Influence of Double Kraft Liner and Old Corrugated Container Origin Recycled Fiber Ratios and Refiner Gap Spacing on Paper Performance

The influence of refinement on the properties of paper produced from recycled double kraft liner (DKL) and old corrugated container (OCC) fiber pulps was evaluated. Five DKL and OCC fiber blend ratios – 100/0, 75/25, 50/50, 25/75, and 0/100 – were assessed under three refiner plate gap settings: 0.15, 0.10, and 0.05 mm. Fiber analyses included consistency, classification, morphological characterization, freeness, and ash content. Moisture content, basis weight, thickness, density, air permeability, brightness, opacity, elongation, breaking length, tear resistance, and folding endurance were the paper properties evaluated. The DKL/OCC fiber ratio significantly affected all pulp properties, as did the refiner plate gap setting, except for ash and moisture contents. Fiber blends containing up to 50% OCC and refined at a plate gap of 0.15 mm performed most favorably in terms of recycled pulp properties. Likewise, significant changes in paper properties were observed before and after refining at a plate gap of 0.15 mm, except for basis weight and brightness, which responded positively at 0.10 mm. Overall, sheets containing OCC fibers at enhanced proportions exhibited reduced breaking length, elongation, and folding endurance when refined at plate gaps of 0.10 and 0.05 mm.