Polypropylene Pipe Composition for Pressure Resistance and Cold Impact
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Solution Overview
Problem
Polypropylene copolymers used in pipe applications face a challenge in achieving a balance between impact resistance and stiffness, particularly at low temperatures, which affects their performance in high-pressure applications without compromising pressure resistance.
Innovation Solution
A polypropylene composition comprising a copolymer of propylene with comonomer units derived from 1-butene or 1-hexene, polymerized in the presence of a single site catalyst system, blended with a copolymer of ethylene with comonomer units from 1-butene and/or 1-hexene, to enhance impact properties while maintaining pressure resistance and stiffness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the amount of comonomer in propylene copolymer is decreased to increase stiffness, then stiffness is improved, but impact resistance deteriorates
Solution Approach 1:
The patent uses a composite material system consisting of propylene copolymer (A) and ethylene copolymer (B) blended together. The propylene copolymer provides stiffness and pressure resistance, while the ethylene copolymer with higher comonomer content contributes impact strength and toughness. This composite approach allows the final pipe material to achieve a balanced combination of stiffness and impact resistance that neither polymer could achieve alone.
2Strength
If propylene copolymer is used for high pressure pipes to ensure pressure resistance, then pressure resistance is improved, but impact strength at low temperatures deteriorates
Solution Approach 1:
The patent changes the compositional parameters by incorporating ethylene copolymer (B) with specific comonomer content (1.0-25.0 wt.-%) and density (910.0-940.0 kg/m³) into the propylene copolymer matrix. This parameter adjustment allows the material to maintain pressure resistance from the propylene component while gaining low-temperature impact strength from the ethylene component with appropriate comonomer incorporation.
3Strength
If single site catalyzed propylene 1-hexene random copolymer is used to achieve good balance of stiffness and pressure resistance, then stiffness and pressure resistance are improved, but impact strength deteriorates
Solution Approach 1:
The ethylene copolymer (B) acts as an intermediary component that mediates between the stiff but brittle propylene copolymer (A) and the required impact strength. By blending these two polymers in specific ratios (70-95 wt.-% propylene copolymer and 5-30 wt.-% ethylene copolymer), the ethylene copolymer serves as a toughening agent that improves impact strength while the propylene copolymer maintains the structural stiffness and pressure resistance.
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 resulting pipes exhibit improved impact strength and pressure resistance, with a balanced stiffness, as demonstrated by increased Charpy notched impact strength and prolonged pipe pressure test stability, making them suitable for both hot and cold water applications.
Implementation Method 1
polymerizing propylene and 1-butene or 1-hexene in a multistage process in the presence of a single site catalyst system to obtain the copolymer of propylene with comonomer units derived from 1-butene or 1-hexene (A)
Data Source
Figure 1
Figure 2~3
AI summary
The present invention relates to a pipe comprising a polypropylene composition, which comprises a copolymer of propylene with comonomer units derived from 1-butene or 1-hexene and a copolymer of ethylene with comonomer units derived from 1-butene and/or 1-hexene, a process for producing said pipe and the use of said polypropylene composition for the production of a pipe.