Ultrafine Cellulose Fiber Sheet Strength and Transparency
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Solution Overview
Problem
Sheets containing ultrafine cellulose fibers with hydrophilic substituents exhibit high hygroscopic properties, leading to swelling and strength loss under high-humidity conditions, while existing solutions focus on improving water vapor barrier properties rather than maintaining strength and transparency.
Innovation Solution
Treating ultrafine cellulose fiber sheets with divalent or higher metal ions and subsequently with a salt of a weak acid to form ion pairs, reducing hydrophilicity and enhancing mechanical properties without compromising transparency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If ultrafine cellulose fiber sheets are treated with divalent or higher metal ions to improve mechanical strength under wet conditions, then strength is improved, but yellowing may occur under high-temperature conditions
Solution Approach 1:
The patent introduces a salt of a weak acid as an intermediary substance that mediates between the metal ion treatment and the cellulose fiber. This intermediary forms ion pairs with the metal ions, preventing direct harmful interactions that cause yellowing while preserving the mechanical strength benefits. The weak acid salt acts as a buffer that controls the chemical environment during metal ion incorporation.
Solution Approach 2:
The patent modifies the chemical parameters of the sheet by controlling the amounts of metal ions and weak acid salt, and by adjusting the pH conditions during treatment. These parameter changes optimize the balance between strength improvement and yellowing suppression, creating controlled ion pairs that enhance mechanics without causing thermal degradation.
2Illumination intensity
If ultrafine cellulose fiber sheets contain hydrophilic substituents to achieve high transparency, then transparency is improved, but hygroscopic properties increase causing swelling and strength loss under high-humidity conditions
Solution Approach 1:
The patent creates a composite structure by incorporating metal ions and weak acid salts into the cellulose fiber matrix. This composite approach combines the transparency benefits of hydrophilic cellulose with the dimensional stability of metal ion cross-links, achieving both optical clarity and mechanical strength in humid conditions through synergistic material combination.
Solution Approach 2:
The patent applies local quality modification by creating localized ion pairs at specific sites within the fiber structure. The metal ions and weak acid salts form discrete cross-linking points that locally reinforce the structure without affecting the overall transparency of the material. This localized treatment allows transparency to be maintained while providing targeted strength enhancement.
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 treated sheets maintain high transparency and mechanical strength under wet conditions while suppressing yellowing, achieving improved durability and optical properties.
Implementation Method 1
treating ultrafine cellulose fiber sheets with divalent or higher metal ions and subsequently with a salt of a weak acid to form ion pairs
Implementation Method 2
The sheet has high transparency; furthermore, the sheet is excellent in mechanical properties in a wet state
Data Source
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AI summary
An object of the present invention is to improve the strength of a sheet containing substituent-introduced ultrafine fiber under high-humidity conditions while maintaining its high transparency. The sheet of the present invention comprises ultrafine fiber having an ionic substituent, and a divalent or higher metal, and has a haze of 10.0% or less.