Modification method for improving flame retardant property of thermoplastic elastomer

Abstract

The invention relates to a modification method for improving the flame retardant property of a thermoplastic elastomer, which comprises the following steps: mixing montmorillonite and inorganic flame retardant particles in a ball mill to form composite flame retardant particles, mixing the composite flame retardant particles with the thermoplastic elastomer, and extruding to obtain the flame-retardant modified thermoplastic elastomer. The flame-retardant modified thermoplastic elastomer has excellent and long-acting flame retardance.

Description

Technical Field

[0001] The present invention relates to the field of thermoplastic elastomers, and particularly to a modification method for improving the flame retardancy of thermoplastic elastomers. Background Art

[0002] Thermoplastic elastomers (also known as TPE) are a kind of polymer material that combines the elastic properties of rubber and the processing properties of thermoplastic plastics. They exhibit rubber elasticity at room temperature and can flow like plastics at high temperatures. They contain a hard segment (such as polystyrene, polyester) to provide physical cross-linking points and a soft segment (polybutadiene, polyether, etc.) to endow it with elasticity. Some thermoplastic elastomers, such as TPU (thermoplastic polyurethane rubber), have poor flame retardancy and usually need to be modified to improve their properties to meet the production requirements. Common modification methods include physical blending modification and chemical structure modification, etc. Among them, the physical blending modification has a lower process difficulty and can improve the flame retardancy of thermoplastic elastomers to a certain extent. CN105038191B discloses a halogen-free flame-retardant thermoplastic elastomer and its preparation method. By using at least one of zinc borate, magnesium borate, and calcium borate as an inorganic salt flame retardant, the flame retardancy can be effectively improved and the generation of smoke during combustion can be reduced. However, such inorganic flame retardants are polar materials, while thermoplastic elastomers are non-polar materials, and their compatibility is poor. They are prone to precipitation during long-term storage. Moreover, the thermal expansion coefficients of inorganic flame retardants and thermoplastic elastomers are quite different. When the thermoplastic elastomer faces a large temperature change, interfacial stress concentration is likely to generate microcracks, further promoting the precipitation of inorganic flame retardants, resulting in the inability to maintain the flame retardancy of thermoplastic elastomers for a long time.

[0003] Therefore, it is necessary to provide a modification method for improving the flame retardancy of thermoplastic elastomers. Summary of the Invention

[0004] In order to solve the problem of poor heat resistance of TPE materials, it is necessary to provide a modification method for improving the flame retardancy of thermoplastic elastomers.

[0005] A modification method for improving the flame retardancy of thermoplastic elastomers includes the following steps: mixing montmorillonite and inorganic flame retardant particles in a ball mill to form composite flame retardant particles, and then mixing the composite flame retardant particles with thermoplastic elastomers and extruding them to obtain flame-retardant modified thermoplastic elastomers.

[0006] In this solution, montmorillonite and inorganic flame retardant particles are pre-placed in a ball mill for ball milling. Montmorillonite is a layered mineral, and the layers are bound by weak van der Waals forces. Therefore, during the ball milling process, montmorillonite is gradually exfoliated to form nanosheets, which are physically adsorbed or chemically bonded to the surface of the inorganic flame retardant particles or inserted into the gaps on the surface of the inorganic flame retardant particles to form a mechanical interlocking structure, thus forming composite flame retardant particles. In this way, when the flame retardant modified thermoplastic elastomer faces a large temperature change (such as the cooling process after extrusion), the thermal shrinkage coefficients of the thermoplastic elastomer and the composite flame retardant particles are quite different, resulting in a large thermal stress. At this time, the nanosheets on the surface of the composite flame retardant particles can disperse the generated thermal stress to prevent the flame retardant modified thermoplastic elastomer from generating microcracks, which may lead to the precipitation of the inorganic flame retardant. At the same time, the nanosheet layer also extends the migration path of the inorganic flame retardant, further inhibiting the precipitation of the flame retardant. Therefore, the above-mentioned flame retardant modified thermoplastic elastomer has excellent and long-lasting flame retardant properties.

[0007] Furthermore, the inorganic flame retardant particles include at least one of aluminum hydroxide particles and magnesium hydroxide particles. Aluminum hydroxide and magnesium hydroxide are environmentally friendly flame retardants. When heated and decomposed, they release crystal water to absorb heat and cool down, and at the same time, the generated oxides can form a covering layer to isolate the contact between oxygen and the elastomer.

[0008] Furthermore, the average particle size of the inorganic flame retardant particles is 5 - 20 μm. If the average particle size of the particles is too small, agglomeration is likely to occur. If the average particle size of the particles is too large, on the one hand, it cannot fully adsorb the nanosheets, and on the other hand, it also leads to an increase in thermal stress.

[0009] Furthermore, the montmorillonite is modified by CTAB. CTAB (cetyltrimethylammonium bromide) is a cationic surfactant, and its long-chain alkyl group can be inserted into the interlayer of montmorillonite to expand the interlayer spacing, thereby improving the efficiency of ball milling exfoliation and the compatibility between the nanosheets and the inorganic flame retardant.

[0010] Furthermore, the parameters of the ball milling are as follows: the mass ratio of balls to materials is (5 - 10):1, the rotation speed is 200 - 500 rpm, and the ball milling time is 3 - 6 h. The above ball milling parameters can avoid excessive refinement of the nanosheets and the flame retardant particles and form stable composite flame retardant particles.

[0011] Furthermore, the composite flame retardant particles account for 5 - 20 wt% of the finished product. If the addition amount of the composite flame retardant particles is too low, the required flame retardant performance may not be achieved. If the addition amount of the composite flame retardant particles is too high, the mechanical properties of the thermoplastic elastomer will be affected.

[0012] Further, the mass ratio of the montmorillonite to the inorganic flame retardant in the composite flame retardant particles is 1:(20 - 50). Under the above ratio, the nanosheets can form a thermal stress buffer layer on the surface of the inorganic flame retardant particles, and will not affect other properties of the thermoplastic elastomer due to excessive use of montmorillonite.

[0013] Further, the thermoplastic elastomer includes at least one of TPV, TPU, and TPEE. This solution can be applied to the modification of various TPE materials.

[0014] Further, the extrusion process is twin-screw extrusion, and the extrusion temperature is 180 - 220 °C. This extrusion process can ensure the uniform dispersion of the composite flame retardant particles in the molten matrix, and the premature decomposition of the inorganic flame retardant will not occur within this temperature range.

[0015] Further, when the composite flame retardant particles are mixed with the thermoplastic elastomer, an interfacial compatibilizer accounting for 0.5 - 3 wt% of the finished product is added. By adding an interfacial compatibilizer such as maleic anhydride grafted product, etc., the interfacial bonding between the composite flame retardant particles and the thermoplastic elastomer can be further improved, and the migration of the flame retardant can be further inhibited. Detailed Embodiments

[0016] To facilitate the understanding of this application, the following will provide a more comprehensive description of this application. This application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the understanding of the disclosure of this application more thorough and comprehensive.

[0017] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of this application, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. In the description of this application, the meaning of "several" is at least one, such as one, two, etc., unless otherwise clearly and specifically defined.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs. The terms used in the description of this application herein are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0019] In this application, among the technically characterized features described in an open-ended manner, it includes a closed technical solution composed of the listed features, and also includes an open technical solution containing the listed features.

[0020] In this application, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are considered continuous and include the minimum and maximum values of the range, as well as each value between such minimum and maximum values. Further, when the range refers to integers, it includes each integer between the minimum and maximum values of the range. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0021] In this application, the percentage mass fraction involved, unless otherwise specified, refers to the mass percentage for solid-liquid mixtures and solid-solid mixtures, and refers to the volume percentage for liquid-liquid mixtures.

[0022] In this application, the percentage concentration involved, unless otherwise specified, refers to the final concentration. The final concentration refers to the proportion of the added component in the system after adding the component.

[0023] In this application, the temperature parameter, unless otherwise specified, allows for both constant temperature treatment and treatment within a certain temperature range. The constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument.

[0024] The "particles" mentioned in this application, or substances with a defined particle size distribution, do not necessarily have a spherical shape and may be irregular. They can be primary particles or secondary particles. The particle size of irregular particles is calculated as the average of the maximum diameter and the minimum diameter.

[0025] Example 1: This example provides a modification method for improving the flame retardancy of thermoplastic elastomers.

[0026] Preparation of composite flame retardant particles: Weigh 10 g of CTAB-modified montmorillonite and 200 g of magnesium hydroxide particles (average particle size of 5 μm), place them in a planetary ball mill for ball milling. The ball milling parameters are: ball milling speed of 200 rpm, ball milling time of 3 h, ball-to-material mass ratio of 5:1. After ball milling, sieve the product.

[0027] Among them, the modification method of CTAB montmorillonite is: Disperse 5 g of montmorillonite (cas: 1318-93-0) in 100 mL of deionized water, stir and mix, add 5 mL of 20% CTAB solution (PERFEMIKER, product number: PM11815), react at 80 °C for 4 h, centrifuge and wash until there is no residual bromide ion, dry at 80 °C, and then sieve through a 200-mesh sieve to obtain CTAB-modified montmorillonite.

[0028] Mixing and extrusion: Mix 10 parts of composite flame retardant particles and 88 parts of TPU particles (BASF, 670A10WHU), 1 part of compatibilizer (MAH-g-PP, Jia Yirong CMG9801), 0.5 part of antioxidant (BASF 1098) and 0.5 part of lubricant (tech-2734, Shanghai Tiger) are mixed and extruded through a twin-screw extruder at an extrusion temperature of 180 °C. After cooling, the flame-retardant modified thermoplastic elastomer is obtained.

[0029] Example 2: This example provides a modification method for improving the flame retardancy of thermoplastic elastomers.

[0030] Preparation of composite flame retardant particles: Weigh 10 g of CTAB-modified montmorillonite and 200 g of aluminum hydroxide particles (average particle size of 20 μm), place them in a planetary ball mill for ball milling. The ball milling parameters are: ball milling speed of 200 rpm, ball milling time of 3 h, ball-to-material mass ratio of 5:1. After ball milling, sieve them.

[0031] Among them, the modification method of CTAB montmorillonite is: Disperse 5 g of montmorillonite (cas: 1318-93-0) in 100 mL of deionized water, stir and mix, add 5 mL of 20% CTAB solution (PERFEMIKER, product number: PM11815), react at 80 °C for 4 h, centrifuge and wash until there is no bromide ion residue, dry at 80 °C, and then sieve through a 200-mesh sieve to obtain CTAB-modified montmorillonite.

[0032] Mixing and extrusion: Mix 10 parts of composite flame retardant particles, 88 parts of TPU particles (BASF, 670A10WHU), 1 part of compatibilizer (MAH-g-PP, Jia Yirong CMG9801), 0.5 part of antioxidant (BASF 1098) and 0.5 part of lubricant (tech-2734, Shanghai Tiger), and extrude through a twin-screw extruder at an extrusion temperature of 180 °C. After cooling, the flame-retardant modified thermoplastic elastomer is obtained.

[0033] Example 3: This example provides a modification method for improving the flame retardancy of thermoplastic elastomers.

[0034] Preparation of composite flame retardant particles: Weigh 10 g of CTAB-modified montmorillonite and 200 g of magnesium hydroxide particles (average particle size of 10 μm), place them in a planetary ball mill for ball milling. The ball milling parameters are: ball milling speed of 200 rpm, ball milling time of 3 h, ball-to-material mass ratio of 5:1. After ball milling, sieve them.

[0035] Among them, the modification method of CTAB montmorillonite is as follows: Disperse 5 g of montmorillonite (cas: 1318-93-0) in 100 mL of deionized water, stir and mix, add 5 mL of 20% CTAB solution (PERFEMIKER, product number: PM11815), react at 80 °C for 4 h, centrifuge and wash until there is no bromide ion residue, dry at 80 °C, and then pass through a 200-mesh sieve to obtain CTAB-modified montmorillonite.

[0036] Mixing and extrusion: Mix 10 parts of composite flame retardant particles, 88 parts of TPU particles (BASF, 670A10WHU), 1 part of interfacial compatibilizer (MAH-g-PP, Jia Yirong CMG9801), 0.5 part of antioxidant (BASF 1098), and 0.5 part of lubricant (tech-2734, Shanghai Tiger), and extrude through a twin-screw extruder. The extrusion temperature is 180 °C, and after cooling, a flame-retardant modified thermoplastic elastomer is obtained.

[0037] Example 4: This example provides a modification method for improving the flame retardancy of thermoplastic elastomers.

[0038] Preparation of composite flame retardant particles: Weigh 10 g of montmorillonite (unmodified) and 200 g of magnesium hydroxide particles (average particle size of 5 μm), place them in a planetary ball mill for ball milling. The ball milling parameters are: ball milling speed of 200 rpm, ball milling time of 3 h, ball-to-material mass ratio of 5:1, and sieve after ball milling.

[0039] Mixing and extrusion: Mix 10 parts of composite flame retardant particles, 88 parts of TPU particles (BASF, 670A10WHU), 1 part of interfacial compatibilizer (MAH-g-PP, Jia Yirong CMG9801), 0.5 part of antioxidant (BASF 1098), and 0.5 part of lubricant (tech-2734, Shanghai Tiger), and extrude through a twin-screw extruder. The extrusion temperature is 180 °C, and after cooling, a flame-retardant modified thermoplastic elastomer is obtained.

[0040] Example 5: This example provides a modification method for improving the flame retardancy of thermoplastic elastomers.

[0041] Preparation of composite flame retardant particles: Weigh 10 g of CTAB-modified montmorillonite and 200 g of magnesium hydroxide particles (average particle size of 5 μm), place them in a planetary ball mill for ball milling. The ball milling parameters are: ball milling speed of 500 rpm, ball milling time of 6 h, ball-to-material mass ratio of 10:1, and sieve after ball milling.

[0042] Among them, the modification method of CTAB montmorillonite is as follows: Disperse 5 g of montmorillonite (cas: 1318-93-0) in 100 mL of deionized water, stir and mix, add 5 mL of 20% CTAB solution (PERFEMIKER, product number: PM11815), react at 80 °C for 4 h, centrifuge and wash until there is no residual bromide ion, dry at 80 °C, and then pass through a 200-mesh sieve to obtain CTAB-modified montmorillonite.

[0043] Mixing and extrusion: Mix 10 parts of composite flame retardant particles, 88 parts of TPU particles (BASF, 670A10WHU), 1 part of interfacial compatibilizer (MAH-g-PP, Jia Yirong CMG9801), 0.5 part of antioxidant (BASF 1098) and 0.5 part of lubricant (tech-2734, Shanghai Tiger), extrude through a twin-screw extruder, and the extrusion temperature is 220 °C. After cooling, the flame retardant modified thermoplastic elastomer is obtained.

[0044] Example 6: This example provides a modification method for improving the flame retardancy of thermoplastic elastomers.

[0045] Preparation of composite flame retardant particles: Weigh 10 g of CTAB-modified montmorillonite and 200 g of magnesium hydroxide particles (average particle size of 5 μm), place them in a planetary ball mill for ball milling, and the ball milling parameters are: the ball milling speed is 200 rpm, the ball milling time is 3 h, the mass ratio of balls to materials is 5:1, and after ball milling, sieve.

[0046] Among them, the modification method of CTAB montmorillonite is as follows: Disperse 5 g of montmorillonite (cas: 1318-93-0) in 100 mL of deionized water, stir and mix, add 5 mL of 20% CTAB solution (PERFEMIKER, product number: PM11815), react at 80 °C for 4 h, centrifuge and wash until there is no residual bromide ion, dry at 80 °C, and then pass through a 200-mesh sieve to obtain CTAB-modified montmorillonite.

[0047] Mixing and extrusion: Mix 5 parts of composite flame retardant particles, 91.5 parts of TPU particles (BASF, 670A10WHU), 1 part of interfacial compatibilizer (MAH-g-PP, Jia Yirong CMG9801), 0.5 part of antioxidant (BASF 1098) and 2 parts of lubricant (tech-2734, Shanghai Tiger), extrude through a twin-screw extruder, and the extrusion temperature is 180 °C. After cooling, the flame retardant modified thermoplastic elastomer is obtained.

[0048] Example 7: This example provides a modification method for improving the flame retardancy of thermoplastic elastomers.

[0049] Preparation of composite flame retardant particles: Weigh 4 g of CTAB-modified montmorillonite and 200 g of magnesium hydroxide particles (average particle size of 5 μm), place them in a planetary ball mill for ball milling. The ball milling parameters are: ball milling speed of 200 rpm, ball milling time of 3 h, mass ratio of balls to materials of 5:1. After ball milling, sieve them.

[0050] Among them, the modification method of CTAB montmorillonite is as follows: Disperse 5 g of montmorillonite (cas: 1318-93-0) in 100 mL of deionized water, stir and mix, add 5 mL of 20% CTAB solution (PERFEMIKER, product number: PM11815), react at 80 °C for 4 h, centrifuge and wash until there is no residual bromide ion, dry at 80 °C, and then sieve through a 200-mesh sieve to obtain CTAB-modified montmorillonite.

[0051] Mixing and extrusion: Mix 10 parts of composite flame retardant particles, 88 parts of TPU particles (BASF, 670A10WHU), 1 part of interfacial compatibilizer (MAH-g-PP, Jia Yirong CMG9801), 0.5 part of antioxidant (BASF 1098), and 0.5 part of lubricant (tech-2734, Shanghai Tiger), and extrude them through a twin-screw extruder. The extrusion temperature is 180 °C. After cooling, the flame retardant modified thermoplastic elastomer is obtained.

[0052] Comparative example 1: TPU particles (BASF, 670A10WHU), without modification.

[0053] Comparative example 2: This comparative example provides a modification method for improving the flame retardant performance of thermoplastic elastomers.

[0054] Mixing and extrusion: Mix 10 parts of magnesium hydroxide particles (average particle size of 5 μm), 88 parts of TPU particles (BASF, 670A10WHU), 1 part of interfacial compatibilizer (MAH-g-PP, Jia Yirong CMG9801), 0.5 part of antioxidant (BASF 1098), and 0.5 part of lubricant (tech-2734, Shanghai Tiger), and extrude them through a twin-screw extruder. The extrusion temperature is 180 °C. After cooling, the flame retardant modified thermoplastic elastomer is obtained.

[0055] Comparative example 3: This comparative example provides a modification method for improving the flame retardant performance of thermoplastic elastomers.

[0056] Mixing and extrusion: Mix 10 parts of magnesium hydroxide particles (average particle size of 5 μm), 0.5 part of montmorillonite (cas: 1318-93-0), 88 parts of TPU particles (BASF, 670 A10 WHU), 1 part of interfacial compatibilizer (MAH-g-PP, Jia Yirong CMG9801), 0.5 part of antioxidant (BASF 1098), and 0.5 part of lubricant (tech-2734, Shanghai Tiger) are mixed and extruded through a twin-screw extruder at an extrusion temperature of 180 °C. After cooling, the flame-retardant modified thermoplastic elastomer is obtained.

[0057] The samples prepared in the above examples and comparative examples were tested for flame retardancy (referring to the UL94 rating standard).

[0058] Long-term flame retardancy performance test: The samples were aged in an oven for 30 days (temperature 80 °C, humidity 50%), and their flame retardancy was detected (referring to the UL94 rating standard).

[0059] Table 1 shows the test results of the flame retardancy and long-term flame retardancy performance of the samples of Examples 1-7 and Comparative Examples 1-2.

[0060]

[0061]

[0062] According to the data in Table 1, it can be seen that the flame retardancy of Comparative Example 2 has been improved compared to Comparative Example 1, but its long-term flame retardancy performance has not been significantly improved. However, the long-term flame retardancy performance of Examples 1-7 has been significantly improved compared to Comparative Example 2. This is because in this solution, montmorillonite and inorganic flame retardant particles are pre-ground in a ball mill. Montmorillonite is a layered mineral, and the layers are bound by weak van der Waals forces. Therefore, during the ball milling process, montmorillonite gradually exfoliates to form nanosheets, which are physically adsorbed or chemically bonded to the surface of the inorganic flame retardant particles or inserted into the surface gaps of the inorganic flame retardant particles to form a mechanical interlocking structure, thus forming composite flame retardant particles. In this way, when the flame-retardant modified thermoplastic elastomer faces a large temperature change (such as the cooling process after extrusion), the thermal shrinkage coefficients of the thermoplastic elastomer and the composite flame retardant particles are quite different, resulting in a large thermal stress. At this time, the nanosheets on the surface of the composite flame retardant particles can disperse the generated thermal stress to prevent the formation of microcracks in the flame-retardant modified thermoplastic elastomer, which may lead to the precipitation of the inorganic flame retardant. At the same time, the nanosheet layer also extends the migration path of the inorganic flame retardant, further inhibiting the precipitation of the flame retardant. Therefore, the above flame-retardant modified thermoplastic elastomer has excellent and long-term flame retardancy performance. There is no obvious improvement in Comparative Example 3 compared to Comparative Example 2 because it does not form composite flame retardant particles by ball milling in advance, and no mechanical interlocking structure can be generated, so microcracks are likely to occur during the cooling process, leading to the precipitation of the flame retardant.

[0063] Example 2 used a combination of aluminum hydroxide and large-particle-size inorganic flame retardants. Aluminum hydroxide has a relatively low decomposition temperature and may undergo partial decomposition during the mixing process. Moreover, the large particle size results in a poor coating effect of montmorillonite nanosheets. Example 4 used unmodified montmorillonite, and the efficiency of exfoliating to produce montmorillonite nanosheets was low, unable to form an effective thermal stress protection layer. Example 5 used ball milling at a higher rotation speed and for a longer time, which may lead to excessive fragmentation of the nanosheets. In Example 6, the addition amount of the composite flame retardant was low, and the flame retardant effect was poor. Example 7 used less montmorillonite, making it difficult for the nanosheets to fully cover the inorganic particles, and the migration ability of the thermoplastic elastomer increased after aging.

[0064] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0065] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A modification method for improving the flame retardant properties of a thermoplastic elastomer, characterized in that: The method comprises the following steps: placing montmorillonite and inorganic flame retardant particles in a ball mill and mixing them to form composite flame retardant particles; mixing the composite flame retardant particles with a thermoplastic elastomer and then extruding the mixture to obtain a flame retardant modified thermoplastic elastomer.

2. The modification method according to claim 1, characterized in that: The inorganic flame retardant particles include at least one of aluminum hydroxide particles and magnesium hydroxide particles.

3. The modification method according to claim 1, characterized in that: The average particle size of the inorganic flame retardant particles is 5-20 μm.

4. The modification method according to claim 1, characterized in that: The montmorillonite is modified by CTAB.

5. The modification method according to claim 1, characterized in that: The parameters of the ball milling are: ball-to-material mass ratio (5-10): 1, rotation speed 200-500 rpm, and ball milling time 3-6 h.

6. The modification method according to claim 1, characterized in that: The composite flame retardant particles account for 5-20 wt % of the finished product.

7. The modification method according to claim 1, characterized in that: The mass ratio of the montmorillonite to the inorganic flame retardant in the composite flame retardant particles is 1:(20-50).

8. The modification method according to claim 1, characterized in that: The thermoplastic elastomer includes at least one of TPV, TPU and TPEE.

9. The modification method according to claim 1, characterized in that: The extrusion process is twin-screw extrusion, and the extrusion temperature is 180-220°C.

10. The modification method according to claim 1, characterized in that: When the composite flame retardant particles are mixed with the thermoplastic elastomer, an interface compatibility agent is added in an amount of 0.5-3 wt % of the finished product.

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