Heat-resistant polyester as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of high polymer material synthesis, and discloses heat-resistant polyester as well as a preparation method and application thereof. The heat-resistant polyester is obtained by esterification and polycondensation of terephthalic acid, isosorbide, 1, 4-cyclohexanedimethanol and ethylene glycol under the action of a composite polycondensation catalyst; the composite polycondensation catalyst comprises a titanium-magnesium bimetallic catalyst, a hindered phenol compound and a phosphite ester compound; the heat-resistant polyester prepared by the invention is good in heat-resistant stability, is small in viscosity reduction in the forming process, and also has the characteristics of being green and environment-friendly, free of heavy metal pollution and excellent in hue.

Description

Technical Field

[0001] The invention relates to the technical field of polymer material synthesis, and in particular to a heat-resistant polyester and a preparation method and application thereof. Background Art

[0002] Polyester is a widely used polymer material, mainly used in the fields of fiber, film, bottle engineering plastics, etc. Traditional polyester mainly refers to polyethylene terephthalate, but due to its glass transition temperature, its use in hot-filled beverage bottles, baby bottles, food packaging and other fields is limited. At present, the main heat-resistant polyester material is bisphenol A polycarbonate, but it will slowly release bisphenol A during use, causing stunted development of infants, inducing cancer, and causing metabolic disorders. Therefore, developing bio-friendly heat-resistant polyesters and increasing the glass transition temperature of polyesters are one of the important directions of polyester research.

[0003] At present, the main methods for modifying heat-resistant polyesters are blending modification and copolymerization modification. Among them, copolymerization modification mainly starts from the monomers of synthetic polyesters, and introduces monomers with rigid structures such as 2,6-naphthalene dicarboxylic acid, 4,4'-biphenyl dicarboxylic acid, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, isosorbide, etc. into the polymer chain to obtain heat-resistant polyesters with high glass transition temperature.

[0004] As a bio-based rigid diol, isosorbide is widely available, safe and non-toxic, and has great potential in replacing petroleum-based polyesters, solving the oil energy crisis, and achieving commercialization. However, the reactivity of the secondary hydroxyl group of isosorbide is low, and because one of the hydroxyl groups of isosorbide is affected by the steric hindrance of the furan ring and the hydrogen bond within the molecule, the high-temperature residence time of polymerization is long. Therefore, the actual composition ratio of isosorbide in the copolyester is less than its feed ratio, the glass transition temperature is not significantly increased, the intrinsic viscosity of the obtained copolyester material is not high, and the intrinsic viscosity drops significantly during the molding process.

[0005] In the copolymerization modification process, catalysts play a vital role. Antimony and titanium catalysts are often used in polyester production. Although antimony catalysts have a good catalytic effect on polymerization reactions, they are toxic and do not conform to the concept of environmental protection development. Titanium catalysts commonly used in tetrabutyl titanate and isopropyl titanate are non-toxic and environmentally friendly, but they have a strong catalytic effect on both the main polymerization reaction and the side reaction, resulting in poor hue of polyester products. In addition, the catalysts are not resistant to hydrolysis and have high consumption. Summary of the invention

[0006] The present invention aims at the above problems and provides a heat-resistant polyester and a preparation method thereof. The present invention adopts a non-toxic, environmentally friendly, hydrolysis-resistant titanium-magnesium bimetallic catalyst under the synergistic effect of hindered phenol compounds and phosphite compounds to solve the problems of low reactivity of isosorbide, poor thermal stability and large viscosity drop during the processing and molding of isosorbide copolyester. The heat-resistant polyester prepared by the present invention has good heat stability and small viscosity drop during the molding process. It is also green and environmentally friendly, has no heavy metal pollution and has excellent color.

[0007] In order to solve the above technical problems, the first aspect of the present invention provides a heat-resistant polyester, which is obtained by esterification and polycondensation of terephthalic acid, isosorbide, 1,4-cyclohexanedimethanol and ethylene glycol under the action of a composite polycondensation catalyst; the composite polycondensation catalyst includes a titanium-magnesium bimetallic catalyst, a hindered phenol compound and a phosphite compound.

[0008] The isosorbide used in the present invention is a rigid diol monomer derived from sugar, with a wide range of raw materials, and has been commercially produced, giving the heat-resistant polyester safe, non-toxic, environmentally friendly characteristics and commercial potential; the non-toxic, environmentally friendly, hydrolysis-resistant titanium-magnesium bimetallic catalyst used gives the prepared heat-resistant polyester outstanding safety, green and environmentally friendly characteristics; in the process of isosorbide participating in the copolymerization reaction, since the reactive group of isosorbide is a secondary hydroxyl group, the activity is lower than that of a primary hydroxyl group, resulting in a low content of isosorbide in the polymer chain, and a long high-temperature residence time of isosorbide during the polymerization reaction; the use of the titanium-magnesium bimetallic catalyst can activate the secondary hydroxyl group, improve the reaction activity of the secondary hydroxyl group of isosorbide, and then improve the copolymerization ratio of the isosorbide monomer, so that the prepared heat-resistant polyester has a high glass transition temperature; it can be seen that the present invention introduces the rigid structure isosorbide monomer into the polymer molecular chain, can give the polyester a high glass transition temperature, and can regulate the glass transition temperature of the polyester by adjusting the amount of isosorbide added.

[0009] The side reaction in the polycondensation reaction process of the present invention is mainly thermal oxidation degradation; the binary composite stabilization system of hindered phenol compounds and phosphite compounds can play a synergistic role in inhibiting the thermal degradation side reaction; at the same time, the phosphorus compound can be complexed with the titanium metal ions of the titanium-magnesium bimetallic catalyst, so as to effectively inhibit the catalytic effect of the titanium-magnesium bimetallic catalyst on the thermal degradation side reaction of the heat-resistant polyester, so that the heat-resistant polyester has good hue and thermal stability; more specifically, the phosphite reacts with the water in the polymer to generate phosphate ester, which can reduce the phenol oxygen free radicals to achieve the regeneration of hindered phenol, and the two play a synergistic mechanism to inhibit the thermal degradation side reaction; the phosphorus compound can coordinate with the titanium metal ions of the titanium-magnesium bimetallic catalyst to form new ions, and the catalytic effect of the new ions on the thermal degradation side reaction of the polyester is significantly lower than that of the single titanium ion; therefore, the ternary composite catalytic system composed of the titanium-magnesium bimetallic catalyst, the hindered phenol compounds and the phosphite compounds can play a synergistic role to obtain polyester with good thermal stability and hue.

[0010] According to some embodiments of the present invention, the molar ratio of terephthalic acid to isosorbide is 1:0.1-1:0.5, the molar ratio of terephthalic acid to 1,4-cyclohexanedimethanol is 1:0.4-1:0.6, and the molar ratio of terephthalic acid to the sum of isosorbide, 1,4-cyclohexanedimethanol, and ethylene glycol is 1:1.05-1:2;

[0011] According to some embodiments of the present invention, relative to the weight of the heat-resistant polyester, the addition amount of the titanium-based bimetallic catalyst is 5-50 ppm, the addition amount of the hindered phenol compound is 8-150 ppm, and the addition amount of the phosphite compound is 20-150 ppm.

[0012] According to some embodiments of the present invention, the structural formula of the titanium-magnesium bimetallic catalyst is as follows:

[0013]

[0014] According to some embodiments of the present invention, the hindered phenol compound is selected from at least one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,6-di-tert-butyl-4-methylphenol, 2,4-dimethyl-6-(1-methylpentadecyl)-phenol, and 4,4'-methylenebis(2,6-di-tert-butylphenol).

[0015] According to some embodiments of the present invention, the phosphite compound is at least one selected from tris(2,4-di-tert-butyl)phenyl phosphite, 4,4'-biphenyl diphosphite, distearyl pentaerythritol diphosphite, and bis(2,4-di-tert-butylphenol) pentaerythritol diphosphite.

[0016] According to some embodiments of the present invention, the heat-resistant polyester has a hue b value of no higher than 10, a terminal carboxyl content of no higher than 15 mol / t, an intrinsic viscosity of 0.5-1.0 dL / g, a diethylene glycol content of no higher than 1.3%, and a glass transition temperature of 90-130°C.

[0017] The heat-resistant polyester prepared by the invention has only one glass transition temperature, indicating that the main chain of the heat-resistant polyester is a quaternary random copolyester composed of terephthalic acid, isosorbide, 1,4-cyclohexanedimethanol and ethylene glycol.

[0018] The second aspect of the present invention provides a method for preparing the above-mentioned heat-resistant polyester, comprising the following steps:

[0019] (1) mixing terephthalic acid, isosorbide, 1,4-cyclohexanedimethanol and ethylene glycol to obtain a slurry;

[0020] (2) mixing a titanium-magnesium bimetallic catalyst, a hindered phenol compound, and a phosphite compound with ethylene glycol to obtain a solution through a complex reaction;

[0021] (3) Adding the solution obtained in step (2) to the slurry obtained in step (1), and subjecting the mixture to esterification and polycondensation, to obtain the heat-resistant polyester. The esterification and polycondensation reactions are carried out in a reactor in a one-pot manner.

[0022] According to some embodiments of the present invention, in step (1), the mixing conditions include: temperature of 80-100° C. and time of 0.3-2 hours.

[0023] The present invention mixes terephthalic acid, isosorbide, 1,4-cyclohexanedimethanol and ethylene glycol under heating conditions, which is beneficial to accelerating the fluidity of the materials and making the raw materials fully and evenly mixed, thereby effectively improving the collision rate between the comonomers, increasing the esterification rate, shortening the reaction time, and also reducing the high-temperature residence time of the isosorbide comonomer.

[0024] According to some embodiments of the present invention, in step (2), the conditions of the complexation reaction include: a temperature of 80-150°C;

[0025] And / or, in step (2), the content of ethylene glycol in the solution is 98-99.5wt%.

[0026] The present invention configures a titanium-magnesium bimetallic catalyst, a hindered phenol compound and a phosphite compound into a solution through a complexation reaction in ethylene glycol, which is beneficial to the complexation of the stabilizer system with the metal ions of the titanium-magnesium bimetallic catalyst, thereby effectively inhibiting the catalytic effect of titanium ions on thermal degradation side reactions during the polymerization reaction.

[0027] According to some embodiments of the present invention, in step (3), the conditions of the esterification reaction include: a temperature of 230-260°C;

[0028] And / or, the polycondensation reaction includes a preliminary polycondensation reaction and a final polycondensation reaction; preferably, the conditions of the polycondensation reaction include: a temperature of 250-280°C; further preferably, a pressure of the preliminary polycondensation reaction is 0.5-5kPa; and a pressure of the final polycondensation reaction is 50-500Pa.

[0029] The heat-resistant polyester of the present invention is prepared by a one-pot method, and the heat-resistant polyester is prepared by in-situ esterification and polycondensation, which avoids multiple reaction operations, ensures the stability of the process for preparing the heat-resistant polyester, and is conducive to controlling the stability of product quality; at the same time, it also reduces the manual operation time cost and improves production efficiency.

[0030] According to some embodiments of the present invention, the polycondensation reaction further includes cooling, solidification and slicing.

[0031] The third aspect of the present invention provides the use of the heat-resistant polyester in food packaging, preferably hot-fill beverage bottles or baby bottles.

[0032] Beneficial effects:

[0033] The heat-resistant polyester of the present invention is polycondensed from terephthalic acid, isosorbide, 1,4-cyclohexanedimethanol and ethylene glycol under the synergistic catalytic action of a titanium-magnesium bimetallic catalyst, a hindered phenol compound and a phosphite compound, and has good thermal stability, excellent hue, and is safe, non-toxic and green.

[0034] The isosorbide monomer used in the present invention is green, environmentally friendly, widely available, and has been commercialized, thus avoiding the situation that the subsequent commercialization of the heat-resistant polyester is limited by the shortage of raw material sources and high costs.

[0035] The catalytic system adopted by the present invention does not contain heavy metal elements and has high catalytic selectivity. The obtained product has high isosorbide unit content and high glass transition temperature; the catalytic activity is high, the high-temperature residence time of isosorbide is reduced, and the thermal decomposition of isosorbide is reduced; the catalytic synergistic effect with hindered phenol compounds and phosphite compounds is good, the occurrence of thermal degradation side reactions in the polymerization process is reduced, and the heat resistance and thermal processing stability of polyester are improved.

[0036] The present invention adopts a one-pot in-situ esterification polycondensation, which reduces the number of steps, ensures the stability of the process for preparing the heat-resistant polyester, and is conducive to controlling the stability of product quality; at the same time, it also reduces the time cost of manual operation and improves production efficiency. DETAILED DESCRIPTION

[0037] The present invention will be further described below in conjunction with the embodiments, but the present invention is not limited by these embodiments.

[0038] In the following examples and comparative examples of the present invention, unless otherwise specified, all raw materials used are commercially available.

[0039] In the Examples and Comparative Examples:

[0040] Terephthalic acid was purchased from Yingkou Kanghui Petrochemical Co., Ltd., industrial grade;

[0041] Isosorbide was purchased from Shanghai Haorui Chemical Co., Ltd., Roquette POLYSORB PA;

[0042] 1,4-Cyclohexanedimethanol was purchased from Guangzhou Haoyi New Materials Technology Co., Ltd., Korean SK industrial grade;

[0043] The synthesis method of titanium-magnesium bimetallic catalyst refers to the literature "Cost-Effective Sustainable Synthesis of High-Performance High-Molecular-Weight Poly(trimethyleneterephthalate) by Eco-Friendly and Highly Active Ti / Mg Catalysts" (DOI: 10.1021 / acssuschemeng.6b02358);

[0044] 4,4′-Methylenebis(2,6-di-tert-butylphenol) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., 98%;

[0045] Distearyl pentaerythritol diphosphite was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., reagent grade;

[0046] Pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate was purchased from Anhui Zesheng Technology Co., Ltd., 98%;

[0047] Phenyl tris(2,4-di-tert-butyl)phosphite was purchased from Shanghai MacLean Biochemical Technology Co., Ltd., 98%;

[0048] 2,6-di-tert-butyl-4-methylphenol was purchased from Shanghai MacLean Biochemical Technology Co., Ltd., AR grade;

[0049] 4,4′-Biphenyl diphosphite was purchased from Shanghai MacLean Biochemical Technology Co., Ltd., 99%;

[0050] 2,4-Dimethyl-6-(1-methylpentadecyl)-phenol was purchased from Shanghai Bid Pharmaceutical Technology Co., Ltd., 97%;

[0051] Bis(2,4-di-tert-butylphenol)pentaerythritol diphosphite was purchased from Shanghai MacLean Biochemical Technology Co., Ltd., 95%.

[0052] Example 1

[0053] This embodiment is used to illustrate the heat-resistant polyester and its preparation method of the present invention.

[0054] (1) Terephthalic acid, isosorbide, 1,4-cyclohexanedimethanol and ethylene glycol are added into a reaction kettle in a molar ratio of 1:0.3:0.55:0.35 to prepare a slurry; wherein the slurry preparation time is 0.5 h and the temperature is 100° C.

[0055] (2) A titanium-magnesium bimetallic catalyst, 4,4'-methylenebis(2,6-di-tert-butylphenol), distearyl pentaerythritol diphosphite and ethylene glycol are mixed and prepared into a solution through a complexation reaction at 120° C., wherein the content of ethylene glycol in the solution is 98 wt %.

[0056] (3) adding the solution obtained in step (2) into a reactor and mixing evenly with the slurry prepared in step (1), adjusting the heat medium temperature of the reactor to 250° C., and performing an esterification reaction to obtain a heat-resistant polyester oligomer; wherein, relative to the weight of the heat-resistant polyester, the amount of the titanium-magnesium bimetallic catalyst added is 50 ppm, the amount of 4,4'-methylenebis(2,6-di-tert-butylphenol) added is 150 ppm, and the amount of distearyl pentaerythritol diphosphite added is 150 ppm.

[0057] (4) The heat medium temperature of the reactor is adjusted to 265° C., and the heat-resistant polyester oligomer obtained in step (3) is subjected to a pre-polycondensation reaction and a final polycondensation reaction in sequence to obtain a heat-resistant polyester melt; wherein the pre-polycondensation reaction pressure is 4 kPa and the final polycondensation reaction pressure is 50 Pa.

[0058] (5) The heat-resistant polyester melt prepared in step (4) is filtered through a filter and then sent to a casting head for cooling and solidification, and then pelletized by a pelletizer to obtain heat-resistant polyester chips.

[0059] Example 2

[0060] This embodiment is used to illustrate the heat-resistant polyester and its preparation method of the present invention.

[0061] (1) Terephthalic acid, isosorbide, 1,4-cyclohexanedimethanol and ethylene glycol are added into a reaction kettle in a molar ratio of 1:0.2:0.55:0.55 to prepare a slurry; wherein the slurry preparation time is 0.3 h and the temperature is 80° C.

[0062] (2) A titanium-magnesium bimetallic catalyst, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, tris(2,4-di-tert-butyl)phenyl phosphite and ethylene glycol are mixed and prepared into a solution through a complex reaction at 150° C.; wherein the ethylene glycol content in the solution is 99 wt %.

[0063] (3) adding the solution obtained in step (2) into a reactor and mixing evenly with the slurry prepared in step (1), adjusting the heat medium temperature of the reactor to 250° C., and performing an esterification reaction to obtain a heat-resistant polyester oligomer; wherein, relative to the weight of the heat-resistant polyester, the amount of the titanium-magnesium bimetallic catalyst added is 25 ppm, the amount of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate added is 50 ppm, and the amount of tris(2,4-di-tert-butyl)phenyl phosphite added is 50 ppm.

[0064] (4) The heat medium temperature of the reactor is adjusted to 280° C., and the heat-resistant polyester oligomer obtained in step (3) is subjected to a pre-polycondensation reaction and a final polycondensation reaction in sequence to obtain a heat-resistant polyester melt; wherein the pre-polycondensation reaction pressure is 5 kPa and the final polycondensation reaction pressure is 100 Pa.

[0065] (5) The heat-resistant polyester melt prepared in step (4) is filtered through a filter and then sent to a casting head for cooling and solidification, and then pelletized by a pelletizer to obtain heat-resistant polyester chips.

[0066] Example 3

[0067] This embodiment is used to illustrate the heat-resistant polyester and its preparation method of the present invention.

[0068] (1) Terephthalic acid, isosorbide, 1,4-cyclohexanedimethanol and ethylene glycol are added into a reaction kettle in a molar ratio of 1:0.4:0.6:0.25 to prepare a slurry; wherein the slurry preparation time is 1.5 hours and the temperature is 90°C.

[0069] (2) A titanium-magnesium bimetallic catalyst, 2,6-di-tert-butyl-4-methylphenol, 4,4'-biphenyl diphosphite and ethylene glycol are mixed and prepared into a solution through a complexation reaction at 80° C., wherein the ethylene glycol content in the solution is 98 wt %.

[0070] (3) adding the solution obtained in step (2) into a reactor and mixing evenly with the slurry prepared in step (1), adjusting the heat medium temperature of the reactor to 240° C., and performing an esterification reaction to obtain a heat-resistant polyester oligomer, wherein the amount of the titanium-magnesium bimetallic catalyst added is 15 ppm, the amount of 2,6-di-tert-butyl-4-methylphenol added is 80 ppm, and the amount of 4,4'-biphenyl diphosphite added is 80 ppm relative to the weight of the heat-resistant polyester.

[0071] (4) The heat medium temperature of the reactor is adjusted to 250° C., and the heat-resistant polyester oligomer obtained in step (3) is subjected to a pre-polycondensation reaction and a final polycondensation reaction in sequence to obtain a heat-resistant polyester melt; wherein the pre-polycondensation reaction pressure is 0.5 kPa and the final polycondensation reaction pressure is 200 Pa.

[0072] (5) The heat-resistant polyester melt prepared in step (4) is filtered through a filter and then sent to a casting head for cooling and solidification, and then pelletized by a pelletizer to obtain heat-resistant polyester chips.

[0073] Example 4

[0074] This embodiment is used to illustrate the heat-resistant polyester and its preparation method of the present invention.

[0075] (1) Terephthalic acid, isosorbide, 1,4-cyclohexanedimethanol and ethylene glycol are added into a reaction kettle in a molar ratio of 1:0.5:0.6:0.9 to prepare a slurry; wherein the slurry preparation time is 2 hours and the temperature is 80°C.

[0076] (2) A titanium-magnesium bimetallic catalyst, 2,4-dimethyl-6-(1-methylpentadecyl)-phenol, bis(2,4-di-tert-butylphenol) pentaerythritol diphosphite and ethylene glycol are mixed and configured into a solution through a complex reaction at 100° C.; wherein the ethylene glycol content in the solution is 99.5 wt %.

[0077] (3) adding the solution obtained in step (2) into a reactor and mixing evenly with the slurry prepared in step (1), adjusting the heat medium temperature of the reactor to 260° C., and performing an esterification reaction to obtain a heat-resistant polyester oligomer; wherein, relative to the weight of the heat-resistant polyester, the amount of the titanium-magnesium bimetallic catalyst added is 20 ppm, the amount of 2,4-dimethyl-6-(1-methylpentadecanyl)-phenol added is 100 ppm, and the amount of bis(2,4-di-tert-butylphenol) pentaerythritol diphosphite added is 100 ppm.

[0078] (4) The heat medium temperature of the reactor is adjusted to 270° C., and the heat-resistant polyester oligomer obtained in step (3) is subjected to pre-polycondensation and final polycondensation reactions in sequence to obtain a heat-resistant polyester melt; wherein the pre-polycondensation reaction pressure is 1 kPa, and the final polycondensation reaction pressure is 500 Pa.

[0079] (5) The heat-resistant polyester melt prepared in step (4) is filtered through a filter and then sent to a casting head for cooling and solidification, and then pelletized by a pelletizer to obtain heat-resistant polyester chips.

[0080] Example 5

[0081] This embodiment is used to illustrate the heat-resistant polyester and its preparation method of the present invention.

[0082] (1) Terephthalic acid, isosorbide, 1,4-cyclohexanedimethanol and ethylene glycol are added into a reaction kettle in a molar ratio of 1:0.1:0.6:0.65 to prepare a slurry; wherein the slurry preparation time is 1 hour and the temperature is 100°C.

[0083] (2) A titanium-magnesium bimetallic catalyst, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, tris(2,4-di-tert-butyl)phenyl phosphite and ethylene glycol are mixed and prepared into a solution through a complex reaction at 150° C.; wherein the ethylene glycol content in the solution is 98.5 wt %.

[0084] (3) adding the solution obtained in step (2) into a reactor and mixing evenly with the slurry prepared in step (1), adjusting the heat medium temperature of the reactor to 230° C., and performing an esterification reaction to obtain a heat-resistant polyester oligomer; wherein, relative to the weight of the heat-resistant polyester, the amount of the titanium-magnesium bimetallic catalyst added is 40 ppm, the amount of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate added is 50 ppm, and the amount of bis(2,4-di-tert-butylphenol)pentaerythritol diphosphite added is 120 ppm.

[0085] (4) The heat medium temperature of the reactor is adjusted to 260° C., and the heat-resistant polyester oligomer obtained in step (3) is subjected to a pre-polycondensation reaction and a final polycondensation reaction in sequence to obtain a heat-resistant polyester melt; wherein the pre-polycondensation reaction pressure is 2 kPa, and the final polycondensation reaction pressure is 400 Pa.

[0086] (5) The heat-resistant polyester melt prepared in step (4) is filtered through a filter and then sent to a casting head for cooling and solidification, and then pelletized by a pelletizer to obtain heat-resistant polyester chips.

[0087] Example 6

[0088] This embodiment is used to illustrate the heat-resistant polyester and its preparation method of the present invention.

[0089] (1) Terephthalic acid, isosorbide, 1,4-cyclohexanedimethanol and ethylene glycol are added into a reaction kettle in a molar ratio of 1:0.1:0.4:0.55 to prepare a slurry; wherein the slurry preparation time is 0.5 h and the temperature is 80° C.

[0090] (2) A titanium-magnesium bimetallic catalyst, 2,4-dimethyl-6-(1-methylpentadecyl)-phenol, distearyl pentaerythritol diphosphite and ethylene glycol are mixed and configured into a solution through a complex reaction at 100° C.; wherein the ethylene glycol content in the solution is 99 wt %.

[0091] (3) adding the solution obtained in step (2) into a reactor and mixing evenly with the slurry prepared in step (1), adjusting the heat medium temperature of the reactor to 230° C., and performing an esterification reaction to obtain a heat-resistant polyester oligomer; wherein, relative to the weight of the heat-resistant polyester, the amount of the titanium-magnesium bimetallic catalyst added is 30 ppm, the amount of 2,4-dimethyl-6-(1-methylpentadecanyl)-phenol added is 8 ppm of the polyester melt, and the amount of distearyl pentaerythritol diphosphite added is 20 ppm of the polyester melt.

[0092] (4) The heat medium temperature of the reaction kettle is adjusted to 250° C., and the heat-resistant polyester oligomer prepared in step (3) is subjected to a pre-polycondensation reaction and a final polycondensation reaction in sequence to obtain a heat-resistant polyester melt; wherein the pre-polycondensation reaction pressure is 5 kPa, and the final polycondensation reaction pressure is 350 Pa.

[0093] (5) The heat-resistant polyester melt prepared in step (4) is filtered through a filter and then sent to a casting head for cooling and solidification, and then pelletized by a pelletizer to obtain heat-resistant polyester chips.

[0094] Example 7

[0095] This embodiment is used to illustrate the heat-resistant polyester and its preparation method of the present invention.

[0096] (1) Terephthalic acid, isosorbide, 1,4-cyclohexanedimethanol and ethylene glycol are added into a reaction kettle in a molar ratio of 1:0.5:0.5:0.2 to prepare a slurry; wherein the slurry preparation time is 1.5 hours and the temperature is 90°C.

[0097] (2) A titanium-magnesium bimetallic catalyst, 2,6-di-tert-butyl-4-methylphenol, tri(2,4-di-tert-butyl)phenyl phosphite and ethylene glycol are mixed and prepared into a solution through a complexation reaction at 120° C., wherein the ethylene glycol content in the solution is 98 wt %.

[0098] (3) adding the solution obtained in step (2) into a reactor and mixing evenly with the slurry prepared in step (1), adjusting the heat medium temperature of the reactor to 240° C., and performing an esterification reaction to obtain a heat-resistant polyester oligomer; wherein, relative to the weight of the polyester, the amount of the titanium-magnesium bimetallic catalyst added is 5 ppm, the amount of 2,6-di-tert-butyl-4-methylphenol added is 50 ppm of the polyester melt, and the amount of tri(2,4-di-tert-butyl)phenyl phosphite added is 80 ppm of the polyester melt.

[0099] (4) The heat medium temperature of the reaction kettle is adjusted to 255° C., and the oligomer obtained in step (3) is subjected to a pre-polycondensation reaction and a final polycondensation reaction in sequence to obtain a heat-resistant polyester melt; wherein the pre-polycondensation reaction pressure is 3 kPa, and the final polycondensation reaction pressure is 250 Pa.

[0100] (5) The heat-resistant polyester melt prepared in step (4) is filtered through a filter and then sent to a casting head for cooling and solidification, and then pelletized by a pelletizer to obtain heat-resistant polyester chips.

[0101] Comparative Example 1

[0102] This comparative example is used to illustrate the heat-resistant polyester and the preparation method thereof of the present invention.

[0103] (1) Terephthalic acid, isosorbide, 1,4-cyclohexanedimethanol and ethylene glycol are added into a reaction kettle in a molar ratio of 1:0.3:0.55:0.35 to prepare a slurry; wherein the slurry preparation time is 0.5 h and the temperature is 100° C.

[0104] (2) The titanium-magnesium bimetallic catalyst and ethylene glycol are prepared into a solution through a complex reaction at 120° C., wherein the ethylene glycol content in the solution is 98 wt %.

[0105] (3) adding the solution obtained in step (2) into a reactor and mixing evenly with the slurry prepared in step (1), adjusting the heat medium temperature of the reactor to 250° C., and performing an esterification reaction to obtain a heat-resistant polyester oligomer; wherein the amount of the titanium-magnesium bimetallic catalyst added is 50 ppm relative to the weight of the heat-resistant polyester.

[0106] (4) The heat medium temperature of the reactor is adjusted to 265° C., and the heat-resistant polyester oligomer obtained in step (3) is subjected to a pre-polycondensation reaction and a final polycondensation reaction in sequence to obtain a heat-resistant polyester melt; wherein the pre-polycondensation reaction pressure is 4 kPa and the final polycondensation reaction pressure is 50 Pa.

[0107] (5) The heat-resistant polyester melt prepared in step (4) is filtered through a filter and then sent to a casting head for cooling and solidification, and then pelletized by a pelletizer to obtain heat-resistant polyester chips.

[0108] Comparative Example 2

[0109] This comparative example is used to illustrate the heat-resistant polyester and the preparation method thereof of the present invention.

[0110] (1) Terephthalic acid, isosorbide, 1,4-cyclohexanedimethanol and ethylene glycol are added into a reaction kettle in a molar ratio of 1:0.3:0.55:0.35 to prepare a slurry; wherein the slurry preparation time is 0.5 h and the temperature is 100° C.

[0111] (2) A titanium-magnesium bimetallic catalyst, distearyl pentaerythritol diphosphite and ethylene glycol are mixed at 120° C. and prepared into a solution through a complexation reaction; wherein the ethylene glycol content in the solution is 98 wt %.

[0112] (3) adding the solution obtained in step (2) into a reactor and mixing evenly with the slurry prepared in step (1), adjusting the heat medium temperature of the reactor to 250° C., and performing an esterification reaction to obtain a heat-resistant polyester oligomer; wherein the amount of the titanium-magnesium bimetallic catalyst added is 50 ppm, and the amount of the distearyl pentaerythritol diphosphite added is 150 ppm relative to the weight of the heat-resistant polyester.

[0113] (4) The heat medium temperature of the reactor is adjusted to 265° C., and the heat-resistant polyester oligomer obtained in step (3) is subjected to a pre-polycondensation reaction and a final polycondensation reaction in sequence to obtain a heat-resistant polyester melt; wherein the pre-polycondensation reaction pressure is 4 kPa and the final polycondensation reaction pressure is 50 Pa.

[0114] (5) The heat-resistant polyester melt prepared in step (4) is filtered through a filter and then sent to a casting head for cooling and solidification, and then pelletized by a pelletizer to obtain heat-resistant polyester chips.

[0115] In order to further illustrate the beneficial effects of the present invention, the properties of the heat-resistant polyester chips prepared in the above-mentioned Examples 1-7 and Comparative Examples 1-2 of the present invention were tested, and the test items are as follows:

[0116] Intrinsic viscosity η (dL / g), test method: refer to GB / T 14190-2008;

[0117] Terminal carboxyl content (mol / t), test method: refer to GB / T 14190-2008;

[0118] Diethylene glycol content (%), test method: refer to GB / T 14190-2008;

[0119] Glass transition temperature (°C), test method: tested by Perkin-Elmer Pyris 1 differential scanning calorimeter at a heating and cooling rate of 20°C / min and a nitrogen purge rate of 50mL / min;

[0120] Chromaticity b value, test method: tested using Konica Minolta's CM-5 spectrophotometer.

[0121] The test results are shown in Table 1.

[0122] Table 1 Performance test results of heat-resistant polyester chips prepared in Examples 1-7 and Comparative Examples 1-2 of the present invention

[0123]

[0124] It can be observed from Table 1 that the chromaticity b value and terminal carboxyl content of the heat-resistant polyester slices prepared in Comparative Examples 1 and 2 are significantly higher than those of the heat-resistant polyester slices prepared in Example 1. In Comparative Example 1, a titanium-magnesium bimetallic catalyst is used as a heat-resistant polyester catalyst. Since titanium ions have a high catalytic activity on the thermal degradation reaction of heat-resistant polyester, the heat-resistant polyester produces severe yellowing, with a chromaticity b value as high as 20 and a terminal carboxyl content as high as 33 mol / t. In Comparative Example 2, while using a titanium-magnesium bimetallic catalyst as a catalyst, a phosphate stabilizer 4,4'-methylenebis(2,6-di-tert-butylphenol) is introduced. The phosphate stabilizer coordinates with the metal titanium ion to form a complex, which effectively controls the yellowing process of the heat-resistant polyester, reduces the polyester chromaticity b value to 12, and reduces the terminal carboxyl content to 24 mol / t. Example 1, based on the use of titanium-magnesium bimetallic catalyst, introduces 4,4'-methylenebis(2,6-di-tert-butylphenol) / distearyl pentaerythritol diphosphite composite stabilizer. Through the synergistic effect of the catalyst and the composite stabilizer, the color-forming side reactions and thermal degradation side reactions in the production process of the heat-resistant polyester are further suppressed, so that the color b value of the prepared heat-resistant polyester chips is reduced to 6 and the terminal carboxyl content is reduced to 12 mol / t.

[0125] Experimental example

[0126] The heat-resistant polyester chips prepared in the above-mentioned Example 1, Comparative Example 1 and Comparative Example 2 of the present invention were vacuum dried at a temperature of 80° C. for 24 hours.

[0127] Then, the dried heat-resistant polyester chips were loaded into the barrel of the high-pressure capillary rheometer Rheograph 25 produced by Gottfort, Germany, under nitrogen protection. The barrel temperature was 280°C, the capillary diameter was 1mm, and the aspect ratio was 40:1. After the slices filled the barrel, the barrel slices were pressed tightly with a piston rod. After constant temperature melting for 5 minutes, the piston rod extruded the heat-resistant polyester melt at a uniform speed of 0.139mm / s. The melt sample was taken every 10 minutes for the intrinsic viscosity test. The intrinsic viscosity data obtained was used to evaluate the thermal stability of the heat-resistant polyester.

[0128] Intrinsic viscosity (η), test method: refer to GB-14190-2008.

[0129] The intrinsic viscosity drop (Δη) is the value of the intrinsic viscosity drop within a certain period of time.

[0130] The test results are shown in Table 2.

[0131] Table 2 Comparison of thermal stability of heat-resistant polyester chips prepared in Example 1 and Comparative Examples 1-2

[0132]

[0133] It can be seen from Table 2 that the intrinsic viscosity drop of the heat-resistant polyester chips prepared in Example 1 is significantly smaller than the intrinsic viscosity drop of the heat-resistant polyester chips prepared in Comparative Example 1 and Comparative Example 2, indicating that under the synergistic effect of phosphite compounds, hindered phenol compounds and titanium-magnesium bimetallic catalysts, the prepared heat-resistant polyester has good thermal stability.

[0134] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A heat-resistant polyester, characterized in that: The heat-resistant polyester is obtained by esterification and polycondensation of terephthalic acid, isosorbide, 1,4-cyclohexanedimethanol and ethylene glycol under the action of a composite polycondensation catalyst; the composite polycondensation catalyst comprises a titanium-magnesium bimetallic catalyst, a hindered phenol compound and a phosphite compound.

2. The heat-resistant polyester according to claim 1, characterized in that The molar ratio of terephthalic acid to isosorbide is 1:0.1-1:0.5, the molar ratio of terephthalic acid to 1,4-cyclohexanedimethanol is 1:0.4-1:0.6, and the molar ratio of terephthalic acid to the sum of isosorbide, 1,4-cyclohexanedimethanol and ethylene glycol is 1:1.05-1:2; And / or, relative to the weight of the heat-resistant polyester, the addition amount of the titanium-based bimetallic catalyst is 5-50 ppm, the addition amount of the hindered phenol compound is 8-150 ppm, and the addition amount of the phosphite compound is 20-150 ppm.

3. The heat-resistant polyester according to claim 1 or 2, characterized in that: The structural formula of the titanium-magnesium bimetallic catalyst is as follows: and / or, the hindered phenol compound is at least one selected from pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,6-di-tert-butyl-4-methylphenol, 2,4-dimethyl-6-(1-methylpentadecyl)-phenol, and 4,4'-methylenebis(2,6-di-tert-butylphenol); And / or, the phosphite compound is at least one selected from tris(2,4-di-tert-butyl)phenyl phosphite, 4,4'-biphenyl diphosphite, distearyl pentaerythritol diphosphite, and bis(2,4-di-tert-butylphenol) pentaerythritol diphosphite.

4. The heat-resistant polyester according to any one of claims 1 to 3, characterized in that The heat-resistant polyester has a hue b value of no more than 10, a terminal carboxyl content of no more than 15 mol / t, an intrinsic viscosity of 0.5-1.0 dL / g, a diethylene glycol content of no more than 1.3%, and a glass transition temperature of 90-130°C.

5. A method for preparing the heat-resistant polyester according to any one of claims 1 to 4, characterized in that: The steps include: (1) mixing terephthalic acid, isosorbide, 1,4-cyclohexanedimethanol and ethylene glycol to obtain a slurry; (2) mixing a titanium-magnesium bimetallic catalyst, a hindered phenol compound, and a phosphite compound with ethylene glycol to obtain a solution through a complex reaction; (3) Adding the solution obtained in step (2) to the slurry obtained in step (1), and subjecting the mixture to esterification reaction and polycondensation reaction, thereby obtaining the heat-resistant polyester.

6. The preparation method according to claim 5, characterized in that: In step (1), the mixing conditions include: temperature of 80-100° C. and time of 0.3-2 hours.

7. The preparation method according to claim 5 or 6, characterized in that: In step (2), the conditions of the complexation reaction include: a temperature of 80-150°C; And / or, in step (2), the content of ethylene glycol in the solution is 98-99.5wt%.

8. The preparation method according to any one of claims 5 to 7, characterized in that: In step (3), the conditions of the esterification reaction include: a temperature of 230-260°C; And / or, the polycondensation reaction includes a preliminary polycondensation reaction and a final polycondensation reaction; preferably, the conditions of the polycondensation reaction include: a temperature of 250-280°C; further preferably, a pressure of the preliminary polycondensation reaction is 0.5-5kPa; and a pressure of the final polycondensation reaction is 50-500Pa.

9. The preparation method according to any one of claims 5 to 8, characterized in that: The polycondensation reaction further includes cooling, solidification and slicing.

10. Use of the heat-resistant polyester according to any one of claims 1 to 4 or the heat-resistant polyester prepared by the preparation method according to any one of claims 5 to 9 in food packaging, preferably hot-fill beverage bottles or baby bottles.

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