Olefin Polymerization Procatalyst with Low Xylene Solubles
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Solution Overview
Problem
Existing Ziegler-Natta procatalysts for polymerization have high xylene solubles values and may contain toxic components, such as benzoyl chloride, and lack control over molecular weight distribution and productivity.
Innovation Solution
A procatalyst system based on a magnesium compound reacted with tetravalent titanium halide, an activator, and an internal donor like 4-[benzoyl(methyl)amino]pentan-2-yl benzoate, with specific compositions and processing steps to achieve improved molecular weight distribution, low xylene solubles, and high productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional Ziegler-Natta procatalysts are used, then catalyst activity is achieved, but xylene solubles values are too high and molecular weight distribution control is poor
Solution Approach 1:
The invention changes the chemical composition parameters of the catalyst system by introducing specific internal donors (compounds of formula A with R1-R6 being alkyl, aryl, or hydrogen) and activators (monoesters), and optimizing their ratios (internal donor/Ti: 0.05-5 mol/mol, activator/Ti: 0.01-1 mol/mol). This parameter optimization resolves the contradiction by achieving both low xylene solubles (<6 wt%, preferably <4 wt%) and controlled molecular weight distribution.
Solution Approach 2:
The invention creates a composite catalyst system combining magnesium compound, tetravalent titanium halide, internal donor (formula A), and activator (monoester) in specific compositions. This composite structure integrates multiple functional components that work synergistically to simultaneously control molecular weight distribution and reduce xylene solubles while maintaining high catalyst productivity.
2Productivity
If benzoyl chloride is used as activator, then catalyst performance is improved, but toxicity increases
Solution Approach 1:
The invention replaces the toxic but effective benzoyl chloride activator with alternative activators having lower toxicity, such as carboxylic acids (acetic acid, propionic acid), esters (ethyl formate, ethyl acetate), or carbon dioxide. These alternative activators achieve comparable catalyst activity and productivity without the toxic hazards of benzoyl chloride, resolving the contradiction between performance and safety.
Solution Approach 2:
The invention transforms the challenge of finding non-toxic activators into an opportunity by discovering that common, low-toxicity compounds like carboxylic acids and esters can effectively activate the catalyst system. This converts the limitation of avoiding toxic substances into a benefit by using safer, more environmentally friendly activators that maintain high catalyst productivity.
3Ease of manufacture
If catalyst composition is simplified, then ease of manufacture is improved, but control over xylene solubles and molecular weight distribution deteriorates
Solution Approach 1:
The internal donor compound of formula A serves multiple functions simultaneously: it controls molecular weight distribution, reduces xylene solubles, and stabilizes the catalyst structure. This multi-functionality allows the catalyst to achieve precise product properties without requiring complex multi-component formulations, thus maintaining ease of manufacture while improving manufacturing precision.
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 procatalyst system provides polyolefins with high molecular weight, narrow molecular weight distribution, low xylene solubles, and enhanced hydrogen response, along with improved catalyst productivity and reduced toxicity, meeting market requirements for stiffness and tensile properties.
Implementation Method 1
halogenating a magnesium compound of the formula MgR'R" wherein R' is an alkoxide or aryloxide group and wherein R" is an alkoxide or aryloxide group or halogen, with a tetravalent titanium halide in the presence of a halohydrocarbon and an activator being a monoester; to form a first intermediate product
Implementation Method 2
contacting the first intermediate product with a mixture of a tetravalent titanium halide and an internal electron donor according to Formula A; to obtain a second intermediate product
Implementation Method 3
A procatalyst for polymerization of olefins
Data Source
AI summary
The present invention relates to a procatalyst for polymerization of olefins, which procatalyst is based on a magnesium compound of the formula MgR'R" wherein R' is an alkoxide or aryloxide group and wherein R" is an alkoxide or aryloxide group or halogen, preferably a tetravalent titanium halide, an activator being a monoester and an internal donor represented by a compound according to formula (A) wherein each R8 group is independently a linear, branched or cyclic hydrocarbyl group selected from alkyl, alkenyl, aryl, aralkyi, or alkylaryl groups, and one or more combinations thereof, preferably having from 1 to 30 carbon atoms; R1, R2, R3, R4, R5, and R6 are each independently selected from hydrogen or a linear, branched or cyclic hydrocarbyl group, selected from alkyl, alkenyl, aryl, aralkyi, or alkylaryl groups, and one or more combinations thereof, preferably having from 1 to 20 carbon atoms; R7 is a hydrogen or a linear, branched or cyclic hydrocarbyl group, selected from alkyl, alkenyl, aryl, aralkyi, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof, preferably having from 1 to 20 carbon atoms; N is nitrogen atom; O is oxygen atom; and C is carbon atom. Moreover, the present invention relates to a polymerization catalyst system comprising the procatalyst, a co-catalyst and optionally an external electron donor; to a process of making a polyolefin, preferably a polypropylene by contacting an olefin with the catalyst system; to a polyolefin, preferably a polypropylene, obtained by or obtainable by the process; to a polyolefin, preferably a polypropylene, having a molecular weight distribution of between 4 and 15, a molecular weight (Mw) of between 300,000 to 1,500,000 g/mol, a melting temperature of more than 150 °C, a value for the xylene solubles of less than 4 wt.% and a shaped article therefrom.