Patent ID: 8038925

Claim:
A process of producing a waterproof and breathable shoe lining structure for a boot having an outer shell, comprising the steps of: (a) forming a pair of interior linings each of which is cut into a boot shape, wherein each of said interior linings is made by the steps of: (a.1) forming a sheet-like waterproof and air breathable foaming cushion layer; (a.2) integrally attaching a lining layer to one side of said foaming cushion layer; and (a.3) integrally attaching a cover layer to another side of said foaming cushion layer; (b) stitching said interior linings edge to edge together to form stitching edges; and (c) thermoplastically seaming said stitching edges of said interior linings to form said shoe lining structure for fitting into said outer shell of said boot; wherein, in the step (a.1), said waterproof and air breathable foaming cushion layer is made by the steps of: (i) forming a pelletized raw material with a low density polyethylene, a foaming agent including azodicarbonamide, a pigment, and additives including Zinc Oxide and Zinc Stearate by the steps of: (i-1) mixing said polyethylene with said foaming agent, said pigment, and said additives in a mixer to form a mixture; and (i-2) extrudingly pelletizing said mixture into master batches comprising said low density polyethylene, said foaming agent, said pigment and said additives in pellet; (ii) extruding said pelletized raw material to make a solid sheet, wherein all said master batches are put into an extruder to be extruded into a mother sheet; (iii) cross-linking said solid sheet by an electron-beam to form an irradiated matrix; and (iv) foaming said irradiated matrix into a sheet-like foaming cushion layer by the step of rolling said irradiated matrix, and the step of putting said irradiated matrix into a foaming oven heated by hot air.