Antibacterial hydrophobic auxiliary agent, nylon composite material and preparation method of nylon composite material

Abstract

The invention belongs to the technical field of nylon composite materials, and particularly relates to an antibacterial hydrophobic auxiliary agent, a nylon composite material and a preparation method of the antibacterial hydrophobic auxiliary agent, and the preparation method of the antibacterial hydrophobic auxiliary agent comprises the following steps: (1) dispersing aldehyde cellulose nanocrystals in water to obtain an aldehyde cellulose nanocrystal dispersion liquid; adjusting the pH value of the aldehyde cellulose nanocrystal dispersion liquid to 7.5-8.5 by using a Tris-HCl buffer solution, then adding dopamine, stirring and reacting for 12-36 hours, centrifuging to be neutral after the reaction is finished, and freeze-drying to obtain polydopamine-coated aldehyde cellulose nanocrystal PDA (at) CNC; (2) dispersing polydopamine-coated aldehyde cellulose nanocrystals PDA (at) CNC in ethanol, then adding thiol-based castor oil, mixing, stirring to react for 3-10 hours, centrifuging to be neutral after the reaction is finished, and freeze-drying to obtain an antibacterial hydrophobic auxiliary agent; the nylon composite material provided by the invention contains an antibacterial hydrophobic auxiliary agent. The nylon composite material obtained by the invention is high in strength, wear-resistant, antibacterial and hydrophobic.

Description

Technical Field

[0001] The present invention belongs to the technical field of nylon composites, and specifically relates to an antibacterial and hydrophobic additive, a nylon composite material and a preparation method thereof. Background Art

[0002] Synthetic polymer materials such as nylon 612 are widely used in medical catheters, industrial filter membranes and high-end textile fields due to their high mechanical strength, wear resistance and chemical inertness. However, the high polarity of amide groups in its molecular chain leads to strong hydrophilicity on the material surface, which is prone to bacterial growth (such as Staphylococcus aureus, Escherichia coli), and poor wear resistance, seriously restricting its application in scenarios such as sterile surgical instruments and antibacterial sportswear. Traditional modification technologies such as surface coating with hydrophobic coatings or blending with silver-based antibacterial agents can partially improve the performance, but often face problems such as easy coating peeling, metal ion migration or matrix mechanical degradation. Therefore, developing an endogenous modification additive that is deeply compatible with the nylon matrix and has both mechanical enhancement and long-term antibacterial and hydrophobic functions has become a technical pain point in the industry.

[0003] In existing modification technologies, the patent document with the publication number CN113773554A discloses the use of graphene composite with nylon to improve wear resistance, but the dispersion of graphene is poor and it has no antibacterial function; the literature (Chemical Engineering Journal, 2021, 405: 126947) proposes to construct a superhydrophobic surface of nylon through plasma treatment, but the process is complex and the durability is insufficient. In addition, although commercial quaternary ammonium salt antibacterial agents can endow nylon with antibacterial properties through physical blending, their hydrophobic segments are poorly compatible with the nylon matrix, resulting in a 20-30% decrease in the toughness of the material. Therefore, existing modification technologies have not been able to achieve the synergistic improvement of mechanical, wear-resistant and antibacterial and hydrophobic properties, and rely on non-environmental protection additives, making it difficult to meet the biosecurity requirements of medical and food contact materials. Summary of the Invention

[0004] Based on the above-mentioned disadvantages and deficiencies existing in the prior art, one of the purposes of the present invention is to at least solve one or more of the above problems existing in the prior art. In other words, one of the purposes of the present invention is to provide an antibacterial and hydrophobic additive, a nylon composite material and a preparation method thereof that meet one or more of the foregoing requirements.

[0005] In order to achieve the above-mentioned invention purpose, the present invention adopts the following technical solutions:

[0006] A preparation method of an antibacterial and hydrophobic additive, comprising the following steps:

[0007] (1)Disperse aldehyde cellulose nanocrystals in water to obtain an aldehyde cellulose nanocrystal dispersion; adjust the pH of the aldehyde cellulose nanocrystal dispersion to 7.5 - 8.5 with Tris-HCl buffer solution, then add dopamine and stir for reaction for 12 - 36 h. After the reaction, centrifuge until neutral and freeze-dry to obtain poly(dopamine)-coated aldehyde cellulose nanocrystals PDA@CNC;

[0008] (2)Disperse poly(dopamine)-coated aldehyde cellulose nanocrystals PDA@CNC in ethanol, then add mercapto castor oil and mix, stir for reaction for 3 - 10 h. After the reaction, centrifuge until neutral and freeze-dry to obtain an antibacterial and hydrophobic additive.

[0009] As a preferred embodiment, in the step (1), the mass ratio of aldehyde cellulose nanocrystals to dopamine is 1:(1 - 3), and the temperature of the stirring reaction is 20 - 40 °C.

[0010] As a preferred embodiment, in the step (2), the mass ratio of poly(dopamine)-coated aldehyde cellulose nanocrystals PDA@CNC to mercapto castor oil is 1:(0.5 - 2), such as 1:0.5, 1:1, 1:1.5 or 1:2.

[0011] As a preferred embodiment, in the step (2), at least one of ethanol, water, methanol, propanol, and ether is used as the centrifugal washing liquid.

[0012] As a preferred embodiment, in the step (1), the preparation process of aldehyde cellulose nanocrystals includes:

[0013] Add microcrystalline cellulose to sodium periodate solution, place it in a water bath at 40 - 80 °C and stir for 1 - 3 h, then centrifuge the suspension until neutral and freeze-dry;

[0014] Among them, the solid-liquid ratio of microcrystalline cellulose to sodium periodate solution is 1:(50 - 100) g / mL; the concentration of sodium periodate solution is 0.3 - 1 M, such as 0.3 M, 0.5 M, 0.8 M or 1 M.

[0015] The present invention also provides a nylon composite material containing the antibacterial and hydrophobic additive prepared by the preparation method described in any one of the above embodiments.

[0016] As a preferred embodiment, the nylon composite material is a fiber or a film.

[0017] The present invention also provides a preparation method of the nylon composite material described in the above embodiment, including:

[0018] Blend the antibacterial and hydrophobic additive with nylon particles, and prepare a high-strength, wear-resistant, antibacterial and hydrophobic nylon composite material by a melt spinning process or a solution blending-casting film method;

[0019] Among them, the mass of the antibacterial and hydrophobic auxiliary is 3-7% of the mass of the nylon particles.

[0020] As a preferred solution, the nylon particles are nylon 612, nylon 66, nylon 6, nylon 610 or nylon 11.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] (1) Through the self-polymerization reaction of dopamine DA under weakly alkaline conditions in the present invention, the amino group of polydopamine PDA reacts with the aldehyde group on the surface of aldehyde group cellulose nanocrystals CNC through a Schiff base reaction (-CHO + -NH2 → -CH=N-), forming a chemical grafting layer; further introducing thiol castor oil, and its mercapto group -SH grafts long-chain alkyl hydrophobic groups through a Michael addition reaction with the quinone structure of polydopamine PDA, and forms a gradient structure of "rigid core-viscoelastic transition layer-flexible hydrophobic shell" on the surface of CNC; this structure can reduce the wear amount by dissipating energy through the slip of flexible chains during the friction process, and at the same time the CNC rigid core inhibits the plastic deformation of the nylon matrix, synergistically improving the wear resistance, so that the wear amount of the prepared nylon composite material can be reduced by 33%;

[0023] (2) The present invention uses sodium periodate oxidation method to selectively oxidize cellulose, generates a dialdehyde group structure through the directional cleavage of C2 / C3 hydroxyl groups, and prepares aldehyde group cellulose nanocrystals CNC; the remaining active group -CHO on the surface of aldehyde group cellulose nanocrystals CNC forms a strong hydrogen bond network with the amide group -NH-CO- in the nylon molecular chain, and at the same time its high modulus characteristic enhances the nylon matrix interface through the "nano-rivet effect", so that the tensile strength of the fibrous nylon composite material is increased by 54.5% and the flexural strength is increased by 50%;

[0024] (3) The nylon composite material of the present invention realizes rapid antibacterial (bacteriostatic rate > 99.9%) in fibrous form through a high specific surface area, and is suitable for antibacterial sportswear and industrial filter materials; in film form, based on the hydrophobic alkyl chain to form a low-energy surface barrier, with a contact angle as high as 139.71°, it can be applied to medical catheter linings or high-durability packaging films; and the preparation method does not require complex post-treatment, the raw materials are green and degradable, and it is compatible with existing nylon processing equipment, having the potential for large-scale production;

[0025] (4) The amide bond of the nylon substrate in the present invention forms multiple interactions (hydrogen bonds, π-π stacking and chain entanglement) with the aldehyde group, amino group and alkyl chain on the surface of the antibacterial and hydrophobic auxiliary, enabling the functionalized CNC to be evenly dispersed during melt spinning or solution film formation, which is beneficial to improving the tensile modulus of the nylon composite fiber, prolonging the wear resistance life of the nylon composite film and enhancing the antibacterial and hydrophobic stability after washing, providing a green solution for disposable medical supplies and long-lasting antibacterial outdoor equipment. Description of the Drawings

[0026] Figure 1 It is a comparative thermogravimetric TGA test chart of the antibacterial and hydrophobic additives in Embodiments 1 to 4 of the present invention;

[0027] Figure 2 It is a comparative Fourier transform infrared spectroscopy chart of the antibacterial and hydrophobic additive in Embodiment 3 of the present invention and each intermediate product in its preparation process;

[0028] Figure 3 It is a field emission scanning electron microscope FE-SEM photograph of the antibacterial and hydrophobic additive in Embodiment 3 of the present invention

[0029] Figure 4 It is a comparative antibacterial chart of the nylon composite fibers in Embodiments 1 to 4 of the present invention;

[0030] Figure 5 It is a comparative antibacterial chart of the nylon composite fibers in Embodiments 1 to 4 of the present invention after 50 washes;

[0031] Figure 6 It is a field emission scanning electron microscope FE-SEM photograph of the nylon composite fiber in Embodiment 3 of the present invention;

[0032] Figure 7 It is a comparative chart of the mechanical properties of the nylon composite fibers in Embodiment 3, Comparative Example 1 and Comparative Example 2 of the present invention and nylon 612 fibers;

[0033] Figure 8 It is a comparative hydrophobicity chart of the nylon composite films in Embodiments 5 to 8 of the present invention;

[0034] Figure 9 It is a field emission scanning electron microscope FE-SEM photograph of the nylon composite film in Embodiment 7 of the present invention;

[0035] Figure 10 It is a comparative chart of the wear amounts of the nylon composite films in Embodiment 7, Comparative Example 3 and Comparative Example 4 of the present invention and nylon 612 films. Detailed implementation manners

[0036] The antibacterial and hydrophobic additives, nylon composite materials and their preparation methods provided by the present invention will be further described below.

[0037] The present invention prepares aldehyde-functionalized cellulose nanocrystals CNC by the sodium periodate oxidation method, and constructs a multifunctional nano-additive (i.e., antibacterial and hydrophobic additive) through dual modification with dopamine / castor oil. Its mechanism of action is as follows:

[0038] (1) Interface enhancement mechanism of aldehyde-functionalized CNC;

[0039] Sodium periodate selectively oxidizes the C2 / C3 hydroxyl groups of microcrystalline cellulose to generate a dialdehyde structure, obtaining aldehyde group CNC. The oxygen atom C=O of the aldehyde group forms a stable hydrogen bond with the N-H of the amide group of nylon. At the same time, the hydrogen C-H of the aldehyde group forms a weak hydrogen bond with the carbonyl oxygen C=O of the amide group. These multi-site hydrogen bond interactions enable CNC to be tightly adsorbed on the nylon molecular chain and be oriented along the axial direction (tensile direction) of the nylon chain, playing the "nano-rivet" effect.

[0040] (2) Dopamine-castor oil synergistic functionalization;

[0041] ① Schiff base anchoring: Dopamine self-polymerizes into polydopamine PDA in Tris buffer. Its primary amino group -NH2 is covalently grafted to the aldehyde group on the surface of CNC through a Schiff base reaction (-CHO + -NH2 → -CH=N-), forming a dense coating layer. The catechol group of PDA further undergoes π-π stacking with the nylon carbonyl C=O, enhancing the interfacial binding energy;

[0042] ② Hydrophobic-abrasion resistance synergy: The mercapto group -SH of thiol-functionalized castor oil is grafted with a long-chain alkyl hydrophobic group through a Michael addition reaction with the quinone structure of PDA, forming a gradient interface of "rigid CNC core - PDA adhesion layer - flexible alkyl shell"; The long-chain alkyl forms topological interlocking with nylon molecules through chain entanglement. During the friction process, the flexible chain slips and dissipates energy, while the rigid CNC resists plastic deformation, synergistically reducing the Taber abrasion loss of the nylon composite film;

[0043] (3) Antibacterial-hydrophobic bifunctional coupling;

[0044] The catechol group of PDA generates reactive oxygen species ROS through a photothermal effect, destroying the integrity of the bacterial cell membrane. At the same time, aldehyde group CNC crosslinks with the peptidoglycan of the bacterial cell wall to inhibit proliferation, achieving a broad-spectrum antibacterial rate of >99.9%; The long-chain alkyl of castor oil constructs a micro-nano rough structure on the material surface to achieve hydrophobicity, blocking the penetration of water molecules based on the Cassie-Baxter effect and simultaneously inhibiting the attachment of microorganisms;

[0045] (4) The antibacterial and hydrophobic additive of the present invention realizes chemical-physical dual binding with nylon through molecular-level interface design, maintains nano-dispersibility during melt spinning and casting film formation, is beneficial to improving the tensile modulus of nylon composite fibers, is beneficial to extending the wear-resistant life of nylon composite films and enhancing the antibacterial and hydrophobic stability after washing, providing a green solution for disposable medical consumables and long-lasting antibacterial outdoor equipment.

[0046] The preparation method of the nylon composite material of the present invention includes the following steps:

[0047] I. Preparation of the antibacterial and hydrophobic additive;

[0048] (1) The aldehyde group cellulose nanocrystals are dispersed in water to obtain an aldehyde group cellulose nanocrystal dispersion; the pH of the aldehyde group cellulose nanocrystal dispersion is adjusted to 7.5 - 8.5 using a Tris-HCl buffer, then dopamine is added and stirred for reaction for 12 - 36 h. After the reaction ends, it is centrifuged until neutral and freeze-dried to obtain poly-dopamine-coated aldehyde group cellulose nanocrystals PDA@CNC;

[0049] (2) The poly-dopamine-coated aldehyde group cellulose nanocrystals PDA@CNC are dispersed in ethanol, then thiol group castor oil is added and mixed, and stirred for reaction for 3 - 10 h. After the reaction ends, it is centrifuged until neutral and freeze-dried to obtain an antibacterial and hydrophobic additive;

[0050] II. Preparation of nylon composite materials;

[0051] (3) The antibacterial and hydrophobic additive is blended with nylon particles, and a high-strength, wear-resistant, antibacterial and hydrophobic nylon composite material is prepared by a melt spinning process or a solution blending-casting film method.

[0052] In one embodiment, in the above step (1), the mass ratio of the aldehyde group cellulose nanocrystals to dopamine is 1:(1 - 3), which is specifically determined according to actual requirements;

[0053] In one embodiment, in the above step (1), the temperature of the stirring reaction is 20 - 40 °C, which is specifically determined according to actual requirements;

[0054] In one embodiment, in the above step (2), the mass ratio of the poly-dopamine-coated aldehyde group cellulose nanocrystals PDA@CNC to thiol group castor oil is 1:(0.5 - 2), which is specifically determined according to actual requirements. The role of the thiol group is to graft the castor oil onto PDA, and the introduction method can refer to the prior art.

[0055] In one embodiment, in the above step (2), ethanol, water, methanol, propanol or ether is used as the centrifugal washing liquid, which is specifically determined according to actual requirements;

[0056] In one embodiment, in the above step (3), the mass of the aldehyde group cellulose nanocrystal composite additive is 3 - 7% of the mass of the nylon particles, which is specifically determined according to actual requirements;

[0057] In one embodiment, in the above step (3), the nylon particles are nylon 612, nylon 66, nylon 6, nylon 610 or nylon 11, which is specifically determined according to actual requirements.

[0058] In one embodiment, in the above step (1), the preparation process of the aldehyde group cellulose nanocrystals includes:

[0059] Add microcrystalline cellulose to sodium periodate solution, place in a 40-80°C water bath and stir for 1-3 hours, then centrifuge the suspension to neutrality and freeze-dry.

[0060] In one embodiment, the solid-liquid ratio of the microcrystalline cellulose to the sodium periodate solution is 1: (50-100) g / mL, and the concentration of the sodium periodate solution is 0.3-1 M, which is determined according to actual needs.

[0061] The neutrality mentioned above in the present invention means a pH of about 7, specifically limited to 6.9 to 7.1.

[0062] The antibacterial hydrophobic additive, nylon composite material and preparation method thereof of the present invention are further described below through specific examples:

[0063] The microcrystalline cellulose in the following embodiments of the present invention adopts the microcrystalline cellulose with CAS No. 9004-34-6 produced by Sinopharm, and the castor oil adopts the castor oil with CAS No. 8001-79-4 produced by Aladdin.

[0064] Embodiment 1:

[0065] The method for preparing the nylon composite fiber of this embodiment comprises the following steps:

[0066] (1) 1 g of microcrystalline cellulose (MCC) and 0.3 M sodium periodate solution were added to a 500 mL round-bottom flask, which was then placed in a 40 °C water bath for 1 h. The suspension was then centrifuged to neutrality and freeze-dried to obtain aldehyde-modified cellulose nanocrystals (CNCs).

[0067] Among them, the solid-liquid ratio of microcrystalline cellulose to sodium periodate solution is 1:50;

[0068] (2) 1 g of cellulose nanocrystal powder CNC was dispersed in 250 mL of deionized water to obtain a cellulose nanocrystal suspension (i.e., cellulose nanocrystal dispersion); then, a Tris-HCl buffer solution with a pH of 8.8 was added to the cellulose nanocrystal suspension to adjust the pH to 7.5; then, 1 g of dopamine DA was added to the suspension, and constant magnetic stirring was performed at ambient temperature and atmospheric conditions for 24 h. After self-polymerization-Schiff base reaction occurred, a polydopamine-coated cellulose nanocrystal water suspension was obtained; then, the suspension was centrifuged with deionized water until it was neutral and freeze-dried to obtain polydopamine-coated cellulose nanocrystals, referred to as PDA@CNC;

[0069] (3) 1 g of PDA@CNC was redispersed in ethanol by ultrasonic treatment and the pH was adjusted with Tris-HCl buffer to prepare a PDA@CNC ethanol suspension with a concentration of 0.5 wt% and a pH of 7.5. The PDA@CNC ethanol suspension was mixed with 0.5 g of mercapto castor oil and stirred at room temperature for 6 h. After the reaction, the mercapto castor oil-modified PDA@CNC was washed with excess methanol and subjected to centrifugal dispersion cycles until the pH reached 7.0, followed by freeze-drying to obtain mercapto castor oil-modified PDA@CNC powder, abbreviated as PDA@CNC-CO-0.5, as an antibacterial and hydrophobic additive;

[0070] Among them, the preparation process of mercapto castor oil was as follows: First, 20 g of castor oil CO, 0.4 g of p-toluenesulfonic acid, 0.1 g of hydroquinone and 100 mL of toluene were mixed in a 250 mL flask, and magnetically stirred and heated to 110 °C. Then, 23.5 g of 3-mercaptopropionic acid MPA was added dropwise, and the mixture was maintained at 130 °C for 3 h. Then, it was diluted with dichloromethane, washed and purified with water, and dried over anhydrous magnesium sulfate overnight to obtain an oily solution. Finally, the oily solution was filtered and evaporated to obtain mercapto castor oil CO-SH;

[0071] (4) After blending PDA@CNC-CO-0.5 with nylon 612 particles, high-strength, wear-resistant, antibacterial and hydrophobic nylon composite fibers were prepared by a melt spinning process, abbreviated as CP / CO-0.5.

[0072] Among them, the mass of PDA@CNC-CO-0.5 was 7% of the mass of nylon 612 particles.

[0073] Example 2:

[0074] The difference between the preparation method of the nylon composite fiber in this example and that in Example 1 was that the amount of mercapto castor oil in step (3) was different;

[0075] Specifically, 1 g of PDA@CNC was redispersed in ethanol by ultrasonic treatment and the pH was adjusted with Tris-HCl buffer to prepare a PDA@CNC ethanol suspension with a concentration of 0.5 wt% and a pH of 7.5. The PDA@CNC ethanol suspension was mixed with 1 g of mercapto castor oil and stirred at room temperature for 6 h. After the reaction, the mercapto castor oil-modified PDA@CNC was washed with excess methanol and subjected to centrifugal dispersion cycles until neutral, followed by freeze-drying to obtain mercapto castor oil-modified PDA@CNC powder, abbreviated as PDA@CNC-CO-1, as an antibacterial and hydrophobic additive;

[0076] Other steps were the same as those in Example 1;

[0077] The high-strength, wear-resistant, antibacterial and hydrophobic nylon composite fiber in this example was abbreviated as CP / CO-1.

[0078] Example 3:

[0079] The preparation method of the nylon composite fiber in this example is different from that in Example 1 in that: the dosage of thiol castor oil in step (3) is different;

[0080] Specifically, 1 g of PDA@CNC was redispersed in ethanol by ultrasonic treatment and the pH was adjusted with Tris-HCl buffer to prepare a PDA@CNC ethanol suspension with a concentration of 0.5 wt% and a pH of 7.5. The PDA@CNC ethanol suspension was mixed with 1.5 g of thiol castor oil and stirred at room temperature for 6 h; after the reaction, the PDA@CNC modified by thiol castor oil was washed with excessive methanol for centrifugal dispersion cycle, centrifuged to neutrality and freeze-dried to obtain the PDA@CNC powder modified by thiol castor oil, abbreviated as PDA@CNC-CO-1.5, as an antibacterial and hydrophobic additive;

[0081] Other steps are the same as those in Example 1.

[0082] The high-strength, wear-resistant, antibacterial and hydrophobic nylon composite fiber of this example is abbreviated as CP / CO-1.5.

[0083] Example 4:

[0084] The preparation method of the nylon composite fiber in this example is different from that in Example 1 in that: the dosage of thiol castor oil in step (3) is different;

[0085] Specifically, 1 g of PDA@CNC was redispersed in ethanol by ultrasonic treatment and the pH was adjusted with Tris-HCl buffer to prepare a PDA@CNC ethanol suspension with a concentration of 0.5 wt% and a pH of 7.5. The PDA@CNC ethanol suspension was mixed with 2 g of thiol castor oil and stirred at room temperature for 6 h; after the reaction, the PDA@CNC modified by thiol castor oil was washed with excessive methanol for centrifugal dispersion cycle, centrifuged to neutrality and freeze-dried to obtain the PDA@CNC powder modified by thiol castor oil, abbreviated as PDA@CNC-CO-2, as an antibacterial and hydrophobic additive;

[0086] Other steps are the same as those in Example 1.

[0087] The high-strength, wear-resistant, antibacterial and hydrophobic nylon composite fiber of this example is abbreviated as CP / CO-2.

[0088] Comparative Example 1:

[0089] The preparation method of the nylon composite fiber in this comparative example is different from that in Example 3 in that: sulfonic acid group cellulose nanocrystals are used to replace aldehyde group cellulose nanocrystals;

[0090] Other steps are the same as those in Example 3;

[0091] Among them, the process of synthesizing the sulfonic acid group cellulose nanocrystal suspension by the sulfuric acid hydrolysis method includes: hydrolyzing 40 g of microcrystalline cellulose MCC with 350 mL of sulfuric acid (64 wt.%) at 45 °C for 60 min while stirring, immediately diluting the suspension with 10 times of ultrapure water to terminate the hydrolysis reaction, and centrifuging to remove the excess acid. The obtained precipitate is centrifuged with deionized water to near neutrality and freeze-dried.

[0092] Comparative Example 2:

[0093] The difference between the preparation method of the nylon composite fiber in this comparative example and that in Example 3 lies in that: step (3) is omitted, that is, directly blend PDA@CNC with nylon 612 particles, and then prepare the nylon composite fiber through the melt spinning process;

[0094] Other steps are the same as those in Example 3.

[0095] The following are the test experiments on the antibacterial and hydrophobic additives prepared in the above Examples 1 to 4:

[0096] 1) As Figure 1 shown, the thermogravimetric TGA test comparison chart of the antibacterial and hydrophobic additives in Examples 1 to 4 of the present invention. It can be seen from the figure that the prepared PDA@CNC-CO-0.5 (-1, -1.5, and -2) has good thermal stability, and when the mass ratio of mercapto castor oil to aldehyde group cellulose nanocrystals PDA@CNC wrapped with polydopamine is (1-2):1, the thermal stability is better; when the mass ratio is 1.5:1, the residual carbon mass is the highest at this time, indicating the best thermal stability performance; the thermogravimetric test analysis shows that the higher the decomposition temperature and the larger the residue amount of the antibacterial and hydrophobic additive at high temperature, usually indicating that the internal structure of the material is more stable, indicating that the molecular chain has stronger heat resistance and can correspond to higher creep resistance and toughness.

[0097] 2) Taking the antibacterial and hydrophobic additive PDA@CNC-CO-1.5 in Example 3 as an example, Fourier transform infrared spectroscopy is performed on the raw materials, intermediate products and final products. As Figure 2 shown, aldehyde groups appear in the cellulose nanocrystals after oxidation with sodium periodate, proving the successful synthesis of cellulose nanocrystals; N-H groups appear after the addition of dopamine reaction, proving that dopamine is successfully coated on the cellulose nanocrystals; then after the addition of mercapto castor oil, a significant change in the peak is observed at 1700 cm -1 ⁻¹, which is attributed to the inherent carbonyl group of the ester bond in CO, proving the successful synthesis of the antibacterial and hydrophobic additive.

[0098] 3) Taking the antibacterial and hydrophobic additive PDA@CNC-CO-1.5 in Example 3 as an example, field emission scanning electron microscopy FE-SEM test is carried out. As Figure 3As shown, the main size of the antibacterial and flame-retardant additive is between 40 - 110 nm, indicating that the size of the antibacterial and flame-retardant additive prepared in the examples of the present invention is at the nanometer level. It can enhance the nylon matrix interface through the "nano-rivet effect", thereby enhancing the mechanical properties of the nylon composite material.

[0099] The following are the test experiments on the high-strength, wear-resistant, antibacterial, and hydrophobic nylon composite fibers prepared in the above Examples 1 to 4:

[0100] 1) The antibacterial activities of CP / CO-0.5 (-1, -1.5, and -2) prepared in Examples 1 - 4 were evaluated by separately measuring the minimum inhibitory concentration (MIC) of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The test results are as Figure 4 shown. It can be seen from the figure that the antibacterial effects of CP / CO-0.5 (-1, -1.5, and -2) against E. coli and S. aureus can reach more than 88%. And when the mass ratio of thiol-functionalized castor oil to aldehyde-functionalized cellulose nanocrystals encapsulated with polydopamine (PDA@CNC) is (1 - 2):1, the antibacterial effects against E. coli and S. aureus can reach more than 91%. When the mass ratio is 1.5:1, the antibacterial effects against E. coli and S. aureus can reach 99.99%.

[0101] In addition, after washing the above high-strength, wear-resistant, antibacterial, and hydrophobic nylon composite fibers 50 times, the previous antibacterial effect test was carried out again. As Figure 5 shown, the antibacterial effects of CP / CO-0.5 (-1, -1.5, and -2) against E. coli and S. aureus can reach more than 78%. And when the mass ratio of thiol-functionalized castor oil to aldehyde-functionalized cellulose nanocrystals encapsulated with polydopamine (PDA@CNC) is (1 - 2):1, the antibacterial effects against E. coli and S. aureus can reach more than 83%. When the mass ratio is 1.5:1, the antibacterial effects against E. coli and S. aureus can reach 95.99%. This shows that the antibacterial and hydrophobic stability is maintained after 50 washes.

[0102] 2) Taking Example 3 as an example, the surface morphology of CP / CO-1.5 was tested. As Figure 6 shown, the surface of the nylon composite fiber CP / CO-1.5 is smooth, indicating that the antibacterial and hydrophobic additive has good compatibility with nylon 612, without phase separation, which is beneficial to improving the mechanical properties of the nylon composite fiber.

[0103] 3) The nylon composite fiber samples prepared in Example 3, Comparative Example 1, and Comparative Example 2, as well as nylon 612 fibers, were subjected to mechanical property tests. All samples were stored at 25°C and a humidity of 65% for 24 h. Rectangular specimens with a width of 10 mm, a thickness of 50 - 60 μm, and a length of 50 mm were tested at a rate of 1 mm·min-1 Stretching at a constant stretching rate to obtain the tensile strength and flexural strength. The results are as Figure 7 shown, indicating that the nylon composite fiber prepared in Example 3 has the best mechanical properties. Compared with nylon 612, the tensile strength is increased by 54.5%, and the flexural strength is increased by 50%.

[0104] Example 5:

[0105] The preparation method of the nylon composite film in this example includes the following steps:

[0106] (1) Add 1 g of microcrystalline cellulose and 1 M sodium periodate solution to a 500 mL round-bottom flask, then place it in a water bath at 80 °C for 3 h, and then centrifuge the suspension to neutrality and freeze-dry it to obtain aldehyde-functionalized cellulose nanocrystals CNC;

[0107] Among them, the solid-liquid ratio of microcrystalline cellulose to sodium periodate solution is 1:100;

[0108] (2) Disperse 1 g of aldehyde-functionalized cellulose nanocrystal powder CNC in 250 mL of deionized water to obtain an aldehyde-functionalized cellulose nanocrystal suspension (i.e., aldehyde-functionalized cellulose nanocrystal dispersion); subsequently, add Tris-HCl buffer solution with a pH of 8.8 to the aldehyde-functionalized cellulose nanocrystal suspension to adjust the pH to 8.5; then add 2 g of dopamine DA to the above suspension, and carry out constant magnetic stirring at ambient temperature and atmospheric conditions for 24 h. After the self-polymerization-Schiff base reaction, a water suspension of aldehyde-functionalized cellulose nanocrystals wrapped with polydopamine is obtained; then centrifuge the suspension with deionized water until neutral and freeze-dry it to obtain aldehyde-functionalized cellulose nanocrystals wrapped with polydopamine, abbreviated as PDA@CNC;

[0109] (3) Redisperse 1 g of PDA@CNC in ethanol by ultrasonic treatment and adjust the pH with Tris-HCl buffer solution to prepare a 0.5 wt% PDA@CNC ethanol suspension with a pH of 7.5. The PDA@CNC ethanol suspension is mixed with 0.5 g of mercapto castor oil and stirred at room temperature for 6 h; after the reaction, wash the PDA@CNC modified with mercapto castor oil with excess methanol for centrifugal dispersion cycle, centrifuge to neutrality and freeze-dry to obtain PDA@CNC powder modified with mercapto castor oil, abbreviated as PDA@CNC-CO-0.5, as an antibacterial and hydrophobic additive;

[0110] Among them, the preparation process of thiol-based castor oil is as follows: First, 20 g of castor oil CO, 0.4 g of p-toluenesulfonic acid, 0.1 g of hydroquinone, and 100 mL of toluene are mixed in a 250 mL flask, and magnetically stirred and heated to 110 °C; then 23.5 g of 3-mercaptopropionic acid MPA is added dropwise, and the mixture is maintained at 130 °C for 3 hours; then it is diluted with dichloromethane, washed and purified with water, and dried overnight with anhydrous magnesium sulfate to obtain an oily solution; finally, the oily solution is filtered and evaporated to obtain thiol-based castor oil CO-SH;

[0111] (4) After blending PDA@CNC-CO-0.5 with nylon 612 particles, a high-strength, wear-resistant, antibacterial, and hydrophobic nylon composite membrane, abbreviated as CP / CO membrane-0.5, is prepared by solution blending-casting film method.

[0112] Among them, the mass of PDA@CNC-CO-0.5 is 5% of the mass of nylon 612 particles.

[0113] Example 6:

[0114] The difference between the preparation method of the nylon composite membrane in this example and that in Example 5 lies in: the dosage of thiol-based castor oil in step (3) is different;

[0115] Specifically, 1 g of PDA@CNC is redispersed in ethanol by ultrasonic treatment and the pH is adjusted with Tris-HCl buffer solution to prepare a PDA@CNC ethanol suspension with a concentration of 0.5 wt% and a pH of 7.5. The PDA@CNC ethanol suspension is mixed with 1 g of thiol-based castor oil and stirred at room temperature for 6 h; after the reaction, the PDA@CNC modified by thiol-based castor oil is washed with excess methanol and centrifuged for dispersion circulation, centrifuged to neutrality and freeze-dried to obtain the PDA@CNC powder modified by thiol-based castor oil, abbreviated as PDA@CNC-CO-1;

[0116] Other steps are the same as those in Example 5;

[0117] The high-strength, wear-resistant, antibacterial, and hydrophobic nylon composite membrane in this example is abbreviated as CP / CO membrane-1.

[0118] Example 7:

[0119] The difference between the preparation method of the nylon composite membrane in this example and that in Example 1 lies in: the dosage of thiol-based castor oil in step (3) is different;

[0120] Specifically, 1 g of PDA@CNC was redispersed in ethanol by ultrasonic treatment and the pH was adjusted with Tris-HCl buffer to prepare a PDA@CNC ethanol suspension with a concentration of 0.5 wt% and a pH of 7.5. The PDA@CNC ethanol suspension was mixed with 1.5 g of thiol-functionalized castor oil and stirred at room temperature for 6 h. After the reaction, the PDA@CNC modified with thiol-functionalized castor oil was washed with excess methanol and subjected to centrifugal dispersion cycles until neutral, and then freeze-dried to obtain the PDA@CNC powder modified with thiol-functionalized castor oil, abbreviated as PDA@CNC-CO-1.5;

[0121] Other steps were the same as in Example 5.

[0122] The high-strength, wear-resistant, antibacterial and hydrophobic nylon composite membrane of this example is abbreviated as CP / CO membrane-1.5.

[0123] Example 8:

[0124] The preparation method of the nylon composite membrane in this example was different from that in Example 1 in that the amount of thiol-functionalized castor oil in step (3) was different;

[0125] Specifically, 1 g of PDA@CNC was redispersed in ethanol by ultrasonic treatment and the pH was adjusted with Tris-HCl buffer to prepare a PDA@CNC ethanol suspension with a concentration of 0.5 wt% and a pH of 7.5. The PDA@CNC ethanol suspension was mixed with 2 g of thiol-functionalized castor oil and stirred at room temperature for 6 h. After the reaction, the PDA@CNC modified with thiol-functionalized castor oil was washed with excess methanol and subjected to centrifugal dispersion cycles until neutral, and then freeze-dried to obtain the PDA@CNC powder modified with thiol-functionalized castor oil, abbreviated as PDA@CNC-CO-2;

[0126] Other steps were the same as in Example 5.

[0127] The high-strength, wear-resistant, antibacterial and hydrophobic nylon composite membrane of this example is abbreviated as CP / CO membrane-2.

[0128] Comparative Example 3:

[0129] The preparation method of the nylon composite membrane in this comparative example was different from that in Example 7 in that sulfonic acid group cellulose nanocrystals were used to replace aldehyde group cellulose nanocrystals;

[0130] Other steps were the same as in Example 7;

[0131] Among them, the process of synthesizing sulfonic acid group cellulose nanocrystal suspension by sulfuric acid hydrolysis method includes: hydrolyzing 40 g of microcrystalline cellulose MCC with 350 mL of sulfuric acid (64 wt.%) at 45°C for 60 min with stirring, immediately diluting the suspension with 10 times of ultrapure water to terminate the hydrolysis reaction, and centrifuging to remove the excess acid. The obtained precipitate is centrifuged with deionized water to near neutrality and freeze-dried.

[0132] Comparative Example 4:

[0133] The difference between the preparation method of the nylon composite film in this comparative example and that in Example 7 lies in: omitting step (3), that is, directly blending PDA@CNC with nylon 612 particles, and then preparing the nylon composite film by solution blending-casting film method; among them, the mass of PDA@CNC is 5% of the mass of nylon 612 particles;

[0134] Other steps are the same as those in Example 5.

[0135] The following are the test experiments on the high-strength, wear-resistant, antibacterial and hydrophobic nylon composite films prepared in the above Examples 5 to 8:

[0136] 1) The hydrophobicity of CP / CO-0.5 (-1, -1.5 and -2) prepared in Examples 1 to 4 was detected by a water contact angle measuring instrument, measured with 3 μL of deionized water, and contacted with the water droplet; five different positions were selected for each sample, and the maximum value max and the minimum value min were taken for comparison; the results are as Figure 8 shown. It can be seen from the figure that the minimum contact angle of the prepared CP / CO-0.5 (-1, -1.5 and -2) reaches more than 96°, and when the mass ratio of mercapto castor oil to poly dopamine-coated aldehyde group cellulose nanocrystals PDA@CNC is (1.5 - 2):1, the minimum contact angle reaches more than 106°; when the mass ratio is 1.5:1, the minimum contact angle reaches 128°, and the maximum reaches 139.71°; while the maximum water contact angle of the nylon composite film in Comparative Example 3 is only 98°.

[0137] 2) The surface morphology of the CP / CO film-1.5 prepared in Example 7 was characterized. As Figure 9 shown, it is a homogeneous phase with a fluctuating morphology and no obvious boundary, proving that the antibacterial and hydrophobic additive is successfully anchored on the nylon 612 film.

[0138] 3) The nylon composite film samples prepared in Example 7, Comparative Example 3 and Comparative Example 4, as well as nylon 612, were subjected to Taber abrasion test (ASTM D4060 standard). The wear amount was measured with a Taber abrasion tester. A specified pressure and number of friction times were applied to the surface of the specimen by a rotating friction wheel, and the mass change of the specimen before and after wear was measured. The larger the wear amount, the worse the wear resistance. As Figure 10As shown, the results indicate that the nylon composite film prepared in Example 7 has the best wear resistance. Compared with the nylon 612 film, the wear amount is reduced by 33.3%.

[0139] Given that there are numerous embodiments in the solution of the present invention, the raw materials and dosages involved can be selected according to actual needs within the limited range. The experimental data of each embodiment are huge and numerous, and it is not suitable to list and explain them one by one here. However, the contents to be verified and the final conclusions obtained in each embodiment are close. Therefore, the verification contents of each embodiment will not be explained one by one here.

[0140] The above is only a detailed description of the preferred embodiments and principles of the present invention. For those of ordinary skill in the art, according to the idea provided by the present invention, there will be changes in the specific implementation manners, and these changes should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of an antibacterial and hydrophobic auxiliary, characterized in that, It includes the following steps: (1) Disperse aldehyde group cellulose nanocrystals in water to obtain an aldehyde group cellulose nanocrystal dispersion; adjust the pH of the aldehyde group cellulose nanocrystal dispersion to 7.5 - 8.5 with Tris-HCl buffer solution, then add dopamine and stir for reaction for 12 - 36 h. After the reaction ends, centrifuge until neutral and freeze-dry to obtain poly-dopamine-coated aldehyde group cellulose nanocrystals PDA@CNC; (2) Disperse the poly-dopamine-coated aldehyde group cellulose nanocrystals PDA@CNC in ethanol, then add mercapto castor oil and mix, stir for reaction for 3 - 10 h. After the reaction ends, centrifuge until neutral and freeze-dry to obtain an antibacterial and hydrophobic auxiliary agent.

2. The preparation method according to claim 1, wherein In the step (1), the mass ratio of the aldehyde group cellulose nanocrystals to dopamine is 1:(1 - 3), and the temperature of the stirring reaction is 20 - 40 °C.

3. The preparation method according to claim 1, wherein, In the step (2), the mass ratio of the poly-dopamine-coated aldehyde group cellulose nanocrystals PDA@CNC to mercapto castor oil is 1:(0.5 - 2).

4. The preparation method according to claim 1, characterized in that, In the step (2), at least one of ethanol, water, methanol, propanol, and ether is used as the centrifugal washing liquid.

5. The preparation method according to any one of claims 1-4, characterized in that, In the step (1), the preparation process of the aldehyde group cellulose nanocrystals includes: Add microcrystalline cellulose into sodium periodate solution, place it in a water bath at 40 - 80 °C and stir for 1 - 3 h, then centrifuge the suspension until neutral and freeze-dry; Among them, the solid-liquid ratio of the microcrystalline cellulose to the sodium periodate solution is 1:(50 - 100) g / mL, and the concentration of the sodium periodate solution is 0.3 - 1 M.

6. A nylon composite material, characterized in that, Containing the antibacterial and hydrophobic auxiliary agent prepared by the preparation method according to any one of claims 1 - 5.

7. The nylon composite material according to claim 6, wherein, The nylon composite material is a fiber or a film.

8. The preparation method of the nylon composite material according to claim 6, characterized in that, It includes: Blend the antibacterial and hydrophobic auxiliary agent with nylon particles, and prepare a high-strength, wear-resistant, antibacterial and hydrophobic nylon composite material by a melt spinning process or a solution blending-casting film method; Among them, the mass of the antibacterial and hydrophobic auxiliary agent is 3 - 7% of the mass of the nylon particles.

9. The preparation method according to claim 8, characterized in that, The nylon particles are nylon 612, nylon 66, nylon 6, nylon 610, or nylon 11.

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