Preparation method of modified polypropylene carbonate material

Abstract

The invention discloses a preparation method of a modified polypropylene carbonate material. The modified polypropylene carbonate material is a high-molecular polymer obtained by ternary polymerization of carbon dioxide, epoxypropane and epichlorohydrin. According to the invention, epichlorohydrin is creatively used as a third monomer and is subjected to ternary polymerization with epoxypropane and carbon dioxide, so that a novel polypropylene carbonate material containing rigid chlorine groups is successfully synthesized. The innovation not only retains the degradability of the PPC material, but also significantly improves various properties of the material by introducing rigid chlorine groups. The maximum molecular weight of the synthesized polymer can reach 59.4 kg / mol, which shows that the preparation method provided by the invention can effectively promote the formation of macromolecular chains and improve the molecular weight of the material, thereby enhancing the physical properties and mechanical strength of the material.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and specifically, to a preparation method of a modified poly(propylene carbonate) material. Background Art

[0002] Poly(propylene carbonate) (PPC) is a degradable plastic copolymerized from carbon dioxide and propylene oxide, and has excellent transparency, biocompatibility, and oxygen / water barrier properties. Therefore, it has broad application prospects in the fields of food packaging and medicine. However, PPC is an amorphous polymer with a relatively low glass transition temperature (Tg), which limits its application in high-temperature environments. To extend the service temperature range of PPC, heat-resistant structural units need to be introduced.

[0003] Currently, most of the third monomers used to modify PPC are aliphatic epoxides, which can increase the glass transition temperature of the polymer and improve its mechanical properties. However, the successful cases of copolymerization of epoxides containing electron-withdrawing groups (such as epichlorohydrin) with carbon dioxide are very limited. Summary of the Invention

[0004] The purpose of the present invention is to provide a modified poly(propylene carbonate) material and its preparation method that can retain the degradability of the PPC material and significantly improve the various properties of the material.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions: A modified poly(propylene carbonate) material is a high molecular polymer obtained by terpolymerization of carbon dioxide, propylene oxide, and epichlorohydrin, and its number average molecular weight is from 10,300 to 59,400; its structure is shown in formula (1); wherein a≥1, b≥1, c≥0, and a, b, c are all integers;

[0006] A preparation method of a modified poly(propylene carbonate) material includes the following steps: In a dry autoclave, add propylene oxide, epichlorohydrin, and a catalyst, introduce carbon dioxide and maintain a constant pressure, and react at a set temperature; after the reaction is completed, cool the autoclave by an ice-water bath, release the unreacted carbon dioxide, and purify the product to obtain the modified poly(propylene carbonate) material.

[0007] Preferably, the preparation method of the modified poly(propylene carbonate) material specifically includes the following steps: (1) Dry the autoclave overnight and heat it in an oven at 110°C, and then transfer it to a glove box under a nitrogen atmosphere; After the autoclave is cooled to room temperature, propylene oxide, epichlorohydrin, and a catalyst are sequentially added to the autoclave. After the autoclave is sealed, it is taken out of the glove box, and hot air at 300 °C is used to purge the CO 2 pipeline to remove moisture and oxygen, and then the CO 2 is connected to the autoclave valve, and at the same time, CO 2 is continuously introduced, and a certain pressure of CO 2 is charged and maintained at a constant pressure; when the internal temperature of the autoclave reaches the reaction temperature, the reaction starts and this temperature is maintained. After the polymerization reaction is completed, the autoclave is cooled in an ice-water bath, and then the valve is slowly opened to release the unreacted CO 2 ; then dichloromethane is added to dilute the product, and then poured into deionized water and stirred to purify the product. After standing for the solution to separate, the upper aqueous solution is poured off, and then deionized water is added and the above operation is repeated 3 times to completely wash away the catalyst and by-products in the sample, and the sample is repeatedly precipitated 3 times in methanol. Subsequently, the purified sample is placed in a fume hood to volatilize most of the solvent, then placed in a blast drying oven at 60 °C for drying, and then placed in a vacuum drying oven at 80 °C for further drying to constant weight, and finally a modified poly(propylene carbonate) material is obtained.

[0008] Preferably, the molar ratio of propylene oxide, epichlorohydrin, and the catalyst is 1000 – 200:100 – 800:1.

[0009] Preferably, the pressure of the CO 2 in step (3) is 1.5 MPa - 3.5 MPa; the reaction temperature is 25 - 50 °C; the reaction time is 16 h - 36 h.

[0010] Preferably, the catalyst is a tetra-nuclear organic boron catalyst.

[0011] Compared with the prior art, the present invention has the following beneficial effects: (1) The modification of traditional PPC (polypropylene carbonate) materials usually introduces polyester segments. However, a major drawback of this approach is the introduction of non-degradable components, which goes against the current trends of environmental protection and sustainable development. On the other hand, although the copolymerization of epichlorohydrin (ECH) monomer with carbon dioxide can theoretically endow the material with new properties, due to the electron-withdrawing property of epichlorohydrin, its ring-opening polymerization becomes extremely difficult. Therefore, attempts to modify PPC with epichlorohydrin are rare. However, with the invention of the tetra-nuclear organic boron catalyst, this problem has been effectively solved. The tetra-nuclear organic boron catalyst is non-toxic, environmentally friendly and has high yield. This catalyst has a windmill-like structure and can achieve the complete alternating copolymerization of carbon dioxide and epichlorohydrin under mild reaction conditions. This catalyst can significantly reduce the activation energy of the ring-opening polymerization of epichlorohydrin, making this reaction relatively easy. Therefore, in the present invention, epichlorohydrin is innovatively used as the third monomer to carry out terpolymerization with propylene oxide (PO) and carbon dioxide (CO 2 ) to successfully synthesize a new type of polypropylene carbonate (PPC) material containing rigid chlorine groups. This innovation not only retains the degradability of the PPC material, but also significantly improves the properties of the material by introducing rigid chlorine groups. The maximum molecular weight of the synthesized polymer can reach 59.4 kg / mol, indicating that the preparation method of the present invention can effectively promote the formation of polymer chains, increase the molecular weight of the material, and thus enhance its physical properties and mechanical strength.

[0012] (2) The glass transition temperature of the modified poly(propylene carbonate) material prepared in the present invention is significantly increased. Compared with the traditional PPC material, its glass transition temperature (Tg) can reach up to 41.2 °C at most, broadening the application temperature range of the PPC material.

[0013] (3) The tensile strength of the modified poly(propylene carbonate) material prepared in the present invention is also enhanced, reaching up to 21.1 MPa at most. The improvement of these properties is mainly attributed to the introduction of chlorine atoms, which increases the rigidity of the polymer main chain and thus effectively improves the mechanical properties of the material.

[0014] (4) The modified poly(propylene carbonate) material prepared in the present invention exhibits excellent water and oxygen barrier properties and can be used in the fields of food packaging and medicine. The oxygen permeability coefficient of the material is as low as 1.31 cm 3 ·mm / (m 2 ·day), and the water vapor permeability coefficient is only 0.033 g·mm / (m²·day). This data is much lower than that of traditional PPC materials, indicating its significant advantage in water and oxygen barrier.

[0015] (5) The polymer used in the present invention is synthesized from carbon dioxide, utilizing the greenhouse gas carbon dioxide, which has the significance of carbon reduction and is environmentally friendly and green.

[0016] (6) The modified poly(propylene carbonate) material prepared in the present invention has good transparency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is the chemical formula of the tetra-nuclear organoboron catalyst used in the examples of the present invention; Figure 2 is the synthesis route diagram of the modified poly(propylene carbonate) material in the examples of the present invention; Figure 3 is the nuclear magnetic resonance hydrogen spectrum of the modified poly(propylene carbonate) material obtained in Example 1 of the present invention; Figure 4 is the transparency comparison diagram of PPC and the modified poly(propylene carbonate) material obtained in Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] The following are specific examples of the present invention, but are not limited thereto. Example 1:

[0019] A 50 mL autoclave was dried overnight and heated in an oven at 110 °C. Then, it was immediately transferred to a glove box under a nitrogen atmosphere. After the autoclave was cooled to room temperature, reactants were added thereto. 18.000 g of propylene oxide, 5.770 g of epichlorohydrin and 0.198 g of catalyst were successively added to the autoclave. After sealing the autoclave, it was taken out of the glove box. The CO 2 pipeline was purged with hot air at 300 °C to remove moisture and oxygen, and then the CO 2 was connected to the autoclave valve while continuously introducing CO 2 . The reaction vessel was quickly filled with CO at a pressure of 2.5 MPa 2 , and the constant pressure was maintained. When the internal temperature of the autoclave reached 40 °C, the reaction was started and this temperature was maintained for 24 h. After the reaction was completed, the reaction kettle was cooled in cold water. After cooling to room temperature, the valve was opened to release carbon dioxide. After adding 30 mL of dichloromethane to dilute the product, it was poured into about 500 mL of deionized water and stirred for about 5 minutes to purify the product. After standing for the solution to layer, the upper aqueous solution was poured off, and then 500 mL of deionized water was added and the above operation was repeated 3 times to completely wash away the catalyst and by-products in the sample. It was precipitated repeatedly 3 times in methanol, and then the purified sample was placed in a fume hood to volatilize most of the solvent, and then placed in a blast oven at 60 °C to dry, and then placed in a vacuum oven at 80 °C to further dry to constant weight. Finally, a modified poly(propylene carbonate) material was obtained, and its nuclear magnetic resonance hydrogen spectrum was as shown in Figure 3As shown. After testing, the prepared modified poly(propylene carbonate) material contains 13.8 mol% of chlorine groups, the number-average molecular weight is 31.2 kg / mol, and the molecular weight distribution index is 1.63. The glass transition temperature is 28.8 °C, the thermal decomposition temperature at 5% mass loss is 277.5 °C, the tensile strength is 2.4 MPa, the elongation at break is 411.2%, and the oxygen transmission coefficient is 2.35 cm 3 ·mm / (m 2 ·day), and the water vapor transmission coefficient is 0.037 g·mm / (m 2 ·day). The transparency comparison diagram of the existing PPC and the modified poly(propylene carbonate) material obtained in Example 1 of the present invention is as shown in Figure 4 As can be seen from Figure 4 the present invention has better transparency. Example 2:

[0020] A 50 mL autoclave was dried overnight and heated in an oven at 110 °C. Then, it was immediately transferred to a glove box under a nitrogen atmosphere. After the autoclave was cooled to room temperature, reactants were added thereto. 14.420 g of propylene oxide, 5.770 g of epichlorohydrin, and 0.198 g of catalyst were sequentially added to the autoclave. After sealing the autoclave, it was taken out of the glove box. The CO 2 pipeline was purged with hot air at 300 °C to remove moisture and oxygen, and then the CO 2 was connected to the autoclave valve while continuously introducing CO 2 . The reaction vessel was quickly filled with CO 2 at a pressure of 2.5 MPa and maintained at a constant pressure. When the internal temperature of the autoclave reached 40 °C, the reaction was started and this temperature was maintained for 24 h. After the reaction was completed, the reaction kettle was cooled in cold water. After cooling to room temperature, the valve was opened to release carbon dioxide. After adding 30 mL of dichloromethane to dilute the product, it was poured into about 500 mL of deionized water and stirred for about 5 minutes to purify the product. After standing for the solution to layer, the upper aqueous solution was poured off, and then 500 mL of deionized water was added and the above operation was repeated 3 times to completely wash away the catalyst and by-products in the sample. It was precipitated repeatedly 3 times in methanol, and then the purified sample was placed in a fume hood to volatilize most of the solvent, and then placed in a blast oven at 60 °C for drying, and then placed in a vacuum oven at 80 °C for further drying to constant weight, and finally a modified poly(propylene carbonate) material was obtained. After testing, the prepared modified poly(propylene carbonate) material contains 16.3 mol% of chlorine groups, the number-average molecular weight is 59.4 kg / mol, and the molecular weight distribution index is 1.21. The glass transition temperature is 34.6 °C, the thermal decomposition temperature at 5% mass loss is 279.2 °C, the tensile strength is 6.6 MPa, and the elongation at break is 382.1%. Example 3:

[0021] A 50 mL autoclave was dried overnight and heated in an oven at 110 °C. Then, it was immediately transferred to a glove box under a nitrogen atmosphere. After the autoclave cooled to room temperature, the reactants were added to it. 10.800 g of propylene oxide, 8.650 g of epichlorohydrin, and 0.198 g of catalyst were added to the autoclave in sequence. After sealing the autoclave, it was taken out of the glove box. The CO 2 pipeline was purged with hot air at 300 °C to remove moisture and oxygen, and then the CO 2 was connected to the autoclave valve while continuously introducing CO 2 . The reaction vessel was quickly filled with CO at a pressure of 2.5 MPa 2 , and the constant pressure was maintained. When the internal temperature of the autoclave reached 40 °C, the reaction started and this temperature was maintained for 24 h. After the reaction ended, the reaction kettle was cooled in cold water. After cooling to room temperature, the valve was opened to release carbon dioxide. After adding 30 mL of dichloromethane to dilute the product, it was poured into about 500 mL of deionized water and stirred for about 5 minutes to purify the product. After standing for the solution to layer, the upper aqueous solution was poured off, and then 500 mL of deionized water was added and the above operation was repeated 3 times to completely wash away the catalyst and by-products in the sample. It was precipitated repeatedly 3 times in methanol. Subsequently, the purified sample was placed in a fume hood to volatilize most of the solvent, then dried in a blast oven at 60 °C, and then further dried in a vacuum oven at 80 °C to constant weight. Finally, a modified poly(propylene carbonate) material was obtained. After testing, the prepared modified poly(propylene carbonate) material contained 24.8 mol% of chlorine groups, the number-average molecular weight was 40.7 kg / mol, and the molecular weight distribution index was 1.25. The glass transition temperature was 35.7 °C, the thermal decomposition temperature at 5% mass loss was 276.5%, the tensile strength was 6.3 MPa, the elongation at break was 277.8%, the oxygen permeability coefficient was 2.76 cm 3 ·mm / (m 2 ·day), and the water vapor permeability coefficient was 0.016 g·mm / (m 2 ·day). Example 4:

[0022] A 50 mL autoclave was dried overnight and heated in an oven at 110 °C. Then, it was immediately transferred to a glove box under a nitrogen atmosphere. After the autoclave cooled to room temperature, the reactants were added to it. 7.700 g of propylene oxide, 12.280 g of epichlorohydrin, and 0.198 g of catalyst were added to the autoclave in sequence. After sealing the autoclave, it was taken out of the glove box. The CO 2 pipeline was purged with hot air at 300 °C to remove moisture and oxygen, and then the CO 2 was connected to the autoclave valve while continuously introducing CO2 Quickly charge CO at a pressure of 2.5 MPa into the reaction vessel 2 , and maintain a constant pressure. When the internal temperature of the autoclave reaches 40 °C, start the reaction and maintain this temperature for 24 h. After the reaction is completed, cool the autoclave in cold water. After cooling to room temperature, open the valve to release carbon dioxide. After adding 30 mL of dichloromethane to dilute the product, pour it into about 500 mL of deionized water and stir for about 5 minutes to purify the product. After standing for the solution to layer, pour off the upper aqueous solution, then add 500 mL of deionized water and repeat the above operation 3 times to completely wash away the catalyst and by-products in the sample. Precipitate repeatedly 3 times in methanol, then place the purified sample in a fume hood to volatilize most of the solvent, then put it in a blast drying oven at 60 °C to dry, and then put it in a vacuum drying oven at 80 °C to further dry to constant weight, and finally obtain the modified poly(propylene carbonate) material. After testing, the prepared modified poly(propylene carbonate) material contains 35.7 mol% of chlorine groups, the number-average molecular weight is 31.6 kg / mol, and the molecular weight distribution index is 1.26. The glass transition temperature is 41.2 °C, the thermal decomposition temperature at 5% mass loss is 252.8%, the tensile strength is 21.1 MPa, the elongation at break is 4.5%, the oxygen permeation coefficient is 1.31 cm 3 ·mm / (m 2 ·day), and the water vapor permeation coefficient is 0.033 g·mm / (m 2 ·day). Example 5:

[0023] Dry a 50 mL autoclave overnight and heat it in an oven at 110 °C. Then, immediately transfer it to a glove box under a nitrogen atmosphere. After the autoclave cools to room temperature, add the reactants to it. Add 4.620 g of propylene oxide, 17.185 g of epichlorohydrin, and 0.198 g of catalyst to the autoclave in sequence. After sealing the autoclave, take it out of the glove box. Use hot air at 300 °C to purge the CO 2 pipeline to remove moisture and oxygen, and then connect the CO 2 to the autoclave valve while continuing to introduce CO 2 . Quickly charge CO at a pressure of 2.5 MPa into the reaction vessel 2, and maintain a constant pressure. When the internal temperature of the autoclave reaches 40 °C, the reaction starts and this temperature is maintained for 24 h. After the reaction is completed, the autoclave is cooled in cold water. After cooling to room temperature, the valve is opened to release carbon dioxide. After adding 30 mL of dichloromethane to dilute the product, it is poured into about 500 mL of deionized water and stirred for about 5 minutes to purify the product. After standing for the solution to layer, the upper aqueous solution is poured off, and then 500 mL of deionized water is added and the above operation is repeated 3 times to completely wash away the catalyst and by-products in the sample. It is precipitated repeatedly 3 times in methanol. Subsequently, the purified sample is placed in a fume hood to volatilize most of the solvent, then placed in a blast drying oven at 60 °C for drying, and then placed in a vacuum drying oven at 80 °C for further drying to constant weight, and finally a modified poly(propylene carbonate) material is obtained. After testing, the prepared modified poly(propylene carbonate) material contains 55.6 mol% of chlorine groups, the number-average molecular weight is 24.2 kg / mol, and the molecular weight distribution index is 1.26. The glass transition temperature is 40.2 °C, the thermal decomposition temperature at 5% mass loss is 256.3 °C, the tensile strength is 10.0 MPa, the elongation at break is 3.4%, and the oxygen permeability coefficient is 2.07 cm 3 ·mm / (m 2 ·day), and the water vapor permeability coefficient is 0.059 g·mm / (m 2 ·day). Example 6:

[0024] A 50 mL autoclave is dried overnight and heated in an oven at 110 °C. Then, it is immediately transferred to a glove box under a nitrogen atmosphere. After the autoclave is cooled to room temperature, the reactants are added to it. 3.080 g of propylene oxide, 20.400 g of epichlorohydrin and 0.198 g of catalyst are added to the autoclave in sequence. After sealing the autoclave, it is taken out of the glove box. The CO 2 pipeline is purged with hot air at 300 °C to remove moisture and oxygen, and then the CO 2 is connected to the autoclave valve while continuing to introduce CO 2 . The reaction vessel is quickly filled with CO at a pressure of 2.5 MPa 2, and maintain a constant pressure. When the internal temperature of the autoclave reaches 40 °C, the reaction starts and this temperature is maintained for 24 h. After the reaction is completed, the autoclave is cooled in cold water. After cooling to room temperature, the valve is opened to release carbon dioxide. After adding 30 mL of dichloromethane to dilute the product, it is poured into about 500 mL of deionized water and stirred for about 5 minutes to purify the product. After standing for the solution to layer, the upper aqueous solution is poured off, and then 500 mL of deionized water is added and the above operation is repeated 3 times to completely wash away the catalyst and by-products in the sample. It is precipitated repeatedly 3 times in methanol. Subsequently, the purified sample is placed in a fume hood to volatilize most of the solvent, then placed in a blast drying oven at 60 °C for drying, and then placed in a vacuum drying oven at 80 °C for further drying to constant weight, and finally the modified poly(propylene carbonate) material is obtained. After testing, the prepared modified poly(propylene carbonate) material contains 68.2 mol% of chlorine groups, the number-average molecular weight is 17.1 kg / mol, and the molecular weight distribution index is 1.33. The glass transition temperature is 40.4 °C, and the thermal decomposition temperature at 5% mass loss is 227.1%.

[0025] Comparative Example 1 A 50 mL autoclave was dried overnight and heated in an oven at 110 °C. Then, it was immediately transferred to a glove box under a nitrogen atmosphere. After the autoclave was cooled to room temperature, the reactants were added thereto. 13.200 g of propylene oxide, 151.5 μl of triethylborane (TEB), and 0.116 g of bis(triphenylphosphine imide) ammonium chloride (PPNCl) were sequentially added to the autoclave. After sealing the autoclave, it was taken out of the glove box. The CO 2 pipeline was purged with hot air at 300 °C to remove moisture and oxygen, and then the CO 2 was connected to the autoclave valve while continuously introducing CO 2 . The reaction vessel was quickly charged with CO at a pressure of 2.5 MPa 2 , and the constant pressure was maintained. When the internal temperature of the autoclave reached 60 °C, the reaction started and this temperature was maintained for 3 h. After the reaction was completed, the autoclave was cooled in cold water. After cooling to room temperature, the valve was opened to release carbon dioxide. After adding 30 mL of dichloromethane to dilute the product, it is poured into about 500 mL of deionized water and stirred for about 5 minutes to purify the product. After standing for the solution to layer, the upper aqueous solution is poured off, and then 500 mL of deionized water is added and the above operation is repeated 3 times to completely wash away the catalyst and by-products in the sample. It is precipitated repeatedly 3 times in methanol. Subsequently, the purified sample is placed in a fume hood to volatilize most of the solvent, then placed in a blast drying oven at 60 °C for drying, and then placed in a vacuum drying oven at 80 °C for further drying to constant weight, and finally the modified poly(propylene carbonate) material is obtained. After testing, the glass transition temperature of the prepared poly(propylene carbonate) material is 27.6 °C, the tensile strength is 8.2 MPa, the elongation at break is 335.4%, and the oxygen permeability coefficient is 2.21 cm3 ·mm / (m 2 ·day), and the water vapor transmission coefficient is 1.17 g·mm / (m 2 ·day).

[0026] It can be seen that the present invention can introduce epichlorohydrin as the third monomer and carry out a ternary copolymerization reaction with CO 2 , propylene oxide by a one-pot method. The steps are simple and the operation is convenient. Moreover, by adjusting different monomer feeding ratios, CO 2 pressure, reaction time, and reaction temperature, etc., a modified poly(propylene carbonate) material can be prepared. The obtained material has a higher glass transition temperature and thermal stability, good oxygen and water vapor barrier properties, as well as certain transparency and mechanical strength.

Claims

1. A modified polypropylene carbonate material, characterized in that A high molecular weight polymer obtained by ternary copolymerization of carbon dioxide, propylene oxide and epichlorohydrin, having a number average molecular weight of 10300 to 59400; its structure is shown in formula (1); wherein a≥1, b≥1, c≥0, a, b, c are all integers; 。 2. A method for preparing the modified polypropylene carbonate material according to claim 1, characterized in that The steps include: In a dry autoclave, propylene oxide, epichlorohydrin and a catalyst are added, carbon dioxide is introduced and a constant pressure is maintained, and the reaction is carried out at a set temperature; after the reaction is completed, the autoclave is cooled by an ice water bath to release unreacted carbon dioxide, and the product is purified to obtain a modified polypropylene carbonate material.

3. The method for preparing the modified polypropylene carbonate material according to claim 2, characterized in that The steps include: (1) Dry the autoclave overnight and heat it in an oven at 110 °C, then transfer it to a glove box with a nitrogen atmosphere; (2) After the autoclave is cooled to room temperature, propylene oxide, epichlorohydrin and a catalyst are added to the autoclave in sequence; (3) After sealing the autoclave, take it out of the glove box, use 300°C hot air to purge the CO2 pipeline to remove moisture and oxygen, then connect CO2 to the autoclave valve, continue to introduce CO2, fill it with a certain pressure of CO2, and maintain a constant pressure; when the internal temperature of the autoclave reaches the reaction temperature, start the reaction and maintain this temperature; (4) After the polymerization reaction is completed, the autoclave is cooled in an ice water bath, and then the valve is slowly opened to release the unreacted CO2; then dichloromethane is added to dilute the product, and deionized water is poured in to purify the product by stirring. After the solution is allowed to stand for stratification, the upper aqueous solution is poured out, and deionized water is added and the above operation is repeated 3 times to completely wash away the catalyst and by-products in the sample, and the product is repeatedly precipitated in methanol 3 times; (5) The purified sample was then placed in a fume hood to evaporate most of the solvent, and then placed in a 60°C forced air oven to dry, and then placed in an 80°C vacuum oven to further dry to constant weight, thereby finally obtaining a modified polypropylene carbonate material.

4. The method for preparing the modified polypropylene carbonate material according to claim 3, characterized in that: The molar ratio of propylene oxide, epichlorohydrin and catalyst is 1000 – 200:100 – 800:

1.

5. The method for preparing the modified polypropylene carbonate material according to claim 3, characterized in that: In the step (3), the CO2 pressure is 1.5 MPa - 3.5 MPa; the reaction temperature is 25 - 50°C; and the reaction time is 16 h - 36 h.

6. The method for preparing the modified polypropylene carbonate material according to claim 2, characterized in that: The catalyst is a tetranuclear organic boron catalyst.

Images