Abstract: Process for the production of a cured pulp product suitable for use in the production of paper, paperboard, tissue paper, filter paper or fluff pulp, comprising the steps of attaching an anionic or amphoteric carboxymethyl cellulose (CMC) to cellulosic fibres in acidic conditions or in the presence of divalent metal ions. Aluminium ions or divalent ions are then added to the slurry to a total molar concentration of from 0.0001 M to 0.5 M in the first pulp slurry. The first pulp slurry is then dewatered and cured in acidic conditions and a cured pulp product is provided. The cured pulp product is subsequently used in a paper making process to provide a paper-based product, whereby higher bulk is provided for the final paper-based product. Alternatively, the curing step is omitted and instead aluminium ions are added to the first pulp slurry and the pulp is directly used in a paper making process.

Abstract: 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 0.0001 M 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.