Method for improving grease and oil resistance of a fiber based article

A method for improving grease and oil resistance of a moulded fiber based article, the method comprising:

• obtaining a fiber stock comprising cellulosic fibers,
• introducing to the fiber stock a composition comprising
• a synthetic polymer component, which is a copolymer of acrylamide and at least one anionic monomer, the polymer component having an anionicity of 1-60 mol-%, and
• a cationic polymer component,
• the synthetic polymer component and cationic polymer component providing the composition with a charge density in the range of
• 0.05-1 meq/g, when measured at pH 2.8, and
• −0.2-−3 meq/g, when measured at pH 7.0,
• introducing polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof to the fiber stock, and
• moulding the fiber stock, wherein the moulding comprises wet forming, wet moulding, vacuum forming, vacuum moulding, extrusion forming, extrusion moulding, thermoforming, dry moulding, hot pressing, hot press drying, hot moulding, heat pressing, heat moulding, thermomoulding or a combination thereof,
• wherein the composition comprising the synthetic polymer component and the cationic polymer component, the synthetic polymer component and the cationic polymer component providing the composition with the defined charge densities, is introduced to the fiber stock in an amount of 5-50 kg/t, based on dry weight of the fiber stock.