SWOLLEN STARCH COMPOSITIONS FOR USE IN PAPERMAKING

A novel filler treatment comprising the preparation of swollen starch compositions, more especially ionic starch compositions, prepared in the presence or absence of co-additives, and the addition of the said composition to a filler suspension, has been developed. Use of the treated filler during papermaking improves filler retention and produces filled papers where addition of the filler has only a minimal negative effect on strength properties. The swollen starch compositions can be prepared in a batch or jet cooker, or by mixing with hot water under controlled conditions (i.e., temperature, pH, mixing, mixing time) in order to make the starch granules swell sufficiently to improve their properties as a filler additive but avoiding excess swelling leading to their rupture. The swollen starch composition is then rapidly mixed with the filler slurry, and added to the papermaking furnish at a point prior to the headbox of the paper machine. The starch composition can be used with wood-free or wood-containing furnishes. The treated filler is easily retained in the web during papermaking, improves drainage, and gives sheets having good formation. Sheets made with the treated fillers have high bonding and tensile strengths. Retention and drainage are further improved when conventional retention aid chemicals are added to the furnish containing the treated filler. The use of swollen starch compositions could allow the papermaker to increase the filler content of the paper without sacrificing dry strength properties or increasing the amount, and hence the cost, of the retention aid added. The combination of swollen starch and latex could be used as furnish additives in the manufacture of both filled grades and grades that contain no filler such as sack papers and paperboard products. Nouveau traitement de charge comprenant la préparation de compositions à base d'amidon gonflé, plus particulièrement des compositions d'amidon ionique, préparées en présence ou en l'absence de co-additifs et l'ajout de ladite composition à une suspension de charge. L'utilisation de la charge traitée pendant la fabrication du papier améliore la rétention de la charge et produit des papiers chargés où l'adjonction de la charge n'a qu'un effet négatif minimum sur les propriétés de résistance. Ces compositions d'amidon gonflé peuvent se préparer dans un bouilleur à céréales par fournée ou dans un bouilleur à jet, ou par mélange avec de l'eau chaude sous des conditions contrôlées (c'est-