Application of HAA and matters needing attention

HAA, also known as hydroxyalkyl amide, is a commonly used curing agent in polyester powder coatings. TGIC (triglycidyl isocyanurate) has been widely used as a pure polyester curing agent for powder coatings for a long time. However, due to the toxicity of TGIC and its environmental hazards, the Ministry of Industry and Information Technology of the People's Republic of China included it in the elimination of backward production process equipment and products in 2011 . Therefore, powder coatings cured with HAA and improved curing agents will gradually become the main force of outdoor weather-resistant powders. ZJ-552 produced by Anhui Huizhou Zhengjie Technology Co., Ltd. is this type of product, which has good coating film pinhole suppression and yellowing resistance.

Technical index of HAA for polyester resin powder coating

Pay attention to the following matters during the use of HAA:

1. The matching problem with polyester resin
Due to the fast reaction activity of HAA, traditional TGIC curing polyester should not be used, but HAA special polyester should be used; for example, ZJ9104 produced by Huangshan Zhengjie New Material Co., Ltd. has a curing ratio of 96/4; ZJ9104B, ZJ9104D, ZJ9104DL The curing ratio is 95/5.

2. Film pinholes and yellowing resistance problems

When HAA reacts with polyester curing, water molecules are generated, and the surface of the coating film is prone to pinholes and other defects. Ordinary polyester is not suitable for thick coating above 100μm. The ZJ9104 polyester produced by Huangshan Zhengjie New Material Co., Ltd. is matched with HAA. With a reasonable formulation process, there are no pinholes on the surface of a thick coating of about 130μm-150μm; in addition, adding about 0.5% of the degassing agent to the formula can achieve the effect of suppressing the pinholes of the coating film. Taking into account the effect of benzoin on the yellowing of the coating film, its dosage should be controlled at about 0.3% of the total film-forming material, and the dosage should be kept as low as possible. When producing white or light-colored powders, add about 0.5% of antioxidant to the formula It can improve the yellowing resistance of the coating film.

3. The problem of powder absorption

Since HAA is a hydrophilic compound, when storing and storing the prepared powder coating, it should be waterproof and moisture-proof. After the powder absorbs moisture, the powder is not well applied, and the adhesion of the coating film is poor.

Reference formula:

Temperature in the first zone: 75℃ Temperature in the second zone: 120℃ Temperature in the third zone: 85℃ Screw speed: 40-50HZ Screen mesh: 160-180 mesh

Baking temperature: 180℃×15min Film thickness: 80-120μm Resin content: 55-60%