Optimizing Chemi-Thermomechanical Pulp Core Fractions for Lightweight Board
Balancing middle ply mechanical pulp freeness preserves sheet caliper and bending resistance while controlling delamination under high-speed scoring.
Spray Starch Application
Starch Deposition
Liquid sizing agents transform raw paper surfaces by raising internal bond strength and sealing pores before final calendering occurs. Spray starch application achieves this outcome on high-speed paper machines through pneumatic atomization nozzles that discharge gelatinized amylose directly onto moving webs prior to the dryer section. Fluid pressure, nozzle geometry, and web velocity dictate wet pick-up rates, which typically range between two and five grams per square metre depending on target porosity.
Surface penetration requires precise viscosity control to prevent excessive pooling that causes picking defects during subsequent printing passes.
Performance Mechanics
Modified biopolymers reinforce structural integrity by bridging surface fibres to restrict dusting and improve ink holdout on uncoated packaging substrates. Shear thinning behaviour allows high-pressure fluid streams to break down into uniform droplets before impacting the sheet at elevated temperatures. Heat transferred from dryer cylinders gelatinizes residual unswollen granules while driving off excess moisture to form a continuous film.
Insufficient thermal energy leaves uncooked starch particles embedded in the sheet, which compromises pick resistance and weakens corrugated box compression performance under humid storage conditions.
Coating Limitations
Heavy binder deposition increases sheet stiffness excessively, leading to converter feed failures and cracked folding cartons along creasing lines during box erection. Inline moisture sensors monitor residual water content continuously to prevent blister formation caused by trapped steam expanding beneath the newly formed film. Converter specifications dictate maximum allowable ash and starch fractions to ensure finished packaging remains compatible with alkaline pulping recycling streams.
Strict viscosity boundaries govern operational limits because highly concentrated solutions plug atomization orifices and disrupt grammage uniformity across wider production widths.