Aldehyde-ketone resin is a neutral non-toxic hard resin formed by the condensation polymerization of ketone-aldehyde. Its molecule contains a large number of saturated cyclic structures and has the advantages of high hardness, high gloss, good resistance to degradation and weathering, and low price. It can improve the adhesion, fullness, dryness and other properties of the coating, and is usually used as an additive for solvent-based coatings.
The aldehyde and ketone resin modified polyurethane dispersion coating film has excellent adhesion, flexibility and water resistance. Experiments have shown that the coating properties of water-based coatings prepared using aldehyde-ketone resin modified polyurethane dispersion (PUD) as the main component are significantly improved compared to before modification. Comparing the PUD coatings before and after modification with aldehyde-ketone resin, the following points can be seen:
1)The aldehyde and ketone resin modified polyurethane dispersion significantly increases the pencil hardness of the coating film, significantly enhances the adhesion, and improves the water resistance, while the flexibility of the coating film is not significantly affected.
2)As the rigidity of polyurethane molecules increases, the hardness of the coating film increases.
3)The high density of polar groups in the aldehyde and ketone resin chain segments helps to improve the adhesion of the coating film.
4)The soft segment allows the polyurethane to maintain flexibility, and the amount of aldehyde and ketone resin in C2/C3 has little impact on the flexibility of the coating film.
It can be seen that aldehyde and ketone resins can significantly improve the performance of polyurethane dispersions. At the same time, lower-priced aldehyde and ketone resins can significantly reduce the cost of PUD for hard substrate coatings.
It is known from many reports that polyurethane dispersions have been modified by various means in order to solve the problems of insufficient hardness, water resistance, and alcohol resistance of polyurethane dispersions (PUD) when used in coatings for wood, metal, plastics, etc. There are problems such as high cost, but the actual application effect is not ideal. According to experiments, based on the obvious advantages of aldehyde and ketone resins, the use of hydroxyl-terminated aldehyde and ketone resins to modify polyurethane dispersions is expected to improve the shortcomings of PUD in coating applications for wood, metal, plastics, etc.