Dry Strength Composition for Paper Using Polyionic Complex
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Solution Overview
Problem
Conventional dry strength agents for paper and board, particularly those using synthetic polymers, face limitations in high filler content and high conductivity environments, leading to suboptimal dry strength and dewatering issues, especially with high cationic demand and recycled fibers.
Innovation Solution
A dry strength composition combining a synthetic polymer component and a cationic starch component, which forms a polyionic complex to enhance retention and interaction with fibers and fillers, improving dry strength and dewatering efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If anionic polymer is added together with cationic component to increase dry strength, then dry strength properties are improved, but the dosage of cationic component is limited by fibre surface consumption and anionic trash, leading to insufficient dry strength increase
Solution Approach 1:
The patent introduces a non-ionic polymer as an intermediary substance that modifies the interaction between cationic and anionic components. This non-ionic polymer acts as a mediator that enhances the effectiveness of the cationic component without being consumed by fibre surfaces or anionic trash, thereby allowing sufficient dosage to achieve the desired dry strength improvement.
Solution Approach 2:
The patent changes the chemical parameters of the dry strength composition by incorporating a non-ionic polymer with specific molecular weight and charge density characteristics. This parameter change allows the system to overcome the limitations of conventional cationic-anionic combinations by altering the charge interaction dynamics in the fibre stock.
2Strength
If dosage of anionic component is increased to improve dry strength, then dry strength properties are improved, but excess anionic content in circulating process water causes other process problems
Solution Approach 1:
The non-ionic polymer serves as an intermediary that enables dry strength improvement through a different mechanism that does not rely on increasing anionic content. By modifying the cationic-anionic interaction dynamics, the system achieves enhanced dry strength while maintaining balanced charge content in the process water, avoiding the harmful effects of excess anionic content.
3Strength
If conventional cationic and anionic polymers are used in high conductivity fibre stock, then ionic bonds are formed, but high conductivity disturbs ionic bonds and replaces them with salt formation, reducing polymer performance
Solution Approach 1:
The patent changes the chemical parameters of the dry strength composition by incorporating a non-ionic polymer that is not affected by high conductivity conditions. This parameter change allows the system to maintain reliable polymer performance in high conductivity fibre stock by eliminating the dependency on ionic bond formation, which is disrupted by high conductivity.
4Quantity of substance
If high amounts of fillers are added to fibre stock, then filler content is increased, but dry strength properties deteriorate and cationic demand increases
Solution Approach 1:
The non-ionic polymer acts as an intermediary that facilitates the interaction between fillers and the cationic-anionic polymer system. This intermediary substance helps maintain dry strength properties even when high amounts of fillers are present by modifying the charge distribution and interaction dynamics in the fibre stock, thereby compensating for the strength deterioration caused by high filler content.
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 composition achieves significant improvements in dry strength and dewatering, reducing energy needs in the drying process and allowing for higher filler content and recycled fiber usage, while maintaining cost-effectiveness and ease of handling.
Implementation Method 1
combining a synthetic polymer component and a cationic starch component, which forms a polyionic complex to enhance retention and interaction with fibers and fillers
Data Source
AI summary
The invention relates to an aqueous dry strength composition suitable for use in manufacture of paper, board or the like. The composition comprises a mixture of a synthetic polymer component, which is a copolymer of acrylamide and at least one anionic monomer, the polymer component having an anionicity of 1 – 60 mol-%, and a cationic starch component. The synthetic polymer component and cationic starch component provide the composition with a charge density in the range of 0.05 – 1 meq/g, when measured at p H 2.8, and 0.2 – -3 meq/g, when measured at p H 7.0. The invention relates also to a method for making of paper, board or the like, where the dry strength composition is diluted with water to obtain a solution of dry strength composition having an end p H > 3, and the solution of the dry strength composition is added to the fibre stock before or after the addition of a cationic strength agent.