The invention relates to a method for the separation of isocyanate monomers from isocyanate-containing mixtures by the provision of the mixture in a solvent and dialysis of the dissolved mixture against the solvent by means of a permeable membrane having a pore size in the range of between 5 and 400 nm. The method may in particular be employed for the separation of isocyanate monomers from prepolymers containing isocyanate groups, with said prepolymers being used for the production of adhesives, insulating, and expanding foams.

The present invention relates to a polyisocyanate composition comprising, on the basis of the total mass of the polyisocyanate composition, 97 weight % or more of a polyisocyanate, and 2.0 mass ppm or more and 1.0×10.sup.4 mass ppm or less of a compound having at least one unsaturated bond in which the compound is a different compound from the polyisocyanate, or 5.0 mass ppm or more and 2.0×10.sup.4 mass ppm or less of at least one inactive compound selected from the group consisting of a hydrocarbon compound, an ether compound, a sulfide compound, a halogenated hydrocarbon compound, a Si-containing hydrocarbon compound, a Si-containing ether compound, and a Si-containing sulfide compound.

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 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 eyewear material is an eyewear material containing thermoplastic polyurethane. The eyewear material has a tan δ peak at both less than 0° C. and 0° C. or more and 70° C. or less observed in dynamic viscoelasticity measurement in tensile mode under the measurement conditions of a temperature increase speed of 5° C./min and a measurement frequency of 10 Hz.

The eyewear material is an eyewear material containing thermoplastic polyurethane. The eyewear material has a tan δ peak at both less than 0° C. and 0° C. or more and 70° C. or less observed in dynamic viscoelasticity measurement in tensile mode under the measurement conditions of a temperature increase speed of 5° C./min and a measurement frequency of 10 Hz.

The eyewear material is an eyewear material containing thermoplastic polyurethane. The eyewear material has a tan δ peak at both less than 0° C. and 0° C. or more and 70° C. or less observed in dynamic viscoelasticity measurement in tensile mode under the measurement conditions of a temperature increase speed of 5° C./min and a measurement frequency of 10 Hz.

Monoisocyanate impurities are removed from a process stream obtained when solvent is separated from a polyisocyanate product. The monoisocyanates are reacted with amine compounds at specific molar ratios to produce ureas. The ureas can be discarded by burning, landfilling or otherwise. Alternatively the ureas can be recycled back into the polyisocyanate manufacturing process, where they are formed into biuret compounds that can remain with the polyisocyanate product.

Monoisocyanate impurities are removed from a process stream obtained when solvent is separated from a polyisocyanate product. The monoisocyanates are reacted with amine compounds at specific molar ratios to produce ureas. The ureas can be discarded by burning, landfilling or otherwise. Alternatively the ureas can be recycled back into the polyisocyanate manufacturing process, where they are formed into biuret compounds that can remain with the polyisocyanate product.

The method for producing pentamethylene diisocyanate includes a reaction step, in which carbonyl chloride is allowed to react with pentamethylenediamine to produce a reaction mixture containing pentamethylene diisocyanate and a tar component containing a chlorine-containing component; a heating step, in which the reaction mixture is heated; and a purification step, in which the reaction mixture after the heating step is purified to separate the pentamethylene diisocyanate from the tar component, wherein in the heating step, the reaction mixture is heated without removing the tar component from the reaction mixture.