A flame-retardant polypropylene carbonate, its preparation method and application

Abstract

This application belongs to the field of flame retardant materials technology, and discloses a flame-retardant polypropylene carbonate, its preparation method, and its applications. The preparation method of the flame-retardant polypropylene carbonate includes: reacting a flame-retardant monomer with an epoxide in a CO2 atmosphere at a pressure of 1-4 MPa under the action of a catalyst; and collecting the flame-retardant polypropylene carbonate from the product of the previous step. The flame-retardant polypropylene carbonate of this application is prepared by ternary copolymerization of a flame-retardant monomer containing DOPO and cyclic anhydrides with CO2 and PO. On the one hand, it has good flame retardancy; its molecular structure is halogen-free and biodegradable; it does not produce smoke or toxic corrosive gases during combustion, making it safe and environmentally friendly. On the other hand, the flame-retardant polypropylene carbonate has a narrow molecular weight distribution and good stability and consistency. The flame-retardant polypropylene carbonate of this application has good application prospects.

Description

Technical Field

[0001] This application belongs to the field of flame retardant materials technology, specifically relating to a flame retardant polypropylene carbonate, its preparation method, and its application. Background Technology

[0002] With the rapid development of modern industry, the burning of large quantities of fossil fuels has led to a year-on-year increase in atmospheric CO2 levels, causing a series of serious environmental problems such as global warming, rising sea levels, and frequent extreme weather events. At the same time, CO2 is also an important carbon resource; therefore, converting carbon dioxide into high-value-added chemical products through chemical transformation is one of the important ways to reduce atmospheric CO2 levels.

[0003] In related technologies, copolymerizing CO2 and propylene oxide (PO) to prepare polypropylene carbonate (PPC) with good oxygen barrier properties, biocompatibility, and biodegradability not only realizes the resource utilization of CO2 but also alleviates the increasingly serious problem of white pollution. However, aliphatic polycarbonates are highly flammable and release a large amount of heat and drippings during combustion, making them extremely prone to causing fires.

[0004] Currently, flame-retardant PPC can be prepared by introducing a halogenated third monomer. For example, patent application CN202211442830.0 discloses a flame-retardant carbon dioxide-based polycarbonate and its preparation method, which adds the flame-retardant functional monomer chlorobrines to the polymerization reaction of CO2 and PO to synthesize flame-retardant polypropylene carbonate. However, flame-retardant PPC prepared by introducing a halogenated third monomer will generate toxic and corrosive hydrogen halide gas when burned, which is harmful to the environment and human health. Summary of the Invention

[0005] This application provides a flame-retardant polypropylene carbonate, its preparation method, and its application, aiming to solve the problem that existing flame-retardant polypropylene carbonate generates toxic and corrosive hydrogen halide gas when burned, which harms the environment and human health.

[0006] To achieve the above objectives, the present application adopts the following technical solution.

[0007] This application provides a flame-retardant polypropylene carbonate, the chemical structure of which is shown in formula (1):

[0008]

[0009] Where n is a positive integer, 149≤n≤216.

[0010] This application also provides a method for preparing the above-mentioned flame-retardant polypropylene carbonate, including:

[0011] In a CO2 atmosphere with a pressure of 1-4 MPa, the flame-retardant monomer and epoxide react under the action of a catalyst.

[0012] Flame-retardant polypropylene carbonate was collected from the product of the previous step;

[0013] The flame-retardant monomer has the chemical structure shown in formula (2):

[0014]

[0015] In some embodiments, the epoxide is any one or a mixture of propylene oxide, butane oxide, hexane oxide, or cyclohexane oxide.

[0016] In some embodiments, the catalyst is any one of a cobalt-salen complex, a metal carboxylate, a metal porphyrin, or a bimetallic cyanide.

[0017] In some embodiments, the molar ratio of the epoxide to the flame-retardant monomer is 100:(1-5).

[0018] In some embodiments, the molar ratio of the catalyst to the flame-retardant monomer is (1-5):1000.

[0019] In some implementations, the reaction occurs at a temperature of 60–90°C for a duration of 12–28 hours.

[0020] In some implementations, the pressure of the CO2 is 3-4 MPa.

[0021] In some embodiments, collecting the flame-retardant polypropylene carbonate from the product of the previous step includes:

[0022] The reaction product was dissolved in chloroform and washed successively with 5% HCl solution and deionized water, repeated 3-5 times. Then, it was distilled, concentrated, and precipitated with methanol to obtain flame-retardant polypropylene carbonate.

[0023] Applications of the above-mentioned flame-retardant polypropylene carbonate and the flame-retardant polypropylene carbonate prepared by the above preparation method in flame-retardant materials.

[0024] Compared with the prior art, the beneficial effects of this application are as follows:

[0025] The flame-retardant polypropylene carbonate of this application is prepared by ternary copolymerization of a flame-retardant monomer containing DOPO and cyclic anhydrides with CO2 and PO. On the one hand, it exhibits excellent flame retardancy; its molecular structure is halogen-free and biodegradable; and it does not produce smoke or toxic corrosive gases during combustion, making it safe and environmentally friendly. On the other hand, the flame-retardant polypropylene carbonate has a narrow molecular weight distribution, exhibiting good stability and consistency. The flame-retardant polypropylene carbonate of this application has promising application prospects.

[0026] The method for preparing flame-retardant polypropylene carbonate disclosed in this application enables the already ring-opened and active PO to more easily combine with the flame-retardant monomers at higher concentrations in the system during the copolymerization reaction, allowing them to rapidly insert into the molecular chain. Conversely, when the flame-retardant monomer insertion concentration is low, PO will combine with CO2. This alternating competition between the flame-retardant monomers and CO2 for insertion into the molecular chain avoids the continuous reaction of propylene oxide to generate the byproduct cyclic carbonate, resulting in a flame-retardant polypropylene carbonate with a narrow molecular weight distribution and good stability and consistency. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 The infrared spectra of the flame-retardant polypropylene carbonate prepared in Example 1, the flame-retardant monomer prepared in Example 1, and commercial PPC are shown.

[0029] Figure 2 This is a comparison chart of the combustion effects of flame-retardant polypropylene carbonate prepared in Example 1 and commercial PPC. Detailed Implementation

[0030] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0031] In the following description of this embodiment, the terms "including", "comprising", "having", and "containing" are all open-ended terms, meaning that they include but are not limited to.

[0032] In the following description of this embodiment, the term "and / or" is used to describe the association relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, B existing alone, and A and B existing simultaneously. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0033] In the following description of this embodiment, the term "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0034] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms "a" and "the" as used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0035] Those skilled in the art should understand that, in the following description of the embodiments of this application, the sequence of numbers does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0036] Those skilled in the art will understand that the numerical ranges in the embodiments of this application should be understood to specifically disclose each intermediate value between the upper and lower limits of the range. Each smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included within the scope of this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0037] Unless otherwise stated, the technical / scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. While this application describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this application. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0038] This application provides a flame-retardant polypropylene carbonate, the chemical structure of which is shown in formula (1):

[0039]

[0040] Where n is a positive integer, 149≤n≤216.

[0041] The flame-retardant polypropylene carbonate of this application involves ternary copolymerization of a flame-retardant monomer as a third monomer with CO2 and PO. The flame-retardant monomer and CO2 alternately compete for insertion into the molecular chain, avoiding the continuous reaction of propylene oxide to generate cyclic carbonates as a byproduct. The resulting flame-retardant polypropylene carbonate has a high molecular weight and excellent flame retardancy. This flame-retardant polypropylene carbonate is halogen-free, biodegradable, and does not produce smoke or toxic corrosive gases during combustion, making it safe and environmentally friendly.

[0042] This application also provides a method for preparing the above-mentioned flame-retardant polypropylene carbonate, including:

[0043] In a CO2 atmosphere with a pressure of 1-4 MPa, the flame-retardant monomer and epoxide react under the action of a catalyst.

[0044] Flame-retardant polypropylene carbonate was collected from the product of the previous step;

[0045] The flame-retardant monomer has the chemical structure shown in formula (2):

[0046]

[0047] The flame-retardant monomer is prepared from DOPO and itaconic anhydride, and the preparation process is as follows:

[0048]

[0049] Based on the DOPO and itaconic anhydride structures, the flame-retardant monomers exhibit high thermal and chemical stability. Furthermore, during the copolymerization reaction, the cyclic anhydride structure and CO2 alternately compete for insertion into the molecular chain, controlling the molecular weight. This not only results in a narrow molecular weight distribution for the flame-retardant polypropylene carbonate but also prevents the continuous reaction of propylene oxide to form cyclic carbonates, promoting the polymerization reaction and increasing the yield. The flame-retardant polypropylene carbonate prepared in this application exhibits good flame-retardant stability and consistency due to its narrow molecular weight distribution.

[0050] In this application, the epoxide is any one or a mixture of propylene oxide, butane oxide, hexane oxide, or cyclohexane oxide. In the embodiments of this application, propylene oxide is selected as the epoxide.

[0051] In this application, the catalyst is any one of a cobalt-salen complex, a metal carboxylate, a metal porphyrin, or a bimetallic cyanide. The metal carboxylate includes iron carboxylates, cobalt carboxylates, or nickel carboxylates. The metal porphyrin includes iron porphyrins, cobalt porphyrins, or nickel porphyrins. Any catalyst capable of catalyzing the synthesis of polypropylene carbonate is acceptable.

[0052] The catalyst is preferably a cobalt-salen complex, which catalyzes the alternating copolymerization of racemic propylene oxide, carbon dioxide, and flame-retardant monomers. It should be noted that the cobalt-salen complex can be levorotatory cobalt-salen or binuclear cobalt-salen. In the embodiments of this application, the cobalt-salen complex is preferably binuclear cobalt-salen, and its chemical structure is shown in formula (3):

[0053]

[0054] In the embodiments of this application, the pressure of the CO2 is 1 to 4 MPa, which can be 1 MPa, 2 MPa, 3 MPa, 4 MPa, or any pressure value within the aforementioned pressure range. More preferably, the pressure of the CO2 is 3 to 4 MPa.

[0055] In the embodiments of this application, the molar ratio of the epoxide to the flame-retardant monomer is 100:(1-5), which can be 100:1, 100:2, 100:3, 100:4, 100:5, or any ratio within the aforementioned range. The molar ratio of the catalyst to the flame-retardant monomer is (1-5):1000, which can be 1:1000, 2:1000, 3:1000, 4:1000, 5:1000, or any ratio within the aforementioned range. Within the above molar ratio range, the prepared flame-retardant polypropylene carbonate has a narrow molecular weight distribution, and exhibits good stability and consistency in flame-retardant effect.

[0056] In the embodiments of this application, the reaction temperature is 60–90°C, which can be 60°C, 70°C, 80°C, 90°C, or any temperature value within the stated temperature range. The reaction time is 12–28 hours. If the temperature is below 60°C, the copolymerization reaction will be incomplete; if the temperature is above 90°C, the probability of side reactions will increase, reducing the performance of the flame-retardant polypropylene carbonate. The flame-retardant polypropylene carbonate prepared within the range of 60–90°C exhibits the best performance.

[0057] In embodiments of this application, collecting flame-retardant polypropylene carbonate from the product of the previous step includes:

[0058] The reaction product was dissolved in chloroform and washed successively with 5% HCl solution and deionized water, repeated 3-5 times. Then, it was subjected to distillation, concentration, and methanol precipitation to obtain flame-retardant polypropylene carbonate. Removing residual catalyst and unreacted propylene carbonate from the reaction product improves the flame-retardant properties, thermal properties, and mechanical properties of the flame-retardant polypropylene carbonate.

[0059] The flame-retardant polypropylene carbonate of this application can be used to prepare flame-retardant materials, or as a flame-retardant material in clothing, petroleum, chemical, metallurgy, shipbuilding and other fields.

[0060] The present invention will be further illustrated by the following examples.

[0061] Example 1

[0062] This embodiment provides a method for preparing flame-retardant polypropylene carbonate, including:

[0063] S1, Preparation of flame retardant monomer: Dissolve 0.1 mol itaconic anhydride and 0.1 mol DOPO in 100 ml tetrahydrofuran, stir and reflux at 50 °C for 7 h, and filter; wash the solid obtained by filtration with anhydrous ethanol, and then dry in a vacuum oven at 50 °C for 24 h to obtain flame retardant monomer.

[0064] S2, 0.036 mmol of a dual-core cobalt selene catalyst and 8 mmol of flame-retardant monomer were added to a 250 ml high-pressure reactor equipped with a magnetic stirrer. The reactor was purged with nitrogen to replace the air inside. Then, 160 mmol of propylene oxide was added, and CO2 was introduced until the pressure inside the reactor reached 4 MPa. The temperature was raised to 70 °C for copolymerization, and the reaction time was 24 h. After the reaction, the high-pressure reactor was cooled and depressurized. The copolymer was dissolved in chloroform and magnetically stirred for about 15 min. It was then washed and separated successively with 5% HCl solution and deionized water, repeated 5 times to remove residual catalyst. The chloroform solution of the copolymer was then placed in a round-bottom flask for rotary evaporation and concentration, and then precipitated three times with methanol to remove a small amount of propylene carbonate, yielding flame-retardant polypropylene carbonate.

[0065] The flame-retardant polypropylene carbonate prepared in Example 1 had a reaction yield of 87% and a molecular weight distribution of 1.04.

[0066] Example 2

[0067] This embodiment provides a method for preparing flame-retardant polypropylene carbonate, including:

[0068] S1, Preparation of flame retardant monomer: Dissolve 0.1 mol itaconic anhydride and 0.1 mol DOPO in 100 ml tetrahydrofuran, stir and reflux at 50 °C for 7 h, and filter; wash the solid obtained by filtration with anhydrous ethanol, and then dry in a vacuum oven at 50 °C for 24 h to obtain flame retardant monomer.

[0069] S2, 0.024 mmol of a dual-core cobalt selene catalyst and 8 mmol of flame-retardant monomer were added to a 250 ml high-pressure reactor equipped with a magnetic stirrer. The reactor was purged with nitrogen to replace the air. Then, 270 mmol of propylene oxide was added, and CO2 was introduced until the pressure inside the reactor reached 3 MPa. The temperature was raised to 60 °C for copolymerization, and the reaction time was 12 h. After the reaction, the high-pressure reactor was cooled and depressurized. The copolymer was dissolved in chloroform and magnetically stirred for about 15 min. It was then washed and separated successively with 5% HCl solution and deionized water, repeated 5 times to remove residual catalyst. The chloroform solution of the copolymer was then concentrated by rotary evaporation in a round-bottom flask, and then precipitated three times with methanol to remove a small amount of propylene carbonate, yielding flame-retardant polypropylene carbonate.

[0070] The flame-retardant polypropylene carbonate prepared in Example 2 had a reaction yield of 83% and a molecular weight distribution of 1.10.

[0071] Example 3

[0072] This embodiment provides a method for preparing flame-retardant polypropylene carbonate, including:

[0073] S1, Preparation of flame retardant monomer: Dissolve 0.1 mol itaconic anhydride and 0.1 mol DOPO in 100 ml tetrahydrofuran, stir and reflux at 50 °C for 7 h, and filter; wash the solid obtained by filtration with anhydrous ethanol, and then dry in a vacuum oven at 50 °C for 24 h to obtain flame retardant monomer.

[0074] S2, 0.008 mmol of dual-core Salen cobalt catalyst and 8 mmol of flame-retardant monomer were added to a 250 ml high-pressure reactor equipped with a magnetic stirrer. The reactor was purged with nitrogen to replace the air. Then, 800 mmol of propylene oxide was added, and CO2 was introduced until the pressure inside the reactor reached 1 MPa. The temperature was raised to 90 °C for copolymerization, and the reaction time was 18 h. After the reaction, the high-pressure reactor was cooled and depressurized. The copolymer was dissolved in chloroform and magnetically stirred for about 15 min. It was then washed and separated successively with 5% HCl solution and deionized water, repeated 5 times to remove residual catalyst. The chloroform solution of the copolymer was then concentrated by rotary evaporation in a round-bottom flask, and then precipitated three times with methanol to remove a small amount of propylene carbonate, yielding flame-retardant polypropylene carbonate.

[0075] The flame-retardant polypropylene carbonate prepared in Example 3 had a reaction yield of 65% and a molecular weight distribution of 1.27.

[0076] The performance of the flame-retardant polypropylene carbonate prepared in Example 1 was tested, as follows:

[0077] 1. Infrared spectroscopy was performed on the flame-retardant polypropylene carbonate prepared in Example 1, the flame-retardant monomer synthesized in Example 1, CO2, and commercial PPC. The test results are as follows: Figure 1 As shown. Figure 1 In this context, PPCD represents the flame-retardant polypropylene carbonate prepared in Example 1, DOPO-ITA represents the flame-retardant monomer, and PPC is commercially available polypropylene carbonate produced by alternating copolymerization of propylene oxide.

[0078] from Figure 1 It can be seen that in the infrared spectrum of PPCD, at 918 cm⁻¹ -1 1118cm -1 and 1194cm -1 The flame retardant monomer exhibits characteristic absorption peaks for the PO-Ph, P-Ph, and P=O bonds of the phosphenanthrene groups at 1430 cm⁻¹. -1 and 1600cm -1 The flame retardant monomer exhibits characteristic absorption peaks at 1780 cm⁻¹ for the PC bond and the C / C backbone on the benzene ring, respectively. Furthermore, the anhydride group in the flame retardant monomer shows a peak at 1780 cm⁻¹. -1 and 1860cm -1 The stretching vibration absorption peak of the C=O bond at 1740 cm⁻¹ completely disappeared. -1 The presence of a stretching vibration peak of the C=O bond in the ester group indicates that the anhydride unit in the flame-retardant monomer breaks into ester bonds of the carbonate chain during copolymerization, proving that the synthesized substance is the target product, flame-retardant polypropylene carbonate.

[0079] 2. Combustion tests were conducted on the flame-retardant polypropylene carbonate prepared in Example 1 and on commercial PPC. The commercial PPC was a commercially available polypropylene carbonate produced by alternating copolymerization of CO2 and propylene oxide.

[0080] The specific testing method is as follows: use tweezers to pick up the flame-retardant polypropylene carbonate and commercial PPC samples prepared in Example 1, place them in the center above an alcohol lamp, light the alcohol lamp and remove it, observe the burning of the samples and record the results, and characterize the flame retardancy of the materials by the flame retardancy rating UL94 and the limiting oxygen index LOI.

[0081] The UL94 flame retardancy rating criteria are as follows:

[0082] HB: The lowest flame retardant rating in the UL94 standard. It requires a burning rate of less than 40 mm per minute for samples 3 to 13 mm thick; less than 70 mm per minute for samples less than 3 mm thick; or extinguishing before reaching the 100 mm mark.

[0083] V-2: After two 10-second burning tests on the sample, the flame extinguishes within 60 seconds. It can ignite cotton wool up to 30cm below.

[0084] V-1: After two 10-second burning tests on the sample, the flame extinguishes within 60 seconds. It cannot ignite cotton wool 30cm below.

[0085] V-0: After two 10-second burning tests on the sample, the flame extinguishes within 30 seconds. No burning material should fall.

[0086] The Limiting Oxygen Index (LOI) refers to a material's oxidative stability at high temperatures and is used to assess its combustion performance and safety. Materials with high LOI values ​​generally have better thermal stability and fire resistance, while materials with low LOI values ​​may burn or decompose at high temperatures, leading to safety issues.

[0087] like Figure 2 As shown in Figure a, the product PPC is a flammable polymer material that burns violently after ignition, accompanied by a large amount of debris falling off, and cannot pass the UL-94 rating, with an LOI value of only 19.8%.

[0088] like Figure 2 As shown in Figure b, the flame-retardant polypropylene carbonate prepared in Example 1 is not easily combustible after ignition, the droplet phenomenon is significantly improved, the average secondary ignition time is 5.5s and 6.8s respectively, the vertical burning rating reaches V-0, and the LOI value increases significantly to 33.2%.

[0089] The flame-retardant polypropylene carbonates prepared in Examples 2 and 3 both achieved a UL94 rating of V-0, with LOI values ​​of 32.9% and 33.0%, respectively. Combustion test results demonstrate that the flame-retardant polypropylene carbonate prepared in this application exhibits excellent flame-retardant properties.

[0090] Although the present invention has been described in detail in this specification with general description and specific embodiments, some modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention are within the scope of protection claimed by the present invention.

Claims

1. A method for preparing flame-retardant polypropylene carbonate, characterized in that, include: In a CO2 atmosphere with a pressure of 1-4 MPa, the flame-retardant monomer and epoxide react under the action of a catalyst. Flame-retardant polypropylene carbonate was collected from the product of the previous step; The flame-retardant monomer has the chemical structure shown in formula (2): 。 2. The preparation method according to claim 1, characterized in that, The epoxide is any one or a mixture of propylene oxide, butane oxide, hexane oxide, or cyclohexane oxide.

3. The preparation method according to claim 1, characterized in that, The catalyst is any one of the following: cobalt-salen complex, metal carboxylates, metal porphyrins, and bimetallic cyanides.

4. The preparation method according to claim 1, characterized in that, The molar ratio of the epoxide to the flame-retardant monomer is 100:(1 ~ 5).

5. The preparation method according to claim 1, characterized in that, The molar ratio of the catalyst to the flame-retardant monomer is (1 ~ 5):1000.

6. The preparation method according to claim 1, characterized in that, The reaction occurs at a temperature of 60 ~ 90 ℃ for 12 ~ 28 h.

7. The preparation method according to claim 1, characterized in that, The pressure of the CO2 is 3-4 MPa.

8. The preparation method according to claim 1, characterized in that, The collection of flame-retardant polypropylene carbonate from the product of the previous step includes: The reaction product was dissolved in chloroform and washed successively with 5% HCl solution and deionized water, repeated 3-5 times. Then, it was distilled, concentrated, and precipitated with methanol to obtain flame-retardant polypropylene carbonate.

9. The application of the flame-retardant polypropylene carbonate prepared by the preparation method according to any one of claims 1-8 in flame-retardant materials.

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