Methods for making peelable easy open plastic bags

Abstract

A woven laminated plastic bag having features that prevent leakage of contents out of the bag, or infestation of organisms into the contents of the bag is provided. In various aspects the bag can be fabricated from woven polypropylene and/or polyethylene layer which can be laminated with a film layer, can form a pinch bottom bag, and can have one or both sides include graphics and/or printing. The bag can also provide a top end and/or a bottom end either or both of which provide a discrete area which may contain discrete graphics and/or printing. The bag can also include a sealed closure that at least a portion of which can be easily peeled open with less force than the remainder of the sealed closure. Methods of making such bags include providing a bag with one wall longer than another wall at one end, treating the interior surface of the longer wall end, the exterior surface of the shorter wall end, or both, folding over the longer end and sealing the interior surface of the longer wall to the exterior surface of the shorter wall to form a sealed end that can be peeled open. The treatment may include two treatments, which may be an ink treatment and/or an ionization treatment, treatment with a resin, or varnish, or polymeric material, or treatment with pressure, temperature, or both.

What is claimed is: 
     
         1 . A method of making a bag, comprising the steps of:
 providing a bag having a first bag wall, a second bag wall, a first side wall and a second side wall, with the first and second bag walls opposing each other, and wherein each bag wall comprises at least a first polymeric layer and a second polymeric layer, with the bag defining a first end and a second end, wherein the first bag wall extends beyond the second bag wall and each of the bag walls have an interior surface and an exterior surface;   adding an ink treatment to a portion of an interior surface of the first bag wall proximal the first end of the bag, an exterior surface of the second bag wall proximal the first end of the bag, or both;   folding the portion of the first bag wall extending beyond the end of the second bag wall over the end of the second bag wall and contacting a portion of the interior surface of the first bag wall proximal the end of the first bag wall with a portion of the exterior surface of the second bag wall proximal the end of the second bag wall, thereby creating an overlay portion of the first and second bag walls;   applying heat, pressure, or both to a first portion of the overlay portion of the first and second bag walls to form a seal between of the first portion of the overlay portion of the first and second bag walls.   
     
     
         2 . The method according to  claim 1  wherein the ink treatment comprises a polyamide ink, a nitrocellulose ink, a urethane-based ink, or a combination thereof. 
     
     
         3 . The method according to  claim 1  wherein the overlay portion comprises a portion of the bag wall approximately ¼ inch to 2 inches from the top end of the bag. 
     
     
         4 . The method according to  claim 1  wherein a second portion of the first bag wall extends beyond the overlay portion and is not sealed to the second bag wall. 
     
     
         5 . The method according to  claim 1  wherein said step of applying heat, pressure, or both, comprises directing heated gas at the overlay portion. 
     
     
         6 . The method according to  claim 5  wherein said heated gas comprises air at or above a predetermined temperature. 
     
     
         7 . The method according to  claim 1  wherein said step of applying heat, pressure, or both, comprises moving the overlay portion of the bag at a predetermined speed past a nozzle blowing heated air within a predetermined temperature range on the overlay portion. 
     
     
         8 . The method according to  claim 1  further comprising the step of adding a second ink treatment to the portion of the interior surface of the first bag wall, the portion of the exterior surface of the second bag wall, or both. 
     
     
         9 . The method according to  claim 1  further comprising the step of applying a second treatment to the portion of the interior surface of the first bag wall, the exterior surface of the second bag wall, or both, wherein the second treatment comprises at least one of:
 an ionization treatment, treatment with a resin, or varnish, or polymeric material, or treatment with pressure, temperature, or both. 
 
     
     
         10 . A bag made according to the process of  claim 1 . 
     
     
         11 . A method of making a bag, comprising the steps of:
 providing a bag having a first bag wall, a second bag wall, a first side wall, and a second side wall, with the first and second bag walls opposing each other, wherein each bag wall comprises a first layer and a second layer, wherein the first layer comprises a woven layer and further comprises polyethylene, polypropylene, or a combination thereof, wherein the second layer comprises a film layer and further comprises polyethylene, polypropylene, or a combination thereof, with the first bag wall and the second bag wall each having a first end and a second end, wherein the first end of the first bag wall extends beyond the first end of the second bag wall;   treating a first portion of an interior surface of the first bag wall proximal the first end of the first bag wall, a first portion of an exterior surface of the second bag wall proximal the first end of the second bag wall, or both, with a first treatment;   treating a second portion of an interior surface of the first bag wall proximal the first end of the first bag wall, a second portion of an exterior surface of the second bag wall proximal the first end of the second bag wall, or both, with a second treatment; and   folding the portion of the first bag wall extending beyond the first end of the second bag wall over the first end of the second bag wall and contacting a portion of the interior surface of the first bag wall proximal the first end of the first bag wall with a portion of the exterior surface of the second bag wall proximal the first end of the second bag wall, thereby creating an overlay portion of the first and second bag walls;   applying heat, pressure, or both to a first portion of the overlay portion of the first and second bag walls to form a seal between the first portion of the overlay portion of the first and second bag walls; and   wherein the first treatment comprises an ink treatment and the second treatment comprises at least one of an ionization treatment, an ink treatment, a treatment with a resin, varnish, or polymer, or a treatment with pressure, temperature, or both.   
     
     
         12 . The method according to  claim 11 , wherein the first treatment comprises application of at least one of the following: a polyamide ink, a urethane-based ink, a nitrocellulose ink, or a combination of any of the foregoing. 
     
     
         13 . The method according to  claim 12 , wherein the second treatment comprises an ionization treatment or application of at least one of the following: a resin, a polyamide ink, a urethane-based ink, a nitrocellulose ink, or a combination of any of the foregoing. 
     
     
         14 . The method according to  claim 12 , wherein a treated portion of the overlay portion has a lower peel strength than an untreated portion of the overlay portion. 
     
     
         15 . The method according to  claim 14 , wherein at least a portion of the first end of the first wall is not sealed to the second bag wall to thereby define a gripable flap. 
     
     
         16 . The method according to  claim 15 , wherein the treated portion of the overlay portion defines an easy open feature allowing a user to peel open and separate at least a portion of the first bag wall and the second bag wall. 
     
     
         17 . The method according to  claim 11 , wherein the treated portion extends from 10% to 100% across the width of the first bag wall, the second bag wall, or both. 
     
     
         18 . A bag made according to the process of  claim 11 .