At present, the primary work of the coating industry is to develop four types of environment-friendly coatings. Secondly, it will take time to achieve this goal, and solvent-based coatings still occupy a considerable proportion of the transition stage. Replacing toxic solvents with efficient and non-toxic solvents is also an important work at present. Starting from the concept of sustainable development, developing renewable organic solvent resources is the third task in front of coating workers. Four types of environment-friendly coatings that the coating industry will focus on in the future include:
1、High solid paint
High solid content solvent based coatings (HSSC) are also called VOC solvent based coatings. The volume (nvv) solids of traditional solvent based thermosetting coatings are usually about 25-35%, and some thermoplastic coatings will be lower.
There is no unified definition of high solid coating. One formulation in China is that high solid coating refers to the coating with a solid content greater than or equal to 70% during spraying. Some international references are that the high solid of automotive flash metallic paint (or finish base color paint) refers to about 45nvv; For the primer with high pigment content, its high solid may be 50nvv. This requires that the molecular weight of synthetic resin used in coatings and the average functionality of each molecule should be reduced, and the molecular weight distribution should be narrowed. In this case, it is difficult to keep the function of the film unchanged at the same time. Therefore, the key to the problem is to develop a new synthesis technology of cross-linked resin and strictly control the curing conditions of the film. At the same time, the realization of such coatings only reduces the amount of some organic solvents.
2、Solvent free coating
The so-called solvent-free coating is an organic solvent called reactive solvent or active diluent used in the coating. It can not only dissolve or disperse the film-forming substances, but also react with the film-forming substances in the film-forming process to form non-volatile components and stay in the film. Because the organic solvent does not overflow in the coating film-forming process, the pollution to the environment and the toxicity to human body are reduced.
At present, the solvent-free products mainly include two-component (two-liquid) epoxy solvent-free coatings and acrylic light curing coatings. The development direction of solvent-free coatings is to expand varieties, increase adaptability to coating methods and develop thin coating products.
3、Waterborne coatings
Water system is colorless, transparent, non-toxic and tasteless liquid, and rich in resources. Using water instead of organic solvent as the dispersion medium of coating resin will undoubtedly completely eliminate the above three hazards caused by the use of organic solvent. Therefore, it has become an important product of developing environment-friendly coatings.
Waterborne coatings can be divided into latex coatings and water-reducing coatings. At present, the mature latex coating products are mainly architectural latex paint, and the water dilution coating is mainly industrial water-based electrophoretic primer.
However, due to the influence of the performance of water-based coatings compared with the corresponding solvent based coatings still needs to be improved, the cost is relatively high and there are specific requirements for the coating environment, some work needs to be done to expand the product and application scope.
4、Powder coating (powder coating)
In theory, powder coating does not contain any volatile substances. It is an absolute zero VOC coating. It is one of the key products for the development of environment-friendly coatings. However, the application of powder coatings is limited and needs to be further improved. For example, its manufacturing cost is high; High temperature baking is required for film formation; Thin film coatings are difficult to obtain. The color matching of paint products is difficult due to the paint making process; Poor uniformity of coating on the surface of irregular objects, etc. These need further research and development.
Based on the above, the development of the above four types of environment-friendly coatings is the unswerving work direction of coating workers in China.
5、Suzhou engine New Material Co., Ltd
