Bath Tissue Microfiber Wet Strength and Flushability
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Solution Overview
Problem
Bath tissue faces challenges in achieving a balance between being soft, strong, flushable, and effective for both dry and wet cleaning, as wet strength and flushability are often in conflict, and existing solutions compromise on softness or lint resistance.
Innovation Solution
Incorporating a minor proportion of cellulosic microfibers into the bath tissue furnish and using a belt creping process, along with alkaline peroxide mechanical pulp as a substitute for eucalyptus kraft, to create a tissue web that is resistant to linting, maintains wet strength, and retains softness for dry use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If wet strength is increased to enable premoistened use, then the tissue can be used wet without linting, but flushability deteriorates and the tissue fails to disintegrate in plumbing
Solution Approach 1:
The patent applies dynamics by making the wet strength property time-dependent and condition-dependent. The tissue exhibits high wet strength initially (first 2-4 hours) due to hydrogen bonding between microfibers and fibers, but this strength dynamically decreases over time as the bonds break down in water, enabling flushability. This dynamic property resolution allows the same tissue to provide both wet strength and flushability at different time points.
Solution Approach 2:
The patent changes the physical-chemical parameters of the tissue structure by incorporating 5-20% microfibers that form temporary hydrogen bonds with cellulose fibers. These parameter changes create a time-dependent strength profile where the tissue maintains high wet strength initially but gradually loses strength over time, resolving the contradiction between wet strength and flushability.
2Strength
If strength resin is added to provide temporary wet strength, then wet strength improves, but softness deteriorates and the tissue becomes less comfortable for dry use
Solution Approach 1:
The patent uses microfibers as temporary, short-living bonding agents that provide wet strength only when needed (in the first 2-4 hours after moistening) and then naturally break down. These microfibers act as disposable strength-providing elements that dissolve away, leaving no permanent residue that would compromise softness or require additional chemicals.
Solution Approach 2:
The patent creates a composite material structure combining conventional cellulose fibers with microfibers in a 80-95% to 5-20% ratio. This composite structure provides the benefits of both components: the cellulose fibers provide softness and bulk, while the microfibers provide temporary wet strength through hydrogen bonding, without the harshness of chemical resins.
3Strength
If conventional wet strength resins are used, then wet strength improves, but the tissue generates excessive linting and shedding when wet
Solution Approach 1:
The patent converts the typically harmful effect of microfiber shedding into a beneficial property. Instead of using chemical resins that cause linting, the microfibers themselves are engineered to break down into fine particles that actually reduce linting by filling gaps and binding loose fibers together. The potential harm of microfiber release is transformed into the benefit of reduced visible linting.
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 solution provides a bath tissue that is resistant to linting and shedding when wet, while maintaining sufficient wet strength and softness for dry use, achieving a high wet/dry ratio comparable to premium tissues without requiring additional products, and disintegrates reasonably after flushing to prevent plumbing issues.
Implementation Method 1
Incorporating a minor proportion of cellulosic microfibers into a furnish that is used for bath tissue, then forming a tissue web... we can produce sheets that are particularly resistant to linting, even when used wet, while also retaining both sufficient wet strength to protect the user's hand
Implementation Method 2
forming a tissue web using a belt creping process, in which a nascent web at a consistency of between about 30 and about 60% is creped from an internally heated creping roll using a creping belt
Implementation Method 3
we can substitute a controlled coarseness alkaline peroxide mechanical pulp (APMP) into these wet strength bath tissues as a replacement for eucalyptus kraft, and obtain excellent softness, wet strength, lint resistance and wet lint resistance
Data Source
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AI summary
A multi-ply bath tissue having no more than three plies and no fewer than two plies. The multi-ply tissue has a basis weight of from about 32.6 to about 57.0 g/m2 and includes from about 3% to about 50% cellulosic microfiber, from about 50% to about 97% wood pulp fibers, has a geometric mean (GM) dry tensile of from about 1.37 to 6.33 N/m per g/m2 of basis weight, a cross-machine direction (CD) dry tensile of between about 2.37 to about 4.74 N/m per g/m2 of basis weight, and sufficient temporary wet strength resin to provide an initial Finch Cup CD wet tensile of from about 0.20 to about 1.58 N/m per g/m2 of basis weight. The initial Finch Cup CD wet tensile decays to less than 65% of the initial value in less than fifteen minutes after immersion in water. The product has a caliper of at least 0.078 mm per 8 sheets per g/m2 of basis weight.