A heterogeneous titanium catalyst for PBAT polymerization and a preparation method and application thereof

Abstract

The present application relates to a kind of PBAT polymerization with heterogeneous titanium catalyst and its preparation method and application, heterogeneous titanium catalyst includes titanium compound, metal salt and active hydrogen-containing organic compound;Active hydrogen functional group of active hydrogen-containing organic compound and the molar ratio of titanium compound is 0.3~30;The molar ratio of metal salt and titanium compound is 0.2~20;Active hydrogen-containing organic compound is selected from C1~C 30 Alkane, cycloalkane, aromatic hydrocarbon, alkene, alkyne or heterocyclic hydrocarbon containing one or more of hydroxyl, phenolic hydroxyl, carboxyl, amino, sulfhydryl, phosphoric acid group, sulfonic group;The general formula of titanium compound is Ti (OR) 4 or Ti (OR) 2 Cl2 compound;Metal salt is selected from one or more of magnesium, lanthanum, cerium, zinc, zirconium, sodium, potassium, calcium, lithium metal salt and its hydrate.The heterogeneous titanium catalyst of the present application has high activity at relatively low temperature.

Description

Technical Field

[0001] This invention belongs to the field of polyester synthesis technology, specifically relating to a heterogeneous titanium catalyst for PBAT polymerization, its preparation method, and its application. Background Technology

[0002] Aliphatic-aromatic copolyesters possess excellent mechanical and biodegradable properties, making them a good alternative to traditional plastics and a solution to the environmental problems they cause. Among them, poly(butylene adipate-butylene terephthalate) (PBAT) is a thermoplastic biodegradable plastic. Its flexible aliphatic segments and rigid aromatic segments combine the characteristics of both polybutylene acrylate (PBA) and polybutylene terephthalate (PBT), exhibiting good ductility and elongation at break, as well as good heat resistance and impact resistance. It is one of the best biodegradable polymers currently available, offering both performance and cost advantages, and is the third largest biodegradable plastic after starch-based plastics and polylactic acid. PBAT is polymerized via direct esterification (PTA method) or transesterification (dimethyl terephthalate, DMT method). The PTA method uses terephthalic acid (PTA), adipic acid (AA), and 1,4-butanediol (BDO) as raw materials, with a certain amount of catalyst and a suitable reaction temperature, to first esterify and then condense to form PBAT. The DMT method first puts dimethyl terephthalate (DMT), 1,4-butanediol (BDO) and a suitable amount of catalyst into a reactor, distills out methanol to the theoretical amount, then adds a certain amount of adipic acid (AA) into the reactor, distills out the corresponding water, and the esterification ends. Then, PBAT is obtained by condensation.

[0003] In the industrial production of polyester, catalysts are crucial to the quality and performance of the polymerized products. Currently, commonly used catalysts in polyester synthesis include tetrabutyl titanate (TBOT), antimony trioxide (Sb₂O₃), antimony glycolate [Sb₂(EG)₃], and magnesium acetate [Mg(OAc)₂]. Among these, highly active TBOT is the most commonly used catalyst in the copolyester PBAT (transesterification method), significantly shortening polymerization time and increasing reaction rate. However, when used in the direct esterification method (PTA method), excessive catalyst content leads to numerous byproducts and lower molecular weight products during polymerization. TBOT is highly susceptible to hydrolysis, requiring strict control of moisture content during addition to the reactor; however, the water produced during the esterification reaction inevitably deactivates it. Furthermore, during PBAT synthesis, on the one hand, 1,4-butanediol (BDO) readily generates tetrahydrofuran during the reaction, and high temperature and pressure accelerate this reaction; on the other hand, the carboxyl groups in terephthalic acid (PTA) also accelerate the dehydration of BDO to produce tetrahydrofuran. In the synthesis of PBAT, catalysts with high activity at lower temperatures and the ability to suppress the side reaction of tetrahydrofuran should be selected. Therefore, it is of great significance to develop new, efficient, and highly selective environmentally friendly catalysts for PBAT polymerization. Summary of the Invention

[0004] Based on the aforementioned shortcomings and deficiencies in the prior art, one of the objectives of this invention is to at least solve one or more of the aforementioned problems in the prior art. In other words, one of the objectives of this invention is to provide a heterogeneous titanium catalyst for PBAT polymerization, its preparation method, and its application, which meet one or more of the aforementioned requirements.

[0005] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0006] A heterogeneous titanium-based catalyst for PBAT polymerization includes a titanium compound, a metal salt, and an organic compound containing active hydrogen.

[0007] Among them, the molar ratio of the active hydrogen functional group of the organic compound containing active hydrogen to the titanium compound is 0.3 to 30; the molar ratio of the metal salt to the titanium compound is 0.2 to 20.

[0008] The organic compound containing active hydrogen is selected from C1 to C2 groups containing one or more of the following groups: hydroxyl, phenolic hydroxyl, carboxyl, amino, mercapto, phosphate, and sulfonyl groups. 30 Branched or straight-chain alkanes, cycloalkanes, aromatics, alkenes, alkynes, or heterocyclic hydrocarbons;

[0009] The titanium compounds have the general formula Ti(OR)4 or Ti(OR)2Cl2, wherein R is selected from C1 to C2. 12 Straight-chain alkyl or branched alkyl.

[0010] The metal salt is selected from one or more of the metal salts and hydrates of magnesium, lanthanum, cerium, zinc, zirconium, sodium, potassium, calcium, and lithium.

[0011] As a preferred embodiment, the organic compound containing active hydrogen is selected from the following structures:

[0012]

[0013]

[0014]

[0015] As a preferred embodiment, the titanium compound is selected from the following structures:

[0016]

[0017] As a preferred embodiment, the anion of the metal salt is selected from C6H5COO. - C2O4 2- PO4 3- HPO4 2- H2PO4 - CO3 2- HCO3 - C6H5SO3 - C6H5O - R'SO3 - R'COO - R' is C1 to C 10 Branched or straight-chain alkanes.

[0018] As a preferred embodiment, the metal salt is selected from the following structures or their hydrates:

[0019]

[0020] The present invention also provides a method for preparing a heterogeneous titanium-based catalyst as described in any of the preceding embodiments, comprising the following steps:

[0021] (1) Dissolve an organic compound containing active hydrogen in an organic solvent to obtain an organic solution of the organic compound containing active hydrogen; the organic solvent is selected from one or more of methanol, ethanol, ethylene glycol, isopropanol, diethylene glycol, glycerol, propylene glycol and butanediol;

[0022] (2) Heating an organic solution containing an organic compound with active hydrogen and adding a titanium compound, so that some of the titanate reacts with the organic compound containing active hydrogen. The reaction temperature is selected from 30 to 150°C depending on the properties of the solvent.

[0023] (3) Then, an organic solution of metal salt was added dropwise to the system in step (2), and the reaction system was heated to obtain a precipitate. Part of the metal salt reacted with the remaining titanium ester. The reaction temperature was the same as in step (2), and the reaction time was 0.5 to 48 h.

[0024] (4) The precipitate obtained in step (3) is washed, dried and ground to obtain a heterogeneous titanium catalyst.

[0025] This invention also provides the application of the heterogeneous titanium-based catalyst as described in any of the preceding embodiments for the synthesis of PBAT, comprising the following steps:

[0026] 1,4-Butanediol, terephthalic acid, and adipic acid are added to a reaction vessel for esterification. The esterification temperature is selected from 150 to 230°C, the pressure is selected from 1 to 3 atmospheres, and the reaction time is selected from 1 to 20 hours.

[0027] After the esterification reaction is completed, a polycondensation reaction is carried out. The polycondensation temperature is selected from 230 to 300℃, the reaction pressure is selected from 3 to 90000 Pa, and the reaction time is selected from 1 to 24 h.

[0028] PBAT is obtained after the polycondensation reaction is completed;

[0029] The molar ratio of 1,4-butanediol to (terephthalic acid + adipic acid) is 1.2 to 2.0; the molar ratio of terephthalic acid to adipic acid is 0.1 to 100; and the ratio of the mass of the heterogeneous titanium catalyst to the sum of the masses of the three raw materials is 0.000001 wt% to 1 wt%.

[0030] The present invention also provides the application of the heterogeneous titanium catalyst as described in any of the preceding embodiments, characterized in that it is used for the polymerization of one or more polyacid monomers and one or more polyol monomers to prepare polyester.

[0031] The general formula of the polybasic acid monomer is HOOC-R1-C0OH, wherein R1 is selected from C1 to C23 straight-chain alkyl or branched, non-substituted or Si, N, O, F substituted alkanes, cycloalkanes, aromatics, alkenes, alkynes or heterocyclic hydrocarbons.

[0032] The polyol monomers are compounds with the general formula HO-R2-OH, wherein R2 is a straight-chain alkyl or branched, non-substituted or substituted with S, Si, N, O, F, or Cl, alkane, cycloalkane, aromatic hydrocarbon, olefin, alkyne, or heterocyclic hydrocarbon from C1 to C26.

[0033] As a preferred embodiment, the polybasic acid monomer is selected from the following structures:

[0034]

[0035] As a preferred embodiment, the polyol monomer is selected from the following structures:

[0036]

[0037]

[0038] Compared with the prior art, the beneficial effects of this invention are:

[0039] (1) By preparing a heterogeneous solid catalyst, the deactivation problem of titanate esters caused by difficulties in storage, easy hydrolysis, and easy coordination and co-precipitation with organic ligands of liquid catalysts such as titanate esters was solved.

[0040] (2) The heterogeneous titanium catalyst preparation method of the present invention is simple, has good dispersion uniformity, maintains high catalytic activity and reduces the amount of catalyst used.

[0041] (3) The poly(butylene adipate-butylene terephthalate) (PBAT) prepared by the heterogeneous titanium catalyst of the present invention has advantages such as better color, higher molecular weight and performance compared with traditional catalysts. Moreover, the catalyst has high activity under relatively low temperature conditions and can catalyze the polymerization of various polyols and polyacids to obtain a variety of polyester products. Detailed Implementation

[0042] The technical solution of the present invention will be further explained and illustrated below through specific embodiments.

[0043] I. Examples 1-43:

[0044] Weigh a certain amount of an organic compound containing active hydrogen (raw material 3) and dissolve it in 10 times its volume of organic solvent (the volume may be adjusted depending on the solubility), then dissolve it in an ultrasonic machine. Weigh a certain amount of a metal salt (raw material 2) and dissolve it in 200 times its mass of organic solvent (the volume may be adjusted depending on the solubility), then dissolve it in an ultrasonic machine. After complete dissolution, remove the solution and set aside. Preheat the mixed solution containing the active hydrogen compound to the reaction temperature (T), add a certain amount of titanium compound (raw material 1), and then add the mixed solution containing the metal salt dropwise. React for a specific time (t) until a precipitate is obtained and completely precipitated. Separate the precipitate, wash it with water and organic solvent, vacuum dry it, and grind it to obtain a white powder product. The specific proportions of raw materials 1 to 3 are shown in Table 1.

[0045] Table 1. Raw materials and process conditions for the heterogeneous titanium catalysts in Examples 1-43

[0046]

[0047]

[0048]

[0049] a When using mixed solvents, the volume ratio of the two solvents is 1:1, but volume ratios of 1:10 to 10:1 also apply.

[0050] II. Application Examples 1-40: Preparation of PBAT using Heterogeneous Titanium Catalysts

[0051] The reaction process is as follows: terephthalic acid, adipic acid, 1,4-butanediol, and the aforementioned catalyst are mixed to form a slurry, which is then added to a polymerization reactor. Esterification is carried out at a specific temperature for a specific time. The water generated during the reaction is discharged through a distillation unit. After esterification, the pressure is reduced and the temperature is raised to a specific temperature for polycondensation. The product is discharged from the bottom of the polymerization reactor after a specific reaction time, cooled in cold water, pelletized, and dried. Subsequent tests are conducted on intrinsic viscosity, relative molecular weight, color value, and mechanical properties. The catalysts used, their concentrations, and the properties of the prepared PBAT are shown in Table 2.

[0052] Note: In application examples 1-10, the ratio of phthalic acid: adipic acid: 1,4-butanediol is 0.5:0.5:1.4;

[0053] In Application Examples 11-20, the ratio of phthalic acid: adipic acid: 1,4-butanediol is 0.4:0.6:1.5.

[0054] In Application Examples 21-30, the ratio of phthalic acid: adipic acid: 1,4-butanediol is 0.8:0.2:1.3.

[0055] In Application Examples 31-40, the ratio of phthalic acid: adipic acid: 1,4-butanediol is 0.4:0.6:2.0.

[0056] In application examples 41-50, the ratio of phthalic acid: adipic acid: 1,4-butanediol is 0.2:0.8:1.4.

[0057] Table 2. Catalysts and PBAT polymerization process and performance.

[0058]

[0059]

[0060]

[0061] III. Application Examples 51-105: Catalyzing the polymerization of other polyacids and polyols to obtain polyesters.

[0062] Since the catalysts have similar catalytic activity and capacity, after careful selection, the following catalysts were chosen as catalytic models to catalyze the polymerization of the following monomers.

[0063] The reaction process is as follows: A certain amount of polycarboxylic acid (monomer 1), polyol (monomer 2) (the ratio of polyol to polycarboxylic acid with corresponding functional groups is 1.4:1), and the above-mentioned catalyst are mixed to form a slurry, which is then added to a polymerization reactor. Esterification is carried out at a certain reaction temperature for a certain time. The water generated during the reaction is discharged through a distillation device. After esterification, the pressure is reduced and the temperature is raised to a specific temperature for polycondensation. The product is discharged from the bottom of the polymerization reactor after a specific reaction time, cooled in cold water, pelletized, and dried. Subsequently, intrinsic viscosity, relative molecular weight, color value, and mechanical properties are tested. The catalyst used and the properties of the prepared polyester are shown in Table 3.

[0064] Table 3 Catalysts used and polyester preparation performance.

[0065]

[0066]

[0067]

[0068] IV. Application Examples 106-125: Catalyzing the polymerization of other polyacids and polyols to obtain polyesters

[0069] To further improve the degree of polymerization, introducing an appropriate amount of multifunctional monomers into the catalytic system can increase the degree of polymerization and prepare polyester products with higher molecular weights. Since the catalytic activity and capacity of the catalysts are similar, after careful selection, the following catalysts were chosen as catalytic models to catalyze the polymerization of the following monomers.

[0070] The reaction process is as follows: A certain amount of polycarboxylic acid (monomer 1), polyol (monomer 2), multifunctional monomer (monomer 3), and the above catalyst are mixed to form a slurry, which is then added to a polymerization reactor. Esterification is carried out at a specific temperature for a specific time. The water generated during the reaction is discharged through a distillation device. After esterification, the pressure is reduced and the temperature is raised to a specific temperature for polycondensation. After a specific reaction time, the product is discharged from the bottom of the polymerization reactor, cooled in cold water, pelletized, and dried. Subsequent tests are conducted on intrinsic viscosity, relative molecular weight, color value, and mechanical properties. The catalysts used and the properties of the prepared polyester are shown in Table 4.

[0071] Table 4. Catalysts used and polyester preparation performance.

[0072]

[0073]

[0074] V. Application Examples 126-129

[0075] Considering the best preparation process, cost, and catalytic effect, four catalysts were selected below and their polymerization effects were compared with those of commonly used catalytic systems.

[0076] The reaction process is as follows: terephthalic acid, adipic acid, 1,4-butanediol, and the aforementioned catalyst are mixed to form a slurry, which is then added to a polymerization reactor. Esterification is carried out at a specific temperature for a specific time. The water generated during the reaction is discharged through a distillation unit. After esterification, the pressure is reduced and the temperature is raised to a specific temperature for polycondensation. The product is discharged from the bottom of the polymerization reactor after a specific reaction time, cooled in cold water, pelletized, and dried. Subsequent tests are conducted on intrinsic viscosity, relative molecular weight, color value, and mechanical properties. The catalysts used, their concentrations, and the properties of the prepared PBAT are shown in Table 5.

[0077] Table 5. Catalyst and PBAT performance during polymerization.

[0078]

[0079] Among them, the polymerization temperature of catalyst Cat.36 was reduced to 230℃, and the PBAT obtained by polymerization under it had the best performance.

[0080] Comparative Examples 1-4:

[0081]

[0082]

[0083] In summary, the heterogeneous titanium catalyst of the present invention has high activity at lower temperatures, and the products obtained by catalyzing the polymerization of PBAT and other polyesters with it have the characteristics of high intrinsic viscosity, high molecular weight and low color value.

[0084] Unless otherwise specified, the raw materials and equipment used in this invention are all commonly used in the field; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0085] The above description is merely a detailed explanation of preferred embodiments and principles of the present invention. For those skilled in the art, there may be changes in specific implementation methods based on the ideas provided by the present invention, and these changes should also be considered within the scope of protection of the present invention.

Claims

1. The application of a heterogeneous titanium-based catalyst for the synthesis of PBAT, characterized in that, Includes the following steps: 1,4-Butanediol, terephthalic acid, adipic acid, and a heterogeneous titanium catalyst were added to a reaction vessel for esterification. The esterification temperature was 190℃, the pressure was selected from 1 to 3 atmospheres, and the reaction time was 2 hours. After the esterification reaction is completed, a polycondensation reaction is carried out at a temperature of 240℃, a reaction pressure of 30Pa, and a reaction time of 2h. PBAT is obtained after the polycondensation reaction is completed; The molar ratio of 1,4-butanediol to (terephthalic acid + adipic acid) is 1.4; the molar ratio of terephthalic acid to adipic acid is 1; and the mass ratio of the heterogeneous titanium catalyst to the sum of the masses of the three raw materials is 0.03 wt%. Among them, heterogeneous titanium-based catalysts include titanium compounds, metal salts, and organic compounds containing active hydrogen. Organic compounds containing active hydrogen are , n The value is 2; the metal salts are Ce(CH3COO)3 and CH3COOK, and the titanium compound is... The molar ratio of titanium compounds, Ce(CH3COO)3, CH3COOK, and organic compounds containing active hydrogen is 1:0.8:1:

6. The preparation method of heterogeneous titanium-based catalysts includes the following steps: An organic compound containing active hydrogen was weighed and dissolved in methanol, and then dissolved in an ultrasonic machine to obtain a mixed solution containing active hydrogen. A metal salt was weighed and dissolved in methanol, and then dissolved in an ultrasonic machine to obtain a mixed solution containing the metal salt. The mixed solution containing active hydrogen was preheated to 30°C, a titanium compound was added, followed by the addition of the mixed solution containing the metal salt. The reaction was carried out for 0.5 h, the precipitate was separated, washed with water and methanol, dried under vacuum, and ground to obtain a heterogeneous titanium catalyst.

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