Articles with thin melt coatings and methods for making same
Assignee3M Innovative Properties Company
InventorsPatrick D. Hyde, Jeffrey M. Imsande, Jayshree Seth, Craig E. Hamer, Rebecca A. Shipman, Robert B. Secor, Michael C. Martin, Pentti K. Loukusa
Life of this patent
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Abstract
Articles with thin caliper melt coatings of high molecular weight, high viscosity materials and methods of making such coatings.
Claims60
An article comprising a substrate having a first surface and a melt coated layer having a first major surface and a second major surface, the first major surface of the melt coated layer being disposed upon the first surface of the substrate, wherein the melt coated layer is substantially continuous and comprises a melt coated composition selected from the group consisting of:
- (a) one or more acrylic polymers having a collective molecular weight of at least about 200,000, and the melt coated layer has a coating weight less than about 25 g/m2, is free of solvents, and contains no more than about 1% by weight of gelled acrylic polymer;
- (b) one or more thermoplastic elastomers having a collective melt viscosity greater than about 20,000 cP, measured at any temperature suitable for hot-melt coating and at shear rates less than 100 sec−1 or frequencies less than 100 rad/sec, and the melt coated layer has a coating weight less than about 12 g/m2;
- (c) one or more natural rubbers or synthetic rubbers, none of which are thermoplastic elastomers, having a collective molecular weight of at least about 200,000 g/mol and a collective melt viscosity greater than about 50,000 cP, measured at any temperature suitable for hot-melt coating and at shear rates less than 100 sec−1 or frequencies less than 100 rad/sec, and the melt coated layer has a coating weight less than about 29 g/m2;
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- (d) one or more nonelastomeric thermoplastic polymers having a collective molecular weight of from about 50,000 to about 3,000,000 g/mol, and the melt coated layer has a coating weight less than about 17 g/m2 and is free of solvents.
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A process for making articles with a melt coated layer thereon, the process comprising the steps of:
- (a) conveying a molten coating composition comprising a polymer through a die slot having a thickness less than about 35 mils;
- (b) directly contacting the molten composition to the entry side of a nip point between a rotating rod having a diameter less than about 3 inches (7.6 cm) and a moving substrate supported on a backup roller, wherein a sufficiently small nipping pressure is employed such that the surface of the backup roller is deformed by no more than a depth of about 20 mils;
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- (c) obtaining a substrate with a melt coated layer thereon on the exit side of the nip point;
- wherein the rotating rod and the compressible backup roller are each rotating in the direction of motion of the moving substrate;
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- wherein the rotating rod is rotating at greater than about 20 rpm, and has surface speed that is between about 1 and about 20% of the speed of the moving substrate.
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Dependencies are inferred from the claim text.