Low Molecular Weight Cationic Retention Agents for Paper Drainage
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Solution Overview
Problem
The paper industry faces challenges with high molecular weight cationic flocculants used in retention and drainage systems, which require costly preparation units, lead to filtration issues, and negatively impact paper quality due to high shear and machine speeds, resulting in increased costs and machine stoppages.
Innovation Solution
A process using a cationic polymer obtained by Hofmann degradation reaction as the main retention agent, combined with a high molecular weight anionic polymer as a secondary retention agent, introduced into the fibrous suspension at specific dosages to improve retention and drainage without the need for complex preparation steps, allowing for instantaneous incorporation into the papermaking process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high molecular weight cationic flocculants are used as retention agents, then retention and drainage properties are improved, but preparation unit costs increase and filtration issues occur
Solution Approach 1:
The patent changes the molecular weight parameter of the cationic flocculant from high (>1 million g/mol) to low (<1 million g/mol, preferably 10,000-500,000 g/mol). This parameter change eliminates the need for complex preparation units while maintaining retention and drainage properties through optimized dosage ranges (100-800 g/t for main agent, 50-800 g/t for secondary agent).
Solution Approach 2:
The patent extracts the problematic high molecular weight characteristic from the retention system and replaces it with low molecular weight polymers. This extraction removes the requirement for costly preparation units and filtration systems while preserving the essential flocculation function through the combination of main and secondary retention agents.
2Reliability
If high molecular weight cationic flocculants are used, then retention performance is improved, but filtration and machine clogging issues worsen
Solution Approach 1:
By changing the molecular weight parameter to lower values (<1 million g/mol), the patent reduces the size and complexity of polymer chains, which prevents filtration clogging and machine blockages while maintaining effective flocculation through optimized chemical composition and dosage.
Solution Approach 2:
The patent uses low molecular weight polymers that are easier to handle and less prone to causing equipment issues. These shorter polymer chains act as effective retention agents without creating the long-term filtration problems associated with high molecular weight materials, effectively replacing problematic materials with simpler alternatives.
3Reliability
If high molecular weight cationic polymers are used, then drainage properties are improved, but paper quality deteriorates due to high shear and machine speeds
Solution Approach 1:
The patent changes the molecular weight parameter to lower values, which makes the polymer chains more resistant to degradation under high shear and machine speeds. This parameter change preserves paper quality by preventing polymer breakdown while maintaining drainage performance through the synergistic combination of main and secondary retention agents.
Solution Approach 2:
The use of low molecular weight polymers with shorter chain lengths makes them more robust against mechanical degradation during high-speed papermaking. These shorter chains maintain their functional integrity under high shear conditions, ensuring consistent drainage performance and paper quality without the deterioration issues caused by high molecular weight polymers.
4Reliability
If high molecular weight cationic flocculants are used, then retention properties are improved, but operational costs increase due to machine stoppages
Solution Approach 1:
By changing the molecular weight to lower values, the patent eliminates the need for complex preparation units and reduces filtration maintenance requirements. This parameter change increases productivity by reducing machine stoppages and operational interruptions while maintaining effective retention through optimized polymer dosing.
Solution Approach 2:
The patent extracts the problematic high molecular weight characteristic that causes machine stoppages and removes the associated costly preparation and filtration infrastructure. This extraction improves operational continuity and reduces downtime-related costs while preserving retention effectiveness through the low molecular weight polymer system.
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 enhances retention and drainage performance significantly, reducing the risk of machine clogging and improving paper quality, while lowering operational costs and maintaining high productivity, even with recycled fibers and increased paper machine speeds.
Implementation Method 1
a main retention agent corresponding to a (co)polymer with a cationic charge density greater than 2 meq/g, obtained by so-called Hofmann degradation reaction
Implementation Method 2
The mode of action of retention agents is based on the flocculation of these materials suspended in water
Implementation Method 3
The mode of action of retention agents is based on the flocculation of these materials suspended in water. In fact, the flocs formed are more easily retained on the forming fabric.
Implementation Method 4
Regarding the drainage (or drainage) properties, this is the ability of the fibrous mat to evacuate or drain the maximum amount of water so that the sheet dries as quickly as possible
Data Source
AI summary
Process for manufacturing a sheet of paper and/or board having improved retention and drainage properties, according to which, before formation of said sheet and/or board, added to the fibrous suspension are at least two retention aids respectively: a main retention aid corresponding to a (co)polymer having a cationic charge density of greater than 2 meq/g, obtained by Hofmann degradation reaction, a secondary retention aid corresponding to a water-soluble or water-swellable polymer having an anionic charge density of greater than 0.1 meq/g, characterized in that: the main retention aid is introduced into the fibrous suspension in a proportion of 100 to 800 g/t of dry pulp, the secondary retention aid is introduced into the fibrous suspension in a proportion of 50 to 800 g/t of dry pulp and has an intrinsic viscosity IV of greater than 3 dl/g.