EVOH Resin Composition Void Prevention High-Temperature Molding
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Solution Overview
Problem
Existing ethylene-vinyl alcohol copolymer (EVOH) resin compositions face challenges with void formation during high-temperature melt molding, which affects productivity and quality, especially in high-speed processes.
Innovation Solution
A resin composition using an EVOH produced with an azonitrile polymerization initiator, where the nitrogen element content is within a specific range (5-60 ppm) and the ratio of nitrogen elements before and after a reprecipitation operation falls between 0.65 and 0.99, inhibiting void formation during high-temperature melt molding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-temperature melt molding is used to improve productivity, then molding speed increases, but voids are produced due to decomposition of the resin
Solution Approach 1:
The patent applies parameter changes by precisely controlling the nitrogen element content from the polymerization initiator to within 5-60 ppm and the ratio NF/NI to within 0.65-0.99. This quantitative control of chemical parameters suppresses resin decomposition at high molding temperatures, enabling high-speed molding without void formation.
Solution Approach 2:
The patent implements feedback control through the reprecipitation operation that removes low molecular weight volatile components containing nitrogen. By measuring and controlling the nitrogen content before and after reprecipitation (ratio NF/NI), the process feedbacks on the resin composition to maintain optimal conditions for high-temperature molding without voids.
2Manufacturing precision
If the EVOH resin composition is controlled to have low moisture content and low alkaline earth metal ions to prevent voids, then void formation is reduced, but further quality improvement is needed for flexible packaging materials
Solution Approach 1:
The patent introduces a new control parameter - nitrogen element content from the polymerization initiator (5-60 ppm) and its ratio after reprecipitation (NF/NI: 0.65-0.99). This provides more precise control over resin decomposition and void formation, enabling further quality improvement beyond traditional moisture and metal ion control for flexible packaging applications.
Data Source
AI summary
A resin composition comprises an ethylene-vinyl alcohol copolymer (A) as a main component, the copolymer (A) being produced using an azonitrile polymerization initiator, wherein the ethylene-vinyl alcohol copolymer (A) has an ethylene unit content from 20 to 60 mol% and a degree of saponification of 85 mol% or more, an amount (NI) of nitrogen elements derived from the polymerization initiator is from 5 to 60 ppm, and a ratio (NF/NI) of an amount (NF) of nitrogen elements contained in a dried solid obtained by an operation (X) below to the amount (NI) of nitrogen elements is from 0.65 to 0.99. The resin composition is less likely to produce voids even during melt molding at high temperatures and thus preferably used for rapid melt molding process at high temperatures. Operation (X): a solution of 5 g of the resin composition dissolved in 100 g of 1,1,1,3,3,3-hexafluoro-2-propanol is dropped in 1000 g of methanol under stirring and a precipitation thus produced is separated and then dried to obtain the dried solid.