Optical grade polycarbonate and its preparation method and application

Abstract

The present invention relates to the field of high-refractive polycarbonates and copolycarbonates, and discloses an optical-grade polycarbonate, its preparation method, and application. The polycarbonate comprises a structural unit represented by Formula I and / or a structural unit represented by Formula II; in Formula I, R1, R2, R3, and R4 are each independently selected from a hydrogen atom, a C1-C6 alkyl group, or a C6-C30 aryl group; in Formula II, R5 and R6 can each be independently selected from a hydrogen atom, a C1-C4 alkyl group, or a C6-C10 aryl group. The polycarbonate of the present invention combines the advantages of high refractive index, high Abbe number, high heat distortion temperature, and high molecular weight, and can meet the application requirements of high-precision optical instruments.

Description

Technical Field

[0001] The present invention relates to the field of high-refractive polycarbonate and copolycarbonate, in particular to an optical-grade polycarbonate and a preparation method and application thereof. Background Art

[0002] Polycarbonate containing 2,2-bis(4-hydroxyphenyl)propane (commonly known as bisphenol A) has excellent mechanical properties, dimensional stability, heat resistance, low water absorption, chemical resistance, and optical transparency, making it suitable for optical materials such as optical discs, transparent containers, optical films, optical lenses, and prisms. However, this resin has a refractive index of 1.58 and exhibits high birefringence, making it difficult to use in imaging and lens applications.

[0003] Patent CN102307930B discloses a polycarbonate material for optical lenses and a molding method thereof. The polycarbonate resin structure comprises a bisether fluorene and a structural unit represented by the general formula (A) The refractive index of the copolycarbonate is 1.64, which is higher than that of bisphenol A polycarbonate, but it does not meet the refractive index requirements in the field of lenses that require a higher refractive index.

[0004] Patent CN111630109A discloses a copolycarbonate with high refractive index and low Abbe number, wherein the polycarbonate resin contains bisether fluorene or phenyl bisether fluorene units and a structural unit represented by the general formula (B) wherein X represents an alkylene group having 1 to 4 carbon atoms, and a and b independently represent integers of 1 to 10. The refractive index of the polycarbonate resin can reach 1.675, and the Abbe number is 19. As can be seen from the manufacturing examples of the patent, the contributions of the (B) structural unit, phenyl bisether fluorene and bisether fluorene units in the copolymer to the refractive index decrease in sequence. It can be considered that the increase in the refractive index of the copolycarbonate is mainly caused by the (B) structural unit. However, the glass transition temperature of the copolycarbonate also decreases, thereby reducing the thermal deformation temperature of the component products made of the polycarbonate, thereby affecting the operating temperature limit. At the same time, the lower Abbe number makes the polycarbonate resin material more obviously dispersed in the application of the lens field. If it is used as a resin material for imaging lenses, due to its lower Abbe number, it is often necessary to combine more concave and convex lenses to correct chromatic aberration.

[0005] Patent CN112175178A discloses a polycarbonate resin comprising a bisether fluorene structure and a structural unit represented by the general formula (C) Wherein, X1 and X2 are each independently selected from a C1-C8 linear or branched alkylene group, a and b are each independently an integer of 1-10, R5 and R6 are each independently selected from a halogen, a substituted or unsubstituted C1-C6 linear or branched alkyl group, or a substituted or unsubstituted C6-C30 aryl group, and n1 and n2 are each independently an integer of 0-4. When X1 and X2 are ethylene, a and b are both 1, n1 and n2 are both 1, and R1 and R2 are naphthyl, and the polycarbonate resin obtained by copolymerization with bisetherfluorene can have a refractive index of 1.725 and an Abbe number of 21. However, the weight-average molecular weight of the copolycarbonate described in this patent is less than 14,000, making the material brittle and difficult to mold, making it difficult to apply.

[0006] Therefore, developing polycarbonate materials with high refractive index, high Abbe number, high heat deformation temperature and high molecular weight to meet their application requirements in high-precision optical instruments is a key research direction in the field of optical polycarbonate. Summary of the Invention

[0007] In view of the problems encountered in the prior art, the purpose of the present invention is to prepare a polycarbonate resin material with high refractive index, high glass transition temperature and high molecular weight to meet its application requirements as an optical resin in the field of optical components.

[0008] One of the objects of the present invention is to provide a polycarbonate comprising a structural unit represented by formula I and / or a structural unit represented by formula II;

[0009]

[0010] In formula I, R1, R2, R3, and R4 are each independently selected from a hydrogen atom, a C1-C6 alkyl group, or a C6-C30 aryl group;

[0011]

[0012] In formula II, R5 and R6 can be independently selected from hydrogen atom, C1-C4 alkyl group, and C6-C10 aryl group.

[0013] In the present invention, R1, R2, R3 and R4 can each be selected from a wide range. In a preferred embodiment of the present invention, in Formula I, R1, R2, R3 and R4 are each independently selected from a hydrogen atom, a C1-C4 straight-chain alkyl group, or a C6-C10 aryl group. Preferably, at least one of R1, R2, R3 and R4 is selected from a hydrogen atom.

[0014] In the present invention, R5 and R6 in Formula II can each be selected within a wide range. In a preferred embodiment of the present invention, R5 and R6 in Formula II are each independently selected from a hydrogen atom, a C1-C4 straight-chain alkyl group, or a C6-C10 aryl group. Preferably, at least one of R5 and R6 is selected from a hydrogen atom or a phenyl group, more preferably a phenyl group.

[0015] According to the present invention, the C1-C4 straight-chain alkyl group refers to at least one of a methyl group, an ethyl group, a n-propyl group, and a n-butyl group.

[0016] According to the present invention, the C6-C10 aryl group refers to a phenyl group and / or a naphthyl group.

[0017] In the present invention, the content range of each structural unit can be selected within a relatively wide range. In a preferred embodiment of the present invention, based on the total amount of the structural units as 100%, the proportion of the structural unit represented by formula I in the polycarbonate is 10-90 mol%, and the proportion of the structural unit represented by formula II is 10-90 mol%.

[0018] More preferably, based on 100% of the total amount of the structural units, the proportion of the structural units represented by formula I in the polycarbonate is 30-70 mol%; the proportion of the structural units represented by formula II is 30-70 mol%;

[0019] More preferably, based on 100% of the total amount of the structural units, the proportion of the structural units represented by formula I in the polycarbonate is 30-50 mol%; the proportion of the structural units represented by formula II is 50-70 mol%.

[0020] According to the present invention, more preferably, based on the total amount of structural units as 100%, the proportion of the structural units represented by Formula I in the polycarbonate is 30-50 mol%; for example, it can be 30 mol%, 40 mol%, 50 mol%, and any value between 30 mol% and 50 mol%, or any interval between any two values.

[0021] According to the present invention, more preferably, the proportion of the structural unit represented by Formula II is 50-70 mol%, based on the total amount of the structural units as 100%. For example, the proportion may be 50 mol%, 60 mol%, 70 mol%, or any value between 50 mol% and 70 mol%, or any interval between any two values.

[0022] Preferably, the sum of the molar ratio of the structural unit represented by formula I and the molar ratio of the structural unit represented by formula II is 100%.

[0023] Specifically, the content of the structural unit can be detected by conventional methods in the art, or can be calculated based on the feed amount. In the present invention, the content of the structural unit is calculated based on the feed amount.

[0024] In the present invention, the weight average molecular weight of the polycarbonate can be selected within a wide range. In a preferred embodiment of the present invention, the weight average molecular weight of the polycarbonate is 20,000-100,000, preferably 30,000-60,000, for example, 30,000, 40,000, 50,000, 60,000, and any two values ​​or any interval between any two values.

[0025] More preferably, the polycarbonate is prepared by reacting the dihydroxy compound of formula (1) and / or formula (2) with a carbonic acid diester compound in the presence of a catalyst through a melt transesterification polycondensation method;

[0026]

[0027] A second object of the present invention is to provide a method for preparing the polycarbonate described above, comprising reacting a dihydroxy compound in formula (1) and / or formula (2) with a carbonic acid diester compound in the presence of a catalyst by a melt transesterification polycondensation method;

[0028]

[0029] In the present invention, the carbonic acid diester compound can be selected from a wide range. In a preferred embodiment of the present invention, the carbonic acid diester compound is selected from at least one of dimethyl carbonate, diphenyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, ditolyl carbonate, dichlorophenyl carbonate and dicyclohexyl carbonate; preferably diphenyl carbonate.

[0030] In the present invention, the dihydroxy compound represented by formula (1) can be selected from a wide range, and R1, R2, R3, and R4 are each independently selected from a hydrogen atom, a C1-C6 alkyl group, or a C6-C30 aryl group. In a preferred embodiment of the present invention, R1, R2, R3, and R4 in formula (1) are each independently selected from a hydrogen atom, a C1-C4 straight-chain alkyl group, or a C6-C10 aryl group, preferably at least one of R1, R2, R3, and R4 is selected from a hydrogen atom. In the present invention, a compound monomer in which R1, R2, R3, and R4 are all hydrogen atoms is preferably used as the polymerization monomer, and this monomer is abbreviated as monomer 1.

[0031] In the present invention, R5 and R6 in formula (2) can be selected from a wide range. For example, R5 and R6 can be independently selected from a hydrogen atom, a C1-C4 alkyl group, or a C6-C10 aryl group. In a preferred embodiment of the present invention, R5 and R6 in formula (2) are independently selected from a hydrogen atom, a C1-C4 straight-chain alkyl group, or a C6-C10 aryl group. Preferably, at least one of R5 and R6 is selected from a hydrogen atom or a phenyl group, and more preferably a phenyl group.

[0032] In a more preferred embodiment of the present invention, the dihydroxy compound represented by formula (2) is at least one selected from 9,9'-bis[4-(2-hydroxyethoxy)phenyl]fluorene, 9,9'-bis[3-methyl-4-(2-hydroxyethoxy)phenyl]fluorene, 9,9'-bis[3-phenyl-4-(2-hydroxyethoxy)phenyl]fluorene, and 9,9'-bis[3-naphthyl-4-(2-hydroxyethoxy)phenyl]fluorene. In the present invention, 9,9'-bis[3-phenyl-4-(2-hydroxyethoxy)phenyl]fluorene, codenamed BPPEF, is preferred.

[0033]

[0034] In the present invention, the catalyst can be selected from a wide range. In a preferred embodiment of the present invention, the catalyst is selected from alkali metal compounds and alkaline earth metal compounds, preferably alkaline earth metal compounds. In the polycarbonate synthesis process, there are four known catalysts: alkali metal compounds, including organic acid salts, inorganic salts, oxides, hydroxides, hydrides or alkoxides of alkali metals, with the alkali metals mainly consisting of lithium, sodium, potassium and cesium; alkaline earth metal compounds, including organic acid salts, inorganic salts, oxides, hydroxides, hydrides or alkoxides of alkaline earth metals, with the alkaline earth metals mainly consisting of magnesium, calcium, strontium and barium; nitrogen-containing compounds, mainly quaternary ammonium hydroxides and their salts, amines and the like; and transesterification catalysts, such as acetates, chlorides and organometallic complexes of zinc, tin, zirconium and lead. The preferred catalyst of the present invention is nano-magnesium oxide catalyst.

[0035] In the present invention, the molar ratio of the total amount of the dihydroxy compounds in formula (1) and formula (2) to the carbonate diester compound can be selected within a wide range. In a preferred embodiment of the present invention, the molar ratio of the total amount of the dihydroxy compounds in formula (1) and formula (2) to the carbonate diester compound is (0.98-1.02):1, preferably (0.98-1):1.

[0036] In the present invention, the molar ratio of the catalyst to the carbonic acid diester compound can be selected within a wide range. In a preferred embodiment of the present invention, the molar ratio of the catalyst to the carbonic acid diester compound is (0.01-0.1):100, preferably (0.02-0.05):100.

[0037] In a preferred embodiment of the present invention, the amount of the dihydroxy compound in formula (1) and formula (2) can be selected within a wide range. Preferably, the ratio of the two is such that in the resulting polymer: based on the total amount of structural units being 100%, the proportion of the structural unit represented by formula I in the polycarbonate is 10-90 mol%, and the proportion of the structural unit represented by formula II is 10-90 mol%; more preferably, based on the total amount of structural units being 100%, the proportion of the structural unit represented by formula I in the polycarbonate is 30-70 mol%; the proportion of the structural unit represented by formula II is 30-70 mol%; further more preferably, based on the total amount of structural units being 100%, the proportion of the structural unit represented by formula I in the polycarbonate is 30-50 mol%; and the proportion of the structural unit represented by formula II is 50-70 mol%.

[0038] The sum of the molar ratio of the structural unit represented by formula I and the molar ratio of the structural unit represented by formula II is 100%.

[0039] In a preferred embodiment of the present invention, the reaction process includes: performing an ester exchange reaction under heating conditions at normal pressure or reduced pressure, then removing small molecular by-products, and then performing a condensation reaction under heating and high vacuum to obtain a polycarbonate resin.

[0040] The specific reaction conditions of the present invention have a wide range of selection. Preferably, the reaction is first carried out at 160-240°C, preferably 180-200°C, for 0.5-6 hours, preferably 2-4 hours; then the decompression is increased and the temperature is raised to 210-220°C to remove small molecule by-products, and then the temperature is raised to 230-240°C and the decompression is reduced to below 1 Torr, preferably 0.1-0.5 Torr, for 0.5-1 hour, and then the reaction is continued under these conditions for 0.5-3 hours.

[0041] In a more preferred embodiment of the present invention, monomer 1 and BPPEF are used as dihydroxy compound monomers and diphenyl carbonate are used as catalysts to prepare polycarbonate by melt transesterification polycondensation method, and the molar ratio of dihydroxy compound to diphenyl carbonate is preferably 0.98-1.02, more preferably 1:1.

[0042] In a more preferred embodiment of the present invention, the melt transesterification polycondensation method uses the aforementioned raw material diphenyl carbonate and monomer 1 or BPPEF, or contains both monomer 1 and BPPEF, and a catalyst, to carry out an ester transesterification reaction under heating, normal pressure or reduced pressure, and remove by-products, and further carry out a polycondensation reaction under heating and high vacuum to obtain a polycarbonate resin.

[0043] Polycarbonate is usually prepared through a two-step process of transesterification and polycondensation. Specifically, the first step is carried out at a temperature of 160-240°C, preferably 180-200°C, for 0.5-6 hours, preferably 2-4 hours. Then, the degree of decompression is gradually increased, and the temperature is gradually raised to fully remove the by-products. After most of the by-products are removed, the temperature is raised to 240°C and the pressure is reduced to below 1 Torr for 0.5 hours. The reaction is then continued under these conditions for 0.2 hours. When the stirring reaches the predetermined torque value, the reaction is stopped and the material is discharged.

[0044] In a preferred embodiment of the present invention, the preparation method further comprises a post-treatment step. Preferably, the post-treatment step comprises: after the reaction is completed, N2 is introduced to restore the pressure in the reaction flask to normal, the product is dissolved using a first solvent such as dichloromethane, and after dissolution, the product is slowly poured into a beaker containing a second solvent such as anhydrous ethanol, and stirred to precipitate the product, washed with ethanol, and then vacuum dried.

[0045] According to the present invention, the present invention also provides a polycarbonate prepared according to the preparation method described above.

[0046] A third object of the present invention is to provide an application of the polycarbonate described above or the polycarbonate prepared by the preparation method described above in optical materials.

[0047] The weight average molecular weight of the polycarbonate material in the present invention is 20,000-100,000, preferably 30,000-60,000; more preferably 35,000-60,000, and even more preferably 38,000-45,000.

[0048] The glass transition temperature of the polycarbonate material in the present invention is 125-155°C, preferably 135-150°C.

[0049] The refractive index nD of the polycarbonate material in the present invention is 1.658-1.685, preferably 1.66-1.685, and more preferably 1.673-1.678.

[0050] The Abbe number v of the polycarbonate material in the present invention is 21-23, preferably 22-23.

[0051] The light transmittance of the polycarbonate material in the present invention is 87.5-89.5%, preferably 88%-89.5%, and more preferably 88.5-89.5%.

[0052] The haze of the polycarbonate material in the present invention is 1-7%, preferably below 3%, and more preferably 1-2.2%.

[0053] The above indicators can be detected by conventional methods in the art, or by the methods of the present invention. The detection methods of the above indicators in the present invention are detected by the methods in the specific embodiments of the present invention.

[0054] According to the above technical solution, the polycarbonate material provided by the present invention has the advantages of high refractive index, high Abbe number, high heat deformation temperature and high molecular weight, meeting its application requirements as an optical resin in the field of optical components.

[0055] The present invention aims to illustrate that developing polycarbonate materials with high refractive index, high Abbe number, high heat deformation temperature and high molecular weight to meet the application requirements of high-precision optical instruments is a key research direction in the field of optical polycarbonate.

[0056] Lenses for high-precision optical instruments often require materials with a weight-average molecular weight of 35,000 or higher, a glass transition temperature of 135°C or higher, a refractive index of 1.66 or higher, an Abbe number of 22 or higher, a transmittance of 88% or higher, and a haze of 3% or lower. Lenses for high-precision optical instruments require superior overall performance in their intended use environments; they cannot simply excel in a single performance metric at the expense of other properties. Molecular weight and glass transition temperature affect the ease of processing and molding, and thus the material's ultimate optical performance. A higher refractive index reduces lens thickness, thereby meeting instrument size requirements. A higher Abbe number reduces dispersion, which is beneficial for optical imaging. Current solutions combine lenses made from materials with varying Abbe numbers, increasing lens thickness and hindering the lightweight, compact design of precision instrument components. Haze affects image clarity; the lower the haze, the better. The examples presented here are based on pilot-scale results; better results will be achieved in large-scale production facilities.

[0057] The polycarbonate resin material of the present invention has the advantages of high refractive index, high glass transition temperature and high molecular weight, can meet the application requirements of it as an optical resin in the field of optical components, and has made great research progress. DETAILED DESCRIPTION

[0058] The present invention will be described in detail below with reference to specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by those skilled in the art to the present invention based on the contents of the present invention still fall within the scope of protection of the present invention.

[0059] 1. The samples used for performance evaluation were prepared using the following method:

[0060] (a) Membrane

[0061] 5 g of the obtained polycarbonate was dissolved in 40 ml of dichloromethane. After it was fully dissolved, it was coated on a small film coating sample making machine with the film thickness set to 0.02 mm. After the solvent evaporated at room temperature, the film sample was removed and placed for 2 hours for optical performance testing.

[0062] (b) Molded sheet

[0063] The injection molding method is adopted, the segment temperature of the injection molding machine is between 220-265℃, the mold temperature is 120-140℃, and the mold parameters are sheet thickness 1mm, length 2cm, and width 1cm.

[0064] 2. Evaluation is carried out using the following method

[0065] (1) Glass transition temperature (Tg)

[0066] The samples were subjected to DSC measurement using a TA DSC 2920 instrument in a nitrogen atmosphere (50 mL / min) at a temperature ramp rate of 10°C / min.

[0067] (2) Weight average molecular weight (Mw)

[0068] The number average molecular weight (Mn), weight average molecular weight (Mw), and molecular weight distribution index (PDI) were measured at 35°C using a Waters 1515 pump and a 2414 refractive index detector with two columns (PLgel 5 mm Mixed-C 300-7.5 mm). Chloroform was used as the eluent at a flow rate of 1 mL / min, and calibration was performed using polystyrene standards.

[0069] (3) Refractive index (nD)

[0070] The refractive index of samples (a) and (b) was measured at a wavelength of 589 nm on an Abbe refractometer (WYA (2WAJ)) at room temperature.

[0071] (4) Abbe number (v)

[0072] According to the method in (3), the refractive indices nC, nD and nF at wavelengths of 486 nm, 589 nm and 656 nm were measured at room temperature, and the Abbe number was calculated using the formula v = (nD-1) / (nF-nC).

[0073] (5) Light transmittance

[0074] Transmittance / Haze Meter Conduct a test.

[0075] (6) Haze

[0076] It is measured by the method in (5).

[0077] 3. The raw materials and preparation methods used in the following examples and comparative examples of the present invention are as follows:

[0078] 9,9'-Bis[3-phenyl-4-(2-hydroxyethoxy)phenyl]fluorene (BPPEF) was purchased from Huanghua Xinnuolixing Fine Chemical Co., Ltd.; diphenyl carbonate was a conventional chemical raw material; monomer 1 was synthesized in-house, and the others were conventional commercial products unless otherwise specified.

[0079] Preparation Example

[0080] The structural formula of monomer 1 is as follows:

[0081]

[0082] The preparation route of monomer 1 is as follows:

[0083]

[0084] Synthesis of compound V

[0085] 20.0 g (124.8 mmol) of naphthalene-1,3-diol, 150 ml of methanol, and 8 ml of hydrochloric acid were added to a three-necked flask, stirred, and heated under reflux to 80°C for 19 hours. The solvent was then removed. 100 ml of dichloromethane and saturated aqueous sodium bicarbonate were added. The organic phase was separated, the solvent was distilled off, and column chromatography was performed to obtain 18.2 g of intermediate V (yield: 85%).

[0086] Synthesis of compound IV

[0087] 9.2 g (53 mmol) of intermediate product V, 150 ml of dichloromethane and 12 ml of trimethylamine were added to a three-necked flask, stirred, cooled to 0°C, and 18 ml of trifluoromethanesulfonic anhydride was added dropwise. The mixture was stirred at room temperature for 15 h. After the reaction was completed, saturated aqueous sodium bicarbonate solution was added, the organic phase was separated and collected, the solvent was distilled off, and then 12.4 g of intermediate product IV was obtained by column chromatography. The yield was 75%.

[0088] Synthesis of compound III

[0089] 7.0 g (40.0 mmol) of intermediate V, 12.4 g (40.4 mmol) of intermediate IV, 100 ml of DMSO, 0.8 g (4.0 mmol) of CuI, 1.0 g (8.0 mmol) of pyridinic acid, and 1.8 g (8.4 mmol) of KPO were added to a three-necked flask, stirred, and heated at 120°C for 22 h. After completion of the reaction, 100 ml of saturated aqueous NaCl solution was added, the organic phase was separated, the solvent was distilled, and column chromatography was performed to obtain 6.8 g of intermediate III (yield: 52%).

[0090] Synthesis of compound II

[0091] 6.6 g (20.0 mmol) of intermediate III and 120 ml of dichloromethane were added to a three-necked flask, stirred, and cooled to 0°C. Then, 120 ml (120.0 mmol) of BBr (dissolved and diluted with 1 M dichloromethane) was slowly added dropwise. After the addition was complete, the mixture was warmed to room temperature and allowed to react for 8 hours. After completion of the reaction, 100 ml of saturated aqueous sodium bicarbonate solution was added, the organic phase was separated, the solvent was distilled off, and column chromatography was performed to obtain 5.8 g of intermediate II (95% yield).

[0092] Synthesis of Compound I

[0093] 5.8 g (19.0 mmol) of Compound II, 4.8 g (54.4 mmol) of ethylene carbonate, 0.6 g of potassium carbonate, and 100 ml of xylene were added to a three-necked reaction flask. After heating under reflux for 5 h, HPLC analysis revealed that the content of Compound II was less than 0.1% (its conversion rate reached 99.9%), and the reaction was stopped. The temperature was lowered to 50°C, 50 g of deionized water was added, and the mixture was stirred for 30 min. The mixture was allowed to stand for separation. The toluene phase was collected and the above steps were repeated until the aqueous phase was neutral. The organic toluene phase was then collected and dried over anhydrous Na2SO4, filtered hot, and the filtrate was collected, stirred, cooled, and crystallized to obtain 6.4 g of crude Compound I. The purity was 97.8% as determined by HPLC, and the yield was 85%. Recrystallization was performed using a mixed solvent of toluene and isopropanol in a ratio of 3:1 toluene to obtain 5.6 g of Compound I with a purity of 99.8% as determined by HPLC, meeting the polymerization requirements.

[0094] Example

[0095] Example 1:

[0096] 0.025 mol of 9,9'-bis[3-phenyl-4-(2-hydroxyethoxy)phenyl]fluorene (hereinafter sometimes referred to as "BPPEF"), 0.025 mol of diphenyl carbonate (hereinafter sometimes referred to as "DPC"), 6.7×10 -5 mol, placed in a 50ml three-necked flask, N2 was passed to replace the air in the system, and heated under N2 atmosphere. The temperature was gradually raised from room temperature to 140-160℃, and the reaction raw materials were completely melted into a colorless transparent liquid. The temperature was further raised to 180℃ and maintained for 0.5 hours. Subsequently, the pressure was slowly reduced to 100Torr over 0.5 hours, the temperature was gradually raised to 220℃, and the reaction was continued for 1 hour. Finally, the temperature was raised to 240℃, the pressure was reduced to below 1Torr over 0.5 hours, and the reaction was continued for 0.2 hours.

[0097] After the reaction is completed, N2 is introduced to restore the reaction flask to normal pressure. The product is dissolved with dichloromethane, slowly poured into a beaker filled with anhydrous ethanol, and stirred to precipitate the product. After washing with ethanol, it is vacuum dried at 100°C for 8 hours.

[0098] Example 2:

[0099] 0.025 mol of 9,9'-bis[4-(2-hydroxyethoxy)phenyl]fluorene (hereinafter sometimes referred to as "BPEF") diphenyl carbonate 0.025 mol, nano magnesium oxide 6.7×10 -5 mol, placed in a reaction flask, and the subsequent process was the same as Example 1.

[0100] Example 3:

[0101] 0.025 mol of monomer 1, 0.025 mol of diphenyl carbonate, 6.7×10 -5 mol, placed in a reaction flask, and the subsequent process was the same as Example 1.

[0102] Example 4:

[0103] 0.015 mol of BPEF and 0.035 mol of monomer 1 (Compound I obtained in the preparation example), 0.05 mol of diphenyl carbonate, 1.3×10 -4 mol, placed in a 100ml three-necked flask, N2 was passed to replace the air in the system, and heated under N2 atmosphere. The temperature was gradually raised from room temperature to the range of 140-160℃, and the reaction raw materials were completely melted into a colorless transparent liquid. The temperature was further raised to 180℃ and maintained for 0.5 hours. Subsequently, the pressure was slowly reduced to 100Torr over 0.5 hours, the temperature was gradually raised to 220℃, and the reaction was continued for 1.5 hours. Finally, the temperature was raised to 240℃, the pressure was reduced to below 1Torr over 0.5 hours, and the reaction was continued for 0.5 hours.

[0104] After the reaction is completed, N2 is introduced to restore the reaction flask to normal pressure. The product is dissolved with dichloromethane, slowly poured into a beaker filled with anhydrous ethanol, and stirred to precipitate the product. After washing with ethanol, it is vacuum dried at 100°C for 8 hours.

[0105] Example 5:

[0106] 0.015 mol of BPPEF, 0.035 mol of monomer 1, 0.05 mol of diphenyl carbonate, 1.3×10 -4 mol, placed in a reaction flask, and the subsequent process was the same as Example 4.

[0107] Example 6:

[0108] 0.025 mol of BPPEF, 0.025 mol of monomer 1, 0.05 mol of diphenyl carbonate, 1.3×10 -4 mol, placed in a reaction flask, and the subsequent process was the same as Example 4.

[0109] Example 7:

[0110] 0.035 mol of BPPEF, 0.015 mol of monomer 1, 0.05 mol of diphenyl carbonate, 1.3×10 -4 mol, placed in a reaction flask, and the subsequent process was the same as Example 4.

[0111] Example 8:

[0112] 0.045 mol of BPPEF, 0.005 mol of monomer 1, 0.05 mol of diphenyl carbonate, 1.3×10 -4 mol, placed in a reaction flask, and the subsequent process was the same as Example 4.

[0113] Comparative Example:

[0114] Comparative Example 1:

[0115] 0.025 mol of 2,2'-bis(2-hydroxyethoxy)-1,1'-binaphthyl (hereinafter sometimes referred to as "BNE"), 0.025 mol of diphenyl carbonate (hereinafter sometimes referred to as "DPC"), 6.7×10 -5 mol, placed in a 50ml three-necked flask, N2 was passed to replace the air in the system, and heated to 140-160°C under N2 atmosphere until the reaction raw materials were completely melted into a colorless transparent liquid. The temperature was further raised to 180°C and maintained for 0.5 hour. Subsequently, the pressure was slowly reduced to 100 Torr over 0.5 hour, the temperature was gradually increased to 220°C, and the reaction was continued for 1 hour. Finally, the temperature was raised to 240°C, the pressure was reduced to below 1 Torr over 0.5 hour, and the reaction was continued for 0.2 hour.

[0116] After the reaction is completed, N2 is introduced to restore the reaction flask to normal pressure. The product is dissolved with dichloromethane, slowly poured into a beaker filled with anhydrous ethanol, and stirred to precipitate the product. After washing with ethanol, it is vacuum dried at 100°C for 8 hours.

[0117] Comparative Example 2:

[0118] 0.025 mol of BNE, 0.025 mol of BPPEF, 0.05 mol of diphenyl carbonate (hereinafter sometimes referred to as "DPC"), 1.3×10 nano-magnesium oxide -4mol, placed in a 100ml three-necked flask, N2 was passed to replace the air in the system, and heated under N2 atmosphere. The temperature was gradually raised from room temperature to the range of 140-160℃, and the reaction raw materials were completely melted into a colorless transparent liquid. The temperature was further raised to 180℃ and maintained for 0.5 hours. Subsequently, the pressure was slowly reduced to 100Torr over 0.5 hours, the temperature was gradually raised to 220℃, and the reaction was continued for 1 hour. Finally, the temperature was raised to 240℃, the pressure was reduced to below 1Torr over 0.5 hours, and the reaction was continued for 0.2 hours.

[0119] After the reaction is completed, N2 is introduced to restore the reaction flask to normal pressure. The product is dissolved with dichloromethane, slowly poured into a beaker filled with anhydrous ethanol, and stirred to precipitate the product. After washing with ethanol, it is vacuum dried at 100°C for 8 hours.

[0120] Comparative Example 3

[0121] 0.025 mol of BNE, 0.025 mol of BPEF, 0.05 mol of diphenyl carbonate (hereinafter sometimes referred to as "DPC"), 1.3×10 -4 mol, placed in a 100ml three-necked flask, and the subsequent process was the same as Comparative Example 2.

[0122] Comparative Example 4

[0123] 0.015 mol of 2,2'-bis(2-hydroxyethoxy)-1,1'-thiobinaphthyl (hereinafter referred to as "BNSE"), 0.035 mol of BPEF, 0.05 mol of diphenyl carbonate (hereinafter referred to as "DPC"), 1.3×10 - 4 mol, placed in a 100ml three-necked flask, and the subsequent process was the same as Comparative Example 2.

[0124] Comparative Example 5

[0125] 0.0075 mol of 2,2'-bis(2-hydroxyethoxy)-1,1'-thiobinaphthyl (hereinafter referred to as "BNSE"), 0.0425 mol of BPEF, 0.05 mol of diphenyl carbonate (hereinafter referred to as "DPC"), 1.3×10 - 4 mol, placed in a 100ml three-necked flask, and the subsequent process was the same as Comparative Example 2.

[0126] The experimental results of the above embodiments and comparative examples are listed in Table 1.

[0127] Table 1

[0128]

[0129] The present invention aims to illustrate that developing polycarbonate materials with high refractive index, high Abbe number, high heat deformation temperature and high molecular weight to meet the application requirements of high-precision optical instruments is a key research direction in the field of optical polycarbonate.

[0130] Lenses for high-precision optical instruments often require a material with a weight-average molecular weight of over 35,000, a glass transition temperature of over 135°C, a refractive index of 1.66 or higher, an Abbe number of 22 or higher, a transmittance of over 88%, and a haze of less than 3% or better. Although the BNSE monomer and BPEF copolymerization scheme in patent CN112175178A achieves a molecular weight of over 25,000 under the catalyst conditions used in this patent, the molecular weight is still insufficient, resulting in insufficient mechanical strength for the molded parts, significant material loss in the finished product, and an insufficient refractive index. As a lens material for high-precision optical instruments, its operating environment requires superior overall performance; it cannot simply excel in a single performance indicator while sacrificing other properties. Molecular weight and glass transition temperature affect the ease of processing and molding a material, and thus its ultimate optical performance. A higher refractive index reduces lens thickness, thereby meeting instrument size requirements. A higher Abbe number reduces dispersion, which is more beneficial for optical imaging. Currently, some solutions combine lenses made from materials with different Abbe numbers, increasing lens thickness and hindering the lightweight, compact size of precision instrument components. Haze affects image clarity; the lower the haze, the better. The examples presented here are based on small-scale test results; larger-scale process equipment will yield even better experimental results.

[0131] As shown in Table 1, the comprehensive indicators of the products in the examples of the present invention are significantly superior to those in the comparative examples. In particular, the products in Examples 5-8 of the present invention meet the performance requirements of lenses for high-precision optical instruments. This indicates that the polycarbonate resin material of the present invention combines the advantages of high refractive index, high glass transition temperature, and high molecular weight, meeting the application requirements of optical resins in the field of optical components. In particular, the products in Examples 6 and 7 surpass the conventional requirements for optical polycarbonate materials for lenses in terms of refractive index, Abbe number, transmittance, and haze, demonstrating significant research progress.

[0132] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation of the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same function.

[0133] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings conventionally understood by those skilled in the art. In the event of conflict, the definitions in this specification shall prevail.

[0134] When this specification uses the prefix "well known to those skilled in the art", "prior art" or similar terms to introduce materials, substances, methods, steps, devices or components, the objects introduced by the prefix include those commonly used in the art when this application is filed, but also include those that are not commonly used at present but will become generally recognized in the art to be suitable for similar purposes.

[0135] The endpoints and any values ​​of the ranges disclosed in this application document are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and a separate point value, and the separate point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered as specifically disclosed in this article. Hereinafter, in principle, each technical solution can be combined with each other to obtain a new technical solution, which should also be considered as specifically disclosed in this article.

[0136] In the context of this specification, any matters or items not mentioned are directly applicable to those known in the art without any changes except those explicitly stated.

[0137] Moreover, any embodiment described herein may be freely combined with one or more other embodiments described herein, and the technical solutions or technical ideas thus formed shall be deemed as part of the original disclosure or original record of the present invention, and shall not be regarded as new content that has not been disclosed or anticipated herein, unless a person skilled in the art considers that the combination is obviously unreasonable.

Claims

1. A polycarbonate comprising a structural unit represented by Formula I and a structural unit represented by Formula II; In formula I, R1, R2, R3, and R4 are each independently selected from a hydrogen atom; In formula II, R5 and R6 are each independently selected from phenyl; The proportion of the structural unit represented by formula I in the polycarbonate is 30-70 mol%; the proportion of the structural unit represented by formula II is 30-70 mol%; The weight average molecular weight of the polycarbonate is 38,000-45,000; The polycarbonate has a glass transition temperature of 135-150° C., a refractive index nD of 1.673-1.678, an Abbe number v of 22-23, a light transmittance of 88.5-89.5%, and a haze of 1-2.2%.

2. The polycarbonate according to claim 1, wherein: The proportion of the structural unit represented by Formula I in the polycarbonate is 30-50 mol %; the proportion of the structural unit represented by Formula II is 50-70 mol %.

3. A method for preparing the polycarbonate according to any one of claims 1 to 2, comprising reacting the dihydroxy compound of formula (1) and formula (2) with a carbonic acid diester compound in the presence of a catalyst by a melt transesterification polycondensation method; Formula (1); In formula (1), R1, R2, R3, and R4 are each independently selected from a hydrogen atom; Formula (2); In formula (2), R5 and R6 are each independently selected from phenyl.

4. The preparation method according to claim 3, wherein: The carbonic acid diester compound is at least one selected from dimethyl carbonate, diphenyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, ditolyl carbonate, dichlorophenyl carbonate and dicyclohexyl carbonate; and / or, The dihydroxy compound represented by formula (2) is selected from 9,9'-bis[3-phenyl-4-(2-hydroxyethoxy)phenyl]fluorene; and / or The catalyst is selected from alkali metal compounds and alkaline earth metal compounds.

5. The preparation method according to claim 3, wherein: The carbonic acid diester compound is selected from diphenyl carbonate; and / or, The catalyst is selected from nano magnesium oxide catalyst.

6. The preparation method according to claim 3, wherein: The molar ratio of the total amount of the dihydroxy compound in formula (1) and formula (2) to the carbonic acid diester compound is (0.98-1.02):1; and / or, The molar ratio of the catalyst to the carbonic acid diester compound is (0.01-0.1):

100.

7. The preparation method according to claim 3, wherein: The molar ratio of the total amount of the dihydroxy compound in formula (1) and formula (2) to the carbonic acid diester compound is (0.98-1):1; and / or, The molar ratio of the catalyst to the carbonic acid diester compound is (0.02-0.05):

100.

8. The preparation method according to claim 3, wherein: The reaction process includes: performing an ester exchange reaction under heating conditions and normal pressure or reduced pressure, then removing small molecular by-products, and then performing a condensation reaction under heating and high vacuum to prepare a polycarbonate resin.

9. The preparation method according to claim 8, characterized in that: The reaction process includes: First, react at 160-240°C for 0.5-6 hours; then increase the pressure reduction and raise the temperature to 210-220°C to remove small molecular by-products, then raise the temperature to 230-240°C and reduce the pressure to below 1 Torr for 0.5-1 hour, and then continue the reaction under these conditions for 0.5-3 hours.

10. The preparation method according to claim 8, characterized in that: The reaction process includes: First, react at 180-200°C for 2-4 hours; then increase the pressure reduction and raise the temperature to 210-220°C to remove small molecule by-products, then raise the temperature to 230-240°C and reduce the pressure to 0.1-0.5 Torr for 0.5-1 hour, and then continue the reaction under these conditions for 0.5-3 hours.

11. Use of the polycarbonate according to any one of claims 1 to 2 or the polycarbonate prepared by the preparation method according to any one of claims 3 to 10 in optical materials.

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