A copolycarbonate and its preparation method

Abstract

The present invention provides a copolycarbonate and a method for preparing the same. Specifically, it relates to a novel copolymer containing a biopolysaccharide segment and a polycarbonate segment in the molecular chain, and a method for preparing the same. The copolymer has a novel structure, in which the biopolysaccharide segment and the quaternary amine segment are introduced into the polycarbonate segment through copolymerization. The resulting copolycarbonate significantly improves the antibacterial properties, biocompatibility, and impact resistance of conventional polycarbonates. The copolymer is prepared by copolymerizing a comonomer and a polycarbonate oligomer in the presence of a catalyst. The copolymer is simple to operate, easy to implement, and can be used in industrial production.

Description

Technical Field

[0001] The present invention belongs to the field of polymer materials, and in particular relates to a copolycarbonate and a preparation method thereof. Background Art

[0002] Polycarbonate (PC), one of the five major engineering plastics, possesses excellent mechanical properties, impact toughness, high light transmittance, dimensional stability, heat resistance, and electrical insulation properties. It is widely used in the automotive industry, electronics, optical discs, mechanical parts, healthcare, and office supplies. However, conventional polycarbonate also has certain drawbacks. For example, when polycarbonate materials are used in the electronics and home appliance industries, they inevitably come into contact with germ-laden human bodies and objects during daily use, and thus may be contaminated and breed various pathogens on the surface, which is detrimental to user health. Directly adding antimicrobial agents and fillers can negatively impact the compatibility of polycarbonate and damage its mechanical properties. Therefore, for better application in this field, it needs to be modified.

[0003] Chinese patent CN107759997A discloses a wear-resistant, flame-retardant, and antibacterial polycarbonate composition. This invention improves the antibacterial properties of the polycarbonate by directly adding silver ion nano-antibacterial agents, silver ion calcium phosphate, and silver ion antibacterial zeolite. Chinese patent CN111320857A discloses an antistatic, antibacterial, and flame-retardant PC / ABS composition. This invention directly adds a silver ion antibacterial agent and produces an antibacterial polycarbonate product by twin-screw extrusion with polycarbonate. Currently, the antibacterial properties of polycarbonate are improved by adding antibacterial agents through blending. However, the addition of fillers often impairs the compatibility of the polycarbonate material, resulting in mechanical defects and reduced mechanical properties.

[0004] In summary, with the expansion of the application of polycarbonate in electronic and electrical appliances, there is a need to improve the antibacterial properties of polycarbonate while retaining the original excellent properties. Summary of the Invention

[0005] The object of the present invention is to provide a copolycarbonate, which improves the antibacterial properties, biocompatibility and impact resistance of polycarbonate materials, broadens the application field of polycarbonate materials, and the molecular weight of the prepared copolycarbonate can be controlled. The method is simple in steps and is easy to implement industrially.

[0006] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0007] A copolycarbonate, comprising at least a polycarbonate segment structure represented by formula (I) and a bio-based polysaccharide structure represented by formula (II):

[0008]

[0009] Optionally, the copolycarbonate further comprises a structure of formula (III):

[0010]

[0011] Wherein, R1, R2 and R3 are each independently one of hydrogen, methyl, ethyl, phenethyl and phenylpropyl, preferably methyl; and n is an integer of 8 to 20.

[0012] In the present invention, the polycarbonate segment of formula (I) in the copolycarbonate is 85-99 wt%, the bio-based polysaccharide segment of formula (II) is 1-10 wt%, and the quaternary ammonium salt segment of formula (III) is 0-5 wt%.

[0013] In the present invention, the weight average molecular weight of the copolycarbonate is 20,000 to 55,000 g / mol.

[0014] Another object of the present invention is to provide a method for preparing copolycarbonate.

[0015] A method for preparing a copolycarbonate, wherein the method prepares the above-mentioned copolycarbonate, and the method comprises the following steps:

[0016] S1: mixing a diphenolic hydroxy compound, a capping agent, an alkali metal hydroxide, and water, and dissolving them to form an aqueous phase A;

[0017] S2: introducing phosgene into a mixer filled with an inert organic solvent to prepare phosgene solution B;

[0018] S3: mixing the bio-based polysaccharide containing the structure of formula (II) with an ionic liquid solvent to prepare a comonomer solution C;

[0019] S4: adding phosgene solution B to aqueous phase A for polymerization reaction, controlling the pH value of the system, and reacting to obtain an oligomer polycarbonate emulsion; separating the aqueous phase, taking out the oil phase, adding comonomer solution C to the oil phase, adding a catalyst, and reacting to obtain a polycarbonate solution D;

[0020] S5: Purifying and removing the solvent from the polycarbonate solution D to obtain the target product.

[0021] In the present invention, the diphenol hydroxy compound described in S1 is one or more of 2,2-bis(4-hydroxyphenyl)propane, 4,4'-dihydroxydiphenylpropane, bis(4-hydroxyphenyl)methane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)methane, 1,3-bis[2-(4-hydroxyphenyl)-2-propyl]benzene and 1,1-bis(4-hydroxyphenyl)cyclohexane.

[0022] In the present invention, the end-capping agent in S1 is one or more of phenol, p-tert-butylphenol, p-methylphenol, hydroquinone, resorcinol, o-methylhydroquinone, o-ethylhydroquinone, 2-methylresorcinol, phenylethylresorcinol and benzylparaben.

[0023] In the present invention, the alkali metal hydroxide in S1 is one or more of sodium hydroxide, potassium hydroxide, lithium hydroxide and cesium hydroxide.

[0024] In the present invention, the molar ratio of the diphenolic hydroxy compound, the capping agent, the alkali metal hydroxide and water in S1 is 1: (0.01-0.08): (2.0-3.0): (20-50).

[0025] In the present invention, the inert solvent described in S2 is one or more of dichloroethane, dichloromethane, trichloroethane, tetrachloroethane, pentachloroethane, toluene, dichloroethylene and chlorobenzene.

[0026] In the present invention, in the phosgene solution described in S2, the weight ratio of phosgene to inert organic matter is 1:(10-40).

[0027] In the present invention, the bio-based polysaccharide described in S3 is one or more of chitosan, glucan, lignin, cellulose (MCC) and sodium alginate, preferably one or more of chitosan, glucan, lignin, cellulose and sodium alginate modified with quaternary ammonium salt, more preferably quaternary ammonium salt modified cellulose (FMCC), which has the following structure:

[0028]

[0029] In one embodiment, the quaternary ammonium salt-modified cellulose is prepared by the following steps:

[0030] SS1: Ultrasonic grinding of cellulose and alkali metal solution, adding epichlorohydrin, removing the remaining alkali metal solution after the reaction, and washing with solvent;

[0031] SS2: Add aliphatic amine to the SS1 product, filter, wash with water, and acid-wash after the reaction to obtain quaternized microcrystalline cellulose (FMCC).

[0032] In the present invention, the mass ratio of cellulose to epichlorohydrin in the SS1 is 1:(20-50).

[0033] In the present invention, the ultrasonic pulverization time in SS1 is 30 to 60 minutes.

[0034] In the present invention, the reaction temperature of SS1 is 60-80° C. and the reaction time is 6-8 h.

[0035] In the present invention, the aliphatic amine in SS2 is one or more of dodecylamine, octaamine, and octadecylamine, preferably dodecylamine.

[0036] In the present invention, the reaction temperature of SS2 is 70-90° C. and the reaction time is 2-4 h.

[0037] In the present invention, the ratio of the bio-based polysaccharide to the ionic liquid solvent in S3 is 1:(15-20).

[0038] In the present invention, the ionic liquid solvent described in S3 is one or more of 1-allyl-3-methylimidazolium chloride ([AMIM]Cl), 1-butyl-3-methylimidazolium chloride ([Bmim]Cl), 1-ethyl-3-methylimidazolium chloride ([EMIM]Cl) and 1-ethyl-3-methylimidazolium acetate ([Emim]Ac), preferably 1-allyl-3-methylimidazolium chloride.

[0039] In the present invention, the pH of the system is controlled to be 11-13 using an alkali metal hydroxide aqueous solution in S4.

[0040] In the present invention, the S4 is reacted at 25-35° C. for 0.2-0.8 h to obtain an oligomer polycarbonate emulsion.

[0041] In the present invention, the catalyst in S4 is one or more of triethylamine, trimethylbenzylammonium chloride and tetra-n-butylammonium bromide; preferably, the molar ratio of the catalyst is 0.1 to 0.5% of the diphenol hydroxy compound.

[0042] In the present invention, S4 is reacted for 1-2 hours to obtain a polycarbonate solution.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] The bio-based polysaccharide copolycarbonate of the present invention improves the antibacterial performance of the polycarbonate material to more than 95%, has relatively good biocompatibility, and has an impact resistance of 750 J / m, thereby broadening the application field of the polycarbonate material. The molecular weight of the prepared copolycarbonate can be controlled between 22,000 and 44,000 g / mol, and the method is simple in steps, making it easy to implement industrially. DETAILED DESCRIPTION

[0045] The present invention can be better understood based on the following examples, but the content of the present invention is not limited to the following examples. In addition, it should be understood that after reading the content of the present invention, those skilled in the art can make some non-essential changes or adjustments to the present invention and still fall within the scope of protection of the present invention.

[0046] The main raw material information involved in the present invention is as follows:

[0047] Drug name effect Drug specifications Drug origin Bisphenol A monomer analytically pure MacLean Chemical Technology Co., Ltd. Triethylamine catalyst analytically pure Shanghai Titan Technology Co., Ltd. cellulose Comonomer analytically pure Tianjin Fuchen Chemical Reagent Factory 4-tert-Butylphenol Capping agent analytically pure Beijing Inokai Technology Co., Ltd. 1-Allyl-3-methylimidazolium chloride solvent analytically pure Beijing Inokai Technology Co., Ltd. Epichlorohydrin solvent analytically pure MacLean Chemical Technology Co., Ltd. dichloromethane solvent analytically pure MacLean Chemical Technology Co., Ltd. Dodecyl tertiary amine Grafting agent analytically pure MacLean Chemical Technology Co., Ltd.

[0048] The main experimental equipment and instruments involved in the present invention are as follows:

[0049] Device Name model supplier Twin-screw extruder RXT26-900-22-58 Nanjing Ruiya Co., Ltd. Injection molding machine MA900IIS / 280 Ningbo Haitian Co., Ltd. Gel chromatography 1260GPC Agilent Technologies Inc. Stretching machine Instron-5966 Instron Corporation Impact testing machine HIT25P PIUS Instron Corporation Scanning electron microscopy JST-4800 Japan JOEL Co., Ltd.

[0050] The analysis and evaluation methods involved in the embodiments or comparative examples are as follows:

[0051] (1) Molecular weight was determined by GPC using a Waters 1515 gel permeation chromatography instrument with dichloromethane as the mobile phase at room temperature for 20 min.

[0052] (2) Antibacterial performance The antibacterial rate was tested according to GB / T 31402-2015 standard, and the experimental bacteria was Escherichia coli;

[0053] (3) Impact resistance is tested according to ASTM D256-1997.

[0054] Example 1

[0055] 342 g of bisphenol A, 375 g of sodium hydroxide, 540 g of water, and 3.375 g of p-tert-butylphenol were added to a reactor protected by nitrogen to form a sodium bisphenol A salt phase; 223 g of phosgene was dissolved in 2230 g of dichloromethane to form an oil phase;

[0056] 3.6 g of chitosan was added to 200 ml of a 32 wt% NaOH solution and ultrasonically crushed for 30 min. Then, 72 g of epichlorohydrin was added. The temperature was maintained at 60° C. and the reaction time was 8 h. The NaOH solution was removed. 3.6 g of dodecylamine was added to the obtained product. The temperature was maintained at 70° C. and the reaction time was 4 h. The product was taken out, filtered, washed with water, and acid washed to obtain quaternized chitosan.

[0057] 6.97 g of quaternized chitosan was dissolved in 104.70 g of 1-allyl-3-methylimidazolium chloride to form a comonomer solution;

[0058] Pour the sodium bisphenol A water phase into the polymerization reactor, add the phosgene solution into the reactor under stirring at 350 rpm, maintain the pH of the reaction system at about 12 by adding 32 wt % sodium hydroxide aqueous solution, and maintain the temperature of the reaction system at 25° C.

[0059] After the reaction was allowed to proceed for 0.5 h, the upper aqueous phase was separated and the chitosan comonomer solution was slowly added dropwise to the oil phase, and 0.15 g of triethylamine was added to react.

[0060] After 0.2 h of reaction, the copolycarbonate was obtained by separation, purification, washing, and drying. GPC analysis of the sample showed a weight average molecular weight of 51,048 and a molecular weight distribution of 1.73.

[0061] Example 2

[0062] 230 g of bisphenol A, 375 g of sodium hydroxide, 500 g of water, and 7.52 g of phenol were added to a reactor protected by nitrogen to form a sodium bisphenol A salt phase; 108.9 g of phosgene was dissolved in 4356 g of dichloromethane to form an oil phase;

[0063] 26.44 g of glucose was added to 1468 ml of a 32 wt% NaOH solution, and ultrasonically crushed for 60 min. Then, 1322 g of epichlorohydrin was added, and the temperature was maintained at 80° C. The reaction time was 6 h. The NaOH solution was removed, and 7.93 g of octaamine was added to the obtained product. The temperature was maintained at 80° C. The reaction time was 2 h. The product was taken out, filtered, washed with water, and acid washed to obtain quaternized glucose.

[0064] 34.36 g of quaternized glucose was dissolved in 515.52 g of 1-allyl-3-methylimidazolium chloride to form a comonomer solution;

[0065] Pour the sodium bisphenol A water phase into the polymerization reactor, add the phosgene solution into the reactor under stirring at 350 rpm, maintain the pH of the reaction system at about 12 by adding 32 wt % sodium hydroxide aqueous solution, and maintain the temperature of the reaction system at 35° C.

[0066] After 0.5 h of reaction, the upper aqueous phase was separated and the glucose comonomer solution was slowly added dropwise to the oil phase, and 1.61 g of tetra-n-butylammonium bromide was added to react;

[0067] After 0.8 h of reaction, the copolycarbonate was obtained by separation, purification, washing, and drying. GPC analysis of the sample showed a weight average molecular weight of 22,185 and a molecular weight distribution of 1.75.

[0068] Example 3

[0069] 384 g of bis(4-hydroxyphenyl)methane, 375 g of sodium hydroxide, 300 g of water, and 13.24 g of p-methylphenol were added to a reactor protected by nitrogen to form a sodium bisphenol A salt phase; 108.9 g of phosgene was dissolved in 3267 g of dichloromethane to form an oil phase;

[0070] 21.5 g of cellulose was added to 1195 ml of a 32 wt% NaOH solution and ultrasonically crushed for 50 min. Then, 645 g of epichlorohydrin was added, the temperature was maintained at 80° C., and the reaction time was 6 h. The NaOH solution was removed, and 21.5 g of octadecylamine was added to the obtained product. The temperature was maintained at 80° C. and the reaction time was 2 h. The product was taken out, filtered, washed with water, and acid washed to obtain quaternized microcrystalline cellulose (FMCC).

[0071] 42.67 g of MCC was dissolved in 768.0 g of 1-allyl-3-methylimidazolium chloride to form a comonomer solution;

[0072] Pour the sodium bisphenol A water phase into the polymerization reactor, add the phosgene solution into the reactor under stirring at 350 rpm, maintain the pH of the reaction system at about 12 by adding 32 wt % sodium hydroxide aqueous solution, and maintain the temperature of the reaction system at 28° C.

[0073] After the reaction was continued for 0.5 h, the upper aqueous phase was separated and the MCC comonomer solution was slowly added dropwise to the oil phase, and 0.558 g of trimethylbenzyl ammonium chloride was added to react;

[0074] After 0.5 h of reaction, the copolycarbonate was obtained by separation, purification, washing, and drying. GPC analysis of the sample showed a weight average molecular weight of 28,970 and a molecular weight distribution of 1.41.

[0075] Example 4

[0076] 228g of bisphenol A, 250g of sodium hydroxide, 300g of water, and 4.5g of p-tert-butylphenol were added to a reactor protected by nitrogen to form a sodium bisphenol A salt phase; 108.9g of phosgene was dissolved in 3267g of dichloromethane to form an oil phase;

[0077] 2.35 g of cellulose was added to 130.57 ml of a 32 wt% NaOH solution and ultrasonically crushed for 50 min. Then, 70.5 g of epichlorohydrin was added, the temperature was maintained at 80° C., and the reaction time was 6 h. The NaOH solution was removed, and 2.35 g of dodecylamine was added to the obtained product. The temperature was maintained at 80° C. and the reaction time was 2 h. The product was taken out, filtered, washed with water, and acid washed to obtain quaternized microcrystalline cellulose (FMCC).

[0078] 4.65 g of FMCC was dissolved in 83.76 g of 1-allyl-3-methylimidazolium chloride to form a comonomer solution;

[0079] Pour the sodium bisphenol A water phase into the polymerization reactor, add the phosgene solution into the reactor under stirring at 350 rpm, maintain the pH of the reaction system at about 12 by adding 32 wt % sodium hydroxide aqueous solution, and maintain the temperature of the reaction system at 28° C.

[0080] After the reaction was continued for 0.5 h, the upper aqueous phase was separated and the sodium alginate comonomer solution was slowly added dropwise to the oil phase, and 0.303 g of triethylamine was added to react;

[0081] After 0.5 h of reaction, the copolycarbonate was obtained by separation, purification, washing, and drying. GPC analysis of the sample showed a weight average molecular weight of 29,851 and a molecular weight distribution of 1.89.

[0082] Example 5

[0083] 228g of bisphenol A, 312.5g of sodium hydroxide, 300g of water, and 4.5g of p-tert-butylphenol were added to a reactor protected by nitrogen to form a sodium bisphenol A salt phase; 108.9g of phosgene was dissolved in 3267g of dichloromethane to form an oil phase;

[0084] 13.0 g of cellulose was added to 722.5 ml of a 32 wt% NaOH solution and ultrasonically crushed for 50 min. Then, 390 g of epichlorohydrin was added, the temperature was maintained at 80° C., and the reaction time was 6 h. The NaOH solution was removed, and 13.0 g of dodecylamine was added to the obtained product. The temperature was maintained at 80° C. and the reaction time was 2 h. The product was taken out, filtered, washed with water, and acid washed to obtain quaternized microcrystalline cellulose (FMCC).

[0085] 25.3 g of FMCC was dissolved in 456.0 g of 1-allyl-3-methylimidazolium chloride to form a comonomer solution;

[0086] Pour the sodium bisphenol A water phase into the polymerization reactor, add the phosgene solution into the reactor under stirring at 350 rpm, maintain the pH of the reaction system at about 12 by adding 32 wt % sodium hydroxide aqueous solution, and maintain the temperature of the reaction system at 28° C.

[0087] After 0.5 h of reaction, the upper aqueous phase was separated and the FMCC comonomer solution was slowly added dropwise to the oil phase, and 0.303 g of triethylamine was added to react;

[0088] After 0.5 h of reaction, the copolycarbonate was obtained by separation, purification, washing, and drying. GPC analysis of the sample showed a weight average molecular weight of 33,451 and a molecular weight distribution of 2.10.

[0089] Example 6

[0090] 228g of bisphenol A, 312.5g of sodium hydroxide, 300g of water, and 4.5g of p-tert-butylphenol were added to a reactor protected by nitrogen to form a sodium bisphenol A salt phase; 108.9g of phosgene was dissolved in 3267g of dichloromethane to form an oil phase;

[0091] 26.8 g of cellulose was added to 1489 ml of a 32 wt% NaOH solution and ultrasonically crushed for 50 min. Then, 804 g of epichlorohydrin was added, the temperature was maintained at 80° C., and the reaction time was 6 h. The NaOH solution was removed, and 13.4 g of dodecylamine was added to the obtained product. The temperature was maintained at 80° C. and the reaction time was 2 h. The product was taken out, filtered, washed with water, and acid washed to obtain quaternized microcrystalline cellulose (FMCC).

[0092] 40.2 g of FMCC was dissolved in 723.6 g of 1-allyl-3-methylimidazolium chloride to form a comonomer solution;

[0093] Pour the sodium bisphenol A water phase into the polymerization reactor, add the phosgene solution into the reactor under stirring at 350 rpm, maintain the pH of the reaction system at about 12 by adding 32 wt % sodium hydroxide aqueous solution, and maintain the temperature of the reaction system at 28° C.

[0094] After 0.5 h of reaction, the upper aqueous phase was separated and the FMCC comonomer solution was slowly added dropwise to the oil phase, and 0.303 g of triethylamine was added to react;

[0095] After 0.5 h of reaction, the copolycarbonate was obtained by separation, purification, washing, and drying. GPC analysis of the sample showed a weight average molecular weight of 38,589 and a molecular weight distribution of 1.63.

[0096] Comparative Example 1

[0097] 228g of bisphenol A, 312.5g of sodium hydroxide, 300g of water, and 4.5g of p-tert-butylphenol were added to a reactor protected by nitrogen to form a sodium bisphenol A salt phase; 108.9g of phosgene was dissolved in 3267g of dichloromethane to form an oil phase;

[0098] Pour the sodium bisphenol A salt phase into a polymerization reactor, add the phosgene solution into the reactor while stirring at 350 rpm, maintain the pH of the reaction system at about 12 by adding a 32 wt % sodium hydroxide aqueous solution, and maintain the temperature of the reaction system at 28° C.; add 0.303 g of triethylamine to carry out the reaction;

[0099] After 0.5 h of reaction, the copolycarbonate was obtained by separation, purification, washing, and drying. GPC analysis of the sample showed a weight average molecular weight of 30,015 and a molecular weight distribution of 1.56.

[0100] Comparative Example 2

[0101] The powder obtained in Comparative Example 1 was added with 5% by mass of FMCC by blending, and the mixture was added to a high-speed mixer and mixed at high speed for 5 minutes. The thoroughly mixed mixture was then placed in a twin-screw extruder with a length-to-diameter ratio of 40:1. The processing temperature was controlled at 260°C and the speed of the twin-screw extruder was controlled at 450 rpm for extrusion and granulation to obtain the product. The sample was analyzed by GPC, and its weight average molecular weight was 31,504, and the molecular weight distribution was 1.55.

[0102] The following are examples and comparative examples of the polycarbonate extrusion and injection molding process:

[0103]

[0104] Note: Compatibility is measured by observing the cross-sectional morphology using a scanning electron microscope. A indicates good, B indicates moderate, and C indicates poor.

[0105] From the above comparative data, it can be seen that compared with conventional polycarbonate, the copolymerized polycarbonate of the present invention has better impact resistance and very good antibacterial properties, as well as good compatibility, which will broaden the application field of polycarbonate.

Claims

1. A copolycarbonate, characterized in that The copolycarbonate comprises at least a polycarbonate segment structure and a bio-based polysaccharide segment as shown in formula (I): The bio-based polysaccharide is quaternary ammonium salt-modified cellulose FMCC; The quaternary ammonium salt-modified cellulose is prepared by the following steps: SS1: Ultrasonic grinding of cellulose and alkali metal solution, adding epichlorohydrin, removing the remaining alkali metal solution after the reaction, and washing with solvent; SS2: Add aliphatic amine to the SS1 product, filter, wash with water, and acid wash after the reaction to obtain quaternized microcrystalline cellulose FMCC.

2. The copolycarbonate according to claim 1, characterized in that The aliphatic amine is one or more of dodecylamine, octaamine and octadecylamine.

3. The copolycarbonate according to claim 1, characterized in that In the copolycarbonate, the polycarbonate segment of formula (I) accounts for 85-99 wt%, the bio-based polysaccharide segment accounts for 1-10 wt%, and the quaternary ammonium salt segment accounts for 0-5 wt%.

4. The copolycarbonate according to claim 1 or 2, characterized in that The weight average molecular weight of the copolycarbonate is 20,000 to 55,000 g / mol.

5. A method for preparing a copolycarbonate, wherein the method is for preparing the copolycarbonate according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: S1: 2,2-bis(4-hydroxyphenyl)propane, a capping agent, an alkali metal hydroxide, and water are mixed and dissolved to form an aqueous phase A; S2: introducing phosgene into a mixer filled with an inert organic solvent to prepare phosgene solution B; S3: mixing the bio-based polysaccharide with the ionic liquid solvent to prepare a comonomer solution C; S4: adding phosgene solution B to aqueous phase A for polymerization reaction, controlling the pH value of the system, and reacting to obtain an oligomer polycarbonate emulsion; separating the aqueous phase, taking out the oil phase, adding comonomer solution C to the oil phase, adding a catalyst, and reacting to obtain a polycarbonate solution D; S5: Purifying and removing the solvent from the polycarbonate solution D to obtain the target product.

6. The preparation method according to claim 5, characterized in that The end-capping agent in S1 is one or more of phenol, p-tert-butylphenol, p-methylphenol, hydroquinone, resorcinol, o-methylhydroquinone, o-ethylhydroquinone, 2-methylresorcinol, phenylethylresorcinol and benzylparaben; And / or, the alkali metal hydroxide in S1 is one or more of sodium hydroxide, potassium hydroxide, lithium hydroxide and cesium hydroxide; And / or, the molar ratio of the diphenol hydroxy compound, the capping agent, the alkali metal hydroxide and water in S1 is 1: (0.01-0.08): (2.0-3.0): (20-50).

7. The preparation method according to claim 5, characterized in that The inert organic solvent S2 is one or more of dichloroethane, dichloromethane, trichloroethane, tetrachloroethane, pentachloroethane, toluene, dichloroethylene and chlorobenzene; And / or, in the phosgene solution described in S2, the weight ratio of phosgene to inert organic is 1:(10-40).

8. The preparation method according to claim 5, characterized in that The ratio of the bio-based polysaccharide to the ionic liquid solvent in S3 is 1:(15-20).

9. The preparation method according to claim 5, characterized in that Said S4 uses an alkali metal hydroxide aqueous solution to control the system pH to 11-13; and / or, the step S4 is reacted at 25-35° C. for 0.2-0.8 h to obtain an oligomer polycarbonate emulsion; And / or, the catalyst in S4 is one or more of triethylamine, trimethylbenzylammonium chloride and tetra-n-butylammonium bromide; And / or, S4 is reacted for 1-2 hours to obtain a polycarbonate solution.

10. The preparation method according to claim 9, characterized in that The molar ratio of the catalyst used in S4 is 0.1 to 0.5% of the diphenol hydroxy compound.

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