Abstract: The invention relates to a method for the modification of starch in such a way that it is suitable for surface sizing at high dry matter contents of >15%, typically >20%, even more than 25%. The modification of starch comprises at least degradation and stabilisation of the starch, whereby the degradation of starch is carried out by means of a chemical treatment, such as hypochlorite oxidation or acid treatment, to such a degree of degradation at which the viscosity of the surface size prepared from the starch, calculated to a dry matter content of 10% and to a temperature of 60° C., still is at >5 mPas, typically >15 mPas, most typically >25 mPas, Brookfield RVTD II 100 rpm. The invention also relates to a starch intended for use in surface sizing at a high dry matter content and its use in surface sizing.

Abstract: A method for the modification of a starch or a starch derivative for decreasing the viscosity of the same in the presence of hydrogen peroxide, a metal catalyst, especially copper sulphate and optionally an agent for increasing the pH so that the dry matter content at the beginning of the modification is at least 60%. The invention also involves use of the modified starch in i.a. surface sizing of paper.

Abstract: The invention relates to a method for the modification of starch in such a way that it is suitable for surface sizing at high dry matter contents of >15%, typically >20%, even more than 25%. The modification of starch comprises at least degradation and stabilisation of the starch, whereby the degradation of starch is carried out by means of a chemical treatment, such as hypochlorite oxidation or acid treatment, to such a degree of degradation at which the viscosity of the surface size prepared from the starch, calculated to a dry matter content of 10% and to a temperature of 60° C., still is at >10 mPas, typically >20 mPas, most typically >25 mPas, Brookfield RVTD II 100 rpm. The invention also relates to a starch intended for use in surface sizing at a high dry matter content and its use in surface sizing.

Abstract: The present invention relates to a process for the preparation of a stable, chlorine free modified starch which is useful in paper coating and sizing. In the process, starch is degraded by catalyzed hydrogen peroxide oxydation, and stabilized by acetyl esterification, combined with crosslinking of the starch.

Abstract: A method for internal sizing of paper using cationic starch is provided. The starch used is cationized with a mixture of epichlorhydrin, trimethylamine, and mono-or dimethylamine or N,N,N′,N′-tetramethylethylenediamine. Cationizing results in a higher molecular size of the starch, which has e.g. a beneficial effect on dewatering on the paper machine forming wire.