Saturated middle hydroxyl polyester resin for high flexibility powder coating and preparation method thereof

Abstract

The present invention relates to a saturated middle hydroxyl value polyester resin for high flexibility powder coating and a preparation method thereof. The curing film of the provided coating has excellent decorative and protective properties. The polyester resin prepared by the method has the characteristics of high molecular weight and narrow molecular weight distribution. A technical scheme is as below: a saturated terminated middle hydroxyl value polyester resin for a closed type isocyanate cured polyurethane powder coating is formed by melting and polymerization of the following main components: a polybasic alcohol component A. The preparation method of the saturated terminated middle hydroxyl value polyester resin comprises the following steps: (1) adding the polybasic alcohol component A, a polybasic alcohol component B, and an esterification catalyst component C; (2) conducting esterification reaction and insulating; (3) adding a first acid-terminated component D; (4) conducting a first pressure reduction reaction; (5) adding a second ethanol-terminated component E; (6) conducting a second pressure reduction reaction; (7) adding an antioxidant component F and a curing accelerator component G; and (8) discharging, cooling and crushing.

Description

technical field [0001] The invention relates to a saturated mid-hydroxyl polyester resin for powder coatings and a preparation method thereof, in particular to a saturated mid-hydroxyl polyester resin for high-flexibility powder coatings and a preparation method thereof. Background technique [0002] Due to its economy, environmental protection, high efficiency, and excellent performance, powder coatings are recognized as green and environmentally friendly coatings. First, its share in the coatings industry is steadily increasing, and it is widely used in home appliances, automobiles, aluminum profiles, construction and other fields. [0003] At present, the curing systems of powder coatings mainly include pure epoxy type, polyester-epoxy hybrid type and pure polyester type. Polyurethane powder coating is composed of hydroxyl polyester resin as the main resin, blocked isocyanate as curing agent, pigments, fillers, additives and other components. It is one of the pure polyes...

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Problems solved by technology

[0005] 1. Medium hydroxyl polyester resin is generally synthesized by one-step method. Due to the large number of end groups and high hydroxyl content, the molecular weight of the resin is small and the molecular weight distribution is wide. The performance of the cured coating film made of polyurethane powder coating is not good.

[0006] 2. Polyurethane powder coatings made of medium-hydroxyl polyester resins have high hydroxyl content, high cross-linking density and high hardness of the cured paint film, which in turn leads to increased brittleness of the paint film, insufficient flexibility and toughness, and poor mechanical properties (impact resistance and bending) poor

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