Multi-Ply Bath Tissue with Temporary Wet Strength Resin
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Solution Overview
Problem
Bath tissues face a challenge in achieving a balance between softness and durability, as making them softer often results in reduced durability and vice versa, with existing solutions like regenerated cellulose microfibers being expensive and temporary wet strength resins decreasing softness.
Innovation Solution
A multi-ply bath tissue structure is developed using a conventional wet press papermaking process with distinct layers in each ply, incorporating temporary wet strength resin strategically to maintain softness while achieving desired durability, without using regenerated cellulose microfibers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If regenerated cellulose microfibers are incorporated to improve softness, then softness is improved, but manufacturing cost increases
Solution Approach 1:
The patent uses temporary wet strength resin that is inexpensive and water-soluble, replacing expensive regenerated cellulose microfibers. The resin provides the necessary strength during use and then dissolves, achieving the desired softness at lower cost.
Solution Approach 2:
The patent changes the physical and chemical parameters of the tissue by incorporating temporary wet strength resin at specific concentrations (0.01-5 weight percent) and controlling fiber composition (40-80 weight percent cellulosic fibers), achieving softness through parameter optimization rather than expensive materials.
2Strength
If temporary wet strength resin is incorporated to improve durability, then durability is improved, but softness decreases
Solution Approach 1:
The patent applies temporary wet strength resin locally within the tissue structure rather than uniformly throughout. The resin is incorporated at specific concentrations in the pulp mixture, providing strength where needed while maintaining softness in the overall tissue structure.
Solution Approach 2:
The patent creates a composite material combining temporary wet strength resin with cellulosic fibers. This composite structure provides both the durability from the resin and the softness from the fiber network, achieving a balance between the two properties.
3Strength
If cross machine direction wet tensile strength is increased to improve durability, then durability is improved, but flushability decreases
Solution Approach 1:
The patent optimizes the parameter of cross machine direction wet tensile strength to a specific range (50-90 grams) and controls the ratio of wet abraded lint area to CD wet tensile strength (less than 0.333 mm2/gram). This parameter optimization achieves durability while maintaining flushability.
Solution Approach 2:
The patent uses temporary wet strength resin that provides the necessary strength during use and then dissolves in water. This temporary strength allows the tissue to be durable during cleaning but easily flushed away afterward, resolving the contradiction between strength and flushability.
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 multi-ply bath tissue achieves a balance of low wet abrasion and high durability, with a cross machine direction wet tensile strength between 50-90 grams and a wet abraded lint area to CD wet tensile strength ratio of less than 0.333 mm2/gram, maintaining softness and durability comparable to or exceeding commercial products.
Implementation Method 1
incorporating a temporary wet strength resin into the structure of the bath tissues. Temporary wet strength resin improves the wet strength of bath tissues
Data Source
AI summary
A multi-ply bath tissue includes a first ply providing a first surface of the bath tissue. The first ply includes first and second layers. The first layer forms the first surface and includes a temporary wet strength resin. The second layer is substantially free from a temporary wet strength resin. A second ply provides a second surface of the bath tissue. The second ply includes first and second layers. The first layer forms the second surface and includes a temporary wet strength resin. The second layer is substantially free from a temporary wet strength resin. The bath tissue is free from regenerated cellulosic microfibers.