Ethylene/alpha-olefin Interpolymer Pellet Flowability
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Solution Overview
Problem
Low molecular weight ethylene/alpha-olefin copolymers exhibit stickiness and poor materials handling due to a low-density, low molecular weight oligomeric fraction, leading to issues with pellet massing and flowability, and high metal residues and melting temperatures.
Innovation Solution
A process for polymerizing ethylene/alpha-olefin interpolymers in solution, with specific reactor conditions such as high ethylene concentration, Reynolds Number, catalyst efficiency, residence time, and alpha-olefin concentration, to produce polymers with reduced High Comonomer Content (HCC) and lower metal residues, resulting in improved pellet flowability and lower melting temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional polymerization processes are used to produce low molecular weight ethylene/alpha-olefin copolymers, then the desired molecular weight and comonomer content are achieved, but pellet stickiness and poor flowability occur due to oligomeric fractions
Solution Approach 1:
The patent applies parameter changes by optimizing reactor ethylene concentration to greater than or equal to 14.0 kg/m³, controlling residence time, and adjusting Reynolds Number to modify the polymerization kinetics. These parameter changes reduce the formation of oligomeric fractions while maintaining desired molecular weight, thereby improving pellet flowability without sacrificing manufacturing precision
Solution Approach 2:
The patent implements feedback control through continuous monitoring of HCC values and molecular weight distribution during polymerization. By measuring these parameters in real-time and adjusting reactor conditions accordingly, the process maintains optimal conditions to minimize stickiness-causing oligomers while achieving target polymer properties
2Productivity
If conventional catalyst systems are used, then polymerization efficiency is achieved, but high metal residues remain in the polymer product
Solution Approach 1:
The patent employs parameter changes by optimizing catalyst concentration, reactor temperature, and residence time to enhance catalyst efficiency. These adjustments maximize polymer production per unit of catalyst while minimizing metal residue accumulation in the final polymer product
Solution Approach 2:
The patent implements catalyst recovery and recycling systems that separate and recover metal catalysts from the polymerization mixture. This approach allows continuous use of catalysts at high efficiency while removing metal residues that would otherwise contaminate the polymer product
3Productivity
If standard reactor conditions are applied, then production rate is maintained, but oligomeric fractions cause pellet massing and handling issues
Solution Approach 1:
The patent applies dynamics by continuously adjusting reactor conditions including ethylene concentration, monomer feed rates, and agitation speed during polymerization. These dynamic adjustments optimize the balance between production rate and oligomer formation, maintaining high productivity while minimizing harmful oligomeric fractions that cause pellet massing
Solution Approach 2:
The patent implements periodic action through pulsed monomer feeding and staged catalyst addition. This periodic approach controls the polymerization rate to prevent excessive oligomer formation while maintaining overall high production rates through optimized cycle timing
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 effectively reduces HCC to less than 6.0%, inorganic content to below 40 ppm, and melting temperatures to below 72°C, enhancing pellet flowability and reducing metal residues, thereby improving handling and processing characteristics.
Implementation Method 1
polymerizing ethylene, in solution, in at least one reactor, in the presence of at least one catalyst
Implementation Method 2
polymerizing ethylene, in solution, in at least one reactor, in the presence of at least one catalyst, and wherein the reactor ethylene concentration is greater than, or equal to 14.0 kg/m³
Data Source
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AI summary
The invention provides compositions, each comprising an ethylene/alpha-olefin interpolymer, which has a reduced level of a low density, low molecular weight oligomeric fraction, as indicated by an HCC value, as described herein, and reduced levels of inorganic content or lower Tm. The invention also provides processes for forming such interpolymers.