Chelated titanium environment-friendly polyester catalyst as well as preparation method and application thereof

Abstract

The invention discloses a chelated titanium environment-friendly polyester catalyst and a preparation method and application thereof.The catalyst is prepared from titanium-containing organic salt, a first organic modifier, a second modifier, a low-boiling-point solvent and a high-boiling-point solvent, and the first organic modifier is a phosphorus-containing compound; the second organic modifier is alpha-hydroxycarboxylic acid containing at least two carboxyl groups in the molecule or an alpha-hydroxycarboxylic acid derivative containing at least two carboxyl groups in the molecule; the low-boiling-point solvent is selected from monohydric alcohol with the boiling point lower than 85 DEG C; the high-boiling-point solvent is selected from monohydric alcohol or dihydric alcohol with the boiling point higher than 95 DEG C. The catalyst is high in catalytic activity, good in selectivity, safe and environment-friendly.

Description

Technical Field

[0001] The present invention relates to the field of polyester catalysts, in particular to a method for preparing a chelated titanium-based environmentally friendly polyester catalyst for synthesizing PET and an application thereof in synthesizing PET by melt polycondensation of terephthalic acid and ethylene glycol. Background Art

[0002] China's polyester PET production capacity will increase from 45.82 million tons in 2016 to 71.37 million tons in 2022, with an average annual growth rate of 7.16%. It is the largest-produced and most widely used variety among polyester products.

[0003] For nearly 30 years, the PET polyester industry, both domestically and internationally, has widely adopted a catalytic melt polycondensation process, typically using heavy metal antimony compounds as catalysts. However, the high cost and toxicity of heavy metal antimony have significantly limited the export of related products.

[0004] With the improvement of living standards, people are paying more and more attention to environmental issues. Green polyester without heavy metals is the future development trend. Therefore, domestic and foreign countries have successively started to develop high-efficiency and environmentally friendly catalysts that can replace antimony.

[0005] Titanium accounts for approximately 0.6% of the Earth's crust, compared to less than one-sixtieth of the common metal copper. Global titanium ore reserves exceed 10 million tons, making titanium resources particularly abundant. Titanium is also an environmentally friendly metal with no impact on human health or the environment. Therefore, titanium-based polyester catalysts, offering both economical and environmental benefits, have become a hot topic in polyester catalyst research both domestically and internationally, becoming the preferred alternative to heavy metal antimony-based catalysts as PET catalysts.

[0006] Germany's Sahali Company, the United States' DuPont, the United Kingdom's Synetix, and Japan's Teijin Group, Mitsui Chemicals, and Mitsubishi Chemical have each developed titanium-based catalysts and achieved varying degrees of industrial application. According to literature reports, titanium-based catalysts in China have become a hot topic of research. However, traditional titanium-based polyester catalysts produced in China still face certain bottlenecks, such as poor stability, easy hydrolysis, and low selectivity. These limitations restrict their widespread use in polyester (PET) production and currently cannot completely replace heavy metal antimony-based catalysts.

[0007] Patent application number: 201911005803.5, patent name: A titanium-based catalyst for polyester and preparation method, its components include titanate, complexing ligands of different functionalities, stabilizers and metal catalysts, the catalyst contains a second metal catalyst other than titanium, and the structure is relatively complex; the specific implementation method is inconsistent with the description of the examples, no second catalyst is added in the examples, and no phosphorus-containing stabilizer is added; and from the test results of each embodiment of synthesizing polyethylene terephthalate using the catalyst, its chromaticity index L is about 60, the a value is about -1.0, and the b value is greater than 6, which does not meet the quality indicators of bottle-grade and fiber-grade polyester products. Patent application number: 201811235000.4, patent name: High-activity titanium-based polyester catalyst and preparation method thereof. The catalyst is a composition. In the first step, the composition reacts a diol with a titanium compound, filters, washes, and dries to obtain a white substance, which is then added to an alcohol. A second metal salt catalyst is then added, followed by hydroxycarboxylic acid and a phosphorus compound. This composition can be used as a catalyst to complete the catalytic synthesis of polyethylene terephthalate at 280°C. Examples show that the product performance indicators meet the standards and solve the problem of poor PET color. However, the catalyst contains a second metal salt catalyst and has complex components. The catalyst preparation process first prepares a white powder, which is a complex process. The process of catalyzing polyester synthesis using this catalyst requires the preparation of a slurry, which involves many steps. In addition, the polyester synthesis temperature is relatively high at 280°C.

[0008] It can be seen that there is still room for optimization of titanium-based polyester catalysts. Summary of the Invention

[0009] In view of the problems existing in the above-mentioned prior art, the present invention provides a chelated titanium-based environmentally friendly polyester catalyst, a preparation method thereof, and an application thereof in synthesizing PET.

[0010] The first aspect of the present invention is to provide a chelated titanium-based environmentally friendly polyester catalyst, which is prepared from a titanium-containing organic salt, a first organic modifier, a second modifier, a low-boiling-point solvent, and a high-boiling-point solvent.

[0011] Wherein, the first organic modifier is a phosphorus-containing compound modifier;

[0012] The second organic modifier is an α-hydroxycarboxylic acid containing at least two carboxyl groups in the molecule, or an α-hydroxycarboxylic acid derivative containing at least two carboxyl groups in the molecule;

[0013] The low boiling point solvent is selected from monohydric alcohols having a boiling point below 85°C, such as methanol, ethanol or isopropanol;

[0014] The high boiling point solvent is selected from monohydric alcohols or dihydric alcohols with a boiling point higher than 95° C., such as n-propanol, n-butanol, isobutanol, n-octanol, isooctanol, ethylene glycol, or 1,2-propylene glycol and 1,3-propylene glycol.

[0015] The active center of this chelated titanium catalyst is a titanium atom, which is hexacoordinated and has a regular octahedral structure. The coordination of titanium with the phosphorus in the phosphorus-containing compound stabilizes the titanium catalyst's structure, while the phosphorus acts as a stabilizer for subsequent polyester synthesis reactions. Furthermore, the coordination of titanium with α-hydroxycarboxylic acid and its derivatives forms two stable five-membered rings. The higher the degree of coordination, the more stable the chelate structure. While this coordinated chelate structure stabilizes the catalyst and makes it less susceptible to hydrolysis, it also does not meet the maximum coordination number requirement for titanium atoms, leaving it electron-deficient and exhibiting good catalytic activity during polyester synthesis.

[0016] In a second aspect, the present invention provides a method for preparing the chelated titanium-based environmentally friendly polyester catalyst of the first aspect, comprising the following steps:

[0017] Step 1: adding a titanium-containing organic salt and a first organic modifier to a low-boiling-point solvent for reaction to obtain a precursor;

[0018] Step 2: adding a second organic modifier to form a preliminary ligand;

[0019] Step 3: adding a high boiling point solvent to react and form a coordination chelate, while removing the low boiling point solvent by fractionation. When the fraction in step 3 is completely removed and the system becomes a clear solution, the reaction is stopped to obtain a chelated titanium polyester catalyst.

[0020] In a third aspect, the present invention provides an application of a chelated titanium-based environmentally friendly polyester catalyst obtained by the preparation method of the first aspect or the second aspect in polyester synthesis.

[0021] The beneficial effects of the chelated titanium-based environmentally friendly polyester catalyst and its preparation method of the present invention include:

[0022] (1) The chelated titanium-based environmentally friendly polyester catalyst of the present invention does not contain toxic metals and corrosive halogens, has no obvious flash point, and is a safe and environmentally friendly catalyst.

[0023] (2) The chelated titanium-based environmentally friendly polyester catalyst of the present invention is formed by a bonded network of titanium, phosphorus, oxygen, and carbon atoms, and has a three-dimensional microcavity structure (three-dimensional network structure). The three-dimensional microcavity structure can accommodate intermediate products at different stages of the polyester reaction, thereby increasing the contact residence time between the intermediate products and the polyester catalyst. At the same time, titanium is distributed as a catalytic center at adjacent nodes inside and outside the three-dimensional microcavity structure, which can enable the catalytic activity to be efficiently exerted and with good selectivity, thereby making the molecular weight growth of the polyester more uniform and continuous.

[0024] (3) The catalytic activity of the chelated titanium-based environmentally friendly polyester catalyst of the present invention is stable and moderate, which balances the problems of excessive side reactions and poor catalytic durability caused by excessive or low activity of previous titanium-based catalysts.

[0025] (4) The chelated titanium-based environmentally friendly polyester catalyst of the present invention has extremely strong hydrolysis resistance and can be stored for a long time without deactivation.

[0026] (5) The chelated titanium-based environmentally friendly polyester catalyst of the present invention is liquid, and the solid content of the main component contained therein is relatively high at 40 to 80%, but the liquid viscosity is relatively low.

[0027] (6) The method for preparing the chelated titanium-based environmentally friendly polyester catalyst of the present invention has the advantages of mild reaction conditions, easy control, all raw materials do not contain heavy metals, are non-toxic and harmless, and have low requirements for reaction equipment and control systems.

[0028] (7) The method for preparing the chelated titanium-based environmentally friendly polyester catalyst of the present invention is designed to have a circulating closed reaction environment, and all materials can be separated and recycled during the reaction process, making the production process environmentally friendly.

[0029] (8) The method for preparing the chelated titanium-based environmentally friendly polyester catalyst of the present invention adopts selective coordination chelation technology. The catalyst has super strong hydrolysis resistance and will not cause water to affect the stability of the catalytic process. It can fully ensure the stability of titanium in the complex environment of PET polymerization reaction, and it is easier to accurately control the titanium content in the polyester reaction system.

[0030] (9) The chelated titanium polyester catalyst of the present invention has good solubility with EG and can be quickly dissolved in the polyester reaction raw material system within a wide temperature range (-15°C-100°C), does not require a pre-dispersion process, and does not require a pulping process during the synthesis of PET.

[0031] (10) The chelated titanium polyester catalyst of the present invention has stable and long-lasting activity release during the synthesis of PET, and the reaction temperature is 272-276°C, which saves energy consumption.

[0032] (11) The amount of this catalyst used in the polyester reaction is relatively small, and the hue level and molecular weight uniformity of the polyester obtained by catalysis have obvious advantages over similar catalysts.

[0033] (12) The prepared polyester chips have a lower crystallization temperature and higher crystallinity, which can reduce processing energy consumption while improving the mechanical strength and barrier properties of plastic products. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The synthesis route of chelated titanium polyester catalyst is shown;

[0035] Figure 2 The appearance of the chelated titanium polyester catalyst C of Example 3 is shown;

[0036] Figure 3 The infrared spectrum of the chelated titanium polyester catalyst C of Example 3 is shown;

[0037] Figure 4 The ultraviolet spectrum of the chelated titanium polyester catalyst C of Example 3 is shown;

[0038] Figure 5 A photo of a polyester PET resin slice synthesized using the chelated environmentally friendly titanium polyester catalyst C of Example 3 is shown;

[0039] Figure 6 The infrared spectrum of the polyester PET resin synthesized using the chelated environmentally friendly titanium polyester catalyst C in Example 3 is shown. DETAILED DESCRIPTION

[0040] The present invention is described in detail below through examples so that the advantages and strengths of the present invention will become clearer and more specific with these descriptions, and will be easier to be understood by those skilled in the art, thereby making a clearer and more specific definition of the protection scope of the present invention.

[0041] The first aspect of the present invention is to provide a chelated titanium-based environmentally friendly polyester catalyst, which is prepared from a titanium-containing organic salt, a first organic modifier, a second modifier, a low-boiling-point solvent, and a high-boiling-point solvent.

[0042] In the present invention, the titanium-containing organic salt refers to a titanate (also referred to as a titanium alcohol salt), wherein the titanate has a structural formula of Ti(OR1)(OR2)(OR3)(OR4), and R1, R2, R3, and R4 are each independently selected from a C1-C10 straight-chain or branched hydrocarbon group; preferably, R1, R2, R3, and R4 are each independently selected from a C1-C8 straight-chain or branched hydrocarbon group; more preferably, R1, R2, R3, and R4 are each independently selected from at least one of a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, and an isooctyl group; further preferably, R1, R2, R3, and R4 are the same, for example, selected from tetraisopropyl titanate and / or tetrabutyl titanate (1-butoxide titanium (IV) salt).

[0043] In the present invention, in order to prepare high-quality polyester catalysts and prevent side reactions from occurring in the polymerization reaction, preferably, the purity of the titanium-containing organic salt is above 99%.

[0044] In the present invention, the raw material formula is designed so that the total concentration of titanium element in the chelated titanium-based environmentally friendly polyester catalyst is 0.1-25 wt%, preferably 0.5-10 wt%, and more preferably 1-8 wt%.

[0045] The first modifier is a phosphorus-containing compound modifier, including at least one of phosphoric acid and its derivatives, phosphorous acid and its derivatives, and metaphosphoric acid and its derivatives, preferably selected from at least one of phosphoric acid, phosphorous acid, sodium hexametaphosphate, potassium phosphate, potassium dihydrogen phosphate, trimethyl phosphate, triphenyl phosphate, triethyl phosphate, tributyl phosphate, triethyl phosphoacetate, and triethylene glycol phosphate, more preferably selected from at least one of phosphorous acid, trimethyl phosphate and sodium hexametaphosphate.

[0046] Adding phosphorus-containing compounds to chelated titanium polyester catalysts can moderately reduce the catalytic activity of titanium and minimize side reactions. It also provides a certain degree of coordination with titanium, stabilizing its structure. However, excessive amounts of phosphide can significantly impact the catalytic activity of titanium, hindering the catalytic reaction. In the present invention, appropriate coordination between titanium and phosphorus is considered to ensure that, after the precursor is formed, sufficient space around the titanium remains for further coordination and deep chelation with the α-hydroxycarboxylic acid or its derivative, forming a chelate with a three-dimensional microcavity structure.

[0047] In the present invention, in order to avoid the introduction of other impurities into the polyester catalyst as much as possible, preferably, the purity of the phosphorus-containing compound is above 99.5%.

[0048] Therefore, in the present invention, the raw material formula is designed so that the total concentration of phosphorus in the chelated titanium-based environmentally friendly polyester catalyst is 0.03-8 wt %, preferably 0.4-5 wt %, and more preferably 0.3-3 wt %.

[0049] The second organic modifier is an α-hydroxycarboxylic acid containing at least two carboxyl groups in the molecule and / or an α-hydroxycarboxylic acid derivative containing at least two carboxyl groups, such as at least one of malic acid, tartaric acid, salicylic acid, citric acid, isocitric acid, triethyl citrate, tributyl citrate and tri-n-hexyl citrate, for example, selected from tartaric acid or triethyl citrate and / or citric acid.

[0050] In the present invention, the presence of the α-hydroxyl group in the α-hydroxycarboxylic acid or its derivative enhances the electronegativity of the carbon atoms in the adjacent carboxyl groups, facilitating a substitutional coordination reaction with the titanium-containing organic salt, forming a titanium-centered ligand intermediate. The byproduct is an alcohol, which facilitates the formation of the catalyst's final chelate structure. Upon addition of a high-boiling-point solvent, the resulting intermediate undergoes structural modification and forms a stable chelate, thereby enhancing the structural stability of the polyester catalyst's main components. This ensures strong hydrolysis resistance and sustained catalytic activity under the harsh conditions of polyester production.

[0051] In the present invention, the low boiling point solvent used is selected from methanol, ethanol and isopropanol;

[0052] The high boiling point solvent used is selected from one or two of n-propanol, n-butanol, isobutanol, n-octanol, isooctanol, ethylene glycol, 1,2-propylene glycol and 1,3-propylene glycol.

[0053] In the present invention, the amount of the low-boiling-point solvent added is 1 to 40 times, preferably 3 to 30 times, and more preferably 5 to 20 times, the amount of the titanium organic salt added on a molar basis. The amount of the high-boiling-point solvent added is 1 to 60 times, preferably 3 to 30 times, and more preferably 5 to 15 times, the amount of the titanium organic salt added on a molar basis.

[0054] The synthesized environmentally friendly chelated titanium polyester catalyst is formed by a bonded network of titanium, phosphorus, oxygen, and carbon atoms, and has a three-dimensional microcavity structure (a three-dimensional network structure). This microcavity structure can accommodate intermediate products at different stages of the polyester reaction, increasing the contact residence time between the intermediate products and the polyester catalyst. Furthermore, the titanium serves as a catalytic center, distributed at adjacent nodes inside and outside the microcavity structure. This allows for efficient and selective catalytic activity, resulting in more uniform and continuous growth of the polyester molecular weight. The polyester catalyst is a low-viscosity liquid, containing a solid content of 20 to 80% by weight of the main component, preferably 30 to 70% by weight, and a liquid density (specific gravity) of 1.2 to 1.6 g / mL.

[0055] The preparation route of the environmentally friendly chelated titanium hydrolysis-resistant polyester catalyst of the second aspect of the present invention is shown in the attached Figure 1 The preparation method mainly comprises the following steps:

[0056] Step 1: Add a titanium-containing organic salt, a first modifier phosphorus-containing compound and a low-boiling-point solvent into a round-bottom flask for reaction at a certain reaction temperature and for a certain reaction time to obtain a titanium-phosphorus coordination precursor.

[0057] In the present invention, the molar ratio of the titanium-containing organic salt to the phosphorus-containing compound is 1:(0.01-10), preferably 1:(0.1-5), and more preferably 1:(0.1-3).

[0058] In the present invention, the reaction temperature of step 1 is -10 to 70°C, preferably 20 to 60°C;

[0059] In the present invention, the reaction time of step 1 is 0.1 to 5 hours, preferably 0.3 to 2 hours.

[0060] In the present invention, in order to accelerate the reaction rate and make the reaction uniform, the reaction process is supplemented with stirring.

[0061] Step 2: Add the second organic modifier α-hydroxycarboxylic acid or its derivative to the titanium phosphorus precursor prepared in step 1, stir and dissolve, and reflux and condense. After it is completely dissolved, further complexation and chelation reaction occurs at a certain temperature.

[0062] In the present invention, the molar ratio of the titanium-containing organic salt to the second modifier α-hydroxycarboxylic acid or its derivative is 1:(0.01-10), preferably 1:(0.1-8), and more preferably 1:(1-5).

[0063] In the present invention, the reaction temperature in step 2 is 30 to 95°C, preferably 50 to 90°C;

[0064] In the present invention, the reaction time in step 2 is 0.5 to 4 hours, preferably 1 to 2 hours.

[0065] Step 3: Add a high-boiling-point solvent to the reaction system of step 2, heat and stir, condense and reflux, and separate and remove the low-boiling-point solvent. During the participation of the high-boiling-point solvent, the hydroxyl group -OH or hydrogen ion H+ of the intermediate product formed in the contact system can complete structural modification and stably form a chelate, thereby consolidating the structural stability of the main components of the polyester catalyst, so that it has relatively strong hydrolysis resistance and stable catalytic activity under the harsh conditions of polyester preparation.

[0066] In the present invention, the reaction temperature of step 3 is controlled to be 50-140°C, preferably 80-130°C;

[0067] The reaction time of step 3 is 0.5 to 6 hours, preferably 1 to 3 hours.

[0068] In the present invention, the molar ratio of the high-boiling-point reaction solvent to the titanium organic salt is 1 to 60 times, preferably 3 to 30 times, and more preferably 5 to 15 times. The reaction solvent is added by dropwise addition or atomized spraying, preferably dropwise addition, wherein the dropwise addition rate is 3 to 15 g / min, preferably 5 to 10 g / min, so that the reaction solvent can be quickly incorporated into the system of step 2, and condensed and fractionated, and the reaction endpoint is determined based on the mass of the fraction.

[0069] In step 3, the chelate reaction further occurs to prepare a chelated titanium polyester catalyst.

[0070] The chelated titanium polyester catalyst provided by the present invention can be used for catalytic reaction to prepare polyethylene glycol phthalate. The active center of the chelated titanium catalyst is a titanium atom, and the titanium is hexa-coordinated, with a regular octahedral structure. Since the titanium in the chelated titanium catalyst coordinates with the phosphorus in the phosphorus-containing compound, on the one hand, the structure of the titanium catalyst itself is stable, and at the same time, the phosphorus acts as a stabilizer for the subsequent polyester synthesis reaction; the chelated titanium catalyst also forms two stable five-membered rings due to the coordination of titanium and α-hydroxycarboxylic acid and its derivatives. The higher the degree of coordination, the more stable the chelate structure. Since the coordinated chelate structure stabilizes the catalyst structure and is not easily hydrolyzed, on the other hand, it does not meet the maximum coordination number requirement of the titanium atom. The catalyst is still an electron-deficient body and has good catalytic activity in the polyester synthesis process.

[0071] Since the synthesized chelated titanium-based environmentally friendly polyester catalyst is formed by a bonded network of titanium, phosphorus, oxygen, and carbon atoms, it has a three-dimensional microcavity structure (three-dimensional network structure). This three-dimensional microcavity structure can accommodate intermediate products at different stages of the polyester reaction, increasing the contact residence time between the intermediate products and the polyester catalyst. At the same time, titanium is distributed as a catalytic center on adjacent nodes inside and outside the three-dimensional microcavity structure, which can enable the catalytic activity to be highly efficient and selective, making the polyester molecular weight growth more uniform and continuous.

[0072] In order to further understand the present invention, the chelated titanium polyester catalyst provided by the present invention is described below with reference to examples.

[0073] Example

[0074] Example 1 Preparation of Chelated Environmentally Friendly Titanium Polyester Catalyst A

[0075] (1) Preparation of environmentally friendly polyester catalyst A precursor

[0076] 44 g (0.2 mol) of methyl titanate and 51 g (1.6 mol) of methanol were weighed and added to a reactor and stirred uniformly to prepare a solution. 24 g (0.3 mol) of phosphorous acid (H3PO3) was weighed and added dropwise to the solution system. The mixture was reacted at 40°C for 30 min to obtain a light yellow titanium-phosphorus coordination precursor solution.

[0077] (2) Preparation of preliminary chelate of environmentally friendly polyester catalyst A

[0078] 27 g (0.1 mol) of triethyl citrate was added to the precursor system at 65 ° C and the reaction was continued for 1 h. 54 g (0.2 mol) of triethyl citrate (C 12 H 20 O7) and reflux for 2h;

[0079] (3) Preparation of chelated environmentally friendly titanium polyester catalyst A

[0080] 100 g (1.66 mol) of n-propanol was added dropwise at a dropwise acceleration rate of 3 to 15 g / min, and the mixture was reacted at 80°C and refluxed for 2 h. At the same time, a methanol-containing by-product fraction of about 105 g was removed by atmospheric distillation. The fraction was recovered and used for standby treatment. The material was discharged after cooling to finally obtain a clear, slightly yellowish liquid catalyst weighing about 191 g, in which the titanium concentration was about 5 wt%.

[0081] Example 2 Chelated environmentally friendly titanium polyester catalyst B

[0082] (1) Preparation of environmentally friendly polyester catalyst B precursor

[0083] 45.6 g (0.2 mol) of tetraethyl titanate and 60 g (about 1.3 mol) of ethanol were weighed and added to a reactor and stirred uniformly to prepare a solution. 36 g (0.2 mol) of triethyl phosphate was weighed and added dropwise to the solution system. The reaction was carried out at 50°C for 50 minutes to obtain a light yellow titanium-phosphorus coordination precursor solution.

[0084] (2) Preparation of preliminary chelate of environmentally friendly polyester catalyst B

[0085] 26.8 g (0.2 mol) of malic acid was added to the precursor system at 75 °C and the reaction was continued for 0.2 h. 26.8 g (0.2 mol) of malic acid was added to the precursor system at 85 °C. 12 H 20 O7) and reflux for 2h;

[0086] (3) Preparation of chelated environmentally friendly titanium polyester catalyst B

[0087] 118 g (1.6 mol) of n-butanol was added dropwise at a dropwise acceleration rate of 3 to 15 g / min. The reaction was carried out at 120°C and refluxed for 2 h. At the same time, about 120 g of the ethanol-containing by-product fraction was removed by atmospheric distillation. After recovery and utilization, a clear, slightly yellowish liquid catalyst was obtained, weighing about 191 g, in which the titanium concentration was about 5 wt%.

[0088] Example 3 Chelated environmentally friendly titanium polyester catalyst C

[0089] (1) Preparation of environmentally friendly polyester catalyst C precursor

[0090] 45.6 g (0.2 mol) of tetraethyl titanate and 60 g (1.3 mol) of ethanol were weighed and added to a reactor and stirred uniformly to prepare a solution. 31 g (0.1 mol) of triphenyl phosphite was weighed and added dropwise to the solution system. The reaction was carried out at 30°C for 50 minutes to obtain a light yellow titanium-phosphorus coordination precursor solution.

[0091] (2) Preparation of preliminary chelate of environmentally friendly polyester catalyst C

[0092] Add 21 g (0.1 mol) of citric acid to the precursor system at 75°C and continue the reaction for 0.5 h. Cool to 75°C, add 21 g (0.1 mol) of citric acid, and reflux at 85°C for 0.5 h.

[0093] (3) Preparation of chelated environmentally friendly titanium polyester catalyst C

[0094] 125 g (2 mol) of ethylene glycol was added dropwise at a dropping rate of 3 to 15 g / min. The reaction was carried out at 130°C and refluxed for 1 hour. At the same time, about 110 g of the ethanol-containing by-product fraction was removed by atmospheric distillation. The fraction was recovered and used for standby use. Finally, a clear yellow liquid catalyst was obtained, weighing about 191 g, in which the titanium concentration was about 5 wt%.

[0095] Example 4 Preparation and Application of Chelated Titanium Polyester Catalyst A in Polyethylene Terephthalate

[0096] (1) Esterification reaction:

[0097] 485 g of ethylene glycol, 1 kg of terephthalic acid, and 0.12 g of chelated titanium polyester catalyst A (the weight of titanium element is 6.0 ppm based on the weight of terephthalic acid) were placed in a 5 L polyester synthesis reactor with magnetic stirring at 235-255 ° C and a pressure of 0.2 MPa. a -0.3MP a , the reaction time is about 3h, the stirring speed is 90r.pm, and the continuous reaction time is 3h.

[0098] (2) Polycondensation

[0099] The esterification reaction system was heated to about 270 ° C, and the temperature was less than 100 ° C. a The polycondensation reaction was carried out under vacuum conditions at a stirring speed of 90 rpm. When the stirring motor power reached 160 watts and the reaction lasted for 2 hours, nitrogen was introduced to eliminate the vacuum, and the melt was cooled and cut into polyester chips using a pelletizer, designated catA-PET.

[0100] Example 5 Preparation and Application of Chelated Titanium Polyester Catalyst B in Polyethylene Terephthalate

[0101] The preparation process was similar to that of Example 4, except that the polyester catalyst B prepared in Example 2 (the weight of titanium element was 5.5 ppm based on the weight of polyester) was added. The obtained polyester chips were designated as catB-PET.

[0102] Example 6 Preparation and Application of Chelated Titanium Polyester Catalyst C in Polyethylene Terephthalate

[0103] The preparation process was similar to that of Example 4, except that the polyester catalyst C prepared in Example 3 (the weight of titanium element was 6.5 ppm based on the weight of polyester) was added. The obtained polyester chips were designated as catC-PET.

[0104] Comparative Example: Preparation of sb-PET using traditional ethylene glycol antimony catalyst

[0105] (1) Esterification reaction:

[0106] 485g of ethylene glycol, 1kg of terephthalic acid, and 0.45g of antimony glycol were placed in a 5L polyester synthesis reactor with magnetic stirring at 235-255℃ and a pressure of 0.2MP. a -0.3MP a , the reaction time is about 3h, the stirring speed is 90r.pm, and the reaction time is 3 hours.

[0107] (2) Polycondensation

[0108] The esterification reaction system was heated to about 282 ° C, and the temperature was less than 100 ° C. a The esterification product was subjected to polycondensation under vacuum conditions at a stirring speed of 90 rpm. When the stirrer torque reached a maximum of 160 / kWh, nitrogen was introduced to eliminate the vacuum and the melt was cooled and cut into polyester chips by a pelletizer.

[0109] The polycondensation reaction parameters of the three polyesters in Examples 4-6 and the polyester prepared in Comparative Example 1, as well as the intrinsic viscosity and hue of the polyester products were tested. The test results are shown in Table 1.

[0110] Among them, the intrinsic viscosity and hue of polyester are tested by the following methods:

[0111] (1) Intrinsic viscosity: Measured at 25°C using a phenol-tetrachloroethane mixture as the solvent using the dilute solution viscosity method with an Ubbelohde viscometer.

[0112] (2) Hue: After the slices were treated at 135℃ for 1 hour, the hue level (L value, a value, and b value) was measured using BYK Gardner's color-view spectrophotometer. The L value represents the brightness of the polyester slice, and the larger the number, the brighter it is. A positive a value represents a reddish tinge to the polyester slice, and the larger the number, the redder it is. A negative a value represents a greenish tinge to the polyester slice, and the larger the number, the greener it is. A positive b value represents a yellowish tinge to the polyester slice, and the larger the number, the yellower it is. A negative b value represents a bluish tinge to the polyester slice, and the larger the number, the bluer it is.

[0113] Table 1 Comparison of catalyst catalytic PET synthesis effects

[0114] CatA-PET CatB-PET CatC-PET Comparative Example 1 Ti addition amount (ppm) 6 5.5 6.5 0 Sb addition amount (ppm) 0 0 0 260 Polycondensation temperature (℃) 273±2 273±2 273±2 282±2 Tm(℃) 247.6 247.5 247.3 248.5 Intrinsic viscosity (dL / g) 0.64 0.64 0.65 0.64 L 88 90 89 82 a -0.8 -0.7 -0.8 -1.1 b 3.4 3.4 2.9 4.1 Crystallization peak Tc (℃) 158 160 162 168.8

[0115] As can be seen from Table 1, in the polyester preparation process, using a relatively small amount of the chelated environmentally friendly titanium-based polyester catalysts in Examples 1-3 can achieve a catalytic effect that is superior to or similar to that of a large amount of ethylene glycol antimony catalyst.

[0116] At the same time, at the same intrinsic viscosity level, the condensation temperature of the polyester catalyzed by the chelated environmentally friendly titanium-based polyester catalyst obtained in Examples 1-3 in Examples 4-6 is significantly lower than that in Comparative Example 1. Therefore, the chelated environmentally friendly titanium-based polyester catalyst of the present invention can significantly reduce the reaction energy consumption and is more suitable for large-scale commercial production.

[0117] As can be seen from Table 1, based on the polyester chips, the polyester chips (catA-PET, catB-PET, catC-PET) in Examples 4-6 all have good brightness and chromaticity, and the hue level is equal to or similar to that of Comparative Example 1. In particular, the L value is significantly higher than that of Comparative Example 1. Therefore, the polyester catalyst of the present invention can produce polyester with better brightness.

[0118] At the same time, at the same intrinsic viscosity level, the crystallization peak temperature of the polyester (catA-PET, catB-PET, catC-PET) chips in Examples 4-6 is relatively lower, which is beneficial to the crystallization control of PET polyester processing, reduces the energy consumption of the secondary heat molding of the polyester chips, and improves the crystallinity of the products.

[0119] As can be seen from Table 1, the polyester (catA-PET, catB-PET, catC-PET) slices in Examples 4-6 are antimony-free polyesters containing a small amount of titanium metal, which are non-toxic to the human body and do not cause heavy metal hazards to water and other environments.

Claims

1. A chelated titanium-based environmentally friendly polyester catalyst, the polyester catalyst is prepared from a titanium-containing organic salt, a first organic modifier, a second modifier, a low-boiling-point solvent, and a high-boiling-point solvent, wherein: The first organic modifier is a phosphorus-containing compound modifier; The second organic modifier is an α-hydroxycarboxylic acid containing at least two carboxyl groups in the molecule, or an α-hydroxycarboxylic acid derivative containing at least two carboxyl groups in the molecule; The low boiling point solvent is selected from monohydric alcohols with a boiling point below 85°C; The high boiling point solvent is selected from monohydric alcohol or dihydric alcohol with a boiling point higher than 95°C.

2. The catalyst according to claim 1, wherein The titanium-containing organic salt is Ti(OR1)(OR2)(OR3)(OR4), wherein R1, R2, R3, and R4 are each independently selected from a C1 to C10 straight or branched hydrocarbon group; Preferably, R1, R2, R3, and R4 are each independently selected from a C1-C8 straight-chain or branched hydrocarbon group; More preferably, R1, R2, R3, and R4 are each independently selected from at least one of methyl, ethyl, n-propyl, isopropyl, n-butyl, and isooctyl. More preferably, R1, R2, R3, and R4 are the same, for example, selected from tetraisopropyl titanate and / or tetrabutyl titanate (1-titanium (IV) butoxide salt).

3. The catalyst according to claim 1, wherein The first organic modifier is a phosphorus-containing compound, selected from at least one of phosphoric acid and its derivatives, phosphorous acid and its derivatives, and metaphosphoric acid and its derivatives, preferably selected from at least one of phosphoric acid, phosphorous acid, sodium hexametaphosphate, potassium phosphate, potassium dihydrogen phosphate, trimethyl phosphate, triphenyl phosphate, triethyl phosphate, tributyl phosphate, triethyl phosphatoacetate, and triethylene glycol phosphate, more preferably selected from at least one of phosphorous acid, trimethyl phosphate and sodium hexametaphosphate.

4. The catalyst according to claim 1, wherein The second organic modifier is an α-hydroxycarboxylic acid containing at least two carboxyl groups in the molecule and / or an α-hydroxycarboxylic acid derivative containing at least two carboxyl groups, such as at least one of malic acid, tartaric acid, salicylic acid, citric acid, isocitric acid, triethyl citrate, tributyl citrate and tri-n-hexyl citrate, preferably selected from tartaric acid or triethyl citrate and / or citric acid.

5. A method for preparing a chelated titanium-based environmentally friendly polyester catalyst, comprising the following steps: Step 1: adding a titanium-containing organic salt and a first organic modifier to a low-boiling-point solvent for reaction to obtain a precursor; Step 2: adding a second organic modifier and reacting to form a preliminary ligand; Step 3: adding a high boiling point solvent to react to form a coordination chelate, and removing the solvent by fractional distillation. When the fraction in step 3 is completely removed and the system becomes a clear solution, the reaction is stopped to obtain a chelated titanium polyester catalyst.

6. The method according to claim 5, wherein: The low boiling point solvent is selected from monohydric alcohols having a boiling point below 85°C, such as methanol, ethanol and isopropanol; The high boiling point solvent is selected from monohydric alcohols or dihydric alcohols with a boiling point higher than 95° C., such as n-propanol, n-butanol, isobutanol, n-octanol, isooctanol, ethylene glycol, 1,2-propylene glycol and 1,3-propylene glycol.

7. The method according to claim 5, wherein: In step 1, The molar ratio of the titanium-containing organic salt to the phosphorus-containing compound is 1:(0.01-10), preferably 1:(0.1-5), more preferably 1:(0.1-3), The amount of the low boiling point solvent added is 1 to 40 times, preferably 3 to 30 times, more preferably 5 to 20 times the amount of the titanium organic salt added in terms of molar weight. The reaction temperature is -10 to 70°C, preferably 20 to 60°C. The reaction time is 0.1 to 5 hours, preferably 0.3 to 2 hours.

8. The method according to claim 5, wherein In step 2, The molar ratio of the titanium-containing organic salt to the second modifier α-hydroxycarboxylic acid or its derivative is 1:(0.01-10), preferably 1:(0.1-8), more preferably 1:(1-5), The reaction temperature is 30-95°C, preferably 50-90°C; The reaction time is 0.5 to 4 hours, preferably 1 to 2 hours.

9. The method according to claim 5, wherein: In step 3, The amount of the high boiling point solvent added is 1 to 60 times, preferably 3 to 30 times, more preferably 5 to 15 times, the amount of the titanium organic salt added in terms of molar weight. The reaction temperature is 50-140°C, preferably 80-130°C; The reaction time is 0.5 to 6 hours, preferably 1 to 3 hours.

10. A method for preparing polyethylene glycol phthalate, which is carried out in the presence of a catalyst according to any one of claims 1 to 4, or in the presence of a catalyst obtained by the preparation method according to any one of claims 5 to 9.

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