Urethane Delay Catalysts Analysis
Polyurethane delay catalysts are an extremely special class of polyurethane catalysts that provide the catalytic activity required for polyurethane maturation while extending the product life and providing more operating time for construction. Unlike inhibitors, polyurethane delay catalysts are relatively delayed rather than absolutely delayed, have low front-end activity compared to conventional catalysts, have comparable overall activity, and do not act to delay the reaction in systems where no catalyst is added.
Depending on the application, we divide the delay catalysts into two main categories.
Delayed catalysts for foam
Delayed catalysts for CASE
(CASE i.e. polyurethane coatings, polyurethane sealants, polyurethane adhesives and polyurethane elastomers)
Delayed catalysts for foams
Polyurethane foam includes polyurethane rigid foam, flexible foam, semi-rigid foam, self-crusting products, etc. The main reactions involved are foaming reaction, gel reaction, trimer reaction, etc. Therefore, the common catalysts for polyurethane foam are mainly divided into two kinds of delayed foaming catalysts and delayed gel catalysts.
Delayed gel catalysts mainly have the common delayed foaming catalyst is mainly GST-225, i.e. modified bis(dimethylaminoethyl) ether diol solution, which can delay the emulsion time and increase the pre-flow to accelerate the later maturation.
Delayed gel catalysts are mainly GST-8154 (modified triethylene diamine solution), GST-300 and so on. Especially GST-8154 is more widely used in hard foam, soft foam, semi-hard foam, self-crusting, etc. It can also be found in some microporous elastomer formulations.
New delay catalysts, these products are different from the common catalysts in the market, a special type of delay catalyst developed by Gusto Chemical, the main products are GST-215 and so on. It has the characteristics of low foaming efficiency, good delay effect and strong gel effect, which can provide pre-fluidity and accelerate post-ripening to speed up the demoulding. It can be used in combination with most catalysts and can replace organotin in some formulations to increase the pre-fluidity without affecting the post-ripening.
Delayed catalyst for CASE
Compared with catalysts for foam, CASE requires catalysts with fast gelation speed, micro-foaming or even no foaming, etc. The common catalysts are GST-12 ((organic bismuth), phenylmercury acetate, etc. Therefore, delayed catalysts for CASE should be comparable to tin catalysts in terms of catalytic activity and should be as close as possible to dibutyltin dilaurate in terms of foaming efficiency, which is difficult to achieve the effect of mercury.
Phenylmercury acetate
At the same time, CASE application area is different from foam production, the raw material and process used are complicated, the choice of polyether polyester type, different isocyanate, as well as the temperature and synthesis step sequence, will bring a lot of differences in the results. Therefore, the choice of delayed catalyst for CASE products cannot be generalized and needs to be determined based on many factors.
The figure below shows the comparison between the cured product without catalyst and the cured product catalyzed by CASE delayed catalyst, it can be seen that the selection of suitable delayed catalyst can achieve the same high efficiency and less bubbling effect of tin-mercury products.
