Preparation method of adipic acid copolyester and obtained adipic acid copolyester

Abstract

The invention discloses a preparation method of adipic acid copolyester and the obtained adipic acid copolymer.The preparation method comprises the step that raw materials including dibasic acid and dihydric alcohol react in the presence of phenolic compounds, and the dibasic acid comprises adipic acid. The phenolic compound is added in the polymerization process to stabilize the hexanedioic acid decarboxylation and dehydration product cyclopentanone and inhibit further self-polymerization of the hexanedioic acid decarboxylation and dehydration product cyclopentanone, so that the preparation of the resin with good hue is realized.

Description

Technical Field

[0001] The present invention belongs to the field of copolyesters, particularly adipic acid copolyesters, and specifically relates to a preparation method of an adipic acid copolyester and the obtained adipic acid copolyester. Background Art

[0002] Synthetic resins are a class of artificially synthesized polymer materials and are the third largest materials after metals and cement. Resin materials represented by polyolefins and polyesters have been widely used in various industries, bringing great convenience to human life. However, the random disposal of such materials has caused serious "white pollution", which has seriously affected the sustainable development of humans and the environment. Therefore, the development of biodegradable polymer materials such as polybutylene succinate (PBS), poly(butylene adipate-co-terephthalate) (PBAT), poly(butylene succinate-co-adipate) (PBSA), polylactic acid (PLA), and polyhydroxyalkanoates (PHA) has received great attention from governments and enterprises of various countries. Among the above biodegradable materials, PBAT has both excellent mechanical properties and stability of aromatic polyesters and good biodegradability of aliphatic polyesters, and has become one of the materials with the best performance and the hottest research in current biodegradable materials.

[0003] Currently, the preparation method of PBAT is mainly obtained by esterification and polycondensation of adipic acid (AA), terephthalic acid (PTA), and butanediol (BDO) under the action of a catalyst and a stabilizer. However, during the polymerization process, adipic acid is prone to decarboxylation and dehydration reactions at high temperatures to obtain cyclopentanone, and this compound will further self-polymerize, especially in the later stage of polycondensation, resulting in poor quality of the PBAT material.

[0004] CN 115286776A discloses a preparation method of PBAT. PTA and AA are respectively subjected to esterification reactions with BDO. In the esterification reaction of AA and BDO, a carbodiimide esterification activator is added. After the esterification is completed, the two esterified products are mixed and subjected to a polycondensation reaction under the action of a catalyst and an auxiliary agent. By increasing the esterification rate of AA, the degradation of AA at high temperatures is inhibited, thereby improving the hue of the PBAT resin.

[0005] CN113667103A discloses a preparation method of a PBAT resin. A titanium EDTA composite catalyst, terephthalic acid, adipic acid, and 1,4-butanediol are subjected to an esterification reaction; after the esterification reaction is completed, a reducing agent 4,4',4″-triaminotriphenylmethane and / or L-polylysine are added, and PBAT pellets are prepared by polycondensation. The PBAT shows lower a values and b values.

[0006] In the above technologies, the hue of PBAT resin is improved by increasing the esterification rate of adipic acid or inhibiting deacidification through reduction. However, there are problems such as many steps in the preparation process, relatively high cost of the reducing agent, and certain toxicity during the operation process. Summary of the Invention

[0007] In order to overcome the problems existing in the prior art, the present invention provides a method for preparing an adipic acid copolyester and the obtained adipic acid copolyester. By adding a phenolic compound during the polymerization process, cyclopentanone, the decarboxylation and dehydration product of adipic acid, is stabilized, and its further self-polymerization is inhibited, thereby realizing the preparation of a resin with good hue (such as PBAT).

[0008] One object of the present invention is to provide a method for preparing an adipic acid copolyester, comprising: reacting raw materials including dibasic acid and diol in the presence of a phenolic compound, wherein the dibasic acid includes adipic acid.

[0009] In a preferred embodiment, the dibasic acid further optionally includes other dibasic acids besides adipic acid. Preferably, the other dibasic acids are selected from at least one of aromatic dibasic acids and aliphatic dibasic acids other than adipic acid.

[0010] In a further preferred embodiment, the other dibasic acids are selected from at least one of terephthalic acid, isophthalic acid, p-phthalic acid, and C2-C10 dibasic acids (such as succinic acid and / or sebacic acid), preferably p-phthalic acid and optionally succinic acid.

[0011] In a preferred embodiment, when the other dibasic acids are contained, based on the total molar amount of 100% of the adipic acid and the other dibasic acids, the molar proportion of the adipic acid is 10-90%, preferably 40-60%; the molar proportion of the other dibasic acids is 10-90%, preferably 40-60%.

[0012] Among them, based on the total molar amount of 100% of the adipic acid and the other dibasic acids, the molar proportion of the adipic acid is 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90%, and the molar proportion of the other dibasic acids is 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90%.

[0013] In a preferred embodiment, the diol is selected from at least one of C2-C12 diols, preferably at least one of C2-C6 diols.

[0014] In a further preferred embodiment, the diol is selected from at least one of ethylene glycol, 1,3-propanediol, and 1,4-butanediol.

[0015] Among them, the adipic acid copolyester may be polybutylene terephthalate adipate or polybutylene succinate adipate.

[0016] In the present invention, it is preferred that both the dibasic acid and the diol do not contain polymerizable unsaturated bonds.

[0017] In a further preferred embodiment, the molar ratio of the diol to the dibasic acid is (1.1 - 2):1, for example, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1 or 2:1.

[0018] Among them, the dibasic acid includes adipic acid and optional other dibasic acids. When the alcohol - acid ratio is too high, it will cause waste of alcohol raw materials, while when the alcohol - acid ratio is too low, it will lead to insufficient esterification, thus affecting the progress of the polymerization reaction.

[0019] In a preferred embodiment, the phenolic compound is selected from at least one of diphenol compounds.

[0020] In a further preferred embodiment, the diphenol compound is selected from at least one of hydroquinone and / or its derivatives, resorcinol and / or its derivatives, catechol and / or its derivatives, biphenol and / or its derivatives, preferably from at least one of hydroquinone and / or its derivatives, biphenol and / or its derivatives.

[0021] In a further preferred embodiment, based on 100 wt% of the theoretical yield of the adipic acid copolymer, the weight dosage of the phenolic compound is 20 - 300 ppm, for example, 20 ppm, 50 ppm, 80 ppm, 100 ppm, 120 ppm, 140 ppm, 160 ppm, 180 ppm, 200 ppm, 220 ppm, 240 ppm, 260 ppm, 280 ppm or 300 ppm.

[0022] Among them, adding a phenolic compound (especially a diphenol compound) to the adipic acid polymerization system, using its ability to undergo a reversible nucleophilic reaction with the carbonyl group on the by - product cyclopentanone of adipic acid to form hemiacetal or acetal, thereby stabilizing cyclopentanone and inhibiting the formation of colored substances caused by the aldol condensation of cyclopentanone itself, especially in the later stage of polymerization when the number of hydroxyl groups (provided by monomer butanediol) in the system is low. When the amount of the phenolic compound (especially the diphenol compound) is small, it is not enough to consume the carbonyl groups in the system, but when the amount is large (especially greater than 300 ppm), it will cause waste of raw materials and also affect the properties of the polyester as a foreign substance.

[0023] In the present invention, the theoretical yield of the adipic acid copolymer is obtained as follows: by multiplying the number of moles of the diacid by the molecular weight of the repeating unit.

[0024] In a preferred embodiment, the reaction is further carried out in the presence of a catalyst, and the catalyst is selected from titanium-based catalysts. Preferably, the titanium-based catalyst is selected from at least one of titanate compounds and chelated titanium compounds.

[0025] In a further preferred embodiment, the catalyst is selected from at least one of alkyl titanates and titanium chelates of organic acids, preferably from at least one of tetraethyl titanate, tetrapropyl titanate, tetrabutyl titanate, titanium lactate, and titanium citrate.

[0026] In a still further preferred embodiment, based on 100 wt% of the theoretical yield of the adipic acid copolyester, the amount of the catalyst used is 50 - 200 ppm, calculated by the weight of titanium element in the catalyst, for example, 50 ppm, 60 ppm, 80 ppm, 100 ppm, 120 ppm, 140 ppm, 160 ppm, 180 ppm, or 200 ppm.

[0027] In a preferred embodiment, a stabilizer is further added to the reaction, and the stabilizer is selected from phosphorus compounds.

[0028] In a further preferred embodiment, the phosphorus compound is selected from at least one of phosphoric acid, trimethyl phosphate, triethyl phosphate, tripropyl phosphate, triisopropyl phosphate, tributyl phosphate, dibutyl phosphate, and triphenyl phosphate.

[0029] In a still further preferred embodiment, based on 100 wt% of the theoretical yield of the adipic acid copolyester, the weight amount of the stabilizer used is 10 - 200 ppm, preferably 20 - 100 ppm, calculated by the weight of phosphorus element in the stabilizer, for example, 10 ppm, 20 ppm, 40 ppm, 60 ppm, 80 ppm, 100 ppm, 120 ppm, 140 ppm, 160 ppm, 180 ppm, or 200 ppm.

[0030] In a preferred embodiment, the reaction includes an esterification process and a polycondensation process.

[0031] In a further preferred embodiment, the diacid, diol, and the catalyst are added in the esterification process, the catalyst is optionally added in the polycondensation process, and / or the stabilizer is added in the esterification process and / or the polycondensation process, and / or the phenolic compound is added in the esterification process and / or the polycondensation process (for example, in the esterification process).

[0032] In a further preferred embodiment, if the catalyst is selected from titanate esters, it is added during the esterification process and the polycondensation process; if the catalyst is selected from chelated titanium, it is added during the esterification process.

[0033] Among them, since titanate is easily hydrolyzed, the water generated in the esterification stage will cause partial deactivation of the catalyst, and the catalyst needs to be added in the polycondensation stage, so it is recommended to add it in batches. The chelated titanium compound has good hydrolysis resistance and can be added all at once during the esterification process.

[0034] If the stabilizer is a phosphate ester, it can be added during the esterification process, or during the polycondensation process, or it can be added in batches during the esterification process and the polycondensation process. If the stabilizer is phosphoric acid, since phosphoric acid has a high reactivity and is easy to form a compound precipitate with titanium, it is preferably added during the polycondensation process and added separately from the titanate.

[0035] In a preferred embodiment, the conditions of the esterification process include: temperature 160-240°C, time 60-180 min; the conditions of the polycondensation process include: temperature 220-260°C, time 60-180 min, pressure <1 kPa.

[0036] In a further preferred embodiment, the conditions of the esterification process include: temperature 170-230° C., time 100-180 min; the conditions of the polycondensation process include: temperature 230-250° C., time 80-180 min, pressure <500 Pa.

[0037] In a preferred embodiment, the method comprises:

[0038] 1) Esterification process: adipic acid, the other dibasic acid, the diol and the phenolic compound are added into a reaction kettle, the temperature is raised to 190-220° C., and the reaction is carried out for 120-180 minutes.

[0039] 2) Polycondensation process: heating to 220-240°C, while gradually reducing the pressure in the reactor to 150 Pa, reacting for 120-180 minutes to obtain adipic acid copolyester.

[0040] The second object of the present invention is to provide adipic acid copolyester obtained by the preparation method described in the first object of the present invention.

[0041] In the ranges disclosed in the present invention, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein. In the following text, in principle, various technical solutions can be combined with each other to obtain new technical solutions, and this should also be regarded as specifically disclosed herein.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] (1) By adding phenolic compounds (especially diphenolic compounds) to the polymerization system, the present invention can effectively inhibit the self-polymerization of cyclopentanone, thereby effectively inhibiting the formation of chromophores, improving the hue of the resin well, and obtaining PBAT resin with good quality, having better technical effects.

[0044] (2) The preparation method described in the present invention is simple and feasible and can be applied to large-scale production. Specific Embodiments

[0045] The present invention will be specifically described below in conjunction with specific embodiments. It is necessary to point out here that the following embodiments are only for further illustration of the present invention and cannot be understood as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art to the present invention based on the content of the present invention still fall within the protection scope of the present invention.

[0046] In addition, it should be noted that the various specific technical features described in the following specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods.

[0047] In addition, any combination can be made between various different embodiments of the present invention as long as it does not violate the idea of the present invention. The technical solutions formed thereby belong to a part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0048] If there is no special limitation on the raw materials used in the examples and comparative examples, they are all disclosed in the prior art, for example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0049] In the present invention, the intrinsic viscosity, hue, etc. of the polyester are tested by the following methods:

[0050] (1) Intrinsic viscosity: Measured with an Ubbelohde viscometer at a temperature of 25 °C using a phenol-tetrachloroethane mixture as the solvent.

[0051] (2) Hue: After the pellet sample is treated at 80 °C for 1 hour, its Hunter L value (brightness), a value (hue of red - green), and b value (hue of yellow - blue) are measured using a color - view automatic color difference meter from BYK Gardner. Among them, the higher the L value, the greater the brightness; a high a value indicates that the polyester chip is more red, and a high b value indicates that the polyester chip is more yellow. For the present invention, a high L value and a low a / b value are desired.

[0052]

Example 1

[0053] Mix 230 g of terephthalic acid, 200 g of adipic acid, 400 g of 1,4 - butanediol, tetrabutyl titanate (the weight of titanium atoms is 60 ppm based on the amount of polyester produced), and hydroquinone (the weight of hydroquinone is 80 ppm based on the amount of polyester produced) to form a slurry, add it to a polymerization kettle, and carry out an esterification reaction. The esterification temperature gradually rises from 190 to 220 °C, the pressure is atmospheric pressure, and the water generated by the reaction is discharged through a rectification device. After the esterification ends (150 min), add triphenyl phosphate (the amount added is 80 ppm in terms of phosphorus element based on the amount of polyester produced) and tetrabutyl titanate (the weight of titanium atoms is 60 ppm based on the amount of polyester produced), and continue stirring for 10 minutes. Then evacuate to reduce the pressure to below 130 Pa, and at the same time gradually raise the temperature to 240 °C. When the system reaction reaches 150 min, stop the reaction. Then extrude the product from the bottom of the polymerization kettle, cool it, and pelletize it for performance testing.

[0054] The test results are listed in Table 1.

[0055]

Example 2

[0056] Mix 230 g of terephthalic acid, 200 g of adipic acid, 400 g of 1,4 - butanediol, tetrabutyl titanate (the weight of titanium atoms is 60 ppm based on the amount of polyester produced), and hydroquinone (the weight of hydroquinone is 160 ppm based on the amount of polyester produced) to form a slurry, add it to a polymerization kettle, and carry out an esterification reaction. The esterification temperature gradually rises from 190 to 220 °C, the pressure is atmospheric pressure, and the water generated by the reaction is discharged through a rectification device. After the esterification ends (150 min), add triphenyl phosphate (the amount added is 80 ppm in terms of phosphorus element based on the amount of polyester produced) and tetrabutyl titanate (the weight of titanium atoms is 60 ppm based on the amount of polyester produced), and continue stirring for 10 minutes. Then evacuate to reduce the pressure to below 130 Pa, and at the same time gradually raise the temperature to 240 °C. When the system reaction reaches 150 min, stop the reaction. Then extrude the product from the bottom of the polymerization kettle, cool it, and pelletize it for performance testing.

[0057] The test results are listed in Table 1.

[0058]

Example 3

[0059] 230 g of terephthalic acid, 200 g of adipic acid, 400 g of 1,4-butanediol, tetrabutyl titanate (the weight of titanium atoms is 60 ppm based on the amount of polyester produced), and hydroquinone (the weight of hydroquinone is 200 ppm based on the amount of polyester produced) were mixed to form a slurry, which was added to a polymerization kettle for esterification reaction. The esterification temperature was gradually increased from 190 to 220 °C at atmospheric pressure, and the water generated by the reaction was discharged through a rectification device. After the esterification was completed (150 min), triphenyl phosphate (the amount added, calculated as phosphorus element, was 80 ppm based on the amount of polyester produced) and tetrabutyl titanate (the weight of titanium atoms was 60 ppm based on the amount of polyester produced) were added, and stirring was continued for 10 minutes. Then, the pressure was reduced by vacuum to a system pressure below 130 Pa, and the temperature was gradually increased to 240 °C at the same time. When the system reaction reached 150 min, the reaction was stopped. Then, the product was extruded from the bottom of the polymerization kettle, cooled, and pelletized for performance testing.

[0060] The test results are listed in Table 1.

[0061]

Example 4

[0062] 230 g of terephthalic acid, 200 g of adipic acid, 400 g of 1,4-butanediol, tetrabutyl titanate (the weight of titanium atoms is 60 ppm based on the amount of polyester produced), and biphenol (the weight of biphenol is 80 ppm based on the amount of polyester produced) were mixed to form a slurry, which was added to a polymerization kettle for esterification reaction. The esterification temperature was gradually increased from 190 to 220 °C at atmospheric pressure, and the water generated by the reaction was discharged through a rectification device. After the esterification was completed (150 min), triphenyl phosphate (the amount added, calculated as phosphorus element, was 80 ppm based on the amount of polyester produced) and tetrabutyl titanate (the weight of titanium atoms was 60 ppm based on the amount of polyester produced) were added, and stirring was continued for 10 minutes. Then, the pressure was reduced by vacuum to a system pressure below 130 Pa, and the temperature was gradually increased to 240 °C at the same time. When the system reaction reached 150 min, the reaction was stopped. Then, the product was extruded from the bottom of the polymerization kettle, cooled, and pelletized for performance testing.

[0063] The test results are listed in Table 1.

[0064]

Example 5

[0065] 230 g of terephthalic acid, 200 g of adipic acid, 400 g of 1,4-butanediol, a citric acid chelated titanium-based catalyst (the weight of titanium atoms is 120 ppm based on the amount of polyester produced. For the preparation method of the catalyst, refer to Example 1 of CN 116003764 A), and hydroquinone (the weight of hydroquinone is 80 ppm based on the amount of polyester produced) are mixed to form a slurry, which is added to a polymerization kettle for esterification reaction. The esterification temperature gradually rises from 190 to 220 °C, the pressure is atmospheric pressure, and the water generated by the reaction is discharged through a rectification device. After the esterification is completed (150 min), triphenyl phosphate (the amount of triphenyl phosphate added in terms of phosphorus element is 80 ppm based on the amount of polyester produced) is added, and stirring is continued for 10 minutes. Then, the pressure is reduced by vacuum to make the system pressure lower than 130 Pa, and at the same time, the temperature is gradually raised to 240 °C. When the system reaction reaches 150 min, the reaction is stopped. Then, the product is extruded from the bottom of the polymerization kettle, cooled, and pelletized for performance testing.

[0066] The test results are listed in Table 1.

[0067]

Example 6

[0068] 270 g of terephthalic acid, 165 g of adipic acid, 400 g of 1,4-butanediol, tetraisopropyl titanate (the weight of titanium atoms is 50 ppm based on the amount of polyester produced), and hydroquinone (the weight of hydroquinone is 70 ppm based on the amount of polyester produced) are mixed to form a slurry, which is added to a polymerization kettle for esterification reaction. The esterification temperature gradually rises from 190 to 220 °C, the pressure is atmospheric pressure, and the water generated by the reaction is discharged through a rectification device. After the esterification is completed (150 min), triethyl phosphate (the amount of triphenyl phosphate added in terms of phosphorus element is 70 ppm based on the amount of polyester produced) and tetrabutyl titanate (the weight of titanium atoms is 60 ppm based on the amount of polyester produced) are added, and stirring is continued for 10 minutes. Then, the pressure is reduced by vacuum to make the system pressure lower than 150 Pa, and at the same time, the temperature is gradually raised to 240 °C. When the system reaction reaches 150 min, the reaction is stopped. Then, the product is extruded from the bottom of the polymerization kettle, cooled, and pelletized for performance testing.

[0069] The test results are listed in Table 1.

[0070]

Example 7

[0071] 183 g of terephthalic acid, 240 g of adipic acid, 350 g of 1,4-butanediol, tetraethyl titanate (the weight of titanium atoms is 60 ppm based on the amount of polyester produced), and hydroquinone (the weight of hydroquinone is 90 ppm based on the amount of polyester produced) were mixed to form a slurry, which was added to a polymerization kettle for esterification reaction. The esterification temperature was gradually increased from 190 to 220 °C at atmospheric pressure, and the water generated by the reaction was discharged through a rectification device. After the esterification was completed (150 min), trimethyl phosphate (the amount added, calculated as phosphorus element, was 90 ppm based on the amount of polyester produced) and tetraethyl titanate (the weight of titanium atoms was 60 ppm based on the amount of polyester produced) were added, and stirring was continued for 10 minutes. Then, the pressure was reduced by vacuum to a system pressure below 150 Pa, and the temperature was gradually increased to 240 °C at the same time. When the system reaction reached 150 min, the reaction was stopped. Then, the product was extruded from the bottom of the polymerization kettle, cooled, and pelletized for performance testing.

[0072] The test results are listed in Table 1.

[0073]

Comparative Example 1

[0074] 230 g of terephthalic acid, 200 g of adipic acid, 400 g of 1,4-butanediol, and tetrabutyl titanate (the weight of titanium atoms is 60 ppm based on the amount of polyester produced) were mixed to form a slurry, which was added to a polymerization kettle for esterification reaction. The esterification temperature was gradually increased from 190 to 220 °C at atmospheric pressure, and the water generated by the reaction was discharged through a rectification device. After the esterification was completed (150 min), tetrabutyl titanate (the weight of titanium atoms was 60 ppm based on the amount of polyester produced) was added, and stirring was continued for 10 minutes. Then, the pressure was reduced by vacuum to a system pressure below 130 Pa, and the temperature was gradually increased to 240 °C at the same time. When the system reaction reached 150 min, the reaction was stopped. Then, the product was extruded from the bottom of the polymerization kettle, cooled, and pelletized for performance testing.

[0075] The test results are listed in Table 1.

[0076]

Comparative Example 2

[0077] 230 g of terephthalic acid, 200 g of adipic acid, 400 g of 1,4-butanediol, tetrabutyl titanate (the weight of titanium atoms is 60 ppm based on the amount of polyester produced) were mixed to form a slurry, which was added to a polymerization kettle for esterification reaction. The esterification temperature was gradually increased from 190 to 220 °C at atmospheric pressure, and the water generated by the reaction was discharged through a rectification device. After the esterification was completed (150 min), triphenyl phosphate (the addition amount was 80 ppm based on the amount of polyester produced, calculated as phosphorus element) and tetrabutyl titanate (the weight of titanium atoms was 60 ppm based on the amount of polyester produced) were added, and stirring was continued for 10 minutes. Then, the pressure was reduced by vacuum to a system pressure below 130 Pa, and the temperature was gradually increased to 240 °C at the same time. When the system reaction reached 150 min, the reaction was stopped. Then, the product was extruded from the bottom of the polymerization kettle, cooled, and pelletized for performance testing.

[0078] The test results are listed in Table 1.

[0079]

Comparative Example 3

[0080] 230 g of terephthalic acid, 200 g of adipic acid, 400 g of 1,4-butanediol, and a citric acid chelated titanium-based catalyst (the weight of titanium atoms was 120 ppm based on the amount of polyester produced. The preparation method of the catalyst can be referred to Example 1 of CN 116003764 A) were mixed to form a slurry, which was added to a polymerization kettle for esterification reaction. The esterification temperature was gradually increased from 190 to 220 °C at atmospheric pressure, and the water generated by the reaction was discharged through a rectification device. After the esterification was completed (150 min), triphenyl phosphate (the addition amount was 80 ppm based on the amount of polyester produced, calculated as phosphorus element) was added, and stirring was continued for 10 minutes. Then, the pressure was reduced by vacuum to a system pressure below 130 Pa, and the temperature was gradually increased to 240 °C at the same time. When the system reaction reached 150 min, the reaction was stopped. Then, the product was extruded from the bottom of the polymerization kettle, cooled, and pelletized for performance testing.

[0081] The test results are listed in Table 1.

[0082] Table 1:

[0083]

[0084] It can be seen from Table 1 that:

[0085] (1) In Comparative Example 1, due to the absence of stabilizers and phenolic compounds (especially diphenolic compounds), the resulting chips had a poor hue, a low L value, and a high a / b value. Compared with Comparative Example 1, in Comparative Example 2, stabilizers were added, and the chip hue was improved well.

[0086] (2) Compared with Comparative Examples 2 and 3, further adding phenolic compounds (especially diphenolic compounds) on the basis of stabilizers in Examples 1-5 can further improve the hue quality of the polyester. When the viscosities are comparable, L is higher and a / b is lower.

[0087] In summary, adding a certain amount of phenolic compounds (especially diphenolic compounds) during polymerization as described in the present invention can further improve the hue of the chips on the basis of stabilizers, showing good technical effects.

[0088] The present invention has been described in detail above in combination with specific embodiments and exemplary examples. However, these descriptions should not be construed as limiting the present invention. Those skilled in the art understand that without departing from the spirit and scope of the present invention, various equivalent substitutions, modifications or improvements can be made to the technical solutions and their implementation manners of the present invention, and these all fall within the scope of the present invention. The protection scope of the present invention is subject to the appended claims.

Claims

1. A method for preparing an adipic acid copolyester, comprising: reacting raw materials including dibasic acids and diols in the presence of a phenolic compound, wherein the dibasic acid includes adipic acid.

2. The preparation method according to claim 1, characterized in that the dibasic acid further optionally includes other dibasic acids besides adipic acid. Preferably, the other dibasic acids are selected from at least one of aromatic dibasic acids and aliphatic dibasic acids other than adipic acid. More preferably, the other dibasic acids are selected from at least one of terephthalic acid, isophthalic acid, phthalic acid, and dibasic acids having 2 to 10 carbon atoms.

3. The preparation method according to claim 2, characterized in that when the other dibasic acid is contained, based on the total molar amount of 100% of the adipic acid and the other dibasic acid, the molar proportion of adipic acid is 10 - 90%, preferably 40 - 60%; the molar proportion of the other dibasic acid is 10 - 90%, preferably 40 - 60%.

4. The preparation method according to claim 2, characterized in that the diol is selected from at least one of diols having 2 to 12 carbon atoms, preferably at least one of diols having 2 to 6 carbon atoms; more preferably, the molar ratio of the diol to the dibasic acid is (1.1 - 2):

1.

5. The preparation method according to claim 1, characterized in that the phenolic compound is selected from at least one of diphenolic compounds, and is selected from at least one of hydroquinone and / or its derivatives, resorcinol and / or its derivatives, catechol and / or its derivatives, and biphenol and / or its derivatives; more preferably, based on 100 wt% of the theoretical yield of the adipic acid copolymer, the weight dosage of the phenolic compound is 20 - 300 ppm.

6. The preparation method according to claim 1, characterized in that the reaction is further carried out in the presence of a catalyst, and the catalyst is selected from titanium-based catalysts; preferably, the titanium-based catalysts are selected from at least one of titanate compounds and chelated titanium compounds, and more preferably from at least one of tetraethyl titanate, tetrapropyl titanate, tetrabutyl titanate, titanium lactate, and titanium citrate; preferably, based on 100 wt% of the theoretical yield of the adipic acid copolyester, the dosage of the catalyst is 50 - 200 ppm in terms of the weight of titanium element in the catalyst.

7. The preparation method according to any one of claims 1 - 6, characterized in that a stabilizer is further added in the reaction, and the stabilizer is selected from phosphorus compounds; preferably, the phosphorus compounds are selected from at least one of phosphoric acid, trimethyl phosphate, triethyl phosphate, tripropyl phosphate, triisopropyl phosphate, tributyl phosphate, dibutyl phosphate, and triphenyl phosphate; more preferably, based on 100 wt% of the theoretical yield of the adipic acid copolyester, the weight dosage of the stabilizer is 10 - 200 ppm, preferably 20 - 100 ppm in terms of the weight of phosphorus element in the stabilizer.

8. The preparation method according to claim 7, characterized in that the reaction includes an esterification process and a polycondensation process.

9. The preparation method according to claim 8, characterized in that The dibasic acid, the diol and the catalyst are added during the esterification process, and / or, The catalyst is optionally added during the polycondensation process, and / or, The stabilizer is added during the esterification process and / or the polycondensation process, and / or, The phenolic compound is added during the esterification process and / or the polycondensation process.

10. According to the preparation method described in claim 8, It is characterized in that The conditions of the esterification process include: temperature 160-240°C, time 60-180 min; and / or, The conditions of the polycondensation process include: temperature 220-260°C, time 60-180 min, pressure <1 kPa.

11. An adipic acid copolyester obtained by using the preparation method described in any one of claims 1-10.

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