Coating Board Paper Making Line: Multi-Layer Forming for Premium Packaging
Coating Board Paper Making Line: Multi-Layer Forming for Premium Packaging
Coating board — including duplex board, triplex board, and white back folding boxboard — is the preferred material for premium packaging in the food, pharmaceutical, and consumer goods industries. A modern coating board production line combines multi-ply forming technology with advanced coating stations to produce board with basis weights of 200–450 gsm, exceptional smoothness, and superior printability.
The production process starts with separate stock preparation lines for each ply: a bleached chemical pulp top layer for whiteness and printability, a mechanical or recycled fiber middle layer for bulk stiffness, and a waste paper-based back layer for cost efficiency. Each layer is formed on individual fourdriniers before combining in the wet state, followed by pre-drying, surface sizing, coating application, and final calendering.
Multi-Ply Forming Equipment
- Top Layer Stock Preparation: Hydrapulper 100–200 TPD, followed by high-density cleaner, pressure screen (0.15 mm slots), and disc refiner (250 kW). Fiber blend typically 70% bleached hardwood kraft + 30% bleached softwood kraft for optimal formation and strength.
- Middle/Filler Layer System: Hydrapulper 200–400 TPD processing mixed waste or mechanical pulp, medium-consistency cleaner, pressure screen (0.25 mm slots), and disc refiner (355–500 kW). This layer provides 50–60% of total board caliper.
- Back Layer Preparation: Similar to filler layer but optimized for strength properties. Screen basket 0.30 mm slots, refiner focus on fiber bonding without excessive cutting.
- Multi-Fourdrinier Forming: Individual wire sections for each ply with suction couch rolls combining layers. Wire width 2800–4500 mm, design speed 200–500 m/min. Layer-to-layer bonding strength >150 J/m².
Coating and Finishing Technology
The coating section applies 2–3 layers of pigment coating (pre-coat, mid-coat, top-coat) to achieve target brightness (>85% ISO) and smoothness (PPS <1.5 μm). Coating formulations typically comprise calcium carbonate, clay, latex binder, and optical brighteners applied via blade or rod coaters at solids content of 58–65%.
Energy consumption for a 350 TPD coating board line averages 380–450 kWh per ton of finished board. The multi-cylinder dryer section accounts for 55% of steam demand at 1.6–2.0 tons per ton. Infrared and air-flotation dryers in the coating section add 8–12% to total energy use. Heat recovery from the drying hood can reclaim up to 18% of exhaust energy for process water heating and building HVAC.
Preventive Maintenance for Coating Lines
- Coating blade inspection: Check blade edge condition daily — a worn blade produces streaks and uneven coat weight. Replace every 8–24 operating hours depending on coating abrasiveness.
- Screen basket monitoring: Top layer screens at 0.15 mm slots are most susceptible to blinding from coating broke returns. Daily ΔP monitoring — clean when differential exceeds 30 kPa above baseline.
- Dryer cylinder surface: Inspect monthly for condensate removal efficiency, scoring, and Teflon coating integrity. Uneven heat transfer causes moisture profile variation and curl.
- Calender roll grinding: Soft calender rolls require grinding every 4–6 months to maintain surface finish. Hard nip rolls every 12 months. Monitor gloss and PPS readings for roll condition indicators.
Integrated Coating Board Solutions
Zhengzhou Leizhan Technology provides complete coating board production lines from waste paper processing through to finished coated board. Turnkey supply includes process engineering, equipment manufacturing, installation, and commissioning support.
For coating board line inquiries and detailed technical proposals, contact leizhanzhang@gmail.com or explore equipment specifications at www.pulprefining.com.