CN114790290B - Synthesis method of hydroxyl modified biphenyl structure PBO composite monomer - Google Patents

Abstract

A synthetic method of a hydroxyl modified biphenyl structure PBO composite monomer comprises the following steps: taking 2, 5-dihydroxyterephthalic acid as a raw material, adding sodium hydroxide and deoxidized water in a nitrogen atmosphere, and then heating to 30-50 ℃ for neutralization reaction for 0.2-0.5 hour to obtain an intermediate sodium 2, 5-dihydroxyterephthalate; then, intermediate sodium 2, 5-dihydroxyterephthalate and 3,3 '-diamino-4, 4' -dihydroxybiphenyl hydrochloride are used as raw materials, stannous chloride is added in a nitrogen atmosphere, and the mixture reacts for 0.3 to 0.6 hour at the temperature of 60 to 80 ℃ to obtain a white solid product of the hydroxyl modified biphenyl structure PBO composite monomer. The reaction process parameters of the scheme of the invention are easy to control, no toxic byproducts are generated, the atomic utilization rate is high, the yield is high, the purity is high, and the post-treatment is simple.

Description

A synthesis method of hydroxyl-modified biphenyl structure PBO composite monomer

(1) Technical field

The invention relates to a synthesis method of a hydroxyl-modified biphenyl structure PBO composite monomer.

(2) Background technology

Formula ﹙1﹚ shows the composite monomer of hydroxyl-modified biphenyl structure PBO. It is the raw material for polymerization to prepare hydroxyl-modified poly-p-phenylenebenzobisoxazole. It can be used in high-performance fibers, optoelectronic materials, and resistant materials. Thermal materials and other fields (Lu Shanshan, Wang Yanhong, Hu Zhen. Research progress on poly-paraphenylene benzobisoxazole fiber modification technology, Synthetic Fiber Industry, 2018, 41(1): 47-52.).

At present, the polymerization method of hydroxyl-modified poly-p-phenylene benzobisoxazole is based on 3,3′-diamino-4,4′-dihydroxybiphenyl hydrochloride and 2,5-dihydroxyterephthalic acid. When the mixed polycondensation reaction is carried out at high temperature in polyphosphoric acid, there are disadvantages such as the difficulty of uniform polycondensation of the two monomers in equal equivalent ratios, which affects the polymerization effect, and the HCl removal process affects the fiber strength. Therefore, starting from the polymerization method of PBO fiber, a hydroxyl-modified biphenyl structure PBO composite monomer is synthesized, and the composite monomer is used to perform a self-condensation polymerization reaction under medium and high temperature conditions of polyphosphoric acid. This method achieves the equalization of the two monomers. The equivalent ratio is uniformly polycondensed, avoiding the degassing process, shortening the reaction time and improving the reaction efficiency. (Wu Chunxin, Chang Yuxi, Chen Dichao, et al. Synthesis of hydroxyl-modified poly-p-phenylenebenzobisoxazole monomer 3,3′-diamino-4,4′-dihydroxybiphenyl hydrochloride, Chemical Engineering Progress ,2020,39(2):696-701.).

In view of the above-mentioned situation of hydroxyl-modified poly-p-phenylene benzobisoxazole, we have explored to find a new method to synthesize hydroxyl-modified biphenyl structure PBO composite monomer that is easy to implement and more reasonable in industry.

﹙3﹚Contents of the invention

The object of the present invention is to provide a method for preparing high-purity hydroxyl-modified biphenyl that ensures an equivalent ratio of two monomers, high reaction selectivity, short reaction time, high atom utilization, simple post-processing, high yield and industrial feasibility. Methods of structuring PBO composite monomers.

In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

In the first aspect, the present invention provides a hydroxyl-modified biphenyl structure PBO composite monomer represented by formula (1),

In a second aspect, the present invention provides a method for synthesizing a hydroxyl-modified biphenyl structure PBO composite monomer represented by the above formula (1). The method is:

Use 2,5-dihydroxyterephthalic acid as raw material, add sodium hydroxide and deoxygenated water under a nitrogen atmosphere, and then heat it up to 30-50°C (preferably 40-50°C) to perform a neutralization reaction for 0.2-0.5 hours ( Preferably 0.3 to 0.4h) to obtain a solution containing the intermediate 2,5-dihydroxysodium terephthalate; add 3,3′-diamino-4,4′-dihydroxybiphenyl hydrochloride and reducing agent, and React at 60-80°C (preferably 70-80°C) for 0.3-0.6 hours (preferably 0.5-0.6h), and the resulting reaction liquid is post-processed to obtain the hydroxyl-modified biphenyl structure PBO composite represented by the formula (1) Monomer; the mass ratio of the 2,5-dihydroxyterephthalic acid and sodium hydroxide is 1:0.3~0.5 (preferably 1:0.4~0.45); the 3,3'-diamino-4 , the mass ratio of 4'dihydroxybiphenyl hydrochloride and 2,5-dihydroxyterephthalic acid is 1:0.6~0.9 (preferably 1:0.7~0.74); the reducing agent and 3,3'-dihydroxyterephthalic acid The mass ratio of amino-4,4'-dihydroxybiphenyl hydrochloride is 1:90-110 (preferably 1:100-110); the reducing agent is stannous chloride, ferrous sulfate or sodium sulfate (preferably stannous chloride).

Further, the volume of the deoxygenated water is 20 to 40 mL/g (preferably 25.5 mL/g) based on the mass of 2,5-dihydroxyterephthalic acid.

Further, the post-treatment is: washing and filtering the obtained reaction liquid with deoxygenated water, and drying the obtained filter cake in a vacuum, thereby obtaining the hydroxyl-modified biphenyl structure PBO composite monomer represented by the formula (1).

After the reaction of the present invention is completed, the purpose of washing and filtering with deoxygenated water is to remove the water-soluble product sodium chloride and the added reducing agent, and obtain the water-insoluble hydroxyl-modified biphenyl structure PBO composite monomer. In addition, the reducing properties of reducing agents such as stannous chloride can prevent the amino group of 3,3′-diamino-4,4′-dihydroxybiphenyl hydrochloride from being oxidized.

The present invention also provides an application of the hydroxyl-modified biphenyl structure PBO composite monomer represented by the above formula (1) in the preparation of modified PBO fibers.

Specifically, the application is: under nitrogen protection, the polyphosphoric acid mixture containing phosphorus pentoxide, the hydroxyl-modified biphenyl structure PBO composite monomer shown in formula (1), and phosphorus pentoxide are stirred at 100°C React for 1 hour, then continue to raise the temperature to 120°C for 1 hour, 140°C for 1 hour, 160°C for 1 hour, 180°C for 1 hour, and then raise the temperature to 190°C for 1 hour. The resulting liquid crystal liquid is then manually drawn, washed, and dried. , that is, the hydroxyl-modified biphenyl structure PBO fiber is obtained;

The total mass of phosphorus pentoxide and phosphorus pentoxide contained in the polyphosphorus pentoxide-containing polyphosphoric acid mixture is 85% of the total mass of the polyphosphorus pentoxide-containing polyphosphoric acid mixture and phosphorus pentoxide. -90% (preferably 87%); the mass of the hydroxyl-modified biphenyl structure PBO composite monomer represented by formula (1) is the polyphosphoric acid mixture containing phosphorus pentoxide, the hydroxyl group represented by formula (1) 10-20% (preferably 16%) of the total mass of the modified biphenyl structure PBO composite monomer and phosphorus pentoxide.

Further, the polyphosphoric acid mixture containing phosphorus pentoxide (polyphosphoric acid in the embodiment) was purchased from Shanghai McLean Biochemical Technology Co., Ltd., Lot#: C12710785, and the phosphorus pentoxide content was ≥85%.

Compared with the existing technology, the beneficial effects of the present invention are: the present invention provides a method that ensures an equivalent ratio of two monomers, high reaction selectivity, short reaction time, high atom utilization, simple post-processing, high yield and industrial It is a feasible method to prepare high-purity hydroxyl-modified biphenyl structure PBO composite monomer. The resulting PBO composite monomer to synthesize modified PBO fiber has better polymerization effect and improved thermal stability, reflecting the larger molecular weight of the polymer.

(4) Description of drawings

Figure 1: HPLC chart of Example 1. Analysis conditions: column temperature 35°C, mobile phase 60% methanol-water buffer solution, ODS C ¹⁸ chromatographic column (6.0×150mm) detection wavelength 254nm, flow rate 1.0mL/min.

Figure 2: HPLC chart of Example 2. Analysis conditions: column temperature 35°C, mobile phase 60% methanol-water buffer solution, ODS C ¹⁸ chromatographic column (6.0×150mm) detection wavelength 254nm, flow rate 1.0mL/min.

Figure 3: HPLC chart of Example 3. Analysis conditions: column temperature 35°C, mobile phase 60% methanol-water buffer solution, ODS C ¹⁸ chromatographic column (6.0×150mm) detection wavelength 254nm, flow rate 1.0mL/min.

Figure 4: HPLC chart of Example 4. Analysis conditions: column temperature 35°C, mobile phase 60% methanol-water buffer solution, ODS C ¹⁸ chromatographic column (6.0×150mm) detection wavelength 254nm, flow rate 1.0mL/min.

Figure 5: HPLC chart of Example 5. Analysis conditions: column temperature 35°C, mobile phase 60% methanol-water buffer solution, ODS C ¹⁸ chromatographic column (6.0×150mm) detection wavelength 254nm, flow rate 1.0mL/min.

(5) Specific implementation methods

The present invention is described in more detail through examples, but the scope of protection of the present invention is not limited by the examples.

Example 1

In a four-necked flask equipped with stirring, condenser tube and thermometer, add 2.35g 2,5-dihydroxyterephthalic acid, 60mL deoxygenated water, 1g sodium hydroxide, add nitrogen, start stirring, heat to increase temperature, and control the reaction temperature Neutralization reaction was carried out at 50℃ for 0.3h. Add 3.2g of 3,3′-diamino-4,4′-dihydroxybiphenyl hydrochloride and 0.03g of stannous chloride into the four-necked flask, continue to raise the temperature to 70°C, and react for 0.6h. After the reaction, the product was washed and filtered with deoxygenated water, and the filter cake was dried under vacuum to obtain 3.63g of a white solid product, a hydroxyl-modified biphenyl structure PBO composite monomer. HPLC analysis showed a mass fraction of 98.36% and a yield of 80.10%.

FT-IR (KBr, cm ^-1 ): 3610.8(s), 3368.9(s), 1658.8(s), 1417.8(s), 1355.1(s), 1108.3(s).

¹ H-NMR (DMSO, δ, ppm): 7.23 (2H, s, CH), 6.91 (2H, s, CH), 6.75 (4H, s, CH).

HPLC analysis conditions of hydroxyl-modified biphenyl structure PBO composite monomer: ODS C ¹⁸ column, 6.0×150mm, mobile phase: methanol/water buffer solution = 60/40 (V/V), detection wavelength 254nm, flow rate 1.0mL/min .

Examples 2 to 10

Examples 2 to 10 adopt the same operating steps as Example 1, and test different parameters according to the parameter range described in the present invention. It can be seen that the purity of the hydroxyl-modified biphenyl structure PBO composite monomer obtained under these process conditions is uniform. The net yields of hydroxyl-modified biphenyl structure PBO composite monomer products are above 91% and above 67%, and can be applied to the industrial synthesis of hydroxyl-modified biphenyl structure PBO composite monomers.

Example 2

In a four-necked flask equipped with stirring, condenser tube and thermometer, add 2.35g 2,5-dihydroxyterephthalic acid, 60mL deoxygenated water, 1g sodium hydroxide, add nitrogen, start stirring, heat to increase temperature, and control the reaction temperature Neutralization reaction was carried out at 40°C for 0.3h. Add 3.2g of 3,3′-diamino-4,4′-dihydroxybiphenyl hydrochloride and 0.03g of stannous chloride into the four-necked flask, continue to raise the temperature to 70°C, and react for 0.6h. After the reaction, the product was washed and filtered with deoxygenated water, and the filter cake was dried under vacuum to obtain 3.64g of the white solid product hydroxyl-modified biphenyl structure PBO composite monomer. HPLC analysis showed a mass fraction of 96.73% and a yield of 78.99%.

Example 3

In a four-necked flask equipped with stirring, condenser tube and thermometer, add 2.35g 2,5-dihydroxyterephthalic acid, 60mL deoxygenated water, 1g sodium hydroxide, add nitrogen, start stirring, heat to increase temperature, and control the reaction temperature Neutralization reaction was carried out at 50℃ for 0.5h. Add 3.2g of 3,3′-diamino-4,4′-dihydroxybiphenyl hydrochloride and 0.03g of stannous chloride into the four-necked flask, continue to raise the temperature to 70°C, and react for 0.6h. After the reaction was completed, the product was washed and filtered with deoxygenated water, and the filter cake was dried under vacuum to obtain 3.55g of the white solid product hydroxyl-modified biphenyl structure PBO composite monomer. The mass fraction analyzed by HPLC was 94.10%, and the yield was 74.95%.

Example 4

In a four-necked flask equipped with stirring, condenser tube and thermometer, add 2.35g 2,5-dihydroxyterephthalic acid, 60mL deoxygenated water, 1g sodium hydroxide, add nitrogen, start stirring, heat to increase temperature, and control the reaction temperature Neutralization reaction was carried out at 50℃ for 0.3h. Add 3.2g of 3,3′-diamino-4,4′-dihydroxybiphenyl hydrochloride and 0.03g of stannous chloride into the four-necked flask, continue to raise the temperature to 60°C, and react for 0.6h. After the reaction, the product was washed and filtered with deoxygenated water, and the filter cake was vacuum-dried to obtain 3.43g of a white solid product, a hydroxyl-modified biphenyl structure PBO composite monomer. HPLC analysis showed a mass fraction of 93.99% and a yield of 72.33%.

Example 5

In a four-necked flask equipped with stirring, condenser tube and thermometer, add 2.35g 2,5-dihydroxyterephthalic acid, 60mL deoxygenated water, 1g sodium hydroxide, add nitrogen, start stirring, heat to increase temperature, and control the reaction temperature Neutralization reaction was carried out at 50℃ for 0.3h. Add 3.2g of 3,3′-diamino-4,4′-dihydroxybiphenyl hydrochloride and 0.03g of stannous chloride into the four-necked flask, continue to raise the temperature to 80°C, and react for 0.6h. After the reaction, the product was washed and filtered with deoxygenated water, and the filter cake was dried under vacuum to obtain 3.44g of a white solid product, a hydroxyl-modified biphenyl structure PBO composite monomer. HPLC analysis showed a mass fraction of 91.08% and a yield of 70.29%.

Example 6

In a four-necked flask equipped with stirring, condenser tube and thermometer, add 2.35g 2,5-dihydroxyterephthalic acid, 60mL deoxygenated water, 1g sodium hydroxide, add nitrogen, start stirring, heat to increase temperature, and control the reaction temperature Neutralization reaction was carried out at 50℃ for 0.3h. Add 3.2g of 3,3′-diamino-4,4′-dihydroxybiphenyl hydrochloride and 0.03g of stannous chloride into the four-necked flask, continue to raise the temperature to 70°C, and react for 0.3h. After the reaction, the product was washed and filtered with deoxygenated water, and the filter cake was vacuum-dried to obtain 3.23g of the white solid product hydroxyl-modified biphenyl structure PBO composite monomer. The mass fraction analyzed by HPLC was 93.21%, and the yield was 67.55%.

Example 7

In a four-necked flask equipped with stirring, condenser tube and thermometer, add 2.35g 2,5-dihydroxyterephthalic acid, 60mL deoxygenated water, 0.94g sodium hydroxide, add nitrogen, start stirring, heat to increase temperature, and control the reaction. The temperature was 50°C, and the neutralization reaction was carried out for 0.3h. Add 3.2g of 3,3′-diamino-4,4′-dihydroxybiphenyl hydrochloride and 0.03g of stannous chloride into the four-necked flask, continue to raise the temperature to 70°C, and react for 0.6h. After the reaction, the product was washed and filtered with deoxygenated water, and the filter cake was vacuum-dried to obtain 3.38g of the white solid product hydroxyl-modified biphenyl structure PBO composite monomer. The mass fraction analyzed by HPLC was 95.56%, and the yield was 72.47%.

Example 8

In a four-necked flask equipped with stirring, condenser tube and thermometer, add 2.35g 2,5-dihydroxyterephthalic acid, 47mL deoxygenated water, 1g sodium hydroxide, add nitrogen, start stirring, heat to increase temperature, and control the reaction temperature Neutralization reaction was carried out at 50℃ for 0.3h. Add 3.2g of 3,3′-diamino-4,4′-dihydroxybiphenyl hydrochloride and 0.03g of stannous chloride into the four-necked flask, continue to raise the temperature to 70°C, and react for 0.6h. After the reaction, the product was washed and filtered with deoxygenated water, and the filter cake was dried under vacuum to obtain 3.47g of a white solid product, a hydroxyl-modified biphenyl structure PBO composite monomer. HPLC analysis showed a mass fraction of 94.78% and a yield of 73.79%.

Example 9

In a four-necked flask equipped with stirring, condenser tube and thermometer, add 2.35g 2,5-dihydroxyterephthalic acid, 60mL deoxygenated water, 1g sodium hydroxide, add nitrogen, start stirring, heat to increase temperature, and control the reaction temperature Neutralization reaction was carried out at 50℃ for 0.3h. Add 2.61g of 3,3′-diamino-4,4′-dihydroxybiphenyl hydrochloride and 0.03g of stannous chloride into the four-necked flask, continue to raise the temperature to 70°C, and react for 0.6h. After the reaction, the product was washed and filtered with deoxygenated water, and the filter cake was vacuum-dried to obtain 3.28g of the white solid product hydroxyl-modified biphenyl structure PBO composite monomer. HPLC analysis showed a mass fraction of 93.72% and a yield of 68.97%.

Example 10

In a four-necked flask equipped with stirring, condenser tube and thermometer, add 2.35g 2,5-dihydroxyterephthalic acid, 60mL deoxygenated water, 1g sodium hydroxide, add nitrogen, start stirring, heat to increase temperature, and control the reaction temperature Neutralization reaction was carried out at 50℃ for 0.3h. Add 3.2g of 3,3′-diamino-4,4′-dihydroxybiphenyl hydrochloride and 0.05g of stannous chloride into the four-necked flask, continue to raise the temperature to 70°C, and react for 0.6h. After the reaction, the product was washed and filtered with deoxygenated water, and the filter cake was dried under vacuum to obtain 3.68g of a white solid product, a hydroxyl-modified biphenyl structure PBO composite monomer. The mass fraction analyzed by HPLC was 92.34%, and the yield was 76.24%.

Examples 11 to 13

The preparation process of Example 1 was adopted and conditions other than the parameters described in the present invention were used for testing. As a result, the effect of the prepared product was very poor.

Example 11

In a four-necked flask equipped with stirring, condenser tube and thermometer, add 2.35g 2,5-dihydroxyterephthalic acid, 30mL deoxygenated water, 1g sodium hydroxide, add nitrogen, start stirring, heat to increase temperature, and control the reaction temperature Neutralization reaction was carried out at 50℃ for 0.3h. Add 3.2g of 3,3′-diamino-4,4′-dihydroxybiphenyl hydrochloride and 0.05g of stannous chloride into the four-necked flask, continue to raise the temperature to 70°C, and react for 0.6h. After the reaction, the product was washed and filtered with deoxygenated water, and the filter cake was vacuum-dried to obtain 3.27g of the white solid product hydroxyl-modified biphenyl structure PBO composite monomer. HPLC analysis showed a mass fraction of 82.34% and a yield of 60.41%.

Example 12

In a four-necked flask equipped with a stirring tube, a condenser tube and a thermometer, add 2.35g 2,5-dihydroxyterephthalic acid, 60mL deoxygenated water, and 2g sodium hydroxide, add nitrogen, start stirring, heat to increase temperature, and control the reaction temperature. Neutralization reaction was carried out at 50℃ for 0.3h. Add 3.2g of 3,3′-diamino-4,4′-dihydroxybiphenyl hydrochloride and 0.05g of stannous chloride into the four-necked flask, continue to raise the temperature to 70°C, and react for 0.6h. After the reaction, the product was washed and filtered with deoxygenated water, and the filter cake was dried under vacuum to obtain 3.67g of the white solid product hydroxyl-modified biphenyl structure PBO composite monomer. HPLC analysis showed a mass fraction of 80.56% and a yield of 66.33%.

Example 13

In a four-necked flask equipped with stirring, condenser tube and thermometer, add 2.35g 2,5-dihydroxyterephthalic acid, 60mL deoxygenated water, 1g sodium hydroxide, add nitrogen, start stirring, heat to increase temperature, and control the reaction temperature Neutralization reaction was carried out at 50℃ for 0.3h. Add 3.2g of 3,3′-diamino-4,4′-dihydroxybiphenyl hydrochloride and 0.05g of stannous chloride into the four-necked flask, continue to raise the temperature to 90°C, and react for 0.6h. After the reaction, the product was washed and filtered with deoxygenated water, and the filter cake was vacuum-dried to obtain 3.52g of the white solid product hydroxyl-modified biphenyl structure PBO composite monomer. HPLC analysis showed a mass fraction of 78.67% and a yield of 62.13%.

Example 14

Weigh the synthesized 3.55g hydroxyl-modified biphenyl structure PBO composite monomer, 2.70g phosphorus pentoxide (content ≥98%), 15.70g polyphosphoric acid (Hn+2PnO3n+1, Shanghai McLean Biochemical Technology Co., Ltd., Lot#:C12710785, phosphorus pentoxide content ≥85%), was added to the glass reactor in sequence, nitrogen was introduced into the reactor, stirring was started, the temperature was raised to 100°C and the reaction was carried out for 1 hour, the reaction system mixture turned black, and continued to be heated to React at 120°C for 1 hour, 140°C for 1 hour, 160°C for 1 hour, 180°C for 1 hour, and then increase the temperature to 190°C for 1 hour. The mixture will show yellow fluorescence and reach the end of the reaction. After the polymerization reaction is completed, the liquid crystal liquid is manually drawn with a clean glass rod to obtain the monofilament fiber, which is then washed in hot water to remove excess polyphosphoric acid. The monofilament fiber was vacuum dried at 100°C to obtain reddish-brown modified PBO fiber.

Comparative example 1

Weigh 2g of 3,3′-diamino-4,4′-dihydroxybiphenyl hydrochloride and 15g of polyphosphoric acid (Hn+2PnO3n+1, Shanghai McLean Biochemical Technology Co., Ltd., Lot#:C12710785, pentoxide Diphosphorus content ≥ 85%) was added to the glass reactor, nitrogen was introduced into the reactor, stirring was started, and the temperature was raised to 80°C to perform the HCl removal process. After 7 hours, the pH test paper was used to detect neutrality, and 1.5g2,5- was added. Dihydroxyterephthalic acid, 2.5g phosphorus pentoxide (content ≥98%), heat up to 100°C and react for 1 hour. The reaction system mixture turns black. Continue to heat up to 120°C for 1 hour, 140°C for 1 hour, and 160°C for 1 hour. , react at 180°C for 1 hour, then raise the temperature to 190°C and react for 1 hour. The mixture will show a small amount of yellow fluorescence and reach the end of the reaction. After the polymerization reaction is completed, the liquid crystal liquid is manually drawn with a clean glass rod, and the monofilament fiber is placed in hot water to wash away the excess polyphosphoric acid to obtain a small piece of solid. The small piece of solid was vacuum dried at 100°C to obtain purple modified PBO fiber.

Table 1

Compared with the two monomer mixing and polycondensation methods, the present invention has positive effects: (1) The reaction process parameters of the composite monomer method provided by the present invention are easy to control, ensuring the equivalent ratio polymerization of the two monomers and avoiding degassing The process can greatly shorten the reaction time, improve reaction efficiency, consume less energy, and have higher industrial feasibility. (2) The composite monomer method used in the present invention to synthesize modified PBO fiber has better drawing effect and improved thermal stability, reflecting the larger molecular weight of the polymer.

Claims (6)

1. A method for synthesizing a hydroxyl-modified biphenyl structure PBO composite monomer represented by formula (1), which is characterized in that the method is: Using 2,5-dihydroxyterephthalic acid as raw material, add sodium hydroxide and deoxygenated water under a nitrogen atmosphere, and then raise the temperature to 30-50°C to perform a neutralization reaction for 0.2-0.5 hours to obtain intermediate 2,5-containing -Sodium dihydroxyterephthalate solution; add 3,3′-diamino-4,4′-dihydroxybiphenyl hydrochloride and reducing agent, react at 60~80°C for 0.3~0.6 hours, and obtain the reaction solution After post-processing, the hydroxyl-modified biphenyl structure PBO composite monomer represented by the formula (1) is obtained; the mass ratio of the 2,5-dihydroxyterephthalic acid and sodium hydroxide is 1:0.3~ 0.5; the mass ratio of the 3,3′-diamino-4,4′dihydroxybiphenyl hydrochloride and 2,5-dihydroxyterephthalic acid is 1:0.6~0.9; the reducing agent and The mass ratio of 3,3′-diamino-4,4′-dihydroxybiphenyl hydrochloride is 1:90-110; the reducing agent is stannous chloride, ferrous sulfate or sodium sulfate. 2. The synthesis method of the hydroxyl-modified biphenyl structure PBO composite monomer represented by formula (1) as claimed in claim 1, characterized in that: the volume of the deoxygenated water is 2,5-dihydroxyterephthalic acid. The mass of formic acid is 20~40mL/g. 3. The method for synthesizing the hydroxyl-modified biphenyl structure PBO composite monomer represented by formula (1) according to claim 1, wherein the reducing agent is stannous chloride. 4. The synthesis method of the hydroxyl-modified biphenyl structure PBO composite monomer shown in formula (1) as claimed in claim 1, characterized in that: the 2,5-dihydroxyterephthalic acid and hydroxide The mass ratio of sodium is 1:0.4~0.45. 5. The synthesis method of the hydroxyl-modified biphenyl structure PBO composite monomer shown in formula (1) as claimed in claim 1, characterized in that: the 3,3′-diamino-4,4′di The mass ratio of hydroxybiphenyl hydrochloride and 2,5-dihydroxyterephthalic acid is 1:0.7~0.74. 6. The synthesis method of the hydroxyl-modified biphenyl structure PBO composite monomer represented by formula (1) as claimed in claim 1, characterized in that the post-treatment is: washing and filtering the obtained reaction liquid with deoxygenated water, and the obtained The filter cake is vacuum dried to obtain the hydroxyl-modified biphenyl structure PBO composite monomer represented by the formula (1).