Dust-free paper, a dry-laid nonwoven fabric produced using air-laid technology, relies heavily on chemical bonding as a key process in its production. This method uses 100% wood pulp fiber as raw material, dispersing the fibers into individual fibers through an opening device, followed by air-laid formation to create a uniform fiber web structure. The introduction of a water-soluble binder is crucial for web curing, its mechanism encompassing binder penetration, fiber cross-linking, curing, and performance control.
During the spraying stage, the water-soluble binder is uniformly applied to the web surface in liquid form. Thanks to its low viscosity, the binder quickly penetrates the web, encapsulating individual fibers and filling the gaps between them. This process depends not only on the binder's flowability but also on its compatibility with the surface chemistry of the wood pulp fiber. The wood pulp fiber surface is rich in hydrophilic groups such as hydroxyl groups, which form initial adsorption with the polar molecules in the water-soluble binder through hydrogen bonding, laying the foundation for subsequent cross-linking reactions.
In the baking stage, the moisture in the binder gradually evaporates under heat, triggering cross-linking reactions between molecular chains. Water-soluble adhesives typically use polymers such as polyvinyl alcohol (PVA) and polyacrylate, whose molecular chains contain numerous hydroxyl or carboxyl groups. Under heating conditions, these groups form covalent bonds through dehydration condensation, connecting the originally independent molecular chains to construct a three-dimensional network structure. This structure tightly binds loose wood pulp fibers, giving the fiber web mechanical strength and dimensional stability. It is noteworthy that controlling the baking temperature and time is crucial: too low a temperature leads to insufficient cross-linking and substandard fiber web strength; too high a temperature may cause thermal degradation of the fibers, affecting the softness and liquid absorption properties of dust-free paper.
The three-dimensional network structure formed by the adhesive has a profound impact on the physical properties of dust-free paper. Mechanically, the cross-linked network acts as a "skeleton" to withstand external forces, giving dust-free paper tensile and tear resistance, meeting the strength requirements of industrial wiping and hygiene products. Regarding liquid absorption, although the adhesive occupies some of the fiber web space, sufficient porosity can be preserved through optimized formulation. These pores form capillary channels, allowing dust-free paper to quickly absorb and lock in liquids while preventing backflow, ensuring a dry feel during use. Furthermore, the uniform distribution of the adhesive reduces localized weak points in the fiber web, preventing fiber shedding or powdering during wiping.
The selection and formulation of water-soluble adhesives must consider both process compatibility and product performance. Different applications have significantly different requirements for dust-free paper: industrial wiping dust-free paper requires high strength and abrasion resistance, making adhesives with high cross-linking density preferable; hygiene product dust-free paper needs to be soft and skin-friendly, requiring controlled adhesive usage to avoid a hardening sensation. Simultaneously, the compatibility of the adhesive with wood pulp fibers and the energy cost of the baking process must also be considered. In modern production, adhesive performance is often optimized through blending modification and the introduction of functional additives, such as adding softeners to reduce the stiffness of the dust-free paper or introducing antibacterial agents to impart additional functions to the product.
From an environmental perspective, the application of water-soluble adhesives also aligns with the concept of sustainable development. Compared to solvent-based adhesives, water-based systems use water as the dispersion medium, avoiding the emission of volatile organic compounds (VOCs) and reducing environmental pollution and health risks during production. Simultaneously, wood pulp fiber, as a renewable resource, combined with water-soluble adhesives, makes dust-free paper biodegradable, allowing it to be composted or incinerated after use, reducing the long-term burden on the ecosystem.
The mechanism of action of water-soluble adhesives in the chemical bonding method of dust-free paper essentially involves constructing a fiber-adhesive composite structure through steps such as permeation adsorption and cross-linking curing. This process not only endows dust-free paper with mechanical strength and liquid absorption properties but also meets diverse application needs through formulation optimization. With advancements in materials science and environmental protection technologies, the performance of water-soluble adhesives will continue to improve, driving dust-free paper towards higher performance and greater environmental friendliness.
