A foamed linear polyamide elastomer and a method for producing and using the same

Abstract

The application belongs to the technical field of polyamide elastomers, and discloses a foaming-grade linear polyamide elastomer, a preparation method and application thereof.The elastomer is formed by copolymerization of specific linear polyamide hard segments, polyether soft segments and small-molecule dihydric alcohol in the presence of a catalyst, an antioxidant and a nucleating agent, and does not strictly contain a multifunctional branching agent or a crosslinking agent.The application mainly eliminates the topological constraint of molecular chain movement by abandoning the chemical crosslinking point, and reduces the internal friction of the material under dynamic cyclic load; meanwhile, the nucleating agent is used to induce the rapid crystallization of the hard segment, and the long forming cycle problem of the linear polymer is solved.The material can also be combined with a specific antioxidant system to realize high melt strength, good resilience and excellent heat aging resistance, which is beneficial to application.

Description

Technical Field

[0001] This invention relates to the field of polyamide elastomer technology, and particularly to a foamed linear polyamide elastomer, its preparation method, and its applications. Background Technology

[0002] Polyamide elastomers are high-performance thermoplastic elastomers whose molecules are composed of rigid crystalline polyamide hard segments and flexible amorphous polyether soft segments linked by chemical bonds. This structure creates a unique microphase separation morphology, where the hard segments act as physical cross-linking points, endowing the material with high strength and thermal stability; while the soft segments provide good low-temperature flexibility and resilience. Therefore, polyamide elastomers combine the elasticity of rubber with the processability of thermoplastics, and are widely used in medical, automotive, and electronics fields.

[0003] In recent years, the midsole materials for professional running shoes have shown a trend towards lightweight design and "ultimate energy return." However, traditional ethylene vinyl acetate copolymer (EVA) foam sole materials have insufficient rebound rate, while thermoplastic polyurethane (TPU) has a high density, making it difficult to balance lightweight and high performance. Polyamide elastomers, due to their low density and good dynamic mechanical properties, have become an ideal material choice for high-end running shoe midsoles.

[0004] However, some existing polyamide elastomers face a trade-off between hysteresis loss and processability. To achieve better energy feedback, it is essential to reduce hysteresis loss caused by internal friction under dynamic loads, requiring the molecular chains to have a regular linear structure to ensure rapid rebound. In the synthesis and processing of existing polyamide elastomers, multifunctional branched additives or crosslinking agents are often introduced to improve melt strength or dimensional stability. While this improves processability, it also introduces molecular "dead knots" that restrict chain segment movement. Under high-frequency compression, these branching points lead to increased internal friction and hysteresis loss, not only reducing energy feedback efficiency and causing sluggish rebound, but also causing internal heat generation and accelerating material fatigue aging. Therefore, balancing high resilience and good processability in polyamide elastomer materials remains a major technological bottleneck. Summary of the Invention

[0005] To overcome the shortcomings of the above technologies, the purpose of this invention is to provide a foamed linear polyamide elastomer, its preparation method, and its application. This invention can prepare polyamide elastomer materials with linear topology. While maintaining excellent energy feedback, this material has good processability, which can solve the problem of long molding cycle of linear structures, and the preparation process is simple and controllable.

[0006] To achieve the above objectives, the present invention adopts the following technical solution.

[0007] On one hand, the present invention provides a method for preparing a foamed linear polyamide elastomer, comprising the following steps:

[0008] S1. A dicarboxylic acid and an amine are reacted to prepare a carboxyl-terminated linear polyamide prepolymer; wherein the amine is a lactam and / or an aliphatic diamine with more than 6 Cs; and the number-average molecular weight of the carboxyl-terminated linear polyamide prepolymer is 1000~5000 g / mol.

[0009] S2. The carboxyl-terminated linear polyamide prepolymer is mixed with polyether glycol, small molecule diol, catalyst, antioxidant and nucleating agent, wherein the small molecule diol is a C2~6 aliphatic diol, and the mixture is reacted in a protective atmosphere at a temperature of 200~280°C to obtain foamed linear polyamide elastomer.

[0010] Preferably, in step S1, the dicarboxylic acid is at least one of adipic acid, sebacic acid, dodecanoic acid, and terephthalic acid; and the amine is at least one of caprolactam, decanediamine, and dodecanediamine.

[0011] Preferably, the reaction in step S1 is carried out in water under a protective atmosphere with stirring. The reaction temperature is 200~240℃, the pressure is 1~20 bar, and the stirring speed is 100~300 r / min. The number average molecular weight of the carboxyl-terminated linear polyamide prepolymer is 1000~3000 g / mol.

[0012] Preferably, in step S2, the polyether glycol is at least one of polyethylene glycol, polytrimethylene glycol, and polytetrahydrofuran ether glycol, with a number average molecular weight of 1000~3000 g / mol.

[0013] Preferably, in step S2, the small molecule diol is at least one of ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol; and the mass ratio of the carboxyl-terminated polyamide prepolymer, polyether diol, and small molecule diol is 100:20~50:5~20.

[0014] Preferably, in step S2, the catalyst is at least one of tetrabutyl titanate, isopropyl titanate, and anhydrous zinc acetate; the antioxidant is antioxidant 1098 and / or antioxidant 1010; and the nucleating agent is talc.

[0015] Preferably, in step S2, polyether glycol, small molecule diol, catalyst, antioxidant and nucleating agent are added to the obtained carboxyl-terminated linear polyamide prepolymer. After a protective atmosphere is introduced, the reaction is carried out at a temperature of 200~240℃, a pressure of 1~5 bar and a stirring speed of 100~300 r / min.

[0016] Preferably, the reaction in step S2 is carried out for 1 to 3 hours, and further includes:

[0017] The pressure was gradually reduced to 5~100Pa, the temperature was increased to 240~280℃, the stirring speed was increased to 150~500r / min, and the reaction was continued for 1~3 hours to obtain the polymer; the obtained polymer was cooled, dried and granulated to obtain foamed linear polyamide elastomer chips.

[0018] The present invention provides a foamed linear polyamide elastomer obtained by the preparation method described above, wherein the melting point of the foamed linear polyamide elastomer is in the range of 180~200℃.

[0019] In addition, the present invention also provides the application of the foam-grade linear polyamide elastomer as described above in the preparation of foamed articles.

[0020] Currently, the preparation of polyamide elastomers and their foamed materials mainly involves introducing branched structures to improve melt strength, constructing complex core-shell structures to improve moldability, or simply using bio-based alternatives. These methods mostly involve complex chemical crosslinking or multi-layer co-extrusion processes, resulting in high hysteresis losses (low energy feedback), demanding process equipment, and difficulties in balancing high resilience and rapid molding. Especially in the field of high-end sports equipment, existing branching modification methods often restrict the free movement of molecular chains, leading to severe heat generation in the material under high-frequency dynamic conditions. Therefore, developing a high-performance polyamide elastomer with a simple process, no chemical crosslinking required, and low hysteresis losses is of great significance.

[0021] This invention proposes a low-hysteresis-loss linear polyamide elastomer and its preparation method. In this method, a specific carboxyl-terminated linear polyamide prepolymer is first prepared using dicarboxylic acids and amines as raw materials. This prepolymer is then polymerized with polyether glycols and small-molecule diols to obtain a foam-grade linear polyamide elastomer material. This invention primarily utilizes the characteristics of linear polymer molecular chains, which rapidly recover after being subjected to stress and exhibit extremely low internal friction. By strictly excluding multifunctional branching agents, employing specific linear hard segments and polyether soft segments in block copolymerization, and using nucleating agents to regulate crystallization behavior, a polyamide elastomer material with a pure linear topology can be prepared. This material maintains excellent energy feedback properties while exhibiting good processability, a short molding cycle, and a simple and controllable process, making it suitable for supercritical fluid foaming and high-performance injection-molded parts. Attached Figure Description

[0022] Figure 1 This is a differential scanning calorimetry (DSC) spectrum of the foamed linear polyamide elastomer of Example 2 of the present invention;

[0023] Figure 2 This is a dynamic cyclic stretching diagram of the foamed linear polyamide elastomer of Embodiment 2 of the present invention. Detailed Implementation

[0024] The technical solutions in the embodiments of this application are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0025] This invention provides a method for preparing foamed linear polyamide elastomers, comprising the following steps:

[0026] S1. A dicarboxylic acid and an amine are reacted to prepare a carboxyl-terminated linear polyamide prepolymer; wherein the amine is a lactam and / or an aliphatic diamine with more than 6 Cs; and the number-average molecular weight of the carboxyl-terminated linear polyamide prepolymer is 1000~5000 g / mol.

[0027] S2. The carboxyl-terminated linear polyamide prepolymer is mixed with polyether glycol, small molecule diol, catalyst, antioxidant and nucleating agent, wherein the small molecule diol is a C2~6 aliphatic diol, and the mixture is reacted in a protective atmosphere at a temperature of 200~280°C to obtain foamed linear polyamide elastomer.

[0028] This invention enables the preparation of polyamide elastomer materials with linear topology. These materials maintain excellent energy feedback properties while exhibiting good processability. Furthermore, the preparation process is simple and controllable, making them suitable for various applications.

[0029] The first step in this embodiment of the invention is the preparation of a carboxyl-terminated linear polyamide prepolymer, which can be carried out using a high-temperature, high-pressure reaction vessel. Specifically, a dicarboxylic acid, an amine, and water (generally deionized water) are added to a reaction vessel equipped with a stirrer, a temperature controller, and a nitrogen inlet. The dicarboxylic acid is preferably at least one of adipic acid, sebacic acid, dodecanoic acid, and terephthalic acid; the amine is a lactam and / or an aliphatic diamine with 6 or more carbon atoms, wherein the lactam is preferably caprolactam, and the diamine is preferably decanediamine or dodecanediamine. The molar ratio of the dicarboxylic acid to the amine is determined based on the number-average molecular weight of the target prepolymer, and the amount of dicarboxylic acid used is sufficient to cap the two ends of the resulting prepolymer with carboxyl groups. Preferably, the polyamide prepolymer structure corresponding to this embodiment of the invention is one of polyamide 1010, polyamide 1210, polyamide 1212, or polyamide 6 prepolymer, which is beneficial to the material's mechanical properties, processing performance, etc.

[0030] The reaction in the first step can be carried out under a protective atmosphere, preferably by purging the air in the reaction vessel with nitrogen. Then, the temperature is preferably raised to 200-240°C, the pressure is increased to 1-20 bar, and the reaction is carried out for 1-3 hours with a stirring speed of 100-300 r / min to obtain a (double) carboxyl-terminated morphological polyamide prepolymer with a number-average molecular weight of 1000-5000 g / mol. Specifically, the reaction temperature can be 230°C or 240°C, and the pressure is preferably 1-10 bar. Anhydrous sodium hypophosphite or other catalytic reactions can also be added. In the early stage of the reaction, the material undergoes preliminary amidation. Subsequently, the pressure can be reduced to atmospheric pressure to continue the reaction while removing small water molecules generated in the reaction, promoting the forward polycondensation reaction. The number-average molecular weight of the carboxyl-terminated morphological polyamide prepolymer is further 1000-3000 g / mol. The number-average molecular weight of the prepolymer can be determined by 1H NMR spectroscopy or by converting the carboxyl content after determining the end-group titration method.

[0031] After the first step reaction is completed, in this embodiment of the invention, the pressure can be adjusted to atmospheric pressure, and polyether glycol, specific small molecule diol, catalyst, antioxidant and nucleating agent can be added; preferably, nitrogen gas is introduced to replace the air in the reactor, and the reaction is carried out under the conditions of temperature of 200~280°C and pressure of 1~5 bar.

[0032] In a preferred embodiment of the present invention, the polyether diol is at least one selected from polyethylene glycol, polytrimethylene glycol, and polytetrahydrofuran ether diol, with a number-average molecular weight of 1000-3000 g / mol. Furthermore, the small molecule diol may specifically be at least one selected from ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol; the preferred mass ratio of the carboxyl-terminated polyamide prepolymer, polyether diol, and small molecule diol is 100:20-50:5-20. The structure and properties of the foamed linear polyamide elastomer described in the embodiments of the present invention can be controlled by adjusting the mass ratio of the carboxyl-terminated linear polyamide prepolymer, polyether diol, and small molecule diol, making the process simple and convenient.

[0033] The catalyst may be a titanate, zinc acetate, or more preferably at least one of tetrabutyl titanate, isopropyl titanate, or anhydrous zinc acetate. The antioxidant may be selected from hindered phenolic antioxidants, more preferably antioxidant 1098 (chemical name N,N'-bis-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hexamethylenediamine), and / or antioxidant 1010 (tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]pentaerythritol ester); the nucleating agent is preferably talc powder with an average particle size of 0.1 μm to 5 μm, used to increase the crystallization rate of linear hard segments, facilitating efficient control of material crystallization behavior. In a preferred embodiment of the present invention, the weight ratio of the double-carboxylated linear polyamide prepolymer, polyether glycol, small molecule diol, catalyst, antioxidant, nucleating agent and water can be 100:(20~50):(5~20):(0.1~0.5):(1~5):(0.1~0.5):(1~5).

[0034] In the synthesis process of this invention, by avoiding the addition of branching agents and introducing a nucleating agent and antioxidant system, the crystallization rate and heat resistance stability of the copolymer are improved, thereby obtaining a low-hysteresis polyamide elastomer. Specifically, the nucleating agent can be used to induce rapid crystallization of hard segments, which helps to solve the problem of long molding cycles for linear polymers; and, preferably, a specific antioxidant system is used to achieve high melt strength and excellent heat aging resistance of the material.

[0035] In this embodiment of the invention, the reaction, including esterification, is carried out at a stirring speed of 100-300 r / min for 1-3 hours. Afterward, the pressure is gradually reduced to 5-100 Pa, the temperature is increased to 240-280℃, the stirring speed is increased to 150-500 r / min, and the reaction continues for another 1-3 hours to obtain the polymer. The obtained polymer is then subjected to conventional cooling, drying, and pelletizing to obtain foam-grade linear polyamide elastomer chips. The cooling mainly involves rapidly immersing the product in water for quenching. The drying process specifically includes drying in a vacuum oven at 60℃ for 24 hours. Through the process described in this embodiment of the invention, linear polyamide elastomer compositions with good resilience and suitable processing performance can be prepared.

[0036] This invention provides a foam-grade linear polyamide elastomer prepared by the method described above, comprising linear polyamide hard segments, polyether soft segments, diols, and nucleating agents; it does not contain multifunctional branched or cross-linked structures and can be a polyamide elastomer material with a pure linear topology. This invention eliminates the topological constraints of molecular chain motion by discarding chemical cross-linking points, thereby reducing the internal friction of the material under dynamic cyclic loading.

[0037] In some preferred embodiments, the melting point range of the foamed linear polyamide elastomer is 180~200℃, specifically 180℃, 181℃, 182℃, 186℃, 188℃, 189℃, 193℃, 198℃, and 199℃.

[0038] In some specific embodiments, the soft segment content of the foamed linear polyamide elastomer can be 15-40%, for example, 15%, 20%, 25%, 30%, 35%, or 40%.

[0039] In the embodiments of the present invention, unless otherwise specified, the number of portions refers to the value under the condition of equal unit mass. Unit mass is the mass of each portion. If each portion is 1 g, the unit mass is 1 g / portion, and 100 portions are equal to 100 g.

[0040] In the embodiments of the present invention, the molecular weight of the polyamide hard segment and the polyether soft segment refers to the number average molecular weight, with the unit being g / mol.

[0041] In embodiments of the present invention, the ratio of soft to hard segments in the material can be determined by nuclear magnetic resonance hydrogen spectrum (NMR 1H N ... 1 The ratio of the characteristic peak area of ​​polyether to that of polyamide in the ¹H-NMR spectrum is used to calculate the value.

[0042] Furthermore, the embodiments of the present invention also conducted mechanical property tests on the obtained polyamide elastomer material. In each embodiment of the present invention, the tensile strength was calculated using a universal testing machine under standard atmospheric conditions, according to the formula σ=F / S0. In this formula, σ is the tensile strength, in megapascals (MPa); F is the maximum load at which the specimen breaks, in newtons (N); and S0 is the original cross-sectional area of ​​the specimen, in square millimeters (mm²). 2 For specific test principles and methods, please refer to GB / T 1040.2-2006 (Determination of tensile properties of plastics - Part 2: Test conditions for molded and extruded plastics).

[0043] In each embodiment of the present invention, the elongation at break is calculated using a universal testing machine under standard atmospheric conditions, according to the formula ε = (L - L0) / L0 × 100%. In this formula, ε is the elongation at break (%), L is the gauge length at break (mm), and L0 is the original gauge length of the specimen (mm). Similarly, the specific testing principle and method are detailed in GB / T 1040.2-2006.

[0044] The melting point (Tm) and crystallization temperature (Tc) in each embodiment of the present invention are obtained by the peak temperatures of the melting peak and crystallization peak in the differential scanning calorimetry (DSC) diagram, with a heating and cooling rate of 10 °C / min.

[0045] This invention employs a dynamic cyclic tensile test method to characterize the hysteresis loss performance (hysteresis loss rate) of materials. Under standard atmospheric conditions, the specimen is stretched to 30% of its original elongation at a speed of 10 mm / min using a universal testing machine, and then returned to its original length at the same speed. The hysteresis loss rate is calculated using the following formula:

[0046] H L =(A load -A unload ) / A load ×100%; Where: H L The lag loss rate (%); A load A represents the area enclosed by the loading curve and the horizontal axis (i.e., the total input work); unload The area enclosed by the unloading curve and the horizontal axis (i.e., the work released); (A) load -A unload H is the area of ​​the closed hysteresis loop (i.e., the energy dissipated). L The lower the value, the better the energy return performance of the material and the smaller the hysteresis loss.

[0047] In embodiments of the present invention, the thermal stability of the material can be assessed by measuring its thermal decomposition temperature and mass loss rate through thermogravimetric analysis (TGA). The melt strength of the material can be reflected by measuring melt flowability and rheological behavior, which directly correlates with its foaming grade. Based on the TGA data and melt flowability data of this application, the elastomer material exhibits high melt strength, classifying it as a foaming-grade material; its linear structure can be indirectly characterized by NMR, end-group titration, mass spectrometry, and chromatography.

[0048] In addition, the present invention also provides the application of the foam-grade linear polyamide elastomer as described above in the preparation of foamed articles.

[0049] In some preferred embodiments, the foamed linear polyamide elastomer should be thoroughly dried before use to ensure its moisture content is below 0.05%, in order to avoid cell defects caused by moisture vaporization during subsequent foaming processes. The foaming process can employ intermittent autoclave foaming, continuous extrusion foaming, or injection molding foaming processes. The foaming gas can be supercritical carbon dioxide, supercritical nitrogen, or chemical foaming agents (such as azodicarbonamide, sodium bicarbonate, etc.). The foaming temperature is typically selected within the range of 5°C to 30°C above the elastomer's melting point. By adjusting the foaming process parameters, foamed materials with different cell structures and densities can be obtained.

[0050] The polyamide elastomer composition prepared by the method described above in this embodiment of the invention has low hysteresis loss (H). LWith a value reaching 32%, it exhibits good energy feedback performance and effectively improves the heating and rebound hysteresis phenomena of traditional branched modified polyether block amide (PEBA) under dynamic loads. It enables the material to maintain its linear structure and springback characteristics while possessing good mold release properties, shortening the injection molding cycle and optimizing the bending fatigue resistance and elongation at break of the finished product. Furthermore, the process formulation of this invention is adjustable, requiring no complex crosslinking control, facilitating large-scale production, and offering good economic benefits.

[0051] This invention introduces polyether soft segments into polyamide hard segments through melt polycondensation and other methods, resulting in a linear polyamide elastomer with good thermo-oxidative stability and excellent low-temperature flexibility. Furthermore, this invention improves the mold sticking problem during the molding and processing of pure linear materials; the viscosity of the reaction system increases steadily during polymerization, the process is relatively stable, and product quality is easy to control; the polymer has a relatively regular molecular chain structure, balanced overall performance, moderate cost, and no solvent contamination during preparation.

[0052] The embodiments of the present invention are further illustrated below with specific examples, but the present invention is not limited to these examples. Unless otherwise specified, all content ratios in this application refer to mass content.

[0053] Example 1

[0054] A method for preparing a foamed linear polyamide elastomer, comprising the following steps:

[0055] Step 1: Add 100 g caprolactam, 5.84 g terephthalic acid, and 5 g deionized water to a 300 mL reactor. After purging the reactor with nitrogen to replace the air, pressurize to 3 bar, and heat to 240 °C with a stirring speed of 100 r / min. React for 2 hours to obtain a double-ended carboxyl polyamide prepolymer with a molecular weight of 3000 g / mol.

[0056] Step 2: After the reaction in Step 1 is complete, adjust the pressure to atmospheric pressure, and add 20 g of polyethylene glycol (molecular weight 1000), 8.73 g of ethylene glycol, 0.145 g of tetrabutyl titanate, 0.145 g of antioxidant 1010, and 0.1 g of talc. After purging the reactor with nitrogen to replace the air, react for 2 hours at a temperature of 240℃, a pressure of 2-3 bar, and a stirring speed of 100 r / min.

[0057] Step 3: Gradually reduce the pressure to 100 Pa, raise the temperature to 260℃, increase the stirring speed to 150 r / min, and continue the reaction for 2 hours to obtain the polymer. Cool and dry the polymer to obtain polyamide elastomer chips. The cooling process involves rapidly immersing the product in water for quenching. The drying process is as follows: dry in a vacuum oven at 60℃ for 24 hours. The same applies to the following examples.

[0058] The polyamide elastomer material obtained in this embodiment was tested according to the method described above, including injection molding the prepared slices into dumbbell-shaped test strips; its tensile strength was 40 MPa, elongation at break was 466%, soft segment content was 15%, melting point was 189℃, and H L The value is 35%.

[0059] Example 2

[0060] A method for preparing a foamed linear polyamide elastomer, comprising the following steps:

[0061] Step 1: Add 100 g caprolactam, 10 g adipic acid, and 5 g deionized water to a 300 mL reactor. After purging the reactor with nitrogen to replace the air, pressurize to 3 bar, and heat to 240 °C with a stirring speed of 100 r / min. React for 2 hours to obtain a double-ended carboxyl polyamide prepolymer with a molecular weight of 1500 g / mol.

[0062] Step 2: After the reaction in Step 1 is complete, adjust the pressure to atmospheric pressure, and add 30 g of polytetrahydrofuran ether glycol (molecular weight 1000), 15.5 g of ethylene glycol, 0.143 g of anhydrous zinc acetate, 0.143 g of antioxidant 1098, and 0.1 g of talc. After purging the reactor with nitrogen to replace the air, react for 2 hours at a temperature of 240℃, a pressure of 2-3 bar, and a stirring speed of 100 r / min.

[0063] Step 3: Gradually reduce the pressure to 100 Pa, raise the temperature to 260℃, increase the stirring speed to 150 r / min, and continue the reaction for 2 hours to obtain the polymer. Cool and dry the polymer to obtain polyamide elastomer slices.

[0064] The polyamide elastomer obtained in this embodiment was tested and found to have a tensile strength of 29 MPa, an elongation at break of 443%, and a soft segment content of 20%. Figure 1 As shown, the melting point of this polyamide elastomer is 199°C; according to Figure 2 The cyclic stress-strain curve, its H L The value is 34% (for example, the H value of some branched elastomer samples). L ~40-55%, melting point 150-210℃).

[0065] Example 3

[0066] A method for preparing a foamed linear polyamide elastomer, comprising the following steps:

[0067] Step 1: Add 100 g caprolactam, 10 g adipic acid, and 5 g deionized water to a 300 mL reactor. After purging the reactor with nitrogen to replace the air, pressurize to 3 bar, and heat to 240 °C with a stirring speed of 100 r / min. React for 2 hours to obtain a double-ended carboxyl polyamide prepolymer with a molecular weight of 1500 g / mol.

[0068] Step 2: After the first step reaction is complete, adjust the pressure to atmospheric pressure, and add 20 g of polytetrahydrofuran ether glycol (molecular weight 2000), 12.6 g of 1,3-propanediol, 0.148 g of anhydrous zinc acetate, 0.148 g of antioxidant 1010, and 0.2 g of talc. After purging the reactor with nitrogen to replace the air, react for 2 hours at a temperature of 240℃, a pressure of 2-3 bar, and a stirring speed of 100 r / min.

[0069] Step 3: Gradually reduce the pressure to 100 Pa, raise the temperature to 260℃, increase the stirring speed to 150 r / min, and continue the reaction for 2 hours to obtain the polymer. Cool and dry the polymer to obtain polyamide elastomer slices.

[0070] The polyamide elastomer obtained in this embodiment has a tensile strength of 25 MPa, an elongation at break of 308%, and a soft segment content of 15%; its melting point is 193°C. L The value is 39%.

[0071] Example 4

[0072] A method for preparing a foamed linear polyamide elastomer, comprising the following steps:

[0073] Step 1: Add 100 g caprolactam, 9.2 g terephthalic acid, and 5 g deionized water to a 300 mL reactor. After purging the reactor with nitrogen to replace the air, pressurize to 3 bar, and heat to 240 °C with a stirring speed of 100 r / min. React for 2 hours to obtain a double-ended carboxyl polyamide prepolymer with a molecular weight of 2000 g / mol.

[0074] Step 2: After the reaction in Step 1 is complete, adjust the pressure to atmospheric pressure, and add 30 g of polytetrahydrofuran ether diol (molecular weight 1000), 20 g of 1,4-butanediol, 0.170 g of tetrabutyl titanate, 0.170 g of antioxidant 1010, and 0.2 g of talc. After purging the reactor with nitrogen to replace the air, react for 2 hours at a temperature of 240℃, a pressure of 2-3 bar, and a stirring speed of 100 r / min.

[0075] Step 3: Gradually reduce the pressure to 100 Pa, raise the temperature to 260℃, increase the stirring speed to 150 r / min, and continue the reaction for 2 hours to obtain the polymer. Cool and dry the polymer to obtain polyamide elastomer slices.

[0076] The polyamide elastomer obtained in this embodiment has a tensile strength of 40 MPa, an elongation at break of 369%, and a soft segment content of 20%; its melting point is 188°C. L The value is 34%.

[0077] Example 5

[0078] A method for preparing a foamed linear polyamide elastomer, comprising the following steps:

[0079] Step 1: Add 100 g caprolactam, 14.1 g adipic acid, and 5 g deionized water to a 300 mL reactor. After purging the reactor with nitrogen to replace the air, pressurize to 3 bar, and heat to 240 °C with a stirring speed of 100 r / min. React for 2 hours to obtain a double-ended carboxyl polyamide prepolymer with a molecular weight of 1000 g / mol.

[0080] Step 2: After the reaction in Step 1 is complete, adjust the pressure to atmospheric pressure, and add 30 g of polytetrahydrofuran ether glycol (molecular weight 1000), 24 g of ethylene glycol, 0.150 g of tetrabutyl titanate, 0.150 g of antioxidant 1010, and 0.1 g of talc. After purging the reactor with nitrogen to replace the air, react for 2 hours at a temperature of 240℃, a pressure of 2-3 bar, and a stirring speed of 100 r / min.

[0081] Step 3: Gradually reduce the pressure to 100 Pa, raise the temperature to 260℃, increase the stirring speed to 150 r / min, and continue the reaction for 2 hours to obtain the polymer. Cool and dry the polymer to obtain polyamide elastomer slices.

[0082] The polyamide elastomer obtained in this embodiment has a tensile strength of 29 MPa, an elongation at break of 443%, and a soft segment content of 25%; its melting point is 199°C. L The value is 32%.

[0083] Example 6

[0084] A method for preparing a foamed linear polyamide elastomer, comprising the following steps:

[0085] Step 1: Add 37 g dodecanediamine, 50 g sebacic acid, 0.092 g anhydrous sodium hypophosphite, and 9 g deionized water to a 300 mL reactor. After purging the reactor with nitrogen to replace the air, pressurize to 3 bar, and heat to 240 °C with a stirring speed of 100 r / min. React for 2 hours to obtain a prepolymer of double-terminated carboxyl polyamide with a molecular weight of 1300 g / mol.

[0086] Step 2: After the reaction in Step 1 is complete, adjust the pressure to atmospheric pressure, and add 26.1 g of polyethylene glycol (molecular weight 2000), 16 g of ethylene glycol, 0.134 g of isopropyl titanate, 0.134 g of antioxidant 1010, and 0.1 g of talc. After purging the reactor with nitrogen to replace the air, react for 2 hours at a temperature of 240℃, 2-3 bar, and a stirring speed of 100 r / min.

[0087] Step 3: Gradually reduce the pressure to 100 Pa, raise the temperature to 260℃, increase the stirring speed to 150 r / min, and continue the reaction for 2 hours to obtain the polymer. Cool and dry the polymer to obtain polyamide elastomer slices.

[0088] The polyamide elastomer obtained in this embodiment has a tensile strength of 22 MPa, an elongation at break of 519%, and a soft segment content of 20%; its melting point is 186°C. L The value is 32%.

[0089] Example 7

[0090] A method for preparing a foamed linear polyamide elastomer, comprising the following steps:

[0091] Step 1: Add 38 g of decanediamine, 54 g of sebacic acid, 9 g of deionized water, and 0.097 g of anhydrous sodium hypophosphite to a 300 mL reactor. After purging the reactor with nitrogen to replace the air, pressurize to 10 bar, and heat to 240 °C with a stirring speed of 100 r / min. React for 1 hour, then reduce to atmospheric pressure and continue the reaction for 1 hour to obtain a double-ended carboxyl polyamide prepolymer with a molecular weight of 2000 g / mol.

[0092] Step 2: After the reaction in Step 1 is complete, adjust the pressure to atmospheric pressure, and add 27.6 g of polytetrahydrofuran ether glycol with a molecular weight of 2000, 19.6 g of ethylene glycol, 0.144 g of isopropyl titanate, 0.144 g of antioxidant 1010, and 0.1 g of talc. After purging the reactor with nitrogen to replace the air, react for 2 hours at a temperature of 240℃, 2-3 bar, and a stirring speed of 100 r / min.

[0093] Step 3: Gradually reduce the pressure to 100 Pa, raise the temperature to 260℃, increase the stirring speed to 150 r / min, and continue the reaction for 2 hours to obtain the polymer. Cool and dry the polymer to obtain polyamide elastomer slices.

[0094] The polyamide elastomer obtained in this embodiment has a tensile strength of 41 MPa, an elongation at break of 253%, and a soft segment content of 20%; its melting point is 182°C. L The value is 46%.

[0095] Example 8

[0096] A method for preparing a foamed linear polyamide elastomer, comprising the following steps:

[0097] Step 1: Add 38 g of decanediamine, 54 g of sebacic acid, 9 g of deionized water, and 0.097 g of anhydrous sodium hypophosphite to a 300 mL reactor. After purging the reactor with nitrogen to replace the air, pressurize to 10 bar, and heat to 240 °C with a stirring speed of 100 r / min. React for 1 hour, then reduce to atmospheric pressure and continue the reaction for 1 hour to obtain a double-ended carboxyl polyamide prepolymer with a molecular weight of 2000 g / mol.

[0098] Step 2: After the reaction in Step 1 is complete, adjust the pressure to atmospheric pressure, and add 47 g of polytrimethylene glycol (molecular weight 2000), 19.6 g of ethylene glycol, 0.150 g of isopropyl titanate, 0.150 g of antioxidant 1010, and 0.1 g of talc. After purging the reactor with nitrogen to replace the air, react for 2 hours at a temperature of 240℃, 2-3 bar, and a stirring speed of 100 r / min.

[0099] Step 3: Gradually reduce the pressure to 100 Pa, raise the temperature to 260℃, increase the stirring speed to 150 r / min, and continue the reaction for 2 hours to obtain the polymer. Cool and dry the polymer to obtain polyamide elastomer slices.

[0100] The polyamide elastomer obtained in this embodiment has a tensile strength of 38 MPa, an elongation at break of 480%, and a soft segment content of 30%; its melting point is 198°C. L The value is 31%.

[0101] Example 9

[0102] A method for preparing a foamed linear polyamide elastomer, comprising the following steps:

[0103] Step 1: Add 45 g dodecanediamine, 57.9 g dodecanoic acid, 10 g deionized water, and 0.108 g anhydrous sodium hypophosphite to a 300 mL reactor. After purging the reactor with nitrogen, pressurize to 1 bar, and heat to 240 °C with a stirring speed of 100 r / min. React for 1 hour, then reduce to atmospheric pressure and continue the reaction for 1 hour to obtain a double-terminated carboxyl polyamide prepolymer with a molecular weight of 3000 g / mol.

[0104] Step 2: After the reaction in Step 1 is complete, adjust the pressure to atmospheric pressure, and add 20 g of polytetrahydrofuran ether glycol (molecular weight 2000), 7.44 g of ethylene glycol, 0.136 g of tetrabutyl titanate, 0.136 g of antioxidant 1098, and 0.1 g of talc. After purging the reactor with nitrogen to replace the air, react for 2 hours at a temperature of 260℃, 2-3 bar, and a stirring speed of 100 r / min.

[0105] Step 3: After the reaction in step 2 is completed, gradually reduce the pressure to 100 Pa, raise the temperature to 260℃, increase the stirring speed to 150 r / min, and continue the reaction for 4 hours to obtain the polymer. Cool and dry the polymer to obtain polyamide elastomer slices.

[0106] The polyamide elastomer obtained in this embodiment has a tensile strength of 41 MPa, an elongation at break of 153%, and a soft segment content of 15%; its melting point is 181°C. L The value is 36%.

[0107] Example 10

[0108] A method for preparing a foamed linear polyamide elastomer, comprising the following steps:

[0109] Step 1: Add 40 g dodecanediamine, 55.3 g dodecanoic acid, 9 g deionized water, and 0.100 g anhydrous sodium hypophosphite to a 300 mL reactor. After purging the reactor with nitrogen, pressurize to 3 bar and heat to 240 °C with a stirring speed of 100 r / min. React for 1 hour, then reduce to atmospheric pressure and continue the reaction for 1 hour to obtain a double-terminated carboxyl polyamide prepolymer with a molecular weight of 2000 g / mol.

[0110] Step 2: After the reaction in Step 1 is complete, adjust the pressure to atmospheric pressure, and add 30 g of polytrimethylene glycol (molecular weight 2000), 30 g of ethylene glycol, 0.170 g of tetrabutyl titanate, 0.170 g of antioxidant 1098, and 0.2 g of talc. After purging the reactor with nitrogen to replace the air, react for 1 hour at a temperature of 240℃, 2-3 bar, and a stirring speed of 100 r / min.

[0111] Step 3: Gradually reduce the pressure to 100 Pa, raise the temperature to 260℃, increase the stirring speed to 150 r / min, and continue the reaction for 2 hours to obtain the polymer. Cool and dry the polymer to obtain polyamide elastomer slices.

[0112] The polyamide elastomer obtained in this embodiment has a tensile strength of 27 MPa, an elongation at break of 642%, and a soft segment content of 25%; its melting point is 181°C. L The value is 32%.

[0113] Example 11

[0114] A method for preparing a foamed linear polyamide elastomer, comprising the following steps:

[0115] Step 1: Add 40 g dodecanediamine, 55.3 g dodecanoic acid, 9 g deionized water, and 0.100 g anhydrous sodium hypophosphite to a 300 mL reactor. After purging the reactor with nitrogen, pressurize to 3 bar and heat to 240 °C with a stirring speed of 100 r / min. React for 1 hour, then reduce to atmospheric pressure and continue the reaction for 1 hour to obtain a double-terminated carboxyl polyamide prepolymer with a molecular weight of 2000 g / mol.

[0116] Step 2: After the first step reaction is complete, adjust the pressure to atmospheric pressure, and add 56 g of polytetrahydrofuran ether glycol (molecular weight 1000), 30 g of ethylene glycol, 0.190 g of tetrabutyl titanate, 0.190 g of antioxidant 1098, and 0.2 g of talc. After purging the reactor with nitrogen to replace the air, react for 1 hour at a temperature of 240℃, 2-3 bar, and a stirring speed of 100 r / min.

[0117] Step 3: Gradually reduce the pressure to 100 Pa, raise the temperature to 260℃, increase the stirring speed to 150 r / min, and continue the reaction for 3 hours to obtain the polymer. Cool and dry the polymer to obtain polyamide elastomer slices.

[0118] The polyamide elastomer obtained in this embodiment has a tensile strength of 35 MPa, an elongation at break of 526%, and a soft segment content of 40%; its melting point is 180°C. L The value is 25%.

[0119] As can be seen from the above embodiments, the present invention provides a copolymer-type, foam-grade linear polyamide elastomer material. This elastomer is mainly composed of linear polyamide hard segments, polyether soft segments, and small molecule diols, copolymerized in the presence of catalysts, etc., and strictly free of multifunctional branching agents or crosslinking agents. The present invention reduces the internal friction of polyamide elastomer materials under dynamic cyclic loading through a simple process; it also achieves high melt strength, good resilience, and excellent heat aging resistance (melting point range 180~200℃), making it suitable for preparing foamed products. Furthermore, it solves the problem of long molding cycles for linear polymers.

[0120] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a foamed linear polyamide elastomer, characterized in that, Includes the following steps: S1. A dicarboxylic acid and an amine are reacted to prepare a carboxyl-terminated linear polyamide prepolymer; wherein the amine is a lactam and / or an aliphatic diamine with more than 6 Cs; and the number-average molecular weight of the carboxyl-terminated linear polyamide prepolymer is 1000~5000 g / mol. S2. The carboxyl-terminated linear polyamide prepolymer is mixed with polyether glycol, small molecule diol, catalyst, antioxidant and nucleating agent, wherein the small molecule diol is a C2~6 aliphatic diol, and the mixture is reacted in a protective atmosphere at a temperature of 200~280°C to obtain foamed linear polyamide elastomer.

2. The preparation method according to claim 1, characterized in that, In step S1, the dicarboxylic acid is at least one of adipic acid, sebacic acid, dodecanoic acid, and terephthalic acid; the amine is at least one of caprolactam, decanediamine, and dodecanediamine.

3. The preparation method according to claim 2, characterized in that, The reaction in step S1 is carried out in water under a protective atmosphere with stirring. The reaction temperature is 200~240℃, the pressure is 1~20 bar, and the stirring speed is 100~300 r / min. The number average molecular weight of the carboxyl-terminated linear polyamide prepolymer is 1000~3000 g / mol.

4. The preparation method according to any one of claims 1-3, characterized in that, In step S2, the polyether glycol is at least one of polyethylene glycol, polytrimethylene glycol, and polytetrahydrofuran ether glycol, with a number average molecular weight of 1000~3000 g / mol.

5. The preparation method according to claim 4, characterized in that, In step S2, the small molecule diol is at least one of ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol; the mass ratio of the carboxyl-terminated polyamide prepolymer, polyether diol, and small molecule diol is 100:20~50:5~20.

6. The preparation method according to claim 4, characterized in that, In step S2, the catalyst is at least one of tetrabutyl titanate, isopropyl titanate, and anhydrous zinc acetate; the antioxidant is antioxidant 1098 and / or antioxidant 1010; and the nucleating agent is talc.

7. The preparation method according to claim 4, characterized in that, In step S2, polyether glycol, small molecule diol, catalyst, antioxidant and nucleating agent are added to the obtained carboxyl-terminated linear polyamide prepolymer. After a protective atmosphere is introduced, the reaction is carried out at a temperature of 200~240℃, a pressure of 1~5 bar and a stirring speed of 100~300 r / min.

8. The preparation method according to claim 7, characterized in that, The reaction described in step S2 is carried out for 1 to 3 hours and also includes: The pressure was gradually reduced to 5~100Pa, the temperature was increased to 240~280℃, the stirring speed was increased to 150~500r / min, and the reaction was continued for 1~3 hours to obtain the polymer; the obtained polymer was cooled, dried and granulated to obtain foamed linear polyamide elastomer chips.

9. The foamed linear polyamide elastomer obtained by the preparation method according to any one of claims 1-8, characterized in that, The melting point range of the foamed linear polyamide elastomer is 180~200℃.

10. The use of the foam-grade linear polyamide elastomer as described in claim 9 in the preparation of foamed articles.

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