EVOH Resin Composition for Stable Melt Molding and Film Appearance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional ethylene-vinyl alcohol copolymer resin compositions suffer from insufficient long-run stability in melt molding, leading to defects such as streaks, flaws, and coloring, and fail to meet requirements for appearance characteristics, adhesion, and resistance to thermal deterioration.
Innovation Solution
The ethylene-vinyl alcohol copolymer is prepared by saponifying a copolymer of ethylene and a vinyl ester, then subjected to a heat treatment in a nitrogen atmosphere, ensuring molecular weights satisfy specific inequalities, and combined with specific amounts of alkali metal salts, multivalent metal salts, inorganic particles, polyolefins, and polyamides to enhance stability and appearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If EVOH-containing resin composition is used for melt molding, then gas barrier properties and mechanical strength are improved, but thermal deterioration products are generated causing gelation and fish eyes
Solution Approach 1:
A boron compound is introduced as an intermediary substance that mediates between the EVOH polymer and the thermal environment. The boron compound specifically interacts with the hydroxyl groups of EVOH to form a protective complex, preventing thermal deterioration and gelation while maintaining the polymer's inherent mechanical strength and gas barrier properties.
Solution Approach 2:
The invention changes the chemical parameter of the resin composition by adding specific metal salts (sodium acetate and magnesium acetate) in controlled amounts. These additives modify the thermal behavior of EVOH during melt molding, suppressing oxidative crosslinking reactions and preventing gelation, thereby improving long-run stability without sacrificing mechanical performance.
2Reliability
If metal salt is added to improve long-run stability, then thermal stability is improved, but molded article tends to be yellowed
Solution Approach 1:
The invention precisely controls the concentration parameters of metal salt additives, specifying sodium acetate at 1-1000 ppm and magnesium acetate at 1-500 ppm. This quantitative optimization achieves the minimum effective concentration for thermal stability while staying below the threshold that causes yellowing, thus resolving the contradiction between stability improvement and appearance quality.
Solution Approach 2:
The invention creates a composite resin composition by combining EVOH with specific ratios of boron compound, sodium acetate, and magnesium acetate. This multi-component composite system synergistically improves thermal stability through the boron-EVOH complex while the controlled metal salt concentrations prevent yellowing, achieving both stability and appearance requirements.
3Loss of substance
If reduction in thickness of molded articles is implemented, then environmental impact is reduced, but film forming defects such as streaks and flaws are generated
Solution Approach 1:
The invention enables the use of thinner EVOH layers by preventing thermal deterioration that typically causes defects in thin films. The boron compound and metal salts protect the polymer during processing, allowing thinner sections to be molded without developing streaks or flaws, thus reducing material usage while maintaining quality.
Solution Approach 2:
The boron compound acts as a protective intermediary in thin-section molding, forming a stable complex with EVOH that prevents thermal degradation during melt molding. This mediation allows thin films to be processed without the generation of streaks and flaws, enabling thickness reduction while preserving manufacturing precision.
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 provides superior long-run stability, inhibits defects and coloring, and improves appearance characteristics, adhesion, and resistance to thermal deterioration, enabling the production of high-quality multilayer structures and containers.
Implementation Method 1
an ethylene-vinyl alcohol copolymer (A) is obtained by saponifying a copolymer of ethylene and a vinyl ester
Implementation Method 2
after subjecting the ethylene-vinyl alcohol copolymer (A) to a heat treatment in a nitrogen atmosphere at 220° C. for 50 hrs
Implementation Method 3
an oxidizing and crosslinking reaction is caused in a molten state at high temperatures even in the interior of an extrusion molding machine in a state being almost free from oxygen
Data Source
AI summary
Provided are an ethylene-vinyl alcohol copolymer, a resin composition and a molded product thereof being superior in long-run stability of melt molding, with inhibited coloring and generation of film forming defects such as flaws in formed film and streaks, and also being superior in appearance characteristics. An ethylene-vinyl alcohol copolymer (A) obtained by saponifying a copolymer of ethylene and a vinyl ester, in which molecular weights determined by using gel permeation chromatography with a differential refractive index detector and an ultraviolet and visible absorbance detector after a heat treatment in a nitrogen atmosphere at 220° C. for 50 hrs satisfy the inequality (1):(Ma−Mb)/Ma<0.45 (1)wherein: Ma represents a molecular weight in terms of polymethyl methacrylate equivalent on a maximum value of a peak measured by the differential refractive index detector; and Mb represents a molecular weight in terms of polymethyl methacrylate equivalent on a maximum value of an absorption peak at a wavelength of 220 nm measured by the ultraviolet and visible absorbance detector.