Multilayer Polypropylene Liquid Packaging Container
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Solution Overview
Problem
Current liquid packaging containers for medical use, such as infusion solution bags, face challenges with flexibility, impact resistance, heat-seal strength, and adhesion issues, particularly when exposed to varying temperatures, and existing materials may leach plasticizers or generate toxic gases upon incineration.
Innovation Solution
A laminate structure comprising an inner layer, an intermediate layer, and an outer layer, where the intermediate layer is formed from a specific resin composition including a polypropylene-based resin, a thermoplastic elastomer, and an ethylene-α-olefin copolymer, which reduces adhesion and enhances crack resistance and strength at both low and normal temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a polypropylene-based resin composition with 5% by mass or less of ethylene-α-olefin copolymer is used for the intermediate layer, then the container achieves sufficient heat-seal strength, but the container becomes susceptible to damage when subjected to impact or dropping
Solution Approach 1:
The patent increases the ethylene-α-olefin copolymer content from 5% or less to 10-40% by mass in the intermediate layer, fundamentally changing the material composition parameters. This parameter change enhances the container's flexibility and impact resistance while maintaining adequate heat-seal strength through the balanced multi-layer structure.
Solution Approach 2:
The patent employs a composite multi-layer structure consisting of an inner layer (polypropylene-based resin), an intermediate layer (polypropylene-based resin with elevated ethylene-α-olefin copolymer content), and an outer layer (polypropylene-based resin). This composite structure allows each layer to perform its specific function: the inner layer provides heat-sealability, the intermediate layer provides flexibility and impact resistance, and the outer layer provides mechanical strength.
2Strength
If the inner layer material is selected for high heat-seal strength, then the container achieves reliable sealing, but the inner layers may adhere to each other making injection difficult
Solution Approach 1:
The patent segments the container into three distinct functional layers: an inner layer for heat-sealing, an intermediate layer for flexibility and adhesion control, and an outer layer for mechanical protection. This segmentation allows the inner layer to be optimized for heat-seal strength without compromising injection ease, as the intermediate layer acts as a buffer that prevents inner layer adhesion.
3Reliability
If glass bags are used for liquid packaging, then sterilization is effective, but the bags are heavier and susceptible to damage from impact or dropping
Solution Approach 1:
The patent transitions from glass material to polypropylene-based resin material, fundamentally changing the material parameter. This change reduces weight and improves impact resistance while maintaining sterilization effectiveness through the appropriate resin composition and multi-layer structure design.
4Ease of operation
If soft vinyl chloride resin bags are used to improve flexibility, then handleability improves, but plasticizers may be eluted into the infusion solution creating safety risks
Solution Approach 1:
The patent uses a composite multi-layer structure with polypropylene-based resins that do not require plasticizers for flexibility. The intermediate layer, with its elevated ethylene-α-olefin copolymer content (10-40%), provides the necessary flexibility and handleability without the harmful plasticizer elution associated with soft vinyl chloride resins.
Data Source
Figure 1~3
AI summary
Provided is a liquid packaging container having satisfactory flexibility and transparency, high heat-seal strength, high bag-breaking strength at normal temperature and low temperatures, and low (inner layer)-(inner layer) adhesiveness, which are properties important for liquid packaging containers for medical use. Specifically, provided is a liquid packaging container formed from a laminate of at least three layers including an inner layer formed from a resin composition (Y) as described below, an intermediate layer, and an outer layer formed from a resin composition (Z) as described below, the intermediate layer being formed from a resin composition (X) as described below: resin composition (X): a resin composition including 100 parts by mass of a polypropylene-based resin (1), 5 parts by mass to 95 parts by mass of a particular thermoplastic elastomer (2), and 10 parts by mass to 95 parts by mass of a particular ethylene-α-olefin copolymer (3); resin composition (Y): a resin composition including 100 parts by mass of a polypropylene-based resin (1'), and 5 parts by mass to 250 parts by mass of a particular thermoplastic elastomer (2') (provided that a particular ethylene-α-olefin copolymer is not included or, if included, the content of the copolymer is less than 10 parts by mass); and resin composition (Z): a resin composition including 100 parts by mass of a polypropylene-based resin (1"), and 0 parts by mass to 35 parts by mass of a particular thermoplastic elastomer (2").