Paperboard with improved light blocking properties

Abstract

The present invention relates to a paperboard with improved light-blocking properties, comprising at least three plies: a top ply, a back ply, and a middle ply. The top ply contains at least 80 wt% chemical pulp. The middle ply contains at least 40 wt% spruce CTMP, calculated based on the total fiber weight of each ply, and the spruce CTMP has a brightness of between 40 and 60 according to ISO 2470-1:2016. The back ply contains at least 80 wt. % unbleached hardwood or softwood sulfate pulp, calculated on the total fiber weight of the back ply, and a) if the unbleached sulfate pulp in the back ply is from hardwood, the unbleached hardwood sulfate pulp has a kappa number according to ISO 302:2015 of at least 15, and b) if the unbleached sulfate pulp in the back ply is from softwood, the softwood sulfate pulp has a kappa number according to ISO 302:2015 of at least 20. The present invention further relates to a packaging material, a liquid packaging container made from the packaging material, and a method for making paperboard.

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