Nylon 6 composite material synthesized by carbon nanotube / caprolactam in-situ body as well as preparation method and application of nylon 6 composite material

Abstract

The invention discloses a carbon nano tube / caprolactam in-situ body synthesized nylon 6 composite material and a preparation method and application thereof, the material is prepared from a carbon nano tube, caprolactam and a catalyst through a body reaction processing technology, and the carbon nano tube is a single-wall or multi-wall carbon nano tube. The preparation method specifically comprises the following steps: firstly, uniformly mixing the raw materials according to a specific proportion, and then sequentially completing the conveying of low-viscosity raw materials, the self-initiation of polymerization reaction, macromolecular growth and the extrusion of high-viscosity products in a double-screw extruder, so that the caprolactam monomer is subjected to continuous chemical reaction and physical forming, and the caprolactam-based composite material is obtained. The conductive carbon nanotube modified nylon 6 composite material is obtained through one-step in-situ bulk polymerization. According to the invention, under the condition that only a trace amount of carbon nanotubes are added, the composite material can present excellent conductivity, the preparation method is simple and efficient, has a remarkable cost advantage and is easy for industrial production, and the morphological structure of the composite material can be flexibly regulated and controlled through molding equipment according to actual use requirements.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer conductive composites, and particularly to a nylon 6 composite material synthesized in-situ by carbon nanotubes / caprolactam and its preparation method and application. Background Art

[0002] Polyamide (commonly known as nylon) is a general term for a class of multi-variety high molecular polymers containing repeating amide groups in the molecular main chain. Among them, nylon 6 entered the field of plastic applications in the 1950s, becoming the earliest developed variety in engineering plastics and also the one with the largest output among polyamides at present. The polar amide groups in the molecular main chain of nylon 6 can enable the polymer to form hydrogen bonds and increase the intermolecular force, so it has relatively high mechanical strength and heat resistance; while the non-polar methylene structure improves the flexibility of the polymer, making nylon 6 easy to process and form. In addition, nylon 6 also has excellent comprehensive properties such as self-lubrication, wear resistance, acid and alkali resistance, and vibration and sound absorption, so it has extremely wide applications in today's industry. However, as an electrically insulating high molecular material, nylon 6 has a volume resistivity as high as 10 15 Ω·cm, so it cannot be directly applied to the conductive field, which hinders the further development of nylon 6.

[0003] Since carbon nanotubes were discovered by Japanese scientist Iijima in 1991, due to the excellent mechanical, electrical, thermal and other properties brought by their unique graphene sheet structure, it has rapidly triggered a research boom worldwide. Carbon nanotubes are a kind of one-dimensional nano-carbon material. When dispersed in a polymer matrix, the one-dimensional carbon nanotubes can form a three-dimensional network structure through ways such as lapping and entanglement, thereby effectively improving the conductivity of the polymer matrix. With the rapid development of the electronics and information industries, preparing conductive composite materials with good performance by filling carbon nanotubes into a nylon 6 matrix through specific processing techniques has attracted more and more attention. The reason is that compared with conventional conductive fillers such as metal powders, carbon blacks, and carbon fibers, due to the ultra-high aspect ratio and specific surface area, excellent comprehensive performance carbon nanotube / nylon 6 conductive composite materials can be obtained with less addition amount of carbon nanotubes.

[0004] The preparation methods of carbon nanotube / nylon 6 composites mainly include solution blending, melt blending, and in-situ copolymerization. Among them, the solution blending method is not suitable for industrial production due to problems such as consuming a large amount of solution and having great technical limitations, and it still remains at the laboratory research and development stage. Chinese patents CN118027660A, CN113980461B, and CN101200563A all disclose a carbon nanotube / nylon 6 composite material, and the process route used is the melt blending method, which is also a commonly used preparation method for modifying nylon 6 with carbon nanotubes in current industrial technologies, that is, directly dispersing carbon nanotubes in the already polymerized nylon 6 melt by means of high temperature and high shear for mixing. Although the melt blending method is simple and easy to operate, due to the inherently high viscosity of the polymer melt, carbon nanotubes are extremely prone to forming agglomerated or bundled aggregates during the processing, resulting in poor dispersion in the polymer matrix, thus severely restricting the full play of the properties of carbon nanotubes. Therefore, a relatively high carbon nanotube addition amount is required. In addition, when preparing composites by this method, various polymer additives such as antioxidants, lubricants, and toughening agents will inevitably be used, which will not only increase the production cost but also have an adverse impact on the conductivity of the material.

[0005] Chinese patent CN110230109B discloses a low-cost and antistatic polyamide and its preparation method. Carbon black and carbon nanotubes are compounded to obtain a nano-composite structure with good conductivity, and then it is in-situ copolymerized with caprolactam, and finally extruded into pellets and melt-spun to prepare carbon nanotube / nano-carbon black modified composite polyamide fibers. The in-situ copolymerization used in this technology is a caprolactam hydrolysis polymerization process, and water needs to be added in the formula, which does not belong to the category of bulk polymerization. And it takes at least 7 hours of polymerization at a high temperature of 250 - 270 °C and a high pressure of 0.5 MPa to complete the reaction, which means the necessity of the pre-polymerization step and will greatly increase the actual production cost at the same time; and there are still about 10 wt% of unreacted monomers and oligomers in the final product, and in industry, removing these residual monomers and oligomers requires a rather cumbersome post-treatment process and causes relatively serious environmental pollution. Adding water in the formula will also increase the initial agglomeration rate of carbon nanotubes and reduce the dispersion degree, which is not conducive to reducing the carbon nanotube dosage or making full use of the excellent properties of carbon nanotubes.

[0006] Chinese Patent CN101469130B discloses an in-situ cast nylon / carbon nanotube nanocomposite and its preparation method, and discloses that a highly crystalline nylon nanocomposite is prepared by using hydroxylated carbon nanotubes and caprolactam through in-situ anionic ring-opening polymerization. This patent discloses the use of surface modification of carbon nanotubes to improve dispersibility, but this will damage the regular structure of the carbon nanotubes themselves, resulting in a decrease in the intrinsic conductivity of the carbon nanotubes and failing to exert the excellent properties of non-hydroxylated carbon nanotubes. In addition, this patent uses isocyanate compounds as initiators, and the research team of the present invention found that they are prone to cause some unpredictable side reactions during the polymerization process, such as branching and crosslinking, which will lead to unstable operation of the subsequent forming (especially spinning) process. In addition, most isocyanate compounds are toxic reagents and pose a great threat to the human body and the environment.

[0007] In summary, the existing preparation methods of carbon nanotube / nylon composites still have significant limitations: (1) The solution blending method is limited to the laboratory stage because it relies on a large amount of solvents and is difficult to industrialize. (2) Although the melt blending method is easy to operate, the high viscosity of the polymer melt results in uneven dispersion of carbon nanotubes, easy formation of agglomerates, and high addition amounts are required to improve the performance. At the same time, the introduced additives (such as antioxidants and toughening agents) will reduce the conductivity and increase the cost. (3) The in-situ copolymerization method uses a caprolactam hydrolysis polymerization process, which requires high temperature and high pressure conditions (250-270 °C, 0.5 MPa) and a polymerization time of up to 7 hours. Residual monomers and oligomers require complex post-treatment, and the moisture in the formula exacerbates the agglomeration of carbon nanotubes; another type of in-situ technology improves the dispersibility by hydroxylated modification of carbon nanotubes, but destroys its intrinsic structure, resulting in a decrease in conductivity, and the use of toxic isocyanate initiators is prone to side reactions, affecting the stability of subsequent processing. In addition, there are also common problems in the existing technology such as high energy consumption, high pollution risk, and complex processes, making it difficult to balance high-efficiency production and performance optimization.

[0008] Therefore, there is an urgent need in the art to develop a new preparation method for carbon nanotube / nylon composites, which shortens the production cycle and reduces energy consumption, avoids the high viscosity limitation of melt blending, reduces the occurrence of agglomeration, and realizes large-scale industrial continuous production. Summary of the Invention

[0009] The object of the present invention is to provide a nylon 6 composite material synthesized by in-situ bulk polymerization of carbon nanotubes / caprolactam, its preparation method and application. On the premise of meeting the use requirements of various conductive nylon 6, the addition amount of carbon nanotubes is reduced as much as possible, so as to prepare a carbon nanotube / nylon 6 conductive composite material with low process cost, high production efficiency, energy conservation and environmental protection, excellent comprehensive performance and suitable for large-scale continuous production.

[0010] To achieve the above object, the technical solutions adopted by the present invention are specifically as follows:

[0011] A nylon 6 composite material synthesized in situ by bulk polymerization of carbon nanotubes / caprolactam, the raw materials of which at least include carbon nanotubes, caprolactam and a catalyst; based on the amount of caprolactam monomer used, the weight percentage of carbon nanotubes is 0.01-10%, and the weight percentage of the catalyst is 0.02-0.5%.

[0012] In the present invention, caprolactam monomer, a catalyst and carbon nanotubes are first mixed in a specific ratio and dispersed evenly, and then fed into a twin-screw extruder to successively complete the transportation of low-viscosity raw materials, self-initiation of polymerization reaction, growth of macromolecules and extrusion of high-viscosity products, and finally processed into corresponding shapes by a forming device, so as to obtain a conductive carbon nanotube / nylon 6 composite material by one-step in-situ copolymerization.

[0013] Specifically, it includes the following steps:

[0014] (1) Weigh caprolactam monomer, a catalyst and carbon nanotubes respectively according to the formula weight fraction ratio: 100 parts of caprolactam monomer, 0.02-0.5 parts of the catalyst, and 0.01-10 parts of carbon nanotubes;

[0015] (2) Under the protection of an inert gas, the raw materials weighed in step (1) are heated to 80-120°C to be melted and evenly dispersed to obtain a formulated mixture;

[0016] (3) Continuously feed the formulated mixture obtained in step (2) into a polymer material reaction and transportation device and a downstream forming device. The temperature of the reaction and transportation device is set at 200-280°C to ensure continuous polymerization of the reaction mixture, and the reaction time is 1-5 minutes; the downstream forming temperature is set at 230-280°C to obtain a carbon nanotube / caprolactam in-situ synthesized nylon 6 composite material.

[0017] Among them, the carbon nanotubes are any one or a combination of single-walled and multi-walled carbon nanotubes, and their production methods, lengths, diameters, purities, and whether post-treatment is performed are not limited.

[0018] Among them, the catalyst is any one of lithium hydride, sodium hydride, potassium hydride, lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium bromide caprolactamate, and sodium caprolactamate.

[0019] Among them, in step (2), a surfactant can also be added to assist in dispersing the carbon nanotubes. The dosage of the surfactant is 10-70% of the weight of the carbon nanotubes; the surfactant is any one of octylphenol polyoxyethylene ether, sorbitan oleate, polyvinylpyrrolidone, polyacrylate, and styrene-maleic anhydride copolymer.

[0020] Among them, the dispersion method in the step (2) is any one or more of mechanical stirring, high-speed shearing, and ultrasonic treatment.

[0021] Among them, in the step (3), the polymer material reaction and conveying device is a twin-screw extruder; the downstream shaping device includes a calendering die, a spinning die head, a blow molding device, or a profile die head.

[0022] Among them, in the step (3), the formulation mixture causes self-initiated anionic ring-opening polymerization of caprolactam.

[0023] In addition, in the preparation process of the carbon nanotube / caprolactam in-situ synthesized nylon 6 composite material of the present invention, various types of polymer material additives such as lubricants, fillers, and reinforcing agents can be added according to needs, and different shaping devices can also be connected after the reactive twin-screw extruder to make products of various shapes according to needs.

[0024] The carbon nanotube / caprolactam in-situ synthesized nylon 6 composite material prepared by the present invention can be products of various shapes such as films, fibers, hollow containers, or profiles. According to actual usage requirements, its morphological structure can be flexibly regulated through corresponding preparation processes.

[0025] The preparation principle of the carbon nanotube / caprolactam in-situ synthesized nylon 6 composite material of the present invention is as follows: The carbon nanotube / caprolactam in-situ synthesized nylon 6 composite material is prepared in one step by a polymer reaction processing technology. The so-called polymer reaction processing refers to continuously carrying out chemical reactions and shaping of polymer monomers, prepolymers, or polymers in a specific device to prepare polymer products with new characteristics. For the smooth progress of the chemical reaction, the present invention is based on the bulk self-initiated anionic polymerization mechanism of caprolactam. The process of generating nylon 6 polymer from caprolactam monomer includes three stages: activation, initiation, and growth. In the activation stage, caprolactam reacts with a strong base (i.e., catalyst) to form free caprolactam anions; in the initiation stage, caprolactam is transformed into acyl caprolactam to form an active center for anionic polymerization; in the growth stage, the caprolactam anion attacks the bridged-ring carbonyl group, undergoes ring-opening reaction and chain growth, and exchanges protons with unactivated caprolactam to form new caprolactam anions. Compared with traditional hydrolysis polymerization and living anionic polymerization, the self-initiated anionic polymerization of caprolactam is simple in operation, very rapid in reaction (only a few minutes are required), has a high monomer conversion rate (up to more than 98%), and does not require the use of any solvents and initiators. While improving production efficiency, it can also greatly reduce costs and emissions, and is a more efficient, energy-saving, and green method for preparing nylon 6.

[0026] The above-mentioned carbon nanotube / caprolactam in-situ synthesized nylon 6 composite material of the present invention can be used to prepare electromagnetic shielding, anti-static films or fibers, and can be applied to industries such as electronic and electrical, aerospace, automotive, medical and health, textile and clothing.

[0027] Compared with the prior art, the outstanding effects of the present invention are as follows:

[0028] (1) The viscosity of the already polymerized nylon 6 resin used in the current prior art is relatively large and its affinity with carbon nanotubes is poor. Therefore, it is very difficult to achieve good dispersion of carbon nanotubes. To make the composite material reach a high conductivity, a large amount of carbon nanotubes needs to be added. In the present invention, carbon nanotubes are directly mixed with caprolactam monomers with extremely low viscosity, and then dispersed inside the nylon 6 matrix through bulk polymerization. Therefore, even without using any dispersant and without any surface modification of carbon nanotubes, the dispersion effect of carbon nanotubes can be significantly improved by means of the above process, and an effective conductive network can be constructed at a lower addition amount, so that the carbon nanotube / nylon 6 composite material exhibits excellent conductive performance.

[0029] (2) By combining the two processes of chemical reaction and polymer processing, the present invention obtains a conductive carbon nanotube-modified nylon 6 composite material by one-step bulk polymerization of caprolactam monomers. This not only omits intermediate processes such as extrusion granulation and secondary melting, making the production continuous and the product forms diverse. Moreover, the caprolactam self-initiated anionic polymerization process adopted is economical, efficient, green and pollution-free, and suitable for industrial production, and has a broader market prospect and application value compared with traditional carbon nanotube / nylon 6 conductive composite materials.

[0030] The following further describes the carbon nanotube / caprolactam in-situ synthesized nylon 6 composite material of the present invention, its preparation method and application in conjunction with the attached drawings and specific embodiments. Description of the Drawings

[0031] Figure 1 It is a schematic diagram of the preparation process of the carbon nanotube / caprolactam in-situ synthesized nylon 6 composite material. Detailed Embodiments

[0032] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work shall fall within the protection scope of the present invention.

[0033] It should be noted that in this application:

[0034] The electrical conductivity of the carbon nanotube / caprolactam in-situ synthesized nylon 6 composite material is represented by volume resistivity, and the smaller the value, the better the electrical conductivity of the material. When the resistivity of the sample is greater than 10 8 Ω·cm, a ZC36 type high resistance meter is used for measurement; if the resistivity of the sample is lower than 10 8 Ω·cm, a ZC46A type high resistance meter is used for measurement. Each sample is measured five times, and the average value is taken as the final resistivity value.

[0035] The electromagnetic shielding effectiveness value of the carbon nanotube / caprolactam in-situ synthesized nylon 6 composite material is obtained by testing with a vector network analyzer N5247A in the X-band (8.2 - 12.4 GHz). According to the different shielding effectiveness of the material, it can be classified. 0 - 10 dB: basically no shielding effectiveness, eliminating 0 - 90% of electromagnetic waves; 10 - 30 dB: very low shielding effectiveness, eliminating 90 - 99.9% of electromagnetic waves; 30 - 60 dB: medium shielding effectiveness, eliminating 99.9 - 99.9999% of electromagnetic waves, suitable for general industrial applications and shielding of industrial and commercial electronic instruments; 60 - 90 dB: high shielding effectiveness, eliminating 99.9999 - 99.9999999% of electromagnetic waves, suitable for electromagnetic shielding of aviation, aerospace and military products.

[0036] The classification of the antistatic grade of the carbon nanotube / caprolactam in-situ synthesized nylon 6 composite material is mainly based on the surface resistance value, and it is divided into three levels: basic antistatic grade (surface resistance value is 10 9 ~10 12 Ω), antistatic grade (surface resistance value is 10 6 ~10 9 Ω) and conductive antistatic grade (surface resistance value is 10 4 ~10 6 Ω). The measurement of the surface resistance value of the material is completed with the help of an AS982 type surface resistance tester. Each sample is measured five times, and the average value is taken as the final resistance value.

[0037] Example 1

[0038] As shown in combination with Figure 1 , the preparation method of the carbon nanotube / caprolactam in-situ bulk synthesized nylon 6 composite material is as follows:

[0039] (1) Weigh caprolactam monomer, catalyst and carbon nanotubes respectively according to the following weight fraction ratio: 100 parts of caprolactam monomer, 0.04 parts of catalyst, and 0.02 parts of single-walled carbon nanotubes;

[0040] (2) Under the protection of inert gas, heat the raw materials weighed in step (1) to 90°C and melt them, and disperse them evenly by ultrasonic treatment to obtain a reaction mixture;

[0041] (3) Feed the reaction mixture obtained in step (2) successively into a reactive twin-screw extruder and a calendering die. Set the reaction temperature at 230 °C to ensure continuous polymerization of the reaction mixture; set the forming temperature at 240 °C to in-situ prepare a carbon nanotube / nylon 6 composite film.

[0042] Example 2

[0043] Except that the amount of single-walled carbon nanotubes in Example 1 is changed to 0.05 part, the sample preparation and measurement methods are the same as those in Example 1.

[0044] Example 3

[0045] Except that the amount of single-walled carbon nanotubes in Example 1 is changed to 0.1 part, the sample preparation and measurement methods are the same as those in Example 1.

[0046] Example 4

[0047] Except that 0.1 part of single-walled carbon nanotubes in Example 3 is changed to the same amount of multi-walled carbon nanotubes, the sample preparation and measurement methods are the same as those in Example 3.

[0048] Example 5

[0049] Except that the amount of multi-walled carbon nanotubes in Example 4 is changed to 0.2 part, the sample preparation and measurement methods are the same as those in Example 4.

[0050] Example 6

[0051] Except that the amount of multi-walled carbon nanotubes in Example 4 is changed to 1.0 part, the sample preparation and measurement methods are the same as those in Example 4.

[0052] Example 7

[0053] Except that 0.2 part of multi-walled carbon nanotubes in Example 5 is changed to the same amount of carboxylated multi-walled carbon nanotubes, the sample preparation and measurement methods are the same as those in Example 5.

[0054] Example 8

[0055] Except that 0.2 part of multi-walled carbon nanotubes in Example 5 is changed to 0.2 part of multi-walled carbon nanotubes and 0.02 part of single-walled carbon nanotubes, the sample preparation and measurement methods are the same as those in Example 5.

[0056] Example 9

[0057] Combined with Figure 1 As shown, the preparation method of a carbon nanotube / caprolactam in-situ bulk synthesized nylon 6 composite material comprises the following specific steps:

[0058] (1) Weigh caprolactam monomer, catalyst, and carbon nanotubes according to the following weight fraction ratios respectively: 100 parts of caprolactam monomer, 0.04 parts of catalyst, and 0.02 parts of single-walled carbon nanotubes;

[0059] (2) Under the protection of inert gas, heat the raw materials weighed in step (1) to 90 °C to melt and disperse them evenly by ultrasonic treatment to obtain a reaction mixture;

[0060] (3) Feed the reaction mixture obtained in step (2) into a reactive twin-screw extruder and a spinning die head successively. Set the reaction temperature to 230 °C to ensure continuous polymerization of the reaction mixture; set the forming temperature to 240 °C to in-situ prepare carbon nanotube / nylon 6 composite fiber non-woven fabric.

[0061] Example 10

[0062] Except that the amount of single-walled carbon nanotubes in Example 9 is changed to 0.05 parts, the sample preparation and measurement methods are the same as those in Example 9.

[0063] Example 11

[0064] Except that 0.02 parts of single-walled carbon nanotubes in Example 9 are changed to 0.2 parts of multi-walled carbon nanotubes, the sample preparation and measurement methods are the same as those in Example 9.

[0065] To highlight the beneficial effects of the present invention, the following comparative examples are given.

[0066] Comparative Example 1

[0067] Except that the amount of single-walled carbon nanotubes in Example 1 is changed to 0 parts, the sample preparation and measurement methods are the same as those in Example 1.

[0068] Comparative Example 2

[0069] Except that the amount of single-walled carbon nanotubes in Example 9 is changed to 0 parts, the sample preparation and measurement methods are the same as those in Example 9. The specific performance is shown in Table 1.

[0070] Comparative Example 3

[0071] Except that 1.0% of toluene-2,4-diisocyanate based on the molar mass of caprolactam monomer is additionally added as an initiator, the sample preparation and measurement methods are the same as those in Example 9. As a result: Due to the cross-linking reaction occurring in the polymerization system, the time from the start of spinning to the complete blockage of the spinneret holes does not exceed 3 minutes, so effective samples cannot be obtained.

[0072] The following comparative examples are carbon nanotube-modified nylon 6 composites prepared by a conventional melt blending method. Even when a high addition amount and a dispersant are used, their resistivity is still relatively large, and their electrical conductivity is far inferior to that of the carbon nanotube / caprolactam in-situ synthesized nylon 6 composites provided by the present invention.

[0073] Comparative Example 4

[0074] First, 100 parts of nylon 6 resin, 1.0 part of multi-walled carbon nanotubes, and 0.5 part of polyvinylpyrrolidone were mixed evenly according to weight fractions. Then, the mixture was placed in a Haake rheometer and kneaded at 260 °C for 10 min and then taken out. Finally, the above materials were hot-pressed into a film at 250 °C using a hot press. The resistivity of the sample was measured using a ZC36 type high resistance meter, and the result was 1.16×10 11 Ω·cm.

[0075] Comparative Example 5

[0076] Except that the amount of multi-walled carbon nanotubes in Comparative Example 3 was changed to 3.0 parts, the sample preparation and measurement methods were the same as those in Comparative Example 3, and the result was 3.07×10 7 Ω·cm.

[0077] Comparative Example 6

[0078] Except that 1.0 part of multi-walled carbon nanotubes in Comparative Example 3 was changed to an equal amount of carboxylated multi-walled carbon nanotubes, the sample preparation and measurement methods were the same as those in Comparative Example 3, and the result was 7.99×10 10 Ω·cm.

[0079] Comparative Example 7

[0080] Except that the amount of carboxylated multi-walled carbon nanotubes in Comparative Example 5 was changed to 3.0 parts, the sample preparation and measurement methods were the same as those in Comparative Example 5, and the result was 4.52×10 9 Ω·cm.

[0081] Table 1 Performance parameters of carbon nanotube / nylon 6 composite films and fiber non-woven fabrics

[0082]

[0083]

[0084] It can be seen by comparing the relevant parameters of the above examples and comparative examples that:

[0085] The carbon nanotube / nylon 6 composite material is prepared by directly mixing carbon nanotubes with caprolactam monomers and then in-situ self-initiated anionic polymerization. Since the dispersion effect of carbon nanotubes in the polymer matrix is improved, an effective conductive network can be constructed with a relatively small addition amount, endowing the composite material with good electrical conductivity. For example, adding 0.1 wt% of single-walled carbon nanotubes to the polymerization system can reduce the resistivity of the nylon 6 composite material to 10 3 Ω·cm. At this time, the antistatic grade of the material has reached the conductive antistatic level, and according to the value of the shielding effectiveness, it can be used for electromagnetic shielding in general industrial applications and industrial and commercial electronic instruments.

[0086] The polymer reaction processing technology adopted in the present invention combines the chemical reaction and the polymer processing processes, and the conductive carbon nanotube-modified nylon 6 composite material is obtained by a one-step method from caprolactam monomers. Compared with the existing preparation methods, this process not only has high production efficiency, energy conservation and environmental protection, and significant cost advantages, but also is suitable for industrial production, and can flexibly regulate the morphological structure of the composite material according to actual usage requirements.

[0087] In summary, the preparation method of the present invention is simple to operate, highly practical and easy to popularize; the prepared carbon nanotube / nylon 6 composite material has excellent electrical conductivity and low cost, and has broad market prospects and application value.

[0088] The embodiments described above are only used to describe the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A carbon nanotube / caprolactam in-situ bulk synthesized nylon 6 composite material, characterized in that: The raw materials at least include carbon nanotubes, caprolactam and a catalyst; based on the amount of caprolactam monomer, the weight percentage of the carbon nanotubes is 0.01-10%, and the weight percentage of the catalyst is 0.02-0.5%.

2. The carbon nanotube / caprolactam in-situ bulk synthesized nylon 6 composite material according to claim 1, characterized in that: The carbon nanotubes are any one of single-walled and multi-walled carbon nanotubes or a combination of the two; the catalyst is any one of lithium hydride, sodium hydride, potassium hydride, lithium hydroxide, sodium hydroxide, potassium hydroxide, caprolactam magnesium bromide and sodium caprolactam.

3. The carbon nanotube / caprolactam in-situ bulk synthesized nylon 6 composite material according to claim 1, characterized in that: The forms include films, fibers, hollow containers or profiles.

4. The method for preparing the carbon nanotube / caprolactam in-situ bulk synthesized nylon 6 composite material by continuous reaction, transportation and molding according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) Weighing caprolactam monomer, catalyst and carbon nanotubes according to the weight fraction ratio of the formula: 100 parts of caprolactam monomer, 0.02-0.5 parts of catalyst, and 0.01-10 parts of carbon nanotubes; (2) Under the protection of inert gas, the raw materials weighed in step (1) are heated to 80-120° C., melted and uniformly dispersed to obtain a formula mixture; (3) continuously conveying the formula mixture obtained in step (2) into a polymer material reaction conveying device and a downstream molding device, wherein the temperature of the reaction conveying device is set to 200 to 280° C. to ensure continuous polymerization of the reaction mixture, and the reaction time is 1 to 5 minutes; The downstream molding temperature is set at 230-280° C. to obtain a carbon nanotube / caprolactam in-situ bulk synthesized nylon 6 composite material.

5. The method for preparing the carbon nanotube / caprolactam in-situ bulk synthesized nylon 6 composite material by continuous reaction, transportation and molding according to claim 4, characterized in that: In the step (2), a surfactant may be added to assist in dispersing the carbon nanotubes.

6. The method for preparing the carbon nanotube / caprolactam in-situ bulk synthesized nylon 6 composite material by continuous reaction, transportation and molding according to claim 4, characterized in that: The amount of the surfactant is 10-70% of the weight of the carbon nanotubes.

7. The method for preparing the carbon nanotube / caprolactam in-situ bulk synthesized nylon 6 composite material by continuous reaction, transportation and molding according to claim 5, characterized in that: The surfactant is any one of octylphenol polyoxyethylene ether, sorbitan oleate, polyvinyl pyrrolidone, polyacrylate, and styrene-maleic anhydride copolymer.

8. The method for preparing the carbon nanotube / caprolactam in-situ bulk synthesized nylon 6 composite material by continuous reaction, transportation and molding according to claim 4, characterized in that: The polymer material reaction conveying device is a twin-screw extruder; the downstream forming device includes a calendering die, a spinning die, a blow molding device or a profile die.

9. The method for preparing the carbon nanotube / caprolactam in-situ bulk synthesized nylon 6 composite material by continuous reaction, transportation and molding according to claim 4, characterized in that: In the step (3), the mixture is formulated to cause a self-initiated anionic ring-opening polymerization of caprolactam.

10. The conductive application of the nylon 6 composite material synthesized in situ by carbon nanotube / caprolactam according to any one of claims 1 to 3, characterized in that: Used to prepare electromagnetic shielding, antistatic films or fibers.

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