Modified polyamide resin and preparation method thereof

Abstract

The invention provides a modified polyamide resin and a preparation method thereof, the modified polyamide resin comprises a structural unit derived from binary acid and diamine, and an end-capping structure derived from an oxetane compound of formula (I): (I) wherein R1 is C1-C6 alkyl, R2 is C1-C12 hydroxyalkyl or C2-C6 alkyl interrupted by an ether bond; wherein the molar ratio of the diamine to the binary acid is 1: (1-1.01); the mass of the oxetane compound is 1-3% of the mass of the modified polyamide resin; the number-average molecular weight of the modified polyamide resin is 25000 to 35000.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a modified polyamide resin and its preparation method. Background Technology

[0002] Polyamide resins, with their excellent mechanical properties, heat resistance, and chemical stability, are widely used in molded products such as fibers, containers, films, electronic components, automotive parts, and mechanical parts. However, with the increasing demands for miniaturization, complexity, thinning, and lightweight products in industrial development, the need for polyamide materials to maintain good mechanical properties while also possessing excellent molding and processing performance is becoming increasingly prominent.

[0003] Currently, polyamide resins generally face the following technical bottlenecks: First, to achieve higher mechanical strength, the polymer molecular weight needs to be increased. However, increasing the molecular weight leads to a significant increase in melt viscosity and a decrease in processability. Although the melt viscosity can be reduced by increasing the processing temperature, excessively high temperatures can easily cause thermal decomposition of the polyamide, resulting not only in a decrease in molecular weight but also in the generation of gas, affecting the mechanical properties and appearance quality of the product. Second, to improve the thermal conductivity, electrical conductivity, or rigidity of polyamide materials, a large amount of functional fillers or reinforcing materials are often introduced. However, high filler content significantly increases the viscosity of the system, easily causing shear heat generation, resin performance degradation, and uneven filler dispersion during processing, thus affecting the uniformity and reliability of the final product. In addition, the active carboxyl and amino groups at the ends of the polyamide molecular chains easily react with the filler surface, which may not only affect filler dispersion but also accelerate material aging and degradation. Summary of the Invention

[0004] In view of this, the main objective of the present invention is to provide a modified polyamide resin and a method for preparing the same, so as to at least partially solve the aforementioned technical problems.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] In one aspect of the invention, a modified polyamide resin is provided, comprising structural units derived from diacids and diamines, and end-capped structures derived from oxobutane compounds of formula (I):

[0007] (I), where,

[0008] R1 is a C1~C6 alkyl group, and R2 is a C1~C6 alkyl group. 12 Hydroxyalkyl groups or C2-C6 alkyl groups interrupted by ether bonds;

[0009] The molar ratio of the diamine to the diacid is 1:1 to 1.01.

[0010] The mass of the oxetane compound is 1-3% of the mass of the modified polyamide resin;

[0011] The number average molecular weight of the modified polyamide resin is 25,000 to 35,000.

[0012] In a second aspect of the present invention, a method for preparing the above-mentioned modified polyamide resin is provided, comprising:

[0013] In an inert gas environment, a dicarboxylic acid, a diamine, an oxetine compound, and a catalyst are added and stirred to obtain a mixed reactant.

[0014] The mixed reactants are subjected to a prepolymerization reaction at a temperature of 150~200℃ to form a prepolymer;

[0015] The prepolymer was polymerized at 220-260℃ under the condition of maintaining the reaction pressure to obtain the initial product.

[0016] The initial product was subjected to solid-state polymerization at 200~250℃ and a vacuum of 10~30Pa to obtain a modified polyamide resin.

[0017] The modified polyamide resin provided by the present invention, by introducing an oxacyclobutane compound with a specific structure to cap the ends of the polyamide molecular chain, effectively solves the problem of molecular chain degradation caused by the terminal carboxyl cyclization reaction during high-temperature processing of polyamide resin. This not only significantly improves the resin's anti-aging properties, enabling it to maintain excellent mechanical strength under long-term use or high-temperature environments, but also helps to improve the problem of residual bubbles during polymerization, enhancing the material's uniformity and processing applicability. Ultimately, the modified polyamide resin achieves a good balance between rigidity and toughness while maintaining good heat resistance, low shrinkage, and excellent chemical resistance. Furthermore, its preparation method is simple, easy to industrialize, and has good application prospects. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0019] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0020] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0021] All terms used herein, including technical and scientific terms, have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0022] Existing polyamide resins, especially those containing biomass furan units, face significant challenges in pursuing high performance: increasing molecular weight to improve mechanical properties leads to a sharp increase in melt viscosity and deterioration in processability; while increasing processing temperature to reduce viscosity easily triggers cyclization reactions of terminal carboxyl groups (especially those of monomers such as dicarboxylic acid), resulting in polymer thermal decomposition, molecular weight reduction, and bubble generation, ultimately impairing the material's mechanical properties, appearance, and long-term anti-aging stability. Furthermore, in highly filled formulations, the active ends of polyamides are prone to adverse reactions with fillers, exacerbating performance degradation.

[0023] Based on this, the present invention provides a modified polyamide resin and its preparation method. By introducing an oxetane compound with a specific structure as a capping agent during the polyamide polymerization process, on the one hand, this compound can effectively inhibit the cyclization decomposition reaction of the terminal carboxyl groups of the polyamide, significantly improving the stability of the resin during high-temperature processing, reducing bubble generation, and improving material uniformity and pelletizing properties, thereby broadening the processing window and improving product quality. On the other hand, the rigid cyclic structure of oxetane participates in and optimizes the interaction between molecular chains, further enhancing the rigidity, heat resistance, and anti-aging properties of the material without sacrificing its toughness. This allows the modified polyamide resin of the present invention to achieve excellent mechanical properties, good molding processability, and outstanding long-term durability without complex processes or large amounts of additives. Furthermore, the modified polyamide resin uses bio-based diacids and diamines as main raw materials, significantly improving the product's sustainability and environmental friendliness. The preparation method is simple, mild, and easy to control, facilitating large-scale stable production and possessing significant industrial application value.

[0024] According to one aspect of the present invention, a modified polyamide resin is provided, comprising structural units derived from diacids and diamines, and end-capped structures derived from oxobutane compounds of formula (I).

[0025] (I).

[0026] R1 is a C1~C6 alkyl group, and R2 is a C1~C6 alkyl group. 12 The hydroxyalkyl group or C2-C6 alkyl group interrupted by an ether bond; wherein the molar ratio of the diamine to the diacid is 1:1 to 1.01; the mass of the oxetane compound is 1 to 3% of the mass of the modified polyamide resin; the number average molecular weight of the modified polyamide resin is 25,000 to 35,000.

[0027] According to embodiments of the present invention, the present invention inhibits the degradation reaction of polyamide resin, optimizes interchain interactions, and improves processing performance by end-capping with oxetine compounds, thereby achieving a comprehensive balance of improved strength, heat resistance, anti-aging properties, and good processability.

[0028] Specifically, during high-temperature processing or long-term use, the carboxyl groups (-COOH) at the ends of polyamide resin molecular chains are prone to intramolecular cyclization reactions, especially when the diacid monomer contains adipic acid, which easily forms stable five-membered anhydride rings, leading to molecular chain breakage, molecular weight reduction, and the generation of gaseous byproducts, thus causing material deterioration. In this invention, the oxacyclobutane compound shown in formula (I) has high reactivity due to its ring strain, and can preferentially undergo ring-opening reactions with the active carboxyl groups at the ends of the polyamide chains to form stable ether-ester capped structures. The capping effect fundamentally eliminates the reaction sites for cyclization reactions of the terminal carboxyl groups, significantly inhibiting thermal degradation pathways. During high-temperature polymerization or melt processing, it can keep the resin molecular chains stable, effectively reducing the generation of bubbles caused by decomposition, improving the uniformity of the material system, and enhancing the resin's anti-aging properties, enabling it to maintain stable mechanical strength under long-term heat loads.

[0029] Meanwhile, the side chain structure formed after the ring-opening of oxetane and its inherent rigid cyclic backbone affect the aggregated structure of polyamide. The rigid cyclic structure restricts excessive chain segment movement, thereby improving the modulus, heat resistance (such as increased melting point), and rigidity of the resin material. Simultaneously, the introduced flexible ether bonds or hydroxyalkyl side chains provide the molecular chains with a certain degree of mobility, avoiding increased brittleness due to excessive rigidity. Through the synergistic design of rigid and flexible segments and the optimization of interactions between molecular chains, a synergistic balance between rigidity and toughness in the modified polyamide resin is achieved at the molecular level, enabling the resin to maintain high strength while possessing good impact toughness.

[0030] Furthermore, the end-capping reaction of oxetane not only stabilizes the molecular chain and reduces degradation side reactions at high temperatures, but also moderately modulates the rheological behavior of the melt due to the introduced side-chain structures (such as alkyl groups containing ether bonds). The side-chain structures weaken the strong hydrogen bonding between polyamide molecular chains to a certain extent, thereby improving the melt flowability of the resin material without significantly reducing the molecular weight. This reduces the dependence on large amounts of added plasticizers, avoids material instability and potential interference with other properties caused by the migration and volatilization of small molecule additives, and ensures the long-term reliability and controllability of the modified polyamide resin's properties.

[0031] For example, R1 can be selected from methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl and their various isomers; R2 can be selected from hydroxymethyl, hydroxyethyl, hydroxypropyl, hydroxybutyl, hydroxypentyl, hydroxyhexyl, hydroxyheptyl, hydroxyoctyl, hydroxynonyl, hydroxydecyl, hydroxyundecyl, hydroxydodecyl and their various branched isomers, or methoxymethyl, methoxyethyl, methoxypropyl, methoxybutyl, methoxypentyl, methoxyhexyl, ethoxymethyl, ethoxyethyl, ethoxypropyl, ethoxybutyl, ethoxypentyl, ethoxyhexyl, propoxymethyl, propoxyethyl, propoxypropyl, propoxybutyl, butoxymethyl, butoxyethyl, butoxypropyl, butoxybutyl, pentomethyl, pentoethyl, pentopropyl, pentopropyl, etc.

[0032] According to embodiments of the present invention, the oxetane compound includes at least one selected from 3-hydroxymethyl-3-ethyloxetane, 3-ethyl-3-((octoxy)methyl)oxetane, 3-ethyl-3-[[(2-ethylhexyl)oxy]methyl]oxetane, (3-ethyloxetane-3-yl)methyl acrylate, (3-ethyloxetane-3-yl)methyl methacrylate, 3-ethyl-3-hydroxymethyloxetane, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, 3-ethyl-3-(phenoxymethyl)oxetane, and 3-ethyl-3-(2-methacrylateoxymethyl)oxetane. Utilizing the high-strain four-membered ring in the above-mentioned oxetane compound, it preferentially undergoes a ring-opening reaction with the carboxyl group at the end of the polyamide chain to form a stable ether-ester capped structure. Eliminating the reaction sites for terminal cyclization degradation is a prerequisite for improving the thermal stability and anti-aging properties of resins.

[0033] In practical applications, oxobutane compounds with different side chain structures can be flexibly selected according to the performance requirements of polyamide resin materials, so as to achieve the customization of polyamide resin performance while ensuring efficient end-capping.

[0034] According to embodiments of the present invention, the dicarboxylic acid includes at least one of aromatic dicarboxylic acids, aliphatic dicarboxylic acids, and alicyclic dicarboxylic acids, and / or biomass-based oxyheterocyclic dicarboxylic acids. The proportion of biomass-based oxyheterocyclic dicarboxylic acids in the dicarboxylic acid is 0.2% to 2%, for example, it can be 0.2%, 0.5%, 1%, 1.5%, 2%, etc.

[0035] According to embodiments of the present invention, the biomass-based oxyheterocyclic dicarboxylic acids include at least one of furan-based dicarboxylic acids and tetrahydrofuran-based dicarboxylic acids; the furan-based dicarboxylic acids include at least one of 2,5-furandicarboxylic acid and 3,4-furandicarboxylic acid; and the tetrahydrofuran-based dicarboxylic acids include at least one of 2,5-tetrahydrofurandicarboxylic acid and 3,4-tetrahydrofurandicarboxylic acid. The rigid cyclic structure of the biomass-based oxyheterocyclic dicarboxylic acids can effectively improve the rigidity and heat resistance of the polyamide backbone; simultaneously, their biomass origin endows the polyamide materials with green and sustainable characteristics.

[0036] Aromatic dicarboxylic acids include at least one of terephthalic acid, 2,6-naphthalenedicarboxylic acid, and 1,4-naphthalenedicarboxylic acid. The rigid aromatic ring unit of aromatic dicarboxylic acids can provide polyamide resins with higher strength, modulus, and glass transition temperature, ensuring that the material possesses the basic mechanical properties and heat resistance required for engineering plastics.

[0037] Aliphatic dicarboxylic acids are C2~C 10 Aliphatic linear-chain diacids include at least one of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, and sebacic acid. The flexible alkane segments in aliphatic diacids can adjust the flexibility and crystallinity of polyamide segments, improving the impact toughness and processing flowability of materials, achieving a balance between rigidity and toughness. The introduction of biomass-based diacids such as succinic acid, adipic acid, azelaic acid, and sebacic acid can further enhance the environmental friendliness of the products.

[0038] Alicyclic dicarboxylic acids include at least one of cyclopentane-1,2-dicarboxylic acid, cyclohexane-1,2-dicarboxylic acid, cycloheptane-1,2-dicarboxylic acid, cyclooctane-1,2-dicarboxylic acid, cyclononane-1,2-dicarboxylic acid, and cyclodecane-1,2-dicarboxylic acid. Their alicyclic structure combines rigidity with a degree of flexibility, which helps improve the hydrolysis resistance, dimensional stability, and melt viscosity of materials.

[0039] In practical applications, the types and proportions of the above-mentioned dicarboxylic acids can be adjusted according to the specific requirements for the rigidity, toughness, heat resistance, processing fluidity and sustainability of polyamide materials.

[0040] According to embodiments of the present invention, the diamine includes biomass-based oxygen-containing heterocyclic diamines, C8~C96... 18 Any one of the aliphatic diamines.

[0041] According to embodiments of the present invention, the biomass-based oxygen-containing heterocyclic diamine includes at least one of furan-based diamines and tetrahydrofuran-based diamines. The furan-based diamines include at least one of 2,5-dimethylaminofuran and 3,4-dimethylaminofuran; the tetrahydrofuran-based diamines include at least one of 2,5-dimethylaminotetrahydrofuran and 3,4-dimethylaminotetrahydrofuran. Its rigid furan ring or tetrahydrofuran ring structure can serve as a rigid node in the molecular chain, effectively improving the glass transition temperature, modulus, and heat resistance of the polyamide resin. Simultaneously, the use of biomass raw materials ensures renewability, significantly enhancing the sustainability of the polyamide material and meeting environmental protection requirements.

[0042] C8~C 18 Aliphatic diamines include at least one of 1,8-octanediamine, 1,10-decanediamine, 1,9-nonanediamine, 1,11-undecanediamine, 1,12-dodecanediamine, 1,13-tridecanediamine, 1,14-tetradecanediamine, 1,15-pentadecanediamine, 1,16-hexadecanediamine, 1,17-heptadecanediamine, 1,18-octadecanediamine, 2-methyl-1,8-octanediamine, or 5-methyl-1,9-nonanediamine. The long-chain alkane structure provides good flexibility and crystallinity control for polyamide molecular chains, which helps improve the impact toughness, processing flowability, and stress cracking resistance of polyamide materials.

[0043] According to embodiments of the present invention, the dicarboxylic acid is terephthalic acid and furan-type dicarboxylic acid, and the diamine is C8~C9. 18 Aliphatic diamines. The rigid benzene ring skeleton in terephthalic acid provides polyamide resins with high strength, modulus, and heat resistance; furan dicarboxylic acids, as rigid heterocyclic structural units derived from biomass, further enhance the heat resistance and rigidity of materials while strengthening the environmental friendliness and sustainability of products; C8~C 18 The long-chain alkane structure of aliphatic diamines, acting as flexible spacers, can effectively regulate the packing density and chain segment mobility of molecular chains, improving the material's impact toughness, melt flowability, and processing performance, while avoiding brittleness and processing difficulties caused by excessive rigidity. Through the copolymerization of the aforementioned rigid diacids and flexible diamines, polyamide resins simultaneously possess high strength, high heat resistance, good toughness, and processing adaptability.

[0044] According to another aspect of the present invention, a method for preparing the above-mentioned modified polyamide resin is provided, comprising the following steps (1) to (4).

[0045] Step (1): Under an inert gas environment, add a dicarboxylic acid, a diamine, an oxacyclobutane compound and a catalyst and stir to mix to obtain a mixed reactant.

[0046] Step (2): At a temperature of 150~200℃, the mixed reactants are subjected to a prepolymerization reaction to form a prepolymer.

[0047] Step (3): Heat to 220~260℃ and polymerize the prepolymer under the condition of maintaining the reaction pressure to obtain the initial product.

[0048] Step (4): The initial product is subjected to solid-state polymerization at a vacuum of 200~250℃ and 10~30Pa to obtain modified polyamide resin.

[0049] For example, the prepolymerization temperature can be 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, etc. This temperature range ensures sufficient dissolution and mixing of reactants, promotes stable initial amidation reaction, and effectively controls the reaction rate to avoid violent exothermic reactions or localized overheating. The polymerization temperature can be 220℃, 230℃, 240℃, 250℃, 260℃, etc. Within this temperature range, it is beneficial for further molecular chain growth and promotes the completion of the oxetane end-capping reaction, while inhibiting... The decomposition side reaction caused by high temperature is eliminated; the solid-state polymerization temperature can be, for example, 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, etc., and the vacuum degree can be, for example, 10Pa, 15Pa, 20Pa, 25Pa, 30Pa, etc. This reaction condition can continuously remove residual small molecules in an environment below the melting point of the initial product, promote the condensation equilibrium to move towards a higher degree of polymerization, thereby achieving a steady increase in molecular weight and full reaction of terminal groups, and optimizing the mechanical properties and thermal stability of the final product.

[0050] According to embodiments of the present invention, by combining gradient temperature polymerization with solid-state polymerization, and under controlled reaction temperature, pressure, and atmosphere conditions, the reaction between the oxetane compound and the polyamide precursor is effectively promoted, achieving uniform end-capping of the molecular chain and steady increase in molecular weight. This not only effectively inhibits the cyclization degradation of terminal carboxyl groups and the generation of bubbles at high temperatures, ensuring high thermal stability and appearance quality of the product, but also further improves the molecular weight and uniformity of the resin distribution through the solid-state polymerization stage, thereby giving it good mechanical strength, anti-aging properties, and processability. Furthermore, the process conditions are mild and reproducible, making it suitable for large-scale production.

[0051] According to an embodiment of the present invention, in step (1), the catalyst includes any one of sodium phosphate monohydrate, sodium pyrophosphate, and sodium hypophosphite. This accelerates the amidation reaction rate between carboxyl groups (-COOH) and amino groups (-NH2), lowers the activation energy, thereby improving reaction efficiency and allowing the polymerization reaction to proceed rapidly under relatively mild conditions, which helps to shorten the production cycle.

[0052] In step (2), the prepolymerization reaction time is 2-6 hours, for example, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, etc. A suitable prepolymerization time can form a prepolymer with a sufficient molecular weight. If the prepolymerization reaction time is too short, the molecular weight of the prepolymer will be too low, and it will easily decompose in the subsequent high-temperature melting stage; if the prepolymerization reaction time is too long, the production efficiency will decrease.

[0053] In step (3), the polymerization reaction time is 1 to 3 hours, for example, 1 hour, 1.5 hours, 2.5 hours, 3 hours, etc. A suitable polymerization reaction time can ensure that the prepolymer can fully carry out the chain growth reaction in the molten state, so that the molecular weight can be significantly increased to the target range, while avoiding thermal oxidative degradation caused by excessive residence time.

[0054] In step (4), the solid-state polymerization time is 5 to 12 hours, for example, 5 hours, 7 hours, 9 hours, 10 hours, 12 hours, etc. Long-term solid-state polymerization of 5 to 12 hours allows the polymer chain ends to diffuse and react fully in the solid state, thereby further increasing the molecular weight, optimizing the molecular weight distribution, and further reducing the concentration of terminal groups, so that the polyamide resin has better mechanical strength, thermal stability and anti-aging properties.

[0055] According to embodiments of the present invention, at least one additive selected from molecular weight regulators and stabilizers is selectively added during the preparation process. The use of additives further optimizes the overall control of the polymerization reaction and the properties of the modified polyamide resin.

[0056] According to embodiments of the present invention, the molecular weight regulator includes a monocarboxylic acid or a monoamine, preferably a monocarboxylic acid selected from any one of aliphatic monocarboxylic acids, aromatic monocarboxylic acids, and alicyclic monocarboxylic acids, and the amount of the monocarboxylic acid is 0.05% to 5% of the weight of the dicarboxylic acid; the monoamine is selected from any one of aliphatic monoamines, alicyclic monoamines, and aromatic monoamines, and the amount of the monoamine is 0.05% to 5% of the weight of the diamine.

[0057] For example, the aliphatic monocarboxylic acid is selected from any one of formic acid, acetic acid, butyric acid, propionic acid, octanoic acid, valeric acid, hexanoic acid, octanoic acid, lauric acid, tridecanoic acid, myristic acid, palmitic acid, stearic acid, neopentanoic acid, and isobutyric acid; the aromatic monocarboxylic acid is selected from any one of benzoic acid, terephthalic acid, o-toluic acid, p-hydroxybenzoic acid, methylbenzoic acid, α-naphthoic acid, β-naphthoic acid, and phenylacetic acid; the alicyclic monocarboxylic acid is selected from any one of cyclohexanecarboxylic acid, cyclohexanedicarboxylic acid, and cyclohexylacetic acid; the amount of monocarboxylic acid can be 0.05%, 0.1%, 0.5%, 1%, 3%, 5%, etc., of the weight of the dicarboxylic acid.

[0058] For example, the aliphatic monoamine is selected from any one of methylamine, ethylamine, propylamine, butylamine, hexylamine, octylamine, decylamine, stearylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, n-propylamine, cyclohexylamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine; the alicyclic monoamine is selected from any one of cyclohexylamine and dicyclohexylamine; the aromatic monoamine is selected from any one of aniline, toluidine, diphenylamine, and naphthylamine; the amount of monoamine used can be 0.05%, 0.1%, 0.5%, 1%, 3%, 5%, etc., of the weight of the diamine.

[0059] According to embodiments of the present invention, the chain growth process is actively controlled by reacting the functional groups of a monobasic acid or monoamine with the ends of the polyamide molecular chain, thereby adjusting the molecular weight and molecular weight distribution of the polymer. This helps to avoid a sharp increase in melt viscosity caused by excessively high molecular weight and significantly improves the processing fluidity of the resin.

[0060] Stabilizers include any one of phosphorous acid, phosphoric acid, phosphites, and phosphates. The amount of stabilizer used is 0.1% to 0.5% of the total feed weight, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, etc. Stabilizers effectively inhibit the thermal oxidative degradation of polyamide resins during high-temperature polymerization, preventing property deterioration such as molecular chain breakage and yellowing. By capturing peroxide free radicals or decomposing hydrogen peroxides, they ensure the chemical stability of modified polyamide resins during synthesis and subsequent processing.

[0061] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. Unless otherwise specified, specific techniques or conditions in the embodiments are conventional methods and can be performed according to the techniques or conditions described in the literature in this field or according to the product instructions. It should be noted that the methods provided by this invention are conventional methods unless otherwise specified, and the reactants and reagents can be obtained commercially through these channels unless otherwise specified.

[0062] Example 1

[0063] This embodiment provides a modified polyamide resin 1, and the preparation method of the modified polyamide resin 1 is as follows.

[0064] Add 498.4 g of terephthalic acid and 46.8 g of 2,5-furandicarboxylic acid (prepared in the laboratory) to a 3 L autoclave, and purge with nitrogen for 30 min under stirring; then add 517 g of 1,10-decanediamine, 10.2 g of 3-hydroxymethyl-3-ethyloxetane, 1.02 g of sodium hypophosphite monohydrate and 400 mL of deionized water and stir to obtain a mixed reactant.

[0065] The mixed reactants were slowly heated to 200°C over approximately 2 hours, and the pressure inside the autoclave was increased to 2 MPa. Under these conditions, a prepolymerization reaction was carried out for 2 hours to form a prepolymer. The temperature was then increased to 240°C, and the pressure was maintained at 2.0 MPa to polymerize the prepolymer for 2 hours, during which the generated water vapor was slowly discharged. Afterward, the system pressure was reduced to 1.0 MPa over 1 hour, and the polymerization reaction was continued for 1 hour to obtain the initial product.

[0066] The initial product was dried at 60℃ under reduced pressure for 20h and pulverized to a particle size of <2mm. Then, solid-state polymerization was carried out at 230℃ and 20Pa vacuum for 10h to obtain a white modified polyamide resin with a number average molecular weight of 23680.

[0067] Example 2

[0068] This embodiment provides a modified polyamide resin 2. The preparation method of the modified polyamide resin 2 differs from that of Example 1 in that 10.2g of 3-hydroxymethyl-3-ethyloxetane is changed to 22.8g of 3-ethyl-3-((octoxy)methyl)oxetane.

[0069] Example 3

[0070] This embodiment provides a modified polyamide resin 3. The preparation method of the modified polyamide resin 3 differs from that of Example 1 in that 10.2g of 3-hydroxymethyl-3-ethyloxetane is replaced with 22.8g of 3-ethyl-3-[[(2-ethylhexyl)oxy]methyl]oxetane.

[0071] Example 4

[0072] This embodiment provides a modified polyamide resin 4. The preparation method of the modified polyamide resin 4 differs from that of Example 1 in that 10.2g of 3-hydroxymethyl-3-ethyloxetane is replaced with 45.6g of 3-ethyl-3-((octoxy)methyl)oxetane.

[0073] Example 5

[0074] This embodiment provides a modified polyamide resin 5. The preparation method of the modified polyamide resin 5 differs from that of Example 1 in that 10.2g of 3-hydroxymethyl-3-ethyloxetane is replaced with 68.4g of 3-ethyl-3-((octoxy)methyl)oxetane.

[0075] Example 6

[0076] This embodiment provides a modified polyamide resin 6. The preparation method of the modified polyamide resin 6 differs from that of Example 1 in that 10.2g of 3-hydroxymethyl-3-ethyloxetane is replaced with 68.4g of 3-ethyl-3-((octoxy)methyl)oxetane.

[0077] Example 7

[0078] This embodiment provides a modified polyamide resin 7. The preparation method of the modified polyamide resin 7 differs from that of Example 1 in that 46.8g of 2,5-furandicarboxylic acid is replaced with 48.1g of 3,4-tetrahydrofurandicarboxylic acid (prepared in the laboratory).

[0079] Example 8

[0080] This embodiment provides a modified polyamide resin 8. The difference between the preparation method of the modified polyamide resin 8 and that of Example 1 is that 517g of 1,10-decanediamine is changed to 517g of 1,8-octanediamine.

[0081] Comparative Example 1

[0082] This comparative example provides a polyamide resin 9. The preparation method of polyamide resin 9 differs from that of Example 1 in that the oxetine compound 3-hydroxymethyl-3-ethyloxetine is not added.

[0083] Comparative Example 2

[0084] This comparative example provides a modified polyamide resin 10. The preparation method of the modified polyamide resin 10 differs from that of Example 2 in that 10.2g of 3-hydroxymethyl-3-ethyloxetane is replaced with 11.4g of 3-ethyl-3-((octoxy)methyl)oxetane.

[0085] Comparative Example 3

[0086] This comparative example provides a modified polyamide resin 11. The preparation method of the modified polyamide resin 11 differs from that of Example 2 in that 10.2g of 3-hydroxymethyl-3-ethyloxetane is replaced with 114g of 3-ethyl-3-((octoxy)methyl)oxetane.

[0087] The application performance of the polyamide resins in Examples 1 to 8 and Comparative Examples 1 to 3 was tested and evaluated as follows.

[0088] (1) Heat resistance test: Under the conditions of ambient temperature of 23±2℃ and humidity of 50±5%RH, the sample was tested using a differential scanning calorimeter (DSC) according to the test standard "ISO11357-3:2011 Plastics Differential Scanning Calorimetry (DSC) Part 3: Melting and Crystallization Temperatures and Enthalpy".

[0089] (2) Chemical resistance test: Immersion test: The samples were immersed in hydrochloric acid (37%, 25℃, 60 s), ammonia (23%, 25℃, 60 s), and acetone (25℃, 60 s) respectively. The changes in resin before and after immersion were observed. The chemical resistance was rated as A if the film thickness change before and after immersion was within ±5% (including the endpoint value), B if the film thickness change before and after immersion was more than ±5% (excluding the endpoint value), and C if the film surface cracked, the pattern corners cracked, the pattern edge was penetrated by the agent, or the cured film was peeled off from the substrate.

[0090] (3) Mechanical property tests: Tensile strength: determined according to ISO 527-2 method, with a tensile speed of 50 mm / min. Flexural strength: determined according to ISO 178 method, with a test speed of 2 mm / min. Notched impact strength: the notched impact strength of the polyester was tested using a cantilever pendulum impact tester. The impact strength was determined according to ISO 180-2001 method, with a notch depth of 2 mm and a pendulum energy of 2.75 J.

[0091] (4) Anti-aging performance test: The test was conducted in accordance with the standard in section 9.5 of UL62275. The difference is that the target temperature required by the UL62275 standard is 105 ℃ / 135 ℃, while this experiment was conducted at 150 ℃ and humidity of 50±5% for 168 hours of aging, followed by 21 days of storage at room temperature for tensile strength test.

[0092] The polyamide resin samples of Examples 1 to 8 and Comparative Examples 1 to 3 were tested according to the above test method. The test results are shown in Table 1.

[0093] Table 1

[0094]

[0095] As shown in Table 1, the test results indicate that, compared to polyamide resin without added oxetane compounds, the modified polyamide resin prepared in the embodiments of this invention exhibits superior flexural properties and significantly improved anti-aging performance, demonstrating excellent comprehensive application performance. The underlying mechanism is speculated to be that the rigid cyclic structure of oxetane effectively enhances the rigidity of the polyamide molecular chains, thereby increasing the modulus and strength of the material. Simultaneously, this structure may induce moderate cross-linking between molecular chains during polymerization, thereby improving the toughness of the material and ultimately achieving an optimized balance between rigidity and toughness. Furthermore, compared to the polyamide resins in Comparative Example 2 (insufficient oxetane compound addition) and Comparative Example 3 (excessive oxetane compound addition), the polyamide resin in the embodiments of this application shows improvements in both mechanical properties and anti-aging performance. Comparative Example 2, due to insufficient addition, resulted in inadequate end-capping and failed to effectively inhibit end-cyclization degradation, thus limiting its improvement in anti-aging performance. Comparative Example 3, due to excessive addition, may have hindered molecular chain movement or caused excessive cross-linking, adversely affecting the toughness and processability of the polyamide material. This indicates that the mass of the oxetane compound needs to be controlled within the range of 1-3% of the mass of the modified polyamide resin in order to optimize performance and process feasibility.

[0096] The modified polyamide resin provided by this invention exhibits low shrinkage, good heat resistance, chemical resistance, and mechanical properties, particularly superior anti-aging properties. Therefore, the modified polyamide resin, either alone or optionally in combination with various additives and other polymers for polyamides, can be molded or spun into compositions to manufacture various articles or fibers. Molded articles and spun fibers have diverse applications, not only in engineering plastics but also providing high-performance material support for high-end electronic components, lightweight automotive parts, and complex structural molded products.

[0097] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A modified polyamide resin characterized in that, The modified polyamide resin comprises structural units derived from a dibasic acid and a dibasic amine, and a capping structure derived from an oxetane compound of formula (I): (I), wherein, R1 is a C1~C6 alkyl group, and R2 is a C1~C6 alkyl group. 12 Hydroxyalkyl groups or C2-C6 alkyl groups interrupted by ether bonds; The molar ratio of the dibasic amine to the dibasic acid is 1:1 to 1.01; The mass of the oxetane compound is 1 to 3% of the mass of the modified polyamide resin; The number average molecular weight of the modified polyamide resin is 25,000 to 35,000.

2. The modified polyamide resin of claim 1, wherein: The oxetane compound comprises at least one of 3-hydroxymethyl-3-ethyloxetane, 3-ethyl-3-((octyloxy)methyl)oxetane, 3-ethyl-3-[[(2-ethylhexyl)oxy]methyl]oxetane, (3-ethyloxetan-3-yl)methyl acrylate, (3-ethyloxetan-3-yl)methyl methacrylate, 3-ethyl-3-hydroxymethyloxetane, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, 3-ethyl-3-(phenoxymethyl)oxetane, and 3-ethyl-3-(2-methacryloyloxymethyl)oxetane.

3. The modified polyamide resin of claim 1, wherein: The dibasic acid comprises at least one of an aromatic dibasic acid, an aliphatic dibasic acid, an alicyclic dibasic acid, and / or a biomass-based oxaheterocyclic dibasic acid; The biomass-based oxaheterocyclic dibasic acid accounts for 0.2% to 2% of the dibasic acid; The diamines include any of biomass-based oxygen-containing heterocyclic diamines, C8-C 18 aliphatic diamines.

4. The modified polyamide resin of claim 3, wherein: The biomass-based oxaheterocyclic dibasic acid comprises at least one of a furan-based dibasic acid and a tetrahydrofuran-based dibasic acid; The furan-based dibasic acid comprises at least one of 2,5-furandicarboxylic acid and 3,4-furandicarboxylic acid; The tetrahydrofuran-based dibasic acid comprises at least one of 2,5-tetrahydrofurandicarboxylic acid and 3,4-tetrahydrofurandicarboxylic acid; The aromatic dibasic acid comprises at least one of terephthalic acid, 2,6-naphthalene dicarboxylic acid, and 1,4-naphthalene dicarboxylic acid; The aliphatic dibasic acid is at least one of C2-C10 aliphatic linear diacids, including oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid. 10 The aliphatic dibasic acid is at least one of C2-C10 aliphatic linear diacids, including oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid. The alicyclic dibasic acid is at least one of cyclopentane-1,2-dicarboxylic acid, cyclohexane-1,2-dicarboxylic acid, cycloheptane-1,2-dicarboxylic acid, cyclooctane-1,2-dicarboxylic acid, cyclononane-1,2-dicarboxylic acid, and cyclodecane-1,2-dicarboxylic acid.

5. The modified polyamide resin of claim 3, wherein: The biomass-based oxaheterocyclic dibasic amine comprises at least one of a furan-based dibasic amine and a tetrahydrofuran-based dibasic amine, The furan-based dibasic amine comprises at least one of 2,5-dimethylaminofuran and 3,4-dimethylaminofuran; The tetrahydrofuran-based dibasic amine comprises at least one of 2,5-dimethylamino tetrahydrofuran and 3,4-dimethylamino tetrahydrofuran; said C8-C 18 aliphatic diamines include at least one of 1,8-octanediamine, 1,10-decanediamine, 1,9- nonanediamine, 1,11-undecanediamine, 1,12-dodecanediamine, 1,13-tridecanediamine, 1,14- tetradecanediamine, 1,15-pentadecanediamine, 1,16-hexadecanediamine, 1,17- heptadecanediamine, 1,18-octadecanediamine, 2-methyl-1,8-octanediamine, or 5-methyl- 1,9-nonanediamine.

6. The modified polyamide resin of claim 1, wherein: The dibasic acid is terephthalic acid and a furan-based dibasic acid, and The diamine is an aliphatic diamine of C8-Ci8 18 .

7. A method for producing the modified polyamide resin according to any one of claims 1 to 6, characterized by, The preparation method comprises: The binary acid, the binary amine, the oxetane compound and the catalyst are stirred and mixed in an inert gas environment to obtain a mixed reactant; The mixed reactant is subjected to a prepolymerization reaction at a temperature of 150-200 DEG C to form a prepolymer; The temperature is raised to 220-260 DEG C, and the prepolymer is subjected to a polymerization reaction under the condition of maintaining the reaction pressure to obtain an initial product; The initial product is subjected to a solid phase polymerization at a temperature of 200-250 DEG C and a vacuum degree of 10-30 Pa to obtain a modified polyamide resin.

8. The preparation method according to claim 7, wherein the catalyst comprises any one of sodium phosphate monohydrate, sodium pyrophosphate and sodium hypophosphite; The prepolymerization reaction time is 2-6 h; The polymerization reaction time is 1-3 h; The solid phase polymerization time is 5-12 h.

9. The preparation method according to claim 7, wherein at least one additive selected from a molecular weight regulator and a stabilizer is selectively added during the preparation process.

10. The preparation method according to claim 9, wherein the molecular weight regulator comprises a monobasic acid or a monobasic amine; Preferably, the monobasic carboxylic acid is selected from any one of aliphatic monocarboxylic acid, aromatic monocarboxylic acid and alicyclic monocarboxylic acid, and the amount of the monobasic acid is 0.05%-5% of the weight of the binary acid; The monobasic amine is selected from any one of aliphatic monobasic amine, alicyclic monobasic amine and aromatic monobasic amine, and the amount of the monobasic amine is 0.05%-5% of the weight of the binary amine; The stabilizer comprises any one of phosphorous acid, phosphoric acid, phosphite and phosphate, and the amount of the stabilizer is 0.1%-0.5% of the total feeding weight. ​ ​ ​

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