Aqueous Polymer Dispersion Stabilization via Carboxyl Neutralization
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Solution Overview
Problem
Existing methods for producing aqueous polymer dispersions with metal cations often result in destabilization, leading to undesirable gel particle formation and coagulum, which interferes with film formation and results in coatings that are not resistant to staining.
Innovation Solution
A process involving radically initiated emulsion polymerization in an aqueous medium using a copolymer A with specific monomer ratios and neutralization of carboxy groups, which eliminates the need for large amounts of dispersants and reduces coagulum formation, producing finely divided polymer dispersions with high wet transparency and resistance to staining.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polyvalent metal cations are added to acid-containing polymers to improve physical and chemical properties, then film formation and crosslinking are enhanced, but the aqueous polymer systems become destabilized leading to gel particle formation and coagulum
Solution Approach 1:
The patent applies preliminary action by pre-neutralizing at least 50 mol% of the carboxyl groups of copolymer A with a base (such as ammonia or alkali metal hydroxide) before adding the metal compound. This preliminary neutralization creates a stable aqueous environment that prevents destabilization and gel particle formation when metal cations are subsequently introduced, while still allowing crosslinking to occur during film formation
2Ease of manufacture
If large amounts of dispersant are used to prepare aqueous polymer dispersions with metal cations, then the polymerization process can be carried out, but undesirable gel particles and coagulum are formed
Solution Approach 1:
The patent changes the chemical parameter of the polymer by neutralizing carboxyl groups to convert the polymer from anionic to nonionic or cationic character. This parameter change eliminates the need for large amounts of dispersant and prevents gel particle formation, as the neutralized polymer does not interact adversely with metal cations during polymerization
3Strength
If metal cations are added to neutralize acid groups in polymer systems, then ionic bonds and crosslinking are formed, but the aqueous systems become destabilized leading to coagulum that interferes with film formation
Solution Approach 1:
The patent applies preliminary action by pre-neutralizing carboxyl groups with a base before introducing metal compounds. This ensures that crosslinking occurs through controlled ionic bonds during film formation without destabilization, maintaining reliable film formation while achieving the desired crosslinked structure
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 process yields aqueous polymer dispersions with improved stability, reduced coagulum content, and high transparency, enabling the production of coatings that are resistant to staining and suitable for various applications, including adhesives and coatings.
Implementation Method 1
a process for the preparation of an aqueous polymer dispersion by free-radical initiated emulsion polymerization
Implementation Method 2
the copolymer A is reacted, prior to the addition and the radical polymerization of the at least one monomer P, in an aqueous medium with a metal compound M selected from the group comprising oxides, hydroxides, carbonates or bicarbonates of magnesium, calcium or zinc and a base B which differs from the metal compound M, in such a way that ≥ 50 mol% of the carboxyl groups contained in the copolymer A are neutralized by the base B
Data Source
AI summary
The invention relates to a method for producing binders which can be used in the production of soiling-resistant coatings.