Organobismuth belongs to Group 15 in the periodic table of elements and is the most metallic element in this group. , the heaviest stable element in the periodic table.
Bismuth compounds have green and safe properties such as low cost, easy handling, low toxicity and low radioactivity. In the past 10 years, both the synthesis of new organobismuth compounds and the research on organobismuth compounds in organic synthesis, catalysts and biomedicine have been at a leading level. Rapid development stage. Organic bismuth products produced in advanced foreign countries have a history of more than 30 years and have been supplied to the European and American markets for many years. These environmentally friendly organobismuth catalysts can be cured at room temperature or under heat, making them an excellent alternative to toxic lead, mercury and tin products.
Advantages of organic bismuth:
1. Safe and environmentally friendly, can replace lead, mercury and tin which are being abolished by legislation;
2. It has better stability against hydrolysis and reduces the selectivity of reaction with water. In water-based PU dispersions, reduce the side reactions between water and NCO groups;
3. Promote NCO/OH reaction, avoid NCO side reactions, and reduce the generation of CO2;
4. In single-component systems , liberate the amines shielded by water instead of promoting the reaction between NCO and water;
5. The combination of bismuth and zinc has a synergistic effect, making the formulation and production more flexible, reducing energy consumption, and increasing profits;
6. Can be used alone or in combination with amines or other organic metal compounds;
Compared with zinc catalysts, organic bismuth has a slower reaction speed; it is a very effective cross-linking catalyst and the surface of the final product is not sticky. Use a bismuth-zinc composite catalyst to replace the mercury catalyst, and add zinc to strengthen the curing. In order to adjust the gel properties or to meet the requirements of some customers to replace the mercury catalyst, we have developed a bimetallic bismuth-zinc composite catalyst. In this kind of catalyst, bismuth provides the gel speed required for curing and generates polyurethane with high selectivity and high rate. Zinc, as a slower gel and better cross-linking catalyst, can reduce the acidity of the system and accelerate the reaction to promote cross-linking. Union. Users can adjust the gel properties by changing the concentration of these two metals in the system. For example, by adding KRZN1 (19% zinc) or KRZN2 (23% zinc) to increase the zinc in the system, extend the kettle operation time during the induction period, and promote post-curing. Due to the different reaction systems of users, the optimal bismuth zinc is also different. Keep the amount of bismuth unchanged, conduct experiments by adding different amounts of zinc, control the bismuth-zinc ratio between 1:1-1:10, and find the bismuth-zinc ratio that best suits your system.
