Thermoplastic Elastomer Composition Dynamic Crosslinking
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Solution Overview
Problem
Existing thermoplastic elastomer compositions produced using twin-screw extruders often fail to achieve sufficient dispersibility of the island phase, resulting in suboptimal mechanical properties and appearance in molded products, with a need for improved production processes to enhance both mechanical properties and productivity.
Innovation Solution
A thermoplastic elastomer composition is produced by dynamically crosslinking an ethylene/α-olefin/non-conjugated polyene copolymer, a polyolefin resin, and a softener, using a batch mixer with intermeshing rotors under specific conditions, including controlled shear rates, temperatures, and crosslinking agent introduction, to achieve better dispersibility and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a twin-screw extruder is used to produce thermoplastic elastomer composition, then production efficiency is improved, but dispersibility of the island phase deteriorates
Solution Approach 1:
The mixing process is divided into two distinct stages: first mixing the rubber and polyolefin-based resin without crosslinking agent, then adding the crosslinking agent in a second step. This segmentation prevents premature crosslinking that would hinder dispersion, while still achieving efficient production through continuous processing.
Solution Approach 2:
The rubber and polyolefin-based resin are pre-mixed and homogenized before the crosslinking agent is introduced. This preliminary action ensures that the base components are properly dispersed and positioned, allowing the crosslinking agent to subsequently form uniformly distributed crosslinked structures without compromising dispersibility.
2Productivity
If crosslinking agent is added early in the mixing process, then crosslinking reaction efficiency is improved, but dispersibility of island phase deteriorates
Solution Approach 1:
The rubber and polyolefin-based resin are pre-mixed and homogenized before the crosslinking agent is introduced. This preliminary action ensures that the base components are properly dispersed and positioned, allowing the crosslinking agent to subsequently form uniformly distributed crosslinked structures without compromising dispersibility.
Solution Approach 2:
The crosslinking agent is extracted or separated from the initial mixing process and introduced at a later stage. This extraction prevents the crosslinking agent from interfering with the initial dispersion of the rubber and resin phases, allowing optimal dispersibility to be achieved before crosslinking begins.
3Strength
If island phase dispersibility is improved, then mechanical properties are improved, but production complexity increases
Solution Approach 1:
The mixing process is divided into two distinct stages: first mixing the rubber and polyolefin-based resin without crosslinking agent, then adding the crosslinking agent in a second step. This segmentation prevents premature crosslinking that would hinder dispersion, while still achieving efficient production through continuous processing.
Solution Approach 2:
The two-stage mixing process is implemented as a continuous operation using a twin-screw extruder, where the first stage mixing is immediately followed by the second stage crosslinking agent addition. This continuity maintains production efficiency while achieving the dispersibility needed for excellent mechanical properties.
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 process results in molded products with enhanced rubber elasticity, appearance, and increased extruder output, improving productivity and mechanical properties while minimizing gel-like substance formation.
Implementation Method 1
dynamically crosslinking an ethylene/α-olefin/non-conjugated polyene copolymer (A), a polyolefin resin (B), a softener (C)... and a crosslinking agent (D), by the use of a batch mixer having intermeshing rotors under the conditions satisfying the following requirements
Implementation Method 2
50≤P1≤300 wherein P1 is defined by the following formula (i): P1=Tave.×γ×t1/1000 wherein the residence time (sec) after the introduction of the crosslinking agent (D) is denoted as t1 sec, and the average rate (sec -1
Implementation Method 3
the polyolefin-based resin constitutes a hard segment (hard phase) which provides a pseudo crosslinked structure
Implementation Method 4
the crosslinking agent (D) is an organic peroxide and the amount of the crosslinking agent (D) compounded is 0.01 to 3.0 parts by mass per 100 parts by mass of the total of the copolymer (A) and the resin (B)
Implementation Method 5
kneading the components under the specific conditions using a batch mixer... by the use of a batch mixer having intermeshing rotors under the conditions satisfying the following requirements
Data Source
AI summary
The present invention is a thermoplastic elastomer composition obtained by dynamically crosslinking an ethylene/α-olefin/non-conjugated polymer copolymer (A), a polyolefin resin (B), a softener (C) in an amount of 1 to 200 parts by mass per 100 parts by mass of the total of the copolymer (A) and the resin (B), and a crosslinking agent (D) by the use of a batch mixer under the conditions satisfying the following requirements (1) to (4): (1) 50≤P1≤300 wherein P1 is defined by the following formula (i) : P1 = γave.×Log(t1) (i) (in the formula (i), t1 denotes a residence time (sec) after the introduction of the crosslinking agent (D), and γave. denotes an average rate (sec-1) of shear rates γ in the t1); (2) 900≤P2≤1450 wherein P2 is defined by the following formula (ii) : P2 = (Tave.+273)×Log(t1) (ii) (in the formula (ii), Tave. denotes an average resin temperature (°C) after the introduction of the crosslinking agent (D), and t1 denotes a residence time (sec) after the introduction of the crosslinking agent (D)); (3) -2.5≤P3≤1.5 wherein P3 is defined by the following formula (iii) : P3 = Log (t1/t2) (iii) (in the formula (iii), t1 denotes a residence time (sec) after the introduction of the crosslinking agent (D), and t2 denotes a time (sec) required for the residual amount of the crosslinking agent (D) to become not more than 1 ppm of the introduction amount thereof at the average resin temperature Tave. after the introduction of the crosslinking agent (D)); and (4) the crosslinking agent (D) is introduced into the batch mixer after the ethylene/α-olefin/non-conjugated polyene copolymer (A), the polyolefin resin (B) and the softener (C) have been introduced. According to the thermoplastic elastomer composition of the present invention, a molded product having excellent mechanical properties such as rubber elasticity and excellent appearance can be produced, and further, melt density and extruder output can be enhanced, and improvement in productivity can be accomplished.