A high-performance flame-retardant nylon 6 and its preparation method

Abstract

The invention relates to a high-performance flame-retardant nylon 6 and a preparation method thereof. The high-performance flame-retardant nylon 6 comprises caprolactam, cyanuric acid, cyanuric acid, a caprolactam hydrolysis ring-opening polymerization initiator, a polymer structure regulator, an impact modifier, and a flame-retardant dispersant. During the caprolactam hydrolysis ring-opening polymerization process, melamine and cyanuric acid are added as two raw materials to participate in the chemical reaction of nylon 6 molding and are connected to the molecular chain of nylon 6. A polymer regulator and an anti-modification impact agent are further added to prepare high-performance flame-retardant nylon 6 with UL94V-0 flame retardancy, better impact strength, excellent tensile properties, and lower cost in a one-step process.

Description

Technical Field

[0001] The present invention relates to the technical field of polyamides, and in particular to high-performance flame-retardant nylon 6 and a preparation method thereof. Background Art

[0002] Nylon 6 boasts excellent mechanical and electrical properties, along with wear resistance, oil resistance, solvent resistance, self-lubrication, self-extinguishing properties, corrosion resistance, and good processability. It is currently the largest-produced, most widely used, and most diverse of the five major engineering plastics. Although it is a self-extinguishing plastic, its oxygen index, rated UL94 V-2 by the US UL standard, is approximately 23% to 26%, making it flammable and falling short of the globally recognized UL94 V-0 flame retardancy rating. Due to the increasing use of nylon 6 in live electrical environments, such as automotive appliances and power tools, and the significant fire risks posed by leakage, short circuits, arcing, and sparks, its flame retardancy has become crucial in many applications. Consequently, flame retardant modification of nylon 6 has become a growing topic of concern.

[0003] Currently, the primary method for flame-retarding nylon 6 is to use additive flame retardants. This involves mechanically mixing the flame retardant into the polyamide to impart flame retardancy. For example, adding a certain ratio of ammonium polyphosphate to talc to PA6 can produce UL94V-0 flame-retardant PA6. While this method offers advantages such as ease of use and wide applicability, mechanical addition can easily lead to problems such as compromised mechanical properties and frosting of the flame retardant. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the present invention provides a high-performance flame-retardant nylon 6 and a preparation method thereof. The specific technical solution is as follows:

[0005] In one aspect, the present invention provides a high-performance flame-retardant nylon 6 comprising, by weight:

[0006] 90-110 parts of caprolactam, 4-6 parts of melamine, 4-6 parts of cyanuric acid, 0.3-5 parts of caprolactam hydrolysis ring-opening polymerization initiator, 0.2-3 parts of polymer structure regulator, 2-5 parts of impact modifier, 0.05-0.5 parts of flame retardant dispersant, wherein the purity of the caprolactam is ≥99.9%, the purity of the melamine is ≥99.8%, and the purity of the cyanuric acid is ≥99.8%.

[0007] As an improvement of the above technical solution, the molar ratio of the melamine to the cyanuric acid is 1:1.

[0008] As an improvement of the above technical solution, the caprolactam hydrolysis ring-opening polymerization initiator is an organic substance, an inorganic substance or a mixture thereof containing active carboxyl groups and hydroxyl groups in its molecular structure.

[0009] As an improvement of the above technical solution, the organic matter, inorganic matter or mixture thereof containing active carboxyl groups and hydroxyl groups in the molecular structure is selected from one or more of methanol, ethanol, aminocaproic acid, benzoic acid and water, preferably water.

[0010] As an improvement of the above technical solution, the polymer structure regulator is an active organic low-molecular compound containing three or more multifunctional groups that can react with carboxyl groups or amino groups in its molecular structure.

[0011] As an improvement of the above technical solution, the organic low molecular compound is selected from one or more of carboxylated styrene-butadiene rubber, pyromellitic acid, and trimellitic anhydride.

[0012] As an improvement of the above technical solution, the impact modifier is selected from one or more of hexamethylenediamine adipate, hexamethylenediamine parabenzoate, hexamethylenediamine metabenzoate, hexamethylenediamine succinate, hexamethylenediamine sebacate, hexamethylenediamine azelaic acid, and hexamethylenediamine dodecanoic acid.

[0013] As an improvement of the above technical solution, the flame retardant dispersant is selected from one or more of silane coupling agents KH550, KH560 or KH570, preferably KH550.

[0014] On the other hand, the present invention provides a method for preparing the high-performance flame-retardant nylon 6, comprising the following steps:

[0015] S1. Material preparation: Add liquid caprolactam to the caprolactam storage tank, and add melamine, cyanuric acid, caprolactam hydrolysis ring-opening polymerization initiator, polymer structure regulator, impact modifier, and flame retardant dispersant in proportion to the additive tank to obtain a mixed additive;

[0016] S2, preheating and mixing: transporting caprolactam and mixed additives to a preheating tower for preheating according to proportion, and then mixing them evenly in a static mixer to obtain a mixed solution;

[0017] S3, prepolymerization reaction: the mixed solution is transported to a prepolymerization tower and polymerized at a pressure of 0.5-0.8 MPa and a temperature of 230-240°C for 1-2 hours;

[0018] S4, prepolymerization reaction: the product of the prepolymerization tower is transported to the prepolymerization tower, and polymerized at a pressure of 0.1-0.2 MPa and a temperature of 250-260°C for 3-5 hours;

[0019] S5, post-polymerization reaction: the product of the pre-polymerization tower is transported to the post-polymerization tower, and the equilibrium polymerization is carried out at a pressure of 0.0 to -0.05 MPa and a temperature of 240 to 250 ° C for 2 to 4 hours;

[0020] S6, pelletizing: pushing the post-polymerization tower product to the casting strip plate for pelletizing;

[0021] S7, extraction: transport the particles to a pre-extraction tower and an extraction tower, extract at 95-105°C for 8-12 hours, with the bath ratio of water to particles in the pre-extraction tower and the extraction tower being 2:1;

[0022] S8, centrifugal drying: centrifugally dehydrate the extracted product, and transport the dehydrated particles to a drying tower for drying at a drying temperature of 110-125°C for 10-12 hours;

[0023] S9, cooling and packaging: packaging the cooled particles to obtain the above-mentioned high-performance flame-retardant nylon 6.

[0024] Beneficial effects of the present invention:

[0025] 1. During the hydrolysis and ring-opening polymerization of caprolactam, melamine and cyanuric acid are added to the chemical reaction of nylon 6 molding and connected to the molecular chain of nylon 6. In addition, a polymer regulator and an anti-modification impact agent are added. This one-step method prepares high-performance flame-retardant nylon 6 with UL94 V-0 flame retardancy, better impact strength, excellent tensile properties, and lower cost. This solves the problems of traditional physical additions that easily lead to damage to the mechanical properties of the material and the easy frosting and precipitation of flame retardants.

[0026] 2. Provides a high-performance flame-retardant nylon 6 preparation technology that simplifies the traditional preparation process, omits multiple processing steps in traditional methods such as shearing, mixing and post-processing, and reduces energy consumption and production costs. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and examples. However, it should be understood by those skilled in the art that the present invention can be implemented without these details. In other cases, well-known structures are not shown or described in detail to avoid unnecessarily obscuring the description of the embodiments. Unless the context requires otherwise, throughout the specification and the appended claims, the word "including" should be interpreted in an open, inclusive sense, that is, as "including but not limited to".

[0028] References throughout this specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic associated with that embodiment is included in at least one embodiment. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. Furthermore, as used in this specification and the appended claims, the singular forms "a / kind," and "the" include plural referents unless the context clearly dictates otherwise. It should also be noted that the term "or" is generally used in its sense including "and / or" unless the context clearly dictates otherwise.

[0029] In the implementation scheme, the purity of caprolactam is ≥99.9%, the purity of melamine is ≥99.8%, and the purity of cyanuric acid is ≥99.8%.

[0030] The chemicals used in the following embodiments can all be obtained from commercial sources, so the sources of the components are not described in detail.

[0031] Example 1:

[0032] A flame-retardant nylon material comprises, by weight, 90 parts of caprolactam, 6 parts of melamine, 6 parts of cyanuric acid, 0.3 parts of water, 3 parts of pyromellitic acid, 2 parts of hexamethylenediamine succinate, and 0.5 parts of a silane coupling agent KH550.

[0033] A method for preparing high-performance flame-retardant nylon 6 comprises the following steps:

[0034] S1. Material preparation: adding liquid caprolactam to a caprolactam storage tank, and adding melamine, cyanuric acid, water, pyromellitic acid, hexamethylenediamine succinate, and silane coupling agent KH550 to an additive tank to obtain a mixed additive;

[0035] S2. Preheating and mixing: Caprolactam and mixed additives are delivered to a preheating tower in proportion by a delivery pump for preheating, and then mixed evenly in a static mixer to obtain a mixed solution;

[0036] Preheating helps to improve the reaction rate and efficiency. The preheated raw materials and additives are fully mixed through a static mixer to ensure uniform distribution of the reactants and create uniform conditions for the polymerization reaction.

[0037] S3, prepolymerization reaction: the mixed solution was transported to a prepolymerization tower and polymerized at a pressure of 0.6 MPa and a temperature of 240° C. for 1.5 hours;

[0038] In the prepolymerization tower, the main chemical reaction is the hydrolysis ring-opening reaction of caprolactam with water to form free aminocaproic acid, and its chemical reaction formula is shown in Chemical Reaction Formula A.

[0039]

[0040] Chemical reaction formula A

[0041] S4, prepolymerization reaction: the prepolymerization product is transported to the prepolymerization tower through the melt gear pump at the bottom of the prepolymerization tower, and polymerized at a pressure of 0.15 MPa and a temperature of 260°C for 4 hours;

[0042] In the pre-polymerization tower, the main chemical reaction is the condensation reaction between aminocaproic acid and carboxyl group to form linear polymer A, and its chemical reaction formula is shown in Chemical Reaction Formula B. Similarly, due to the addition of hexamethylenediamine succinate, a condensation reaction also occurs between hexamethylenediamine and succinic acid to form linear polymer B, and its chemical reaction formula is shown in Chemical Reaction Formula C.

[0043]

[0044] Chemical reaction formula B

[0045] Where n≥2, m=n-1.

[0046]

[0047] Where j≥1.

[0048] Chemical reaction formula C

[0049] S5, post-polymerization reaction: the product of the pre-polymerization tower is transported to the post-polymerization tower, and the equilibrium polymerization is carried out at a pressure of -0.05 MPa and a temperature of 240°C for 4 hours;

[0050] In the post-polymerization tower, the main chemical reactions that occur are the reaction of the amino group at one end of the linear polymer A formed in step S4 with the hydroxyl group of cyanuric acid, and the reaction of the carboxyl group at the other end with the amino group of melamine, to form a flame-retardant polymer A, as shown in Chemical Reaction Formula D. In addition, the linear polymer B can also react with the hydroxyl group of cyanuric acid and the amino group of melamine to form a flame-retardant polymer B, as shown in Chemical Reaction Formula E. Simultaneously, due to the addition of pyromellitic acid, the amino groups of the flame-retardant polymers A and B are connected to the hydroxyl group of the pyromellitic acid, transforming the nylon polymer chain from a linear structure to a branched structure, further improving the mechanical properties of the flame-retardant nylon 6 composite material and completing its modification. Partial chemical formulas of the obtained product are shown in Formulas 1 and 2 (Formulas 1 and 2 schematically illustrate the branch on carbon atom 1 on the benzene ring of pyromellitic acid, and the branches on carbon atoms 2, 4, and 5 are either one of the branches on carbon atom 1 in Formulas 1 and 2 or remain unchanged).

[0051]

[0052] Chemical reaction formula D

[0053]

[0054] Chemical reaction formula E

[0055] Formula 1

[0056]

[0057] Formula 2

[0058] In the reaction, a small amount of linear polymer A and linear polymer B react with the hydroxyl group of cyanuric acid or the amino group of melamine at only one end, and the chemical formula is not described here.

[0059] It should be noted that the above chemical reactions occur in the three reaction towers, namely the pre-polymerization tower, the front-polymerization tower and the post-polymerization tower. The article describes the position of the reaction tower where the main reaction occurs.

[0060] S6, pelletizing: pushing the post-polymerization tower product to the casting strip plate for pelletizing;

[0061] After the polymerization is completed, the casting strip plate and casting strip pellets are pushed vigorously by the gear pump at the bottom of the post-polymerization tower to form granular materials suitable for subsequent processing;

[0062] S7, extraction: transport the particles to a pre-extraction tower and an extraction tower, extract at 95-105°C for 8-12 hours, with the bath ratio of water to particles in the pre-extraction tower and the extraction tower being 2:1;

[0063] The bath ratio of water / particles = 2 / 1 is based on the distribution law and mass transfer efficiency. It aims to optimize the extraction process, improve extraction efficiency, control costs, and reduce emulsification during the extraction process. This process can remove unreacted caprolactam monomer and additives, thereby improving product purity.

[0064] S8, centrifugal drying: centrifugally dehydrate the extracted product, and transport the dehydrated particles to a drying tower for drying at a drying temperature of 120° C. for 10 hours;

[0065] The mixture of sliced ​​particles and water is transported by a slurry pump to the centrifugal dehydrator on the top of the drying tower for dehydration and then enters the drying tower for drying. This process is designed to remove excess moisture and ensure that the product reaches the required degree of dryness;

[0066] S9, cooling and packaging: packaging the cooled particles to obtain the high performance flame retardant nylon 6 of the present invention.

[0067] Example 2: The materials used in this example are: 95 parts of caprolactam, 5.5 parts of melamine, 5.5 parts of cyanuric acid, 1 part of water, 2.5 parts of pyromellitic acid, 2.5 parts of hexamethylenediamine succinate, and 0.4 parts of silane coupling agent KH550.

[0068] Example 3: The materials used in this example are: 100 parts of caprolactam, 5 parts of melamine, 5 parts of cyanuric acid, 2.5 parts of water, 1.5 parts of pyromellitic acid, 3.5 parts of hexamethylenediamine succinate, and 0.3 parts of silane coupling agent KH550.

[0069] Example 4: The materials used in this example are: 105 parts of caprolactam, 4.5 parts of melamine, 4.5 parts of cyanuric acid, 4 parts of water, 0.8 parts of pyromellitic acid, 4 parts of hexamethylenediamine succinate, and 0.2 parts of silane coupling agent KH550.

[0070] Example 5: The materials used in this example are: 110 parts of caprolactam, 4 parts of melamine, 4 parts of cyanuric acid, 5 parts of water, 0.2 parts of pyromellitic acid, 5 parts of hexamethylenediamine succinate, and 0.05 parts of silane coupling agent KH550.

[0071] Comparative Example 1: The materials used in this comparative example are: 100 parts of caprolactam, 3 parts of melamine, 3 parts of cyanuric acid, 2.5 parts of water, 1.5 parts of pyromellitic acid, 3.5 parts of hexamethylenediamine succinate, and 0.3 parts of silane coupling agent KH550.

[0072] Comparative Example 2: The materials used in this comparative example are: 100 parts of caprolactam, 7 parts of melamine, 7 parts of cyanuric acid, 2.5 parts of water, 1.5 parts of pyromellitic acid, 3.5 parts of hexamethylenediamine succinate, and 0.3 parts of silane coupling agent KH550.

[0073] Comparative Example 3: The nylon 6 used in this comparative example was purchased from the market and contained red phosphorus and melamine compounds as the flame retardant system.

[0074] Comparative Example 4: The nylon 6 used in this comparative example was purchased from the market and was nylon 6 to which MCA salt was physically added as a flame retardant system.

[0075] The nylon 6 material particles obtained in the above examples and comparative examples were injection molded into standard national standard specimens on a 120-ton injection molding machine and tested according to the following test contents and standards:

[0076] A 120T Shuangsheng all-electric injection molding machine is used with a nozzle temperature of 240°C, a front section temperature of 250°C, a middle section temperature of 240°C, a rear section temperature of 220°C, and a mold temperature of 60°C to mold the required product shape and size.

[0077] Charpy notched impact strength is tested in accordance with ISO 179-1. The specimen size is 80×10×4mm, the notch is machined, and the testing equipment is a Charpy notched impact tester.

[0078] The tensile strength performance test was performed according to ISO 527-2, with a specimen size of 150×10×4 mm, an electronic universal testing machine, and a tensile speed of 10 mm / min.

[0079] The flexural strength performance test was carried out according to ISO 178, with a specimen size of 80×10×4mm, a bending speed of 2mm / min, a span of 64mm, and an electronic universal testing machine.

[0080] The flame retardancy test is carried out according to UL94 vertical burning test, and the sample size is 100×10×1mm;

[0081] The simulated frost precipitation was carried out according to GB / T 2918-2018 using the accelerated precipitation method. The specimen size was 100×10×1mm. The specimen was placed in an environment with a temperature of 85°C and a humidity of 85% RH for 72 hours for flame retardancy testing.

[0082] The test results are shown in Table 1.

[0083]

[0084] Table 1

[0085] As shown in Table 1, the products prepared according to the ratio of Examples 1 to 5 are all high-performance flame-retardant nylon 6 with UL94 V-0 flame retardancy, good impact strength, and excellent tensile properties, and the flame retardant effect is still good after simulated bloom precipitation. The difference between Comparative Example 1 and Example 3 is that the addition amount of melamine and cyanuric acid is insufficient, and the mechanical properties of the prepared nylon 6 are higher, but its flame retardancy is UL94 V-0. V-1 grade, this is due to the lack of sufficient flame retardant nitrogen elements provided by melamine and cyanuric acid; the difference between Comparative Example 2 and Example 3 is that the amount of melamine and cyanuric acid added is too much, and the excessive linear polymer A and linear polymer B, when the molecular chain length is insufficient, participate in the reaction of chemical reaction formula D and chemical reaction formula E with melamine and cyanuric acid, resulting in a lower molecular weight of the nylon 6 prepared in this comparative example and a decrease in mechanical properties; the nylon 6 of Comparative Examples 3 and 4 are both commercially available, and the flame retardant is physically added. The mechanical properties of the nylon 6 prepared are poor, and the flame retardant properties decrease after accelerated precipitation.

[0086] In order to further verify the effect of the ratio between melamine and cyanuric acid on the high-performance flame-retardant nylon 6 obtained, given that the molecular weights of melamine and cyanuric acid are close, the weight ratio was directly used for verification. Based on Example 3, the inventors designed Examples 6-7 and Comparative Examples 8-11.

[0087] Example 6: The materials used in this example are: 100 parts of caprolactam, 4.5 parts of melamine, 5.5 parts of cyanuric acid, 2.5 parts of water, 1.5 parts of pyromellitic acid, 3.5 parts of hexamethylenediamine succinate, and 0.3 parts of silane coupling agent KH550.

[0088] Example 7: The materials used in this example are: 100 parts of caprolactam, 4 parts of melamine, 6 parts of cyanuric acid, 2.5 parts of water, 1.5 parts of pyromellitic acid, 3.5 parts of hexamethylenediamine succinate, and 0.3 parts of silane coupling agent KH550.

[0089] Example 8: The materials used in this example are: 100 parts of caprolactam, 5.5 parts of melamine, 4.5 parts of cyanuric acid, 2.5 parts of water, 1.5 parts of pyromellitic acid, 3.5 parts of hexamethylenediamine succinate, and 0.3 parts of silane coupling agent KH550.

[0090] Example 9: The materials used in this example are: 100 parts of caprolactam, 6 parts of melamine, 4 parts of cyanuric acid, 2.5 parts of water, 1.5 parts of pyromellitic acid, 3.5 parts of hexamethylenediamine succinate, and 0.3 parts of silane coupling agent KH550.

[0091] Comparative Example 5: The materials used in this comparative example are: 100 parts of caprolactam, 3 parts of melamine, 7 parts of cyanuric acid, 2.5 parts of water, 1.5 parts of pyromellitic acid, 3.5 parts of hexamethylenediamine succinate, and 0.3 parts of silane coupling agent KH550.

[0092] Comparative Example 6: The materials used in this comparative example are: 100 parts of caprolactam, 7 parts of melamine, 3 parts of cyanuric acid, 2.5 parts of water, 1.5 parts of pyromellitic acid, 3.5 parts of hexamethylenediamine succinate, and 0.3 parts of silane coupling agent KH550.

[0093] The products obtained in Examples 6-9, Example 3 and Comparative Examples 5-6 were tested in the same manner. The test results are shown in Table 2.

[0094]

[0095] Table 2

[0096] By comparing the test results of Example 3 with those of Examples 6-9 and Comparative Examples 5-6 and combining them with Chemical Reaction Formula D and Chemical Reaction Formula E, it can be seen that when melamine and cyanuric acid are added in equal proportions (molar ratio) within the implementation range, the molecular weights of the flame-retardant polymer A and the flame-retardant polymer B formed are the largest, and the mechanical properties of the nylon 6 material finally obtained are the best. When melamine and cyanuric acid are added in unequal proportions, only one end of the linear polymer A and the linear polymer B reacts with the hydroxyl group of cyanuric acid or the amino group of melamine, and the molecular weights of the flame-retardant polymer A and the flame-retardant polymer B formed become smaller, and the amount of flame-retardant polymer A and the flame-retardant polymer B that eventually transform from a linear structure to a branched structure becomes less, the molecular weight of nylon 6 becomes lower, and some of the excess melamine or cyanuric acid does not participate in the reaction and is eventually precipitated during extraction. When the melamine and cyanuric acid exceed the implementation range and the difference in proportion is too large, the mechanical properties and flame retardancy of the obtained nylon 6 product decrease sharply.

[0097] The molecular weight of polymer materials has a great influence on the mechanical properties of the materials. In order to verify the effect of the addition amount of polymer regulator in this formula on the properties of the prepared nylon 6, the inventors designed Examples 10-13 and Comparative Examples 7-8 based on Example 3 for analysis and verification.

[0098] Example 10: The materials used in this example are: 100 parts of caprolactam, 5 parts of melamine, 5 parts of cyanuric acid, 2.5 parts of water, 1 part of pyromellitic acid, 3.5 parts of hexamethylenediamine succinate, and 0.3 part of silane coupling agent KH550.

[0099] Example 11: The materials used in this example are: 100 parts of caprolactam, 5 parts of melamine, 5 parts of cyanuric acid, 2.5 parts of water, 2 parts of pyromellitic acid, 3.5 parts of hexamethylenediamine succinate, and 0.3 parts of silane coupling agent KH550.

[0100] Example 12: The materials used in this example are: 100 parts of caprolactam, 5 parts of melamine, 5 parts of cyanuric acid, 2.5 parts of water, 2.5 parts of pyromellitic acid, 3.5 parts of hexamethylenediamine succinate, and 0.3 parts of silane coupling agent KH550.

[0101] Example 12: The materials used in this example are: 100 parts of caprolactam, 5 parts of melamine, 5 parts of cyanuric acid, 2.5 parts of water, 3 parts of pyromellitic acid, 3.5 parts of hexamethylenediamine succinate, and 0.3 parts of silane coupling agent KH550.

[0102] Comparative Example 7: The materials used in this comparative example are: 100 parts of caprolactam, 5 parts of melamine, 5 parts of cyanuric acid, 2.5 parts of water, 0.1 parts of pyromellitic acid, 3.5 parts of hexamethylenediamine succinate, and 0.3 parts of silane coupling agent KH550.

[0103] Comparative Example 8: The materials used in this comparative example are: 100 parts of caprolactam, 5 parts of melamine, 5 parts of cyanuric acid, 2.5 parts of water, 4 parts of pyromellitic acid, 3.5 parts of hexamethylenediamine succinate, and 0.3 parts of silane coupling agent KH550.

[0104] The products obtained in Examples 10-13, Example 3 and Comparative Examples 7-8 were tested in the same manner. The test results are shown in Table 3.

[0105]

[0106] Table 3

[0107] The test results of Examples 3 and 10-13 in Table 3 show that, within the implementation range, as the amount of the polymer regulator pyromellitic acid added increases, the mechanical properties of the resulting nylon 6 material show a trend of first increasing and then decreasing. This is because an appropriate amount of pyromellitic acid can convert the flame retardant polymer A and the flame retardant polymer B from a linear structure to a branched structure during the chemical reaction, thereby increasing the molecular weight of nylon 6 and improving the mechanical properties of the resulting product. Combined with the test results of Comparative Examples 7-8, it can be analyzed that too little addition of the polymer regulator pyromellitic acid is insufficient to convert the flame retardant polymer A and the flame retardant polymer B from a linear structure to a branched structure. Excessive addition of pyromellitic acid results in insufficient molecular chain length of the flame retardant polymer A and the flame retardant polymer B, resulting in premature conversion from a linear structure to a branched structure. Both of these results in a lower molecular weight of the resulting nylon 6 and a decrease in mechanical properties. When the amount of the polymer regulator pyromellitic acid added exceeds the implementation range, the mechanical properties of the resulting nylon 6 material are significantly reduced.

[0108] The addition of an anti-impact modifier will change the mechanical properties of nylon 6. In order to verify the effect of the anti-impact modifier on nylon 6 and prepare high-performance flame-retardant nylon 6 with UL94 V-0 flame retardancy, better impact strength, and excellent tensile properties, the inventors designed Examples 14-17 and Comparative Examples 9-10 based on Example 3 for analysis and verification.

[0109] Example 14: The materials used in this example are: 100 parts of caprolactam, 5 parts of melamine, 5 parts of cyanuric acid, 2.5 parts of water, 1.5 parts of pyromellitic acid, 2 parts of hexamethylenediamine succinate, and 0.3 parts of silane coupling agent KH550.

[0110] Example 15: The materials used in this example are: 100 parts of caprolactam, 5 parts of melamine, 5 parts of cyanuric acid, 2.5 parts of water, 1.5 parts of pyromellitic acid, 3 parts of hexamethylenediamine succinate, and 0.3 parts of silane coupling agent KH550.

[0111] Example 16: The materials used in this example are: 100 parts of caprolactam, 5 parts of melamine, 5 parts of cyanuric acid, 2.5 parts of water, 1.5 parts of pyromellitic acid, 4 parts of hexamethylenediamine succinate, and 0.3 parts of silane coupling agent KH550.

[0112] Example 17: The materials used in this example are: 100 parts of caprolactam, 5 parts of melamine, 5 parts of cyanuric acid, 2.5 parts of water, 1.5 parts of pyromellitic acid, 5 parts of hexamethylenediamine succinate, and 0.3 parts of silane coupling agent KH550.

[0113] Comparative Example 9: The materials used in this comparative example are: 100 parts of caprolactam, 5 parts of melamine, 5 parts of cyanuric acid, 2.5 parts of water, 1.5 parts of pyromellitic acid, 1 part of hexamethylenediamine succinate, and 0.3 parts of silane coupling agent KH550.

[0114] Comparative Example 10: The materials used in this comparative example are: 100 parts of caprolactam, 5 parts of melamine, 5 parts of cyanuric acid, 2.5 parts of water, 1.5 parts of pyromellitic acid, 6 parts of hexamethylenediamine succinate, and 0.3 parts of silane coupling agent KH550.

[0115] The products obtained in Examples 14-17, Example 3 and Comparative Examples 9-10 were tested in the same manner. The test results are shown in Table 4.

[0116]

[0117] Table 4

[0118] As can be seen from Table 4, with the increase of the addition amount of the anti-modifying impact agent hexamethylenediamine succinate, the impact resistance of the prepared nylon 6 material is improved, but its tensile strength and flexural strength show a downward trend. When the addition amount of the anti-modifying impact agent is insufficient, the obtained nylon 6 has excellent tensile strength and flexural strength, but its impact strength is obviously insufficient. When the addition amount of the anti-modifying impact agent exceeds the implementation range, the impact strength is improved to a certain extent, but its tensile strength and flexural strength are seriously reduced. According to the addition range provided by the present invention, high-performance flame-retardant nylon 6 with UL94 V-0 flame retardancy, better impact strength and excellent tensile properties can be obtained.

[0119] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A high-performance flame-retardant nylon 6, characterized in that: Calculated by weight, including: 90-110 parts of caprolactam; 4-6 parts of melamine; 4-6 parts of cyanuric acid; 0.3-5 parts of caprolactam hydrolysis ring-opening polymerization initiator; 0.2-3 parts of polymer structure regulator; 2-5 parts of impact modifier; 0.05-0.5 parts of flame retardant dispersant; The caprolactam purity is ≥99.9%; The purity of the melamine is ≥99.8%; The purity of the cyanuric acid is ≥99.8%; The polymer structure regulator is pyromellitic acid; The impact modifier is hexamethylenediamine succinate.

2. The high-performance flame-retardant nylon 6 according to claim 1, characterized in that: The molar ratio of melamine to cyanuric acid is 1:

1.

3. The high performance flame retardant nylon 6 according to claim 1, characterized in that: The caprolactam hydrolysis ring-opening polymerization initiator is an organic substance, an inorganic substance or a mixture thereof containing active carboxyl groups and hydroxyl groups in the molecular structure.

4. The high-performance flame-retardant nylon 6 according to claim 3, characterized in that: The organic matter, inorganic matter and mixture thereof containing active carboxyl and hydroxyl groups in the molecular structure are selected from one or more of methanol, ethanol, aminocaproic acid, benzoic acid and water.

5. The high performance flame retardant nylon 6 according to claim 1, characterized in that: The flame retardant dispersant is selected from one or more of silane coupling agents KH550, KH560 or KH570.

6. A method for preparing a high-performance flame-retardant nylon 6 according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Material preparation: adding liquid caprolactam to a caprolactam storage tank, and adding melamine, cyanuric acid, a caprolactam hydrolysis ring-opening polymerization initiator, pyromellitic acid, hexamethylenediamine succinate, and a flame retardant dispersant to an additive tank in proportion to obtain a mixed additive; S2, preheating and mixing: transporting caprolactam and mixed additives to a preheating tower for preheating according to proportion, and then mixing them evenly in a static mixer to obtain a mixed solution; S3, prepolymerization reaction: the mixed solution is transported to a prepolymerization tower and polymerized at a pressure of 0.5-0.8 MPa and a temperature of 230-240°C for 1-2 hours; S4, prepolymerization reaction: the product of the prepolymerization tower is transported to the prepolymerization tower, and polymerized at a pressure of 0.1-0.2 MPa and a temperature of 250-260°C for 3-5 hours; S5, post-polymerization reaction: the product of the pre-polymerization tower is transported to the post-polymerization tower, and the equilibrium polymerization is carried out at a pressure of 0.0 to -0.05 MPa and a temperature of 240 to 250 ° C for 2 to 4 hours; S6, pelletizing: pushing the post-polymerization tower product to the casting strip plate for pelletizing; S7, extraction: transport the particles to a pre-extraction tower and an extraction tower, extract at 95-105°C for 8-12 hours, with the bath ratio of water to particles in the pre-extraction tower and the extraction tower being 2:1; S8, centrifugal drying: centrifuge the extracted solution to dehydrate it, and then transfer it to a drying tower for drying. The drying tower has a drying temperature of 110-125°C and a drying time of 10-12 hours. S9, cooling and packaging: packaging the cooled particles to obtain the high performance flame retardant nylon 6 of the present invention.

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