Propylene Terpolymer Pipe Composition for Impact and Brittle Failure Balance
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Solution Overview
Problem
There is a need for a propylene-based terpolymer composition that balances high impact resistance and long time to brittle failure, particularly for hot and cold water pressure pipes, which are currently challenging to achieve with existing propylene/ethylene/1-hexene terpolymers.
Innovation Solution
A polypropylene composition comprising a terpolymer with at least 1.5 wt% ethylene and 1.5 wt% 1-hexene derived units, a melt flow rate of 0.10 to 0.70 g/10 min, and a weight average molecular weight to number average molecular weight ratio of 7.0 to 20.0, optimized for improved impact resistance and processability, using a Ziegler-Natta catalyst system for polymerization and potentially incorporating additives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If propylene/ethylene/1-hexene terpolymers are used for pipe production, then processability and extrusion speed are improved, but impact resistance and time to brittle failure are insufficient
Solution Approach 1:
The patent applies parameter changes by precisely controlling the comonomer content ratios (ethylene 1.5-7.0 wt%, 1-hexene 1.5-5.0 wt%) and molecular weight distribution (Mw/Mn ratio of 7.0-20.0) to achieve optimal balance between processability and mechanical properties. This quantitative adjustment of compositional parameters resolves the contradiction between extrusion speed and brittles failure resistance
Solution Approach 2:
The invention creates a composite polymer structure by incorporating two different comonomers (ethylene and 1-hexene) with distinct properties into the propylene matrix. Ethylene contributes to impact resistance while 1-hexene enhances processability, and their synergistic combination in specific proportions achieves both high extrusion speed and long time to brittle failure simultaneously
2Strength
If ethylene content is increased to improve impact resistance, then impact resistance is improved, but time to brittle failure decreases
Solution Approach 1:
The patent resolves this contradiction by changing the compositional parameters to include not just increased ethylene content (1.5-7.0 wt%) but also specific 1-hexene content (1.5-5.0 wt%) and controlled Mw/Mn ratio (7.0-20.0). This multi-parameter optimization ensures that impact resistance improves while time to brittle failure is maintained or enhanced, rather than degraded
3Productivity
If 1-hexene content is increased to improve processability, then extrusion speed is improved, but impact resistance decreases
Solution Approach 1:
The invention applies parameter changes by controlling 1-hexene content within 1.5-5.0 wt% alongside ethylene content (1.5-7.0 wt%) and Mw/Mn ratio (7.0-20.0). This balanced parameter set ensures that processability and extrusion speed are improved while impact resistance is maintained at acceptable levels, avoiding the trade-off that would occur with 1-hexene alone
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 exhibits enhanced impact resistance and extended time to brittle failure, allowing for higher extrusion speeds and reduced energy consumption, resulting in increased throughput and cost-effectiveness, while maintaining environmental benefits.
Implementation Method 1
using a Ziegler-Natta catalyst system for polymerization
Data Source
AI summary
The invention relates to a polypropylene composition comprising a terpolymer containing propylene, ethylene and 1-hexene wherein the polypropylene composition (i) has a content of ethylene derived units of at least 1.5 wt %; (ii) has a content of 1-hexene derived units of at least 1.5 wt %; (iii) has a melt flow rate of 0.10 to 0.70 g/10 min determined by ISO 1133-1:2011 (230° C., 2.16 kg); and (iv) has a ratio of weight average molecular weight (Mw) to numeric average molecular (Mn) weight of the terpolymer of 7.0 to 20.0, wherein Mw and Mn are measured according to ASTM D6474-12.