A fully bio-based degradable nylon and a preparation method and application thereof

Abstract

The application discloses a kind of full biobased degradable nylon and its preparation method and application, belong to high polymer material preparation technical field.Full biobased degradable nylon provided in the application includes the polymerization product of first nylon salt and second nylon salt;The first nylon salt is one or more of nylon 512, nylon 56, nylon 510;The second nylon salt is synthesized by the following monomer composition reaction;The monomer composition includes carboxyl-terminated PLA oligomer monomer, 1,5-pentanediamine and antioxidant.Full biobased degradable nylon made in the application has excellent barrier property, mechanical property, toughness, and excellent thermodynamic property while realizing high molecular weight, and the mass degradation loss rate reaches 63.3% in 180 days, has wide application prospect in food packaging, medical devices, agricultural production, daily necessities and other fields.

Description

Technical Field

[0001] This application belongs to the field of polymer material preparation technology, and in particular relates to a fully bio-based biodegradable nylon, its preparation method and application. Background Technology

[0002] Biodegradable nylon is a high-performance polyamide material synthesized from renewable biomass through bio-fermentation or chemical conversion technologies. It combines the dual characteristics of being bio-based and environmentally degradable, making it widely used in electronics, rail transportation, and the automotive industry. Current methods typically employ chemical or biological modification to improve the mechanical and biodegradability of nylon. However, existing modification strategies often struggle to balance mechanical properties with biodegradability. Therefore, there is a need to develop nylons with superior overall performance to expand their application scenarios.

[0003] For example, the prior art with application publication number CN 112300384 A discloses a fully bio-based nylon, which uses pentanediamine and furan dicarboxylic acid derived from biomass as monomers and prepares fully bio-based nylon resin by high-temperature and high-compression polymerization using a specific catalyst.

[0004] However, the above-mentioned fully bio-based nylon resin has the following problems: First, furanyl dicarboxylic acid is prone to decarboxylation at high temperatures, which leads to a decrease in monomer conversion rate and an increase in molecular chain defects, making it difficult to form high-performance resin; Second, its aromatic ring structure forms a strong conjugation effect with the amide bond, making the molecular chain rigid and chemically stable. There are very few microorganisms and enzymes in nature that can secrete and decompose this type of aromatic polyamide, and the enzymes have very low catalytic activity for this structure, making it difficult to achieve efficient biodegradation. Summary of the Invention

[0005] This application discloses a fully bio-based biodegradable nylon, its preparation method and application, aiming to solve the technical problems of poor mechanical properties and limited biodegradability of existing fully bio-based nylon resins.

[0006] To achieve the above objectives, the technical solution of this application is:

[0007] The first aspect of this application provides a fully bio-based biodegradable nylon, comprising a polymer product of a first nylon salt and a second nylon salt;

[0008] The first nylon salt is one or more of nylon 512, nylon 56, and nylon 510;

[0009] The second nylon salt is synthesized by reacting the following monomer composition;

[0010] The monomer composition comprises a carboxyl-terminated PLA oligomer monomer, 1,5-pentanediamine, and an antioxidant.

[0011] Preferably, in conjunction with the first aspect, the carboxyl-terminated PLA oligomer monomer is prepared by reacting lactide and a diacid;

[0012] The dicarboxylic acid includes one or more of succinic acid, adipic acid, octanoic acid, and sebacic acid.

[0013] Preferably, in conjunction with the first aspect, the method for preparing the carboxyl-terminated PLA oligomer monomer includes:

[0014] Under catalytic conditions, lactide and dicarboxylic acid are reacted at 130-190 °C for 0.5-1 h. After separation and purification, the mixture is dried under vacuum to obtain the terminal carboxyl group PLA oligomer monomer.

[0015] Preferably, in conjunction with the first aspect, the molar ratio of lactide to dicarboxylic acid is 1:(1.5-3).

[0016] The catalyst is stannous octoate.

[0017] The second aspect of this application provides a method for preparing the fully bio-based biodegradable nylon described in the first aspect, the method comprising:

[0018] The second nylon salt was obtained by reacting the terminal carboxyl group PLA oligomer monomer, 1,5-pentanediamine and antioxidant in a solvent.

[0019] The first nylon salt and the second nylon salt are subjected to high-pressure polymerization, followed by cooling and vacuum drying to obtain the fully bio-based biodegradable nylon.

[0020] Preferably, in conjunction with the second aspect, the molar ratio of the terminal carboxyl group PLA oligomer monomer to 1,5-pentanediamine is (0.95-1.25):1.

[0021] In conjunction with the second aspect, preferably, the antioxidant is one or more of antioxidant 1098 and antioxidant 168;

[0022] The amount of antioxidant added accounts for 0.1%-0.5% of the total monomer content.

[0023] Preferably, in conjunction with the second aspect, the solvent is one or a combination of ethanol, dichloromethane, or similar substances.

[0024] In conjunction with the second aspect, preferably, the mass ratio of the first nylon salt to the second nylon salt is 1:(0.005-0.03).

[0025] The third aspect of this application provides the use of the fully bio-based biodegradable nylon described in the first aspect or the fully bio-based biodegradable nylon prepared by the preparation method described in the second aspect in nylon articles.

[0026] Compared with the prior art, the advantages or beneficial effects of the embodiments of this application include at least the following:

[0027] The carboxyl-terminated PLA oligomer monomer provided in this application is prepared by reacting lactide and a diacid. On the one hand, the terminal carboxyl group (-COOH) of the carboxyl-terminated PLA oligomer can form hydrogen bonds with the amide group (-CONH-) and unreacted amine group (-NH2) in the main chain of the first nylon salt. These hydrogen bonds have a synergistic effect with the inherent hydrogen bonds between the main chains of the first nylon salt itself, which can significantly enhance the interaction force between molecular chains, effectively suppress the slippage and dislocation of molecular chains under external forces, and thus improve the tensile strength and bending resistance of the material. On the other hand, the carboxyl-terminated PLA oligomer can also act as a heterogeneous nucleating agent, which can promote the crystallization of the first nylon salt matrix by providing crystallization sites, and help form a more perfect crystalline network structure. It can still maintain the stability and integrity of the structure under high temperature environment, thereby significantly improving the thermodynamic properties of nylon such as heat resistance. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 Here are schematic diagrams and carbon spectra of the carboxyl-terminated PLA oligomer monomers prepared in the embodiments of this application;

[0030] Figure 2 Here are schematic diagrams and proton NMR spectra of the carboxyl-terminated PLA oligomer monomers prepared in the embodiments of this application;

[0031] Figure 3 A schematic diagram of the structure of the carboxyl-terminated PLA oligomer monomer prepared in the embodiments of this application and its two-dimensional nuclear magnetic resonance correlation spectrum;

[0032] Figure 4 Here are schematic diagrams of the structure and HMQC diagram of the carboxyl-terminated PLA oligomer monomers prepared in the embodiments of this application;

[0033] Figure 5 Stability graphs of A1-fully bio-based biodegradable nylon (PA512-C 0.5%), A2-fully bio-based biodegradable nylon (PA512-C 1%), A3-fully bio-based biodegradable nylon (PA512-C 2%), and A4-fully bio-based biodegradable nylon (P512-C 3%) prepared for the embodiments of this application;

[0034] Figure 6 The thermal degradation diagram shows the fully bio-based biodegradable nylon prepared in the embodiments of this application. Detailed Implementation

[0035] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0036] In the following description of this embodiment, the term "and / or" is used to describe the association relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, B existing alone, and A and B existing simultaneously. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0037] In the following description of this embodiment, the term "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0038] Those skilled in the art should understand that, in the following description of the embodiments of this application, the sequence of numbers does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0039] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms "a" and "the" as used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0040] It should be noted that all raw materials and reagents in the embodiments of this application were purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0041] In a first aspect, embodiments of this application provide a carboxyl-terminated PLA oligomer monomer, comprising a polymerization product containing a first nylon salt and a second nylon salt;

[0042] The first nylon salt is one or more of nylon 512, nylon 56, and nylon 510;

[0043] The second nylon salt is synthesized by reacting the following monomer composition;

[0044] The monomer composition comprises a carboxyl-terminated PLA oligomer monomer, 1,5-pentanediamine, and an antioxidant.

[0045] On one hand, the terminal carboxyl groups (-COOH) of the carboxyl-terminated PLA oligomers can form hydrogen bonds with the amide groups (-CONH-) and unreacted amine groups (-NH2) in the PA512 main chain. These hydrogen bonds, in conjunction with the inherent hydrogen bonds between the PA512 main chains, significantly enhance the intermolecular forces, effectively suppressing chain slippage and dislocation under external forces, thereby improving the tensile strength and flexural properties of the material. On the other hand, the carboxyl-terminated PLA oligomers can also act as heterogeneous nucleating agents, providing crystallization sites to promote the crystallization process of the PA512 matrix and helping to form a more complete crystalline network structure. This crystalline network can maintain structural stability and integrity even at high temperatures, thus significantly improving the thermodynamic properties of PA512 material, such as its heat resistance.

[0046] It should be noted that the first nylon salt used in this application includes, but is not limited to, salt solutions prepared from nylon 512, nylon 56, nylon 510, etc.

[0047] In this embodiment, the carboxyl-terminated PLA oligomer monomer is prepared by reacting lactide and a diacid; the diacid is preferably one or more of succinic acid, adipic acid, octanoic acid, and sebacic acid. The structural formula of the carboxyl-terminated PLA oligomer monomer obtained by reacting adipic acid and lactide is shown in Formula 1:

[0048]

[0049] Formula 1.

[0050] In this embodiment, the preparation method of the carboxyl-terminated PLA oligomer monomer includes: reacting lactide and a dicarboxylic acid at 130-190 °C for 0.5-1 h under catalytic conditions; after separation and purification, drying under vacuum to obtain the carboxyl-terminated PLA oligomer monomer. It should be noted that the catalyst is preferably 0.5% stannous octoate by mass. The crude product after the reaction is dissolved in dichloromethane, precipitated with methanol or anhydrous ethanol, filtered, and then dried under vacuum at 50 °C for 24 h to obtain the carboxyl-terminated PLA oligomer monomer.

[0051] In the embodiments of this application, the molar ratio of lactide to diacid is 1:(1.5-3); under catalytic conditions, lactide can undergo ring opening and react with diacid, and diacid can be grafted to both ends of lactide.

[0052] It should be noted that the key monomers used in the preparation process of this application are all derived from bio-based raw materials. The carboxyl-terminated PLA oligomer monomer is generated by reacting lactide (obtained through lactic acid cyclization via bio-fermentation) with adipic acid (a bio-based source); the bio-based diamine is 1,5-pentanediamine; and the raw material for the first nylon salt is also a bio-based component, ensuring that the entire raw material system originates from renewable biomass resources. Therefore, the entire raw material system is derived from renewable biomass resources and can achieve fully bio-based degradation over a long period.

[0053] It should be noted that this application utilizes the terminal carboxyl group (-COOH) of the terminal carboxyl group PLA oligomer to form hydrogen bonds (-COOH…HN-) with the amide group (-CONH-) or unreacted amine group (-NH2) in the PA512 main chain. These intermolecular hydrogen bonds, in conjunction with the strong hydrogen bonds between the amide bonds of PA512 itself, significantly improve the bonding force between molecular chains, reduce the tendency of molecular chains to slip under external forces, and thus enhance the tensile and flexural strength of the material. When the PLA block content is 1%, the tensile strength increases from 90 MPa in pure PA512 to 92 MPa, and the flexural strength increases from 120 MPa to 145 MPa, confirming the improvement in mechanical properties due to enhanced intermolecular forces.

[0054] It should be noted that the carboxyl-terminated PLA oligomers are aliphatic polyester segments with a certain degree of flexibility (the internal rotation barrier of the ester bond is relatively low), while the first nylon salt has a polyamide structure with a relatively rigid amide bond (the conjugation effect restricts bond rotation). The rigid-flexible block structure formed by the two can disperse external forces through the synergistic effect of the chain segments: when the material is stretched or bent, the flexible PLA segments can absorb some stress through chain segment folding and stretching, reducing stress concentration; while the rigid PA512 main chain provides skeletal support, avoiding excessive deformation. This balance of rigidity and flexibility allows the material to maintain its strength while improving its resistance to deformation (e.g., the flexural modulus increases from 2920 MPa in pure PA512 to 3420 MPa in Example 2).

[0055] It should be noted that the carboxyl-terminated PLA oligomers can act as heterogeneous nucleating agents, promoting the crystallization process of the first nylon salt matrix. The locally ordered structure of the PLA segments can provide crystallization sites for the amide bonds of the first nylon salt, improving the overall crystallinity. As shown in Table 3, the enthalpy of melting ΔH increases after the introduction of PLA blocks. m Slightly improved, higher than the 60.0 J / g of Comparative Example 1. The crystalline region has a tightly packed and ordered molecular chain arrangement and strong intermolecular forces, which can significantly improve the tensile strength and flexural strength of the material; while the PLA chain segments in the amorphous region provide a certain degree of flexibility, avoiding the material from being too brittle, thus achieving synergistic optimization of mechanical properties.

[0056] Secondly, this application provides a method for preparing the fully bio-based biodegradable nylon described in the first aspect, the method comprising:

[0057] The second nylon salt was obtained by reacting the terminal carboxyl group PLA oligomer monomer, 1,5-pentanediamine and antioxidant in a solvent.

[0058] The first nylon salt and the second nylon salt are subjected to high-pressure polymerization, followed by cooling and vacuum drying to obtain the fully bio-based biodegradable nylon.

[0059] It should be noted that: 1. Enhanced thermal stability of the molecular chain structure: The covalent connection between the terminal carboxyl group PLA oligomer and the first nylon salt reduces the free volume at the molecular chain ends. From a polymer physics perspective, chain ends are thermodynamically unstable regions, susceptible to high-temperature attack and chain breakage. The introduction of PLA blocks reduces the probability of chain breakage at high temperatures by lengthening the molecular chain or reducing the number of ends. Furthermore, both the ester bonds in the PLA segments and the amide bonds in the first nylon salt are polar groups. The intermolecular interactions and hydrogen bond network together construct a more stable molecular framework, enabling the material to maintain structural integrity at high temperatures. This is reflected in the fact that the melting temperature of PA512-C (207.0-208.4 ℃) is close to and stable with that of pure PA512 (208.4 ℃). 2. Thermal stability of the crystalline network: The PLA blocks promote the crystallization of the first nylon salt, forming a more complete crystalline network. The molecular chains in the crystalline region are tightly packed through strong hydrogen bonds and van der Waals forces, exhibiting higher thermal resistance. Table 3 shows the melting enthalpy ΔH of PA512-C. m The higher concentration of PLA segments compared to pure PA512 indicates more complete crystallization, thus ensuring the stability of thermodynamic properties. The PLA segments are encapsulated within the PA512 main chain, reducing direct contact with the external environment. Simultaneously, the addition of antioxidants inhibits the thermal oxidative degradation of PLA ester bonds, while the strong amide bond network of the PA512 main chain provides overall thermal stability support for the material. Therefore, the thermodynamic properties of PA512-C did not decrease due to the introduction of PLA; on the contrary, they became more stable due to the increased crystallinity.

[0060] In this embodiment of the application, the mass ratio of the first nylon salt to the second nylon salt is preferably 1:(0.005-0.03). By controlling the mass ratio of the first nylon salt to the second nylon salt, the structure of the generated molecular chain can be controlled, thereby achieving reasonable optimization of the nylon performance.

[0061] It should be noted that: 1. Bio-based monomers are readily available and low in cost. 2. The synthesis and modification processes of bio-based monomers are simple and easily scaled up. 3. The polymerization process of this fully bio-based nylon is green and solvent-free, with mild and controllable reaction conditions, enabling the preparation of high-quality, high-molecular-weight nylon resins. 4. The ester bonds in the introduced PLA structure are easily hydrolyzed, making this fully bio-based nylon biodegradable, environmentally friendly, and improving recyclability.

[0062] Thirdly, this application also provides the application of the fully bio-based biodegradable nylon described in the first aspect or the fully bio-based biodegradable nylon prepared by the method described in the second aspect in nylon products. The nylon prepared based on these methods possesses excellent mechanical properties, thermodynamic properties, and biodegradability, and is environmentally friendly, showing broad application prospects in industry.

[0063] The technical solution of this application will be further described below with reference to specific embodiments.

[0064] Example 1

[0065] This embodiment provides a method for preparing carboxyl-terminated PLA oligomer monomers, specifically including:

[0066] Lactide was placed in a two-necked flask and heated to 140 °C under normal pressure until it was completely melted. The temperature was then raised to 160 °C, and 0.5% (w / w) of stannous octoate was immediately added dropwise. After reacting for approximately 1.5 min, 25 wt% (w / w) of adipic acid was added, and the reaction was continued for 0.5–1 h to obtain carboxyl-terminated polylactic acid copolymer. Purification: The crude product was dissolved in dichloromethane, precipitated with methanol or anhydrous ethanol, filtered, and then dried under vacuum at 50 °C for 24 h to obtain carboxyl-terminated PLA oligomer monomers.

[0067] The structure of the carboxyl-terminated PLA oligomer monomers prepared in Example 1 was characterized as follows:

[0068] Figure 1 The image shows the carbon spectrum of the terminal carboxyl group PLA oligomer monomer. It can be seen that the carbon atom at about 170 ppm is the carboxyl group, and the carbon atom at 69 ppm is identified as the carbon atom on the polylactic acid backbone. The chemical shift of 65 ppm is because some polylactic acid is not capped. The ketone group at the γ position loses its ability to withdraw electrons from the carbon atom. Since it is at the γ position, the chemical shift is reduced slightly.

[0069] Figure 2 The image shows the 1H NMR spectrum of the terminal carboxyl group PLA oligomer monomer. It can be seen that the H at around 5.2 ppm is affected by the ketone group and oxygen heteroatoms, and the 2.6 ppm peak is obviously the hydrogen atom on the carbon connected to the ester group. The hydrogen in the saturated hydrocarbon region is divided into 3 peaks. The hydrogen at 1.4 ppm in the middle is the hydrogen on the branched methyl group, and the other two peaks are attributed to the hydrogen on the branched methyl group when it is not capped. A peak of 4 ppm appears. Based on C-NMR, HMQC is attributed to the hydrogen on the main chain carbon of polylactic acid near the chain end.

[0070] Figure 3The image shows a two-dimensional nuclear magnetic resonance correlation spectrum of the terminal carboxyl group PLA oligomer monomer. It can be seen that the hydrogen at 4.0 ppm is coupled with the two peaks on the left and right sides of the saturated hydrocarbon, which further confirms the saturated hydrocarbon region. The two hydrogen peaks on the left and right sides belong to the hydrogen on the main chain carbon near the end of the chain in the uncapped case, and the hydrogen at 4.0 ppm belongs to the hydrogen on the main chain carbon near the end of the polylactic acid chain.

[0071] Figure 4 The HMQC chromatogram of carboxyl-terminated PLA oligomer monomers shows the following: A: 1.45 ppm H coupled with 17 ppm C; B: two small peaks, 20 ppm C and 1.2 ppm H coupled, belonging to uncapped polylactic acid with carboxyl groups at the end; C: 24 ppm C coupled with 1.62 ppm H, representing the β-hydrogen of the ester group; D: 2.6 ppm H coupled with 29 ppm C, representing the ester group's alfa H; E: 46 ppm C coupled with 2.5 ppm H, representing the solvent peak of DMSO, mixed with the 2.6 ppm H; F: 4.0 ppm H and 64 ppm C coupled near the chain segment in uncapped polylactic acid; G: polylactic acid main chain carbon (69 ppm) coupled with 5.0 ppm H... H coupling at ppm; I: long-range coupling between the main chain C of uncapped polylactic acid near the chain segment and the hydrogen of the branched methyl group; J: long-range coupling between the main chain carbon of polylactic acid and the branched methyl group; H: the hydrogen peak at 1.45 is the superposition of hydrogen peaks on the long carbon chain of adipic acid and hydrogen peaks on the methyl group.

[0072] Example 2

[0073] This embodiment provides a method for preparing A1-fully biodegradable nylon (PA512-C 0.5%), specifically including:

[0074] S201: 1 mol of 1,5-pentanediamine and 1.03 mol of the carboxyl-terminated PLA oligomer monomer prepared in Example 1 were reacted at 40°C and completely dissolved in anhydrous ethanol at a pH of approximately 7.0. The mixture was then dried overnight in a vacuum drying oven at 50°C to prepare a copolynylon salt.

[0075] S202: Transfer PA512 salt and 0.5% copolymerized nylon salt to a polymerization reactor, introduce high-purity nitrogen and evacuate, repeating this process 5 times to fully replace the air inside the reactor. Under sealed conditions, start stirring and control the stirring speed at 60-120 rpm, raise the temperature to 100 ℃ and hold for 1 hour. Then raise the temperature to 220 ℃ and react for 1.5 hours. First, switch the sealed reaction system to nitrogen purging mode and purge for 0.5 hours, controlling the nitrogen flow rate at 20-50 mL / min. Start evacuation and control the vacuum degree at 200-500 Pa. The polycondensation reaction can be completed in 0.5 hours. Finally, purge with high-purity nitrogen until the pressure inside the reactor is positive. After standing for a period of time, open the discharge valve at the bottom of the reactor to allow the material to pass through a cooling water tank. After drawing, pelletizing, and vacuum drying, A1-fully biodegradable nylon (PA512-C 0.5%) can be obtained.

[0076] Example 3

[0077] This embodiment provides a method for preparing A2-fully biodegradable nylon (PA512-C 1%), specifically including:

[0078] S301: 1 mol of 1,5-pentanediamine and 1.03 mol of the carboxyl-terminated PLA oligomer monomer prepared in Example 1 were reacted at 40°C and completely dissolved in anhydrous ethanol at a pH of approximately 7.0. The mixture was then dried overnight in a vacuum drying oven at 50°C to prepare a copolynylon salt.

[0079] S302: Transfer PA512 salt and 1% copolymerized nylon salt to a polymerization reactor, introduce high-purity nitrogen and evacuate, repeating this process 5 times to fully replace the air inside the reactor. Under sealed conditions, start stirring and control the stirring speed at 60-120 rpm, raise the temperature to 100℃ and hold for 1 hour. Then raise the temperature to 220℃ and react for 1.5 hours. First, switch the sealed reaction system to nitrogen purging mode and purge for 0.5 hours, controlling the nitrogen flow rate at 20-50 mL / min. Start evacuation and control the vacuum degree at 200-500 Pa. The polycondensation reaction can be completed after 0.5 hours of reaction. Finally, purge with high-purity nitrogen until the pressure inside the reactor is positive. After standing for a period of time, open the discharge valve at the bottom of the reactor to allow the material to pass through a cooling water tank. After drawing, pelletizing, and vacuum drying, A2-fully biodegradable nylon (PA512-C 1%) can be obtained.

[0080] Example 4

[0081] This embodiment provides a method for preparing A3-fully biodegradable nylon (PA512-C 2%), specifically including:

[0082] S401: 1 mol of 1,5-pentanediamine and 1.03 mol of the carboxyl-terminated PLA oligomer monomer prepared in Example 1 were reacted at 40°C and completely dissolved in anhydrous ethanol at a pH of approximately 7.0. The mixture was then dried overnight in a vacuum drying oven at 50°C to prepare a copolynylon salt.

[0083] S402: Transfer PA512 salt and 2% copolymerized nylon salt to a polymerization reactor, introduce high-purity nitrogen and evacuate, repeating this process 5 times to fully replace the air inside the reactor. Under sealed conditions, start stirring and control the stirring speed at 60-120 rpm, raise the temperature to 100℃ and hold for 1 hour. Then raise the temperature to 220℃ and react for 1.5 hours. First, switch the sealed reaction system to nitrogen purging mode and purge for 0.5 hours, controlling the nitrogen flow rate at 20-50 mL / min. Start evacuation and control the vacuum degree at 200-500 Pa. The polycondensation reaction can be completed after 0.5 hours of reaction. Finally, purge with high-purity nitrogen until the pressure inside the reactor is positive. After standing for a period of time, open the discharge valve at the bottom of the reactor to allow the material to pass through a cooling water tank. After drawing, pelletizing, and vacuum drying, A3-fully biodegradable nylon (PA512-C 2%) can be obtained.

[0084] Example 5

[0085] This embodiment provides a method for preparing A4-fully biodegradable nylon (P512-C 3%), specifically including:

[0086] S501: 1 mol of 1,5-pentanediamine and 1.03 mol of the carboxyl-terminated PLA oligomer monomer prepared in Example 1 were reacted at 40°C and completely dissolved in anhydrous ethanol at a pH of approximately 7.0. The mixture was then dried overnight in a vacuum drying oven at 50°C to prepare a copolynylon salt.

[0087] S502: Transfer PA512 salt and 3% copolymerized nylon salt to a polymerization reactor, introduce high-purity nitrogen and evacuate, repeating this process 5 times to fully replace the air inside the reactor. Under sealed conditions, start stirring and control the stirring speed at 60-120 rpm, raise the temperature to 100℃ and hold for 1 hour. Then raise the temperature to 220℃ and react for 1.5 hours. First, switch the sealed reaction system to nitrogen purging mode and purge for 0.5 hours, controlling the nitrogen flow rate at 20-50 mL / min. Start evacuation and control the vacuum degree at 200-500 Pa. The polycondensation reaction can be completed after 0.5 hours of reaction. Finally, purge with high-purity nitrogen until the pressure inside the reactor is positive. After standing for a period of time, open the discharge valve at the bottom of the reactor to allow the material to pass through a cooling water tank. After drawing, pelletizing, and vacuum drying, A4-fully biodegradable nylon (P512-C 3%) can be obtained.

[0088] Meanwhile, to verify the physicochemical properties of the fully bio-based biodegradable nylon prepared in the above embodiments, this application provides the following comparative examples for detailed illustration.

[0089] Comparative Example 1

[0090] This comparative example provides a method for preparing B1-nylon, specifically including:

[0091] 1 mol of 1,5-pentanediamine and 1.03 mol of dodecanoic acid were placed in a three-necked flask, and an appropriate amount of anhydrous ethanol was added as a solvent. The mixture was stirred at 40 °C (80-100 rpm) to completely dissolve the two monomers and react for 30-40 minutes to obtain a PA512 salt solution. The PA512 salt solution was transferred to a rotary evaporator, and some ethanol was removed by vacuum distillation at 60 °C. The concentrate was dried overnight in a vacuum drying oven at 50 °C to thoroughly remove residual solvent and moisture, and then ground into an 80-100 mesh powder for later use. The dried PA512 salt powder was transferred to a polymerization reactor, and high-purity nitrogen was introduced and a vacuum was created. This process was repeated 5 times to fully replace the air in the reactor. Under sealed conditions, stirring was started and the stirring speed was controlled at 60-120 rpm. The temperature was raised to 100 °C and held for 1 h. The temperature was then raised to 220 °C and reacted for 1.5 h, followed by purging with nitrogen for 0.5 h. The vacuum was started and controlled at 200~500Pa. The polycondensation reaction was completed in 0.5 hours. Finally, high-purity nitrogen was introduced until the pressure inside the reactor was positive. After standing for a period of time, the bottom discharge valve was opened. The material was cooled through a cooling water tank, drawn into fibers, granulated, and vacuum dried to obtain B1-nylon (pure PA512 resin).

[0092] The difference between this comparative example and Example 3 is that no biodegradable blocks were added to the PA512 resin.

[0093] Comparative Example 2

[0094] This comparative example provides a method for preparing B2-nylon, specifically including:

[0095] S601: 1 mol of 1,5-pentanediamine and 1.03 mol of terminal carboxyl PLA oligomer monomers before separation and purification in Example 1 were reacted at 40 °C and dissolved in anhydrous ethanol at a monitored pH of around 7.0 to prepare a copolymerized nylon salt, which was then dried overnight in a vacuum drying oven at 50 °C.

[0096] S602: Transfer PA512 salt and 1% copolymerized nylon salt to a polymerization reactor, introduce high-purity nitrogen and evacuate, repeating this process 5 times to fully replace the air inside the reactor. Under sealed conditions, start stirring and control the stirring speed at 60-120 rpm, raise the temperature to 100℃ and hold for 1 h. Then raise the temperature to 220℃ and react for 1.5 h. First, switch the sealed reaction system to nitrogen purging mode and purge for 0.5 h, controlling the nitrogen flow rate at 20-50 mL / min. Start evacuation and control the vacuum degree at 200-500 Pa. The polycondensation reaction is completed after 0.5 h. Finally, purge with high-purity nitrogen until the pressure inside the reactor is positive. After standing for a period of time, open the discharge valve at the bottom of the reactor to allow the material to pass through a cooling water tank. After drawing, pelletizing, and vacuum drying, B2-nylon can be obtained.

[0097] The difference between this comparative example and Example 3 is that the terminal carboxyl group PLA oligomer monomer was not purified.

[0098] Comparative Example 3

[0099] This comparative example provides a method for preparing B3-nylon, specifically including:

[0100] PA512 salt and 1% of the carboxyl-terminated PLA oligomer monomer from the example were transferred to a polymerization reactor. High-purity nitrogen was introduced and a vacuum was drawn, repeated 5 times to fully replace the air inside the reactor. Under sealed conditions, stirring was started and the stirring speed was controlled at 60-120 rpm. The temperature was raised to 100 ℃ and held for 1 h. The temperature was then raised to 220 ℃ and reacted for 1.5 h. The sealed reaction system was then switched to nitrogen purging mode and purged for 0.5 h, with the nitrogen flow rate controlled at 20-50 mL / min. Vacuuming was then started and the vacuum degree was controlled at 200-500 Pa. The polycondensation reaction was completed after 0.5 h of reaction. Finally, high-purity nitrogen was introduced until the pressure inside the reactor was positive. After standing for a period of time, the discharge valve at the bottom of the reactor was opened, allowing the material to pass through a cooling water tank. After drawing, pelletizing, and vacuum drying, B3-nylon was obtained.

[0101] The difference between this comparative example and Example 3 is that the carboxyl-terminated PLA oligomer monomer was not salted and polymerized with pentanediamine.

[0102] The nylon materials prepared in Examples 2-5 and Comparative Examples 1-3 were subjected to the following tests, and the test results are shown in Table 1.

[0103] (1) Transmittance (%): Transmittance was tested using a UV spectrophotometer;

[0104] (2) Water vapor transmission rate (cc / m2.day.atm): The water vapor transmission rate was tested in accordance with the standard ASTM F1249-2001;

[0105] (3) Oxygen transmission rate (cc / m2.day.atm): The oxygen transmission rate was tested in accordance with the standard GB / T19798-2005;

[0106] (4) Relative viscosity: The relative viscosity of the bio-based nylon material with a concentration of 0.5 g / dL was measured using an Ubbelohde viscometer in a concentrated sulfuric acid solution with a temperature of (25±0.01)℃ and a mass fraction of 98%.

[0107] (5) Tensile strength (MPa): Tensile strength test shall be performed in accordance with standard ISO 527-1 / -2;

[0108] (6) Bending strength (MPa): Bending strength test shall be performed in accordance with standard ISO 178.

[0109] (7) Bending modulus (MPa): The bending modulus was tested in accordance with the standard GB / T 9341-2008;

[0110] Table 1 Results of various performance tests

[0111]

[0112] As shown in Table 1, the PA512-C series with readily biodegradable PLA blocks prepared in the embodiments of this application all maintain excellent water absorption, light transmittance, and oxygen transmittance. A comparison of Examples 1-4 reveals that as the amount of readily biodegradable PLA blocks introduced increases (from 0.5% to 3%), the relative viscosity of the nylon material decreases slightly, but still maintains a relatively high viscosity. Therefore, we can achieve biodegradable bio-based nylon materials with high molecular weight. A comparison of Example 1 and Comparative Examples 2-3 shows that purifying the carboxyl-terminated polylactic acid copolymer monomer and then forming a salt with pentanediamine can significantly increase the relative viscosity of the entire product. Comparative examples and Comparative Example 1 show that the PA512-C series nylon material exhibits excellent tensile strength, flexural strength, and flexural modulus in terms of mechanical properties. This indicates that the PA512-C series nylon material with easily degradable PLA blocks not only achieves high molecular weight but also possesses excellent barrier properties (oxygen permeability as low as 4.2 cc / m2.day.atm), mechanical properties (tensile strength up to 92 MPa), and toughness (flexural strength up to 145 MPa). It has broad application prospects in food packaging, medical devices, agricultural production, and daily necessities.

[0113] Mass degradation loss rate test:

[0114] 1. For the fully bio-based biodegradable nylons of Examples 1-4 and Comparative Examples 1-3, the mass degradation loss rate test was performed. First, the sample was preheated to a temperature higher than the melting temperature. 1.8 g of sample was wrapped in a tetrafluoroethylene film and preheated for 5 minutes to melt the sample. Then, it was pressed for 30 seconds to release the gas and then pressed for another 5 minutes to release the gas.

[0115] 2. PA512-C (Examples 1-4) with polylactic acid oligomers at contents of 0.5%, 1%, 2%, and 3% were added, and Comparative Examples 1-3 were prepared into films with the same mass. The samples were weighed, and the prepared polylactic acid films were cut into 3 cm × 3 cm pieces. After weighing and recording, they were placed in a 50 mL hydrothermal reactor and reacted at 160 ℃ for 10 minutes. After that, they were taken out, cooled to room temperature with cold water, dried, and weighed. The mass after the reaction was measured, and the mass loss rate was calculated. The mass loss rate = [(initial mass - mass after reaction) / initial mass] × 100%, and then converted to the loss rate over 180 days. The test results of the degradation mass loss rate are listed in Table 2.

[0116] Table 2. Test results of degradation mass loss rate for each example and comparative example.

[0117]

[0118] As shown in Table 2, the examples incorporating readily degradable PLA blocks exhibited a greater degradation loss rate compared to those without. Therefore, the fully bio-based biodegradable nylon PA512-C series demonstrates significant degradability. Furthermore, the mass loss rate and degradability increase with the increase in the number of readily degradable PLA blocks introduced.

[0119] Thermodynamic stability test:

[0120] Heating program: First heating from -10°C to 250°C at 10°C / min; first cooling from 250°C to -10°C; second heating from -10°C to 250°C; enthalpy of cold crystallization ΔH c and enthalpy of fusion ΔH m The performance stability test results are shown in Table 3 and Figure 5 As shown.

[0121] Table 3. Thermodynamic stability test results of nylon materials prepared in the examples and comparative examples.

[0122]

[0123] According to Table 3 and Figure 5 It can be seen that a) represents the first cooling from 250 ℃ to -10 ℃, and b) represents the second heating from -10 ℃ to 250 ℃. The melting temperature (T) of the PA512-C series samples prepared in the example is... mThe enthalpy of cold crystallization ΔH of the PA512-C series samples is between 207.0 and 208.4 °C, and the crystallization temperature is between 165.0 and 175.4 °C. As shown in Examples 1-4, with the increase of easily degradable PLA blocks, the enthalpy of cold crystallization ΔH of the PA512-C series samples increases. c The enthalpy of cold crystallization shows a trend of first increasing and then decreasing. Furthermore, the enthalpy of cold crystallization is highest when approximately 1% of easily degradable blocks are introduced. Combined with the mechanical test results of Examples 1-4 in Table 2, the tensile strength, flexural strength, and flexural modulus also show a trend of first increasing and then decreasing. The best mechanical test results are found when approximately 1% of easily degradable blocks are introduced, indicating that the higher the content of cold crystals, the better the thermodynamic properties.

[0124] according to Figure 6 It can be seen that cutting the prepared polylactic acid film into 3 cm × 3 cm pieces, weighing and recording the weight, and placing it in a 50 mL hydrothermal reactor, adding 25 mL of hydrochloric acid solution (pH=1), and keeping it at 160 ℃ is a decomposition experiment of weak acid hydrolysis. As the holding time increases, the polylactic acid film obviously decomposes under the hydrolysis of the holding water.

[0125] Therefore, when the carboxyl-terminated PLA oligomer monomers prepared in this application are applied to nylon materials, the resulting nylon materials achieve both high molecular weight and excellent barrier properties (with an oxygen permeability as low as 4.2 cc / m). 2 .day.atm), mechanical properties (tensile strength up to 92 MPa) and toughness (flexural strength up to 145 MPa), cold crystallization enthalpy ΔH c With a strength of 70 kJ / kg, it possesses excellent thermodynamic properties and a mass degradation loss rate of 63.3% after 180 days, making it a promising candidate for applications in food packaging, medical devices, agricultural production, and daily necessities.

[0126] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0127] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of this application.

Claims

1. A fully bio-based biodegradable nylon, characterized in that, Polymer products containing a first nylon salt and a second nylon salt; The first nylon salt is one or more of nylon 512, nylon 56, and nylon 510; The second nylon salt is synthesized by reacting the following monomer composition; The monomer composition comprises a carboxyl-terminated PLA oligomer monomer, 1,5-pentanediamine, and an antioxidant. The carboxyl-terminated PLA oligomer monomer is prepared by reacting lactide and a dicarboxylic acid. The dicarboxylic acid includes one or more of succinic acid, adipic acid, octanoic acid, and sebacic acid; The molar ratio of lactide to dicarboxylic acid is 1:(1.5-3).

2. The fully bio-based biodegradable nylon according to claim 1, characterized in that, The method for preparing the terminal carboxyl group PLA oligomer monomer includes: Under catalytic conditions, lactide and dicarboxylic acid are reacted at 130-190 °C for 0.5-1 h. After separation and purification, the mixture is dried under vacuum to obtain the terminal carboxyl group PLA oligomer monomer.

3. The fully bio-based biodegradable nylon according to claim 2, characterized in that, The catalyst is stannous octoate.

4. A method for preparing the fully bio-based biodegradable nylon according to any one of claims 1-3, characterized in that, The preparation method includes: The second nylon salt is obtained by reacting the terminal carboxyl group PLA oligomer monomer, 1,5-pentanediamine and antioxidant in a solvent. The first nylon salt and the second nylon salt are subjected to high-pressure polymerization, followed by cooling and vacuum drying to obtain the fully bio-based biodegradable nylon.

5. The method for preparing fully bio-based biodegradable nylon according to claim 4, characterized in that, The molar ratio of the terminal carboxyl group PLA oligomer monomer to 1,5-pentanediamine is (0.95-1.25):

1.

6. The method for preparing fully bio-based biodegradable nylon according to claim 4, characterized in that, The antioxidant is one or more of antioxidant 1098 and antioxidant 168; The amount of antioxidant added accounts for 0.1%-0.5% of the total monomer content.

7. The method for preparing fully bio-based biodegradable nylon according to claim 4, characterized in that, The solvent is one or a combination of ethanol, dichloromethane.

8. The method for preparing fully bio-based biodegradable nylon according to claim 4, characterized in that, The mass ratio of the first nylon salt to the second nylon salt is 1:(0.005-0.03).

9. The use of a fully biodegradable nylon according to any one of claims 1-3 or a fully biodegradable nylon prepared by any one of claims 4-8 in nylon articles.

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