阅读说明：本技术 一种hdpe管的制备方法 (Preparation method of HDPE (high-density polyethylene) pipe ) 是由 张业毅 于 2019-10-30 设计创作，主要内容包括：本发明属于塑料管材制备技术领域,具体涉及一种HDPE管的制备方法。本发明将高岭土、氧化铝、钛白粉、磷酸铝与水搅拌,将外胶管层用硅铝增强纤维缠结包覆装入双层波纹管模具内层中,填充内层填充胶液,将双层波纹管模具置于热压设备中热压后挤出HDPE管,本发明中细度为200目的石墨粉导热系数相对较大,起到降温作用,硅铝增强纤维对HDPE管有保护作用；以高密度聚乙烯粉末为主要原料硫化成型制备外胶管层,通过硅铝增强纤维层包覆来增强HDPE管,使EPDM具有低温弹性,提高HDPE管的韧性和弹性,而且EPDM具有耐油,耐酸碱腐蚀性能较好,提供了一层防腐保护膜,同时甲基丙烯酸锌作为耐热抗氧化剂,提高了HDPE管中掺杂成分的相容性,提升防腐性能,具有广阔的应用前景。(The invention belongs to the technical field of plastic pipe preparation, and particularly relates to a preparation method of an HDPE pipe. According to the invention, kaolin, alumina, titanium dioxide, aluminum phosphate and water are stirred, the outer rubber tube layer is wrapped by the aluminum silicon reinforced fibers in an intertwined manner and is filled into the inner layer of the double-layer corrugated tube mold, the inner layer filling rubber solution is filled, the double-layer corrugated tube mold is placed in hot-pressing equipment for hot pressing and then the HDPE tube is extruded, the heat conductivity coefficient of graphite powder with the fineness of 200 meshes is relatively large, the cooling effect is achieved, and the aluminum silicon reinforced fibers have a protection effect on the HDPE tube; the outer hose layer is prepared by taking high-density polyethylene powder as a main raw material through vulcanization molding, the HDPE pipe is reinforced through coating of the silicon-aluminum reinforced fiber layer, so that the EPDM has low-temperature elasticity, the toughness and the elasticity of the HDPE pipe are improved, the EPDM has oil resistance and better acid-base corrosion resistance, an anticorrosion protective film is provided, meanwhile, zinc methacrylate is used as a heat-resistant antioxidant, the compatibility of doped components in the HDPE pipe is improved, the anticorrosion performance is improved, and the application prospect is wide.)

1. A preparation method of HDPE pipe is characterized by comprising the following specific preparation steps:

(1) mixing high-density polyethylene powder, epoxidized soybean oil, EPDM virgin rubber with the ethylene content of 50-55%, zinc oxide and aluminum aliphatate to obtain a mixing raw material, feeding the mixing raw material into a composite double-layer corrugated pipe die, carrying out hot-pressing forming on the mixing raw material into a composite strip under the conditions that the temperature is 70-80 ℃ and the pressure is 1.4-1.6 MPa, feeding the composite strip into a plastic spiral pipe composite winding forming machine for forming, cooling, and then carrying out high-energy electron beam irradiation crosslinking with the dosage of 20-25 kGy to obtain an outer rubber pipe layer;

(2) according to the weight parts, 30-35 parts of nano aluminum oxide, 20-25 parts of calcium borate and 10-15 parts of graphite powder with the fineness of 200 meshes are added into a crusher to be crushed and then poured into a sand mixer, 8-10 parts of zinc methacrylate, 3-5 parts of zirconium dioxide and 5-8 parts of graphene are added into the sand mixer to be stirred and mixed for 10-20 min, 8-10 parts of interfacial bonding agent are sequentially added, and then the mixture is subjected to ball milling and 200-mesh sieving to obtain an inner layer heat insulation filler;

(3) mixing the inner-layer heat-insulation filler and the silica sol precursor according to a mass ratio of 3: 1 to obtain inner-layer filling glue solution, winding and coating the outer glue layer with silica-alumina reinforced fibers, then loading the outer layer into the outer layer of the double-layer corrugated pipe mold treated by the release agent, then filling the inner-layer filling glue solution into the inner layer of the double-layer corrugated pipe mold, placing the double-layer corrugated pipe mold into a hot-pressing device for hot-pressing for 30-35 min, and extruding to obtain an HDPE (high-density polyethylene) pipe after cooling to normal temperature;

the silicon-aluminum reinforced fiber is prepared by the following specific steps:

(1) adding kaolin, alumina, titanium dioxide and aluminum phosphate into water, stirring and dispersing to prepare suspension slurry, adding a phosphoric acid solution with the mass fraction of 20% into the suspension slurry to adjust the pH value of the suspension slurry to 5-6, heating to 50-60 ℃, and preserving heat for 10-15 hours to obtain slurry;

(2) mixing 30-50 parts of nano silica aerogel, 30-40 parts of montmorillonite and 200-300 parts of water to obtain nano silica aerogel slurry, then mixing the slurry and the nano silica aerogel slurry, putting the mixture into a crucible in a muffle furnace, heating, preheating for 40-50 min, heating again, keeping the temperature for 30-35 min to obtain molten feed liquid, and spinning to obtain silicon-aluminum reinforced fibers;

the preparation method of the silica sol precursor comprises the following specific steps:

mixing 200-220 mL of ethyl orthosilicate and 300-350 mL of absolute ethyl alcohol, putting the mixture into a beaker, adding 60-80 mL of hydrochloric acid into the beaker, stirring the mixture for 1-2 hours by using a magnetic stirrer at the rotating speed of 400-450 r/min to obtain silica sol, adding 20-30 mL of polyvinyl alcohol with the mass fraction of 5% into the silica sol, and aging the mixture for 20-24 hours at room temperature to obtain a silica sol precursor.

2. The method of claim 1, wherein the HDPE pipe is prepared by: the HDPE pipe is characterized in that the raw materials in the step (1) are mixed, and the raw materials comprise, by weight, 40-50 parts of high-density polyethylene powder, 10-15 parts of epoxidized soybean oil, 10-12 parts of EPDM virgin rubber with the ethylene content of 50-55%, 5-10 parts of zinc oxide and 7-8 parts of aluminum stearate.

3. The method of claim 1, wherein the HDPE pipe is prepared by: in the preparation step (1) of the HDPE pipe body, the molecular weight of the high-density polyethylene powder is 2-5 ten thousand, and the crystallinity is 80-85%.

4. The method of claim 1, wherein the HDPE pipe is prepared by: the HDPE pipe is prepared by dispersing 40-50 g of zirconium boride powder into 300-350 mL of deionized water, and stirring and dispersing to obtain the interface binding agent in the specific preparation step (2) of the HDPE pipe.

5. The method of claim 1, wherein the HDPE pipe is prepared by: the HDPE pipe is prepared in the step (3) by controlling the hot pressing pressure to be 10-20 MPa and the hot pressing temperature to be 200-300 ℃.

6. The method of claim 1, wherein the HDPE pipe is prepared by: the HDPE pipe is characterized in that in the specific preparation step (3), the release agent is one of silicone oil, polyethylene glycol and low molecular weight polyethylene.

7. The method of claim 1, wherein the HDPE pipe is prepared by: the silicon-aluminum reinforced fiber is prepared by specifically preparing raw materials of each component of the suspension slurry in the step (1), wherein the raw materials comprise, by weight, 400-500 parts of water, 70-80 parts of kaolin, 20-30 parts of alumina, 10-15 parts of titanium dioxide and 20-22 parts of aluminum phosphate.

8. The method of claim 1, wherein the HDPE pipe is prepared by: the mixing volume ratio of the slurry to the nano silicon dioxide aerogel slurry in the concrete preparation step (2) of the silicon-aluminum reinforced fiber is 4: 1.

9. The method of claim 1, wherein the HDPE pipe is prepared by: the preheating temperature in the specific preparation step (2) of the silicon-aluminum reinforced fiber is preferably 700-800 ℃, and the temperature when the molten material liquid is prepared is preferably 1300-1350 ℃.

Technical Field

The invention belongs to the technical field of plastic pipe preparation, and particularly relates to a preparation method of an HDPE pipe.

Background

Almost all polymers are accompanied by aging phenomena, HDPE is no exception. The aging resistance of HDPE materials is critical because the HDPE materials are subjected to heat, oxygen, light and the like during storage, processing and use, and the structure of the HDPE is changed, the relative molecular mass is reduced or cross-linking is generated, so that the performance of the HDPE materials is reduced or even damaged. To inhibit HDPE aging, maintain material properties, extend service life, the most common and effective method is to add an antioxidant thereto; the antioxidants mainly comprise amines, phenols, phosphorus-containing compounds, sulfur-containing compounds and the like, and some of the traditional antioxidants have poor stability and high toxicity; some antioxidants are easy to migrate and short in action time, and the traditional antioxidants cannot solve the problem of aging of the HDPE pipe so as not to obtain the HDPE pipe with good antioxidant effect; therefore, the research on an antioxidant with good antioxidant effect to prepare the HDPE pipe with good antioxidant effect, good weather resistance and good stability and the preparation method thereof are still needed.

Polyethylene is a crystalline polymer with excellent performance, low price and wide application, and is a general plastic with the largest dosage. But it must have good antistatic performance for underground coal mine. Since the surface resistivity of the polymer material is high, electric charges are easily accumulated, thereby causing a safety accident. In order to have excellent conductive or antistatic performance, the volume resistivity or surface resistivity of polymer materials used in coal mines is generally reduced by adding conductive carbon black. In order to meet the antistatic requirement of the underground coal mine, the addition amount of the conductive carbon black in the high polymer material is usually more than or equal to 12-15 percent, so that the antistatic requirement of the underground coal mine on the high polymer material can be met. Such high carbon black contents necessarily lead to changes in the properties of the matrix material HDPE, such as a reduction in toughness and plasticity. Therefore, how to prepare the HDPE material with low carbon black content and high antistatic property is always a hot spot for researching and developing high polymer material products used in coal mines. The invention mainly aims at the preparation of an HDPE antistatic raw material for an HDPE extruded pipe. And has no applicability to other forming methods or articles. The technical principle of the invention is mainly to utilize the molecular weight grading effect of polymer fluid and the preferential surface adsorption effect of carbon black in the pipe extrusion process. The HDPE pipe raw material with low carbon black content and high antistatic performance is prepared by utilizing the grading effect of molecular weight and the preferential adsorption effect of carbon black and adopting a proper formula and a preparation method.

High-concentration polyethylene (HDPE) is widely used in daily life and industrial and agricultural production as a thermoplastic resin with high crystallinity and non-polarity, and has the characteristics of no toxicity, low price, excellent moisture resistance, good mechanical property, good chemical stability, excellent cold resistance, easy molding and processing and the like. For example, HDPE double-wall corrugated pipe, is used in municipal drainage and sewerage pipe system engineering; underground burying drainage and pollution discharge in apartments and residential districts; pre-buried pipelines of the expressway and a water seepage pipe network under the golf course; irrigation works such as irrigation and water delivery, drainage and the like; chemical engineering and mines are used for conveying and ventilating fluid and the like; the protective sleeve of underground pipeline and communication cable sheath pipe. However, due to the defects of insufficient toughness, low hardness, insufficient environmental stress cracking resistance and the like of HDPE, the HDPE double-wall corrugated pipe generally has a fluid such as sewage containing chemical substances passing through the HDPE double-wall corrugated pipe, and the HDPE is degraded under the dual action of the chemical substances and external stress, so that the HDPE double-wall corrugated pipe is damaged, and the use range of the HDPE double-wall corrugated pipe is restricted.

The other HDEP steel belt winding pipe solves the defects of the HDPE double-wall corrugated pipe that the toughness is not high enough, the hardness is low, the environmental stress cracking resistance is not high enough, and the like to a certain extent. The HDEP steel strip-wound pipe is formed by winding a metal strip, such as a steel strip, on the outer side wall of a pipe material taking HDPE as a matrix. The metal strip is the main support structure of HDPE double-wall corrugated pipe, and the toughness, hardness and environmental stress crack resistance of metal are all higher than those of HDPE. The HDPE is corrosion and wear resistant and therefore requires less material in the HDEP steel-strip-wound pipe. However, the price of the metal material is much higher than that of the HDPE, so that the cost of the manufactured HDPE steel strip winding pipe is high.

HDPE pipes currently exist: poor toughness, poor heat-resistant stability, easy corrosion and the like.

Therefore, the invention of the excellent HDPE pipe has positive significance in the technical field of plastic pipe preparation.

Disclosure of Invention

The invention mainly solves the technical problems that the prior HDPE pipe has poor toughness, cannot be bent greatly in the laying process, has poor heat-resistant stability and is easy to corrode as a conveying pipeline, and provides a preparation method of the HDPE pipe.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows:

a preparation method of HDPE pipe is characterized by comprising the following specific preparation steps:

(1) mixing high-density polyethylene powder, epoxidized soybean oil, EPDM virgin rubber with the ethylene content of 50-55%, zinc oxide and aluminum aliphatate to obtain a mixing raw material, feeding the mixing raw material into a composite double-layer corrugated pipe die, carrying out hot-pressing forming on the mixing raw material into a composite strip under the conditions that the temperature is 70-80 ℃ and the pressure is 1.4-1.6 MPa, feeding the composite strip into a plastic spiral pipe composite winding forming machine for forming, cooling, and then carrying out high-energy electron beam irradiation crosslinking with the dosage of 20-25 kGy to obtain an outer rubber pipe layer;

(2) according to the weight parts, 30-35 parts of nano aluminum oxide, 20-25 parts of calcium borate and 10-15 parts of graphite powder with the fineness of 200 meshes are added into a crusher to be crushed and then poured into a sand mixer, 8-10 parts of zinc methacrylate, 3-5 parts of zirconium dioxide and 5-8 parts of graphene are added into the sand mixer to be stirred and mixed for 10-20 min, 8-10 parts of interfacial bonding agent are sequentially added, and then the mixture is subjected to ball milling and 200-mesh sieving to obtain an inner layer heat insulation filler;

(3) mixing the inner-layer heat-insulation filler and the silica sol precursor according to a mass ratio of 3: 1 to obtain inner-layer filling glue solution, winding and coating the outer glue layer with silica-alumina reinforced fibers, then loading the outer layer into the outer layer of the double-layer corrugated pipe mold treated by the release agent, then filling the inner-layer filling glue solution into the inner layer of the double-layer corrugated pipe mold, placing the double-layer corrugated pipe mold into a hot-pressing device for hot-pressing for 30-35 min, and extruding to obtain an HDPE (high-density polyethylene) pipe after cooling to normal temperature;

the silicon-aluminum reinforced fiber is prepared by the following specific steps:

(1) adding kaolin, alumina, titanium dioxide and aluminum phosphate into water, stirring and dispersing to prepare suspension slurry, adding a phosphoric acid solution with the mass fraction of 20% into the suspension slurry to adjust the pH value of the suspension slurry to 5-6, heating to 50-60 ℃, and preserving heat for 10-15 hours to obtain slurry;

(2) mixing 30-50 parts of nano silica aerogel, 30-40 parts of montmorillonite and 200-300 parts of water to obtain nano silica aerogel slurry, then mixing the slurry and the nano silica aerogel slurry, putting the mixture into a crucible in a muffle furnace, heating, preheating for 40-50 min, heating again, keeping the temperature for 30-35 min to obtain molten feed liquid, and spinning to obtain silicon-aluminum reinforced fibers;

the preparation method of the silica sol precursor comprises the following specific steps:

mixing 200-220 mL of ethyl orthosilicate and 300-350 mL of absolute ethyl alcohol, putting the mixture into a beaker, adding 60-80 mL of hydrochloric acid into the beaker, stirring the mixture for 1-2 hours by using a magnetic stirrer at the rotating speed of 400-450 r/min to obtain silica sol, adding 20-30 mL of polyvinyl alcohol with the mass fraction of 5% into the silica sol, and aging the mixture for 20-24 hours at room temperature to obtain a silica sol precursor.

The HDPE pipe is characterized in that the raw materials in the step (1) are mixed, and the raw materials comprise, by weight, 40-50 parts of high-density polyethylene powder, 10-15 parts of epoxidized soybean oil, 10-12 parts of EPDM virgin rubber with the ethylene content of 50-55%, 5-10 parts of zinc oxide and 7-8 parts of aluminum stearate.

In the preparation step (1) of the HDPE pipe body, the molecular weight of the high-density polyethylene powder is 2-5 ten thousand, and the crystallinity is 80-85%.

The HDPE pipe is prepared by dispersing 40-50 g of zirconium boride powder into 300-350 mL of deionized water, and stirring and dispersing to obtain the interface binding agent in the specific preparation step (2) of the HDPE pipe.

The HDPE pipe is prepared in the step (3) by controlling the hot pressing pressure to be 10-20 MPa and the hot pressing temperature to be 200-300 ℃.

The HDPE pipe is characterized in that in the specific preparation step (3), the release agent is one of silicone oil, polyethylene glycol and low molecular weight polyethylene.

The silicon-aluminum reinforced fiber is prepared by specifically preparing raw materials of each component of the suspension slurry in the step (1), wherein the raw materials comprise, by weight, 400-500 parts of water, 70-80 parts of kaolin, 20-30 parts of alumina, 10-15 parts of titanium dioxide and 20-22 parts of aluminum phosphate.

The slurry and the nano-silica aerogel slurry in the concrete preparation step (2) of the silicon-aluminum reinforced fiber are mixed, the preheating temperature in the concrete preparation step (2) of the silicon-aluminum reinforced fiber is preferably 700-800 ℃, and the temperature when the molten material liquid is prepared is preferably 1300-1350 ℃.

The invention has the beneficial effects that:

(1) the invention mixes kaolin, alumina, titanium dioxide, aluminum phosphate and water, stirs and disperses to prepare suspension slurry, adds phosphoric acid solution to the suspension slurry to adjust pH value, obtains slurry, mixes montmorillonite and nano-silica aerogel to prepare nano-silica aerogel slurry, mixes the slurry and the nano-silica aerogel slurry, heats and melts them to obtain molten feed liquid, obtains silicon-aluminum reinforced fiber by spinning, uses nano-alumina, calcium borate, graphite powder with 200 meshes of fineness, alumina powder, zinc methacrylate, zirconium dioxide, graphene and so on as raw materials, uses zirconium boride as interface binder, ball-mills and screens to obtain filler with inner layer, finally mixes the filler with silica sol precursor to obtain inner layer filling glue solution, wraps and packs the outer glue tube layer in the inner layer of the double-layer corrugated tube mould by silicon-aluminum reinforced fiber entanglement, the inner layer of the outer layer of the tubular double-layer corrugated pipe mould is filled with glue solution, the double-layer corrugated pipe mould is placed in a hot pressing device for hot pressing, and then an HDPE pipe is extruded, the glue pipe is a heat insulation fireproof layer formed by an outer glue pipe layer, a reinforcing layer wound by silicon-aluminum reinforced fibers, inner layer heat insulation filler and a silicon dioxide sol precursor, the heat conductivity coefficient of graphite powder with the fineness of 200 meshes is relatively large, the inner surface of the HDPE pipe is rapidly heated in the heat transfer process, the graphite powder can slightly expand from a curling state to a relaxation state, the heat dissipation area of the outer surface of the heat insulation fireproof layer is increased, the inner layer of the HDPE pipe is cooled, and the used silicon-aluminum reinforced fibers also play a role in enhancing and protecting the;

(2) the invention takes high-density polyethylene powder as a main raw material to prepare an outer hose layer through vulcanization molding, the HDPE pipe is reinforced through coating of a silicon-aluminum reinforced fiber layer, the damage of the outer hose layer during bending is reduced, the high-density polyethylene powder is doped and modified by EPDM virgin rubber, the ethylene content of the EPDM virgin rubber is 50-55%, the formation of propylene blocks can be avoided, the random distribution of propylene and ethylene in EPDM molecules is ensured, the EPDM has low-temperature elasticity, although the molecular chain flexibility of the high-density polyethylene powder is poor, the cohesive energy of the EPDM molecules is lower, a large number of side groups do not obstruct the movement of the molecular chain, the molecular chain can keep good flexibility and elasticity in a wider range, so the toughness and elasticity of the HDPE pipe can be effectively improved by the EPDM doping modification, and the EPDM has oil resistance, good acid-base corrosion resistance, which is equivalent to providing an anticorrosive protective film for the HDPE pipe, meanwhile, zinc methacrylate is added into the inner-layer heat-insulating filling material to serve as a heat-resistant antioxidant, and the zinc methacrylate can also serve as an auxiliary vulcanizing agent to promote crosslinking of rubber in the outer hose layer, divalent zinc ions in the zinc methacrylate are firstly used as Lewis acid to catalyze epoxy compounds such as EPDM (ethylene-propylene-diene monomer) or epoxy soybean oil in the HDPE (high-density polyethylene) pipe to perform a ring-opening reaction and generate hydroxyl groups along with the reaction, and the hydroxyl groups generated by the ring-opening reaction further perform a nucleophilic addition reaction with double bonds on metal salts of unsaturated carboxylic acid, namely an oxa-Michael reaction, so that the compatibility of doped components in the HDPE pipe is improved, the adhesive force of the inorganic inner-layer heat-insulating filling material to the outer hose layer of the HDPE.

Detailed Description

Adding 70-80 parts of kaolin, 20-30 parts of alumina, 10-15 parts of titanium dioxide and 20-22 parts of aluminum phosphate into 400-500 parts of water by weight, stirring and dispersing to prepare suspension slurry, adding a phosphoric acid solution with the mass fraction of 20% into the suspension slurry to adjust the pH value of the suspension slurry to 5-6, heating to 50-60 ℃, and preserving heat for 10-15 hours to obtain slurry; mixing 30-50 parts of nano silica aerogel, 30-40 parts of montmorillonite and 200-300 parts of water to obtain nano silica aerogel slurry, then mixing the slurry and the nano silica aerogel slurry according to a volume ratio of 4: 1, putting the mixture into a crucible in a muffle furnace, heating to 700-800 ℃, preheating for 40-50 min, heating to 1300-1350 ℃, preserving heat for 30-35 min to obtain molten feed liquid, and spinning to obtain silicon-aluminum reinforced fibers for later use; mixing 200-220 mL of tetraethoxysilane and 300-350 mL of absolute ethyl alcohol, putting the mixture into a beaker, adding 60-80 mL of hydrochloric acid with the mass fraction of 10% into the beaker, stirring the mixture for 1-2 hours by using a magnetic stirrer at the rotating speed of 400-450 r/min to obtain silica sol, adding 20-30 mL of polyvinyl alcohol with the mass fraction of 5% into the silica sol, and aging the mixture for 20-24 hours at room temperature to obtain a silica sol precursor for later use; mixing 40-50 parts by weight of high-density polyethylene powder, 10-15 parts by weight of epoxidized soybean oil, 10-12 parts by weight of EPDM virgin rubber with the ethylene content of 50-55%, 5-10 parts by weight of zinc oxide and 7-8 parts by weight of aluminum stearate to obtain a mixing raw material, feeding the mixing raw material into a composite double-layer corrugated pipe die, carrying out hot press forming on the mixing raw material into a composite strip under the conditions that the temperature is 70-80 ℃ and the pressure is 1.4-1.6 MPa, feeding the composite strip into a plastic spiral pipe composite winding forming machine for forming, cooling, and then carrying out high-energy electron beam irradiation crosslinking with the dosage of 20-25 kGy to obtain an outer rubber pipe layer, wherein the molecular weight of the high-density polyethylene powder is 2-5 ten thousand, and the crystallinity is 80-; according to the weight parts, 30-35 parts of nano aluminum oxide, 20-25 parts of calcium borate and 10-15 parts of graphite powder with the fineness of 200 meshes are added into a pulverizer to be pulverized and then poured into a sand mixer, 8-10 parts of zinc methacrylate, 3-5 parts of zirconium dioxide and 5-8 parts of graphene are added into the sand mixer to be stirred and mixed for 10-20 min, 8-10 parts of interfacial bonding agent are sequentially added, and then the mixture is subjected to ball milling and 200-mesh sieving to obtain an inner-layer heat insulation filler, wherein the interfacial bonding agent is obtained by dispersing 40-50 g of zirconium boride powder into 300-350 mL of deionized water and stirring and dispersing; mixing the inner-layer heat-insulating filler and a standby silica sol precursor according to a mass ratio of 3: 1 to obtain inner-layer filling glue solution, winding and coating the outer glue layer on the outer glue layer by using silica-alumina reinforced fibers, then loading the outer glue layer into an outer layer of a double-layer corrugated pipe mold treated by a release agent, filling the inner-layer filling glue solution into the inner layer of the double-layer corrugated pipe mold, placing the double-layer corrugated pipe mold into a hot pressing device for hot pressing for 30-35 min, controlling the hot pressing pressure to be 10-20 MPa and the hot pressing temperature to be 200-300 ℃, cooling to normal temperature, and then extruding to obtain the HDPE pipe, wherein the release agent is one of silicone oil, polyethylene glycol and low molecular weight polyethylene.