Yet Another Way to Make Isocyanate Prepolymers with Low Free Monomeric Isocyanate


 Number/Link: WO2013092564 (in German)

Applicant/Assignee: Bayer

Publication date: 27-06-2013

Gist”: A prepolymer with very low free diisocyanate content and relatively low viscosity can be prepared by reacting MDI having a high 2,4′ isomer content with a low MW diol in a first step and adding a high MW polyol in a second step.

Why it is interesting: The use of asymmetric diisocyanates (having isocyanate groups with different reactivities) to prepare prepolymers with low free monomers is well known.  Prepolymers prepared using diisocyanates with high levels of 2,4′-MDI, 2,4-TDI, IPDI etc. will however still show a very high viscosity at low isocyanate content. Bayer has now found that prepolymers with lower free monomer and lower viscosity can be prepared by using two polyols reacted in seperate stages. In a first step an MDI with >95% 2,4′ isomer is reacted with a (pref) diol with a molecular weight between 60 and 700 to produce a prepolymer with an NCO content of more than 15%. In a second step this prepolymer is then further reacted with a ‘conventional’polyol to obtain the final prepolymer.  In an example a prepolymer with less than 0.1% free MDI and a viscosity of 25 Pa.s at 40°C was prepared.



Leave a comment

1 Comment

  1. first blog I have seen in which its chemical diagram is given. thanks


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

  • Pages

  • Categories

  • Enter your email address to follow this blog and receive notifications of new posts by email.

    Join 1,089 other subscribers
  • Follow Innovation in PU on Twitter

%d bloggers like this: