Aqueous Adhesive Polymer Shear Stability via Ion Exchange
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Solution Overview
Problem
Highly concentrated aqueous adhesive polymer dispersions face issues with shear stability and water-whitening resistance, leading to increased viscosity and instability, which can result in coagulation and unwanted particle growth, affecting the quality of pressure-sensitive adhesives and laminates.
Innovation Solution
Treating the aqueous adhesive polymer compositions with an anion exchange resin, while avoiding cation exchange or mixed bed ion exchange resins, to improve shear stability and water-whitening resistance, thereby maintaining a suitable viscosity and enhancing the adhesive properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the polymer content in aqueous adhesive dispersion is increased to minimize drying time and energy consumption, then productivity and energy efficiency are improved, but viscosity increases exponentially leading to shear instability and coagulation
Solution Approach 1:
The patent removes harmful cations (calcium, magnesium, aluminum ions) from the aqueous adhesive dispersion through ion exchange with cation exchange resin. This extraction of destabilizing ions prevents coagulation and shear instability, enabling the use of high polymer content (≥55 wt.%) without the exponential viscosity increase that would otherwise cause processing problems.
Solution Approach 2:
The patent changes the ionic composition parameters of the dispersion by eliminating multivalent cations and controlling calcium ion content to ≤10 ppm. This parameter change fundamentally alters the stability characteristics of the high-concentration dispersion, allowing it to maintain low viscosity and high shear stability at polymer contents that would normally be unstable.
2Object-affected harmful factors
If conventional ion exchange methods (cation exchange or mixed bed) are used to treat the adhesive composition, then water-whitening resistance is improved, but shear stability deteriorates due to increased viscosity and coagulation
Solution Approach 1:
The patent segments the ion exchange process into two distinct stages: first treating with cation exchange resin to remove harmful cations and improve shear stability, then treating with anion exchange resin to remove anions and improve water-whitening resistance. This segmentation allows each treatment to optimize one property without compromising the other, unlike conventional single-step or mixed bed approaches.
Solution Approach 2:
The patent applies cation exchange treatment as a preliminary action before anion exchange treatment. By first removing cations that cause coagulation and viscosity increase, the dispersion is stabilized against shear instability before the subsequent anion exchange step that improves water-whitening resistance. This preliminary stabilization prevents the harmful effects that would otherwise occur with conventional treatment sequences.
3Use of energy by stationary object
If high polymer content is used to reduce drying time, then energy consumption is reduced, but the adhesive composition becomes unstable under shearing during processing
Solution Approach 1:
The patent extracts harmful multivalent cations (Ca²⁺, Mg²⁺, Al³⁺) from the dispersion using cation exchange resin. These extracted ions are the primary cause of coagulation and shear instability in high-concentration dispersions. By removing them, the patent enables the use of high polymer content (≥55 wt.%) for energy-efficient drying while maintaining processing stability throughout manufacturing operations.
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 achieves improved shear stability and water-whitening resistance, ensuring the quality and performance of pressure-sensitive adhesives and laminates, particularly in high-solids-content applications, with reduced migratable components and enhanced bonding properties.
Implementation Method 1
treating the aqueous adhesive polymer composition with at least one anion exchange resin
Data Source
AI summary
Method of improving shear stability of highly concentrated aqueous adhesive polymer compositions comprising a specific adhesive polymer which has been prepared by emulsion polymerization and which is dispersed in the aqueous adhesive composition. Said method comprises treating the aqueous adhesive polymer composition with at least one anion exchange resin.