Anionic Polymer Dispersion Stable in High Organic Solvent and Low pH
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Solution Overview
Problem
Existing aqueous polymer dispersions destabilize when exposed to high amounts of organic solvents and acidic conditions (pH < 2.0), leading to coagulation due to increased ionic force compressing the ionic repulsive double layer, which existing technologies fail to stabilize without grafted surfactants or cationic groups.
Innovation Solution
An anionic polymer dispersion is created through emulsion polymerization using monomers with strong acid functionalities and specific initiators, ensuring stability in high organic solvent concentrations and low pH conditions without the need for grafted surfactants or cationic groups, by incorporating a sufficient amount of anionic groups and hydroxy groups within the polymer particles.
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 functional groups (sulfonic, carboxylic, phosphonic acids) with specific pKa values and concentrations. This chemical modification allows the polymer to maintain stability through parameter changes in the environment (organic solvent content, pH) that would normally cause coagulation, as the strong acid groups provide electrostatic repulsion independent of conventional surfactant layers.
Solution Approach 2:
The patent creates a composite polymer structure combining hydrophobic backbone (from acrylic, vinyl, or styrene monomers) with hydrophilic strong acid functional groups. This composite material architecture allows the polymer to interact favorably with both organic solvents and water, preventing phase separation and coagulation even at high organic solvent concentrations up to 80% by weight.
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 utilizes parameter changes in the acid groups themselves - specifically using strong acid functional groups with pKa values below 2.0 (sulfonic acids pKa≈-2, carboxylic acids pKa≈4-5, phosphonic acids pKa≈2). These parameter changes in acid strength ensure that the groups remain ionized and provide electrostatic repulsion even in highly acidic conditions where conventional polymers would coagulate.
Solution Approach 2:
The patent converts the harmful effect of high ionic force at low pH into a beneficial effect. The strong acid functional groups, which would normally be expected to cause coagulation at low pH, instead provide enhanced electrostatic repulsion because their strong acidity ensures complete ionization even in highly acidic environments, transforming the low pH condition from a destabilizing factor into a stabilizing mechanism.
3Reliability
If conventional aqueous polymer dispersions are used with strong acid groups, then they show some stability, but they still coagulate in high organic solvent content and very low pH conditions
Solution Approach 1:
The patent implements specific parameter changes in the strong acid functional groups - using sulfonic acid groups (pKa≈-2), carboxylic acid groups (pKa≈4-5), and phosphonic acid groups (pKa≈2) at controlled concentrations (0.1-10 mmol/g). These parameter changes in acid strength and concentration provide a threshold effect where the electrostatic repulsion becomes strong enough to resist coagulation even in extreme conditions of high organic solvent content (up to 80% by weight) and very low pH (below 2.0).
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 polymer dispersion remains stable for at least 12 hours when diluted with high amounts of organic solvents and at pH < 2.0, preventing coagulation and maintaining particle stability, as demonstrated by examples showing reduced pre-coagulum content and zeta potential measurements.
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
produced by emulsion polymerization of a specific mixture of monomers selected from acrylic (meaning acrylic or methacrylic), allylic and vinylic monomers
Data Source
AI summary
The invention relates to an aqueous polymer dispersion which is stable for at least 12 h, when dissolved in a high amount of organic solvents and eventually acidified at very low pH (pH < 2). The said polymer comprises units and/or groups issued from : a) at least one (meth)acrylic monomer which is a (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 below : b1 ) at least one vinylic, allylic or (meth)acrylic monomer, bearing an anionic grou 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 d) optionally, at least one carboxy-functional ethylenically unsaturated monomer e) optionally, at least one vinylic monomer bearing only one vinyl group, without any other functional group than vinylic group f) optionally, at least one vinylic or (meth)acrylic monomer bearing at least one functional group selected from : nitrile, amide, acetoacetoxy, diacetone, free silane or alkoxy-blocked silane, epoxy, urea or ure'i'do g) optionally, at least one multifunctional vinylic or (meth)acrylic monomer 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.