Heat-seal paper having air permeabillty

Abstract

A laminate integrated by firmly jointing a heat-seal layer in web form made from a mixture of synthetic pulp having a branched configuration and synthetic short fiber to a substrate layer made from natural fiber. The synthetic pulp is made from a resin composition comprised of ethylene-α,β-unsaturated carboxylic acid copolymer and polyethylene. This laminate has a high degree of air permeability and exhibits a high heat-seal strength and good hot tack even at a temperature of 130° C. On account of said properties it is adequately used as heat-seal paper suited for filter use, in particular raw material paper for tea bags.

What we claim is:  
     
         1 . A heat-seal paper having air permeability, which comprises a laminated body integrating a heat-seal layer (A) principally comprised of a synthetic fiber having a branched configuration and a substrate layer (B) principally comprised of a natural fiber.  
     
     
         2 . A heat-seal paper having air permeability according to  claim 1 , wherein said synthetic fiber having the branched configuration is a polyolefin synthetic pulp.  
     
     
         3 . A heat-seal paper having air permeability according to  claim 2 , wherein said polyolefin synthetic pulp has an average fiber length of 0.1 to 10 mm and a freeness of 700 cc or less.  
     
     
         4 . A heat-seal paper having air permeability according to  claim 2  or  3 , wherein said polyolefin synthetic pulp is constructed of a resin composition comprised of 50 to 100% by weight of an ethylene-α,β-unsaturated carboxylic acid copolymer containing 1 to 20% by weight of an α,β-unsaturated carboxylic acid and 0 to 50% by weight of a polyethylene resin.  
     
     
         5 . A heat-seal paper having air permeability according to either one of  claims 1  to  4 , wherein said heat-seal layer (A) is comprised of 50 to 100% by weight of the polyolefin synthetic pulp and 0 to 50% by weight of at least one type of fiber selected from the group consisting of polyethylene fiber, polypropylene fiber, polyester fiber and conjugate fiber thereof.  
     
     
         6 . A heat-seal paper having air permeability according to either one of  claims 1  to  4 , wherein said heat-seal layer (A) is comprised of 50 to 90% by weight of the polyolefin synthetic pulp and 10 to 50% by weight of at least one type selected from the group consisting of polyethylene fiber, polypropylene fiber, polyester fiber and conjugate fiber thereof.  
     
     
         7 . A heat-seal paper having air permeability, which is a laminated body integrating a heat-seal layer (A) and a substrate layer (B) principally containing a natural fiber, wherein said heat-seal layer (A) is comprised of 1 to 99% by weight of a polyolefin synthetic pulp having a branched configuration and an average fiber length of 0.1 to 10 mm and 1 to 99% by weight of a synthetic fiber having a fineness of 0.1 to 10 deniers and an average fiber length of 0.1 to 30 mm, and said synthetic pulp is constructed of a resin composition comprised of 50 to 99% by weight of an ethylene-α,β-unsaturated carboxylic acid copolymer containing 1 to 20% by weight of an α,β-unsaturated carboxylic acid and 1 to 50% by weight of a polyethylene resin.  
     
     
         8 . A heat-seal paper having air permeability according to  claim 7 , wherein said heat-seal layer (A) is comprised of 50 to 99% by weight of the polyolefin synthetic pulp and 1 to 50% by weight of the synthetic fiber.  
     
     
         9 . A heat-seal paper having air permeability according to  claim 7 , wherein said heat-seal layer (A) is comprised of 50 to 90% by weight of the polyolefin synthetic pulp and 10 to 50% by weight of the synthetic fiber.  
     
     
         10 . A heat-seal paper having air permeability according to either one of  claims 7  to  9 , wherein said synthetic fiber is at least one type of fiber selected from the group consisting of polyethylene fiber, polypropylene fiber, polyester fiber and conjugate fiber thereof.  
     
     
         11 . A heat-seal paper having air permeability according to either one of  claims 7  to  10 , wherein said ethylene-α,β-unsaturated carboxylic acid copolymer is an ethylene-acrylic acid copolymer or an ethylene-methacrylic acid copolymer.  
     
     
         12 . A heat-seal paper having air permeability according to either one of  claims 7  to  11 , wherein said polyethylene resin has a density of 0.941 to 0.970 (g/cm 3 ) and a melt flow rate of 0.1 to 100 (g/10 min.).  
     
     
         13 . A heat-seal paper having air permeability according to either one of  claims 7  to  12 , wherein said polyolefin synthetic pulp has a freeness of 700 cc or less.  
     
     
         14 . A heat-seal paper having air permeability according to either one of  claims 7  to  13 , wherein said heat-seal layer (A) has a thickness corresponding to a grammage of 1 to 10 (g/m 2 ).  
     
     
         15 . A heat-seal paper having air permeability according to either one of  claims 7  to  14 , wherein said substrate layer (B) has a thickness corresponding to a grammage of 10 to 30 (g/m 2 )  
     
     
         16 . A heat-seal paper having air permeability according to either one of  claims 7  to  15 , wherein said substrate layer (B) is comprised of an abaca pulp.  
     
     
         17 . A heat-seal paper having air permeability according to either one of  claims 7  to  16 , wherein said laminated body is comprised of 15 to 30% by weight of the heat-seal layer (A) and 70 to 85% by weight of the substrate layer (B).  
     
     
         18 . A heat-seal paper having air permeability according to either one of  claims 7  to  17 , wherein said laminated body has a thickness corresponding to a grammage of 11 to 40 (g/m 2 ).  
     
     
         19 . A heat-seal paper having air permeability according to either one of  claims 7  to  18 , wherein said laminated body has a Frazier air permeability of 100 to 300 (cm 3 /cm 2 /s)  
     
     
         20 . A heat-seal paper having air permeability according to either one of  claims 7  to  19 , wherein said laminated body has a heat-seal strength at a temperature of 130° C. of 100 to 300 (g/15 mm).  
     
     
         21 . A heat-seal paper having air permeability according to either one of  claims 7  to  20 , wherein said laminated body has a hot tack as represented by a peel distance at a temperature of 130° C. is 1 to 100 mm.  
     
     
         22 . A heat-seal paper having air permeability according to either one of  claims 7  to  21 , wherein said laminated body is a filter bag paper.  
     
     
         23 . A heat-seal paper having air permeability according to either one of  claims 7  to  21 , wherein said laminated body is a tea bag paper.  
     
     
         24 . A heat-seal paper having air permeability according to either one of  claims 7  to  23 , wherein said heat-seal layer (A) and said substrate layer (B) constituting the laminated body do not substantially contain any halogen atom.