Papermaking Retention System for Drainage and Formation
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Solution Overview
Problem
Modern papermaking machines face limitations in machine speed due to water retention in the fibre web, and standard retention and drainage aid systems can negatively impact paper quality, particularly in terms of formation, strength, and optical properties.
Innovation Solution
A papermaking process involving a treatment system with a cationic organic polymer of high charge density, a cationic polymer with moderate charge density, and a microparticulate material, where the latter two are added after the last shear stage and the first before it, to enhance retention and drainage without compromising paper properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single polymeric retention aid is added to increase drainage rate, then drainage performance is improved, but formation quality is damaged
Solution Approach 1:
The patent divides the retention aid system into multiple components: a cationic polymer added before the shear stage and an anionic polymer added after the shear stage. This segmentation allows each polymer to perform its specific function optimally - the cationic polymer provides initial flocculation while the anionic polymer restores formation quality after shearing, thus resolving the contradiction between drainage rate and formation quality.
Solution Approach 2:
The cationic polymer is added to the stock before the shear stage to establish initial flocculation and drainage structure. This preliminary action prepares the stock for efficient water removal, while the subsequent anionic polymer addition after shearing corrects any formation damage, thereby achieving both high drainage rate and good formation quality.
2Productivity
If machine speed is increased to boost output, then productivity is improved, but water retention in fibre web increases
Solution Approach 1:
The patent changes the chemical parameters of the retention system by using a combination of cationic and anionic polymers with specific molecular weights and charge densities. This parameter optimization enables effective water removal at high machine speeds, allowing increased productivity without excessive water retention in the fibre web.
3Productivity
If standard retention and drainage aids are used to improve drainage, then drainage performance is improved, but paper quality is negatively impacted
Solution Approach 1:
The patent employs a composite retention aid system combining cationic and anionic polymers. This composite approach leverages the complementary properties of both polymer types - the cationic polymer's strong flocculation capability and the anionic polymer's formation-restoring ability - achieving superior drainage performance while maintaining high paper quality.
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 process improves retention and drainage performance without negatively affecting the final paper properties, allowing for increased machine speed and better paper quality.
Implementation Method 1
a treatment system which is applied to the thin stock and comprises a cationic organic polymer of charge density of at least 3.0 meq/g and a cationic polymer
Implementation Method 2
employing a treatment system which is applied to the thin stock and comprises a cationic organic polymer... and a microparticulate material
Data Source
AI summary
The present invention concerns a process of making paper, board or paperboard in which a cellulosic thin stock is provided and subjected to one or more shear stages and then drained on a moving screen to form a sheet which is dried, wherein the process employs a treatment system which is applied to the thin stock, said treatment system comprising as components, a) a cationic organic polymer of charge density of at least 3.0 meq/g with a molar mass Mw of up to 3 million Daltons or poly aluminium chloride (PAC), b) a cationic polymer having an average molar mass Mw of at least 500,000 Daltons and a charge density not exceeding 4.0 meq/g; c) a microparticulate material; in which components (b) and (c) are added to the cellulosic thin stock after the last shear stage before the head box and component (a) is added to the cellulosic thin stock before the said last shear stage.