LensCellulose fibers
Figure 1: Cellulose fibers dissolved in NMMNO derive from natural cellulose, with fewer environmental emissions than rayon. LIST technology plays a central role in cellulose fiber production.
Cellulose spinning solution
Figure 2: Cellulose spinning solution taken directly from the LIST KneaderReactor is glass-clear, uniform in composition, and fully degassed.
LensLIST KneaderReactor Dissolving Technology
Figure 3: LIST KneaderReactor Dissolving Technology for cellulosics is a two-stage process that mixes, dissolves and degasses.
Continuous pulp pre-mixer
The continuous pulp pre-mixer aids uniformity by ensuring a steady supply of well-mixed material to the continuous dissolver.
Proprietary pulp feeder
The proprietary pulp feeder provides a constant volumetric flowrate and maintains the vacuum environment of the dissolver.

Cellulosics are versatile and high-quality fibers obtained by dissolving natural cellulose in N-Methylmorpholine-N-Oxide (NMMNO). Compared to acetate and viscose rayon, cellulosics dissolved in NMMNO are environment-friendly fibers, with a conceptually simple manufacturing process (Figure 1).

Cellulose, additives, and NMMNO are processed continuously in the LIST Dissolver, which provides thermal treatment, evaporation, and degassing along with intensive mixing. The result is a glass-clear, light yellow spinning solution that is highly homogeneous and free from bubbles and dissolved gases (Figure 2).

LIST KneaderReactor Dissolving Technology for cellulosics is a complete solution based around two LIST machines: a pre-mixer followed by a dissolver, plus auxiliary equipment (Figure 3). In support, LIST provides all the technical know-how required for installation, plus help with commissioning and operation.

LIST MasterConti process creates new opportunities for emerging technology. 

An emerging industrial process for the textile market is the production of a cellulose fiber made from regenerated wood pulp. Production involves chemically dissolving cellulose then filtering and wet-spinning the resulting dope into fibers. The resulting textile material has commercially attractive properties. However, production has, until now, been limited by challenges in processing.    

Dissolving the cellulose at a fast enough rate to make it commercially profitable requires the cellulose dope to be in a highly viscous and concentrated state. Once the viscous mass reaches the spinnerets, it is difficult to force through the spinneret nozzles.

In approaching the problem, LIST re-thought the process; the result is an innovative multi-stage solution known as the MasterConti process.  

LIST’s MasterConti process separates the highly viscous dissolution phase from the downstream phases that require a less viscous state in order to be most productive. LIST provides a continuous masterbatch process, to overcome these limitations by separating the dissolution process from the downstream processes.

The MasterConti process features a robust LIST kneader reactor, able to easily handle the highly viscous cellulose dope. The dope then enters a LIST mixer-diluter that reduces the viscosity to a consistency that is optimal for spinning. By keeping the two processes separate, the LIST MasterConti process enables manufacturers to maintain the best environment for each phase.  As a result, producers are able to:

  • improve product quality
  • achieve higher shear for better homogenization
  • realize greater process intensification with multi-step processing

Case Study

Based on tests conducted on a commercially available cellulose product, using both batch and continuous processing, the material produced the best quality cellulose dope when dissolved to a concentration of 16-22%. Using standard spinnerets with a typical nozzle aperture, tests reveal that the optimum viscosity for spinning is 11-12%. Employing the LIST MasterConti process, producers are able to isolate the two processes - decreasing the concentration from 16-18% to 11-12% as the dope moves from dissolution to spinning – without significantly slowing production. The result is a 50-100% improvement in throughput.