Sanitary Tissue MD Elongation via Patterned Through-Air Drying
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Solution Overview
Problem
Current methods for creating machine direction (MD) elongation in sanitary tissue products, such as bath tissue and paper towels, using fibrous structures with pulp fibers are limited, as process-induced foreshortening negatively impacts tensile strength and fails to achieve consumer-desired MD elongation to total foreshortening ratios greater than 2.22.
Innovation Solution
The use of through-air-drying fabrics and patterned through-air-drying belts with cross-machine direction (CD) oriented line elements and semi-continuous knuckles, which impart MD elongation without significantly affecting tensile strength, allowing for MD elongation to total foreshortening ratios greater than 2.25 and 2.5.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If process-induced foreshortening operations are used to create MD elongation, then MD elongation is improved, but tensile strength deteriorates
Solution Approach 1:
The invention segments the foreshortening operation into two distinct types: process-induced foreshortening (which does affect tensile strength) and structure-induced foreshortening (which does not). By separating these mechanisms, the invention allows formulators to use structure-induced foreshortening methods that achieve MD elongation without the harmful side effects on tensile strength associated with traditional process-induced methods.
Solution Approach 2:
The invention inverts the traditional approach by showing that reducing process-induced foreshortening and increasing structure-induced foreshortening can actually improve or maintain MD elongation while preserving tensile strength. This counterintuitive approach challenges the conventional wisdom that more foreshortening operations are needed for better elongation.
2Length of moving object
If process-induced foreshortening operations are used to create MD elongation, then MD elongation is improved, but the MD elongation to total foreshortening ratio deteriorates
Solution Approach 1:
The invention changes the parameters of foreshortening operations by distinguishing between process-induced and structure-induced mechanisms. By adjusting the mix of these two types of foreshortening, formulators can optimize the MD elongation to total foreshortening ratio to exceed the conventional limit of 2.22, achieving superior performance metrics.
3Strength
If structure-induced foreshortening is used instead of process-induced foreshortening, then tensile strength is maintained, but MD elongation may be insufficient
Solution Approach 1:
The invention merges process-induced and structure-induced foreshortening operations into a unified approach. By combining these two types of foreshortening in optimal proportions, the invention achieves both sufficient MD elongation and maintained tensile strength, resolving the trade-off between these two critical properties.
Data Source
AI summary
Fibrous structures and/or sanitary tissue products comprising fibrous structure, and more particularly to fibrous structures comprising pulp fibers, wherein the fibrous structures exhibit unique elongation (stretch) and total foreshortening properties, and methods for making such fibrous structures.