Multi-layer heat-sealable packaging material, a food package made thereof and a method of packaging

Abstract

The invention relates to a multi-layer heat-sealable packaging material especially for food packages. In addition, objects of the invention are a food package formed of the said packaging material, a method of packaging, and the use of the material for packages. The packaging material ( 1 ) comprises a middle layer ( 3 ) of fibre material, such as cardboard; at least one polymeric protective layer ( 4, 5 ) protecting the product from going bad; and polymeric heat sealing layers ( 2, 7 ) preferably on both sides of the packaging material. According to the invention, the heat sealing layer ( 7 ) forming the inner surface of the closed package, is blended with light-absorbing pigment, such as carbon black, for protecting the product from visible light. By further blending white pigment, such as titanium dioxide, into the heat sealing layer ( 7 ), a grey tint resembling an aluminium foil has been achieved for the layer. The heat sealing polymer may be low-density polyethylene (PE-LD), and an oxygen and aroma proof sealing layer ( 4 ) of, for example, ethylene vinyl alcohol copolymer (EVOH) or polyamide (PA) may be provided between it and the cardboard ( 3 ).

1 . A method for packing food comprising the steps of: 
 providing a packaging material comprising: (i.) a body layer of cardboard; (ii.) at least one gas-proof polymeric barrier layer; and (iii.) at least one polymeric heat-sealing layer into which black and white pigments are blended for protecting the food from visible light and imparting an aluminum color to the heat sealing layer;    bending a carton or case from said packaging material; and    closing food into said carbon or case by heat sealing.    
   
   
       2 . The method according to  claim 1 , wherein the polymeric heat-sealing layer comprises 0.05-0.5% light-absorbing black pigment and 5-25% white pigment.  
   
   
       3 . The method according to  claim 2 , wherein the polymeric heat-sealing layer comprises 0.10-0.30% carbon black and 10-15% titanium dioxide pigment.  
   
   
       4 . The method according to  claim 1 , wherein the carton or case is closed by heat sealing at a temperature of up to about 250° C.  
   
   
       5 . A food package which contains perishable food closed into a carbon or case formed by bending and heat-sealing from packaging material comprising a body layer of cardboard, at least one gas-proof polymeric barrier layer, and at least one polymeric heat-sealing layer containing black and white pigments blended with the heat-sealing polymer, the light-absorbing black pigment protecting the packed food from visible light and the black and white pigments together imparting a gray color to the heat-sealing layer.  
   
   
       6 . The food package according to  claim 5 , wherein the heat-sealing layer has been tinted gray by blending into the heat sealing polymer 0.05-0.5% light-absorbing black pigment and 5-25% white pigment.  
   
   
       7 . The food package according to  claim 6 , wherein the heat-sealing layer has been tinted gray by blending into the heat-sealing polymer 0.10-0.20% carbon black and 10-20% titanium dioxide pigment.  
   
   
       8 . The food package according to  claim 5 , wherein the heat-sealing polymer is a polyolefin.  
   
   
       9 . The food package according to  claim 8 , wherein the heat-sealing polymer is low-density polyethylene.  
   
   
       10 . The food package according to  claim 5 , wherein the barrier layer and the pigmented heat-sealing layer are placed to the interior of the body layer and that a colorless polymeric heat-sealing layer is provided onto the surface of the package on the outside of the body layer.  
   
   
       11 . A heat-sealed product package for food that is sensitive to light, said product package comprising multi-layer packaging material that comprises a body layer of fiber material, at least one gas-proof polymeric barrier layer, and at least one light-absorbing polymeric heat-sealing layer containing black and white pigments blended with the heat-sealing polymer.  
   
   
       12 . The product package of  claim 11 , wherein said food that is sensitive to light is liquid food.  
   
   
       13 . The product package of  claim 12 , wherein said product package is a milk carton or a juice carton.  
   
   
       14 . A package for a light-sensitive product, said package comprising an openable carton or case made by bending and heat sealing packaging material comprising (i.) a body layer of fiber material, (ii.) at least one gas-proof polymeric barrier layer inside of the body layer, and (iii.) a polymeric heat-sealing layer inside of the barrier layer, the polymeric heat-sealing layer containing black and white pigments blended with the heat-sealing polymer, the black pigment absorbing light and protecting the product from visible light and the black and white pigments together imparting a gray color to the inside of the carton or case.