Acrylic coatings mainly include thermoplastic acrylic coatings, thermosetting acrylic coatings, high solid acrylic coatings, acrylic latex coatings, water-diluted acrylic resin coatings.
(1) The main component of thermoplastic acrylic coatings is polymethyl methacrylate, but the pure polymethyl methacrylate is too brittle, and the adhesion to the substrate is poor, the solvent is not easy to play out, because of its high glass transition temperature. Solvent-based thermoplastic acrylic coatings have a low solid content (about 12% volume concentration). Since the 1970s, the consumption of solvent-based thermoplastic acrylic coatings has dropped sharply. Instead, thermosetting acrylic coatings have been developed, especially high solid acrylic coatings.
(2) Thermosetting acrylic resin can increase the content of non-volatile substances in the coating, and cross-linking occurs during the curing process after the coating is applied. Thermosetting acrylic coatings not only have higher solid content, but also have better gloss and appearance, better chemical resistance, solvent resistance, alkali resistance, heat resistance, etc. The disadvantage is that they can not be stored for a long time. Thermosetting acrylic coatings are melamine formaldehyde resin or polyisocyanate as crosslinking agent.
(3) it is difficult to prepare acrylic resin for high solid coatings. In general, the volume solid content of high solid polyester coatings can reach 65% ~ 70%. Polyester is easy to ensure that each molecule has more than two hydroxyl groups, but acrylic resin is difficult to achieve more than two hydroxyl groups per molecule. To solve this problem, one is to increase the amount of hydroxyethyl methacrylate (HEMA), such as 15%; the other is to make the molecular weight distribution of the resin as narrow as possible, the distribution of polar groups as uniform as possible. The latter is very important in high solid coatings. At present, the volume solid content of high solid acrylic resin coatings under spraying viscosity can reach 54% - 56% (the weight solid content can reach 70% - 72%).
(4) acrylate latex is the best and most important latex. Compared with polyvinyl acetate emulsion, acrylic emulsion improved the flexibility and adhesion of the coating, and the cost was moderate. In addition, its outdoor durability, including anti-ultraviolet degradation, has been significantly improved, so it has been used in wall building coatings, scrubbable floor varnish, pigment printing paste.
(5) Water-diluted acrylic resin is a thermosetting resin. The water-soluble polymer is first prepared and then crosslinked into a water-resistant and tough film. Water-diluted acrylic coatings can be used in spraying, dipping and other occasions, the most successful application is canned interior coating. Another important application is electrophoretic paint.