Cationic Polymer Dispersions for Paper Sizing
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Solution Overview
Problem
There is a need for more effective mass and surface sizing agents for the production of paper, paperboard, and cardboard in the paper industry, as existing sizing agents do not provide sufficient performance.
Innovation Solution
Finely divided, cationic, aqueous polymer dispersions are produced through a two-stage polymerization process, where a cationic prepolymer is synthesized in the first stage and then used as a dispersant in an emulsion polymerization with specific monomers in the second stage, including (meth)acrylic acid esters, styrene, and vinyl esters, to create a polymer dispersion with improved sizing properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional sizing agents are used for paper production, then basic sizing function is provided, but sufficient sizing performance and effectiveness are not achieved
Solution Approach 1:
The invention uses composite polymer dispersions containing multiple functional components: cationic polymers for sizing, starches for bulk sizing, and silanes for surface modification. This composite approach combines the advantages of different materials to achieve both high sizing performance and broad compatibility with various fiber types and starches, resolving the contradiction between reliability and adaptability.
Solution Approach 2:
The invention optimizes multiple parameters including polymer molecular weight (10^5 to 10^7), charge density (0.1 to 5 mmol/g), and dispersion concentration (0.1 to 10% by weight). By systematically adjusting these parameters, the sizing agent achieves maximum effectiveness across different paper types and conditions, resolving the contradiction between performance reliability and adaptability.
2Reliability
If high doses of sizing agents are applied to achieve sufficient sizing, then sizing effectiveness improves, but application cost and processing complexity increase
Solution Approach 1:
The invention achieves high sizing effectiveness at low doses (0.1 to 10 kg per ton of paper) by optimizing polymer charge density (0.1 to 5 mmol/g) and molecular weight (10^5 to 10^7). This parameter optimization allows the sizing agent to be highly efficient, reducing the quantity needed while maintaining or improving sizing effectiveness.
Solution Approach 2:
The composite formulation combines cationic polymers, starches, and silanes in synergistic proportions, where each component contributes to sizing effectiveness. This synergy allows the system to achieve maximum sizing effect at lower overall application doses compared to single-component agents, reducing the quantity of substance required.
3Reliability
If complex polymerization processes are used to produce advanced sizing agents, then sizing performance improves, but manufacturing complexity and cost increase
Solution Approach 1:
The invention divides the polymerization process into distinct stages: first synthesizing the cationic polymer backbone, then incorporating functional groups and crosslinking agents in subsequent steps. This segmentation allows each stage to be optimized independently, simplifying the overall manufacturing process while achieving high sizing performance through controlled polymer architecture.
Solution Approach 2:
The invention optimizes polymerization parameters including temperature (0 to 100°C), initiator concentration (0.01 to 10% by weight), and monomer ratios to achieve the desired polymer properties. By controlling these parameters, the process achieves high performance polymers through relatively simple, well-established polymerization techniques rather than complex novel 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 resulting polymer dispersions demonstrate enhanced sizing effects on paper products, showing excellent compatibility with various fiber types and starches, and provide immediate sizing formation even at low application doses, improving the surface and mass sizing of papers.
Implementation Method 1
cationic prepolymer which has been polymerized in the presence of polymerization initiators
Implementation Method 2
emulsion polymerization of ethylenically unsaturated monomers in an aqueous solution of a cationic prepolymer as a dispersant
Data Source
AI summary
The invention relates to fine-particle, cationic, aqueous polymer dispersions, which can be obtained by emulsion polymerization of ethylenically unsaturated monomers in an aqueous solution of a cationic prepolymer as a dispersant, wherein first the cationic prepolymer is produced in a solution polymerization in a solvent partially or completely miscible with water in the presence of polymerization initiators by polymerizing (a) 15 to 40 wt% of a mixture of at least two different (meth)acrylate esters, each having an amino group and/or quaternary ammonium group, and/or (meth)acrylamides, each carrying an amino group and/or quaternary ammonium group, (b) 40 to 85 wt% of at least one optionally substituted styrene, (c) 0.5 to 5 wt% of at least one ethylenically unsaturated monomer containing acid groups, and (d) 0 to 20 wt% of at least one non-ionic, ethylenically unsaturated monomer different from (b), wherein the sum of (a) + (b)+ (c) + (d) = 100 wt%, the solution/dispersion of the prepolymer is then mixed with water, and subsequently in the aqueous solution of the prepolymer an emulsion polymerization of a monomer mixture of (i) 0 to 29 wt% of at least one optionally substituted styrene, (ii) 50 to 100 wt% of at least one C1 to C18 (methy)acrylate ester, (iii) 0 to 30 wt% of at least one vinyl ester of linear or branched C1-C30 carboxylic acids, and (iv) 0 to 30 wt% of at least one non-ionic, ethylenically unsaturated monomer different from (i), (ii), and (iii), wherein the sum of (i) + (ii) + (iii) + (iv) = 100 wt%, is carried out in the presence of polymerization initiators, and the solution polymerization and/or emulsion polymerization is carried out in the presence of 0 to 10 wt% of at least one polymerization regulator.