The invention relates to a method for the production of 4,4-methylenebis(phenylisocyanate) dimer (MDI dimer) which is distinguished by an MDI dimer being obtained which is present in high purity. The MDI dimer which is produced according to the method according to the invention is distinguished by being essentially free of MDI and also urea derivatives. Furthermore, the invention relates to a corresponding MDI dimer and also the use thereof as crosslinker for polyurethanes.

The invention relates to a method for the production of 4,4-methylenebis(phenylisocyanate) dimer (MDI dimer) which is distinguished by an MDI dimer being obtained which is present in high purity. The MDI dimer which is produced according to the method according to the invention is distinguished by being essentially free of MDI and also urea derivatives. Furthermore, the invention relates to a corresponding MDI dimer and also the use thereof as crosslinker for polyurethanes.

An alkali metal amide is dissolved in a cyclic alkylene urea represented by the formula (1) (wherein each of R.sub.1 and R.sub.2 represents a C1 to C3 alkyl group, and R.sub.3 represents a C1 to C4 alkylene group). ##STR00001##

An alkali metal amide is dissolved in a cyclic alkylene urea represented by the formula (1) (wherein each of R.sub.1 and R.sub.2 represents a C1 to C3 alkyl group, and R.sub.3 represents a C1 to C4 alkylene group). ##STR00001##

A compound having an uretonimine group contains, as a structural unit, a carbodiimide compound derived from at least one of an aliphatic diisocyanate and an aromatic diisocyanate, and also contains an isocyanate compound as a structural unit, wherein the residue obtained by removing an isocyanate group from the isocyanate compound and the residue obtained by removing a carbodiimide group from the carbodiimide compound are different.

A compound having an uretonimine group contains, as a structural unit, a carbodiimide compound derived from at least one of an aliphatic diisocyanate and an aromatic diisocyanate, and also contains an isocyanate compound as a structural unit, wherein the residue obtained by removing an isocyanate group from the isocyanate compound and the residue obtained by removing a carbodiimide group from the carbodiimide compound are different.

A butane diisocyanate derivative having an isocyanurate group and a uretdione group, wherein the molar ratio of the isocyanurate groups to the uretdione groups is 20/80 to 80/20, and wherein the weight average molecular weight based on gel permeation chromatography is 790 g/mol or less.

Disclosed herein are compounds, combinations, and kits that can be used to more quickly remove radionuclides from a subject, preferably a human being. Said compounds, combinations and kits can also be used to increase the tumor-to-blood ratio, or to more rapidly and/or conveniently achieve such an increase, of a label in targeted imaging or targeted radiotherapy in a subject, preferably a human being.

Disclosed herein are compounds, combinations, and kits that can be used to more quickly remove radionuclides from a subject, preferably a human being. Said compounds, combinations and kits can also be used to increase the tumor-to-blood ratio, or to more rapidly and/or conveniently achieve such an increase, of a label in targeted imaging or targeted radiotherapy in a subject, preferably a human being.