Citric acid-catalysed curran modified card board materials

A process for obtaining a paper material having a high wetted conformal stability, the process comprising the steps of:

• a) providing a cellulose-containing parenchymal microparticulate plant material, preferably comprising microparticles having an average particle diameter of from 10 μm to 500 μm as determined by ISO method NO. 20998-3:2017;
• b) suspending the cellulose-containing parenchymal microparticulate plant material in a solution, preferably an aqueous solution;
• c) mixing the suspension of cellulose-containing parenchymal microparticulate plant material with a suspension of a wood pulp, preferably an aqueous suspension of a kraft pulp;
• d) providing one or more linker compounds and one or more esterification catalysts to the mixed suspension, wherein each of the one or more linker compounds comprise two or more carboxylic acid moieties, under conditions that allow the mixture to react at least in part;
• e) isolating the solids from the suspension;
• optionally, f) drying the isolated solids or the shaped article.