Multimodal Propylene Copolymer Pipe Composition
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Solution Overview
Problem
Existing polypropylene random copolymers for pipe applications face a trade-off between impact and stiffness properties, and variations in nucleating agents used for coloration can lead to dimensional issues due to differing shrinkage effects, while also affecting processing properties like extrusion rates and surface quality.
Innovation Solution
A multimodal propylene random copolymer composition with a specific molecular weight distribution and nucleating agent, comprising a low molecular weight and high molecular weight fraction, along with a nucleating agent other than beta-nucleating agents, to achieve a balanced mechanical and processing performance suitable for pressure pipe applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the impact strength of propylene random copolymer is increased, then the flexibility and toughness are improved, but the stiffness and flexural modulus deteriorate
Solution Approach 1:
The patent applies parameter changes by precisely controlling the comonomer content (4.5-9.5 mol%) and implementing a multimodal molecular weight distribution with specific weight average molecular weights (10,000-100,000 g/mol). This resolves the contradiction by adjusting compositional parameters to achieve both high impact strength (≥4.0 kJ/m² at 0°C) and adequate flexural modulus (>800 MPa) simultaneously
Solution Approach 2:
The patent creates a composite-like structure within the copolymer by incorporating a multimodal molecular weight distribution with distinct low, medium, and high molecular weight fractions. Each fraction contributes different properties: low MW provides processability, medium MW provides impact strength, and high MW provides stiffness, thereby resolving the contradiction between impact strength and flexural modulus
2Illumination intensity
If different pigments are used for coloration, then the aesthetic properties are improved, but the dimensional stability deteriorates due to varying nucleation effects and shrinkage
Solution Approach 1:
The patent applies parameter changes by establishing a controlled range for nucleating agent content (0.01-1.0 wt%) and selecting specific nucleating agent types that provide consistent nucleation effects. This resolves the contradiction by standardizing the nucleation parameters regardless of pigment variations, thereby maintaining dimensional stability (shrinkage <5%) while allowing coloration flexibility
3Stress or pressure
If the stiffness of propylene random copolymer is increased, then the creep resistance is improved, but the impact strength and flexibility deteriorate
Solution Approach 1:
The patent creates a composite-like structure within the copolymer by incorporating a multimodal molecular weight distribution with distinct low, medium, and high molecular weight fractions. Each fraction contributes different properties: low MW provides processability, medium MW provides impact strength, and high MW provides stiffness, thereby resolving the contradiction between impact strength and flexural modulus
4Strength
If the molecular weight is increased to improve mechanical properties, then the strength and stiffness are improved, but the processability and extrusion output rate deteriorate
Solution Approach 1:
The patent applies parameter changes by implementing a multimodal molecular weight distribution with specific weight average molecular weights (10,000-100,000 g/mol) and controlling the melt flow rate (0.5-5.0 g/10 min at 230°C). This resolves the contradiction by adjusting molecular weight parameters to achieve both improved mechanical properties and maintained processability with adequate extrusion output rate
Solution Approach 2:
The patent segments the molecular weight distribution into distinct fractions (low, medium, and high MW) rather than using a single molecular weight. This segmentation allows each fraction to contribute specific properties: low MW provides processability and extrusion output rate, while high MW provides mechanical strength, thereby resolving the contradiction
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 balanced flexural modulus and impact strength, ensuring flexibility and creep resistance, while maintaining uniform shrinkage and improved processing behavior, making it suitable for hot and cold water pressure pipes with enhanced surface quality.
Implementation Method 1
a nucleating agent (B), wherein the nucleating agent is other than beta-nucleating agent
Data Source
AI summary
The present invention relates to a polypropylene composition comprising a propylene random copolymer (A) with at least one comonomer selected from alpha-olefins with 2 or 4 to 8 carbon atoms and a nucleating agent (B), wherein the polypropylene composition has a polydispersity index (PI) of from 2.0 to 7.0, a melt flow rate MFR2 (2:16 kg, 230°C) of from 0.05 to 1.0 g/10 min, determined according to ISO 1133 and a Charpy Notched Impact Strength at 0°C of at least 4.0 kJ/m2, determined according to ISO 179/1eA:2000 using notched injection moulded specimens, a process for producing said polypropylene composition, an article comprising said polypropylene composition and the use of said polypropylene composition for the production of an article.