Continuous Diene Elastomer Synthesis with Gas Phase
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Solution Overview
Problem
Current mass or semi-mass polymerization processes for diene elastomers face limitations in achieving high conversion rates without medium expansion, flexibility in temperature control, and productivity, especially due to the challenges of maintaining reaction temperature and handling large volumes of unconverted monomers.
Innovation Solution
A continuous process for polymerizing conjugated dienes in a very concentrated medium using specific reactors with a gas phase, stirring wheels, and controlled residence time distribution, allowing for high conversion rates up to 100% and flexible temperature operation while minimizing solvent use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If bulk or semi-bulk polymerization is used to reduce solvent use and costs, then economic and environmental advantages are achieved, but the conversion rate is limited to below 40% due to medium expansion
Solution Approach 1:
The invention changes the physical state parameter of the reaction medium by introducing a gas phase (superheated steam or inert gas) into the polymerization system. This allows the reaction to proceed in a three-phase system (gas-liquid-solid) where the gas phase absorbs the expansion energy and prevents medium expansion, enabling conversion rates above 40% while maintaining bulk/semi-bulk conditions with minimal solvent use.
Solution Approach 2:
The gas phase acts as an intermediary that mediates between the polymerization reaction and the reaction medium. It absorbs the expansion energy and provides a pathway for heat removal, allowing high conversion rates to be achieved without the harmful expansion effects that normally limit bulk polymerization processes.
2Productivity
If conversion rate is increased above 40% in bulk polymerization, then productivity improves, but medium expansion occurs making temperature control impossible
Solution Approach 1:
The gas phase serves as an intermediary that absorbs expansion energy and provides efficient heat transfer pathways. This mediation allows the system to maintain temperature control even at conversion rates above 40%, as the gas phase can be circulated and temperature-controlled externally, preventing the runaway expansion that normally occurs in bulk polymerization.
Solution Approach 2:
The invention utilizes phase transition by introducing a gas phase into the liquid polymerization medium. The gas-liquid interface provides enhanced heat and mass transfer, and the gas phase can undergo pressure-volume changes that absorb expansion energy, thereby maintaining temperature control at high conversion rates.
3Loss of energy
If unconverted monomer volume is reduced by increasing conversion rate, then energy and economic costs decrease, but reaction temperature control becomes difficult
Solution Approach 1:
The gas phase acts as an intermediary heat transfer medium that enables efficient thermal management. It provides a large surface area for heat exchange and can be circulated through heat exchangers, allowing reaction temperature to be controlled even as conversion rate increases and monomer volume decreases, thereby reducing energy costs without sacrificing temperature control.
Solution Approach 2:
The gas phase enables continuous heat removal throughout the polymerization process. By maintaining gas circulation and phase contact throughout the reaction, the system can continuously manage the exothermic heat of polymerization, allowing conversion rates to increase to near 100% while maintaining temperature control through the continuous action of the gas phase heat transfer mechanism.
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
This process enhances productivity, reduces energy and environmental impacts, and maintains reaction control without medium expansion, making it economically and environmentally advantageous for industrial production.
Implementation Method 1
the polymerization of the monomer(s) into a diene elastomer in a stirred polymerization medium
Implementation Method 2
continuous movement of at least one stirring wheel around a rotating axis
Implementation Method 3
continuous discharge of the elastomer paste resulting from the polymerization
Implementation Method 4
the cutting of the discharged elastomer paste into particles
Implementation Method 5
the removal of the solvent from the particles obtained in the previous step
Implementation Method 6
the recovery of the diene elastomer from the particles thus obtained
Data Source
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AI summary
The present invention relates to a process for continuous synthesis, in a highly concentrated medium, of diene elastomers with a high degree of conversion, which comprises the following simultaneous steps: a) continuously introducing, into a polymerization reactor which has a gas phase and is equipped with at least one stirrer rotor and with a discharge device, at least i. one or more monomers to be polymerized, including at least one conjugated diene monomer, and ii. from 0% to 70% by weight of an organic solvent, calculated relative to the total weight of monomers + solvent, b) continuously polymerizing the monomer(s), c) stirring the polymerization medium by continuous movement of at least one stirrer rotor about a rotary shaft, d) continuously discharging the elastomer paste resulting from the polymerization, e) continuously conveying the discharged elastomer paste to a cutting device and cutting said paste into particles, and f) removing the solvent from the particles of the elastomer paste and g) recovering the diene elastomer from the particles obtained, and is characterized in that 1? the degree of conversion is at least 60%, at the limit of the first third of the reaction volume of the polymerization reactor, and 2? the standard deviation of the distribution function for residence time in the polymerization reactor is greater than the mean residence time divided by 2?3. This polymerization process, which is applicable in a highly concentrated medium, exhibits increased productivity, in particular making it possible to achieve a high degree of conversion which can be up to 100%, and allows flexibility in terms of the implementation thereof.