Process for preparing low-monomer-content TDI trimers
AssigneeBayer Aktiengesellschaft
InventorsMartin Brahm, Oswald Wilmes, Joachim Simon
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Abstract
The invention relates to a novel process for preparing low-monomer-content trimers based on 2,4- and/or 2,6-diisocyanatotoluene (TDI). A catalytic trimerization is carried out in a mixture of from 20 to 80% by weight of a diisocyanate component containing at least 80% by weight of 2,4- and/or 2,6-diisocyanatotoluene, from 20 to 80% by weight of solvent, and 0-20% by weight of an alcohol component, and also phenolic catalysts containing dialkylamino-methyl groups. In the course of ongoing trimerization, in one or more steps, additional monomeric 2,v4-diisocyanatotoluene is metered in.
Claims7
Process for preparing solvent-containing polyisocyanates based on 2,4-and/or 2,6-diisocyanatotoluene which contain isocyanurate groups and <0.1% by weight of monomeric diisocyanate comprising
- a) reacting, at a temperature from 20° C. to 120° C., a mixture of
- A) from 20 to 80% by weight of a diisocyanate component containing at least 80% by weight of 2,4- and/or 2,6-diisocyanatotoluene,
- B) from 20 to 80% by weight of solvent and
- C) 0-20% by weight of an alcohol component, and also
- D) phenolic catalysts containing dialkylaminomethyl groups;
- b) metering in, in one or more steps, in the course of ongoing trimerization additionally 0.1-25% by weight, based on the amount of diisocyanates employed, of monomeric 2,4-diisocyanatotoluene;
- and
- c) ending the reaction by adding catalyst poisons.
Dependencies are inferred from the claim text.