Functional caprolactam, intrinsic flame-retardant nylon material as well as preparation method and application of functional caprolactam and intrinsic flame-retardant nylon material

Abstract

The invention discloses functional caprolactam, an intrinsic flame-retardant nylon material as well as a preparation method and application thereof, and relates to the technical field of flame-retardant nylon materials. The preparation method comprises the following steps: preparing an alpha-amino-epsilon-caprolactam intermediate by taking lysine as an initial raw material through one-step efficient cyclization, then reacting with a reagent containing a flame-retardant group to obtain functional caprolactam, and finally introducing the flame-retardant group into a side chain of nylon 6 by utilizing ring-opening copolymerization of the functional caprolactam and caprolactam to prepare the intrinsic flame-retardant nylon material. The flame-retardant nylon material can effectively avoid the migration and loss of the flame retardant, improve the dispersity of the flame retardant and enhance the flame-retardant effect, can keep the main chain structure of the nylon 6 unchanged, reduces the influence on the inherent performance of the nylon 6, is expected to directly replace the existing nylon 6 material, and is applied to the fields of automobiles, textiles, electronics and electrics, buildings, packaging and the like. In addition, a renewable lysine resource is used for partially replacing a petroleum resource, so that the method has the advantages of resource conservation, environmental friendliness, simple process, low cost and the like.

Description

Technical Field

[0001] The invention relates to the technical field of flame-retardant nylon materials, and in particular to a functional caprolactam, an intrinsic flame-retardant nylon material, and a preparation method and application thereof. Background Art

[0002] Nylon 6 (polycaprolactam), also known as polyamide, is a thermoplastic resin containing repeated amide groups on the main chain of the molecule. It has good toughness, elasticity, wear resistance, chemical corrosion resistance, light weight and non-toxicity, and is widely used in the fields of automobiles, textiles, electronics and electrical, construction and packaging. However, nylon 6 has poor flame retardancy and is a type of flammable polymer material. It will generate a lot of heat and droplets when burning, which can easily cause secondary fires and seriously threaten people's lives and property safety.

[0003] At present, the flame retardant modification methods of nylon 6 are mainly: 1) Blending flame retardant modification, that is, preparing flame retardant nylon materials by melt blending flame retardants and nylon 6 masterbatch. This method has the advantages of simple process, easy operation, low cost and wide application, and is the main method for producing flame retardant nylon 6. However, it is difficult to control the distribution of flame retardants in the material by this method, and agglomeration will occur. In addition, there is microphase separation between the flame retardant and the nylon base material, which has a great influence on the mechanical properties of the composite material. At the same time, during use, there may be problems such as migration and precipitation of flame retardants leading to poor flame retardant durability. 2) Fabric finishing flame retardant modification, that is, a finishing method in which flame retardants are applied to nylon 6 fibers or fabrics by physical or chemical means in the form of adsorption deposition, chemical bonding, etc. This method has the advantages of low cost, simple process and applicability to various fiber fabrics. However, the demand for flame retardants is often large, which has a great impact on the feel, strength, color, etc. of the fabric, and often lacks flame retardant durability.

[0004] Copolymer flame retardant modification, that is, through monomer structure design, directly introduces flame retardant units into the main chain or side chain of the polymer to give flame retardant properties. In this method, the flame retardant unit is bonded to the nylon main chain or side chain in the form of a chemical bond, avoiding the migration and precipitation of the flame retardant and poor compatibility with the base material. The flame retardant property is long-lasting and has little impact on the performance of the material.

[0005] There are many research reports on the flame retardant modification of nylon 6 copolymer. For example, in the document JAppl PolymSci.2019,136,47829, caprolactam was melt-condensed with two phosphorus-containing monomers, 2-carboxyethylphenylphosphite (3-HPP) and [(6-oxo-6H-dibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]succinic acid (DDP), to prepare a copolymer flame-retardant nylon 6 material. In the document Polym Degrad Stabil.2019,163,151, 2,3-dicarboxypropyldiphenylphosphine oxide (DPDPO) was introduced into the nylon molecular chain as a reactive flame retardant monomer through melt polycondensation to prepare a flame-retardant nylon 6 material. The document J Polym Sci. 2024, 62, 547 uses a diacid monomer containing 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) in the side chain to melt-condense caprolactam and hexamethylenediamine to prepare a flame-retardant nylon 6 material. The Chinese invention patent document CN105153414A discloses a method of first using a flame retardant to react with a diamine or a diol to obtain a flame retardant prepolymer, and then further reacting with a nylon 6 prepolymer to obtain a block-type permanent flame-retardant nylon 6 material. The Chinese invention patent document CN111057367A uses a reactive phosphorus-based flame retardant containing DOPO, a phosphorus-nitrogen-based flame retardant, a vinyl nano-silicon ball, etc., copolymerized with caprolactam to prepare a highly durable flame-retardant nylon 6 material. However, the above method is to prepare flame-retardant nylon 6 by ring-opening copolymerization of dibasic acid or diamine containing flame-retardant units with caprolactam, and the introduction of dibasic acid or diamine will change the main chain structure of nylon 6 and affect the inherent properties of the material. At the same time, the dibasic acid or diamine currently used mainly comes from petroleum resources, which is not conducive to the stability and sustainable development of the industry.

[0006] Lysine (also known as 2,6-diaminohexanoic acid) is a natural renewable resource with abundant output and low price. α-amino-ε-caprolactam can be obtained through lysine cyclization, and the amino group is further modified to obtain functional caprolactam, which has the same seven-membered ring structure as caprolactam. The copolymerization of the two provides a unique idea for the preparation of intrinsic functional nylon 6 materials with unchanged main chain structure. In this regard, the document Chem. Eng. J. 2021, 426, 130760 uses lysine cyclization to obtain α-amino-ε-caprolactam, which is further reacted with DOPO to synthesize a new type of phosphimide comonomer (DOPO-α-CLM), and finally copolymerized with caprolactam to prepare flame-retardant nylon 6 material. However, the prepared flame-retardant nylon 6 material has significantly lower tensile properties than pure nylon 6. At the same time, in this document, a large excess of aluminum oxide (Al2O3) is required as a catalyst and expensive hexanol is used as a solvent, which increases production costs, and the product yield is low (the crude product yield is only 70%), which is not conducive to industrial production. Summary of the invention

[0007] In order to solve the problem that the ring-opening copolymerization of dibasic acid or diamine with caprolactam affects the inherent properties of the material, and the existing preparation method using lysine as raw material is difficult to industrialize, the present invention proposes a functional caprolactam, an intrinsic flame-retardant nylon material, and a preparation method and application thereof.

[0008] The technical solution of the present invention is as follows:

[0009] A functional caprolactam, the structural formula of which is shown in the following formula I:

[0010]

[0011] Wherein, R is selected from one of the structural formulas shown in the following formula II:

[0012]

[0013] Wherein, Z1 and Z2 are independently selected from hydrogen, C 1～10 One of a linear / branched aliphatic hydrocarbon group, hydroxyl group, methoxy group, tert-butoxy group, cyano group, boric acid, and boric acid ester;

[0014] Z3, Z4, and Z5 are independently selected from C 1～10 One of a linear / branched aliphatic hydrocarbon group, a substituted / unsubstituted aryl group, and a substituted / unsubstituted aralkyl group;

[0015] X1 and X2 are each independently selected from an oxygen atom or an imino group.

[0016] More preferably, Z1 and Z2 are independently selected from hydrogen, C 1～5 One of a straight chain / branched aliphatic hydrocarbon group, methoxy group, tert-butoxy group, cyano group, and boric acid; Z3, Z4, and Z5 are independently selected from C 1～5 One of a linear / branched aliphatic hydrocarbon group, a substituted / unsubstituted aryl group, and a substituted / unsubstituted aralkyl group.

[0017] The present invention also provides a method for preparing the functional caprolactam, comprising the following steps:

[0018] Step 1: Mix the raw material containing lysine with methanol, dehydrate to form a ring at 120°C to 200°C, evaporate to dryness and recover methanol, and extract with ethyl acetate to obtain the intermediate product α-amino-ε-caprolactam;

[0019] Step 2: dissolving the α-amino-ε-caprolactam in a solvent, adding a reagent containing a flame retardant group to react, and obtaining functional caprolactam after post-treatment.

[0020] Preferably, the raw material containing lysine in step 1 is selected from one or a combination of at least two of lysine, lysine hydrochloride, lysine sulfate, and an aqueous solution containing lysine; when lysine hydrochloride or lysine sulfate is selected, an equimolar equivalent of sodium hydroxide is also required to be added.

[0021] Preferably, the reaction time of the dehydration cyclization in step 1 is 1 h to 6 h.

[0022] More preferably, the raw material containing lysine in step 1 is selected from one of lysine, lysine hydrochloride, and an aqueous solution containing more than 50% (mass fraction) of lysine; and the reaction time is further preferably 2 h to 4 h.

[0023] Preferably, the solvent in step 2 is selected from one or a combination of at least two of dichloromethane, chloroform, acetonitrile, acetone, tetrahydrofuran, toluene, xylene, mesitylene, dioxane, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide. More preferably, it is one of dichloromethane, acetonitrile, toluene, N,N-dimethylformamide, and dimethyl sulfoxide.

[0024] Preferably, the reaction temperature in step 2 is -40°C to 200°C, and the reaction time is 1h to 24h.

[0025] Preferably, the flame retardant group-containing reagent in step 2 is directly obtained by commercial purchase or is prepared by reacting a structure shown in Formula III below with an amine / aldehyde / phenol / phosphoramide compound;

[0026]

[0027] Preferably, the post-treatment method is selected from one or a combination of at least two of filtration, washing, solvent extraction, recrystallization, vacuum distillation, vacuum sublimation, and column chromatography.

[0028] The present invention also provides an intrinsic flame retardant nylon material, comprising the above-mentioned functional caprolactam; the structural formula of the intrinsic flame retardant nylon material is shown in the following formula IV:

[0029]

[0030] Wherein, x and y represent the molar proportion of each part of the repeating unit respectively, x is selected from 0.01 to 0.50, y is selected from 0.50 to 0.99, and x+y=1.

[0031] Preferably, the functional performance caprolactam, caprolactam, water and a molecular weight regulator are added into a polymerization kettle to carry out a ring-opening copolymerization reaction to obtain an intrinsic flame-retardant nylon material.

[0032] Preferably, the molecular weight regulator is selected from one of acetic acid, adipic acid and benzoic acid;

[0033] The molar ratio of the functional caprolactam, caprolactam, water and molecular weight regulator is (1-100):100:(0.1-5):(0-5);

[0034] The copolymerization reaction temperature is 140°C to 320°C, the reaction time is 2h to 96h, and the reaction pressure is -0.1MPa to 5MPa.

[0035] Furthermore, the copolymerization process can be divided into three stages: pressure reaction, normal pressure reaction and reduced pressure reaction, and the reaction conditions of each stage are as follows:

[0036] Pressurized reaction stage: polymerization temperature is 140℃~230℃; polymerization time is 2h~24h; polymerization pressure is 0.3MPa~5MPa; Normal pressure reaction stage: polymerization temperature is 180℃~280℃; polymerization time is 0.5h~10h; polymerization pressure is -0.05MPa~0.1MPa; Reduced pressure reaction stage: polymerization temperature is 200℃~320℃; polymerization time is 2h~36h; polymerization pressure is -0.1MPa~0MPa.

[0037] Preferably, the copolymerization reaction can be directly extruded into granules, and then the granules can be directly washed with a solvent and dried. The solvent is selected from one or more of water, methanol, ethanol, dichloromethane, acetone, and ethyl acetate; the washing time is 0.1h to 24h, and the washing temperature is 25°C to 100°C.

[0038] The present invention also provides an application of the intrinsic flame retardant nylon material, which is specifically applied to the fields of automobile, textile, electrical and electronic, construction and packaging.

[0039] Compared with the prior art, the specific beneficial effects of the present invention are:

[0040] The present invention uses lysine as the starting material, prepares an α-amino-ε-caprolactam intermediate through a one-step efficient cyclization, and then further reacts with a reagent containing a flame retardant group to prepare a functional caprolactam monomer with different flame retardant groups, and finally copolymerizes with caprolactam to introduce a flame retardant group into the side chain of nylon 6 to prepare an intrinsic flame retardant nylon material. Compared with the existing method of preparing flame retardant nylon 6 by ring-opening copolymerization of a dibasic acid or diamine containing a flame retardant unit with caprolactam, the method provided by the present invention can not only give nylon 6 good flame retardant properties, but also keep the main chain structure of nylon 6 unchanged, reducing the impact on its inherent properties; at the same time, the present invention partially replaces petroleum resources with renewable lysine resources, which can effectively alleviate the dependence of synthetic polymers on petroleum resources, and meet the needs of the dual carbon strategy and sustainable development strategy.

[0041] Compared with the existing method of preparing α-amino-ε-caprolactam by cyclization of lysine, further modifying to obtain functional caprolactam monomer, and finally ring-opening copolymerizing with caprolactam to prepare flame-retardant nylon 6, the present invention prepares functional caprolactam monomers with different flame-retardant groups, and by optimizing the process of ring-opening copolymerization with caprolactam, the tensile properties of the prepared flame-retardant nylon material are improved, and the difference between the properties of the prepared flame-retardant nylon material and pure nylon 6 is reduced. At the same time, the preparation method provided in the present invention is simpler and more efficient, with low production cost and high yield, and is more suitable for industrial production.

[0042] In summary, the intrinsic flame-retardant nylon material prepared by the present invention not only has good flame-retardant properties, but also can keep the main chain structure of nylon 6 unchanged, reducing the impact on its inherent properties. It is expected to directly replace the existing nylon 6 material and be used in the fields of automobiles, textiles, electronics and electrical, construction and packaging. DETAILED DESCRIPTION

[0043] In order to make the technical solution of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below. It should be noted that the following embodiments are only used to better understand the technical solution of the present invention and should not be understood as limiting the present invention.

[0044] Example 1.

[0045] 1) Preparation of intermediate product α-amino-ε-caprolactam:

[0046] In a 5L reactor, add 3.5mol of lysine hydrochloride, 3.5mol of sodium hydroxide and 3.5L of methanol, stir and react at 175℃ for 2h. Cool to room temperature, filter, remove insoluble matter, evaporate to dryness and recover methanol, extract with ethyl acetate to obtain α-amino-ε-caprolactam, with a yield of 92%, and a purity of 99% according to H-NMR spectrum analysis. 1 H NMR (300MHz, D2O) δ3.69-3.72(dd,1H),3.22-3.26(m,2H),1.26-1.99(m,6H).

[0047] 2) Preparation of functional caprolactam monomer (the structural formula is shown in Formula I, wherein R is the structure A in Formula II, and Z1 and Z2 are both hydrogen):

[0048] Weigh 0.5 mol of α-amino-ε-caprolactam prepared in step 1), add 1 L of dichloromethane to dissolve, add 1.5 mol of triethylamine and 0.55 mol of diphenylphosphine chloride at 0 ° C, gradually return to room temperature, stir and react for 24 hours, add saturated ammonium chloride solution, extract with dichloromethane, and recrystallize to obtain a functional caprolactam monomer with a yield of 80%. The purity is 95% according to H NMR analysis.1 H NMR(300MHz, CDCl3)δ7.75-7.80(m,4H),7.48-7.54(m,6H),6.06(s,1H),4.04-4.08 (m,1H),3.55-3.64(m,1H),3.26-3.35(m,1H),2.06-2.18(m,1H),1.40-1.80(m,6H).

[0049] 3) Preparation of intrinsic flame retardant nylon 6 material:

[0050] Weigh 10 mmol of the functional caprolactam prepared in step 2) and 1000 mmol of caprolactam into a polymerization reactor, then add 1 mmol of water, replace with nitrogen and maintain a nitrogen atmosphere, react under pressure at 180°C and 0.8 MPa for 4 hours, then heat to 210°C and react at normal pressure for 5 hours, and finally react under reduced pressure at 230°C and -0.1 MPa for 3 hours. Discharge and directly pelletize, wash with water and dry to obtain an intrinsic antibacterial nylon material (structural formula as Formula IV, wherein R is the A structure in Formula II, and Z1 and Z2 are both hydrogen), with a yield of 85%.

[0051] Example 2.

[0052] 1) Preparation of intermediate product α-amino-ε-caprolactam:

[0053] In a 5L reactor, add 3.5mol of lysine hydrochloride, 3.5mol of sodium hydroxide and 3.5L of methanol, stir and react at 150℃ for 4h. Cool to room temperature, filter, remove insoluble matter, evaporate to dryness and recover methanol, extract with ethyl acetate to obtain α-amino-ε-caprolactam, with a yield of 88%, and a purity of 98% according to H-NMR spectrum analysis. 1 H NMR (300MHz, D2O) δ3.69-3.72(dd,1H),3.22-3.26(m,2H),1.26-1.99(m,6H).

[0054] 2) Preparation of functional caprolactam monomer (the structural formula is shown in Formula Ⅰ, wherein R is the B structure in Formula Ⅱ, Z1 is methoxy, and Z2 is hydrogen):

[0055] Weigh 0.5 mol of α-amino-ε-caprolactam prepared in step 1), add 1 L of dichloromethane to dissolve, add 1.5 mol of triethylamine and 0.55 mol of methyl phenylchlorophosphonate at 0°C, gradually return to room temperature, stir and react for 20 hours, add saturated ammonium chloride solution, extract with dichloromethane, and obtain functional caprolactam monomer after recrystallization, with a yield of 75%. The purity is 96% according to H NMR spectrum analysis. 1H NMR (300MHz, CDCl3) δ7.72-7.77(m,2H),7.42-7.48(m,3H),5.71(s,1H),4.04-4.08(m,1H),3.76-3. 80(d,3H),3.29-3.33(m,2H),2.37-2.47(m,1H),1.88-1.99(m,1H),1.41-1.66(m,4H),0.73(s,1H).

[0056] 3) Preparation of intrinsic flame retardant nylon 6 material:

[0057] Weigh 100 mmol of the functional caprolactam prepared in step 2) and 1000 mmol of caprolactam into a polymerization reactor, then add 10 mmol of water, replace with nitrogen and maintain a nitrogen atmosphere, react under pressure at 190°C and 1.0 MPa for 2 hours, then heat to 220°C and react at normal pressure for 4 hours, and finally react under reduced pressure at 250°C and -0.1 MPa for 8 hours. Discharge and directly pelletize, wash with water and dry to obtain an intrinsic antibacterial nylon material (structural formula as Formula IV, wherein R is the B structure in Formula II, Z1 is methoxy, and Z2 is hydrogen), with a yield of 86%.

[0058] Example 3.

[0059] 1) Preparation of intermediate product α-amino-ε-caprolactam:

[0060] In a 5L reactor, add 1.75mol of lysine hydrochloride, 1.75mol of sodium hydroxide and 3.5L of methanol, stir and react at 180℃ for 4h. Cool to room temperature, filter, remove insoluble matter, evaporate to dryness and recover methanol, extract with ethyl acetate to obtain α-amino-ε-caprolactam, with a yield of 94%, and a purity of 98% according to H-NMR spectrum analysis. 1 H NMR (300MHz, D2O) δ3.69-3.72(dd,1H),3.22-3.26(m,2H),1.26-1.99(m,6H).

[0061] 2) Preparation of functional caprolactam monomer (the structural formula is shown in Formula I, wherein R is the C structure in Formula II, Z2 is hydrogen, Z3 is methoxy, and X1 is oxygen):

[0062] Weigh 0.5 mol of α-amino-ε-caprolactam prepared in step 1), add 1 L of dichloromethane to dissolve, add 1.5 mol of triethylamine and 0.55 mol of phenyl chlorophosphonate at 0 ° C, gradually return to room temperature, stir and react for 15 hours, add saturated ammonium chloride solution, extract with dichloromethane, and recrystallize to obtain a functional caprolactam monomer with a yield of 72%. The purity is 95% according to H NMR analysis. 1H NMR (300MHz, CDCl3) δ7.71-7.78(m,2H),7.32-7.47(m,5H),7.17-7.24(m,3H),6.11(s,1H),4 .04-4.08(m,1H),3.50-3.58(m,1H),3.28-3.37(m,1H),1.98-2.10(m,1H),1.40-1.74(m,6H).

[0063] 3) Preparation of intrinsic flame retardant nylon 6 material:

[0064] Weigh 100 mmol of the functional caprolactam prepared in step 2) and 1000 mmol of caprolactam into a polymerization reactor, then add 10 mmol of water and 10 mmol of benzoic acid, replace with nitrogen and maintain a nitrogen atmosphere, react under pressure at 200°C and 1.0 MPa for 5 hours, then heat to 230°C and react at normal pressure for 5 hours, and finally react under reduced pressure at 230°C and -0.1 MPa for 5 hours, discharge the material and directly cut into pellets, wash with water and dry to obtain an intrinsic antibacterial nylon material (structural formula as Formula IV, wherein R is the C structure in Formula II, Z2 is hydrogen, Z3 is methoxy, and X1 is oxygen), with a yield of 90%.

[0065] Example 4.

[0066] 1) Preparation of intermediate product α-amino-ε-caprolactam:

[0067] In a 5L reactor, add 1.75mol of lysine hydrochloride, 1.75mol of sodium hydroxide and 3.5L of methanol, stir and react at 150℃ for 4h. Cool to room temperature, filter, remove insoluble matter, evaporate to dryness and recover methanol, extract with ethyl acetate to obtain α-amino-ε-caprolactam, with a yield of 90%, and a purity of 98% according to H-NMR spectrum analysis. 1 H NMR (300MHz, D2O) δ3.69-3.72(dd,1H),3.22-3.26(m,2H),1.26-1.99(m,6H).

[0068] 2) Preparation of functional caprolactam monomer (the structural formula is shown in Formula I, wherein R is the D structure in Formula II, Z1 and Z2 are both hydrogen, and X1 is an imino group):

[0069] Weigh 0.5 mol of α-amino-ε-caprolactam prepared in step 1), add 1 L of dichloromethane to dissolve, add 1.5 mol of triethylamine and 0.55 mol of N,N'-diphenylphosphoryl chloride diammonium at 0°C, gradually return to room temperature, stir and react for 15 hours, add saturated ammonium chloride solution, extract with dichloromethane, and obtain functional caprolactam monomer after recrystallization, with a yield of 80%. The purity is 96% according to H NMR spectrum analysis.1 H NMR (300MHz, CDCl3) δ7.09-7.17(m,4H),6.78-6.85(m,2H),6.67-6.72(m,4H),5.80(s,1H),4 .04-4.08(m,1H),3.28-3.36(m,1H),3.07-3.16(m,1H),2.25-2.36(m,3H),1.41-1.76(m,6H).

[0070] 3) Preparation of intrinsic flame retardant nylon 6 material:

[0071] Weigh 100 mmol of the functional caprolactam prepared in step 2) and 1000 mmol of caprolactam into a polymerization reactor, then add 10 mmol of water and 10 mmol of benzoic acid, replace with nitrogen and maintain a nitrogen atmosphere, react under pressure at 190°C and 1.5 MPa for 4 hours, then heat to 210°C and react at normal pressure for 5 hours, and finally react under reduced pressure at 230°C and -0.1 MPa for 5 hours, discharge the material and directly pelletize it, wash it with water and dry it to obtain an intrinsic antibacterial nylon material (structural formula as Formula IV, wherein R is the D structure in Formula II, Z1 and Z2 are both hydrogen, and X1 is an amino group), with a yield of 92%.

[0072] Example 5.

[0073] 1) Preparation of intermediate product α-amino-ε-caprolactam:

[0074] In a 5L reactor, add 1.75mol of lysine hydrochloride, 1.75mol of sodium hydroxide and 3.5L of methanol, stir and react at 180℃ for 4h. Cool to room temperature, filter, remove insoluble matter, evaporate to dryness and recover methanol, extract with ethyl acetate to obtain α-amino-ε-caprolactam, with a yield of 94%, and a purity of 98% according to H-NMR spectrum analysis. 1 H NMR (300MHz, D2O) δ3.69-3.72(dd,1H),3.22-3.26(m,2H),1.26-1.99(m,6H).

[0075] 2) Preparation of functional caprolactam monomer (the structural formula is shown in Formula I, wherein R is the E structure in Formula II, Z1 is hydrogen, X1 is imino, and X2 is oxygen):

[0076] First, phosphorus oxychloride is reacted with pentaerythritol phosphate and aniline to prepare an intermediate product R-Cl containing a flame retardant group. Then 0.5 mol of the α-amino-ε-caprolactam prepared in step 1) is weighed, 1 L of dichloromethane is added to dissolve, 1.5 mol of triethylamine and 0.55 mol of the intermediate product R-Cl containing a flame retardant group are added at 0°C, the temperature is gradually restored to room temperature, the reaction is stirred for 15 hours, a saturated ammonium chloride solution is added, the liquid is extracted with dichloromethane, and the functional caprolactam monomer is obtained after recrystallization, with a yield of 70%, and a purity of 96% according to nuclear magnetic hydrogen spectrum analysis. 1 H NMR (300MHz, CDCl3) δ8.86(s,1H),7.09-7.16(m,2H),6.78-6.85(m,1H),6.67-6.72(m,2H),6.08(s, 1H),3.72-4.08(m,9H),3.59-3.68(m,1H),3.29-3.38(m,1H),2.05-2.16(m,1H),1.40-1.76(m,6H).

[0077] 3) Preparation of intrinsic flame retardant nylon 6 material:

[0078] Weigh 200 mmol of the functional caprolactam prepared in step 2) and 1000 mmol of caprolactam into a polymerization reactor, then add 20 mmol of water and 20 mmol of benzoic acid, replace with nitrogen and maintain a nitrogen atmosphere, react under pressure at 190°C and 1.5 MPa for 4 hours, then heat to 210°C and react at normal pressure for 5 hours, and finally react under reduced pressure at 230°C and -0.1 MPa for 5 hours, discharge the material and directly pelletize it, wash it with water and dry it to obtain an intrinsic antibacterial nylon material (structural formula as Formula IV, wherein R is the E structure in Formula II, Z1 is hydrogen, X1 is an imino group, and X2 is oxygen), with a yield of 90%.

[0079] Example 6.

[0080] 1) Preparation of intermediate product α-amino-ε-caprolactam:

[0081] In a 5L reactor, 1.75mol of lysine and 3.5L of methanol were added and stirred at 180°C for 4h. The mixture was cooled to room temperature, evaporated to dryness and methanol was recovered. After extraction with ethyl acetate, α-amino-ε-caprolactam was obtained with a yield of 95% and a purity of 98% according to H-NMR analysis. 1 H NMR (300MHz, D2O) δ3.69-3.72(dd,1H),3.22-3.26(m,2H),1.26-1.99(m,6H).

[0082] 2) Preparation of functional caprolactam monomer (the structural formula is shown in Formula I, wherein R is the F structure in Formula II, X1 and X2 are imino groups, and Z4 and Z5 are phenyl groups):

[0083] First, 2-amino-4,6-dichloro-S-triazine is reacted with aniline to obtain 2,4-diphenyl-melamine, which is then further reacted with phosphorus oxychloride to prepare an intermediate product R-Cl containing a flame retardant group. Finally, the intermediate product R-Cl is reacted with the α-amino-ε-caprolactam prepared in step 1) to prepare a functional caprolactam monomer (refer to Example 5 for the specific experimental steps), with a yield of 72% and a purity of 96% according to H-NMR spectrum analysis. 1 H NMR(300MHz, DMSO-d6)δ7.71-7.76(m,8H),7.26-7.34(m,8H),6.98-7.05(m,4H),6.02(s,1H),5.33(s,4H), 4.03-4.09(m,1H),3.71-3.80(m,1H),3.24-3.33(m,1H),2.30(s,2H),1.90-2.13(m,2H),1.40-1.79(m,7H).

[0084] 3) Preparation of intrinsic flame retardant nylon 6 material:

[0085] Weigh 50 mmol of the functional caprolactam prepared in step 2) and 1000 mmol of caprolactam and add them to a polymerization reactor, then add 20 mmol of water and 20 mmol of benzoic acid, replace with nitrogen and maintain the nitrogen atmosphere, react under pressure at 200°C and 2.5 MPa for 2 hours, then heat to 230°C and react at normal pressure for 4 hours, and finally react under reduced pressure at 250°C and -0.1 MPa for 3 hours, discharge the material and directly cut into pellets, wash with water and dry to obtain an intrinsic antibacterial nylon material (structural formula as Formula IV, wherein R is the F structure in Formula II, X1 and X2 are imino groups, and Z4 and Z5 are phenyl groups), with a yield of 93%.

[0086] Example 7.

[0087] 1) Preparation of intermediate product α-amino-ε-caprolactam:

[0088] In a 5L reactor, add 1.75mol lysine sulfate, 3.5mol sodium hydroxide and 3.5L methanol, stir and react at 180℃ for 4h. Cool to room temperature, filter, remove insoluble matter, evaporate to dryness and recover methanol, extract with ethyl acetate to obtain α-amino-ε-caprolactam, the yield is 92%, and the purity is 98% according to nuclear magnetic hydrogen spectrum analysis. 1H NMR (300MHz, D2O) δ3.69-3.72(dd,1H),3.22-3.26(m,2H),1.26-1.99(m,6H).

[0089] 2) Preparation of functional caprolactam monomer (the structural formula is shown in Formula I, wherein R is the G structure in Formula II, and Z4 and Z5 are both hydrogen):

[0090] First, diphenylphosphine chloride is reacted with piperazine to obtain an intermediate, which is then reacted with phenylphosphine dichloride (P structure in formula III) to prepare an intermediate product R-Cl containing a flame retardant group, and finally the intermediate is reacted with the α-amino-ε-caprolactam prepared in step 1) to prepare a functional caprolactam monomer (refer to Example 5 for specific experimental steps), with a yield of 75% and a purity of 95% according to H NMR spectrum analysis. 1 H NMR (300MHz, DMSO-d6) δ7.75-7.81(m,4H),7.48-7.54(m,6H),7.23-7.34(m,5H),5.67(s,1H),4.03-4 .08(m,1H),3.27-3.31(m,2H),2.99(s,8H),2.37-2.49(m,1H),1.76-1.87(m,1H),1.41-1.65(m,5H).

[0091] 3) Preparation of intrinsic flame retardant nylon 6 material:

[0092] Weigh 200 mmol of the functional caprolactam prepared in step 2) and 1000 mmol of caprolactam into a polymerization reactor, then add 10 mmol of water and 10 mmol of benzoic acid, replace with nitrogen and maintain a nitrogen atmosphere, react under pressure at 200°C and 2.5 MPa for 2 hours, then heat to 230°C and react at normal pressure for 4 hours, and finally react under reduced pressure at 250°C and -0.1 MPa for 3 hours. Discharge and directly pelletize, wash with water and dry to obtain an intrinsic antibacterial nylon material (structural formula as Formula IV, wherein R is the G structure in Formula II, and Z4 and Z5 are both hydrogen), with a yield of 83%.

[0093] Example 8.

[0094] 1) Preparation of intermediate product α-amino-ε-caprolactam:

[0095] In a 5L reactor, add 730g of lysine fermentation liquid (lysine content is 50%) and 2L of methanol, stir and react at 180°C for 4h. Cool to room temperature, filter, remove insoluble matter, evaporate to dryness and recover methanol, extract with ethyl acetate to obtain α-amino-ε-caprolactam, the yield is 90%, and the purity is 98% according to nuclear magnetic hydrogen spectrum analysis. 1H NMR (300MHz, D2O) δ3.69-3.72(dd,1H),3.22-3.26(m,2H),1.26-1.99(m,6H).

[0096] 2) Preparation of functional caprolactam monomer (structural formula is shown in Formula Ⅰ, wherein R is the H structure in Formula Ⅱ, and Z3 is phenyl):

[0097] 0.5 mol of α-amino-ε-caprolactam prepared in step 1) and 0.5 mol of benzaldehyde were dissolved in 100 ml of methanol, and stirred at 80° C. for 4 h under a nitrogen atmosphere. Then, 0.5 mol of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO, O structure in formula III) was added thereto, and the stirring reaction was continued at 80° C. for 8 h. The solvent was removed and a functional caprolactam monomer was obtained after recrystallization with a yield of 76%. The purity was 95% according to H NMR spectrum analysis. 1 H NMR (300MHz, DMSO-d6) δ7.86-8.01(m,3H),7.41-7.57(m,4H),7.26-7.36(m,6H),5.75(s,1H),3.95-4 .12(m,1H),3.34-3.43(m,1H),3.13-3.25(m,2H),2.49(s,1H),2.09-2.21(m,2H),1.40-1.66(m,4H).

[0098] 3) Preparation of intrinsic flame retardant nylon 6 material:

[0099] Weigh 300 mmol of the functional caprolactam prepared in step 2) and 1000 mmol of caprolactam into a polymerization reactor, then add 10 mmol of water, replace with nitrogen and maintain a nitrogen atmosphere, react under pressure at 200°C and 0.9 MPa for 2 hours, then heat to 220°C and react at normal pressure for 4 hours, and finally react under reduced pressure at 230°C and -0.1 MPa for 5 hours. Discharge and directly pelletize, wash with water and dry to obtain an intrinsic antibacterial nylon material (structural formula as Formula IV, wherein R is the H structure in Formula II, and Z3 is phenyl), with a yield of 85%.

[0100] Example 9.

[0101] 1) Preparation of intermediate product α-amino-ε-caprolactam:

[0102] The preparation method is the same as that in Example 5.

[0103] 2) Preparation of functional caprolactam monomer (structural formula is shown in formula Ⅰ, wherein R is structure I in formula Ⅱ):

[0104] Weigh 0.5 mol of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO, O structure in Formula III) and dissolve it in 100 ml of dichloromethane. Maintain a nitrogen atmosphere, drop 0.5 mol of thionyl chloride at 0°C, gradually return to room temperature, stir and react for 3 hours, cool to 0°C again, continue to add 1.0 mol of triethylamine and 0.5 mol of α-amino-ε-caprolactam prepared in step 1), gradually return to room temperature, stir and react for 15 hours, add saturated ammonium chloride solution, extract and separate with dichloromethane, and obtain functional caprolactam monomer after recrystallization with a yield of 80%. The purity is 95% according to nuclear magnetic hydrogen spectrum analysis. 1 H NMR (300MHz, DMSO-d6) δ7.86-8.18(m,3H),7.44-7.75(m,4H),7.26-7.32(m,1H),5.88(s,1H), 5.45-5.42(m,1H), 3.32-3.37(m,2H), 2.58-2.70(m,1H), 2.13-2.25(m,1H), 1.41-1.66(m,5H).

[0105] 3) Preparation of intrinsic flame retardant nylon 6 material:

[0106] Weigh 700 mmol of the functional caprolactam prepared in step 2) and 1000 mmol of caprolactam into a polymerization reactor, then add 50 mmol of water, replace with nitrogen and maintain a nitrogen atmosphere, react under pressure at 210°C and 0.6 MPa for 3 hours, then heat to 220°C and react at normal pressure for 5 hours, and finally react under reduced pressure at 250°C and -0.1 MPa for 5 hours. Discharge and directly pelletize, wash with water and dry to obtain an intrinsic antibacterial nylon material (structural formula is as shown in Formula IV, wherein R is structure I in Formula II), with a yield of 88%.

[0107] Example 10.

[0108] 1) Preparation of intermediate product α-amino-ε-caprolactam:

[0109] The preparation method is the same as that in Example 5.

[0110] 2) Preparation of functional caprolactam monomer (structural formula is shown in Formula Ⅰ, wherein R is the J structure in Formula Ⅱ):

[0111] Weigh 0.5 mol of α-amino-ε-caprolactam prepared in step 1), add 1 L of dichloromethane to dissolve, add 1.5 mol of triethylamine and 0.55 mol of 5,5-dimethyl-2-chloro-1,3,2-dioxaphosphacaprolactam phosphate (S structure in formula III) at 0°C, gradually return to room temperature, stir and react for 24 hours, add saturated ammonium chloride solution, extract and separate with dichloromethane, and obtain functional caprolactam monomer after recrystallization, with a yield of 90%. The purity is 96% according to H NMR spectrum analysis. 1 H NMR(300MHz, DMSO-d6)δ5.98(s,1H),4.04-4.08(m,1H),3.87-3.90(m,4H),3.56-3 .63(m,1H),3.25-3.34(m,1H),1.82-1.93(m,1H),0.96(s,6H),1.38-1.69(m,6H).

[0112] 3) Preparation of intrinsic flame retardant nylon 6 material:

[0113] Weigh 600 mmol of the functional caprolactam prepared in step 2) and 1000 mmol of caprolactam into a polymerization reactor, then add 100 mmol of water, replace with nitrogen and maintain a nitrogen atmosphere, react under pressure at 180°C and 0.6 MPa for 3 hours, then heat to 200°C and react at normal pressure for 4 hours, and finally react under reduced pressure at 230°C and -0.1 MPa for 5 hours. Discharge and directly pelletize, wash with water and dry to obtain an intrinsic antibacterial nylon material (structural formula is as shown in Formula IV, wherein R is the J structure in Formula II), with a yield of 80%.

[0114] Example 11.

[0115] 1) Preparation of intermediate product α-amino-ε-caprolactam:

[0116] The preparation method is the same as that in Example 5.

[0117] 2) Preparation of functional caprolactam monomer (the structural formula is shown in Formula I, wherein R is the K structure in Formula II, Z4 is phenyl, and X1 is oxygen):

[0118] First, 3,9-dichloro-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane 3,9-dioxide (T structure in formula III) is reacted with phenol to prepare an intermediate product R-Cl containing a flame retardant group, and finally the intermediate product R-Cl is reacted with the α-amino-ε-caprolactam prepared in step 1) to prepare a functional caprolactam monomer (refer to Example 5 for specific experimental steps), with a yield of 80% and a purity of 96% according to H NMR spectrum analysis. 1H NMR(300MHz, DMSO-d6)δ7.14-7.31(m,5H),5.75(s,1H),4.03-4.08(m,1H), 3.87-3.90(m,8H),3.24-3.44(m,2H),2.22-2.34(m,2H),1.41-1.65(m,5H).

[0119] 3) Preparation of intrinsic flame retardant nylon 6 material:

[0120] Weigh 100 mmol of the functional caprolactam prepared in step 2) and 1000 mmol of caprolactam into a polymerization reactor, then add 50 mmol of water, replace with nitrogen and maintain a nitrogen atmosphere, react under pressure at 200°C and 0.6 MPa for 3 hours, then heat to 220°C and react at normal pressure for 4 hours, and finally react under reduced pressure at 240°C and -0.1 MPa for 8 hours. Discharge and directly pelletize, wash with water and dry to obtain an intrinsic antibacterial nylon material (structural formula as Formula IV, wherein R is the K structure in Formula II, Z4 is phenyl, and X1 is oxygen), with a yield of 85%.

[0121] Example 12.

[0122] 1) Preparation of intermediate product α-amino-ε-caprolactam:

[0123] The preparation method is the same as that in Example 5.

[0124] 2) Preparation of functional caprolactam monomer (the structural formula is shown in Formula Ⅰ, wherein R is the L structure in Formula Ⅱ, and X1 and X2 are imino groups):

[0125] First, o-phenylenediamine is reacted with phosphorus oxychloride to prepare an intermediate product R-Cl containing a flame retardant group, and finally the intermediate product R-Cl is reacted with the α-amino-ε-caprolactam prepared in step 1) to prepare a functional caprolactam monomer (refer to Example 5 for the specific experimental steps), with a yield of 85% and a purity of 96% according to H-NMR spectrum analysis. 1 H NMR(300MHz, DMSO-d6)δ6.95-7.19(m,4H),6.06(s,1H),4.03-4.08(m,1H),3.57-3 .66(m,1H),3.28-3.36(m,1H),2.27(s,2H),2.03-2.15(m,1H),1.41-1.74(m,6H).

[0126] 3) Preparation of intrinsic flame retardant nylon 6 material:

[0127] Weigh 100 mmol of the functional caprolactam prepared in step 2) and 1000 mmol of caprolactam into a polymerization reactor, then add 50 mmol of water, replace with nitrogen and maintain a nitrogen atmosphere, react under pressure at 200°C and 0.6 MPa for 3 hours, then heat to 220°C and react at normal pressure for 4 hours, and finally react under reduced pressure at 240°C and -0.1 MPa for 8 hours. Discharge and directly pelletize, wash with water and dry to obtain an intrinsic antibacterial nylon material (structural formula as Formula IV, wherein R is the L structure in Formula II, and X1 and X2 are imino groups), with a yield of 88%.

[0128] Example 13.

[0129] 1) Preparation of intermediate product α-amino-ε-caprolactam:

[0130] The preparation method is the same as that in Example 5.

[0131] 2) Preparation of functional caprolactam monomer (the structural formula is shown in Formula I, wherein R is the M structure in Formula II, X1 and X2 are imino groups, and Z4 and Z5 are phenyl groups):

[0132] First, 2,4,6-trichloro-1,3,5-triazine (R structure in Formula III) is reacted with aniline to prepare an intermediate product R-Cl containing a flame retardant group, and finally the intermediate product R-Cl is reacted with the α-amino-ε-caprolactam prepared in step 1) to prepare a functional caprolactam monomer (refer to Example 5 for specific experimental steps), with a yield of 83% and a purity of 96% according to H-NMR spectrum analysis. 1 H NMR (300MHz, DMSO-d6) δ7.72-7.76(m,4H),7.26-7.34(m,4H),6.98-7.05(m,2H),6.02(s,1H),5.49-5.54(m ,1H),5.19(s,2H),3.78(s,1H),3.62-3.71(m,1H),3.31-3.39(m,1H),2.25-2.37(m,1H),1.41-1.88(m,5H).

[0133] 3) Preparation of intrinsic flame retardant nylon 6 material:

[0134] Weigh 100 mmol of the functional caprolactam prepared in step 2) and 1000 mmol of caprolactam into a polymerization reactor, then add 20 mmol of water, replace with nitrogen and maintain a nitrogen atmosphere, react under pressure at 200°C and 3.0 MPa for 2 h, then heat to 220°C and react at normal pressure for 8 h, finally react under reduced pressure at 240°C and -0.1 MPa for 8 h, discharge the material and directly pelletize it, wash it with water and dry it to obtain an intrinsic antibacterial nylon material (structural formula as Formula IV, wherein R is the M structure in Formula II, X1 and X2 are imino groups, and Z4 and Z5 are phenyl groups), with a yield of 92%.

[0135] Example 14.

[0136] 1) Preparation of intermediate product α-amino-ε-caprolactam:

[0137] The preparation method is the same as that in Example 5.

[0138] 2) Preparation of functional caprolactam monomer (the structural formula is shown in Formula I, wherein R is the N structure in Formula II, X1 and X2 are imino groups, and Z4 and Z5 are phenyl groups):

[0139] First, hexachlorocyclotriphosphine (Q structure in Formula III) is reacted with aniline to prepare an intermediate product R-Cl containing a flame retardant group, and finally the intermediate product R-Cl is reacted with the α-amino-ε-caprolactam prepared in step 1) to prepare a functional caprolactam monomer (refer to Example 5 for the specific experimental steps), with a yield of 75% and a purity of 96% according to H NMR spectrum analysis. 1 H NMR (300MHz, DMSO-d6) δ7.09-7.17(m,10H),6.78-6.85(m,5H),6.67-6.72(m,10H),5.93(s,1H),3. 45-3.49(m,1H),3.14-3.35(m,2H),3.11(s,1H),2.41(s,4H),1.93-2.07(m,2H),1.41-1.66(m,5H).

[0140] 3) Preparation of intrinsic flame retardant nylon 6 material:

[0141] Weigh 100 mmol of the functional caprolactam prepared in step 2) and 1000 mmol of caprolactam into a polymerization reactor, then add 20 mmol of water, replace with nitrogen and maintain a nitrogen atmosphere, react under pressure at 200°C and 3.0 MPa for 2 h, then heat to 220°C and react at normal pressure for 8 h, finally react under reduced pressure at 240°C and -0.1 MPa for 8 h, discharge the material and directly pelletize it, wash it with water and dry it to obtain an intrinsic antibacterial nylon material (structural formula as Formula IV, wherein R is the N structure in Formula II, X1 and X2 are imino groups, and Z4 and Z5 are phenyl groups), with a yield of 88%.

[0142] Comparative Example 1.

[0143] Weigh 1000 mmol of caprolactam and add it into the polymerization reactor, then add 20 mmol of water, replace with nitrogen and maintain the nitrogen atmosphere, pressurize and react at 200°C and 3.0 MPa for 2 hours, then increase the temperature to 220°C and react at normal pressure for 8 hours, finally, reduce the pressure and react at 240°C and -0.1 MPa for 8 hours, discharge the material and directly cut into pellets, wash with water and dry to obtain ordinary nylon material with a yield of 90%.

[0144] Comparative Example 2.

[0145] Weigh 2000mmol of the functional caprolactam prepared in step 2) of Example 1 and 1000mmol of caprolactam into a polymerization reactor, then add 1mmol of water, replace with nitrogen and maintain the nitrogen atmosphere, react under pressure at 180°C and 0.8MPa for 4h, then heat to 210°C and react at normal pressure for 5h, and finally react under reduced pressure at 230°C and -0.1MPa for 3h, discharge the material and directly pelletize it, wash it with water and dry it to obtain an intrinsic antibacterial nylon material (structural formula as Formula IV, wherein R is the A structure in Formula II, and Z1 and Z2 are both hydrogen), with a yield of 80%.

[0146] Comparative Example 3.

[0147] Weigh 5 mmol of the functional caprolactam prepared in step 2) of Example 1 and 1000 mmol of caprolactam into a polymerization reactor, then add 1 mmol of water, replace with nitrogen and maintain a nitrogen atmosphere, react under pressure at 180°C and 0.8 MPa for 4 hours, then heat to 210°C and react at normal pressure for 5 hours, and finally react under reduced pressure at 230°C and -0.1 MPa for 3 hours, discharge the material and directly pelletize it, wash it with water and dry it to obtain an intrinsic antibacterial nylon material (structural formula as Formula IV, wherein R is the A structure in Formula II, and Z1 and Z2 are both hydrogen), with a yield of 85%.

[0148] In order to evaluate the flame retardant properties and tensile properties of the intrinsic flame retardant nylon materials prepared in Examples 1 to 14 and the nylon materials prepared in Comparative Examples 1 to 3, the pellets were made into strips according to the standard, and then tested according to the following test method. The results are shown in Table 1:

[0149] Vertical burning test (UL-94): Test the samples in accordance with GB / T 2408-2021 standard;

[0150] Limiting oxygen index (LOI) test: Test the samples according to GB / T 2406.2-2009 standard;

[0151] Tensile performance test: Test the samples according to GB / T 1040.2-2022 standard

[0152] Table 1

[0153]

[0154]

[0155] As shown in the data of Table 1, the intrinsic flame retardant nylon material of the present invention has a significant flame retardant effect and a tensile property substantially equivalent to that of the conventional nylon 6 material (Comparative Example 1). In contrast, the tensile property of the nylon material of Comparative Example 2 is poor, and the flame retardant property of the nylon material of Comparative Example 3 is insufficient.

[0156] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0157] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0158] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the content of the present invention.

Claims

1. A functional caprolactam, characterized in that: Its structural formula is shown in the following formula I: Wherein, R is selected from one of the structural formulas shown in the following formula II: Wherein, Z1 and Z2 are independently selected from hydrogen, C 1～10 One of a linear / branched aliphatic hydrocarbon group, hydroxyl group, methoxy group, tert-butoxy group, cyano group, boric acid, and boric acid ester; Z3, Z4, and Z5 are independently selected from C 1～10 One of a linear / branched aliphatic hydrocarbon group, a substituted / unsubstituted aryl group, and a substituted / unsubstituted aralkyl group; X1 and X2 are each independently selected from an oxygen atom or an imino group.

2. A method for preparing functional caprolactam according to claim 1, characterized in that: The following steps are involved: Step 1: Mix the raw material containing lysine with methanol, dehydrate to form a ring at 120°C to 200°C, evaporate to dryness and recover methanol, and extract with ethyl acetate to obtain the intermediate product α-amino-ε-caprolactam; Step 2: dissolving the α-amino-ε-caprolactam in a solvent, adding a reagent containing a flame retardant group to react, and obtaining functional caprolactam after post-treatment.

3. The method for preparing functional caprolactam according to claim 2, characterized in that: The raw material containing lysine in step 1 is selected from one of lysine, lysine hydrochloride, lysine sulfate, and an aqueous solution containing lysine, or a combination of at least two thereof; when lysine hydrochloride or lysine sulfate is selected, an equimolar equivalent of sodium hydroxide is also added; The reaction time of the dehydration ring formation is 1 h to 6 h.

4. The method for preparing functional caprolactam according to claim 2, characterized in that: The solvent in step 2 is selected from one or a combination of at least two of dichloromethane, chloroform, acetonitrile, acetone, tetrahydrofuran, toluene, xylene, mesitylene, dioxane, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide; The reaction temperature is -40°C to 200°C, and the reaction time is 1h to 24h.

5. The method for preparing functional caprolactam according to claim 2, characterized in that: The flame retardant group-containing reagent in step 2 is prepared by reacting a structure shown in Formula III below with an amine / aldehyde / phenol / phosphoramide compound; 6. An intrinsic flame retardant nylon material, characterized in that: The functional caprolactam as claimed in claim 1 is included, and the structural formula of the intrinsic flame retardant nylon material is shown in the following formula IV: Wherein, x and y represent the molar proportion of each part of the repeating unit respectively, x is selected from 0.01 to 0.50, y is selected from 0.50 to 0.99, and x+y=1.

7. A method for preparing an intrinsic flame retardant nylon material as claimed in claim 6, characterized in that: The steps include: The functional performance caprolactam, caprolactam, water and a molecular weight regulator are added into a polymerization kettle to carry out a ring-opening copolymerization reaction to obtain an intrinsic flame-retardant nylon material.

8. The method for preparing an intrinsic flame-retardant nylon material according to claim 7, characterized in that: The molecular weight regulator is selected from one of acetic acid, adipic acid and benzoic acid; The molar ratio of the functional caprolactam, caprolactam, water and molecular weight regulator is (1-100):100:(0.1-5):(0-5); The copolymerization reaction temperature is 140°C to 320°C, the reaction time is 2h to 96h, and the reaction pressure is -0.1MPa to 5MPa.

9. The method for preparing an intrinsic flame-retardant nylon material according to claim 7, characterized in that: Also includes: Directly extruding the obtained intrinsic flame-retardant nylon material into granules, then washing the granules with a solvent, and finally drying; The solvent is selected from one or more of water, methanol, ethanol, dichloromethane, acetone, and ethyl acetate; the washing time is 0.1h to 24h, and the washing temperature is 25°C to 100°C.

10. Use of the intrinsic flame retardant nylon material according to claim 6 or the intrinsic flame retardant nylon material obtained by the preparation method according to any one of claims 7 to 9, characterized in that: Used in automotive, textile, electrical and electronic, construction and packaging fields.

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