Electric Heating Constant-Temperature Drum Dryer (Taizhou Kest Industrial Furnace Co., Ltd.); Gloss Tester (Guangzhou Baogeda Precision Instrument Co., Ltd.); BGD 881/S Programmable Salt Spray Corrosion Test Chamber (Guangzhou Baogeda Precision Instrument Co., Ltd.), etc.

2.2 Raw materials

NH3307, NH3309 (Guangzhou Qingtian Material Technology Co., LTD); GH3326, GH3327, GH2209 (Zhejiang Guanghua Technology Co., Ltd.); 9310TG, 9510,9309,9331, P9337PR (XinZhongFa Polymer Materials Co., Ltd.); SJ4868, SJ5101, SJ4B (Anhui Shenjian New Material Co., Ltd.); FL2006 (Yantai Fenglin New Material Co., Ltd.); 2441-2, 2630-2 (Zhanxin Resin Co., Ltd.) ZJ9104, ZJ9104DW (Anhui Zhengjie Technology Co., Ltd.); LR-01 (Guangdong Yinyang Resin Co., Ltd.); L2019 Matteing Curing Agent and Leveling Agent L88, Benzoin L307, Defoaming Agent L307B (Wuhan Yincai Technology Co., Ltd.); Matting Barium Sulfate and Ultra-fine Barium Sulfate (Hanyu New Materials Co., Ltd.); Precipitated Barium Sulfate (Shanxi Fuhua Chemical Co., Ltd.).

2.3 Testing and characterization methods

The gloss measurement was conducted in accordance with the national standard GB/T 9754-2007 "Color Paints and Coatings-Measurement of 20 °, 60 °, and 85 ° Gloss for Metal-Free Paints". The impact resistance performance tests followed the national standard GB/T1732-93. "Test Method for Impact Resistance of Paint Film". Salt spray performance test is according to the national standard GB/T1771-2007 "Test Method for Neutral Salt Spray Resistance of Paint and Clearing".

2.4 Powder coatings and coating preparation

     The components were weighed according to the mass ratio of various substances in the formula, and then fully crushed and pre-mixed with a pulverizer. After uniform preparation, the material undergoes melt extrusion in a twin-screw extruder at specified temperatures. The extruded sheet is cooled, crushed, and sieved before being electrostatically sprayed onto tinplate for thermal curing and film formation. Subsequent performance tests are conducted on the coated film. Extrusion conditions: Zone 1 at 100℃, Zone 2 at 110℃. Curing conditions: 200℃ * 15min。

III. Results and discussion

3.1 Conduct gloss test with different amount of L2019 in outdoor polyester, observe the effect of different amount on the board surface and determine the appropriate amount range.

In outdoor polyester boards, gloss levels initially decrease and then increase with higher L2019 matting curing agent percentage. This behavior stems from the dual functionality of L2019 curing agents in the reaction system – their simultaneous matting and curing properties. When added in low percentage, insufficient curing leads to slightly inferior impact performance. However, beyond 3%, increased dosage results in enhanced gloss levels, a characteristic distinct from conventional matting agents. At the minimum 3%, the gloss reaches approximately 25°.

3.2 Select some common different models of outdoor polyester to test the matting effect of L2019 matting curing agent on different outdoor TGIC polyester and HAA polyester.

Through testing common TGIC and HAA polyester types in the market, we found that the 3% dosage of L2019 matting curing agent achieves a gloss level of around 25° in most TGIC polyesters, while reaching approximately 30° in HAA polyesters. Notably, a specific silver-plated polyester model can achieve a minimum gloss of 15°. This may be attributed to variations in polyester formulations, monomer compositions, and acid value levels. However, within the same system, L2019 matting curing agent demonstrates satisfactory gloss stability and exhibits good adaptability to various polyester materials.

3.3 With the increase dosage of L2019 matting curing agent, the gloss also increases. Different from the use method of conventional matting curing agent, in order to avoid mistakes in practical use, L2019 matting curing agent can be combined with HAA to adjust the matting.

When HAA curing agent is used to replace part of L2019 matting curing agent, the gloss of the plate will increase. The more the replacement is done, the higher the gloss. The L2019 matting curing agent can be partially replaced by HAA curing agent in order to adjust gloss.

3.4 Barium sulfate is the primary filler in powder coatings, available in two forms: natural and synthetic. Based on manufacturing processes, preparation methods, purity levels, and particle sizes, it is classified into three types: matting barium sulfate, ultra-fine barium sulfate, and precipitated barium sulfate. These three categories are currently the most widely used in the powder coating industry. This study investigates their effects on L2019 matting curing agents.

The L2019 matting curing agent has little difference in the matting effect in different fillers, so there is no selective for filler.

3.5 The effect of extrusion and melting can be affected by the difference in length-to-diameter ratio, equipment process and extrusion screw of different manufacturers. The effect of different extruders on the gloss of L2019 matting curing agent was tested.

Different extruders have little effect on the gloss of L2019 matting curing agent, and L2019 matting curing agent has good adaptability to different extruders, and the coating gloss is stable.

3.6 Many matting agents fluctuate greatly in gloss during cold oven baking and hot oven baking. The gloss change of L2019 matting curing agent during cold oven baking and hot oven baking is tested.

The gloss fluctuation of L2019 matte curing agent in cold oven baking and normal baking is not significant, and it has good adaptability.

3.7 The effect of different extrusion temperatures on the gloss of L2019 matting curing agent was tested.

The effect of different extrusion temperature on the gloss of L2019 matting curing agent is negligible, only slight fluctuation.

3.8 Test the neutral salt spray resistance of several different polyester coatings.

The test substrate is tinplate, and two diagonal lines are drawn on the coating, and the scratch depth is to the substrate.

The neutral salt spray resistance of the matte coating prepared from several polyesters is excellent, which can meet the application requirements of aluminum profiles and other industries.

IV. CONCLUSION

In recent years, powder coatings have flourished due to their advantages of being solvent-free, non-polluting, environmentally friendly, and energy-efficient. With the world's growing emphasis on environmental protection, it is likely that the TGIC system will be replaced by other systems. Wuhan Yincai has always adhered to eco-friendly principles and has been dedicated to the research and development of HAA system matting. The L2019 matting curing agent demonstrates remarkable matting performance in outdoor HAA systems, which is highly encouraging. Compared to conventional HAA dry-mixed matting, the L2019 curing agent allows one-step extrusion matting with simplified processes, stable matting performance, and broad adaptability to polyester materials, achieving 15%-50% gloss, coating leveling is excellent. Until today, domestic industrial production, Wuhan Yincai is the only one.