Microfibrillated Cellulose Spray Nozzle Shear Thinning
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Solution Overview
Problem
Existing methods fail to achieve a stable and homogeneous coating of microfibrillated cellulose with high solids content onto various surfaces without mechanical contact, as they often result in uneven or flaky coatings due to the high viscosity of the cellulose paste.
Innovation Solution
A process utilizing a nozzle with a specific geometry that induces a pressure drop between the upstream and downstream volume segments, allowing for the reproducible and continuous spraying of microfibrillated cellulose onto diverse surfaces, including paper, cardboard, and other materials, without mechanical contact, and subsequent drying to stabilize the coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If microfibrillated cellulose with high solids content is sprayed onto a surface, then a stable and homogeneous film coating is formed, but the high viscosity of the paste makes spraying difficult and results in uneven coatings
Solution Approach 1:
The patent applies parameter changes by utilizing the shear-thinning property of microfibrillated cellulose paste. The high viscosity at rest provides coating stability, while the viscosity decreases under shear stress during spraying, enabling easy atomization and uniform deposition. This parameter change resolves the contradiction between coating homogeneity and sprayability.
Solution Approach 2:
The invention employs dynamic viscosity adjustment through shear stress. The paste exhibits non-Newtonian behavior where viscosity is not constant but changes with shear rate. During spraying, high shear rates reduce viscosity for easy application, while after deposition, low shear rates allow viscosity to increase for stable film formation, thus resolving the contradiction between ease of operation and manufacturing precision.
2Ease of manufacture
If conventional coating methods such as rolling or blade coating are used, then mechanical application is achieved, but mechanical contact is required and even coating of high viscosity substance is difficult
Solution Approach 1:
The patent replaces conventional mechanical coating methods (rolling, blade coating) with a spray deposition system. Instead of using mechanical contact through rollers or blades, the invention uses fluid dynamics and aeratomization to apply the microfibrillated cellulose coating, eliminating the need for mechanical contact while achieving even coating distribution.
Solution Approach 2:
The invention utilizes pneumatic principles by employing compressed gas to atomize and propel the microfibrillated cellulose paste onto the substrate. This hydraulic-pneumatic approach replaces mechanical contact methods, allowing the high viscosity paste to be broken into fine droplets and deposited evenly without requiring mechanical rollers or blades.
3Manufacturing precision
If deposition processes such as vapor deposition are used, then thin films can be formed, but these methods are not suitably adaptable for MFC suspension
Solution Approach 1:
The patent changes the physical state and delivery parameters of microfibrillated cellulose from vapor phase (as in vapor deposition) to liquid spray phase. By maintaining MFC in its native suspension form and delivering it through aerosolization, the invention achieves thin film formation compatible with MFC's colloidal properties, thus resolving the contradiction between thin film capability and adaptability to MFC suspension.
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 process ensures a thin, homogeneous, and stable microfibrillated cellulose film that adheres well to different surfaces, providing a continuous barrier and reducing solvent evaporation time, while allowing for optional mechanical adjustment of film thickness and morphology.
Implementation Method 1
the MFC of the comparatively high solids content is subjected to a pressure drop in a nozzle, which pressure drop exerts shear pressure onto the MFC, thus lowering the viscosity during the spraying and coating process
Implementation Method 2
spraying of microfibrillated cellulose (MFC), which has a comparatively high solids content, onto a surface, thus forming a stable and homogeneous film coating of MFC on said surface
Implementation Method 3
comparatively high solids content is subjected to a pressure drop in a nozzle
Data Source
AI summary
A process for the spraying of microfibrillated cellulose (MFC) is presented, which has a comparatively high solids content, onto a surface, thus forming a stable and homogeneous film coating of MFC on said surface. Therein, the MFC of the comparatively high solids content is subjected to a pressure drop in a nozzle, which pressure drop exerts shear pressure onto the MFC, thus lowering the viscosity during the spraying and coating process.