Paper Dry Strength via Cationic and Amphoteric Polymer Additives
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Solution Overview
Problem
Despite existing processes for producing papers with high dry strength, there is a continuous need for new alternative methods that can further enhance dry strength properties and improve drainage rates in the paper industry.
Innovation Solution
A process involving the addition of at least one trivalent cation, a water-soluble cationic polymer containing vinylamine or ethyleneimine units, and a water-soluble amphoteric polymer to the paper stock, followed by dewatering and drying, which can include varying the order of addition of these components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional polymer combinations are used to increase dry strength, then dry strength is improved, but drainage rate deteriorates
Solution Approach 1:
The patent changes the chemical parameters of the polymer system by selecting specific polymers with defined charge densities and molecular weights. The cationic polymer has a charge density of 2-10 meq/g and the anionic polymer has a charge density of 1-5 meq/g, with their ratios and concentrations optimized to achieve both high dry strength and acceptable drainage rates
Solution Approach 2:
The patent uses a composite polymer system combining cationic and anionic polymers in specific ratios. This composite approach creates synergistic effects where the oppositely charged polymers interact to form a network structure that enhances dry strength while the specific composition maintains drainage properties
2Strength
If polymer concentration is increased to improve dry strength, then dry strength is improved, but cost and process complexity increase
Solution Approach 1:
The patent optimizes polymer concentration parameters to achieve effective dry strength enhancement at minimal doses. The cationic polymer is applied at 0.01-2.0 wt% and anionic polymer at 0.01-1.0 wt% based on dry fiber weight, with specific ratios that maximize effectiveness while minimizing complexity
Solution Approach 2:
The patent applies polymers in a predetermined sequence where the cationic polymer is added first to the fiber suspension, followed by the anionic polymer. This preliminary ordering of operations ensures optimal interaction between polymers and fibers, as well as between the two polymers themselves, simplifying the overall process
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
This process significantly increases the dry strength of paper products and enhances drainage rates compared to traditional methods, as demonstrated by improved burst pressure, strip compression resistance, and wet rice length values.
Implementation Method 1
a water-soluble cationic polymer and a water-soluble anionic polymer are added to a fiber suspension
Implementation Method 2
This process significantly increases the dry strength of paper products and enhances drainage rates compared to traditional methods
Data Source
AI summary
The invention relates to a method for producing paper, paperboard, and cardboard having high dry strength, by adding (a) at least one trivalent cation in form of a salt; (b) at least one water-soluble cationic polymer; and (c) at least one water-soluble amphoteric polymer to the paper pulp, dehydrating the paper pulp while forming sheets, and subsequent drying of the paper product, wherein the water-soluble cationic polymer (b) is selected from the group of polymers containing vinylamine units (i), and from polymers containing ethylenimine units.