polyurethane (Polyurethane, referred to as PU) is an important class of polymer materials, widely used in coatings, adhesives, elastomers, foam plastics and other fields. During its preparation, the selection and use of catalyst plays a vital role in the performance of the product. Catalysts can promote the synthesis reaction of polyurethane, increase the reaction rate, regulate the degree of polymerization, and affect the structure and performance of the product.
1. Metal catalyst Metal catalyst is one of the most common polyurethane synthesis catalysts. Among them, organotin compounds (such as dibutyltin dimercapto) are widely used in the preparation of polyurethane. They catalyze the addition reaction between isocyanates and polyols to form polyurethane chains. The advantages of this type of catalyst are high reaction rate and stable product quality, but there are also problems such as metal pollution and toxicity.
2. Organic catalysts Organic catalysts are a class of environmentally friendly options, and their common representatives are organic Acids, such as imidazoles, pyridines, etc. These catalysts promote the condensation of isocyanates and polyols through acid-base neutralization or proton transfer reactions. Organic catalysts reduce the environmental and safety hazards brought by metal catalysts in the preparation of polyurethane, but the reaction rate is relatively slow.
3. Ionic liquid catalyst Ionic liquid catalyst has received extensive attention in recent years. They are a class of catalysts with excellent catalytic performance and tunability, which can replace traditional organic acids or metal catalysts in polyurethane preparation. The structure of ionic liquids can be optimized through rational design to enhance their catalytic activity and selectivity while also reducing catalyst toxicity and environmental risks.
4. Enzyme catalyst In recent years, enzyme catalyst as a green catalyst has been gradually applied to the synthesis of polyurethane . Enzyme catalysts do not require high temperature and toxic solvents in the reaction process, and have the advantages of high efficiency, high selectivity and environmental friendliness. However, the application of enzyme catalysts is also limited by factors such as their stability and cost.
In summary, there are various types of polyurethane catalysts, covering metal catalysts, organic catalysts, Ionic liquid catalysts and enzyme catalysts and other fields. In practical applications, it is necessary to select the appropriate catalyst type based on the requirements of the specific synthesis process, product performance requirements, and environmental health and safety factors to achieve the best synthesis effect and economic benefits. With the advancement of science and technology, new innovations and developments will continue to emerge in the field of polyurethane catalysts in the future.
