High-performance flame-retardant nylon 6 and preparation method thereof

Abstract

The invention relates to high-performance flame-retardant nylon 6 and a preparation method thereof, and the high-performance flame-retardant nylon 6 comprises caprolactam, cyanuric acid, cyanuric acid, a caprolactam hydrolysis ring-opening polymerization initiator, a macromolecular structure regulator, an impact modifier and a flame-retardant dispersant. In the hydrolysis ring-opening polymerization process of caprolactam, two raw materials including melamine and cyanuric acid are added to participate in a chemical reaction of nylon 6 forming and are connected to a molecular chain of nylon 6, a polymer regulator and an anti-modification impact agent are added, and the high-performance flame-retardant nylon 6 with UL94V-0 flame retardance, better impact strength, excellent tensile property and lower cost is prepared through a one-step method.

Description

Technical Field

[0001] The 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 has excellent mechanical properties and good electrical properties. It is also wear-resistant, oil-resistant, solvent-resistant, self-lubricating, self-extinguishing, corrosion-resistant and has good processing properties. It is the engineering plastic with the largest output, the widest application and the most varieties among the five major engineering plastics. Although it is a self-extinguishing plastic, it is UL94 V-2 according to the US UL standard, and its oxygen index value is about 23% to 26%, which is still a combustible material and does not reach the world's UL94 V-0 flame retardant level. As nylon 6 is increasingly used in live working environments such as automotive electrical appliances and power tools, and the danger of fire caused by leakage, short circuit, arc, electric spark, etc. is extremely high, the flame retardant properties of nylon 6 have become a crucial factor in many occasions. Therefore, the flame retardant modification of nylon 6 has also become a topic of increasing concern.

[0003] At present, the flame retardant method of nylon 6 is mainly to use additive flame retardants, that is, to add flame retardants to polyamide through mechanical mixing to make it flame retardant. For example, adding a certain ratio of ammonium polyphosphate / talcum powder to PA6 can obtain UL94V-0 flame retardant PA6, which has the advantages of easy use and wide application, but the mechanical addition method is easy to cause problems such as damage to the mechanical properties of the material and easy frosting and precipitation 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 scheme 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 the 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 having three or more multifunctional groups in its molecular structure that can react with carboxyl groups or amino groups.

[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 benzoate, hexamethylenediamine isobenzoate, hexamethylenediamine succinate, hexamethylenediamine sebacate, hexamethylenediamine azelaate, and hexamethylenediamine dodecane dioate.

[0013] As an improvement of the above technical solution, the anti-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: adding liquid caprolactam to a caprolactam storage tank, and adding melamine, cyanuric acid, a caprolactam hydrolysis ring-opening polymerization initiator, a polymer structure regulator, an impact modifier, and a flame retardant dispersant to an additive tank in proportion 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, 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. The drying tower has a drying temperature of 110-125°C and a drying time of 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, two raw materials, melamine and cyanuric acid, are added to the chemical reaction of nylon 6 molding and connected to the molecular chain of nylon 6. A polymer regulator and an anti-modified impact agent are also added to prepare high-performance flame-retardant nylon 6 with UL94 V-0 flame retardancy, better impact strength, excellent tensile properties and lower cost in one step, which solves the problems of traditional physical additions that easily lead to damage to the mechanical properties of materials and easy frosting and precipitation of flame retardants.

[0026] 2. Provides a high-performance flame-retardant nylon 6 preparation technology, 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 scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with 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] "One embodiment" or "embodiment" mentioned throughout this specification means that in at least one embodiment, specific features, structures or characteristics related to the embodiment are included. Therefore, the phrases "in one embodiment" or "in an embodiment" appearing in various places throughout this specification do not necessarily all refer to the same embodiment. In addition, specific features, structures or characteristics can be combined in any suitable manner in one or more embodiments. In addition, as used in this specification and the appended claims, the singular forms "one / kind" and "the" include plural indicators unless the context clearly dictates otherwise. It should also be noted that the term "or" is generally used in its meaning that includes "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] Embodiment 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 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 the caprolactam storage tank, adding melamine, cyanuric acid, water, pyromellitic acid, hexamethylenediamine succinate, and silane coupling agent KH550 to the additive tank to obtain a mixed additive;

[0035] S2, preheating and mixing: The caprolactam and the mixed additives are transported to the preheating tower in proportion by a delivery pump for preheating, and then mixed evenly by 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 is 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 and 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] 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;

[0041] In the prepolymerization 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.

[0042]

[0043] Where n≥2, m=n-1.

[0044]

[0045] Where j≥1.

[0046] Chemical reaction formula C

[0047] 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;

[0048] In the post-polymerization tower, the main chemical reaction is that the amino group at one end of the linear polymer A formed in step S4 reacts with the hydroxyl group of cyanuric acid, and the carboxyl group at the other end reacts with the amino group of melamine to form a flame-retardant polymer A, and its chemical reaction formula is 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, and its chemical reaction formula is shown in chemical reaction formula E. At the same time, due to the addition of pyromellitic acid, the amino groups of the flame-retardant polymer A and the flame-retardant polymer B will be connected to the hydroxyl group of pyromellitic acid, so that the nylon polymer chain is transformed from a linear structure to a branched structure, further improving the mechanical properties of the flame-retardant nylon 6 composite material, completing its modification, and the partial chemical formulas of the obtained product are shown in Formulas 1 and 2 (Formulas 1 and 2 illustrate the branch on the No. 1 carbon atom on the benzene ring of pyromellitic acid, and the branch on the No. 2, 4, and 5 carbon atoms is one of the branches on the No. 1 carbon atom in Formulas 1 and 2 or remains the same).

[0049]

[0050]

[0051] 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.

[0052] It should be noted that the above chemical reactions occur in the three reaction towers, namely the prepolymerization tower, the front polymerization tower and the post-polymerization tower. The article describes the positions of the reaction towers where the main reactions occur.

[0053] S6, pelletizing: pushing the post-polymerization tower product to the casting strip plate for pelletizing;

[0054] After the polymerization is completed, the casting strip plate casting strip pelletizing is strongly pushed by the gear pump at the bottom of the post-polymerization tower to form granular materials suitable for subsequent processing;

[0055] S7, extraction: transport the particles to a pre-extraction tower and an extraction tower, extract at 95-105°C for 8-12 hours, the bath ratio of water to particles in the pre-extraction tower and the extraction tower being 2:1;

[0056] The bath ratio of water / particles = 2 / 1 is based on the distribution law and mass transfer efficiency, aiming to optimize the extraction process, improve the extraction efficiency, control costs, and reduce the emulsification phenomenon in the extraction process. This process can remove the caprolactam monomer and additives that have not participated in the reaction and improve the purity of the product.

[0057] S8, centrifugal drying: centrifugally dehydrate the extracted product, and transport the dehydrated particles to a drying tower for drying. The drying tower has a drying temperature of 120° C. and a drying time of 10 hours;

[0058] The mixture of sliced ​​particles and water is transported to the centrifugal dehydrator at the top of the drying tower by a mud pump 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;

[0059] S9, cooling and packaging: packaging the cooled particles to obtain the high performance flame retardant nylon 6 of the present invention.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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 of nylon 6.

[0067] Comparative Example 4: The nylon 6 used in this comparative example was purchased from the market and was nylon 6 with MCA salt physically added as the flame retardant system.

[0068] 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:

[0069] 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.

[0070] The simply supported beam notch impact strength is carried out according to ISO 179-1, the specimen size is 80×10×4mm, the notch is machined, and the testing equipment is a simply supported beam notch impact testing machine;

[0071] The tensile strength performance test was carried out according to ISO 527-2, the specimen size was 150×10×4mm, the test equipment was an electronic universal testing machine, and the tensile speed was 10mm / min;

[0072] The bending 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.

[0073] The flame retardancy test was carried out according to UL94 vertical burning test, and the sample size was 100×10×1mm;

[0074] The simulated frost precipitation is carried out according to GB / T 2918-2018, using the accelerated precipitation method. The sample size is 100×10×1mm. The sample is placed in an environment of temperature 85℃ and humidity 85%RH for 72 hours for flame retardancy testing.

[0075] The test results are shown in Table 1.

[0076]

[0077]

[0078] Table 1

[0079] As can be seen from Table 1, the products prepared according to the ratio of Examples 1-5 are all high-performance flame-retardant nylon 6 with UL94V-0 flame retardancy, good impact strength and excellent tensile properties, and the flame retardant effect is still good after simulated blooming 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 UL94V-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 the 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, thereby causing the molecular weight of nylon 6 obtained in this comparative example to become lower and the mechanical properties to decrease; 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 obtained are poor, and the flame retardant property decreases after accelerated precipitation.

[0080] In order to further verify the effect of the ratio of melamine to cyanuric acid on the high-performance flame-retardant nylon 6 obtained, in view of the close molecular weights of melamine and cyanuric acid, the weight ratio was directly used for verification. Based on Example 3, the inventors designed Examples 6-7 and Comparative Examples 8-11.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] The products obtained in Examples 6-9 and Comparative Examples 5-6 were tested in the same manner. The test results are shown in Table 2.

[0088]

[0089]

[0090] Table 2

[0091] By comparing the test results of Example 3 and Examples 6-9 and Comparative Examples 5-6 and combining the chemical reaction formula D and the 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 weight of the flame retardant polymer A and the flame retardant polymer B formed is the largest, and the mechanical properties of the nylon 6 material finally obtained are optimal. When melamine and cyanuric acid are not in equal 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 weight of the flame retardant polymer A and the flame retardant polymer B formed becomes smaller, and the flame retardant polymer A and the flame retardant polymer B that are finally transformed from a linear structure to a branched structure become less, the molecular weight of nylon 6 becomes lower, and part of the excess melamine or cyanuric acid does not participate in the reaction and is finally precipitated during extraction. When 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 drop sharply.

[0092] The molecular weight of the polymer material has a great influence on the mechanical properties of the material. In order to verify the effect of the amount of polymer regulator added in this formula on the performance of the prepared nylon 6, the inventor designed Examples 10-13 and Comparative Examples 7-8 on the basis of Example 3 for analysis and verification.

[0093] 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 parts of silane coupling agent KH550.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] The products obtained in Examples 10-13 and Comparative Examples 7-8 were tested in the same manner. The test results are shown in Table 3.

[0100]

[0101]

[0102] Table 3

[0103] It can be seen from the test results of Examples 3 and 10-13 in Table 3 that within the implementation range, as the amount of the polymer regulator pyromellitic acid added increases, the mechanical properties of the obtained 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, increase the molecular weight of nylon 6, and increase the mechanical properties of the obtained product. Combined with the test results of Comparative Examples 7-8, too little addition of the polymer regulator pyromellitic acid is insufficient to convert enough flame retardant polymer A and flame retardant polymer B from a linear structure to a branched structure. Too much pyromellitic acid is added to make the molecular chain length of the flame retardant polymer A and the flame retardant polymer B too early to change from a linear structure to a branched structure, which will make the molecular weight of the obtained nylon 6 lower and the mechanical properties decrease. When the amount of the polymer regulator pyromellitic acid added exceeds the implementation range, the mechanical properties of the obtained nylon 6 material are greatly reduced.

[0104] The addition of anti-modified impact agent will change the mechanical properties of nylon 6. In order to verify the effect of anti-modified impact agent 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 on the basis of Example 3 for analysis and verification.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] The products obtained in Examples 14-17 and Comparative Examples 9-10 were tested in the same manner. The test results are shown in Table 4.

[0112]

[0113]

[0114] Table 4

[0115] It can be seen from Table 4 that with the increase of the addition amount of the anti-modified 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-modified impact agent is insufficient, the prepared nylon 6 has excellent tensile strength and flexural strength, but its impact strength is obviously insufficient. When the addition amount of the anti-modified 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.

[0116] 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 principle of the present invention should be included in the protection scope of the present invention.

Claims

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

2. A high performance flame retardant nylon 6 as claimed in 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 polymer structure regulator is an active organic low molecular compound having three or more multifunctional groups capable of reacting with carboxyl groups or amino groups in its molecular structure.

6. The high performance flame retardant nylon 6 according to claim 5, characterized in that: The organic low molecular compound is selected from one or more of carboxylated styrene-butadiene rubber, pyromellitic acid, and trimellitic anhydride.

7. The high performance flame retardant nylon 6 according to claim 1, characterized in that: The impact modifier is selected from one or more of hexamethylenediamine adipate, hexamethylenediamine benzoate, hexamethylenediamine isobenzoate, hexamethylenediamine succinate, hexamethylenediamine sebacate, hexamethylenediamine azelaate, and hexamethylenediamine dodecane dioate.

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

9. A method for preparing a high-performance flame-retardant nylon 6 as claimed in claims 1 to 8, 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, a polymer structure regulator, an impact modifier, 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, 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 transport 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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