Use of a paper or paperboard product as a middle layer in a paperboard

摘要

The present invention relates to a process for the production of a bulky multi-layer paperboard comprising a middle layer produced from a cured pulp product produced by a method comprising the steps of: i)providing a first aqueous pulp slurry comprising cellulosic fibres and having a pulp consistency of from 0.1%to 40 % by weight, calculated as dry weight of the cellulosic fibres in the first pulp slurry; ii)adding to the first pulp slurry an aluminium metal salt comprising Al3+ - ions to a total molar concentration of aluminium ions of from 0.0001M to 0.5 M in the first pulp slurry; iii) adjusting the pH of the first pulp slurry to a pH of from pH 3.0 to pH 6.0; iv) dewatering and curing the first pulp slurry at a temperature of at least 60°C and thus provide a cured pulp product.