Wet-Pressed Tissue Macro-Ridges via Texturizing Fabric
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Solution Overview
Problem
Existing processes for combining bulk-generating through-drying with dewatering efficiency in wet-pressing fall short, particularly for lightweight tissue webs, due to difficulties in transferring low basis weight wet webs and resulting in gritty, insufficiently soft products.
Innovation Solution
The use of special texturizing fabrics with a three-dimensional surface contour, combined with upstream wet-pressing and creping, creates tissue sheets with continuous undulating macro-ridges and mini-ridges, achieving high bulk and softness similar to through-dried products while maintaining aesthetic appeal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If web-structuring fabrics are used to impart texture to the web, then product texture is improved, but the tissue becomes gritty feeling with insufficient softness
Solution Approach 1:
The patent applies local quality by creating distinct macro-ridge and macro-valley regions with different fiber densities and surface properties. The macro-ridges provide structural definition while the macro-valleys provide softness, allowing different parts of the tissue to have different functional qualities. This resolves the contradiction by localizing the texturizing effect to ridges while preserving softness in valleys.
Solution Approach 2:
The patent introduces a new dimensional scale by creating macro-ridges and macro-valleys that are significantly larger than traditional fabric-imparted textures. These macro-features are formed by controlling fiber deposition and consolidation at a macroscopic level during the papermaking process, rather than relying on fabric surface geometry alone. This dimensional change allows for smoother transitions and softer overall hand feel while maintaining textural definition.
2Productivity
If conventional wet-pressing processes are used, then dewatering efficiency is improved, but bulk and softness are reduced
Solution Approach 1:
The patent applies local quality by creating distinct macro-ridge and macro-valley regions with different fiber densities and surface properties. The macro-ridges provide structural definition while the macro-valleys provide softness, allowing different parts of the tissue to have different functional qualities. This resolves the contradiction by localizing the texturizing effect to ridges while preserving softness in valleys.
Solution Approach 2:
The patent introduces a new dimensional scale by creating macro-ridges and macro-valleys that are significantly larger than traditional fabric-imparted textures. These macro-features are formed by controlling fiber deposition and consolidation at a macroscopic level during the papermaking process, rather than relying on fabric surface geometry alone. This dimensional change allows for smoother transitions and softer overall hand feel while maintaining textural definition.
3Weight of moving object
If lightweight tissue webs are processed, then basis weight is reduced, but transfer difficulty increases due to virtually no strength
Solution Approach 1:
The patent applies preliminary action by forming the macro-ridge and macro-valley structure during the wet-web formation stage, before the tissue gains sufficient strength for conventional handling. The controlled fiber deposition and early consolidation create a mechanically robust structure that can be transferred reliably even at low basis weights, solving the transfer difficulty problem preemptively.
Solution Approach 2:
The patent creates a composite structure with macro-ridges and macro-valleys that have different mechanical properties. The macro-ridge regions provide structural integrity and transferability, while the macro-valley regions maintain softness and low basis weight. This composite architecture allows lightweight tissue to be processed reliably without sacrificing the desired softness characteristics.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The resulting creped, wet-pressed tissue sheets exhibit enhanced bulk, softness, and aesthetic qualities, with minimal basis weight variation, outperforming traditional through-air-dried tissues by maintaining density differences between ridge and valley regions.
Implementation Method 1
the sheet is molded during transfer onto the topographical texturizing fabric, thereby creating the precursors to the final macro-ridges and valleys
Implementation Method 2
During processing, the tissue sheet is densified uniformly by an upstream wet-pressing water removal step
Implementation Method 3
the sheet, supported by the texturizing fabric, is pressed against the surface of the dryer and adhered to the dryer surface
Implementation Method 4
When the web is creped, 'mini-ridges' having crests running in the cross-machine direction of the sheet are created within the valleys
Implementation Method 5
The dewatered web is then transferred to a 'web-structuring' woven fabric with the aid of a vacuum roll
Data Source
AI summary
Wet-pressed creped tissue sheets exhibit continuous undulating valleys separated by continuous mono-planar macro-ridges running in the machine direction of the sheet, the macro-ridges being of a lower fiber density relative to the fiber density of the undulating valleys. The tissue structure can be created by pressing a densified tissue web against the surface of a Yankee dryer while the web is supported by a texturizing (molding) fabric having a web-supporting surface having highly topographic continuous or substantially continuous ridges and valleys and thereafter creping the web.