Preparation method and application of high-temperature-resistant transparent modified polyamide

Abstract

The invention relates to the field of high polymer materials, and discloses a preparation method and application of high-temperature-resistant transparent modified polyamide. The preparation method comprises the following steps: 1) blending 9, 9-di-[(4-phenylphenoxy) dibenzoic acid] fluorene with diacid and diamine, and carrying out esterification reaction; and 2) carrying out condensation polymerization on the esterification product to obtain the high-temperature-resistant transparent modified polyamide with the glass transition temperature of more than 130 DEG C. According to the invention, 9, 9-di-[(4-phenylphenoxy) dibenzoic acid] fluorene is used as a modification monomer, and is copolymerized with other binary acid and diamine to synthesize the modified polyamide, and the modified polyamide not only has high transparency, but also still has good mechanical properties and dimensional stability at high temperature. Therefore, the high-temperature-resistant transparent modified polyamide is applicable to the application fields of optical films, optical lenses, reflective protective films, optical fibers or liquid crystal displays and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a preparation method and application of a high-temperature resistant transparent modified polyamide, which is particularly suitable for the field of engineering plastics requiring both high transparency and excellent mechanical properties. Background Art

[0002] Polyamide (PA) is a class of polymer materials formed through the condensation reaction of amino and carboxylic acid groups. Its molecular backbone contains recurring amide bonds (–CONH–). Due to its high strength, excellent heat resistance, and chemical stability, polyamides have long been widely used in engineering plastics, fibers, automotive parts, and membranes. However, while traditional polyamides such as PA6 and PA66 possess excellent mechanical properties, they suffer from high hygroscopicity, poor dimensional stability, and low optical clarity, making them difficult to use in high-end optical applications. For example, PA66 is a crystalline material, often exhibiting a cloudy, opaque appearance after molding, limiting its use in lenses, optical components, or transparent structural parts.

[0003] To address these issues, researchers have begun developing non-crystalline or low-crystalline polyamide materials and have attempted to introduce monomers with nonlinear or cyclic structures to disrupt the regular stacking of condensation polymers, reduce crystallinity, and improve transparency. In particular, p-aminocyclohexylmethane (PACM) is an aliphatic diamine with a rigid saturated cyclic structure. Because its molecule contains cyclohexane and para-amine groups, it offers excellent dimensional stability, thermal stability, and low birefringence, making it ideal for use in optical films or molded lenses. On the other hand, dodecanedicarboxylic acid (DDA), a long-chain aliphatic acid, can reduce the material's crystallization rate and rigidity, further improving processing fluidity and molded transparency.

[0004] Furthermore, further copolymerizing PACM with DDA with a small amount of aromatic dibasic acid (such as terephthalic acid (TPA), isophthalic acid (IPA), or benzoic acid (BA)) not only increases the polyamide's glass transition temperature (Tg) and heat distortion temperature (HDT), but also enhances optical stability and heat resistance through the rigidity of the aromatic rings. It also regulates the material's structural stacking, maintaining transparency and low birefringence. Therefore, developing a highly transparent, low-crystalline, high-Tg copolyamide composed of PACM, DDA, and an aromatic dibasic acid would overcome the application limitations of traditional polyamides in the optical field and possess significant industrial value and practical application potential. Summary of the Invention

[0005] This invention proposes a novel dibasic acid, DBPPFA9,9-bis-[(4-phenylphenoxy)dibenzoate]fluorene, which has a complex benzene ring structure. The steric hindrance of this structure allows it to react with a diamine to produce a polyamide polymer material with a high glass transition temperature and low crystallization resistance. This material maintains excellent mechanical properties and dimensional stability even at high temperatures, making it suitable for applications such as high-transparency films, optical lenses, high-temperature-resistant structural materials, and special packaging materials. The specific technical solutions of this invention are as follows:

[0006] A method for preparing a high-temperature resistant transparent modified polyamide, characterized by comprising the following steps:

[0007] 1) mixing 9,9-bis-[(4-phenylphenoxy)dibenzoic acid]fluorene with a dibasic acid and a diamine, and performing an esterification reaction; the 9,9-bis-[(4-phenylphenoxy)dibenzoic acid]fluorene accounts for 0.01-99 mol% of the total amount of the 9,9-bis-[(4-phenylphenoxy)dibenzoic acid]fluorene and the dibasic acid;

[0008] 2) The esterification product continues to undergo polycondensation reaction to obtain modified polyamide.

[0009] In step 1), the 9,9-bis-[(4-phenylphenoxy)dibenzoyl]fluorene accounts for 5-40 mol% of the total amount of the remaining dibasic acids.

[0010] In step 1), the synthesis method of 9,9-bis-[(4-phenylphenoxy)dibenzoate]fluorene includes:

[0011] a) uniformly mixing bisphenol fluorene, a base, and an organic solvent, heating for reaction, and then adding 4-chlorobenzonitrile to react after cooling for the first time; the reaction product is cooled for the second time, added to an acid for precipitation, purified, and dried to obtain a dicyanide; b) uniformly mixing the dicyanide obtained in step (a), a base, and an organic solvent, heating for reaction; cooling, adding to an acid, stirring, and filtering to obtain an aromatic dicarboxylic acid; dispersing the obtained aromatic dicarboxylic acid in an acid, heat-treating, filtering, rinsing, drying, and recrystallizing to obtain 9,9-bis-[(4-phenylphenoxy)dibenzoyl]fluorene.

[0012] In step a), the heating reaction temperature is 105-115° C.; the first cooling is cooling to 98-102° C.; the molar ratio of bisphenol fluorene to 4-chlorobenzonitrile is 1:(2-3); after adding 4-chlorobenzonitrile, the reaction is continued for 2-4 hours; and the second cooling is cooling to room temperature.

[0013] In step b), the heating reaction temperature is 150-170° C., and the time is 1.5-2.5 hours; the heat treatment temperature is 75-85° C.; and the solvent for the recrystallization is dioxin.

[0014] In step 1), the dibasic acid is selected from aromatic dibasic acids and / or aliphatic dibasic acids; the diamine is selected from alicyclic diamines. The dibasic acid is selected from one or more of dodecanedicarboxylic acid, isophthalic acid, or naphthalene dicarboxylic acid; and the diamine is selected from one or more of 4,4'-diaminodicyclohexylmethane (PACM / HMDA), 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane (DMDC / MACM), methylcyclohexanediamine (HTDA), or 1,3-cyclohexanedimethylamine (1,3-BAC).

[0015] In step 1), the molar ratio of the total amount of 9,9-bis-[(4-phenylphenoxy)dibenzoyl]fluorene and the dibasic acid to the diamine is 1:(0.9-1.1).

[0016] In step 1), the temperature of the esterification reaction is 180-240°C; in step 2), the temperature of the polycondensation reaction is 270-280°C.

[0017] The present invention uses 9,9-bis-[(4-phenylphenoxy)dibenzoate]fluorene (structural formula shown below) as a modified monomer of polyamide, and copolymerizes it with other dibasic acids and diamines to synthesize a high-temperature resistant transparent modified polyamide material.

[0018]

[0019] The above structural formula demonstrates that: first, 9,9-bis-[(4-phenylphenoxy)dibenzoyl]fluorene has a carboxyl group attached to each of its two benzene rings. Therefore, it can act as a dibasic acid monomer in polyamide copolymerization, thus providing a prerequisite for its use as a polyamide-modifying monomer. Secondly, the compound contains a phenyl ether structure. The present invention found that when the compound is used as a modified monomer in the copolymerization of polyamide, the resulting polyamide has the following excellent optical and mechanical properties: (1) high transparency: the rigid structure of the benzene ring and the non-polar characteristics of the ether bond can reduce the disordered stacking of molecular chains, reduce Rayleigh scattering, and improve transparency; (2) low birefringence: the symmetrical structure of the benzene ring and the ether bond can reduce the orientation of the molecular chain and reduce the birefringence of the condensation polymer; (3) high thermal stability: the benzene ring structure can enhance the heat resistance of the condensation polymer and increase the glass transition temperature (Tg) and melting point; (4) good mechanical properties: the presence of the benzene ring and the ether bond can promote the close stacking of molecular chains and improve the tensile strength and bending modulus; (5) flexibility: by adjusting the ratio of benzene ether diacid to flexible diamine, the flexibility of the polyamide can be controlled to meet different application requirements.

[0020] In order to further improve the modification effect of 9,9-di-[(4-phenylphenoxy)dibenzoic acid]fluorene. In theory, the collision frequency of the terminal groups in the polycondensation reaction is closely related to the mobility of the condensation polymer chain segment. Due to its rigid structure, the traditional fluorene-containing diacids often slow down the reaction kinetics in the later stage of the reaction due to the limited movement of the chain segments, resulting in the inability to further increase the molecular weight. Therefore, in the synthesis of polyamides, the dosage of most modified monomers should not be too much, otherwise it will bring a series of negative effects (such as mechanical properties, decreased fluidity, etc.). The flexible phenyl ether segment in the modified monomer of the present invention can significantly improve the softness of the entire molecular chain without losing the inherent high modulus effect of the fluorene skeleton, so that the terminal group can still maintain a high collision frequency during the high molecular weight generation process. This design can extend the effective reaction period of the polycondensation reaction, promote the formation of high molecular weight condensation polymers, and make the overall molecular weight reach a higher level, while reducing the reaction stagnation phenomenon caused by insufficient diffusion effect at the end of the reaction. Furthermore, while retaining the high modulus and heat resistance of the polycondensate imparted by the fluorene structure, the present invention reduces the rigidity of the entire molecular chain, thereby improving the fluidity of the polyamide in the molten state and further enhancing its thermal processing properties. Therefore, even with a high content of the modified monomer, the present invention can still achieve a balance between high modulus and flexibility in the polyamide material, resulting in the final product possessing excellent mechanical properties, impact resistance, and processability, expanding its application potential in high-performance engineering plastics, electronics, optoelectronics, and other fields.

[0021] The technical advantages of the present invention are as follows:

[0022] High glass transition temperature: Due to the benzene ring structure of DBPPFA, the resulting polyamide material has a high glass transition temperature, which enables the material to maintain good mechanical properties and dimensional stability at high temperatures.

[0023] Not easy to crystallize: The steric hindrance of DBPPFA makes the polyamide material it produces not easy to crystallize, which is of great significance for applications that require high transparency and optical uniformity, such as optical lenses and high-transparency films.

[0024] Wide application: This new polyamide material is suitable for a variety of applications such as high-transparency films, optical lenses, high-temperature resistant structural materials and special packaging materials, and has broad industrial application prospects.

[0025] This invention provides a novel method for regulating the crystallinity of polyamide materials by modifying the dibasic acid structure, which has broad industrial application prospects. By using the dibasic acid DBPPFA, which has a complex benzene ring structure, the resulting polyamide material has a high glass transition temperature and is resistant to crystallization, making it suitable for a variety of high-performance applications. This technology not only overcomes the crystallinity issues of traditional polyamide materials but also provides a method for preparing a novel material with significant technical and economic value. DETAILED DESCRIPTION

[0026] Example 1

[0027] (1) Synthesis of 9,9-bis-[(4-phenylphenoxy)dibenzoate]fluorene:

[0028] Step 1: 74.64 g (0.213 mol) of bisphenolfluorene, 29.90 g (0.533 mol) of potassium hydroxide, 50 g of toluene, and 790 g of dimethylformamide were placed in a 2-liter, four-necked flask equipped with a stirrer, thermometer, Dean-Stark reactor, and reflux condenser. While stirring the mixture, the system was heated to 110°C under a nitrogen atmosphere to allow the generated water to distill azeotropically with the toluene. After the water was distilled, the system temperature was lowered to 100°C. 79.0 g (0.533 mol) of 4-nitrobenzonitrile was added to the flask, and the reaction was allowed to proceed at this temperature for 3 hours. After the reaction was complete, the reaction mixture was cooled to room temperature and then poured into 1500 g of a 5% hydrochloric acid solution. The precipitated crystals were collected by filtration. The collected crude crystals were rinsed with 1000 g of water and then filtered to remove residual inorganic salts. The crystals were rinsed again with water and filtered. The crystals were then rinsed with 500 g of methanol and filtered. After repeated methanol rinsing and drying, the crystals were dried to obtain 80.97 g of a dicyanide compound. The yield of the dicyanide compound was 88.3%.

[0029] Step 2: Pour 27.85 g (0.188 mol) of p-nitrobenzonitrile (4-cyanonitrobenzene), 104 g of potassium hydroxide, and 832 g of ethylene glycol into a two-liter, four-necked flask equipped with a stirrer, thermometer, and reflux condenser. The mixture is reacted at 160°C for 2 hours. After the reaction is complete, cool the reaction mixture and pour it into 3 liters of 10% sulfuric acid solution. Stir at room temperature for 1 hour. Then, separate the free aromatic dicarboxylic acid by filtration. Disperse the aromatic dicarboxylic acid in 1.5 liters of 10% sulfuric acid solution and heat-treat at 80°C. Filter the mixture to separate the solid aromatic dicarboxylic acid and rinse twice with 1.5 liters of boiling distilled water. The resulting aromatic dicarboxylic acid is dried with hot air and recrystallized using 400 g of dioxin to obtain 79.27 g of 9,9-bis-[(4-phenylphenoxy)dibenzoyl]fluorene. The yield of the product based on the dicyanide is 90.0%.

[0030] (2) Synthesis of polyamide:

[0031] To a high-pressure reactor equipped with mechanical stirring, nitrogen blanketing, and vacuum switching capabilities (such as a stainless steel jacketed reactor), add the following: 18 kg of pure water, 8.6 kg of PACM, 9.22 kg of dodecanedicarboxylic acid, 0.47 kg of 9,9-bis-[(4-phenylphenoxy)dibenzoyl]fluorene, 0.09 kg of benzoic acid (capping agent), and 0.0036 kg of sodium hypophosphite. Repeat the nitrogen-filling and vacuum-evacuation cycles three times to remove oxygen from the reactor and prevent high-temperature oxidation. Initially raise the temperature to 180°C to form a slurry and initially react to form the nylon salt. Maintain this temperature for 1 hour to promote the condensation reaction while stirring continuously. Then, slowly raise the temperature to 200–240°C (adjustable to 240°C depending on experimental results) while maintaining the pressure at 3 MPa. Stirring should begin at this point, while maintaining the speed at 80 rpm. Maintain this temperature for 2 hours. During this stage, the reactants gradually increase in viscosity and release water vapor as a byproduct. After cooling to atmospheric pressure, the temperature was raised to 270°C and held for 1 hour. Over 30 minutes, the pressure was evacuated from 760 torr to 0.1 torr with continuous stirring to fully remove moisture and increase molecular weight. After polycondensation, the heating and vacuum systems were turned off, and the mixture was cooled to approximately 150°C under nitrogen. The viscous polymer was removed from the pan and chopped into small pellets using a cooling pelletizer. The mixture was then vacuum-dried (80–100°C for 12 hours) to remove residual volatiles and oligomers.

[0032] Example 2

[0033] The steps of Example 1 were repeated, but the monomer ratios for the polymerization reaction were adjusted to: 18 kg of pure water, 8.6 kg of PACM, 9.04 kg of dodecanedicarboxylic acid, 0.94 kg of 9,9-bis-[(4-phenylphenoxy)dibenzoyl]fluorene, 0.09 kg of benzoic acid (end-capping agent), and 0.0036 kg of sodium hypophosphite. The reactor was evacuated to 100 mmHg and then filled with nitrogen to 0.1 MPa. The temperature was raised to 180°C and held for 1 hour, then raised to 240°C while maintaining the pressure at 3 MPa. Stirring was initiated at this point and the rotational speed was maintained at 80 rpm. After holding for 2 hours, the pressure was reduced to atmospheric pressure and the temperature was raised to 270°C and held for 1 hour. The pressure was then evacuated from 760 Torr to 0.1 Torr over 30 minutes while stirring was continued. The polycondensation reaction was carried out at 270°C. After the polycondensation reaction reached a specific torque value, the product was removed from the reactor and granulated to produce polyamide particles.

[0034] Example 3

[0035] The steps of Example 1 were repeated, but the following monomer ratios were added: 18 kg of pure water, 8.6 kg of PACM, 8.67 kg of dodecanedicarboxylic acid, 1.88 kg of 9,9-bis-[(4-phenylphenoxy)dibenzoyl]fluorene, 0.09 kg of benzoic acid, and 0.0036 kg of sodium hypophosphite. The reactor was evacuated to 100 mmHg and filled with nitrogen to 0.1 MPa. The temperature was raised to 180°C and held for 1 hour, then raised to 240°C while maintaining the pressure at 3 MPa. Stirring was initiated and the rotation speed was maintained at 80 rpm. After holding for 2 hours, the pressure was reduced to atmospheric pressure, and the temperature was raised to 270°C and held for 1 hour. The pressure was then reduced from 760 torr to 0.1 torr over 30 minutes while stirring was continued. The polycondensation reaction was carried out at 270°C. After the polycondensation reaction reached a specific torque value, the product was removed from the reactor and granulated to produce polyamide particles.

[0036] Example 4

[0037] The steps of Example 1 were repeated, but the following monomer ratios were added: 18 kg of pure water, 8.6 kg of PACM, 7.92 kg of dodecanedicarboxylic acid, 3.76 kg of 9,9-bis-[(4-phenylphenoxy)dibenzoyl]fluorene, 0.09 kg of benzoic acid, and 0.0036 kg of sodium hypophosphite. The reactor was evacuated to 100 mmHg and then filled with nitrogen to 0.1 MPa. The temperature was raised to 180°C and held for 1 hour, then raised to 240°C while maintaining the pressure at 3 MPa. Stirring was initiated at this point and the rotational speed was maintained at 80 rpm. After holding for 2 hours, the pressure was reduced to atmospheric pressure, and the temperature was raised to 270°C and held for 1 hour. The pressure was then evacuated from 760 torr to 0.1 torr over 30 minutes while stirring was continued. The polycondensation reaction was carried out at 270°C. After the polycondensation reaction reached a specific torque value, the product was removed from the reactor and granulated to produce polyamide particles.

[0038] Comparative Example 1

[0039] 18 kg of pure water, 8.6 kg of PACM, 9.41 kg of dodecanedicarboxylic acid, 0.09 kg of benzoic acid, and 0.0036 kg of sodium hypophosphite were placed in a reactor, evacuated to 100 mm Hg, and then filled with nitrogen to 0.1 MPa. The temperature was raised to 180°C and held for 1 hour, then raised to 240°C and maintained at 3 MPa. Stirring was initiated at this point and the rotation speed was maintained at 80 rpm. After holding for 2 hours, the pressure was reduced to atmospheric pressure and the temperature was raised to 270°C and held for 1 hour. The pressure was then evacuated from 760 torr to 0.1 torr over 30 minutes while stirring continuously. A polycondensation reaction was carried out at 270°C. After the polycondensation reaction reached a specific torque value, the product was removed from the reactor and granulated to produce polyamide particles.

[0040] Comparative Example 2

[0041] 18 kg of pure water, 8.6 kg of PACM, 9.41 kg of dodecanedicarboxylic acid, 0.47 kg of isophthalic acid, 0.09 kg of benzoic acid, and 0.0036 kg of sodium hypophosphite were placed in a reactor. The reactor was evacuated to 100 mm Hg and then filled with nitrogen to 0.1 MPa. The temperature was raised to 180°C and held for 1 hour. The temperature was then raised to 240°C and the pressure was controlled at 3 MPa. Stirring was then initiated and the rotation speed was maintained at 80 rpm. After holding for 2 hours, the pressure was reduced to atmospheric pressure and the temperature was raised to 270°C and held for 1 hour. The pressure was then evacuated from 760 Torr to 0.1 Torr over 30 minutes while stirring continuously. A polycondensation reaction was carried out at 270°C. After the polycondensation reaction reached a specific torque value, the product was removed from the reactor and granulated to produce polyamide particles.

[0042] Performance Testing

[0043] The polyamide particles obtained in the above embodiments and comparative examples were tested for various properties. The test results are shown in Tables 1 and 2:

[0044] Table 1 Effects of different modified monomer contents and types on Tg and transparency of polyamide

[0045]

[0046] Table 2: Effects of different modified monomer contents and types on the mechanical properties of polyamide

[0047]

[0048] By comparing the data in Table 1 and Table 2, we can see that:

[0049] (1) The main difference between Comparative Example 1 and Examples 1-4 is the different proportions of 9,9-bis-[(4-phenylphenoxy)dibenzoyl]fluorene in the total amount of dibasic acid. Comparative Example 1 does not contain the modified monomer 9,9-bis-[(4-phenylphenoxy)dibenzoyl]fluorene, and the resulting polyamide has the lowest glass transition temperature and the best indicators such as transparency and flexibility. In Examples 1-3, as the content of the modified monomer increases, the resulting glass transition temperature continues to increase, and the resulting polyamide also has indicators such as flexibility at a relatively good level.

[0050] In theory, the end group collision frequency is closely related to the mobility of the polymer segment in the polycondensation reaction. Traditional fluorenyl diacids, due to their rigid structure, often make the reaction kinetics become slow in the later stage of the reaction due to the limited movement of the segment, causing the molecular weight to be unable to be further improved. Therefore, in polyamide synthesis, the amount of most modified monomers should not be too much, otherwise a series of negative impacts (such as mechanical properties, fluidity decline, etc.) will be brought. The flexible phenyl ether segment in the modified monomer of the present invention can significantly improve the flexibility of the entire molecular chain without losing the inherent high modulus effect of the fluorene skeleton, so that the end group can still maintain a higher collision frequency during the high molecular weight generation process. This design can extend the effective reaction period of the polycondensation reaction, promote the formation of high molecular weight polymers, make the overall molecular weight reach a higher level, and reduce the reaction stagnation phenomenon caused by the insufficient diffusion effect in the late reaction period. In addition, the present invention reduces the rigidity of the entire molecular chain on the basis of retaining the high modulus and heat resistance of the polymer given by the fluorene structure, thereby improving the fluidity of the polyamide in the molten state and further improving the hot processing performance. Therefore, even when the content of the modified monomer is relatively high, the present invention can still achieve a balance between high modulus and flexibility of the polyamide material, so that the final product has both excellent mechanical properties and processability.

[0051] (2) The difference between Comparative Example 2 and Example 1 is that other modified monomers are used. The results show that the two modified monomers in Comparative Examples 2-3 are both in the form of dibasic acids, which have an excellent effect on the crystallization destruction of the polyamide structure, but are slightly insufficient in improving the Tg temperature and mechanical properties.

[0052] The present invention relates to 9,9-di-[(4-phenylphenoxy)dibenzoic acid]fluorene and its application technology in the synthesis of novel polyamides, aiming to overcome the deficiencies of traditional polyamides containing fluorene structures in terms of polycondensation reaction kinetics, molecular weight growth and thermal processing performance. Although the polyamides synthesized traditionally using fluorene diacid as a monomer can improve the modulus and heat resistance of the material by virtue of the high rigidity of the fluorene skeleton, the molecular chain is too rigid due to its huge cardo group, and ultimately problems such as limited diffusion of reaction end groups, stagnant molecular weight growth, and excessive melt viscosity often occur, which limits the development of such materials in thermal processing and practical applications. In response to the above problems, the present invention introduces a flexible connecting segment (such as an alkyl chain, an ether chain or other flexible functional group) into the molecular skeleton of fluorene diacid to adjust the rigidity and flexibility balance of the entire molecular chain, retaining the characteristics of high modulus and heat resistance given to the polymer by the fluorene structure, and significantly improving the segment mobility in the polycondensation reaction, promoting effective collision of the end groups, thereby obtaining a high molecular weight polyamide, and at the same time reducing the viscosity in the molten state and improving thermal processing performance.

[0053] The preparation of traditional polyamide mainly uses terephthalic acid (or its derivatives) and ethylene glycol to further extend the molecular chain through polycondensation reaction after esterification or transesterification reaction. Although the introduction of fluorene dicarboxylic acid can improve the modulus and heat resistance of the polymer by utilizing its rigid structure, the steric hindrance effect of the fluorene structure itself will limit the polycondensation reaction in the later stage of the reaction: as the molecular chain gradually grows, the terminal groups are difficult to fully collide due to steric hindrance, making it difficult to form a high molecular weight; at the same time, the increased rigidity of the polymer chain will also reduce the fluidity in the molten state, further affecting the processability. Therefore, how to improve the reaction kinetics and thermal processability without sacrificing high modulus and heat resistance has become a major challenge in the design of polyamide materials.

[0054] Unless otherwise specified, the raw materials and equipment used in the present invention are commonly used in the art; the methods used in the present invention are conventional methods in the art unless otherwise specified.

[0055] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent transformation made to the above embodiment based on the technical essence of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing a high temperature resistant transparent modified polyamide, characterized in that: The steps include: 1) 9,9-bis-[(4-phenylphenoxy)dibenzoyl]fluorene is mixed with a dibasic acid and a diamine to carry out an esterification reaction; the 9,9-bis-[(4-phenylphenoxy)dibenzoyl]fluorene accounts for 0.01-99 mol% of the total amount of the dibasic acid; 2) The esterification product continues to undergo polycondensation reaction to obtain modified polyamide.

2. The method for preparing a high-temperature resistant transparent modified polyamide according to claim 1, wherein: In step 1), the 9,9-bis-[(4-phenylphenoxy)dibenzoyl]fluorene accounts for 5-40 mol% of the total amount of the 9,9-bis-[(4-phenylphenoxy)dibenzoyl]fluorene and the dibasic acid.

3. The method for preparing a high temperature resistant transparent modified polyamide according to claim 1, wherein: In step 1), the synthesis method of 9,9-bis-[(4-phenylphenoxy)dibenzoate]fluorene includes: a) mixing bisphenol fluorene, a base, and an organic solvent, heating for reaction, cooling for the first time, and then adding 4-chlorobenzonitrile for reaction; cooling the reaction product for the second time, adding it to an acid for precipitation, purifying, and drying to obtain a dicyanide; b) uniformly mixing the dicyanide obtained in step (a), a base, and an organic solvent, and heating for reaction; after cooling, adding the mixture to an acid, stirring, and filtering to obtain an aromatic dicarboxylic acid; dispersing the obtained aromatic dicarboxylic acid in an acid, heat-treating, filtering, rinsing, drying, and recrystallizing to obtain 9,9-bis-[(4-phenylphenoxy)dibenzoyl]fluorene.

4. The method for preparing a high-temperature resistant transparent modified polyamide according to claim 3, characterized in that: In step a), the heating reaction temperature is 105-115° C.; the first cooling is cooling to 98-102° C.; the molar ratio of bisphenol fluorene to 4-chlorobenzonitrile is 1:(2-3); after adding 4-chlorobenzonitrile, the reaction is continued for 2-4 hours; and the second cooling is cooling to room temperature.

5. The method for preparing a high temperature resistant transparent modified polyamide according to claim 3, wherein: In step b), the heating reaction temperature is 150-170° C., and the time is 1.5-2.5 hours; the heat treatment temperature is 75-85° C.; and the solvent for the recrystallization is dioxin.

6. The method for preparing a high temperature resistant transparent modified polyamide according to any one of claims 1 or 2, characterized in that: In step 1), the dibasic acid is selected from aromatic diacids and / or aliphatic diacids; and the diamine is selected from aliphatic diamines.

7. The method for preparing a high temperature resistant transparent modified polyamide according to claim 6, characterized in that: The dibasic acid is selected from one or more of dodecanedicarboxylic acid, isophthalic acid or naphthalene dicarboxylic acid; the diamine is selected from one or more of 4,4'-diaminodicyclohexylmethane, 3,3'-dimethyl-4,4'-diamino-dicyclohexylmethane, methylcyclohexanediamine or 1,3-cyclohexanedimethylamine (1,3-BAC).

8. The method for preparing a high temperature resistant transparent modified polyamide according to claim 1, wherein: In step 1), the molar ratio of the total amount of 9,9-bis-[(4-phenylphenoxy)dibenzoyl]fluorene and the dibasic acid to the diamine is 1:(0.9-1.1).

9. The method for preparing a high temperature resistant transparent modified polyamide according to claim 1, wherein: In step 1), the temperature of the esterification reaction is 180-240°C; in step 2), the temperature of the polycondensation reaction is 270-280°C.

10. Use of the polyamide obtained by the preparation method according to any one of claims 1 to 9 in the preparation of optical films, optical lenses, reflective protective films, optical fibers or liquid crystal displays.

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