Paper Dry Strength via Cationic-Anionic Polymer Ratio
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Solution Overview
Problem
Existing methods for producing paper and cardboard with high dry strength do not adequately improve dry strength properties and often result in slower dewatering processes.
Innovation Solution
A process involving the addition of water-soluble cationic polymers containing vinylamine units and ethyleneimine units to the paper stock, with a weight ratio of 10:1 to 1:10, followed by dewatering and drying, to enhance dry strength and accelerate dewatering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional cationic and anionic polymers are added to paper stock, then dry strength is improved, but dewatering rate decreases
Solution Approach 1:
The patent changes the chemical parameters of the polymer additives by specifying precise charge densities (cationic polymer: 1.0-2.0 meq/g, anionic polymer: 0.5-1.5 meq/g) and molecular weights (cationic: 10,000-1,000,000 daltons, anionic: 50,000-1,000,000 daltons). These parameter optimizations enable the polymers to form effective bridges between fibers while maintaining appropriate water drainage characteristics, thus improving dry strength without excessively slowing dewatering
Solution Approach 2:
The patent employs a composite approach by combining two different types of polymers (cationic and anionic) with complementary properties. The cationic polymer provides initial fiber bonding and charge neutralization, while the anionic polymer enhances strength through electrostatic interactions and bridge formation. This composite system achieves synergistic effects that simultaneously improve dry strength and maintain acceptable dewatering rates
2Strength
If higher concentrations of polymeric additives are used, then dry strength increases, but production time increases
Solution Approach 1:
The patent applies partial action by using moderate concentrations of polymers (0.01-1.0% by weight of cationic polymer and 0.01-0.5% by weight of anionic polymer based on dry fiber weight) rather than excessive amounts. This optimized dosage provides sufficient strength improvement while avoiding the diminishing returns and excessive production time delays that would result from higher concentrations
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 significantly improves the dry strength and drainage rate of paper and cardboard products compared to conventional methods, resulting in enhanced strength properties and faster production.
Implementation Method 1
a polymeric anionic compound which can form a polyelectrolyte complex with polyvinylamine
Data Source
AI summary
Method for producing paper, paperboard and cardboard having a high dry strength by adding at least one water-soluble (a) polymer comprising vinyl amine units and at least one (b) polymer comprising ethylene imine units and at least one water-soluble polymeric anionic compound to form a paper material, dewatering the paper material during the formation of sheets, and drying the paper product, wherein the water-soluble cationic polymers (a) and (b) are metered in an arbitrary sequence or as a mixture to form a paper material, and paper products obtained according to the method.