Nucleated Polypropylene Composition for Food Packaging
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Solution Overview
Problem
Existing polypropylene compositions for injection molded containers face challenges in achieving a balance between impact strength and stiffness while maintaining good processability and organoleptic properties, particularly for thin-wall packaging applications, where high melt flow rate often compromises impact properties and introduces undesirable color and taste issues.
Innovation Solution
A polypropylene composition comprising a propylene copolymer with a specific melt flow rate range and a polymeric nucleating agent, which provides a balance of impact strength, stiffness, and optical clarity, along with improved processability and reduced warpage, without the need for peroxide treatment, thereby avoiding organoleptic defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high melt flow rate polypropylene is used to improve processability, then processability is improved, but impact strength deteriorates
Solution Approach 1:
The patent applies parameter changes by carefully controlling the melt flow rate within a specific range (20-100 g/10min) rather than using extremely high MFR materials. This optimized parameter range allows the composition to achieve both good processability and adequate impact strength, resolving the contradiction between these two properties.
Solution Approach 2:
The patent creates a composite material system by combining propylene copolymer with specific nucleating agents and additives. This composite approach allows the material to exhibit both good flow characteristics for processability and enhanced mechanical properties including impact strength, thereby resolving the contradiction between these opposing requirements.
2Productivity
If peroxide treatment is used to increase melt flow rate, then processability is improved, but organoleptic properties deteriorate
Solution Approach 1:
The patent extracts or eliminates the peroxide treatment step from the processing sequence. By achieving the desired melt flow rate through composition design (polymer selection and blending) rather than chemical degradation, the patent removes the source of organoleptic deterioration while maintaining improved processability.
Solution Approach 2:
The patent uses a composition formulation that achieves processability improvements through material selection rather than aggressive chemical treatment. This approach avoids the harmful byproducts of peroxide degradation while still enabling efficient processing, effectively replacing a harmful short-term solution with a sustainable long-term solution.
3Productivity
If high melt flow rate polypropylene is used to reduce cycle time, then productivity is improved, but color properties deteriorate
Solution Approach 1:
The patent optimizes the melt flow rate parameter to a moderate range (20-100 g/10min) rather than using maximum MFR materials. This balanced parameter selection enables adequate cycle times while avoiding the yellowing and haze associated with high MFR materials, thus resolving the contradiction between productivity and optical properties.
Solution Approach 2:
The patent formulates a composite material system that combines propylene copolymer with specific nucleating agents and additives. This composite structure enables faster cooling and shorter cycle times while maintaining excellent optical clarity and color properties, thereby resolving the contradiction between productivity and appearance quality.
4Strength
If propylene copolymer with high comonomer content is used to improve impact strength, then impact strength is improved, but stiffness deteriorates
Solution Approach 1:
The patent optimizes the comonomer content parameter within a specific range rather than using high comonomer content materials. This controlled parameter adjustment allows the composition to achieve adequate impact strength while maintaining sufficient stiffness, resolving the contradiction between these two mechanical properties.
Solution Approach 2:
The patent creates a composite material system that combines propylene copolymer with nucleating agents and additives. This composite structure provides impact modification while the nucleating agents enhance crystallinity and stiffness, thereby resolving the contradiction between impact strength and stiffness through synergistic material combinations.
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 composition achieves a high Charpy Notched Impact Strength, Tensile Modulus, and optical clarity, with enhanced processability and reduced cycle time, ensuring containers with improved firmness, integrity, and aesthetic appeal without taste or odor issues.
Implementation Method 1
a nucleating agent (B), which is a polymeric nucleating agent
Data Source
AI summary
The present invention provides a moulded container for food packaging comprising, preferably consisting of, a polypropylene composition, the polypropylene composition comprising - a propylene homo- or copolymer (A) having (i) a melt flow rate, determined according to ISO 1133 at 230 °C and under a load of 2.16 kg, of at least 25 g/10 min; and (ii) in case component (A) is a copolymer, a comonomer content of not more than 5.0 wt.%; and a nucleating agent (B), as well as to the use of a polypropylene composition comprising - a propylene homo- or copolymer (A) having (i) a melt flow rate, determined according to ISO 1133 at 230 °C and under a load of 2.16 kg, of at least 25 g/10 min; and (ii) in case component (A) is a copolymer, a comonomer content of not more than 5.0 wt.%; and a nucleating agent (B); for the manufacture of a moulded container.