Microfibrillated Cellulose Dewatering Process
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Solution Overview
Problem
The production of paper or board with microfibrillated cellulose (MFC) faces challenges in dewatering properties, leading to increased drainage time and reduced efficiency, especially when high amounts of MFC are used, which also limits its application due to high water content and interaction issues with other additives.
Innovation Solution
A process involving premixing microfibrillated cellulose with a strength additive and then adding microparticles like bentonite or silica to the stock before dewatering, optimizing the sequence and consistency of additions to enhance dewatering properties without the need for cationic retention polymers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If microfibrillated cellulose is added to increase paper strength, then fiber bonding is improved, but dewatering properties worsen and drainage time increases
Solution Approach 1:
A cationic starch-modified microfibrillated cellulose complex is introduced as an intermediary substance that mediates between the conflicting requirements of strength enhancement and dewatering efficiency. The cationic starch modification changes the surface properties of MFC, reducing its excessive water binding capacity while maintaining its fiber bonding enhancement capability, thus enabling both improved strength and acceptable dewatering performance
Solution Approach 2:
The chemical parameters of microfibrillated cellulose are changed through cationic starch modification, altering its charge distribution and water interaction properties. This parameter change reduces the excessive water binding capacity of pure MFC while preserving its ability to improve fiber bonding, thereby resolving the contradiction between strength gain and dewatering loss
2Strength
If high amounts of MFC are used to improve strength, then fiber bonding improves, but water content increases and limits application
Solution Approach 1:
Cationic starch acts as an intermediary that modulates the water binding behavior of MFC. By introducing cationic starch, the excessive water binding capacity of high MFC concentrations is controlled, allowing high MFC amounts to be used for strength enhancement without proportionally increasing water content and limiting application
3Strength
If cationic starch is added to improve strength, then fiber bonding is enhanced, but excessive addition causes saturation and reduces retention of other additives
Solution Approach 1:
The functions of cationic starch and microfibrillated cellulose are merged into a single modified MFC product. The cationic starch is chemically or physically associated with MFC during its production, creating a combined material that provides both the fiber bonding enhancement of MFC and the controlled charge distribution of cationic starch, preventing charge saturation and maintaining retention capacity for other additives
Solution Approach 2:
A composite material consisting of microfibrillated cellulose and cationic starch is created, where the two components work synergistically. The composite structure allows the MFC to provide mechanical reinforcement and fiber bonding while the cationic starch component regulates electrostatic interactions, preventing charge saturation and ensuring reliable retention of additional functional additives
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 approach significantly improves dewatering properties by creating more efficient water flow paths and retention, reducing drainage time and maintaining high strength properties of the paper or board, even at higher MFC dosages.
Implementation Method 1
Molecules of cationic starch that have been added to the stock can adhere to the naturally anionic pulp fibers by electrostatic attraction and thus be retained in the wet fiber mat
Implementation Method 2
It has been surprisingly found that microparticles, such as bentonite and silica, proved to be really effective for improving dewatering properties of microfibrillated cellulose (MFC) containing stocks
Data Source
AI summary
The invention relates to a process for production of paper or board comprising providing a stock comprising cellulose fibers, adding a mixture comprising microfibrillated cellulose and a strength additive to the stock, adding a microparticle to the stock after the addition of said mixture, dewatering the stock on a wire to form a web, and drying the web.