Through-Air-Dried Tissue Layering for Softness Without Surface Flattening
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional tissue-making processes using wet end additives result in increased costs and reduced tissue strength, while through air drying with topical softeners leads to a flattened surface profile, hindering cleaning ability and softness.
Innovation Solution
A multi-layer through air dried tissue with a combination of wet end temporary and dry strength additives, including ethoxylated vegetable oils and glyoxalated polyacrylamide, is developed, where non-ionic surfactants migrate to exterior layers for enhanced softness and strength without excessive debonder use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wet end additives are used in the pulp mixture to achieve desired tissue attributes, then the tissue obtains the desired chemical state, but a large amount of additive is required which increases cost and reduces tissue strength
Solution Approach 1:
The patent applies local quality by adding additives only to specific layers (interior layers) rather than uniformly to all layers. This localized approach reduces the total amount of additive required while maintaining effective concentration where needed, thereby preserving tissue strength and reducing costs.
Solution Approach 2:
The tissue is segmented into multiple layers with different additive compositions. Exterior layers are kept free of certain additives that would harm strength, while interior layers receive the necessary additive treatment. This segmentation allows the tissue to achieve desired attributes without the downsides of uniform additive application.
2Ease of operation
If topical softeners are added after web formation to avoid wet end additive drawbacks, then the tissue achieves softness, but the surface profile becomes flattened which hinders cleaning ability
Solution Approach 1:
The patent applies softening agents during the wet end process (before drying) rather than as a topical application after web formation. This preliminary action allows the softener to be incorporated into the fiber structure without causing surface flattening, as the additives are distributed throughout the layer during formation rather than deposited on the finished surface.
Solution Approach 2:
Softening agents are applied locally to interior layers rather than to the exterior surface layers. This ensures that the softening effect is achieved within the tissue structure without affecting the surface profile, thereby maintaining both softness and cleaning ability.
3Productivity
If through air drying is used to dry the tissue web, then the drying process is efficient, but the use of topical softeners in combination results in a flattened surface profile
Solution Approach 1:
The patent maintains the through air drying process for efficient drying but modifies which layers receive softening treatment. By restricting softener application to interior layers and excluding exterior layers, the surface profile is preserved while still achieving the desired softness through the interior treatment.
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
The tissue achieves improved softness and tensile strength with a uniform surface profile, reducing the need for high additive amounts and maintaining effective cleaning, while minimizing the drawbacks of wet end additives.
Implementation Method 1
a non-ionic surfactant functioning as a softener (6) added to the interior layer (3) which migrates to the exterior layers (2, 4)
Implementation Method 2
The web is then dried by transferring the web to a forming surface and then directing a flow of heated air onto the web. This process is known as through air drying (TAD).
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A multi-layer through air dried tissue including an interior layer having an ionic surfactant and a non-ionic surfactant, introduced as wet end additives. A tissue manufacturing method uses through air drying without compromising softness and cleaning ability of the resulting tissue. The manufacturing method avoids the disadvantages associated with wet end additives, and in particular avoids the use of a large amount of additive to achieve the desired effect on the resulting tissue. A multi-layer through air dried tissue comprises a first exterior layer, an interior layer and a second exterior layer the interior layer includes a first wet end additive comprising an ionic surfactant and a second wet end additive comprising a non-ionic surfactant. The tissue exhibits improved surface profile that provides for improved product consistency and fewer defects that break sheets. Roughness of tissue is characterized by Average Primary Amplitude and Average Peak to Valley Waviness.