Hot melt adhesives for multilayer structure enclosures

Abstract

The invention provides enclosure adhesives, methods of using the adhesives to bond for enclosing a multilayer structure and to articles of manufacture comprising the adhesives. The multilayer structure is a laminant of at least one composite film and at least one Kraft paper substrates. It has been discovered that an adhesive that comprises (a) a mixture of 1:1 to 5:2 of a metallocene catalyzed polyolefin copolymer with a density greater than or equal to 0.880 g/cm 3 to a metallocene catalyzed polyolefin copolymer with a density less than 0.880 g/cm 3 ; (b) a compatible tackifier; and (c) a compatible wax, has high adhesion to both Kraft and composite film with low blocking properties.

I/We claim: 
     
         1 . A composite adhesive comprising:
 a) a mixture of a metallocene catalyzed polyolefin copolymer;   b) a tackifier;   c) a wax; and   
       wherein the mixture is a combination of a metallocene catalyzed polyolefin copolymer with a density less than 0.880 g/cm 3  and a metallocene catalyzed polyolefin copolymer with a greater than or equal to than 0.880 g/cm 3 . 
     
     
         2 . The composite adhesive of  claim 1  wherein the mixture has a ratio of 1:1 to 5:2 of the lower density to higher density polyolefin copolymer. 
     
     
         3 . The composite adhesive of  claim 1  wherein the copolymer comprises an ethylene comonomer. 
     
     
         4 . The composite adhesive of  claim 3  wherein the copolymer further comprises a C 2 -C 10  alpha olefin comonomer. 
     
     
         5 . The composite adhesive of  claim 4  wherein the C 2 -C 10  alpha olefin comonomer is an ethylene-octene comonomer and mixtures thereof. 
     
     
         6 . The composite adhesive of  claim 1  wherein the tackifier has a softening point less than about 110° C. 
     
     
         7 . The composite adhesive of  claim 6  wherein the tackifier is natural and modified rosins, rosin ester, synthetic hydrocarbon resins, copolymers and terpolymers of natured terpenes, including, aliphatic and aromatic petroleum hydrocarbon resins; cyclic or acyclic C 5  resins, aromatic modified acyclic and cyclic resins, or mixtures thereof. 
     
     
         8 . The composite adhesive of  claim 7  wherein the plasticizer is a mixture of cyclic or acyclic C 5  resins with rosin ester. 
     
     
         9 . The composite adhesive of  claim 1  wherein the wax has a viscosity of about 20 to about 10,000 cps at 140° C. 
     
     
         10 . The composite adhesive of  claim 9  wherein the wax is a maleic anhydride grafted polyethylene or polypropylene with a saponification number of about 2 to about 90 mg KOH/g. 
     
     
         11 . The composite adhesive of  claim 1  further comprising a radiation curable agents, antioxidant, blooming agents, defoamer, colorants, and mixtures thereof. 
     
     
         12 . A composite adhesive comprising:
 a) a mixture of an ethylene vinyl acetate polymer;   b) a tackifier;   c) a wax; and   wherein the mixture has a ratio of 1:1 to 5:2 of an ethylene vinyl acetate polymer with a vinyl acetate content greater than or equal to 28% and an ethylene vinyl acetate polymer with a vinyl acetate content less than 28%.   
     
     
         13 . An article comprising the adhesive of  claim 1 . 
     
     
         14 . The article of  claim 13  which is a multilayer ply. 
     
     
         15 . The article of  claim 14  which is a pinch bottom bag. 
     
     
         16 . The article of  claim 15  comprising at least one composite film, at least one Kraft paper ply, and optionally a plastic liner. 
     
     
         17 . The article of  claim 15  wherein the composite film is selected from the group consisting of nylon, polyethylene, polypropylene, polyester, and mixture thereof. 
     
     
         18 . A process of sealing a pinch bottom bags comprising:
 (i) applying the adhesive of  claim 1  onto both open end flaps of a pre-formed tube, wherein the pre-formed tube comprises a composite film, Kraft paper and optionally a plastic liner;   (ii) folding over a sufficient amount of one flap to seal one end, whereby the adhesive seals one end of the tube; and   (iii) cooling the remaining adhesive layer to room temperature.   
     
     
         19 . The process of  claim 15  further comprising:
 (iv) reactivating the remaining adhesive with heat; and 
 (v) folding over a sufficient amount of the remaining flap to seal the remaining end, 
 
       whereby the reactivated adhesive seals the remaining end.