Late GPAM Addition at Floc Junctions for Paper Dry Strength
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Solution Overview
Problem
Existing methods for enhancing dry strength in paper products often interfere with other additives, require excessive amounts of chemicals, and do not effectively utilize residence time, leading to suboptimal performance.
Innovation Solution
A method involving the addition of a cationic wet strength agent, flocculant, and glyoxalated polyacrylamide (GPAM) copolymer in the wet-end papermaking process, specifically at the last possible moment before entering the headbox, using acrylamide-acrylic acid copolymer intermediates with controlled molecular weights and residence times to target junction points between flocs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If glyoxalated polyacrylamide copolymer is added earlier in the process, then there is more time for the polymer to interact with fibers, but the polymer distributes uniformly throughout the sheet rather than concentrating at junction points
Solution Approach 1:
The patent applies preliminary action by adding the GPAM copolymer at the very last moment before the slurry enters the headbox (within 18 seconds), after flocculation has already occurred. This timing allows the polymer to find and bind to junction points between flocs without having time to distribute uniformly throughout the entire sheet, thereby achieving precise spatial targeting through controlled timing of addition.
2Strength
If vinylamine-containing polymers are used to enhance dry strength, then dry strength increases, but optical brightening agent performance is negatively affected
Solution Approach 1:
The patent changes the chemical parameter of the polymer by using glyoxalated polyacrylamide copolymer instead of vinylamine-containing polymers. This parameter change maintains the dry strength enhancement function while eliminating the harmful interaction with optical brightening agents, as GPAM does not contain vinylamine groups that quench OBA fluorescence.
3Strength
If more than optimal amounts of additives are used to enhance dry strength, then dry strength improves, but the process becomes difficult and cumbersome
Solution Approach 1:
The patent applies self-service by utilizing the natural flocculation process to create junction points that automatically serve as binding sites for the GPAM copolymer. The polymer adds itself to the most critical locations (junction points between flocs) without requiring complex application systems or excessive amounts of additive, as the floc structure guides the polymer to where it is most needed.
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 significantly increases dry strength in paper substrates by concentrating GPAM at floc junction points, resulting in superior dry strength properties compared to conventional methods.
Implementation Method 1
concentrating GPAM at floc junction points
Implementation Method 2
adding a cationic wet strength agent and flocculant to a tissue or towel paper substrate
Data Source
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AI summary
The invention provides methods and compositions for increasing the dry strength of paper. The invention utilizes a tailored strength agent whose size and shape is tailored to fit into the junction points between flocs of a paper sheet. The strength agents is in contact with the slurry for just enough time to collect at the junction points but not so much that it can migrate away from there.