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FlusHABlE FIBrEs world pulppaper22 Another important factor to influence the flushability of a product is the choice of the right pressure levels during hydro- entanglement a high momentum transfer via the narrow sides and transfers the force of the water into the wipe as shown in b while the fibres can be separated easily via the wide sides which leads to a quick dispersion of the wipe. Biodegradability As illustrated in figure 2 Viloft is biodegradable according to DIN EN 134322000-12. Biodegradability is a requirement of the EDANA III guideline to guarantee not only flushability through the waste water system but also environmental sustainability in water. This avoids the contamination of the seas with synthetic particles and microparticles known as marine litter introduced by fibres that are not biodegradable. Both length and cross-section of the fibre have a crucial influence on the flushability of the fibre which is illustrated in figure 3. Here fibre dispersions were flushed through sieve as described in the EDANA III guidelines. The y-axis shows the remaining amount of fibres on the sieve. According to EDANA III more than 25 of an articles initial dry must pass the sieve so less than 75 can remain on the sieve. The fibres are already completely dispersed but the modifications of Viloft show a clear improvement in terms of flushability compared to a standard viscose fibre with round cross- section. At the same time it becomes clear that a fibre length of 16mm is too long to fulfil the requirements of EDANA III. It can be safely assumed that a maximum fibre length of 12mm should not be exceeded. For further analysis of qualitative differences in flushability the Slosh Box Disintegration Test described in EDANA III has been implemented in Kelheim. First results confirm the improved flushability of wipes using Viloft fibres. uNDEr PrEssurE Another important factor to influence the flushability of a product is the choice Figure 2. Microscopic image of Viloft during biodegradation. Picture provided by IPS labs Appleton Figure 3. Remaining fibres on a 12.5mm sieve Figure 5. Comparison of one wipe made of Viloft using two different waterjet pressures Figure 4. Influence of water jet pressure on tensile strength and required hydromechanical force for break-up and dispersion of the wipe. of the right pressure levels during hydroentanglement. Figure 4 shows that after reaching a certain pressure level the tensile strength of the wipe does not increase blue curve whereas the flushability of the wipe is reduced significantly at the same time. The tensile strength only increases slightly once a level of about 80 is reached. Just at this point the required force for break-up and dispersion of the wipe increases steeply. In addition to that significant savings in the application of energy during hydroentanglement can be made by adjusting the water jet pressure to a minimum. For every producer the goal is to identify the optimum settings with respect to the chosen raw materials and the required product properties. The increasing compaction of the wipe as shown in figure 5 will also prevent the water opening up the web between pulp and fibres bringing it to complete dispersion. Moreover a lower water jet pressure and a lower compaction will be beneficial in terms of softness and handling of the end products. coNclusIoN The new wetlaid-hydroentanglement technology allows the production of flushable products certified according to EDANA III guidelines using one in-line process. There are various requirements for such products it is therefore crucial to respect a manifold of parameters to implement all required product properties. Kelheim Fibres GmbH uses the versatility of the viscose manufacturing process for the production of specialty fibres like Viloft dedicated for flushable products. By using these fibres in combination with the right process settings and other suitable raw materials paper manufacturers and nonwoven producers already create innovative sustainable products with added value due to their flushability.