New softening technology for premium tissue
Softness has become the defining product characteristic for premium tissue products such as toilet, facial and handkerchief. It is leveraged more than any other attribute to define and differentiate brand identity. Here, Buckman’s tissue experts tell TW about how its “wet end lotion” technology increases softness.
As the demand for premium product softness accelerates, many manufacturers have turned to chemical softeners to gain a competitive advantage. Unfortunately, many of these chemistries cause a significant loss of tensile strength and can negatively impact the Yankee coating. Due to this, there are practical limits for the use and softness obtainable from these traditional softening chemistries.
The softening technology examined in this paper allows significant increases in handfeel while minimising the negative side effects of previous softening chemistries.
This new “wet end lotion” technology increases softness without impacting Yankee coating or significantly reducing sheet strength. The presented case studies and data analysis support the effectiveness of this chemistry for improved softness, with minimum runnability and strength issues. This new softener is a synergistic combination of materials which are effective as a softening agent in tissue manufacturing. The product is water dispersible, concentrated, with low foaming potential. The particular combination of active ingredients provides a strong softening effect at reduced levels of cationic additive. This product should be added just prior to the fan pump after makedown and dilution to ensure good product mixing and application. The recommended addition rate is 2 – 5 kg/ ton depending on the desired results.
Several trials have been run and converted to permanent applications in North America, South America and Europe. The graph entitled Buckman® 691 trials: Handfeel vs. GMT shows the handfeel improvement vs. GMT from a trial made with this new softener. Basis weight, tensile, furnish and Yankee coating add-on rates were held stable.
New Softener Trial – Mill Results: Final product handfeel of the paper was improved across the product portfolio. The transition to the new Buckman softener chemistry had no negative impact on the runnability of the machine or performance of the Yankee coating chemistries.
Standard debonders, as mentioned previously, contain a combination of cationic and nonionic surfactants which results in the following impact in the process and final product:
- Increased inter-fibre debonding
- Thinning of the Yankee coating chemistry
- Increased drying energy if refining used to offset tensile drop
- Improved surface feel
- Reduced tensile strength
- Higher break frequency due to poorer sheet handling from crepe blade to reel
The cationic surfactants in traditional debonding and softening products are primarily quaternary ammonium compounds which are highly substantive to the fibres. They contain long chain fatty alkyl groups which increase the soft feel and surface lubricity and function as debonders to increase bulk and softness.
The hydrogen bonding of fibres is dependent on water bound in the fibre. Debonding chemistry can replace the water at these sites and block one fibre from bonding to another. Bond interference lowers stiffness and increases unattached fibre ends on the surface of the tissue sheet. However, the bond interference also significantly affects the strength properties of the sheet. The quantity of debonder/ softener added is often low and contact time with the fibre is critical to avoid undesirable issues on both the tissue machine and in converting.
Tissue manufacturers add debonders to the furnish in the wet end mainly to impart softness through disruption of inter-fibre hydrogen bonds and to develop surface softness through the presence of the fatty alkyl groups, but often softener/debonder chemistries are the main cause of lower machine runnability due to higher sheet break frequency and via their impact on the Yankee coating chemistry.
Another disadvantage of the usage of standard softener/debonder products is the increasing environmental restrictions requiring a tightly controlled balance of the addition rate. Solvents and specialty surfactants are often added to these formulations to ensure their liquidity and cold water dispersion, but they can contribute to Volatile Organic Compound (VOC) levels and can accumulate in the white water circuit.
The new Buckman wet end lotion addresses those limitations mentioned above, offering a forgiving product to the tissue making process that allows softness improvement without negatively impacting the Yankee coating chemistry. This technical solution allows tissue makers to maintain an optimised Yankee coating package while using a wet end softener chemistry.
The difference in the mechanism of this innovative chemistry (inter-fibre bond versus fibre bond) compared with the standard softener/debonder allows the tissue maker to enhance softness without the negative impact on sheet tensile strength, often with the result of refining and drying energy savings. Additionally, the components of this new wet end lotion product are approved for food contact and meet the highest environmental compliance.