Patterned Calender Roll Design for Bulky Tissue with Smooth Surface
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional calendering processes result in significant loss of Sheet Bulk and stiffness when producing spirally wound tissue products, leading to reduced Roll Bulk and undesirable firmness.
Innovation Solution
The use of a patterned calender roll with male elements covering 60 to 95% of the surface area, which reduces Z-direction variability and maintains web bulk while improving surface smoothness without excessive compression, allowing for a smoother, bulkier tissue product when wound into a roll.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If conventional calendering with smooth unpatterned rolls is used, then surface smoothness is improved, but Sheet Bulk is significantly lost
Solution Approach 1:
The calender roll surface is designed with localized male elements (protrusions) rather than a uniformly smooth surface. These male elements are distributed across the roll surface at specific locations, providing targeted compression and smoothing only where needed, while leaving other areas to preserve bulk. This localised action resolves the contradiction by applying smoothing pressure selectively rather than uniformly across the entire sheet surface.
Solution Approach 2:
The calender roll surface is segmented into discrete male elements rather than being a continuous smooth surface. Each male element acts as an independent compression zone, allowing the sheet to be smoothed at multiple discrete locations simultaneously. This segmentation enables selective compression that improves surface smoothness while maintaining bulk in areas between the elements.
2Shape
If conventional calendering is used to smooth the tissue product, then surface smoothness is improved, but Roll Bulk is reduced
Solution Approach 1:
The patterned calender roll applies compression locally through male elements rather than uniformly across the entire sheet. This localized compression smooths the surface while preserving the three-dimensional bulk structure in areas not directly compressed, thereby maintaining Roll Bulk when the sheet is wound into a roll.
Solution Approach 2:
The male elements on the calender roll are designed with specific geometric characteristics (size, spacing, height) that allow dynamic control of compression zones. By optimizing the distribution and dimensions of male elements, the process achieves surface smoothing while preserving the sheet's ability to maintain bulk during the dynamic winding process into a roll.
3Shape
If conventional calendering is used, then surface smoothness is improved, but firmness becomes undesirable
Solution Approach 1:
The patterned calender roll provides localized smoothing through male elements while leaving other areas of the sheet uncompressed. This selective compression maintains the sheet's overall firmness and structural integrity, preventing the undesirable softening and stiffness loss that occurs with conventional uniform calendering.
Solution Approach 2:
The male elements cover a controlled percentage (e.g., 30-70%) of the calender roll surface, providing partial rather than complete compression. This partial action is sufficient to achieve the desired surface smoothness while leaving enough uncompressed areas to maintain the sheet's firmness and prevent excessive softening.
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 patterned calendering method preserves Sheet Bulk and caliper, achieving improved Roll Bulk and Roll Structure with enhanced surface smoothness and reduced stiffness, resulting in a product that maintains consumer-desired firmness and aesthetics.
Implementation Method 1
The male elements, which may generally be any shape, have a surface area greater than about 300 mm2, such as from about 300 to about 8,000 mm2 and more preferably from about 1,750 to about 3,000 mm2 and cover from about 60 to about 98 percent of the surface of the roll and more preferably from about 70 to 95 percent of the surface of the roll
Data Source
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 that yields a web having a smooth surface without subjecting the web to excessive compression forces and preventing excessive caliper loss. Thus, webs converted according to the present invention have comparable or better surface smoothness compared to webs converted using conventional calendering means and also retain a greater percentage of their caliper and bulk.