Dissolvable Sheet Pore Structure via Inverted Drying
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Solution Overview
Problem
Existing processes for making flexible, porous dissolvable sheets suffer from slow dissolution rates due to denser bottom regions and rate-limiting factors, which also increase operating costs and hinder scalability for commercial production.
Innovation Solution
A process involving a wet pre-mixture of a water-soluble polymer and surfactant with controlled viscosity and density, aerated to form a sheet, then dried with a temperature gradient that opposes gravity, creating a more uniform and porous structure with larger pore openings on the top surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If traditional batch drying processes are used to form porous sheets with open-celled foam structures, then the dissolution rate is improved compared to non-porous sheets, but the bottom region becomes denser with thicker cell walls which negatively impacts water flow and overall dissolution rate
Solution Approach 1:
The patent inverts the conventional drying approach by controlling the process to prevent densification at the bottom region. Instead of accepting the natural gradient that forms in batch drying, the continuous drying process with impingement airflow reverses the adverse effect by maintaining uniform pore structure throughout the sheet thickness, ensuring the bottom region does not become denser than the top region.
Solution Approach 2:
The patent changes the drying parameters from batch processing with conventional airflow to continuous processing with impingement airflow. This parameter change transforms the pore structure development during drying, preventing the formation of thick cell walls at the bottom region while maintaining high open cell content throughout the sheet.
2Manufacturing precision
If continuous drying with impingement oven is used to improve pore structure uniformity, then the consistency across regions is improved, but the top surface develops a crust-like region with smaller pore openings which slows down water flow and dissolution
Solution Approach 1:
The patent applies local quality control by optimizing the impingement airflow parameters to affect different regions of the sheet differently during drying. The airflow is directed to prevent crust formation at the top surface while maintaining uniform pore structure in the bulk, creating localized conditions that prevent surface densification without compromising overall uniformity.
Solution Approach 2:
The patent uses partial action by applying impingement airflow to specific zones during the drying process. Rather than uniform heating and drying throughout, the impingement airflow is targeted to prevent crust formation at the surface while allowing the interior to develop the desired open cell structure, thus preventing the harmful surface effect without over-drying the entire sheet.
3Ease of manufacture
If batch processing methods are used to form porous sheets, then the process is simpler to implement, but the manufacturing speed is slow and it is hard to scale up for commercial production
Solution Approach 1:
The patent transitions from batch processing to continuous processing, where the useful action of drying occurs continuously rather than in discrete batches. The impingement oven operates continuously with sheets passing through the drying zone, eliminating idle time between batches and enabling steady-state production that is both efficient and scalable while maintaining process control.
Solution Approach 2:
The patent introduces dynamic elements to the manufacturing process by using a continuous moving belt or conveyor system that transports sheets through the impingement drying zone. This dynamic approach allows for adjustable line speeds to match production requirements, enables easy scaling by adjusting throughput, and maintains consistent drying conditions through continuous airflow and material movement.
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 enhances the dissolution rate and structural integrity of the sheets, making them more cost-effective and scalable for commercial production while maintaining aesthetic appeal.
Implementation Method 1
drying said formed sheet for a drying time of from about 1 minute to about 60 minutes, preferably from about 2 minutes to about 30 minutes, more preferably from about 2 minutes to about 15 minutes, still more preferably from about 2 minutes to about 10 minutes, most preferably from about 2 minutes to about 5 minutes, at a drying temperature of from about 70° C. to about 200° C., preferably from about 80° C. to about 170° C., preferably from about 90° C. to about 150° C., more preferably from about 100° C. to about 140° C.
Implementation Method 2
drying said formed sheet for a drying time of from about 1 minute to about 60 minutes, preferably from about 2 minutes to about 30 minutes, more preferably from about 2 minutes to about 15 minutes, still more preferably from about 2 minutes to about 10 minutes, most preferably from about 2 minutes to about 5 minutes, at a drying temperature of from about 70° C. to about 200° C., preferably from about 80° C. to about 170° C., preferably from about 90° C. to about 150° C., more preferably from about 100° C. to about 140° C., along a heating direction that forms a temperature gradient decreasing from the first side to the second side of said formed sheet
Implementation Method 3
aerating said wet pre-mixture to form an aerated wet pre-mixture having a density of from about 0.05 to about 0.5 g/ml, preferably from about 0.08 to about 0.4 g/ml, more preferably from about 0.1 to about 0.35 g/ml, still more preferably from about 0.15 to about 0.3 g/ml, most preferably from about 0.2 to about 0.25 ml
Data Source
AI summary
This provides an improved process for making a flexible, porous, dissolvable solid sheet article with improved pore structures.