Paper Retention System Using Segmented Cationic Polymers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional paper and paperboard production processes face challenges in achieving optimal retention and drainage, often requiring higher doses of retention and drainage aid chemicals, which can negatively impact paper quality and necessitate reducing machine speeds, especially for higher basis weight sheets.
Innovation Solution
A process employing a retention system comprising a blend of cationic polymers with specific charge densities and molar masses, combined with microparticulate materials like silica-based particles, where the polymers are dosed before the final shearing stage and the microparticulates after, to enhance retention and drainage independently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single polymeric retention aid is added to increase drainage rate, then drainage improves, but formation is damaged
Solution Approach 1:
The patent divides the retention aid system into two separate polymeric materials added in sequence: a first polymeric retention aid (added before shear stage) that provides formation control and a second polymeric retention aid (added after shear stage) that provides drainage enhancement. This segmentation allows each material to perform its specific function without compromising the other, resolving the contradiction between drainage rate and formation quality.
2Productivity
If higher doses of retention and drainage aid chemicals are used, then retention and drainage improve, but paper quality deteriorates
Solution Approach 1:
The patent segments the chemical aid system into two distinct polymeric retention aids with different functions and optimal dosing levels. The first retention aid (e.g., cationic starch or high molecular weight polyacrylamide) is dosed at lower levels for formation control, while the second retention aid (e.g., low molecular weight polyacrylamide or polyethyleneimine) is dosed at higher levels for drainage enhancement. This segmentation allows optimization of each chemical's dosage to achieve maximum productivity while maintaining paper quality.
3Productivity
If machine speed is increased to boost output, then productivity improves, but optimal retention and drainage balance is lost
Solution Approach 1:
The patent applies preliminary action by adding the first polymeric retention aid before the shear stage to establish proper formation and retention characteristics in advance. This preliminary formation control creates a stable base that can withstand high-speed operation, allowing the machine to run at higher speeds while maintaining the optimal retention-drainage balance through the subsequent addition of the second retention aid.
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 allows for increased paper machine speeds, improved retention without excessive drainage, better formation and strength, and increased productivity, particularly suitable for producing folding box board.
Implementation Method 1
flocculating a cellulosic thin stock by the addition of polymeric retention aid
Implementation Method 2
a retention system which is applied to the thin stock, said retention system comprising a blend of different cationic polymers and microparticulate material
Data Source
AI summary
Process for the Manufacture of Paper and Paperboard The present invention relates to a process of making paper or paperboard in which a cellulosic thin stock is provided and subjected to one or more shear stages and then drained and a moving screen to form a sheet which is dried, wherein the process employs a retention system which is applied to the thin stock, said retention system comprising as components i) a blend of different cationic polymers and ii) a microparticulate material, in which the blend of cationic polymers comprises, a) a cationic polymer having a charge density of from 0.5 and below 3 mEq per gram and a molar mass of greater than 700,000 Da, which cationic polymer is selected from polymers containing vinyl amine units and polyethylenimine, b) a cationic polymer having a charge density of below 3 mEq per gram and an intrinsic viscosity of at least 3 dl/g, wherein one of the components of the retention system is dosed into the thin stock after the final shearing stage and the other is dosed into the thin stock before the final shearing stage.