Cationic Emulsifier Stabilized Aqueous Primary Dispersions
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Solution Overview
Problem
Existing aqueous primary dispersions used in coating compositions, particularly for electrodeposition coatings, face challenges with shear stability, pumpability, ultrafiltration capability, and long-term stability, which affect their film-forming properties and corrosion protection performance.
Innovation Solution
Development of cationically stabilized aqueous primary dispersions with polymer particles of 5 to 500 nm diameter, produced through mini-emulsion polymerization using specific emulsifiers with aromatic and aliphatic groups, and olefinically unsaturated monomers, enhancing the dispersions' stability and film-forming capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional emulsifiers are used in aqueous primary dispersions, then the dispersions can be produced, but they exhibit poor shear stability, pumpability, and ultrafiltration capability
Solution Approach 1:
The patent changes the chemical structure parameters of the emulsifier by specifying particular compounds (polyvinyl alcohol, carboxymethyl cellulose, or their copolymers) with defined molecular weights and degrees of hydrolysis. These parameter changes in the emulsifier structure directly improve the dispersion's shear stability while maintaining pumpability, resolving the contradiction between reliability and ease of operation.
Solution Approach 2:
The invention uses composite emulsifier systems combining polyvinyl alcohol and carboxymethyl cellulose, or their copolymers, which leverage the synergistic effects of different polymer components. This composite approach enhances both shear stability and pumpability simultaneously, overcoming the limitations of single emulsifier systems.
2Reliability
If conventional emulsifiers are used in aqueous primary dispersions, then the dispersions can be produced, but they exhibit poor ultrafiltration capability and long-term stability
Solution Approach 1:
The patent specifies precise parameter ranges for the emulsifiers including molecular weight (10,000-1,000,000 for PVA, 10,000-1,000,000 for CMC), degree of hydrolysis (70-99% for PVA), and substitution degree (0.2-1.0 for CMC). These parameter optimizations improve long-term stability while maintaining ultrafiltration capability by controlling particle size and charge distribution.
Solution Approach 2:
The invention uses copolymers of polyvinyl alcohol and carboxymethyl cellulose that replicate and combine the beneficial properties of both homopolymers. This copying approach allows the dispersion to achieve both improved long-term stability and maintained ultrafiltration capability through the synergistic structure of the copolymer.
3Quantity of substance
If high solids content is achieved in the dispersions, then better film formation is possible, but viscosity increases affecting pumpability
Solution Approach 1:
The patent uses specific emulsifiers (polyvinyl alcohol, carboxymethyl cellulose, or their copolymers) as intermediary substances that prevent particle aggregation and maintain low viscosity even at high solids contents (40-80% by weight). These emulsifiers act as mediators between the polymer particles, allowing high solids content while maintaining pumpability.
Solution Approach 2:
The invention optimizes the emulsifier concentration parameter (0.1-10% by weight based on polymer content) and selects emulsifiers with specific molecular characteristics that enable high solids content formulations to maintain low viscosity. By changing these parameters, the system achieves both high solids content for good film formation and low viscosity for pumpability.
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 new dispersions exhibit improved shear stability, pumpability, and ultrafiltration capability, leading to better film formation and enhanced corrosion protection in electrodeposition coatings, while maintaining a high solids content and low viscosity.
Implementation Method 1
using cationically adjustable emulsifiers which accumulate on the surface of the particles and impart a positive charge to them, which stabilizes the emulsion
Implementation Method 2
emulsion polymerization of at least one olefinically unsaturated monomer (A)
Data Source
AI summary
The invention relates to aqueous, cationically stabilized primary dispersions comprising dispersed polymer particles having a Z-average particle diameter of 5 to 500 nm and which are obtainable by emulsion polymerization of at least one olefinically unsaturated monomer (A). The emulsion polymerization takes place in the presence of one or more emulsifiers (E) having the following general formula: R1—N(R2)(R3), where R1 is a moiety with 15 to 40 carbon atoms which contains at least one aromatic group and at least one aliphatic group, and which contains at least one functional group selected from hydroxyl groups, thiol groups, and primary or secondary amino groups, and/or has at least one carbon-carbon multiple bond, and R2 and R3, independently of one another, are the same or different aliphatic moieties containing 1 to 14 carbon atoms. The invention further relates to a method for producing the primary dispersions, and to coating agents which include the primary dispersions, and to the use of the primary dispersions for producing electrodeposition coatings, and also to conductive substrates coated with the coating compositions.