Multistage Emulsion Polymerization for Binder Latices
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Solution Overview
Problem
Existing methods for producing aqueous core-shell polymer particles for use as binders in water-borne base coats for base coat/clear coat two-layer coatings do not effectively utilize olefinically polyunsaturated monomers across all stages of emulsion polymerization, resulting in inadequate crosslinked structures for optimal performance.
Innovation Solution
A multistage emulsion polymerization process where olefinically polyunsaturated monomers are copolymerized in all stages, and acid groups are neutralized after the first stage, ensuring a crosslinked or gel structure is formed, with specific ratios and conditions for monomer mixtures A and B, and the use of conventional emulsifiers and initiators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If olefinically polyunsaturated monomers are not copolymerized in all stages of emulsion polymerization, then the polymer structure lacks adequate crosslinking, but implementing multistage polymerization with polyunsaturated monomers in all stages increases process complexity
Solution Approach 1:
The polymerization process is divided into multiple stages where different monomer mixtures are used. In the first stage, olefinically unsaturated monomers with acid groups are polymerized. In subsequent stages, olefinically polyunsaturated monomers are copolymerized. This segmentation allows the crosslinked structure to be built up progressively while managing process complexity through systematic stage-by-stage approach.
Solution Approach 2:
Olefinically unsaturated monomers with acid groups are polymerized in the first stage before introducing olefinically polyunsaturated monomers in subsequent stages. This preliminary action establishes the foundation for crosslinking, and the subsequent addition of polyunsaturated monomers enhances the crosslinked structure without requiring all monomers to be present from the beginning, thus managing process complexity.
2Ease of operation
If acid groups are neutralized before 90 wt. % of monomers are polymerized to completion, then neutralization timing is flexible, but incomplete polymerization reduces the effectiveness of crosslinked structure formation
Solution Approach 1:
The process specifies that at least 90 wt. % of monomers must be polymerized to completion before neutralization is begun. This preliminary requirement ensures that the polymerization framework is sufficiently established to support effective crosslinking, while still allowing operational flexibility in the exact timing within that constraint.
Solution Approach 2:
The process establishes a critical parameter threshold of 90 wt. % monomer polymerization completion before neutralization can begin. This parameter change requirement ensures that the polymerization state is sufficiently advanced to support effective crosslinking structure formation, while still allowing operational flexibility in the exact timing within that constraint.
3Stability of the object's composition
If olefinically polyunsaturated monomers are used in all stages of emulsion polymerization, then crosslinked or gel structure is ensured, but the process requires precise control of monomer ratios and polymerization conditions
Solution Approach 1:
The polymerization process is segmented into distinct stages with specific monomer compositions. The first stage uses olefinically unsaturated monomers with acid groups, while subsequent stages incorporate olefinically polyunsaturated monomers. This segmentation ensures crosslinked structure formation while managing process control through systematic stage-by-stage approach with defined composition ranges.
Solution Approach 2:
The process specifies precise parameter ranges for monomer composition (0.5 to 5 wt. % olefinically polyunsaturated monomer) and polymerization conditions. By defining these parameters within specific ranges rather than requiring exact values, the process achieves stable crosslinked structure while reducing the complexity of precise control requirements.
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 produces aqueous binder latices with pronounced pseudoplasticity and thixotropic properties, enabling the formulation of coating compositions with excellent sagging resistance and special effect development, such as metallic effects, while minimizing mottling.
Implementation Method 1
free-radical polymerization of a mixture A of olefinically unsaturated, free-radically polymerizable monomers
Implementation Method 2
neutralization of acid groups of the polymer formed in process step 1)
Implementation Method 3
multistage emulsion polymerization in the aqueous phase
Data Source
AI summary
A process for the production of aqueous binder latices by multistage emulsion polymerization in the aqueous phase, comprising the successive steps:1) free-radical polymerization of a mixture A of olefinically unsaturated, free-radically polymerizable monomers, comprising at least one monomer with at least one acid group in a proportion corresponding to an acid value of mixture A of 10 to 100 mg of KOH/g and 0.5 to 5 wt. % of at least one olefinically polyunsaturated monomer, in the aqueous phase,2) neutralization of acid groups of the polymer formed in process step 1) and3) free-radical polymerization of at least one mixture B of olefinically unsaturated, free-radically polymerizable monomers, comprising at least one monomer with at least one acid group in a proportion corresponding to an acid value of mixture B or each of the mixtures B of 0 to below 5 mg of KOH/g, at least one monomer with at least one hydroxyl group in a proportion corresponding to a hydroxyl value of mixture B or each of the mixtures B of 0 to below 5 mg of KOH/g and at least one olefinically polyunsaturated monomer in a proportion of 0.5 to 5 wt. %, relative to mixture B or each of the mixtures B, in the presence of the product obtained in process step 2),wherein the ratio by weight of mixture A to the at least one mixture B is from 15:85 to 85:15 and wherein neutralization is not begun in process step 2) until at least 90 wt. % of the monomers of mixture A have been polymerized to completion.