Fibrous Web Coating With Pre-Cooling and Staged Drying
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for applying microfibrillated cellulose (MFC) to fibrous webs face inefficiencies due to its highly viscous gel form, requiring high dilution and intensive drying, which can damage the barrier layer and result in craters or holes.
Innovation Solution
A method involving pre-cooling the fibrous web to below 55°C, followed by air and contact drying, with air drying removing at least 50% of the moisture before contact drying, to ensure a smooth and intact barrier coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If microfibrillated cellulose is highly diluted to enable processing, then the coating can be applied, but intensive drying is required which damages the barrier layer
Solution Approach 1:
The drying process is divided into multiple stages with different temperature profiles. The first drying stage uses lower temperatures (up to 100°C) to remove excess water, followed by a second stage at higher temperatures (100-200°C) to complete drying. This segmentation allows water removal while protecting the barrier layer from thermal damage.
Solution Approach 2:
The fibrous web is pre-cooled to below 55°C before applying the coating medium. This preliminary cooling prevents excessive heat transfer during coating application, reducing the risk of barrier layer damage and ensuring proper coating formation before the drying process begins.
2Productivity
If intensive drying is used to remove water from the diluted coating, then the coating dries, but the barrier layer is damaged resulting in craters or holes
Solution Approach 1:
The drying process is divided into multiple stages with different temperature profiles. The first drying stage uses lower temperatures (up to 100°C) to remove excess water, followed by a second stage at higher temperatures (100-200°C) to complete drying. This segmentation allows water removal while protecting the barrier layer from thermal damage.
Solution Approach 2:
The drying process uses periodic action by alternating between different drying conditions - initially gentler drying to set the coating, then more intensive drying to remove remaining moisture. This periodic approach ensures complete water removal while maintaining coating integrity.
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
Ensures reliable application of highly diluted coating media, preventing damage to the barrier layer and achieving a flawless, continuous coating without craters or holes.
Implementation Method 1
Providing a fiber web with a temperature below 55°C before entering the coating unit
Implementation Method 2
drying the fiber web by first drying in the form of air drying
Implementation Method 3
then a second drying in the form of contact drying
Data Source
Figure 1
AI summary
A method for applying at least one application medium to a running fibrous web using an application aggregate, which method comprises the following steps: - providing a fibrous web having a temperature below 55°C before said web enters into the application aggregate; - applying the application medium to at least one side of the fibrous web; - drying the fibrous web by a first drying process in the form of air drying and a subsequent second drying process in the form of contact drying, wherein more than 50%, preferably between 80% and 90%, of the amount of water removed by the drying process is removed by air drying.