Carboxylic acid functional polyurethane polymers and blends thereof used in magnetic recording media

Abstract

The invention provides novel macromonomer and carboxyl functional polyurethanes having a high carboxyl content. The invention further provides dispersions, coatings and magnetic recording media comprising these polyurethanes, or blends or copolymers of these polyurethanes with quaternary ammonium compounds. The invention further provides novel dispersions, coatings and magnetic recording media comprising combinations of carboxyl functional polyurethanes having a high carboxyl content with quaternary ammonium polymers.

1 . A carboxylic acid functional graft carboxyl polyurethane polymer comprising the reaction product of a mixture comprising: 
 (a) one or more polyisocyanates;    (b) a macromonomer(s) having a number average molecular weight greater than about 500 and one to two isocyanate-reactive groups selected from the group consisting of hydroxyl, primary amino, secondary amino and mercapto groups; and wherein if two isocyanate-reactive groups are present, they are separated by no more than about 10 atoms within the macromonomer molecule;    (c) a carboxylic acid functional polyol;    (d) optionally one or more quaternary ammonium polyols;    (e) optionally one or more polyols, wherein the polyols(s) of element (e) are defined to exclude components of elements (b), (c), and (d);    wherein the number of isocyanate-reactive groups present in the mixture prior to reaction exceeds the number of isocyanate groups; and wherein the macromonomer (b) content comprises from about 5% to about 95% by weight based on the weight of the graft carboxyl poiyurethane polymer; and wherein at least about 0.2 meq of carboxylic acid groups are present on the graft carboxyl polyurethane polymer per gram of graft carboxyl polyurethane polymer.    
     
     
         2 . The graft carboxyl polyurethane polymer of  claim 1  wherein the macromonomer (b) content comprises from about 20% to about 80% by weight based on the weight of the graft carboxyl polyurethane polymer.  
     
     
         3 . The graft carboxyl polyurethane polymer of  claim 1  wherein at least about 0.4 meq of carboxylic acid group are present on the graft carboxyl polyurethane polymer per gram of polymer.  
     
     
         4 . The graft carboxyl polyurethane polymer of  claim 1  wherein the carboxylic acid functional polyol is 2,2-bis(hydroxymethyl)propionic acid.  
     
     
         5 . A dispersion comprising: 
 (a) one or more of the graft carboxyl polyurethane polymers of  claim 1;     (b) optionally a quaternary ammonium compound(s);    (c) one or more pigments selected from the group consisting of magnetic pigments, non-magnetic pigments, and mixtures thereof;    (d) an organic solvent; and    (e) optionally a polyisocyanate curative.    
     
     
         6 . The dispersion of  claim 5  wherein about 0.3 to about 30 millimoles of quaternary ammonium group are present in the dispersion per kilogram of pigment.  
     
     
         7 . The dispersion of  claim 5  wherein a quaternary ammonium compound is present and the quaternary ammonium compound is a quaternary ammonium polyurethane.  
     
     
         8 . The dispersion of  claim 5  wherein a quaternary ammonium compound is present and the quaternary ammonium compound is a quaternary ammonium functional nonhalogenated vinyl copolymer.  
     
     
         9 . A coating comprising the dispersion of  claim 5  dried of solvent.  
     
     
         10 . A coating comprising the coating of  claim 6  dried of solvent.  
     
     
         11 . A coating comprising the coating of  claim 7  dried of solvent.  
     
     
         12 . The coating of  claim 9  wherein about 20 to about 60 percent by weight of the polyisocyanate curative 5(e) is present based upon the total weight of the coating exclusive of pigment, and said polyisocyanate curative is the reaction product of a mixture comprising: 
 (i) one or more diisocyanates; and  
 (ii) one or more polyols;  
 wherein at least one of the polyols of (ii) is an oligomeric polyol of number average molecular weight between about 500 and 5000 having a glass transition temperature less than about 0° C. and wherein said oligomeric polyol comprises between about 10 and about 80% by weight of the curative and wherein the overall ratio of hydroxyl to isocyanate functionality in the mixture comprising (I) and (ii) prior to reaction is less than 1.  
 
     
     
         13 . A magnetic recording medium comprising the coating of  claim 9  on at least one side of a substrate.  
     
     
         14 . A magnetic recording medium comprising the coating of  claim 10  on at least one side of a substrate.  
     
     
         15 . A magnetic recording medium comprising the coating of  claim 11  on at least one side of a substrate.  
     
     
         16 . A magnetic recording medium comprising the coating of  claim 12  on at least one side of a substrate.  
     
     
         17 . A magnetic recording medium comprising the coating of  claim 9  on one side of a substrate wherein one or more non-magnetic pigments are present.  
     
     
         18 . A dispersion comprising: 
 (a) one or more of carboxyl polyurethane polymers comprising the reaction product of a mixture comprising: 
 (i) one or more polyisocyanates;  
 (ii) a carboxylic acid functional polyol(s);  
 (iii) optionally one or more polyols, wherein the polyols(s) of element (iii) are defined to exclude components of element(s) (a)(ii);  
   wherein the number of isocyanate-reactive groups present in the mixture prior to reaction exceeds the number of isocyanate groups and wherein at least about 0.2 meq of carboxylic acid group are present on the carboxyl polyurethane polymer per gram of carboxyl polyurethane polymer;    (b) a polymeric quaternary ammonium compound(s) having a number average molecular weight of at least about 500;    (c) one or more pigments selected from the group consisting of magnetic pigments, non-magnetic pigments, and mixtures thereof; and    (d) an organic solvent; and    (e) optionally a polyisocyanate curative    
     
     
         19 . The dispersion of  claim 18  wherein about 0.3 to about 30 millimoles of quaternary ammonium group are present in the dispersion per kilogram of pigment.  
     
     
         20 . The dispersion of  claim 18  wherein the quaternary ammonium compound is a quaternary ammonium polyurethane.  
     
     
         21 . The dispersion of  claim 18  wherein the quaternary ammonium compound is a quaternary ammonium functional non-halogenated vinyl copolymer.  
     
     
         22 . The dispersion of  claim 18  wherein at least about 1.0 meq of carboxylic acid group are present on the carboxyl polyurethane polymer per gram of carboxyl polyurethane polymer.  
     
     
         23 . A coating comprising the dispersion of  claim 18  dried of solvent  
     
     
         24 . A coating comprising the dispersion of  claim 19  dried of solvent  
     
     
         25 . A coating comprising the dispersion of  claim 20  dried of solvent  
     
     
         26 . A coating comprising the dispersion of  claim 21  dried of solvent.  
     
     
         27 . A coating comprising the dispersion of  claim 22  dried of solvent  
     
     
         28 . The coating of  claim 23  wherein about 20 to about 60 percent by weight of the polyisocyanate curative  18 (e) is present based upon the total weight of the coating exclusive of pigment, and said polyisocyanate curative is the reaction product of a mixture comprising: 
 (i) one or more diisocyanates; and  
 (ii) one or more polyols;  
 wherein at least one of the polyols of (ii) is an oligomeric polyol of number average molecular weight between about 500 and 5000 having a glass transition temperature less than about 0° C. and wherein said oligomeric polyol comprises between about 10 and about 80% by weight of the curative and wherein the overall ratio of hydroxyl to isocyanate functionality in the mixture comprising (1) and (ii) prior to reaction is less than 1.  
 
     
     
         29 . A magnetic recording medium comprising the coating of  claim 23  on at least one side of a substrate.  
     
     
         30 . A magnetic recording medium comprising the coating of  claim 24  on at least one side of a substrate  
     
     
         31 . A magnetic recording medium comprising the coating of  claim 25  on at least one side of a substrate.  
     
     
         32 . A magnetic recording medium comprising the coating of  claim 26  on at least one side of a substrate.  
     
     
         33 . A magnetic recording medium comprising the coating of  claim 27  on at least one side of a substrate  
     
     
         34 . A magnetic recording medium comprising the coating of  claim 28  on at least one side of a substrate.  
     
     
         35 . A magnetic recording medium comprising the coating of  claim 29  on at least one side of a substrate wherein one or more non-magnetic pigments are present.  
     
     
         36 . A coating comprising the dispersion of  claim 8  dried of solvent.  
     
     
         37 . A magnetic recording medium comprising the coating of  claim 36  on at least one side of a substrate.