Multifunctional macromolecular p-n flame retardant, efficient flame-retardant epoxy resin and application thereof in fiber composite material

Abstract

The application provides a multifunctional macromolecular P-N flame retardant, an efficient flame-retardant epoxy resin and application of the flame-retardant epoxy resin in fiber composite materials, wherein a multifunctional macromolecular P-N flame retardant containing a conjugated structure of formula (III) is obtained by reacting a DOPO derivative and a solution of hexachlorotriphosphazene or trichloroisocyanuric acid under an inert atmosphere, the DOPO derivative is a conjugated structure organic matter, and the DOPO derivative is provided with an amino group or a hydroxyl active group; and a structural formula of the multifunctional macromolecular P-N flame retardant is shown as (I) and (II). The application is used in flame-retardant epoxy resin, polyurethane and other materials, has a good flame-retardant effect, has a simple preparation method, does not need special equipment, and is easy to control and suitable for large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of flame retardant materials technology, specifically relating to a multifunctional macromolecular PN flame retardant, a high-efficiency flame retardant epoxy resin, and their application in fiber composite materials. Background Technology

[0002] With the development of industrial technology, epoxy resins have found wide application in many fields, such as electronics, rail transportation, aerospace, and automobiles. As a polymer material, the flammability of epoxy resins severely limits their application in many fields. Therefore, flame-retardant modification of epoxy resins is essential to broaden their applications. Since the promulgation of the EU RoHS and WEEE directives, the call for developing green, halogen-free, and environmentally friendly flame retardants has grown increasingly louder. Traditional halogenated flame retardants, which produce toxic gases such as dioxins during combustion, will inevitably be phased out. Therefore, developing environmentally friendly flame retardants with high flame-retardant efficiency is crucial.

[0003] DOPO-based flame retardants are currently a research hotspot in the field of flame retardants. Due to the presence of biphenyl and phenanthrene rings in their molecular structure, they exhibit higher thermal and chemical stability than general organophosphates, resulting in better flame retardant performance. However, small-molecule DOPO flame retardants have poor compatibility with resin groups and are prone to migration; their flame retardant effect decreases with increasing service life. Furthermore, the addition of flame retardants often leads to a decrease in the mechanical properties of the material. Therefore, how to design the chemical structure of multifunctional macromolecular PN compounds to improve flame retardant efficiency, significantly enhancing the flame retardant performance of epoxy resins at low addition levels (≤10wt%) while maintaining other properties such as mechanical properties, is the key problem that this invention aims to solve and disclose. Summary of the Invention

[0004] To address the problems in existing technologies, this invention provides a multifunctional macromolecular PN flame retardant, a high-efficiency flame-retardant epoxy resin, and their application in fiber composite materials. The preparation method of this invention is simple, requires no special equipment, and the reaction is easily controlled, making it suitable for large-scale production. When applied to flame-retardant epoxy resins, polyurethanes, and other materials, it exhibits excellent flame-retardant effects.

[0005] The technical problem solved by this invention is achieved by the following technical solution: The first objective of this invention is to provide a method for preparing a multifunctional macromolecular PN flame retardant, characterized in that: a DOPO derivative is reacted with a hexachlorocyclotriphosphazene or cyanuric chloride solution under an inert atmosphere to obtain a multifunctional macromolecular PN flame retardant containing a conjugated structure of formula (III), wherein the DOPO derivative is a conjugated organic compound with amino or hydroxyl active groups; the structural formula of the multifunctional macromolecular PN flame retardant is shown in (I) and (II). (I) (II) Where R1 is equation (Ⅲ), and R2 is equation (Ⅳ) (m1=0~3, m2=0~1) or equation (Ⅴ) (n1=0~3, n2=0~1). (III) (IV) (V) Furthermore, the structural formula of the DOPO derivative is shown in (VI): (VI) The preferred structural formula of DOPO derivatives is as follows: (VII) (VIII) (IX) Furthermore, the preparation method of the multifunctional macromolecular PN flame retardant is as follows: DOPO derivative is dissolved in a solvent by stirring. After complete dissolution, an acid-binding agent is added. Hexachlorocyclotriphosphazene or cyanuric chloride solution is slowly added dropwise to the solution at 0°C. The temperature is raised to 60°C to 120°C under a nitrogen atmosphere, and the reaction is carried out for 12 to 48 hours. Then, the liquid is collected by filtration and rotary evaporation. The liquid after rotary evaporation is dropped into deionized water to precipitate solids. The solids are collected by vacuum filtration and freeze-dried for 24 hours to obtain the multifunctional macromolecular PN flame retardant.

[0006] Furthermore, the solvent is DMF, DMSO, or THF.

[0007] Furthermore, the acid-binding agent is selected from pyridine, triethylamine, or triethanolamine.

[0008] Furthermore, the hexachlorocyclotriphosphazene or cyanuric chloride solution is obtained by dissolving hexachlorocyclotriphosphazene or cyanuric chloride in DMF, DMSO or THF.

[0009] The second objective of this invention is to provide a highly efficient flame-retardant epoxy resin comprising a macromolecular PN flame retardant prepared by the above method, characterized in that it comprises an epoxy resin, a curing agent, and a macromolecular PN flame retardant.

[0010] Furthermore, the mass ratio of the epoxy resin, curing agent, and macromolecular PN flame retardant is 100:28:0.5 to 5.

[0011] Furthermore, the curing agent is selected from 4,4'-diaminodiphenylmethane (DDM) or 4,4'-dioxydiphenyl sulfone (DDS).

[0012] The third objective of this invention is to provide a method for preparing the above-mentioned high-efficiency flame-retardant epoxy resin, characterized by the following steps: weighing epoxy resin and multifunctional macromolecular PN flame retardant are mixed, stirred and pre-dispersed, then poured into a grinder and ground evenly, and then placed in a water bath at 55℃~90℃ and stirred; molten curing agent is added and stirred for 5~10 minutes, vacuum degassing is performed for 10 minutes, and then injected into a mold and cured in an oven to obtain the high-efficiency flame-retardant epoxy resin.

[0013] Furthermore, the curing process of the high-efficiency flame-retardant epoxy resin is to cure at 100℃ for 2 hours and then at 150℃ for 2 hours.

[0014] The fourth objective of this invention is to provide the application of the above-mentioned high-efficiency flame-retardant epoxy resin in the preparation of flame-retardant fiber composite materials.

[0015] Furthermore, the uncured high-efficiency flame-retardant epoxy resin is repeatedly laminated with the fabric and then molded to form the flame-retardant fiber composite material.

[0016] Furthermore, the molding process is as follows: First stage: 1~3MPa, 100℃ / 2h; Second stage: 5~10MPa, 150℃ / 2h.

[0017] Compared with the prior art, the beneficial technical effects of the present invention are as follows: The multifunctional macromolecular PN flame retardant of the present invention contains P and N flame retardant elements and has a high flame retardant efficiency. When this flame retardant is used on flame-retardant epoxy resins, polyurethanes and other materials, it has a very good flame retardant effect.

[0018] The multifunctional macromolecular PN flame retardant of this invention has a large molecular weight, is not easily precipitated in the resin matrix, and its flame retardant effect changes little over time.

[0019] The addition of multifunctional macromolecular PN flame retardant significantly improves the flame retardant properties of flame-retardant epoxy resin, achieving a UL-94 rating of V-0.

[0020] The preparation method of this invention is simple, requires no special equipment, the reaction is easy to control, and it is suitable for large-scale production.

[0021] The epoxy resin used in this invention can be any commercially available epoxy resin. The flame retardant of this invention can be used to obtain a highly efficient flame-retardant epoxy resin without affecting this invention. The flame retardant of this invention can also be used in polyurethane resins.

[0022] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0023] Figure 1 The thermogravimetric curves of cured samples of a multifunctional macromolecular PN flame retardant, a high-efficiency flame-retardant epoxy resin, and their application in fiber composite materials are shown in the present invention.

[0024] Figure 2 These are UL-94 vertical burning test images of a multifunctional macromolecular PN flame retardant, a high-efficiency flame-retardant epoxy resin, and its application in fiber composite materials, before and after modification.

[0025] Figure 3 The images show UL-94 vertical burning test photos of epoxy resin / aramid composite material samples before and after modification, which are based on a multifunctional macromolecular PN flame retardant, a high-efficiency flame-retardant epoxy resin, and its application in fiber composite materials. Detailed Implementation

[0026] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0027] In addition, unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be obtained by purchasing them from the market or prepared by existing methods.

[0028] It should be noted that the epoxy resin used in this invention is a commercially available epoxy resin. Through experiments, it has been shown that changing the epoxy resin does not affect the technical effect of the flame-retardant epoxy resin in this invention. Therefore, the type of epoxy resin will not affect the implementation effect of this invention or the scope of patent protection of this invention.

[0029] Example 1: Preparation of a multifunctional macromolecular PN flame retardant A method for preparing a multifunctional macromolecular PN flame retardant, comprising the following steps: Cyanurium chloride (1.84 g, 0.01 mol) was dissolved in 50 ml of THF and set aside. DOPO derivative (formula VII) (8.13 g, 0.03 mol) was added to a three-necked flask, followed by 100 ml of THF. The mixture was magnetically stirred until the DOPO derivative was completely dissolved. Then, pyridine (2.4 g, 0.03 mol) was added as an acid-binding agent. The cyanurium chloride solution was slowly added dropwise to the flask at 0 °C, and the temperature was raised to 60 °C under a nitrogen atmosphere for 24 h. The liquid was then collected by filtration and rotary evaporation. The evaporated liquid was added dropwise to deionized water to precipitate a solid. The solid was collected by vacuum filtration and freeze-dried for 24 h to obtain a multifunctional macromolecular PN flame retardant.

[0030] The reaction formula is:

[0031] Example 2: Preparation of a multifunctional macromolecular PN flame retardant A method for preparing a multifunctional macromolecular PN flame retardant, comprising the following steps: Hexachlorocyclotriphosphazene (3.5 g, 0.01 mol) was dissolved in 50 mL of DMSO and set aside. DOPO derivative of formula (VIII) (20.1 g, 0.06 mol) was added to a three-necked flask, followed by 100 mL of DMSO. The mixture was magnetically stirred until the DOPO derivative was completely dissolved. Then, triethylamine (6.07 g, 0.06 mol) was added as an acid-binding agent. A cyanuric chloride solution was slowly added dropwise to the flask at 0 °C, and the temperature was raised to 100 °C under a nitrogen atmosphere for 48 h. The liquid was then collected by filtration and rotary evaporation. The evaporated liquid was added dropwise to deionized water to precipitate a solid. The solid was collected by vacuum filtration and freeze-dried for 24 h to obtain a multifunctional macromolecular PN flame retardant.

[0032] The reaction formula is:

[0033] Example 3: Preparation of Multifunctional Macromolecular PN Flame Retardant A method for preparing a multifunctional macromolecular PN flame retardant, comprising the following steps: Cyanurium chloride (1.84 g, 0.01 mol) was dissolved in 50 mL of DMF and set aside. A DOPO derivative of formula (IX) (10 g, 0.03 mol) was added to a three-necked flask, followed by 100 mL of DMF. The mixture was magnetically stirred until the DOPO derivative was completely dissolved. Then, triethanolamine (4.48 g, 0.03 mol) was added as an acid-binding agent. The cyanurium chloride solution was slowly added dropwise to the flask at 0 °C, and the temperature was raised to 90 °C under a nitrogen atmosphere for 36 h. The liquid was then collected by filtration and rotary evaporation. The evaporated liquid was added dropwise to deionized water to precipitate a solid. The solid was collected by vacuum filtration and freeze-dried for 24 h to obtain a multifunctional macromolecular PN flame retardant.

[0034] The reaction formula is:

[0035] Example 4: Preparation method of high-efficiency flame-retardant epoxy resin A method for preparing a high-efficiency flame-retardant epoxy resin, comprising the following steps: First, 100 parts of epoxy resin and 0.5 parts of the multifunctional macromolecular PN flame retardant obtained in Example 2 were added to a three-roll mill and ground evenly. Then, the mixture was placed in a 90°C water bath and stirred. 28 parts of melted DDM were added and stirred for 10 minutes. After vacuum degassing for 10 minutes, the mixture was poured into a mold and cured in an oven. The curing process was: 100°C / 2h + 150°C / 2h.

[0036] Example 5: Preparation method of high-efficiency flame-retardant epoxy resin A method for preparing a high-efficiency flame-retardant epoxy resin, comprising the following steps: First, 100 parts of epoxy resin and 3 parts of the multifunctional macromolecular PN flame retardant obtained in Example 2 were added to a three-roll mill and ground evenly. Then, the mixture was placed in an 80°C water bath and stirred. 28 parts of melted DDM were added and stirred for 5 minutes. After vacuum degassing for 10 minutes, the mixture was poured into a mold and cured in an oven. The curing process was: 100°C / 2h + 150°C / 2h.

[0037] Example 6: Preparation method of high-efficiency flame-retardant epoxy resin A method for preparing a high-efficiency flame-retardant epoxy resin, comprising the following steps: First, 100 parts of epoxy resin and 5 parts of the multifunctional macromolecular PN flame retardant obtained in Example 2 were added to a three-roll mill and ground evenly. Then, the mixture was placed in a 60°C water bath and stirred. 28 parts of melted DDS were added and stirred for 5 minutes. After vacuum degassing for 10 minutes, the mixture was poured into a mold and cured in an oven. The curing process was: 100°C / 2h + 150°C / 2h.

[0038] Example 7: Preparation method of flame-retardant fiber composite material The preparation method of flame-retardant fiber composite material includes the following steps: A layer of aramid fabric was laid flat on the lower template of a flat mold. The uncured flame-retardant epoxy resin obtained in Example 4 was applied to the aramid fabric and evenly distributed on the aramid fabric using a scraper. The process of laying the fabric and applying the flame-retardant epoxy resin was repeated, with a total of 13 fabric layers. The upper template of the flat mold was then placed on top. The mold was placed in a molding press for molding and curing. The molding process was as follows: First stage: 1 MPa, 100℃ / 2h; Second stage: 8 MPa; 150℃ / 2h.

[0039] Example 8: Preparation method of flame-retardant fiber composite material The preparation method of flame-retardant fiber composite material includes the following steps: A layer of aramid fabric was laid flat on the lower template of a flat mold. The uncured flame-retardant epoxy resin obtained in Example 5 was applied to the aramid fabric and evenly distributed on the aramid fabric using a scraper. The process of laying the fabric and applying the flame-retardant epoxy resin was repeated, with a total of 13 fabric layers. The upper template of the flat mold was then placed on top. The mold was placed in a molding press for molding and curing. The molding process was as follows: First stage: 2 MPa, 100℃ / 2h; Second stage: 5 MPa, 150℃ / 2h.

[0040] Example 9: Preparation method of flame-retardant fiber composite material The preparation method of flame-retardant fiber composite material includes the following steps: A layer of aramid fabric was laid flat on the lower template of a flat mold. The uncured flame-retardant epoxy resin obtained in Example 6 was applied to the aramid fabric and evenly distributed on the aramid fabric using a scraper. The process of laying the fabric and applying the flame-retardant epoxy resin was repeated, with a total of 13 fabric layers. The upper template of the flat mold was then placed on top. The mold was placed in a molding press for molding and curing. The molding process was as follows: First stage: 3 MPa, 100℃ / 2h; Second stage: 10 MPa; 150℃ / 2h.

[0041] Comparative Example 1: The preparation method of flame-retardant epoxy resin includes the following steps: First, add 100 parts of epoxy resin to a three-roll mill and grind it evenly. Then, place it in an 80℃ water bath and stir. Add 28 parts of melted DDM and stir for 5 minutes. After vacuum degassing for 10 minutes, pour it into a mold and cure it in an oven. The curing process is: 100℃ / 2h + 150℃ / 2h.

[0042] Comparative Example 2: Preparation method of flame-retardant fiber composite material The preparation method of flame-retardant fiber composite material includes the following steps: A layer of aramid fabric was laid flat on the lower template of a flat mold. The uncured flame-retardant epoxy resin obtained in Comparative Example 1 was applied to the aramid fabric, and a scraper was used to distribute it evenly on the aramid fabric. The process of laying the fabric and applying the flame-retardant epoxy resin was repeated, with a total of 13 fabric layers. The upper template of the flat mold was then placed on top. The mold was placed in a molding press to form and cure the material. The molding process was as follows: First stage: 2 MPa, 100℃ / 2h; Second stage: 5 MPa, 150℃ / 2h.

[0043] The specific raw material formulations and phosphorus and nitrogen contents of Examples 5-9 and comparative examples are shown in Table 1.

[0044] Table 1. Formulations and phosphorus and nitrogen contents of the comparative examples and embodiments. Comparative Example 100 28 0 0 3.091 Example 4 100 28 2 0.201 3.074 Example 5 100 28 3 0.299 3.065 Example 6 100 28 5 0.491 3.049 Table 2 Performance Tests of Flame-Retardant Epoxy Resins Test Standards ISO 4589-2 ASTM D3801 ASTM D638 ISO 179 Comparative Example 25.5 Intense burning 71.2 18.1 Example 4 31.9 V1 78.3 26.2 Example 5 33.5 V0 82.2 29.7 Example 6 34.5 V0 84.2 28.4 Table 3: Performance Testing of Flame-Retardant Fiber Composite Materials Test Standards ISO 4589-2 ASTM D3801 ASTM D638 ASTM D2344 Comparative Example 2 33 Intense burning 460 22.7 Example 8 37 Afterburning time 70 seconds 478 24.1 Example 9 39 Afterburning time 37 seconds 504 25.3 See Table 2 and appendix. Figure 1-2 It can be seen that the addition of multifunctional macromolecular PN flame retardant improves the char residue of epoxy resin and enhances the flame retardant performance of the material. With increasing amounts of multifunctional macromolecular PN flame retardant, the oxygen index and flame retardant rating of the epoxy resin increase, and its combustion behavior changes from intense combustion to self-extinguishing, with a reduced afterflame time. When the amount of multifunctional macromolecular PN flame retardant added is 2 parts, the afterflame time of the epoxy resin is limited to within 5 seconds; when the amount of multifunctional macromolecular PN flame retardant added is 5 parts, the afterflame time of the epoxy resin is limited to within 2 seconds. With increasing amounts of multifunctional macromolecular PN flame retardant added, the mechanical properties of the epoxy resin are improved, with significant increases in tensile strength and impact strength.

[0045] See Table 3 and appendix. Figure 3 The flame-retardant fiber composite material obtained by this invention improves the oxygen index of the fiber composite material, reduces the afterflame time, alleviates the intensity of combustion, and at the same time, the mechanical properties of the material, such as tensile strength and shear strength, are significantly improved.

[0046] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0047] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A method for preparing a multifunctional macromolecular PN flame retardant, characterized in that: A DOPO derivative with added acid-binding agent is reacted with hexachlorocyclotriphosphazene or cyanuric chloride solution at 60℃~120℃ for 12~48h under an inert atmosphere to obtain a multifunctional macromolecular PN flame retardant containing the conjugated structure of formula (Ⅲ) DOPO. The acid-binding agent is selected from pyridine, triethylamine or triethanolamine. The DOPO derivative is a conjugated organic compound with amino or hydroxyl active groups, and the structural formula of the DOPO derivative is shown in (VI); the structural formula of the multifunctional macromolecular PN flame retardant is shown in (I) and (II). （Ⅰ） （Ⅱ） Where R1 is equation (Ⅲ), and R2 is equation (Ⅳ) or equation (Ⅴ). （Ⅲ） ， （Ⅵ）， （Ⅳ） （Ⅴ）， In the formula, m1=0~3, m2=0~1, n1=0~3, n2=0~1.

2. The preparation method of the multifunctional macromolecular PN flame retardant as described in claim 1, characterized in that, The DOPO derivative was dissolved in a solvent by stirring. After complete dissolution, an acid-binding agent was added. Hexachlorocyclotriphosphazene or cyanuric chloride solution was slowly added dropwise to the solution at 0°C. The temperature was raised to 60°C–120°C under a nitrogen atmosphere and the reaction was carried out for 12–48 hours. The liquid was then collected by filtration and rotary evaporation. The liquid after rotary evaporation was added dropwise to deionized water to precipitate the solid. The solid was collected by vacuum filtration and freeze-dried for 24 hours to obtain the multifunctional macromolecular PN flame retardant.

3. The preparation method of the multifunctional macromolecular PN flame retardant as described in claim 2, characterized in that: The solvent is DMF, DMSO or THF.

4. A high-efficiency flame-retardant epoxy resin using a multifunctional macromolecular PN flame retardant prepared according to any one of claims 1-3, characterized in that: It includes epoxy resin, curing agent, and multifunctional macromolecular PN flame retardant in a mass ratio of 100:28:0.5 to 5.

5. A method for preparing the high-efficiency flame-retardant epoxy resin according to claim 4, characterized in that, Includes the following steps: After weighing the epoxy resin and multifunctional macromolecular PN flame retardant, mix and stir to pre-disperse them, then pour them into a grinder and grind them evenly. Then put them into a water bath at 55℃~90℃ and stir. Add the melted curing agent and stir for 5~10 minutes. After vacuum degassing for 10 minutes, pour it into a mold and cure it in an oven to obtain a high-efficiency flame-retardant epoxy resin.

6. The application of the high-efficiency flame-retardant epoxy resin according to claim 4 in the preparation of flame-retardant fiber composite materials.

7. The application as described in claim 6, characterized in that: The uncured high-efficiency flame-retardant epoxy resin is repeatedly laminated with fabric and then molded to form the flame-retardant fiber composite material.

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