Papermaking Method Using G-PAM for Wet Strength and Smoothness
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Solution Overview
Problem
In papermaking, it is challenging to produce paper with high bending resistance and smooth surfaces simultaneously, as well as achieving good formation, low porosity, and recyclability, due to conflicting properties such as wet strength and dewatering issues.
Innovation Solution
A method involving a pulp mixture of hardwood and softwood, with cationic glyoxylated polyacrylamide (G-PAM) and anionic polymer additions, along with hydrophobic sizes and alum, under specific pH and consistency conditions, to produce paper with high wet strength, low porosity, and low surface roughness without excessive density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If calendering operation is used to smoothen surfaces, then surface roughness is reduced, but paper density increases making it floppy
Solution Approach 1:
The patent changes the chemical parameters of the pulp by adding cationic G-PAM and anionic polymer, adjusting pH levels (6.5-8.0 when anionic polymer is added, 4.8-5.5 when cationic G-PAM is added). This chemical modification allows the paper to achieve smooth surfaces and high bending resistance without excessive densification during calendering
Solution Approach 2:
The patent uses a composite approach by combining hardwood pulp and softwood pulp in specific ratios, and further combines cationic G-PAM with anionic polymer. This composite material system creates synergistic effects that simultaneously improve surface smoothness and bending resistance while controlling density
2Strength
If wet strength is increased, then paper durability in wet conditions improves, but recyclability deteriorates due to hampered repulping
Solution Approach 1:
The patent modifies the chemical composition parameters by introducing cationic G-PAM with specific functional groups that provide wet strength through hydrogen bonding and physical crosslinking rather than strong chemical bonds. This parameter change allows wet strength improvement while maintaining repulping capability for recyclability
3Shape
If low porosity is achieved through highly refined pulp, then paper density and smoothness improve, but dewatering becomes difficult
Solution Approach 1:
The patent introduces retention chemicals as intermediary substances that facilitate dewatering of highly refined pulp. These retention aids act as mediators between the refined pulp fibers and water, enabling efficient water removal while maintaining the low porosity structure needed for smooth paper surfaces
Solution Approach 2:
The patent optimizes headbox consistency and retention chemical dosage as controllable parameters to achieve the balance between dewatering efficiency and formation quality, allowing low porosity to be achieved without severe dewatering problems
4Productivity
If headbox consistency is increased to overcome dewatering problems, then dewatering rate improves, but formation deteriorates
Solution Approach 1:
The patent uses retention chemicals as intermediaries that enable effective dewatering at optimized (not excessively high) headbox consistencies. These retention aids prevent fiber flocculation during dewatering, maintaining good formation while achieving adequate dewatering rates
Solution Approach 2:
The patent optimizes the headbox consistency parameter within a specific range and combines it with retention chemical addition, creating a new operational parameter regime that achieves both good dewatering and good formation, avoiding the need for excessively high consistency
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 method successfully produces paper with high wet strength, good formation, low porosity, and low surface roughness while maintaining an acceptable density, making it recyclable and durable in wet conditions.
Implementation Method 1
adding an anionic polymer to the pulp before the cationic G-PAM is added
Implementation Method 2
adding cationic glyoxylated polyacrylamide (G-PAM) to the pulp
Implementation Method 3
adding at least one hydrophobic size to the pulp
Data Source
AI summary
There is provided a method of producing a paper on a paper machine, comprising the steps of: a) providing a pulp, such as a mixture of hardwood pulp and softwood pulp; b) adding cationic glyoxylated polyacrylamide (G-PAM) to the pulp; c) forming a web from the pulp in a forming section comprising a head box; d) pressing the web in a press section; e) drying the web in a drying section; and f) optionally calendering the web in a calender.