Halogen-free flame-retardant nylon material and preparation method thereof

Abstract

The invention relates to the technical field of nylon, and discloses a halogen-free flame-retardant nylon material and a preparation method thereof.The halogen-free flame-retardant nylon material comprises, by weight, 70-85 parts of nylon resin and 15-30 parts of modified polystyrene; the epoxy group of the modified polystyrene can react with the amino-terminated group of the nylon, so that the interface bonding force between the nylon resin and the polystyrene molecular chain is improved, and the material has higher tensile strength and mechanical property. The modified polystyrene contains a large amount of phosphate flame-retardant groups, has a cohesive flame-retardant effect, generates phosphoric acid substances during combustion, promotes dehydration and charring of polystyrene with high carbon content, can isolate oxygen and prevent heat conduction, has a very good flame-retardant effect, improves the limit oxygen index of the nylon material, and the UL-94 grade reaches V-1 to V-0 grade.

Description

Technical Field

[0001] The present invention relates to the technical field of nylon, in particular to a halogen-free flame-retardant nylon material and a preparation method thereof. Background Art

[0002] Nylon, a polyamide polymer, boasts excellent corrosion resistance, good wear resistance, and high temperature resistance, making it widely used. However, its low limiting oxygen index (LOI) makes it flammable, significantly limiting its practical application. Polystyrene offers excellent transparency, insulation, low-temperature resistance, and chemical stability. By introducing flame-retardant groups such as phosphate and bromine into the polystyrene molecular chain, it can be produced into a high-performance polymer flame retardant.

[0003] Blending nylon resin with polystyrene creates a plastic alloy material with improved mechanical strength and other properties. Patent publication number CN105802210B discloses polystyrene organic rigid particle-modified nylon filament for 3D printing and its preparation method. While the polystyrene organic rigid particles improve the strength and other properties of nylon, the patent does not address the poor flame retardancy of nylon materials. Summary of the Invention

[0004] In view of the deficiencies in the prior art, the present invention provides a halogen-free flame-retardant nylon material and a preparation method thereof, which solves the problem of poor compatibility between nylon and polystyrene and improves the flame retardant properties of the nylon material.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a halogen-free flame-retardant nylon material and a preparation method thereof, wherein the halogen-free flame-retardant nylon material comprises 70-85 parts by weight of nylon resin and 15-30 parts by weight of modified polystyrene; the preparation method of the halogen-free flame-retardant nylon material is:

[0006] (1) Add styrene and phosphate styrene monomers to a solvent, stir, and then add an initiator in a nitrogen atmosphere. After the polymerization reaction, pour the solution into ethanol, filter, wash the precipitate with ethanol, and dry to obtain modified polystyrene.

[0007] (2) Nylon resin and modified polystyrene are mixed, extruded in a twin-screw extruder, and granulated to obtain a halogen-free flame-retardant nylon material.

[0008] Furthermore, the polymerization reaction temperature in (1) is 60-75° C., and the reaction time is 5-8 h.

[0009] Furthermore, the solvent in (1) includes toluene, tetrahydrofuran or N,N-dimethylformamide.

[0010] Furthermore, the molar ratio of styrene, phosphate styrene monomer, and initiator is (60-80):(20-40):(0.32-0.46).

[0011] Furthermore, the initiator includes azobisisobutyronitrile.

[0012] Furthermore, the temperature of zones 1-5 of the twin-screw extruder in (2) is 180-240°C.

[0013] Furthermore, the preparation method of the phosphate ester styrene monomer is as follows: under an ice bath and a nitrogen atmosphere, phenyl dichloride phosphate and triethylamine are added to tetrahydrofuran, a tetrahydrofuran solution containing (4-vinylphenyl) methanol is added dropwise with stirring, and the reaction is carried out for 4-6 hours, and then a tetrahydrofuran solution containing glycidol is added dropwise, and the reaction is carried out at 15-25° C. for 5-8 hours. After filtering, the filtrate is concentrated under reduced pressure, the crude product is washed with petroleum ether, and then recrystallized and purified in chloroform to obtain the phosphate ester styrene monomer.

[0014] Furthermore, the molar ratio of phenyl dichloride phosphate, triethylamine, (4-vinylphenyl)methanol, and glycidol is 1:(2-2.2):1:(1-1.2).

[0015] (3) Beneficial technical effects: The present invention copolymerizes a phosphate styrene monomer containing phosphate and epoxy groups with styrene to obtain modified polystyrene, which is then blended and extruded with a nylon resin. The modified polystyrene contains epoxy groups. During the high-temperature melt extrusion process, the epoxy groups can react with the terminal amino groups of nylon, thereby improving the interfacial bonding force between the nylon resin and the polystyrene molecular chain, resulting in better compatibility between the two and exhibiting higher tensile strength and mechanical properties.

[0016] The modified polystyrene of the present invention contains a large number of phosphate flame retardant groups, has a cohesive flame retardant effect, generates phosphoric acid substances during combustion, promotes the dehydration of polystyrene with a high carbon content into carbon, can isolate oxygen, prevent heat conduction, and has a good flame retardant effect, thereby improving the limiting oxygen index of nylon materials and achieving a UL-94 grade of V-1 to V-0. DETAILED DESCRIPTION

[0017] The present invention may be more readily understood by referring to the following detailed description of preferred embodiments of the present invention and the included Examples. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention pertains. In the event of a conflict, the definitions in this specification shall prevail.

[0018] The following nylon resin model is PA6 M2800, which comes from Shanghai Hehongcheng Plastic Technology Co., Ltd.

[0019] Example 1:

[0020] (1) In an ice bath and nitrogen atmosphere, 0.3 mol of phenyl dichloride phosphate and 0.6 mol of triethylamine were added to 350 mL of tetrahydrofuran, and 120 mL of a tetrahydrofuran solution containing 0.3 mol of (4-vinylphenyl)methanol was added dropwise with stirring. The mixture was reacted for 6 h, and then 150 mL of a tetrahydrofuran solution containing 0.3 mol of glycidol was added dropwise. The mixture was reacted at 15° C. for 8 h. After filtration, the filtrate was concentrated under reduced pressure. The crude product was washed with petroleum ether and then purified by recrystallization from chloroform to obtain a phosphate styrene monomer. The preparation reaction formula is:

[0021]

[0022] (2) 0.8 mol of styrene and 0.2 mol of phosphate styrene monomer were added to 700 mL of toluene. After stirring, 4 mmol of initiator azobisisobutyronitrile was added in a nitrogen atmosphere. The mixture was heated to 75°C and reacted for 5 h. The solution was poured into ethanol, filtered, and the precipitate was washed with ethanol and dried to obtain modified polystyrene.

[0023] (3) 8.5 kg of nylon resin and 1.5 kg of modified polystyrene were mixed and extruded in a twin-screw extruder with the temperatures in zones 1-5 being 180° C., 215° C., 230° C., 240° C., and 235° C., and pelletized to obtain a halogen-free flame-retardant nylon material.

[0024] Example 2:

[0025] (1) In an ice bath and nitrogen atmosphere, 0.3 mol of phenyl dichloride phosphate and 0.66 mol of triethylamine were added to 400 mL of tetrahydrofuran, and 140 mL of a tetrahydrofuran solution containing 0.3 mol of (4-vinylphenyl)methanol was added dropwise with stirring. The mixture was reacted for 4 h, and then 170 mL of a tetrahydrofuran solution containing 0.36 mol of glycidol was added dropwise. The mixture was reacted at 25° C. for 5 h. After filtration, the filtrate was concentrated under reduced pressure. The crude product was washed with petroleum ether and then purified by recrystallization from chloroform to obtain a phosphate styrene monomer.

[0026] (2) 0.67 mol of styrene and 0.33 mol of phosphate styrene monomer were added to 700 mL of N,N-dimethylformamide. After stirring, 4.6 mmol of initiator azobisisobutyronitrile was added in a nitrogen atmosphere. The mixture was heated to 70°C and reacted for 5 h. The solution was poured into ethanol, filtered, and the precipitate was washed with ethanol and dried to obtain modified polystyrene.

[0027] (3) 8 g of nylon resin and 2 kg of modified polystyrene were mixed and extruded in a twin-screw extruder with the temperatures in zones 1-5 being 180° C., 215° C., 230° C., 240° C., and 235° C., and pelletized to obtain a halogen-free flame-retardant nylon material.

[0028] Example 3:

[0029] (1) To 900 mL of tetrahydrofuran were added 0.6 mol of styrene and 0.4 mol of phosphate styrene monomer (prepared in Example 1). After stirring, 3.2 mmol of initiator azobisisobutyronitrile was added in a nitrogen atmosphere. The mixture was heated to 70° C. and reacted for 8 h. The solution was poured into ethanol, filtered, and the precipitate was washed with ethanol and dried to obtain modified polystyrene.

[0030] (2) 7.5 kg of nylon resin and 2.5 kg of modified polystyrene were mixed and extruded in a twin-screw extruder with the temperatures in zones 1-5 being 180° C., 215° C., 230° C., 240° C., and 235° C., and pelletized to obtain a halogen-free flame-retardant nylon material.

[0031] Example 4:

[0032] (1) To 700 mL of N,N-dimethylformamide, 0.73 mol of styrene and 0.27 mol of phosphate styrene monomer (prepared in Example 1) were added. After stirring, 4.2 mmol of initiator azobisisobutyronitrile was added in a nitrogen atmosphere. The mixture was heated to 60° C. and reacted for 8 h. The solution was poured into ethanol, filtered, and the precipitate was washed with ethanol and dried to obtain modified polystyrene.

[0033] (2) 7 kg of nylon resin and 3 kg of modified polystyrene were mixed and extruded in a twin-screw extruder with the temperatures in zones 1-5 being 180°C, 215°C, 230°C, 240°C and 235°C, and pelletized to obtain a halogen-free flame-retardant nylon material.

[0034] Comparative Example 1:

[0035] (2) 1 mol of styrene was added to 700 mL of toluene. After stirring, 4 mmol of initiator azobisisobutyronitrile was added in a nitrogen atmosphere. The mixture was heated to 75°C and reacted for 5 h. The solution was poured into ethanol, filtered, and the precipitate was washed with ethanol and dried to obtain polystyrene.

[0036] (3) 8.5 kg of nylon resin and 1.5 kg of polystyrene were mixed and extruded in a twin-screw extruder at temperatures of 180° C., 215° C., 230° C., 240° C., and 235° C. in zones 1-5, and pelletized to obtain a nylon material.

[0037] Comparative Example 2:

[0038] (1) 0.8 mol of styrene and 0.2 mol of glycidyl methacrylate were added to 700 mL of toluene. After stirring, 4 mmol of initiator azobisisobutyronitrile was added in a nitrogen atmosphere. The mixture was heated to 75°C and reacted for 5 h. The solution was poured into ethanol, filtered, and the precipitate was washed with ethanol and dried to obtain modified polystyrene.

[0039] (2) 8.5 kg of nylon resin and 1.5 kg of modified polystyrene were mixed and extruded in a twin-screw extruder at temperatures of 180° C., 215° C., 230° C., 240° C., and 235° C. in zones 1-5, and pelletized to obtain a nylon material.

[0040] Comparative Example 3:

[0041] (1) In an ice bath and nitrogen atmosphere, 0.3 mol of phenyl dichloride phosphate and 0.6 mol of triethylamine were added to 350 mL of tetrahydrofuran, and 120 mL of a tetrahydrofuran solution containing 0.3 mol of hydroxyethyl acrylate was added dropwise with stirring. The mixture was reacted for 6 h, and then 150 mL of a tetrahydrofuran solution containing 0.3 mol of glycidol was added dropwise. The mixture was reacted at 15° C. for 8 h. After filtration, the filtrate was concentrated under reduced pressure. The crude product was washed with petroleum ether and then purified by recrystallization in chloroform to obtain a phosphate acrylate monomer. The structural formula is

[0042] (2) 0.8 mol of styrene and 0.2 mol of phosphate acrylate monomer were added to 700 mL of toluene. After stirring, 4 mmol of initiator azobisisobutyronitrile was added in a nitrogen atmosphere. The mixture was heated to 75°C and reacted for 5 h. The solution was poured into ethanol, filtered, and the precipitate was washed with ethanol and dried to obtain modified polystyrene.

[0043] (3) 8.5 kg of nylon resin and 1.5 kg of modified polystyrene were mixed and extruded in a twin-screw extruder with the temperatures in zones 1-5 being 180° C., 215° C., 230° C., 240° C., and 235° C., and pelletized to obtain a halogen-free flame-retardant nylon material.

[0044] Nylon material was injection molded into test strips, and the flammability of the test strips was tested according to GB / T 2406.1-2008 and UL-94. The tensile strength was tested according to GB / T 1040.1-2018.

[0045] Table 1 Properties of nylon materials

[0046] Limiting oxygen index (%) UL-94 rating Tensile strength (MPa) Example 1 26.7 V-1 44.2 Example 2 27.2 V-1 45.9 Example 3 28.5 V-0 42.0 Example 4 27.9 V-0 38.1 Comparative Example 1 21.6 - 38.7 Comparative Example 2 20.8 - 41.3 Comparative Example 3 25.4 V-2 40.6

[0047] Modified polystyrene containing epoxy groups is added to the nylon materials of Examples 1 to 4. During the high-temperature melt extrusion process, the epoxy groups can react with the terminal amino groups of nylon, thereby improving the interfacial bonding force between the nylon resin and the polystyrene molecular chain. The two have better compatibility and exhibit higher tensile strength and mechanical properties. In addition, the modified polystyrene contains a large number of phosphate flame retardant groups and has a cohesive flame retardant effect. It produces phosphoric acid substances during combustion, which promotes the dehydration of high-carbon polystyrene into carbon, can isolate oxygen, prevent heat conduction, and have a good flame retardant effect. It improves the limiting oxygen index of the nylon material, and the UL-94 grade reaches V-1 to V-0.

[0048] Compared with Example 1, Comparative Example 1 blends nylon resin and polystyrene, and the compatibility between the two is poor, resulting in low tensile strength of the material, low limiting oxygen index, failure of the UL-94 test, no grade, and poor flame retardant performance.

[0049] In Comparative Example 2, styrene and glycidyl methacrylate are copolymerized. The resulting modified polystyrene contains epoxy groups, which can react with the terminal amino groups of nylon, thereby improving the interfacial bonding force between the nylon resin and the polystyrene molecular chains, which is beneficial to improving the tensile strength of the nylon material. However, the glycidyl methacrylate copolymer does not contain a styrene structure. After copolymerization with styrene, polyacrylate molecular chains are introduced into the polystyrene molecular chain, which affects the mechanical properties of the polystyrene. After blending with nylon, the tensile strength of the material is lower than that of Example 1.

[0050] In Comparative Example 3, the modified polystyrene obtained by copolymerizing phosphate acrylate monomers with styrene contained polyacrylate molecular chains, which affected the mechanical properties of the polystyrene. When blended with nylon, the tensile strength of the material was lower than that of Example 1. Furthermore, the char-forming ability of the acrylate was lower than that of the benzene ring structure, resulting in poor flame retardancy of the nylon material in Comparative Example 3. Its limiting oxygen index was lower than that of Example 1, and its UL-94 rating was only V-2.

[0051] The embodiments described above are merely illustrative, serving to illustrate some of the features of the present invention. The appended claims are intended to claim the broadest possible scope that can be imagined, and the embodiments presented herein are merely illustrations of selected implementations according to the combination of all possible embodiments.

Claims

1. A halogen-free flame-retardant nylon material, characterized in that: The halogen-free flame-retardant nylon material comprises 70-85 parts by weight of nylon resin and 15-30 parts by weight of modified polystyrene; The preparation method of the modified polystyrene comprises: adding styrene and phosphate styrene monomers to a solvent, stirring, adding an initiator in a nitrogen atmosphere, pouring the solution into ethanol after polymerization, filtering, washing the precipitate, and drying to obtain the modified polystyrene; The structural formula of the phosphate styrene monomer is 2. The halogen-free flame-retardant nylon material according to claim 1, characterized in that: The polymerization reaction temperature is 60-75° C., and the reaction time is 5-8 hours.

3. The halogen-free flame-retardant nylon material according to claim 1, characterized in that: The solvent includes toluene, tetrahydrofuran or N,N-dimethylformamide.

4. The halogen-free flame-retardant nylon material according to claim 1, characterized in that: The molar ratio of styrene, phosphate styrene monomer and initiator is (60-80):(20-40):(0.32-0.46).

5. The halogen-free flame-retardant nylon material according to claim 4, characterized in that: The initiator includes azobisisobutyronitrile.

6. The halogen-free flame-retardant nylon material according to claim 4, characterized in that: The preparation method of the phosphate styrene monomer comprises: adding phenyl dichloride phosphate and triethylamine to tetrahydrofuran in an ice bath and a nitrogen atmosphere, adding dropwise a tetrahydrofuran solution containing (4-vinylphenyl)methanol with stirring, reacting for 4-6 hours, then adding dropwise a tetrahydrofuran solution containing glycidol, reacting at 15-25° C. for 5-8 hours, filtering, concentrating the filtrate under reduced pressure, washing the crude product, and then recrystallizing and purifying it to obtain the phosphate styrene monomer.

7. The halogen-free flame-retardant nylon material according to claim 6, characterized in that: The molar ratio of the dichlorophenyl phosphate, triethylamine, (4-vinylphenyl)methanol and glycidol is 1:(2-2.2):1:(1-1.2).

8. A method for preparing the halogen-free flame-retardant nylon material according to any one of claims 1 to 7, characterized in that: The preparation method comprises the following steps: mixing nylon resin and modified polystyrene, extruding the mixture in a twin-screw extruder, and granulating the mixture to obtain a halogen-free flame-retardant nylon material.

9. The method for preparing the halogen-free flame-retardant nylon material according to claim 8, characterized in that: The temperature of zones 1-5 of the twin-screw extruder is 180-240°C.

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