Water-dissipatable polyesters and amides containing near infrared fluorescent compounds copolymerized therein

A method for invisibly marking, for identification purposes, an article with a water-dispersible polymer, wherein said polymer has from about 0.1 to about 10.0 ppm of a residue of a near infrared flourescing compound copolymerized therein, which comprises applying to said article a composition comprising

• (I) about 20 weight percent to about 35 weight percent of a water-dissipatable polyester comprising:
• (i) monomer residues of at least one dicarboxylic acid;
• (ii) about 4 to 25 mole percent, based on the total of all acid, hydroxy and amino equivalents, of monomer residues of at least one difunctional sulfo monomer containing at least one sulfonate group bonded to an aromatic ring where the functional groups are hydroxy, carboxyl or amino;
• (iii) monomer residues of at least one diol or a mixture of a diol and a diamine;
• and optionally
• (iv) monomer residues of at least one difunctional monomer reactant selected from hydroxycarboxylic acids, aminocarboxylic acids and aminoalkanols;
• provided that at least 20 percent of the groups linking the monomeric units are ester linkages;
• said water dissipatable polyester having from about 0.1 ppm by weight to about 10% by weight of a thermally stable near infrared flouorphoric residue copolymerized therein;
• and
• (II) about 65 weight percent to about 80 weight percent of water.