Anionic Copolymer Thickener for High-Shear Slurry Viscosity Control
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Solution Overview
Problem
Current thickening agents for aqueous slurries of inorganic particles used in paper coating colors fail to effectively manage viscosity under different shear gradients, leading to issues like overflowing, smears, and poor water retention, which affect the quality and processing of paper coatings.
Innovation Solution
A copolymer obtained by polymerization of at least three monomers: an anionic monomer with olefinic unsaturation, a monomer with hydrophobic groups, and a cross-linking monomer, which balances viscosity under high and low shear gradients and improves water retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the viscosity under low shear gradient is increased to improve application effectiveness, then the apparent viscosity increases, but the viscosity under high shear gradient also increases, making it difficult to remove excess slurry and control coat weight
Solution Approach 1:
The patent introduces a dynamic viscosity response to shear rate changes through the use of associative thickening agents. These agents create a viscosity that automatically adapts to the operating conditions: high viscosity at low shear rates for effective application, and low viscosity at high shear rates for easy excess removal and coat weight control.
Solution Approach 2:
The patent changes the rheological parameters of the slurry by incorporating associative thickening agents that modify the viscosity-shear rate relationship. This creates a non-Newtonian flow behavior where viscosity is not constant but varies with shear rate, allowing optimization of both application and excess removal processes.
2Stability of the object's composition
If the viscosity under high shear gradient is increased to improve coating stability, then the ACAV viscosity increases, but excessive blade pressure is required and overflowing, smears, and beads form
Solution Approach 1:
The associative thickening agents provide dynamic viscosity control that reduces viscosity under the high shear conditions of coating application. This prevents the slurry from becoming too thick during the coating process, eliminating overflowing, smears, and beads while maintaining coating stability through the agents' thickening effect at rest.
Solution Approach 2:
The viscosity of the slurry periodically changes during the coating process: high viscosity during storage and application preparation for stability, then low viscosity during the high-shear coating operation for smooth application, automatically cycling between these states based on shear conditions.
3Stability of the object's composition
If the viscosity of the slurry is increased to prevent particle settling, then the apparent viscosity increases, but water migration through the paper increases, changing the rheology of recycled coating colour
Solution Approach 1:
The associative thickening agents create a dynamic system where viscosity is high at low shear rates to prevent particle settling during storage and handling, but the agents allow controlled water migration at high shear rates during the coating process, maintaining particle suspension while managing water retention in recycled colour.
4Area of moving object
If conventional thickening agents are used to increase slurry viscosity, then the apparent viscosity increases, but the compromise between viscosity under high and low shear gradients deteriorates
Solution Approach 1:
The patent changes the rheological parameters by introducing associative thickening agents that create a non-linear viscosity-shear rate relationship. This optimizes the viscosity balance across different shear gradients, achieving high apparent viscosity for stability while maintaining low viscosity under high shear for easy processing, unlike conventional agents that cannot adapt to varying shear conditions.
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 copolymer enhances the viscosity balance under various shear conditions, reduces water migration, and stabilizes the slurry, preventing defects like smears and improving the optical and mechanical properties of paper coatings.
Implementation Method 1
The copolymer according to the invention makes it possible to improve the compromise between the viscosity under a high shear gradient and the viscosity under a low shear gradient
Implementation Method 2
It is thus necessary to effectively control the water retention of the paper coating colour
Data Source
AI summary
The invention relates to a copolymer obtained by polymerisation reaction of at least three comonomers: a first anionic monomer, a second monomer comprising an olefin unsaturation, and a third monomer comprising a hydrophobic group. The invention likewise relates to the use of said copolymer as a thickening agent, in particular in aqueous suspensions of mineral particles with high solids content. The copolymer according to the invention makes it possible to improve the compromise between viscosity with high shear gradient and viscosity with low shear gradient, while also improving water retention inside the suspension.