Chemi-Thermomechanical Pulp Core Optimization for Low Grammage Boxboard Manufacturing
Optimizing CTMP core sulfonation and bulk yields lower grammage boxboard that maintains flexural rigidity while reducing landed carton cost.
Shive Content
Contaminant Metric
Quantitative presence of incompletely defibrated wood particle bundles in pulp furnishes reflects the mechanical separation efficiency of pulping and screening systems. Measuring shive content provides a direct index of structural purity in virgin mechanical, thermomechanical, and semi-chemical pulp slurries. Shives consist of coarse, stiff fiber clusters that failed to separate into individual flexible cellulose fibers during refining or chemical digestion.
These unrefined bundles introduce structural weak spots, lower tensile strength, and disrupt web smoothness on paper and paperboard machines.
Processing Source
Incomplete mechanical refining of wood chips in disk refiners or insufficient cooking liquor penetration in chemical digesters generates coarse fiber aggregates. Multi-stage pressure screens and forward centricleaners separate shives from the refined furnish based on particle diameter, length, and specific gravity. Laboratory quantification utilizes slotted Somerville screens with 0.15-millimetre slot widths, optical pulp analyzers, or laser-based image analysis systems that count and size individual shive particles per gram of dry pulp.
Modern optical sensors measure shive dimensions continuously in pulp transport pipelines, tracking length, width, and projected surface area.
Print Consequence
Papermaking runs and subsequent printing operations suffer severe operational disruptions when excessive shives pass into the final paper web. Coarse shives resting on the sheet surface possess poor internal bonding and lift out easily during offset lithographic printing, causing blanket contamination and white ring defects. In rotogravure printing, rigid shives prevent intimate contact between paper and gravure cylinders, resulting in unprinted missing dots across solid tones and half-tone screens.
Shive content establishes a fundamental quality limit for mechanical pulps intended for publication papers and coated folding boxboard top liners.