Patent ID: 8557357

Claim:
Packaging material for forming at least a part of a package for a product releasing gasses and being provided with an integral, normally closed pressure relief valve ( 18 ) that opens at an excess of pressure within the package overpressure outside the package, said pressure relief valve including a first inner film ( 10 ) preferably a polymer film, to be an inner film of the package and having at least one inlet opening ( 13 , 14 ; 28 : 39 : 41 ), and a second outer film ( 11 ) to be an outer film of the package and covering the inlet opening in the first inner film ( 10 ) and being bonded to the first inner film ( 10 ) to form a channel or pocket portion ( 12 ; 32 ) between the first inner and the second outer film, said channel or pocket portion ( 12 ; 32 ) communicating with the surroundings of the package through at least one outlet opening ( 15 ; 33 , 34 ) spaced apart from the inlet opening, the first inner film ( 10 ) having a first surface ( 20 ) and a second surface ( 21 ) and the second outer film ( 11 ) having a first surface ( 22 ) and a second surface ( 3 ), the second surface ( 21 ) of the first inner film ( 10 ) facing the second surface ( 23 ) of the second outer film ( 11 ), said pressure relief valve ( 18 ) further comprising a liquid ( 19 ) provided in the channel or pocket portion and solid spacer means ( 17 ; 29 : 37 ; 40 ) provided in the channel or pocket portion proximate to the inlet opening ( 13 , 14 ; 28 ; 39 ; 41 ), said spacer means providing an interspace between the second surface ( 21 ) of the first inner film ( 10 ) and the second surface ( 23 ) of the second outer film ( 11 ), wherein the second outer film ( 11 ) is a film having such a flexibility or elasticity that in a tensile test a force of less than 5N is needed for elongating a test piece thereof having a width of 15 mm by 5%, the tensile test being carried out according to ISO 527/ASTM D 638, wherein a test piece of a width of 15 mm is gripped between two sets of jaws interspaced by exactly 100 mm and pulled in tension at a speed of 100 mm/min and at 5% elongation, i.e. 5 mm, the force is registered.