Styrenic Latex Preservation by Residual Monomer Reduction
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Solution Overview
Problem
Existing aqueous dispersions of polymer particles used in the coatings industry face challenges in microbial resistance without biocides, as traditional biocides face regulatory scrutiny and alternative non-biocidal methods like high pH formulations or metal ions can be impractical or harmful.
Innovation Solution
A method involving emulsion polymerization of styrene and ethylenically unsaturated monomers, followed by reduction of residual monomers with a t-C4-C10-alkyl hydroperoxide and reductant at specific mole ratios, to create styrenic copolymer particles with reduced residual monomer concentrations, achieving microbial resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional biocides (e.g., isothiazolinones) are used to preserve latex, then microbial growth is inhibited, but health and environmental safety deteriorates due to regulatory scrutiny and potential bans
Solution Approach 1:
The patent removes harmful biocides from the latex formulation entirely, extracting the preservation function from toxic substances and replacing it with a safe chemical modification of the polymer particles themselves through epoxidation
Solution Approach 2:
The patent converts potentially harmful residual monomers and polymer unsaturation into beneficial antimicrobial features by introducing epoxy groups through oxidation, transforming chemical imperfections into protective characteristics that inhibit microbial growth
2Reliability
If high pH formulations (pH 10-12.5) are used to preserve paint, then microbial growth is inhibited, but safety and health concerns worsen due to corrosiveness
Solution Approach 1:
The patent changes the chemical parameter of the polymer particles by introducing epoxy groups through oxidation, creating a new preservation mechanism that operates at neutral pH rather than relying on extreme pH conditions
3Reliability
If silver or zinc ions are added to preserve paint, then microbial growth is inhibited, but paint properties deteriorate and regulatory scrutiny increases
Solution Approach 1:
The patent converts the harmful effect of residual monomers and polymer unsaturation into beneficial antimicrobial properties by epoxidation, transforming chemical defects into protective features without adding external metal ions
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 method produces latexes resistant to microbial attack, eliminating the need for biocides and avoiding safety and regulatory concerns, while maintaining paint properties.
Implementation Method 1
contacting the dispersion of the styrenic copolymer particles with a reductant and a t-C4-C10-alkyl hydroperoxide to reduce the concentration of residual monomers
Implementation Method 2
contacting styrene and an ethylenically unsaturated monomer under emulsion polymerization conditions to form an aqueous dispersion of styrenic copolymer particles
Data Source
AI summary
The present invention relates to a method comprising the steps of: a) contacting styrene and an ethylenically unsaturated monomer under emulsion polymerization conditions to form an aqueous dispersion of styrenic copolymer particles and residual monomers; and b) contacting the dispersion of the styrenic copolymer particles with a reductant and a t-C4-C10-alkyl hydroperoxide to reduce the concentration of residual monomers in the aqueous dispersion to less than 1000 ppm of residual monomers; wherein the mole-to-mole ratio of the t-C4-C10-alkyl hydroperoxide to reductant is in the range of from 3:1 to 50:1. The method of the present invention provides a way of preserving a styrenic latex even in the absence of a biocide.