A flame-retardant PA6 composite material and its preparation method, and a phosphorus-nitrogen flame retardant and its preparation method.

Abstract

This invention discloses a flame-retardant PA6 composite material and its preparation method, as well as a phosphorus-nitrogen flame retardant and its preparation method. The preparation method of the flame-retardant PA6 composite material includes the following steps: dried PA6 is placed in the main feed inlet of a twin-screw extruder, and the phosphorus-nitrogen flame retardant and catalyst are placed in the side feed inlet. The extruder temperature is 220–240°C, and the screw speed is 80–85 rpm. PA6, the phosphorus-nitrogen flame retardant, and the catalyst are melt-blended and reacted in situ. The mixture is then extruded through a die, cooled, and pelletized to obtain the flame-retardant PA6 composite material. The phosphorus-nitrogen flame retardant is a phosphorus-nitrogen flame retardant with terminal hydroxyl or carboxyl groups. This invention achieves chemical bonding between the flame retardant and the PA6 molecular chain, obtaining an intrinsically flame-retardant PA6 composite material. This improves the flame-retardant properties of the PA6 composite material while reducing the negative impact on its mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of nylon preparation, and particularly to a flame-retardant PA6 composite material and its preparation method, and a phosphorus-nitrogen flame retardant and its preparation method. Background Technology

[0002] Nylon 6 (PA6) is prepared by polymerization of ε-caprolactam monomers and is one of the most widely used engineering plastics. PA6 is widely used in automotive manufacturing, electronics, and building materials due to its excellent mechanical properties, abrasion resistance, electrical insulation, and ease of processing. However, due to its inherent flammability and severe dripping during combustion, PA6 poses a certain fire safety hazard. Therefore, improving the flame retardant properties of PA6 has become an important research topic.

[0003] To address the flammability issue of PA6, flame-retardant modification can be achieved through copolymerization and blending. Copolymerization involves co-polymerizing flame-retardant monomers with PA6 monomers, embedding or grafting the flame-retardant onto the PA6 chains. Composites prepared using this method exhibit good flame-retardant properties, but the chemical synthesis process is complex and production costs are high. Blending involves combining flame-retardant agents and PA6 through melt blending. This method is currently the main approach for PA6 flame retardancy, offering simplicity and lower production costs. However, due to the compatibility between the flame-retardant agent and the PA6 matrix, the resulting flame-retardant PA6 composites exhibit poor mechanical properties. Summary of the Invention

[0004] To overcome the aforementioned shortcomings and deficiencies of the prior art, the present invention aims to provide a method for preparing flame-retardant PA6 composite materials. The flame retardant prepared according to the present invention is added to the PA6 matrix through melt blending. Based on the inevitable degradation of PA6 during melt processing, the flame retardant reacts chemically with the end groups (amino and carboxyl groups) of the degraded PA6, achieving chemical bonding between the flame retardant and the PA6 molecular chain, thus obtaining an intrinsically flame-retardant PA6 composite material. This method improves the flame-retardant properties of the PA6 composite material while reducing the negative impact on its mechanical properties.

[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 objective of this invention is achieved through the following technical solution:

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

[0010] The dried PA6 is placed in the main feed inlet of a twin-screw extruder, and the phosphorus-nitrogen flame retardant and catalyst are placed in the side feed inlet. The extruder temperature is 220-240℃ and the screw speed is 80-85 rpm. PA6, phosphorus-nitrogen flame retardant and catalyst are melt-blended and reacted in situ. The mixture is then extruded through the die head, cooled and pelletized to obtain a flame-retardant PA6 composite material. 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 phosphorus-nitrogen flame retardant is prepared as follows:

[0013] Vanillin was dissolved in an anhydrous organic solvent and the temperature was maintained at -2 to -2℃. Then, an alkaline reagent was added to adjust the pH to 7 to 8. Dichlorophosphate was added dropwise while stirring, and the temperature was gradually raised to 20 to 30℃. The reaction was stirred continuously for 3 to 5 hours. After the reaction was completed, water was added to the reaction system to quench the reaction. The reaction product was extracted with organic matter. The organic matter containing the reaction product was dried with anhydrous sodium sulfate and the solvent was removed by rotary evaporation to obtain the intermediate product.

[0014] Ethylenediamine was dissolved in an anhydrous solvent and stirred to obtain an ethylenediamine solution; the intermediate product was dissolved in an anhydrous solvent and added to the ethylenediamine solution, and the mixture was heated to 40-60℃ and reacted for 4-6 hours; after the reaction was completed, the mixture was filtered, washed with anhydrous ethanol, and dried under vacuum to obtain a phosphorus-nitrogen flame retardant.

[0015] Preferably, the catalyst is at least one of an organotitanium compound or an organotin compound; more preferably, the organotitanium compound is titanium tetrachloride; and the organotin 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, dichloroethylphosphine, and dichloroethylphosphine.

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

[0019] Preferably, the molar ratio of ethylenediamine to the intermediate product is 2:1 to 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, with an optimal ratio of 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, with an optimal ratio of 1.2:1.

[0022] Preferably, the organic material used for extraction is one or more of ethanol, acetone, etc.; the temperature of rotary evaporation is 30-40℃, with 30℃ being optimal.

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

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

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

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

[0027] Vanillin was dissolved in an anhydrous organic solvent and the temperature was maintained at -2 to -2℃. Then, an alkaline reagent was added to adjust the pH to 7 to 8. Dichlorophosphate was added dropwise while stirring, and the temperature was gradually raised to 20 to 30℃. The reaction was stirred continuously for 3 to 5 hours. After the reaction was completed, water was added to the reaction system to quench the reaction. The reaction product was extracted with organic matter. The organic matter containing the reaction product was dried with anhydrous sodium sulfate and the solvent was removed by rotary evaporation to obtain the intermediate product.

[0028] Ethylenediamine was dissolved in an anhydrous solvent and stirred to obtain an ethylenediamine solution; the intermediate product was dissolved in an anhydrous solvent and added to the ethylenediamine solution, and the mixture was heated to 40-60℃ and reacted for 4-6 hours; after the reaction was completed, the mixture was filtered, washed with anhydrous ethanol, and dried under vacuum to obtain a phosphorus-nitrogen flame retardant.

[0029] The present 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 flame-retardant PA6 composite material by extending the chain of flame retardant in PA6, and can reduce the amount of flame retardant precipitated from PA6 matrix and improve the migration resistance of flame retardant in PA6 matrix.

[0032] (2) In the hot processing of this invention, the prepared phosphorus-nitrogen flame retardant is introduced into the PA6 molecular chain under the action of a catalyst. The operation method of this invention is simple, and the flame retardant and PA6 are connected by 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 with terminal hydroxyl or terminal carboxyl groups. Taking advantage of the fact that PA6 is easy to degrade to generate terminal amino and terminal carboxyl groups during thermal processing, the terminal hydroxyl or terminal carboxyl groups in the phosphorus-nitrogen flame retardant and the terminal amino and terminal carboxyl groups in PA6 undergo a re-amidation reaction under heating conditions to obtain an intrinsic flame-retardant PA6 composite material. Attached Figure Description

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

[0035] Figure 2 This is a flowchart illustrating the preparation process of the flame-retardant PA6 composite material according to an embodiment of the present invention. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to the embodiments, but the implementation of the present invention is not limited thereto.

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

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

[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 retardants is as follows:

[0048] (1) Vanillin (30.43 g, 0.2 mol) was dissolved in 80 mL of anhydrous dichloromethane and kept at a low temperature of 0 °C. Then, triethylamine (24.29 g, 0.24 mol) was slowly added to adjust the pH value, and dichloromethylphosphine (13.29 g, 0.1 mol) was added dropwise while stirring. Finally, the temperature was gradually raised to 25 °C and stirred continuously for 4 h to ensure the reaction was complete.

[0049] (2) After the reaction is complete, 10 mL of water is added to the reaction system to quench the reaction. The reaction mixture is extracted with dichloromethane (3 × 10 mL), dried with anhydrous sodium sulfate, and the solvent is removed by rotary evaporation at 30 °C to obtain the 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. The mixture was stirred until homogeneous and then heated to 50 °C and stirred continuously for 5 h. After the reaction was completed, the mixture was filtered, washed three times with anhydrous ethanol, and dried under vacuum at 80 °C for 4 h to obtain the phosphorus-nitrogen flame retardant.

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

[0052] (1) Nylon 6 (160g), titanium tetrachloride (2g) and the phosphorus-nitrogen flame retardant (40g) prepared in this invention were dried in an oven at 80°C for 12h 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 in this invention are placed in the side feed. After melt blending and in-situ reaction at 230°C and 80 rpm, the flame-retardant PA6 composite material is obtained by extrusion through the die head.

[0054] Example 2

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

[0056] (1) Vanillin (30.43 g, 0.2 mol) was dissolved in 80 mL of anhydrous dichloromethane and kept at a low temperature of 0 °C. Then, triethylamine (24.29 g, 0.24 mol) was slowly added to adjust the pH value, and ethylphosphoric acid dichloride (14.69 g, 0.1 mol) was added dropwise while stirring. Finally, the temperature was gradually raised to 25 °C and stirred continuously for 4 h to ensure the reaction was complete.

[0057] (2) After the reaction is complete, 10 mL of water is added to the reaction system to quench the reaction. The reaction mixture is extracted with dichloromethane (3 × 10 mL), dried with anhydrous sodium sulfate, and the solvent is removed by rotary evaporation at 30 °C to obtain the 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. The mixture was stirred until homogeneous and then heated to 50 °C and stirred continuously for 5 h. After the reaction was completed, the mixture was filtered, washed three times with anhydrous ethanol, and dried under vacuum at 80 °C for 4 h to obtain the phosphorus-nitrogen flame retardant.

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

[0060] (1) Nylon 6 (160g), titanium tetrachloride (2g) and the phosphorus-nitrogen flame retardant (40g) prepared in this invention were dried in an oven at 80°C for 12h 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 in this invention are placed in the side feed. After melt blending and in-situ reaction at 230°C and 80 rpm, the flame-retardant PA6 composite material is obtained by extrusion through the die head.

[0062] Example 3

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

[0064] (1) Vanillin (30.43 g, 0.2 mol) was dissolved in 80 mL of anhydrous dichloromethane and kept at a low temperature of 0 °C. Then, triethylamine (24.29 g, 0.24 mol) was slowly added to adjust the pH value, and ethyl dichlorophosphate (16.29 g, 0.1 mol) was added dropwise while stirring. Finally, the temperature was gradually raised to 25 °C and stirred continuously for 4 h to ensure the reaction was complete.

[0065] (2) After the reaction is complete, 10 mL of water is added to the reaction system to quench the reaction. The reaction mixture is extracted with dichloromethane (3 × 10 mL), dried with anhydrous sodium sulfate, and the solvent is removed by rotary evaporation at 30 °C to obtain the 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. The mixture was stirred until homogeneous and then heated to 50 °C and stirred continuously for 5 h. After the reaction was completed, the mixture was filtered, washed three times with anhydrous ethanol, and dried under vacuum at 80 °C for 4 h to obtain the phosphorus-nitrogen flame retardant.

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

[0068] (1) Nylon 6 (160g), titanium tetrachloride (2g) and the phosphorus-nitrogen flame retardant (40g) prepared in this invention were dried in an oven at 80°C for 12h 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 in this invention are placed in the side feed. After melt blending and in-situ reaction at 230°C and 80 rpm, the flame-retardant PA6 composite material is obtained by extrusion through the die head.

[0070] Example 4

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

[0072] (1) Vanillin (30.43 g, 0.2 mol) was dissolved in 80 mL of anhydrous dichloromethane and kept at a low temperature of 0 °C. Then, triethylamine (24.2 g, 0.24 mol) was slowly added to adjust the pH value, and phenyl phosphate dichloride (21.10 g, 0.1 mol) was added dropwise while stirring. Finally, the temperature was gradually raised to 25 °C and stirred continuously for 4 h to ensure the reaction was complete.

[0073] (2) After the reaction is complete, 10 mL of water is added to the reaction system to quench the reaction. The reaction mixture is extracted with dichloromethane (3 × 10 mL), dried with anhydrous sodium sulfate, and the solvent is removed by rotary evaporation at 30 °C to obtain the 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. The mixture was stirred until homogeneous and then heated to 50 °C and stirred continuously for 5 h. After the reaction was completed, the mixture was filtered, washed three times with anhydrous ethanol, and dried under vacuum at 80 °C for 4 h to obtain the phosphorus-nitrogen flame retardant.

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

[0076] (1) Nylon 6 (160g), titanium tetrachloride (2g) and the phosphorus-nitrogen flame retardant (40g) prepared in this invention were dried in an oven at 80°C for 12h 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 in this invention are placed in the side feed. After melt blending and in-situ reaction at 230°C and 80 rpm, the flame-retardant PA6 composite material is obtained by extrusion through the die head.

[0078] Example 5

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

[0080] (1) Vanillin (30.43 g, 0.2 mol) was dissolved in 80 mL of anhydrous dichloromethane and kept at a low temperature of 0 °C. Then, triethylamine (24.29 g, 0.24 mol) was slowly added to adjust the pH value, and dichloromethylphosphine (13.29 g, 0.1 mol) was added dropwise while stirring. Finally, the temperature was gradually raised to 25 °C and stirred continuously for 4 h to ensure the reaction was complete.

[0081] (2) After the reaction is complete, 10 mL of water is added to the reaction system to quench the reaction. The reaction mixture is extracted with dichloromethane (3 × 10 mL), dried with anhydrous sodium sulfate, and the solvent is removed by rotary evaporation at 30 °C to obtain the 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. The mixture was stirred until homogeneous and then heated to 50 °C and stirred continuously for 5 h. After the reaction was completed, the mixture was filtered, washed three times with anhydrous ethanol, and dried under vacuum at 80 °C for 4 h to obtain the phosphorus-nitrogen flame retardant.

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

[0084] (1) Nylon 6 (160g), tetrabutyltin chloride (2g) and the phosphorus-nitrogen flame retardant (40g) prepared in this invention were dried in an oven at 80°C for 12h 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 in this invention are placed in the side feed. After melt blending and in-situ reaction at 230°C and 80 rpm, the flame-retardant PA6 composite material is obtained by extrusion through the die head.

[0086] Example 6

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

[0088] (1) Vanillin (30.43 g, 0.2 mol) was dissolved in 80 mL of anhydrous dichloromethane and kept at a low temperature of 0 °C. Then, triethylamine (24.29 g, 0.24 mol) was slowly added to adjust the pH value, and ethylphosphoric acid dichloride (14.69 g, 0.1 mol) was added dropwise while stirring. Finally, the temperature was gradually raised to 25 °C and stirred continuously for 4 h to ensure the reaction was complete.

[0089] (2) After the reaction is complete, 10 mL of water is added to the reaction system to quench the reaction. The reaction mixture is extracted with dichloromethane (3 × 10 mL), dried with anhydrous sodium sulfate, and the solvent is removed by rotary evaporation at 30 °C to obtain the 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. The mixture was stirred until homogeneous and then heated to 50 °C and stirred continuously for 5 h. After the reaction was completed, the mixture was filtered, washed three times with anhydrous ethanol, and dried under vacuum at 80 °C for 4 h to obtain the phosphorus-nitrogen flame retardant.

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

[0092] (1) Nylon 6 (160g), tetrabutyltin chloride (2g) and the phosphorus-nitrogen flame retardant (40g) prepared in this invention were dried in an oven at 80°C for 12h 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 in this invention are placed in the side feed. After melt blending and in-situ reaction at 230°C and 80 rpm, the flame-retardant PA6 composite material is obtained by extrusion through the die head.

[0094] Example 7

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

[0096] (1) Vanillin (30.43 g, 0.2 mol) was dissolved in 80 mL of anhydrous dichloromethane and kept at a low temperature of 0 °C. Then, triethylamine (24.29 g, 0.24 mol) was slowly added to adjust the pH value, and ethyl dichlorophosphate (16.29 g, 0.1 mol) was added dropwise while stirring. Finally, the temperature was gradually raised to 25 °C and stirred continuously for 4 h to ensure the reaction was complete.

[0097] (2) After the reaction is complete, 10 mL of water is added to the reaction system to quench the reaction. The reaction mixture is extracted with dichloromethane (3 × 10 mL), dried with anhydrous sodium sulfate, and the solvent is removed by rotary evaporation at 30 °C to obtain the 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. The mixture was stirred until homogeneous and then heated to 50 °C and stirred continuously for 5 h. After the reaction was completed, the mixture was filtered, washed three times with anhydrous ethanol, and dried under vacuum at 80 °C for 4 h to obtain the phosphorus-nitrogen flame retardant.

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

[0100] (1) Nylon 6 (160g), tetrabutyltin chloride (2g) and the phosphorus-nitrogen flame retardant (40g) prepared in this invention were dried in an oven at 80°C for 12h 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 in this invention are placed in the side feed. After melt blending and in-situ reaction at 230°C and 80 rpm, the flame-retardant PA6 composite material is obtained by extrusion through the die head.

[0102] Example 8

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

[0104] (1) Vanillin (30.43 g, 0.2 mol) was dissolved in 80 mL of anhydrous dichloromethane and kept at a low temperature of 0 °C. Then, triethylamine (24.2 g, 0.24 mol) was slowly added to adjust the pH value, and phenyl phosphate dichloride (21.10 g, 0.1 mol) was added dropwise while stirring. Finally, the temperature was gradually raised to 25 °C and stirred continuously for 4 h to ensure the reaction was complete.

[0105] (2) After the reaction is complete, 10 mL of water is added to the reaction system to quench the reaction. The reaction mixture is extracted with dichloromethane (3 × 10 mL), dried with anhydrous sodium sulfate, and the solvent is removed by rotary evaporation at 30 °C to obtain the 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. The mixture was stirred until homogeneous and then heated to 50 °C and stirred continuously for 5 h. After the reaction was completed, the mixture was filtered, washed three times with anhydrous ethanol, and dried under vacuum at 80 °C for 4 h to obtain the phosphorus-nitrogen flame retardant.

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

[0108] (1) Nylon 6 (160g), tetrabutyltin chloride (2g) and the phosphorus-nitrogen flame retardant (40g) prepared in this invention were dried in an oven at 80°C for 12h 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 in this invention are placed in the side feed. After melt blending and in-situ reaction at 230°C and 80 rpm, the flame-retardant PA6 composite material is obtained by extrusion through the die head.

[0110] Comparative Example 1

[0111] The formulation of the PA6 composite material in this comparative example is as follows: 80 wt% PA6 material and 20 wt% dimethyl methyl phosphate. The preparation process is the same as that in the example.

[0112] Comparative Example 2

[0113] The formulation of the PA6 composite material in this comparative example is as follows: 80 wt% PA6 material and 20 wt% ammonium polyphosphate by mass fraction. The preparation process is the same as that in the example.

[0114] Example and comparative performance test results

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

[0116] Tensile property test: The 125mm×4mm×1.6mm sample is clamped on the tensile testing machine using a fixture, and the tensile strength and elongation at break of the sample are read by the tensile testing machine.

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

[0118] Oxygen Index Method: A 130mm × 6.5mm × 3.2mm sample is placed vertically in the center of a glass chimney, and the top of the sample is ignited with a burner. The minimum oxygen concentration required for the sample to burn is recorded.

[0119] Cone calorimeter method: A 100mm×100mm×3mm sample is exposed in a cone-shaped radiant 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. Results of PA6 composite material performance testing

[0122]

[0123] Table 2. Cone calorimetry results of PA6 composite materials

[0124]

[0125] As can be seen from the above examples, by adding the phosphorus-nitrogen flame retardant prepared in this 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, achieving V-0 rating and oxygen index of 31.4%.

[0126] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the embodiments described above. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a flame-retardant PA6 composite material, characterized in that, Includes the following steps: The dried PA6 was placed in the main feed inlet of a twin-screw extruder, and the phosphorus-nitrogen flame retardant and catalyst were placed in the side feed inlet. The extruder temperature was 220~240℃, and the screw speed was 80~85 rpm. PA6, phosphorus-nitrogen flame retardant and catalyst were melt-blended and reacted in situ. The mixture was then extruded through the die head, cooled and pelletized to obtain a flame-retardant PA6 composite material. The mass ratio of the phosphorus-nitrogen flame retardant to PA6 was 1:3-1:

5. The phosphorus-nitrogen flame retardant is prepared as follows: Vanillin was dissolved in an anhydrous organic solvent and the temperature was maintained at -2 to -2℃. Then, an alkaline reagent was added to adjust the pH to 7 to 8. Under stirring, a dichlorophosphorus compound was added dropwise, and the temperature was gradually raised to 20 to 30℃ while stirring continuously. The reaction temperature was 20 to 30℃ and the reaction time was 3 to 5 hours. After the reaction was completed, water was added to the reaction system to quench the reaction. The reaction product was extracted with organic matter. The organic matter containing the reaction product was dried with anhydrous sodium sulfate and the solvent was removed by rotary evaporation to obtain the intermediate product. The dichlorophosphorus compound is at least one of dichloromethylphosphine, ethyl phosphoric acid dichloride, and ethyl dichlorophosphate; Ethylenediamine was dissolved in an anhydrous solvent and stirred to obtain an ethylenediamine solution; the intermediate product was dissolved in an anhydrous solvent and added to the ethylenediamine solution, and the mixture was heated to 40-60℃ and reacted for 4-6 h; after the reaction was completed, the mixture was filtered, washed with anhydrous ethanol, and dried under 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 organotitanium compound or an organotin 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 molar ratio of dichlorophosphate to vanillin is 1:2 to 1:

3.

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

1.

6. 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.

7. A flame-retardant PA6 composite material, characterized in that, It is prepared by the method for preparing flame-retardant PA6 composite material according to any one of claims 1 to 6.

Images