Flame-retardant polymer, preparation method thereof and application of flame-retardant polymer in preparation of flame retardant

Abstract

The invention discloses a flame-retardant polymer, a preparation method thereof and application of the flame-retardant polymer in preparation of a flame retardant. The invention relates to a flame-retardant polymer, the flame-retardant polymer has a structure as shown in formula I. In the formula I, R1 is selected from one of phenyl and phenoxy; r2 is selected from one of methyl and phenyl; r3 is selected from one of methyl and phenyl; r4 is selected from one of tertiary butyl and methyl; r5 is selected from one of methyl and phenyl, the value ranges of n1 and n2 are both 0-20, and the value range of n1 + n2 is 0-40. Through molecular modification and design, the flame-retardant polymer has better compatibility with PC resin and PC / ABS engineering plastic, and compared with a traditional phosphate flame retardant, the flame-retardant polymer can improve and reduce the physical performance and weather resistance of the flame-retardant polymer.

Description

Technical fields:

[0001] This invention relates to the field of flame retardant materials technology, and in particular to a flame retardant polymer, its preparation method, and its application in the preparation of flame retardants. Background technology:

[0002] In recent years, phosphorus-silicon-based flame retardant polymers have become a research hotspot in the field of flame retardant materials due to their high efficiency, environmental friendliness, and multifunctionality. Compared with traditional halogen-based flame retardants, their core advantage lies in combining the gas-phase flame retardant mechanism of phosphorus with the condensed-phase charring effect of silicon, significantly improving flame retardant efficiency through a synergistic effect. Furthermore, they do not release toxic gases or corrosive substances during combustion, meeting relevant environmental regulations. Moreover, these flame retardants are widely available, possessing advantages such as environmental friendliness, high flame retardant efficiency, strong reactivity, and ease of modification, making them a common choice for flame retardant modification of copolymers. In recent years, these flame retardants have been widely used in the electronics and electrical appliance fields, building insulation materials, and new energy vehicle components. However, most existing silicon-phosphorus-based flame retardant polymers suffer from poor substrate compatibility and easy exudation. These problems lead to reduced impact resistance, uneven flame retardant performance, and poor weather resistance in plastic products. These issues significantly limit the application of silicon-phosphorus-based polymers in flame retardancy. Summary of the Invention:

[0003] This invention addresses the problems of poor compatibility and easy precipitation of existing phosphorus-silicon polymer flame retardants with existing substrates. It provides a flame-retardant polymer, its preparation method, and its application in flame retardant preparation. Through the modification and design of polymer molecules, this invention enables the product flame-retardant polymer to achieve better compatibility with PC resin and PC / ABS engineering plastics compared to traditional phosphorus-silicon flame retardants, while significantly improving both physical and flame-retardant properties.

[0004] This invention provides a flame-retardant polymer with adjustable silicon content, the flame-retardant polymer having the structure shown in Formula I:

[0005]

[0006] in:

[0007] R1 is selected from phenyl or phenoxy;

[0008] R2 is selected from methyl or phenyl;

[0009] R3 is selected from methyl or phenyl;

[0010] R4 is selected from tert-butyl or methyl;

[0011] R5 is selected from methyl or phenyl;

[0012] The values ​​of n1 and n2 are both in the range of 0-20, and the value of n1+n2 is in the range of 0-40.

[0013] Preferably, the value of n1 is in the range of 0-9, the value of n2 is in the range of 9-20, and the value of n1+n2 is in the range of 18-20.

[0014] Preferably, the molar content of silicon in the flame-retardant polymer is 0%-13%. The molar content of silicon can be adjusted between 0% and 13%.

[0015] More preferably, the molar content of silicon in the flame-retardant polymer is 3%-10%.

[0016] The present invention also provides a method for preparing the flame-retardant polymer, comprising the following steps:

[0017] S1. Premixing stage: Add coupling agent and solvent to reaction vessel, purge with nitrogen and start stirring, add precursor and catalyst in sequence, start heating, raise temperature to 65℃-75℃, keep warm for 10-20min, the coupling agent is silane coupling agent and / or phosphorus coupling agent.

[0018] S2, Prepolymerization stage: Under nitrogen protection, heat to 80℃-100℃ and stir for 2-4 hours;

[0019] S3, High Polymerization Stage: Under nitrogen protection, the temperature is raised to 140℃-160℃ and maintained for 0.4-0.6h, then slowly raised to 200℃-220℃ and maintained for 1.5-2.5h, and vacuum is turned on to separate low-boiling impurities at a pressure of -0.1MPa.

[0020] S4. Post-treatment: Cool the reaction solution to 100℃-130℃, add the end-capping agent, then raise the temperature to 190℃-210℃ and perform a vacuum reaction for 0.4-0.6 hours to end-cap. After the reaction is complete, stop heating and stirring, and allow it to naturally return to room temperature to obtain the flame-retardant polymer.

[0021] Preferably, in step S1, the silane coupling agent is selected from diphenyldichlorosilane and dimethyldichlorosilane; the phosphorus coupling agent is selected from phenylphosphoryl dichloride and phenoxyphosphoryl dichloride; the solvent is selected from toluene, xylene, dimethyltetrahydrofuran, mineral oil, N-methylpyrrolidone, and N,N-dimethylformamide; and the molar ratio of coupling agent to solvent is 0.2-0.3:1.

[0022] When the coupling agent is a silane coupling agent and a phosphorus coupling agent, the molar ratio of the silane coupling agent to the phosphorus coupling agent is 1:1.

[0023] Preferably, in step S1, the precursor is selected from 2-(bisphenylphosphoxy)-1,4-benzenediol and 2-(bismethylphosphoxy)-1,4-benzenediol, the catalyst is selected from aluminum trichloride, dibutyltin dilaurate and ferric chloride, the molar ratio of coupling agent to phosphorus-based precursor is 0.8-1.2:1, and the molar ratio of coupling agent to catalyst is 40-60:1.

[0024] Preferably, in step S4, the capping agent is selected from sodium tert-butoxide and sodium methoxide, and the molar ratio of coupling agent to capping agent is 40-60:3.

[0025] This invention also protects the use of the flame-retardant polymer as a flame-retardant additive in the preparation of flame retardants.

[0026] Preferably, the flame retardant additive is applied to flame retardant PC resin or PC / ABS engineering plastic.

[0027] The present invention also protects a flame retardant comprising, by weight, the following components: 80-95 parts of PC resin or PC / ABS engineering plastic, 10-15 parts of the flame retardant polymer, and 0.5-1 parts of additives.

[0028] Preferably, when the flame retardant is based on PC resin, it comprises, by weight parts: 80-90 parts PC resin, 10-15 parts flame retardant polymer, and 0.5-1 parts additives. More preferably, when the flame retardant is based on PC resin, it comprises, by weight parts: 87 parts PC resin, 12 parts flame retardant polymer, and 1 part additives.

[0029] Preferably, when the flame retardant is based on PC / ABS engineering plastic, it comprises, by weight parts: 90-95 parts PC / ABS engineering plastic, 10-15 parts flame retardant polymer, and 0.5-1 part additives, with a PC resin to ABS resin mass ratio of 60-70:20-30. More preferably, when the flame retardant is based on PC / ABS engineering plastic, it comprises, by weight parts: 92 parts PC / ABS engineering plastic, 15 parts flame retardant polymer, and 1 part additives, with a PC resin to ABS resin mass ratio of 33:13.

[0030] Preferably, the additive is the compatibilizer SMA.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] 1. The flame-retardant polymer proposed in this invention is added to PC and ABS engineering plastics in the form of flame-retardant additives. It can maintain extremely low exudation and migration rates even under long-term high temperature and high humidity environments, which is significantly better than traditional phosphate ester flame retardants. At the same time, since the molecular structure of the product can be adjusted according to application requirements, it can achieve a dynamic balance of flame retardant performance, impact resistance, light transmission, and anti-exudation performance in different application scenarios, and has a wide range of application prospects.

[0033] 2. When the flame-retardant polymer proposed in this invention is used as a flame-retardant additive in flame-retardant PC / ABS resin, it can more effectively reduce the negative impact of the addition of flame retardants on its physical properties and significantly improve the brittleness problem of PC / ABS plastic caused by the use of traditional phosphate ester flame-retardant schemes.

[0034] 3. This invention, through molecular modification and design, enables the obtained flame-retardant polymer molecules to have better compatibility with PC resin and PC / ABS engineering plastics. Furthermore, because the molecules have multiple tunable modification reaction sites, the product can be more precisely adjusted during the reaction process by changing the material ratio and substrate type. This results in a significant improvement in the exudation resistance of the silicon-containing flame-retardant polymer compared to commonly used organosilicon flame retardants. At the same time, the impact resistance of flame-retardant PC resin and PC / ABS engineering plastics can be specifically optimized and adjusted according to different product requirements. Attached image description:

[0035] Figure 1 It is the silicon phosphate flame retardant prepared in Example 1. 1 H-NMR spectrum;

[0036] Figure 2 It is the silicon phosphate flame retardant prepared in Example 1. 31 P-NMR spectrum. Detailed implementation method:

[0037] The following embodiments are further illustrations of the present invention, but not limitations thereof.

[0038] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention. Unless otherwise specified, the experimental materials and reagents used herein are all commercially available products conventional in this technical field. Phosphate flame retardant BDP, phosphate flame retardant RDP, and compatibilizer SMA were purchased from Zhejiang Wansheng Co., Ltd., and organosilicon flame retardants FCA117 and FCA107 were purchased from Dow Chemical.

[0039] In Examples 1-4 below, "parts" refers to the amount of substance.

[0040] Example 1

[0041]

[0042] Take 50 parts of dimethyldichlorosilane and 200 parts of xylene, and add them to a reaction flask equipped with a stirrer, thermometer, reflux device, and tail gas absorption device. After purging with nitrogen three times, maintain nitrogen purging at a rate of 0.1 L / min. Turn on the stirrer and control the speed at 300 rpm. Add 50 parts of 2-(dimethylphosphoxy)-1,4-benzenediol and 1 part of dibutyltin dilaurate. Turn on the heater and stir for 15 min at 70°C.

[0043] The temperature was raised to 95℃, and the reaction was continued at this temperature for 2 hours. A significant increase in the viscosity of the system was observed, with continuous bubble release. The temperature was then raised to 150℃, and the stirring speed was adjusted to 200 rpm to continue the reaction for 0.5 hours. Subsequently, a vacuum was applied, and the temperature was slowly raised to 220℃ for 2 hours, maintaining stirring while using a vacuum to separate low-boiling impurities at a pressure of -0.1 MPa. The temperature was lowered to 130℃, and 3 parts of sodium methoxide were added. After the addition was complete, the temperature was gradually raised to 200℃, and the reaction was carried out under vacuum for 0.5 hours. The mixture was then allowed to cool naturally to room temperature to obtain the target polymer (with repeating units n=20). XRF testing showed a silicon content of 10%.

[0044] Figure 1 For this silicon phosphate flame retardant 1 The H-NMR spectrum shows multiple peak groups: a series of relatively small peaks in the low-field region (7-8.0 ppm), the intensity and distribution of which indicate the presence of multiple aromatic protons, typical of a benzene ring environment. Due to the coupling effect between aromatic protons in the flame-retardant polymer structure, the peak shape in this region exhibits multiple splitting; comparison and integration reveal the number of benzene ring protons in the structure. In the high-field region, two significant peaks are observed: a peak with extremely high signal intensity at 3.41 ppm, and a peak at 2.50 ppm; the former indicates the presence of methyl groups in the same chemical environment, consistent with the four allomethyl groups attached to the phosphorus atom in the formula; the latter, at approximately 2.50 ppm, is commonly found in solvent peaks such as DMSO-d6.

[0045] Figure 2 For this silicon phosphate flame retardant 31 The P-NMR spectrum shows a single signal peak, indicating the presence of only one type of phosphorus atom in the structure, consistent with the highly symmetrical phosphorus atoms in the structural formula. Based on the NMR data, the obtained compound is identified as a silicon phosphate compound.

[0046] Example 2

[0047]

[0048] Take 25 parts of dimethyldichlorosilane, 25 parts of phenylphosphonodichloro, and 200 parts of xylene, and add them to a reaction flask equipped with a stirrer, thermometer, reflux device, and tail gas absorption device. After purging with nitrogen three times, maintain nitrogen purging at a rate of 0.1 L / min. Turn on the stirrer and control the speed at 300 rpm. Add 50 parts of 2-(dimethylphosphonoxy)-1,4-benzenediol and 1 part of dibutyltin dilaurate. Turn on the heater and stir for 15 min at 70°C.

[0049] The temperature was raised to 95℃, and the reaction was continued at this temperature for 2 hours. A significant increase in the viscosity of the system was observed, with continuous bubble release. The temperature was then raised to 150℃, and the stirring speed was adjusted to 200 rpm to continue the reaction for 0.5 hours. Subsequently, a vacuum was applied, and the temperature was slowly raised to 210℃ for 2 hours, maintaining stirring while a vacuum was applied to separate low-boiling impurities at -0.1 MPa pressure. The temperature was lowered to 130℃, and 3 parts of sodium methoxide were added. After the addition was complete, the temperature was gradually raised to 200℃, and the reaction was carried out under vacuum for 0.5 hours. The mixture was then allowed to cool naturally to room temperature to obtain the target polymer (with repeating units n1 = 9 and n2 = 9). XRF analysis showed a silicon content of 6%.

[0050] Example 3

[0051]

[0052] Take 25 parts of dimethyldichlorosilane, 25 parts of phenoxyphosphonodichloro, and 200 parts of toluene, and add them to a reaction flask equipped with a stirrer, thermometer, reflux device, and tail gas absorption device. After purging with nitrogen three times, maintain nitrogen purging at a rate of 0.1 L / min. Turn on the stirrer and control the speed at 300 rpm. Add 50 parts of 2-(dimethylphosphono)-1,4-benzenediol and 1 part of aluminum trichloride. Turn on the heater and stir for 15 min at 70°C.

[0053] The temperature was raised to 95℃, and the reaction was continued at this temperature for 2 hours. A significant increase in the viscosity of the system was observed, with continuous bubble release. The temperature was then raised to 150℃, and the stirring speed was adjusted to 200 rpm to continue the reaction for 0.5 hours. Subsequently, a vacuum was applied, and the temperature was slowly raised to 210℃ for 2 hours, maintaining stirring while using a vacuum to separate low-boiling impurities at -0.1 MPa pressure. The temperature was lowered to 130℃, and 3 parts of sodium methoxide were added. After the addition was complete, the temperature was gradually raised to 200℃, and the reaction was carried out under vacuum for 0.5 hours. The mixture was then allowed to cool naturally to room temperature to obtain the target polymer (with repeating units n1 = 9 and n2 = 9). XRF testing showed a silicon content of 5%.

[0054] Example 4

[0055]

[0056] Take 25 parts of diphenyldichlorosilane, 25 parts of phenylphosphonodichloro, and 200 parts of toluene, and add them to a reaction flask equipped with a stirrer, thermometer, reflux device, and tail gas absorption device. After purging with nitrogen three times, maintain nitrogen purging at a rate of 0.1 L / min. Turn on the stirrer and control the speed at 300 rpm. Add 50 parts of 2-(bisphenylphosphoxy)-1,4-benzenediol and 1 part of aluminum trichloride. Turn on the heater and stir for 15 min at 70°C.

[0057] The temperature was raised to 95℃, and the reaction was continued at this temperature for 2 hours. A significant increase in the viscosity of the system was observed, with continuous bubble release. The temperature was then raised to 150℃, and the stirring speed was adjusted to 200 rpm to continue the reaction for 0.5 hours. Subsequently, a vacuum was applied, and the temperature was slowly raised to 210℃ for 2 hours, maintaining stirring while using a vacuum to separate low-boiling impurities at -0.1 MPa pressure. The temperature was lowered to 130℃, and 3 parts of sodium tert-butoxide were added. After the addition was complete, the temperature was gradually raised to 200℃, and the reaction was carried out under vacuum for 0.5 hours. The mixture was then allowed to cool naturally to room temperature to obtain the target polymer (with repeating units n1 = 9 and n2 = 9). XRF testing showed a silicon content of 3%.

[0058] Application Example 1

[0059] 1. Formulas for each group:

[0060] Flame retardants, by parts by mass, comprise the following components:

[0061] 87 parts of PC resin;

[0062] 12 parts of a silicon phosphate flame retardant additive (any polymer material prepared in Examples 1-4);

[0063] 1 part of compatibilizer SMA.

[0064] Control group (conventional flame-retardant PC)

[0065] Based on parts by mass, it includes the following components:

[0066] 89 parts of PC resin;

[0067] Five parts of phosphate flame retardant BDP or RDP;

[0068] 5 parts of organosilicon flame retardant FCA117 or FCA107;

[0069] 1 part of compatibilizer SMA.

[0070] The pure PC group (non-flame retardant control) includes the following components by mass parts:

[0071] 100 parts of PC resin.

[0072] 2. Preparation process of each group

[0073] The preparation process of flame retardants includes the following steps:

[0074] (1) Pre-drying: Vacuum dry the PC resin at 110℃ for 4 hours.

[0075] (2) Premixing: According to the above formula ratio, add the dried PC resin, flame retardant additives and other auxiliaries into a high-speed mixer and mix at room temperature and 500 rpm for 20 minutes until uniform.

[0076] (3) Melt blending and granulation: The mixed material is added to a twin-screw extruder and melt extruded at the set temperatures of each zone of the barrel: 230℃, 250℃, 260℃, 265℃, 260℃, die head temperature 255℃, and rotation speed 250 rpm. After the extrudate is cooled in a water tank, it is granulated by a pelletizer to obtain flame-retardant PC composite material granules.

[0077] (4) Injection molding: The above granules were dried at 110°C for 4 hours. Standard test specimens were injection molded using an injection molding machine at a barrel temperature of 270°C, a mold temperature of 80°C, an injection pressure of 70MPa, and a holding pressure of 50MPa, according to the corresponding test standards. The control group and pure PC group samples were prepared using the same process.

[0078] 3. Performance Testing and Results:

[0079] 1) Notched impact strength: The notched impact strength of the specimen was determined at 23°C using a cantilever beam impact testing machine in accordance with ASTM D256 standard.

[0080] 2) Flame retardant performance: According to UL94 standard, a vertical burning test is conducted using a 1mm thick sample strip to evaluate the flame retardant rating.

[0081] The performance test results of the flame retardant and the control group are shown in Table 1 below:

[0082] Table 1

[0083] Test Project Example 1 Example 2 Example 3 Example 4 control group Pure PC group <![CDATA[Izod impact strength (kJ / m 2 , 23 °C)]]> 72 64 68 67 53 80 UL94 rating V-0 V-0 V-0 V-0 V-0 V2

[0084] Table 1 shows that the flame-retardant PC composite material prepared using the silica-phosphate ester of this invention achieves V-0 flame retardant performance while exhibiting significantly higher notched impact strength (53 kJ / m²) than the control group flame-retardant PC material using conventional flame retardants. 2 Impact resistance is improved. Although compared with non-flame-retardant pure PC (80kJ / m²), it has improved impact resistance. 2 While there is still a gap compared to other methods, the flame retardant additive proposed in this invention greatly alleviates the negative impact of flame retardants on PC toughness, achieving a good balance between flame retardancy and high toughness.

[0085] Application Example 2

[0086] 1. Formulas for each group:

[0087] Flame-retardant PC / ABS, by parts by weight, comprises the following components:

[0088] 66 parts PC resin, 26 parts ABS resin;

[0089] 15 parts of silicone phosphate flame retardant additive (any silicone phosphate prepared in Examples 1-4);

[0090] 1 part SMA compatibilizer.

[0091] The control group (conventional flame-retardant PC / ABS) comprises the following components by weight:

[0092] 66 parts PC resin, 26 parts ABS resin;

[0093] 10 parts of phosphate flame retardant BDP;

[0094] 5 parts of organosilicon flame retardant FCA117;

[0095] 1 part SMA compatibilizer.

[0096] The pure PC / ABS group (non-flame retardant control) comprises the following components by weight:

[0097] 80 parts PC resin, 20 parts ABS resin;

[0098] 1 part SMA compatibilizer.

[0099] 2. Preparation process of each group

[0100] The preparation process of flame retardants includes the following steps:

[0101] (1) Premixing: Add the resin, flame retardant additives and other auxiliaries to a high-speed mixer according to the above formula ratio, and mix at room temperature and 500 rpm for 15 minutes until evenly dispersed.

[0102] (2) Melt blending and granulation: The mixed material is added to a twin-screw extruder and melt extruded at temperatures of 195℃, 200℃, 215℃, 220℃, and 230℃ in each zone of the barrel, and 220℃ at the die head, at 200 rpm. After the extrudate is cooled in a water tank, it is granulated by a pelletizer to obtain flame-retardant ABS composite material granules.

[0103] (3) Injection molding: The above granules are dried at 90°C for 3 hours; the standard test strips are injection molded using an injection molding machine at a barrel temperature of 210°C, a mold temperature of 50°C, an injection pressure of 60MPa, and a holding pressure of 40MPa.

[0104] The control group and the pure PC / ABS group samples were prepared using the same process.

[0105] 3. Performance Testing and Results:

[0106] 1) Notched impact strength: The notched impact strength (unit: J / m) of the specimen was determined using a cantilever beam impact testing machine at 23°C in accordance with ASTM D256 standard.

[0107] 2) Flame retardant performance: According to UL94 standard, a vertical burning test is conducted using a 1mm thick sample strip to evaluate the flame retardant rating.

[0108] The performance test results of the flame retardant and the control group are shown in Table 2 below:

[0109] Table 2

[0110]

[0111]

[0112] Table 2 shows that the flame-retardant PC / ABS composite material prepared using the silica-containing phosphate ester obtained in this invention as a flame-retardant additive exhibits a significantly higher notched impact strength (210 J / m) than the control group material using phosphate esters, while achieving V-0 flame retardancy. This demonstrates that the flame-retardant additive proposed in this invention can more effectively reduce the negative impact of flame retardant addition on the toughness of flame-retardant PC / ABS resin, significantly improving the brittleness problem of flame-retardant PC / ABS plastics.

[0113] 3) Compatibility and anti-exudation test: The samples were subjected to high-temperature aging (85℃×400h), humidity cycling (85%RH×30 days), and long-term static light transmittance retention (85℃×30 days) tests to detect changes in the physical properties of the samples. The results are shown in Table 3.

[0114] Table 3

[0115]

[0116] As shown in Table 3, PC and ABS engineering plastics using the silicon phosphate flame retardant additive proposed in this invention can maintain extremely low exudation and migration rates under long-term high temperature and high humidity environments, which is significantly better than traditional phosphate ester flame retardants. At the same time, since the molecular structure of the product can be adjusted according to application requirements, it can achieve a balance between flame retardant performance, impact resistance, light transmission, and anti-exudation performance in different application scenarios, and has a wide range of application prospects.

[0117] The above description of the embodiments is only for the purpose of helping to understand the technical solution and core idea of ​​the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A flame-retardant polymer with adjustable silicon content, characterized in that, The flame-retardant polymer has the structure shown in Formula I: in: R1 is selected from phenyl or phenoxy; R2 is selected from methyl or phenyl; R3 is selected from methyl or phenyl; R4 is selected from tert-butyl or methyl; R5 is selected from methyl or phenyl; The values ​​of n1 and n2 are both in the range of 0-20, and the value of n1+n2 is in the range of 0-40.

2. The flame-retardant polymer according to claim 1, characterized in that, The molar content of silicon in the flame-retardant polymer is 0%-13%.

3. The flame-retardant polymer according to claim 2, characterized in that, The molar content of silicon in the flame-retardant polymer is 3%-10%.

4. The method for preparing the flame-retardant polymer according to claim 1, characterized in that, Includes the following steps: S1. Premixing stage: Add coupling agent and solvent to reaction vessel, purge with nitrogen and start stirring, add precursor and catalyst in sequence, start heating, raise temperature to 65℃-75℃, keep warm for 10-20min, the coupling agent is silane coupling agent and / or phosphorus coupling agent. S2, Prepolymerization stage: Under nitrogen protection, heat to 80℃-100℃ and stir for 2-4 hours; S3, High Polymerization Stage: Under nitrogen protection, the temperature is raised to 140℃-160℃ and maintained for 0.4-0.6h, then slowly raised to 200℃-220℃ and maintained for 1.5-2.5h, and vacuum is turned on to separate low-boiling impurities at a pressure of -0.1MPa. S4. Post-treatment: Cool the reaction solution to 100℃-130℃, add the end-capping agent, then raise the temperature to 190℃-210℃ and perform a vacuum reaction for 0.4-0.6 hours to end-cap. After the reaction is complete, stop heating and stirring, and allow it to naturally return to room temperature to obtain the flame-retardant polymer.

5. The preparation method according to claim 4, characterized in that, In step S1, the silane coupling agent is selected from diphenyldichlorosilane and dimethyldichlorosilane; the phosphorus coupling agent is selected from phenylphosphoryl dichloride and phenoxyphosphoryl dichloride; the solvent is selected from toluene, xylene, dimethyltetrahydrofuran, mineral oil, N-methylpyrrolidone, and N,N-dimethylformamide; and the molar ratio of coupling agent to solvent is 0.2-0.3:

1.

6. The preparation method according to claim 4 or 5, characterized in that, In step S1, the precursor is selected from 2-(bisphenylphosphoxy)-1,4-benzenediol and 2-(bismethylphosphoxy)-1,4-benzenediol, and the catalyst is selected from aluminum trichloride, dibutyltin dilaurate, and ferric chloride. The molar ratio of coupling agent to precursor is 0.8-1.2:1, and the molar ratio of coupling agent to catalyst is 40-60:

1.

7. The preparation method according to claim 4, characterized in that, In step S4, the capping agent is selected from sodium methoxide or sodium tert-butoxide, and the molar ratio of coupling agent to capping agent is 40-60:

3.

8. The use of the flame-retardant polymer according to any one of claims 1-3 as a flame-retardant additive in the preparation of flame retardants.

9. The application according to claim 8, characterized in that, The flame retardant is applied to flame-retardant PC resin or PC / ABS engineering plastics.

10. A flame retardant, characterized in that, The product comprises, by weight parts, the following components: 80-95 parts of PC resin or PC / ABS engineering plastic, 10-15 parts of the flame-retardant polymer as described in any one of claims 1-3, and 0.5-1 parts of additives.

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