Polymer Barrier Coatings and Pulpability Test Standards
Polymer barrier paperboard compliance requires passing 0.15mm laboratory slot screening with under 15 percent reject mass to prevent EPR fee penalties.
Press Felt Deposition
Process Fouling
Accumulation of organic and inorganic solids within the porous structure of the dewatering fabrics on a paper machine leads to reduced efficiency. Papermakers monitor press felt deposition to prevent marks on the finished sheet and to maintain consistent drainage rates.
Contaminant Source
Stickies and resins and fillers and chemical additives migrate from the pulp furnish into the synthetic fibres of the felt. This press felt deposition fills the voids that are necessary for carrying water away from the paper web. Reduced permeability increases the energy required for vacuum systems and drying.
Periodic cleaning with high-pressure showers and chemical detergents is necessary.
Operational Impact
Obstructions in the fabric create uneven pressure profiles that cause moisture streaks or crushing of the paper. Severe press felt deposition results in unplanned downtime for felt changes or intensive washing cycles. Conditioning systems use specific chemical treatments to keep the surface hydrophilic and free of pitch.
Sensors track the water removal rate at each press nip to identify early signs of fouling. If the fabric becomes too compacted, the sheet leaves the press section with high moisture content. This increases the steam demand in the dryer section and slows the machine speed.
Long-term management involves optimizing the wet-end chemistry to keep contaminants in the water phase.