Continuous Waterborne Heat Seal Coating Process
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Solution Overview
Problem
Current batch dispersion processes for waterborne heat seal coatings are costly due to long cycle times and batch-to-batch variations, and the EVA resin is prone to hydrolysis in strong base environments, leading to quality issues and performance variability.
Innovation Solution
A continuous process involving melt blending of ethylene vinyl acetate copolymer with a tackifier and surfactant, followed by contact with an aqueous stream containing a neutralizing agent and subsequent dilution to form a waterborne heat seal coating composition, reducing residence time and mitigating hydrolysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If batch dispersion process is used, then EVA resin can be processed, but production cost increases and batch-to-batch variations occur due to long cycle time
Solution Approach 1:
The patent implements a continuous dispersion process where the EVA resin is continuously processed through the dispersion medium rather than being processed in discrete batches. This continuous operation eliminates idle time between batches, maintains consistent processing conditions, and ensures uniform product quality across all production runs, directly resolving the contradiction between productivity and manufacturing precision.
Solution Approach 2:
The patent performs preliminary blending of the EVA resin with the dispersion medium and process aids before the main dispersion operation. This pre-mixing ensures uniform distribution of the resin throughout the medium from the outset, preventing localized variations that could lead to batch-to-batch inconsistencies while maintaining efficient continuous production.
2Ease of manufacture
If batch dispersion process with strong base environment at high temperature is used, then dispersion can be achieved, but EVA resin undergoes hydrolysis leading to quality issues
Solution Approach 1:
The patent modifies the processing parameters by using a continuous process with reduced residence time at elevated temperatures compared to batch processing. The continuous flow through the extruder maintains the necessary temperature for dispersion while minimizing the time exposure to conditions that cause hydrolysis, thereby preserving resin stability while achieving effective dispersion.
Solution Approach 2:
The patent rapidly processes the EVA resin through the dispersion zone in the continuous extruder, minimizing the residence time at high temperature and strong base conditions. This 'rushing through' approach allows the dispersion to be achieved while significantly reducing the opportunity for hydrolytic degradation to occur, thus maintaining resin reliability.
3Ease of manufacture
If significant waxes as process aids are added to batch dispersion process, then dispersibility improves, but adhesion properties are compromised
Solution Approach 1:
The patent changes the processing method from batch to continuous dispersion, which fundamentally alters how process aids interact with the resin. The continuous shear mixing in the extruder achieves effective dispersion with minimal or no waxes, eliminating the need to use excessive process aids that would compromise adhesion properties while still maintaining good dispersibility.
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 process lowers production costs, improves batch consistency, and minimizes EVA resin hydrolysis, resulting in a higher-quality waterborne heat seal coating with enhanced performance and extended shelf stability.
Implementation Method 1
contacting the melt blend with an initial aqueous stream comprising a neutralizing agent, water, and optionally a surfactant in an emulsification zone to form a dispersion
Implementation Method 2
the EVA resin is likely to be subject to hydrolysis in the batch dispersion process due to longer processing in a strong base environment at high temperature, so a continuous dispersion process with short residence time is highly desired to significantly mitigate EVA hydrolysis
Data Source
AI summary
A process for preparing a waterborne heat seal coating composition comprising the steps of: a) melt blending ethylene vinyl acetate copolymer, at least one tackifier, and optionally a surfactant in a mixing and conveying zone to form a melt blend; b) contacting the melt blend with an initial aqueous stream comprising a neutralizing agent, water, and optionally a surfactant in an emulsification zone to form a dispersion; and c) diluting the dispersion with water in a dilution zone to form the waterborne heat seal coating composition wherein the process is a continuous process, is disclosed.