Cross-Linked Thermoplastic Elastomer Composition for Heat-Aging Extrusion
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Solution Overview
Problem
Existing thermoplastic elastomer compositions, such as those described in Patent Literature 1, lack sufficient heat aging resistance, hardness, and mechanical properties, particularly when exposed to high-temperature environments, and exhibit issues with surface roughness during extrusion molding.
Innovation Solution
A thermoplastic elastomer composition comprising a cross-linked ethylene/α-olefin/nonconjugated polyene copolymer with specific molecular weight, intrinsic viscosity, ethylene content, and nonconjugated polyene content, combined with a phenolic resin-based cross-linking agent, crystalline polyolefin, softener, and fatty acid-based lubricant, to achieve improved heat aging resistance, hardness, and extrusion processability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a thermoplastic elastomer composition including a softener is used to form a slidable covering body, then the covering body achieves basic flexibility and processability, but the difference in softener concentration between the covering body and substrate causes softener migration and bleeding phenomenon at high temperature
Solution Approach 1:
The invention changes the chemical composition parameters by introducing a specific cross-linked polyolefin resin with controlled molecular weight (350,000 or more) and intrinsic viscosity (4.0 dL/g or more), and adjusting the softener content to 80 parts by mass or more based on 100 parts by mass of the copolymer, to achieve both processability and heat aging resistance without softener bleeding
Solution Approach 2:
The invention creates a composite material system combining a cross-linked ethylene/α-olefin/nonconjugated polyene copolymer with a phenolic resin-based cross-linking agent, crystalline polyolefin, softener, and fatty acid-based lubricant in specific proportions, where the synergistic interaction of components achieves both extrusion processability and excellent heat aging resistance
2Ease of operation
If the softener content is increased to improve flexibility and processability, then the material becomes easier to process, but the heat aging resistance deteriorates due to increased softener migration tendency
Solution Approach 1:
The invention optimizes the softener content parameter to 80 parts by mass or more based on 100 parts by mass of the copolymer, combined with specific molecular weight and intrinsic viscosity parameters of the cross-linked polyolefin resin, to achieve a balance where high softener content provides processability while the cross-linked structure prevents bleeding
Solution Approach 2:
The invention applies different functional components in specific proportions: the cross-linked polyolefin resin provides structural stability to prevent migration, while the softener provides flexibility and processability, creating local functional zones within the material structure
3Strength
If the molecular weight of the polyolefin is increased to improve mechanical strength, then the tensile strength increases, but the extrusion processability deteriorates due to reduced flowability
Solution Approach 1:
The invention sets the molecular weight parameter to 350,000 or more and intrinsic viscosity to 4.0 dL/g or more, which provides high tensile strength while the cross-linked structure and specific composition maintain adequate flowability for extrusion processing
Solution Approach 2:
The invention adjusts the melting point parameter to 150-170°C for the crystalline propylene, which optimizes the balance between mechanical strength (higher melting point) and extrusion processability (adequate flow at processing temperatures)
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 demonstrates excellent heat aging resistance, hardness, and mechanical properties, including tensile modulus and strength, while maintaining good extrusion processability, resulting in improved performance of molded articles.
Implementation Method 1
a cross-linked product of an ethylene/α-olefin/nonconjugated polyene copolymer (A), wherein the α-olefin has 3 or more carbon atoms, satisfying the following requirements (a1) to (a4), with a phenolic resin-based cross-linking agent (E)
Implementation Method 2
the thermoplastic elastomer composition (I) has a 1⁄2 crystallization time at 120° C. of 200 seconds or less, and a polyolefin component comprised in the thermoplastic elastomer composition (I) has a maximum spherulite size in a range of 8 μm or less
Data Source
AI summary
Provided is, for example, a thermoplastic elastomer composition having excellent heat aging resistance when exposed to a high-temperature environment for a long period of time, also excellent hardness and mechanical properties as well as excellent extrusion processability.A thermoplastic elastomer composition (I) including a cross-linked product of an ethylene/α-olefin/nonconjugated polyene copolymer (A) having a weight-average molecular weight of 350,000 or more, with a phenolic resin-based cross-linking agent (E), and including 360 to 460 parts by mass of a crystalline polyolefin (B), 2 to 6 parts by mass of a fatty acid-based lubricant (D), and 80 parts by mass or more of a softener (C1), relative to 100 parts by mass of the copolymer (A), in which the thermoplastic elastomer composition (I) has a ½ crystallization time at 120° C. of 200 seconds or less, and a polyolefin component included in the thermoplastic elastomer composition (I) has a maximum spherulite size in a range of 8 μm or less.