The molding process of chemical fiber paper tubes is a core element determining their mechanical strength, dimensional accuracy, and functional stability, encompassing the entire process from substrate preparation and molding method selection to structural solidification. This process not only requires achieving the geometric shaping of the paper tube but also striking a precise balance in fiber arrangement, interlayer bonding, and stress control to meet the stringent performance requirements of high-speed winding and diverse applications of chemical fibers.
The first step in the molding process is substrate preparation and pretreatment. The main raw material for paper tubes is wood pulp fiber, selected based on product performance targets: softwood pulp, hardwood pulp, or blended with cotton linters or recycled pulp. The pulp needs to be beaten to adjust fiber length and bonding strength, and thickened to obtain suitable rheological properties, ensuring uniform fiber distribution and sufficient interlayer bonding during molding. When necessary, environmentally friendly additives, such as reinforcing starch or synthetic emulsions, are added to improve wet strength and water resistance, laying a solid foundation for subsequent molding.
In terms of forming methods, the industry generally adopts two mainstream processes: winding and lamination. Winding involves spirally winding pre-treated wet paper webs onto a steel or paper mandrel using a special mold. During winding, tension and speed control ensure a tight bond between the paper layers, eliminating air bubbles and wrinkles. Glue is then applied, and the paper is cured by heating or pressure to form a single-layer or multi-layer tube blank. This method offers high production efficiency and is suitable for mass production of conventional paper tubes, but it relies heavily on precise control of process parameters for interlayer bonding strength and radial uniformity. Lamination involves first cross-laminating dried paper strips along the fiber direction, then applying glue and hot-pressing to form a plate-like composite blank, which is then wrapped around the mandrel for secondary bonding and curing. This process allows for flexible design of fiber orientation and interlayer structure, significantly improving ring crush strength and impact toughness, and is particularly suitable for paper tubes made of high-performance industrial filaments and specialty fibers.
Structural curing is a critical stage in the forming process, directly determining the dimensional stability and mechanical properties of the paper tube. Hot-press curing melts or cross-links the adhesive through heating, promoting interfacial bonding between fibers and reinforcements; cold-press curing relies on mechanical pressure and room-temperature reactive adhesives to achieve interlayer bonding. Curing temperature, time, and pressure need to be optimized based on the material system and operating environment to avoid fiber embrittlement due to overheating or interlayer delamination due to insufficient pressure. For paper tubes requiring moisture resistance, temperature resistance, or antistatic properties, functional coatings can be applied before or after curing, integrating performance requirements into the structural body during the forming stage.
Post-forming finishing processes include length cutting and end-face trimming. CNC tube cutting machines and high-precision grinding devices are used to ensure that inner diameter, outer diameter, and length tolerances are controlled within a minimal range, and that end-face parallelism and perpendicularity meet the mandrel fitting requirements of the winding equipment. The precision at this stage directly determines the paper tube's ability to maintain its shape under high-speed rotation and stacking loads.
Overall, the chemical fiber paper tube forming process prioritizes substrate optimization, achieves geometric construction through winding or lamination, and locks in performance through curing and finishing. Each link in this process chain requires systematic control based on material properties and product applications to produce high-quality paper tubes that combine high strength, high precision, and functional adaptability, providing reliable structural support for the efficient and stable operation of the chemical fiber industry.
