Chemically Modified Cellulose Fibers for Barrier Sheets
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Solution Overview
Problem
The production of cellulose-based sheets with barrier properties faces challenges due to the hydrophilicity of cellulose nanofibrils, leading to long dewatering times and high energy demands, making industrial-scale production inefficient.
Innovation Solution
Introducing chargeable groups into cellulose fibers through chemical modifications like oxidation, alkoxylation, phosphorylation, sulfoethylation, or sulfonation, without breaking the fiber structure, to create chemically modified fibers with a specific charge density, which are then processed into sheets without carboxymethyl cellulose, using established paper machine protocols.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cellulose nanofibrils are used to produce barrier sheets, then barrier properties and transparency are improved, but dewatering time increases and energy consumption increases due to hydrophilicity
Solution Approach 1:
The patent applies parameter changes by chemically modifying cellulose fibers through oxidation, alkoxylation, phosphorylation, sulfoethylation, or sulfonation to introduce chargeable groups. This changes the surface charge density parameter of the fibers, enabling electrostatic interaction with filler particles and improving dewatering efficiency while maintaining barrier properties.
Solution Approach 2:
The chemically modified cellulose fibers act as an intermediary between the hydrophilic cellulose nanofibrils and the hydrophobic filler particles. The chargeable groups on the modified fibers mediate the interaction, allowing effective dewatering through electrostatic attraction while preserving the barrier-forming capability of the nanofibrils.
2Reliability
If cellulose nanofibrils are used to produce barrier sheets, then barrier properties and transparency are improved, but energy consumption increases due to evaporation requirements
Solution Approach 1:
The chemical modification of cellulose fibers changes their surface properties, introducing chargeable groups that enable electrostatic interaction with fillers. This parameter change allows for more efficient water removal during processing, reducing the energy required for evaporation and drying steps while maintaining the barrier properties of the final sheet.
3Productivity
If chargeable groups are introduced into cellulose fibers, then dewatering efficiency is improved, but fiber structure may be compromised if fibrillation occurs
Solution Approach 1:
The patent carefully controls the chemical modification parameters to introduce chargeable groups into the cellulose fiber structure without causing excessive fibrillation. By adjusting the degree of substitution and selecting appropriate modification methods, the fiber structure is preserved while achieving sufficient charge density for improved dewatering efficiency.
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
This method enables the efficient production of cellulose-based sheets with improved barrier properties, such as reduced oxygen transmission rates, while maintaining a high dry matter content and density, facilitating industrial-scale production.
Implementation Method 1
The chemically modified fibres have undergone a chemical treatment selected from the group consisting of oxidation, alkoxylation, phosphorylation, sulfonation and sulfoethylation to introduce the chargeable moiety
Implementation Method 2
introducing chargeable groups in cellulose fibres through chemical modifications like oxidation, alkoxylation, phosphorylation, sulfoethylation, or sulfonation
Data Source
AI summary
There is provided a method of producing a sheet having a density of 0.6-1.3 g/cm3 measured according to ISO 534:2011, the sheet comprising chemically modified cellulose fibres, wherein the method comprises: a. providing chemically modified cellulose fibres, wherein charge density measured according to SCAN-CM 65:02 of the chemically modified cellulose fibres is 1200-2400 µeq/g; b. forming a fibre web by dewatering a slurry comprising the chemically modified cellulose fibres on a forming wire; and c. drying the fibre web to obtain the sheet, with the proviso that no carboxymethyl cellulose (CMC) is added to the chemically modified cellulose fibres during or prior to step b.