Aqueous radiation curable polyurethane compositions

Abstract

The invention relates to radiation-curable aqueous composition comprising a high molecular weight ethylenically unsaturated polyurethane obtained from the reaction of a polyisocyanate, at least one hydrophilic compound which is capable to render the polyurethane prepolymer dispersible in aqueous medium, an ethylenically unsaturated compound containing at least two reactive groups capable to react with isocyanate groups and an active hydrogen containing chain extender and a low molecular weight ethylenically unsaturated polyurethane end-capped with an ethylenically unsaturated compound containing essentially one reactive group capable to react with isocyanate groups.

1 - 15 . (canceled) 
     
     
         16 . An aqueous radiation-curable composition comprising
 at least one high molecular weight ethylenically unsaturated polyurethane (A) obtained from the reaction of
 at least one polyisocyanate compound (Ai), 
 at least one ethylenically unsaturated compound (Aii) containing at least two reactive groups capable to react with isocyanate groups, 
 at least one hydrophilic compound (Aiii) containing at least one reactive group capable to react with isocyanate groups and which is capable to render the polyurethane prepolymer dispersible in aqueous medium either directly or after the reaction with a neutralizing agent to provide a salt, 
 at least one active hydrogen-containing chain extender (Avii) capable to react with isocyanate groups and provide chain extension, and, 
 optionally one or more polyol (Avi); and 
 at least one low molecular weight ethylenically unsaturated polyurethane (B), different from polyurethane (A), obtained from the reaction of 
 at least one polyisocyanate compound (Bi), 
 at least one ethylenically unsaturated compound (Bii) containing at least two reactive groups capable to react with isocyanate groups, 
 at least one hydrophilic compound (Biii) containing at least one reactive group capable to react with isocyanate groups and which is capable to render the polyurethane prepolymer dispersible in aqueous medium either directly or after the reaction with a neutralizing agent to provide a salt, 
 at least one ethylenically unsaturated compound (Biv) containing one reactive group capable to react with isocyanate groups, and, 
 optionally, one or more polyol (Bvi) and/or one or more active hydrogen-containing chain extender (Bvii). 
   
     
     
         17 . The radiation curable composition according to  claim 16 , wherein the polyurethane (A) has a weight average molecular weight of more than 100000 Dalton. 
     
     
         18 . The radiation curable composition according to  claim 16 , wherein the polyurethane (B) has a weight average molecular weight of 1000 to 100000 Dalton. 
     
     
         19 . A method of producing an aqueous radiation-curable composition comprising at least one high molecular weight ethylenically unsaturated polyurethane (A) and at least one low molecular weight ethylenically unsaturated polyurethane (B), different from polyurethane (A), comprising adding polyurethane (A) into an aqueous composition comprising polyurethane (B), or vice versa,
 wherein the process for producing polyurethane (A) comprises
 forming a polyurethane prepolymer by reacting
 at least one polyisocyanate compound (Ai), 
 at least one ethylenically unsaturated compound (Ali) containing at least two reactive groups capable to react with isocyanate groups, 
 at least one hydrophilic compound (Aiii) containing at least one reactive group capable to react with isocyanate groups and which is capable to render the polyurethane prepolymer dispersible in aqueous medium either directly or after the reaction with a neutralizing agent to provide a salt, and, 
 optionally, one or more polyol (Avi); 
 
 optionally, converting the hydrophilic groups provided by compound (Aiii) into anionic salts by reaction with a neutralizing agent; 
 dispersing the polyurethane prepolymer in an aqueous medium; and 
 reacting the ethylenically unsaturated polyurethane prepolymer with at least one active hydrogen-containing chain extender (Avii), and 
   wherein the process for producing polyurethane (B) comprises
 forming a polyurethane prepolymer by reacting
 at least one polyisocyanate compound (Bi), 
 at least one ethylenically unsaturated compound (Bii) containing at least two reactive groups capable to react with isocyanate groups, 
 at least one hydrophilic compound (Biii) containing at least one reactive group capable to react with isocyanate groups and which is capable to render the polyurethane prepolymer dispersible in aqueous medium either directly or after the reaction with a neutralizing agent to provide a salt, and 
 optionally, one or more polyol (Bvi); 
 
 reacting the polyurethane prepolymer with at least one ethylenically unsaturated compound (Biv) containing essentially one reactive group capable to react with an isocyanate group; 
 optionally, converting the hydrophilic groups provided by compound (Biii) into salts by reaction with a neutralizing agent; 
 dispersing the polyurethane prepolymer in an aqueous medium; and 
 optionally, reacting the ethylenically unsaturated polyurethane with at least one active hydrogen containing chain extender (Bvii). 
   
     
     
         20 . The method of producing an aqueous radiation-curable composition according to  claim 19 , wherein the polyurethane (A) has a weight average molecular weight of more than 100000 Dalton. 
     
     
         21 . The method of producing an aqueous radiation-curable composition according to  claim 19 , wherein the polyurethane (B) has a weight average molecular weight of 1000 to 100000 Dalton. 
     
     
         22 . The method of producing an aqueous radiation-curable composition according to  claim 19 , wherein the equivalent ratio of isocyanate groups provided by compound (Ai) to isocyanate-reactive groups provided by compounds (Aii), (Aiii) and, optionally, (Avi) is from about 1.1:1 to about 2:1. 
     
     
         23 . The method of producing an aqueous radiation-curable composition according to  claim 19 , wherein the equivalent ratio of isocyanate groups provided by compound (Ai) to isocyanate-reactive groups provided by compounds (Aii), (Aiii) and, optionally, (Avi) is from about 1.3:1 to 1.9:1. 
     
     
         24 . The method of producing an aqueous radiation-curable composition according to  claim 19 , wherein compounds (Aii) and (Aiii) are used in a molar ratio (ii):(iii) of from 1:1 to 3:1. 
     
     
         25 . The method of producing an aqueous radiation-curable composition according to  claim 19 , wherein compounds (Aii) and (Aiii) are used in a molar ratio (ii):(iii) of from 1.5:1 to 2.5:1. 
     
     
         26 . The method of producing an aqueous radiation-curable composition according to  claim 19 , wherein, in the process for producing polyurethane (A), the ratio of isocyanate groups in the prepolymer to the active hydrogen groups in the chain extender (Avii) during the chain extension is in the range of from about 1:0.7 to about 1:1.3 on an equivalent basis. 
     
     
         27 . The method of producing an aqueous radiation-curable composition according to  claim 19 , wherein, in the process for producing polyurethane (A), the ratio of isocyanate groups in the prepolymer to the active hydrogen groups in the chain extender (Avii) during the chain extension is in the range of from about 1:0.9 to about 1:1 on an equivalent basis. 
     
     
         28 . The method of producing an aqueous radiation-curable composition according to  claim 19 , wherein, in the process for producing polyurethane (A), the ratio of isocyanate groups in the prepolymer to the active hydrogen groups in the chain extender (Avii) during the chain extension is 1:1 on an equivalent basis. 
     
     
         29 . The method of producing an aqueous radiation-curable composition according to  claim 19 , wherein the equivalent ratio of isocyanate groups provided by compound (Bi) to isocyanate-reactive groups provided by compounds (Bii), (Biii) and, optionally, (Bvi), of from about 1.05:1 to about 2:1. 
     
     
         30 . The method of producing an aqueous radiation-curable composition according to  claim 19 , wherein the equivalent ratio of isocyanate groups provided by compound (Bi) to isocyanate-reactive groups provided by compounds (Bii), (Biii) and, optionally, (Bvi), of from about 1.3:1 to 1.9:1. 
     
     
         31 . The method of producing an aqueous radiation-curable composition according to  claim 19 , wherein compounds (Bii) and (Biii) are used in a molar ratio (ii):(iii) of from 0.5:1 to 1.5:1. 
     
     
         32 . The method of producing an aqueous radiation-curable composition according to  claim 19 , wherein compounds (Bii) and (Biii) are used in a molar ratio (ii):(iii) of from 0.8:1 to 1.2:1. 
     
     
         33 . The method of producing an aqueous radiation-curable composition according to  claim 19 , wherein, in the process for producing polyurethane (B), the equivalent ratio of isocyanate groups provided by the prepolymer to isocyanate-reactive groups provided by compound (Biv) is from about 2:1 to 1:1. 
     
     
         34 . The method of producing an aqueous radiation-curable composition according to  claim 19 , wherein, in the process for producing polyurethane (B), the equivalent ratio of isocyanate groups provided by the prepolymer to isocyanate-reactive groups provided by compound (Biv) is from about 1.7:1 to 1.25:1.