Retort container, and hot melt adhesive therefor

Abstract

A retort container comprises a container body structured and arranged for holding a food product, the container body defining an opening and a sealing surface surrounding the opening, and a lid bonded to the sealing surface of the container body to close the opening, the lid being bonded to the sealing surface with a hot melt adhesive. The adhesive comprises a polyamide resin blended with a second resin that raises the glass transition temperature of the adhesive above the glass transition temperature of the polyamide resin alone, the adhesive bonding the lid to the sealing surface with a temperature-dependent bond strength that is relatively low at room temperature and substantially higher at retort temperatures of 100° C. to 120° C.

1 . A retort container, comprising: 
 a container body structured and arranged for holding a food product, the container body defining an opening and a sealing surface surrounding the opening; and    a lid bonded to the sealing surface of the container body to close the opening, the lid being bonded to the sealing surface with a hot melt adhesive, the adhesive comprising a polyamide resin blended with a second resin that raises the glass transition temperature of the adhesive above the glass transition temperature of the polyamide resin alone, the adhesive bonding the lid to the sealing surface with a temperature-dependent bond strength that is relatively low at room temperature and substantially higher at retort temperatures of 100° C. to 120° C.    
     
     
         2 . The retort container of  claim 1 , wherein the second resin comprises a maleic modified rosin ester.  
     
     
         3 . The retort container of  claim 2 , wherein the adhesive comprises about 10 to 20 weight percent of the maleic modified rosin ester.  
     
     
         4 . The retort container of  claim 1 , wherein the container body is formed entirely of polymer material.  
     
     
         5 . The retort container of  claim 1 , wherein the lid is formed entirely of polymer material.  
     
     
         6 . The retort container of  claim 1 , wherein the lid and the container body each is formed entirely of polymer material.  
     
     
         7 . The retort container of  claim 1 , wherein the container body comprises a multi-layer body wall.  
     
     
         8 . The retort container of  claim 7 , wherein the container body comprises a thermoformed multi-layer sheet.  
     
     
         9 . The retort container of  claim 7 , wherein the container body comprises a coextrusion blow-molded structure.  
     
     
         10 . The retort container of  claim 7 , wherein the multi-layer sheet includes a first polymer layer providing moisture barrier performance and a second polymer layer providing oxygen barrier performance.  
     
     
         11 . The retort container of  claim 10 , wherein the first polymer layer comprises polypropylene and the second polymer layer comprises ethylene vinyl alcohol copolymer.  
     
     
         12 . The retort container of  claim 11 , wherein the multi-layer sheet further comprises a third polymer layer of polypropylene, the ethylene vinyl alcohol copolymer layer being disposed between the polypropylene layers.  
     
     
         13 . The retort container of  claim 1 , wherein the lid comprises a multi-layer structure.  
     
     
         14 . The retort container of  claim 13 , wherein the lid includes at least a first polymer layer providing moisture barrier performance and a second polymer layer providing oxygen barrier performance.  
     
     
         15 . A retort container, comprising: 
 a container body structured and arranged for holding a food product, the container body defining an opening and a sealing surface surrounding the opening; and    a lid bonded to the sealing surface of the container body to close the opening, the lid being bonded to the sealing surface with a hot melt adhesive, the adhesive having a glass transition temperature of about 20° C. to 40° C., the adhesive bonding the lid to the sealing surface with a temperature-dependent bond strength that is relatively low at room temperature and substantially higher at retort temperatures of 100° C. to 120° C.    
     
     
         16 . The retort container of  claim 15 , wherein the hot melt adhesive predominantly comprises a polyamide resin.  
     
     
         17 . The retort container of  claim 15 , wherein the hot melt adhesive comprises a first resin having a glass transition temperature substantially lower than 20° C., and a second resin added to the first resin to raise the glass transition temperature of the adhesive to about 20° C. to 40° C.  
     
     
         18 . The retort container of  claim 17 , wherein the first resin comprises polyamide.  
     
     
         19 . The retort container of  claim 17 , wherein the second resin comprises maleic modified rosin ester.  
     
     
         20 . The retort container of  claim 17 , wherein the first resin comprises polyamide and the second resin comprises maleic modified rosin ester.  
     
     
         21 . A hot melt adhesive suitable for retort containers, comprising: 
 a polyamide resin having a glass transition temperature less than or equal to about 0° C.; and    a maleic modified rosin ester blended with the polyamide resin to form the hot melt adhesive, the maleic modified rosin ester being present in the hot melt adhesive in sufficient proportion to give the hot melt adhesive a glass transition temperature of about room temperature.    
     
     
         22 . The hot melt adhesive of  claim 21 , wherein the polyamide resin comprises about 70 to 95 weight percent of the adhesive and the maleic modified rosin ester comprises about 30 to 5 weight percent of the adhesive.  
     
     
         23 . The hot melt adhesive of  claim 21 , wherein the polyamide resin comprises about 80 to 90 weight percent of the adhesive and the maleic modified rosin ester comprises about 20 to 10 weight percent of the adhesive.