WO2020257627A1 - Synthèse de polypropylène ramifié à longue chaîne au moyen de catalyseurs ziegler-natta hétérogènes - Google Patents

Synthèse de polypropylène ramifié à longue chaîne au moyen de catalyseurs ziegler-natta hétérogènes Download PDF

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WO2020257627A1
WO2020257627A1 PCT/US2020/038699 US2020038699W WO2020257627A1 WO 2020257627 A1 WO2020257627 A1 WO 2020257627A1 US 2020038699 W US2020038699 W US 2020038699W WO 2020257627 A1 WO2020257627 A1 WO 2020257627A1
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lcb
groups
carbon atoms
bst
polymer
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Tze-Chiang Chung
Tsutomu Uzawa
Keisuke Goto
Toshiya Uozumi
Toshihiko Sugano
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The Penn State Research Foundation
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F210/00—Copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
    • C08F210/04—Monomers containing three or four carbon atoms
    • C08F210/06—Propene

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  • the present invention relates to a process of preparing long-chain branched polypropylene using heterogeneous Ziegler-Natta catalysts.
  • Polypropylene-based resin is one of the most important thermoplastic materials because of its lightweight properties, thermo- and chemical stability and good cost performance.
  • polypropylene with high isotacticity is widely used due to its excellent mechanical and thermal properties.
  • U.S. Patent No. 7,511,105 discloses the method for producing polypropylene containing a long-chain branching structure by copolymerization of propylene and p-(3-butenyl)styrene using metallocene catalysts.
  • the homogeneous catalysts such as metallocene compounds allow the production of the long-chain branched polypropylene.
  • Supported Ziegler-Natta catalysts are not suitable for this method due to their heterogeneity.
  • the reference Macromolecules, 2009, 42, 3750 reports the copolymer of propylene and p-(3-butenyl)styrene having pendant styrene group made using a certain metallocene catalyst. It is also reported that the copolymer shows good cross-linking properties when the copolymer solution in xylene was subjected to heating above 60 °C. However, the copolymer is not suitable for molding articles because of the narrow molecular weight distribution. Furthermore, gel fraction can be produced in this method.
  • this method tends to produce the gel fraction because it is difficult to control higher order side reaction that makes branched structure.
  • U.S. Patent No. 4,916,198 discloses the method to produce long-chain branched polypropylene by electron-beam irradiation. However, production costs tend to be expensive using this method. Furthermore, this method could produce the gel fraction because it is difficult to control higher order side reactions that make branched structures.
  • Patent document JP6332093 discloses the method for producing polypropylene having branched structure using specific metallocene catalysts which allow producing macromer containing chain-end vinyl groups followed by copolymerization of the macromer and propylene to give the branched polypropylene.
  • specific metallocene catalysts which allow producing macromer containing chain-end vinyl groups followed by copolymerization of the macromer and propylene to give the branched polypropylene.
  • problems such as low productivity and thermostability of the branched polypropylene.
  • melt strength is a desirable mechanical property that is essential to thermoforming, extrusion coating, film blowing, and blow molding processes
  • HMS-PP high melt strength PP
  • the copolymerization reaction creates a lightly cross-linked network with some un-processible PP product.
  • the incorporation of the PP macromonomer involves the tandem catalyst system and multiple reaction steps.
  • the synthesis of the PP macromonomer with a terminal a-olefin group requires a special catalyst system, and the subsequent propylene copolymerization with PP macromonomers (with few thousands molecular weight) is highly inefficient, resulting in many free PP macromonomers mixed into the product.
  • Macromolecules 2002, 35, 9352-9359 creates the LCB structure.
  • BSt diene simultaneously serves as the comonomer and chain transfer agent during the polymerization in forming the LCB-PP polymer structure.
  • BSt molecules only involving single enchainment during the reaction.
  • Some PP polymers containing pendant styrene moieties were identified, which must be hydrogenated before melt-processing to avoid a thermally induced crosslinking reaction.
  • All production processes are expensive and difficult in controlling the LCB-PP molecular structure (branch length, branch density, and impurity).
  • Embodiments of this invention are directed to an efficient and economic method following a commercial PP production process (i.e., polymerization, then extrusion).
  • the direct-polymerization step is centered on an asymmetric diene comonomer p-(3- butenyl)styrene (BSt) that can be randomly incorporated in the PP chain with a monoenchainment fashion by the 4th generation MgCk-supported TiCL catalyst in the slurry polymerization process.
  • BSt asymmetric diene comonomer p-(3- butenyl)styrene
  • the predominate coordination/1, 2-insertion of the a-olefin moiety in the BSt comonomer forms linear PP-co-BSt copolymer (granules), with few pendant styrene moieties randomly distributed along the polymer chain.
  • the molten PP-co-BSt copolymer engages the in situ coupling reaction between pendant styrene units in neighboring polymer chains to spontaneously form PP branches with long branch lengths.
  • the branch density in the resulting LCB-PP pellets are controlled by the BSt content in the copolymer and the degree of the thermal-induced coupling reaction.
  • the resulting LCB-PP polymer with an average of one to four LCB structures per chain, are completely melt-processible, exhibiting high melt strength under elongation flows.
  • the same strain-hardening phenomenon was also observed in the polymer blends between these LCB-PP polymers and linear PP homopolymer with the composition up to 1/1 weight ratio.
  • Embodiments provide a simple method for producing polypropylene resin with a high melting point, good heat resistance, good processability, broad molecular weight distribution and high melt strength without containing gel.
  • One embodiment is directed to a process for preparing long-chain branched isotactic polypropylene (LCB-PP) that includes copolymerizing propylene with an asymmetric diene of formula I using a heterogeneous iso-specific MgCh-supported Ziegler-Natta catalyst, n is an integer from 1 to 10, preferably from 1 to 4.
  • the copolymerization results in an isotactic polypropylene with serval pendantstyrene units (PP-co-BSt) copolymer of formula II.
  • x is an integer from 500 and 10,000
  • y is an integer from 1 to 10, preferably from 2 to 4.
  • the process further includes pelletizing the PP-co-BSt copolymer in an extruder to produce the LCB-PP polymer.
  • the pelletizing is conducted at about 200 °C. ⁇
  • pendant styrene groups in formula II dimerize by either [2+2] or [2+4] cycloaddition reactions to form the LCB-PP polymer
  • the LCB-PP is a mixture of dimerization adducts (L) that connect neighboring polymer chains, and LCB-PP is represented by formula (III)
  • the LCB-PP has an average of one to four LCB branches per chain.
  • a melt kneading of the PP-St conducts above 170 °C, and (L) comprises one or more of the following:
  • the LCB-PP is completely melt-processible.
  • the heterogeneous iso-specific MgCk-supported Ziegler-Natta catalyst includes magnesium, titanium, a halogen, one or more internal electron-donating compounds, one or more organoaluminium compounds, and one or more external electron- donating compounds.
  • the one or more internal electron-donating compounds are selected from the group consisting of dicarboxylic acid esters, diethers, dicarbonates, ether- carboxylic acid esters and ether-carbonates.
  • the one or more organoaluminium compounds are an organoaluminium compound represented by formula (IV): R ! p AlQ3- P (IV).
  • R 1 is one or more alkyl groups having 1 to 6 carbon atoms. Each R 1 group is the same or different.
  • Q is one or more hydrogen atoms or halogen atoms. Each Q is the same or different, and p is a number satisfying 0 ⁇ p ⁇ 3.
  • the one or more external electron-donating compounds are an organosilicon compound represented by formula (V): R 2 q Si(OR 3 )4- (V).
  • R 2 is one or more alkyl groups having 1 to 12 carbon atoms, vinyl groups, alkenyl groups having 3 to 12 carbon atoms, cycloalkyl groups having 3 to 12 carbon atoms, cycloalkenyl groups having 3 to 12 carbon atoms, aromatic hydrocarbon groups having 6 to 15 carbon atoms, or substituted aromatic hydrocarbon groups.
  • Each R 2 group is the same or different.
  • R 3 is one or more alkyl groups having 1 to 4 carbon atoms, vinyl groups, alkenyl groups having 3 to 12 carbon atoms, cycloalkyl groups having 3 to 6 carbon atoms, aromatic hydrocarbon groups having 6 to 12 carbon atoms, or substituted aromatic hydrocarbon groups having 7 to 12 carbon atoms.
  • Each R 3 group is the same or different q is an integer from 0 to 3.
  • the external electron donating compound also includes an aminosilane compound having a Si-N-C bond and represented by formula (VI): R 4 2Si(NR 5 R 6 )(NR 7 R 8 ) (VI).
  • R 4 is one or more alkyl groups having 1 to 12 carbon atoms, vinyl groups, allyl groups, aralkyl groups, cycloalkyl groups having 3 to 12 carbon atoms, or phenyl groups. Each R 4 group is the same or different.
  • R 5 , R 6 , R 7 and R 8 are one or more hydrogens, alkyl groups having 1 to 4 carbon atoms, vinyl groups, allyl groups, aralkyl groups, cycloalkyl groups having 3 to 6 carbon atoms, or phenyl groups.
  • Each R 5 , R 6 , R 7 and R 8 group is the same or different.
  • R 9 and R 10 are hydrogen, an alkyl group having 1 to 4 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms or a phenyl group.
  • R 9 and R 10 are the same or different, and n is an integer satisfying 0 ⁇ n ⁇ 10.
  • the copolymer has a melting point above 155 °C.
  • the resulting LCB-PP is gel-free.
  • the LCB-PP has a branching density between 2 and 4 per polymer chain and exhibits a strain hardening elongational viscosity.
  • the LCB-PP is represented by formula (III):
  • L is a mixture of dimerization adducts.
  • FIG. 1 The reaction mechanism in the formation of PP-co-BSt granules (A) and then LCB- PP pellets (B) and two reference comonomers with individual olefinic moieties in BSt comonomer.
  • FIG. 2 3 ⁇ 4 NMR spectra of PP-co-BSt copolymers prepared by heterogeneous Ziegler-Natta catalyst, (top) without and (bottom) with the presence of hydrogen chain transfer agent.
  • FIG. 3. H-NMR spectrum of poly(propylene-co-BSt) copolymer prepared by homogeneous rac-Me2Si[2-Me-4-Ph-(Ind)]2ZrCb metallocene catalyst.
  • FIG. 4 ⁇ -NMR spectrum of poly(propylene-co-styrene) copolymer prepared by
  • FIG. 5. H-NMR spectrum of poly(propylene-co-styrene) copolymer prepared by
  • FIG. 6 Comparison of catalyst activity vs. initial comonomer concentration for MgCb-supported Ziegler-Natta catalyst mediated propylene polymerization to form PP homo- and co-polymers, including (a) PP homopolymer (control- 1, with 3 ⁇ 4), (b) PP homopolymer (control-2, without 3 ⁇ 4), (c) PP-co-BSt copolymers (A set, with 3 ⁇ 4), (d) PP-co-BSt copolymers (B set, without 3 ⁇ 4), (e) PP-co-St copolymer (C set, without Fb), and (f) PP-co- BTo copolymers (D set, without Fb).
  • FIG. 7 (Top) comonomer content vs. initial comonomer concentration and (bottom) Tm of copolymer vs. comonomer content for (a) PP-co-BSt copolymers (A set, with Fb), (b) PP-co- BSt copolymers (B set, without 3 ⁇ 4), (c) PP-co-BTo copolymers (D set, without Fb).
  • FIG. 8 GPC curves of (a) LCB-PP pellet prepared by extruding and pelletizing PP-co-BSt copolymer (BSt content: 0.20 mol%) at 200 °C, and (b) a commercial HMS-PP product (Daploy WB130HMS).
  • FIG. 9. 3 ⁇ 4 NMR spectra comparison between (a) starting PP-co-BSt granules (run A-3) and (b) the resulting LCB-PP pellets after heat treatment at 200 °C under vacuum.
  • FIG. 10 Comparison of intrinsic viscosity and branch index between (a) LCB-PP pellet prepared by extruding and pelletizing PP-co-BSt copolymer (BSt content: 0.20 mol%) at 200 °C, and (b) a commercial HMS-PP product (Daploy WB130HMS).
  • FIG. 11 Comparison of storage modulus (G’) and complex viscosity (h*) vs. time between LCB-PP copolymer (run A-3) and linear PP homopolymer (control 1) under isothermal condition at 190 °C.
  • FIG 12. Extensional stress growth function at various strain rates for LCB-PP polymer prepared by extruding and pelletizing PP-co-BSt copolymer (BSt content: 0.20 mol%) at 200 °C and a linear PP homopolymer.
  • FIG 13 Comparison of extensional stress growth function at 0.5 s 1 extension rate various for (a) LCB-PP polymer (Table 2) and two corresponding LCB-PP/PP blends with (b) 1/1 and (c) 1/3 weight ratios (PP from commercial source).
  • the methods and devices of the present disclosure can comprise, consist of, or consist essentially of the essential elements and limitations of the embodiments described herein, as well as any additional or optional components or limitations described herein or otherwise useful.
  • ranges can be expressed as from“about” one particular value, and/or to“about” another particular value. It is also understood that there are a number of values disclosed herein, and that each value is also herein disclosed as“about” that particular value in addition to the value itself. For example, if the value“10” is disclosed, then“about 10” is also disclosed. It is also understood that each unit between two particular units are also disclosed. For example, if 10 and 15 are disclosed, then 11, 12, 13, and 14 are also disclosed.
  • the halogen can be F, Cl, Br or I.
  • a group is“substituted”, it can be substituted with a halogen, nitro or methoxy.
  • Embodiments are directed to an improved method of using a commercial PP production process to prepare LCB-PP polymers.
  • This process involves commercial MgCh- supported Ziegler-Natta catalyst in slurry copolymerization between propylene and the BSt comonomer, with or without the 3 ⁇ 4 chain transfer agent.
  • the resulting linear PP-co-BSt copolymer (granules) were extruded and pelletized to obtain the pelletized LCB-PP products.
  • the resulting LCB-PP shows a similar branching parameter (g’ value) and exhibits similar strain hardening behaviors under extensional flows.
  • a direct slurry polymerization process to prepare long-chain branched isotactic polypropylene (LCB-PP) products that exhibit high melt strength polypropylene (HMS-PP) properties is provided
  • the process uses heterogeneous iso-specific MgCk-supported Ziegler- Natta catalyst and an asymmetric diene comonomer that contains both alpha-olefin and styrene moieties, in which the asymmetric diene comonomer is represented by formula (I) with n is an integer between 1 and 10, preferably between 1 and 4. (see FIG.
  • the alpha-olefin moiety in the diene comonomer is selectively copolymerized with propylene monomer to form isotactic polypropylene (PP- co-BSt) copolymer containing few units of pendent styrene (St) groups.
  • the PP-co-BSt copolymer is represented by formula (II) (in FIG. 1) with n is an integer between 1 and 10, preferably between 1 and 4; x is an integer between 500 and 10,000, preferably between 1,000 and 5,000; and y is an integer between 1 and 10, preferably between 2 and 4.
  • the resulting PP-co-BSt copolymer (granules) shown in (A) of FIG. 1 is a linear polymer chain structure and is completely (melt and solution) processible.
  • the pendant styrene groups in molten PP-co-BSt copolymer engages the in situ dimerization reaction between two pendant styrene units via either [2+2] or [2+4] cycloaddition reactions to form a mixture of dimerization adducts (L) that connect neighboring polymer chains.
  • the resulting long-chain branched polypropylene (LCB-PP) polymer is represented by formula (III) (FIG. 1).
  • the branch density in the resulting LCB-PP pellets shown in B of FIG.
  • the 4th generation heterogeneous Ziegler-Natta catalyst (MgCk-supported T1CI4 catalysts containing phthalate internal donor) was produced by Toho Titanium Co., Ltd. with the published procedure. (Minoru, T.; Atsushi, M.; Masuo, L;
  • Triethylaluminum 1.0 M solution in hexane, Aldrich
  • Dicyclopentyldimethoxysilane Shin- Etsu Chemical Co., Ltd.
  • Allylmagnesium bromide 1.0 M solution in diethyl ether
  • Film samples for the extensional viscosity tests were prepared using polymer pellets containing 0.1 wt% of Irganox 1010 and Irgafos 168 by preheating at 210 °C for 3 min. followed by molding at 210 °C for 3 min.
  • the film (size: 14 mm x 10 mm x 0.7 mm) was attached on an equipment for the measurement (MCR302, Anton Paar GmbH) and placed in a chamber filled with nitrogen at 180 °C. Then, the film was extended at a constant rate.
  • a series of polymerization was carried out using a dried 300 mL Parr stainless steel autoclave.
  • the autoclave was conditioned by filling with 30 psi of nitrogen and heated to 110 °C followed by purging nitrogen to remove moisture trace from the reactor.
  • the autoclave was then cooled to room temperature and was charged with 60 psi of propylene gas. Hexane was introduced to the autoclave reactor so that the total volume of hexane and comonomer was 100 mL.
  • Triethylaluminum (6.6x10 3 mol), dicyclopentyldimethoxysilane (6.6x10 4 mol), a specific quantity of comonomer (Table 1), and 1.7xl0 5 mol-Ti of supported Ziegler-Natta catalyst were injected into the autoclave. Then, the autoclave was heated and maintained at 60 °C for 15 min. under constant mechanical stirring. The reaction was terminated by the addition of the mixture of toluene (10 mL) and methanol (10 mL). The solution was poured into a large amount of acidic methanol to precipitate the resulting polymer. The product was filtered and rinsed with methanol and dried under vacuum at 60 °C for 6 h.
  • the propylene/p-(3-butenyl)styrene copolymerization was scaled up using a 1.5 L autoclave reactor.
  • the similar reactor conditioning procedure was carried out by filling the autoclave with nitrogen and heated to 110 °C, followed by purging nitrogen to remove moisture trace in the reactor.
  • the autoclave was then cooled to room temperature and was charged with 44 psi of propylene gas and 700 mL of n-heptane.
  • Table 1 Summary of propylene/BSt copolymerization reactions using MgCk-support Ziegler-Natta catalyst and control reactions.
  • a ZN the 4th generation heterogeneous Ziegler-Natta catalyst (MgCk-supported TiCU catalysts containing phthalate internal donor), Met: rac- Me 2 Si[2-Me-4-Ph-(Ind)] 2 ZrCl 2 /MAO metallocene catalyst.
  • Tm melting temperature
  • Tc crystallization temperature
  • a dried 300 mL Parr stainless steel autoclave was filled with 30 psi of nitrogen and heated to 110 °C followed by purging nitrogen to remove moisture from the autoclave.
  • the autoclave was cooled to room temperature and was charged with 30 psi of propylene gas.
  • Toluene was introduced to the autoclave so that total volume of toluene and comonomer was 100 mL.
  • 2.0> ⁇ 10 2 mol of MMAO, BSt and 5.0 c 10 6 mol-Zr of rac-Me 2 Si[2-Me-4-Ph-(Ind)] 2 ZrCh were injected to the autoclave.
  • the autoclave was heated and maintained at 45 °C for 15 min. under mechanical stirring.
  • the reaction was terminated by the addition of the mixture of toluene (10 mL) and methanol (10 mL).
  • the solution was poured into a large amount of acidic methanol to precipitate the resulting polymer.
  • the product was filtered and rinsed with methanol and dried under vacuum at 60 °C for 6 h.
  • FIG. 1 illustrates the reaction scheme in the preparation of LCB-PP polymer (pellets).
  • the process includes two consecutive steps with two distinctive chemical reactions.
  • the first step is the 4th generation heterogeneous Ziegler-Natta catalyst mediated slurry copolymerization between propylene and p-(3-butenyl)styrene (BSt) comonomer, with or without the 3 ⁇ 4 chain transfer agent, to form linear PP-co-BSt copolymer containing several pendant styrene moieties (granules).
  • BSt p-(3-butenyl)styrene
  • the iso-specific heterogeneous Ziegler-Natta catalyst mostly engage 1,2-insertion of the a-olefm moiety in the BSt comonomer.
  • the facile cycloaddition reaction between pendant styrene moieties happens to form long-chain branches in the pelletized LCB-PP products.
  • the resulting LCB- PP products are melt-processible and show high melt strength (strain hardening) under extensional flows.
  • Table 1 summarizes the experiment conditions and results of several sets of comparative propylene homo- and co-polymerization reactions to understand the details of propylene/BSt copolymerization reactions using the 4th generation MgCh-supported Ziegler- Natta catalyst.
  • the study includes two series of propylene/BSt copolymerization reactions using the heterogeneous Ziegler-Natta catalyst with and without the 3 ⁇ 4 chain transfer agent (A and B sets, respectively).
  • Two parallel propylene homo-polymerization runs control-1 and control-2, with and without 3 ⁇ 4 chain transfer agent, respectively) were also performed to understand the effect of the BSt comonomer to the catalyst activity and the resulting copolymer structure and properties.
  • FIG. 2 shows two 3 ⁇ 4 NMR spectra of PP-co-BSt copolymers (runs A-3 and B-3), prepared under the same reaction condition, except with and without the presence of the 3 ⁇ 4 chain transfer agent. Both spectra are very similar, indicating a minimum effect of 3 ⁇ 4 chain transfer reaction to the copolymer composition. In addition to three major peaks at 0.9, 1.3, and 1.7 ppm, corresponding to methyl, methylene, and methine protons in PP chain, there are several secondary chemical shifts associated with the incorporated BSt comonomer units.
  • FIG. 3 shows the 3 ⁇ 4 NMR spectrum of the PP-co-BSt copolymer prepared by homogeneous rac-Me 2 Si[2-Me-4-Ph-(Ind)] 2 ZrCl 2 metallocene catalyst in the presence of hydrogen.
  • the BSt asymmetric diene effectively acts as both a comonomer and a chain transfer agent and hydrogen is required to complete the chain transfer reaction.
  • This double-enchainment fashion of the BSt comonomer creates long-chain branched structure.
  • This iso-specific Ziegler-Natta catalyst is known to be highly stereo- and regio-selective during the coordination/insertion process, and the selective 1,2-insertion fashion of olefinic moieties is highly favorable to a-olefm than styrene incorporation. Comparing all parallel runs between C and D sets, BTo comonomer shows much better incorporation than the styrene
  • FIG. 4 shows the 3 ⁇ 4 NMR spectrum for this propylene/styrene (PP-co-St) copolymer (run C-l).
  • PP-co-St propylene/styrene
  • FIG. 5 shows the 3 ⁇ 4 NMR spectrum of the
  • FIG. 6 compares catalyst activity vs. initial comonomer concentration during these MgCk-supported Ziegler-Natta catalyst mediate propylene homo- and co-polymerization reactions (Table 1). Overall, catalyst activity slightly but proportionally decreases with the increase of the comonomer concentration, regardless of the comonomer used in the copolymerization reaction. The bulky comonomer slows down the coordination/insertion process, but the 1,2-fashion minimizes the effect. It is also known that the Ziegler-Natta catalyst activity increases with the presence of the 3 ⁇ 4 chain transfer agent due to the in situ regeneration of dormant catalyst sites.
  • the consistent lower catalyst activity in the propylene/BSt case implies that some weak acid-base interaction between the active site and p-electrons in the styrene moiety may exist, as illustrated in Scheme 2.
  • the catalyst activity in the propylene/BSt copolymerization is recovered to near the propylene homo-polymerization level (with 3 ⁇ 4). From the industrial perspective, hydrogen is already used in the industry to control PP molecular weight and chain end structure. Therefore, it is logical to apply the same 3 ⁇ 4 condition during the preparation of PP-co-BSt copolymers.
  • FIG. 7 shows a side-by-side comparison for (top) comonomer incorporation vs. the comonomer feed and (bottom) the effect of comonomer content to the melting temperature (Tm) of PP copolymers, including PP-co-BSt copolymers prepared with and without the 3 ⁇ 4 chain transfer agent and PP-co-BTo copolymers (without 3 ⁇ 4).
  • Tm melting temperature
  • FIG. 7 compares melting temperature (Tm) of the same three sets of PP copolymers.
  • Tm melting temperature
  • the melting point of the copolymer is strongly dependent on the density of the comonomer; the higher the density the lower the Tm.
  • Even a small amount of comonomer incorporation has some effect to the crystallization of PP copolymers, consistent with Flory’s prediction for semicrystalline random copolymers.
  • LCB-PP Polymer Pellets As shown in FIG. 1, the propylene/BSt copolymerization is followed with an extruding and pelletizing procedure at 200 °C. Under this thermal condition with strong agitation, the incorporated BSt units in the resulting PP-co-BSt copolymer melt in situ engage the cycloaddition reaction between pendant styrene moieties to form the long-chain branches in the pelletized LCB-PP products.
  • FIG. 8 compares two GPC curves between an LCB-PP polymer obtained after extruding and pelletizing a PP-co-BSt copolymer (BSt content: 0.20 mol%) at 200 °C and a commercially available HMS-PP product (Daploy WB130HMS) that contains a significant fraction of high molecular weight polymers. Based on the shape of the GPC curves, the direct polymerization process, with the branch points pre-determined by the randomly incorporated BSt units, seems to produce more uniform LCB structures in the PP chain.
  • Table 2 Summary of polymer molecular weight before and after thermal process and a common commercial HMS-PP product (Daploy WB130HMS).
  • Table 2 summarizes polymer molecular weight before and after thermal treatment for the PP-co-BSt copolymer and the commercial HMS-PP product (Daploy WB130HMS).
  • FIG. 10 compares the Mark-Houwink plot and the associated branching parameter (g’ value) (Sun, T.; Brant, P.; Chance, R. R.; Graessley, W. W.; Lohse, D. J. A Study of the Separation Principle in Size Exclusion Chromatography.
  • FIG. 11 shows complex viscosity (h*) and storage modulus (G’) of the resulting LCP-PP specimen and the corresponding linear PP homopolymer (control- 1) under an isothermal condition at 190 °C (a common PP process condition) for more than 3 hours.
  • PP homopolymer maintains constant h* and G’ (flat lines) throughout the entire isothermal heating at 190 °C for more than 3 hours.
  • the LCB-PP sample shows a slow but continuous increase in both complex viscosity and storage modulus.
  • the polymer maintains completely melt-processible for many hours.
  • the overall experimental results seem to indicate that a relatively fast coupling reaction happens during the extrusion/pelletization step at 200 °C to transform a linear PP-co-BSt copolymer into the LCB-PP structure.
  • the resulting LCB-PP structure becomes relatively stable for future melt-processes.
  • the combination of increased viscosity and reduced styrene concentration in the LCB-PP copolymer may dramatically reduce the coupling reaction rate and prevents forming a polymer network during the melt-processing at 190 °C.
  • FIG. 12 shows the stress growth function at various extension rates for the LCB-PP polymer that was prepared by extruding and pelletizing the PP-co-BSt copolymer with 0.20 mol% of BSt content (Table 2).
  • extension rates from 0.1 to 5 s 1 show strain hardening behavior in this LCB-PP polymer that has in average two LCB structures per chain, showing a sharp increase of viscosity above the value for the corresponding linear PP homopolymer that tracks the linear viscoelastic response under 0.5 s 1 extension rate.
  • Such strain hardening in this extension rate range is highly desirable for polymer processing operations, such as film blowing, large-part blow molding, foam extrusion, profile extrusion, extrusion coating, and fiber spinning, etc., requiring high melt strength during extensional flows.
  • FIG. 13 compares the extension stress function at the 0.5 s 1 extension rate for two LCB-PP/PP blend films with 1/1 and 1/3 weight ratios and the corresponding LCB-PP polymer.
  • the LCB-PP/PP blending with up to 50% linear PP polymer, still exhibits a similar strain-hardening behavior.
  • HMS-PP high melt strength PP
  • BSt comonomer (branching agent) is introduced during the propylene polymerization to obtain the PP-co-BSt copolymer (granules) containing several incorporated BSt units (in average 1-4 units per polymer chain) randomly distributed along the PP chain.
  • the incorporated BSt units act as the branching sites, engaging in a thermal-induced coupling reaction between the pendant styrene units (without any external agent or by-product) to form the LCB structures. They are controlled by the BSt
  • this new production technology shall offer an efficient, economic, and easily adoptable method in the industry to prepare new HMS-PP products for thermoforming, extrusion coating, blow molding, film blowing, and fiber spinning, with the operational processes involving predominately elongation flows.

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Abstract

L'invention concerne un procédé de préparation de polypropylène isotactique ramifié à longue chaîne (LCB-PP). Le procédé comprend la copolymérisation de propylène avec un diène asymétrique de formule I à l'aide d'un catalyseur Ziegler-Natta supporté sur MgCl2 isospécifique hétérogène. La copolymérisation permet d'obtenir un copolymère de polypropylène-styrène (PP-St) isotactique de formule II. Le procédé comprend la granulation du copolymère PP-co-BSt dans une extrudeuse pour produire le LCB-PP. n est un nombre entier de 1 à 4, x est un nombre entier compris entre 500 et 10 000, et y est un nombre entier compris entre 1 et 10.
PCT/US2020/038699 2019-06-20 2020-06-19 Synthèse de polypropylène ramifié à longue chaîne au moyen de catalyseurs ziegler-natta hétérogènes WO2020257627A1 (fr)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2006007512A1 (fr) * 2004-07-01 2006-01-19 The Penn State Research Foundation Processus en un pot et reactifs permettant de preparer des polymeres ramifies de chaine longue
WO2010066906A2 (fr) * 2008-12-12 2010-06-17 Total Petrochemicals Research Feluy Préparation de polypropylène isotactique ramifié à longue chaîne
CN101891851A (zh) * 2009-05-22 2010-11-24 中国科学院化学研究所 一种制备长链支化等规聚丙烯的方法

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2006007512A1 (fr) * 2004-07-01 2006-01-19 The Penn State Research Foundation Processus en un pot et reactifs permettant de preparer des polymeres ramifies de chaine longue
WO2010066906A2 (fr) * 2008-12-12 2010-06-17 Total Petrochemicals Research Feluy Préparation de polypropylène isotactique ramifié à longue chaîne
CN101891851A (zh) * 2009-05-22 2010-11-24 中国科学院化学研究所 一种制备长链支化等规聚丙烯的方法

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