Flame-retardant PA6 composite material and preparation method thereof, and phosphorus-nitrogen flame retardant and preparation method thereof

Abstract

The invention discloses a flame-retardant PA6 composite material and a preparation method thereof, and a phosphorus-nitrogen flame retardant and a preparation method thereof. The preparation method of the flame-retardant PA6 composite material comprises the following steps: placing dried PA6 in a main feeding port of a double-screw extruder, placing a phosphorus-nitrogen flame retardant and a catalyst in a side feeding port, carrying out melt blending and in-situ reaction on the PA6, the phosphorus-nitrogen flame retardant and the catalyst at the temperature of 220-240 DEG C and the rotating speed of screws of 80-85 rpm, extruding through a machine head, cooling, and pelletizing to obtain the flame-retardant PA6 composite material. The flame-retardant PA6 composite material is obtained; the phosphorus-nitrogen flame retardant is a phosphorus-nitrogen flame retardant with a terminal hydroxyl group or a terminal carboxyl group. According to the invention, chemical bond connection between the flame retardant and a PA6 molecular chain is realized, the intrinsic flame-retardant PA6 composite material is obtained, and the negative influence on the mechanical properties of the flame-retardant PA6 composite material is reduced while the flame-retardant property of the PA6 composite material is improved.

Description

Technical Field

[0001] The invention relates to the field of nylon preparation, and in particular to a flame-retardant PA6 composite material and a preparation method thereof, a phosphorus-nitrogen flame retardant and a preparation method thereof. Background Art

[0002] Nylon 6 (PA6) is prepared by polymerizing ε-caprolactam monomers and is one of the most widely used engineering plastics. PA6 is widely used in automobile manufacturing, electronic appliances, construction materials and other fields due to its excellent mechanical properties, wear resistance, electrical insulation and easy processing. However, due to the flammability of PA6 itself and the serious droplet phenomenon during the combustion process, it has certain fire safety hazards. Therefore, how to improve the flame retardant properties of PA6 has become an important topic in PA6 research.

[0003] In order to solve the flammability problem of PA6, it can be flame-retardant modified by copolymerization and blending. Copolymerization refers to the polymerization of flame retardant monomers and PA6 monomers to embed or graft the flame retardant onto the PA6 chain. The composite material prepared by this method has good flame retardant properties, but the chemical synthesis process is relatively complex and the production cost is high. Blending refers to the compounding of flame retardants and PA6 by melt blending. This method is currently the main way to flame retard PA6, and it is simple to operate and has low production costs, but due to the compatibility of flame retardants with PA6 matrix, the mechanical properties of the flame-retardant PA6 composite material obtained by blending are poor. Summary of the invention

[0004] In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the object of the present invention is to provide a method for preparing a flame-retardant PA6 composite material, wherein the flame retardant prepared by the present invention is added to a PA6 matrix by melt blending, and based on the inevitable degradation of PA6 during the melt processing, the flame retardant reacts chemically with the end groups (amino groups, carboxyl groups) of the degraded PA6 to achieve chemical bond connection between the flame retardant and the PA6 molecular chain, thereby obtaining an intrinsic flame-retardant PA6 composite material, thereby improving the flame retardant properties of the PA6 composite material and reducing the negative impact on the mechanical properties of the flame-retardant PA6 composite material.

[0005] Another object of the present invention is to provide a flame retardant PA6 composite material.

[0006] Another object of the present invention is to provide a method for preparing a phosphorus-nitrogen flame retardant.

[0007] Another object of the present invention is to provide a phosphorus-nitrogen flame retardant.

[0008] The purpose of the present invention is achieved through the following technical solutions:

[0009] The present invention provides a method for preparing a flame retardant PA6 composite material, comprising the following steps:

[0010] The dried PA6 is placed in the main feeding port of the twin-screw extruder, and the phosphorus-nitrogen flame retardant and the catalyst are placed in the side feeding port. The extruder temperature is 220-240°C, the screw speed is 80-85rpm, PA6, the phosphorus-nitrogen flame retardant and the catalyst are melt-blended, reacted in situ, and then extruded through a die, cooled, and pelletized to obtain a flame-retardant PA6 composite material; wherein the mass ratio of the phosphorus-nitrogen flame retardant to PA6 is 1:3-1:5.

[0011] Preferably, the mass ratio of phosphorus nitrogen flame retardant to PA6 is 1:4; the optimal extruder temperature is 230° C., and the screw speed is 80 rpm.

[0012] The preparation of the phosphorus-nitrogen flame retardant is as follows:

[0013] Dissolve vanillin in an anhydrous organic solvent and keep the temperature at -2-2°C; then add an alkaline reagent to adjust the pH value to 7-8, add dichlorophosphate dropwise under stirring, gradually raise the temperature to 20-30°C, and continue to stir the reaction. The reaction temperature is 20-30°C and the reaction time is 3-5h; after the reaction is completed, add water to the reaction system to quench the reaction, extract the reaction product with organic matter, dry the organic matter containing the reaction product with anhydrous sodium sulfate, and remove the solvent by rotary evaporation to obtain an intermediate product;

[0014] Dissolve ethylenediamine in an anhydrous solvent and stir to obtain an ethylenediamine solution; dissolve the intermediate product in an anhydrous solvent, add it to the ethylenediamine solution, heat it to 40-60° C. and react for 4-6 hours; after the reaction is completed, filter, wash with anhydrous ethanol, and dry in vacuum to obtain a phosphorus nitrogen flame retardant.

[0015] Preferably, the catalyst is at least one of an organic titanium compound or an organic tin compound; more preferably, the organic titanium compound is titanium tetrachloride; and the organic tin compound is tetrabutyltin chloride.

[0016] Preferably, the mass ratio of the catalyst to the phosphorus-nitrogen flame retardant is 1:15-1:25.

[0017] Preferably, the dichlorophosphate is at least one of dichloromethylphosphine, dichloroethylphosphoric acid, and dichloroethylphosphoric acid.

[0018] Preferably, the molar ratio of dichlorophosphate to vanillin is 1:2-1:3.

[0019] Preferably, the molar ratio of ethylenediamine to the intermediate product is 2:1-3:1.

[0020] Preferably, the anhydrous solvent is at least one of ethanol and acetone.

[0021] Preferably, the volume ratio of the anhydrous solvent to vanillin is controlled at 15:1-25:1, and the optimal ratio is 20:1; the alkaline reagent can be triethylamine or pyridine, and the molar ratio of the alkaline reagent to vanillin is controlled at 1.1:1-1.5:1, and the optimal ratio is 1.2:1.

[0022] Preferably, the organic matter used for extraction is one or a combination of two or more of ethanol, acetone, etc.; the temperature of rotary evaporation is 30-40°C, and the optimal temperature is 30°C.

[0023] Preferably, the volume ratio of the anhydrous solvent to ethylenediamine or the intermediate product is controlled at 15:1-25:1, and the optimal volume ratio is 20:1.

[0024] Preferably, the vacuum drying temperature is 70-90°C, the drying time is 3-5h, the optimal drying temperature is 80°C, and the optimal drying time is 4h.

[0025] The present invention also provides a flame retardant PA6 composite material, which is prepared by the preparation method of the flame retardant PA6 composite material.

[0026] The present invention also provides a method for preparing a phosphorus-nitrogen flame retardant, comprising the following steps:

[0027] Dissolve vanillin in an anhydrous organic solvent and keep the temperature at -2-2°C; then add an alkaline reagent to adjust the pH value to 7-8, add dichlorophosphate dropwise under stirring, gradually raise the temperature to 20-30°C, and continue to stir the reaction. The reaction temperature is 20-30°C and the reaction time is 3-5h; after the reaction is completed, add water to the reaction system to quench the reaction, extract the reaction product with organic matter, dry the organic matter containing the reaction product with anhydrous sodium sulfate, and remove the solvent by rotary evaporation to obtain an intermediate product;

[0028] Dissolve ethylenediamine in an anhydrous solvent and stir to obtain an ethylenediamine solution; dissolve the intermediate product in an anhydrous solvent, add it to the ethylenediamine solution, heat it to 40-60° C. and react for 4-6 hours; after the reaction is completed, filter, wash with anhydrous ethanol, and dry in vacuum to obtain a phosphorus nitrogen flame retardant.

[0029] The invention also provides a phosphorus-nitrogen flame retardant, which is prepared by the preparation method of the phosphorus-nitrogen flame retardant.

[0030] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0031] (1) The present invention improves the mechanical properties of the flame-retardant PA6 composite material through the chain extension effect of the flame retardant in PA6, reduces the amount of the flame retardant leaching out of the PA6 matrix, and improves the migration resistance of the flame retardant in the PA6 matrix.

[0032] (2) In the present invention, the prepared phosphorus-nitrogen flame retardant is introduced into the PA6 molecular chain under the action of a catalyst during the thermal processing process. The present invention has a simple operation method and connects the flame retardant and PA6 through chemical bonds, thereby improving the compatibility of the flame retardant in PA6.

[0033] (3) The present invention designs and synthesizes a phosphorus-nitrogen flame retardant having a terminal hydroxyl group or a terminal carboxyl group, and utilizes the characteristic that PA6 is easily degraded to generate a terminal amino group and a terminal carboxyl group during thermal processing, so that the terminal hydroxyl group or the terminal carboxyl group in the phosphorus-nitrogen flame retardant and the terminal amino group and the terminal carboxyl group in PA6 undergo amidation reaction again under heating conditions, thereby obtaining an intrinsically flame-retardant PA6 composite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The figure is a preparation route of the phosphorus-nitrogen flame retardant according to an embodiment of the present invention.

[0035] Figure 2 This is a preparation route map of the flame retardant PA6 composite material according to an embodiment of the present invention. DETAILED DESCRIPTION

[0036] The present invention will be further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

[0037] In the following examples, the sample preparation methods for various performance tests are as follows:

[0038] The flame retardant PA6 composite material extruded from the extruder is cooled by a water trough, a water curtain or a cooling roller and solidified. Then, the solidified strips are cut into uniform small particles by a pelletizer and dried in an oven at 80°C for 12 hours to remove moisture. The flame retardant PA6 composite pellets are pressed and molded by a press to prepare test specimens of different sizes, such as 125mm×4mm×1.6mm (tensile properties), 125mm×3mm×13mm (vertical combustion), 130mm×6.5mm×3.2mm (oxygen index) and 100mm×100mm×3mm (cone calorimetry). Among them, the parameters of the press are pre-pressing time 3min, pre-pressing temperature 230°C, pre-pressing pressure 5MPa, hot pressing time 10min, hot pressing temperature 230°C, and hot pressing pressure 10MPa.

[0039] In the following examples, vanillin has the following structure:

[0040]

[0041] Dichlorophosphate has the following structure:

[0042]

[0043] in,

[0044] Ethylenediamine has the following structure:

[0045]

[0046] Example 1

[0047] like Figure 1 As shown, the preparation method of phosphorus nitrogen flame retardant is as follows:

[0048] (1) Dissolve vanillin (30.43 g, 0.2 mol) in 80 mL of anhydrous dichloromethane and keep the temperature at 0°C. Then slowly add triethylamine (24.29, 0.24 mol) to adjust the pH value, and add dichloromethylphosphine (13.29 g, 0.1 mol) dropwise under stirring. Finally, gradually raise the temperature to 25°C and continue stirring for 4 hours to ensure that the reaction is complete.

[0049] (2) After the reaction was completed, 10 mL of water was added to the reaction system to quench the reaction. The reaction mixture was extracted with dichloromethane (3×10 mL), dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation at 30° C. to obtain an intermediate product.

[0050] (3) Under stirring, ethylenediamine (12.02 g, 0.2 mol) was dissolved in 50 mL of anhydrous ethanol. The intermediate product (36.43 g, 0.1 mol) was dissolved in 80 mL of anhydrous ethanol, and then slowly added to the ethylenediamine solution, stirred evenly, and heated to 50°C and stirred for 5 hours. After the reaction was completed, the mixture was filtered, washed three times with anhydrous ethanol, and vacuum dried at 80°C for 4 hours to obtain a phosphorus nitrogen flame retardant.

[0051] like Figure 2 As shown, the preparation method of the flame retardant PA6 composite material is as follows:

[0052] (1) Nylon 6 (160 g), titanium tetrachloride (2 g) and the phosphorus-nitrogen flame retardant prepared in the present invention (40 g) were dried in an oven at 80° C. for 12 h to remove moisture.

[0053] (2) PA6 is placed in the main feed of a twin-screw extruder, and the phosphorus-nitrogen flame retardant and titanium tetrachloride prepared by the present invention are placed in the side feed. At 230° C. and 80 rpm, the mixture is melt-blended and reacted in situ, and then extruded through a die to obtain a flame-retardant PA6 composite material.

[0054] Example 2

[0055] The preparation method of phosphorus nitrogen flame retardant is as follows:

[0056] (1) Dissolve vanillin (30.43 g, 0.2 mol) in 80 mL of anhydrous dichloromethane and keep the temperature at 0°C. Then slowly add triethylamine (24.29, 0.24 mol) to adjust the pH value, and add dichloroethylphosphoric acid (14.69 g, 0.1 mol) dropwise under stirring. Finally, gradually raise the temperature to 25°C and continue stirring for 4 hours to ensure that the reaction is complete.

[0057] (2) After the reaction was completed, 10 mL of water was added to the reaction system to quench the reaction. The reaction mixture was extracted with dichloromethane (3×10 mL), dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation at 30° C. to obtain an intermediate product.

[0058] (3) Under stirring, ethylenediamine (12.02 g, 0.2 mol) was dissolved in 50 mL of anhydrous ethanol. The intermediate product (37.83 g, 0.1 mol) was dissolved in 80 mL of anhydrous ethanol, and then slowly added to the ethylenediamine solution, stirred evenly, and heated to 50°C and stirred for 5 hours. After the reaction was completed, the mixture was filtered, washed three times with anhydrous ethanol, and vacuum dried at 80°C for 4 hours to obtain a phosphorus nitrogen flame retardant.

[0059] The preparation method of flame retardant PA6 composite material is as follows:

[0060] (1) Nylon 6 (160 g), titanium tetrachloride (2 g) and the phosphorus-nitrogen flame retardant prepared in the present invention (40 g) were dried in an oven at 80° C. for 12 h to remove moisture.

[0061] (2) PA6 is placed in the main feed of a twin-screw extruder, and the phosphorus-nitrogen flame retardant and titanium tetrachloride prepared by the present invention are placed in the side feed. At 230° C. and 80 rpm, the mixture is melt-blended and reacted in situ, and then extruded through a die to obtain a flame-retardant PA6 composite material.

[0062] Example 3

[0063] The preparation method of phosphorus nitrogen flame retardant is as follows:

[0064] (1) Dissolve vanillin (30.43 g, 0.2 mol) in 80 mL of anhydrous dichloromethane and keep the temperature at 0°C. Then slowly add triethylamine (24.29, 0.24 mol) to adjust the pH value, and add ethyl dichlorophosphate (16.29 g, 0.1 mol) dropwise under stirring. Finally, gradually raise the temperature to 25°C and continue stirring for 4 hours to ensure that the reaction is complete.

[0065] (2) After the reaction was completed, 10 mL of water was added to the reaction system to quench the reaction. The reaction mixture was extracted with dichloromethane (3×10 mL), dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation at 30° C. to obtain an intermediate product.

[0066] (3) Under stirring, ethylenediamine (12.02 g, 0.2 mol) was dissolved in 50 mL of anhydrous ethanol. The intermediate product (39.43 g, 0.1 mol) was dissolved in 80 mL of anhydrous ethanol, and then slowly added to the ethylenediamine solution, stirred evenly, and heated to 50°C and stirred for 5 hours. After the reaction was completed, the mixture was filtered, washed three times with anhydrous ethanol, and vacuum dried at 80°C for 4 hours to obtain a phosphorus nitrogen flame retardant.

[0067] The preparation method of flame retardant PA6 composite material is as follows:

[0068] (1) Nylon 6 (160 g), titanium tetrachloride (2 g) and the phosphorus-nitrogen flame retardant prepared in the present invention (40 g) were dried in an oven at 80° C. for 12 h to remove moisture.

[0069] (2) PA6 is placed in the main feed of a twin-screw extruder, and the phosphorus-nitrogen flame retardant and titanium tetrachloride prepared by the present invention are placed in the side feed. At 230° C. and 80 rpm, the mixture is melt-blended and reacted in situ, and then extruded through a die to obtain a flame-retardant PA6 composite material.

[0070] Example 4

[0071] The preparation method of phosphorus nitrogen flame retardant is as follows:

[0072] (1) Dissolve vanillin (30.43 g, 0.2 mol) in 80 mL of anhydrous dichloromethane and keep the temperature at 0°C. Then slowly add triethylamine (24.29, 0.24 mol) to adjust the pH value, and add phenyl dichlorophosphate (21.10 g, 0.1 mol) dropwise under stirring. Finally, gradually raise the temperature to 25°C and continue stirring for 4 hours to ensure that the reaction is complete.

[0073] (2) After the reaction was completed, 10 mL of water was added to the reaction system to quench the reaction. The reaction mixture was extracted with dichloromethane (3×10 mL), dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation at 30° C. to obtain an intermediate product.

[0074] (3) Under stirring, ethylenediamine (12.02 g, 0.2 mol) was dissolved in 50 mL of anhydrous ethanol. The intermediate product (44.24 g, 0.1 mol) was dissolved in 80 mL of anhydrous ethanol, and then slowly added to the ethylenediamine solution, stirred evenly, and heated to 50°C and stirred for 5 hours. After the reaction was completed, the mixture was filtered, washed three times with anhydrous ethanol, and vacuum dried at 80°C for 4 hours to obtain a phosphorus nitrogen flame retardant.

[0075] The preparation method of flame retardant PA6 composite material is as follows:

[0076] (1) Nylon 6 (160 g), titanium tetrachloride (2 g) and the phosphorus-nitrogen flame retardant prepared in the present invention (40 g) were dried in an oven at 80° C. for 12 h to remove moisture.

[0077] (2) PA6 is placed in the main feed of a twin-screw extruder, and the phosphorus-nitrogen flame retardant and titanium tetrachloride prepared by the present invention are placed in the side feed. At 230° C. and 80 rpm, the mixture is melt-blended and reacted in situ, and then extruded through a die to obtain a flame-retardant PA6 composite material.

[0078] Example 5

[0079] The preparation method of phosphorus nitrogen flame retardant is as follows:

[0080] (1) Dissolve vanillin (30.43 g, 0.2 mol) in 80 mL of anhydrous dichloromethane and keep the temperature at 0°C. Then slowly add triethylamine (24.29, 0.24 mol) to adjust the pH value, and add dichloromethylphosphine (13.29 g, 0.1 mol) dropwise under stirring. Finally, gradually raise the temperature to 25°C and continue stirring for 4 hours to ensure that the reaction is complete.

[0081] (2) After the reaction was completed, 10 mL of water was added to the reaction system to quench the reaction. The reaction mixture was extracted with dichloromethane (3×10 mL), dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation at 30° C. to obtain an intermediate product.

[0082] (3) Under stirring, ethylenediamine (12.02 g, 0.2 mol) was dissolved in 50 mL of anhydrous ethanol. The intermediate product (36.43 g, 0.1 mol) was dissolved in 80 mL of anhydrous ethanol, and then slowly added to the ethylenediamine solution, stirred evenly, and heated to 50°C and stirred for 5 hours. After the reaction was completed, the mixture was filtered, washed three times with anhydrous ethanol, and vacuum dried at 80°C for 4 hours to obtain a phosphorus nitrogen flame retardant.

[0083] The preparation method of flame retardant PA6 composite material is as follows:

[0084] (1) Nylon 6 (160 g), tetrabutyltin chloride (2 g) and the phosphorus-nitrogen flame retardant prepared in the present invention (40 g) were dried in an oven at 80° C. for 12 h to remove moisture.

[0085] (2) PA6 is placed in the main feed of a twin-screw extruder, and the phosphorus-nitrogen flame retardant and tetrabutyltin chloride prepared by the present invention are placed in the side feed. At 230° C. and 80 rpm, the mixture is melt-blended and reacted in situ, and then extruded through a die to obtain a flame-retardant PA6 composite material.

[0086] Example 6

[0087] The preparation method of phosphorus nitrogen flame retardant is as follows:

[0088] (1) Dissolve vanillin (30.43 g, 0.2 mol) in 80 mL of anhydrous dichloromethane and keep the temperature at 0°C. Then slowly add triethylamine (24.29, 0.24 mol) to adjust the pH value, and add dichloroethylphosphoric acid (14.69 g, 0.1 mol) dropwise under stirring. Finally, gradually raise the temperature to 25°C and continue stirring for 4 hours to ensure that the reaction is complete.

[0089] (2) After the reaction was completed, 10 mL of water was added to the reaction system to quench the reaction. The reaction mixture was extracted with dichloromethane (3×10 mL), dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation at 30° C. to obtain an intermediate product.

[0090] (3) Under stirring, ethylenediamine (12.02 g, 0.2 mol) was dissolved in 50 mL of anhydrous ethanol. The intermediate product (37.83 g, 0.1 mol) was dissolved in 80 mL of anhydrous ethanol, and then slowly added to the ethylenediamine solution, stirred evenly, and heated to 50°C and stirred for 5 hours. After the reaction was completed, the mixture was filtered, washed three times with anhydrous ethanol, and vacuum dried at 80°C for 4 hours to obtain a phosphorus nitrogen flame retardant.

[0091] The preparation method of flame retardant PA6 composite material is as follows:

[0092] (1) Nylon 6 (160 g), tetrabutyltin chloride (2 g) and the phosphorus-nitrogen flame retardant prepared in the present invention (40 g) were dried in an oven at 80° C. for 12 h to remove moisture.

[0093] (2) PA6 is placed in the main feed of a twin-screw extruder, and the phosphorus-nitrogen flame retardant and tetrabutyltin chloride prepared by the present invention are placed in the side feed. At 230° C. and 80 rpm, the mixture is melt-blended and reacted in situ, and then extruded through a die to obtain a flame-retardant PA6 composite material.

[0094] Example 7

[0095] The preparation method of phosphorus nitrogen flame retardant is as follows:

[0096] (1) Dissolve vanillin (30.43 g, 0.2 mol) in 80 mL of anhydrous dichloromethane and keep the temperature at 0°C. Then slowly add triethylamine (24.29, 0.24 mol) to adjust the pH value, and add ethyl dichlorophosphate (16.29 g, 0.1 mol) dropwise under stirring. Finally, gradually raise the temperature to 25°C and continue stirring for 4 hours to ensure that the reaction is complete.

[0097] (2) After the reaction was completed, 10 mL of water was added to the reaction system to quench the reaction. The reaction mixture was extracted with dichloromethane (3×10 mL), dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation at 30° C. to obtain an intermediate product.

[0098] (3) Under stirring, ethylenediamine (12.02 g, 0.2 mol) was dissolved in 50 mL of anhydrous ethanol. The intermediate product (39.43 g, 0.1 mol) was dissolved in 80 mL of anhydrous ethanol, and then slowly added to the ethylenediamine solution, stirred evenly, and heated to 50°C and stirred for 5 hours. After the reaction was completed, the mixture was filtered, washed three times with anhydrous ethanol, and vacuum dried at 80°C for 4 hours to obtain a phosphorus nitrogen flame retardant.

[0099] The preparation method of flame retardant PA6 composite material is as follows:

[0100] (1) Nylon 6 (160 g), tetrabutyltin chloride (2 g) and the phosphorus-nitrogen flame retardant prepared in the present invention (40 g) were dried in an oven at 80° C. for 12 h to remove moisture.

[0101] (2) PA6 is placed in the main feed of a twin-screw extruder, and the phosphorus-nitrogen flame retardant and tetrabutyltin chloride prepared by the present invention are placed in the side feed. At 230° C. and 80 rpm, the mixture is melt-blended and reacted in situ, and then extruded through a die to obtain a flame-retardant PA6 composite material.

[0102] Example 8

[0103] The preparation method of phosphorus nitrogen flame retardant is as follows:

[0104] (1) Dissolve vanillin (30.43 g, 0.2 mol) in 80 mL of anhydrous dichloromethane and keep the temperature at 0°C. Then slowly add triethylamine (24.29, 0.24 mol) to adjust the pH value, and add phenyl dichlorophosphate (21.10 g, 0.1 mol) dropwise under stirring. Finally, gradually raise the temperature to 25°C and continue stirring for 4 hours to ensure that the reaction is complete.

[0105] (2) After the reaction was completed, 10 mL of water was added to the reaction system to quench the reaction. The reaction mixture was extracted with dichloromethane (3×10 mL), dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation at 30° C. to obtain an intermediate product.

[0106] (3) Under stirring, ethylenediamine (12.02 g, 0.2 mol) was dissolved in 50 mL of anhydrous ethanol. The intermediate product (44.24 g, 0.1 mol) was dissolved in 80 mL of anhydrous ethanol, and then slowly added to the ethylenediamine solution, stirred evenly, and heated to 50°C and stirred for 5 hours. After the reaction was completed, the mixture was filtered, washed three times with anhydrous ethanol, and vacuum dried at 80°C for 4 hours to obtain a phosphorus nitrogen flame retardant.

[0107] The preparation method of flame retardant PA6 composite material is as follows:

[0108] (1) Nylon 6 (160 g), tetrabutyltin chloride (2 g) and the phosphorus-nitrogen flame retardant prepared in the present invention (40 g) were dried in an oven at 80° C. for 12 h to remove moisture.

[0109] (2) PA6 is placed in the main feed of a twin-screw extruder, and the phosphorus-nitrogen flame retardant and tetrabutyltin chloride prepared by the present invention are placed in the side feed. At 230° C. and 80 rpm, the mixture is melt-blended and reacted in situ, and then extruded through a die to obtain a flame-retardant PA6 composite material.

[0110] Comparative Example 1

[0111] The formula of the PA6 composite material of this comparative example is: 80wt% of PA6 material and 20wt% of dimethyl methyl phosphate, calculated by mass fraction. The preparation process is the same as that of the embodiment.

[0112] Comparative Example 2

[0113] The formula of the PA6 composite material of this comparative example is: calculated by mass fraction, PA6 material 80wt%, ammonium polyphosphate 20wt%. The preparation process is the same as that of the embodiment.

[0114] Example, comparative example performance test results

[0115] Performance test: refer to the national standards "GB / T 1040 Determination of tensile properties", "GB 2409-84 Vertical combustion method", "GB / T 5454-1997 Combustion performance experiment oxygen index method" and "SN / T 5240-2020 Cone calorimeter method".

[0116] Tensile property test: A sample of 125 mm × 4 mm × 1.6 mm was clamped on a tensile testing machine using a clamp, and the tensile strength and elongation at break of the sample were read by the tensile testing machine.

[0117] Vertical combustion method: Prepare a sample strip of 125mm×3mm×13mm. The distance between the top of the burner and the bottom of the sample is 10mm. Record the time from exposure to flame to extinguishment after withdrawal twice to determine the flame retardant performance level.

[0118] Oxygen index method: Place a 130mm×6.5mm×3.2mm sample vertically in the center of a glass chimney and ignite the top of the sample with a burner. Record the minimum oxygen concentration required to make the sample burn.

[0119] Cone calorimeter method: A 100mm×100mm×3mm sample is exposed to a conical radiation electric heater and combustion is triggered by an electric spark. The heat release rate and peak heat release rate are calculated by measuring the gas flow rate and oxygen concentration.

[0120] The results are shown in Tables 1 and 2.

[0121] Table 1. PA6 composite material performance test results

[0122]

[0123] Table 2. Cone calorimetry results for PA6 composites

[0124]

[0125] It can be seen from the above examples that by adding the phosphorus-nitrogen flame retardant prepared by the present invention, the flame-retardant PA6 composite material has excellent tensile strength, flame retardant properties and limiting oxygen index, which can reach up to 96 MPa, reaching V-0 grade, and the oxygen index reaches 31.4%.

[0126] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing a flame retardant PA6 composite material, characterized in that: The following steps are involved: The dried PA6 is placed in the main feeding port of the twin-screw extruder, and the phosphorus nitrogen flame retardant and the catalyst are placed in the side feeding port. The extruder temperature is 220-240°C, the screw speed is 80-85rpm, PA6, phosphorus nitrogen flame retardant and catalyst are melt-blended, reacted in situ, and then extruded through the die, cooled, and pelletized to obtain a flame-retardant PA6 composite material; wherein the mass ratio of the phosphorus nitrogen flame retardant to PA6 is 1:3-1:5; The preparation of the phosphorus-nitrogen flame retardant is as follows: Dissolve vanillin in an anhydrous organic solvent and keep the temperature at -2-2°C; then add an alkaline reagent to adjust the pH value to 7-8, add dichlorophosphate dropwise under stirring, gradually raise the temperature to 20-30°C, and continue to stir the reaction. The reaction temperature is 20-30°C and the reaction time is 3-5h; after the reaction is completed, add water to the reaction system to quench the reaction, extract the reaction product with organic matter, dry the organic matter containing the reaction product with anhydrous sodium sulfate, and remove the solvent by rotary evaporation to obtain an intermediate product; Dissolve ethylenediamine in an anhydrous solvent and stir to obtain an ethylenediamine solution; dissolve the intermediate product in an anhydrous solvent, add it to the ethylenediamine solution, heat it to 40-60° C. and react for 4-6 hours; after the reaction is completed, filter, wash with anhydrous ethanol, and dry in vacuum to obtain a phosphorus nitrogen flame retardant.

2. The method for preparing the flame retardant PA6 composite material according to claim 1, characterized in that: The catalyst is at least one of an organic titanium compound or an organic tin compound.

3. The method for preparing the flame-retardant PA6 composite material according to claim 1 or 2, characterized in that: The mass ratio of the catalyst to the phosphorus nitrogen flame retardant is 1:15-1:

25.

4. The method for preparing the flame-retardant PA6 composite material according to claim 1, characterized in that: The dichlorophosphate is at least one of dichloromethylphosphine, dichloroethylphosphoric acid, and dichloroethylphosphoric acid.

5. The method for preparing the flame retardant PA6 composite material according to claim 4, characterized in that: The molar ratio of dichlorophosphate to vanillin is 1:2-1:

3.

6. The method for preparing the flame retardant PA6 composite material according to claim 1, characterized in that: The molar ratio of the ethylenediamine to the intermediate product is 2:1-3:

1.

7. The method for preparing the flame-retardant PA6 composite material according to claim 1, characterized in that: The anhydrous solvent is at least one of ethanol and acetone.

8. A flame retardant PA6 composite material, characterized in that: The flame retardant PA6 composite material is prepared by the preparation method of any one of claims 1 to 7.

9. A method for preparing a phosphorus-nitrogen flame retardant, characterized in that: The following steps are involved: Dissolve vanillin in an anhydrous organic solvent and keep the temperature at -2-2°C; then add an alkaline reagent to adjust the pH value to 7-8, add dichlorophosphate dropwise under stirring, gradually raise the temperature to 20-30°C, and continue to stir the reaction. The reaction temperature is 20-30°C and the reaction time is 3-5h; after the reaction is completed, add water to the reaction system to quench the reaction, extract the reaction product with organic matter, dry the organic matter containing the reaction product with anhydrous sodium sulfate, and remove the solvent by rotary evaporation to obtain an intermediate product; Dissolve ethylenediamine in an anhydrous solvent and stir to obtain an ethylenediamine solution; dissolve the intermediate product in an anhydrous solvent, add it to the ethylenediamine solution, heat it to 40-60° C. and react for 4-6 hours; after the reaction is completed, filter, wash with anhydrous ethanol, and dry in vacuum to obtain a phosphorus nitrogen flame retardant.

10. A phosphorus-nitrogen flame retardant prepared by the method for preparing the phosphorus-nitrogen flame retardant according to claim 9.

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