Phosphorus-containing lactam compound, preparation method thereof and flame-retardant polyamide 6 material

Abstract

The invention relates to a phosphorus-containing lactam compound, a preparation method thereof and a flame-retardant polyamide 6 material.The method comprises the following steps that in a solvent, a compound A with the structure shown in the formula (III) and a compound B with the structure shown in the formula (IV) are subjected to a first reaction, and an intermediate product is obtained; carrying out second reaction on the intermediate product and a compound C formed by a group containing at least one part shown as a formula (II) to obtain a phosphorus-containing lactam compound; the phosphorus-containing lactam compound provided by the invention can realize multi-element synergistic flame retardance, the synthesis method is simple and efficient, and the flame retardant requirement of a polyamide material is met.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of flame-retardant materials, in particular to a phosphorus-containing lactam compound, a preparation method thereof and a flame-retardant polyamide 6 material. BACKGROUND

[0002] Polyamide, also known as nylon, is a general term for a class of polymers containing amide repeating units in the main chain. Polyamide is one of the important thermoplastic engineering plastics, which has the advantages of strong corrosion resistance, high mechanical strength, good self-lubricating property, wear resistance, oil resistance and easy molding processing. However, as a typical organic polymer material, polyamide has a low oxygen index and can only reach UL94 V-2 level in vertical burning test, and it also produces dripping during burning, which belongs to flammable materials and is prone to cause fire during use. Therefore, when polyamide is applied to products with fire safety requirements such as electronics and electrical appliances, automobiles and new energy, flame-retardant treatment measures must be taken to ensure the safety of the products.

[0003] Adding flame retardants to polyamide is a common means to improve the flame-retardant properties of polyamide materials. The flame retardants commonly used for polyamide mainly include halogen-based flame retardants and halogen-free flame retardants. Halogen-based flame retardants generate a large amount of smoke and corrosive toxic gases during thermal cracking or burning, which cannot meet environmental protection requirements, and their use is limited to a certain extent. Therefore, the development of halogen-free flame retardants has far-reaching significance for the development of environmentally friendly flame-retardant polyamide materials. Among halogen-free flame retardants, phosphorus-based and nitrogen-based flame retardants are the most widely used, and phosphorus-nitrogen synergism has become the latest direction of research and development of phosphorus-based and nitrogen-based flame retardants. The flame-retardant mechanism is the comprehensive effect of condensed phase flame retardation and gas phase flame retardation. Flame retardants will decompose to generate inorganic acids such as phosphoric acid and polyphosphoric acid during the heating process of burning, which can form a protective film on the surface of the substrate to isolate air. At the same time, ammonia, nitrogen, water vapor and nitrogen oxides and other non-combustible gases are easily released after heating, which block the supply of oxygen and achieve the purpose of flame retardation. The use of multiple flame-retardant elements to compensate for the shortcomings of single flame-retardant elements can better balance the relationship between the amount of flame retardant, performance and cost, and meet the growing requirements of environmental protection and safety. CN115466384A discloses a series of phosphorus-containing reactive flame retardants, which are applied in polyamides such as PA66, PA6 and PA46 to prepare a series of flame-retardant copolymer polyamide materials. However, due to the complex structure of the flame retardant, the synthesis is difficult and the cost is high, which makes it difficult to be applied on a large scale.

[0004] Most of the current phosphorus-nitrogen type flame retardants are small molecule additives. Since the additive type flame retardant lacks groups available for reaction, and is prone to migration or precipitation during the processing and use of polymer products. Therefore, from the perspective of molecular design of flame retardants, designing a multi-element synergistic halogen-free flame retardant with reactive groups has great application potential. The stable combination of the flame retardant with the polymer resin substrate in need of flame-retardant modification through chemical bonds can realize the efficient, environmental protection and long-term of the flame-retardant polymer materials. SUMMARY

[0005] The purpose of the present disclosure is to provide a novel phosphorus-containing halogen-free phosphorus-containing lactam compound and its preparation method, and a flame-retardant polyamide 6 material, which can realize multi-element synergistic flame retardation, and the synthesis method is simple and efficient, meeting the flame-retardant demand of polyamide materials.

[0006] In order to achieve the above-mentioned purpose, the first aspect of the present disclosure provides a preparation method of a phosphorus-containing lactam compound, comprising the following steps:

[0007] In a solvent, compound A with formula (III) and compound B with formula (IV) are subjected to a first reaction to obtain an intermediate product;

[0008] The intermediate product is subjected to a second reaction with compound C selected from a group comprising at least one formula (II) moiety to obtain a phosphorus-containing lactam compound;

[0009]

[0010] In formula (III), n is selected from an integer from 0 to 4; R1 is selected from hydrogen, hydroxyl, mercapto, nitrile group, amino, substituted or unsubstituted C 1-24 alkyl, substituted or unsubstituted C 3-12 cycloalkyl, substituted or unsubstituted C 3-10 heterocycloalkyl, substituted or unsubstituted C 6-30 aryl;

[0011] In formula (IV), R2 is selected from substituted or unsubstituted C 1-24 alkyl, substituted or unsubstituted C 3-12 cycloalkyl, substituted or unsubstituted C 3-10 heterocycloalkyl, substituted or unsubstituted C 6-30 aryl;

[0012] In formula (II), X1 is selected from nitrogen, oxygen; R4 and X2 are connected to form a ring or not; X2 is selected from nitrogen, oxygen, hydroxyl; R4 is selected from substituted or unsubstituted C 1-24 alkyl, substituted or unsubstituted C 3-12 cycloalkyl, substituted or unsubstituted C 3-10 heterocycloalkyl, substituted or unsubstituted C 6-30 aryl.

[0013] Optionally, the method comprises:

[0014] reacting the compound A with the compound B to obtain the intermediate product by Schiff base reaction; and adding the intermediate product with the compound C by addition reaction;

[0015] wherein the compound A has a structure as shown in the following formula (A):

[0016] the compound B has a structure as shown in the following formula (B):

[0017] in formula (B), group A is selected from C 6-30 aryl or C 3-30 heteroaryl; R is selected from a hydrogen atom, a nitro group, a hydroxyl group, an amino group, a cyano group, a thiol group, an ester group, a sulfonic acid group, a substituted or unsubstituted C 1-10 alkyl, a substituted or unsubstituted C 1-6 alkoxy, a substituted or unsubstituted C 2-10 alkenyl, a substituted or unsubstituted C 2-10 alkynyl, a substituted or unsubstituted C 6-20 aryl or a substituted or unsubstituted C 3-20 heteroaryl; optionally, the substituent of R is selected from deuterium, a nitro group, a hydroxyl group, a C 1-10 alkyl, a C 3-10 cycloalkyl, a C 2-10 alkenyl, a C 2-10 alkynyl, a C 6-20 aryl, a C 3-20 heteroaryl, a C 2-10 heterocycloalkyl, a C 1-6 alkoxy, an amino group, a cyano group, a thiol group, an ester group or a sulfonic acid group; m represents the number of methylene groups, m is 0, 1, 2, 3 or 4; x represents the number of R, x is 0, 1, 2, 3, 4 or 5;

[0018] the compound C has a structure as shown in the following formula (C):

[0019] optionally, in formula (B), group A is selected from C 6-12 aryl or C 3-12 heteroaryl; R is selected from a hydrogen atom, a nitro group, a hydroxyl group, an amino group, a cyano group, a thiol group, an ester group, a sulfonic acid group, a substituted or unsubstituted C 1-6 alkyl, a substituted or unsubstituted C 1-2 alkoxy, a substituted or unsubstituted C 2-6 alkenyl, a substituted or unsubstituted C 2-6 alkynyl, a substituted or unsubstituted C 6-12substituted or unsubstituted C 3-12 heteroaryl;

[0020] Optionally, the substituent of R is selected from deuterium, nitro, hydroxyl, C 1-6 alkyl, C 3-6 cycloalkyl, C 2-6 alkenyl, C 2-6 alkynyl, C 6-12 aryl, C 3-12 heteroaryl, C 2-6 heterocycloalkyl, C 1-2 alkoxy, amino, cyano, thiol, ester or sulfonic acid group.

[0021] Preferably, the group A is selected from a benzene ring, a naphthalene ring, a furan ring, a thiophene ring, a pyrrole ring, a thiazole ring, an imidazole ring, a pyridine ring, a pyrimidine ring or a pyrazine ring.

[0022] Optionally, the R is selected from a hydrogen atom, nitro, hydroxyl, amino, cyano, methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, tert-butyl, phenyl, naphthyl, methoxy, ethoxy, carboxyl, acryl, epoxy, vinyl, vinyl ether, acetylamino, dimethylamino, acetylene, methyl ester, ethyl ester, thiol or isocyanate group.

[0023] Optionally, the substituent of R is selected from deuterium, nitro, hydroxyl, C

[0024] Preferably, m is 1 or 2; x is 0, 1 or 2.

[0025] Optionally, the compound B comprises one or more of benzaldehyde, p-hydroxybenzaldehyde, p-cyanobenzaldehyde, phenylacetaldehyde, furfural, 5-hydroxymethylfurfural, syringaldehyde, 2-thiophenecarboxaldehyde and vanillin.

[0026] Optionally, the molar ratio of the compound A to the compound B is 1:0.3-3, preferably 1:0.8-1.2.

[0027] Preferably, the molar ratio of the compound A to the compound C is 1:0.3-3, preferably 1:0.8-1.2.

[0028] The second aspect of the present disclosure provides a phosphorus-containing lactam compound prepared by the method according to the first aspect of the present disclosure.

[0029] The third aspect of the present disclosure provides a phosphorus-containing lactam compound, which has a structure as shown in the following formula (I):

[0030]

[0031] In formula (I), n is selected from an integer from 0 to 4; R1is selected from hydrogen, hydroxyl, thiol, nitrile, amino, substituted or unsubstituted C 1-24 alkyl, substituted or unsubstituted C 3-12 cycloalkyl, substituted or unsubstituted C 3-10 heterocycloalkyl, substituted or unsubstituted C 6-30 aryl;

[0032] R2is selected from substituted or unsubstituted C 1-24 alkyl, substituted or unsubstituted C 3-12 cycloalkyl, substituted or unsubstituted C 3-10 heterocycloalkyl, substituted or unsubstituted C 6-30 aryl;

[0033] R3is selected from a group comprising a moiety having at least one structure as shown in formula (II) below;

[0034]

[0035] In formula (II), X1is selected from nitrogen, oxygen; R4and X2are connected to form a ring or not; X2is selected from nitrogen, oxygen, hydroxyl; R4is selected from substituted or unsubstituted C 1-24 alkyl, substituted or unsubstituted C 3-12 cycloalkyl, substituted or unsubstituted C 3-10 heterocycloalkyl, substituted or unsubstituted C 6-30 aryl.

[0036] Optionally, the phosphorus-containing lactam compound has a structure as shown in formula (V) below:

[0037]

[0038] In formula (V), U has a structure as shown in formula (D) below:

[0039] In formula (D), group A is selected from C 6-30 aryl or C 3-20 heteroaryl; * indicates that formula (D) is connected to formula (V);

[0040] R is selected from a hydrogen atom, nitro, hydroxyl, amino, cyano, thiol, ester, sulfonic acid, substituted or unsubstituted C 1-10 alkyl, substituted or unsubstituted C 1-6 alkoxy, substituted or unsubstituted C 2-10 alkenyl, substituted or unsubstituted C 2-10 alkynyl, substituted or unsubstituted C6-20 aryl or C 3-20 heteroaryl; optionally, a substituent of R is selected from deuterium, nitro, hydroxyl, C 1-10 alkyl, C 3-10 cycloalkyl, C 2-10 alkenyl, C 2-10 alkynyl, C 6-20 aryl, C 3-20 heteroaryl, C 2-10 heterocycloalkyl, C 1-6 alkoxy, amino, cyano, thiol, ester, or sulfonic acid;

[0041] m represents the number of methylene groups, m is 0, 1, 2, 3, or 4; x represents the number of R, x is 0, 1, 2, 3, 4, or 5.

[0042] Optionally, in formula (D), the group A is selected from a C 6-12 aryl or C 3-12 heteroaryl;

[0043] R is selected from a hydrogen atom, nitro, hydroxyl, amino, cyano, thiol, ester, sulfonic acid, C 1-6 alkyl, C 1-2 alkoxy, C 2-6 alkenyl, C 2-6 alkynyl, C 6-12 aryl or C 3-12 heteroaryl;

[0044] Optionally, a substituent of R is selected from deuterium, nitro, hydroxyl, C 1-6 alkyl, C 3-6 cycloalkyl, C 2-6 alkenyl, C 2-6 alkynyl, C 6-12 aryl, C 3-12 heteroaryl, C 2-6 heterocycloalkyl, C 1-2 alkoxy, amino, cyano, thiol, ester, or sulfonic acid.

[0045] Optionally, the group A is selected from a benzene ring, naphthalene ring, furan ring, thiophene ring, pyrrole ring, thiazole ring, imidazole ring, pyridine ring, pyrimidine ring, or pyrazine ring;

[0046] Optionally, R is selected from a hydrogen atom, nitro, hydroxyl, amino, cyano, methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, phenyl, naphthyl, methoxy, ethoxy, carboxyl, acryloyl, epoxy, vinyl, vinyl ether, acetylamino, dimethylamino, ethynyl, methyl ester, ethyl ester, thiol, or isocyanate;

[0047] Optionally, the substituent of R is selected from deuterium, nitro, hydroxyl, amino, cyano, methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, tert-butyl, phenyl, naphthyl, methoxy, ethoxy, carboxyl, acryloyl, epoxy, vinyl, vinyl ether, acetylamino, dimethylamino, ethynyl, methyl ester, ethyl ester, mercapto or isocyanate;

[0048] Preferably, m is 1 or 2; x is 0, 1 or 2.

[0049] The fourth aspect of the present disclosure provides a flame-retardant polyamide 6 material, which is obtained by blending a polyamide 6 material with the phosphorus-containing lactam compound according to the second aspect or the third aspect of the present disclosure.

[0050] Optionally, the content of the phosphorus-containing lactam compound is 1-40 wt%, preferably 5-20 wt%, based on the total weight of the flame-retardant polyamide 6 material.

[0051] The fifth aspect of the present disclosure provides a flame-retardant polyamide 6 material, which comprises a repeating unit having a structure as shown in the following formula (VI):

[0052]

[0053] wherein Q has a structure as shown in the following formula (VII):

[0054]

[0055] Optionally, the molar content of the repeating unit having the structure shown in formula (VI) is 0.1-30%, preferably 1-20%, based on the total molar amount of the flame-retardant polyamide 6 material.

[0056] By the above technical solution, the present disclosure provides a phosphorus-containing lactam compound, a preparation method thereof and a flame-retardant polyamide 6 material. Compound A is subjected to a first reaction with compound B to obtain an intermediate product, and then the intermediate product is subjected to a second reaction with compound C to obtain the phosphorus-containing lactam compound The phosphorus-containing lactam compound contains phosphorus, nitrogen flame-retardant elements and aromatic benzene ring structure, and can play a synergistic flame-retardant role; the phosphorus-containing lactam compound also has a cyclic lactam structure, can participate in ring-opening polymerization of caprolactam, and endows the prepared polyamide 6 material with persistent and stable flame-retardant performance; the preparation method of the phosphorus-containing lactam compound is simple and efficient, the raw material used is bio-based aminocaprolactam, which is prepared from biomass lysine, is a low-toxicity and environmentally-friendly halogen-free flame retardant, and conforms to the concept of green environmental protection and sustainable development; application of the phosphorus-containing lactam compound provided in the present disclosure to a flame-retardant polyamide 6 material can meet the flame-retardant requirements of the polyamide material, and also does not cause great influence on the mechanical properties of the polyamide 6 material itself.

[0057] Other features and advantages of the present disclosure will be described in detail in the following specific embodiments section. BRIEF DESCRIPTION OF DRAWINGS

[0058] Figure 1 is a thermogravimetric curve of the phosphorus-containing lactam compound prepared in the embodiment A1 of the present disclosure. DETAILED DESCRIPTION

[0059] The specific embodiments of the present disclosure are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure, and are not used to limit the present disclosure. The endpoints and any values of the ranges disclosed herein are not limited to the precise values or ranges stated, and are intended to encompass values approximately around those ranges. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0060] The first aspect of the present disclosure provides a preparation method of a phosphorus-containing lactam compound, comprising the following steps:

[0061] In a solvent, compound A with the structure of formula (III) and compound B with the structure of formula (IV) are subjected to a first reaction to obtain an intermediate product;

[0062] The intermediate product is subjected to a second reaction with compound C selected from a group comprising at least one moiety of formula (II) to obtain a phosphorus-containing lactam compound;

[0063]

[0064] In formula (III), n is selected from an integer from 0 to 4; R1 is selected from hydrogen, hydroxyl, mercapto, nitrile, amino, substituted or unsubstituted C 1-24 substituted or unsubstituted C 3-12 substituted or unsubstituted C 3-10heterocycloalkyl, substituted or unsubstituted C 6-30 aryl;

[0065] In formula (IV), R2 is selected from substituted or unsubstituted C 1-24 alkyl, substituted or unsubstituted C 3-12 cycloalkyl, substituted or unsubstituted C 3-10 heterocycloalkyl, substituted or unsubstituted C 6-30 aryl;

[0066] In formula (II), X1 is selected from nitrogen, oxygen; R4 and X2 are connected or not connected to form a ring; X2 is selected from nitrogen, oxygen, hydroxyl; R4 is selected from substituted or unsubstituted C 1-24 alkyl, substituted or unsubstituted C 3-12 cycloalkyl, substituted or unsubstituted C 3-10 heterocycloalkyl, substituted or unsubstituted C 6-30 aryl.

[0067] The present disclosure provides a preparation method of a phosphorus-containing lactam compound. First, a reactant A (an amino caprolactam compound) is subjected to a first reaction with a reactant B (an aldehyde compound) to connect the reactant B (the aldehyde compound) to the N atom of the amino group in the reactant A (the amino caprolactam compound), to obtain an intermediate product having a Schiff base structure, wherein the C=N double bond can be used for a subsequent addition reaction, and the aldehyde compound structure is introduced into the phosphorus-containing lactam compound, which can improve the thermal stability of the phosphorus-containing lactam compound and promote carbon formation; then the intermediate product is subjected to an addition reaction with a compound C containing a structure, and the active P-H bond in the molecular structure of the compound C can be subjected to an addition reaction with an unsaturated group, so that the nitrogen atom of the cyclic lactam side group amine is connected to a structure, which has higher thermal stability and chemical stability than a general non-cyclic organic phosphate flame-retardant system. The preparation method provided by the present disclosure is simple and efficient, and the raw material used is a bio-based amino caprolactam prepared from biomass lysine, which is a low-toxicity and environmentally friendly halogen-free flame retardant, and conforms to the concepts of green environmental protection and sustainable development.

[0068] The reactants used in the present disclosure can be obtained through ordinary commercial channels or prepared by known methods.

[0069] The present disclosure does not have special limitations on the source of the reactant A. For example, amino caprolactam is used as the reactant A, and the amino caprolactam can be synthesized from L-lysine. This method is well known to those skilled in the art, and will not be described here.

[0070] In the present disclosure, the number of carbon atoms indicates the total number of carbon atoms included in the group and the substituents on the group.

[0071] In one embodiment, n in the compound A is selected from an integer from 0 to 4, i.e. n is selected from 0, 1, 2, 3, 4, preferably 2, 3, more preferably 3.

[0072] In one embodiment, R1in the compound A is selected from hydrogen, hydroxyl, thiol, nitrile, amino, substituted or unsubstituted C 1-10 alkyl, substituted or unsubstituted C 3-6 cycloalkyl, substituted or unsubstituted C 3-6 heterocycloalkyl.

[0073] In one embodiment, R1in the compound A is selected from hydrogen, hydroxyl, nitrile, substituted or unsubstituted C 1-5 alkyl; more preferably, R1in the compound A is selected from hydrogen, C 1-3 alkyl.

[0074] In one preferred embodiment, the compound A includes, but is not limited to, DL- aminocaproamide, 2-aminopentamide, and the like.

[0075] In one embodiment, R4in the compound C is selected from substituted or unsubstituted C 1-10 alkyl, substituted or unsubstituted C 3-6 cycloalkyl, substituted or unsubstituted C 6-12 aryl.

[0076] In one preferred embodiment, R4in the compound C is selected from substituted or unsubstituted C 1-5 alkyl, substituted or unsubstituted C 6-12 aryl; more preferably, R4is selected from substituted or unsubstituted C 6-12 aryl.

[0077] In one embodiment, the compound C includes, but is not limited to, DOPO (9,10- dihydro-9-oxa-10-phosphaphenanthrene-10-oxide), 5,6-dihydro-6-oxide dibenz[c,e][1,2] azaphosphorine, and the like.

[0078] In one preferred embodiment, R1, R2, and R4in the compound A, the compound B, and the compound C are each independently selected from a group, the substituent group is selected from hydroxyl, thiol, nitrile, amino, C 1-5 alkyl, preferably selected from hydroxyl, amino, C 1-3 alkyl, more preferably selected from hydroxyl, amino, methyl, ethyl.

[0079] In one embodiment, the method includes:

[0080] The compound A and the compound B undergo a Schiff base reaction to obtain the intermediate product; the intermediate product is contacted with the compound C to perform an addition reaction;

[0081] Wherein, the compound A has a structure as shown in the following formula (A):

[0082] The compound B has a structure as shown in the following formula (B):

[0083] In formula (B), group A is selected from C 6-30 Aryl or C 3-30 heteroaryl;

[0084] R is selected from hydrogen atom, nitro, hydroxyl, amino, cyano, thiol, ester, sulfonic acid, substituted or unsubstituted C 1-10 Alkyl, substituted or unsubstituted C 1-6 Alkoxy, substituted or unsubstituted C 2-10 Alkenyl, substituted or unsubstituted C 2-10 Alkynyl, substituted or unsubstituted C 6-20 Aryl or substituted or unsubstituted C 3-20 Heteroaryl; Optionally, the substituent of R is selected from deuterium, nitro, hydroxyl, C 1-10 Alkyl, C 3-10 Cycloalkyl, C 2-10 Alkenyl, C 2-10 Alkynyl, C 6-20 Aryl, C 3-20 Heteroaryl, C 2-10 Heterocycloalkyl, C 1-6 Alkoxy, amino, cyano, mercapto, ester or sulfonic acid; m represents the number of methylene groups, m is 0, 1, 2, 3 or 4; x represents the number of R, x is 0, 1, 2, 3, 4 or 5;

[0085] The compound C has a structure as shown in the following formula (C):

[0086] In this embodiment, compound A is aminocaprolactam, and group A in the structural formula of compound B is an aromatic group or a heteroaromatic group. The intermediate product obtained by reacting compound A with compound B is reacted with compound C (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, DOPO). The phosphorus-containing lactam compound obtained contains a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide structure containing a biphenyl ring and a phenanthrene ring structure, and the side phosphorus group is introduced in the form of a cyclic O=PO bond, which has higher thermal stability and chemical stability than general non-annulated organic phosphate flame retardant systems. In addition, an aromatic group is connected to the central C atom in the molecular structure of the flame retardant, which is easy to form carbon during combustion, thereby improving the flame retardant effect.

[0087] In a preferred embodiment, in formula (B), group A is selected from C 6-12 Aryl or C 3-12 heteroaryl;

[0088] R is selected from hydrogen atom, nitro, hydroxyl, amino, cyano, thiol, ester, sulfonic acid, substituted or unsubstituted C 1-6 Alkyl, substituted or unsubstituted C 1-2 Alkoxy, substituted or unsubstituted C 2-6 Alkenyl, substituted or unsubstituted C 2-6 Alkynyl, substituted or unsubstituted C 6-12 Aryl or substituted or unsubstituted C 3-12 Heteroaryl; when the group types in the structural formula of compound B are within the scope of this embodiment, a phosphorus-containing lactam compound with better flame retardant properties can be prepared.

[0089] In one embodiment, the substituent of R is selected from deuterium, nitro, hydroxyl, C 1-6 Alkyl, C 3-6 Cycloalkyl, C 2-6 Alkenyl, C 2-6 Alkynyl, C 6-12 Aryl, C 3-12 Heteroaryl, C 2-6 Heterocycloalkyl, C 1-2 an alkoxy group, an amino group, a cyano group, a mercapto group, an ester group or a sulfonic acid group.

[0090] In a preferred embodiment, the group A is selected from a benzene ring Naphthalene ring Furan ring Thiophene ring Pyrrole ring Thiazole ring Imidazole ring Pyridine ring Pyrimidine ring or pyrazine ring In formula (B), R and -(CH2) m -CHO can be attached to any position on the A ring.

[0091] In a specific embodiment, in formula (B), R is selected from a hydrogen atom, a nitro group, a hydroxyl group, an amino group, a cyano group, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a phenyl group, a naphthyl group, a methoxy group, an ethoxy group, a carboxyl group, an acryloyl group, an epoxy group, a vinyl group, a vinyl ether group, an acetamido group, a dimethylamino group, an ethynyl group, a methyl group, an ethyl group, a mercapto group or an isocyanate group;

[0092] In a specific embodiment, in formula (B), the substituent of R is selected from deuterium, nitro, hydroxyl, amino, cyano, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, phenyl, naphthyl, methoxy, ethoxy, carboxyl, acryloyl, epoxy, vinyl, vinyl ether, acetamido, dimethylamino, ethynyl, methyl ester, ethyl ester, mercapto or isocyanate;

[0093] In a preferred embodiment, in formula (B), m is 1 or 2, and x is 0, 1 or 2. When the types of groups in the structural formula of compound B are within the range of this embodiment, a phosphorus-containing lactam compound with better flame retardancy can be prepared.

[0094] In one embodiment, the compound B comprises one or more of benzaldehyde, p-hydroxybenzaldehyde, p-cyanobenzaldehyde, phenylacetaldehyde, furfural, 5-hydroxymethylfurfural, syringaldehyde, 2-thiophenecarboxaldehyde, and vanillin. Using the compound B reagent type provided in this embodiment, a phosphorus-containing lactam compound with improved flame retardancy can be prepared.

[0095] In one embodiment, the molar ratio of compound A:compound B is 1:0.3-3, including but not limited to 1:0.3, 1:0.8, 1:1, 1:1.2, 1:1.5, 1:2, 1:3, and any value in the range of any two values, preferably 1:0.8-1.2;

[0096] Preferably, the molar ratio of compound A:compound C is 1:0.3-3, including but not limited to 1:0.3, 1:0.8, 1:1, 1:1.2, 1:1.5, 1:2, 1:3, and any value in a range consisting of any two values, preferably 1:0.8-1.2. The phosphorus-containing lactam compound prepared by carrying out the first reaction and the second reaction according to the raw material ratio in this embodiment (especially according to the preferred raw material ratio) has better flame retardant properties.

[0097] In one embodiment, the conditions of the first reaction include: temperature of 20-180℃, including but not limited to 20℃, 60℃, 70℃, 80℃, 90℃, 100℃, 120℃, 150℃, 180℃, and any value in the range between any two values; preferably 60-90℃; time of 0.25-72h, preferably 1-3h.

[0098] Preferably, the conditions of the second reaction include: temperature of 20-180℃, including but not limited to 20℃, 60℃, 70℃, 80℃, 90℃, 100℃, 120℃, 150℃, 180℃, and any value in the range between any two values; preferably 60-90℃; time of 3-72h, preferably 6-12h. The reaction under the process conditions in this embodiment, especially under the preferred process conditions, can achieve a better reaction effect.

[0099] In one embodiment, the solvent includes at least one of methanol, ethanol, propanol, acetone, dichloromethane, trichloromethane, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, 1,4-dioxane and ethyl acetate, preferably one or more selected from methanol, ethanol and propanol.

[0100] In one embodiment, the method further includes: sequentially removing the solvent from the product obtained from the second reaction and separating to obtain the phosphorus-containing lactam compound. The separation method includes but is not limited to extraction, crystallization, distillation, ion exchange, adsorption separation, column chromatography separation, etc.

[0101] In one embodiment, a catalyst is further added in the first reaction; the catalyst includes one or more of formic acid, glacial acetic acid, hydrochloric acid and hydrofluoric acid; the addition of the catalyst can improve the conversion rate of compound A (e.g. aminocaproamide) and the selectivity of the phosphorus-containing lactam flame retardant.

[0102] In one preferred embodiment, the weight ratio of the compound A to the catalyst is 1:(0.05-0.5), including but not limited to 1:0.05, 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5; preferably 1:(0.05-0.2). The catalytic reaction under the weight ratio in this embodiment has a better reaction effect.

[0103] The second aspect of the present disclosure provides a phosphorus-containing lactam compound prepared by the method according to the first aspect of the present disclosure.

[0104] The third aspect of the present disclosure provides a phosphorus-containing lactam compound, which has a structure as shown in the following formula (I):

[0105] In formula (I), n is an integer selected from 0 to 4; R1is selected from hydrogen, hydroxyl, thiol, nitrile, amino, substituted or unsubstituted C 1-24 alkyl, substituted or unsubstituted C 3-12 cycloalkyl, substituted or unsubstituted C 3-10 heterocycloalkyl, substituted or unsubstituted C 6-30 aryl;

[0106] R2is selected from substituted or unsubstituted C 1-24 alkyl, substituted or unsubstituted C 3-12 cycloalkyl, substituted or unsubstituted C 3-10 heterocycloalkyl, substituted or unsubstituted C 6-30 aryl;

[0107] R3is selected from a group comprising a moiety having at least one structure as shown in formula (II) below;

[0108]

[0109] In formula (II), X1is selected from nitrogen, oxygen; R4and X2are connected to form a ring or not; X2is selected from nitrogen, oxygen, hydroxyl; R4is selected from substituted or unsubstituted C 1-24 alkyl, substituted or unsubstituted C 3-12 cycloalkyl, substituted or unsubstituted C 3-10 heterocycloalkyl, substituted or unsubstituted C 6-30 aryl. The specific group types have been described in detail in the foregoing, and will not be described here again.

[0110] In a preferred embodiment, the phosphorus-containing lactam compound has a structure as shown in formula (V) below:

[0111]

[0112] In formula (V), U has a structure as shown in formula (D) below:

[0113] In formula (D), group A is selected from C 6-30 aryl or C 3-30 heteroaryl; * indicates that formula (D) is connected to formula (V);

[0114] R is selected from hydrogen atom, nitro, hydroxyl, amino, cyano, thiol, ester, sulfonic acid, substituted or unsubstituted C 1-10 alkyl, substituted or unsubstituted C 1-6 alkoxy, substituted or unsubstituted C 2-10 alkenyl, substituted or unsubstituted C 2-10 alkynyl, substituted or unsubstituted C 6-20aryl or substituted or unsubstituted C 3-20 heteroaryl;

[0115] Optionally, the substituent of R is selected from deuterium, nitro, hydroxyl, C 1-10 alkyl, C 3-10 cycloalkyl, C 2-10 alkenyl, C 2-10 alkynyl, C 6-20 aryl, C 3-20 heteroaryl, C 2-10 heterocycloalkyl, C 1-6 alkoxy, amino, cyano, thiol, ester or sulfonic acid group;

[0116] m represents the number of methylene groups, m is 0, 1, 2, 3 or 4; x represents the number of R, x is 0, 1, 2, 3, 4 or 5.

[0117] The phosphorus-containing lactam compound provided by the present disclosure has the structure shown in the above formula (V), simultaneously has phosphorus and nitrogen elements, and can realize multi-element synergistic flame retardation. The 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide structure contained in the molecular structure contains a biphenyl ring and a phenanthrene ring structure, and the side phosphorus group is introduced in the form of a cyclic O=P-O bond, which has higher thermal stability and chemical stability than general non-cyclic organic phosphate flame retardant systems. In addition, the aryl group is connected to the central C atom in the molecular structure of the phosphorus-containing lactam compound, which is easy to form carbon during combustion, thereby improving the flame retardation effect. The synthesis method is simple and efficient, the raw material used is bio-based amino caprolactam, which is prepared from biomass lysine, is a low-toxicity and environmentally friendly halogen-free flame retardant, and conforms to the concept of green environmental protection and sustainable development. The application of the phosphorus-containing lactam compound provided by the present disclosure to the flame-retardant polyamide 6 material can meet the flame-retardant requirements of the polyamide material, and has little effect on the mechanical properties of the polyamide 6 material itself. In addition, the side amine group of the amino caprolactam in the molecular structure of the phosphorus-containing lactam compound provided by the present disclosure does not contain active hydrogen, has low activity, and only retains the activity of the cyclic structure, thereby avoiding the influence of the active hydrogen of the side amine group on the copolymerization reaction during the preparation of the flame-retardant polyamide 6 material by copolymerization of caprolactam, and causing negative effects on the performance of the flame-retardant polyamide 6 material.

[0118] In a preferred embodiment, in formula (D), the group A is selected from C 6-12 aryl or C 3-12 heteroaryl; R is selected from a hydrogen atom, a nitro group, a hydroxyl group, an amino group, a cyano group, a thiol group, an ester group, a sulfonic acid group, a substituted or unsubstituted C 1-6 alkyl, substituted or unsubstituted C 1-2 alkoxy, substituted or unsubstituted C 2-6 alkenyl, substituted or unsubstituted C 2-6 alkynyl, substituted or unsubstituted C6-12 aryl or substituted or unsubstituted C 3-12 heteroaryl; optionally, the substituent of R is selected from deuterium, nitro, hydroxyl, C 1-6 alkyl, C 3-6 cycloalkyl, C 2-6 alkenyl, C 2-6 alkynyl, C 6-12 aryl, C 3-12 heteroaryl, C 2-6 heterocycloalkyl, C 1-2 alkoxy, amino, cyano, thiol, ester or sulfonic acid group.

[0119] In a preferred embodiment, the group A is selected from a benzene ring, a naphthalene ring, a furan ring, a thiophene ring, a pyrrole ring, a thiazole ring, an imidazole ring, a pyridine ring, a pyrimidine ring or a pyrazine ring.

[0120] Optionally, the R is selected from a hydrogen atom, a nitro group, a hydroxyl group, an amino group, a cyano group, a methyl group, an ethyl group, a n-propyl group, an i-propyl group, a n-butyl group, an i-butyl group, a t-butyl group, a phenyl group, a naphthyl group, a methoxy group, an ethoxy group, a carboxyl group, an acryl group, an epoxy group, a vinyl group, a vinyl ether group, an acetylamino group, a dimethylamino group, an ethynyl group, a methyl ester group, an ethyl ester group, a thiol group or an isocyanate group.

[0121] Optionally, the substituent of R is selected from deuterium, nitro, hydroxyl, amino, cyano, methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, phenyl, naphthyl, methoxy, ethoxy, carboxyl, acryl, epoxy, vinyl, vinyl ether, acetylamino, dimethylamino, ethynyl, methyl ester, ethyl ester, thiol or isocyanate.

[0122] Preferably, m is 1 or 2; x is 0, 1 or 2. The phosphorus-containing lactam compound having the structure of the present embodiment can have a better flame-retardant effect.

[0123] The fourth aspect of the present disclosure provides a flame-retardant polyamide 6 material, which is obtained by blending a polyamide 6 material with the phosphorus-containing lactam compound of the second aspect or the third aspect of the present disclosure; wherein the polyamide 6 material can be pre-sliced and dried. In the present disclosure, the phosphorus-containing lactam compound can be mixed with the polyamide 6 to obtain the flame-retardant polyamide 6 material through a simple blending process.

[0124] In a specific embodiment, the blending process can be performed using a twin-screw extruder, and conventional process conditions in the art can be used.

[0125] In a preferred embodiment, the content of the phosphorus-containing lactam compound is 1-40 wt%, preferably 5-20 wt%, based on the total weight of the flame-retardant polyamide 6 material. Blending according to the content provided in the present embodiment, especially according to the preferred content, can ensure that the flame-retardant polyamide 6 material has good flame-retardant properties while maintaining good mechanical properties of the flame-retardant polyamide 6 material.

[0126] In a specific embodiment, the flame-retardant polyamide 6 material has a flame-retardant rating of UL94 V-0, an elongation at break of 6-10%, and a breaking strength of 70-80 MPa.

[0127] The fifth aspect of the present disclosure provides a flame-retardant polyamide 6 material, which comprises a repeating unit having a structure as shown in the following formula (VI):

[0128]

[0129] wherein Q has a structure as shown in the following formula (VII):

[0130]

[0131] In formula (VII), group A is selected from C 6-30 aryl or C 3-30 heteroaryl; R is selected from a hydrogen atom, a nitro group, a hydroxyl group, an amino group, a cyano group, a thiol group, an ester group, a sulfonic acid group, a substituted or unsubstituted C 1-10 alkyl, a substituted or unsubstituted C 1-6 alkoxy, a substituted or unsubstituted C 2-10 alkenyl, a substituted or unsubstituted C 2-10 alkynyl, a substituted or unsubstituted C 6-20 aryl, or a substituted or unsubstituted C 3-20 heteroaryl; the substituent on R is selected from deuterium, a nitro group, a hydroxyl group, a C 1-10 alkyl group, a C 3-10 cycloalkyl group, a C 2-10 alkenyl group, a C 2-10 alkynyl group, a C 6-20 aryl group, a C 3-20 heteroaryl group, a C 2-10 heterocycloalkyl group, a C 1-6 alkoxy group, an amino group, a cyano group, a thiol group, an ester group, or a sulfonic acid group; n represents the number of methylene groups, and n is 0, 1, 2, 3, or 4; x represents the number of R, and x is 0, 1, 2, 3, 4, or 5. The specific types of groups have been described in detail in the foregoing, and will not be described here again.

[0132] The present disclosure provides an intrinsically flame-retardant flame-retardant polyamide 6 material, which introduces a flame-retardant structure into the polyamide 6 repeating unit, has the effect of significantly improving the flame-retardant performance of the material, improving the combustion behavior, and maintaining or improving the mechanical properties.

[0133] In a preferred embodiment, the molar content of the repeating unit having the structure shown in formula (VII) is 0.1-30%, preferably 1-20%, based on the total molar amount of the flame-retardant polyamide 6 material. When the content of the (VII) structure unit in the flame-retardant polyamide 6 material is within the range of the present embodiment, especially within the preferred range, the flame-retardant performance and mechanical properties of the flame-retardant polyamide 6 material are better.

[0134] In a specific embodiment, the flame-retardant polyamide 6 material is obtained by copolymerization of caprolactam monomers and the phosphorus-containing lactam compound of the second or third aspect of the present disclosure. The phosphorus-containing lactam compound provided by the present disclosure as a copolymerization monomer, in the molecular structure of the phosphorus-containing lactam compound, the side amine group of aminocaprolactam does not contain active hydrogen, and the activity is low, only the activity of the cyclic structure is retained, avoiding the influence of the active hydrogen of the side amine group on the copolymerization reaction in the process of preparing the flame-retardant polyamide 6 material by copolymerization of caprolactam, causing negative effects on the performance of the flame-retardant polyamide 6 material.

[0135] In a preferred embodiment, the molar ratio of the phosphorus-containing lactam compound to the caprolactam reactant is 1:2-50, preferably 1:4-25. According to the molar ratio provided in the present embodiment, especially according to the preferred molar ratio, a better polymerization reaction effect can be obtained.

[0136] In a specific embodiment, the conditions of the copolymerization reaction include a reaction temperature of 150-280°C and a reaction time of 3-20h, preferably a reaction temperature of 220-280°C and a reaction time of 6-10h.

[0137] In a specific embodiment, the flame-retardant polyamide 6 material has a flame-retardant grade of UL94 V-0, an elongation at break of 6-10%, and a breaking strength of 70-80MPa.

[0138] The present disclosure is further described in detail by the following examples. Unless otherwise specifically indicated, the various raw materials, reagents, instruments and equipment used in the present disclosure can be purchased on the market or can be prepared by existing methods.

[0139] The synthesis process of the phosphorus-containing halogen-free lactam is analyzed by liquid chromatography and quantified by external standard method.

[0140] The conversion rate of DL-aminocaprolactam and the selectivity of the phosphorus-containing halogen-free lactam are calculated by the following formula (4)-(5):

[0141]

[0142] The mass of converted aminocaprolactam = the mass of aminocaprolactam – the residual mass of aminocaprolactam.

[0143] The reaction products in the examples were subjected to H NMR spectrum testing using a Burker AV-300 liquid superconducting NMR spectrometer with deuterated dimethyl sulfoxide as solvent at room temperature.

[0144] The reaction products in the examples were subjected to matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALD I-TOF) analysis. The testing instrument was AXIMAPerformance, DHB matrix, and data were collected in positive ion reflection mode and automatic data acquisition mode.

[0145] The following examples are used to illustrate the preparation method of the flame retardant.

[0146] Example A1

[0147] Synthesis of a phosphorus-containing halogen-free lactam flame retardant ( The structure is m is 0):

[0148] A three-necked flask was filled with 200 mL of anhydrous ethanol (solvent), and 10 g of DL-aminocaprolactam (reactant A, 0.0781 mol) and 9.1 g of benzaldehyde (reactant B, 0.0858 mol, ) was subjected to a first reaction (temperature 80°C, time 2 hours). The resulting intermediate product was then added with 16.9 g of DOPO (0.0782 mol) for a second reaction (temperature 80°C, time 8 hours). The molar ratio of Compound A:Compound B was 1:1.1, and the molar ratio of Compound A:Compound C was 1:1. After the reaction, the reaction mixture was cooled to room temperature and analyzed by liquid chromatography. The conversion of DL-aminocaprolactam was 98%, and the selectivity for the phosphorus-containing lactam flame retardant was 92%. The solvent was evaporated to obtain a crude solid product, which was separated by column chromatography using a mixture of dichloromethane and methanol (volume ratio 30:1) to obtain a white powder with a yield of 85%.

[0149] The characterization data of the obtained white powder are as follows:

[0150] 1 H NMR (400MHz, DMSO) δ = 1.46, 1.51, 1.52, 1.54, 1.56, 1.75, 3.17, 3.20, 3.47, 3 .81,7.29,7.31,7.31,7.31,7.31,7.41,7.43,7.47,7.50,7.50,7.75,8.00.

[0151] The molecular structure was confirmed by matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS): m / z theoretical value [M+H] + = 433.4598, [M+Na] + = 455.4598, found value [M+H] + = 433.3858, [M+Na] + = 455.4094.

[0152] The above phosphorus-containing lactam compound S1 was subjected to thermogravimetric analysis by SDT 2960 thermogravimetric analyzer under nitrogen atmosphere, and the temperature range was 25-600°C, as shown in Figure 1 The weight loss of the above phosphorus-containing lactam compound occurred at 200-400°C, which met the requirements of weight loss range and gentle weight loss as a flame retardant.

[0153] The above test results show that the method provided by the present disclosure can obtain a phosphorus-containing lactam compound with a target structure Based on the total weight of the above phosphorus-containing lactam compound, the phosphorus content was 7.2 wt%, and the nitrogen content was 6.5 wt%.

[0154] Example A2

[0155] Synthesis of a phosphorus-containing halogen-free lactam flame retardant The structure is m is 1):

[0156] DL-aminocaprolactam (reactant A, 12.8 g, 0.1 mol), phenylacetaldehyde (reactant B, 0.11 mol, 13.2 g), and ethanol (solvent, 200 mL) were added to a reaction kettle, and the reaction was carried out at 60°C for 2 h (Schiff base reaction). After the first step reaction, without separation, DOPO (reactant C, 0.12 mol, 25.92 g) was continuously added, and the reaction was carried out at 75°C for 8 h (addition reaction); wherein the molar ratio of reactant A to reactant B was 1:1.1, and the molar ratio of reactant A to reactant C was 1:1.2. After the reaction was completed, it was cooled to room temperature, and the obtained reaction liquid was sampled for liquid chromatography analysis. The conversion rate of DL-aminocaprolactam was 94%, and the selectivity of the phosphorus-containing lactam flame retardant was 83%. The solvent was evaporated to obtain a solid crude product, which was recrystallized with ethanol and petroleum ether, and then vacuum dried at 80°C for 24 h to obtain a pure product with a yield of 74%. The structure of the obtained product is shown as follows:

[0157] The molecular structure was confirmed by matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS): m / z theoretical value [M+H] + = 446.4868, [M+Na]+ = 468.4868, found [M+H] + = 446.4123, [M+Na] + = 468.4267.

[0158] Example A3

[0159] Synthesis of a phosphorus-containing halogen-free lactam flame retardant The structure is m is 0)

[0160] Into a reaction kettle, DL-aminocaprolactam (reactant A, 12.8 g, 0.1 mol), furfural (reactant B, 0.1 mol, 9.6 g), ethanol (solvent, 200 mL) were added, and the reaction was carried out at 60°C for 2 h (Schiff base reaction). After the first step reaction, without separation, DOPO (reactant C, 0.11 mol, 23.76 g) was continuously added, and the reaction was carried out at 75°C for 10 h (addition reaction); wherein the molar ratio of reactant A: reactant B was 1:1, and the molar ratio of reactant A: reactant C was 1:1.1. After the reaction was completed, it was cooled to room temperature, and the obtained reaction liquid was sampled for liquid chromatography analysis. The conversion rate of DL-aminocaprolactam was 96%, and the selectivity of the phosphorus-containing lactam flame retardant was 87%. The solid crude product was obtained by evaporating the solvent, recrystallized with ethanol and n-hexane, and dried at 80°C under vacuum for 24 h to obtain the pure product, with a yield of 79%. The structure of the obtained product is shown below: Example A4

[0161] Synthesis of a phosphorus-containing halogen-free lactam flame retardant

[0162] The structure is m is 0) Into a reaction kettle, DL-aminocaprolactam (reactant A, 12.8 g, 0.1 mol), syringaldehyde (reactant B, 0.1 mol, 18.2 g), ethanol (solvent, 200 mL) were added, and the reaction was carried out at 60°C for 2 h (Schiff base reaction). After the first step reaction, without separation, DOPO (reactant C, 0.11 mol, 23.76 g) was continuously added, and the reaction was carried out at 75°C for 10 h (addition reaction); wherein the molar ratio of reactant A: reactant B was 1:1, and the molar ratio of reactant A: reactant C was 1:1.1. After the reaction was completed, it was cooled to room temperature, and the obtained reaction liquid was sampled for liquid chromatography analysis. The conversion rate of DL-aminocaprolactam was 96%, and the selectivity of the phosphorus-containing lactam flame retardant was 85%. The solid crude product was obtained by evaporating the solvent, recrystallized with ethanol and n-hexane, and dried at 80°C under vacuum for 24 h to obtain the pure product, with a yield of 79%. The structure of the obtained product is shown below:

[0163] Example A4

[0161] Synthesis of a phosphorus-containing halogen-free lactam flame retardant

[0162] The structure is m is 0) Into a reaction kettle, DL-aminocaprolactam (reactant A, 12.8 g, 0.1 mol), syringaldehyde (reactant B, 0.1 mol, 18.2 g), ethanol (solvent, 200 mL) were added, and the reaction was carried out at 60°C for 2 h (Schiff base reaction). After the first step reaction, without separation, DOPO (reactant C, 0.11 mol, 23.76 g) was continuously added, and the reaction was carried out at 75°C for 10 h (addition reaction); wherein the molar ratio of reactant A: reactant B was 1:1, and the molar ratio of reactant A: reactant C was 1:1.1. After the reaction was completed, it was cooled to room temperature, and the obtained reaction liquid was sampled for liquid chromatography analysis. The conversion rate of DL-aminocaprolactam was 96%, and the selectivity of the phosphorus-containing lactam flame retardant was 85%. The solid crude product was obtained by evaporating the solvent, recrystallized with ethanol and n-hexane, and dried at 80°C under vacuum for 24 h to obtain the pure product, with a yield of 79%. The structure of the obtained product is shown below:

[0163] Example A4

[0161] Synthesis of a phosphorus-containing halogen-free lactam flame retardant

[0162] The structure is m is 0) Into a reaction kettle, DL-aminocaprolactam (reactant A, 12.8 g, 0.1 mol), syringaldehyde (reactant B, 0.1 mol, 18.2 g), ethanol (solvent, 200 mL) were added, and the reaction was carried out at 60°C for 2 h (Schiff base reaction). After the first step reaction, without separation, DOPO (reactant C, 0.11 mol, 23.76 g) was continuously added, and the reaction was carried out at 75°C for 10 h (addition reaction); wherein the molar ratio of reactant A: reactant B was 1:1, and the molar ratio of reactant A: reactant C was 1:1.1. After the reaction was completed, it was cooled to room temperature, and the obtained reaction liquid was sampled for liquid chromatography analysis. The conversion rate of DL-aminocaprolactam was 96%, and the selectivity of the phosphorus-containing lactam flame retardant was 85%. The solid crude product was obtained by evaporating the solvent, recrystallized with ethanol and n-hexane, and dried at 80°C under vacuum for 24 h to obtain the pure product, with a yield of 79%. The structure of the obtained product is shown below:

[0163] Example A4

[0161] Synthesis of a phosphorus-containing halogen-free lactam flame retardant

[0162] The structure is m is 0) Into a reaction kettle, DL-aminocaprolactam (reactant A, 12.8 g, 0.1 mol), syringaldehyde (reactant B, 0.1 mol, 18.2 g), ethanol (solvent, 200 mL) were added, and the reaction was carried out at 60°C for 2 h (Schiff base reaction). After the first step reaction, without separation, DOPO (reactant C, 0.11 mol, 23.76 g) was continuously added, and the reaction was carried out at 75°C for 10 h (addition reaction); wherein the molar ratio of reactant A: reactant B was 1:1, and the molar ratio of reactant A: reactant C was 1:1.1. After the reaction was completed, it was cooled to room temperature, and the obtained reaction liquid was sampled for liquid chromatography analysis. The conversion rate of DL-aminocaprolactam was 96%, and the selectivity of the phosphorus-containing lactam flame retardant was 85%. The solid crude product was obtained by evaporating the solvent, recrystallized with ethanol and n-hexane, and dried at 80°C under vacuum for 24 h to obtain the pure product, with a yield of 79%. The structure of the obtained product is shown below:

[0163] Example A4

[0161] Synthesis of a phosphorus-containing halogen-free lactam flame retardant

[0162] The structure is m is 0) Into a reaction kettle, DL-aminocaprolactam (reactant A, 12.8 g, 0.1 mol), syringaldehyde (reactant B, 0.1 mol, 18.2 g), ethanol (solvent, 200 mL) were added, and the reaction was carried out at 60°C for 2 h (Schiff base reaction). After the first step reaction, without separation, DO

[0164]

[0165] Example A5

[0166] Synthesis of a phosphorus-containing halogen-free lactam flame retardant ( The structure is m is 0)

[0167] DL-aminocaprolactam (reactant A, 12.8 g, 0.1 mol), 5-hydroxymethylfurfural ( Reactant B (0.1 mol, 12.6 g) and ethanol (solvent, 200 mL) were reacted at 50°C for 3 hours (Schiff base reaction). After the first reaction, DOPO (0.11 mol, 23.76 g) was added without separation and allowed to react at 75°C for 10 hours (addition reaction). The molar ratio of reactant A:reactant B was 1:1, and the molar ratio of reactant A:reactant C was 1:1.1. After the reaction, the reaction mixture was cooled to room temperature and analyzed by liquid chromatography. The conversion of DL-aminocaprolactam was 95%, and the selectivity for the phosphorus-containing lactam flame retardant was 85%. The solvent was evaporated to obtain a crude solid product, which was recrystallized from ethanol and n-hexane and dried under vacuum at 80°C for 24 hours to obtain the pure product in a 76% yield. The structure of the resulting product is shown below:

[0168]

[0169] Example A6

[0170] Synthesis of a phosphorus-containing halogen-free lactam flame retardant ( The structure is m is 0)

[0171] DL-aminocaprolactam (reactant A, 12.8 g, 0.1 mol), 2-thiophenecarboxaldehyde ( Reactant B (0.11 mol, 12.32 g) and ethanol (solvent, 200 mL) were reacted at 50°C for 3 h (Schiff base reaction). After the first reaction, DOPO (0.13 mol, 28.08 g) was added without separation and allowed to react at 75°C for 10 h (addition reaction). The molar ratio of reactant A:reactant B was 1:1.1, and the molar ratio of reactant A:reactant C was 1:1.3. After the reaction, the reaction mixture was cooled to room temperature and analyzed by liquid chromatography. The conversion of DL-aminocaprolactam was 97%, and the selectivity for the phosphorus-containing lactam flame retardant was 88%. The solvent was evaporated to obtain a crude solid product, which was recrystallized from ethanol and n-hexane and dried under vacuum at 80°C for 24 h to obtain the pure product in an 80% yield. The structure of the resulting product is shown below:

[0172]

[0173] Example A7

[0174] Synthesis of a phosphorus-containing halogen-free lactam flame retardant ( The structure is m is 0):

[0175] DL-aminocaprolactam (reactant A, 12.8 g, 0.1 mol), p-cyanobenzaldehyde ( Reactant B (0.12 mol, 15.72 g) and methanol (solvent, 200 mL) were reacted at 60°C for 1 hour (Schiff base reaction). After the first reaction, DOPO (0.13 mol, 28.08 g) was added without separation and allowed to react at 75°C for 12 hours (addition reaction). The molar ratio of reactant A:reactant B was 1:1.2, and the molar ratio of reactant A:reactant C was 1:1.3. After the reaction, the reaction mixture was cooled to room temperature and analyzed by liquid chromatography. The conversion of DL-aminocaprolactam was 97%, and the selectivity for the phosphorus-containing lactam flame retardant was 84%. The solvent was evaporated to obtain a crude solid product, which was recrystallized from ethanol and petroleum ether and dried under vacuum at 80°C for 24 hours to obtain the pure product in a 78% yield. The structure of the resulting product is shown below:

[0176]

[0177] Example A8

[0178] Synthesis of a phosphorus-containing halogen-free lactam flame retardant ( The structure is m is 0):

[0179] DL-aminocaprolactam (reactant A, 12.8 g, 0.1 mol), vanillin ( Reactant B (0.12 mol, 18.24 g) and ethanol (200 mL, solvent) were reacted at 60°C for 1 h (Schiff base reaction). After the first reaction, DOPO (0.13 mol, 28.08 g, reactant C) was added without separation and allowed to react at 80°C for 8 h (addition reaction). The molar ratio of reactant A:reactant B was 1:1.2, and the molar ratio of reactant A:reactant C was 1:1.3. After the reaction, the reaction mixture was cooled to room temperature and analyzed by liquid chromatography. The conversion of DL-aminocaprolactam was 97%, and the selectivity for the phosphorus-containing lactam flame retardant was 85%. The solvent was evaporated to obtain a crude solid product, which was recrystallized from ethanol and petroleum ether and dried under vacuum at 80°C for 24 h to obtain the pure product in a 79% yield. The structure of the resulting product is shown below:

[0180]

[0181] Example A9

[0182] Synthesis of a phosphorus-containing halogen-free lactam flame retardant ( The structure is m is 0):

[0183] DL-aminocaprolactam (reactant A, 12.8 g, 0.1 mol), p-hydroxybenzaldehyde ( Reactant B (0.12 mol, 14.65 g) and ethanol (200 mL, solvent) were reacted at 60°C for 1 hour (Schiff base reaction). After the first reaction, DOPO (0.12 mol, 25.92 g, reactant C) was added without separation and allowed to react at 80°C for 10 hours (addition reaction). The molar ratios of reactant A:reactant B and reactant C were 1:1.2 and 1:1.2, respectively. After the reaction, the reaction mixture was cooled to room temperature and analyzed by liquid chromatography. The conversion of DL-aminocaprolactam was 97%, and the selectivity for the phosphorus-containing lactam flame retardant was 84%. The solvent was evaporated to obtain a crude solid product, which was recrystallized from ethanol and petroleum ether and dried under vacuum at 80°C for 24 hours to obtain a yellow powder with a yield of 78%. The structure of the resulting product is shown below:

[0184]

[0185] Example A10

[0186] This example refers to the preparation method of Example A2, and the difference from Example A2 is:

[0187] Acetic acid (2 g) was added as a catalyst in the Schiff base reaction, wherein the weight ratio of reactant A to catalyst was 1:0.15. The conversion of DL-aminocaprolactam increased to 98%, and the selectivity of the phosphorus-containing lactam flame retardant was 90%.

[0188] Example A11

[0189] This example refers to the preparation method in Example A1, and the difference from Example A1 is:

[0190] The reaction temperature in the Schiff base reaction (first reaction) in Example A1 was increased to 120° C., and the remaining process was the same as Example A1. The DL-aminocaprolactam conversion rate decreased to 80%, and the phosphorus-containing lactam flame retardant selectivity decreased to 65%.

[0191] Example A12

[0192] This example refers to the preparation method in Example A1, and the difference from Example A1 is:

[0193] The molar ratio of reactant A: reactant B: reactant C was adjusted to 1:0.6:1.6, and the rest of the process was the same as in Example Al. The DL-aminolactam conversion rate was reduced to 90%, and the phosphorus-containing lactam flame retardant selectivity was reduced to 75%.

[0194] Comparative Example Al

[0195] This comparative example refers to the preparation method in Example Al, and the difference from Example Al is that:

[0196] Formaldehyde was used instead of benzaldehyde in Example Al, and the rest of the process was the same as in Example 1. The DL-aminolactam conversion rate of the obtained flame retardant was 98%, and the flame retardant selectivity was 87%.

[0197] Comparative Example A2

[0198] The flame retardant with the structure shown in the following formula was prepared according to the following steps:

[0199] DOPO (21.6 g, 0.1 mol) was dissolved in 200 mL of dichloromethane, stirring was started, and sulfuryl chloride (9.7 mL, 0.12 mol) was slowly added dropwise at 0°C. After the solid was completely dissolved, the reaction was heated to reflux at 45°C for 3 h. After the reaction was completed, the excess sulfuryl chloride was removed by distillation under reduced pressure to obtain white solid DOPO-Cl; DOPO-Cl (25.1 g, 0.1 mol) was dissolved in 200 mL of dichloromethane, triethylamine (15.4 mL, 0.11 mol) and aminolactam (11.5 g, 0.09 mol) were slowly added dropwise at 0°C, and then the temperature was raised to room temperature and stirred for 12 h. After the reaction was completed, the unreacted triethylamine was removed by hydrochloric acid, and the lower organic phase was collected and dried over anhydrous sodium sulfate. After the organic phase solution was concentrated under reduced pressure, a small amount of dichloromethane was added to dissolve it, and the insoluble material was collected by filtration to obtain white solid DOPO-ACL. The reaction flow of this comparative example is as follows:

[0200]

[0201] The aminolactam conversion rate of the obtained flame retardant was 97%, the flame retardant selectivity was 70%, and the actual yield after workup was 50%. In the synthesis method of this comparative example, toxic chemicals such as sulfuryl chloride were used, the reaction conditions were harsh, and it was not suitable for industrial production and did not meet the requirements of green and environmental protection.

[0202] The aminolactam conversion rates of the flame retardants (phosphorus-containing lactam compounds) prepared in the above examples and comparative examples, and the phosphorus-containing lactam flame retardant selectivities are listed in Table 1 below.

[0203] Table 1

[0204] ​

[0205] From the data in Table 1 above, it can be seen that:

[0206] The DL-aminocapro lactam conversion rate and the selectivity of the phosphorus-containing lactam compound can be higher when the method provided by the present disclosure is used to prepare the flame retardant in Examples Al to A12.

[0207] When Example Al is compared with Example Al l, the DL-aminocapro lactam conversion rate and the selectivity of the phosphorus-containing lactam compound can be higher when the reaction is carried out according to the optimized conditions provided by the present disclosure in Example Al.

[0208] When Example Al is compared with Example A12, the DL-aminocapro lactam conversion rate and the selectivity of the phosphorus-containing lactam compound can be higher when the reaction is carried out according to the preferred molar ratio of raw materials provided by the present disclosure in Example Al.

[0209] The following examples are used to illustrate the use of the flame retardant (phosphorus-containing lactam compound) prepared in the above examples in flame-retardant polyamide 6 materials.

[0210] The polyamide 6 resins obtained in the following examples are subjected to composite material flame retardant performance tests, including: limiting oxygen index, UL-94 vertical burning test and mechanical property test.

[0211] The limiting oxygen index tester is a JF-3 type oxygen index tester, and the test is performed in accordance with the standard GB / T54541997.

[0212] The UL-94 vertical burning tester is a CZF-3 type horizontal and vertical burning tester, and the test is performed in accordance with the standard UL-94.

[0213] The mechanical property tester is a H10K-S type electronic universal tensile testing machine, and the test is performed in accordance with the standard GB / T1040.3-2006, and the tensile strength and elongation at break are recorded.

[0214] Examples Bl to B9

[0215] The flame-retardant polyamide 6 material is prepared: polyamide 6 chips are vacuum dried at 120°C for 24h, and a twin-screw extruder is used to blend the polyamide 6 chips with the flame retardant (phosphorus-containing lactam compound) of Examples Al to A9 at a mass ratio of 92:8 at 240°C to obtain a flame-retardant polyamide 6 material, and the content of the flame retardant (phosphorus-containing lactam compound) is 8% by weight based on the total weight of the flame-retardant polyamide 6 material. The limiting oxygen index, UL-94 flame retardant grade, elongation at break and tensile strength of the obtained polyamide 6 material are listed in Table 2.

[0216] Example BlO

[0217] Preparation of intrinsic flame-retardant polyamide 6: under nitrogen atmosphere, the flame retardant (phosphorus-containing lactam compound) of Example Al was mixed with molten caprolactam in a high-speed blender at a molar ratio of 1:10, water was added as an initiator and ring-opening reaction was carried out at 230°C for 6h, then the polymer was poured from the polymerizer into a water tank to cast a strip, granulated, extracted and dried to obtain flame-retardant polyamide 6 chips, the molar content of the repeating unit having the structure shown in formula (VI) was 3% based on the total weight of the flame-retardant polyamide 6. The obtained flame-retardant polyamide 6 material comprises repeating units having the structure shown in the following formula (VI):

[0218] wherein Q has the structure shown in the following formula (VII):

[0219] wherein the structure is m is 0.

[0220] Comparative Example B1

[0221] Referring to the preparation method in Example B1, the difference between Example B1 and Comparative Example B1 is that the phosphorus-containing lactam compound of Example Al is replaced by the phosphorus-containing lactam compound of Comparative Example Al, and the rest of the process is the same as Example B1.

[0222] Comparative Example B2

[0223] Referring to the preparation method in Example B1, the difference between Example B1 and Comparative Example B2 is that the phosphorus-containing lactam compound of Example Al is replaced by the phosphorus-containing lactam compound of Comparative Example A2, and the rest of the process is the same as Example B1.

[0224] The properties of the flame-retardant polyamide 6 materials obtained in the above examples and comparative examples are listed in Table 2 below.

[0225] Table 2

[0226]

[0227] According to the data in Table 2 above, it can be seen that:

[0228] The phosphorus-containing lactam compounds used in Comparative Examples B1-B2 have less aromatic structure in structure, resulting in a decrease in the flame-retardant properties and mechanical properties of the material. Compared with Comparative Examples B1-B2, the flame-retardant polyamide 6 materials prepared by using the phosphorus-containing lactam compounds provided by the present disclosure in Examples B1-B10 have better limiting oxygen index, elongation at break and tensile strength, and also have higher UL-94 flame-retardant grade.

[0229] The preferred embodiments of the present disclosure are described in detail above, but the present disclosure is not limited to the specific details described in the above embodiments. Within the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all belong to the protection scope of the present disclosure.

[0230] In addition, it should be noted that each specific technical feature described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, various possible combinations are not described again in the present disclosure.

[0231] In addition, any combination of various different embodiments of the present disclosure can also be made, as long as it does not deviate from the idea of the present disclosure, and it should also be considered as disclosed by the present disclosure.

Claims

1. A method for producing a phosphorus-containing lactam compound, characterized by, The method comprises the following steps: carrying out a first reaction of a compound A having a structure of formula (III) and a compound B having a structure of formula (IV) in a solvent to obtain an intermediate product; carrying out a second reaction of the intermediate product with a compound C selected from a group comprising at least one moiety of formula (II) to obtain a phosphorus-containing lactam compound; In formula (III), n is selected from an integer from 0 to 4; R1is selected from hydrogen, hydroxyl, thiol, nitrile, amino, substituted or unsubstituted C 1-24 alkyl, substituted or unsubstituted C 3-12 cycloalkyl, substituted or unsubstituted C 3-10 heterocycloalkyl, substituted or unsubstituted C 6-30 aryl; In formula (IV), R2is selected from substituted or unsubstituted C 1-24 substituted or unsubstituted C 3-12 substituted or unsubstituted C 3-10 substituted or unsubstituted C 6-30 aryl; In formula (II), X1is selected from the group consisting of nitrogen, oxygen; R4and X2are linked to form a ring or not; X2is selected from the group consisting of nitrogen, oxygen, hydroxyl; R4is selected from the group consisting of substituted or unsubstituted C 1-24 alkyl, substituted or unsubstituted C 3-12 cycloalkyl, substituted or unsubstituted C 3-10 heterocycloalkyl, substituted or unsubstituted C 6-30 aryl.

2. The production method according to claim 1, characterized by, The method comprises: carrying out a Schiff base reaction of the compound A and the compound B to obtain the intermediate product; and carrying out an addition reaction of the intermediate product with the compound C; The compound A has a structure as shown in the following formula (A): The compound B has a structure as shown in the following formula (B): In formula (B), group A is selected from C 6-30 Aryl or C 3-30 Heteroaryl; R is selected from hydrogen, nitro, hydroxy, amino, cyano, thiol, ester, sulfonic acid, substituted or unsubstituted C 1-10 Alkyl, substituted or unsubstituted C 1-6 Alkoxy, substituted or unsubstituted C 2-10 Alkenyl, substituted or unsubstituted C 2-10 Alkynyl, substituted or unsubstituted C 6-20 Aryl or substituted or unsubstituted C 3-20 Heteroaryl; Optionally, the substituent of R is selected from deuterium, nitro, hydroxyl, C 1-10 Alkyl, C 3-10 Cycloalkyl, C 2-10 Alkenyl, C 2-10 Alkynyl, C 6-20 Aryl, C 3-20 Heteroaryl, C 2-10 Heterocycloalkyl, C 1-6 Alkoxy, amino, cyano, mercapto, ester or sulfonic acid; m represents the number of methylene groups, m is 0, 1, 2, 3 or 4; x represents the number of R, x is 0, 1, 2, 3, 4 or 5; The compound C has a structure as shown in the following formula (C):

3. The method of claim 2, wherein, In formula (B), the group A is selected from C 6-12 aryl or C 3-12 heteroaryl; R is selected from a hydrogen atom, a nitro group, a hydroxyl group, an amino group, a cyano group, a thiol group, an ester group, a sulfonic acid group, a substituted or unsubstituted C 1-6 alkyl, a substituted or unsubstituted C 1-2 alkoxy, a substituted or unsubstituted C 2-6 alkenyl, a substituted or unsubstituted C 2-6 alkynyl, a substituted or unsubstituted C 6-12 aryl or a substituted or unsubstituted C 3-12 heteroaryl; Optionally, the substituents of R are selected from deuterium, nitro, hydroxyl, C 1-6 alkyl, C 3-6 cycloalkyl, C 2-6 alkenyl, C 2-6 alkynyl, C 6-12 aryl, C 3-12 heteroaryl, C 2-6 heterocycloalkyl, C 1-2 alkoxy, amino, cyano, thiol, ester, or sulfonic acid; Preferably, the group A is selected from a benzene ring, a naphthalene ring, a furan ring, a thiophene ring, a pyrrole ring, a thiazole ring, an imidazole ring, a pyridine ring, a pyrimidine ring or a pyrazine ring. Optionally, the R is selected from a hydrogen atom, a nitro group, a hydroxyl group, an amino group, a cyano group, a methyl group, an ethyl group, a n-propyl group, an i-propyl group, a n-butyl group, an i-butyl group, a t-butyl group, a phenyl group, a naphthyl group, a methoxy group, an ethoxy group, a carboxyl group, an acryl group, an epoxy group, a vinyl group, a vinyl ether group, an acetylamino group, a dimethylamino group, an ethynyl group, a methyl ester group, an ethyl ester group, a mercapto group or an isocyanate group. Optionally, the substituent of the R is selected from a deuterium, a nitro group, a hydroxyl group, an amino group, a cyano group, a methyl group, an ethyl group, a n-propyl group, an i-propyl group, a n-butyl group, an i-butyl group, a t-butyl group, a phenyl group, a naphthyl group, a methoxy group, an ethoxy group, a carboxyl group, an acryl group, an epoxy group, a vinyl group, a vinyl ether group, an acetylamino group, a dimethylamino group, an ethynyl group, a methyl ester group, an ethyl ester group, a mercapto group or an isocyanate group. Preferably, m is 1 or 2; and x is 0, 1 or 2.

4. The method of claim 1, wherein, The compound B comprises one or more of benzaldehyde, p-hydroxybenzaldehyde, p-cyanobenzaldehyde, phenylacetaldehyde, furfural, 5-hydroxymethylfurfural, syringaldehyde, 2-thiophenecarboxaldehyde and vanillin.

5. The production method according to any one of claims 1 to 4, characterized by, The molar ratio of the compound A to the compound B is 1:0.3-3, preferably 1:0.8-1.

2. Preferably, the molar ratio of the compound A to the compound C is 1:0.3-3, preferably 1:0.8-1.

2.

6. The production method according to any one of claims 1 to 4, characterized by, The conditions of the first reaction comprise: a temperature of 20-180°C, preferably 60-90°C; and a time of 0.25-72h, preferably 1-3h. Preferably, the conditions of the second reaction comprise: a temperature of 20-180°C, preferably 60-90°C; and a time of 3-72h, preferably 6-12h. Preferably, the solvent comprises at least one of methanol, ethanol, propanol, acetone, dichloromethane, trichloromethane, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, 1,4-dioxane and ethyl acetate, preferably one or more of methanol, ethanol and propanol. Preferably, the method further comprises: sequentially removing the solvent from the product obtained in the second reaction, and separating to obtain the phosphorus-containing lactam compound.

7. The preparation method according to claim 6, characterized in that A catalyst is further added in the first reaction; the catalyst comprises one or more of formic acid, glacial acetic acid, hydrochloric acid and hydrofluoric acid. Preferably, the weight ratio of the compound A to the catalyst is 1:(0.05-0.5), preferably 1:(0.05-0.2).

8. The phosphorus-containing lactam compound prepared by the method according to any one of claims 1-7.

9. A phosphorus-containing lactam compound, characterized by, The phosphorus-containing lactam compound has a structure as shown in the following formula (I): In formula (I), n is selected from an integer from 0 to 4; R1is selected from hydrogen, hydroxyl, thiol, nitrile, amino, substituted or unsubstituted C 1-24 alkyl, substituted or unsubstituted C 3-12 cycloalkyl, substituted or unsubstituted C 3-10 heterocycloalkyl, substituted or unsubstituted C 6-30 aryl; R2is selected from substituted or unsubstituted C 1-24 alkyl, substituted or unsubstituted C 3-12 cycloalkyl, substituted or unsubstituted C 3-10 heterocycloalkyl, substituted or unsubstituted C 6-30 aryl; R3is selected from a group comprising a moiety having a structure as shown in the following formula (II); In formula (II), X1is selected from the group consisting of nitrogen, oxygen; R4and X2are linked to form a ring or not; X2is selected from the group consisting of nitrogen, oxygen, hydroxyl; R4is selected from the group consisting of substituted or unsubstituted C 1-24 alkyl, substituted or unsubstituted C 3-12 cycloalkyl, substituted or unsubstituted C 3-10 heterocycloalkyl, substituted or unsubstituted C 6-30 aryl.

10. The phosphorus-containing lactam compound according to claim 9, characterized by The phosphorus-containing lactam compound has a structure as shown in the following formula (V): In formula (V), U has a structure as shown in the following formula (D): In formula (D), the group A is selected from C 6-30 aryl or C 3-20 heteroaryl; * indicates the attachment of formula (D) to formula (V); R is selected from a hydrogen atom, a nitro group, a hydroxyl group, an amino group, a cyano group, a thiol group, an ester group, a sulfonic acid group, a substituted or unsubstituted C 1-10 alkyl group, a substituted or unsubstituted C 1-6 alkoxy group, a substituted or unsubstituted C 2-10 alkenyl group, a substituted or unsubstituted C 2-10 alkynyl group, a substituted or unsubstituted C 6-20 aryl group, or a substituted or unsubstituted C 3-20 heteroaryl group; optionally, the substituents of R are selected from deuterium, a nitro group, a hydroxyl group, a C 1-10 alkyl group, a C 3-10 cycloalkyl group, a C 2-10 alkenyl group, a C 2-10 alkynyl group, a C 6-20 aryl group, a C 3-20 heteroaryl group, a C 2-10 heterocycloalkyl group, a C 1-6 alkoxy group, an amino group, a cyano group, a thiol group, an ester group, or a sulfonic acid group; m represents the number of methylene groups, m is 0, 1, 2, 3 or 4; x represents the number of R, x is 0, 1, 2, 3, 4 or 5.

11. The phosphorus-containing lactam compound according to claim 10, characterized by In formula (D), group A is selected from C 6-12 Aryl or C 3-12 heteroaryl; R is selected from the group consisting of a hydrogen atom, a nitro group, a hydroxyl group, an amino group, a cyano group, a thiol group, an ester group, a sulfonic acid group, a substituted or unsubstituted C 1-6 alkyl group, a substituted or unsubstituted C 1-2 alkoxy group, a substituted or unsubstituted C 2-6 alkenyl group, a substituted or unsubstituted C 2-6 alkynyl group, a substituted or unsubstituted C 6-12 aryl group, or a substituted or unsubstituted C 3-12 heteroaryl group; Optionally, the substituents of R are selected from deuterium, nitro, hydroxyl, C 1-6 alkyl, C 3-6 cycloalkyl, C 2-6 alkenyl, C 2-6 alkynyl, C 6-12 aryl, C 3-12 heteroaryl, C 2-6 heterocycloalkyl, C 1-2 alkoxy, amino, cyano, thiol, ester, or sulfonic acid.

12. The phosphorus-containing lactam compound according to claim 11, characterized by The group A is selected from a benzene ring, a naphthalene ring, a furan ring, a thiophene ring, a pyrrole ring, a thiazole ring, an imidazole ring, a pyridine ring, a pyrimidine ring or a pyrazine ring; Optionally, the R is selected from a hydrogen atom, a nitro group, a hydroxyl group, an amino group, a cyano group, a methyl group, an ethyl group, a n-propyl group, an i-propyl group, a n-butyl group, an i-butyl group, a t-butyl group, a phenyl group, a naphthyl group, a methoxy group, an ethoxy group, a carboxyl group, an acryl group, an epoxy group, a vinyl group, a vinyl ether group, an acetylamino group, a dimethylamino group, an ethynyl group, a methyl ester group, an ethyl ester group, a mercapto group or an isocyanate group; Optionally, the substituent of the R is selected from a deuterium, a nitro group, a hydroxyl group, an amino group, a cyano group, a methyl group, an ethyl group, a n-propyl group, an i-propyl group, a n-butyl group, an i-butyl group, a t-butyl group, a phenyl group, a naphthyl group, a methoxy group, an ethoxy group, a carboxyl group, an acryl group, an epoxy group, a vinyl group, a vinyl ether group, an acetylamino group, a dimethylamino group, an ethynyl group, a methyl ester group, an ethyl ester group, a mercapto group or an isocyanate group; Preferably, m is 1 or 2; x is 0, 1 or 2.

13. A flame retardant polyamide 6 material characterized in that, The flame-retardant polyamide 6 material is obtained by blending a polyamide 6 material with the phosphorus-containing lactam compound as claimed in any one of claims 8 to 12; Preferably, the content of the phosphorus-containing lactam compound is 1 to 40% by weight, preferably 5 to 20% by weight, based on the total weight of the flame-retardant polyamide 6 material.

14. A flame retardant polyamide 6 material characterized in that, The flame-retardant polyamide 6 material comprises a repeating unit having a structure as shown in the following formula (VI): wherein Q has a structure as shown in the following formula (VII): Preferably, the molar content of the repeating unit having a structure as shown in formula (VI) is 0.1 to 30%, preferably 1 to 20%, based on the total molar amount of the flame-retardant polyamide 6 material.

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