Composite Strength Agent for Paper Using Refined Cellulose and Cationic Polymer
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Solution Overview
Problem
Existing methods for enhancing the strength properties of paper and board, particularly when using mechanical pulp or recycled fibers with high filler content, are inefficient and costly, necessitating the development of a cost-effective and easily producible strength agent.
Innovation Solution
A strength agent comprising refined cellulosic fibers with a high refining level and a synthetic cationic polymer with specific charge density and molecular weight is added to the fiber stock, enhancing the bonding between fibers and improving the structural integrity of paper and board.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If synthetic cationic polymers are used as strength agents in fiber stock, then strength properties of paper can be improved, but the ability to increase strength is limited when using mechanical pulp, recycled pulp, or high filler content
Solution Approach 1:
The invention uses a composite strength agent comprising both refined cellulosic fibers and synthetic cationic polymer. The refined cellulosic fibers (with refining level >70° SR) provide a fibrous network that bridges and reinforces the paper structure, while the cationic polymer provides chemical bonding. This composite approach overcomes the limitations of using synthetic polymer alone with mechanical pulp and recycled fibers.
Solution Approach 2:
The invention changes the physical state and properties of the cellulosic fibers through intensive refining (>70° SR), transforming them into a fine, highly reactive fibrous material that can effectively interact with mechanical pulp and recycled fibers. This parameter change enables the natural fiber-based strength agent to work effectively with challenging fiber sources.
2Strength
If nanocellulose is used to improve strength properties, then initial wet strength can be improved, but large scale production is intricate and costly
Solution Approach 1:
Instead of using expensive nanocellulose requiring complex production, the invention uses conventional cellulosic fibers that are refined to a high level (>70° SR). These refined fibers provide sufficient strength improvement and can be produced at scale using standard papermaking refining equipment, avoiding the need for intricate chemical and mechanical nanocellulose production processes.
Solution Approach 2:
The invention achieves nanocellulose-like performance by changing the refining parameter of conventional cellulosic fibers to >70° SR. This intensive refining creates a fine fibrous structure that mimics nanocellulose properties while maintaining the ease and low cost of conventional fiber production.
3Strength
If excessive synthetic polymer is used to increase strength, then strength properties improve, but process economy deteriorates
Solution Approach 1:
The invention merges refined cellulosic fibers with synthetic cationic polymer in a single strength agent formulation. The refined fibers provide the primary strength enhancement through physical networking, while the polymer provides additional bonding. This combination allows reduced polymer dosage while maintaining or improving strength, thereby improving process economy.
Solution Approach 2:
The refined cellulosic fibers in the strength agent provide self-reinforcement through their highly developed fiber network, reducing dependence on synthetic polymer for strength enhancement. The fibers themselves contribute significantly to strength improvement, making the system more economical by reducing polymer requirements.
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 use of this strength agent significantly increases the Scott Bond strength of paper and board, optimizing bonding between components while maintaining acceptable refining energy and drainage performance, and reducing the need for excessive synthetic polymer usage, thus improving overall process economy.
Implementation Method 1
a second component, which is a synthetic cationic polymer
Implementation Method 2
highly refined cellulosic fibres are able to effectively increase the relative bonded area between the fibres in paper structure
Data Source
AI summary
The invention relates to a strength agent for paper, board or the like. The strength agent comprises a first component, which is refined cellulosic fibres having a refining level of >70 °SR, and a second component, which is a synthetic cationic polymer having a charge density of 0.1 – 2.5 meq/g, determined at pH 2.7, and an average molecular weight of > 300 000 g/mol. The invention relates also to a use of the strength agent and to a method for increasing strength properties of paper, board or the like.