Starch Retention in Paper via Biocide and Ionic Polymer Fixation
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Solution Overview
Problem
The paper manufacturing process generates significant chemical oxygen demand (COD) in wastewater due to starch degradation, leading to increased costs and environmental concerns, as starch is not effectively retained in the paper sheet and contributes to microbiological activity, pH drop, and electrical conductivity issues.
Innovation Solution
A method involving pulping of cellulosic material with starch, treating it with biocides to prevent microbial degradation, and adding cationic polymers to fixate non-degraded starch to cellulose fibers, reducing COD and improving paper strength and machine efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If starch is added to papermaking furnish to improve paper strength and retention, then paper strength is improved, but chemical oxygen demand (COD) in wastewater increases due to starch degradation
Solution Approach 1:
The patent extracts the harmful aspect (starch degradation products) by using biocides to prevent degradation, thereby separating the beneficial retention function from the harmful COD generation. The starch is retained on fibers through ionic polymer fixation while preventing its breakdown into harmful effluent constituents.
Solution Approach 2:
The patent changes the chemical state of starch by using ionic polymers to fixate starch to cellulose fibers. This parameter change (from free starch to fiber-bound starch) improves retention and reduces COD while maintaining paper strength enhancement.
2Object-generated harmful factors
If biocides are added to prevent starch degradation and reduce COD, then chemical oxygen demand decreases, but microbiological activity is suppressed which may affect paper quality
Solution Approach 1:
The patent applies partial biocide treatment - enough to prevent starch degradation and reduce COD, but not excessive to completely eliminate all microbiological activity. This partial action maintains paper quality while achieving COD reduction goals.
3Loss of substance
If ionic polymers are used to fixate starch to fibers, then starch retention improves and COD reduces, but device complexity increases due to additional chemicals and process steps
Solution Approach 1:
The patent merges multiple functions into the ionic polymer addition step: starch fixation, retention improvement, and COD reduction are achieved simultaneously through a single chemical intervention, reducing overall process complexity despite the advanced chemistry involved.
4Strength
If starch is not retained in paper sheet, then paper strength is reduced, but COD in wastewater increases due to starch degradation
Solution Approach 1:
The ionic polymer acts as an intermediary between starch and cellulose fibers, facilitating starch fixation to the fiber network. This intermediary mechanism ensures starch retention for paper strength while preventing starch degradation that would otherwise increase COD in wastewater.
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 reduces COD in wastewater, enhances paper strength, and decreases the need for fresh starch, leading to cost savings and improved operational efficiency by re-fixating starch to fibers, thus minimizing microbiological activity and pH fluctuations.
Implementation Method 1
treating the cellulosic material containing the starch with one or more biocides, preferably in the thick stock area
Implementation Method 2
adding an ionic polymer and an auxiliary ionic polymer to the cellulosic material; wherein the ionic polymer comprises cationic monomer units
Data Source
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AI summary
The invention relates to a method for increasing the benefit from starch in pulped, preferably repulped cellulosic material at paper or paperboard manufacturing comprising the steps of (a) pulping a cellulosic material containing a starch; (b) treating the cellulosic material containing the starch with one or more biocides, preferably in the thick stock area; and (h) adding an ionic polymer and preferably, an auxiliary ionic polymer to the cellulosic material; wherein the ionic polymer and the optionally added auxiliary ionic polymer preferably have a different average molecular weight and preferably a different ionicity, wherein the tonicity Is the molar content of ionic monomer units relative to the total amount of monomer units.