CN116239804A - Long-chain branched high-density polyethylene and preparation method thereof - Google Patents

Long-chain branched high-density polyethylene and preparation method thereof Download PDF

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Publication number
CN116239804A
CN116239804A CN202111487775.2A CN202111487775A CN116239804A CN 116239804 A CN116239804 A CN 116239804A CN 202111487775 A CN202111487775 A CN 202111487775A CN 116239804 A CN116239804 A CN 116239804A
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density polyethylene
compound
high density
chain branched
long chain
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高克京
荔栓红
黄强
祝文亲
李兵
周京生
秦睿
徐春燕
李稳
蔡玉东
张丽洋
杜斌
张瑀健
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Petrochina Co Ltd
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Petrochina Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J3/00—Processes of treating or compounding macromolecular substances
    • C08J3/24—Crosslinking, e.g. vulcanising, of macromolecules
    • C08J3/242—Applying crosslinking or accelerating agent onto compounding ingredients such as fillers, reinforcements
    • 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
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
    • C08J2323/04—Homopolymers or copolymers of ethene
    • C08J2323/06—Polyethene
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/16—Nitrogen-containing compounds
    • C08K5/315—Compounds containing carbon-to-nitrogen triple bonds
    • 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

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  • Chemical Kinetics & Catalysis (AREA)
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Abstract

The invention relates to a long chain branched high-density polyethylene, which is obtained by melt mixing high-density polyethylene with azo initiator, wherein the high-density polyethylene is prepared by the following steps of: 88.0 to 99.999 parts by weight; the azo initiator: 0.001-2 parts by weight; the high-density polyethylene is ethylene homopolymer or copolymer, the double bond content is 0.01-0.5 mol%, the melt index is 0.001-10g/10min, and the density is 0.940-0.970g/cm 3 Between them. The invention also relates to a preparation method of the long-chain branched high-density polyethylene.

Description

Long-chain branched high-density polyethylene and preparation method thereof
Technical Field
The invention relates to a preparation method of high-density polyethylene, in particular to a preparation method of high-density polyethylene containing long chain branching.
Background
High Density Polyethylene (HDPE) is a general resin material which is very widely used nowadays, and compared with LLDPE and LDPE, the HDPE has superior mechanical properties such as stretching and bending, and meanwhile, the HDPE has good chemical resistance and electrical insulation, and is widely used in various blow molded products, injection products, films, wires and cables, and pipes. However, the molecular chain does not contain a long branched chain structure, so that the entanglement degree of the molecular chain in a molten state is low, and the melt strength is low. The melt cannot show strain hardening phenomenon during elongational flow, which can lead HDPE to edge curling and shrinkage easily during extrusion coating, fluid flow instability phenomenon during multilayer coextrusion, and defects such as cell collapse during extrusion foaming. Limiting the application of HDPE in the molding processing fields of thermoforming, large-size molding, foaming and the like.
The long-chain branched high-density polyethylene is a polyethylene with high melt strength and obvious strain hardening characteristics. By melt strength is meant the maximum stress that the polymer melt can withstand before breaking when stretched. While strain hardening refers to the phenomenon in which the tensile stress increases sharply with increasing tensile strain when the polymer melt is stretched. The polymer with strain hardening phenomenon has increased elasticity in a molten state, has self-recovering ability, has an increased uniform deformation range of a melt, and exhibits high melt strength. The existence of the long branched chain structure can improve the processing temperature range of HDPE, and overcome the defects of edge curling and shrinkage of HDPE during high-speed extrusion coating, foam collapse during extrusion foaming and the like. The long-chain branched polyethylene has excellent rheological property and high melt strength, and the product prepared by the long-chain branched polyethylene has the advantages of good dimensional stability, higher heat distortion temperature, good environmental effect and the like. Long chain branched high density polyethylene has therefore become one of the research hotspots in the field of polyolefins in recent years.
The preparation method of the Long Chain Branched Polyethylene (LCBPE) mainly comprises a direct synthesis method, a high-energy radiation method, a melt branching method and the like. Wherein the direct synthesis method uses a proper ethylene polymerization catalyst, and introduces long-chain branches on the main chain of the polyethylene in the polymerization process; the high-energy radiation method is to use high-energy electron beams or rays to enable polyethylene to generate macromolecular free radicals, and long-chain branching can be formed between the macromolecular free radicals through coupling reaction; melt branching is a process in which polyethylene in the molten state is caused to generate macromolecular chain radicals under the action of an initiator, and long chain branching is formed between these radicals by coupling reaction. The invention belongs to the field of preparing long-chain branched polyethylene by a melt branching method.
Disclosure of Invention
The invention aims to provide long-chain branched high-density polyethylene and a preparation method thereof. The invention uses azo initiator, which only reacts with double bond in molecular chain to form macromolecule free radical, and can form crosslinking of polyethylene through coupling between macromolecule free radical, the crosslinking mode can not cause degradation of polyethylene chain, and the branching degree of polyethylene can be improved to the greatest extent.
To this end, the present invention provides a long chain branched high density polyethylene obtained by melt mixing a high density polyethylene with an azo-type initiator, wherein,
(1) The high density polyethylene: 88.0 to 99.999 parts by weight;
(2) The azo initiator: 0.001-2 parts by weight;
the high-density polyethylene is ethylene homopolymer or copolymer, the double bond content is 0.01-0.5 mol%, the melt index is 0.001-10g/10min, and the density is 0.940-0.970g/cm 3 Between them.
The high-density polyethylene used in the present invention is a specific polyethylene and must contain double bonds. The aim is to introduce a certain amount of double bonds in the polyethylene segment.
The long chain branching high-density polyethylene is preferably obtained by catalyzing ethylene to homopolymerize or copolymerize under the condition of 65-85 ℃ (further preferably 75-85 ℃) by using an olefin polymerization catalyst, wherein the olefin polymerization catalyst comprises a main catalyst and a cocatalyst, and the molar ratio of aluminum in the cocatalyst to titanium in the main catalyst is controlled to be 1-500:1;
wherein the main catalyst is prepared by reacting a magnesium compound, a liquid titanium compound and an organosilane compound,
the magnesium compound is represented by the general formula (I) Mg (OR) 1 ) n Cl 2-n In the formula, R is C 2 ～C 20 Is a saturated or unsaturated straight chain, branched chain or cyclic chain, n is more than or equal to 0 and less than or equal to 2;
the titanium compound is represented by the general formula (II) Ti (OR) 2 ) n Cl 4-n In the formula, R is 2 Is C 2 ～C 20 Is a saturated or unsaturated straight chain, branched chain or cyclic chain, n is more than or equal to 0 and less than or equal to 4;
the general formula of the organosilane compound is R 3 m SiX n (OR 4 ) k Wherein R is 3 Is C 2 -C 20 And R is a hydrocarbon group of 3 Containing double bonds, X being halogen, R 4 Is C 1 -C 20 M is an integer from 2 to 3, n is an integer from 1 to 2, k is an integer from 0 to 2, and m+n+k=4;
wherein the cocatalyst has a general formula of AlR' n X 3-n An organoaluminum compound represented by the formula wherein R' is hydrogen or an alkyl group having 1 to 20 carbon atoms, X is halogen, and n is 1<n is less than or equal to 3;
further preferably the cocatalyst is AlEt 3 、Al(iso-Bu) 3 、Al(n-C 6 H 13 ) 3 、Al(n-C 8 H 17 ) 3 Or AlEt 2 Cl。
The long-chain branched high-density polyethylene according to the invention is preferably one in which, in the preparation of the procatalyst, the magnesium compound is in particular Mg (OEt) Cl, mg (OEt) 2 And long-chain alkoxymagnesium compounds, and the organomagnesium compounds used in the reaction are more preferably diethoxymethyl magnesium, dipropoxymagnesium, dibutoxymagnesium, and dioctyloxymagnesium. Even more preferably, the particulate solid is spherical or spheroid, having an average particle size in the range of 10-100 microns.
The long chain branched high density polyethylene of the present invention, wherein it is preferable that in the preparation of the procatalyst, the titanium compound is preferably a tetravalent titanium compound because they are usually liquid at ordinary temperature and are also excellent in compatibility with some solvents in general. Specific further preferred titanium compounds are titanium tetrachloride, triethoxy titanium chloride, dibutoxy titanium chloride, trimethoxy titanium chloride, dimethoxy titanium chloride, trihexyloxy titanium chloride or diethoxy titanium chloride, of which titanium tetrachloride is still further preferred.
The long chain branched high density polyethylene according to the present invention, wherein it is preferable that in the preparation of the main catalyst, the organosilane compound is at least one of 7-octenyl allyl dichlorosilane, 7-octenyl vinyl dichlorosilane, 5-hexenyl allyl dichlorosilane, 7-octenyl di (allyl) chlorosilane, di (7-octenyl) allyl chlorosilane, di (7-octenyl) dichlorosilane, tri (allyl) chlorosilane, di (allyl) dichlorosilane, di [2- (5-ethylidene-2-norbornene) ethyl ] dichlorosilane, 2- (5-ethylidene-2-norbornene) ethyl allyl dichlorosilane, and di [2- (3-cyclopentadienyl) ethylene ] dichlorosilane.
The invention also recommends a preparation method of the main catalyst, and the preparation process preferably comprises the following steps:
(1) Contacting a solid magnesium compound with a liquid titanium compound;
(2) The reaction product obtained in the step (1) is contacted and reacted with organosilane;
(3) And (3) further reacting the reaction product obtained in the step (2) with a liquid titanium compound, and finally washing and drying with an inert solvent to obtain the powdery main catalyst.
The more preferable scheme is as follows:
(1) The solid magnesium compound and the liquid titanium compound are contacted and reacted in the temperature range of-20 ℃ to 10 ℃;
(2) The reaction product obtained in the step (1) is contacted and reacted with organosilane at the temperature of 30-80 ℃;
(3) And (3) further reacting the reaction product obtained in the step (2) with a liquid titanium compound at 80-130 ℃, and finally washing and drying with an inert solvent to obtain the powdery main catalyst.
The amount of the liquid titanium compound used for the first time is controlled to be 0.01 to 50 moles, preferably 0.05 to 20 moles, and the organosilane compound is controlled to be 0.01 to 3 moles, preferably 0.02 to 0.8 moles, per mole of the magnesium compound, and the liquid titanium compound used for the second time is controlled to be 0.01 to 50 moles, per mole of the magnesium compound.
In the first step of preparing the above-mentioned procatalyst, in order to ensure the smooth progress of the reaction, it is preferred that the magnesium compound is first dispersed in an inert diluent, which is usually selected from aliphatic or aromatic hydrocarbons such as benzene, toluene, xylene, isobutane, pentane, hexane, heptane or cyclohexane and mixtures thereof, and toluene or xylene is generally a suitable inert solvent. The temperature at which the magnesium compound and the liquid titanium compound are contacted with each other depends on the nature of the reactants, and it is generally chosen to carry out the contact reaction at a relatively low temperature, typically-10 to 20 c, and typically-5 to 10 c. The liquid titanium compound is generally added dropwise, and after the addition, the reaction is carried out for 10 to 120 minutes at a low temperature, and then the temperature is gradually increased to 80 to 150 ℃ and the reaction is carried out for 20 to 180 minutes.
The second step in the preparation of the above-mentioned procatalyst is mainly to introduce an organosilane compound containing a double bond, which compound can participate in the polymerization of ethylene, intercalated into the polyethylene chain. If the two double bonds contained in the organosilane compound participate in the polymerization reaction, the crosslinking reaction of the polyethylene chain segment is caused, if only one double bond in the organosilane compound participates in the polymerization reaction, the remained double bond can be used as an active site for reacting with a subsequent azo initiator, the polyethylene chain containing the double bond forms macromolecular free radicals under the initiation of the azo compound, and the macromolecular free radicals can be coupled to form crosslinking, so that the long-chain branched polyethylene is finally formed.
In the second step of preparing the main catalyst, liquid titanium compound is added again, and the liquid titanium compound is added to remove excessive organosilane compound, so that the activity of the catalyst is improved, the strength of particles is enhanced, and the particle shape of the final catalyst is adjusted. The reaction temperature of the step is controlled between 80 ℃ and 150 ℃ and the reaction time is controlled between 20 minutes and 180 minutes.
After the third reaction step, washing is generally performed to remove excess reactants and byproducts formed during the preparation process, and any inert solvent may be used for this washing step, for example, isobutane, pentane, hexane, heptane or cyclohexane and mixtures thereof may be selected, hexane is generally selected as the inert solvent for washing in the experiment. After washing, the catalyst suspension may be dried by purging with nitrogen under heating to give a main catalyst powder.
The long chain branched high density polyethylene according to the present invention, wherein preferably, the azo initiator comprises azobisisobutyronitrile, azobisisoheptonitrile, azobisisovaleronitrile, 1' -azo-cyanocyclohexane.
In general, in a chemical crosslinking method of polyethylene, peroxide is used as an initiator to initiate crosslinking of polyethylene, and a radical formed by decomposition of the peroxide abstracts a hydrogen atom on a polyethylene chain to form a polyethylene radical, and the polyethylene radical completes crosslinking of the polyethylene by coupling, but the polyethylene radical is unstable and is subject to dehydrogenation reaction to degrade the polyethylene. In the prior art, auxiliary crosslinking agents are developed to reduce the degradation reaction of polyethylene, thereby achieving the purpose of crosslinking the polyethylene. It is thought that the radical decomposed by the azo initiator cannot abstract a hydrogen atom on a polyethylene chain and cannot initiate crosslinking of polyethylene, but the present invention has found that the use of the azo initiator can initiate crosslinking of the polyethylene chain as long as a certain amount of double bonds are contained in the polyethylene chain, and the crosslinking reaction does not accompany side reactions of degradation.
The invention also provides a preparation method of the long-chain branched high-density polyethylene, which is to melt and mix the high-density polyethylene containing double bonds with azo initiator at 160-230 ℃ to obtain the long-chain branched high-density polyethylene.
The melt reaction method of the high-density polyethylene and the azo initiator can adopt two methods as follows:
firstly, 88.0 to 99.999 weight parts of high-density polyethylene is added into an internal mixer, the temperature of the internal mixer is controlled to be 170 to 210 ℃, 0.001 to 2 weight parts of azo initiator is added after stirring for 1 to 5 minutes, and long-chain branched high-density polyethylene is obtained after stirring for 1 to 10 minutes.
Secondly, 88.0 to 99.999 weight parts of high-density polyethylene and 0.001 to 2 weight parts of azo initiator are added into a screw extruder to react for 10 to 7 minutes, thus obtaining the long-chain branched high-density polyethylene. Wherein the temperature of each section of the extruder is controlled between 160 and 230 ℃ and the rotating speed of the screw is controlled between 50 and 200rpm.
The invention is different from the prior similar technology, the prior technology mainly adopts a peroxide initiator, the free radical obtained by decomposing the initiator can abstract hydrogen atoms on a polyethylene chain to form a polyethylene macromolecule free radical, the free radical is unstable, meanwhile, chain segment degradation is easy to occur, and other components are needed to stabilize the polyethylene macromolecule free radical in order to reduce the degradation reaction of the polyethylene macromolecule free radical, thereby increasing the complexity of the technology. The invention uses azo initiator, which only reacts with double bond in molecular chain to form macromolecule free radical, and can form crosslinking of polyethylene through coupling between macromolecule free radical, the crosslinking mode can not cause degradation of polyethylene chain, and the branching degree of polyethylene can be improved to the greatest extent.
Detailed Description
The following describes embodiments of the present invention in detail: the present example is implemented on the premise of the technical scheme of the present invention, and detailed implementation modes and processes are given, but the protection scope of the present invention is not limited to the following examples, and experimental methods without specific conditions are not noted in the following examples, and generally according to conventional conditions.
Melt strength test
The experimental device for testing the melt strength consists of a single-screw extruder with a capillary and a melt strength tester. Firstly, extruding a melt of high-density polyethylene resin from an extruder die, then, pulling the obtained extruded melt beam spline by using two rollers with opposite movement directions, which are arranged on a balance beam, uniformly accelerating the movement of the rollers until the melt beam breaks, and defining the force applied by the broken melt beam as the melt strength. The melt temperature at the time of the test was controlled at 190 ℃.
Example 1
Preparing a main catalyst:
(1) Into a 200 ml dry reactor which is anhydrous and oxygen-free, 10g of magnesium ethoxide (average particle diameter of 25 μm) and 80 ml of toluene were added, and the mixture was stirred and dispersed at 0℃for 15 minutes to form a suspension;
(2) 15 ml of titanium tetrachloride is added dropwise under the condition that the system temperature is kept at 0 ℃, after the dropwise addition is completed, the system temperature is raised to 90 ℃, stirring is carried out for 3 hours, finally, the temperature is reduced to 50 ℃, 1.2g of diallyl dichlorosilane is added, and stirring is carried out for 2 hours at 50 ℃.
(3) Stopping stirring for 30 minutes, settling the particles to the bottom of the reactor, extruding supernatant, adding 100 ml of toluene again, stirring for 15 minutes at 90 ℃, repeating the above operation for 1 time, and washing the particles;
(4) After the washing was completed, a mixture of 80 ml of toluene and 20 ml of titanium tetrachloride was added, and the reaction was stirred at 115℃for 2 hours, and then washed four times or more with hexane, and dried under vacuum to obtain a main catalyst sample.
Ethylene polymerization
After sufficient displacement with ethylene in the gas phase in a 2L polymerizer, 5mL of triethylaluminum (AlEt) was added at room temperature 3 ) Hexane solution (AlEt) 3 Concentration of 0.5 mmol/mL), 1L of anhydrous hexane and 10mg of main catalyst component, introducing 0.15MPa of hydrogen, stabilizing the polymerization pressure at 1.0MPa by using ethylene, raising the temperature to 80 ℃ to start polymerization timing, continuously adding ethylene during the polymerization period to maintain the polymerization pressure at 1.0MPa all the time, and discharging after 2h of polymerization to prepare the high-density polyethylene. The polyethylene powder was weighed after drying, the activity of the catalyst was calculated, and the melt strength of the polyethylene resin was measured, and the results are shown in Table 1.
Preparation of long chain branched high density polyethylene
1000g of the prepared high-density polyethylene was added with 800ppm of azobisisobutyronitrile, 1000ppm of antioxidant 1010 and 1000ppm of antioxidant 168, and after high-speed stirring and mixing, melt extrusion reaction was carried out using a twin-screw extruder, the temperature of the feeding section and the die temperature of the extruder were set to 190℃and the other sections were set to 210℃and the screw speed was set to 80rpm.
Example 2
Preparing a main catalyst:
(1) In a 200 ml dry reactor without water and oxygen, 10g of magnesium ethoxide (average particle size 25 μm) and 80 ml of toluene were added, and the mixture was stirred and dispersed at-10℃for 15 minutes to form a suspension;
(2) Under the condition that the temperature of the system is kept at minus 10 ℃,10 milliliters of titanium tetrachloride is added dropwise, after the dropwise addition is finished, the temperature of the system is raised to 80 ℃, stirring is carried out for 3 hours, finally, the temperature is reduced to 50 ℃, 1.5g of tri (allyl) chlorosilane is added, and stirring is carried out for 2 hours at 80 ℃.
(3) Stopping stirring for 30 minutes, settling the particles to the bottom of the reactor, extruding supernatant, adding 100 ml of toluene again, stirring for 15 minutes at 90 ℃, repeating the above operation for 1 time, and washing the particles;
(4) After the washing was completed, a mixture of 80 ml of toluene and 20 ml of titanium tetrachloride was added, and the reaction was stirred at 130℃for 2 hours, and then washed four times or more with hexane, and dried under vacuum to obtain a main catalyst sample.
Ethylene polymerization
After sufficient displacement with ethylene in the gas phase in a 2L polymerizer, 5mL of triethylaluminum (AlEt) was added at room temperature 3 ) Hexane solution (AlEt) 3 Concentration of 0.5 mmol/mL), 1L of anhydrous hexane and 11mg of main catalyst component, introducing 0.15MPa of hydrogen, stabilizing the polymerization pressure at 1.0MPa by using ethylene, raising the temperature to 80 ℃ to start polymerization timing, continuously adding ethylene during the polymerization period to maintain the polymerization pressure at 1.0MPa all the time, and discharging after 2h of polymerization to prepare the high-density polyethylene. The polyethylene powder was weighed after drying, the activity of the catalyst was calculated, and the melt strength of the polyethylene resin was measured, and the results are shown in Table 1.
Preparation of long chain branched high density polyethylene
1000g of the prepared high-density polyethylene was added with 800ppm of azobisisobutyronitrile, 1000ppm of antioxidant 1010 and 1000ppm of antioxidant 168, and after high-speed stirring and mixing, melt extrusion reaction was carried out using a twin-screw extruder, the temperature of the feeding section and the die temperature of the extruder were set to 190℃and the other sections were set to 210℃and the screw speed was set to 80rpm.
Example 3
Preparing a main catalyst:
(1) 10g of magnesium ethoxide (average particle size 25 μm) and 80 ml of toluene were added to a 200 ml dry reactor free of water and oxygen, and dispersed at-20℃for 15 minutes with stirring to form a suspension;
(2) Under the condition that the system temperature is kept at minus 20 ℃, 20 milliliters of titanium tetrachloride is added dropwise, after the dropwise addition is finished, the system temperature is raised to 100 ℃, stirring is carried out for 3 hours, finally, the temperature is reduced to 50 ℃, 1.6g of bis (7-octenyl) dichlorosilane is added, and stirring is carried out for 2 hours at 30 ℃.
(3) Stopping stirring for 30 minutes, settling the particles to the bottom of the reactor, extruding supernatant, adding 100 ml of toluene again, stirring for 15 minutes at 90 ℃, repeating the above operation for 1 time, and washing the particles;
(4) After the washing was completed, a mixture of 80 ml of toluene and 20 ml of titanium tetrachloride was added, and the reaction was stirred at 80℃for 2 hours, and then washed four times or more with hexane, and dried under vacuum to obtain a main catalyst sample.
Ethylene polymerization
After sufficient displacement with ethylene in the gas phase in a 2L polymerizer, 5mL of triethylaluminum (AlEt) was added at room temperature 3 ) Hexane solution (AlEt) 3 Concentration of 0.5 mmol/mL), 1L of anhydrous hexane and 12mg of main catalyst component, introducing 0.15MPa of hydrogen, stabilizing the polymerization pressure at 1.0MPa by using ethylene, raising the temperature to 80 ℃ to start polymerization timing, continuously adding ethylene during the polymerization period to maintain the polymerization pressure at 1.0MPa all the time, and discharging after 2h of polymerization to prepare the high-density polyethylene. The polyethylene powder was weighed after drying, the activity of the catalyst was calculated, and the melt strength of the polyethylene resin was measured, and the results are shown in Table 1.
Preparation of long chain branched high density polyethylene
1000g of the prepared high-density polyethylene was added with 900ppm of azobisisovaleronitrile, 1000ppm of antioxidant 1010 and 1000ppm of antioxidant 168, and after stirring and mixing at a high speed, melt extrusion reaction was carried out using a twin screw extruder, the temperature of the feeding section and the die temperature of the extruder were set at 160℃and the other sections were set at 200℃and the screw speed was set at 60rpm.
Example 4
Preparing a main catalyst:
(1) Into a 200 ml dry reactor which is anhydrous and oxygen-free, 10g of magnesium ethoxide (average particle diameter of 25 μm) and 80 ml of toluene were added, and the mixture was stirred and dispersed at 10℃for 15 minutes to form a suspension;
(2) 15 ml of titanium tetrachloride was added dropwise while keeping the system temperature at 10℃and, after completion of the dropwise addition, the system temperature was raised to 50℃and the reaction was stirred for 3 hours, 1.6g of tris (7-octenyl) chlorosilane was added and the reaction was stirred for 2 hours at 70 ℃.
(3) Stopping stirring for 30 minutes, settling the particles to the bottom of the reactor, extruding supernatant, adding 100 ml of toluene again, stirring for 15 minutes at 90 ℃, repeating the above operation for 1 time, and washing the particles;
(4) After the washing was completed, a mixture of 80 ml of toluene and 20 ml of titanium tetrachloride was added, and the reaction was stirred at 120℃for 2 hours, and then washed four times or more with hexane, and dried under vacuum to obtain a main catalyst sample.
Ethylene polymerization
After sufficient displacement with ethylene in the gas phase in a 2L polymerizer, 5mL of triethylaluminum (AlEt) was added at room temperature 3 ) Hexane solution (AlEt) 3 Concentration of 0.5 mmol/mL), 1L of anhydrous hexane and 11.5mg of main catalyst component, introducing 0.20MPa of hydrogen, stabilizing the polymerization pressure at 1.0MPa by using ethylene, raising the temperature to 80 ℃ to start polymerization timing, continuously adding ethylene during the polymerization period to maintain the polymerization pressure at 1.0MPa all the time, and discharging after 2h of polymerization to prepare the high-density polyethylene. The polyethylene powder was weighed after drying, the activity of the catalyst was calculated, and the melt strength of the polyethylene resin was measured, and the results are shown in Table 1.
Preparation of long chain branched high density polyethylene
1000g of the prepared high-density polyethylene was added with 1000ppm of azobisisoheptonitrile, 1000ppm of antioxidant 1010 and 1000ppm of antioxidant 168, and after stirring and mixing at a high speed, melt extrusion reaction was carried out using a twin screw extruder, the temperature of the feeding section and the die temperature of the extruder were set at 160℃and the other sections were set at 200℃and the screw speed was set at 60rpm.
Example 5
Preparing a main catalyst:
(1) 10g of magnesium ethoxide (average particle size 25 μm) and 80 ml of toluene were added to a 200 ml dry reactor free of water and oxygen, and dispersed at-5℃for 15 minutes with stirring to form a suspension;
(2) Under the condition that the system temperature is kept at minus 5 ℃, 30 milliliters of titanium tetrachloride is added dropwise, after the dropwise addition is finished, the system temperature is raised to 100 ℃, stirring is carried out for 3 hours, finally, the temperature is reduced to 50 ℃, 1.6g of tris (7-octenyl) chlorosilane is added, and stirring is carried out for 2 hours at 60 ℃.
(3) Stopping stirring for 30 minutes, settling the particles to the bottom of the reactor, extruding supernatant, adding 100 ml of toluene again, stirring for 15 minutes at 90 ℃, repeating the above operation for 1 time, and washing the particles;
(4) After the washing was completed, a mixture of 80 ml of toluene and 20 ml of titanium tetrachloride was added, and the reaction was stirred at 100℃for 2 hours, and then washed four times or more with hexane, and dried under vacuum to obtain a main catalyst sample.
Ethylene polymerization
After sufficient displacement with ethylene in the gas phase in a 2L polymerizer, 5mL of triethylaluminum (AlEt) was added at room temperature 3 ) Hexane solution (AlEt) 3 Concentration of 0.5 mmol/mL), 1L of anhydrous hexane and 9.5mg of main catalyst component, introducing 0.10MPa of hydrogen, stabilizing the polymerization pressure at 1.0MPa by using ethylene, raising the temperature to 80 ℃ to start polymerization timing, continuously adding ethylene during the polymerization period to maintain the polymerization pressure at 1.0MPa all the time, and discharging after 2h of polymerization to prepare the high-density polyethylene. The polyethylene powder was weighed after drying, the activity of the catalyst was calculated, and the melt strength of the polyethylene resin was measured, and the results are shown in Table 1.
Preparation of long chain branched high density polyethylene
1000g of the prepared polyethylene was added with 1200ppm of 1,1' -azo-cyanocyclohexane, 1000ppm of antioxidant 1010 and 1000ppm of antioxidant 168, and after stirring and mixing at a high speed, melt extrusion was carried out using a twin screw extruder, the temperature of the feeding section and the die temperature of the extruder were set at 180℃and the other sections were set at 210℃and the screw speed was set at 90rpm.
Comparative example 1
Preparation of the procatalyst
(1) Into a 200 ml dry reactor which is anhydrous and oxygen-free, 10g of magnesium ethoxide (average particle diameter of 25 μm) and 80 ml of toluene were added, and the mixture was stirred and dispersed at 0℃for 15 minutes to form a suspension;
(2) 15 ml of titanium tetrachloride was added dropwise while keeping the system temperature at 0℃and, after completion of the addition, the system temperature was raised to 90℃and the reaction was stirred for 3 hours.
(3) Stopping stirring for 30 minutes, settling the particles to the bottom of the reactor, extruding supernatant, adding 100 ml of toluene again, stirring for 15 minutes at 90 ℃, repeating the above operation for 1 time, and washing the particles;
(4) After the washing was completed, a mixture of 80 ml of toluene and 20 ml of titanium tetrachloride was added, and the reaction was stirred at 115℃for 2 hours, and then washed four times or more with hexane, and dried under vacuum to obtain a main catalyst sample.
Ethylene polymerization
After sufficient displacement with ethylene in the gas phase in a 2L polymerizer, 5mL of triethylaluminum (AlEt) was added at room temperature 3 ) Hexane solution (AlEt) 3 Concentration of 0.5 mmol/mL), 1L of anhydrous hexane and 10mg of main catalyst component, introducing 0.15MPa of hydrogen, stabilizing the polymerization pressure at 1.0MPa by using ethylene, raising the temperature to 80 ℃ to start polymerization timing, continuously adding ethylene during the polymerization period to maintain the polymerization pressure at 1.0MPa all the time, and discharging after 2h of polymerization to prepare the high-density polyethylene. The polyethylene powder was weighed after drying, the activity of the catalyst was calculated, and the melt strength of the polyethylene resin was measured, and the results are shown in Table 1.
Preparation of long chain branched high density polyethylene
1000g of the prepared high-density polyethylene was added with 800ppm of azobisisobutyronitrile, 1000ppm of antioxidant 1010 and 1000ppm of antioxidant 168, and after high-speed stirring and mixing, melt extrusion reaction was carried out using a twin-screw extruder, the temperature of the feeding section and the die temperature of the extruder were set to 190℃and the other sections were set to 210℃and the screw speed was set to 80rpm.
Comparative example 2
Preparation of the procatalyst
(1) Into a 200 ml dry reactor which is anhydrous and oxygen-free, 10g of magnesium ethoxide (average particle diameter of 25 μm) and 80 ml of toluene were added, and the mixture was stirred and dispersed at 0℃for 15 minutes to form a suspension;
(2) 15 ml of titanium tetrachloride is added dropwise under the condition that the system temperature is kept at 0 ℃, after the dropwise addition is completed, the system temperature is raised to 90 ℃, stirring is carried out for 3 hours, finally, the temperature is reduced to 50 ℃, 1.2g of diallyl dichlorosilane is added, and stirring is carried out for 2 hours at 50 ℃.
(3) Stopping stirring for 30 minutes, settling the particles to the bottom of the reactor, extruding supernatant, adding 100 ml of toluene again, stirring for 15 minutes at 90 ℃, repeating the above operation for 1 time, and washing the particles;
(4) After the washing was completed, a mixture of 80 ml of toluene and 20 ml of titanium tetrachloride was added, and the reaction was stirred at 115℃for 2 hours, and then washed four times or more with hexane, and dried under vacuum to obtain a main catalyst sample.
Ethylene polymerization
After sufficient displacement with ethylene in the gas phase in a 2L polymerizer, 5mL of triethylaluminum (AlEt) was added at room temperature 3 ) Hexane solution (AlEt) 3 Concentration of 0.5 mmol/mL), 1L of anhydrous hexane and 10mg of main catalyst component, introducing 0.15MPa of hydrogen, stabilizing the polymerization pressure at 1.0MPa by using ethylene, raising the temperature to 80 ℃ to start polymerization timing, continuously adding ethylene during the polymerization period to maintain the polymerization pressure at 1.0MPa all the time, and discharging after 2h of polymerization. The polyethylene powder was weighed after drying, the activity of the catalyst was calculated, and the melt strength of the polyethylene resin was measured, and the results are shown in Table 1.
Preparation of long chain branched high density polyethylene
1000g of the prepared polyethylene was added with 800ppm of 2, 5-dimethyl-2, 5-di-t-butylperoxy hexane, 1000ppm of antioxidant 1010 and 1000ppm of antioxidant 168, and after stirring and mixing at a high speed, melt extrusion reaction was carried out using a twin screw extruder, the temperature of the feeding section and the die temperature of the extruder were set at 190℃and the screw speed at 210℃were set at 80rpm, and after melt extrusion of the polyethylene, the melt index and melt strength of the polyethylene were measured, and the results are shown in Table 1.
TABLE 1
Figure BDA0003396681180000151
It can be seen from the examples that the catalyst can cause partial crosslinking of polyethylene when catalyzing ethylene polymerization due to the introduction of an organosilane compound having two or more double bonds during the preparation of the catalyst, and the degree of crosslinking of polyethylene increases after the extrusion reaction, and the melt strength further increases.
In the comparative example, the main catalyst of comparative example 1 does not use an organosilane compound with two or more double bonds in the preparation process, the catalyst does not have the characteristic of crosslinking, and in the subsequent extrusion reaction, an azo initiator is used, so that the crosslinking of polyethylene cannot be initiated; the main catalyst of comparative example 2 was prepared using an organosilane compound having two or more double bonds, but the use of a peroxide initiator in the extrusion reaction resulted in degradation of polyethylene, an increase in melt index and a decrease in melt strength.
Of course, the present invention is capable of other various embodiments and its several details are capable of modification and variation in light of the present invention by one skilled in the art without departing from the spirit and scope of the invention.

Claims (11)

1. A long chain branched high density polyethylene, characterized in that the polyethylene is obtained by melt mixing a high density polyethylene with an azo initiator, wherein,
the high density polyethylene: 88.0 to 99.999 parts by weight;
the azo initiator: 0.001-2 parts by weight;
the high-density polyethylene is ethylene homopolymer or copolymer, the double bond content is 0.01-0.5 mol%, the melt index is 0.001-10g/10min, and the density is 0.940-0.970g/cm 3 Between them.
2. The long chain branched high density polyethylene according to claim 1, wherein the high density polyethylene is obtained by homo-or copolymerizing ethylene under the condition of 75-85 ℃ by an olefin polymerization catalyst, the olefin polymerization catalyst comprises a main catalyst and a cocatalyst, and the molar ratio of aluminum in the cocatalyst to titanium in the main catalyst is controlled to be 1-500:1;
wherein the main catalyst is prepared by reacting a magnesium compound, a liquid titanium compound and an organosilane compound,
the magnesium compound is represented by the general formula (I) Mg (OR) 1 ) n Cl 2-n In the formula, R is C 2 ～C 20 Is a saturated or unsaturated straight chain, branched chain or cyclic chain, n is more than or equal to 0 and less than or equal to 2;
the titanium compound is represented by the general formula (II) Ti (OR) 2 ) n Cl 4-n In the formula, R is 2 Is C 2 ～C 20 Is a saturated or unsaturated straight chain, branched chain or cyclic chain, n is more than or equal to 0 and less than or equal to 4;
the general formula of the organosilane compound is R 3 m SiX n (OR 4 ) k Wherein R is 3 Is C 2 -C 20 And R is a hydrocarbon group of 3 Containing double bonds, X being halogen, R 4 Is C 1 -C 20 M is an integer from 2 to 3, n is an integer from 1 to 2, k is an integer from 0 to 2, and m+n+k=4;
wherein the cocatalyst has a general formula of AlR' n X 3-n An organoaluminum compound represented by the formula wherein R' is hydrogen or an alkyl group having 1 to 20 carbon atoms, X is halogen, and n is 1<n is less than or equal to 3;
preferably the cocatalyst is AlEt 3 、Al(iso-Bu) 3 、Al(n-C 6 H 13 ) 3 、Al(n-C 8 H 17 ) 3 Or AlEt 2 Cl。
3. The long chain branched high density polyethylene according to claim 2, wherein the organosilane compound is at least one of 7-octenyl allyl dichlorosilane, 7-octenyl vinyl dichlorosilane, 5-hexenyl allyl dichlorosilane, 7-octenyl di (allyl) chlorosilane, di (7-octenyl) allyl chlorosilane, di (7-octenyl) dichlorosilane, tri (allyl) chlorosilane, di (allyl) dichlorosilane, di [2- (5-ethylidene-2-norbornene) ethyl ] dichlorosilane, 2- (5-ethylidene-2-norbornene) ethyl allyl dichlorosilane, di [2- (3-cyclopentadienyl) ethylidene ] dichlorosilane.
4. The long chain branched high density polyethylene of claim 2 wherein the titanium compound is titanium tetrachloride, triethoxy titanium chloride, dibutoxy titanium chloride, trimethoxy titanium chloride, dimethoxy titanium chloride, trihexyloxy titanium chloride or diethoxy titanium chloride.
5. The long chain branched high density polyethylene of claim 2 wherein the magnesium compound is Mg (OEt) Cl, diethoxy magnesium, dipropoxy magnesium, dibutoxy magnesium or dioctyloxy magnesium; preferably spherical or spheroidal particulate solids having an average particle size in the range of 10 to 100 microns.
6. The long chain branched high density polyethylene of claim 2 wherein the procatalyst is prepared by a process comprising:
(1) Contacting a solid magnesium compound with a liquid titanium compound;
(2) The reaction product obtained in the step (1) is contacted and reacted with organosilane;
(3) And (3) further reacting the reaction product obtained in the step (2) with a liquid titanium compound, and finally washing and drying with an inert solvent to obtain the powdery main catalyst.
7. The long chain branched high density polyethylene according to claim 6, wherein the amount of the liquid titanium compound used for the first time is controlled to be 0.01 to 50 moles, preferably 0.05 to 20 moles, and the organosilane compound is controlled to be 0.01 to 3 moles, preferably 0.02 to 0.8 moles, per mole of the magnesium compound during the preparation of the procatalyst, and the titanium compound used for the second time is controlled to be 0.01 to 50 moles.
8. The long chain branched high density polyethylene of claim 2 wherein the procatalyst is prepared by a process comprising:
(1) The solid magnesium compound and the liquid titanium compound are contacted and reacted in the temperature range of-20 ℃ to 10 ℃;
(2) The reaction product obtained in the step (1) is contacted and reacted with organosilane at the temperature of 30-80 ℃;
(3) And (3) further reacting the reaction product obtained in the step (2) with a titanium compound at 80-130 ℃, and finally washing and drying with an inert solvent to obtain the powdery main catalyst.
9. The long chain branched high density polyethylene according to claim 1, wherein the azo initiator is azobisisobutyronitrile, azobisisoheptonitrile, azobisisovaleronitrile or 1,1' -azo-cyanocyclohexane.
10. A process for the preparation of a long chain branched high density polyethylene comprising the steps of: melting and mixing the high-density polyethylene and azo initiator at 160-230 ℃ to obtain long-chain branched polyethylene.
11. The method for producing a long chain branched high density polyethylene according to claim 10, wherein said melt mixing uses an internal mixer or a screw extruder.
CN202111487775.2A 2021-12-07 2021-12-07 Long-chain branched high-density polyethylene and preparation method thereof Pending CN116239804A (en)

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