High-Basis-Weight Creped Tissue for Low Stiffness and Softness
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Solution Overview
Problem
Conventional tissue products face a dilemma in achieving high basis weight for softness, absorbency, and durability while maintaining low stiffness, as increased basis weight typically results in reduced softness and impaired processing due to limited creping chemistries at higher weights.
Innovation Solution
The development of multi-ply tissue products with basis weights greater than 20 gsm, featuring altered creping conditions such as increased machine-direction stretch and conventional creping compositions, which maintain low stiffness and high absorbency without the use of surface modifiers or additional treatments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If basis weight is increased to achieve softness, absorbency, and durability, then these properties are improved, but stiffness increases and softness is reduced
Solution Approach 1:
The patent changes the physical-chemical parameters of the tissue web by controlling machine-direction stretch (increasing to greater than 30%) and geometric mean slope (decreasing to less than 14). These parameter changes allow the tissue to achieve high basis weight (40-60 gsm) while maintaining low stiffness (Stiffness Index less than 20) and high softness, resolving the contradiction between durability and softness
Solution Approach 2:
The patent introduces dynamic mechanical properties by significantly increasing machine-direction stretch (greater than 30%) and controlling geometric mean slope. This creates a dynamic tissue structure that can deform and recover, providing both durability through high tensile strength (GMT 500-900 g/3') and softness through controlled stiffness, allowing the tissue to adapt to handling forces
2Quantity of substance
If basis weight is increased to achieve thickness and absorbency, then these properties are improved, but creping performance deteriorates
Solution Approach 1:
The patent successfully crepes tissue webs with high basis weight (40-60 gsm) by changing key parameters: increasing machine-direction stretch to greater than 30% and decreasing geometric mean slope to less than 14. These parameter changes overcome the conventional limitation where high basis weight impairs creping, enabling the production of soft, thick tissue with low Stiffness Index (less than 20) that would otherwise be difficult to manufacture
Solution Approach 2:
The patent creates a dynamic creped structure in high basis weight tissue by achieving greater than 30% machine-direction stretch. This dynamic structure allows the thick tissue (40-60 gsm) to be successfully creped while maintaining low stiffness and high softness, resolving the contradiction between quantity of substance and ease of manufacture
3Strength
If basis weight is increased to achieve durability, then strength is improved, but stiffness increases reducing softness
Solution Approach 1:
The patent changes the mechanical parameters of the tissue by increasing machine-direction stretch to greater than 30% and controlling geometric mean slope to less than 14. This allows the tissue to achieve high geometric mean tensile strength (500-900 g/3') for durability while maintaining low stiffness (Stiffness Index less than 20) for softness, resolving the contradiction between strength and ease of operation
Solution Approach 2:
The patent introduces dynamic mechanical behavior by achieving greater than 30% machine-direction stretch in the creped tissue. This creates a flexible, durable structure with high geometric mean tensile strength (500-900 g/3') that can deform and recover, maintaining low stiffness and high softness despite the high basis weight, resolving the contradiction between strength and stiffness
Data Source
AI summary
The present invention provides multi-ply creped tissue products, and in particular embodiments creped wet pressed tissue products, having substantially higher per-ply basis weights, such as from about 20 to about 30 gsm, without the negative effects often associated with higher basis weight. As such, the tissue products are generally soft and flexible, having a softness value (measured as TS7) less than about 12.0 and a Stiffness Index less than about 20. While being soft and flexible, the instant tissue products are durable enough to withstand use, such as having a GMT greater than about 600 g/3″ and a Burst Index greater than about 12.0.