HAA-cured high-leveling and anti-thick-coating pinhole polyester resin, preparation method and application thereof

Abstract

The invention, which belongs to the technical field of preparation of polyester resin, particularly relates to polyester resin for a high-leveling and anti-thick pinhole type HAA system as well as a preparation method and application of the polyester resin. The HAA-cured high-leveling and anti-thick pinhole coating polyester resin provided by the invention is characterized in that the polyester resin is mainly prepared by carrying out polymerization reaction on terephthalic acid, flexible long-chain dicarboxylic acid, neopentyl glycol, pentaerythritol dioleate, polypropylene glycol 400, 1, 2-octanediol and hexamethylene diisocyanate. According to the polyester resin and the preparation method thereof, when polyester resin is prepared, no small molecular substance escapes in the curing process; the thick pinhole resistance is ensured, the finally obtained polyester resin and the curing agent HAA can be cured at a low temperature (140 DEG C / 15 min) by combining proper synthesis process conditions, the finally cured film has good leveling property and strong thick pinhole resistance; and the basic performance also completely meets the conventional requirements of the powder coating.

Description

Technical field [0001] The invention belongs to the technical field of polyester resin preparation, and in particular relates to a polyester resin for high-leveling, thick-coating-resistant pinhole HAA systems and a preparation method thereof, and the application of the above-mentioned polyester resin in powder coatings. Background technique [0002] Traditional HAA powder coatings are cured using carboxyl-terminated pure polyester and HAA hydroxyl groups. Due to the curing process, small molecules of water will escape from the coating film, resulting in obvious pinholes on the surface of the cured coating film. Especially for the film with a large coating thickness, such as the film thickness ≥110μm, it is especially serious. Due to this problem, it is difficult to obtain the coating film of the HAA system powder coating that can achieve both low temperature curing and high leveling. [0003] Patent document ZL201810445015.7 is a high-leveling coating film obtained by reducing the...

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Problems solved by technology

[0002] The traditional HAA powder coating is cured by carboxy-terminated pure polyester and HAA hydroxyl groups. Since the curing process produces small molecules of water, it will escape from the coating film, resulting in obvious pinholes on the surface of the cured coating film. Especially for the thicker film layer such as film thickness ≥ 110μm, due to the existence of this problem, it is difficult to obtain a coating film that can achieve low temperature curing and high leveling in HAA system powder coatings

[0003] Patent document ZL201810445015.7 is to reduce the softening point of polyester resin, enhance fluidity, and at the same time use high temperature (180°C / 15min) during curing to reduce the hardness of the coating film and facilitate the escape of water molecules to obtain a high leveling coating film. However, the thickness of the coating film is conventional, such as 60-80 μm, and high leveling cannot be achieved for thick coatings (film thickness ≥ 110 μm) that require high corrosion resistance.

ZL201811478412.0 is to reduce the acid value of polyester resin, and then reduce the amount of HAA in the powder coating formulation to reduce the curing speed, so as to delay the escape of water from the coating film and reduce the number of pinholes. However, due to the low activity of carboxyl groups, As a result, the curing time is too long. Generally, it takes about 30 minutes to cure completely at 180°C. Moreover, due to the large reduction in the amount of four-functional HAA, the hardness and water resistance of the coating film are also poor, and finally it cannot fundamentally solve the problem of thick coating (film Thickness ≥ 130μm) the problem of obvious pinholes

ZL 201110112793.2 is mainly aimed at improving the pinhole problem caused by too fast rise in viscosity during the curing process of powder coatings, by reducing the curing speed to improve the pinhole situation, but because the raw materials for curing include polyurethane resin, carboxyl polyester resin, etc., Uneven curing speed is prone to extinction phenomenon, which brings no change to production, and because it reduces the curing speed, it leads to a longer curing time, reaching 20min, which is not conducive to energy saving. At the same time, due to the existence of carboxy polyester resin , the curing principle has not changed, and small molecules of water still escape during the curing process, and pinholes are still unavoidable, especially for thick coatings with a film size of 110 μm or more.

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