Abstract: Several alkyl rosin ester rosin sizes and glycerin rosin ester rosin size were prepared and used for paper sizing under neutral alkaline conditions.The sizing results indicated that the glycerin rosin ester rosin size could be quite effectively used in neutral alkaline paper sizing whereas the alkyl rosin ester rosin sizes lost the sizing efficiency,implying that the preparation of neutral rosin sizes would not depend only on the simple modification of carboxyl groups in rosin acids but relate to the structure of rosin ester.Although the addition of alkaline filler CaCO₃ decreased its sizing efficiency,the glycerin rosin ester rosin size exhibited good sizing even applied in the pulp suspension containing about 20% alkaline filler.

Key words: alkyl rosin ester, glycerin rosin ester, neutral-alkaline paper sizing, sizing efficiency