Soft Single-Ply Tissue via Calendering and Throughdrying
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Solution Overview
Problem
Single-ply tissue products are often stiff and harsh due to their structural surface features, which cannot be adequately mitigated by post-treatment surface additions like lotions or polysiloxanes, leading to a need for a single-ply product that provides a soft feel to consumers.
Innovation Solution
A method combining throughdrying with specific process features to create a single-ply tissue sheet with high basis weight, low stiffness, one-sided surface feel, and high cross-machine direction stretch, involving rush transfer to a transfer fabric, molding into a textured throughdrying fabric, and calendering to impart three-dimensionality and reduce bulk, using blended or layered fibers for enhanced softness and strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If single-ply tissue products are used, then manufacturing cost is reduced and ply separation is eliminated, but the product becomes stiff and harsh with two-sided surface feel
Solution Approach 1:
The patent applies local quality by creating asymmetric surface properties on the single-ply tissue sheet. One surface is treated to be soft and smooth while the other surface maintains different characteristics. This is achieved through selective application of softening agents and controlled calendering that affects one surface more than the other, allowing the tissue to have a soft feel on the user-contact surface while maintaining structural integrity.
Solution Approach 2:
The patent changes physical parameters of the tissue sheet through controlled calendering pressure and temperature treatment. By adjusting the calendering parameters (pressure, temperature, nip width), the tissue undergoes thermal and mechanical modification that reduces stiffness and softens the harsh surface features without compromising the single-ply structure. This transforms the tissue from a stiff, harsh state to a softer, more comfortable state.
2Object-affected harmful factors
If post-treatment surface addition of lotions or polysiloxanes is applied, then harsh surface feel is mitigated, but added expense occurs and underlying structural harshness remains
Solution Approach 1:
The patent applies preliminary action by incorporating softening treatment during the tissue manufacturing process itself, rather than as a post-treatment step. The softening agents and calendering treatment are applied while the tissue is still in its wet or semi-dried state, allowing the structural harshness to be modified at the source. This prevents the underlying structural harshness from developing in the first place, making subsequent post-treatments unnecessary or less effective.
Solution Approach 2:
The tissue sheet performs self-service by having its harsh surface features mitigated through inherent structural modifications during manufacturing. The controlled calendering and fiber arrangement create a naturally softer surface that does not require heavy reliance on external lotions or polysiloxanes. The tissue essentially softens itself through the manufacturing process, reducing the need for additional substance applications.
3Object-affected harmful factors
If throughdrying with high bulk is used, then three-dimensionality and softness are improved, but bulk must be reduced through heavy calendering
Solution Approach 1:
The patent applies periodic action through a sequence of bulk-modifying steps. First, the tissue undergoes throughdrying that creates high bulk and three-dimensionality. Then, controlled calendering is applied to reduce bulk to acceptable levels. Finally, additional softening treatments or surface modifications are applied to restore softness. This periodic modification of bulk and softness properties allows the tissue to achieve both characteristics at different stages, resulting in a final product with balanced properties.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Results in a soft, single-ply tissue sheet with desirable properties such as low stiffness, good durability, suitable bulk, dry resiliency, and superior absorbent capacity, addressing the harshness issues of single-ply products while maintaining high basis weight and consumer preference for 'substance in hand'.
Implementation Method 1
molding the web into the topography of the throughdrying fabric; throughdrying the web to form a sheet having a bulk of about 15 cubic centimeters or greater per gram
Implementation Method 2
calendering the sheet with a Compression Energy of about 0.35 Newton-millimeter or greater per square millimeter, wherein the sheet bulk is reduced about 20 percent or greater
Implementation Method 3
rush transferring the dewatered web from the forming fabric to a transfer fabric, said forming fabric traveling from about 20 to about 35 percent faster than the transfer fabric
Data Source
AI summary
A soft single-ply tissue sheet is produced by making a textured, high bulk, through dried tissue sheet and calendering the sheet with a high level of compression energy to substantially reduce the bulk and impart improved properties to the sheet.