Heated-sealed sterilised product package packaging material for the same and use of the packaging material

Abstract

The invention relates to a polymer-coated heat-sealable packaging material, to a heat-sterilised package formed from this and to the use of the packaging material. The material comprises a fibre base ( 4 ), which is e.g. a packaging board made of bleached pulp, and polymer heat-seal layers ( 1, 9 ) located on both sides of this. In accordance with the invention, the package comprises, outside the fibre base, a polymer coating layer ( 2 ), which contains white pigment for covering the fibre base from sight, and a second coating layer ( 8 ), which contains light-absorbing pigment. A coating layer pigmented grey inside the fibre base, for instance, provides a light shield for the packaged product. The absorbent black pigment may also be located outside the fibre base underneath a white layer in order to stabilise the brightness of the material. The package may be e.g. a food package heat-sterilised in an autoclave, in which yellowing of the fibre-based material has been avoided by means of a white pigment.

1 . A heat-sealed heat-sterilised product package made of a fibre-based packaging material having polymer coating layers on both sides of a bleached fibre base, characterised in that a polymer coating layer outside the fibre base in the package contains white pigment for toning against yellowing of the fibre base caused by heating, and in that a second polymer coating layer included in the packaging material contains a light-absorbing pigment.  
   
   
       2 . A package as defined in  claim 1 , characterised in that the coating layer containing a light-absorbing pigment is located inside the fibre base in the package.  
   
   
       3 . A package as defined in  claim 2 , characterised in that the polymer coating outside the fibre base contains only white pigment, which hides the fibre base from sight.  
   
   
       4 . A package as defined in  claim 2 , characterised in that outside the fibre base in the package there are two successive pigmented polymer layers, with the outer polymer layer containing 5 to 25% of white pigment and the inner polymer layer located closer to the fibre base containing black pigment, and that inside the fibre base there is a polymer layer containing light-absorbing pigment to provide a light shield for the packaged product.  
   
   
       5 . A package as defined in  claim 2 , characterised in that inside the fibre base the polymer layer has been toned grey by mixing black and white pigments.  
   
   
       6 . A package as defined in  claim 2 , characterised in that, both outside and inside the fibre base, the pigments are located in the innermost polymer layers covered by a transparent heat-sealable overlay layer.  
   
   
       7 . A package as defined in  claim 1 , characterised in that outside the fibre base of the package there are two successive pigmented polymer layers, with the outer polymer layer containing 5 to 25% of white pigment and the inner polymer layer located closer to the fibre base containing a light-absorbing black pigment.  
   
   
       8 . A package as defined in  claim 1 , characterised in that inside the fibre base of the package there is at least one polymer oxygen-barrier layer.  
   
   
       9 . A package as defined in  claim 1 , characterised in that the outside of the heat-sterilised package has a brightness above 80% ISO.  
   
   
       10 . A package as defined in  claim 1 , characterised in being a food package sterilised in an autoclave.  
   
   
       11 . A polymer-coated heat-sealable packaging material intended for the product package of  claim 1 , comprising a bleached fibre base and polymer heat-sealable layers on both sides of the substrate, characterised in that pigment has been incorporated in the polymer layers on both sides of the fibre base, with white pigment on one side of the fibre base hiding the fibre base and with a light-absorbing pigment on the opposite side of the fibre base forming a light shield for the product to be packaged.  
   
   
       12 . A packaging material as defined in  claim 11 , characterised in that the brightness of the material is above 80% ISO on one side of the fibre base, where the polymer layer contains white pigment.  
   
   
       13 . A packaging material as defined in  claim 11 , characterised in that one side of the fibre base is provided with two successive pigmented polymer layers, with the outer polymer layer containing 5 to 25% of white pigment and the inner polymer layer located closer to the fibre base containing black pigment for stabilising the brightness of said material side despite any change during heating, and in that a pigmented light-shield polymer layer is provided on the opposite side of the fibre base.  
   
   
       14 . A packaging material as defined in  claim 13 , characterised in that black and white pigments have been mixed in said inner polymer layer and in that the outer polymer layer contains exclusively white pigment.  
   
   
       15 . A packaging material as defined in  claim 11 , characterised in that 
 the light shield on the opposite side of the fibre base has been achieved by tinting the polymer layer grey with black and white pigments.    
   
   
       16 . A packaging material as defined in  claim 11 , characterised in that on both sides of the fibre base the material comprises an outer transparent heat-seal layer and at least one inner pigmented polymer layer.  
   
   
       17 . A packaging material as defined in  claim 16 , characterised in that the inner pigmented layer contains the same heat-sealable polymer as the outer layer.  
   
   
       18 . A packaging material as defined in  claim 11 , characterised in that the polymer in the heat-seal layers has a fusion point of at least 130° C.  
   
   
       19 . A packaging material as defined in  claim 18 , characterised in that the heat-seal polymer is polypropene.  
   
   
       20 . A packaging material as defined in  claim 11 , characterised in that the material comprises at least one polymer oxygen-barrier layer.  
   
   
       21 . A packaging material as defined in  claim 20 , characterised in that the oxygen-barrier layer is located between the fibre base and the light-shield layer.  
   
   
       22 . A packaging material as defined in  claim 21 , characterised in that the material of the oxygen-barrier layer or layers is ethylene vinyl alcohol polymer (EVOH) or polyamide (PA).  
   
   
       23 . A packaging material as defined in  claim 11 , characterised in that the fibre base consists of bleached packaging paper or board.  
   
   
       24 . Use of the packaging material of  claim 11  for packages to be sterilised in an autoclave.  
   
   
       25 . Use as defined in  claim 24  for food packages to be sterilised in an autoclave.