CN115505057B - Low ash polyethylene powder production system and production method - Google Patents
Low ash polyethylene powder production system and production method Download PDFInfo
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- CN115505057B CN115505057B CN202211171641.4A CN202211171641A CN115505057B CN 115505057 B CN115505057 B CN 115505057B CN 202211171641 A CN202211171641 A CN 202211171641A CN 115505057 B CN115505057 B CN 115505057B
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- 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
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- 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
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- 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
- Y02P20/54—Improvements relating to the production of bulk chemicals using solvents, e.g. supercritical solvents or ionic liquids
Abstract
The invention provides a low ash polyethylene powder production system, which is sequentially connected with a gas-phase fluidized bed reactor and at least one slurry reactor in series. The invention also provides a production method of the low ash polyethylene powder, which comprises the following steps: the preparation method comprises the steps of ethylene refining, catalyst composition preparation and polyethylene preparation by a gas phase method, then discharging a polymer material into a slurry reactor, continuing the polymerization reaction in the presence of a solvent, controlling the polymerization temperature at 75-95 ℃, the pressure at 0.3-1.5MPa, controlling the material residence time at 40-80min and the material level at 35-75%, and obtaining the low ash polyethylene powder through aftertreatment. According to the invention, the gas phase reactor and the slurry reactor are combined, the materials in the fluidized bed gas phase reaction to a certain stage are transferred into the slurry reactor, and the polymerization reaction is continued, so that the low molecular weight components in the polyethylene powder can be greatly reduced, the catalyst release efficiency is improved, the ash residue is reduced, and the quality of the final product is improved.
Description
Technical Field
The invention relates to the technical field of polyethylene preparation, in particular to a production method of low ash polyethylene powder.
Background
Polyethylene (PE) is the most productive species in general synthetic resins and mainly includes Low Density Polyethylene (LDPE), linear Low Density Polyethylene (LLDPE), high Density Polyethylene (HDPE) and some products with special properties. The composite material has very wide application, is mainly used for manufacturing films, containers, pipelines, monofilaments, wires, cables, daily necessities and the like, and can be used as a high-frequency insulating material for televisions, radars and the like. The coating machine is also suitable for various paste points, powder scattering, coating machines and glue spraying machine products; the method is widely used in industries such as clothing, clothing fabric compounding, shoemaking, packaging, books, wireless binding, children toys, household appliances and the like.
The production method of polyethylene mainly comprises a slurry method, a solution method and a gas phase method. The slurry process is mainly used for producing high density polyethylene, while the solution process and the gas phase process can produce not only high density polyethylene but also medium and low density polyethylene, also called linear low density polyethylene, by adding a comonomer.
The existing gas phase reactor has the advantages of small occupied area, large single kettle capacity, wide molecular weight distribution of a polymerization product, particularly incapability of separating a small amount of short chain segments and even wax components, and capability of meeting the requirements of conventional membrane material production and application, but is used for the following purposes: when the chlorinated polyethylene is used, the fine powder and wax components affect the subsequent processing, and the number of processing steps is increased.
The technology is based on slurry loop reactor and fluidized bed gas phase reactor connected serially, and includes ethylene polymerization with supercritical propane as diluent in the loop reactor, and the produced product is fed into the gas phase reactor connected serially for further reaction to produce low density high molecular weight polyethylene product base material. The produced polyethylene polymer is made into a bimodal polyethylene polymer by optimizing the main and branched chain structures and the molecular weight distribution of the polyethylene. However, the above production process cannot obtain low ash polyethylene.
Disclosure of Invention
The invention aims to provide a production method of low ash polyethylene powder, which is completely different from the prior art, and is based on a gas-phase fluidized bed reactor and a slurry reactor which are sequentially connected in series to obtain the low ash polyethylene powder.
The invention is realized by adopting the following technical scheme:
in a first aspect, the present invention provides a low ash polyethylene powder production system, comprising a gas phase fluidized bed reactor and at least one slurry reactor in series, said gas phase fluidized bed reactor and slurry reactor being in communication via a pressure reducing connecting line.
Preferably, when the slurry reactor is two or more, a parallel combination is used. Two or more slurry reactors are connected in parallel, and the method is suitable for the characteristics of larger capacity of the gas phase reactor and small capacity of the slurry reactor. The slurry reactor may also be independently connected to a hydrogen input unit, as required by the product specifications.
Further, the low ash polyethylene powder production system of the invention is sequentially connected with the following process units in series: the device comprises a raw material preparation unit, a gas-phase fluidized bed reactor, at least one slurry reactor, a degassing bin unit, a drying bin unit and a powder storage unit.
The raw material preparation unit comprises an ethylene refining unit and a catalyst prefabrication unit which are independently connected with the gas-phase fluidized bed reactor. Further, the ethylene refining unit sequentially comprises a desulfurization and dechlorination tower, a CO removal tower, a deoxidization tower and a drying tower. The catalyst pre-unit is used to pre-mix the catalyst components, for example, to mix the catalyst and cocatalyst to form a catalyst composition.
The degassing bin unit and the drying bin unit are respectively used for removing unreacted monomers and drying powder; the powder storage unit is treated with nitrogen containing a small amount of water vapor to sufficiently remove the activity of the unconsumed cocatalyst.
The inventor surprisingly found that by combining the gas phase reactor and the slurry stasis reactor, transferring the material of the fluidized bed gas phase reaction to a certain stage into the slurry stasis reactor, and continuing the polymerization reaction, the low molecular weight component in the polyethylene powder can be greatly reduced, the catalyst release efficiency is improved, the ash residue is reduced, and the quality of the final product is improved. The inventors completed the present invention based on the above findings.
The powder storage unit can be further sequentially connected with a processing aid metering and feeding unit and a granulating unit in series.
In a second aspect, the invention provides a method for producing low ash polyethylene powder, comprising the steps of:
s1, injecting ethylene into an ethylene refining unit, and removing impurities and moisture through a desulfurization and dechlorination tower, a CO removal tower, a deoxidization tower and a drying tower to obtain refined ethylene;
s2, injecting the catalyst and the cocatalyst into a catalyst prefabrication unit, and fully mixing to obtain a catalyst composition;
s3, respectively injecting refined ethylene and the catalyst composition into a gas-phase fluidized bed reactor for polymerization reaction, controlling the polymerization temperature to be 85-105 ℃, controlling the pressure to be 2.5-3.5MPa, controlling the gas flow rate to be 0.5-1.2m/S and controlling the residence time to be 0.5-1.5h;
s4, discharging a polymer material into a slurry reactor, continuing the polymerization reaction in the presence of a solvent, controlling the polymerization temperature at 75-95 ℃ and the pressure at 0.3-1.5MPa, controlling the material retention time at 40-80min and the material level at 35-75%;
s5, the discharged powder enters a degassing tower (namely a degassing bin unit) and a drying tower (namely a drying bin unit) to remove unreacted monomers, then enters a treatment unit, is treated by nitrogen containing a small amount of water vapor to fully remove the activity of the unconsumed cocatalyst, and finally the low ash polyethylene powder is obtained.
In the step S2, the dosages of the catalyst and the cocatalyst are respectively as follows: the molar ratio of cocatalyst to catalyst is 10-200:1, preferably 30-80:1.
preferably, the catalyst uses Ti as an active center, for example, ether or ester compounds are used as internal electron donors, including but not limited to cyclobutyl-1, 1-dimethanol dimethyl ether, 1, 3-diethers, 1, 3-propanediol dimethyl ether, 2-diisobutyl-1, 3-propanediol dimethyl ether, cyclopentyl-1, 1-dimethanol dimethyl ether, 1, 3-diol ester compounds, di-n-butyl phthalate, diisobutyl phthalate, ethyl benzoate, dibutyl phthalate and the like, and the internal electron donors are preferably used as catalysts of ether compounds, and mixtures of ether and ester compounds can also be used.
The cocatalyst includes, but is not limited to, organoaluminum compounds such as trimethylaluminum, triethylaluminum, triisobutylaluminum, diisoaluminum monochloride, and the like, preferably triethylaluminum.
In step S4, the solvent may be at least one selected from hexane, heptane, pentane, isopentane. Depending on the end product characteristics, hydrogen may additionally be used to adjust the MFR and the relative molecular mass and distribution thereof. The level is preferably controlled between 50 and 55% by means of a polymerization level control feeding procedure.
The invention reduces the post-treatment total amount of the solvent under the same scale yield, and removes wax and micromolecular components from the production source, thereby reducing energy consumption and material consumption compared with reprocessing when modifying by downstream factories; the pressure difference between the gas phase reactor and the slurry reactor can be fully utilized to realize material conveying, so that energy sources are saved; the reactors can be combined differently according to the production needs, thereby meeting the production needs of different products. The prepared low ash polyethylene powder has excellent processability, thereby improving the product quality.
The invention is further illustrated by the following examples in conjunction with the accompanying drawings.
Drawings
FIG. 1 is a schematic diagram of the process flow of the present invention.
FIG. 2 is a schematic process flow diagram of a raw material preparation unit.
Detailed Description
The following description is presented to enable one of ordinary skill in the art to make and use the invention. The preferred embodiments in the following description are by way of example only and are not intended to limit the scope of the invention, as other obvious variations will occur to those skilled in the art. The basic principles of the invention defined in the following description may be applied to other embodiments, variations, modifications, equivalents, and other technical solutions without departing from the spirit and scope of the invention.
The apparatus, industrial equipment or reagents in the embodiments of the present invention are not manufacturer-specific, and are conventional commercial apparatus, industrial equipment or reagents. Wherein propylene is polymer grade propylene.
As shown in fig. 1 and 2, the low ash polyethylene powder production system of the invention is sequentially connected with the following process units in series: the device comprises a raw material preparation unit, a gas-phase fluidized bed reactor, two slurry reactors connected in parallel, a degassing bin unit, a drying bin unit and a powder storage unit, wherein the gas-phase fluidized bed reactor and the slurry reactors are communicated through a decompression connecting pipeline. Wherein the raw material preparation unit comprises an ethylene refining unit and a catalyst prefabrication unit which are independently connected with the gas-phase fluidized bed reactor. The ethylene refining unit sequentially comprises a desulfurization and dechlorination tower, a CO removal tower, a deoxidization tower and a drying tower.
According to the yield of the gas-phase fluidized bed reactor, the factors such as the capacity and the production efficiency requirement of a single slurry reactor are combined, a plurality of slurry reactors can be further used in parallel at the same time, so that the problem that the slurry reactor can not be increased in material receiving capacity at will for controlling the solid concentration due to the large polymerization amount of the fluidized bed reactor is solved.
The production method of the low ash polyethylene powder comprises the following steps:
s1, injecting ethylene into an ethylene refining unit, and removing impurities and moisture through a desulfurization and dechlorination tower, a CO removal tower, a deoxidization tower and a drying tower to obtain refined ethylene;
s2, injecting the catalyst and the cocatalyst into a catalyst prefabrication unit, and fully mixing to obtain a catalyst composition;
s3, respectively injecting refined ethylene and the catalyst composition into a gas-phase fluidized bed reactor for polymerization reaction, controlling the polymerization temperature to be 95+/-5 ℃, controlling the pressure to be 3.0 MPa+/-0.3 MPa, controlling the gas flow rate to be 0.8 m/s+/-0.2 m/S, and controlling the residence time to be 1h;
s4, discharging a polymer material into a slurry reactor, continuing the polymerization reaction in the presence of a solvent, controlling the polymerization temperature at 90+/-5 ℃ and the pressure at 0.6 MPa+/-0.1 MPa, controlling the material retention time at 70min and controlling the material level at 55+/-5%;
s5, the discharged powder enters a degassing tower (namely a degassing bin unit) and a drying tower (namely a drying bin unit) to remove unreacted monomers, then enters a treatment unit, is treated by nitrogen containing a small amount of water vapor to fully remove the activity of the unconsumed cocatalyst, and finally the low ash polyethylene powder is obtained.
Example 1
The catalyst is a Z-N catalyst containing lipid internal electron donor, and is matched with triethylaluminum as a cocatalyst, wherein the Al/Ti molar ratio is 75/1.
Example 2
The catalyst is a Z-N catalyst containing an ether internal electron donor, and is matched with triethylaluminum as a cocatalyst, wherein the Al/Ti molar ratio is 70/1.
Example 3
The catalyst is a Z-N catalyst containing an ether internal electron donor, and is matched with triethylaluminum as a cocatalyst, wherein the Al/Ti molar ratio is 70/1.
Comparative example
The polypropylene powder was produced using only a gas-phase fluidized-bed reactor, and the polymerization time was prolonged to 2.5 hours, otherwise as in example 3.
The powder products obtained in each example and comparative example were tested for each property and the results are shown in Table 1:
table 1 sample test results
Wherein, MFR is tested according to GB/T3682.1-2018, tensile yield stress and tensile fracture nominal strain are tested according to GB/T1040.1-2006, normal temperature impact strength is tested according to GB/T1043.1-2008, and ash is tested according to GB/T9345.1-2008.
As can be seen from the detection data in Table 1, the ash content of the polyethylene material prepared by the method and the production system is reduced by 65% compared with that of the comparative example, and the mechanical strength is improved to different degrees, so that unexpected technical effects are generated, and the process has the effects of unexpectedly and obviously reducing the ash content of the polypropylene material and improving the product quality.
It will be appreciated by persons skilled in the art that the embodiments of the invention described above and shown in the drawings are by way of example only and are not limiting. The objects of the present invention have been fully and effectively achieved. The functional and structural principles of the present invention have been shown and described in the examples and embodiments of the invention may be modified or practiced without departing from the principles described.
Claims (8)
1. A low ash polyethylene powder production system is characterized in that the following process units are connected in series in sequence: the low ash polyethylene powder is obtained by catalyzing and polymerizing by using a Ziegler-Natta catalyst.
2. The low ash polyethylene powder production system according to claim 1, wherein when the slurry reactor is two or more, a parallel combination is employed.
3. The low ash polyethylene powder production system according to claim 1, wherein said feedstock formulation unit comprises an ethylene refining unit and a catalyst preforming unit, both separately connected to a gas phase fluidized bed reactor.
4. The low ash polyethylene powder production system according to claim 3, wherein the ethylene refining unit comprises a desulfurizing and dechlorinating tower, a CO removing tower, a deoxidizing tower and a drying tower in this order.
5. A method for producing low ash polyethylene powder, comprising the steps of:
s1, injecting ethylene into an ethylene refining unit, and removing impurities and moisture through a desulfurization and dechlorination tower, a CO removal tower, a deoxidization tower and a drying tower to obtain refined ethylene;
s2, injecting a catalyst and a cocatalyst into a catalyst prefabrication unit, and fully mixing to obtain a catalyst composition, wherein the catalyst takes Ti as an active center;
s3, respectively injecting refined ethylene and the catalyst composition into a gas-phase fluidized bed reactor for polymerization reaction, controlling the polymerization temperature to be 85-105 ℃, controlling the pressure to be 2.5-3.5MPa, controlling the gas flow rate to be 0.5-1.2m/S and controlling the residence time to be 0.5-1.5h;
s4, discharging a polymer material into a slurry reactor, continuing the polymerization reaction in the presence of a solvent, controlling the polymerization temperature at 75-95 ℃ and the pressure at 0.3-1.5MPa, controlling the material retention time at 40-80min and the material level at 35-75%;
s5, the discharged powder enters a degassing tower and a drying tower to remove unreacted monomers, then enters a treatment unit to be treated by nitrogen containing a small amount of water vapor so as to fully remove the activity of the unconsumed cocatalyst, and finally the low ash polyethylene powder is obtained by catalytic polymerization by using a Ziegler-Natta catalyst.
6. The process of claim 5, wherein in step S2, the molar ratio of cocatalyst to catalyst is from 10 to 200:1.
7. the process of claim 6, wherein in step S2, the molar ratio of cocatalyst to catalyst is from 30 to 80:1.
8. the method of claim 5, wherein the cocatalyst is selected from at least one of trimethylaluminum, triethylaluminum, triisobutylaluminum, diisobutylaluminum monochloride.
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Citations (3)
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|---|---|---|---|---|
| US5001205A (en) * | 1988-06-16 | 1991-03-19 | Exxon Chemical Patents Inc. | Process for production of a high molecular weight ethylene α-olefin elastomer with a metallocene alumoxane catalyst |
| WO2000015676A1 (en) * | 1998-09-16 | 2000-03-23 | Univation Technologies, Llc | Monocyclopentadienyl metal catalyst composition for the polymerization of olefins |
| RU2759723C1 (en) * | 2020-12-23 | 2021-11-17 | Публичное Акционерное Общество "Нижнекамскнефтехим" | Method for continuous promotion of a titanium-magnesium ziegler-natta catalyst in the processes of olefin (co)polymerisation |
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|---|---|---|---|---|
| EP1655339A1 (en) * | 2004-11-03 | 2006-05-10 | Borealis Technology Oy | Multimodal polyethylene composition obtainable with high activity catalyst |
| EP2346912B9 (en) * | 2008-11-07 | 2013-02-13 | Borealis AG | Process for the preparation of polyethylene |
| EP2228395A1 (en) * | 2009-02-24 | 2010-09-15 | Borealis AG | Improved multi-stage process for producing multi-modal ethylene polymer composition |
| BR112017001515B1 (en) * | 2014-08-14 | 2021-09-14 | Basell Polyolefine Gmbh | AQUEOUS PULP POLYMERIZATION PROCESSES FROM MULTIPLE REACTORS WITH HIGH PURITY ETHYLENE |
| CN112300312B (en) * | 2020-11-05 | 2023-03-14 | 杭州双安科技有限公司 | Synthetic method of polyethylene |
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| US5001205A (en) * | 1988-06-16 | 1991-03-19 | Exxon Chemical Patents Inc. | Process for production of a high molecular weight ethylene α-olefin elastomer with a metallocene alumoxane catalyst |
| WO2000015676A1 (en) * | 1998-09-16 | 2000-03-23 | Univation Technologies, Llc | Monocyclopentadienyl metal catalyst composition for the polymerization of olefins |
| RU2759723C1 (en) * | 2020-12-23 | 2021-11-17 | Публичное Акционерное Общество "Нижнекамскнефтехим" | Method for continuous promotion of a titanium-magnesium ziegler-natta catalyst in the processes of olefin (co)polymerisation |
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