Antistatic polypropylene and preparation method thereof

Abstract

The invention discloses an antistatic polypropylene and carbon nanotube compound and a preparation method thereof. The polypropylene and the carbon nanotubes are connected through dynamic covalent bonds with thermal reversibility, and the aggregation phenomenon of the carbon nanotubes in the polypropylene is completely inhibited while the melt processing performance of the compound is retained, so that the compound obtains excellent antistatic performance under the condition of extremely low addition amount of the carbon nanotubes, and the antistatic property of the compound is improved. Meanwhile, due to the carbon nano tubes with low addition amount, the composite film has light transmission.

Description

Technical Field

[0001] The present invention relates to antistatic polypropylene and a preparation method thereof, in particular to a preparation method of a transparent antistatic polypropylene and carbon nanotube composite resin. Background Art

[0002] Polypropylene has excellent chemical resistance, easy processing and recyclability, and has become one of the most widely used polymer materials today. Especially with the rapid development of the electronics industry, chemically inert polypropylene films are becoming more and more common in electronic device packaging. However, the significant electrical insulation properties of polypropylene make its surface resistivity between 10 18 ~10 16 During production and use, static electricity is generated and accumulated on the surface of materials due to friction, peeling, and induction. This accumulation of static electricity can cause electrostatic hazards, including dust attraction, discharge, cracking, and, in extreme cases, combustion or explosion. In complex electronic device packaging, even small amounts of static electricity and dust can cause substantial damage. Therefore, there is an urgent need to improve the antistatic properties of polypropylene.

[0003] The surface resistivity of polymers used as antistatic materials generally needs to be around 10 11 ~10 6The addition of carbon-based nanofillers such as carbon black, carbon nanotubes, and graphene to polymer matrices is an effective method for improving antistatic properties. Carbon nanotubes (CNTs) offer excellent electrical, thermal, mechanical, and chemical properties, a large specific surface area, and are readily available and inexpensive, making them highly cost-effective carbon-based nanofillers. However, due to their high surface energy and specific surface area, CNTs are prone to aggregation, especially in typical non-polar polymers such as polypropylene. Aggregation significantly reduces the effectiveness of the CNTs in forming a percolation network, thereby weakening their ability to enhance the polymer's electrical properties. Even with high-shear melt processing equipment to promote uniform dispersion of CNTs, a mass loading of CNTs in the polypropylene matrix often requires exceeding 5% to ensure stable antistatic properties. This is due to the weak interaction between polypropylene and CNTs, and evenly dispersed CNTs tend to reaggregate during the molding and repeated processing of polymer products. Therefore, despite the long-standing research and extensive application of CNT-modified polymers, effectively enhancing the interaction between polypropylene and CNTs remains a challenge for researchers. Patent CN118388885A reports a method for fundamentally enhancing the interaction between polypropylene and carbon nanotubes by forming covalent bonds through the Diels-Alder (DA) reaction. Because the DA reaction is a thermally dissociated, dynamically reversible covalent bond, the DA bonds dissociate during polypropylene melt processing, breaking the covalent bonds between the polypropylene and carbon nanotubes. The bonds then re-bond during cooling and molding, without affecting the high-temperature processing properties of polypropylene. This method addresses the difficulty in processing permanent crosslinked polymers formed by conventional covalent bonds. Because the covalent bonds dissociate during melt processing at high temperatures, it is difficult to effectively suppress the aggregation tendency of carbon nanotubes in the polypropylene melt. Therefore, this method requires a carbon nanotube loading of at least 2% by mass, with an optimal loading of 5-10%. However, at this loading, the polypropylene / carbon nanotube composite already appears black and loses transparency, limiting its potential use as a transparent packaging material.

[0004] Therefore, it is essential to develop a new material that can maintain the covalent bond between polypropylene and carbon nanotubes under melt processing conditions while also being adaptable to rapid processing and molding. By more effectively suppressing the aggregation of carbon nanotubes in polypropylene melts at high temperatures, the carbon nanotube loading can be further reduced, potentially yielding polypropylene and carbon nanotube composite resins that are both antistatic and transparent, broadening the application areas of antistatic polypropylene. Summary of the Invention

[0005] The present invention provides an antistatic polypropylene and carbon nanotube composite and a method for preparing the same. In the composite, the polypropylene and carbon nanotubes are connected via a special ester bond. This ester bond contains a carboxyl group adjacent to the carbon nanotube, which in situ catalyzes an ester exchange reaction. This ester exchange reaction forms an associative, dynamically reversible covalent bond with the hydroxyl groups on the carbon nanotube surface (the exchange rate accelerates with increasing temperature). This ensures that the covalent bond between the polypropylene and carbon nanotubes remains intact even at high temperatures, while the composite adapts to melt processing through the ongoing ester exchange reaction, thereby achieving both bonding and processability.

[0006] To achieve the above objectives, the composite of polypropylene and carbon nanotubes of the present invention has the following characteristics:

[0007] The composite of polypropylene and carbon nanotubes of the present invention is prepared by reacting polypropylene and hydroxylated carbon nanotubes. The polypropylene and carbon nanotubes in the composite are connected by ester bonds and have the following structure:

[0008]

[0009] Wherein, x, y, and z are integers, x=200-20000, preferably x=200-10000; y=0.00005x-0.05x, preferably y=0.0001x-0.01x; z=0.00005x-0.05x, preferably z=0.0001x-0.01x.

[0010] In the composite of polypropylene and carbon nanotubes of the present invention, the number of the ester bonds connecting the polypropylene and the carbon nanotubes is equal to the number of the carboxyl groups adjacent to the ester bonds.

[0011] In the composite of polypropylene and carbon nanotubes of the present invention, the mass content of the polypropylene component is 97% to 99.9%, preferably 99% to 99.9%; the mass content of the carbon nanotube component is 0.1% to 3%, preferably 0.1% to 1%.

[0012] The polypropylene and carbon nanotubes of the present invention are connected by dynamic covalent bonds with thermal reversibility. While retaining the melt processing performance of the composite, the aggregation of carbon nanotubes in the polypropylene is completely suppressed, so that the composite obtains excellent antistatic properties at an extremely low addition amount of carbon nanotubes. At the same time, the low addition amount of carbon nanotubes also makes the composite film light-transmitting.

[0013] Another object of the present invention is to provide a method for preparing the composite of polypropylene and carbon nanotubes, which can be prepared by either method 1 or method 2. The specific method is as follows:

[0014] Method 1: Preparation by two-step method

[0015] (1) Using polypropylene, maleic anhydride, initiator, and thermal stabilizer as raw materials, reacting in a melt processing device;

[0016] (2) using the product obtained in step (1), hydroxylated carbon nanotubes, and a thermal stabilizer as raw materials, reacting in a melt processing device to obtain the composite of polypropylene and carbon nanotubes;

[0017] Method 2: Preparation by one-step method

[0018] The preparation is carried out in a reactive melt processing equipment with a side feed port. Polypropylene, maleic anhydride, an initiator, and a thermal stabilizer are used as raw materials and added to the processing equipment from a main feed port. Hydroxylated carbon nanotubes are added to the processing equipment from a side feed port to react to obtain the composite of polypropylene and carbon nanotubes.

[0019] The reaction mechanism of polypropylene and hydroxylated carbon nanotubes of the present invention is as follows:

[0020]

[0021] Among them, a, x, y1, y, and z are integers, a=x+y1, y1=y+z, x=200~20000, preferably x=200~10000; y=0.00005x~0.05x, preferably y=0.0001x~0.01x; z=0.00005x~0.05x, preferably z=0.0001x~0.01x.

[0022] Furthermore, the reactive melt processing equipment with a side feed port includes a main feed port, a side feed port and an outlet port, wherein the side feed port is located between the main feed port and the outlet port, and preferably the side feed port is located at 1 / 2 to 2 / 3 between the main feed port and the outlet port.

[0023] Furthermore, when the polypropylene and carbon nanotube composite is prepared by method 1, in step (1), the mass ratio of the polypropylene to maleic anhydride is 99.9:0.1 to 90:10, preferably 99:1 to 95:5; the mass ratio of the polypropylene to the initiator is 100:0.01 to 100:1, preferably 100:0.1 to 100:1; the mass ratio of the polypropylene to the thermal stabilizer is 100:0.1 to 100:1, preferably 100:0.5 to 100:1; in step (2), the mass ratio of the product obtained in step (1) to the hydroxylated carbon nanotubes is 99.9:0.1 to 97:3, preferably 99.9:0.1 to 99:1; the mass ratio of the product obtained in step (1) to the thermal stabilizer is 100:0.1 to 100:1, preferably 100:0.5 to 100:1.

[0024] Furthermore, when the polypropylene and carbon nanotube composite is prepared by method 2, the mass ratio of the polypropylene to maleic anhydride is 99.9:0.1 to 90:10, preferably 99:1 to 95:5; the mass ratio of the polypropylene to the initiator is 100:0.01 to 100:1, preferably 100:0.1 to 100:1; the mass ratio of the polypropylene to the heat stabilizer is 100:0.1 to 100:1, preferably 100:0.5 to 100:1; the mass ratio of the polypropylene to the hydroxylated carbon nanotubes is 99.9:0.1 to 97:3, preferably 99.9:0.1 to 99:1.

[0025] Furthermore, when the polypropylene and carbon nanotube composite is prepared by method 1, the melt processing equipment used in step (1) and step (2) is one of a single-screw extruder, a twin-screw extruder, and an internal mixer; the processing temperature of step (1) is 170°C to 230°C, preferably 190°C to 210°C, and the processing time is 1 to 10 minutes, preferably 3 to 8 minutes; the processing temperature of step (2) is 170°C to 230°C, preferably 180°C to 200°C, and the processing time is 1 to 10 minutes, preferably 2 to 6 minutes.

[0026] Furthermore, when method 2 is used to prepare the polypropylene and carbon nanotube composite, the melt processing equipment is a single-screw extruder or a twin-screw extruder with a side feed port; the processing temperature between the main feed port and the side feed port is 170°C to 230°C, preferably 200°C to 220°C, and the residence time is 1 to 10 minutes, preferably 2 to 5 minutes; the processing temperature from the side feed port section to the outlet section is 170°C to 230°C, preferably 180°C to 200°C, and the residence time is 1 to 10 minutes, preferably 2 to 4 minutes.

[0027] In the above-mentioned method for preparing a composite of polypropylene and carbon nanotubes, the initiator is a thermal decomposition free radical initiator selected from an organic peroxide, preferably one or more of an alkyl peroxide, an alkynyl peroxide, a hydroperoxide, an acyl peroxide, and a peroxycarbonate. More preferably, the initiator component is selected from one or more of benzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, diisopropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, 2,5-dimethyl-2,5-di-tert-butylperoxyhexane, and 2,5-dimethyl-2,5-di-tert-butylperoxy-3-hexyne.

[0028] Furthermore, when the polypropylene and carbon nanotube composite is prepared by method 1, the initiator used in step (1) is preferably an alkynyl peroxide initiator, and the mass ratio of the polypropylene to the initiator is 100:0.01 to 100:1, preferably 100:0.1 to 100:0.5.

[0029] Furthermore, when the polypropylene and carbon nanotube composite is prepared by method 2, the initiator is preferably an alkyl peroxide initiator, and the mass ratio of the polypropylene to the initiator is 100:0.01 to 100:1, preferably 100:0.1 to 100:0.5.

[0030] In the above-mentioned method for preparing the composite of polypropylene and carbon nanotubes, the heat stabilizer is at least one of a hindered phenol antioxidant, a phosphite antioxidant, or an alkyl ester antioxidant, for example, phenol, trimethylphenol, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (commonly known as 1010), tris(2,4-di-tert-butyl)phenyl phosphite (commonly known as 168), tris(nonylphenyl)phosphite, and tris(2,4-di-tert-butylphenyl)phosphite.

[0031] In the preparation method of the above-mentioned composite of polypropylene and carbon nanotubes, the diameter of the hydroxylated carbon nanotubes is 1 to 50 nm, preferably 5 to 20 nm, the length is 1 to 500 μm, preferably 10 to 100 μm, the aspect ratio is 10 to 5000, preferably 50 to 1000, and the mass content of hydroxyl groups is 0.1 to 10%, preferably 1 to 6%.

[0032] The composite of polypropylene and carbon nanotubes of the present invention is used as a transparent antistatic resin material.

[0033] The invention relates to the use of the composite of polypropylene and carbon nanotubes in the preparation of polypropylene molded products.

[0034] The present invention constructs a self-catalytic ester exchange type dynamic reversible covalent bond between polypropylene macromolecules and carbon nanotubes, making the formed covalent bond exchangeable without breaking, while meeting the material's processability and the function of inhibiting carbon nanotube aggregation. This method also significantly reduces the carbon nanotube content required when the composite is used as an antistatic resin, greatly improving the material's light transmittance. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematic diagram of a screw extruder with a side feed port.

[0036] Figure 2 It is the infrared spectra of comparative example and embodiment.

[0037] Figure 3 The curves of the complex viscosity of the comparative example and the embodiment as a function of shear frequency are shown in FIG.

[0038] Figure 4 The following are transmission electron microscope photos of comparative examples and embodiments.

[0039] Figure 5The transparency comparison photos of the comparative example and example sample films are shown in FIG. DETAILED DESCRIPTION

[0040] The present invention provides the following examples as further illustrations, but they are not intended to limit the scope of protection of the claims of the present invention.

[0041] Polypropylene: purchased from Lanzhou Petrochemical, brand T30S.

[0042] Carbon nanotubes, hydroxylated carbon nanotubes, and carboxylated carbon nanotubes were all purchased from Chengdu Organic Chemistry Co., Ltd., Chinese Academy of Sciences. The carbon nanotubes, hydroxylated carbon nanotubes, and carboxylated carbon nanotubes had diameters of 5-15 nm, lengths of 10-30 μm, and aspect ratios of 100-1000. The hydroxylated carbon nanotubes had a hydroxyl content of 5.58% by mass, while the carboxylated carbon nanotubes had a carboxyl content of 3.86% by mass.

[0043] 2,5-Dimethyl-2,5-di-tert-butylperoxy-3-hexyne: purchased from Anaiji Chemical (CAS: 1068-27-5).

[0044] 2,5-Dimethyl-2,5-di-tert-butylperoxyhexane: purchased from Anaiji Chemical (CAS: 78-63-7).

[0045] Comparative Example 1

[0046] 100 parts by mass of polypropylene, 0.1 parts of antioxidant 1010, and 0.2 parts of antioxidant 168 were mixed and added to a twin-screw extruder. The extruder temperature was set at 190°C and the residence time was 3 minutes to obtain a product. The product properties are shown in Table 1.

[0047] Comparative Example 2

[0048] 99.8 parts by weight of polypropylene, 0.1 part of antioxidant 1010, 0.2 part of antioxidant 168, and 0.2 part of carbon nanotubes were mixed and added to a twin-screw extruder. The extruder temperature was set at 190°C and the residence time was 3 minutes to obtain a product. Product properties are shown in Table 1.

[0049] Comparative Example 3

[0050] 99 parts by weight of polypropylene, 0.1 parts of antioxidant 1010, 0.2 parts of antioxidant 168, and 1 part of carbon nanotubes were mixed and added to a twin-screw extruder. The extruder temperature was set at 190°C and the residence time was 3 minutes to obtain a product. Product properties are shown in Table 1.

[0051] Comparative Example 4

[0052] 97 parts by weight of polypropylene, 0.1 parts of antioxidant 1010, 0.2 parts of antioxidant 168, and 3 parts of carbon nanotubes were mixed and added to a twin-screw extruder. The extruder temperature was set at 190°C and the residence time was 3 minutes to obtain a product. Product properties are shown in Table 1.

[0053] Comparative Example 5

[0054] Preparation of carbon nanotubes containing maleimide groups: 10.0g of maleic anhydride was added to a three-necked flask containing 20mL of anhydrous methanol. The flask was placed in an ice-water bath at 0°C and stirred. Then, 3.7g of ethanolamine was slowly added to the flask and the temperature was slowly raised to about 65°C and refluxed for 24 hours. After the reaction, the solution temperature was cooled to room temperature and placed in a refrigerator to freeze until crystals precipitated. The solid was filtered and collected, and dried in a vacuum oven to obtain 4-(2,3-dimethyl)maleimidobutanol. 50g of carboxylated carbon nanotubes were dispersed in 1L of dichloromethane, and 9.8g of the prepared 4-(2,3-dimethyl)maleimidobutanol and 0.5g of p-toluenesulfonic acid were added. The solution was heated to about 40°C and refluxed, the water was separated, and the reaction was stirred for 2 hours. The reaction solution was washed with saturated NaHCO3 solution until neutral and filtered to obtain carbon nanotubes containing maleimide groups.

[0055] In parts by mass, 98 parts of polypropylene, 2 parts of 2-[[(4-vinylphenyl)methoxy]methyl]-furan The mixture was prepared by mixing 0.1 part of antioxidant 1010, 0.2 part of antioxidant 168, and 0.2 part of initiator 2,5-dimethyl-2,5-di-tert-butylperoxy-3-hexyne (synthesized with reference to Macromolecules, 1998, 31, 314-321) and adding the mixture to a twin-screw extruder. The extruder temperature was 200°C, and the residence time was 3 minutes. The extrudate was cooled in a circulating water bath and pelletized to obtain intermediate product A.

[0056] 99 parts by mass of intermediate product A, 0.1 parts of antioxidant 1010, 0.2 parts of antioxidant 168, and 1 part of carbon nanotubes containing maleimide groups were mixed and added to a single-screw extruder at a temperature of 190° C. and a residence time of 4 minutes to obtain a product.

[0057] The product is a composite of polypropylene and carbon nanotubes connected by thermally dissociated DA dynamic reversible covalent bonds. The product properties are shown in Table 1.

[0058] Example 1

[0059] 98 parts by mass of polypropylene, 2 parts of maleic anhydride, 0.1 parts of antioxidant 1010, 0.2 parts of antioxidant 168, and 0.2 parts of initiator 2,5-dimethyl-2,5-di-tert-butylperoxy-3-hexyne were mixed and added to a twin-screw extruder. The extruder temperature was 200°C, and the residence time was 3 minutes. The extrudate was cooled in a circulating water bath and pelletized to obtain intermediate product A.

[0060] 99.9 parts by weight of Intermediate Product A, 0.1 parts of Antioxidant 1010, 0.2 parts of Antioxidant 168, and 0.1 parts of hydroxylated carbon nanotubes were mixed and added to a single-screw extruder. The extruder temperature was set at 190°C and the residence time was 4 minutes to obtain the product. Product properties are shown in Table 1.

[0061] Example 2

[0062] 98 parts by mass of polypropylene, 2 parts of maleic anhydride, 0.1 parts of antioxidant 1010, 0.2 parts of antioxidant 168, and 0.2 parts of initiator 2,5-dimethyl-2,5-di-tert-butylperoxy-3-hexyne were mixed and added to a twin-screw extruder. The extruder temperature was 200°C, and the residence time was 3 minutes. The extrudate was cooled in a circulating water bath and pelletized to obtain intermediate product A.

[0063] 99.8 parts by weight of Intermediate Product A, 0.1 part of Antioxidant 1010, 0.2 part of Antioxidant 168, and 0.2 part of hydroxylated carbon nanotubes were mixed and added to a single-screw extruder. The extruder temperature was set at 190°C and the residence time was 4 minutes to obtain the product. Product properties are shown in Table 1.

[0064] Example 3

[0065] 97 parts by mass of polypropylene, 3 parts of maleic anhydride, 0.1 parts of antioxidant 1010, 0.2 parts of antioxidant 168, and 0.3 parts of initiator 2,5-dimethyl-2,5-di-tert-butyl peroxyhexane were mixed and added to the main feed of a twin-screw extruder. 0.4 parts of hydroxylated carbon nanotubes were added to the side feed of the twin-screw extruder (located halfway between the main feed and the discharge). The temperature between the main feed and the side feed of the extruder was 210°C, and the residence time was 3 minutes. The temperature between the side feed and the discharge of the extruder was 190°C, and the residence time was 3 minutes. The properties of the resulting product are shown in Table 1.

[0066] Example 4

[0067] 97 parts by mass of polypropylene, 3 parts of maleic anhydride, 0.1 parts of antioxidant 1010, 0.2 parts of antioxidant 168, and 0.3 parts of initiator 2,5-dimethyl-2,5-di-tert-butyl peroxyhexane were mixed and added to the main feed of a twin-screw extruder. 0.6 parts of hydroxylated carbon nanotubes were added to the side feed of the twin-screw extruder (located halfway between the main feed and the discharge). The temperature between the main feed and the side feed of the extruder was 210°C, and the residence time was 3 minutes. The temperature between the side feed and the discharge was 180°C, and the residence time was 4 minutes. The resulting product properties are shown in Table 1.

[0068] Example 5

[0069] 96 parts by mass of polypropylene, 3 parts of maleic anhydride, 0.1 parts of antioxidant 1010, 0.2 parts of antioxidant 168, and 0.3 parts of initiator 2,5-dimethyl-2,5-di-tert-butyl peroxyhexane were mixed and added to the main feed of a twin-screw extruder. 0.8 parts of hydroxylated carbon nanotubes were added to the side feed of the twin-screw extruder (located halfway between the main feed and the discharge). The temperature between the main feed and the side feed of the extruder was 210°C, with a residence time of 3 minutes; the temperature between the side feed and the discharge was 185°C, with a residence time of 3 minutes. The resulting product properties are shown in Table 1.

[0070] Example 6

[0071] 96 parts by mass of polypropylene, 4 parts of maleic anhydride, 0.1 parts of antioxidant 1010, 0.2 parts of antioxidant 168, and 0.5 parts of initiator 2,5-dimethyl-2,5-di-tert-butylperoxy-3-hexyne were mixed and added to a twin-screw extruder. The extruder temperature was 200°C, and the residence time was 4 minutes. The extrudate was cooled in a circulating water bath and pelletized to obtain intermediate product A.

[0072] 99 parts by weight of Intermediate Product A, 0.1 part of Antioxidant 1010, 0.2 part of Antioxidant 168, and 1 part of hydroxylated carbon nanotubes were mixed and added to a single-screw extruder. The extruder temperature was set at 190°C and the residence time was 4 minutes to obtain the product. Product properties are shown in Table 1.

[0073] Example 7

[0074] 96 parts by mass of polypropylene, 4 parts of maleic anhydride, 0.1 parts of antioxidant 1010, 0.2 parts of antioxidant 168, and 0.5 parts of initiator 2,5-dimethyl-2,5-di-tert-butylperoxy-3-hexyne were mixed and added to a twin-screw extruder. The extruder temperature was 200°C, and the residence time was 4 minutes. The extrudate was cooled in a circulating water bath and pelletized to obtain intermediate product A.

[0075] 97 parts by weight of Intermediate Product A, 0.1 parts of Antioxidant 1010, 0.2 parts of Antioxidant 168, and 3 parts of hydroxylated carbon nanotubes were mixed and added to a single-screw extruder. The extruder temperature was set at 190°C and the residence time was 4 minutes to obtain the product. Product properties are shown in Table 1.

[0076] Table 1 Polymer composition and properties

[0077]

[0078] From Table 1 and Figures 2 to 5 It can be seen that the polypropylene composite material prepared by the present invention has the following characteristics:

[0079] (1) The ester bond between polypropylene and carbon nanotubes can be confirmed from the infrared spectrum of the product, such as Figure 2 The polypropylene raw material of Comparative Example 1 was -1 The characteristic peak at 1850 cm -1 and 1780cm -1 The peaks at 1730 cm correspond to the asymmetric stretching vibration and symmetric stretching vibration of the carbonyl group in the anhydride. -1 The small peak at 1780 cm is related to the carbonyl formed by partial hydrolysis of the anhydride. In Examples 2, 4, 6 and 7, after the anhydride ring is opened, the carbonyl intensity in the anhydride is 1780 cm -1 The newly formed ester group gradually decreases at 1730 cm -1 The absorption at the point gradually increases, indicating that the content of ester bonds gradually increases with the increase of carbon nanotube addition amount.

[0080] (2) The formation of the polypropylene cross-linked network can be confirmed from the melt rheology test (190 ° C) curve of the product, such as Figure 3 As shown. The curve of the complex viscosity of the product as a function of shear frequency shows that: first, the complex viscosity of the polypropylene raw material (Comparative Example 1) is basically constant in the low frequency region, showing the Newtonian platform phenomenon of linear polymers. Secondly, the samples of Example 2 and Example 4 have carbon nanotube mass contents of 0.2% and 0.6% respectively, and there are also ester bonds between the polypropylene and the carbon nanotubes ( Figure 1(as evidenced by infrared spectra), the Newtonian plateau of the linear polymer was maintained. This indicates that, under the catalysis of the adjacent carboxyl groups, the crosslinked network can rapidly undergo transesterification, allowing the material to adapt to melt shear and flow, thus achieving processability. This is consistent with the melt index results in Table 1. Furthermore, Example 6 exhibits a significant increase in the complex viscosity in the low-frequency region, exhibiting an upward trend, a typical manifestation of entanglement due to the crosslinked structure. This indicates that the upward trend becomes more pronounced with increasing crosslinking. These results directly demonstrate the presence of a dynamic crosslinked network structure in the system.

[0081] (3) The ester bond between polypropylene and carbon nanotubes enhances the interaction between them, which makes the carbon nanotubes less likely to agglomerate. Figure 4 The carbon nanotubes in Comparative Example 3 and Example 6 both have a mass content of 1%, but the carbon nanotubes in Example 6 are very uniformly dispersed in the polypropylene matrix, while the carbon nanotubes in Comparative Example 3 exhibit significant agglomeration.

[0082] (4) Since the carbon nanotubes of the present invention are very uniformly dispersed in the polypropylene matrix, the carbon nanotubes can form a significant percolation network at extremely low concentrations, which makes the products prepared in the examples have lower surface resistivity than the products prepared by the conventional blending method (Comparative Examples 2, 3, and 4), as shown in Table 1. It should be noted that Comparative Example 5 prepared a polypropylene and carbon nanotube composite based on a thermally dissociated DA dynamic reversible covalent bond, and its carbon nanotube mass content was equivalent to that of Example 6, while the surface resistivity of Example 6 was four orders of magnitude lower than that of Comparative Example 5. This is precisely because the associative dynamic covalent bond (non-dissociated) adopted in the present invention completely suppressed the problem of separation of carbon nanotubes and polypropylene at high temperatures, and the antistatic property of the material was significantly improved.

[0083] (5) The composite of polypropylene and carbon nanotubes prepared by the present invention has excellent light transmittance, as shown in Table 1 and Figure 5 The surface resistivity of the composite film of the present invention is reduced to 10 8 ~10 7 When the surface resistivity is Ω, only 0.2% to 0.6% carbon nanotubes by mass need to be added, and the film has good light transmittance. However, under similar surface resistivity, the conventional blending method requires the addition of 3% carbon nanotubes by mass (Comparative Example 4), and the DA dynamically reversible covalently bonded polypropylene and carbon nanotube composite requires the addition of 1% carbon nanotubes by mass (Comparative Example 5). Under these conditions, the film has basically lost its light transmittance and cannot be used as a transparent / translucent packaging material.

Claims

1. A composite of polypropylene and carbon nanotubes, characterized in that: The composite is prepared by reacting polypropylene and hydroxylated carbon nanotubes. The polypropylene and carbon nanotubes in the composite are connected by ester bonds and have the following structure: Wherein, x, y, and z are integers, x=200 to 20000, y=0.00005x to 0.05x, and z=0.00005x to 0.05x.

2. The polypropylene and carbon nanotube composite according to claim 1, wherein: The mass content of the polypropylene component is 97% to 99.9%, preferably 99% to 99.9%; the mass content of the carbon nanotube component is 0.1% to 3%, preferably 0.1% to 1%.

3. The method for preparing the polypropylene and carbon nanotube composite according to claim 1 or 2, characterized in that: The method is prepared by method 1 or method 2, comprising the following steps: Method 1: Two-step preparation (1) Using polypropylene, maleic anhydride, initiator and thermal stabilizer as raw materials, the reaction is carried out in a melt processing equipment. (2) using the product obtained in step (1), hydroxylated carbon nanotubes, and a thermal stabilizer as raw materials, reacting in a melt processing device to obtain the composite of polypropylene and carbon nanotubes; Method 2: One-step preparation The preparation is carried out in a reactive melt processing equipment with a side feed port. Polypropylene, maleic anhydride, an initiator, and a thermal stabilizer are used as raw materials and added to the processing equipment from a main feed port. Hydroxylated carbon nanotubes are added to the processing equipment from a side feed port to react and obtain the composite of polypropylene and carbon nanotubes.

4. The method for preparing a composite of polypropylene and carbon nanotubes according to claim 3, wherein: When the polypropylene and carbon nanotube composite is prepared by method 1, in step (1), the mass ratio of the polypropylene to maleic anhydride is 99.9:0.1 to 90:10, the mass ratio of the polypropylene to the initiator is 100:0.01 to 100:1, and the mass ratio of the polypropylene to the thermal stabilizer is 100:0.1 to 100:1; in step (2), the mass ratio of the product obtained in step (1) to the hydroxylated carbon nanotubes is 99.9:0.1 to 97:3; and the mass ratio of the product obtained in step (1) to the thermal stabilizer is 100:0.1 to 100:1; When the polypropylene and carbon nanotube composite is prepared by method 2, the mass ratio of the polypropylene to maleic anhydride is 99.9:0.1 to 90:10, the mass ratio of the polypropylene to the initiator is 100:0.01 to 100:1, the mass ratio of the polypropylene to the heat stabilizer is 100:0.1 to 100:1, and the mass ratio of the polypropylene to the hydroxylated carbon nanotubes is 99.9:0.1 to 97:

3.

5. The method for preparing a composite of polypropylene and carbon nanotubes according to claim 3, wherein: When the polypropylene and carbon nanotube composite is prepared by method 1, the melt processing equipment used in step (1) and step (2) is one of a single-screw extruder, a twin-screw extruder, and an internal mixer; the processing temperature of step (1) is 170° C. to 230° C., preferably 190° C. to 210° C., and the processing time is 1 to 10 minutes, preferably 3 to 8 minutes; the processing temperature of step (2) is 170° C. to 230° C., preferably 180° C. to 200° C., and the processing time is 1 to 10 minutes, preferably 2 to 6 minutes; When the polypropylene and carbon nanotube composite is prepared by method 2, the melt processing equipment is a single-screw extruder or a twin-screw extruder with a side feed port; the processing temperature between the main feed port and the side feed port is 170°C to 230°C, preferably 200°C to 220°C, and the residence time is 1 to 10 minutes, preferably 2 to 5 minutes; the processing temperature from the side feed port section to the outlet section is 170°C to 230°C, preferably 180°C to 200°C, and the residence time is 1 to 10 minutes, preferably 2 to 4 minutes.

6. The method for preparing a composite of polypropylene and carbon nanotubes according to claim 3, wherein: The initiator is a thermal decomposition free radical initiator selected from organic peroxides, preferably one or more of alkyl peroxides, alkynyl peroxides, hydroperoxides, acyl peroxides and peroxycarbonates. When the polypropylene and carbon nanotube composite is prepared by method 1, the initiator used in step (1) is preferably an alkynyl peroxide initiator; When the polypropylene and carbon nanotube composite is prepared by method 2, the initiator is preferably an alkyl peroxide initiator.

7. The method for preparing a composite of polypropylene and carbon nanotubes according to claim 3, wherein: The heat stabilizer is at least one of a hindered phenol antioxidant, a phosphite antioxidant or an alkyl ester antioxidant.

8. The method for preparing a composite of polypropylene and carbon nanotubes according to claim 3, wherein: The hydroxylated carbon nanotubes have a diameter of 1 to 50 nm, preferably 5 to 20 nm, a length of 1 to 500 μm, preferably 10 to 100 μm, an aspect ratio of 10 to 5000, preferably 50 to 1000, and a hydroxyl content of 0.1 to 10%, preferably 1 to 6%.

9. Use of the composite of polypropylene and carbon nanotubes according to any one of claims 1 to 8 as a transparent antistatic resin material.

10. The use according to claim 9, characterized in that The composite of polypropylene and carbon nanotubes is used in the preparation of polypropylene molded products.

Images