Anionic Polyacrylamide Surface Treatment for Paper Strength
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Solution Overview
Problem
Current papermaking technologies face challenges in achieving high and controllable molecular weight polymers for wet and dry strength enhancement while maintaining cost-effectiveness and repulpability, particularly in alkaline papermaking conditions and with declining mill water discharge volumes.
Innovation Solution
A surface treatment composition comprising anionic polyacrylamide with an average molecular weight of 100,000-2,000,000 g/mol, combined with free glyoxal, applied during the paper manufacturing process to form glyoxylated polyacrylamide, which increases polymer molecular weight and forms strong covalent bonds with cellulose fibers, enhancing wet and dry strength properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If higher molecular weight polymers are used to increase paper strength properties, then dry strength and wet strength are improved, but the viscosity of the polymer solution increases making size press application difficult
Solution Approach 1:
The patent divides the polymer application into two stages: first applying a low molecular weight polymer solution (easy to apply) to the paper surface, then crosslinking it in-situ to form high molecular weight gel structures (high strength). This segmentation allows achieving both low viscosity for application and high molecular weight for strength.
Solution Approach 2:
The patent performs preliminary action by applying the polymer solution to the paper surface before crosslinking. The low molecular weight polymer is first deposited on the paper, creating a precursor layer that will later be transformed into high strength gel structures through crosslinking with glyoxal.
2Strength
If higher concentration of polymer is used to improve strength performance, then paper strength is increased, but the cost effectiveness decreases due to higher material consumption
Solution Approach 1:
The patent changes the molecular weight parameter of the polymer from high to low, and changes the concentration parameter to optimize cost-effectiveness. By using low molecular weight polymer at optimized concentration and then crosslinking to achieve high strength, the process reduces material consumption costs while maintaining strength performance.
Solution Approach 2:
The patent creates a composite structure by combining low molecular weight polymer with glyoxal crosslinker. This composite approach allows the polymer to achieve high strength properties through crosslinking rather than relying on high initial molecular weight or concentration, reducing material costs.
3Strength
If polyamidoamine epichlorohydrin is used to increase permanent wet strength, then wet strength is improved, but repulpability of the paper deteriorates
Solution Approach 1:
The patent extracts the permanent wet strength function from polyamidoamine epichlorohydrin and transfers it to the crosslinked polyacrylamide-glyoxal system. By removing the harmful polyamidoamine epichlorohydrin and replacing it with an alternative crosslinking mechanism, the patent achieves wet strength while preserving repulpability.
Solution Approach 2:
The patent uses a temporary low molecular weight polymer that can be easily repulped, and then transforms it into a permanent strength structure through controlled crosslinking. The original polymer molecules are replaced by crosslinked gel structures that provide permanent wet strength without compromising repulpability of the paper matrix.
4Object-affected harmful factors
If more chemicals with starch are used to control fluid penetration, then sizing properties are improved, but the complexity of the composition increases
Solution Approach 1:
The patent makes the polymer-glyoxal system multi-functional: it provides permanent wet strength, controls fluid penetration (sizing), and maintains repulpability. This single crosslinked gel structure performs multiple functions that previously required separate chemical additives, simplifying the overall composition.
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
The solution effectively improves dry tensile strength, permanent wet strength, and STFI compression strength, reducing the need for polyamidoamine epichlorohydrin dosage and maintaining repulpability, while also enhancing starch film forming properties and reducing waste at paper mills.
Implementation Method 1
free glyoxal, which is a component comprising at least two aldehyde functional groups, capable of forming covalent bonds to amide group present in the anionic polyacrylamide
Implementation Method 2
forming strong covalent bonds with cellulose fibres
Data Source
AI summary
A surface treatment composition is disclosed including anionic polyacrylamide, which has a weight average molecular weight, MW, in the range of 100 000-2 000 000 g/mol, and free glyoxal. Further disclosed is a use of the surface treatment composition, a method for producing paper, board or the like and a paper product.