A high-speed film polyester and a method for preparing the same

Abstract

The application provides a polyester for high-speed film and a preparation method thereof, and the comprehensive effects of reducing the crystallization rate, improving the adhesion, reducing the viscosity drop and the crystallinity are achieved by exerting the synergistic effect of each additive in the polyester melt, and the high-speed film is prepared. Compared with the existing medium-speed and high-speed production line film polyester with the same performance index, the melt specific resistance of the polyester prepared by the application is reduced by more than 50%, the polyester viscosity drop after melt extrusion is reduced by more than 45%, the semi-crystallization time is increased by more than 15%, the molecular weight distribution index is increased by 10%, and the maximum tensile strain rate of the casting sheet is increased by more than 20%, which has a significant high-speed stretching advantage.

Description

TECHNICAL FIELD

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

[0002] Biaxially oriented polyethylene terephthalate (BOPET) is a kind of green, environmentally friendly, high polymer film material with excellent comprehensive performance. By the end of 2019, China's biaxially oriented polyester film (BOPET) total capacity reached 3.42 million tons, ranking first in the world. China has become the world's most important production base and consumer market. It is estimated that more than 1.5 million tons of capacity will be released from 2020 to 2022, marking the largest capacity release peak in the history of China's BOPET industry. Film enterprises have done a lot of work in equipment upgrading, process optimization, etc., and have put forward higher requirements for polyester special materials, hoping to carry out systematic research on equipment, process, raw materials, etc., and develop a high-speed BOPET production process package with a speed of more than 500 m / min.

[0003] The preparation process of polyester film includes processes such as chip melting, chip forming, stretching and shaping. The problems caused by thickness, such as chip heat transfer and stretching stress, can be solved by equipment improvement and process optimization, but the requirement of high-speed production also needs to be realized by raw materials cooperating with specific production process. In order to meet the requirements of high-speed production of BOPET, relevant scholars have done a lot of work in improving the conductivity of polyester formula, optimizing production equipment, etc. Chinese patent 02157295.X improves the static cling ability of polyester by adding resistance adjuster and stabilizer in PTA method, which can be used for producing film and sewing thread, etc. This patent does not further study from the aspects of reducing the crystallization ability of polyester and improving the molecular weight distribution index, and does not involve the specific implementation scheme of improving the stretching rate. Chinese patent 201711431810.2 discloses a method for changing the conductivity of PET product for high-speed film, which is prepared by adding potassium salt, magnesium salt and phosphorus compound in situ polymerization process, which changes the conductivity of PET product. However, this invention does not involve the structure and performance of polyester raw material such as crystallization performance and molecular weight distribution, and does not compare and evaluate the specific implementation effects such as viscosity reduction and product color value degradation. Although it can improve the conductivity of polyester, the stability of polyester will be poor when the amount of corresponding metal ions is too high. Chinese utility model 201921595626.6 discloses a full-automatic high-speed laminating machine pressing mechanism, which improves the film tension on the surface of the feeding roller, prevents the film from being uneven, and is beneficial to cutting the film. This utility model does not involve the improvement of polyester raw material formula.

[0004] PET is a crystalline polymer, and the crystallization of the cast sheet is closely related to the melt cooling speed and uniformity. Therefore, the closer the melt is attached to the cooling drum surface, the better the heat conduction, and the faster the melt cooling speed. At this time, the crystallinity of the thick sheet is small, the spherulites are fine and uniform, which is beneficial to the longitudinal stretching orientation and the uniform and stable quality of the finished film. In the production process of BOPET film, PET undergoes high-temperature melting and extrusion, and the edge film and waste film need to be recycled. Therefore, the stability of the polyester raw material will affect the melt flowability and crystallization performance, thereby affecting the quality of the cast sheet. And appropriately reducing the melt specific resistance of the polyester, improving the effect of the attached sheet, making the melt film more closely attached to the cold drum surface, reducing the temperature difference in the thickness direction of the film, making the structure and performance more uniform, also helps to improve the production speed. In actual production, high-voltage electrostatic is generally used to make the melt closely attached to the cold drum, and the melt has strong melt conductivity. Therefore, the thick sheet has good attachment effect, the melt cooling speed is fast, and it is beneficial to obtain a thick sheet with smooth surface and stable size. In addition, with the increase of the stretching ratio and speed, the stretching stress increases continuously, which is the embodiment of the relaxation characteristics of the viscoelastic process. When the stretching stress increases, the orientation degree of the film increases. Under the same other conditions, the relaxation process requires a long time. If the molecular chain segment cannot relax enough, the uneven relaxation of the molecular chain segment will lead to warping during storage or use.

[0005] In summary, from the perspective of polyester raw materials, the main factors affecting the film production line speed include the thermal stability, crystallization performance and molecular weight distribution index of the polyester, and the electrostatic attachment performance of the cast sheet during the melting and extrusion process. Therefore, with the increasing application and production capacity of polyester products, the demand for developing special polyester for high-speed production lines above 500 m / min is increasing. However, the existing polyester varieties are difficult to meet the requirements of high-speed production, so it is necessary to systematically study the reduction of polyester crystallization speed, the improvement of attachment performance, the reduction of melt extrusion viscosity, and the appropriate increase of molecular weight distribution index, and to prepare film polyester products suitable for high-speed production of film production lines. SUMMARY

[0006] In order to overcome the technical difficulties that the existing polyester is difficult to meet the requirements of high-speed production line, the present application provides a preparation method of polyester for high-speed production line, which introduces an electrostatic attachment coordinator and a stabilizer during in-situ polymerization, and introduces a chain extender at the end of polyester polycondensation reaction or during the melting and extrusion process. In the process of polyester melting and extrusion of cast sheet, the electrostatic attachment coordinator, stabilizer and chain extender in the polyester melt cooperate to prepare the polyester for high-speed production line and the film.

[0007] The object of the present application can be achieved by the following technical solutions:

[0008] A high-speed film polyester, the melt specific resistance of the high-speed film polyester is less than 2.2*10 8 Ω·cm.

[0009] The polyester is prepared by using diacid and diol as raw materials, performing esterification reaction under the action of a catalyst, adding static adhesion coordinator, stabilizer and chain extender after the esterification reaction is completed, stirring for 5-15 min, performing pre-polycondensation reaction under vacuum at 260-275 DEG C for 40-50 min, performing polycondensation reaction after the pre-polycondensation reaction is completed, and obtaining the high-speed film polyester after melt pump extrusion, granulation and drying.

[0010] The application discloses a preparation method of a high-speed film polyester.

[0011] In the technical scheme, the diacid is terephthalic acid, the diol is ethylene glycol, and the molar ratio of the terephthalic acid to the ethylene glycol is 1:(1.1-1.9).

[0012] In the technical scheme, the catalyst is an antimony catalyst, preferably the catalyst is an ethylene glycol antimony catalyst, and the mass content of the ethylene glycol antimony in the polyester is 0.025%-0.040%.

[0013] In the technical scheme, the stabilizer is a phosphorus stabilizer, preferably the phosphorus stabilizer is triphenyl phosphate, trimethyl phosphate or phosphoric acid, and the mass fraction of the phosphorus element in the PET polyester is 0.0010%-0.0030%.

[0014] In the technical scheme, the static adhesion coordinator is an alkali metal or alkali earth metal compound, preferably the static adhesion coordinator is potassium phosphate, sodium pyrophosphate, sodium tripolyphosphate, magnesium acetate, zinc acetate, magnesium oxide, zinc oxide, potassium hydride or zinc hydroxide, and the mass fraction of the metal element in the PET polyester is 0.0015%-0.0030%.

[0015] In the technical scheme, the chain extender is pentaerythritol, isocyanate, an epoxy compound, dioxazoline or a diacid anhydride compound, and the mass fraction of the chain extender in the PET polyester is 0.0001%-0.0040%.

[0016] In the technical scheme of the present application, the esterification reaction time is 1.5-2.5 hours, the temperature is 245-255 DEG C, and the reaction pressure is 0.2-0.3 MPa; the polycondensation reaction temperature is 275-285 DEG C, the reaction pressure is below 100 Pa, and the polycondensation reaction time is 110-120 minutes.

[0017] In the technical scheme of the present application, the polyester for high-speed film is prepared by the method of combining additives in the preparation of PET, the synergistic effect of the additives is achieved in the polyester melt casting process, the static adhesion coordinator and stabilizer are added after the esterification reaction, the chain extender can be added after the esterification reaction or in the melt extrusion process, and the polyester for high-speed film is prepared. In the process of melt extrusion and casting of the polyester for high-speed film, the static adhesion coordinator, the stabilizer and the chain extender are used to achieve the effects of reducing the crystallization rate of the polyester, improving the antistatic ability of the polyester melt, reducing the melt extrusion viscosity drop and the crystallinity of the thick sheet, and appropriately improving the molecular weight distribution index, so that the high-speed production of the film is realized. The polyester melt specific resistance and the maximum stretching strain rate in the biaxial stretching during the evaluation of the film forming property are used for evaluation.

[0018] The combination of additives in the polyester for high-speed film includes the static adhesion coordinator, the stabilizer and the chain extender.

[0019] The static adhesion coordinator and the stabilizer need to be added after the esterification reaction and stirring for 5-15 minutes, and then enter the pre-polycondensation reaction stage, so as to achieve the effects of improving the adhesion performance and reducing the viscosity drop in the melt extrusion process of the polyester for high-speed film.

[0020] The crystallization rate is characterized by the half-crystallization period (t 1 / 2 ), which is calculated according to the melting and crystallization peak of the polyester by using a differential scanning calorimeter (DSC) to test the thermal properties of the polyester, and the time required for half of the crystallization during the melting and crystallization process, that is, the half-crystallization period, and the greater the value, the slower the crystallization.

[0021] The melt conductivity is characterized by the melt specific resistance, which is tested by using a polyester chip melt specific resistance tester (practical new type patent 201020282659.8 resin melt specific resistance measuring instrument), and the test conditions are 283 DEG C and a melt weight of 10.5 g, and the smaller the melt specific resistance, the better the antistatic effect.

[0022] The melt extrusion viscosity drop is the difference between the inherent viscosity of the polyester and the inherent viscosity of the thick sheet, and the greater the viscosity drop, the more serious the degradation of the polyester in the melt extrusion process. In the present application, the inherent viscosity test method is tested and characterized according to 5.1 in GB / T14190-2017 Test Methods for Fiber Grade Polyester Chips.

[0023] The thick piece crystallinity is tested by DSC method, and the value is calculated by integrating the melting crystallization peak of the thick piece. The greater the value is, the higher the crystallinity is, and the less the film is stretched.

[0024] The molecular weight distribution index (PD) is calculated by GPC, and the value is the ratio of the weight average molecular weight (Mw) and the number average molecular weight (Mn). The greater the PD value is, the wider the molecular weight distribution is. The film forming test evaluates the processing technology of the conventional polyester film, including polyester pre-crystallization, drying, melt blending, and two-way stretching process. The maximum stretching strain rate is evaluated at the preheating temperature of 100℃, the preheating time of 20s, and the gradual stretching ratio of 4.0*4.0.

[0025] The high-speed film polyester has a melt specific resistance of less than 2.5*10 8 Ω·cm, a semi-crystallization period of more than 2.9min, a molecular weight distribution index of 2.00-2.35, and a maximum stretching strain rate of the polyester for high-speed film is increased by more than 20% compared with the conventional polyester.

[0026] Advantages

[0027] The high-speed film polyester and the film are prepared from the principle of improving the static adhesion performance in the film polyester casting process, reducing the melt extrusion viscosity, and increasing the molecular weight distribution index. Compared with the existing medium and high-speed production line film polyester with the same performance index, the melt specific resistance of the high-speed film polyester prepared by the application is reduced by more than 20%, the melt extrusion polyester viscosity is reduced by more than 45%, the semi-crystallization time is increased by more than 15%, the molecular weight distribution index is increased by 10%, and the maximum stretching strain rate of the film is increased by more than 20% under the same conditions. DETAILED DESCRIPTION

[0028] The application is further illustrated by the following examples, but the protection scope of the application is not limited to the following:

[0029] Example 1

[0030] In a 20L general polymerization reactor, add 5000g of terephthalic acid (PTA), 3000g of ethylene glycol (EG), and 2.015g of ethylene glycol antimony catalyst. Perform esterification at a pressure of 0.25Mpa and a temperature of 250°C for 120min. After the esterification reaction is complete, add 0.91g of triphenyl phosphate, 1.04g of magnesium acetate, and 0.145g of pentaerythritol. Stir for 10min, then perform pre-polycondensation at a vacuum of 260°C-275°C for 45min. Finally, control the polycondensation reaction temperature at 281°C to perform the final polycondensation reaction, with an absolute pressure below 100pa. After the reaction is complete, extrude, pelletize, and dry the product. The polycondensation reaction time is 115min. The resulting high-speed film polyester has an intrinsic viscosity of 0.645dL / g, a molecular weight distribution index (PD) of 2.31, a melt crystallization half-crystallization period (t 1 / 2 ) of 3.69min, and a melt specific resistance of 0.45*10 8 Ω·cm.

[0031] The high-speed film polyester is dried and melt-extruded into a high-speed film polyester thick sheet. The melt heat enthalpy of the thick sheet is 9.7J / g, and the viscosity drop before and after melt-extrusion is 0.021dl / g. The thick sheet is placed for one day, then stretched on a two-way stretching machine. The maximum stretching strain rate is 235% at a synchronous stretching ratio of 4.0*4.0 under a preheating temperature of 100°C and a preheating time of 20s.

[0032] Example 2

[0033] In a 20L general polymerization reactor, add 5000g of terephthalic acid (PTA), 3000g of ethylene glycol (EG), and 2.015g of ethylene glycol antimony catalyst. Perform esterification at a pressure of 0.25Mpa and a temperature of 250°C for 110min. After the esterification reaction is complete, add 0.62g of triphenyl phosphate, 0.78g of magnesium acetate, and 0.06g of pentaerythritol. Stir for 10min, then perform pre-polycondensation at a vacuum of 260°C-275°C for 45min. Finally, control the polycondensation reaction temperature at 281°C to perform the final polycondensation reaction, with an absolute pressure below 100pa. After the reaction is complete, extrude, pelletize, and dry the product. The polycondensation reaction time is 113min. The resulting high-speed film polyester has an intrinsic viscosity of 0.638dL / g, a molecular weight distribution index (PD) of 2.24, a melt crystallization half-crystallization period (t 1 / 2 ) of 3.31min, and a melt specific resistance of 2.16*10 8 Ω·cm.

[0034] The high-speed film polyester is dried and melt-extruded to form a high-speed film polyester thick sheet. The melting heat enthalpy of the thick sheet is 8.4 J / g, and the viscosity drop before and after melt-extrusion is 0.025 dl / g. The thick sheet is placed for one day, and then stretched in a biaxial stretching machine. The maximum stretching strain rate is 220% at a synchronous stretching ratio of 4.0*4.0 under the conditions of a preheating temperature of 100°C and a preheating time of 20 s.

[0035] Example 3

[0036] In a 20 L general polymerization reactor, 5000 g of terephthalic acid (PTA), 3000 g of ethylene glycol (EG), and 2.015 g of ethylene glycol antimony catalyst are added. Esterification is carried out at a pressure of 0.25 MPa and a temperature of 250°C for 120 min. After the esterification reaction is completed, 1.82 g of triphenyl phosphate, 2.01 g of sodium pyrophosphate, and 0.03 g of pentaerythritol are added, stirred for 10 min, and then pre-polycondensation is carried out at a vacuum of 260°C-275°C for 45 min. Finally, the temperature of the final polycondensation reaction is controlled at 281°C, and the absolute pressure is below 100 pa. After the reaction is completed, the melt pump is extruded, pelletized, and dried. The polycondensation reaction time is 122 min. The intrinsic viscosity of the high-speed film polyester obtained is 0.649 dL / g, the molecular weight distribution index (PD) of the polyester is 2.22, the half-crystallization period (t 1 / 2 ) of the melt crystallization is 3.25 min, and the melt specific resistance is 0.34*10 8 Ω·cm.

[0037] The high-speed film polyester is dried and melt-extruded to form a high-speed film polyester thick sheet. The melting heat enthalpy of the thick sheet is 8.4 J / g, and the viscosity drop before and after melt-extrusion is 0.025 dl / g. The thick sheet is placed for one day, and then stretched in a biaxial stretching machine. The maximum stretching strain rate is 220% at a synchronous stretching ratio of 4.0*4.0 under the conditions of a preheating temperature of 100°C and a preheating time of 20 s.

[0038] Example 4

[0039] In a 20L general polymerization reactor, add 5000g of terephthalic acid (PTA), 3000g of ethylene glycol (EG), and 2.015g of ethylene glycol antimony catalyst. Perform esterification at a pressure of 0.25Mpa and a temperature of 250°C for 140min. After the esterification reaction is completed, add 0.91g of triphenyl phosphate, 1.04g of magnesium acetate, and 0.23g of pentaerythritol. Stir for 10min, then perform pre-polycondensation at a vacuum of 260-275°C for 45min. Finally, control the polycondensation reaction temperature at 281°C to perform the final polycondensation reaction, with an absolute pressure below 100pa. After the reaction is completed, extrude, pelletize, and dry the product. The polycondensation reaction time is 118min. The resulting high-speed film polyester has an intrinsic viscosity of 0.644dL / g, a molecular weight distribution index (PD) of 2.45, a half-crystallization period (t 1 / 2 ) of 3.81min, and a melt specific resistance of 0.57*10 8 Ω·cm.

[0040] The high-speed film polyester is dried and melt-extruded into a high-speed film polyester thick sheet. The melt heat enthalpy of the thick sheet is 6.8J / g, and the viscosity drop before and after melt-extrusion is 0.024dl / g. The thick sheet is placed for one day, then stretched on a two-way stretching machine. The maximum stretching strain rate is 240% at a synchronous stretching ratio of 4.0*4.0 under a preheating temperature of 100°C and a preheating time of 20s.

[0041] Example 5

[0042] In a 20L general polymerization reactor, add 5000g of terephthalic acid (PTA), 3000g of ethylene glycol (EG), and 2.015g of ethylene glycol antimony catalyst. Perform esterification at a pressure of 0.25Mpa and a temperature of 250°C for 125min. After the esterification reaction is completed, add 0.78g of trimethyl phosphate and 0.23g of zinc oxide. Stir for 10min, then perform pre-polycondensation at a vacuum of 260-275°C for 45min. Finally, control the polycondensation reaction temperature at 281°C to perform the final polycondensation reaction, with an absolute pressure below 100pa. After the reaction is completed, extrude, pelletize, and dry the product. The polycondensation reaction time is 125min. The resulting high-speed film polyester has an intrinsic viscosity of 0.639dL / g, a molecular weight distribution index (PD) of 2.04, a half-crystallization period (t 1 / 2 ) of 2.94min, and a melt specific resistance of 0.81*10 8 Ω·cm.

[0043] The high-speed film polyester 4000 g was dried, 0.12 g of isocyanate was added, and a high-speed film polyester sheet was prepared by melt extrusion. The melting enthalpy of the sheet was 5.4 J / g by DSC method, and the viscosity drop before and after melt extrusion was 0.025 dl / g. The sheet was placed for one day, and then stretched on a biaxial stretching machine, with a preheating temperature of 100°C, a preheating time of 20 s, and a maximum stretching strain rate of 235% at a synchronous stretching ratio of 4.0*4.0.

[0044] Reference Example 1

[0045] In a 20 L general polymerization reactor, 5000 g of terephthalic acid (PTA), 3000 g of ethylene glycol (EG), and 2.015 g of ethylene glycol antimony catalyst were added, and esterification was carried out at a pressure of 0.25 MPa and a temperature of 250°C for 120 min. After the esterification reaction was completed, pre-polycondensation was carried out at a vacuum of 260°C to 275°C for 45 min, and finally the temperature of the polycondensation reaction was controlled at 281°C, the absolute pressure was below 100 pa, and the polycondensation reaction time was 105 min. The obtained conventional polyester had a specific viscosity of 0.645 dL / g, a molecular weight distribution index (PD) of 1.99, a melting and crystallization half-crystallization period (t 1 / 2 ) of 2.81 min, and a melting specific resistance of 5.51*10 8 Ω·cm.

[0046] The conventional polyester was dried and melt-extruded to prepare a conventional film polyester sheet. The melting enthalpy of the sheet was 13.1 J / g by DSC method, and the viscosity drop before and after melt extrusion was 0.048 dl / g. The sheet was placed for one day, and then stretched on a biaxial stretching machine, with a preheating temperature of 100°C, a preheating time of 20 s, and a maximum stretching strain rate of 100% at a synchronous stretching ratio of 4.0*4.0.

[0047] Reference Example 2

[0048] In a 20L general polymerization reactor, add 5000g of terephthalic acid (PTA), 3000g of ethylene glycol (EG), and 2.015g of ethylene glycol antimony catalyst. Perform esterification reaction under the conditions of 0.25Mpa of gauge pressure and 250℃ of temperature for 115min. After the esterification reaction is completed, add 3.05g of triphenyl phosphate, stir for 10min, then perform pre-polycondensation reaction under vacuum at 260℃-275℃ for 45min, and finally perform final polycondensation reaction by controlling the polycondensation reaction temperature at 281℃, with the absolute pressure being below 100pa. After the reaction is completed, extrude, pelletize, and dry by melt pump, with the polycondensation reaction time being 175min, to obtain a film polyester, with the intrinsic viscosity being 0.507dL / g, the molecular weight distribution index (PD) of the polyester being 2.81, the half-crystallization period (t 1 / 2 ) of the melt crystallization being 2.91min, and the melt specific resistance being 4.97*10 8 Ω·cm.

[0049] The polyester is dried and melt-extruded to obtain a film polyester thick sheet. The melt heat enthalpy of the thick sheet is tested by DSC method to be 13.4J / g, and the viscosity drop before and after melt-extrusion is 0.044dl / g. After the thick sheet is placed for one day, it is stretched on a two-way stretching machine, with the preheating temperature being 100℃ and the preheating time being 20s. The maximum stretching strain rate is 40% when the synchronous stretching ratio is 4.0*4.0.

[0050] Reference Example 3

[0051] In a 20L general polymerization reactor, add 5000g of terephthalic acid (PTA), 3000g of ethylene glycol (EG), and 2.015g of ethylene glycol antimony catalyst. Perform esterification at a pressure of 0.25Mpa and a temperature of 250°C for 125min. After the esterification reaction is completed, add 0.91g of triphenyl phosphate, 0.25g of magnesium acetate, and 0.03g of pentaerythritol. Stir for 10min, then perform pre-polycondensation at a vacuum of 260°C-275°C for 45min. Finally, control the polycondensation reaction temperature at 281°C to perform the final polycondensation reaction, with an absolute pressure below 100pa. After the reaction is completed, extrude, pelletize, and dry the product. The polycondensation reaction time is 100min. The resulting high-speed film polyester has an intrinsic viscosity of 0.658dL / g, a molecular weight distribution index (PD) of 2.17, a half-crystallization period (t1 / 2) of 3.31min, and a melt specific resistance of 5.28*108Ω·cm. The high-speed film polyester is dried and melt-extruded into a high-speed film polyester thick sheet. The melt heat enthalpy of the thick sheet is 9.4J / g, and the viscosity drop before and after melt-extrusion is 0.027dl / g. The thick sheet is placed for one day, then stretched on a two-way stretching machine. The maximum stretching strain rate is 105% at a synchronous stretching ratio of 4.0*4.0 under a preheating temperature of 100°C and a preheating time of 20s.

[0052] Reference Example 4

[0053] In a 20L general polymerization reactor, add 5000g of terephthalic acid (PTA), 3000g of ethylene glycol (EG), and 2.015g of ethylene glycol antimony catalyst. Perform esterification at a pressure of 0.25Mpa and a temperature of 250°C for 115min. After the esterification reaction is completed, add 0.91g of triphenyl phosphate, 2.08g of magnesium acetate, and 0.06g of pentaerythritol. Stir for 10min, then perform pre-polycondensation at a vacuum of 260°C-275°C for 45min. Finally, control the polycondensation reaction temperature at 281°C to perform the final polycondensation reaction, with an absolute pressure below 100pa. After the reaction is completed, extrude, pelletize, and dry the product. The polycondensation reaction time is 75min. The resulting high-speed film polyester has an intrinsic viscosity of 0.649dL / g, a molecular weight distribution index (PD) of 2.19, a half-crystallization period (t1 / 2) of 3.34min, and a melt specific resistance of 0.33*108Ω·cm. 1 / 2 8

[0054] ​​The high-speed film polyester was dried and melt-extruded to form a high-speed film polyester thick sheet. The melting heat enthalpy of the thick sheet was 8.8 J / g, and the viscosity drop before and after melt-extrusion was 0.055 dl / g. The thick sheet was placed for one day, and then stretched in a biaxial stretching machine. The maximum stretching strain rate was 90% at a synchronous stretching ratio of 4.0*4.0 under the conditions of a preheating temperature of 100°C and a preheating time of 20 s.

[0055] Reference Example 5

[0056] In a 20 L general polymerization reactor, 5000 g of terephthalic acid (PTA), 3000 g of ethylene glycol (EG), 2.015 g of ethylene glycol antimony catalyst were added, and esterification was carried out at a pressure of 0.25 MPa and a temperature of 250°C for 125 min. After the esterification reaction was completed, 0.91 g of triphenyl phosphate, 1.04 g of magnesium acetate, and 0.35 g of pentaerythritol were added, stirred for 10 min, and then pre-polycondensation was carried out at a vacuum of 260°C-275°C for 45 min. Finally, the temperature of the polycondensation reaction was controlled at 281°C, and the absolute pressure was below 100 pa. After the reaction was completed, the melt pump was extruded, pelletized, and dried. The polycondensation reaction time was 112 min. The high-speed film polyester obtained had a specific viscosity of 0.629 dL / g, a molecular weight distribution index (PD) of 2.65, a melting and crystallization half-crystallization period (t 1 / 2 ) of 4.06 min, and a melting specific resistance of 0.52*10 8 Ω·cm.

[0057] The high-speed film polyester was dried and melt-extruded to form a high-speed film polyester thick sheet. The melting heat enthalpy of the thick sheet was 1.7 J / g, and the viscosity drop before and after melt-extrusion was 0.031 dl / g. The thick sheet was placed for one day, and then stretched in a biaxial stretching machine. The maximum stretching strain rate was 100% at a synchronous stretching ratio of 4.0*4.0 under the conditions of a preheating temperature of 100°C and a preheating time of 20 s.

[0058] Performance test:

[0059] The main raw materials, reaction process parameters of the embodiments and reference examples of the present application are listed in Table 1, and the performance indicators of the polyesters used in the films are listed in Table 2. Embodiments 1-5 are copolyesters prepared according to the claims of the present application, and compared with the tensile rate of reference example 1, each embodiment has a significant effect of improving the film tensile rate. Reference example 1 does not add the stabilizer, static cling modifier and chain extender used in the present application, and its reaction parameters and polyester performance are the reference of conventional polyester. The comparison results of reference example 2 and reference example 1 show that when the content of the stabilizer exceeds the range of the present application, it will seriously affect the polymerization rate, the prepared polyester sample has low intrinsic viscosity and small tensile rate. The test results of reference example 3 and embodiment 2 show that when the content of the static cling modifier is too low, it will not have obvious effect on improving the static cling, and the melt specific resistance of the polyester will be high, and the improvement of the tensile rate compared with reference example 1 is not obvious. The comparison results of reference example 4 and embodiment 4 show that when the content of the static cling agent is too high, although it will improve the polymerization rate, it will also catalyze the degradation of the polyester during the polymerization and subsequent processing process, and the viscosity reduction index is significantly higher than that of each embodiment of the present application, and also slightly higher than that of conventional polyester, and the final drawing performance is poor, resulting in a small tensile rate. The comparison results of reference example 5 and embodiment 4 show that when the content of the chain extender in the polyester molecule is too high, it will lead to a too wide molecular weight distribution, which is not conducive to the improvement of the drawing performance, and the maximum drawing rate is significantly lower than that of embodiment 4. The test results of each embodiment and reference example show that within the research range, the stabilizer, static cling modifier and chain extender only play a coordinating role within a certain range, so as to play a comprehensive role in improving the melt static cling performance, reducing the melt extrusion viscosity reduction, improving the molecular weight distribution index, reducing the crystallization, and thus preparing high-speed film polyester.

[0060] The present application prepares high-speed film polyester by screening and combining stabilizers, static cling modifiers and chain extenders, and playing a synergistic effect of the three additives during melt extrusion. Compared with the conventional polyester in reference example 1 with the same performance indicators, the melt specific resistance of the high-speed film polyester prepared by the present application is reduced by more than 50%, the viscosity reduction of the polyester after melt extrusion is improved by more than 45%, the half crystallization time is increased by more than 15%, the molecular weight distribution index is increased by 10%, and the maximum tensile strain rate of the film is increased by more than 20% under the same conditions.

[0061]

[0062]

Claims

1. A method for preparing a polyester for high speed film characterized by: The polyester is prepared by using diacid and diol as raw materials, conducting esterification reaction under the action of a catalyst, adding static adhesion coordinator, stabilizer and chain extender after the esterification reaction and stirring for 5-15 min, conducting pre-polycondensation reaction, conducting polycondensation reaction after the pre-polycondensation reaction, and obtaining the polyester for high-speed film through melt pump extrusion, granulation and drying after the reaction is completed; Or: the polyester is prepared by using diacid and diol as raw materials, conducting esterification reaction under the action of a catalyst, adding static adhesion coordinator and stabilizer after the esterification reaction and stirring for 5-15 min, conducting pre-polycondensation reaction, conducting polycondensation reaction after the pre-polycondensation reaction, and obtaining polyester 1 for high-speed film through melt pump extrusion, granulation and drying after the reaction is completed; and the polyester 1 for high-speed film is blended with a chain extender in sequence and melt-extruded to prepare the polyester for high-speed film; The diacid is terephthalic acid, the diol is ethylene glycol, and the molar ratio of terephthalic acid to ethylene glycol is 1:(1.1-1.9); The pre-polycondensation reaction is a pre-polycondensation reaction under vacuum at 260-275 DEG C for 40-50 min; The catalyst is ethylene glycol antimony catalyst, and the mass content of ethylene glycol antimony in the polyester is 0.025%-0.040%; The stabilizer is triphenyl phosphate, trimethyl phosphate or phosphoric acid, and the mass fraction of phosphorus in the PET polyester is 0.0010%-0.0030%; The static adhesion coordinator is potassium phosphate, sodium pyrophosphate, sodium tripolyphosphate, magnesium acetate, zinc acetate, magnesium oxide, zinc oxide, potassium hydride or zinc hydroxide, and the mass fraction of metal elements in the PET polyester is 0.0015%-0.0030%; The chain extender is pentaerythritol, isocyanate, epoxy compound, dioxazoline or diacid anhydride compound, and the mass fraction of the chain extender in the PET polyester is 0.0001%-0.0040%; The melt specific resistance of the high speed film polyester is less than 2.2*10 8 Ω·cm.

2. The method of claim 1, wherein: The esterification reaction time is 1.5-2.5 h, the reaction temperature is 245-255 DEG C, the reaction pressure is 0.2-0.3 MPa, the polycondensation reaction temperature is 275-285 DEG C, the reaction pressure is below 100 Pa, and the polycondensation reaction time is 110-125 min.

Images