Aqueous Polymer Dispersion Copolymerization with Degraded Starch
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Solution Overview
Problem
Existing aqueous polymer dispersions based on vinyl aromatic compounds and aliphatic dienes have poor binding power and are prone to coagulum formation, making them unsuitable as binders in paper coating slips and lacking in surface strength.
Innovation Solution
Copolymerizing vinyl aromatic compounds, conjugated aliphatic dienes, and ethylenically unsaturated carboxylic acid nitriles in an aqueous medium with degraded starch and radical-forming initiators, where ethylenically unsaturated carboxylic acid nitriles are added after initial polymerization, and using a controlled addition process to minimize coagulum formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If ethylenically unsaturated carboxylic acid nitriles are added at the beginning of polymerization, then the binding power is improved, but coagulum formation increases significantly
Solution Approach 1:
The patent applies preliminary action by first polymerizing vinyl aromatic compounds and conjugated aliphatic dienes to form a stable polymer base before adding ethylenically unsaturated carboxylic acid nitriles. This sequence prevents coagulum formation that would occur if nitriles were added at the beginning, while still achieving high binding power in the final product.
Solution Approach 2:
The patent segments the polymerization process into distinct stages: first polymerizing vinyl aromatic compounds and dienes, then separately adding carboxylic acid nitriles after initial polymerization has occurred. This segmentation allows each monomer type to polymerize under optimal conditions, preventing harmful interactions that cause coagulum.
2Device complexity
If conventional polymerization methods are used, then the process is simple, but the surface strength and wet/dry pick resistance are insufficient
Solution Approach 1:
The patent uses preliminary action by pre-forming polymer particles from vinyl aromatic compounds and dienes before introducing carboxylic acid nitriles. This creates a stable foundation that enhances surface strength and pick resistance while maintaining a relatively simple overall process structure.
Solution Approach 2:
The patent changes the temporal parameter of monomer addition by delaying the introduction of carboxylic acid nitriles until after initial polymerization. This parameter change optimizes both process simplicity and final product performance, achieving high surface strength without excessive complexity.
3Productivity
If all monomers are polymerized simultaneously, then the manufacturing time is reduced, but coagulum formation and instability increase
Solution Approach 1:
The patent applies preliminary action by completing the polymerization of vinyl aromatic compounds and dienes before adding carboxylic acid nitriles. This staged approach maintains dispersion stability and prevents coagulum while still achieving efficient overall polymerization throughput.
Solution Approach 2:
The patent segments the simultaneous polymerization into sequential stages, first polymerizing vinyl aromatic compounds and dienes, then adding and polymerizing carboxylic acid nitriles. This segmentation ensures dispersion stability while maintaining acceptable manufacturing efficiency.
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 polymer dispersions with high binding force, reduced coagulum formation, and excellent surface strength, ensuring good running behavior on high-speed machines and improved wet and dry pick resistance.
Implementation Method 1
radical-forming initiators... at least some of the monomers other than ethylenically unsaturated carboxylic acid nitriles being polymerized before the ethylenically unsaturated carboxylic acid nitriles are added
Implementation Method 2
in the presence of a degraded starch... the dispersions having a high binding force, the lowest possible coagulum formation
Data Source
AI summary
What is described is a method for preparing aqueous polymer dispersions, wherein a vinyl aromatic compound such as styrene, a conjugated aliphatic diene such as butadiene and an ethylenically unsaturated carboxylic acid nitrile such as acetonitrile are copolymerized in an aqueous medium. The copolymerization is done in the presence of a decomposed starch and radical-forming initiators. At least a portion of the various monomers of ethylenically unsaturated carboxylic acid nitriles are polymerized before the ethylenically unsaturated carboxylic acid nitriles are added to the polymerization mixture.