Isosorbide-type polycarbonates and methods of preparation

Abstract

The application discloses a preparation method of an isosorbide polycarbonate, and relates to the technical field of polyesters, and aims at solving the problem that existing catalysts can cause a large number of side reactions to occur in a reaction, and the isosorbide polycarbonate generated by the side reactions is yellowish, and the yield is reduced. The preparation method comprises the following steps: under the action of a tin composite catalyst, taking isosorbide and diphenyl carbonate as raw materials, and sequentially performing a melt ester exchange reaction and a polycondensation reaction to obtain the isosorbide polycarbonate. The tin composite catalyst comprises a metal oxide and a tin catalyst. The preparation method is used for preparing the isosorbide polycarbonate. The isosorbide polycarbonate and the preparation method can improve the color of the isosorbide polycarbonate.

Description

Technical Field

[0001] This invention relates to the field of polyester technology, and in particular to an isosorbide-based polycarbonate and its preparation method. Background Technology

[0002] Isosorbide-based polycarbonate is a bio-based polycarbonate. Compared to traditional resins, the main advantages of isosorbide-based polycarbonate are high transparency, excellent optical properties, and high abrasion resistance. Isosorbide-based polycarbonate can be used to manufacture resin lenses, automotive interiors, and high-end optical materials.

[0003] Currently, isosorbide-based polycarbonates are generally prepared by transesterification and polycondensation with dimethyl carbonate or diphenyl carbonate, using isosorbide as a raw material. The transesterification and polycondensation processes are continuous, and typically require different catalysts for each. Furthermore, existing technologies generally use alkali metal salt catalysts or titanium-based catalysts for the polycondensation reaction, leading to numerous side reactions that result in a yellowish color and reduced yield of the isosorbide-based polycarbonate. Summary of the Invention

[0004] The purpose of this invention is to provide an isosorbide-based polycarbonate and its preparation method, which reduces by-products, improves the color of the isosorbide-based polycarbonate, and increases the yield.

[0005] In a first aspect, the present invention provides a method for preparing isosorbide-based polycarbonate, comprising:

[0006] Under the action of a tin-based composite catalyst, isosorbide and diphenyl carbonate are used as raw materials to undergo a melt transesterification reaction and a polycondensation reaction in sequence to obtain isosorbide-type polycarbonate. The tin-based composite catalyst includes metal oxides and tin-based catalysts.

[0007] Compared with existing technologies, the method for preparing isosorbide-based polycarbonate provided in this invention involves mixing isosorbide and diphenyl carbonate as raw materials with a tin-based composite catalyst, melting the mixture, and then sequentially performing transesterification and polycondensation reactions in the molten state. During the transesterification reaction, the tin-based composite catalyst, comprising metal oxides and tin-based catalysts, utilizes the high specific surface area of ​​the metal oxides to act as a support for the tin-based catalysts. This allows the tin-based catalysts to exhibit higher catalytic activity towards isosorbide and diphenyl carbonate, resulting in a more efficient transesterification reaction between the isosorbide and diphenyl carbonate raw materials. Meanwhile, during the polycondensation reaction, the metal in the metal oxide has empty orbitals, which can easily accept the lone pair of electrons from the oxygen atoms in the isosorbide carbonate after the transesterification reaction. This makes it easier to activate the carbon atoms on the carbonyl group of the isosorbide carbonate and then attack the oxygen atoms in the hydroxyl groups at the end of the isosorbide carbonate oligomer, thereby forming isosorbide-type polycarbonate. This reduces the probability of byproducts and prevents isosorbide-type polycarbonate from turning yellow.

[0008] Furthermore, the embodiments of this invention demonstrate through experiments that tin-based composite catalysts are effective in improving the efficiency of both transesterification and polycondensation reactions, and that using tin-based composite catalysts can improve the overall catalytic efficiency of the reaction. When using a tin-based composite catalyst containing both tin and metal oxides to catalyze the transesterification reaction, it is possible to drive the subsequent polycondensation reaction while ensuring the transesterification reaction proceeds fully. This is beneficial for the continuous production of isosorbide-based polycarbonate. Therefore, on the one hand, it avoids the reaction tendency to catalyze the transesterification reaction alone, resulting in excessive transesterification intermediates and insufficient polycondensation leading to low product molecular weight, thus improving the continuity of the reaction. On the other hand, it also avoids the tendency for a large amount of intermediates to remain in the final product, improving the continuity of the reaction and reducing the probability of degradation in the performance of isosorbide-based polycarbonate products, including yellowness.

[0009] Furthermore, the inventors have discovered through research that tin-based catalysts are particularly useful for improving the efficiency of transesterification reactions, while metal oxides are particularly useful for improving the efficiency of polycondensation reactions.

[0010] In addition, the method for preparing isosorbide-based polycarbonate provided in this embodiment of the invention does not require changing the catalyst during the transesterification and polycondensation reactions, thus avoiding the mutual influence between different catalysts in the transesterification and polymerization stages, simplifying the production process and improving the yield.

[0011] As can be seen from the above, the isosorbide-based polycarbonate provided by the present invention reduces by-products, improves the color of isosorbide-based polycarbonate, and increases the yield.

[0012] Secondly, the present invention also provides an isosorbide-based polycarbonate, which is prepared by the method for preparing isosorbide-based polycarbonate described in the first aspect.

[0013] Compared with the prior art, the beneficial effects of the isosorbide-type polycarbonate provided by the present invention are the same as the beneficial effects of the preparation method of isosorbide-type polycarbonate in the first aspect, and will not be repeated here. Detailed Implementation

[0014] To make the technical problems, solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0015] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. "Several" means one or more, unless otherwise explicitly specified.

[0016] It should be noted that in this invention, the terms "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in this disclosure should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0017] In this invention, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can represent: a, b, c, a combination of a and b, a combination of a and c, a combination of b and c, or a, b, and c, where a, b, and c can be single or multiple.

[0018] Isosorbide is an important biomass sugar alcohol with wide applications in the food, pharmaceutical, fine chemical, chemical intermediate, and polymer materials industries. Isosorbide is widely available, obtained from cellulose, starch, and other materials through hydrolysis-hydrogenation-dehydration reactions, offering advantages such as abundant raw material sources and environmentally friendly products. Furthermore, due to its chiral and rigid structures, isosorbide exhibits great potential for application in the synthesis of polymers with special properties.

[0019] Isosorbide polycarbonate is a bio-based polycarbonate suitable for a range of engineering applications. Traditional bisphenol A polycarbonates, with their estrogenic effects and chronic toxicity, pose harm to human health and the environment, and have been gradually banned from use in food packaging and other materials. Compared to traditional polyester resins, isosorbide-based polycarbonates offer the main advantages of high transparency, excellent optical properties, and high abrasion resistance, making them suitable for manufacturing resin lenses, automotive interiors, and high-end optical materials.

[0020] Currently, isosorbide-based polycarbonates are generally prepared by transesterification and polycondensation with dimethyl carbonate or diphenyl carbonate, using isosorbide as a raw material. The transesterification and polycondensation processes are continuous, and typically require different catalysts for each. Furthermore, existing technologies generally use alkali metal salt catalysts or titanium-based catalysts for the polycondensation reaction, leading to numerous side reactions that result in a yellowish color and reduced yield of the isosorbide-based polycarbonate.

[0021] To address the aforementioned problems, this invention provides a method for preparing isosorbide-based polycarbonate. This method reduces byproducts during the reaction process, improves the color of isosorbide-based polycarbonate, and increases the yield. It solves the problem that existing catalysts cause a large number of side reactions, resulting in a yellowish color and reduced yield of isosorbide-based polycarbonate.

[0022] The method for preparing isosorbide-based polycarbonate provided in this invention includes, under the action of a tin-based composite catalyst, using isosorbide and diphenyl carbonate as raw materials, sequentially performing a melt transesterification reaction and a polycondensation reaction to obtain isosorbide-based polycarbonate. The tin-based composite catalyst includes metal oxides and tin-based catalysts. It should be understood that the tin-based composite catalyst can be obtained by combining metal oxides and tin-based catalysts, and the combination method can be a mixture of metal oxides and tin-based catalysts.

[0023] For example, in this embodiment of the invention, diphenyl carbonate, isosorbide and a tin-based composite catalyst are heated and stirred in an inert environment until the reactants are completely melted to obtain a homogeneous mixture. Then, isosorbide-type polycarbonate is synthesized through an atmospheric pressure transesterification process and a depressurization and heating polycondensation process without changing the type of catalyst.

[0024] The method for preparing isosorbide-based polycarbonate provided in this invention involves mixing isosorbide and diphenyl carbonate as raw materials with a tin-based composite catalyst, melting the mixture, and then sequentially performing transesterification and polycondensation reactions in the molten state. During the transesterification reaction, the tin-based composite catalyst, comprising metal oxides and tin-based catalysts, utilizes the high specific surface area of ​​the metal oxides to act as a support for the tin-based catalysts. This allows the tin-based catalysts to exhibit higher catalytic activity towards isosorbide and diphenyl carbonate, resulting in a more efficient transesterification reaction. Simultaneously, during the polycondensation reaction, the metal oxides contain empty orbitals, which readily accept the lone pairs of electrons from the oxygen atoms in the isosorbide carbonate after the transesterification reaction. This facilitates the activation of the carbonyl carbon atoms in the isosorbide carbonate, which then attack the oxygen atoms at the terminal hydroxyl groups of the isosorbide carbonate oligomers, forming isosorbide-based polycarbonate. This reduces the probability of reaction byproducts and prevents the isosorbide-based polycarbonate from yellowing.

[0025] In addition, the method for preparing isosorbide-based polycarbonate provided in this embodiment of the invention does not require changing the catalyst during the transesterification and polycondensation reactions, thus avoiding the mutual influence between different catalysts in the transesterification and polymerization stages, simplifying the production process and improving the yield.

[0026] As can be seen from the above, the isosorbide-based polycarbonate provided by the present invention reduces by-products, improves the color of isosorbide-based polycarbonate, and increases the yield.

[0027] In one feasible embodiment, the molar ratio of metal oxide to tin catalyst in this invention is 1:(1-10), preferably 1:(1-5). By controlling the molar ratio of metal oxide to tin catalyst within this range, this invention allows for the complete loading of the tin catalyst using only a small amount of metal oxide when the metal oxide is used as a support, while also preventing the metal oxide from agglomerating due to excessive addition, thus improving reaction efficiency.

[0028] In one alternative embodiment, the tin-based catalyst of this invention comprises an organotin catalyst and / or an inorganic tin catalyst. It should be understood that the organotin catalyst can be an organotin salt, and the inorganic tin catalyst can be an inorganic tin salt.

[0029] For example, the organotin catalysts described above may include at least one of alkyl tin oxide catalysts, dialkyl tin oxide catalysts, dialkyl tin oxide catalysts of fatty acids, and tin moieties of fatty acids.

[0030] When the above-mentioned organotin catalyst is an alkyl tin oxide catalyst, the alkyl tin oxide catalyst may include at least one of monobutyl tin oxide, ethyl tin oxide, heptyl tin oxide and other alkyl tin oxide catalysts, which are not limited here.

[0031] When the above-mentioned organotin catalyst is a dialkyl tin oxide catalyst, the dialkyl tin oxide catalyst may include at least one of diethyl tin oxide, dipropyl tin oxide, dibutyl tin oxide, dihexyl tin oxide, dioctyl tin oxide and other dialkyl tin oxide catalysts, which are not limited here.

[0032] When the above-mentioned organotin catalyst is a dialkyltin dicarboxylic acid catalyst, the dialkyltin dicarboxylic acid catalyst may include at least one of the following: dibutyltin dibutyrate, dimethyltin dibutyrate, dioctyltin dibutyrate, dibutyltin diacetate, dimethyltin diacetate, dioctyltin diacetate, dibutyltin dilaurate, dimethyltin dilaurate, dioctyltin dilaurate, dibutyltin dioleate, dimethyltin dioleate, dioctyltin dioleate, dibutyltin dioctyldecanoate, dimethyltin dioctyldecanoate, dioctyltin diacetate, dioctyltin diacetate, dibutyltin dimaleate, dimethyltin maleate, dioctyltin maleate, and other dialkyltin dicarboxylic acid catalysts, without limitation herein.

[0033] When the above-mentioned organotin catalyst is a dialkyltin dialkyl alkanoate, the dialkyltin dialkyl alkanoate may include at least one of dibutyltin dibutyrate, dimethyltin dibutyrate, dioctyltin dibutyrate, dibutyltin diacetate, dimethyltin diacetate, dioctyltin diacetate, dibutyltin dilaurate, dimethyltin dilaurate, dioctyltin dilaurate, and other dialkyltin dialkyl alkanoate catalysts, without limitation herein.

[0034] When the above-mentioned organotin catalyst is a fatty acid stannous catalyst, the fatty acid stannous catalyst may include at least one of stannous octoate, stannous oxalate and other fatty acid stannous catalysts, which are not limited here.

[0035] Preferably, the organotin catalyst described above can be at least one of dibutyltin oxide, stannous octoate, and dibutyltin dilaurate.

[0036] For example, the inorganic tin catalysts described above may include at least one of tin tetrachloride, tin iodide, stannous iodide, tin phosphide, stannous fluorophosphate, and stannous fluoroborate.

[0037] In one feasible embodiment, the metal oxide of this invention comprises a main group metal oxide, wherein the metal element contained in the main group metal oxide includes at least one selected from magnesium, calcium, barium, zinc, and antimony. For example, the metal oxide may include at least one selected from magnesium oxide, calcium oxide, antimony trioxide, zinc oxide, and barium oxide. Preferably, the metal oxide includes at least one selected from magnesium oxide, calcium oxide, and antimony trioxide. During the polycondensation reaction, since the metal contained in the above-mentioned metal oxide has empty orbitals, it can easily accept the lone pair of electrons from the oxygen atoms contained in the isosorbide carbonate after the transesterification reaction, thereby more easily activating the carbon atom on the carbonyl group of the isosorbide carbonate and then attacking the oxygen atom contained in the hydroxyl group at the terminal position of the isosorbide carbonate oligomer, reducing the probability of reaction byproducts.

[0038] In one optional embodiment, the reaction conditions for the molten transesterification reaction of the present invention include: a melting temperature of 80°C to 200°C, a transesterification reaction temperature of 150°C to 220°C, a reaction pressure of atmospheric pressure, and a reaction time of 0.5h to 5h.

[0039] For example, the reaction conditions for the polycondensation reaction in this embodiment of the invention include: a reaction temperature of 160°C to 280°C, a reaction pressure of 5Pa to 1000Pa, and a reaction time of 0.5h to 12h.

[0040] In other words, in this embodiment of the invention, a tin-based composite catalyst, isosorbide, and diphenyl carbonate are added to a reactor filled with an inert atmosphere. After being mixed evenly, the mixture is first melted at 80°C–200°C (preferably 100°C–140°C) and atmospheric pressure. Then, the molten mixture undergoes a transesterification reaction at 150°C–220°C (preferably 180°C–210°C) and atmospheric pressure for 0.5 h–1 h (preferably 1 h–3 h). After the transesterification reaction is completed, the system pressure is slowly reduced to 5 Pa–1000 Pa (preferably 5 Pa–500 Pa, more preferably 50 Pa–300 Pa), and then a polycondensation reaction is carried out at 160°C–280°C (preferably 180°C–240°C) for 0.5 h–12 h to obtain isosorbide-based polycarbonate. It should be understood that the inert atmosphere may include at least one of N2, helium, argon, or other inert gases, and is not limited here.

[0041] In one alternative embodiment, the molar ratio of isosorbide to diphenyl carbonate in this invention is (0.5–1.5):1, preferably (0.8–1.3):1. The mass of the tin-based composite catalyst is 0.001‰–10% of the mass of isosorbide, preferably 0.01‰–5%, more preferably 0.05‰–5%. It is evident that this invention can utilize a very small amount of tin-based composite catalyst for transesterification and polycondensation reactions, avoiding the problem of poor separation between the catalyst and isosorbide-based polycarbonate caused by excessive catalyst addition, thus improving the color of the isosorbide-based polycarbonate.

[0042] The method for preparing isosorbide-based polycarbonate provided in this invention involves mixing isosorbide and diphenyl carbonate as raw materials with a tin-based composite catalyst, melting the mixture, and then sequentially performing transesterification and polycondensation reactions in the molten state. During the transesterification reaction, the tin-based composite catalyst, comprising metal oxides and tin-based catalysts, utilizes the high specific surface area of ​​the metal oxides to act as a support for the tin-based catalysts. This allows the tin-based catalysts to exhibit higher catalytic activity towards isosorbide and diphenyl carbonate, resulting in a more efficient transesterification reaction. Simultaneously, during the polycondensation reaction, the metal oxides contain empty orbitals, which readily accept the lone electron pairs from the oxygen atoms in the isosorbide carbonate after the transesterification reaction. This facilitates the activation of the carbonyl carbon atoms in the isosorbide carbonate, which then attack the oxygen atoms at the terminal hydroxyl groups of the isosorbide carbonate oligomers, thereby forming isosorbide-based polycarbonate. This reduces the probability of byproduct formation and prevents the isosorbide-based polycarbonate from yellowing.

[0043] To verify the effectiveness of the isosorbide-based polycarbonate provided in the embodiments of the present invention, the present invention uses a comparison of embodiments and comparative examples for demonstration.

[0044] In the examples below, the weight-average molecular weight of isosorbide-based polycarbonate was determined by gel permeation chromatography (GPC) using chloroform as solvent and polystyrene as standard. The intrinsic viscosity of polycarbonate was measured using dichloromethane as solvent. The yield of polycarbonate was the ratio of the actual mass of polymer obtained to the theoretical mass. The yellow index of the polymer was tested according to the method provided in GB / T39822-2021.

[0045] Example 1

[0046] Embodiment 1 of this invention provides a method for preparing isosorbide-based polycarbonate, which uses a tin-based composite catalyst. The tin-based composite catalyst is a composite catalyst of dibutyltin oxide and antimony trioxide (molar ratio of 3:1). The method includes:

[0047] Isosorbide, diphenyl carbonate, and a composite catalyst of dibutyltin oxide and antimony trioxide in a molar ratio of 1:1 were added to a round-bottom flask purged with N2. The weight ratio of catalyst to isosorbide was 0.1‰. Under N2 atmosphere, the mixture was melt-stirred at 140°C for 0.5 h, then heated to 180°C and reacted for 1.5 h to complete the transesterification reaction stage. The pressure of the reaction system was then reduced to 100 Pa, the reaction temperature was raised to 220°C, and the reaction was carried out for 1 h to complete the polycondensation, thus synthesizing isosorbide-based polycarbonate. The molecular weight of the polymer was determined by gel permeation chromatography to be Mw = 46200, the yield was 89.8%, and the yellow index (YI) was 1.3.

[0048] Example 2

[0049] Example 2 of this invention provides a method for preparing isosorbide-based polycarbonate, using a tin-based composite catalyst, specifically a catalyst composed of stannous octoate and antimony trioxide (molar ratio 3:1). The method includes:

[0050] Isosorbide, diphenyl carbonate, and a composite catalyst of stannous octoate and antimony trioxide in a molar ratio of 1:1 were added to a round-bottom flask purged with N2. The weight ratio of catalyst to isosorbide was 0.1‰. Under N2 atmosphere, the mixture was melt-stirred at 140°C for 0.5 h, then heated to 180°C and reacted for 1.5 h to complete the transesterification reaction stage. The pressure of the reaction system was then reduced to 100 Pa, the reaction temperature was raised to 220°C, and the reaction was carried out for 1 h to complete the polycondensation, thus synthesizing isosorbide-based polycarbonate. The molecular weight of the polymer was determined by gel permeation chromatography to be Mw = 52320, the yield was 91.2%, and the yellow index was 2.1.

[0051] Example 3

[0052] Example 3 of this invention provides a method for preparing isosorbide-based polycarbonate, using a tin-based composite catalyst. The tin-based composite catalyst is a composite catalyst of dibutyltin dilaurate and antimony trioxide (molar ratio of 3:1). The method includes:

[0053] A composite catalyst consisting of isosorbide, diphenyl carbonate, and dibutyltin dilaurate and antimony trioxide in a molar ratio of 1:1 was added to a round-bottom flask purged with N2. The weight ratio of catalyst to isosorbide was 0.1‰. The mixture was melt-stirred at 140°C for 0.5 h under N2 atmosphere, then heated to 180°C and reacted for 1.5 h to complete the transesterification reaction. The pressure of the reaction system was then reduced to 100 Pa, the reaction temperature was raised to 220°C, and the reaction was allowed to proceed for 1 h to complete the polycondensation, thus synthesizing isosorbide-based polycarbonate. The molecular weight of the polymer was determined by gel permeation chromatography to be Mw = 55800, the yield was 90.5%, and the yellow index was 2.5.

[0054] Example 4

[0055] Example 4 of this invention provides a method for preparing isosorbide-based polycarbonate, using a tin-based composite catalyst. The tin-based composite catalyst is a composite catalyst of dibutyltin oxide and antimony trioxide (molar ratio of 3:1). The method includes:

[0056] Isosorbide, diphenyl carbonate, and a composite catalyst of dibutyltin oxide and antimony trioxide in a molar ratio of 1:1 were added to a round-bottom flask purged with N2. The weight ratio of catalyst to isosorbide was 0.1‰. Under N2 atmosphere, the mixture was melt-stirred at 140°C for 0.5 h, then heated to 180°C and reacted for 1.5 h to complete the transesterification reaction stage. The pressure of the reaction system was then reduced to 100 Pa, the reaction temperature was raised to 230°C, and the reaction was carried out for 1 h to complete the polycondensation, thus synthesizing isosorbide-based polycarbonate. The molecular weight of the polymer was determined by gel permeation chromatography to be Mw = 50500, the yield was 83.5%, and the yellow index was 5.5.

[0057] Example 5

[0058] Example 5 of this invention provides a method for preparing isosorbide-based polycarbonate, using a tin-based composite catalyst, specifically a catalyst composed of stannous octoate and antimony trioxide (molar ratio 3:1). The method includes:

[0059] Isosorbide, diphenyl carbonate, and a composite catalyst of stannous octoate and antimony trioxide in a molar ratio of 1:1 were added to a round-bottom flask purged with N2. The weight ratio of catalyst to isosorbide was 0.1‰. Under N2 atmosphere, the mixture was melt-stirred at 140°C for 0.5 h, then heated to 180°C and reacted for 1.5 h to complete the transesterification reaction stage. The pressure of the reaction system was then reduced to 100 Pa, the reaction temperature was raised to 230°C, and the reaction was carried out for 1 h to complete the polycondensation, thus synthesizing isosorbide-based polycarbonate. The molecular weight of the polymer was determined by gel permeation chromatography to be Mw = 55700, the yield was 82.2%, and the yellow index was 6.5.

[0060] Example 6

[0061] Example 6 of this invention provides a method for preparing isosorbide-based polycarbonate, using a tin-based composite catalyst. The tin-based composite catalyst is a composite catalyst of dibutyltin dilaurate and antimony trioxide (molar ratio of 3:1). The method includes:

[0062] A composite catalyst consisting of isosorbide, diphenyl carbonate, and dibutyltin dilaurate and antimony trioxide in a molar ratio of 1:1 was added to a round-bottom flask purged with N2. The weight ratio of catalyst to isosorbide was 0.1‰. Under N2 atmosphere, the mixture was melt-stirred at 140°C for 0.5 h, then heated to 180°C and reacted for 1.5 h to complete the transesterification reaction stage. The pressure of the reaction system was then reduced to 100 Pa, the reaction temperature was raised to 230°C, and the reaction was carried out for 1 h to complete the polycondensation, thus synthesizing isosorbide-based polycarbonate. The molecular weight of the polymer was determined by gel permeation chromatography to be Mw = 58800, the yield was 82.8%, and the yellow index was 6.2.

[0063] Comparative Example 1

[0064] Comparative Example 1 of this invention provides a method for preparing isosorbide-based polycarbonate, using a cesium carbonate catalyst, the method comprising:

[0065] Isosorbide, diphenyl carbonate, and cesium carbonate catalyst in a molar ratio of 1:1 were added to a round-bottom flask purged with N2. The weight ratio of catalyst to isosorbide was 0.1‰. The mixture was melt-stirred at 140°C for 0.5 h under N2 atmosphere, then heated to 180°C and reacted for 1.5 h to complete the transesterification reaction. The pressure of the reaction system was then reduced to 100 Pa, the reaction temperature was raised to 220°C, and the reaction was carried out for 1 h to complete the polycondensation, thus synthesizing isosorbide-based polycarbonate. The molecular weight of the polymer was determined by gel permeation chromatography to be Mw = 56200, the yield was 85.8%, and the yellow index was 15.6.

[0066] Comparative Example 2

[0067] A TiO2-SiO2 composite catalyst (with polyvinylpyrrolidone as the precipitant) was prepared by precipitation method, wherein the molar ratio of Ti to Si was 1:4 and the molar ratio of N to Ti was 4.

[0068] Isosorbide, diphenyl carbonate, and TiO2 / SiO2 (polyvinylpyrrolidone) composite catalyst in a 1:1 molar ratio were added to a round-bottom flask purged with N2. The weight ratio of catalyst to isosorbide was 0.1‰. Under N2 atmosphere, the mixture was melt-stirred at 140℃ for 0.5 h, then heated to 180℃ and reacted for 1.5 h to complete the transesterification reaction stage. The pressure of the reaction system was then reduced to 100 Pa, the reaction temperature was raised to 220℃, and the reaction was carried out for 1 h to complete the polycondensation, thus synthesizing isosorbide-based polycarbonate. The molecular weight of the polymer was determined by gel permeation chromatography to be Mw = 36200, the yield was 78.1%, and the yellow index was 34.8.

[0069] Comparative Example 3

[0070] Comparative Example 3 of this invention provides a method for preparing isosorbide-based polycarbonate, using a dibutyltin oxide catalyst, the method comprising:

[0071] Isosorbide, diphenyl carbonate, and dibutyltin oxide catalyst in a molar ratio of 1:1 were added to a round-bottom flask purged with N2. The weight ratio of catalyst to isosorbide was 0.1‰. The mixture was melt-stirred at 140°C for 0.5 h under N2 atmosphere, then heated to 180°C and reacted for 1.5 h to complete the transesterification reaction. The pressure of the reaction system was then reduced to 100 Pa, the reaction temperature was raised to 220°C, and the reaction was carried out for 1 h to complete the polycondensation, thus synthesizing isosorbide-based polycarbonate. The molecular weight of the polymer was determined by gel permeation chromatography to be Mw = 31400, the yield was 82.6%, and the yellow index was 9.8.

[0072] As can be seen from the above examples and comparative examples, Examples 1 to 6 of the present invention used tin-based composite catalysts, and the yields of isosorbide-type polycarbonates prepared were between 82.2% and 91.2%, with yellow indices between 1.3 and 6.5. Comparative Example 1 used a cesium carbonate catalyst, achieving a yield of 85.8% and a yellow index of 15.6. Comparative Example 2 used a TiO2 / SiO2 (polyvinylpyrrolidone) composite catalyst, achieving a yield of 78.1% and a yellow index of 34.8. Comparative Example 3 used a dibutyltin oxide catalyst, achieving a yield of 82.6% and a yellow index of 9.8. It is evident that the tin-based composite catalysts of the present invention produce isosorbide-type polycarbonates with better yellow indices than Comparative Examples 1 to 3. In other words, using the tin-based composite catalysts of the present invention can significantly improve the color and yield of isosorbide-type polycarbonates. Meanwhile, the reaction temperature of the polycondensation reaction in Examples 4 and 6 is higher than that in Examples 1 and 3, and their yellowness is also relatively higher. Therefore, the lower the temperature of the polycondensation reaction, the better the color of the isosorbide-type polycarbonate.

[0073] The above description is merely a specific embodiment of the present invention. Obviously, various modifications and combinations can be made without departing from the spirit and scope of the present invention. Accordingly, this specification is merely an exemplary description of the present invention as defined by the appended claims, and is considered to cover any and all modifications, variations, combinations, or equivalents within the scope of the present invention. Clearly, those skilled in the art can make various alterations and modifications to the present invention without departing from its spirit and scope. Thus, if these modifications and variations of the present invention fall within the scope of the claims and their equivalents, the intent of the present invention includes these modifications and variations. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing isosorbide-based polycarbonate, characterized in that, The method includes: Under the action of a tin-based composite catalyst, isosorbide and diphenyl carbonate are used as raw materials to undergo a melt transesterification reaction and a polycondensation reaction in sequence to obtain isosorbide-type polycarbonate; the tin-based composite catalyst includes metal oxides and tin-based catalysts, and the metal oxides include antimony trioxide.

2. The method for preparing isosorbide-based polycarbonate according to claim 1, characterized in that, The molar ratio of the metal oxide to the tin catalyst is 1:(1~10).

3. The method for preparing isosorbide-based polycarbonate according to claim 1, characterized in that, The tin-based catalysts include organotin catalysts and / or inorganic tin catalysts.

4. The method for preparing isosorbide-based polycarbonate according to claim 3, characterized in that, The organotin catalyst includes at least one of alkyl tin oxide catalysts, dialkyl tin dicarboxylic acid catalysts, and tin ferrous acid catalysts.

5. The method for preparing isosorbide-based polycarbonate according to claim 3, characterized in that, The inorganic tin catalyst includes at least one of tin tetrachloride, tin iodide, stannous iodide, tin phosphide, stannous fluorophosphate, and stannous fluoroborate.

6. The method for preparing isosorbide-based polycarbonate according to claim 1, characterized in that, The reaction conditions for the molten transesterification reaction include: a melting temperature of 80℃ to 200℃, a transesterification reaction temperature of 150℃ to 220℃, a reaction pressure of atmospheric pressure, and a reaction time of 0.5h to 5h.

7. The method for preparing isosorbide-based polycarbonate according to claim 1, characterized in that, The reaction conditions for the polycondensation reaction include: a reaction temperature of 160℃ to 280℃, a reaction pressure of 5Pa to 1000Pa, and a reaction time of 0.5h to 12h.

8. The method for preparing isosorbide-based polycarbonate according to any one of claims 1 to 7, characterized in that, The molar ratio of isosorbide to diphenyl carbonate is (0.5–1.5):1; and / or, The mass of the tin-based composite catalyst is 0.001‰ to 10% of the mass of isosorbide.

9. An isosorbide-based polycarbonate, wherein the isosorbide-based polycarbonate is prepared by the preparation method of the isosorbide-based polycarbonate according to any one of claims 1 to 8.