A biobased polycarbonate and a method for its preparation

Abstract

A kind of bio-based polycarbonate and its preparation method belong to the technical field of polymer materials.The method includes dissolving isosorbide in organic solvent, adding catalyst, continuously passing in carbon dioxide, carrying out polycondensation reaction under specific temperature and pressure, and obtaining finished product by precipitation, washing and drying after reaction is finished.The biomass source proportion of the material is improved by optimizing reaction conditions, and the hardness and mechanical properties are significantly improved, which provides a feasible technical scheme for replacing traditional bisphenol A type polycarbonate.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically designing a bio-based polycarbonate formed by the direct condensation polymerization of isosorbide and carbon dioxide and its preparation method. Background Technology

[0002] Polycarbonate, as an important polymer material, is widely used in electronics, automotive, and construction due to its excellent mechanical properties, thermal stability, and transparency. However, traditional polycarbonate materials suffer from problems such as low biomass content, insufficient hardness, and poor environmental friendliness. Bisphenol A (BPA) polycarbonate, in particular, has faced increasing restrictions and demand for alternatives in recent years due to the potential harm of its raw material, bisphenol A, to human health and the environment. To address these issues, researchers have begun exploring pathways for preparing polycarbonate using bio-based raw materials to improve the material's sustainability and environmental performance.

[0003] Isosorbide, a biomass-derived diol monomer, is considered an ideal alternative feedstock due to its rigid structure and renewable properties. Compared to traditional bisphenol A, isosorbide not only has a higher biomass content but also imparts greater hardness and thermal stability to polycarbonate.

[0004] Therefore, developing an efficient, environmentally friendly method for preparing high-performance bio-based polycarbonates has become an important research direction in the field of polymer materials. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a bio-based polycarbonate with high biomass content and high hardness and a method for preparing the same.

[0006] The technical solution adopted by this invention to solve its technical problem is: the bio-based polycarbonate has the following structural formula:

[0007] The aforementioned bio-based polycarbonate is polymerized from isosorbide and carbon dioxide through a condensation reaction, and has a bio-based content of over 70%.

[0008] This invention prepares bio-based polycarbonate by direct polycondensation of isosorbide and carbon dioxide. Both isosorbide and carbon dioxide used can be prepared by bio-based methods, which not only increases the proportion of biomass source in the material, but also significantly improves its hardness and mechanical properties, providing a feasible technical solution to replace traditional bisphenol A type polycarbonate.

[0009] A method for preparing the above-mentioned bio-based polycarbonate, the synthetic route including:

[0010] .

[0011] Specifically, the method is as follows: dissolve isosorbide in an organic solvent, add a hydroxyl activator, continuously pass carbon dioxide through, add an alkaline catalyst dropwise to the reaction system, and carry out a polycondensation reaction under pressure at room temperature (25°C) or under heating conditions. After the reaction is completed, the finished product is obtained by precipitation, washing, and drying.

[0012] This invention achieves the direct reaction of isosorbide and carbon dioxide under the action of a large number of hydroxyl activators and alkaline catalysts to produce bio-based polyisosorbide carbonate, reducing raw material costs and carbon footprint, and overcoming dependence on petroleum raw materials. If only isosorbide is prepared using bio-based methods, the bio-based content is higher than 70%; if carbon dioxide is also prepared using bio-based methods, the bio-based content of the raw materials can reach 100%.

[0013] Preferably, the organic solvent includes acetonitrile, N,N-dimethylformamide, or N-methylpyrrolidone. These solvents can effectively dissolve isosorbide and provide a favorable reaction environment during the reaction.

[0014] Preferably, the hydroxyl activator includes p-toluenesulfonyl chloride, bromoethane, or dibromomethane. Toluenesulfonyl chloride, bromoethane, and dibromomethane can convert the hydroxyl groups of isosorbide into derivatives (sulfonates or haloalkyl ethers) with excellent leaving groups through sulfonation or etherification / alkylation, thereby significantly improving the reactivity of the hydroxyl groups, especially their ability as leaving groups or the introduction of excellent leaving groups in their vicinity, thus greatly promoting the formation of carbonate bonds with carbon dioxide in subsequent polycondensation reactions.

[0015] The alkaline catalysts include triethylamine, cesium carbonate, pyridine, DBU, and TMP. They not only provide alkaline conditions (neutralizing acids and activating hydroxyl groups to form RO⁻), but more importantly, they play a catalytic role in activating CO2 and promoting the nucleophilic addition reaction between CO2 and alkoxides / activated intermediates.

[0016] Preferably, the heating temperature is 180℃~250℃, and the pressure is increased to 1.1MPa~4.0MPa by carbon dioxide. This temperature and pressure range ensures efficient reaction while avoiding side reactions, ensuring full participation of carbon dioxide in the reaction, and preventing the carbon dioxide concentration in the reaction system from being too high or too low.

[0017] Preferably, the molar ratio of isosorbide to hydroxyl activator is 1:1 to 3; the molar ratio of isosorbide to alkaline catalyst is 1:1 to 5. This molar ratio ensures sufficient site activation. Excess activator overcomes the steric hindrance effect of the dihydroxyl groups in the isosorbide molecule, improving the efficiency of hydroxyl group conversion to sulfonate esters or haloethers, laying the foundation for subsequent carbonate bond formation; it also compensates for possible side reaction consumption. More preferably, the molar ratio of isosorbide to hydroxyl activator is 1:1.5 to 2.5. The wide range of isosorbide to alkaline catalyst ratios provides operational flexibility. Sufficient or excessive alkali not only effectively neutralizes the strong acid (HCl / HBr) byproducts of sulfonation or alkylation, preventing polymer chain degradation, but also provides a highly alkaline environment to maintain the alkoxide anion concentration, continuously activating the introduced CO2 and catalyzing its insertion reaction. This ratio range synergistically promotes high-conversion chain-growth polycondensation reactions, which is beneficial for synthesizing high-molecular-weight, structurally controllable polycarbonate products.

[0018] Preferably, the polycondensation reaction time is 1 to 12 hours. This reaction time ensures that the reaction proceeds fully while avoiding side reactions caused by excessively long reaction times.

[0019] Preferably, the precipitant is methanol, ethanol, or acetone. These precipitants can effectively precipitate the reaction products, facilitating subsequent washing and drying operations.

[0020] Preferably, the drying temperature is 40℃~80℃, and the drying time is 2~24 hours. These drying conditions ensure that the reaction product is fully dried while avoiding the influence of high temperature on the product properties.

[0021] Specifically, in the above-mentioned method for preparing bio-based polycarbonate, the amount of organic solvent used is 5 to 20 times the mass of isosorbide. This amount ensures the complete dissolution of isosorbide in the solvent while avoiding the influence of excessive solvent on the reaction.

[0022] Specifically, in the above-mentioned method for preparing bio-based polycarbonate, the stirring speed of the polycondensation reaction is 100-500 revolutions per minute. This stirring speed ensures the homogeneity of the reaction system while avoiding the influence of excessively fast or slow stirring speeds on the reaction.

[0023] Specifically, in the above-mentioned method for preparing bio-based polycarbonate, the amount of precipitant used is 2 to 10 times the volume of the reaction liquid. This amount ensures sufficient precipitation of the reaction product while avoiding the negative impact of excessive precipitant on the product.

[0024] Specifically, in the above-mentioned method for preparing bio-based polycarbonate, the washing process involves 2 to 5 washes, with each wash using 2 to 5 times the amount of water as the precipitate. These washing conditions ensure thorough washing of the reaction product while avoiding the negative impact of excessive or insufficient washing.

[0025] Specifically, in the above-mentioned method for preparing bio-based polycarbonate, the moisture content of the dried finished product is less than 1%. This moisture content ensures the stability and performance of the product.

[0026] Specifically, in the above-mentioned method for preparing bio-based polycarbonate, the molecular weight of the finished product is 1000 g / mol to 100000 g / mol. This molecular weight range ensures that the product has good mechanical properties and thermal stability.

[0027] Compared with the prior art, the present invention has the following beneficial effects: The present invention prepares bio-based polycarbonate by direct polycondensation of isosorbide and carbon dioxide, which not only increases the proportion of biomass source in the material, but also significantly improves its hardness and mechanical properties, providing a feasible technical solution to replace traditional bisphenol A type polycarbonate. Detailed Implementation

[0028] The present invention will now be described in detail through examples. Unless otherwise stated, all raw materials used are commercially available.

[0029] Example 1

[0030] Isosorbide, acetonitrile, and p-toluenesulfonyl chloride were added to a reaction vessel. The molar ratio of isosorbide to p-toluenesulfonyl chloride was 1:1, and the amount of acetonitrile was 5 times the mass of isosorbide. Carbon dioxide was continuously introduced at room temperature until the pressure reached 2.5 MPa. Triethylamine was added dropwise to the reaction system at a molar ratio of isosorbide to triethylamine of 1:1 to carry out a polycondensation reaction. The stirring speed was 300 rpm, and the reaction time was 12 hours. After the reaction was completed, bio-based polycarbonate was obtained by methanol precipitation, washing, and drying. The mass content of the components that conformed to the structural formula in the obtained bio-based polycarbonate was 97.8% by nuclear magnetic resonance and Fourier transform infrared spectroscopy.

[0031] Example 2

[0032] Isosorbide, N,N-dimethylformamide, and bromoethane were added to a reaction vessel. The molar ratio of isosorbide to bromoethane was 1:2, and the amount of N,N-dimethylformamide was 10 times the mass of isosorbide. The temperature was raised to 100°C, and carbon dioxide was continuously introduced until the pressure reached 2.0 MPa. Triethylamine was added dropwise to the reaction system at a molar ratio of isosorbide to triethylamine of 1:2 to carry out a polycondensation reaction. The stirring speed was 300 rpm, and the reaction time was 6 hours. After the reaction was completed, the bio-based polycarbonate was obtained by ethanol precipitation, washing, and drying. The mass content of the components that conformed to the structural formula in the obtained bio-based polycarbonate was determined to be 97.7% by nuclear magnetic resonance and Fourier transform infrared spectroscopy.

[0033] Example 3

[0034] Isosorbide, N-methylpyrrolidone, and dibromomethane were added to a reaction vessel. The molar ratio of isosorbide to dibromomethane was 1:5, and the amount of N-methylpyrrolidone was 20 times the mass of isosorbide. The temperature was raised to 200°C, and carbon dioxide was continuously introduced until the pressure reached 2.5 MPa. Triethylamine was added dropwise to the reaction system at a molar ratio of isosorbide to triethylamine of 1:3 to carry out a polycondensation reaction. The stirring speed was 300 rpm, and the reaction time was 1 hour. After the reaction was completed, the bio-based polycarbonate was obtained by precipitation with acetone, washing, and drying. The mass content of the components that conformed to the structural formula in the obtained bio-based polycarbonate was determined to be 98.0% by nuclear magnetic resonance and Fourier transform infrared spectroscopy.

[0035] Example 4

[0036] Isosorbide, acetonitrile, and p-toluenesulfonyl chloride were added to a reaction vessel. The molar ratio of isosorbide to p-toluenesulfonyl chloride was 1:3, and the amount of acetonitrile was 15 times the mass of isosorbide. The temperature was raised to 50°C, and carbon dioxide was continuously introduced until the pressure reached 2 MPa. Triethylamine was added dropwise to the reaction system at a molar ratio of isosorbide to triethylamine of 1:5 to carry out a polycondensation reaction. The stirring speed was 300 rpm, and the reaction time was 8 hours. After the reaction was completed, bio-based polycarbonate was obtained by methanol precipitation, washing, and drying. The mass content of the components that conformed to the structural formula in the obtained bio-based polycarbonate was determined to be 96.4% by nuclear magnetic resonance and Fourier transform infrared spectroscopy.

[0037] Example 5

[0038] Isosorbide, N,N-dimethylformamide, and bromoethane were added to a reaction vessel. The molar ratio of isosorbide to bromoethane was 1:4, and the amount of N,N-dimethylformamide was 12 times the mass of isosorbide. The temperature was raised to 150°C, and carbon dioxide was continuously introduced until the pressure reached 2.0 MPa. Triethylamine was added dropwise to the reaction system at a molar ratio of isosorbide to triethylamine of 1:5 to carry out a polycondensation reaction. The stirring speed was 300 rpm, and the reaction time was 3 hours. After the reaction was completed, bio-based polycarbonate was obtained by ethanol precipitation, washing, and drying. The mass content of the components that conformed to the structural formula in the obtained bio-based polycarbonate was determined to be 88.6% by nuclear magnetic resonance and Fourier transform infrared spectroscopy.

[0039] Example 6

[0040] Isosorbide, N-methylpyrrolidone, and dibromomethane were added to a reaction vessel. The molar ratio of isosorbide to dibromomethane was 1:2, and the amount of N-methylpyrrolidone was 18 times the mass of isosorbide. The temperature was raised to 80°C, and carbon dioxide was continuously introduced until the pressure reached 2.5 MPa. Triethylamine was added dropwise to the reaction system at a molar ratio of isosorbide to triethylamine of 1:1 to carry out a polycondensation reaction. The stirring speed was 300 rpm, and the reaction time was 4 hours. After the reaction was completed, the bio-based polycarbonate was obtained by precipitation with acetone, washing, and drying. The mass content of the components that conformed to the structural formula in the obtained bio-based polycarbonate was determined to be 92.4% by nuclear magnetic resonance and Fourier transform infrared spectroscopy.

[0041] Example 7

[0042] Isosorbide, acetonitrile, and p-toluenesulfonyl chloride were added to a reaction vessel. The molar ratio of isosorbide to p-toluenesulfonyl chloride was 1:5, and the amount of acetonitrile was 20 times the mass of isosorbide. The temperature was raised to 120°C, and carbon dioxide was continuously introduced until the pressure reached 1.5 MPa. Triethylamine was added dropwise to the reaction system at a molar ratio of isosorbide to triethylamine of 1:1 at a rate of 60 mL per minute. The stirring speed was 300 rpm, and the polycondensation reaction was carried out for 10 hours. After the reaction, the product was precipitated with methanol, washed, and dried to obtain bio-based polycarbonate. The mass content of the components conforming to the structural formula in the obtained bio-based polycarbonate was determined to be 93.5% by nuclear magnetic resonance and Fourier transform infrared spectroscopy.

[0043] Example 8

[0044] Isosorbide, N,N-dimethylformamide, and bromoethane were added to a reaction vessel at a molar ratio of 1:1 (isosorbide to bromoethane) and an amount of N,N-dimethylformamide equal to 8 times the mass of isosorbide. The temperature was raised to 70°C, and carbon dioxide was continuously introduced until the pressure reached 4 MPa. Triethylamine was then added dropwise to the reaction system at a molar ratio of 1:1 (isosorbide to triethylamine) to initiate a polycondensation reaction. The stirring speed was 100 rpm, and the reaction time was 2 hours. After the reaction, the bio-based polycarbonate was obtained by ethanol precipitation, washing, and drying. The mass content of the components conforming to the structural formula in the obtained bio-based polycarbonate was determined to be 84.3% by nuclear magnetic resonance and Fourier transform infrared spectroscopy.

[0045] Example 9

[0046] Isosorbide, N-methylpyrrolidone, and dibromomethane were added to a reaction vessel. The molar ratio of isosorbide to dibromomethane was 1:3, and the amount of N-methylpyrrolidone was 16 times the mass of isosorbide. The temperature was raised to 180°C, and carbon dioxide was continuously introduced until the pressure reached 1.5 MPa. Cesium carbonate was added dropwise to the reaction system at a molar ratio of isosorbide to cesium carbonate of 1:1 to carry out a polycondensation reaction. The stirring speed was 500 rpm, and the reaction time was 11 hours. After the reaction was completed, the bio-based polycarbonate was obtained by precipitation with acetone, washing, and drying. The mass content of the components that conformed to the structural formula in the obtained bio-based polycarbonate was determined to be 88.7% by nuclear magnetic resonance and Fourier transform infrared spectroscopy.

[0047] Example 10

[0048] Isosorbide, acetonitrile, and p-toluenesulfonyl chloride were added to a reaction vessel. The molar ratio of isosorbide to p-toluenesulfonyl chloride was 1:2, and the amount of acetonitrile was 10 times the mass of isosorbide. The temperature was raised to 60°C, and carbon dioxide was continuously introduced until the pressure reached 2.5 MPa. TMP was added dropwise to the reaction system at a molar ratio of isosorbide to TMP of 1:1 at a rate of 50 mL per minute to carry out the polycondensation reaction. The stirring speed was 300 rpm, and the reaction time was 5 hours. After the reaction was completed, bio-based polycarbonate was obtained by methanol precipitation, washing, and drying. The mass content of the components that conformed to the structural formula in the obtained bio-based polycarbonate was determined to be 97.8% by nuclear magnetic resonance and Fourier transform infrared spectroscopy.

[0049] The performance comparisons of the bio-based polycarbonate prepared in the embodiments of the present invention are shown in Table 1. The glass transition temperature (Tg) was determined using differential scanning calorimetry (DSC), tensile strength and elongation at break were tested according to ISO 527 standard, and Rockwell hardness was tested according to ASTM D785 standard.

[0050] Table 1

[0051] Example Tg (°C) Tensile strength (MPa) Elongation at break (%) Rockwell hardness (R scale) Example 1 123 65 15 118 Example 2 125 70 18 120 Example 3 130 85 8 125 Example 4 115 60 20 115 Example 5 112 48 35 105 Example 6 128 55 25 110 Example 7 116 63 17 117 Example 8 109 40 50 98 Example 9 127 75 12 122 Example 10 128 80 10 124

[0052] The Tg values ​​of the embodiments of the present invention are all much higher than those of traditional carbon dioxide copolymer polycarbonates, which is due to the rigid furan ring structure of isosorbide.

[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing bio-based polycarbonate, characterized in that: Isosorbide is dissolved in an organic solvent, a hydroxyl activator is added, carbon dioxide is continuously bubbled through, and an alkaline catalyst is added dropwise to the reaction system. The polycondensation reaction is carried out under pressure at room temperature or under heating conditions. After the reaction is completed, the product is obtained by precipitation, washing, and drying. Its bio-based content is higher than 70%. The organic solvents include acetonitrile, N,N-dimethylformamide, or N-methylpyrrolidone; the hydroxyl activators include p-toluenesulfonyl chloride, bromoethane, or dibromomethane; and the basic catalysts include triethylamine, cesium carbonate, pyridine, DBU, and TMP. The molar ratio of isosorbide to hydroxyl activator is 1:1 to 3; the molar ratio of isosorbide to alkaline catalyst is 1:1 to 5.

2. The method for preparing a bio-based polycarbonate according to claim 1, characterized in that, The heating temperature is 180℃~250℃, and the pressure is increased to 1.1MPa~4.0MPa by carbon dioxide.

3. The method for preparing a bio-based polycarbonate according to claim 1, wherein the polycondensation reaction time is 1-12 hours.

4. The method for preparing a bio-based polycarbonate according to claim 1, wherein the precipitant is methanol, ethanol or acetone.

5. The method for preparing a bio-based polycarbonate according to claim 1, wherein the drying temperature is 40℃~80℃ and the drying time is 2~24 hours.