Monitoring the composition of spinning solution

Sollinger and Voges at Akzo Nobel (Obemburg, Germany) used off-line transmission NIR to monitor the key quality parameters in cellulose hber (viscose) spinning solutions over time. The business value lay both 

There were many challenges involved in this work. 

The spinning solutions are not stable over time, since CS2 continues to react with the cellulose, increasing the xanthogenate content or ripeness (which is why monitoring is needed in the first place). This was dealt with by carrying out the NIR and reference methods simultaneously, where possible, or by storing the samples at -30 °C (where they are stable) until the reference analysis could be performed. 

The calibration models needed to be insensitive to variations in the levels of minor additives ( 1 wt%) or process impurities. This was achieved by including samples from different production lines, containing varying concentrations (including zero) of different spinning additives, in the designed experiment sample set. 

Parameter Units Concentration range Wavelength range (nm) Number of PLSl factors Regression coefficient RMSEC RMSEP 

Sample type Polymer type Sources Samples % correct (absorbance model) % correct (second-derivative model) 

The spinning solution composition was measured off-line using a Foss NIRSystems Model 6500 VIS-NIR analyzer (wavelength range 400-2500 nm), equipped with a 

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