Abstract: 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 sp3 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.

Abstract: A method is described for preparing a tricondensate polyfunctional isocyanate composition, preferably having at least an isocyanurate and/or biuret group, which includes adding to a tricondensate polyfunctional isocyanate, or a mixture of different tricondensate polyfunctional isocyantes, obtained by (cyclo)condensation, in particular (cyclo)trimerization of one or several identical or different isocyanate monomers and optionally of another monomer, an allophanate of one or several identical or different isocyanates, or a mixture of different allophanates. The isocyanates or isocyanate monomer mixtures used for preparing the polyfunctional isocyanate(s) may be identical to or different from the isocyanate(s) or isocyanate mixture used for preparing the allophanate(s).

Abstract: A composition of at least partially masked isocyanates. The isocyanates are masked by at least two different masking agents, selected such that in the octanol test at 110° C., the ratio: D=percentage in equivalents of masking agents unblocking first at 110° C./percentage in equivalents of masking agents unblocking last at 110° C., is greater than 4/3, advantageously greater then 1.5, preferably greater than 2. When a masking agent comprises a phenol function as a masking function, it does not comprise a COOH function.

Abstract: 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 sp3 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.

Abstract: This invention relates to a process for separating one (or more) oligomeric or polymeric compound(s) (A) obtained by polymerization of isocyanate monomers (A1) or copolymerization of isocyanate monomers with another polymerizable compound (A2), in particular a polyol, the said compound(s) A having a viscosity (a), from the unconverted monomer(s), this process comprising addition to the said compound(s) (A) of one (or more) compound(s) (B) consisting of the product of polymerization of isocyanate monomers (B1) or of copolymerization of isocyanate monomers with another polymerizable compound (B2), in particular a polyol, the said compound(s) (B) having a viscosity (b) and the ratio of the viscosities b/a being less than 1/1.5, preferably less than 1/2, and co-distillation of (A) and (B), in order to separate the compound(s) (A) from the corresponding unconverted monomers.