High-molecular-weight poly (butylene carbonate-terephthalate) based on carbon dioxide polycondensation and preparation method of high-molecular-weight poly (butylene carbonate-terephthalate)

Abstract

The invention belongs to the technical field of carbon dioxide conversion and polymer synthesis, and particularly relates to high-molecular-weight poly (butylene carbonate-terephthalate) based on carbon dioxide polycondensation and a preparation method of the high-molecular-weight poly (butylene carbonate-terephthalate). According to the invention, carbon dioxide and 1, 4-butanediol are subjected to dehydration polycondensation to prepare a polycarbonate oligomer, and then the polycarbonate oligomer and dibutylene terephthalate are copolymerized by a melt polycondensation process in series to prepare high-molecular-weight polycarbonate-butylene terephthalate. According to the method, carbon dioxide and terephthalic acid are directly used as monomers, diester carbonate and dimethyl terephthalate are prevented from being used, the production process is greatly shortened, and the utilization rate of carbon dioxide is effectively increased. The method has the advantages of simple process, low cost, controllable molecular weight of the product, large-scale production and excellent industrial prospect. Meanwhile, a carbon-carbon resource, namely carbon dioxide, is effectively converted in the synthesis of the polymer, so that the method has important promotion significance on the realization of a carbon neutralization strategy.

Description

Technical Field

[0001] The invention belongs to the technical field of carbon dioxide conversion and polymer synthesis, and specifically relates to a high molecular weight polycarbonate-butylene terephthalate based on carbon dioxide polycondensation and a preparation method thereof. Background Art

[0002] With the increasing consumption of unsustainable resources such as oil, carbon emissions from downstream industries are increasing day by day. At the same time, as one of the major transformation products of petrochemical resources, polymers have become a major threat to the current environment due to the non-degradability of most varieties, and the white pollution problem they bring has become a major threat to the current environment. Therefore, reducing carbon emissions and eliminating white pollution have become obstacles that must be overcome in the upgrading of the chemical industry (especially the polymer industry). In this regard, many polymers prepared based on carbon dioxide as raw materials, as well as various degradable polymers, have been reported and even commercially produced, which has played an important role in promoting the implementation of the current "dual carbon" policy and sustainable development strategy.

[0003] Polybutylene carbonate terephthalate (PBCT) is a polyester carbonate copolymer with excellent comprehensive performance. Similar to the current mainstream commercial degradable polyester, polybutylene terephthalate adipate (PBAT), the polymer chain contains aliphatic polycarbonate units, which gives the polymer excellent degradability and flexibility. Compared with PBAT, PBCT has higher barrier properties and lower cost advantages, and the carbonate segment can be introduced from carbon dioxide chemical conversion products, dimethyl carbonate (DMC) or diphenyl carbonate (DPC). Vigorously developing new market polymers such as PBCT is in line with the needs of promoting degradable plastics.

[0004] Patent Publication No. CN103265689A introduces aromatic monomers such as terephthalic acid and isophthalic acid into the main chain of polycarbonate, and uses a step-by-step esterification method to prepare an aromatic-aliphatic polycarbonate copolymer with excellent performance. Patent Publication No. CN115873223A discloses a method for preparing PBCT, which is prepared from DMC, dimethyl terephthalate, and 1,4-butanediol (BDO) under a composite catalyst. The polymer has an intrinsic viscosity of 1.2-2.0 dL / g, and the final shrinkage time is shortened, which improves production efficiency. However, the carbonate carbon source in the PBCT polymer chain prepared in the above patent application comes from DMC or DPC, and has a high dependence on epoxy raw material monomers, and the process flow from carbon dioxide to polymer is relatively long. If the polycarbonate units can be obtained by direct polymerization of carbon dioxide and diols, the entire chain production process of PBCT can be greatly shortened, and the utilization rate of carbon dioxide can be effectively improved. Therefore, how to reduce PBCT’s high dependence on epoxy raw material monomers and long production process while improving carbon dioxide utilization is a technical problem that needs to be solved urgently. Summary of the invention

[0005] In order to solve the technical problems that the existing PBCT preparation process relies on epoxy raw material monomers, has high catalyst cost, harsh reaction conditions, and is difficult to mass produce, the present invention provides a type of high molecular weight polycarbonate-butylene terephthalate based on carbon dioxide polycondensation and a preparation method thereof. The present invention uses carbon dioxide and aliphatic diol dehydration polycondensation to prepare polycarbonate oligomers, and then connects the melt polycondensation process in series with dibutylene terephthalate copolymerization to prepare high molecular weight polycarbonate-butylene terephthalate PBCT.

[0006] This method directly uses carbon dioxide and terephthalic acid (PTA) as monomers, avoiding the use of carbonic acid diesters and dimethyl terephthalate, greatly shortening the production process of PBCT and effectively improving the utilization rate of carbon dioxide. This method does not require the use of epoxy raw material monomers, has a simple process, low cost, controllable product molecular weight, and can be produced on a large scale, with excellent industrial prospects.

[0007] In the first aspect, the present invention provides a type of high molecular weight polycarbonate-butylene terephthalate based on carbon dioxide polycondensation, wherein the high molecular weight polycarbonate-butylene terephthalate is a random copolymer of dibutylene terephthalate blocks and oligocarbonate blocks, and the structural formula is: ; Among them, x and y are both natural numbers, and x:y=1-9900:100.

[0008] Furthermore, the intrinsic viscosity of the high molecular weight polybutylene carbonate terephthalate is 1.2-2.0 dL / g.

[0009] Further, x:y=3:7-7:3.

[0010] In a second aspect, the present invention provides a method for preparing a type of high molecular weight polycarbonate-butylene terephthalate based on carbon dioxide polycondensation, wherein carbon dioxide and 1,4-butanediol are dehydrated and polycondensed to obtain a low polycarbonate under the action of an organic base catalyst and a condensation agent; and the low polycarbonate and dibutylene terephthalate are melt cocondensed to obtain the high molecular weight polycarbonate-butylene terephthalate under the action of a melt copolymerization catalyst.

[0011] Furthermore, the dibutylene terephthalate is obtained by esterification reaction of 1,4-butanediol and terephthalate in the presence of an esterification catalyst.

[0012] Furthermore, the organic base catalyst is selected from at least one of N,N,N',N'-tetramethylethylenediamine (TMEDA), 4-dimethylaminopyridine (DMAP), 4-pyrrolidinylpyridine (PPY), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5,7-triazabicyclo[4.4.0]decene-5-ene (TBD), 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD), 1,1,3,3-tetramethylguanidine (TMG), and 2-tert-butyl-1,1,3,3-tetramethylguanidine (t-Bu-TMG), preferably DBU, MTBD, and t-Bu-TMG.

[0013] Furthermore, the condensing agent is at least one of dicyclohexylcarbodiimide and diisopropylcarbodiimide, preferably diisopropylcarbodiimide.

[0014] Furthermore, the esterification catalyst is selected from at least one of magnesium acetate, zinc acetate, antimony trioxide, germanium dioxide, diethylene glycol titanate, tetra-tert-butyl titanate, tetrabutyl titanate, and tetraisopropyl titanate, preferably tetrabutyl titanate.

[0015] Furthermore, the melt copolymerization catalyst is selected from at least one of sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, lithium acetylacetonate, zirconium acetylacetonate, and cesium carbonate, preferably sodium methoxide.

[0016] Furthermore, the feed mass ratio of the oligocarbonate to the melt copolymerization catalyst is 1:(0.0005-0.005).

[0017] Furthermore, the specific preparation steps are: R1, 1,4-butanediol, an organic base catalyst and a condensation agent are placed in a pressure-resistant autoclave, heated to 130°C in a carbon dioxide atmosphere at 1 MPa for dehydration polycondensation, reacted for 6-24 hours, and then post-treated to obtain an oligocarbonate; R2. Place low-molecular-weight polycarbonate, dibutylene terephthalate and a melt copolymerization catalyst in a pressure-resistant autoclave, and heat them for reaction under a nitrogen atmosphere and mechanical stirring to obtain high molecular weight polycarbonate-dibutylene terephthalate.

[0018] Furthermore, the post-treatment method of step R1 is: after the reaction is completed, adding an appropriate amount of solvent at -20-0°C to fully dissolve the oligomer, filtering, acid-washing the filtrate, drying, rotary evaporation and vacuum drying.

[0019] Furthermore, in the step R2, the mixture is first heated to a first temperature at normal pressure and reacted for 1-3 hours to perform a co-esterification reaction, and then slowly heated to a second temperature and decompressed to 10-50 Pa to perform melt polycondensation, and reacted for 4-8 hours; the first temperature is 140-180°C, and the second temperature is 220-280°C.

[0020] Furthermore, the preparation method of dibutylene terephthalate is: terephthalic acid, 1,4-butanediol and an esterification catalyst are added into a reactor, heated to 230°C-250°C in a nitrogen atmosphere and reacted for 2-4 hours to obtain dibutylene terephthalate.

[0021] Beneficial effects: The high molecular weight polycarbonate-butylene terephthalate and preparation method thereof provided by the present invention adopts carbon dioxide as a direct polymerization monomer, meets the strategic requirements of carbon neutrality and does not rely on DMC or DPC in the traditional method. At the same time, the process of melt polycondensation of carbon dioxide prepolymer in series can ensure that the polyester carbonate has a sufficiently high molecular weight, and can also be applied to the current existing production equipment and technology, which is very easy to scale up and has important significance in terms of environmental protection and economic value. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The synthetic route for high molecular weight polycarbonate-butylene terephthalate is shown below; Figure 2 The high molecular weight polycarbonate-terephthalate-butylene glycol ester in Example 4 1 H-NMR spectrum. DETAILED DESCRIPTION

[0023] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the scheme of the present invention will be further described below. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0024] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all of the embodiments.

[0025] The preferred embodiments of the present invention will be described in detail below in conjunction with examples. It should be understood that the following examples are provided only for the purpose of illustration and are not intended to limit the scope of the present invention. Those skilled in the art may make various modifications and substitutions to the present invention without departing from the purpose and spirit of the present invention.

[0026] Test instrument model: The nuclear magnetic resonance spectrometer used was Vaian DLG400 (Varian, USA).

[0027] Example 1 (Preparation of oligobutylene carbonate) 4.506g of 1,4-butanediol (50mmol), 0.0761g of DBU (0.5mmol) and 5.679g of diisopropylcarbodiimide (45mmol) were placed in a pressure autoclave, and high-purity carbon dioxide was charged into the autoclave to 1MPa, and then the pressure was released to normal pressure, and repeated three times. Carbon dioxide was then charged to 1MPa, and the reaction was heated to 130℃ for 24h. After cooling to room temperature, the pressure was released, and 15mL of dichloromethane was added to the system, filtered, and the filtrate was washed with 10mL of 1.0M hydrochloric acid and 10mL of deionized water, respectively, and then dried with anhydrous magnesium sulfate, filtered, rotary evaporated and vacuum dried at 50℃ for 12h to obtain oligobutylene carbonate (PBC).

[0028] Example 2 (Preparation of dibutylene terephthalate) 16.613 g of PTA (0.1 mol), 19.826 g of BDO (0.22 mol) and 0.0166 g of tetrabutyl titanate were added into a reactor and reacted at 230° C. for 2 h under a nitrogen atmosphere until the system was clear. The mixture was cooled to room temperature to obtain dibutylene terephthalate.

[0029] Example 3 (Preparation of PBCT by melt co-polycondensation: the molar ratio of PBT unit to PBC unit is 3:7) 9.31g of dibutylene terephthalate (30mmol), 8.128g of oligomeric PBC (70mmol of PBC unit) and 0.0081g of sodium methoxide were put into a three-necked flask, and the nitrogen atmosphere was replaced three times. Then, the mixture was heated to 160℃ and co-esterified for 2h under mechanical stirring. The system pressure was slowly reduced to about 30Pa, and then the temperature was slowly raised to 230℃ and reacted for 6h to obtain high molecular weight PBCT; the intrinsic viscosity was 1.27dL / g.

[0030] Example 4 (Preparation of PBCT by melt co-polycondensation: the molar ratio of PBT unit to PBC unit is 5:5) 15.518g of dibutylene terephthalate (50mmol), 5.806g of oligomeric PBC (PBC unit is 50mmol) and 0.0058g of sodium methoxide were put into a three-necked flask, and the nitrogen atmosphere was replaced three times. Then, the mixture was heated to 160℃ and co-esterified for 2h under mechanical stirring. The system pressure was slowly reduced to about 30Pa, and then the temperature was slowly raised to 230℃ and reacted for 6h to obtain high molecular weight PBCT; the intrinsic viscosity was 1.39dL / g.

[0031] Example 5 (Preparation of PBCT by melt co-condensation: the molar ratio of PBT unit to PBC unit is 7:3) 21.723g of dibutylene terephthalate (70mmol), 3.484g of oligomeric PBC (PBC unit is 30mmol) and 0.0035g of sodium methoxide were put into a three-necked flask, and the nitrogen atmosphere was replaced three times. Then, it was heated to 160℃ and co-esterified for 2h under mechanical stirring. The system pressure was slowly reduced to about 30Pa, and then the temperature was slowly raised to 230℃ and reacted for 6h to obtain high molecular weight PBCT; the intrinsic viscosity was 1.68dL / g.

[0032] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited thereto. Any equivalent structure or equivalent process transformation made by using the specification of the present invention, or directly or indirectly applied in other related technical fields, are also included in the protection scope of the present invention.

Claims

1. A high molecular weight polycarbonate-butylene terephthalate based on carbon dioxide polycondensation, characterized in that: The high molecular weight polycarbonate-butylene terephthalate is a random copolymer of dibutylene terephthalate blocks and oligocarbonate blocks, and the structural formula is: ； Among them, x and y are both natural numbers, and x:y=1-9900:

100.

2. The high molecular weight polycarbonate-butylene terephthalate based on carbon dioxide polycondensation according to claim 1, characterized in that: The intrinsic viscosity of the high molecular weight polybutylene carbonate terephthalate is 1.2-2.0 dL / g.

3. A method for preparing high molecular weight polycarbonate-butylene terephthalate based on carbon dioxide polycondensation as claimed in any one of claims 1 to 2, characterized in that: Under the action of an organic base catalyst and a condensation agent, carbon dioxide and 1,4-butanediol are dehydrated and polycondensed to obtain a low-molecular-weight polycarbonate; under the action of a melt copolymerization catalyst, the low-molecular-weight polycarbonate and dibutylene terephthalate are melt co-condensed to obtain the high molecular weight polycarbonate-terephthalate-butylene terephthalate based on carbon dioxide polycondensation; The organic base catalyst is selected from at least one of N,N,N',N'-tetramethylethylenediamine, 4-dimethylaminopyridine, 4-pyrrolidinylpyridine, 1,8-diazabicyclo[5.4.0]undec-7-ene, 1,5,7-triazabicyclo[4.4.0]decene-5-ene, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1,1,3,3-tetramethylguanidine and 2-tert-butyl-1,1,3,3-tetramethylguanidine; The condensing agent is at least one of dicyclohexylcarbodiimide and diisopropylcarbodiimide.

4. The method for preparing high molecular weight polycarbonate-butylene terephthalate based on carbon dioxide polycondensation according to claim 3, characterized in that: The melt copolymerization catalyst is selected from at least one of sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, lithium acetylacetonate, zirconium acetylacetonate and cesium carbonate.

5. The method for preparing high molecular weight polycarbonate-butylene terephthalate based on carbon dioxide polycondensation according to claim 4, characterized in that: The feed mass ratio of the oligocarbonate to the melt copolymerization catalyst is 1:(0.0005-0.005).

6. The method for preparing high molecular weight polycarbonate-butylene terephthalate based on carbon dioxide polycondensation according to claim 3, characterized in that: The dibutylene terephthalate is obtained by esterification reaction of 1,4-butanediol and terephthalate in the presence of an esterification catalyst.

7. The method for preparing high molecular weight polycarbonate-butylene terephthalate based on carbon dioxide polycondensation according to claim 6, characterized in that: The esterification catalyst is selected from at least one of magnesium acetate, zinc acetate, antimony trioxide, germanium dioxide, diethylene glycol titanate, tetra-tert-butyl titanate, tetrabutyl titanate, and tetraisopropyl titanate.

8. The method for preparing high molecular weight polycarbonate-butylene terephthalate based on carbon dioxide polycondensation according to claim 5, characterized in that: The following steps are involved: R1, 1,4-butanediol, an organic base catalyst and a condensation agent are placed in a pressure-resistant autoclave, heated to 130°C in a carbon dioxide atmosphere at 1 MPa for dehydration polycondensation, reacted for 6-24 hours, and then post-treated to obtain an oligocarbonate; R2. Place low-molecular-weight polycarbonate, dibutylene terephthalate and a melt copolymerization catalyst in a pressure-resistant autoclave, and heat them for reaction under a nitrogen atmosphere and mechanical stirring to obtain a high molecular weight polycarbonate-butylene terephthalate based on carbon dioxide polycondensation.

9. The method for preparing high molecular weight polycarbonate-butylene terephthalate based on carbon dioxide polycondensation according to claim 8, characterized in that: The post-treatment method of step R1 is: after the reaction is completed, add an appropriate amount of solvent at -20-0°C to fully dissolve the oligomer, filter, acid-wash the filtrate, dry, rotary evaporate and vacuum dry.

10. The method for preparing high molecular weight polycarbonate-butylene terephthalate based on carbon dioxide polycondensation according to claim 8, characterized in that: In the step R2, the mixture is first heated to a first temperature at normal pressure and reacted for 1-3 hours to perform a co-esterification reaction, and then slowly heated to a second temperature and decompressed to 10-50 Pa to perform melt polycondensation, and reacted for 4-8 hours; the first temperature is 140-180°C, and the second temperature is 220-280°C.

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