Propylene Copolymer for Bottles with High Appearance and Low Hexane
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Solution Overview
Problem
Developing a propylene copolymer with high bottle appearance factor (BAF) values and low hexane solubles content is challenging, as existing soft heterophasic propylene copolymers often compromise on optical properties and hexane content, particularly in extrusion blow molded articles.
Innovation Solution
A propylene copolymer with a high overall comonomer content and moderate xylene cold soluble (XCS) content, featuring a bimodal comonomer content and molecular weight distribution, and an α-nucleated composition to achieve high BAF values and low hexane solubles, while maintaining thermal stability and suitable optical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If soft heterophasic propylene copolymer is used to achieve good impact behavior, then the matrix contains dispersed elastomeric copolymer inclusions, but the optical properties (haze and visual appearance) deteriorate
Solution Approach 1:
The patent applies local quality by creating distinct phases with different properties: a crystalline polypropylene matrix providing structural integrity and optical clarity, and dispersed elastomeric copolymer inclusions providing impact resistance. The inclusions are finely dispersed throughout the matrix, with each phase optimized for its specific function while maintaining overall optical properties through controlled inclusion size and distribution.
2Adaptability or versatility
If high comonomer content is used to achieve softness and flexibility, then the polymer becomes more processable, but the hexane soluble content increases which is unacceptable in food and health sectors
Solution Approach 1:
The patent employs composite materials by combining polypropylene with controlled comonomer content (4.5-10.0 wt.-%) and adding specific amounts of elastomeric copolymer (5-50 wt.-%) as a separate phase. This composite structure allows the base polypropylene to maintain low hexane solubility while the elastomeric phase provides the required softness and flexibility, thus achieving the desired properties without increasing harmful hexane soluble content.
Solution Approach 2:
The patent applies parameter changes by precisely controlling the comonomer content within a narrow range (4.5-10.0 wt.-%) and regulating the xylene cold soluble fraction (25.0-35.0 wt.-%). These controlled parameter changes optimize the balance between softness/flexibility and hexane solubility, ensuring the material meets food and health sector requirements while maintaining the desired mechanical properties.
3Adaptability or versatility
If xylene cold soluble fraction is increased to achieve desired softness, then the polymer becomes more flexible, but the optical properties and hexane content become unacceptable
Solution Approach 1:
The patent applies parameter changes by precisely controlling the xylene cold soluble fraction within the range of 25.0-35.0 wt.-%. This controlled parameter adjustment allows the polymer to achieve the desired flexibility and softness while maintaining acceptable optical properties and hexane content, resolving the contradiction between flexibility and optical/hexane properties.
Data Source
AI summary
Propylene copolymer having a melt flow rate MFR2 (230° C.) in the range of more than 0.8 to below 2.5 g/10 min, a xylene cold soluble content (XCS) in the range of 25.0 to 35.0 wt.-%, a comonomer content in the range of more than 4.5 to 10.0 wt.-%, wherein further the xylene cold soluble (XCS) fraction of the propylene copolymer has comonomer content in the range of 12.0 to 22.0 wt.-% and the xylene cold insoluble (XCI) fraction of the propylene copolymer has a Mw/Mn of more than 4.9 to 10.0.