EVOH Multilayer Stand-Up Pouch Structure With Hydrocarbon Resin Interlayer
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Solution Overview
Problem
Existing standup pouches face issues with high water vapor permeability, reduced heat seal strength, and significant gas barrier property changes after retort treatment, compromising the quality and integrity of packaged contents.
Innovation Solution
A multilayer structure comprising a protective layer, an ethylene-vinyl alcohol copolymer (EVOH) layer, an intermediate layer with polypropylene and hydrocarbon resin, and a heat seal resin layer, which enhances water vapor barrier, heat seal strength, and maintains gas barrier properties post-retort treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an elastomer component is added to the heat seal resin layer to improve bag drop impact resistance, then impact resistance is improved, but water vapor permeability increases significantly
Solution Approach 1:
The invention divides the heat seal resin layer into two distinct layers: a first heat seal resin layer containing the elastomer component for impact resistance, and a second heat seal resin layer with low water vapor permeability. This segmentation allows each layer to perform its specific function without compromising the other, resolving the contradiction between impact resistance and water vapor barrier properties.
2Reliability
If the multilayer structure is designed to maintain gas barrier properties after retort treatment, then oxygen barrier property is preserved, but the structure becomes more complex
Solution Approach 1:
The invention employs a composite multilayer structure combining different resin materials with specific properties: polypropylene-based heat seal layers for heat resistance, EVOH layer for oxygen barrier, and elastomer-containing layer for impact resistance. This composite approach achieves reliable gas barrier stability after retort treatment while maintaining a manageable structural complexity through functional specialization of each layer.
3Object-affected harmful factors
If aluminum foil is used as the barrier layer to ensure sufficient oxygen barrier property, then oxygen barrier is improved, but microwave usability is lost
Solution Approach 1:
The invention replaces the durable but microwave-incompatible aluminum foil with a polymer-based EVOH (ethylene-vinyl alcohol copolymer) barrier layer. While EVOH has shorter-term stability concerns, it enables microwave usability and is cost-effective for single-use or limited-use packaging applications, achieving the trade-off between barrier performance and adaptability.
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 multilayer structure provides lower water vapor permeability, improved heat seal strength, and reduced gas barrier property changes, ensuring the quality and stability of packaged contents while maintaining impact resistance and storage stability.
Implementation Method 1
an ethylene-vinyl alcohol copolymer (EVOH) layer
Implementation Method 2
an intermediate layer with polypropylene and hydrocarbon resin
Implementation Method 3
a heat seal resin layer, which enhances water vapor barrier, heat seal strength
Data Source
Figure 1~2
AI summary
A multilayer structure (10) includes a protective layer (1), an ethylene-vinyl alcohol copolymer layer (2b), a heat seal resin layer (3b), and an intermediate layer (3a) provided between the ethylene-vinyl alcohol copolymer layer (2b) and the heat seal resin layer (3b) and containing a polypropylene resin, wherein the intermediate layer (3a) further contains a hydrocarbon resin having a number average molecular weight of 100 to 3,000, and a softening point of not less than 60°C and less than 170°C. The multilayer structure satisfies requirements for a lower water vapor permeability and a sufficient heat seal strength, and provides a standup pouch having a smaller gas barrier property change rate after retort treatment.