Smooth and bulky rolled tissue products
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Solution Overview
Problem
Conventional calendering processes result in significant Sheet Bulk loss and stiffness in tissue products when spirally wound into rolls, failing to maintain desired softness and bulk under tension.
Innovation Solution
Employing a calender roll with male elements covering a significant surface area, providing a nip with variable loading to reduce Z-direction variability and prevent excessive compression, resulting in a smoother, bulkier tissue product without excessive caliper loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If conventional calendering is used to smooth tissue products, then surface smoothness is improved, but sheet bulk is significantly lost and the product becomes stiff when wound into rolls
Solution Approach 1:
The calender roll surface is divided into different functional zones: smooth areas for general contact and patterned areas with raised elements for localized smoothing. This selective application of smoothing pressure provides surface smoothness while preserving bulk in critical areas where compression would be excessive.
Solution Approach 2:
The calender roll incorporates a compliant or resilient coating material that allows the surface to dynamically adapt to the tissue web during calibration. This dynamic response enables the roll to apply smoothing pressure only where needed while accommodating variations in web thickness and preventing excessive bulk reduction.
2Shape
If conventional calendering is used to smooth tissue products, then surface smoothness is improved, but the product becomes stiff when wound under tension
Solution Approach 1:
The patterned calender roll applies smoothing pressure locally through raised elements rather than uniformly across the entire surface. This localized approach smooths the tissue surface while leaving other areas relatively uncompressed, thereby maintaining softness and flexibility when the product is wound into rolls.
Solution Approach 2:
The calender roll uses a compliant coating material with specific mechanical properties that allow it to deform and recover during the calibration process. This parameter change in the roll surface material enables gentle smoothing that does not permanently stiffen the tissue structure.
3Volume of moving object
If through-air drying is used to maintain sheet bulk and softness, then bulk is preserved, but operational efficiency may be reduced compared to conventional methods
Solution Approach 1:
The tissue web undergoes through-air drying before calibration to pre-establish the desired bulk and softness characteristics. This preliminary action ensures that the web is in optimal condition for subsequent calibration, allowing the calender roll to smooth the surface without significantly compromising the bulk structure that was already established.
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 process produces tissue products with improved Sheet Bulk and Surface Smoothness, maintaining Roll Bulk and Roll Structure when wound into rolls, offering a balance of softness and firmness.
Implementation Method 1
a calender roll comprising male elements and landing areas... providing a nip with variable loading to reduce Z-direction variability and prevent excessive compression
Data Source
Figure 1
Figure 2~3
AI summary
The novel tissue products of the present invention are generally produced by calendering a tissue basesheet using at least one patterned roll. In one embodiment the patterned roll replaces the flat steel roll commonly used in calendering. The elements on the patterned roll provide a means of providing a nip having variable loading such that Z-direction variability in the web is reduced, yielding a smoother web, but without subjecting the web to excessive compression forces and preventing excessive caliper loss. Thus, webs converted according to the present invention tend to retain a greater percentage of their caliper and bulk when converted compared to webs converted using conventional calendering means.