MPP pipe and preparation method thereof
By grafting amino-hindered phenolic siloxane and KH-540 silane coupling agent onto polypropylene resin to functionalize nano-calcium carbonate, the flexibility and antioxidant properties of polypropylene materials were improved, the low-temperature brittleness and aging problems of conventional polypropylene materials were solved, and standard-compliant MPP pipes were prepared.
Patent Information
- Application Number
- CN202511471917.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-15
- Publication Date
- 2025-12-16
AI Technical Summary
Conventional polypropylene materials suffer from low-temperature brittleness, low impact strength and low elongation at break, and are prone to aging, leading to a gradual decline in the performance of PP pipes.
Modified polypropylene is formed by grafting amino-hindered phenolic siloxane and KH-540 silane coupling agent onto polypropylene resin to functionalize nano-calcium carbonate, thereby enhancing the material's flexibility and antioxidant properties and preparing MPP pipes.
The prepared MPP pipes exhibit excellent impact toughness and aging resistance, meeting the DL/T 802.7-2010 standard, and demonstrating excellent overall performance.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of cable conduit technology, specifically to an MPP pipe and its preparation method. Background Technology
[0002] Polypropylene (PP) has become the mainstream material for manufacturing cable conduits due to its non-toxic, lightweight, corrosion-resistant, excellent electrical insulation, and ease of processing properties. PP pipes are widely used for the protection of underground cables and communication lines, effectively resisting external mechanical damage, chemical corrosion, and the effects of humid environments, thereby extending the service life of the cables.
[0003] However, conventional polypropylene materials generally suffer from problems such as low-temperature brittleness, low impact strength, and low elongation at break. Furthermore, the presence of tertiary carbon atoms in the polypropylene structure makes it prone to chain oxidation reactions that cause aging, resulting in poor impact toughness and aging resistance in PP pipes, leading to a gradual decline in performance after long-term use. Therefore, the development of modified polypropylene materials (MPP materials) and modified polypropylene pipes (MPP pipes) is of great significance.
[0004] Research has found that the relatively long bond length and large bond angle of the silicon-oxygen bond (Si-O) result in high rotational freedom. This structure allows molecular chains containing silicon-oxygen bonds to maintain flexibility at low temperatures, preventing them from becoming brittle due to restricted molecular motion. Existing technologies have reported the use of materials with flexible silicon-oxygen chains to improve the impact toughness of polypropylene. Furthermore, nano-calcium carbonate, an inorganic nanoparticle with toughening and reinforcing functions, forms stress concentrations within the polypropylene matrix, thereby generating localized plastic shear bands that significantly improve the toughness of polypropylene materials.
[0005] Hindered phenols are a class of organic compounds with significant antioxidant capabilities and are widely used in polymer materials such as polypropylene. However, commonly used hindered phenol antioxidants are usually small molecules, and direct addition can easily lead to migration risks. Summary of the Invention
[0006] This invention develops a compound containing flexible silica chains and hindered phenolic groups based on molecular design. The compound and nano-calcium carbonate are then grafted onto the polypropylene resin molecular chain through chemical bonding. The resulting MPP pipe exhibits excellent impact toughness and aging resistance, and meets the technical requirements specified in DL / T 802.7-2010 "Technical Conditions for Conduits for Power Cables Part 7: Modified Polypropylene Plastic Cable Conduits for Trenchless Construction" standard.
[0007] An MPP pipe, wherein the raw material formula used in the manufacture of the MPP pipe is as follows:
[0008] 50-70 parts by weight of polypropylene resin;
[0009] 30-50 parts by weight of modified polypropylene;
[0010] The modified polypropylene consists of component I and component II. Component I is prepared by modifying maleic anhydride-grafted polypropylene resin with amino-hindered phenolic siloxane through an amidation reaction of amino-acid anhydride. Component II is prepared by modifying maleic anhydride-grafted polypropylene resin with KH-540 silane coupling agent-functionalized nano-calcium carbonate through an amidation reaction of amino-acid anhydride.
[0011] Preferably, the mass ratio of amino-hindered phenolic siloxane to maleic anhydride-grafted polypropylene resin in component I is 1:(1-2).
[0012] Preferably, the mass ratio of KH-540 silane coupling agent functionalized nano-calcium carbonate to maleic anhydride grafted polypropylene resin in component II is 1:(6-10).
[0013] Preferably, the mass ratio of component I to component II in the modified polypropylene is 1:(0.8-1.2).
[0014] A method for preparing an MPP pipe includes the following steps:
[0015] Step 1: Prepare amino-hindered phenolic siloxane and KH-540 silane coupling agent functionalized nano-calcium carbonate, modify maleic anhydride-grafted polypropylene resin with amino-hindered phenolic siloxane to obtain component I, and modify maleic anhydride-grafted polypropylene resin with KH-540 silane coupling agent functionalized nano-calcium carbonate to obtain component II.
[0016] Step 2: According to the MPP pipe formula, first add component I and component II into the high-speed mixer and mix evenly to obtain modified polypropylene. Then add polypropylene resin into the high-speed mixer and stir evenly to obtain premix.
[0017] Step 3: Add the premix to a twin-screw extruder, and extrude and granulate the mixture to obtain the MPP composite material;
[0018] Step 4: Add the MPP composite material into the pipe extruder and extrude it to obtain an MPP pipe with a nominal inner diameter of 90-110mm and a nominal wall thickness of 7-9mm.
[0019] Preferably, the method for preparing the amino-hindered phenolic siloxane is as follows:
[0020] Intermediate 1 is generated by an addition reaction between the Si-H functional group of 1 molar equivalent 1,1,5,5-tetramethyl-3,3-diphenyltrisiloxane and the alkenyl functional group of 2.01-2.09 molar equivalent vinyldimethylethoxysilane.
[0021] Based on the silanol condensation reaction mechanism, intermediate 2 is generated by the condensation reaction of 1 molar equivalent intermediate 1 with 2.01-2.09 molar equivalents of (3-aminopropyl)dimethylethoxysilane.
[0022] An amidation reaction is carried out via 1 molar equivalent of the amino functional group of intermediate 2 and 0.91-0.95 molar equivalents of the carboxyl functional group of 3,5-di-tert-butyl-4-hydroxybenzoic acid to generate an amino-hindered phenolic siloxane.
[0023] Preferably, the preparation method of KH-540 silane coupling agent functionalized nano-calcium carbonate is as follows: 3-8 parts by weight of nano-calcium carbonate are surface modified with 0.5-2 parts by weight of KH-540 silane coupling agent, and the silanol functional groups obtained by the hydrolysis reaction of KH-540 silane coupling agent undergo a dehydration condensation reaction with the hydroxyl functional groups on the surface of nano-calcium carbonate to obtain KH-540 silane coupling agent functionalized nano-calcium carbonate.
[0024] Preferably, the particle size of the nano-calcium carbonate is 80-120 nm.
[0025] Preferably, the temperatures of zones 1-6 of the twin-screw extruder in step three are set to 125-135℃, 140-160℃, 150-170℃, 170-185℃, 190-200℃, and 185-195℃, respectively.
[0026] Preferably, the process parameters of the pipe extruder in step four are set as follows: the temperatures of zones 1-5 of the barrel are 160-180℃, 170-185℃, 180-195℃, 200-210℃, and 190-205℃, respectively, and the temperatures of zones 1-3 of the die head are 190-205℃, 200-215℃, and 190-200℃, respectively.
[0027] An MPP pipe is used as a cable conduit.
[0028] Beneficial effects:
[0029] This invention uses 1,1,5,5-tetramethyl-3,3-diphenyltrisiloxane, vinyldimethylethoxysilane, (3-aminopropyl)dimethylethoxysilane and 3,5-di-tert-butyl-4-hydroxybenzoic acid as raw materials to synthesize amino-hindered phenolic siloxanes through hydrosilylation, silanol condensation and amidation reactions.
[0030] Component I was prepared by modifying maleic anhydride-grafted polypropylene resin with amino-hindered phenolic siloxane via an amidation reaction of amino-acid anhydride.
[0031] Component II was prepared by functionalizing nano-calcium carbonate with KH-540 silane coupling agent and modifying maleic anhydride-grafted polypropylene resin by amidation reaction of amino-anhydride.
[0032] Modified polypropylene is obtained by uniformly mixing component I and component II, and then adding modified polypropylene to the polypropylene resin matrix. The mixture is premixed in a high-speed mixer, extruded and granulated in a twin-screw extruder, and extruded and molded in a pipe extruder to obtain MPP pipe.
[0033] The performance test results show that the MPP pipe prepared by this invention has excellent impact toughness and aging resistance, and all properties meet the technical requirements specified in DL / T 802.7-2010 standard. It has excellent comprehensive performance and practical application value. Detailed Implementation
[0034] Example 1:
[0035] The synthesis process of amino-hindered phenolic siloxanes is as follows:
[0036] Process 1: An addition reaction occurs between the Si-H functional group of 1 molar equivalent of 1,1,5,5-tetramethyl-3,3-diphenyltrisiloxane and the alkenyl functional group of 2.05 molar equivalent of vinyldimethylethoxysilane to generate intermediate 1, whose chemical structural formula is as follows:
[0037] ;
[0038] Process 2: Based on the silanol condensation reaction mechanism, intermediate 2 is generated by the condensation reaction of 1 molar equivalent of intermediate 1 and 2.02 molar equivalents of (3-aminopropyl)dimethylethoxysilane. Its chemical structural formula is as follows:
[0039] ;
[0040] Process 3: An amidation reaction occurs between the amino functional group of 1 molar equivalent intermediate 2 and the carboxyl functional group of 0.93 molar equivalent 3,5-di-tert-butyl-4-hydroxybenzoic acid, yielding an amino-hindered phenolic siloxane with the following chemical structural formula:
[0041] ;
[0042] The specific experimental steps for synthesizing amino-hindered phenolic siloxanes are as follows:
[0043] Under nitrogen protection, 3.3 g of 1,1,5,5-tetramethyl-3,3-diphenyltrisiloxane and 30 mL of anhydrous tetrahydrofuran were added to a three-necked flask and stirred at room temperature until completely dissolved. Then, 20 mL of anhydrous tetrahydrofuran solution containing 2.7 g of vinyldimethylethoxysilane and 5 drops of caster catalyst were added to the three-necked flask. The mixture was heated to 70 °C and stirred for 6 h. After cooling to room temperature, activated carbon was added to absorb and remove the caster catalyst, the mixture was filtered, the solvent was removed by rotary evaporation, and the mixture was dried under vacuum to obtain intermediate 1.
[0044] 3.0 g of intermediate 1, 30 mL of anhydrous tetrahydrofuran, and 10 mL of deionized water were added to a three-necked flask and stirred at room temperature for 30 min. Then, 20 mL of (3-aminopropyl)dimethylethoxysilane solution (prepared from 1.6 g of (3-aminopropyl)dimethylethoxysilane, 15 mL of anhydrous tetrahydrofuran, and 5 mL of deionized water) and 1.5 mL of glacial acetic acid were added to the three-necked flask. The mixture was heated to 60 °C and stirred for 8 h. After cooling to room temperature, the solvent was removed by rotary evaporation and dried under vacuum to obtain intermediate 2.
[0045] Under nitrogen protection, 2.6 g of intermediate 2, 0.8 g of 3,5-di-tert-butyl-4-hydroxybenzoic acid and 30 mL of anhydrous tetrahydrofuran were added to a three-necked flask equipped with a water separator. The mixture was stirred at room temperature for 30 min. Then, 10 mL of N,N-dimethylformamide solution containing 0.8 g of N,N'-dicyclohexylcarbodiimide catalyst was added to the three-necked flask. The mixture was heated to 70 °C and stirred for 8 h. After cooling to room temperature, the solvent was removed by rotary evaporation. The mixture was washed with dichloromethane and dried under vacuum to obtain amino-hindered phenolic siloxane.
[0046] The 1H NMR characterization of amino-hindered phenolic siloxanes is as follows: 1 H NMR (DMSO-d6, 400MHz) δ: 0.02 (s, 12H), 0.06 (s, 12H), 0.12 (s, 12H), 0.71-0.76 (m, 8H), 0.83-0.86 (t, 4H), 1.40 (s, 18H), 1.45-1.52 (m, 2H), 1.56- 1.64 (m, 2H), 1.73-1.77 (t, 2H), 2.63-2.69 (m, 2H), 3.15-3.20 (m, 2H), 6.75 (s, 1H), 7.28-7.55 (m, 12H), 8.25-8.28 (t, 1H).
[0047] Example 2:
[0048] Preparation of KH-540 silane coupling agent functionalized nano-calcium carbonate: Nano-calcium carbonate was surface-modified using KH-540 silane coupling agent. The silanol functional groups obtained from the hydrolysis of KH-540 silane coupling agent underwent a dehydration condensation reaction with the hydroxyl functional groups on the surface of the nano-calcium carbonate, yielding KH-540 silane coupling agent functionalized nano-calcium carbonate. The specific preparation steps were as follows: 5g of hydrophilic nano-calcium carbonate powder (particle size 80-120nm), 20mL of... Ionized water and 80 mL of ethanol were added to a three-necked flask, ultrasonically dispersed for 1 h, and stirred at room temperature for 2 h. Then, 10 mL of KH-540 silane coupling agent solution (prepared from 1 g KH-540 silane coupling agent, 8 mL of ethanol and 2 mL of deionized water) and two drops of glacial acetic acid were added to the three-necked flask. The mixture was heated to 60 °C and stirred for 4 h. After cooling to room temperature, the mixture was centrifuged and separated. The mixture was repeatedly washed with deionized water, centrifuged, and dried under vacuum to obtain KH-540 silane coupling agent functionalized nano-calcium carbonate.
[0049] Example 3:
[0050] Preparation of Component I: Maleic anhydride-grafted polypropylene resin was modified by amino-hindered phenolic siloxane. Component I was obtained by amidation reaction between the amino functional groups of the amino monomer and the anhydride groups on the molecular side chains of the maleic anhydride-grafted polypropylene resin.
[0051] The specific experimental steps for preparing component I are as follows: 6g of maleic anhydride-grafted polypropylene resin (model QF500T), 4g of amino-hindered phenolic siloxane and 0.5g of triethylamine catalyst are added into a twin-screw extruder through the feed port. After melting and processing in the twin-screw extruder for 10 minutes, the mixture is extruded and granulated to obtain component I.
[0052] The process parameters of the twin-screw extruder are set as follows: the temperatures of sections 1-6 are 170℃, 180℃, 185℃, 185℃, 190℃, and 185℃, respectively, and the rotation speed is 100r / min.
[0053] Example 4:
[0054] Preparation of Component II: Maleic anhydride-grafted polypropylene resin was modified by functionalizing nano-calcium carbonate with KH-540 silane coupling agent. Component II was obtained by amidation reaction between the amino functional groups on the surface of the KH-540 silane coupling agent-functionalized nano-calcium carbonate and the anhydride groups on the molecular side chains of the maleic anhydride-grafted polypropylene resin.
[0055] The specific experimental steps for preparing component II are as follows: 9g of maleic anhydride-grafted polypropylene resin (model QF500T), 1g of KH-540 silane coupling agent functionalized nano-calcium carbonate and 0.5g of triethylamine catalyst are added into a twin-screw extruder through the feed port. After being melt-processed in the twin-screw extruder for 10 minutes, the mixture is extruded and granulated to obtain component II.
[0056] The process parameters of the twin-screw extruder are set as follows: the temperatures of sections 1-6 are 170℃, 180℃, 190℃, 195℃, 195℃, and 190℃, respectively, and the rotation speed is 150r / min.
[0057] Example 5:
[0058] An MPP pipe material I, the raw material formula used in its manufacturing is as follows:
[0059] 60 parts by weight of polypropylene resin (model J340);
[0060] 40 parts by weight of modified polypropylene;
[0061] The 40 parts by weight of modified polypropylene consists of 20 parts by weight of component I and 20 parts by weight of component II.
[0062] Example 6:
[0063] A method for preparing an MPP pipe I includes the following steps:
[0064] Step 1: According to the formula of MPP pipe I, first add component I and component II into the high-speed mixer and stir at room temperature for 10 minutes at a speed of 150 r / min to obtain modified polypropylene. Then add polypropylene resin into the high-speed mixer and stir at room temperature for 30 minutes at a speed of 150 r / min to obtain premix.
[0065] Step 2: Add the premixed material prepared in Step 1 into a twin-screw extruder. Set the temperatures of zones 1-6 of the twin-screw extruder to 130℃, 150℃, 160℃, 180℃, 195℃, and 190℃, respectively, and set the rotation speed to 200 r / min. Extrude and granulate the material through the twin-screw extruder to obtain MPP composite material I.
[0066] Step 3: Add the MPP composite material I prepared in Step 2 into the pipe extruder. The process parameters of the pipe extruder are set as follows: the temperatures of zones 1-5 of the barrel are 170℃, 180℃, 190℃, 205℃, and 200℃, respectively; the temperatures of zones 1-3 of the die head are 200℃, 210℃, and 195℃, respectively. The pipe is extruded and formed by the pipe extruder at a speed of 0.5m / min to obtain MPP pipe I with a nominal inner diameter of 100mm and a nominal wall thickness of 8mm.
[0067] Example 7:
[0068] An MPP pipe II is manufactured using the following raw material formula:
[0069] 50 parts by weight of polypropylene resin (model J340);
[0070] 50 parts by weight of modified polypropylene;
[0071] Among them, 50 parts by weight of modified polypropylene consists of 25 parts by weight of component I and 25 parts by weight of component II;
[0072] The preparation methods of MPP composite material II and MPP pipe II are the same as those of MPP composite material I and MPP pipe I in Example 6.
[0073] Example 8:
[0074] An MPP pipe material III, the raw material formula used in its manufacture is as follows:
[0075] 70 parts by weight of polypropylene resin (model J340);
[0076] 30 parts by weight of modified polypropylene;
[0077] Among them, 30 parts by weight of modified polypropylene consists of 15 parts by weight of component I and 15 parts by weight of component II;
[0078] The preparation methods of MPP composite material III and MPP pipe III are the same as those of MPP composite material I and MPP pipe I in Example 6.
[0079] Performance testing:
[0080] 1. The MPP composite material was dried in a 100℃ oven for 5 hours to remove moisture. Then, it was injection molded into standard test specimens using an injection molding machine (the temperatures of zones 1-3 of the barrel were 170℃, 190℃, and 205℃, respectively; the mold temperature was 60℃; and the injection pressure was 60MPa). The following performance tests were then conducted:
[0081] (1) Impact toughness test: According to GB / T 1043.1-2008 "Determination of impact performance of plastic simply supported beams - Part 1: Non-instrumental impact test", a type 1 specimen with an A-notch was used for lateral impact test, and the initial impact strength of the specimen was recorded.
[0082] (2) Antioxidant performance test: The antioxidant capacity of the sample was characterized by DPPH free radical scavenging rate. The specific test steps are as follows: The 80mm×10mm×4mm sample was placed in a brown sample bottle containing 40mL of methanol and soaked for 7 days to obtain the sample soaking solution. 3mL of the sample soaking solution and 1mL of 10% methanol were taken. 3 A mol / L DPPH methanol solution was thoroughly mixed and allowed to stand in the dark for 24 hours. The absorbance of the reaction solution system at 517 nm was then measured. The absorbance of the DPPH methanol solution was measured using the same method, and the DPPH free radical scavenging rate was calculated. The specific method is as follows:
[0083] DPPH free radical scavenging rate (%) = (absorbance of DPPH methanol solution - absorbance of the mixture of sample soaking solution and DPPH methanol solution) / absorbance of DPPH methanol solution × 100%;
[0084] (3) Aging resistance test: The sample was placed in a 60℃ constant temperature drying oven and kept for 240h. After that, it was taken out and placed at room temperature for 24h. According to GB / T 1043.1-2008 "Determination of impact properties of simply supported plastic beams - Part 1: Non-instrumental impact test", a type 1 specimen with an A-notch was used to conduct a lateral impact test. The impact strength of the sample was recorded, and the change rate of impact strength of the sample after 240h treatment at 60℃ was calculated. The specific method is as follows:
[0085] Impact strength change rate (%) = (initial impact strength - impact strength after treatment at 60℃ for 240h) / initial impact strength × 100%;
[0086] The performance test results are shown in Table 1 below.
[0087] Table 1 Performance test results of MPP composite materials
[0088] Product Type <![CDATA[Impact strength (kJ / m 2 )]]> DPPH free radical scavenging rate (%) Impact strength change rate (%) after treatment at 60℃ for 240h MPP composite material I 20.7 66.8 8.1 MPP composite material II 23.6 71.4 5.7 MPP composite material III 17.2 63.5 11.9 Comparative Example 4.9 1.6 76.0
[0089] Note: The only difference between the comparative example and MPP composite material I is that the formulation is 100 parts of polypropylene resin (model J340).
[0090] The following conclusions can be drawn from the analysis of the performance experiment results in Table 1:
[0091] The present invention utilizes a modified polypropylene material developed in-house to prepare an MPP composite material, which, compared with conventional polypropylene material, achieves significant improvements in impact toughness, oxidation resistance, and aging resistance.
[0092] II. The performance of MPP pipes was tested according to DL / T 802.7-2010 "Technical Conditions for Conduits for Power Cables Part 7: Modified Polypropylene Plastic Conduits for Trenchless Applications" standard. The test results are shown in Table 2 below.
[0093] Table 2 Performance test results of MPP pipes
[0094] Product Type Ring stiffness (kPa) Flattening test Drop hammer impact Tensile strength (MPa) Elongation at break (%) Bending strength (MPa) Thermo-oxidative stability (min) MPP Pipe I 39.5 No cracks or breaks were found. No cracks or breaks were found. 31.9 543 47.0 85 MPP Pipe II 35.4 No cracks or breaks were found. No cracks or breaks were found. 30.5 561 45.6 98 MPP Pipes III 41.3 No cracks or breaks were found. No cracks or breaks were found. 33.6 507 49.2 74 Technical Requirements ≥32kPa The sample did not show cracks or breakage. The sample did not show cracks or breakage. ≥25MPa ≥400% ≥36MPa At 200℃, ≥50 min
[0095] Based on the performance test results in Table 2, the following conclusions can be drawn:
[0096] The MPP pipes prepared by this invention meet all the technical requirements specified in the DL / T 802.7-2010 standard, and have superior overall performance, making them valuable for practical applications.
Claims
1. An MPP pipe, characterized in that, The raw material formula used in the manufacturing of the MPP pipe is as follows: 50-70 parts by weight of polypropylene resin; 30-50 parts by weight of modified polypropylene; The modified polypropylene consists of component I and component II. Component I is prepared by modifying maleic anhydride-grafted polypropylene resin with amino-hindered phenolic siloxane through an amidation reaction of amino-acid anhydride. Component II is prepared by modifying maleic anhydride-grafted polypropylene resin with KH-540 silane coupling agent-functionalized nano-calcium carbonate through an amidation reaction of amino-acid anhydride. The chemical structural formula of the amino-hindered phenolic siloxane is: 。 2. The MPP pipe according to claim 1, characterized in that, The mass ratio of amino-hindered phenolic siloxane to maleic anhydride-grafted polypropylene resin in component I is 1:(1-2).
3. The MPP pipe according to claim 1, characterized in that, The mass ratio of KH-540 silane coupling agent-functionalized nano-calcium carbonate to maleic anhydride-grafted polypropylene resin in component II is 1:(6-10).
4. The MPP pipe according to claim 1, characterized in that, The mass ratio of component I to component II in the modified polypropylene is 1:(0.8-1.2).
5. A method for preparing an MPP pipe according to any one of claims 1-4, characterized in that, Includes the following steps: Step 1: Prepare amino-hindered phenolic siloxane and KH-540 silane coupling agent functionalized nano-calcium carbonate, modify maleic anhydride-grafted polypropylene resin with amino-hindered phenolic siloxane to obtain component I, and modify maleic anhydride-grafted polypropylene resin with KH-540 silane coupling agent functionalized nano-calcium carbonate to obtain component II. Step 2: According to the MPP pipe formula, first add component I and component II into the high-speed mixer and mix evenly to obtain modified polypropylene. Then add polypropylene resin into the high-speed mixer and stir evenly to obtain premix. Step 3: Add the premix to a twin-screw extruder, and extrude and granulate the mixture to obtain the MPP composite material; Step 4: Add the MPP composite material into the pipe extruder and extrude it to obtain an MPP pipe with a nominal inner diameter of 90-110mm and a nominal wall thickness of 7-9mm.
6. The method for preparing an MPP pipe according to claim 5, characterized in that, The method for preparing the amino-hindered phenolic siloxane is as follows: Intermediate 1 is generated by an addition reaction between the Si-H functional group of 1 molar equivalent 1,1,5,5-tetramethyl-3,3-diphenyltrisiloxane and the alkenyl functional group of 2.01-2.09 molar equivalent vinyldimethylethoxysilane. Based on the silanol condensation reaction mechanism, intermediate 2 is generated by the condensation reaction of 1 molar equivalent intermediate 1 with 2.01-2.09 molar equivalents of (3-aminopropyl)dimethylethoxysilane. An amidation reaction is carried out via 1 molar equivalent of the amino functional group of intermediate 2 and 0.91-0.95 molar equivalents of the carboxyl functional group of 3,5-di-tert-butyl-4-hydroxybenzoic acid to generate an amino-hindered phenolic siloxane.
7. The method for preparing an MPP pipe according to claim 5, characterized in that, The preparation method of KH-540 silane coupling agent functionalized nano-calcium carbonate is as follows: 0.5-2 parts by weight of KH-540 silane coupling agent are used to modify the surface of 3-8 parts by weight of nano-calcium carbonate. The silanol functional groups obtained by the hydrolysis reaction of KH-540 silane coupling agent undergo a dehydration condensation reaction with the hydroxyl functional groups on the surface of nano-calcium carbonate to obtain KH-540 silane coupling agent functionalized nano-calcium carbonate.
8. The method for preparing an MPP pipe according to claim 7, characterized in that, The particle size of the nano-calcium carbonate is 80-120 nm.
9. The method for preparing an MPP pipe according to claim 5, characterized in that, In step three, the temperatures of zones 1-6 of the twin-screw extruder are set to 125-135℃, 140-160℃, 150-170℃, 170-185℃, 190-200℃, and 185-195℃, respectively. In step four, the process parameters of the pipe extruder are set as follows: the temperatures of zones 1-5 of the barrel are 160-180℃, 170-185℃, 180-195℃, 200-210℃, and 190-205℃, respectively; and the temperatures of zones 1-3 of the die head are 190-205℃, 200-215℃, and 190-200℃, respectively.
10. The application of an MPP pipe according to any one of claims 1-4, characterized in that, The MPP tubing is used as a cable conduit.