Application of novel pipeline material in anhydrous hydrogen fluoride device

Abstract

The invention relates to the technical field of chemical anticorrosion pipeline materials, and discloses an application of a novel pipeline material in an anhydrous hydrogen fluoride device, the novel pipeline material is prepared from an ethylene monomer, an alpha olefin comonomer, rutile type nanometer titanium dioxide and anhydrous magnesium chloride, the anhydrous magnesium chloride is used as a carrier to load a titanium compound to form a polymerization catalyst, and the polymerization catalyst is used as a catalyst. The nano titanium dioxide is loaded on the surface of the rutile type nano titanium dioxide; the rutile type nano titanium dioxide is used as a polymerization core to construct bimodal molecular weight distribution, and the thermal conductivity of the rutile type nano titanium dioxide is utilized to induce the tube wall to form a gradient crystal structure with the crystallinity decreasing from the outer surface to the inner surface in the forming process. Through in-situ anchoring polymerization and gradient thermal history regulation and control, synergy of high barrier property, high strength and toughness and good processability of the material is realized, the problems of permeation, swelling, cracking and failure of a lining under the working condition of anhydrous hydrogen fluoride are solved, the service life of equipment is prolonged, and the production safety is improved.

Description

Technical Field

[0001] This invention relates to the field of chemical corrosion-resistant pipeline materials technology, specifically the application of a novel pipeline material in an anhydrous hydrogen fluoride plant. Background Technology

[0002] Anhydrous hydrogen fluoride, as a basic fluorochemical raw material, is highly corrosive and toxic. In the industrial production, storage, and transportation equipment of anhydrous hydrogen fluoride, steel-lined composite pipes with inner linings of polymer materials are usually used to prevent corrosion of the metal pipe walls. High-density polyethylene or ultra-high molecular weight polyethylene are often chosen as the inner lining material for anhydrous hydrogen fluoride transportation pipelines due to their chemical stability and economy.

[0003] Existing technologies for manufacturing lined pipes typically employ extrusion molding or rotational molding processes to form a protective layer inside the steel pipe. The lining material mainly relies on the chemical inertness of the polyethylene saturated alkane structure to isolate corrosive media from the steel pipe. To ensure mechanical strength, industrial applications typically use polyethylene resin with high crystallinity or high molecular weight to manufacture the lining layer, which is used to withstand the working pressure and temperature fluctuations during fluid transportation.

[0004] However, due to the extremely small size and high permeability of hydrofluoric acid molecules, they easily diffuse through the amorphous regions between polymer crystals during long-term operation. Existing polyethylene lining materials typically have a uniform crystalline structure, and the continuous amorphous phase provides a permeation channel for hydrofluoric acid. Once hydrofluoric acid permeates to the interface between the lining and the steel pipe, it reacts with the steel pipe to produce gas or accumulates under negative pressure conditions, leading to bulging, peeling, or collapse of the lining layer. In addition, due to the contradiction between melt flow rate and molecular weight, increasing the molecular weight of polyethylene to improve its resistance to environmental stress cracking will lead to a significant increase in melt viscosity, making it difficult to extrude dense pipes. On the other hand, reducing the molecular weight weakens the ability of polyethylene material to resist stress-induced cracking by corrosive media, leading to brittle failure of the pipeline. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a novel pipeline material for use in anhydrous hydrogen fluoride devices. It aims to solve the problems of existing polyethylene lining materials, which suffer from lining bulging failure due to hydrofluoric acid penetration caused by continuous amorphous phase permeation channels, and the inability to simultaneously achieve excellent environmental stress cracking resistance and processing fluidity.

[0006] To achieve the above objectives, the present invention provides the following technical solution: The first aspect of this invention provides a novel pipe material for an anhydrous hydrogen fluoride device, employing the following technical solution: A novel piping material for an anhydrous hydrogen fluoride device, made from raw materials comprising the following parts by weight: 92.0-96.0 parts of ethylene monomer; 1.5-2.5 parts of α-olefin comonomer; 2.5-5.0 parts of rutile nano-titanium dioxide; 0.5-1.0 parts of anhydrous magnesium chloride; wherein the anhydrous magnesium chloride is used as a support to load titanium compounds to form a polymerization catalyst and is supported on the surface of the rutile nano-titanium dioxide; wherein the rutile nano-titanium dioxide is used as a polymerization core to construct a bimodal molecular weight distribution, and the thermal conductivity of the rutile nano-titanium dioxide is used to induce the formation of a gradient crystallization structure in the tube wall during the molding process, with the crystallinity decreasing from the outer surface to the inner surface.

[0007] By adopting the above technical solution, this invention utilizes in-situ polymerization and gradient crystallization control technology to obtain excellent comprehensive performance, and its mechanism of action is as follows: In-situ catalyst loading and active site dispersion mechanism: Anhydrous magnesium chloride, acting as a Lewis base, chemically coordinates with hydroxyl groups on the surface of rutile nano-titanium dioxide, forming a stable intermediate layer. Titanium compounds (such as titanium tetrachloride) then complex with defect sites on the magnesium chloride lattice surface, forming active catalytic centers. This reaction process utilizes chemical bonding to restrict the aggregation of inorganic fillers, achieving uniform dispersion of active sites at the nanoscale.

[0008] Interface enhancement and path detour effect: Ethylene monomers undergo coordination insertion reactions directly on the active centers supported on the surface of titanium dioxide. Polymer segments grow outward from the surface of inorganic particles, forming a coating structure with nano-titanium dioxide as the core and polyethylene as the shell. This growth method establishes a tight interfacial bond between the inorganic and organic phases, reducing the free volume at the microscopic interface. At the same time, the dispersed nanoparticles increase the tortuosity of the diffusion path of gas molecules in the matrix, thereby reducing the permeation rate of hydrofluoric acid molecules.

[0009] Mechanism of gradient crystallization induced by heat conduction: Taking advantage of the significantly higher thermal conductivity of rutile nano-titanium dioxide compared to the polyethylene matrix, a radial thermal conduction difference is established during pipe forming and annealing. The outer wall region of the pipe exhibits a rapid heat dissipation rate, maintaining a suitable degree of supercooling at specific annealing temperatures. This promotes molecular chain folding and lattice alignment, forming a highly crystalline, dense layer. Conversely, the inner wall region experiences relatively slower heat dissipation, retaining lower crystallinity and a greater number of amorphous banded molecules, resulting in a highly tough layer.

[0010] Preferably, the α-olefin comonomer is selected from 1 octene and 1 hexene; the titanium compound is titanium tetrachloride, and the molar ratio of titanium tetrachloride to anhydrous magnesium chloride is 6:1 to 10:1.

[0011] By employing the above technical solution, the introduction of long-chain α-olefins (1 octene or 1 hexene) forms n-butyl or n-hexyl short branches on the polyethylene backbone. These branches disrupt the linear regularity of the molecular chain, thereby controlling the lamellar thickness; simultaneously, the branches, acting as physical crosslinking points, increase the density of interlamellar ligands, thus improving the material's resistance to environmental stress cracking. Controlling the titanium-magnesium ratio to 6:1 to 10:1 ensures that titanium compounds form monolayer or sub-monolayer adsorption on the support surface, avoiding catalytic efficiency reduction due to excessive self-reduction or aggregation of titanium compounds.

[0012] Preferably, the matrix resin of the novel pipe material has a bimodal molecular weight distribution, and the molecular weight distribution index (PDI) of the matrix resin is 17.0-22.0, wherein the mass percentage of low molecular weight polyethylene fraction is 25%-40%, and the mass percentage of ultra-high molecular weight polyethylene fraction is 60%-75%.

[0013] By employing the above technical solution, a wider molecular weight distribution index balances processability and mechanical properties. The low molecular weight fraction acts as a carrier resin and internal lubricant, effectively unwinding ultra-high molecular weight segments and reducing the apparent viscosity of the melt; the ultra-high molecular weight fraction provides mechanical strength. This formulation ensures that the material can be extruded using a conventional single-screw extruder while maintaining structural integrity in a hydrofluoric acid medium.

[0014] Preferably, the gradient crystallization structure exhibits the following characteristics: an absolute crystallinity of 70%-75% at a distance of 0-1.5 mm from the outer surface of the novel pipe material, and an absolute crystallinity of 55%-60% at a distance of 0-1.5 mm from the inner surface of the novel pipe material; the hydrofluoric acid permeation rate of the novel pipe material is less than or equal to 0.051 g·mm·m. -2 ·d -1 .

[0015] By adopting the above technical solution, the high crystallinity layer (70%-75%) in the region 0-1.5mm from the outer surface reduces the proportion of amorphous regions and blocks the diffusion channels of small molecule media; the low crystallinity layer (55%-60%) in the region 0-1.5mm from the inner surface retains the flexible amorphous region, dissipates the stress at the crack tip through plastic deformation, and prevents the inner wall from cracking under complex stress conditions.

[0016] The second aspect of this invention provides a method for preparing a novel pipeline material in an anhydrous hydrogen fluoride device, employing the following technical solution: A method for preparing a novel pipe material for an anhydrous hydrogen fluoride device includes the following steps: (a) Disperse rutile nano-titanium dioxide in a solvent, add anhydrous magnesium chloride and titanium compounds to react, and prepare a supported catalyst slurry; (b) Add a co-catalyst to the supported catalyst slurry, first pass high-concentration hydrogen gas to ethylene for the first stage of polymerization, and then pass ethylene to α-olefin comonomer for the second stage of polymerization to obtain composite powder; (c) The composite powder is melt-extruded into a pipe blank, which is then subjected to isothermal induced crystallization in a constant temperature annealing environment, followed by water cooling for shaping.

[0017] By employing the above technical solution, this method achieves precise construction of microstructures through stepwise reaction control: Hydrogen regulation chain transfer mechanism: In the first stage of polymerization, high-concentration hydrogen acts as a chain transfer agent, rapidly terminating chain growth through hydrogenolysis to generate low molecular weight fractions.

[0018] In the second-stage polymerization, hydrogen is removed and α-olefins are introduced to eliminate chain transfer inhibition. Ethylene and comonomers continue to insert, generating ultra-high molecular weight fractions with long branches. The two-stage products are generated in situ on the surface of the nanocatalyst, forming a homogeneous mixture at the molecular level, thus avoiding the phase separation problems caused by physical blending.

[0019] Annealing-induced crystallization mechanism: During the isothermal annealing step following extrusion, the polymer chains acquire rearrangement capabilities within a specific temperature range below their melting point. With the assistance of nano-titanium dioxide thermally conductive channels, the outer molecular chains stack orderly along the temperature gradient, perfecting the crystal structure and eliminating internal stresses generated by extrusion shearing.

[0020] Preferably, in step (b), the molar ratio of hydrogen to ethylene in the gas phase during the first stage polymerization is 0.8-1.2, and the polymerization yield accounts for 25%-40% of the total polymer mass; before the second stage polymerization, the molar ratio of hydrogen to ethylene in the gas phase is controlled to be 0-0.005 by flash evaporation.

[0021] By adopting the above technical solution, the hydrogen content in the second stage is controlled to be close to zero (0-0.005), which aims to block the chain transfer reaction and ensure that the molecular weight of the polyethylene generated in this stage reaches the ultra-high molecular weight level (the weight average molecular weight is usually greater than 1.5 million), thereby giving the material the necessary wear resistance and impact resistance.

[0022] Preferably, in step (c), the constant temperature annealing environment is provided by a constant temperature annealing chamber, a constant temperature medium, or a constant temperature annealing section; the temperature of the constant temperature annealing environment is 128-132℃, and the residence time of the pipe blank in the constant temperature annealing environment is 8-15 minutes.

[0023] By adopting the above technical solution, 128-132℃ falls between the upper limit of the crystallization temperature and the lower limit of the melting temperature of high-density polyethylene (α-relaxation range). Within this temperature range, polyethylene lamellar crystals thicken, and the crystal lattice structure tends to be more complete. The residence time is controlled at 8-15 minutes to ensure that the depth of heat transfer from the outside to the inside matches the crystal growth cycle, thereby forming a preset gradient distribution.

[0024] Preferably, step (c) is followed by a lining composite molding step: the water-cooled and shaped pipe is mechanically compressed to 85%-90% of its original outer diameter at 20-30°C, inserted into the steel pipe, and heated to 100-110°C to restore its shape using the shape memory effect to fit the inner wall of the steel pipe.

[0025] By employing the above technical solution, the entropy elasticity of ultra-high molecular weight polyethylene is utilized. At room temperature (20-30℃), external force is applied to force the molecular chains to undergo high-elastic deformation and become fixed. When heated to 100-110℃ (above the phase transformation temperature but below the melting point), the fixed deformation recovers, and the molecular chains tend to return to a disordered coiled state, causing the pipe to expand radially, thereby forming a high-tightness interference fit with the inner wall of the steel pipe.

[0026] The third aspect of this invention provides the application of a novel pipeline material in anhydrous hydrogen fluoride production, storage and transportation equipment.

[0027] By adopting the above technical solution, the novel pipe material with in-situ anchoring filler and gradient crystallization structure is applied to the anhydrous hydrogen fluoride working condition. The high crystallinity layer on its outer surface blocks the penetration of HF molecules, and the tough layer on its inner surface resists stress cracking, which can extend the service life of the lining pipe in the chemical plant and reduce the risk of leakage.

[0028] This invention provides an application of a novel pipeline material in an anhydrous hydrogen fluoride device. It offers the following advantages: 1. This invention disperses rutile nano-titanium dioxide in a polyethylene matrix using in-situ polymerization technology. Utilizing the difference in thermal conductivity between the rutile nano-titanium dioxide and the polyethylene matrix, a gradient structure with decreasing crystallinity from the outer surface to the inner surface is induced in the pipe material during the molding and annealing process. The higher crystallinity on the outer surface of the pipe material reduces the free volume of the amorphous regions. Combined with the hindering effect of the nanofiller on the diffusion path, this helps to reduce the permeation rate of anhydrous hydrogen fluoride molecules, mitigating bulging or peeling of the lining layer caused by media penetration.

[0029] 2. This invention employs a bimodal molecular weight distribution design, utilizing the branched structure formed by ultra-high molecular weight polyethylene fractions and long-chain α-olefin comonomers such as 1 octene or 1 hexene to increase the tethered molecular density between crystallites. Combined with the tough regions preserved by the lower crystallinity of the inner surface of the pipe material, this facilitates the dissipation of stress energy at crack tips when subjected to external forces or internal pressure fluctuations, thereby enhancing the pipe material's resistance to slow crack growth during long-term contact with corrosive media.

[0030] 3. This invention introduces low-molecular-weight polyethylene fractions to provide internal lubrication, improving the rheological behavior of ultra-high molecular weight polyethylene melt and enabling the new pipe material to adapt to conventional screw extrusion processes. Furthermore, utilizing the shape memory properties of the new pipe material for composite molding helps achieve a tight bond between the lining and the steel pipe without the use of adhesives, mitigating the problem of the lining easily collapsing or sinking under negative pressure conditions, and thus ensuring the stable operation of chemical plants. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the specification of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Preparation Examples 1-4: Preparation Example 1: This preparation example provides a method for preparing titanium dioxide-modified bimodal ultra-high molecular weight polyethylene composite powder, including the following steps: Under nitrogen protection, 500 mL of dehydrated n-hexane and 4.0 g of rutile nano-titanium dioxide calcined at 400 °C for 4 hours were added to a reactor equipped with a stirring device. The stirring was started and the speed was maintained at 600 r / min. 0.6 g of anhydrous magnesium chloride was added, the temperature was raised to 65 °C and stirred at a constant temperature for 2 hours. Titanium tetrachloride was then added dropwise, controlling the molar ratio of titanium tetrachloride to magnesium chloride at 8:1, and the temperature was raised to 85°C for 3 hours. After the reaction, the mixture was allowed to settle, the supernatant was removed, and the solid precipitate was washed four times with n-hexane at 50°C to obtain a supported catalyst slurry. 1 L of n-hexane and all of the above-prepared supported catalyst slurry were added to a 2 L stainless steel polymerization reactor, and triethylaluminum solution was added to make the molar ratio of Al to Ti in the system 80. The temperature was raised to 80°C, and a mixture of hydrogen and ethylene was introduced, controlling the molar ratio of hydrogen to ethylene in the gas phase at 1.0. The partial pressure of ethylene in the polymerization reactor was maintained at 0.6 MPa, and the polymerization reaction was carried out for 45 minutes to obtain a low molecular weight polyethylene fraction with a yield of 30% of the preset total polymer mass.

[0033] The hydrogen supply was then stopped and flash evaporation was performed until the molar ratio of hydrogen to ethylene in the gas phase was below 0.005. 2.0% (by mass) of the first-stage product's comonomer, 1-octene, was injected into the reactor, the reaction temperature was adjusted to 70°C, and ethylene monomer was continuously introduced, maintaining an ethylene partial pressure of 0.5 MPa. The reaction was carried out for 2.5 hours, yielding an ultra-high molecular weight polyethylene fraction with a yield of 70% of the preset total polymer mass. After the reaction, the solvent was removed by flash evaporation, and the resulting powder was dried at 60°C for 6 hours under a nitrogen stream to obtain titanium dioxide-modified bimodal ultra-high molecular weight polyethylene composite powder.

[0034] Preparation Example 2: This preparation example provides a method for preparing titanium dioxide-modified bimodal ultra-high molecular weight polyethylene composite powder, including the following steps: Under nitrogen protection, 500 mL of n-hexane and 6.0 g of rutile nano-titanium dioxide calcined at 400 °C for 4 hours were added to the reactor. The stirring speed was 600 r / min, and 0.8 g of anhydrous magnesium chloride was added. The mixture was stirred at 65 °C for 2 hours. Titanium tetrachloride was added dropwise, and the molar ratio of titanium tetrachloride to magnesium chloride was controlled at 10:1. The reaction was carried out at 90 °C for 3 hours. After sedimentation and washing with n-hexane 5 times, a supported catalyst slurry was obtained. 1 L of n-hexane and all the catalyst slurry were added to a 2 L polymerization reactor. Triethylaluminum solution was added to make the molar ratio of Al to Ti 100. The temperature was raised to 82 °C, and the molar ratio of hydrogen to ethylene in the gas phase was controlled at 1.2. The ethylene partial pressure was maintained at 0.6 MPa, and the polymerization reaction was carried out for 40 minutes to obtain a low molecular weight fraction accounting for 25% of the preset total polymer mass. Subsequently, hydrogen was removed by flash evaporation to reduce the molar ratio of H2 to C2H4 to below 0.005. Then, 2.5% (by mass) of the first-stage product was injected with the comonomer 1-octene. The temperature was adjusted to 68°C, and the ethylene partial pressure was maintained at 0.5 MPa. The reaction was carried out for 2.2 hours, yielding a skeletal phase fraction accounting for 75% of the preset total polymer mass. After flash solvent removal and nitrogen drying, titanium dioxide-modified bimodal ultra-high molecular weight polyethylene composite powder was obtained.

[0035] Preparation Example 3: This preparation example provides a method for preparing titanium dioxide-modified bimodal ultra-high molecular weight polyethylene composite powder, including the following steps: Under nitrogen protection, 500 mL of n-hexane and 3.5 g of rutile nano-titanium dioxide calcined at 400 °C for 4 hours were added to the reactor. The stirring speed was 600 r / min, and 0.5 g of anhydrous magnesium chloride was added. The mixture was stirred at 65 °C for 2 hours. Titanium tetrachloride was added dropwise, and the molar ratio of titanium tetrachloride to magnesium chloride was controlled at 6:1. The reaction was carried out at 85 °C for 3 hours. After sedimentation and washing with n-hexane 4 times, a supported catalyst slurry was obtained. 1 L of n-hexane and all the catalyst slurry were added to a 2 L polymerization reactor. Triethylaluminum solution was added to make the Al to Ti molar ratio 60. The temperature was raised to 78 °C, and the molar ratio of hydrogen to ethylene in the gas phase was controlled at 0.8. The ethylene partial pressure was maintained at 0.6 MPa, and the polymerization reaction was carried out for 50 minutes to obtain a low molecular weight fraction accounting for 35% of the preset total polymer mass. Subsequently, hydrogen was removed by flash evaporation to reduce the molar ratio of H2 to C2H4 to below 0.005. Then, 1.5% (by mass) of the first-stage product comonomer 1-hexene was injected to replace 1-octene. The temperature was adjusted to 65°C, and the ethylene partial pressure was maintained at 0.4 MPa. The reaction was carried out for 3 hours, yielding a skeletal phase fraction accounting for 65% of the preset total polymer mass. After flash solvent removal and nitrogen drying, titanium dioxide-modified bimodal ultra-high molecular weight polyethylene composite powder was obtained.

[0036] Preparation Example 4: This preparation example provides a method for preparing titanium dioxide-modified bimodal ultra-high molecular weight polyethylene composite powder, including the following steps: The preparation process parameters of the catalyst components were completely consistent with those in Preparation Example 1. 1L of n-hexane and all the catalyst slurry were added to a 2L polymerization reactor, and triethylaluminum solution was added to make the Al to Ti molar ratio 80. The temperature was raised to 80℃, the hydrogen to ethylene molar ratio in the gas phase was controlled at 1.0, the ethylene partial pressure was maintained at 0.6 MPa, and the polymerization reaction time was extended to 60 minutes, so that the yield of low molecular weight fractions accounted for 40% of the preset total polymer mass. Subsequently, hydrogen was flash-evaporated to make the H2 to C2H4 molar ratio below 0.005, and 2.0% (by mass) of the first-stage product comonomer 1 octene was injected. The temperature was adjusted to 70℃, the ethylene partial pressure was maintained at 0.5 MPa, and the reaction time was shortened to 2 hours, so that the yield of ultra-high molecular weight fractions accounted for 60% of the preset total polymer mass. After flash evaporation and nitrogen drying, titanium dioxide modified bimodal ultra-high molecular weight polyethylene composite powder was obtained.

[0037] Examples 1-4: Example 1: This embodiment provides a method for preparing a novel pipeline material in an anhydrous hydrogen fluoride device, including the following steps: The titanium dioxide-modified bimodal ultra-high molecular weight polyethylene composite powder obtained in Preparation Example 1 was selected as raw material and directly fed into a single-screw extruder equipped with a grooved feed bushing and a separable screw with a length-to-diameter ratio of 30:1. The temperatures of the feed section in zone one of the single-screw extruder were set at 150°C, the compression section in zone two at 180°C, the metering section in zone three at 190°C, and the die temperature at the die head at 200°C. The melt pressure at the die head was controlled at 30 MPa, and the melt was extruded into a pipe preform with an outer diameter of 110 mm and a wall thickness of 10 mm. The pipe preform corresponds to a DN100 liner pipe.

[0038] Immediately afterwards, the tube blank leaving the die is introduced into a constant-temperature annealing chamber filled with dimethyl silicone oil, and the annealing temperature is controlled at 130°C for a dwell time of 10 minutes. The thermal conductivity of titanium dioxide is used to induce the formation of a highly crystalline structure in the tube wall. Subsequently, the tube is introduced into a water bath at 25°C for rapid cooling and shaping, resulting in a modified polyethylene tube with a gradient crystalline structure.

[0039] Subsequently, the cooled modified polyethylene pipe is passed through a multi-stage reducing machine to physically compress its outer diameter to 88% of its original diameter (approximately 96.8 mm) at room temperature, making the outer diameter of the modified polyethylene pipe smaller than the inner diameter of the DN100 carbon steel pipe. The compressed liner is then inserted into the DN100 carbon steel pipe, which has undergone sandblasting and rust removal. The entire composite pipe is then heated to 105°C and held for 1 hour. Utilizing the material's shape memory effect, the liner expands radially and tightly adheres to the inner wall of the steel pipe, achieving an interfacial contact pressure of 1.0 MPa. Finally, the pipe ends are heated to 140°C for mechanical flanging, with the flanging width covering the flange sealing surface, resulting in the finished pipe.

[0040] Example 2: This embodiment provides a method for preparing a novel pipeline material in an anhydrous hydrogen fluoride device, including the following steps: The titanium dioxide-modified bimodal ultra-high molecular weight polyethylene composite powder obtained in Preparation Example 2 was selected as the raw material. The same single-screw extruder as in Example 1 was used, and the temperature parameters were adjusted to accommodate the viscosity changes caused by the high filler content. The temperatures were set as follows: Zone 1 temperature 155°C, Zone 2 temperature 185°C, Zone 3 temperature 195°C, and die temperature 205°C. The die melt pressure was controlled at 32 MPa, and a pipe preform with an outer diameter of 160 mm was extruded, corresponding to a DN150 liner pipe.

[0041] Next, the pipe blank is introduced into a constant temperature medium at 128°C for annealing treatment, and the residence time is 8 minutes. Then it is introduced into circulating water at 20°C for cooling and shaping.

[0042] Subsequently, the outer diameter of the pipe is compressed to 90% of its original size (i.e., 144mm) and inserted into a pre-treated DN150 carbon steel pipe (with an inner diameter of approximately 154mm). The entire pipe is then heated to 100℃ to induce recovery, forming an interference fit. Finally, the ends are flanged to obtain the finished pipe.

[0043] Example 3: This example provides a method for preparing a novel pipeline material in an anhydrous hydrogen fluoride device, including the following steps: The titanium dioxide-modified bimodal ultra-high molecular weight polyethylene composite powder obtained in Preparation Example 3 was selected as the raw material. Given the high molecular weight of the titanium dioxide-modified bimodal ultra-high molecular weight polyethylene composite powder, the processing temperature was increased to ensure plasticization. The temperatures of the single-screw extruder were set at 160℃ in zone one, 190℃ in zone two, and 200℃ in zone three, with the die temperature set at 210℃. The melt pressure at the die head was maintained at 35MPa to ensure densification, resulting in the extrusion of a large-diameter pipe preform with an outer diameter of 315mm, corresponding to a DN300 liner pipe.

[0044] Next, the tube is introduced into a constant temperature annealing section at 132°C, and the dwell time is extended to 15 minutes to ensure effective heat conduction in the core and external crystal growth. Then, it is water-cooled at 25°C for shaping.

[0045] Subsequently, a multi-stage diameter reduction process was used to compress the outer diameter of the pipe to 85% (i.e., 267.75 mm). After successfully inserting it into a DN300 carbon steel pipe (with an inner diameter of approximately 305 mm), it was heated to 110°C for heat recovery, generating a high interfacial clamping force. After completing the flanging, the finished pipe was obtained.

[0046] Example 4: This embodiment provides a method for preparing a novel pipeline material in an anhydrous hydrogen fluoride device, including the following steps: The titanium dioxide-modified bimodal ultra-high molecular weight polyethylene composite powder obtained in Preparation Example 4 was selected as the raw material. Due to the high proportion of low molecular weight fractions, the processing temperature was appropriately reduced to save energy. The temperature of Zone 1 was set at 145℃, Zone 2 at 175℃, Zone 3 at 185℃, and the die temperature at the die head was set at 195℃. The melt pressure at the die head was controlled at 28MPa, and a pipe blank with an outer diameter of 225mm was extruded. The pipe blank corresponded to a DN200 lining pipe.

[0047] Next, the pipe was annealed at 130°C for 12 minutes, followed by water cooling for shaping.

[0048] Subsequently, the pipe is reduced to 88% of its original outer diameter, inserted, and then restored at 105°C to complete the flanging process, thus producing the finished pipe.

[0049] Comparative Examples 1-5: Comparative Example 1: This comparative example provides a polyethylene pipe material without titanium dioxide loading. The difference from Example 1 is that rutile nano-titanium dioxide was not added during the catalyst preparation process of Example 1.

[0050] Specifically, the catalyst preparation process in Example 1 was adjusted to only add anhydrous magnesium chloride to prepare a catalyst without titanium dioxide, and finally a bimodal ultra-high molecular weight polyethylene powder without titanium dioxide was obtained. The subsequent pipe extrusion and molding processes were consistent with those in Example 1.

[0051] Comparative Example 2: This comparative example provides a composite pipe material of physically blended titanium dioxide. The difference from Example 1 is that titanium dioxide is introduced by mechanical blending instead of in-situ polymerization.

[0052] Specifically, pure bimodal ultra-high molecular weight polyethylene powder was prepared using a catalyst without added titanium dioxide. Before extrusion molding, 3.5 wt% of rutile nano-titanium dioxide was physically mixed with the polyethylene powder using a high-speed mixer, and then extrusion granulation and pipe forming were carried out. The rest was consistent with Example 1.

[0053] Comparative Example 3: This comparative example provides a unimodal polyethylene pipe material, which differs from Example 1 in that the polymerization process is changed to prepare unimodal ultra-high molecular weight polyethylene.

[0054] Specifically, the first stage polymerization in Preparation Example 1 was omitted to eliminate the synthesis of the lubricating phase. In the second stage polymerization, the total polymerization time was kept constant, and a single-distribution ultra-high molecular weight polyethylene was directly synthesized. The remaining raw material ratios and subsequent pipe forming processes were kept consistent with those in Example 1.

[0055] Comparative Example 4: This comparative example provides a pipe material without gradient crystallization treatment. The difference from Example 1 is that the isothermal annealing treatment after extrusion is omitted. Specifically, after the pipe blank leaves the die, it is not subjected to isothermal crystallization in an isothermal annealing chamber, but is directly placed into a 25°C water bath for cooling and shaping. All other aspects are consistent with Example 1.

[0056] Comparative Example 5: This comparative example provides a composite pipe bonded with adhesive. The difference from Example 1 is that an adhesive bonding process is used instead of the non-adhesive shape memory lining process.

[0057] Specifically, without performing physical compression and heat recovery operations on the modified polyethylene pipe, the un-reduced diameter modified polyethylene pipe is directly bonded to the inner wall of the carbon steel pipe using an acid-resistant epoxy resin adhesive, and everything else remains the same as in Example 1.

[0058] Test Examples 1-4: Test Example 1: Verification of Basic Physicochemical Parameters and Molecular Structure Characterization This test case aims to verify whether the composite powders prepared in Examples 1-4 successfully achieved the preset bimodal molecular weight distribution structure and quantitative loading of inorganic fillers, and to explore the influence of different polymerization processes on the microstructure parameters of the materials.

[0059] Experimental steps: The titanium dioxide-modified bimodal ultra-high molecular weight polyethylene composite powders obtained in Preparation Examples 1-4, the unloaded polyethylene powder obtained in Comparative Example 1, and the unimodal polyethylene powder obtained in Comparative Example 3 were selected as the test samples.

[0060] First, the molecular weight and molecular weight distribution of the samples were determined using high-temperature gel permeation chromatography (GPC). 5.0 mg of each sample was accurately weighed and placed in a sample vial, and 10 mL of 1,2,4-trichlorobenzene solvent containing 0.1% 2,6-di-tert-butyl-p-cresol (BHT) antioxidant was added. The sample vials were placed in a swelling heater at 160°C and shaken for 4 hours until the samples were completely dissolved and no visible gel particles remained. The GPC column temperature was set to 150°C, the flow rate to 1.0 mL / min, and the injection volume to 200 μL. Universal calibration was performed using polystyrene standards. The elution curves were recorded, and the number-average molecular weight (Mn), weight-average molecular weight (Mw), and molecular weight distribution index (PDI) were calculated.

[0061] The inorganic filler content was then determined using the muffle furnace ash content determination method. 2.0 g of the dried polymer powder was accurately weighed and placed in a pre-weighed porcelain crucible. The crucible was placed on an electric furnace and slowly heated to carbonize until no smoke was emitted, then transferred to a muffle furnace. The heating program was set to increase to 800 °C at a rate of 10 °C / min and calcined at that temperature for 4 hours. After the muffle furnace cooled to 200 °C, the porcelain crucible was removed, placed in a desiccator to cool to room temperature, and weighed. The percentage of residual ash relative to the original sample mass was calculated, and this value was used as the actual titanium dioxide loading.

[0062] Table 1. Test data on molecular weight parameters and filler content of powders prepared by the same process

[0063] in conclusion: The test data in Table 1 show that the samples obtained in Preparation Examples 1-4 differ significantly from those in Comparative Example 3 in terms of molecular weight distribution. The molecular weight distribution index (PDI) of the sample in Preparation Example 1 is 17.37, exhibiting a broad distribution characteristic, while the PDI of the sample in Comparative Example 3, polymerized using a constant hydrogen concentration, is only 2.74, exhibiting a typical narrow distribution characteristic. This result confirms that by controlling the hydrogen concentration in two stages, two fractions with significantly different molecular weights were successfully synthesized in the same catalytic system, achieving the expected bimodal distribution structure.

[0064] Regarding the loading of inorganic fillers, the measured titanium dioxide content in Preparation Examples 1-4 was highly close to the theoretical feed amount, with an error range within ±0.2%. For example, the theoretical value for Preparation Example 2 was 5.00%, while the measured value was 4.88%; the theoretical value for Preparation Example 3 was 2.50%, while the measured value was 2.56%. The data indicate that during the in-situ polymerization process, the loading reaction conversion rate of titanium tetrachloride and magnesium chloride on the surface of nano-titanium dioxide was high, and the subsequent solvent washing step did not cause a significant loss of the carrier.

[0065] The 0.03% (mainly catalyst residual ash) in Comparative Example 1 and 3.44% in Preparation Example 1 demonstrate that regardless of the polymerization process adjustment, in-situ polymerization technology can ensure the effective filling of inorganic particles in the polymer matrix. Preparation Example 4, by extending the first-stage polymerization time, increased the proportion of low molecular weight fractions, resulting in a decrease in the number-average molecular weight Mn to 11.95 × 10⁻⁶. 4 g / mol, PDI increased to 19.92, and the changing trends of various physicochemical indicators are consistent with the process setting logic.

[0066] In summary, the data from this test example validates the feasibility of the two-stage hydrogen regulation mechanism and in-situ polymerization loading technology proposed in this invention, and proves that the process in the preparation example can stably synthesize composite powders with a specific bimodal distribution structure and quantitatively loaded nanoparticles. Test Example 2: Verification of Crystallinity Gradient in Pipe Wall Thickness This test case aims to verify, through stratified sampling tests, whether the preparation process of Example 1 successfully induced a gradient crystallization structure with higher outer and lower inner thickness in the direction of pipe wall thickness, and to explore the synergistic influence mechanism of titanium dioxide thermal conductivity and isothermal annealing process on crystallization behavior.

[0067] Experimental steps: The finished pipe prepared in Example 1, the unloaded titanium dioxide pipe prepared in Comparative Example 1, and the pipe prepared in Comparative Example 4 without gradient crystallization treatment were selected as the test objects. A precision slicer was used to sample the pipes radially. A slice from 0 to 1.5 mm from the outer surface of the pipe was taken as the outer layer sample, a slice from the center of the pipe wall thickness was taken as the core layer sample, and a slice from 0 to 1.5 mm from the inner surface of the pipe was taken as the inner layer sample.

[0068] The melting behavior and crystallinity of each layer of the sample were determined using differential scanning calorimetry (DSC). 5.0 to 8.0 mg of sample was weighed, placed in an aluminum crucible, compacted, and sealed. The test was conducted under a high-purity nitrogen atmosphere at a flow rate of 50 mL / min. The heating program was set to raise the sample from room temperature to 180 °C at a rate of 10 °C / min. The melting curve of the first heating process was recorded to characterize the aggregated structure of the formed pipe. The enthalpy of fusion was obtained by integrating the melting peak area. Based on the theoretical enthalpy of fusion of fully crystalline polyethylene (293 J / g) and the actual mass fraction of inorganic fillers in each sample, the absolute crystallinity of each layer of the sample was calculated.

[0069] Table 2. Test data on the crystallinity of the pipe in the wall thickness direction.

[0070] in conclusion: Table 2 shows the decisive influence of different material compositions and molding processes on the microstructure of the pipe. The pipes from Examples 1 to 4 all exhibited a clear gradient crystalline structure, and the crystallinity data showed a regular change with the annealing process conditions. Specifically, Example 2 used a lower annealing temperature (128℃) and a shorter time (8 minutes), resulting in an outer layer crystallinity of 70.21%, which was at the lower limit of the preset range. Example 3, however, increased the annealing temperature (132℃) and extended the time (15 minutes), increasing the outer layer crystallinity to 74.90%, reaching the upper limit of the preset range. This indicates that by fine-tuning the isothermal annealing parameters, the density of the outer wall of the pipe (70%-75%) and the retention of toughness of the inner wall (55%-60%) can be controlled.

[0071] Taking Example 1 as an example, the crystallinity of the outer layer is 71.26%, while the crystallinity of the inner layer drops to 59.73%, a difference of over 11%. This structure is attributed to the synergistic effect of the high thermal conductivity of rutile nano-titanium dioxide and the isothermal annealing process. During the annealing stage, the titanium dioxide dispersed in the matrix acts as a heat conduction channel, accelerating the exchange and transfer of heat to the outside of the pipe. Combined with isothermal conditions, this induces the outer layer molecular chains to fully fold and arrange themselves into the crystal lattice, forming a dense, highly crystalline outer shell. As heat transfer to the inside becomes slower, the degree of crystallinity in the core and inner layers decreases progressively. This gradient structure is ultimately fixed by rapid water cooling. The highly crystalline outer layer effectively blocks the penetration of hydrogen fluoride molecules, while the relatively less crystalline inner layer retains more entangled chains in the amorphous regions, providing the pipe with excellent toughness and impact resistance.

[0072] Although Comparative Example 1 used the same annealing process, due to the lack of highly thermally conductive titanium dioxide filler in the matrix, the poor thermal conductivity of polyethylene itself hindered the effective conduction of heat energy and the induction of crystallization, resulting in the overall crystallinity of the pipe fluctuating between 52% and 53%, and no obvious gradient difference was formed in the wall thickness direction. This proves the important induction role of nanofillers in constructing gradient structures.

[0073] Comparative Example 4 eliminated the isothermal annealing step, and the melt was directly quenched in contact with the refrigerant after extrusion. The extreme supercooling caused the polymer chains to freeze before they could arrange themselves in a regular pattern, resulting in the lowest overall crystallinity. Furthermore, due to the skin effect, the outer layer, which was in direct contact with water, cooled the fastest, but its crystallinity was actually lower than that of the core layer. This structure is not conducive to the barrier of small molecule media.

[0074] In summary, the data from this test case strongly demonstrates the feasibility and necessity of using titanium dioxide thermally induced annealing combined with isothermal annealing to construct a gradient crystallization structure with external impermeability and internal toughening. It also proves that the present invention can stably obtain the expected gradient crystallization index under a wide process window.

[0075] Test Example 3: Comparison Test of Processing Rheological and Mechanical Properties This test case aims to verify the effect of the bimodal distribution structure of the present invention on improving the processing flowability of ultra-high molecular weight polyethylene, and the advantages of in-situ polymerization loading process over physical blending process in improving the mechanical properties of materials.

[0076] Experimental steps: The modified polyethylene particles prepared in Examples 1 to 4, the physically blended polyethylene particles prepared in Comparative Example 2, and the unimodal polyethylene particles prepared in Comparative Example 3 were selected as the test samples.

[0077] The processing rheological properties of each group of samples were tested using a melt flow rate (MFR) meter. 4.0 to 6.0 g of the sample was weighed and added to the barrel. The test temperature was set to 190℃, and the nominal load was 21.6 kg, which are considered high-load test conditions. After preheating for 6 minutes, the extruded sample was automatically cut and weighed. The MFR was calculated to characterize the material's flowability during the extrusion process.

[0078] The mechanical properties of the samples were tested using a pendulum impact testing machine and a universal testing machine. Each group of particle samples was prepared into standard test specimens using an injection molding machine at 200℃. The notched impact strength of a simply supported beam was tested according to ISO 179 standard, with a V-notch cut on the specimens, and the impact energy absorbed at fracture was recorded. Tensile properties were tested according to ISO 527 standard, with a tensile rate set at 50 mm / min, and the elongation at break and tensile yield strength were recorded.

[0079] Table 3. Test data of processing rheological and mechanical properties

[0080] Note: - indicates that this item is not available. The four data points for Comparative Example 3 in the table are blank because this sample is unimodal ultra-high molecular weight polyethylene, lacking low molecular weight lubricating components, and has extremely high melt viscosity. Under test conditions of 190℃ and 21.6kg, the melt could not be extruded, making it impossible to measure the MFR value. Furthermore, this material does not meet the flowability requirements for injection molding machine feeding and mold filling, making it impossible to prepare standard injection molding test specimens; therefore, relevant mechanical property data are missing. in conclusion: Table 3 presents the test data, which clearly demonstrates the significant effectiveness of bimodal molecular weight distribution and in-situ polymerization technology in solving the two core problems of difficult processing and filler dispersion in ultra-high molecular weight polyethylene (UHMWPE). The sample from Example 1, under a high load of 21.6 kg and 190 °C, showed a melt flow rate of 4.25 g / 10 min, exhibiting good melt flowability. This is because the low molecular weight fraction synthesized in-situ in the bimodal structure, with a number average molecular weight of approximately 160,000, acts as an internal lubricant and plasticizer in the system, effectively untangling the UHMWPE molecular chain network with a weight average molecular weight exceeding 2 million, thus significantly reducing melt viscosity. In contrast, the unimodal UHMWPE in Comparative Example 3, lacking the lubricating effect of the low molecular weight fraction, barely flowed under the same test conditions, with a melt flow rate of less than 0.1 g / 10 min, failing to meet the process requirements for continuous pipe extrusion. This also indirectly verifies the necessity of the bimodal structure designed in this invention.

[0081] In terms of mechanical properties, the notched impact strength of the simply supported beam in Example 1 reaches as high as 128.6 kJ / m. 2 It is much higher than the 85.3 kJ / m² of Comparative Example 2. 2 Both examples share the same matrix resin structure, differing only in the method of titanium dioxide introduction. Comparative Example 2 employed physical-mechanical blending, where nano-titanium dioxide readily aggregated, forming micron-sized inorganic aggregates. These aggregates became stress concentration points under stress, inducing crazes and leading to premature brittle fracture. Example 1, however, utilized in-situ polymerization, with the catalyst component directly loaded onto the surface of the nano-titanium dioxide. The grown polyethylene segments tightly encapsulated the inorganic particles, forming a unique core-shell structure. This structure not only achieved uniform nanoscale dispersion of the filler but also enhanced interfacial bonding through strong chemical bonding and physical entanglement. When the material was impacted, the nanoparticles could generate a pinning effect and induce plastic deformation in the matrix to absorb energy, thereby significantly improving toughness.

[0082] Furthermore, Example 4 increased the proportion of low molecular weight fractions by adjusting the process, resulting in an MFR of 5.88 g / 10 min and further enhanced processing performance, although the impact strength decreased slightly to 119.5 kJ / m.2 However, it remains at a high level, indicating that processability and mechanical properties can be flexibly balanced by fine-tuning the polymerization process.

[0083] In summary, the data from this test example confirms that the material prepared by this invention possesses both excellent processing fluidity and superior impact toughness, which helps to overcome the difficulties in processing and molding traditional ultra-high molecular weight polyethylene and the problem that physical filler modification can easily lead to a decline in mechanical properties.

[0084] Test Example 4: Resistance to Chemical Permeation and Environmental Stress Cracking This test case aims to evaluate the protective barrier capability and long-term service durability of the prepared pipe under harsh chemical environments, with a focus on verifying the synergistic enhancement effect of gradient crystal structure and inorganic filler introduction on blocking the penetration of corrosive media and inhibiting slow crack growth.

[0085] Experimental steps: The finished pipes prepared in Examples 1 to 4, the unloaded titanium dioxide pipe prepared in Comparative Example 1, the single-peak polyethylene pressed sheet prepared in Comparative Example 3, and the non-gradient structure pipe prepared in Comparative Example 4 were selected as the test samples.

[0086] The chemical permeation resistance of the pipe was tested using the weight loss method. Standard 200mm sections of pipe were cut, one end was heat-sealed, and a 40% hydrofluoric acid solution was injected to 80% of the pipe volume. The other end was then sealed. The sealed pipe sections were placed in a 60°C fume hood, and the total mass of the pipe sections was weighed every 24 hours for 30 consecutive days. The hydrofluoric acid permeation rate was calculated by determining the mass loss per unit surface area per unit time.

[0087] The environmental stress cracking resistance of the pipe was tested using a full-notch creep test. According to ISO 16770 standard, specimens were cut along the wall thickness of the pipe, and coplanar notches of varying depths were machined on all four sides of the specimens. The specimens were immersed in an aqueous solution containing 2% Arkopal N-100 surfactant at 80°C, and a constant tensile stress of 4.0 MPa was applied. The time from the onset of stress to complete fracture failure was automatically recorded.

[0088] Table 4. Test data on chemical penetration resistance and environmental stress cracking resistance

[0089] Note: - indicates that this item is not available; the data for Comparative Example 3 in the table is blank. Because this sample is unimodal ultra-high molecular weight polyethylene, it cannot be manufactured into pipes using conventional extrusion processes and can only be molded into sheets. Since the molding thermal history and orientation structure of the sheets and pipes are completely different, and a permeation test on a sealed pipe section cannot be performed, the sample does not meet the basic conditions for conducting this comparative experiment.

[0090] in conclusion: Table 4 shows the test data, revealing the key role of gradient crystallization structure and nano-titanium dioxide filler in improving the protective performance of pipes. The hydrofluoric acid permeation rate in Example 1 was only 0.042 g·mm·m. -2 ·d -1 The value was significantly lower than 0.156 for Comparative Example 1 and 0.284 for Comparative Example 4. This superior barrier performance stems from two mechanisms: First, as demonstrated in Test Example 2, the highly crystalline layer on the outer wall of the pipe forms a dense lattice defense, which significantly reduces the free volume of the amorphous region and increases the resistance to the diffusion of corrosive molecules. Secondly, the in-situ dispersed lamellar or spherical nano-titanium dioxide creates a tortuous path effect in the matrix, forcing the permeating molecules to detour and significantly lengthening the diffusion path. In Comparative Example 4, due to the lack of isothermal annealing induction, the outer wall has low crystallinity and is porous, resulting in a nearly 7-fold increase in the permeation rate.

[0091] In terms of environmental stress cracking resistance, Example 1 exhibited a FNCT failure time of up to 2450 hours, which is 3.7 times that of Comparative Example 1 and 7.6 times that of Comparative Example 4. This result verifies the effectiveness of the inner layer low crystallinity toughening design. The inner wall of the pipe retains a large number of entangled molecules and physical entanglement networks, which can effectively dissipate the stress energy at the crack tip; at the same time, the chemically bonded nanoparticles, as physical cross-linking points, can pin the development of crevice and prevent it from transforming into destructive cracks. Although Comparative Example 4 has the same overall molecular weight, due to rapid cooling resulting in large residual internal stress and a lack of microstructure optimization, it rapidly underwent brittle fracture under the dual attack of activator and thermal stress.

[0092] Furthermore, Example 2 exhibited the lowest permeation rate due to its higher titanium dioxide loading and stronger tortuous path effect; while Example 3 exhibited the longest crack resistance life due to its higher proportion of ultra-high molecular weight fraction and strongest molecular chain entanglement.

[0093] In summary, the data from this test case confirms that the pipe prepared by this invention achieves a balance between high barrier properties and high durability by constructing a gradient structure with an outer hardness and an inner toughness and introducing an inorganic barrier network, making it particularly suitable for harsh chemical fluid transportation applications.

Claims

1. A novel pipe material for an anhydrous hydrogen fluoride device, characterized in that, Made from raw materials comprising the following percentages by weight: 92.0-96.0 parts of ethylene monomer; 1.5-2.5 parts of α-olefin comonomer; Rutile nano-titanium dioxide, 2.5-5.0 parts; 0.5-1.0 parts of anhydrous magnesium chloride; The anhydrous magnesium chloride is used as a support to load titanium compounds to form a polymerization catalyst and is supported on the surface of the rutile nano-titanium dioxide. The rutile nano-titanium dioxide is used as a polymerization core to construct a bimodal molecular weight distribution, and the thermal conductivity of the rutile nano-titanium dioxide is used to induce the formation of a gradient crystallization structure in the tube wall during the molding process, with the crystallinity decreasing from the outer surface to the inner surface.

2. The novel pipe material in an anhydrous hydrogen fluoride device according to claim 1, characterized in that, The α-olefin comonomer is selected from 1 octene and 1 hexene; the titanium compound is titanium tetrachloride, and the molar ratio of titanium tetrachloride to anhydrous magnesium chloride is (6-10):

1.

3. The novel pipeline material in an anhydrous hydrogen fluoride device according to claim 1, characterized in that, The matrix resin of the novel pipe material has a bimodal molecular weight distribution, and the molecular weight distribution index (PDI) of the matrix resin is 17.0-22.

0. The mass percentage of low molecular weight polyethylene fraction is 25%-40%, and the mass percentage of ultra-high molecular weight polyethylene fraction is 60%-75%.

4. The novel pipe material in an anhydrous hydrogen fluoride device according to claim 1, characterized in that, The gradient crystallization structure is characterized as follows: The absolute crystallinity at a distance of 0-1.5 mm from the outer surface of the novel pipe material is 70%-75%, and the absolute crystallinity at a distance of 0-1.5 mm from the inner surface of the novel pipe material is 55%-60%. The hydrofluoric acid permeation rate of the novel pipe material is ≤0.051 g·mm·m. -2 ·d -1 .

5. A method for preparing a novel pipe material for use in an anhydrous hydrogen fluoride device according to any one of claims 1 to 4, characterized in that, Includes the following steps: (a) Disperse rutile nano-titanium dioxide in a solvent, add anhydrous magnesium chloride and titanium compounds to react, and prepare a supported catalyst slurry; (b) Add a co-catalyst to the supported catalyst slurry, first pass high-concentration hydrogen gas to ethylene for the first stage of polymerization, and then pass ethylene to α-olefin comonomer for the second stage of polymerization to obtain composite powder; (c) The composite powder is melt-extruded into a pipe blank, which is then subjected to isothermal induced crystallization in a constant temperature annealing environment, followed by water cooling for shaping.

6. The method for preparing a novel pipeline material in an anhydrous hydrogen fluoride device according to claim 5, characterized in that, In step (b), the molar ratio of hydrogen to ethylene in the gas phase during the first stage of polymerization is 0.8-1.2, and the polymerization yield accounts for 25%-40% of the total polymer mass. Before the second stage of polymerization, the molar ratio of hydrogen to ethylene in the gas phase is controlled to be 0-0.005 by flash evaporation.

7. The method for preparing a novel pipeline material in an anhydrous hydrogen fluoride device according to claim 5, characterized in that, In step (c), the constant temperature annealing environment is provided by a constant temperature annealing chamber, a constant temperature medium, or a constant temperature annealing section; the temperature of the constant temperature annealing environment is 128-132℃, and the residence time of the pipe blank in the constant temperature annealing environment is 8-15 minutes.

8. The method for preparing a novel pipeline material in an anhydrous hydrogen fluoride device according to claim 5, characterized in that, Step (c) is followed by a lining composite molding step: After water cooling and shaping, the pipe is mechanically compressed to 85%-90% of its original outer diameter at 20-30℃, inserted into a steel pipe, and heated to 100-110℃ to restore its shape using the shape memory effect to fit the inner wall of the steel pipe.

9. The application of the novel pipeline material in the anhydrous hydrogen fluoride device according to any one of claims 1 to 4 in the equipment for the production, storage and transportation of anhydrous hydrogen fluoride.

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