Tissue Rush Transfer Speed Differential for Cross-Direction Strength
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Solution Overview
Problem
Existing tissue products have significantly different machine direction (MD) and cross-machine direction (CD) tensile strengths, with CD strengths often being weaker, leading to product failure, and attempts to equalize them have not been successful, along with challenges in improving CD properties like tensile energy absorption and stretch.
Innovation Solution
A papermaking process involving high-speed rush transfer of the embryonic web from the forming fabric to the transfer fabric, with a speed differential of 30-70%, achieving CD tensile strength equal to or greater than MD tensile strength, and improving CD properties to parity with MD properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the CD tensile strength is increased to equal or exceed MD tensile strength through conventional methods, then the product reliability improves, but the manufacturing complexity increases and other CD properties (stretch, TEA) remain inadequate
Solution Approach 1:
The patent applies parameter changes by modifying the rush transfer speed differential parameter in the papermaking process. By increasing the speed differential between the forming fabric and transfer fabric to 30-70%, the process achieves CD tensile strength equal to or exceeding MD tensile strength while simultaneously improving stretch and TEA properties. This single parameter change resolves the contradiction by achieving multiple performance goals without adding manufacturing complexity.
2Strength
If high rush transfer (30-70% speed differential) is applied during papermaking, then CD tensile strength and stretch properties improve to parity with MD properties, but the manufacturing process complexity increases
Solution Approach 1:
The patent applies dynamics by introducing a dynamic speed differential during the rush transfer process. The forming fabric and transfer fabric operate at different speeds (30-70% differential), creating a dynamic mechanical action that enhances fiber bonding in the CD direction. This dynamic approach improves CD tensile strength and stretch without requiring additional equipment or complex multi-step processes, as it utilizes the existing papermaking line with adjusted operational parameters.
3Ease of manufacture
If conventional papermaking processes are used without high rush transfer, then the manufacturing process remains simple, but CD tensile strength is significantly weaker than MD tensile strength leading to product failure
Solution Approach 1:
The patent resolves this contradiction by changing a single operational parameter - the rush transfer speed differential - to 30-70%. This parameter change transforms the papermaking process to achieve CD tensile strength equal to or exceeding MD tensile strength. The solution maintains manufacturing simplicity because it uses existing equipment and processes, requiring only adjustment of speed differentials rather than adding complex new machinery or process steps.
Data Source
AI summary
The present invention provides tissue products having an MD/CD Tensile Ratio less than about 0.95, yet relatively high geometric tensile strength, such as geometric mean tensile strengths greater than about 1500 g/3″ and more preferably greater than about 2000 g/3″. The combination of a tough, yet relatively supple sheet is preferably achieved by subjecting the embryonic web to a speed differential as it is passed from one fabric in the papermaking process to another, commonly referred to as rush transfer.