Coated Paper Production Using Microfibrillated Cellulose and Drying Equipment
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Solution Overview
Problem
Producing paper, paperboard, or film with high microfibrillated cellulose that balances both good barrier and strength properties is challenging due to the gel-forming properties of microfibrillated cellulose, which requires large water additions, and the use of longer cellulose fibers or strength-enhancing chemicals often compromises barrier properties or increases production costs.
Innovation Solution
A method involving a two-suspension process where a first suspension with coarse microfibrillated cellulose is applied to a substrate to form a fibrous web, and a second suspension with fine microfibrillated cellulose is added to the drying equipment surface, allowing the web to be coated and dried simultaneously, reducing water usage and maintaining barrier properties while enhancing strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high amounts of microfibrillated cellulose are added to improve barrier properties, then barrier properties are improved, but large amounts of water need to be added due to gel forming properties
Solution Approach 1:
The patent uses longer cellulose fibers as an intermediary substance to replace water as the primary suspension medium. The microfibrillated cellulose is suspended in a controlled amount of water along with longer cellulose fibers, which prevent excessive gel formation while maintaining suspension stability. This intermediary approach allows high MFC content (70-100% by weight of dry solids) without requiring large water additions.
Solution Approach 2:
The patent changes the consistency parameter of the MFC suspension to optimize performance. By controlling the suspension consistency to 2-10% and using a coating weight of 1-10 gsm, the process achieves high barrier properties without excessive water content. The drying process then transforms the wet coating into a dry film with controlled moisture content.
2Strength
If longer cellulose fibers are added to improve strength properties, then strength is improved, but barrier properties deteriorate
Solution Approach 1:
The patent applies local quality by using different fiber types in different functional roles. Longer cellulose fibers (1-5 mm) are used specifically for providing strength and tear resistance, while microfibrillated cellulose (0.1-10 µm) provides the barrier function. This spatial and functional differentiation allows each component to excel at its primary function without compromising the other.
Solution Approach 2:
The patent creates a composite material system combining microfibrillated cellulose and longer cellulose fibers. The composite structure leverages the unique properties of each component: MFC provides dense barrier properties against oxygen and moisture, while longer fibers provide mechanical strength and tear resistance. The synergistic combination achieves both barrier and strength requirements simultaneously.
3Strength
If strength-enhancing chemicals are added to improve strength properties, then strength is improved, but barrier properties are negatively affected and production cost increases
Solution Approach 1:
The patent replaces expensive strength-enhancing chemicals with natural cellulose fibers as the strengthening mechanism. The longer cellulose fibers provide mechanical strength through their physical structure and networking capabilities, eliminating the need for chemical additives. This approach maintains barrier properties by avoiding chemical contaminants while reducing production costs through the use of natural, abundant cellulose materials.
4Ease of manufacture
If microfibrillated cellulose is sprayed onto substrate to form coating, then coating is applied, but large amounts of water are added and production efficiency is reduced
Solution Approach 1:
The patent applies preliminary action by pre-forming the MFC coating on the substrate surface before final drying. The coating suspension is applied to the substrate, allowing the MFC to adhere and form a preliminary coating layer. This preliminary action enables subsequent drying and finishing steps to proceed more efficiently, as the coating structure is already established.
Solution Approach 2:
The patent implements continuous coating and drying operations to maintain production efficiency. The MFC suspension is continuously applied to the moving substrate, and drying occurs simultaneously during the coating process. This continuous operation eliminates idle time between coating and drying steps, maintaining high productivity while achieving thorough water removal through the controlled drying process.
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 produces a thin, high-density film with improved barrier and strength properties, reduced water usage, and increased production efficiency, while maintaining the optical and heat-sealing properties of the final product.
Implementation Method 1
applying the second suspension to a surface of a drying equipment and conducting said fibrous web through the drying equipment whereby the second suspension is added to the first side of the web forming the coated paper, paperboard or film
Data Source
Figure 1
AI summary
The present invention relates to a method for the production of a coated paper, paperboard or film, wherein the method comprises the steps of; providing a first suspension comprising cellulose fibers, applying the first suspension on a substrate to forma fibrous web, wherein the web has a first and a second side, providing a second suspension comprising micro fibrillated cellulose, applying the second suspension either to the first side of the fibrous web or to a surface of a drying equipment and conducting said fibrous web through the drying equipment whereby the second suspension is added to the first side of the web forming the coated paper, paperboard or film. The invention also relates to a paper, paperboard or film produced according to the method.