Conjugated Diene Polymer Composition for Compression Set and Cold Resistance
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Solution Overview
Problem
Conventional rubber compositions using EPDM face challenges in elevating crosslinking density, achieving favorable compression set, and improving cold resistance in terms of polymer design.
Innovation Solution
A conjugated diene-based polymer with a specified structure, characterized by specific molar ratios of structure units, Mooney viscosity, glass transition temperature, heat of crystallization, and aromatic vinyl monomer content, is developed to address these challenges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If EPDM rubber composition is used to achieve heat resistance and sealing properties, then heat resistance is improved, but crosslinking density and compression set cannot be sufficiently improved
Solution Approach 1:
The patent changes the chemical composition parameters by introducing specific structure units (1,2-vinyl bond units and hydrogenated 1,2-vinyl bond units) with controlled molar ratios. This parameter change enables the rubber to achieve both high heat resistance and improved compression set by optimizing the molecular structure while maintaining the base EPDM composition.
Solution Approach 2:
The patent creates a composite rubber structure by combining multiple structure units (1,4-cis bond units, 1,2-vinyl bond units, hydrogenated 1,2-vinyl bond units, and butylene structure units) in specific proportions. This composite approach allows the material to simultaneously exhibit heat resistance from the saturated backbone and improved compression set from the strategic placement of vinyl and hydrogenated vinyl units.
2Strength
If rubber hardness is increased to improve sealing properties, then sealing properties are improved, but cold resistance deteriorates
Solution Approach 1:
The patent adjusts the molar ratio parameters of different structure units, specifically controlling the content of 1,2-vinyl bond units and hydrogenated 1,2-vinyl bond units. This parameter optimization allows the rubber to maintain adequate hardness for sealing while improving cold resistance by preventing excessive crystallization at low temperatures.
Solution Approach 2:
The patent introduces local structural variations through hydrogenated 1,2-vinyl bond units distributed within the polymer chain. These localized structural features provide flexibility and prevent rigid crystallization at low temperatures, thereby improving cold resistance while maintaining overall sealing properties through the bulk material's hardness.
3Reliability
If crosslinking density is elevated to improve compression set, then compression set is improved, but processability deteriorates
Solution Approach 1:
The patent optimizes the molar ratio of 1,2-vinyl bond units and hydrogenated 1,2-vinyl bond units to achieve balanced crosslinking. This parameter control allows sufficient crosslinking density for good compression set while maintaining enough uncrosslinked chains for acceptable processability during manufacturing.
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 conjugated diene-based polymer composition exhibits improved processability, heat resistance, compression set, and cold resistance, making it suitable for practical applications.
Implementation Method 1
having a glass transition temperature of −50° C. or less measured by differential scanning calorimetry (DSC)
Implementation Method 2
having a crystallization peak-derived heat of crystallization of 2.5 J/g or more and 50 J/g or less
Data Source
AI summary
Provided are a conjugated diene-based polymer, a conjugated diene-based polymer composition, and a crosslinked product of a conjugated diene-based polymer, etc. that have no problems in practical use with processability and heat resistance and are excellent in compression set and cold resistance. The present invention provides a conjugated diene-based polymer satisfying the following mathematical expression (A): mathematical expression (A): 35 (%)≤100*(b+d)/(a+b+c+d)≤99 (%) wherein constituent molar ratios of respective structure units represented by the following structural formulas (1) to (4) are defined as a, b, c, and d, respectively, having a Mooney viscosity at 100° C. of 25 or more and 125 or less, having a glass transition temperature of −50° C. or less measured by differential scanning calorimetry (DSC), and having a crystallization peak-derived heat of crystallization of 2.5 J/g or more and 50 J/g or less.