Cationic Copolymer-Starch Coating for Paper Dry Strength
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Solution Overview
Problem
The paper industry faces challenges in enhancing the strength of recycled fibers, as repeated recycling processes reduce pulp and fiber-fiber bonding strength, and existing wet end strength additives reach a performance plateau, while surface applied additives can interfere with paper machine operations and have limitations in viscosity and stability.
Innovation Solution
A stable dry strength composition comprising a cationic copolymer, starch, and optionally a viscosity modifying agent is applied to formed paper, enhancing surface dry strength through hydrogen bonding with paper fibers and starch molecules, allowing for improved starch performance without precipitation or gel formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If wet end strength additives are used to improve paper strength, then paper strength is improved, but performance reaches a plateau and interference with recycled additives occurs
Solution Approach 1:
Instead of adding strength chemicals at the wet end where they interfere with recycled additives and reach performance plateaus, the invention applies strength additives at the dry end of the papermaking process. This reverse approach allows the cationic copolymer-starch composition to be applied to formed paper, avoiding interference with wet end chemistry while achieving superior and sustained strength improvement without reaching a performance plateau.
Solution Approach 2:
The invention uses a cationic copolymer as an intermediary carrier that binds starch to paper fibers through electrostatic attraction and hydrogen bonding. The copolymer acts as a mediator between starch and fiber, enabling effective strength enhancement while avoiding the interference problems associated with direct wet end additive application.
2Strength
If surface applied additives are used to improve paper strength, then paper strength is improved, but viscosity control and stability become problematic
Solution Approach 1:
The invention creates a composite material system consisting of cationic copolymer, starch, and optionally viscosity modifying agents. This composite approach allows the components to work synergistically: the copolymer provides charge density for fiber binding, starch provides bulk strength, and viscosity modifiers maintain solution stability and controllability during application.
Solution Approach 2:
The invention adjusts key parameters including charge density of the copolymer, starch concentration, and viscosity through additives to optimize performance. By controlling these parameters, the composition achieves both high dry strength and solution stability without precipitation or gel formation during storage and application.
3Productivity
If recycled fibers are used to reduce costs and improve sustainability, then cost savings and environmental sustainability are achieved, but fiber-fiber bonding strength decreases
Solution Approach 1:
The cationic copolymer in the composition serves a dual function: it binds starch to fibers and simultaneously enhances fiber-fiber bonding through its charge density and hydrogen bonding capability. This self-service approach allows a single additive system to address multiple strength deficiencies in recycled paper.
Solution Approach 2:
The invention changes the chemical parameters of recycled paper by introducing cationic copolymer-starch compositions that modify the surface chemistry and bonding characteristics of recycled fibers, enabling strength enhancement without requiring additional refining that would further degrade fiber 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
The composition effectively enhances the dry strength of paper, improving bursting and compression resistance without interfering with paper machine operations, and can be applied at the dry end of the papermaking process, offering a solution for recycled fibers and other paper grades.
Implementation Method 1
improve the surface dry strength of the formed paper through hydrogen bonding with paper fiber and starch molecules
Data Source
AI summary
Stable, coating compositions are disclosed. The compositions comprise an aqueous solution of cationic polymer, starch, and a stabilizing agent. Method of using the coating composition to improve the dry strength of paper is also disclosed.