Supported Catalyst Drying for Copolymer Molecular Weight Control
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Solution Overview
Problem
Current methods for producing copolymers of ethylene and α-olefins using supported polymerization catalysts struggle with controlling the molecular weight component, particularly the high molecular weight fraction (>1,000,000), which affects the properties and productivity of the resulting polymers.
Innovation Solution
A method involving a supported polymerization catalyst system where the support material is dried at a temperature range of 0° C. to 195° C. in an inert atmosphere and treated with an organometallic compound, specifically trialkylaluminium, to reduce the high molecular weight component fraction to less than 6%, preferably less than 4%, and most preferably less than 2.5%, thereby enhancing catalyst productivity and controlling polymer properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the support material is dried at high temperature (200-850°C) during calcination, then the water content and hydroxyl content of the support are reduced, but the catalyst productivity decreases and the fraction of high molecular weight component increases
Solution Approach 1:
The patent changes the drying temperature parameter from the conventional high range (200-850°C) to a low range (0-195°C). This parameter change fundamentally alters the catalyst's molecular weight control capability, reducing the high molecular weight fraction to less than 6% while maintaining high productivity. The low temperature drying prevents excessive hydroxyl group formation that would otherwise lead to high molecular weight polymer components.
2Reliability
If the support material undergoes traditional calcination treatment, then the hydroxyl content is reduced, but the fraction of high molecular weight component (>1,000,000) in copolymers increases to above 6%
Solution Approach 1:
The invention changes the thermal treatment parameter from high temperature calcination to low temperature drying (0-195°C). This parameter modification produces the opposite effect of traditional calcination: instead of reducing hydroxyl content through high heat, the low temperature process preserves sufficient hydroxyl groups that act as chain transfer agents, thereby controlling molecular weight and reducing the high molecular weight fraction to below 6%.
3Ease of manufacture
If conventional drying temperatures are used, then the support material is adequately prepared, but the catalyst productivity is reduced by almost 50%
Solution Approach 1:
The patent inverts the conventional wisdom by using low temperature (0-195°C) instead of high temperature for drying the support material. This counterintuitive parameter change actually enhances catalyst productivity by almost 50% compared to conventional high temperature treatment. The low temperature process maintains beneficial surface properties that promote higher catalytic activity and polymerization efficiency.
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 approach significantly reduces the fraction of high molecular weight components in copolymers, improving catalyst productivity by almost 50% and enabling the production of polymers with reduced gel formation in films, thus enhancing the quality and process efficiency of ethylene and α-olefin copolymers.
Implementation Method 1
By dried is meant the partial or total removal of volatile elements, for example water, from the support material. The volatile elements may be removed by passing nitrogen over the support material or more preferably by heating the support material.
Implementation Method 2
A preferred method of drying is by heating the support at a temperature in the range 25°C to 195°C, more preferably in the range 30°C to 180°C and most preferred in the range 30 to 95°C.
Implementation Method 3
The porous supports are pretreated with the organometallic compound preferably an organoaluminium compound and most preferably a trialkylaluminium compound in a dilute solvent.
Data Source
AI summary
A method for the preparation of copolymers of ethylene and α-olefins having a fraction (%) of the molecular weight component of >1,000,000 of less than 6% comprises polymerising ethylene and an α-olefin in the presence of a supported polymerisation catalyst system comprising (a) a transition metal compound (b) a porous support material, and (c) an activator characterized in that the support material has been (i) dried at a temperature in the range 0° C. to 195° C. in an inert atmosphere, and (ii) treated with an organometallic compound. The resultant supported catalyst systems show improved productivity and allow for control of the resultant polymer properties. Particularly preferred supported catalyst systems are those comprising metallocene complexes.