Polypropylene Resin Composition for Retort Pouches
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Solution Overview
Problem
Existing polypropylene-based resin compositions are not suitable for film moldings required for retort pouches, as they fail to meet mechanical and chemical property standards, including high heat sealability, impact resistance at low temperatures, and reduced elution in FDA tests.
Innovation Solution
A polypropylene-based resin composition comprising a propylene polymer and an ethylene/α-olefin copolymer, with specific molecular weight ratios and ethylene-derived unit contents, is developed. This composition is produced using a catalyst system including a solid catalyst, an organoaluminum compound, and an organosilicon compound, ensuring excellent balance of mechanical and chemical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a polypropylene-based resin composition with high MFR is used to improve flowability and ease of molding, then the molding process becomes easier, but the mechanical properties such as rigidity and impact resistance deteriorate
Solution Approach 1:
The patent applies parameter changes by precisely controlling the MFR within 0.5 to 4.0 g/10 min, the molecular weight ratio Mw/Mn to be less than 7, and the ethylene content to be 0.5% by weight or less. These parameter optimizations enable the resin to achieve both good flowability for molding and excellent mechanical properties including rigidity and impact resistance.
2Strength
If the resin composition is optimized for mechanical properties such as rigidity and impact resistance, then the structural strength is improved, but the chemical properties such as elution resistance into n-hexane deteriorate
Solution Approach 1:
The patent achieves both mechanical strength and chemical stability by optimizing specific parameters: controlling the MFR at 0.5 to 4.0 g/10 min, limiting the molecular weight distribution (Mw/Mn < 7), and restricting ethylene content to 0.5% by weight or less. These parameter controls ensure the resin maintains rigidity and impact resistance while achieving FDA elution standards of 2.6 μg or less in n-hexane.
3Ease of operation
If the resin composition is modified to improve heat sealability and weldability, then the sealing performance is improved, but the appearance quality and resistance to whitening due to bending deteriorate
Solution Approach 1:
The patent optimizes the balance between heat sealability and appearance quality by controlling the MFR within 0.5 to 4.0 g/10 min and the molecular weight ratio Mw/Mn to be less than 7. This parameter optimization enables the resin to exhibit excellent heat sealability and weldability while maintaining high resistance to whitening due to bending and excellent appearance quality.
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 resulting film molding exhibits excellent rigidity, low-temperature impact strength, weldability, and whitening resistance, while meeting FDA standards for elution in n-hexane, making it suitable for retort pouches and other food contact applications.
Implementation Method 1
This composition is produced using a catalyst system including a solid catalyst, an organoaluminum compound, and an organosilicon compound
Data Source
AI summary
The present invention provides a polypropylene-based resin composition comprising a polypropylene-based resin (A) including a continuous phase consisting of a propylene polymer (a1) and a rubber phase consisting of a copolymer (a2) of ethylene and α-olefin having 3-10 carbon atoms, and an optional component ethylene/α-olefin copolymer (B) which is a copolymer of ethylene and α-olefin having 3-10 carbon atoms.