A flame-retardant nylon 6 and its preparation method

Abstract

The present invention relates to a flame-retardant nylon 6 and a preparation method thereof. The method comprises: mixing caprolactam, DOPO derivative dibasic acid A and diamine, and reacting at 220-260 °C for 6-10 h; the mass ratio of caprolactam, DOPO derivative dibasic acid A and diamine is 90-97.3:2-5:0.7-5; or, mixing caprolactam, DOPO derivative dibasic acid A, dibasic acid B and diamine, and reacting at 220-260 °C for 6-10 h; the mass ratio of caprolactam, DOPO derivative dibasic acid A, dibasic acid B and diamine is 80-85:1.5-3:7.2-10:6.3-8.5. The method of the present invention has a simple process, and the prepared flame-retardant nylon 6 has a relatively high molecular weight.

Description

Technical Field

[0001] The present invention belongs to the technical field of novel flame retardant materials, and relates to a flame retardant nylon 6 and a preparation method thereof. Background Art

[0002] Nylon 6 is widely used in fields such as fibers and engineering plastics. It is the earliest developed and applied variety in engineering plastics and is also one of the varieties with the largest output in polyamide plastics at present. The LOI value of nylon 6 is about 21%, and the UL-94 rating is V-2. A large amount of smoke will be released during a fire, and there is serious melting and dripping, which may cause secondary injuries. This severely limits the use of nylon 6 under high temperature conditions, especially in fields such as clothing and home furnishings. Therefore, nylon 6 needs to improve its flame retardancy or increase its scope of use by copolymerization.

[0003] To improve the flame retardant performance of nylon 6, the flame retardant can be incorporated into nylon 6 by physical methods to increase the flame retardancy of the material, or chemical methods can be used to insert it into the nylon 6 molecular chain to obtain an inherently flame retardant nylon 6 material. In the nylon 6 industry, most flame retardant materials are prepared by two-step or three-step methods, and a large amount of solvent may be required; the synthesis process is complex, time-consuming and laborious, and does not conform to the principle of green environmental protection. Using in-situ copolymerization to disperse flame retardant molecules containing flame retardant groups or elements in the polymer, or directly introducing flame retardant molecules into the main chain of nylon 6 to obtain inherently flame retardant nylon 6 is the research focus in recent years. Among them, using DOPO derivatives as flame retardants is a popular direction in recent years.

[0004] However, there are some problems in the copolymerization of DOPO derivatives and caprolactam to prepare flame retardant nylon 6 at present. One of the problems is that the copolymerization of reactive DOPO derivatives and caprolactam will cause the main chain of the molecule to break, resulting in a low molecular weight, which cannot meet the requirements of spinning, injection molding processing and use. For example: Patent CN106675007B discloses a preparation method of flame retardant polyamide 6. This method is to make water and cyclohexanone caprolactam generate a nylon 6 prepolymer, and then carry out polycondensation with a flame retardant salt. However, the salt is unstable and may decompose during the reaction, resulting in an imbalance in the ratio of acid and amine in the system. One of the components becomes a chain terminator, thus causing the molecular weight of the polymer to decrease and it is difficult to reach about 10000 g / mol.

[0005] Therefore, a study is made on a preparation method of flame retardant nylon 6 and its copolymer to solve the problem of the low molecular weight of the product obtained by the copolymerization of reactive DOPO derivatives and caprolactam in the prior art. Summary of the Invention

[0006] The purpose of the present invention is to solve the problems existing in the prior art and provide a flame retardant nylon 6 and a preparation method thereof.

[0007] To achieve the above object, the technical solution of the present invention is as follows:

[0008] A preparation method of flame-retardant nylon 6, comprising mixing caprolactam, DOPO derivative dibasic acid A and diamine, and reacting at 220-260 °C for 6-10 h to obtain flame-retardant nylon 6; the mass ratio of caprolactam, DOPO derivative dibasic acid A and diamine is 90-97.3:2-5:0.7-5;

[0009] Alternatively, mixing caprolactam, DOPO derivative dibasic acid A, dibasic acid B and diamine, and reacting at 220-260 °C for 6-10 h to obtain flame-retardant nylon 6; the mass ratio of caprolactam, DOPO derivative dibasic acid A, dibasic acid B and diamine is 80-85:1.5-3:7.2-10:6.3-8.5;

[0010] The dibasic acid and the diamine must be in an equimolar ratio to ensure the smooth progress of the polycondensation reaction. Otherwise, either the dibasic acid is in excess or the diamine is in excess, and they will both act as chain terminators, terminating the reaction, thereby affecting the smooth progress of the polymerization, that is, preventing the molecular chain from continuing to grow, and thus resulting in a polymer with a lower molecular weight;

[0011] All DOPO derivative dibasic acid A is prepared from DOPO and dibasic acid C containing carbon-carbon double bonds through Michael addition reaction.

[0012] Compared with patent CN106675007B, the present invention has the following advantages:

[0013] ① It is not necessary to pre-form salts;

[0014] ② The molar ratio of the diacid and the diamine can be ensured by fine-tuning the ratio of the derivative and the diamine, further ensuring that the molecular weight is not affected by the imbalance of the ratio;

[0015] ③ It is not necessary to add water to initiate the ring-opening of caprolactam to prepare the flame-retardant nylon 6 prepolymer. Instead, the binary acid derivative is used to provide active protons to activate the carbonyl group of caprolactam, and the diamine directly initiates the ring-opening polymerization of caprolactam or the dibasic acid reacts with the diamine to form a new polymer and then the caprolactam is ring-opened to form a copolymer to prepare the flame-retardant nylon 6. The specific principle is as follows:

[0016] In liquid caprolactam, the active protons on the carboxyl groups at both ends of the DOPO derivative dibasic acid will transfer to the carbonyl oxygen atom of caprolactam, making the carbon atom on the carbonyl carry a positive charge, thereby activating the carbonyl. Then, the amino group on the diamine dissolved in the caprolactam solution will attack the carbocation, undergoing nucleophilic attack, that is, causing ring-opening polymerization of caprolactam to form a prepolymer. The prepolymer then undergoes polycondensation reaction with the DOPO derivative dibasic acid to form the target flame-retardant copolyamide nylon. In this process, some DOPO derivative dibasic acids and diamines will also undergo polycondensation with each other. Since the polycondensate contains carbonyl and amino groups, caprolactam will also undergo ring-opening polymerization through the above mechanism.

[0017] As a preferred technical solution:

[0018] In a method for preparing flame-retardant nylon 6 as described above, the dibasic acid C containing a carbon-carbon double bond is itaconic acid (ITA) or maleic anhydride (MA).

[0019] In a method for preparing flame-retardant nylon 6 as described above, the dibasic acid B is adipic acid, succinic acid, glutaric acid, terephthalic acid or isophthalic acid.

[0020] In a method for preparing flame-retardant nylon 6 as described above, the diamine is ethylenediamine, propylenediamine, hexamethylenediamine, cyclohexanediamine, p-phenylenediamine, polyetheramine, 4,4'-methylenedianiline or 2,2-bis[4-(4-aminophenoxy)phenyl]propane.

[0021] In a method for preparing flame-retardant nylon 6 as described above, the diamine is hexamethylenediamine, p-phenylenediamine or polyetheramine.

[0022] In a method for preparing flame-retardant nylon 6 as described above, all mixing is carried out by mechanical stirring. The rotation speed of the mechanical stirring is 10 - 100 rpm, and the reaction kettle used can be a high-pressure reaction kettle, a stainless-steel reaction kettle, or an electrically heated reaction kettle.

[0023] The present invention also provides flame-retardant nylon 6 prepared by using the method for preparing flame-retardant nylon 6 described in any one of the above. The relative viscosity of the flame-retardant nylon 6 is 1.57 - 2.45, the weight-average molecular weight is 21000 - 37200 g / mol, the number-average molecular weight is 8500 - 16600 g / mol, the polydispersity index is 2.14 - 2.97, the limiting oxygen index is 26 - 34%, and UL-94 reaches V-0 or V-1 level.

[0024] Beneficial effects

[0025] (1) Compared with the traditional method for preparing flame-retardant nylon 6 by hydrolysis ring-opening polymerization, the method of the present invention can significantly shorten the polymerization reaction time, and does not require additional use of water or 6-aminocaproic acid as a ring-opening agent, which is an efficient, safe and green process production route;

[0026] (2) The number-average molecular weight of the product of the present invention can reach about 10,000 g / mol. Description of the Drawings

[0027] Figure 1 It is the three-dimensional TG-FTIR spectrum of the product obtained in Example 11;

[0028] Figure 2 It is the FTIR spectrum of the product obtained in Example 11;

[0029] Figure 3 It is the SEM image of the carbon layer of the product obtained in Example 11;

[0030] Figure 4 It is the SEM image of the carbon layer of the product obtained in Example 11;

[0031] Figure 5 It is the SEM image of the carbon layer of the product obtained in Example 11. Detailed Description of the Invention

[0032] The present invention will be further described below in conjunction with the specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0033] In the following examples:

[0034] The structural formula of DOPO-ITA is:

[0035] The structural formula of DOPO-MA is:

[0036] The manufacturer of the polyetheramine is Huntsman, and the grade is D400.

[0037] In the following examples, the detection methods for the relevant properties of the prepared nylon 6 are as follows:

[0038] Relative viscosity: Detected with reference to the standard GB12006.1-89;

[0039] LOI value: Detected with reference to the standard GB2406-80;

[0040] UL-94 rating: Detected with reference to the standard GB / T 2408-2008.

[0041] Example 1

[0042] A preparation method of flame-retardant nylon 6, the specific steps are as follows:

[0043] (1) Prepare raw materials:

[0044] Caprolactam;

[0045] DOPO derivative dibasic acid A: DOPO-ITA;

[0046] Diamine: Hexamethylenediamine;

[0047] Tetraphenyltin;

[0048] (2) Prepare flame-retardant nylon 6:

[0049] Add tetraphenyltin, caprolactam, DOPO derivative dibasic acid A, and diamine into the polymerization kettle, stir and mix at a speed of 50 rpm. After purging with nitrogen for 0.5 h, adjust the temperature to 220 °C and continue to react for 6 h to obtain flame-retardant nylon 6; among them, the mass ratio of caprolactam, DOPO derivative dibasic acid A, and diamine is 97.3:2:0.7, and the dosage of tetraphenyltin is 0.1% of the total mass of the materials in the polymerization kettle.

[0050] Example 2

[0051] A preparation method of flame-retardant nylon 6, the specific steps are as follows:

[0052] (1) Prepare raw materials:

[0053] Caprolactam;

[0054] DOPO derivative dibasic acid A: DOPO-ITA;

[0055] Diamine: Hexamethylenediamine;

[0056] Tetraphenyltin;

[0057] (2) Prepare flame-retardant nylon 6:

[0058] Add tetraphenyltin, caprolactam, DOPO derivative dibasic acid A, and diamine into the polymerization kettle, stir and mix at a speed of 50 rpm. After purging with nitrogen for 0.5 h, adjust the temperature to 220 °C and continue to react for 6 h to obtain flame-retardant nylon 6; among them, the mass ratio of caprolactam, DOPO derivative dibasic acid A, and diamine is 96.7:2.5:0.8, and the dosage of tetraphenyltin is 0.1% of the total mass of the materials in the polymerization kettle.

[0059] Example 3

[0060] A preparation method of flame-retardant nylon 6, the specific steps are as follows:

[0061] (1) Prepare raw materials:

[0062] Caprolactam;

[0063] DOPO derivative dibasic acid A: DOPO-ITA;

[0064] Diamine: hexamethylenediamine;

[0065] Tetraphenyltin;

[0066] (2) Preparation of flame-retardant nylon 6:

[0067] Add tetraphenyltin, caprolactam, DOPO derivative dibasic acid A, and diamine into the polymerization kettle, stir and mix at a speed of 50 rpm, adjust the temperature to 260 °C after purging with nitrogen for 0.5 h, and continue to react for 6 h to obtain flame-retardant nylon 6; among them, the mass ratio of caprolactam, DOPO derivative dibasic acid A, and diamine is 96:3:1, and the dosage of tetraphenyltin is 0.3% of the total mass of the materials in the polymerization kettle.

[0068] Example 4

[0069] A preparation method of flame-retardant nylon 6, the specific steps are as follows:

[0070] (1) Prepare raw materials:

[0071] Caprolactam;

[0072] DOPO derivative dibasic acid A: DOPO-ITA;

[0073] Diamine: hexamethylenediamine;

[0074] Tetraphenyltin;

[0075] (2) Prepare flame-retardant nylon 6:

[0076] Add tetraphenyltin, caprolactam, DOPO derivative dibasic acid A, and diamine into the polymerization kettle, stir and mix at a speed of 50 rpm, adjust the temperature to 220 °C after purging with nitrogen for 0.5 h, and continue to react for 6 h to obtain flame-retardant nylon 6; among them, the mass ratio of caprolactam, DOPO derivative dibasic acid A, and diamine is 95.3:3.5:1.2, and the dosage of tetraphenyltin is 1% of the total mass of the materials in the polymerization kettle.

[0077] Example 5

[0078] A preparation method of flame-retardant nylon 6, the specific steps are as follows:

[0079] (1) Prepare raw materials:

[0080] Caprolactam;

[0081] DOPO derivative dibasic acid A: DOPO-ITA;

[0082] Diamine: hexamethylenediamine;

[0083] Tetraphenyltin;

[0084] (2) Preparation of flame-retardant nylon 6:

[0085] Add tetraphenyltin, caprolactam, DOPO derivative dibasic acid A, and diamine into a polymerization kettle, stir and mix at a speed of 50 rpm, adjust the temperature to 220 °C after purging with nitrogen for 0.5 h, and continue the reaction for 6 h to obtain flame-retardant nylon 6; among them, the mass ratio of caprolactam, DOPO derivative dibasic acid A, and diamine is 94.7:4:1.3, and the dosage of tetraphenyltin is 0.5% of the total mass of the materials in the polymerization kettle.

[0086] Example 6

[0087] A preparation method of flame-retardant nylon 6, the specific steps are as follows:

[0088] (1) Prepare raw materials:

[0089] Caprolactam;

[0090] DOPO derivative dibasic acid A: DOPO-ITA;

[0091] Diamine: hexamethylenediamine;

[0092] Tetraphenyltin;

[0093] (2) Preparation of flame-retardant nylon 6:

[0094] Add tetraphenyltin, caprolactam, DOPO derivative dibasic acid A, and diamine into a polymerization kettle, stir and mix at a speed of 50 rpm, adjust the temperature to 260 °C after purging with nitrogen for 0.5 h, and continue the reaction for 6 h to obtain flame-retardant nylon 6; among them, the mass ratio of caprolactam, DOPO derivative dibasic acid A, and diamine is 93.3:5:1.7, and the dosage of tetraphenyltin is 0.4% of the total mass of the materials in the polymerization kettle.

[0095] Example 7

[0096] A preparation method of flame-retardant nylon 6, the specific steps are as follows:

[0097] (1) Prepare raw materials:

[0098] Caprolactam;

[0099] DOPO derivative dibasic acid A: DOPO-ITA;

[0100] Diamine: hexamethylenediamine;

[0101] Tetraphenyltin;

[0102] (2) Preparation of flame-retardant nylon 6:

[0103] Add tetraphenyltin, caprolactam, DOPO derivative dibasic acid A, and diamine into a polymerization kettle, stir and mix at a rotation speed of 50 rpm. After purging with nitrogen for 0.5 h, adjust the temperature to 220 °C and continue the reaction for 10 h to obtain flame-retardant nylon 6. Among them, the mass ratio of caprolactam, DOPO derivative dibasic acid A, and diamine is 94.7:4:1.3, and the dosage of tetraphenyltin is 0.5% of the total mass of the materials in the polymerization kettle.

[0104] Example 8

[0105] A preparation method of flame-retardant nylon 6 is as follows:

[0106] (1) Prepare raw materials:

[0107] Caprolactam;

[0108] DOPO derivative dibasic acid A: DOPO-ITA;

[0109] Diamine: hexamethylenediamine;

[0110] Tetraphenyltin;

[0111] (2) Prepare flame-retardant nylon 6:

[0112] Add tetraphenyltin, caprolactam, DOPO derivative dibasic acid A, and diamine into a polymerization kettle, stir and mix at a rotation speed of 50 rpm. After purging with nitrogen for 0.5 h, adjust the temperature to 260 °C and continue the reaction for 10 h to obtain flame-retardant nylon 6. Among them, the mass ratio of caprolactam, DOPO derivative dibasic acid A, and diamine is 94.7:4:1.3, and the dosage of tetraphenyltin is 0.6% of the total mass of the materials in the polymerization kettle.

[0113] Example 9

[0114] A preparation method of flame-retardant nylon 6 is as follows:

[0115] (1) Prepare raw materials:

[0116] Caprolactam;

[0117] DOPO derivative dibasic acid A: DOPO-ITA;

[0118] Diamine: hexamethylenediamine;

[0119] Tetraphenyltin;

[0120] (2) Prepare flame-retardant nylon 6:

[0121] Add tetraphenyltin, caprolactam, DOPO derivative dibasic acid A, and diamine into a polymerization kettle, stir and mix at a rotation speed of 50 rpm, purge with nitrogen for 0.5 h, then adjust the temperature to 260 °C and continue the reaction for 6 h to obtain flame-retardant nylon 6; among them, the mass ratio of caprolactam, DOPO derivative dibasic acid A, and diamine is 94.7:4:1.3, and the dosage of tetraphenyltin is 1% of the total mass of the materials in the polymerization kettle.

[0122] Example 10

[0123] A preparation method of flame-retardant nylon 6 is as follows:

[0124] (1) Prepare raw materials:

[0125] Caprolactam;

[0126] DOPO derivative dibasic acid A: DOPO-ITA;

[0127] Diamine: hexamethylenediamine;

[0128] Tetraphenyltin;

[0129] (2) Prepare flame-retardant nylon 6:

[0130] Add tetraphenyltin, caprolactam, DOPO derivative dibasic acid A, and diamine into a polymerization kettle, stir and mix at a rotation speed of 100 rpm, purge with nitrogen for 0.5 h, then adjust the temperature to 240 °C and continue the reaction for 10 h to obtain flame-retardant nylon 6; among them, the mass ratio of caprolactam, DOPO derivative dibasic acid A, and diamine is 93.3:5:1.7, and the dosage of tetraphenyltin is 0.8% of the total mass of the materials in the polymerization kettle.

[0131] Example 11

[0132] A preparation method of flame-retardant nylon 6 is as follows:

[0133] (1) Prepare raw materials:

[0134] Caprolactam;

[0135] DOPO derivative dibasic acid A: DOPO-ITA;

[0136] Diamine: hexamethylenediamine;

[0137] Tetraphenyltin;

[0138] (2) Prepare flame-retardant nylon 6:

[0139] Add tetraphenyltin, caprolactam, DOPO derivative dibasic acid A, and diamine into a polymerization kettle, stir and mix at a rotation speed of 100 rpm, adjust the temperature to 220 °C after purging with nitrogen for 0.5 h, and continue the reaction for 10 h to obtain flame-retardant nylon 6; among them, the mass ratio of caprolactam, DOPO derivative dibasic acid A, and diamine is 93.3:5:1.7, and the dosage of tetraphenyltin is 0.1% of the total mass of the materials in the polymerization kettle.

[0140] The three-dimensional TG-FTIR spectrum of the finally obtained flame-retardant nylon 6 is as Figure 1 shown, and the FTIR spectrum is as Figure 2 shown. Observe the microscopic morphology of the carbon layer formed after the combustion of the product obtained in Example 11 through a scanning electron microscope ( Figures 3 to 5 ), and it can be seen that the carbon layer after combustion is a uniform and dense carbonized layer without obvious defects. The carbonized layer can hinder the heat exchange with air during the combustion of the material and also prevent oxygen from continuously entering the combustion site of the material. Therefore, it can prevent the unburned part from burning.

[0141] Example 12

[0142] A preparation method of flame-retardant nylon 6, the specific steps are as follows:

[0143] (1) Prepare raw materials:

[0144] Caprolactam;

[0145] DOPO derivative dibasic acid A: DOPO-ITA;

[0146] Diamine: hexamethylenediamine;

[0147] Tetraphenyltin;

[0148] (2) Prepare flame-retardant nylon 6:

[0149] Add tetraphenyltin, caprolactam, DOPO derivative dibasic acid A, and diamine into a polymerization kettle, stir and mix at a rotation speed of 100 rpm, adjust the temperature to 260 °C after purging with nitrogen for 0.5 h, and continue the reaction for 10 h to obtain flame-retardant nylon 6; among them, the mass ratio of caprolactam, DOPO derivative dibasic acid A, and diamine is 93.3:5:1.7, and the dosage of tetraphenyltin is 0.8% of the total mass of the materials in the polymerization kettle.

[0150] Example 13

[0151] A preparation method of flame-retardant nylon 6, the specific steps are as follows:

[0152] (1) Prepare raw materials:

[0153] Caprolactam;

[0154] DOPO derivative dibasic acid A: DOPO-MA;

[0155] Diamine: hexamethylenediamine;

[0156] Tetraphenyltin;

[0157] (2) Preparation of flame-retardant nylon 6:

[0158] Add tetraphenyltin, caprolactam, DOPO derivative dibasic acid A, and diamine into the polymerization kettle, stir and mix at a speed of 100 rpm, adjust the temperature to 220 °C after purging with nitrogen for 0.5 h, and continue to react for 6 h to obtain flame-retardant nylon 6; among them, the mass ratio of caprolactam, DOPO derivative dibasic acid A, and diamine is 93.2:5:1.8, and the dosage of tetraphenyltin is 0.3% of the total mass of the materials in the polymerization kettle.

[0159] Example 14

[0160] A preparation method of flame-retardant nylon 6, the specific steps are as follows:

[0161] (1) Prepare raw materials:

[0162] Caprolactam;

[0163] DOPO derivative dibasic acid A: DOPO-MA;

[0164] Diamine: hexamethylenediamine;

[0165] Tetraphenyltin;

[0166] (2) Prepare flame-retardant nylon 6:

[0167] Add tetraphenyltin, caprolactam, DOPO derivative dibasic acid A, and diamine into the polymerization kettle, stir and mix at a speed of 100 rpm, adjust the temperature to 220 °C after purging with nitrogen for 0.5 h, and continue to react for 10 h to obtain flame-retardant nylon 6; among them, the mass ratio of caprolactam, DOPO derivative dibasic acid A, and diamine is 93.2:5:1.8, and the dosage of tetraphenyltin is 0.8% of the total mass of the materials in the polymerization kettle.

[0168] Example 15

[0169] A preparation method of flame-retardant nylon 6, the specific steps are as follows:

[0170] (1) Prepare raw materials:

[0171] Caprolactam;

[0172] DOPO derivative dibasic acid A: DOPO-MA;

[0173] Diamine: hexamethylenediamine;

[0174] Tetraphenyltin;

[0175] (2) Preparation of flame-retardant nylon 6:

[0176] Add tetraphenyltin, caprolactam, DOPO derivative dibasic acid A, and diamine into the polymerization kettle, stir and mix at a rotation speed of 100 rpm, adjust the temperature to 260 °C after purging with nitrogen for 0.5 h, and continue to react for 10 h to obtain flame-retardant nylon 6; among them, the mass ratio of caprolactam, DOPO derivative dibasic acid A, and diamine is 93.2:5:1.8, and the dosage of tetraphenyltin is 0.5% of the total mass of the materials in the polymerization kettle.

[0177] Example 16

[0178] A preparation method of flame-retardant nylon 6, the specific steps are as follows:

[0179] (1) Prepare raw materials:

[0180] Caprolactam;

[0181] DOPO derivative dibasic acid A: DOPO-ITA;

[0182] Diamine: p-phenylenediamine;

[0183] Tetraphenyltin;

[0184] (2) Preparation of flame-retardant nylon 6:

[0185] Add tetraphenyltin, caprolactam, DOPO derivative dibasic acid A, and diamine into the polymerization kettle, stir and mix at a rotation speed of 100 rpm, adjust the temperature to 220 °C after purging with nitrogen for 0.5 h, and continue to react for 10 h to obtain flame-retardant nylon 6; among them, the mass ratio of caprolactam, DOPO derivative dibasic acid A, and diamine is 93.4:5:1.6, and the dosage of tetraphenyltin is 0.3% of the total mass of the materials in the polymerization kettle.

[0186] Example 17

[0187] A preparation method of flame-retardant nylon 6, the specific steps are as follows:

[0188] (1) Prepare raw materials:

[0189] Caprolactam;

[0190] DOPO derivative dibasic acid A: DOPO-ITA;

[0191] Diamine: polyetheramine;

[0192] Tetraphenyltin;

[0193] (2) Preparation of flame-retardant nylon 6:

[0194] Add tetraphenyltin, caprolactam, DOPO derivative dibasic acid A, and diamine into a polymerization kettle, stir and mix at a rotation speed of 100 rpm. After purging with nitrogen for 0.5 h, adjust the temperature to 220 °C and continue the reaction for 10 h to obtain flame-retardant nylon 6. Among them, the mass ratio of caprolactam, DOPO derivative dibasic acid A, and diamine is 90:5:5, and the dosage of tetraphenyltin is 0.1% of the total mass of the materials in the polymerization kettle.

[0195] Example 18

[0196] A preparation method of flame-retardant nylon 6 is as follows:

[0197] (1) Prepare raw materials:

[0198] Caprolactam;

[0199] DOPO derivative dibasic acid A: DOPO-ITA;

[0200] Dibasic acid B: Adipic acid;

[0201] Diamine: Hexamethylenediamine;

[0202] Tetraphenyltin;

[0203] (2) Prepare flame-retardant nylon 6:

[0204] Add tetraphenyltin, caprolactam, DOPO derivative dibasic acid A, dibasic acid B, and diamine into a polymerization kettle, stir and mix at a rotation speed of 100 rpm. After purging with nitrogen for 0.5 h, adjust the temperature to 220 °C and continue the reaction for 6 h to obtain flame-retardant nylon 6. Among them, the mass ratio of caprolactam, DOPO derivative dibasic acid A, dibasic acid B, and diamine is 80:3:8.9:8.1, and the dosage of tetraphenyltin is 0.1% of the total mass of the materials in the polymerization kettle.

[0205] Example 19

[0206] A preparation method of flame-retardant nylon 6 is as follows:

[0207] (1) Prepare raw materials:

[0208] Caprolactam;

[0209] DOPO derivative dibasic acid A: DOPO-ITA;

[0210] Dibasic acid B: Adipic acid;

[0211] Diamine: Hexamethylenediamine;

[0212] Tetraphenyltin;

[0213] (2) Prepare flame-retardant nylon 6:

[0214] Add tetraphenyltin, caprolactam, DOPO derivative dibasic acid A, dibasic acid B, and diamine into a polymerization kettle, stir and mix at a rotation speed of 100 rpm. After purging with nitrogen for 0.5 h, adjust the temperature to 260 °C and continue the reaction for 6 h to obtain flame-retardant nylon 6. Among them, the mass ratio of caprolactam, DOPO derivative dibasic acid A, dibasic acid B, and diamine is 80:1.5:10:8.5, and the dosage of tetraphenyltin is 0.5% of the total mass of the materials in the polymerization kettle.

[0215] Example 20

[0216] A preparation method of flame-retardant nylon 6 is as follows:

[0217] (1) Prepare raw materials:

[0218] Caprolactam;

[0219] DOPO derivative dibasic acid A: DOPO-ITA;

[0220] Dibasic acid B: Adipic acid;

[0221] Diamine: Hexamethylenediamine;

[0222] Tetraphenyltin;

[0223] (2) Prepare flame-retardant nylon 6:

[0224] Add tetraphenyltin, caprolactam, DOPO derivative dibasic acid A, dibasic acid B, and diamine into a polymerization kettle, stir and mix at a rotation speed of 100 rpm. After purging with nitrogen for 0.5 h, adjust the temperature to 260 °C and continue the reaction for 10 h to obtain flame-retardant nylon 6. Among them, the mass ratio of caprolactam, DOPO derivative dibasic acid A, dibasic acid B, and diamine is 85:1.5:7.2:6.3, and the dosage of tetraphenyltin is 1% of the total mass of the materials in the polymerization kettle.

[0225] The performance test results of the nylon 6 prepared in Examples 1 to 20 are shown in Table 1:

[0226] Table 1

[0227]

[0228]

[0229]

[0230] In summary, it can be seen that in the present invention, the LOI value of the flame-retardant nylon 6 prepared can reach up to 34 at most, and the UL-94 can reach up to the V-0 level at most. The preparation method has many advantages such as a short process flow, no need to add organic solvents, easy operation in the process, low energy consumption, safe and efficient production process, green and environmental protection, and is suitable for large-scale industrialization. The preparation method of the present invention can efficiently and safely prepare materials of nylon 6 and its copolymers with excellent flame retardancy.

Claims

1. A preparation method of flame-retardant nylon 6, characterized in that, caprolactam, DOPO derivative dibasic acid A and diamine are mixed and reacted at 220 - 260 °C for 6 - 10 h to obtain flame-retardant nylon 6; the mass ratio of caprolactam, DOPO derivative dibasic acid A and diamine is 90 - 97.3:2 - 5:0.7 - 5; or, caprolactam, DOPO derivative dibasic acid A, dibasic acid B and diamine are mixed and reacted at 220 - 260 °C for 6 - 10 h to obtain flame-retardant nylon 6; the mass ratio of caprolactam, DOPO derivative dibasic acid A, dibasic acid B and diamine is 80 - 85:1.5 - 3:7.2 - 10:6.3 - 8.5; All DOPO derivative dibasic acid A is prepared from DOPO and dibasic acid C containing carbon-carbon double bond through Michael addition reaction, and dibasic acid C containing carbon-carbon double bond is itaconic acid or maleic anhydride.

2. A preparation method of flame-retardant nylon 6 according to claim 1, characterized in that, dibasic acid B is adipic acid, succinic acid, glutaric acid, terephthalic acid or isophthalic acid.

3. A preparation method of flame-retardant nylon 6 according to claim 1, characterized in that, diamine is ethylenediamine, propylenediamine, hexamethylenediamine, cyclohexanediamine, p-phenylenediamine, polyetheramine, 4,4'-methylenedianiline or 2,2-bis[4-(4-aminophenoxy)phenyl]propane.

4. A preparation method of flame-retardant nylon 6 according to claim 3, characterized in that, diamine is hexamethylenediamine, p-phenylenediamine or polyetheramine.

5. A preparation method of flame-retardant nylon 6 according to claim 1, characterized in that, all mixing is carried out by mechanical stirring, and the rotation speed of mechanical stirring is 10 - 100 rpm.

6. Flame-retardant nylon 6 prepared by using the preparation method of flame-retardant nylon 6 according to any one of claims 1 - 5, characterized in that, the relative viscosity of flame-retardant nylon 6 is 1.57 - 2.45, the weight-average molecular weight is 21000 - 37200 g / mol, the number-average molecular weight is 8500 - 16600 g / mol, the polydispersity index is 2.14 - 2.97, the limiting oxygen index is 26 - 34%, and UL-94 reaches V-0 or V-1 level.

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