CN114426718A - Polyethylene resin with anti-sagging performance and preparation and application thereof - Google Patents
Polyethylene resin with anti-sagging performance and preparation and application thereof Download PDFInfo
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- 229920013716 polyethylene resin Polymers 0.000 title claims abstract description 44
- 238000007665 sagging Methods 0.000 title claims abstract description 27
- 238000002360 preparation method Methods 0.000 title abstract description 7
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 claims abstract description 43
- 239000005977 Ethylene Substances 0.000 claims abstract description 43
- 239000004711 α-olefin Substances 0.000 claims abstract description 24
- 238000009826 distribution Methods 0.000 claims abstract description 14
- 230000002902 bimodal effect Effects 0.000 claims abstract description 13
- 238000007334 copolymerization reaction Methods 0.000 claims abstract description 11
- 239000011347 resin Substances 0.000 claims abstract description 5
- 229920005989 resin Polymers 0.000 claims abstract description 5
- 239000002131 composite material Substances 0.000 claims abstract description 4
- 239000007789 gas Substances 0.000 claims description 39
- 239000004698 Polyethylene Substances 0.000 claims description 26
- -1 polyethylene Polymers 0.000 claims description 26
- 229920000573 polyethylene Polymers 0.000 claims description 23
- 238000006243 chemical reaction Methods 0.000 claims description 22
- 239000001257 hydrogen Substances 0.000 claims description 21
- 229910052739 hydrogen Inorganic materials 0.000 claims description 21
- 229920000642 polymer Polymers 0.000 claims description 20
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 17
- 239000000463 material Substances 0.000 claims description 17
- 239000003054 catalyst Substances 0.000 claims description 15
- 239000003085 diluting agent Substances 0.000 claims description 14
- VXNZUUAINFGPBY-UHFFFAOYSA-N 1-Butene Chemical compound CCC=C VXNZUUAINFGPBY-UHFFFAOYSA-N 0.000 claims description 12
- LIKMAJRDDDTEIG-UHFFFAOYSA-N 1-hexene Chemical compound CCCCC=C LIKMAJRDDDTEIG-UHFFFAOYSA-N 0.000 claims description 12
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 claims description 12
- ZGEGCLOFRBLKSE-UHFFFAOYSA-N 1-Heptene Chemical compound CCCCCC=C ZGEGCLOFRBLKSE-UHFFFAOYSA-N 0.000 claims description 10
- AFFLGGQVNFXPEV-UHFFFAOYSA-N 1-decene Chemical compound CCCCCCCCC=C AFFLGGQVNFXPEV-UHFFFAOYSA-N 0.000 claims description 10
- KWKAKUADMBZCLK-UHFFFAOYSA-N 1-octene Chemical compound CCCCCCC=C KWKAKUADMBZCLK-UHFFFAOYSA-N 0.000 claims description 10
- 238000006116 polymerization reaction Methods 0.000 claims description 10
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 8
- 239000004215 Carbon black (E152) Substances 0.000 claims description 6
- 239000000428 dust Substances 0.000 claims description 6
- 229930195733 hydrocarbon Natural products 0.000 claims description 6
- 150000002430 hydrocarbons Chemical class 0.000 claims description 6
- 238000000034 method Methods 0.000 claims description 6
- 239000001294 propane Substances 0.000 claims description 6
- 238000011084 recovery Methods 0.000 claims description 6
- 238000004519 manufacturing process Methods 0.000 claims description 5
- 239000000155 melt Substances 0.000 claims description 5
- 238000002844 melting Methods 0.000 claims description 5
- 230000008018 melting Effects 0.000 claims description 5
- TVMXDCGIABBOFY-UHFFFAOYSA-N n-Octanol Natural products CCCCCCCC TVMXDCGIABBOFY-UHFFFAOYSA-N 0.000 claims description 5
- 241000446313 Lamella Species 0.000 claims description 4
- UQZIWOQVLUASCR-UHFFFAOYSA-N alumane;titanium Chemical compound [AlH3].[Ti] UQZIWOQVLUASCR-UHFFFAOYSA-N 0.000 claims description 4
- 150000002431 hydrogen Chemical class 0.000 claims description 4
- 229910052757 nitrogen Inorganic materials 0.000 claims description 4
- 239000002685 polymerization catalyst Substances 0.000 claims description 4
- 239000000843 powder Substances 0.000 claims description 4
- 230000001681 protective effect Effects 0.000 claims description 4
- 239000011261 inert gas Substances 0.000 claims description 3
- 238000000926 separation method Methods 0.000 claims description 3
- 238000007599 discharging Methods 0.000 claims description 2
- 238000001035 drying Methods 0.000 claims description 2
- 238000001704 evaporation Methods 0.000 claims description 2
- 230000008020 evaporation Effects 0.000 claims description 2
- 238000001914 filtration Methods 0.000 claims description 2
- 238000003860 storage Methods 0.000 claims description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 abstract description 6
- 239000000498 cooling water Substances 0.000 description 4
- 238000001125 extrusion Methods 0.000 description 4
- 238000005227 gel permeation chromatography Methods 0.000 description 4
- 239000004743 Polypropylene Substances 0.000 description 3
- 229920001155 polypropylene Polymers 0.000 description 3
- PPBRXRYQALVLMV-UHFFFAOYSA-N Styrene Chemical compound C=CC1=CC=CC=C1 PPBRXRYQALVLMV-UHFFFAOYSA-N 0.000 description 2
- IAQRGUVFOMOMEM-UHFFFAOYSA-N butene Natural products CC=CC IAQRGUVFOMOMEM-UHFFFAOYSA-N 0.000 description 2
- 238000007906 compression Methods 0.000 description 2
- 230000006835 compression Effects 0.000 description 2
- 239000002826 coolant Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005469 granulation Methods 0.000 description 2
- 230000003179 granulation Effects 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 229920001519 homopolymer Polymers 0.000 description 2
- 230000002687 intercalation Effects 0.000 description 2
- 238000009830 intercalation Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000012802 nanoclay Substances 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- RELMFMZEBKVZJC-UHFFFAOYSA-N 1,2,3-trichlorobenzene Chemical compound ClC1=CC=CC(Cl)=C1Cl RELMFMZEBKVZJC-UHFFFAOYSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 1
- 238000005481 NMR spectroscopy Methods 0.000 description 1
- 239000004793 Polystyrene Substances 0.000 description 1
- 238000003556 assay Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 229920001577 copolymer Polymers 0.000 description 1
- 238000004132 cross linking Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 238000005984 hydrogenation reaction Methods 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 229920002521 macromolecule Polymers 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 150000001282 organosilanes Chemical class 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 229920002223 polystyrene Polymers 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000004611 spectroscopical analysis Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229920002554 vinyl polymer Polymers 0.000 description 1
- 239000003643 water by type Substances 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
- C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
- C08L23/04—Homopolymers or copolymers of ethene
- C08L23/06—Polyethene
-
- 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
- C08F110/00—Homopolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
- C08F110/02—Ethene
-
- 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
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
- C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
- C08L23/04—Homopolymers or copolymers of ethene
- C08L23/08—Copolymers of ethene
- C08L23/0807—Copolymers of ethene with unsaturated hydrocarbons only containing more than three carbon atoms
- C08L23/0815—Copolymers of ethene with aliphatic 1-olefins
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2203/00—Applications
- C08L2203/18—Applications used for pipes
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2205/00—Polymer mixtures characterised by other features
- C08L2205/02—Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2308/00—Chemical blending or stepwise polymerisation process with the same catalyst
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Abstract
The invention provides a polyethylene resin with anti-sagging performance, and preparation and application thereof. The polyethylene resin comprises an ethylene homopolymerization part of a low molecular weight part and an alpha-olefin copolymerization part of a high molecular weight part, the molecular weight is in bimodal distribution, and the mass ratio of the low molecular weight part to the high molecular weight part is 4: 6-6: 4; the weight average molecular weight Mw of the composite material is 200000-240000, and the molecular weight distribution is 8-20; melt flow rate MFR5 of 0.20-0.32g/10min, resin density of 0.945-0.952g/cm 3. The polyethylene resin provided by the invention has excellent anti-sagging performance, can be applied to the field of pipes, and particularly has good application prospects in the fields of water supply pipes, gas pipes and the like.
Description
Technical Field
The invention relates to the technical field of polymer pipes, in particular to polyethylene resin with excellent anti-sagging performance, and preparation and application thereof.
Background
PE pipe material is an important application direction for polyethylene resin. Polyethylene pipes have been widely used in town gas and water distribution systems. Because the polyethylene pipe has the characteristics of unique connection integrity, sealing property, firmness, flexibility, light weight and the like, the polyethylene pipe is simple and feasible in industrial application and wide in application due to the combination of the factors. Currently, polyethylene pipes have been industrially applied to temporary water supply pipelines, various bypass pipelines, oil and gas pipelines.
Such pipe materials are mostly used in the fields of gas pipelines, sewer pipelines and the like, so that the pipe materials resist the sagging of melt due to the action of gravity, namely, the characteristic of 'anti-sagging', is one of the key indexes of polyethylene pipe materials, and has become the key point for polyethylene pipe material manufacturers, pipe material manufacturers and gas operators to research and evaluate high-performance pipe materials. The excellent anti-sagging property is the basis for producing the special material for the large-caliber PE pipe.
Chinese patent CN200910078136.3 discloses an anti-sagging polypropylene and a preparation method thereof, wherein a polymer macromolecule chain is inserted between lamella with a stack structure of nano-clay through extrusion to obtain a polypropylene/nano-clay composite material with an intercalation structure, and the intercalation plays a role of a physical cross-linking point in a polypropylene melt to improve the anti-sagging performance. Chinese patent CN201610503761.8 discloses a high-strength nuclear power polyethylene pipe, which is prepared by blending and extruding vinyl polymer, fluorine-containing styrene and organosilane, and has good anti-sagging performance. The anti-sagging pipes are prepared in an extrusion mode, the performance improvement is limited, and the anti-sagging pipes with better performance can be obtained through in-situ polymerization. The bimodal polyethylene is a polyethylene product with molecular weight in bimodal distribution, the low molecular weight part determines the processing performance of the product, the high molecular weight part determines the anti-sagging performance of the material, and the bimodal polyethylene is the preferred design direction of the anti-sagging pipe. Thus, there is a need for a bimodal polyethylene pipe that has higher sag resistance when polymerized.
In view of such a consideration, the inventors of the present invention have conducted studies with the object of solving the problems exposed by the prior art in the related art, and it is desirable to provide a polyethylene pipe excellent in properties.
Disclosure of Invention
The invention aims to provide a polyethylene resin with anti-sagging performance and preparation and application thereof. The polyethylene resin provided by the invention has excellent anti-sagging performance, can be applied to the field of pipes, and particularly has good application prospects in the fields of water supply pipes, gas pipes and the like.
The technical scheme of the invention is as follows:
the invention provides a polyethylene resin with anti-sagging performance, which comprises an ethylene homopolymerization part of a low molecular weight part and an alpha-olefin copolymerization part of a high molecular weight part, wherein the molecular weight is in bimodal distribution, and the mass ratio of the low molecular weight part to the high molecular weight part is 4: 6-6: 4; the weight average molecular weight Mw of the composite material is 200000-240000, and the molecular weight distribution is 8-20; melt flow rate MFR5 of 0.20-0.32g/10min, resin density of 0.945-0.952g/cm 3.
Further, the polyethylene resin comprises an ethylene homopolymerization part with a low molecular weight part and an alpha-olefin copolymerization part with a high molecular weight part, the molecular weight is in bimodal distribution, and the mass ratio of the low molecular weight part to the high molecular weight part is 5: 5; the weight average molecular weight Mw is 220000-230000, and the molecular weight distribution is 12-15; the melt flow rate MFR5 is 0.25 to 0.3g/10min, and the resin density is 0.948 to 0.95g/cm 3.
Further, the polyethylene resin has an alpha-olefin content of 0.5-2.5 wt%, and the alpha-olefin is selected from one or more of 1-butene, 1-hexene, 1-heptene, 1-octene and 1-decene.
Furthermore, the melting temperature of the polyethylene resin is 120-140 ℃, the crystallinity is 55-65, and the thickness of the lamella is 25-28 nm.
Furthermore, the melting temperature of the polyethylene resin is 125-135 ℃, the crystallinity is 57-62, and the thickness of the lamella is 25.5-26.5 nm.
Further, the melting temperature of the polyethylene resin is 130-132 ℃, and the crystallinity of the polyethylene resin is 59-60.
The invention also provides a preparation method of the polyethylene resin with the anti-sagging property, which comprises the following steps:
step (1): adding ethylene, alpha-olefin comonomer, hydrogen and circulating diluent from a diluent recovery area into a prepolymerization reactor, wherein the molar flow ratio of the ethylene, the alpha-olefin comonomer and the hydrogen is controlled to be 1000: 100-150: 60, the volume fraction of the added amount of the diluent is 40-60%, and a prepolymerization reaction is carried out under a polymerization catalyst system, so that a protective film with moderate thickness is formed on the surface of the catalyst, the mechanical strength of catalyst particles is improved, and a prepolymerization product is obtained;
step (2): introducing the prepolymerization product prepared in the step (1) into a loop reactor to carry out ethylene homopolymerization reaction to obtain a low molecular weight part, continuously introducing ethylene and hydrogen in the reaction process, and controlling the molar flow ratio of the ethylene to the hydrogen to be 1000: 1-1000: 100, respectively; the materials in the reactor circulate at a linear speed of 5-9m/s under the action of a circulating pump; discharging the product in the loop reactor to a settling leg, settling in the settling leg, and then sending into a flash tank;
and (3): decompressing and flashing the materials in a flash tank, separating polymer powder from hydrocarbon gas, filtering dust of the separated hydrocarbon gas by a flash gas bag filter and a protective filter, sending the filtered dust to a diluent gas separation tank of a diluent recovery area, and introducing the polymer into a gas-phase fluidized bed reactor;
and (4): the polymer entering the fluidized bed reactor was also very active, at a fluidizing gas velocity of 0.7m/s, ethylene, alpha-olefin comonomer, hydrogen, and propane and nitrogen as inert gases were added again to continue the copolymerization reaction, producing a high molecular weight fraction of bimodal polyethylene;
and (5): and (4) introducing the polyethylene resin prepared in the step (4) into a post-treatment system, separating by a flash evaporation tank, extruding and granulating by an extruder, collecting in a storage bin, deashing and drying to obtain the polyethylene resin with the anti-sagging performance.
Further, the alpha-olefin comonomer in the step (1) is selected from one or more of 1-butene, 1-hexene, 1-heptene, 1-octene and 1-decene.
Further, the polymerization catalyst system in the step (1) is composed of a catalyst cocatalyst TEA and a catalyst Z-N, and the aluminum-titanium ratio of the catalyst cocatalyst TEA to the catalyst Z-N is 100-800.
Further, the aluminum-titanium ratio of the cocatalyst TEA to the Z-N catalyst is 200-400 Al/Ti.
Further, the prepolymerization reaction temperature in the step (1) is 65-70 ℃, and the polymerization pressure is 6.5-7.5 MPa; the pressure difference between the prepolymerization reactor and the loop reactor is 0.1-0.15 MPa.
Further, the temperature of the ethylene homopolymerization reaction in the step (2) is 70-85 ℃, and the polymerization pressure is 6.5-7.5 MPa.
Further, in the ethylene homopolymerization in the step (2), the ratio of hydrogen to ethylene is 40-80mol/kmol, preferably 55-65 mol/kmol.
Further, the copolymerization reaction temperature in the step (4) is 80-100 ℃, and the polymerization pressure is 1.5-2.5 MPa.
Further, in the copolymerization reaction in the step (4), the ratio of the alpha-olefin comonomer to ethylene is 50 to 200mol/kmol, preferably 100 to 150 mol/kmol; the ratio of hydrogen to ethylene is from 10 to 20mol/kmol, preferably from 14 to 17 mol/kmol.
Further, the polymerization temperature of the gas-phase fluidized bed reactor in the step (4) is controlled by the temperature of the cooling water inlet of the circulating gas cooler, and when the temperature difference between the circulating gas outlet temperature and the cooling water inlet temperature reaches the minimum temperature difference of 10 ℃, propane is added; the cooler outlet gas temperature must be 3 deg.c above its dew point temperature.
Still another object of the present invention is to provide the use of the polyethylene resin with anti-sagging property in pipe products, especially pipe products such as water supply pipes or gas pipes.
The polyethylene resin provided by the invention has excellent anti-sagging performance, can be applied to the field of pipes, and particularly has good application prospects in the fields of water supply pipes, gas pipes and the like.
Drawings
FIG. 1 is a schematic reaction scheme of the polyethylene resin of the present invention.
Wherein, R301-prepolymerization reactor; r302-loop reactor; v304-flash evaporator; r401-fluidized bed reactor.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that it would be apparent to those skilled in the art that several modifications and improvements can be made without departing from the inventive concept. All falling within the scope of the present invention.
The reagents and instruments used in the following examples are not indicated by manufacturers, and are all conventional products commercially available.
The polyethylene resin of the present invention can be deconvoluted into two different components as evidenced by the molecular weight distribution curve obtained by Gel Permeation Chromatography (GPC). The polyethylene resin exhibits two distinct peaks, which correspond to two components of different molecular weights. The polyethylene resin comprises a low molecular weight fraction of ethylene homopolymer (low molecular weight component a) and a high molecular weight fraction of ethylene homopolymer (high molecular weight component B); wherein the high molecular weight component B is a copolymer of ethylene and one or more alpha-olefin comonomers, and the alpha-olefin comonomer is selected from one or more of 1-butene, 1-hexene, 1-heptene, 1-octene and 1-decene.
Examples 1 to 5
Step 1:
in the plant scheme shown in fig. 1, ethylene, alpha-olefin comonomer, hydrogen are controlled to have a molar flow ratio of 1000: 130: 60, adding 40-60% of diluent by volume, simultaneously adding a cocatalyst TEA and a Z-N catalyst (the aluminum-titanium ratio of the cocatalyst TEA to the Z-N catalyst is Al/Ti-300), and carrying out prepolymerization reaction in a prepolymerization reactor (R-301) at the reaction pressure of 6.5MPa and the reaction temperature of 70 ℃ to obtain a prepolymerization product;
the prepolymerization reactor (R-301) was a jacketed, water-cooled, loop reactor with two 12 inch legs. The pressure difference between the prepolymerization reactor and the loop reactor is 0.1-0.15 MPa. The polymerization rate is controlled by the amount of catalyst used, the polymer density is controlled by the ratio of ethylene to alpha-olefin, the polymer molecular weight is controlled by hydrogen, the solids concentration is controlled by the amount of diluent added, the reaction temperature is controlled by jacket coolant, and the reaction pressure is determined by the pressure of the loop reactor. The purpose of prepolymerization is to form a protective film with moderate thickness on the surface of the catalyst so as to improve the mechanical strength of catalyst particles and avoid the problems of crushing and the like caused by insufficient mechanical strength of the catalyst in the subsequent polymerization process.
Step 2:
and (2) introducing the prepolymerization product obtained in the step (1) into a loop reactor with the volume of 250 liters, wherein the control mode of the loop reactor is similar to that of the prepolymerization reactor, ethylene and hydrogen are required to be continuously introduced in the reaction process, and the molar flow ratio is 1000: 1-1000: 100, carrying out ethylene homopolymerization to obtain a low molecular weight part, and carrying out reaction in a loop reactor at the temperature of 80 ℃ and under the pressure of 60 bar; the material in the reactor was circulated at a linear velocity of 7m/s by a circulation pump. The material in the loop reactor is discharged to the settling legs, settled in the settling legs and sent to a flash tank (V-304).
In the loop reactor, the ethylene content in the fluid phase was 1.8 mol% and the polymer production rate was 14 kg/h. The hydrogen to ethylene ratio in the loop reactor was the same as shown in table 1 below.
The reaction temperature is controlled by jacket coolant, and the reaction pressure is controlled by the circulating opening and closing of discharge valves of six settling legs.
And step 3:
the material in the settling legs is discharged through a jacketed product discharge line into a flash drum (V-304) where it is depressurized and flashed, the polymer powder is separated from the hydrocarbon gas, and the separated hydrocarbon gas is passed through a flash gas bag filter and a guard filter to filter dust and then sent to a diluent gas separation tank in a diluent recovery zone. The separated dust is recycled to the V-304 through a bag filter rotary valve.
And 4, step 4:
the gas phase reactor was a fluidized bed reactor, the polyethylene powder entering the reactor was also very active, and at a fluidizing gas velocity of 0.7m/s, copolymerization was continued with the reactants in the recycle gas (reaction materials were ethylene, alpha-olefin comonomer, hydrogen, recycle gas was inert gas propane and nitrogen), and the high molecular weight fraction of bimodal polyethylene was produced. The gas phase reactor was operated at a temperature of 85 ℃ and a pressure of 2 bar. The production rate of the polymer in the gas phase reactor was 16kg/h, so as to control the production ratio between the loop and the gas phase reactor to be 45/55, and the total production rate was 34 kg/h. The hydrogen to ethylene ratio and comonomer to ethylene ratio in the gas phase reactor were as shown in table 1 below.
The reactor temperature is controlled by the recycle gas inlet temperature. The recycle gas inlet temperature is controlled by the recycle gas cooler cooling water inlet temperature. The temperature difference between the recycle gas outlet temperature and the cooling water inlet temperature has to be monitored. When the minimum temperature difference of 10 ℃ is reached, more propane must be added. The cooler outlet gas temperature must be 3 c above its dew point temperature to avoid the formation of condensate. The reactor pressure was controlled by the addition of nitrogen and propane. The ethylene partial pressure was controlled by adjusting the ethylene feed rate. The space between the reactor wall and the inlet line at the bottom of the reactor is separated by a basin to prevent polymer build-up and is flushed with recycle gas at a pressure slightly above the reactor pressure to fluidize the bed and carry away the heat of reaction.
And 5:
and (3) introducing the polyethylene resin prepared in the step (4) into an extrusion granulation system, controlling the operating temperature of an extruder according to five sections, controlling the temperatures of three sections (a feeding section, a compression section and a metering section) of a machine body part to be 160-170 ℃, 170-180 ℃ and 180-190 ℃, controlling the temperatures of two sections (a machine head and a mouth mold) of the machine head part to be 190-200 ℃, controlling the rotating speed of a granulator to be 20rpm, and carrying out extrusion granulation on a polyethylene product to obtain the polyethylene resin with the anti-sagging property.
The polyethylene resins having anti-sagging properties prepared in the above examples were subjected to the performance test, and the results are shown in table 2.
TABLE 1
Note: in Table 1, C2 represents ethylene, C4 represents butene, and C6 represents hexene
TABLE 2
Density of polyethylene on compression molded specimens prepared according to EN ISO 1872-2-2007 according to ISO 1183-1: 2004 method A assay;
the melt flow rate MFR5 of the polyethylene is determined according to ISO 1133 at 190 ℃ under a temperature and load of 5 kg;
the Molecular Weight (MW) and Molecular Weight Distribution (MWD) of the polyethylene were determined according to ISO 16014-4-2012 and ASTM D6474-2012 on an Alliance GPC2000 type Gel Permeation Chromatography (GPC) instrument, Waters corporation, USA, with a test temperature of 150 ℃, polystyrene as a standard, trichlorobenzene as a solvent, and a flow rate of 1.0 ml/min;
the comonomer content of the polyethylene is determined by nuclear magnetic resonance carbon spectroscopy according to randall rev.macromol.chem.chryss, C29(2&3), pages 285-297;
the melting point and crystallinity of the polyethylene were measured on a differential thermal scanner from PE DSC 7 of Perking-Elmer, USA, as follows: heating to 160 deg.C at a speed of 10 deg.C/min, standing for 5min, cooling to 50 deg.C at 10 deg.C/min, standing for 1min, and heating to 160 deg.C at 10 deg.C/min;
melt strength is characterized by melt elasticity, which is an indication of the elastic recovery properties of a polymer, and there is a direct relationship between melt elasticity and melt strength. The steady state compliance of the polymer melt was measured using a rotational rheometer at a constant shear stress of 1000dyn/cm2(0.1 kPa).
From the comparison of example 1 and example 5 above, it can be seen that the steady state compliance and zero shear viscosity of the hexene copolymerized bimodal polyethylene are both greater than those of the butene copolymerized product, indicating that the polymer product has stronger sag resistance with higher comonomer C number. Comparing example 5 with example 2, it can be seen that the higher the comonomer content, the stronger the sag resistance of the polymer, and comparing example 5 with example 3, it can be seen that the hydrogenation content has a greater effect on the density and molecular weight of the polymer and a smaller effect on the melt strength, but an increase in the hydrogen to ethylene ratio decreases the melt strength of the polymer.
While the preferred embodiments of the present invention have been described in detail, it will be understood by those skilled in the art that the invention is not limited thereto, and that various changes and modifications may be made without departing from the spirit of the invention, and the scope of the appended claims is to be accorded the full scope of the invention.
Claims (11)
1. A polyethylene resin with anti-sagging property, comprising an ethylene homopolymerization part of a low molecular weight part and an alpha-olefin copolymerization part of a high molecular weight part, the molecular weights being in a bimodal distribution, the mass ratio of the low molecular weight part to the high molecular weight part being 4: 6-6: 4; the weight average molecular weight Mw of the composite material is 200000-240000, and the molecular weight distribution is 8-20; melt flow rate MFR5 of 0.20-0.32g/10min, resin density of 0.945-0.952g/cm 3.
2. A polyethylene resin having sag resistance according to claim 1, wherein: the polyethylene resin comprises an ethylene homopolymerization part of a low molecular weight part and an alpha-olefin copolymerization part of a high molecular weight part, the molecular weight is in bimodal distribution, and the mass ratio of the low molecular weight part to the high molecular weight part is 5: 5; the weight average molecular weight Mw is 220000-230000, and the molecular weight distribution is 12-15; the melt flow rate MFR5 is 0.25 to 0.3g/10min, and the resin density is 0.948 to 0.95g/cm 3.
3. A polyethylene resin having sag resistance according to claim 1, wherein: the polyethylene resin has an alpha-olefin content of 0.5-2.5 wt%, and the alpha-olefin is selected from one or more of 1-butene, 1-hexene, 1-heptene, 1-octene and 1-decene.
4. A polyethylene resin having sag resistance according to claim 1, wherein: the melting temperature of the polyethylene resin is 120-140 ℃, the crystallinity is 55-65, and the thickness of the lamella is 25-28 nm.
5. A process for preparing a polyethylene resin having sag resistance according to any one of claims 1 to 4, comprising the steps of:
step (1): adding ethylene, alpha-olefin comonomer, hydrogen and circulating diluent from a diluent recovery area into a prepolymerization reactor, wherein the molar flow ratio of the ethylene, the alpha-olefin comonomer and the hydrogen is controlled to be 1000: 100-150: 60, the volume fraction of the added amount of the diluent is 40-60%, and a prepolymerization reaction is carried out under a polymerization catalyst system to obtain a prepolymerization product;
step (2): introducing the prepolymerization product prepared in the step (1) into a loop reactor to carry out ethylene homopolymerization reaction to obtain a low molecular weight part, continuously introducing ethylene and hydrogen in the reaction process, and controlling the molar flow ratio of the ethylene to the hydrogen to be 1000: 1-1000: 100, respectively; the materials in the reactor circulate at a linear speed of 5-9m/s under the action of a circulating pump; discharging the product in the loop reactor to a settling leg, settling in the settling leg, and then sending into a flash tank;
and (3): decompressing and flashing the materials in a flash tank, separating polymer powder from hydrocarbon gas, filtering dust of the separated hydrocarbon gas by a flash gas bag filter and a protective filter, sending the filtered dust to a diluent gas separation tank of a diluent recovery area, and introducing the polymer into a gas-phase fluidized bed reactor;
and (4): the polymer entering the fluidized bed reactor was also very active, at a fluidizing gas velocity of 0.7m/s, ethylene, alpha-olefin comonomer, hydrogen, and propane and nitrogen as inert gases were added again to continue the copolymerization reaction, producing a high molecular weight fraction of bimodal polyethylene;
and (5): and (4) introducing the polyethylene resin prepared in the step (4) into a post-treatment system, separating by a flash evaporation tank, extruding and granulating by an extruder, collecting in a storage bin, deashing and drying to obtain the polyethylene resin with the anti-sagging performance.
6. The method for preparing a polyethylene resin having sag resistance according to claim 5, wherein: the alpha-olefin comonomer in the step (1) is selected from one or more of 1-butene, 1-hexene, 1-heptene, 1-octene and 1-decene.
7. The method for preparing a polyethylene resin having sag resistance according to claim 5, wherein: the polymerization catalyst system in the step (1) consists of a cocatalyst TEA and a Z-N catalyst, and the aluminum-titanium ratio of the cocatalyst TEA to the Z-N catalyst is 100-800.
8. The method for preparing a polyethylene resin having sag resistance according to claim 5, wherein: the prepolymerization reaction temperature in the step (1) is 65-70 ℃, and the polymerization pressure is 6.5-7.5 MPa; the pressure difference between the prepolymerization reactor and the loop reactor is 0.1-0.15 MPa; the temperature of the ethylene homopolymerization reaction in the step (2) is 70-85 ℃, and the polymerization pressure is 6.5-7.5 MPa.
9. The method for preparing a polyethylene resin having sag resistance according to claim 5, wherein: and (3) performing ethylene homopolymerization in the step (2), wherein the ratio of hydrogen to ethylene is 40-80 mol/kmol.
10. The method for preparing a polyethylene resin having sag resistance according to claim 5, wherein: the copolymerization reaction temperature in the step (4) is 80-100 ℃, the polymerization pressure is 1.5-2.5MPa, the ratio of alpha-olefin comonomer to ethylene is 50-200mol/kmol, and the ratio of hydrogen to ethylene is 10-20 mol/kmol.
11. Use of a polyethylene resin having anti-sagging properties according to any of claims 1-4 in service pipe or gas pipe products.
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