Thermoplastic elastomer composition and molded body of same
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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 extrusion processability, particularly when exposed to high-temperature environments for extended periods.
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, fatty acid-based lubricant, and softener, achieving a 1/2 crystallization time of 200 seconds or less and a maximum spherulite size of 8 µm or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a thermoplastic elastomer composition includes a softener to improve flexibility and processability, then extrusion processability is improved, but heat aging resistance deteriorates due to softener migration and bleeding at high temperatures
Solution Approach 1:
The patent changes the molecular weight parameter of the crystalline polyolefin to 350,000 or more (weight-average molecular weight) and controls the softener content within specific ranges (80-140 parts by mass based on 100 parts of copolymer). These parameter changes optimize the balance between processability and heat aging resistance by ensuring sufficient molecular entanglement to restrict softener mobility while maintaining extrusion flow characteristics.
Solution Approach 2:
The patent creates a composite material system combining cross-linked ethylene/α-olefin/nonconjugated polyene copolymer with crystalline polyolefin and softener. The cross-linked network structure of the copolymer acts as a matrix that traps and restrains the softener, while the crystalline polyolefin provides structural support. This composite structure prevents softener migration while maintaining processability.
2Ease of operation
If the softener content is increased to improve flexibility and moldability, then extrusion processability is improved, but oil bleeding phenomenon occurs at high temperatures
Solution Approach 1:
The patent optimizes the softener content parameter within the range of 80-140 parts by mass based on 100 parts of copolymer, and controls the crystalline polyolefin content at 360-460 parts by mass. This parameter optimization ensures adequate softener for moldability while the cross-linked structure and crystalline matrix prevent excessive softener migration and oil bleeding.
Solution Approach 2:
The crystalline polyolefin acts as an intermediary substance between the cross-linked copolymer matrix and the softener. It provides a structured environment that accommodates the softener while restricting its mobility, thereby preventing oil bleeding while maintaining moldability.
3Ease of manufacture
If a thermoplastic elastomer composition uses conventional materials to achieve basic mechanical properties, then manufacturing is simplified, but heat aging resistance and mechanical strength are insufficient
Solution Approach 1:
The patent specifies precise parameter ranges: weight-average molecular weight of 350,000 or more, intrinsic viscosity of 4.0 dL/g or more, ethylene content of 57.0% by mass or more, and nonconjugated polyene content of 4.0% by mass or more. These parameter specifications ensure adequate mechanical strength and heat aging resistance while maintaining manufacturability through clear formulation guidelines.
Solution Approach 2:
The patent employs a composite material system with cross-linked copolymer, crystalline polyolefin, and softener in specific proportions. This composite structure provides enhanced mechanical strength and heat aging resistance compared to conventional single-phase thermoplastic elastomers, while the clear composition specifications facilitate manufacturing.
4Productivity
If the crystallization time is reduced to improve production efficiency, then productivity is improved, but spherulite size control becomes more difficult affecting surface quality
Solution Approach 1:
The patent controls the 1/2 crystallization time at 120°C to be 200 seconds or less by optimizing the crystalline polyolefin characteristics (melt flow rate of 8.0 g/10 min or less) and composition ratios. This parameter control achieves rapid crystallization for high productivity while the resulting fine spherulite structure (maximum size 8 μm or less) ensures good surface quality.
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 excellent heat aging resistance, hardness, and extrusion processability, with improved mechanical properties such as tensile modulus and strength, suitable for applications like window frame seals and glass run channels.
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
Figure 1~2
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 1/2 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.