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AssigneeStora Enso OYJ
InventorsIsto Heiskanen, Janne Myllykangas, Timo Räisänen
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The invention relates to a polymer-coated, heat-sealable liquid packaging board that resists solvents, such as strong alcoholic drinks, to a method of manufacturing the same and to a drinking cup made of the same. In the invention, resistance to solvents is achieved by lowering the raw edge penetration to the board. For this, the fibre base of the board contains at least 1.3 kg of hydrophobic size containing alkyl ketene dimer (AKD) per 1 tonne of dry matter, and at least 1.0 kg of wet-strength size per 1 tonne of dry matter, the density of the fibre base is 630-800 kg/m3 and the amount of heat-sealable polymer in the top layer is higher than the Bristow wheel roughness volume of the uncoated fibre base and/or at least 14 g/m2. When manufacturing the board, the AKD size, the length of the carbon chain of which is preferably at least C18, and the wet-strength size, such as polyamidoamine epichlorohydrin resin (PAAE), are added into the stock on the wire of the paper or board machine or before the same. At the same time, the pH of the tail water is adjusted so as to be alkaline, preferably to a value of over 9, whereby the pH of the water extract of the obtained board is in the order of about 7 or more. The drinking cup made of the board resists an ethanol solution of 30% by weight at 23° C. for at least 1 h.
1-20. (canceled)
A heat-sealable liquid packaging board that resists solvents, particularly a cup board comprising a fibre base, which on at least one side is provided with a polymeric coating layer, characterized in that, to lower the raw edge penetration to the board, the fibre base comprises at least 1.3 kg of hydrophobic size containing alkyl ketene dimer (AKD) per 1 tonne of dry matter and at least 1.0 kg of wet-strength size per 1 tonne of dry matter, that the density of the fibre base is 630-800 kg/m3, that the amount of heat-sealable polymer in the coating layer is higher than the Bristow wheel roughness volume of the uncoated fibre base and/or at least 14 g/m2, and that the pH of the water extract of the board, which is measured by the ISO 6588 method, is over 7.0.
A heat-sealed cardboard drinking cup, which resists alcoholic drinks and which is formed from cup board that comprises a fibre base and a polymeric coating layer that constitutes the inner surface of the cup, characterized in that, to lower the raw edge penetration to the board, the fibre base comprises, at the inner seal of the cup, at least 1.3 kg of hydrophobic size containing alkyl ketene dimer (AKD) per 1 tonne of dry matter, and at least 1.0 kg of wet-strength size per 1 tonne of dry matter, that the density of the fibre base is 630-800 kg/m3, that the amount of polymer in the coating layer is higher than the Bristow wheel roughness volume of the uncoated fibre base and/or at least 14 g/m2, and that the pH of the water extract of the board, which is measured by the ISO 6588 method, is over 7.0.
Dependencies are inferred from the claim text.