US 5,071,578 AGranted

Sulfonated hydroxy-functional polyurethane binder for magnetic recording media

AssigneeMinnesota Mining and Manufacturing Company

InventorsTakatoshi Ohkubo, James G. Carlson

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Abstract

The present invention concerns magnetic recording media comprising fine, magnetizable pigment or particles dispersed within a binder and supported on a substrate. The invention particularly concerns the nature of the binder polymer and its preparation. The binder polymer is a curable polymer comprising a sulfonated, hydroxy-functional polyurethane polymer. A plurality of SO.sub.3 M groups are pendant from the polyurethane polymer backbone. The SO.sub.3 M groups have an equivalent weight of from about 2,000 to about 100,000. M is selected from the group consisting of H.sup.+, Li.sup.+, Na.sup.+, K.sup.+, NR.sub.4.sup.+ where R can be H.sup.+ or an alkyl group, and mixtures thereof. A plurality of hydrophobic polymer chain segments are incorporated into the polyurethane polymer that comprise residues of a polyol having a molecular weight of at least about 180. The hydrophobic chain segments have a carbon atom to polar functionality of at least about 60. The polyurethane polymer also comprises a plurality of cross-linkable hydroxy groups having an equivalent weight of from about 500 to about 10,000. At least a majority of the hydroxy groups are pendant from hydrophobic chain segments.

Claims16

Dependent claims

A curable sulfonated, hydroxy-functional polyurethane polymer which comprises:

(a) a plurality of SO.sub.3 M groups pendant from the polyurethane polymer backbone, wherein the polyurethane polymer has an SO.sub.3 M equivalent weight of from about 2,000 to about 100,000, and wherein M is selected from the group consisting of H.sup.+, Li.sup.+, Na.sup.+,K.sup.+, Nr.sub.4.sup.+ where R can be H.sup.+ or an alkyl group, and mixtures thereof;
and
(b) a plurality of hydrophobic polymer chain segments incorporated into the polyurethane polymer that comprise residues of a polyol having an average molecular weight of at least about 180 and a hydroxy equivalent weight of at least about 60, wherein the hydrophobic polymer chain segments have a carbon atom to polar functionality of at least about 3:1;
and
(c) a plurality of cross-linkable hydroxy groups, wherein the polyurethane polymer has a hydroxy equivalent weight of from about 500 to about 10,000 and wherein at least a majority of the hydroxy groups are pendant from the hydrophobic polymer chain segments;
wherein said polymer is obtained by reacting a sulfonated polyisocyanate having at least two reactive isocyanate groups and having substantially no hydroxy functionality;
and a hydrophobic polyol having at least three reactive hydroxy groups, wherein sad hydrophobic polyol is present in a sufficient amount relative to the sulfonated polyisocyanate such that there is at least about a 67% excess of reactive hydroxy groups relative to reactive isocyanate groups.

4 more elements

A dispersion for use in magnetic recording media, comprising:

(a) a sulfonated, hydroxy-functional polyurethane polymer which comprises:
(i) a plurality of SO.sub.3 M groups pendant from the polyurethane polymer backbone, wherein the SO.sub.3 M groups have an equivalent weight of from about 2,000 to about 100,000, and wherein M is selected from the group consisting of H.sup.+, Li.sup.+, Na.sup.+, K.sup.+, NR.sub.4.sup.+ where R can be H.sup.+ or an alkyl group, and mixtures thereof;
and
(ii) a plurality of hydrophobic polymer chain segments incorporated into the polyurethane polymer that comprise residues of a polyol having an average molecular weight of at least about 180, wherein the hydrophobic polymer chain segments have a carbon atom to polar functionality of at least about 3:1 and a hydroxy equivalent weight of at least about 60;
and
(iii) a plurality of cross-linkable hydroxy groups, wherein the hydroxy groups have an equivalent weight of from about 500 to about 10,000 and wherein at least a majority of the hydroxy groups are pendant from the hydrophobic polymer chain segments;
wherein said polymer is obtained by reacting a sulfonated polyisocyanate having at least two reactive isocyanate groups and having substantially no hydroxy functionality;
and a hydrophobic polyol having at least three reactive hydroxy groups, wherein said hydrophobic polyol is present in a sufficient amount relative to the sulfonated polyisocyanate such that there is at least about a 67% excess of reactive hydroxy groups relative to reactive isocyanate groups.
(b) a magnetizable pigment dispersed in said polyurethane polymer.

6 more elements

Dependencies are inferred from the claim text.

Facts

Application: 07/429,720Filed 31 Oct 1989 · continuation in part
Priority: 6 Jan 1989
Granted: 10 Dec 1991
Term ends: Not estimatedThe source records don’t support an estimate.

Classification6 codes

C08G 18/0828
Containing anionic or anionogenic groups: containing sulfonate groups or groups forming them
G11B 5/7021
Characterised by the bonding agent: containing a polyurethane or a polyisocyanate
Y10S 428/90
Stock material or miscellaneous articles: magnetic feature
C08G
Macromolecular compounds obtained otherwise than by reactions only involving unsaturated carbon-to-carbon bonds