1. Why Yankee Coating Systems Increasingly Rely on High-Performance PVOH
With the upgrading of global tissue paper consumption, the market's comprehensive requirements for the softness, strength, bulkiness, and absorbency of tissues are constantly increasing. To achieve this balance of performance, traditional DCT (Dry Crepe Technology) is gradually becoming insufficient to meet the demands, and structured forming technologies such as TAD, NTT, eTAD, and QRT are widely used.
The advantages of PVOH are:
Good water solubility and high system compatibility
Tuned molecular structure and high application flexibility
Predictable impact on peel force and wrinkling behavior
This makes it a "structural material" in the high-end tissue paper Yankee coating system, rather than a simple additive.
2. The Influence of PVOH Viscosity and Concentration on Coating Rheological Behavior
At the same concentration, the viscosity of solutions with different molecular weights of PVOH varies significantly. However, in actual coating, the extended viscosity behavior as a function of concentration is more important.
Low-viscosity PVOH (Kuraray Poval 22-88): Easy to handle and sprayable, but with limited support under high-load peeling.
Medium-high viscosity PVOH (Kuraray Poval 22-88): Achieves a good balance between coating integrity and operational stability.
Ultra-high molecular weight PVOH (Kuraray Poval 200-88 KX): Forms a highly ductile coating network even at lower concentrations, contributing to improved "effective adhesion time" on Yankee surfaces.
3. Performance Focus Due to Differences in Hydrolysis Degree
Besides molecular weight, the degree of hydrolysis also determines the application boundaries of PVOH:
88% Hydrolysis Degree: Good water solubility, suitable for coating systems with large dynamic changes, and is the mainstream choice for current structured tissues.
99% Hydrolysis Degree (Elvanol 90-50): Dense film formation, stronger water resistance, suitable for paper machines requiring longer coating life or high humidity operating conditions.
In practical formulations, the adhesion and peelability of coatings are often precisely controlled by blending PVOHs with different degrees of hydrolysis.
4. PVOH Selection Approach Based on Application Objectives
When selecting PVOH for the Yankee coating system, the following factors should be given priority consideration:
Paper machine speed and Yankee surface temperature
The balance between the softness and strength of the target paper
The synergistic effect of the overall coating chemical system
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