CN113801311A - Process for preparing polyester - Google Patents
Process for preparing polyester Download PDFInfo
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- CN113801311A CN113801311A CN202010539585.XA CN202010539585A CN113801311A CN 113801311 A CN113801311 A CN 113801311A CN 202010539585 A CN202010539585 A CN 202010539585A CN 113801311 A CN113801311 A CN 113801311A
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- acid
- titanium
- polyester
- hydroxycarboxylic acid
- catalyst
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/78—Preparation processes
- C08G63/82—Preparation processes characterised by the catalyst used
- C08G63/85—Germanium, tin, lead, arsenic, antimony, bismuth, titanium, zirconium, hafnium, vanadium, niobium, tantalum, or compounds thereof
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
- C08G63/12—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from polycarboxylic acids and polyhydroxy compounds
- C08G63/16—Dicarboxylic acids and dihydroxy compounds
- C08G63/18—Dicarboxylic acids and dihydroxy compounds the acids or hydroxy compounds containing carbocyclic rings
- C08G63/181—Acids containing aromatic rings
- C08G63/183—Terephthalic acids
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts
Abstract
The invention relates to a polyester preparation method, which mainly solves the problem of poor thermal stability of titanium polyester prepared in the prior art. The invention adopts a polyester preparation method, takes dicarboxylic acid and dihydric alcohol as raw materials, and comprises the steps of carrying out esterification reaction and then carrying out polycondensation reaction in the presence of a titanium catalyst to obtain a polyester product; wherein the titanium catalyst comprises a reaction product of a titanium compound, a hydroxycarboxylic acid and a metal salt; the molar ratio of the hydroxycarboxylic acid to the titanium compound is 0.2:1-1.5:1, the molar ratio of the metal salt to the hydroxycarboxylic acid is 0.01:1-0.5:1, and the molar content of free hydroxycarboxylic acid in the titanium catalyst is less than or equal to 10% of the total amount of the hydroxycarboxylic acid, so that the problem of thermal stability of the titanium polyester caused by modification of the hydroxycarboxylic acid is well solved, and the titanium polyester can be used in industrial production of the polyester.
Description
Technical Field
The invention relates to a polyester preparation method.
Background
Polyethylene terephthalate (polyester for short) is the variety with the largest yield in chemical fibers. The world production capacity of polyester is 10020 ten thousand tons/year and the demand is 7258 ten thousand tons by 2018. It is expected that worldwide polyester production will increase to 12014 ten thousand tons per year and demand will reach 9320 ten thousand tons by 2025.
With the development of the polyester industry, catalysts for polyester synthesis have also been intensively studied. Although most main-subgroup metal elements show certain catalytic activity, three series of catalysts, namely antimony, germanium and titanium, are mainly used and researched in industry at present. Among them, antimony catalysts are most commonly used, which account for about 90% of the polyester catalyst market, however, antimony is a heavy metal and has adverse effects on human bodies and the environment during the use. The polyester product obtained by the germanium catalyst has excellent quality, but the germanium resource is less, the price is high, the polyester product is not suitable for large-scale use, and the polyester product is only suitable for high-grade polyester products.
Titanium-based catalysts have received much attention and research since the last 70 th century. Titanium catalysts used in the early days are mainly inorganic salts and organic acid esters of titanium, and although the catalysts show high activity, the catalysts have the problems of poor stability, yellowing and turbidity of polyester products and the like. With further advances in theory and technology, a number of effective technical solutions have been proposed and used to solve the above-mentioned problems. For example, to solve the hue problem, a titanium-based catalyst is generally used together with metallic cobalt or an organic toner; in order to solve the problem of poor thermal stability of titanium polyester, a phosphorus stabilizer is often added; in order to solve the hydrolysis problem of the titanium catalyst, organic compounds such as alpha-hydroxycarboxylic acid and the like are usually adopted to chelate the titanium compound to improve hydrolysis resistance, or titanium is loaded on carriers such as molecular sieves, activated carbon and the like, or coprecipitated metal oxides such as Ti/Si and the like are prepared. The technical means can also be used together, so that the titanium polyester catalyst with better balanced catalyst activity, polyester color and other properties can be developed and obtained.
Among the above technical means, organic compound chelation is an important modification mode. The titanium-based catalyst obtained by the method is liquid and has good hydrolysis resistance, and can be used conveniently and has excellent polymerization performance by being further matched with other metal additives, stabilizers and the like. For example, CN102504226A modifies titanate by citric acid and further reacts with alkali to obtain a liquid titanium polyester catalyst, and a polyester product with good performance is obtained based on the catalyst. For example, CN 102382287a reacts a titanium compound, ethyl orthosilicate, hydroxycarboxylic acid, etc. in a solvent, and then acetate, a phosphorus compound, etc. are added to obtain a liquid titanium catalyst, which can be dissolved in ethylene glycol, and can prepare polyesters and copolyesters with good color phase and narrow molecular weight distribution. CN101270185A adopts titanate to react with glycol and ethyl orthosilicate, and then hydroxy acid is added to obtain the liquid titanium catalyst with better performance.
Disclosure of Invention
The inventor finds that the content of the hydroxycarboxylic acid and the modification mode of the titanium compound have important influence on the performance of the catalyst through a large amount of experimental research. When the ratio of hydroxycarboxylic acid to titanate is too high (e.g. a molar ratio of hydroxycarboxylic acid to titanate of 2.5: 1, 2.0: 1), or when a polyol reactive with titanate is introduced (e.g. ethylene glycol) when the hydroxycarboxylic acid chelates a titanium compound, some or even more of the hydroxycarboxylic acid is liberated into the polymerization system in the catalyst. The free hydroxycarboxylic acid is polymerized into the molecular main chain along with the addition of the catalyst, so that the color phase of the polyester is increased, the thermal stability is reduced, and meanwhile, the free hydroxycarboxylic acid enters the recycled ethylene glycol along with a vacuum system, so that the quality of the recycled ethylene glycol is reduced. There is therefore a need for effective control of free hydroxycarboxylic acids in catalyst systems when using hydroxycarboxylic acid chelating titanium compounds. Although the amount of free hydroxycarboxylic acid can be reduced by reducing the amount of hydroxycarboxylic acid to be added, for example, by a molar ratio of not more than 1.5:1 to the titanate, the resulting hydroxycarboxylic acid-chelated liquid titanium-based catalyst has a problem of poor stability, gel or precipitate in addition to an aqueous solution or an ethylene glycol solution, and this problem becomes more pronounced with the decrease in the content of hydroxycarboxylic acid, thereby limiting the use of the catalyst.
In order to solve the problems, the invention controls the content of free hydroxycarboxylic acid in the catalyst by controlling the molar ratio of the hydroxycarboxylic acid to the titanium compound and a direct reaction mode, and improves the stability of the catalyst by adding a metal salt when the hydroxycarboxylic acid chelates the titanium compound, thereby preparing the liquid titanium catalyst which has high reaction degree of the hydroxycarboxylic acid (low content of the free hydroxycarboxylic acid) and has good stability in an aqueous solution and an ethylene glycol solution. On the basis, the titanium polyester with good hue and thermal stability is prepared by adopting the catalyst.
The invention aims to solve the technical problems that in the prior art, the content of free hydroxy acid in a titanium polyester catalyst is high and the prepared titanium polyester has poor thermal stability, and provides a novel polyester preparation method. The method uses the titanium catalyst with low free hydroxycarboxylic acid to prepare the polyester, and the obtained polyester has the advantages of good thermal stability and the like.
The second technical problem to be solved by the invention is the problems of high content of free hydroxy acid existing in the titanium polyester catalyst in the prior art and poor thermal stability of the prepared titanium polyester, and the invention provides the titanium catalyst which has low content of free hydroxy carboxylic acid and high stability, and the prepared polyester has good hue and thermal stability.
The third technical problem to be solved by the present invention is to provide a method for preparing a titanium-based catalyst corresponding to the second technical problem.
In order to solve one of the above technical problems, the invention adopts the technical scheme that: a polyester preparation method, take dicarboxylic acid and dihydric alcohol as raw materials, include in the presence of titanium catalyst, carry on the esterification reaction, the step of the polycondensation reaction, get polyester product; wherein the titanium catalyst comprises a reaction product of a titanium compound, a hydroxycarboxylic acid and a metal salt; wherein the molar ratio of the hydroxycarboxylic acid to the titanium compound is 0.2:1-1.5:1, the molar ratio of the metal salt to the hydroxycarboxylic acid is 0.01:1-0.5:1, and the molar content of free hydroxycarboxylic acid in the titanium catalyst is less than or equal to 10% of the total amount of hydroxycarboxylic acid.
In the above technical scheme, the titanium catalyst may be added before the esterification reaction starts or before the polycondensation reaction starts.
In the above technical solution, the dicarboxylic acid is preferably at least one of terephthalic acid, phthalic acid, isophthalic acid, naphthalenedicarboxylic acid, biphenyldicarboxylic acid, and cyclohexanedicarboxylic acid.
In the above technical solution, the diol is preferably at least one selected from ethylene glycol, 1, 2-propylene glycol, 1, 3-propylene glycol, 1, 4-butanediol, 1, 6-hexanediol, and 1, 4-cyclohexanedimethanol.
In the above technical scheme, the titanium compound has a structure of a general formula (I):
wherein R is1～R4Are independently selected from aliphatic groups with 1-10 carbon atoms; preferably: r1～R4Are independently preferably selected from straight-chain or branched alkyl with 1-10 carbon atoms; more preferably, the titanium compound is at least one compound selected from the group consisting of tetramethyl titanate, tetraethyl titanate, tetrapropyl titanate, tetraisopropyl titanate, and tetrabutyl titanate.
In the technical scheme, the hydroxycarboxylic acid is preferably carboxylic acid containing 1-n hydroxyl groups, and n is more than or equal to 2; more preferably a carboxylic acid containing 1-2 hydroxyl groups; most preferably one or more of citric acid, lactic acid, malic acid, tartaric acid, and 2-hydroxyglutaric acid.
In the above technical solution, the metal element in the metal salt is preferably at least one of group IA, IIA, IIB, VIIB or VIII; more preferably, the metal salt is a carbonate, bicarbonate or C of the metal2～C4Salts of carboxylic acids.
In the technical scheme, the dosage of the titanium catalyst is 1-10 mu g of Ti/g of polyester, preferably 3-8 mu g of Ti/g of polyester, calculated by titanium atoms.
In the technical scheme, the reaction temperature of the esterification reaction is preferably 230-280 ℃, and the reaction pressure is preferably normal pressure-0.5 MPa (gauge pressure).
In the above technical scheme, the reaction temperature of the melt polycondensation reaction is preferably 250 to 320 ℃, and the reaction pressure is preferably less than 150Pa (absolute pressure).
In order to solve the second technical problem, the technical scheme adopted in the invention is as follows: a titanium-based catalyst comprising the reaction product of a titanium compound, a hydroxycarboxylic acid, and a metal salt; wherein the molar ratio of the hydroxycarboxylic acid to the titanium compound is 0.2:1-1.5: 1; the molar ratio of the metal salt to the hydroxycarboxylic acid is 0.01:1-0.5: 1; in the catalyst, the molar content of free hydroxycarboxylic acid is less than or equal to 10% of the total amount of hydroxycarboxylic acid.
In the above technical solution, the titanium compound preferably has a structure of general formula (i):
wherein R is1～R4Are independently selected from aliphatic groups with 1-10 carbon atoms; preferably: r1～R4Are independently preferably selected from straight-chain or branched alkyl with 1-10 carbon atoms; more preferably: the titanium compound is preferably at least one compound of tetramethyl titanate, tetraethyl titanate, tetrapropyl titanate, tetraisopropyl titanate or tetrabutyl titanate.
In the technical scheme, the hydroxycarboxylic acid is preferably carboxylic acid containing 1-n hydroxyl groups, and n is more than or equal to 2; more preferably a carboxylic acid containing 1-2 hydroxyl groups; most preferably one or more of citric acid, lactic acid, malic acid, tartaric acid, and 2-hydroxyglutaric acid.
In the above technical solution, the metal element in the metal salt is preferably at least one of group IA, IIA, IIB, VIIB or VIII; more preferably, the metal salt is a carbonate, bicarbonate or C of the metal2～C4Salts of carboxylic acids.
In order to solve the third technical problem, the invention adopts the technical scheme that: a method for preparing the titanium catalyst according to any one of the two technical solutions to solve the technical problems comprises the following steps:
1) preparing the hydroxycarboxylic acid, the metal salt and a solvent into a mixed solution;
2) mixing the titanium compound with the mixed solution, reacting to obtain a clear viscous solution, and performing post-treatment to obtain the titanium catalyst.
In the technical scheme, the solvent in the step 1) is one or more of monohydric alcohol with 2-10 carbon atoms and polyhydric alcohol with 2-10 carbon atoms; the monohydric alcohol having 2 to 10 carbon atoms is, for example, ethanol, isopropanol, etc., and the polyhydric alcohol having 2 to 10 carbon atoms is, for example, diethylene glycol, propylene glycol, butylene glycol, etc.
In the above technical solution, the titanium compound is preferably added to the mixed solution in a manner of mixing with the mixed solution.
In the above preparation method, the reaction conditions in the step 2) are preferably: the reaction temperature is 30-200 ℃, and the reaction time is 0.2-24 h.
In the above technical solution, the post-treatment preferably comprises a step of vacuum pumping out small molecules.
In the above technical solution, the titanium catalyst may be optionally added with a solvent (such as ethylene glycol) after preparation or during use to obtain a titanium catalyst solution with a certain concentration.
In the present invention, the intrinsic viscosity, hue, etc. of the polyester are measured by the following methods:
(1) intrinsic viscosity: the phenol-tetrachloroethane mixture is used as a solvent, and is measured by an Ubbelohde viscometer at the temperature of 25 ℃.
(2) Hue: the pellet samples were treated at 135 ℃ for 1 hour and measured for Hunter L value (lightness), a value (red-green hue) and b value (yellow-blue hue) using a color-view automatic color difference meter from BYK Gardner. Wherein, the higher the L value, the larger the brightness; when the value of b is high, the polyester chip is yellowish. For the present invention, a high L value and a low b value are desired.
(3) Free hydroxy acids: the catalyst sample is diluted 100 times and then injected for analysis by HPLC (C18, 95% ACN isocratic elution, detection wavelength 205 nm).
(4) Thermal stability analysis: a tube furnace is adopted, and the treatment is carried out for 30min at 270 ℃ under nitrogen atmosphere.
By adopting the technical scheme of the invention, the content of the obtained titanium polyester catalytic free hydroxy acid is low, and the prepared polyester has the characteristics of excellent thermal stability and good hue, so that better technical effects are obtained.
The invention is further illustrated by the following examples.
Detailed Description
It should be noted that the following examples are given solely for the purpose of illustration and are not to be construed as limitations of the present invention, as many insubstantial modifications and variations of the invention may be made by those skilled in the art in light of the teachings herein.
The raw materials used in the examples and comparative examples are disclosed in the prior art if not particularly limited, and may be, for example, directly purchased or prepared according to the preparation methods disclosed in the prior art.
[ example 1 ]
Preparation of catalyst A
1.0mol of citric acid and 0.2mol of sodium acetate are added into a reactor provided with a stirrer, a condenser and a thermometer, then a proper amount of isopropanol is added, and the mixture is stirred for 2 hours at room temperature to obtain a clear and transparent citric acid/metal salt solution. Slowly dropwise adding 1.0mol of tetraisopropyl titanate into the solution, heating to reflux reaction for 2 hours after dropwise adding is finished to obtain a transparent clear solution, removing small molecules in vacuum, and adding a certain amount of glycol for dilution to obtain a catalyst solution A with the free citric acid content of 7.9 wt% of the added amount and the titanium content of 3.0 wt%.
Preparation of polyesters
500 g of terephthalic acid, 316 g of ethylene glycol and a catalyst A (based on the amount of the polyester produced, the weight of titanium atoms is 5 mu g of Ti/g of PET) are mixed to prepare slurry, the slurry is added into a polymerization kettle for esterification reaction, the esterification temperature is 230-250 ℃, the pressure is 0.25MPa, and water produced by the reaction is discharged through a rectifying device. Reducing the pressure to normal pressure after the esterification is finished, vacuumizing and reducing the pressure to a system pressure lower than 130Pa, simultaneously gradually increasing the reaction temperature to 280 ℃, stopping the reaction when the system reaction reaches 150min, then extruding the reaction product from the bottom of the polymerization kettle, cooling, granulating, and performing performance test
And placing the obtained slices in a vacuum oven, drying at 150 ℃ for 12 hours, then placing the slices in a tube furnace equipped with nitrogen atmosphere, carrying out heat treatment at 270 ℃ for 30min, and carrying out intrinsic viscosity test on samples before and after the heat treatment.
The test results are shown in Table 1.
[ example 2 ]
Preparation of polyesters
500 g of terephthalic acid and 316 g of ethylene glycol are mixed to prepare slurry, the slurry is added into a polymerization kettle for esterification reaction, the esterification temperature is 230-. Reducing the pressure to normal pressure after the esterification is finished, adding a catalyst A (based on the amount of the generated polyester, the weight of titanium atoms is 5 mu g Ti/g PET), vacuumizing and reducing the pressure to be lower than 130Pa, gradually increasing the reaction temperature to 280 ℃, stopping the reaction when the system reaction reaches 150min, extruding the reaction product from the bottom of a polymerization kettle, cooling, cutting into granules, and performing a performance test
And placing the obtained slices in a vacuum oven, drying at 150 ℃ for 12 hours, then placing the slices in a tube furnace equipped with nitrogen atmosphere, carrying out heat treatment at 270 ℃ for 30min, and carrying out intrinsic viscosity test on samples before and after the heat treatment.
The test results are shown in Table 1.
[ example 3 ]
Preparation of catalyst B
Adding 0.5mol of citric acid and 0.2mol of sodium acetate into a reactor provided with a stirrer, a condenser and a thermometer, then adding a proper amount of isopropanol, and stirring for 2 hours at room temperature to obtain a clear and transparent citric acid/metal salt solution. Slowly dropwise adding 1.0mol of tetraisopropyl titanate into the solution, heating to reflux reaction for 2 hours after dropwise adding is finished to obtain a transparent clear solution, removing small molecules in vacuum, and adding a certain amount of glycol for dilution to obtain a catalyst solution B with the free citric acid content of 7.1 wt% of the added amount and the titanium content of 3.0 wt%.
Preparation of polyesters
A polyester was produced in the same manner as in example 1, using catalyst B as a catalyst, and the weight of titanium atom was 5. mu.g Ti/g PET based on the amount of the polyester produced
The test results are shown in Table 1.
[ example 4 ]
Preparation of catalyst C
Adding 0.3mol of citric acid and 0.2mol of sodium acetate into a reactor provided with a stirrer, a condenser and a thermometer, then adding a proper amount of isopropanol, and stirring for 2 hours at room temperature to obtain a clear and transparent citric acid/metal salt solution. Slowly dropwise adding 1.0mol of tetraisopropyl titanate into the solution, heating to reflux reaction for 2 hours after dropwise adding is finished to obtain a transparent clear solution, removing small molecules in vacuum, and adding a certain amount of glycol for dilution to obtain a catalyst solution C with the free citric acid content of 7.7 wt% of the added amount and the titanium content of 3.0 wt%.
Preparation of polyesters
A polyester was produced in the same manner as in example 1, using catalyst C as a catalyst, and the weight of titanium atom was 5. mu.g Ti/g PET based on the amount of the polyester produced
The test results are shown in Table 1.
[ example 5 ]
Preparation of polyesters
A polyester was produced in the same manner as in example 1, using catalyst A as a catalyst, and the weight of titanium atom was 4. mu.g Ti/g PET based on the amount of the polyester produced
The test results are shown in Table 1.
[ example 6 ]
Preparation of polyesters
A polyester was produced in the same manner as in example 1, using catalyst A as a catalyst, and the weight of titanium atom was 6. mu.g Ti/g PET based on the amount of the polyester produced
The test results are shown in Table 1.
[ example 7 ]
Preparation of catalyst D
0.5mol of citric acid and 0.1mol of magnesium acetate are added into a reactor provided with a stirrer, a condenser and a thermometer, then a proper amount of diethylene glycol is added, and the mixture is stirred for 2 hours at room temperature to obtain a clear and transparent citric acid/metal salt solution. Slowly dropwise adding 1.0mol of tetraisopropyl titanate into the solution, heating to reflux reaction for 2 hours after dropwise adding is finished to obtain a transparent clear solution, removing small molecules in vacuum, and adding a certain amount of glycol for dilution to obtain a catalyst solution D with the free citric acid content of 7.4 wt% of the added amount and the titanium content of 3.0 wt%.
Preparation of polyesters
A polyester was produced in the same manner as in example 1, using catalyst D as a catalyst, and the weight of titanium atom was 5. mu.g Ti/g PET based on the amount of the polyester produced
The test results are shown in Table 1.
Comparative example 1
Preparation of catalyst E
Adding 1.0mol of tetraisopropyl titanate into a reactor provided with a stirrer, a condenser and a thermometer, slowly dropwise adding 2.5mol of citric acid aqueous solution into the solution, heating the solution until reflux reaction is carried out for 2 hours after dropwise adding is finished to obtain turbid solution, and adding a certain amount of glycol for dilution after removing small molecules in vacuum to obtain slightly turbid catalyst solution E with the free citric acid content of 40.0 wt% of the added amount and the titanium content of 3.0 wt%.
Preparation of polyesters
A polyester was produced in the same manner as in example 1, using catalyst E as a catalyst, and the weight of titanium atom was 5. mu.g Ti/g PET based on the amount of the polyester produced
The test results are shown in Table 1.
Comparative example 2
Preparation of catalyst F
Adding 1.0mol of tetraisopropyl titanate into a reactor provided with a stirrer, a condenser and a thermometer, slowly dropwise adding an ethylene glycol solution (200g) into the solution, heating to 80 ℃ after the dropwise adding is finished, reacting for 2 hours to obtain a turbid solution, removing small molecules in vacuum, adding an ethylene glycol citrate solution (the citric acid content is 1mol) to obtain a clear and transparent solution, and then adding ethylene glycol to dilute to obtain a catalyst solution with the free citric acid content of 32.4 wt% of the added amount and the titanium content of 3.0 wt%.
Preparation of polyesters
A polyester was produced in the same manner as in example 1, using catalyst F as a catalyst, and the weight of titanium atom was 5. mu.g Ti/g PET based on the amount of the polyester produced
The test results are shown in Table 1.
The test results in table 1 show that the titanium catalyst of the present invention has good activity, the color of the polyester is good, and the viscosity of the polyester is low, which indicates that the thermal stability of the polyester prepared by the catalyst of the present invention is significantly improved.
Table 1.
Claims (10)
1. A polyester preparation method, take dicarboxylic acid and dihydric alcohol as raw materials, include in the presence of titanium catalyst, carry on the esterification reaction, the step of the polycondensation reaction, get polyester product; wherein the titanium catalyst comprises a reaction product of a titanium compound, a hydroxycarboxylic acid and a metal salt; wherein the molar ratio of the hydroxycarboxylic acid to the titanium compound is 0.2:1-1.5:1, the molar ratio of the metal salt to the hydroxycarboxylic acid is 0.01:1-0.5:1, and the molar content of free hydroxycarboxylic acid in the titanium catalyst is less than or equal to 10% of the total amount of hydroxycarboxylic acid.
2. The method for preparing polyester according to claim 1, wherein the dicarboxylic acid is at least one selected from terephthalic acid, phthalic acid, isophthalic acid, naphthalene dicarboxylic acid, biphenyl dicarboxylic acid, and cyclohexane dicarboxylic acid;
and/or: the dihydric alcohol is at least one of ethylene glycol, 1, 2-propylene glycol, 1, 3-propylene glycol, 1, 4-butanediol, 1, 6-hexanediol or 1, 4-cyclohexanedimethanol.
3. The process for preparing polyester according to claim 1, wherein the titanium compound has a structure of general formula (i):
wherein R is1～R4Are independently selected from aliphatic groups with 1-10 carbon atoms; preferably: r1～R4Are independently preferably selected from straight-chain or branched alkyl with 1-10 carbon atoms; more preferably: the titanium compound is preferably at least one compound of tetramethyl titanate, tetraethyl titanate, tetrapropyl titanate, tetraisopropyl titanate or tetrabutyl titanate.
4. The method for producing polyester according to claim 1, wherein the hydroxycarboxylic acid is a carboxylic acid containing 1 to n hydroxyl groups, n is 2 or more; more preferably, the hydroxycarboxylic acid is one or more of citric acid, lactic acid, malic acid, tartaric acid and 2-hydroxyglutaric acid;
and/or: the metal element in the metal salt is at least one of IA, IIA, IIB, VIIB or VIII group; preferably: the metal salt is carbonate, bicarbonate or C of the metal2～C4Salts of carboxylic acids.
5. The method for producing polyester according to claim 1, wherein the amount of the titanium catalyst is 1 to 10 μ g of Ti/g of polyester, preferably 3 to 8 μ g of Ti/g of polyester, in terms of titanium atom.
6. The method for producing polyester according to claim 1, wherein the esterification reaction is carried out at a reaction temperature of 230 to 280 ℃ and a reaction pressure of normal pressure to 0.5MPa (gauge pressure);
and/or: the reaction temperature of the melt polycondensation reaction is 250-320 ℃, and the reaction pressure is less than 150Pa (absolute pressure).
7. A titanium-based catalyst comprising the reaction product of a titanium compound, a hydroxycarboxylic acid, and a metal salt; wherein the molar ratio of the hydroxycarboxylic acid to the titanium compound is 0.2:1-1.5: 1; the molar ratio of the metal salt to the hydroxycarboxylic acid is 0.01:1-0.5: 1; in the catalyst, the molar content of free hydroxycarboxylic acid is less than or equal to 10% of the total amount of hydroxycarboxylic acid.
8. The titanium-based catalyst according to claim 7, wherein said titanium compound has a structure of the general formula (I):
wherein R is1～R4Are independently selected from aliphatic groups with 1-10 carbon atoms; preferably: r1～R4Are independently preferably selected from straight-chain or branched alkyl with 1-10 carbon atoms; more preferably: the titanium compound is preferably at least one compound of tetramethyl titanate, tetraethyl titanate, tetrapropyl titanate, tetraisopropyl titanate or tetrabutyl titanate;
and/or: the hydroxycarboxylic acid is carboxylic acid containing 1-n hydroxyl groups, and n is more than or equal to 2; preferably, the hydroxycarboxylic acid is one or more than two of citric acid, lactic acid, malic acid, tartaric acid and 2-hydroxyglutaric acid;
and/or: the metal element in the metal salt is at least one of IA, IIA, IIB, VIIB or VIII group; more preferably: the metal salt is preferably a carbonate, bicarbonate or C of the metal2～C4A carboxylate salt.
9. A method for producing the titanium-based catalyst according to claim 7 or 8, comprising the steps of:
1) preparing a mixed solution of hydroxycarboxylic acid, metal salt and a solvent;
2) mixing a titanium compound with the mixed solution, reacting to obtain a clear viscous solution, and performing post-treatment to obtain the titanium catalyst.
10. The method for producing a titanium-based catalyst according to claim 9, wherein the titanium compound is mixed with the mixed solution by adding the titanium compound to the mixed solution;
and/or: the post-treatment comprises the step of vacuum pumping out small molecules;
and/or: the solvent in the step 1) is one or more of monohydric alcohol with 2-10 carbon atoms and polyhydric alcohol with 2-10 carbon atoms.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114989405A (en) * | 2022-07-11 | 2022-09-02 | 青岛大学 | Titanium catalyst for synthesizing polyester by DMT method, preparation method and application thereof |
| WO2023202449A1 (en) * | 2022-04-19 | 2023-10-26 | 浙江理工大学 | Solid bimetallic titanium-based polyester catalyst, preparation method therefor, and use thereof |
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