Secondary Functional Polyols

I can only suggest looking at the various catalyst systems, either fully substituted amines or metallics. Mercury compounds are excellent but have environmental concerns. Bismuth compounds are useful. You might contact King catalysts, they have proved useful before. I might suggest the addition of molecular sieves as dehydrators, if you are not making water blown foams, that is.

dmap

What are you using for isocyanaye(s)? King Industries KKat348 is a viable alternative organometallic. I assume you have used stannous octoate and DBTDL already? Try blending the catalyst(s) with the polyol(s) for at least 4 hours before adding the isocyanate. You can only go so far with temperature before you start to reach an equilibrium rx. You might also try a basic catalyst, but beware of gelation reactions. The bismouth catalysts, titanites, et al are not as reactive as the tin catalysts. Guanidine is the strongest organic base, and it acts as a rapid catalyst for a lot of difficult isocyanate reactions, but one has to worry about gellation and also burns to one's skin! DuPont marketed Guanidine as a PU catalyst back some 30 years ago, but pulled it due to its extreme basicity. Are you familiar with resonance structures? The high basicity of guanidine is due to the 3 identical structures which can be written. Nitroguanidine used to be commonly used in "gun powder" and explosives, as it explodes w/o producing a flash. The Japanese used nitroguanidine mixed with cellulose nitrate to produce the 1st flashless powder for naval rifles of all calibers for use in night sea battles the early 1940s, with excellent results around Guadalcanal, Iron Bottom Sound, The Slot, etc. If you are using 4,4'-MDI, you shouldn't need too strong a catalyst, but mixed isomer MDI (ambient stable liquid MDI) and of course the aliphatics require a good push to get an economical reaction. Be sure to experiment with small lab batches before you try anything too large. Heating the MDI plus a small amount (ppm) of catalyst before introducing it into the reaction may also help.