Through-Air-Dried Tissue Layering for Softness and Low Lint
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Solution Overview
Problem
Conventional tissue manufacturing methods struggle to produce soft and strong tissues with low lint, as adding binders or softeners to enhance softness often compromises strength, while reducing lint typically makes tissues less soft.
Innovation Solution
A multi-layer through air dried tissue is manufactured using a combination of hardwood and softwood fibers, with an interior layer containing an ionic surfactant as a debonder and a non-ionic surfactant as a softener, along with dry and wet strength additives, to control fiber bonding and reduce lint without sacrificing softness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If binders or softeners are added to enhance softness, then softness is improved, but strength deteriorates
Solution Approach 1:
The tissue is divided into multiple layers with different functions: outer layers provide strength and lint control, while the inner layer provides softness. This segmentation allows each layer to be optimized for its specific function without compromising the other properties.
Solution Approach 2:
Different layers have different chemical compositions and properties. The outer layers contain binders for strength and lint control, while the inner layer contains softeners for softness. This local differentiation of quality allows simultaneous achievement of strength and softness.
2Strength
If binders are added to increase strength, then strength is improved, but lint increases
Solution Approach 1:
The tissue structure separates the functions of strength provision and lint control into different layers. The outer layers contain binders for strength while the inner layer manages lint, reducing overall lint generation.
Solution Approach 2:
The binder chemistry is optimized to control lint generation rather than simply increase strength. The specific binder formulation creates a matrix that holds fibers together strongly while minimizing fiber liberation during use.
3Shape
If conventional creping and calendering are used to influence surface topography, then surface smoothness is improved, but fiber damage increases leading to higher lint
Solution Approach 1:
The patent replaces mechanical creping and calendering processes with a chemical approach using wet-end additives. These additives modify fiber bonding and surface properties during the papermaking process itself, eliminating the need for aggressive mechanical processing that damages fibers.
Solution Approach 2:
The surface properties and fiber bonding are controlled during the papermaking process through wet-end additives, rather than relying on subsequent mechanical processing. This preliminary chemical treatment prevents fiber damage before it can occur during creping or calendering.
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 method results in a tissue with exceptional softness and low lint levels, achieving a softness value of 91 HF and a lint value of 5.0 or less, while maintaining structural integrity.
Implementation Method 1
The interior layer includes a first wet end additive comprising an ionic surfactant
Implementation Method 2
a second wet end additive comprising a non-ionic surfactant
Data Source
AI summary
A multi-ply through air dried structured tissue having a bulk softness of less than 10 TS7 and a lint value of 5.0 or less. Each ply of the tissue has a first exterior layer that includes a wet end temporary wet strength additive in an amount of approximately 0.25 kg/ton and a wet end dry strength additive in an amount of approximately 0.25 kg/ton, an interior layer that includes a first wet end additive comprising an ionic surfactant, and a second wet end additive comprising a non-ionic surfactant, and a second exterior layer.