Ultrafine Fiber Sheet Structure for Thin, Soft, Strong Surfaces
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Solution Overview
Problem
Existing sheet-like articles fail to achieve a balance between being thin, soft-to-the-touch, and high in strength, with previous methods either compromising on thickness or surface quality due to issues with fiber distribution and elastic polymer localization.
Innovation Solution
A sheet-like article comprising ultrafine fibers with a specific diameter range and an elastic polymer containing polyurethane as the primary component, where the fiber density and elastic polymer density are strategically distributed across the sheet's thickness to create a dense, soft surface while maintaining high strength, achieved through a production method involving nonwoven fabric preparation, impregnation, and controlled napping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If elastic polymer is localized near the surface region to achieve high strength and pilling resistance, then strength and pilling resistance are improved, but fiber density becomes insufficient leading to poor surface quality and rough feel
Solution Approach 1:
The patent applies local quality by creating distinct density zones within the sheet thickness. The surface region (0-50% from surface) has lower fiber density (0.15-0.35 g/cm³) to ensure softness and smooth surface quality, while the inner region (50%-100% from surface) has higher fiber density (0.25-0.45 g/cm³) to provide strength and pilling resistance. This spatial variation in density resolves the contradiction between surface quality and mechanical properties.
2Strength
If high-strength woven fabric is inserted into nonwoven fabric to increase strength, then strength is improved, but product thickness increases making thin products difficult to achieve
Solution Approach 1:
The patent changes the structural parameters of the nonwoven fabric itself rather than adding external reinforcement layers. By controlling fiber density distribution (creating low-density surface zone and high-density inner zone) and using ultrafine fibers (0.5-5 μm diameter), the patent achieves high strength in thin sheets (0.2-1.0 mm thickness) without inserting woven fabric, thus resolving the contradiction between strength and thickness.
3Strength
If fiber density is increased to achieve high strength, then strength is improved, but surface softness and density are compromised
Solution Approach 1:
The patent resolves the contradiction by transitioning from uniform density to three-dimensional density variation. The sheet structure is divided into two dimensional zones along the thickness direction: a surface zone with lower fiber density for softness and an inner zone with higher fiber density for strength. This dimensional approach allows both soft surface and strong structure to coexist.
Data Source
AI summary
The present invention provides: a sheet-shaped object which is thin and, despite this, has a surface that is dense and is soft to the touch and which has practicable strength; and a process for producing the sheet-shaped object. This sheet-shaped object comprises ultrafine fibers having an average single-fiber diameter of 0.1-7 µm and a polymeric elastomer comprising a polyurethane as a major component, wherein when a layer extending from one surface to a depth of 50% of the thickness is referred to as layer (A) and a layer extending from the other surface to a depth of 50% of the thickness is referred to as layer (B), then the ratio of the density of fibers (A') in the layer (A) to the density of fibers (B') in the layer (B) satisfies the following expression (a) and the ratio of the density of the polymeric elastomer comprising a polyurethane as a major component (A") in the layer (A) to the density thereof (B") in the layer (B) satisfies the following expression (b). The sheet-shaped object as a whole has a density of 0.2-0.6 g/cm3. 1>(A')/(B')≥0.5 (a) 1>(A")/(B")≥0.6 (b)