A low-extracting polyester and a method for preparing the same

Abstract

The application discloses a kind of low precipitation polyester and its preparation method, belong to high polymer field.This method with binary acid and binary alcohol as raw material, esterification is carried out under the action of catalyst, esterification is carried out under the condition that temperature is 260~275 DEG C after precondensation reaction, after precondensation reaction, final condensation reaction is carried out, and polyester base chip is obtained after reaction is finished;The polyester base chip is prepared low precipitation polyester finished chip after solid phase tackiness test.Compared with conventional polyester, the low precipitation polyester oligomer content prepared by the application is reduced to 0.1% or less from 1.2%, reduced by more than 90%, the haze fluctuation value of film after heating is reduced by more than 80%, fiber dyeing rate is increased by more than 20%, with the advantage of significantly reducing precipitate.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of high polymers, in particular to a low-extraction polyester and a preparation method thereof. BACKGROUND

[0002] As of 2020, the production capacity of polyethylene terephthalate (hereinafter referred to as polyester) in China has exceeded 600 million tons / year. Polyester is a material with excellent comprehensive performance and can be widely used in the fields of fibers, films, bottle blanks, engineering plastics, etc. With the continuous expansion of the application range of polyester, the requirements of downstream users for product quality are becoming higher and higher, and more and more attention is paid to the reduction of oligomers in polyester. It is hoped to further improve the quality of polyester and improve the processing performance and downstream application performance of polyester.

[0003] The molecular weight of polyester directly affects the final use field and purpose, and the content of oligomers in polyester also affects the processing and molding process and the weight of the product. In the spinning process, oligomers will form thermal decomposition products and condense on the spinning equipment, thereby polluting the spinneret and filter assembly, and forming fiber defects such as foreign matter deposited on the surface of the fiber, thereby degrading the quality of the product. In the heat setting process of textile processing, the oligomers on the surface of the fiber will form "small particles", affecting the heat setting and dyeing and finishing effects. In the film processing process, when the high-temperature PET melt with pressure is extruded from the die, due to the sudden change of temperature and pressure, part of the oligomers will volatilize and condense on the attached silk or attached tape of the die, which will cause uneven attachment and reduce the attachment effect, and in severe cases, the attached silk or tape will be broken and the film will be broken. At the same time, it will also pollute the die and produce longitudinal stripes, and the oligomers will deposit on the surface of the roller, affecting the quality of the film, so it is necessary to stop and clean the machine from time to time. In addition, high-melting-point cyclic oligomers will accumulate in the film, forming "crystal points" and affecting the quality of the film. In the process of preparing bottle blanks, oligomers will also cause problems such as pollution of the die, thereby causing poor quality of the bottle blanks.

[0004] In summary, with the increasing application of polyester products, the requirements for the low-extraction performance of polyester are also increasing. However, the low-extraction polyester and products prepared by the existing methods of polyester processing, adding nano additives, and improving the discharge equipment generally have the problems of poor improvement effect, uneven additive blending effect, or difficulty in large-scale application, etc. Therefore, it is necessary to optimize and improve the formula and production method of polyester to prepare polyester and products with better low-extraction effect. SUMMARY

[0005] In order to overcome the technical problems of the existing PET polyester oligomer and other precipitates, which affect the processing performance and use performance, the application provides a preparation method of low-precipitation polyester, which adopts an in-situ polymerization and solid-phase tackifying two-step method to prepare the low-precipitation polyester.

[0006] The object of the application can be achieved by the following technical scheme:

[0007] A preparation method of low-precipitation polyester, which comprises the following steps: taking diacid and diol as raw materials, and performing esterification reaction under the action of a catalyst; performing pre-polycondensation reaction at a temperature of 260-275 DEG C after the esterification reaction; performing final polycondensation reaction after the pre-polycondensation reaction; and obtaining polyester base chips after the reaction, wherein the intrinsic viscosity of the polyester base chips is 0.4-0.7 dL / g, and the terminal carboxyl content is 10.0-15.0 mol / t; and performing solid-phase tackifying test on the polyester base chips to prepare low-precipitation polyester finished chips, wherein the vacuum degree of tackifying is less than 150 pa, the tackifying temperature is 215-220 DEG C, the tackifying time is 10-16 h, the intrinsic viscosity of the prepared low-precipitation polyester is 0.6-0.8 dL / g, and the terminal carboxyl content is 5-10 mol / t.

[0008] A low-precipitation polyester, wherein the content of oligomers with a number average molecular weight less than 1200 in the low-precipitation polyester is less than 0.1%, and the fluctuation value of haze of a film prepared from the low-precipitation polyester is within 0.5% after heat treatment at 150 DEG C for 60 min.

[0009] The polyester is prepared by taking diacid and diol as raw materials, and performing esterification reaction under the action of a catalyst; performing pre-polycondensation reaction at a temperature of 260-275 DEG C after the esterification reaction; performing final polycondensation reaction after the pre-polycondensation reaction; and obtaining polyester base chips after the reaction, wherein the intrinsic viscosity of the polyester base chips is 0.4-0.7 dL / g, and the terminal carboxyl content is 10.0-15.0 mol / t; and performing solid-phase tackifying test on the polyester base chips to prepare low-precipitation polyester finished chips, wherein the vacuum degree of tackifying is less than 150 pa, the tackifying temperature is 215-220 DEG C, the tackifying time is 10-16 h, the intrinsic viscosity of the prepared low-precipitation polyester is 0.6-0.8 dL / g, and the terminal carboxyl content is 5-10 mol / t.

[0010] In the technical scheme, the esterification reaction is performed under the conditions of a pressure of 0.2-0.3 MPa and a reaction temperature of 250-260 DEG C.

[0011] The esterification reaction pressure is 0.25 MPa, and the reaction temperature is 256 DEG C.

[0012] In the technical scheme of the present application, the pre-polycondensation reaction time is 40-50 min.

[0013] In the technical scheme of the present application, the final polycondensation reaction condition is absolute pressure below 100 Pa, the reaction temperature is 277-281 DEG C, and the final polycondensation reaction time is 65-110 min.

[0014] In the technical scheme of the present application, the catalyst is ethylene glycol antimony catalyst, and the mass content of ethylene glycol antimony in the polyester product is 0.025%-0.040%.

[0015] In the technical scheme of the present application, the molar ratio of the binary acid to the binary alcohol is 1:(1.80-2.00), the binary acid is terephthalic acid, and the binary alcohol is ethylene glycol.

[0016] The present application provides a preparation method of low-extraction polyester, which adopts the mode of strengthening esterification reaction condition and weakening polycondensation reaction condition, strictly limits the end carboxyl group and intrinsic viscosity of base chip, and prepares low-extraction polyester through the mode of in-situ polymerization and solid-phase tackifying two-step method, so as to reduce the low polymer extraction in the process of polyester film, fiber, bottle and other post-processing production and use. Firstly, the mode of improving esterification reaction temperature is adopted in the in-situ polymerization process to strictly limit the intrinsic viscosity and end carboxyl group index, and the polycondensation reaction temperature is weakened to prepare base polyester chip, and then the low-extraction polyester is prepared through the mode of solid-phase tackifying. The low-extraction polyester prepared through the mode of in-situ polymerization-solid-phase tackifying two-step method reduces the low polymer extraction in the process of polyester film, fiber, bottle and other post-processing production and use, so as to reduce the low polymer content, improve the haze thermal stability of polyester film, and improve the dyeing performance of fiber. The low-extraction finished polyester is evaluated in terms of low polymer content in polyester through extraction. The low-extraction polyester is prepared into fiber through spinning and drafting according to the conventional spinning process, and the dyeing performance thereof is tested. The film is prepared through melt extrusion and bidirectional stretching according to the conventional film forming process, and the thermal stability of the film haze is tested.

[0017] The esterification reaction temperature is 2-6 DEG C higher than the conventional esterification temperature, which reduces the end carboxyl group from the perspective of esterification reaction process.

[0018] The intrinsic viscosity and end carboxyl group testing method in the application is tested and characterized according to 5.1 and 5.4 in GB / T14190-2017 Fiber Grade Polyester Chip Test Method.

[0019] The polycondensation temperature is 2 DEG C-5 DEG C lower than the conventional polyester polycondensation temperature.

[0020] The oligomer content evaluation test instrument is a Soxhlet extractor (CN200920040767.1 An oligomer extraction device), the extraction time is 24 h, the extraction temperature is 85℃, and the oligomer content is calculated according to the mass difference before and after the slice extraction.

[0021] The film thermal stability evaluation is that the haze H0 of the film is tested by a haze meter, the film haze value is calculated according to the method of 4.6.3 in ASTM D 1003-2013, the haze H1 of the film after heating is tested after the film is heated at 150℃ for 60 min, the difference AH between the haze before and after heating is calculated, the difference between the haze before and after heating is represented by AH, and the thermal stability of the haze is evaluated.

[0022] The dyeing performance is represented by the dye-uptake rate and K / S value. The dye-uptake rate is tested under the conditions of temperature 130℃, pH value 5.5, bath ratio 1:100, using disperse blue dye, and time 60 min. The dye-uptake rate is calculated according to the absorbance difference of the dye liquor before and after dyeing, and the dye-uptake rate = 100*(1-A1 / A0), wherein A0 and A1 are the absorbance of the dye liquor before and after dyeing, respectively. The K / S value of the dyed fiber is measured at the maximum absorption wavelength by a colorimeter.

[0023] The oligomer content of the low-extraction polyester is less than 0.1%, the haze stability of the film prepared from the low-extraction polyester before and after heating is good, the difference in the haze of the film is less than 0.5% after heating at 150℃ for 60 min.

[0024] Advantages:

[0025] Compared with the conventional polyester, the oligomer content of the low-extraction polyester prepared in the application is reduced from 1.2% to less than 0.1%, which is reduced by more than 90%, the fluctuation value of the haze of the film after heating is reduced by more than 80%, the dye-uptake rate of the fiber is increased by more than 20%, and the low-extraction polyester has the advantage of significantly reducing the extractives. DETAILED DESCRIPTION

[0026] The application will be further described below in combination with examples, but the protection scope of the application is not limited thereto:

[0027] Example 1

[0028] In a 20L general polymerization reactor, add 5000g of terephthalic acid (PTA), 3000g of ethylene glycol (EG), and 1.6624g of ethylene glycol antimony catalyst. Perform a conventional esterification reaction under the conditions of a gauge pressure of 0.25MPa and a temperature of 256°C. After the esterification reaction is completed, perform a pre-polycondensation reaction at 260°C-275°C for 45min, and finally control the temperature of the final polycondensation reaction at 277°C. The final polycondensation reaction pressure is below 100Pa, and the final polycondensation reaction time is 110min. After the reaction is completed, extrude, pelletize, and dry to obtain low-extraction polyester base chips. The intrinsic viscosity of the low-extraction polyester base chips is 0.598dL / g, and the carboxyl end group content is 12.5mol / t. Perform a solid-phase tackifying test using a rotating drum to prepare low-extraction polyester finished chips. The tackifying temperature is 220°C, the tackifying time is 10h, and the vacuum degree during the solid-phase tackifying is 100pa. The intrinsic viscosity of the prepared low-extraction polyester is 0.678dL / g, the carboxyl end group content is 7.5mol / t, and the oligomer content is 0.027%.

[0029] Dry and extrude the low-extraction polyester to obtain a low-extraction polyester thick sheet with a thickness of 150μm. Place the thick sheet for one day, and then perform stretching on a two-way stretching machine. The stretching conditions of the thick sheet are a preheating temperature of 95°C, a time of 20s, and a stretching ratio of 3.5*3.5. The thickness of the prepared low-extraction film is 12.4μm, the haze is 0.21, and the film is placed in a 150°C air oven for 60min. The haze is 0.50, and the haze fluctuation value ΔH is 0.29.

[0030] Dry and melt-spin the low-extraction polyester to perform a conventional spinning test. The heating temperature is 290°C. After drawing, the low-extraction polyester is prepared into a low-extraction fiber. The dye uptake is 91.8, and the K / S value is 22.5.

[0031] Example 2

[0032] In a 20L general polymerization reactor, add 5000g of terephthalic acid (PTA), 3000g of ethylene glycol (EG), and 1.6624g of ethylene glycol antimony catalyst. Perform a conventional esterification reaction under the conditions of a gauge pressure of 0.25MPa and a temperature of 256°C. After the esterification reaction is completed, then perform a pre-polycondensation reaction at 260°C-275°C for 45min, and finally control the temperature of the final polycondensation reaction at 277°C. The pressure of the final polycondensation reaction is below 100Pa, and the time of the final polycondensation reaction is 65min. After the reaction is completed, extrude, pelletize, and dry to obtain low-extraction polyester base chips, which have an intrinsic viscosity of 0.462dL / g and a carboxyl end group content of 14.8mol / t. Perform a solid-phase tackifying test using a rotating drum to prepare low-extraction polyester finished chips, the tackifying temperature is 215°C, the tackifying time is 16h, and the vacuum degree during the solid-phase tackifying is 120pa. The prepared low-extraction polyester has an intrinsic viscosity of 0.610dL / g and a carboxyl end group content of 9.7mol / t, and the oligomer content is 0.085%.

[0033] Dry and extrude the low-extraction polyester to obtain low-extraction polyester thick sheets, which have a thickness of 158μm. Place the thick sheets for one day, then perform stretching in a two-way stretching machine, the stretching conditions of the thick sheets are a preheating temperature of 95°C, a time of 20s, and a stretching ratio of 3.5*3.5. The prepared low-extraction polyester film has a thickness of 12.8μm, a haze of 0.17, and a haze fluctuation value ΔH of 0.24.

[0034] Dry and melt-spin the low-extraction polyester to perform a conventional spinning test, the heating temperature is 290°C. After drawing, the low-extraction polyester is prepared into a low-extraction fiber, which has a dye uptake of 90.6 and a K / S value of 22.4.

[0035] Example 3

[0036] In a 20L general polymerization reactor, add 5000g of terephthalic acid (PTA), 3000g of ethylene glycol (EG), and 1.6624g of ethylene glycol antimony catalyst. Perform a conventional esterification reaction under the conditions of 0.25MPa of gauge pressure and 256°C of temperature. After the esterification reaction is completed, perform a pre-polycondensation reaction at 260°C-275°C for 45min, and finally control the temperature of the final polycondensation reaction at 281°C. The pressure of the final polycondensation reaction is below 100Pa of absolute pressure, and the time of the final polycondensation reaction is 90min. After the reaction is completed, extrude, pelletize, and dry to obtain low-extraction polyester base chips, which have a specific viscosity of 0.554dL / g and a carboxyl end group content of 10.8mol / t. Perform a solid-phase tackifying test using a rotating drum to prepare low-extraction polyester finished chips. The tackifying temperature is 218°C, the tackifying time is 10h, and the vacuum degree during the solid-phase tackifying is 80pa. The prepared low-extraction polyester has a specific viscosity of 0.654dL / g and a carboxyl end group content of 8.6mol / t, and the oligomer content is 0.064%.

[0037] Dry and extrude the low-extraction polyester to prepare low-extraction polyester thick sheets, which have a thickness of 151μm. Place the thick sheets for one day, and then perform stretching in a two-way stretching machine. The stretching conditions of the thick sheets are a preheating temperature of 95°C, a time of 20s, and a stretching ratio of 3.5*3.5. The prepared low-extraction thin film has a thickness of 12.1μm, a haze of 0.18, and a haze fluctuation value ΔH of 0.30.

[0038] Dry and melt-spin the low-extraction polyester to perform a conventional spinning test. The heating temperature is 290°C. After drawing, the low-extraction polyester is prepared into low-extraction fibers, which have a dyeing rate of 91.5 and a K / S value of 22.6.

[0039] Example 4

[0040] In a 20L general polymerization reactor, add 5000g of terephthalic acid (PTA), 3000g of ethylene glycol (EG), and 1.6624g of ethylene glycol antimony catalyst. Perform a conventional esterification reaction at a pressure of 0.25Mpa and a temperature of 256°C. After the esterification reaction is completed, perform a pre-polycondensation reaction at a temperature of 260°C to 275°C for 45 minutes. Finally, control the temperature of the final polycondensation reaction at 279°C. The pressure of the final polycondensation reaction is below 100pa, and the time of the final polycondensation reaction is 110 minutes. After the reaction is completed, extrude, pelletize, and dry to obtain a low-extraction polyester base chip. The intrinsic viscosity of the low-extraction polyester base chip is 0.594dL / g, and the carboxyl end group content is 12.4mol / t. Perform a solid-phase tackifying test using a drum to prepare a low-extraction polyester finished chip. The tackifying temperature is 218°C, the tackifying time is 16 hours, and the vacuum degree during the solid-phase tackifying is 100pa. The intrinsic viscosity of the prepared low-extraction polyester is 0.784dL / g, the carboxyl end group content is 5.2mol / t, and the oligomer content is 0.011%.

[0041] Dry and extrude the low-extraction polyester to obtain a low-extraction polyester thick sheet with a thickness of 155μm. Place the thick sheet for one day, then perform stretching on a two-way stretching machine. The stretching conditions of the thick sheet are a preheating temperature of 95°C, a time of 20s, and a stretching ratio of 3.5*3.5. The thickness of the prepared low-extraction thin film is 12.4μm, the haze is 0.22, and the haze fluctuation value ΔH is 0.16.

[0042] Dry and melt the low-extraction polyester to perform a conventional spinning test. The heating temperature is 290°C. After drawing, the low-extraction polyester is prepared into a low-extraction fiber. The dye uptake rate is 91.7, and the K / S value is 21.8.

[0043] Example 5

[0044] In a 20L general polymerization reactor, add 5000g of terephthalic acid (PTA), 3000g of ethylene glycol (EG), and 1.6624g of ethylene glycol antimony catalyst, and perform a conventional esterification reaction under the conditions of a gauge pressure of 0.25Mpa and a temperature of 256°C. After the esterification reaction is completed, perform a pre-polycondensation reaction at 260°C-275°C for 45min, and finally control the polycondensation reaction temperature at 279°C to perform a final polycondensation reaction, the absolute pressure is below 100pa, and the polycondensation reaction time is controlled at 110min. After the reaction is completed, the melt pump is extruded, pelletized, and dried to obtain a low-extraction polyester base chip, the intrinsic viscosity is 0.594dL / g, and the carboxyl end group content is 12.4mol / t. A drum is used to prepare a low-extraction polyester finished chip by solid-phase tackifying test, the tackifying temperature is 220°C, the tackifying time is 13h, and the vacuum degree is 100pa during solid-phase tackifying. The prepared low-extraction polyester has an intrinsic viscosity of 0.745dL / g, a carboxyl end group content of 6.7mol / t, and a low polymer content of 0.024%.

[0045] The low-extraction polyester is dried and extruded into a low-extraction polyester thick sheet with a thickness of 152μm. The thick sheet is placed for one day and then stretched in a two-way stretching machine, the stretching conditions of the thick sheet are a preheating temperature of 95°C, a time of 20s, and a stretching ratio of 3.5*3.5, the prepared low-extraction film has a thickness of 12.3μm, the haze is 0.26, the film is placed in a 150°C air oven for 60min, the haze is 0.62, and the haze fluctuation value ΔH is 0.36.

[0046] The low-extraction polyester is dried and melt-spun to perform a conventional spinning test, the heating temperature is 290°C, and the low-extraction fiber is prepared after drawing, the dye uptake is 92.1, and the K / S value is 22.3.

[0047] Reference Example 1

[0048] In a 20L general polymerization reactor, add 5000g of terephthalic acid (PTA), 3000g of ethylene glycol (EG), and 1.6624g of ethylene glycol antimony catalyst, and perform a conventional esterification reaction under the conditions of a gauge pressure of 0.25Mpa and a temperature of 250°C. After the esterification reaction is completed, perform a pre-polycondensation reaction at 260°C-275°C for 45min, and finally control the polycondensation reaction temperature at 282°C to perform a final polycondensation reaction, the absolute pressure is below 100pa, and the polycondensation reaction time is controlled at 125min. After the reaction is completed, the melt pump is extruded, pelletized, and dried to obtain a conventional polyester chip, the intrinsic viscosity is 0.675dL / g, the carboxyl end group content is 23.8mol / t, and the low polymer content is 1.231%.

[0049] The conventional polyester was dried and extruded to form a conventional polyester thick sheet having a thickness of 153 μm. The thick sheet was left for one day and then stretched in a biaxial stretching machine under the following conditions: preheating temperature 95°C, time 20 s, and stretching ratio 3.5*3.5. The prepared film had a thickness of 12.1 μm, and its haze was 0.27. The film was placed in a 150°C air oven for 60 min, and its haze was 5.51. The haze fluctuation value ΔH was 5.24.

[0050] The conventional polyester was dried and melt-spun to perform a conventional spinning test under the following conditions: heating temperature 290°C. The drawn conventional fiber had a dye-uptake of 75.2 and a K / S value of 17.5.

[0051] Reference Example 2

[0052] Into a 20 L general-purpose polymerization reactor were introduced 5000 g of terephthalic acid (PTA) and 3000 g of ethylene glycol (EG), and 1.6624 g of ethylene glycol antimony catalyst. Esterification was performed at a pressure of 0.25 MPa and a temperature of 252°C. After the esterification was completed, pre-polycondensation was performed at 260-275°C for 45 min, and final polycondensation was performed at a temperature of 279°C and an absolute pressure of 100 Pa or less for 100 min. The polycondensation reaction product was extruded through a melt pump, pelletized, and dried to obtain polyester chips having an intrinsic viscosity of 0.587 dL / g and a carboxyl end group content of 26.7 mol / t. The chips were subjected to solid-phase tackifying test using a rotating drum at a tackifying temperature of 220°C for 10 h under a vacuum of 100 Pa to obtain finished chips. The prepared low-extractable polyester had an intrinsic viscosity of 0.667 dL / g and a carboxyl end group content of 20.8 mol / t, and the oligomer content was 0.635%.

[0053] The polyester chips were dried and extruded to form a polyester thick sheet having a thickness of 156 μm. The thick sheet was left for one day and then stretched in a biaxial stretching machine under the following conditions: preheating temperature 95°C, time 20 s, and stretching ratio 3.5*3.5. The prepared film had a thickness of 12.2 μm, and its haze was 0.28. The film was placed in a 150°C air oven for 60 min, and its haze was 3.87. The haze fluctuation value ΔH was 3.59.

[0054] The polyester was dried and melt-spun to perform a conventional spinning test under the following conditions: heating temperature 290°C. The drawn conventional fiber had a dye-uptake of 82.1 and a K / S value of 18.1.

[0055] Compared with Example 2, the base chips of Reference Example 2 had a high carboxyl end group content, and the prepared polyester had a high oligomer content after tackifying, which did not reduce the oligomer content.

[0056] Reference Example 3

[0057] In a 20L general polymerization reactor, add 5000g of terephthalic acid (PTA), 3000g of ethylene glycol (EG), and 1.6624g of ethylene glycol antimony catalyst, and perform a conventional esterification reaction under the conditions of a gauge pressure of 0.25Mpa and a temperature of 256°C. After the esterification reaction is completed, perform a pre-polycondensation reaction at 260°C-275°C for 45min, and finally control the polycondensation reaction temperature at 278°C to perform a final polycondensation reaction, with the absolute pressure being below 100pa, and control the polycondensation reaction time to be 120min. After the reaction is completed, extrude, pelletize, and dry to obtain low-extraction polyester base chips, with an intrinsic viscosity of 0.638dL / g and a carboxyl end group content of 8.9mol / t. Perform a solid-phase tackifying test using a rotating drum to prepare low-extraction polyester finished chips, with a tackifying temperature of 220°C and a tackifying time of 13h, and a vacuum degree of 80pa during the solid-phase tackifying. The prepared low-extraction polyester has an intrinsic viscosity of 0.681dL / g and a carboxyl end group content of 4.1mol / t, and the oligomer content is 0.009%.

[0058] The low-extraction polyester is dried and extruded to form polyester thick sheets, with a thickness of 155μm. The thick sheets are placed for one day, and then stretched in a two-way stretching machine, with a preheating temperature of 95°C, a time of 20s, and a stretching ratio of 3.5*3.5. The prepared low-extraction film has a thickness of 12.2μm, and the haze is 0.24. The film is placed in a 150°C air oven for 60min, and the haze is 0.48, and the haze fluctuation value ΔH is 0.24.

[0059] The low-extraction polyester is dried and melt-spun to perform a conventional spinning test, with a heating temperature of 290°C. After drawing, low-extraction fibers are prepared, and the dye uptake is 91.5 and the K / S value is 21.7.

[0060] The base chips of Reference Example 3 have a too low carboxyl end group, and the calculation results of the solid-phase tackifying rate show that when the carboxyl end group is lower than the requirement of the present application, the carboxyl end group value of the base chips is too low, which results in a slow molecular chain growth reaction rate during the tackifying process. Although the prepared polyester has a low oligomer content, the solid-phase reaction rate is too slow, and therefore it has no practical application significance.

[0061] Reference Example 4

[0062] In a 20L general polymerization reactor, add 5000g of terephthalic acid (PTA), 3000g of ethylene glycol (EG), and 1.6624g of ethylene glycol antimony catalyst, and perform a conventional esterification reaction under the conditions of a gauge pressure of 0.25Mpa and a temperature of 250°C. After the esterification reaction is completed, perform a pre-polycondensation reaction at 260°C-275°C for 45min, and finally control the polycondensation reaction temperature at 277°C to perform a final polycondensation reaction, with an absolute pressure below 100pa, and control the polycondensation reaction time for 55min. After the reaction is completed, extrude, pelletize, and dry to obtain polyester base chips, with an intrinsic viscosity of 0.431dL / g and a terminal carboxyl group content of 30.8mol / t. Perform a solid-phase tackifying test using a drum to prepare polyester product chips, with a tackifying temperature of 220°C and a tackifying time of 20h, and a vacuum degree of 70pa during solid-phase tackifying. The prepared polyester product has an intrinsic viscosity of 0.501dL / g, a terminal carboxyl group content of 23.7mol / t, and a low polymer content of 1.326%.

[0063] The polyester product is dried and extruded to form a polyester thick sheet with a thickness of 155μm. The thick sheet is placed for one day, and then stretched in a two-way stretching machine, with a preheating temperature of 95°C, a time of 20s, and a stretching ratio of 3.5*3.5. The prepared film has a thickness of 12.1μm, a haze of 0.31, and a haze fluctuation value ΔH of 5.5.

[0064] The polyester is dried and melt-spun to perform a conventional spinning test, with a heating temperature of 290°C. After drawing, a low-extraction fiber is prepared, with a dye uptake of 74.1 and a K / S value of 16.8.

[0065] The intrinsic viscosity of the base chips prepared in Reference Example 4 is too low, the solid-phase tackifying rate is reduced, and the low polymer content in the prepared polyester is high.

[0066] Reference Example 5

[0067] In a 20L general polymerization reactor, add 5000g of terephthalic acid (PTA), 3000g of ethylene glycol (EG), and 1.6624g of ethylene glycol antimony catalyst, and perform a conventional esterification reaction under the conditions of a gauge pressure of 0.25Mpa and a temperature of 250°C. After the esterification reaction is completed, perform a pre-polycondensation reaction at 260°C-275°C for 45min, and finally control the polycondensation reaction temperature at 282°C to perform a final polycondensation reaction, with an absolute pressure below 100pa, and control the polycondensation reaction time for 145min. After the reaction is completed, extrude, pelletize, and dry to obtain polyester chips, with an intrinsic viscosity of 0.735dL / g and a terminal carboxyl group content of 18.9mol / t, and a low polymer content of 1.142%.

[0068] The polyester product was dried and extruded to form a polyester thick sheet with a thickness of 157 μm. After the sheet was left for one day, it was stretched in a two-way stretching machine, with a preheating temperature of 95°C for 20 s, a stretching ratio of 3.5*3.5, to form a film with a thickness of 12.3 μm. The haze of the film was 0.29. The film was placed in a 150°C air oven for 60 min, and the haze was 5.31. The haze fluctuation value ΔH was 5.02.

[0069] The polyester product was dried and melt-spun to perform a conventional spinning test, with a heating temperature of 290°C. After drawing, a low-extraction fiber was formed, with a dye-uptake of 76.4 and a K / S value of 17.9.

[0070] Table 1: Reaction parameters and polyester performance indicators of examples and reference examples

[0071]

[0072]

[0073] Table 2: Film haze and fiber dyeing performance

[0074]

[0075] The present application controls the intrinsic viscosity and terminal carboxyl group of the base chip to prepare the base chip, and uses solid-phase tackifying to prepare the low-extraction polyester chip product. As shown in the implementation effects of the examples and reference examples in Tables 1 and 2, compared with the conventional polyester of reference example 1, the oligomer content of the low-extraction polyester in examples 1-5 is reduced to less than 0.1%, which is more than 90% lower, the haze fluctuation value ΔH of the film after heating is reduced by more than 80%, and the fiber dye-uptake is increased by more than 20%, which has a significant effect. Reference examples 2, 4 and 5 show that the polyester prepared from a base chip with too high terminal carboxyl group does not have the low-extraction feature, and reference example 3 shows that a base chip with too low terminal carboxyl group will seriously affect the solid-phase tackifying rate, and the practical application effect is limited; reference examples 4 and 5 show that too high or too low intrinsic viscosity also has the disadvantage of high oligomer content. In addition, the present application uses a two-step method to prepare the polyester product, and examples 1 and 5 and reference examples 1 and 5 respectively show that under the premise of the same intrinsic viscosity, the two-step method has the advantage of significantly reducing the oligomer content.

[0076] In summary, the present application uses the method of strengthening the esterification reaction conditions and weakening the polycondensation reaction conditions, strictly limits the terminal carboxyl group and intrinsic viscosity of the base chip, and prepares the low-extraction polyester by the two-step method of in-situ polymerization and solid-phase tackifying, to achieve the purposes of reducing the oligomer content, improving the haze thermal stability of the polyester film and improving the fiber dyeing performance.

Claims

1. A low-extraction polyester characterized by: The low-extraction polyester has an oligomer content less than 0.1% with a number average molecular weight less than 1200, and a fluctuation value of haze ΔH of the film prepared by using the low-extraction polyester is less than 0.5% after heat treatment at 150 ℃ for 60 min. The preparation method of the low-extraction polyester comprises the following steps: performing esterification reaction on raw materials of diacid and diol under the action of a catalyst, performing pre-polycondensation reaction at a temperature of 260-275 ℃ after the esterification reaction, performing final polycondensation reaction after the pre-polycondensation reaction, and obtaining polyester base chips after the reaction, wherein the intrinsic viscosity of the polyester base chips is 0.4-0.7 dL / g, and the carboxyl end group content is 10.0-15.0 mol / t; and the polyester base chips are subjected to solid-phase tackifying test to prepare low-extraction polyester finished chips, wherein the intrinsic viscosity of the prepared low-extraction polyester is 0.6-0.8 dL / g, and the carboxyl end group content is 5-10 mol / t. The esterification reaction is performed at a pressure of 0.2-0.3 MPa and a reaction temperature of 250-260 ℃; the tackifying vacuum degree is less than 150 pa, the tackifying temperature is 215-220 ℃, and the tackifying time is 10-16 h.

2. The low-extraction polyester according to claim 1, characterized in that: The esterification reaction is performed at a pressure of 0.25 MPa and a reaction temperature of 256 ℃.

3. The low-extraction polyester according to claim 1, characterized in that: The pre-polycondensation reaction is performed for 40-50 min.

4. The low-extraction polyester according to claim 1, characterized in that: The final polycondensation reaction is performed at an absolute pressure of less than 100 Pa, a reaction temperature of 277-281 ℃, and a reaction time of 65-110 min.

5. The low-exudation polyester of claim 1, wherein: The catalyst is ethylene glycol antimony catalyst, and the mass content of the ethylene glycol antimony in the polyester product is 0.025%-0.040%.

6. The low-exudation polyester of claim 1, wherein: The molar ratio of the diacid to the diol is 1:(1.80-2.00), the diacid is terephthalic acid, and the diol is ethylene glycol.

7. A method of making a low-extractable polyester characterized by: The preparation method of the low-extraction polyester comprises the following steps: performing esterification reaction on raw materials of diacid and diol under the action of a catalyst, performing pre-polycondensation reaction at a temperature of 260-275 ℃ after the esterification reaction, performing final polycondensation reaction after the pre-polycondensation reaction, and obtaining polyester base chips after the reaction, wherein the intrinsic viscosity of the polyester base chips is 0.4-0.7 dL / g, and the carboxyl end group content is 10.0-15.0 mol / t; and the polyester base chips are subjected to solid-phase tackifying test to prepare low-extraction polyester finished chips, wherein the intrinsic viscosity of the prepared low-extraction polyester is 0.6-0.8 dL / g, and the carboxyl end group content is 5-10 mol / t; the esterification reaction is performed at a pressure of 0.2-0.3 MPa and a reaction temperature of 250-260 ℃; the tackifying vacuum degree is less than 150 pa, the tackifying temperature is 215-220 ℃, and the tackifying time is 10-16 h. The low-extraction polyester has an oligomer content less than 0.1% with a number average molecular weight less than 1200, and a fluctuation value of haze ΔH of the film prepared by using the low-extraction polyester is less than 0.5% after heat treatment at 150 ℃ for 60 min.

8. The method of claim 7, wherein: The pre-polycondensation reaction is performed for 40-50 min; and the final polycondensation reaction is performed at an absolute pressure of less than 100 Pa, a reaction temperature of 277-281 ℃, and a reaction time of 65-110 min.

9. The method of claim 8, wherein: The esterification reaction is carried out at a pressure of 0.25 MPa and a temperature of 256 DEG C.

10. The method of claim 7, wherein: The catalyst is ethylene glycol antimony catalyst, the mass content of ethylene glycol antimony in the polyester product is 0.025%~0.040%, the molar ratio of the dibasic acid to the dihydric alcohol is 1: (1.80~2.00), and the dibasic acid is terephthalic acid and the dihydric alcohol is ethylene glycol.

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