CN117384315A - Method for preparing polyethylene resin by utilizing two reactors in series/parallel connection, polyethylene resin and application - Google Patents
Method for preparing polyethylene resin by utilizing two reactors in series/parallel connection, polyethylene resin and application Download PDFInfo
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- CN117384315A CN117384315A CN202210792599.1A CN202210792599A CN117384315A CN 117384315 A CN117384315 A CN 117384315A CN 202210792599 A CN202210792599 A CN 202210792599A CN 117384315 A CN117384315 A CN 117384315A
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- 229920013716 polyethylene resin Polymers 0.000 title claims abstract description 148
- 238000000034 method Methods 0.000 title claims abstract description 43
- -1 polyethylene Polymers 0.000 claims abstract description 40
- 239000004698 Polyethylene Substances 0.000 claims abstract description 39
- 239000003054 catalyst Substances 0.000 claims abstract description 39
- 229920000573 polyethylene Polymers 0.000 claims abstract description 37
- 238000009826 distribution Methods 0.000 claims abstract description 36
- 150000001336 alkenes Chemical class 0.000 claims abstract description 29
- 239000000178 monomer Substances 0.000 claims abstract description 29
- JRZJOMJEPLMPRA-UHFFFAOYSA-N olefin Natural products CCCCCCCC=C JRZJOMJEPLMPRA-UHFFFAOYSA-N 0.000 claims abstract description 29
- 239000002002 slurry Substances 0.000 claims abstract description 29
- 239000013078 crystal Substances 0.000 claims abstract description 27
- 239000002245 particle Substances 0.000 claims abstract description 22
- 238000006116 polymerization reaction Methods 0.000 claims abstract description 20
- 238000002156 mixing Methods 0.000 claims abstract description 18
- 239000000463 material Substances 0.000 claims abstract description 14
- 238000007334 copolymerization reaction Methods 0.000 claims abstract description 10
- LIKMAJRDDDTEIG-UHFFFAOYSA-N 1-hexene Chemical compound CCCCC=C LIKMAJRDDDTEIG-UHFFFAOYSA-N 0.000 claims description 36
- 238000002360 preparation method Methods 0.000 claims description 26
- 238000006243 chemical reaction Methods 0.000 claims description 20
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 claims description 19
- 239000005977 Ethylene Substances 0.000 claims description 19
- QWTDNUCVQCZILF-UHFFFAOYSA-N isopentane Chemical compound CCC(C)C QWTDNUCVQCZILF-UHFFFAOYSA-N 0.000 claims description 16
- 239000004711 α-olefin Substances 0.000 claims description 13
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 claims description 12
- 238000012805 post-processing Methods 0.000 claims description 9
- VXNZUUAINFGPBY-UHFFFAOYSA-N 1-Butene Chemical compound CCC=C VXNZUUAINFGPBY-UHFFFAOYSA-N 0.000 claims description 8
- KWKAKUADMBZCLK-UHFFFAOYSA-N 1-octene Chemical compound CCCCCCC=C KWKAKUADMBZCLK-UHFFFAOYSA-N 0.000 claims description 8
- 239000011954 Ziegler–Natta catalyst Substances 0.000 claims description 8
- AFABGHUZZDYHJO-UHFFFAOYSA-N dimethyl butane Natural products CCCC(C)C AFABGHUZZDYHJO-UHFFFAOYSA-N 0.000 claims description 8
- 238000005243 fluidization Methods 0.000 claims description 7
- IMNFDUFMRHMDMM-UHFFFAOYSA-N N-Heptane Chemical compound CCCCCCC IMNFDUFMRHMDMM-UHFFFAOYSA-N 0.000 claims description 6
- AFFLGGQVNFXPEV-UHFFFAOYSA-N 1-decene Chemical compound CCCCCCCCC=C AFFLGGQVNFXPEV-UHFFFAOYSA-N 0.000 claims description 4
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 4
- OFBQJSOFQDEBGM-UHFFFAOYSA-N Pentane Chemical compound CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 claims description 4
- 238000000071 blow moulding Methods 0.000 claims description 4
- 229910052804 chromium Inorganic materials 0.000 claims description 4
- 239000011651 chromium Substances 0.000 claims description 4
- 238000009776 industrial production Methods 0.000 claims description 4
- 238000001746 injection moulding Methods 0.000 claims description 4
- TVMXDCGIABBOFY-UHFFFAOYSA-N n-Octanol Natural products CCCCCCCC TVMXDCGIABBOFY-UHFFFAOYSA-N 0.000 claims description 4
- YWAKXRMUMFPDSH-UHFFFAOYSA-N pentene Chemical compound CCCC=C YWAKXRMUMFPDSH-UHFFFAOYSA-N 0.000 claims description 4
- 238000001175 rotational moulding Methods 0.000 claims description 4
- XDTMQSROBMDMFD-UHFFFAOYSA-N Cyclohexane Chemical compound C1CCCCC1 XDTMQSROBMDMFD-UHFFFAOYSA-N 0.000 claims description 2
- 238000012685 gas phase polymerization Methods 0.000 claims description 2
- 239000012968 metallocene catalyst Substances 0.000 claims description 2
- QQONPFPTGQHPMA-UHFFFAOYSA-N propylene Natural products CC=C QQONPFPTGQHPMA-UHFFFAOYSA-N 0.000 claims description 2
- 125000004805 propylene group Chemical group [H]C([H])([H])C([H])([*:1])C([H])([H])[*:2] 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
- 239000007789 gas Substances 0.000 description 32
- 239000007787 solid Substances 0.000 description 12
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 10
- 230000000052 comparative effect Effects 0.000 description 9
- 239000007788 liquid Substances 0.000 description 8
- 239000000203 mixture Substances 0.000 description 8
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 7
- 239000001257 hydrogen Substances 0.000 description 7
- 229910052739 hydrogen Inorganic materials 0.000 description 7
- 238000004519 manufacturing process Methods 0.000 description 7
- 239000000047 product Substances 0.000 description 7
- 229910052757 nitrogen Inorganic materials 0.000 description 5
- 239000000155 melt Substances 0.000 description 4
- 239000004705 High-molecular-weight polyethylene Substances 0.000 description 3
- 230000003197 catalytic effect Effects 0.000 description 3
- 239000012530 fluid Substances 0.000 description 3
- 239000011268 mixed slurry Substances 0.000 description 3
- 229920000642 polymer Polymers 0.000 description 3
- 229920000098 polyolefin Polymers 0.000 description 3
- 238000004064 recycling Methods 0.000 description 3
- 238000000926 separation method Methods 0.000 description 3
- 230000002902 bimodal effect Effects 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000000835 fiber Substances 0.000 description 2
- 238000011065 in-situ storage Methods 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 238000001228 spectrum Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- VOITXYVAKOUIBA-UHFFFAOYSA-N triethylaluminium Chemical compound CC[Al](CC)CC VOITXYVAKOUIBA-UHFFFAOYSA-N 0.000 description 2
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 238000005227 gel permeation chromatography Methods 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 230000000379 polymerizing effect Effects 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 239000012066 reaction slurry Substances 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
Classifications
-
- 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
- C08F210/16—Copolymers of ethene with alpha-alkenes, e.g. EP rubbers
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts
Abstract
The invention relates to the technical field of olefin polymerization, and discloses a method for preparing polyethylene resin by utilizing two reactors in series/parallel connection, the polyethylene resin and application. The method for preparing the polyethylene resin A in series comprises the following steps: (1-1) contacting olefin monomer and condensate in a first reactor in the presence of a first catalyst to perform a copolymerization reaction to obtain a slurry discharge comprising polyethylene active particles and a portion of the condensate; (1-2) introducing the discharged slurry directly into a second reactor, continuing the olefin polymerization reaction in the presence of a second catalyst, and carrying out melt blending treatment on the discharged material of the second reactor to obtain the polyethylene resin A with the cross-crystal structure. The method can obtain polyethylene with a serial crystal structure, and has wide molecular weight distribution, good mechanical property and processability.
Description
Technical Field
The invention relates to the technical field of olefin polymerization, in particular to a method for preparing polyethylene resin by utilizing two reactors in series/parallel connection, the polyethylene resin and application.
Background
Olefin polymers are widely used in various fields, and have rigidity, toughness, and light weight, which are not replaced by many materials. However, in the preparation of polyethylene, there is a serious structural shortage of high-end specialty materials, which is largely dependent on importation. Therefore, the development of the high-end polyethylene resin production technology is an urgent need for promoting the safe and high-speed development of petrochemical industry in China and ensuring the market competitiveness of polyolefin industry.
It is difficult for conventional polyethylene products to satisfy both good processability and mechanical strength. The high molecular weight polyethylene has good mechanical properties, but has poor rheological properties and high processing difficulty. The low molecular weight polyethylene has good processing rheological properties but poor mechanical properties. In order to improve the use properties of polyethylene, it is possible to produce polyethylene having a multi/broad peak molecular weight distribution by expanding the molecular weight distribution of polyethylene.
In the conventional olefin polymerization process, a typical method is to use a series of reactors to polymerize a polyolefin having a double/broad peak molecular weight distribution, which can give a product excellent in use properties and processability, thereby achieving high performance of the product.
EP-A-691353 discloses a process for producing broad/bimodal polyethylene in series with two conventional gas phase reactors; the process has problems of reactant cross-flow between two gas phase reactors, non-uniform residence time of polymer particles in the two gas phase reactors, etc. EP-B-517868, US6642323 and US7115687B disclose a process in which a first loop reactor and a second gas phase fluidized bed reactor are connected in series; this process has a problem in that residence time distribution of polymer particles in two gas phase reactors is not uniform and resin fines produced in the first reactor are large. EP 0887379B1 uses a loop in series with a fluidized bed reactor to produce bimodal PE. The monomer and the prepolymerized catalyst are added into a loop reactor, and the polymerized slurry discharge is subjected to flash evaporation, gas-solid separation and dry powder conveying, and PE particles are sent into a fluidized bed. In the process, particles enter a fluidized bed in a dry powder form, so that the particles are extremely easy to explode and agglomerate, the agglomeration risk is high, the energy consumption is high, and the problem of pipeline blockage caused by polymerization also exists.
On the one hand, there is still a further need in the market for polyethylene having both good processability and mechanical strength, and on the other hand, the current multimodal molecular weight distribution polyethylene and its preparation process still have the problems of poor performance and complex process, based on which, a method for preparing high performance polyethylene resin by using two reactors in series/parallel is provided, which is expected to solve the problems exposed by the prior art in the related art.
Disclosure of Invention
The invention aims to solve the problems that the polyethylene product in the prior art is difficult to simultaneously meet good processability and mechanical strength, and the existing multimodal molecular weight distribution polyethylene and the preparation process thereof still have the problems of poor performance and complex process.
In order to achieve the above object, a first aspect of the present invention provides a method for producing polyethylene resin a using two reactors in series, wherein the production method comprises:
(1-1) contacting olefin monomer and condensate in a first reactor in the presence of a first catalyst to perform a copolymerization reaction to obtain a slurry discharge comprising polyethylene active particles and a portion of the condensate;
(1-2) introducing the slurry discharge directly into a second reactor, continuing the olefin polymerization reaction in the presence of an optional second catalyst, and carrying out melt blending treatment on the discharge of the second reactor to obtain the polyethylene resin A with the cross-crystal structure.
The second aspect of the present invention provides a method for preparing polyethylene resin using two reactors in parallel, wherein the preparation method comprises:
(2-1) in the presence of a first catalyst, contacting a first olefin monomer with a first condensate in a first reactor to carry out a copolymerization reaction to obtain a polyethylene resin discharge 1;
(2-2) carrying out polymerization reaction on a second olefin monomer in the presence or absence of a second condensate in a second reactor under the action of a second catalyst to obtain a polyethylene resin discharge 2;
(2-3) carrying out melt blending treatment on the discharge material 1 and the discharge material 2 to obtain polyethylene resin B with a serial crystal structure; and/or the number of the groups of groups,
(2-4) subjecting the discharge 1 and the discharge 2 to post-processing treatment, respectively, to obtain a polyethylene resin C and a polyethylene resin D.
In a third aspect, the present invention provides a polyethylene resin a prepared by the tandem preparation method described above.
The fourth aspect of the invention provides a polyethylene resin prepared by the parallel preparation method, wherein the polyethylene resin comprises one or more of polyethylene resin B, polyethylene resin C and polyethylene resin D with a serial crystal structure.
In a fifth aspect the present invention provides the use of a polyethylene resin a or a polyethylene resin as described hereinbefore in one or more of film materials, pipes, fibres, blow moulding, injection moulding and rotational moulding.
In a sixth aspect, the present invention provides a method for producing a polyethylene resin in industrial production, wherein the method comprises freely switching between a series connection and a parallel connection to produce a polyethylene resin, wherein the series connection is the method described above, and the parallel connection is the method described above.
Through the technical scheme, the polyethylene with the serial crystal structure has wide molecular weight distribution, good mechanical property and processability and can be widely used in various fields such as film materials, pipes, fibers, blow molding, injection molding, rotational molding and the like.
Drawings
FIG. 1 is a schematic flow diagram of a simplified apparatus for preparing polyethylene resins using two reactors in series in accordance with the present invention;
FIG. 2 is a schematic flow diagram of a simplified apparatus for preparing polyethylene resins in parallel using two reactors in accordance with the present invention;
FIG. 3 is a scanning electron microscope spectrum of polyethylene resin A prepared by using two reactors in series according to example 1 of the present invention;
fig. 4 is a scanning electron microscope spectrum of a polyethylene resin B prepared using two reactors in parallel according to example 2 of the present invention.
Description of the reference numerals
1-a first reactor (loop reactor); 2-a second reactor (fluidized bed reactor); 3-compressors; 4-a heat exchanger; 5-a gas-liquid separator; and 6, a post-processing procedure.
Detailed Description
The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.
As described above, the first aspect of the present invention provides a method for preparing polyethylene resin a using two reactors in series, wherein the preparation method comprises:
(1-1) contacting olefin monomer and condensate in a first reactor in the presence of a first catalyst to perform a copolymerization reaction to obtain a slurry discharge comprising polyethylene active particles and a portion of the condensate;
(1-2) introducing the slurry discharge directly into a second reactor, continuing the olefin polymerization reaction in the presence of an optional second catalyst, and carrying out melt blending treatment on the discharge of the second reactor to obtain the polyethylene resin A with the cross-crystal structure.
The second aspect of the present invention provides a method for preparing polyethylene resin using two reactors in parallel, wherein the preparation method comprises:
(2-1) in the presence of a first catalyst, contacting a first olefin monomer with a first condensate in a first reactor to carry out a copolymerization reaction to obtain a polyethylene resin discharge 1;
(2-2) carrying out polymerization reaction on a second olefin monomer in the presence or absence of a second condensate in a second reactor under the action of a second catalyst to obtain a polyethylene resin discharge 2;
(2-3) carrying out melt blending treatment on the discharge material 1 and the discharge material 2 to obtain polyethylene resin B with a serial crystal structure; and/or the number of the groups of groups,
(2-4) subjecting the discharge 1 and the discharge 2 to post-processing treatment, respectively, to obtain a polyethylene resin C and a polyethylene resin D.
The inventors of the present invention found that: slurry polymerization in a first reactor grows high molecular weight polyethylene chains on some active sites of a catalyst, active particles and a solvent thereof are sprayed into a second reactor, and medium and low molecular weight polyethylene chains grow on other active sites of the catalyst under the condition of the second reactor, so that molecular chain-level mixing of polyethylenes with different molecular weights can be realized, and further polyethylene resin with a serial crystal structure, wide molecular weight distribution, wide melt index distribution and wide density distribution is obtained. On the other hand, the high molecular weight polyethylene produced in the first reactor and the medium and low molecular weight polyethylene produced in the second reactor can be subjected to post-treatment steps such as melt blending, etc., to obtain a polyethylene having a broad molecular weight distribution.
According to the invention, the olefin monomers include ethylene and alpha-olefins, in which case ethylene is the monomer and alpha-olefin is the comonomer. In addition, in the present invention, preferably, the α -olefin is selected from one or more of propylene, 1-butene, 1-pentene, 1-hexene, 1-octene and 1-decene, and preferably, the α -olefin is selected from one or more of 1-butene, 1-hexene and 1-octene.
According to the invention, the alpha-olefin is used in an amount of 0.01 to 8mol%, preferably 0.5 to 4mol%, based on the total molar amount of the olefin monomers.
According to the invention, the condensate is selected from one or more of n-pentane, isopentane, cyclohexane, n-hexane and n-heptane, preferably the condensate is isopentane and/or n-hexane.
According to the invention, the first catalyst and the second catalyst are the same or different and are each selected from one or more of a ziegler-natta catalyst, a metallocene catalyst, a transition metal catalyst, an inorganic chromium catalyst and an organic chromium catalyst, preferably a ziegler-natta catalyst.
According to the invention, the first catalyst is used in an amount of 0.003 to 0.01wt%, preferably 0.005 to 0.01wt%, based on the total weight of the olefin monomers, respectively; the second catalyst is used in an amount of 0 to 0.03wt%, preferably 0.005 to 0.03wt%, more preferably 0.01 to 0.02wt%.
According to the invention, in step (1-1), the polyethylene active particles are present in an amount of 10 to 50 wt.%, preferably 25 to 40 wt.%, based on the total weight of the slurry discharge.
According to the invention, in step (1-2), the superficial fluidization gas velocity in the second reactor is from 0.1 to 3m/s, preferably from 0.3 to 0.8m/s.
According to the invention, in step (2-2), the second catalyst is used in an amount of 0.005 to 0.03wt%, preferably 0.01 to 0.02wt%, based on the total weight of the second olefin monomer.
According to the invention, the second condensate is used in an amount of 0 to 50mol%, preferably 0 to 40mol%, based on the total molar amount of the second olefin monomer.
According to the invention, in step (2-2), the superficial fluidization gas velocity in the second reactor is from 0.1 to 3m/s, preferably from 0.3 to 0.8m/s.
According to the invention, in step (2-3), the polyethylene resin take-off 1 is used in an amount of 5-40 wt.%, preferably 10-28 wt.%, based on the total weight of the polyethylene resin take-off 1 and the polyethylene resin take-off 2.
According to the invention, the first reactor is a slurry polymerization reactor, preferably a slurry loop reactor.
According to the invention, the second reactor is a gas phase polymerization reactor, preferably a fluidized bed reactor.
According to the invention, the temperature of the second reactor is higher than the temperature of the first reactor; preferably, the temperature of the second reactor is at least 5 ℃, preferably 10-25 ℃ higher than the temperature of the first reactor.
According to the invention, the pressure of the second reactor is lower than the pressure of the first reactor; preferably, the pressure of the second reactor is at least 1MPa lower than the pressure of the first reactor, preferably 1.5-2MPa lower.
According to the invention, the reaction temperature of the first reactor is 45-75 ℃, preferably 55-65 ℃, and the reaction pressure is 1-7MPa, preferably 3.5-4.5MPa.
According to the invention, the reaction temperature of the second reactor is 65-100 ℃, preferably 80-90 ℃, and the reaction pressure is 0.5-6MPa, preferably 2-2.5MPa.
According to the present invention, in the method for producing polyethylene resins in parallel, the post-processing treatment refers to melt blending.
According to the invention, the first reactor and the second reactor can be freely selected to be connected in series or in parallel according to production requirements in industrial production.
In a third aspect, the present invention provides a polyethylene resin a prepared by the tandem preparation method described above.
According to the present invention, the polyethylene resin A has a weight average molecular weight of 300000-2000000, a molecular weight distribution index of 10-50, and a density of 0.910-0.960g/cm 3 Melt index MI at 190 ℃ temperature 21.6 0.1-20g/10min, young's modulus 400-900MPa, tensile strength 35-90MPa, impact strength 40-90kJ/m 2 。
In the present invention, "melt index MI" is used 21.6 "means testing at 21.6 kg.
According to the present invention, the cross-linked content in the polyethylene resin A is 2 to 40wt%.
According to the present invention, the cross-linked content in the polyethylene resin B is 1 to 30wt%.
According to the present invention, the cross-linked content in the polyethylene resin a is higher than that in the polyethylene resin B.
The fourth aspect of the invention provides a polyethylene resin prepared by the parallel preparation method, wherein the polyethylene resin comprises one or more of polyethylene resin B, polyethylene resin C and polyethylene resin D with a serial crystal structure.
According to the present invention, the polyethylene resin B has a weight average molecular weight of 350000-600000, a molecular weight distribution index of 25-40, and a density of 0.920-0.980g/cm 3 Melt index MI at 190 ℃ temperature 21.6 0.02-30g/10min, young's modulus 400-800MPa, tensile strength 30-78MPa, impact strength 30-80kJ/m 2 。
According to the present invention, the polyethylene resin C has a weight average molecular weight of 1000000-5000000, a molecular weight distribution index of 6.5 to 15.1, and a density of 0.920 to 0.950g/cm 3 Melt index MI at 230 ℃ temperature 21.6 0.01-5g/10min, young's modulus of 700-900MPa, tensile strength of 30-90MPa, impact strength of 60-190kJ/m 2 。
According to the present invention, the polyethylene resin D has a weight average molecular weight of 100000-300000, a molecular weight distribution index of 2.5-14.3, and a density of 0.912-0.980g/cm 3 Melt index MI at 190 ℃ temperature 21.6 6-30g/10min, young's modulus of 250-450MPa, tensile strength of 24-36MPa, and impact strength of 15-50kJ/m 2 。
In a fifth aspect the present invention provides the use of a polyethylene resin a or a polyethylene resin as described hereinbefore in one or more of film materials, pipes, fibres, blow moulding, injection moulding and rotational moulding.
In a sixth aspect, the present invention provides a method for producing a polyethylene resin in industrial production, wherein the method comprises freely switching between a series connection and a parallel connection to produce a polyethylene resin, wherein the series connection is the method described above, and the parallel connection is the method described above.
According to a particularly preferred embodiment of the present invention, the method for preparing polyethylene resin a using two reactors in series comprises:
as shown in fig. 1.
(1) Introducing condensate, monomer ethylene and comonomer alpha-olefin into a first reactor 1 (slurry loop reactor), and carrying out monomer/comonomer polymerization under the action of a catalyst to obtain polyethylene active particles with high molecular weight and containing a certain branched chain, wherein part of solvent (condensate) and solid particles in the first reactor are discharged as slurry;
(2) And part of mixed slurry in the first reactor is discharged and led out, and enters a second reactor 2 (gas-solid fluidized bed reactor) through a delivery pipeline by a nozzle, wherein solid particles in slurry feed in the second reactor are fluidized under the action of circulating gas and undergo monomer/comonomer polymerization reaction to generate the polyethylene with medium and low molecular weight. The recycle gas is obtained by mixing the top outlet gas of the reactor with ethylene feed and hydrogen feed, compressing the mixture by a compressor 3, mixing the mixture with comonomer feed and condensate feed, condensing the mixture by a heat exchanger 4, separating the mixture by a gas-liquid separator 5, and recycling the obtained liquid back to the first reactor. Finally, the polyethylene resin with the molecular weight, the melt index and the wide density distribution of the serial crystal structure is obtained by in-situ blending.
According to a particularly preferred embodiment of the present invention, a method for preparing polyethylene resin using two reactors in parallel comprises:
as shown in fig. 2.
(1) Introducing condensate, monomer ethylene and comonomer alpha-olefin into a first reactor 1 (slurry loop reactor), and carrying out monomer/comonomer polymerization under the action of a catalyst to obtain a polyethylene resin discharge 1 with high molecular weight and a certain branched chain;
(2) In a second reactor 2 (gas-solid fluidized bed reactor), after the gas at the top of the reactor is mixed with ethylene feed and hydrogen feed and compressed by a compressor 3, the mixture is mixed with comonomer feed and condensate feed, the mixture is condensed by a heat exchanger 4, the gas obtained after separation by a gas-liquid separator 5 is taken as circulating gas to enter the reactor from the bottom of the reactor, the obtained liquid enters the reactor from the side wall of the reactor, and the reaction is continuously carried out in the second reactor to generate a polyethylene resin discharge 2 with medium and low molecular weight;
polyethylene resin discharge 1 and discharge 2 in the two reactors can obtain polyethylene resin discharge 3 with wide distribution of molecular weight, melt index and density through post-processing procedure 8.
The present invention will be described in detail by examples.
In the following examples and comparative examples:
the tandem structure was observed by a scanning electron microscope, available from FEI company, usa, under the model Nova Nano SEM450;
the molecular weight and molecular weight distribution were tested by high temperature gel permeation chromatography available from pritaike instruments, inc, model PL-GPC220;
melt index was measured by a melt index apparatus, commercially available from Gottfert, germany, model MI-3; the test standard is ASTM1238.
The mechanical properties (Young modulus and tensile strength) are detected by adopting a national standard detection method of the people's republic of China, and the standard is GB/T1040-2006; impact strength was measured using American Standard ASTM-D256.
Example 1
This example illustrates the preparation of polyethylene resins using a preparation process in which two reactors are connected in series.
As shown in fig. 1.
(1) Introducing condensed fluid isopentane, ethylene and 1-hexene into a first reactor (slurry loop reactor), and carrying out ethylene/1-hexene copolymerization under the action of a hybrid Ziegler-Natta catalyst to obtain polyethylene with high molecular weight and a certain branched chain; wherein the first reactor is operated at a temperature of 60 ℃ and a pressure of 4.0MPa; the slurry density in the first reactor was 695kg/m 3 The catalyst feeding amount is 0.68kg/h, the 1-hexene concentration in the reactor is 1.1mol percent, and the mass fraction of the solid polyethylene active particles is 40wt%;
(2) Discharging part of mixed slurry in the first reactor, introducing the mixed slurry into a second reactor (gas-solid fluidized bed reactor), mixing gas obtained from the top outlet of the second reactor with feed gas and condensate feed, performing gas-liquid separation, introducing the separated gas into the second reactor as circulating gas for continuous reaction, and further polymerizing under the catalysis of a hybrid Ziegler-Natta catalyst to generate low molecular weight polyethylene; wherein the reaction temperature is 85 ℃, the reaction pressure is 2.3MPa, the apparent fluidization gas velocity is 0.7m/s, the ethylene molar concentration in the circulating gas is 28mol%, the hydrogen molar concentration is 3mol%, the nitrogen molar concentration is 56mol%, the 1-hexene molar concentration is 3mol%, and the isopentane molar concentration is 10mol%;
finally, the polyethylene resin discharge A with a cross-crystal structure and wide distribution of molecular weight, melt index and density is obtained by in-situ blending.
The obtained polyethylene resin A can observe a serial crystal structure shown in figure 3 under a scanning electron microscope, wherein the serial crystal structure consists of a central fiber and lamellar crystals which grow in a serial manner along a central backbone; the density of the polyethylene resin A obtained was 0.95g/cm 3 A weight average molecular weight of 500000; the molecular weight distribution index was 34.52, melt index MI 21.6 (190 ℃) 9.31g/10min, young's modulus 630MPa, tensile strength 74MPa, impact strength 72kJ/m 2 。
Example 2
This example illustrates the preparation of polyethylene resins using a preparation process in which two reactors are connected in series.
Polyethylene resin a was prepared in the same manner as in example 1, except that: the mass fraction of solid polyethylene active particles in the slurry in the first reactor is 35wt%, and the slurry density is 650kg/m 3 。
The prepared polyethylene resin A has a serial crystal structure; the density of the polyethylene resin A obtained was 0.94g/cm 3 A weight average molecular weight of 430000; a molecular weight distribution index of 30.51; melt index MI 21.6 (190 ℃) 11.37g/10min, young's modulus 560MPa, tensile strength 67MPa, impact strength 69kJ/m 2 。
Example 3
This example illustrates the preparation of polyethylene resins using a preparation process in which two reactors are connected in series.
Polyethylene resin a was prepared in the same manner as in example 1, except that: the condensing agent is n-hexane, the ethylene molar concentration in the circulating gas of the second reactor is 34mol%, the hydrogen molar concentration is 5mol%, the nitrogen molar concentration is 48mol%, the 1-hexene molar concentration is 6mol%, and the n-hexane molar concentration is 7mol%.
The polyethylene resin A prepared by the method has a serial crystal structure; the density of the polyethylene resin A obtained was 0.94g/cm 3 The weight average molecular weight was 450000; a molecular weight distribution index of 28.76; melt index MI 21.6 (190 ℃) 10.68g/10min, young's modulus 580MPa, tensile strength 68MPa, impact strength 70kJ/m 2 。
Example 4
This example illustrates the preparation of polyethylene resins using a preparation process in which two reactors are connected in parallel.
As shown in fig. 2.
(1) Introducing condensed fluid isopentane, ethylene and 1-hexene into a first reactor (slurry loop reactor), and carrying out ethylene/1-hexene copolymerization under the action of a hybrid Ziegler-Natta catalyst to obtain a polyethylene discharge 1 with high molecular weight and a certain branched chain; wherein the first reactor is operated at a temperature of 65 ℃ and a pressure of 4.2MPa; slurry density 663kg/m in the first reactor 3 The catalyst feed was 1.35kg/h, the 1-hexene concentration in the reactor was 1.5mol% and the mass fraction of polyethylene active particles was 40wt%.
(2) Filling a hybrid Ziegler-Natta and triethylaluminum catalytic system in a second reactor (a gas-solid fluidized bed reactor), and recycling gas obtained by mixing the top outlet gas of the reactor with raw material gas and condensate feed and separating the mixture by a gas-liquid separator to the second reactor for continuous reaction to generate a low molecular weight polyethylene resin discharge 2; wherein the reaction temperature in the second reactor is 85 ℃, the reaction pressure is 2.0Mpa, the apparent fluidization gas velocity is 0.68m/s, the ethylene molar concentration in the circulating gas is 36mol%, the hydrogen molar concentration is 6mol%, the nitrogen molar concentration is 56mol%, and the 1-hexene molar concentration is 2mol%;
the polyethylene resin discharge 1 and discharge 2 in the two reactors are melted by a post-processing melt blending process and then recrystallized to obtain a polyethylene resin discharge 3, labeled as polyethylene resin B.
The obtained polyethylene resin B had a structure in which a serial crystal structure as shown in FIG. 4 was observed under a scanning electron microscope, and the density of the obtained polyethylene resin B was 0.96g/cm 3 A weight average molecular weight of 480000; a molecular weight distribution index of 27.95; melt index MI 21.6 (190 ℃) 10.34g/10min, young's modulus 620MPa, tensile strength 62MPa, impact strength 70kJ/m 2 。
Example 5
This example illustrates the preparation of polyethylene resins using a preparation process in which two reactors are connected in parallel.
A polyethylene resin was prepared in the same manner as in example 4 except that: the apparent gas velocity in the second reactor is 0.5m/s, and the reaction temperature is 88 ℃.
As a result, the obtained polyethylene resin B had a cross-linked structure, and the density of the obtained polyethylene resin B was 0.95g/cm 3 A weight average molecular weight of 390000; a molecular weight distribution index of 25.38; melt index MI 21.6 (190 ℃) was 12.46g/10min, young's modulus was 559MPa, tensile strength was 51MPa, impact strength was 65kJ/m 2 。
Example 6
This example illustrates the preparation of polyethylene resins using a preparation process in which two reactors are connected in parallel.
(1) Introducing condensed fluid isopentane, ethylene and 1-hexene into a first reactor (slurry loop reactor), and carrying out ethylene/1-hexene copolymerization under the action of a hybrid Ziegler-Natta catalyst to obtain a polyethylene discharge 1 with high molecular weight and a certain branched chain; wherein the first reactor is operated at a temperature of 65 ℃ and a pressure of 4.5MPa; the slurry density in the first reactor was 675kg/m 3 Catalytic reactionThe feed amount of the catalyst was 1.1kg/h, the 1-hexene concentration in the reactor was 1.2mol% and the mass fraction of solids was 40wt%.
(2) Filling a hybrid Ziegler-Natta and triethylaluminum catalytic system in a second reactor (a gas-solid fluidized bed reactor), and recycling gas obtained by mixing the top outlet gas of the reactor with raw material gas and condensate feed and separating the mixture by a gas-liquid separator to the second reactor for continuous reaction to further generate a low molecular weight polyethylene resin discharge 2; wherein the reaction temperature in the second reactor is 83 ℃, the reaction pressure is 2.3Mpa, the apparent fluidization gas velocity is 0.58m/s, the ethylene molar concentration in the circulating gas is 40mol%, the hydrogen molar concentration is 11mol%, the nitrogen molar concentration is 46mol%, and the 1-hexene molar concentration is 3mol%;
and respectively carrying out post-processing melting crystallization on the polyethylene resin discharge 1 and the polyethylene resin discharge 2 in the two reactors to respectively obtain polyethylene resin C and polyethylene resin D.
As a result, the obtained polyethylene resin C had a cross-linked structure, and the density of the obtained polyethylene resin C was 0.94g/cm 3 A weight average molecular weight of 3000000, a molecular weight distribution index of 7.63, a melt index MI 21.6 (230 ℃) 0.2g/10min, young's modulus 783MPa, tensile strength 85MPa, impact strength 145kJ/m 2 。
The prepared polyethylene resin D has a serial crystal structure, and the density of the prepared polyethylene resin D is 0.96g/cm 3 A weight average molecular weight of 240000, a molecular weight distribution index of 5.71, a melt index MI 21.6 (190 ℃) 13.39g/10min, young's modulus 273MPa, tensile strength 36MPa, impact strength 21kJ/m 2 。
Comparative example 1
A polyethylene resin was prepared in the same manner as in example 1 except that: the mass concentration of the solid polyethylene active particles in the discharged material of the first reaction slurry is 5wt%.
As a result, the obtained polyethylene resin had no cross-linked structure, and the density of the obtained polyethylene resin was 0.94g/cm 3 A weight average molecular weight of 300000; the molecular weight distribution index was 16.32; meltingMelt index MI 21.6 (190 ℃) of 22.16g/10min, young's modulus of 290MPa, tensile strength of 23MPa, impact strength of 39kJ/m 2 。
Comparative example 2
A polyethylene resin was prepared in the same manner as in example 4 except that: the slurry stream polyethylene active particles in the first reactor had a mass concentration of 3wt%.
As a result, no obvious cross-crystal structure was observed in the polyethylene resin obtained, and the density of the polyethylene resin obtained was 0.93g/cm 3 The weight average molecular weight is 200000; a molecular weight distribution index of 15.32; melt index MI 21.6 (190 ℃) 24.78g/10min, young's modulus 350MPa, tensile strength 30MPa, impact strength 43kJ/m 2 。
Comparative example 3
A polyethylene resin was prepared in the same manner as in example 1 except that: the reaction temperature in the second reactor is 50 ℃.
As a result, the obtained polyethylene resin had no cross-linked structure, and the density of the obtained polyethylene resin was 0.93g/cm 3 A weight average molecular weight of 300000; a molecular weight distribution index of 11.46; melt index MI 21.6 (190 ℃) of 19.81g/10min, young's modulus of 350MPa, tensile strength of 43MPa, impact strength of 45kJ/m 2 。
Comparative example 4
A polyethylene resin was prepared in the same manner as in example 6 except that: the molar concentration of ethylene in the recycle gas in the second reactor was 32mol%, the molar concentration of hydrogen was 7mol%, the molar concentration of nitrogen was 61mol% and the molar concentration of 1-hexene was 0mol%.
As a result, no obvious cross-crystal structure was observed in the polyethylene resin D obtained, and the density of the polyethylene resin obtained was 0.95g/cm 3 A weight average molecular weight of 220000; a molecular weight distribution index of 15.32; melt index MI 21.6 (190 ℃) 20.53g/10min, young's modulus 216MPa, tensile strength 32MPa, impact strength 18kJ/m 2 。
The results show that the polyethylene with the serial crystal structure obtained by the method has wide molecular weight distribution and good mechanical property and processability.
Comparative example 1 since the mass concentration of the active particles of polyethylene in the slurry stream in the first reactor was too small, the resulting polymerization product had no cross-crystal structure and its mechanical properties were poor.
Comparative example 2 since the mass concentration of polyethylene active particles in the first reactor was too small, polyethylene discharge 1 and discharge 2 were melt-blended by post-processing, and the resulting product also had no cluster structure and had poor mechanical properties.
In comparative example 3, the polymerization rate was remarkably reduced due to the excessively low temperature in the second reactor, the ethylene polymerization was difficult to be performed normally, and the resulting product had no crystal structure and the mechanical properties were also reduced.
Comparative example 4 the insertion amount of alpha-olefin in the polymer chain in the second reactor was too low due to too low alpha-olefin content in the second reactor, and the final product had no cluster structure and had poor mechanical properties.
The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, a number of simple variants of the technical solution of the invention are possible, including combinations of the individual technical features in any other suitable way, which simple variants and combinations should likewise be regarded as being disclosed by the invention, all falling within the scope of protection of the invention.
Claims (16)
1. A method for preparing polyethylene resin a by using two reactors in series, which is characterized in that the preparation method comprises the following steps:
(1-1) contacting olefin monomer and condensate in a first reactor in the presence of a first catalyst to perform a copolymerization reaction to obtain a slurry discharge comprising polyethylene active particles and a portion of the condensate;
(1-2) introducing the slurry discharge directly into a second reactor, continuing the olefin polymerization reaction in the presence of an optional second catalyst, and carrying out melt blending treatment on the discharge of the second reactor to obtain the polyethylene resin A with the cross-crystal structure.
2. A method for preparing polyethylene resin by adopting two reactors in parallel is characterized in that the preparation method comprises the following steps:
(2-1) in the presence of a first catalyst, contacting a first olefin monomer with a first condensate in a first reactor to carry out a copolymerization reaction to obtain a polyethylene resin discharge 1;
(2-2) carrying out polymerization reaction on a second olefin monomer in the presence or absence of a second condensate in a second reactor under the action of a second catalyst to obtain a polyethylene resin discharge 2;
(2-3) carrying out melt blending treatment on the discharge material 1 and the discharge material 2 to obtain polyethylene resin B with a serial crystal structure; and/or the number of the groups of groups,
(2-4) subjecting the discharge 1 and the discharge 2 to post-processing treatment, respectively, to obtain a polyethylene resin C and a polyethylene resin D.
3. The process of claim 1 or 2, wherein the olefin monomers comprise ethylene and alpha-olefins;
and/or the alpha-olefin is used in an amount of 0.01 to 8mol%, preferably 0.5 to 4mol%, based on the total molar amount of the olefin monomers;
and/or the alpha-olefin is selected from one or more of propylene, 1-butene, 1-pentene, 1-hexene, 1-octene and 1-decene, preferably the alpha-olefin is selected from one or more of 1-butene, 1-hexene and 1-octene;
and/or the condensate is selected from one or more of n-pentane, isopentane, cyclohexane, n-hexane and n-heptane, preferably the condensate is isopentane and/or n-hexane;
and/or the first catalyst and the second catalyst are the same or different and are each selected from one or more of a ziegler-natta catalyst, a metallocene catalyst, a transition metal catalyst, an inorganic chromium catalyst and an organic chromium catalyst, preferably a ziegler-natta catalyst.
4. The process according to claim 1, wherein in step (1-1), the first catalyst is used in an amount of 0.003-0.01wt%, preferably 0.005-0.01wt%, based on the total weight of the olefin monomers; the polyethylene active particles are present in an amount of 10 to 50wt%, preferably 25 to 40wt%, based on the total weight of the slurry discharge;
and/or in step (1-2), the second catalyst is used in an amount of 0 to 0.03wt%, preferably 0.005 to 0.03wt%, based on the total weight of the olefin monomers; the superficial fluidization gas velocity in the second reactor is from 0.1 to 3m/s, preferably from 0.3 to 0.8m/s.
5. The process according to claim 2, wherein in step (2-1), the first catalyst is used in an amount of 0.003-0.01wt%, preferably 0.005-0.01wt%, based on the total weight of the first olefin monomer;
and/or in step (2-2), the second condensate is used in an amount of 0 to 50mol%, preferably 0 to 40mol%, based on the total molar amount of the second olefin monomer; the second catalyst is used in an amount of 0.005 to 0.03wt%, preferably 0.01 to 0.02wt%, based on the total weight of the second olefin monomer;
and/or in step (2-2), the superficial fluidization gas velocity in the second reactor is from 0.1 to 3m/s, preferably from 0.3 to 0.8m/s;
and/or in step (2-3), the polyethylene resin take-off 1 is used in an amount of 5-40wt%, preferably 10-28wt%, based on the total weight of the polyethylene resin take-off 1 and the polyethylene resin take-off 2.
6. The process according to claim 1 or 2, wherein the first reactor is a slurry polymerization reactor and the second reactor is a gas phase polymerization reactor, preferably a fluidized bed reactor;
and/or the temperature of the second reactor is higher than the temperature of the first reactor;
and/or the pressure of the second reactor is lower than the pressure of the first reactor.
7. The process according to claim 6, wherein the temperature of the second reactor is at least 5 ℃, preferably 10-25 ℃ higher than the temperature of the first reactor;
and/or the pressure of the second reactor is at least 1MPa, preferably 1.5-2MPa lower than the pressure of the first reactor.
8. The process according to claim 1 or 2, wherein the reaction temperature of the first reactor is 45-75 ℃, preferably 55-65 ℃; the reaction pressure is 1-7MPa, preferably 3.5-4.5MPa;
and/or the reaction temperature of the second reactor is 65-100 ℃, preferably 80-90 ℃; the reaction pressure is 0.5-6MPa, preferably 2-2.5MPa.
9. A polyethylene resin a having a tandem structure, which is prepared by the tandem preparation method of any one of claims 1, 3 to 4, 6 to 8.
10. The polyethylene resin a according to claim 9, wherein the polyethylene resin a has a weight average molecular weight of 300000-2000000, a molecular weight distribution index of 10-50, a density of 0.91-0.96g/cm 3 Melt index MI at 190 ℃ temperature 21.6 0.1-20g/10min, young's modulus 400-900MPa, tensile strength 35-90MPa, impact strength 40-90kJ/m 2 。
11. Polyethylene resin a according to claim 9 or 10, wherein the cross-crystal content in the polyethylene resin a is 2-40wt%.
12. A polyethylene resin prepared by the parallel preparation method of any one of claims 2, 3, 5, 6 to 8, wherein the polyethylene resin comprises one or more of polyethylene resin B, polyethylene resin C, and polyethylene resin D having a tandem structure.
13. The polyethylene resin according to claim 12, wherein the polyethylene resin B has a weight average molecular weight of 350000-600000, a molecular weight distribution index of 25-40, and a density of 0.92-0.98g/cm 3 Melt index MI at 190 ℃ temperature 21.6 0.02-30g/10min, young's modulus 400-800MPa, tensile strength 30-78MPa, impact strength 30-80kJ/m 2 ；
And/or the polyethylene resin C has a weight average molecular weight of 1000000-5000000, a molecular weight distribution index of 6.5-15.1, and a density of 0.92-0.95g/cm 3 Melt index MI at 230 ℃ temperature 21.6 0.01-5g/10min, young's modulus of 700-900MPa, tensile strength of 30-90MPa, impact strength of 60-190kJ/m 2 ；
And/or the polyethylene resin D has a weight average molecular weight of 100000-300000, a molecular weight distribution index of 2.5-14.3, and a density of 0.912-0.98g/cm 3 Melt index MI at 190 ℃ temperature 21.6 6-30g/10min, young's modulus of 250-450MPa, tensile strength of 24-36MPa, and impact strength of 15-50kJ/m 2 。
14. The polyethylene resin according to claim 12 or 13, wherein the cross-linked content in the polyethylene resin B is 1 to 30wt%.
15. Use of a polyethylene resin a according to any one of claims 9 to 11 or a polyethylene resin according to any one of claims 12 to 14 in one or more of film materials, pipes, fibres, blow moulding, injection moulding and rotational moulding.
16. A method for preparing polyethylene resin in industrial production, characterized in that the method comprises freely switching between series connection and parallel connection to prepare polyethylene resin, wherein the series connection is the method of any one of claims 1, 3-4 and 6-8, and the parallel connection is the method of any one of claims 2, 3, 5 and 6-8.
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