Cable Insulation Polypropylene Copolymer for Flexibility and Recyclability
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Solution Overview
Problem
Existing polypropylene resins used in electric power cables face challenges with low flexibility, high rigidity, and production stability issues due to high rubber content, and crosslinked polymers are difficult to recycle, leading to environmental concerns and performance limitations.
Innovation Solution
An ethylene-propylene block copolymer resin is developed through staged polymerization in reactors using a Ziegler-Natta catalyst with a combination of non-aromatic alkoxy ester and phthalic acid ester-based internal electron donors, achieving a melting temperature of 150-160°C, optimal solvent extract content, and intrinsic viscosity ratios for improved flowability and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If crosslinked polymers (XLPE) are used to maintain mechanical and electrical characteristics at operating temperature, then thermal resistance and mechanical strength are improved, but recyclability deteriorates
Solution Approach 1:
The patent changes the fundamental parameter of polymer crosslinking state from crosslinked to non-crosslinked. The polypropylene resin is specifically designed to be non-crosslinked while achieving high thermal resistance through controlled crystallinity (40-70%) and molecular weight (intrinsic viscosity 2.0-4.0 dl/g), allowing it to withstand cable operating temperatures without crosslinking, thus enabling recyclability.
2Temperature
If polypropylene is used to raise operating temperature to 110°C, then thermal resistance is improved, but flexibility deteriorates due to high rigidity
Solution Approach 1:
The patent creates a composite material system by blending polypropylene resin with ethylene-propylene rubber copolymer. The rubber component (30-70 parts by weight) provides flexibility and impact resistance, while the polypropylene resin (70-30 parts by weight) maintains high melting point and thermal resistance. This composite approach allows the insulation layer to achieve both flexibility for cable bending and thermal resistance for high-temperature operation.
Solution Approach 2:
The patent applies local quality by creating a heterogeneous blend where different components perform different functions. The polypropylene resin provides thermal resistance and structural stability, while the ethylene-propylene rubber copolymer provides flexibility and impact resistance. This localized functional distribution within the composite material resolves the contradiction between rigidity and flexibility.
3Ease of operation
If rubber is added to improve flexibility of polypropylene, then flexibility is improved, but production stability deteriorates due to stickiness of powders
Solution Approach 1:
The patent changes the molecular weight parameter of the ethylene-propylene rubber copolymer to an optimized range (intrinsic viscosity 1.5-3.0 dl/g). This parameter control prevents excessive stickiness of powder during polymerization while maintaining sufficient flexibility. The specific viscosity range balances the rubber's flexibility contribution with powder flowability for stable continuous production.
4Temperature
If organic nucleating agent is added to reduce crystal size, then heat deformation resistance is improved, but cost increases and adverse effects occur
Solution Approach 1:
The patent extracts and eliminates the organic nucleating agent from the formulation. Instead of using chemical additives to control crystal size, the patent achieves heat deformation resistance through physical parameters: controlling the polypropylene resin's crystallinity (40-70%) and molecular weight (intrinsic viscosity 2.0-4.0 dl/g). This approach reduces crystal size and improves heat resistance without adding costly chemicals or causing adverse effects.
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 ethylene-propylene block copolymer resin exhibits excellent production stability, flexibility, low-temperature impact resistance, and dielectric breakdown strength, making it suitable for high-voltage electric power cables while being recyclable and environmentally friendly.
Implementation Method 1
polymerization of a propylene homopolymer or an ethylene-propylene random copolymer with an ethylene-propylene rubber copolymer in stages in reactors in the presence of a Ziegler-Natta catalyst
Implementation Method 2
the ethylene-propylene block copolymer has a melting temperature (Tm) of 150 to 160°C
Data Source
AI summary
An ethylene-propylene block copolymer resin is provided that is suitable as an insulation layer of an electric power cable. The ethylene-propylene block copolymer is obtained by polymerization of a propylene homopolymer or an ethylene-propylene random copolymer with an ethylene-propylene rubber copolymer in stages in reactors in the presence of a Ziegler-Natta catalyst obtained using two internal electron donors, wherein one of the two internal electron donors is a compound comprising an ester group and an alkoxy group, the ethylene-propylene block copolymer has a melting temperature of 150 to 160° C., the content of the solvent extract thereof when extracted at room temperature with xylene is 30 to 50% by weight, and the intrinsic viscosity of the solvent extract is 1.5 to 3.0 dl/g.