Droplet-free polypropylene-based low-smoke halogen-free flame-retardant cable material and preparation method thereof

Abstract

The invention discloses a drippage-free polypropylene-based low-smoke halogen-free flame-retardant cable material and a preparation method thereof, and belongs to the field of flame retardance of high polymer materials. The invention aims to solve the problems of low flame-retardant efficiency and poor mechanical and physical properties of the existing polypropylene-based low-smoke halogen-free cable material. The composite material is prepared from the following components in parts by weight: 0-100 parts of thermoplastic polypropylene, 10-50 parts of maleic anhydride grafted polypropylene, 0-80 parts of aluminum hydroxide, 0-30 parts of expanded graphite, 0-30 parts of elastomer and 0.1-3 parts of antioxidant. According to the polypropylene-based low-smoke halogen-free flame-retardant cable material, LOI can be not lower than 31.5%, vertical combustion can reach V-0 level under the UL-94 standard, drippings are not generated during combustion, and the polypropylene-based low-smoke halogen-free flame-retardant cable material is environmentally friendly, low in smoke and even free of smoke in the flame-retardant process and has excellent mechanical performance.

Description

Technical Field

[0001] The invention belongs to the field of flame retardant polymer materials, and in particular relates to a drip-free polypropylene-based low-smoke halogen-free flame retardant cable material and a preparation method thereof. Background Art

[0002] In the field of cable materials, polyethylene (PE) is widely used due to its excellent thermal stability and electrical properties, but its linear molecular structure makes it difficult to be used directly in high-temperature cables, and it must be cross-linked to improve its heat resistance and mechanical properties. However, cross-linked polyethylene (XLPE) not only produces cross-linked by-products that pollute the air environment during the production process, but also discarded cables are difficult to degrade naturally, causing serious impacts on the natural environment, and not meeting the environmental protection requirements of carbon peak and carbon neutrality. In contrast, thermoplastic polypropylene (PP) has become the preferred material to replace XLPE due to its chemical corrosion resistance, excellent electrical insulation properties and 100% recyclability. However, the flammability of PP (oxygen index is only 17-20%) makes it extremely easy to ignite when exposed to flames, and severe melt dripping will occur during combustion, causing the risk of secondary combustion, posing a huge potential threat to personnel safety, and limiting the application of PP in the field of flame-retardant cables.

[0003] Previous studies have shown that while traditional halogen flame retardant systems can effectively improve the flame retardancy of PP, they release toxic and corrosive gases (such as HCl) during combustion, causing secondary damage to personnel safety and the environment. With technological advancements, halogen-free flame retardant systems (such as aluminum hydroxide and magnesium hydroxide) have become the mainstream due to their environmental advantages. However, when a single hydroxide flame retardant is added, its excellent flame retardancy can only be achieved at a high filling level (usually 60-70 parts). This will inevitably lead to a significant decrease in the mechanical properties of the PP matrix, and the flame retardant has poor dispersion and is prone to agglomeration. Summary of the Invention

[0004] The present invention aims to synergistically improve the problems of low flame retardant efficiency and poor mechanical and physical properties of polypropylene-based low-smoke halogen-free cable materials. The present invention selects aluminum hydroxide (ATH) as the main flame retardant and constructs a synergistic flame retardant system by introducing expanded graphite (EG), aiming to solve the problems of low flame retardant efficiency of a single flame retardant and serious PP combustion droplet phenomenon. On this basis, by introducing PP grafted maleic anhydride (PP-g-MAH) as a system compatibility regulator, the disadvantages of low mechanical properties of the system and difficulty in effectively exerting the flame retardant effect caused by poor compatibility between the flame retardant and the matrix are further improved, thereby comprehensively improving the performance of the flame retardant system. The invention provides a better solution for the application of PP materials in the field of flame retardancy, promotes the development of related technologies, and has significant application value and broad market prospects.

[0005] The present invention provides a drip-free polypropylene-based low-smoke, halogen-free flame-retardant cable material, which is prepared by melt blending the following raw materials in parts by weight:

[0006]

[0007] Preferably, it is made from the following raw materials in parts by weight:

[0008]

[0009] More preferably, it is made from the following raw materials in parts by weight:

[0010]

[0011] It is further defined that the thermoplastic polypropylene is a random copolymer, and its brand is one of K8303, K8003, K7002, K4912, B4808 or a polypropylene mixture composed of several of them in any ratio.

[0012] It is further defined that the maleic anhydride grafted polypropylene is a purchased PP-g-MAH mixture, the grafting rate of the grafted modified polypropylene is 1-2%, purchased from DuPont Company of the United States, model number Fusabond P353, which is a chemically modified polypropylene.

[0013] It is further defined that the elastomer is POP, purchased from The Dow Chemical Company, model number is Versify 2200.

[0014] It is further defined that the flame retardant is aluminum hydroxide (ATH).

[0015] It is further defined that the auxiliary agent is an antioxidant.

[0016] It is further defined that the antioxidant is one of antioxidant 1010, antioxidant 1035, antioxidant 1076, and antioxidant 300, or a combination of several of them in any ratio.

[0017] Furthermore, the elastomer is POP, purchased from Dow Chemical Company, model number is Versify 2200.

[0018] The present invention also provides a method for preparing the above-mentioned drip-free polypropylene-based low-smoke, halogen-free flame-retardant cable material, comprising the following steps:

[0019] The temperature of each zone of the torque rheometer is set between 170℃ and 185℃. After the temperature is reached, PP, PP-g-MAH, and POP are added to the torque rheometer, the speed is set to 60rpm, and mixing is carried out for 3 to 5 minutes. After the torque curve is stable, the speed is adjusted to 30rpm, and the flame retardant pellets are added twice and mixed for 3 minutes. After the torque curve is stable, the EG pellets are added and mixed for 3 minutes. Finally, the auxiliary agent is added and mixed for 3 minutes. Finally, the speed is adjusted to 60rpm. After mixing for 10 minutes, the pellets are taken out and cut into pieces to obtain PP-based flame-retardant cable material pellets.

[0020] It is further defined that before the flame retardant is added, the speed of the torque rheometer is set to 60 rpm, and during the addition of the flame retardant, the speed is set to 30 rpm.

[0021] The present invention also provides a method for preparing a polypropylene-based flame-retardant material, comprising placing the above-mentioned cable material or the cable material prepared by the above-mentioned method in a flat-plate vulcanizer, hot-pressing the material in a step-by-step pressurization manner, pressurizing and cooling the material using a water-cooled flat-plate vulcanizer, and then vacuum drying the material to obtain the flame-retardant material.

[0022] It is further defined that, under the temperature condition of 170°C-185°C, the step-by-step pressurization method is to set the pressure to 5MPa, 10MPa, and 15MPa respectively, and press for 5 minutes each; the pressurization cooling time is 5 minutes.

[0023] The beneficial effects achieved by the present invention are:

[0024] The present invention uses MAH to graft-modify PP, thereby enhancing the interfacial adhesion between the metal hydroxide flame retardant and the PP matrix, thereby improving the dispersibility and compatibility of the flame retardant in the PP matrix, and significantly enhancing the mechanical properties of the flame retardant system. On this basis, the combination of ATH and EG can exert an excellent flame retardant effect at a relatively low addition amount, and successfully constructs a PP / PP-g-MAH / ATH / EG synergistic flame retardant system.

[0025] During the combustion process, EG expands rapidly when heated to form a dense carbon shell, effectively wrapping the material and suppressing the molten droplet phenomenon produced when PP burns. ATH decomposes when heated to produce water vapor, absorbs heat, and dilutes the oxygen concentration. The aluminum oxide generated can serve as an adhesive for the expanded carbon layer. The synergistic effect of the two improves the density and integrity of the residual carbon, making the flame retardant performance of the material more excellent. The flame retardant cable material of the present invention can greatly reduce the filling amount of the flame retardant while ensuring the flame retardant performance, and can achieve an LOI of not less than 31.5%. Vertical combustion can reach the V-0 level under the UL-94 standard. No dripping is produced during combustion. During the flame retardant process, it is environmentally friendly, low-smoke or even smokeless, and has excellent mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a vertical combustion effect diagram of Example PPg-1;

[0027] Figure 2 This is a vertical combustion effect diagram of Example PPg-2;

[0028] Figure 3 This is a vertical combustion effect diagram of Example PPg-3;

[0029] Figure 4 This is the vertical combustion effect diagram of the comparison group PPh-1;

[0030] Figure 5 This is the vertical combustion effect diagram of the comparison group PPh-2;

[0031] Figure 6 is the limiting oxygen index of the flame retardant system;

[0032] Figure 7 is the smoke release rate curve;

[0033] Figure 8 is the total smoke release curve. DETAILED DESCRIPTION

[0034] Example 1: This example provides a drip-free polypropylene-based low-smoke, halogen-free, flame-retardant cable material prepared by melt blending the following raw materials in parts by weight:

[0035]

[0036] In this embodiment, a preparation method of a drip-free polypropylene-based low-smoke, halogen-free flame-retardant cable material is carried out according to the following steps: the temperature of each zone of the torque rheometer is set to 180°C. After the temperature is reached, the speed is adjusted to 60 rpm, PP, PP-g-MAH, and POP are added and mixed for 3 minutes. After the torque curve is stable, the speed is adjusted to 30 rpm, and then the accurately weighed ATH flame retardant is added twice and mixed for 3 minutes. After the torque curve is stable, the antioxidant 1010 is added and mixed for 3 minutes. Finally, the speed is adjusted to 60 rpm and mixed for 10 minutes. After the torque curve is stable again, the pellets are taken out and cut into pieces to finally obtain a PP-based low-smoke, halogen-free, synergistic flame-retardant cable material.

[0037] The preparation method of the polypropylene-based flame-retardant material in this embodiment is carried out according to the following steps: the PP-based low-smoke halogen-free synergistic flame-retardant cable material is melted at 180°C using a flat-plate vulcanizer, and then pressed into shape at 5MPa, 10MPa, and 15MPa for 5 minutes each by a step-by-step pressurization method, and then cooled in a water-cooled flat-plate vulcanizer to finally obtain Example PPg-1.

[0038] Example 2: A drip-free polypropylene-based low-smoke, halogen-free flame-retardant cable material provided in this example is prepared by melt blending the following raw materials in parts by weight:

[0039]

[0040] In this embodiment, a preparation method of a drip-free polypropylene-based low-smoke, halogen-free flame-retardant cable material is carried out according to the following steps: the temperature of each zone of the torque rheometer is set to 180°C, and after the temperature is reached, the speed is adjusted to 60 rpm, PP, PP-g-MAH, and POP are added, and mixed for 3 minutes. After the torque curve is stable, the speed is adjusted to 30 rpm, and the accurately weighed ATH flame retardant is added twice and mixed for 3 minutes. After the torque curve is stable, the accurately weighed EG synergistic flame retardant is added and mixed for 3 minutes. Finally, the antioxidant 1010 is added and mixed for 3 minutes. Finally, the speed is adjusted to 60 rpm and mixed for 10 minutes. After the torque curve is stable again, the pellets are taken out and cut into pieces to finally obtain the PP-based low-smoke, halogen-free synergistic flame-retardant cable material.

[0041] The preparation method of the polypropylene-based flame retardant material in this embodiment is carried out according to the following steps: the PP-based low-smoke halogen-free synergistic flame retardant cable material is melted at 180°C using a flat-plate vulcanizer, and then pressed into shape at 5MPa, 10MPa, and 15MPa for 5 minutes each by a step-by-step pressure increase method, and then cooled in a water-cooled flat-plate vulcanizer to finally obtain Example PPg-2.

[0042] Example 3: A drip-free polypropylene-based low-smoke, halogen-free flame-retardant cable material provided in this example is prepared by melt blending the following raw materials in parts by weight:

[0043]

[0044]

[0045] In this embodiment, a drip-free polypropylene-based low-smoke, halogen-free flame-retardant cable material is prepared according to the following steps: the temperature of each zone of the torque rheometer is set at 180°C. After the temperature is reached, the speed is adjusted to 60 rpm, PP, PP-g-MAH, and POP are added and mixed for 3 minutes. After the torque curve is stable, the speed is adjusted to 30 rpm, and the accurately weighed ATH flame retardant is added twice and mixed for 3 minutes. After the torque curve is stable, the accurately weighed EG synergistic flame retardant is added and mixed for 3 minutes. Finally, the antioxidant 1010 is added and mixed for 3 minutes. Finally, the speed is adjusted to 60 rpm and mixed for 10 minutes. After the torque curve is stable again, the pellets are taken out and cut into pieces to finally obtain the PP-based low-smoke, halogen-free synergistic flame-retardant cable material.

[0046] The preparation method of the polypropylene-based flame retardant material in this embodiment is carried out according to the following steps: the PP-based low-smoke halogen-free synergistic flame retardant cable material is melted at 180°C using a flat-plate vulcanizer, and then pressed into shape at 5MPa, 10MPa, and 15MPa for 5 minutes each by a step-by-step pressure increase method, and then cooled in a water-cooled flat-plate vulcanizer to finally obtain Example PPg-3.

[0047] Example 4: A drip-free polypropylene-based low-smoke, halogen-free flame-retardant cable material provided in this example is prepared by melt blending the following raw materials in parts by weight:

[0048]

[0049] In this embodiment, a preparation method of a drip-free polypropylene-based low-smoke, halogen-free flame-retardant cable material is carried out according to the following steps: the temperature of each zone of the torque rheometer is set to 180°C. After the temperature is reached, the speed is adjusted to 60 rpm, PP, PP-g-MAH, and POP are added and mixed for 3 minutes. After the torque curve is stable, the speed is adjusted to 30 rpm, and the accurately weighed ATH flame retardant is added twice and mixed for 3 minutes. After the torque curve is stable, the accurately weighed EG synergistic flame retardant is added and mixed for 3 minutes. Finally, the antioxidant 1010 is added and mixed for 3 minutes. Finally, the speed is adjusted to 60 rpm and mixed for 10 minutes. After the torque curve is stable again, the pellets are taken out to finally obtain the PP-based low-smoke, halogen-free synergistic flame-retardant cable material.

[0050] The preparation method of the polypropylene-based flame retardant material in this embodiment is carried out according to the following steps: the PP-based low-smoke halogen-free synergistic flame retardant cable material is melted at 180°C using a flat-plate vulcanizer, and then pressed into shape at 5MPa, 10MPa, and 15MPa for 5 minutes each by a step-by-step pressure increase method, and then cooled in a water-cooled flat-plate vulcanizer to finally obtain Example PPg-4.

[0051] Example 5: A drip-free polypropylene-based low-smoke, halogen-free flame-retardant cable material provided in this example is prepared by melt blending the following raw materials in parts by weight:

[0052]

[0053] In this embodiment, a preparation method for a drip-free polypropylene-based low-smoke, halogen-free flame-retardant cable material is carried out according to the following steps: the temperature of each zone of the torque rheometer is set to 180°C. After the temperature is reached, the speed is adjusted to 60 rpm, PP, PP-g-MAH, and POP are added and mixed for 3 minutes. After the torque curve is stable, the speed is adjusted to 30 rpm, and then the accurately weighed EG synergistic flame retardant is added twice and mixed for 3 minutes. After the torque curve is stable, the antioxidant 1010 is added and mixed for 3 minutes. Finally, the speed is adjusted to 60 rpm and mixed for 10 minutes. After the torque curve is stable again, the pellets are taken out to finally obtain the PP-based low-smoke, halogen-free synergistic flame-retardant cable material.

[0054] The preparation method of the polypropylene-based flame-retardant material in this embodiment is carried out according to the following steps: the PP-based low-smoke halogen-free synergistic flame-retardant cable material is melted at 180°C using a flat-plate vulcanizer, and then pressed into shape at 5MPa, 10MPa, and 15MPa for 5 minutes each by a step-by-step pressurization method, and then cooled in a water-cooled flat-plate vulcanizer to finally obtain Example PPg-5.

[0055] Comparative Example 1:

[0056] This comparative group is a preparation method of a polypropylene-based flame-retardant cable material, which is prepared by melt blending the following raw materials in parts by weight:

[0057]

[0058] The temperature of each zone of the torque rheometer is set to 180℃. After the temperature is reached, the speed is adjusted to 60rpm, PP and POP are added and mixed for 3min. After the torque curve is stable, the speed is adjusted to 30rpm, and the accurately weighed ATH flame retardant is added twice and mixed for 3min. After the torque curve is stable, the antioxidant 1010 is finally added and mixed for 3min. Finally, the speed is adjusted to 60rpm and mixed for 10min. After the torque curve is stable again, the pellets are taken out and cut into pieces to finally obtain the PP-based flame-retardant cable material. Then, a flat vulcanizer is used to melt it at 180℃, and it is pressed into shape at 5MPa, 10MPa, and 15MPa for 5min each by step-by-step pressure increase. After that, it is cooled in a water-cooled flat vulcanizer to finally obtain the comparison group PPh-1.

[0059] Comparative Example 2:

[0060] This comparative group is a preparation method of a polypropylene-based flame-retardant cable material, which is prepared by melt blending the following raw materials in parts by weight:

[0061]

[0062] The temperature of each zone of the torque rheometer is set to 180℃. After the temperature is reached, the speed is adjusted to 60rpm, PP and POP are added and mixed for 3min. After the torque curve is stable, the speed is adjusted to 30rpm, and the accurately weighed ATH flame retardant is added in three times and mixed for 3min. After the torque curve is stable, the antioxidant 1010 is finally added and mixed for 3min. Finally, the speed is adjusted to 60rpm and mixed for 10min. After the torque curve is stable again, the pellets are taken out and cut into pieces to finally obtain the PP-based flame-retardant cable material. Then, a flat vulcanizer is used to melt it at 180℃, and it is pressed into shape at 5MPa, 10MPa, and 15MPa for 5min each by step-by-step pressure increase. After that, it is cooled in a water-cooled flat vulcanizer to finally obtain the comparison group PPh-2.

[0063] The following experiments were used to verify the effects of the invention:

[0064] (1) Vertical combustion

[0065] As a method for simulating the burning behavior of materials in a laboratory environment, the vertical burning test experiment can make a preliminary evaluation of the flame retardant properties of the materials. The present invention uses the CZF-3 model horizontal / vertical burning tester for testing and the test results are evaluated according to the UL-94 standard. According to the UL-94 test standard, the level of the vertical burning test can be specifically divided into three flame retardant levels: V-0, V-1, and V-2. The specific parameters of each level are shown in Table 1, and the picture of the burning process is shown in Table 1. Figure 1 , 2, 3, 4, and 5 are shown. Flame retardant grade V-0 is the highest and has the best flame retardant effect, while V-2 has the worst flame retardant effect. The standard specimen size used for testing is 100mm × 13mm × 3mm. A custom mold is used to cut the pressed sample into standard-sized specimen strips. Five specimens are required for each test.

[0066] Table 1

[0067]

[0068] Analysis of the comparison groups PPh-1 and PPh-2 revealed that a flame retardant effect only occurred when a large amount of ATH was added. However, the extinguishing time was 36 seconds, and the dripping of combustible materials could not be improved. Comparing Example PPg-1 with the comparison group PPh-1, which contain the same ATH component, revealed that the addition of PP-g-MAH did not effectively reduce the ATH content to achieve a flame retardant effect. During the combustion process, Example PPg-3 clearly shows that under the action of EG, a physical barrier is formed on the surface of the material, preventing the dripping of molten droplets. Furthermore, both Example PPg-2 and Example PPg-3 can achieve flame retardancy in a relatively short period of time, all reaching the V-0 rating according to the UL-94 standard, and significantly reducing the flame retardant content.

[0069] (2) Limiting oxygen index

[0070] The LOI test was conducted using a JF-3 Limiting Oxygen Index Tester. The test method of GB / T 2406.2-2009 was followed, and the standard specimen size used for the test was 100 mm × 6.5 mm × 3 mm.

[0071] The limiting oxygen index ( Figure 6 Observe that when flame-retarding unmodified PP and a small amount of ATH in the comparative group PPh-1, the LOI had no significant effect due to the low amount of flame retardant added. However, when flame-retarding unmodified PP and a large amount of ATH alone in the comparative group PPh-2, the LOI improved somewhat. Among them, Example PPg-3 achieved the highest LOI value, demonstrating the best flame retardant effect, significantly outperforming the comparative example and other examples. The addition of EG not only significantly reduced the amount of ATH added but also significantly improved the flame retardant properties of the composite material.

[0072] (3) Tensile properties

[0073] The tensile test was performed on each dumbbell-shaped specimen using an electronic universal testing machine to evaluate the mechanical properties of each group of samples. The test results are shown in Table 2.

[0074] Table 2

[0075] sample tensile strength Elongation at break Example PPg-1 28.01 760.32 Example PPg-2 20.03 561.93 Example PPg-3 19.67 539.04 Control group PPh-1 21.87 263.07 Control group PPh-2 14.02 85.85

[0076] Analysis of the comparative groups PPh-1 and PPh-2 reveals that while the addition of a large amount of ATH provides a good flame retardant effect, it significantly reduces the tensile strength and elongation at break of the comparative group PPh-2, significantly deteriorating its mechanical properties. However, a comparison of Example PPg-1, which contains the same ATH component, with the comparative group PPh-1 reveals that Example PPg-1 significantly outperforms the comparative group PPh-1 in tensile strength and elongation at break, further demonstrating that the mechanical properties of the PP matrix and ATH flame retardant system are significantly improved after MAH grafting modification of PP. Comparative analysis of the various example groups reveals that excessive addition of EG leads to a certain decrease in tensile strength and elongation at break, but the mechanical properties remain significantly superior to those of the comparative groups PPh-1 and PPh-2.

[0077] (4) Smoke release behavior

[0078] The smoke release behavior of the two components of the comparative example PPg-2 and the comparative group PPh-1 during the combustion process.

[0079] Depend on Figure 7 The middle curve shows that the control group PPh-1 reaches the maximum smoke release rate of 0.10m at 200s. 2 / s, while the component of Example PPg-2 reached a peak value of 0.04m at 69s.2 / s, which has a significant effect in suppressing the smoke release rate. Figure 8 The total smoke release of the comparison group PPh-1 is 15.3m 2 , while the total smoke release of Example PPg-2 is 9.04m 2 , reduced by 6.26m 2 , the inhibitory effect is significant.

[0080] The PP / PP-g-MAH / ATH / EG flame-retardant cable material of the present invention exhibits excellent mechanical properties, flame retardancy, and environmental friendliness. Experiments show that while the control groups PPh-1 and PPh-2 exhibited some flame retardancy with excess ATH, severe ATH agglomeration significantly reduced the tensile strength and elongation at break of the PP / ATH material. The addition of PP-g-MAH effectively improved the dispersibility of ATH, increasing the tensile strength and elongation at break. Regarding flame retardancy, Examples PPg-2 and PPg-3, by incorporating a certain amount of EG, achieved a UL-94 V-0 rating within 5 seconds and 3.6 seconds, respectively, without any dripping. Furthermore, the synergistic effect of EG and ATH significantly increased the material's limiting oxygen index (LOI), achieving excellent flame retardancy even with a significantly reduced ATH content. Smoke release performance testing showed that the maximum smoke release rate and total smoke release of Example PPg-2 were significantly lower than those of the control group PPh-1, demonstrating excellent smoke suppression. In summary, the flame-retardant cable material of the present invention successfully reduces the ATH content while improving the flame retardant properties, mechanical properties and smoke suppression properties by introducing a synergistic flame retardant system of PP-g-MAH and ATH / EG, meets environmental protection and safety requirements, and has important practical application value and broad market prospects.

Claims

1. A drip-free polypropylene-based low-smoke, halogen-free flame-retardant cable material, characterized in that: It is made from the following raw materials in parts by weight:

2. The cable material according to claim 1, characterized in that: It is made from the following raw materials in parts by weight:

3. The cable material according to claim 1, characterized in that: It is made from the following raw materials in parts by weight:

4. The cable material according to claim 1, characterized in that: The flame retardant is aluminum hydroxide (ATH).

5. The cable material according to claim 1, characterized in that: The auxiliary agent is an antioxidant, and the antioxidant is one or more of antioxidant 1010, antioxidant 1035, antioxidant 1076, and antioxidant 300.

6. The cable material according to claim 1, characterized in that: The grafting rate of the polypropylene grafted with maleic anhydride is 1% to 2%.

7. The cable material according to claim 1, characterized in that: The elastomer is POP.

8. The method for preparing a drip-free polypropylene-based low-smoke, halogen-free flame-retardant cable material according to any one of claims 1 to 7, characterized in that: The following steps are involved: The temperature of each zone of the torque rheometer is set between 170℃ and 185℃. After the temperature is reached, PP, PP-g-MAH, and POP are added to the torque rheometer at a speed of 60rpm and mixed for 3 to 5 minutes. After the torque curve is stable, the speed is adjusted to 30rpm, and the flame retardant pellets are added twice and mixed for 3 minutes. After the torque curve is stable, the EG pellets are added and mixed for 3 minutes. Finally, the auxiliary agent is added and mixed for 3 minutes. Finally, the speed is adjusted to 60rpm. After mixing for 10 minutes, the pellets are taken out and cut into pieces to obtain PP-based flame-retardant cable material pellets.

9. A method for preparing a drip-free polypropylene-based low-smoke, halogen-free flame-retardant cable material, characterized in that: The cable material according to any one of claims 1 to 7 or the cable material prepared by the method according to claim 8 is placed in a flat-plate vulcanizer, hot-pressed in a step-by-step pressure manner, pressurized and cooled using a water-cooled flat-plate vulcanizer, and then vacuum-dried to obtain the flame-retardant material.

10. The method according to claim 9, characterized in that: Under the condition of temperature of 170℃-185℃, the step-by-step pressurization method is to set the pressure to 5MPa, 10MPa, and 15MPa respectively for 5 minutes each; the pressurization cooling time is 5 minutes.

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