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Discussion on waterborne coating resin

Water based coatings are an important development direction among the four environmentally friendly coatings products (water-based coatings, powder coatings, high solid coatings and radiation curing coatings) for sustainable development. Compared with other kinds of green coatings, waterborne coatings have many advantages, such as many ways, wide application, simple coating, etc. In China, the development of water-based coatings is concerned and loved by the majority of coating people. Water based coatings have been widely used in the field of architectural coatings, but in the field of industrial coatings, water-based coatings still account for a small proportion. From the point of view of the basic composition of the coating, the resin used in water-based coating is one of the most important factors. There are many disadvantages in waterborne coatings, such as poor quick drying, easy water absorption after film forming, and insufficient mechanical properties of the film. In recent years, the development of high-performance water-based coating resins suitable for different application scenarios has become a hot research and key development direction in the field of water-based coatings.

Types of waterborne coating resins

The resin for high performance waterborne coatings was first introduced from abroad, and new products of waterborne coatings were gradually developed in China. Later, it began to develop high-performance water-based resins by itself. With the introduction of advanced new water-based resin products, the film performance of its coating products gradually developed to meet the requirements of resins for industrial water-based coatings. The commonly used resins in waterborne coatings include water-resistant soap free acrylic lotion, waterborne polyurethane resin, waterborne epoxy resin, waterborne alkyd resin, etc. Some scientists and technicians have developed organic-inorganic hybrid waterborne resin (carbon titanium cage waterborne resin), and its application field is being further explored.

Application of Waterborne Coatings

In the application of wood paint, the proportion of water-based paint is not high. The existing application types are mainly acrylic lotion. One component self crosslinking acrylic lotion and two-component acrylic polyurethane can be used for primer and surface coating respectively. The performance of the two-component resin system can be comparable to that of the solvent based resin.

The application of water-based coatings on the surface of plastic products mainly lies in that the surface tension of PE, PP and other plastics is too small, the polarity is low, and the adhesion of water-based resins on their surfaces is weak. For the technical development of water-based coatings for plastic products, how to improve the interaction between coatings and substrates is a key technical problem that must be solved. At present, the comprehensive application performance of waterborne two-component polyurethane on the surface of plastic products is the best, and the performance of other types of waterborne coatings needs to be continuously improved.

In the light anti-corrosion field, water-based resin can also meet the relatively low anti-corrosion requirements, and has been applied in agricultural machinery, machine tools, hardware appliances and other fields. The overall hydration of automotive coatings is difficult. The primer can be watered by electrophoretic coating, while the intermediate coating and finishing coat need to integrate the advantages of all parties to develop innovative technologies under the requirements of national policies and environmental protection regulations.

Water based coatings are also being developed in leather textile and other fields. Polyurethane is the main water-based coating resin used for leather, which has the advantages of brightness, good hand feel and wear resistance. There are also a small amount of acrylic water-based products. In the textile industry, in recent years, there have been many powerful enterprises developing related businesses in the field of water-based paint ink in China. Products that are more in line with the personalized requirements of young people and the characteristics of small batch customization are developing rapidly. However, the proportion of water-based in this field in China is still very low and the market potential is huge.

Typical products of Waterborne Coatings

Bayer, BASF, Rohm Haas and Mitsui abroad; Domestic Wanhua, huajingsi, Qixiang Qingchen and other enterprises have corresponding high-performance waterborne resin products.

Problems in Waterborne Coatings

Water-based resins generally have a large number of hydrophilic groups, and the water resistance of the coating formed a group of contradictions with these hydrophilic substances. At present, soap free lotion and self crosslinking lotion have been developed to reduce the use of hydrophilic emulsifiers and reduce the absorption of water by increasing the crosslinking density. However, there is still a big gap between the overall water resistance and the solvent type. In addition, the form of waterborne resin is mainly lotion (such as acrylic acid) or dispersion (such as polyurethane). The gloss after film forming is not as good as that of solvent type. The use of water-based resins is limited in the application fields with high requirements for high gloss.