Application of non-metallic organic compounds in the catalytic synthesis of polyesters, the polyesters therein and their preparation methods

Abstract

This invention discloses the application of a non-metallic organic compound in the catalytic synthesis of polyester, the polyester itself, and its preparation method. The non-metallic organic compound acts as a polycondensation catalyst and copolymer monomer, catalyzing its own polycondensation reaction with polyester esters (such as BHET). The non-metallic organic compound is a hydroxyl-containing benzimidazole derivative. It is obtained by esterification or transesterification of a benzimidazole compound with a diol, followed by neutralization and purification of the esterified solution. This compound can replace traditional metal-based polycondensation catalysts, catalyzing its own melt polycondensation with polyester raw material monomers to prepare a metal-catalyst-free copolyester, avoiding the adverse effects of residual metal catalysts.

Description

Technical Field

[0001] This invention relates to the field of polyester synthesis technology, and more specifically to the application of a non-metallic organic compound in the catalytic synthesis of polyester. Background Technology

[0002] Semi-aromatic polyesters, such as PET, PTT, and PBT, possess excellent comprehensive properties including mechanical strength, chemical resistance, and weather resistance, and are widely used in fiber textiles, packaging, optical films, and engineering plastics. Semi-aromatic polyesters are mainly produced by the melt polycondensation reaction of aromatic dicarboxylic acids and aliphatic diols. Traditional methods include direct esterification of terephthalic acid (PTA) and transesterification of dimethyl terephthalate (DMT). Taking terephthalic acid and ethylene glycol as examples, the direct esterification of PTA first involves an esterification reaction to produce ethylene terephthalate (BHET), followed by polycondensation of BHET under a metal catalyst to remove one mole of ethylene glycol, yielding PET. Similarly, the transesterification of dimethyl terephthalate (DMT) first involves a transesterification reaction under a catalyst to produce ethylene terephthalate (BHET), followed by polycondensation of BHET under a metal catalyst to remove one mole of ethylene glycol, yielding PET. It is understood that the second step in both methods is a polycondensation reaction, in which metal catalysts have always played a very important role. A suitable polycondensation catalyst can significantly improve the production efficiency of related products.

[0003] Currently, the catalysts used in polyester melt polycondensation reactions are mainly metal-based catalysts. For example, antimony-based catalysts are commonly used in PET polyester production, while titanium-based catalysts are commonly used in PBT polyester production. These metal-based catalysts have certain problems with ecological safety, polymerization activity, and polyester performance and quality. For instance, antimony-based catalysts can cause heavy metal pollution during the later dyeing and finishing processes of PET fibers; titanium-based catalysts generally have disadvantages such as easy hydrolysis, poor stability, and aggravated side reactions, resulting in poor color (excessive yellowness) of the synthesized polyester. In recent years, with increasing concerns about residual metal catalysts in synthetic polymers, polymerization reactions catalyzed by small organic molecules have received unprecedented attention and development.

[0004] In existing PTA direct esterification technology, patent CN108395526A discloses a flame-retardant and anti-dripping copolyester based on a benzimidazole structure and its preparation method. First, terephthalic acid and ethylene glycol react to generate (BHET). Then, BHET undergoes a polycondensation reaction under the action of a metal catalyst to generate PET. Under the action of the metal catalyst, a third monomer with a benzimidazole structure is copolymerized into the polyester molecular chain as a flame-retardant unit. In existing DMT transesterification technology, patent CN114989406A discloses a novel non-metallic organic transesterification catalyst. Under the action of this catalyst, dimethyl phthalate and ethylene glycol undergo a transesterification reaction to generate BHET. Then, under the action of a metal catalyst, BHET undergoes polycondensation to generate PET. Both of these schemes still use a metal catalyst in the polycondensation reaction process. Summary of the Invention

[0005] This invention addresses the problem of residual metal catalysts in the polycondensation reaction during the synthesis of polyester in the prior art. It provides an application of using non-metallic organic compounds as polycondensation catalysts to synthesize polyester. These compounds can replace traditional metal polycondensation catalysts and catalyze themselves to produce metal-free copolyesters through melt polycondensation with polyester raw material monomers, thus avoiding the adverse effects of residual metal catalysts.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] The application of a non-metallic organic compound in the catalytic synthesis of polyester, wherein the non-metallic organic compound acts as a polycondensation catalyst and a copolymerization monomer, catalyzing its own polycondensation reaction with polyester esters (such as BHET), wherein the non-metallic organic compound is a hydroxyl-containing benzimidazole derivative, and its structural formula is any one of A, E, and E.

[0008]

[0009] Wherein, n is an integer from 1 to 7, m is an integer from 1 to 7, R1 is H, halogen, C1-C6 alkyl or alkoxy, and R2 is phenylene or C1-C10 alkylene. The non-metallic organic compound prepared by this invention contains a polymerizable functional group—an ester group—which allows it to act as a copolymerizing monomer in the polycondensation process, incorporating it into the polyester molecular chain through melt polycondensation. Simultaneously, like BHET, it contains hydroxyl groups at its ends, potentially lowering the activation energy of the polycondensation process. The hydroxyl groups can also form hydrogen bonds with BHET, further lowering the reaction energy barrier. This allows it to replace metal catalysts in catalyzing its own polycondensation reaction with polyester esters (such as BHET) to prepare copolyesters, avoiding the adverse effects of small-molecule transesterification catalysts.

[0010] In some embodiments, the hydroxyl group is any one of hydroxyethyl, hydroxypropyl, or hydroxybutyl.

[0011] The method for preparing the non-metallic organic compound involves esterifying or transesterifying a benzimidazole compound with the structural formula A1-E1 with a diol, and neutralizing and purifying the esterified solution to obtain a benzimidazole derivative with the structural formula AE containing hydroxyl groups.

[0012]

[0013] Where m is an integer from 1 to 7, R1 is H, halogen, C1 to C6 alkyl or alkoxy, and R2 is phenylene or C1 to C10 alkylene.

[0014] The diol is one of ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,4-pentanediol, and 1,4-hexanediol.

[0015] The benzimidazole compounds with the structural formula A1-E1 are obtained by cyclizing o-phenylenediamine or its derivatives with aldehydes in the presence of a catalyst or oxidant. Generally, this involves two steps: first, o-phenylenediamine or its derivatives condense with an aldehyde group to form a Schiff base; then, the Schiff base undergoes a ring-closing reaction, followed by oxidative dehydrogenation to obtain the benzimidazole compound. Alternatively, o-phenylenediamine or its derivatives react with a carboxylic acid compound in an acidic reagent under H₂O. + It is obtained by cyclization under catalysis.

[0016] The esterification solution obtained after the above esterification reaction can also be used directly as a non-metallic catalyst and copolymerization monomer in the polyester synthesis polycondensation process.

[0017] And / or, the polycondensation reaction is the second step polycondensation reaction in the PTA direct esterification method and the DMT transesterification method, including pre-polycondensation and polycondensation processes. The pre-polycondensation is carried out at 230-250°C under low vacuum for 0.20-1.0 hours, and the polycondensation is carried out at 250-280°C under high vacuum for 1-3 hours.

[0018] This invention provides a method for synthesizing polyester based on non-metallic organic compounds, comprising the steps of: esterification reaction and melt polycondensation reaction of dicarboxylic acid, diol and said non-metallic organic compound or its esterification solution to obtain a copolyester without a metal catalyst;

[0019] Alternatively, a dicarboxylic acid ester and a diol may undergo transesterification under the action of a catalyst, followed by the addition of a non-metallic organic compound or its esterification solution for melt polycondensation to obtain a copolyester without a metal catalyst.

[0020] Non-metallic organic compounds can act as both condensation catalysts and copolymerization monomers.

[0021] The molar amount of the non-metallic organic compound added is at least 0.3% of the molar amount of the dicarboxylic acid or carboxylic acid ester monomer. This invention has found that when the molar amount of the non-metallic organic compound in the system is 0.3 mol% or more of the molar amount of the dicarboxylic acid or carboxylic acid ester monomer, it can effectively achieve the condensation polymerization catalytic effect. Since this compound can also act as a comonomer, further increasing its content will not result in any residual condensation polymerization catalyst. Furthermore, when the amount used is within a certain range, it can even have a certain synergistic effect, achieving, for example, the flame-retardant and anti-dripping effects and increased glass transition temperature as described in patent CN108395526A.

[0022] The molar amount of the non-metallic organic compound added is 0.3% to 20% of the molar amount of the dicarboxylic acid or carboxylic acid ester polymer monomer. The dicarboxylic acid is at least one of terephthalic acid, isophthalic acid, and sodium isophthalic acid-5-sulfonate, and the dicarboxylic acid ester is at least one of the following: a diol ester of terephthalic acid or an ester obtained by direct esterification of the above dicarboxylic acid and a diol.

[0023] The molar amount of the non-metallic organic compound added is 0.3% to 10% of the molar amount of the dicarboxylic acid or carboxylic ester polymer monomer. This is mainly because, due to the large rigid ring structure of the non-metallic organic compound itself, introducing too much of it will reduce the regularity of the polyester molecular chain, severely damage the crystallization properties of the polyester, and make it unsuitable for later applications.

[0024] And / or, the esterification reaction is carried out at a certain pressure and at 180–240°C for 1.0–2.5 h.

[0025] The preparation process of the above copolyester is similar to that of conventional direct esterification, DMT transesterification, or BHET direct polycondensation. The non-metallic organic compound or its esterification solution can be added to the polymerization system along with the reaction raw materials before esterification, or it can be added to the polymerization system after esterification (or transesterification) and before polycondensation begins. Generally, the latter is more effective.

[0026] The molar ratio of the dicarboxylic acid ester, the diol, and the non-metallic organic compound is determined according to conventional knowledge in the art, typically with a total molar ratio of carboxyl and ester groups to hydroxyl groups of 1.0-1.3:1. The structure of the diol is as follows:

[0027] HO-R 10 -OH

[0028] In the formula, R 10 Indicates C2-C12 alkylene, mesylate, or alkoxy groups;

[0029] In some embodiments, the diol includes at least one selected from ethylene glycol, 1,3-propanediol, 1,4-butanediol, and polyethylene glycol;

[0030] And / or, functional additives are added to the method for preparing polyester based on non-metallic organic catalysts. The functional additives include stabilizers and titanium dioxide digesters. The stabilizers include one or more of trimethyl phosphate, triethyl phosphate, tripropyl phosphate, triisopropyl phosphate, tributyl phosphate, triphenyl phosphate, tripropyloctyl phosphate, phosphoric acid, and phosphorous acid. The addition of functional additives and their content are selected based on the actual product usage requirements (flask flakes, glossy, semi-digested, full matte).

[0031] The present invention also provides a metal-free catalyst polyester based on the synthesis of non-metallic organic compounds. In the polyester preparation process, the above-mentioned non-metallic organic compounds are used as both polycondensation catalysts and copolymerization monomers. The resulting polyester has an intrinsic viscosity of 0.50 to 0.80 dL / g. The polyester does not contain any metal catalysts, and the polyester macromolecular structure contains any one of the following copolymerization structural units from A2 to E2.

[0032]

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. This invention applies non-metallic organic compounds to the catalytic synthesis of polyester and finds that they can simultaneously act as polycondensation catalysts. When the addition amount is above 0.3 mol%, ideal catalytic effects can be achieved without other metal catalysts. They can replace metal catalysts and obtain high-quality polyester without catalytic metal residues.

[0035] 2. The non-metallic organic catalyst in this invention can not only catalyze polyester synthesis, but also, due to the polymeric functional groups of the non-metallic organic compounds used, copolymerize with the polymer raw material monomers during the polycondensation stage, incorporating into the macromolecular chain of the copolyester. This reduces the side effects caused by the residue of small-molecule non-metallic organic catalysts. Furthermore, when used within a certain range, it can even have a certain synergistic effect, achieving, for example, the flame-retardant and anti-dripping effects and increased glass transition temperature described in patent CN108395526A.

[0036] 3. This invention provides a polyester without metal catalysts and its preparation method, which solves the long-standing problem of residual metal catalysts in polyesters, has good application prospects, and meets the huge demand for green and sustainable development in the polyester industry. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Modifications or equivalent substitutions made by those skilled in the art based on their understanding of the technical solutions of this invention, without departing from the spirit and scope of the invention, should be covered within the protection scope of this invention.

[0038] The non-metallic organic compounds used in the following specific embodiments were purchased or prepared according to literature, and other raw materials were purchased from the market.

[0039] Additionally, it is worth noting that the intrinsic viscosity [η] of the copolymers and comparative copolymers obtained in the following examples were all prepared into solutions with a concentration of 5 g / dL using phenol / 1,1,2,2-tetrachloroethane (1:1, v:v) as solvent and tested at 25°C using an Ubbelohde viscometer.

[0040] Example 1

[0041] Preparation of 2-(3,5-dimethoxycarbonylphenyl)-1H-benzimidazole: Equimolar amounts of 3,5-dimethylbenzoic acid and o-phenylenediamine were dissolved in polyphosphoric acid and reacted at 170°C for 12 hours. After neutralization, the mixture was recrystallized from ethanol to obtain 2-(3,5-dimethylphenyl)-1H-benzimidazole, which was then oxidized with alkaline potassium permanganate solution to obtain 2-(3,5-dimethoxycarbonylphenyl)-1H-benzimidazole. The obtained 2-(3,5-dimethoxycarbonylphenyl)-1H-benzimidazole was esterified with ethylene glycol under the catalysis of concentrated sulfuric acid. After neutralization, solvent removal, and purification, 2-(3,5-dihydroxyethoxycarbonylphenyl)-1H-benzimidazole was obtained.

[0042] Preparation of polyester:

[0043] 498g of terephthalic acid, 210mL of ethylene glycol, and 3.33g of 2-(3,5-dihydroxyethoxycarbonylphenyl)-1H-benzimidazole (equivalent to 0.3% of the molar PTA) were added to a reactor. Nitrogen gas was used to purge the air from the reactor. The temperature was raised to 200-230℃ to initiate the esterification reaction, which was maintained for 2 hours. The temperature was then gradually increased to 240℃, and a vacuum was applied. Polycondensation was carried out at 240-260℃ under low vacuum for 0.2-1 hour, followed by high vacuum (pressure <80Pa) polycondensation at 260-280℃ for 1.8-3.0 hours. The product was then discharged. The intrinsic viscosity [η] of this polyester was 0.50 dL / g.

[0044] Example 2

[0045] 498g of terephthalic acid, 210mL of ethylene glycol, and 5.55g of 2-(3,5-dihydroxyethoxycarbonylphenyl)-1H-benzimidazole (equivalent to 0.5% of the molar PTA) were added to a reactor. Nitrogen gas was used to purge the air from the reactor. The temperature was raised to 200-230℃ to initiate the esterification reaction, which was maintained for 2 hours. The temperature was then gradually increased to 240℃, and a vacuum was applied. Polycondensation was carried out at 240-260℃ under low vacuum for 0.2-1 hour, followed by high vacuum (pressure <80Pa) polycondensation at 260-280℃ for 1.8-3.0 hours. The product was then discharged. The intrinsic viscosity [η] of this polyester was 0.60 dL / g.

[0046] Example 3

[0047] 498g of terephthalic acid, 210mL of ethylene glycol, and 11.1g of 2-(3,5-dihydroxyethoxycarbonylphenyl)-1H-benzimidazole (equivalent to 1% of the molar amount of PTA) were added to a reactor. Nitrogen gas was used to purge the air from the reactor. The temperature was raised to 200-230℃ to initiate the esterification reaction, which was maintained for 2 hours. The temperature was then gradually increased to 240℃, and a vacuum was applied. Polycondensation was carried out at 240-260℃ under low vacuum for 0.2-1 hour, followed by polycondensation at 260-280℃ under high vacuum (pressure <80Pa) for 1.8-3.0 hours. The product was then discharged. The intrinsic viscosity [η] of this polyester was 0.67 dL / g.

[0048] Example 4

[0049] 498g of terephthalic acid, 7.5g of sodium isophthalic acid-5-sulfonate, 220mL of ethylene glycol, and 33.3g of 2-(3,5-dihydroxyethoxycarbonylphenyl)-1H-benzimidazole (equivalent to 3% of the molar PTA) were added to a reactor. Nitrogen gas was purged to remove air from the reactor. The temperature was raised to 200-230℃ to initiate the esterification reaction, which was maintained for 2 hours. The temperature was then gradually increased to 240℃, and a vacuum was applied. Polycondensation was carried out at 240-260℃ under low vacuum for 0.2-1 hour, followed by high vacuum (pressure <80Pa) polycondensation at 260-280℃ for 1.8-3.0 hours. The product was then discharged. The intrinsic viscosity [η] of this polyester was 0.71 dL / g.

[0050] Example 5

[0051] 498g of terephthalic acid, 220mL of ethylene glycol, and 33.3g of 2-(3,5-dihydroxyethoxycarbonylphenyl)-1H-benzimidazole (equivalent to 3% of the molar PTA) were added to a reactor. Nitrogen gas was used to purge the air from the reactor. The temperature was raised to 200-230℃ to initiate the esterification reaction, which was maintained for 2 hours. The temperature was then gradually increased to 240℃, and a vacuum was applied. Polycondensation was carried out at 240-260℃ under low vacuum for 0.2-1 hour, followed by polycondensation at 260-280℃ under high vacuum (pressure <80Pa) for 1.8-3.0 hours. The product was then discharged. The intrinsic viscosity [η] of this polyester was 0.80 dL / g.

[0052] Example 6

[0053] 498g of terephthalic acid, 230mL of ethylene glycol, 111g of 2-(3,5-dihydroxyethoxycarbonylphenyl)-1H-benzimidazole (equivalent to 10% of the PTA molar) and a small amount of trimethyl phosphite were added to a reactor. Nitrogen gas was purged to remove air from the reactor. The temperature was raised to 200-230℃ to initiate the esterification reaction, which was maintained for 2 hours. The temperature was then gradually increased to 240℃, and a vacuum was applied. Polycondensation was carried out at 240-260℃ under low vacuum for 0.2-1 hour, followed by high vacuum (pressure <80Pa) polycondensation at 260-280℃ for 1.8-3.0 hours. The product was then discharged. The intrinsic viscosity [η] of this polyester was 0.75 dL / g.

[0054] Example 7

[0055] 498g of terephthalic acid, 250mL of ethylene glycol, 444g of 2-(3,5-dihydroxyethoxycarbonylphenyl)-1H-benzimidazole (equivalent to 20% of the PTA molar) and a small amount of trimethyl phosphite were added to a reactor. Nitrogen gas was purged to remove air from the reactor. The temperature was raised to 200-230℃ to initiate the esterification reaction, which was maintained for 2 hours. The temperature was then gradually increased to 240℃, and a vacuum was applied. Polycondensation was carried out at 240-260℃ under low vacuum for 0.2-1 hour, followed by high vacuum (pressure <80Pa) polycondensation at 260-280℃ for 1.8-3.0 hours. The product was then discharged. The intrinsic viscosity [η] of this polyester was 0.72 dL / g.

[0056] Example 8

[0057] 498g of terephthalic acid, 288mL of 1,3-propanediol, and 33.3g of 2-(3,5-dihydroxyethoxycarbonylphenyl)-1H-benzimidazole (equivalent to 3% of the molar PTA) were added to a reactor. Nitrogen gas was used to purge the air from the reactor. The temperature was raised to 200-230℃ to initiate the esterification reaction, which was maintained for 2 hours. The temperature was then gradually increased to 240℃, and a vacuum was applied. Polycondensation was carried out at 240-260℃ under low vacuum for 0.2-1 hour, followed by polycondensation at 260-280℃ under high vacuum (pressure <80Pa) for 1.8-3.0 hours. The product was then discharged. The intrinsic viscosity [η] of this polyester was 0.70 dL / g.

[0058] Example 9

[0059] 498g of terephthalic acid, 320mL of 1,4-butanediol, and 33.3g of 2-(3,5-dihydroxyethoxycarbonylphenyl)-1H-benzimidazole (equivalent to 3% of the molar PTA) were added to a reactor. Nitrogen gas was purged to remove air from the reactor. The temperature was raised to 200-230℃ to initiate the esterification reaction, which was maintained for 2 hours. The temperature was then gradually increased to 240℃, and a vacuum was applied. Polycondensation was carried out at 240-260℃ under low vacuum for 0.2-1 hour, followed by high vacuum (pressure <80Pa) polycondensation at 260-280℃ for 1.8-3.0 hours. The product was then discharged. The intrinsic viscosity [η] of this polyester was 0.78 dL / g.

[0060] Example 10

[0061] 498g of terephthalic acid and 230mL of ethylene glycol were added to a reactor, and nitrogen was purged to remove air. The temperature was raised to 200-230℃ to initiate the esterification reaction, which was maintained for 2 hours. Then, 22.2g of 2-(3,5-dihydroxyethoxycarbonylphenyl)-1H-benzimidazole (equivalent to 2% of the molar amount of PTA) was added, and the temperature was gradually raised to 240℃. Vacuum was applied, and polycondensation was carried out at 240-260℃ under low vacuum for 0.2-1 hours. Then, polycondensation was carried out at 260-280℃ under high vacuum (pressure <80Pa) for 1.8-3.0 hours before discharging. The intrinsic viscosity [η] of this polyester is 0.80 dL / g.

[0062] Example 11

[0063] Preparation of 2-(4-hydroxyethoxycarbonylphenyl)-1H-benzimidazole-5-carboxylic acid ethylene glycol ester: Equimolar amounts of methyl p-aldehyde benzoate, methyl 3,4-diaminobenzoate, and sodium metabisulfite were dissolved in DMF and reacted at 130°C for 12 hours. After removing the solvent, the mixture was recrystallized from ethanol to obtain methyl 2-(4-methoxycarbonylphenyl)-1H-benzimidazole-5-carboxylic acid. The obtained methyl 2-(4-methoxycarbonylphenyl)-1H-benzimidazole-5-carboxylic acid was reacted with ethylene glycol in the presence of a DBU catalyst to obtain ethylene glycol 2-(4-hydroxyethoxycarbonylphenyl)-1H-benzimidazole-5-carboxylic acid.

[0064] Preparation of polyester:

[0065] 498g of terephthalic acid and 230mL of ethylene glycol were added to a reactor, and nitrogen was purged to remove air. The temperature was raised to 200-230℃ to initiate the esterification reaction, which was maintained for 2 hours. Then, 3.33g of 2-(4-hydroxyethoxycarbonylphenyl)-1H-benzimidazole-5-carboxylic acid ethylene glycol ester (equivalent to 0.3% of the PTA molar) was added, and the temperature was gradually raised to 240℃. Vacuum was applied, and polycondensation was carried out at 240-260℃ under low vacuum for 0.2-1 hour. Then, polycondensation was carried out at 260-280℃ under high vacuum (pressure <80Pa) for 1.8-3.0 hours, and the product was discharged. The intrinsic viscosity [η] of this polyester is 0.61dL / g.

[0066] Example 12

[0067] 498g of terephthalic acid and 230mL of ethylene glycol were added to a reactor, and nitrogen was purged to remove air. The temperature was raised to 200-230℃ to initiate the esterification reaction, which was maintained for 2 hours. Then, 5.55g of 2-(4-hydroxyethoxycarbonylphenyl)-1H-benzimidazole-5-carboxylic acid ethylene glycol ester (equivalent to 0.5% of the PTA molar) was added, and the temperature was gradually raised to 240℃. Vacuum was applied, and polycondensation was carried out at 240-260℃ under low vacuum for 0.2-1 hours. Then, polycondensation was carried out at 260-280℃ under high vacuum (pressure <80Pa) for 1.8-3.0 hours, and the product was discharged. The intrinsic viscosity [η] of this polyester is 0.65 dL / g.

[0068] Example 13

[0069] 498g of terephthalic acid and 230mL of ethylene glycol were added to a reactor, and nitrogen was purged to remove air. The temperature was raised to 200-230℃ to initiate the esterification reaction, which was maintained for 2 hours. Then, 11.1g of 2-(4-hydroxyethoxycarbonylphenyl)-1H-benzimidazole-5-carboxylic acid ethylene glycol ester (equivalent to 1% of the molar PTA) was added, and the temperature was gradually raised to 240℃. Vacuum was applied, and polycondensation was carried out at 240-260℃ under low vacuum for 0.2-1 hours. Then, polycondensation was carried out at 260-280℃ under high vacuum (pressure <80Pa) for 1.8-3.0 hours before discharging. The intrinsic viscosity [η] of this polyester is 0.69 dL / g.

[0070] Example 14

[0071] 582g of dimethyl terephthalate, 360mL of ethylene glycol, and 2.9g of 1-ethyl-3-methylimidazolium acetate were added to a reactor. Nitrogen gas was purged to remove air from the reactor. The temperature was raised to 190-230℃ to initiate the transesterification reaction, which was maintained for 2 hours. Then, 11.1g of 2-(4-hydroxyethoxycarbonylphenyl)-1H-benzimidazole-5-carboxylic acid ethylene glycol ester (equivalent to 1% of the PTA molar) was added. The temperature was gradually raised to 240℃, and a vacuum was applied. Polycondensation was carried out at 240-260℃ under low vacuum for 0.2-1 hour, followed by high vacuum (pressure <80Pa) polycondensation at 260-280℃ for 1.8-3.0 hours. The product was then discharged. The intrinsic viscosity [η] of this polyester was 0.67 dL / g.

[0072] Example 15

[0073] 582g of dimethyl terephthalate, 360mL of ethylene glycol, and 3.5g of 1-ethyl-3-methylimidazolium dibenzo[c,e][1,2]oxophosphonate were added to a reactor. Nitrogen gas was purged to remove air from the reactor. The temperature was raised to 190-230℃ to initiate the transesterification reaction, which was maintained for 2 hours. Then, 11.1g of 2-(4-hydroxyethoxycarbonylphenyl)-1H-benzimidazole-5-carboxylic acid ethylene glycol ester (equivalent to 1% of the PTA molar) was added. The temperature was gradually raised to 240℃, and a vacuum was applied. Polycondensation was carried out at 240-260℃ under low vacuum for 0.2-1 hour, followed by polycondensation at 260-280℃ under high vacuum (pressure <80Pa) for 1.8-3.0 hours. The product was then discharged. The intrinsic viscosity [η] of this polyester was 0.65 dL / g.

[0074] Example 16

[0075] Esterification solution of 2-(4-hydroxycarbonylphenyl)-1H-benzimidazole-5-carboxylic acid: Equimolar amounts of p-aldehyde benzoic acid, 3,4-diaminobenzoic acid, and sodium metabisulfite were dissolved in DMF and reacted at 130°C for 12 hours. After removing the solvent, the solution was recrystallized from ethanol to obtain 2-(4-hydroxycarbonylphenyl)-1H-benzimidazole-5-carboxylic acid. The obtained 2-(4-hydroxycarbonylphenyl)-1H-benzimidazole-5-carboxylic acid was esterified with excess ethylene glycol at 200-230°C for 3 hours to obtain the esterification solution of 2-(4-hydroxycarbonylphenyl)-1H-benzimidazole-5-carboxylic acid, which could be used directly for polymerization without separation.

[0076] Preparation of polyester:

[0077] 498g of terephthalic acid and 230mL of ethylene glycol were added to a reactor, and nitrogen was purged to remove air. The temperature was raised to 200-230℃ to initiate the esterification reaction, which was maintained for 2 hours. Then, a certain amount of esterification solution of 2-(4-hydroxycarbonylphenyl)-1H-benzimidazole-5-carboxylic acid (calculated as 2% of the solute molar of PTA) was added, and the temperature was gradually raised to 240℃. Vacuum was applied, and polycondensation was carried out at 240-260℃ under low vacuum for 0.2-1 hours. Then, polycondensation was carried out at 260-280℃ under high vacuum (pressure <80Pa) for 1.8-3.0 hours before discharging. The intrinsic viscosity [η] of this polyester is 0.68 dL / g.

[0078] Example 17

[0079] Preparation of 2,2'-(1,3-phenylene)bis(1H-benzimidazole-5-carboxylic acid ethylene glycol ester) esterification solution: Stoichiometric amounts of isophthalaldehyde, 3,4-diaminobenzoic acid, and sodium metabisulfite were dissolved in DMF and reacted at 130°C for 12 hours. The solvent was removed, and the solution was recrystallized from ethanol to obtain 2,2'-(1,3-phenylene)bis(1H-benzimidazole-5-carboxylic acid). The obtained 2,2'-(1,3-phenylene)bis(1H-benzimidazole-5-carboxylic acid) was esterified with excess ethylene glycol at 200-230°C for 3 hours to obtain the 2,2'-(1,3-phenylene)bis(1H-benzimidazole-5-carboxylic acid ethylene glycol ester) esterification solution. The esterification solution did not require separation and purification and was used directly for polymerization.

[0080] Preparation of polyester:

[0081] 498g of terephthalic acid and 230mL of ethylene glycol were added to a reactor. Nitrogen gas was purged to remove air from the reactor. The temperature was raised to 200-230℃ to initiate the esterification reaction, which was maintained for 2 hours. Then, a certain amount of esterification solution of 2,2'-(1,3-phenylene)bis(1H-benzimidazole-5-carboxylic acid ethylene glycol ester) (calculated as 3% of the solute molar amount of PTA) was added. The temperature was gradually raised to 240℃, and a vacuum was applied. Polycondensation was carried out at 240-260℃ under low vacuum for 0.2-1 hour, followed by polycondensation at 260-280℃ under high vacuum (pressure <80Pa) for 1.8-3.0 hours. The product was then discharged. The intrinsic viscosity [η] of this polyester was 0.66 dL / g.

[0082] Comparative Example 1

[0083] 498g of terephthalic acid and 230mL of ethylene glycol were added to a reactor, and nitrogen was purged to remove air. The temperature was raised to 200-230℃ to initiate the esterification reaction, which was maintained for 2 hours. The temperature was then gradually increased to 240℃, and a vacuum was applied. Polycondensation was carried out at 240-260℃ under low vacuum for 0.2-1 hour, followed by polycondensation at 260-280℃ under high vacuum (pressure <80Pa) for 1.8-3.0 hours. The product was then discharged. Ultimately, polyester was not obtained.

Claims

1. The application of a non-metallic organic compound in the catalytic synthesis of polyester, characterized in that, The non-metallic organic compound serves as a polycondensation catalyst and copolymerization monomer in the polyester synthesis process; the non-metallic organic compound is a hydroxyl-containing benzimidazole derivative with any one of the structural formulas in C, E, etc. Where n is an integer from 1 to 7, m is an integer from 1 to 7, R1 is H, halogen, C1 to C6 alkyl or alkoxy, and R2 is phenylene or C1 to C10 alkylene.

2. The application of the non-metallic organic compound according to claim 1 in the catalytic synthesis of polyester, characterized in that, The hydroxyl group is any one of hydroxyethyl, hydroxypropyl, or hydroxybutyl.

3. A method for preparing polyester based on the non-metallic organic compound of claim 1, characterized in that, A metal-free copolyester is obtained by esterification and melt polycondensation of dicarboxylic acids, diols, and the aforementioned non-metallic organic compounds or their esterification solutions. Non-metallic organic compounds can act as both condensation catalysts and copolymerization monomers.

4. The polyester preparation method according to claim 3, characterized in that, The molar amount of the non-metallic organic compound added is at least 0.3% of the molar amount of the dicarboxylic acid or carboxylic ester polymer monomer.

5. The polyester preparation method according to claim 3, characterized in that, The molar amount of the non-metallic organic compound added is 0.3-20% of the molar amount of the dicarboxylic acid or carboxylic ester polymer monomer; And / or, the esterification reaction is carried out at 180~240 °C for 1.0~2.5 h; And / or, the polycondensation reaction includes a pre-polycondensation and a polycondensation process, wherein the pre-polycondensation is carried out at 230~250 °C for 0.20~1.0 hours under low vacuum, and the polycondensation is carried out at 250~280 °C for 1~3 hours under high vacuum; And / or, the non-metallic organic compound or its esterification solution is added to the polymerization system before esterification or before polycondensation begins after esterification; And / or, the non-metallic organic compound or its esterification solution is added to the polymerization system before transesterification or before polycondensation begins after transesterification.

6. The polyester preparation method according to claim 3, characterized in that, Functional additives are also added to the raw materials, including titanium dioxide matting agent and stabilizer.

7. The polyester synthesized by the method according to any one of claims 3-6, characterized in that, The polyester contains no metal catalysts and its macromolecular structure contains any of the following copolymer structural units from B1 to E1. 。 8. The polyester according to claim 7, characterized in that, The copolymer structural unit is 0.3-20% of the number of terephthalic acid structural units, and the resulting polyester has an intrinsic viscosity of 0.50-0.80 dL / g. The polyester does not contain any metal catalysts.

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