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1. US4493778 - Water-based magnetic coating composition

Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

[ EN ]
What is claimed is:
1. In an aqueous coating composition for forming a magnetic recording layer, this layer including magnetic pigment material and a water-based polymeric matrix therefor, this matrix including binder material comprising high molecular weight poly blends of hard and soft polymers adapted to form "interpenetrating elastomeric networks" in the presence of the magnetic pigment;
the improvement comprising the use of sufficient polyacrylic latex polymer, as a dispersant in an aqueous solution to which the pigment is added, to adequately stabilize the pigment material, after mixing, and bond it to the binder material with little or no migration to the surface of the finished recording layer, and also so as to avoid flocculation and aggravated foaming.
2. The aqueous coating composition of claim 1 wherein the polyacrylic latex polymer comprises a terpolymer including styrene and a member selected from the group consisting of butyl acrylate and methylmethacrylate.
3. The aqueous coating composition of claim 2 wherein styrene is present in the polyacrylic latex in an amount between approximately 10-20% by weight and the remaining acrylate is present in the polyacrylic latex in an amount between approximately 80-90% by weight.
4. The aqueous coating composition of claim 2 wherein said copolymer is of a molecular weight between approximately 20,000 to 40,000.
5. The aqueous coating composition of claim 1 further comprising a water insoluble polymeric binder having both a hard and a soft component.
6. The aqueous coating composition of claim 5 wherein the hard component comprises a member selected from the group consisting of copolymers and terpolymers of acrylonitrile, ethyl acrylate, butylacrylate, methylmethacrylate and mixtures thereof.
7. The aqueous coating composition of claim 6 wherein the hard component comprises a copolymer of approximately 10-20% by weight of acrylonitrile and approximately 80-90% by weight of a member selected from the group consisting of ethylacrylate and butylacrylate.
8. The aqueous coating composition of claim 6 wherein the hard component comprises a terpolymer of approximately 6-20% by weight of acrylonitrile, approximately 60-80% by weight ethylacrylate or butylacrylate and approximately 10-20% by weight methylmethacrylate.
9. The aqueous coating composition of claim 5 wherein the soft component comprises a polymer emulsion of a polyurethane having a glass transition temperature of between approximately -10° C. to -40° C.
10. The aqueous coating composition of claim 5 further comprising a flow agent, antifoaming agent, wetting agent and lubricant.
11. The aqueous coating composition of claim 10 wherein said flow agent is an alkyline-soluble emulsion of ethyl acrylate and acrylic acid.
12. The aqueous coating composition of claim 10 wherein said lubricant comprises a member selected from the group consisting of aliphatic and aromatic stearates, silicone oils, perfluoro alkyl polyethers and fluorinated fluids having one of the following structures: wherein n=40-90
m=40-90 and
F--CF(CF 3)CF 2 O] n' C 2 F 5
wherein N'=14-45 and mixtures thereof.
13. The aqueous coating composition of claim 1 wherein the polyacrylic latex dispersant polymer comprises a terpolymer of styrene and a member selected from the group consisting of butyl acrylate and methylmethacrylate, wherein the binder material is comprised of high molecular weight latexes of hard and soft polymers adapted to form "interpenetrating elastomeric networks" in the presence of magnetic pigment.
14. The aqueous coating composition of claim 13 wherein styrene is present in the polyacrylic latex in an amount between approximately 10-20% by weight and the remaining acrylate is present in the polyacrylic latex in an amount between approximately 80-90% by weight, with said copolymer having a molecular weight between approximately 20,000 to 40,000.
15. The aqueous coating composition of claim 14 wherein the hard component polymer comprises a member selected from the group consisting of copolymers and terpolymers of acrylonitrile, ethyl acrylate, butylacrylate, methylmethacrylate and mixtures thereof.
16. The aqueous coating composition of claim 15 wherein the hard component comprises a copolymer of approximately 10-20% by weight of acrylonitrile and approximately 80-90% by weight of a member selected from the group consisting of ethylacrylate and butylacrylate.
17. The aqueous coating composition of claim 14 wherein the soft component polymer comprises a polymer emulsion of a polyurethane having a glass transition temperature of between approximately -10° C. to -40° C.
18. The aqueous coating composition of claim 14 wherein the soft component polymer comprises a polymer emulsion of a polyurethane having a glass transition temperature of between approximately -10° C. to -40° C.; and wherein this aqueous coating composition further comprises a flow agent, antifoaming agent, wetting agent and lubricant; said flow agent comprising an alkyline-soluble emulsion of ethyl acrylate and acrylic acid.
19. The aqueous coating composition of claim 18 wherein said lubricant comprises a member selected from the group consisting of aliphatic and aromatic stearates, silicone oils, perfluoro alkyl polyethers and fluorinated fluids having one of the following structures: wherein n=40-90
m=40-90 and
F--CF(CF 3)CF 2 O] n' C 2 F 5
wherein n'=14-45 and mixtures thereof.
20. The aqueous coating composition of claim 6 wherein the hard component comprises a copolymer or terpolymer of approximately 10-20% by weight of acrylonitrile and approximately 90-80 wt.% ethylacrylate or butylacrylate.