Flexible bag with vent for pressure release

Abstract

A flexible bag having a reclosable zipper construction in which material is provided on the inside face of one or both zipper flanges that results in a weak seal area or an unsealed area when the side seals are made. The weak seal area or unsealed area is located on the product side of the zipper closure profiles. Elevated pressure inside the bag will cause the weak seal area of the side seal to fail as intended or will cause the zipper flanges in the unsealed area to separate, resulting in a venting action during cooking of the bag contents. For example, steam inside the bag can escape through the vent or vents while the zipper remains closed. Preferably the bag has a bottom gusset so that it can stand upright in a microwave oven. The bag may be opened to add contents, resealed and then heated.

1 . A bag comprising a receptacle having a mouth and an interior volume, and a reclosable structure installed in said mouth of said receptacle, said receptacle comprising first and second walls that bound said interior volume and first and second side seal regions that include respective marginal portions of said first and second walls, said reclosable structure comprising first and second zipper strips, said first zipper strip comprising a first base web attached to said first wall and a first closure profile projecting from said first base web, and said second zipper strip comprising a second base web attached to said second wall and a second closure profile projecting from said second base web, said first and second closure profiles being mutually interlockable, wherein a first portion of said first base web is weakly sealed to a first portion of said second base web in a weak seal area of said first side seal region, and a second portion of said first base web is weakly sealed to a second portion of said second base web in a weak seal area of said second side seal region, said first portions of said first and second base webs in said first weak seal area having a seal strength such that said first portions of said first and second base webs will separate from each other, thereby forming a vent, when the pressure inside said interior volume of said receptacle increases to a sufficient level, thereby allowing gas to escape from said interior volume into the ambient atmosphere via said vent during cooking of product contained within said interior volume of said receptacle while said mouth of said receptacle is in a fully closed state. 
   
   
       2 . The bag as recited in  claim 1 , wherein said first portion of said first base web in said weak seal area of said first side seal region comprises a layer of a first resin, and a second portion of said first base web adjacent said first portion of said first base web and not in said weak seal area of said first side seal region is made of a second resin different than said first resin. 
   
   
       3 . The bag as recited in  claim 2 , wherein said second resin is a polyethylene-based material and said first resin is selected from a group of resins which do not seal well to that polyethylene-based material. 
   
   
       4 . The bag as recited in  claim 3 , wherein said first resin is a polypropylene-based material or a polyester-based material. 
   
   
       5 . The bag as recited in  claim 2 , wherein said second resin is a polypropylene-based material and said first resin is selected from a group of resins which do not seal well to that polypropylene-based material. 
   
   
       6 . The bag as recited in  claim 5 , wherein said first resin is a polyethylene-based material. 
   
   
       7 . The bag as recited in  claim 2 , wherein said first resin is a biodegradable resin such as polylactic acid or a polyhydroxyalkanoate. 
   
   
       8 . The bag as recited in  claim 2 , wherein said first resin is a peel seal resin. 
   
   
       9 . The bag as recited in  claim 2 , wherein said first portion of said second base web in said weak seal area of said first side seal region comprises a layer of a third resin different than said first and second resins, and a second portion of said second base web adjacent said first portion of said first base web and not in said weak seal area of said first side seal region is made of said second resin. 
   
   
       10 . A bag comprising a receptacle having a mouth and an interior volume, and a reclosable structure installed in said mouth of said receptacle, said receptacle comprising first and second walls that bound said interior volume and first and second side seal regions that include respective marginal portions of said first and second walls, said reclosable structure comprising first and second zipper strips, said first zipper strip comprising a first base web attached to said first wall and a first closure profile projecting from said first base web, and said second zipper strip comprising a second base web attached to said second wall and a second closure profile projecting from said second base web, said first and second closure profiles being mutually interlockable, wherein a first portion of said first base web is not sealed to a first portion of said second base web in a portion of said first side seal region, and a second portion of said first base web is not sealed to a second portion of said second base web in a portion of said second side seal region, said first portions of said first and second base webs forming a vent when the pressure inside said interior volume of said receptacle increases to a sufficient level, thereby allowing gas to escape from said interior volume into the ambient atmosphere via said vent during cooking of product contained within said interior volume of said receptacle while said mouth of said receptacle is in a fully closed state. 
   
   
       11 . The bag as recited in  claim 10 , wherein said first portion of said first base web is coated with a heat-resistant material. 
   
   
       12 . The bag as recited in  claim 11 , wherein said heat-resistant material is nitrocellulose. 
   
   
       13 . A bag comprising a receptacle having a mouth and an interior volume, and a reclosable structure installed in said mouth of said receptacle, said receptacle comprising first and second walls that bound said interior volume and first and second side seal regions that include respective marginal portions of said first and second walls, said reclosable structure comprising first and second extruded plastic zipper strips, said first zipper strip comprising a first base web attached to said first wall and a first closure profile projecting from said first base web, and said second zipper strip comprising a second base web attached to said second wall and a second closure profile projecting from said second base web, said first and second closure profiles being mutually interlockable, wherein prior to formation of said first and second side seal regions, said first base web comprised a band-shaped surface area which extended the entire length of a face of said first base web, said band-shaped surface area being made of a first resin that forms a weak seal area with an opposing surface area made of a second resin different than said first resin during formation of said first side seal region. 
   
   
       14 . The bag as recited in  claim 13 , wherein said second resin is a polyethylene-based material and said first resin is selected from a group of resins which do not seal well to that polyethylene-based material. 
   
   
       15 . The bag as recited in  claim 14 , wherein said first resin is a polypropylene-based material or a polyester-based material. 
   
   
       16 . The bag as recited in  claim 13 , wherein said second resin is a polypropylene-based material and said first resin is selected from a group of resins which do not seal well to that polypropylene-based material. 
   
   
       17 . The bag as recited in  claim 16 , wherein said first resin is a polyethylene-based material. 
   
   
       18 . The bag as recited in  claim 13 , wherein said first resin is a biodegradable resin such as polylactic acid or a polyhydroxyalkanoate. 
   
   
       19 . The bag as recited in  claim 13 , wherein said first resin is a peel seal resin. 
   
   
       20 . The bag as recited in  claim 13 , wherein said first resin is totally resistant to heat sealing.