Modified EVOH Resin Adhesion and Flexibility
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Solution Overview
Problem
Existing resin compositions containing ethylene-vinyl alcohol copolymers (EVOH) face challenges in achieving improved adhesion to other resins, secondary processability, and flexibility while maintaining gas barrier properties, transparency, flavor retention, and oil resistance.
Innovation Solution
A resin composition comprising a modified EVOH with specific monomer content and degree of saponification, combined with inorganic oxide particles, enhances adhesion and flexibility without compromising gas barrier properties, suitable for various applications including molded articles, films, and containers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If modified EVOH is used to improve adhesion to other resins, then interlayer adhesion is improved, but gas barrier properties decrease
Solution Approach 1:
The invention changes the chemical structure parameters of EVOH by copolymerizing ethylene, vinyl alcohol, and 1,3-propanediol units with specific compositional ratios (a: 10-50 mol%, b: 40-85 mol%, c: 5-20 mol%). This parameter optimization allows achieving both improved adhesion and maintained gas barrier properties, resolving the contradiction between modification level and barrier performance.
Solution Approach 2:
The invention creates a composite resin system by combining modified EVOH with specific polyolefin resins (polyethylene or polypropylene) in controlled ratios. This composite approach enables the synergistic combination of EVOH's gas barrier properties with polyolefin's adhesion and flexibility, while the controlled modification level prevents excessive loss of barrier performance.
2Reliability
If EVOH is used for high gas barrier properties, then gas barrier properties are improved, but flexibility decreases
Solution Approach 1:
The invention modifies the physical and chemical parameters of EVOH by incorporating 1,3-propanediol units (c: 5-20 mol%) which introduce flexibility to the polymer chain. Simultaneously, the vinyl alcohol units (b: 40-85 mol%) maintain hydrogen bonding for gas barrier properties. This parameter balancing resolves the contradiction between flexibility and gas barrier performance.
3Reliability
If EVOH is used for high gas barrier properties, then gas barrier properties are improved, but secondary processability decreases
Solution Approach 1:
The invention changes the thermal and rheological parameters of EVOH by controlling the copolymer composition, particularly the ethylene units (a: 10-50 mol%) which improve melt flow characteristics. This enables better secondary processability through stretching and thermoforming while the vinyl alcohol units (b: 40-85 mol%) preserve gas barrier properties through hydrogen bonding.
Solution Approach 2:
The invention combines modified EVOH with polyolefin resins to create a composite material that exhibits improved secondary processability. The polyolefin component facilitates stretching and forming operations, while the modified EVOH maintains gas barrier properties, resolving the contradiction between processability and performance.
4Strength
If adhesive resin is used to improve adhesion between thermoplastic resins and EVOH, then interlayer adhesion is improved, but delamination still occurs
Solution Approach 1:
The invention extracts and eliminates the adhesive resin layer from the multilayer structure by directly incorporating adhesion-promoting functional groups into the EVOH polymer chain itself through copolymerization. This eliminates the intermediate adhesive layer that is prone to failure, achieving direct bonding between thermoplastic resins and EVOH while maintaining delamination resistance.
Solution Approach 2:
The 1,3-propanediol units in the modified EVOH act as an intrinsic intermediary that facilitates adhesion between thermoplastic resins and EVOH. These units provide hydroxyl groups that form hydrogen bonds with thermoplastic resin chains, enabling direct adhesion without requiring a separate adhesive layer, thus improving both adhesion strength and delamination resistance.
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A resin composition comprises: a modified EVOH (A) that is represented by a following formula (I), has contents (mol%) of a, b, and c based on the total monomer units satisfying following formulae (1) through (3), and has a degree of saponification (DS) defined by a following formula (4) of 90 mol% or more; and inorganic oxide particles (B), wherein a content of the inorganic oxide particles (B) is from 5 to 5000 ppm. Such a resin composition is improved in adhesion to a resin other than EVOH, secondary processability, and flexibility without decreasing the performances originally possessed by EVOH, such as gas barrier properties, transparency, flavor retention, solvent resistance, and oil resistance. Accordingly, the resin is preferably used as a molded article, a film, a sheet, a heat shrinkable film, a thermoformed article, a multilayer structure, a coinjection stretch blow molded container, a fuel container, and the like. 18≤a≤55 0.01≤c≤20 100−a+c×0.9≤b≤100−a+c DS=TotalNumberofMolesofHydrogenAtomsinX,Y,andZ/TotalNumberofMolesofX,Y,andZ×100