Modification of starch for surface sizing, involves degrading starch by hypochlorite oxidation or acid treatment, and stabilization

摘要

Modification of starch at dry matter content of more than 15%, preferably more than 25%, involves degrading and stabilizing starch. The degradation is performed by hypochlorite oxidation or acid treatment to a degree of degradation at which the viscosity of surface size prepared from starch is more than 10 mPas, preferably more than 25 mPas. The viscosity is calculated to a dry matter content of 10%, at 60degreesC using Brookfield RVTD II at 100 rpm. Independent claims are included for the following: (1) starch which has been modified at least by degradation and stabilization; (2) use of starch in surface sizing based on film transfer technology, where a smooth rod or blade is used for spreading the surface size on the film transfer surface such as a roll; (3) method for regulating porosity of a paper web which involves regulating a starch content in surface size; and (4) method for surface sizing of paper which involves using size application device and surface size solution prepared from modified starch.