Stable aqueous polymer dispersions
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Solution Overview
Problem
Existing aqueous polymer dispersions destabilize in the presence of high amounts of organic solvents and at low pH due to increased ionic force compressing the ionic repulsive double layer, leading to coagulation, which existing technologies fail to address effectively without using grafted surfactants or cationic groups.
Innovation Solution
An aqueous polymer dispersion is stabilized by incorporating strong acid functionalities through monomers and initiators with anionic groups, achieving stability in high organic solvent and low pH conditions without grafted surfactants or cationic groups, using emulsion polymerization with specific monomer and initiator compositions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high amount of organic solvents are added to aqueous polymer dispersion, then solubility of surfactants increases and they deplete from particle surface, but this destabilizes the dispersion and causes coagulation
Solution Approach 1:
The patent changes the chemical composition parameters of the polymer by incorporating strong acid groups (sulfonic, phosphonic, carboxylic acid functionalities) from specific monomers (b1) and initiators (b2). This chemical modification enables the polymer to maintain stability in high organic solvent environments without relying on traditional surfactant stabilization mechanisms, thus resolving the contradiction between solvent compatibility and dispersion stability.
Solution Approach 2:
The patent creates a composite polymer structure containing multiple functional groups including strong acid groups from monomers (b1) and initiators (b2), along with other polymer backbone components. This composite functional structure provides both solubility compatibility with organic solvents and colloidal stability through the synergistic effect of different functional groups, preventing coagulation while allowing high organic solvent content.
2Quantity of substance
If acid substances are added to decrease pH to low values (under 2.0), then ionic force increases and compresses the ionic repulsive double layer, but this decreases repulsion forces and causes coagulation
Solution Approach 1:
The patent fundamentally changes the pH buffer capacity parameter of the system by incorporating strong acid groups with high dissociation constants. These strong acid groups maintain ionization and electrostatic repulsion even at very low pH values (under 2.0), preventing the compression of the ionic double layer that occurs with weak acid systems. The strong acid functionalities act as internal pH buffers that maintain dispersion stability across a wide pH range.
3Reliability
If strong acid groups are incorporated to improve stability in organic solvents and low pH, then stability is achieved, but this requires specific monomer and initiator compositions
Solution Approach 1:
The patent achieves multi-functionality by selecting monomers (b1) and initiators (b2) that simultaneously provide strong acid groups for pH stability, participate in emulsion polymerization, and contribute to polymer chain formation. These dual-functional components eliminate the need for separate stabilizing agents, simplifying the overall composition while achieving stability in both organic solvents and low pH conditions through the inherent properties of the polymerized strong acid groups.
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 dispersion maintains stability for at least 12 hours in high organic solvent concentrations and at pH <2.0, preventing coagulation, as demonstrated by zeta potential measurements and visual stability tests.
Implementation Method 1
the medium ionic force is increased compressing the ionic repulsive double layer. This leads to a strong decrease of the repulsion forces
Implementation Method 2
anionic polymer dispersion, produced by emulsion polymerization of a specific mixture of monomers
Implementation Method 3
polymer obtained by emulsion polymerisation of a specific monomeric and initiator composition
Data Source
AI summary
The invention relates to aqueous polymer dispersions stable for at least 12 h, when dissolved in high amount of organic solvents and acidified at low pH (pH<2). The polymer comprises units and/or groups issued from: a) at least one (meth)acrylic monomer which is (meth)acrylic ester of a C1-C12 alcohol without any other functional group than (meth)acrylate, b) at least monomer b1) or initiator b2) or both as defined: b1) at least one vinylic, allylic or (meth)acrylic monomer, bearing an anionic group derived from strong acids with pKa<3, b2) at least one initiator, bearing the same anionic group as b1), c) at least one hydroxy-functional vinylic, allylic or (meth)acrylic monomer, and optional monomers, and which polymer bears: the anionic groups as defined in b) in an amount of at least 0.05 meq/g and hydroxy groups as defined in c) in an amount of at least 0.1 meq/g.