Chitosan grafting modified bio-based nylon material, and preparation method and application thereof

Abstract

The application belongs to the technical field of polymer material modification, and provides a chitosan grafted modified bio-based nylon material, a preparation method and application thereof.The preparation method comprises the following steps: mixing bio-based nylon salt, water, a catalyst and chitosan quaternary ammonium salt under a protective atmosphere, sequentially performing pre-polymerization and final polymerization to obtain the chitosan grafted modified bio-based nylon material.The chitosan quaternary ammonium salt is selected to react with the bio-based nylon salt, so that the number of positive charges on the surface of the original polyamide is increased, a large number of positive charges can promote the flocculation of the polyamide and the proteins, teichoic acid, lipopolysaccharide and the like with negative charges on the surface of the bacterial cell, and then the osmotic barrier effect of the cytoplasmic membrane is destroyed, the integrity of the bacterial cell is destroyed, and the nutrients are lost, so that the intrinsic antibacterial effect is achieved.The chitosan grafted modified bio-based nylon material has excellent antibacterial performance, mechanical properties and high-temperature resistance.

Description

Technical Field

[0001] This invention relates to the field of polymer material modification technology, and in particular to a chitosan-grafted modified bio-based nylon material, its preparation method, and its application. Background Technology

[0002] Existing bio-based nylon materials possess advantages such as environmental friendliness and renewability, but their insufficient antibacterial properties limit their application in fields such as medical treatment and food packaging. Chitosan, with its excellent biocompatibility, blood compatibility, safety, and microbial degradability, has wide applications in pharmaceuticals, food, chemicals, cosmetics, water treatment, and metal extraction and recycling. Grafting chitosan onto bio-based nylon materials holds promise for improving their antibacterial properties. However, challenges arise during preparation, including compatibility issues between chitosan and bio-based nylon, controllability of the grafting polymerization reaction, and the stability and durability of the antibacterial function. To overcome these challenges, it is necessary to strengthen research on the interaction mechanism between chitosan and bio-based nylon, optimize the conditions and parameters of the grafting polymerization reaction, and explore more stable and durable methods for achieving antibacterial functionality. On the other hand, compared to metals or other engineering plastics, nylon is often not the optimal choice for applications requiring high tensile, flexural, or torsional rigidity; furthermore, nylon is prone to softening or melting under high-temperature conditions, thus losing its original mechanical properties and shape stability. Therefore, improving the mechanical properties and high-temperature resistance of nylon is also a problem we need to solve. In summary, providing a new method for preparing chitosan-grafted modified bio-based nylon materials, thereby obtaining a modified bio-based nylon material with excellent antibacterial properties, as well as good mechanical properties and high-temperature resistance, is of great significance. Summary of the Invention

[0003] The purpose of this invention is to overcome the problems existing in the prior art and provide a chitosan-grafted modified bio-based nylon material, its preparation method, and its application.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0005] This invention provides a method for preparing chitosan-grafted modified bio-based nylon materials, comprising the following steps:

[0006] Under a protective atmosphere, bio-based nylon salt, water, catalyst, and chitosan quaternary ammonium salt are mixed and subjected to prepolymerization and final polymerization reactions in sequence to obtain the chitosan grafted modified bio-based nylon material.

[0007] Preferably, the bio-based nylon salt includes nylon 56 salt, nylon 54 salt, nylon 510 salt, nylon 512 salt, or nylon 513 salt.

[0008] Preferably, the catalyst includes sodium hydroxide, toluene diisocyanate, titanium-based catalyst, phosphorus-containing compound, or boric acid compound.

[0009] Preferably, the chitosan quaternary ammonium salt is hydroxypropyltrimethylammonium chloride chitosan, and the degree of deacetylation of the hydroxypropyltrimethylammonium chloride chitosan is 97-99%.

[0010] Preferably, the mass ratio of nylon salt, water, catalyst and chitosan quaternary ammonium salt is 80-100:50-70:0.3-0.5:2-8.

[0011] Preferably, the mixing temperature is 45–55°C, the mixing pressure is 8–12 kPa, and the mixing time is 0.3–0.7 h.

[0012] Preferably, the temperature of the prepolymerization reaction is 150–200°C, the pressure of the prepolymerization reaction is 5–9 kPa, and the time of the prepolymerization reaction is 1–8 h.

[0013] Preferably, the final polymerization reaction temperature is 210–280°C, the final polymerization reaction vacuum degree is 0.005–0.015 MPa, and the final polymerization reaction time is 1–8 h.

[0014] The present invention also provides a method for preparing chitosan-grafted modified bio-based nylon materials, resulting in chitosan-grafted modified bio-based nylon materials.

[0015] The present invention also provides the application of the chitosan-grafted modified bio-based nylon material in medical product packaging or food packaging.

[0016] The beneficial effects of this invention are:

[0017] This invention provides a method for preparing chitosan-grafted modified bio-based nylon materials, comprising the following steps: under a protective atmosphere, bio-based nylon salt, water, a catalyst, and chitosan quaternary ammonium salt are mixed and sequentially subjected to prepolymerization and final polymerization reactions to obtain chitosan-grafted modified bio-based nylon materials. This invention utilizes the reaction of chitosan quaternary ammonium salt with bio-based nylon salt to increase the number of positive charges on the surface of the original polyamide. The abundant positive charge promotes flocculation of the polyamide with negatively charged proteins, teichoic acid, lipopolysaccharides, etc., on the surface of bacterial cells, thereby disrupting the permeability barrier of the cell membrane, leading to the destruction of bacterial cell integrity and nutrient loss, thus achieving an intrinsic antibacterial effect. The chitosan-grafted modified bio-based nylon material prepared by the method of this invention exhibits excellent antibacterial properties, effectively inhibiting the growth of various bacteria. Furthermore, the modified bio-based nylon material possesses good biocompatibility, making it suitable for applications such as medical product packaging and food packaging. Simultaneously, the chitosan-grafted modified bio-based nylon material is environmentally friendly, renewable, and possesses good processing performance, making it easy to manufacture products of various shapes. In addition, the mechanical properties and high-temperature resistance of the chitosan-grafted modified bio-based nylon material prepared by the method of this invention are significantly improved, broadening its applications in high-temperature resistance and tensile / bending strength. Detailed Implementation

[0018] This invention provides a method for preparing chitosan-grafted modified bio-based nylon materials, comprising the following steps:

[0019] Under a protective atmosphere, bio-based nylon salt, water, catalyst, and chitosan quaternary ammonium salt are mixed and subjected to prepolymerization and final polymerization reactions in sequence to obtain the chitosan grafted modified bio-based nylon material.

[0020] In this invention, the bio-based nylon salt preferably includes nylon 56 salt, nylon 54 salt, nylon 510 salt, nylon 512 salt, or nylon 513 salt.

[0021] In this invention, the method for preparing the bio-based nylon salt preferably includes the following steps:

[0022] Under a nitrogen atmosphere, pentanediamine, aliphatic dicarboxylic acid and solvent are mixed and reacted to obtain a bio-based nylon salt solution; the bio-based nylon salt solution is then purified to obtain a bio-based nylon salt.

[0023] In this invention, the aliphatic dicarboxylic acid preferably includes adipic acid, succinic acid, sebacic acid, dodecanoic acid, or tridecanoic acid; the solvent is preferably ethanol or water.

[0024] In this invention, when the aliphatic dicarboxylic acid is adipic acid, the bio-based nylon salt is nylon 56 salt; when the aliphatic dicarboxylic acid is succinic acid, the bio-based nylon salt is nylon 54 salt; when the aliphatic dicarboxylic acid is sebacic acid, the bio-based nylon salt is nylon 510 salt; when the aliphatic dicarboxylic acid is dodecanoic acid, the bio-based nylon salt is nylon 512 salt; and when the aliphatic dicarboxylic acid is tridecanoic acid, the bio-based nylon salt is nylon 513 salt.

[0025] In this invention, the mass ratio of the pentanediamine, aliphatic dicarboxylic acid and solvent is preferably 60-100:25-50:10-30, more preferably 70-90:30-45:15-25, and even more preferably 80-80.9:35-38.83:20-22.

[0026] In this invention, the reaction is preferably carried out in a water bath, the reaction temperature is preferably 30-120°C, more preferably 40-80°C, and even more preferably 55-60°C; the reaction time is preferably 0.5-2h, more preferably 0.75-1.5h, and even more preferably 1h.

[0027] In this invention, the catalyst preferably includes sodium hydroxide, toluene diisocyanate, titanium-based catalyst, phosphorus-containing compound, or borate compound; the titanium-based catalyst is preferably titanium dioxide; the phosphorus-containing compound preferably includes phosphoric acid, phosphorous acid, hypophosphite, sodium hypophosphite, sodium hypophosphite, alkyl-substituted phosphoric acid, aryl-substituted phosphoric acid, aryl-substituted hypophosphite, phosphorus-containing alkanes, phosphorus-containing aryl esters, phosphorus-containing metal salts, or phosphorus-containing ammonium salts; the borate compound is preferably boric acid; this invention does not limit the alkyl-substituted phosphoric acid, aryl-substituted phosphoric acid, aryl-substituted hypophosphite, phosphorus-containing alkanes, phosphorus-containing aryl esters, phosphorus-containing metal salts, or phosphorus-containing ammonium salts, and compounds commonly used in the art can be used.

[0028] In this invention, the chitosan quaternary ammonium salt is preferably hydroxypropyltrimethylammonium chloride chitosan, and the degree of deacetylation of the hydroxypropyltrimethylammonium chloride chitosan is preferably 97-99%, more preferably 97.5-98.5%, and even more preferably 98%; the hydroxypropyltrimethylammonium chloride chitosan is preferably purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0029] In this invention, the preferred mass ratio of nylon salt, water, catalyst, and chitosan quaternary ammonium salt is 80-100:50-70:0.3-0.5:2-8, more preferably 85-95:55-65:0.35-0.45:3-7, and even more preferably 90:59.6:0.45:4-5.

[0030] In this invention, the protective atmosphere is preferably a nitrogen atmosphere; the setting of the nitrogen atmosphere preferably includes the following steps: after adding each raw material to the polymerization reactor, the polymerization reactor is sealed, and the reactor is purged with nitrogen to replace the air in the reactor 5 times. The nitrogen input pressure during purging is preferably 1 to 2 MPa, more preferably 1.2 to 1.8 MPa, and more preferably 1.5 MPa; then the pressure is reduced to the mixing pressure, and mixing and subsequent prepolymerization and final polymerization reactions are carried out.

[0031] In this invention, the mixing temperature is preferably 45-55°C, more preferably 47-53°C, and even more preferably 50°C; the mixing pressure is preferably 8-12 kPa, more preferably 9-11 kPa, and even more preferably 10 kPa; and the mixing time is preferably 0.3-0.7 h, more preferably 0.4-0.6 h, and even more preferably 0.5 h.

[0032] In this invention, the temperature of the prepolymerization reaction is preferably 150-200°C, more preferably 160-190°C, and even more preferably 170-180°C; the pressure of the prepolymerization reaction is preferably 5-9 kPa, more preferably 6-8 kPa, and even more preferably 7-7.3 kPa; and the time of the prepolymerization reaction is preferably 1-8 h, more preferably 2-7 h, and even more preferably 3-6 h.

[0033] In this invention, after the prepolymerization reaction is completed, the pressure relief valve on the reactor is opened to release water vapor and other low-boiling-point substances until the vacuum degree reaches the vacuum degree of the final polymerization reaction. Then, the pressure relief valve is closed, and the temperature is raised to the temperature of the final polymerization reaction to carry out the final polymerization reaction. After the final polymerization reaction is completed, the vacuum is drawn to obtain the chitosan grafted modified bio-based nylon material.

[0034] In this invention, the temperature of the final polymerization reaction is preferably 210–280°C, more preferably 220–270°C, and even more preferably 230–260°C; the vacuum degree of the final polymerization reaction is preferably 0.005–0.015 MPa, more preferably 0.008–0.012 MPa, and even more preferably 0.01 MPa; the time of the final polymerization reaction is preferably 1–8 h, more preferably 2–7 h, and even more preferably 3–6 h; after the final polymerization reaction is completed, the vacuum is evacuated to the target vacuum degree, which is preferably 0.005–0.015 MPa, more preferably 0.008–0.012 MPa, and even more preferably 0.01 MPa.

[0035] The present invention also provides a method for preparing chitosan-grafted modified bio-based nylon materials, resulting in chitosan-grafted modified bio-based nylon materials.

[0036] The present invention also provides the application of the chitosan-grafted modified bio-based nylon material in medical product packaging or food packaging.

[0037] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0038] Example 1

[0039] Under a nitrogen atmosphere, pentanediamine, sebacic acid, and water (mass ratio of pentanediamine, sebacic acid, and water: 80.9:38.83:20) were mixed and heated in a water bath at 55°C for 0.5 h to obtain a nylon 510 salt solution. The nylon 510 salt solution was purified to obtain nylon 510 salt. 90 g of nylon 510 salt, 59.6 g of water, and 0.45 g of sodium hypophosphite were mixed to obtain a salt solution, which was placed in a polymerization reactor. Then, 2 g of hydroxypropyltrimethylammonium chloride chitosan (degree of deacetylation 98%) was added, the polymerization reactor was sealed, and the reactor was purged with nitrogen (nitrogen input pressure 1.5 MPa) to replace the air in the reactor. The mixture was stirred five times, then depressurized to 10 kPa and mixed at 50°C for 0.5 h. The temperature was then raised to 200°C and subjected to a prepolymerization reaction at 7.3 kPa for 2 h. After the prepolymerization reaction, the pressure relief valve on the reactor was opened to release water vapor and other low-boiling-point substances until the vacuum reached 0.01 MPa. The pressure relief valve was then closed, and the temperature was raised to 270°C for the final polymerization reaction, which was set to 80 min. After the reaction, a vacuum was applied and adjusted to 0.01 MPa to obtain chitosan-grafted modified bio-based nylon material.

[0040] Example 2

[0041] Keeping other conditions unchanged in Example 1, the mass of hydroxypropyltrimethylammonium chloride chitosan was modified to 3g to obtain chitosan-grafted modified bio-based nylon material.

[0042] Example 3

[0043] Keeping other conditions unchanged in Example 1, the mass of hydroxypropyltrimethylammonium chloride chitosan was modified to 4g to obtain chitosan-grafted modified bio-based nylon material.

[0044] Example 4

[0045] Keeping other conditions unchanged in Example 1, the mass of hydroxypropyltrimethylammonium chloride chitosan was modified to 5g to obtain chitosan-grafted modified bio-based nylon material.

[0046] Comparative Example 1

[0047] 0.45 g of chitosan was dissolved in 250 mL of 1% acetic acid solution, and then 6 g of benzaldehyde was added. The mixture was reacted at room temperature for 24 h. After the reaction was completed, 50 mL of 1% sodium hydroxide solution was added dropwise, causing a precipitate to form. The system was filtered, and the resulting filter cake was washed sequentially with ethanol and then with deionized water to obtain Schiff base-protected chitosan. 0.6 g of Schiff base-protected chitosan was added to 100 mL of 1.5% sodium hydroxide solution, stirred until homogeneous, and then 0.8 g of epichlorohydrin was added. The mixture was stirred at 50 °C for 6 h. After the reaction was completed, the system was filtered, and the resulting filter cake was washed sequentially with ethanol and then with deionized water to obtain epoxidized Schiff base chitosan.

[0048] 0.2 g of epoxidized Schiff base chitosan was added to 50 mL of dimethyl sulfoxide and stirred at 80 °C for 12 h. Then, 0.09 g of DL-aspartic acid was added and stirred at 95 °C for 16 h. The resulting sample was added to 100 mL of 3% hydrochloric acid solution and stirred at room temperature for 24 h. After the reaction was completed, the solvent was filtered, and the resulting product was washed sequentially with ethanol and deionized water to obtain polycarboxylated hydrophilic modified chitosan.

[0049] Nylon 510 salt was prepared using the same method as in Example 1;

[0050] 90g of nylon 510 salt, 60g of water, and 0.45g of sodium hypophosphite were mixed to obtain a salt solution, which was placed in a polymerization reactor. Then, 3g of polycarboxylated hydrophilic modified chitosan was added to the solution. The polymerization reactor was sealed and purged with nitrogen (nitrogen input pressure of 1.5MPa) to replace the air in the reactor 5 times. The pressure was then reduced to 10kPa, and the mixture was stirred at 50℃ for 0.5h. The temperature was then raised to 200℃, and a prepolymerization reaction was carried out at 7.3kPa for 2h. After the prepolymerization reaction was completed, the pressure relief valve on the reactor was opened to release water vapor and other low-boiling-point substances until the vacuum degree reached 0.01MPa. The pressure relief valve was then closed, and the temperature was raised to 270℃ for the final polymerization reaction, which was carried out for 80min. After the reaction was completed, a vacuum was drawn and the vacuum degree was adjusted to 0.01MPa to obtain the modified bio-based nylon material.

[0051] The chitosan-grafted modified bio-based nylon materials prepared in Examples 1-4 and the modified bio-based nylon material prepared in Comparative Example 1 were subjected to performance tests, including inhibition zone diameter testing, melting point testing, and tensile strength testing. The inhibition zone diameter testing method was as follows: in a clean bench, 25 mL of agar medium was poured into sterile petri dishes and allowed to cool and solidify naturally; a 1×10⁻⁶ concentration of agar medium was then pipette-tested. 8100 μL of CFU / mL *E. coli* suspension was inoculated onto the culture medium and evenly spread onto the surface of the agar medium using a spreader. Chitosan-grafted modified bio-based nylon materials prepared in Examples 1-4 and the modified bio-based nylon material prepared in Comparative Example 1 were injection molded into circular samples with a diameter of 6 mm * 1 mm (1 mm being the thickness of the circular sample). These samples were placed on the center surface of the agar medium, covered with the petri dish lid, and incubated upside down in a 37℃ incubator for 24 h. The results were then observed. Tensile strength testing was conducted according to national standard GB / T 1040-92 on a CMT 5104 microcomputer-controlled electronic universal testing machine (tensile rate 20.0 mm / min, experimental temperature 18℃). The performance test results of the chitosan-grafted modified bio-based nylon materials in Examples 1-4 and the modified bio-based nylon material in Comparative Example 1 are shown in Table 1.

[0052] Table 1. Performance test results of chitosan-grafted modified bio-based nylon materials in Examples 1-4 and the modified bio-based nylon material in Comparative Example 1.

[0053] Case Diameter of the inhibition zone (mm) Melting point (°C) Tensile strength (MPa) Example 1 5.8±0.2 258.9 76 Example 2 6.2±0.2 268.7 82 Example 3 6.1±0.2 265.0 81 Example 4 5.9±0.2 257.6 74 Comparative Example 1 2.0±0.2 245.0 67

[0054] As shown in Table 1, with the increase of hydroxypropyltrimethylammonium chloride chitosan content, the antibacterial effect, tensile strength, and melting point of the chitosan-grafted modified bio-based nylon material all showed a trend of first increasing and then decreasing. The chitosan-grafted modified bio-based nylon material obtained in Example 2 had the best antibacterial effect, tensile strength, and melting point. After replacing hydroxypropyltrimethylammonium chloride chitosan with polycarboxylic hydrophilic modified chitosan, the various properties of the modified bio-based nylon material were significantly reduced.

[0055] As can be seen from the above embodiments, the present invention provides a method for preparing chitosan-grafted modified bio-based nylon materials, comprising the following steps: under a protective atmosphere, bio-based nylon salt, water, catalyst, and chitosan quaternary ammonium salt are mixed and subjected to prepolymerization and final polymerization reactions in sequence to obtain chitosan-grafted modified bio-based nylon materials. The present invention uses chitosan quaternary ammonium salt to react with bio-based nylon salt, increasing the number of positive charges on the surface of the original polyamide. A large number of positive charges can promote flocculation of the polyamide with negatively charged proteins, teichoic acid, lipopolysaccharides, etc., on the surface of bacterial cells, thereby disrupting the permeability barrier of the cell membrane, leading to the destruction of the integrity of the bacterial cells and the loss of nutrients, thus achieving an intrinsic antibacterial effect. The chitosan-grafted modified bio-based nylon material prepared by the method of this invention exhibits excellent antibacterial properties, effectively inhibiting the growth of various bacteria. Furthermore, the modified bio-based nylon material possesses good biocompatibility, making it suitable for applications such as medical product packaging and food packaging. Simultaneously, the chitosan-grafted modified bio-based nylon material is environmentally friendly, renewable, and possesses good processing performance, making it easy to manufacture products of various shapes. In addition, the mechanical properties and high-temperature resistance of the chitosan-grafted modified bio-based nylon material prepared by the method of this invention are significantly improved, broadening its applications in high-temperature resistance and tensile / bending strength.

[0056] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a chitosan-grafted modified bio-based nylon material, characterized in that, Includes the following steps: Under a protective atmosphere, bio-based nylon salt, water, catalyst and chitosan quaternary ammonium salt are mixed and subjected to prepolymerization and final polymerization reactions in sequence to obtain the chitosan grafted modified bio-based nylon material. The chitosan quaternary ammonium salt is hydroxypropyltrimethylammonium chloride chitosan, and the degree of deacetylation of the hydroxypropyltrimethylammonium chloride chitosan is 97-99%. The mass ratio of nylon salt, water, catalyst, and chitosan quaternary ammonium salt is 80~100:50~70:0.3~0.5:2~8; The temperature of the prepolymerization reaction is 150~200℃, the pressure of the prepolymerization reaction is 5~9kPa, and the time of the prepolymerization reaction is 1~8h.

2. The method for preparing chitosan-grafted modified bio-based nylon material as described in claim 1, characterized in that, The bio-based nylon salts include nylon 56 salt, nylon 54 salt, nylon 510 salt, nylon 512 salt, or nylon 513 salt.

3. The method for preparing chitosan-grafted modified bio-based nylon material as described in claim 2, characterized in that, The catalyst includes sodium hydroxide, toluene diisocyanate, titanium-based catalysts, phosphorus-containing compounds, or boric acid compounds.

4. The method for preparing chitosan-grafted modified bio-based nylon material as described in claim 1, characterized in that, The mixing temperature is 45~55℃, the mixing pressure is 8~12kPa, and the mixing time is 0.3~0.7h.

5. The method for preparing chitosan-grafted modified bio-based nylon material as described in claim 1, characterized in that, The final polymerization reaction temperature is 210~280℃, the vacuum degree of the final polymerization reaction is 0.005~0.015MPa, and the final polymerization reaction time is 1~8h.

6. The chitosan-grafted modified bio-based nylon material prepared by the method of any one of claims 1 to 5.

7. The application of the chitosan-grafted modified bio-based nylon material according to claim 6 in medical product packaging or food packaging.