Heat-Sealable Structure for Aluminum Disposable Beverage-Brewing Containers

Abstract

The present invention relates to a heat-sealable structure comprising an aluminum foil and a heat-seal lacquer, said structure exhibiting a seal strength, according to ASTM F2824, of more than 23 N/15mm when heat- sealed to another heat-sealable structure comprising an aluminum foil and the same heat-seal lacquer, the heat-seal lacquers of both structures contacting each other for heat sealing, said seal lacquer comprising a copolymer blend comprising: - from 30 to 80% by weight, preferably 40 to 70% by weight, more preferably from 50 to 60% by weight of a copolymer A based on (meth)acrylate ester (co)polymers, olefm (co)polymers and block or grafted copolymers comprising (met)acrylate ester sequences and olefm sequences, - from 20 to 70% by weight, preferably 30 to 60% by weight, more preferably from 40 to 50% by weight of a copolymer (B) based on vinyl halides, vinyl esters of carboxylic acids and ethylenically unsaturated (poly)carboxylic acids.

1 . Heat-sealable structure comprising an aluminum foil and a heat-seal lacquer, said structure exhibiting a seal strength, according to ASTM F2824, of more than 23 N/15 mm, preferably more than 25 N/15 mm when heat-sealed to another heat-sealable structure comprising an aluminum foil and the same heat-seal lacquer, the heat-seal lacquers of both structures contacting each other for heat sealing, said seal lacquer comprising a copolymer blend comprising:
 from 30 to 80% by weight, preferably 40 to 70% by weight, more preferably from 50 to 60% by weight of a copolymer A based on (meth)acrylate ester (co)polymers, olefin (co)polymers and block or grafted copolymers comprising (met)acrylate ester sequences and olefin sequences,   from 20 to 70% by weight, preferably 30 to 60% by weight, more preferably from 40 to 50% by weight of a copolymer (B) based on vinyl halides, vinyl esters of carboxylic acids and ethylenically unsaturated (poly)carboxylic acids.   
     
     
         2 . The heat-sealable structure according to  claim 1  characterized in that:
 copolymer (A) of the heat-seal lacquer comprises from 5 to 70% by weight of one or more (meth)acrylate ester (co)polymer, from 5 to 70% by weight of one or more olefin (co)polymer) and from 1 to 90% by weight of one or more copolymers comprising (meth)acrylate ester sequences and olefin sequences; 
 copolymer (B) of the heat-seal lacquer comprises from 70 to 95% by weight of one or more vinyl halide, from 1 to 30% by weight of one or more vinyl esters of C1 to C20 carboxylic acids and from 0.1 to 10% by weight of one or more ethylenically unsaturated (poly)carboxylic acids. 
 
     
     
         3 . The heat-sealable structure according to  claim 1 , characterized in that the thickness of the aluminum foil is comprised between 20 and 160 micron, preferably between 30 and 120 micron and that the thickness of the heat-seal layer is comprised between 1 and 20 μm, preferable between 2 and 15 μm. 
     
     
         4 . The heat-sealable structure according to  claim 1  comprising one or more stoving paints or varnishes, preferably a polyester-based stoving paint and/or varnish, and/or one or more printings. 
     
     
         5 . Method for the preparation of the heat-sealable structure according to  claim 1  comprising the steps of:
 a) supplying an aluminum foil; 
 b) contacting one side of the aluminum foil with a heat-seal lacquer composition comprising copolymer (A), copolymer (B) and one or more organic solvents and characterized by a solid content comprised between 20 and 80% by weight; 
 c) evaporating the solvent of the heat-seal lacquer formulation; 
 d) cooling down the heat-seal lacquer to form the heat-sealable structure comprising an aluminum foil and a solid heat-seal film. 
 
     
     
         6 . The method according to  claim 5 , characterised in that the aluminum foil of step a) comprises one or more stoving paints and/or varnishes and/or one or more printings. 
     
     
         7 . The method according to  claim 5 , characterised in that step b) and step c) are repeated at least once before initiating step d). 
     
     
         8 . The method according to  claim 5 , characterised in that the heat-seal lacquer formulation of step b) comprises from 5 to 65% by weight, preferably from 7 to 50% by weight and, more preferably from 10 to 40% by weight of copolymer (A), from 5 to 55% weight, preferably from 5 to 45% by weight and more preferably from 5 to 35% by weight of copolymer (B) and from 20 to 80% by weight, preferably from 35 to 75% by weight and more preferably from 50 to 70% by weight of organic solvent. 
     
     
         9 . The method according to  claim 5 , characterised in that:
 copolymer (A) of the heat-seal lacquer formulation of step b) comprises 5 to 70% by weight of one or more (meth)acrylate ester (co)polymer, from 5 to 70% by weight of one or more olefin (co)polymer and from 1 to 90% by weight of one or more copolymers comprising (meth)acrylate ester sequences and olefin sequences;   copolymer (B) of the heat-seal lacquer formulation of step b) comprises from 70 to 95% by weight of one or more vinyl halide, from 1 to 30% by weight of one or more vinyl esters of C1 to C20 carboxylic acids and from 0.1 to 10% by weight of one or more ethylenically unsaturated (poly)carboxylic acids;   the one or more organic solvents of the heat-seal lacquer formulation of step b) are selected from the group consisting of esters of aliphatic carboxylic acids with aliphatic alcohols, ketones and aliphatic hydrocarbons.   
     
     
         10 . The method according to  claim 5 , characterised in that:
 copolymer (A) of the heat-seal layer formulation of step b) comprises butyl methacrylate and propylene;   copolymer (B) of the heat-seal layer formulation of step b) comprises vinyl chloride, vinyl acetate and fumaric acid   the one or more organic solvents of the heat-seal layer formulation of step b) comprise butyl acetate, acetone and methyl ethyl ketone.   
     
     
         11 . The method according to  claim 5  comprising the additional step of embossing the heat-sealable structure of step d). 
     
     
         12 . Use of the heat-sealable structure according to  claim 1 , for the production of lidding foils and capsules.