Container for hot fill food packaging applications

Abstract

A plastic container suitable for hot-fill food packaging applications is disclosed which is characterized by walls of proportionately decreasing thickness from the mouth of the container to a predetermined collapsible point. The wall thickness is designed such that the container walls will collapse, or deform, only at the collapsible point during cooling after hot-filling of food product or during transportation of the container between locations of varying altitudes and pressures. The container preferably collapses in the base area such that the collapse is not visible to the consumer and also the collapse does not affect stability of the container while in use or during loading and storage. The container of the invention is advantageous in that it requires less plastic material to form than other known hot-fill containers, and also can be formed out of any suitable food-grade plastic material or by any process.

1 . A plastic container, comprising: 
 a mouth;    a bottom surface; and    a container wall between the mouth and the bottom surface,    wherein one of the bottom surface or the container wall flexes inward into the cavity of the plastic container;    wherein further the inward flexing of the bottom surface of the container wall reduces a pressure differential between the inside of the container and atmospheric pressure when either the container is hot-filled with food product or when the container is transported from a locale of lower atmospheric pressure to higher atmospheric pressure; and    wherein further the non-flexing surface maintains the same form from prior to hot-filling or transport.    
   
   
       2 . The plastic container of  claim 1 , wherein the thickness of the container walls decreases from a point substantially at the mouth to a point substantially at the bottom surface.  
   
   
       3 . The plastic container of  claim 1 , wherein the bottom surface flexes inward into the container cavity.  
   
   
       4 . The plastic container of  claim 3 , wherein the circumference of the mouth is greater than the circumference of the bottom surface.  
   
   
       5 . The plastic container of  claim 4 , wherein the plastic comprises a plastic suitable for solid phase pressure forming.  
   
   
       6 . The plastic container of  claim 5 , wherein the plastic further comprises polypropylene.  
   
   
       7 . The plastic container of  claim 6 , wherein the plastic further comprises a barrier enhancement agent.  
   
   
       8 . The plastic container of  claim 7 , wherein the barrier enhancement agent comprises ethylene vinyl acetate-vinyl alcohol.  
   
   
       9 . The plastic container of  claim 8 , wherein the plastic further comprises an adhesive suitable for solid phase pressure forming.  
   
   
       10 . The plastic container of  claim 9 , wherein the adhesive comprises an antioxidant  
   
   
       11 . The plastic container of  claim 5 , wherein the plastic container is formed from a plastic sheet comprising up to about 15 volume % ethylene vinyl acetate-vinyl alcohol, about 80 to about 90 volume % polypropylene and about 15 to about 20 volume % adhesive.  
   
   
       12 . The plastic container of  claim 1 , wherein the plastic container is formed from a plastic sheet having one or more layers, and wherein further the thickness of the container walls are about 70-80 volume % of the thickness of the plastic sheet at a location substantially adjacent to the container mouth and about 20-40 volume % of the sheet at a location substantially adjacent to the bottom surface, and the thickness of the bottom surface is about 15-20 volume % of the thickness of the plastic sheet.  
   
   
       13 . The plastic container of  claim 12 , wherein the container wall thickness uniformly decreases from a location substantially adjacent to the container mouth to a point substantially adjacent to the bottom surface.  
   
   
       14 . The plastic container of  claim 13 , wherein the container walls are about 0.7 mm thick at a location substantially adjacent to the container mouth and about 0.28 mm thick at a point substantially adjacent to the bottom surface, and the thickness of the bottom surface is about 0.16 mm.  
   
   
       15 . A method for forming a plastic container, comprising: 
 selecting at least one polymer for a plastic container; and    forming the plastic container;    wherein the plastic container comprises:    a mouth;    a bottom surface; and    a container wall between the mouth and the bottom surface,    wherein one of the bottom surface or the container wall flexes inward into the cavity of the plastic container;    wherein further the inward flexing of the bottom surface of the container wall reduces a pressure differential between the inside of the container and atmospheric pressure when either the container is hot-filled with food product or when the container is transported from a locale of lower atmospheric pressure to higher atmospheric pressure; and    wherein further the non-flexing surface maintains the same form from prior to hot-filling or transport.    
   
   
       16 . The method of  claim 15 , wherein forming the container comprises: 
 heating the plastic sheet to its VICAT temperature; and    thermoforming the container.    
   
   
       17 . The method of  claim 15 , wherein forming the container comprises extrusion, vacuum forming, injection molding, blister packaging, melt phase forming or blow molding.  
   
   
       18 . A method of manufacturing a plastic container with a selectively deformable surface, comprising: 
 selecting at least one polymer;    heating the at least one polymer to its VICAT temperature; and    thermoforming a container from the heated polymer;    wherein the plastic container comprises:    a mouth;    a bottom surface; and    a container wall between the mouth and the bottom surface,    wherein one of the bottom surface or the container wall flexes inward into the cavity of the plastic container;    wherein further the inward flexing of the bottom surface of the container wall reduces a pressure differential between the inside of the container and atmospheric pressure when either the container is hot-filled with food product or when the container is transported from a locale of lower atmospheric pressure to higher atmospheric pressure; and    wherein further the non-flexing surface maintains the same form from prior to hot-filling or transport.    
   
   
       19 . The method of  claim 18 , wherein the thickness of the container walls decreases from a point substantially at the mouth to a point substantially at the bottom surface.  
   
   
       20 . The method of  claim 18 , wherein the bottom surface flexes inward into the container cavity.  
   
   
       21 . The method of  claim 20 , wherein the circumference of the mouth is greater than the circumference of the bottom surface.  
   
   
       22 . The method of  claim 21 , wherein the plastic comprises a plastic suitable for solid phase pressure forming.  
   
   
       23 . The method of  claim 22 , wherein the plastic further comprises polypropylene.  
   
   
       24 . The method of  claim 23 , wherein the plastic further comprises a barrier enhancement agent.  
   
   
       25 . The method of  claim 24 , wherein the barrier enhancement agent comprises ethylene vinyl acetate-vinyl alcohol.  
   
   
       26 . The plastic container of  claim 25 , wherein the plastic further comprises an adhesive suitable for solid phase pressure forming.  
   
   
       27 . The plastic container of  claim 26 , wherein the adhesive comprises an antioxidant  
   
   
       28 . The plastic container of  claim 22 , wherein the plastic container is formed from a plastic sheet comprising up to about 15 volume % ethylene vinyl acetate-vinyl alcohol, about 80 to about 90 volume % polypropylene and about 15 to about 20 volume % adhesive.  
   
   
       29 . The plastic container of  claim 18 , wherein the plastic container is formed from a plastic sheet having one or more layers, and wherein further the thickness of the container walls are about 70-80 volume % of the thickness of the plastic sheet at a location substantially adjacent to the container mouth and about 20-40 volume % of the sheet at a location substantially adjacent to the bottom surface, and the thickness of the bottom surface is about 15-20 volume % of the thickness of the plastic sheet.  
   
   
       30 . The plastic container of  claim 29 , wherein the container wall thickness uniformly decreases from a location substantially adjacent to the container mouth to a point substantially adjacent to the bottom surface.  
   
   
       31 . The plastic container of  claim 30 , wherein the container walls are about 0.7 mm thick at a location substantially adjacent to the container mouth and about 0.28 mm thick at a point substantially adjacent to the bottom surface, and the thickness of the bottom surface is about 0.16 mm.