CN115160471A - Special resin for bimodal PE-RT II type pipe for large-diameter pipe and preparation method thereof - Google Patents

Special resin for bimodal PE-RT II type pipe for large-diameter pipe and preparation method thereof Download PDF

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CN115160471A
CN115160471A CN202210765760.6A CN202210765760A CN115160471A CN 115160471 A CN115160471 A CN 115160471A CN 202210765760 A CN202210765760 A CN 202210765760A CN 115160471 A CN115160471 A CN 115160471A
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reactor
pipe
molecular weight
ethylene
antioxidant
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张威
张娜
马国玉
王辉
曹建秋
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China Petroleum and Chemical Corp
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F210/00—Copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
    • C08F210/16—Copolymers of ethene with alpha-alkenes, e.g. EP rubbers
    • 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
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/04—Oxygen-containing compounds
    • C08K5/13—Phenols; Phenolates
    • C08K5/134—Phenols containing ester groups
    • C08K5/1345—Carboxylic esters of phenolcarboxylic acids
    • 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
    • C08K5/49—Phosphorus-containing compounds
    • C08K5/51—Phosphorus bound to oxygen
    • C08K5/52—Phosphorus bound to oxygen only
    • C08K5/527—Cyclic esters

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  • Health & Medical Sciences (AREA)
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  • Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)

Abstract

The invention discloses a special resin for a bimodal PE-RT II pipe for a large-caliber pipe and a preparation method thereof. The resin melt index is 0.5-1.0g/10min; density 0.945-0.955gcm 3 (ii) a The number average molecular weight Mn is 10000-15000, the weight average molecular weight Mw is 250000-350000, and the molecular weight distribution breadth index PD is 16-35; the resin has excellent long-term hydrostatic strength, cannot be subjected to brittle failure under the temperature condition below 110 ℃, bears higher internal pressure at the temperature of 110 ℃ and the pressure of 2.4MPa, has hydrostatic thermal stability of more than or equal to 8760h, and has good oxygen resistance, and the produced pipe is suitable for the field of secondary heating pipe networks.

Description

Special resin for bimodal PE-RT II type pipe for large-diameter pipe and preparation method thereof
Technical Field
The invention relates to a special resin for a bimodal PE-RT II type pipe for a large-diameter pipe and a preparation method thereof, wherein the conventional PE-RT has two types of I and II. The large caliber is compared with the metallocene floor heating pipe, the caliber of the general floor heating pipe is DN20-DN32mm, and the large caliber pipe prepared by the invention is usually more than or equal to DN110mm. In particular to a preparation method for producing special resin for high-density polyethylene pipes with long-term high-temperature resistance and excellent pressure resistance by adopting a high-activity Ziegler-Natta catalyst on an Innovene S slurry double-loop high-density polyethylene device.
Background
At present, in heat supply pipe networks in China, no matter a primary pipe network or a secondary pipe network, a working pipe generally adopts a common steel pipe. The steel pipe has the characteristics of temperature resistance and high pressure resistance, but has poor corrosion resistance, and after the steel pipe runs for a period of time, the pipeline is easy to corrode, and the corrosion is accelerated under the condition of high temperature. Corrosion in a short time can cause pipeline blockage, so that the conveying energy consumption is increased and the heating effect is reduced; with the development of corrosion, the problems of leakage, overflow, dripping and leakage of the pipeline become normal state, and the heat supply safety is seriously influenced.
The PE-RT II type material is a novel pipeline material which is developed on the basis of the PE-RT I type material and is specially applied to the field of high-temperature fluid conveying, has better low-temperature impact property, cracking resistance and excellent long-term high-temperature resistance and pressure resistance, and is an ideal material which can be used for a secondary heat supply pipe network at present.
The PE-RT II type heat supply pipeline has the characteristics of corrosion resistance, long service life, small hydraulic loss, good heat preservation effect and convenient and quick construction, the heat conductivity coefficient of the PE-RT II type heat supply pipeline is less than 1 percent of that of a common steel pipe, and the temperature reduction per kilometer is less than 0.1 ℃. The PE-RT II heat supply pipeline is used for replacing a traditional steel pipe according to 8000 kilometers per year, the energy-saving efficiency can be improved by more than 20%, the standard coal is saved by about 100 ten thousand tons per year, the water supplement of a pipe network is reduced by more than 1000 ten thousand tons, and clean heat supply is facilitated.
The special resins for PE-RT II type pipes are developed earlier in foreign countries, such as Dadaler XRT70, basel 4731B, korean LG chemical company SP988, korean SK energy company DX900 and DOW chemical company 2388. The foreign product can not be brittle-damaged under the temperature condition below 110 ℃, and the hydrostatic thermal stability is more than or equal to 8760h at 110 ℃ and the pressure of 2.4 MPa. With the popularization of the Chinese floor heating technology, the PE-RT pipe has excellent performance which gradually becomes the first choice in the fields of floor heating, heating power pipe networks and the like, the demand of the PE-RT in China is about 35-45 ten thousand tons/year, raw materials in the field of the domestic heating power pipe networks basically depend on import, XRT70 is taken as the main raw material, 4731B is used in a small amount, the current domestic bimodal PE-RT II pipe resin is blank, the distribution of a high molecular weight polyethylene part and a low molecular weight polyethylene part in the polymerization process of the current polyethylene pipe resin is uncontrollable, the distribution of the molecular weight is unreasonable, and the balance of large caliber, long-term high temperature resistance and pressure resistance can not be met; at present, the gaseous separation performance of traditional plastics tubular product is on the low side, and a large amount of bacterium or algae biology are easily bred to inside the pipeline, will lead to plastic conduit internal diameter wall to be covered by seriously in a few for the pipeline water output reduces gradually, and the entering of oxygen also can lead to some metal component corrodes in addition, thereby influences the life of pipeline.
Disclosure of Invention
The invention provides a special bimodal PE-RT II type pipe resin for a large-diameter pipe and a preparation method thereof. The bimodal PE-RT II type pipe resin prepared by the preparation method disclosed by the invention has excellent long-term hydrostatic strength, cannot be subjected to brittle failure under various temperature conditions below 110 ℃, has hydrostatic thermal stability of more than or equal to 8760h at 110 ℃ and 2.4MPa, can bear higher internal pressure, and has good oxygen resistance, and the produced pipe is suitable for the field of secondary heating power pipe networks.
The invention aims to solve the first technical problem of producing the special resin for the bimodal PE-RT II type pipe for the large-caliber pipe, which has excellent long-term hydrostatic strength, hydrostatic thermal stability of more than or equal to 8760 hours at 110 ℃ and 2.4MPa, and good oxygen resistance.
The second technical problem to be solved by the invention is to provide the preparation method of the pipe raw material, which is simple in process and simple and convenient to operate.
The technical scheme of the invention is as follows:
the invention provides a special resin for a bimodal PE-RT II type pipe for a large-caliber pipe, wherein the melt index of the pipe resin is 0.5-1.0g/10min; the density is 0.945 to 0.955g/cm 3 (ii) a The number average molecular weight Mn is 10000-15000, the weight average molecular weight Mw is 250000-350000, and the molecular weight distribution breadth index is 16-35.
The special resin for the bimodal PE-RT II type pipe for the large-caliber pipe is characterized in that the hydrostatic thermal stability is not less than 8760h at the test temperature of 110 ℃ and the pressure of 2.4 MPa.
The special resin for the bimodal PE-RT II type pipe for the large-diameter pipe is characterized in that the oxygen resistance of the resin is improved by more than 45%, and the oxygen resistance of the product is improved on the basis of meeting the requirement of the PE-RT II type.
The invention also provides a preparation method of the special resin for the bimodal PE-RT II type pipe for the large-caliber pipe, which is characterized by comprising the following steps:
adding ethylene, hydrogen and a catalyst into a slurry double-loop first reactor, controlling the pressure of the first reactor to be 3.0-4.0 MPa and the reaction temperature to be 90-95 ℃, and carrying out polymerization reaction; after removing hydrogen from ethylene, 1-hexene and a polymerization product of the first reactor, adding the mixture into a slurry double-loop second reactor, controlling the pressure of the second reactor to be 2.5-2.8 MPa and the reaction temperature to be 90-95 ℃ to carry out polymerization reaction; the first reactor obtains low molecular weight polyethylene powder, the second reactor obtains high molecular weight ethylene-1-hexene copolymer powder, the ratio of the high molecular weight part to the low molecular weight part is adjusted by adjusting the yield of the two reactors, and the yield ratio of the first loop reactor yield to the second loop reactor yield is controlled to be 45:55-49: 51;
and (2) granulating the ethylene-1-hexene copolymer powder prepared in the step (1) by using a double-screw extruder, wherein the length-diameter ratio of the double screws is 40-60, and the temperature of an antioxidant, a nucleating agent and a halogen absorbent which are stably and continuously added in the granulation process is controlled to be 170-220 ℃, so that the special resin for the bimodal PE-RT type II pipe for the large-diameter pipe is prepared.
In the step (1), the molar ratio of ethylene to hydrogen is 0.015-0.03; the comonomer is 1-hexene, and the molar ratio of the comonomer to ethylene is 0.2-0.6;
the polymerization catalyst described in the step (1) is a Ziegler-Natta catalyst, which is a high-efficiency catalyst, can distribute the yield in two reactors, and has excellent hydrogen response.
In the step (2), the antioxidant is a phenolic antioxidant, the phenolic antioxidant comprises a mixture of an antioxidant 1076 and an antioxidant 626 in a weight ratio of 1-3; the nucleating agent is 20e, and the addition amount of the nucleating agent is 0.05-0.2% of the total mass of the polyethylene powder; the halogen absorbent is magnesium stearate, and the addition amount of the magnesium stearate is 0.1-0.2% of the total mass of the polyethylene powder.
The antioxidant comprises a main antioxidant and an auxiliary antioxidant, wherein the main antioxidant mainly protects resin from thermal aging in a processing process, the auxiliary antioxidant mainly protects resin from thermal aging in a storage process, and the proportion of the main antioxidant and the auxiliary antioxidant is also required; the addition of the nucleating agent mainly improves the oxygen resistance of the resin; halogen absorbers are used primarily to neutralize residual chlorine in the polymer, preventing it from corroding equipment during processing.
The device has the process flow as shown in figure 1, and ethylene, hydrogen and comonomer are polymerized in a series reactor in the presence of a polymerization catalyst to prepare ethylene-1-hexene copolymer powder, wherein the series reactor consists of two loop reactors and a dehydrogenation processor; firstly, adding ethylene, hydrogen and a catalyst into a first reactor, and polymerizing to obtain a low molecular weight part; secondly, the product of the first reactor passes through a dehydrogenation processor, and enters a second reactor after hydrogen is removed; meanwhile, adding the comonomer and ethylene into the second reactor to continuously perform polymerization reaction with the product of the first reactor to obtain ethylene-1-hexene copolymer powder.
The invention has the beneficial effects that: the invention discloses a special resin for a bimodal PE-RT II pipe for a large-caliber pipe and a preparation method thereof. The resin melt index is 0.5-1.0g/10min; the density is 0.945 to 0.955g/cm 3 (ii) a The number average molecular weight Mn is 10000-15000, the weight average molecular weight Mw is 250000-350000, and the molecular weight distribution breadth index PD is 16-35; the bimodal polyethylene composition has controllable distribution of a high molecular weight part and a low molecular weight part, reasonable molecular weight distribution, excellent long-term hydrostatic strength, no brittle failure under the temperature condition below 110 ℃, high internal pressure bearing capacity of more than 8760 hours at 110 ℃ and pressure of 2.4MPa, and good oxygen resistance, and the produced pipe is suitable for the field of secondary heat pipe networks.
Drawings
FIG. 1: process flow chart of device of the invention
Detailed Description
Example 1:
adding ethylene, hydrogen and a catalyst into a slurry double-loop first reactor, controlling the pressure of the first reactor at 3.0MPa and the reaction temperature at 90 ℃, and carrying out polymerization reaction; after removing hydrogen from ethylene, 1-hexene and a polymerization product of the first reactor, adding the ethylene, the 1-hexene and the polymerization product of the first reactor into a slurry double-loop second reactor, controlling the pressure of the second reactor to be 2.5MPa and the reaction temperature to be 90 ℃, and carrying out polymerization reaction; the first reactor obtains low molecular weight polyethylene powder, the second reactor obtains high molecular weight ethylene-1-hexene copolymer powder, the ratio of the high molecular weight part to the low molecular weight part is adjusted by adjusting the yield of the two reactors, and the yield ratio of the first loop reactor yield to the second loop reactor yield is controlled to be 45:55.
and (2) granulating the ethylene-1-hexene copolymer powder prepared in the step (1) by using a double-screw extruder, wherein the length-diameter ratio of the double screws is 40, stably and continuously adding an antioxidant, a nucleating agent and a halogen absorbent in the granulating process, and controlling the temperature at 170 ℃ to prepare the special resin for the bimodal PE-RT II pipe for the large-diameter pipe.
The bimodal polyethylene resin powder comprises, by mass, 100 parts of high-density polyethylene (melt index: 0.50, density: 0.948, molecular weight distribution 29.16), 0.05 part of a nucleating agent 20e (produced by Milliken & company), 0.1 part of a halogen absorbent magnesium stearate, 0.2 part of an antioxidant 1076 and an antioxidant 626 in a weight ratio of 1.
Example 2:
adding ethylene, hydrogen and a catalyst into a slurry double-loop first reactor, controlling the pressure of the first reactor at 3.2MPa and the reaction temperature at 92 ℃, and carrying out polymerization reaction; after removing hydrogen from ethylene, 1-hexene and a polymerization product of the first reactor, adding the ethylene, the 1-hexene and the polymerization product of the first reactor into a slurry double-loop second reactor, controlling the pressure of the second reactor to be 2.6MPa and the reaction temperature to be 91 ℃ to perform polymerization reaction; the first reactor obtains low molecular weight polyethylene powder, the second reactor obtains high molecular weight ethylene-1-hexene copolymer powder, the ratio of the high molecular weight part to the low molecular weight part is adjusted by adjusting the yield of the two reactors, and the yield ratio of the first loop reactor yield to the second loop reactor yield is controlled at 46:54.
and (2) granulating the ethylene-1-hexene copolymer powder prepared in the step (1) by using a double-screw extruder, wherein the length-diameter ratio of the double screws is 48, stably and continuously adding an antioxidant, a nucleating agent and a halogen absorbent in the granulating process, and controlling the temperature at 180 ℃ to prepare the special resin for the bimodal PE-RT II type pipe for the large-diameter pipe.
The bimodal polyethylene resin powder comprises, by mass, 100 parts of high-density polyethylene (melt index: 0.80, density: 0.945, molecular weight distribution 21.42), 0.15 part of nucleating agent 20e,0.15 part of halogen absorbent magnesium stearate, 0.4 part of antioxidant 1076 and antioxidant 626 in a weight ratio of 2.
Example 3:
adding ethylene, hydrogen and a catalyst into a slurry double-loop first reactor, controlling the pressure of the first reactor at 3.5MPa and the reaction temperature at 93 ℃ to carry out polymerization reaction; after removing hydrogen from ethylene, 1-hexene and a polymerization product of the first reactor, adding the ethylene, the 1-hexene and the polymerization product into a slurry double-loop second reactor, controlling the pressure of the second reactor to be 2.7MPa and the reaction temperature to be 94 ℃ to perform polymerization reaction; the first reactor obtained low molecular weight polyethylene powder, the second reactor obtained high molecular weight ethylene-1-hexene copolymer powder, the ratio of the high molecular weight part to the low molecular weight part was adjusted by adjusting the yields of the two reactors, the ratio of the yield of the first loop reactor to the yield of the second loop reactor was controlled at 47:53.
and (2) granulating the ethylene-1-hexene copolymer powder prepared in the step (1) by using a double-screw extruder, wherein the length-diameter ratio of the double screws is 52, stably and continuously adding an antioxidant, a nucleating agent and a halogen absorbent in the granulating process, and controlling the temperature at 190 ℃ to prepare the special resin for the bimodal PE-RT II type pipe for the large-diameter pipe.
The bimodal polyethylene resin powder comprises, by mass, 100 parts of high-density polyethylene (melt index: 1.0, density: 0.950, molecular weight distribution 16.67), 0.10 part of nucleating agent 20e,0.20 part of halogen absorbent magnesium stearate, 0.1 part of antioxidant 1076 and antioxidant 626 in a weight ratio of 3.
Example 4:
adding ethylene, hydrogen and a catalyst into a slurry double-loop first reactor, controlling the pressure of the first reactor at 3.7MPa and the reaction temperature at 95 ℃ to perform a polymerization reaction; after removing hydrogen from ethylene, 1-hexene and a polymerization product of the first reactor, adding the ethylene, the 1-hexene and the polymerization product of the first reactor into a slurry double-loop second reactor, controlling the pressure of the second reactor to be 2.8MPa and the reaction temperature to be 93 ℃ to carry out polymerization reaction; the first reactor obtains low molecular weight polyethylene powder, the second reactor obtains high molecular weight ethylene-1-hexene copolymer powder, the ratio of the high molecular weight part to the low molecular weight part is adjusted by adjusting the yield of the two reactors, and the yield ratio of the first loop reactor yield to the second loop reactor yield is controlled to be 48:52.
and (2) granulating the ethylene-1-hexene copolymer powder prepared in the step (1) by using a double-screw extruder, wherein the length-diameter ratio of the double screws is 56, stably and continuously adding an antioxidant, a nucleating agent and a halogen absorbent in the granulating process, and controlling the temperature to be 200 ℃ to prepare the special resin for the bimodal PE-RT II type pipe for the large-diameter pipe.
The bimodal polyethylene resin powder comprises, by mass, 100 parts of high-density polyethylene (melt index: 0.56, density: 0.955, molecular weight distribution 35), 0.20 part of nucleating agent 20e,0.1 part of halogen absorbent magnesium stearate, 0.3 part of antioxidant 1076 and antioxidant 626 in a weight ratio of 2.
Example 5:
adding ethylene, hydrogen and a catalyst into a slurry double-loop first reactor, controlling the pressure of the first reactor at 3.8MPa and the reaction temperature at 95 ℃, and carrying out polymerization reaction; after removing hydrogen from ethylene, 1-hexene and a polymerization product of the first reactor, adding the ethylene, the 1-hexene and the polymerization product of the first reactor into a slurry double-loop second reactor, controlling the pressure of the second reactor to be 2.7MPa and the reaction temperature to be 93 ℃ to carry out polymerization reaction; the first reactor obtained low molecular weight polyethylene powder, the second reactor obtained high molecular weight ethylene-1-hexene copolymer powder, the ratio of the high molecular weight fraction to the low molecular weight fraction was adjusted by adjusting the yields of the two reactors, the ratio of the yield of the first loop reactor/the yield of the second loop reactor was controlled at 49:51.
and (2) granulating the ethylene-1-hexene copolymer powder prepared in the step (1) by using a double-screw extruder, wherein the length-diameter ratio of the double screws is 48, stably and continuously adding an antioxidant, a nucleating agent and a halogen absorbent in the granulating process, and controlling the temperature to be 210 ℃, so as to prepare the special resin for the bimodal PE-RT II pipe for the large-diameter pipe.
The bimodal polyethylene resin powder comprises, by mass, 100 parts of high-density polyethylene (melt index: 0.62, density: 0.953, molecular weight distribution 23.33), 0.15 part of nucleating agent 20e,0.15 part of halogen absorbent magnesium stearate, 0.25 part of antioxidant 1076 and antioxidant 626 in a weight ratio of 2.
Example 6:
adding ethylene, hydrogen and a catalyst into a slurry double-loop first reactor, controlling the pressure of the first reactor to be 4.0MPa and the reaction temperature to be 92 ℃, and carrying out a polymerization reaction; after removing hydrogen from ethylene, 1-hexene and a polymerization product of the first reactor, adding the ethylene, the 1-hexene and the polymerization product of the first reactor into a slurry double-loop second reactor, controlling the pressure of the second reactor to be 2.6MPa and the reaction temperature to be 95 ℃ to carry out polymerization reaction; the first reactor obtains low molecular weight polyethylene powder, the second reactor obtains high molecular weight ethylene-1-hexene copolymer powder, the ratio of the high molecular weight part to the low molecular weight part is adjusted by adjusting the yield of the two reactors, and the yield ratio of the first loop reactor output to the second loop reactor output is controlled to be 46:54.
and (2) granulating the ethylene-1-hexene copolymer powder prepared in the step (1) by using a double-screw extruder, wherein the length-diameter ratio of the double screws is 60, stably and continuously adding an antioxidant, a nucleating agent and a halogen absorbent in the granulating process, and controlling the temperature to be 220 ℃ to prepare the special resin for the bimodal PE-RT II type pipe for the large-diameter pipe.
The bimodal polyethylene resin powder comprises, by mass, 100 parts of high-density polyethylene (melt index: 0.75, density: 0.949, molecular weight distribution 26.43), 0.20 part of nucleating agent 20e,0.10 part of halogen absorbent magnesium stearate, 0.3 part of antioxidant 1076 and antioxidant 626 in a weight ratio of 3.
Testing the physical properties of the resin according to national standards; see table 1.
The results of the performance test of the special resin for high-density polyethylene pipes are shown in table 1:
TABLE 1 Performance test results
Figure BDA0003725493790000071
The above tests show that: the test results of the embodiments 1 to 6 reach the expected design, wherein the oxygen resistance is improved by more than 45 percent, the thermal stability test reaches 8760 hours under the test condition of 110 ℃ and the test pressure of 2.4MPa, and the requirement of PE-RT II type pipe resin is met.
While the methods and techniques of the present invention have been described in terms of preferred embodiments, it will be apparent to those of ordinary skill in the art that variations and/or modifications of the methods and techniques described herein may be made without departing from the spirit and scope of the invention. It is expressly intended that all such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and content of the invention.

Claims (8)

1. The special resin for the bimodal PE-RT II type pipe for the large-caliber pipe is characterized in that the melt index of the pipe resin is 0.5-1.0g/10min; the density is 0.945 to 0.955g/cm 3 (ii) a The number average molecular weight Mn is 10000-15000, the weight average molecular weight Mw is 250000-350000, and the molecular weight distribution breadth index is 16-35.
2. The special resin for the bimodal PE-RT II type pipe used for the large-caliber pipe as claimed in claim 1, wherein the oxygen barrier property of the resin is improved by more than 45%.
3. The preparation method of the special bimodal PE-RT II pipe resin for the large-caliber pipe as claimed in claim 1, characterized by comprising the following steps:
(1) Adding ethylene, hydrogen and a catalyst into a slurry double-loop first reactor, controlling the pressure of the first reactor to be 3.0-4.0 MPa and the reaction temperature to be 90-95 ℃ to carry out polymerization reaction; after removing hydrogen from ethylene, 1-hexene and a polymerization product of the first reactor, adding the mixture into a slurry double-loop second reactor, controlling the pressure of the second reactor to be 2.5-2.8 MPa and the reaction temperature to be 90-95 ℃ to carry out polymerization reaction; the first reactor obtains low molecular weight polyethylene powder, and the second reactor obtains high molecular weight ethylene-1-hexene copolymer powder; the ratio of the production of the first loop reactor to the production of the second loop reactor was controlled at 45:55-49:51.
(2) And (2) granulating the ethylene-1-hexene copolymer powder prepared in the step (1) by using a double-screw extruder, wherein the length-diameter ratio of the double screws is 40-60, adding an antioxidant, a nucleating agent and a halogen absorbent in the granulating process, and controlling the temperature to be 170-220 ℃ to prepare the special resin for the bimodal PE-RT II type pipe for the large-diameter pipe.
4. The process according to claim 3, wherein in the step (1), the molar ratio of ethylene to hydrogen is from 0.015 to 0.03; the comonomer is 1-hexene, the molar ratio of the comonomer to ethylene is 0.2-0.6:1.
5. the method according to claim 3, wherein in the step (1), the polymerization catalyst is a Ziegler-Natta catalyst.
6. The preparation method according to claim 3, wherein in the step (2), the antioxidant is a phenolic antioxidant, the phenolic antioxidant comprises a mixture of 1-3 wt% of antioxidant 1076 and antioxidant 626, and the amount of the antioxidant added is 0.1-0.4% of the total mass of the polyethylene powder.
7. The process according to claim 3, wherein in the step (2), the nucleating agent is 20e, and the addition amount is 0.05 to 0.2 percent of the total mass of the polyethylene powder.
8. The process according to claim 3, wherein in the step (2), the halogen absorbent is magnesium stearate, and the amount of magnesium stearate added is 0.1 to 0.2% of the total mass of the polyethylene powder.
CN202210765760.6A 2022-07-01 2022-07-01 Special resin for bimodal PE-RT II type pipe for large-diameter pipe and preparation method thereof Withdrawn CN115160471A (en)

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