Citric acid-catalysed curran modified card board materials

A process for obtaining a paper material with a high wetted conformal stability comprising: Providing cellulose containing parenchymal microparticulates, preferably 10 to 100 µm; suspending the material in a solution, preferably aqueous; mixing the suspension with one of wood pulp, preferrable an aqueous kraft pulp suspension; providing one or more linker compounds. Comprising two or more carboxylic acid moieties, and one or more esterification catalysts under conditions that allow at least part reaction an then isolating the solids from the suspension. Optionally drying the isolated solids. Further optional steps including modifying/shaping the materials which may include pressing and heating the pressed article in the mould tool an my also include a further finishing treatment step. Sources of parenchymal material preferably including sugar beet, carrot, parsnip, turnip or swede, apples, pears, citrus or grapes, potato, sweet potato, yam, rutabaga and yacca root. The esterification catalysts may comprise salts of sulfuric, phosphoric, nitric, hydrochloric or acetic acids, preferrable sodium hypophosphite. Also included are claims to a material obtained by the above process, use of parenchymal microparticulate material to enhance paper pulp and a barrier coating for a paperboard comprising a water borne polymer and parenchymal microparticulate material.