Cationic Polymer Composition for Paper Drainage
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Solution Overview
Problem
Conventional polymer compositions used in paper and board making, such as polyacrylamides, face challenges in maintaining effective drainage and dewatering efficiency, especially in environments with high conductivity and anionic trash, leading to reduced productivity and paper quality.
Innovation Solution
A polymer composition comprising a first host polymer and a second polymer, both copolymers of (meth)acrylamide with cationic monomers, where the first polymer has higher cationicity than the second, polymerized in the presence of the first host polymer, enhancing floc formation and stability for improved drainage and dewatering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high molecular weight linear cationic or anionic polyacrylamides are used for drainage, then initial flocculation is improved, but press dewatering efficiency decreases due to poor floc structure
Solution Approach 1:
The invention uses a composite polymer system combining high molecular weight polyacrylamide (for flocculation) with a graft copolymer containing cationic groups and hydrophobic segments (for floc structure enhancement). This composite approach allows simultaneous achievement of good flocculation and dense floc structure that improves press dewatering, resolving the contradiction between flocculation performance and dewatering efficiency.
Solution Approach 2:
The graft copolymer introduces localized hydrophobic segments and cationic groups at specific positions along the polymer chain. These local structural features enhance the density and strength of floc formation without compromising the overall flocculation performance provided by the high molecular weight polyacrylamide backbone, thereby improving press dewatering while maintaining drainage efficiency.
2Reliability
If polymer dosage is increased to maintain drainage efficiency in high conductivity water, then drainage performance is maintained, but over-flocculation occurs reducing press dewatering and paper strength
Solution Approach 1:
The invention changes the chemical parameters of the polymer by introducing graft copolymers with specific cationic group densities and hydrophobic segment lengths. This allows the polymer to maintain effective drainage performance in high conductivity water through enhanced interaction mechanisms rather than increased dosage, avoiding over-flocculation and preserving press dewatering efficiency and paper strength.
3Productivity
If low molecular weight polymers with high charge density are used to improve dewatering, then pressing efficiency is improved, but retention capability is insufficient requiring increased dosage
Solution Approach 1:
The invention creates a composite system where the graft copolymer combines features of both low and high molecular weight polymers. The graft structure provides high charge density for effective pressing (like low molecular weight polymers) while the extended backbone structure maintains retention capability (like high molecular weight polymers), eliminating the need to choose between these conflicting properties.
Solution Approach 2:
The graft copolymer structure places cationic groups and hydrophobic segments at localized positions along the polymer chain, creating regions of high charge density that enhance pressing efficiency while the overall polymer architecture maintains sufficient molecular weight for retention, allowing both functions to coexist in a single polymer molecule.
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 polymer composition achieves improved drainage and dewatering efficiency, even in challenging conditions, with reduced polymer dosage and minimal over-cationization, leading to enhanced paper quality and productivity.
Implementation Method 1
a first host polymer and a second polymer, both copolymers of (meth)acrylamide with cationic monomers
Implementation Method 2
enhancing floc formation and stability for improved drainage and dewatering
Data Source
AI summary
The invention relates to a polymer composition comprising a first host polymer, which is a copolymer of (meth)acrylamide and at least one cationic first monomer, and a second polymer, which is a copolymer of (meth)acrylamide and at least one cationic second monomer. The second polymer is polymerised in presence of the first host polymer, and the first host polymer has a higher cationicity than the second polymer, the difference in cationicity of the first host polymer and the second polymer being at least 3 mol-%, preferably at least 5 mol-%, more preferably at least 7 mol-%. The polymer composition has a standard viscosity of > 2.0 m Pas, measured at 0.1 weight-% solids content in an aqueous Na Cl solution (1 M), at 25 ° C, using Brookfield DVII T viscometer with UL adapter. The invention relates also to uses of said polymer composition.