Preparation method of carbon dioxide-based polycarbonate diol

Abstract

The invention discloses a preparation method of carbon dioxide-based polycarbonate dihydric alcohol, and the dihydric alcohol is prepared by taking aromatic micromolecular dihydric alcohol as a chain transfer agent through one-pot one-step polymerization reaction of epoxide and carbon dioxide under the action of a non-metal catalyst. The method for adjusting copolymerization by using carbon dioxide and epoxide has the innovation that aromatic micromolecular dihydric alcohol is used as a chain transfer agent for the first time, a benzene ring structure is introduced to polycarbonate dihydric alcohol, and a rigid group is introduced to a molecular structure, so that the thermal stability is improved while the degradability of the polymer dihydric alcohol is ensured. The end of the carbon dioxide based polycarbonate diol prepared by the invention is completely hydroxyl, the number-average molecular weight range is 1400-6300g / mol, the polycarbonate content in a chain segment is adjustable and can reach 71-87%, and the carbon dioxide based polycarbonate diol has good heat resistance and biodegradability.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer material synthesis, and more specifically, to a method for preparing carbon dioxide-based polycarbonate diol. Background Art

[0002] Polycarbonate diol is a type of diol with excellent properties. It has repeating polar polycarbonate groups in its main chain and hydroxyl groups at both ends of the main chain, and is often used as the main raw material for the synthesis of polyurethane coatings, finishing agents, and elastomers. Compared with polyester-based and polyether-based polyurethanes, polycarbonate-based polyurethanes have good hydrolysis resistance, antioxidant properties, and biocompatibility. However, the polyurethane materials prepared from existing ordinary polycarbonate diols often have low wear resistance and temperature resistance, which limits the further application of downstream products. Therefore, polyester polycarbonate diol obtained by introducing a benzene ring into the main chain of polycarbonate diol introduces a rigid group from the molecular structure, which helps to improve the performance of downstream polyurethane products, enabling them to have both the advantages of hydrolysis resistance and antioxidant properties of polycarbonate-based polyurethanes and the advantages of wear resistance, temperature resistance, and oil resistance of polyester-based polyurethanes.

[0003] In the synthesis methods of polycarbonate diol, the phosgene method has safety hazards and environmental protection problems due to the use of highly toxic raw materials and high costs. In addition, the transesterification method is also a commonly used method, but the traditional transesterification method has an energy consumption 30 - 40% higher than that of the present invention and by-products need to be removed during the preparation process, so the requirements for equipment are very high, and the equipment investment cost increases by about 50%. Due to its non-toxic safety and simple equipment requirements, the regulated copolymerization method of carbon dioxide and epoxide has significant cost-effectiveness and environmental friendliness. While realizing the efficient resource utilization of greenhouse gases, it can also endow the diol with rich structural designability through the selection of diverse epoxides. In addition, the precise regulation of the dosage of the chain transfer agent enables the molecular weight of the prepared diol to be controllable. Summary of the Invention

[0004] The object of the present invention is to overcome the deficiencies of the prior art and provide a method for preparing carbon dioxide-based polycarbonate diol with good heat resistance and biodegradability.

[0005] To achieve the above object, the present invention adopts the following technical scheme:

[0006] A method for preparing carbon dioxide-based polycarbonate diol, the structural characteristics of the carbon dioxide-based polycarbonate diol are shown in Formula 1, where a≥1, b≥1, and R is an aliphatic hydrocarbon group with 2 - 6 carbon atoms;

[0007]

[0008] The preparation method comprises the following steps: adding propylene oxide, a catalyst, and an aromatic small-molecule chain transfer agent into a high-pressure reactor in sequence, filling with carbon dioxide, and then carrying out a reaction under the conditions of heating and stirring; after the reaction is completed, dissolving the product in dichloromethane, pouring it into deionized water, stirring for purification, and drying to obtain carbon dioxide-based polycarbonate diol;

[0009] The structural formula of the aromatic small-molecule chain transfer agent is shown in Formula 2, wherein R is an aliphatic hydrocarbon group with 2 to 6 carbon atoms;

[0010]

[0011]

[0012] Preferably, the catalyst is a Lewis acid-base pair composite catalyst in a non-metallic catalyst system; the Lewis acid is an organoboron compound; the Lewis base is an organic amine or an organic amine salt, and the molar ratio of the Lewis acid to the Lewis base is 5 to 12:1; the molar ratio of propylene oxide to the Lewis base is 2000 to 4000:1, and the molar ratio of propylene oxide to the chain transfer agent is 60 to 250:1.

[0013] Preferably, the pressure of the carbon dioxide is 0.5 to 3.0 MPa, the temperature of the reaction is 40 to 60 °C, and the time of the reaction is 12 to 48 h.

[0014] Compared with the prior art, the present invention has the following beneficial effects: the method of regulating copolymerization by using carbon dioxide and epoxide in the present invention is innovative in that an aromatic small-molecule diol is first used as a chain transfer agent to introduce a benzene ring structure onto the polycarbonate diol, introducing a rigid group into the molecular structure, while ensuring the degradability of the polymer diol, improving the thermal stability. The carbon dioxide-based polycarbonate diol prepared by the present invention has 100% hydroxyl groups at the ends, the number-average molecular weight ranges from 1400 to 6300 g / mol, the polycarbonate content in the chain segment is adjustable, and the polycarbonate content can be as high as 71 to 87%, with good heat resistance and biodegradability. Description of the Drawings

[0015] Figure 1 1H NMR spectrum of the carbon dioxide-based polycarbonate diol prepared in Example 1 of the present invention 1 1H NMR diagram.

[0016] Figure 2 SEM diagrams of the polycarbonate-based polyurethane before enzymatic hydrolysis (a) and after enzymatic hydrolysis for a period of time (b) prepared in Example 4 of the present invention. Detailed Embodiments

[0017] The present invention can be further explained and illustrated in combination with the following specific embodiments, but the specific embodiments do not impose any form of limitation on the present invention:

[0018] Example 1

[0019] In an anhydrous and anaerobic environment, using a 50 mL high-pressure reactor as the reaction vessel, 10 g of propylene oxide, 23.9 mg of n-butylammonium chloride, 1030 μL of triethylboron solution, and 656 mg of bis(2-hydroxyethyl) terephthalate (Formula 2, R is -CH2CH2-) were successively added to the high-pressure reactor. 1.0 MPa of carbon dioxide was charged, and the reaction was carried out at 40 °C for 12 h. After the reaction, the unreacted raw materials and catalyst were washed off with deionized water. After the polymer was dried in vacuo, molecular weight testing, NMR analysis, hydroxyl value analysis, and glass transition temperature determination were performed, and the specific data are listed in Table 1. The 1H NMR spectrum of the prepared carbon dioxide-based polycarbonate diol 1 HNMR spectrum is as Figure 1 shown.

[0020] Example 2

[0021] In an anhydrous and anaerobic environment, using a 50 mL high-pressure reactor as the reaction vessel, 20 g of propylene oxide, 23.9 mg of n-butylammonium chloride, 1030 μL of triethylboron solution, and 547 mg of bis(2-hydroxyethyl) terephthalate (Formula 2, R is -CH2CH2-) were successively added to the high-pressure reactor. 1.5 MPa of carbon dioxide was charged, and the reaction was carried out at 45 °C for 24 h. After the reaction, the unreacted raw materials and catalyst were washed off with deionized water. After the polymer was dried in vacuo, molecular weight testing, NMR analysis, hydroxyl value analysis, and glass transition temperature determination were performed, and the specific data are listed in Table 1.

[0022] Example 3

[0023] In an anhydrous and anaerobic environment, using a 50 mL high-pressure reactor as the reaction vessel, 20 g of propylene oxide, 23.9 mg of n-butylammonium chloride, 1030 μL of triethylboron solution, and 801 mg of bis(4-hydroxybutyl) terephthalate (Formula 2, R is -CH2CH2CH2CH2-) were successively added to the high-pressure reactor. 2.0 MPa of carbon dioxide was charged, and the reaction was carried out at 50 °C for 12 h. After the reaction, the unreacted raw materials and catalyst were washed off with deionized water. After the polymer was dried in vacuo, molecular weight testing, NMR analysis, hydroxyl value analysis, and glass transition temperature determination were performed, and the specific data are listed in Table 1.

[0024] Comparative Example 1

[0025] For comparison, in an anhydrous and anaerobic environment, 20 g of propylene oxide, 49.4 mg of bis(triphenylphosphine)iminium chloride, 1030 μL of triethylboron solution, and 388 μL of 1,4-butanediol were successively added to a 50 mL high-pressure reactor as the reaction vessel. 1.0 MPa of carbon dioxide was charged, and the reaction was carried out at 40 °C for 24 h. After the reaction, the unreacted raw materials and catalyst were washed off with deionized water. After vacuum drying the polymer, molecular weight measurement, NMR analysis, hydroxyl value analysis, and glass transition temperature determination were performed. The specific data are listed in Table 1.

[0026] Table 1 Molecular weight, composition, and glass transition temperature of polycarbonate diol

[0027]

[0028] In Table 1, the PPC mol% is the molar percentage of the polycarbonate units obtained by copolymerization of propylene oxide and carbon dioxide; the benzene ring mol% is the molar percentage of the benzene ring in the diol chain.

[0029] It can be seen from Table 1 that: by the method of regulating the copolymerization of carbon dioxide and epoxide, carbon dioxide-based polycarbonate diol was successfully obtained by one-pot one-step polymerization under the action of a non-metallic catalyst. Using small molecule aromatic diol as a chain transfer agent, a benzene ring structure was introduced into the main chain of the diol, while ensuring the degradability of the polymer diol, the thermal stability was significantly improved. By adjusting the feeding molar ratio of epoxide and chain transfer agent, the number average molecular weight of the diol and the polycarbonate content in the chain segment can be effectively regulated.

[0030] Example 4

[0031] 10 g of the carbon dioxide-based polycarbonate diol described in Example 1 was added to a 100 mL three-necked round-bottom flask and vacuum dehydrated at 110 °C for 3 h. Then, it was cooled to 85 °C under the protection of a nitrogen atmosphere, and 3.03 g of dicyclohexylmethane diisocyanate and 80 mg of the catalyst tin octoate were slowly added. After pre-polymerization at this temperature for 4 h, 0.30 g of the chain extender 1,4-butanediol was added and reacted for 2 h. After the reaction, it was purified with ethanol and vacuum dried to obtain a polycarbonate-based polyurethane with a hard segment content of 25 wt%.

[0032] The obtained polycarbonate-based polyurethane was subjected to enzymatic hydrolysis treatment, as Figure 2 shown in (b) below. After enzymatic hydrolysis for a period of time, small holes and cracks appeared in the local area on the surface of the polycarbonate-based polyurethane product, indicating that the product has good degradation performance.

[0033] Example 5

[0034] 10 g of the carbon dioxide-based polycarbonate diol described in Example 2 was added to a 100 mL three-necked round-bottom flask and vacuum dehydrated at 110 °C for 3 h. Then, the temperature was lowered to 85 °C under the protection of a nitrogen atmosphere, and 2.97 g of dicyclohexylmethane diisocyanate and 80 mg of the catalyst tin octoate were slowly added. After pre-polymerization at this temperature for 4 h, 0.36 g of the chain extender 1,4-butanediol was added and reacted for 2 h. After the reaction, it was purified with ethanol and vacuum dried to obtain a polycarbonate-based polyurethane with a hard segment content of 25 wt%.

[0035] Comparative Example 2

[0036] 10 g of a commercial polycarbonate diol (hydroxyl value 75 mg KOH / g) was added to a 100 mL three-necked round-bottom flask and vacuum dehydrated at 110 °C for 3 h. Then, the temperature was lowered to 85 °C under the protection of a nitrogen atmosphere, and 3.00 g of dicyclohexylmethane diisocyanate and 80 mg of the catalyst tin octoate were slowly added. After pre-polymerization at this temperature for 4 h, 0.33 g of the chain extender 1,4-butanediol was added and reacted for 2 h. After the reaction, it was purified with ethanol and vacuum dried to obtain a polycarbonate-based polyurethane with a hard segment content of 25 wt%.

[0037] The test data of various properties of the examples and Comparative Example 2 are shown in Table 2 in detail. Among them, the hardness was tested according to the Shore A hardness specified in ASTM D2240; the mechanical properties were tested according to the method specified in GB / T 1040.1-2006; the polyurethane of Example 4 and 5 and the comparative example was placed in a water bath at 70 °C for hydrolysis stability test. After 6 weeks, the tensile strength was tested according to ASTM D412, and the tensile strength retention rate was measured to evaluate the hydrolysis resistance of the polyurethane.

[0038] Table 2 Related properties of polycarbonate-based polyurethane

[0039]

[0040] As can be seen from Table 2, the polyurethane prepared from the carbon dioxide-based polycarbonate diol of the present invention has good mechanical properties and hydrolysis resistance. Based on the carbon dioxide-based polycarbonate diol containing a benzene ring structure, the polyurethane prepared can obtain higher Shore hardness and strength.

Claims

1. A preparation method of a carbon dioxide-based polycarbonate diol, the structural characteristics of the carbon dioxide-based polycarbonate diol are shown in Formula 1, where a≥1, b≥1, and R is an aliphatic hydrocarbon group with 2 to 6 carbon atoms; The preparation method comprises the following steps: adding propylene oxide, a catalyst, and an aromatic small molecule chain transfer agent into a high-pressure reactor in sequence, filling with carbon dioxide, and then reacting under heating and stirring conditions; after the reaction is completed, dissolving the product in dichloromethane, pouring it into deionized water and stirring for purification, and drying to obtain the carbon dioxide-based polycarbonate diol; It is characterized in that The structural formula of the aromatic small molecule chain transfer agent is shown in Formula 2, where R is an aliphatic hydrocarbon group with 2 to 6 carbon atoms; 2. The preparation method of the carbon dioxide-based polycarbonate diol according to claim 1, characterized in that The catalyst is a Lewis acid-base pair composite catalyst in a non-metal catalyst system; the Lewis acid is an organic boron compound; the Lewis base is an organic amine or an organic amine salt, and the molar ratio of the Lewis acid to the Lewis base is 5 to 12:1; the molar ratio of propylene oxide to the Lewis base is 2000 to 4000:1, and the molar ratio of propylene oxide to the chain transfer agent is 60 to 250:

1.

3. The preparation method of the carbon dioxide-based polycarbonate diol according to claim 1, wherein The pressure of the carbon dioxide is 0.5 to 3.0 MPa, the temperature of the reaction is 40 to 60 °C, and the time of the reaction is 12 to 48 h.

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