Hesperaloe Fiber Tissue Composition for Softness and Strength Balance
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Solution Overview
Problem
The challenge in producing tissue products is to balance softness and durability, as increasing one property often adversely affects the other, and the scarcity of Northern Softwood Kraft fibers necessitates an alternative that maintains or improves softness and strength without increasing stiffness or reducing bulk.
Innovation Solution
The use of hesperaloe fibers, processed through high yield pulping, replaces conventional wood fibers, particularly Northern Softwood Kraft fibers, to create tissue products with enhanced softness, strength, and bulk, while maintaining or improving durability and reducing costs by blending with Southern Softwood Kraft fibers in a multi-layered tissue structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If fiber length is reduced to increase softness, then surface softness is improved, but durability decreases
Solution Approach 1:
The tissue product employs a multi-layer structure where different fiber types are strategically positioned: outer layers contain short, low-coarseness hardwood fibers for surface softness, while inner layers contain long, high-coarseness softwood fibers for durability and strength. This local differentiation allows each layer to optimize its specific function without compromising the other.
Solution Approach 2:
The invention uses a composite fiber furnish blending hardwood fibers (for softness) and softwood fibers (for strength) in specific proportions and configurations. This composite approach combines the advantageous properties of both fiber types to achieve both softness and durability simultaneously.
2Strength
If long fibers are used to increase durability, then tensile strength is improved, but surface softness decreases
Solution Approach 1:
Long, coarse softwood fibers are confined to inner layers where they provide tensile strength and durability, while the outer surface layers use short, fine hardwood fibers to maintain softness. This spatial separation allows long fibers to contribute strength without directly affecting surface softness.
Solution Approach 2:
The solution moves the fiber length parameter into the dimensional domain by creating a multi-layer structure. Fiber length variations are exploited in the through-thickness direction (z-dimension) rather than compromising surface properties in the plane of the sheet.
3Ease of manufacture
If Northern Softwood Kraft fibers are replaced with alternatives, then cost is reduced and supply security is improved, but softness and strength properties may be compromised
Solution Approach 1:
Hardwood fibers serve as an intermediary component in the fiber blend, replacing a portion of the NSWK while maintaining the necessary softness and strength properties. The hardwood fibers mediate between the need for cost reduction and the requirement to preserve product performance characteristics.
Solution Approach 2:
The invention modifies the fiber furnish composition by changing the proportion and type of fibers used. Specifically, it adjusts the NSWK content to lower levels while supplementing with hardwood fibers and reducing SSWK content, thereby changing the physical and chemical parameters of the pulp mixture to achieve both cost savings and property maintenance.
Data Source
AI summary
The present invention provides soft, durable and bulky tissue products comprising non-wood fibers and more particularly hesperaloe fiber. The inventors have discovered that high yield hesperaloe pulp fiber, when incorporated in amounts of at least about 5 percent by weight of the tissue product, produces products having a GMT less than about 1000 g/3″ and a GM Slope less than about 7.0 kg. At the foregoing tensile strengths and modulus the tissue products of the present invention are also generally soft, such as having a Stiffness Index less than about 10.0, and more preferably less than about 9.0, such as from about 7.0 to about 9.0.