Dual Polymer Filler Preflocculation for Shear-Resistant Flocs
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Solution Overview
Problem
Existing preflocculation technologies face challenges in producing shear-resistant filler flocs with a defined size distribution at high filler solids, as low molecular weight coagulants result in small, unstable flocs, while high molecular weight flocculants produce broad, uncontrollable distributions due to poor mixing of viscous solutions in papermaking processes.
Innovation Solution
A method involving a cationic polymeric flocculant and an anionic polymer with lower molecular weight, along with optional microparticles, is introduced to control the surface charge of filler particles, allowing even distribution of the viscous flocculant and forming stable flocs through controlled shear, maintaining stability under varying shear conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a low molecular weight coagulant alone is used for filler preflocculation, then the floc formation is easy to achieve, but the resulting flocs have small particle size that breaks down under high shear forces of the paper machine
Solution Approach 1:
The flocculation process is divided into two distinct stages: first using a low molecular weight coagulant to initiate floc formation, then adding a high molecular weight flocculant to build shear-resistant floc structures. This segmentation allows each agent to perform its optimal function without compromise.
Solution Approach 2:
The patent combines two different polymeric materials with distinct molecular weight characteristics into a dual-polymer system. The composite approach leverages the rapid action of low molecular weight coagulants and the structural strength of high molecular weight flocculants to create stable, shear-resistant flocs.
2Length of moving object
If a single high molecular weight flocculant is used for filler preflocculation, then the floc size can be increased, but the particle size distribution becomes broad and difficult to control
Solution Approach 1:
The low molecular weight coagulant is added first to preliminarily condition the filler particles and initiate uniform floc nucleation. This preliminary action creates a foundation that enables subsequent high molecular weight flocculant to produce more uniform and controllable floc sizes.
Solution Approach 2:
The patent changes the molecular weight parameter of the polymer system by using a combination of low and high molecular weight polymers rather than a single polymer. This parameter change enables both rapid floc formation and controlled size distribution through the synergistic interaction of the two polymer types.
3Length of moving object
If a high molecular weight flocculant is used at higher filler solids levels, then the floc size can be maintained, but the mixing of viscous flocculant solution into the slurry becomes poor
Solution Approach 1:
The addition process is segmented into two steps: first adding the low molecular weight coagulant which forms less viscous solutions and mixes easily, then adding the high molecular weight flocculant. This segmentation eliminates mixing difficulties while preserving the benefits of high molecular weight flocculation.
Solution Approach 2:
The low molecular weight coagulant acts as an intermediary that facilitates the subsequent addition and mixing of the high molecular weight flocculant. By first conditioning the slurry with the coagulant, the system becomes more receptive to the viscous flocculant solution, improving mixing 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 approach achieves stable, shear-resistant filler flocs with a narrow size distribution, enhancing sheet strength, uniformity, and printability while maintaining economic feasibility, as demonstrated by improved mechanical and optical properties in paper products.
Implementation Method 1
A method involving a cationic polymeric flocculant and an anionic polymer with lower molecular weight, along with optional microparticles, is introduced to control the surface charge of filler particles
Implementation Method 2
The term preflocculation means the modification of filler particles into agglomerates through treatment with coagulants and/or flocculants
Implementation Method 3
The term preflocculation means the modification of filler particles into agglomerates through treatment with coagulants and/or flocculants
Implementation Method 4
The flocculation treatment and shear forces of the process determine the size distribution and stability of the flocs prior to addition to the paper stock
Data Source
Figure 1
AI summary
A method of preparing a stable dispersion of flocculated filler particles for use in papermaking processes comprises sequential addition of high and low molecular weight flocculating agents to an aqueous dispersion of filler particles followed by shearing of the resultant filler flocs to the desired particle size resulting in shear resistant filler flocs with a defined and controllable size distribution.