At present, the primary work of the coatings industry is to develop four types of environmentally friendly coatings. Secondly, it takes time to achieve this goal. Solvent-based coatings also occupy a considerable proportion of the transitional stage. It is also a system to replace toxic solvents with efficient and non-toxic solvents. An important task at present. Starting from the concept of sustainable development, the development of renewable organic solvent resources is the third task before paint workers. The four types of environmentally friendly coatings that the coatings industry will focus on in the future include:
1,high solids coating
High solids solvent-based coatings (HSSC) are also called VOC solvent-based coatings. The volume of solids (NVV) of traditional solvent-based thermosetting coatings is usually about 25-35%, and some thermoplastic coatings will be lower.
There is no unified statement on the definition of high-solids coatings. There is a reference in our country that high-solids coatings refer to coatings with a solid content greater than or equal to 70% when sprayed. Some international references are that for car flash metallic paints (or topcoat base paints), the high solids refer to around 45NVV; for high pigment primers, the high solids may be 50NVV. This requires that the molecular weight of the synthetic resin used in the coating and the average functionality of each molecule must be reduced and the molecular weight distribution narrowed. In this case, it is difficult to maintain the function of the coating film at the same time. Therefore, the development of new cross-linking resin synthesis technology and strict control of the curing conditions of the coating film have become the key to the problem. At the same time, the realization of this type of coating also only reduces the amount of some organic solvents.
2, solvent-free paint
The so-called solvent-free coating is to use an organic solvent called reactive solvent or reactive diluent in the coating. It can not only dissolve or disperse the film-forming substances, but also chemically react with the film-forming substances during the film-forming process, forming non-volatile components and remaining in the film. Since the organic solvent does not overflow during the coating and film forming process, the pollution to the environment and the toxicity to the human body are reduced.
The currently used solvent-free products mainly include two-component (two-component) epoxy-based solvent-free coatings and acrylic-based photocurable coatings. The development direction of solvent-free coatings is to expand the variety, increase the adaptability to the coating method and develop thin coating products.
3, water-based paint
The water system is colorless, transparent, non-toxic and tasteless, and rich in resources. Replacing the organic solvent with water as the dispersion medium for the coating resin will undoubtedly completely eliminate the above three hazards brought about by the use of organic solvents. Therefore, it has become an important product in the development of environmentally friendly coatings.
Water-based coatings can be divided into two categories: latex coatings and water-reducible coatings. At present, mature latex coating products are mainly architectural latex paints, and water-diluted coatings are mainly industrial water-based electrophoretic primers.
The water-based industrial coatings are affected by the performance of the water-based coatings and the corresponding solvent-based coatings that need to be improved, the cost is relatively high, and there are specific requirements for the coating environment. work.
4, powder coating (powder coating)
Powder coatings theoretically do not contain any volatile substances, are absolutely zero VOC coatings, and are one of the key development products of environmentally friendly coating products. However, powder coatings are subject to certain restrictions in expanding their applications and need to be further improved. For example, its manufacturing cost is high; high temperature baking is required to form a film; it is difficult to obtain a thin film coating. It is difficult to adjust the color of the paint products due to the paint making process; the uniform coating on the surface of irregular objects is poor. These all need further research and development.
Based on the above, the development of the above four types of environmentally friendly coatings is the unwavering work direction of my country's coating workers.