A bio-based polycarbonate and its preparation method and application

Abstract

The present invention provides a bio-based polycarbonate and its preparation method and application, which uses isosorbide and diphenyl carbonate as raw materials, adds dimerized fatty acid with a cyclic structure for modification, first performs a prepolymerization reaction, and then performs a final polymerization reaction to obtain the bio-based polycarbonate; the molecular weight is ≥35000, and the glass transition temperature ( T g) ≤100℃, elongation at break ≥140%, impact strength ≥70kJ / m 2 The present invention uses the aliphatic carbon chain in the dimer fatty acid with a cyclic structure to give the dimer acid considerable flexibility. Integrating the dimer acid into the polycarbonate chain can increase the elasticity of the main chain, improve its processing performance, and reduce the processing temperature. The cyclic structure has rigidity, ensuring the high mechanical strength of the copolymer product. The addition of the dimer fatty acid helps to remove phenol, promotes the reaction, and the generated polycarbonate has a larger molecular weight.

Description

Technical Field

[0001] The present invention relates to bio-based materials, and in particular to a modified bio-based polycarbonate and a preparation method thereof. Background Art

[0002] Polycarbonate (PC) is a general term for polymer compounds containing carbonate groups in their molecular chains. It is a widely used engineering plastic in industry. Characterized by colorless transparency and excellent impact resistance and mechanical properties, it is widely used in building panels, electronics, office machinery, packaging, sports equipment, and other fields. It is also rapidly expanding into high-tech fields such as aerospace and optical discs. Polycarbonate can also be blended with other plastics to improve its solvent resistance and wear resistance.

[0003] In recent years, the synthesis of bio-based polycarbonates using isosorbide as a raw material has attracted widespread interest. Isosorbide (IS) can be produced from renewable resources (such as sugar) rather than petroleum-based feedstocks. As a raw material for polycarbonate, it can replace the controversial bisphenol A (BPA), meeting the requirements of green chemistry while also exhibiting superior optical properties.

[0004] Wang Tiantian et al. (Synthesis of isosorbide-based polycarbonate by melt transesterification [J]. Engineering Plastics Application, 2016(5):39-42.) used isosorbide and diphenyl carbonate as raw materials, and obtained isosorbide-based polycarbonate under the optimized conditions of polycondensation temperature of 245℃ and prepolymerization pressure of 0.03MPa under the catalysis of tetraethylammonium hydroxide. The product had good transparency, intrinsic viscosity of 34.61 mL / g, and Mn of 1.22×10 4 .

[0005] Shen Tao et al. (Study on the Synthesis of Isosorbide-Based Polycarbonate [J]. Modern Chemical Industry, 2017(8).) used isosorbide and diphenyl carbonate as the main raw materials and synthesized isosorbide-based polycarbonate by melt transesterification. The amount of catalyst lithium acetylacetonate was 13.5×10 -4 mol / (mol IS), the molar ratio of diphenyl carbonate to isosorbide was 1:1, the polycondensation temperature was 210°C, the prepolymerization temperature was 110°C, and the prepolymerization pressure was 0.04 MPa. The intrinsic viscosity of the obtained PIC was 46.72 mL / g, and the number average molecular weight was 1.98×10 4 , color difference is 3.89, glass transition temperature ( T g ) is 144℃.

[0006] However, the highly rigid molecular chain structure of IS leads to poor toughness, high melt viscosity, and difficulty in mechanical processing, hindering the development and promotion of PIC. Modification methods can improve the flowability of PIC, such as reducing the polymer molecular weight, adding flow promoters or polymer-compatible internal flow additives, and copolymerization. Copolymerization can enhance the flexibility of the molecular chain through structural design, improving the processing properties of PIC.

[0007] Chen Liu et al. (Study on the copolymerization modification of isosorbide-based polycarbonate [J]. Modern Chemical Industry, 2018, v.38; No.382(08):136-140) used LiAcac as a catalyst and isosorbide, aliphatic diols, and DPC as raw materials to synthesize a series of PIAC random copolymers through transesterification. The addition of linear diols promoted the growth of molecular chains, reduced the rigidity of the products, and improved their processability and toughness.

[0008] Li et al. (A non-phosgene process to homopolycarbonate and copolycarbonatesof

[0009] IS / aliphatic diol random copolycarbonate was synthesized by transesterification polycondensation with IS, aliphatic diol and dimethyl carbonate as raw materials. In order to improve the poor reactivity of IS hydroxyl group, dimethyl terephthalate was introduced into the reaction process. An IS-based PC / polybutylene terephthalate random copolymer was obtained by melt polycondensation. The glass transition temperature of the bio-based PC was 146℃.

[0010] However, in the above-mentioned copolymerization process, the auxiliary agent is a linear alcohol, and the modification of polycarbonate is mainly reflected in improving melt fluidity and enhancing its processing flow properties. Although the flexibility of PIC is improved to a certain extent, the mechanical strength and other properties are also greatly reduced, which also creates difficulties for industrial application. Summary of the Invention

[0011] In response to the shortcomings of the existing technology, the present invention provides a method for preparing modified bio-based polycarbonate. The method uses a bio-based dimer acid with a cyclic structure, isosorbide, and diphenyl carbonate as raw materials for melt copolymerization to produce a dimer fatty acid-modified bio-based polycarbonate. The flexible long-chain structure of the dimer fatty acid molecule is utilized to improve the processing fluidity of PC and reduce its low-temperature viscosity, thereby lowering its processing temperature (to below 100°C). At the same time, the rigid cyclic structure of the dimer acid ensures that the modified PC can retain good mechanical properties.

[0012] The technical purpose of the first aspect of the present invention is to provide a method for preparing bio-based polycarbonate, comprising the following steps:

[0013] Diphenyl carbonate (DPC), isosorbide (IS) and a copolymer modifier are mixed, an ionic liquid is added as a catalyst, and the temperature is raised under inert atmosphere until the raw materials are completely melted, and then the temperature is raised to 140-180° C., preferably 150-160° C., and maintained for 20-60 minutes, preferably 30-40 minutes, to allow a prepolymerization reaction to occur. Thereafter, the temperature is raised to 160-200° C., preferably 180-190° C., and maintained for 20-60 minutes, preferably 30-40 minutes, to allow a final polymerization reaction to occur, thereby obtaining the bio-based polycarbonate; wherein the copolymer modifier is a dimerized fatty acid having a cyclic structure.

[0014] Taking a dimerized fatty acid containing a single ring structure as an example, the reaction formula for the copolymerization to form a modified bio-based polycarbonate is as follows:

[0015]

[0016] In the above formula, the arrangement of the A group and the B group in the product is in no fixed order, and the content of a certain group in the product depends on the amount of each reaction raw material added.

[0017] Furthermore, the dimer fatty acid with a cyclic structure in the copolymer modifier accounts for no less than 50% by mass of the total dimer fatty acid, preferably no less than 70%, more preferably no less than 85%, and the cyclic structure is a monocyclic or bicyclic ring.

[0018] Furthermore, the dimer fatty acid is a homemade dimer fatty acid or a commercial dimer fatty acid. As one specific embodiment, the homemade dimer fatty acid is prepared from eleostearic acid as a raw material, in the presence of a polymerization inhibitor and a regulator, with stirring and nitrogen purging, and the temperature is raised to 180-230°C, preferably 200-220°C, for reaction; the reaction time is 2-7 hours, preferably 3-5 hours, to obtain the dimer fatty acid.

[0019] In the above-mentioned method for preparing a self-made dimerized fatty acid, the iodine value of the eleostearic acid is 140-160 g / 100 g, and the acid value is 150-200 mgKOH / g. The polymerization inhibitor can be selected from one or more of phenolic polymerization inhibitors, quinone polymerization inhibitors, and aromatic nitro compound polymerization inhibitors, preferably at least one of hydroquinone, p-benzoquinone, methylhydroquinone, tert-butylhydroquinone, and phenothiazine, preferably tert-butylhydroquinone and / or phenothiazine, and the amount used is 0.1%-2.0% of the mass of the eleostearic acid, preferably 0.5%-1.0%. The regulating agent comprises an alkyl quaternary ammonium salt and a lithium-containing compound, the mass ratio of the two being 1-3:1; the alkyl quaternary ammonium salt is at least one of tetradecyl ammonium chloride, hexadecyltrimethylammonium chloride, and octadecyltrimethylammonium chloride. The lithium-containing compound is at least one of lithium carbonate, lithium chloride, and lithium hydroxide. The amount of the regulator is 0.1%-1.0% of the mass of eleostearic acid, preferably 0.1%-0.5%. The stirring speed is 50-500rpm, preferably 200-400rpm. The nitrogen purge time is 1-30min, preferably 20-30min. Furthermore, a trace amount of nitrogen purge is maintained throughout the reaction, with a flow rate of 0.1-1.0mL / min, preferably 0.5-0.7mL / min, which is conducive to the reaction. After the reaction is completed, it is cooled, generally cooled to room temperature, i.e. 10-40°C. Furthermore, a trace amount of nitrogen purge is maintained during the cooling process, with a flow rate of 0.1-1.0mL / min, preferably 0.5-0.7mL / min.

[0020] By adopting the above method, a C36 unsaturated fatty acid dimer with a cyclic structure can be obtained, and its mass content is higher than 85%.

[0021] Furthermore, the amount of the dimer fatty acid having a cyclic structure added is 5-20%, preferably 10-15%, based on the total weight of DPC and IS.

[0022] Furthermore, the molar ratio of DPC to IS is 0.8:1-1.2:1, preferably 0.85-1:1.

[0023] Furthermore, the catalyst is selected from the group consisting of anions [BF4] - The ionic liquid is, more specifically, at least one of [Bmim][BF4], [C4mim][BF4], [C8mim][BF4] and [Rpy][BF4].

[0024] Furthermore, the amount of the catalyst used is 0.1%-10% by weight of isosorbide, preferably 2%-5%.

[0025] Furthermore, the pressure of the prepolymerization reaction is 0.05-0.1 MPa, preferably 0.06-0.08 MPa.

[0026] Furthermore, the pressure of the final polymerization reaction is 0.1-0.5 kPa, preferably 0.2-0.3 kPa.

[0027] Furthermore, after the final polymerization reaction, the method further includes a step of maintaining CO2 purge during the cooling process.

[0028] Furthermore, after the final polymerization reaction, the process further comprises the steps of adding a solvent to dissolve the product, filtering, and precipitating the product in the filtrate.

[0029] Furthermore, specifically, during post-processing of the final polymer product, dichloromethane is first added to dissolve the product, and then ethanol is added to obtain a precipitate, which is the bio-based polycarbonate. The mass ratio of the added dichloromethane to the crude product is 1:1-4:1, preferably 2:1-3:1. The ethanol and the filtrate are mixed in a mass ratio of 1:1-4:1, preferably 2:1-3:1.

[0030] Furthermore, the inert atmosphere is nitrogen, and the temperature is first raised to 80-110° C. to completely melt the raw materials, and maintained for 10-50 minutes, preferably 20-40 minutes.

[0031] The second aspect of the present invention is to provide a modified bio-based polycarbonate prepared by the above method. The polycarbonate prepared by the above method has a molecular weight of ≥35,000 and a glass transition temperature ( T g) ≤100℃, elongation at break ≥140%, impact strength ≥70kJ / m 2 .

[0032] The technical purpose of the third aspect of the present invention is to provide the application of the above-mentioned modified bio-based polycarbonate, which can be used in the fields of preparing electronic instrument product parts, food packaging materials, decoration and decorative materials.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] (1) Compared with isosorbide-based polycarbonate, the aliphatic carbon chain in the dimer fatty acid with a cyclic structure gives the dimer acid considerable flexibility. Incorporating the dimer acid into the polycarbonate chain can increase the elasticity of the main chain, improve its processing performance, and reduce the processing temperature; the cyclic structure is rigid, which ensures the high mechanical strength of the copolymer product.

[0035] (2) During the polycarbonate synthesis reaction, as the reaction proceeds, the viscosity of the generated product gradually increases, and the generated phenol is difficult to remove in the later stage. The addition of dimerized fatty acid has a certain flow agent effect, which helps to remove phenol and promote the reaction, resulting in a polycarbonate with a larger molecular weight.

[0036] (3) Ionic liquid catalysts have good chemical stability, are easily miscible with raw materials, and can effectively reduce the reaction temperature.

[0037] (4) Dimerized fatty acids are mainly derived from natural oils and fats, which are renewable resources and can be biodegraded, thus greatly retaining the bio-based advantages of isosorbide-based polycarbonate.

[0038] Other features and advantages of the present invention will be described in detail in the following detailed description. DETAILED DESCRIPTION

[0039] The following non-limiting examples may enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0040] The following examples further illustrate the preparation method and effects of the modified bio-based polycarbonate of the present invention. The examples are implemented based on the technical solutions of the present invention, and provide detailed implementation methods and specific operating processes. However, the scope of protection of the present invention is not limited to the following examples.

[0041] The experimental methods in the following examples, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, were purchased from conventional biochemical reagent stores.

[0042] The equipment model and analysis conditions used in the gas chromatography test in the present invention are as follows: sample preparation refers to GB / T17376 "Preparation of Animal and Vegetable Oils and Fatty Acid Methyl Esters"; the instrument uses Thermo DSQ II, and the chromatographic column uses Aglient DB-1HT; the conditions are: starting temperature 170°C, holding for 1 min, heating to 350°C at a rate of 5°C / min, holding for 5 min, injection port temperature 260°C, detector temperature 280°C, split ratio 20:1, and injection volume 1 µL.

[0043] The molecular weight of the polycarbonate in the embodiment of the present invention was obtained by GPC test: Agilent 1100 gel permeation chromatograph, polystyrene as a standard sample, THF as an eluent, elution rate of 1 mL / min, and test temperature of 20°C.

[0044] Glass transition temperature of the product in the embodiment T g The DSC test was carried out using METTLER TOLEDO DSC822, N2 atmosphere (40 mL / min), and a heating rate of 10 °C / min.

[0045] The tensile properties of the products in the examples were tested using an Instron 3365 universal testing machine (Instron). Sample preparation conditions were the same as for the DMA test, using dumbbell-shaped specimens measuring 10.0 mm long, 4.0 mm wide, and 2.0 mm thick. The tensile rate was set at 5 mm / min, and the spacing was set at 5 cm. The tensile strength, tensile modulus, and elongation at break values ​​are the averages of five or more specimens.

[0046] The notched impact test of the product in the embodiment was analyzed by a TA DMA-Q800 dynamic mechanical analyzer, using a single cantilever beam mode, a frequency of 1 Hz, an amplitude of 25 μm, a temperature of 0-200° C., and a heating rate of 3° C. / min.

[0047] In the following examples, the commercial dimer fatty acids used in Examples 1-8 were purchased from Shanghai Yien Chemical Technology Co., Ltd. The cyclic structure content was determined by GC-MS: the anti-wear agent product was first hydrogenated to saturate the double bonds in the molecule, followed by methyl esterification and GC-MS analysis. Testing revealed that the dimer fatty acids with cyclic structures accounted for 65% of the total weight of the commercial dimer acid.

[0048] Example 1

[0049] 193g DPC (0.9 mol), 146g IS (1 mol), and 78g commercial dimer fatty acid (50g of cyclic dimer fatty acid) were placed in a 1000mL three-necked flask, along with 7.3g [Bmim][BF4] catalyst. A nitrogen purge was performed for 25 minutes, followed by heating to 90°C with stirring for 30 minutes until all the raw materials were completely melted. The temperature was slowly raised to 160°C, and the reaction was stirred at a prepolymerization pressure of 0.06 MPa for 30 minutes. During the polycondensation stage, the temperature was raised to 190°C, the pressure was adjusted to 0.2 kPa, and the reaction was completed for 30 minutes. After the reaction was completed, the reaction was cooled to room temperature, dissolved in 743g dichloromethane, and filtered. The filtrate was added to 1487g ethanol, and the resulting precipitate was filtered to obtain the bio-based polycarbonate product.

[0050] After testing, the molecular weight of the polycarbonate product is 43,000. T g At 75℃, the elongation at break is 150% and the impact strength is 80kJ / m 2 .

[0051] Example 2

[0052] 214g DPC (1 mol), 146g IS (1 mol), and 55g commercial dimer acid (36g of a cyclic dimer fatty acid) were placed in a 1000mL three-necked flask, along with 2.92g of [Bmim][BF4] catalyst. A nitrogen purge was performed for 20 minutes, followed by heating to 90°C with stirring for 30 minutes until all the raw materials were melted. The temperature was slowly raised to 160°C, and the reaction was stirred at a prepolymerization pressure of 0.08 MPa for 30 minutes. During the polycondensation stage, the temperature was raised to 180°C, the pressure was adjusted to 0.2 kPa, and the reaction was completed for 30 minutes. After the reaction was completed, the reaction was cooled to room temperature, dissolved in 455g of dichloromethane, and filtered. The filtrate was added to 910g of ethanol, and the resulting precipitate was filtered to obtain the polycarbonate product.

[0053] After testing, the molecular weight of the polycarbonate product is 36,000. T g The temperature is 89℃, the elongation at break is 140%, and the impact strength is 72kJ / m 2 .

[0054] Example 3

[0055] 214g DPC (1 mol), 146g IS (1 mol), and 83g commercial dimer acid (54g of cyclic dimer fatty acid) were placed in a 1000mL three-necked flask, along with 7.3g of [Bmim][BF4] catalyst. A nitrogen purge was performed for 30 minutes, followed by heating to 90°C with stirring for 30 minutes until all the raw materials were melted. The temperature was slowly raised to 150°C, and the reaction was stirred at a prepolymerization pressure of 0.07 MPa for 40 minutes. During the polycondensation stage, the temperature was raised to 185°C, the pressure was adjusted to 0.3 kPa, and the reaction was completed for 40 minutes. After the reaction was completed, the reaction was cooled to room temperature, dissolved in 765g of dichloromethane, and filtered. The filtrate was added to 2297g of ethanol, and the resulting precipitate was filtered to obtain the polycarbonate product.

[0056] After testing, the molecular weight of the polycarbonate product is 39,000. T g The temperature is 83℃, the elongation at break is 145%, and the impact strength is 78kJ / m 2 .

[0057] Example 4

[0058] 171g DPC (0.8 mol), 146g IS (1 mol), and 97g commercial dimer acid (63g of a cyclic dimer fatty acid) were placed in a 1000mL three-necked flask, along with 5.84g of [Bmim][BF4] catalyst. A nitrogen purge was performed for 25 minutes, followed by heating to 90°C with stirring for 30 minutes until all the raw materials were melted. The temperature was slowly raised to 155°C, and the reaction was stirred at a prepolymerization pressure of 0.06 MPa for 35 minutes. During the polycondensation stage, the temperature was raised to 190°C, the pressure was adjusted to 0.3 kPa, and the reaction was completed for 40 minutes. After the reaction was completed, the reaction was cooled to room temperature, dissolved in 528g of dichloromethane, and filtered. The filtrate was added to 1586g of ethanol, and the resulting precipitate was filtered to obtain the polycarbonate product.

[0059] After testing, the molecular weight of the polycarbonate product is 38,000. T g The elongation at break is 153% at 78°C and the impact strength is 83kJ / m 2 .

[0060] Example 5

[0061] The preparation process and operating conditions are the same as those in Example 1, except that the catalyst used is [C4mim][BF4]. The molecular weight of the polycarbonate product is 41,000. T g The elongation at break is 146% at 77°C and the impact strength is 77kJ / m 2 .

[0062] Example 6

[0063] The preparation process and operating conditions are the same as those in Example 1, except that the catalyst used is [C8mim][BF4]. The molecular weight of the polycarbonate product is 40,000. T g The elongation at break is 146% at 78°C and the impact strength is 75kJ / m 2 .

[0064] Example 7

[0065] The preparation process and operating conditions are the same as those in Example 1, except that the catalyst used is [Rpy][BF4]. The molecular weight of the polycarbonate product is 39,000. T g At 80℃, the elongation at break is 142% and the impact strength is 73kJ / m 2 .

[0066] Example 8

[0067] The preparation process and operating conditions were the same as those in Example 1, except that a trace amount of CO2 was maintained during the cooling process at a flow rate of 0.7 mL / min. The molecular weight of the polycarbonate was determined to be 43,000. T g The elongation at break is 145% at 78°C and the impact strength is 78kJ / m 2 .

[0068] Example 9

[0069] The preparation process and operating conditions are the same as those in Example 1, except that homemade dimerized fatty acid is used. The preparation method is as follows:

[0070] Commercial eleostearic acid with an iodine value of 150 g / 100 g and an acid value of 180 mgKOH / g was used. 100 g of commercial eleostearic acid was placed in a 250 mL four-necked flask. 0.5 g of hydroquinone and 0.25 g of a modifier (tetradecyl ammonium chloride and lithium carbonate) were added in a 1:1 mass ratio. Nitrogen was purged for 30 minutes, stirring at 300 rpm, and the temperature was raised to 220°C for 4 hours. After completion, the reaction was cooled to room temperature in ice water to obtain a crude product. A two-stage molecular distillation process was employed: the first stage was conducted at a temperature of 150°C, a pressure of ≤4 Pa, and a scraping speed of 400 rpm. The primary distillation primarily removed unreacted monoacids. The heavy components after the primary distillation were then subjected to a secondary molecular distillation at a temperature of 150°C, a pressure of ≤4 Pa, and a scraping speed of 200 rpm to obtain the dimerized fatty acid. Testing revealed that the content of cyclic C36 unsaturated fatty acid dimers in the product was 90.5%.

[0071] The above dimer acid was used as a modifier to synthesize polycarbonate. The molecular weight of the polycarbonate was determined to be 47,000. T g The elongation at break is 160% at 72°C and the impact strength is 82kJ / m 2 .

[0072] Comparative Example 1

[0073] The preparation process and operating conditions are the same as those in Example 1, except that a conventional NaOH catalyst is used. Under the same reaction conditions, the molecular weight of the polycarbonate is 25,000. T g At 100℃, the elongation at break is 98% and the impact strength is 60kJ / m 2 .

[0074] Comparative Example 2

[0075] The preparation process and operating conditions were the same as those in Example 1, except that no dimer acid was added for copolymerization modification. Under the same reaction conditions, the obtained polycarbonate had a molecular weight of 29,000. Tg At 130℃, the elongation at break is 35% and the impact strength is 61kJ / m 2 .

[0076] Comparative Example 3

[0077] The preparation process and operating conditions were the same as those in Example 1, except that octadecane dioic acid without a ring structure was used instead of dimer fatty acid for copolymerization modification. Under the same reaction conditions, the obtained polycarbonate had a molecular weight of 35,000. T g is 73℃, the elongation at break is 152%, and the impact strength is 63kJ / m 2 .

Claims

1. A method for preparing a bio-based polycarbonate, comprising the following steps: Diphenyl carbonate, isosorbide and a copolymer modifier are mixed, an ionic liquid is added as a catalyst, and the temperature is raised under inert atmosphere until the raw materials are completely melted, and then the temperature is raised to 140-180° C. and maintained for 20-60 minutes to allow a prepolymerization reaction to occur, and then the temperature is raised to 160-200° C. and maintained for 20-60 minutes to allow a final polymerization reaction to occur, thereby obtaining the bio-based polycarbonate; The copolymer modifier is prepared by the following method: using eleostearic acid as a raw material, stirring while purging with nitrogen in the presence of a polymerization inhibitor and a regulator, heating to 180-230° C. for reaction for 2-7 hours to obtain a dimerized fatty acid; wherein the polymerization inhibitor is selected from at least one of hydroquinone, p-benzoquinone, methylhydroquinone, tert-butylhydroquinone and phenothiazine, and the amount used is 0.1%-2.0% of the mass of the eleostearic acid; the regulator comprises an alkyl quaternary ammonium salt and a lithium-containing compound, and the mass ratio of the two is 1-3:1, the alkyl quaternary ammonium salt is selected from at least one of tetradecyl ammonium chloride, hexadecyltrimethylammonium chloride and octadecyltrimethylammonium chloride, and the lithium-containing compound is selected from at least one of lithium carbonate, lithium chloride and lithium hydroxide, and the amount of the regulator is 0.1%-1.0% of the mass of the eleostearic acid; The copolymer modifier is a C36 unsaturated fatty acid dimer with a cyclic structure, and the mass content of the C36 unsaturated fatty acid dimer is higher than 85%.

2. The preparation method according to claim 1, characterized in that After the raw materials are melted, the temperature is raised to 150-160°C and maintained for 30-40 minutes to allow a prepolymerization reaction to occur, and then the temperature is raised to 180-190°C and maintained for 30-40 minutes to allow a final polymerization reaction to occur.

3. The preparation method according to claim 1, characterized in that Calculated on the basis of the C36 unsaturated fatty acid dimer having a cyclic structure, the added amount is 5-20% of the total weight of diphenyl carbonate and isosorbide.

4. The preparation method according to claim 3, characterized in that Calculated on the basis of the C36 unsaturated fatty acid dimer having a cyclic structure, the added amount is 10-15% of the total weight of diphenyl carbonate and isosorbide.

5. The preparation method according to claim 1, characterized in that The molar ratio of diphenyl carbonate to isosorbide is 0.8:1-1.2:

1.

6. The preparation method according to claim 1, characterized in that The catalyst is selected from the group consisting of anions [BF4] - of ionic liquids.

7. The preparation method according to claim 6, characterized in that The catalyst is at least one of [Bmim][BF4], [C4mim][BF4], [C8mim][BF4] and [Rpy][BF4], and the amount used is 0.1%-10% of the weight of isosorbide.

8. The preparation method according to claim 1, characterized in that The pressure of the prepolymerization reaction is 0.05-0.1Mpa, and the pressure of the final polymerization reaction is 0.1-0.5kPa.

9. The preparation method according to claim 1, characterized in that After the final polymerization reaction, the method further includes a step of maintaining CO2 purge during the cooling process.

10. The preparation method according to claim 1, characterized in that After the final polymerization reaction, the method further comprises the steps of adding a solvent to dissolve the product, filtering, and precipitating the product in the filtrate.

11. The preparation method according to claim 10, characterized in that: During post-processing of the final polymerization product, dichloromethane is first added to dissolve the product, and then ethanol is added to obtain a precipitate, which is the bio-based polycarbonate.

12. The preparation method according to claim 1, characterized in that The inert atmosphere is nitrogen. The temperature is first raised to 80-110° C. to completely melt the raw materials and maintained for 10-50 minutes.

13. Bio-based polycarbonate prepared by the method according to any one of claims 1 to 12.

14. The bio-based polycarbonate according to claim 13, characterized in that Molecular weight ≥ 35000, glass transition temperature T g≤100℃, elongation at break≥140%, impact strength≥70kJ / m 2 .

15. Use of the bio-based polycarbonate according to claim 13 in the preparation of electronic instrument product parts, food packaging materials and decoration materials.

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