Antistatic polyamide composite material and preparation method thereof

Abstract

The invention discloses a kind of antistatic polyamide composite material and preparation method thereof, belong to the field of antistatic material preparation technology.The above-mentioned method comprises the following steps: (1) conductive carbon black is surface-modified using liquid phase ozone oxidation method to obtain carboxyl modified carbon black; (2) diamine and diprotic acid are dissolved in a certain amount of deionized water and added to a high temperature and high pressure reactor, and nitrogen protection, after reacting 1 3h, diprotic acid or diamine is used to adjust pH to 6.5 7.5; (3) then catalyst, antioxidant, lubricant and end group modifier are added to the above-mentioned reactor, react for one end time, then carboxyl modified carbon black is added and prepolymerized; (4) vacuum polycondensation is performed afterwards to obtain antistatic polyamide composite material.Preparation method of the present invention can significantly improve the electrical conductivity of polyamide composite material, realize antistatic modification of polyamide material, and improve mechanical property.

Description

Technical Field

[0001] The present invention relates to the technical field of polyamide composite material preparation, in particular to an antistatic polyamide composite material and a preparation method thereof. Background Art

[0002] Polyamide, commonly known as nylon, is widely used in automobiles, industrial devices, electronic appliances, and other fields due to its excellent mechanical properties, heat resistance, wear resistance, and corrosion resistance. However, due to its molecular structure, its high insulation properties and poor antistatic properties make it prone to accidents caused by static electricity in some special fields, thus requiring antistatic modification.

[0003] The commonly used polyamide antistatic modification technologies are: (1) Adding conductive fillers: Adding conductive fillers to nylon to form a conductive network structure to achieve an antistatic effect. Commonly used conductive fillers include carbon black, metal powder, metal fiber, etc. These conductive fillers can form a conductive path in nylon, effectively conduct electricity, and reduce the surface resistance of nylon, thereby reducing the possibility of static electricity accumulation. (2) Surface coating: Coating an antistatic coating on the surface of nylon to form a protective layer that prevents static electricity accumulation. This coating is usually composed of a conductive polymer or conductive coating, which can effectively reduce the resistance of the nylon surface, thereby reducing static electricity accumulation. (3) Chemical modification: By introducing conductive groups into the nylon molecular chain, the nylon as a whole has conductive properties. This method can be achieved through copolymerization, cross-linking or functionalization. For example, by introducing monomers containing conductive groups into nylon, such as benzimidazole, thiophene, etc., the conductive properties of nylon can be improved. However, the compatibility of antistatic agents with resin matrices in the prior art is poor, which affects the mechanical properties of the prepared materials. Summary of the Invention

[0004] In view of this, an object of the present invention is to provide an antistatic polyamide composite material and a method for preparing the same. The present invention utilizes in-situ polymerization technology to perfectly disperse an antistatic agent in the polyamide resin during its preparation, thereby resolving the problem of poor compatibility between the filler and the resin and enabling the preparation of a high-performance antistatic resin. This method can significantly reduce the electrical resistance of the polyamide resin and enhance the antistatic properties of the polyamide material.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] In one aspect, the present invention provides a method for preparing an antistatic polyamide composite material, comprising the following steps:

[0007] (1) Surface modification of conductive carbon black using liquid phase ozone oxidation to obtain carboxyl-modified carbon black;

[0008] (2) dissolving the diamine and dibasic acid in a certain amount of deionized water and adding them to a high-temperature and high-pressure reactor under nitrogen protection. After reacting for 1-3 hours, adjust the pH to 6.5-7.5 using the dibasic acid or diamine;

[0009] (3) Then, a catalyst, an antioxidant, a lubricant, and an end group modifier are added to the above-mentioned reactor, and under a nitrogen atmosphere, the pressure is controlled at 0.6-1.8 MPa, and prepolymerization is carried out at 140-220° C. for 0.5-3 h; then, carboxyl-modified carbon black is added through a constant pressure feeding tank, and the constant temperature and pressure reaction is continued for 1-3 h to obtain a carbon black-modified polyamide prepolymer; the end group modifier is a diamine or a diisocyanate;

[0010] (4) Slowly open the vent valve to discharge the water in the system, raise the temperature to 240-280°C, and perform vacuum polycondensation to obtain an antistatic polyamide composite material.

[0011] The diamine is selected from one or more of pentamethylenediamine, hexamethylenediamine, nonamethylenediamine, decanediamine and dodecanediamine, and the dibasic acid is selected from one or more of adipic acid, sebacic acid and dodecanedicarboxylic acid.

[0012] Preferably, the end group modifier is a compound that can react with both polyamide molecules and carboxyl-modified carbon black, which can ensure that the polyamide prepolymer has highly active end groups and successfully link the polyamide prepolymer to the surface of the conductive carbon black by chemical bonds. Preferably, the end group modifier is pentamethylenediamine, hexamethylenediamine, decamethylenediamine, toluene diisocyanate, and isophorone diisocyanate, and the amount used is 0.2%-5% of the total mass of the diamine and dibasic acid.

[0013] The content of carboxyl groups in step (1) is characterized by the ratio of oxygen and nitrogen elements, and the group content is regulated by the surface treatment time and controlled within 0.2-5%.

[0014] Furthermore, step 1 specifically comprises: mixing 5 parts of conductive carbon black and 100 parts of deionized water, introducing ozone for oxidation for 1 hour, then adjusting the pH to 13-14 with a NaOH aqueous solution and continuing oxidation for 5-8 hours. After the oxidation is completed, the oxidized carbon black is filtered and the pH is adjusted to 2-5 with hydrochloric acid, and repeatedly washed with water to separate the carboxyl-modified carbon black.

[0015] Furthermore, the specific amount of each substance used in steps (2)-(3) is:

[0016] 70-130 parts by weight of diamine, 100-180 parts by weight of dibasic acid, 70-180 parts by weight of deionized water, 0.5-3 parts by weight of catalyst, 0.1-3 parts by weight of antioxidant, 0.5-5 parts by weight of lubricant, and 0.5-5 parts by weight of carboxyl-modified carbon black.

[0017] Preferably, the catalyst is one or more of phosphoric acid, phosphorous acid, sodium hydrogen phosphate, disodium hydrogen phosphate, and sodium hypophosphite monohydrate, more preferably phosphoric acid and sodium hypophosphite monohydrate; the antioxidant is selected from one or more of antioxidant 1010, antioxidant H3322, antioxidant H3332, antioxidant 168, and antioxidant SEED, more preferably antioxidant SEED; and the lubricant is silicone oil.

[0018] Furthermore, the step (4) is specifically as follows: exhausting water vapor within 30-60 minutes and controlling the temperature to slowly rise to 240-280°C until normal pressure is restored; the vacuum polycondensation temperature is 240-280°C, the vacuum degree is strictly controlled, the vacuum degree is increased by 0.020MPa every 10 minutes until it reaches -0.099MPa, and after constant pressure reaction for 5-20 minutes, nitrogen is filled in to restore normal pressure, discharging, casting, cooling, and pelletizing.

[0019] On the other hand, the present invention also provides an antistatic polyamide composite material prepared by the above method. The surface / volume resistance of the antistatic polyamide composite material is less than 1×10 10 Ω.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention modifies the conductive carbon black with functional groups so that the carboxyl groups on its surface can be evenly and stably dispersed with polyamide in the preparation system, react with the end groups of the polyamide molecular chain, and realize in-situ polymerization of polyamide on the carbon black surface. This perfectly solves the problem of poor compatibility of carbon black in polyamide resin and difficulty in dispersion. In addition, after the polyamide monomer is pre-polymerized to a certain extent, reactive conductive carbon black is added for staged polymerization, and a special end group modifier is introduced. This can effectively prevent the introduction of conductive carbon black from causing an imbalance in the acid-amine ratio and the loss of polymerization activity of the product, thereby ensuring that the polyamide molecules are effectively polymerized on the carbon black surface. The conductive carbon black polyamide composite material obtained by the present invention not only has good antistatic properties, but also has excellent mechanical properties. DETAILED DESCRIPTION

[0022] In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, a detailed description will be given below with reference to specific embodiments.

[0023] In the present invention, the materials and reagents used, unless otherwise specified, can be obtained from commercial sources.

[0024] The present invention provides an antistatic polyamide composite material and a preparation method thereof, and specific embodiments are as follows.

[0025] Example 1

[0026] A method for preparing an antistatic polyamide composite material is achieved by the following steps:

[0027] (1) Disperse 5 parts of conductive carbon black into 100 parts of deionized water and mix well. Place in an ozone generator, introduce ozone, and oxidize for 1 hour. Then adjust the pH to 13 with a 0.5 mol / L NaOH aqueous solution and continue oxidation for 6 hours. After the oxidation is completed, filter to obtain oxidized carbon black and adjust the pH to 4 with concentrated hydrochloric acid. After repeated water washing and separation, obtain carboxyl-modified carbon black.

[0028] (2) 100 parts by weight of adipic acid was dissolved in 100 parts of deionized water, 69.9 parts of pentamethylenediamine was slowly added, and the mixture was stirred at 60° C. for 1 hour. The pH was adjusted to about 7.2 with pentamethylenediamine to obtain a PA56 salt solution;

[0029] (3) Add 100 parts of PA56 salt solution, 0.5 parts of catalyst, 0.3 parts of antioxidant, 2 parts of lubricant, and 2 parts of pentamethylenediamine end-group modifier to a reactor, evacuate and fill with nitrogen to replace the air in the reactor, and prepolymerize at 200°C and 1.4 MPa for 0.5 h to obtain a low molecular weight polyamide prepolymer. Then, add 2 parts of carboxyl-modified carbon black and 10 parts of deionized water through a constant pressure feeding tank, and continue the reaction at constant temperature and pressure for 2.5 h to obtain a carbon black-modified PA56 prepolymer;

[0030] (4) Slowly open the vent valve and set the temperature to 240°C. Release the air during the heating process. When the temperature reaches 240°C, the pressure in the kettle is 0.6 MPa and the release time is 40 minutes. Continue to heat up to 260°C and slowly release the air to normal pressure. The control time is about 20 minutes. Slowly evacuate the air, increase the vacuum degree by 0.020 MPa every 10 minutes, until it reaches -0.099 MPa. After constant pressure reaction for 10 minutes, fill with nitrogen to restore normal pressure, discharge, cast, cool, and pelletize. Dry in a vacuum oven at 90°C for 6 hours to obtain carboxyl-modified carbon black modified antistatic polyamide 56 resin.

[0031] Example 2

[0032] In step (3) of this example, 100 parts of a PA56 salt solution, 0.5 parts of a catalyst, 0.3 parts of an antioxidant, 2 parts of a lubricant, and 2 parts of a pentamethylenediamine end-group modifier were added to a reaction kettle. The reaction kettle was evacuated and filled with nitrogen to replace the air in the reaction kettle. Prepolymerization was carried out at 200°C and 1.4 MPa for 1.0 hour to obtain a low molecular weight polyamide prepolymer. Then, 2 parts of carboxyl-modified carbon black and 10 parts of deionized water were added via a constant pressure feeding tank. The reaction was continued at constant temperature and pressure for 2.0 hours to obtain a carbon black-modified PA56 prepolymer. The remaining formulation and process parameters were the same as those in Example 1.

[0033] Example 3

[0034] In step (3) of this example, 100 parts of a PA56 salt solution, 0.5 parts of a catalyst, 0.3 parts of an antioxidant, 2 parts of a lubricant, and 2 parts of a pentamethylenediamine end-group modifier were added to a reactor. The reactor was evacuated and filled with nitrogen to displace the air in the reactor. Prepolymerization was carried out at 200°C and 1.4 MPa for 2.0 hours to obtain a low molecular weight polyamide prepolymer. Then, 2 parts of carboxyl-modified carbon black and 10 parts of deionized water were added via a constant pressure feeding tank. The reaction was continued at constant temperature and pressure for 1.0 hour to obtain a carbon black-modified PA56 prepolymer. The remaining formulation and process parameters were the same as those in Example 1.

[0035] Example 4

[0036] A method for preparing an antistatic polyamide composite material is achieved by the following steps:

[0037] (1) Disperse 5 parts of conductive carbon black in 100 parts of deionized water and mix well. Place in an ozone generator, introduce ozone, and oxidize for 1 hour. Then adjust the pH to 13 with a 0.5 mol / L NaOH aqueous solution and continue oxidation for 6 hours. After the oxidation is completed, filter to obtain oxidized carbon black, adjust the pH to 4 with concentrated hydrochloric acid, and repeatedly wash and separate to obtain carboxyl-modified carbon black.

[0038] (2) 100 parts by weight of adipic acid was dissolved in 100 parts of deionized water, 69.9 parts of pentamethylenediamine was slowly added, and the mixture was stirred at 60° C. for 1 hour. The pH was adjusted to about 7.2 with pentamethylenediamine to obtain a PA56 salt solution.

[0039] (3) 100 parts of PA56 salt solution, 0.5 parts of catalyst, 0.3 parts of antioxidant, 2 parts of lubricant, and 2 parts of decanediamine end-group modifier were added to a reactor, which was evacuated and filled with nitrogen to replace the air in the reactor. Prepolymerization was carried out at 200°C and 1.4 MPa for 1 hour to obtain a low molecular weight polyamide prepolymer. Then, 2 parts of carboxyl-modified carbon black and 10 parts of deionized water were added through a constant pressure feeding tank, and the reaction was continued at constant temperature and pressure for 2 hours to obtain a carbon black-modified PA56 prepolymer.

[0040] (4) Slowly open the vent valve and set the temperature to 240°C. Release the air during the heating process. When the temperature reaches 240°C, the pressure in the kettle is 0.6 MPa and the venting time is 40 minutes. Continue to heat up to 260°C and slowly release the air to normal pressure. The control time is about 20 minutes.

[0041] (5) Slowly evacuate the vacuum, increasing the vacuum degree by 0.020 MPa every 10 minutes until reaching -0.099 MPa. After reacting at constant pressure for 10 minutes, nitrogen is injected to restore the normal pressure, and the material is discharged, cast into a strip, cooled, and pelletized. The material is dried in a vacuum oven at 90°C for 6 hours to obtain an antistatic polyamide 56 resin modified with carboxyl-modified carbon black.

[0042] Example 5

[0043] In step (3) of this embodiment, 100 parts of a PA56 salt solution, 0.5 parts of a catalyst, 0.3 parts of an antioxidant, 2 parts of a lubricant, and 2 parts of a toluene diisocyanate end-group modifier were added to a reactor. The reactor was evacuated and filled with nitrogen to replace the air in the reactor. Prepolymerization was carried out at 200°C and 1.4 MPa for 0.5 h to obtain a low molecular weight polyamide prepolymer. Then, 2 parts of carboxyl-modified carbon black and 10 parts of deionized water were added via a constant pressure feeding tank. The reaction was continued at constant temperature and pressure for 2.5 h to obtain a carbon black-modified PA56 prepolymer. The remaining formulations and process parameters were the same as those in Example 1.

[0044] Example 6

[0045] In this embodiment, the amount of carboxyl-modified carbon black added is 4 parts, and the rest of the formula composition and process parameters are the same as those in Example 1.

[0046] Example 7

[0047] In this embodiment, the amount of carboxyl-modified carbon black added is 6 parts, and the rest of the formula composition and process parameters are the same as those in Example 1.

[0048] To further illustrate the beneficial effects of the present invention, due to limited space, only Example 1 is used as an example to construct a comparative example as follows.

[0049] Comparative Example 1

[0050] In this comparative example, step (1) was omitted, and conductive carbon black was not added. The remaining conditions were the same as those in Example 1.

[0051] Comparative Example 2

[0052] In this comparative example, step (1) is omitted, and in step (3), 2 parts of conductive carbon black and 10 parts of deionized water are directly added through the constant pressure feeding tank. The other conditions are the same as those in Example 1.

[0053] Comparative Example 3

[0054] In step (3) of this comparative example, 100 parts of a PA56 salt solution, 0.5 parts of a catalyst, 0.3 parts of an antioxidant, 2 parts of a lubricant, 2 parts of a pentamethylenediamine end-group modifier, 2 parts of carboxyl-modified carbon black, and 10 parts of deionized water were added to a reaction kettle. The reaction kettle was evacuated and filled with nitrogen to replace the air in the kettle. Prepolymerization was then carried out at 200° C. and 1.4 MPa for 3.0 hours to obtain a carbon black-modified PA56 prepolymer. The remaining formulation and process parameters were the same as those in Example 1.

[0055] Comparative Example 4

[0056] In step (3) of this comparative example, 100 parts of a PA56 salt solution, 0.5 parts of a catalyst, 0.3 parts of an antioxidant, 2 parts of a lubricant, and 2 parts of a pentamethylenediamine end-group modifier were added to a reactor. The reactor was evacuated and filled with nitrogen to displace the air in the reactor. Prepolymerization was carried out at 200°C and 1.4 MPa for 3.0 hours to obtain a low molecular weight polyamide prepolymer. Then, 2 parts of carboxyl-modified carbon black and 10 parts of deionized water were added via a constant pressure feeding tank to obtain a carbon black-modified PA56 prepolymer. The remaining formulation and process parameters were the same as those in Example 1.

[0057] Comparative Example 5

[0058] In this comparative example, the pentamethylenediamine end group modifier in step (3) was omitted, and the remaining conditions were the same as those in Example 1.

[0059] Comparative Example 6

[0060] In this comparative example, the polyamide 56 resin prepared in Comparative Example 1 was mechanically blended with conductive carbon black to prepare a blended modified antistatic polyamide 56 composite material. Specifically, 100 parts of polyamide 56 resin, 2 parts of conductive carbon black, 5 parts of white oil, and 5 parts of compatibilizer were fully mixed in a high-speed mixer and melt-blended in a twin-screw extruder. The screw temperatures were set to 255°C, 260°C, 270°C, and 265°C, and the screw speed was 80 r / min.

[0061] Comparative Example 7

[0062] In this comparative example, the polyamide 56 resin prepared in comparative example 1 was mechanically blended with carboxyl-modified carbon black to prepare a blended modified antistatic polyamide 56 composite material. Specifically, the detailed preparation process is as follows: 100 parts of polyamide 56 resin, 2 parts of conductive carbon black, 5 parts of white oil, and 5 parts of compatibilizer were fully mixed in a high-speed mixer and melt-blended in a twin-screw extruder. The screw temperatures were set to 255°C, 260°C, 270°C, and 265°C, and the screw speed was 80 r / min.

[0063] The performance of the polyamide materials prepared in the examples and comparative examples was tested, and the results are shown in Table 1-2. The test methods are as follows:

[0064] (1) Antistatic polyamide pellets were dried in a vacuum oven at 100°C for 6 h. Tensile and flexural specimens were then injection molded using a WZS10 micro-injection molding machine under the following processing conditions: barrel temperature of 265°C, mold temperature of 60°C, and injection pressure of 0.7 MPa. Tensile and flexural specimens were then subjected to tensile and flexural tests. An Instron 5567 universal testing machine was used to measure the tensile and flexural properties at a tensile rate of 5 mm / min and a temperature of 25°C. The bending test was performed at a compression rate of 2 mm / min, a span of 64°C, and a temperature of 25°C.

[0065] (2) Antistatic polyamide pellets were dried in a vacuum oven at 100°C for 6 h. Disc specimens with a diameter of 58 mm and a thickness of 3.5 mm were injection molded using a WZS10 microinjection molding machine under the following processing conditions: a barrel temperature of 265°C, a mold temperature of 60°C, and an injection pressure of 0.7 MPa. Surface and volume resistivities were measured according to GB / T 1410.

[0066] Table 1

[0067]

[0068] As shown in Table 1, the present invention, by introducing carboxyl-modified carbon black into the polyamide preparation system for in-situ polymerization, imparts excellent antistatic properties to the polyamide material while simultaneously addressing dispersibility issues. Furthermore, the polyamide segments chemically bonded to the surface of the conductive carbon black exhibit good compatibility with the resin matrix, resulting in excellent mechanical properties.

[0069] As shown in Example 1 and Example 4-5, the antistatic polyamide composites using different end group modifiers show different mechanical properties. Diamines can react with part of the carboxyl group in the molecular chain, increase the amino content in the polyamide resin, make it easier to combine with carbon black, and its reactivity is consistent with polyamide polymerization, which has a smaller impact on the polycondensation system. Short-chain diamines have better rigidity, while long-chain diamines have a higher elongation at break as end group modifiers, a lower flexural modulus, and better toughness. Diisocyanates are highly active and easily react in the early stage of prepolymerization, so carbon black should be added earlier. In addition, diisocyanate end group modifiers have greater rigidity, and antistatic polyamides show better bending properties and dimensional stability. As shown in Example 4-5, introducing carboxyl or amino groups on the surface of conductive carbon black can achieve functional group modification of conductive carbon black, which can perfectly react with the polyamide matrix and provide excellent antistatic properties. As shown in Examples 6-7, as the content of carboxyl-modified carbon black increases, the mechanical properties of the antistatic polyamide composite material first increase and then decrease. This is because the introduction of nanofillers provides physical crosslinking points, which can effectively transfer stress and prevent crack propagation, thus achieving an enhanced effect. However, when the addition amount is too large, the excessive introduction of carboxyl groups causes the polymer molecular weight to decrease, resulting in a slight decrease in strength. However, with the introduction of conductive fillers, its resistance is significantly reduced, and the antistatic properties are significantly enhanced.

[0070] Table 2

[0071]

[0072] Comparing Examples 1-3 with Comparative Example 1, the polyamide material can be endowed with good antistatic properties and excellent mechanical properties by introducing carboxyl-modified carbon black into the polyamide preparation system for in-situ polymerization.

[0073] Comparing Example 1 with Comparative Example 2 shows that pure conductive carbon black, without surface functional group modification, cannot be well dispersed into the polyamide resin matrix during the polymerization stage. Because the nanoparticles easily agglomerate and lack hydrophilic groups, they easily precipitate and separate during the polyamide resin polymerization process, failing to form a homogeneous system with the polyamide. This results in poor mechanical properties and no significant improvement in conductivity. Therefore, functionalizing conductive carbon black is essential for the in-situ preparation of antistatic polyamides.

[0074] As can be seen from Examples 1-3 and Comparative Examples 3-4, the time when carboxyl-modified carbon black is introduced into the polymerization system is crucial. When added too early, due to the presence of a large number of small-molecule monomers in the polymerization system, their high activity can quickly react with the carbon black surface active groups, causing an imbalance of the polyamide monomer acid amine. On the other hand, after more small molecules react with carbon black, it is difficult for the polymer chain to connect with the carbon black, ultimately causing a decrease in product molecular weight, reduced compatibility between carbon black and the resin matrix, and decreased interfacial properties. When added in the second half of the entire prepolymerization process, since the carboxyl-modified carbon black does not have sufficient time to mix with the prepolymerization system, the reaction efficiency of the carbon black surface groups with the polyamide molecules is low, the viscosity increases rapidly when outgassing enters the final polymerization stage, and the carbon black is more difficult to disperse, resulting in decreased mechanical properties and uneven conductivity.

[0075] Comparison of Example 1 and Comparative Example 3 shows that stage prepolymerization is crucial for the in-situ preparation of high molecular weight antistatic polyamide composite materials. This is because after a one-time feeding, a large amount of diamine reacts rapidly with carboxyl modified carbon black, resulting in an imbalance of acid and amine. After a certain period of prepolymerization of polyamide before the introduction of conductive carbon black, a low molecular weight prepolymer is formed, the reaction activity is reduced, and a mixed system with excessive terminal amine groups is formed under the action of the end group modifier. At this time, the introduction of carboxyl modified carbon black can play a coupling chain extension role, so that the prepolymer molecules are fully combined with the carbon black particles to form polymer chain modified conductive carbon black particles. The polymer chain modified conductive carbon black particles formed, on the one hand, the polymer chains on the carbon black surface can continue to form crosslinking points with the macromolecular system through polycondensation, and on the other hand, the polymer chains on the carbon black surface can play a good role in promoting compatibility and transferring stress, so that its interface performance is better.

[0076] Furthermore, to ensure sufficient reaction between the carboxyl-modified carbon black and the polyamide molecules, the addition of an end-group modifier is also crucial. Comparison of Examples 1, 4, and 5 with Comparative Example 5 reveals that the use of an end-group modifier capable of reacting simultaneously with the carboxyl-modified carbon black and the polyamide significantly improves the mechanical properties of the antistatic polyamide. This is because the end-group modifier effectively bonds the polyamide molecules to the carbon black.

[0077] Comparison of Example 1 with Comparative Examples 6-7 reveals that the in-situ polymerization of the present invention to prepare the antistatic polyamide composite material can significantly enhance the mechanical properties of the material and achieve uniform dispersion of the inorganic filler in the resin system. Furthermore, the introduction of carboxyl groups onto the carbon black surface can also effectively enhance the overall performance of the composite material during mechanical blending. This is because surface functionalization enhances the interaction between the carbon black and the resin, resulting in improved interfacial bonding. Furthermore, during melt blending, the small amount of terminal amine groups in the polyamide can react with the carboxyl groups on the surface of the carboxyl-modified carbon black, forming a favorable chemical link.

[0078] In summary, the present invention modifies conductive carbon black with functional groups, allowing it to contain carboxyl groups on its surface, allowing it to be evenly and stably dispersed in the preparation system with polyamide. These groups then react with the end groups of the polyamide molecular chains, achieving in-situ polymerization of the polyamide on the carbon black surface. The resulting conductive carbon black-polyamide composite material exhibits not only excellent antistatic properties but also outstanding mechanical properties.

[0079] The above is a preferred embodiment of the present invention. For ordinary technicians in this technical field, making several improvements and modifications without departing from the principles of the present invention should also be considered as the scope of protection of the present invention.

Claims

1. A method for preparing an antistatic polyamide composite material, characterized in that: The steps include: (1) Surface modification of conductive carbon black by liquid-phase ozone oxidation to obtain carboxyl-modified carbon black; specifically, 5 parts of conductive carbon black and 100 parts of deionized water were mixed evenly, and ozone was introduced for oxidation for 1 hour, and then the pH was adjusted to 13-14 with a NaOH aqueous solution and oxidation was continued for 5-8 hours; after the oxidation was completed, the oxidized carbon black was filtered and the pH was adjusted to 2-5 with hydrochloric acid, and the carboxyl-modified carbon black was separated by repeated water washing; (2) dissolving a diamine and a dibasic acid in a certain amount of deionized water and adding the solution to a high-temperature and high-pressure reactor under nitrogen protection, reacting for 1-3 hours, and adjusting the pH to 6.5-7.5 using the dibasic acid or diamine to obtain a salt solution; the diamine is used in an amount of 70-130 parts by weight, the dibasic acid is used in an amount of 100-180 parts by weight, and the deionized water is used in an amount of 70-180 parts; the diamine is pentamethylenediamine, and the dibasic acid is adipic acid; (3) Then, a salt solution, a catalyst, an antioxidant, a lubricant and an end group modifier are added to the above-mentioned reactor, and under a nitrogen atmosphere, the pressure is controlled at 0.6-1.8 MPa, and prepolymerization is carried out at 200°C for 0.5-2 hours; then, carboxyl-modified carbon black is added through a constant pressure feeding tank, and the constant temperature and constant pressure reaction is continued for 1-2.5 hours to obtain a carbon black-modified polyamide prepolymer; the end group modifier is pentamethylenediamine, hexamethylenediamine, decamethylenediamine, toluene diisocyanate or isophorone diisocyanate, the amount of the salt solution is 100 parts by weight, the amount of the catalyst is 0.5-3 parts by weight, the amount of the antioxidant is 0.1-3 parts by weight, the amount of the lubricant is 0.5-5 parts by weight, the amount of the end group modifier is 0.2-5 parts by weight, and the amount of the carboxyl-modified carbon black is 2-6 parts by weight; (4) Slowly open the vent valve to discharge the water in the system, raise the temperature to 240-280°C, and perform vacuum polycondensation to obtain an antistatic polyamide composite material.

2. The preparation method according to claim 1, characterized in that The catalyst is one or more of phosphoric acid, phosphorous acid, sodium hydrogen phosphate, disodium hydrogen phosphate, and sodium hypophosphite monohydrate; the antioxidant is one or more of antioxidant 1010, antioxidant 168, and antioxidant SEED; and the lubricant is silicone oil.

3. The preparation method according to claim 2, characterized in that The step 4 specifically comprises: exhausting water vapor within 30-60 minutes and controlling the temperature to slowly rise to 240-280° C. until normal pressure is restored; then increasing the vacuum degree by 0.020 MPa every 10 minutes until reaching -0.099 MPa, reacting at constant pressure for 5-20 minutes, then filling with nitrogen to restore normal pressure, discharging, casting, cooling, and pelletizing.

4. An antistatic polyamide composite material, characterized in that: Prepared by the method according to any one of claims 1 to 3.

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