CN103788275B - A kind of method of preparing low density polyethylene (LDPE) - Google Patents
A kind of method of preparing low density polyethylene (LDPE) Download PDFInfo
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- CN103788275B CN103788275B CN201210419408.3A CN201210419408A CN103788275B CN 103788275 B CN103788275 B CN 103788275B CN 201210419408 A CN201210419408 A CN 201210419408A CN 103788275 B CN103788275 B CN 103788275B
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Abstract
The invention discloses a kind of method of preparing low density polyethylene (LDPE), it comprises that ethene and alpha-olefin carry out polymerization under the existence of hydrogen, inert gas and carried metallocene catalyst in single-reactor, the mol ratio of described alpha-olefin and ethene is 0.02:1 ~ 0.2:1, and in reactor, the concentration of hydrogen is 200 ~ 10000ppv; Described poly melt index is 5 ~ 50g/10min, and molecular weight distribution is 2 ~ 10, and density is 0.910 ~ 0.925g/cm3. Utilize method provided by the invention, ethene and alpha-olefin can directly obtain LLDPE in as gas-phase fluidized-bed reactor under the existence of hydrogen, inert gas and carried metallocene catalyst in single-reactor, the polyethylene obtaining has compared with high fusion index, distribution as unimodal, and good mechanical performance, can be used in injection mo(u)lding field.
Description
Technical field
The present invention relates to one and prepare poly method, be specifically related to a kind of side of preparing LLDPEMethod.
Background technology
LLDPE (LLDPE) can be widely used in the manufacturing of packaging product. The production of LLDPE is generally adoptedWith traditional Ziegler-Natta catalyst manufacture. But because traditional Z iegler-Natta catalyst is a kind of dynamics modelCatalyst, the product molecular weight distribution making is wider, and contains part low-molecular weight polymer; And this part low-molecular-weight polymericThing is easily separated out from product, and therefore some low-density high index naval stores (melt index 10 ~ 50g/10min) are in food product packetsThe fields such as dress are difficult to application.
In addition, Ziegler-Natta catalyst need to add a large amount of hydrogen while producing this low-density high index product,Its hydrogen/ethene reaches 0.5, and catalyst activity declines a lot compared with producing low index product, thereby produces fine polymer powder,Bring risk to the operation of process units, and metallocene catalyst have excellent comonomer and hydrogen is adjusted responding ability, makesIt is in the time producing this class low-density high index LLDPE product, and compared with Z/N catalyst, the comonomer and the hydrogen that need are little,Catalyst performance changes little.
Summary of the invention
For deficiency of the prior art, the invention provides one and utilize metallocene catalyst to prepare low-density high indexPoly method, utilizing the poly density that the method makes is 0.910 ~ 0.925g/cm3, melt index is 10 ~ 50g/10min, molecular weight distribution is 2 ~ 10, can be used in injection mo(u)lding.
According to an aspect of the present invention, provide a kind of method of preparing low density polyethylene (LDPE), it comprise ethene and α-Alkene carries out polymerization under the existence of hydrogen, inert gas and carried metallocene catalyst in single-reactor, described α-The mol ratio of alkene and ethene is 0.02:1 ~ 0.2:1, and in described reactor, the concentration of hydrogen is 200ppm ~ 10000ppm; DescribedPoly melt index is 5 ~ 50g/10min, and molecular weight distribution is 2 ~ 10, and density is 0.910 ~ 0.925g/cm3。
In said method, preferably described poly melt index is 10 ~ 50g/10min, and molecular weight distribution is 2 ~ 3.Described polyethylene is distribution as unimodal, has narrow molecular weight distribution.
In said method, described carried metallocene catalyst is by loading on the metallocene compound on carrier and helping and urgeAgent composition, described metallocene compound is the organo-metallic compound of bridging or non-bridging, and contains more than one η-part,Described metal is selected from the 4th, 5 and 6 subgroup metals; Described co-catalyst is MAO or modified methylaluminoxane; Described yearBody is selected from inorganic oxide, butter. Described inorganic oxide is as aluminium oxide; Described butter is as magnesium chloride. InstituteStating carrier can be also polymer, as polystyrene spheres. In an instantiation in said method, described metallocene chemical combinationThing is the organo-metallic compound of non-bridging, and described η-part is the part that contains cyclopentadiene, described metal be Ti, Zr orHf; Described co-catalyst is MAO; Described carrier is silica gel.
In said method, described polymerization comprises slurry polymerization, gas-phase polymerization and polymerisation in solution. The described gas phase that is polymerized to is gatheredWhile closing, wherein polymerization temperature is 60 ~ 120 DEG C, and reaction pressure is 1.0 ~ 2.5Mpa, and the time of staying is 1 ~ 8 hour.
In a specific embodiment of said method, described inert gas is nitrogen. Described single-reactor is as gas phaseFluid bed.
In said method, described alpha-olefin is used for regulating poly density, and described alpha-olefin comprises butylene, hexeneDeng. Pass into hydrogen for regulating poly molecular weight. The concentration of preferred described hydrogen is 200 ~ 800ppm. .
According to another aspect of the present invention, provide the LLDPE of preparing according to said method at noteMould the application in field.
Utilize method provided by the invention, ethene and alpha-olefin are at hydrogen, inert gas and carried metallocene catalystExistence under in single-reactor as can be directly obtained LLDPE in gas-phase fluidized-bed reactor, obtainPolyethylene has compared with high fusion index, and distribution as unimodal, and good mechanical performance, can be used in injection mo(u)lding field.
Brief description of the drawings
Fig. 1 is poly drip washing classification figure according to an embodiment of the invention.
Detailed description of the invention
The assay method of parameter:
The mensuration of melt index: measure according to the method in GB3682;
The mensuration of molecular weight and molecular weight distribution: employing PL-GPC220 is the mensuration at 150 DEG C taking trichloro-benzenes as solvent(standard specimen: PS, flow velocity: 1.0ml/min, pillar: 3xPlgel10umM1xED-B300x7.5nm)
The mensuration of mechanical performance: adopt the method in GB1040 to measure.
Drip washing classification (TREF): for measuring the fraction distribution situation instrument of polymer: TREF300 type temperature rising elutionAnalyzer, PolymerCharSA company of Spain. Polymer is warming up to 160 under nitrogen protection with 1,2,4-trichloro-benzenesDEG C, constant temperature 60min, is then transferred in analytical column, fast cooling to 95 ~ 100 DEG C, and constant temperature 45min, then with different cooling speedDegree is slowly down to 35 DEG C, and keeps 30min, heats up subsequently, with the pouring of 0.5mL/min flow rate pump with the speed of 1.0 DEG C/minWash analytical column, drench the content of fraction in fluid with infrared detector analysis.
From the drip washing classification figure of Fig. 1, can find out, be Unimodal Distribution, this just illustrates prepared according to the methods of the invention obtainingPolyethylene there is narrow side chain and distribute, there is distribution as unimodal.
Embodiment 1 ~ 4
Catalyst preparation
Under nitrogen atmosphere, add 300g 600 DEG C of activation silica-gel carrier of 4 hours under nitrogen atmosphere, then addThe toluene solution of the MAO of 1100g10%, then adds two (1-butyl-3-methyl cyclopentadienyl) the zirconium chloride 2LiCl of 10gThe toluene solution of THF, reacted after 1 hour, and filtration, washing are dried, and obtain the good powder of mobility, and loaded metallocene is urgedAgent.
Polymer preparation
The carried metallocene catalyst of ethene, hexene, hydrogen and nitrogen and above-mentioned preparation is joined to gas phase fluidizationIn bed bioreactor, under 85 DEG C, 2.01MPa, react. Different polymerization process condition parameters are in table 1, the different polymer that obtainPerformance in table 2.
Comparative example 1 ~ 2
With embodiment 1, difference be to use catalyst and reaction condition different. Specifically in table 3. WhereinZiegler-Natta is the M catalyst that current gas phase polymerization of ethylene is conventional. Comparative example 1 is Ziegler-Natta catalysisLower index polyethylene product is produced in agent, when comparative example 2 is Ziegler-Natta catalyst production high index polyethylene productProcess conditions.
Table 1
Table 2
| Embodiment 1 | Embodiment 2 | Embodiment 3 | Embodiment 4 | |
| MI2.16 | 24.3 | 22.3 | 23.4 | 22 |
| Density g/cm3 | 0.920 | 0.919 | 0.921 | 0.912 |
| Mw*104 | 5.5 | 5.5 | 5.3 | 5.8 |
| Mn*104 | 2.1 | 1.96 | 1.8 | 2.4 |
| Mw/Mn | 2.6 | 2.8 | 2.8 | 2.4 |
| Yield strength, MPa | 9.2 | 9.1 | 8.8 -- | |
| Elongation at yield rate, % | 63 | 64.8 | 63 -- | |
| Hot strength, mPa | 17.5 | 16.2 | 10.4 -- | |
| Percentage elongation % | ＞739 | 685 | 588 -- | |
| Shrinkage factor, longitudinally | 1.50 | 1.60 | 1.54 -- | |
| Laterally | 1.40 | 1.35 | 1.35 -- | |
| Hardness/HD | 46 | 45 | 44 -- |
Table 3
From table 3, can learn, prepare the low density polyethylene (LDPE) with approximate equal densities and melt index, utilizeMethod provided by the invention, only needs a small amount of comonomer and a small amount of hydrogen just can direct polymerization in single-reactorObtain. Its technique of method in the present invention is simple to operation, has good application prospect.
It should be noted in the discussion above that above-described embodiment, only for explaining the present invention, does not form of the present invention anyRestriction. By with reference to exemplary embodiments, invention has been described, be descriptive but should be understood to word wherein usedWith explanatory vocabulary, instead of limited vocabulary. Can in the scope of the claims in the present invention, make the present invention in accordance with regulationsAmendment, and the present invention is revised not deviating from scope and spirit of the present invention. Although the present invention who wherein describes relates toAnd specific method, material and embodiment, but and do not mean that the present invention is limited to wherein disclosed particular case, on the contrary, thisBright other all methods and applications with identical function that extend to.
Claims (8)
1. prepare a method for low density polyethylene (LDPE), it comprise ethene and alpha-olefin luxuriant at hydrogen, inert gas and support typeUnder the existence of metallic catalyst, in single-reactor, carry out polymerization, the mol ratio of described alpha-olefin and ethene be 0.06:1～0.12:1, in reactor, the concentration of hydrogen is 200ppm～10000ppm; Described poly melt index is 5～50g/10min, molecular weight distribution is 2～10, density is 0.910～0.921g/cm3。
2. method according to claim 1, is characterized in that, described poly melt index is 10～50g/10min,Molecular weight distribution is 2～3.
3. method according to claim 1, is characterized in that, described carried metallocene catalyst is by loading on carrierMetallocene compound and co-catalyst composition, described metallocene compound is the organo-metallic compound of bridging or non-bridging,And contain more than one η-part, described metal is selected from the 4th, 5 and 6 subgroup metals; Described co-catalyst be MAO orModified methylaluminoxane; Described carrier is selected from inorganic oxide, butter.
4. method according to claim 3, is characterized in that, the organic metal that described metallocene compound is non-bridgingCompound, described η-part is the part that contains cyclopentadiene, described metal is Ti, Zr or Hf; Described co-catalyst is methylAikyiaiurnirsoxan beta; Described carrier is silica gel.
5. method according to claim 1, is characterized in that, the concentration of described hydrogen is 200～800ppm.
6. according to the method described in any one in claim 1～5, it is characterized in that, described in be polymerized to gas-phase polymerization, whereinPolymerization temperature is 60～120 DEG C, and reaction pressure is 1.0～2.5Mpa, and the time of staying is 1～8 hour.
7. according to the method described in any one in claim 1～5, it is characterized in that, described inert gas is nitrogen.
One kind according to the LLDPE that in claim 1～7, prepared by method described in any one in injection moulding fieldIn application.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN105273115B (en) * | 2014-07-15 | 2017-12-22 | 中国石油化工股份有限公司 | A kind of low temperature suitable polyethylenes and its injection moulding composition |
| CN106699948B (en) * | 2015-11-13 | 2020-05-12 | 中国石油化工股份有限公司 | Preparation method of ultra-low density polyethylene |
| CN107459598B (en) * | 2016-06-03 | 2020-05-12 | 中国石油化工股份有限公司 | Polyethylene for film |
| CN107458059B (en) * | 2016-06-03 | 2019-10-22 | 中国石油化工股份有限公司 | A kind of polyethylene heat-shrinkage film |
| CN115677893A (en) * | 2022-11-11 | 2023-02-03 | 山东京博石油化工有限公司 | Gas-liquid mixing feeding method in polyolefin polymerization reaction process |
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| EP1225201A1 (en) * | 2001-01-12 | 2002-07-24 | ATOFINA Research | High shrink polyethylene films |
| CN101472964A (en) * | 2006-06-27 | 2009-07-01 | 尤尼威蒂恩技术有限责任公司 | Improved polymerization processes using metallocene catalysts, their polymer products and end uses |
| CN102453124A (en) * | 2010-10-21 | 2012-05-16 | 中国石油化工股份有限公司 | Supported metallocene catalyst and olefin polymer, and preparation methods thereof |
| CN103087240A (en) * | 2011-10-31 | 2013-05-08 | 中国石油化工股份有限公司 | Method for preparing ethylene polymer |
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Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
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| JPH11140240A (en) * | 1997-11-04 | 1999-05-25 | Asahi Chem Ind Co Ltd | Polyethylene-based resin composition for heavy duty packaging and polyethylene-based film for heavy duty packaging |
| CN1250058A (en) * | 1998-10-06 | 2000-04-12 | 中国石油化工集团公司 | Catalyst for synthesis of polyolefine with wide or two-peak molecular weight distribution and its preparation |
| EP1225201A1 (en) * | 2001-01-12 | 2002-07-24 | ATOFINA Research | High shrink polyethylene films |
| CN101472964A (en) * | 2006-06-27 | 2009-07-01 | 尤尼威蒂恩技术有限责任公司 | Improved polymerization processes using metallocene catalysts, their polymer products and end uses |
| CN102453124A (en) * | 2010-10-21 | 2012-05-16 | 中国石油化工股份有限公司 | Supported metallocene catalyst and olefin polymer, and preparation methods thereof |
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