A carbon dioxide-based polycarbonate tetraol containing tertiary amine and its preparation method

Abstract

This invention discloses a carbon dioxide-based polycarbonate tetraol containing a tertiary amine and its preparation method. The polycarbonate tetraol is obtained by polymerizing epoxides and carbon dioxide in the presence of an organoboron catalyst, a dual-terminal active initiator, and a tertiary amine containing four terminal hydroxyl groups as a chain transfer agent. The three-active-center organoboron catalyst combined with the dual-terminal active initiator avoids the defect of metal residue in the product and exhibits excellent catalytic performance, high selectivity, and superior proton tolerance under mild reaction conditions. The tertiary amine chain transfer agent containing four terminal hydroxyl groups is prepared in situ from an aliphatic diamine and an epoxide, exhibiting good solubility in epoxides, high activity, and easy control of the molecular weight of the carbon dioxide-based polycarbonate tetraol. The polycarbonate tetraol prepared by this invention is low in cost and can be used as a raw material for preparing high-strength, biodegradable rigid polyurethane foam materials, possessing significant value for widespread application.

Description

Technical Field

[0001] This invention relates to the field of polymer material synthesis technology, and more specifically, to a method for preparing a biodegradable carbon dioxide-based polycarbonate tetraol. Background Technology

[0002] Polycarbonate polyols are oligomers containing carbonate groups and two or more terminal hydroxyl groups in their main chain. They combine the advantages of traditional polyether polyols and polyester polyols, exhibiting excellent hydrolytic stability, outstanding heat and oxidation resistance, high mechanical strength, and good chemical and weather resistance. Traditional methods for synthesizing polycarbonate polyols include the phosgene method, transesterification polymerization, and ring-opening polymerization of cyclic carbonates. These methods either involve highly toxic materials or require harsh conditions and complex routes, and have high raw material costs, hindering the structural diversity design and large-scale production of polycarbonate polyols. In recent years, the preparation of carbon dioxide-based polycarbonate polyols using CO2 and epoxides has attracted widespread attention. Using CO2 as a raw material to synthesize polymer materials not only aligns with the concept of sustainable development, enabling high-value utilization of CO2 and reducing dependence on petroleum resources, but also offers low cost, facilitating downstream applications.

[0003] Currently, carbon dioxide-based polycarbonate polyols are mainly synthesized using small-molecule polyols as chain transfer agents and metal complexes or non-metal Lewis acid-base pairs as catalysts. Bimetallic cyanides have been applied to the large-scale production of carbon dioxide-based polycarbonate polyols, but the synthesized carbon dioxide-based polyols have low carbonate segment content. The non-metallic triethylboron (TEB) / quaternary ammonium salt system (J. Am. Chem. Soc., 2016, 138: 11117-11120) can catalyze the copolymerization of carbon dioxide and epoxides to form carbon dioxide-based polymers with high carbonate ester content, but high loadings of carboxylic acid ammonium salt and TEB are required to obtain low molecular weight polyols (Macromolecules, 2019, 52: 2431–2438). Introducing chain transfer into the triethylboron (TEB) / quaternary ammonium salt catalyst system can reduce the loading of ammonium salt and TEB, resulting in low molecular weight polycarbonate polyols. However, the amount of TEB used is still too high, leading to high costs (J CO2Util, 2023, 75: 102571). Bifunctional catalysts (J Am Chem Soc, 2020, 142: 12245-12255) exhibit good tolerance to impurities containing active hydrogen, but epoxides are prone to self-polymerization, resulting in excessively high polyether content in the polyol. Patent (CN116162233A) discloses a bifunctional catalyst catalyzing the copolymerization of epoxides, carbon dioxide, and phthalic anhydride into polyarylate-polycarbonate terpolymers using a small-molecule diol chain transfer agent for the preparation of thermoplastic polyurethanes. However, linear polycarbonate diols synthesized from small-molecule diols are difficult to meet the requirements of rigid polyurethane foam materials. Developing branched polycarbonate tetraols with high hydroxyl values ​​holds great potential for achieving biodegradable polyurethane foam materials. However, chain transfer agents containing four hydroxyl or carboxyl groups have poor solubility in epoxides, making it difficult to obtain low molecular weight tetraols. Summary of the Invention

[0004] The purpose of this invention is to solve the technical problems of existing methods for preparing polycarbonate tetraols and to provide an efficient, green, and economical carbon dioxide-based polycarbonate tetraol containing tertiary amines and its preparation method. This invention utilizes a small-molecule dialiphatic amine reacting in situ with epoxides to generate a highly soluble polyhydroxy compound as a chain transfer agent, providing a solution for the successful preparation of polycarbonate tetraols. Furthermore, this chain transfer agent can introduce tertiary amine groups into the polycarbonate tetraol, exhibiting a self-catalytic effect for the subsequent synthesis of polyurethane foam materials.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A carbon dioxide-based polycarbonate tetraol containing a tertiary amine has the structure shown in formula (1), where a / (a+b) = 0.7~0.9, a and b are positive integers, n = 2-10, R = H or CH3, and the number-average molecular weight of the carbon dioxide-based polycarbonate tetraol is in the range of 1000-4000 Da.

[0006] The preparation method of the above-mentioned carbon dioxide-based polycarbonate tetraol containing tertiary amine includes the following steps: first, add epoxide alkane and aliphatic diamine to a high-pressure reactor, stir at 30-60°C to completely hydroxylate the aliphatic diamine, then add a trinuclear organoboron catalyst and a dual-terminal active initiator, introduce carbon dioxide, heat to copolymerize, after the reaction is completed, pour the product into a mixed solvent and stir to purify, heat to 50°C to volatilize the epoxide alkane, remove the upper aqueous phase, add dichloromethane to dissolve the product, then add deionized water and stir to purify, finally extract the polymer organic layer by liquid separation, and vacuum dry to remove the solvent to obtain carbon dioxide-based polycarbonate tetraol.

[0007] The structure of the trinuclear organoboron catalyst is shown in formula (2).

[0008] The dual-terminal active initiator is tetrabutylammonium isophthalate.

[0009] The molar ratio of the epoxide alkane to the dual-terminal active initiator is 1250~6000:1, the molar ratio of the trinuclear organoboron catalyst to the dual-terminal active initiator is 1~2:1, and the molar ratio of the aliphatic diamine to the dual-terminal active initiator is 15~90:1.

[0010] The carbon dioxide is introduced into the high-pressure reactor, and the internal pressure ranges from 1.0 to 3.0 MPa. The reaction temperature is 30 to 60°C, and the reaction time is 2 to 24 hours.

[0011] The mixed solvent is ethanol and deionized water in a volume ratio of 2:8.

[0012] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention uses aliphatic diamines and epoxy alkanes to generate tertiary amine chain transfer agents containing tetrahydroxyl groups in situ to adjust the molecular weight, thereby ensuring the synthesis of tetraol oligomers with controllable molecular weight.

[0013] (2) The combination of the trinuclear organoboron catalyst and the dual-terminal active initiator used in this invention has excellent catalytic activity, selectivity and proton tolerance, and high carbonate content. At the same time, it can overcome the defects of metal catalyst residue and large catalyst dosage in organic two-component catalytic systems, and has economic benefits and is suitable for large-scale production of tetraols.

[0014] (3) The carbon dioxide-based polycarbonate tetraol containing tertiary amine synthesized in this invention not only has biodegradability, but also has a self-catalytic effect in the subsequent preparation of polyurethane.

[0015] (4) The synthesis process of the present invention is simple, reproducible, controllable and the raw materials involved in the reaction are inexpensive, and it has important value for promotion and use.

[0016] (5) High-strength, biodegradable rigid polyurethane foam plastics can be prepared using the carbon dioxide-based polycarbonate tetraol containing tertiary amine provided by the present invention as raw material, which has important value for promotion and use. Attached Figure Description

[0017] Figure 1 The 1H NMR spectrum of the carbon dioxide-based polycarbonate tetraol containing tertiary amine prepared in Example 1 of this invention. 1 H NMR spectrum. Detailed Implementation

[0018] The present invention can be further explained and illustrated in conjunction with the following specific embodiments, but the specific embodiments do not limit the present invention in any way.

[0019] Example 1: A reaction was carried out using a molar ratio of PO: trinuclear organoboron catalyst: tetrabutylammonium isophthalate: ethylenediamine = 3000:1:1:50: 4.3g of ethylenediamine and 250g of propylene oxide were added to a 500ml high-pressure reactor, and the reaction was carried out at 50°C with stirring for 1 hour for hydroxylation. Then, 0.93g of tetrabutylammonium isophthalate and 9.4ml of catalyst dissolved in THF (concentration 0.153mol / L) were added, and the reactor was charged to 1MPa. CO2 was heated and stirred at 45℃ for 10 h. After the reaction, the mixture was cooled to room temperature and carbon dioxide was released. The product was then poured into a mixed solvent of ethanol and deionized water in a volume ratio of 2:8 and stirred once to remove residual catalyst. The mixture was heated to 50℃ to volatilize the epoxides, and the upper aqueous phase was removed. A suitable amount of dichloromethane was added to dissolve the product, and then deionized water was added and stirred for purification. This process was repeated three times. Finally, the polymer organic layer was extracted by liquid-liquid extraction, and the solvent was removed by vacuum drying to obtain carbon dioxide-based polycarbonate tetraol. Molecular weight and NMR analysis were performed, and the results are listed in Table 1. The product's 1H NMR spectrum... 1 H NMR image as follows Figure 1 As shown.

[0020] Example 2: A reaction was carried out using a molar ratio of PO:trinuclear organoboron catalyst:tetrabutylammonium isophthalate:ethylenediamine = 4000:2:1:90: 3.9g of ethylenediamine and 250g of propylene oxide were added to a 500ml high-pressure reactor, and the reaction was carried out at 60°C with stirring for 2 hours for hydroxylation. Then, 0.70g of tetrabutylammonium isophthalate and 14.1ml of catalyst dissolved in THF (concentration 0.153mol / L) were added, and the reactor was charged to 1.5MPa. CO2 was heated and stirred at 50°C for 20 hours. After the reaction was completed, the mixture was cooled to room temperature and carbon dioxide was released. The product was then poured into a mixed solvent of ethanol and deionized water in a volume ratio of 2:8 and stirred once to remove residual catalyst. The mixture was heated to 50°C to volatilize epoxides and the upper aqueous phase was removed. A suitable amount of dichloromethane was added to dissolve the product. Deionized water was then added and stirred to purify the product. This process was repeated three times. Finally, the polymer organic layer was extracted by liquid separation and dried under vacuum to remove the solvent, yielding carbon dioxide-based polycarbonate tetraol. Molecular weight and NMR analysis were performed on the product, and the results are listed in Table 1.

[0021] Example 3: The reaction was carried out according to the following molar ratio: EO: trinuclear organoboron catalyst: tetrabutylammonium isophthalate: ethylenediamine = 5000:1:1:30: 2.0g of ethylenediamine and 250g of ethylene oxide were added to a 500ml high-pressure reactor and hydroxylated for 1 hour under stirring at room temperature; 0.74g of tetrabutylammonium isophthalate and 7.4ml of catalyst dissolved in THF (concentration of 0.153mol / L) were added, and CO2 was introduced at 3.0MPa. The reaction was carried out under stirring at room temperature for 12 hours. After the reaction was completed, EO and carbon dioxide were released. The product was poured into a mixed solvent of ethanol and deionized water in a volume ratio of 2:8 and stirred to remove residual catalyst once. The upper aqueous phase was removed, and an appropriate amount of dichloromethane was added to dissolve the product. Then, deionized water was added and stirred to purify the product. This process was repeated 3 times. Finally, the polymer organic layer was extracted by liquid separation, and the solvent was removed by vacuum drying to obtain carbon dioxide-based polycarbonate tetraol. The molecular weight and NMR were measured and analyzed. The results are listed in Table 1.

[0022] Example 4: The reaction was carried out according to the following molar ratio: EO: trinuclear organoboron catalyst: tetrabutylammonium isophthalate: butanediamine = 1500:1:1:15: 3.3g ethylenediamine and 250g ethylene oxide were added to a 500ml high-pressure reactor and hydroxylated at 40℃ for 1 hour with stirring. Then, 2.46g tetrabutylammonium isophthalate and 24.7ml of catalyst dissolved in THF (concentration of 0.153mol / L) were added, and CO2 was introduced at 2.0MPa. The reaction was carried out at room temperature with stirring for 3 hours. After the reaction was completed, EO and carbon dioxide were released. The product was poured into a mixed solvent of ethanol and deionized water in a volume ratio of 2:8 and stirred to remove residual catalyst once. The upper aqueous phase was removed, and an appropriate amount of dichloromethane was added to dissolve the product. Then, deionized water was added and stirred to purify the product. This process was repeated 3 times. Finally, the polymer organic layer was extracted by liquid separation, and the solvent was removed by vacuum drying to obtain carbon dioxide-based polycarbonate tetraol. The molecular weight and NMR were measured and the results are listed in Table 1.

[0023] Comparative Example 1: The reaction was carried out according to the following formula: PO: trinuclear organoboron catalyst: tetrabutylammonium isophthalate: pentaerythritol = 2000:2:1:15: 1.41 g tetrabutylammonium isophthalate, 4.4 g pentaerythritol, 250 g propylene oxide, and 28.1 ml of catalyst dissolved in THF (concentration 0.153 mol / L) were sequentially added to a 500 mL high-pressure reactor, and 2.0 mL of propylene oxide was added to the reactor. The product was first reacted with MPa of carbon dioxide at 110℃ with stirring for 0.5 h, and then at 45℃ with stirring for 15 h. After the reaction was completed, the product was cooled to room temperature and carbon dioxide was released. A suitable amount of dichloromethane was added to dissolve the product. The product was then poured into a mixed solvent of ethanol and deionized water in a volume ratio of 2:8 and stirred to remove residual catalyst once. The product was heated to 50℃ to volatilize the epoxides and the upper aqueous phase was removed. A suitable amount of dichloromethane was added to dissolve the product, and then deionized water was added to purify the product by stirring. This process was repeated 3 times. Finally, the organic layer of the polymer was extracted by liquid separation and the solvent was removed by vacuum drying to obtain carbon dioxide-based polycarbonate tetraol. The molecular weight and NMR were measured and analyzed. The results are listed in Table 1.

[0024] Comparative Example 2: The reaction was carried out according to the following formula: PO: trinuclear organoboron catalyst: tetrabutylammonium isophthalate: ethylenediamine = 3000:1:1:50. 0.93g of tetrabutylammonium isophthalate, 4.3g of ethylenediamine, 250g of propylene oxide, and 9.4ml of catalyst dissolved in THF (concentration of 0.153mol / L) were added sequentially to a 500ml high-pressure reactor. 2.0MPa CO2 was introduced, and the reaction was carried out at 45℃ with stirring for 16h. After the reaction was completed, the mixture was cooled to room temperature and carbon dioxide was released. A precipitate was formed and poured into a mixed solvent of ethanol and deionized water in a volume ratio of 2:8. The mixture was stirred to remove the residual catalyst once. The mixture was heated to 50℃ to volatilize the alkyl epoxides and the upper aqueous phase was removed. An appropriate amount of dichloromethane was added to dissolve the product. Deionized water was then added and stirred for purification. This process was repeated 3 times. Finally, the organic layer of the polymer was extracted by liquid separation. After vacuum drying to remove the solvent, no polymer was obtained.

[0025] Table 1. Molecular weight and composition of polycarbonate tetraols

[0026] As shown in Table 1, this invention successfully obtained carbon dioxide-based polycarbonate tetraols through copolymerization of carbon dioxide and epoxy monomers in the presence of a tertiary amine tetraol chain transfer agent. The number-average molecular weight of the tetraol can be controlled by adjusting the molar ratio of the epoxy monomer and the chain transfer agent. The combination of the trinuclear organoboron catalyst and the dual-terminal active initiator exhibited excellent catalytic activity and selectivity under low loading, and maintained good catalytic activity even in the presence of the tetraol chain transfer agent, indicating its excellent proton tolerance. Meanwhile, Comparative Example 1 shows that the preparation of pentaerythritol using this method was not effective, including high polyether content and high molecular weight; analysis of Comparative Example 2 shows that ethylenediamine was not hydroxylated and polymerized with CO2 to form polyurea, thus no polycarbonate tetraol was generated.

[0027] Example 5: 30 g of the carbon dioxide-based polycarbonate tetraol described in Example 1 was added to a 150 ml polytetrafluoroethylene beaker and dehydrated under vacuum at 80°C for 3 h. After dehydration, the mixture was cooled to room temperature, and 0.60 g of deionized water, 0.10 g of foaming catalyst A33 (a liquid catalyst containing 33% triethylenediamine), 0.30 g of gel catalyst T9 (stannous isooctanoate), 0.36 g of foaming agent silicone oil (UF5880), 0.90 g of flexible foaming agent (UF365), and 7.5 g of anhydrous acetonitrile (ACN) and other additives were added. The mixture was then mechanically stirred at 1500 r / min for 2 min. Then, gPAPI (NCOwt%=32.8%) was quickly poured into the mixture and stirred at the same speed for 20 s. The mixture was then poured into an open mold, allowed to foam freely at ambient temperature, and then transferred to a 60°C oven for curing for 24 h to obtain a yellow polycarbonate-type foamed polyurethane. The compression performance was tested according to GB / T 8813—2020 standard, and the compressive strength was 57.1 kPa at a strain of 10%.

[0028] Comparative Example 3: 30 g of commercial polyether tetraol (hydroxyl value 218 mg KOH / g) was added to a 150 ml polytetrafluoroethylene beaker and dehydrated under vacuum at 80 °C for 3 h. After the dehydration was completed, the mixture was cooled to room temperature and 0.60 g of deionized water, 0.30 g of foaming catalyst A33 (liquid catalyst containing 33% triethylenediamine), 0.30 g of gel catalyst T9 (stannous isooctanoate), 0.36 g of foam leveling agent silicone oil (UF5880), 0.90 g of foaming agent (UF365), and 7.5 g of anhydrous acetonitrile (ACN) and other additives were added. The mixture was then stirred mechanically at 1500 r / min for 2 min. Then, 18g of PAPI (NCOwt%=32.8%) was quickly poured into the above mixture and stirred at the same speed for 20s. The mixture was then poured into an open mold and allowed to foam freely at ambient temperature before being transferred to a 60℃ oven for curing for 24h to obtain yellow polyether-type foamed polyurethane. The compression performance was tested according to GB / T 8813—2020 standard, and the compressive strength was 41.8kPa at a strain of 10%.

[0029] Comparing Example 5 and Comparative Example 3, it can be seen that when preparing foamed polyurethane using carbon dioxide-based polycarbonate tetraol as raw material, less catalyst can be added and the resulting polyurethane foam has higher strength.

Claims

1. A carbon dioxide-based polycarbonate tetraol containing a tertiary amine, the structure of which is shown in formula (1), wherein a / (a+b) = 0.7~0.9, a and b are positive integers, n = 2-10, R = H or CH3, and the number average molecular weight of the carbon dioxide-based polycarbonate tetraol is in the range of 1000-4000 Da. 。 2. The method for preparing the carbon dioxide-based polycarbonate tetraol containing tertiary amine as described in claim 1, characterized in that... The process includes the following steps: First, add epoxide alkane and aliphatic diamine to a high-pressure reactor, stir at 30-60°C to completely hydroxylate the aliphatic diamine, then add a trinuclear organoboron catalyst and a dual-terminal active initiator, introduce carbon dioxide, and heat to copolymerize. After the reaction is complete, pour the product into a mixed solvent and stir to purify. Heat to 50°C to volatilize the epoxide alkane, remove the upper aqueous phase, add dichloromethane to dissolve the product, then add deionized water and stir to purify. Finally, extract the polymer organic layer by liquid-liquid separation, and remove the solvent by vacuum drying to obtain carbon dioxide-based polycarbonate tetraol.

3. The method for preparing carbon dioxide-based polycarbonate tetraol as described in claim 1, characterized in that... The structure of the trinuclear organoboron catalyst is shown in formula (2). 。 4. The method for preparing carbon dioxide-based polycarbonate tetraol as described in claim 1, characterized in that... The dual-terminal active initiator is tetrabutylammonium isophthalate.

5. The method for preparing carbon dioxide-based polycarbonate tetraol as described in claim 1, characterized in that... The molar ratio of the epoxide alkane to the dual-terminal active initiator is 1250~6000:1, the molar ratio of the trinuclear organoboron catalyst to the dual-terminal active initiator is 1~2:1, and the molar ratio of the aliphatic diamine to the dual-terminal active initiator is 15~90:

1.

6. The method for preparing carbon dioxide-based polycarbonate tetraol as described in claim 1, characterized in that... The carbon dioxide is introduced into the high-pressure reactor, and the internal pressure ranges from 1.0 to 3.0 MPa. The reaction temperature is 30 to 60°C, and the reaction time is 2 to 24 hours.

7. The method for preparing carbon dioxide-based polycarbonate tetraol as described in claim 1, characterized in that... The mixed solvent is ethanol and deionized water in a volume ratio of 2:

8.

8. The use of the carbon dioxide-based polycarbonate tetraol of claim 1 in the preparation of foamed polyurethane.

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