Figure 1 shows the kinetics of the Epi reaction, fundamental point of our study. The final level of mCPD in a kitchen roll on the shelf in the supermarket is not a mere function of the WSR but has multiple root causes. Thus, it requires a systematic end to end survey to capture all factors affecting the mCPD content in the finished tissue product. To run a full scope study requires competent technological resources as well as a close co-operation between the WSR experts and the paper machine staff. Mare has all the analytical means and skills for a systematic survey to identify the potential contaminant sources and quantify the impact. Our team focuses on selected areas of investigation (Furnish, PM-Wet End, Yankee Cylinder, and Converting) to cover the entire chain from the fiber to the tissue product as a summary of the diagram in Figure 2. The fiber material is the most important factor for designing the optimum WSR product and its application.
With respect to contaminants it has to be considered how much is introduced through the furnish delivering already a certain baseline for the final mCPD content.
Wet End System Conditions – WSR Interactions
Additives:
- Functional and Process Chemicals
- Addition Points an Sequence
Process Conditions
- System Parameters:
pH, Temperature, Conductivity, Zeta Potential, Retention
Equipment modifications:
- White water loop closure (=fresh water consumption)
- Drainage (=moisture into the dryer section)
Production Program:
- Paper Grades and sequence, length of campaigns
Figure 3: Variables that affect the mechanism.
Project structure – Wet Strength Solution Concept
Analytical survey
- Collection of relevant process and machine data from the wet end to converting
- Testing of respective samples throughout the wet-end line to the finished tissue
- Evaluating the analytical findings for tailoring the individual WSR formulation
Implementation of new Product Application
- Qualification of new product
- Corrective measures in wet end chemistry and conditions
- Monitoring performance and compliance data with analytical support
Persistent service
- Regular control of relevant technical parameters and cost performance
- Regular adjustments according to system changes
- Modifications in equipment and process condition
- Changes in production program
Figure 4: Process of our approach to the WSR solution.
Applying Carboxy Methyl Celluloseat the right stage can provide a massive synergy for optimum WSR fixation at the same time boosting its wet strength contribution. This way the WSR consumption is minimized resulting in respective cost savings and reduction of potential contaminant input. In an optimized application using Mare’s specialized CMC grades Niklacell savings of more than 40% of the WSR demand have been achieved. The PAAE resin has a high reactivity and cationicity causing strong interaction with the other wet-end chemicals and the varying conditions from the pulper to the head box. Figure 3 shows some of the variables to be taken into account. Changes in any of the listed system conditions can affect the WSR performance and the contaminants level, thus a continued monitoring of all relevant parameters is absolutely recommended. Certain adhesives used for the Yankee cylinder treatment are based on similar chemistry like WSR and a transfer into the tissue paper causes a direct contamination with the by-products like mCPD. Finally the tissue raw paper is exposed to mechanical and thermal treatments like embossing to convert it into the consumer good like a package of kitchen rolls. There is still a lot of manipulation until the tissue is nicely packed sitting on the shelf in the super market. The full scope investigation delivers a collection of all relevant data plus the analytical findings from a systematic set of samples. This base information allows to select the proper product formulation and to specify corrective measures for the use of other additives and the process conditions from end to end. In Figure 4 we outline the process involved in our approach. The end to end approach is certainly a complex matter and one need to shift the focus to a close partnership between the experts on both sides.
Joining the forces of the experienced technologist on the tissue machine with the competence in chemistry of the WSR manufacturer will enable a successful project.
Learn more about Mare’s Wet Strength Solution Concept@.
