Polypropylene Composition for Transparent Extrusion Blow Molded Bottles
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Solution Overview
Problem
Extrusion blow molding processes face challenges in producing large bottles with high transparency, stiffness, and uniform surface properties due to difficulties in removing air between the polymer tube and mold, leading to non-uniform inner and outer surfaces and reduced transparency compared to injection molded articles.
Innovation Solution
A polypropylene composition combining a random propylene copolymer, high melt strength polypropylene, and a clarifier, with specific properties such as a melt flow rate of at least 2.0 g/10 min, strain hardening behavior, and moderate gel content, is used to enhance the transparency, stiffness, and weight swell of extrusion blown bottles, maintaining compatibility with commercial products.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If extrusion blow molding process is used to produce bottles, then manufacturing cost and flexibility are improved, but transparency and surface uniformity deteriorate due to air removal difficulties and non-uniform polymer tube contact with mold
Solution Approach 1:
The patent modifies the polymer material parameters by using visbroken polypropylene with specific melt strength characteristics and adding clarifiers (0.01-5 wt%) to change the optical properties. This allows the extrusion blow molding process to produce bottles with improved transparency and surface uniformity while maintaining the cost and flexibility advantages of the extrusion process.
Solution Approach 2:
The patent creates a composite polymer system by combining visbroken polypropylene with clarifiers and other additives. This composite material approach allows simultaneous optimization of transparency, surface quality, and processability, resolving the contradiction between ease of manufacture and surface uniformity.
2Manufacturing precision
If visbreaking polypropylene is applied to improve transparency, then haze is reduced, but melt strength decreases limiting applicability to small bottles only
Solution Approach 1:
The patent carefully controls the visbreaking process to achieve optimal melt strength for bottle formation while still obtaining sufficient transparency improvement. By adjusting visbreaking degree and adding clarifiers, the invention enables production of large bottles (1L and above) with both good transparency and adequate melt strength.
Solution Approach 2:
The patent introduces clarifiers as intermediary substances that mediate between the visbroken polymer and the final product requirements. These clarifiers help restore optical properties and stabilize melt characteristics, allowing the use of visbroken polypropylene in large bottle production where melt strength is critical.
3Ease of operation
If wall thickness is reduced to improve stackability and filling performance, then stiffness must be maintained through material composition rather than increased wall thickness
Solution Approach 1:
The patent changes the material parameters by using visbroken polypropylene with optimized melt strength and adding stiffening agents and clarifiers. This allows the bottle to achieve sufficient stiffness with reduced wall thickness, improving stackability and filling performance while maintaining structural integrity through enhanced material properties rather than increased thickness.
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 composition achieves bottles with low haze, exceptional gloss, high top load, and weight swell similar to commercial products, addressing the limitations of traditional extrusion blow molding by improving mechanical properties and surface quality.
Implementation Method 1
the polypropylene composition has a melt flow suitable for extrusion blow molding processes... a high melt strength polypropylene (HMS-PP)... obtaining a composition with a melt flow suitable for extrusion blow molding processes
Implementation Method 2
the clarifier (C) comprises at least one alpha-nucleating agent (N)... achieving bottles with low haze, exceptional gloss
Data Source
AI summary
A polypropylene composition comprising a random propylene copolymer, a high melt strength polypropylene having a branching index g′ of 0.9 or less and a clarifier, wherein the polypropylene composition has a MFR2 (230° C.) of at least 2.0 g/10 min.