Polyester material and preparation method thereof

Abstract

The invention provides a polyester material and a preparation method thereof. The preparation method comprises the following steps: S1, mixing an acid monomer, dihydric alcohol, a catalyst and a stabilizer, and carrying out esterification reaction to obtain an esterification product; s2, carrying out condensation polymerization on the esterification product under a negative pressure condition to obtain a condensation polymerization product melt; s3, mixing the polycondensation product melt with an active auxiliary agent, and carrying out melt condensation to obtain polyester; wherein the active auxiliary agent is a bifunctional epoxy compound. The bifunctional epoxy compound is added as an active auxiliary agent and can react with terminal hydroxyl groups and carboxyl groups in a system, so that the occurrence of formation of cyclic oligomers by the terminal hydroxyl groups and the carboxyl groups in the system is reduced, the content of the oligomers in the polyester is reduced, the migration amount of the oligomers in the polyester is reduced, and the yield of the polyester is improved. Therefore, the polyester is more suitable for preparing products in contact with food, and the application field of the polyester is further widened. In addition, the preparation method is simple and easy to operate and has a good application prospect.

Description

Technical Field

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

[0002] Polyester is a synthetic polymer material widely used in various industries. Due to its excellent physical properties, chemical stability and processing performance, polyester is widely used around the world. For example, polybutylene succinate (PBS) has a high heat deformation temperature (HDT), and the use temperature of its materials and products exceeds 100°C. It is the only type of biodegradable plastic suitable for contact with hot food. It has extremely high popularity and broad application prospects in hot food fields such as paper cup coating, milk tea straws, disposable tableware, coffee capsules, etc.

[0003] However, in terms of current synthesis technology, the two monomers of aliphatic dicarboxylic acid and aliphatic diol will inevitably undergo cyclization during the synthesis process of polyester prepared by polycondensation reaction, and the hydroxyl and carboxyl groups at the ends of the two monomers will undergo esterification to form annular oligomers. These cyclic oligomers are easy to migrate and diffuse. When polyester products are used in food contact areas, there is a risk that such cyclic impurities will precipitate from plastics into food, which may not only cause the overall migration amount of food contact to exceed the limit value of the regulations (GB 4806.7-2016 The limit requirement for the total migration amount of plastic products (10mg / dm 2 )), and there are extremely high risks to food safety.

[0004] At present, some methods for the above-mentioned problems are disclosed, such as the patent application with publication number CN 117402341 A, which discloses a production process of recyclable food-grade PBS polyester, wherein PBS is extracted with methanol to reduce the migratable substances in the polyester, but the method of using methanol extraction will cause problems such as uncontrollable molecular weight of the polymer, solvent residue, and uncontrollable changes in mechanical properties. The patent application with publication number CN 114957201 A discloses a method for preparing polybutylene succinate (PBS) with low cyclic byproducts, wherein the generation of byproducts is suppressed by the synergistic effect of a catalyst Schiff base titanium complex and an auxiliary quaternary phosphonium salt, but the method involves the synthesis of a complex catalyst, the process is complicated, and it is not easy to operate. Summary of the invention

[0005] The main purpose of the present invention is to provide a polyester material and a preparation method thereof, so as to solve the problem that the polyester material in the prior art easily generates small molecules that are easy to migrate and diffuse.

[0006] In order to achieve the above-mentioned purpose, according to one aspect of the present invention, a method for preparing a polyester material is provided, and the method comprises: step S1, mixing an acid monomer, a diol, a catalyst and a stabilizer to carry out an esterification reaction to obtain an esterification product; step S2, carrying out a polycondensation reaction of the esterification product under negative pressure conditions to obtain a polycondensation product melt; step S3, mixing the polycondensation product melt with an active auxiliary agent to carry out melt condensation to obtain a polyester; wherein the active auxiliary agent is a difunctional epoxy compound.

[0007] Furthermore, the acid monomer is a monomer that can provide double-terminal carboxyl groups. Preferably, the acid monomer includes any one or more of terephthalic acid, succinic acid, succinic anhydride and dimethyl succinate;

[0008] The diol includes any one or more of ethylene glycol, 1,3-propylene glycol and 1,4-butanediol;

[0009] The molar ratio of the acid monomer to the diol is 1:1.2 to 1:1.8;

[0010] The catalyst is a titanate catalyst;

[0011] The stabilizer is a phosphorus-containing heat stabilizer.

[0012] Further, the catalyst includes any one or more of tetrabutyl titanate, tetraisopropyl titanate and tetraethyl titanate;

[0013] The amount of the catalyst used is 0.3-2 wt % of the mass of the acid monomer, preferably 0.5-1.5 wt %.

[0014] Further, the stabilizer includes any one or more of phosphoric acid, trimethyl phosphate and triphenyl phosphate;

[0015] The phosphorus content of the stabilizer is 10-100 ppm, preferably 20-60 ppm, based on the theoretical mass of the polyester produced.

[0016] Further, the amount of the coagent is 0.5-3wt% of the weight of the acid monomer, preferably 1-2wt%;

[0017] The active auxiliary agent includes one or more of diglycidyl adipate and 1,4-butanediol diglycidyl ether.

[0018] Further, the temperature of the esterification reaction is 130-220°C;

[0019] Preferably, the esterification reaction is completed when the amount of by-products distilled out during the esterification reaction is more than 95% of the theoretical amount of by-products.

[0020] Further, the polycondensation reaction temperature is 220-290°C and the time is 3-8h;

[0021] The vacuum degree during the polycondensation reaction is less than 100Pa.

[0022] Further, the polyester material has a polyester intrinsic viscosity of 1.0 to 1.66 dL / g;

[0023] The oligomer content of the polyester material is less than 1.0%.

[0024] Furthermore, the polyester migration amount of the polyester material is less than 10 mg / dm 2 .

[0025] In order to achieve the above object, according to one aspect of the present invention, a polyester material is provided. The polyester material is prepared by any one of the above preparation methods.

[0026] By applying the technical solution of the present invention, a bifunctional epoxy compound is added as an active auxiliary agent. Since it contains two epoxy groups, a secondary hydroxyl group can be generated in the reaction process with the carboxyl group, and then reacts with the carboxyl group as an active point to generate a long branched chain; the active auxiliary agent of this structure is melt-condensed with the polycondensation product, and can react with the terminal hydroxyl group and the carboxyl group in the system, reducing the occurrence of the formation of cyclic oligomers by the terminal hydroxyl group and the terminal carboxyl group in the system, thereby reducing the oligomer content in the polyester, reducing the migration amount of the oligomer in the polyester, making it more suitable for the preparation of products in contact with food, and further broadening the application field of polyester. Moreover, the above-mentioned preparation method is simple and easy to operate, and has a good application prospect. DETAILED DESCRIPTION

[0027] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0028] As analyzed in the background technology of this application, there is a problem in the prior art that polyester materials are prone to produce small molecules that are easy to migrate and diffuse, which limits their use in food contact materials or brings safety hazards. In order to solve this problem, this application provides a polyester material and a preparation method thereof.

[0029] According to a typical embodiment of the present application, a method for preparing a polyester material is provided, and the method comprises: step S1, mixing an acid monomer, a diol, a catalyst and a stabilizer to carry out an esterification reaction to obtain an esterification product; step S2, carrying out a polycondensation reaction of the esterification product under negative pressure conditions to obtain a polycondensation product melt; step S3, mixing the polycondensation product melt with an active auxiliary agent to carry out melt condensation to obtain a polyester; wherein the active auxiliary agent is a difunctional epoxy compound.

[0030] The preparation method of the present application adds a bifunctional epoxy compound as an active auxiliary agent. Since it contains two epoxy groups, a secondary hydroxyl group can be generated during the reaction with the carboxyl group, and then reacts with the carboxyl group as an active point to produce a long branched chain; the active auxiliary agent of this structure is melt-condensed with the polycondensation product, and can react with the terminal hydroxyl group and carboxyl group in the system, reducing the occurrence of the formation of cyclic oligomers by the terminal hydroxyl group and the terminal carboxyl group in the system, thereby reducing the oligomer content in the polyester, reducing the migration amount of the oligomer in the polyester, making it more suitable for the preparation of products in contact with food, and further broadening the application field of polyester. Moreover, the above preparation method is simple and easy to operate, and has a good application prospect.

[0031] The above-mentioned bifunctional epoxy compound used as an active auxiliary agent is a compound having two epoxy groups, and there is no limitation on the specific type, and those skilled in the art can select it from the existing technology. Compounds having one epoxy group cannot play a good branching role, and compounds having more than two epoxy functional groups will introduce a cross-linking reaction, so that the intrinsic viscosity of the prepared polyester material is higher or gelation occurs, which is not conducive to the application of polyester processing as food contact materials.

[0032] The acid monomer is a monomer that can provide a double-terminal carboxyl group, and can be a carboxylic acid or anhydride having a double-terminal carboxyl group, or an ester monomer that can provide a double-terminal carboxyl group, or a monomer containing both a carboxylic acid group and an ester group. In some typical embodiments of the present application, the acid monomer includes any one or more of terephthalic acid, succinic acid, succinic anhydride, and dimethyl succinate, which are relatively cheap and easy to obtain, and the polyester material prepared by the method of the present application meets the relevant requirements of food contact grade polyester.

[0033] The type of diol can be selected from those in the prior art. For example, the diol includes but is not limited to any one or more of ethylene glycol, 1,3-propylene glycol and 1,4-butanediol.

[0034] In some preferred embodiments of the present application, the molar ratio of the acid monomer to the diol is 1:1.2 to 1:1.8, specifically 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, etc., but is not limited thereto.

[0035] In some embodiments of the present application, the catalyst is a titanate catalyst. The specific type of the titanate catalyst can be selected from the prior art. For example, the titanate catalyst includes but is not limited to any one or more of tetrabutyl titanate, tetraisopropyl titanate and tetraethyl titanate. Preferably, the amount of the catalyst is 0.3-2wt% of the mass of the acid monomer, and more preferably 0.5-1.5wt%, which can better play the role of the catalyst and accelerate the reaction rate.

[0036] In some embodiments of the present application, the stabilizer is a phosphorus-containing heat stabilizer, for example, the stabilizer includes but is not limited to any one or more of phosphoric acid, trimethyl phosphate and triphenyl phosphate.

[0037] Based on the theoretical mass of the polyester produced, the stabilizer has a phosphorus content of 10-100 ppm, preferably 20-60 ppm, which helps to improve the stability of the polyester material.

[0038] In order to better play the role of the active auxiliary and further reduce the mobility of the polyester material, the amount of the active auxiliary is 0.5-3wt% of the weight of the acid monomer, preferably 1-2wt%, specifically 1wt%, 1.1wt%, 1.2wt%, 1.3wt%, 1.4wt%, 1.5wt%, 1.6wt%, 1.7wt%, 1.8wt%, 1.9wt%, 2.0wt%, etc., and can also be other values ​​within the above range.

[0039] In some embodiments of the present application, the active auxiliary agent includes one or more of diglycidyl adipate and 1,4-butanediol diglycidyl ether, which, after melt condensation with the polycondensation product, can effectively reduce the occurrence of cyclic oligomers formed by terminal hydroxyl groups and terminal carboxyl groups in the system, thereby further reducing the migration amount of oligomers in the polyester.

[0040] In some embodiments of the present application, the temperature of the esterification reaction is 130-220°C, specifically 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, etc., and of course, it can also be other values ​​within the above range, or the temperature of the esterification reaction is variable, such as gradually increasing within a certain range within the above range.

[0041] In some embodiments of the present application, the esterification reaction is completed when the amount of by-products distilled out in the esterification reaction is more than 95% of the theoretical amount of by-products (for example, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, etc., but not limited to this), and the above-mentioned by-products can be water or alcohol or a mixture of the two. For example, when the acid monomer is a carboxylic acid or anhydride having a double-terminal carboxyl group, the by-product is water, and when the acid monomer is an ester that can provide a double-terminal carboxyl group, the by-product is alcohol.

[0042] After the esterification reaction is completed, the esterification product is subjected to a polycondensation reaction under vacuum conditions. In some embodiments of the present application, the temperature of the polycondensation reaction is 220-290°C and the time is 3-8h. Specifically, the temperature of the polycondensation reaction can be 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, 290°C, etc., but is not limited thereto, and the time of the polycondensation reaction can be 3h, 4h, 5h, 6h, 7h, 8h, etc., or other values ​​within the above range.

[0043] In some embodiments of the present application, the vacuum degree during the polycondensation reaction is less than 100 Pa, so that the reaction equilibrium proceeds in the direction of the polycondensation product, further accelerating the rate of the polycondensation reaction.

[0044] After the polycondensation reaction is completed, the present application adds an active auxiliary to the polycondensation product. The active auxiliary can react with the terminal carboxyl group and produce long chain branches, which can more effectively reduce the occurrence of cyclic oligomers formed by terminal hydroxyl groups and terminal carboxyl groups in the system, thereby further reducing the migration amount of oligomers in the polyester.

[0045] In some embodiments of the present application, the above-mentioned melt condensation is carried out under stirring conditions, and preferably, the stirring time is 5 to 20 minutes.

[0046] In some embodiments of the present application, the polyester characteristic viscosity of the polyester material prepared by the above method of the present application is 1.0-1.66dL / g, specifically 1.0dL / g, 1.1dL / g, 1.2dL / g, 1.3dL / g, 1.4dL / g, 1.5dL / g, 1.6dL / g, etc., or other values ​​within the above range.

[0047] In some embodiments of the present application, the oligomer content of the polyester material is less than 1.0%, and the lower oligomer content makes it have a lower mobility. Specifically, the oligomer content of the polyester material can be 0.1%, 0.2%, 0.3%, 0.4%, 0.45%, 0.5%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, etc., or other values ​​within the above range.

[0048] In some typical embodiments of the present application, the polyester migration amount of the prepared polyester material is less than 10 mg / dm 2 , meets the GB 4806.7-2016 food contact standard, and broadens the application areas of polyester.

[0049] According to another typical embodiment of the present application, a polyester material is provided. The polyester material is prepared by any one of the above-mentioned preparation methods.

[0050] Since the above preparation method adds a bifunctional epoxy compound as an active auxiliary agent, since it contains two epoxy groups, a secondary hydroxyl group can be generated during the reaction with the carboxyl group, and then reacts with the carboxyl group as an active point to generate a long branched chain; the active auxiliary agent with this structure is melt-condensed with the condensation product melt, and can react with the terminal hydroxyl group and carboxyl group in the system, thereby reducing the occurrence of the terminal hydroxyl group and the terminal carboxyl group in the system to form an annular oligomer, reducing the oligomer content in the polyester, thereby reducing the migration amount of the oligomer in the polyester material, making it more suitable for the preparation of products in contact with food, and further broadening the application field of the polyester material.

[0051] In some embodiments of the present application, the polyester characteristic viscosity of the polyester material prepared by the above method of the present application is 1.0-1.66dL / g, specifically 1.0dL / g, 1.1dL / g, 1.2dL / g, 1.3dL / g, 1.4dL / g, 1.5dL / g, 1.6dL / g, etc., or other values ​​within the above range.

[0052] In some embodiments of the present application, the oligomer content of the polyester material is less than 1.0%, and the mobility is less than 10 mg / dm 2 .

[0053] The beneficial effects that can be achieved by the present application will be further illustrated below in combination with embodiments and comparative examples.

[0054] In the examples and comparative examples of the application, the basic properties of the polyester material were tested by the following methods:

[0055] (1) Migration: Referring to GB / T 31604.1-2015, a certain mass of polyester chips was immersed in a 70°C aqueous solution containing 50% ethanol and boiled for 2 h, and the mass loss was calculated.

[0056] (2) Oligomer content: Add a certain amount of polyester chips, prepare a mixed solvent of chloroform and 1,4-dioxane (the volume ratio of the two is 1:2) and add it to the reaction bottle, set up a Soxhlet extraction device, gradually increase the temperature to reflux, and stop after reflux for 18 hours. The liquid in the reaction bottle is rotary evaporated to remove the solvent, and finally the rotary evaporator is vacuum dried in a vacuum oven at 50°C for 2 hours, and the oligomer content is calculated based on the mass difference before and after the bottle.

[0057] (3) Intrinsic viscosity: Phenol-tetrachloroethane with a mass ratio of 6:4 is used as the solvent. The viscosity is measured using an Ubbelohde viscometer in a constant temperature bath at 25°C. A 0.5 g sample is placed in a 100 ml volumetric flask and dissolved. The outflow time of the pure solvent and the solution is measured, and the intrinsic viscosity is calculated according to the formula.

[0058]

[0059] Here, ηr is the relative viscosity, c is the solution concentration, and [η] is the intrinsic viscosity.

[0060] Example 1

[0061] In a 1L polyester kettle, 350g of succinic anhydride, 472.8g of 1,4-butanediol, 3.5g of tetraisopropyl titanate and 0.19g of phosphoric acid were added, stirred at a constant speed, and the temperature was gradually raised to 190°C. When the amount of by-product water distilled out in the reactor reached 95% of the theoretical water output, the esterification process was completed. The reactor was gradually evacuated to a vacuum degree of 2000Pa within 1h, and then gradually evacuated to 10Pa, and the temperature was raised to 250°C for polycondensation reaction. The reaction was continued for 5h, and 4.2g of diglycidyl adipic acid was added and stirred for 10min to obtain a polymer melt, which was then water-cooled and pelletized to obtain polyester.

[0062] The synthetic polyester has an intrinsic viscosity of 1.55 dL / g, an oligomer content of 0.64%, and a mobility of 6 mg / dm 2 .

[0063] Example 2

[0064] In a 1L polyester kettle, 350g of succinic anhydride, 472.8g of 1,4-butanediol, 7.0g of tetraethyl titanate and 0.19g of triphenyl phosphate were added, stirred at a constant speed, and the temperature was gradually raised to 190°C. When the amount of by-product water distilled out in the reactor reached 95% of the theoretical water output, the esterification process was completed. The reactor was gradually evacuated to a vacuum degree of 2000Pa within 1h, and then gradually evacuated to 10Pa, and the temperature was raised to 250°C for polycondensation reaction. The reaction was reacted for 3h, 4.2g of diglycidyl adipic acid was added and stirring was continued for 10min to obtain a polymer melt, which was then water-cooled and pelletized to obtain polyester.

[0065] The synthetic polyester has an intrinsic viscosity of 1.28 dL / g, an oligomer content of 0.72%, and a mobility of 8 mg / dm 2 .

[0066] Example 3

[0067] In a 1L polyester kettle, 350g of succinic anhydride, 567.4g of 1,4-butanediol, 3.5g of tetraisopropyl titanate and 0.06g of triphenyl phosphate were added, stirred at a constant speed, and the temperature was gradually raised to 190°C. When the amount of by-product water distilled out in the reactor reached 95% of the theoretical water output, the esterification process was completed. The reactor was gradually evacuated to a vacuum degree of 2000Pa within 1h, and then gradually evacuated to 10Pa, and the temperature was raised to 250°C for polycondensation reaction. The reaction was continued for 5h, and 4.2g of 1,4-butanediol diglycidyl ether was added and stirred for 5min to obtain a polymer melt, which was water-cooled and pelletized to obtain polyester.

[0068] The synthetic polyester has an intrinsic viscosity of 1.30 dL / g, an oligomer content of 0.70%, and a mobility of 7 mg / dm 2 .

[0069] Example 4

[0070] In a 1L polyester kettle, 413g of succinic acid, 472.8g of 1,4-butanediol, 0.82g of tetraisopropyl titanate and 0.19g of triphenyl phosphate were added, stirred at a constant speed, and the temperature was gradually raised to 200°C. When the amount of by-product water distilled out in the reactor reached 95% of the theoretical water output, the esterification process was completed. The reactor was gradually evacuated to a vacuum degree of 2000Pa within 1h, and then gradually evacuated to 10Pa, and the temperature was raised to 220°C for polycondensation reaction. The reaction was carried out for 8h, and 4.96g of diglycidyl adipate was added and stirring was continued for 10min to obtain a polymer melt, which was then water-cooled and pelletized to obtain polyester.

[0071] The synthetic polyester has an intrinsic viscosity of 1.34 dL / g, an oligomer content of 0.68%, and a mobility of 7 mg / dm 2 .

[0072] Example 5

[0073] In a 1L polyester kettle, 511g of dimethyl succinate, 472.8g of 1,4-butanediol, 5.1g of tetraisopropyl titanate and 0.19g of triphenyl phosphate were added, stirred at a constant speed, and the temperature was gradually raised to 168°C. When the amount of by-product methanol distilled out in the reactor reached 95% of the theoretical production amount, the esterification process was completed. The reactor was gradually evacuated to a vacuum degree of 2000Pa within 1h, and then gradually evacuated to 10Pa, and the temperature was raised to 240°C for polycondensation reaction. The reaction was continued for 5h, and 6.13g of diglycidyl adipate was added and stirred for 10min to obtain a polymer melt. The polyester was obtained by water cooling and pelletizing.

[0074] The synthetic polyester has an intrinsic viscosity of 1.34 dL / g, an oligomer content of 0.77%, and a mobility of 7 mg / dm 2 .

[0075] Example 6

[0076] In a 1L polyester kettle, 350g of succinic anhydride, 472.8g of 1,4-butanediol, 3.5g of tetrabutyl titanate and 0.63g of triphenyl phosphate were added, stirred at a constant speed, and the temperature was gradually raised to 190°C. When the amount of by-product water distilled out in the reactor reached 95% of the theoretical water output, the esterification process was completed. The reactor was gradually evacuated to a vacuum degree of 2000Pa within 1h, and then gradually evacuated to 10Pa, and the temperature was raised to 250°C for polycondensation reaction. The reaction was continued for 5h, and 4.2g of diglycidyl adipic acid was added and stirred for 10min to obtain a polymer melt, which was then water-cooled and pelletized to obtain polyester.

[0077] The synthetic polyester has an intrinsic viscosity of 1.27 dL / g, an oligomer content of 0.73%, and a mobility of 7 mg / dm 2 .

[0078] Example 7

[0079] In a 1L polyester kettle, 581.0g of terephthalic acid, 243.5g of 1,4-butanediol, 93.1g of ethylene glycol, 3.5g of tetrabutyl titanate and 0.19g of trimethyl phosphate were added, stirred at a constant speed, and the temperature was gradually raised to 250°C. When the amount of by-product water distilled out in the reactor reached 95% of the theoretical water output, the esterification process was completed. The reactor was gradually evacuated to a vacuum degree of 2000Pa within 1h, and then gradually evacuated to 10Pa, and the temperature was raised to 290°C for polycondensation reaction. The reaction was continued for 5h, and 4.2g of diglycidyl adipic acid was added and stirred for 10min to obtain a polymer melt. The polyester chips were obtained by water cooling and pelletizing.

[0080] The synthetic polyester has an intrinsic viscosity of 1.0 dL / g, an oligomer content of 0.93%, and a mobility of 9 mg / dm 2 .

[0081] Example 8

[0082] In a 1L polyester kettle, 581.0g of terephthalic acid, 337.6g of 1,4-butanediol, 114.2g of 1,3-propylene glycol, 3.5g of tetrabutyl titanate and 0.19g of triphenyl phosphate were added. The mixture was stirred at a constant speed and gradually heated to 240°C. When the amount of by-product water distilled out in the reactor reached 96% of the theoretical water output, the esterification process was completed. The reactor was gradually evacuated to a vacuum degree of 2000Pa within 1h, and then gradually evacuated to 10Pa. The temperature was raised to 270°C for polycondensation reaction. The reaction was continued for 5h, and 4.2g of diglycidyl adipic acid was added and stirring was continued for 20min to obtain a polymer melt. The polyester chips were obtained by water cooling and pelletizing.

[0083] The synthetic polyester has an intrinsic viscosity of 1.1 dL / g, an oligomer content of 0.85%, and a mobility of 6 mg / dm 2 .

[0084] Example 9

[0085] The difference from Example 1 is that the added amount of diglycidyl adipate is 3.5 g.

[0086] The synthetic polyester has an intrinsic viscosity of 1.45 dL / g, an oligomer content of 0.75%, and a mobility of 7.5 mg / dm 2 .

[0087] Example 10

[0088] The difference from Example 1 is that the added amount of diglycidyl adipate is 1.8 g.

[0089] The intrinsic viscosity of the synthesized polyester is 1.40 dL / g, the oligomer content is 0.95%, and the mobility is 9.6 mg / dm 2 .

[0090] Embodiment 11

[0091] The difference from Example 1 is that the added amount of diglycidyl adipate is 7 g.

[0092] The intrinsic viscosity of the synthesized polyester is 1.63 dL / g, the oligomer content is 0.59%, and the mobility is 5.9 mg / dm 2 .

[0093] Example 12

[0094] The difference from Example 1 is that the added amount of diglycidyl adipate is 10.5 g.

[0095] The intrinsic viscosity of the synthesized polyester is 1.66 dL / g, the oligomer content is 0.58%, and the mobility is 6.5 mg / dm 2 .

[0096] Example 13

[0097] In a 1L polyester kettle, 350g of succinic anhydride, 472.8g of 1,4-butanediol, 3.5g of tetraisopropyl titanate and 0.19g of phosphoric acid were added, stirred at a constant speed, and the temperature was gradually raised to 190°C. When the amount of by-product water distilled out in the reactor reached 95% of the theoretical water output, the esterification process was completed. The reactor was gradually evacuated to a vacuum degree of 2000Pa within 1h, and then gradually evacuated to 10Pa, and the temperature was raised to 250°C for polycondensation reaction. The reaction was reacted for 5h, and 4.2g of 1,6-hexanediol diglycidyl ether was added and stirred for 10min to obtain a polymer melt, which was water-cooled and pelletized to obtain polyester.

[0098] The intrinsic viscosity of the synthesized polyester is 1.40 dL / g, the oligomer content is 1.22%, and the mobility is 16.5 mg / dm 2 .

[0099] Comparative Example 1

[0100] In a 1L polyester kettle, 350g of succinic anhydride, 472.8g of 1,4-butanediol, 3.5g of tetraisopropyl titanate and 0.19g of phosphoric acid were added, stirred at a constant speed, and the temperature was gradually raised to 190°C. When the amount of by-product water distilled out in the reactor reached 95% of the theoretical water output, the esterification process was completed. The reactor was gradually evacuated to a vacuum degree of 2000Pa within 1h, and then gradually evacuated to 10Pa, and the temperature was raised to 250°C for polycondensation reaction. The reaction was carried out for 5h to obtain a polymer melt, which was water-cooled and pelletized to obtain polyester.

[0101] The synthetic polyester has an intrinsic viscosity of 1.42 dL / g, an oligomer content of 1.26%, and a mobility of 23 mg / dm 2 .

[0102] Comparative Example 2

[0103] In a 1L polyester kettle, 350g of succinic anhydride, 472.8g of 1,4-butanediol, 3.5g of tetraisopropyl titanate and 0.19g of phosphoric acid were added. The mixture was stirred at a constant speed and the temperature was gradually raised from 130°C to 190°C. When the amount of by-product water distilled out in the reactor reached 95% of the theoretical water output, the esterification process was completed. The reactor was gradually evacuated to a vacuum degree of 2000Pa within 1h, and then gradually evacuated to 10Pa. The temperature was raised to 250°C for polycondensation reaction. The reaction was continued for 5h. 4.2g of pentaerythritol was added and stirring was continued for 10min to obtain a polymer melt. The polyester was obtained by water cooling and pelletizing.

[0104] The intrinsic viscosity of the synthesized polyester is 1.58 dL / g, the oligomer content is 1.30%, and the mobility is 25 mg / dm 2 .

[0105] Comparative Example 3

[0106] In a 1L polyester kettle, 350g of succinic anhydride, 472.8g of 1,4-butanediol, 4.2g of diglycidyl adipate, 3.5g of tetraisopropyl titanate and 0.19g of phosphoric acid were added. The mixture was stirred at a constant speed and the temperature was gradually raised from 130°C to 190°C. When the amount of by-product water distilled out in the reactor reached 95% of the theoretical water output, the esterification process was completed. The reactor was gradually evacuated to a vacuum degree of 2000Pa within 1h, and then gradually evacuated to 10Pa. The temperature was raised to 250°C for polycondensation reaction. The reaction was continued for 5h to obtain a polymer melt, which was then water-cooled and pelletized to obtain polyester.

[0107] The intrinsic viscosity of the synthesized polyester is 0.98 dL / g, the oligomer content is 2.60%, and the mobility is 32 mg / dm 2 .

[0108] Comparative Example 4

[0109] In a 1L polyester kettle, 350g of succinic anhydride, 472.8g of 1,4-butanediol, 3.5g of tetraisopropyl titanate and 0.19g of phosphoric acid were added, and the temperature was gradually raised from 130°C to 190°C with constant stirring. When the amount of by-product water distilled out in the reactor reached 95% of the theoretical water output, the esterification process was completed. The reactor was gradually evacuated to a vacuum degree of 2000Pa within 1h, and then gradually evacuated to 10Pa, and the temperature was raised to 250°C for polycondensation reaction. The reaction was continued for 5h, and 4.2 trimethylolpropane triglycidyl ether was added and stirred for 10min to obtain a polymer melt, which was then water-cooled and pelletized to obtain polyester.

[0110] The intrinsic viscosity of the synthesized polyester is 1.87 dL / g (partial gel), the oligomer content is 0.89%, and the mobility is 15.8 mg / dm 2 .

[0111] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects: the preparation method of the present application adds a bifunctional epoxy compound as an active auxiliary agent. Since it contains two epoxy groups, a secondary hydroxyl group can be generated during the reaction with the carboxyl group, and then reacts with the carboxyl group as an active point to produce a long branched chain; the active auxiliary agent of this structure is melt-condensed with the polycondensation product, and can react with the terminal hydroxyl group and carboxyl group in the system, reducing the occurrence of the formation of cyclic oligomers by the terminal hydroxyl group and the terminal carboxyl group in the system, thereby reducing the oligomer content in the polyester, reducing the migration amount of the oligomer in the polyester, making it more suitable for the preparation of products in contact with food, and further broadening the application field of polyester. Moreover, the above preparation method is simple and easy to operate, and has a good application prospect.

[0112] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a polyester material, characterized in that: include: Step S1, mixing an acid monomer, a diol, a catalyst and a stabilizer to carry out an esterification reaction to obtain an esterification product; Step S2, the esterification product is subjected to a polycondensation reaction under negative pressure to obtain a polycondensation product melt; Step S3, mixing the polycondensation product melt with an active auxiliary agent for melt condensation to obtain the polyester; The active auxiliary agent is a bifunctional epoxy compound.

2. The method for preparing the polyester material according to claim 1, characterized in that: The acid monomer is a monomer that can provide double-terminal carboxyl groups. Preferably, the acid monomer includes any one or more of terephthalic acid, succinic acid, succinic anhydride and dimethyl succinate; The diol includes any one or more of ethylene glycol, 1,3-propylene glycol and 1,4-butanediol; The molar ratio of the acid monomer to the diol is 1:1.2 to 1:1.8; The catalyst is a titanate catalyst; The stabilizer is a phosphorus-containing heat stabilizer.

3. The method for preparing the polyester material according to claim 2, characterized in that: The catalyst includes any one or more of tetrabutyl titanate, tetraisopropyl titanate and tetraethyl titanate; The amount of the catalyst used is 0.3-2 wt % of the mass of the acid monomer, preferably 0.5-1.5 wt %.

4. The method for preparing the polyester material according to claim 2, characterized in that: The stabilizer includes any one or more of phosphoric acid, trimethyl phosphate and triphenyl phosphate; The phosphorus content of the stabilizer is 10-100 ppm, preferably 20-60 ppm, based on the theoretical mass of the polyester produced.

5. The method for preparing a polyester material according to claim 1, characterized in that: The amount of the active agent is 0.5-3wt% of the weight of the acid monomer, preferably 1-2wt%; The active auxiliary agent includes one or more of diglycidyl adipate and 1,4-butanediol diglycidyl ether.

6. The method for preparing a polyester material according to claim 1, characterized in that: The temperature of the esterification reaction is 130-220°C; Preferably, the esterification reaction is completed when the amount of by-products distilled out during the esterification reaction is more than 95% of the theoretical amount of by-products.

7. The method for preparing a polyester material according to claim 1, characterized in that: The polycondensation reaction temperature is 220-290°C and the time is 3-8h; The vacuum degree during the polycondensation reaction is less than 100 Pa.

8. The method for preparing a polyester material according to claim 1, characterized in that: The polyester intrinsic viscosity of the polyester material is 1.0 to 1.66 dL / g; The polyester material has an oligomer content of less than 1.0%.

9. The method for preparing a polyester material according to claim 1, characterized in that: The polyester migration amount of the polyester material is less than 10 mg / dm 2 .

10. A polyester material, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 9.

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