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Unreasonable filler gradient distribution is an overlooked root cause of uneven optical and mechanical performance of multi-layer composite paper. During multi-layer forming, inorganic fillers such as calcium carbonate and talcum powder tend to sink to the bottom fiber layer due to gravity settlement, forming a dense high-filler bottom layer and a loose low-filler surface layer. This vertical gradient difference creates obvious gaps between layers: the bottom layer has strong hiding power but low tensile strength, while the surface layer features smooth handfeel yet poor opacity. After printing, the inconsistent filler content leads to uneven ink absorption depth, mottled color rendering and mismatched gloss between front and back sides. In long-term storage, the unbalanced filler gradient accelerates differential fiber shrinkage, triggering sheet warping and layered separation. Most factories adjust filler adding volume separately for each pulp layer, but manual proportional control cannot restrain gravity settlement of tiny filler particles, resulting in unstable batch gradient consistency and high composite paper rejection rate.

Shandong Ludao Energy Technology Co., Ltd. provides filler gradient balancing optimization technology. By adding uniform suspension modifiers to layered pulp, we reduce the settlement speed of fine filler particles, realize uniform vertical filler distribution from surface to bottom layer of composite paper. The solution balances opacity, surface smoothness and overall tensile strength simultaneously, eliminates front-back printing color difference, restrains layered shrinkage deformation, improves interlayer bonding fastness of multi-layer paper, reduces post-processing defective rate, and stabilizes mass production quality of composite packaging and art paper.