A microcellular polypropylene composite material, its preparation method and application

Abstract

The present invention discloses a microcellular polypropylene composite material, a preparation method thereof and an application thereof, belonging to the technical field of polymer materials. The microcellular polypropylene composite material comprises a polypropylene composite material and a foaming agent. The polypropylene composite material comprises the following components in parts by weight: 47-79 parts of polypropylene resin; 5-30 parts of toughening agent; 3-8 parts of modified nano-sepiolite; 0.5-1.5 parts of compatibilizer; 0.1-2 parts of auxiliary agent. The modified nano-sepiolite comprises one or more of nano-sepiolite with mPEG-silane bonded on the surface, nano-sepiolite with γ-aminopropyltriethoxysilane bonded on the surface or nano-sepiolite with n-octyltriethoxysilane bonded on the surface. The weight-average molecular weight of the mPEG-silane is 1000-5000. The microcellular polypropylene composite material of the present invention has the characteristics of excellent mechanical properties after foaming, low density after foaming, low pit percentage and good appearance.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and more specifically, to a microcellular polypropylene composite material, a preparation method thereof, and an application thereof. Background Art

[0002] Polypropylene (PP) has the advantages of low density, easy processing, excellent mechanical properties, etc., and has been widely used in the automotive industry, household appliances, and mechanical fields. Automobile lightweighting is an important development direction in the automotive industry. Currently, the main technical solutions are low density, thin wall, and microcellular foaming. Among them, microcellular foaming has the largest weight reduction ratio and will be more and more widely used in the future. In addition to the requirement of weight reduction ratio, a good appearance of the parts is also essential. Therefore, it is necessary to develop a microcellular polypropylene composition with a high weight reduction ratio and a good appearance. Since the gas generated by the decomposition of the foaming agent escapes, it affects the surface appearance of the parts. Therefore, the surface of the microcellular polypropylene composite material is prone to pits, and the appearance cannot meet the requirements.

[0003] In order to improve the foaming effect of polypropylene materials, the prior art adds a gas adsorbent and a gas barrier agent to the polypropylene materials to regulate the dissolution, diffusion, and migration of gas in the polymer melt, and obtains a foamed polypropylene material with a better surface appearance. The prior art adds high melt strength PP to the polypropylene materials to improve the foaming performance and the appearance of the parts. The microcellular polypropylene materials prepared by these current solutions all have low mechanical properties.

[0004] The prior art discloses a lightweight microcellular polypropylene composite material, which modifies sepiolite with an anionic surfactant and a quaternary ammonium salt intercalating agent, improves the hydrophobic property of sepiolite, and improves the compatibility between sepiolite and polypropylene. However, its notch impact strength cannot meet the requirements. Moreover, since its anionic surfactant is a small molecule and has a lubricating effect, it reduces the melt strength of the material, resulting in pits on the surface of the microcellular polypropylene composite material, and the anionic surfactant is prone to precipitation, resulting in oil on the surface of the microcellular polypropylene composite material and poor appearance. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the defects and deficiencies that the appearance of the existing microcellular polypropylene composite material is prone to pits and the notch impact strength is low, and to provide a microcellular polypropylene composite material with excellent mechanical properties, low density, low pit percentage, and good appearance after foaming.

[0006] Another object of the present invention is to provide a preparation method of a microcellular polypropylene composite material.

[0007] Another object of the present invention is to provide an application of a microcellular polypropylene composite material in the preparation of automotive interiors.

[0008] The above object of the present invention is achieved by the following technical solutions:

[0009] A microcellular polypropylene composite material, the microcellular polypropylene composite material comprising a polypropylene composite material and a foaming agent, and the polypropylene composite material comprises the following components by weight:

[0010]

[0011] The modified nano-sepiolite includes one or more of nano-sepiolite surface-bonded with mPEG-silane, nano-sepiolite surface-bonded with γ-aminopropyltriethoxysilane, or nano-sepiolite surface-bonded with n-octyltriethoxysilane;

[0012] The weight-average molecular weight of the mPEG-silane is 1000-5000;

[0013] The weight ratio of the foaming agent to the polypropylene composite material is (0.01-0.04):1.

[0014] The mPEG-silane is a methoxy-polyethylene glycol-silane block copolymer.

[0015] The nano-sepiolite surface-bonded with mPEG-silane refers to the group structure formed by the dehydration condensation of the silanol groups of mPEG-silane on the surface of the nano-sepiolite.

[0016] The nano-sepiolite surface-bonded with γ-aminopropyltriethoxysilane refers to the group structure formed by the dehydration condensation of the silanol groups of γ-aminopropyltriethoxysilane on the surface of the nano-sepiolite.

[0017] The nano-sepiolite surface-bonded with n-octyltriethoxysilane refers to the group structure formed by the dehydration condensation of the silanol groups of n-octyltriethoxysilane on the surface of the nano-sepiolite.

[0018] In the present invention, the modified nano-sepiolite and the compatibilizer act synergistically to improve the melt strength of the polypropylene material and the dispersion of the nano-sepiolite, thereby improving the mechanical properties of the polypropylene composite material and improving the appearance defects of the foamed parts.

[0019] This is because in an acidic environment, the siloxane hydrolyzes into silanol groups, and the silanol groups undergo dehydration condensation with the hydroxyl groups on the surface of the nano-sepiolite, thereby obtaining modified nano-sepiolite surface-bonded with mPEG-silane, modified nano-sepiolite surface-bonded with γ-aminopropyltriethoxysilane, or modified nano-sepiolite surface-bonded with n-octyltriethoxysilane.

[0020] Moreover, since the surface of the modified nano-sepiolite contains alkyl chain segments, the compatibility between nano-sepiolite and PP is improved. And the compatibilizer and the modified nano-sepiolite can interact with each other, further improving the dispersibility of nano-sepiolite and its compatibility with PP. At the same time, the melt strength of the polypropylene material is increased, making the foaming effect of the material improved. Therefore, by adding the nano-sepiolite treated with mPEG-silane and the compatibilizer to the polypropylene material simultaneously and synergistically, a microcellular foamed polypropylene material with excellent mechanical properties, high melt strength and good appearance can be prepared.

[0021] Preferably, the weight-average molecular weight of the mPEG-silane is 1500 - 3000.

[0022] Preferably, the modified nano-sepiolite includes nano-sepiolite with mPEG-silane bonded to its surface.

[0023] Since the nano-sepiolite with mPEG-silane bonded to its surface contains ethylene glycol alkyl chain segments, and ethylene glycol is a polar group, the surface of the material can absorb moisture to form a conductive layer, achieving an antistatic effect. Therefore, it can also improve the antistatic performance of the microcellular foamed polypropylene composite material.

[0024] Preferably, the weight ratio of the compatibilizer to the modified nano-sepiolite is (0.1 - 0.3):1.

[0025] Preferably, the mesh number of the modified nano-sepiolite is 200 - 500 mesh.

[0026] More preferably, the mesh number of the modified nano-sepiolite is 350 - 450 mesh.

[0027] Preferably, in the modified nano-sepiolite, the weight ratio of mPEG-silane to the modified nano-sepiolite is (0.048 - 0.23):1.

[0028] Preferably, in the modified nano-sepiolite, the weight ratio of γ-aminopropyltriethoxysilane to the modified nano-sepiolite is (0.048 - 0.23):1.

[0029] Preferably, in the modified nano-sepiolite, the weight ratio of n-octyltriethoxysilane to the modified nano-sepiolite is (0.048 - 0.23):1.

[0030] Optionally, the treatment method of the modified nano-sepiolite with mPEG-silane bonded to its surface may include the following steps:

[0031] S1. Heat and acidify the nano-sepiolite, the heating temperature is 70 - 90 °C, the heating pH is 1 - 3, and the heating time is 2 - 4 h; wherein, the pH can be controlled at 1 - 3 by adding hydrochloric acid;

[0032] S2. Mix the nano-sepiolite after the S1 treatment with mPEG-silane and react. The reaction temperature is 70-90 °C and the reaction time is 2-4 h;

[0033] The weight ratio of mPEG-silane to nano-sepiolite is (0.05-0.3):1.

[0034] The treatment method of the modified nano-sepiolite with mPEG-silane bonded on the surface may not be limited to this method.

[0035] Optionally, the treatment method of the modified nano-sepiolite with γ-aminopropyltriethoxysilane bonded on the surface may include the following steps:

[0036] S1. Heat and acidify the nano-sepiolite. The heating temperature is 70-90 °C, the heating pH is 1-3, and the heating time is 2-4 h; among them, the pH can be controlled at 1-3 by adding hydrochloric acid;

[0037] S2. Mix the nano-sepiolite after the S1 treatment with γ-aminopropyltriethoxysilane and react. The reaction temperature is 70-90 °C and the reaction time is 2-4 h;

[0038] The weight ratio of γ-aminopropyltriethoxysilane to nano-sepiolite is (0.05-0.3):1.

[0039] The treatment method of the modified nano-sepiolite with γ-aminopropyltriethoxysilane bonded on the surface may not be limited to this method.

[0040] Optionally, the treatment method of the modified nano-sepiolite with n-octyltriethoxysilane bonded on the surface may include the following steps:

[0041] S1. Heat and acidify the nano-sepiolite. The heating temperature is 70-90 °C, the heating pH is 1-3, and the heating time is 2-4 h; among them, the pH can be controlled at 1-3 by adding hydrochloric acid;

[0042] S2. Mix the nano-sepiolite after the S1 treatment with n-octyltriethoxysilane and react. The reaction temperature is 70-90 °C and the reaction time is 2-4 h;

[0043] The weight ratio of n-octyltriethoxysilane to nano-sepiolite is (0.05-0.3):1.

[0044] The treatment method of the modified nano-sepiolite with n-octyltriethoxysilane bonded on the surface may not be limited to this method.

[0045] The detection method of silanol groups in the microcellular polypropylene composite material of the present invention: Through infrared detection, no 3400 cm -1Absorption peaks indicate that no silanol groups are detected, which can show that in the micro-foamed polypropylene composite material described in the present invention, mPEG-silane, γ-aminopropyltriethoxysilane or n-octyltriethoxysilane have completely reacted.

[0046] Preferably, the polypropylene resin is a homopolypropylene resin and / or a copolymerized polypropylene resin.

[0047] Preferably, the melt mass flow rate of the polypropylene resin is 10-60 g / 10 min, the test standard is ISO1133-2011, and the test conditions are 230 °C / 2.162 g.

[0048] Preferably, the polypropylene composite material comprises the following components by weight parts:

[0049]

[0050] Preferably, the compatibilizer is maleic anhydride grafted polyolefin; in the compatibilizer, the mass grafting rate of maleic anhydride is 0.7-1.3%.

[0051] More preferably, the grafting rate of the maleic anhydride grafted polypropylene is 0.8-1.1%.

[0052] Optionally, the compatibilizer is maleic anhydride grafted polypropylene and / or maleic anhydride grafted POE.

[0053] Preferably, the compatibilizer is maleic anhydride grafted polypropylene.

[0054] In the maleic anhydride grafted polyolefin, the test method for the grafting rate is chemical titration: weigh 0.5 g of maleic anhydride grafted polyolefin and place it in a 250 ml distillation flask, add 80 ml of xylene, heat under reflux for 30 min until the grafted product dissolves, cool, add an excessive amount of 0.05 N KOH-ethanol standard solution (10 ml), then heat to 80 °C, react for 2 h, cool to below the boiling point of ethanol, use phenolphthalein as an indicator, and titrate the excessive KOH-ethanol standard solution with HCl-isopropanol standard solution while it is hot. Record the amount of alkali consumed in excess and the amount of acid neutralized, and calculate the grafting rate G = 9.806(V1C1 - V2C2) / 2m according to the formula, where C1 is the concentration of the KOH-ethanol standard solution in mol / L, C2 is the concentration of the HCl-isopropanol standard solution in mol / L, V1 is the volume of the excessive KOH-ethanol standard solution added in mL, V2 is the volume of the HCl-isopropanol standard solution consumed for back-titrating and neutralizing the alkali in mL, and m is the mass of the maleic anhydride grafted PP sample in g.

[0055] Preferably, the foaming agent is sodium bicarbonate.

[0056] Preferably, the toughening agent is one or more of ethylene-butene copolymer, ethylene-octene copolymer or styrene copolymer elastomer.

[0057] More preferably, the toughening agent is ethylene-butene copolymer.

[0058] Preferably, the auxiliary agent is antioxidant and / or light stabilizer; the antioxidant is hindered phenol antioxidant and / or phosphite antioxidant; the light stabilizer is hindered amine light stabilizer.

[0059] Optionally, the antioxidant is one or a mixture of two or more of 1010, 1076, 3114, 168 or PEP-36.

[0060] Optionally, the light stabilizer is one or a mixture of two or more of UV-3808PP5 and LA-402AF.

[0061] The present invention also protects a method for preparing the microcellular polypropylene composite material described in any one of the above, comprising the following steps:

[0062] S1. Mix polypropylene resin, toughening agent, modified nano-sepiolite, compatibilizer and auxiliary agent, melt-extrude and pelletize through an extruder, and obtain the polypropylene composite material after drying;

[0063] S2. Mix the polypropylene composite material prepared in step S1 with a foaming agent, and injection mold to obtain the microcellular polypropylene composite material.

[0064] The extruder can be a twin-screw extruder.

[0065] The microcellular polypropylene composite material prepared by the present invention has the characteristics of excellent mechanical properties after foaming, low density after foaming, low pit percentage and good appearance, and can be widely used in the preparation of plastic products. The present invention particularly protects the application of the microcellular polypropylene composite material in the preparation of automotive interiors.

[0066] The automotive interior can be one or more of door panels, lower instrument panels and roof racks.

[0067] Compared with the prior art, the beneficial effects of the present invention are:

[0068] The microcellular polypropylene composite material of the present invention can be prepared into a microcellular polypropylene material with excellent mechanical properties and good appearance through the synergistic effect of adding modified nano-sepiolite treated with γ-aminopropyltriethoxysilane and a compatibilizer to polypropylene resin. Specific Embodiments

[0069] The present invention will be further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the raw material reagents used in the embodiments of the present invention are conventional raw material reagents purchased regularly.

[0070] The raw material components of each embodiment and comparative example of the present invention are shown in Table 1 below:

[0071] Table 1

[0072]

[0073]

[0074] The treatment method of the modified nano-sepiolite includes the following steps: S1. Take nano-sepiolite, put it into a beaker containing deionized water, stir evenly, then adjust the pH value to 1 with hydrochloric acid, heat up to 80 °C, and stir for 3 h. S2. Add mPEG-silane, γ-aminopropyltriethoxysilane or n-octyltriethoxysilane to the nano-sepiolite treated in S1 respectively for mixed reaction, and stir at a constant temperature for 3 h. Finally, filter and dehydrate, wash with deionized water, then filter again, and finally dry in a vacuum drying oven at 120 °C, and grind to obtain nano-sepiolite with mPEG-silane bonded on the surface, nano-sepiolite with γ-aminopropyltriethoxysilane bonded on the surface or nano-sepiolite with n-octyltriethoxysilane bonded on the surface respectively.

[0075] The treatment method of the modified nano-sepiolite in the embodiments of the present invention is shown in Table 2 below:

[0076] Table 2

[0077]

[0078]

[0079] Examples 1 to 15

[0080] A micro-foamed polypropylene composite material includes a polypropylene composite material and a foaming agent. The polypropylene composite material is mainly prepared from the following components by weight: polypropylene resin; toughening agent; modified nano-sepiolite; compatibilizer; auxiliary agent; the auxiliary agent includes an antioxidant and a light stabilizer;

[0081] Among them, the modified nano-sepiolite is the modified nano-sepiolite obtained after being treated with mPEG-silane, γ-aminopropyltriethoxysilane or n-octyltriethoxysilane as described above.

[0082] The specific contents of each component raw material are shown in Table 3 below.

[0083] Composition of the micro-foamed polypropylene composite material in each example of Table 3 (by weight)

[0084] Component 1 2 3 4 5 Polypropylene resin 1 72 47 79 72 72 Toughening agent 1 20 30 5 20 20 Modified nano-sepiolite 1 5 8 3 5.45 4.6 Foaming agent 2 1 3 2 2 Compatibilizer 1 1 0.5 1.5 0.55 1.4 Antioxidant 0.2 0.05 1 0.2 0.2 Light stabilizer 0.2 0.05 1 0.2 0.2

[0085] Continued Table 3

[0086]

[0087]

[0088] The preparation method of the above-mentioned microcellular polypropylene composite material comprises the following steps:

[0089] S1. Mix polypropylene resin, toughener, compatibilizer, modified nano-sepiolite and additives evenly, then add them into a twin-screw extruder for melt mixing. The melt mixing temperature is 170-220°C, the screw speed is 350-450 revolutions per minute, and then extrude and pelletize to obtain a polypropylene composite material;

[0090] S2. Mix the polypropylene composite material obtained in S1 with a foaming agent, and then injection mold to obtain a microcellular polypropylene composite material.

[0091] Comparative Examples 1-8

[0092] A microcellular polypropylene composite material, comprising a polypropylene composite material and a foaming agent. The polypropylene composite material is mainly prepared from the following components by weight: polypropylene resin; toughener; modified nano-sepiolite; compatibilizer; additives, and the additives include antioxidant and light stabilizer.

[0093] The specific contents of the raw materials of each component are shown in Table 4 below.

[0094] Table 4 Composition of the microcellular polypropylene composite materials of each comparative example (by weight)

[0095]

[0096] The preparation method of the above-mentioned microcellular polypropylene composite material is the same as that of the example, and will not be elaborated here.

[0097] Result Detection

[0098] The microcellular polypropylene composite materials of each example and comparative example are tested according to the following method:

[0099] (1) Izod notched impact strength: Test the Izod notched impact strength of the material according to ISO 180 "Plastics - Determination of impact strength". The notch type is A, the size of the specimen is 80*10*4mm, the notch depth is 2mm, and the pendulum impact energy is 2.75J.

[0100] (2) Tensile strength: Test the tensile property of the material according to ISO 527 "Plastics - Determination of tensile properties", and the tensile rate is 50mm / min.

[0101] (3) Density: The density of the material was tested in accordance with ISO 1183, "Determination of the Density of Plastics".

[0102] (4) Dimple percentage: The appearance quality was evaluated by the dimple percentage on the foamed square plate. The ratio of the dimple defect area on the micro-foamed square plate to the area of the foamed square plate was calculated. The larger the ratio, the more dimples and the worse the appearance.

[0103] (5) Melt strength: It was tested using a melt strength tester at a test temperature of 200 °C, a screw speed of 30 rpm, a traction rate of 50 mm / s, and an acceleration of 12 mm / s.

[0104] (6) Surface resistance: The surface resistance of the material was tested in accordance with GB / T 1410, "Test Methods for Volume Resistivity and Surface Resistivity of Solid Insulating Materials", at a test voltage of 100 V and an electrification time of 1 min. The smaller the surface resistance, the better the antistatic effect.

[0105] The specific test results of the micro-foamed polypropylene composites of each example and comparative example are as described in Table 5 below:

[0106] Table 5

[0107]

[0108]

[0109] As can be seen from the above data, the micro-foamed polypropylene composite of the present invention has excellent mechanical properties after foaming, low density after foaming, low dimple percentage, and good appearance. The micro-foamed polypropylene composite of the present invention has a density of 0.69 - 0.74 g / cm 3 , a melt strength of 50 - 60 mN, a notched impact strength after foaming of up to 14.1 or more, up to 17.1 KJ / m 2 , a tensile strength after foaming of up to 12.3 MPa or more, up to 14.2 MPa, and surface dimples of 0 - 4%.

[0110] As can be seen from Comparative Example 1, without adding a foaming agent, the polypropylene composition does not foam, the material has a high density, high notched impact strength and tensile strength, and no dimples.

[0111] As can be seen from Comparative Example 2, when the addition amount of the foaming agent is too much, over-foaming occurs, the cell size is large, the notched impact strength and tensile strength of the material decrease, and the gas easily escapes, resulting in many dimples.

[0112] As can be seen from Comparative Example 3, without adding nano-sepiolite, the melt strength of the material is low, the foaming effect of the material is poor, the density is high, the notched impact strength and tensile strength are low, and there are many dimples.

[0113] As can be seen from Comparative Example 4, when the addition amount of nano-sepiolite is too large, the density of the material is high, which is not conducive to weight reduction. Moreover, the uniformity of the material components becomes poor, the foaming effect is worse, the notched impact strength and tensile strength are lower, and there are more pits.

[0114] As can be seen from Comparative Example 5, without adding a compatibilizer, the dispersion of nano-sepiolite in polypropylene is poor, the melt strength is low, the foaming effect is poor, the notched impact strength and tensile strength are low, and there are many pits.

[0115] As can be seen from Comparative Example 6, when the addition amount of the compatibilizer is too large, the melt strength of the material is even lower, the foaming effect is poor, the notched impact strength and tensile strength are even lower, and there are more pits.

[0116] As can be seen from Comparative Example 7, the nano-sepiolite is not treated with mPEG-silane. The compatibility between nano-sepiolite and PP is poor, and it is easy to agglomerate due to poor dispersion in PP. The melt strength of the material is low, the foaming effect is poor, the notched impact strength and tensile strength are even lower, and there are more pits.

[0117] As can be seen from Comparative Example 8, when the nano-sepiolite is treated with mPEG-silane with a weight-average molecular weight exceeding 5000, the melt strength of the obtained material is low, the foaming effect is poor, and there are many pits.

[0118] As can be seen from Example 1 and Examples 4 to 5, when the weight ratio of maleic anhydride-grafted polypropylene to the nano-sepiolite is (0.1 to 0.3):1, it is more beneficial to the dispersion of nano-sepiolite in PP and the melt strength of the material. The notched impact strength and tensile strength of the material are high, and there are few pits.

[0119] As can be seen from Example 1 and Examples 7 to 8, when the toughening agent is ethylene-butene copolymer, it is more beneficial to foaming. The density of the material is lower, the notched impact strength and tensile strength are higher, and there are fewer pits.

[0120] As can be seen from Example 1 and Examples 9 to 10, when the compatibilizer is maleic anhydride-grafted PP with a grafting rate of 0.8 to 1.0%, it is more beneficial to the compatibility between nano-sepiolite and PP and to improve the melt strength, and the foaming effect of the material is better.

[0121] As can be seen from Example 1 and Example 11, when the mesh number of nano-sepiolite is 350 to 450 mesh, it is more beneficial to improve the melt strength and foaming. The notched impact strength and tensile strength of the material are higher, and there are fewer pits.

[0122] As can be seen from Example 1 and Examples 12 to 13, when the molecular weight of mPEG-silane is in the range of 1500 to 3000, it is more beneficial to improve the dispersion of nano-sepiolite and its compatibility with PP, thereby improving the melt strength and foaming effect of the material, and the surface resistance is lower.

[0123] It can be seen from Example 1 and Examples 14 to 15 that the properties of the nano-sepiolite with mPEG-silane surface-bonded are more excellent, and the antistatic performance is better.

[0124] Obviously, the above-mentioned embodiments of the present invention are only examples for clearly explaining the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation manners here. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the claims of the present invention.

Claims

1. A microcellular polypropylene composite material, the microcellular polypropylene composite material comprising a polypropylene composite material and a foaming agent, characterized in that, The polypropylene composite material comprises the following components by weight parts: The modified nano-sepiolite is nano-sepiolite surface-bonded with mPEG-silane, nano-sepiolite surface-bonded with γ-aminopropyltriethoxysilane or nano-sepiolite surface-bonded with n-octyltriethoxysilane; The weight-average molecular weight of the mPEG-silane is 1000-5000; The weight ratio of the foaming agent to the polypropylene composite material is (0.01-0.04):1; The compatibilizer is maleic anhydride grafted polyolefin.

2. The microcellular polypropylene composite material according to claim 1, wherein The weight ratio of the compatibilizer to the modified nano-sepiolite is (0.1-0.3):1; and / or the mesh number of the modified nano-sepiolite is 200-500 mesh.

3. The micro-foamed polypropylene composite material according to claim 1, wherein, In the modified nano-sepiolite, the weight ratio of mPEG-silane to the modified nano-sepiolite is (0.048-0.23):1; in the modified nano-sepiolite, the weight ratio of γ-aminopropyltriethoxysilane to the modified nano-sepiolite is (0.048-0.23):1; in the modified nano-sepiolite, the weight ratio of n-octyltriethoxysilane to the modified nano-sepiolite is (0.048-0.23):

1.

4. The micro-foamed polypropylene composite material according to claim 1, characterized in that, The polypropylene resin is homopolypropylene resin and / or copolymer polypropylene resin, the melt mass flow rate of the polypropylene resin is 10-60 g / 10 min, the test standard is ISO 1133-2011, and the test condition is 230 °C / 2.16 kg.

5. The microcellular polypropylene composite material according to claim 1, wherein The polypropylene composite material comprises the following components by weight parts:

6. The microcellular polypropylene composite material according to claim 1, wherein In the compatibilizer, the mass grafting rate of maleic anhydride is 0.7-1.3%; the compatibilizer is maleic anhydride grafted polypropylene and / or maleic anhydride grafted POE.

7. The microcellular polypropylene composite material according to claim 1, wherein The toughening agent is one or more of ethylene-butene copolymer, ethylene-octene copolymer or styrenic copolymer elastomer.

8. The micro-foamed polypropylene composite material according to claim 1, characterized in that The auxiliary agent is antioxidant and / or light stabilizer; the antioxidant is hindered phenol antioxidant and / or phosphite antioxidant; the light stabilizer is hindered amine light stabilizer.

9. The preparation method of the microcellular polypropylene composite material according to any one of claims 1 to 8, characterized in that, Comprising the following steps: S1. Mix the polypropylene resin, toughening agent, modified nano-sepiolite, compatibilizer and auxiliary agent, melt-extrude and pelletize through an extruder, and obtain the polypropylene composite material after drying; S2. Mix the polypropylene composite material prepared in step S1 with the foaming agent, and injection mold to obtain the microcellular polypropylene composite material.

10. Use of the microcellular polypropylene composite material according to any one of claims 1-8 in the preparation of automotive interiors.

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