Cationic Surface Sizing Agent Particle Size Control
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Solution Overview
Problem
Existing cationic sizing agents for paper and paperboard surface sizing suffer from large particle size distributions, leading to weak sizing performance due to high ratios of water-containing quaternary amine acrylate monomers.
Innovation Solution
An aqueous polymer dispersion is developed by free radical emulsion copolymerizing a blend of styrene, alkyl (meth)acrylate, and ethylenically unsaturated quaternary amine monomers in a polymerization solvent containing C1-6-carboxylic acid and anhydride, resulting in a prepolymer composition that is further copolymerized with a water-soluble redox system to produce a dispersion with fine particle sizes suitable for efficient surface sizing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high ratio of water containing quaternary amine acrylate monomers is used, then cationic sizing agent provides sufficient charge for sizing, but particle size distribution becomes large leading to weak sizing performance
Solution Approach 1:
The patent applies segmentation by conducting two-stage polymerization: first forming a prepolymer dispersion with controlled particle size, then adding water-containing quaternary amine acrylate monomers in a second stage. This segmented approach allows the system to achieve sufficient cationic charge without creating large particle size distribution, as the monomers are incorporated into existing particles rather than forming new large aggregates.
Solution Approach 2:
The patent applies preliminary action by pre-forming a dispersion of polymer particles with controlled size distribution before introducing the water-containing quaternary amine acrylate monomers. This preliminary preparation ensures that when the cationic monomers are added, they do not cause excessive particle growth, thereby maintaining narrow particle size distribution while achieving adequate sizing performance.
2Ease of operation
If too high particle size is used in cationic sizing agent, then easier processing is achieved, but sizing performance becomes weak
Solution Approach 1:
The patent applies parameter changes by controlling the particle size parameter through two-stage polymerization. The first stage produces particles of optimal size for sizing performance, while the second stage modifies chemical composition without significantly increasing particle size. This parameter control ensures both good sizing performance and adequate processability.
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 resulting polymer dispersion achieves improved sizing efficiency with smaller particle sizes, enhancing the surface properties of paper and paperboard while maintaining effective sizing performance.
Implementation Method 1
free radical emulsion copolymerizing a first ethylenically unsaturated monomer blend
Implementation Method 2
copolymetized with a water-soluble redox system
Data Source
AI summary
Provided herein is an aqueous polymer dispersion (A) obtainable by free radical emulsion copolymerizing a first ethylenically unsaturated monomer blend having 15 to 100% by weight of at least one C1-C4-alkyl (meth)acrylate, in the presence of a water-soluble redox system having a first free radical initiator for free radical emulsion copolymerization and an aqueous prepolymer composition (B) obtainable by free radical emulsion copolymerizing in a polymerization solvent having C1-6-carboxylic acid and C1-6-carboxylic acid anhydride a second ethylenically unsaturated monomer blend with 5 to 50% by weight of at least one ethylenically unsaturated quaternary amine, and 10 to 95% by weight of at least one optionally substituted styrene, in the presence of a second free radical initiator.