Thermally insulating sheet formed from a down core structure and method of fabrication

Abstract

A thermally insulating sheet formed by a down core structure which is comprised solely of down feather material mixed with binding material which is heat fused together to form a homogeneous sheet core. The method of fabricating the homogeneous thermally insulating sheet to form the down core structure is described. This novel method restrains the down clusters and binding material during the process of mixing, depositing, conveying and heat fusing to form a homogeneous down core sheet. The down core structure is subjected to two separate heat treatments which produces a down core sheet having at least some of its outer surfaces being of higher bond density than the inside of the core.

1 . A thermally insulating sheet formed by a down core structure comprising down feathers mixed with binding material which when subjected to heat is capable of bonding together and with said down feathers to form a homogeneous core, said down feathers being down clusters each having a central quill with fluffy tentacles projecting therefrom in all directions creating a three dimensional cluster structure which traps air, said clusters attaching to one another by said tentacles and said binder material, said binding material being comprised of glue particles and/or polymer fibers, said polymer fibers having a low melting point in the range of from about 80 degrees C. to 160 degrees C., said down core structure having a top and bottom outer surface and opposed side surfaces and wherein said outer surfaces are bonded at a higher density than the internal portion of said core thereof. 
     
     
         2 . The thermally insulating sheet as claimed in  claim 1  wherein said binding material is comprised solely of said polymer fibers, there being from about 2% to 30% of said polymer fibers by weight of said mixture and preferably 6% to 15% by weight of said polymer mixture. 
     
     
         3 . The thermally insulating sheet as claimed in  claim 2  wherein said binding material is comprised of a mixture of said polymer fibers and said glue particles, there being from about 2% to 30% by weight of said glue particles in said mixture, and preferably 6% to 15% by weight of said glue particles. 
     
     
         4 . The thermally insulating sheet as claimed in  claim 2  wherein at least some of said polymer fibers are stretchable polyester fibers capable of bonding together and to said down clusters when heat treated whereby to form said homogeneous sheet which exhibits elastic properties to permit said down core structure to stretch with no or minimal fracture to said down core structure and capable of recovering substantially its original relaxed form after deformation and/or stretching. 
     
     
         5 . The thermally insulating sheet as claimed in  claim 4  wherein said polyester fibers are one of or a mixture of polyurethane resin fibers, styrene fibers, hollow bi-component fibers, styrene fibers, twisted fibers and other similar fibers and wherein at least some of said polymer fibers are capable of stretching. 
     
     
         6 . The thermally insulating sheet as claimed in  claim 1  wherein said binding material is comprised solely of said polymer fibers, there being 5% to 90% by weight of fibers mixed with said down feathers, said down polymer fibers occupying preferably of from about 10% to 25% by weight of said mixture with said down feathers. 
     
     
         7 . The thermally insulating sheet as claimed in  claim 2  wherein said binding material is comprised of a mix of said polymer fibers and said glue particles in equal proportions or in a proportion of 30% polymer fibers and 70% glue particles or variations thereof, said binding material occupying a volume of from about 6% to 15% by weight with said down feathers. 
     
     
         8 . (canceled) 
     
     
         9 . The thermally insulating sheet as claimed in  claim 1  wherein said down core structure further comprises other components in the form of chemical additives or fibers to provide fire retardants or to improve the tensile strength of the core.