阅读说明：本技术 一种低卤高聚合度磷酸酯阻燃剂及其制备方法 (Low-halogen high-polymerization-degree phosphate flame retardant and preparation method thereof ) 是由 李章武 陈志钊 周侃 陈伟杰 雷自华 于 2020-11-25 设计创作，主要内容包括：本发明属于磷系阻燃剂技术领域,具体涉及一种低卤高聚合度磷酸酯阻燃剂的制备方法,包括如下步骤：(1)以双羟基或双胺基类化合物、磷酰二氯类化合物为原料进行制备低聚磷酸酯溶液；(2)将低聚磷酸酯溶液进行浓缩至其呈粘稠状混合物,向粘稠状混合物中加入溶剂使其溶解成溶液状态,随后升温至溶剂的沸点温度,并在该温度下保温聚合反应1～6h,经过滤,获得聚磷酸酯团聚物；(3)将聚磷酸酯团聚物高温聚合后,再经冷却制得低卤高聚合度磷酸酯阻燃剂。相对于现有技术由合成的低聚磷酸酯直接聚合形成高聚磷酸酯的方式相比,本申请采用分段聚合的方式,有效降低了成品聚磷酸酯中缚酸剂盐的残留。(The invention belongs to the technical field of phosphorus flame retardants, and particularly relates to a preparation method of a low-halogen high-polymerization-degree phosphate flame retardant, which comprises the following steps: (1) preparing oligomeric phosphate solution by using dihydroxyl or diamine compounds and phosphorus oxychloride compounds as raw materials; (2) concentrating the oligomeric phosphate solution to form a viscous mixture, adding a solvent into the viscous mixture to dissolve the viscous mixture into a solution state, then heating to the boiling point temperature of the solvent, carrying out heat preservation polymerization reaction for 1-6 h at the temperature, and filtering to obtain a polyphosphate aggregate; (3) after the polyphosphate ester aggregate is polymerized at high temperature, the phosphate ester flame retardant with low halogen and high polymerization degree is prepared by cooling. Compared with the mode of directly polymerizing the synthesized oligomeric phosphate to form high polyphosphate in the prior art, the method adopts a segmented polymerization mode, and effectively reduces the residue of acid-binding agent salt in the finished polyphosphate.)

1. The preparation method of the low-halogen high-polymerization-degree phosphate flame retardant is characterized by comprising the following steps of:

(1) adding a dihydroxyl or diamine compound into a protective agent containing an acid-binding agent to form a mixed solution, adding a phosphoryl dichloride compound into the mixed solution at 0-40 ℃, reacting for 2-10 hours at 0-40 ℃, filtering and removing impurities to obtain an oligomeric phosphate solution;

(2) concentrating the oligomeric phosphate solution to a viscous mixture, adding a solvent into the viscous mixture to dissolve the mixture into a solution state, then heating to the boiling point temperature of the solvent, carrying out heat preservation polymerization reaction for 1-6 h at the temperature, and filtering to obtain a polyphosphate aggregate;

(3) and (3) carrying out heat preservation polymerization reaction on the polyphosphate ester aggregate at the temperature of 150-250 ℃ for 1-8 h, and cooling to obtain the low-halogen high-polymerization-degree phosphate ester flame retardant.

2. The method for preparing a low-halogen high-polymerization-degree phosphate ester flame retardant according to claim 1, wherein in the step (1), the molar ratio of the phosphoryl dichloride compound to the dihydroxy or diamine compound is 1: (1.0-1.5).

3. The method of claim 2, wherein the dihydroxy or diamine compound is any one of bisphenol a, ethylene glycol, ethylenediamine, resorcinol, hydroquinone, 1, 2-propanediol, 1, 3-butanediol, 1, 3-propanediol, piperazine, m-phenylenediamine, and p-phenylenediamine.

4. The method for preparing a low-halogen high-polymerization degree phosphate ester flame retardant according to claim 2, wherein the phosphoryl dichloride compound is any one of methyl phosphoryl dichloride, ethyl phosphoryl dichloride and phenyl phosphoryl dichloride.

5. The preparation method of the low-halogen high-polymerization-degree phosphate flame retardant according to any one of claims 1 to 4, wherein the protective agent is dichloromethane or trichloromethane; the solvent is any one of methanol, ethanol and water.

6. The preparation method of the low-halogen high-polymerization-degree phosphate flame retardant according to any one of claims 1 to 4, wherein the molar ratio of the phosphoryl dichloride compound to the acid-binding agent is 1: (2.0-3.0).

7. The method for preparing a low-halogen high-polymerization-degree phosphate flame retardant according to claim 6, wherein the acid-binding agent is triethylamine or pyridine.

8. A low-halogen high-polymerization-degree phosphoric ester flame retardant obtained by the production process according to claim 1,2, 3, 4 or 6.

9. The low-halogen high-polymerization-degree phosphate flame retardant of claim 8, wherein the phosphate in the flame retardant is a high-polyphosphate containing a dihydroxyl group or a diamine group.

Technical Field

The invention belongs to the technical field of phosphorus flame retardants, and particularly relates to a low-halogen high-polymerization-degree phosphate flame retardant and a preparation method thereof.

Background

With the improvement of living standard of people, each application field of engineering plastics puts more and more strict requirements on the flame retardant property of materials, in particular to the electronic information industry. In recent years, the application industry of flame-retardant engineering plastics is increasingly expanding, and among five engineering plastics, the flame-retardant engineering plastics are often required to be subjected to flame-retardant modification so as to meet the requirements of various users.

The traditional flame-retardant engineering plastics are almost all brominated products, such as decabromodiphenyl ether, decabromodiphenylethane, tetrabromobisphenol A and the like, but because the brominated flame retardant can generate carcinogenic substance dioxin during combustion, the environmental protection problem exists. Later, some low molecular weight phosphorus flame retardants were developed but have a large effect on the performance of engineering plastics due to their low decomposition temperature and high volatility. Along with the requirement of environmental protection and sustainable development, the flame retardant engineering plastics are not halogenated, and a plurality of brominated flame retardants are forbidden day by day, people synthesize a phosphate flame retardant with high polymerization degree on the basis of a low molecular weight phosphorus compound, the flame retardant has large molecular weight, high thermal decomposition temperature, low volatility and good compatibility with materials, and the phosphate flame retardant is greatly used in the application of engineering plastics such as PC/ABS alloy and PPE/HIPS alloy due to high efficiency, environmental protection and small influence on material performance.

At present, the synthesis processes of the flame retardant of the phosphate with high polymerization degree mainly comprise two processes: 1. the method is characterized by comprising the following steps of synthesizing in a solvent, absorbing hydrochloric acid by an acid-binding agent, removing acid-binding agent salt by suction filtration, removing the solvent by distillation, and finally forming the high-polymerization-degree phosphate flame retardant at high temperature, wherein although the hydrochloric acid generated in the reaction can be removed by the process, the solvent has certain solubility on the acid-binding agent salt, so that the chlorine content of the product is higher due to the residue of the acid-binding agent salt in the generated product, and the quality of the product is influenced; 2. the phosphate flame retardant is synthesized by a solid phase method, raw materials are subjected to high-temperature melting reaction, and then generated hydrochloric acid gas is absorbed by alkali to obtain the phosphate flame retardant with high polymerization degree.

Disclosure of Invention

Aiming at the problem of incomplete removal of acid-binding agent salt in the existing process for preparing the high-polymerization-degree phosphate flame retardant, the invention adopts a mode of sectional polymerization and gradual removal of the acid-binding agent salt, so that the content of the acid-binding agent salt in the high-polymerization-degree phosphate flame retardant is remarkably reduced.

Based on the purpose, the invention adopts the following technical scheme:

in a first aspect, the invention provides a preparation method of a low-halogen high-polymerization degree phosphate ester flame retardant, which comprises the following steps:

(1) adding a dihydroxyl or diamine compound into a protective agent containing an acid-binding agent to form a mixed solution, adding a phosphoryl dichloride compound into the mixed solution at 0-40 ℃, reacting for 2-10 hours at 0-40 ℃, filtering and removing impurities to obtain an oligomeric phosphate solution; filtering and impurity removal are used for removing white acid-binding agent salt particles in the reacted solution, a small amount of acid-binding agent salt in a dissolved state is still contained in the polyphosphate ester solution after filtering and impurity removal, and at the moment, the polyphosphate ester in the oligomeric phosphate ester solution is oligomeric polyphosphate ester;

(2) concentrating the oligomeric phosphate solution to a viscous mixture, adding a solvent into the viscous mixture to dissolve the mixture into a solution state, then heating to the boiling point temperature of the solvent, carrying out heat preservation polymerization reaction for 1-6 h at the temperature, and filtering to obtain a polyphosphate aggregate; after a solvent is added into the viscous mixture, acid-binding agent salt in the viscous mixture is also dissolved in the solvent, the acid-binding agent salt is still dissolved in the solvent when oligomeric phosphate in the solution is further polymerized and agglomerated to form polyphosphate aggregates to be separated out, and the polyphosphate aggregates are separated from the solvent through filtration, so that the residue of the acid-binding agent salt in the polyphosphate aggregates is further reduced;

(3) and (3) carrying out heat preservation polymerization reaction on the polyphosphate ester aggregate at the temperature of 150-250 ℃ for 1-8 h, and cooling to obtain the low-halogen high-polymerization-degree phosphate ester flame retardant.

Preferably, in the step (1), the molar ratio of the phosphoryl dichloride compound to the dihydroxy or diamine compound is 1: (1.0-1.5), experiments show that the phosphoryl dichlorine compound and the dihydroxyl or diamine compound react more fully under the molar ratio, so that the yield of the final product is relatively high.

Preferably, the dihydroxy or diamine compound is any one of bisphenol a, ethylene glycol, ethylenediamine, resorcinol, hydroquinone, 1, 2-propanediol, 1, 3-butanediol, 1, 3-propanediol, piperazine, m-phenylenediamine, and p-phenylenediamine.

Preferably, the phosphoryl dichloride compound is any one of methyl phosphoryl dichloride, ethyl phosphoryl dichloride and phenyl phosphoryl dichloride.

Preferably, the protective agent is dichloromethane or trichloromethane; the solvent is any one of methanol, ethanol and water, and is used for dissolving and removing acid-binding agent salt remained in the viscous mixture, so as to further reduce the halogen content in the final product.

Preferably, the molar ratio of the phosphoryl dichloride compound to the acid-binding agent is 1: (2.0-3.0), the relative excess of the acid-binding agent is favorable for accelerating the acylation reaction process under the molar ratio, and the redundant acid-binding agent can be dissolved and removed by a solvent, so that adverse effects on reactants and reaction liquid are avoided.

Preferably, the acid scavenger is triethylamine or pyridine.

In a second aspect, the invention also provides a low-halogen high-polymerization degree phosphate flame retardant which is prepared by the preparation method.

Preferably, the phosphate ester in the flame retardant is a high polyphosphate ester containing a dihydroxy group or a diamine group.

Compared with the prior art, the invention has the following remarkable technical effects:

compared with the prior art that after oligophosphate is synthesized in a solvent, acid-binding agent salt is removed by filtration, after the solvent is removed by reduced pressure distillation, high-polymerization-degree phosphate is formed at high temperature, the invention adopts the steps that viscous mixture after reduced pressure distillation is dissolved by a dissolving agent to form solution, then heat-preservation polymerization reaction is carried out to generate polyphosphate with medium polymerization degree, the acid-binding agent salt remaining in the solution is discharged along with the solution, and then the polyphosphate with medium polymerization degree is polymerized at high temperature to form high polyphosphate. In the synthesis process, the oligomeric phosphate is firstly synthesized, then the oligomeric phosphate is further polymerized to form polyphosphate with medium polymerization degree, and then the polyphosphate with medium polymerization degree is further polymerized to form polyphosphate with high polymerization degree.

Drawings

FIG. 1 is a TG/DTG graph of sample 1 in example 1;

FIG. 2 is a TG/DTG graph of comparative example 1;

FIG. 3 is a TG/DTG graph of control 2 in example 1.

Detailed Description

To better illustrate the objects, aspects and advantages of the present invention, the present invention will be further described with reference to the accompanying drawings and specific embodiments. The raw materials used in the following examples are all commercially available general-purpose products unless otherwise specified.

Example 1

A preparation method of low-halogen high-polymerization-degree phosphate ester flame retardant comprises the following steps:

1) 22.83kg of bisphenol A was added to a reaction vessel containing 50L of methylene chloride, 22.26kg of triethylamine was added to the reaction vessel, and the temperature in the reaction vessel was controlled to 0 to 10 ℃ with ice brine.

2) Controlling the temperature of the reaction kettle to be 10 ℃, slowly dropwise adding 19.50kg of phenylphosphoryl dichloride into the reaction kettle, after the dropwise adding is finished, keeping the temperature at 10 ℃ for reaction for 2 hours, after the reaction is finished, carrying out suction filtration on reaction liquid in the reaction kettle, and filtering to remove white triethylamine salt to obtain the oligomeric phosphate solution.

3) And (2) carrying out reduced pressure distillation on the oligomeric phosphate solution subjected to preliminary filtration to remove triethylamine salt, evaporating the solvent to obtain a viscous mixture, wherein the viscous mixture is a mixture of oligomeric phosphate and a small amount of residual white triethylamine hydrochloride, adding 20L of ethanol into the viscous mixture to dissolve the mixture, heating to the boiling point of the ethanol, carrying out thermal polymerization reaction for 1h, further polymerizing the oligomeric phosphate in the reaction process to form an agglomerate which is separated out from the solvent, reducing the temperature in the reaction kettle to room temperature, then discharging and recovering the solvent, and obtaining the agglomerated phosphate compound with the medium polymerization degree in the reaction kettle.

4) Heating the reaction kettle filled with the phosphate ester compound with the medium polymerization degree to 250 ℃, preserving heat at the temperature for reaction for 1 hour to obtain white transparent phosphate ester with the high polymerization degree, pouring the white transparent phosphate ester from the reaction kettle, cooling the white transparent phosphate ester to obtain hard blocks, and crushing the hard blocks to obtain white powder to obtain the low-halogen phosphate ester flame retardant with the high polymerization degree.

Example 2

This example provides a method for preparing a low-halogen high-polymerization phosphate flame retardant, which is different from example 1 in the preparation raw materials, the molar ratio between the raw materials, and the specific reaction parameters.

In the embodiment, ethylenediamine and methyl phosphoryl dichloride are used as raw materials to prepare the low-halogen high-polymerization-degree phosphate flame retardant, and the preparation method comprises the following specific steps:

1) adding 6.01kg of ethylenediamine into a reaction kettle filled with 12L of dichloromethane, then adding 20.24kg of triethylamine into the reaction kettle, and controlling the temperature in the reaction kettle to be 0-10 ℃ by using brine ice.

2) Controlling the temperature of the reaction kettle to be 0 ℃, slowly dripping 13.29kg of methyl phosphoryl dichlorinated compound into the reaction kettle, preserving the temperature for 5 hours at 0 ℃ after finishing dripping, carrying out suction filtration on reaction liquid in the reaction kettle after finishing reaction, and filtering to remove white triethylamine hydrochloride to obtain an oligomeric phosphate solution.

3) Placing the oligomeric phosphate solution subjected to preliminary filtration to remove triethylamine salt into a reaction kettle, carrying out reduced pressure distillation, evaporating a solvent to obtain a viscous mixture, wherein the viscous mixture is a mixture of oligomeric phosphate and a small amount of residual white triethylamine hydrochloride, adding 6L of methanol into the viscous mixture to dissolve the mixture, heating to a methanol boiling point, carrying out thermal polymerization reaction for 4 hours, further polymerizing the oligomeric phosphate in the reaction process to form an aggregate, separating out the aggregate from the solvent, reducing the temperature in the reaction kettle to room temperature, discharging and recovering the solvent, and obtaining an aggregated phosphate compound with medium polymerization degree in the reaction kettle.

4) Heating the reaction kettle filled with the phosphate ester compound with the medium polymerization degree to 200 ℃, preserving heat at the temperature for reaction for 6 hours to obtain a white transparent phosphate ester flame retardant with the high polymerization degree, pouring the white transparent phosphate ester flame retardant from the reaction kettle, cooling the white transparent phosphate ester flame retardant to obtain a hard block, and crushing the hard block to obtain white powder to obtain the low-halogen phosphate ester flame retardant with the high polymerization degree.

Example 3

This example provides a method for preparing a low-halogen high-polymerization phosphate flame retardant, which is different from example 1 in the preparation raw materials, the molar ratio between the raw materials, and the specific reaction parameters.

In the embodiment, ethylene glycol and ethyl phosphoryl dichloride are used as raw materials to prepare the low-halogen high-polymerization-degree phosphate flame retardant, and the preparation method comprises the following steps:

1) 6.83kg of ethylene glycol was added to a reaction vessel containing 15L of chloroform, 18.19kg of pyridine was then added to the reaction vessel, and the temperature in the reaction vessel was controlled to 0 to 40 ℃ with ice brine.

2) Controlling the temperature of the reaction kettle to be 40 ℃, slowly dripping 16.29kg of ethyl phosphoryl dichloride into the reaction kettle, preserving the temperature for 10 hours at 40 ℃ after finishing dripping, carrying out suction filtration on reaction liquid in the reaction kettle after the reaction is finished, and filtering to remove pyridine hydrochloride to obtain oligomeric phosphate solution.

3) And (2) placing the oligophosphate solution subjected to preliminary filtration to remove pyridinium hydrochloride into a reaction kettle, carrying out reduced pressure distillation, evaporating the solvent to obtain a viscous mixture, wherein the viscous mixture is a mixture of oligophosphate and a small amount of residual white pyridinium hydrochloride, adding 10L of ethanol into the viscous mixture to dissolve the mixture, heating to the boiling point of ethanol, carrying out thermal polymerization reaction for 6h, further polymerizing the oligophosphate in the reaction process to form an agglomerate, separating out the oligophosphate from the solvent, reducing the temperature in the reaction kettle to room temperature, discharging the solvent for recycling, and obtaining the agglomerated phosphate compound with medium polymerization degree in the reaction kettle.

4) Heating the reaction kettle filled with the phosphate ester compound with the medium polymerization degree to 150 ℃, preserving heat at the temperature for reaction for 8 hours to obtain a white transparent phosphate ester flame retardant with the high polymerization degree, pouring the white transparent phosphate ester flame retardant from the reaction kettle, cooling the white transparent phosphate ester flame retardant to obtain a hard block, and crushing the hard block to obtain white powder to obtain the low-halogen phosphate ester flame retardant with the high polymerization degree.

Example 4

This example differs from example 1 only in that the molar ratio of bisphenol a to phenylphosphoryl dichloride in the starting material is 1.5:1, the molar ratio of phenylphosphoryl dichloride to triethylamine is 1: 3; namely, in this example, 34.25Kg of bisphenol A, 19.5Kg of phenylphosphoryl dichloride and 30.35Kg of triethylamine were used, and the process for preparing a low-halogen high-polymerization degree phosphate flame retardant in this example was the same as in example 1.

Example 5

This example differs from example 1 only in that bisphenol a in the starting material was replaced by equimolar amounts of piperazine, the amount of piperazine added was 8.61kg, and the other process parameters were unchanged.

Example 6

The difference between the embodiment and the embodiment 3 is only that the ethylene glycol in the raw material is replaced by the equal mole of hydroquinone, the addition amount of the hydroquinone is 12.11kg, then the temperature of the reaction kettle of the phosphate compound with polymerization degree in the step 4) is increased from 150 ℃ to 200 ℃ in the embodiment 3, and the heat preservation reaction is carried out at 200 ℃, and other process parameters are not changed.

Example 7

This example differs from example 1 only in that the solvent used to dissolve the viscous mixture is water.

EXAMPLE 8 Effect test

In this example, halogen content detection was performed on samples prepared by the method of the present invention and the method of the prior art, respectively, to investigate the influence of the segmented polymerization on the halogen residual amount in the finished polyphosphate flame retardant.

First, sample preparation

The polyphosphate flame retardant sample prepared by the method of the invention is marked as sample 1, and the polyphosphate flame retardant samples prepared by the prior art method are respectively marked as reference 1 and reference 2.

Sample 1 was prepared as follows:

1) 22.83kg of bisphenol A was added to a reaction vessel containing 50L of methylene chloride, 22.26kg of triethylamine was added to the reaction vessel, and the temperature in the reaction vessel was controlled to 0 to 10 ℃ with ice brine.

2) Controlling the temperature of the reaction kettle to be 10 ℃, slowly dropwise adding 19.50kg of phenylphosphoryl dichloride into the reaction kettle, after the dropwise adding is finished, keeping the temperature at 10 ℃ for reacting for 4 hours, after the reaction is finished, carrying out suction filtration on reaction liquid in the reaction kettle, and filtering to remove white triethylamine salt to obtain the oligomeric phosphate solution.

3) And (2) carrying out reduced pressure distillation on the oligomeric phosphate solution subjected to preliminary filtration to remove triethylamine salt, evaporating the solvent to obtain a viscous mixture, wherein the viscous mixture is a mixture of oligomeric phosphate and a small amount of residual white triethylamine hydrochloride, adding 20L of ethanol into the viscous mixture to dissolve the mixture, heating to the boiling point of the ethanol, carrying out thermal polymerization reaction for 2 hours, further polymerizing the oligomeric phosphate in the reaction process to form an agglomerate which is separated out from the solvent, reducing the temperature in the reaction kettle to room temperature, then discharging and recycling the solvent, and obtaining the agglomerated phosphate compound with the medium polymerization degree in the reaction kettle.

4) Heating the reaction kettle filled with the phosphate ester compound with medium polymerization degree to 240 ℃, preserving heat at the temperature for reaction for 3 hours to obtain white transparent phosphate ester with high polymerization degree, pouring the white transparent phosphate ester from the reaction kettle, cooling the white transparent phosphate ester to obtain a hard block, and crushing the hard block to obtain white powder to obtain the low-halogen phosphate ester flame retardant with high polymerization degree (sample 1).

The preparation of control 1 was as follows:

(1) 22.83kg of bisphenol A is added into a reaction kettle filled with 50L of dichloromethane, then 22.26kg of triethylamine is added into the reaction kettle, and the temperature in the reaction kettle is controlled to be 0-10 ℃ by using brine ice.

(2) Controlling the temperature of the reaction kettle to be 10 ℃, slowly dropwise adding 19.50kg of phenyl phosphoryl dichlorinated compound into the reaction kettle, preserving the temperature at 10 ℃ for 4 hours after dropwise adding, carrying out suction filtration on reaction liquid in the reaction kettle after the reaction is finished, and filtering to remove white triethylamine hydrochloride to obtain an oligomeric phosphate solution.

(3) Distilling the oligomeric phosphate solution under reduced pressure, evaporating the solvent to obtain a viscous mixture, heating the reaction kettle to 240 ℃, preserving heat at the temperature for 3 hours to obtain a white transparent phosphate flame retardant with high polymerization degree, pouring the white transparent phosphate flame retardant from the reaction kettle, reducing the temperature to obtain a hard block, and crushing the hard block to obtain white powder, namely the control sample 1.

Control 2 was prepared as follows:

22.83kg of bisphenol A and 19.50kg of phenyl phosphoryl dichloride are added into a reaction kettle with a hydrochloric acid absorption device, stirring and heating are started, a large amount of hydrochloric acid is discharged and absorbed in the process, when the temperature is raised to 240 ℃, the reaction is carried out for 3 hours under the condition of heat preservation, a white transparent phosphate flame retardant with high polymerization degree is obtained, the white transparent phosphate flame retardant is poured out and cooled to become a hard block, and white powder, namely the control 2, is obtained after crushing.

Secondly, sample detection and result analysis

The chlorine content in the sample 1, the control sample 1 and the control sample 2 was measured by using an ICS-1600 ion chromatograph, and the measurement results are shown in Table 1 and FIGS. 1 to 3.

TABLE 1 chlorine content of sample 1, control 2

Sample (I)	Sample 1	Control 1	Control 2
				Chlorine content (ppm)	156	28650	205

As can be seen from Table 1, the chlorine content in sample 1 was lower than that in control 2 and significantly lower than that in control 1, indicating that the residual amount of halogen was the lowest in the high polymerization degree phosphate flame retardant produced by the method of the present invention. Although the chlorine content in the control 2 is slightly higher than that in the sample 1, a large amount of hydrochloric acid needs to be absorbed in the preparation process of the control 2, and the absorbed hydrochloric acid needs to be treated, so that the preparation process of the control 2 is complicated and is difficult to be industrially produced.

As can be seen from FIGS. 1 to 3, the decomposition temperature of sample 1 is higher than that of control 1 and control 2; also, in the TG/DTG graph of control 1, there was a small distinct peak at 400 ℃ indicating that other impurities were also present in control 1, which is consistent with the test results in Table 1.

In conclusion, the analysis shows that compared with the two existing methods for preparing the high polyphosphate flame retardant, the method for preparing the high polyphosphate flame retardant has the advantages that the process is relatively simple, and the halogen residual amount in the prepared high polyphosphate flame retardant is relatively low.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the protection scope of the present invention, and although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.