An ionic liquid catalyst and a method for catalytic synthesis of polycarbonate by using the same

Abstract

This invention provides an ionic liquid catalyst and a method for catalytically synthesizing polycarbonate thereof. The cation of the ionic liquid catalyst is a quaternary phosphine cation, a quaternary ammonium cation, or an imidazole cation, and the anion of the ionic liquid catalyst is a benzoic acid anion. The ionic liquid catalyst of this invention is characterized by being environmentally friendly, having low residue, and exhibiting high catalytic activity, and can produce high-quality bio-based polycarbonate.

Description

Technical Field

[0001] This invention belongs to the field of chemical catalysis technology, and relates to an ionic liquid catalyst and a method for catalytic synthesis of polycarbonate. Background Technology

[0002] Traditional bisphenol A (BPA) polycarbonate (PC) is a thermoplastic engineering plastic with excellent mechanical properties, including good light transmittance, good impact resistance, and good thermal stability. It is widely used in household appliances, electronic equipment, building materials, the automotive industry, and aerospace. BPA, as one of the main monomers used in the synthesis of PC, not only has estrogenic effects but also originates from fossil resources. To reduce the consumption of fossil resources and the impact of BPA-type PC on human health (especially infants), the development of bio-based polycarbonates is of great significance. Isosorbide, with its rigid bicyclic structure, is considered one of the ideal monomers to replace BPA in the synthesis of polycarbonates.

[0003] Currently reported catalysts for the synthesis of polycarbonate mainly include basic metal salt catalysts. These include lithium hydroxide, lithium acetylacetonate, and cesium carbonate (Eo, Yong Seok, Rhee, Hee Woo Shin, Seunghan, Catalyst screening for the melt polymerization of isosorbide-based polycarbonate, Journal of Industrial and Engineering Chemistry, 2016, 37, 42-46; Li, Qian, Zhu, Wenxiang, Li, Chuncheng, et al, A On-Phosgene process to homopolycarbonate and copolycarbonates, Journal of Polymer Science, Part A: Polymer Chemistry, 2013, 51, 1387-1397). Despite the large variety of reported catalysts, the internal hydroxyl groups of isosorbide are difficult to activate due to their tendency to form intramolecular hydrogen bonds. Therefore, the activity of the internal hydroxyl groups of isosorbide is significantly lower than that of the external hydroxyl groups, making it difficult to synthesize high-performance bio-based polycarbonates. Developing highly active catalysts to simultaneously activate different types of hydroxyl groups, thereby synthesizing high-performance polycarbonates, is of great significance. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide an ionic liquid catalyst and a method for catalytic synthesis of polycarbonate.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] On one hand, the present invention provides an ionic liquid catalyst, wherein the cation of the ionic liquid catalyst is a quaternary phosphine cation, a quaternary ammonium cation, or an imidazole cation, and the anion of the ionic liquid catalyst is a benzoic acid anion.

[0007] or

[0008]

[0009] Where M is either a nitrogen atom or a phosphine atom, and any one of R1, R2, R3 and R4 is a substituted or unsubstituted alkyl group;

[0010] R5, R6, R7, R8, R9 and R 10 The group is selected from one of hydrogen atom, halogen atom, substituted or unsubstituted alkyl group, substituted or unsubstituted aryl group, substituted or unsubstituted alkoxy group, substituted or unsubstituted hydroxyl group, substituted or unsubstituted cyano group, substituted or unsubstituted carboxyl group, and substituted or unsubstituted anionic group, and R5, R6, R7, R8, R9 and R 10 At least one of them is selected from substituted or unsubstituted carboxyl groups.

[0011] The ionic liquid catalyst of this invention has the characteristics of being green and environmentally friendly, having low residue, and high catalytic activity, and can produce high-quality bio-based polycarbonate.

[0012] Preferably, the cation of the ionic liquid catalyst is any or a combination of at least two of the following: tetrabutylphosphine cation, trihexyltetradecylphosphine cation, tetraethylammonium cation, or 1-methyl-3-ethylimidazolium cation or 1-methyl-3-butylimidazolium cation.

[0013] Preferably, the benzoic acid anion is selected from at least one of the following anions: 4-butylbenzoic acid, m-nitrobenzoic acid, 3-iodobenzoic acid, 3-fluorobenzoic acid, 4-heptylbenzoic acid, p-iodobenzoic acid, 4-mercaptobenzoic acid, 4-propylbenzoic acid, p-bromobenzoic acid, benzoic acid anion, 4-cyanobenzoic acid, 4-hydroxymethylbenzoic acid, 4-ethylbenzoic acid, 4-methylaminobenzoic acid, 4-ethoxybenzoic acid, or 4-phenoxybenzoic acid.

[0014] Preferably, the benzoic acid anion is selected from at least one of the following anions: benzoic acid, 4-hydroxymethylbenzoic acid, 4-ethylbenzoic acid, 4-methylaminobenzoic acid, or 4-cyanobenzoic acid.

[0015] On the other hand, the present invention provides a method for preparing polycarbonate, the method comprising the following steps:

[0016] S1. Mix the dihydroxy compound and the diester compound, heat them, and melt them;

[0017] S2. The ionic liquid catalyst described above is added to the melt obtained in S1 to carry out an ester exchange reaction, followed by a polycondensation reaction to obtain the polycarbonate.

[0018] Preferably, the dihydroxy compound includes at least one of isosorbide, an aliphatic dihydroxy compound, or an aromatic dihydroxy compound.

[0019] Preferably, the aliphatic dihydroxy compound includes ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,10-decanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 2-methyl-1,4-cyclohexanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, neopentyl glycol, isosorbide diol, and hydrogenated diol. The alcohol is selected from at least one of the following: 2-ethyl-1,6-hexanediol, 2,2,4-trimethyl-1,6-hexanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,5-naphthylanediol, 2,3-naphthylanediol, 2,6-naphthylanediol, 2,3-norbornanediol, 2,5-norbornanediol, or 1,3-adamantanediol.

[0020] Preferably, the aromatic dihydroxy compound includes 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-methylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-isobutylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-tert-butylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-cyclohexylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-phenylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3,5-dimethylphenyl)fluorene, 9,9-bis(4-( (2-hydroxyethoxy)-3-tert-butyl-6-methylphenyl)fluorene, 9,9-bis(4-(3-hydroxy-2,2-dimethylpropoxy)phenyl)fluorene, 4,4'-(1-phenylethyl)bisphenol, 2,2-bis(4-hydroxyphenyl)butane, 4,4'-ethylidene bisphenol, 4,4'-dihydroxydiphenylmethane, 1,3-bis[2-(4-hydroxyphenyl)-2-propyl]benzene, 4,4'-dihydroxytetraphenylmethane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, 2,2-bis(4-hydroxy-3-tolyl)propane, 2,2-bis(4-hydroxyphenyl)propane or hydroquinone.

[0021] Preferably, the carbonate diester compound is selected from at least one of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, dipentyl carbonate, dioctyl carbonate, or diphenyl carbonate.

[0022] When using ionic liquids composed of the aforementioned quaternary phosphine cations or other cations and benzoic acid anions as catalysts, different substituents (Ar-COO) are introduced onto the benzoic acid. - The presence of quaternary phosphine cations and other cations alters the electron cloud density distribution on the benzene ring, making it easier to form intermolecular hydrogen bonds with the -OH group in dihydroxy compounds. This allows for the efficient activation of hydroxyl groups in these dihydroxy compounds (especially the internal hydroxyl group of isosorbide). Therefore, this type of catalyst can activate the internal hydroxyl group of isosorbide or other types of hydroxyl groups. Furthermore, quaternary phosphine cations or other cations can interact with the carbonyl group of diphenyl carbonate, making it easier for the phenoxy group or other functional groups on the diphenyl carbonate diester to detach and undergo transesterification with the hydroxyl group activated by the carboxyl group on benzoic acid, yielding high-molecular-weight bio-based polycarbonate. Therefore, ionic liquids composed of quaternary phosphine cations or other cations and benzoic acid anions can activate dihydroxy compounds and diester compounds, thereby synthesizing high-molecular-weight bio-based polycarbonate.

[0023] Preferably, the molar ratio of the dihydroxy compound to the diester compound is 1:(0.5-10), for example 1:0.5, 1:0.7, 1:0.9, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:8, 1:9 or 1:10, preferably 1:(0.95-5).

[0024] Preferably, the molar ratio of the ionic liquid catalyst to the dihydroxy compound is 1 × 10⁻⁶. -7 -5×10 -2 :1, for example, 1×10 -7 1, 3×10 -7 1. 5×10 -7 1, 1×10 -6 1, 3×10 -6 1. 8×10 -6 1, 1×10 -5 1. 5×10 -5 1. 8×10 -5 1, 1×10 -4 1. 5×10 -4 1. 8×10 -4 1, 1×10 -3 1. 5×10 -3 1. 8×10 -3 1, 1×10 -2 :1 or 5×10 -2 :1, preferably 1×10 -5 ~1×10 -4 :1.

[0025] Preferably, the temperature of the transesterification reaction is 90℃-160℃, for example 90℃, 95℃, 98℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃ or 160℃, preferably 130℃-150℃.

[0026] Preferably, the transesterification reaction time is 0.5h-5h, for example 0.50h, 0.8h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h or 5h.

[0027] Preferably, the pressure of the transesterification reaction is 0.8-1.2 atm, for example 0.8 atm, 0.9 atm, 1.0 atm, 1.1 atm or 1.2 atm.

[0028] Preferably, the transesterification reaction is carried out in a nitrogen atmosphere.

[0029] Preferably, the temperature of the polycondensation reaction is 200℃-280℃, for example 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, 260℃, 270℃ or 280℃, preferably 230℃-260℃.

[0030] Preferably, the polycondensation reaction time is 0.5h-6h, for example 0.50h, 0.8h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h or 6h.

[0031] Preferably, the vacuum degree of the polycondensation reaction is less than or equal to 100 Pa, such as 5 Pa, 10 Pa, 20 Pa, 30 Pa, 40 Pa, 50 Pa, 60 Pa, 70 Pa, 80 Pa, 90 Pa or 100 Pa, preferably 20 Pa-100 Pa.

[0032] On the other hand, the present invention provides polycarbonate prepared by the preparation method described above.

[0033] Preferably, the polycarbonate has a weight-average molecular weight of 50,000-150,000, such as 50,000, 70,000, 90,000, 100,000, 120,000, 140,000 or 150,000.

[0034] Preferably, the light transmittance of the polycarbonate is greater than or equal to 85%, such as 85%, 86%, 87%, 88%, 89%, 90%, etc., and more preferably 85%-89%.

[0035] The polycarbonate obtained using the above reaction conditions was used to synthesize a high molecular weight bio-based polycarbonate due to the good catalytic activity of the ionic liquid catalyst.

[0036] On the other hand, the present invention provides the application of polycarbonate as described above in optical materials or food plastics.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] (1) The ionic liquid catalyst of the present invention has the advantages of high catalytic activity, reduced side reaction, shortened reaction time, green environmental protection and low residue. It can activate different types of hydroxyl groups such as isosorbide, aliphatic dihydroxy compounds and aromatic dihydroxy compounds, and can also activate carbonate diesters to synthesize high-performance polycarbonate.

[0039] (2) The polycarbonate preparation method provided by the present invention has mild reaction conditions, easy collection of by-products, and can be recycled to prevent pollution; compared with the traditional phosgene method, it does not use toxic phosgene and is environmentally friendly.

[0040] (3) The high-performance polycarbonate provided by the present invention has a weight-average molecular weight of 30,000-150,000 when the dihydroxy compound is isosorbide. Attached Figure Description

[0041] Figure 1 The ionic liquid described in Example 2 of this application 1 H-NMR spectrum. Detailed Implementation

[0042] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0043] Synthesis example 1

[0044] Taking the synthesis of tetrabutylphosphine-4-cyanobenzoic acid ionic liquid catalyst as an example, at room temperature, 6.91 g of tetrabutylphosphine hydroxide and 1.47 g of 4-cyanobenzoic acid were added to a 100 mL round-bottom flask and reacted for 24 h. The mixture was then rotary evaporated, washed, and vacuum dried to obtain the product. The structure of the synthesized ionic liquid was confirmed to be correct by nuclear magnetic resonance characterization.

[0045] Ionic liquid synthesis process:

[0046]

[0047] Example 1

[0048] Under a nitrogen atmosphere, 4.38 g of isosorbide and 6.42 g of diphenyl carbonate (isosorbide:diphenyl carbonate = 1:1 molar ratio) were added to a 250 mL three-necked glass flask equipped with a mechanical stirrer, heated to 150 °C, and 5 × 10⁻⁶ g of [unspecified substance] was added. -5 Tetrabutylphosphine-4-cyanobenzoic acid (mol / mol relative to isosorbide) was subjected to transesterification under normal pressure for 0.5 h to synthesize a prepolymer. The reaction temperature was then slowly increased to 240 °C and the vacuum was slowly decreased to 100 Pa for another 0.5 h to finally obtain bio-based polycarbonate. The yield of the bio-based polycarbonate was 87%, the weight average molecular weight was 75000 g / mol, and the molecular weight distribution was 1.95.

[0049] The reaction equation and the structure of the ionic liquid used in Example 1 are shown below:

[0050] Reaction equation:

[0051]

[0052] Structure of tetrabutylphosphine-4-cyanobenzoic acid ionic liquid catalyst:

[0053]

[0054] Example 2

[0055] Under a nitrogen atmosphere, 4.38 g of isosorbide and 6.42 g of diphenyl carbonate (isosorbide:diphenyl carbonate = 1:1 molar ratio) were added to a 250 mL three-necked glass flask equipped with a mechanical stirrer, heated to 150 °C, and 5 × 10⁻⁶ g of [unspecified substance] was added. -5 Tetrabutylphosphine benzoic acid (mol / mol relative to isosorbide) was subjected to transesterification under normal pressure for 0.5 h to synthesize a prepolymer. Then, the reaction temperature was slowly increased to 240 °C and the vacuum was slowly increased to 100 Pa, and the reaction was continued for another 0.5 h to finally obtain bio-based polycarbonate. The yield of the bio-based polycarbonate was 95%, the number average molecular weight was 52000 g / mol, and the molecular weight distribution was 1.93.

[0056] The reaction equation in Example 2 is the same as that in Example 1, and the structure of the ionic liquid used is shown below:

[0057] Structure of tetrabutylphosphine ionic liquid catalyst:

[0058]

[0059] Example 3

[0060] Under a nitrogen atmosphere, 4.38 g of isosorbide and 6.42 g of diphenyl carbonate (isosorbide:diphenyl carbonate = 1:1 molar ratio) were added to a 250 mL three-necked glass flask equipped with a mechanical stirrer, heated to 150 °C, and 5 × 10⁻⁶ g of [unspecified substance] was added. -5 Tetrabutylphosphine-4-hydroxymethylbenzoic acid (mol / mol relative to isosorbide) was subjected to transesterification under normal pressure for 0.5 h to synthesize a prepolymer. The reaction temperature was then slowly increased to 240 °C and the vacuum was slowly increased to 100 Pa for another 0.5 h to finally obtain bio-based polycarbonate. The yield of the bio-based polycarbonate was 99%, the number average molecular weight was 70,000 g / mol, and the molecular weight distribution was 1.97.

[0061] The reaction equation in Example 3 is the same as that in Example 1, and the structure of the ionic liquid used is shown below:

[0062] Structure of tetrabutylphosphine-4-hydroxymethylbenzoic acid ionic liquid catalyst:

[0063]

[0064] Example 4

[0065] Under a nitrogen atmosphere, 4.38 g of isosorbide and 6.42 g of diphenyl carbonate (isosorbide:diphenyl carbonate = 1:1 molar ratio) were added to a 250 mL three-necked glass flask equipped with a mechanical stirrer, heated to 150 °C, and 5 × 10⁻⁶ g of [unspecified substance] was added. -5 Tetrabutylphosphine-4-ethylbenzoic acid (mol / mol relative to isosorbide) was subjected to transesterification under normal pressure for 0.5 h to synthesize a prepolymer. Then, the reaction temperature was slowly increased to 240 °C and the vacuum was slowly increased to 100 Pa, and the reaction was continued for another 0.5 h to finally obtain bio-based polycarbonate. The yield of the bio-based polycarbonate was 91%, the number average molecular weight was 52000 g / mol, and the molecular weight distribution was 1.93.

[0066] The reaction equation in Example 4 is the same as that in Example 1, and the structure of the ionic liquid used is shown below:

[0067] Structure of tetrabutylphosphine-4-ethylbenzoic acid ionic liquid catalyst:

[0068]

[0069] Example 5

[0070] Under a nitrogen atmosphere, 4.38 g of isosorbide and 6.42 g of diphenyl carbonate (isosorbide:diphenyl carbonate = 1:1 molar ratio) were added to a 250 mL three-necked glass flask equipped with a mechanical stirrer, heated to 150 °C, and 5 × 10⁻⁶ g of [unspecified substance] was added. -5 Tetrabutylphosphine-4-methylaminobenzoic acid (mol / mol relative to isosorbide) was subjected to transesterification under normal pressure for 0.5 h to synthesize a prepolymer. Then, the reaction temperature was slowly increased to 240 °C and the vacuum was slowly increased to 100 Pa for another 0.5 h to finally obtain bio-based polycarbonate. The yield of the bio-based polycarbonate was 92%, the number average molecular weight was 52000 g / mol, and the molecular weight distribution was 1.93.

[0071] The reaction equation in Example 5 is the same as that in Example 1, and the structure of the ionic liquid used is shown below:

[0072] Structure of tetrabutylphosphine-4-methylaminobenzoic acid ionic liquid catalyst:

[0073]

[0074] Example 6

[0075] Under a nitrogen atmosphere, 4.38 g of isosorbide and 6.42 g of diphenyl carbonate (isosorbide:diphenyl carbonate = 1:1 molar ratio) were added to a 250 mL three-necked glass flask equipped with a mechanical stirrer, heated to 150 °C, and 5 × 10⁻⁶ g of [unspecified substance] was added. -5Tetrabutylphosphine-4-ethoxybenzoic acid (mol / mol relative to isosorbide) was subjected to transesterification under normal pressure for 0.5 h to synthesize a prepolymer. The reaction temperature was then slowly increased to 240 °C and the vacuum was slowly increased to 100 Pa for another 0.5 h to finally obtain bio-based polycarbonate. The yield of the bio-based polycarbonate was 92%, the number average molecular weight was 46000 g / mol, and the molecular weight distribution was 1.97.

[0076] The reaction equation in Example 6 is the same as that in Example 1, and the structure of the ionic liquid used is shown below:

[0077] Structure of tetrabutylphosphine-4-ethoxybenzoic acid ionic liquid catalyst:

[0078]

[0079] Example 7

[0080] Under a nitrogen atmosphere, 4.38 g of isosorbide and 6.42 g of diphenyl carbonate (isosorbide:diphenyl carbonate = 1:1 molar ratio) were added to a 250 mL three-necked glass flask equipped with a mechanical stirrer, heated to 150 °C, and 5 × 10⁻⁶ g of [unspecified substance] was added. -5 Tetrabutylphosphine-4-phenoxybenzoic acid (mol / mol relative to isosorbide) was subjected to transesterification under normal pressure for 0.5 h to synthesize a prepolymer. The reaction temperature was then slowly increased to 240 °C and the vacuum was slowly increased to 100 Pa for another 0.5 h to finally obtain bio-based polycarbonate. The yield of the bio-based polycarbonate was 90%, the number average molecular weight was 45000 g / mol, and the molecular weight distribution was 1.95.

[0081] The reaction equation in Example 7 is the same as that in Example 1, and the structure of the ionic liquid used is shown below:

[0082] Structure of tetrabutylphosphine-4-phenoxybenzoic acid ionic liquid catalyst:

[0083]

[0084] Examples 8-12

[0085] The catalysts, reactants, and reaction methods used in Examples 8-12 were the same as in Example 1, except for the molar ratio of the catalyst (tetrabutylphosphine-4-hydroxymethylbenzoic acid) to the dihydroxy compound (isosorbide). The weight-average molecular weights of the polycarbonates obtained by changing the ratio are shown in Table 1.

[0086] Table 1

[0087] Example Molar ratio of catalyst to dihydroxy compound weight average molecular weight Yield 8 <![CDATA[1×10 -5 :1]]> 82000 86％ 9 <![CDATA[2.5×10 -5 :1]]> 88000 91％ 10 <![CDATA[5.0×10 -5 :1]]> 136000 98％ 11 <![CDATA[7.5×10 -5 :1]]> 142000 95％ 12 <![CDATA[1×10 -4 :1]]> 162000 96％

[0088] Examples 13-17

[0089] The catalysts, the ratio of catalyst to dihydroxy compound, and the types and ratios of reactants used in Examples 13-17 were the same as in Example 3, except for the polycondensation temperature. The weight-average molecular weights of the polycarbonates obtained by changing the polycondensation temperature are shown in Table 2.

[0090] Table 2

[0091]

[0092]

[0093] Examples 18-22

[0094] The catalysts, molar ratios of catalysts to dihydroxy compounds, and types and proportions of reactants used in Examples 18-22 were the same as in Example 4, except for the polycondensation time. The weight-average molecular weights of the polycarbonates obtained by changing the polycondensation time are shown in Table 3.

[0095] Table 3

[0096] Example Condensation time weight average molecular weight Yield 18 0min 58000 85％ 19 15min 113000 88％ 20 30min 136000 98％ 21 45min 110000 93％ 22 60min 88000 90％

[0097] Comparative Example 1

[0098] A method for preparing polycarbonate using other catalysts, comprising the following steps:

[0099]

[0100] The steps are as follows: Under a nitrogen atmosphere, 4.38 g of isosorbide and 6.42 g of diphenyl carbonate (isosorbide: diphenyl carbonate = 1:1 molar ratio) were added to a 250 mL three-necked glass flask equipped with a mechanical stirrer. The mixture was heated to 150 °C, and 5 × 10⁻⁶ g of [unspecified substance] was added. -5 A transesterification reaction was carried out at atmospheric pressure using tetraethylammonium acetate ionic liquid catalyst (the synthesis method was the same as in Synthesis Example 1, except for 1.46 g of tetraethylammonium hydroxide and 0.06 g of acetic acid). The reaction was allowed to proceed for 0.5 h to synthesize the prepolymer. Then, the reaction temperature was slowly increased to 240 °C and the vacuum was slowly increased to 100 Pa. The reaction was continued for another 0.5 h to finally obtain bio-based polycarbonate. The yield of the bio-based polycarbonate was 90%, the number average molecular weight was 36000 g / mol, and the molecular weight distribution was 1.86.

[0101] Comparative Example 2

[0102] The difference from Comparative Example 1 is that the catalyst used was 5 × 10⁻⁶. -5The polycarbonate yield was 91% with mol of lithium acetylacetone (relative to the amount of isosorbide), the number average molecular weight was 32200 g / mol, and the molecular weight distribution was 1.69.

[0103] All yields described in this invention are mass percentages.

[0104] By comparing Examples 1-2 with Example 1, it can be seen that without using the ionic liquid catalyst of the present invention for catalytic reaction, the resulting bio-based polycarbonate has a lower molecular weight and does not achieve the technical effect of the present invention.

[0105] The applicant declares that the present invention is illustrated by the above embodiments to demonstrate the ionic liquid catalyst and the method for catalytic synthesis of polycarbonate, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. An ionic liquid catalyst, characterized in that, The cation of the ionic liquid catalyst is a quaternary phosphine cation, a quaternary ammonium cation, or an imidazole cation, and the anion of the ionic liquid catalyst is a benzoic acid anion.

2. The ionic liquid catalyst according to claim 1, characterized in that, The structure of the ionic liquid catalyst is as follows: or Wherein, M is either a nitrogen atom or a phosphine atom, and any one of R1, R2, R3, R4, R1' and R2' is a substituted or unsubstituted alkyl group, etc. R5, R6, R7, R8, R9 and R 10 The group is selected from one of the following: hydrogen atom, halogen atom, substituted or unsubstituted alkyl group, substituted or unsubstituted aryl group, substituted or unsubstituted alkoxy group, substituted or unsubstituted hydroxyl group, substituted or unsubstituted cyano group, substituted or unsubstituted carboxyl group, and substituted or unsubstituted anionic group, and R5, R6, R7, R8, R9 and R 10 At least one of them is selected from substituted or unsubstituted carboxyl groups.

3. The ionic liquid catalyst according to claim 1 or 2, characterized in that, The cation of the ionic liquid catalyst is any combination of at least two of the following: tetrabutylphosphine cation, trihexyltetradecylphosphine cation, tetraethylammonium cation, or 1-methyl-3-ethylimidazolium cation or 1-methyl-3-butylimidazolium cation.

4. The ionic liquid catalyst according to any one of claims 1-3, characterized in that, The benzoic acid anion is selected from at least one of the following anions: 4-butylbenzoic acid, m-nitrobenzoic acid, 3-iodobenzoic acid, 3-fluorobenzoic acid, 4-heptylbenzoic acid, p-iodobenzoic acid, 4-mercaptobenzoic acid, 4-propylbenzoic acid, p-bromobenzoic acid, benzoic acid anion, 4-cyanobenzoic acid, 4-hydroxymethylbenzoic acid, 4-ethylbenzoic acid, 4-methylaminobenzoic acid, 4-ethoxybenzoic acid, or 4-phenoxybenzoic acid; Preferably, the benzoic acid anion is selected from at least one of the following anions: benzoic acid, 4-hydroxymethylbenzoic acid, 4-ethylbenzoic acid, 4-methylaminobenzoic acid, or 4-cyanobenzoic acid.

5. A method for preparing polycarbonate, characterized in that, The preparation method includes the following steps: S1. Mix the dihydroxy compound and the diester compound, heat them, and melt them; S2. The ionic liquid catalyst as described in any one of claims 1-4 is added to the melt obtained in S1 to carry out an ester exchange reaction, followed by a polycondensation reaction to obtain the polycarbonate.

6. The preparation method according to claim 5, characterized in that, The dihydroxy compound includes at least one of isosorbide, an aliphatic dihydroxy compound, or an aromatic dihydroxy compound; Preferably, the aliphatic dihydroxy compound includes ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,10-decanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 2-methyl-1,4-cyclohexanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, neopentyl glycol, isosorbide diol, and hydrogenated diol. The alcohol is selected from at least one of the following: 2-ethyl-1,6-hexanediol, 2,2,4-trimethyl-1,6-hexanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,5-naphthylanediol, 2,3-naphthylanediol, 2,6-naphthylanediol, 2,3-norbornanediol, 2,5-norbornanediol, or 1,3-adamantanediol.

7. The preparation method according to claim 5 or 6, characterized in that, The aromatic dihydroxy compounds include 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-methylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-isobutylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-tert-butylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-cyclohexylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-phenylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3,5-dimethylphenyl)fluorene, 9,9-bis(4-(2-)- Fluorene (hydroxyethoxy)-3-tert-butyl-6-methylphenyl), 9,9-bis(4-(3-hydroxy-2,2-dimethylpropoxy)phenyl)fluorene, 4,4'-(1-phenylethyl)bisphenol, 2,2-bis(4-hydroxyphenyl)butane, 4,4'-ethylidene bisphenol, 4,4'-dihydroxydiphenylmethane, 1,3-bis[2-(4-hydroxyphenyl)-2-propyl]benzene, 4,4'-dihydroxytetraphenylmethane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, 2,2-bis(4-hydroxy-3-tolyl)propane, 2,2-bis(4-hydroxyphenyl)propane or hydroquinone; Preferably, the carbonate diester compound is selected from at least one of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, dipentyl carbonate, dioctyl carbonate, or diphenyl carbonate.

8. The preparation method according to any one of claims 5-7, characterized in that, The molar ratio of the dihydroxy compound to the diester carbonate compound is 1:(0.5-10), preferably 1:(0.95-5); Preferably, the molar ratio of the ionic liquid catalyst to the dihydroxy compound is 1 × 10⁻⁶. -7 -5×10 -2 :1, preferably 1×10 -5 ~1×10 -4 :1; Preferably, the temperature of the transesterification reaction is 90℃-160℃, more preferably 130℃-150℃; Preferably, the transesterification reaction takes 0.5 h to 5 h; Preferably, the pressure of the transesterification reaction is 0.8-1.2 atm; Preferably, the transesterification reaction is carried out in a nitrogen atmosphere; Preferably, the temperature of the polycondensation reaction is 200℃-280℃, more preferably 230℃-260℃; Preferably, the polycondensation reaction takes 0.5-6 hours. Preferably, the vacuum degree of the polycondensation reaction is less than or equal to 100 Pa, and more preferably 20 Pa to 100 Pa.

9. The polycarbonate prepared by the method according to any one of claims 5-8; Preferably, the polycarbonate has a weight-average molecular weight of 30,000-150,000; Preferably, the light transmittance of the polycarbonate is greater than or equal to 85%.

10. The use of the polycarbonate according to claim 9 in optical materials or food plastics.

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