Magnetic recording medium whose magnetic layer incorporates nonhalogenated vinyl copolymer and specified polyurethane polymer

A magnetic recording medium, comprising a magnetic layer provided on a nonmagnetizable substrate, wherein the magnetic layer comprises a magnetic pigment dispersed in a polymeric binder, and wherein the polymeric binder comprises:

• (a) a nonhalogenated vinyl copolymer, wherein the vinyl copolymer comprises a plurality of pendant nitrile groups, a plurality of pendant hydroxyl groups, and at least one pendant dispersing group;
• and
• (b) a polyurethane polymer, wherein the polyurethane polymer comprises a pendant dispersing group of the formula ##STR7## wherein R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are independently selected from the group consisting of --H, --OH, --COOM, --SSO.sub.3 M, --SH, --CH.sub.2 COOM, --SCH.sub.2 COOM, --P(.dbd.O)(OM).sub.2, --OP(.dbd.O)(OM).sub.2, and --Y, wherein at least one of R.sup.1, R.sup.2, R.sup.3, and R.sup.4 comprises a moiety other than --H or --Y;
• Y is selected from the group consisting of linear alkyl groups comprising from about 1 to about 10 carbon atoms, branched alkyl groups comprising from about 1 to about 10 carbon atoms, and aryl groups comprising from about 6 to about 10 carbon atoms;
• M is a cation selected from the group consisting of alkali metal cations, H.sup.+ and ammonium cations;
• R.sup.1 and R.sup.2 together or R.sup.3 and R.sup.4 together can be cis or trans .dbd.CHCOOH;
• X is a divalent moiety independently selected from the group consisting of --CR.sup.5 R.sup.6 and --NR.sup.7 ;
• n represents an integer selected from the group consisting of 0 and 1;
• R.sup.5 and R.sup.6 are independently selected from the group consisting of --H, --OH, --COOM, --SO.sub.3 M, --SH, --CH.sub.2 COOM, --SCH.sub.2 COOM, --P(.dbd.O)(OM).sub.2, --OP(.dbd.O)(OM).sub.2, and --Y, wherein M and Y are as defined above;
• R.sup.7 is a monovalent moiety independently selected from the group consisting of --CH.sub.2 COOH, --CH.sub.2 CH.sub.2 COOH, --CH.sub.2 CH.sub.2 N(CH.sub.2 COOH).sub.2, --(CH.sub.2).sub.6 N(CH.sub.2 COOH).sub.2, --(CH.sub.2 CH.sub.2 O).sub.2 CH.sub.2 CH.sub.2 N(CH.sub.2 COOH).sub.2, and --CH.sub.2 CH.sub.2 N(CH.sub.2 COOH)CH.sub.2 CH.sub.2 OH.