Catalysts are an important additive in the synthesis of resins, and this is no exception for polyurethane. Polyurethane catalysts shorten reaction time, improve production efficiency, selectively promote the main reaction and inhibit side reactions. In many polyurethane production processes, catalysts are commonly used as additives. Although the amount used is small, the effect is significant.
In the formulations of polyurethane elastomers, adhesives, coatings, sealants, waterproof coatings, and paving materials, organometallic catalysts such as dibutyltin dilaurate are commonly used, which are very effective in promoting the reaction between isocyanate groups and hydroxyl groups. However, in formulations with water, they also accelerate the reaction between water and isocyanates to some extent, so special catalysts such as organic lead are used in formulations such as plastic tracks. Strong gelling tertiary amines like triethylenediamine can also be used in some flexible polyurethane formulations. When choosing a catalyst suitable for polyurethane and its raw materials, not only the catalyst's catalytic activity and selectivity should be considered, but also its physical state, ease of operation, compatibility with other components, stability in mixed raw material systems, toxicity, price, and whether the residual catalyst in the product has a detrimental effect on polymer performance.
There are many types of polyurethane catalysts, and considering various factors, more than 20 catalysts are commonly used in polyurethane production. For emerging industries and special processes that require more specialized catalysts, more new catalysts and special properties will be developed with the continuous development of the industry.
The polyurethane foam plastics industry has high requirements for polyurethane catalysts. Catalysts are indispensable for converting viscous polyols and isocyanates into solid porous materials through mixing and stirring. They need to have both foaming and gelling effects, and some products also require delayed trimerization effects. Therefore, multiple catalysts are often mixed and used in the preparation process of polyurethane foam plastics. Tertiary amine catalysts, alkyl metal compounds, and organic amine salt catalysts are widely used in the foam industry.
Most elastomers have strict requirements for the moisture content in the system, as the introduction of water can generate bubbles in the elastomer system, which can affect product quality. In the elastomer field, polyurethane synthetic leather resin is an important branch, and the industry's requirements for bubbles in the system are not very strict, as almost all resin factories use recycled materials with relatively high moisture content, which confirms this point. In the production of wet-process materials, contact with water is unavoidable. The selection of polyurethane catalysts in this industry is similar to that in the coatings and adhesives industry and faces the same environmental issues.
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