Inline Calcium Carbonate Precipitation for Paperboard Strength
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Solution Overview
Problem
The existing papermaking processes face challenges in achieving desirable visual appearance and optimized elastic modulus in board top ply while using low-cost fillers, as traditional fillers like precipitated calcium carbonate (PCC) interfere with fiber bonding, reduce tensile strength, and increase weight without enhancing bending stiffness.
Innovation Solution
An inline production method where carbon dioxide and lime milk are fed into the papermaking stock's short circulation, simultaneously with microfibrillated cellulose, allowing calcium carbonate to precipitate onto the cellulose surface, forming complexes that enhance strength and optical properties without the drawbacks of traditional filler use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If traditional fillers like precipitated calcium carbonate (PCC) are added to papermaking pulp, then optical properties like whiteness and opacity are improved, but tensile strength and tensile stiffness are reduced due to interference with inter-fiber bonding
Solution Approach 1:
The patent changes the particle size parameter of calcium carbonate from conventional ranges to ultrafine particles (d90 < 1 μm, d50 < 0.5 μm). This parameter change allows the filler to penetrate fiber networks more effectively and bond with fibers at multiple points, thereby improving tensile strength while maintaining optical properties like whiteness and opacity.
Solution Approach 2:
The patent creates a composite structure where ultrafine calcium carbonate particles are distributed within the fiber matrix. The composite effect of ultrafine PCC combined with fibers produces synergistic properties: the filler provides optical enhancement while its ultrafine size allows it to act as a bonding agent between fibers, simultaneously improving both whiteness and tensile strength.
2Illumination intensity
If fillers are added to papermaking pulp, then optical properties and surface smoothness are improved, but paper tensile stiffness is reduced
Solution Approach 1:
The patent applies parameter change by reducing calcium carbonate particle size to ultrafine dimensions (d90 < 1 μm). This enables the filler to reinforce the fiber network rather than disrupt it, maintaining tensile stiffness while achieving improved brightness and surface smoothness through enhanced light scattering at the ultrafine particle level.
Solution Approach 2:
The patent applies local quality by distributing ultrafine PCC particles specifically within the fiber bonding zones and surface layers. This localized distribution ensures that filler particles enhance surface brightness and smoothness while simultaneously reinforcing inter-fiber bonds, preventing the loss of tensile stiffness that occurs with conventional filler placement.
3Illumination intensity
If fillers are used in board top ply, then whiteness and visual appearance are improved, but bending stiffness is reduced due to reduced elastic modulus
Solution Approach 1:
The patent changes the particle size parameter to ultrafine dimensions (d90 < 1 μm), which allows the filler to act as a reinforcement agent rather than a weakening agent. The ultrafine particles create additional bonding sites within the fiber matrix, maintaining elastic modulus and bending stiffness while providing the desired whiteness and visual appearance enhancement.
Solution Approach 2:
The patent creates a fiber-ultrafine PCC composite where the ultrafine filler particles form a reinforcing network within the fiber matrix. This composite structure maintains the elastic modulus necessary for bending stiffness while the high surface area to volume ratio of ultrafine particles provides superior light scattering for enhanced whiteness and appearance.
4Adaptability or versatility
If conventional PCC is produced separately from the papermaking process, then production flexibility is maintained, but investment costs and retention chemical requirements increase
Solution Approach 1:
The patent merges the PCC production process with the papermaking process by integrating the precipitation reactor directly into the paper machine's short circulation system. This combination eliminates the need for separate PCC production facilities and reduces investment costs while maintaining production flexibility through inline adjustment of filler dosage and particle characteristics.
Solution Approach 2:
The patent applies self-service by using the papermaking process itself to produce the filler. The short circulation water and lime milk from the paper machine are utilized as feedstocks for in-situ PCC precipitation, eliminating the need for external filler production facilities and reducing retention chemical requirements through direct precipitation onto fibers.
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 improves whiteness, reduces cloudiness, increases elastic modulus, and maintains porosity, leading to a cleaner papermaking process with reduced chemical costs and improved board smoothness and printability, while minimizing the need for retention chemicals and maintaining bending stiffness.
Implementation Method 1
allowing calcium carbonate to precipitate onto the cellulose surface, forming complexes
Implementation Method 2
the additives reacts or start nucleation onto the surface of cellulose or precipitate on the surface of the microfibrillated cellulose
Implementation Method 3
carbon dioxide and lime milk are fed into the papermaking stock's short circulation, allowing calcium carbonate to precipitate
Data Source
Figure 1~2
Figure 3a~3b
Figure 4~5
AI summary
An in-line production method for providing a liquid flow of at least one additive in the short circulation and into the liquid flow of a paper making stock of a fiber web machine by feeding, the liquid flow of the at least one additive to the liquid flow of the short circulation, wherein a suitable amount of a microfibrillated cellulose or nanofibrillated polysaccharide is provided substantially simultaneously with the feeding of liquid flow of the at least one additive.