CN110684140B - Method for preparing heat-resistant polyethylene, heat-resistant polyethylene prepared by same and composition thereof - Google Patents
Method for preparing heat-resistant polyethylene, heat-resistant polyethylene prepared by same and composition thereof Download PDFInfo
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- CN110684140B CN110684140B CN201810725718.5A CN201810725718A CN110684140B CN 110684140 B CN110684140 B CN 110684140B CN 201810725718 A CN201810725718 A CN 201810725718A CN 110684140 B CN110684140 B CN 110684140B
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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
- 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
Abstract
The invention provides a preparation method of heat-resistant polyethylene, heat-resistant polyethylene prepared by the preparation method and a composition of the heat-resistant polyethylene. The preparation method comprises the following steps: (a) carrying out first polymerization reaction on ethylene, hydrogen and a catalyst in the presence of a first solvent to form a first polymerization solution; (b) adding ethylene, hydrogen, 1-butene and 1-hexene into the first polymerization liquid to carry out a second polymerization reaction to form a second polymerization liquid; (c) further adding ethylene, hydrogen, 1-butene and 1-hexene into the second polymerization liquid to carry out a third polymerization reaction to obtain heat-resistant polyethylene, wherein the partial pressure ratio of the hydrogen to the ethylene in the step (a) is 3-4: 1; the partial pressure ratio of the hydrogen to the ethylene in the step (b) is 0.2-0.5: 1; the partial pressure ratio of the hydrogen to the ethylene in the step (c) is 0.02-0.1: 1. The method has simple process and easy operation, is suitable for industrial application, and the prepared heat-resistant polyethylene and the composition thereof have improved processing performance.
Description
Technical Field
The invention relates to the field of high polymer materials, in particular to a preparation method of heat-resistant polyethylene, heat-resistant polyethylene prepared by the preparation method and a composition of the heat-resistant polyethylene.
Background
The heat-resistant Polyethylene (PE-RT) is non-crosslinked Polyethylene which can be used for cold and hot water pipes, and has good flexibility and processability by properly controlling the number and distribution of branched chains on a Polyethylene molecular chain in polymerization reaction and good hydrostatic pressure resistance under the condition of high temperature. The PE-RT pipe is mainly used for a household cold and hot water conveying pipe and comprises a floor heating pipe, a heat exchanger, a solar panel, a heat circulating system and the like.
In the initial stages of the development of PE-RT pipes, only pipes in which ethylene and octene are copolymerized. With the continuous progress of catalyst technology and polymerization process, the PE-RT polymerization process technology has evolved from solution polymerization process technology to gas phase polymerization process technology and slurry polymerization process technology. Comonomers are developed into hexene and butene from original octene, the types and the brands of PE-RT pipes are continuously increased, and the PE-RT pipes are divided into 2 types, namely I type and II type, by the international standard ISO22391-2: 2009. According to the standard requirements, the type I PE-RT pipe is allowed to have brittle fracture under the temperature condition below 110 ℃, namely, the hydrostatic curve can have inflection points. The II type PE-RT pipe is not allowed to have brittle failure under the temperature condition below 110 ℃, namely, the hydrostatic pressure curve can not have inflection points.
The preparation method of the heat-resistant polyethylene in the prior art, the heat-resistant polyethylene prepared by the preparation method and the composition thereof mainly have the following defects:
defect one: the preparation process is complex, the operation is complicated and the method is not suitable for industrial application.
And defect two: the polyethylene prepared by the metallocene catalyst has narrow molecular weight distribution, relatively poorer processability and higher cost of the metallocene catalyst.
And a third defect: the preparation process adopts a single comonomer, and the relationship between the production cost and the high-temperature creep resistance of the product cannot be well balanced.
For the above reasons, further research on a preparation method of heat-resistant polyethylene, heat-resistant polyethylene prepared by the same and a composition thereof is needed to solve the problems that the preparation process is complex, the operation is complicated, the preparation method is not suitable for industrial application, the molecular weight distribution of polyethylene is narrow, the processability is relatively poor, the cost of metallocene catalyst is high, and the relationship between the production cost and the high-temperature creep resistance of the product cannot be well balanced.
Disclosure of Invention
The invention mainly aims to provide a preparation method of heat-resistant polyethylene, heat-resistant polyethylene prepared by the preparation method and a composition of the heat-resistant polyethylene, and aims to solve the problems that the preparation process in the prior art is complex, the operation is complicated, the preparation method is not suitable for industrial application, the molecular weight distribution of the polyethylene is narrow, the processability is relatively poor, the cost of a metallocene catalyst is high, and the relationship between the production cost and the high-temperature creep resistance of a product cannot be well balanced.
In order to achieve the above object, according to one aspect of the present invention, there is provided a method for preparing a heat-resistant polyethylene, the method comprising the steps of: (a) carrying out first polymerization reaction on ethylene, hydrogen and a catalyst in the presence of a first solvent to form a first polymerization solution; (b) adding ethylene, hydrogen, 1-butene and 1-hexene into the first polymerization liquid to carry out a second polymerization reaction to form a second polymerization liquid; and (c) further adding ethylene, hydrogen, 1-butene and 1-hexene into the second polymerization liquid to carry out a third polymerization reaction to obtain the heat-resistant polyethylene, wherein the partial pressure ratio of the hydrogen to the ethylene in the step (a) is 3-4: 1; the partial pressure ratio of the hydrogen to the ethylene in the step (b) is 0.2-0.5: 1; the partial pressure ratio of the hydrogen to the ethylene in the step (c) is 0.02-0.1: 1.
Further, the catalyst is a ziegler-natta catalyst; preferably, the first solvent is one or more of n-hexane, 2-methylpentane and 3-methylpentane; in the step (a), the weight of the ethylene accounts for 45-60% of the total weight of the raw materials of the first polymerization reaction; preferably, this step (a) is carried out at a temperature of from 75 ℃ to 85 ℃; preferably, this step (a) is carried out at a pressure of between 0.7MPa and 0.9 MPa; preferably, the reaction time of the first polymerization reaction in the step (a) is 2h to 2.5 h.
Further, in the step (b), the weight of the ethylene accounts for 25 to 35 percent of the total weight of the raw materials for the second polymerization reaction; preferably, this step (b) is carried out at a temperature of between 80 ℃ and 85 ℃; preferably, this step (b) is carried out at a pressure of between 0.3MPa and 0.5 MPa; preferably, the reaction time of the second polymerization reaction in the step (b) is 2 h-2.5 h; preferably, the amount of the 1-butene and 1-hexene used in the step (b) is 5 to 10 parts by weight based on 100 parts by weight of the total amount of ethylene used in the process; preferably, the weight ratio of the 1-butene to the 1-hexene is 9:1 to 8: 2.
Further, in the step (c), the weight of the ethylene is 5 to 30 percent of the total weight of the raw materials for the third polymerization reaction in percentage by weight; preferably, this step (c) is carried out at a temperature of from 80 ℃ to 85 ℃; preferably, this step (c) is carried out at a pressure of between 0.3MPa and 0.5 MPa; preferably, the reaction time of the third polymerization reaction in the step (c) is 1h to 1.5 h; preferably, the parts by weight of the 1-butene and 1-hexene used in the step (c) is 5 to 10 parts by weight based on 100 parts by weight of the total amount of ethylene used in the process; preferably, the weight ratio of the 1-butene to the 1-hexene is 9:1 to 8: 2.
According to another aspect of the present invention, there is provided a heat resistant polyethylene prepared by the above method.
According to another aspect of the present invention, there is provided a heat-resistant polyethylene composition, the composition comprising the heat-resistant polyethylene as described above, an antacid, a heat stabilizer, an elastomer processing aid, and a chain extender.
Further, the antacid is 0.1 to 0.2 parts by weight, the heat stabilizer is 0.5 to 0.8 parts by weight, the elastomer processing aid is 0.03 to 0.1 parts by weight, and the chain extender is 0.05 to 0.1 parts by weight, based on 100 parts by weight of the heat-resistant polyethylene.
Further, the composition is prepared by the following method: mixing the raw materials of the composition, and then performing extrusion granulation to obtain the heat-resistant polyethylene composition; preferably, the mixing is carried out for 1min to 2min under the stirring speed of 500r/min to 800 r/min; preferably, the extrusion is carried out at a temperature of 220 ℃ to 240 ℃.
Further, the antacid is one or more of calcium stearate, zinc oxide and hydrotalcite; preferably, the thermal stabilizer is one or more of pentaerythritol tetrakis [ β - (3 ', 5' -di-tert-butyl-4 '-hydroxyphenyl) propionate ] (antioxidant 1010), octadecyl β - (4' -hydroxy-3 ', 5' -di-tert-butylphenyl) propionate (antioxidant 1076), tris (2, 4-di-tert-butylphenyl) phosphite (antioxidant 168), 4 '-thiobis (6-tert-butyl-2-methylphenol) (antioxidant 736), and 4, 4' -thiobis (6-tert-butyl-3-methylphenol) (antioxidant 300); preferably, the weight ratio of the antioxidant 1010 to the antioxidant 168 is 1: 1; preferably, the weight ratio of the antioxidant 1076 to the antioxidant 168 is 1: 1; preferably, the elastomer processing aid is a fluoroelastomer processing aid, preferably a fluorocarbon polymer; preferably, the elastomeric processing aid is a fluorocarbon copolymer and/or homopolymer; preferably, the elastomer processing aid is a copolymer and/or homopolymer of one or more of tetrafluoroethylene, hexafluoroethylene, and vinylidene fluoride; preferably, the chain extender is 1, 6-bismaleimidohexane.
Further, the weight ratio of the calcium stearate to the zinc stearate is 1: 1.
By applying the technical scheme of the invention, the preparation method of the heat-resistant polyethylene comprises the following steps: (a) carrying out first polymerization reaction on ethylene, hydrogen and a catalyst in the presence of a first solvent to form a first polymerization solution; (b) adding ethylene, hydrogen, 1-butene and 1-hexene into the first polymerization liquid to carry out a second polymerization reaction to form a second polymerization liquid; and (c) further adding ethylene, hydrogen, 1-butene and 1-hexene into the second polymerization liquid to carry out a third polymerization reaction to obtain the heat-resistant polyethylene, wherein the partial pressure ratio of the hydrogen to the ethylene in the step (a) is 3-4: 1; the partial pressure ratio of the hydrogen to the ethylene in the step (b) is 0.2-0.5: 1; the partial pressure ratio of the hydrogen to the ethylene in the step (c) is 0.02-0.1: 1. The preparation method has simple process and easy operation, is suitable for industrial application, and the heat-resistant polyethylene prepared by the preparation method and the composition thereof have improved processing performance.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail with reference to examples.
The present application is described in further detail below with reference to specific examples, which should not be construed as limiting the scope of the invention as claimed.
As described in the background art, the existing preparation method of heat-resistant polyethylene cannot effectively solve the problems of complex preparation process, complicated operation and unsuitability for industrial application. In order to solve the above problems, the present invention provides a method for preparing heat-resistant polyethylene, comprising the steps of: (a) carrying out first polymerization reaction on ethylene, hydrogen and a catalyst in the presence of a first solvent to form a first polymerization solution; (b) adding ethylene, hydrogen, 1-butene and 1-hexene into the first polymerization liquid to carry out a second polymerization reaction to form a second polymerization liquid; and (c) further adding ethylene, hydrogen, 1-butene and 1-hexene into the second polymerization liquid to carry out a third polymerization reaction to obtain the heat-resistant polyethylene, wherein the partial pressure ratio of the hydrogen to the ethylene in the step (a) is 3-4: 1; the partial pressure ratio of the hydrogen to the ethylene in the step (b) is 0.2-0.5: 1; the partial pressure ratio of the hydrogen to the ethylene in the step (c) is 0.02-0.1: 1.
The preparation method has simple process and easy operation and is suitable for industrial application.
In order to further optimize the preparation process of the heat-resistant polyethylene to obtain a heat-resistant polyethylene with better physicochemical properties, in a preferred embodiment, the catalyst is a ziegler-natta catalyst; preferably, the first solvent is one or more of n-hexane, 2-methylpentane and 3-methylpentane; in the step (a), the weight of the ethylene accounts for 45-60% of the total weight of the raw materials of the first polymerization reaction; preferably, this step (a) is carried out at a temperature of from 75 ℃ to 85 ℃; preferably, this step (a) is carried out at a pressure of between 0.7MPa and 0.9 MPa; preferably, the reaction time of the first polymerization reaction in the step (a) is 2h to 2.5 h.
In order to further optimize the preparation method of the heat-resistant polyethylene so as to obtain the heat-resistant polyethylene with better physical and chemical properties, in a preferred embodiment, in the step (b), the weight of the ethylene accounts for 25-35% of the total weight of the raw materials of the second polymerization reaction; preferably, this step (b) is carried out at a temperature of from 80 ℃ to 85 ℃; preferably, this step (b) is carried out at a pressure of between 0.3MPa and 0.5 MPa; preferably, the reaction time of the second polymerization reaction in the step (b) is 2h to 2.5 h; preferably, the amount of the 1-butene and 1-hexene used in the step (b) is 5 to 10 parts by weight based on 100 parts by weight of the total amount of ethylene used in the process; preferably, the weight ratio of the 1-butene to the 1-hexene is 9:1 to 8: 2.
In order to further optimize the preparation method of the heat-resistant polyethylene so as to obtain the heat-resistant polyethylene with better physical and chemical properties, in a preferred embodiment, in the step (c), the weight of the ethylene is 5 to 30 percent of the total weight of the raw materials of the third polymerization reaction in percentage by weight; preferably, this step (c) is carried out at a temperature of between 80 ℃ and 85 ℃; preferably, this step (c) is carried out at a pressure of between 0.3MPa and 0.5 MPa; preferably, the reaction time of the third polymerization reaction in the step (c) is 1h to 1.5 h; preferably, the parts by weight of the 1-butene and 1-hexene used in the step (c) is 5 to 10 parts by weight based on 100 parts by weight of the total amount of ethylene used in the process; preferably, the weight ratio of the 1-butene to the 1-hexene is 9:1 to 8: 2.
The application provides a preparation method of heat-resistant polyethylene, which adopts a three-kettle series continuous slurry polymerization process, wherein a solvent is n-hexane, a molecular weight regulator and hydrogen, and comonomers are 1-butene and 1-hexene. The first reaction kettle produces low molecular weight ethylene homopolymer under the condition of high hydrogen concentration, the second reaction kettle produces high molecular weight ethylene copolymer in the presence of a small amount of hydrogen, the third reaction kettle produces ultrahigh molecular weight ethylene copolymer under the condition of very little hydrogen, and the hydrogen partial pressure in the second reaction kettle and the third reaction kettle is controlled by a flash tank.
In addition, according to another aspect of the present invention, there is provided a heat-resistant polyethylene prepared by the above method. The heat-resistant polyethylene prepared by the invention has improved processability and wide molecular weight distribution, and can well balance the relationship between the production cost and the high-temperature creep resistance of the product.
In addition, according to another aspect of the present invention, there is provided a heat-resistant polyethylene composition, the raw materials of which comprise the above heat-resistant polyethylene, and further comprise one or more of an antacid, a heat stabilizer, an elastomer processing aid, and a chain extender.
The heat-resistant polyethylene composition prepared by the invention improves the length and the number of frenum molecules in the polymer due to the introduction of the comonomer 1-hexene, and is beneficial to further improving the toughness and the long-term high-temperature creep resistance of the heat-resistant polyethylene composition. Compared with a bimodal series process, the third kettle forms a copolymer with higher molecular weight, which is beneficial to the increase of the length of the tie chain and the increase of the number of tie molecules; the molecular weight is composed of three parts of molecular weight, the molecular weight distribution is wider, and the improvement of the product processing performance is facilitated. In the scheme, through the synergistic effect among the components, the oxidation induction period of the heat-resistant polyethylene composition is longer than 60min, the processing performance of the heat-resistant polyethylene composition is improved, the energy consumption is reduced, the appearance gloss of a finished product of the heat-resistant polyethylene composition pipe is improved, and the short-term hydrostatic strength and the slow crack growth resistance of the pipe are improved.
In order to further balance the effects of the components and to more fully exert the synergistic effect between the components, in a preferred embodiment, the antacid is 0.1 to 0.2 parts by weight, the heat stabilizer is 0.5 to 0.8 parts by weight, the elastomer processing aid is 0.03 to 0.1 parts by weight, and the chain extender is 0.05 to 0.1 parts by weight, based on 100 parts by weight of the heat-resistant polyethylene.
In order to further obtain a heat-resistant polyethylene composition having superior physicochemical properties, in a preferred embodiment, the composition is prepared by the following method: mixing the raw materials of the composition, and then performing extrusion granulation to obtain the heat-resistant polyethylene composition; preferably, the mixing is carried out for 1min to 2min under the stirring speed of 500r/min to 800 r/min; preferably, the extrusion is carried out at a temperature of 220 ℃ to 240 ℃.
In a preferred embodiment, the antacid is one or more of calcium stearate, zinc oxide, hydrotalcite. The antacid of the present application can effectively neutralize the catalyst residues with reactivity, and has a direct contribution to the color stabilization and corrosion prevention of polyolefins, compared to other antacids.
In a preferred embodiment, the thermal stabilizer is one or more of pentaerythrityl tetrakis [ β - (3 ', 5' -di-tert-butyl-4 '-hydroxyphenyl) propionate ] (antioxidant 1010), octadecyl β - (4' -hydroxy-3 ', 5' -di-tert-butylphenyl) propionate (antioxidant 1076), tris (2, 4-di-tert-butylphenyl) phosphite (antioxidant 168), 4 '-thiobis (6-tert-butyl-2-methylphenol) (antioxidant 736), and 4, 4' -thiobis (6-tert-butyl-3-methylphenol) (antioxidant 300); preferably, the weight ratio of the antioxidant 1010 to the antioxidant 168 is 1: 1; preferably, the weight ratio of the antioxidant 1076 to the antioxidant 168 is 1: 1. Compared with other heat stabilizers, the heat stabilizer disclosed by the application has the advantage that the heat-resistant polyethylene composition has better heat aging resistance due to the addition of the heat stabilizer.
In a preferred embodiment, the elastomer processing aid is a fluoroelastomer processing aid, preferably a fluorocarbon polymer; preferably, the elastomeric processing aid is a fluorocarbon copolymer and/or homopolymer; preferably, the elastomer processing aid is a copolymer and/or homopolymer of one or more of tetrafluoroethylene, hexafluoroethylene, and vinylidene fluoride. Compared with other elastomer processing aids, the elastomer processing aid disclosed by the application can improve the processing performance of the heat-resistant polyethylene composition resin and improve the surface gloss of a pipe product in the production process of the compound.
In an embodiment, the chain extender is 1, 6-bismaleimidohexane. The chain extender can react with functional groups on a linear polymer chain to expand the molecular chain and increase the molecular weight, and can effectively improve the mechanical property and the process property of the thermal polyethylene composition.
In order to further balance the effects of the components and to more fully exert the synergistic effect between the components, in a preferred embodiment the weight ratio of the calcium stearate to the zinc stearate is 1: 1.
Example 1
Ziegler-Natta catalyst (prepared from titanium tetrachloride-triethyl aluminium [ TiCl ] in presence of n-hexane4-Al(C2H5)3Catalyst) and ethylene and hydrogen were fed into the first reactor, the ethylene amount was 60% of the total amount fed (36t/h), the reactor temperature was 75 ℃, the reaction pressure was 0.8MPa, the hydrogen-ethylene partial pressure ratio was 4.0, and the reaction time was 2.5 h. And then discharging the slurry into a second reaction kettle, wherein the addition amount of ethylene in the second reaction kettle accounts for 25 percent of the total addition amount (36t/h), the temperature of the reactor is 85 ℃, the pressure of the reactor is 0.5MPa, the partial pressure ratio of hydrogen to ethylene is 0.3, the addition amount of 1-butene and 1-hexene is 5 percent of the weight of ethylene in the three reaction kettles, the mass ratio of 1-butene to 1-hexene is 9:1, and the reaction time is 2 h. And then discharging the slurry into a third reaction kettle, wherein the addition of ethylene in the third reaction kettle accounts for 15 percent of the total addition (36t/h), the temperature of the reactor is 80 ℃, the pressure of the reactor is 0.5MPa, the partial pressure ratio of hydrogen to ethylene is 0.05, the addition of 1-butene and 1-hexene accounts for 10 percent of the weight of ethylene in the three reaction kettles, the mass ratio of 1-butene to 1-hexene is 8:2, and the reaction time is 1.5 h.
100 parts of the heat-resistant polyethylene resin, 0.05 part of zinc stearate, 0.05 part of calcium stearate, 10100.25 parts of antioxidant, 1680.25 parts of antioxidant, 0.03 part of fluoroelastomer processing aid and 0.05 part of 1, 6-bismaleimide hexane are mixed and then placed into a high-speed mixer, and the mixture is stirred for 1min at the stirring speed of 800r/min at room temperature. Then extruding and granulating by a double-screw extruder at 220-240 ℃ to obtain the heat-resistant polyethylene composition. And (3) evaluating the high-temperature creep resistance of the PE-RT by adopting a pipe hydrostatic test method. Specific results are shown in table 1.
Example 2
Ziegler-Natta catalyst (prepared from titanium tetrachloride-triethyl aluminium [ TiCl ] in presence of n-hexane4-Al(C2H5)3Catalyst) and ethylene and hydrogen were fed into the first reactor, the ethylene feed amounted to 45% of the total feed (36t/h), the reactor temperature was 80 ℃, the reaction pressure was 0.9MPa, the hydrogen-ethylene partial pressure ratio was 3.5, and the reaction time was 2 h. And then discharging the slurry into a second reaction kettle, wherein the addition amount of ethylene in the second reaction kettle accounts for 30 percent of the total addition amount (36t/h), the temperature of the reactor is 80 ℃, the pressure of the reactor is 0.4MPa, the partial pressure ratio of hydrogen to ethylene is 0.4, the addition amount of 1-butene and 1-hexene accounts for 8 percent of the weight of ethylene in the three reaction kettles, the mass ratio of 1-butene to 1-hexene is 8:2, and the reaction time is 2.4 h. And then discharging the slurry into a third reaction kettle, wherein the addition amount of ethylene in the third reaction kettle accounts for 25 percent of the total addition amount (36t/h), the temperature of the reactor is 85 ℃, the pressure of the reactor is 0.3MPa, the partial pressure ratio of hydrogen to ethylene is 0.05, the addition amount of 1-butene and 1-hexene accounts for 8 percent of the weight of ethylene in the three reaction kettles, the mass ratio of 1-butene to 1-hexene is 8.5:1.5, and the reaction time is 1 h.
100 parts of the heat-resistant polyethylene resin, 0.1 part of zinc stearate, 0.1 part of calcium stearate, 10760.3 parts of antioxidant, 1680.3 parts of antioxidant, 0.05 part of fluoroelastomer processing aid and 0.1 part of 1, 6-bismaleimide hexane are mixed and then placed into a high-speed mixer, and the mixture is stirred for 1.3min at room temperature and at the stirring speed of 700 r/min. Then extruding and granulating by a double-screw extruder at 220-240 ℃ to obtain the heat-resistant polyethylene composition. And (3) evaluating the high-temperature creep resistance of the PE-RT by adopting a pipe hydrostatic test method. Specific results are shown in table 1.
Example 3
Ziegler-Natta catalyst (prepared from titanium tetrachloride-triethyl aluminium [ TiCl ] in the presence of n-hexane4-Al(C2H5)3Catalyst) of ethylene and hydrogen were fed into a first reactor at a reactor temperature of 85 ℃ and a reaction pressure of 0.7MPa with a hydrogen-ethylene partial pressure ratio of 3.0 in an amount of 50% of the total feed (36t/h) to reactThe time is 2.2 h. And then discharging the slurry into a second reaction kettle, wherein the addition amount of ethylene in the second reaction kettle accounts for 20 percent of the total addition amount (36t/h), the temperature of the reactor is 82 ℃, the pressure of the reactor is 0.3MPa, the partial pressure ratio of hydrogen to ethylene is 0.2, the addition amount of 1-butene and 1-hexene is 10 percent of the weight of ethylene in the three reaction kettles, the mass ratio of 1-butene to 1-hexene is 8:2, and the reaction time is 2.3 h. And then discharging the slurry into a third reaction kettle, wherein the addition amount of ethylene in the third reaction kettle accounts for 30 percent of the total addition amount (36t/h), the temperature of the reactor is 81 ℃, the pressure of the reactor is 0.3MPa, the partial pressure ratio of hydrogen to ethylene is 0.02, the addition amount of 1-butene and 1-hexene accounts for 5 percent of the weight of ethylene in the three reaction kettles, the mass ratio of 1-butene to 1-hexene is 9:1, and the reaction time is 1.4 h.
100 parts of the heat-resistant polyethylene resin, 0.08 part of zinc stearate, 0.08 part of calcium stearate, 7360.8 parts of antioxidant, 0.1 part of fluoroelastomer processing aid and 0.08 part of 1, 6-bismaleimide hexane are mixed, then placed into a high-speed mixer and stirred for 2min at room temperature and at a stirring speed of 500 r/min. Then extruding and granulating by a double-screw extruder at 220-240 ℃ to obtain the heat-resistant polyethylene composition. And (3) evaluating the high-temperature creep resistance of the PE-RT by adopting a pipe hydrostatic test method. Specific results are shown in table 1.
Example 4
Ziegler-Natta catalyst (prepared from titanium tetrachloride-triethyl aluminium [ TiCl ] in presence of n-hexane4-Al(C2H5)3Catalyst) and ethylene and hydrogen were fed into the first reactor, the ethylene feed amounted to 45% of the total feed (36t/h), the reactor temperature was 85 ℃, the reaction pressure was 0.7MPa, the hydrogen-ethylene partial pressure ratio was 3.0, and the reaction time was 2.2 h. And then discharging the slurry into a second reaction kettle, wherein the addition amount of ethylene in the second reaction kettle accounts for 35% of the total addition amount (36t/h), the temperature of the reactor is 82 ℃, the pressure of the reactor is 0.3MPa, the partial pressure ratio of hydrogen to ethylene is 0.2, the addition amount of 1-butene and 1-hexene is 10% of the weight of ethylene in the three reaction kettles, the mass ratio of 1-butene to 1-hexene is 8:2, and the reaction time is 2.3 h. Then discharging the slurry into a third reaction kettle, wherein the addition of the ethylene in the third reaction kettle accounts for the total addition(36t/h), the reactor temperature is 81 ℃, the reactor pressure is 0.3MPa, the hydrogen-ethylene partial pressure ratio is 0.02, the adding amount of 1-butene and 1-hexene is 5 percent of the weight of ethylene in the three reaction kettles, wherein the mass ratio of 1-butene to 1-hexene is 9:1, and the reaction time is 1.4 h.
100 parts of the heat-resistant polyethylene resin, 0.08 part of zinc stearate, 0.08 part of calcium stearate, 3000.8 parts of antioxidant, 0.1 part of fluoroelastomer processing aid and 0.08 part of 1, 6-bismaleimide hexane are mixed, then placed into a high-speed mixer and stirred for 2min at room temperature and at a stirring speed of 500 r/min. Then extruding and granulating by a double-screw extruder at 220-240 ℃ to obtain the heat-resistant polyethylene composition. And (3) evaluating the high-temperature creep resistance of the PE-RT by adopting a pipe hydrostatic test method. Specific results are shown in table 1.
Example 5
Ziegler-Natta catalyst (prepared from titanium tetrachloride-triethyl aluminium [ TiCl ] in presence of n-hexane4-Al(C2H5)3Catalyst) and ethylene and hydrogen were fed into the first reactor, the ethylene amount was 60% of the total amount fed (36t/h), the reactor temperature was 75 ℃, the reaction pressure was 0.8MPa, the hydrogen-ethylene partial pressure ratio was 4.0, and the reaction time was 2.5 h. And then discharging the slurry into a second reaction kettle, wherein the addition amount of ethylene in the second reaction kettle accounts for 25 percent of the total addition amount (36t/h), the temperature of the reactor is 85 ℃, the pressure of the reactor is 0.5MPa, the partial pressure ratio of hydrogen to ethylene is 0.5, the addition amount of 1-butene and 1-hexene is 5 percent of the weight of ethylene in the three reaction kettles, the mass ratio of 1-butene to 1-hexene is 9:1, and the reaction time is 2 h. And then discharging the slurry into a third reaction kettle, wherein the addition of ethylene in the third reaction kettle accounts for 15 percent of the total addition (36t/h), the temperature of the reactor is 80 ℃, the pressure of the reactor is 0.5MPa, the partial pressure ratio of hydrogen to ethylene is 0.05, the addition of 1-butene and 1-hexene accounts for 10 percent of the weight of ethylene in the three reaction kettles, the mass ratio of 1-butene to 1-hexene is 8:2, and the reaction time is 1.5 h.
100 parts of the heat-resistant polyethylene resin, 0.05 part of zinc stearate, 0.05 part of calcium stearate, 10100.25 parts of antioxidant, 1680.25 parts of antioxidant, 0.03 part of fluoroelastomer processing aid and 0.05 part of 1, 6-bismaleimide hexane are mixed and then placed into a high-speed mixer, and the mixture is stirred for 1min at the stirring speed of 800r/min at room temperature. Then extruding and granulating by a double-screw extruder at 220-240 ℃ to obtain the heat-resistant polyethylene composition. And (3) evaluating the high-temperature creep resistance of the PE-RT by adopting a pipe hydrostatic test method. Specific results are shown in table 1.
Example 6
Ziegler-Natta catalyst (prepared from titanium tetrachloride-triethyl aluminium [ TiCl ] in presence of n-hexane4-Al(C2H5)3Catalyst) and ethylene and hydrogen were fed into the first reactor, the ethylene feed amounted to 60% of the total feed (36t/h), the reactor temperature was 75 ℃, the reaction pressure was 0.8MPa, the hydrogen-ethylene partial pressure ratio was 4.0, and the reaction time was 2.5 h. And then discharging the slurry into a second reaction kettle, wherein the addition amount of ethylene in the second reaction kettle accounts for 25 percent of the total addition amount (36t/h), the temperature of the reactor is 85 ℃, the pressure of the reactor is 0.5MPa, the partial pressure ratio of hydrogen to ethylene is 0.3, the addition amount of 1-butene and 1-hexene is 5 percent of the weight of ethylene in the three reaction kettles, the mass ratio of 1-butene to 1-hexene is 9:1, and the reaction time is 2 h. And then discharging the slurry into a third reaction kettle, wherein the addition amount of ethylene in the third reaction kettle accounts for 15% of the total addition amount (36t/h), the temperature of the reactor is 80 ℃, the pressure of the reactor is 0.5MPa, the partial pressure ratio of hydrogen to ethylene is 0.1, the addition amount of 1-butene and 1-hexene is 10% of the weight of ethylene in the three reaction kettles, the mass ratio of 1-butene to 1-hexene is 8:2, and the reaction time is 1.5 h.
100 parts of the heat-resistant polyethylene resin, 0.05 part of zinc stearate, 0.05 part of calcium stearate, 10100.25 parts of antioxidant, 1680.25 parts of antioxidant, 0.03 part of fluoroelastomer processing aid and 0.05 part of 1, 6-bismaleimide hexane are mixed and then placed into a high-speed mixer, and the mixture is stirred for 1min at the stirring speed of 800r/min at room temperature. Then extruding and granulating by a double-screw extruder at 220-240 ℃ to obtain the heat-resistant polyethylene composition. And (3) evaluating the high-temperature creep resistance of the PE-RT by adopting a pipe hydrostatic test method. Specific results are shown in table 1.
Comparative example 1
Ziegler-Natta catalyst (prepared from titanium tetrachloride-triethyl aluminium [ TiCl ] in presence of n-hexane4-Al(C2H5)3Catalyst) and ethylene and hydrogen were fed into the first reactor, the ethylene feed amounted to 60% of the total feed (36t/h), the reactor temperature was 75 ℃, the reaction pressure was 0.8MPa, the hydrogen-ethylene partial pressure ratio was 2.5, and the reaction time was 2.5 h. And then discharging the slurry into a second reaction kettle, wherein the addition amount of ethylene in the second reaction kettle accounts for 25 percent of the total addition amount (36t/h), the temperature of the reactor is 85 ℃, the pressure of the reactor is 0.5MPa, the partial pressure ratio of hydrogen to ethylene is 0.15, the addition amount of 1-butene and 1-hexene is 5 percent of the weight of ethylene in the three reaction kettles, the mass ratio of 1-butene to 1-hexene is 9:1, and the reaction time is 2 h. And then discharging the slurry into a third reaction kettle, wherein the addition of ethylene in the third reaction kettle accounts for 15 percent of the total addition (36t/h), the temperature of the reactor is 80 ℃, the pressure of the reactor is 0.5MPa, the partial pressure ratio of hydrogen to ethylene is 0.01, the addition of 1-butene and 1-hexene accounts for 10 percent of the weight of ethylene in the three reaction kettles, the mass ratio of 1-butene to 1-hexene is 8:2, and the reaction time is 1.5 h.
100 parts of the heat-resistant polyethylene resin, 0.05 part of zinc stearate, 0.05 part of calcium stearate, 10100.25 parts of antioxidant, 1680.25 parts of antioxidant, 0.03 part of fluoroelastomer processing aid and 0.05 part of 1, 6-bismaleimide hexane are mixed and then placed into a high-speed mixer, and the mixture is stirred for 1min at the stirring speed of 800r/min at room temperature. Then extruding and granulating by a double-screw extruder at 220-240 ℃ to obtain the heat-resistant polyethylene composition. And (3) evaluating the high-temperature creep resistance of the PE-RT by adopting a pipe hydrostatic test method. Specific results are shown in table 1.
TABLE 1 pipe Performance test results
From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects: the preparation method has simple process and easy operation, is suitable for industrial application, and the heat-resistant polyethylene and the composition thereof prepared by the preparation method improve the length and the number of frenulum molecules in the polymer due to the introduction of the comonomer 1-hexene, thereby being beneficial to further improving the toughness and the long-term high-temperature creep resistance of the heat-resistant polyethylene composition. Compared with a bimodal series process, the third kettle forms a copolymer with higher molecular weight, which is beneficial to the increase of the length of the tie chain and the increase of the number of tie molecules; the molecular weight is composed of three parts of molecular weight, the molecular weight distribution is wider, and the improvement of the product processing performance is facilitated. In the scheme, through the synergistic effect among the components, the oxidation induction period of the heat-resistant polyethylene composition is longer than 60min, the processing performance of the heat-resistant polyethylene composition is improved, the energy consumption is reduced, the appearance gloss of a finished product of the heat-resistant polyethylene composition pipe is improved, and the short-term hydrostatic strength and the slow crack growth resistance of the pipe are improved.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (27)
1. A preparation method of heat-resistant polyethylene is characterized by comprising the following steps:
(a) carrying out first polymerization reaction on ethylene, hydrogen and a catalyst in the presence of a first solvent to form a first polymerization solution;
(b) adding ethylene, hydrogen, 1-butene and 1-hexene into the first polymerization liquid to carry out a second polymerization reaction to form a second polymerization liquid; and
(c) further adding ethylene, hydrogen, 1-butene and 1-hexene into the second polymerization liquid to carry out third polymerization reaction to obtain the heat-resistant polyethylene,
wherein the partial pressure ratio of hydrogen to ethylene in the step (a) is 3-4: 1; the partial pressure ratio of the hydrogen to the ethylene in the step (b) is 0.2-0.5: 1; the partial pressure ratio of the hydrogen to the ethylene in the step (c) is 0.02-0.1: 1; in the step (a), the weight of the ethylene accounts for 45-60% of the total weight of the raw materials of the first polymerization reaction; the amount of the 1-butene and 1-hexene used in the step (b) is 5 to 10 parts by weight based on 100 parts by weight of the total amount of ethylene used in the process, and the weight ratio of the 1-butene to the 1-hexene is 9:1 to 8: 2; the weight parts of the 1-butene and 1-hexene used in the step (c) are 5 to 10 parts by weight based on 100 parts by weight of the total amount of ethylene used in the process, and the weight ratio of the 1-butene to the 1-hexene is 9:1 to 8: 2.
2. The process of claim 1, wherein the catalyst is a ziegler-natta catalyst.
3. The method of claim 2, wherein the first solvent is one or more of n-hexane, 2-methylpentane, and 3-methylpentane.
4. The process according to claim 2, wherein step (a) is carried out at a temperature of 75 ℃ to 85 ℃.
5. The process according to claim 4, wherein step (a) is carried out at a pressure of from 0.7MPa to 0.9 MPa.
6. The method according to claim 5, wherein the reaction time of the first polymerization reaction in the step (a) is 2 to 2.5 hours.
7. The process of claim 1, wherein in step (b), the weight of ethylene is 25 to 35% by weight of the total weight of the second polymerization raw material.
8. The method of claim 7, wherein step (b) is performed at a temperature of 80 ℃ to 85 ℃.
9. The method of claim 8, wherein step (b) is performed at a pressure of 0.3MPa to 0.5 MPa.
10. The method of claim 9, wherein the second polymerization reaction in step (b) is carried out for a reaction time of 2 to 2.5 hours.
11. The method according to claim 1, wherein in the step (c), the weight of the ethylene is 5-30% of the total weight of the raw materials for the third polymerization reaction.
12. The method of claim 11, wherein step (c) is performed at a temperature of 80 ℃ to 85 ℃.
13. The method of claim 12, wherein step (c) is performed at a pressure of 0.3MPa to 0.5 MPa.
14. The method according to claim 13, wherein the reaction time of the third polymerization reaction in the step (c) is 1 to 1.5 hours.
15. A heat resistant polyethylene prepared according to the method of any one of claims 1 to 14.
16. A heat-resistant polyethylene composition, wherein the raw materials for the composition comprise the heat-resistant polyethylene of claim 15, and further comprise an antacid, a heat stabilizer, an elastomer processing aid, and a chain extender.
17. The composition of claim 16, wherein the antacid is 0.1 to 0.2 parts by weight, the heat stabilizer is 0.5 to 0.8 parts by weight, the elastomer processing aid is 0.03 to 0.1 parts by weight, and the chain extender is 0.05 to 0.1 parts by weight, based on 100 parts by weight of the heat-resistant polyethylene.
18. The composition according to claim 16 or 17, wherein the composition is prepared by a process comprising: and mixing the raw materials of the composition, and then performing extrusion granulation to obtain the heat-resistant polyethylene composition.
19. The composition of claim 18, wherein the mixing is at a stirring speed of 500r/min to 800r/min for 1min to 2 min.
20. The composition of claim 19, wherein the extruding is carried out at a temperature of 220 ℃ to 240 ℃.
21. The composition of claim 16 or 17, wherein the antacid is one or more of calcium stearate, zinc oxide, hydrotalcite.
22. The composition of claim 21, wherein the thermal stabilizer is one or more of antioxidant 1010, antioxidant 1076, antioxidant 168, antioxidant 736, and antioxidant 300.
23. The composition as claimed in claim 22, wherein the weight ratio of the antioxidant 1010 to the antioxidant 168 is 1: 1; the weight ratio of the antioxidant 1076 to the antioxidant 168 is 1: 1.
24. The composition of claim 22, wherein the elastomer processing aid is a fluoroelastomer processing aid and the elastomer processing aid is a fluorocarbon copolymer and/or homopolymer.
25. The composition of claim 24, wherein the elastomer processing aid is a copolymer and/or homopolymer of one or more of tetrafluoroethylene, vinylidene fluoride.
26. The composition as recited in claim 22 wherein the chain extender is 1, 6-bismaleimidohexane.
27. The composition of claim 21, wherein the weight ratio of the calcium stearate to the zinc stearate is 1: 1.
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|---|---|---|---|---|
| US6252017B1 (en) * | 1997-09-27 | 2001-06-26 | Fina Research, S.A. | Production of polyethylene having improved crack and/or impact resistance |
| CN1717448A (en) * | 2002-12-19 | 2006-01-04 | 巴塞尔聚烯烃有限公司 | Polyethylene blow molding composition for producing small containers |
| CN105440192A (en) * | 2014-08-14 | 2016-03-30 | 中国石化扬子石油化工有限公司 | Preparing method of pipe material of polyethylene of raised temperature resistance (PE-RT) |
| CN106317585A (en) * | 2015-07-01 | 2017-01-11 | 中国石油天然气股份有限公司 | Heat-resistant polyethylene resin composition and application thereof |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6252017B1 (en) * | 1997-09-27 | 2001-06-26 | Fina Research, S.A. | Production of polyethylene having improved crack and/or impact resistance |
| CN1717448A (en) * | 2002-12-19 | 2006-01-04 | 巴塞尔聚烯烃有限公司 | Polyethylene blow molding composition for producing small containers |
| CN105440192A (en) * | 2014-08-14 | 2016-03-30 | 中国石化扬子石油化工有限公司 | Preparing method of pipe material of polyethylene of raised temperature resistance (PE-RT) |
| CN106317585A (en) * | 2015-07-01 | 2017-01-11 | 中国石油天然气股份有限公司 | Heat-resistant polyethylene resin composition and application thereof |
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