Starch Retention in Recycled Pulp Using Amphoteric Polymer
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Solution Overview
Problem
In pulp, paper, and board making processes, low molecular weight starch from recycled fibers is not effectively retained on fibers, leading to increased microbial growth, wastewater treatment costs, and paper defects, as it is washed away into water circulation and treated as part of the wastewater.
Innovation Solution
A method involving the addition of amylase enzyme inhibitors, such as zinc ions, and an amphoteric polyacrylamide copolymerized with cationic and anionic monomers to the pulp flow, which prevents starch degradation and improves retention by forming agglomerates with surface charges that adhere to fibers, reducing the amount of starch in water circulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If low molecular weight starch is retained on fibers, then microbial growth is reduced and process yield is improved, but starch naturally retains poorly on fibers due to lack of charge
Solution Approach 1:
A cationic polymer is introduced as an intermediary substance that binds to the anionic starch molecules and facilitates their attachment to fibers. The cationic polymer acts as a bridge between the negatively charged starch and the fiber surface, enabling effective retention without modifying the starch itself.
Solution Approach 2:
The charge characteristics of the starch are modified by adjusting pH conditions or adding chemical agents that alter the electrical charge distribution. This parameter change enables the previously uncharged or anionic starch to interact electrostatically with fiber surfaces, improving retention.
2Stability of the object's composition
If biocides are added to prevent starch degradation, then starch preservation is improved, but process chemistry complexity increases
Solution Approach 1:
Instead of using harsh biocides to prevent degradation, the invention utilizes the natural charge properties of starch and employs mild cationic polymers that achieve both preservation and retention. The harmful aspect of complex biocide chemistry is replaced by a beneficial electrostatic interaction system.
3Object-affected harmful factors
If starch is removed to wastewater treatment, then microbial growth risk is reduced, but wastewater treatment costs increase due to higher COD load
Solution Approach 1:
The harmful free starch is extracted from the water circulation by binding it to fibers through the cationic polymer. This removes the starch that would otherwise contribute to microbial growth and COD load, while keeping it in the productive fiber stream rather than sending it to wastewater treatment.
4Reliability
If cationic polymer is added to fix starch to fibers, then starch retention is improved, but charge neutralization may occur reducing effectiveness
Solution Approach 1:
Rather than attempting to completely neutralize all charges, the invention uses a controlled amount of cationic polymer that provides sufficient charge for retention without excessive neutralization. This partial action maintains enough charge availability for the polymer to continue functioning as an effective retention agent.
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 method significantly reduces starch in water circulation, improves paper strength, reduces wastewater treatment costs, and enhances process yield by retaining more starch on fibers, thereby decreasing the need for additional starch and energy consumption.
Implementation Method 1
adding amylase enzyme inhibitor comprising zinc ions and/or at least one biocide to pulp flow or to an aqueous process flow comprising starch for preventing starch degradation
Implementation Method 2
adding an amphoteric polyacrylamide obtained by copolymerisation of (meth)acrylamide with cationic and anionic monomers, which amphoteric polyacrylamide has the mass average molecular weight in the range of 1 500 000 - 12 000 000 g/mol, to pulp flow or to an aqueous process flow comprising starch for binding starch to the fibres
Data Source
AI summary
The invention relates to a method for treating starch in pulp, paper and board making processes, in which processes recycled fibre material is used as raw material wherein the recycled fibre material is pulped in a pulper and obtaining a pulp flow comprising an aqueous phase and at least recycled fibres and starch dispersed in the aqueous phase. The method comprising the following steps: - adding amylase enzyme inhibitor and/or at least one biocide to pulp flow or to an aqueous process flow comprising starch for preventing starch degradation, and - adding an amphoteric polymer obtained by copolymerisation of (meth)acrylamide with cationic and anionic monomers to pulp flow or to an aqueous process flow comprising starch for binding starch to the fibres.