Heat-sealable structure for aluminum disposable beverage-brewing containers

A method for creating a heat sealed structure, said heat sealed structure providing a seal strength, according to ASTM F2824, of more than 23 N/15 mm, said method comprising:

• contacting one side of a first aluminum foil with a heat-seal lacquer formulation,
• contacting one side of a second aluminum foil with the heat-seal lacquer formulation said heat seal lacquer formulation comprising copolymer (A), copolymer (B), and one or more organic solvents, and having a solids content between 20 and 80% by weight;
• evaporating the one or more organic solvents of the heat seal lacquer formulation on the first and second aluminum foil;
• cooling down the first and second aluminum foils to form a first heat-sealable structure comprising the first aluminum foil and a heat seal lacquer, and a second heat-sealable structure comprising the second aluminum foil and the heat-seal lacquer,
• said heat seal lacquer comprising:
• (a) from 30 to 80% by weight of copolymer (A) based on (meth)acrylate ester (co)polymers, olefin (co)polymers and block or grafted copolymers comprising (meth)acrylate ester sequences and olefin sequences, and
• (b) from 20 to 70% by weight of copolymer (B) based on vinyl halides, vinyl esters of carboxylic acids and ethylenically unsaturated (poly)carboxylic acids,
• contacting the heat-seal lacquer of the first and second heat sealable structures, and
• heat sealing the first and second heat-sealable structures together at a heat-sealing temperature between 150 to 350° C., a heat-sealing pressure between 1 and 10 bar and a sealing time between 0.1 and 2.0 sec,
• wherein:
• copolymer (A) of the heat seal lacquer comprises butyl methacrylate and propylene;
• copolymer (B) of the heat seal lacquer comprises vinyl chloride, vinyl acetate and dicarbonic acid;
• and
• the one or more organic solvents of the heat seal lacquer formulation comprise butyl acetate, acetone and methyl ethyl ketone.