Polyurethane resin, a coating composition comprising a polyurethane resin, use of a polyurethane resin for printing plastic substrates, method of producing a polyurethane resin, a method of producing a laminate carrying a printed image

A polyurethane resin produced by first reacting a mixture comprising a first group of at least one polyol and a second group of at least one polyol with at least one diisocyanate to a first prepolymer, wherein all polyols of said first group have an average molecular weight from 1000 to 10000 g/mol, wherein all polyols of said second group have an average molecular weight in excess of 10000 up to 20000 and wherein the equivalent ratio of the diisocyanate to the entirety of the polyols of the first and of the second group is from 3.6:1 to 2.3:1, and then reacting said first isocyanate terminated prepolymer with an amount of a third component comprising a third group of at least one polyol, all polyols of said third group having an average molecular weight of equal to or less than 800 g/mol, said amount being sufficient to form a saturated polyurethane resin containing substantially no unreacted polyisocyanate.

A coating composition, preferably printing ink, comprising a solvent and at least one polyurethane resin as film forming binder, said polyurethane being the reaction product of at least one diisocyanate and components having isocyanate reactive functional groups, said components comprising a first group of at least one polyol, a second group of at least one polyol and a third group of at least one polyol, wherein all polyols of said first group have an average molecular weight from 1000 to 10000 g/mol, wherein all polyols of said second group have an average molecular weight in excess of 10000 up to 20000 g/mol, wherein all polyols of said third group have an average molecular weight of equal to or less than 800 g/mol and wherein the equivalent ratio of the diisocyanate to the components having isocyanate reactive functional groups is selected such that essentially all of the isocyanate groups of the diisocyanate are present as the reaction product with one of said isocyanate reactive functional groups.

A method of using a polyurethane resin as at least one film forming binder in printing inks for printing on plastic substrates, said method comprising steps of

• providing a polyurethane resin by reacting at least one diisocyanate and components having isocyanate reactive functional groups, said components comprising a first group of at least one polyol, a second group of at least one polyol and a third group of at least one polyol, wherein all polyols of said first group have an average molecular weight from 1000 to 10000 g/mol, wherein all polyols of said second group have an average molecular weight in excess of 10000 up to 20000 g/mol, wherein all polyols of said third group having an average molecular weight equal to or less than 800 g/mol and wherein the equivalent ratio of the diisocyanate to the components having isocyanate reactive functional groups is selected such that essentially all of the isocyanate groups of the diisocyanate are present as the reaction product with one of said isocyanate reactive functional groups,
• providing a printing ink comprising said polyurethane resin as a film forming binder, and
• printing said printing ink on a plastic substrate.

A method of producing a saturated polyurethane resin comprising the steps of

• a) providing a mixture comprising a first group of at least one polyol and a second group of at least one polyol, wherein all polyols of said first group have an average molecular weight from 1000 to 10000 g/mol and all polyols of said second group have an average molecular weight in excess of 10000 up to 20000 g/mol;
• b) reacting said mixture provided in step a) with at least one diisocyanate, wherein the equivalent ratio of the diisocyanate to the sum of the polyols of the first and of the second group is from 3.6:1 to 2.3:1.

A polyurethane resin comprising the reaction product of an isocyanate group of at least one diisocyanate and a hydroxy group of at least one dihydroxy polyether polyol of an average molecular weight in excess of 10000 up to 20000 g/mol, further comprising the reaction product of an isocyanate group of at least one diisocyanate with a hydroxy group of at least one polyol of an average molecular weight from 1000 to 10000 g/mol, selected from the group consisting of dihydroxy- and trihydroxy polyether polyols, and further comprising the reaction product of an isocyanate group with a hydroxy group of at least one polyol of an average molecular weight of equal to or less 800 g/mol, selected from the group consisting of monomeric diols, dihydroxy polyether polyols and polyester polyols having a hydroxy value of at least 140 mg KOH/g.