High Consistency Refining Cellulose Nanofilaments
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Solution Overview
Problem
Current methods for producing cellulose nanofibrils from wood or agricultural fibers result in low aspect ratio and degree of polymerization, limiting their reinforcing performance in paper and composite materials, and are not scalable for commercial production due to fiber cutting and energy inefficiencies.
Innovation Solution
High consistency refining using disk refiners at low intensity, applying specific energy levels between 2,000 and 20,000 kWh/t, with multiple passes to produce cellulose nanofilaments with aspect ratios up to 5,000 and minimal degradation of cellulose chains, allowing for continuous or batch production on existing industrial equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional low consistency refining or homogenization methods are used to produce cellulose nanofibrils, then the fibers can be processed through small orifices, but the fiber length is severely reduced and aspect ratio is limited to below 100
Solution Approach 1:
The patent changes the consistency parameter from conventional low consistency (5-15%) to high consistency (20-65%), which fundamentally alters the refining mechanism. At high consistency, fibers are refined through direct contact and friction between fibers rather than through small orifices, preserving fiber length while achieving nanofibril dimensions (30-500 nm diameter) and aspect ratios up to 5000
Solution Approach 2:
The patent inverts the conventional refining approach by rejecting the traditional low consistency method with small orifices. Instead, it uses high consistency refining where fibers are processed in a dense mat without requiring passage through small openings, thereby avoiding fiber cutting while still achieving nanofibril production
2Manufacturing precision
If mechanical and chemical treatments are applied to reduce fiber diameter, then nanofibrils can be produced, but the degree of polymerization is significantly reduced due to cellulose chain degradation
Solution Approach 1:
The patent replaces severe chemical treatments (acidic hydrolysis that reduces DP to 100-200) and intensive mechanical homogenization with a refined mechanical refining process at high consistency. This process achieves nanofibril production through controlled friction and shear between fibers, preserving the cellulose chain integrity and maintaining high degree of polymerization
Solution Approach 2:
The patent converts the potential harm of high energy input during refining into a benefit by using high consistency conditions. The dense fiber mat creates controlled friction that fibrillates fibers without causing chain scission, transforming what would normally be damaging mechanical energy into a beneficial fibrillation mechanism that preserves molecular weight
3Manufacturing precision
If high energy input is applied during refining to reduce fiber diameter, then nanofibrils are produced, but fiber length is severely reduced and production is not scalable
Solution Approach 1:
The patent makes existing industrial high consistency refiners multi-functional by optimizing their operation for nanofibril production. These refiners, already designed for mechanical pulp production, are adapted to produce cellulose nanofibrils with high aspect ratio by adjusting operational parameters (consistency 20-65%, specific energy 2000-20000 kWh/t), enabling commercial-scale production without requiring new specialized equipment
Solution Approach 2:
The patent applies excessive specific energy input (2000-20000 kWh/t, much higher than conventional refining) but distributes it across multiple passes through the refiner at high consistency. This partial application of energy across multiple stages achieves complete fibrillation while preserving fiber length, making the process scalable to commercial production
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 method generates cellulose nanofilaments with superior aspect ratio and degree of polymerization, enabling enhanced reinforcement in paper, tissue, and plastic composite products, with reduced energy impact and scalability to commercial scales, surpassing previous methods in production efficiency and product performance.
Implementation Method 1
high consistency refining using disk refiners at low intensity, applying specific energy levels between 2,000 and 20,000 kWh/t
Implementation Method 2
refining cellulose fibers at a very high level of specific energy using disk refiners
Data Source
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Figure 3~4a
Figure 4b~4c
AI summary
A novel method is disclosed to produce on a commercial scale, high aspect ratio cellulose nanofilaments (CNF) from natural lignocellulosic fibers. The method consists of a multi-pass high consistency refining (HCR) of chemical or mechanical fibers using specific combinations of refining intensity and specific energy. The CNF produced by this invention represents a mixture of fine filaments with widths in the submicron and lengths from tens of micrometers to few millimeters. The resultant product is made of a population of free filaments and filaments bound to the fiber core from which they were produced. The proportion of free and bound filaments is governed in large part by total specific energy applied to the pulp in the refiner. These CNF products differ from other cellulose fibrillar materials by their higher aspect ratio and the preserved degree of polymerization (DP) of cellulose. The CNF products made by this invention are excellent additives for the reinforcement of paper, tissue, paperboard and packaging products, plastic composite materials and coating formulations. They display exceptional strengthening power for never-dried paper webs.