Papermaking Fabric Topography for Bulkier, Firmer Tissue Rolls
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Solution Overview
Problem
Tissue manufacturers face challenges in producing rolled tissue products with high bulk and firmness while maintaining cost-effectiveness, as loosely wound rolls are prone to deformation and perceived as soft, making it difficult to balance bulk, firmness, and sheet smoothness, especially in through-air dried products.
Innovation Solution
The use of papermaking fabrics with interwoven shute and warp filaments featuring machine direction (MD) and cross-machine direction (CD) oriented protuberances, which enhance sheet bulk and firmness by modifying the surface topography, allowing for the production of tissue products with high geometric mean tensile strength, bulk, and roll firmness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the tissue roll is wound loosely to increase roll bulk, then the roll diameter increases, but the roll firmness decreases and the roll becomes easily deformed
Solution Approach 1:
The fabric surface is modified with protuberances and valleys that create localized structural features. These features provide mechanical interlocking points that enhance roll firmness locally while allowing the overall roll to maintain high bulk through loose winding.
Solution Approach 2:
The fabric combines woven and nonwoven elements with different mechanical properties. The woven base provides structural integrity while the nonwoven protuberances add surface texture and interlocking capability, creating a composite structure that simultaneously achieves high bulk and firmness.
2Strength
If the tissue sheet surface is made smooth to increase perceived softness, then the user perceives the product as softer, but the ability to wind into firm high bulk finished products decreases
Solution Approach 1:
The fabric has smooth valleys that contact the tissue sheet to provide softness, while protuberances extend above the surface to create mechanical interlocking. This local differentiation allows the sheet to feel smooth against the skin while the protruding features enable firm winding.
Solution Approach 2:
The fabric surface features extend in the z-direction (height) with protuberances rising above the base fabric plane. This three-dimensional structure allows the sheet to maintain smoothness at the contact level while gaining bulk and firmness from the elevated features during winding.
3Volume of moving object
If through-air dried tissue products are molded to achieve bulk, then the embryonic tissue web is molded into the fabric, but at higher basis weights the molding becomes increasingly difficult and the molded structure requires calendering to increase sheet smoothness
Solution Approach 1:
The fabric is pre-formed with protuberances and valleys before the tissue web is deposited. This preliminary structuring creates natural molding cavities that guide the web into the desired bulk configuration during the forming process, reducing the need for subsequent calendering operations.
Solution Approach 2:
The fabric structure parameters are optimized with specific protuberance heights, spacing, and distributions that facilitate web molding at higher basis weights. The geometric features are designed to accommodate thicker webs while maintaining effective molding contact.
Data Source
AI summary
The present invention discloses tissue products, specifically rolled bath tissue products, having a three-dimensional surface topography comprising substantially continuous machine direction (MD) oriented elements, discrete cross-machine direction (CD) oriented elements and discrete MD oriented valleys having valley sidewalls formed by the MD oriented elements and valley endwalls formed by the CD oriented elements. The discrete valleys generally have a length greater than about 10.0 mm. The CD oriented elements comprise a relatively small percentage of the tissue surface area, such as less than about 15 percent, yet the tissue products display good anti-nesting properties when spirally wound into rolls, such as a Roll Structure greater than about 0.75.