Special polypropylene random copolymer pipe material prepared by adopting bifunctional catalytic system and preparation method of special polypropylene random copolymer pipe material

Abstract

The invention provides a special material for a polypropylene random copolymer pipe prepared by adopting a bifunctional catalytic system and a preparation method of the special material. The preparation method comprises the following steps: a) by taking propylene as a raw material, a magnesium chloride supported titanium tetrachloride catalyst as a main catalyst, aluminum alkyl as a cocatalyst, alkoxy silane as an external electron donor and a macromolecular nucleating agent as a functional aid, adding ethylene by adopting a prepolymerization process and hydrogen as a molecular weight regulator, so as to prepare polypropylene resin powder; and b) mixing the polypropylene resin powder, the main antioxidant, the auxiliary antioxidant and the halogen absorbing agent, and extruding to obtain the special material for the random copolymer polypropylene pipe. According to the preparation method, a high-molecular nucleating agent is introduced in a prepolymerization reaction stage, so that a traditional manner of physically blending and adding the nucleating agent in a granulation stage is changed, the problems of non-uniform dispersion, agglomeration and the like of the nucleating agent are effectively avoided, the temperature required by processing is further reduced, and the risk of thermal degradation is reduced; the material keeps excellent mechanical properties, and also has a lower processing melting point and a higher pressure-resistant grade.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, and particularly relates to a method for preparing random copolymer polypropylene pipe material using a bifunctional catalytic system. Background Technology

[0002] Random copolymer polypropylene (PP-R) pipes are widely used in building hot and cold water supply systems due to their advantages such as high temperature resistance, corrosion resistance, and hygiene and non-toxicity. However, traditional PP-R pipe materials have two significant drawbacks: (1) high processing energy consumption, and (2) pressure resistance needs to be improved.

[0003] To address the aforementioned issues, the industry commonly employs the addition of nucleating agents to improve the performance of polypropylene. Existing technologies typically involve adding traditional nucleating agents, such as inorganic salts and sorbitols, through physical blending during the granulation stage. However, this method has significant drawbacks: the nucleating agent is unevenly dispersed within the polypropylene matrix, easily agglomerating and affecting nucleation efficiency, leading to large fluctuations in product performance and poor quality stability. This uneven dispersion results in insufficient improvement in pressure resistance, especially long-term creep resistance, and sometimes even sacrifices the material's mechanical properties to improve processability. Furthermore, the addition of nucleating agents further increases the material's melting point, leading to increased processing temperatures.

[0004] Therefore, developing a PP-R pipe material that can significantly reduce processing energy consumption and improve pressure resistance has become an urgent technical problem to be solved in this field. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a special material for random copolymer polypropylene pipes and a method for preparing the same, which, while maintaining excellent mechanical properties, has a lower processing melting point and a higher pressure resistance rating.

[0006] This invention provides a method for preparing random copolymer polypropylene pipe material using a bifunctional catalytic system, comprising the following steps:

[0007] a) Using propylene as raw material, magnesium chloride-supported titanium tetrachloride catalyst as main catalyst, alkyl aluminum as co-catalyst, alkoxysilane as external electron donor, and polymer nucleating agent as functional additive, ethylene-propylene random copolymer polypropylene resin powder is prepared through a prepolymerization process, using hydrogen as molecular weight regulator and adding ethylene.

[0008] b) The polypropylene resin powder, main antioxidant, co-antioxidant and halogen absorber are mixed and extruded to obtain random copolymer polypropylene pipe material.

[0009] Preferably, step a) specifically includes:

[0010] (a1) Propylene was prepolymerized under the combined action of magnesium chloride-supported titanium tetrachloride catalyst, polymer nucleating agent, co-catalyst and external electron donor to obtain prepolymerized product;

[0011] (a2) The prepolymer product, propylene, ethylene and hydrogen are polymerized to obtain polypropylene powder;

[0012] (a3) The polypropylene powder, propylene, ethylene and hydrogen are further polymerized to obtain ethylene-propylene random copolymer polypropylene resin powder.

[0013] Preferably, the main catalyst is selected from one or more of ZN101 catalyst, ZN118 catalyst, ZN128M catalyst, HR catalyst, DQC401 catalyst, CS-2 catalyst, SP-2 catalyst and SP-4 catalyst;

[0014] The mass ratio of the main catalyst to the polymer nucleating agent is 1:0.2~8.

[0015] Preferably, the concentration of hydrogen in step (a2) is 200~1000ppm;

[0016] The total flow rate of propylene and ethylene is 20~40 t / h;

[0017] The polymerization reaction temperature is 70~75℃.

[0018] Preferably, the concentration of hydrogen in step (a3) ​​is 200~1000ppm;

[0019] The total flow rate of propylene and ethylene is 10~20 t / h;

[0020] The polymerization reaction temperature is 70~75℃.

[0021] Preferably, the maximum temperature used in the extrusion is 235°C.

[0022] Preferably, the melt flow rate of the random copolymer polypropylene pipe material is 0.2~0.3 g / 10 min, and the ethylene content is 3.45%.

[0023] This invention provides a random copolymer polypropylene pipe material, which, by mass parts, comprises the following components:

[0024] 100 parts of ethylene-propylene random copolymer polypropylene resin, 0.1-0.3 parts of main antioxidant, 0.1-0.3 parts of co-antioxidant, and 0.02-0.1 parts of halogen absorber;

[0025] The ethylene content in the ethylene-propylene random copolymer polypropylene resin is 3.0~4.0 wt%, and the melt index at 230℃ and 2.16 kg is 0.1~0.5 g / 10 min;

[0026] The raw materials for the prepolymerization stage of preparing ethylene-propylene random copolymer polypropylene resin include a polymeric nucleating agent, wherein the polymeric nucleating agent is selected from at least one of polyvinylcyclopentane, polyvinylcyclohexane, polyvinyl-2-methylcyclohexane, poly-3-methyl-1-butene, poly-3-ethyl-1-hexene, poly-3-methyl-1-pentene, and polystyrene.

[0027] Preferably, the primary antioxidant is selected from one or more of antioxidant 2246, antioxidant 1010, antioxidant 1076, and antioxidant 1330;

[0028] The antioxidant is selected from one or more of antioxidant 168, antioxidant 626 and antioxidant 9228.

[0029] Preferably, the halogen absorber is selected from one or more of sodium stearate, calcium stearate, and zinc stearate.

[0030] This invention provides a method for preparing random copolymer polypropylene pipe material using a bifunctional catalytic system, comprising the following steps: a) using propylene as raw material, magnesium chloride-supported titanium tetrachloride catalyst as the main catalyst, alkyl aluminum as the co-catalyst, alkoxysilane as the external electron donor, and a polymeric nucleating agent as a functional additive, through a prepolymerization process, using hydrogen as a molecular weight regulator, and adding ethylene to obtain ethylene-propylene random copolymer polypropylene resin powder; b) mixing the polypropylene resin powder, the main antioxidant, the co-antioxidant, and the halogen absorber, and extruding to obtain the random copolymer polypropylene pipe material. This invention, by introducing a polymeric nucleating agent during the polymerization reaction stage, changes the traditional method of physically adding nucleating agents during the granulation stage, effectively avoiding problems such as uneven dispersion and agglomeration of the nucleating agent, thereby reducing the processing temperature and the risk of thermal degradation; this material maintains excellent mechanical properties while also having a lower processing melting point and a higher pressure resistance rating. Detailed Implementation

[0031] This invention provides a method for preparing random copolymer polypropylene pipe material using a bifunctional catalytic system, comprising the following steps:

[0032] a) Using propylene as raw material, magnesium chloride-supported titanium tetrachloride catalyst as main catalyst, alkyl aluminum as co-catalyst, alkoxysilane as external electron donor, and polymer nucleating agent as functional additive, ethylene-propylene random copolymer polypropylene resin powder is prepared through a prepolymerization process, using hydrogen as molecular weight regulator and adding ethylene.

[0033] b) The polypropylene resin powder, main antioxidant, co-antioxidant and halogen absorber are mixed and extruded to obtain random copolymer polypropylene pipe material.

[0034] The method provided by this invention is simple and suitable for large-scale industrial production. By introducing a polymeric nucleating agent during the prepolymerization stage of the polymerization reaction, this invention changes the traditional method of adding nucleating agents through physical blending during the granulation stage. This effectively avoids problems such as uneven dispersion and agglomeration of the nucleating agent, thereby reducing the processing temperature and the risk of thermal degradation; it also significantly reduces energy consumption and production costs in the pipe manufacturing process. Because the polymeric nucleating agent participates in situ during polymerization, it promotes the optimization of the polypropylene crystal structure, forming more uniform and finer grains, thus significantly improving the material's mechanical strength and creep resistance.

[0035] The present invention specifically includes the following steps for preparing ethylene-propylene random copolymer polypropylene resin powder:

[0036] (a1) Propylene was prepolymerized under the combined action of magnesium chloride-supported titanium tetrachloride catalyst, polymer nucleating agent, co-catalyst and external electron donor to obtain prepolymerized product;

[0037] (a2) The prepolymer product, propylene, ethylene and hydrogen are polymerized to obtain polypropylene powder;

[0038] (a3) The polypropylene powder, propylene, ethylene and hydrogen are further polymerized to obtain ethylene-propylene random copolymer polypropylene resin powder.

[0039] In this invention, the magnesium chloride-supported titanium tetrachloride catalyst, the polymeric nucleating agent, the co-catalyst, and the external electron donor together constitute a bifunctional catalytic system, and the prepolymerized product is prepared under their combined action. In this invention, the main catalyst is selected from one or more of the following catalysts: ZN101, ZN118, ZN128M, HR, DQC401, CS-2, SP-2, and SP-4; the mass ratio of the main catalyst to the polymeric nucleating agent is 1:0.2~8, specifically 1:0.2, 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, or 1:8.

[0040] In this invention, the polymeric nucleating agent is selected from at least one of polyvinylcyclopentane, polyvinylcyclohexane (PVCH), polyvinyl-2-methylcyclohexane, poly-3-methyl-1-butene, poly-3-ethyl-1-hexene, poly-3-methyl-1-pentene, and polystyrene, preferably polyvinylcyclohexane. This invention introduces the polymeric nucleating agent during the polymerization reaction stage, changing the traditional method of adding the nucleating agent through physical blending during the granulation stage. This effectively avoids problems such as uneven dispersion and agglomeration of the nucleating agent, resulting in more uniform dispersion and better performance. Because the polymeric nucleating agent participates in situ during polymerization, it promotes the optimization of the polypropylene crystal structure, forming more uniform and finer grains, thereby significantly improving the material's mechanical strength and creep resistance.

[0041] The polymer nucleating agent is added to the reaction system at the early stage of polymerization, so that it is uniformly distributed in the polypropylene matrix at the molecular level, avoiding the agglomeration problem caused by later addition. This makes the nucleation effect more efficient and controllable, the crystallization pattern more uniform, and improves the consistency of the material's microstructure. The product has small performance fluctuations between batches and high quality stability, making it suitable for large-scale industrial production.

[0042] In this invention, the co-catalyst is selected from one or more of triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum, diethylaluminum chloride, and methylaluminoxane (MAO), preferably triethylaluminum; the external electron donor is selected from alkoxysilanes, more preferably vinyltriethoxysilane, vinyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, diethyldimethoxysilane, dipropyldimethoxysilane, diisopropyldimethoxysilane, dibutyldimethoxysilane, diisobutyldimethoxysilane, di-tert-butyldimethoxysilane, di-tert-hexyldimethoxysilane, diphenyldimethoxysilane, dicyclohexyldimethoxysilane, and dicyclopentyldimethoxysilane. The product comprises one or more of the following: methoxysilane, dimethyldiethoxysilane, diethyldiethoxysilane, dipropyldiethoxysilane, diisopropyldiethoxysilane, dibutyldiethoxysilane, diisobutyldiethoxysilane, di-tert-butyldiethoxysilane, di-tert-hexyldiethoxysilane, diphenyldiethoxysilane, dicyclohexyldiethoxysilane, dicyclopentyldiethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, cyclopentylmethyldiethoxysilane, cyclopentyltrimethoxysilane, cyclohexylmethyldiethoxysilane, cyclohexyltrimethoxysilane, tert-hexyltrimethoxysilane, tert-butyltrimethoxysilane, and tert-hexyltrimethoxysilane. In this invention, the prepolymerization temperature is 0–20°C, and the prepolymerization residence time is 20–30 min.

[0043] This invention involves polymerizing the prepolymerized product, propylene, ethylene, and hydrogen to obtain polypropylene powder. In this invention, the concentration of hydrogen is 200-1000 ppm, specifically 200 ppm, 300 ppm, 400 ppm, 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, or 1000 ppm; the total flow rate of propylene and ethylene is 20-40 t / h, specifically 20 t / h, 25 t / h, 30 t / h, 35 t / h, or 40 t / h; and the polymerization temperature is 70-75℃, specifically 70℃, 71℃, 72℃, 73℃, 74℃, or 75℃.

[0044] After obtaining polypropylene powder, the polypropylene powder, propylene, ethylene, and hydrogen are further polymerized to obtain ethylene-propylene random copolymer polypropylene resin powder. The concentration of hydrogen is 200~1000ppm, specifically 200ppm, 300ppm, 400ppm, 500ppm, 600ppm, 700ppm, 800ppm, 900ppm, or 1000ppm; the total flow rate of propylene and ethylene is 10~20t / h, specifically 10t / h, 12t / h, 14t / h, 16t / h, 18t / h, or 20t / h; the polymerization temperature is 70~75℃, specifically 70℃, 71℃, 72℃, 73℃, 74℃, or 75℃.

[0045] This invention involves mixing the ethylene-propylene random copolymer polypropylene resin powder, a primary antioxidant, a co-antioxidant, and a halogen absorber, and then extruding the mixture to obtain a special material for random copolymer polypropylene pipes.

[0046] In this invention, the primary antioxidant is selected from one or more of antioxidant 2246, antioxidant 1010, antioxidant 1076, and antioxidant 1330; preferably antioxidant 1010. The co-antioxidant is selected from one or more of antioxidant 168, antioxidant 626, and antioxidant 9228, preferably antioxidant 168.

[0047] After being mixed, the materials are extruded using an extruder at temperatures ranging from 180℃ to 235℃ to 190℃, with a maximum temperature of 235℃. The resulting random copolymer polypropylene pipe material has a melt flow rate of 0.2~0.3 g / 10 min and an ethylene content of 3.0~4.0%, preferably 3.45%.

[0048] The random copolymer polypropylene pipe material prepared by this invention has a melting point of 143~144℃, significantly lower than the 145.5~147℃ of traditional technologies. Its notched impact strength for a simply supported beam at 23℃ is 65~70 kJ / m. 2 Compared to the traditional technology of 51~57 kJ / m2 It improves by approximately 14% to 37%; the oxidation induction time (OIT) reaches 54 to 66 minutes, which is better than the 35 to 45 minutes of the traditional technology, significantly improving the thermal and oxygen stability of the material, inhibiting aging and degradation during processing and use, ensuring long-term performance stability, and making it more suitable for long-term operation in high-temperature hot water environments; no damage or leakage was found in the hydrostatic test.

[0049] This invention also provides a random copolymer polypropylene pipe material prepared using a bifunctional catalytic system, wherein the raw materials comprise the following components by mass:

[0050] 100 parts of ethylene-propylene random copolymer polypropylene resin, 0.1-0.3 parts of main antioxidant, 0.1-0.3 parts of co-antioxidant, and 0.02-0.1 parts of halogen absorber;

[0051] The ethylene content in the ethylene-propylene random copolymer polypropylene resin is 3.0~4.0 wt%, and the melt index at 230℃ and 2.16 kg is 0.1~0.5 g / 10 min;

[0052] The raw materials for the prepolymerization stage of preparing ethylene-propylene random copolymer polypropylene resin include a bifunctional catalytic system, wherein the bifunctional catalytic system includes a polymeric nucleating agent selected from at least one of polyvinylcyclopentane, polyvinylcyclohexane, polyvinyl-2-methylcyclohexane, poly-3-methyl-1-butene, poly-3-ethyl-1-hexene, poly-3-methyl-1-pentene, and polystyrene.

[0053] The raw materials for preparing random copolymer polypropylene pipe material provided by this invention include 100 parts of ethylene-propylene random copolymer polypropylene resin; the ethylene-propylene random copolymer polypropylene resin is in powder form and is prepared by the method described in the above technical solution. The ethylene content in the ethylene-propylene random copolymer polypropylene resin is 3.0~4.0 wt%, specifically 3.1 wt%, 3.15 wt%, 3.2 wt%, 3.25 wt%, 3.3 wt%, 3.35 wt%, 3.4 wt%, 3.45 wt%, 3.5 wt%, 3.55 wt%, 3.6 wt%, 3.65 wt%, 3.7 wt%, 3.75 wt%, 3.8 wt%, 3.85 wt%, 3.9 wt%, 3.95 wt%, or 4.0 wt%; the melt index at 230℃ and 2.16 kg is 0.1~0.5 g / 10 min, preferably 0.2~0.3 g / 10 min.

[0054] The prepolymerization stage for preparing ethylene-propylene random copolymer polypropylene resin includes a polymeric nucleating agent, wherein the polymeric nucleating agent accounts for 0.0005~0.0020% of the mass of the ethylene-propylene random copolymer polypropylene resin, specifically 0.0005%, 0.001%, 0.0015%, or 0.002%. The polymeric nucleating agent is selected from at least one of polyvinylcyclopentane, polyvinylcyclohexane, polyvinyl-2-methylcyclohexane, poly-3-methyl-1-butene, poly-3-ethyl-1-hexene, poly-3-methyl-1-pentene, and polystyrene.

[0055] The raw materials for preparing random copolymer polypropylene pipe materials provided by this invention include 0.1 to 0.3 parts of a primary antioxidant, specifically 0.1, 0.15, 0.2, 0.25, or 0.3 parts. In this invention, the primary antioxidant is selected from one or more of antioxidants 2246, 1010, 1076, and 1330.

[0056] The raw materials for preparing random copolymer polypropylene pipes provided by this invention include 0.1 to 0.3 parts of an antioxidant, specifically 0.1, 0.15, 0.2, 0.25, or 0.3 parts. The antioxidant is selected from one or more of antioxidant 168, antioxidant 626, and antioxidant 9228.

[0057] The raw materials for preparing random copolymer polypropylene pipe materials provided by this invention include 0.02 to 0.1 parts of a halogen absorber, specifically 0.02 parts, 0.03 parts, 0.04 parts, 0.05 parts, 0.06 parts, 0.07 parts, 0.08 parts, 0.09 parts, or 0.1 parts. In this invention, the halogen absorber is selected from one or more of sodium stearate, calcium stearate, and zinc stearate.

[0058] This invention utilizes the aforementioned raw materials combined with a polymer nucleating agent, moving the process forward to the polymerization stage to introduce this technology. This allows the special material to improve its pressure resistance, impact resistance, and thermal stability while lowering its melting point.

[0059] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, of a special material for random copolymer polypropylene pipes using a bifunctional catalytic system and its preparation method, is provided by the present invention, but should not be construed as limiting the scope of protection of the present invention.

[0060] Unless otherwise specified, the experimental methods used in these examples are conventional methods, and the materials and reagents used are also standard.

[0061] Unless otherwise specified, all are available through commercial channels.

[0062] The testing method is as follows:

[0063] ① Melting point: Tested according to GB / T 19466.3-2004;

[0064] ②Notched impact strength of simply supported beam at 23℃: Tested according to GB / T 1043.1-2008;

[0065] ③Oxidation induction time: Tested according to GB / T 19466.6-2009;

[0066] ④ Hydrostatic test: The test shall be conducted in accordance with GB / T 6111-2003. The specific test conditions are 20℃ and 16MPa. After 1 hour of hydrostatic testing, observe whether the PPR pipe is cracked or leaking.

[0067] Example 1

[0068] A method for preparing a transparent polypropylene resin includes the following steps:

[0069] (1) Using the Spheripol polymerization process, propylene is prepolymerized under the combined action of ZN101 catalyst, polyvinylcyclohexane, triethylaluminum and methylcyclohexyldimethoxysilane, wherein the mass ratio of ZN101 catalyst to polyvinylcyclohexane (PVCH) is 1:0.2.

[0070] (2) The prepolymerized product, propylene and hydrogen obtained in step (1) are fed into the first loop reactor for polymerization reaction to obtain polypropylene powder. The hydrogen concentration in the first loop reactor is controlled to be 200 ppm, the total flow rate of ethylene and propylene is 30 t / h, and the reaction temperature is 72℃.

[0071] (3) The polypropylene powder, propylene and hydrogen obtained in step (2) are fed into the second loop reactor to continue the polymerization reaction to obtain polypropylene resin powder. The hydrogen in the second loop reactor is controlled.

[0072] The gas concentration is 200 ppm, the total flow rate of ethylene and propylene is 15 t / h, and the reaction temperature is 72℃;

[0073] (4) Mix the polypropylene resin powder, main antioxidant, auxiliary antioxidant and halogen absorber obtained in step (3) evenly to obtain a mixture, the formula of which is shown in Table 1.

[0074] (5) The mixture obtained in step (4) is extruded through an extruder, and the maximum temperature of the extruder barrel is controlled at 235℃ to prepare polypropylene resin. The performance test results and test methods are shown in Table 2.

[0075] Example 2

[0076] The preparation method is the same as in Example 1, except that the mass ratio of ZN101 catalyst to polyvinylcyclohexane is 1:0.4.

[0077] Example 3

[0078] The preparation method is the same as in Example 1, except that the mass ratio of ZN101 catalyst to polyvinylcyclohexane is 1:0.8.

[0079] Comparative Example 1

[0080] A method for preparing a transparent polypropylene resin includes the following steps:

[0081] (1) Using the Spheripol polymerization process, propylene is prepolymerized in the presence of ZN101 catalyst, triethylaluminum and methylcyclohexyldimethoxysilane;

[0082] (2) The prepolymerized product, propylene and hydrogen obtained in step (1) are fed into the first loop reactor for polymerization reaction to obtain polypropylene powder. The hydrogen concentration in the first loop reactor is controlled to be 200 ppm, the total flow rate of ethylene and propylene is 30 t / h, and the reaction temperature is 72℃.

[0083] (3) The polypropylene powder, propylene and hydrogen obtained in step (2) are fed into the second loop reactor to continue the polymerization reaction to obtain polypropylene resin powder. The hydrogen concentration in the second loop reactor is controlled to be 200 ppm, the total flow rate of ethylene and propylene is 15 t / h, and the reaction temperature is 72℃.

[0084] (4) Mix the polypropylene resin powder obtained in step (3), the main antioxidant, the co-antioxidant, the halogen absorber and 20 ppm polymer nucleating agent (PVCH) evenly to obtain a mixture, the formula of which is shown in Table 1.

[0085] (5) The mixture obtained in step (4) is extruded through an extruder, and the maximum temperature of the extruder barrel is controlled at 235℃ to prepare polypropylene resin. The performance test results and test methods are shown in Table 2.

[0086] Comparative Example 2

[0087] The preparation method is the same as that of Comparative Example 1, except that the polymer nucleating agent is replaced by nano-calcium carbonate, and the dosage is 20 ppm.

[0088] Comparative Example 3

[0089] The preparation method is the same as that of Comparative Example 1, except that the polymer nucleating agent is replaced by nano-calcium carbonate, and the dosage is 3000 ppm.

[0090] Comparative Example 4

[0091] The preparation method is the same as that of Comparative Example 1, except that no polymer nucleating agent is added in step (4).

[0092] Table 1

[0093]

[0094] Table 2

[0095]

[0096] As shown in the table above, comparing Examples 1-3 with Comparative Examples 1-4, it can be seen that adding the polymer nucleating agent during the polymerization stage can effectively improve the impact resistance, thermo-oxidative aging resistance, and pressure resistance of PP-R; at the same time, it can effectively reduce the melting point of the material. Comparing Example 3 with Comparative Example 1, it can be seen that adding the polymer nucleating agent during the processing and granulation stage has no significant effect on improving the material properties. Comparing Example 3 with Comparative Examples 2-3, it can be seen that the polymer nucleating agent significantly improves the material properties compared to traditional small-molecule nucleating agents. Comparing Examples 1-3 with Comparative Example 4, it can be seen that the use of the polymer nucleating agent can effectively reduce the melting point of the material and improve the pressure resistance of the product.

[0097] As can be seen from the above embodiments, this invention successfully solves the contradiction between the high melting point leading to high energy consumption and insufficient pressure resistance of traditional PP-R materials by introducing this core technological innovation by moving the polymer nucleating agent to the prepolymerization stage. While lowering the melting point, it simultaneously improves pressure resistance, impact resistance, and thermal stability, achieving synergistic performance optimization. It not only overcomes the technical bottleneck of uneven nucleating agent dispersion in traditional physical blending methods but also possesses good processing performance and industrial feasibility, demonstrating outstanding technological innovation and market application value.

[0098] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing random copolymer polypropylene pipe material using a bifunctional catalytic system, comprising the following steps: a) Using propylene as raw material, magnesium chloride-supported titanium tetrachloride catalyst as main catalyst, alkyl aluminum as co-catalyst, alkoxysilane as external electron donor, and polymer nucleating agent as functional additive, ethylene-propylene random copolymer polypropylene resin powder is prepared through a prepolymerization process, using hydrogen as molecular weight regulator and adding ethylene. b) The polypropylene resin powder, main antioxidant, co-antioxidant and halogen absorber are mixed and extruded to obtain random copolymer polypropylene pipe material.

2. The method according to claim 1, characterized in that, Step a) specifically includes: (a1) Propylene was prepolymerized under the combined action of magnesium chloride-supported titanium tetrachloride catalyst, polymer nucleating agent, co-catalyst and external electron donor to obtain prepolymerized product; (a2) The prepolymer product, propylene, ethylene and hydrogen are polymerized to obtain polypropylene powder; (a3) The polypropylene powder, propylene, ethylene and hydrogen are further polymerized to obtain ethylene-propylene random copolymer polypropylene resin powder.

3. The method according to claim 2, characterized in that, The magnesium chloride-supported titanium tetrachloride is selected from one or more of the following catalysts: ZN101 catalyst, ZN118 catalyst, ZN128M catalyst, HR catalyst, DQC401 catalyst, CS-2 catalyst, SP-2 catalyst, and SP-4 catalyst. The mass ratio of the main catalyst to the polymer nucleating agent is 1:0.2~8.

4. The method according to claim 2, characterized in that, In step (a2), the concentration of hydrogen is 200~1000ppm; The total flow rate of propylene and ethylene is 20~40 t / h; The polymerization reaction temperature is 70~75℃.

5. The method according to claim 2, characterized in that, In step (a3), the concentration of hydrogen is 200~1000ppm; The total flow rate of propylene and ethylene is 10~20 t / h; The polymerization reaction temperature is 70~75℃.

6. The method according to claim 1, characterized in that, The highest temperature used in the extrusion is 235°C.

7. The method according to claim 1, characterized in that, The melt flow rate of the random copolymer polypropylene pipe material is 0.2~0.3 g / 10 min, and the ethylene content is 3.0~4.0%.

8. A random copolymer polypropylene pipe material prepared using a bifunctional catalytic system, wherein the raw materials comprise the following components by mass parts: 100 parts of ethylene-propylene random copolymer polypropylene resin, 0.1-0.3 parts of main antioxidant, 0.1-0.3 parts of co-antioxidant, and 0.02-0.1 parts of halogen absorber; The ethylene content in the ethylene-propylene random copolymer polypropylene resin is 3.0~4.0 wt%, and the melt index at 230℃ and 2.16 kg is 0.1~0.5 g / 10 min; The raw materials for the prepolymerization stage of preparing ethylene-propylene random copolymer polypropylene resin include a bifunctional catalytic system, wherein the bifunctional catalytic system includes a polymeric nucleating agent selected from at least one of polyvinylcyclopentane, polyvinylcyclohexane, polyvinyl-2-methylcyclohexane, poly-3-methyl-1-butene, poly-3-ethyl-1-hexene, poly-3-methyl-1-pentene, and polystyrene.

9. The random copolymer polypropylene pipe material according to claim 8, characterized in that, The primary antioxidant is selected from one or more of antioxidant 2246, antioxidant 1010, antioxidant 1076, and antioxidant 1330; The antioxidant is selected from one or more of antioxidant 168, antioxidant 626 and antioxidant 9228.

10. The random copolymer polypropylene pipe material according to claim 8, characterized in that, The halogen absorber is selected from one or more of sodium stearate, calcium stearate, and zinc stearate.

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