Non-charge polysaccharides:Effects on runnability of wet web and efficiency of fibre material

There are many known additives for improving the dry strength of the end product, such as starch. In contrast, though, the existing range of chemicals for enhancing initial wet web strength in paper production is limited. G-PAM, used for a number of paper grades, is one of the few known paper machine runnability additives. The utilization of non-charge low cost additives, such as xyloglucan, offers interesting potential for influencing the bonding properties of fibres without disturbing the white water system. The wet and dry strength of paper samples increased when xyloglucan and, especially, xyloglucan with borax was introduced to the fibre network. Xyloglucan synergism with borax was not observed with decreased molecular weight xyloglucan. These results indicate that when cross-linked by borax, long bridging polymers are needed for improving the adhesive forces between fibres in the wet web and in the creation of strong fibre bonds and a large bonding area in drying. Due to the low solids content (50-60%) after wet pressing, minimal hydrogen bonding occurs in the web at this stage and, therefore, the creation of covalent bonds, e.g. by a xyloglucan-borax complex or by introducing aldehyde groups to xyloglucan, can play an important role in strengthening the wet fibre network. This theory was supported by xyloglucan oxidation results which showed that aldehyde groups strongly enhanced wet and dry strength properties. The effect of oxidised xyloglucan on dry tensile strength was much higher than with the xyloglucan borax complex. Based on this research, many of these chemicals could be replaced by oxidised xyloglucan or guar gum alone. This can contribute to achieving chemical savings and more simplified and stable wet end chemistry