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

A carboxylic acid and hydroxyl functional polyurethane polymer comprising the reaction product of:

• (a) one or more polyisocyanates;
• (b) one or more polyols;
• (c) one or more compounds selected from the group consisting of cyclic dicarboxylic acid anhydrides derived from carboxylic acids having a pKa of less than 2.0;
• and
• (d) at least one vinyl polymeric macromonomer diol prepared from monomers which do not have reactive sites towards polyisocyanates;
• wherein the hydroxyl content of the polyurethane is at least about 0.01 meq/g;
• and
• wherein the molar ratio of hydroxyl groups to the sum of the isocyanate groups plus anhydride groups of reactants from which the polyurethane is formed is greater than 1.1.

A polyurethane polymer having pendant therefrom at least one pendant group selected from the group consisting of Formula IV:

• ##STR6## wherein R.sup.5 is independently selected from the group consisting of --Cl, --Br, --I, --F, and --H;
• R.sup.6 is independently selected from the group consisting of --Cl, --Br, --I, --F, and --H;
• wherein R.sup.5 and R.sup.6 cannot simultaneously represent --H;
• and
• wherein R.sup.5 and R.sup.6 may alternatively form a cyclopentyl group;
• and Formula V:
• ##STR7## wherein R.sup.1 is independently selected from the group consisting of --Cl, --Br, --I, --F, and --H;
• R.sup.2 is independently selected from the group consisting of --Cl, --Br, --I, --F, and --H;
• R.sup.3 is independently selected from the group consisting of --Cl, --Br, --I, --F, and --H;
• R.sup.4 is independently selected from the group consisting of --Cl, --Br, --I, --F, and --H;
• and
• wherein at least two of said R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are other than --H;
• and combinations of Formula IV and Formula V;
• wherein the hydroxyl functionality of the polyurethane polymer is at least about 0.01 meq/g;
• wherein the polyurethane polymer optionally has one or more pendant vinyl polymeric segments;
• and
• wherein the polyurethane polymer has an acid content of about 0.01 to about 0.3 meq/g.

A carboxylic acid-functional polyurethane polymer comprising:

• a plurality of --COOH groups, a plurality of --OH groups, and optionally one or more vinyl polymeric segments pendant from a polyurethane polymer backbone, wherein the polyurethane polymer has a --COOH content of about 0.01 to 0.3 meq/g, and wherein said carboxylic acid-functional polyurethane polymer is obtained by the condensation reaction(s) of a hydroxyl group(s) pendant from said polyurethane polymer backbone with an anhydride selected from the group consisting of 2-chloromaleic acid anhydride;
• 2,3-dichloromaleic acid anhydride;
• tetrafluorphthalic acid anhydride;
• 3,6-dinitrophthalic acid anhydride;
• tetrafluorosuccinic acid anhydride;
• tetrabromosuccinic acid anhydride;
• tetrachlorosuccinic acid anhydride;
• cyclobut-1-ene-1,2-dicarboxylic acid anhydride;
• tetraiodophthalic acid anhydride;
• tetrabromophthalic acid anhydride;
• tetrachlorophthalic acid anhydride;
• 2,3-dibromomaleic acid anhydride;
• bicyclo 2.2.1!hepta-2,5-diene-2,3-dicarboxylic acid anhydride;
• bicyclo 2.2.1!hepta-2-ene-2,3-dicarboxylic acid anhydride;
• 3,6-dichlorophthalic acid anhydride;
• 2,3-dibromosuccinic acid anhydride;
• furan-3,4-dicarboxylic acid anhydride;
• 2-bromomaleic acid anhydride;
• 4,5-dichlorophthalic acid anhydride;
• and cyclopent-1-ene-1,2-dicarboxylic acid anhydride;
• and wherein the hydroxyl functionality of the polyurethane polymer is at least about 0.01 meq/g.