Stain resistant, abrasion resistant polyurethane coating composition, substrate coated therewith and production thereof

Homogeneous, unitary, crosslinked polyurethane coating on a substrate wherein the nitrogen atoms of the polyurethane structures are joined to alicyclic rings or to straight aliphatic chains and the crosslinkages consist essentially of crosslinks between polyurethane structures, via isocyanate residues and triol or tetrol residues forming in combination, urethane group crosslinkages in the polyurethane structures;

• and crosslinks between polyurethane structures, deriving from double bonds in diacrylates, triacrylates or tetra acrylates and acrylate moieties which esterify alkane or polyether diol, triol or tetrol residues, which residues are linked as urethanes to the polyurethane structures;
• said coating also having urea groups linking the polyurethane structures;
• and wherein on an equivalent basis the ratio of double bond crosslinkages:urethane group crosslinkages joining polyurethane structures, formed by triol or tetrol residues, is between 1.0 and 2.5;
• where the number of equivalents of double bond crosslinkage in the coating is taken as being equal to the number of equivalents of carbon-carbon double bond in the uncured coating composition, and the number of equivalents of urethane crosslinkage in the coating is taken as being equal to the number of equivalents of hydroxyl group provided by the triols and the tetrols in the uncured coating composition;
• and in said coating the content of urethane groups in the main polyurethane chains amounts on an equivalent weight basis to about 40% up to no more than 70% of the total of urethane groups in the main polymer chains plus urethane crosslinkages plus urea groups present in said coating;
• the content of urethane group crosslinkages, formed from triol or tetrol residues, amounts to between about 20 and about 40 equivalent weight percent of said total of main chain urethane groups, urethane crosslinkages and urea groups and the content of urea groups in said coating amounts to between about 5 to about 25 equivalent percent of the total of said urethane main chain groups, urethane crosslinkages and urea groups and calculated as weight of unreacted isocyanate groups available for conversion to urea groups, amounts to about 0.5 to about 5 percent by weight of said coating;
• and in said coating, the vinyl groups other than those of acrylate groups incorporated by urethane links in the polyurethane structures, are combined via double bond linkages with each other and with said acrylate groups incorporated in the polyurethane structures.