Polyurethane delayed catalyst is a very special type of catalyst in polyurethane catalysts. This type of catalyst can provide the catalytic activity required for curing polyurethane, at the same time, it can extend the service life of products and provide more operation time for construction. Unlike inhibitors, polyurethane delay catalysts have relatively delayed rather than absolute delays. They have low front-end activity and comparable overall activity compared to conventional catalysts, and they do not have the effect of delaying reactions in systems without catalysts. Depending on the application, we have divided the delay catalysts into two categories: delayed catalysts for foams; delayed catalysts for CASEs (CASE, polyurethane coatings, polyurethane sealants, polyurethane adhesives, and polyurethane elastomers).
1. Delayed catalyst for foam
Polyurethane foams include polyurethane rigid foams, soft foams, semi-rigid foams, and self-skinning products. The main reactions involved are foaming reactions, gel reactions, and trimerization reactions. Therefore, polyurethane foam commonly used catalysts are mainly divided into delayed foaming catalysts, delayed gelation catalysts. The commonly used delayed foaming catalyst is mainly DY-225, which is a diol solution of modified bis(dimethylaminoethyl) ether, which can delay milking time and increase the pre-flowing accelerated aging. Delayed gel catalysts mainly include DY-8154 (modified triethylenediamine solution) and DY-300. In particular, DY-8154 is more widely used, and is widely used in fields such as rigid foam, soft foam, semi-rigid foam, and self-crust, and it can be seen in some microcellular elastomer formulations. New delayed catalysts, which are different from common catalysts on the market, are a type of delayed catalyst specially developed. The main product is DY-215. With the characteristics of low foaming efficiency, good delay effect and strong gel effect, it can provide early fluidity and accelerate post-curing and accelerate demoulding. It can be used with most of the catalysts. It can be used as a substitute for organic tin in some formulations to increase the early fluidity without affecting the later maturation.
2. Delayed catalyst for CASE
Compared with foam catalysts, the catalysts required by CASE are characterized by fast gelling speed, micro-foaming, and even no foaming. Common catalysts include DY-12 (dibutyltin dilaurate) and DY-20 (organic germanium). , phenylmercuric acetate and so on. Therefore, the delayed catalyst for CASE is required to have the same catalytic activity as tin and other catalysts, and it is difficult to achieve the effect of mercury in the foaming efficiency and the effect of dibutyltin dilaurate should be as close as possible. At the same time, the application of CASE is different from that of foam production. The raw materials and processes used are complex, the choice of polyether polyester, the different isocyanate, and the temperature and sequence of the synthesis steps will bring about different results. Therefore, the choice of CASE products for delayed catalysts cannot be generalized and needs to be determined based on many factors. Compared with conventional catalysts, the delay of early activation of the catalyst is similar to that of the later maturation. The following figure shows the comparison of catalyst-free cured products versus delayed catalyst-cured products. It can be seen that tin mercuric products can be obtained by using a suitable delayed catalyst. The efficient little bubble effect.