Cationic Polymer Starch Retention in Recycled Fibre Stock
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Solution Overview
Problem
In paper and board production, recycled fibre materials often contain significant amounts of starch that are not effectively retained during stock preparation, leading to starch being washed away with the aqueous phase, increasing wastewater treatment loads and microbial growth, which negatively affects product quality and process efficiency.
Innovation Solution
A method involving the addition of a cationic polymer, obtained by copolymerizing (meth)acrylamide with at least 25 mol-% cationic monomers, during the thickening step of fibre stock preparation to associate starch with cellulosic fibres, thereby reducing starch content in the aqueous phase and improving retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If starch is added to fibre stock to improve web properties, then strength properties are improved, but starch is lost to wastewater increasing COD load
Solution Approach 1:
A cationic polymer is introduced as an intermediary substance that binds to both starch and fibres. The polymer acts as a mediator that retains starch on fibres through electrostatic interactions, preventing starch from being washed away while maintaining its strength-enhancing function in the final product.
Solution Approach 2:
The invention changes the chemical parameter of the starch-fibre system by adding a cationic polymer that modifies the electrostatic properties. This parameter change enables starch to be retained on fibres through charge interactions, transforming the system from one where starch is lost to water to one where starch is retained on the fibre network.
2Strength
If starch is present in fibre stock, then web strength is improved, but microbial growth is promoted
Solution Approach 1:
The cationic polymer serves as an intermediary that binds starch to fibres, removing the nutrient source from the aqueous phase where microbes thrive. By sequestering starch on fibres, the polymer eliminates the food supply for microorganisms in the water circulation system.
Solution Approach 2:
The invention converts the harmful effect of starch (as a microbial nutrient) into a beneficial retention mechanism. The same starch that feeds microbes is now bound to fibres through the cationic polymer, transforming it from a harmful nutrient source into a retained component that improves web strength without promoting microbial growth.
3Object-affected harmful factors
If biocides are used to control microbial growth, then microbial problems are reduced, but starch retention is not improved
Solution Approach 1:
The cationic polymer acts as a more effective intermediary for starch retention than biocides. While biocides only address microbial growth, the polymer simultaneously achieves starch retention on fibres, solving both the microbial nutrition problem and the starch loss problem in one mechanism.
Solution Approach 2:
The cationic polymer provides multi-functionality by simultaneously addressing starch retention and indirectly controlling microbial growth. Unlike biocides that only kill or inhibit microbes, the polymer performs the dual function of retaining starch on fibres and removing the nutrient source for microbes, making it a more comprehensive solution.
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 approach effectively reduces starch content in the aqueous phase, minimizes microbial load, and potentially decreases the need for biocides, leading to improved process efficiency and reduced carbon emissions by enhancing starch retention on fibres.
Implementation Method 1
a cationic polymer obtained by copolymerisation of (meth)acrylamide and at least 25 mol-% of solely cationic monomer(s)... in order to associate the starch with the cellulosic fibres
Implementation Method 2
a cationic polymer obtained by copolymerisation of (meth)acrylamide and at least 25 mol-% of solely cationic monomer(s)
Data Source
AI summary
The invention relates to a method for reducing starch content of an aqueous phase, which is removed from a fibre stock preparation in a manufacturing process of paper, board, tissue or the like. The fibre stock preparation comprises a thickening step, where a fibre stock comprising cellulosic fibres originating from recycled fibre material and/or broke as well as starch dispersed in an aqueous phase is thickened from a first concentration to a second concentration by removing a part of the aqueous phase from the fibre stock. A cationic polymer obtained by copolymerisation of (meth)acrylamide and at least 25 mol-% of solely cationic monomer(s), having a standard viscosity SV of at least 1.7 mPas, is added to the fibre stock at the latest at the thickening step in order to associate the starch with the cellulosic fibres of the fibre stock.