Method for the preparation of low-viscosity (poly) isocyanates
View Patent ↗A low viscosity polyisocyanate composition containing at least one isocyanate dimer having a uretidinedione unit is prepared from a reaction medium containing at least one isocyanate monomer in which the isocyanate groups are borne by sp 3 carbon atoms. The reaction medium is heated, in the absence of a dimerization catalyst, to a temperature of at least 50° C. and not more than 200° C. for a period of not more than 24 hours.
1. A low-viscosity polyfunctional isocyanate composition comprising at least one uretidinedione isocyanate dimer and at least one trimer having a biuret function, wherein said biuret function containing trimer represents at least 10% by weight based on the weight of the composition and the ratio of true dimer units to the total composition is less than 15% on a mass/mass basis.
2. A low-viscosity polyfunctional isocyanate composition comprising at least one uretidinedione isocyanate dimer and at least one trimer having a biuret function, wherein said biuret function containing trimer represents at least 20% by weight based on the weight of the composition and the ratio of true dimer units to the total composition is less than 15% on a mass/mass basis.
3. A composition comprising:
(a) at least one polyisocyanate composition according to claim 2 ; and
(b) a polyol.
4. A composition comprising:
(a) at least one polyisocyanate composition according to claim 2 ; and
(b) an acrylate polyol which satisfies the following conditions for a dry extract:
(i) Mw (weight-average molecular weight) not greater than 10,000;
(ii) Mn (number-average molecular weight) of not greater than 5000;
(iii) Mw/Mn (dispersity ratio) of not greater than 5; and
(iv) number of OHs/molecule of greater than or equal to 2.
5. A composition comprising:
(a) at least one polyisocyanate composition according to claim 2 ; and
(b) a polyester polyol having a viscosity of not greater than 10,000 mPa·s at 25° C., and an Mw of between 250 and 8000.
6. A composition according to claim 3 , further comprising a crosslinking catalyst.
7. A composition according to claim 6 wherein the crosslinking catalyst is a latent catalyst.