A method for preparing rigid polyurethane (PUR) foams or rigid polyisocyanurate (PIR) foams in which method the rigid PUR or PIR foam is prepared by reacting a composition (C) comprising: at least one isocyanate-reactive component (B1) having functional groups selected from hydroxyl, amine and thiol groups; at least one isocyanate component (A1) having an average functionality of less than 2.70; and at least one blowing agent [blowing agent (BA), herein after]; with the proviso that the overall average functionality [F.sub.n,avg(A), herein after] of all isocyanate components present in the composition (C) is less than 2.70; wherein the composition (C) is characterized by an isocyanate index X, wherein the rigid PUR or PIR foams are produced by depositing the composition (C) between two gas-tight facing sheets and wherein the rigid PUR or PIR foam is characterized by a difference Δλ between the initial thermal conductivity value λ.sub.ini and the aged thermal conductivity value λ.sub.aged of said rigid PUR or PIR foam wherein: when X≤200 then Δλ<1.35; and when X>200 then Δλ<[6.49−(4.46*F.sub.n,avg(A))−(0.02348*X)+(0.492*F.sub.n,avg(A)*F.sub.n,avg(A))+(0.01343*F.sub.n,avg(A)*X)+0.3].

The present invention relates to a new process for preparing polyisocyanates containing isocyanurate groups and being flocculation-stable in solvents from (cyclo)aliphatic diisocyanates.

The invention relates to innovative, water-dispersible, hydrophilic polyisocyanates and polyisocyanate mixtures, to a process for preparing them, to compositions comprising the hydrophilic polyisocyanates of the invention, and to their use as a starting component in the production of polyurethane plastics, more particularly as crosslinkers for water-soluble or water-dispersible film-forming, adhesives or sealant binders or binder components having groups which are reactive towards isocyanate groups.

The present invention relates to a composition comprising 10 to less than 50 wt.-% of at least one oligomeric polyisocyanate a-1) based on hexamethylene diisocyanate and more than 50 to 90 wt.-% of at least one polyisocyanate a-2) based on isophorone diisocyanate, comprising monomeric isophorone diisocyanate and at least one oligomeric isophorone diisocyanate, and an isocyanate-reactive component selected from the group consisting of polyester polyol, polyether polyol and mixtures thereof. It has been shown that the above mentioned mixture of the specific isocyanate group containing components improves the thermal and mechanical properties of a cured composition. Thus prepared molded articles are particularly suitable for the preparation of spectacle lenses, inter alia due to these properties.

The invention relates to a method for producing polyisocyanates having a low monomer content, said method comprising the following steps: (i) modifying at least one monomeric diisocyanate to obtain a mixture containing at least one polyisocyanate and unconverted monomeric diisocyanate, (ii) separating the mixture obtained in step (i) into at least one gaseous stream containing monomeric diisocyanate and a liquid stream depleted of monomeric diisocyanate, (iii) partially condensing the gaseous stream from (ii) in at least one condenser, so that a liquid condensate and an uncondensed vapour stream are obtained, (iv) post-condensing the uncondensed vapour stream obtained in step (iii) in at least one post-condenser, so that a post-condensate and an uncondensed waste gas are obtained, and (v) delivering the uncondensed waste gas from step (iv) to the suction side of a vacuum pump, characterised in that the at least one post-condenser in step (iv) is operated at a post-condenser temperature, and the at least one condenser in step (iii) is operated at a condenser temperature, wherein the post-condenser temperature is lower by ≥1 to ≤168 K than the condenser temperature.

The present invention relates to a composition comprising 10 to 50 wt.-% of at least one polyisocyanate a-1) based on hexamethylene diisocyanate, comprising at least one oligomeric polyisocyanate based on hexamethylene diisocyanate and optionally monomeric hexamethylene diisocyanate and 50 to 90 wt.-% of at least one polyisocyanate a-2) based on isophorone diisocyanate, comprising at least one oligomeric polyisocyanate based on isophorone diisocyanate and optionally monomeric isophorone diisocyanate, with the proviso that at least one of the components a-1) and a-2) additionally comprises monomeric isocyanate of the named kind, as well as at least one sulfur-containing component. It has been shown that the above mentioned mixture of the specific isocyanate group containing components improves the thermal and mechanical properties of a cured composition. Thus prepared molded articles are particularly suitable for the preparation of spectacle lenses, inter alia due to these properties.

The present invention provides a polyisocyanate composition wherein the composition is obtained from an aliphatic diisocyanate unit including 1,6-diisocyanatohexane, and has an isocyanurate group, a uretdione group, a uretonimine group, and an iminooxadiazinedione group, and the molar ratio of the uretonimine group to the isocyanurate group is 0.0010 to 0.0050, and the molar ratio of the iminooxadiazinedione group to the isocyanurate group is 0.00050 to 0.30.

A polyurethane elastomer composition includes a polycarbonate diol and an aliphatic isocyanate, and lacking any solvent. The composition is used for leading edge protection (LEP), preferably of wind turbine rotor blades.

Described in preferred embodiments are UV curable coating compositions including a unique blend of aliphatic urethane acrylate resins. Also described are coated articles and methods for their production involving the use of the coating compositions.

The present invention provides a blocked polyisocyanate composition comprising a blocked polyisocyanate formed through blocking at least a part of isocyanate groups possessed by a polyisocyanate derived from one or two or more diisocyanates selected from the group consisting of an aliphatic diisocyanate and an alicyclic diisocyanate with an active methylene-based compound comprising a malonic acid diester, wherein a specific molar ratio calculated from contents (mol %) of isocyanurate groups, iminooxadiazinedione groups, uretdione groups, and allophanate groups is 0.05 or more and 0.60 or less.