Rush-Transferred Tissue Sheet for High Strength and Low Stiffness
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Solution Overview
Problem
Conventional tissue products face a challenge in achieving high geometric mean tensile strength while maintaining low machine direction (MD) slope, which affects durability and hand feel, with existing methods often resulting in reduced MD stretch and increased stiffness.
Innovation Solution
The process involves subjecting the embryonic web to a high degree of rush transfer during the papermaking process, specifically between the forming fabric and the transfer fabric, with a speed differential of 30 to 70 percent, to increase MD stretch and decrease MD slope, thereby enhancing tissue product properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional papermaking methods are used to produce tissue with high geometric mean tensile strength, then tensile strength is improved, but machine direction slope increases and machine direction stretch decreases
Solution Approach 1:
The invention applies dynamic speed differential control during the papermaking process, specifically varying the speed between the forming fabric and transfer fabric during web transfer. This dynamic adjustment creates rush transfer effects that modify fiber orientation and bonding, achieving low MD slope and high stretch while maintaining high tensile strength. The speed differential is changed from static to dynamic, allowing optimization of multiple properties simultaneously.
Solution Approach 2:
The invention changes the operational parameters of the papermaking process by introducing a significant speed differential (30-70%) between the forming fabric and transfer fabric. This parameter change in the transfer process creates unique fiber arrangement patterns that result in tissue products with simultaneously high tensile strength, low MD slope, and high MD stretch, resolving the traditional trade-off between these properties.
2Strength
If conventional papermaking methods are used to produce tissue with high geometric mean tensile strength, then tensile strength is improved, but machine direction stretch decreases
Solution Approach 1:
The dynamic speed variation during web transfer creates rush transfer that induces fiber reorientation and creates more flexible bonding patterns. This dynamic process allows the tissue to elongate more in the machine direction while maintaining high tensile strength, as the fibers can rearrange and stretch more effectively under the dynamic transfer conditions.
Solution Approach 2:
By changing the speed parameter during fabric transfer, the invention creates a rush transfer effect that fundamentally alters fiber arrangement and bonding characteristics. This parameter change enables the tissue to achieve both high tensile strength and high machine direction stretch, breaking the conventional inverse relationship between these two properties.
3Ease of manufacture
If conventional papermaking methods are used, then manufacturing process is simple, but tissue product stiffness increases and hand feel deteriorates
Solution Approach 1:
The invention introduces dynamic speed control during the transfer process, creating rush transfer that produces a more open and flexible fiber network. This dynamic approach creates tissue with lower stiffness and better hand feel while maintaining ease of manufacture, as the basic papermaking process remains unchanged but with optimized transfer parameters.
Solution Approach 2:
By adjusting the speed differential parameter during fabric transfer, the invention creates tissue products with improved hand feel and reduced stiffness. This parameter change in the transfer process creates a more flexible internal structure without complicating the manufacturing process, maintaining simplicity while improving product quality.
Data Source
AI summary
The present invention provides tissue products having a high degree of stretch and low modulus at relatively high tensile strengths, 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.