Radiation curable aqueous dispersions

A stable radiation curable aqueous dispersion comprising a mixture of a first dispersion and a second dispersion, and a photoinitiator,

• wherein said first dispersion comprises at least one (meth)acrylated pre-polymer (A) and, optionally, at least one ethylenically unsaturated compound (C), and
• said second dispersion comprises at least one thiol-functional compound (B) and is different from said first dispersion,
• wherein an equivalent ratio between (i) a concentration of thiol groups and (ii) a concentration of meth(acrylate) groups and, if present, of ethylenically unsaturated groups is 0.30 or less, wherein said concentrations are expressed in milli-equivalents per gram of solid contained in said aqueous dispersion,
• wherein said first dispersion comprises dispersed particles having a global positive or negative charge and said second dispersion comprises dispersed particles having a global charge with the same sign as said dispersed particles of said first dispersion,
• wherein the dispersed particles of the first dispersion are different from the dispersed particles of the second dispersion,
• wherein the at least one ethylenically unsaturated compound (C) is at least one (poly)(meth)acryloyl-containing compound,
• wherein said (meth)acrylated pre-polymer (A) is selected from (meth)acrylated (poly)urethane pre-polymers (A) obtained from the reaction of:
• at least one polyisocyanate compound (ia),
• optionally, at least one polyol (iia),
• at least one hydrophilic compound (iiia) containing at least one reactive group capable of reacting with isocyanate groups, said hydrophilic compound (iiia) being capable of rendering the (poly)urethane pre-polymer dispersible in aqueous medium either directly or after a reaction with a neutralizing agent to provide a salt,
• at least one (meth)acrylated compound (iva) containing at least two reactive groups capable of reacting with isocyanate groups, and
• at least one (meth)acrylated compound (va) containing one reactive group capable of reacting with isocyanate groups, and
• wherein said at least one thiol-functional compound (B) comprises at least one thiol-functional (poly)urethane pre-polymer (B1) which carries groups which impart water dispersibility to the (poly)urethane and/or at least one thiol-functional pre-polymer (B2) which carries groups which impart water dispersibility to the pre-polymer (B2), and which is prepared from monomers capable of free radical polymerization and having C═C double bonds by the method of free radical mass or solution polymerization,
• the thiol-functional (poly)urethane pre-polymer (B1) and the thiol-functional pre-polymer (B2) carrying from 0.05 to 5 meq of thiol groups per gram of thiol-functional (poly)urethane pre-polymer (B1) or thiol-functional pre-polymer (B2) respectively.