Figure 1. Representation of the fluorescent tagged carbohydrate binding modules attaching to their respective bonding sites on a fiber.
The soft and strong competition
Strength and softness are the key basic product parameters for tissue and towel producers. They must balance these in the creation of their products. There are almost a countless number of ways these parameters can be impacted with varying implications for cost and final product attributes. To complicate things further, strength is almost always inversely proportional to perceived softness unless careful consideration is given to how that strength will be developed. Tissue makers and product development staff spend a lot of time determining the right counterbalance between how much strength a tissue product needs and how it is best developed to minimize the negative impact on some other attribute of the product.
A few well-known examples of this are shown in Table 1.
Improve both the quality of tissue and operation’s efficiency
Because of the inherent tradeoffs in the prevailing strength improvement methods in tissue, fiber modification enzymes (FME) have become ubiquitous in their manufacture to either replace or reduce the need for the approaches listed above. There are many classes of cellulases in nature. The ones that are useful for tissue makers are those that only react with the surface of the fibers. These specific enzymes break the bonds necessary to create fibrils that remain attached to the fiber. Breaking these bonds allows for refining to be more effective at lower energy input.
This lowered energy input reduces cutting and flattening of the fibers while maintaining the desired bonding strength. Given that a refiner can be the single biggest consumer of electrical energy on the machine, a significant reduction in energy costs is a secondary benefit. Although the use of enzymes by tissue makers for strength and other quality improvements in tissue is now common, there was still potential to improve performance and efficiency over what the first and second generation enzyme products were capable of. Third generation products have built upon the advances of the second generation, with third generation products using synergism by combining cellulases of different classes. Also, some non-enzyme additives that increase the activity rate of the cellulase are used.