Polypropylene Resin Composition for Lightweight Blow Molded Containers
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Solution Overview
Problem
Polypropylene resins used in stretch and direct blow molding lack sufficient transparency, mechanical strength, and moldability, which are essential for producing containers with excellent impact resistance and flexibility, and they also have a high specific gravity, making them unsuitable for volume reduction and oil resource conservation.
Innovation Solution
Development of polypropylene resins with a specific composition, including random polypropylene and homopolypropylene with controlled ethylene content and the addition of organic phosphate metal salt or sorbitol nucleating agents, which allows for a broad DSC melting curve and improved moldability, resulting in lightweight containers with high transparency and impact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polypropylene resins are used for blow molded containers, then chemical properties and forming properties are excellent, but transparency and mechanical strength are insufficient
Solution Approach 1:
The patent uses a composite resin composition comprising propylene/ethylene copolymer (30-70 parts by weight) and homopolypropylene (30-70 parts by weight), where the specific gravity of the copolymer is 0.860 or less and the melting point is 100°C or less. This composite structure combines the advantages of both materials to achieve both excellent forming properties and high mechanical strength, resolving the contradiction between ease of manufacture and strength.
2Strength
If PET or polycarbonate resins are used for stretch blow molded articles, then transparency and mechanical strength are good, but specific gravity is 1.2 or more, making volume reduction and oil resource conservation difficult
Solution Approach 1:
The patent changes the key parameters of the resin composition by using propylene/ethylene copolymer with specific gravity of 0.860 or less and melting point of 100°C or less, combined with homopolypropylene in specific proportions. This parameter optimization achieves both low specific gravity (enabling volume reduction) and high mechanical strength, resolving the contradiction between weight and strength.
3Illumination intensity
If nucleating agents are added to polypropylene resins to enhance transparency, then transparency improves, but mechanical strength and moldability deteriorate
Solution Approach 1:
The patent employs a composite resin system where the propylene/ethylene copolymer component inherently provides good transparency without requiring additional nucleating agents. The combination of copolymer (30-70 parts) and homopolypropylene (30-70 parts) achieves both high transparency and high mechanical strength, eliminating the need to trade strength for transparency through nucleating agent addition.
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 polypropylene resins enable the production of lightweight, flexible, and transparent containers with improved moldability, achieving a 30% reduction in specific gravity and enhanced flexibility, making them suitable for volume reduction and conservation of oil resources.
Implementation Method 1
the resin showing a broad DSC melting curve which has a single melting point peak and in which the maximum intensity peak temperature (Tm) is not more than 120° C. and the half-value width on a higher temperature side from the maximum intensity peak is not less than 20° C.
Implementation Method 2
the resin showing a broad DSC melting curve which has a single melting point peak and in which the maximum intensity peak temperature (Tm) is not more than 120° C.
Data Source
AI summary
Polypropylene resins of the present invention give blow molded containers excellent in transparency, impact resistance and flexibility. Stretch blow molded containers obtained from the polypropylene resins enable volume reduction and weight reduction. A polypropylene resin includes a random polypropylene (P1) having MFR (ASTM D 1238, 230° C., 2.16 kg load) of 0.5 to 100 g/10 min and an ethylene content of 3.0 wt % to less than 7.0 wt %, (i) the resin containing the random polypropylene (P1) at not less than 80 wt %, (ii) the resin showing a broad DSC melting curve which has a single melting point peak and in which the maximum intensity peak temperature (Tm) is not more than 120° C. and the half-value width on a higher temperature side from the maximum intensity peak is not less than 20° C.