High-quality tissue paper is today produced using TAD (through-air-drying) technology, which is widely established as the most efficient drying method to increase bulk and softness in commercial tissue production. In the TAD process, it is essential to ensure uniform temperature distribution in the stream of drying air in order to achieve superior quality in terms of the softness and absorption capacity of the product. Sulzer Chemtech’s SMV mixing elements create even temperature profiles very efficiently and at low pressure drops.
In traditional tissue making, a flat sheet is dry-creped and embossed. Creping is the process of crinkling a sheet of paper to increase its softness. In a TAD system, the pressing procedure is eliminated, thus reducing web compaction. TAD technology removes water by passing high temperature air through the sheet. A TAD sheet has up to 75% more bulk than a conventional drycrepe sheet. In paper making, bulk is the reverse of density and describes the fluffiness of the material.
Increase in Toweling Capacity
The most striking effect of TAD is that it increases the tissue’s capacity to hold water. Unlike pressing, TAD does not change the 3-dimensional web of irregularly intervening cellulose fibers and freezes the shape between them. When the tissue gets wet during use, the sheet retains its void volumes and does not collapse. The effect on toweling is particularly dramatic. A TAD towel can hold up to 16 times its own weight in water, which is twice the capacity of a conventional dry-crepe paper towel