Intrinsic flame-retardant nylon and preparation method and application thereof

Abstract

The application discloses intrinsic flame-retardant nylon and a preparation method and application thereof, relates to the technical field of preparation of flame-retardant high polymer materials, and the preparation method comprises the following steps: after dimethyl glutarate, hexanediamine and a catalyst are reacted, a prepolymer product is collected; after the prepolymer product, a functional auxiliary agent and water are subjected to polycondensation reaction, intrinsic flame-retardant nylon is collected. The method can make the intrinsic flame-retardant nylon have the characteristics of high molecular weight, narrow distribution, low yellowing performance, high flame-retardant performance and faster crystallization rate, and is beneficial to rapid forming of the nylon product.

Description

Technical Field

[0001] This application relates to the field of flame-retardant polymer material preparation technology, specifically to an intrinsically flame-retardant nylon, its preparation method, and its application. Background Technology

[0002] Nylon 66 is a polymer material formed by the condensation polymerization of adipic acid and hexamethylenediamine. Due to its regular molecular chain arrangement, strong hydrogen bonding, and high crystallinity, it possesses excellent mechanical properties, processing performance, corrosion resistance, wear resistance, self-lubrication, and chemical resistance, making it widely used in electronics, automotive, packaging films, clothing fibers, and aerospace industries. However, Nylon 66 has a limiting oxygen index (LOI) of no more than 24%, and its vertical burning test rating is UL94 V-2, classifying it as a flammable material. During combustion, Nylon 66 often produces flammable drippings, easily leading to rapid fire spread. This drawback severely limits its application and promotion in high-end civilian and military textile fibers and engineering plastics. Although the flame retardant properties of Nylon 66 can be improved through blending or copolymerization, a series of problems remain.

[0003] In related technologies, a halogen-free flame-retardant nylon 66 copolymer and its preparation method are disclosed. This method involves first reacting a reactive DOPO derivative with a diamine or diacid to form a salt, and then polycondensing it with a nylon 66 salt to obtain a high molecular weight, high decomposition temperature, and high strength halogen-free flame-retardant nylon 66 polymer and its fiber products. However, the above method still has drawbacks: the introduction of a new monomer structure may affect the aggregation state of nylon 66, and DOPO is prone to causing deacidification side reactions during polymerization, leading to yellowing of the nylon 66 material. Another example is a method for preparing melamine cyanurate flame-retardant polyamide material, using MCA, nano-silica, and metal oxides as synergistic flame retardants, and preparing flame-retardant polyamide through in-situ polymerization. However, this method does not consider the potential impact of filler addition on the system's mechanical and processing properties, nor the actual situation where, for systems with high melting points such as nylon 66, the reaction continues at high temperatures, easily leading to partial decomposition of MCA.

[0004] Nylon 65 is a material with comprehensive properties comparable to nylon 66, including heat resistance and mechanical properties. It is prepared by the polycondensation of hexamethylenediamine and glutaric acid. Glutaric acid monomer is typically a byproduct of the industrial synthesis of adipic acid; approximately 36 kg of glutaric acid is generated for every ton of adipic acid produced. Therefore, developing the polymerization of nylon 65 aligns with the requirements of a green circular economy and has significant practical implications. Currently, most domestic and international methods employ interfacial polymerization, specifically the reaction of glutaryl chloride with 1,6-hexamethylenediamine, to prepare nylon 65. This method suffers from complex processes, significant environmental pollution, and difficulty in large-scale production. Solid-state polymerization, which synthesizes nylon 65 from glutaric acid and hexamethylenediamine, is also complex, has challenges in product quality control, and is prone to yellowing and discoloration. Summary of the Invention

[0005] To address the aforementioned technical problems in the existing technology, this application provides an intrinsic flame-retardant nylon, its preparation method, and its application. This intrinsic flame-retardant nylon preparation method achieves low yellowing performance, high molecular weight distribution, and high flame-retardant properties, making it suitable for applications in electronics, electrical appliances, and textile fibers.

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

[0007] In a first aspect, embodiments of this application provide a method for preparing high-temperature resistant nylon, the method comprising the following steps:

[0008] After reacting dimethyl glutarate, hexamethylenediamine, and a catalyst, the prepolymer product is collected.

[0009] After the prepolymer, functional additives and water are subjected to a polycondensation reaction, the intrinsic flame-retardant nylon is collected.

[0010] In some embodiments, when the dimethyl glutarate, hexamethylenediamine, and catalyst react, the molar ratio of the dimethyl glutarate to the hexamethylenediamine is 1:0.95-1.05.

[0011] In some embodiments, when the prepolymer, functional additive, and water undergo a polycondensation reaction, the mass ratio of the functional additive to the prepolymer is 1:500.

[0012] In some embodiments, when the dimethyl glutarate, hexamethylenediamine, and catalyst react, the total monomer mass ratio of the dimethyl glutarate and the hexamethylenediamine to the catalyst is 500-5000:1.

[0013] In some embodiments, the catalyst includes guanidine catalysts, amidine catalysts, and titanium catalysts.

[0014] In some embodiments, the guanidine catalyst includes 1,5,7-triazabicyclo[4.4.0]decen-5-ene, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, and 2,3,5,6-tetrahydro-1H-imidazo[1,2-A]imidazolium; the amidine catalyst includes 1,8-diazabicyclo[5.4.0]undec-7-ene and 1,5-diazabicyclo[4.3.0]non-5-ene; and the titanium catalyst includes titanium isopropoxy and titanium citrate.

[0015] In some embodiments, the functional additives include diphenylacetylene, azobenzene, and phenylmaleimide.

[0016] In some embodiments, when the prepolymer, functional additive, and water undergo a polycondensation reaction, the solid content of the reaction system formed by the prepolymer, the functional additive, and the water is 80%-84%.

[0017] Secondly, this application also provides an intrinsically flame-retardant nylon, which is prepared by the method described in any of the above-mentioned methods.

[0018] Thirdly, this application also provides the application of the intrinsically flame-retardant nylon described in the second aspect in the preparation of flame-retardant materials.

[0019] The intrinsic flame-retardant nylon and its preparation method of this application, by adopting the above technical solution, can achieve the following beneficial effects compared with the prior art:

[0020] The preparation method described in this application, employing a specific ester-amine exchange prepolymerization process and catalyst system, can produce high-molecular-weight, low-yellowing-index high-performance nylon. This is attributed to two main factors: firstly, the milder and simpler ester-amine exchange reaction conditions allow for the preparation of higher molecular weight prepolymers, significantly reducing the probability of side reactions during polycondensation and thus achieving the high molecular weight and low yellowing properties of intrinsically flame-retardant nylon. Secondly, the introduction of functional additives contributes to the process. These additives can induce cross-linking reactions during nylon combustion, improving melt strength and providing synergistic flame-retardant effects. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this application clearer, this application will be described in further detail below. The described embodiments should not be regarded as limitations on this application. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] In the following description, references to "some embodiments" refer to a subset of all possible embodiments. However, it is understood that "some embodiments" may be the same or different subsets of all possible embodiments and may be combined with each other without conflict. Unless otherwise defined, all technical and scientific terms used in the embodiments of this application have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments of this application pertain. The terminology used in the embodiments of this application is for the purpose of describing the embodiments of this application only and is not intended to limit the application.

[0023] In the following description of this embodiment, the terms "including", "comprising", "having", and "containing" are all open-ended terms, meaning that they include but are not limited to.

[0024] It should be noted that all raw materials / reagents in the embodiments of this application can be purchased on the market or prepared according to conventional methods known to those skilled in the art; the term "and / or" in the embodiments of this application is only used to describe the relationship between related objects, indicating that there can be three relationships. For example, A and / or B means three cases: A exists alone, B exists alone, and A and B exist simultaneously. A and B can be singular or plural. The character " / " generally indicates that the related objects before and after are in an "or" relationship.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] Those skilled in the art will understand that the numerical ranges in the embodiments of this application should be understood to specifically disclose each intermediate value between the upper and lower limits of the range. Each smaller range between any stated value and an intermediate value within the stated range, as well as any other stated value or an intermediate value within the stated range, is also included in this application. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0029] Unless otherwise stated, the technical / scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art described herein. While this application describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may be used in embodiments or test examples of this application. All references to this specification are generally incorporated herein by reference to disclose and describe methods and / or materials associated with said references. In the event of any conflict with any incorporated references, the content of this application shall prevail.

[0030] In a first aspect, embodiments of this application provide a method for preparing intrinsically flame-retardant nylon. The preparation method of this application includes:

[0031] After reacting dimethyl glutarate, hexamethylenediamine, and a catalyst, the prepolymer product is collected.

[0032] After the prepolymer, functional additives and water are subjected to a polycondensation reaction, the intrinsic flame-retardant nylon is collected.

[0033] The preparation method disclosed in this application includes a prepolymerization process involving transesterification between dimethyl glutarate and hexamethylenediamine, and a polycondensation reaction between the polymer and functional additives. Specifically, under the catalysis of a catalyst, dimethyl glutarate and hexamethylenediamine undergo a transesterification reaction to generate a high molecular weight prepolymer. The nylon generated by the polycondensation reaction has low yellowing properties, which avoids the polymerization side reactions in the aqueous solution polycondensation process. Furthermore, by introducing functional additives, the nylon can induce cross-linking during combustion, which can significantly improve multiple flame retardant performance indicators, increase melt strength, and play a synergistic flame retardant role.

[0034] It should be noted that the reaction conditions for the reaction of dimethyl glutarate, hexamethylenediamine, and the catalyst in the embodiments of this application can be a heating reaction in a closed environment under a nitrogen atmosphere and at a certain temperature to ensure the uniformity and purity of the mixture. For example, dimethyl glutarate, hexamethylenediamine, and the catalyst can be reacted in a closed environment under a nitrogen atmosphere at 80°C for 2 hours. Then, the nitrogen purging mode is activated, the nitrogen flow rate is controlled at 40 ml / min, the temperature is raised to 150°C, and the reaction is carried out for 4 hours.

[0035] It should be noted that the catalysts in the embodiments of this application should be understood as guanidine catalysts, amidine catalysts, and titanium catalysts. For example, guanidine catalysts may include 1,5,7-triazabicyclo[4.4.0]decen-5-ene, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, and 2,3,5,6-tetrahydro-1H-imidazo[1,2-A]imidazolium; amidine catalysts may include 1,8-diazabicyclo[5.4.0]undec-7-ene and 1,5-diazabicyclo[4.3.0]non-5-ene; and titanium catalysts may include titanium isopropoxide and titanium citrate.

[0036] It should be noted that when the prepolymer, functional additive, and water undergo a polycondensation reaction in the embodiments of this application, the functional additive and the prepolymer need to maintain a certain mass ratio to ensure that the probability of side reactions occurring during the polycondensation process can be significantly reduced. For example, the mass ratio of the functional additive to the prepolymer can be 1:500.

[0037] It should be noted that the amount of catalyst added in the embodiments of this application needs to maintain a certain mass ratio to ensure that high-molecular-weight and low-yellowing-index high-performance nylon 65 resin can be prepared.

[0038] It should be noted that the functional additives in the embodiments of this application can significantly improve flame retardant performance indicators such as glow wire flame retardant temperature and UL flame retardant rating. For example, the functional additives may include diphenylacetylene, azobenzene, and phenylmaleimide.

[0039] It should be noted that when the prepolymer, functional additives, and water undergo a polycondensation reaction in the embodiments of this application, the solid content of the reaction system (formed from the prepolymer, functional additives, and water) needs to be maintained within a certain range to ensure that the nylon 65 resin after the polycondensation reaction has high molecular weight, low yellowing, and high flame retardant properties. For example, the solid content of the reaction system here can be 80%-84%.

[0040] Secondly, embodiments of this application also provide intrinsically flame-retardant nylon prepared by the method described in the first aspect. This intrinsically flame-retardant nylon possesses characteristics such as a simple and mild polymerization process, high molecular weight distribution, low yellowing properties, and high flame-retardant performance.

[0041] Thirdly, based on the aforementioned characteristics of intrinsically flame-retardant nylon, such as simple and mild polymerization process, high molecular weight distribution, low yellowing properties, and high flame-retardant performance, it can effectively improve the flame-retardant properties of flame-retardant materials when used in their preparation. This makes it suitable for a wide range of applications in high-end electronics, textiles, and defense industries.

[0042] The technical methods of this application will be further described below with reference to specific embodiments.

[0043] Example 1

[0044] This embodiment 1 provides a method for preparing intrinsic flame-retardant nylon PA1, the specific steps of which are as follows:

[0045] (1) After reacting dimethyl glutarate, hexamethylenediamine, and the catalyst, the prepolymer product is collected:

[0046] 10 mol of dimethyl glutarate, 10.3 mol of hexamethylenediamine, and 1.5 g of 1,5,7-triazabicyclo[4.4.0]decene-5-ene were added to a 5 L reaction vessel and reacted at 80 °C for 2 h under a nitrogen atmosphere in a closed environment. Then, nitrogen purging mode was turned on, with the nitrogen flow rate controlled at 40 ml / min, and the temperature was raised to 150 °C for 4 h to obtain a white precipitate mixture. Finally, the white precipitate mixture was subjected to solid-liquid separation to obtain the prepolymer product.

[0047] (2) After the prepolymer, functional additives and water are subjected to a polycondensation reaction, the intrinsic flame-retardant nylon is collected:

[0048] 2.5 kg of prepolymer, 5 g of azobenzene, and 3 kg of deionized water were placed in a 10 L high-pressure polymerization reactor, and the air inside the reactor was replaced with nitrogen at least three times. Under a sealed environment and nitrogen protection, the temperature was raised to 150 °C, and 2.5 kg of water was drained. The temperature was further raised to 200 °C, and the reaction was carried out for 1 hour. Finally, the pressure was released, the temperature was raised to 255 °C, and a vacuum was drawn to -0.06 to -0.08 MPa. After a condensation reaction for 1 hour, nylon 65 resin, namely intrinsically flame-retardant nylon PA1, was obtained.

[0049] Example 2

[0050] This embodiment 2 provides a method for preparing intrinsic flame-retardant nylon PA2, the specific steps of which are as follows:

[0051] (1) After reacting dimethyl glutarate, hexamethylenediamine, and the catalyst, the prepolymer product is collected:

[0052] 10 mol of dimethyl glutarate, 10.3 mol of hexamethylenediamine, and 1.5 g of titanium citrate were added to a 5 L reaction vessel and reacted at 100 °C for 1 h under a nitrogen atmosphere in a closed environment. Then, nitrogen purging mode was turned on, with the nitrogen flow rate controlled at 40 ml / min, and the temperature was raised to 160 °C for 2 h to obtain a white precipitate mixture. Finally, the white precipitate mixture was subjected to solid-liquid separation to obtain the prepolymer product.

[0053] (2) After the prepolymer, functional additives and water are subjected to a polycondensation reaction, the intrinsic flame-retardant nylon is collected:

[0054] 2.5 kg of prepolymer, 5 g of diphenylacetylene, and 3 kg of deionized water were placed in a 10 L high-pressure polymerization reactor, and the air inside the reactor was replaced with nitrogen at least three times. Under a sealed environment and nitrogen protection, the temperature was raised to 150 °C, and 2.5 kg of water was drained. The temperature was further raised to 210 °C, and the reaction was carried out for 1 hour. Finally, the pressure was released, the temperature was raised to 255 °C, and a vacuum was drawn to -0.06 to -0.08 MPa. After a condensation reaction for 1 hour, nylon 65 resin, namely intrinsically flame-retardant nylon PA2, was obtained.

[0055] Example 3

[0056] This embodiment 3 provides a method for preparing intrinsic flame-retardant nylon PA3, the specific steps of which are as follows:

[0057] (1) After reacting dimethyl glutarate, hexamethylenediamine, and the catalyst, the prepolymer product is collected:

[0058] 10 mol of dimethyl glutarate, 10.3 mol of hexamethylenediamine, and 1.5 g of 1,8-diazabicyclo[5.4.0]undec-7-ene were added to a 5 L reaction vessel and reacted at 120 °C for 0.5 h under a nitrogen atmosphere in a closed environment. Then, nitrogen purging mode was turned on, with the nitrogen flow rate controlled at 40 ml / min, and the temperature was raised to 180 °C and reacted for 1 h to obtain a white precipitate mixture. Finally, the white precipitate mixture was subjected to solid-liquid separation to obtain the prepolymer product.

[0059] (2) After the prepolymer, functional additives and water are subjected to a polycondensation reaction, the intrinsic flame-retardant nylon is collected:

[0060] 2.5 kg of prepolymer, 5 g of phenylmaleimide, and 3 kg of deionized water were placed in a 10 L high-pressure polymerization reactor, and the air inside the reactor was replaced with nitrogen at least three times. Under a sealed environment and nitrogen protection, the temperature was raised to 150 °C, and 2.5 kg of water was drained. The temperature was further raised to 220 °C, and the reaction was carried out for 0.5 h. Finally, the pressure was released, the temperature was raised to 255 °C, and a vacuum was drawn to -0.06 to -0.08 MPa. After a condensation reaction for 1 h, nylon 65 resin, namely intrinsically flame-retardant nylon PA3, was obtained.

[0061] Comparative Example 1

[0062] Comparative Example 1 provides a method for preparing intrinsically flame-retardant nylon PA4, the specific steps of which are as follows:

[0063] (1) After reacting dimethyl glutarate, hexamethylenediamine, and the catalyst, the prepolymer product is collected:

[0064] 10 mol of dimethyl glutarate and 10.3 mol of hexamethylenediamine were added to a 5 L reaction vessel and reacted at 80 °C for 2 h in a closed nitrogen atmosphere. Then, nitrogen purging mode was turned on, with the nitrogen flow rate controlled at 40 ml / min, and the temperature was raised to 150 °C for 4 h to obtain a white precipitate mixture. Finally, the white precipitate mixture was subjected to solid-liquid separation to obtain the prepolymer product.

[0065] (2) After the prepolymer, functional additives and water are subjected to a polycondensation reaction, the intrinsic flame-retardant nylon is collected:

[0066] 2.5 kg of prepolymer, 5 g of phenylmaleimide, and 3 kg of deionized water were placed in a 10 L high-pressure polymerization reactor, and the air inside the reactor was replaced with nitrogen at least three times. Under a sealed environment and nitrogen protection, the temperature was raised to 150 °C, and 2.5 kg of water was drained. The temperature was further raised to 200 °C, and the reaction was carried out for 2 hours. Finally, the pressure was released, the temperature was raised to 255 °C, and a vacuum was drawn to -0.06 to -0.08 MPa. After a condensation reaction for 1 hour, nylon 65 resin, namely intrinsically flame-retardant nylon PA4, was obtained.

[0067] Comparative Example 2

[0068] Comparative Example 2 provides a method for preparing intrinsically flame-retardant nylon PA5, the specific steps of which are as follows:

[0069] (1) After reacting dimethyl glutarate, hexamethylenediamine, and the catalyst, the prepolymer product is collected:

[0070] 10 mol of dimethyl glutarate, 10.3 mol of hexamethylenediamine and 1.5 g of 1,8-diazabicyclo[5.4.0]undec-7-ene were added to a 5 L reaction vessel. Nitrogen purging mode was turned on, and the nitrogen flow rate was controlled at 40 ml / min. The temperature was raised to 150 °C and the reaction was carried out for 4 h to obtain a white precipitate mixture. Finally, the white precipitate mixture was subjected to solid-liquid separation to obtain the prepolymer product.

[0071] (2) After the prepolymer, functional additives and water are subjected to a polycondensation reaction, the intrinsic flame-retardant nylon is collected:

[0072] 2.5 kg of prepolymer, 5 g of phenylmaleimide, and 3 kg of deionized water were placed in a 10 L high-pressure polymerization reactor, and the air inside the reactor was replaced with nitrogen at least three times. Under a sealed environment and nitrogen protection, the temperature was raised to 150 °C, and 2.5 kg of water was drained. The temperature was further raised to 220 °C, and the reaction was carried out for 0.5 h. Finally, the pressure was released, the temperature was raised to 255 °C, and a vacuum was drawn to -0.06 to -0.08 MPa. After a condensation reaction for 1 h, nylon 65 resin, namely intrinsically flame-retardant nylon PA5, was obtained.

[0073] Comparative Example 3

[0074] Comparative Example 3 provides a method for preparing intrinsically flame-retardant nylon PA6, the specific steps of which are as follows:

[0075] (1) After reacting dimethyl glutarate, hexamethylenediamine, and the catalyst, the prepolymer product is collected:

[0076] 10 mol of dimethyl glutarate, 10.3 mol of hexamethylenediamine and 1.5 g of 1,8-diazabicyclo[5.4.0]undec-7-ene were added to a 5 L reaction vessel and reacted at 120 °C for 0.5 h in a closed environment under nitrogen atmosphere to obtain a white precipitate mixture. Finally, the white precipitate mixture was subjected to solid-liquid separation to obtain the prepolymer product.

[0077] (2) After the prepolymer, functional additives and water are subjected to a polycondensation reaction, the intrinsic flame-retardant nylon is collected:

[0078] 2.5 kg of prepolymer, 5 g of phenylmaleimide, and 3 kg of deionized water were placed in a 10 L high-pressure polymerization reactor, and the air inside the reactor was replaced with nitrogen at least three times. Under a sealed environment and nitrogen protection, the temperature was raised to 150 °C, and 2.5 kg of water was drained. The temperature was further raised to 220 °C, and the reaction was carried out for 0.5 h. Finally, the pressure was released, the temperature was raised to 255 °C, and a vacuum was drawn to -0.06 to -0.08 MPa. After a condensation reaction for 1 h, nylon 65 resin, namely intrinsically flame-retardant nylon PA6, was obtained.

[0079] Comparative Example 4

[0080] Comparative Example 4 provides a method for preparing intrinsically flame-retardant nylon PA7, the specific steps of which are as follows:

[0081] (1) After reacting dimethyl glutarate, hexamethylenediamine, and the catalyst, the prepolymer product is collected:

[0082] 10 mol of dimethyl glutarate, 10.3 mol of hexamethylenediamine, and 1.5 g of 1,8-diazabicyclo[5.4.0]undec-7-ene were added to a 5 L reaction vessel and reacted at 120 °C for 0.5 h under a nitrogen atmosphere in a closed environment. Then, nitrogen purging mode was turned on, with the nitrogen flow rate controlled at 40 ml / min, and the temperature was raised to 180 °C and reacted for 1 h to obtain a white precipitate mixture. Finally, the white precipitate mixture was subjected to solid-liquid separation to obtain the prepolymer product.

[0083] (2) After the prepolymer, functional additives and water are subjected to a polycondensation reaction, the intrinsic flame-retardant nylon is collected:

[0084] 2.5 kg of prepolymer and 3 kg of deionized water were placed in a 10 L high-pressure polymerization reactor, and the air inside the reactor was replaced with nitrogen at least three times. Under a sealed environment and nitrogen protection, the temperature was raised to 150 °C, and 2.5 kg of water was drained. The temperature was further raised to 220 °C, and the reaction was carried out for 0.5 h. Finally, the pressure was released, the temperature was raised to 255 °C, and a vacuum was drawn to -0.06 to -0.08 MPa. After the polycondensation reaction was carried out for 1 h, nylon 65 resin, namely intrinsic flame-retardant nylon PA7, was obtained.

[0085] Comparative Example 5

[0086] Comparative Example 5 provides a method for preparing intrinsically flame-retardant nylon PA8, the specific steps of which are as follows:

[0087] (1) After reacting dimethyl glutarate, hexamethylenediamine, and the catalyst, the prepolymer product is collected:

[0088] 10 mol of glutaric acid, 10.3 mol of hexamethylenediamine and 5 kg of ethanol were added to a 10 L glass reactor. The reaction was carried out in a closed environment under nitrogen atmosphere at 70 °C and pH 7.5 to obtain a nylon 65 salt solution. After purification and drying, high-purity nylon 65 salt was obtained.

[0089] (2) After the prepolymer, functional additives and water are subjected to a polycondensation reaction, the intrinsic flame-retardant nylon is collected:

[0090] 2 kg of high-purity nylon 65 refined salt and 2 kg of deionized water were placed in a 10 L high-pressure polymerization reactor. The reactor was closed, and the air inside was replaced with nitrogen at least three times. Under a sealed environment and nitrogen protection, the temperature was raised to 130 °C, and 1.5 kg of water was drained. The temperature was further raised to 180 °C, and the reaction was carried out for 3 hours. Finally, the pressure was released, the temperature was raised to 255 °C, and a vacuum was drawn to -0.06 to -0.08 MPa. After a condensation reaction for 1 hour, nylon 65 resin, namely intrinsically flame-retardant nylon PA8, was obtained.

[0091] The melting point, viscosity, mechanical properties, heat resistance, and other properties of the intrinsic flame-retardant nylon PA1-8 were tested, and the test results are shown in Table 1.

[0092] Table 1 is a comparison table of various performance parameters of Examples 1-3 and Comparative Examples 1-5 provided in this application.

[0093]

[0094]

[0095] It should be noted that the prepolymer product in Comparative Example 5 refers to the reaction product obtained by reacting at 180°C for 3 hours and then immediately discharging the material.

[0096] The test methods and standards for each performance parameter in the above embodiments and comparative examples are as follows:

[0097] The relative viscosity test method in the above examples and comparative examples is as follows: the relative viscosity of the product with a concentration of 0.5 g / dL is measured using an Ubbelohde viscometer in a 98% concentrated sulfuric acid solution at (25±0.01)℃.

[0098] The melting point test method in the above embodiments and comparative examples is as follows: DSC test instrument, nitrogen atmosphere, heating rate of 10℃ / min.

[0099] The mechanical properties tested in the above embodiments and comparative examples are as follows: tensile strength is tested according to standard ISO 527-1 / -2, flexural strength and flexural modulus are tested according to standard ISO 178, and notched impact strength of simply supported beams is tested according to standard ISO 179 / 1eA.

[0100] The test method for the yellowing index YI in the above embodiments and comparative examples is as follows: referring to ASTM D1925, using a 3600D calibrator, the yellowing index of a 2mm standard measurement thickness sample is evaluated using CLE lab color difference.

[0101] The molecular weight and its distribution in the above examples and comparative examples were tested using gel permeation chromatography (GPC) with hexafluoroisopropanol as the mobile phase and a PMMA standard column.

[0102] The test methods for flame retardant performance in the above embodiments and comparative examples are as follows: referring to standard UL94, vertical burning with a thickness of 1.6 mm, the sample size is 125 mm × 13 mm × 5 mm; the glow wire refers to standard GB-T 5169.10-2017; the limiting oxygen index (LOI) refers to standard ISO 4589-2.

[0103] As can be seen from Table 1, the overall performance of the examples is superior to that of the comparative examples, especially in terms of mechanical properties (i.e., multiple strength parameters and multiple impact toughness parameters in Table 1), yellowing resistance (i.e., yellowing index YI in Table 1), and flame retardant properties (i.e., glow wire resistance temperature, UL flame retardant rating, and limiting oxygen index parameters in Table 1). The performance comparison results of Comparative Examples 1, 2, 3, and 5 and Examples 1-3 show that the traditional salt-forming-polymerization reaction cannot solve the problems of easy yellowing and wide molecular weight distribution of nylon 65 resin. Only by using a specific ester-amine exchange prepolymerization process and catalyst system can high molecular weight, low yellowing index, high-performance nylon 65 resin be prepared by condensation polymerization. This may be due to the fact that the milder ester-amine exchange reaction can prepare a higher molecular weight prepolymer, thereby greatly reducing the probability of side reactions during the condensation polymerization process, thus achieving high molecular weight and low yellowing properties of nylon 65 resin. The comparative test results of Comparative Example 4 and the examples show that the introduction of functional additives can greatly improve flame retardant performance indicators such as glow wire resistance temperature and UL flame retardant rating. This may be attributed to the fact that functional additives can induce cross-linking reactions during the combustion of nylon 65 resin, thereby increasing melt strength and playing a synergistic flame-retardant role.

[0104] In summary, the intrinsic flame-retardant nylon preparation technology of this application has the characteristics of simple and mild polymerization process, high molecular weight and narrow distribution, low yellowing performance and high flame retardant performance, and has a wide range of applications in high-end electronic appliances, textile fibers and national defense industries.

[0105] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for preparing intrinsically flame-retardant nylon, characterized in that, Includes the following steps: After reacting dimethyl glutarate, hexamethylenediamine, and a catalyst, the prepolymer product is collected. In this process, dimethyl glutarate, hexamethylenediamine, and the catalyst are first reacted in a closed environment under a nitrogen atmosphere at 80°C for 2 hours, or at 100°C for 1 hour, or at 120°C for 0.5 hours. Then turn on the nitrogen purging mode, control the nitrogen flow rate at 40 ml / min, and heat to 150℃ for 4 hours, or heat to 160℃ for 2 hours, or heat to 180℃ for 1 hour. After the prepolymer, functional additives and water are subjected to a polycondensation reaction, the intrinsic flame-retardant nylon is collected. The catalyst is selected from guanidine catalysts, amidine catalysts, and titanium catalysts; The guanidine catalyst is selected from 1,5,7-triazabicyclo[4.4.0]decen-5-ene, 7-methyl-1,5,7-triazabicyclo[4.4.0]decen-5-ene, and 2,3,5,6-tetrahydro-1H-imidazo[1,2-A]imidazo; The amidine catalyst is selected from 1,8-diazabicyclo[5.4.0]undec-7-ene and 1,5-diazabicyclo[4.3.0]non-5-ene; The titanium catalyst is selected from titanium isopropoxy and titanium citrate; The functional additives are selected from diphenylacetylene, azobenzene and phenylmaleimide.

2. The method for preparing intrinsically flame-retardant nylon according to claim 1, characterized in that, When the dimethyl glutarate, hexamethylenediamine, and catalyst react, the molar ratio of the dimethyl glutarate to the hexamethylenediamine is 1:0.95-1.

05.

3. The method for preparing intrinsically flame-retardant nylon according to claim 1, characterized in that, When the prepolymer, functional additive, and water undergo a polycondensation reaction, the mass ratio of the functional additive to the prepolymer is 1:

500.

4. The method for preparing intrinsically flame-retardant nylon according to claim 1, characterized in that, When the dimethyl glutarate, hexamethylenediamine, and catalyst react, the total monomer mass ratio of the dimethyl glutarate and the hexamethylenediamine to the catalyst is 500-5000:

1.

5. The method for preparing intrinsically flame-retardant nylon according to claim 1, characterized in that, When the prepolymer, functional additive, and water undergo a polycondensation reaction, the solid content of the reaction system formed by the prepolymer, the functional additive, and the water is 80%-84%.

6. An intrinsic flame-retardant nylon prepared by the preparation method according to any one of claims 1-5.

7. The use of the intrinsically flame-retardant nylon according to claim 6 in the preparation of flame-retardant materials.

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