Gas-Phase Polypropylene Catalyst Pre-Contacting Bulk Density
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Solution Overview
Problem
Gas-phase polymerization processes for polyolefins, such as polypropylene, often result in lower bulk densities compared to slurry processes, which is a challenge in achieving high polymer quality.
Innovation Solution
A gas-phase process involving a catalyst system comprising a magnesium-containing support, a halogen-containing titanium compound, a phthalate-free internal electron donor, and an alkyl aluminum co-catalyst, where a portion of the co-catalyst and optionally the external electron donor are pre-contacted with the procatalyst before addition to the polymerization reactor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If gas-phase polymerization process is used, then productivity is improved, but bulk density decreases
Solution Approach 1:
The patent applies preliminary action by pre-contacting the co-catalyst and external electron donor with the procatalyst before adding to the polymerization reactor. This pre-contacting step modifies the catalyst system in advance to control polymer particle morphology and achieve higher bulk density in gas-phase polymerization. Specifically, the pre-contacted catalyst system allows for better control of polymerization kinetics and particle structure, resulting in bulk densities of at least 400 g/100 ml while maintaining high productivity
2Object-affected harmful factors
If phthalate-free internal electron donor is used, then environmental compatibility is improved, but bulk density decreases
Solution Approach 1:
The patent applies parameter changes by optimizing the combination of phthalate-free internal electron donor with specific external electron donors and co-catalysts. This changes the chemical parameters of the catalyst system to achieve both environmental compatibility and high bulk density. The patent specifies using internal electron donors without phthalate groups combined with external electron donors in specific molar ratios, which modifies the polymerization mechanism to produce particles with higher bulk density while maintaining the environmental benefit of phthalate-free formulation
3Volume of stationary object
If pre-contacting of co-catalyst with procatalyst is performed, then bulk density is improved, but process complexity increases
Solution Approach 1:
The patent applies merging by combining the pre-contacting step with the catalyst preparation process. Instead of treating pre-contacting as a separate complex operation, the patent integrates it into the catalyst formulation step, where the co-catalyst and external electron donor are pre-contacted with the procatalyst in a controlled manner before addition to the reactor. This merging of steps simplifies the overall process while achieving the desired bulk density improvement
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 significantly increases the bulk density of the resulting polyolefins, achieving densities of at least 400 g/100 ml, improving polymer quality and properties.
Implementation Method 1
a catalyst system comprising: a procatalyst comprising 1) a magnesium-containing support, 2) titanium, preferably a halogen-containing titanium compound, 3) a phthalate free internal electron donor; and 4) optionally an activator
Data Source
AI summary
The present invention relates to a process for the polymerization of a polyolefin, preferably polypropylene, in a polymerization reactor by contacting one or more olefins, preferably propylene, with a catalyst system in said reactor while stirring, said catalyst system comprising: * a procatalyst comprising 1) a magnesium-containing support, 2) titanium, 3) a phthalate-free internal electron donor; and 4) optionally an activator; wherein said procatalyst is obtained by the following process: i) contacting a compound R4, MgX42—, with an alkoxy- or aryloxy-containing silane compound to give a first intermediate reaction product, being a solid Mg(OR1)xX12-x, R4 is the same as R1 being a linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and preferably has between 1 and 20 carbon atoms; wherein X4 and X1 are each independently a halide; z is in a range of larger than 0 and smaller than 2, being 0<z<2; x is in a range of larger than 0 and smaller than 2, being 0<x<2; ii) optionally contacting the solid Mg(OR1)xX12-x obtained in step ii) with at least one activating compound selected from the group formed by activating electron donors and metal alkoxide compounds of formula M′(OR2), w(ORI)w or M2 (OR2)v-w(RI)w, to obtain a second intermediate product; wherein: M1 is a metal selected from the group consisting of Ti, Zr, Hf, Al or Si; v is the valency of M1; M2 is a metal being Si; v is the valency of M2; R2 and R3 are each independently a hydrocarbyl group; w is smaller than v, v is preferably 3 or 4; iii) contacting the first or second intermediate reaction product, obtained respectively in step i) or ii), with the halogen-containing Ti-compound, the internal electron donor and optionally an activator; * optionally an external electron donor; and * a co-catalyst, being a alkyl aluminum co-catalyst preferably having formula AlHnR3-n, wherein H is a hydride; n is 0, 1 or 2, preferably 0; wherein R is a C1-C12 alkyl group, preferably ethyl; wherein a portion of the co-catalyst and optionally a portion of the external electron donor is (are) pre-contacted with the procatalyst prior to the addition of the catalyst system to the polymerization reactor. The present invention also relates to a polyolefin and a shaped article comprising said polyolefin.