Packaging laminate for a retortable packaging container

Abstract

A packaging laminate ( 10 ) for a retortable packaging container of the type which is produced by fold forming and thermosealing of a web or a prefabricated blank of the packaging laminate. The packaging laminate ( 10 ) includes a base layer ( 11 ) of paper or paperboard which has been rendered hydrophobic by stock sizing. The base layer ( 11 ) is preferably rendered hydrophobic by stock sizing by means of an aqueous dispersion or emulsion of an alkyl ketene dimer or mixture of alkyl ketene dimers with a different number of carbon atoms in their respective fat tails. Most preferably, the base layer ( 11 ) is rendered hydrophobic by stock sizing by means of an aqueous dispersion or emulsion of an alkyl ketene dimer containing 18 carbon atoms in its fat tail. The quantity of alkyl ketene dimers is suitably at least approx. 0.25 weight %, preferably 0.25-0.4 weight %, most preferably approx. 0.4 weight %, calculated on the dry weight of the base layer ( 11 ).

What is claimed is:  
     
         1 . A packaging laminate for a retortable packaging container of the type which is produced by fold forming and sealing of a sheet or web-shaped blank of the packaging laminate, the packaging laminate ( 10 ;  20 ) including a base layer ( 11 ;  21 ) of paper or paperboard and outer, liquid-tight coatings ( 12 ,  13 ;  22 ,  23 ) of thermosealable plastic on both sides of the plastic layer ( 11 ;  21 ), characterised in that the paper or paperboard layer is rendered hydrophobic by so-called stock sizing by means of an aqueous suspension or emulsion of an alkyl ketene dimer or mixture of alkyl ketene dimers.  
     
     
         2 . The packaging laminate as claimed in  claim 1 , characterised in that the paper or paperboard layer ( 11 ;  21 ) contains said alkyl ketene dimers in a quantity of at least 0.25 weight %, calculated on the dry weight of the paper or paperboard layer ( 11 ;  21 ).  
     
     
         3 . The packaging laminate as claimed in  claim 1  or  2 , characterised in that the paper or paperboard layer ( 11 ;  21 ) contains between 2.5 and 4 kg of alkyl ketene dimers per tonne of paper or paperboard in the dry paper or paperboard layer ( 11 ;  21 ).  
     
     
         4 . The packaging laminate as claimed in any of the preceding claims, characterised in that said alkyl ketene dimers are selected from the group essentially comprising alkyl ketene dimers with 16-22 carbon atoms in their respective fat tails.  
     
     
         5 . The packaging laminate as claimed in  claim 4 , characterised in that said alkyl ketene dimers have 18 carbon atoms in their fat tail.  
     
     
         6 . Use of a paper or paperboard layer ( 11 ;  21 ) rendered hydrophobic as base layer in a packaging laminate ( 10 ;  20 ) as claimed in any of the preceding claims.  
     
     
         7 . A retortable packaging container of a packaging laminate comprising a core layer ( 11 ;  21 ) of paper or paperboard and outer, liquid-tight coatings ( 12 ,  13 ;  22 ,  23 ) of thermosealable plastic on both sides of the base layer ( 11 ;  21 ), characterised in that the paper or paperboard layer ( 11 ;  21 ) is rendered hydrophobic by so-called stock sizing by means an aqueous suspension or emulsion of at least one alkyl ketene dimer.