Papermaking Filler Preflocculation With Controlled Floc Size
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Solution Overview
Problem
Existing papermaking processes face challenges in maintaining even distribution and stability of filler particles, particularly calcium carbonate and clay, which reduce sheet strength and uniformity when increased filler content is used, and existing preflocculation methods fail to provide stable, shear-resistant flocs with controlled size distribution.
Innovation Solution
A method involving the use of an amphoteric first flocculating agent, followed by a cationic second flocculating agent, and the addition of microparticles before flocculation, to create stable, shear-resistant filler flocs with controlled size distribution, using specific dosages and shearing to achieve optimal particle size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If filler content is increased to improve product quality and reduce costs, then raw material and energy costs are reduced, but sheet strength decreases and distribution uniformity deteriorates
Solution Approach 1:
The filler population is segmented into different size ranges through controlled flocculation. Flocs are formed with a specific size distribution (median diameter 10-100 μm) to optimize both strength retention and cost reduction. This segmentation allows larger filler aggregates that maintain strength while accommodating higher overall filler content.
Solution Approach 2:
The patent changes the physical and chemical parameters of filler particles through flocculation treatment. By controlling floc size distribution, charge density, and morphology, the patent enables higher filler content to be incorporated while maintaining sheet strength. The floc structure parameters are specifically optimized to balance filler loading with mechanical properties.
2Quantity of substance
If filler content is increased, then costs are reduced, but distribution evenness across the sheet structure deteriorates
Solution Approach 1:
The patent controls the size distribution parameter of filler flocs to improve distribution evenness. By optimizing the median diameter and size range of flocs, the patent ensures uniform dispersion throughout the paper sheet structure even at high filler contents. The size distribution parameters are specifically tuned to prevent both aggregation and excessive fines.
3Manufacturing precision
If low molecular weight coagulant is used for preflocculation, then particle size is reduced, but shear stability deteriorates under paper machine conditions
Solution Approach 1:
The patent uses a composite flocculation approach combining multiple coagulants and flocculants with different molecular weights and mechanisms. This composite treatment creates flocs with both controlled size distribution and enhanced shear stability. The combination of different chemical agents produces a synergistic effect that simultaneously achieves precise particle size control and resistance to paper machine shear forces.
4Reliability
If high molecular weight flocculant is used for preflocculation, then flocs are formed, but particle size distribution becomes broad and difficult to control, especially at higher filler solids
Solution Approach 1:
The patent segments the flocculation process into multiple stages with different chemical agents. This multi-stage approach divides the overall flocculation into controlled steps, each contributing to a specific aspect of floc formation. The segmentation enables precise control of particle size distribution while maintaining effective floc formation, even at high filler solids concentrations.
Solution Approach 2:
The patent changes the chemical parameters during the flocculation process by using different coagulants and flocculants in sequence. This parameter variation allows optimization of both floc formation and size distribution control. The chemical composition and concentration parameters are adjusted at different stages to achieve the desired balance between floc strength and size uniformity.
5Reliability
If viscous flocculant solution is mixed into slurry at higher filler solids, then flocculation occurs, but mixing becomes poor and particle size distribution deteriorates
Solution Approach 1:
The patent segments the addition of flocculating agents into multiple separate steps rather than adding all at once. This segmented addition improves mixing efficiency by distributing the viscous flocculant throughout the slurry in portions, ensuring better dispersion and more uniform flocculation. The multi-step addition process maintains flocculation effectiveness while overcoming mixing difficulties at high filler solids.
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 produces filler flocs with improved shear stability and controlled size distribution, enhancing sheet strength and uniformity while maintaining economic feasibility.
Implementation Method 1
adding a first flocculating agent to the dispersion in an amount sufficient to mix uniformly in the dispersion without causing significant flocculation of the filler particles, and the first flocculating agent being amphoteric
Implementation Method 2
adding the second flocculating agent to the dispersion in an amount sufficient to initiate flocculation of the filler particles in the presence of the first flocculating agent wherein the second flocculating agent has opposite charge to the net charge of the first amphoteric flocculating agent
Implementation Method 3
adding a microparticle to the dispersion in an amount insufficient cause significant flocculation of the filler particles before, simultaneous to, and/or after adding the first flocculating agent
Implementation Method 4
shearing the flocculated dispersion to provide a dispersion of filler flocs having the desired particle size
Data Source
AI summary
A method of preparing a stable dispersion of flocculated filler particles for use in papermaking processes comprises use of microparticle prior to, simultaneous to, and/or after addition of a first flocculating agent to an aqueous dispersion of filler particles, followed by addition of a second flocculating agent to the dispersion and further optional shearing of the resultant filler flocs to the desired particle size resulting in shear resistant filler flocs with a defined and controllable size distribution. In addition, a neutralizing coagulant can be added to the dispersion to partially or completely neutralize the charge of the filler before the microparticle and/or the first flocculating agent is added.