A phosphorus-containing flame retardant and preparation method thereof

Abstract

The present invention discloses a phosphorus-containing flame retardant and a preparation method thereof, the preparation method comprising the following steps: adding a dihydroxyl-terminated unsaturated polyester and a monohydroxyl-terminated unsaturated olefin monomer to a solvent for dissolution to form a mixture solution; adding an organic base catalyst to the mixture solution, then adding a phenylphosphonyl dichloride solution dropwise to obtain a reactant solution after reaction; adding a DOPO monomer to the reactant solution to undergo a grafting reaction, then filtering and rotary evaporating to obtain the phosphorus-containing flame retardant. Compared with traditional flame retardants, the present invention utilizes industrial raw materials to prepare a non-polar phosphorus-containing flame retardant containing different valence states, which has an excellent synergistic flame retardant effect, and the flame retardant has good compatibility with currently common non-polar rubbers. At the same time, the flame retardant can participate in rubber vulcanization, reducing the migration and precipitation of the flame retardant during storage and use.

Description

Technical Field

[0001] The invention relates to the preparation of a flame retardant, in particular to a phosphorus-containing flame retardant and a preparation method thereof. Background Art

[0002] Most traditional rubber materials are non-polar rubbers, which are mainly composed of carbon, hydrogen and other elements. After adding various additives and vulcanization, rubber material elastomers can be formed. Since rubber is cracked under high temperature conditions to produce carbon and hydrogen elements that are easy to burn in the air, traditional rubber materials are generally flammable. According to statistics, rubber burning accidents cause serious casualties and property losses to human society every year. Therefore, the preparation of rubber with flame retardant function is a goal that the industry and industrial sectors are constantly pursuing.

[0003] The traditional strategy to solve the flame retardant problem of rubber materials is to add appropriate flame retardants. This method has low impact on the rubber processing and production process and good economic performance. Therefore, various flame retardants have been widely developed. The traditional solution to rubber flame retardancy is to add flame retardants to suppress the combustion of rubber materials after they are ignited. Based on this idea, various types of flame retardants have been developed, such as: (1) The flame retardant decomposes to produce relatively inert free radicals to terminate the active free radicals produced by the combustion chain reaction; (2) The flame retardant decomposes to produce inert gases (such as carbon dioxide and ammonia) to dilute the oxygen concentration and suffocate the flame; (3) The flame retardant decomposes to produce strong dehydrating agents (such as polyphosphoric acid) to catalyze the dehydrogenation of rubber materials to form a protective carbon layer to extinguish the flame; (4) The flame retardant decomposes to absorb the heat of the material to reduce the temperature of the combustion area of ​​the material, thereby stopping the combustion reaction.

[0004] Traditional halogen-containing flame retardants produce a large amount of toxic hydrogen halide during the flame retardant process, so phosphorus-containing flame retardants are an important direction for the development of flame retardants, such as ammonium polyphosphate and melamine polyphosphate, which are currently used more. In order to obtain excellent flame retardant properties, a large amount of flame retardants are often needed to be added. However, phosphorus-containing flame retardants are generally polar substances, while rubber matrices are usually non-polar, causing the flame retardant to be incompatible with the rubber matrix, which will inevitably deteriorate the mechanical properties of the rubber material. At the same time, due to the phase separation of the flame retardant in the material, the flame retardant properties of the material will also be reduced. Summary of the invention

[0005] In view of the problem that the above-mentioned phosphorus-containing flame retardants have poor compatibility with rubber materials and deteriorate the mechanical properties of rubber materials, the present invention provides a phosphorus-containing flame retardant and a preparation method thereof. The phosphorus-containing flame retardant prepared by the method has good compatibility with rubber materials, can maintain the mechanical properties of the material itself, and has excellent flame retardant properties.

[0006] In order to achieve the above object, the present invention provides a method for preparing a phosphorus-containing flame retardant, which comprises the following steps:

[0007] S1, adding a dihydroxyl-terminated unsaturated polyester and a monohydroxyl-terminated unsaturated olefin monomer into a solvent for dissolving to form a mixture solution;

[0008] S2, adding an organic base catalyst to the mixture solution, and then adding a phenylphosphonic dichloride solution dropwise to obtain a reactant solution after reaction;

[0009] S3, adding DOPO monomer (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) to the reactant solution to cause a grafting reaction, and then filtering and rotary evaporating to remove the solvent to obtain the phosphorus-containing flame retardant.

[0010] The present invention uses unsaturated polyester, DOPO, phenylphosphonyl dichloride, and hydroxyl-terminated unsaturated olefin monomers as raw materials, and prepares a non-polar polymer phosphorus-containing flame retardant through a simple chain extension reaction and a Michael addition reaction. Through molecular design, a flame retardant with relatively excellent comprehensive performance is synthesized. The phosphorus-containing flame retardant polymer side chain contains a classic DOPO structural unit, the polymer main chain is connected by a phenylphosphonate structure, and the polymer chain end is a structure similar to a polyisoprene repeating unit structure. The phosphorus-containing flame retardant contains phosphorus of different valence states, has a coordinated flame retardant effect, and has a good flame retardant effect. At the same time, the polymer used to prepare the flame retardant is non-polar, has good compatibility with rubber, can participate in the vulcanization process of rubber, and achieves a balance between the flame retardant performance and other properties of the rubber material.

[0011] The flame retardant polymer terminal synthesized by the present invention contains the same structural unit as the rubber molecule, and can participate in the reaction cross-linking of the rubber, that is, the flame retardant polymer terminal can form a covalent bond with the rubber molecular chain, which has the following advantages: 1) after the flame retardant reacts with the rubber, the flame retardant is a part of the rubber polymer chain (connected by covalent bonds), thereby achieving efficient dispersion of the flame retardant; 2) avoiding the migration of the flame retardant during storage; and 3) the flame retardant performance of the rubber material will not decrease during storage.

[0012] The preparation method is simple and easy to operate. The prepared phosphorus-containing flame retardant contains phosphine of different valence states and has good flame retardant effect. The end of the flame retardant polymer chain is connected with a polyisoprene structural group, which can participate in the traditional sulfur vulcanization reaction, and also solves the incompatibility problem between the polar flame retardant and the non-polar rubber, avoids its migration and precipitation in the rubber body, and improves the comprehensive performance of the flame retardant rubber.

[0013] In step S1, the solvent is preferably chloroform or dichloroethane.

[0014] Preferably, in step S1, the dihydroxy-terminated unsaturated polyester is one or both of hydroxy-terminated polymaleic acid diol ester and hydroxy-terminated polyitaconic acid diol ester, and the molecular weight is 1000-4000 g / mol.

[0015] The active sites of the dihydroxy-terminated unsaturated polyester reaction are the two terminal hydroxyl groups in the molecule. When using unsaturated polyesters in this molecular weight range, the chain extension reaction between phenylphosphonyl dichloride is more efficient, and it is easy to obtain unsaturated polyphosphonates with higher molecular weights. This ensures that in the subsequent reaction, the unsaturated polyphosphonate polymer chain can be grafted with more DOPO, thereby improving the flame retardant properties of the flame retardant. Note: The phosphonate structural unit and DOPO structural unit in the flame retardant molecule are the main structures that provide flame retardant properties.

[0016] Preferably, in step S1, the monohydroxy-terminated unsaturated olefin monomer is one or more of farnesol, geraniol, nerol and geranylgeraniol, and the structural formula of each monomer is as follows:

[0017]

[0018] Preferably, in step S1, the molar ratio of the dihydroxy-terminated unsaturated polyester to the monohydroxy-terminated unsaturated olefin monomer is (2-5):1, so that a flame retardant with a relatively high molecular weight can be obtained.

[0019] Preferably, in step S2, the molar ratio of the phenylphosphonic dichloride to the total number of hydroxyl groups in the dihydroxy-terminated unsaturated polyester and the monohydroxy-terminated unsaturated olefin monomer is 1:2.

[0020] In the above technical solution, the phosphoryl chloride group in phenylphosphonyl dichloride can fully react with the hydroxyl group in the system to obtain a flame retardant with a higher molecular weight.

[0021] Preferably, in step S2, the organic base catalyst is one or more of triethylamine, tripropylamine and tributylamine, preferably triethylamine.

[0022] In the above technical solution, organic amine catalysts such as triethylamine mainly absorb the hydrochloric acid generated by the reaction, increase the reaction rate, and improve the molecular weight of the flame retardant. At the same time, the organic base is easily removed from the system.

[0023] Furthermore, the molar ratio of the organic base catalyst to the phenylphosphonic dichloride is (5-10):1, and the reaction time is 10-24 hours.

[0024] An excess of organic base catalyst ensures high efficiency in neutralizing the reaction by-product hydrochloric acid and increasing the reaction rate. If the excess is too much, it will not significantly affect the efficiency improvement, but will increase the material cost.

[0025] Preferably, in step S3, the molar ratio of the DOPO monomer to the carbon-carbon double bonds in the dihydroxy-terminated unsaturated polyester is 1:(5-10).

[0026] In the above technical solution, the grafting amount of DOPO on the flame retardant polymer chain can be adjusted to adjust the flame retardant properties of the flame retardant on the one hand; on the other hand, the physical properties of the flame retardant polymer, such as the glass transition temperature of the polymer flame retardant, can be adjusted.

[0027] Preferably, in step S3, the grafting reaction is carried out at 25-45° C. for 12-40 hours.

[0028] The second aspect of the present invention provides a phosphorus-containing flame retardant prepared by the above-mentioned preparation method.

[0029] Through the above technical solution, the present invention achieves the following beneficial effects:

[0030] 1. Compared with traditional flame retardants, the present invention uses industrial raw materials to prepare non-polar phosphorus-containing flame retardants with different valence states, which have excellent synergistic flame retardant effects. The flame retardant has good compatibility with currently common non-polar rubbers. At the same time, the flame retardant can participate in rubber vulcanization, reducing the migration and precipitation of the flame retardant during storage and use.

[0031] 2. The preparation method of the phosphorus-containing flame retardant proposed in the present invention is convenient and easy to implement. The prepared flame retardant has excellent flame retardant properties. At the same time, the flame retardant has good compatibility with rubber, and the application scenarios of the flame retardant are more extensive. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is the reaction route diagram of the phosphorus-containing flame retardant in the embodiment of the present invention. DETAILED DESCRIPTION

[0033] The specific implementation of the present invention is described in detail below in conjunction with the examples. It should be understood that the specific implementation described herein is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0034] Unless otherwise specified, the reagents used in the following examples are all commercially available products.

[0035] Example 1

[0036] The preparation method of phosphorus-containing flame retardant is as follows:

[0037] (1) 20 g of hydroxyl-terminated polybutylene maleate (number average molecular weight of 1850) and 0.51 g of geraniol monomer were dissolved in 200 ml of chloroform, and then 6.74 g of triethylamine was added. Under stirring conditions, 2.43 g of phenylphosphinoyl dichloride monomer was added dropwise to the above solution, and stirring was continued to react. The reaction conditions were 20° C. and the reaction time was 24 h. After the reaction, a geraniol-terminated compound solution 1 was obtained;

[0038] (2) Add 2.5 g of DOPO monomer to solution 1 and stir to react. Stir and react at room temperature for 1 h, then heat the system to 30° C. and continue to react for 32 h.

[0039] (3) Filter and remove insoluble matter, and then remove the solvent by rotary evaporation to obtain the phosphorus-containing flame retardant.

[0040] Example 2

[0041] like Figure 1 As shown, the preparation method of the phosphorus-containing flame retardant is as follows:

[0042] (1) 20 g of hydroxyl-terminated polybutylene maleate (number average molecular weight of 1040) and 0.89 g of farnesol monomer were dissolved in 200 ml of chloroform, and then 20.24 g of triethylamine was added. Under stirring conditions, 4.14 g of phenylphosphoryl dichloride monomer was added dropwise to the above solution, and stirring was continued to react. The reaction conditions were 20° C. and the reaction time was 20 h. After the reaction, farnesol-terminated compound solution 1 was obtained;

[0043] (2) Add 2.6 g of DOPO monomer to solution 1 and stir to react. Stir and react at room temperature for 1 h, then heat the system to 45° C. and continue to react for 20 h.

[0044] (3) Filter and remove insoluble matter, and remove the solvent by rotary evaporation to obtain the phosphorus-containing flame retardant flame retardant material.

[0045] Example 3

[0046] The preparation method of phosphorus-containing flame retardant is as follows:

[0047] (1) 20 g of hydroxyl-terminated polybutylene maleate (number average molecular weight of 3950) and 0.48 g of geranylgeraniol monomer were dissolved in 200 ml of chloroform, and then 4.71 g of triethylamine was added. Under stirring conditions, 1.15 g of phenylphosphinoyl dichloride monomer was added dropwise to the above solution, and stirring was continued to react. The reaction conditions were 20° C. and the reaction time was 24 h. After the reaction, a geranylgeraniol-terminated compound solution 1 was obtained;

[0048] (2) 3.6 g of DOPO monomer was added to solution 1 and stirred for reaction. The reaction was stirred for 1 h at room temperature, and then the system was heated to 45° C. and reacted for 18 h.

[0049] (3) Filter and remove insoluble matter, and then remove the solvent by rotary evaporation to obtain the phosphorus-containing flame retardant.

[0050] Example 4

[0051] The preparation method of phosphorus-containing flame retardant is as follows:

[0052] (1) 20 g of hydroxyl-terminated polypentylene maleate (number average molecular weight of 1800) and 0.43 g of nerol monomer were dissolved in 200 ml of chloroform, and then 8.9 g of triethylamine was added. Under stirring conditions, 2.44 g of phenylphosphinoyl dichloride monomer was added dropwise to the above solution, and stirring was continued to react. The reaction conditions were 22° C. and the reaction time was 20 h. After the reaction, a nerol-terminated compound solution 1 was obtained;

[0053] (2) 2.8 g of DOPO monomer was added to solution 1 and stirred for reaction. The reaction was stirred for 1 h at room temperature, and then the system was heated to 30° C. and reacted for 36 h.

[0054] (3) Filter and remove insoluble matter, and then remove the solvent by rotary evaporation to obtain the phosphorus-containing flame retardant.

[0055] Example 5

[0056] The preparation method of phosphorus-containing flame retardant is as follows:

[0057] (1) 20 g of hydroxyl-terminated polypentylene maleate (number average molecular weight of 1100) and 0.81 g of farnesol monomer were dissolved in 200 ml of chloroform, and then 12.8 g of triethylamine was added. Under stirring conditions, 3.9 g of phenylphosphoryl dichloride monomer was added dropwise to the above solution, and stirring was continued to react. The reaction conditions were 20° C. and the reaction time was 20 h. After the reaction, farnesol-terminated compound solution 1 was obtained;

[0058] (2) 2.7 g of DOPO monomer was added to solution 1 and stirred for reaction. The reaction was stirred for 1 h at room temperature, and then the system was heated to 35° C. and reacted for 30 h.

[0059] (3) Filter and remove insoluble matter, and then remove the solvent by rotary evaporation to obtain the phosphorus-containing flame retardant.

[0060] Example 6

[0061] The preparation method of phosphorus-containing flame retardant is as follows:

[0062] (1) 20 g of hydroxyl-terminated polypentylene maleate (number average molecular weight of 3800) and 0.51 g of geranylgeraniol monomer were dissolved in 200 ml of chloroform, and then 4.1 g of triethylamine was added. Under stirring conditions, 1.25 g of phenylphosphinoyl dichloride monomer was added dropwise to the above solution, and stirring was continued to react. The reaction conditions were 20° C. and the reaction time was 24 h. After the reaction, a geranylgeraniol-terminated compound solution 1 was obtained;

[0063] (2) 3.27 g of DOPO monomer was added to solution 1 and stirred for reaction. The reaction was stirred for 1 h at room temperature, and then the system was heated to 45° C. and reacted for 16 h.

[0064] (3) Filter and remove insoluble matter, and then remove the solvent by rotary evaporation to obtain the phosphorus-containing flame retardant.

[0065] Example 7

[0066] The preparation method of phosphorus-containing flame retardant is as follows:

[0067] (1) 20 g of hydroxyl-terminated polyitaconate (number average molecular weight of 1900) and 0.41 g of nerol monomer were dissolved in 200 ml of chloroform, and then 9.5 g of triethylamine was added. Under stirring conditions, 2.31 g of phenylphosphoryl dichloride monomer was added dropwise to the above solution, and stirring was continued to react. The reaction conditions were 24° C. and the reaction time was 20 h. After the reaction, a nerol-terminated compound solution 1 was obtained;

[0068] (2) 3.5 g of DOPO monomer was added to solution 1 and stirred for reaction. The reaction was stirred for 1 h at room temperature, and then the system was heated to 25° C. and reacted for 40 h.

[0069] (3) Filter and remove insoluble matter, and then remove the solvent by rotary evaporation to obtain the phosphorus-containing flame retardant.

[0070] Example 8

[0071] The preparation method of phosphorus-containing flame retardant is as follows:

[0072] (1) 20 g of hydroxyl-terminated polyitaconate (number average molecular weight of 1200) and 0.74 g of farnesol monomer were dissolved in 200 ml of chloroform, and then 12.8 g of triethylamine was added. Under stirring conditions, 3.58 g of phenylphosphoryl dichloride monomer was added dropwise to the above solution, and stirring was continued to react. The reaction conditions were 25° C. and the reaction time was 24 h. After the reaction, farnesol-terminated compound solution 1 was obtained;

[0073] (2) 2.26 g of DOPO monomer was added to solution 1 and stirred for reaction. The reaction was stirred for 1 h at room temperature, and then the system was heated to 30° C. and reacted for 36 h.

[0074] (3) Filter and remove insoluble matter, and then remove the solvent by rotary evaporation to obtain the phosphorus-containing flame retardant.

[0075] Example 9

[0076] The preparation method of phosphorus-containing flame retardant is as follows:

[0077] (1) 20 g of hydroxyl-terminated polyitaconate (number average molecular weight of 3950) and 0.73 g of geranylgeraniol monomer were dissolved in 200 ml of chloroform, and then 2 g of triethylamine and 2.5 g of tripropylamine were added. Under stirring conditions, 1.23 g of phenylphosphinoyl dichloride monomer was added dropwise to the above solution, and stirring was continued to react. The reaction conditions were 25° C. and the reaction time was 10 h. After the reaction, a geranylgeraniol-terminated compound solution 1 was obtained;

[0078] (2) 4.26 g of DOPO monomer was added to solution 1 and stirred for reaction. The reaction was stirred for 1 h at room temperature, and then the system was heated to 30° C. and reacted for 40 h.

[0079] (3) Filter and remove insoluble matter, and then remove the solvent by rotary evaporation to obtain the phosphorus-containing flame retardant.

[0080] Example 10

[0081] The preparation method of phosphorus-containing flame retardant is as follows:

[0082] (1) 20 g of hydroxyl-terminated polybutylene itaconate (number average molecular weight of 2100) and 0.49 g of nerol monomer were dissolved in 200 ml of ethylene dichloride, and then 3 g of triethylamine and 5 g of tributylamine were added. Under stirring conditions, 2.17 g of phenylphosphinoyl dichloride monomer was added dropwise to the above solution, and stirring was continued to react. The reaction conditions were 25° C. and the reaction time was 12 h. After the reaction, a nerol-terminated compound solution 1 was obtained;

[0083] (2) Add 2.25 g of DOPO monomer to solution 1 and stir to react. Stir and react at room temperature for 1 h. Then, heat the system to 45° C. and react for 12 h.

[0084] (3) Filter and remove insoluble matter, and then remove the solvent by rotary evaporation to obtain the phosphorus-containing flame retardant.

[0085] Embodiment 11

[0086] The preparation method of phosphorus-containing flame retardant is as follows:

[0087] (1) 20 g of hydroxyl-terminated polybutylene itaconate (number average molecular weight of 1050), 0.71 g of farnesol monomer and 0.48 g of geraniol monomer were dissolved in 200 ml of chloroform, and then 15.8 g of triethylamine was added. Under stirring conditions, 4.33 g of phenylphosphoryl dichloride monomer was added dropwise to the above solution, and stirring was continued to react. The reaction conditions were 25° C. and the reaction time was 18 h. After the reaction, farnesol-terminated compound solution 1 was obtained;

[0088] (2) 2.68 g of DOPO monomer was added to solution 1 and stirred for reaction. The reaction was stirred for 1 h at room temperature, and then the system was heated to 30° C. and reacted for 36 h.

[0089] (3) Filter and remove insoluble matter, and then remove the solvent by rotary evaporation to obtain the phosphorus-containing flame retardant.

[0090] Example 12

[0091] The preparation method of phosphorus-containing flame retardant is as follows:

[0092] (1) 10 g of hydroxyl-terminated polybutylene itaconate with a number average molecular weight of 3900, 10 g of hydroxyl-terminated polymaleic acid diol with a number average molecular weight of 3950 and 0.74 g of geranylgeraniol monomer were dissolved in 200 ml of chloroform, and then 4.1 g of triethylamine was added. Under stirring conditions, 1.32 g of phenylphosphinoyl dichloride monomer was added dropwise to the above solution, and stirring was continued to react. The reaction conditions were 22° C. and the reaction time was 20 h. After the reaction, a geranylgeraniol-terminated compound solution 1 was obtained;

[0093] (2) 2.55 g of DOPO monomer was added to solution 1 and stirred for reaction. The reaction was stirred for 1 h at room temperature, and then the system was heated to 40° C. and reacted for 26 h.

[0094] (3) Filter and remove insoluble matter, and then remove the solvent by rotary evaporation to obtain the phosphorus-containing flame retardant.

[0095] Performance Testing

[0096] The flame retardant styrene butadiene rubber formula is shown in Table 1.

[0097] Table 1 Different types of styrene butadiene rubber formula

[0098]

[0099] Use an open mill to mix the rubber, the roller temperature is room temperature, and the cooling water needs to be turned on during the mixing process. First, plasticize the styrene-butadiene rubber several times, then add stearic acid, zinc oxide, prepared phosphorus-containing flame retardant, accelerator, vulcanizer, etc. to the rubber, turn over and roll, and finally make triangle packages and thin passes 4 times before producing sheets. After parking for one day, turn over the sample three times on the open mill, produce sheets, and use a flat sheet press to vulcanize at 170°C and 20MPa to obtain a flame-retardant styrene-butadiene rubber sample.

[0100] The limiting oxygen index (LOI) of the flame retardant styrene-butadiene rubber vulcanized sample was measured according to the ASTM-D2863 standard, and the size of the sample was 120mm×6.5mm×3.0mm. The mechanical properties of the rubber sample were tested according to the GB / T528-1998 standard.

[0101] The test results are shown in Table 2.

[0102] Table 2 Flame retardant properties test results of flame retardant styrene butadiene rubber

[0103]

[0104] The mechanical properties test results of the samples are shown in Table 3.

[0105] Table 3 Mechanical properties test results of flame retardant styrene butadiene rubber

[0106]

[0107] As can be seen from Table 2, by adding the flame retardants prepared in Examples 1 to 12, the flame retardant properties of styrene-butadiene rubber are significantly improved.

[0108] As can be seen from Table 3, compared with the sample without adding flame retardant, after adding traditional APP flame retardant, the tensile strength of the material decreased significantly by about 20.6%, and the elongation at break decreased by 15.4%; while after adding the phosphorus-containing flame retardant of the present invention, the mechanical properties did not decrease significantly, and the flame retardant properties of the rubber were significantly improved. The reduction in mechanical properties of the sample with traditional flame retardant is caused by the low compatibility of polar APP flame retardant with non-polar styrene-butadiene rubber. The phosphorus-containing flame retardant molecules prepared by the present invention have low polarity and good compatibility with styrene-butadiene rubber. At the same time, the flame retardant molecules also participate in the vulcanization of rubber, thereby promoting the compatibility of the flame retardant with styrene-butadiene rubber. While improving the flame retardant properties of the sample, the mechanical properties did not decrease significantly.

[0109] The preferred implementation modes of the present invention are described in detail above in combination with the embodiments; however, the present invention is not limited to the specific details in the above implementation modes. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical scheme of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0110] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0111] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for preparing a phosphorus-containing flame retardant, characterized in that: The steps include: S1, adding a dihydroxyl-terminated unsaturated polyester and a monohydroxyl-terminated unsaturated olefin monomer into a solvent for dissolution to form a mixture solution, wherein the dihydroxyl-terminated unsaturated polyester is one or both of hydroxyl-terminated polymaleic acid diol ester and hydroxyl-terminated polyitaconic acid diol ester, and the monohydroxyl-terminated unsaturated olefin monomer is one or more of farnesol, geraniol, nerol and geranylgeraniol; S2, adding an organic base catalyst to the mixture solution, and then adding a benzenephosphonyl dichloride solution dropwise, and obtaining a reactant solution after reaction, wherein the molar ratio of the benzenephosphonyl dichloride to the total number of hydroxyl groups in the dihydroxy-terminated unsaturated polyester and the monohydroxy-terminated unsaturated olefin monomer is 1:2; S3, adding DOPO monomer to the reactant solution to cause a grafting reaction, and then filtering and rotary evaporating to remove the solvent to obtain the phosphorus-containing flame retardant.

2. The preparation method according to claim 1, characterized in that: In step S1, the molecular weight of the dihydroxy-terminated unsaturated polyester is 1000-4000 g / mol.

3. The preparation method according to claim 1, characterized in that: In step S1, the molar ratio of the dihydroxy-terminated unsaturated polyester to the monohydroxy-terminated unsaturated olefin monomer is (2-5):

1.

4. The preparation method according to claim 1, characterized in that: In step S2, the organic base catalyst is one or more of triethylamine, tripropylamine and tributylamine.

5. The preparation method according to claim 4, characterized in that: The molar ratio of the organic base catalyst to the phenylphosphonic acid dichloride is (5-10):1, and the reaction time is 10-24 hours.

6. The preparation method according to claim 1, characterized in that: In step S3, the molar ratio of the DOPO monomer to the carbon-carbon double bonds in the dihydroxy-terminated unsaturated polyester is 1:(5-10).

7. The preparation method according to claim 1, characterized in that: In step S3, the grafting reaction is carried out at 25-45° C. for 12-40 hours.

8. The phosphorus-containing flame retardant prepared by the preparation method according to any one of claims 1 to 7.

Images