Water vapor permeable shrinkable-fabric
A shrinkable-stretchable polymeric laminated structure is made up of a shrink-stretch film on the outside and a nonwoven on the inside, with or without an adhesive. Preferably the film, nonwoven and adhesive are made from the same polymer family, including copolymers, which renders the laminate 100% recyclable. The film, nonwoven, and adhesive are modified to provide different responses to heat in addition to controlled water vapor permeability. The structure allows for water vapor permeability in one direction (inside-to-outside) and not in the opposite direction to allow wrapped article to dry or to keep wrapped articles dry and prevent corrosion related damage.
1. A packaging material in sheet form having a first side for contacting with an object to be packaged and a second side opposite the first to be exposed comprising:
a. a water vapor permeable thermoplastic film;
b. a hydrophilic non-woven fabric in contact with the water vapor permeable thermoplastic film along an interface; and
c. a hot melt adhesive in the interface that intermittently bonds the water vapor permeable thermoplastic film to the hydrophilic non-woven fabric,
wherein the water vapor permeable thermoplastic film has three or more individual layers characterized by increasing water vapor transmission rate with increasing distance from the interface, and wherein the hydrophilic non-woven fabric has two or more individual layers characterized by fibers of different denier, fibers of different hydrophilicity, or both.
2. The packaging material according to claim 1 , wherein the water vapor permeable thermoplastic film and hydrophilic non-woven fabric are based on homopolymers and/or copolymers of ethylene, and the fibers of the hydrophilic non-woven fabric are characterized by a heat deflection temperature of 70° C. or higher.
3. The packaging material according to claim 2 , wherein the water vapor permeable thermoplastic film comprises a plurality of carboxylate groups neutralized with potassium ions.
4. The packaging, material according to claim 2 , wherein the water vapor permeable thermoplastic film comprises low density polyethylene (LDPE), or linear low density polyethylene (LLDPE).
5. The packaging material according to claim 2 , wherein the water vapor permeable thermoplastic film comprises a plurality of co-extruded layers, including an interface layer adjacent the interface, a skin layer forming an outside layer of the sheet, and one or more intermediate layers disposed between the interface and skin layers.
6. The packaging material according to claim 5 , wherein the water vapor permeability and hydrophilicity of the skin layer is higher than that of the interface layer.
7. The packaging material according to claim 6 , wherein the interface layer comprises calcium carbonate and the skin layer comprises a plurality of potassium neutralized carboxylate groups.
8. The packaging material according to claim 2 , wherein the hydrophilic non-woven fabric comprises a plurality of layers including an interface layer adjacent the interface with the water vapor permeable thermoplastic film and an outside layer forming the first side of the sheet, wherein the hydrophilicity of the outside layer is less than the hydrophilicity of the interface layer.
9. The packaging material according to claim 8 , wherein the interface layer and the outside layer contain fibers of different size, the fibers in the interface layer being greater in diameter than the fibers in the outside layer.
10. The packaging material according to claim 8 , wherein the hydrophilic non-woven fabric comprises staple fibers of LLDPE.
11. The packaging material according to claim 9 , wherein the hydrophilic non-woven fabric comprises fibers of 1.2-1.5 denier.
12. A packaging product in sheet form, the sheet made up of materials to build up a laminate, the laminate comprising:
a first material comprising a shrink-stretch film with water vapor permeability of no less than 30 grams per square meter per day and forming a first side of the laminate;
a second material forming a second side of the laminate and comprising a multilayer non-woven fabric, the multilayer non-woven fabric having a plurality of layers of differing hydrophilicity; and
a third material comprising a hot melt adhesive disposed at an interface between and bonding together the first and second material;
wherein the shrink-stretch film, the multilayer non-woven fabric and hot melt adhesive comprise homopolymers or copolymers of ethylene.
13. The packaging product according to claim 12 , wherein the shrink-stretch film comprises calcium carbonate filler.
14. The packaging product according to claim 12 , wherein the shrink-stretch film comprises a polyolefin and an ionomer having a plurality of carboxylate groups at least partially neutralized with potassium and/or sodium.
15. The packaging product according to claim 12 , wherein the shrink-stretch film comprises a plurality of layers including an interface layer adjacent the interface and one or more outside layers disposed on the interface layer, wherein the layers exhibit increasing vapor permeability in order of increasing distance from the interface.
16. The packaging product according to claim 12 , wherein the shrink-stretch film thickness is from 3 mils to 9 mils.
17. The packaging product according to claim 12 , wherein the multilayer non-woven fabric is made of layers having differing fiber sizes.
18. The packaging product according to claim 17 , wherein the layers comprise crimped staple fibers.
19. The packaging product according to claim 12 , wherein the hydrophilicity of the layers of the multilayer non-woven fabric increases in order from the second side of the sheet material to the interface.