Tissue Web Two-Stage Rush Transfer for High CD Stretch
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Solution Overview
Problem
Conventional methods for increasing cross machine direction (CD) stretch in tissue products often compromise tensile strength, and there is a need for tissue basesheets with higher CD stretch and tensile strength while maintaining other important sheet properties.
Innovation Solution
A papermaking process involving two distinct rush transfers: one from the forming fabric to the transfer fabric and another from the transfer fabric to the through-air drying fabric, with an overall speed differential of 10 to 50%, to achieve enhanced CD stretch and tensile strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If conventional methods (creping, foreshortening) are used to increase CD stretch, then CD stretch is improved, but tensile strength deteriorates
Solution Approach 1:
The single rush transfer process is segmented into two distinct rush transfers: first from forming fabric to transfer fabric, then from transfer fabric to through-air drying fabric. This segmentation allows independent optimization of stretch and strength parameters at each transfer stage, resolving the contradiction between achieving high CD stretch and maintaining tensile strength.
Solution Approach 2:
The invention changes the process parameters by introducing a second rush transfer with specific speed differentials (10-50% overall). By controlling the timing and magnitude of speed differentials at two separate positions, the process achieves CD stretch greater than 15% while maintaining CD tensile strength greater than 750 grams per 7.62cm, overcoming the traditional trade-off.
2Strength
If refining or strengthening agents are used to increase tensile strength, then tensile strength is improved, but softness deteriorates
Solution Approach 1:
The invention replaces chemical methods (refining and strengthening agents) with a mechanical approach - the two-rush-transfer process. By using controlled speed differentials during web formation and drying, the process achieves high tensile strength (greater than 750 grams per 7.62cm) without adding chemicals that would compromise softness, thus substituting mechanical process control for chemical modification.
3Shape
If single rush transfer is used to increase CD stretch, then CD stretch is improved, but manufacturing complexity increases
Solution Approach 1:
The transfer fabric serves multiple functions: it acts as an intermediate carrier between forming and drying sections, and simultaneously provides the second rush transfer mechanism. This multi-functionality achieves high CD stretch (greater than 15%) without requiring separate dedicated equipment, thereby limiting the increase in manufacturing complexity while still achieving the desired technical effect.
Data Source
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AI summary
The present invention provides tissue products having increased CD stretch, which may be manufactured using a process in which the nascent web is subjected to two distinct rush transfers. The first rush transfer occurs when the web is transferred from the forming fabric to the transfer fabric, i.e., the "first position," and the second occurs when the web is transferred from the transfer fabric to the through-air drying fabric (TAD) fabric, i.e., the "second position." The overall speed differential between the forming fabric and the TAD fabric may be, for example, from about 10 to about 50 percent, with the amount of rush transfer being divided between the first and second position in a manner sufficient to achieve the desired CD stretch and other sheet properties.