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 cover image. 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.
Driving cost effectiveness in third generation enzymes
Wood is a complex matrix of many intricately interwoven biopolymers and the fiber surface chemistry plays an integral role in determining the properties of the final paper products. Traditional methods of characterizing surface chemistry are tedious and time consuming. Utilizing four florescent tags and combining them with four substrate-specific enzyme binding domains, we were able to rapidly determine the relative quantities of crystalline cellulose, amorphous cellulose, xylans and mannans, respectively.
The relative concentration of the moieties identified by the tagged enzyme binding domains directly predict paper properties and have successfully been used to support the development of the third generation enzymes to drive maximum cost effectiveness. This has allowed for the identification of the most efficient cellulases for various types of virgin and recycled furnish types.
Driving increased traceability in third generation enzymes
For years, the immunochemical assay principle “ELISA” (Enzyme Linked Immuno Sorbent Assay) has been used to enable quantification of enzyme proteins, like those that enzymes are comprised of, with a low limit of determination. The test is used by some manufacturers in many industries to test for residual enzyme activity in the final product to confirm that the enzyme is not present in its active form in the final product.
Some industries use it to characterize air samples collected from the manufacturing floor where enzymes are in use to ensure workers were not being exposed in any way due misting or atomization of the normal process. Unfortunately, the ELISA method left much to be desired for testing in the fast-paced manufacturing space related to the turn around times for results, the need to send samples to a specialized lab and the high cost.
To that end, a new alternative technology known as Magnetic Immuno-Chromatographic Test (MICT), is now available that addresses many of the shortfalls related to the ELISA test. In the end, the overall activity and speed of activity leads to lower end use costs. The third generation enzyme products address the concerns of the previous two. Stability, specificity, purity and cost of use have all been improved. The following case history shows the value of using third generation enzymes for strength development.
CASE HISTORY
A tissue customer in EMENA producing Bath and Towel tissue with varying furnish ratios of both virgin and recycled fiber was using a previous cellulase enzyme concentrate in order to drive energy savings with positive results. Unfortunately the customer was not able to use the existing enzyme product across all grades effectively to drive savings due to limited performance with the recycled portion of the furnish.
When local Buckman technical experts audited the system, they determined that the newer generation enzymatic offering could both allow for greater refiner energy reduction and be applicable across more of the production grade structure. Maximyze® 3531 was proposed and trialed.
After several weeks of application of the new fiber modification technology, analysis of the results showed the customer was able to achieve the goals of greater energy savings and use across more grades.
