Styrene Acrylate Polymer Dispersion for Low-Migration Paper Sizing
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Solution Overview
Problem
There is a need for more efficient and safe surface sizing agents for paper and board, particularly for food packaging applications, that minimize the migration of chemical constituents and improve hydrophobicity and barrier properties.
Innovation Solution
A polymer dispersion comprising a styrene acrylate polymer, prepared through a two-stage polymerization process with controlled oligomer content, is used as a surface sizing agent, achieving low oligomer levels and improved hydrophobation performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional surface sizing agents are used, then hydrophobicity and barrier properties are improved, but safety for food packaging is compromised due to chemical migration
Solution Approach 1:
The patent changes the chemical composition parameters by using only food-grade monomers (styrene, acrylates) and controlling oligomer content to below 1.4%, thereby eliminating harmful chemical migration while maintaining sizing performance
Solution Approach 2:
The patent employs a disposable approach by using water-soluble polymer dispersions that can be easily removed or degraded, minimizing long-term chemical presence and migration risks in food packaging applications
2Ease of manufacture
If polymer dispersion with high oligomer content is used, then manufacturing is simpler, but hydrophobation performance is reduced
Solution Approach 1:
The patent optimizes the oligomer content parameter to below 1.4% through controlled polymerization conditions, achieving a balance between manufacturing feasibility and superior hydrophobation performance
Solution Approach 2:
The patent implements feedback control in the polymerization process by monitoring and adjusting reaction conditions to maintain oligomer content within the specified range, ensuring consistent performance
3Strength
If internal sizing is used, then strength properties are improved, but process complexity and cost increase
Solution Approach 1:
The patent segments the sizing function by developing a surface sizing agent that provides both surface protection and strength enhancement, separating the sizing process from internal processing steps
Solution Approach 2:
The patent creates a universal surface sizing agent that simultaneously provides hydrophobicity, barrier properties, and strength enhancement, eliminating the need for separate internal and surface sizing processes
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 provides enhanced surface sizing results, including improved strength and barrier properties, while ensuring safety for food packaging by minimizing oligomer migration.
Implementation Method 1
The polymer dispersion provides enhanced surface sizing results, including improved strength and barrier properties
Implementation Method 2
a styrene acrylate polymer, which is obtainable by free-radical polymerisation of 1-90 weight-% of monomer (a), which comprises at least one optionally substituted styrene, and 10-99 weight-% of monomer (b), which comprises at least one alkyl (meth)acrylate
Data Source
AI summary
The invention relates to an aqueous polymer dispersion and its preparation. The dispersion comprises a styrene acrylate polymer, which is obtainable by free-radical polymerisation of 1-90 weight-% of monomer (a), which comprises at least one optionally substituted styrene; 10-99 weight-% of monomer (b), which comprises at least one alkyl (meth)acrylate, and 0-9 weight-% of monomer (c), which comprises at least one ethylenically unsaturated monomer, which is different from monomer (b). The polymerisation is conducted in a polymerisation medium comprising a cationic prepolymer, which is obtainable by free radical polymerisation of at least 10-55 weight-% of a monomer (i), which comprises at least one ethylenically unsaturated quaternary and/or tertiary amine, 35-90 weight-% of a monomer (ii), which comprises at least one optionally substituted styrene, and 0-55 weight-% of a monomer (iii), which comprises at least one alkyl (meth)acrylate. The oligomer content in the polymer dispersion is ≤1.4 weight-%, calculated from the dry polymer content.