To obtain a surface sizing agent for paper comprising a modified polyvinyl alcohol containing a hydroxyalkyl group at the side chain as a main agent, extremely improving the z-axis strength of coated paper.
A vinyl ester such as vinyl acetate, etc., is polymerized with a hydroxyl group-containing olefin such as 7-octen-1-ol, etc., by using 2,2'- azobisisobutyronitrile as a catalyst, purified and saponified to give a modified polyvinyl alcohol containing 0.1-30mol%, preferably 0.3-20mol% of a 2-20C hydroxyalkyl group at the side chain. The modified polyvinyl alcohol is used as a main agent to prepare a surface sizing agent for paper. A paper substrate is coated with 0.1-10g/m2, preferably 0.3-3g/m2 expressed in terms of solid content based on the base paper of the surface sizing agent for paper to improve peel strength between paper layers.
OTAKE KAZUHIKO
KUSUFUJI TAKESHI
