MPP power cable protection pipe and production process thereof

Abstract

This invention relates to an MPP power cable protection pipe and its manufacturing process, belonging to the field of composite material technology. The invention prepares a macromolecular flame-retardant modifier containing phosphate groups in its structure, and utilizes the reaction of the phosphate groups in this flame-retardant modifier with calcium ions on the surface of nano-calcium carbonate to coat and modify the nano-calcium carbonate, thus preparing a modified nano-calcium carbonate with a "core-shell structure". This modification method can encapsulate the highly polar phosphate groups and the hydrophilic nano-calcium carbonate core within a low-polarity borosilicate-organic shell, significantly reducing the overall surface polarity of the modified nano-calcium carbonate. This not only greatly improves the dispersibility of nano-calcium carbonate in the modified polypropylene matrix, effectively reducing the risk of agglomeration, but also effectively alleviates the phase separation problem caused by the large polarity difference between the added phosphate ester flame retardant and the polypropylene matrix, thereby improving the overall mechanical properties of the protection pipe.

Description

Technical Field

[0001] This invention belongs to the field of composite material technology, specifically relating to an MPP power cable protection pipe and its manufacturing process. Background Technology

[0002] With the rapid development of power grid construction and municipal renovation projects in my country, the demand for power cable protection pipes, as an important supporting facility for underground cable laying, is increasing day by day. MPP (modified polypropylene) power cable protection pipes are widely used in the laying and protection of high-voltage power transmission lines due to their advantages such as good insulation performance, corrosion resistance, low coefficient of friction, and convenient construction.

[0003] During long-term operation, especially under overload or short-circuit faults, power cables generate a large amount of heat, which can cause a rapid increase in the temperature of the cable itself and the surrounding environment, posing a fire hazard. Therefore, stringent requirements are placed on the flame-retardant performance of MPP power cable protection pipes. While halogenated flame retardants have high flame-retardant efficiency, they produce large amounts of smoke and toxic, corrosive hydrogen halide gases during combustion, posing a serious threat to environmental safety and personnel escape, and their use is gradually being restricted. Inorganic flame retardants, although environmentally friendly and non-toxic, typically require extremely high dosages to achieve the desired flame-retardant effect. This often severely degrades the mechanical properties of the polypropylene matrix, leading to decreased pipe toughness, processing difficulties, and making it difficult to meet the rigidity and compressive strength requirements of power cable protection pipes. Phosphate ester flame retardants have the advantages of being safe and environmentally friendly, and requiring low dosage. However, there is a significant difference in polarity between phosphate ester flame retardants and the polypropylene matrix. This not only leads to phase separation within the polypropylene matrix, affecting the overall mechanical properties of the polypropylene matrix, but also greatly increases the difficulty of dispersing the reinforcing fillers in the polypropylene matrix. To address these technical defects, this invention provides an MPP power cable protection pipe and its manufacturing process. Summary of the Invention

[0004] The purpose of this invention is to provide an MPP power cable protection pipe and its manufacturing process to solve the problems mentioned in the background art.

[0005] The objective of this invention can be achieved through the following technical solutions: An MPP power cable protection pipe comprises the following raw materials in parts by weight: 100 parts polypropylene masterbatch, 40-50 parts modified nano calcium carbonate, 0.3-0.6 parts initiator, 0.5-1 part antioxidant, and 0.8-1.5 parts lubricant. Furthermore, the initiator is at least one of di-tert-butyl peroxide and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane.

[0006] Furthermore, the antioxidant is at least one of antioxidant 1010, antioxidant 1035, antioxidant 168, and antioxidant 626.

[0007] Furthermore, the lubricant is at least one of polyethylene wax, polypropylene wax, and oxidized polyethylene wax.

[0008] Furthermore, the modified nano-calcium carbonate can be prepared by the following steps: S1. A flame retardant modifier precursor is obtained by condensing p-aminophenylboronic acid with allyltriethoxysilane. The reaction process is as follows: 16.8–32.2 parts by mass of p-aminophenylboronic acid, 10–16 parts of allyltriethoxysilane, and 80–144 parts of cyclopentyl methyl ether are mixed in a reaction vessel and reacted at 80–100 °C for 4–8 h. After the reaction is completed, the solvent is removed by rotary evaporation of the reaction solution, and the remaining solid is purified by recrystallization (recrystallization solvent: anhydrous ethanol: n-hexane = 2:8) to obtain the flame retardant modifier precursor.

[0009] S2. The flame retardant modifier precursor is obtained by hydrolysis after undergoing a phosphoramidation reaction with phosphorus oxychloride. The reaction process is as follows: By mass, 12-18 parts of phosphorus oxychloride, 8-12 parts of triethylamine, and 60-90 parts of tetrahydrofuran are mixed in a reaction vessel under ice-water bath conditions. A solution prepared by 14-20 parts of flame retardant modifier precursor and 56-80 parts of tetrahydrofuran is added dropwise to the system. After the addition is complete, the reaction is continued under ice-water bath conditions for 10-30 minutes. After the reaction is completed, the ice-water bath is removed, and 12-18 parts of deionized water are added to the system. After hydrolysis at a temperature of 5-15℃ for 30-60 minutes, the reaction solution is poured into deionized water to precipitate. After filtering to separate the precipitate, the precipitate is washed with deionized water and dried to obtain the flame retardant modifier.

[0010] S3. Modified nano-calcium carbonate is obtained by loading a flame retardant modifier onto the surface of nano-calcium carbonate. The reaction process is as follows: 40-50 nano-calcium carbonate, 10-12 parts of flame retardant modifier, and 320-400 parts of anhydrous ethanol are mixed in a reaction vessel and reacted at 60-80℃ for 50-90 minutes. After the reaction is completed, the solid is filtered out, dried, and ground and dispersed to obtain modified nano-calcium carbonate.

[0011] Furthermore, the coating rate of the modified nano-calcium carbonate is 13.6–16.2 ​​wt%.

[0012] The present invention also provides a manufacturing process for the MPP power cable protection pipe.

[0013] A manufacturing process for an MPP power cable protection pipe includes the following steps: The MPP power cable protection pipe is obtained by mixing polypropylene masterbatch, modified nano calcium carbonate, initiator, antioxidant, and lubricant, adding it to a twin-screw extruder, melt extruding it, and then vacuum cooling and shaping it in a die.

[0014] Furthermore, the parameters for the melt extrusion are an extrusion temperature of 210–230°C and a screw speed of 35–45 r / min.

[0015] Furthermore, the parameters for vacuum cooling and shaping are: cooling water temperature of 30–40°C, vacuum degree of 0.3–0.4 MPa, and shaping time of 5–10 min.

[0016] In summary, the present invention has at least the following beneficial effects: 1) This invention prepares a macromolecular flame retardant modifier integrating four flame retardant elements: phosphorus, silicon, boron, and nitrogen. The phosphate groups in the flame retardant modifier react with calcium ions on the surface of nano-calcium carbonate to coat the nano-calcium carbonate, resulting in modified nano-calcium carbonate with a "core-shell structure." This modification method encapsulates the highly polar phosphate groups and the hydrophilic nano-calcium carbonate core within a low-polarity borosilicate-organic shell, significantly reducing the overall surface polarity of the modified nano-calcium carbonate. This not only greatly improves the dispersibility of nano-calcium carbonate in the modified polypropylene matrix, effectively reducing the risk of agglomeration, but also effectively alleviates the phase separation problem caused by the large polarity difference between the added phosphate ester flame retardant and the polypropylene matrix, thereby improving the overall mechanical properties of the protective tube.

[0017] 2) The flame retardant modifier introduced in this invention contains four highly synergistic flame retardant elements: phosphorus, silicon, boron, and nitrogen. During combustion, these elements work synergistically to promote rapid char formation in the polymer matrix and the formation of a dense and stable expanded char layer, thereby more effectively blocking heat transfer and oxygen contact. This multi-element synergistic mechanism allows for achieving high-level flame retardant standards with relatively low addition amounts, minimizing the impact on the original properties of the matrix while achieving excellent flame retardant effects.

[0018] 3) The modified nano-calcium carbonate prepared in this invention introduces reactive double bonds on its surface. Under the action of an initiator, these double bonds can be grafted onto the polypropylene molecular chain via free radical polymerization, establishing a strong chemical bond interface between the inorganic filler and the organic matrix. This chemical connection changes the interface state of traditional fillers that rely solely on physical blending. When the protective tube is subjected to external impact or load, stress can be efficiently transferred from the flexible polypropylene matrix to the rigid nano-calcium carbonate particles, fully utilizing the reinforcing effect of the nanoparticles and effectively improving the rigidity and mechanical properties of the protective tube. Detailed Implementation

[0019] This invention provides an MPP power cable protection pipe and its manufacturing process. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve the desired result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and fall within the scope of this invention. The methods and applications of this invention have been described through preferred embodiments. Those skilled in the art can clearly modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0020] It should be understood that the expression “one or more of…” individually includes each of the objects described after the expression, as well as various different combinations of two or more of the described objects, unless otherwise understood from the context and usage. The expression “and / or” combined with three or more described objects should be understood to have the same meaning, unless otherwise understood from the context.

[0021] The terms “including,” “having,” or “containing,” including the use of their grammatical synonyms, should generally be understood as open-ended and non-restrictive, for example, not excluding other unstated elements or steps, unless otherwise specifically stated or understood from the context.

[0022] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural.

[0023] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items.

[0024] It should be understood that the order of the steps or the order in which certain actions are performed is not important as long as the invention remains operational. Furthermore, two or more steps or actions can be performed simultaneously.

[0025] The use of any and all instances or exemplary language such as “e.g.” or “including” in this document is merely intended to better illustrate the invention and is not intended to limit the scope of the invention unless the claims are made. No language in this specification should be construed as indicating that any unclaimed element is essential to the practice of the invention.

[0026] Furthermore, the numerical ranges and parameters used to define the present invention are approximate values, and the relevant values ​​in the specific embodiments have been presented as precisely as possible. However, any value inevitably contains standard deviations due to individual test methods. Therefore, unless explicitly stated otherwise, it should be understood that all ranges, quantities, values, and percentages used in this disclosure are modified with the word "approximately". Here, "approximately" generally means that the actual value is within plus or minus 10%, 5%, 1%, or 0.5% of a specific value or range.

[0027] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0028] The embodiments and comparative examples of this invention describe some examples, in which the embodiments illustrate certain implementations of the invention. However, this does not mean that the effects of the invention can only be achieved in these examples.

[0029] To further illustrate the present invention, the following describes in detail an MPP power cable protection pipe and its manufacturing process provided by the present invention with reference to embodiments.

[0030] Example 1 An MPP power cable protection pipe comprises the following raw materials in parts by weight: 100 parts polypropylene masterbatch, 40 parts modified nano calcium carbonate, 0.3 parts initiator, 0.5 parts antioxidant, and 0.8 parts lubricant.

[0031] In this embodiment, the initiator used is 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, the antioxidant used is a mixture of 0.4 parts by weight of antioxidant 1010 and 0.1 parts by weight of antioxidant 168, the lubricant used is polyethylene wax, and the modified nano-calcium carbonate used is prepared by the following steps: S1. By mass, 16.8 parts of p-aminophenylboronic acid, 10 parts of allyltriethoxysilane, and 80 parts of cyclopentyl methyl ether were mixed in a reaction vessel and reacted at 80°C for 8 hours. After the reaction was completed, the solvent was removed by rotary evaporation of the reaction solution, and the remaining solid was purified by recrystallization (recrystallization solvent: anhydrous ethanol: n-hexane = 2:8) to obtain the flame retardant modifier precursor. S2. By mass fraction, 12 parts of phosphorus oxychloride, 8 parts of triethylamine, and 60 parts of tetrahydrofuran were mixed in a reaction vessel under ice-water bath conditions. A solution prepared from 14 parts of flame retardant modifier precursor and 56 parts of tetrahydrofuran was added dropwise to the system. After the addition was completed, the reaction was continued for 10 minutes under ice-water bath conditions. After the reaction was completed, the ice-water bath was removed and 12 parts of deionized water were added to the system. After hydrolysis at 5°C for 60 minutes, the reaction solution was poured into deionized water to precipitate. After filtering to separate the precipitate, the precipitate was washed with deionized water and dried to obtain the flame retardant modifier.

[0032] S3. By mass, 40 parts of nano-calcium carbonate, 10 parts of flame retardant modifier, and 320 parts of anhydrous ethanol are mixed in a reaction vessel and reacted at 60°C for 90 minutes. After the reaction is completed, the solid is filtered out, dried, ground and dispersed to obtain modified nano-calcium carbonate.

[0033] The coating rate of the modified nano-calcium carbonate in this embodiment was 13.6%, as determined by thermogravimetric analysis.

[0034] A manufacturing process for an MPP power cable protection pipe includes the following steps: The MPP power cable protection pipe is obtained by mixing polypropylene masterbatch, modified nano calcium carbonate, initiator, antioxidant, and lubricant, adding it to a twin-screw extruder, melt extruding it, and then vacuum cooling and shaping it in a die.

[0035] In this embodiment, the parameters for melt extrusion are set as follows: extrusion temperature 210℃, screw speed 35r / min; and the parameters for vacuum cooling and shaping are set as follows: cooling water temperature 30℃, vacuum degree 0.3MPa, and shaping time 10min.

[0036] Example 2 An MPP power cable protection pipe comprises the following raw materials in parts by weight: 100 parts polypropylene masterbatch, 45 parts modified nano calcium carbonate, 0.45 parts initiator, 0.75 parts antioxidant, and 1.15 parts lubricant.

[0037] In this embodiment, the initiator used is di-tert-butyl peroxide, the antioxidant used is a mixture of 0.6 parts by weight of antioxidant 1010 and 0.15 parts by weight of antioxidant 626, the lubricant used is polypropylene wax, and the modified nano-calcium carbonate used is prepared by the following steps: S1. By mass, 24.5 parts of p-aminophenylboronic acid, 13 parts of allyltriethoxysilane, and 112 parts of cyclopentyl methyl ether were mixed in a reaction vessel and reacted at 90°C for 6 hours. After the reaction was completed, the solvent was removed by rotary evaporation of the reaction solution, and the remaining solid was purified by recrystallization (recrystallization solvent: anhydrous ethanol: n-hexane = 2:8) to obtain the flame retardant modifier precursor. S2. By mass fraction, 15 parts of phosphorus oxychloride, 10 parts of triethylamine, and 75 parts of tetrahydrofuran were mixed in a reaction vessel under ice-water bath conditions. A solution prepared from 17 parts of flame retardant modifier precursor and 68 parts of tetrahydrofuran was added dropwise to the system. After the addition was completed, the reaction was continued under ice-water bath conditions for 20 minutes. After the reaction was completed, the ice-water bath was removed and 15 parts of deionized water were added to the system. After hydrolysis at 10°C for 45 minutes, the reaction solution was poured into deionized water to precipitate. After filtering to separate the precipitate, the precipitate was washed with deionized water and dried to obtain the flame retardant modifier.

[0038] S3. By mass, 45 nano-calcium carbonate, 11 parts flame retardant modifier, and 360 parts anhydrous ethanol are mixed in a reaction vessel and reacted at 70°C for 70 min. After the reaction is completed, the solid is filtered out, dried, ground and dispersed to obtain modified nano-calcium carbonate.

[0039] The coating rate of the modified nano-calcium carbonate in this embodiment was 16.2%, as determined by thermogravimetric analysis.

[0040] A manufacturing process for an MPP power cable protection pipe includes the following steps: The MPP power cable protection pipe is obtained by mixing polypropylene masterbatch, modified nano calcium carbonate, initiator, antioxidant, and lubricant, adding it to a twin-screw extruder, melt extruding it, and then vacuum cooling and shaping it in a die.

[0041] In this embodiment, the parameters for melt extrusion are set as follows: extrusion temperature 220℃, screw speed 40r / min; and the parameters for vacuum cooling and shaping are set as follows: cooling water temperature 35℃, vacuum degree 0.35MPa, and shaping time 7.5min.

[0042] Example 3 An MPP power cable protection pipe comprises the following raw materials in parts by weight: 100 parts polypropylene masterbatch, 50 parts modified nano calcium carbonate, 0.6 parts initiator, 1 part antioxidant, and 1.5 parts lubricant.

[0043] In this embodiment, the initiator used is di-tert-butyl peroxide, the antioxidant used is a mixture of 0.75 parts by weight of antioxidant 1035 and 0.25 parts by weight of antioxidant 626, the lubricant used is oxidized polyethylene wax, and the modified nano-calcium carbonate used is prepared by the following steps: S1. By mass, 32.2 parts of p-aminophenylboronic acid, 16 parts of allyltriethoxysilane, and 144 parts of cyclopentyl methyl ether were mixed in a reaction vessel and reacted at 100°C for 4 hours. After the reaction was completed, the solvent was removed by rotary evaporation of the reaction solution, and the remaining solid was purified by recrystallization (recrystallization solvent: anhydrous ethanol: n-hexane = 2:8) to obtain the flame retardant modifier precursor. S2. By mass fraction, 18 parts of phosphorus oxychloride, 12 parts of triethylamine, and 90 parts of tetrahydrofuran were mixed in a reaction vessel under ice-water bath conditions. A solution prepared from 20 parts of flame retardant modifier precursor and 80 parts of tetrahydrofuran was added dropwise to the system. After the addition was completed, the reaction was continued under ice-water bath conditions for 30 minutes. After the reaction was completed, the ice-water bath was removed, and 18 parts of deionized water were added to the system. After hydrolysis at 15°C for 30 minutes, the reaction solution was poured into deionized water to precipitate. After filtering to separate the precipitate, the precipitate was washed with deionized water and dried to obtain the flame retardant modifier.

[0044] S3. By mass, 50 nano-calcium carbonate, 12 parts of flame retardant modifier, and 400 parts of anhydrous ethanol are mixed in a reaction vessel and reacted at 80°C for 50 minutes. After the reaction is completed, the solid is filtered out, dried, ground and dispersed to obtain modified nano-calcium carbonate.

[0045] The coating rate of the modified nano-calcium carbonate in this embodiment was 14.4%, as determined by thermogravimetric analysis.

[0046] A manufacturing process for an MPP power cable protection pipe includes the following steps: The MPP power cable protection pipe is obtained by mixing polypropylene masterbatch, modified nano calcium carbonate, initiator, antioxidant, and lubricant, adding it to a twin-screw extruder, melt extruding it, and then vacuum cooling and shaping it in a die.

[0047] In this embodiment, the parameters for melt extrusion are set as follows: extrusion temperature 230℃, screw speed 45r / min; and the parameters for vacuum cooling and shaping are set as follows: cooling water temperature 40℃, vacuum degree 0.4MPa, and shaping time 5min.

[0048] Comparative Example 1 The difference between this comparative example and Example 2 is that no additional modified nano-calcium carbonate is prepared. Instead, 7.3 parts by weight of flame retardant diethyl phosphite and 37.7 parts by weight of unmodified nano-calcium carbonate are used to replace the modified nano-calcium carbonate. The other raw materials and their parts by weight remain unchanged.

[0049] An MPP power cable protection pipe comprises the following raw materials in parts by weight: 100 parts polypropylene masterbatch, 37.7 parts nano calcium carbonate, 7.3 parts flame retardant diethyl phosphite, 0.45 parts initiator, 0.75 parts antioxidant, and 1.15 parts lubricant.

[0050] In this embodiment, the initiator used is di-tert-butyl peroxide, the antioxidant used is a mixture of 0.6 parts by weight of antioxidant 1010 and 0.15 parts by weight of antioxidant 626, and the lubricant used is polypropylene wax.

[0051] A manufacturing process for an MPP power cable protection pipe includes the following steps: The polypropylene masterbatch, nano-calcium carbonate, flame retardant diethyl phosphite, initiator, antioxidant, and lubricant are mixed and added to a twin-screw extruder. After melt extrusion and vacuum cooling and shaping in a die, the MPP power cable protection pipe is obtained.

[0052] In this embodiment, the parameters for melt extrusion are set as follows: extrusion temperature 220℃, screw speed 40r / min; and the parameters for vacuum cooling and shaping are set as follows: cooling water temperature 35℃, vacuum degree 0.35MPa, and shaping time 7.5min.

[0053] Experimental Example The MPP power cable protection pipes prepared in Examples 1-3 and Comparative Example 1 were subjected to performance tests. The tensile strength of each component sample was tested according to GB / T 1040.2 "Determination of Tensile Properties of Plastics", the flexural modulus of each component sample was tested according to GB / T 9341 "Determination of Flexural Properties of Plastics", and the limiting oxygen index of each component sample was tested according to GB / T 2406.2 "Determination of Combustion Behavior of Plastics by Oxygen Index Method". The test results are shown in Table 1. Table 1 As can be seen from Table 1, the rigidity, mechanical properties, and flame retardant properties of the MPP power cable protection pipe materials prepared using the production process of the present invention in Examples 1 to 3 are significantly better than those in Comparative Example 1. Although the mass of flame retardant added to the MPP power cable protection pipe in Comparative Example 1 is approximately the same as that in Example 2, the small molecule flame retardant cannot be effectively dispersed in the polypropylene matrix due to the large polarity difference between it and the polypropylene matrix. Furthermore, the flame retardant effect of a single phosphorus-based flame retardant is not as good as that of the flame retardant modifier with multiple flame retardant elements in the present invention. Therefore, there is a significant difference in flame retardant performance.

[0054] 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. An MPP power cable protection pipe, characterized in that, It contains the following raw materials: polypropylene masterbatch, modified nano-calcium carbonate, initiator, antioxidant, and lubricant; The modified nano-calcium carbonate is prepared by the following steps: S1. A flame retardant modifier precursor is obtained by condensing p-aminophenylboronic acid with allyltriethoxysilane. S2. The flame retardant modifier precursor is obtained by hydrolysis after undergoing a phosphoramidation reaction with phosphorus oxychloride. S3. Modified nano-calcium carbonate is obtained by loading a flame retardant modifier onto the surface of nano-calcium carbonate.

2. The MPP power cable protection pipe according to claim 1, characterized in that, The raw materials contain the following parts by weight: 100 parts polypropylene masterbatch, 40-50 parts modified nano calcium carbonate, 0.3-0.6 parts initiator, 0.5-1 part antioxidant, and 0.8-1.5 parts lubricant.

3. The MPP power cable protection pipe according to claim 1, characterized in that, The initiator is at least one of di-tert-butyl peroxide and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane.

4. The MPP power cable protection pipe according to claim 1, characterized in that, The antioxidant is at least one of antioxidant 1010, antioxidant 1035, antioxidant 168, and antioxidant 626.

5. The MPP power cable protection pipe according to claim 1, characterized in that, The lubricant is at least one of polyethylene wax, polypropylene wax, and oxidized polyethylene wax.

6. The MPP power cable protection pipe according to claim 1, characterized in that, The modified nano-calcium carbonate is prepared by the following steps: S1. By mass, 16.8–32.2 parts of p-aminophenylboronic acid, 10–16 parts of allyltriethoxysilane, and 80–144 parts of cyclopentyl methyl ether are mixed in a reaction vessel and reacted at 80–100°C for 4–8 hours to obtain a flame retardant modifier precursor. S2. By mass, 12-18 parts of phosphorus oxychloride, 8-12 parts of triethylamine, and 60-90 parts of tetrahydrofuran are mixed in a reaction vessel under ice-water bath conditions. A solution prepared by 14-20 parts of flame retardant modifier precursor and 56-80 parts of tetrahydrofuran is added dropwise to the system. After the addition is complete, the reaction is continued under ice-water bath conditions for 10-30 minutes. After the reaction is completed, the ice-water bath is removed and 12-18 parts of deionized water are added to the system. The flame retardant modifier is obtained after hydrolysis at a temperature of 5-15℃ for 30-60 minutes. S3. By mass, 40-50 nano-calcium carbonate, 10-12 parts of flame retardant modifier, and 320-400 parts of anhydrous ethanol are mixed in a reaction vessel and reacted at 60-80℃ for 50-90 minutes to obtain modified nano-calcium carbonate.

7. The MPP power cable protection pipe according to claim 1, characterized in that, The coating rate of the modified nano-calcium carbonate is 13.6–16.2 ​​wt%.

8. A manufacturing process for an MPP power cable protection pipe as described in any one of claims 1 to 7, characterized in that, Includes the following steps: The MPP power cable protection pipe is obtained by mixing polypropylene masterbatch, modified nano calcium carbonate, initiator, antioxidant, and lubricant, adding it to a twin-screw extruder, melt extruding it, and then vacuum cooling and shaping it in a die.

9. The manufacturing process of an MPP power cable protection pipe according to claim 8, characterized in that, The parameters for the melt extrusion are an extrusion temperature of 210–230°C and a screw speed of 35–45 r / min.

10. The manufacturing process of an MPP power cable protection pipe according to claim 8, characterized in that, The parameters for vacuum cooling and shaping are: cooling water temperature of 30-40℃, vacuum degree of 0.3-0.4MPa, and shaping time of 5-10min.

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