Mineral Filler Agglomerates for Paper Strength
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Solution Overview
Problem
Increasing the filler content in paper production while maintaining strength and optical properties is challenging due to the interference of filler particles with fibre-fibre bonds, which reduces paper strength and causes retention problems in the papermaking process.
Innovation Solution
A method involving the creation of an aqueous mineral filler dispersion with a cationic pre-treatment agent that forms larger flocs by increasing the mean chord length value, allowing for a higher filler content without compromising paper strength or optical properties, by combining the pre-treated filler dispersion with a fibre stock.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If filler content is increased to reduce costs and improve optical properties, then paper strength decreases due to interference with fibre-fibre bonds
Solution Approach 1:
The invention segments filler particles into different size groups (first filler particles with D(50) of 1.5-4.0 μm and second filler particles with D(50) of 0.5-2.4 μm) where smaller particles fill spaces between larger particles, optimizing both retention and strength properties while maintaining high filler content
Solution Approach 2:
The invention changes the particle size distribution parameters of fillers, specifically controlling the D(50) values and size ratio between different filler types, to achieve optimal balance between filler retention and paper strength
2Strength
If large filler particles are used to reduce interference with fibre-fibre bonding, then retention problems occur at the wet-end of the paper machine under high shear forces
Solution Approach 1:
The invention divides filler into two size segments where larger particles (1.5-4.0 μm) provide good retention and smaller particles (0.5-2.4 μm) fill interstices, creating a synergistic effect that improves both retention and strength compared to using only large particles
Solution Approach 2:
The invention creates a composite filler system combining two different mineral filler types with different size characteristics, where the combination provides superior performance compared to individual filler types, achieving both good retention and strength properties
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 method enables a significant increase in filler content by up to 5% while maintaining acceptable paper strength and keeping the light scattering coefficient constant, optimizing floc size distribution to enhance retention and strength properties.
Implementation Method 1
bringing a cationic pre-treatment agent capable of initiating flocculation of the filler particles in the dispersion into a contact with the particles of the first mineral filler, and forming a pre-treated filler dispersion comprising flocs
Data Source
AI summary
The invention relates to a method for producing paper, board or the like. In the method is obtained an aqueous filler dispersion, comprising particles of at least one first filler, the filler dispersion having a floc size distribution with original mean chord length value. The particles of the first mineral filler are brought into a contact with a cationic pre-treatment agent, which is capable of initiating flocculation of the filler particles in the dispersion, whereby a pre-treated filler dispersion comprising flocs, which comprise first mineral particles, is formed. The pre-treated filler dispersion is combined with a stock of fibers. The floc size distribution of the filler dispersion is changed with the pre-treatment agent, which is a natural and/or synthetic polymer, so that the mean chord length value increases at least with 2% from the original mean chord length value. The invention relates also to an agglomerate comprising at least one first mineral filler particle, a plurality of second mineral filler particles attached to at least one first filler particle by a pre-treatment agent, which is a natural and/or synthetic polymer. The average particle size by weight of the first mineral filler particles is 1.5-4.0 μm, the average particle size by weight of the second mineral filler particles is 0.5-2.4 μm, provided that the second mineral filler particles are smaller than the first mineral filler particles, and the mean chord length of the agglomerate is <40 μm.