CN118420820A - Method for producing polypropylene by serially connecting multiple reactors - Google Patents
Method for producing polypropylene by serially connecting multiple reactors Download PDFInfo
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- CN118420820A CN118420820A CN202410521813.9A CN202410521813A CN118420820A CN 118420820 A CN118420820 A CN 118420820A CN 202410521813 A CN202410521813 A CN 202410521813A CN 118420820 A CN118420820 A CN 118420820A
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- -1 polypropylene Polymers 0.000 title claims abstract description 102
- 239000004743 Polypropylene Substances 0.000 title claims abstract description 95
- 229920001155 polypropylene Polymers 0.000 title claims abstract description 95
- 238000004519 manufacturing process Methods 0.000 title abstract description 18
- 238000006116 polymerization reaction Methods 0.000 claims abstract description 86
- QQONPFPTGQHPMA-UHFFFAOYSA-N propylene Natural products CC=C QQONPFPTGQHPMA-UHFFFAOYSA-N 0.000 claims abstract description 38
- 125000004805 propylene group Chemical group [H]C([H])([H])C([H])([*:1])C([H])([H])[*:2] 0.000 claims abstract description 37
- 238000007334 copolymerization reaction Methods 0.000 claims abstract description 30
- HQQADJVZYDDRJT-UHFFFAOYSA-N ethene;prop-1-ene Chemical group C=C.CC=C HQQADJVZYDDRJT-UHFFFAOYSA-N 0.000 claims abstract description 29
- 238000000034 method Methods 0.000 claims abstract description 29
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 claims abstract description 28
- 239000005977 Ethylene Substances 0.000 claims abstract description 28
- 238000006243 chemical reaction Methods 0.000 claims abstract description 25
- 239000002245 particle Substances 0.000 claims abstract description 21
- 230000008569 process Effects 0.000 claims abstract description 20
- 239000003054 catalyst Substances 0.000 claims abstract description 17
- 239000012752 auxiliary agent Substances 0.000 claims abstract description 11
- 229920001384 propylene homopolymer Polymers 0.000 claims abstract description 6
- 238000003756 stirring Methods 0.000 claims description 29
- 239000000203 mixture Substances 0.000 claims description 18
- 229920001577 copolymer Polymers 0.000 claims description 13
- 150000001335 aliphatic alkanes Chemical class 0.000 claims description 10
- 239000004711 α-olefin Substances 0.000 claims description 9
- 125000004432 carbon atom Chemical group C* 0.000 claims description 5
- 150000001924 cycloalkanes Chemical class 0.000 claims description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 4
- 229910052799 carbon Inorganic materials 0.000 claims description 4
- 239000011949 solid catalyst Substances 0.000 claims description 4
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 2
- 239000011651 chromium Substances 0.000 claims description 2
- 229910052804 chromium Inorganic materials 0.000 claims description 2
- 230000003247 decreasing effect Effects 0.000 claims description 2
- 239000012968 metallocene catalyst Substances 0.000 claims description 2
- 229910052723 transition metal Inorganic materials 0.000 claims description 2
- 150000003624 transition metals Chemical class 0.000 claims description 2
- 125000005234 alkyl aluminium group Chemical group 0.000 claims 1
- 125000000217 alkyl group Chemical group 0.000 claims 1
- 239000000758 substrate Substances 0.000 claims 1
- 230000003197 catalytic effect Effects 0.000 abstract 1
- 239000012071 phase Substances 0.000 description 40
- 239000011159 matrix material Substances 0.000 description 31
- 229920000642 polymer Polymers 0.000 description 25
- QWTDNUCVQCZILF-UHFFFAOYSA-N isopentane Chemical compound CCC(C)C QWTDNUCVQCZILF-UHFFFAOYSA-N 0.000 description 24
- 239000000178 monomer Substances 0.000 description 17
- 239000007789 gas Substances 0.000 description 15
- CTQNGGLPUBDAKN-UHFFFAOYSA-N O-Xylene Chemical compound CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 description 14
- 238000010574 gas phase reaction Methods 0.000 description 14
- AFABGHUZZDYHJO-UHFFFAOYSA-N dimethyl butane Natural products CCCC(C)C AFABGHUZZDYHJO-UHFFFAOYSA-N 0.000 description 12
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 10
- 239000001257 hydrogen Substances 0.000 description 10
- 229910052739 hydrogen Inorganic materials 0.000 description 10
- 239000004698 Polyethylene Substances 0.000 description 7
- 239000011954 Ziegler–Natta catalyst Substances 0.000 description 7
- JWCYDYZLEAQGJJ-UHFFFAOYSA-N dicyclopentyl(dimethoxy)silane Chemical compound C1CCCC1[Si](OC)(OC)C1CCCC1 JWCYDYZLEAQGJJ-UHFFFAOYSA-N 0.000 description 7
- 229920000573 polyethylene Polymers 0.000 description 7
- 238000000926 separation method Methods 0.000 description 7
- 239000007787 solid Substances 0.000 description 7
- VOITXYVAKOUIBA-UHFFFAOYSA-N triethylaluminium Chemical compound CC[Al](CC)CC VOITXYVAKOUIBA-UHFFFAOYSA-N 0.000 description 7
- 230000002776 aggregation Effects 0.000 description 6
- 238000009826 distribution Methods 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 238000005054 agglomeration Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 4
- 238000011065 in-situ storage Methods 0.000 description 4
- 238000001000 micrograph Methods 0.000 description 4
- 150000001336 alkenes Chemical class 0.000 description 3
- 238000001493 electron microscopy Methods 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- JRZJOMJEPLMPRA-UHFFFAOYSA-N olefin Natural products CCCCCCCC=C JRZJOMJEPLMPRA-UHFFFAOYSA-N 0.000 description 3
- 239000002002 slurry Substances 0.000 description 3
- 229920000089 Cyclic olefin copolymer Polymers 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- 230000001276 controlling effect Effects 0.000 description 2
- 238000013021 overheating Methods 0.000 description 2
- 239000004033 plastic Substances 0.000 description 2
- 229920003023 plastic Polymers 0.000 description 2
- 229920005629 polypropylene homopolymer Polymers 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 238000010924 continuous production Methods 0.000 description 1
- 239000011258 core-shell material Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000005243 fluidization Methods 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 238000001746 injection moulding Methods 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000011146 organic particle Substances 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 238000002464 physical blending Methods 0.000 description 1
- 229920000915 polyvinyl chloride Polymers 0.000 description 1
- 239000004800 polyvinyl chloride Substances 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
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- 239000000126 substance Substances 0.000 description 1
- 238000009827 uniform distribution Methods 0.000 description 1
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- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
- Polymerisation Methods In General (AREA)
Abstract
The invention provides a method for producing polypropylene by serially connecting multiple reactors. Propylene is prepolymerized in a prepolymerization reactor under a catalyst system; the catalytic active particles obtained by the prepolymerization reaction enter a first reactor to carry out propylene homopolymerization; the propylene homopolymer enters a second reactor to continue propylene homopolymerization or ethylene propylene copolymerization; and (3) enabling the product of the second reactor to enter a third reactor for ethylene polymerization or ethylene propylene copolymerization to obtain a polypropylene product. The present invention can obtain a variety of high performance polypropylene products by selecting the reaction forms in the second and third reactors. The performance of the obtained polypropylene product can be further enhanced by selecting a series combination process of a prepolymerization reactor, a horizontal reactor and a fluidized bed reactor, and/or further adding an inert auxiliary agent into the first and/or second and/or third reactor, and/or enabling the discharge flow of the subsequent reactor to be optionally recycled to the preceding reactor, etc.
Description
Technical Field
The invention belongs to the field of olefin polymerization, and particularly relates to a method for producing polypropylene by serially connecting multiple reactors.
Background
Polypropylene is a plastic material widely applied to industrial production, and has the advantages of high chemical stability, high mechanical strength, good plasticity, high heat resistance and the like. The current annual output of polypropylene in the world exceeds 8000 ten thousand tons, and the annual demand is large, and the polypropylene is the third largest general plastic after polyethylene and polyvinyl chloride. Impact-resistant copolymerized polypropylene products with high rigidity and high toughness are in great demand in the injection molding field, however, the toughness of the products is greatly improved by introducing a rubber phase into a polypropylene matrix, but the rigidity loss is often larger. If the rigid organic particles are adopted to toughen the impact copolymer polypropylene by a physical blending method, the problems of high energy consumption, uneven dispersion of rubber phase and unstable product property are brought. It follows that how to form in situ in the reactor an impact copolymer polypropylene with balanced stiffness and toughness is a very challenging challenge for the industry. On the basis, if the impact copolymer polypropylene with the rigidity, toughness and glossiness can be produced through in-situ polymerization, the impact copolymer polypropylene plays an important role in the fields of automobiles, high-grade household appliances, aerospace and the like.
It is known in the art to synthesize impact copolymer polypropylene, typically using a series of reaction vessels. For example, the spheirisol process, which is a loop-fluidized bed series connection, is one of the most widely used processes for producing impact copolymer polypropylene at present, which comprises homopolymerizing propylene in a loop reactor to form a polypropylene matrix, and further copolymerizing ethylene and propylene in a fluidized bed reactor to form a rubber phase. The polypropylene product obtained by the Spheripol process has improved impact strength, but the modulus of the introduced rubber phase is extremely low, so that the rigidity is reduced. The Cataloy process adopts three fluidized bed reactors connected in series, and the Horizone process adopts a self-cleaning stirring paddle horizontal reactor, which are matched with a large ball catalyst. Although the processes can produce high-rubber-content high-toughness impact polypropylene, the products have the defects of high ash content and poor fluidity.
In order to solve the problem that the polymer generated by the series reactor is easy to be sticky, the patent CN111269491A adjusts the composition and the concentration of olefin monomers in the particles by adding a proper amount of inert condensing medium in a gas phase copolymerization stage to form a micro-area with concentration gradient, thereby adjusting and controlling the distribution of multiphase polypropylene particle rubber phase, realizing the surface visbreaking of the particles, and further avoiding the problems of sticky agglomeration among polypropylene composition particles in the polymerization process.
It is known in the art that after the introduction of the rubber phase, the polypropylene is transformed from the original homogeneous structure to a heterogeneous structure, the copolymer component is dispersed in the polypropylene in the form of a dispersed phase, and the incompatibility between the phases results in a deterioration of the toughness and toughness properties. Therefore, the prior art adopts a multi-zone circulating reactor to circulate materials through two polymerization zones to obtain multi-layer onion-like polymer particles, and when the circulation rate is fast enough, the mixing of the polymers on the approximate molecular scale can be realized, thereby ensuring that the polymers have more uniform structures. For example, patent CN116568389a proposes a gas-phase olefin polymerization reactor comprising two polymerization zones, the growing polymer particles flowing through the first polymerization zone under fast fluidization conditions, leaving the first polymerization zone and entering the second polymerization zone, they flowing through the second polymerization zone in a dense form under the action of gravity, leaving the second polymerization zone and reintroducing into the first polymerization zone, thus establishing a polymer circulation between the two, obtaining a polymer of uniform structure and good compatibility of the different components. In addition, the patent CN116874651a performs ethylene-propylene copolymerization by periodically changing the concentration ratio of ethylene monomer and propylene monomer in the reaction environment, and obtains a polypropylene resin with excellent impact property and good low-temperature toughness, but with lower rubber phase content.
Disclosure of Invention
The invention provides a method for producing polypropylene by serially connecting multiple reactors, which is characterized by comprising the following steps:
S1: propylene is prepolymerized in a prepolymerization reactor under a catalyst system;
S2: in the first polymerization stage, the catalytically active particles obtained by the prepolymerization reaction enter a first reactor for propylene homopolymerization;
s3: in the second polymerization stage, propylene homopolymer enters a second reactor to carry out propylene homopolymerization or ethylene propylene copolymerization continuously;
S4: in the third polymerization stage, the product of the second reactor enters a third reactor to carry out ethylene polymerization or ethylene propylene copolymerization to obtain a polypropylene product.
According to an alternative of the invention, the product of the second reactor can be withdrawn directly as polypropylene product; when propylene homopolymerization is carried out in the first reactor and the second reactor, the second reactor can lead out a homopolymerized brand polypropylene product; when the first reactor performs propylene homopolymerization and the second reactor performs ethylene-propylene copolymerization, the second reactor can lead out an impact-resistant brand polypropylene product.
Preferably, the second reactor and the third reactor are controlled to carry out ethylene-propylene copolymerization, and the method is used for producing high-rubber-phase-content polypropylene with the rubber phase content of more than 35 weight percent;
controlling the second reactor to carry out ethylene-propylene copolymerization and the third reactor to carry out ethylene homopolymerization, wherein the method is used for producing polypropylene with toughness improved by more than 30% and modulus loss less than 10%;
The second reactor is controlled to carry out ethylene-propylene copolymerization, the third reactor is controlled to carry out ethylene-alpha-olefin copolymerization, and the method is used for producing polypropylene with impact strength of more than 70KJ/m 2, flexural modulus of more than 200MPa and glossiness of more than 70 Gu.
Preferably, the inert auxiliary is added to the first and/or second and/or third reactor in a single or multiple point addition from the side wall, bottom or top of the reactor.
Preferably, when the inert auxiliary agent is added in a multi-point mode, the addition amount of the inert auxiliary agent is uniformly distributed along the axial direction of the reactor or gradually decreased or increased along the axial direction of the reactor in a gradient of 1% -50%. Preferably, the inert auxiliary agent is injected in an amount which enables the reactor to be above the dew point of circulating gas, so that the heat removal is enhanced, the catalyst activity is improved, and the surface viscosity of polymer particles is reduced.
Preferably, the effluent stream of the subsequent reactor is optionally recycled to the preceding reactor, i.e. the second reactor effluent stream is optionally recycled to the first reactor with a recycle ratio of 0.1 to 30, and the third reactor effluent stream is optionally recycled to the second reactor with a recycle ratio of 0.1 to 30.
Preferably, the catalyst system used in the prepolymerization, the first polymerization stage, the second polymerization stage, and the third polymerization stage comprises a solid catalyst component, an aluminum alkyl or an aluminum alkyl oxygen alkyl, and at least one external electron donor; the solid catalyst component is selected from Ziegler-Natta catalysts, chromium-based catalysts, metallocene catalysts, late transition metal catalysts, or mixtures thereof.
Preferably, the first reactor is selected from a vertical stirred reactor, a horizontal stirred reactor, a loop reactor or a fluidized bed reactor, preferably a horizontal stirred reactor.
Preferably, the second reactor is selected from a vertical stirred reactor, a horizontal stirred reactor or a fluidized bed reactor, preferably a horizontal stirred reactor.
Preferably, the third reactor is selected from a vertical stirred reactor, a horizontal stirred reactor or a fluidized bed reactor, preferably a fluidized bed reactor.
According to a preferred embodiment of the present invention, the present invention is preferably a combined process of a prepolymerization reactor + a horizontal reactor + a fluidized bed reactor in series, and when a third reactor is not required, a combined process of a prepolymerization reactor + a horizontal reactor in series is preferred. Preferably, the ethylene polymerization comprises ethylene homo-or ethylene co-polymerization with an alpha-olefin having a carbon number of 4-18.
Preferably, the inert auxiliary agent is selected from one or more of straight-chain alkane, branched alkane and cycloalkane with 3-18 carbon atoms.
As is known in the art, the aim of the prepolymerization is to produce, at lower temperatures and/or lower monomer concentrations, an appropriate amount of polymer-coated catalyst particles, increasing the propylene diffusion resistance, in order to increase the stability of the homopolymerization stage, while preventing the reactor from being blocked by local overheating agglomerations due to too high activity. Thus, the present invention first performs the prepolymerization in a prepolymerization reactor and then enters the first reactor for the homopolymerization.
Preferably, the temperature of the prepolymerization is 0 to 40 ℃, more preferably 25 to 35 ℃; the prepolymerization pressure is 1 to 30bar, more preferably 1 to 8bar; the prepolymerization time is 1 to 30 minutes, more preferably 10 to 15 minutes.
The catalytically active wet particles obtained in the prepolymerization stage enter a first polymerization stage, which may be carried out in slurry, liquid phase bulk or gas phase state, preferably in gas phase. The inert auxiliary agent is selected from one or more of straight-chain alkane, branched alkane and cycloalkane with 3-18 carbon atoms, preferably isopentane. Propylene homopolymerization is carried out in the presence of the active particles obtained in the prepolymerization stage. As known in the art, the reaction condition of the horizontal reactor is easy to control, the flow and the temperature of reactants can be controlled by adjusting the flow of a feed pump, so that the reaction condition is stable, materials in the horizontal reactor keep continuous and stable flow in the reaction process, and the reactor is not easy to be blocked due to heating agglomeration. Thus, the first reactor is preferably a horizontal stirred reactor.
Preferably, the first polymerization stage temperature is from 0 to 90 ℃, more preferably from 60 to 90 ℃; the polymerization pressure is 2 to 30bar, more preferably 5 to 30bar, and the polymerization time is 20 to 240min, more preferably 30 to 180min.
The homo-polypropylene particles obtained in the first polymerization stage are passed to a second polymerization stage, which may be carried out in slurry or gas phase, preferably in gas phase. The inert auxiliary agent is selected from one or more of straight-chain alkane, branched alkane and cycloalkane with 3-18 carbon atoms, preferably isopentane. The production of propylene homopolymers or ethylene and propylene copolymers is carried out in the presence of the polypropylene particles obtained in the first polymerization stage. As is known in the art, a horizontal stirred reactor has typical plug flow characteristics, a narrow residence time distribution of the material, and a low short circuit, and when the catalyst activity is released relatively smoothly, a uniform and stable rubber phase can be produced. Thus, the second reactor is preferably a horizontal stirred reactor, which allows for continuous production of propylene homopolymer or for production of a rubber phase of uniform and stable size and distribution.
Preferably, the temperature at which the second polymerization stage produces a propylene homopolymer is from 0 to 90 ℃, more preferably from 60 to 90 ℃; the polymerization pressure is 2 to 30bar, more preferably 5 to 30bar, and the polymerization time is 20 to 240min, more preferably 30 to 180min; the second polymerization stage produces a rubber phase at a temperature of 50 to 90 ℃, more preferably 70 to 85 ℃; the polymerization pressure is 2 to 40bar, more preferably 6 to 35bar, and the polymerization time is 20 to 180min, more preferably 30 to 120min.
The homo-polypropylene particles or the second copolymer mixture obtained in the second polymerization stage are passed to a third polymerization stage, which may be carried out in slurry or gas phase, preferably in gas phase. The inert auxiliary agent is selected from one or more of straight-chain alkane, branched alkane and cycloalkane with 3-18 carbon atoms, preferably isopentane. The production of an ethylene-propylene copolymer or a polyethylene or an alpha-olefin copolymer of ethylene and a carbon number of 4-18 is carried out in the presence of the ethylene-propylene copolymer obtained in the second polymerization stage. As is known in the art, when ethylene polymerization is carried out in the third polymerization stage, the polyethylene will enter the impact polypropylene under thermodynamic driving as an equivalent rubber phase, further toughening the polypropylene; and when ethylene propylene copolymerization is carried out in the third polymerization stage, the content of the rubber phase is further increased, and the polypropylene with high rubber content is obtained. However, the ethylene polymerization and the continuous ethylene-propylene copolymerization have large heat release, local hot spot agglomeration is liable to occur, and heat is preferably removed by convection, so that the third reactor is preferably a fluidized bed reactor. The reactor can solve the problem of high heat release caused by ethylene polymerization or continuous ethylene-propylene copolymerization on one hand and reduce the influence of rubber phase stickiness on the other hand.
Preferably, the temperature is 50 to 90 ℃, more preferably 65 to 90 ℃ when the ethylene-propylene copolymer is produced in the third polymerization stage; the polymerization pressure is 2 to 40bar, more preferably 6 to 35bar, and the polymerization time is 20 to 180min, more preferably 30 to 120min; in the third polymerization stage, the temperature is 50 to 100 ℃, more preferably 65 to 90 ℃, when producing polyethylene or an alpha-olefin copolymer of ethylene and a carbon number of 4 to 18; the polymerization pressure is 5 to 40bar, more preferably 8 to 35bar, and the polymerization time is 20 to 120min, more preferably 20 to 60min.
As is known in the art, the in situ incorporation of polyethylene can enhance the interfacial interaction between the rubbery dispersed phase and the polypropylene matrix, tending to form a core-shell structure with the polyethylene as the core and the rubbery phase as the shell under thermodynamic driving. In order to further improve the compatibility between the polypropylene matrix and the disperse phase, the invention adopts a material circulation mode to enable the discharge flow of the second reactor to be optionally returned to the first reactor and/or the discharge flow of the third reactor to be optionally returned to the second reactor, and the circulation ratio is 0.1-30, so that the mixing of different polymer components in microscopic scale is enhanced.
The invention provides a production process for switching the grades of conventional polypropylene, which is characterized in that different grades of products can be produced by adopting different reactor combinations. The prepolymerization reactor, the first reactor and the second reactor are connected in series, wherein the first reactor and the second reactor are used for propylene homopolymerization, and the homopolymerization brand can be produced; the prepolymerization reactor, the first reactor and the second reactor are connected in series, wherein the first reactor performs propylene homopolymerization, and the second reactor performs ethylene propylene copolymerization, so that an impact-resistant mark can be produced; adopting a prepolymerization reactor, a first reactor, a second reactor and a third reactor to be connected in series, wherein when the second reactor and the third reactor are both subjected to ethylene propylene copolymerization, an anti-impact polypropylene grade with the rubber phase content of more than 30% can be produced; when the second reactor carries out ethylene-propylene copolymerization, the third reactor carries out ethylene homopolymerization to produce polypropylene grade with balanced rigidity and toughness (namely, the toughness is improved by more than 30 percent and the rigidity loss is less than 10 percent); when ethylene-propylene copolymerization is carried out in the second reactor, and ethylene and alpha-olefin copolymerization is carried out in the third reactor, the polypropylene brand with rigidity and toughness light balance (namely, the impact strength is more than 70KJ/m 2, the flexural modulus is more than 200MPa, and the glossiness is more than 70 Gu) can be produced.
Compared with the prior art, the invention has the following beneficial effects:
1. The prepolymerization reactor is matched with the first horizontal reactor to generate the polypropylene matrix, so that on one hand, the activity release of the catalyst and the sphericity of polypropylene matrix particles are effectively controlled, and on the other hand, the narrow residence time distribution of the horizontal reactor ensures that the chain structure, the aggregation state structure, the particle size and the like of the polypropylene matrix are uniform and stable, the stable release of the catalyst activity is ensured, the morphology of the polypropylene particles is optimized, and the reactor is prevented from being blocked by local overheating agglomeration.
2. The rubber phase generated by the horizontal reactor has uniform and stable size and microphase structure and good dispersibility, and can be used for realizing the generation of polypropylene polymers with more uniform properties, and the rubber content is greatly improved.
3. According to the invention, the fluidized bed reactor is selected to continue ethylene-propylene copolymerization, ethylene homopolymerization or ethylene copolymerization, and the convection heat removal mode can effectively avoid local caking hot spots.
4. In the preferred embodiment of the invention, inert auxiliary agents are added in a uniform distribution or gradient distribution mode to enable the reactor to be above the dew point of circulating gas, so that on one hand, heat removal is enhanced, on the other hand, the distribution of rubber phases in polypropylene particles can be regulated and controlled, the rubber content and the viscosity reduction on the particle surfaces are improved, and the polymerization environment in the reactor can be regulated and controlled simultaneously on the time and space scale, the polymerization of the reaction monomer composition in a plurality of reaction areas is realized, and the toughness of the product is further improved.
5. In the preferred embodiment of the invention, the first, second and third reactors adopt a mode of horizontal type+horizontal type+fluidized bed reactor to introduce polyethylene components in situ, so that the flexural modulus and impact strength of the product are improved, and further, the regulation and control of the glossiness of the product can be realized by changing the types and the content of the comonomer in the fluidized bed reactor, and finally, the polypropylene product with balanced rigid and tough light performance can be obtained.
6. In the preferred embodiment of the invention, the material circulation mode is adopted, so that the compatibility between the polypropylene matrix and the rubber disperse phase is improved, the mixing of different molecular chains can be promoted, and the mechanical property of the product is further improved.
Drawings
FIG. 1 is a schematic illustration of an exemplary process flow for producing a polypropylene product in accordance with embodiments of the present invention.
FIG. 2 is a diagram showing an example of a process flow for producing a polypropylene product in comparative example 3 of the present invention.
In FIG. 1, R0-prepolymerization reactor, R1-horizontal stirring reactor, R2-horizontal stirring reactor, R3-fluidized bed reactor, S1 and S2 are flow separators.
In FIG. 2, R0 '-prepolymerization reactor, R1' -vertical stirring reactor, R2 '-vertical stirring reactor, R3' -fluidized bed reactor, S1', S2' are flow separators.
Detailed Description
The present invention is described in detail below with reference to the following examples and the accompanying drawings, which are only for exemplary purposes of the present invention and are not intended to limit the scope of the present invention in any way, and all reasonable variations and combinations included in the scope of the present invention are within the scope of the present invention.
Example 1
In a method for producing polypropylene by serially connecting a plurality of reactors shown in fig. 1, a Ziegler-Natta catalyst, an external electron donor dicyclopentyl dimethoxy silane and a cocatalyst triethyl aluminum are added into a prepolymerization reactor R0, quantitative hydrogen is added through a hydrogen pipeline, propylene monomer is added through a propylene pipeline, the system pressure is maintained at 1bar, the reaction temperature is 30 ℃, and the prepolymerization is carried out for 15min. The pre-agglomerated polymer was fed into a horizontal stirred reactor R1, and propylene monomer was introduced to maintain the system pressure at 6bar and the temperature at 70 ℃. After the homopolymerization is finished, the polypropylene matrix in the first stage enters a horizontal stirring reactor R2, and meanwhile, the molar ratio of the polypropylene matrix to the stirring reactor R2 is 1:1, carrying out second-stage polymerization reaction on the ethylene/propylene mixed gas at the temperature of 70 ℃ and the pressure of 8bar for 30min. After the second polymerization stage is completed, the polypropylene matrix and the polymer composition obtained in the second polymerization stage are subjected to gas-solid separation and enter a fluidized bed reactor R3, and meanwhile, the polypropylene matrix and the polymer composition are added into the fluidized bed reactor through a pipeline in a molar ratio of 1:1 in the gas phase reaction of the third polymerization stage. The gas phase reaction temperature was 70℃and the pressure was 8bar, the reaction residence time was 20min. After the obtained product is graded by dimethylbenzene, the rubber phase content is 32.0%, the impact strength is 80KJ/m 2, the flexural modulus is 230MPa, and the glossiness is 74Gu. The electron microscope image can observe that the rubber phase is uniformly distributed, and the average size is about 0.5-1 mu m.
Example 2
In a method for producing polypropylene by serially connecting a plurality of reactors shown in fig. 1, a Ziegler-Natta catalyst, an external electron donor dicyclopentyl dimethoxy silane and a cocatalyst triethyl aluminum are added into a prepolymerization reactor R0, quantitative hydrogen is added through a hydrogen pipeline, propylene monomer is added through a propylene pipeline, the system pressure is maintained at 1bar, the reaction temperature is 30 ℃, and the prepolymerization is carried out for 15min. The pre-agglomerated polymer was fed into a horizontal stirred reactor R1, and propylene monomer was introduced to maintain the system pressure at 6bar and the temperature at 70 ℃. After the homopolymerization is finished, the polypropylene matrix in the first stage enters a horizontal stirring reactor R2, and meanwhile, the molar ratio of the polypropylene matrix to the stirring reactor R2 is 1:1, carrying out second-stage polymerization reaction on the ethylene/propylene mixed gas at the temperature of 70 ℃ and the pressure of 8bar for 30min. After the second polymerization stage is completed, the polypropylene matrix and the polymer composition obtained in the second polymerization stage are subjected to gas-solid separation and enter a fluidized bed reactor R3, and simultaneously ethylene is introduced into the bottom of the reactor for gas phase reaction in the third polymerization stage. The gas phase reaction temperature was 70℃and the pressure was 8bar, the reaction residence time was 20min. After the obtained product is graded by dimethylbenzene, the rubber phase content is 30.0%, the impact strength is 75KJ/m 2, the flexural modulus is 250MPa, and the glossiness is 76Gu. The electron microscope image can observe that the rubber phase is uniformly distributed, and the average size is about 0.5-1 mu m.
Example 3
In the production of the polypropylene composition by the method for producing the high-end polypropylene product shown in fig. 1, a ziegler-natta catalyst, an external electron donor dicyclopentyl dimethoxy silane and a cocatalyst triethylaluminum are added into a prepolymerization reactor R0, quantitative hydrogen is added through a hydrogen pipeline, propylene monomer is added through a propylene pipeline, the system pressure is maintained at 1bar, the reaction temperature is 30 ℃, and the prepolymerization is carried out for 15min. The pre-agglomerated polymer is fed into a horizontal stirred reactor R1, the propylene monomer is introduced to maintain the system pressure at 6bar, the temperature is controlled at 70℃and inert auxiliary is injected from the bottom of the reactor, the inert auxiliary preferably being isopentane in this example. After the homopolymerization is finished, the polypropylene matrix in the first stage enters a horizontal stirring reactor R2, and meanwhile, the polypropylene matrix is added into the reactor through a pipeline according to the molar ratio of 1:1, carrying out second-stage polymerization reaction on the ethylene/propylene mixed gas at the temperature of 70 ℃ and the pressure of 8bar for 30min. An inert auxiliary, preferably isopentane in this example, is injected from the top of the reactor. After the second polymerization stage is completed, the polypropylene matrix and the polymer composition obtained in the second polymerization stage are subjected to gas-solid separation and enter a fluidized bed reactor R3, and simultaneously ethylene and alpha-olefin are introduced into the bottom of the reactor for gas phase reaction in the third polymerization stage. The gas phase reaction temperature was 70℃and the pressure was 8bar, the reaction residence time was 20min. Inert auxiliary is injected from the side wall of the reactor, which in this example is preferably isopentane. After the obtained product is graded by dimethylbenzene, the EPR content is 42.7%, the impact strength is 100KJ/m 2, the flexural modulus is 270MPa, and the glossiness is 76Gu. The electron microscope image can observe that the rubber phase is uniformly distributed, and the average size is about 0.5-0.8 mu m.
Example 4
In the production of the polypropylene composition by the method for producing the high-end polypropylene product shown in fig. 1, a ziegler-natta catalyst, an external electron donor dicyclopentyl dimethoxy silane and a cocatalyst triethylaluminum are added into a prepolymerization reactor R0, quantitative hydrogen is added through a hydrogen pipeline, propylene monomer is added through a propylene pipeline, the system pressure is maintained at 1bar, the reaction temperature is 30 ℃, and the prepolymerization is carried out for 15min. The pre-agglomerated polymer is fed into a horizontal stirred reactor R1, the propylene monomer is introduced to maintain the system pressure at 6bar, the temperature is controlled at 70℃and inert auxiliary is injected from the top of the reactor, in this case preferably isopentane. After the homopolymerization is finished, the polypropylene matrix in the first stage enters a horizontal stirring reactor R2, and meanwhile, the molar ratio of the polypropylene matrix to the stirring reactor R2 is 1:1, carrying out second-stage polymerization reaction on the ethylene/propylene mixed gas at the temperature of 70 ℃ and the pressure of 8bar for 30min. From the top of the reactor, inert auxiliary, preferably isopentane in this example, is injected progressively in the axial direction of the reactor at a rate of 5%. After the second polymerization stage is completed, the polypropylene matrix and the polymer composition obtained in the second polymerization stage are subjected to gas-solid separation, enter a fluidized bed reactor R3, and ethylene and alpha-olefin are introduced into the bottom of the reactor to carry out gas phase reaction in the third polymerization stage. Inert auxiliary is injected from the side wall of the reactor, which in this example is preferably isopentane. The gas phase reaction temperature was 70℃and the pressure was 8bar, the reaction residence time was 20min. Simultaneously, the discharge flow of the horizontal stirring reactor R2 flows back to the horizontal stirring reactor R1, and the discharge flow of the fluidized bed reactor R3 flows back to the horizontal stirring reactor R2, and the circulation ratio is 0.3. After the obtained product is graded by dimethylbenzene, the EPR content is 45.0%, the impact strength is 120KJ/m 2, the flexural modulus is 260MPa, and the glossiness is 80Gu. The electron microscope image can observe that the rubber phase is uniformly distributed, and the average size is about 0.5-0.8 mu m.
Comparative example 1
In the method for producing polypropylene by using the multi-reactor series connection shown in fig. 1, a Ziegler-Natta catalyst, an external electron donor dicyclopentyl dimethoxy silane and a cocatalyst triethyl aluminum are added into a horizontal stirring reactor R1, propylene monomers are introduced to keep the system pressure at 6bar, and the temperature is controlled at 70 ℃. After the homopolymerization is finished, the polypropylene matrix in the first stage enters a horizontal stirring reactor R2, and meanwhile, the molar ratio of the polypropylene matrix to the stirring reactor R2 is 1:1, carrying out second-stage polymerization reaction on the ethylene/propylene mixed gas at the temperature of 70 ℃ and the pressure of 8bar for 30min. After the second polymerization stage is completed, the polypropylene matrix and the polymer composition obtained in the second polymerization stage are subjected to gas-solid separation and enter a fluidized bed reactor R3, and meanwhile, the polypropylene matrix and the polymer composition are added into the fluidized bed reactor through a pipeline in a molar ratio of 1:1 in the gas phase reaction of the third polymerization stage. The gas phase reaction temperature was 70℃and the pressure was 8bar, the reaction residence time was 20min. After the obtained product is graded by dimethylbenzene, the EPR content is 24.7%, the impact strength is 35KJ/m 2, the flexural modulus is 1.0GPa, and the glossiness is 48Gu. The electron microscopy showed that the rubber phase was unevenly distributed with an average size of about 2 μm.
Comparative example 2
In the method for producing polypropylene by using the multi-reactor series connection shown in fig. 1, a Ziegler-Natta catalyst, an external electron donor dicyclopentyl dimethoxy silane and a cocatalyst triethyl aluminum are added into a horizontal stirring reactor R1, propylene monomers are introduced to keep the system pressure at 6bar, and the temperature is controlled at 70 ℃. After the homopolymerization is finished, the polypropylene matrix in the first stage enters a horizontal stirring reactor R2, and meanwhile, the molar ratio of the polypropylene matrix to the stirring reactor R2 is 1:1, carrying out second-stage polymerization reaction on the ethylene/propylene mixed gas at the temperature of 70 ℃ and the pressure of 8bar for 30min. After the second polymerization stage is completed, the polypropylene matrix and the polymer composition obtained in the second polymerization stage are subjected to gas-solid separation and enter a fluidized bed reactor R3, and simultaneously ethylene is introduced into the bottom of the reactor for gas phase reaction in the third polymerization stage. The gas phase reaction temperature was 70℃and the pressure was 8bar, the reaction residence time was 10min. After the obtained product is graded by dimethylbenzene, the EPR content is 20.0%, the impact strength is 32KJ/m 2, the flexural modulus is 1.5GPa, and the glossiness is 48Gu. The electron microscopy showed that the rubber phase was unevenly distributed with an average size of about 2 μm.
Comparative example 3
In a polypropylene composition produced by a method for producing polypropylene by a multi-reactor series connection shown in fig. 2, a ziegler-natta catalyst, an external electron donor dicyclopentyl dimethoxy silane and a cocatalyst triethylaluminum are added into a prepolymerization reactor R0', quantitative hydrogen is added through a hydrogen pipeline, propylene monomer is added through a propylene pipeline, the system pressure is maintained at 1bar, the reaction temperature is 30 ℃, and the prepolymerization is carried out for 15min. The pre-agglomerated polymer is fed into a vertical stirred reactor R1', the propylene monomer is introduced to maintain the system pressure at 6bar, the temperature is controlled at 70℃and inert auxiliary is injected from the side wall of the reactor, the inert auxiliary preferably being isopentane in this example. After the homopolymerization is finished, the polypropylene matrix in the first stage enters a vertical stirring reactor R2', and meanwhile, the molar ratio of the polypropylene matrix to the vertical stirring reactor R2 is 1:1, and spraying an inert auxiliary agent, preferably isopentane in this embodiment, from the side wall of the reactor. The reaction temperature was 70℃and the pressure was 8bar, and the reaction was carried out for 30min. After the second polymerization stage is completed, the polypropylene matrix and the polymer composition obtained in the second polymerization stage are subjected to gas-solid separation, enter a fluidized bed reactor R3', and ethylene is introduced into the bottom of the reactor to carry out gas phase reaction in the third polymerization stage. Inert auxiliary is injected from the side wall of the reactor, which in this example is preferably isopentane. The gas phase reaction temperature was 70℃and the pressure was 8bar, the reaction residence time was 20min. Meanwhile, the discharge flow of the vertical stirring reactor R2 'is optionally refluxed to the vertical stirring reactor R1', the discharge flow of the fluidized bed reactor R3 'is optionally refluxed to the vertical stirring reactor R2', and the circulation ratio is 0.3. After the obtained product is graded by dimethylbenzene, the EPR content is 22.0%, the impact strength is 33KJ/m 2, the flexural modulus is 1.1GPa, and the glossiness is 50Gu. The electron microscopy showed that the rubber phase was unevenly distributed with an average size of about 2 μm.
The foregoing examples illustrate only a few embodiments of the invention and are described in detail herein without thereby limiting the scope of the invention. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit of the invention.
Claims (10)
1. A process for producing polypropylene in series in a plurality of reactors, said process comprising the steps of:
S1: propylene is prepolymerized in a prepolymerization reactor under a catalyst system;
S2: in the first polymerization stage, the catalytically active particles obtained by the prepolymerization reaction enter a first reactor for propylene homopolymerization;
s3: in the second polymerization stage, propylene homopolymer enters a second reactor to carry out propylene homopolymerization or ethylene propylene copolymerization continuously;
S4: in the third polymerization stage, the product of the second reactor enters a third reactor to carry out ethylene polymerization or ethylene propylene copolymerization to obtain a polypropylene product.
2. The process according to claim 1, wherein the product of the second reactor can be withdrawn directly as polypropylene product; when propylene homopolymerization is carried out in the first reactor and the second reactor, the second reactor can lead out a homopolymerized polypropylene product; when the first reactor performs propylene homopolymerization and the second reactor performs ethylene-propylene copolymerization, the second reactor can lead out an impact copolymer polypropylene product.
3. The method of claim 1, wherein the step of determining the position of the substrate comprises,
Controlling the second reactor and the third reactor to carry out ethylene-propylene copolymerization, and producing high-rubber-phase-content polypropylene with the rubber phase content of more than 35 weight percent by the method;
controlling the second reactor to carry out ethylene-propylene copolymerization and the third reactor to carry out ethylene homopolymerization, wherein the method is used for producing polypropylene with toughness improved by more than 30% and modulus loss less than 10%;
The second reactor is controlled to carry out ethylene-propylene copolymerization, the third reactor is controlled to carry out ethylene-alpha-olefin copolymerization, and the method is used for producing polypropylene with impact strength of more than 70KJ/m 2, flexural modulus of more than 200MPa and glossiness of more than 70 Gu.
4. The process according to claim 1, wherein inert auxiliary is added to the first and/or second and/or third reactor in a single or multiple point manner from the side wall, bottom or top of the reactor.
5. The process according to claim 4, wherein the inert auxiliary is added in a multipoint manner in an amount which is uniformly distributed along the axial direction of the reactor or is gradually decreased or increased in a gradient of 1 to 50wt% along the axial direction of the reactor.
6. The process according to claim 1, characterized in that the second reactor discharge stream is optionally recycled to the first reactor with a recycle ratio of 0.1 to 30 and/or the third reactor discharge stream is optionally recycled to the second reactor with a recycle ratio of 0.1 to 30.
7. The process of claim 1, wherein the catalyst system used in the prepolymerization, the first polymerization stage, the second polymerization stage, and the third polymerization stage comprises a solid catalyst component, an alkyl aluminum or alkyl aluminoxane, and not less than one external electron donor; the solid catalyst component is selected from Ziegler-Natta catalysts, chromium-based catalysts, metallocene catalysts, late transition metal catalysts, or mixtures thereof.
8. The process according to claim 1, wherein the first reactor is selected from a vertical stirred reactor, a horizontal stirred reactor, a loop reactor or a fluidized bed reactor, preferably a horizontal stirred reactor; the second reactor is selected from a vertical stirring reactor, a horizontal stirring reactor or a fluidized bed reactor, preferably a horizontal stirring reactor; the third reactor is selected from a vertical stirred reactor, a horizontal stirred reactor or a fluidized bed reactor, preferably a fluidized bed reactor.
9. The process according to claim 1, wherein the ethylene polymerization comprises ethylene homo-polymerization or ethylene copolymerization with an alpha-olefin having a carbon number of 4-18.
10. The method according to claim 4, wherein the inert auxiliary agent is one or more selected from the group consisting of linear alkanes, branched alkanes and cycloalkanes having 3 to 18 carbon atoms.
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