Variable Dosing Aqueous Polymer Dispersion for Coating Water Resistance
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Solution Overview
Problem
Aqueous polymer dispersions used in coatings and binders for mineral and non-mineral surfaces suffer from high water absorption, leading to issues like whitening, embrittlement, and reduced mechanical stability, which affects the strength and appearance of coated materials over time.
Innovation Solution
The development of an aqueous polymer dispersion with a polar monomer having a water solubility of greater than 50 g/liter, polymerized using a radical emulsion polymerization process with a variable dosage gradient, which improves the water sensitivity and whitening resistance of the coatings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If stabilizing monomers (acrylic acid or acrylamide) are used in aqueous polymer dispersions, then film stability is improved, but water absorption increases leading to whitening, embrittlement, and reduced mechanical stability
Solution Approach 1:
The patent changes the dosing parameters of polar monomers from constant to variable speed during polymerization. By controlling the monomer addition rate as a gradient (higher initially, then decreasing), the polymer structure is optimized to achieve both film stability and reduced water absorption. This parameter optimization allows the coating to maintain mechanical properties while resisting water uptake that causes whitening and embrittlement.
2Manufacturing precision
If polar monomers are added in multi-stage process (0.1 to 10% in first stage, remaining in second stage), then polymerization control is improved, but production complexity increases
Solution Approach 1:
The patent transforms the static multi-stage polymerization process into a dynamic continuous process with variable dosing speed. Instead of discrete stages with fixed compositions, the polar monomer is added continuously at a varying rate throughout the polymerization. This dynamic approach maintains precise polymerization control while simplifying the process into a single continuous operation, reducing the complexity of switching between stages.
3Ease of manufacture
If polar monomers are metered at constant speed during polymerization, then process simplicity is maintained, but coating water resistance and optical appearance are compromised
Solution Approach 1:
The patent implements a periodic dosing pattern where the polar monomer addition rate varies systematically during polymerization. The dosing speed follows a gradient pattern (higher initially, then decreasing) rather than remaining constant. This periodic variation in monomer supply optimizes the polymer structure to reduce water absorption and prevent whitening, while the systematic nature of the variation keeps the process relatively simple to implement.
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 solution significantly enhances the water resistance and optical appearance of coatings, preventing whitening and maintaining mechanical stability even after prolonged exposure to moisture, while ensuring excellent efflorescence protection for mineral surfaces.
Implementation Method 1
radical form polymerized form, obtainable by radically initiated aqueous emulsion polymerization
Data Source
AI summary
The invention relates to an aqueous polymer dispersion, the polymer P thereof having a dispersed distribution. Said aqueous polymer is characterised in that the polymer P of the aqueous polymer dispersion contains copolymerised, at least one polar monomer having a solubility in water of more than 50g/litre (measured at 20 °C) in a radically polymerised form, obtained by radically initiated aqueous emulsion polymerisation. The polar monomer, during the polymerisation process, is dosed to the reaction mixture at a variable speed, i.e. non-constant speed, e.g. in terms of a speed gradient. The invention also relates to a method for producing said aqueous polymer dispersions and to the use thereof as binding agents and/or in coatings, and to coatings containing the inventive polymer dispersion.