Organic flame retardant containing phosphorus, nitrogen and sulfur as well as preparation method and application thereof

Abstract

The invention discloses an organic flame retardant containing phosphorus, nitrogen and sulfur as well as a preparation method and application thereof, and belongs to the technical field of flame retardance of epoxy resin. The organic flame retardant containing phosphorus, nitrogen and sulfur is obtained by reacting an aldehyde compound, a sulfonic acid compound and DOPO according to a Schiff base principle. The flame retardant disclosed by the invention has multiple flame-retardant elements, and the flame-retardant property is improved through the mutual synergistic effect of the elements, so that the high flame-retardant technical effect of the V-0 grade in UL-94 can be achieved under the condition that a small amount of flame-retardant elements are added. Specific experimental results show that when the dosage of the flame retardant is 5wt%, UL-94 test reaches V-0 level, LOI (Limit Oxygen Index) test reaches about 30%, and the impact strength is greater than 30kJ / m < 2 >.

Description

Technical Field

[0001] The present invention relates to the technical field of epoxy resin flame retardants, and particularly relates to an organic phosphorus, nitrogen and sulfur-containing flame retardant, a preparation method thereof and an application thereof. Background Art

[0002] Epoxy resin (EP), as one of the thermosetting materials, is closely related to our daily life. Due to its excellent mechanical and electrical properties, relatively low curing shrinkage rate, superior adhesion to substrates, as well as good heat resistance, chemical resistance and corrosion resistance, it has been widely used in various fields such as coatings, adhesives, electronic devices, laminates and encapsulation in the field of life. However, the large amount of heat and smoke released during the combustion of epoxy resin not only threatens the safety of human life and property, but also damages the surrounding environment. In addition, in some specific fields, high fire resistance is also required. Therefore, in order to meet the needs and attention of people for the high fire resistance performance of epoxy resin composites, the research on the flame retardant performance of epoxy resin has received increasing attention.

[0003] In terms of flame retardancy of epoxy resin, adding flame retardants is a method with low cost and simple operation. Phosphorus-based flame retardants are the most widely used flame retardants after halogen-based flame retardants. Phosphorus-containing functional groups have the advantages of diverse structures, easy preparation, low toxicity and little secondary pollution. Introducing them into the epoxy resin structure can prepare products with excellent flame retardant performance, electrical performance and environmental friendliness. For example, the invention patent with publication number CN116355284A discloses a DOPO-based reactive flame retardant for flame-retarding epoxy resin. Specifically, N-hydroxybenzamidine is first obtained by reacting benzonitrile and hydroxylamine in an organic solvent, and then the N-hydroxybenzamidine and terephthalaldehyde are reacted in an organic solvent to obtain a Schiff base intermediate. After that, DOPO (9,10-diamino-9-oxa-10-phosphaphenanthrene-10-oxide) is added and the mixture is reacted to obtain the product. The reactive flame retardant described in this invention can significantly improve the flame retardant performance of epoxy resin. When the addition amount of the flame retardant in the epoxy system is 1 wt%, it can reach the V-1 grade in the vertical burning test (UL-94), and when the proportion is 5 wt%, it reaches the V-0 grade in UL-94. Although DOPO has good flame retardant performance due to the presence of phosphorus element, those skilled in the art know that DOPO has a small molecular weight, and after addition, the mechanical properties and thermal properties decrease significantly due to the obvious plasticizing effect, which is more obvious when the addition amount is large (such as 4-5 wt%), restricting the application of the obtained epoxy resin composite material. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an organic phosphorus, nitrogen and sulfur-containing flame retardant, its preparation method and application in view of the deficiencies existing in the prior art. The applicant has found through experiments that when this flame retardant is applied to an epoxy resin system, it can improve the flame retardancy of the obtained epoxy resin composite material while also improving its mechanical properties and thermal stability.

[0005] To solve the above technical problems, the present invention adopts the following technical solutions:

[0006] An organic phosphorus, nitrogen and sulfur-containing flame retardant has a structure shown in the following formula (I):

[0007]

[0008] Among them, R1 is a sulfonic acid group, a benzenesulfonic acid group or a sulfinic acid group.

[0009] The present invention uses an aldehyde compound, a sulfonic acid compound and DOPO to react according to the Schiff base principle to obtain an organic phosphorus, nitrogen and sulfur-containing flame retardant. Among them, DOPO contains phosphorus elements and thus has good flame retardant performance. The sulfonic acid compound has sulfur element flame retardancy. During combustion, it can not only release incombustible gases such as sulfur dioxide, but also promote the matrix to form carbon better to form a stable carbon layer, thereby blocking the release of smoke. At the same time, due to the presence of DOPO and aromatic compounds, its benzene ring structure can improve the thermal stability of the composite epoxy resin, realizing the improvement of its impact strength and bending strength without reducing the thermal stability of the composite material. And in the presence of double DOPO, the phosphorus content is increased, which greatly improves its flame retardant effect. Therefore, the flame retardant of the present invention can improve the flame retardancy of the obtained epoxy resin composite material while also improving the mechanical properties of the obtained epoxy resin composite material.

[0010] The preparation method of the above-mentioned organic phosphorus, nitrogen and sulfur-containing flame retardant includes the following steps:

[0011] S1: Take a sulfonic acid compound and an aldehyde compound and place them in an organic solvent, and react under heating conditions to obtain reaction solution I; among them, the sulfonic acid compound is an aromatic or hydrocarbon compound containing one sulfonic acid group or sulfinic acid group;

[0012] S2: Take DOPO (9,10-diamino-9-oxa-10-phosphaphenanthrene-10-oxide) and add it to reaction solution I, and react under heating conditions to obtain reaction solution II;

[0013] S3: Filter the obtained reaction solution II, recover the solvent from the filtrate, and dry it to obtain the organic phosphorus, nitrogen and sulfur-containing flame retardant.

[0014] Furthermore, the sulfonic acid compound can specifically be p-aminobenzenesulfonic acid, formamidine sulfinic acid or taurine.

[0015] The aldehyde compound refers to an aromatic or hydrocarbon compound with an aldehyde functional group, and preferably can be terephthalaldehyde, 2-hydroxyterephthalaldehyde, p-hydroxybenzaldehyde, p-aminobenzaldehyde, benzaldehyde, cinnamaldehyde or citral.

[0016] From the perspective of facilitating the reaction, in step S2, it is preferred to first dissolve DOPO in an appropriate amount of organic solvent and then add it to the reflux liquid I.

[0017] The organic solvent involved in this application can be at least one selected from methanol, xylene, toluene, acetonitrile, chloroform and tetrahydrofuran, and preferably acetonitrile or toluene. The dosage of the organic solvent can be determined as needed, and generally it is appropriate to be able to fully dissolve the raw materials to participate in the reaction. For example, in step S1, calculated based on 0.1 mol of aldehyde compound, the total dosage of the organic solvent used for all raw materials is usually 100 - 400 mL.

[0018] In steps S1 and S2, the reaction is preferably carried out under the condition of 50 - 80 °C. The reaction is tracked and detected by TLC until the reaction is complete. According to the applicant's experience, in step S1, when carrying out the reflux reaction under the condition of 50 - 80 °C, the reaction time is preferably controlled within 3 - 6 h; in step S2, when carrying out the reflux reaction under the condition of 50 - 80 °C, the reaction time is preferably controlled within 5 - 8 h.

[0019] In this application, the ratio of the sulfonic acid compound, the aldehyde compound and DOPO is the stoichiometric ratio. In specific operations, the molar ratio of the sulfonic acid compound, the aldehyde compound and DOPO can be 1 - 2:1:2 - 3.

[0020] The present invention also provides the application of the above-mentioned organic phosphorus, nitrogen and sulfur-containing flame retardant in a flame-retardant epoxy resin system. Specifically, the organic phosphorus, nitrogen and sulfur-containing flame retardant is cross-linked and used with an epoxy resin and a curing agent. Among them, in the applied epoxy resin system, the dosage proportion of the organic phosphorus, nitrogen and sulfur-containing flame retardant is 1 - 5 wt%.

[0021] Furthermore, the curing agent is preferably 2,4-diaminodiphenylmethane (DDM) or methyltetrahydrophthalic anhydride (MeTHPA).

[0022] Furthermore, when the curing agent is DDM, the epoxy resin system includes, by weight parts: 75 - 100 parts of epoxy resin, 20 - 25 parts of curing agent, and 0.96 - 6.58 parts of organic phosphorus, nitrogen and sulfur-containing flame retardant; at this time, the curing process is usually 100 °C / 2 h + 140 °C / 2 h.

[0023] When the curing agent is MeTHPA, the epoxy resin system includes, by weight: 75 to 100 parts of epoxy resin, 60 to 80 parts of curing agent, and 1.36 to 9.47 parts of organic phosphorus, nitrogen, and sulfur-containing flame retardant; at this time, the curing process is usually 80°C / 1h + 100°C / 1h + 130°C / 2h + 150°C / 4h.

[0024] Compared with the prior art, the characteristics of the flame retardant of the present invention are as follows:

[0025] 1. Based on the relationship between the material structure and performance, the present invention designs a reactive halogen-free flame retardant with multiple flame retardant elements, and utilizes the synergistic effect of each element to improve the flame retardant performance; on the other hand, DOPO and aromatic compounds are used to improve the thermal stability of the composite epoxy resin, and at the same time improve the impact strength and flexural strength of the composite material. In the presence of bis-DOPO, the phosphorus content is increased, which greatly improves its flame retardant effect. Therefore, the flame retardant of the present invention can improve the flame retardant performance of the obtained epoxy resin composite material while also improving the mechanical properties and thermal stability of the obtained epoxy resin composite material.

[0026] 2. The preparation method of the flame retardant of the present invention adjusts the molecular weight of the macromolecular compound by controlling the component ratio, which is beneficial to the full and uniform mixing of the additive and the epoxy resin, increases the fluidity of the epoxy resin after mixing, is beneficial to the processing process of casting molding, and reduces the requirements of the preparation process. Description of the Drawings

[0027] Figure 1 1H-NMR spectrum of the final product prepared in Example 1; 1 1H-NMR spectrum;

[0028] Figure 2 1H-NMR spectrum of the final product prepared in Example 1; 31 31P-NMR spectrum;

[0029] Figure 3 UL-94 combustion test photo of the epoxy resin composite material prepared in Application Example 1. Detailed Embodiments

[0030] Example 1

[0031] A preparation method of a novel organic phosphorus, nitrogen, and sulfur-containing flame retardant includes the following steps:

[0032] S1 Dissolve 0.1 mol (12.5 g) of taurine and 0.1 mol (12.2 g) of p-hydroxybenzaldehyde in 150 mL of acetonitrile solvent, add them to a three-necked flask, and perform magnetic stirring in an oil bath at 70°C for 5 h with condensation reflux to obtain reaction solution I;

[0033] Take 0.1 mol (21.6 g) of DOPO and dissolve it in 50 mL of acetonitrile solvent. Add the resulting solution to Reaction Solution I, and continue the condensation reflux reaction at 70 °C for 8 h. After the reaction is completed, obtain Reaction Solution II;

[0034] Filter Reaction Solution II under reduced pressure, collect the filtrate, obtain a solid product by rotary evaporation, and dry it in an oven at 100 °C for 24 h to obtain the organophosphorus, nitrogen, and sulfur-containing flame retardant of the present invention, whose 1 1H-NMR spectrum and 31 31P-NMR spectrum are respectively as Figure 1 and Figure 2 shown.

[0035] Example 2

[0036] A preparation method of a novel organophosphorus, nitrogen, and sulfur-containing flame retardant, comprising the following steps:

[0037] S1 Dissolve 0.2 mol (25 g) of taurine and 0.1 mol (13.4 g) of terephthalaldehyde in 300 mL of acetonitrile solvent, add it to a three-necked flask, carry out magnetic stirring in an oil bath at 70 °C, and carry out condensation reflux for 5 h to obtain Reaction Solution I;

[0038] S2 Take 0.2 mol (43.2 g) of DOPO and dissolve it in 100 mL of acetonitrile solvent. Add the resulting solution to Reaction Solution I, and continue the condensation reflux reaction at 70 °C for 8 h. After the reaction is completed, obtain Reaction Solution II;

[0039] S3 Filter Reaction Solution II under reduced pressure, take the liquid and obtain a solid product by rotary evaporation, and dry it in an oven at 100 °C for 24 h to obtain the organophosphorus, nitrogen, and sulfur-containing flame retardant of the present invention.

[0040] Example 3

[0041] A preparation method of a novel organophosphorus, nitrogen, and sulfur-containing flame retardant, comprising the following steps:

[0042] S1 Dissolve 0.2 mol (34.6 g) of p-aminobenzenesulfonic acid and 0.1 mol (13.4 g) of terephthalaldehyde in 300 mL of acetonitrile solvent, add it to a three-necked flask, carry out magnetic stirring in an oil bath at 70 °C, and carry out condensation reflux for 5 h to obtain Reaction Solution I;

[0043] S2 Take 0.2 mol (43.2 g) of DOPO and dissolve it in 100 mL of acetonitrile solvent. Add the resulting solution to Reaction Solution I, and continue the condensation reflux reaction at 70 °C for 8 h. After the reaction is completed, obtain Reaction Solution II;

[0044] S3: Filter the reaction solution II under reduced pressure, take the liquid and obtain a solid product by rotary evaporation, place the solid product in an oven at 100° C. and dry it for 24 hours to obtain the organic phosphorus-nitrogen-sulfur flame retardant of the present invention.

[0045] Example 4

[0046] A method for preparing a novel organic phosphorus-nitrogen-sulfur flame retardant comprises the following steps:

[0047] S1: 0.1 mol (17.3 g) of p-aminobenzenesulfonic acid and 0.1 mol (12.2 g) of p-hydroxybenzaldehyde were dissolved in 150 mL of acetonitrile solvent, added to a three-necked flask, and magnetically stirred in an oil bath at 70°C, and condensed and refluxed for 5 h to obtain reaction solution I;

[0048] S2: 0.1 mol (21.6 g) of DOPO was dissolved in 50 mL of acetonitrile solvent, and the obtained solution was added to reaction solution I. The reaction was continued at 70°C for 8 h under condensation reflux. After the reaction was completed, reaction solution II was obtained.

[0049] S3: Filter the reaction solution II under reduced pressure, take the liquid and obtain a solid product by rotary evaporation, place the solid product in an oven at 100° C. and dry it for 24 hours to obtain the organic phosphorus-nitrogen-sulfur flame retardant of the present invention.

[0050] Example 5

[0051] The same as Example 1, except that: in step S1, p-aminobenzaldehyde is used instead of p-hydroxybenzaldehyde, methanol is used instead of acetonitrile, and the reaction temperature is changed to 50°C until the reaction is complete; in step S2, methanol is used instead of acetonitrile, and the reaction temperature is changed to 50°C until the reaction is complete. Finally, the organic phosphorus-nitrogen-sulfur flame retardant of the present invention is obtained.

[0052] Example 6

[0053] The same as Example 1, except that: in step S1, formamidine sulfinic acid is used instead of taurine, cinnamaldehyde is used instead of p-hydroxybenzaldehyde, tetrahydrofuran is used instead of acetonitrile, and the reaction temperature is changed to 60°C until the reaction is complete; in step S2, tetrahydrofuran is used instead of acetonitrile, and the reaction temperature is changed to 60°C until the reaction is complete. Finally, the organic phosphorus-nitrogen-sulfur flame retardant of the present invention is obtained.

[0054] The parts involved in the following application examples are all parts by weight.

[0055] Application Example 1

[0056] Weigh 85 parts of E-51 epoxy resin, 25 parts of DDM curing agent, and 4.6 parts of the organophosphorus, nitrogen, and sulfur-containing flame retardant prepared in Example 1. Mechanically stir them under vacuum at 60 °C for 10 min, then pour them into a mold, and carry out a curing reaction through a programmed temperature rise process of 100 °C / 2 h + 140 °C / 2 h to obtain a flame-retardant modified epoxy resin composite material.

[0057] Application Example 2

[0058] Weigh 85 parts of E-51 epoxy resin, 25 parts of DDM curing agent, and 5.78 parts of the organophosphorus, nitrogen, and sulfur-containing flame retardant prepared in Example 2. Mechanically stir them under vacuum at 60 °C for 10 min, then pour them into a mold, and carry out a curing reaction through a programmed temperature rise process of 100 °C / 2 h + 140 °C / 2 h to obtain a flame-retardant modified epoxy resin composite material.

[0059] Application Example 3

[0060] Weigh 85 parts of E-51 epoxy resin, 25 parts of DDM curing agent, and 4.6 parts of the organophosphorus, nitrogen, and sulfur-containing flame retardant prepared in Example 3. Mechanically stir them under vacuum at 60 °C for 10 min, then pour them into a mold, and carry out a curing reaction through a programmed temperature rise process of 100 °C / 2 h + 140 °C / 2 h to obtain a flame-retardant modified epoxy resin composite material.

[0061] Application Example 4

[0062] Weigh 85 parts of E-51 epoxy resin, 25 parts of DDM curing agent, and 5.78 parts of the organophosphorus, nitrogen, and sulfur-containing flame retardant prepared in Example 4. Mechanically stir them under vacuum at 60 °C for 10 min, then pour them into a mold, and carry out a curing reaction through a programmed temperature rise process of 100 °C / 2 h + 140 °C / 2 h to obtain a flame-retardant modified epoxy resin composite material.

[0063] Application Example 5

[0064] Weigh 100 parts of E-51 epoxy resin, 80 parts of MeTHPA curing agent, and 7.5 parts of the organophosphorus, nitrogen, and sulfur-containing flame retardant prepared in Example 1. Mechanically stir them under vacuum at 50 °C for 30 min, then pour them into a mold, and carry out a curing reaction through a programmed temperature rise process of 80 °C / 1 h + 100 °C / 1 h + 130 °C / 2 h + 150 °C / 4 h to obtain a flame-retardant modified epoxy resin composite material.

[0065] Application Example 6

[0066] Weigh 100 parts of E-51 epoxy resin, 80 parts of MeTHPA curing agent, and 7.5 parts of the organophosphorus, nitrogen, and sulfur-containing flame retardant prepared in Example 2. Mechanically stir them under vacuum at 50 °C for 30 min, then pour them into a mold, and carry out a curing reaction through a programmed temperature rise process of 80 °C / 1 h + 100 °C / 1 h + 130 °C / 2 h + 150 °C / 4 h to obtain a flame-retardant modified epoxy resin composite material.

[0067] Application Example 7

[0068] Weigh 100 parts of E-51 epoxy resin, 80 parts of MeTHPA curing agent, and 9.47 parts of the organophosphorus, nitrogen, and sulfur-containing flame retardant prepared in Example 3. Mechanically stir them under vacuum at 50 °C for 30 min, then pour them into a mold, and carry out a curing reaction through a programmed temperature rise process of 80 °C / 1 h + 100 °C / 1 h + 130 °C / 2 h + 150 °C / 4 h to obtain a flame-retardant modified epoxy resin composite material.

[0069] Application Example 8

[0070] Weigh 100 parts of E-51 epoxy resin, 80 parts of MeTHPA curing agent, and 7.5 parts of the organophosphorus, nitrogen, and sulfur-containing flame retardant prepared in Example 4. Mechanically stir them under vacuum at 50 °C for 30 min, then pour them into a mold, and carry out a curing reaction through a programmed temperature rise process of 80 °C / 1 h + 100 °C / 1 h + 130 °C / 2 h + 150 °C / 4 h to obtain a flame-retardant modified epoxy resin composite material.

[0071] Application Example 9 (compared with 8, the flame retardant addition amount is increased to 5%)

[0072] Weigh 100 parts of E-51 epoxy resin, 80 parts of MeTHPA curing agent, and 9.47 parts of the organophosphorus, nitrogen, and sulfur-containing flame retardant prepared in Example 4. Mechanically stir them under vacuum at 50 °C for 30 min, then pour them into a mold, and carry out a curing reaction through a programmed temperature rise process of 80 °C / 1 h + 100 °C / 1 h + 130 °C / 2 h + 150 °C / 4 h to obtain a flame-retardant modified epoxy resin composite material.

[0073] Application Example 10

[0074] Weigh 75 parts of E-51 epoxy resin, 25 parts of DDM curing agent, and 3.1 parts of the organophosphorus, nitrogen, and sulfur-containing flame retardant prepared in Example 5. Mechanically stir them under vacuum at 60 °C for 10 min, then pour them into a mold, and carry out a curing reaction through a programmed temperature rise process of 100 °C / 2 h + 140 °C / 2 h to obtain a flame-retardant modified epoxy resin composite material.

[0075] Application Example 11

[0076] Weigh 75 parts of E-51 epoxy resin, 60 parts of MeTHPA curing agent, and 4.18 parts of the organophosphorus, nitrogen, and sulfur-containing flame retardant prepared in Example 5. Mechanically stir them under vacuum at 50 °C for 30 min, then pour them into a mold, and carry out a curing reaction through a programmed temperature rise process of 80 °C / 1 h + 100 °C / 1 h + 130 °C / 2 h + 150 °C / 4 h to obtain a flame-retardant modified epoxy resin composite material.

[0077] Application Example 12

[0078] Weigh 100 parts of E-51 epoxy resin, 20 parts of DDM curing agent, and 5 parts of the organophosphorus, nitrogen, and sulfur-containing flame retardant prepared in Example 6. Mechanically stir them under vacuum at 60 °C for 10 min, then pour them into a mold, and carry out a curing reaction through a programmed temperature rise process of 100 °C / 2 h + 140 °C / 2 h to obtain a flame-retardant modified epoxy resin composite material.

[0079] Application Example 13

[0080] Repeat Application Example 12, except that the dosage of the organophosphorus, nitrogen, and sulfur-containing flame retardant is 1.22 parts.

[0081] Comparative Application Example 1

[0082] Weigh 85 parts of E-51 epoxy resin and 25 parts of DDM curing agent. Mechanically stir them under vacuum at 60 °C for 10 min, then pour them into a mold, and carry out a curing reaction through a programmed temperature rise process of 100 °C / 2 h + 130 °C / 2 h to obtain an epoxy resin composite material.

[0083] Comparative Application Example 2

[0084] Weigh 100 parts of E-51 epoxy resin and 80 parts of MeTHPA curing agent. Mechanically stir them under vacuum at 50 °C for 30 min, then pour them into a mold, and carry out a curing reaction through a programmed temperature rise process of 80 °C / 1 h + 100 °C / 1 h + 130 °C / 2 h + 150 °C / 4 h to obtain an epoxy resin composite material.

[0085] Comparative Application Example 3

[0086] Repeat Example 2, except that the organophosphorus-nitrogen-sulfur flame retardant is replaced by the P / N / S type flame retardant (STP) reported in the existing literature (C. Wan, H. Duan, C. Zhang, J. Cao, J. Zou, J. Zhang, H. Ma, A P / N / S-containing compound toward enhanced fire safety epoxy resin with well-balanced performance, Polymer Degradation and Stability 192 (2021) 109698), and the addition amount remains unchanged.

[0087] Test the performance such as the fire prevention effect of the epoxy resin composites prepared in the above Application Examples 1-13 and Comparative Application Examples 1-3. The test methods for each performance parameter are as follows:

[0088] Vertical burning test (UL-94): Refer to the standard GB / T 2408-2008, the test instrument is CZF-3, and the sample size is 125×13×3 mm 3 。

[0089] Limiting oxygen index test (LOI): Refer to the standard GB / T 2406.2-2009, the test instrument is JF-3, and the sample size is 125×6.5×3 mm 3 。

[0090] Impact strength: Refer to the standard GB / T 1843-2008, the test instrument is TCJ pendulum impact testing machine, and the sample size is 90×10×4 mm 3 。

[0091] Flexural strength: Refer to the standard ASTM D 790-2007E1, SUNS universal testing machine, and the sample size is 135×13×4 mm 3 。

[0092] Heat distortion temperature: Refer to the standard GB / T 1634.1-2004, microcomputer-controlled Vicat softening point testing machine, and the sample size is 125×6.5×3 mm 3 。

[0093] The test results are shown in Table 1 below.

[0094] Table 1:

[0095]

[0096] As can be seen from the above table, compared with Application Comparative Examples 1-2, when the organic phosphorus, nitrogen and sulfur flame retardant of the present invention is introduced into the epoxy resin curing system in a certain proportion, the flame retardant performance of the epoxy resin composite material is significantly improved; moreover, through the mechanical property test, it can be seen that both the impact strength and the flexural strength of the obtained epoxy resin composite material are significantly improved, and at the same time, the heat distortion temperature is also increased.

[0097] Figure 3 It is a photo of the UL-94 combustion test of the epoxy resin composite material prepared in Application Example 2. As can be seen from this figure, this epoxy resin composite material has passed the V-0 level test, proving its excellent flame retardant performance.

[0098] The above are only the preferred embodiments of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be changed within the scope of the concept described herein through the above teachings or the technology or knowledge in related fields. And any changes and modifications made by those skilled in the art without departing from the spirit and scope of the present invention shall fall within the protection scope of the appended claims of the present invention.

Claims

1. An organic phosphorus, nitrogen and sulfur-containing flame retardant, the structure of which is shown in the following formula (I): Among them, R1 is a sulfonic acid group, a benzenesulfonic acid group or a sulfinic acid group.

2. A method for preparing the organic phosphorus, nitrogen and sulfur-containing flame retardant according to claim 1, comprising the following steps: S1: Take a sulfonic acid compound and an aldehyde compound and place them in an organic solvent, and react under heating conditions to obtain reaction solution I; wherein, the sulfonic acid compound is an aromatic or hydrocarbon compound containing one sulfonic acid group or sulfinic acid group; S2: Take DOPO and add it to reaction solution I, and react under heating conditions to obtain reaction solution II; S3: Filter the obtained reaction solution II, recover the solvent from the filtrate, and dry it to obtain the organic phosphorus, nitrogen and sulfur-containing flame retardant.

3. The preparation method according to claim 2, characterized in that, In step S1, the sulfonic acid compound is p-aminobenzenesulfonic acid, formamidine sulfinic acid or taurine.

4. The preparation method according to claim 2, characterized in that, In step S1, the aldehyde compound is terephthalaldehyde, 2-hydroxyterephthalaldehyde, p-hydroxybenzaldehyde, p-aminobenzaldehyde, benzaldehyde, cinnamaldehyde or citral.

5. The preparation method according to claim 2, characterized in that, In step S2, DOPO is first dissolved in an organic solvent and then added to reflux solution I.

6. The preparation method according to any one of claims 2 to 5, characterized in that, The organic solvent is at least one selected from methanol, xylene, toluene, acetonitrile, chloroform and tetrahydrofuran.

7. The preparation method according to any one of claims 2 to 5, characterized in that, In steps S1 and S2, the reaction is carried out at 50-80 °C.

8. Use of the organophosphorus, nitrogen and sulfur-containing flame retardant according to claim 1 in a flame-retardant epoxy resin system, characterized in that, The organic phosphorus, nitrogen and sulfur-containing flame retardant is cross-linked and used with an epoxy resin and a curing agent. Among them, in the applied epoxy resin system, the dosage proportion of the organic phosphorus, nitrogen and sulfur-containing flame retardant is 1-5 wt%.

9. The application according to claim 8, characterized in that, The curing agent is 2,4-diaminodiphenylmethane or methyltetrahydrophthalic anhydride.

10. According to the application described in claim 9, the characteristics are as follows: When the curing agent is 2,4-diaminodiphenylmethane, the epoxy resin system includes, by weight: 75-100 parts of epoxy resin, 20-25 parts of curing agent, and 0.96-6.58 parts of organic phosphorus, nitrogen and sulfur-containing flame retardant; When the curing agent is methyltetrahydrophthalic anhydride, the epoxy resin system includes, by weight: 75-100 parts of epoxy resin, 60-80 parts of curing agent, and 1.36-9.47 parts of organic phosphorus, nitrogen and sulfur-containing flame retardant.

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