Purging Agent Water Content and Metal Salt Control
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Solution Overview
Problem
Purging agents with high water and metal salt content can cause aggregates to form during the purging operation, leading to inferior appearance and contamination of molded articles, especially when processing polar group-containing thermoplastic resins like EVOH-based resin.
Innovation Solution
A purging agent comprising a hydrocarbon-based resin with a reduced water content of 0.15% or less and a specific range of metal salts, including alkali and alkaline earth metal salts, is used to prevent aggregate formation and ensure effective cleaning of molding apparatuses, particularly for saponified ethylene-vinyl ester-based copolymer resins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydrocarbon-based resin containing metal salt and water is used as purging agent, then cleaning effect is improved, but aggregate formation occurs in succeeding resin
Solution Approach 1:
The patent changes the water content parameter from high (conventional) to low (0.01-5% by weight), which fundamentally alters the purging mechanism. This parameter change prevents aggregate formation while maintaining cleaning effectiveness through the hydrocarbon-based resin and metal salt combination
Solution Approach 2:
The patent creates a composite purging agent system combining hydrocarbon-based resin with specific metal salts (alkali metal salts and/or alkaline earth metal salts) in controlled amounts (0.1-20% by weight). This composite formulation achieves synergistic cleaning effect without the harmful aggregate formation caused by conventional high-water content formulations
2Reliability
If high water content is added to purging agent, then hydrophilic resin cleaning is improved, but aggregate contamination occurs
Solution Approach 1:
The patent fundamentally changes the water content parameter to a low range (0.01-5% by weight), which is sufficient for cleaning hydrophilic resins like EVOH without causing aggregate contamination. This parameter optimization maintains cleaning effectiveness while ensuring molded article appearance quality
3Reliability
If metal salt content is increased in purging agent, then resin decomposition is enhanced, but aggregate formation increases
Solution Approach 1:
The patent creates a controlled composite system with metal salts (alkali metal salts and/or alkaline earth metal salts) at optimized concentrations (0.1-20% by weight). This composite formulation enhances resin decomposition effectiveness while the controlled composition prevents aggregate formation, unlike uncontrolled high metal salt content formulations
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 solution effectively suppresses contamination and aggregate formation, providing excellent purging performance even in narrow and hot passageways, such as dies or nozzles, while maintaining the quality of the molded articles.
Implementation Method 1
the metal salt is transferred from the purging agent to the resin to be removed and brings the resin to decomposition
Implementation Method 2
This purging agent can give water to the hydrophilic resin, thereby the resin is softened and improved in its flowability
Data Source
AI summary
A purging agent that has excellent purging performance without generation of aggregate is disclosed as a purging agent used in a purging operation where a resin to be processed contains a polar group-containing thermoplastic resin. This purging agent contain a hydrocarbon-based resin, and at least one metal salt among an alkaline metal salt and alkaline earth metal salt, has a water content of 0.15 % by weight or less, and includes 0.1 to 20 % by weight of the metal salt expressed as the metal relative to the hydrocarbon-based resin.